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Sample records for amplitude collective motion

  1. Microscopic description of large amplitude collective motion in the nuclear astrophysics context

    NASA Astrophysics Data System (ADS)

    Lacroix, Denis; Tanimura, Yusuke; Scamps, Guillaume; Simenel, Cédric

    2015-08-01

    In the last 10 years, we have observed an important increase of interest in the application of time-dependent energy density functional (TD-EDF) theory. This approach allows to treat nuclear structure and nuclear reaction from small to large amplitude dynamics in a unified framework. The possibility to perform unrestricted three-dimensional simulations using state-of-the-art effective interactions has opened new perspectives. In the present paper, an overview of applications where the predictive power of TD-EDF has been benchmarked is given. A special emphasize is made on processes that are of astrophysical interest. Illustrations discussed here include giant resonances, fission, binary and ternary collisions leading to fusion, transfer and deep inelastic processes.

  2. Recent progress in the microscopic description of small and large amplitude collective motion

    SciTech Connect

    Lacroix, D. Tanimura, Y.; Ayik, S.; Scamps, G.; Simenel, C.; Yilmaz, B.

    2015-10-15

    Dynamical mean-field theory has recently attracted much interests to provide a unified framework for the description of many aspects of nuclear dynamics [1, 2, 3, 4, 5] (for recent reviews see [6, 7]). In particular, the inclusion of pairing correlation has opened new perspectives [8, 9, 10, 11, 12]. A summary of recent applications including giant resonances and transfer reactions will be made in this talk [13, 14, 15, 16]. While new progresses have been made with the use of sophisticated effective interactions and the development of symmetry unrestricted applications, mean-field dynamics suffer from the poor treatment of quantum fluctuations in collective space. As a consequence, these theories are successful in describing average properties of many different experimental observations but generally fail to account realistically for the width of experimental distribution. The increase of predictive power of dynamical mean-field theory is facing the difficulty of going beyond the independent particle or quasi-particle picture. Nevertheless, in the last decade, novel methods have been proposed to prepare the next generation of microscopic mean-field codes able to account for both average properties and fluctuations around the average. A review of recent progresses in this direction as well as recent applications to heavy-ion collisions will be given [17, 18].

  3. Collective motion

    NASA Astrophysics Data System (ADS)

    Vicsek, Tamás; Zafeiris, Anna

    2012-08-01

    We review the observations and the basic laws describing the essential aspects of collective motion - being one of the most common and spectacular manifestation of coordinated behavior. Our aim is to provide a balanced discussion of the various facets of this highly multidisciplinary field, including experiments, mathematical methods and models for simulations, so that readers with a variety of background could get both the basics and a broader, more detailed picture of the field. The observations we report on include systems consisting of units ranging from macromolecules through metallic rods and robots to groups of animals and people. Some emphasis is put on models that are simple and realistic enough to reproduce the numerous related observations and are useful for developing concepts for a better understanding of the complexity of systems consisting of many simultaneously moving entities. As such, these models allow the establishing of a few fundamental principles of flocking. In particular, it is demonstrated, that in spite of considerable differences, a number of deep analogies exist between equilibrium statistical physics systems and those made of self-propelled (in most cases living) units. In both cases only a few well defined macroscopic/collective states occur and the transitions between these states follow a similar scenario, involving discontinuity and algebraic divergences.

  4. Stochastic aspects of nuclear large amplitude motion

    SciTech Connect

    Kolomietz, V.M.

    1995-08-01

    A consistent description of the macroscopic large amplitude dynamics and processes of internal excitation of a nucleus is suggested. The cranking model approach is used for the calculation of the response function of the nucleus in a moving frame. Using spectral statistics smearing, the collective mass, friction, and diffusion coefficients are derived. The relation of the response function in a moving frame to the correlation function in a classical chaotic system is established. The rate of dissipation due to the Landau-Zener transitions and through the Kubo mechanism is considered.

  5. Algebraic Nonlinear Collective Motion

    NASA Astrophysics Data System (ADS)

    Troupe, J.; Rosensteel, G.

    1998-11-01

    Finite-dimensional Lie algebras of vector fields determine geometrical collective models in quantum and classical physics. Every set of vector fields on Euclidean space that generates the Lie algebra sl(3, R) and contains the angular momentum algebra so(3) is determined. The subset of divergence-free sl(3, R) vector fields is proven to be indexed by a real numberΛ. TheΛ=0 solution is the linear representation that corresponds to the Riemann ellipsoidal model. The nonlinear group action on Euclidean space transforms a certain family of deformed droplets among themselves. For positiveΛ, the droplets have a neck that becomes more pronounced asΛincreases; for negativeΛ, the droplets contain a spherical bubble of radius |Λ|1/3. The nonlinear vector field algebra is extended to the nonlinear general collective motion algebra gcm(3) which includes the inertia tensor. The quantum algebraic models of nonlinear nuclear collective motion are given by irreducible unitary representations of the nonlinear gcm(3) Lie algebra. These representations model fissioning isotopes (Λ>0) and bubble and two-fluid nuclei (Λ<0).

  6. Collective motion of dimers.

    PubMed

    Penington, Catherine J; Korvasová, Karolína; Hughes, Barry D; Landman, Kerry A

    2012-11-01

    We consider a discrete agent-based model on a one-dimensional lattice and a two-dimensional square lattice, where each agent is a dimer occupying two sites. Agents move by vacating one occupied site in favor of a nearest-neighbor site and obey either a strict simple exclusion rule or a weaker constraint that permits partial overlaps between dimers. Using indicator variables and careful probability arguments, a discrete-time master equation for these processes is derived systematically within a mean-field approximation. In the continuum limit, nonlinear diffusion equations that describe the average agent occupancy of the dimer population are obtained. In addition, we show that multiple species of interacting subpopulations give rise to advection-diffusion equations. Averaged discrete simulation data compares very well with the solution to the continuum partial differential equation models. Since many cell types are elongated rather than circular, this work offers insight into population-level behavior of collective cellular motion.

  7. Resolving High Amplitude Surface Motion with Diffusing Light

    NASA Technical Reports Server (NTRS)

    Wright, W.; Budakian, R.; Putterman, Seth J.

    1996-01-01

    A new technique has been developed for the purpose of imaging high amplitude surface motion. With this method one can quantitatively measure the transition to ripple wave turbulence. In addition, one can measure the phase of the turbulent state. These experiments reveal strong coherent structures in turbulent range of motion.

  8. Small-amplitude viscous motion on arbitrary potential flows

    NASA Astrophysics Data System (ADS)

    Goldstein, M. E.

    1984-02-01

    This paper is concerned with small-amplitude, unsteady, vortical and entropic motion imposed on steady potential flows. It is restricted to the case where the spatial scale of the unsteady motion is small compared to that of the mean flow. Under such conditions, the unsteady motion may be influenced by viscosity even if the mean flow is not. An exact high-frequency (small-wavelength) solution is obtained for the small-amplitude viscous motion imposed on a steady potential flow. It generalizes the one obtained by Pearson (1959) for the homogeneous-strain case to the case of quasi-homogeneous strain. This result is used to study the effect of viscosity on rapidly distorted turbulent flows. Specific numerical results are given for a turbulent flow near a two-dimensional stagnation point.

  9. Large-amplitude inviscid fluid motion in an accelerating container

    NASA Technical Reports Server (NTRS)

    Perko, L. M.

    1968-01-01

    Study of dynamic behavior of the liquid-vapor interface of an inviscid fluid in an accelerating cylindrical container includes an analytical-numerical method for determining large amplitude motion. The method is based on the expansion of the velocity potential in a series of harmonic functions with time dependent coefficients.

  10. High amplitude surging and plunging motions at low Reynolds number

    NASA Astrophysics Data System (ADS)

    Choi, Jeesoon; Colonius, Tim; Williams, David; Caltech Collaboration; IIT Collaboration

    2014-11-01

    Aerodynamic forces and flow structures associated with high amplitude oscillations of an airfoil in the streamwise (surging) and transverse (plunging) direction are investigated in two-dimensional simulations at low Reynolds number (Re = 102 ~ 103). While the unsteady aerodynamic forces for low-amplitude motions were mainly affected by the leading-edge vortex (LEV) acting in- or out-of phase with the quasi-component of velocity, large-amplitude motions involve complex vortex interactions of LEVs and trailing-edge vortices (TEVs) with the moving body. For high-amplitude surging, the TEV, instead of the LEV, induces low-pressure regions above the airfoil during the retreating portion of the cycle near the reduced frequency, k = 0.5, and enhances the time-average forces. The time required for the LEV to convect along the chord becomes an intrinsic time scale, and for plunging motions, there is a sudden change of flow structure when the period of the motion is not long enough for the LEV to convect through the whole chord.

  11. The Dynamics of Large-Amplitude Motion in Energized Molecules

    SciTech Connect

    Perry, David S.

    2016-05-27

    Chemical reactions involve large-amplitude nuclear motion along the reaction coordinate that serves to distinguish reactants from products. Some reactions, such as roaming reactions and reactions proceeding through a loose transition state, involve more than one large-amplitude degree of freedom. Because of the limitation of exact quantum nuclear dynamics to small systems, one must, in general, define the active degrees of freedom and separate them in some way from the other degrees of freedom. In this project, we use large-amplitude motion in bound model systems to investigate the coupling of large-amplitude degrees of freedom to other nuclear degrees of freedom. This approach allows us to use the precision and power of high-resolution molecular spectroscopy to probe the specific coupling mechanisms involved, and to apply the associated theoretical tools. In addition to slit-jet spectra at the University of Akron, the current project period has involved collaboration with Michel Herman and Nathalie Vaeck of the Université Libre de Bruxelles, and with Brant Billinghurst at the Canadian Light Source (CLS).

  12. Attenuation of ground-motion spectral amplitudes in southeastern Australia

    USGS Publications Warehouse

    Allen, T.I.; Cummins, P.R.; Dhu, T.; Schneider, J.F.

    2007-01-01

    A dataset comprising some 1200 weak- and strong-motion records from 84 earthquakes is compiled to develop a regional ground-motion model for southeastern Australia (SEA). Events were recorded from 1993 to 2004 and range in size from moment magnitude 2.0 ??? M ??? 4.7. The decay of vertical-component Fourier spectral amplitudes is modeled by trilinear geometrical spreading. The decay of low-frequency spectral amplitudes can be approximated by the coefficient of R-1.3 (where R is hypocentral distance) within 90 km of the seismic source. From approximately 90 to 160 km, we observe a transition zone in which the seismic coda are affected by postcritical reflections from midcrustal and Moho discontinuities. In this hypocentral distance range, geometrical spreading is approximately R+0.1. Beyond 160 km, low-frequency seismic energy attenuates rapidly with source-receiver distance, having a geometrical spreading coefficient of R-1.6. The associated regional seismic-quality factor can be expressed by the polynomial: log Q(f) = 3.66 - 1.44 log f + 0.768 (log f)2 + 0.058 (log f)3 for frequencies 0.78 ??? f ??? 19.9 Hz. Fourier spectral amplitudes, corrected for geometrical spreading and anelastic attenuation, are regressed with M to obtain quadratic source scaling coefficients. Modeled vertical-component displacement spectra fit the observed data well. Amplitude residuals are, on average, relatively small and do not vary with hypocentral distance. Predicted source spectra (i.e., at R = 1 km) are consistent with eastern North American (ENA) Models at low frequencies (f less than approximately 2 Hz) indicating that moment magnitudes calculated for SEA earthquakes are consistent with moment magnitude scales used in ENA over the observed magnitude range. The models presented represent the first spectral ground-motion prediction equations develooed for the southeastern Australian region. This work provides a useful framework for the development of regional ground-motion relations

  13. Collective organization in aerotactic motion

    NASA Astrophysics Data System (ADS)

    Mazza, Marco G.

    Some bacteria exhibit interesting behavior in the presence of an oxygen concentration. They perform an aerotactic motion along the gradient until they reach their optimal oxygen concentration. But they often organize collectively by forming dense regions, called 'bands', that travel towards the oxygen source. We have developed a model of swimmers with stochastic interaction rules moving in proximity of an air bubble. We perform molecular dynamics simulations and also solve advection-diffusion equations that reproduce the aerotactic behavior of mono-flagellated, facultative anaerobic bacteria. If the oxygen concentration in the system sinks locally below a threshold value, the formation of a migrating aerotactic band toward the bubble can be observed.

  14. Optimality, reduction and collective motion

    PubMed Central

    Justh, Eric W.; Krishnaprasad, P. S.

    2015-01-01

    The planar self-steering particle model of agents in a collective gives rise to dynamics on the N-fold direct product of SE(2), the rigid motion group in the plane. Assuming a connected, undirected graph of interaction between agents, we pose a family of symmetric optimal control problems with a coupling parameter capturing the strength of interactions. The Hamiltonian system associated with the necessary conditions for optimality is reducible to a Lie–Poisson dynamical system possessing interesting structure. In particular, the strong coupling limit reveals additional (hidden) symmetry, beyond the manifest one used in reduction: this enables explicit integration of the dynamics, and demonstrates the presence of a ‘master clock’ that governs all agents to steer identically. For finite coupling strength, we show that special solutions exist with steering controls proportional across the collective. These results suggest that optimality principles may provide a framework for understanding imitative behaviours observed in certain animal aggregations. PMID:27547087

  15. Comparison of damping in buildings under low-amplitude and strong motions

    USGS Publications Warehouse

    Celebi, M.

    1996-01-01

    This paper presents a comprehensive assessment of damping values and other dynamic characteristics of five buildings using strong-motion and low-amplitude (ambient vibration) data. The strong-motion dynamic characteristics of five buildings within the San Francisco Bay area are extracted from recordings of the 17 October 1989 Loma Prieta earthquake (LPE). Ambient vibration response characteristics for the same five buildings were inferred using data collected in 1990 following LPE. Additional earthquake data other than LPE for one building and ambient vibration data collected before LPE for two other buildings provide additional confirmation of the results obtained. For each building, the percentages of critical damping and the corresponding fundamental periods determined from low-amplitude test data are appreciably lower than those determined from strong-motion recordings. These differences are attributed mainly to soil-structure interaction and other non-linear behavior affecting the structures during strong shaking. Significant contribution of radiation damping to the effective damping of a specific building is discussed in detail.

  16. Collective motion of microswimmers in viscoelastic fluids

    NASA Astrophysics Data System (ADS)

    Li, Gaojin; Ardekani, Arezoo

    2015-11-01

    The dynamics of suspension of self-propelled microorganisms show fascinating hydrodynamic phenomena, such as, large scale swarming motion, locally correlated motion, enhanced particle diffusion, and enhanced fluid mixing. Even though many studies have been conducted in a Newtonian fluid, the collective motion of microorganisms in non-Newtonian fluids is less understood. The non-Newtonian fluid rheological properties, such as viscoelasticity and shear-dependent viscosity in saliva, mucus and biofilm, significantly affect the swimming properties and hydrodynamic interaction of microorganisms. In this work, we use direct numerical simulation to investigate the collective motion of rod-like swimmers in viscoelastic fluids. Two swimming types, pusher and puller, are investigated. The background viscoelastic fluid is modeled using an Oldroyd-B constitutive equation. This work is supported by NSF CBET-1445955 and Indiana CTSI TR001108.

  17. Large amplitude ship motions and bow flare slamming pressures in regular head seas

    SciTech Connect

    Tao, Z.; Incecik, A.

    1996-12-31

    In this paper, the motion equations incorporating nonlinear terms due to large amplitude motions and bow flare slamming pressures are described in regular head seas. Numerical predictions of ship motions based on a small amplitude linear theory and large amplitude nonlinear method and experimental data are compared with each other in the frequency and time domain. The nonlinear restoring force, nonlinear damping force and nonlinear fluid momentum force are considered in predicting ship motions. The frequency dependent added mass and damping coefficient are computed at the instantaneous submerged sections of the ship. The momentum slamming theory and Wagner theory are used to predict the bow flare slamming pressure. The total impact pressure is expressed as the sum of water immersion impact pressure and wave striking impact pressure. There is a satisfactory agreement between theoretical predictions and model test measurements.

  18. Emergence of collective motion in bacterial suspensions

    NASA Astrophysics Data System (ADS)

    Liu, Song

    It is well known that bacterial suspensions will exhibit collective motion at high concentrations, in which both steric and hydrodynamic interactions play important roles. We aim to investigate whether steric and hydrodynamic interactions are of equal importance to the emergence of collective motion. Here we will present our efforts to experimentally tune the relative strength of these interactions in bacterial suspensions. Our preliminary results suggest that the transition to collective motion may depend on the interplay between steric and hydrodynamic interactions. Mailing address: Room 306 Science Centre North Block, The Chinese University of Hong Kong, Shatin, N.T. Hong Kong SAR. Phone: +852-3943-6354. Fax: +852-2603-5204. E-mail: songliuphy@gmail.com.

  19. Locust Collective Motion and Its Modeling

    PubMed Central

    Ariel, Gil; Ayali, Amir

    2015-01-01

    Over the past decade, technological advances in experimental and animal tracking techniques have motivated a renewed theoretical interest in animal collective motion and, in particular, locust swarming. This review offers a comprehensive biological background followed by comparative analysis of recent models of locust collective motion, in particular locust marching, their settings, and underlying assumptions. We describe a wide range of recent modeling and simulation approaches, from discrete agent-based models of self-propelled particles to continuous models of integro-differential equations, aimed at describing and analyzing the fascinating phenomenon of locust collective motion. These modeling efforts have a dual role: The first views locusts as a quintessential example of animal collective motion. As such, they aim at abstraction and coarse-graining, often utilizing the tools of statistical physics. The second, which originates from a more biological perspective, views locust swarming as a scientific problem of its own exceptional merit. The main goal should, thus, be the analysis and prediction of natural swarm dynamics. We discuss the properties of swarm dynamics using the tools of statistical physics, as well as the implications for laboratory experiments and natural swarms. Finally, we stress the importance of a combined-interdisciplinary, biological-theoretical effort in successfully confronting the challenges that locusts pose at both the theoretical and practical levels. PMID:26656851

  20. Amplitude and phase variations of the chandler wobble from 164-yr polar motion series

    NASA Astrophysics Data System (ADS)

    Malkin, Z. M.; Miller, N. O.

    2011-10-01

    This paper is aimed at investigation of the Chandler wobble (CW) at the 164-year interval to search for the major CW amplitude and phase variations. The CW signal was extracted from the IERS polar motion series using digital filtering. The CW amplitude and phase variations were examined by means of several methods which yield very similar results. Results of our analysis have shown that, besides the well-known CW phase jump in the 1920s, two other large phase jumps have been found in the 1850s and 2000s, all three contemporarily with a sharp decrease in the CW amplitude.

  1. Collective motion in populations of colloidal robots

    NASA Astrophysics Data System (ADS)

    Bartolo, Denis; Bricard, Antoine; Caussin, Jean-Baptiste; Dauchot, Olivier; Desreumaux, Nicolas

    2014-03-01

    Could the behavior of bacteria swarms, fish schools, and bird flocks be understood within a unified framework? Can one ignore the very details of the interaction mechanisms at the individual level to elucidate how strikingly similar collective motion emerges at the group level in this broad range of motile systems? These seemingly provocative questions have triggered significant advance in the physics and the biology, communities over the last decade. In the physics language these systems, made of motile individuals, can all be though as different realizations of ``active matter.'' In this talk, I will show how to gain more insight into this vivid field using self-propelled colloids as a proxy for motile organism. I will show how to motorize colloidal particles capable of sensing the orientation of their neighbors. Then, I will demonstrate that these archetypal populations display spontaneous transitions to swarming motion, and to global directed motion with very few density and orientation fluctuations.

  2. Topological and behavioral disorder in collective motion

    NASA Astrophysics Data System (ADS)

    Quint, David

    2014-03-01

    A major underlying assumption in many studies on the collective motion of self-propelled agents has been that the environment is continuous, isotropic and ordered and agents are all identical. In the natural world there are many examples of disordered environments or heterogeneous swarms where collective motion can exist. Examples include bats that navigate natural caverns via echolocation, schools of fish that maneuver through dark and light areas, microbial colonies that move about in heterogeneous soil, quorum sensing bacteria, crowds of people that are evacuating a building and traffic flow in major cities. In general disorder can arise from two basic sources that inhibit/augment both movement and information flow, those that represent physical obstacles (i.e topological), (extrinsic), and those that arise from behavioral heterogeneties within the swarm itself (intrinsic). In either case, extrinsic or intrinsic, disorder can be quenched or dynamic in space or time or both. To understand the effect of the various forms of disorder that can be present in the environment of the agents, we study both discrete and continuous 2 d agent based models that utilize only local interactions and study the transition to the collectively moving state as a function of the amount of disorder or behavioral heterogeneities present in the environment. I will present our recent results and discuss the effect that disorder has on collective motion and the general physical mechanisms that swarms, either real or artificial, could utilize in order to overcome disorder in their environment.

  3. Role of latency jittering correction in motion-onset VEP amplitude decay during prolonged visual stimulation.

    PubMed

    Kremláček, J; Hulan, M; Kuba, M; Kubová, Z; Langrová, J; Vít, F; Szanyi, J

    2012-06-01

    Visual evoked potentials to motion-onset stimulation (M-VEPs) gradually attenuate in amplitude during examination. The observed decline in averaged responses can be caused by decreases in single response magnitudes and/or increased variability in a response delays, that is, latency jittering. To illuminate the origins of the suppression of M-VEPs during stimuli repetition, we used correlation technique to estimate an upper bound of possible latency jittering of single sweeps and we evaluated the effect of its correction on the amplitudes of three M-VEP dominant peaks P1, N2 and P3. During prolonged visual motion stimulation, the variability of corrective latency shifts in the occipital region increased (r = 0.35: 0.44) and the number of single responses corresponding to the average curve declined in occipital and parietal derivations (r = -0.48: -0.62). While the P1 peak amplitude did not exhibit any time-specific behaviour, the N2 amplitude exhibited a significant decay of 29.4% that was partially reduced to 16.6% in the central occipital derivation by the latency jitter and non-correspondence corrections. The strongest attenuation (32.7%) was observed in the P3 amplitude and was less sensitive to the corrections, dropping only to 27.9%. The main part of the response suppression to repeated motion stimulation was caused by amplitude drop and represents non-stationary process that likely correspond to a fatigue model. The rise of variability in latency jitter correction and the reduction in single responses correlated with the M-VEP were significant factors associated with prolonged motion stimulation. The relation of these parameters to a hypothetical veridical response is ambiguous and can be caused by a time shift of the response or by a change of signal-to-noise ratio. Using selective averaging and latency jitter correction, the effect of response suppression was partially removed.

  4. Large amplitude collective nuclear motion and soliton concept

    SciTech Connect

    Kartavenko, V.G. |

    1993-12-31

    An application of a soliton theory methods to some nonlinear problems in low and intermediate energies (E {approx} 10--100MeV/nucleon) nucleus - nucleus collisions are presented. Linear and nonlinear excitations of the nuclear density are investigated in the framework of nuclear hydrodynamics. The problem of dynamical instability and clusterization phenomena in a breakup of excited nuclear systems are considered from the points of view of a soliton concept.

  5. A Hybrid Program for Fitting Rotationally Resolved Spectra of Floppy Molecules with One Large-Amplitude Rotatory Motion and One Large-Amplitude Oscillatory Motion

    PubMed Central

    Kleiner, Isabelle; Hougen, Jon T.

    2015-01-01

    A new hybrid-model fitting program for methylamine-like molecules has been developed, based on an effective Hamiltonian in which the ammonia-like inversion motion is treated using a tunneling formalism, while the internal-rotation motion is treated using an explicit kinetic energy operator and potential energy function. The Hamiltonian in the computer program is set up as a 2×2 partitioned matrix, where each diagonal block contains a traditional torsion-rotation Hamiltonian (as in the earlier program BELGI), and the two off-diagonal blocks contain tunneling terms. This hybrid formulation permits the use of the permutation-inversion group G6 (isomorphic to C3v) for terms in the two diagonal blocks, but requires G12 for terms in the off-diagonal blocks. The first application of the new program is to 2-methylmalonaldehyde. Microwave data for this molecule were previously fit using an all-tunneling Hamiltonian formalism to treat both large-amplitude-motions. For 2-methylmalonaldehyde, the hybrid program achieves the same quality of fit as was obtained with the all-tunneling program, but fits with the hybrid program eliminate a large discrepancy between internal rotation barriers in the OH and OD isotopologs of 2-methylmalonaldehyde that arose in fits with the all-tunneling program. This large isotopic shift in internal rotation barrier is thus almost certainly an artifact of the all-tunneling model. Other molecules for application of the hybrid program are mentioned. PMID:26439709

  6. Collective motion in populations of colloidal bots

    NASA Astrophysics Data System (ADS)

    Bartolo, Denis

    One of the origins of active matter physics was the idea that flocks, herds, swarms and shoals could be quantitatively described as emergent ordered phases in self-driven materials. From a somehow dual perspective, I will show how to engineer active materials our of colloidal flocks. I will show how to motorize colloidal particles capable of sensing the orientation of their neighbors and how to handle them in microfluidic chips. These populations of colloidal bots display a non-equilibrium transition toward collective motion. A special attention will be paid to the robustness of the resulting colloidal flocks with respect to geometrical frustration and to quenched disorder.

  7. Local disalignment can promote coherent collective motion

    NASA Astrophysics Data System (ADS)

    Meschede, M.; Hallatschek, O.

    2013-04-01

    When particles move at a constant speed and have the tendency to align their directions of motion, ordered large-scale movement can emerge despite significant levels of noise. Many variants of this model of self-propelled particles have been studied to explain the coherent motion of groups of birds, fish or microbes. Here, we generalize the aligning interaction rule of many classical self-propelled particle models to the case where particles after the interaction tend to move in slightly different directions away from each other, as characterized by a deflection angle α. We map out the resulting phase diagram and find that, in sufficiently dense systems, small local disalignment can lead to higher global alignment of particle movement directions. We show that in this dense regime, global alignment is accompanied by a grid-like spatial structure which allows information to rapidly percolate across the system by a ‘domino’ effect. Our results elucidate the relevance of disalignment for the emergence of collective motion in models with repulsive interaction terms.

  8. Collective cell motion in endothelial monolayers

    PubMed Central

    Szabó, A.; Ünnep, R.; Méhes, E.; Twal, W. O.; Argraves, S. W.; Cao, Y.; Czirók, A.

    2011-01-01

    Collective cell motility is an important aspect of several developmental and pathophysiological processes. Despite its importance, the mechanisms that allow cells to be both motile and adhere to one another are poorly understood. In this study we establish statistical properties of the random streaming behavior of endothelial monolayer cultures. To understand the reported empirical findings, we expand the widely used cellular Potts model to include active cell motility. For spontaneous directed motility we assume a positive feedback between cell displacements and cell polarity. The resulting model is studied with computer simulations, and is shown to exhibit behavior compatible with experimental findings. In particular, in monolayer cultures both the speed and persistence of cell motion decreases, transient cell chains move together as groups, and velocity correlations extend over several cell diameters. As active cell motility is ubiquitous both in vitro and in vivo, our model is expected to be a generally applicable representation of cellular behavior. PMID:21076204

  9. Effect of limited amplitude and rate of flap motion on vane-controlled gust alleviation system

    NASA Technical Reports Server (NTRS)

    Barker, L. K.; Crawford, D. J.; Sparrow, G. W.

    1972-01-01

    An airplane (light transport type) is assumed to be in level flight (no pitching) through atmospheric turbulence which has a mean-square vertical gust intensity of 9.3 (m/sec)sq. The power spectral density of the vertical acceleration due to gusts is examined with and without a gust-alleviation system in operation. The gust-alleviation system consisted of wing flaps that were used in conjunction with a vane mounted ahead of the airplane to sense the vertical gust velocity. The primary purpose of this study was to examine the change in the effectiveness of the gust-alleviation system when the flap motion is limited in amplitude and rate. The alleviation system was very effective if no restrictions were placed on flap motion (rate and amplitude). Restricting the flap amplitude to 0.5 radian did not appreciably change the effectiveness. However, restricting the flap rate did reduce the gust alleviation, and restricting the flap rate to 0.25 rad/sec actually caused the alleviation system to increase the vertical acceleration above that for the no-alleviation situation. Based upon this analysis, rate limiting appears to be rather significant in gust-alleviation systems designed for passenger comfort.

  10. Complex amplitude correlation for compensation of large in-plane motion in digital speckle pattern interferometry

    SciTech Connect

    Svanbro, Angelica; Sjoedahl, Mikael

    2006-12-01

    The use of complex amplitude correlation to compensate for large in-plane motion in digital speckle pattern interferometry is investigated. The result is compared with experiments where digital speckle photography (DSP) is used for compensation. An advantage of using complex amplitude correlation instead of intensity correlation (as in DSP) is that the phase change describing the deformation is retrieved directly from the correlation peak, and there is no need to compensate for the large movement and then use the interferometric algorithms. A discovered drawback of this method is that the correlation values drop quickly if a phase gradient larger than {pi} is present in the subimages used for cross correlation. This means that, for the complex amplitude correlation to be used, the size of the subimages must be well chosen or a third parameter in the cross-correlation algorithm that compensates for the phase variation is needed.Correlation values and wrapped phase maps from the two techniques (intensity and complex amplitude correlation) are presented.

  11. On large amplitude motions of simplest amides in the ground and excited electronic states

    NASA Astrophysics Data System (ADS)

    Tukachev, N. V.; Bataev, V. A.; Godunov, I. A.

    2016-12-01

    For the formamide, acetamide, N-methylformamide and N-methylacetamide molecules in the ground (S0) and lowest excited singlet (S1) and triplet (T1) electronic states equilibrium geometry parameters, harmonic vibrational frequencies, barriers to conformational transitions and conformer energy differences were estimated by means of MP2, CCSD(T), CASSCF, CASPT2 and MRCI ab initio methods. One-, two- and three-dimensional potential energy surface (PES) sections corresponding to different large amplitude motions (LAM) were calculated by means of MP2/aug-cc-pVTZ (S0) and CASPT2/cc-pVTZ (S1,T1). For these molecules, in each excited electronic state six minima were found on 2D PES sections. Using PES sections, different anharmonic vibrational problems were solved and the frequencies of large amplitude vibrations were determined.

  12. Aerodynamic and flowfield hysteresis of slender wing aircraft undergoing large-amplitude motions

    NASA Technical Reports Server (NTRS)

    Nelson, Robert C.; Arena, Andrew S., Jr.; Thompson, Scott A.

    1991-01-01

    The implication of maneuvers through large angles of incidence is discussed by examining the unsteady aerodynamic loads, surface pressures, vortical position, and breakdown on slender, flat plate delta wings. Two examples of large amplitude unsteady motions are presented. First, the unsteady characteristics of a 70 degree swept delta wing undergoing pitch oscillation from 0 to 60 degrees is examined. Data is presented that shows the relationship between vortex breakdown and the overshoot and undershoot of the aerodynamic loads and surface pressure distribution. The second example examines the leading edge vortical flow over an 80 degree swept wing undergoing a limit cycle roll oscillation commonly called wing rock.

  13. Structure of the Small Amplitude Motion on Transversely Sheared Mean Flows

    NASA Technical Reports Server (NTRS)

    Goldstein, Marvin E.; Afsar, Mohamed Z.; Leib, Stewart J.

    2013-01-01

    This paper considers the small amplitude unsteady motion of an inviscid non-heat conducting compressible fluid on a transversely sheared mean flow. It extends a previous result given in Goldstein (1978(b) and 1979(a)) which shows that the hydrodynamic component of the motion is determined by two arbitrary convected quantities in the absence of solid surfaces or other external sources. The result is important because it can be used to specify appropriate boundary conditions for unsteady surface interaction problems on transversely sheared mean flows in the same way that the vortical component of the Kovasznay (1953) decomposition is used to specify these conditions for surface interaction problems on uniform mean flows. But unlike the Kovasznay (1953) case the arbitrary convected quantities no longer bear a simple relation to the physical variables. One purpose of this paper is to derive a formula that relates these quantities to the (physically measurable) vorticity and pressure fluctuations in the flow.

  14. Electron diffraction analysis for the molecules with degenerate large amplitude motions: Intramolecular dynamics in arsenic pentafluoride

    NASA Astrophysics Data System (ADS)

    Kochikov, Igor V.; Kovtun, Dmitry M.; Tarasov, Yury I.

    2017-03-01

    There exists a noticeable disagreement in the difference of axial and equatorial bond lengths in D3h symmetry arsenic and phosphorus pentafluorides between the GED data and high level quantum chemical results. In order to resolve this disagreement, a new structural analysis of the original experiment of (Clippard & Bartell, Inorg. Chem., 9 (1970) 805-811) was undertaken on the basis of modern approach incorporating spectroscopic evidence and quantum chemical information and allowing for intramolecular large-amplitude motion. The results of the analysis prove the internal insufficiency of the experimental material in the description of the accurate positions of the peaks on the radial distribution function. Additional experimental investigation of pentahalide molecules, especially at high temperatures, is of interest.

  15. Electron holographic visualization of collective motion of electrons through electric field variation.

    PubMed

    Shindo, Daisuke; Aizawa, Shinji; Akase, Zentaro; Tanigaki, Toshiaki; Murakami, Yasukazu; Park, Hyun Soon

    2014-08-01

    This study demonstrates the accumulation of electron-induced secondary electrons by utilizing a simple geometrical configuration of two branches of a charged insulating biomaterial. The collective motion of these secondary electrons between the branches has been visualized by analyzing the reconstructed amplitude images obtained using in situ electron holography. In order to understand the collective motion of secondary electrons, the trajectories of these electrons around the branches have also been simulated by taking into account the electric field around the charged branches on the basis of Maxwell's equations.

  16. Determination of functional collective motions in a protein at atomic resolution using coherent neutron scattering

    PubMed Central

    Hong, Liang; Jain, Nitin; Cheng, Xiaolin; Bernal, Ana; Tyagi, Madhusudan; Smith, Jeremy C.

    2016-01-01

    Protein function often depends on global, collective internal motions. However, the simultaneous quantitative experimental determination of the forms, amplitudes, and time scales of these motions has remained elusive. We demonstrate that a complete description of these large-scale dynamic modes can be obtained using coherent neutron-scattering experiments on perdeuterated samples. With this approach, a microscopic relationship between the structure, dynamics, and function in a protein, cytochrome P450cam, is established. The approach developed here should be of general applicability to protein systems. PMID:27757419

  17. Determination of functional collective motions in a protein at atomic resolution using coherent neutron scattering

    DOE PAGES

    Hong, Liang; Jain, Nitin; Cheng, Xiaolin; ...

    2016-10-14

    Protein function often depends on global, collective internal motions. However, the simultaneous quantitative experimental determination of the forms, amplitudes, and time scales of these motions has remained elusive. We demonstrate that a complete description of these large-scale dynamic modes can be obtained using coherent neutron-scattering experiments on perdeuterated samples. With this approach, a microscopic relationship between the structure, dynamics, and function in a protein, cytochrome P450cam, is established. The approach developed here should be of general applicability to protein systems.

  18. Reducing dynamic disorder in small-molecule organic semiconductors by suppressing large-amplitude thermal motions

    PubMed Central

    Illig, Steffen; Eggeman, Alexander S.; Troisi, Alessandro; Jiang, Lang; Warwick, Chris; Nikolka, Mark; Schweicher, Guillaume; Yeates, Stephen G.; Henri Geerts, Yves; Anthony, John E.; Sirringhaus, Henning

    2016-01-01

    Thermal vibrations and the dynamic disorder they create can detrimentally affect the transport properties of van der Waals bonded molecular semiconductors. The low-energy nature of these vibrations makes it difficult to access them experimentally, which is why we still lack clear molecular design rules to control and reduce dynamic disorder. In this study we discuss the promising organic semiconductors rubrene, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothio-phene and 2,9-di-decyl-dinaphtho-[2,3-b:20,30-f]-thieno-[3,2-b]-thiophene in terms of an exceptionally low degree of dynamic disorder. In particular, we analyse diffuse scattering in transmission electron microscopy, to show that small molecules that have their side chains attached along the long axis of their conjugated core are better encapsulated in their crystal structure, which helps reduce large-amplitude thermal motions. Our work provides a general strategy for the design of new classes of very high mobility organic semiconductors with a low degree of dynamic disorder. PMID:26898754

  19. Notation Confusion of Symmetry Species for Molecules with Several Large-Amplitude Internal Motions

    NASA Astrophysics Data System (ADS)

    Groner, P.

    2011-06-01

    The Mulliken convention has become the standard notation for symmetry species (irreducible representations) of point groups for quasi-rigid molecules. No such convention exists for symmetry species of symmetry groups for semi-rigid or non-rigid molecules with large amplitude internal motions (LAMs). As a result, we have a situation where we create notations in a do-it-yourself fashion or adopt them from the literature, sometimes even without proper reference to its derivation or to the character table on which it is based. This may be just a nuisance for those who are comfortable enough with group theory and molecular symmetry groups to figure "it" out, but it represents a real problem for everybody else. The notation confusion is illustrated with examples from the literature (both old and new) on molecules with two or more LAMs. Most authors use the notation introduced by Myers and Wilson for molecules such as acetone or propane. No universal notation is in use for molecules with two methyl groups but lower overall symmetry. For example, the notation G_1_8 is used for one of these groups. As it turns out, different people use the same notation for different groups. This presentation is an attempt to bring some light into the dark and to combat confusion with a call for an anti-confusion convention. R. S. Mulliken, Phys. Rev. 43, 279 (1933). R. J. Myers, E. B. Wilson, J. Chem. Phys. 33, 186 (1960).

  20. An Efficient and Accurate Formalism for the Treatment of Large Amplitude Intramolecular Motion.

    PubMed

    Reinisch, Guillaume; Miki, Kenji; Vignoles, Gérard L; Wong, Bryan M; Simmons, Chris S

    2012-08-14

    We propose a general approach to describe large amplitude motions (LAM) with multiple degrees of freedom (DOF) in molecules or reaction intermediates, which is useful for the computation of thermochemical or kinetic data. The kinetic part of the LAM Lagrangian is derived using a Z-matrix internal coordinate representation within a new numerical procedure. This derivation is exact for a classical system, and the uncertainties on the prediction of observable quantities largely arise from uncertainties on the LAM potential energy surface (PES) itself. In order to rigorously account for these uncertainties, we present an approach based on Bayesian theory to infer a parametrized physical model of the PES using ab initio calculations. This framework allows for quantification of uncertainties associated with a PES model as well as the forward propagation of these uncertainties to the quantity of interest. A selection and generalization of some treatments accounting for the coupling of the LAM with other internal or external DOF are also presented. Finally, we discuss and validate the approach with two applications: the calculation of the partition function of 1,3-butadiene and the calculation of the high-pressure reaction rate of the CH(3) + H → CH(4) recombination.

  1. An Efficient and Accurate Formalism for the Treatment of Large Amplitude Intramolecular Motion

    PubMed Central

    2012-01-01

    We propose a general approach to describe large amplitude motions (LAM) with multiple degrees of freedom (DOF) in molecules or reaction intermediates, which is useful for the computation of thermochemical or kinetic data. The kinetic part of the LAM Lagrangian is derived using a Z-matrix internal coordinate representation within a new numerical procedure. This derivation is exact for a classical system, and the uncertainties on the prediction of observable quantities largely arise from uncertainties on the LAM potential energy surface (PES) itself. In order to rigorously account for these uncertainties, we present an approach based on Bayesian theory to infer a parametrized physical model of the PES using ab initio calculations. This framework allows for quantification of uncertainties associated with a PES model as well as the forward propagation of these uncertainties to the quantity of interest. A selection and generalization of some treatments accounting for the coupling of the LAM with other internal or external DOF are also presented. Finally, we discuss and validate the approach with two applications: the calculation of the partition function of 1,3-butadiene and the calculation of the high-pressure reaction rate of the CH3 + H → CH4 recombination. PMID:22904694

  2. Reducing dynamic disorder in small-molecule organic semiconductors by suppressing large-amplitude thermal motions

    NASA Astrophysics Data System (ADS)

    Illig, Steffen; Eggeman, Alexander S.; Troisi, Alessandro; Jiang, Lang; Warwick, Chris; Nikolka, Mark; Schweicher, Guillaume; Yeates, Stephen G.; Henri Geerts, Yves; Anthony, John E.; Sirringhaus, Henning

    2016-02-01

    Thermal vibrations and the dynamic disorder they create can detrimentally affect the transport properties of van der Waals bonded molecular semiconductors. The low-energy nature of these vibrations makes it difficult to access them experimentally, which is why we still lack clear molecular design rules to control and reduce dynamic disorder. In this study we discuss the promising organic semiconductors rubrene, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothio-phene and 2,9-di-decyl-dinaphtho-[2,3-b:20,30-f]-thieno-[3,2-b]-thiophene in terms of an exceptionally low degree of dynamic disorder. In particular, we analyse diffuse scattering in transmission electron microscopy, to show that small molecules that have their side chains attached along the long axis of their conjugated core are better encapsulated in their crystal structure, which helps reduce large-amplitude thermal motions. Our work provides a general strategy for the design of new classes of very high mobility organic semiconductors with a low degree of dynamic disorder.

  3. Collective motion in Proteus mirabilis swarms

    NASA Astrophysics Data System (ADS)

    Haoran, Xu

    Proteus mirabilisis a Gram-negative, rod-shaped bacterium. It is widely distributed in soil and water, and it is well known for exhibiting swarming motility on nutrient agar surfaces. In our study, we focused on the collective motility of P. mirabilis and uncovered a range of interesting phenomena. Here we will present our efforts to understand these phenomena through experiments and simulation. Mailing address: Room 306 Science Centre North Block, The Chinese University of Hong Kong, Shatin, N.T. Hong Kong SAR. Phone: +852-3943-6354. Fax: +852-2603-5204. E-mail:xhrphx@gmail.com.

  4. Large Amplitude Motions and Information Transfer Along Conjugated Bonds: the Case of Paratolualdehyde

    NASA Astrophysics Data System (ADS)

    Saal, Hilkka; Grabow, Jens-Uwe; Hight-Walker, Angela R.; Hougen, Jon T.; Caminati, Walther; Kleiner, Isabelle

    2010-06-01

    Historically, barriers to large amplitude motions are often related, using steric hinderance arguments, to the local atom arrangement. More recently, large changes have been found in the barrier inhibiting methyl rotation, when electronic excitation or ionization of a substituted toluene occurs, suggesting molecular orbital occupancy as a dominant factor in aromatic molecules. Theoretically, the relation can also be made to the molecular orbital and electron density structure. Experimentally, we examine the situation by comparing toluene with paratolualdehyde. In particular, the barrier in toluene, CH3-C6H5, is six-fold by symmetry. In paratolualdehyde, CH3-C6H4-CHO, the aldehyde group is far enough from the methyl rotor that direct through-space interactions should be rather small. Thus, a three-fold contribution to the barrier would leave electron orbital effects in the π-system as the primary causal agent. Microwave spectroscopy is well suited for discriminating between V3 and V6 contributions - but only if torsionally exited states can be accessed which typically requires temperatures much higher that than those encountered in pulsed-jet expansions. Thus, the supersonic-jet FT-MW spectrometers in Hannover and Gaithersburg as well as the free-jet CW mm-wave spectrometer in Bologna were needed to take the spectra. Analyzing 5 torsional species using the Belgi program, the barrier was found to vastly be dominated by the V3 vs. a minor V6 contribution, thus revealing the information transfer though conjugated π-electron systems. L. H. Spangler, J Rev. Phys. Chem. 48 (1997) 481-510

  5. Predatory fish select for coordinated collective motion in virtual prey.

    PubMed

    Ioannou, C C; Guttal, V; Couzin, I D

    2012-09-07

    Movement in animal groups is highly varied and ranges from seemingly disordered motion in swarms to coordinated aligned motion in flocks and schools. These social interactions are often thought to reduce risk from predators, despite a lack of direct evidence. We investigated risk-related selection for collective motion by allowing real predators (bluegill sunfish) to hunt mobile virtual prey. By fusing simulated and real animal behavior, we isolated predator effects while controlling for confounding factors. Prey with a tendency to be attracted toward, and to align direction of travel with, near neighbors tended to form mobile coordinated groups and were rarely attacked. These results demonstrate that collective motion could evolve as a response to predation, without prey being able to detect and respond to predators.

  6. Collective motion of cells: from experiments to models.

    PubMed

    Méhes, Előd; Vicsek, Tamás

    2014-09-01

    Swarming or collective motion of living entities is one of the most common and spectacular manifestations of living systems that have been extensively studied in recent years. A number of general principles have been established. The interactions at the level of cells are quite different from those among individual animals, therefore the study of collective motion of cells is likely to reveal some specific important features which we plan to overview in this paper. In addition to presenting the most appealing results from the quickly growing related literature we also deliver a critical discussion of the emerging picture and summarize our present understanding of collective motion at the cellular level. Collective motion of cells plays an essential role in a number of experimental and real-life situations. In most cases the coordinated motion is a helpful aspect of the given phenomenon and results in making a related process more efficient (e.g., embryogenesis or wound healing), while in the case of tumor cell invasion it appears to speed up the progression of the disease. In these mechanisms cells both have to be motile and adhere to one another, the adherence feature being the most specific to this sort of collective behavior. One of the central aims of this review is to present the related experimental observations and treat them in light of a few basic computational models so as to make an interpretation of the phenomena at a quantitative level as well.

  7. A Turing test for collective motion

    PubMed Central

    Herbert-Read, J. E.; Romenskyy, M.; Sumpter, D. J. T.

    2015-01-01

    A widespread problem in biological research is assessing whether a model adequately describes some real-world data. But even if a model captures the large-scale statistical properties of the data, should we be satisfied with it? We developed a method, inspired by Alan Turing, to assess the effectiveness of model fitting. We first built a self-propelled particle model whose properties (order and cohesion) statistically matched those of real fish schools. We then asked members of the public to play an online game (a modified Turing test) in which they attempted to distinguish between the movements of real fish schools or those generated by the model. Even though the statistical properties of the real data and the model were consistent with each other, the public could still distinguish between the two, highlighting the need for model refinement. Our results demonstrate that we can use ‘citizen science’ to cross-validate and improve model fitting not only in the field of collective behaviour, but also across a broad range of biological systems. PMID:26631244

  8. Correlation properties of collective motion in bacterial suspensions

    NASA Astrophysics Data System (ADS)

    Ryan, Shawn D.; Sokolov, Andrey; Berlyand, Leonid; Aranson, Igor S.

    2013-10-01

    The study of collective motion in bacterial suspensions has been of significant recent interest. To better understand the non-trivial spatio-temporal correlations emerging in the course of collective swimming in suspensions of motile bacteria, a simple model is employed: a bacterium is represented as a force dipole with size, through the use of a short-range repelling potential, and shape. The model emphasizes two fundamental mechanisms: dipolar hydrodynamic interactions and short-range bacterial collisions. Using direct particle simulations validated by a dedicated experiment, we show that changing the swimming speed or concentration alters the time scale of sustained collective motion, consistent with experiment. Also, the correlation length in the collective state is almost constant as concentration and swimming speed change even though increasing each greatly increases the input of energy to the system. We demonstrate that the particle shape is critical for the onset of collective effects. In addition, new experimental results are presented illustrating the onset of collective motion with an ultrasound technique. This work exemplifies the delicate balance between various physical mechanisms governing collective motion in bacterial suspensions and provides important insights into its mesoscopic nature.

  9. Depletion force induced collective motion of microtubules driven by kinesin.

    PubMed

    Inoue, Daisuke; Mahmot, Bulbul; Kabir, Arif Md Rashedul; Farhana, Tamanna Ishrat; Tokuraku, Kiyotaka; Sada, Kazuki; Konagaya, Akihiko; Kakugo, Akira

    2015-11-21

    Collective motion is a fascinating example of coordinated behavior of self-propelled objects, which is often associated with the formation of large scale patterns. Nowadays, the in vitro gliding assay is being considered a model system to experimentally investigate various aspects of group behavior and pattern formation by self-propelled objects. In the in vitro gliding assay, cytoskeletal filaments F-actin or microtubules are driven by the surface immobilized associated biomolecular motors myosin or dynein respectively. Although the F-actin/myosin or microtubule/dynein system was found to be promising in understanding the collective motion and pattern formation by self-propelled objects, the most widely used biomolecular motor system microtubule/kinesin could not be successfully employed so far in this regard. Failure in exhibiting collective motion by kinesin driven microtubules is attributed to the intrinsic properties of kinesin, which was speculated to affect the behavior of individual gliding microtubules and mutual interactions among them. In this work, for the first time, we have demonstrated the collective motion of kinesin driven microtubules by regulating the mutual interaction among the gliding microtubules, by employing a depletion force among them. Proper regulation of the mutual interaction among the gliding microtubules through the employment of the depletion force was found to allow the exhibition of collective motion and stream pattern formation by the microtubules. This work offers a universal means for demonstrating the collective motion using the in vitro gliding assay of biomolecular motor systems and will help obtain a meticulous understanding of the fascinating coordinated behavior and pattern formation by self-propelled objects.

  10. Microswimmers - From Single Particle Motion to Collective Behavior

    NASA Astrophysics Data System (ADS)

    Gompper, Gerhard; Bechinger, Clemens; Herminghaus, Stephan; Isele-Holder, Rolf; Kaupp, U. Benjamin; Löwen, Hartmut; Stark, Holger; Winkler, Roland G.

    2016-11-01

    Locomotion of autonomous microswimmers is a fascinating field at the cutting edge of science. It combines the biophysics of self-propulsion via motor proteins, artificial propulsion mechanisms, swimming strategies at low Reynolds numbers, the hydrodynamic interaction of swimmers, and the collective motion and synchronisation of large numbers of agents. The articles of this Special Issue are based on the lecture notes of an international summer school, which was organized by the DFG Priority Programme 1726 "Microswimmers - From Single Particle Motion to Collective Behaviour" in the fall of 2015. The minireviews provide a broad overview of the field, covering both elementary and advanced material, as well as selected areas from current research.

  11. Amplitude equations for collective spatio-temporal dynamics in arrays of coupled systems

    SciTech Connect

    Yanchuk, S.; Wolfrum, M.; Perlikowski, P.; Stefański, A.; Kapitaniak, T.

    2015-03-15

    We study the coupling induced destabilization in an array of identical oscillators coupled in a ring structure where the number of oscillators in the ring is large. The coupling structure includes different types of interactions with several next neighbors. We derive an amplitude equation of Ginzburg-Landau type, which describes the destabilization of a uniform stationary state and close-by solutions in the limit of a large number of nodes. Studying numerically an example of unidirectionally coupled Duffing oscillators, we observe a coupling induced transition to collective spatio-temporal chaos, which can be understood using the derived amplitude equations.

  12. New vibration-rotation code for tetraatomic molecules exhibiting wide-amplitude motion: WAVR4

    NASA Astrophysics Data System (ADS)

    Kozin, Igor N.; Law, Mark M.; Tennyson, Jonathan; Hutson, Jeremy M.

    2004-11-01

    A general computational method for the accurate calculation of rotationally and vibrationally excited states of tetraatomic molecules is developed. The resulting program is particularly appropriate for molecules executing wide-amplitude motions and isomerizations. The program offers a choice of coordinate systems based on Radau, Jacobi, diatom-diatom and orthogonal satellite vectors. The method includes all six vibrational dimensions plus three rotational dimensions. Vibration-rotation calculations with reduced dimensionality in the radial degrees of freedom are easily tackled via constraints imposed on the radial coordinates via the input file. Program summaryTitle of program: WAVR4 Catalogue number: ADUN Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADUN Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: Persons requesting the program must sign the standard CPC nonprofit use license Computer: Developed under Tru64 UNIX, ported to Microsoft Windows and Sun Unix Operating systems under which the program has been tested: Tru64 Unix, Microsoft Windows, Sun Unix Programming language used: Fortran 90 Memory required to execute with typical data: case dependent No. of lines in distributed program, including test data, etc.: 11 937 No. of bytes in distributed program, including test data, etc.: 84 770 Distribution format: tar.gz Nature of physical problem: WAVR4 calculates the bound ro-vibrational levels and wavefunctions of a tetraatomic system using body-fixed coordinates based on generalised orthogonal vectors. Method of solution: The angular coordinates are treated using a finite basis representation (FBR) based on products of spherical harmonics. A discrete variable representation (DVR) [1] based on either Morse-oscillator-like or spherical-oscillator functions [2] is used for the radial coordinates. Matrix elements are computed using an efficient Gaussian quadrature in the angular coordinates and

  13. Nutritional state and collective motion: from individuals to mass migration.

    PubMed

    Bazazi, Sepideh; Romanczuk, Pawel; Thomas, Sian; Schimansky-Geier, Lutz; Hale, Joseph J; Miller, Gabriel A; Sword, Gregory A; Simpson, Stephen J; Couzin, Iain D

    2011-02-07

    In order to move effectively in unpredictable or heterogeneous environments animals must make appropriate decisions in response to internal and external cues. Identifying the link between these components remains a challenge for movement ecology and is important in understanding the mechanisms driving both individual and collective motion. One accessible way of examining how internal state influences an individual's motion is to consider the nutritional state of an animal. Our experimental results reveal that nutritional state exerts a relatively minor influence on the motion of isolated individuals, but large group-level differences emerge from diet affecting inter-individual interactions. This supports the idea that mass movement in locusts may be driven by cannibalism. To estimate how these findings are likely to impact collective migration of locust hopper bands, we create an experimentally parametrized model of locust interactions and motion. Our model supports our hypothesis that nutrient-dependent social interactions can lead to the collective motion seen in our experiments and predicts a transition in the mean speed and the degree of coordination of bands with increasing insect density. Furthermore, increasing the interaction strength (representing greater protein deprivation) dramatically reduces the critical density at which this transition occurs, demonstrating that individuals' nutritional state could have a major impact on large-scale migration.

  14. Group theoretic approaches to nuclear and hadronic collective motion

    SciTech Connect

    Biedenharn, L.C.

    1982-01-01

    Three approaches to nuclear and hadronic collective motion are reviewed, compared and contrasted: the standard symmetry approach as typified by the Interacting Boson Model, the kinematic symmetry group approach of Gell-Mann and Tomonaga, and the recent direct construction by Buck. 50 references.

  15. Physical Properties of Collective Motion in Suspensions of Bacteria

    NASA Astrophysics Data System (ADS)

    Sokolov, Andrey; Aranson, Igor S.

    2012-12-01

    A suspension of microswimmers, the simplest realization of active matter, exhibits novel material properties: the emergence of collective motion, reduction in viscosity, increase in diffusivity, and extraction of useful energy. Bacterial dynamics in dilute suspensions suggest that hydrodynamic interactions and collisions between the swimmers lead to collective motion at higher concentrations. On the example of aerobic bacteria Bacillus subtilis, we report on spatial and temporal correlation functions measurements of collective state for various swimming speeds and concentrations. The experiments produced a puzzling result: while the energy injection rate is proportional to the swimming speed and concentration, the correlation length remains practically constant upon small speeds where random tumbling of bacteria dominates. It highlights two fundamental mechanisms: hydrodynamic interactions and collisions; for both of these mechanisms, the change of the swimming speed or concentration alters an overall time scale.

  16. Emergence of collective motion in suspensions of swimming cells

    NASA Astrophysics Data System (ADS)

    Roffin, Maria Chiara; Denissenko, Petr; Kantsler, Vasily

    2015-11-01

    Collective motion is one of the most fascinating manifestations of self-organization in non-equilibrium systems. The phenomena emerges with the increase in concentration of motile individuals ranging from molecular motors to large animals like fish and humans. We have studied the suspension of swimming sperm cells in a microfluidic device which gradually concentrates motile cells in the region of interest. The onset of collective motion is identified by investigating correlations of fluid velocity and image brightness associated with the cell orientation. Cell concentration and the noise parameter are varied to switch on/off the collective interaction. The level of noise is controlled by adjusting the cell motility which depends on the temperature in the microfluidic chip. Fluid velocity is measured by tracing passive fluorescent beads in the suspension.

  17. Zero-field NMR of small-amplitude motions in a polycrystalline solid

    SciTech Connect

    Millar, J.M.; Thayer, A.M.; Zax, D.B.; Pines, A.

    1986-08-20

    The librational motions of the water molecules in polycrystalline barium chlorate monohydrate have been studied by using proton and deuterium zero-field NMR. In contrast to high-field NMR, subtle molecular motions produce readily observable changes in the zero-field spectrum. Computer simulations and application of a novel-pulsed zero-field technique confirm that the splitting observed in the zero-field spectrum of the hydrate results from the motionally induced asymmetry of the magnetic dipole-dipole coupling tensor.

  18. Collective motion and density fluctuations in swimming bacteria

    NASA Astrophysics Data System (ADS)

    Zhang, Hepeng

    2011-03-01

    The emergence of collective motion such as in fish schools, mammal herds, and insect swarms is a ubiquitous self-organization phenomenon. Such collective behavior plays an important role in a range of problems, such as spreading of deceases in animal or fish groups. Current models have provided a qualitative understanding of collective motion, but progress in quantitative modeling in hindered by the lack of experimental data. Here we examine a model microscopic system, where we are able to measure simultaneously the positions, velocities, and orientations of up to a thousand bacteria in a colony. The motile bacteria form closely-packed dynamic clusters within which they move cooperatively. The number of bacteria in a cluster exhibits a power-law distribution truncated by an exponential tail, and the probability of finding large clusters grows markedly as bacterial density increases. Mobile clusters cause anomalous fluctuations in bacterial density as found in mathematical theories and numerical models. Our results demonstrate that bacteria are an excellent system to study general phenomena of collective motion.

  19. An underwater robo-leader for collective motion studies

    NASA Astrophysics Data System (ADS)

    Sanchez, Yair; Wilhelmus, Monica M.

    2016-11-01

    A wide range of aquatic species, from bacteria to large tuna, exhibits collective behavior. It has long been hypothesized that the formation of complex configurations brings an energetic advantage to the members of a group as well as protection against larger predators or harmful agents. Lately, however, laboratory experiments have suggested that both the physics and the behavioral aspects of collective motion yield more complexity than previously attributed. With the goal to understand the fluid mechanical implications behind collective motion in a laboratory setting, we have developed a new device to induce this behavior on demand. Following recent studies of lab-induced vertical migration of Artemia salina, we have designed and constructed a remotely controlled underwater robotic swimmer that acts as a leader for groups of phototactic organisms. Preliminary quantitative flow visualizations done during vertical migration of brine shrimp show that this new instrument does induce collective motion in the laboratory. With this setup, we can address the hydrodynamic effect of having different swarm configurations, a variable that so far has been challenging to study in a controllable and reproducible manner.

  20. Trend-Centric Motion Visualization: Designing and Applying a new Strategy for Analyzing Scientific Motion Collections

    PubMed Central

    Schroeder, David; Korsakov, Fedor; Knipe, Carissa Mai-Ping; Thorson, Lauren; Ellingson, Arin M.; Nuckley, David; Carlis, John; Keefe, Daniel F

    2017-01-01

    In biomechanics studies, researchers collect, via experiments or simulations, datasets with hundreds or thousands of trials, each describing the same type of motion (e.g., a neck flexion-extension exercise) but under different conditions (e.g., different patients, different disease states, pre- and post-treatment). Analyzing similarities and differences across all of the trials in these collections is a major challenge. Visualizing a single trial at a time does not work, and the typical alternative of juxtaposing multiple trials in a single visual display leads to complex, difficult-to-interpret visualizations. We address this problem via a new strategy that organizes the analysis around motion trends rather than trials. This new strategy matches the cognitive approach that scientists would like to take when analyzing motion collections. We introduce several technical innovations making trend-centric motion visualization possible. First, an algorithm detects a motion collection’s trends via time-dependent clustering. Second, a 2D graphical technique visualizes how trials leave and join trends. Third, a 3D graphical technique, using a median 3D motion plus a visual variance indicator, visualizes the biomechanics of the set of trials within each trend. These innovations are combined to create an interactive exploratory visualization tool, which we designed through an iterative process in collaboration with both domain scientists and a traditionally-trained graphic designer. We report on insights generated during this design process and demonstrate the tool’s effectiveness via a validation study with synthetic data and feedback from expert musculoskeletal biomechanics researchers who used the tool to analyze the effects of disc degeneration on human spinal kinematics. PMID:26356978

  1. Collective motion in an active suspension of Escherichia coli bacteria

    NASA Astrophysics Data System (ADS)

    Gachelin, J.; Rousselet, A.; Lindner, A.; Clement, E.

    2014-02-01

    We investigate experimentally the emergence of collective motion in the bulk of an active suspension of Escherichia coli bacteria. When increasing the concentration from a dilute to a semi-dilute regime, we observe a continuous crossover from a dynamical cluster regime to a regime of ‘bio-turbulence’ convection patterns. We measure a length scale characterizing the collective motion as a function of the bacteria concentration. For bacteria fully supplied with oxygen, the increase of the correlation length is almost linear with concentration and at the largest concentrations tested, the correlation length could be as large as 24 bacterial body sizes (or 7-8 when including the flagella bundle). In contrast, under conditions of oxygen shortage the correlation length saturates at a value of around 7 body lengths.

  2. Collective amplitude mode fluctuations in a flat band superconductor formed at a semimetal surface

    NASA Astrophysics Data System (ADS)

    Kauppila, V. J.; Hyart, T.; Heikkilä, T. T.

    2016-01-01

    We study the fluctuations of the amplitude (i.e., the Higgs-Anderson) mode in a superconducting system of coupled Dirac particles proposed as a model for possible surface or interface superconductivity in rhombohedral graphite. This system also serves as a generic model of a topological semimetal with an interaction-driven transition on its surface. We show that the absence of Fermi energy and vanishing of the excitation gap of the collective amplitude mode in the model leads to a large fluctuation contribution to thermodynamic quantities, such as the heat capacity. As a consequence, the mean-field theory becomes inaccurate, indicating that the interactions lead to a strongly correlated state. We also present a microscopic derivation of the Ginzburg-Landau theory corresponding to this model.

  3. Satellite Motion Effects on Current Collection in Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    Zhang, T. X.; Hwang, K. S.; Wu, S. T.; Stone, N. H.; Chang, C. L.; Drobot, A.; Wright, K. H., Jr.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    Results from the Tethered Satellite System (TSS) missions unambiguously show that the electrodynamic tether system produced 2 to 3 times the predicted current levels in the tether. The pre-mission predictions were based on the well-known Parker-Murphy (PM) model, which describes the collection of current by an electrically biased satellite in the ionospheric plasma. How the TSS satellite was able to collect 2-3 times the PM current has remained an open question. In the present study, self-consistent potential and motional effects are introduced into the Thompson and Dobrowolny sheath models. As a result, the magnetic field aligned sheath-an essential variable in determining current collection by a satellite-is derived and is shown to be explicitly velocity dependent. The orientation of the satellite's orbital motion relative to the geomagnetic field is also considered in the derivation and a velocity dependent expression for the collected current is obtained. The resulting model provides a realistic treatment of current collection by a satellite in low earth orbit. Moreover, the predictions, using the appropriate parameters for TSS, are in good agreement with the tether currents measured during the TSS-1R mission.

  4. Collective Motion of Mammalian Cell Cohorts in 3D

    PubMed Central

    Sharma, Yasha; Vargas, Diego A.; Pegoraro, Adrian F.; Lepzelter, David; Weitz, David A.; Zaman, Muhammad H

    2016-01-01

    Collective cell migration is ubiquitous in biology, from development to cancer; it occurs in complex systems comprised of heterogeneous cell types, signals and matrices, and requires large scale regulation in space and time. Understanding how cells achieve organized collective motility is crucial to addressing cellular and tissue function and disease progression. While current two-dimensional model systems recapitulate the dynamic properties of collective cell migration, quantitative three-dimensional equivalent model systems have proved elusive. To establish such a model system, we study cell collectives by tracking individuals within cell cohorts embedded in three dimensional collagen scaffolding. We develop a custom algorithm to quantify the temporal and spatial heterogeneity of motion in cell cohorts during motility events. In the absence of external driving agents, we show that these cohorts rotate in short bursts, <2 hours, and translate for up to 6 hours. We observe, track, and analyze three dimensional motion of cell cohorts composed of 3–31 cells, and pave a path toward understanding cell collectives in 3D as a complex emergent system. PMID:26549557

  5. Photoionization-induced large-amplitude pendular motion in phenol(+)-Kr.

    PubMed

    Miyazaki, Mitsuhiko; Takeda, Akihiro; Ishiuchi, Shun-ichi; Sakai, Makoto; Dopfer, Otto; Fujii, Masaaki

    2011-02-21

    The dynamics of the intermolecular motion of the phenol(+)-Kr cation generated by photoionization of the neutral π-structure is probed by picosecond time-resolved infrared spectroscopy. The spectrum at zero delay displays only the free OH stretch band of the π-structure. The appearance of the hydrogen-bonded OH stretch band of the H-structure after a few ps is due to ionization-induced π → H site switching. Spectra at long delay (>20 ns) show that the Kr atom delocalizes from one π-site of the aromatic ring to the opposite π-site via the OH-site, like a pendular motion in the classical picture.

  6. Directed collective motion of bacteria under channel confinement

    NASA Astrophysics Data System (ADS)

    Wioland, H.; Lushi, E.; Goldstein, R. E.

    2016-07-01

    Dense suspensions of swimming bacteria are known to exhibit collective behaviour arising from the interplay of steric and hydrodynamic interactions. Unconfined suspensions exhibit transient, recurring vortices and jets, whereas those confined in circular domains may exhibit order in the form of a spiral vortex. Here we show that confinement into a long and narrow macroscopic ‘racetrack’ geometry stabilises bacterial motion to form a steady unidirectional circulation. This motion is reproduced in simulations of discrete swimmers that reveal the crucial role that bacteria-driven fluid flows play in the dynamics. In particular, cells close to the channel wall produce strong flows which advect cells in the bulk against their swimming direction. We examine in detail the transition from a disordered state to persistent directed motion as a function of the channel width, and show that the width at the crossover point is comparable to the typical correlation length of swirls seen in the unbounded system. Our results shed light on the mechanisms driving the collective behaviour of bacteria and other active matter systems, and stress the importance of the ubiquitous boundaries found in natural habitats.

  7. Collective motion of binary self-propelled particle mixtures.

    PubMed

    Menzel, Andreas M

    2012-02-01

    In this study, we investigate the phenomenon of collective motion in binary mixtures of self-propelled particles. More precisely, we consider two particle species, each of which consisting of pointlike objects that propel with a velocity of constant magnitude. Within each species, the particles try to achieve polar alignment of their velocity vectors, whereas we analyze the cases of preferred polar, antiparallel, as well as perpendicular alignment between particles of different species. Our focus is on the effect that the interplay between the two species has on the threshold densities for the onset of collective motion and on the nature of the solutions above onset. For this purpose, we start from suitable Langevin equations in the particle picture, from which we derive mean field equations of the Fokker-Planck type and finally macroscopic continuum field equations. We perform particle simulations of the Langevin equations and linear stability analyses of the Fokker-Planck and macroscopic continuum equations, and we numerically solve the Fokker-Planck equations. Both spatially homogeneous and inhomogeneous solutions are investigated, where the latter correspond to stripelike flocks of collectively moving particles. In general, the interaction between the two species reduces the threshold density for the onset of collective motion of each species. However, this interaction also reduces the spatial organization in the stripelike flocks. The case that shows the most interesting behavior is the one of preferred perpendicular alignment between different species. There a competition between polar and truly nematic orientational ordering of the velocity vectors takes place within each particle species. Finally, depending on the alignment rule for particles of different species and within certain ranges of particle densities, identical and inverted spatial density profiles can be found for the two particle species. The system under investigation is confined to two spatial

  8. Amplitude modulation of vorticity and dissipation by large-scale motions in turbulent channel flow

    NASA Astrophysics Data System (ADS)

    Yao, Yi-Chen; Deng, Bing-Qing; Huang, Wei-Xi; Xu, Chun-Xiao; Turbulence Research Team

    2015-11-01

    Amplitude modulation of both vorticity and dissipation by large-scale out-layer structures is studied using the DNS data of turbulent channel flow at Reynolds numbers up to Reτ = 1000. Carrier and modulated signals are scale decomposed in both streamwise and spanwise directions, and small-scale envelop is extracted by Hilbert transformation. Two-point amplitude modulation correlation is calculated at a range of wall-normal locations. The modulation strength on the vorticity and the dissipation rate of turbulent kinetic energy is found to be much stronger than on all the three components of velocity fluctuations. Distinct peak value of correlation is observed when large-scale signals are extracted from center log region and the corresponding modulated information from below y+ = 10. Also the strength of this peak value increases with Reynolds number, thus supporting the top-down mechanism that the near-wall layer is becoming more influenced by the large-scale structures which gradually emerge as Reynolds number increases. The work was supported by National Natural Science Foundation of China (11490551, 11132005, 11322221).

  9. Does amplitude scaling of ground motion records result in biased nonlinear structural drift responses?

    USGS Publications Warehouse

    Luco, N.; Bazzurro, P.

    2007-01-01

    Limitations of the existing earthquake ground motion database lead to scaling of records to obtain seismograms consistent with a ground motion target for structural design and evaluation. In the engineering seismology community, acceptable limits for 'legitimate' scaling vary from one (no scaling allowed) to 10 or more. The concerns expressed by detractors of scaling are mostly based on the knowledge of, for example, differences in ground motion characteristics for different earthquake magnitude-distance (Mw-Rclose) scenarios, and much less on their effects on structures. At the other end of the spectrum, proponents have demonstrated that scaling is not only legitimate but also useful for assessing structural response statistics for Mw-Rclose scenarios. Their studies, however, have not investigated more recent purposes of scaling and have not always drawn conclusions for a wide spectrum of structural vibration periods and strengths. This article investigates whether scaling of records randomly selected from an Mw-Rclose bin (or range) to a target fundamental-mode spectral acceleration (Sa) level introduces bias in the expected nonlinear structural drift response of both single-degree-of-freedom oscillators and one multi-degree-of-freedom building. The bias is quantified relative to unscaled records from the target Mw-Rclose bin that are 'naturally' at the target Sa level. We consider scaling of records from the target Mw-Rclose bin and from other Mw-Rclose bins. The results demonstrate that scaling can indeed introduce a bias that, for the most part, ca be explained by differences between the elastic response spectra of the scaled versus unscaled records. Copyright ?? 2007 John Wiley & Sons, Ltd.

  10. Collective motion and density fluctuations in bacterial colonies

    NASA Astrophysics Data System (ADS)

    Zhang, Hepeng; Be'Er, Avraham; Florin, E.-L.; Swinney, Harry L.

    2010-03-01

    The emergence of collective motion such as in fish schools and swarming bacteria is a ubiquitous self-organization phenomenon. Such collective behavior plays an important role in a range of phenomenon, such as formation and migration of animal or fish groups. To understand the collective motion, tracking of large numbers of individuals is needed, but such measurements have been lacking. Here we examine a microscopic system, where we are able to measure simultaneously the positions, velocities, and orientations of up to a thousand bacteria in a colony. The motile bacteria form closely-packed dynamic clusters within which they move cooperatively. The number of bacteria in a cluster exhibits a power-law distribution truncated by an exponential tail, and the probability of finding large clusters grows markedly as bacterial density increases. Mobile clusters exhibit anomalous fluctuations in bacterial density: the standard deviation (δN) grows with the mean (N) of the number of bacteria as δN˜N^3/4 rather than δN˜N^1/2, as in thermal equilibrium systems.

  11. Collective Motion of Microorganisms in a Viscoelastic Fluid

    NASA Astrophysics Data System (ADS)

    Li, Gaojin; Ardekani, Arezoo M.

    2016-09-01

    We study the collective motion of a suspension of rodlike microswimmers in a two-dimensional film of viscoelastic fluids. We find that the fluid elasticity has a small effect on a suspension of pullers, while it significantly affects the pushers. The attraction and orientational ordering of the pushers are enhanced in viscoelastic fluids. The induced polymer stresses break down the large-scale flow structures and suppress velocity fluctuations. In addition, the energy spectra and induced mixing in the suspension of pushers are greatly modified by fluid elasticity.

  12. The added mass, Basset, and viscous drag coefficients in nondilute bubbly liquids undergoing small-amplitude oscillatory motion

    SciTech Connect

    Sangani, A.S. ); Zhang, D.Z.; Prosperetti, A. )

    1991-12-01

    The motion of bubbles dispersed in a liquid when a small-amplitude oscillatory motion is imposed on the mixture is examined in the limit of small frequency and viscosity. Under these conditions, for bubbles with a stress-free surface, the motion can be described in terms of added mass and viscous force coefficients. For bubbles contaminated with surface-active impurities, the introduction of a further coefficient to parametrize the Basset force is necessary. These coefficients are calculated numerically for random configurations of bubbles by solving the appropriate multibubble interaction problem exactly using a method of multipole expansion. Results obtained by averaging over several configurations are presented. Comparison of the results with those for periodic arrays of bubbles shows that these coefficients are, in general, relatively insensitive to the detailed spatial arrangement of the bubbles. On the basis of this observation, it is possible to estimate them via simple formulas derived analytically for dilute periodic arrays. The effect of surface tension and density of bubbles (or rigid particles in the case where the no-slip boundary condition is applicable) is also examined and found to be rather small.

  13. Effects of curvilinear motion in large-amplitude bending of C3

    NASA Technical Reports Server (NTRS)

    Hansen, C. F.; Pearson, W. E.; Henderson, B. J.

    1974-01-01

    The geometry of the bending of a linear triatomic molecule is analyzed, and an expression for the average rotational constant is derived. A harmonic oscillator model of C3 is fitted to the observed rotational constant within 0.6%. The bond distance between atoms at zero bending is 1.287 A according to this model; this is noticeably larger than the average internuclear distance of 1.277 A for the vibrational ground state. The first order perturbation solutions for the vibrational energy levels, taking into account the effect of a quartic perturbation potential, closely match observed levels. For a square well potential model of C3, the effect of curvilinear motion in bending is similar to that found for the harmonic oscillator model, though the decreases in energy are about twice as large. In both models, the average energy decrease is relatively constant at approximately 10% over a wide range of vibrational quantum number.

  14. Time series analysis of collective motions in proteins

    NASA Astrophysics Data System (ADS)

    Alakent, Burak; Doruker, Pemra; ćamurdan, Mehmet C.

    2004-01-01

    The dynamics of α-amylase inhibitor tendamistat around its native state is investigated using time series analysis of the principal components of the Cα atomic displacements obtained from molecular dynamics trajectories. Collective motion along a principal component is modeled as a homogeneous nonstationary process, which is the result of the damped oscillations in local minima superimposed on a random walk. The motion in local minima is described by a stationary autoregressive moving average model, consisting of the frequency, damping factor, moving average parameters and random shock terms. Frequencies for the first 50 principal components are found to be in the 3-25 cm-1 range, which are well correlated with the principal component indices and also with atomistic normal mode analysis results. Damping factors, though their correlation is less pronounced, decrease as principal component indices increase, indicating that low frequency motions are less affected by friction. The existence of a positive moving average parameter indicates that the stochastic force term is likely to disturb the mode in opposite directions for two successive sampling times, showing the modes tendency to stay close to minimum. All these four parameters affect the mean square fluctuations of a principal mode within a single minimum. The inter-minima transitions are described by a random walk model, which is driven by a random shock term considerably smaller than that for the intra-minimum motion. The principal modes are classified into three subspaces based on their dynamics: essential, semiconstrained, and constrained, at least in partial consistency with previous studies. The Gaussian-type distributions of the intermediate modes, called "semiconstrained" modes, are explained by asserting that this random walk behavior is not completely free but between energy barriers.

  15. Quantification of mouse in vivo whole-body vibration amplitude from motion-blur using x-ray imaging

    NASA Astrophysics Data System (ADS)

    Hu, Zhengyi; Welch, Ian; Yuan, Xunhua; Pollmann, Steven I.; Nikolov, Hristo N.; Holdsworth, David W.

    2015-08-01

    Musculoskeletal effects of whole-body vibration on animals and humans have become an intensely studied topic recently, due to the potential of applying this method as a non-pharmacological therapy for strengthening bones. It is relatively easy to quantify the transmission of whole-body mechanical vibration through the human skeletal system using accelerometers. However, this is not the case for small-animal pre-clinical studies because currently available accelerometers have a large mass, relative to the mass of the animals, which causes the accelerometers themselves to affect the way vibration is transmitted. Additionally, live animals do not typically remain motionless for long periods, unless they are anesthetized, and they are required to maintain a static standing posture during these studies. These challenges provide the motivation for the development of a method to quantify vibrational transmission in small animals. We present a novel imaging technique to quantify whole-body vibration transmission in small animals using 280 μm diameter tungsten carbide beads implanted into the hind limbs of mice. Employing time-exposure digital x-ray imaging, vibrational amplitude is quantified based on the blurring of the implanted beads caused by the vibrational motion. Our in vivo results have shown this technique is capable of measuring vibration amplitudes as small as 0.1 mm, with precision as small as  ±10 μm, allowing us to distinguish differences in the transmitted vibration at different locations on the hindlimbs of mice.

  16. Shape matters: Near-field fluid mechanics dominate the collective motions of ellipsoidal squirmers.

    PubMed

    Kyoya, K; Matsunaga, D; Imai, Y; Omori, T; Ishikawa, T

    2015-12-01

    Microswimmers show a variety of collective motions. Despite extensive study, questions remain regarding the role of near-field fluid mechanics in collective motion. In this paper, we describe precisely the Stokes flow around hydrodynamically interacting ellipsoidal squirmers in a monolayer suspension. The results showed that various collective motions, such as ordering, aggregation, and whirls, are dominated by the swimming mode and the aspect ratio. The collective motions are mainly induced by near-field fluid mechanics, despite Stokes flow propagation over a long range. These results emphasize the importance of particle shape in collective motion.

  17. Infrared Spectroscopic Studies of OCS Trapped in Solid Parahydrogen: Indirect Evidence of Large Amplitude Motions

    NASA Astrophysics Data System (ADS)

    Anderson, David T.

    2016-06-01

    The high-resolution infrared rovibrational spectroscopy of OCS clustered with multiple hydrogen molecules has previously been studied in helium nanodroplets and in the gas-phase in search of another substance other than helium that displays superfluidity. Para-hydrogen (pH2) is one of the most likely candidates because it is a spinless (I=0) composite boson with a light mass similar to helium. However, compared to helium, the pH2-pH2 intermolecular potential is significantly stronger and thus pH2 solidifies at higher temperatures than the predicted superfluid transition temperature thereby blocking access to the superfluid state. Both of these previous studies reveal intriguing results linked to the microscopic details of superfluidity. We were therefore interested to characterize the IR spectrum of OCS in solid pH2. The conventional wisdom is that because pH2 solidifies into a quantum solid, the effects of superfluidity detected in the finite sized clusters should not be manifest in solid pH2. However, the OCS-H2 intermolecular potential strongly favors arranging the first 5 pH2 molecules in a ring around the equator of the OCS (R=3.2 Å). Isolation of OCS in bulk pH2 therefore may result in a solvation site where 6 pH2 molecules in the same basal plane form a ring around the OCS and are pulled inward decoupling them from the bulk. If the periodic barriers to motion around the ring are small, one might expect the 6 equatorial pH2 molecules to become delocalized while still maintaining the permutation symmetry of bosons. These 6 particles-on-a-ring may only show this behavior at low temperatures when thermal excitations are minimized. Analysis of the IR spectroscopy of OCS in solid pH2 indicates 1) the OCS molecule does not freely rotate and 2) there are at least two preferred OCS solvation sites. In principle, the measured OCS peak frequency for these two solvation sites should depend sensitively on the "structure" of the first pH2 solvation shell and therefore

  18. A study of the nonlinear aerodynamics of bodies in nonplanar motion. Ph.D. Thesis - Stanford Univ., Calif.; [numerical analysis of aerodynamic force and moment systems during large amplitude, arbitrary motions

    NASA Technical Reports Server (NTRS)

    Schiff, L. B.

    1974-01-01

    Concepts from the theory of functionals are used to develop nonlinear formulations of the aerodynamic force and moment systems acting on bodies in large-amplitude, arbitrary motions. The analysis, which proceeds formally once the functional dependence of the aerodynamic reactions upon the motion variables is established, ensures the inclusion, within the resulting formulation, of pertinent aerodynamic terms that normally are excluded in the classical treatment. Applied to the large-amplitude, slowly varying, nonplanar motion of a body, the formulation suggests that the aerodynamic moment can be compounded of the moments acting on the body in four basic motions: steady angle of attack, pitch oscillations, either roll or yaw oscillations, and coning motion. Coning, where the nose of the body describes a circle around the velocity vector, characterizes the nonplanar nature of the general motion.

  19. Phase Diagram of Collective Motion of Bacterial Cells in a Shallow Circular Pool

    NASA Astrophysics Data System (ADS)

    Wakita, Jun-ichi; Tsukamoto, Shota; Yamamoto, Ken; Katori, Makoto; Yamada, Yasuyuki

    2015-12-01

    The collective motion of bacterial cells in a shallow circular pool is systematically studied using the bacterial species Bacillus subtilis. The ratio of cell length to pool diameter (i.e., the reduced cell length) ranges from 0.06 to 0.43 in our experiments. Bacterial cells in a circular pool show various types of collective motion depending on the cell density in the pool and the reduced cell length. The motion is classified into six types, which we call random motion, turbulent motion, one-way rotational motion, two-way rotational motion, random oscillatory motion, and ordered oscillatory motion. Two critical values of reduced cell lengths are evaluated, at which drastic changes in collective motion are induced. A phase diagram is proposed in which the six phases are arranged.

  20. The role of large-amplitude motions in the spectroscopy and dynamics of H{sub 5}{sup +}

    SciTech Connect

    Lin, Zhou; McCoy, Anne B.

    2014-03-21

    Protonated hydrogen dimer, H{sub 5}{sup +}, is the intermediate in the astrochemically important proton transfer reaction between H{sub 3}{sup +} and H{sub 2}. To understand the mechanism for this process, we focus on how large amplitude motions in H{sub 5}{sup +} result in scrambling of the five hydrogen atoms in the collision complex. To this end, the one-dimensional zero-point corrected potential surfaces were mapped out as functions of reaction coordinates for the H{sub 3}{sup +} + H{sub 2} collision using minimized energy path diffusion Monte Carlo [C. E. Hinkle and A. B. McCoy, J. Phys. Chem. Lett. 1, 562 (2010)]. In this study, the previously developed approach was extended to allow for the investigation of selected excited states that are expected to be involved in the proton scrambling dynamics. Specifically, excited states in the shared proton motion between the two H{sub 2} groups, and in the outer H{sub 2} bending motions were investigated. Of particular interest is the minimum distance between H{sub 3}{sup +} and H{sub 2} at which all five hydrogen atoms become free to exchange. In addition, this diffusion Monte Carlo-based approach was used to determine the zero-point energy E{sub 0}, the dissociation energy D{sub 0}, and excitation energies associated with the vibrational motions that were investigated. The evolution of the wave functions was also studied, with a focus on how the intramolecular vibrations in H{sub 5}{sup +} evolve into motions of H{sub 3}{sup +} or H{sub 2}. In the case of the proton scrambling, we find that the relevant transition states become fully accessible at separations between H{sub 3}{sup +} and H{sub 2} of approximately 2.15 Å, a distance that is accessed by the excited states of H{sub 5}{sup +} with two or more quanta in the shared proton stretch. The implications of this finding on the vibrational spectroscopy of H{sub 5}{sup +} are also discussed.

  1. Modeling closure of circular wounds through coordinated collective motion

    NASA Astrophysics Data System (ADS)

    Li, David S.; Zimmermann, Juliane; Levine, Herbert

    2016-02-01

    Wound healing enables tissues to restore their original states, and is achieved through collective cell migration into the wound space, contraction of the wound edge via an actomyosin filament ‘purse-string,’ as well as cell division. Recently, experimental techniques have been developed to create wounds with various regular morphologies in epithelial monolayers, and these experiments of circular closed-contour wounds support coordinated lamellipodial cell crawling as the predominant driver of gap closure. Through utilizing a particle-based mechanical tissue simulation, exhibiting long-range coordination of cell motility, we computationally model these closed-contour experiments with a high level of agreement between experimentally observed and simulated wound closure dynamics and tissue velocity profiles. We also determine the sensitivity of wound closure time in the model to changes in cell motility force and division rate. Our simulation results confirm that circular wounds can close due to collective cell migration without the necessity for a purse-string mechanism or for cell division, and show that the alignment mechanism of cellular motility force with velocity, leading to collective motion in the model, may speed up wound closure.

  2. Large-amplitude nuclear motion formulated in terms of dissipation of quantum fluctuations

    NASA Astrophysics Data System (ADS)

    Kuzyakin, R. A.; Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.

    2017-01-01

    The potential-barrier penetrability and quasi-stationary thermal-decay rate of a metastable state are formulated in terms of microscopic quantum diffusion. Apart from linear coupling in momentum between the collective and internal subsystems, the formalism embraces the more general case of linear couplings in both the momentum and the coordinates. The developed formalism is then used for describing the process of projectile-nucleus capture by a target nucleus at incident energies near and below the Coulomb barrier. The capture partial probability, which determines the cross section for formation of a dinuclear system, is derived in analytical form. The total and partial capture cross sections, mean and root-mean-square angular momenta of the formed dinuclear system, astrophysical -factors, logarithmic derivatives, and barrier distributions are derived for various reactions. Also investigated are the effects of nuclear static deformation and neutron transfer between the interacting nuclei on the capture cross section and its isotopic dependence, and the entrance-channel effects on the capture process. The results of calculations for reactions involving both spherical and deformed nuclei are in good agreement with available experimental data.

  3. Leadership, collective motion and the evolution of migratory strategies.

    PubMed

    Guttal, Vishwesha; Couzin, Iain D

    2011-05-01

    Migration is a hallmark life history strategy of a diverse range of organisms, and also ubiquitous in ontogenic processes including normal embryonic development as well as tumor progression. In such scenarios, individual organisms/cells typically respond to long range (and often noisy) environmental cues. In addition, individuals may interact socially with one another leading to emergent group-level navigational abilities. Although much progress has been made in understanding the mechanisms of taxis, there is a lack of theoretical and quantitative understanding of how individuals trade-off information obtained through their own migratory ability and that via social interactions. Here, we discuss results and insights from a recent computational model developed to investigate the evolution of leadership and collective motion in migratory populations. It is shown that, for a broad range of parameter values, only a small proportion of the population gather directional information while the majority employ social cues alone. More generally, ecological conditions for the evolution of resident, solitary and collective migratory strategies are obtained. We discuss how consideration of both proximate and ultimate factors within the same framework may provide insights into preserving migratory patterns that are in grave danger due to anthropogenic pressures.

  4. Myosin lever arm directs collective motion on cellular actin network.

    PubMed

    Hariadi, Rizal F; Cale, Mario; Sivaramakrishnan, Sivaraj

    2014-03-18

    The molecular motor myosin teams up to drive muscle contraction, membrane traffic, and cell division in biological cells. Myosin function in cells emerges from the interaction of multiple motors tethered to a scaffold, with surrounding actin filaments organized into 3D networks. Despite the importance of myosin function, the influence of intermotor interactions on collective motion remains poorly understood. In this study, we used precisely engineered myosin assemblies to examine emergence in collective myosin movement. We report that tethering multiple myosin VI motors, but not myosin V motors, modifies their movement trajectories on keratocyte actin networks. Single myosin V and VI dimers display similar skewed trajectories, albeit in opposite directions, when traversing the keratocyte actin network. In contrast, tethering myosin VI motors, but not myosin V motors, progressively straightens the trajectories with increasing myosin number. Trajectory shape of multimotor scaffolds positively correlates with the stiffness of the myosin lever arm. Swapping the flexible myosin VI lever arm for the relatively rigid myosin V lever increases trajectory skewness, and vice versa. A simplified model of coupled motor movement demonstrates that the differences in flexural rigidity of the two myosin lever arms is sufficient to account for the differences in observed behavior of groups of myosin V and VI motors. In accordance with this model trajectory, shapes for scaffolds containing both myosin V and VI are dominated by the myosin with a stiffer lever arm. Our findings suggest that structural features unique to each myosin type may confer selective advantages in cellular functions.

  5. Collective Motions in A = 100-112 Nuclei

    SciTech Connect

    Hamilton, J. H.; Ramayya, A. V.; Hwang, J. K.; Goodin, C.; Zhu, S. J.; Luo, Y. X.; Rasmussen, J. O.; Frauendorf, S.; Ter-Akopian, G. M.

    2010-10-11

    With a very high statistics data set with 5.7x10{sup 11} triple and higher fold {gamma} coincidences from the spontaneous fission of {sup 252}Cf, a wealth of fascinating new collective motions in nuclei with A = 100-112 have been observed. Nothing was known previously about one- and two-phonon {gamma}-bands in odd-A nuclei. We discovered the first one-and two- phonon {gamma} vibrational bands in an odd N-even Z nucleus, {sup 105}Mo. The energies of the one- and two- phonon bands in {sup 104}Mo, {sup 105}Mo, {sup 106}Mo and {sup 108}Mo were recently studied and are remarkably similar in energies. The first chiral doublet bands in e-e nuclei were observed in triaxial {sup 106,108}Mo and {sup 110,112}Ru while such chiral band in {sup 108}Ru are perturbed by its {gamma}-soft shape. The experimental evidences, including our recent angular correlation studies are presented along with what these new bands are telling us about the evolving collective structures and deformation in this region.

  6. Continuum Mechanical Analysis of Collective Motion of Robots

    NASA Astrophysics Data System (ADS)

    Itami, Teturo

    Group of robots that works mainly in macroscopic systems is considered as a continuum. We need not mount specific sensors for mutual information among these robots. Increasing number of the robots makes it difficult to predict collective motion of the robots. To give a well organized strategy of designing the task, we describe these robots as that like fluid in continuum mechanics, where number density f_1 (\\vec{x},\\vec{p}; t) of the robots located at around \\vec{x} with momentum around \\vec{p} at time t is a main variable. Also we propose methods to move these robots by external potential energy V(\\vec{x};t). To specify a concept, we take a transportation system by group of robots. The objects located at \\vec{X}(t) that do not feel a potential V(\\vec{X}(t);t) can be transported by a collision with the robots moving aimlessly under the potential force -\\frac{\\partial V(\\vec{x};t)}{\\partial \\vec{x}}. The new scheme of a design based on continuum mechanics is validated by direct method of dynamical development of the system in time.

  7. Dimensionality reduction of collective motion by principal manifolds

    NASA Astrophysics Data System (ADS)

    Gajamannage, Kelum; Butail, Sachit; Porfiri, Maurizio; Bollt, Erik M.

    2015-01-01

    While the existence of low-dimensional embedding manifolds has been shown in patterns of collective motion, the current battery of nonlinear dimensionality reduction methods is not amenable to the analysis of such manifolds. This is mainly due to the necessary spectral decomposition step, which limits control over the mapping from the original high-dimensional space to the embedding space. Here, we propose an alternative approach that demands a two-dimensional embedding which topologically summarizes the high-dimensional data. In this sense, our approach is closely related to the construction of one-dimensional principal curves that minimize orthogonal error to data points subject to smoothness constraints. Specifically, we construct a two-dimensional principal manifold directly in the high-dimensional space using cubic smoothing splines, and define the embedding coordinates in terms of geodesic distances. Thus, the mapping from the high-dimensional data to the manifold is defined in terms of local coordinates. Through representative examples, we show that compared to existing nonlinear dimensionality reduction methods, the principal manifold retains the original structure even in noisy and sparse datasets. The principal manifold finding algorithm is applied to configurations obtained from a dynamical system of multiple agents simulating a complex maneuver called predator mobbing, and the resulting two-dimensional embedding is compared with that of a well-established nonlinear dimensionality reduction method.

  8. Visually induced motion sickness when viewing visual oscillations of different frequencies along the fore-and-aft axis: keeping velocity versus amplitude constant.

    PubMed

    Chen, Daniel Jinzhao; Bao, Beisheng; Zhao, Yue; So, Richard H Y

    2016-04-01

    Exposure to visual oscillations (VOs) can lead to visually induced motion sickness (VIMS). The level of VIMS among viewers has been shown to vary when the frequency of the VOs is changed either by manipulating their amplitude or velocity. The present study investigates whether the level of VIMS would change if we keep the root mean square (rms) velocity or amplitude of VOs constant while manipulating the VO frequency. A total of 25 individuals were exposed to random-dot and checkerboard VOs along the fore-and-aft axis in two experiments. Changing the amplitude (or frequency) of VOs while keeping the rms velocity constant did not affect the level of VIMS; however, increasing the rms velocity (or frequency) of VOs while keeping the amplitude constant made VIMS significantly worse. Practitioner Summary: Exposure to VOs of the same frequency can cause different levels of nausea depending on the combination of oscillation amplitude and velocity. Results suggest an opportunity for game designers to reduce symptoms of game sickness by using the correct combinations of velocity and amplitude of the visual motions.

  9. Simulation study of amplitude-modulated (AM) harmonic motion imaging (HMI) for stiffness contrast quantification with experimental validation.

    PubMed

    Maleke, Caroline; Luo, Jianwen; Gamarnik, Viktor; Lu, Xin L; Konofagou, Elisa E

    2010-07-01

    The objective of this study is to show that Harmonic Motion Imaging (HMI) can be used as a reliable tumor-mapping technique based on the tumor's distinct stiffness at the early onset of disease. HMI is a radiation-force-based imaging method that generates a localized vibration deep inside the tissue to estimate the relative tissue stiffness based on the resulting displacement amplitude. In this paper, a finite-element model (FEM) study is presented, followed by an experimental validation in tissue-mimicking polyacrylamide gels and excised human breast tumors ex vivo. This study compares the resulting tissue motion in simulations and experiments at four different gel stiffnesses and three distinct spherical inclusion diameters. The elastic moduli of the gels were separately measured using mechanical testing. Identical transducer parameters were used in both the FEM and experimental studies, i.e., a 4.5-MHz single-element focused ultrasound (FUS) and a 7.5-MHz diagnostic (pulse-echo) transducer. In the simulation, an acoustic pressure field was used as the input stimulus to generate a localized vibration inside the target. Radiofrequency (rf) signals were then simulated using a 2D convolution model. A one-dimensional cross-correlation technique was performed on the simulated and experimental rf signals to estimate the axial displacement resulting from the harmonic radiation force. In order to measure the reliability of the displacement profiles in estimating the tissue stiffness distribution, the contrast-transfer efficiency (CTE) was calculated. For tumor mapping ex vivo, a harmonic radiation force was applied using a 2D raster-scan technique. The 2D HMI images of the breast tumor ex vivo could detect a malignant tumor (20 x 10 mm2) surrounded by glandular and fat tissues. The FEM and experimental results from both gels and breast tumors ex vivo demonstrated that HMI was capable of detecting and mapping the tumor or stiff inclusion with various diameters or

  10. Rotational Spectrum and Large Amplitude Motions of 3,4-, 2,5- and 3,5-DIMETHYL-BENZALDEHYDE

    NASA Astrophysics Data System (ADS)

    Kleiner, I.; Tudorie, M.; Jahn, M.; Grabow, J.-U.; Goubet, M.

    2012-06-01

    The microwave spectra of the 3,4-, 2,5- and 3,5-Dimethyl-Benzaldehyde (DMBA) molecules have been recorded for the first time in the 2-26.5 GHz frequency range, using the COBRA-FTMW spectrometer in Hannover, with an instrumental uncertainty of 0.5 kHz for unblended lines. The experimental assignments and fits are supplemented by ab initio quantum chemical calculations,conformational energy landscape, and dipole moment components. The analysis of the spectra for the three isomers are in progress. The latest results, including spectroscopic constants and large amplitude motion parameters, will be presented. This investigation follows the study of the spectra of the 4-Methyl-Benzaldehyde molecule. The DMBA isomers belong to a similar series of molecules formally obtained by adding a second methyl group at the aromatic ring. These molecules serve as prototype systems for the development of the theoretical model of asymmetric top molecules having Cs symmetry while containing two inequivalent methyl tops (C3v), exhibiting different barrier heights and coupling terms to methyl internal rotation. Thus, the DMBA isomers represent benchmark species for testing the two-top internal rotors BELGI program written recently. Supported by the ANR-08-BLAN-0054 contract (France), the Deutsche Forschungsgemeinschaft, and the Land Niedersachsen (Germany). H. Saal, W. Caminati, I. Kleiner, A. R. Hight-Walker, J. T. Hougen, J.-U. Grabow, to be published. M. Tudorie, I. Kleiner, J. T. Hougen, S. Melandri, L. W. Sutikdja, W. Stahl, J. Mol. Spectrosc., 269 (2011), 211-225

  11. Collective nonaffine displacements in amorphous materials during large-amplitude oscillatory shear

    NASA Astrophysics Data System (ADS)

    Priezjev, Nikolai V.

    2017-02-01

    Using molecular dynamics simulations, we study the transient response of a binary Lennard-Jones glass subjected to periodic shear deformation. The amorphous solid is modeled as a three-dimensional Kob-Andersen binary mixture at a low temperature. The cyclic loading is applied to slowly annealed, quiescent samples, which induces irreversible particle rearrangements at large strain amplitudes, leading to stress-strain hysteresis and a drift of the potential energy towards higher values. We find that the initial response to cyclic shear near the critical strain amplitude involves disconnected clusters of atoms with large nonaffine displacements. In contrast, the amplitude of shear stress oscillations decreases after a certain number of cycles, which is accompanied by the initiation and subsequent growth of a shear band.

  12. Two Decades of Advances in High-Resolution Spectroscopy of Large-Amplitude Motions in N-Fold Potential Wells, as Illustrated by Methanol

    NASA Astrophysics Data System (ADS)

    Xu, Li-Hong

    2016-06-01

    Methanol is a simple and intensively studied organic molecule possessing one large-amplitude torsional motion. It has, for nearly a century, been a favorite of researchers in many fields, e.g., instrument builders, for whom methanol is often the first molecule chosen for testing an improved or a newly built instrument (including HIFI, the Heterodyne Instrument for the Far Infrared on board the Herschel space mission); theorists and/or dynamicists studying the challenging effects of a large-amplitude motion coupling with small-amplitude motions to enhance intramolecular vibrational energy redistribution; astronomers who have elevated methanol to their #1 interstellar weed because of its rich and omnipresent spectrum in the interstellar garden, where it serves as a unique probe for diagnosing conditions in star-forming regions; astrochemists studying isotopic ratios as clues to the chemical evolution of the universe; and fundamentalists seeking possible time variation of the proton/electron mass ratio in the standard model; just to name a few. From high-resolution to high-precision spectroscopy, the large-amplitude internal rotation of the methyl top against its OH framework in methanol has never failed to produce new surprises in spectral regions from the microwave all the way to the near IR. The very recent observation of completely unexpected large methanol hyperfine splittings is a vivid testimonial that the large-amplitude torsional motion can still lead us to unexplored landscapes. This talk will focus on the complicated vibration-torsion-rotation energy networks and interactions deduced from high resolution spectra; our efforts to understand some of them using ab-initio-assisted approaches and the modeling of torsion-rotation and torsionally mediated spin-rotation hyperfine splittings in methanol. These topics represent one part of the much larger fascinating world inhabited by methanolics.

  13. Master equation for collective spontaneous emission with quantized atomic motion

    NASA Astrophysics Data System (ADS)

    Damanet, François; Braun, Daniel; Martin, John

    2016-02-01

    We derive a Markovian master equation for the internal dynamics of an ensemble of two-level atoms including all effects related to the quantization of their motion. Our equation provides a unifying picture of the consequences of recoil and indistinguishability of atoms beyond the Lamb-Dicke regime on both their dissipative and conservative dynamics, and applies equally well to distinguishable and indistinguishable atoms. We give general expressions for the decay rates and the dipole-dipole shifts for any motional states, and we find closed-form formulas for a number of relevant states (Gaussian states, Fock states, and thermal states). In particular, we show that dipole-dipole interactions and cooperative photon emission can be modulated through the external state of motion.

  14. Effective temperature and spontaneous collective motion of active matter

    NASA Astrophysics Data System (ADS)

    Wang, Shenshen; Wolynes, Peter

    2012-02-01

    Spontaneous directed motion, a hallmark of cell biology, is unusual in classical statistical physics. Here we study, using both numerical and analytical methods, organized motion in models of the cytoskeleton in which constituents are driven by energy-consuming motors. Although systems driven by small-step motors are described by an effective temperature and are thus quiescent, at higher order in step size, both homogeneous and inhomogeneous, flowing and oscillating behavior emerges. Motors that respond with a negative susceptibility to imposed forces lead to an apparent negative temperature system in which beautiful structures form resembling the asters seen in cell division.

  15. Quantifying and controlling collective motion in externally guided cells

    NASA Astrophysics Data System (ADS)

    Parker, Joshua; Guven, Can; Wang, Chenlu; Ott, Edward; Losert, Wolfgang

    2015-03-01

    Many motile cells use chemical signals to coordinate their motion to aid in performing a larger task, be it healing a wound or aggregating to form a spore. This coordination can vary from subtle variations in overall alignment to broad, visibly structured patterns. Of particular interest of study are two organisms We introduce a model for motion towards a chemical signal and study these spatio-temporal correlations in the context of autocrine relay, such as seen in Dictyostelium discoideum, where we demonstrate that adhesion and chemical degradation both enhance visible ``streaming'' structures. We also study a model of paracrine signal relay relevant to human neutrophil migration and demonstrate how temporally varying chemical signals can be used to coordinate cell migration. We discuss both of these results in the context of their relevance to the survival of the organism and highlight future experimental tests.

  16. Three-quark light-cone amplitudes of the proton and quark orbital-motion-dependent observables

    NASA Astrophysics Data System (ADS)

    Ji, Xiangdong; Ma, Jian-Ping; Yuan, Feng

    2003-03-01

    We study the three-quark light-cone amplitudes of the proton including quarks' transverse momenta. We classify these amplitudes using a newly-developed method in which light-cone wave functions are constructed from a class of light-cone matrix elements. We derive the constraints on the amplitudes from parity and time-reversal symmetries. We use the amplitudes to calculate the physical observables which vanish when the quark orbital angular momentum is absent. These include transverse-momentum dependent parton distributions Δ qT( x, k⊥), qT( x, k⊥), δq( x, k⊥), and δqL( x, k⊥), twist-three parton distributions gT( x) and hL( x), helicity-flip generalized parton distributions E( x, ξ=0, Q2) and its associates, and the Pauli form factor F2( Q2).

  17. Wobbling motion in 135Pr within a collective Hamiltonian

    NASA Astrophysics Data System (ADS)

    Chen, Q. B.; Zhang, S. Q.; Meng, J.

    2016-11-01

    The recently reported wobbling bands in 135Pr are investigated by the collective Hamiltonian, in which the collective parameters, including the collective potential and the mass parameter, are respectively determined from the tilted axis cranking (TAC) model and the harmonic frozen alignment (HFA) formula. It is shown that the experimental energy spectra of both yrast and wobbling bands are well reproduced by the collective Hamiltonian. It is confirmed that the wobbling mode in 135Pr changes from transverse to longitudinal with the rotational frequency. The mechanism of this transition is revealed by analyzing the effective moments of inertia of the three principal axes, and the corresponding variation trend of the wobbling frequency is determined by the softness and shapes of the collective potential.

  18. Inherent noise can facilitate coherence in collective swarm motion

    PubMed Central

    Yates, Christian A.; Erban, Radek; Escudero, Carlos; Couzin, Iain D.; Buhl, Jerome; Kevrekidis, Ioannis G.; Maini, Philip K.; Sumpter, David J. T.

    2009-01-01

    Among the most striking aspects of the movement of many animal groups are their sudden coherent changes in direction. Recent observations of locusts and starlings have shown that this directional switching is an intrinsic property of their motion. Similar direction switches are seen in self-propelled particle and other models of group motion. Comprehending the factors that determine such switches is key to understanding the movement of these groups. Here, we adopt a coarse-grained approach to the study of directional switching in a self-propelled particle model assuming an underlying one-dimensional Fokker–Planck equation for the mean velocity of the particles. We continue with this assumption in analyzing experimental data on locusts and use a similar systematic Fokker–Planck equation coefficient estimation approach to extract the relevant information for the assumed Fokker–Planck equation underlying that experimental data. In the experiment itself the motion of groups of 5 to 100 locust nymphs was investigated in a homogeneous laboratory environment, helping us to establish the intrinsic dynamics of locust marching bands. We determine the mean time between direction switches as a function of group density for the experimental data and the self-propelled particle model. This systematic approach allows us to identify key differences between the experimental data and the model, revealing that individual locusts appear to increase the randomness of their movements in response to a loss of alignment by the group. We give a quantitative description of how locusts use noise to maintain swarm alignment. We discuss further how properties of individual animal behavior, inferred by using the Fokker–Planck equation coefficient estimation approach, can be implemented in the self-propelled particle model to replicate qualitatively the group level dynamics seen in the experimental data. PMID:19336580

  19. Evidence from the motions of galaxies for a large-scale, large-amplitude flow toward the great attractor

    SciTech Connect

    Burstein, D.; Faber, S.M.; Dressler, A. Lick Observatory, Santa Cruz, CA Mount Wilson and Las Campanas Observatories, Pasadena, CA )

    1990-05-01

    The available distances of galaxies are combined to produce a unified view of galaxy motions within the so-called great attractor (GA) region. The data base includes 253 galaxies within 40 deg of the nominal GA center. Spirals and ellipticals are grouped into clusters to reduce Malmquist bias. Checks are made for systematic errors in the motions of ellipticals that are correlated with cluster richness, structural parameters of the galaxies, or errors in Galactic absorption, and no significant effects on the observed large-scale motions are found. Other evidence strongly supporting the current distance indicators is reviewed, and arguments are presented in favor of the cosmic background radiation defining the correct velocity rest frame. The basic conclusion of the study is the affirmation of the fundamental correctness of the present body of measured galaxy motions. 49 refs.

  20. Motion of individual and coupled amoebae during collective migration

    NASA Astrophysics Data System (ADS)

    Wang, Chenlu; Driscoll, Meghan; Chowdhury, Sagar; Gupta, Satyandra K.; Parent, Carole; Losert, Wolfgang

    2013-03-01

    Collective migration is a ubiquitous natural phenomenon. We analyzed the migration of Dictyostelium Discoideum amoebae, which migrate both individually and collectively. We previously found that individually and collectively migrating cells have similar speed and straightness. We analyzed the effects of cell-cell contact and cell-surface contact on cell characteristics, such as adhesion, speed, and shape. We found that in the absence of cell-surface contact, cells form irregular clumps, yet are still able to migrate collectively in response to an external signal. Individually migrating cells exhibit waves of high boundary curvature that travel from the fronts to the backs of cells. By comparing the shape dynamics of individual cells and groups of cells, we found that these boundary curvature waves can be transmitted from one cell to another.

  1. Generator coordinate method and nuclear collective motions (VII): the preservation of symmetry properties

    SciTech Connect

    XU Gong-ou

    1985-01-01

    In order to preserve all the symmetry properties for the effective collective Hamiltonian obtained with the generator coordinate method, it is necessary for the trial wave function to have proper transformation properties. The generator coordinates should then transform in the same way as the represented collective operators. Also, the center-of-mass motion should be independent of the internal motion in conformity with the invariance of the nuclear Hamiltonian with respect to space rotation and Galilean transformation.

  2. Emergent Structural Mechanisms for High-Density Collective Motion Inspired by Human Crowds

    NASA Astrophysics Data System (ADS)

    Bottinelli, Arianna; Sumpter, David T. J.; Silverberg, Jesse L.

    2016-11-01

    Collective motion of large human crowds often depends on their density. In extreme cases like heavy metal concerts and black Friday sales events, motion is dominated by physical interactions instead of conventional social norms. Here, we study an active matter model inspired by situations when large groups of people gather at a point of common interest. Our analysis takes an approach developed for jammed granular media and identifies Goldstone modes, soft spots, and stochastic resonance as structurally driven mechanisms for potentially dangerous emergent collective motion.

  3. Collective motion with anticipation: Flocking, spinning, and swarming

    NASA Astrophysics Data System (ADS)

    Morin, Alexandre; Caussin, Jean-Baptiste; Eloy, Christophe; Bartolo, Denis

    2015-01-01

    We investigate the collective dynamics of self-propelled particles able to probe and anticipate the orientation of their neighbors. We show that a simple anticipation strategy hinders the emergence of homogeneous flocking patterns. Yet anticipation promotes two other forms of self-organization: collective spinning and swarming. In the spinning phase, all particles follow synchronous circular orbits, while in the swarming phase, the population condensates into a single compact swarm that cruises coherently without requiring any cohesive interactions. We quantitatively characterize and rationalize these phases of polar active matter and discuss potential applications to the design of swarming robots.

  4. Living liquid crystal: collective bacteria motion in anisotropic viscoelastic media

    NASA Astrophysics Data System (ADS)

    Zhou, Shuang; Sokolov, Andrey; Lavrentovich, Oleg D.; Aranson, Igor S.

    2014-03-01

    By transducing energy stored in the environment to drive systematic movements, bio-mechanical hybrids can move and reconfigure their structure and properties in response to external stimuli. Here, we create a fundamentally new class of bio-mechanical hybrid - living liquid crystals (LLCs), by combining two seemingly incompatible concepts, living swimming bacteria and inanimate but orientationally ordered lyotropic liquid crystal. The coupling between the activity-triggered flows and director reorientations results in a wealth of phenomena, including: (a) a characteristic length ξ to describe the coupling between the orientation of LLC and the bacterial motion, (b) periodic stripe instabilities of the director in surface-anchored LLCs, (c) director pattern evolution into an array of disclinations with positive and negative topological charges as the surface anchoring is weakened or when the bacterial activity is enhanced. Our study provides an insight in understanding hierarchy of spatial scales in other active matter systems, as well as providing basis for devices with new functionalities, including specific responses to chemical agents, toxins, or photons. This work is supported by US DOE under the Contract No. DE AC02-06CH11357 and NSF grants DMR 1104850 and 1121288.

  5. Wireless System and Method for Collecting Motion and Non-Motion Related Data of a Rotating System

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

    2011-01-01

    A wireless system for collecting data indicative of a tire's characteristics uses at least one open-circuit electrical conductor in a tire. The conductor is shaped such that it can store electrical and magnetic energy. In the presence of a time-varying magnetic field, the conductor resonates to generate a harmonic response having a frequency, amplitude and bandwidth. A magnetic field response recorder is used to (i) wirelessly transmit the time-varying magnetic field to the conductor, and (ii) wirelessly detect the harmonic response and the frequency, amplitude and bandwidth, associated therewith. The recorder is adapted to be positioned in a location that is fixed with respect to the tire as the tire rotates.

  6. String-like collective atomic motion in the melting and freezing of nanoparticles.

    PubMed

    Zhang, Hao; Kalvapalle, Pranav; Douglas, Jack F

    2011-12-08

    The melting of a solid represents a transition between a solid state in which atoms are localized about fixed average crystal lattice positions to a fluid state that is characterized by relative atomic disorder and particle mobility so that the atoms wander around the material as a whole, impelled by the random thermal impulses of surrounding atoms. Despite the fundamental nature and practical importance of this particle delocalization transition, there is still no fundamental theory of melting and instead one often relies on the semi-phenomenological Lindemann-Gilvarry criterion to estimate roughly the melting point as an instability of the crystal lattice. Even the earliest simulations of melting in hexagonally packed hard discs by Alder and Wainwright indicated the active role of nonlocal collective atomic motions in the melting process, and here we utilize molecular dynamics (MD) simulation to determine whether the collective particle motion observed in melting has a similar geometrical form as those in recent studies of nanoparticle (NP) interfacial dynamics and the molecular dynamics of metastable glass-forming liquids. We indeed find string-like collective atomic motion in NP melting that is remarkably similar in form to the collective interfacial motions in NPs at equilibrium and to the collective motions found in the molecular dynamics of glass-forming liquids. We also find that the spatial localization and extent of string-like motion in the course of NP melting and freezing evolves with time in distinct ways. Specifically, the collective atomic motion propagates from the NP surface and from within the NP in melting and freezing, respectively, and the average string length varies smoothly with time during melting. In contrast, the string-like cooperative motion peaks in an intermediate stage of the freezing process, reflecting a general asymmetry in the dynamics of NP superheating and supercooling.

  7. Unsteady aerodynamic characteristics of a fighter model undergoing large-amplitude pitching motions at high angles of attack

    NASA Technical Reports Server (NTRS)

    Brandon, Jay M.; Shah, Gautam H.

    1990-01-01

    The effects of harmonic or constant-rate-ramp pitching motions (giving angles of attack from 0 to 75 deg) on the aerodynamic performance of a fighter-aircraft model with highly swept leading-edge extensions are investigated experimentally in the NASA Langley 12-ft low-speed wind tunnel. The model configuration and experimental setup are described, and the results of force and moment measurements and flow visualizations are presented graphically and discussed in detail. Large force overshoots and hysteresis are observed and attributed to lags in vortical-flow development and breakup. The motion variables have a strong influence on the persistence of dynamic effects, which are found to affect pitch-rate capability more than flight-path turning performance.

  8. Embedding dual function into molecular motors through collective motion.

    PubMed

    Saito, Nen; Kaneko, Kunihiko

    2017-03-10

    Protein motors, such as kinesins and dyneins, bind to a microtubule and travel along it in a specific direction. Previously, it was thought that the directionality for a given motor was constant in the absence of an external force. However, the directionality of the kinesin-5 Cin8 was recently found to change as the number of motors that bind to the same microtubule is increased. Here, we introduce a simple mechanical model of a microtubule-sliding assay in which multiple motors interact with the filament. We show that, due to the collective phenomenon, the directionality of the motor changes (e.g., from minus- to plus- end directionality), depending on the number of motors. This is induced by a large diffusive component in the directional walk and by the subsequent frustrated motor configuration, in which multiple motors pull the filament in opposite directions, similar to a game of tug-of-war. A possible role of the dual-directional motors for the mitotic spindle formation is also discussed. Our framework provides a general mechanism to embed two conflicting tasks into a single molecular machine, which works context-dependently.

  9. Embedding dual function into molecular motors through collective motion

    PubMed Central

    Saito, Nen; Kaneko, Kunihiko

    2017-01-01

    Protein motors, such as kinesins and dyneins, bind to a microtubule and travel along it in a specific direction. Previously, it was thought that the directionality for a given motor was constant in the absence of an external force. However, the directionality of the kinesin-5 Cin8 was recently found to change as the number of motors that bind to the same microtubule is increased. Here, we introduce a simple mechanical model of a microtubule-sliding assay in which multiple motors interact with the filament. We show that, due to the collective phenomenon, the directionality of the motor changes (e.g., from minus- to plus- end directionality), depending on the number of motors. This is induced by a large diffusive component in the directional walk and by the subsequent frustrated motor configuration, in which multiple motors pull the filament in opposite directions, similar to a game of tug-of-war. A possible role of the dual-directional motors for the mitotic spindle formation is also discussed. Our framework provides a general mechanism to embed two conflicting tasks into a single molecular machine, which works context-dependently. PMID:28281683

  10. Social behaviour and collective motion in plant-animal worms

    PubMed Central

    Grant, Katherine A. J.; Gorman, Alice R.; Vizard, Victoria; Plackett, Harriet; Gamble, Margaret L.

    2016-01-01

    Social behaviour may enable organisms to occupy ecological niches that would otherwise be unavailable to them. Here, we test this major evolutionary principle by demonstrating self-organizing social behaviour in the plant-animal, Symsagittifera roscoffensis. These marine aceol flat worms rely for all of their nutrition on the algae within their bodies: hence their common name. We show that individual worms interact with one another to coordinate their movements so that even at low densities they begin to swim in small polarized groups and at increasing densities such flotillas turn into circular mills. We use computer simulations to: (i) determine if real worms interact socially by comparing them with virtual worms that do not interact and (ii) show that the social phase transitions of the real worms can occur based only on local interactions between and among them. We hypothesize that such social behaviour helps the worms to form the dense biofilms or mats observed on certain sun-exposed sandy beaches in the upper intertidal of the East Atlantic and to become in effect a super-organismic seaweed in a habitat where macro-algal seaweeds cannot anchor themselves. Symsagittifera roscoffensis, a model organism in many other areas in biology (including stem cell regeneration), also seems to be an ideal model for understanding how individual behaviours can lead, through collective movement, to social assemblages. PMID:26911961

  11. Perspectives in the theory of nuclear collective motion

    SciTech Connect

    Klein, A.

    1980-03-13

    This report discusses three different subjects. The first is the development of a generalized version of the VMI (variable moment of inertia) model that ties it to the original form of the IBM (interacting boson model) and provides a possibility of fitting vibrational spectra with generalized vibrational formulas. The second is a suggestion for fitting band crossing calculations of the phenomenological type more completely than has hitherto been done into the framework of the VMI method. The third, which is the most important and far reaching, is the description f a complete mathematical method for the microscopic derivation of the IBM from a conventional shell-model Hamiltonian. In addition to elements already foreseen by previous authors, there is proposed a solution for the most important problem outstanding, not only within the framework of the IBM, but also in all previous work on boson expansion. This is the problem of actually selecting, in a general fashion, the most collective excitations. A criterion is introduced that the subspace constructed from these excitations should possess an average energy that is lower than the rest of the shell model space; the actual implementation of this criterion is explained. 8 tables, 62 references.

  12. Social behaviour and collective motion in plant-animal worms.

    PubMed

    Franks, Nigel R; Worley, Alan; Grant, Katherine A J; Gorman, Alice R; Vizard, Victoria; Plackett, Harriet; Doran, Carolina; Gamble, Margaret L; Stumpe, Martin C; Sendova-Franks, Ana B

    2016-02-24

    Social behaviour may enable organisms to occupy ecological niches that would otherwise be unavailable to them. Here, we test this major evolutionary principle by demonstrating self-organizing social behaviour in the plant-animal, Symsagittifera roscoffensis. These marine aceol flat worms rely for all of their nutrition on the algae within their bodies: hence their common name. We show that individual worms interact with one another to coordinate their movements so that even at low densities they begin to swim in small polarized groups and at increasing densities such flotillas turn into circular mills. We use computer simulations to: (i) determine if real worms interact socially by comparing them with virtual worms that do not interact and (ii) show that the social phase transitions of the real worms can occur based only on local interactions between and among them. We hypothesize that such social behaviour helps the worms to form the dense biofilms or mats observed on certain sun-exposed sandy beaches in the upper intertidal of the East Atlantic and to become in effect a super-organismic seaweed in a habitat where macro-algal seaweeds cannot anchor themselves. Symsagittifera roscoffensis, a model organism in many other areas in biology (including stem cell regeneration), also seems to be an ideal model for understanding how individual behaviours can lead, through collective movement, to social assemblages.

  13. Collective motion of humans in mosh and circle pits at heavy metal concerts.

    PubMed

    Silverberg, Jesse L; Bierbaum, Matthew; Sethna, James P; Cohen, Itai

    2013-05-31

    Human collective behavior can vary from calm to panicked depending on social context. Using videos publicly available online, we study the highly energized collective motion of attendees at heavy metal concerts. We find these extreme social gatherings generate similarly extreme behaviors: a disordered gaslike state called a mosh pit and an ordered vortexlike state called a circle pit. Both phenomena are reproduced in flocking simulations demonstrating that human collective behavior is consistent with the predictions of simplified models.

  14. Collective Motion of Humans in Mosh and Circle Pits at Heavy Metal Concerts

    NASA Astrophysics Data System (ADS)

    Silverberg, Jesse L.; Bierbaum, Matthew; Sethna, James P.; Cohen, Itai

    2013-05-01

    Human collective behavior can vary from calm to panicked depending on social context. Using videos publicly available online, we study the highly energized collective motion of attendees at heavy metal concerts. We find these extreme social gatherings generate similarly extreme behaviors: a disordered gaslike state called a mosh pit and an ordered vortexlike state called a circle pit. Both phenomena are reproduced in flocking simulations demonstrating that human collective behavior is consistent with the predictions of simplified models.

  15. Local collective motion analysis for multi-probe dynamic imaging and microrheology

    NASA Astrophysics Data System (ADS)

    Khan, Manas; Mason, Thomas G.

    2016-08-01

    Dynamical artifacts, such as mechanical drift, advection, and hydrodynamic flow, can adversely affect multi-probe dynamic imaging and passive particle-tracking microrheology experiments. Alternatively, active driving by molecular motors can cause interesting non-Brownian motion of probes in local regions. Existing drift-correction techniques, which require large ensembles of probes or fast temporal sampling, are inadequate for handling complex spatio-temporal drifts and non-Brownian motion of localized domains containing relatively few probes. Here, we report an analytical method based on local collective motion (LCM) analysis of as few as two probes for detecting the presence of non-Brownian motion and for accurately eliminating it to reveal the underlying Brownian motion. By calculating an ensemble-average, time-dependent, LCM mean square displacement (MSD) of two or more localized probes and comparing this MSD to constituent single-probe MSDs, we can identify temporal regimes during which either thermal or athermal motion dominates. Single-probe motion, when referenced relative to the moving frame attached to the multi-probe LCM trajectory, provides a true Brownian MSD after scaling by an appropriate correction factor that depends on the number of probes used in LCM analysis. We show that LCM analysis can be used to correct many different dynamical artifacts, including spatially varying drifts, gradient flows, cell motion, time-dependent drift, and temporally varying oscillatory advection, thereby offering a significant improvement over existing approaches.

  16. Probing the Role of Mobility in the Collective Motion of Nonequilibrium Systems

    NASA Astrophysics Data System (ADS)

    Shen, Hongchuan; Tan, Peng; Xu, Lei

    2016-01-01

    By systematically varying the mobility of self-propelled particles in a 2D lattice, we experimentally study the influence of particle mobility on system's collective motion. Our system is intrinsically nonequilibrium due to the lack of energy equipartition. By constructing the covariance matrix of spatial fluctuations and solving for its eigenmodes, we obtain the collective motions of the system with various magnitudes. Interestingly, our structurally ordered nonequilibrium system exhibits properties almost identical to disordered glassy systems under thermal equilibrium: the modes with large overall motions are spatially correlated and quasilocalized while the modes with small collective motions are highly localized, resembling the low- and high-frequency modes in glass. More surprisingly, a peak similar to the boson peak forms in our nonequilibrium system as the number of mobile particles increases, revealing the possible origin of the boson peak from a dynamic aspect. We further illustrate that the spatially correlated large-movement modes can be produced by the cooperation of highly active particles above a threshold fraction, while the localized small-movement modes can be created by adding individual inactive particles. Our study clarifies the role of mobility in collective motions, and further suggests a promising possibility of extending the powerful mode analysis approach to nonequilibrium systems.

  17. Flocking and Turning: a New Model for Self-organized Collective Motion

    NASA Astrophysics Data System (ADS)

    Cavagna, Andrea; Del Castello, Lorenzo; Giardina, Irene; Grigera, Tomas; Jelic, Asja; Melillo, Stefania; Mora, Thierry; Parisi, Leonardo; Silvestri, Edmondo; Viale, Massimiliano; Walczak, Aleksandra M.

    2015-02-01

    Birds in a flock move in a correlated way, resulting in large polarization of velocities. A good understanding of this collective behavior exists for linear motion of the flock. Yet observing actual birds, the center of mass of the group often turns giving rise to more complicated dynamics, still keeping strong polarization of the flock. Here we propose novel dynamical equations for the collective motion of polarized animal groups that account for correlated turning including solely social forces. We exploit rotational symmetries and conservation laws of the problem to formulate a theory in terms of generalized coordinates of motion for the velocity directions akin to a Hamiltonian formulation for rotations. We explicitly derive the correspondence between this formulation and the dynamics of the individual velocities, thus obtaining a new model of collective motion. In the appropriate overdamped limit we recover the well-known Vicsek model, which dissipates rotational information and does not allow for polarized turns. Although the new model has its most vivid success in describing turning groups, its dynamics is intrinsically different from previous ones in a wide dynamical regime, while reducing to the hydrodynamic description of Toner and Tu at very large length-scales. The derived framework is therefore general and it may describe the collective motion of any strongly polarized active matter system.

  18. Robust preparation of four-qubit decoherence-free states for superconducting quantum interference devices against collective amplitude damping

    NASA Astrophysics Data System (ADS)

    Shao, Xiao-Qiang; Zheng, Tai-Yu; Zhang, Shou

    2013-11-01

    Based on the quantum Zeno dynamics, we present an approach for deterministic preparation of arbitrary four-qubit decoherence-free state of superconducting quantum interference devices with respective to collective amplitude damping in a decoherence-free way, namely, not only the form of the target state is free of decoherence, but also the whole process for preparation. The operation is fast and convenient since we only need to manipulate three weak laser pulses sequentially. Other decoherence effects such as cavity decay and the spontaneous emission of qubits are also taken into account in virtue of master equation, and the strictly numerical simulation signifies the final fidelity is high corresponding to the current experimental technology.

  19. Observation of collective atomic recoil motion in a degenerate fermion gas.

    PubMed

    Wang, Pengjun; Deng, L; Hagley, E W; Fu, Zhengkun; Chai, Shijie; Zhang, Jing

    2011-05-27

    We demonstrate collective atomic recoil motion with a dilute, ultracold, degenerate fermion gas in a single spin state. By utilizing an adiabatically decompressed magnetic trap with an aspect ratio different from that of the initial trap, a momentum-squeezed fermion cloud is achieved. With a single pump pulse of the proper polarization, we observe, for the first time, multiple wave-mixing processes that result in distinct collective atomic recoil motion modes in a degenerate fermion cloud. Contrary to the case with Bose condensates, no pump-laser detuning asymmetry is present.

  20. Conformational equilibria and large-amplitude motions in dimers of carboxylic acids: rotational spectrum of acetic acid-difluoroacetic acid.

    PubMed

    Gou, Qian; Feng, Gang; Evangelisti, Luca; Caminati, Walther

    2014-10-06

    We report the rotational spectra of two conformers of the acetic acid-difluoroacetic acid adduct (CH3COOH-CHF2COOH) and supply information on its internal dynamics. The two conformers differ from each other, depending on the trans or gauche orientation of the terminal -CHF2 group. Both conformers display splittings of the rotational transitions, due to the internal rotation of the methyl group of acetic acid. The corresponding barriers are determined to be V3(trans)=99.8(3) and V3(gauche)=90.5(9) cm(-1) (where V3 is the methyl rotation barrier height). The gauche form displays a further doubling of the rotational transitions, due to the tunneling motion of the -CHF2 group between its two equivalent conformations. The corresponding B2 barrier is estimated to be 108(2) cm(-1). The increase in the distance between the two monomers upon OH→OD deuteration (the Ubbelohde effect) is determined.

  1. Effects of sea water on elongated duration of ground motion as well as variation in its amplitude for offshore earthquakes

    NASA Astrophysics Data System (ADS)

    Todoriki, Masaru; Furumura, Takashi; Maeda, Takuto

    2017-01-01

    We investigated the effects of sea water on the propagation of seismic waves using a 3-D finite-difference-method simulation of seismic wave propagation following offshore earthquakes. When using a 1-D layered structure, the simulation results showed strong S- to P-wave conversion at the sea bottom; accordingly, S-wave energy was dramatically decreased by the sea water layer. This sea water de-amplification effect had strong frequency dependence, therefore resembling a low-pass filter in which the cut-off frequency and damping coefficients were defined by the thickness of the sea water layer. The sea water also acted to elongate the duration of Rayleigh wave packet. The importance of the sea water layer in modelling offshore earthquakes was further demonstrated by a simulation using a realistic 3-D velocity structure model with and without sea water for a shallow (h = 14 km) outer-rise Nankai Trough event, the 2004 SE Off Kii Peninsula earthquake (Mw = 7.2). Synthetic seismograms generated by the model when sea water was included were in accordance with observed seismograms for long-term longer period motions, particularly those in the shape of Rayleigh waves.

  2. Generator coordinate method and nuclear collective motions (IV)-TDGCM versus ATDHF

    SciTech Connect

    Xu, G.

    1982-04-01

    Considering the time-dependent generator coordinate method, the time-dependent Schroedinger equation for nuclear collective motions is obtained. It is then possible to obtain through the Wigner matrix a variational expression for mean collective properties q-bar(t) and p-bar(t) in classical limits. Under adiabatic approximation this is just the expression by which Villars has obtained the ATDHF results.

  3. Scaling laws and accurate small-amplitude stationary solution for the motion of a planar vortex filament in the Cartesian form of the local induction approximation.

    PubMed

    Van Gorder, Robert A

    2013-04-01

    We provide a formulation of the local induction approximation (LIA) for the motion of a vortex filament in the Cartesian reference frame (the extrinsic coordinate system) which allows for scaling of the reference coordinate. For general monotone scalings of the reference coordinate, we derive an equation for the planar solution to the derivative nonlinear Schrödinger equation governing the LIA. We proceed to solve this equation perturbatively in small amplitude through an application of multiple-scales analysis, which allows for accurate computation of the period of the planar vortex filament. The perturbation result is shown to agree strongly with numerical simulations, and we also relate this solution back to the solution obtained in the arclength reference frame (the intrinsic coordinate system). Finally, we discuss nonmonotone coordinate scalings and their application for finding self-intersections of vortex filaments. These self-intersecting vortex filaments are likely unstable and collapse into other structures or dissipate completely.

  4. Small amplitude transverse waves on taut strings: exploring the significant effects of longitudinal motion on wave energy location and propagation

    NASA Astrophysics Data System (ADS)

    Rowland, David R.

    2013-03-01

    Introductory discussions of energy transport due to transverse waves on taut strings universally assume that the effects of longitudinal motion can be neglected, but this assumption is not even approximately valid unless the string is idealized to have a zero relaxed length, a requirement approximately met by the slinky spring. While making this additional idealization is probably the best approach to take when discussing waves on strings at the introductory level, for intermediate to advanced undergraduate classes in continuum mechanics and general wave phenomena where somewhat more realistic models of strings can be investigated, this paper makes the following contributions. First, various approaches to deriving the general energy continuity equation are critiqued and it is argued that the standard continuum mechanics approach to deriving such equations is the best because it leads to a conceptually clear, relatively simple derivation which provides a unique answer of greatest generality. In addition, a straightforward algorithm for calculating the transverse and longitudinal waves generated when a string is driven at one end is presented and used to investigate a cos2 transverse pulse. This example illustrates much important physics regarding energy transport in strings and allows the ‘attack waves’ observed when strings in musical instruments are struck or plucked to be approximately modelled and analysed algebraically. Regarding the ongoing debate as to whether the potential energy density in a string can be uniquely defined, it is shown by coupling an external energy source to a string that a suggested alternative formula for potential energy density requires an unphysical potential energy to be ascribed to the source for overall energy to be conserved and so cannot be considered to be physically valid.

  5. Adding flexibility to the “particles-on-a-sphere” model for large-amplitude motion: POSflex force field for protonated methane

    SciTech Connect

    Uhl, Felix; Walewski, Łukasz; Forbert, Harald; Marx, Dominik

    2014-09-14

    The so-called “particles-on-a-sphere” (POS) model has been introduced a while ago in order to describe in simple terms large-amplitude motion of polyatomic hydrides, XH{sub n}. The POS model of protonated methane, CH{sub 5}{sup +}, has been shown to capture well the essence of the fluxional nature of this enigmatic floppy molecule. Here, we extend this model to the POSflex force field by adding flexibility to the C–H bonds, which are constrained to a common fixed bond length in the original model. This makes the present model extremely efficient for computer simulation, including path integral molecular dynamics in order to assess the crucial quantum effects on nuclear motion at low temperatures. Moreover, the POSflex force field can be conveniently used to study microsolvation effects upon combining it with intermolecular pair potentials to account for solute-solvent interactions. Upon computing static properties as well as thermal and quantum fluctuation effects at ambient and low temperatures, respectively, it is shown that the POSflex model is very well suited to describe the structural properties of bare CH{sub 5}{sup +}, including hydrogen scrambling and thus fluxionality in the first place. The far- to mid-infrared spectrum up to the bending band is roughly described, whereas the model fails to account for the well-structured stretching band by construction.

  6. Adding flexibility to the "particles-on-a-sphere" model for large-amplitude motion: POSflex force field for protonated methane.

    PubMed

    Uhl, Felix; Walewski, Łukasz; Forbert, Harald; Marx, Dominik

    2014-09-14

    The so-called "particles-on-a-sphere" (POS) model has been introduced a while ago in order to describe in simple terms large-amplitude motion of polyatomic hydrides, XH(n). The POS model of protonated methane, CH₅⁺, has been shown to capture well the essence of the fluxional nature of this enigmatic floppy molecule. Here, we extend this model to the POSflex force field by adding flexibility to the C-H bonds, which are constrained to a common fixed bond length in the original model. This makes the present model extremely efficient for computer simulation, including path integral molecular dynamics in order to assess the crucial quantum effects on nuclear motion at low temperatures. Moreover, the POSflex force field can be conveniently used to study microsolvation effects upon combining it with intermolecular pair potentials to account for solute-solvent interactions. Upon computing static properties as well as thermal and quantum fluctuation effects at ambient and low temperatures, respectively, it is shown that the POSflex model is very well suited to describe the structural properties of bare CH₅⁺, including hydrogen scrambling and thus fluxionality in the first place. The far- to mid-infrared spectrum up to the bending band is roughly described, whereas the model fails to account for the well-structured stretching band by construction.

  7. Nuclear collective motion with a coherent coupling interaction between quadrupole and octupole modes

    NASA Astrophysics Data System (ADS)

    Minkov, N.; Yotov, P.; Drenska, S.; Scheid, W.; Bonatsos, D.; Lenis, D.; Petrellis, D.

    2006-04-01

    A collective Hamiltonian for the rotation-vibration motion of nuclei is considered in which the axial quadrupole and octupole degrees of freedom are coupled through the centrifugal interaction. The potential of the system depends on the two deformation variables β2 and β3. The system is considered to oscillate between positive and negative β3 values by rounding an infinite potential core in the (β2,β3) plane with β2>0. By assuming a coherent contribution of the quadrupole and octupole oscillation modes in the collective motion, the energy spectrum is derived in an explicit analytic form, providing specific parity shift effects. On this basis several possible ways in the evolution of quadrupole-octupole collectivity are outlined. A particular application of the model to the energy levels and electric transition probabilities in alternating parity spectra of the nuclei Nd150, Sm152, Gd154, and Dy156 is presented.

  8. Collective motion of two-electron atom in hyperspherical adiabatic approximation

    SciTech Connect

    Mohamed, A. S.; Nikitin, S. I.

    2015-03-30

    This work is devoted to calculate bound states in the two-electron atoms. The separation of variables has carried out in hyper spherical coordinate system (R, θ, α). Assuming collective motion of the electrons, where the hper angle (α∼π/4) and (θ∼π). The separation of the rotational variables leads to system of differential equations with more simple form as compared with non restricted motion. Energy of doubly excited P{sup e} and D{sup 0} states are calculated semi classically by using quantization condition of Bohr -Somerfield. The results compared with previously published data.

  9. Theory of collective proton motion at interfaces with densely packed protogenic surface groups.

    PubMed

    Golovnev, Anatoly; Eikerling, Michael

    2013-01-30

    We present a theoretical study of collective proton transport at a 2D array of end-grafted protogenic surface groups with sulfonic acid head groups. The graft positions of the surface groups form a regular hexagonal lattice. We consider the interfacial array at a high packing density of the surface groups and under minimal hydration with one water molecule added per head group. For these conditions, the stable interfacial conformation consists of a bicomponent lattice of hexagonally ordered sulfonate anions and interstitial hydronium cations. Hydronium ion motion occurs as a travelling solitary wave. We analyse the microscopic parameters of the solitons and study the influence of different potential profiles on the proton motion created by rotation and tilting of sidechains and sulfonate anions. Using soliton solutions of the equation of motion, we establish relations between the energy and mobility of the solitons and the microscopic structural and interaction parameters of the array.

  10. Extended Fluid-Dynamics and Collective Motion of Two Trapped Fermion Species with Pairing Interactions

    NASA Astrophysics Data System (ADS)

    Hernández, E. S.; Capuzzi, P.; Szybisz, L.

    2011-02-01

    We extend our earlier fluid-dynamical description of fermion superfluids incorporating the particle energy flow together with the equation of motion for the internal kinetic energy of the pairs. The formal scheme combines a set of equations similar to those of classical hydrodynamics with the equations of motion for the anomalous density and for its related momentum density and kinetic energy density. This dynamical frame represents a second order truncation of an infinite hierarchy of equations of motion isomorphic to the full time dependent Hartree-Fock-Bogoliubov equations in coordinate representation. We analyze the equilibrium solutions and fluctuations for a homogeneous, unpolarized fermion system of two species, and show that the collective spectrum presents the well-known Anderson-Bogoliubov low energy mode of homogeneous superfluids and a pairing vibration near the gap energy.

  11. Seeds of Locally Aligned Motion and Stress Coordinate a Collective Cell Migration

    PubMed Central

    Zaritsky, Assaf; Welf, Erik S.; Tseng, Yun-Yu; Angeles Rabadán, M.; Serra-Picamal, Xavier; Trepat, Xavier; Danuser, Gaudenz

    2015-01-01

    We find how collective migration emerges from mechanical information transfer between cells. Local alignment of cell velocity and mechanical stress orientation—a phenomenon dubbed “plithotaxis”—plays a crucial role in inducing coordinated migration. Leader cells at the monolayer edge better align velocity and stress to migrate faster toward the open space. Local seeds of enhanced motion then generate stress on neighboring cells to guide their migration. Stress-induced motion propagates into the monolayer as well as along the monolayer boundary to generate increasingly larger clusters of coordinately migrating cells that move faster with enhanced alignment of velocity and stress. Together, our analysis provides a model of long-range mechanical communication between cells, in which plithotaxis translates local mechanical fluctuations into globally collective migration of entire tissues. PMID:26682808

  12. Nontoxic colloidal particles impede antibiotic resistance of swarming bacteria by disrupting collective motion and speed.

    PubMed

    Lu, Shengtao; Liu, Fang; Xing, Bengang; Yeow, Edwin K L

    2015-12-01

    A monolayer of swarming B. subtilis on semisolid agar is shown to display enhanced resistance against antibacterial drugs due to their collective behavior and motility. The dynamics of swarming motion, visualized in real time using time-lapse microscopy, prevents the bacteria from prolonged exposure to lethal drug concentrations. The elevated drug resistance is significantly reduced when the collective motion of bacteria is judiciously disrupted using nontoxic polystyrene colloidal particles immobilized on the agar surface. The colloidal particles block and hinder the motion of the cells, and force large swarming rafts to break up into smaller packs in order to maneuver across narrow spaces between densely packed particles. In this manner, cohesive rafts rapidly lose their collectivity, speed, and group dynamics, and the cells become vulnerable to the drugs. The antibiotic resistance capability of swarming B. subtilis is experimentally observed to be negatively correlated with the number density of colloidal particles on the engineered surface. This relationship is further tested using an improved self-propelled particle model that takes into account interparticle alignment and hard-core repulsion. This work has pertinent implications on the design of optimal methods to treat drug resistant bacteria commonly found in swarming colonies.

  13. Nontoxic colloidal particles impede antibiotic resistance of swarming bacteria by disrupting collective motion and speed

    NASA Astrophysics Data System (ADS)

    Lu, Shengtao; Liu, Fang; Xing, Bengang; Yeow, Edwin K. L.

    2015-12-01

    A monolayer of swarming B. subtilis on semisolid agar is shown to display enhanced resistance against antibacterial drugs due to their collective behavior and motility. The dynamics of swarming motion, visualized in real time using time-lapse microscopy, prevents the bacteria from prolonged exposure to lethal drug concentrations. The elevated drug resistance is significantly reduced when the collective motion of bacteria is judiciously disrupted using nontoxic polystyrene colloidal particles immobilized on the agar surface. The colloidal particles block and hinder the motion of the cells, and force large swarming rafts to break up into smaller packs in order to maneuver across narrow spaces between densely packed particles. In this manner, cohesive rafts rapidly lose their collectivity, speed, and group dynamics, and the cells become vulnerable to the drugs. The antibiotic resistance capability of swarming B. subtilis is experimentally observed to be negatively correlated with the number density of colloidal particles on the engineered surface. This relationship is further tested using an improved self-propelled particle model that takes into account interparticle alignment and hard-core repulsion. This work has pertinent implications on the design of optimal methods to treat drug resistant bacteria commonly found in swarming colonies.

  14. Crossing scales, crossing disciplines: collective motion and collective action in the Global Commons†

    PubMed Central

    Levin, Simon

    2010-01-01

    Two conflicting tendencies can be seen throughout the biological world: individuality and collective behaviour. Natural selection operates on differences among individuals, rewarding those who perform better. Nonetheless, even within this milieu, cooperation arises, and the repeated emergence of multicellularity is the most striking example. The same tendencies are played out at higher levels, as individuals cooperate in groups, which compete with other such groups. Many of our environmental and other global problems can be traced to such conflicts, and to the unwillingness of individual agents to take account of the greater good. One of the great challenges in achieving sustainability will be in understanding the basis of cooperation, and in taking multicellularity to yet a higher level, finding the pathways to the level of cooperation that is the only hope for the preservation of the planet. PMID:20008381

  15. GDR as a Probe of the Collective Motion in Nuclei at High Spins, Temperatures or Isospins

    SciTech Connect

    Maj, Adam

    2008-11-11

    The gamma-decay of the Giant Dipole Resonance (GDR), the high-frequency collective vibration of protons against neutrons, has been proven to be a basic probe for the shapes of hot nuclei, especially to study the effective shape evolution caused by the collective rotation of a nucleus. In this context an interesting question arises: what is the nuclear shape at extreme values of spin or temperatures, close to the limit impose by another collective motion--fission, and how evolves the giant dipole collective vibrations as a function of isospin. Short overview of the results from the experiments aimed to answer these questions are presented and possible perspectives of these type of studies for exotic nuclei to be obtained with the novel gamma-calorimeter PARIS and soon available intense radioactive beams are discussed.

  16. Motion.

    ERIC Educational Resources Information Center

    Brand, Judith, Ed.

    2002-01-01

    This issue of Exploratorium Magazine focuses on the topic of motion. Contents include: (1) "First Word" (Zach Tobias); (2) "Cosmic Collisions" (Robert Irion); (3) "The Mobile Cell" (Karen E. Kalumuck); (4) "The Paths of Paths" (Steven Vogel); (5) "Fragments" (Pearl Tesler); (6) "Moving Pictures" (Amy Snyder); (7) "Plants on the Go" (Katharine…

  17. Motion.

    ERIC Educational Resources Information Center

    Gerhart, James B.; Nussbaum, Rudi H.

    This monograph was written for the Conference on the New Instructional Materials in Physics held at the University of Washington in summer, 1965. It is intended for use in an introductory course in college physics. It consists of an extensive qualitative discussion of motion followed by a detailed development of the quantitative methods needed to…

  18. Analysis of electron diffraction data for several symmetric coordinates of large-amplitude motions in the case of the 1,3,5-trinitrobenzene molecule

    NASA Astrophysics Data System (ADS)

    Khaikin, L. S.; Kochikov, I. V.; Tikhonov, D. S.; Grikina, O. E.

    2015-06-01

    A brief description of a solution of the problem on electron diffraction analysis using the potential procedure for nonrigid molecules with large-amplitude motions along several symmetric internal coordinates was given. The efficiency of the approach was demonstrated for determination of the equilibrium geometry of the 1,3,5-trinitrobenzene molecule with three equivalent internal rotation coordinates of NO2 groups. The results of the electron diffraction experiment and quantum-chemical calculation at the MP2( full)/ cc-pVTZ level were considered along with the vibrational spectra of 1,3,5-trinitrobenzene and a planar equilibrium D 3 h symmetry conformation for the molecule was found reliably for the first time. The geometrical parameters of the molecule were determined ( r e , the bond lengths are given in Å, the angles in deg): CC 1.387(2), CN 1.474(4), NO 1.220(1), CH 1.072(31), ONO 125.8(2), CC(H)C 116.6(3), HCC* 121.7(1), CC(N)C* 123.4(3), NCC* 118.3(1), and CNO* 117.1(1); the asterisk marks the dependent parameters.

  19. Collective atomic scattering and motional effects in a dense coherent medium

    PubMed Central

    Bromley, S. L.; Zhu, B.; Bishof, M.; Zhang, X.; Bothwell, T.; Schachenmayer, J.; Nicholson, T. L.; Kaiser, R.; Yelin, S. F.; Lukin, M. D.; Rey, A. M.; Ye, J.

    2016-01-01

    We investigate collective emission from coherently driven ultracold 88Sr atoms. We perform two sets of experiments using a strong and weak transition that are insensitive and sensitive, respectively, to atomic motion at 1 μK. We observe highly directional forward emission with a peak intensity that is enhanced, for the strong transition, by >103 compared with that in the transverse direction. This is accompanied by substantial broadening of spectral lines. For the weak transition, the forward enhancement is substantially reduced due to motion. Meanwhile, a density-dependent frequency shift of the weak transition (∼10% of the natural linewidth) is observed. In contrast, this shift is suppressed to <1% of the natural linewidth for the strong transition. Along the transverse direction, we observe strong polarization dependences of the fluorescence intensity and line broadening for both transitions. The measurements are reproduced with a theoretical model treating the atoms as coherent, interacting radiating dipoles. PMID:26984643

  20. Collective atomic scattering and motional effects in a dense coherent medium

    NASA Astrophysics Data System (ADS)

    Bromley, S. L.; Zhu, B.; Bishof, M.; Zhang, X.; Bothwell, T.; Schachenmayer, J.; Nicholson, T. L.; Kaiser, R.; Yelin, S. F.; Lukin, M. D.; Rey, A. M.; Ye, J.

    2016-03-01

    We investigate collective emission from coherently driven ultracold 88Sr atoms. We perform two sets of experiments using a strong and weak transition that are insensitive and sensitive, respectively, to atomic motion at 1 μK. We observe highly directional forward emission with a peak intensity that is enhanced, for the strong transition, by >103 compared with that in the transverse direction. This is accompanied by substantial broadening of spectral lines. For the weak transition, the forward enhancement is substantially reduced due to motion. Meanwhile, a density-dependent frequency shift of the weak transition (~10% of the natural linewidth) is observed. In contrast, this shift is suppressed to <1% of the natural linewidth for the strong transition. Along the transverse direction, we observe strong polarization dependences of the fluorescence intensity and line broadening for both transitions. The measurements are reproduced with a theoretical model treating the atoms as coherent, interacting radiating dipoles.

  1. Mosh pits and Circle pits: Collective motion at heavy metal concerts

    NASA Astrophysics Data System (ADS)

    Bierbaum, Matthew; Silverberg, Jesse L.; Sethna, James P.; Cohen, Itai

    2013-03-01

    Heavy metal concerts present an extreme environment in which large crowds (~102 -105) of humans experience very loud music (~ 130 dB) in sync with bright, flashing lights, often while intoxicated. In this setting, we find two types of collective motion: mosh pits, in which participants collide with each other randomly in a manner resembling an ideal gas, and circle pits, in which participants run collectively in a circle forming a vortex of people. We model these two collective behaviors using a flocking model and find qualitative and quantitative agreement with the behaviors found in videos of metal concerts. Futhermore, we find a phase diagram showing the transition from a mosh pit to a circle pit as well as a predicted third phase, lane formation.

  2. Theoretical investigation of polarization effects in solution: Importance of solvent collective motions

    SciTech Connect

    Ishida, Tateki

    2015-01-22

    Recent theoretical studies on interesting topics related to polarization effects in solutions are presented. As one of interesting topics, ionic liquids (ILs) solvents are focused on. The collective dynamics of electronic polarizability through interionic dynamics and the effect of polarization in ILs, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF{sub 6}]), are studied with molecular dynamics simulation. Also, the time-dependent polarization effect on the probe betaine dye molecule, pyridinium N-phenoxide, in water is investigated by a time-dependent reference interaction site model self-consistent field (time-dependent RISM-SCF) approach. The importance of considering polarization effects on solution systems related to solvent collective motions is shown.

  3. Theoretical investigation of polarization effects in solution: Importance of solvent collective motions

    NASA Astrophysics Data System (ADS)

    Ishida, Tateki

    2015-01-01

    Recent theoretical studies on interesting topics related to polarization effects in solutions are presented. As one of interesting topics, ionic liquids (ILs) solvents are focused on. The collective dynamics of electronic polarizability through interionic dynamics and the effect of polarization in ILs, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]), are studied with molecular dynamics simulation. Also, the time-dependent polarization effect on the probe betaine dye molecule, pyridinium N-phenoxide, in water is investigated by a time-dependent reference interaction site model self-consistent field (time-dependent RISM-SCF) approach. The importance of considering polarization effects on solution systems related to solvent collective motions is shown.

  4. Physics of microswimmers--single particle motion and collective behavior: a review.

    PubMed

    Elgeti, J; Winkler, R G; Gompper, G

    2015-05-01

    Locomotion and transport of microorganisms in fluids is an essential aspect of life. Search for food, orientation toward light, spreading of off-spring, and the formation of colonies are only possible due to locomotion. Swimming at the microscale occurs at low Reynolds numbers, where fluid friction and viscosity dominates over inertia. Here, evolution achieved propulsion mechanisms, which overcome and even exploit drag. Prominent propulsion mechanisms are rotating helical flagella, exploited by many bacteria, and snake-like or whip-like motion of eukaryotic flagella, utilized by sperm and algae. For artificial microswimmers, alternative concepts to convert chemical energy or heat into directed motion can be employed, which are potentially more efficient. The dynamics of microswimmers comprises many facets, which are all required to achieve locomotion. In this article, we review the physics of locomotion of biological and synthetic microswimmers, and the collective behavior of their assemblies. Starting from individual microswimmers, we describe the various propulsion mechanism of biological and synthetic systems and address the hydrodynamic aspects of swimming. This comprises synchronization and the concerted beating of flagella and cilia. In addition, the swimming behavior next to surfaces is examined. Finally, collective and cooperate phenomena of various types of isotropic and anisotropic swimmers with and without hydrodynamic interactions are discussed.

  5. Physics of microswimmers—single particle motion and collective behavior: a review

    NASA Astrophysics Data System (ADS)

    Elgeti, J.; Winkler, R. G.; Gompper, G.

    2015-05-01

    Locomotion and transport of microorganisms in fluids is an essential aspect of life. Search for food, orientation toward light, spreading of off-spring, and the formation of colonies are only possible due to locomotion. Swimming at the microscale occurs at low Reynolds numbers, where fluid friction and viscosity dominates over inertia. Here, evolution achieved propulsion mechanisms, which overcome and even exploit drag. Prominent propulsion mechanisms are rotating helical flagella, exploited by many bacteria, and snake-like or whip-like motion of eukaryotic flagella, utilized by sperm and algae. For artificial microswimmers, alternative concepts to convert chemical energy or heat into directed motion can be employed, which are potentially more efficient. The dynamics of microswimmers comprises many facets, which are all required to achieve locomotion. In this article, we review the physics of locomotion of biological and synthetic microswimmers, and the collective behavior of their assemblies. Starting from individual microswimmers, we describe the various propulsion mechanism of biological and synthetic systems and address the hydrodynamic aspects of swimming. This comprises synchronization and the concerted beating of flagella and cilia. In addition, the swimming behavior next to surfaces is examined. Finally, collective and cooperate phenomena of various types of isotropic and anisotropic swimmers with and without hydrodynamic interactions are discussed.

  6. Exploring the Contribution of Collective Motions to the Dynamics of Forced-Unfolding in Tubulin

    PubMed Central

    Joshi, Harshad; Momin, Farhana; Haines, Kelly E.; Dima, Ruxandra I.

    2010-01-01

    Abstract Decomposition of the intrinsic dynamics of proteins into collective motions among distant regions of the protein structure provides a physically appealing approach that couples the dynamics of the system with its functional role. The cellular functions of microtubules (an essential component of the cytoskeleton in all eukaryotic cells) depend on their dynamic instability, which is altered by various factors among which applied forces are central. To shed light on the coupling between forces and the dynamic instability of microtubules, we focus on the investigation of the response of the microtubule subunits (tubulin) to applied forces. We address this point by adapting an approach designed to survey correlations for the equilibrium dynamics of proteins to the case of correlations for proteins forced-dynamics. The resulting collective motions in tubulin have a number of functional implications, such as the identification of long-range couplings with a role in blocking the dynamic instability of microtubules. A fundamental implication of our study for the life of a cell is that, to increase the likelihood of unraveling of large cytoskeletal filaments under physiological forces, molecular motors must use a combination of pulling and torsion rather than just pulling. PMID:20159162

  7. Collective Motion of Swarming Agents Evolving on a Sphere Manifold: A Fundamental Framework and Characterization

    PubMed Central

    Li, Wei

    2015-01-01

    Collective motion of self-propelled agents has attracted much attention in vast disciplines. However, almost all investigations focus on such agents evolving in the Euclidean space, with rare concern of swarms on non-Euclidean manifolds. Here we present a novel and fundamental framework for agents evolving on a sphere manifold, with which a variety of concrete cooperative-rules of agents can be designed separately and integrated easily into the framework, which may perhaps pave a way for considering general spherical collective motion (SCM) of a swarm. As an example, one concrete cooperative-rule, i.e., the spherical direction-alignment (SDA), is provided, which corresponds to the usual and popular direction-alignment rule in the Euclidean space. The SCM of the agents with the SDA has many unique statistical properties and phase-transitions that are unexpected in the counterpart models evolving in the Euclidean space, which unveils that the topology of the sphere has an important impact on swarming emergence. PMID:26350632

  8. Amplitudes and time scales of picosecond-to-microsecond motion in proteins studied by solid-state NMR: a critical evaluation of experimental approaches and application to crystalline ubiquitin.

    PubMed

    Haller, Jens D; Schanda, Paul

    2013-11-01

    Solid-state NMR provides insight into protein motion over time scales ranging from picoseconds to seconds. While in solution state the methodology to measure protein dynamics is well established, there is currently no such consensus protocol for measuring dynamics in solids. In this article, we perform a detailed investigation of measurement protocols for fast motions, i.e. motions ranging from picoseconds to a few microseconds, which is the range covered by dipolar coupling and relaxation experiments. We perform a detailed theoretical investigation how dipolar couplings and relaxation data can provide information about amplitudes and time scales of local motion. We show that the measurement of dipolar couplings is crucial for obtaining accurate motional parameters, while systematic errors are found when only relaxation data are used. Based on this realization, we investigate how the REDOR experiment can provide such data in a very accurate manner. We identify that with accurate rf calibration, and explicit consideration of rf field inhomogeneities, one can obtain highly accurate absolute order parameters. We then perform joint model-free analyses of 6 relaxation data sets and dipolar couplings, based on previously existing, as well as new data sets on microcrystalline ubiquitin. We show that nanosecond motion can be detected primarily in loop regions, and compare solid-state data to solution-state relaxation and RDC analyses. The protocols investigated here will serve as a useful basis towards the establishment of a routine protocol for the characterization of ps-μs motions in proteins by solid-state NMR.

  9. Collective motion of self-propelled particles with density-dependent switching effect

    NASA Astrophysics Data System (ADS)

    Chen, Qiu-shi; Ma, Yu-qiang

    2016-05-01

    We study the effect of density-dependent angular response on large scale collective motion, that particles are more likely to switch their moving direction within lower local density region. We show that the presence of density-dependent angular response leads to three typical phases: polar liquid, micro-phase separation and disordered gas states. In our model, the transition between micro-phase separation and disordered gas is discontinuous. Giant number fluctuation is observed in polar liquid phase with statistically homogeneous order. In the micro-phase separation parameter space, high order and high density bands dominate the dynamics. We also compare our results with Vicsek model and show that the density-dependent directional switching response can stabilize the band state to very low noise condition. This band stripe could recruit almost all the particles in the system, which greatly enhances the coherence of the system. Our results could be helpful for understanding extremely coherent motion in nature and also would have practical implications for designing novel self-organization pattern.

  10. Slow dynamics in glycerol: collective de gennes narrowing and independent angstrom motion

    NASA Astrophysics Data System (ADS)

    Saito, Makina; Kobayashi, Yasuhiro; Masuda, Ryo; Kurokuzu, Masayuki; Kitao, Shinji; Yoda, Yoshitaka; Seto, Makoto

    2016-12-01

    The slow dynamics of microscopic density correlations in supercooled glycerol was studied by time-domain interferometry using 57Fe-nuclear resonant scattering gamma rays of synchrotron radiation. The dependence of the relaxation time at 250 K on the momentum transfer q is maximum near the first peak of the static structure factor S( q) at q ˜ 15 nm -1. The q-dependent behavior of the relaxation time known as de Gennes narrowing was confirmed in glycerol. Conversely, de Gennes narrowing around the second and third peaks of S( q) at q ˜ 26 nm -1 and 54 nm -1 was not detected. The q dependence of the relaxation time was found to follow a power-law equation with power-law index of 1.9(2) in the q region well above the first peak of S( q) up to ˜ 60 nm -1, which corresponds to angstrom scale, within experimental error. This suggests that in the angstrom-scale dynamics of supercooled glycerol, independent motions dominate over collective motion.

  11. Collective concerted motion in a molecular adlayer visualized through the surface diffusion of isolated vacancies

    NASA Astrophysics Data System (ADS)

    Urban, Christian; Otero, Roberto; Écija, David; Trelka, Marta; Martín, Nazario; Gallego, José M.; Miranda, Rodolfo

    2016-10-01

    We have measured STM movies to study the diffusion of individual vacancies in a self-assembled layer of a tetrathiafulvalene derivative (exTTF) on Au(111) at room temperature. The diffusion is anisotropic, being faster along the compact direction of the molecular lattice. A detailed analysis of the anisotropic displacement distribution of the single vacancies shows that the relative abundance of double jumps (that is, the collective motion of molecular dimers) with respect to single jumps is rather large, the number of double jumps being more than 20% of the diffusion events. We conjecture that the relative abundances of long jumps might be related to the strength of the intermolecular bonding and the misfit of the molecular overlayer with the substrate lattice.

  12. The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures.

    PubMed

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; Liang, Liangbo; West, Damien; Meunier, Vincent; Zhang, Shengbai

    2016-05-10

    The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the interface. Application to the MoS2/WS2 heterostructure yields good agreement with experiments, indicating near complete charge transfer within a timescale of 100 fs.

  13. Density fluctuations and topological structures in collective surface motion of microswimmers

    NASA Astrophysics Data System (ADS)

    Gao, Tong; Shelley, Michael

    2014-11-01

    Active matter that consists of self-propelled particles, such as bacterial suspensions and assays of self-driven biofilaments, can exhibit collective motions with large-scale complex flows and topological defect dynamics. Using a Doi-Onsager kinetic theory, we study suspensions of microswimmers confined to an air/liquid interface, and identify correlations between particle density fluctuations, defect structures, nematic order, and surface flows. When considering a free-standing liquid film where the microswimmers are distributed on the air/liquid interfaces, we capture hydrodynamic coupling of the two active surface, characterized by synchronization of motile disclination defects. We estimate the effective ``penetration distance'' between the two coupled surfaces through a linear stability analysis.

  14. The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures

    PubMed Central

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; Liang, Liangbo; West, Damien; Meunier, Vincent; Zhang, Shengbai

    2016-01-01

    The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the interface. Application to the MoS2/WS2 heterostructure yields good agreement with experiments, indicating near complete charge transfer within a timescale of 100 fs. PMID:27160484

  15. Why and how does collective red blood cells motion occur in the blood microcirculation?

    NASA Astrophysics Data System (ADS)

    Ghigliotti, Giovanni; Selmi, Hassib; Asmi, Lassaad El; Misbah, Chaouqi

    2012-10-01

    The behaviour of red blood cells (RBCs), modelled as vesicles, in Poiseuille flow, mimicking the microvasculature, is studied with numerical simulations in two dimensions. RBCs moving in the centre of the Poiseuille flow (as in blood capillaries) are shown to attract each other and form clusters only due to hydrodynamic interactions, provided that their distance at a given time is below a certain critical value. This distance depends on physical parameters, such as the flow strength. Our simulations reveal that clusters are unstable above a threshold value in the number of forming RBCs, beyond which one or few cells escape the pack by a self-regulating mechanism that select the marginally stable size. This size selection depends on the flow strength as well as on the RBC swelling ratio. The results are interpreted via the analysis of the perturbation of the flow field induced by the vesicles and the interplay with bending and tension forces. This sheds a novel light on the process of collective motion of RBCs observed in vivo.

  16. d-alpha correlation functions and collective motion in Xe+Au collisions at E/A=50 MeV

    SciTech Connect

    Verde, G; Danielewicz, P; Lynch, W; Chan, C; Gelbke, C; Kwong, L; Liu, T; Liu, X; Seymour, D; Tan, W; Tsang, M; Wagner, A; Xu, H; Brown, D; Davin, B; Larochelle, Y; de Souza, R; Charity, R; Sobotka, L

    2006-07-27

    The interplay of the effects of geometry and collective motion on d-{alpha} correlation functions is investigated for central Xe+Au collisions at E/A=50 MeV. The data cannot be explained with out collective motion, which could be partly along the beam axis. A semi-quantitative description of the data can be obtained using a Monte -Carlo model, where thermal emission is superimposed on collective motion. Both the emission volume and the competition between the thermal and collective motion influence significantly the shape of the correlation function, motivating new strategies for extending intensity interferometry studies to massive particles.

  17. The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures

    DOE PAGES

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; ...

    2016-05-10

    Here, the success of van der Waals (vdW) heterostructures, made of graphene, metal dichalcogenides, and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that vdW heterostructues can exhibit ultra-fast charge transfer despite the weak binding of the heterostructure. Using time-dependent density functional theory molecular dynamics, we identify a strong dynamic coupling between the vdW layers associated with charge transfer. This dynamic coupling results in rapid nonlinear coherentmore » charge oscillations which constitute a purely electronic phenomenon and are shown to be a general feature of vdW heterostructures provided they have a critical minimum dipole coupling. Application to MoS2/WS2 heterostructure yields good agreement with experiment, indicating near complete charge transfer within a timescale of 100 fs.The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the

  18. The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures

    SciTech Connect

    Wang, Han; Bang, Junhyeok; Sun, Yiyang; West, Damien; Meunier, Vincent; Zhang, Shengbai; Liang, Linagbo

    2016-05-10

    Here, the success of van der Waals (vdW) heterostructures, made of graphene, metal dichalcogenides, and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that vdW heterostructues can exhibit ultra-fast charge transfer despite the weak binding of the heterostructure. Using time-dependent density functional theory molecular dynamics, we identify a strong dynamic coupling between the vdW layers associated with charge transfer. This dynamic coupling results in rapid nonlinear coherent charge oscillations which constitute a purely electronic phenomenon and are shown to be a general feature of vdW heterostructures provided they have a critical minimum dipole coupling. Application to MoS2/WS2 heterostructure yields good agreement with experiment, indicating near complete charge transfer within a timescale of 100 fs.The success of van der Waals heterostructures made of graphene, metal dichalcogenides and other layered materials, hinges on the understanding of charge transfer across the interface as the foundation for new device concepts and applications. In contrast to conventional heterostructures, where a strong interfacial coupling is essential to charge transfer, recent experimental findings indicate that van der Waals heterostructues can exhibit ultrafast charge transfer despite the weak binding of these heterostructures. Here we find, using time-dependent density functional theory molecular dynamics, that the collective motion of excitons at the interface leads to plasma oscillations associated with optical excitation. By constructing a simple model of the van der Waals heterostructure, we show that there exists an unexpected criticality of the oscillations, yielding rapid charge transfer across the interface

  19. Single-particle and collective motion in unbound deformed 39Mg

    NASA Astrophysics Data System (ADS)

    Fossez, K.; Rotureau, J.; Michel, N.; Liu, Quan; Nazarewicz, W.

    2016-11-01

    Background: Deformed neutron-rich magnesium isotopes constitute a fascinating territory where the interplay between collective rotation and single-particle motion is strongly affected by the neutron continuum. The unbound f p -shell nucleus 39Mg is an ideal candidate to study this interplay. Purpose: In this work, we predict the properties of low-lying resonant states of 39Mg, using a suite of realistic theoretical approaches rooted in the open quantum system framework. Method: To describe the spectrum and decay modes of 39Mg we use the conventional shell model, Gamow shell model, resonating group method, density matrix renormalization group method, and the nonadiabatic particle-plus-rotor model formulated in the Berggren basis. Results: The unbound ground state of 39Mg is predicted to be either a Jπ=7/2 - state or a 3/2 - state. A narrow Jπ=7/2 - ground-state candidate exhibits a resonant structure reminiscent of that of its one-neutron halo neighbor 37Mg, which is dominated by the f7 /2 partial wave at short distances and a p3 /2 component at large distances. A Jπ=3/2 - ground-state candidate is favored by the large deformation of the system. It can be associated with the 1/2 -[321 ] Nilsson orbital dominated by the ℓ =1 wave; hence its predicted width is large. The excited Jπ=1/2 - and 5 /2- states are expected to be broad resonances, while the Jπ=9/2 - and 11/2 - members of the ground-state rotational band are predicted to have very small neutron decay widths. Conclusion: We demonstrate that the subtle interplay between deformation, shell structure, and continuum coupling can result in a variety of excitations in an unbound nucleus just outside the neutron drip line.

  20. Effects of non-idealities and quantization of the center of mass motion on symmetric and asymmetric collective states in a collective state atomic interferometer

    NASA Astrophysics Data System (ADS)

    Sarkar, Resham; Kim, May E.; Fang, Renpeng; Tu, Yanfei; Shahriar, Selim M.

    2015-09-01

    We investigate the behavior of an ensemble of ? non-interacting, identical atoms excited by a laser. In general, the ?-th atom sees a Rabi frequency ?, an initial position dependent laser phase ?, and a motion induced Doppler shift of ?. When ? or ? is distinct for each atom, the system evolves into a superposition of ? intercoupled states, of which there are ? symmetric and ? asymmetric collective states. For a collective state atomic interferometer (COSAIN), we recently proposed, it is important to understand the behavior of all the collective states under various conditions. In this paper, we show how to formulate the properties of these states under various non-idealities, and use this formulation to understand the dynamics thereof. We also consider the effect of treating the center of mass degree of freedom of the atoms quantum mechanically on the description of the collective states, illustrating that it is indeed possible to construct a generalized collective state, as needed for the COSAIN, when each atom is assumed to be in a localized wave packet. The analysis presented in this paper is important for understanding the dynamics of the COSAIN, and will help advance the analysis and optimization of spin squeezing in the presence of practically unavoidable non-idealities as well as in the domain where the center of mass motion of the atoms is quantized.

  1. Collective coordinate models of domain wall motion in perpendicularly magnetized systems under the spin hall effect and longitudinal fields

    NASA Astrophysics Data System (ADS)

    Nasseri, S. Ali; Moretti, Simone; Martinez, Eduardo; Serpico, Claudio; Durin, Gianfranco

    2017-03-01

    Recent studies on heterostructures of ultrathin ferromagnets sandwiched between a heavy metal layer and an oxide have highlighted the importance of spin-orbit coupling (SOC) and broken inversion symmetry in domain wall (DW) motion. Specifically, chiral DWs are stabilized in these systems due to the Dzyaloshinskii-Moriya interaction (DMI). SOC can also lead to enhanced current induced DW motion, with the Spin Hall effect (SHE) suggested as the dominant mechanism for this observation. The efficiency of SHE driven DW motion depends on the internal magnetic structure of the DW, which could be controlled using externally applied longitudinal in-plane fields. In this work, micromagnetic simulations and collective coordinate models are used to study current-driven DW motion under longitudinal in-plane fields in perpendicularly magnetized samples with strong DMI. Several extended collective coordinate models are developed to reproduce the micromagnetic results. While these extended models show improvements over traditional models of this kind, there are still discrepancies between them and micromagnetic simulations which require further work.

  2. Alignment vs noise in self-propelled particles: minimal models for collective motion and their continuous descriptions

    NASA Astrophysics Data System (ADS)

    Chate, Hugues

    2012-02-01

    Two important 1995 papers have marked the birth of collective motion studies in physics: Vicsek et al introduced what could now be described as the ``Ising model'' of this new subfield. This prompted Toner and Tu to propose a continuum theory of flocks which they showed to give rise to long-range orientational order even in two space dimensions. In this setting, the complexity of most natural instances of collective motion is reduced to the competition between local alignment and noise in interacting self-propelled particles. As I will show, this nevertheless gives rise to important and new physics. In this talk, I will give an update of our current knowledge about the Vicsek model, the Toner-Tu theory, and their relationship. I will also present the emerging picture of universality classes brought about by recent progress in the study of Vicsek-like models together with their continuous descriptions.

  3. A Collection and Statistical Analysis of Biophysical Data to Predict Motion Sickness Incidence

    DTIC Science & Technology

    1986-12-01

    control interval. Surface. Skin TemperaturA In most cases, the subject’s skin temperature, which is measured on the finger, decreased during pre...motion sickness response. 2. Chair control console which controls the chair’s rotation speed. 3. NDM Corporation Silvon Stress Test ECG electrodes and

  4. Correction of motion artifacts in OCT-AFI data collected in airways (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Abouei, Elham; Lane, Pierre M.; Pahlevaninezhad, Hamid; Lee, Anthony; Lam, Stephen; MacAulay, Calum E.

    2016-03-01

    Abstract: Optical coherence tomography (OCT) provides in vivo imaging with near-histologic resolution of tissue morphology. OCT has been successfully employed in clinical practice in non-pulmonary fields of medicine such as ophthalmology and cardiology. Studies suggest that OCT has the potential to be a powerful tool for the detection and localization of malignant and non-malignant pulmonary diseases. The combination of OCT with autofluorescence imaging (AFI) provides valuable information about the structural and metabolic state of tissues. Successful application of OCT or OCT-AFI to the field of pulmonary medicine requires overcoming several challenges. This work address those associated with motion: cardiac cycle, breathing and non-uniform rotation distortion (NURD) artifacts. Mechanically rotated endoscopic probes often suffer from image degradation due to NURD. In addition cardiac and breathing motion artifacts may be present in-vivo that are not seen ex-vivo. These motion artifacts can be problematic in OCT-AFI systems with slower acquisition rates and have been observed to generate identifiable prominent artifacts which make confident interpretation of observed structures (blood vessels, etc) difficult. Understanding and correcting motion artifact could improve the image quality and interpretation. In this work, the motion artifacts in pulmonary OCT-AFI data sets are estimated in both AFI and OCT images using a locally adaptive registration algorithm that can be used to correct/reduce such artifacts. Performance of the algorithm is evaluated on images of a NURD phantom and on in-vivo OCT-AFI datasets of peripheral lung airways.

  5. Collective Cell Motion in an Epithelial Sheet Can Be Quantitatively Described by a Stochastic Interacting Particle Model

    PubMed Central

    Cochet, Olivier; Grasland-Mongrain, Erwan; Silberzan, Pascal; Hakim, Vincent

    2013-01-01

    Modelling the displacement of thousands of cells that move in a collective way is required for the simulation and the theoretical analysis of various biological processes. Here, we tackle this question in the controlled setting where the motion of Madin-Darby Canine Kidney (MDCK) cells in a confluent epithelium is triggered by the unmasking of free surface. We develop a simple model in which cells are described as point particles with a dynamic based on the two premises that, first, cells move in a stochastic manner and, second, tend to adapt their motion to that of their neighbors. Detailed comparison to experimental data show that the model provides a quantitatively accurate description of cell motion in the epithelium bulk at early times. In addition, inclusion of model “leader” cells with modified characteristics, accounts for the digitated shape of the interface which develops over the subsequent hours, providing that leader cells invade free surface more easily than other cells and coordinate their motion with their followers. The previously-described progression of the epithelium border is reproduced by the model and quantitatively explained. PMID:23505356

  6. Molecular dynamics simulation of the M2 helices within the nicotinic acetylcholine receptor transmembrane domain: structure and collective motions.

    PubMed

    Hung, Andrew; Tai, Kaihsu; Sansom, Mark S P

    2005-05-01

    Multiple nanosecond duration molecular dynamics simulations were performed on the transmembrane region of the Torpedo nicotinic acetylcholine receptor embedded within a bilayer mimetic octane slab. The M2 helices and M2-M3 loop regions were free to move, whereas the outer (M1, M3, M4) helix bundle was backbone restrained. The M2 helices largely retain their hydrogen-bonding pattern throughout the simulation, with some distortions in the helical end and loop regions. All of the M2 helices exhibit bending motions, with the hinge point in the vicinity of the central hydrophobic gate region (corresponding to residues alphaL251 and alphaV255). The bending motions of the M2 helices lead to a degree of dynamic narrowing of the pore in the region of the proposed hydrophobic gate. Calculations of Born energy profiles for various structures along the simulation trajectory suggest that the conformations of the M2 bundle sampled correspond to a closed conformation of the channel. Principal components analyses of each of the M2 helices, and of the five-helix M2 bundle, reveal concerted motions that may be relevant to channel function. Normal mode analyses using the anisotropic network model reveal collective motions similar to those identified by principal components analyses.

  7. Nuclear dissipation as damping of collective motion in the time-dependent RPA and extensions of it

    SciTech Connect

    Yannouleas, C.P.

    1982-07-01

    We have formulated a nonperturbative, microscopic dissipative process in the limit of an infinite mean free path which does not require any statistical assumptions. It attributes the damping of the collective motion to real transitions from the collective state to degenerate, more complicated nucelar states. The dissipation is described through wave packets which solve an approximate Schroedinger equation within extended subspaces, larger than the original subspace of the undamped motion. When the simple RPA is used, this process associates the dissipation with the escape width for direct particle emission. When the Second RPA is used, it associates the dissipation with the spreading width for transitions to the 2p-2h components of the nuclear compound states. The energy loss rate for sharp n-phonon initial states is proportional to the total collective energy. The classical dissipation, however, is obtained for coherent, multiphonon, initial packets which describe the damping of the mean field oscillations, and allow a theoretical connection with the Vibrating Potential Model, and thereby with models of one-body dissipation. The present model contrasts with linear response theories. Canonical coordinates for the collective degree of freedom are explicitly introduced. This allows the construction of a nonlinear frictional Hamiltonian which provides a connection with quantal friction. The dissipation process developed here is properly reversible rather than irreversible, in the sense that it is described by an approximate Schroedinger equation which honors time reversibility, rather than by a coarse grained master equation which violates it. Thus, the present theory contrasts with transport theories.

  8. a Diatomic Molecule with Extremely Large Amplitude Motion in its Vibrational States that have Lengths of at Least 12,000 Angstroms.

    NASA Astrophysics Data System (ADS)

    Dattani, Nikesh S.

    2016-06-01

    The state-of-the-art empirical potential, and the state-of-the-art ab initio potential for the b(1^3Π2_u) state of 7,7Li_2 agree with each other that the (v=100,J=0) ro-vibrational state has an outer classical turning point larger than the diameter of most bacteria and many animal cells. The 2015 empirical potential based on a significant amount of spectroscopic data, predicts the (v=100,J=0) level to be bound by only 0.000 000 000 004 cm-1 (<0.2 Hz). The outer turning point of the vibrational wavefunction is about 671 000 Å or 0.07 mm. Here, the two Li atoms are bound to each other, despite being nearly as far apart as the lines on a macroscopic ruler. The 2014 ab initio calculation based on a powerful Fock space MRCC method and with the long-range tail anchored by C_3^7{Li}/r^3 with the ultra-high precision 2015 value of C_3^7{Li}, has this same level bound by 0.000 000 000 1 cm-1 (<3 Hz), with an outer turning point of >0.01 mm. While this discovery occurred during a study of Li_2, the b(1^3Π2_u) states of heavier alkali diatomics are expected to have even larger amplitude vibrational states. While it might be tempting to call these very large molecules ``Rydberg molecules", it is important to remember that this term is already used to describe highly excited electronic states whose energy levels follow a formula similar to that for the famous Rydberg series. The highly delocalized vibrational states are a truly unfamiliar phenomenon. Dattani (2015) http://arxiv.org/abs/1508.07184v1 Musial & Kucharski (2014) Journal of Chemical Theory and Computation, 10, 1200

  9. Promoting collective motion of self-propelled agents by distance-based influence.

    PubMed

    Yang, Han-Xin; Zhou, Tao; Huang, Liang

    2014-03-01

    We propose a dynamic model for a system consisting of self-propelled agents in which the influence of an agent on another agent is weighted by geographical distance. A parameter α is introduced to adjust the influence: The smaller value of α means that the closer neighbors have a stronger influence on the moving direction. We find that there exists an optimal value of α leading to the highest degree of direction consensus. The value of optimal α increases as the system size increases, while it decreases as the absolute velocity, the sensing radius, and the noise amplitude increase.

  10. Detection of collective motions in dielectric spectra and the meaning of the generalized Vogel-Fulcher-Tamman equation

    NASA Astrophysics Data System (ADS)

    Nigmatullin, Raoul R.

    2009-02-01

    Based on the reduction property of dielectric spectra associated with the power-law function [∼( jωτ) ± ν] that appears in the frequency domain, one can develop an effective procedure for detection of different reduced motions (described by the corresponding power-law exponents) in temperature domain. If the power-law exponent ν is related to characteristic relaxation time τ by the relationship ν= ν0 ln( τ/ τ s)/ln( τ/ τ0) (here τ s, τ0 are the characteristic times characterizing a movement over fractal cluster that is defined in Ref. [Ya.E. Ryabov, Yu. Feldman, J. Chem. Phys. 116 (2002) 8610]) and the simple temperature dependence of τ( T)= τ A exp( E/ T) obeys the traditional Arrhenius relationship, then one can prove that any extreme point figuring in the complex permittivity ε( jω) spectra (characterized by the values [ ω m, y( ω m)]) obeys the generalized Vogel-Fulcher-Tamman (VFT) equation. This important statement confirms the existence of the ‘universal’ response (UR) (discovered and classified by Jonscher in frequency domain) and opens new possibilities in the detection of the ‘hidden’ collective motions in temperature region for self-similar (heterogeneous) systems. It gives also the extended interpretation of the VFT equation and allows one to differentiate collective motions passing through an extreme point. This differentiation, in turn, allows one to select the proper fitting function containing one or two (at least) relaxation times for the fitting of the complex permittivity function ε( jω) in the limited frequency domain. This conclusion can allow for the classification of dielectric spectroscopy as the spectroscopy of the reduced ( collective) motions, which are described by different power-law exponents on the mesoscale region. The verification of this approach on available DS data (poly(ethylene glycol)-based-single-ion conductors) completely confirms the basic statements of this theory and opens new possibilities

  11. Cooling the Collective Motion of Trapped Ions to Initialize a Quantum Register

    DTIC Science & Technology

    2016-09-13

    electronic states. We find that heating of the modes of relative ion motion is substantially suppressed relative to that of the center-of-mass modes...MHz. Figure 1 shows two ions confined in the trap and imaged with an fy3 lens system onto a position-sensitive photo- multiplier tube. The ions are...tion, which allows us to detect the ion’s electronic state (j #l or j "l) with nearly unit detection efficiency . Beams R1 (s1ys2 polarized) and R2 (p

  12. Collective motion of macroscopic spheres floating on capillary ripples: Dynamic heterogeneity and dynamic criticality

    NASA Astrophysics Data System (ADS)

    Sanlı, Ceyda; Saitoh, Kuniyasu; Luding, Stefan; van der Meer, Devaraj

    2014-09-01

    When a densely packed monolayer of macroscopic spheres floats on chaotic capillary Faraday waves, a coexistence of large scale convective motion and caging dynamics typical for glassy systems is observed. We subtract the convective mean flow using a coarse graining (homogenization) method and reveal subdiffusion for the caging time scales followed by a diffusive regime at later times. We apply the methods developed to study dynamic heterogeneity and show that the typical time and length scales of the fluctuations due to rearrangements of observed particle groups significantly increase when the system approaches its largest experimentally accessible packing concentration. To connect the system to the dynamic criticality literature, we fit power laws to our results. The resultant critical exponents are consistent with those found in densely packed suspensions of colloids.

  13. The crossover from collective motion to periphery diffusion for two-dimensional adatom-islands on Cu(111).

    PubMed

    Karim, Altaf; Kara, Abdelkader; Trushin, Oleg; Rahman, Talat S

    2011-11-23

    The diffusion of two-dimensional adatom-islands (up to 100 atoms) on Cu(111) has been studied, using the self-learning kinetic Monte Carlo method (Trushin et al 2005 Phys. Rev. B 72 115401). A variety of multiple- and single-atom processes are revealed in the simulations, and the size dependences of the diffusion coefficients and effective diffusion barriers are calculated for each. From the tabulated frequencies of events found in the simulation, we show a crossover from diffusion due to the collective motion of the island to a regime in which the island diffuses through periphery-dominated mass transport. This crossover occurs for island sizes between 13 and 19 atoms. For islands containing 19-100 atoms the scaling exponent is 1.5, which is in good agreement with previous work. The diffusion of islands containing 2-13 atoms can be explained primarily on the basis of a linear increase of the barrier for the collective motion with the size of the island.

  14. Collective motion in selected central collisions of Au on Au at 150A MeV

    NASA Astrophysics Data System (ADS)

    Jeong, S. C.; Herrmann, N.; Fan, Z. G.; Freifelder, R.; Gobbi, A.; Hildenbrand, K. D.; Krämer, M.; Randrup, J.; Reisdorf, W.; Schüll, D.; Sodan, U.; Teh, K.; Wessels, J. P.; Pelte, D.; Trzaska, M.; Wienold, T.; Alard, J. P.; Amouroux, V.; Basrak, Z.; Bastid, N.; Belayev, I. M.; Berger, L.; Bini, M.; Blaich, Th.; Boussange, S.; Buta, A.; Čaplar, R.; Cerruti, C.; Cindro, N.; Coffin, J. P.; Dona, R.; Dupieux, P.; Erö, J.; Fintz, P.; Fodor, Z.; Fraysse, L.; Frolov, S.; Grigorian, Y.; Guillaume, G.; Hölbling, S.; Houari, A.; Jundt, F.; Kecskemeti, J.; Koncz, P.; Korchagin, Y.; Kotte, R.; Kuhn, C.; Ibnouzahir, M.; Legrand, I.; Lebedev, A.; Maguire, C.; Manko, V.; Maurenzig, P.; Mgebrishvili, G.; Mösner, J.; Moisa, D.; Montarou, G.; Montbel, I.; Morel, P.; Neubert, W.; Olmi, A.; Pasquali, G.; Petrovici, M.; Poggi, G.; Rami, F.; Ramillien, V.; Sadchikov, A.; Seres, Z.; Sikora, B.; Simion, V.; Smolyankin, S.; Tezkratt, R.; Vasiliev, M. A.; Wagner, P.; Wilhelmi, Z.; Wohlfarth, D.; Zhilin, A. V.

    1994-05-01

    Using the FOPI facility at GSI Darmstadt complete data of Au on Au collisions at 150A MeV were collected for charged products (Z=1-15) at laboratory angles 1°<=Θlab<=30°. Central collisions were selected by applying various criteria. The kinetic energy spectra of fragments from an isolated midrapidity source are investigated in detail for center-of-mass angles 25°<=Θc.m.<=45°. The heavy products (Z>=3) are used to determine the collective energy which is found to be at least 10A MeV.

  15. Lattice-free descriptions of collective motion with crowding and adhesion.

    PubMed

    Johnston, Stuart T; Simpson, Matthew J; Plank, Michael J

    2013-12-01

    Cell-to-cell adhesion is an important aspect of malignant spreading that is often observed in images from the experimental cell biology literature. Since cell-to-cell adhesion plays an important role in controlling the movement of individual malignant cells, it is likely that cell-to-cell adhesion also influences the spatial spreading of populations of such cells. Therefore, it is important for us to develop biologically realistic simulation tools that can mimic the key features of such collective spreading processes to improve our understanding of how cell-to-cell adhesion influences the spreading of cell populations. Previous models of collective cell spreading with adhesion have used lattice-based random walk frameworks which may lead to unrealistic results, since the agents in the random walk simulations always move across an artificial underlying lattice structure. This is particularly problematic in high-density regions where it is clear that agents in the random walk align along the underlying lattice, whereas no such regular alignment is ever observed experimentally. To address these limitations, we present a lattice-free model of collective cell migration that explicitly incorporates crowding and adhesion. We derive a partial differential equation description of the discrete process and show that averaged simulation results compare very well with numerical solutions of the partial differential equation.

  16. Modeling the Emergence of Modular Leadership Hierarchy During the Collective Motion of Herds Made of Harems

    NASA Astrophysics Data System (ADS)

    Ozogány, Katalin; Vicsek, Tamás

    2015-02-01

    Gregarious animals need to make collective decisions in order to keep their cohesiveness. Several species of them live in multilevel societies, and form herds composed of smaller communities. We present a model for the development of a leadership hierarchy in a herd consisting of loosely connected sub-groups (e.g. harems) by combining self organization and social dynamics. It starts from unfamiliar individuals without relationships and reproduces the emergence of a hierarchical and modular leadership network that promotes an effective spreading of the decisions from more capable individuals to the others, and thus gives rise to a beneficial collective decision. Our results stemming from the model are in a good agreement with our observations of a Przewalski horse herd (Hortobágy, Hungary). We find that the harem-leader to harem-member ratio observed in Przewalski horses corresponds to an optimal network in this approach regarding common success, and that the observed and modeled harem size distributions are close to a lognormal.

  17. Transition to collective motion and mixing in suspensions of micro-rotors

    NASA Astrophysics Data System (ADS)

    Vlahovska, Petia; Lushi, Enkeleida

    2015-11-01

    Self-organization of active objects has attracted considerable attention recently, in particular in the context of living matter. Hydrodynamic interactions play a crucial role in the emerging behavior when the objects are immersed in fluid, especially in the low Reynolds number regime. While self-propelled active objects have been extensively investigated, the collective behavior of rotating active particle has received limited attention.To elucidate the transition to collective behavior and especially the role of multi-body hydrodynamic interactions, we numerically study systems of co- and counter-rotating spheres by varying the mixture ratio as well as the total volume fraction. We show that while macroscopic patterns emerge with increasing volume fraction in all the mixtures, the organization of the 100-0 and 50-50 mixtures are different in nature. The 50-50 rotor mixtures generate macroscopic fluid flows that are larger in magnitude and more chaotic, due to the propensity of rotors of opposite spins to pair up and co-swim. The properties of these generated fluid flows are investigated, and in particular we show that the mixing of a passive dye field is more efficiently done by 50-50 rotor mixtures. We acknowledge support from NSF CBET 1437545 and NSF CBET 1544196.

  18. Dynamical signatures of collective quality grading in a social activity: attendance to motion pictures.

    PubMed

    Escobar, Juan V; Sornette, Didier

    2015-01-01

    We investigate the laws governing people's decisions and interactions by studying the collective dynamics of a well-documented social activity for which there exist ample records of the perceived quality: the attendance to movie theaters in the US. We picture the flows of attendance as impulses or "shocks" driven by external factors that in turn can create new cascades of attendances through direct recommendations whose effectiveness depends on the perceived quality of the movies. This corresponds to an epidemic branching model comprised of a decaying exponential function determining the time between cause and action, and a cascade of actions triggered by previous ones. We find that the vast majority of the ~3,500 movies studied fit our model remarkably well. From our results, we are able to translate a subjective concept such as movie quality into a probability of the deriving individual activity, and from it we build concrete quantitative predictions. Our analysis opens up the possibility of understanding other collective dynamics for which the perceived quality or appeal of an action is also known.

  19. Steady-state spin synchronization through the collective motion of trapped ions

    NASA Astrophysics Data System (ADS)

    Shankar, Athreya; Cooper, John; Bohnet, Justin G.; Bollinger, John J.; Holland, Murray

    2017-03-01

    Ultranarrow-linewidth atoms coupled to a lossy optical cavity mode synchronize, i.e., develop correlations, and exhibit steady-state superradiance when continuously repumped. This type of system displays rich collective physics and promises metrological applications. These features inspire us to investigate if analogous spin synchronization is possible in a different platform that is one of the most robust and controllable experimental testbeds currently available: ion-trap systems. We design a system with a primary and secondary species of ions that share a common set of normal modes of vibration. In analogy to the lossy optical mode, we propose to use a lossy normal mode, obtained by sympathetic cooling with the secondary species of ions, to mediate spin synchronization in the primary species of ions. Our numerical study shows that spin-spin correlations develop, leading to a macroscopic collective spin in steady state. We propose an experimental method based on Ramsey interferometry to detect signatures of this spin synchronization; we predict that correlations prolong the visibility of Ramsey fringes, and that population statistics at the end of the Ramsey sequence can be used to directly infer spin-spin correlations.

  20. Dynamical Signatures of Collective Quality Grading in a Social Activity: Attendance to Motion Pictures

    PubMed Central

    Escobar, Juan V.; Sornette, Didier

    2015-01-01

    We investigate the laws governing people’s decisions and interactions by studying the collective dynamics of a well-documented social activity for which there exist ample records of the perceived quality: the attendance to movie theaters in the US. We picture the flows of attendance as impulses or “shocks” driven by external factors that in turn can create new cascades of attendances through direct recommendations whose effectiveness depends on the perceived quality of the movies. This corresponds to an epidemic branching model comprised of a decaying exponential function determining the time between cause and action, and a cascade of actions triggered by previous ones. We find that the vast majority of the ~3,500 movies studied fit our model remarkably well. From our results, we are able to translate a subjective concept such as movie quality into a probability of the deriving individual activity, and from it we build concrete quantitative predictions. Our analysis opens up the possibility of understanding other collective dynamics for which the perceived quality or appeal of an action is also known. PMID:25612292

  1. Low work-function thermionic emission and orbital-motion-limited ion collection at bare-tether cathodic contact

    SciTech Connect

    Chen, Xin Sanmartín, J. R.

    2015-05-15

    With a thin coating of low-work-function material, thermionic emission in the cathodic segment of bare tethers might be much greater than orbital-motion-limited (OML) ion collection current. The space charge of the emitted electrons decreases the electric field that accelerates them outwards, and could even reverse it for high enough emission, producing a potential hollow. In this work, at the conditions of high bias and relatively low emission that make the potential monotonic, an asymptotic analysis is carried out, extending the OML ion-collection analysis to investigate the probe response due to electrons emitted by the negatively biased cylindrical probe. At given emission, the space charge effect from emitted electrons increases with decreasing magnitude of negative probe bias. Although emitted electrons present negligible space charge far away from the probe, their effect cannot be neglected in the global analysis for the sheath structure and two thin layers in between sheath and the quasineutral region. The space-charge-limited condition is located. It is found that thermionic emission increases the range of probe radius for OML validity and is greatly more effective than ion collection for cathodic contact of tethers.

  2. Characterization of Protein Flexibility Using Small-Angle X-Ray Scattering and Amplified Collective Motion Simulations

    PubMed Central

    Wen, Bin; Peng, Junhui; Zuo, Xiaobing; Gong, Qingguo; Zhang, Zhiyong

    2014-01-01

    Large-scale flexibility within a multidomain protein often plays an important role in its biological function. Despite its inherent low resolution, small-angle x-ray scattering (SAXS) is well suited to investigate protein flexibility and determine, with the help of computational modeling, what kinds of protein conformations would coexist in solution. In this article, we develop a tool that combines SAXS data with a previously developed sampling technique called amplified collective motions (ACM) to elucidate structures of highly dynamic multidomain proteins in solution. We demonstrate the use of this tool in two proteins, bacteriophage T4 lysozyme and tandem WW domains of the formin-binding protein 21. The ACM simulations can sample the conformational space of proteins much more extensively than standard molecular dynamics (MD) simulations. Therefore, conformations generated by ACM are significantly better at reproducing the SAXS data than are those from MD simulations. PMID:25140431

  3. Single-particle and collective motion in nuclear open quantum systems

    NASA Astrophysics Data System (ADS)

    Fossez, Kevin

    2017-01-01

    The properties of drip-line nuclei are profoundly affected by the environment of continuum states and the presence of decay channels. Their description requires the development of realistic theoretical approaches rooted in the open quantum system framework. However this formidable task presents many challenges and calls for closer collaborations between theorists and experimentalists. In this presentation a brief introduction to the problem of the description of weakly bound and unbound nuclei will be given with an emphasis on the relationship between nuclear structure and reactions. This will be illustrated by two recent investigations on the nuclei 11Be and 39Mg, where the role of the interplay between the collectivity and the continuum on single-particle structure has been studied. Finally the question of the existence of a nuclear system in the continuum is discussed for the case of the four-neutron system.

  4. Spatio-temporal correlations in models of collective motion ruled by different dynamical laws

    NASA Astrophysics Data System (ADS)

    Cavagna, Andrea; Conti, Daniele; Giardina, Irene; Grigera, Tomas S.; Melillo, Stefania; Viale, Massimiliano

    2016-12-01

    Information transfer is an essential factor in determining the robustness of biological systems with distributed control. The most direct way to study the mechanisms ruling information transfer is to experimentally observe the propagation across the system of a signal triggered by some perturbation. However, this method may be inefficient for experiments in the field, as the possibilities to perturb the system are limited and empirical observations must rely on natural events. An alternative approach is to use spatio-temporal correlations to probe the information transfer mechanism directly from the spontaneous fluctuations of the system, without the need to have an actual propagating signal on record. Here we test this method on models of collective behaviour in their deeply ordered phase by using ground truth data provided by numerical simulations in three dimensions. We compare two models characterized by very different dynamical equations and information transfer mechanisms: the classic Vicsek model, describing an overdamped noninertial dynamics and the inertial spin model, characterized by an underdamped inertial dynamics. By using dynamic finite-size scaling, we show that spatio-temporal correlations are able to distinguish unambiguously the diffusive information transfer mechanism of the Vicsek model from the linear mechanism of the inertial spin model.

  5. Emergence of Swarming Behavior: Foraging Agents Evolve Collective Motion Based on Signaling

    PubMed Central

    Ikegami, Takashi

    2016-01-01

    Swarming behavior is common in biology, from cell colonies to insect swarms and bird flocks. However, the conditions leading to the emergence of such behavior are still subject to research. Since Reynolds’ boids, many artificial models have reproduced swarming behavior, focusing on details ranging from obstacle avoidance to the introduction of fixed leaders. This paper presents a model of evolved artificial agents, able to develop swarming using only their ability to listen to each other’s signals. The model simulates a population of agents looking for a vital resource they cannot directly detect, in a 3D environment. Instead of a centralized algorithm, each agent is controlled by an artificial neural network, whose weights are encoded in a genotype and adapted by an original asynchronous genetic algorithm. The results demonstrate that agents progressively evolve the ability to use the information exchanged between each other via signaling to establish temporary leader-follower relations. These relations allow agents to form swarming patterns, emerging as a transient behavior that improves the agents’ ability to forage for the resource. Once they have acquired the ability to swarm, the individuals are able to outperform the non-swarmers at finding the resource. The population hence reaches a neutral evolutionary space which leads to a genetic drift of the genotypes. This reductionist approach to signal-based swarming not only contributes to shed light on the minimal conditions for the evolution of a swarming behavior, but also more generally it exemplifies the effect communication can have on optimal search patterns in collective groups of individuals. PMID:27119340

  6. Emergence of Swarming Behavior: Foraging Agents Evolve Collective Motion Based on Signaling.

    PubMed

    Witkowski, Olaf; Ikegami, Takashi

    2016-01-01

    Swarming behavior is common in biology, from cell colonies to insect swarms and bird flocks. However, the conditions leading to the emergence of such behavior are still subject to research. Since Reynolds' boids, many artificial models have reproduced swarming behavior, focusing on details ranging from obstacle avoidance to the introduction of fixed leaders. This paper presents a model of evolved artificial agents, able to develop swarming using only their ability to listen to each other's signals. The model simulates a population of agents looking for a vital resource they cannot directly detect, in a 3D environment. Instead of a centralized algorithm, each agent is controlled by an artificial neural network, whose weights are encoded in a genotype and adapted by an original asynchronous genetic algorithm. The results demonstrate that agents progressively evolve the ability to use the information exchanged between each other via signaling to establish temporary leader-follower relations. These relations allow agents to form swarming patterns, emerging as a transient behavior that improves the agents' ability to forage for the resource. Once they have acquired the ability to swarm, the individuals are able to outperform the non-swarmers at finding the resource. The population hence reaches a neutral evolutionary space which leads to a genetic drift of the genotypes. This reductionist approach to signal-based swarming not only contributes to shed light on the minimal conditions for the evolution of a swarming behavior, but also more generally it exemplifies the effect communication can have on optimal search patterns in collective groups of individuals.

  7. Disentangling random thermal motion of particles and collective expansion of source from transverse momentum spectra in high energy collisions

    NASA Astrophysics Data System (ADS)

    Wei, Hua-Rong; Liu, Fu-Hu; Lacey, Roy A.

    2016-12-01

    In the framework of a multisource thermal model, we describe experimental results of the transverse momentum spectra of final-state light flavor particles produced in gold-gold (Au-Au), copper-copper (Cu-Cu), lead-lead (Pb-Pb), proton-lead (p-Pb), and proton-proton (p -p) collisions at various energies, measured by the PHENIX, STAR, ALICE, and CMS Collaborations, by using the Tsallis-standard (Tsallis form of Fermi-Dirac or Bose-Einstein), Tsallis, and two- or three-component standard distributions which can be in fact regarded as different types of ‘thermometers’ or ‘thermometric scales’ and ‘speedometers’. A central parameter in the three distributions is the effective temperature which contains information on the kinetic freeze-out temperature of the emitting source and reflects the effects of random thermal motion of particles as well as collective expansion of the source. To disentangle both effects, we extract the kinetic freeze-out temperature from the intercept of the effective temperature (T) curve as a function of particle’s rest mass (m 0) when plotting T versus m 0, and the mean transverse flow velocity from the slope of the mean transverse momentum (< {p}T> ) curve as a function of mean moving mass (\\overline{m}) when plotting < {p}T> versus \\overline{m}.

  8. Visual and motion cueing in helicopter simulation

    NASA Technical Reports Server (NTRS)

    Bray, R. S.

    1985-01-01

    Early experience in fixed-cockpit simulators, with limited field of view, demonstrated the basic difficulties of simulating helicopter flight at the level of subjective fidelity required for confident evaluation of vehicle characteristics. More recent programs, utilizing large-amplitude cockpit motion and a multiwindow visual-simulation system have received a much higher degree of pilot acceptance. However, none of these simulations has presented critical visual-flight tasks that have been accepted by the pilots as the full equivalent of flight. In this paper, the visual cues presented in the simulator are compared with those of flight in an attempt to identify deficiencies that contribute significantly to these assessments. For the low-amplitude maneuvering tasks normally associated with the hover mode, the unique motion capabilities of the Vertical Motion Simulator (VMS) at Ames Research Center permit nearly a full representation of vehicle motion. Especially appreciated in these tasks are the vertical-acceleration responses to collective control. For larger-amplitude maneuvering, motion fidelity must suffer diminution through direct attenuation through high-pass filtering washout of the computer cockpit accelerations or both. Experiments were conducted in an attempt to determine the effects of these distortions on pilot performance of height-control tasks.

  9. Normal-state conductivity in underdoped La2-xSrxCuO4 thin films: Search for nonlinear effects related to collective stripe motion

    NASA Astrophysics Data System (ADS)

    Lavrov, A. N.; Tsukada, I.; Ando, Yoichi

    2003-09-01

    We report a detailed study of the electric-field dependence of the normal-state conductivity in La2-xSrxCuO4 thin films for two concentrations of doped holes, x=0.01 and 0.06, where formation of diagonal and vertical charged stripes was recently suggested. In order to elucidate whether high electric fields are capable of depinning the charged stripes and inducing their collective motion, we have measured current-voltage characteristics for various orientations of the electric field with respect to the crystallographic axes. However, even for the highest possible fields (˜1000 V/cm for x=0.01 and ˜300 V/cm for x=0.06) we observed no nonlinear conductivity features except for those related to the conventional Joule heating of the films. Our analysis indicates that Joule heating, rather than collective electron motion, may also be responsible for the nonlinear conductivity observed in some other two-dimensional transition-metal oxides as well. We discuss that a possible reason why moderate electric fields fail to induce a collective stripe motion in layered oxides is that fairly flexible and compressible charged stripes can adjust themselves to the crystal lattice and individual impurities, which makes their pinning much stronger than in the case of conventional rigid charge-density waves.

  10. Theory of dielectric relaxation in non-crystalline solids: from a set of micromotions to the averaged collective motion in the mesoscale region

    NASA Astrophysics Data System (ADS)

    Nigmatullin, R. R.

    2005-04-01

    Based on the rather general decoupling procedure that reduces a set of micromotions to the averaged collective motion in the mesoscale region, a consistent and general theory of dielectric relaxation describing a wide set of dielectric spectroscopy (DS) data measured in a certain frequency/temperature range can be developed. The new theory explains and generalizes the Vogel-Fulcher-Tamman (VFT) equation and leads to the new type of kinetic equation, containing non-integer operators of differentiation and integration combined in the specific triads. Each triad combines three operators: the first non-integer operator has a real exponent, the other two form a pair of non-integer operators having the complex conjugate power-law exponents. This approach explains naturally the ‘universal response’ (UR) phenomenon discovered by Jonscher in a wide class of heterogeneous materials and confirms the justified data-curve fitting approach developed previously as a phenomenological tool for the analysis of raw complex permittivity data. It explains and generalizes some well-established experimental facts and contains also new predictions that can be verified in the experiment. This general approach helps to find the proper place for the DS as a science studying the different types of the ‘reduced’ collective motions and their various interactions with each other in the mesoscale region. This new theory explains also the fact why kinetic equations containing non-integer operators are realized in reality. They are necessary for description of slow collective motions which are probably realized in the intermediate range of scales not only in DS. Reology and mechanical relaxation represent also interesting and not well-understood phenomena, where the ‘fractional’ kinetics will find its proper place.

  11. Large Amplitude Oscillations of a Double Pendulum

    NASA Astrophysics Data System (ADS)

    Gerres, Jeffrey M.; Jacobs, Robert M.; Kasun, Sara F.; Bacon, Margaret E.; Nagolu, Chakravarthi M.; Owens, Erin L.; Siehl, Kevin F.; Thomsen, Marshall; Troyer, Jon S.

    2008-03-01

    The nature of the normal modes of oscillation in the small angle regime of a double pendulum is well established. However, for large amplitude oscillations, a closed form solution of the differential equations of motion does not exist. Using Lagrange formalism, we explore both the in-phase and out-of-phase normal modes of oscillation of a double pendulum as a function of the mass ratio of the two bobs and their initial angular positions. We conduct the analysis using MatLab, where we initially verify our code in the known small amplitude limit. Among our results we find that certain symmetries between the in-phase and out-of-phase normal modes that exist in the small amplitude limit are no longer present at large amplitudes.

  12. Collective motion in a fluid complex plasma induced by interaction with a slow projectile under microgravity conditions

    NASA Astrophysics Data System (ADS)

    Zhukhovitskii, Dmitry; Ivlev, Alexei; Thomas, Hubertus; Fortov, Vladimir; Lipaev, Andrey; Morfill, Gregor; Molotkov, Vladimir; Naumkin, Vadim

    Subsonic motion of a large particle (projectile) moving through the bulk of a dust crystal formed by negatively charged small particles is investigated using the PK-3 Plus laboratory onboard the International Space Station. Tracing the dust particle trajectories show that the projectile moves almost freely through the bulk of plasma crystal, while dust particles move along characteristic alpha-shaped pathways near the large particle. We develop a theory of nonviscous dust particles motion about a projectile and calculate particle trajectories. The deformation of a cavity around a subsonic projectile in the cloud of small dust particles is investigated with due regard for friction between the dust particles and atoms of neutral gas. The pressure of a dust cloud at the surface of a cavity around the projectile can become negative, which entails the emergence of a considerable asymmetry of the cavity, i.e., the cavity deformation. Corresponding threshold velocity is calculated, which is found to decrease with increasing cavity size. Developed theory makes it possible to estimate the static pressure of dust particles in a cloud on the basis of experimental data. A good agreement with experiment validates our approach.

  13. PULSE AMPLITUDE ANALYZER

    DOEpatents

    Greenblatt, M.H.

    1958-03-25

    This patent pertains to pulse amplitude analyzers for sorting and counting a serles of pulses, and specifically discloses an analyzer which ls simple in construction and presents the puise height distribution visually on an oscilloscope screen. According to the invention, the pulses are applied to the vertical deflection plates of an oscilloscope and trigger the horizontal sweep. Each pulse starts at the same point on the screen and has a maximum amplitude substantially along the same vertical line. A mask is placed over the screen except for a slot running along the line where the maximum amplitudes of the pulses appear. After the slot has been scanned by a photocell in combination with a slotted rotating disk, the photocell signal is displayed on an auxiliary oscilloscope as vertical deflection along a horizontal time base to portray the pulse amplitude distribution.

  14. Real topological string amplitudes

    NASA Astrophysics Data System (ADS)

    Narain, K. S.; Piazzalunga, N.; Tanzini, A.

    2017-03-01

    We discuss the physical superstring correlation functions in type I theory (or equivalently type II with orientifold) that compute real topological string amplitudes. We consider the correlator corresponding to holomorphic derivative of the real topological amplitude G_{χ } , at fixed worldsheet Euler characteristic χ. This corresponds in the low-energy effective action to N=2 Weyl multiplet, appropriately reduced to the orientifold invariant part, and raised to the power g' = -χ + 1. We show that the physical string correlator gives precisely the holomorphic derivative of topological amplitude. Finally, we apply this method to the standard closed oriented case as well, and prove a similar statement for the topological amplitude F_g.

  15. Data Collection and Analysis Using Wearable Sensors for Monitoring Knee Range of Motion after Total Knee Arthroplasty

    PubMed Central

    Chiang, Chih-Yen; Chen, Kun-Hui; Liu, Kai-Chun; Hsu, Steen Jun-Ping; Chan, Chia-Tai

    2017-01-01

    Total knee arthroplasty (TKA) is the most common treatment for degenerative osteoarthritis of that articulation. However, either in rehabilitation clinics or in hospital wards, the knee range of motion (ROM) can currently only be assessed using a goniometer. In order to provide continuous and objective measurements of knee ROM, we propose the use of wearable inertial sensors to record the knee ROM during the recovery progress. Digitalized and objective data can assist the surgeons to control the recovery status and flexibly adjust rehabilitation programs during the early acute inpatient stage. The more knee flexion ROM regained during the early inpatient period, the better the long-term knee recovery will be and the sooner early discharge can be achieved. The results of this work show that the proposed wearable sensor approach can provide an alternative for continuous monitoring and objective assessment of knee ROM recovery progress for TKA patients compared to the traditional goniometer measurements. PMID:28241434

  16. Role of string-like collective atomic motion on diffusion and structural relaxation in glass forming Cu-Zr alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Zhong, Cheng; Douglas, Jack F.; Wang, Xiaodong; Cao, Qingping; Zhang, Dongxian; Jiang, Jian-Zhong

    2015-04-01

    We investigate Cu-Zr liquid alloys using molecular dynamics simulation and well-accepted embedded atom method potentials over a wide range of chemical composition and temperature as model metallic glass-forming (GF) liquids. As with other types of GF materials, the dynamics of these complex liquids are characterized by "dynamic heterogeneity" in the form of transient polymeric clusters of highly mobile atoms that are composed in turn of atomic clusters exhibiting string-like cooperative motion. In accordance with the string model of relaxation, an extension of the Adam-Gibbs (AG) model, changes in the activation free energy ΔGa with temperature of both the Cu and Zr diffusion coefficients D, and the alpha structural relaxation time τα can be described to a good approximation by changes in the average string length, L. In particular, we confirm that the strings are a concrete realization of the abstract "cooperatively rearranging regions" of AG. We also find coexisting clusters of relatively "immobile" atoms that exhibit predominantly icosahedral local packing rather than the low symmetry packing of "mobile" atoms. These two distinct types of dynamic heterogeneity are then associated with different fluid structural states. Glass-forming liquids are thus analogous to polycrystalline materials where the icosahedrally packed regions correspond to crystal grains, and the strings reside in the relatively disordered grain boundary-like regions exterior to these locally well-ordered regions. A dynamic equilibrium between localized ("immobile") and wandering ("mobile") particles exists in the liquid so that the dynamic heterogeneity can be considered to be type of self-assembly process. We also characterize changes in the local atomic free volume in the course of string-like atomic motion to better understand the initiation and propagation of these fluid excitations.

  17. Role of string-like collective atomic motion on diffusion and structural relaxation in glass forming Cu-Zr alloys.

    PubMed

    Zhang, Hao; Zhong, Cheng; Douglas, Jack F; Wang, Xiaodong; Cao, Qingping; Zhang, Dongxian; Jiang, Jian-Zhong

    2015-04-28

    We investigate Cu-Zr liquid alloys using molecular dynamics simulation and well-accepted embedded atom method potentials over a wide range of chemical composition and temperature as model metallic glass-forming (GF) liquids. As with other types of GF materials, the dynamics of these complex liquids are characterized by "dynamic heterogeneity" in the form of transient polymeric clusters of highly mobile atoms that are composed in turn of atomic clusters exhibiting string-like cooperative motion. In accordance with the string model of relaxation, an extension of the Adam-Gibbs (AG) model, changes in the activation free energy ΔGa with temperature of both the Cu and Zr diffusion coefficients D, and the alpha structural relaxation time τα can be described to a good approximation by changes in the average string length, L. In particular, we confirm that the strings are a concrete realization of the abstract "cooperatively rearranging regions" of AG. We also find coexisting clusters of relatively "immobile" atoms that exhibit predominantly icosahedral local packing rather than the low symmetry packing of "mobile" atoms. These two distinct types of dynamic heterogeneity are then associated with different fluid structural states. Glass-forming liquids are thus analogous to polycrystalline materials where the icosahedrally packed regions correspond to crystal grains, and the strings reside in the relatively disordered grain boundary-like regions exterior to these locally well-ordered regions. A dynamic equilibrium between localized ("immobile") and wandering ("mobile") particles exists in the liquid so that the dynamic heterogeneity can be considered to be type of self-assembly process. We also characterize changes in the local atomic free volume in the course of string-like atomic motion to better understand the initiation and propagation of these fluid excitations.

  18. Role of string-like collective atomic motion on diffusion and structural relaxation in glass forming Cu-Zr alloys

    SciTech Connect

    Zhang, Hao; Zhong, Cheng; Wang, Xiaodong; Cao, Qingping; Jiang, Jian-Zhong E-mail: jack.douglas@nist.gov; Douglas, Jack F. E-mail: jack.douglas@nist.gov; Zhang, Dongxian

    2015-04-28

    We investigate Cu-Zr liquid alloys using molecular dynamics simulation and well-accepted embedded atom method potentials over a wide range of chemical composition and temperature as model metallic glass-forming (GF) liquids. As with other types of GF materials, the dynamics of these complex liquids are characterized by “dynamic heterogeneity” in the form of transient polymeric clusters of highly mobile atoms that are composed in turn of atomic clusters exhibiting string-like cooperative motion. In accordance with the string model of relaxation, an extension of the Adam-Gibbs (AG) model, changes in the activation free energy ΔG{sub a} with temperature of both the Cu and Zr diffusion coefficients D, and the alpha structural relaxation time τ{sub α} can be described to a good approximation by changes in the average string length, L. In particular, we confirm that the strings are a concrete realization of the abstract “cooperatively rearranging regions” of AG. We also find coexisting clusters of relatively “immobile” atoms that exhibit predominantly icosahedral local packing rather than the low symmetry packing of “mobile” atoms. These two distinct types of dynamic heterogeneity are then associated with different fluid structural states. Glass-forming liquids are thus analogous to polycrystalline materials where the icosahedrally packed regions correspond to crystal grains, and the strings reside in the relatively disordered grain boundary-like regions exterior to these locally well-ordered regions. A dynamic equilibrium between localized (“immobile”) and wandering (“mobile”) particles exists in the liquid so that the dynamic heterogeneity can be considered to be type of self-assembly process. We also characterize changes in the local atomic free volume in the course of string-like atomic motion to better understand the initiation and propagation of these fluid excitations.

  19. Collective responses of a large mackerel school depend on the size and speed of a robotic fish but not on tail motion.

    PubMed

    Kruusmaa, Maarja; Rieucau, Guillaume; Montoya, José Carlos Castillo; Markna, Riho; Handegard, Nils Olav

    2016-10-06

    So far, actuated fish models have been used to study animal interactions in small-scale controlled experiments. This study, conducted in a semi-controlled setting, investigates robot(5) interactions with a large wild-caught marine fish school (∼3000 individuals) in their natural social environment. Two towed fish robots were used to decouple size, tail motion and speed in a series of sea-cage experiments. Using high-resolution imaging sonar and sonar-video blind scoring, we monitored and classified the school's collective reaction towards the fish robots as attraction or avoidance. We found that two key releasers-the size and the speed of the robotic fish-were responsible for triggering either evasive reactions or following responses. At the same time, we found fish reactions to the tail motion to be insignificant. The fish evaded a fast-moving robot even if it was small. However, mackerels following propensity was greater towards a slow small robot. When moving slowly, the larger robot triggered significantly more avoidance responses than a small robot. Our results suggest that the collective responses of a large school exposed to a robotic fish could be manipulated by tuning two principal releasers-size and speed. These results can help to design experimental methods for in situ observations of wild fish schools or to develop underwater robots for guiding and interacting with free-ranging aggregated aquatic organisms.

  20. Collective cargo hauling by a bundle of parallel microtubules: bi-directional motion caused by load-dependent polymerization and depolymerization

    NASA Astrophysics Data System (ADS)

    Ghanti, Dipanwita; Chowdhury, Debashish

    2015-01-01

    A microtubule (MT) is a hollow tube of approximately 25 nm diameter. The two ends of the tube are dissimilar and are designated as ‘plus’ and ‘minus’ ends. Motivated by the collective push and pull exerted by a bundle of MTs during chromosome segregation in a living cell, we have developed here a much simplified theoretical model of a bundle of parallel dynamic MTs. The plus-end of all the MTs in the bundle is permanently attached to a movable ‘wall’ by a device whose detailed structure is not treated explicitly in our model. The only requirement is that the device allows polymerization and depolymerization of each MT at the plus-end. In spite of the absence of external force and direct lateral interactions between the MTs, the group of polymerizing MTs attached to the wall create a load force against the group of depolymerizing MTs and vice versa; the load against a group is shared equally by the members of that group. Such indirect interactions among the MTs give rise to the rich variety of possible states of collective dynamics that we have identified by computer simulations of the model in different parameter regimes. The bi-directional motion of the cargo, caused by the load-dependence of the polymerization kinetics, is a ‘proof-of-principle’ that the bi-directional motion of chromosomes before cell division does not necessarily need active participation of motor proteins.

  1. Coherent quantum states from classical oscillator amplitudes

    NASA Astrophysics Data System (ADS)

    Briggs, John S.; Eisfeld, Alexander

    2012-05-01

    In the first days of quantum mechanics Dirac pointed out an analogy between the time-dependent coefficients of an expansion of the Schrödinger equation and the classical position and momentum variables solving Hamilton's equations. Here it is shown that the analogy can be made an equivalence in that, in principle, systems of classical oscillators can be constructed whose position and momenta variables form time-dependent amplitudes which are identical to the complex quantum amplitudes of the coupled wave function of an N-level quantum system with real coupling matrix elements. Hence classical motion can reproduce quantum coherence.

  2. 78 FR 17701 - Agency Information Collection Activities: Notice of Appeal or Motion, Form I-290B; Revision of a...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-22

    ... SECURITY U.S. Citizenship and Immigration Services Agency Information Collection Activities: Notice of...: The Department of Homeland Security (DHS), U.S. Citizenship and Immigration Services (USCIS) invites....S. Citizenship and Immigration Services. (4) Affected public who will be asked or required...

  3. Mass of nonrelativistic meson from leading twist distribution amplitudes

    NASA Astrophysics Data System (ADS)

    Braguta, V. V.

    2011-01-01

    In this paper distribution amplitudes of pseudoscalar and vector nonrelativistic mesons are considered. Using equations of motion for the distribution amplitudes, relations are derived which allow one to calculate the masses of nonrelativistic pseudoscalar and vector meson if the leading twist distribution amplitudes are known. These relations can be also rewritten as relations between the masses of nonrelativistic mesons and infinite series of QCD operators, what can be considered as an exact version of Gremm-Kapustin relation in NRQCD.

  4. Protostring scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Thorn, Charles B.

    2016-11-01

    We calculate some tree-level scattering amplitudes for a generalization of the protostring, which is a novel string model implied by the simplest string bit models. These bit models produce a light-cone world sheet which supports s integer moded Grassmann fields. In the generalization we supplement this Grassmann world-sheet system with d =24 -s transverse coordinate world-sheet fields. The protostring corresponds to s =24 and the bosonic string to s =0 . The interaction vertex is a simple overlap with no operator insertions at the break/join point. Assuming that s is even we calculate the multistring scattering amplitudes by bosonizing the Grassmann fields, each pair equivalent to one compactified bosonic field, and applying Mandelstam's interacting string formalism to a system of s /2 compactified and d uncompactified bosonic world-sheet fields. We obtain all amplitudes for open strings with no oscillator excitations and for closed strings with no oscillator excitations and zero winding number. We then study in detail some simple special cases. Multistring processes with maximal helicity violation have much simpler amplitudes. We also specialize to general four-string amplitudes and discuss their high energy behavior. Most of these models are not covariant under the full Lorentz group O (d +1 ,1 ). The exceptions are the bosonic string whose Lorentz group is O (25 ,1 ) and the protostring whose Lorentz group is O (1 ,1 ). The models in between only enjoy an O (1 ,1 )×O (d ) spacetime symmetry.

  5. Oscillations of a Simple Pendulum with Extremely Large Amplitudes

    ERIC Educational Resources Information Center

    Butikov, Eugene I.

    2012-01-01

    Large oscillations of a simple rigid pendulum with amplitudes close to 180[degrees] are treated on the basis of a physically justified approach in which the cycle of oscillation is divided into several stages. The major part of the almost closed circular path of the pendulum is approximated by the limiting motion, while the motion in the vicinity…

  6. Amplitudes of Field Theories

    SciTech Connect

    Feng Bo

    2007-11-20

    In this talk, we will present recent progresses in perturbative calculations of scattering amplitudes at tree and one-loop levels. At tree level, we will discuss MHV-diagram method and on-shell recursion relation. At one-loop level, we will establish the framework of Unitarity cut method.

  7. Reinforcing Saccadic Amplitude Variability

    ERIC Educational Resources Information Center

    Paeye, Celine; Madelain, Laurent

    2011-01-01

    Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we…

  8. Planar amplitude ammonia sensor

    NASA Astrophysics Data System (ADS)

    Karasinski, Pawel; Rogozinski, Roman

    2004-09-01

    The paper presents the results of investigation involving the influence of the change of launching conditions on the characteristics of amplitude ammonia sensors produced with the application of strip waveguides of different refractive profiles. Strip waveguides were produced using ion exchange technique, and the absorption sensitive films were produced using sol-gel technology.

  9. Movement amplitude and tempo change in piano performance

    NASA Astrophysics Data System (ADS)

    Palmer, Caroline

    2004-05-01

    Music performance places stringent temporal and cognitive demands on individuals that should yield large speed/accuracy tradeoffs. Skilled piano performance, however, shows consistently high accuracy across a wide variety of rates. Movement amplitude may affect the speed/accuracy tradeoff, so that high accuracy can be obtained even at very fast tempi. The contribution of movement amplitude changes in rate (tempo) is investigated with motion capture. Cameras recorded pianists with passive markers on hands and fingers, who performed on an electronic (MIDI) keyboard. Pianists performed short melodies at faster and faster tempi until they made errors (altering the speed/accuracy function). Variability of finger movements in the three motion planes indicated most change in the plane perpendicular to the keyboard across tempi. Surprisingly, peak amplitudes of motion before striking the keys increased as tempo increased. Increased movement amplitudes at faster rates may reduce or compensate for speed/accuracy tradeoffs. [Work supported by Canada Research Chairs program, HIMH R01 45764.

  10. Collective motion in fully reconstructed gold on gold collisions between 2 and 8 GeV per nucleon

    NASA Astrophysics Data System (ADS)

    Liu, Heng

    Quark Gluon Plasma (QGP), is believed to have been formed at an early stage of the universe, about 10-6 sec after the Big Bang. QGP is a state of matter in which the quarks are deconfined and can move freely in the sea of gluons. According to the theory of quantum chromodynamics (QCD), conditions for a phase transition to QGP are reached at a critical temperature Tc /approx 150 MeV, or a critical energy density ɛc = 2 - 3 GeV/fm3 (roughly 10 times that of the nuclear ground state). These conditions might be achieved when two nuclei collide at relativistic energies where we expect deposition of energy in the overlap region is more than sufficient for ɛc to be exceeded. To create a QGP in the laboratory environment and to explore its properties is currently the most visible goal of relativistic heavy-ion physics. The E895 experiment was conducted at the Alternating Gradient Synchrotron accelerator at Brookhaven National Laboratory with the state-of-the-art EOS Time Projection Chamber (TPC) which effectively imaged the trajectories of charged fragments emerging from each collision in a three-dimensional array of 2+ million pixels. The TPC was located inside a large aperture dipole magnet with a field of 0.75 or 1 T. The TPC provided nearly 4π solid angle acceptance and particle identification via energy loss measurement. During January 1996 and November 1996, high statistics Au beam data were recorded at four beam energies: 2, 4, 6 and 8 GeV/nucleon. The 2-8 GeV/nucleon energy range is one of only two regions between a few MeV/nucleon and 160 GeV/nucleon where heavy-ion collisions are still largely unexplored. Collective effects observed at both higher and lower beam energies suggest that a measurable sideward flow signal (a type of first moment of fragment momenta with respect to the event reaction plane) should be observed in this experiment. Hydrodynamic and transport models indicate that collective effects are sensitive to various features of the nuclear

  11. Steric interactions lead to collective tilting motion in the ribosome during mRNA–tRNA translocation

    PubMed Central

    Nguyen, Kien; Whitford, Paul C.

    2016-01-01

    Translocation of mRNA and tRNA through the ribosome is associated with large-scale rearrangements of the head domain in the 30S ribosomal subunit. To elucidate the relationship between 30S head dynamics and mRNA–tRNA displacement, we apply molecular dynamics simulations using an all-atom structure-based model. Here we provide a statistical analysis of 250 spontaneous transitions between the A/P–P/E and P/P–E/E ensembles. Consistent with structural studies, the ribosome samples a chimeric ap/P–pe/E intermediate, where the 30S head is rotated ∼18°. It then transiently populates a previously unreported intermediate ensemble, which is characterized by a ∼10° tilt of the head. To identify the origins of head tilting, we analyse 781 additional simulations in which specific steric features are perturbed. These calculations show that head tilting may be attributed to specific steric interactions between tRNA and the 30S subunit (PE loop and protein S13). Taken together, this study demonstrates how molecular structure can give rise to large-scale collective rearrangements. PMID:26838673

  12. Effects of Motion Sickness Severity on the Vestibular-Evoked Myogenic Potentials

    PubMed Central

    Fowler, Cynthia G.; Sweet, Amanda; Steffel, Emily

    2015-01-01

    Background Motion sickness is a common debilitating condition associated with both actual and perceived motion. Despite the commonality, little is known about the underlying physiological mechanisms. One theory proposes that motion sickness arises from a mismatch between reality and past experience in vertical motions. Physiological tests of the vestibular system, however, have been inconclusive regarding the underlying pathogenesis. Cervical vestibular-evoked myogenic potentials (cVEMPs) arise from the saccule, which responds to vertical motion. If vertical motion elicits motion sickness, the cVEMP should be affected. Purpose The purpose of this investigation was to determine if cVEMP characteristics differ among individuals with a range of motion sickness susceptibility from negligible to severe. The hypothesis was that individuals with high susceptibility would have larger cVEMP amplitudes and shorter cVEMP latencies relative to those who are resistant to motion sickness. Research Design The study had two parts. The first was quasi-experimental in which participants comprised three groups based on susceptibility to motion sickness (low, mild-moderate, high) as identified on the short version of the Motion Sickness Susceptibility Questionnaire (MSSQ-S). The second part of the study was correlational and evaluated the specific relationships between the degree of motion sickness susceptibility and characteristics of the VEMPs. Study Sample A total of 24 healthy young adults (ages 20–24 yr) were recruited from the university and the community without regard to motion sickness severity. Data Collection and Analysis Participants took the MSSQ-S, which quantifies susceptibility to motion sickness. The participants had a range of motion sickness susceptibility with MSSQ raw scores from 0.0–36.6, which correspond to percent susceptibility from 0.0–99.3%. VEMPs were elicited by 500 Hz tone-bursts monaurally in both ears at 120 dB pSPL. MSSQ-S percent scores were

  13. Weak boson production amplitude zeros; equalities of the helicity amplitudes

    NASA Astrophysics Data System (ADS)

    Mamedov, Fizuli

    2002-08-01

    We investigate the radiation amplitude zeros exhibited by many standard model amplitudes for triple weak gauge boson production processes. We show that WZγ production amplitudes have an especially rich structure in terms of zeros; these amplitudes have zeros originating from several different sources. It is also shown that the type-I current null zone is the special case of the equality of the specific helicity amplitudes.

  14. Syzygies probing scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Liu, Junyu; Xie, Ruofei; Zhang, Hao; Zhou, Yehao

    2016-09-01

    We propose a new efficient algorithm to obtain the locally minimal generating set of the syzygies for an ideal, i.e. a generating set whose proper subsets cannot be generating sets. Syzygy is a concept widely used in the current study of scattering amplitudes. This new algorithm can deal with more syzygies effectively because a new generation of syzygies is obtained in each step and the irreducibility of this generation is also verified in the process. This efficient algorithm can also be applied in getting the syzygies for the modules. We also show a typical example to illustrate the potential application of this method in scattering amplitudes, especially the Integral-By-Part(IBP) relations of the characteristic two-loop diagrams in the Yang-Mills theory.

  15. Amplitude Modulator Chassis

    SciTech Connect

    Erbert, G

    2009-09-01

    The Amplitude Modulator Chassis (AMC) is the final component in the MOR system and connects directly to the PAM input through a 100-meter fiber. The 48 AMCs temporally shape the 48 outputs of the MOR using an arbitrary waveform generator coupled to an amplitude modulator. The amplitude modulation element is a two stage, Lithium Niobate waveguide device, where the intensity of the light passing through the device is a function of the electrical drive applied. The first stage of the modulator is connected to a programmable high performance Arbitrary Waveform Generator (AWG) consisting of 140 impulse generators space 250 ps apart. An arbitrary waveform is generated by independently varying the amplitude of each impulse generator and then summing the impulses together. In addition to the AWG a short pulse generator is also connected to the first stage of the modulator to provide a sub 100-ps pulse used for timing experiments. The second stage of the modulator is connect to a square pulse generator used to further attenuate any pre or post pulse light passing through the first stage of the modulator. The fast rise and fall time of the square pulse generator is also used to produce fast rise and fall times of the AWG by clipping the AWG pulse. For maximum extinction, a pulse bias voltage is applied to each stage of the modulator. A pulse voltage is applied as opposed to a DC voltage to prevent charge buildup on the modulator. Each bias voltage is adjustable to provide a minimum of 50-dB extinction. The AMC is controlled through ICCS to generate the desired temporal pulse shape. This process involves a closed-loop control algorithm, which compares the desired temporal waveform to the produced optical pulse, and iterates the programming of the AWG until the two waveforms agree within an allowable tolerance.

  16. PULSE AMPLITUDE ANALYZER

    DOEpatents

    Gray, G.W.; Jensen, A.S.

    1957-10-22

    A pulse-height analyzer system of improved design for sorting and counting a series of pulses, such as provided by a scintillation detector in nuclear radiation measurements, is described. The analyzer comprises a main transmission line, a cathode-ray tube for each section of the line with its deflection plates acting as the line capacitance; means to bias the respective cathode ray tubes so that the beam strikes a target only when a prearranged pulse amplitude is applied, with each tube progressively biased to respond to smaller amplitudes; pulse generating and counting means associated with each tube to respond when the beam is deflected; a control transmission line having the same time constant as the first line per section with pulse generating means for each tube for initiating a pulse on the second transmission line when a pulse triggers the tube of corresponding amplitude response, the former pulse acting to prevent successive tubes from responding to the pulse under test. This arrangement permits greater deflection sensitivity in the cathode ray tube and overcomes many of the disadvantages of prior art pulse-height analyzer circuits.

  17. Amplitudes of Spiral Perturbations

    NASA Astrophysics Data System (ADS)

    Grosbol, P.; Patsis, P. A.

    2014-03-01

    It has proven very difficult to estimate the amplitudes of spiral perturbations in disk galaxies from observations due to the variation of mass-to-light ratio and extinction across spiral arms. Deep, near-infrared images of grand-design spiral galaxies obtained with HAWK-I/VLT were used to analyze the azimuthal amplitude and shape of arms, which, even in the K-band may, be significantly biased by the presence of young stellar populations. Several techniques were applied to evaluate the relative importance of young stars across the arms, such as surface brightness of the disk with light from clusters subtracted, number density of clusters detected, and texture of the disk. The modulation of the texture measurement, which correlates with the number density of faint clusters, yields amplitudes of the spiral perturbation in the range 0.1-0.2. This estimate gives a better estimate of the mass perturbation in the spiral arms, since it is dominated by old clusters.

  18. A demonstration of motion base design alternatives for the National Advanced Driving Simulator

    NASA Technical Reports Server (NTRS)

    Mccauley, Michael E.; Sharkey, Thomas J.; Sinacori, John B.; Laforce, Soren; Miller, James C.; Cook, Anthony

    1992-01-01

    A demonstration of the capability of NASA's Vertical Motion Simulator to simulate two alternative motion base designs for the National Advanced Driving simulator (NADS) is reported. The VMS is located at ARC. The motion base conditions used in this demonstration were as follows: (1) a large translational motion base; and (2) a motion base design with limited translational capability. The latter had translational capability representative of a typical synergistic motion platform. These alternatives were selected to test the prediction that large amplitude translational motion would result in a lower incidence or severity of simulator induced sickness (SIS) than would a limited translational motion base. A total of 10 drivers performed two tasks, slaloms and quick-stops, using each of the motion bases. Physiological, objective, and subjective measures were collected. No reliable differences in SIS between the motion base conditions was found in this demonstration. However, in light of the cost considerations and engineering challenges associated with implementing a large translation motion base, performance of a formal study is recommended.

  19. PULSE AMPLITUDE DISTRIBUTION RECORDER

    DOEpatents

    Cowper, G.

    1958-08-12

    A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.

  20. Adaptation to real motion reveals direction-selective interactions between real and implied motion processing.

    PubMed

    Lorteije, Jeannette A M; Kenemans, J Leon; Jellema, Tjeerd; van der Lubbe, Rob H J; Lommers, Marjolein W; van Wezel, Richard J A

    2007-08-01

    Viewing static pictures of running humans evokes neural activity in the dorsal motion-sensitive cortex. To establish whether this response arises from direction-selective neurons that are also involved in real motion processing, we measured the visually evoked potential to implied motion following adaptation to static or moving random dot patterns. The implied motion response was defined as the difference between evoked potentials to pictures with and without implied motion. Interaction between real and implied motion was found as a modulation of this difference response by the preceding motion adaptation. The amplitude of the implied motion response was significantly reduced after adaptation to motion in the same direction as the implied motion, compared to motion in the opposite direction. At 280 msec after stimulus onset, the average difference in amplitude reduction between opposite and same adapted direction was 0.5 muV on an average implied motion amplitude of 2.0 muV. These results indicate that the response to implied motion arises from direction-selective motion-sensitive neurons. This is consistent with interactions between real and implied motion processing at a neuronal level.

  1. Coupling of Large Amplitude Inversion with Other States

    NASA Astrophysics Data System (ADS)

    Pearson, John; Yu, Shanshan

    2016-06-01

    The coupling of a large amplitude motion with a small amplitude vibration remains one of the least well characterized problems in molecular physics. Molecular inversion poses a few unique and not intuitively obvious challenges to the large amplitude motion problem. In spite of several decades of theoretical work numerous challenges in calculation of transition frequencies and more importantly intensities persist. The most challenging aspect of this problem is that the inversion coordinate is a unique function of the overall vibrational state including both the large and small amplitude modes. As a result, the r-axis system and the meaning of the K-quantum number in the rotational basis set are unique to each vibrational state of large or small amplitude motion. This unfortunate reality has profound consequences to calculation of intensities and the coupling of nearly degenerate vibrational states. The case of NH3 inversion and inversion through a plane of symmetry in alcohols will be examined to find a general path forward.

  2. Chaotic ion motion in magnetosonic plasma waves

    NASA Technical Reports Server (NTRS)

    Varvoglis, H.

    1984-01-01

    The motion of test ions in a magnetosonic plasma wave is considered, and the 'stochasticity threshold' of the wave's amplitude for the onset of chaotic motion is estimated. It is shown that for wave amplitudes above the stochasticity threshold, the evolution of an ion distribution can be described by a diffusion equation with a diffusion coefficient D approximately equal to 1/v. Possible applications of this process to ion acceleration in flares and ion beam thermalization are discussed.

  3. Measurement, characterization, and prediction of strong ground motion

    USGS Publications Warehouse

    Joyner, William; Boore, David M.

    1988-01-01

    A number of predictive relationships derived from regression analysis of strong-motion data are available for horizontal peak acceleration, velocity, and response spectral values. Theoretical prediction of ground motion calls for stochastic source models because source heterogeneities control the amplitude of ground motion at most, if not all, frequencies of engineering interest. Theoretical methods have been developed for estimation of ground-motion parameters and simulation of ground-motion time series. These methods are particularly helpful for regions such, as eastern North America where strong-motion data are sparse. The authors survey the field, first reviewing developments in ground-motion measurement and data processing. The authors then consider the choice of parameters for characterizing strong ground motion and describe the wave-types involved in strong ground motion and the factors affecting ground-motion amplitudes. They conclude by describing methods for predicting ground motion.

  4. Plate motion

    SciTech Connect

    Gordon, R.G. )

    1991-01-01

    The motion of tectonic plates on the earth is characterized in a critical review of U.S. research from the period 1987-1990. Topics addressed include the NUVEL-1 global model of current plate motions, diffuse plate boundaries and the oceanic lithosphere, the relation between plate motions and distributed deformations, accelerations and the steadiness of plate motions, the distribution of current Pacific-North America motion across western North America and its margin, plate reconstructions and their uncertainties, hotspots, and plate dynamics. A comprehensive bibliography is provided. 126 refs.

  5. CHY formula and MHV amplitudes

    NASA Astrophysics Data System (ADS)

    Du, Yi-Jian; Teng, Fei; Wu, Yong-Shi

    2016-05-01

    In this paper, we study the relation between the Cachazo-He-Yuan (CHY) formula and the maximal-helicity-violating (MHV) amplitudes of Yang-Mills and gravity in four dimensions. We prove that only one special rational solution of the scattering equations found by Weinzierl supports the MHV amplitudes. Namely, localized at this solution, the integrated CHY formula produces the Parke-Taylor formula for MHV Yang-Mills amplitudes as well as the Hodges formula for MHV gravitational amplitudes, with an arbitrary number of external gluons/gravitons. This is achieved by developing techniques, in a manifestly Möbius covariant formalism, to explicitly compute relevant reduced Pfaffians/determinants. We observe and prove two interesting properties (or identities), which facilitate the computations. We also check that all the other ( n - 3)! - 1 solutions to the scattering equations do not support the MHV amplitudes, and prove analytically that this is indeed true for the other special rational solution proposed by Weinzierl, that actually supports the anti-MHV amplitudes. Our results reveal a mysterious feature of the CHY formalism that in Yang-Mills and gravity theory, solutions of scattering equations, involving only external momenta, somehow know about the configuration of external polarizations of the scattering amplitudes.

  6. Off-shell CHY amplitudes

    NASA Astrophysics Data System (ADS)

    Lam, C. S.; Yao, York-Peng

    2016-06-01

    The Cachazo-He-Yuan (CHY) formula for on-shell scattering amplitudes is extended off-shell. The off-shell amplitudes (amputated Green's functions) are Möbius invariant, and have the same momentum poles as the on-shell amplitudes. The working principles which drive the modifications to the scattering equations are mainly Möbius covariance and energy momentum conservation in off-shell kinematics. The same technique is also used to obtain off-shell massive scalars. A simple off-shell extension of the CHY gauge formula which is Möbius invariant is proposed, but its true nature awaits further study.

  7. Small amplitude quasibreathers and oscillons

    SciTech Connect

    Fodor, Gyula; Lukacs, Arpad; Forgacs, Peter; Horvath, Zalan

    2008-07-15

    Quasibreathers (QB) are time-periodic solutions with weak spatial localization introduced in G. Fodor et al. in [Phys. Rev. D 74, 124003 (2006)]. QB's provide a simple description of oscillons (very long-living spatially localized time dependent solutions). The small amplitude limit of QB's is worked out in a large class of scalar theories with a general self-interaction potential, in D spatial dimensions. It is shown that the problem of small amplitude QB's is reduced to a universal elliptic partial differential equation. It is also found that there is the critical dimension, D{sub crit}=4, above which no small amplitude QB's exist. The QB's obtained this way are shown to provide very good initial data for oscillons. Thus these QB's provide the solution of the complicated, nonlinear time dependent problem of small amplitude oscillons in scalar theories.

  8. Motion compensation and noise tolerance in phase-shifting digital in-line holography.

    PubMed

    Stenner, Michael D; Neifeld, Mark A

    2006-05-15

    We present a technique for phase-shifting digital in-line holography which compensates for lateral object motion. By collecting two frames of interference between object and reference fields with identical reference phase, one can estimate the lateral motion that occurred between frames using the cross-correlation. We also describe a very general linear framework for phase-shifting holographic reconstruction which minimizes additive white Gaussian noise (AWGN) for an arbitrary set of reference field amplitudes and phases. We analyze the technique's sensitivity to noise (AWGN, quantization, and shot), errors in the reference fields, errors in motion estimation, resolution, and depth of field. We also present experimental motion-compensated images achieving the expected resolution.

  9. Tempo and amplitude in growth.

    PubMed

    Hermanussen, Michael

    2011-01-01

    Growth is defined as an increase of size over time with time usually defined as physical time. Yet, the rigid metric of physical time is not directly relevant to the internal dynamics of growth. Growth is linked to maturation. Children and adolescents differ in the tempo at which they mature. One calendar year differs in its meaning in a fast maturing, and in a slow maturing child. The slow child needs more calendar years for completing the same stage of maturity. Many characteristics in the human growth curve are tempo characteristics. Tempo - being fast or slow maturing - has to be carefully separated from amplitude - being tall or short. Several characteristic phenomena such as catch-up growth after periods of illness and starvation are largely tempo phenomena, and do usually not affect the amplitude component of growth. Applying Functional Data Analysis and Principal Component Analysis, the two main sources of height variance: tempo and amplitude can statistically be separate and quantified. Tempo appears to be more sensitive than amplitude to nutrition, health and environmental stress. An appropriate analysis of growth requires disentangling its two major components: amplitude and tempo. The assessment of the developmental tempo thus is an integral part of assessing child and adolescent growth. Though an Internet portal is currently available to process small amounts of height data (www.willi-will-wachsen.com) for separately determining amplitude and tempo in growth, there is urgent need of better and practical solutions for analyzing individual growth.

  10. Modeling the interaction of microbubbles: Effects of proximity, confinement, and excitation amplitude

    NASA Astrophysics Data System (ADS)

    Wiedemair, W.; Tukovic, Z.; Jasak, H.; Poulikakos, D.; Kurtcuoglu, V.

    2014-06-01

    The interaction of closely spaced microbubbles (MBs) exposed to a transient external pressure field is relevant for a variety of industrial and medical applications. We present a computational framework employing an interface tracking approach to model the transient dynamics of multiple, interacting, insonated MBs in arbitrary settings. In particular, this technique allows studying the effects of mutual proximity, confinement, and variations in excitation amplitude on the translatory motion of pairs of differently sized MBs. Domains of mutual repulsion or attraction are observed for closely spaced MBs in the investigated range of excitation frequencies. The repulsion domain widens and shifts to lower frequencies with increasing excitation pressure amplitude. When the MBs are confined in rigid tubes of decreasing diameters, we observe a shift of the translatory patterns towards lower frequencies, accompanied by a change in relative strength of the two translation modes. This effect is correlated to a decrease of the resonance frequency due to confinement which causes changes in oscillation amplitude and phase shift between the bubble vibrations. Coupling to the viscous host liquid gives rise to phenomena such as collective MB drift, non-symmetric attraction or repulsion, and reversal of translation direction. A system comprising six MBs inside a narrow tube highlights the potential of the computational framework to treat complex setups with multiple bubbles.

  11. Brownian motion

    NASA Astrophysics Data System (ADS)

    Lavenda, B. H.

    1985-02-01

    Brownian motion, the doubly random motion of small particles suspended in a liquid due to molecular collisions, and its implications and applications in the history of modern science are discussed. Topics examined include probabilistic phenomena, the kinetic theory of gases, Einstein's atomic theory of Brownian motion, particle displacement, diffusion measurements, the determination of the mass of the atom and of Avogadro's number, the statistical mechanics of thermodynamics, nonequilibrium systems, Langevin's equation of motion, time-reversed evolution, mathematical analogies, and applications in economics and radio navigation. Diagrams and drawings are provided.

  12. Nonlinear amplitude approximation for bilinear systems

    NASA Astrophysics Data System (ADS)

    Jung, Chulwoo; D'Souza, Kiran; Epureanu, Bogdan I.

    2014-06-01

    An efficient method to predict vibration amplitudes at the resonant frequencies of dynamical systems with piecewise-linear nonlinearity is developed. This technique is referred to as bilinear amplitude approximation (BAA). BAA constructs a single vibration cycle at each resonant frequency to approximate the periodic steady-state response of the system. It is postulated that the steady-state response is piece-wise linear and can be approximated by analyzing the response over two time intervals during which the system behaves linearly. Overall the dynamics is nonlinear, but the system is in a distinct linear state during each of the two time intervals. Thus, the approximated vibration cycle is constructed using linear analyses. The equation of motion for analyzing the vibration of each state is projected along the overlapping space spanned by the linear mode shapes active in each of the states. This overlapping space is where the vibratory energy is transferred from one state to the other when the system switches from one state to the other. The overlapping space can be obtained using singular value decomposition. The space where the energy is transferred is used together with transition conditions of displacement and velocity compatibility to construct a single vibration cycle and to compute the amplitude of the dynamics. Since the BAA method does not require numerical integration of nonlinear models, computational costs are very low. In this paper, the BAA method is first applied to a single-degree-of-freedom system. Then, a three-degree-of-freedom system is introduced to demonstrate a more general application of BAA. Finally, the BAA method is applied to a full bladed disk with a crack. Results comparing numerical solutions from full-order nonlinear analysis and results obtained using BAA are presented for all systems.

  13. Computing Maximally Supersymmetric Scattering Amplitudes

    NASA Astrophysics Data System (ADS)

    Stankowicz, James Michael, Jr.

    This dissertation reviews work in computing N = 4 super-Yang--Mills (sYM) and N = 8 maximally supersymmetric gravity (mSUGRA) scattering amplitudes in D = 4 spacetime dimensions in novel ways. After a brief introduction and overview in Ch. 1, the various techniques used to construct amplitudes in the remainder of the dissertation are discussed in Ch. 2. This includes several new concepts such as d log and pure integrand bases, as well as how to construct the amplitude using exactly one kinematic point where it vanishes. Also included in this chapter is an outline of the Mathematica package on shell diagrams and numerics.m (osdn) that was developed for the computations herein. The rest of the dissertation is devoted to explicit examples. In Ch. 3, the starting point is tree-level sYM amplitudes that have integral representations with residues that obey amplitude relations. These residues are shown to have corresponding residue numerators that allow a double copy prescription that results in mSUGRA residues. In Ch. 4, the two-loop four-point sYM amplitude is constructed in several ways, showcasing many of the techniques of Ch. 2; this includes an example of how to use osdn. The two-loop five-point amplitude is also presented in a pure integrand representation with comments on how it was constructed from one homogeneous cut of the amplitude. On-going work on the two-loop n-point amplitude is presented at the end of Ch. 4. In Ch. 5, the three-loop four-point amplitude is presented in the d log representation and in the pure integrand representation. In Ch. 6, there are several examples of four- through seven-loop planar diagrams that illustrate how considerations of the singularity structure of the amplitude underpin dual-conformal invariance. Taken with the previous examples, this is additional evidence that the structure known to exist in the planar sector extends to the full theory. At the end of this chapter is a proof that all mSUGRA amplitudes have a pole at

  14. Lorentzian proper vertex amplitude: Asymptotics

    NASA Astrophysics Data System (ADS)

    Engle, Jonathan; Vilensky, Ilya; Zipfel, Antonia

    2016-09-01

    In previous work, the Lorentzian proper vertex amplitude for a spin-foam model of quantum gravity was derived. In the present work, the asymptotics of this amplitude are studied in the semiclassical limit. The starting point of the analysis is an expression for the amplitude as an action integral with action differing from that in the Engle-Pereira-Rovelli-Livine (EPRL) case by an extra "projector" term. This extra term scales linearly with spins only in the asymptotic limit, and is discontinuous on a (lower dimensional) submanifold of the integration domain in the sense that its value at each such point depends on the direction of approach. New tools are introduced to generalize stationary phase methods to this case. For the case of boundary data which can be glued to a nondegenerate Lorentzian 4-simplex, the asymptotic limit of the amplitude is shown to equal the single Feynman term, showing that the extra term in the asymptotics of the EPRL amplitude has been eliminated.

  15. Visible Motion Blur

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B. (Inventor); Ahumada, Albert J. (Inventor)

    2014-01-01

    A method of measuring motion blur is disclosed comprising obtaining a moving edge temporal profile r(sub 1)(k) of an image of a high-contrast moving edge, calculating the masked local contrast m(sub1)(k) for r(sub 1)(k) and the masked local contrast m(sub 2)(k) for an ideal step edge waveform r(sub 2)(k) with the same amplitude as r(sub 1)(k), and calculating the measure or motion blur Psi as a difference function, The masked local contrasts are calculated using a set of convolution kernels scaled to simulate the performance of the human visual system, and Psi is measured in units of just-noticeable differences.

  16. Factorization of chiral string amplitudes

    NASA Astrophysics Data System (ADS)

    Huang, Yu-tin; Siegel, Warren; Yuan, Ellis Ye

    2016-09-01

    We re-examine a closed-string model defined by altering the boundary conditions for one handedness of two-dimensional propagators in otherwise-standard string theory. We evaluate the amplitudes using Kawai-Lewellen-Tye factorization into open-string amplitudes. The only modification to standard string theory is effectively that the spacetime Minkowski metric changes overall sign in one open-string factor. This cancels all but a finite number of states: as found in earlier approaches, with enough supersymmetry (e.g., type II) the tree amplitudes reproduce those of the massless truncation of ordinary string theory. However, we now find for the other cases that additional fields, formerly thought to be auxiliary, describe new spin-2 states at the two adjacent mass levels (tachyonic and tardyonic). The tachyon is always a ghost, but can be avoided in the heterotic case.

  17. Integrated Verification Experiment data collected as part of the Los Alamos National Laboratory`s Source Region Program. Appendix B: Surface ground motion

    SciTech Connect

    Weaver, T.A.; Baker, D.F.; Edwards, C.L.; Freeman, S.H.

    1993-10-01

    Surface ground motion was recorded for many of the Integrated Verification Experiments using standard 10-, 25- and 100-g accelerometers, force-balanced accelerometers and, for some events, using golf balls and 0.39-cm steel balls as surface inertial gauges (SIGs). This report contains the semi-processed acceleration, velocity, and displacement data for the accelerometers fielded and the individual observations for the SIG experiments. Most acceleration, velocity, and displacement records have had calibrations applied and have been deramped, offset corrected, and deglitched but are otherwise unfiltered or processed from their original records. Digital data for all of these records are stored at Los Alamos National Laboratory.

  18. Stability of a steady, large amplitude whistler wave.

    NASA Technical Reports Server (NTRS)

    Palmadesso, P. J.; Schmidt, G.

    1972-01-01

    Study of the behavior of weak electrostatic waves in a collisionless magnetoplasma supporting a steady large amplitude whistler wave. All waves are assumed to propagate parallel to a uniform background magnetic field B sub zero. In the presence of the whistler wave fields each particle executes an oscillatory motion parallel to B sub zero, in addition to a translation along B sub zero and transverse motions. This oscillation causes the Landau resonance to be replaced by a series of new resonances between particles and the electrostatic modes. A distribution function for the perturbed plasma is constructed by solving the Vlasov equation, linearized in the electrostatic wave amplitudes. A dispersion relation is obtained and solved approximately for the growth/damping rate of the perturbations. Growing electrostatic modes are found to be approximately uncoupled. Trapped particles have a strong influence on the stability of the system.

  19. Human motion analysis and modeling

    NASA Astrophysics Data System (ADS)

    Prussing, Keith; Cathcart, J. Michael; Kocher, Brian

    2011-06-01

    Georgia Tech has investigated methods for the detection and tracking of personnel in a variety of acquisition environments. This research effort focused on a detailed phenomenological analysis of human physiology and signatures with the subsequent identification and characterization of potential observables. As a fundamental part of this research effort, Georgia Tech collected motion capture data on an individual for a variety of walking speeds, carrying loads, and load distributions. These data formed the basis for deriving fundamental properties of the individual's motion and supported the development of a physiologically-based human motion model. Subsequently this model aided the derivation and analysis of motion-based observables, particularly changes in the motion of various body components resulting from load variations. This paper will describe the data acquisition process, development of the human motion model, and use of the model in the observable analysis. Video sequences illustrating the motion data and modeling results will also be presented.

  20. Simplified theory of large-amplitude wave propagation

    NASA Technical Reports Server (NTRS)

    Kim, H.

    1976-01-01

    An orbit perturbation procedure was applied to the description of monochromatic, large-amplitude, electrostatic plasma wave propagation. In the lowest order approximation, untrapped electrons were assumed to follow constant-velocity orbits and trapped electrons were assumed to execute simple harmonic motion. The deviations of these orbits from the actual orbits were regarded as perturbations. The nonlinear damping rate and frequency shift were then obtained in terms of simple functions. The results are in good agreement with previous less approximate analyses.

  1. Respiratory Amplitude Guided 4-Dimensional Magnetic Resonance Imaging

    SciTech Connect

    Hu, Yanle; Caruthers, Shelton D.; Low, Daniel A.; Parikh, Parag J.; Mutic, Sasa

    2013-05-01

    Purpose: To evaluate the feasibility of prospectively guiding 4-dimensional (4D) magnetic resonance imaging (MRI) image acquisition using triggers at preselected respiratory amplitudes to achieve T{sub 2} weighting for abdominal motion tracking. Methods and Materials: A respiratory amplitude-based triggering system was developed and integrated into a commercial turbo spin echo MRI sequence. Initial feasibility tests were performed on healthy human study participants. Four respiratory states, the middle and the end of inhalation and exhalation, were used to trigger 4D MRI image acquisition of the liver. To achieve T{sub 2} weighting, the echo time and repetition time were set to 75 milliseconds and 4108 milliseconds, respectively. Single-shot acquisition, together with parallel imaging and partial k-space imaging techniques, was used to improve image acquisition efficiency. 4D MRI image sets composed of axial or sagittal slices were acquired. Results: Respiratory data measured and logged by the MRI scanner showed that the triggers occurred at the appropriate respiratory levels. Liver motion could be easily observed on both 4D MRI image datasets by sensing either the change of liver in size and shape (axial) or diaphragm motion (sagittal). Both 4D MRI image datasets were T{sub 2}-weighted as expected. Conclusions: This study demonstrated the feasibility of achieving T{sub 2}-weighted 4D MRI images using amplitude-based respiratory triggers. With the aid of the respiratory amplitude-based triggering system, the proposed method is compatible with most MRI sequences and therefore has the potential to improve tumor-tissue contrast in abdominal tumor motion imaging.

  2. Toward complete pion nucleon amplitudes

    DOE PAGES

    Mathieu, Vincent; Danilkin, Igor V.; Fernández-Ramírez, Cesar; ...

    2015-10-05

    We compare the low-energy partial wave analyses πN scattering with a high-energy data via finite energy sum rules. We also construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy, Regge parametrization and then reconstruct the real parts using dispersion relations.

  3. Large amplitude drop shape oscillations

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Wang, T. G.

    1982-01-01

    An experimental study of large amplitude drop shape oscillation was conducted in immiscible liquids systems and with levitated free liquid drops in air. In liquid-liquid systems the results indicate the existence of familiar characteristics of nonlinear phenomena. The resonance frequency of the fundamental quadrupole mode of stationary, low viscosity Silicone oil drops acoustically levitated in water falls to noticeably low values as the amplitude of oscillation is increased. A typical, experimentally determined relative frequency decrease of a 0.5 cubic centimeters drop would be about 10% when the maximum deformed shape is characterized by a major to minor axial ratio of 1.9. On the other hand, no change in the fundamental mode frequency could be detected for 1 mm drops levitated in air. The experimental data for the decay constant of the quadrupole mode of drops immersed in a liquid host indicate a slight increase for larger oscillation amplitudes. A qualitative investigation of the internal fluid flows for such drops revealed the existence of steady internal circulation within drops oscillating in the fundamental and higher modes. The flow field configuration in the outer host liquid is also significantly altered when the drop oscillation amplitude becomes large.

  4. Nonlinear ionospheric responses to large-amplitude infrasonic-acoustic waves generated by undersea earthquakes

    NASA Astrophysics Data System (ADS)

    Zettergren, M. D.; Snively, J. B.; Komjathy, A.; Verkhoglyadova, O. P.

    2017-02-01

    Numerical models of ionospheric coupling with the neutral atmosphere are used to investigate perturbations of plasma density, vertically integrated total electron content (TEC), neutral velocity, and neutral temperature associated with large-amplitude acoustic waves generated by the initial ocean surface displacements from strong undersea earthquakes. A simplified source model for the 2011 Tohoku earthquake is constructed from estimates of initial ocean surface responses to approximate the vertical motions over realistic spatial and temporal scales. Resulting TEC perturbations from modeling case studies appear consistent with observational data, reproducing pronounced TEC depletions which are shown to be a consequence of the impacts of nonlinear, dissipating acoustic waves. Thermospheric acoustic compressional velocities are ˜±250-300 m/s, superposed with downward flows of similar amplitudes, and temperature perturbations are ˜300 K, while the dominant wave periodicity in the thermosphere is ˜3-4 min. Results capture acoustic wave processes including reflection, onset of resonance, and nonlinear steepening and dissipation—ultimately leading to the formation of ionospheric TEC depletions "holes"—that are consistent with reported observations. Three additional simulations illustrate the dependence of atmospheric acoustic wave and subsequent ionospheric responses on the surface displacement amplitude, which is varied from the Tohoku case study by factors of 1/100, 1/10, and 2. Collectively, results suggest that TEC depletions may only accompany very-large amplitude thermospheric acoustic waves necessary to induce a nonlinear response, here with saturated compressional velocities ˜200-250 m/s generated by sea surface displacements exceeding ˜1 m occurring over a 3 min time period.

  5. Circular Motion.

    ERIC Educational Resources Information Center

    Lee, Paul D.

    1995-01-01

    Provides a period-long activity using battery powered cars rolling in a circular motion on a tile floor. Students measure the time and distance as the car moves to derive the equation for centripetal acceleration. (MVL)

  6. Modeling the polar motion of Titan

    NASA Astrophysics Data System (ADS)

    Coyette, Alexis; Van Hoolst, Tim; Baland, Rose-Marie; Tokano, Tetsuya

    2016-02-01

    The angular momentum of the atmosphere and of the hydrocarbon lakes of Titan have a large equatorial component that can excite polar motion, a variable orientation of the rotation axis of Titan with respect to its surface. We here use the angular momentum obtained from a General Circulation Model of the atmosphere of Titan and from an Ocean Circulation Model for Titan's polar lakes to model the polar motion of Titan as a function of the interior structure. Besides the gravitational torque exerted by Saturn on Titan's aspherical mass distribution, the rotational model also includes torques arising due to the presence of an ocean under a thin ice shell as well as the influence of the elasticity of the different layers. The Chandler wobble period of a solid and rigid Titan without its atmosphere is about 279 years. The period of the Chandler wobble is mainly influenced by the atmosphere of Titan (-166 years) and the presence of an internal global ocean (+135 to 295 years depending on the internal model) and to a lesser extent by the elastic deformations (+3.7 years). The forced polar motion of a solid and rigid Titan is elliptical with an amplitude of about 50 m and a main period equal to the orbital period of Saturn. It is mainly forced by the atmosphere of Titan while the lakes of Titan are at the origin of a displacement of the mean polar motion, or polar offset. The subsurface ocean can largely increase the polar motion amplitude due to resonant amplification with a wobble free mode of Titan. The amplitudes as well as the main periods of the polar motion depend on whether and which forcing period is close to the period of a free mode. For a thick ice shell, the polar motion mainly has an annual period and an amplitude of about 1 km. For thinner ice shells, the polar motion amplitude can reach several tens of km and shorter periods become dominant. We demonstrate that for thick ice shells, the ice shell rigidity weakly influences the amplitude of the polar motion

  7. Pulse amplitude modulated chlorophyll fluorometer

    DOEpatents

    Greenbaum, Elias; Wu, Jie

    2015-12-29

    Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.

  8. Genus dependence of superstring amplitudes

    SciTech Connect

    Davis, Simon

    2006-11-15

    The problem of the consistency of the finiteness of the supermoduli space integral in the limit of vanishing super-fixed point distance and the genus-dependence of the integral over the super-Schottky coordinates in the fundamental region containing a neighborhood of |K{sub n}|=0 is resolved. Given a choice of the categories of isometric circles representing the integration region, the exponential form of bounds for superstring amplitudes is derived.

  9. Phase variation of hadronic amplitudes

    SciTech Connect

    Dedonder, J.-P.; Gibbs, W. R.; Nuseirat, Mutazz

    2008-04-15

    The phase variation with angle of hadronic amplitudes is studied with a view to understanding the underlying physical quantities that control it and how well it can be determined in free space. We find that unitarity forces a moderately accurate determination of the phase in standard amplitude analyses but that the nucleon-nucleon analyses done to date do not give the phase variation needed to achieve a good representation of the data in multiple scattering calculations. Models are examined that suggest its behavior near forward angles is related to the radii of the real and absorptive parts of the interaction. The dependence of this phase on model parameters is such that if these radii are modified in the nuclear medium (in combination with the change due to the shift in energy of the effective amplitude in the medium) then the larger magnitudes of the phase needed to fit the data might be attainable but only for negative values of the phase variation parameter.

  10. Crisis in Amplitude Control Hides in Multistability

    NASA Astrophysics Data System (ADS)

    Li, Chunbiao; Sprott, Julien Clinton; Xing, Hongyan

    2016-12-01

    A crisis of amplitude control can occur when a system is multistable. This paper proposes a new chaotic system with a line of equilibria to demonstrate the threat to amplitude control from multistability. The new symmetric system has two coefficients for amplitude control, one of which is a partial amplitude controller, while the other is a total amplitude controller that simultaneously controls the frequency. The amplitude parameter rescales the basins of attraction and triggers a state switch among different states resulting in a failure of amplitude control to the desired state.

  11. Calculation of multi-loop superstring amplitudes

    NASA Astrophysics Data System (ADS)

    Danilov, G. S.

    2016-12-01

    The multi-loop interaction amplitudes in the closed, oriented superstring theory are obtained by the integration of local amplitudes. The local amplitude is represented by a sum over the spinning string local amplitudes. The spinning string local amplitudes are given explicitly through super-Schottky group parameters and through interaction vertex coordinates on the (1| 1) complex, non-split supermanifold. The obtained amplitudes are free from divergences. They are consistent with the world-sheet spinning string symmetries. The vacuum amplitude vanishes along with 1-, 2- and 3-point amplitudes of massless states. The vanishing of the above-mentioned amplitude occurs after the integration of the corresponding local amplitude has been performed over the super-Schottky group limiting points and over interaction vertex coordinate, except for those (3| 2) variables which are fixed due to SL(2)-symmetry.

  12. Joint amplitude and frequency analysis of tremor activity.

    PubMed

    Foerster, F; Smeja, M

    1999-01-01

    Clinical tremor analysis mostly is used for the measurement of tremor frequency. The analysis is based on short segments of EMG recordings and on clinical ratings of tremor intensity. Accelerometry appears to have some practical advantages. The present study was concerned with the development of a methodology for assessing tremor activity using the three parameters, frequency (Hz), amplitude (g), and occurrence of tremor (in per cent of time). These parameters were derived from joint amplitude frequency analysis of the calibrated accelerometer raw signal and from appropriate decision rules. This methodology was used in connection with 27 patients with Parkinson's disease, to investigate the aforesaid parameters of tremor activity. Postural tremor had a higher occurrence time (right-hand only) and higher frequency (left-hand only) than resting tremor, however, the average amplitudes did not differ. The correlations between right-hand and left-hand measures were higher during postural tremor test. Frequency was not correlated to amplitude or occurrence time, however, moderate correlations did exist between amplitude and occurrence time. In addition to the assessment of tremor activity, multi-channel accelerometry may be used for the detection of posture and motion. Further applications of this methodology, for example, in 24 hr ambulatory monitoring of tremor, are discussed.

  13. Amplitude analysis of the charmed decay D0 to KKpipi

    NASA Astrophysics Data System (ADS)

    Skidmore, Nicola

    2017-01-01

    An amplitude analysis of the 4-body charmed decay D0 -> KKππ is presented using data collected from electron-positron collisions at the CLEO experiment. Both flavour tagged and CP tagged data are utilized in the analysis making it unique from amplitude analyses performed at other colliders and providing extra sensitivity to the phases of the amplitude components. The amplitude model is used to search for CP violation in the D0 decay by analysing D0 and D0 decays separately. The model is also crucial input for a model-dependent measurement of the CP-violating phase γ using B+/- ->D0(-> KKππ) K+/- decays, which remains one of the least constrained parameters of the Standard Model. Forum on International Physics Distinguished Student Seminar Program, and European Research Council

  14. Muscle motion and EMG activity in vibration treatment.

    PubMed

    Fratini, Antonio; La Gatta, Antonio; Bifulco, Paolo; Romano, Maria; Cesarelli, Mario

    2009-11-01

    The aim of this study is to highlight the relationship between muscle motion, generated by whole body vibration, and the correspondent electromyographic (EMG) activity and to suggest a new method to customize the stimulation frequency. Simultaneous recordings of EMG and tri-axial accelerations of quadriceps rectus femoris from fifteen subjects undergoing vibration treatments were collected. Vibrations were delivered via a sinusoidal oscillating platform at different frequencies (10-45 Hz). Muscle motion was estimated by processing the accelerometer data. Large EMG motion artifacts were removed using sharp notch filters centred at the vibration frequency and its superior harmonics. EMG-RMS values were computed and analyzed before and after artifact suppression to assess muscular activity. Muscles acceleration amplitude increased with frequency. Muscle displacements revealed a mechanical resonant-like behaviour of the muscle. Resonance frequencies and dumping factors depended on subject. Moreover, RMS of artifact-free EMG was found well correlated (R(2)=0.82) to the actual muscle displacement, while the maximum of the EMG response was found related to the mechanical resonance frequency of muscle. Results showed that maximum muscular activity was found in correspondence to the mechanical resonance of the muscle itself. Assuming the hypothesis that muscle activation is proportional to muscle displacement, treatment optimization (i.e. to choose the best stimulation frequency) could be obtained by simply monitoring local acceleration (resonance), leading to a more effective muscle stimulation. Motion artifact produced an overestimation of muscle activity, therefore its removal was essential.

  15. Natural and systematic polar motion jumps

    NASA Astrophysics Data System (ADS)

    Chapanov, Y.; Vondrak, J.; Ron, C.; Pachalieva, R.

    2014-12-01

    Polar motion consists mainly of two harmonic oscillations with variable phases and amplitudes and small irregular variations. The small irregular variations may be due to various geophysical excitations and observation inaccuracy (mostly in the first half of the last century). A part of irregular polar motion variations consists of fast jumps of the mean values of polar motion coordinates. The direct determination of the polar motion jumps is difficult, because the jump values are very small relative to the seasonal and Chandler amplitudes. A useful high sensitive method of data jumps determination is proposed. The method consists of data integration and piecewise linear or parabolic trends determina- tion. This method is applied to determine the natural and systematic polar motion jumps existing in pole coordinates from the solutions OA10 for the period 1899.7ñ1962.0 and C04 for the period 1962.0- 2013.5. Only a few of the determined polar motion jumps can be interpreted as systematic biases due to observational errors. The major part of the detected polar motion jumps occurs almost regularly near the epochs of minimum amplitude (due to the beat of seasonal and Chandler wobbles), so the natural origin of these jumps is supposed.

  16. Ground motion input in seismic evaluation studies

    SciTech Connect

    Sewell, R.T.; Wu, S.C.

    1996-07-01

    This report documents research pertaining to conservatism and variability in seismic risk estimates. Specifically, it examines whether or not artificial motions produce unrealistic evaluation demands, i.e., demands significantly inconsistent with those expected from real earthquake motions. To study these issues, two types of artificial motions are considered: (a) motions with smooth response spectra, and (b) motions with realistic variations in spectral amplitude across vibration frequency. For both types of artificial motion, time histories are generated to match target spectral shapes. For comparison, empirical motions representative of those that might result from strong earthquakes in the Eastern U.S. are also considered. The study findings suggest that artificial motions resulting from typical simulation approaches (aimed at matching a given target spectrum) are generally adequate and appropriate in representing the peak-response demands that may be induced in linear structures and equipment responding to real earthquake motions. Also, given similar input Fourier energies at high-frequencies, levels of input Fourier energy at low frequencies observed for artificial motions are substantially similar to those levels noted in real earthquake motions. In addition, the study reveals specific problems resulting from the application of Western U.S. type motions for seismic evaluation of Eastern U.S. nuclear power plants.

  17. Brownian Motion.

    ERIC Educational Resources Information Center

    Lavenda, Bernard H.

    1985-01-01

    Explains the phenomenon of Brownian motion, which serves as a mathematical model for random processes. Topics addressed include kinetic theory, Einstein's theory, particle displacement, and others. Points out that observations of the random course of a particle suspended in fluid led to the first accurate measurement of atomic mass. (DH)

  18. Motion Sickness

    MedlinePlus

    ... but it is more common in children, pregnant women, and people taking certain medicines. Motion sickness can start suddenly, with a queasy feeling and cold sweats. It can then lead to dizziness and nausea and vomiting. Your brain senses movement by getting signals from your inner ears, eyes, ...

  19. Quasidistribution amplitude of heavy quarkonia

    NASA Astrophysics Data System (ADS)

    Jia, Yu; Xiong, Xiaonu

    2016-11-01

    The recently proposed quasidistributions point out a promising direction for lattice QCD to investigate the light-cone correlators, such as parton distribution functions and distribution amplitudes (DAs), directly in the x space. Owing to its excessive simplicity, heavy quarkonium can serve as an ideal theoretical laboratory to ascertain certain features of quasi-DAs. In the framework of nonrelativistic QCD factorization, we compute the order-αs correction to both light-cone distribution amplitudes (LCDAs) and quasi-DAs associated with the lowest-lying quarkonia, with the transverse-momentum UV cutoff interpreted as the renormalization scale. We confirm analytically that the quasi-DA of a quarkonium does reduce to the respective LCDA in the infinite-momentum limit. We also observe that, provided that the momentum of a charmonium reaches about 2-3 times its mass, the quasi-DAs already converge to the LCDAs to a decent level. These results might provide some useful guidance for the future lattice study of quasidistributions.

  20. Motion artifacts of pulse inversion-based tissue harmonic imaging.

    PubMed

    Shen, Che-Chou; Li, Pai-Chi

    2002-09-01

    Motion artifacts of the pulse inversion technique were studied for finite amplitude distortion-based harmonic imaging. Motion in both the axial and the lateral directions was considered. Two performance issues were investigated. One is the harmonic signal intensity relative to the fundamental intensity and the other is the potential image quality degradation resulting from spectral leakage. A one-dimensional (1-D) correlation-based correction scheme also was used to compensate for motion artifacts. Results indicated that the tissue harmonic signal is significantly affected by tissue motion. For axial motion, the tissue harmonic intensity decreases much more rapidly than with lateral motion. The fundamental signal increases for both axial and lateral motion. Thus, filtering is still required to remove the fundamental signal, even if the pulse inversion technique is applied. The motion also potentially decreases contrast resolution because of the uncancelled spectral leakage. Also, it was indicated that 1-D motion correction is not adequate if nonaxial motion is present.

  1. [Motion sickness].

    PubMed

    Taillemite, J P; Devaulx, P; Bousquet, F

    1997-01-01

    Motion sickness is a general term covering sea-sickness, car-sickness, air-sickness, and space-sickness. Symptoms can occur when a person is exposed to unfamiliar movement whether real or simulated. Despite progress in the technology and comfort of modern transportation (planes, boats, and overland vehicles), a great number of travelers still experience motion sickness. Bouts are characterized by an initial phase of mild discomfort followed by neurologic and gastro-intestinal manifestations. The delay in onset depends on specific circumstances and individual susceptibility. Attacks are precipitated by conflicting sensory, visual, and vestibular signals but the underlying mechanism is unclear. Most medications used for prevention and treatment (e.g. anticholinergics and antihistamines) induce unwanted sedation. Furthermore no one drug is completely effective or preventive under all conditions.

  2. Mapping Pn amplitude spreading and attenuation in Asia

    SciTech Connect

    Yang, Xiaoning; Phillips, William S; Stead, Richard J

    2010-12-06

    Pn travels most of its path in the mantle lid. Mapping the lateral variation of Pn amplitude attenuation sheds light on material properties and dynamics of the uppermost region of the mantle. Pn amplitude variation depends on the wavefront geometric spreading as well as material attenuation. We investigated Pn geometric spreading, which is much more complex than a traditionally assumed power-law spreading model, using both synthetic and observed amplitude data collected in Asia. We derived a new Pn spreading model based on the formulation that was proposed previously to account for the spherical shape of the Earth (Yang et. al., BSSA, 2007). New parameters derived for the spreading model provide much better correction for Pn amplitudes in terms of residual behavior. Because we used observed Pn amplitudes to construct the model, the model incorporates not only the effect of the Earth's spherical shape, but also the effect of potential upper-mantle velocity gradients in the region. Using the new spreading model, we corrected Pn amplitudes measured at 1, 2, 4 and 6 Hz and conducted attenuation tomography. The resulting Pn attenuation model correlates well with the regional geology. We see high attenuation in regions such as northern Tibetan Plateau and the western Pacific subduction zone, and low attenuation for stable blocks such as Sichuan and Tarim basins.

  3. SU-E-J-115: Correlation of Displacement Vector Fields Calculated by Deformable Image Registration Algorithms with Motion Parameters of CT Images with Well-Defined Targets and Controlled-Motion

    SciTech Connect

    Jaskowiak, J; Ahmad, S; Ali, I; Alsbou, N

    2015-06-15

    Purpose: To investigate correlation of displacement vector fields (DVF) calculated by deformable image registration algorithms with motion parameters in helical axial and cone-beam CT images with motion artifacts. Methods: A mobile thorax phantom with well-known targets with different sizes that were made from water-equivalent material and inserted in foam to simulate lung lesions. The thorax phantom was imaged with helical, axial and cone-beam CT. The phantom was moved with a cyclic motion with different motion amplitudes and frequencies along the superior-inferior direction. Different deformable image registration algorithms including demons, fast demons, Horn-Shunck and iterative-optical-flow from the DIRART software were used to deform CT images for the phantom with different motion patterns. The CT images of the mobile phantom were deformed to CT images of the stationary phantom. Results: The values of displacement vectors calculated by deformable image registration algorithm correlated strongly with motion amplitude where large displacement vectors were calculated for CT images with large motion amplitudes. For example, the maximal displacement vectors were nearly equal to the motion amplitudes (5mm, 10mm or 20mm) at interfaces between the mobile targets lung tissue, while the minimal displacement vectors were nearly equal to negative the motion amplitudes. The maximal and minimal displacement vectors matched with edges of the blurred targets along the Z-axis (motion-direction), while DVF’s were small in the other directions. This indicates that the blurred edges by phantom motion were shifted largely to match with the actual target edge. These shifts were nearly equal to the motion amplitude. Conclusions: The DVF from deformable-image registration algorithms correlated well with motion amplitude of well-defined mobile targets. This can be used to extract motion parameters such as amplitude. However, as motion amplitudes increased, image artifacts increased

  4. Large amplitude relativistic plasma waves

    SciTech Connect

    Coffey, Timothy

    2010-05-15

    Relativistic, longitudinal plasma oscillations are studied for the case of a simple water bag distribution of electrons having cylindrical symmetry in momentum space with the axis of the cylinder parallel to the velocity of wave propagation. The plasma is required to obey the relativistic Vlasov-Poisson equations, and solutions are sought in the wave frame. An exact solution for the plasma density as a function of the electrostatic field is derived. The maximum electric field is presented in terms of an integral over the known density. It is shown that when the perpendicular momentum is neglected, the maximum electric field approaches infinity as the wave phase velocity approaches the speed of light. It is also shown that for any nonzero perpendicular momentum, the maximum electric field will remain finite as the wave phase velocity approaches the speed of light. The relationship to previously published solutions is discussed as is some recent controversy regarding the proper modeling of large amplitude relativistic plasma waves.

  5. Constructing Amplitudes from Their Soft Limits

    SciTech Connect

    Boucher-Veronneau, Camille; Larkoski, Andrew J.; /SLAC

    2011-12-09

    The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an (n-1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which 'soft' particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedure and relate it to Britto-Cachazo-Feng-Witten recursion. We show that all tree-level amplitudes in gauge theory and gravity up through seven points can be constructed in this way, as well as certain classes of NMHV gauge-theory amplitudes with any number of external legs. This provides us with a systematic procedure for constructing amplitudes solely from their soft limits.

  6. Using Dual Regression to Investigate Network Shape and Amplitude in Functional Connectivity Analyses

    PubMed Central

    Nickerson, Lisa D.; Smith, Stephen M.; Öngür, Döst; Beckmann, Christian F.

    2017-01-01

    Independent Component Analysis (ICA) is one of the most popular techniques for the analysis of resting state FMRI data because it has several advantageous properties when compared with other techniques. Most notably, in contrast to a conventional seed-based correlation analysis, it is model-free and multivariate, thus switching the focus from evaluating the functional connectivity of single brain regions identified a priori to evaluating brain connectivity in terms of all brain resting state networks (RSNs) that simultaneously engage in oscillatory activity. Furthermore, typical seed-based analysis characterizes RSNs in terms of spatially distributed patterns of correlation (typically by means of simple Pearson's coefficients) and thereby confounds together amplitude information of oscillatory activity and noise. ICA and other regression techniques, on the other hand, retain magnitude information and therefore can be sensitive to both changes in the spatially distributed nature of correlations (differences in the spatial pattern or “shape”) as well as the amplitude of the network activity. Furthermore, motion can mimic amplitude effects so it is crucial to use a technique that retains such information to ensure that connectivity differences are accurately localized. In this work, we investigate the dual regression approach that is frequently applied with group ICA to assess group differences in resting state functional connectivity of brain networks. We show how ignoring amplitude effects and how excessive motion corrupts connectivity maps and results in spurious connectivity differences. We also show how to implement the dual regression to retain amplitude information and how to use dual regression outputs to identify potential motion effects. Two key findings are that using a technique that retains magnitude information, e.g., dual regression, and using strict motion criteria are crucial for controlling both network amplitude and motion-related amplitude

  7. Using Dual Regression to Investigate Network Shape and Amplitude in Functional Connectivity Analyses.

    PubMed

    Nickerson, Lisa D; Smith, Stephen M; Öngür, Döst; Beckmann, Christian F

    2017-01-01

    Independent Component Analysis (ICA) is one of the most popular techniques for the analysis of resting state FMRI data because it has several advantageous properties when compared with other techniques. Most notably, in contrast to a conventional seed-based correlation analysis, it is model-free and multivariate, thus switching the focus from evaluating the functional connectivity of single brain regions identified a priori to evaluating brain connectivity in terms of all brain resting state networks (RSNs) that simultaneously engage in oscillatory activity. Furthermore, typical seed-based analysis characterizes RSNs in terms of spatially distributed patterns of correlation (typically by means of simple Pearson's coefficients) and thereby confounds together amplitude information of oscillatory activity and noise. ICA and other regression techniques, on the other hand, retain magnitude information and therefore can be sensitive to both changes in the spatially distributed nature of correlations (differences in the spatial pattern or "shape") as well as the amplitude of the network activity. Furthermore, motion can mimic amplitude effects so it is crucial to use a technique that retains such information to ensure that connectivity differences are accurately localized. In this work, we investigate the dual regression approach that is frequently applied with group ICA to assess group differences in resting state functional connectivity of brain networks. We show how ignoring amplitude effects and how excessive motion corrupts connectivity maps and results in spurious connectivity differences. We also show how to implement the dual regression to retain amplitude information and how to use dual regression outputs to identify potential motion effects. Two key findings are that using a technique that retains magnitude information, e.g., dual regression, and using strict motion criteria are crucial for controlling both network amplitude and motion-related amplitude effects

  8. Vibrations of moderately thick shallow spherical shells at large amplitudes

    NASA Astrophysics Data System (ADS)

    Sathyamoorthy, M.

    1994-04-01

    A shallow shell theory is presented for the geometrically nonlinear analysis of moderately thick isotropic spherical shells. Effects of transverse shear deformation and rotatory inertia are included in the governing equations of motion by means of tracing constants. When these effects are ignored, the governing equations readily reduce to those applicable for thin shallow spherical shells. Solutions to the system of thick shell equations are obtained by means of Galerkin's method and the numerical Runge-Kutta procedure. Numerical results are presented for certain cases of shallow spherical shells considering different geometric shell parameters. Transverse shear and rotatory inertia effects are found to be important in linear as well as nonlinear responses of shallow spherical shells. The nonlinear frequency-amplitude behavior is of the softening type for shallow spherical shells and of the hardening type for circular plates. Frequency ratios are lower at any given amplitude when the effects of transverse shear and rotatory inertia are included in the analysis.

  9. Tilts in strong ground motion

    USGS Publications Warehouse

    Graizer, V.

    2006-01-01

    Most instruments used in seismological practice to record ground motion are pendulum seismographs, velocigraphs, or accelerographs. In most cases it is assumed that seismic instruments are only sensitive to the translational motion of the instrument's base. In this study the full equation of pendulum motion, including the inputs of rotations and tilts, is considered. It is shown that tilting the accelerograph's base can severely impact its response to the ground motion. The method of tilt evaluation using uncorrected strong-motion accelerograms was first suggested by Graizer (1989), and later tested in several laboratory experiments with different strong-motion instruments. The method is based on the difference in the tilt sensitivity of the horizontal and vertical pendulums. The method was applied to many of the strongest records of the Mw 6.7 Northridge earthquake of 1994. Examples are shown when relatively large tilts of up to a few degrees occurred during strong earthquake ground motion. Residual tilt extracted from the strong-motion record at the Pacoima Dam-Upper Left Abutment reached 3.1?? in N45??E direction, and was a result of local earthquake-induced tilting due to high-amplitude shaking. This value is in agreement with the residual tilt measured by using electronic level a few days after the earthquake. The method was applied to the building records from the Northridge earthquake. According to the estimates, residual tilt reached 2.6?? on the ground floor of the 12-story Hotel in Ventura. Processing of most of the strongest records of the Northridge earthquake shows that tilts, if happened, were within the error of the method, or less than about 0.5??.

  10. Logarithmic intensity and speckle-based motion contrast methods for human retinal vasculature visualization using swept source optical coherence tomography

    PubMed Central

    Motaghiannezam, Reza; Fraser, Scott

    2012-01-01

    We formulate a theory to show that the statistics of OCT signal amplitude and intensity are highly dependent on the sample reflectivity strength, motion, and noise power. Our theoretical and experimental results depict the lack of speckle amplitude and intensity contrasts to differentiate regions of motion from static areas. Two logarithmic intensity-based contrasts, logarithmic intensity variance (LOGIV) and differential logarithmic intensity variance (DLOGIV), are proposed for serving as surrogate markers for motion with enhanced sensitivity. Our findings demonstrate a good agreement between the theoretical and experimental results for logarithmic intensity-based contrasts. Logarithmic intensity-based motion and speckle-based contrast methods are validated and compared for in vivo human retinal vasculature visualization using high-speed swept-source optical coherence tomography (SS-OCT) at 1060 nm. The vasculature was identified as regions of motion by creating LOGIV and DLOGIV tomograms: multiple B-scans were collected of individual slices through the retina and the variance of logarithmic intensities and differences of logarithmic intensities were calculated. Both methods captured the small vessels and the meshwork of capillaries associated with the inner retina in en face images over 4 mm2 in a normal subject. PMID:22435098

  11. A comparison between amplitude sorting and phase-angle sorting using external respiratory measurement for 4D CT

    SciTech Connect

    Lu Wei; Parikh, Parag J.; Hubenschmidt, James P.; Bradley, Jeffrey D.; Low, Daniel A.

    2006-08-15

    Respiratory motion can cause significant dose delivery errors in conformal radiation therapy for thoracic and upper abdominal tumors. Four-dimensional computed tomography (4D CT) has been proposed to provide the image data necessary to model tumor motion and consequently reduce these errors. The purpose of this work was to compare 4D CT reconstruction methods using amplitude sorting and phase angle sorting. A 16-slice CT scanner was operated in cine mode to acquire 25 scans consecutively at each couch position through the thorax. The patient underwent synchronized external respiratory measurements. The scans were sorted into 12 phases based, respectively, on the amplitude and direction (inhalation or exhalation) or on the phase angle (0-360 deg.) of the external respiratory signal. With the assumption that lung motion is largely proportional to the measured respiratory amplitude, the variation in amplitude corresponds to the variation in motion for each phase. A smaller variation in amplitude would associate with an improved reconstructed image. Air content, defined as the amount of air within the lungs, bronchi, and trachea in a 16-slice CT segment and used by our group as a surrogate for internal motion, was correlated to the respiratory amplitude and phase angle throughout the lungs. For the 35 patients who underwent quiet breathing, images (similar to those used for treatment planning) and animations (used to display respiratory motion) generated using amplitude sorting displayed fewer reconstruction artifacts than those generated using phase angle sorting. The variations in respiratory amplitude were significantly smaller (P<0.001) with amplitude sorting than those with phase angle sorting. The subdivision of the breathing cycle into more (finer) phases improved the consistency in respiratory amplitude for amplitude sorting, but not for phase angle sorting. For 33 of the 35 patients, the air content showed significantly improved (P<0.001) correlation with the

  12. The Chandler wobble of the poles and its amplitude modulation

    NASA Astrophysics Data System (ADS)

    Sidorenkov, N.

    2015-08-01

    It is shown that the period of the Chandler wobble of the poles (CWP) is a combined oscillation caused by three periodic processes experienced by the Earth: (a) lunisolar tides, (b) the precession of the orbit of the Earth's monthly revolution around the barycenter of the Earth-Moon system, and (c) the motion of the perigee of this orbit. The addition of the 1.20 - year Chandler wobble to sidereal, anomalistic, and synodic lunar yearly forcing gives rise slow periodic variations in the CWP amplitude with periods of 32 to 51 years.

  13. Oculometric indices of simulator and aircraft motion

    NASA Technical Reports Server (NTRS)

    Comstock, J. R.

    1984-01-01

    The effects on eye scan behavior of both simulator and aircraft motion and sensitivity of an oculometric measure to motion effects was demonstrated. It was found that fixation time is sensitive to motion effects. Differences between simulator motion and no motion conditions during a series of simulated ILS approaches were studied. The mean fixation time for the no motion condition was found to be significantly longer than for the motion conditions. Eye scan parameters based on data collected in flight, and in fixed base simulation were investigated. Motion effects were evident when the subject was viewing a display supplying attitude and flight path information. The nature of the information provided by motion was examined. The mean fixation times for the no motion condition were significantly longer than for either motion condition, while the two motion conditions did not differ. It is shown that motion serves an alerting function, providing a cue or clue to the pilot that something happened. It is suggested that simulation without motion cues may represent an understatement of the true capacity of the pilot.

  14. Reduction of wing rock amplitudes using leading-edge vortex manipulations

    NASA Technical Reports Server (NTRS)

    Walton, James; Katz, Joseph

    1992-01-01

    A mechanically operated leading edge flap system was used to perturb leading edge vortex position on a free-to-roll double-delta wing. The motion of the flaps was synchronized with the wing rolling oscillations and the effect of the phase shift between the oscillations of the wing and the flaps was investigated. Experimental results indicated that this simple approach was effective in reducing the amplitude of the unintended rolling motion and its implementation to actual airplane configurations is rather simple.

  15. Clinical evaluations of an amplitude-based binning algorithm for 4DCT reconstruction in radiation therapy

    SciTech Connect

    Li Hua; Noel, Camille; Garcia-Ramirez, Jose; Low, Daniel; Bradley, Jeffrey; Robinson, Clifford; Mutic, Sasa; Parikh, Parag

    2012-02-15

    Purpose: Phase-binning algorithms are commonly utilized in 4DCT image reconstruction for characterization of tumor or organ shape and respiration motion, but breathing irregularities occurring during 4DCT acquisition can cause considerable image distortions. Recently, amplitude-binning algorithms have been evaluated as a potential improvement to phase-binning algorithms for 4DCT image reconstruction. The purpose of this study was to evaluate the performance of the first commercially available on-line retrospective amplitude-binning algorithm for comparison to the traditional phase-binning algorithm. Methods: Both phantom and clinical data were used for evaluation. A phantom of known geometry was mounted on a 4D motion platform programmed with seven respiratory waves (two computer generated and five patient trajectories) and scanned with a Philips Brilliance Big bore 16-slice CT simulator. 4DCT images were reconstructed using commercial amplitude- and phase-binning algorithms. Image quality of the amplitude- and phase-binned image sets was compared by evaluation of shape and volume distortions in reconstructed images. Clinical evaluations were performed on 64 4DCT patient image sets in a blinded review process. The amplitude- and phase-binned 4DCT maximum intensity projection (MIP) images were further evaluated for 28 stereotactic body radiation therapy (SBRT) cases of total 64 cases. A preliminary investigation of the effects of respiratory amplitude and pattern irregularities on motion artifact severity was conducted. Results: The phantom experiments illustrated that, as expected, maximum inhalation occurred at the 0% amplitude and maximum exhalation occurred at the 50% amplitude of the amplitude-binned 4DCT image sets. The phantom shape distortions were more severe in the images reconstructed from the phase-binning algorithm. In the clinical study, compared to the phase-binning algorithm, the amplitude-binning algorithm yielded fewer or less severe motion

  16. Bifurcation theory applied to aircraft motions

    NASA Technical Reports Server (NTRS)

    Hui, W. H.; Tobak, M.

    1985-01-01

    Bifurcation theory is used to analyze the nonlinear dynamic stability characteristics of single-degree-of-freedom motions of an aircraft or a flap about a trim position. The bifurcation theory analysis reveals that when the bifurcation parameter, e.g., the angle of attack, is increased beyond a critical value at which the aerodynamic damping vanishes, a new solution representing finite-amplitude periodic motion bifurcates from the previously stable steady motion. The sign of a simple criterion, cast in terms of aerodynamic properties, determines whether the bifurcating solution is stable (supercritical) or unstable (subcritical). For the pitching motion of a flap-plate airfoil flying at supersonic/hypersonic speed, and for oscillation of a flap at transonic speed, the bifurcation is subcritical, implying either that exchanges of stability between steady and periodic motion are accompanied by hysteresis phenomena, or that potentially large aperiodic departures from steady motion may develop. On the other hand, for the rolling oscillation of a slender delta wing in subsonic flight (wing rock), the bifurcation is found to be supercritical. This and the predicted amplitude of the bifurcation periodic motion are in good agreement with experiments.

  17. Earthquake mechanisms from linear-programming inversion of seismic-wave amplitude ratios

    USGS Publications Warehouse

    Julian, B.R.; Foulger, G.R.

    1996-01-01

    The amplitudes of radiated seismic waves contain far more information about earthquake source mechanisms than do first-motion polarities, but amplitudes are severely distorted by the effects of heterogeneity in the Earth. This distortion can be reduced greatly by using the ratios of amplitudes of appropriately chosen seismic phases, rather than simple amplitudes, but existing methods for inverting amplitude ratios are severely nonlinear and require computationally intensive searching methods to ensure that solutions are globally optimal. Searching methods are particularly costly if general (moment tensor) mechanisms are allowed. Efficient linear-programming methods, which do not suffer from these problems, have previously been applied to inverting polarities and wave amplitudes. We extend these methods to amplitude ratios, in which formulation on inequality constraint for an amplitude ratio takes the same mathematical form as a polarity observation. Three-component digital data for an earthquake at the Hengill-Grensdalur geothermal area in southwestern Iceland illustrate the power of the method. Polarities of P, SH, and SV waves, unusually well distributed on the focal sphere, cannot distinguish between diverse mechanisms, including a double couple. Amplitude ratios, on the other hand, clearly rule out the double-couple solution and require a large explosive isotropic component.

  18. Polar motion of Titan forced by the atmosphere

    NASA Astrophysics Data System (ADS)

    Tokano, Tetsuya; Van Hoolst, Tim; Karatekin, Özgür

    2011-05-01

    Titan's atmosphere possesses an equatorial component of angular momentum, which can be transferred to the surface and can excite polar motion of Titan. The atmospheric excitation of Titan's polar motion is calculated using the wind and pressure data prediction from a general circulation model. The polar motion equation is solved considering Titan's triaxial shape and different hypothetical interior models. Titan's polar motion basically consists of a superposition of small diurnal wobbles and larger semiannual and annual wobbles caused by seasonal redistribution of wind and pressure pattern. If the entire interior of Titan is solid, the polar motion has total amplitudes of a few meters, but the diurnal and seasonal wobble may be intermingled due to preferential damping of the seasonal wobble by Saturn's gravitational torque. If instead there is a subsurface ocean underneath the crust, the wobble amplitude could be larger by an order of magnitude. If the crust is thin, a resonance between the seasonal and Chandler wobble further increases the polar motion amplitude and makes the polar motion path elliptical. The seasonal wobble of a crust lying on a subsurface ocean experiences damping by either gravitational and pressure torque or elastic torque, but the relative reduction of the polar motion amplitude by these torques is likely to be smaller than that of the length-of-day variations.

  19. Motion Simulator

    NASA Technical Reports Server (NTRS)

    1993-01-01

    MOOG, Inc. supplies hydraulic actuators for the Space Shuttle. When MOOG learned NASA was interested in electric actuators for possible future use, the company designed them with assistance from Marshall Space Flight Center. They also decided to pursue the system's commercial potential. This led to partnership with InterActive Simulation, Inc. for production of cabin flight simulators for museums, expositions, etc. The resulting products, the Magic Motion Simulator 30 Series, are the first electric powered simulators. Movements are computer-guided, including free fall to heighten the sense of moving through space. A projection system provides visual effects, and the 11 speakers of a digital laser based sound system add to the realism. The electric actuators are easier to install, have lower operating costs, noise, heat and staff requirements. The U.S. Space & Rocket Center and several other organizations have purchased the simulators.

  20. Amplitude death of coupled hair bundles with stochastic channel noise

    NASA Astrophysics Data System (ADS)

    Kim, Kyung-Joong; Ahn, Kang-Hun

    2014-04-01

    Hair cells conduct auditory transduction in vertebrates. In lower vertebrates such as frogs and turtles, due to the active mechanism in hair cells, hair bundles (stereocilia) can be spontaneously oscillating or quiescent. Recently an amplitude death phenomenon has been proposed [K.-H. Ahn, J. R. Soc. Interface, 10, 20130525 (2013)] as a mechanism for auditory transduction in frog hair-cell bundles, where sudden cessation of the oscillations arises due to the coupling between nonidentical hair bundles. The gating of the ion channel is intrinsically stochastic due to the stochastic nature of the configuration change of the channel. The strength of the noise due to the channel gating can be comparable to the thermal Brownian noise of hair bundles. Thus, we perform stochastic simulations of the elastically coupled hair bundles. In spite of stray noisy fluctuations due to its stochastic dynamics, our simulation shows the transition from collective oscillation to amplitude death as interbundle coupling strength increases. In its stochastic dynamics, the formation of the amplitude death state of coupled hair bundles can be seen as a sudden suppression of the displacement fluctuation of the hair bundles as the coupling strength increases. The enhancement of the signal-to-noise ratio through the amplitude death phenomenon is clearly seen in the stochastic dynamics. Our numerical results demonstrate that the multiple number of transduction channels per hair bundle is an important factor to the amplitude death phenomenon, because the phenomenon may disappear for a small number of transduction channels due to strong gating noise.

  1. SU-E-J-62: Breath Hold for Left-Sided Breast Cancer: Visually Monitored Deep Inspiration Breath Hold Amplitude Evaluated Using Real-Time Position Management

    SciTech Connect

    Conroy, L; Quirk, S; Smith, WL; Yeung, R; Phan, T; Hudson, A

    2015-06-15

    Purpose: We used Real-Time Position Management (RPM) to evaluate breath hold amplitude and variability when gating with a visually monitored deep inspiration breath hold technique (VM-DIBH) with retrospective cine image chest wall position verification. Methods: Ten patients with left-sided breast cancer were treated using VM-DIBH. Respiratory motion was passively collected once weekly using RPM with the marker block positioned at the xiphoid process. Cine images on the tangent medial field were acquired on fractions with RPM monitoring for retrospective verification of chest wall position during breath hold. The amplitude and duration of all breath holds on which treatment beams were delivered were extracted from the RPM traces. Breath hold position coverage was evaluated for symmetric RPM gating windows from ± 1 to 5 mm centered on the average breath hold amplitude of the first measured fraction as a baseline. Results: The average (range) breath hold amplitude and duration was 18 mm (3–36 mm) and 19 s (7–34 s). The average (range) of amplitude standard deviation per patient over all breath holds was 2.7 mm (1.2–5.7 mm). With the largest allowable RPM gating window (± 5 mm), 4 of 10 VM-DIBH patients would have had ≥ 10% of their breath hold positions excluded by RPM. Cine verification of the chest wall position during the medial tangent field showed that the chest wall was greater than 5 mm from the baseline in only 1 out of 4 excluded patients. Cine images verify the chest wall/breast position only, whether this variation is acceptable in terms of heart sparing is a subject of future investigation. Conclusion: VM-DIBH allows for greater breath hold amplitude variability than using a 5 mm gating window with RPM, while maintaining chest wall positioning accuracy within 5 mm for the majority of patients.

  2. Control Strategies for Guided Collective Motion

    DTIC Science & Technology

    2015-02-27

    Rorres and H. Anton, “ Elementary linear algebra applications version,” 9th Edition, Wiley India Pvt. Ltd., 2011. [20] S.H. Strogatz, “From Kuramoto to... linear cyclic pursuit in which an agent pursues its leader with an angle of deviation. The sufficient conditions for the stability of such systems are...Generalized Hierarchical Cyclic Pursuit 6. D. Mukherjee and D. Ghose: Deviated Linear Cyclic Pursuit 7. D. Mukherjee and D. Ghose; On Synchronous and

  3. Control Strategies for Guided Collective Motion

    DTIC Science & Technology

    2015-01-30

    Control, Atlanta, GA, USA, December 2010, pp. 5468-5473. [19] C. Rorres and H. Anton, “ Elementary linear algebra applications version,” 9th Edition...work addresses and analyses deviated linear cyclic pursuit in which an Distribution Code A: Approved for public release, distribution is unlimited...Pursuit 6. D. Mukherjee and D. Ghose: Deviated Linear Cyclic Pursuit 7. D. Mukherjee and D. Ghose; On Synchronous and Asynchronous Heterogeneous Cyclic

  4. Collective motion: Disorder in the wild

    NASA Astrophysics Data System (ADS)

    Reichhardt, C. J. Olson; Reichhardt, C.

    2017-01-01

    Simple models have given us surprising insight into how animals flock, but most assume they do so through a homogeneous landscape. Colloidal experiments now suggest that a little disorder can have unexpected -- and spectacular -- effects.

  5. SU-C-210-01: Are Clinically Relevant Dosimetric Endpoints Significantly Better with Gating of Lung SBRT Vs. ITV-Based Treatment?: Results of a Large Cohort Investigation Analyzing Predictive Dosimetric Indicators as a Function of Tumor Volume and Motion Amplitude

    SciTech Connect

    Kim, J; Zhao, B; Ajlouni, M; Movsas, B; Chetty, I.J.

    2015-06-15

    Purpose: To quantitatively compare patient internal target volume (ITV)-based plans with retrospectively generated gated plans to evaluate potential dosimetric improvements in lung toxicity from gated radiotherapy. Methods: Evaluation was conducted for 150 stereotactic body radiation therapy (SBRT) treatment plans for 128 early-stage (T1–T3, <5cm) NSCLC patients. PTV margins were: ITV+5 mm (ITV-plan) and GTV+5 mm (Gated-plan). ITV-based and gated treatment plans were compared on the same free-breathing CT. ITV-based plan constraints were used to re-optimize and recalculate new gated plans. Plans were generated for 3 fractionation regimens: 3×18Gy, 4×12Gy (original), and 5×10Gy. Physical dose was converted to equivalent dose in 2Gy fractions (EQD2), which was used to determine mean lung dose (MLD) and percent volume of lung receiving ≥20Gy (V20). MLD and V20 differences between gating and ITV-based plans were analyzed as a function of both three-dimensional (3D) motion and tumor volume. The low dose region, V5, was also evaluated. Results: MLD and V20 differences between gated and ITV-based plans were larger for lower (1.48±1.32Gy and 1.44±1.29%) than for upper lobe tumors (0.89±0.74Gy and 0.92±0.71%) due to smaller tumor motion (2.9±3.4mm) compared to lower lobe tumors (8.1±6.1mm). Average differences of <1–2% were noted in V5 between ITV and gated plans. Dosimetric differences between gating and ITV-based methods increased with increasing tumor motion and decreasing tumor volume. Overall, average MLD (8.04±3.92Gy) and V20 (8.29±4.33%) values for ITV-based plans were already well below clinical guidelines, even for the 3×18Gy dose scheme, for which largest differences were noted relative to gated plans. Similar results were obtained for 5×10Gy and 4×12Gy regimens. Conclusion: Clinically relevant improvement in pulmonary toxicity, based on predictors of radiation pneumonitis (MLD and V20) was not generally observed, though improvement for tumors

  6. Motion Magnification in Coronal Seismology

    NASA Astrophysics Data System (ADS)

    Anfinogentov, Sergey; Nakariakov, Valery M.

    2016-11-01

    We introduce a new method for the investigation of low-amplitude transverse oscillations of solar plasma non-uniformities, such as coronal loops, individual strands in coronal arcades, jets, prominence fibrils, polar plumes, and other contrast features that have been observed with imaging instruments. The method is based on the two-dimensional dual-tree complex wavelet transform (DTℂWT). It allows us to magnify transverse, in the plane-of-the-sky, quasi-periodic motions of contrast features in image sequences. The tests performed on the artificial data cubes that imitated exponentially decaying, multi-periodic and frequency-modulated kink oscillations of coronal loops showed the effectiveness, reliability, and robustness of this technique. The algorithm was found to give linear scaling of the magnified amplitudes with the original amplitudes, provided these are sufficiently small. In addition, the magnification is independent of the oscillation period in a broad range of the periods. The application of this technique to SDO/AIA EUV data cubes of a non-flaring active region allowed for the improved detection of low-amplitude decay-less oscillations in the majority of loops.

  7. On the distribution of seismic reflection coefficients and seismic amplitudes

    SciTech Connect

    Painter, S.; Paterson, L.; Beresford, G.

    1995-07-01

    Reflection coefficient sequences from 14 wells in Australia have a statistical character consistent with a non-Gaussian scaling noise model based on the Levy-stable family of probability distributions. Experimental histograms of reflection coefficients are accurately approximated by symmetric Levy-stable probability density functions with Levy index between 0.99 and 1.43. These distributions have the same canonical role in mathematical statistics as the Gaussian distribution, but they have slowly decaying tails and infinite moments. The distribution of reflection coefficients is independent of the spatial scale (statistically self-similar), and the reflection coefficient sequences have long-range dependence. These results suggest that the logarithm of seismic impedance can be modeled accurately using fractional Levy motion, which is a generalization of fractional Brownian motion. Synthetic seismograms produced from the authors` model for the reflection coefficients also have Levy-stable distributions. These isolations include transmission losses, the effects of reverberations, and the loss of resolution caused by band-limited wavelets, and suggest that actual seismic amplitudes with sufficient signal-to-noise ratio should also have a Levy-stable distribution. This prediction is verified using post-stack seismic data acquired in the Timor Sea and in the continental USA. However, prestack seismic amplitudes from the Timor Sea are nearly Gaussian. They attribute the difference between prestack and poststack data to the high level of measurement noise in the prestack data.

  8. Local Nanomechanical Motion In Single Cells.

    NASA Astrophysics Data System (ADS)

    Pelling, Andrew; Gimzewski, James

    2004-03-01

    We present new evidence that the nanoscale motion of the cell wall of Saccharomyces cerevisiae exhibits local bionanomechanical motion at characteristic frequencies and which is not caused by random or Brownian processes. This motion is measured with the AFM tip which acts as a nanomechanical sensor, permitting the motion of the cell wall to be recorded as a function of time, applied force, etc. We present persuasive evidence which shows that the local nanomechanical motion is characteristic of metabolic processes taking place inside the cell. This is demonstrated by clear differences between living cells and living cells treated with a metabolic inhibitor. This inhibitor specifically targets cytochrome oxidase inside the mitochondria and inhibits ATP production. The cells observed in this study display characteristic local cell wall motion with amplitudes between 1 and 3 nm and frequencies between 500 and 1700 Hz. The motion is temperature dependant which also suggests the mechanism for the observed motion has biological origins. In addition to a stringent series of control experiments we also discuss local measurements of the cell's mechanical properties and their influence on the observed bionanomechanical motion.

  9. Discontinuities of multi-Regge amplitudes

    NASA Astrophysics Data System (ADS)

    Fadin, V. S.

    2015-04-01

    In the BFKL approach, discontinuities of multiple production amplitudes in invariant masses of produced particles are discussed. It turns out that they are in evident contradiction with the BDS ansatz for n-gluon amplitudes in the planar N = 4 SYM at n ≥ 6. An explicit expression for the NLO discontinuity of the two-to-four amplitude in the invariant mass of two produced gluons is is presented.

  10. Minimal Basis for Gauge Theory Amplitudes

    SciTech Connect

    Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Vanhove, Pierre

    2009-10-16

    Identities based on monodromy for integrations in string theory are used to derive relations between different color-ordered tree-level amplitudes in both bosonic and supersymmetric string theory. These relations imply that the color-ordered tree-level n-point gauge theory amplitudes can be expanded in a minimal basis of (n-3)exclamation amplitudes. This result holds for any choice of polarizations of the external states and in any number of dimensions.

  11. Gravity and Yang-Mills amplitude relations

    SciTech Connect

    Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Soendergaard, Thomas; FengBo

    2010-11-15

    Using only general features of the S matrix and quantum field theory, we prove by induction the Kawai-Lewellen-Tye relations that link products of gauge theory amplitudes to gravity amplitudes at tree level. As a bonus of our analysis, we provide a novel and more symmetric form of these relations. We also establish an infinite tower of new identities between amplitudes in gauge theories.

  12. DVCS amplitude with kinematical twist-3 terms

    SciTech Connect

    Radyushkin, A.V.; Weiss, C.

    2000-08-01

    The authors compute the amplitude of deeply virtual Compton scattering (DVCS) using the calculus of QCD string operators in coordinate representation. To restore the electromagnetic gauge invariance (transversality) of the twist-2 amplitude they include the operators of twist-3 which appear as total derivatives of twist-2 operators. The results are equivalent to a Wandzura-Wilczek approximation for twist-3 skewed parton distributions. They find that this approximation gives a finite result for the amplitude of a longitudinally polarized virtual photon, while the amplitude for transverse polarization is divergent, i.e., factorization breaks down in this term.

  13. SU-E-T-133: Dosimetric Impact of Scan Orientation Relative to Target Motion During Spot Scanning Proton Therapy

    SciTech Connect

    Stoker, J; Summers, P; Li, X; Gomez, D; Sahoo, N; Zhu, X; Gillin, M

    2014-06-01

    Purpose: This study seeks to evaluate the dosimetric effects of intra-fraction motion during spot scanning proton beam therapy as a function of beam-scan orientation and target motion amplitude. Method: Multiple 4DCT scans were collected of a dynamic anthropomorphic phantom mimicking respiration amplitudes of 0 (static), 0.5, 1.0, and 1.5 cm. A spot-scanning treatment plan was developed on the maximum intensity projection image set, using an inverse-planning approach. Dynamic phantom motion was continuous throughout treatment plan delivery.The target nodule was designed to accommodate film and thermoluminescent dosimeters (TLD). Film and TLDs were uniquely labeled by location within the target. The phantom was localized on the treatment table using the clinically available orthogonal kV on-board imaging device. Film inserts provided data for dose uniformity; TLDs provided a 3% precision estimate of absolute dose. An inhouse script was developed to modify the delivery order of the beam spots, to orient the scanning direction parallel or perpendicular to target motion.TLD detector characterization and analysis was performed by the Imaging and Radiation Oncology Core group (IROC)-Houston. Film inserts, exhibiting a spatial resolution of 1mm, were analyzed to determine dose homogeneity within the radiation target. Results: Parallel scanning and target motions exhibited reduced target dose heterogeneity, relative to perpendicular scanning orientation. The average percent deviation in absolute dose for the motion deliveries relative to the static delivery was 4.9±1.1% for parallel scanning, and 11.7±3.5% (p<<0.05) for perpendicularly oriented scanning. Individual delivery dose deviations were not necessarily correlated to amplitude of motion for either scan orientation. Conclusions: Results demonstrate a quantifiable difference in dose heterogeneity as a function of scan orientation, more so than target amplitude. Comparison to the analyzed planar dose of a single

  14. Auditory Motion Elicits a Visual Motion Aftereffect

    PubMed Central

    Berger, Christopher C.; Ehrsson, H. Henrik

    2016-01-01

    The visual motion aftereffect is a visual illusion in which exposure to continuous motion in one direction leads to a subsequent illusion of visual motion in the opposite direction. Previous findings have been mixed with regard to whether this visual illusion can be induced cross-modally by auditory stimuli. Based on research on multisensory perception demonstrating the profound influence auditory perception can have on the interpretation and perceived motion of visual stimuli, we hypothesized that exposure to auditory stimuli with strong directional motion cues should induce a visual motion aftereffect. Here, we demonstrate that horizontally moving auditory stimuli induced a significant visual motion aftereffect—an effect that was driven primarily by a change in visual motion perception following exposure to leftward moving auditory stimuli. This finding is consistent with the notion that visual and auditory motion perception rely on at least partially overlapping neural substrates. PMID:27994538

  15. Human motion analysis and characterization

    NASA Astrophysics Data System (ADS)

    Cathcart, J. Michael; Prussing, Keith; Kocher, Brian

    2011-06-01

    Georgia Tech has investigated methods for the detection and tracking of personnel in a variety of acquisition environments. This research effort focused on a detailed phenomenological analysis of human physiology and signatures with the subsequent identification and characterization of potential observables. Both aspects are needed to support the development of personnel detection and tracking algorithms. As a fundamental part of this research effort, Georgia Tech collected motion capture data on an individual for a variety of walking speeds, carrying loads, and load distributions. These data formed the basis for deriving fundamental properties of the individual's motion and the derivation of motionbased observables, and changes in these fundamental properties arising from load variations. Analyses were conducted to characterize the motion properties of various body components such as leg swing, arm swing, head motion, and full body motion. This paper will describe the data acquisition process, extraction of motion characteristics, and analysis of these data. Video sequences illustrating the motion data and analysis results will also be presented.

  16. Detection of radial motion depends on spatial displacement.

    PubMed

    de la Malla, Cristina; López-Moliner, Joan

    2010-06-01

    Nakayama and Tyler (1981) disentangled the use of pure motion (speed) information from spatial displacement information for the detection of lateral motion. They showed that when positional cues were removed the contribution of motion or spatial information was dependent on the temporal frequency: for temporal frequencies lower than 1Hz the mechanism used to detect motion relied on speed information while for higher temporal frequencies a mechanism based on displacement information was used. Here we test whether the same dependency is also revealed in radial motion. In order to do so, we adapted the paradigm previously used by Nakayama and Tyler to obtain detection thresholds for lateral and radial motion by using a 2-IFC procedure. Subjects had to report which of the intervals contained the signal stimulus (33% coherent motion). We replicated the temporal frequency dependency for lateral motion but results indicate, however, that the detection of radial is always consistent with detecting a spatial displacement amplitude.

  17. Magnetospheric chorus - Amplitude and growth rate

    NASA Technical Reports Server (NTRS)

    Burtis, W. J.; Helliwell, R. A.

    1975-01-01

    A new study of the amplitude of magnetospheric chorus with 1966-1967 data from the Stanford University/Stanford Research Institute VLF receivers on Ogo 1 and Ogo 3 has confirmed the band-limited character of magnetospheric chorus in general and the double-banding of near-equatorial chorus. Chorus amplitude tended to be inversely correlated with frequency, implying lower intensities at lower L values. Individual chorus emissions often showed a characteristic amplitude variation, with rise times of 10 to 300 ms, a short duration at peak amplitude, and decay times of 100 to 3000 msec. Growth was often approximately exponential, with rates from 200 to nearly 2000 dB/sec. Rate of change of frequency was found in many cases to be independent of emission amplitude, in agreement with the cyclotron feedback theory of chorus (Helliwell, 1967, 1970).

  18. Amplitude image processing by diffractive optics.

    PubMed

    Cagigal, Manuel P; Valle, Pedro J; Canales, V F

    2016-02-22

    In contrast to the standard digital image processing, which operates over the detected image intensity, we propose to perform amplitude image processing. Amplitude processing, like low pass or high pass filtering, is carried out using diffractive optics elements (DOE) since it allows to operate over the field complex amplitude before it has been detected. We show the procedure for designing the DOE that corresponds to each operation. Furthermore, we accomplish an analysis of amplitude image processing performances. In particular, a DOE Laplacian filter is applied to simulated astronomical images for detecting two stars one Airy ring apart. We also check by numerical simulations that the use of a Laplacian amplitude filter produces less noisy images than the standard digital image processing.

  19. Multidimensional Large Amplitude Dynamics in the Pyridine-Water Complex.

    PubMed

    Mackenzie, Rebecca B; Dewberry, Christopher T; Cornelius, Ryan D; Smith, C J; Leopold, Kenneth R

    2017-02-02

    Aqueous pyridine plays an important role in a variety of catalytic processes aimed at harnessing solar energy. In this work, the pyridine-water interaction is studied by microwave spectroscopy and density functional theory calculations. Water forms a hydrogen bond to the nitrogen with the oxygen tilted slightly toward either of the ortho-hydrogens of the pyridine, and a tunneling motion involving in-plane rocking of the water interconverts the resulting equivalent structures. A pair of tunneling states with severely perturbed rotational spectra is identified and their energy separation, ΔE, is inferred from the perturbations and confirmed by direct measurement. Curiously, values of ΔE are 10404.45 and 13566.94 MHz for the H2O and D2O complexes, respectively, revealing an inverted isotope effect upon deuteration. Small splittings in some transitions suggest an additional internal motion making this complex an interesting challenge for theoretical treatments of large amplitude motion. The results underscore the significant effect of the ortho-hydrogens on the intermolecular interaction of pyridine.

  20. Thermal cracking and amplitude dependent attenuation

    SciTech Connect

    Johnston, D.H.; Toksoez, M.N.

    1980-02-10

    The role of crack and grain boundary contacts in determining seismic wave attenuation in rock is investigated by examining Q as a function of thermal cycling (cracking) and wave strain amplitude. Q values are obtained using a longitudinal resonant bar technique in the 10- to 20-kHz range for maximum strain amplitudes varying from roughly 10/sup -8/ to 10/sup -5/. The samples studied include the Berea and Navajo sandstones, Plexiglas, Westerly granite, Solenhofen limestone, and Frederick diabase, the latter two relatively crack free in their virgin state. Measurements were made at room temperature and pressure in air. Q values for both sandstones are constant at low strains (<10/sup -6/) but decrease rapidly with amplitude at higher strains. There is no hysteresis of Q with amplitude. Q values for Plexiglas show no indication of amplitude dependent behavior. The granite, limestone, and diabase are thermally cycled at both fast and slow heating rates in order to induce cracking. Samples slowly cycled at 400/sup 0/C show a marked increase in Q that cannot be entirely explained by outgassing of volatiles. Cycling may also widen thin cracks and grain boundaries, reducing contact areas. Samples heated beyond 400/sup 0/C, or rapidly heated, result in generally decreasing Q values. The amplitude dependence of Q is found to be coupled to the effects of thermal cycling. For rock slowly cycled 400)C or less, the transition from low-amplitude contant Q to high-amplitude variable Q behavior decreases to lower amplitudes as a function of maximum temperature. Above 400/sup 0/C, and possibly in th rapidly heated samples also, the transition moves to higher amplitudes.

  1. Self Motion Perception and Motion Sickness

    NASA Technical Reports Server (NTRS)

    Fox, Robert A. (Principal Investigator)

    1991-01-01

    The studies conducted in this research project examined several aspects of motion sickness in animal models. A principle objective of these studies was to investigate the neuroanatomy that is important in motion sickness with the objectives of examining both the utility of putative models and defining neural mechanisms that are important in motion sickness.

  2. Theoretical analysis of the Ca2+ spark amplitude distribution.

    PubMed Central

    Izu, L T; Wier, W G; Balke, C W

    1998-01-01

    A difficulty of using confocal microscopy to study Ca2+ sparks is the uncertainty of the linescan position with respect to the source of Ca2+ release. Random placement of the linescan is expected to result in a broad distribution of measured Ca2+ spark amplitudes (a) even if all Ca2+ sparks were generated identically. Thus variations in Ca2+ spark amplitude due to positional differences between confocal linescans and Ca2+ release site are intertwined with variations due to intrinsic differences in Ca2+ release properties. To separate these two sources of variations on the Ca2+ spark amplitude, we determined the effect changes of channel current or channel open time--collectively called the source strength, alpha--had on the measured Ca2+ spark amplitude histogram, N(a). This was done by 1) simulating Ca2+ release, Ca2+ and fluo-3 diffusion, and Ca2+ binding reactions; 2) simulation of image formation of the Ca2+ spark by a confocal microscope; and 3) using a novel automatic Ca2+ spark detector. From these results we derived an integral equation relating the probability density function of source strengths, f alpha (alpha), to N(a), which takes into account random positional variations between the source and linescan. In the special, but important, case that the spatial distribution of Ca(2+)-bound fluo-3 is Gaussian, we show the following: 1) variations of Ca2+ spark amplitude due to positional or intrinsic differences can be separated, and 2) f alpha (alpha) can, in principle, be calculated from the Ca2+ spark amplitude histogram since N(a) is the sum of shifted hyperbolas, where the magnitudes of the shifts and weights depend on f alpha (alpha). In particular, if all Ca2+ sparks were generated identically, then the plot of 1/N(a) against a will be a straight line. Multiple populations of channels carrying distinct currents are revealed by discontinuities in the 1/N(a) plot. 3) Although the inverse relationship between Ca2+ spark amplitude and decay time might be

  3. Relations of latitudinal characteristics of sunspot groups to the 11-year cycle amplitude at different phases

    NASA Astrophysics Data System (ADS)

    Miletskii, E. V.; Ivanov, V. G.

    2016-12-01

    Using sunspot data for cycles 12 to 23, we have investigated relations of some latitude characteristics of sunspot groups to the 11-year cycle amplitude at different phases. We have revealed a high correlation (with correlation coefficients >0.9) between the middle latitude of sunspot groups at phases of rise, maximum, and decay, on the one hand, and the amplitude of the corresponding cycle, on the other hand. We have shown that the maxima of the velocity of the motion of the sunspot formation zone to the equator have a special physical meaning: the rise phase of the 11-year cycle is characterized by significant correlations between the cycle amplitude and the maximum for the lowest boundary, and the cycle decay phase is characterized by the same maximum for the highest boundary. We have built equations allowing one to determine the amplitude of the 11-year cycle on the basis of data on the given latitudinal characteristics of sunspots groups.

  4. Effects of ion motion on linear Landau damping

    NASA Astrophysics Data System (ADS)

    Xu, Hui; Sheng, Zheng-Ming; Kong, Xiang-Mu; Su, Fu-Fang

    2017-02-01

    The effects of ion motion on Landau damping has been studied by the use of one-dimensional Vlasov-Poisson simulation. It is shown that the ion motion may significantly change the development of the linear Landau damping. When the ion mass is multiple of proton mass, its motion will halt the linear Landau damping at some time due to the excitation of ion acoustic waves. The latter will dominate the system evolution at the later stage and hold a considerable fraction of the total energy in the system. With very small ion mass, such as in electron-positron plasma, the ion motion can suppress the linear Landau damping very quickly. When the initial field amplitude is relatively high such as with the density perturbation amplitude δn/n0 > 0.1, the effect of ion motion on Landau damping is found to be weak or even ignorable.

  5. Self-Motion Perception and Motion Sickness

    NASA Technical Reports Server (NTRS)

    Fox, Robert A.

    1991-01-01

    Motion sickness typically is considered a bothersome artifact of exposure to passive motion in vehicles of conveyance. This condition seldom has significant impact on the health of individuals because it is of brief duration, it usually can be prevented by simply avoiding the eliciting condition and, when the conditions that produce it are unavoidable, sickness dissipates with continued exposure. The studies conducted examined several aspects of motion sickness in animal models. A principle objective of these studies was to investigate the neuroanatomy that is important in motion sickness with the objectives of examining both the utility of putative models and defining neural mechanisms that are important in motion sickness.

  6. Scattering amplitudes in gauge theories: progress and outlook Scattering amplitudes in gauge theories: progress and outlook

    NASA Astrophysics Data System (ADS)

    Roiban, Radu; Spradlin, Marcus; Volovich, Anastasia

    2011-11-01

    oscillator. In the much more complicated realm of four-dimensional quantum field theories, developments over the past several years have led to the extremely exciting, and already partially realized, prospect of completely solving SYM theory (at least in the planar approximation). This alone is a thrilling prospect for theorists, but the great interest in this subject stems in particular from the fact that this is not some obscure field theory but rather a gauge theory, and hence a close cousin of QCD. As reviewed in several of the articles in this issue, many of the insights and methods developed for SYM theory can be applied, with suitable care, to arbitrary gauge theories. It has occasionally been noted that the study of amplitudes is an experimental science in which expressions for, or empirically observed properties of, various scattering amplitudes serve as the 'data' to be collected and analyzed. The rapid pace of progress is made possible in part by the fact that new data is often available at the click of a mouse. The articles in this issue offer testament to the riches which have been discovered hiding in these data, and there is no doubt that more rewards await theorists with the ambition to seek them out.

  7. Development and clinical evaluation of a simple optical method to detect and measure patient external motion.

    PubMed

    Barbés, Benigno; Azcona, Juan Diego; Prieto, Elena; de Foronda, José Manuel; García, Marina; Burguete, Javier

    2015-09-08

    A simple and independent system to detect and measure the position of a number of points in space was devised and implemented. Its application aimed to detect patient motion during radiotherapy treatments, alert of out-of-tolerances motion, and record the trajectories for subsequent studies. The system obtains the 3D position of points in space, through its projections in 2D images recorded by two cameras. It tracks black dots on a white sticker placed on the surface of the moving object. The system was tested with linear displacements of a phantom, circular trajectories of a rotating disk, oscillations of an in-house phantom, and oscillations of a 4D phantom. It was also used to track 461 trajectories of points on the surface of patients during their radiotherapy treatments. Trajectories of several points were reproduced with accuracy better than 0.3 mm in the three spatial directions. The system was able to follow periodic motion with amplitudes lower than 0.5 mm, to follow trajectories of rotating points at speeds up to 11.5 cm/s, and to track accurately the motion of a respiratory phantom. The technique has been used to track the motion of patients during radiotherapy and to analyze that motion. The method is flexible. Its installation and calibration are simple and quick. It is easy to use and can be implemented at a very affordable price. Data collection does not involve any discomfort to the patient and does not delay the treatment, so the system can be used routinely in all treatments. It has an accuracy similar to that of other, more sophisticated, commercially available systems. It is suitable to implement a gating system or any other application requiring motion detection, such as 4D CT, MRI or PET.

  8. The SCEC Broadband Platform: Open-Source Software for Strong Ground Motion Simulation and Validation

    NASA Astrophysics Data System (ADS)

    Goulet, C.; Silva, F.; Maechling, P. J.; Callaghan, S.; Jordan, T. H.

    2015-12-01

    The Southern California Earthquake Center (SCEC) Broadband Platform (BBP) is a carefully integrated collection of open-source scientific software programs that can simulate broadband (0-100Hz) ground motions for earthquakes at regional scales. The BBP scientific software modules implement kinematic rupture generation, low and high-frequency seismogram synthesis using wave propagation through 1D layered velocity structures, seismogram ground motion amplitude calculations, and goodness of fit measurements. These modules are integrated into a software system that provides user-defined, repeatable, calculation of ground motion seismograms, using multiple alternative ground motion simulation methods, and software utilities that can generate plots, charts, and maps. The BBP has been developed over the last five years in a collaborative scientific, engineering, and software development project involving geoscientists, earthquake engineers, graduate students, and SCEC scientific software developers. The BBP can run earthquake rupture and wave propagation modeling software to simulate ground motions for well-observed historical earthquakes and to quantify how well the simulated broadband seismograms match the observed seismograms. The BBP can also run simulations for hypothetical earthquakes. In this case, users input an earthquake location and magnitude description, a list of station locations, and a 1D velocity model for the region of interest, and the BBP software then calculates ground motions for the specified stations. The SCEC BBP software released in 2015 can be compiled and run on recent Linux systems with GNU compilers. It includes 5 simulation methods, 7 simulation regions covering California, Japan, and Eastern North America, the ability to compare simulation results against GMPEs, updated ground motion simulation methods, and a simplified command line user interface.

  9. Phase and amplitude errors in FM radars

    NASA Astrophysics Data System (ADS)

    Griffiths, Hugh D.

    The constraints on phase and amplitude errors are determined for various types of FM radar by calculating the range sidelobe levels on the point target response due to the phase and amplitude modulation of the target echo. It is shown that under certain circumstances the constraints on phase linearity appropriate for conventional pulse compression radars are unnecessarily stringent, and quite large phase errors can be tolerated provided the relative delay of the local oscillator with respect to the target echo is small compared with the periodicity of the phase error characteristic. The constraints on amplitude flatness, however, are severe under almost all circumstances.

  10. Amplitude- and rise-time-compensated filters

    DOEpatents

    Nowlin, Charles H.

    1984-01-01

    An amplitude-compensated rise-time-compensated filter for a pulse time-of-occurrence (TOOC) measurement system is disclosed. The filter converts an input pulse, having the characteristics of random amplitudes and random, non-zero rise times, to a bipolar output pulse wherein the output pulse has a zero-crossing time that is independent of the rise time and amplitude of the input pulse. The filter differentiates the input pulse, along the linear leading edge of the input pulse, and subtracts therefrom a pulse fractionally proportional to the input pulse. The filter of the present invention can use discrete circuit components and avoids the use of delay lines.

  11. A link representation for gravity amplitudes

    NASA Astrophysics Data System (ADS)

    He, Song

    2013-10-01

    We derive a link representation for all tree amplitudes in supergravity, from a recent conjecture by Cachazo and Skinner. The new formula explicitly writes amplitudes as contour integrals over constrained link variables, with an integrand naturally expressed in terms of determinants, or equivalently tree diagrams. Important symmetries of the amplitude, such as supersymmetry, parity and (partial) permutation invariance, are kept manifest in the formulation. We also comment on rewriting the formula in a GL( k)-invariant manner, which may serve as a starting point for the generalization to possible Grassmannian contour integrals.

  12. One-degree-of-freedom motion induced by modeled vortex shedding

    NASA Technical Reports Server (NTRS)

    Yates, L. A.; Unal, A.; Szady, M.; Chapman, G. T.

    1989-01-01

    The motion of an elastically supported cylinder forced by a nonlinear, quasi-static, aerodynamic model with the unusual feature of a motion-dependent forcing frequency was studied. Numerical solutions for the motion and the Lyapunov exponents are presented for three forcing amplitudes and two frequencies (1.0 and 1.1 times the Strouhal frequency). Initially, positive Lyapunov exponents occur and the motion can appear chaotic. After thousands of characteristic times, the motion changes to a motion (verified analytically) that is periodic and damped. This periodic, damped motion was not observed experimentally, thus raising questions concerning the modeling.

  13. Amplitude dynamics favors synchronization in complex networks

    PubMed Central

    Gambuzza, Lucia Valentina; Gómez-Gardeñes, Jesus; Frasca, Mattia

    2016-01-01

    In this paper we study phase synchronization in random complex networks of coupled periodic oscillators. In particular, we show that, when amplitude dynamics is not negligible, phase synchronization may be enhanced. To illustrate this, we compare the behavior of heterogeneous units with both amplitude and phase dynamics and pure (Kuramoto) phase oscillators. We find that in small network motifs the behavior crucially depends on the topology and on the node frequency distribution. Surprisingly, the microscopic structures for which the amplitude dynamics improves synchronization are those that are statistically more abundant in random complex networks. Thus, amplitude dynamics leads to a general lowering of the synchronization threshold in arbitrary random topologies. Finally, we show that this synchronization enhancement is generic of oscillators close to Hopf bifurcations. To this aim we consider coupled FitzHugh-Nagumo units modeling neuron dynamics. PMID:27108847

  14. Amplitude dynamics favors synchronization in complex networks

    NASA Astrophysics Data System (ADS)

    Gambuzza, Lucia Valentina; Gómez-Gardeñes, Jesus; Frasca, Mattia

    2016-04-01

    In this paper we study phase synchronization in random complex networks of coupled periodic oscillators. In particular, we show that, when amplitude dynamics is not negligible, phase synchronization may be enhanced. To illustrate this, we compare the behavior of heterogeneous units with both amplitude and phase dynamics and pure (Kuramoto) phase oscillators. We find that in small network motifs the behavior crucially depends on the topology and on the node frequency distribution. Surprisingly, the microscopic structures for which the amplitude dynamics improves synchronization are those that are statistically more abundant in random complex networks. Thus, amplitude dynamics leads to a general lowering of the synchronization threshold in arbitrary random topologies. Finally, we show that this synchronization enhancement is generic of oscillators close to Hopf bifurcations. To this aim we consider coupled FitzHugh-Nagumo units modeling neuron dynamics.

  15. Feynman amplitudes and limits of heights

    NASA Astrophysics Data System (ADS)

    Amini, O.; Bloch, S. J.; Burgos Gil, J. I.; Fresán, J.

    2016-10-01

    We investigate from a mathematical perspective how Feynman amplitudes appear in the low-energy limit of string amplitudes. In this paper, we prove the convergence of the integrands. We derive this from results describing the asymptotic behaviour of the height pairing between degree-zero divisors, as a family of curves degenerates. These are obtained by means of the nilpotent orbit theorem in Hodge theory.

  16. Amplitude Metrics for Cellular Circadian Bioluminescence Reporters

    PubMed Central

    St. John, Peter C.; Taylor, Stephanie R.; Abel, John H.; Doyle, Francis J.

    2014-01-01

    Bioluminescence rhythms from cellular reporters have become the most common method used to quantify oscillations in circadian gene expression. These experimental systems can reveal phase and amplitude change resulting from circadian disturbances, and can be used in conjunction with mathematical models to lend further insight into the mechanistic basis of clock amplitude regulation. However, bioluminescence experiments track the mean output from thousands of noisy, uncoupled oscillators, obscuring the direct effect of a given stimulus on the genetic regulatory network. In many cases, it is unclear whether changes in amplitude are due to individual changes in gene expression level or to a change in coherence of the population. Although such systems can be modeled using explicit stochastic simulations, these models are computationally cumbersome and limit analytical insight into the mechanisms of amplitude change. We therefore develop theoretical and computational tools to approximate the mean expression level in large populations of noninteracting oscillators, and further define computationally efficient amplitude response calculations to describe phase-dependent amplitude change. At the single-cell level, a mechanistic nonlinear ordinary differential equation model is used to calculate the transient response of each cell to a perturbation, whereas population-level dynamics are captured by coupling this detailed model to a phase density function. Our analysis reveals that amplitude changes mediated at either the individual-cell or the population level can be distinguished in tissue-level bioluminescence data without the need for single-cell measurements. We demonstrate the effectiveness of the method by modeling experimental bioluminescence profiles of light-sensitive fibroblasts, reconciling the conclusions of two seemingly contradictory studies. This modeling framework allows a direct comparison between in vitro bioluminescence experiments and in silico ordinary

  17. Bootstrapping One-Loop QCD Amplitudes

    SciTech Connect

    Berger, Carola F.; /SLAC

    2006-09-08

    We review the recently developed bootstrap method for the computation of high-multiplicity QCD amplitudes at one loop. We illustrate the general algorithm step by step with a six-point example. The method combines (generalized) unitarity with on-shell recursion relations to determine the not cut-constructible, rational terms of these amplitudes. Our bootstrap approach works for arbitrary configurations of gluon helicities and arbitrary numbers of external legs.

  18. Amplitude metrics for cellular circadian bioluminescence reporters.

    PubMed

    St John, Peter C; Taylor, Stephanie R; Abel, John H; Doyle, Francis J

    2014-12-02

    Bioluminescence rhythms from cellular reporters have become the most common method used to quantify oscillations in circadian gene expression. These experimental systems can reveal phase and amplitude change resulting from circadian disturbances, and can be used in conjunction with mathematical models to lend further insight into the mechanistic basis of clock amplitude regulation. However, bioluminescence experiments track the mean output from thousands of noisy, uncoupled oscillators, obscuring the direct effect of a given stimulus on the genetic regulatory network. In many cases, it is unclear whether changes in amplitude are due to individual changes in gene expression level or to a change in coherence of the population. Although such systems can be modeled using explicit stochastic simulations, these models are computationally cumbersome and limit analytical insight into the mechanisms of amplitude change. We therefore develop theoretical and computational tools to approximate the mean expression level in large populations of noninteracting oscillators, and further define computationally efficient amplitude response calculations to describe phase-dependent amplitude change. At the single-cell level, a mechanistic nonlinear ordinary differential equation model is used to calculate the transient response of each cell to a perturbation, whereas population-level dynamics are captured by coupling this detailed model to a phase density function. Our analysis reveals that amplitude changes mediated at either the individual-cell or the population level can be distinguished in tissue-level bioluminescence data without the need for single-cell measurements. We demonstrate the effectiveness of the method by modeling experimental bioluminescence profiles of light-sensitive fibroblasts, reconciling the conclusions of two seemingly contradictory studies. This modeling framework allows a direct comparison between in vitro bioluminescence experiments and in silico ordinary

  19. Quartic Amplitudes for Minkowski Higher Spin

    NASA Astrophysics Data System (ADS)

    Bengtsson, Anders K. H.

    The old problem of finding general quartic interaction terms between fields of higher helicities on the light-front is discussed from the point of view of calculating the corresponding amplitudes directly from the cubic vertices using BCFW recursion. Amplitude based no-go results that has appeared in the literature are reviewed and discussed and it is pointed out how they may perhaps be circumvented.

  20. Quantitative assessment of human motion using video motion analysis

    NASA Technical Reports Server (NTRS)

    Probe, John D.

    1990-01-01

    In the study of the dynamics and kinematics of the human body, a wide variety of technologies was developed. Photogrammetric techniques are well documented and are known to provide reliable positional data from recorded images. Often these techniques are used in conjunction with cinematography and videography for analysis of planar motion, and to a lesser degree three-dimensional motion. Cinematography has been the most widely used medium for movement analysis. Excessive operating costs and the lag time required for film development coupled with recent advances in video technology have allowed video based motion analysis systems to emerge as a cost effective method of collecting and analyzing human movement. The Anthropometric and Biomechanics Lab at Johnson Space Center utilizes the video based Ariel Performance Analysis System to develop data on shirt-sleeved and space-suited human performance in order to plan efficient on orbit intravehicular and extravehicular activities. The system is described.

  1. Twistor-strings and gravity tree amplitudes

    NASA Astrophysics Data System (ADS)

    Adamo, Tim; Mason, Lionel

    2013-04-01

    Recently we discussed how Einstein supergravity tree amplitudes might be obtained from the original Witten and Berkovits twistor-string theory when external conformal gravitons are restricted to be Einstein gravitons. Here we obtain a more systematic understanding of the relationship between conformal and Einstein gravity amplitudes in that twistor-string theory. We show that although it does not in general yield Einstein amplitudes, we can nevertheless obtain some partial twistor-string interpretation of the remarkable formulae recently been found by Hodges and generalized to all tree amplitudes by Cachazo and Skinner. The Hodges matrix and its higher degree generalizations encode the world sheet correlators of the twistor string. These matrices control both Einstein amplitudes and those of the conformal gravity arising from the Witten and Berkovits twistor-string. Amplitudes in the latter case arise from products of the diagonal elements of the generalized Hodges matrices and reduced determinants give the former. The reduced determinants arise if the contractions in the worldsheet correlator are restricted to form connected trees at MHV. The (generalized) Hodges matrices arise as weighted Laplacian matrices for the graph of possible contractions in the correlators and the reduced determinants of these weighted Laplacian matrices give the sum of the connected tree contributions by an extension of the matrix-tree theorem.

  2. Amplitude suppression and chaos control in epileptic EEG signals.

    PubMed

    Majumdar, Kaushik; Myers, Mark H

    2006-03-01

    In this paper we have proposed a novel amplitude suppression algorithm for EEG signals collected during epileptic seizure. Then we have proposed a measure of chaoticity for a chaotic signal, which is somewhat similar to measuring sensitive dependence on initial conditions by measuring Lyapunov exponent in a chaotic dynamical system. We have shown that with respect to this measure the amplitude suppression algorithm reduces chaoticity in a chaotic signal (EEG signal is chaotic). We have compared our measure with the estimated largest Lyapunov exponent measure by the largelyap function, which is similar to Wolf's algorithm. They fit closely for all but one of the cases. How the algorithm can help to improve patient specific dosage titration during vagus nerve stimulation therapy has been outlined.

  3. Modeling and Analysis of Large Amplitude Flight Maneuvers

    NASA Technical Reports Server (NTRS)

    Anderson, Mark R.

    2004-01-01

    Analytical methods for stability analysis of large amplitude aircraft motion have been slow to develop because many nonlinear system stability assessment methods are restricted to a state-space dimension of less than three. The proffered approach is to create regional cell-to-cell maps for strategically located two-dimensional subspaces within the higher-dimensional model statespace. These regional solutions capture nonlinear behavior better than linearized point solutions. They also avoid the computational difficulties that emerge when attempting to create a cell map for the entire state-space. Example stability results are presented for a general aviation aircraft and a micro-aerial vehicle configuration. The analytical results are consistent with characteristics that were discovered during previous flight-testing.

  4. Inverse synthetic aperture radar imaging of maneuvering target based on cubic chirps model with time-varying amplitudes

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Zhang, Qingxiang; Zhao, Bin

    2016-01-01

    Inverse synthetic aperture radar (ISAR) imaging of maneuvering target is a main topic in the field of radar signal processing, and the received signal in a range bin can usually be characterized as multicomponent cubic chirps with constant amplitudes after motion compensation. In fact, the phenomenon of migration through resolution cell (MTRC) often occurs for the target's complex motion, and this will induce the time-varying character for the amplitudes of cubic chirps. An algorithm for the parameters estimation of multicomponent cubic chirps with time-varying amplitudes based on the extension form of match Fourier transform is proposed, and by using it in ISAR imaging of maneuvering target, the quality of images can be improved significantly compared with the constant amplitudes model. Results of simulated and real data validate the effectiveness of the algorithm in this paper.

  5. Design and performance of a respiratory amplitude gating device for PET/CT imaging

    SciTech Connect

    Chang Guoping; Chang Tingting; Clark, John W. Jr.; Mawlawi, Osama R.

    2010-04-15

    Purpose: Recently, the authors proposed a free-breathing amplitude gating (FBAG) technique for PET/CT scanners. The implementation of this technique required specialized hardware and software components that were specifically designed to interface with commercial respiratory gating devices to generate the necessary triggers required for the FBAG technique. The objective of this technical note is to introduce an in-house device that integrates all the necessary hardware and software components as well as tracks the patient's respiratory motion to realize amplitude gating on PET/CT scanners. Methods: The in-house device is composed of a piezoelectric transducer coupled to a data-acquisition system in order to monitor the respiratory waveform. A LABVIEW program was designed to control the data-acquisition device and inject triggers into the PET list stream whenever the detected respiratory amplitude crossed a predetermined amplitude range. A timer was also programmed to stop the scan when the accumulated time within the selected amplitude range reached a user-set interval. This device was tested using a volunteer and a phantom study. Results: The results from the volunteer and phantom studies showed that the in-house device can detect similar respiratory signals as commercially available respiratory gating systems and is able to generate the necessary triggers to suppress respiratory motion artifacts. Conclusions: The proposed in-house device can be used to implement the FBAG technique in current PET/CT scanners.

  6. Amplitude Modulations of Acoustic Communication Signals

    NASA Astrophysics Data System (ADS)

    Turesson, Hjalmar K.

    2011-12-01

    In human speech, amplitude modulations at 3 -- 8 Hz are important for discrimination and detection. Two different neurophysiological theories have been proposed to explain this effect. The first theory proposes that, as a consequence of neocortical synaptic dynamics, signals that are amplitude modulated at 3 -- 8 Hz are propagated better than un-modulated signals, or signals modulated above 8 Hz. This suggests that neural activity elicited by vocalizations modulated at 3 -- 8 Hz is optimally transmitted, and the vocalizations better discriminated and detected. The second theory proposes that 3 -- 8 Hz amplitude modulations interact with spontaneous neocortical oscillations. Specifically, vocalizations modulated at 3 -- 8 Hz entrain local populations of neurons, which in turn, modulate the amplitude of high frequency gamma oscillations. This suggests that vocalizations modulated at 3 -- 8 Hz should induce stronger cross-frequency coupling. Similar to human speech, we found that macaque monkey vocalizations also are amplitude modulated between 3 and 8 Hz. Humans and macaque monkeys share similarities in vocal production, implying that the auditory systems subserving perception of acoustic communication signals also share similarities. Based on the similarities between human speech and macaque monkey vocalizations, we addressed how amplitude modulated vocalizations are processed in the auditory cortex of macaque monkeys, and what behavioral relevance modulations may have. Recording single neuron activity, as well as, the activity of local populations of neurons allowed us to test both of the neurophysiological theories presented above. We found that single neuron responses to vocalizations amplitude modulated at 3 -- 8 Hz resulted in better stimulus discrimination than vocalizations lacking 3 -- 8 Hz modulations, and that the effect most likely was mediated by synaptic dynamics. In contrast, we failed to find support for the oscillation-based model proposing a

  7. Can mobile phones used in strong motion seismology?

    NASA Astrophysics Data System (ADS)

    D'Alessandro, Antonino; D'Anna, Giuseppe

    2013-04-01

    Micro Electro-Mechanical Systems (MEMS) accelerometers are electromechanical devices able to measure static or dynamic accelerations. In the 1990s MEMS accelerometers revolutionized the automotive-airbag system industry and are currently widely used in laptops, game controllers and mobile phones. Nowadays MEMS accelerometers seems provide adequate sensitivity, noise level and dynamic range to be applicable to earthquake strong motion acquisition. The current use of 3 axes MEMS accelerometers in mobile phone maybe provide a new means to easy increase the number of observations when a strong earthquake occurs. However, before utilize the signals recorded by a mobile phone equipped with a 3 axes MEMS accelerometer for any scientific porpoise, it is fundamental to verify that the signal collected provide reliable records of ground motion. For this reason we have investigated the suitability of the iPhone 5 mobile phone (one of the most popular mobile phone in the world) for strong motion acquisition. It is provided by several MEMS devise like a three-axis gyroscope, a three-axis electronic compass and a the LIS331DLH three-axis accelerometer. The LIS331DLH sensor is a low-cost high performance three axes linear accelerometer, with 16 bit digital output, produced by STMicroelectronics Inc. We have tested the LIS331DLH MEMS accelerometer using a vibrating table and the EpiSensor FBA ES-T as reference sensor. In our experiments the reference sensor was rigidly co-mounted with the LIS331DHL MEMS sensor on the vibrating table. We assessment the MEMS accelerometer in the frequency range 0.2-20 Hz, typical range of interesting in strong motion seismology and earthquake engineering. We generate both constant and damped sine waves with central frequency starting from 0.2 Hz until 20 Hz with step of 0.2 Hz. For each frequency analyzed we generate sine waves with mean amplitude 50, 100, 200, 400, 800 and 1600 mg0. For damped sine waves we generate waveforms with initial amplitude

  8. Probabilistic Relationships between Ground‐Motion Parameters and Modified Mercalli Intensity in California

    USGS Publications Warehouse

    Worden, C.B.; Wald, David J.; Rhoades, D.A.

    2012-01-01

    We use a database of approximately 200,000 modified Mercalli intensity (MMI) observations of California earthquakes collected from USGS "Did You Feel It?" (DYFI) reports, along with a comparable number of peak ground-motion amplitudes from California seismic networks, to develop probabilistic relationships between MMI and peak ground velocity (PGV), peak ground acceleration (PGA), and 0.3-s, 1-s, and 3-s 5% damped pseudospectral acceleration (PSA). After associating each ground-motion observation with an MMI computed from all the DYFI responses within 2 km of the observation, we derived a joint probability distribution between MMI and ground motion. We then derived reversible relationships between MMI and each ground-motion parameter by using a total least squares regression to fit a bilinear function to the median of the stacked probability distributions. Among the relationships, the fit to peak ground velocity has the smallest errors, though linear combinations of PGA and PGV give nominally better results. We also find that magnitude and distance terms reduce the overall residuals and are justifiable on an information theoretic basis. For intensities MMI≥5, our results are in close agreement with the relations of Wald, Quitoriano, Heaton, and Kanamori (1999); for lower intensities, our results fall midway between Wald, Quitoriano, Heaton, and Kanamori (1999) and those of Atkinson and Kaka (2007). The earthquakes in the study ranged in magnitude from 3.0 to 7.3, and the distances ranged from less than a kilometer to about 400 km from the source.

  9. Behavioral analysis of signals that guide learned changes in the amplitude and dynamics of the vestibulo-ocular reflex

    NASA Technical Reports Server (NTRS)

    Raymond, J. L.; Lisberger, S. G.

    1996-01-01

    We characterized the dependence of motor learning in the monkey vestibulo-ocular reflex (VOR) on the duration, frequency, and relative timing of the visual and vestibular stimuli used to induce learning. The amplitude of the VOR was decreased or increased through training with paired head and visual stimulus motion in the same or opposite directions, respectively. For training stimuli that consisted of simultaneous pulses of head and target velocity 80-1000 msec in duration, brief stimuli caused small changes in the amplitude of the VOR, whereas long stimuli caused larger changes in amplitude as well as changes in the dynamics of the reflex. When the relative timing of the visual and vestibular stimuli was varied, brief image motion paired with the beginning of a longer vestibular stimulus caused changes in the amplitude of the reflex alone, but the same image motion paired with a later time in the vestibular stimulus caused changes in the dynamics as well as the amplitude of the VOR. For training stimuli that consisted of sinusoidal head and visual stimulus motion, low-frequency training stimuli induced frequency-selective changes in the VOR, as reported previously, whereas high-frequency training stimuli induced changes in the amplitude of the VOR that were more similar across test frequency. The results suggest that there are at least two distinguishable components of motor learning in the VOR. One component is induced by short-duration or high-frequency stimuli and involves changes in only the amplitude of the reflex. A second component is induced by long-duration or low-frequency stimuli and involves changes in the amplitude and dynamics of the VOR.

  10. LARGE-AMPLITUDE LONGITUDINAL OSCILLATIONS IN A SOLAR FILAMENT

    SciTech Connect

    Luna, M.

    2012-05-01

    We have developed the first self-consistent model for the observed large-amplitude oscillations along filament axes that explains the restoring force and damping mechanism. We have investigated the oscillations of multiple threads formed in long, dipped flux tubes through the thermal nonequilibrium process, and found that the oscillation properties predicted by our simulations agree with the observed behavior. We then constructed a model for the large-amplitude longitudinal oscillations that demonstrates that the restoring force is the projected gravity in the tube where the threads oscillate. Although the period is independent of the tube length and the constantly growing mass, the motions are strongly damped by the steady accretion of mass onto the threads by thermal nonequilibrium. The observations and our model suggest that a nearby impulsive event drives the existing prominence threads along their supporting tubes, away from the heating deposition site, without destroying them. The subsequent oscillations occur because the displaced threads reside in magnetic concavities with large radii of curvature. Our model yields a powerful seismological method for constraining the coronal magnetic field and radius of curvature of dips. Furthermore, these results indicate that the magnetic structure is most consistent with the sheared-arcade model for filament channels.

  11. Large-Amplitude Longitudinal Oscillations in a Solar Filament

    NASA Technical Reports Server (NTRS)

    Luna, M.; Karpen, J.

    2012-01-01

    We have developed the first self-consistent model for the observed large-amplitude oscillations along filament axes that explains the restoring force and damping mechanism. We have investigated the oscillations of multiple threads formed in long, dipped flux tubes through the thermal nonequilibrium process, and found that the oscillation properties predicted by our simulations agree with the observed behavior. We then constructed a model for the large-amplitude longitudinal oscillations that demonstrates that the restoring force is the projected gravity in the tube where the threads oscillate. Although the period is independent of the tube length and the constantly growing mass, the motions are strongly damped by the steady accretion of mass onto the threads by thermal nonequilibrium. The observations and our model suggest that a nearby impulsive event drives the existing prominence threads along their supporting tubes, away from the heating deposition site, without destroying them. The subsequent oscillations occur because the displaced threads reside in magnetic concavities with large radii of curvature. Our model yields a powerful seismological method for constraining the coronal magnetic field and radius of curvature of dips. Furthermore, these results indicate that the magnetic structure is most consistent with the sheared-arcade model for filament channels.

  12. Comparison of Flight Simulators Based on Human Motion Perception Metrics

    NASA Technical Reports Server (NTRS)

    Valente Pais, Ana R.; Correia Gracio, Bruno J.; Kelly, Lon C.; Houck, Jacob A.

    2015-01-01

    In flight simulation, motion filters are used to transform aircraft motion into simulator motion. When looking for the best match between visual and inertial amplitude in a simulator, researchers have found that there is a range of inertial amplitudes, rather than a single inertial value, that is perceived by subjects as optimal. This zone, hereafter referred to as the optimal zone, seems to correlate to the perceptual coherence zones measured in flight simulators. However, no studies were found in which these two zones were compared. This study investigates the relation between the optimal and the coherence zone measurements within and between different simulators. Results show that for the sway axis, the optimal zone lies within the lower part of the coherence zone. In addition, it was found that, whereas the width of the coherence zone depends on the visual amplitude and frequency, the width of the optimal zone remains constant.

  13. Visual-Motion Cueing in Altitude and Yaw Control

    NASA Technical Reports Server (NTRS)

    Johnson, Walter W.; Schroeder, Jeffery; Statler, Irving C. (Technical Monitor)

    1994-01-01

    Research conducted using the Vertical Motion Simulator at the NASA Ames Research Center examined the contributions of platform motion and visual level-of-detail (LOD) cueing to tasks that required altitude and/or yaw control in a simulated AH-64 Apache helicopter. Within the altitude control tasks the LOD manipulation caused optical density to change across altitudes by a small, moderate, or large amount; while platform motion was either present or absent. The results from these tasks showed that both constant optical density and platform motion improved altitude awareness in an altitude repositioning task, while the presence of platform motion also led to improved performance in a vertical rate control task. The yaw control tasks had pilots'sit 4.5 ft in front of the center of rotation, thus subjecting them to both rotational and lateral motions during a yaw. The pilots were required to regulate their yaw, while the platform motion was manipulated in order to present all combinations of the resulting rotational and lateral motion components. Ratings of simulation fidelity and sensed platform motion showed that the pilots were relatively insensitive to the rotational component, but highly aware of the lateral component. Together these findings show that: 1) platform motion cues are important when speed regulation is required during altitude change; 2) platform motion contributes to the perception of movement amplitude; 3) lateral, but not rotational, motion cues are essential to the perception of vehicle yaw; and 4) LOD management yielding constant optical density across altitudes improves altitude awareness.

  14. SU-E-J-150: Four-Dimensional Cone-Beam CT Algorithm by Extraction of Physical and Motion Parameter of Mobile Targets Retrospective to Image Reconstruction with Motion Modeling

    SciTech Connect

    Ali, I; Ahmad, S; Alsbou, N

    2015-06-15

    Purpose: To develop 4D-cone-beam CT (CBCT) algorithm by motion modeling that extracts actual length, CT numbers level and motion amplitude of a mobile target retrospective to image reconstruction by motion modeling. Methods: The algorithm used three measurable parameters: apparent length and blurred CT number distribution of a mobile target obtained from CBCT images to determine actual length, CT-number value of the stationary target, and motion amplitude. The predictions of this algorithm were tested with mobile targets that with different well-known sizes made from tissue-equivalent gel which was inserted into a thorax phantom. The phantom moved sinusoidally in one-direction to simulate respiratory motion using eight amplitudes ranging 0–20mm. Results: Using this 4D-CBCT algorithm, three unknown parameters were extracted that include: length of the target, CT number level, speed or motion amplitude for the mobile targets retrospective to image reconstruction. The motion algorithms solved for the three unknown parameters using measurable apparent length, CT number level and gradient for a well-defined mobile target obtained from CBCT images. The motion model agreed with measured apparent lengths which were dependent on the actual target length and motion amplitude. The gradient of the CT number distribution of the mobile target is dependent on the stationary CT number level, actual target length and motion amplitude. Motion frequency and phase did not affect the elongation and CT number distribution of the mobile target and could not be determined. Conclusion: A 4D-CBCT motion algorithm was developed to extract three parameters that include actual length, CT number level and motion amplitude or speed of mobile targets directly from reconstructed CBCT images without prior knowledge of the stationary target parameters. This algorithm provides alternative to 4D-CBCT without requirement to motion tracking and sorting of the images into different breathing phases

  15. A motion phantom study on helical tomotherapy: the dosimetric impacts of delivery technique and motion

    NASA Astrophysics Data System (ADS)

    Kanagaki, Brian; Read, Paul W.; Molloy, Janelle A.; Larner, James M.; Sheng, Ke

    2007-01-01

    Helical tomotherapy (HT) can potentially be used for lung cancer treatment including stereotactic radiosurgery because of its advanced image guidance and its ability to deliver highly conformal dose distributions. However, previous theoretical and simulation studies reported that the effect of respiratory motion on statically planned tomotherapy treatments may cause substantial differences between the calculated and actual delivered radiation isodose distribution, particularly when the treatment is hypofractionated. In order to determine the dosimetric effects of motion upon actual HT treatment delivery, phantom film dosimetry measurements were performed under static and moving conditions using a clinical HT treatment unit. The motion phantom system was constructed using a programmable motor, a base, a moving platform and a life size lung heterogeneity phantom with wood inserts representing lung tissue with a 3.0 cm diameter spherical tumour density equivalent insert. In order to determine the effects of different motion and tomotherapy delivery parameters, treatment plans were created using jaw sizes of 1.04 cm and 2.47 cm, with incremental gantry rotation periods between the minimum allowed (10 s) and the maximum allowed (60 s). The couch speed varied from 0.009 cm s-1 to 0.049 cm s-1, and delivered to a phantom under static and dynamic conditions with peak-to-peak motion amplitudes of 1.2 cm and 2 cm and periods of 3 and 5 s to simulate human respiratory motion of lung tumours. A cylindrical clinical target volume (CTV) was contoured to tightly enclose the tumour insert. 2.0 Gy was prescribed to 95% of the CTV. Two-dimensional dose was measured by a Kodak EDR2 film. Dynamic phantom doses were then quantitatively compared to static phantom doses in terms of axial dose profiles, cumulative dose volume histograms (DVH), percentage of CTV receiving the prescription dose and the minimum dose received by 95% of the CTV. The larger motion amplitude resulted in more

  16. Periodic amplitude variations in Jovian continuum radiation

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.

    1986-01-01

    An analysis of periodic variations in the amplitude of continuum radiation near 3 kHz trapped in the Jovian magnetosphere shows structure with periods near both five and ten hours. Contrary to a plausible initial idea, the continuum amplitudes are not organized by position of the observer relative to the dense plasma sheet. Instead, there seem to be preferred orientations of system III longitude with respect to the direction to the sun which account for the peaks. This implies a clock-like modulation of the continuum radiation intensity as opposed to a searchlight effect. The importance of the dipole longitude-solar wind alignment to the amplitude of the continuum radiation implies the source region of the radiation is near the magnetopause and may indirectly tie the generation of the radio waves to the clocklike modulation of energetic electron fluxes from Jupiter.

  17. Cut-constructible part of QCD amplitudes

    SciTech Connect

    Britto, Ruth; Feng Bo; Mastrolia, Pierpaolo

    2006-05-15

    Unitarity cuts are widely used in analytic computation of loop amplitudes in gauge theories such as QCD. We expand upon the technique introduced in hep-ph/0503132 to carry out any finite unitarity cut integral. This technique naturally separates the contributions of bubble, triangle and box integrals in one-loop amplitudes and is not constrained to any particular helicity configurations. Loop momentum integration is reduced to a sequence of algebraic operations. We discuss the extraction of the residues at higher-order poles. Additionally, we offer concise algebraic formulas for expressing coefficients of three-mass triangle integrals. As an application, we compute all remaining coefficients of bubble and triangle integrals for nonsupersymmetric six-gluon amplitudes.

  18. Analytic representations of Yang-Mills amplitudes

    NASA Astrophysics Data System (ADS)

    Bjerrum-Bohr, N. E. J.; Bourjaily, Jacob L.; Damgaard, Poul H.; Feng, Bo

    2016-12-01

    Scattering amplitudes in Yang-Mills theory can be represented in the formalism of Cachazo, He and Yuan (CHY) as integrals over an auxiliary projective space-fully localized on the support of the scattering equations. Because solving the scattering equations is difficult and summing over the solutions algebraically complex, a method of directly integrating the terms that appear in this representation has long been sought. We solve this important open problem by first rewriting the terms in a manifestly Möbius-invariant form and then using monodromy relations (inspired by analogy to string theory) to decompose terms into those for which combinatorial rules of integration are known. The result is the foundations of a systematic procedure to obtain analytic, covariant forms of Yang-Mills tree-amplitudes for any number of external legs and in any number of dimensions. As examples, we provide compact analytic expressions for amplitudes involving up to six gluons of arbitrary helicities.

  19. A description of seismic amplitude techniques

    NASA Astrophysics Data System (ADS)

    Shadlow, James

    2014-02-01

    The acquisition of seismic data is a non-invasive technique used for determining the sub surface geology. Changes in lithology and fluid fill affect the seismic wavelet. Analysing seismic data for direct hydrocarbon indicators (DHIs), such as full stack amplitude anomalies, or amplitude variation with offset (AVO), can help a seismic interpreter relate the geophysical response to real geology and, more importantly, to distinguish the presence of hydrocarbons. Inversion is another commonly used technique that attempts to tie the seismic data back to the geology. Much has been written about these techniques, and attempting to gain an understanding on the theory and application of them by reading through various journals can be quite daunting. The purpose of this paper is to briefly outline DHI analysis, including full stack amplitude anomalies, AVO and inversion and show the relationship between all three. The equations presented have been included for completeness, but the reader can pass over the mathematical detail.

  20. Modified π π amplitude with σ pole

    NASA Astrophysics Data System (ADS)

    Bydžovský, P.; Kamiński, R.; Nazari, V.

    2014-12-01

    A set of well-known once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multichannel S (π π , K K ¯, and η η ) and P (π π , ρ 2 π , and ρ σ ) wave amplitudes mostly below 1 GeV. Before the modifications, these amplitudes significantly did not satisfy the crossing symmetry condition and did not describe the π π threshold region. Moreover, the pole of the S wave amplitude related with the f0(500 ) meson (former f0(600 ) or σ ) had much smaller imaginary part and bigger real one in comparison with those in the newest Particle Data Group Tables. Here, these amplitudes are supplemented by near threshold expansion polynomials and refitted to the experimental data in the effective two pion mass from the threshold to 1.8 GeV and to the dispersion relations up to 1.1 GeV. In result the self consistent, i.e., unitary and fulfilling the crossing symmetry condition, S and P wave amplitudes are formed and the σ pole becomes much narrower and lighter. To eliminate doubts about the uniqueness of the so obtained sigma pole position short and purely mathematical proof of the uniqueness of the results is also presented. This analysis is addressed to a wide group of physicists and aims at providing a very effective and easy method of modification of, many presently used, π π amplitudes with a heavy and broad σ meson without changing of their original mathematical structure.

  1. Singularity structure of maximally supersymmetric scattering amplitudes.

    PubMed

    Arkani-Hamed, Nima; Bourjaily, Jacob L; Cachazo, Freddy; Trnka, Jaroslav

    2014-12-31

    We present evidence that loop amplitudes in maximally supersymmetric (N=4) Yang-Mills theory (SYM) beyond the planar limit share some of the remarkable structures of the planar theory. In particular, we show that through two loops, the four-particle amplitude in full N=4 SYM has only logarithmic singularities and is free of any poles at infinity--properties closely related to uniform transcendentality and the UV finiteness of the theory. We also briefly comment on implications for maximal (N=8) supergravity theory (SUGRA).

  2. Topographic quantitative EEG amplitude in recovered alcoholics.

    PubMed

    Pollock, V E; Schneider, L S; Zemansky, M F; Gleason, R P; Pawluczyk, S

    1992-05-01

    Topographic measures of electroencephalographic (EEG) amplitude were used to compare recovered alcoholics (n = 14) with sex- and age-matched control subjects. Delta, alpha, and beta activity did not distinguish the groups, but regional differences in theta distribution did. Recovered alcoholics showed more uniform distributions of theta amplitudes in bilateral anterior and posterior regions compared with controls. Because a minimum of 5 years had elapsed since the recovered alcoholic subjects fulfilled DSM-III-R criteria for alcohol abuse or dependence, it is unlikely these EEG theta differences reflect the effects of withdrawal.

  3. Dual amplitude pulse generator for radiation detectors

    DOEpatents

    Hoggan, Jerry M.; Kynaston, Ronnie L.; Johnson, Larry O.

    2001-01-01

    A pulsing circuit for producing an output signal having a high amplitude pulse and a low amplitude pulse may comprise a current source for providing a high current signal and a low current signal. A gate circuit connected to the current source includes a trigger signal input that is responsive to a first trigger signal and a second trigger signal. The first trigger signal causes the gate circuit to connect the high current signal to a pulse output terminal whereas the second trigger signal causes the gate circuit to connect the low current signal to the pulse output terminal.

  4. Amplitude Models for Discrimination and Yield Estimation

    SciTech Connect

    Phillips, William Scott

    2016-09-01

    This seminar presentation describes amplitude models and yield estimations that look at the data in order to inform legislation. The following points were brought forth in the summary: global models that will predict three-component amplitudes (R-T-Z) were produced; Q models match regional geology; corrected source spectra can be used for discrimination and yield estimation; three-component data increase coverage and reduce scatter in source spectral estimates; three-component efforts must include distance-dependent effects; a community effort on instrument calibration is needed.

  5. Amplitude for N-gluon superstring scattering.

    PubMed

    Stieberger, Stephan; Taylor, Tomasz R

    2006-11-24

    We consider scattering processes involving N gluonic massless states of open superstrings with a certain Regge slope alpha'. At the semiclassical level, the string world-sheet sweeps a disk and N gluons are created or annihilated at the boundary. We present exact expressions for the corresponding amplitudes, valid to all orders in alpha', for the so-called maximally helicity violating configurations, with N = 4, 5 and N = 6. We also obtain the leading O(alpha '2) string corrections to the zero-slope N-gluon Yang-Mills amplitudes.

  6. Amplitude for N-Gluon Superstring Scattering

    SciTech Connect

    Stieberger, Stephan; Taylor, Tomasz R.

    2006-11-24

    We consider scattering processes involving N gluonic massless states of open superstrings with a certain Regge slope {alpha}{sup '}. At the semiclassical level, the string world-sheet sweeps a disk and N gluons are created or annihilated at the boundary. We present exact expressions for the corresponding amplitudes, valid to all orders in {alpha}{sup '}, for the so-called maximally helicity violating configurations, with N=4, 5 and N=6. We also obtain the leading O({alpha}{sup '2}) string corrections to the zero-slope N-gluon Yang-Mills amplitudes.

  7. Nonlinear (super)symmetries and amplitudes

    NASA Astrophysics Data System (ADS)

    Kallosh, Renata

    2017-03-01

    There is an increasing interest in nonlinear supersymmetries in cosmological model building. Independently, elegant expressions for the all-tree amplitudes in models with nonlinear symmetries, like D3 brane Dirac-Born-Infeld-Volkov-Akulov theory, were recently discovered. Using the generalized background field method we show how, in general, nonlinear symmetries of the action, bosonic and fermionic, constrain amplitudes beyond soft limits. The same identities control, for example, bosonic E 7(7) scalar sector symmetries as well as the fermionic goldstino symmetries.

  8. Ground-motion prediction from tremor

    USGS Publications Warehouse

    Baltay, Annemarie S.; Beroza, Gregory C.

    2013-01-01

    The widespread occurrence of tremor, coupled with its frequency content and location, provides an exceptional opportunity to test and improve strong ground-motion attenuation relations for subduction zones. We characterize the amplitude of thousands of individual 5 min tremor events in Cascadia during three episodic tremor and slip events to constrain the distance decay of peak ground acceleration (PGA) and peak ground velocity (PGV). We determine the anelastic attenuation parameter for ground-motion prediction equations (GMPEs) to a distance of 150 km, which is sufficient to place important constraints on ground-motion decay. Tremor PGA and PGV show a distance decay that is similar to subduction-zone-specific GMPEs developed from both data and simulations; however, the massive amount of data present in the tremor observations should allow us to refine distance-amplitude attenuation relationships for use in hazard maps, and to search for regional variations and intrasubduction zone differences in ground-motion attenuation.

  9. Short-amplitude high-frequency wing strokes determine the aerodynamics of honeybee flight.

    PubMed

    Altshuler, Douglas L; Dickson, William B; Vance, Jason T; Roberts, Stephen P; Dickinson, Michael H

    2005-12-13

    Most insects are thought to fly by creating a leading-edge vortex that remains attached to the wing as it translates through a stroke. In the species examined so far, stroke amplitude is large, and most of the aerodynamic force is produced halfway through a stroke when translation velocities are highest. Here we demonstrate that honeybees use an alternative strategy, hovering with relatively low stroke amplitude (approximately 90 degrees) and high wingbeat frequency (approximately 230 Hz). When measured on a dynamically scaled robot, the kinematics of honeybee wings generate prominent force peaks during the beginning, middle, and end of each stroke, indicating the importance of additional unsteady mechanisms at stroke reversal. When challenged to fly in low-density heliox, bees responded by maintaining nearly constant wingbeat frequency while increasing stroke amplitude by nearly 50%. We examined the aerodynamic consequences of this change in wing motion by using artificial kinematic patterns in which amplitude was systematically increased in 5 degrees increments. To separate the aerodynamic effects of stroke velocity from those due to amplitude, we performed this analysis under both constant frequency and constant velocity conditions. The results indicate that unsteady forces during stroke reversal make a large contribution to net upward force during hovering but play a diminished role as the animal increases stroke amplitude and flight power. We suggest that the peculiar kinematics of bees may reflect either a specialization for increasing load capacity or a physiological limitation of their flight muscles.

  10. Fast antibody fragment motion: flexible linkers act as entropic spring.

    PubMed

    Stingaciu, Laura R; Ivanova, Oxana; Ohl, Michael; Biehl, Ralf; Richter, Dieter

    2016-03-29

    A flexible linker region between three fragments allows antibodies to adjust their binding sites to an antigen or receptor. Using Neutron Spin Echo Spectroscopy we observed fragment motion on a timescale of 7 ns with motional amplitudes of about 1 nm relative to each other. The mechanistic complexity of the linker region can be described by a spring model with Brownian motion of the fragments in a harmonic potential. Displacements, timescale, friction and force constant of the underlying dynamics are accessed. The force constant exhibits a similar strength to an entropic spring, with friction of the fragment matching the unbound state. The observed fast motions are fluctuations in pre-existing equilibrium configurations. The Brownian motion of domains in a harmonic potential is the appropriate model to examine functional hinge motions dependent on the structural topology and highlights the role of internal forces and friction to function.

  11. Fast antibody fragment motion: flexible linkers act as entropic spring

    SciTech Connect

    Stingaciu, Laura R.; Ivanova, Oxana; Ohl, Michael; Biehl, Ralf; Richter, Dieter

    2016-03-29

    A flexible linker region between three fragments allows antibodies to adjust their binding sites to an antigen or receptor. Using Neutron Spin Echo Spectroscopy we observed fragment motion on a timescale of 7 ns with motional amplitudes of about 1 nm relative to each other. The mechanistic complexity of the linker region can be described by a spring model with Brownian motion of the fragments in a harmonic potential. Displacements, timescale, friction and force constant of the underlying dynamics are accessed. The force constant exhibits a similar strength to an entropic spring, with friction of the fragment matching the unbound state. The observed fast motions are fluctuations in pre-existing equilibrium configurations. In conclusion, the Brownian motion of domains in a harmonic potential is the appropriate model to examine functional hinge motions dependent on the structural topology and highlights the role of internal forces and friction to function.

  12. Fast antibody fragment motion: flexible linkers act as entropic spring

    DOE PAGES

    Stingaciu, Laura R.; Ivanova, Oxana; Ohl, Michael; ...

    2016-03-29

    A flexible linker region between three fragments allows antibodies to adjust their binding sites to an antigen or receptor. Using Neutron Spin Echo Spectroscopy we observed fragment motion on a timescale of 7 ns with motional amplitudes of about 1 nm relative to each other. The mechanistic complexity of the linker region can be described by a spring model with Brownian motion of the fragments in a harmonic potential. Displacements, timescale, friction and force constant of the underlying dynamics are accessed. The force constant exhibits a similar strength to an entropic spring, with friction of the fragment matching the unboundmore » state. The observed fast motions are fluctuations in pre-existing equilibrium configurations. In conclusion, the Brownian motion of domains in a harmonic potential is the appropriate model to examine functional hinge motions dependent on the structural topology and highlights the role of internal forces and friction to function.« less

  13. Fast antibody fragment motion: flexible linkers act as entropic spring

    PubMed Central

    Stingaciu, Laura R.; Ivanova, Oxana; Ohl, Michael; Biehl, Ralf; Richter, Dieter

    2016-01-01

    A flexible linker region between three fragments allows antibodies to adjust their binding sites to an antigen or receptor. Using Neutron Spin Echo Spectroscopy we observed fragment motion on a timescale of 7 ns with motional amplitudes of about 1 nm relative to each other. The mechanistic complexity of the linker region can be described by a spring model with Brownian motion of the fragments in a harmonic potential. Displacements, timescale, friction and force constant of the underlying dynamics are accessed. The force constant exhibits a similar strength to an entropic spring, with friction of the fragment matching the unbound state. The observed fast motions are fluctuations in pre-existing equilibrium configurations. The Brownian motion of domains in a harmonic potential is the appropriate model to examine functional hinge motions dependent on the structural topology and highlights the role of internal forces and friction to function. PMID:27020739

  14. Ground Motion Modeling in the Eastern Caucasus

    NASA Astrophysics Data System (ADS)

    Pitarka, Arben; Gok, Rengin; Yetirmishli, Gurban; Ismayilova, Saida; Mellors, Robert

    2016-08-01

    In this study, we analyzed the performance of a preliminary three-dimensional (3D) velocity model of the Eastern Caucasus covering most of the Azerbaijan. The model was developed in support to long-period ground motion simulations and seismic hazard assessment from regional earthquakes in Azerbaijan. The model's performance was investigated by simulating ground motion from the damaging Mw 5.9, 2012 Zaqatala earthquake, which was well recorded throughout the region by broadband seismic instruments. In our simulations, we use a parallelized finite-difference method of fourth-order accuracy. The comparison between the simulated and recorded ground motion velocity in the modeled period range of 3-20 s shows that in general, the 3D velocity model performs well. Areas in which the model needs improvements are located mainly in the central part of the Kura basin and in the Caspian Sea coastal areas. Comparisons of simulated ground motion using our 3D velocity model and corresponding 1D regional velocity model were used to locate areas with strong 3D wave propagation effects. In areas with complex underground structure, the 1D model fails to produce the observed ground motion amplitude and duration, and spatial extend of ground motion amplification caused by wave propagation effects.

  15. Visualizing the Motion of Graphene Nanodrums.

    PubMed

    Davidovikj, Dejan; Slim, Jesse J; Cartamil-Bueno, Santiago J; van der Zant, Herre S J; Steeneken, Peter G; Venstra, Warner J

    2016-04-13

    Membranes of suspended two-dimensional materials show a large variability in mechanical properties, in part due to static and dynamic wrinkles. As a consequence, experiments typically show a multitude of nanomechanical resonance peaks, which make an unambiguous identification of the vibrational modes difficult. Here, we probe the motion of graphene nanodrum resonators with spatial resolution using a phase-sensitive interferometer. By simultaneously visualizing the local phase and amplitude of the driven motion, we show that unexplained spectral features represent split degenerate modes. When taking these into account, the resonance frequencies up to the eighth vibrational mode agree with theory. The corresponding displacement profiles, however, are remarkably different from theory, as small imperfections increasingly deform the nodal lines for the higher modes. The Brownian motion, which is used to calibrate the local displacement, exhibits a similar mode pattern. The experiments clarify the complicated dynamic behavior of suspended two-dimensional materials, which is crucial for reproducible fabrication and applications.

  16. Frequencies and amplitudes of high-degree solar oscillations

    NASA Astrophysics Data System (ADS)

    Kaufman, James Morris

    Measurements of some of the properties of high-degree solar p- and f-mode oscillations are presented. Using high-resolution velocity images from Big Bear Solar Observatory, we have measured mode frequencies, which provide information about the composition and internal structure of the Sun, and mode velocity amplitudes (corrected for the effects of atmospheric seeing), which tell us about the oscillation excitation and damping mechanisms. We present a new and more accurate table of the Sun's acoustic vibration frequencies, nunl, as a function of radial order n and spherical harmonic degree l. These frequencies are averages over azimuthal order m and approximate the normal mode frequencies of a nonrotating spherically symmetric Sun near solar minimum. The frequencies presented here are for solar p- and f-modes with 180 less than or = l less than or = 1920, 0 less than or = n less than or = 8, and 1.7 mHz less than or = nunl less than or = 5.3 mHz. The uncertainties, sigmanl, in the frequencies areas are as low as 3.1 micro-Hz. The theoretically expected f-mode frequencies are given by omega squared = gkh approx. = gl/R, where g is the gravitational acceleration at the surface, kh is the horizontal component of the wave vector, and R is the radius of the Sun. We find that the observed frequencies are significantly less than expected for l greater than 1000, for which we have no explanation. Observations of high-degree oscillations, which have very small spatial features, suffer from the effects of atmospheric image blurring and image motion (or 'seeing'), thereby reducing the amplitudes of their spatial-frequency components. In an attempt to correct the velocity amplitudes for these effects, we simultaneously measured the atmospheric modulation transfer function (MTF) by looking at the effects of seeing on the solar limb. We are able to correct the velocity amplitudes using the MTF out to l approx. = 1200. We find that the frequency of the peak velocity power (as a

  17. Regional Multi-station Discriminants: Magnitude, Distance and Amplitude Corrections and Sources of Error

    SciTech Connect

    Anderson, D N; Walter, W R; Fagan, D K; Mercier, T M; Taylor, S R

    2008-10-06

    Magnitude, distance and amplitude corrections (MDAC) made to observed regional amplitudes are necessary so that what remains in the corrected amplitude is mostly information about the seismic source-type. Corrected amplitudes can be used in ratios to discriminate between earthquakes and explosions. However, there remain source effects such as those due to depth, focal mechanism, local material property and apparent stress variability that cannot easily be determined and applied as amplitude corrections. We develop a mathematical model to capture these near source effects as random (unknown) giving an error partition of three sources: model inadequacy, station noise and amplitude correlations. This mathematical model is the basis for a general multi-station regional discriminant formulation. The standard error of the discriminant includes these three sources of error in its formulation. The developed methods are demonstrated with a collection of Nevada Test Site (NTS) events observed at regional stations. Importantly, the proposed formulation includes all corrected amplitude information through the construction of multi-station discriminants. In contrast, previous studies have only computed discriminants from single stations having both P and S amplitudes. The proposed multi-station approach has similarities to the well established m{sub b} versus M{sub s} discriminant and represents a new paradigm for the regional discrimination problem.

  18. A Study of Motion Sickness: Mathematical Modeling and Data Analysis

    DTIC Science & Technology

    1988-12-01

    levels of motion sick- ness experienced by a test subject during the course of an experiment (21:97; 25:59; 27:84). In 1987, Drylie, Fix, and Gaudreault ...pro- cedures. Drylie and Gaudreault reported additional conclusions concerning motion sickness trends (11; 17). Fix developed a new equation for...and Gaudreault also noted low frequency EEG signals in the 0.1 Hz range (17:28). However, only one of their subjects had EEG signals with an amplitude

  19. A classification of large amplitude oscillations of a spring-pendulum system

    NASA Technical Reports Server (NTRS)

    Broucke, R.

    1977-01-01

    We present a detailed classification of large amplitude oscillations of a non-integrable autonomous system with two degrees of freedom: the spring pendulum system. The classification is made with the method of invariant curves. The results show the importance of three types of motion: periodic, quasi-periodic and semi-ergodic. The numerical results are given for nine different values of the energy constant.

  20. Effects of line-of-sight motion on hyperspectral Fourier transform measurements

    NASA Astrophysics Data System (ADS)

    Miecznik, Grzegorz; Johnson, Brian R.

    2015-01-01

    Atmospheric spectra reconstructed from interferometric measurements are susceptible to scene motion, which can be caused by changing environment or instrument jitter. This leads to a coupling between the time series of the modulated scene radiance and the interferogram collected as a function of time. Spectral artifacts are generated when this occurs and appear as both narrow, isolated spikes in the measurement wavelength band as well as broad, out-of-band features. Here, we derive an analytical relationship that depends on jitter frequency, amplitude and phase, and the scene gradient. The observed radiance is expressed as a spatially weighted mixture of radiance originating from various points within the scene. Spectral artifacts created by relative scene motion are shown to be proportional to the radiometric scene difference within the instrument field of view (FOV) and jitter amplitude, and vary significantly with the jitter frequency. The analytical solution can be useful in various applications, where image instability is expected to have an effect on measurements in question, ranging from spectroscopy of turbine plumes, through airborne measurements of smoke density and chemical composition in natural fire or volcanic events, to atmospheric sounding from space.

  1. Particle Distribution Modification by Low Amplitude Modes

    SciTech Connect

    White, R. B.; Gorelenkov, N.; Heidbrink, W. W.; Van Zeeland, M. A.

    2009-08-28

    Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.

  2. The CMU Baryon Amplitude Analysis Program

    NASA Astrophysics Data System (ADS)

    Bellis, Matt

    2007-05-01

    The PWA group at Carnegie Mellon University has developed a comprehensive approach and analysis package for the purpose of extracting the amplitudes for photoproduced baryon resonances. The end goal is to identify any missing resonances that are predicted by the constituent quark model, but not definitively observed in experiments. The data comes from the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab.

  3. Audio steganography by amplitude or phase modification

    NASA Astrophysics Data System (ADS)

    Gopalan, Kaliappan; Wenndt, Stanley J.; Adams, Scott F.; Haddad, Darren M.

    2003-06-01

    This paper presents the results of embedding short covert message utterances on a host, or cover, utterance by modifying the phase or amplitude of perceptually masked or significant regions of the host. In the first method, the absolute phase at selected, perceptually masked frequency indices was changed to fixed, covert data-dependent values. Embedded bits were retrieved at the receiver from the phase at the selected frequency indices. Tests on embedding a GSM-coded covert utterance on clean and noisy host utterances showed no noticeable difference in the stego compared to the hosts in speech quality or spectrogram. A bit error rate of 2 out of 2800 was observed for a clean host utterance while no error occurred for a noisy host. In the second method, the absolute phase of 10 or fewer perceptually significant points in the host was set in accordance with covert data. This resulted in a stego with successful data retrieval and a slightly noticeable degradation in speech quality. Modifying the amplitude of perceptually significant points caused perceptible differences in the stego even with small changes of amplitude made at five points per frame. Finally, the stego obtained by altering the amplitude at perceptually masked points showed barely noticeable differences and excellent data recovery.

  4. Travel-Time and Amplitude Sensitivity Kernels

    DTIC Science & Technology

    2011-09-01

    amplitude sensitivity kernels shown in the lower panels concentrate about the corresponding eigenrays . Each 3D kernel exhibits a broad negative...in 2 and 3 dimensions have similar 11 shapes to corresponding travel-time sensitivity kernels (TSKs), centered about the respective eigenrays

  5. Amplitude Frequency Response Measurement: A Simple Technique

    ERIC Educational Resources Information Center

    Satish, L.; Vora, S. C.

    2010-01-01

    A simple method is described to combine a modern function generator and a digital oscilloscope to configure a setup that can directly measure the amplitude frequency response of a system. This is achieved by synchronously triggering both instruments, with the function generator operated in the "Linear-Sweep" frequency mode, while the oscilloscope…

  6. Connected formulas for amplitudes in standard model

    NASA Astrophysics Data System (ADS)

    He, Song; Zhang, Yong

    2017-03-01

    Witten's twistor string theory has led to new representations of S-matrix in massless QFT as a single object, including Cachazo-He-Yuan formulas in general and connected formulas in four dimensions. As a first step towards more realistic processes of the standard model, we extend the construction to QCD tree amplitudes with massless quarks and those with a Higgs boson. For both cases, we find connected formulas in four dimensions for all multiplicities which are very similar to the one for Yang-Mills amplitudes. The formula for quark-gluon color-ordered amplitudes differs from the pure-gluon case only by a Jacobian factor that depends on flavors and orderings of the quarks. In the formula for Higgs plus multi-parton amplitudes, the massive Higgs boson is effectively described by two additional massless legs which do not appear in the Parke-Taylor factor. The latter also represents the first twistor-string/connected formula for form factors.

  7. PET Motion Compensation for Radiation Therapy Using a CT-Based Mid-Position Motion Model: Methodology and Clinical Evaluation

    SciTech Connect

    Kruis, Matthijs F.; Kamer, Jeroen B. van de; Houweling, Antonetta C.; Sonke, Jan-Jakob; Belderbos, José S.A.; Herk, Marcel van

    2013-10-01

    Purpose: Four-dimensional positron emission tomography (4D PET) imaging of the thorax produces sharper images with reduced motion artifacts. Current radiation therapy planning systems, however, do not facilitate 4D plan optimization. When images are acquired in a 2-minute time slot, the signal-to-noise ratio of each 4D frame is low, compromising image quality. The purpose of this study was to implement and evaluate the construction of mid-position 3D PET scans, with motion compensated using a 4D computed tomography (CT)-derived motion model. Methods and Materials: All voxels of 4D PET were registered to the time-averaged position by using a motion model derived from the 4D CT frames. After the registration the scans were summed, resulting in a motion-compensated 3D mid-position PET scan. The method was tested with a phantom dataset as well as data from 27 lung cancer patients. Results: PET motion compensation using a CT-based motion model improved image quality of both phantoms and patients in terms of increased maximum SUV (SUV{sub max}) values and decreased apparent volumes. In homogenous phantom data, a strong relationship was found between the amplitude-to-diameter ratio and the effects of the method. In heterogeneous patient data, the effect correlated better with the motion amplitude. In case of large amplitudes, motion compensation may increase SUV{sub max} up to 25% and reduce the diameter of the 50% SUV{sub max} volume by 10%. Conclusions: 4D CT-based motion-compensated mid-position PET scans provide improved quantitative data in terms of uptake values and volumes at the time-averaged position, thereby facilitating more accurate radiation therapy treatment planning of pulmonary lesions.

  8. Influence of Continuous Table Motion on Patient Breathing Patterns

    SciTech Connect

    Wilbert, Juergen; Baier, Kurt; Richter, Anne; Herrmann, Christian; Ma Lei; Flentje, Michael; Guckenberger, Matthias

    2010-06-01

    Purpose: To investigate the influence of continuous table motion on patient breathing patterns for compensation of moving targets by a robotic treatment couch. Methods and Materials: Fifteen volunteers were placed on a robotic treatment couch, and the couch was moved on different breathing-correlated and -uncorrelated trajectories. External abdominal breathing motion of the patients was measured using an infrared camera system. The influence of table motion on breathing range and pattern was analyzed. Results: Continuous table motion was tolerated well by all test persons. Volunteers reacted differently to table motion. Four test persons showed no change of breathing range and pattern. Increased irregular breathing was observed in 4 patients; however, irregularity was not correlated with table motion. Only 4 test persons showed an increase in mean breathing amplitude of more than 2mm during motion of the couch. The mean cycle period decreased by more than 1 s for 2 test persons only. No abrupt changes in amplitude or cycle period could be observed. Conclusions: The observed small changes in breathing patterns support the application of motion compensation by a robotic treatment couch.

  9. ABJM amplitudes and the positive orthogonal Grassmannian

    NASA Astrophysics Data System (ADS)

    Huang, Yu-tin; Wen, CongKao

    2014-02-01

    A remarkable connection between perturbative scattering amplitudes of four dimensional planar SYM, and the stratification of the positive Grassmannian, was revealed in the seminal work of Arkani-Hamed et al. Similar extension for three-dimensional ABJM theory was proposed. Here we establish a direct connection between planar scattering amplitudes of ABJM theory, and singularities thereof, to the stratification of the positive orthogonal Grassmannian. In particular, scattering processes are constructed through on-shell diagrams, which are simply iterative gluing of the fundamental four-point amplitude. Each diagram is then equivalent to the merging of fundamental OG2 orthogonal Grassmannian to form a larger OG k , where 2 k is the number of external particles. The invariant information that is encoded in each diagram is precisely this stratification. This information can be easily read off via permutation paths of the on-shell diagram, which also can be used to derive a canonical representation of OG k that manifests the vanishing of consecutive minors as the singularity of all on-shell diagrams. Quite remarkably, for the BCFW recursion representation of the tree-level amplitudes, the on-shell diagram manifests the presence of all physical factorization poles, as well as the cancellation of the spurious poles. After analytically continuing the orthogonal Grassmannian to split signature, we reveal that each on-shell diagram in fact resides in the positive cell of the orthogonal Grassmannian, where all minors are positive. In this language, the amplitudes of ABJM theory is simply an integral of a product of d log forms, over the positive orthogonal Grassmannian.

  10. Optimization and small-amplitude analysis of Purcell's three-link microswimmer model.

    PubMed

    Wiezel, O; Or, Y

    2016-08-01

    This work studies the motion of Purcell's three-link microswimmer in viscous flow, by using perturbation expansion of its dynamics under small-amplitude strokes. Explicit leading-order expressions and next-order correction terms for the displacement of the swimmer are obtained for the cases of a square or circular gait in the plane of joint angles. The correction terms demonstrate the reversal in movement direction for large stroke amplitudes, which has previously only been shown numerically. In addition, asymptotic expressions for Lighthill's energetic efficiency are obtained for both gaits. These approximations enable calculating optimal stroke amplitudes and swimmer's geometry (i.e. ratio of links' lengths) for maximizing either net displacement or Lighthill's efficiency.

  11. Optimization and small-amplitude analysis of Purcell's three-link microswimmer model

    NASA Astrophysics Data System (ADS)

    Wiezel, O.; Or, Y.

    2016-08-01

    This work studies the motion of Purcell's three-link microswimmer in viscous flow, by using perturbation expansion of its dynamics under small-amplitude strokes. Explicit leading-order expressions and next-order correction terms for the displacement of the swimmer are obtained for the cases of a square or circular gait in the plane of joint angles. The correction terms demonstrate the reversal in movement direction for large stroke amplitudes, which has previously only been shown numerically. In addition, asymptotic expressions for Lighthill's energetic efficiency are obtained for both gaits. These approximations enable calculating optimal stroke amplitudes and swimmer's geometry (i.e. ratio of links' lengths) for maximizing either net displacement or Lighthill's efficiency.

  12. Speckle interferometric sensor to measure low-amplitude high frequency Ocular Microtremor (OMT)

    NASA Astrophysics Data System (ADS)

    Ryle, James P.; Al-Kalbani, Mohammed; Gopinathan, Unnikrishnan; Boyle, Gerard; Coakley, Davis; Sheridan, John T.

    2009-08-01

    Ocular microtremor (OMT) is a physiological high frequency (up to 150Hz) low amplitude (150-2500nm) involuntary tremor of the human eye. It is one of the three fixational ocular motions described by Adler and Fliegelman in 1934 as well as microsaccades and drift. Clinical OMT investigations to date have used eye-contacting piezoelectric probes or piezoelectric strain gauges. Before contact can be made, the eye must first be anaesthetised. In some cases, this induces eyelid spasms (blepharospasm) making it impossible to measure OMT. Using the contact probe method, the eye motion is mechanically damped. In addition to this, it is not possible to obtain exact information about the displacement. Results from clinical studies to date have given electrical signal amplitudes from the probe. Recent studies suggest a number of clinical applications for OMT, these include monitoring the depth of anaesthesia of a patient in surgery, prediction of outcome in coma, diagnosis of brainstem death. In addition to this, abnormal OMT frequency content is present in patients with neurological disorders such as Multiple sclerosis and Parkinson's disease. However for ongoing clinical investigations the contact probe method falls short of a non-contact accurate measurement solution. In this paper, we design a compact non contact phase modulating optical fiber speckle interferometer to measure eye motions. We present our calibration results using a calibrated piezoelectric vibration simulator. Digital signal processing is then performed to extract the low amplitude high frequency displacement information.

  13. Objects in Motion

    ERIC Educational Resources Information Center

    Damonte, Kathleen

    2004-01-01

    One thing scientists study is how objects move. A famous scientist named Sir Isaac Newton (1642-1727) spent a lot of time observing objects in motion and came up with three laws that describe how things move. This explanation only deals with the first of his three laws of motion. Newton's First Law of Motion says that moving objects will continue…

  14. Bifurcation analysis of aircraft pitching motions near the stability boundary

    NASA Technical Reports Server (NTRS)

    Hui, W. H.; Tobak, M.

    1984-01-01

    Bifuraction theory is used to analyze the nonlinear dynamic stability characteristics of an aircraft subject to single degree of freedom pitching-motion perturbations about a large mean angle of attack. The requisite aerodynamic information in the equations of motion is represented in a form equivalent to the response to finite-amplitude pitching oscillations about the mean angle of attack. This information is deduced from the case of infinitesimal-amplitude oscillations. The bifurcation theory analysis reveals that when the mean angle of attack is increased beyond a critical value at which the aerodynamic damping vanishes, new solutions representing finite-amplitude periodic motions bifurcate from the previously stable steady motion. The sign of a simple criterion, cast in terms of aerodynamic properties, determines whether the bifurcating solutions are stable (supercritical) or unstable (subcritical). For flat-plate airfoils flying at supersonic/hypersonic speed, the bifurcation is subcritical, implying either that exchanges of stability between steady and periodic motion are accompanied by hysteresis phenomena, or that potentially large aperiodic departures from steady motion may develop.

  15. Quantitative assessment of human motion using video motion analysis

    NASA Technical Reports Server (NTRS)

    Probe, John D.

    1993-01-01

    In the study of the dynamics and kinematics of the human body a wide variety of technologies has been developed. Photogrammetric techniques are well documented and are known to provide reliable positional data from recorded images. Often these techniques are used in conjunction with cinematography and videography for analysis of planar motion, and to a lesser degree three-dimensional motion. Cinematography has been the most widely used medium for movement analysis. Excessive operating costs and the lag time required for film development, coupled with recent advances in video technology, have allowed video based motion analysis systems to emerge as a cost effective method of collecting and analyzing human movement. The Anthropometric and Biomechanics Lab at Johnson Space Center utilizes the video based Ariel Performance Analysis System (APAS) to develop data on shirtsleeved and space-suited human performance in order to plan efficient on-orbit intravehicular and extravehicular activities. APAS is a fully integrated system of hardware and software for biomechanics and the analysis of human performance and generalized motion measurement. Major components of the complete system include the video system, the AT compatible computer, and the proprietary software.

  16. Active Phase and Amplitude Fluctuations of Flagellar Beating

    NASA Astrophysics Data System (ADS)

    Ma, Rui; Klindt, Gary S.; Riedel-Kruse, Ingmar H.; Jülicher, Frank; Friedrich, Benjamin M.

    2014-07-01

    The eukaryotic flagellum beats periodically, driven by the oscillatory dynamics of molecular motors, to propel cells and pump fluids. Small but perceivable fluctuations in the beat of individual flagella have physiological implications for synchronization in collections of flagella as well as for hydrodynamic interactions between flagellated swimmers. Here, we characterize phase and amplitude fluctuations of flagellar bending waves using shape mode analysis and limit-cycle reconstruction. We report a quality factor of flagellar oscillations Q =38.0±16.7 (mean±s.e.). Our analysis shows that flagellar fluctuations are dominantly of active origin. Using a minimal model of collective motor oscillations, we demonstrate how the stochastic dynamics of individual motors can give rise to active small-number fluctuations in motor-cytoskeleton systems.

  17. Dual motion valve with single motion input

    NASA Technical Reports Server (NTRS)

    Belew, Robert (Inventor)

    1987-01-01

    A dual motion valve includes two dual motion valve assemblies with a rotary input which allows the benefits of applying both rotary and axial motion to a rotary sealing element with a plurality of ports. The motion of the rotary sealing element during actuation provides axial engagement of the rotary sealing element with a stationary valve plate which also has ports. Fluid passages are created through the valve when the ports of the rotary sealing element are aligned with the ports of the stationary valve plate. Alignment is achieved through rotation of the rotary sealing element with respect to the stationary valve plate. The fluid passages provide direct paths which minimize fluid turbulence created in the fluid as it passes through the valve.

  18. Tip-surface forces, amplitude, and energy dissipation in amplitude-modulation (tapping mode) force microscopy

    NASA Astrophysics Data System (ADS)

    Paulo, Álvaro San; García, Ricardo

    2001-11-01

    Amplitude-modulation (tapping mode) atomic force microscopy is a technique for high resolution imaging of a wide variety of surfaces in air and liquid environments. Here by using the virial theorem and energy conservation principles we have derived analytical relationships between the oscillation amplitude, phase shift, and average tip-surface forces. We find that the average value of the interaction force and oscillation and the average power dissipated by the tip-surface interaction are the quantities that control the amplitude reduction. The agreement obtained between analytical and numerical results supports the analytical method.

  19. Polar motion prediction by KASI

    NASA Astrophysics Data System (ADS)

    Na, Sung-Ho; Cho, Jung-Ho; Baek, Jeongho; Kwak, Young-Hee

    2010-05-01

    Korea Astronomy and Space Science Institute(KASI) recently started researches about Earth Rotation. One of KASI's those studies is analysis and prediction of the Earth's pole position - i.e. polar motion. Fitting temporary coefficients of three main components only - Chandler wobble, annual wobble, and 500 day period term has been studied as preliminary one. Both Xp and Yp are modeled as time series composed of constant off set, linear term, and sine and cosine terms for each three periods. The coefficients are determined by using least square error method for each time span of 6.4 years - which is about the beat period of annual wobble and Chandler wobble. Then the prediction of Xp and Yp are made as direct continuation. This approach has been found stable and been applicable to predicting polar motion up to three years. More elaborate models composed of variable coefficients and other minor components are being tested. So far linearly varying amplitude model has been found to be unstable and quite often divergent.

  20. COMPENSATORY POSTURAL ADAPTATIONS DURING CONTINUOUS, VARIABLE AMPLITUDE PERTURBATIONS REVEAL GENERALIZED RATHER THAN SEQUENCE-SPECIFIC LEARNING

    PubMed Central

    Van Ooteghem, K; Frank, JS; Allard, F; Buchanan, JJ; Oates, AR; Horak, FB

    2010-01-01

    We examined changes in the motor organization of postural control in response to continuous, variable amplitude oscillations evoked by a translating platform and explored whether these changes reflected implicit sequence learning. The platform underwent random amplitude (maximum ± 15 cm) and constant frequency (0.5 Hz) oscillations. Each trial was composed of three 15-second segments containing seemingly random oscillations. Unbeknownst to participants, the middle segment was repeated in each of 42 trials on the first day of testing and in an additional seven trials completed approximately 24 hours later. Kinematic data were used to determine spatial and temporal components of total body centre of mass (COM) and joint segment coordination. Results showed that with repeated trials, participants reduced the magnitude of horizontal body COM displacement, shifted from a COM phase lag to a phase lead relative to platform motion and increased correlations between ankle/platform motion and hip/platform motion as they evolved from an ankle strategy to a multi-segment control strategy involving the ankle and hip. Maintenance of these changes across days provided evidence for learning. Similar improvements for the random and repeated segments, however, indicate that participants did not exploit the sequence of perturbations to improve balance control. Rather, the central nervous system (CNS) may have been tuning into more general features of platform motion. These findings provide important insight into the generalizabilty of improved compensatory balance control with training. PMID:18327574

  1. Constructing QCD one-loop amplitudes

    SciTech Connect

    Forde, Darren; /SLAC /UCLA

    2008-02-22

    In the context of constructing one-loop amplitudes using a unitarity bootstrap approach we discuss a general systematic procedure for obtaining the coefficients of the scalar bubble and triangle integral functions of one-loop amplitudes. Coefficients are extracted after examining the behavior of the cut integrand as the unconstrained parameters of a specifically chosen parameterization of the cut loop momentum approach infinity. Measurements of new physics at the forthcoming experimental program at CERN's Large Hadron Collider (LHC) will require a precise understanding of processes at next-to-leading order (NLO). This places increased demands for the computation of new one-loop amplitudes. This in turn has spurred recent developments towards improved calculational techniques. Direct calculations using Feynman diagrams are in general inefficient. Developments of more efficient techniques have usually centered around unitarity techniques [1], where tree amplitudes are effectively 'glued' together to form loops. The most straightforward application of this method, in which the cut loop momentum is in D = 4, allows for the computation of 'cut-constructible' terms only, i.e. (poly)logarithmic containing terms and any related constants. QCD amplitudes contain, in addition to such terms, rational pieces which cannot be derived using such cuts. These 'missing' rational parts can be extracted using cut loop momenta in D = 4-2 {var_epsilon}. The greater difficulty of such calculations has restricted the application of this approach, although recent developments [3, 4] have provided new promise for this technique. Recently the application of on-shell recursion relations [5] to obtaining the 'missing' rational parts of one-loop processes [6] has provided an alternative very promising solution to this problem. In combination with unitarity methods an 'on-shell bootstrap' approach provides an efficient technique for computing complete one-loop QCD amplitudes [7]. Additionally

  2. Amplitudes of MHD Waves in Sunspots

    NASA Astrophysics Data System (ADS)

    Norton, Aimee Ann; Cally, Paul; Baldner, Charles; Kleint, Lucia; Tarbell, Theodore D.; De Pontieu, Bart; Scherrer, Philip H.; Rajaguru, Paul

    2016-05-01

    The conversion of p-modes into MHD waves by strong magnetic fields occurs mainly in the sub-photospheric layers. The photospheric signatures of MHD waves are weak due to low amplitudes at the beta=1 equipartion level where mode-conversion occurs. We report on small amplitude oscillations observed in the photosphere with Hinode SOT/SP in which we analyze time series for sunspots ARs 12186 (11.10.2014) and 12434 (17.10.2015). No significant magnetic field oscillations are recovered in the umbra or penumbra in the ME inversion. However, periodicities in the inclination angle are found at the umbral/penumbral boundary with 5 minute periods. Upward propagating waves are indicated in the intensity signals correlated between HMI and AIA at different heights. We compare SP results with the oscillations observed in HMI data. Simultaneous IRIS data shows transition region brightening above the umbral core.

  3. Multilayered models for electromagnetic reflection amplitudes

    NASA Technical Reports Server (NTRS)

    Linlor, W. I.

    1976-01-01

    The remote sensing of snowpack characteristics with surface installations or with an airborne system could have important applications in water resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multilayer snow models is analyzed. Normally incident plane waves are assumed at frequencies ranging from 10 to the 6th power to 10 to the 10th power Hz, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice sheets. Layers are defined by a thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients, versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the reflection coefficient variations as a function of frequency.

  4. Large Amplitude Oscillatory Shear near Jamming

    NASA Astrophysics Data System (ADS)

    Tighe, Brian; Dagois-Bohy, Simon; Somfai, Ellak; van Hecke, Martin

    2014-11-01

    Jammed solids such as foams and emulsions can be driven with oscillatory shear at finite strain amplitude and frequency. On a macro scale, this induces nonlinearities such as strain softening and shear thinning. On the micro scale one observes the onset of irreversibility, caging, and long-time diffusion. Using simulations of soft viscous spheres, we systematically vary the distance to the jamming transition. We correlate crossovers in the microscopic and macroscopic response, and construct scaling arguments to explain their relationships.

  5. Amplitude calibration experiment for SIR-B

    NASA Technical Reports Server (NTRS)

    Held, D. N.; Ulaby, F. T.

    1984-01-01

    The objectives, approach, and expected results of the amplitude calibration experiment for the Shuttle Imaging Radar-B (SIR-B) are outlined. Specific objectives include: (1) the determination of the repeatability (stability) of the SIR-B; (2) the absolute and relative calibration of the system; and (3) the ground truth verification of the calibration accuracy using measurements made by a ground spectrometer and an airborne synthetic aperture radar.

  6. Photon Counting Chirped Amplitude Modulation Ladar

    DTIC Science & Technology

    2008-03-01

    22202-4302. Respondents should be aware that notwithstanding any other provision of law , no person shall be subject to any penalty for failing to...135 S. Taylor Ave., Room 103, Louisville, CO 80027-3025 14. ABSTRACT This work developed a method using Geiger -mode avalanche photodiode (GM-APD...architecture are discussed. 15. SUBJECT TERMS laser radar, ladar, avalanche photo-detectors, Geiger mode detectors, chirped amplitude modulation

  7. Chiral extrapolation of SU(3) amplitudes

    SciTech Connect

    Ecker, Gerhard

    2011-05-23

    Approximations of chiral SU(3) amplitudes at NNLO are proposed to facilitate the extrapolation of lattice data to the physical meson masses. Inclusion of NNLO terms is essential for investigating convergence properties of chiral SU(3) and for determining low-energy constants in a controllable fashion. The approximations are tested with recent lattice data for the ratio of decay constants F{sub K}/F{sub {pi}}.

  8. Understanding the amplitudes of noise correlation measurements

    USGS Publications Warehouse

    Tsai, Victor C.

    2011-01-01

    Cross correlation of ambient seismic noise is known to result in time series from which station-station travel-time measurements can be made. Part of the reason that these cross-correlation travel-time measurements are reliable is that there exists a theoretical framework that quantifies how these travel times depend on the features of the ambient noise. However, corresponding theoretical results do not currently exist to describe how the amplitudes of the cross correlation depend on such features. For example, currently it is not possible to take a given distribution of noise sources and calculate the cross correlation amplitudes one would expect from such a distribution. Here, we provide a ray-theoretical framework for calculating cross correlations. This framework differs from previous work in that it explicitly accounts for attenuation as well as the spatial distribution of sources and therefore can address the issue of quantifying amplitudes in noise correlation measurements. After introducing the general framework, we apply it to two specific problems. First, we show that we can quantify the amplitudes of coherency measurements, and find that the decay of coherency with station-station spacing depends crucially on the distribution of noise sources. We suggest that researchers interested in performing attenuation measurements from noise coherency should first determine how the dominant sources of noise are distributed. Second, we show that we can quantify the signal-to-noise ratio of noise correlations more precisely than previous work, and that these signal-to-noise ratios can be estimated for given situations prior to the deployment of seismometers. It is expected that there are applications of the theoretical framework beyond the two specific cases considered, but these applications await future work.

  9. Simulation of ground motion using the stochastic method

    USGS Publications Warehouse

    Boore, D.M.

    2003-01-01

    A simple and powerful method for simulating ground motions is to combine parametric or functional descriptions of the ground motion's amplitude spectrum with a random phase spectrum modified such that the motion is distributed over a duration related to the earthquake magnitude and to the distance from the source. This method of simulating ground motions often goes by the name "the stochastic method." It is particularly useful for simulating the higher-frequency ground motions of most interest to engineers (generally, f>0.1 Hz), and it is widely used to predict ground motions for regions of the world in which recordings of motion from potentially damaging earthquakes are not available. This simple method has been successful in matching a variety of ground-motion measures for earthquakes with seismic moments spanning more than 12 orders of magnitude and in diverse tectonic environments. One of the essential characteristics of the method is that it distills what is known about the various factors affecting ground motions (source, path, and site) into simple functional forms. This provides a means by which the results of the rigorous studies reported in other papers in this volume can be incorporated into practical predictions of ground motion.

  10. Zeroing in on Supersymmetric Radiation Amplitude Zeros

    SciTech Connect

    Hewett, JoAnne L.; Ismail, Ahmed; Rizzo, Thomas G.; /SLAC

    2012-02-15

    Radiation amplitude zeros have long been used to test the Standard Model. Here, we consider the supersymmetric radiation amplitude zero in chargino-neutralino associated production, which can be observed at the luminosity upgraded LHC. Such an amplitude zero only occurs if the neutralino has a large wino fraction and hence this observable can be used to determine the neutralino eigenstate content. We find that this observable can be measured by comparing the p{sub T} spectrum of the softest lepton in the trilepton {tilde {chi}}{sub 1}{sup {+-}} {tilde {chi}}{sub 2}{sup 0} decay channel to that of a control process such as {tilde {chi}}{sub 1}{sup +} {tilde {chi}}{sub 1}{sup -} or {tilde {chi}}{sub 2}{sup 0} {tilde {chi}}{sub 2}{sup 0}. We test this technique on a previously generated model sample of the 19 dimensional parameter space of the phenomenological MSSM, and find that it is effective in determining the wino content of the neutralino.

  11. Continuous phase and amplitude holographic elements

    NASA Technical Reports Server (NTRS)

    Maker, Paul D. (Inventor); Muller, Richard E. (Inventor)

    1995-01-01

    A method for producing a phase hologram using e-beam lithography provides n-ary levels of phase and amplitude by first producing an amplitude hologram on a transparent substrate by e-beam exposure of a resist over a film of metal by exposing n is less than or equal to m x m spots of an array of spots for each pixel, where the spots are randomly selected in proportion to the amplitude assigned to each pixel, and then after developing and etching the metal film producing a phase hologram by e-beam lithography using a low contrast resist, such as PMMA, and n-ary levels of low doses less than approximately 200 micro-C/sq cm and preferably in the range of 20-200 micro-C/sq cm, and aggressive development using pure acetone for an empirically determined time (about 6 s) controlled to within 1/10 s to produce partial development of each pixel in proportion to the n-ary level of dose assigned to it.

  12. [Amplitude modulation in sound signals by mammals].

    PubMed

    Nikol'skiĭ, A A

    2012-01-01

    Periodic variations in amplitude of a signal, or amplitude modulation (AM), affect the structure of communicative messages spectrum. Within the spectrum of AM-signals, side frequencies are formed both above and below the carrier frequency that is subjected to modulation. In case of harmonic signal structure they are presented near fundamental frequency as well as near harmonics. Thus, AM may by viewed as a relatively simple mechanism for controlling the spectrum of messages transmitted by mammals. Examples of AM affecting the spectrum structure of functionally different sound signals are discussed as applied to representatives of four orders of mammals: rodents (Reodentia), duplicidentates (Lagomorpha), pinnipeds (Pinnipedia), and paridigitates (Artiodactia). For the first time, the classification of AM in animals' sound signals is given. Five forms of AM are picked out in sound signals by mammals: absence of AM, continuous AM, fragmented, heterogeneous, and multilevel one. AM presence/absence is related neither with belonging to any specific order nor with some particular function of a signal. Similar forms of AM can occur in different orders of mammals in parallel. On the contrary, different forms of AM can be detected in signals meant for similar functions. The assumption is made about AM-signals facilitating information encoding and jamprotection of messages transmitted by mammals. Preliminry analysis indicates that hard-driving amplitude modulation is incompatible with hard-driving frequency modulation.

  13. An exact variational method to calculate rovibrational spectra of polyatomic molecules with large amplitude motion.

    PubMed

    Yu, Hua-Gen

    2016-08-28

    We report a new full-dimensional variational algorithm to calculate rovibrational spectra of polyatomic molecules using an exact quantum mechanical Hamiltonian. The rovibrational Hamiltonian of system is derived in a set of orthogonal polyspherical coordinates in the body-fixed frame. It is expressed in an explicitly Hermitian form. The Hamiltonian has a universal formulation regardless of the choice of orthogonal polyspherical coordinates and the number of atoms in molecule, which is suitable for developing a general program to study the spectra of many polyatomic systems. An efficient coupled-state approach is also proposed to solve the eigenvalue problem of the Hamiltonian using a multi-layer Lanczos iterative diagonalization approach via a set of direct product basis set in three coordinate groups: radial coordinates, angular variables, and overall rotational angles. A simple set of symmetric top rotational functions is used for the overall rotation whereas a potential-optimized discrete variable representation method is employed in radial coordinates. A set of contracted vibrationally diabatic basis functions is adopted in internal angular variables. Those diabatic functions are first computed using a neural network iterative diagonalization method based on a reduced-dimension Hamiltonian but only once. The final rovibrational energies are computed using a modified Lanczos method for a given total angular momentum J, which is usually fast. Two numerical applications to CH4 and H2CO are given, together with a comparison with previous results.

  14. Large amplitude motion of the acetylene molecule within acetylene-neon complexes hosted in helium droplets.

    PubMed

    Briant, M; Mengesha, E; de Pujo, P; Gaveau, M-A; Soep, B; Mestdagh, J-M; Poisson, L

    2016-06-28

    Superfluid helium droplets provide an ideal environment for spectroscopic studies with rotational resolution. Nevertheless, the molecular rotation is hindered because the embedded molecules are surrounded by a non-superfluid component. The present work explores the dynamical role of this component in the hindered rotation of C2H2 within the C2H2-Ne complex. A HENDI experiment was built and near-infrared spectroscopy of C2H2-Ne and C2H2 was performed in the spectral region overlapping the ν3/ν2 + ν4 + ν5 Fermi-type resonance of C2H2. The comparison between measured and simulated spectra helped to address the above issue.

  15. An exact variational method to calculate rovibrational spectra of polyatomic molecules with large amplitude motion

    NASA Astrophysics Data System (ADS)

    Yu, Hua-Gen

    2016-08-01

    We report a new full-dimensional variational algorithm to calculate rovibrational spectra of polyatomic molecules using an exact quantum mechanical Hamiltonian. The rovibrational Hamiltonian of system is derived in a set of orthogonal polyspherical coordinates in the body-fixed frame. It is expressed in an explicitly Hermitian form. The Hamiltonian has a universal formulation regardless of the choice of orthogonal polyspherical coordinates and the number of atoms in molecule, which is suitable for developing a general program to study the spectra of many polyatomic systems. An efficient coupled-state approach is also proposed to solve the eigenvalue problem of the Hamiltonian using a multi-layer Lanczos iterative diagonalization approach via a set of direct product basis set in three coordinate groups: radial coordinates, angular variables, and overall rotational angles. A simple set of symmetric top rotational functions is used for the overall rotation whereas a potential-optimized discrete variable representation method is employed in radial coordinates. A set of contracted vibrationally diabatic basis functions is adopted in internal angular variables. Those diabatic functions are first computed using a neural network iterative diagonalization method based on a reduced-dimension Hamiltonian but only once. The final rovibrational energies are computed using a modified Lanczos method for a given total angular momentum J, which is usually fast. Two numerical applications to CH4 and H2CO are given, together with a comparison with previous results.

  16. LETTERS AND COMMENTS: Note on the 'log formulae' for pendulum motion valid for any amplitude

    NASA Astrophysics Data System (ADS)

    Qing-Xin, Yuan; Pei, Ding

    2010-01-01

    In this note, we present an improved approximation to the solution of Lima (2008 Eur. J. Phys. 29 1091), which decreases the maximum relative error from 0.6% to 0.084% in evaluating the exact pendulum period.

  17. Experimental investigation of irregular motion impact on 4D PET-based particle therapy monitoring

    NASA Astrophysics Data System (ADS)

    Tian, Y.; Stützer, K.; Enghardt, W.; Priegnitz, M.; Helmbrecht, S.; Bert, C.; Fiedler, F.

    2016-01-01

    Particle therapy positron emission tomography (PT-PET) is an in vivo and non-invasive imaging technique to monitor treatment delivery in particle therapy. The inevitable patient respiratory motion during irradiation causes artefacts and inaccurate activity distribution in PET images. Four-dimensional (4D) maximum likelihood expectation maximisation (4D MLEM) allows for a compensation of these effects, but has up to now been restricted to regular motion for PT-PET investigations. However, intra-fractional motion during treatment might differ from that during acquisition of the 4D-planning CT (e.g. amplitude variation, baseline drift) and therefore might induce inaccurate 4D PET reconstruction results. This study investigates the impact of different irregular analytical one-dimensional (1D) motion patterns on PT-PET imaging by means of experiments with a radioactive source and irradiated moving phantoms. Three sorting methods, namely phase sorting, equal amplitude sorting and event-based amplitude sorting, were applied to manage the PET list-mode data. The influence of these sorting methods on the motion compensating algorithm has been analysed. The event-based amplitude sorting showed a superior performance and it is applicable for irregular motions with  ⩽4 mm amplitude elongation and drift. For motion with 10 mm baseline drift, the normalised root mean square error was as high as 10.5% and a 10 mm range deviation was observed.

  18. Drop motion induced by vertical vibrations

    NASA Astrophysics Data System (ADS)

    Sartori, Paolo; Quagliati, Damiano; Varagnolo, Silvia; Pierno, Matteo; Mistura, Giampaolo; Magaletti, Francesco; Massimo Casciola, Carlo

    2015-11-01

    We have studied the motion of liquid drops on an inclined plate subject to vertical vibrations. The liquids comprised distilled water and different aqueous solutions of glycerol, ethanol and isopropanol spanning the range 1-39 mm2 s-1 in kinematic viscosities and 40-72 mN m-1 in surface tension. At sufficiently low oscillating amplitudes, the drops are always pinned to the surface. Vibrating the plate above a certain amplitude yields sliding of the drop. Further increasing the oscillating amplitude drives the drop upward against gravity. In the case of the most hydrophilic aqueous solutions, this motion is not observed and the drop only slides downward. Images taken with a fast camera show that the drop profile evolves in a different way during sliding and climbing. In particular, the climbing drop experiences a much bigger variation in its profile during an oscillating period. Complementary numerical simulations of 2D drops based on a diffuse interface approach confirm the experimental findings. The overall qualitative behavior is reproduced suggesting that the contact line pinning due to contact angle hysteresis is not necessary to explain the drop climbing.

  19. INTERNAL PROPER MOTIONS IN THE ESKIMO NEBULA

    SciTech Connect

    García-Díaz, Ma. T.; Gutiérrez, L.; Steffen, W.; López, J. A.; Beckman, J. E-mail: leonel@astro.unam.mx E-mail: jal@astro.unam.mx

    2015-01-10

    We present measurements of internal proper motions at more than 500 positions of NGC 2392, the Eskimo Nebula, based on images acquired with WFPC2 on board the Hubble Space Telescope at two epochs separated by 7.695 yr. Comparisons of the two observations clearly show the expansion of the nebula. We measured the amplitude and direction of the motion of local structures in the nebula by determining their relative shift during that interval. In order to assess the potential uncertainties in the determination of proper motions in this object, in general, the measurements were performed using two different methods, used previously in the literature. We compare the results from the two methods, and to perform the scientific analysis of the results we choose one, the cross-correlation method, because it is more reliable. We go on to perform a ''criss-cross'' mapping analysis on the proper motion vectors, which helps in the interpretation of the velocity pattern. By combining our results of the proper motions with radial velocity measurements obtained from high resolution spectroscopic observations, and employing an existing 3D model, we estimate the distance to the nebula to be 1.3 kpc.

  20. Motion management during IMAT treatment of mobile lung tumors—A comparison of MLC tracking and gated delivery

    PubMed Central

    Falk, Marianne; Pommer, Tobias; Keall, Paul; Korreman, Stine; Persson, Gitte; Poulsen, Per; Munck af Rosenschöld, Per

    2014-01-01

    Purpose: To compare real-time dynamic multileaf collimator (MLC) tracking, respiratory amplitude and phase gating, and no compensation for intrafraction motion management during intensity modulated arc therapy (IMAT). Methods: Motion management with MLC tracking and gating was evaluated for four lung cancer patients. The IMAT plans were delivered to a dosimetric phantom mounted onto a 3D motion phantom performing patient-specific lung tumor motion. The MLC tracking system was guided by an optical system that used stereoscopic infrared (IR) cameras and five spherical reflecting markers attached to the dosimetric phantom. The gated delivery used a duty cycle of 35% and collected position data using an IR camera and two reflecting markers attached to a marker block. Results: The average gamma index failure rate (2% and 2 mm criteria) was <0.01% with amplitude gating for all patients, and <0.1% with phase gating and <3.7% with MLC tracking for three of the four patients. One of the patients had an average failure rate of 15.1% with phase gating and 18.3% with MLC tracking. With no motion compensation, the average gamma index failure rate ranged from 7.1% to 46.9% for the different patients. Evaluation of the dosimetric error contributions showed that the gated delivery mainly had errors in target localization, while MLC tracking also had contributions from MLC leaf fitting and leaf adjustment. The average treatment time was about three times longer with gating compared to delivery with MLC tracking (that did not prolong the treatment time) or no motion compensation. For two of the patients, the different motion compensation techniques allowed for approximately the same margin reduction but for two of the patients, gating enabled a larger reduction of the margins than MLC tracking. Conclusions: Both gating and MLC tracking reduced the effects of the target movements, although the gated delivery showed a better dosimetric accuracy and enabled a larger reduction of the

  1. Equivalent mechanical model of large-amplitude liquid sloshing under time-dependent lateral excitations in low-gravity conditions

    NASA Astrophysics Data System (ADS)

    Nan, Miao; Junfeng, Li; Tianshu, Wang

    2017-01-01

    Subjected to external lateral excitations, large-amplitude sloshing may take place in propellant tanks, especially for spacecraft in low-gravity conditions, such as landers in the process of hover and obstacle avoidance during lunar soft landing. Due to lateral force of the order of gravity in magnitude, the amplitude of liquid sloshing becomes too big for the traditional equivalent model to be accurate. Therefore, a new equivalent mechanical model, denominated the "composite model", that can address large-amplitude lateral sloshing in partially filled spherical tanks is established in this paper, with both translational and rotational excitations considered. The hypothesis of liquid equilibrium position following equivalent gravity is first proposed. By decomposing the large-amplitude motion of a liquid into bulk motion following the equivalent gravity and additional small-amplitude sloshing, a better simulation of large-amplitude liquid sloshing is presented. The effectiveness and accuracy of the model are verified by comparing the slosh forces and moments to results of the traditional model and CFD software.

  2. Present-day plate motions

    NASA Technical Reports Server (NTRS)

    Minster, J. B.; Jordan, T. H.

    1977-01-01

    A data set comprising 110 spreading rates, 78 transform fault azimuths and 142 earthquake slip vectors was inverted to yield a new instantaneous plate motion model, designated RM2. The mean averaging interval for the relative motion data was reduced to less than 3 My. A detailed comparison of RM2 with angular velocity vectors which best fit the data along individual plate boundaries indicates that RM2 performs close to optimally in most regions, with several notable exceptions. On the other hand, a previous estimate (RM1) failed to satisfy an extensive set of new data collected in the South Atlantic Ocean. It is shown that RM1 incorrectly predicts the plate kinematics in the South Atlantic because the presently available data are inconsistent with the plate geometry assumed in deriving RM1. It is demonstrated that this inconsistency can be remedied by postulating the existence of internal deformation with the Indian plate, although alternate explanations are possible.

  3. Motion through syntactic frames.

    PubMed

    Feist, Michele I

    2010-04-01

    The introduction of Talmy's (1985, 2000) typology sparked significant interest in linguistic relativity in the arena of motion language. Through careful analysis of the conflation patterns evident in the language of motion events, Talmy noted that one class of languages, V-languages, tends to encode path along with the fact of motion in motion verbs, while a second class, S-languages, tends to encode manner. In the experimental literature, it was reasoned that speakers may be expected to extend novel verbs in accordance with the lexicalization patterns of their native languages. However, the results regarding this prediction are mixed. In this paper, I examine the interplay between the meaning encoded in the motion verb itself and the meaning encoded in the motion description construction, offering a Gricean explanation for co-occurrence patterns and, by extension, for the mixed results. I then explore the implications of this argument for research on possible language effects on thought in this domain.

  4. Motion Tracking System

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Integrated Sensors, Inc. (ISI), under NASA contract, developed a sensor system for controlling robot vehicles. This technology would enable a robot supply vehicle to automatically dock with Earth-orbiting satellites or the International Space Station. During the docking phase the ISI-developed sensor must sense the satellite's relative motion, then spin so the robot vehicle can adjust its motion to align with the satellite and slowly close until docking is completed. ISI used the sensing/tracking technology as the basis of its OPAD system, which simultaneously tracks an object's movement in six degrees of freedom. Applications include human limb motion analysis, assembly line position analysis and auto crash dummy motion analysis. The NASA technology is also the basis for Motion Analysis Workstation software, a package to simplify the video motion analysis process.

  5. Magnitude, Location, and Ground Motion Estimates Derived From the Community Internet Intensity Maps

    NASA Astrophysics Data System (ADS)

    Quitoriano, V.; Wald, D. J.; Hattori, M. F.; Ebel, J. E.

    2002-12-01

    As is typical for stable continental region events, the 2002 Au Sable Forks, NY, and Evansville, IN, earthquakes had a dearth of ground motion recordings. In contrast, the USGS collected over 9,300 and 6600 Internet responses for these two events, respectively, through the Community Internet Intensity Map (CIIM) Web pages providing a valuable collection of intensity data. CIIM is an automatic system for rapidly generating seismic intensity maps based on shaking and damage reports collected from Internet users immediately following felt earthquakes in the United States. These intensities (CII) have been shown to be comparable to USGS Modified Mercalli Intensities (MMI). Given the CII for an event, we have developed tools to make it possible to generate ground motion estimates in the absence of data from seismic instruments. We compare both mean ground motion estimates based on the ShakeMap instrumental intensity relations with values computed from a Bayesian approach, based on combining probabilities of ground motion amplitudes for a given intensity with those for regionally-appropriate attenuation relationships. We also present a method for deriving earthquake magnitude and location automatically, updated as a function of time, from online responses based on the algorithm of Bakun and Wentworth. We perform a grid search centered on the area with the highest intensity responses, treat each node as a `trial epicenter', and determine the magnitude and intensity centroid that best fits the CII observation points according a region-dependent intensity-distance attenuation relation. We use the M4.9 2002 Gilroy, CA, event to test all these new tools since it was well recorded by strong motion instruments and had an impressive CIIM response. We show that the epicenter and ground motions determined from the CIIM data correlate well with instrumentally derived parameters. We then apply these methods to the Au Sable Forks, NY, and Evansville, IN, events. To show the

  6. Report on progress at the Center for Engineering Strong Motion Data (CESMD)

    USGS Publications Warehouse

    Haddadi, H.; Shakal, A.; Huang, M.; Parrish, J.; Stephens, C.; Savage, William U.; Leith, William S.

    2012-01-01

    The CESMD now provides strong-motion records from lower magnitude (amplitude (<0.5%g) records for use in developing ground motion prediction equations in areas with less frequent earthquakes, such as the Central and Eastern US.

  7. In vivo monitoring of focused ultrasound surgery using local harmonic motion.

    PubMed

    Curiel, Laura; Chopra, Rajiv; Hynynen, Kullervo

    2009-01-01

    The present study established the feasibility of a technique for monitoring focused ultrasound (FUS) lesion formation in vivo using localized harmonic motion (LHM) measurements. Oscillatory motion (frequencies between 50 and 300 Hz) was generated within tissues by induction of a periodic radiation force with a FUS transducer. The harmonic motion was estimated using cross correlation of RF ultrasonic signals acquired at different instances during the motion by using a confocal diagnostic ultrasound transducer. The technique was evaluated in vivo in rabbit muscle (14 locations) in an magnetic resonance (MR) imager for simultaneous ultrasound harmonic motion tracking and MR thermometry. The measured maximum amplitude of the induced harmonic motion before and after the lesion formation was significantly different for all the tested motion frequencies, and decreased between 17 and 81% depending on the frequency and location. During the FUS exposure a drop in the maximum amplitude value was observed and a threshold value could be associated to the formation of a thermal lesion. A series of controlled sonications was performed by stopping the exposure when the threshold value in LHM amplitude was reached and the presence of a thermal lesion was confirmed by MR imaging. LHM measurements were also used to perform a spatial scan of the tissues across the exposure region and the thermal lesions could be detected as a reduction in the maximum motion amplitude value at the sonication region.

  8. The Personal Motion Platform

    NASA Technical Reports Server (NTRS)

    Park, Brian Vandellyn

    1993-01-01

    The Neutral Body Posture experienced in microgravity creates a biomechanical equilibrium by enabling the internal forces within the body to find their own balance. A patented reclining chair based on this posture provides a minimal stress environment for interfacing with computer systems for extended periods. When the chair is mounted on a 3 or 6 axis motion platform, a generic motion simulator for simulated digital environments is created. The Personal Motion Platform provides motional feedback to the occupant in synchronization with their movements inside the digital world which enhances the simulation experience. Existing HMD based simulation systems can be integrated to the turnkey system. Future developments are discussed.

  9. Measurement of visual motion

    SciTech Connect

    Hildreth, E.C.

    1984-01-01

    This book examines the measurement of visual motion and the use of relative movement to locate the boundaries of physical objects in the environment. It investigates the nature of the computations that are necessary to perform this analysis by any vision system, biological or artificial. Contents: Introduction. Background. Computation of the Velocity Field. An Algorithm to Compute the Velocity Field. The Computation of Motion Discontinuities. Perceptual Studies of Motion Measurement. The Psychophysics of Discontinuity Detection. Neurophysiological Studies of Motion. Summary and Conclusions. References. Author and Subject Indexes.

  10. Phase amplitude conformal symmetry in Fourier transforms

    NASA Astrophysics Data System (ADS)

    Kuwata, S.

    2015-04-01

    For the Fourier transform ℑ : L2(R) → L2(R) of a complex-valued even or odd function ψ, it is found that the amplitude invariance |ℑψ| = |ψ| leads to a phase invariance or inversion as arg(ℑψ) = ±argψ + θ (θ = constant). The converse holds unless arg ψ = constant. The condition |ψ| = |ℑψ| is required in dealing with, for example, the minimum uncertainty relation between position and momentum. Without the evenness or oddness of ψ, |ℑψ| = |ψ| does not necessarily imply arg(ℑψ) = ±argψ + θ, nor is the converse.

  11. In-Medium Pion Valence Distribution Amplitude

    NASA Astrophysics Data System (ADS)

    Tsushima, K.; de Melo, J. P. B. C.

    2017-03-01

    After a brief review of the quark-based model for nuclear matter, and some pion properties in medium presented in our previous works, we report new results for the pion valence wave function as well as the valence distribution amplitude in medium, which are presented in our recent article. We find that both the in-medium pion valence distribution and the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.

  12. Fatigue damage analysis under variable amplitude cycling

    NASA Technical Reports Server (NTRS)

    Leis, B. N.; Forte, T. P.

    1983-01-01

    This paper explores the suitability of a recently proposed mean stress parameter and introduces a nonlinear damage accumulation procedure. Data covering a range of positive and negative stress ratios from +0.6 to -2.66, for several aluminum alloys and steels, are assembled and shown to be well correlated by a simple damage parameter. A nonlinear damage accumulation postulate is advanced to replace the usual linear procedure. Results of critical experiments performed to assess the suitability of the postulate are introduced and shown to support a non-linear criterion. The implications of this work related to variable amplitude life prediction are discussed.

  13. Loop-quantum-gravity vertex amplitude.

    PubMed

    Engle, Jonathan; Pereira, Roberto; Rovelli, Carlo

    2007-10-19

    Spin foam models are hoped to provide the dynamics of loop-quantum gravity. However, the most popular of these, the Barrett-Crane model, does not have the good boundary state space and there are indications that it fails to yield good low-energy n-point functions. We present an alternative dynamics that can be derived as a quantization of a Regge discretization of Euclidean general relativity, where second class constraints are imposed weakly. Its state space matches the SO(3) loop gravity one and it yields an SO(4)-covariant vertex amplitude for Euclidean loop gravity.

  14. Fatigue crack growth under variable amplitude loading

    NASA Technical Reports Server (NTRS)

    Sidawi, Jihad A.

    1994-01-01

    Fatigue crack growth tests were conducted on an Fe 510 E C-Mn steel and a submerged arc welded joint from the same material under constant, variable, and random loading amplitudes. Paris-Erdogan's crack growth rate law was tested for the evaluation of m and C using the stress intensity factor K, the J-integral, the effective stress intensity factor K(sub eff), and the root mean square stress intensity factor K(sub rms) fracture mechanics concepts. The effect of retardation and residual stresses resulting from welding was also considered. It was found that all concepts gave good life predictions in all cases.

  15. Amplitude analysis of B-→D+π-π- decays

    NASA Astrophysics Data System (ADS)

    Aaij, R.; Adeva, B.; Adinolfi, M.; Ajaltouni, Z.; Akar, S.; Albrecht, J.; Alessio, F.; Alexander, M.; Ali, S.; Alkhazov, G.; Alvarez Cartelle, P.; Alves, A. A.; Amato, S.; Amerio, S.; Amhis, Y.; An, L.; Anderlini, L.; Andreassi, G.; Andreotti, M.; Andrews, J. E.; Appleby, R. B.; Aquines Gutierrez, O.; Archilli, F.; d'Argent, P.; Arnau Romeu, J.; Artamonov, A.; Artuso, M.; Aslanides, E.; Auriemma, G.; Baalouch, M.; Babuschkin, I.; Bachmann, S.; Back, J. J.; Badalov, A.; Baesso, C.; Baker, S.; Baldini, W.; Barlow, R. J.; Barschel, C.; Barsuk, S.; Barter, W.; Batozskaya, V.; Batsukh, B.; Battista, V.; Bay, A.; Beaucourt, L.; Beddow, J.; Bedeschi, F.; Bediaga, I.; Bel, L. J.; Bellee, V.; Belloli, N.; Belous, K.; Belyaev, I.; Ben-Haim, E.; Bencivenni, G.; Benson, S.; Benton, J.; Berezhnoy, A.; Bernet, R.; Bertolin, A.; Betti, F.; Bettler, M.-O.; van Beuzekom, M.; Bezshyiko, I.; Bifani, S.; Billoir, P.; Bird, T.; Birnkraut, A.; Bitadze, A.; Bizzeti, A.; Blake, T.; Blanc, F.; Blouw, J.; Blusk, S.; Bocci, V.; Boettcher, T.; Bondar, A.; Bondar, N.; Bonivento, W.; Borgheresi, A.; Borghi, S.; Borisyak, M.; Borsato, M.; Bossu, F.; Boubdir, M.; Bowcock, T. J. V.; Bowen, E.; Bozzi, C.; Braun, S.; Britsch, M.; Britton, T.; Brodzicka, J.; Buchanan, E.; Burr, C.; Bursche, A.; Buytaert, J.; Cadeddu, S.; Calabrese, R.; Calvi, M.; Calvo Gomez, M.; Camboni, A.; Campana, P.; Campora Perez, D.; Campora Perez, D. H.; Capriotti, L.; Carbone, A.; Carboni, G.; Cardinale, R.; Cardini, A.; Carniti, P.; Carson, L.; Carvalho Akiba, K.; Casse, G.; Cassina, L.; Castillo Garcia, L.; Cattaneo, M.; Cauet, Ch.; Cavallero, G.; Cenci, R.; Charles, M.; Charpentier, Ph.; Chatzikonstantinidis, G.; Chefdeville, M.; Chen, S.; Cheung, S.-F.; Chobanova, V.; Chrzaszcz, M.; Cid Vidal, X.; Ciezarek, G.; Clarke, P. E. L.; Clemencic, M.; Cliff, H. V.; Closier, J.; Coco, V.; Cogan, J.; Cogneras, E.; Cogoni, V.; Cojocariu, L.; Collazuol, G.; Collins, P.; Comerma-Montells, A.; Contu, A.; Cook, A.; Coquereau, S.; Corti, G.; Corvo, M.; Costa Sobral, C. M.; Couturier, B.; Cowan, G. A.; Craik, D. C.; Crocombe, A.; Cruz Torres, M.; Cunliffe, S.; Currie, R.; D'Ambrosio, C.; Dall'Occo, E.; Dalseno, J.; David, P. N. Y.; Davis, A.; De Aguiar Francisco, O.; De Bruyn, K.; De Capua, S.; De Cian, M.; De Miranda, J. M.; De Paula, L.; De Serio, M.; De Simone, P.; Dean, C.-T.; Decamp, D.; Deckenhoff, M.; Del Buono, L.; Demmer, M.; Derkach, D.; Deschamps, O.; Dettori, F.; Dey, B.; Di Canto, A.; Dijkstra, H.; Dordei, F.; Dorigo, M.; Dosil Suárez, A.; Dovbnya, A.; Dreimanis, K.; Dufour, L.; Dujany, G.; Dungs, K.; Durante, P.; Dzhelyadin, R.; Dziurda, A.; Dzyuba, A.; Déléage, N.; Easo, S.; Ebert, M.; Egede, U.; Egorychev, V.; Eidelman, S.; Eisenhardt, S.; Eitschberger, U.; Ekelhof, R.; Eklund, L.; Elsasser, Ch.; Ely, S.; Esen, S.; Evans, H. M.; Evans, T.; Falabella, A.; Farley, N.; Farry, S.; Fay, R.; Fazzini, D.; Ferguson, D.; Fernandez Albor, V.; Fernandez Prieto, A.; Ferrari, F.; Ferreira Rodrigues, F.; Ferro-Luzzi, M.; Filippov, S.; Fini, R. A.; Fiore, M.; Fiorini, M.; Firlej, M.; Fitzpatrick, C.; Fiutowski, T.; Fleuret, F.; Fohl, K.; Fontana, M.; Fontanelli, F.; Forshaw, D. C.; Forty, R.; Franco Lima, V.; Frank, M.; Frei, C.; Fu, J.; Furfaro, E.; Färber, C.; Gallas Torreira, A.; Galli, D.; Gallorini, S.; Gambetta, S.; Gandelman, M.; Gandini, P.; Gao, Y.; Garcia Martin, L. M.; García Pardiñas, J.; Garra Tico, J.; Garrido, L.; Garsed, P. J.; Gascon, D.; Gaspar, C.; Gavardi, L.; Gazzoni, G.; Gerick, D.; Gersabeck, E.; Gersabeck, M.; Gershon, T.; Ghez, Ph.; Gianı, S.; Gibson, V.; Girard, O. G.; Giubega, L.; Gizdov, K.; Gligorov, V. V.; Golubkov, D.; Golutvin, A.; Gomes, A.; Gorelov, I. V.; Gotti, C.; Grabalosa Gándara, M.; Graciani Diaz, R.; Granado Cardoso, L. A.; Graugés, E.; Graverini, E.; Graziani, G.; Grecu, A.; Griffith, P.; Grillo, L.; Gruberg Cazon, B. R.; Grünberg, O.; Gushchin, E.; Guz, Yu.; Gys, T.; Göbel, C.; Hadavizadeh, T.; Hadjivasiliou, C.; Haefeli, G.; Haen, C.; Haines, S. C.; Hall, S.; Hamilton, B.; Han, X.; Hansmann-Menzemer, S.; Harnew, N.; Harnew, S. T.; Harrison, J.; Hatch, M.; He, J.; Head, T.; Heister, A.; Hennessy, K.; Henrard, P.; Henry, L.; Hernando Morata, J. A.; van Herwijnen, E.; Heß, M.; Hicheur, A.; Hill, D.; Hombach, C.; Hulsbergen, W.; Humair, T.; Hushchyn, M.; Hussain, N.; Hutchcroft, D.; Idzik, M.; Ilten, P.; Jacobsson, R.; Jaeger, A.; Jalocha, J.; Jans, E.; Jawahery, A.; Jiang, F.; John, M.; Johnson, D.; Jones, C. R.; Joram, C.; Jost, B.; Jurik, N.; Kandybei, S.; Kanso, W.; Karacson, M.; Kariuki, J. M.; Karodia, S.; Kecke, M.; Kelsey, M.; Kenyon, I. R.; Kenzie, M.; Ketel, T.; Khairullin, E.; Khanji, B.; Khurewathanakul, C.; Kirn, T.; Klaver, S.; Klimaszewski, K.; Koliiev, S.; Kolpin, M.; Komarov, I.; Koopman, R. F.; Koppenburg, P.; Kozachuk, A.; Kozeiha, M.; Kravchuk, L.; Kreplin, K.; Kreps, M.; Krokovny, P.; Kruse, F.; Krzemien, W.; Kucewicz, W.; Kucharczyk, M.; Kudryavtsev, V.; Kuonen, A. K.; Kurek, K.; Kvaratskheliya, T.; Lacarrere, D.; Lafferty, G.; Lai, A.; Lambert, D.; Lanfranchi, G.; Langenbruch, C.; Latham, T.; Lazzeroni, C.; Le Gac, R.; van Leerdam, J.; Lees, J.-P.; Leflat, A.; Lefrançois, J.; Lefèvre, R.; Lemaitre, F.; Lemos Cid, E.; Leroy, O.; Lesiak, T.; Leverington, B.; Li, Y.; Likhomanenko, T.; Lindner, R.; Linn, C.; Lionetto, F.; Liu, B.; Liu, X.; Loh, D.; Longstaff, I.; Lopes, J. H.; Lucchesi, D.; Lucio Martinez, M.; Luo, H.; Lupato, A.; Luppi, E.; Lupton, O.; Lusiani, A.; Lyu, X.; Machefert, F.; Maciuc, F.; Maev, O.; Maguire, K.; Malde, S.; Malinin, A.; Maltsev, T.; Manca, G.; Mancinelli, G.; Manning, P.; Maratas, J.; Marchand, J. F.; Marconi, U.; Marin Benito, C.; Marino, P.; Marks, J.; Martellotti, G.; Martin, M.; Martinelli, M.; Martinez Santos, D.; Martinez Vidal, F.; Martins Tostes, D.; Massacrier, L. M.; Massafferri, A.; Matev, R.; Mathad, A.; Mathe, Z.; Matteuzzi, C.; Mauri, A.; Maurin, B.; Mazurov, A.; McCann, M.; McCarthy, J.; McNab, A.; McNulty, R.; Meadows, B.; Meier, F.; Meissner, M.; Melnychuk, D.; Merk, M.; Merli, A.; Michielin, E.; Milanes, D. A.; Minard, M.-N.; Mitzel, D. S.; Mogini, A.; Molina Rodriguez, J.; Monroy, I. A.; Monteil, S.; Morandin, M.; Morawski, P.; Mordà, A.; Morello, M. J.; Moron, J.; Morris, A. B.; Mountain, R.; Muheim, F.; Mulder, M.; Mussini, M.; Müller, D.; Müller, J.; Müller, K.; Müller, V.; Naik, P.; Nakada, T.; Nandakumar, R.; Nandi, A.; Nasteva, I.; Needham, M.; Neri, N.; Neubert, S.; Neufeld, N.; Neuner, M.; Nguyen, A. D.; Nguyen-Mau, C.; Nieswand, S.; Niet, R.; Nikitin, N.; Nikodem, T.; Novoselov, A.; O'Hanlon, D. P.; Oblakowska-Mucha, A.; Obraztsov, V.; Ogilvy, S.; Oldeman, R.; Onderwater, C. J. G.; Otalora Goicochea, J. M.; Otto, A.; Owen, P.; Oyanguren, A.; Pais, P. R.; Palano, A.; Palombo, F.; Palutan, M.; Panman, J.; Papanestis, A.; Pappagallo, M.; Pappalardo, L. L.; Parker, W.; Parkes, C.; Passaleva, G.; Pastore, A.; Patel, G. D.; Patel, M.; Patrignani, C.; Pearce, A.; Pellegrino, A.; Penso, G.; Pepe Altarelli, M.; Perazzini, S.; Perret, P.; Pescatore, L.; Petridis, K.; Petrolini, A.; Petrov, A.; Petruzzo, M.; Picatoste Olloqui, E.; Pietrzyk, B.; Pikies, M.; Pinci, D.; Pistone, A.; Piucci, A.; Playfer, S.; Plo Casasus, M.; Poikela, T.; Polci, F.; Poluektov, A.; Polyakov, I.; Polycarpo, E.; Pomery, G. J.; Popov, A.; Popov, D.; Popovici, B.; Poslavskii, S.; Potterat, C.; Price, E.; Price, J. D.; Prisciandaro, J.; Pritchard, A.; Prouve, C.; Pugatch, V.; Puig Navarro, A.; Punzi, G.; Qian, W.; Quagliani, R.; Rachwal, B.; Rademacker, J. H.; Rama, M.; Ramos Pernas, M.; Rangel, M. S.; Raniuk, I.; Raven, G.; Redi, F.; Reichert, S.; dos Reis, A. C.; Remon Alepuz, C.; Renaudin, V.; Ricciardi, S.; Richards, S.; Rihl, M.; Rinnert, K.; Rives Molina, V.; Robbe, P.; Rodrigues, A. B.; Rodrigues, E.; Rodriguez Lopez, J. A.; Rodriguez Perez, P.; Rogozhnikov, A.; Roiser, S.; Romanovskiy, V.; Romero Vidal, A.; Ronayne, J. W.; Rotondo, M.; Rudolph, M. S.; Ruf, T.; Ruiz Valls, P.; Saborido Silva, J. J.; Sadykhov, E.; Sagidova, N.; Saitta, B.; Salustino Guimaraes, V.; Sanchez Mayordomo, C.; Sanmartin Sedes, B.; Santacesaria, R.; Santamarina Rios, C.; Santimaria, M.; Santovetti, E.; Sarti, A.; Satriano, C.; Satta, A.; Saunders, D. M.; Savrina, D.; Schael, S.; Schellenberg, M.; Schiller, M.; Schindler, H.; Schlupp, M.; Schmelling, M.; Schmelzer, T.; Schmidt, B.; Schneider, O.; Schopper, A.; Schubert, K.; Schubiger, M.; Schune, M.-H.; Schwemmer, R.; Sciascia, B.; Sciubba, A.; Semennikov, A.; Sergi, A.; Serra, N.; Serrano, J.; Sestini, L.; Seyfert, P.; Shapkin, M.; Shapoval, I.; Shcheglov, Y.; Shears, T.; Shekhtman, L.; Shevchenko, V.; Shires, A.; Siddi, B. G.; Silva Coutinho, R.; Silva de Oliveira, L.; Simi, G.; Simone, S.; Sirendi, M.; Skidmore, N.; Skwarnicki, T.; Smith, E.; Smith, I. T.; Smith, J.; Smith, M.; Snoek, H.; Sokoloff, M. D.; Soler, F. J. P.; Souza, D.; Souza De Paula, B.; Spaan, B.; Spradlin, P.; Sridharan, S.; Stagni, F.; Stahl, M.; Stahl, S.; Stefko, P.; Stefkova, S.; Steinkamp, O.; Stemmle, S.; Stenyakin, O.; Stevenson, S.; Stoica, S.; Stone, S.; Storaci, B.; Stracka, S.; Straticiuc, M.; Straumann, U.; Sun, L.; Sutcliffe, W.; Swientek, K.; Syropoulos, V.; Szczekowski, M.; Szumlak, T.; T'Jampens, S.; Tayduganov, A.; Tekampe, T.; Tellarini, G.; Teubert, F.; Thomas, C.; Thomas, E.; van Tilburg, J.; Tilley, M. J.; Tisserand, V.; Tobin, M.; Tolk, S.; Tomassetti, L.; Tonelli, D.; Topp-Joergensen, S.; Toriello, F.; Tournefier, E.; Tourneur, S.; Trabelsi, K.; Traill, M.; Tran, M. T.; Tresch, M.; Trisovic, A.; Tsaregorodtsev, A.; Tsopelas, P.; Tully, A.; Tuning, N.; Ukleja, A.; Ustyuzhanin, A.; Uwer, U.; Vacca, C.; Vagnoni, V.; Valat, S.; Valenti, G.; Vallier, A.; Vazquez Gomez, R.; Vazquez Regueiro, P.; Vecchi, S.; van Veghel, M.; Velthuis, J. J.; Veltri, M.; Veneziano, G.; Venkateswaran, A.; Vernet, M.; Vesterinen, M.; Viaud, B.; Vieira, D.; Vieites Diaz, M.; Vilasis-Cardona, X.; Volkov, V.; Vollhardt, A.; Voneki, B.; Voong, D.; Vorobyev, A.; Vorobyev, V.; Voß, C.; de Vries, J. A.; Vázquez Sierra, C.; Waldi, R.; Wallace, C.; Wallace, R.; Walsh, J.; Wang, J.; Ward, D. R.; Wark, H. M.; Watson, N. K.; Websdale, D.; Weiden, A.; Whitehead, M.; Wicht, J.; Wilkinson, G.; Wilkinson, M.; Williams, M.; Williams, M. P.; Williams, M.; Williams, T.; Wilson, F. F.; Wimberley, J.; Wishahi, J.; Wislicki, W.; Witek, M.; Wormser, G.; Wotton, S. A.; Wraight, K.; Wright, S.; Wyllie, K.; Xie, Y.; Xing, Z.; Xu, Z.; Yang, Z.; Yin, H.; Yu, J.; Yuan, X.; Yushchenko, O.; Zangoli, M.; Zarebski, K. A.; Zavertyaev, M.; Zhang, L.; Zhang, Y.; Zhang, Y.; Zhelezov, A.; Zheng, Y.; Zhokhov, A.; Zhu, X.; Zhukov, V.; Zucchelli, S.; LHCb Collaboration

    2016-10-01

    The Dalitz plot analysis technique is used to study the resonant substructures of B-→D+π-π- decays in a data sample corresponding to 3.0 fb-1 of p p collision data recorded by the LHCb experiment during 2011 and 2012. A model-independent analysis of the angular moments demonstrates the presence of resonances with spins 1, 2 and 3 at high D+π- mass. The data are fitted with an amplitude model composed of a quasi-model-independent function to describe the D+π- S wave together with virtual contributions from the D*(2007 )0 and B*0 states, and components corresponding to the D2*(2460 )0 , D1*(2680 )0 , D3*(2760 )0 and D2*(3000 )0 resonances. The masses and widths of these resonances are determined together with the branching fractions for their production in B-→D+π-π- decays. The D+π- S wave has phase motion consistent with that expected due to the presence of the D0*(2400 )0 state. These results constitute the first observations of the D3*(2760 )0 and D2*(3000 )0 resonances, with significances of 10 σ and 6.6 σ , respectively.

  16. Localization of source with unknown amplitude using IPMC sensor arrays

    NASA Astrophysics Data System (ADS)

    Abdulsadda, Ahmad T.; Zhang, Feitian; Tan, Xiaobo

    2011-04-01

    The lateral line system, consisting of arrays of neuromasts functioning as flow sensors, is an important sensory organ for fish that enables them to detect predators, locate preys, perform rheotaxis, and coordinate schooling. Creating artificial lateral line systems is of significant interest since it will provide a new sensing mechanism for control and coordination of underwater robots and vehicles. In this paper we propose recursive algorithms for localizing a vibrating sphere, also known as a dipole source, based on measurements from an array of flow sensors. A dipole source is frequently used in the study of biological lateral lines, as a surrogate for underwater motion sources such as a flapping fish fin. We first formulate a nonlinear estimation problem based on an analytical model for the dipole-generated flow field. Two algorithms are presented to estimate both the source location and the vibration amplitude, one based on the least squares method and the other based on the Newton-Raphson method. Simulation results show that both methods deliver comparable performance in source localization. A prototype of artificial lateral line system comprising four ionic polymer-metal composite (IPMC) sensors is built, and experimental results are further presented to demonstrate the effectiveness of IPMC lateral line systems and the proposed estimation algorithms.

  17. Topographic Structure from Motion

    NASA Astrophysics Data System (ADS)

    Fonstad, M. A.; Dietrich, J. T.; Courville, B. C.; Jensen, J.; Carbonneau, P.

    2011-12-01

    The production of high-resolution topographic datasets is of increasing concern and application throughout the geomorphic sciences, and river science is no exception. Consequently, a wide range of topographic measurement methods have evolved. Despite the range of available methods, the production of high resolution, high quality digital elevation models (DEMs) generally requires a significant investment in personnel time, hardware and/or software. However, image-based methods such as digital photogrammetry have steadily been decreasing in costs. Initially developed for the purpose of rapid, inexpensive and easy three dimensional surveys of buildings or small objects, the "structure from motion" photogrammetric approach (SfM) is a purely image based method which could deliver a step-change if transferred to river remote sensing, and requires very little training and is extremely inexpensive. Using the online SfM program Microsoft Photosynth, we have created high-resolution digital elevation models (DEM) of rivers from ordinary photographs produced from a multi-step workflow that takes advantage of free and open source software. This process reconstructs real world scenes from SfM algorithms based on the derived positions of the photographs in three-dimensional space. One of the products of the SfM process is a three-dimensional point cloud of features present in the input photographs. This point cloud can be georeferenced from a small number of ground control points collected via GPS in the field. The georeferenced point cloud can then be used to create a variety of digital elevation model products. Among several study sites, we examine the applicability of SfM in the Pedernales River in Texas (USA), where several hundred images taken from a hand-held helikite are used to produce DEMs of the fluvial topographic environment. This test shows that SfM and low-altitude platforms can produce point clouds with point densities considerably better than airborne LiDAR, with

  18. Effects of image noise, respiratory motion, and motion compensation on 3D activity quantification in count-limited PET images

    NASA Astrophysics Data System (ADS)

    Siman, W.; Mawlawi, O. R.; Mikell, J. K.; Mourtada, F.; Kappadath, S. C.

    2017-01-01

    The aims of this study were to evaluate the effects of noise, motion blur, and motion compensation using quiescent-period gating (QPG) on the activity concentration (AC) distribution—quantified using the cumulative AC volume histogram (ACVH)—in count-limited studies such as 90Y-PET/CT. An International Electrotechnical Commission phantom filled with low 18F activity was used to simulate clinical 90Y-PET images. PET data were acquired using a GE-D690 when the phantom was static and subject to 1-4 cm periodic 1D motion. The static data were down-sampled into shorter durations to determine the effect of noise on ACVH. Motion-degraded PET data were sorted into multiple gates to assess the effect of motion and QPG on ACVH. Errors in ACVH at AC90 (minimum AC that covers 90% of the volume of interest (VOI)), AC80, and ACmean (average AC in the VOI) were characterized as a function of noise and amplitude before and after QPG. Scan-time reduction increased the apparent non-uniformity of sphere doses and the dispersion of ACVH. These effects were more pronounced in smaller spheres. Noise-related errors in ACVH at AC20 to AC70 were smaller (<15%) compared to the errors between AC80 to AC90 (>15%). The accuracy of ACmean was largely independent of the total count. Motion decreased the observed AC and skewed the ACVH toward lower values; the severity of this effect depended on motion amplitude and tumor diameter. The errors in AC20 to AC80 for the 17 mm sphere were  -25% and  -55% for motion amplitudes of 2 cm and 4 cm, respectively. With QPG, the errors in AC20 to AC80 of the 17 mm sphere were reduced to  -15% for motion amplitudes  <4 cm. For spheres with motion amplitude to diameter ratio  >0.5, QPG was effective at reducing errors in ACVH despite increases in image non-uniformity due to increased noise. ACVH is believed to be more relevant than mean or maximum AC to calculate tumor control and normal tissue complication probability

  19. Statistical modeling of in situ hiss amplitudes using ground measurements

    NASA Astrophysics Data System (ADS)

    Golden, D. I.; Spasojevic, M.; Li, W.; Nishimura, Y.

    2012-05-01

    Plasmaspheric hiss is a naturally occurring extremely low frequency electromagnetic emission that is often observed within the Earth's plasmasphere. Plasmaspheric hiss plays a major role in the scattering and loss of electrons from the Earth's radiation belts, thereby contributing to the maintenance of the slot region between the inner and outer electron belt. Traditionally, in situ satellite observations have been the measurement modality of choice for studies of plasmaspheric hiss due to their ability to directly measure the hiss source region. However, satellite studies are relatively short-lived and very few satellite receivers remain operational for an entire 11-year solar cycle. Ground stations, in contrast, may collect multiple solar cycles' worth of data during their lifetime, yet they cannot directly measure the hiss source region. This study aims to determine the extent to which measurements of hiss at midlatitude ground stations may be used to predict the mean amplitude of in situ measurements of plasmaspheric hiss. We use coincident measurements between Palmer Station, Antarctica (L = 2.4, 50°S invariant latitude) and the THEMIS spacecraft from June 2008 through May 2010, during solar minimum. Using an autoregressive multiple regression model, we show that in the local time sector from 00 < MLT < 12, when the ionosphere above Palmer Station is in darkness and hiss is observed at Palmer, the amplitude of plasmaspheric hiss observed by the THEMIS spacecraft is 1.4 times higher than when hiss is not observed at Palmer. In the same local time sector when the ground station is in daylight and hiss is observed, the THEMIS observed amplitudes are not significantly different from those when hiss is not observed on the ground. A stronger relationship is found in the local time sector from 12 < MLT < 24 where, when Palmer is in daylight and hiss is observed, THEMIS plasmaspheric hiss amplitudes are 2 times higher compared to when hiss is not observed at Palmer

  20. Characterization of Non-Linearized Spacecraft Relative Motion using Nonlinear Normal Modes

    DTIC Science & Technology

    2016-04-20

    AFRL-RV-PS- AFRL-RV-PS- TR-2015-0182 TR-2015-0182 CHARACTERIZATION OF NON-LINEARIZED SPACECRAFT RELATIVE MOTION USING NONLINEAR NORMAL MODES Eric...Non-Linearized Spacecraft Relative Motion using Nonlinear Normal Modes 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62601F...public release; distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT Characterize the nonlinear dynamics for large amplitude relative motion

  1. Seismic design technology for breeder reactor structures. Volume 1. Special topics in earthquake ground motion

    SciTech Connect

    Reddy, D.P.

    1983-04-01

    This report is divided into twelve chapters: seismic hazard analysis procedures, statistical and probabilistic considerations, vertical ground motion characteristics, vertical ground response spectrum shapes, effects of inclined rock strata on site response, correlation of ground response spectra with intensity, intensity attenuation relationships, peak ground acceleration in the very mean field, statistical analysis of response spectral amplitudes, contributions of body and surface waves, evaluation of ground motion characteristics, and design earthquake motions. (DLC)

  2. Wrist Proprioception: Amplitude or Position Coding?

    PubMed Central

    Marini, Francesca; Squeri, Valentina; Morasso, Pietro; Masia, Lorenzo

    2016-01-01

    This work examines physiological mechanisms underlying the position sense of the wrist, namely, the codification of proprioceptive information related to pointing movements of the wrist toward kinesthetic targets. Twenty-four healthy subjects participated to a robot-aided assessment of their wrist proprioceptive acuity to investigate if the sensorimotor transformation involved in matching targets located by proprioceptive receptors relies on amplitude or positional cues. A joint position matching test was performed in order to explore such dichotomy. In this test, the wrist of a blindfolded participant is passively moved by a robotic device to a preset target position and, after a removal movement from this position, the participant has to actively replicate and match it as accurately as possible. The test involved two separate conditions: in the first, the matching movements started from the same initial location; in the second one, the initial location was randomly assigned. Target matching accuracy, precision, and bias in the two conditions were then compared. Overall results showed a consistent higher performance in the former condition than in the latter, thus supporting the hypothesis that the joint position sense is based on vectorial or amplitude coding rather than positional. PMID:27807417

  3. Small-amplitude synchrotron tune near transition

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2010-05-01

    The separatrices of the rf buckets near transition are mapped when the synchronous phase is neither 0 or {pi}. The small-amplitude synchronous tune is derived when the rf frequency is changed. Synchrotron radiation is present in all electron storage ring. As a result, the synchronous phase is always offset from {phi}{sub s} = {pi} to compensate for the power loss. Even for proton storage rings with negligible synchrotron radiation, the synchronous phase is also required to be offset from {phi}{sub s} = 0 or {pi} slightly to compensate for beam loading. Thus for all storage rings operating near transition, beam particles reside in accelerating buckets instead of stationary bucket. It is of interest to map these buckets and see how they evolve near transition. When the rf frequency is varied, the closed orbit is pushed radially inward or outward. The momentum of the particle synchronous with the rf is thus changed. By measuring the small-amplitude synchrotron tune as a function of the rf frequency, the lowest first few orders of the slip factor can be inferred. Here, we derive this relationship up to the lowest first three orders of the slip factor when the particle velocity is not ultra-relativistic.

  4. Amplitude enhancement by a gold dimer

    NASA Astrophysics Data System (ADS)

    Hong, Xin; Wang, Jingxin; Jin, Zheng

    2016-10-01

    The unique optical properties such as brightness, non-bleaching, good bio-compatibility make gold particles ideal label candidates for molecular probes. Due to the strongly enhanced field, aggregation of gold nanoparticles finds themselves plenty of applications in bio-imaging. But limited by its small cross-section associated with nanometer sized particle, it is a big challenge to employ it in a single molecular detection. The field enhancement results from the effect of plasmonic coupling between two closely attached gold nanoparticle under the right excitation condition. With the aim to apply the gold dimer probe to find the molecules in our recently established optical detection method, we compared of the amplitude enhancement by the dimer relative to a single particle. The amplitude distribution under a highly focused illumination objective was calculated, whose results suggest that at the optimized excitation condition, the local field can be enhanced 190 fold. In consequence, experimental detection was carried out. Gold dimers were linked together by the hybridization of two single chain DNAs. Dimer and single particle probes were mixed together in one detection. Overwhelming contrast between these two kinds of probes were clearly exhibited in the experimental detection image. This method can provide a way to a high specific detection in early diagnosis.

  5. Motion compensator for holographic motion picture camera

    NASA Technical Reports Server (NTRS)

    Kurtz, R. L.

    1973-01-01

    When reference beam strikes target it undergoes Doppler shift dependent upon target velocity. To compensate, object beam is first reflected from rotating cylinder that revolves in direction opposite to target but at same speed. When beam strikes target it is returned to original frequency and is in phase with reference beam. Alternatively this motion compensator may act on reference beam.

  6. Phase and amplitude inversion of crosswell radar data

    USGS Publications Warehouse

    Ellefsen, Karl J.; Mazzella, Aldo T.; Horton, Robert J.; McKenna, Jason R.

    2011-01-01

    Phase and amplitude inversion of crosswell radar data estimates the logarithm of complex slowness for a 2.5D heterogeneous model. The inversion is formulated in the frequency domain using the vector Helmholtz equation. The objective function is minimized using a back-propagation method that is suitable for a 2.5D model and that accounts for the near-, intermediate-, and far-field regions of the antennas. The inversion is tested with crosswell radar data collected in a laboratory tank. The model anomalies are consistent with the known heterogeneity in the tank; the model’s relative dielectric permittivity, which is calculated from the real part of the estimated complex slowness, is consistent with independent laboratory measurements. The methodologies developed for this inversion can be adapted readily to inversions of seismic data (e.g., crosswell seismic and vertical seismic profiling data).

  7. Frequency domain optoacoustic tomography using amplitude and phase

    PubMed Central

    Mohajerani, Pouyan; Kellnberger, Stephan; Ntziachristos, Vasilis

    2014-01-01

    We introduce optoacoustic tomographic imaging using intensity modulated light sources and collecting amplitude and phase information in the frequency domain. Imaging is performed at multiple modulation frequencies. The forward modeling uses the Green's function solution to the pressure wave equation in frequency domain and the resulting inverse problem is solved using regularized least squares minimization. We study the effect of the number of frequencies and of the bandwidth employed on the image quality achieved. The possibility of employing an all-frequency domain optoacoustic imaging for experimental measurements is studied as a function of noise. We conclude that frequency domain optoacoustic tomography may evolve to a practical experimental method using light intensity modulated sources, with advantages over time-domain optoacoustics. PMID:25431755

  8. Critically ill patients in emergency department may be characterized by low amplitude and high variability of amplitude of pulse photoplethysmography

    PubMed Central

    2013-01-01

    Background The aim of the present pilot study was to determine if pulse photoplethysmography amplitude (PPGA) could be used as an indicator of critical illness and as a predictor of higher need of care in emergency department patients. Methods This was a prospective observational study. We collected vital signs and one minute of pulse photoplethysmograph signal from 251 consecutive patients admitted to a university hospital emergency department. The patients were divided in two groups regarding to the modified Early Warning Score (mEWS): > 3 (critically ill) and ≤ 3 (non-critically ill). Photoplethysmography characteristics were compared between the groups. Results Sufficient data for analysis was acquired from 212 patients (84.5%). Patients in critically ill group more frequently required intubation and invasive hemodynamic monitoring in the ED and received more intravenous fluids. Mean pulse photoplethysmography amplitude (PPGA) was significantly lower in critically ill patients (median 1.105 [95% CI of mean 0.9946-2.302] vs. 2.476 [95% CI of mean 2.239-2.714], P = 0.0257). Higher variability of PPGA significantly correlated with higher amount of fluids received in the ED (r = 0.1501, p = 0.0296). Conclusions This pilot study revealed differences in PPGA characteristics between critically ill and non-critically ill patients. Further studies are needed to determine if these easily available parameters could help increase accuracy in triage when used in addition to routine monitoring of vital signs. PMID:23799988

  9. Objects in Motion

    ERIC Educational Resources Information Center

    Ashbrook, Peggy

    2008-01-01

    Objects in motion attract children. The following activity helps children explore the motion of bodies riding in a vehicle and safely demonstrates the answer to their questions, "Why do I need a seatbelt?" Children will enjoy moving the cup around, even if all they "see" is a cup rather than understanding it represents a car. They will understand…

  10. Teaching Projectile Motion

    ERIC Educational Resources Information Center

    Summers, M. K.

    1977-01-01

    Described is a novel approach to the teaching of projectile motion of sixth form level. Students are asked to use an analogue circuit to observe projectile motion and to graph the experimental results. Using knowledge of basic dynamics, students are asked to explain the shape of the curves theoretically. (Author/MA)

  11. Making Sense of Motion

    ERIC Educational Resources Information Center

    King, Kenneth

    2005-01-01

    When watching a small child with a toy car, it is seen that interest in motion comes early. Children often suggest speed through sounds such as "RRRrrrRRRooooommMMMmmmm" as the toy car is made to speed up, slow down, or accelerate through a turn. Older children start to consider force and motion studies in more detail, and experiences in school…

  12. Aristotle, Motion, and Rhetoric.

    ERIC Educational Resources Information Center

    Sutton, Jane

    Aristotle rejects a world vision of changing reality as neither useful nor beneficial to human life, and instead he reaffirms both change and eternal reality, fuses motion and rest, and ends up with "well-behaved" changes. This concept of motion is foundational to his world view, and from it emerges his theory of knowledge, philosophy of…

  13. Body Motion and Graphing.

    ERIC Educational Resources Information Center

    Nemirovsky, Ricardo; Tierney, Cornelia; Wright, Tracy

    1998-01-01

    Analyzed two children's use of a computer-based motion detector to make sense of symbolic expressions (Cartesian graphs). Found three themes: (1) tool perspectives, efforts to understand graphical responses to body motion; (2) fusion, emergent ways of talking and behaving that merge symbols and referents; and (3) graphical spaces, when changing…

  14. Naive Conceptions of Motion.

    ERIC Educational Resources Information Center

    McCloskey, Michael

    Two experiments were conducted to characterize the system of beliefs that make up the naive impetus theory of motion and to determine what effects physics instruction has on students' conceptions of motion. Thirteen college students were asked to solve several quantitative problems and were interviewed about their answers in the first experiment.…

  15. Measuring mandibular motions

    NASA Technical Reports Server (NTRS)

    Dimeff, J.; Rositano, S.; Taylor, R. C.

    1977-01-01

    Mandibular motion along three axes is measured by three motion transducers on floating yoke that rests against mandible. System includes electronics to provide variety of outputs for data display and processing. Head frame is strapped to test subject's skull to provide fixed point of reference for transducers.

  16. Object motion analysis study

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The use of optical data processing (ODP) techniques for motion analysis in two-dimensional imagery was studied. The basic feasibility of this approach was demonstrated, but inconsistent performance of the photoplastic used for recording spatial filters prevented totally automatic operation. Promising solutions to the problems encountered are discussed, and it is concluded that ODP techniques could be quite useful for motion analysis.

  17. Color-kinematic duality in ABJM theory without amplitude relations

    NASA Astrophysics Data System (ADS)

    Sivaramakrishnan, Allic

    2017-01-01

    We explicitly show that the Bern-Carrasco-Johansson color-kinematic duality holds at tree level through at least eight points in Aharony-Bergman-Jafferis-Maldacena theory with gauge group SU(N) × SU(N). At six points we give the explicit form of numerators in terms of amplitudes, displaying the generalized gauge freedom that leads to amplitude relations. However, at eight points no amplitude relations follow from the duality, so the diagram numerators are fixed unique functions of partial amplitudes. We provide the explicit amplitude-numerator decomposition and the numerator relations for eight-point amplitudes.

  18. Spurious cross-frequency amplitude-amplitude coupling in nonstationary, nonlinear signals

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Lo, Men-Tzung; Hu, Kun

    2016-07-01

    Recent studies of brain activities show that cross-frequency coupling (CFC) plays an important role in memory and learning. Many measures have been proposed to investigate the CFC phenomenon, including the correlation between the amplitude envelopes of two brain waves at different frequencies - cross-frequency amplitude-amplitude coupling (AAC). In this short communication, we describe how nonstationary, nonlinear oscillatory signals may produce spurious cross-frequency AAC. Utilizing the empirical mode decomposition, we also propose a new method for assessment of AAC that can potentially reduce the effects of nonlinearity and nonstationarity and, thus, help to avoid the detection of artificial AACs. We compare the performances of this new method and the traditional Fourier-based AAC method. We also discuss the strategies to identify potential spurious AACs.

  19. EDITORIAL: Nanotechnology in motion Nanotechnology in motion

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2012-02-01

    Microscopes provide tools of inimitable value for probing the building blocks of the world around us. The identity of the inventor of the first microscope remains under debate, but a name unequivocally linked with early developments in microscopy is Robert Hooke. His Micrographia published in 1665, was the first ever bestseller in science and brought topics in microscopy to the broader public eye with pages of detailed micrographs, most famously the fly's eye and plant cells. Since the first microscopes in the late 16th century, ingenious alternatives to the original optical microscopes have been developed to create images of the world at ever smaller dimensions. Innovations include scanning probe techniques such as the atomic force microscope [1]. As Toshio Ando describes in a review in this issue [2], these devices have also entered a new era in the past decade with the development of high-speed atomic force microscopy. Now, we can not only see the nanoscale components that make up the world around us, but we can watch them at work. One of the first innovations in optical microscopy was the use of dyes. This principle first came into practice with the use of ultraviolet light to reveal previously indistinguishable features. As explained by a researcher in the early 1930s, 'It is obvious that if the dyes used for selective staining in ordinary microscopical work are supplemented by substances which cause a particular detail of the structure to fluoresce with a specific colour in ultraviolet light, then many strings will be added to the bow of the practical microscopist' [3]. More recently, emphasis on the role of plasmons—collective oscillations of electrons in nanoscale metal structures—has received considerable research attention. Plasmons enhance the local electromagnetic field and can lead to increased fluorescence rates from nearby fluorophores depending on the efficiency of the counteracting process, non-radiative transfer [4]. The 1930s also saw the

  20. Surface Chest Motion Decomposition for Cardiovascular Monitoring

    PubMed Central

    Shafiq, Ghufran; Veluvolu, Kalyana C.

    2014-01-01

    Surface chest motion can be easily monitored with a wide variety of sensors such as pressure belts, fiber Bragg gratings and inertial sensors, etc. The current applications of these sensors are mainly restricted to respiratory motion monitoring/analysis due to the technical challenges involved in separation of the cardiac motion from the dominant respiratory motion. The contribution of heart to the surface chest motion is relatively very small as compared to the respiratory motion. Further, the heart motion spectrally overlaps with the respiratory harmonics and their separation becomes even more challenging. In this paper, we approach this source separation problem with independent component analysis (ICA) framework. ICA with reference (ICA-R) yields only desired component with improved separation, but the method is highly sensitive to the reference generation. Several reference generation approaches are developed to solve the problem. Experimental validation of these proposed approaches is performed with chest displacement data and ECG obtained from healthy subjects under normal breathing and post-exercise conditions. The extracted component morphologically matches well with the collected ECG. Results show that the proposed methods perform better than conventional band pass filtering. PMID:24865183

  1. SITE AMPLIFICATION OF EARTHQUAKE GROUND MOTION.

    USGS Publications Warehouse

    Hays, Walter W.

    1986-01-01

    When analyzing the patterns of damage in an earthquake, physical parameters of the total earthquake-site-structure system are correlated with the damage. Soil-structure interaction, the cause of damage in many earthquakes, involves the frequency-dependent response of both the soil-rock column and the structure. The response of the soil-rock column (called site amplification) is controversial because soil has strain-dependent properties that affect the way the soil column filters the input body and surface seismic waves, modifying the amplitude and phase spectra and the duration of the surface ground motion.

  2. Digital anthropomorphic phantoms of non-rigid human respiratory and voluntary body motion for investigating motion correction in emission imaging

    NASA Astrophysics Data System (ADS)

    Könik, Arda; Connolly, Caitlin M.; Johnson, Karen L.; Dasari, Paul; Segars, Paul W.; Pretorius, P. H.; Lindsay, Clifford; Dey, Joyoni; King, Michael A.

    2014-07-01

    The development of methods for correcting patient motion in emission tomography has been receiving increased attention. Often the performance of these methods is evaluated through simulations using digital anthropomorphic phantoms, such as the commonly used extended cardiac torso (XCAT) phantom, which models both respiratory and cardiac motion based on human studies. However, non-rigid body motion, which is frequently seen in clinical studies, is not present in the standard XCAT phantom. In addition, respiratory motion in the standard phantom is limited to a single generic trend. In this work, to obtain a more realistic representation of motion, we developed a series of individual-specific XCAT phantoms, modeling non-rigid respiratory and non-rigid body motions derived from the magnetic resonance imaging (MRI) acquisitions of volunteers. Acquisitions were performed in the sagittal orientation using the Navigator methodology. Baseline (no motion) acquisitions at end-expiration were obtained at the beginning of each imaging session for each volunteer. For the body motion studies, MRI was again acquired only at end-expiration for five body motion poses (shoulder stretch, shoulder twist, lateral bend, side roll, and axial slide). For the respiratory motion studies, an MRI was acquired during free/regular breathing. The magnetic resonance slices were then retrospectively sorted into 14 amplitude-binned respiratory states, end-expiration, end-inspiration, six intermediary states during inspiration, and six during expiration using the recorded Navigator signal. XCAT phantoms were then generated based on these MRI data by interactive alignment of the organ contours of the XCAT with the MRI slices using a graphical user interface. Thus far we have created five body motion and five respiratory motion XCAT phantoms from the MRI acquisitions of six healthy volunteers (three males and three females). Non-rigid motion exhibited by the volunteers was reflected in both respiratory

  3. Stochastic ground motion simulation

    USGS Publications Warehouse

    Rezaeian, Sanaz; Xiaodan, Sun; Beer, Michael; Kougioumtzoglou, Ioannis A.; Patelli, Edoardo; Siu-Kui Au, Ivan

    2014-01-01

    Strong earthquake ground motion records are fundamental in engineering applications. Ground motion time series are used in response-history dynamic analysis of structural or geotechnical systems. In such analysis, the validity of predicted responses depends on the validity of the input excitations. Ground motion records are also used to develop ground motion prediction equations(GMPEs) for intensity measures such as spectral accelerations that are used in response-spectrum dynamic analysis. Despite the thousands of available strong ground motion records, there remains a shortage of records for large-magnitude earthquakes at short distances or in specific regions, as well as records that sample specific combinations of source, path, and site characteristics.

  4. MGRA: Motion Gesture Recognition via Accelerometer.

    PubMed

    Hong, Feng; You, Shujuan; Wei, Meiyu; Zhang, Yongtuo; Guo, Zhongwen

    2016-04-13

    Accelerometers have been widely embedded in most current mobile devices, enabling easy and intuitive operations. This paper proposes a Motion Gesture Recognition system (MGRA) based on accelerometer data only, which is entirely implemented on mobile devices and can provide users with real-time interactions. A robust and unique feature set is enumerated through the time domain, the frequency domain and singular value decomposition analysis using our motion gesture set containing 11,110 traces. The best feature vector for classification is selected, taking both static and mobile scenarios into consideration. MGRA exploits support vector machine as the classifier with the best feature vector. Evaluations confirm that MGRA can accommodate a broad set of gesture variations within each class, including execution time, amplitude and non-gestural movement. Extensive evaluations confirm that MGRA achieves higher accuracy under both static and mobile scenarios and costs less computation time and energy on an LG Nexus 5 than previous methods.

  5. Geophysical Effects of the Earth's Monthly Motion

    NASA Astrophysics Data System (ADS)

    Sidorenkov, N. S.; Zhigailo, T. S.

    The generation of a lunar tidal force is a major geophysical effect of the Earth's monthly motion.It is shown that synoptic processes vary simultaneously with tidal oscillations of the Earth's rotation rate and weather exhibits changes near their extremes, i.e., when the Earth is in certain positions on its monthly orbit.It is found that the quasi-biennial oscillation of the wind direction in the equatorial stratosphere is a combined oscillation caused by three periodic processes experienced by the atmosphere: (a) lunisolar tides, (b) the precession of the orbit of the Earth's monthly rotation around the barycenter of the Earth-Moon system, and (c) the motion of the perigee of this orbit.Interference of the 1.20-year Chandler wobble with sidereal, anomalistic, and synodic lunar oscillations gives rise to beats, i.e., to slow periodic variations in the wobble amplitude with periods of 32 to 51 years.

  6. Tidal deceleration of the moon's mean motion

    NASA Technical Reports Server (NTRS)

    Cheng, M. K.; Eanes, R. J.; Tapley, B. D.

    1992-01-01

    The secular change in the mean motion of the moon, n, caused by the tidal dissipation in the ocean and solid earth is due primarily to the effect of the diurnal and semidiurnal tides. The long-period ocean tides produce an increase in n, but the effects are only 1 percent of the diurnal and semidiurnal ocean tides. In this investigation, expressions for these effects are obtained by developing the tidal potential in the ecliptic reference system. The computation of the amplitude of equilibrium tide and the phase corrections is also discussed. The averaged tidal deceleration of the moon's mean motion, n, from the most recent satellite ocean tide solutions is -25.25 +/- 0.4 arcseconds/sq century. The value for n inferred from the satellite-determined ocean-tide solution is in good agreement with the value obtained from the analysis of 20 years of lunar laser-ranging observations.

  7. MGRA: Motion Gesture Recognition via Accelerometer

    PubMed Central

    Hong, Feng; You, Shujuan; Wei, Meiyu; Zhang, Yongtuo; Guo, Zhongwen

    2016-01-01

    Accelerometers have been widely embedded in most current mobile devices, enabling easy and intuitive operations. This paper proposes a Motion Gesture Recognition system (MGRA) based on accelerometer data only, which is entirely implemented on mobile devices and can provide users with real-time interactions. A robust and unique feature set is enumerated through the time domain, the frequency domain and singular value decomposition analysis using our motion gesture set containing 11,110 traces. The best feature vector for classification is selected, taking both static and mobile scenarios into consideration. MGRA exploits support vector machine as the classifier with the best feature vector. Evaluations confirm that MGRA can accommodate a broad set of gesture variations within each class, including execution time, amplitude and non-gestural movement. Extensive evaluations confirm that MGRA achieves higher accuracy under both static and mobile scenarios and costs less computation time and energy on an LG Nexus 5 than previous methods. PMID:27089336

  8. Investigation of the effect of bilayer membrane structures and fluctuation amplitudes on SANS/SAXS profile for short membrane wavelength

    NASA Astrophysics Data System (ADS)

    Lee, Victor; Hawa, Takumi

    2013-09-01

    The effect of bilayer membrane structures and fluctuation amplitudes on small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) profile is investigated based on harmonic motions of the surfactant bilayers with bending as well as thickness fluctuation motions. In this study we consider the case in which the wavelength of the bilayer membrane is shorter than the thickness of the membrane. We find that the thickness of the surfactant bilayer membrane, dm, affects both qdip and qpeak of I(q,0) profile, and that the fluctuation amplitude, a, of the membrane changes the peak of I(q,0). A simple formula is derived to estimate the thickness of the bilayer based on the qdip of the profile obtained from the simulation. The resulting estimates of the thickness of the bilayer with harmonic motion showed accuracy within 1%. Moreover, the bilayer thicknesses estimated from the proposed formula show an excellent agreement with the SANS and SAXS experimental results available in the literatures. We also propose a curve fit model, which describes the relationship between the fluctuation amplitude and the normalized qpeak ratio. The present results show the feasibility of the simple formula to estimate the fluctuation amplitude based on the SANS and SAXS profiles.

  9. Investigation of the effect of bilayer membrane structures and fluctuation amplitudes on SANS/SAXS profile for short membrane wavelength

    SciTech Connect

    Lee, Victor; Hawa, Takumi

    2013-09-28

    The effect of bilayer membrane structures and fluctuation amplitudes on small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) profile is investigated based on harmonic motions of the surfactant bilayers with bending as well as thickness fluctuation motions. In this study we consider the case in which the wavelength of the bilayer membrane is shorter than the thickness of the membrane. We find that the thickness of the surfactant bilayer membrane, d{sub m}, affects both q{sub dip} and q{sub peak} of I(q,0) profile, and that the fluctuation amplitude, a, of the membrane changes the peak of I(q,0). A simple formula is derived to estimate the thickness of the bilayer based on the q{sub dip} of the profile obtained from the simulation. The resulting estimates of the thickness of the bilayer with harmonic motion showed accuracy within 1%. Moreover, the bilayer thicknesses estimated from the proposed formula show an excellent agreement with the SANS and SAXS experimental results available in the literatures. We also propose a curve fit model, which describes the relationship between the fluctuation amplitude and the normalized q{sub peak} ratio. The present results show the feasibility of the simple formula to estimate the fluctuation amplitude based on the SANS and SAXS profiles.

  10. A comparison of shell theories for large-amplitude vibrations of circular cylindrical shells: Lagrangian approach

    NASA Astrophysics Data System (ADS)

    Amabili, M.

    2003-07-01

    Large-amplitude (geometrically non-linear) vibrations of circular cylindrical shells subjected to radial harmonic excitation in the spectral neighbourhood of the lowest resonances are investigated. The Lagrange equations of motion are obtained by an energy approach, retaining damping through Rayleigh's dissipation function. Four different non-linear thin shell theories, namely Donnell's, Sanders-Koiter, Flügge-Lur'e-Byrne and Novozhilov's theories, which neglect rotary inertia and shear deformation, are used to calculate the elastic strain energy. The formulation is also valid for orthotropic and symmetric cross-ply laminated composite shells. The large-amplitude response of perfect and imperfect, simply supported circular cylindrical shells to harmonic excitation in the spectral neighbourhood of the lowest natural frequency is computed for all these shell theories. Numerical responses obtained by using these four non-linear shell theories are also compared to results obtained by using the Donnell's non-linear shallow-shell equation of motion. A validation of calculations by comparison with experimental results is also performed. Both empty and fluid-filled shells are investigated by using a potential fluid model. The effects of radial pressure and axial load are also studied. Boundary conditions for simply supported shells are exactly satisfied. Different expansions involving from 14 to 48 generalized co-ordinates, associated with natural modes of simply supported shells, are used. The non-linear equations of motion are studied by using a code based on an arclength continuation method allowing bifurcation analysis.

  11. Harmonic motion detection in a vibrating scattering medium.

    PubMed

    Urban, Matthew W; Chen, Shigao; Greenleaf, James

    2008-09-01

    Elasticity imaging is an emerging medical imaging modality that seeks to map the spatial distribution of tissue stiffness. Ultrasound radiation force excitation and motion tracking using pulse-echo ultrasound have been used in numerous methods. Dynamic radiation force is used in vibrometry to cause an object or tissue to vibrate, and the vibration amplitude and phase can be measured with exceptional accuracy. This paper presents a model that simulates harmonic motion detection in a vibrating scattering medium incorporating 3-D beam shapes for radiation force excitation and motion tracking. A parameterized analysis using this model provides a platform to optimize motion detection for vibrometry applications in tissue. An experimental method that produces a multifrequency radiation force is also presented. Experimental harmonic motion detection of simultaneous multifrequency vibration is demonstrated using a single transducer. This method can accurately detect motion with displacement amplitude as low as 100 to 200 nm in bovine muscle. Vibration phase can be measured within 10 degrees or less. The experimental results validate the conclusions observed from the model and show multifrequency vibration induction and measurements can be performed simultaneously.

  12. Harmonic Motion Detection in a Vibrating Scattering Medium

    PubMed Central

    Urban, Matthew W.; Chen, Shigao; Greenleaf, James F.

    2008-01-01

    Elasticity imaging is an emerging medical imaging modality that seeks to map the spatial distribution of tissue stiffness. Ultrasound radiation force excitation and motion tracking using pulse-echo ultrasound have been used in numerous methods. Dynamic radiation force is used in vibrometry to cause an object or tissue to vibrate, and the vibration amplitude and phase can be measured with exceptional accuracy. This paper presents a model that simulates harmonic motion detection in a vibrating scattering medium incorporating 3-D beam shapes for radiation force excitation and motion tracking. A parameterized analysis using this model provides a platform to optimize motion detection for vibrometry applications in tissue. An experimental method that produces a multifrequency radiation force is also presented. Experimental harmonic motion detection of simultaneous multifrequency vibration is demonstrated using a single transducer. This method can accurately detect motion with displacement amplitude as low as 100 to 200 nm in bovine muscle. Vibration phase can be measured within 10° or less. The experimental results validate the conclusions observed from the model and show multifrequency vibration induction and measurements can be performed simultaneously. PMID:18986892

  13. Motion sickness in migraine sufferers.

    PubMed

    Marcus, Dawn A; Furman, Joseph M; Balaban, Carey D

    2005-12-01

    Motion sickness commonly occurs after exposure to actual motion, such as car or amusement park rides, or virtual motion, such as panoramic movies. Motion sickness symptoms may be disabling, significantly limiting business, travel and leisure activities. Motion sickness occurs in approximately 50% of migraine sufferers. Understanding motion sickness in migraine patients may improve understanding of the physiology of both conditions. Recent literature suggests important relationships between the trigeminal system and vestibular nuclei that may have implications for both motion sickness and migraine. Studies demonstrating an important relationship between serotonin receptors and motion sickness susceptibility in both rodents and humans suggest possible new motion sickness prevention therapies.

  14. SU-E-J-252: A Motion Algorithm to Extract Physical and Motion Parameters of a Mobile Target in Cone-Beam Computed Tomographic Imaging Retrospective to Image Reconstruction

    SciTech Connect

    Ali, I; Ahmad, S; Alsbou, N

    2014-06-01

    Purpose: A motion algorithm was developed to extract actual length, CT-numbers and motion amplitude of a mobile target imaged with cone-beam-CT (CBCT) retrospective to image-reconstruction. Methods: The motion model considered a mobile target moving with a sinusoidal motion and employed three measurable parameters: apparent length, CT number level and gradient of a mobile target obtained from CBCT images to extract information about the actual length and CT number value of the stationary target and motion amplitude. The algorithm was verified experimentally with a mobile phantom setup that has three targets with different sizes manufactured from homogenous tissue-equivalent gel material embedded into a thorax phantom. The phantom moved sinusoidal in one-direction using eight amplitudes (0–20mm) and a frequency of 15-cycles-per-minute. The model required imaging parameters such as slice thickness, imaging time. Results: This motion algorithm extracted three unknown parameters: length of the target, CT-number-level, motion amplitude for a mobile target retrospective to CBCT image reconstruction. The algorithm relates three unknown parameters to measurable apparent length, CT-number-level and gradient for well-defined mobile targets obtained from CBCT images. The motion model agreed with measured apparent lengths which were dependent on actual length of the target and motion amplitude. The cumulative CT-number for a mobile target was dependent on CT-number-level of the stationary target and motion amplitude. The gradient of the CT-distribution of mobile target is dependent on the stationary CT-number-level, actual target length along the direction of motion, and motion amplitude. Motion frequency and phase did not affect the elongation and CT-number distributions of mobile targets when imaging time included several motion cycles. Conclusion: The motion algorithm developed in this study has potential applications in diagnostic CT imaging and radiotherapy to extract

  15. Evaluating the Influence of Spatial Resampling for Motion Correction in Resting-State Functional MRI

    PubMed Central

    Yuan, Lisha; He, Hongjian; Zhang, Han; Zhong, Jianhui

    2016-01-01

    Head motion is one of major concerns in current resting-state functional MRI studies. Image realignment including motion estimation and spatial resampling is often applied to achieve rigid-body motion correction. While the accurate estimation of motion parameters has been addressed in most studies, spatial resampling could also produce spurious variance, and lead to unexpected errors on the amplitude of BOLD signal. In this study, two simulation experiments were designed to characterize these variance related with spatial resampling. The fluctuation amplitude of spurious variance was first investigated using a set of simulated images with estimated motion parameters from a real dataset, and regions more likely to be affected by spatial resampling were found around the peripheral regions of the cortex. The other simulation was designed with three typical types of motion parameters to represent different extents of motion. It was found that areas with significant correlation between spurious variance and head motion scattered all over the brain and varied greatly from one motion type to another. In the last part of this study, four popular motion regression approaches were applied respectively and their performance in reducing spurious variance was compared. Among them, Friston 24 and Voxel-specific 12 model (Friston et al., 1996), were found to have the best outcomes. By separating related effects during fMRI analysis, this study provides a better understanding of the characteristics of spatial resampling and the interpretation of motion-BOLD relationship. PMID:28082860

  16. Strong motion duration and earthquake magnitude relationships

    SciTech Connect

    Salmon, M.W.; Short, S.A.; Kennedy, R.P.

    1992-06-01

    Earthquake duration is the total time of ground shaking from the arrival of seismic waves until the return to ambient conditions. Much of this time is at relatively low shaking levels which have little effect on seismic structural response and on earthquake damage potential. As a result, a parameter termed ``strong motion duration`` has been defined by a number of investigators to be used for the purpose of evaluating seismic response and assessing the potential for structural damage due to earthquakes. This report presents methods for determining strong motion duration and a time history envelope function appropriate for various evaluation purposes, for earthquake magnitude and distance, and for site soil properties. There are numerous definitions of strong motion duration. For most of these definitions, empirical studies have been completed which relate duration to earthquake magnitude and distance and to site soil properties. Each of these definitions recognizes that only the portion of an earthquake record which has sufficiently high acceleration amplitude, energy content, or some other parameters significantly affects seismic response. Studies have been performed which indicate that the portion of an earthquake record in which the power (average rate of energy input) is maximum correlates most closely with potential damage to stiff nuclear power plant structures. Hence, this report will concentrate on energy based strong motion duration definitions.

  17. Effect of vertical motion on current meters

    USGS Publications Warehouse

    Kallio, Nicholas A.

    1966-01-01

    The effect of vertical motion on the performance of current meters at various stream velocities was evaluated to determine whether accurate discharge measurements can be made from a bobbing boat. Three types of current meters--Ott, Price, and vane types--were tested under conditions simulating a bobbing boat. A known frequency and amplitude of vertical motion were imparted to the current meter, and the related effect on the measured stream velocity was determined. One test of the Price meter was made under actual conditions, using a boat and standard measuring gear. The results of the test under actual conditions verified those obtained by simulating the vertical movements of a boat. The tests show that for stream velocities below 2.5 feet per second the accuracy of all three meters is significantly affected when the meters are subjected to certain conditions of vertical motion that can occur during actual field operations. Both the rate of vertical motion and the frequency of vertical oscillation affect the registration of the meter. The results of these tests, presented in the form of graphs and tables, can be used as a guide to determine whether wind and stream flow are within an acceptable range for a reliable discharge measurement from a boat.

  18. Collective behavior states in animal groups

    NASA Astrophysics Data System (ADS)

    Cambui, Dorílson S.

    2017-02-01

    In this work, we study some states of collective behavior observed in groups of animals. For this end we consider an agent-based model with biologically motivated behavioral rules where the speed is treated as an independent stochastic variable, and the motion direction is adjusted in accord with alignment and attractive interactions. Four types of collective behavior have been observed: disordered motion, collective rotation, coherent collective motion, and formation flight. We investigate the case when transitions between collective states depend on both the speed and the attraction between individuals. Our results show that, to any size of the attraction, small speeds are associated to the coherent collective motion, while collective rotation is more and more pronounced for high speed since the attraction radius is large enough.

  19. Amplitude Scaling of Active Separation Control

    NASA Technical Reports Server (NTRS)

    Stalnov, Oksana; Seifert, Avraham

    2010-01-01

    Three existing and two new excitation magnitude scaling options for active separation control at Reynolds numbers below one Million. The physical background for the scaling options was discussed and their relevance was evaluated using two different sets of experimental data. For F+ approx. 1, 2D excitation: a) The traditional VR and C(mu) - do not scale the data. b) Only the Re*C(mu) is valid. This conclusion is also limited for positive lift increment.. For F+ > 10, 3D excitation, the Re corrected C(mu), the St corrected velocity ratio and the vorticity flux coefficient, all scale the amplitudes equally well. Therefore, the Reynolds weighted C(mu) is the preferred choice, relevant to both excitation modes. Incidence also considered, using Ue from local Cp.

  20. Speech recognition with amplitude and frequency modulations

    NASA Astrophysics Data System (ADS)

    Zeng, Fan-Gang; Nie, Kaibao; Stickney, Ginger S.; Kong, Ying-Yee; Vongphoe, Michael; Bhargave, Ashish; Wei, Chaogang; Cao, Keli

    2005-02-01

    Amplitude modulation (AM) and frequency modulation (FM) are commonly used in communication, but their relative contributions to speech recognition have not been fully explored. To bridge this gap, we derived slowly varying AM and FM from speech sounds and conducted listening tests using stimuli with different modulations in normal-hearing and cochlear-implant subjects. We found that although AM from a limited number of spectral bands may be sufficient for speech recognition in quiet, FM significantly enhances speech recognition in noise, as well as speaker and tone recognition. Additional speech reception threshold measures revealed that FM is particularly critical for speech recognition with a competing voice and is independent of spectral resolution and similarity. These results suggest that AM and FM provide independent yet complementary contributions to support robust speech recognition under realistic listening situations. Encoding FM may improve auditory scene analysis, cochlear-implant, and audiocoding performance. auditory analysis | cochlear implant | neural code | phase | scene analysis

  1. Evaluation of new spin foam vertex amplitudes

    NASA Astrophysics Data System (ADS)

    Khavkine, Igor

    2009-06-01

    The Christensen-Egan algorithm is extended and generalized to efficiently evaluate new spin foam vertex amplitudes proposed by Engle, Pereira and Rovelli and Freidel and Krasnov, with or without (factored) boundary states. A concrete pragmatic proposal is made for comparing the different models using uniform methodologies, applicable to the behavior of large spin asymptotics and of expectation values of specific semiclassical observables. The asymptotics of the new models exhibit non-oscillatory, power-law decay similar to that of the Barrett-Crane model, though with different exponents. Also, an analysis of the semiclassical wave packet propagation problem indicates that the Magliaro, Rovelli and Perini's conjecture of good semiclassical behavior of the new models does not hold for generic factored states, which neglect spin-spin correlations.

  2. Low Amplitude Impact of Damaged PBX 9501

    NASA Astrophysics Data System (ADS)

    Idar, Deanne

    1999-06-01

    Low amplitude impact tests on damaged, baseline and aged, PBX 9501 specimens have been performed to determine the critical impact-velocity threshold for violent reaction. Tests were performed using 3.0-in. diameter, 2 kg. mild-steel projectiles launched from a spigot gun at lightly confined modified Steven targets. Prior damage on the seven targets was induced by a single impact ranging in velocity from 36.9 to 52.7 m/s. External blast gauge data were coupled with ballistic pendulum data to evaluate the level of reaction violence relative to a steady-state detonation. Strain gage data were used to evaluate the response of the explosive to impact and characterize subsequent reaction profiles. The effect of PBX 9501 lots, age, and prior level of damage on threshold behavior will be discussed and compared to single impact test results.

  3. Presynaptic spike broadening reduces junctional potential amplitude.

    PubMed

    Spencer, A N; Przysiezniak, J; Acosta-Urquidi, J; Basarsky, T A

    1989-08-24

    Presynaptic modulation of action potential duration may regulate synaptic transmission in both vertebrates and invertebrates. Such synaptic plasticity is brought about by modifications to membrane currents at presynaptic release sites, which, in turn, lead to changes in the concentration of cytosolic calcium available for mediating transmitter release. The 'primitive' neuromuscular junction of the jellyfish Polyorchis penicillatus is a useful model of presynaptic modulation. In this study, we show that the durations of action potentials in the motor neurons of this jellyfish are negatively correlated with the amplitude of excitatory junctional potentials. We present data from in vitro voltage-clamp experiments showing that short duration voltage spikes, which elicit large excitatory junctional potentials in vivo, produce larger and briefer calcium currents than do long duration action potentials, which elicit small excitatory junctional potentials.

  4. Revisions to some parameters used in stochastic-method simulations of ground motion

    USGS Publications Warehouse

    Boore, David; Thompson, Eric M.

    2015-01-01

    The stochastic method of ground‐motion simulation specifies the amplitude spectrum as a function of magnitude (M) and distance (R). The manner in which the amplitude spectrum varies with M and R depends on physical‐based parameters that are often constrained by recorded motions for a particular region (e.g., stress parameter, geometrical spreading, quality factor, and crustal amplifications), which we refer to as the seismological model. The remaining ingredient for the stochastic method is the ground‐motion duration. Although the duration obviously affects the character of the ground motion in the time domain, it also significantly affects the response of a single‐degree‐of‐freedom oscillator. Recently published updates to the stochastic method include a new generalized double‐corner‐frequency source model, a new finite‐fault correction, a new parameterization of duration, and a new duration model for active crustal regions. In this article, we augment these updates with a new crustal amplification model and a new duration model for stable continental regions. Random‐vibration theory (RVT) provides a computationally efficient method to compute the peak oscillator response directly from the ground‐motion amplitude spectrum and duration. Because the correction factor used to account for the nonstationarity of the ground motion depends on the ground‐motion amplitude spectrum and duration, we also present new RVT correction factors for both active and stable regions.

  5. Bootstrapping an NMHV amplitude through three loops

    NASA Astrophysics Data System (ADS)

    Dixon, Lance J.; von Hippel, Matt

    2014-10-01

    We extend the hexagon function bootstrap to the next-to-maximally-helicity-violating (NMHV) configuration for six-point scattering in planar = 4 super-Yang-Mills theory at three loops. Constraints from the differential equation, from the operator product expansion (OPE) for Wilson loops with operator insertions, and from multi-Regge factorization, lead to a unique answer for the three-loop ratio function. The three-loop result also predicts additional terms in the OPE expansion, as well as the behavior of NMHV amplitudes in the multi-Regge limit at one higher logarithmic accuracy (NNLL) than was used as input. Both predictions are in agreement with recent results from the flux-tube approach. We also study the multi-particle factorization of multi-loop amplitudes for the first time. We find that the function controlling this factorization is purely logarithmic through three loops. We show that a function U , which is closely related to the parity-even part of the ratio function V , is remarkably simple; only five of the nine possible final entries in its symbol are non-vanishing. We study the analytic and numerical behavior of both the parity-even and parity-odd parts of the ratio function on simple lines traversing the space of cross ratios ( u, v, w), as well as on a few two-dimensional planes. Finally, we present an empirical formula for V in terms of elements of the coproduct of the six-gluon MHV remainder function R 6 at one higher loop, which works through three loops for V (four loops for R 6).

  6. Visualizing motion in video

    NASA Astrophysics Data System (ADS)

    Brown, Lisa M.; Crayne, Susan

    2000-05-01

    In this paper, we present a visualization system and method for measuring, inspecting and analyzing motion in video. Starting from a simple motion video, the system creates a still image representation which we call a digital strobe photograph. Similar to visualization techniques used in conventional film photography to capture high-speed motion using strobe lamps or very fast shutters, and to capture time-lapse motion where the shutter is left open, this methodology creates a single image showing the motion of one or a small number of objects over time. Based on digital background subtraction, we assume that the background is stationary or at most slowing changing and that the camera position is fixed. The method is capable of displaying the motion based on a parameter indicating the time step between successive movements. It can also overcome problems of visualizing movement that is obscured by previous movements. The method is used in an educational software tool for children to measure and analyze various motions. Examples are given using simple physical objects such as balls and pendulums, astronomical events such as the path of the stars around the north pole at night, or the different types of locomotion used by snakes.

  7. Compositions of bosonic string amplitudes with cylinder topology

    SciTech Connect

    Trisnadi, J.I.

    1989-01-01

    Many issues in string theory are conveniently addressed and handled in a quantum fleld theoretical framework, from which Feynman rules can then be derived. Although at present a generally acceptable quantum field theory of closed strings does not yet exist, the Feynman rules are known. This is due to another development in string theory, namely, the Polyakov path integral approach. In this approach, scattering amplitudes are calculated directly without appealing to the quantum fleld theoretical description. It is therefore important to examine if the scattering amplitude can be reconstructed by composing propagators and vertices. In general, the author is interested in knowing if Polyakov amplitudes can be consistently composed. Composition of amplitudes in general has been studied formally. Explicit composition, however, is limited to amplitudes that have been calculated explicitly. Among them is the amplitude with cylinder topology. In this dissertation, the author will rederive this cylinder amplitude. The author uses the action principle in the evaluation of the path integral. This way, the contributions of the ghost zero modes, which are usually introduced by hand, come out automatically. Then, the author studies three compositions of the cylinder amplitude: two cylinder amplitudes into one, a single cylinder amplitude into a torus amplitude, and a cylinder amplitude into a Klein-bottle amplitude. The author shows that the resulting amplitudes agree with known results. Using the cylinder amplitude, the author also demonstrates the derivation of the (imaginary time) Schrodinger equation for the free closed bosonic string. Finally, the author applies the techniques to derive the composable transition amplitude of gravity in a Friedmann-RobertsonWalker cosmology.

  8. Chiral closed strings: four massless states scattering amplitude

    NASA Astrophysics Data System (ADS)

    Leite, Marcelo M.; Siegel, Warren

    2017-01-01

    We compute the scattering amplitudes of four massless states for chiral (closed) bosonic and type II superstrings using the Kawai-Lewellen-Tye ( KLT ) factorization method. The amplitude in the chiral bosonic case is identical to a field theory amplitude corresponding to the spin-2 tachyon, massless gravitational sector and massive spin-2 tardyon states of the spectrum. Chiral type II superstrings amplitude only possess poles associated with the massless gravitational sector. We briefly discuss the extension of the calculation to heterotic superstrings.

  9. Art in Motion: A Sailboat Regatta

    ERIC Educational Resources Information Center

    Angle, Julie; Foster, Gayla

    2011-01-01

    The activity described here uses the creative natures of visual art and music to enhance students' potential for creativity while increasing their understanding of the science associated with force and motion. Students design, test, and redesign a sailboat vehicle; collect data; make interpretations; and then defend their design. Music is used to…

  10. An analysis of nearfield normal mode amplitude anomalies of the Landers earthquake

    NASA Technical Reports Server (NTRS)

    Watada, Shingo; Kanamori, Hiroo; Anderson, Don L.

    1993-01-01

    The 1992 Landers earthquake (M(sub w) = 7.3) occurred in the middle of the TERRAscope network. Long-period Rayleigh waves recorded at the TERRAscope stations (delta less than or = 3 deg) after traveling around the Earth show large amplitude anomalies, one order of magnitude larger than spherical Earth predictions up to a period of about 600 s. The ground motions over the epicentral region at and after the arrival of R4-5 are in phase at all stations. These observations are inconsistent with the nearly vertical strike slip mechanism of the Landers earthquake. Synthetic seismograms for a rotating, elliptic, and laterally heterogeneous Earth model calculated by the variational method agree well with the observed waveforms. Calculations for various 3D Earth models demonstrate that the amplitudes are very sensitive to the large scale aspherical structure in the crust and the mantle. The anomalies for modes shorter than 300 s period can be explained by lateral heterogeneity shallower than the upper mantle. Rotation of the Earth and lower mantle heterogeneity are required to explain mode amplitudes at longer periods. Current whole mantle seismic tomographic models can fully explain the observed amplitudes longer than 300 s. To assess the effect of the high order lateral heterogeneity in the mantle more precise estimate of the crustal correction is required.

  11. On the interpretation of the amplitude decay of noise correlations computed along a line of receivers

    NASA Astrophysics Data System (ADS)

    Stehly, Laurent; Boué, Pierre

    2017-01-01

    Measuring seismic wave attenuation is critical to the prediction of accurate ground motion and for earthquake hazard analysis. In the present article, we carefully investigate to what extent noise correlations can be used to unambigously measure the attenuation of the Earth crust. More precisely, we explore the different ways to interpret the amplitude decay of noise correlations computed along two lines of broadband receivers located nearby the french Pyrenees. To this end, we first study how the distribution of seismic noise sources affects the amplitude of noise correlations by computing of the noise-source kernels in PREM. Numerical experiments in a two-dimensional homogeneous medium are then used to intepret the amplitude decay of the noise correlations measured along two lines of broadband receivers located in southwest France. We find that in the 5-10s period band, where Rayleigh waves are sensitive to the upper-crust, the noise correlations have stronger amplitude decay along the northern Pyrenees than along the Aquitain basin. However this difference cannot be interpreted unambigously as a contrast of attenuation as it is also possible to find a distribution of noise sources that explains our observations. This shows that even when considering a line of receivers, it is not possible to use noise correlations to measure the attenuation of the medium without making strong assumptions about or taking into account the distribution of the noise sources.

  12. Motion Recognition and Modifying Motion Generation for Imitation Robot Based on Motion Knowledge Formation

    NASA Astrophysics Data System (ADS)

    Okuzawa, Yuki; Kato, Shohei; Kanoh, Masayoshi; Itoh, Hidenori

    A knowledge-based approach to imitation learning of motion generation for humanoid robots and an imitative motion generation system based on motion knowledge learning and modification are described. The system has three parts: recognizing, learning, and modifying parts. The first part recognizes an instructed motion distinguishing it from the motion knowledge database by the continuous hidden markov model. When the motion is recognized as being unfamiliar, the second part learns it using locally weighted regression and acquires a knowledge of the motion. When a robot recognizes the instructed motion as familiar or judges that its acquired knowledge is applicable to the motion generation, the third part imitates the instructed motion by modifying a learned motion. This paper reports some performance results: the motion imitation of several radio gymnastics motions.

  13. Inflation and cyclotron motion

    NASA Astrophysics Data System (ADS)

    Greensite, Jeff

    2017-01-01

    We consider, in the context of a braneworld cosmology, the motion of the Universe coupled to a four-form gauge field, with constant field strength, defined in higher dimensions. It is found, under rather general initial conditions, that in this situation there is a period of exponential inflation combined with cyclotron motion in the inflaton field space. The main effect of the cyclotron motion is that slow roll conditions on the inflaton potential, which are typically necessary for exponential inflation, can be evaded. There are Landau levels associated with the four-form gauge field, and these correspond to quantum excitations of the inflaton field satisfying unconventional dispersion relations.

  14. Generalized compliant motion primitive

    NASA Astrophysics Data System (ADS)

    Backes, Paul G.

    1994-08-01

    This invention relates to a general primitive for controlling a telerobot with a set of input parameters. The primitive includes a trajectory generator; a teleoperation sensor; a joint limit generator; a force setpoint generator; a dither function generator, which produces telerobot motion inputs in a common coordinate frame for simultaneous combination in sensor summers. Virtual return spring motion input is provided by a restoration spring subsystem. The novel features of this invention include use of a single general motion primitive at a remote site to permit the shared and supervisory control of the robot manipulator to perform tasks via a remotely transferred input parameter set.

  15. A novel smart rotor support with shape memory alloy metal rubber for high temperatures and variable amplitude vibrations

    NASA Astrophysics Data System (ADS)

    Ma, Yanhong; Zhang, Qicheng; Zhang, Dayi; Scarpa, Fabrizio; Liu, Baolong; Hong, Jie

    2014-12-01

    The work describes the design, manufacturing and testing of a smart rotor support with shape memory alloy metal rubber (SMA-MR) elements, able to provide variable stiffness and damping characteristics with temperature, motion amplitude and excitation frequency. Differences in damping behavior and nonlinear stiffness between SMA-MR and more traditional metal rubber supports are discussed. The mechanical performance shown by the prototype demonstrates the feasibility of using the SMA-MR concept for active vibration control in rotordynamics, in particular at high temperatures and large amplitude vibrations.

  16. Locomotion of Helical Bodies in Viscoelastic Fluids: Enhanced Swimming at Large Helical Amplitudes

    NASA Astrophysics Data System (ADS)

    Spagnolie, Saverio E.; Liu, Bin; Powers, Thomas R.

    2013-08-01

    The motion of a rotating helical body in a viscoelastic fluid is considered. In the case of force-free swimming, the introduction of viscoelasticity can either enhance or retard the swimming speed and locomotive efficiency, depending on the body geometry, fluid properties, and the body rotation rate. Numerical solutions of the Oldroyd-B equations show how previous theoretical predictions break down with increasing helical radius or with decreasing filament thickness. Helices of large pitch angle show an increase in swimming speed to a local maximum at a Deborah number of order unity. The numerical results show how the small-amplitude theoretical calculations connect smoothly to the large-amplitude experimental measurements.

  17. Subharmonic excitation in amplitude modulation atomic force microscopy in the presence of adsorbed water layers

    SciTech Connect

    Santos, Sergio; Barcons, Victor; Verdaguer, Albert; Chiesa, Matteo

    2011-12-01

    In ambient conditions, nanometric water layers form on hydrophilic surfaces covering them and significantly changing their properties and characteristics. Here we report the excitation of subharmonics in amplitude modulation atomic force microscopy induced by intermittent water contacts. Our simulations show that there are several regimes of operation depending on whether there is perturbation of water layers. Single period orbitals, where subharmonics are never induced, follow only when the tip is either in permanent contact with the water layers or in pure noncontact where the water layers are never perturbed. When the water layers are perturbed subharmonic excitation increases with decreasing oscillation amplitude. We derive an analytical expression which establishes whether water perturbations compromise harmonic motion and show that the predictions are in agreement with numerical simulations. Empirical validation of our interpretation is provided by the observation of a range of values for apparent height of water layers when subharmonic excitation is predicted.

  18. Motion Direction Biases and Decoding in Human Visual Cortex

    PubMed Central

    Wang, Helena X.; Merriam, Elisha P.; Freeman, Jeremy

    2014-01-01

    Functional magnetic resonance imaging (fMRI) studies have relied on multivariate analysis methods to decode visual motion direction from measurements of cortical activity. Above-chance decoding has been commonly used to infer the motion-selective response properties of the underlying neural populations. Moreover, patterns of reliable response biases across voxels that underlie decoding have been interpreted to reflect maps of functional architecture. Using fMRI, we identified a direction-selective response bias in human visual cortex that: (1) predicted motion-decoding accuracy; (2) depended on the shape of the stimulus aperture rather than the absolute direction of motion, such that response amplitudes gradually decreased with distance from the stimulus aperture edge corresponding to motion origin; and 3) was present in V1, V2, V3, but not evident in MT+, explaining the higher motion-decoding accuracies reported previously in early visual cortex. These results demonstrate that fMRI-based motion decoding has little or no dependence on the underlying functional organization of motion selectivity. PMID:25209297

  19. Localized harmonic motion imaging for focused ultrasound surgery targeting.

    PubMed

    Curiel, Laura; Hynynen, Kullervo

    2011-08-01

    Recently, an in vivo real-time ultrasound-based monitoring technique that uses localized harmonic motion (LHM) to detect changes in tissues during focused ultrasound surgery (FUS) has been proposed to control the exposure. This technique can potentially be used as well for targeting imaging. In the present study, we evaluated the potential of using LHM to detect changes in stiffness and the feasibility of using it for imaging purposes in phantoms and in vivo tumor detection. A single-element FUS transducer (80 mm focal length, 100 mm diameter, 1.485 MHz) was used for inducing a localized harmonic motion and a separate ultrasound diagnostic transducer excited by a pulser/receiver (5 kHz PRF, 5 MHz) was used to track motion. The motion was estimated using cross-correlation techniques on the acquired radio-frequency (RF) signal. Silicon phantom studies were performed to determine the size of inclusion that was possible to detect using this technique. Inclusions were discerned from the surroundings as a reduction on LHM amplitude and it was possible to depict inclusions as small as 4 mm. The amplitude of the induced LHM was always lower at the inclusions compared with the one obtained at the surroundings. Ten New Zealand rabbits had VX2 tumors implanted on their thighs and LHM was induced and measured at the tumor region. Tumors (as small as 10 mm in length and 4 mm in width) were discerned from the surroundings as a reduction on LHM amplitude.

  20. Strong motion from surface waves in deep sedimentary basins

    USGS Publications Warehouse

    Joyner, W.B.

    2000-01-01

    It is widely recognized that long-period surface waves generated by conversion of body waves at the boundaries of deep sedimentary basins make an important contribution to strong ground motion. The factors controlling the amplitude of such motion, however, are not widely understood. A study of pseudovelocity response spectra of strong-motion records from the Los Angeles Basin shows that late-arriving surface waves with group velocities of about 1 km/sec dominate the ground motion for periods of 3 sec and longer. The rate of amplitude decay for these waves is less than for the body waves and depends significantly on period, with smaller decay for longer periods. The amplitude can be modeled by the equation log y = f(M, RE) + c + bRB where y is the pseudovelocity response, f(M, RE) is an attenuation relation based on a general strong-motion data set, M is moment magnitude, RE is the distance from the source to the edge of the basin, RB is the distance from the edge of the basin to the recording site, and b and c are parameters fit to the data. The equation gives values larger by as much as a factor of 3 than given by the attenuation relationships based on general strong-motion data sets for the same source-site distance. It is clear that surface waves need to be taken into account in the design of long-period structures in deep sedimentary basins. The ground-motion levels specified by the earthquake provisions of current building codes, in California at least, accommodate the long-period ground motions from basin-edge-generated surface waves for periods of 5 sec and less and earthquakes with moment magnitudes of 7.5 or less located more than 20 km outside the basin. There may be problems at longer periods and for earthquakes located closer to the basin edge. The results of this study suggest that anelastic attenuation may need to be included in attempts to model long-period motion in deep sedimentary basins. To obtain better data on surface waves in the future

  1. Optimal Stimulus Amplitude for Vestibular Stochastic Stimulation to Improve Sensorimotor Function

    NASA Technical Reports Server (NTRS)

    Goel, R.; Kofman, I.; DeDios, Y. E.; Jeevarajan, J.; Stepanyan, V.; Nair, M.; Congdon, S.; Fregia, M.; Cohen, H.; Bloomberg, J. J.; Mulavara, A. P.

    2014-01-01

    Sensorimotor changes such as postural and gait instabilities can affect the functional performance of astronauts when they transition across different gravity environments. We are developing a method, based on stochastic resonance (SR), to enhance information transfer by applying non-zero levels of external noise on the vestibular system (vestibular stochastic resonance, VSR). Our previous work has shown the advantageous effects of VSR in a balance task of standing on an unstable surface. This technique to improve detection of vestibular signals uses a stimulus delivery system that is wearable or portable and provides imperceptibly low levels of white noise-based binaural bipolar electrical stimulation of the vestibular system. The goal of this project is to determine optimal levels of stimulation for SR applications by using a defined vestibular threshold of motion detection. A series of experiments were carried out to determine a robust paradigm to identify a vestibular threshold that can then be used to recommend optimal stimulation levels for SR training applications customized to each crewmember. Customizing stimulus intensity can maximize treatment effects. The amplitude of stimulation to be used in the VSR application has varied across studies in the literature such as 60% of nociceptive stimulus thresholds. We compared subjects' perceptual threshold with that obtained from two measures of body sway. Each test session was 463s long and consisted of several 15s sinusoidal stimuli, at different current amplitudes (0-2 mA), interspersed with 20-20.5s periods of no stimulation. Subjects sat on a chair with their eyes closed and had to report their perception of motion through a joystick. A force plate underneath the chair recorded medio-lateral shear forces and roll moments. First we determined the percent time during stimulation periods for which perception of motion (activity above a pre-defined threshold) was reported using the joystick, and body sway (two

  2. Fourier decomposition of polymer orientation in large-amplitude oscillatory shear flow

    DOE PAGES

    Giacomin, A. J.; Gilbert, P. H.; Schmalzer, A. M.

    2015-03-19

    In our previous work, we explored the dynamics of a dilute suspension of rigid dumbbells as a model for polymeric liquids in large-amplitude oscillatory shear flow, a flow experiment that has gained a significant following in recent years. We chose rigid dumbbells since these are the simplest molecular model to give higher harmonics in the components of the stress response. We derived the expression for the dumbbell orientation distribution, and then we used this function to calculate the shear stress response, and normal stress difference responses in large-amplitude oscillatory shear flow. In this paper, we deepen our understanding of themore » polymer motion underlying large-amplitude oscillatory shear flow by decomposing the orientation distribution function into its first five Fourier components (the zeroth, first, second, third, and fourth harmonics). We use three-dimensional images to explore each harmonic of the polymer motion. Our analysis includes the three most important cases: (i) nonlinear steady shear flow (where the Deborah number λω is zero and the Weissenberg number λγ 0 is above unity), (ii) nonlinear viscoelasticity (where both λω and λγ 0 exceed unity), and (iii) linear viscoelasticity (where λω exceeds unity and where λγ 0 approaches zero). We learn that the polymer orientation distribution is spherical in the linear viscoelastic regime, and otherwise tilted and peanut-shaped. We find that the peanut-shaping is mainly caused by the zeroth harmonic, and the tilting, by the second. The first, third, and fourth harmonics of the orientation distribution make only slight contributions to the overall polymer motion.« less

  3. Fourier decomposition of polymer orientation in large-amplitude oscillatory shear flow

    SciTech Connect

    Giacomin, A. J.; Gilbert, P. H.; Schmalzer, A. M.

    2015-03-19

    In our previous work, we explored the dynamics of a dilute suspension of rigid dumbbells as a model for polymeric liquids in large-amplitude oscillatory shear flow, a flow experiment that has gained a significant following in recent years. We chose rigid dumbbells since these are the simplest molecular model to give higher harmonics in the components of the stress response. We derived the expression for the dumbbell orientation distribution, and then we used this function to calculate the shear stress response, and normal stress difference responses in large-amplitude oscillatory shear flow. In this paper, we deepen our understanding of the polymer motion underlying large-amplitude oscillatory shear flow by decomposing the orientation distribution function into its first five Fourier components (the zeroth, first, second, third, and fourth harmonics). We use three-dimensional images to explore each harmonic of the polymer motion. Our analysis includes the three most important cases: (i) nonlinear steady shear flow (where the Deborah number λω is zero and the Weissenberg number λγ 0 is above unity), (ii) nonlinear viscoelasticity (where both λω and λγ 0 exceed unity), and (iii) linear viscoelasticity (where λω exceeds unity and where λγ 0 approaches zero). We learn that the polymer orientation distribution is spherical in the linear viscoelastic regime, and otherwise tilted and peanut-shaped. We find that the peanut-shaping is mainly caused by the zeroth harmonic, and the tilting, by the second. The first, third, and fourth harmonics of the orientation distribution make only slight contributions to the overall polymer motion.

  4. Amplitude Analysis of the Decay B0->K+pi-pi0

    SciTech Connect

    Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prencipe, E.; Prudent, X.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Lopez, L.; Palano, Antimo; Pappagallo, M.; Eigen, G.; Stugu, Bjarne; Sun, L.; Abrams, G.S.; Battaglia, M.; Brown, D.N.; Cahn, Robert N.; Jacobsen, R.G.; /LBL, Berkeley /Birmingham U. /Ruhr U., Bochum /Bristol U. /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UCLA /UC, Riverside /UC, San Diego /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /Ferrara U. /INFN, Ferrara /Frascati /Genoa U. /INFN, Genoa /Harvard U. /Heidelberg U. /Humboldt U., Berlin /Imperial Coll., London /Iowa U. /Iowa State U. /Johns Hopkins U. /Orsay, LAL /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Louisville U. /Mainz U., Inst. Kernphys. /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT /McGill U. /Consorzio Milano Ricerche /INFN, Milan /Mississippi U. /Montreal U. /Mt. Holyoke Coll. /Napoli Seconda U. /INFN, Naples /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /Padua U. /INFN, Padua /Paris U., VI-VII /Pennsylvania U. /Perugia U. /INFN, Perugia /INFN, Pisa /Princeton U. /Banca di Roma /Frascati /Rostock U. /Rutherford /DAPNIA, Saclay /South Carolina U. /SLAC /Stanford U., Phys. Dept. /SUNY, Albany /Tennessee U. /Texas U. /Texas U., Dallas /Turin U. /INFN, Turin /Trieste U. /INFN, Trieste /Valencia U., IFIC /Victoria U. /Warwick U. /Wisconsin U., Madison

    2008-09-03

    We report an updated amplitude analysis of the charmless hadronic decays of neutral B mesons to K{sup +} {pi}{sup -}{pi}{sup 0}. With a sample of 454 million {Upsilon}(4S) {yields} B{bar B} decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we measure the magnitudes and phases of the intermediate resonant and nonresonant amplitudes for B{sup 0} and B{sup 0} decays and determine the corresponding CP-averaged fit fractions and charge asymmetries.

  5. Projectile Motion with Mathematica.

    ERIC Educational Resources Information Center

    de Alwis, Tilak

    2000-01-01

    Describes how to use the computer algebra system (CAS) Mathematica to analyze projectile motion with and without air resistance. These experiments result in several conjectures leading to theorems. (Contains 17 references.) (Author/ASK)

  6. Projectile Motion Details.

    ERIC Educational Resources Information Center

    Schnick, Jeffrey W.

    1994-01-01

    Presents an exercise that attempts to correct for the common discrepancies between theoretical and experimental predictions concerning projectile motion using a spring-loaded projectile ball launcher. Includes common correction factors for student use. (MVL)

  7. Toying with Motion.

    ERIC Educational Resources Information Center

    Galus, Pamela J.

    2002-01-01

    Presents a variety of activities that support the development of an understanding of Newton's laws of motion. Activities use toy cars, mobile roads, and a seat-of-nails. Includes a scoring rubric. (DDR)

  8. Vision and Motion Pictures.

    ERIC Educational Resources Information Center

    Grambo, Gregory

    1998-01-01

    Presents activities on persistence of vision that involve students in a hands-on approach to the study of early methods of creating motion pictures. Students construct flip books, a Zoetrope, and an early movie machine. (DDR)

  9. Motion Sickness: First Aid

    MedlinePlus

    ... soon as the motion stops. The more you travel, the more easily you'll adjust to being ... at least 30 to 60 minutes before you travel. Expect drowsiness as a side effect. Consider scopolamine ( ...

  10. A Projectile Motion Bullseye.

    ERIC Educational Resources Information Center

    Lamb, William G.

    1985-01-01

    Explains a projectile motion experiment involving a bow and arrow. Procedures to measure "muzzle" velocity, bow elastic potential energy, range, flight time, wind resistance, and masses are considered. (DH)

  11. Motion Alters Color Appearance

    PubMed Central

    Hong, Sang-Wook; Kang, Min-Suk

    2016-01-01

    Chromatic induction compellingly demonstrates that chromatic context as well as spectral lights reflected from an object determines its color appearance. Here, we show that when one colored object moves around an identical stationary object, the perceived saturation of the stationary object decreases dramatically whereas the saturation of the moving object increases. These color appearance shifts in the opposite directions suggest that normalization induced by the object’s motion may mediate the shift in color appearance. We ruled out other plausible alternatives such as local adaptation, attention, and transient neural responses that could explain the color shift without assuming interaction between color and motion processing. These results demonstrate that the motion of an object affects both its own color appearance and the color appearance of a nearby object, suggesting a tight coupling between color and motion processing. PMID:27824098

  12. Explanations of Superluminal Motion

    NASA Astrophysics Data System (ADS)

    Scheuer, P. A. G.

    Recent developments in models of core-jet sources with apparent superluminal motions are reviewed. Emphasis is given to new versions of the so-called "Christmas tree" model and the relativistic beaming model.

  13. Resonance, particle trapping, and Landau damping in finite amplitude obliquely propagating waves

    NASA Technical Reports Server (NTRS)

    Palmadesso, P. J.

    1972-01-01

    The equations of motion for a particle in resonance with a small finite amplitude wave are solved approximately, using secularity free perturbation theory. The wave propagates at an arbitrary angle to a uniform background magnetic field in an infinite collisionless plasma. The wave fields include a longitudinal electrostatic component and elliptically polarized transverse electric and magnetic components. The trajectories of trapped and resonant untrapped particles are described, for each of the possible wave-particle resonances. These trajectories are used to construct an estimate of the nonlinear time dependent Landau damping rate of the wave.

  14. Influence of vibration amplitude on dynamic triggering of slip in sheared granular layers.

    PubMed

    Griffa, M; Ferdowsi, B; Guyer, R A; Daub, E G; Johnson, P A; Marone, C; Carmeliet, J

    2013-01-01

    We perform a systematic statistical investigation of the effect of harmonic boundary vibrations on a sheared granular layer undergoing repetitive, fully dynamic stick-slip motion. The investigation is performed using two-dimensional discrete element method simulations. The main objective consists of improving the understanding of dynamic triggering of slip events in the granular layer. Here we focus on how the vibration amplitude affects the statistical properties of the triggered slip events. The results provide insight into the granular physical controls of dynamic triggering of failure in sheared granular layers.

  15. Meridional Flow Variations in Cycles 23 and 24: Active Latitude Control of Sunspot Cycle Amplitudes

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.; Upton, Lisa

    2013-01-01

    We have measured the meridional motions of magnetic elements observed in the photosphere over sunspot cycles 23 and 24 using magnetograms from SOHO/MDI and SDO/HMI. Our measurements confirm the finding of Komm, Howard, and Harvey (1993) that the poleward meridional flow weakens at cycle maxima. Our high spatial and temporal resolution analyses show that this variation is in the form of a superimposed inflow toward the active latitudes. This inflow is weaker in cycle 24 when compared to the inflow in 23, the stronger cycle. This systematic modulation of the meridional flow can modulate the amplitude of the following sunspot cycle through its influence on the Sun's polar fields.

  16. Determine Optimal Stimulus Amplitude for Using Vestibular Stochastic Stimulation to Improve Balance Function

    NASA Technical Reports Server (NTRS)

    Goel, R.; Kofman, I.; DeDios, Y. E.; Jeevarajan, J.; Stepanyan, V.; Nair, M.; Congdon, S.; Fregia, M.; Cohen, H.; Bloomberg, J.J.; Mulavara, A.P.

    2015-01-01

    Sensorimotor changes such as postural and gait instabilities can affect the functional performance of astronauts when they transition across different gravity environments. We are developing a method, based on stochastic resonance (SR), to enhance information transfer by applying non-zero levels of external noise on the vestibular system (vestibular stochastic resonance, VSR). Our previous work has shown the advantageous effects of VSR in a balance task of standing on an unstable surface [1]. This technique to improve detection of vestibular signals uses a stimulus delivery system that provides imperceptibly low levels of white noise-based binaural bipolar electrical stimulation of the vestibular system. The goal of this project is to determine optimal levels of stimulation for SR applications by using a defined vestibular threshold of motion detection. A series of experiments were carried out to determine a robust paradigm to identify a vestibular threshold that can then be used to recommend optimal stimulation levels for sensorimotor adaptability (SA) training applications customized to each crewmember. The amplitude of stimulation to be used in the VSR application has varied across studies in the literature such as 60% of nociceptive stimulus thresholds [2]. We compared subjects' perceptual threshold with that obtained from two measures of body sway. Each test session was 463s long and consisted of several 15s long sinusoidal stimuli, at different current amplitudes (0-2 mA), interspersed with 20-20.5s periods of no stimulation. Subjects sat on a chair with their eyes closed and had to report their perception of motion through a joystick. A force plate underneath the chair recorded medio-lateral shear forces and roll moments. Comparison of threshold of motion detection obtained from joystick data versus body sway suggests that perceptual thresholds were significantly lower. In the balance task, subjects stood on an unstable surface and had to maintain balance

  17. The use of dual vacuum stabilization device to reduce kidney motion for stereotactic radiotherapy planning.

    PubMed

    Pham, Daniel; Kron, Tomas; Styles, Colin; Whitaker, May; Bressel, Mathias; Foroudi, Farshad; Schneider, Michal; Devereux, Thomas; Dang, Kim; Siva, Shankar

    2015-04-01

    Abdominal stereotactic ablative body radiotherapy is aided by motion management strategies to ensure accurate dose delivery as targets such as the kidney are easily influenced by breathing motion. Commercial devices such as compression plates and dual vacuum technology have been demonstrated to reduce the motion of lung and liver tumors. The aim of this study was to evaluate the effectiveness of a dual vacuum system in reducing kidney motion as well to investigate any relationship between abdominal wall motions with kidney motion. Ten healthy volunteers were set up with and without vacuum compression (Elekta BodyFIX(TM)) to simulate free and dampened breathing. Ultrasound imaging was used to visualize kidney motion at the same time an abdominal surface marker was monitored using infrared imaging (Varian, Real Time Position Management). The resulting kidney and abdominal motion tracks were imported into motion analysis (Physmo(TM)) and custom built software (Matlab) to calculate amplitude of motion independent of shifting baselines. Thirty-four kidney datasets were available for analysis, with six datasets unable to be retrieved. With vacuum compression six out of nine participants showed a mean reduction of kidney motion ranging between 1.6 and 8 mm (p < 0.050). One participant showed an increase in motion of 8.2 mm (p < 0.001) with vacuum compression. Two participants showed no significant change (<1 mm) in kidney motion. No relationship was observed for abdominal wall motion and motion changes in the left kidney (r = 0.345, p = 0.402) or right kidney (r = 0.527, p = 0.145). Vacuum compression reduced kidney motion in the majority of participants; however larger breathing motion can also result from its use. No pattern emerged regarding which patients may benefit from vacuum immobilization as abdominal wall motion was not found to be an adequate surrogate for kidney motion.

  18. A simple model for strong ground motions and response spectra

    USGS Publications Warehouse

    Safak, Erdal; Mueller, Charles; Boatwright, John

    1988-01-01

    A simple model for the description of strong ground motions is introduced. The model shows that response spectra can be estimated by using only four parameters of the ground motion, the RMS acceleration, effective duration and two corner frequencies that characterize the effective frequency band of the motion. The model is windowed band-limited white noise, and is developed by studying the properties of two functions, cumulative squared acceleration in the time domain, and cumulative squared amplitude spectrum in the frequency domain. Applying the methods of random vibration theory, the model leads to a simple analytical expression for the response spectra. The accuracy of the model is checked by using the ground motion recordings from the aftershock sequences of two different earthquakes and simulated accelerograms. The results show that the model gives a satisfactory estimate of the response spectra.

  19. Lorentz-force-induced motion in conductive media.

    PubMed

    Basford, Alexandra T; Basford, Jeffrey R; Kugel, Jennifer; Ehman, Richard L

    2005-06-01

    This project was designed to assess whether MRI imaging could detect Lorentz-force-induced motion in conductive samples. Experiments were performed by applying alternating voltages across 2% agar and 18% bovine gels placed in the field of a 1.5-T MRI scanner. Motion-sensitized time-gated MRI images that were obtained and analyzed with custom-developed software used in previous studies revealed the production of movement in both agar and gel samples. Motion was most pronounced in the plane vertical to the sample and had the greatest amplitude when the current path was perpendicular to the scanner's magnetic field. These findings are compatible with the vector cross product nature of the Lorentz force and suggest that the imaging of Lorentz-force-induced motion in conductive samples is feasible. Whether this approach can be extended to study electrically active tissues such as the peripheral nerves, brain and heart remains to be seen.

  20. Differential cortical processing of local and global motion information in biological motion: an event-related potential study.

    PubMed

    Hirai, Masahiro; Kakigi, Ryusuke

    2008-12-15

    To reveal the neural dynamics underlying biological motion processing, we introduced a novel golf-swing point-light motion (PLM) stimulus with an adaptation paradigm and measured event-related potentials (ERPs). In the adaptation phase, PLM and scrambled PLM (sPLM) stimuli were presented; a static point-lights stimulus was also presented as a control condition. In the subsequent test phase, PLM or sPLM stimuli were presented. We measured ERPs from the onset of the test phase. Two negative components were observed and modulated differently: the amplitude of the N1 component was significantly attenuated by PLM and sPLM adaptation stimuli compared with the static point-light adaptation stimulus, whereas the amplitude of the N2 component in response to the PLM test stimulus was significantly attenuated only by the PLM adaptation stimulus. The amplitude of the N2 component in response to the PLM test stimulus was significantly larger than that in response to the sPLM test stimulus when a sPLM or static adaptation stimulus was used. These findings indicate that the N1 component is sensitive to local motion information while the N2 component is sensitive to the presence of a coherent form conveyed by global motion.