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Sample records for path integrals physically

  1. Path-integral approach to 't Hooft's derivation of quantum physics from classical physics

    SciTech Connect

    Blasone, Massimo; Jizba, Petr; Kleinert, Hagen

    2005-05-15

    We present a path-integral formulation of 't Hooft's derivation of quantum physics from classical physics. The crucial ingredient of this formulation is Gozzi et al.'s supersymmetric path integral of classical mechanics. We quantize explicitly two simple classical systems: the planar mathematical pendulum and the Roessler dynamical system.

  2. The universal path integral

    NASA Astrophysics Data System (ADS)

    Lloyd, Seth; Dreyer, Olaf

    2016-02-01

    Path integrals calculate probabilities by summing over classical configurations of variables such as fields, assigning each configuration a phase equal to the action of that configuration. This paper defines a universal path integral, which sums over all computable structures. This path integral contains as sub-integrals all possible computable path integrals, including those of field theory, the standard model of elementary particles, discrete models of quantum gravity, string theory, etc. The universal path integral possesses a well-defined measure that guarantees its finiteness. The probabilities for events corresponding to sub-integrals can be calculated using the method of decoherent histories. The universal path integral supports a quantum theory of the universe in which the world that we see around us arises out of the interference between all computable structures.

  3. Discrete Coherent State Path Integrals

    NASA Astrophysics Data System (ADS)

    Marchioro, Thomas L., II

    1990-01-01

    The quantum theory provides a fundamental understanding of the physical world; however, as the number of degrees of freedom rises, the information required to specify quantum wavefunctions grows geometrically. Because basis set expansions mirror this geometric growth, a strict practical limit on quantum mechanics as a numerical tool arises, specifically, three degrees of freedom or fewer. Recent progress has been made utilizing Feynman's Path Integral formalism to bypass this geometric growth and instead calculate time -dependent correlation functions directly. The solution of the Schrodinger equation is converted into a large dimensional (formally infinite) integration, which can then be attacked with Monte Carlo techniques. To date, work in this area has concentrated on developing sophisticated mathematical algorithms for evaluating the highly oscillatory integrands occurring in Feynman Path Integrals. In an alternative approach, this work demonstrates two formulations of quantum dynamics for which the number of mathematical operations does not scale geometrically. Both methods utilize the Coherent State basis of quantum mechanics. First, a localized coherent state basis set expansion and an approximate short time propagator are developed. Iterations of the short time propagator lead to the full quantum dynamics if the coherent state basis is sufficiently dense along the classical phase space path of the system. Second, the coherent state path integral is examined in detail. For a common class of Hamiltonians, H = p^2/2 + V( x) the path integral is reformulated from a phase space-like expression into one depending on (q,dot q). It is demonstrated that this new path integral expression contains localized damping terms which can serve as a statistical weight for Monte Carlo evaluation of the integral--a process which scales approximately linearly with the number of degrees of freedom. Corrections to the traditional coherent state path integral, inspired by a

  4. Handbook of Feynman Path Integrals

    NASA Astrophysics Data System (ADS)

    Grosche, Christian, Steiner, Frank

    The Handbook of Feynman Path Integrals appears just fifty years after Richard Feynman published his pioneering paper in 1948 entitled "Space-Time Approach to Non-Relativistic Quantum Mechanics", in which he introduced his new formulation of quantum mechanics in terms of path integrals. The book presents for the first time a comprehensive table of Feynman path integrals together with an extensive list of references; it will serve the reader as a thorough introduction to the theory of path integrals. As a reference book, it is unique in its scope and will be essential for many physicists, chemists and mathematicians working in different areas of research.

  5. Path integral simulations for nanoelectronics

    NASA Astrophysics Data System (ADS)

    Shumway, John

    2007-10-01

    As computer circuits shrink, devices are entering the nanoscale regime and quantum physics is becoming important. The biggest barrier to further decreases in size and increases in clock speed is excessive heat generation. Some physicists are proposing that many-body correlated quantum states of electrons may be exploited to make more energy efficient switches. In our research we are developing new simulation techniques to study highly correlated electron states in realistic device geometries and finite temperatures. The simulations are based on Feynman path integrals, which cast quantum statistical mechanics as a sum over worldlines, a mathematically equivalent alternative Schroedinger's differetial equation. Using Monte Carlo sampling on dozens to hundreds of electrons, we can simulate properties of an interacting electron fluid in a nanowire. Linear response theory relates fluctuations about equilibrium to conductivity. This gives us a new perspective on quantum phenomena, including quantized conductance steps and spin-charge separation.

  6. Scattering theory with path integrals

    SciTech Connect

    Rosenfelder, R.

    2014-03-15

    Starting from well-known expressions for the T-matrix and its derivative in standard nonrelativistic potential scattering, I rederive recent path-integral formulations due to Efimov and Barbashov et al. Some new relations follow immediately.

  7. Fermionic path integrals and local anomalies

    NASA Astrophysics Data System (ADS)

    Roepstorff, G.

    2003-05-01

    No doubt, the subject of path integrals proved to be an immensely fruitful human, i.e. Feynman's idea. No wonder it is more timely than ever. Some even claim that it is the most daring, innovative and revolutionary idea since the days of Heisenberg and Bohr. It is thus likely to generate enthusiasm, if not addiction among physicists who seek simplicity together with perfection. Professor Devreese's long-lasting interest in, if not passion on the subject stems from his firm conviction that, beyond being the tool of choice, path integration provides the key to all quantum phenomena, be it in solid state, atomic, molecular or particle physics as evidenced by the impressive list of publications at the address http://lib.ua.ac.be/AB/a867.html. In this note, I review a pitfall of fermionic path integrals and a way to get around it in situations relevant to the Standard Model of particle physics.

  8. Squeezed states and path integrals

    NASA Technical Reports Server (NTRS)

    Daubechies, Ingrid; Klauder, John R.

    1992-01-01

    The continuous-time regularization scheme for defining phase-space path integrals is briefly reviewed as a method to define a quantization procedure that is completely covariant under all smooth canonical coordinate transformations. As an illustration of this method, a limited set of transformations is discussed that have an image in the set of the usual squeezed states. It is noteworthy that even this limited set of transformations offers new possibilities for stationary phase approximations to quantum mechanical propagators.

  9. Polymer quantum mechanics some examples using path integrals

    SciTech Connect

    Parra, Lorena; Vergara, J. David

    2014-01-14

    In this work we analyze several physical systems in the context of polymer quantum mechanics using path integrals. First we introduce the group averaging method to quantize constrained systems with path integrals and later we use this procedure to compute the effective actions for the polymer non-relativistic particle and the polymer harmonic oscillator. We analyze the measure of the path integral and we describe the semiclassical dynamics of the systems.

  10. Perturbative Methods in Path Integration

    NASA Astrophysics Data System (ADS)

    Johnson-Freyd, Theodore Paul

    This dissertation addresses a number of related questions concerning perturbative "path" integrals. Perturbative methods are one of the few successful ways physicists have worked with (or even defined) these infinite-dimensional integrals, and it is important as mathematicians to check that they are correct. Chapter 0 provides a detailed introduction. We take a classical approach to path integrals in Chapter 1. Following standard arguments, we posit a Feynman-diagrammatic description of the asymptotics of the time-evolution operator for the quantum mechanics of a charged particle moving nonrelativistically through a curved manifold under the influence of an external electromagnetic field. We check that our sum of Feynman diagrams has all desired properties: it is coordinate-independent and well-defined without ultraviolet divergences, it satisfies the correct composition law, and it satisfies Schrodinger's equation thought of as a boundary-value problem in PDE. Path integrals in quantum mechanics and elsewhere in quantum field theory are almost always of the shape ∫ f es for some functions f (the "observable") and s (the "action"). In Chapter 2 we step back to analyze integrals of this type more generally. Integration by parts provides algebraic relations between the values of ∫ (-) es for different inputs, which can be packaged into a Batalin--Vilkovisky-type chain complex. Using some simple homological perturbation theory, we study the version of this complex that arises when f and s are taken to be polynomial functions, and power series are banished. We find that in such cases, the entire scheme-theoretic critical locus (complex points included) of s plays an important role, and that one can uniformly (but noncanonically) integrate out in a purely algebraic way the contributions to the integral from all "higher modes," reducing ∫ f es to an integral over the critical locus. This may help explain the presence of analytic continuation in questions like the

  11. Integrated assignment and path planning

    NASA Astrophysics Data System (ADS)

    Murphey, Robert A.

    2005-11-01

    A surge of interest in unmanned systems has exposed many new and challenging research problems across many fields of engineering and mathematics. These systems have the potential of transforming our society by replacing dangerous and dirty jobs with networks of moving machines. This vision is fundamentally separate from the modern view of robotics in that sophisticated behavior is realizable not by increasing individual vehicle complexity, but instead through collaborative teaming that relies on collective perception, abstraction, decision making, and manipulation. Obvious examples where collective robotics will make an impact include planetary exploration, space structure assembly, remote and undersea mining, hazardous material handling and clean-up, and search and rescue. Nonetheless, the phenomenon driving this technology trend is the increasing reliance of the US military on unmanned vehicles, specifically, aircraft. Only a few years ago, following years of resistance to the use of unmanned systems, the military and civilian leadership in the United States reversed itself and have recently demonstrated surprisingly broad acceptance of increasingly pervasive use of unmanned platforms in defense surveillance, and even attack. However, as rapidly as unmanned systems have gained acceptance, the defense research community has discovered the technical pitfalls that lie ahead, especially for operating collective groups of unmanned platforms. A great deal of talent and energy has been devoted to solving these technical problems, which tend to fall into two categories: resource allocation of vehicles to objectives, and path planning of vehicle trajectories. An extensive amount of research has been conducted in each direction, yet, surprisingly, very little work has considered the integrated problem of assignment and path planning. This dissertation presents a framework for studying integrated assignment and path planning and then moves on to suggest an exact

  12. Two-path plasmonic interferometer with integrated detector

    DOEpatents

    Dyer, Gregory Conrad; Shaner, Eric A.; Aizin, Gregory

    2016-03-29

    An electrically tunable terahertz two-path plasmonic interferometer with an integrated detection element can down convert a terahertz field to a rectified DC signal. The integrated detector utilizes a resonant plasmonic homodyne mixing mechanism that measures the component of the plasma waves in-phase with an excitation field that functions as the local oscillator in the mixer. The plasmonic interferometer comprises two independently tuned electrical paths. The plasmonic interferometer enables a spectrometer-on-a-chip where the tuning of electrical path length plays an analogous role to that of physical path length in macroscopic Fourier transform interferometers.

  13. Selecta from a Life-Long Obsession with Path Integrals

    SciTech Connect

    Klauder, John R.

    2008-06-18

    The definition and interpretation of canonical, phase space path integrals has evolved over many years to achieve a form that now admits a correct and rigorous formulation, which is also covariant under canonical coordinate transformations. Such formulations involve coherent state representations, which, in their modern version, were originally introduced as an alternative tool to construct phase space path integrals. Moreover, coherent state representations lead to physical interpretations that are more natural than those afforded by more traditional representations. Suitable continuous time regularization procedures lead to a covariant phase space path integral formulation that greatly clarifies the vague phrase that canonical quantization requires Cartesian coordinates.

  14. Selecta from a Life-Long Obsession with Path Integrals

    NASA Astrophysics Data System (ADS)

    Klauder, John R.

    2008-06-01

    The definition and interpretation of canonical, phase space path integrals has evolved over many years to achieve a form that now admits a correct and rigorous formulation, which is also covariant under canonical coordinate transformations. Such formulations involve coherent state representations, which, in their modern version, were originally introduced as an alternative tool to construct phase space path integrals. Moreover, coherent state representations lead to physical interpretations that are more natural than those afforded by more traditional representations. Suitable continuous time regularization procedures lead to a covariant phase space path integral formulation that greatly clarifies the vague phrase that canonical quantization requires Cartesian coordinates.

  15. Ant navigation: resetting the path integrator.

    PubMed

    Knaden, Markus; Wehner, Rüdiger

    2006-01-01

    Desert ants use path integration as their predominant system of long-distance navigation, but they also make use of route-defining and nest-defining visual landmarks. Such landmark-gained information might override the information provided by the path integrator, but nevertheless the path integrator keeps running. Here we show that only cues that are associated with the ant being inside the nest are able to reset the path integrator to zero state. Ants were captured at a feeder, i.e. without having run off their home vector, and were forced to enter the nest. On their next outbound run their walking direction differed by 180 degrees from that of ants that had also been captured at the feeder but instead of having been forced to enter the interior of the nest were released at its entrance. Whereas these latter ants still ran off their home vector pointing in the feeder-nest direction (and by this departed from the nest in a direction opposite to the feeder direction) the former ants had reset their home vector to zero state, and had therefore been able to reload their learned feeder vector, and consequently departed from the nest in the feeder direction. Owing to its egocentric nature the path-integrator is error prone. Hence, it is a suitable strategy to reset the path integrator if the ant has appeared at its final goal, the nest. Otherwise during consecutive foraging runs navigational errors would steadily increase.

  16. Local-time representation of path integrals

    NASA Astrophysics Data System (ADS)

    Jizba, Petr; Zatloukal, Václav

    2015-12-01

    We derive a local-time path-integral representation for a generic one-dimensional time-independent system. In particular, we show how to rephrase the matrix elements of the Bloch density matrix as a path integral over x -dependent local-time profiles. The latter quantify the time that the sample paths x (t ) in the Feynman path integral spend in the vicinity of an arbitrary point x . Generalization of the local-time representation that includes arbitrary functionals of the local time is also provided. We argue that the results obtained represent a powerful alternative to the traditional Feynman-Kac formula, particularly in the high- and low-temperature regimes. To illustrate this point, we apply our local-time representation to analyze the asymptotic behavior of the Bloch density matrix at low temperatures. Further salient issues, such as connections with the Sturm-Liouville theory and the Rayleigh-Ritz variational principle, are also discussed.

  17. Local-time representation of path integrals.

    PubMed

    Jizba, Petr; Zatloukal, Václav

    2015-12-01

    We derive a local-time path-integral representation for a generic one-dimensional time-independent system. In particular, we show how to rephrase the matrix elements of the Bloch density matrix as a path integral over x-dependent local-time profiles. The latter quantify the time that the sample paths x(t) in the Feynman path integral spend in the vicinity of an arbitrary point x. Generalization of the local-time representation that includes arbitrary functionals of the local time is also provided. We argue that the results obtained represent a powerful alternative to the traditional Feynman-Kac formula, particularly in the high- and low-temperature regimes. To illustrate this point, we apply our local-time representation to analyze the asymptotic behavior of the Bloch density matrix at low temperatures. Further salient issues, such as connections with the Sturm-Liouville theory and the Rayleigh-Ritz variational principle, are also discussed.

  18. The quantum bouncer by the path integral method

    NASA Astrophysics Data System (ADS)

    Goodings, D. A.; Szeredi, T.

    1991-10-01

    The path integral formulation of quantum mechanics in the semiclassical or WKB approximation provides a physically intuitive way of relating a classical system to its quantum analog. A fruitful way of studying quantum chaos is based upon applying the Gutzwiller periodic orbit sum rule, a result derived by the path integral method in the WKB approximation. This provides some motivation for learning about path integral techniques. In this paper a pedagogical example of the path integral formalism is presented in the hope of conveying the basic physical and mathematical concepts. The ``quantum bouncer'' is studied—the quantum version of a particle moving in one dimension above a perfectly reflecting surface while subject to a constant force directed toward the surface. The classical counterpart of this system is a ball bouncing on a floor in a constant gravitational field, collisions with the floor being assumed to be elastic. Path integration is used to derive the energy eigenvalues and eigenfunctions of the quantum bouncer in the WKB or semiclassical approximation. The results are shown to be the same as those obtained by solving the Schrödinger equation in the same approximation.

  19. Quantum state of wormholes and path integral

    SciTech Connect

    Garay, L.J. )

    1991-08-15

    The quantum state of a wormhole can be represented by a path integral over all asymptotically Euclidean four-geometries and all matter fields which have prescribed values, the arguments of the wave function, on a three-surface {ital S} which divides the spacetime manifold into two disconnected parts. The ground-state wave function is picked out by requiring that there be no matter excitations in the asymptotic region. Once the path integrals over the lapse and shift functions are evaluated, the requirement that the spacetime be asymptotically Euclidean can be accomplished by fixing the asymptotic gravitational momentum in the remaining path integral. It is claimed that no wave function exists which corresponds to asymptotic field configurations such that the effective gravitational constant is negative in the asymptotic region. The wormhole wave functions are worked out in minisuperspace models with massless minimal and conformal scalar fields.

  20. Optical tomography with discretized path integral

    PubMed Central

    Yuan, Bingzhi; Tamaki, Toru; Kushida, Takahiro; Mukaigawa, Yasuhiro; Kubo, Hiroyuki; Raytchev, Bisser; Kaneda, Kazufumi

    2015-01-01

    Abstract. We present a framework for optical tomography based on a path integral. Instead of directly solving the radiative transport equations, which have been widely used in optical tomography, we use a path integral that has been developed for rendering participating media based on the volume rendering equation in computer graphics. For a discretized two-dimensional layered grid, we develop an algorithm to estimate the extinction coefficients of each voxel with an interior point method. Numerical simulation results are shown to demonstrate that the proposed method works well. PMID:26839903

  1. Evolving neural models of path integration.

    PubMed

    Vickerstaff, R J; Di Paolo, E A

    2005-09-01

    We use a genetic algorithm to evolve neural models of path integration, with particular emphasis on reproducing the homing behaviour of Cataglyphis fortis ants. This is done within the context of a complete model system, including an explicit representation of the animal's movements within its environment. We show that it is possible to produce a neural network without imposing a priori any particular system for the internal representation of the animal's home vector. The best evolved network obtained is analysed in detail and is found to resemble the bicomponent model of Mittelstaedt. Because of the presence of leaky integration, the model can reproduce the systematic navigation errors found in desert ants. The model also naturally mimics the searching behaviour that ants perform once they have reached their estimate of the nest location. The results support possible roles for leaky integration and cosine-shaped compass response functions in path integration.

  2. Hidden Topological Angles in Path Integrals

    NASA Astrophysics Data System (ADS)

    Behtash, Alireza; Sulejmanpasic, Tin; Schäfer, Thomas; Ünsal, Mithat

    2015-07-01

    We demonstrate the existence of hidden topological angles (HTAs) in a large class of quantum field theories and quantum mechanical systems. HTAs are distinct from theta parameters in the Lagrangian. They arise as invariant angles associated with saddle points of the complexified path integral and their descent manifolds (Lefschetz thimbles). Physical effects of HTAs become most transparent upon analytic continuation in nf to a noninteger number of flavors, reducing in the integer nf limit to a Z2 valued phase difference between dominant saddles. In N =1 super Yang-Mills theory we demonstrate the microscopic mechanism for the vanishing of the gluon condensate. The same effect leads to an anomalously small condensate in a QCD-like S U (N ) gauge theory with fermions in the two-index representation. The basic phenomenon is that, contrary to folklore, the gluon condensate can receive both positive and negative contributions in a semiclassical expansion. In quantum mechanics, a HTA leads to a difference in semiclassical expansion of integer and half-integer spin particles.

  3. Local-time representation of path integrals.

    PubMed

    Jizba, Petr; Zatloukal, Václav

    2015-12-01

    We derive a local-time path-integral representation for a generic one-dimensional time-independent system. In particular, we show how to rephrase the matrix elements of the Bloch density matrix as a path integral over x-dependent local-time profiles. The latter quantify the time that the sample paths x(t) in the Feynman path integral spend in the vicinity of an arbitrary point x. Generalization of the local-time representation that includes arbitrary functionals of the local time is also provided. We argue that the results obtained represent a powerful alternative to the traditional Feynman-Kac formula, particularly in the high- and low-temperature regimes. To illustrate this point, we apply our local-time representation to analyze the asymptotic behavior of the Bloch density matrix at low temperatures. Further salient issues, such as connections with the Sturm-Liouville theory and the Rayleigh-Ritz variational principle, are also discussed. PMID:26764662

  4. A taxonomy of integral reaction path analysis

    SciTech Connect

    Grcar, Joseph F.; Day, Marcus S.; Bell, John B.

    2004-12-23

    W. C. Gardiner observed that achieving understanding through combustion modeling is limited by the ability to recognize the implications of what has been computed and to draw conclusions about the elementary steps underlying the reaction mechanism. This difficulty can be overcome in part by making better use of reaction path analysis in the context of multidimensional flame simulations. Following a survey of current practice, an integral reaction flux is formulated in terms of conserved scalars that can be calculated in a fully automated way. Conditional analyses are then introduced, and a taxonomy for bidirectional path analysis is explored. Many examples illustrate the resulting path analysis and uncover some new results about nonpremixed methane-air laminar jets.

  5. How to (path-) integrate by differentiating

    NASA Astrophysics Data System (ADS)

    Kempf, Achim; Jackson, David M.; Morales, Alejandro H.

    2015-07-01

    Path integrals are at the heart of quantum field theory. In spite of their covariance and seeming simplicity, they are hard to define and evaluate. In contrast, functional differentiation, as it is used, for example, in variational problems, is relatively straightforward. This has motivated the development of new techniques that allow one to express functional integration in terms of functional differentiation. In fact, the new techniques allow one to express integrals in general through differentiation. These techniques therefore add to the general toolbox for integration and for integral transforms such as the Fourier and Laplace transforms. Here, we review some of these results, we give simpler proofs and we add new results, for example, on expressing the Laplace transform and its inverse in terms of derivatives, results that may be of use in quantum field theory, e.g., in the context of heat traces.

  6. An alternative path integral for quantum gravity

    NASA Astrophysics Data System (ADS)

    Krishnan, Chethan; Kumar, K. V. Pavan; Raju, Avinash

    2016-10-01

    We define a (semi-classical) path integral for gravity with Neumann boundary conditions in D dimensions, and show how to relate this new partition function to the usual picture of Euclidean quantum gravity. We also write down the action in ADM Hamiltonian formulation and use it to reproduce the entropy of black holes and cosmological horizons. A comparison between the (background-subtracted) covariant and Hamiltonian ways of semi-classically evaluating this path integral in flat space reproduces the generalized Smarr formula and the first law. This "Neumann ensemble" perspective on gravitational thermodynamics is parallel to the canonical (Dirichlet) ensemble of Gibbons-Hawking and the microcanonical approach of Brown-York.

  7. Path integral learning of multidimensional movement trajectories

    NASA Astrophysics Data System (ADS)

    André, João; Santos, Cristina; Costa, Lino

    2013-10-01

    This paper explores the use of Path Integral Methods, particularly several variants of the recent Path Integral Policy Improvement (PI2) algorithm in multidimensional movement parametrized policy learning. We rely on Dynamic Movement Primitives (DMPs) to codify discrete and rhythmic trajectories, and apply the PI2-CMA and PIBB methods in the learning of optimal policy parameters, according to different cost functions that inherently encode movement objectives. Additionally we merge both of these variants and propose the PIBB-CMA algorithm, comparing all of them with the vanilla version of PI2. From the obtained results we conclude that PIBB-CMA surpasses all other methods in terms of convergence speed and iterative final cost, which leads to an increased interest in its application to more complex robotic problems.

  8. Fractional Levy motion through path integrals

    SciTech Connect

    Calvo, Ivan; Sanchez, Raul; Carreras, Benjamin A

    2009-01-01

    Fractional Levy motion (fLm) is the natural generalization of fractional Brownian motion in the context of self-similar stochastic processes and stable probability distributions. In this paper we give an explicit derivation of the propagator of fLm by using path integral methods. The propagators of Brownian motion and fractional Brownian motion are recovered as particular cases. The fractional diffusion equation corresponding to fLm is also obtained.

  9. Quantitative Molecular Thermochemistry Based on Path Integrals

    SciTech Connect

    Glaesemann, K R; Fried, L E

    2005-03-14

    The calculation of thermochemical data requires accurate molecular energies and heat capacities. Traditional methods rely upon the standard harmonic normal mode analysis to calculate the vibrational and rotational contributions. We utilize path integral Monte Carlo (PIMC) for going beyond the harmonic analysis, to calculate the vibrational and rotational contributions to ab initio energies. This is an application and extension of a method previously developed in our group.

  10. Path integration: effect of curved path complexity and sensory system on blindfolded walking.

    PubMed

    Koutakis, Panagiotis; Mukherjee, Mukul; Vallabhajosula, Srikant; Blanke, Daniel J; Stergiou, Nicholas

    2013-02-01

    Path integration refers to the ability to integrate continuous information of the direction and distance traveled by the system relative to the origin. Previous studies have investigated path integration through blindfolded walking along simple paths such as straight line and triangles. However, limited knowledge exists regarding the role of path complexity in path integration. Moreover, little is known about how information from different sensory input systems (like vision and proprioception) contributes to accurate path integration. The purpose of the current study was to investigate how sensory information and curved path complexity affect path integration. Forty blindfolded participants had to accurately reproduce a curved path and return to the origin. They were divided into four groups that differed in the curved path, circle (simple) or figure-eight (complex), and received either visual (previously seen) or proprioceptive (previously guided) information about the path before they reproduced it. The dependent variables used were average trajectory error, walking speed, and distance traveled. The results indicated that (a) both groups that walked on a circular path and both groups that received visual information produced greater accuracy in reproducing the path. Moreover, the performance of the group that received proprioceptive information and later walked on a figure-eight path was less accurate than their corresponding circular group. The groups that had the visual information also walked faster compared to the group that had proprioceptive information. Results of the current study highlight the roles of different sensory inputs while performing blindfolded walking for path integration.

  11. Path Integration: Effect of Curved Path Complexity and Sensory System on Blindfolded Walking

    PubMed Central

    Koutakis, Panagiotis; Mukherjee, Mukul; Vallabhajosula, Srikant; Blanke, Daniel J.; Stergiou, Nicholas

    2012-01-01

    Path integration refers to the ability to integrate continuous information of the direction and distance travelled by the system relative to the origin. Previous studies have investigated path integration through blindfolded walking along simple paths such as straight line and triangles. However, limited knowledge exists regarding the role of path complexity in path integration. Moreover, little is known about how information from different sensory input systems (like vision and proprioception) contributes to accurate path integration. The purpose of the current study was to investigate how sensory information and curved path complexity affect path integration. Forty blindfolded participants had to accurately reproduce a curved path and return to the origin. They were divided into four groups that differed in the curved path, circle (simple) or figure-eight (complex), and received either visual (previously seen) or proprioceptive (previously guided) information about the path before they reproduced it. The dependent variables used were average trajectory error, walking speed, and distance travelled. The results indicated that (a) both groups that walked on a circular path and both groups that received visual information produced greater accuracy in reproducing the path. Moreover, the performance of the group that received proprioceptive information and later walked on a figure-eight path was less accurate than their corresponding circular group. The groups that had the visual information also walked faster compared to the group that had proprioceptive information. Results of the current study highlight the roles of different sensory inputs while performing blindfolded walking for path integration. PMID:22840893

  12. Path integration in desert ants, Cataglyphis fortis.

    PubMed

    Müller, M; Wehner, R

    1988-07-01

    Foraging desert ants, Cataglyphis fortis, continually keep track of their own posotions relative to home- i.e., integrate their tortuous outbound routes and return home along straight (inbound) routes. By experimentally manipulating the ants' outbound trajectories we show that the ants solve this path integration problem not by performing a true vector summation (as a human navigator does) but by employing a computationally simple approximation. This approximation is characterized by small, but systematic, navigational errors that helped us elucidate the ant's way of computing its mean home vector.

  13. BOOK REVIEW: Path Integrals in Field Theory: An Introduction

    NASA Astrophysics Data System (ADS)

    Ryder, Lewis

    2004-06-01

    In the 1960s Feynman was known to particle physicists as one of the people who solved the major problems of quantum electrodynamics, his contribution famously introducing what are now called Feynman diagrams. To other physicists he gained a reputation as the author of the Feynman Lectures on Physics; in addition some people were aware of his work on the path integral formulation of quantum theory, and a very few knew about his work on gravitation and Yang--Mills theories, which made use of path integral methods. Forty years later the scene is rather different. Many of the problems of high energy physics are solved; and the standard model incorporates Feynman's path integral method as a way of proving the renormalisability of the gauge (Yang--Mills) theories involved. Gravitation is proving a much harder nut to crack, but here also questions of renormalisability are couched in path-integral language. What is more, theoretical studies of condensed matter physics now also appeal to this technique for quantisation, so the path integral method is becoming part of the standard apparatus of theoretical physics. Chapters on it appear in a number of recent books, and a few books have appeared devoted to this topic alone; the book under review is a very recent one. Path integral techniques have the advantage of enormous conceptual appeal and the great disadvantage of mathematical complexity, this being partly the result of messy integrals but more fundamentally due to the notions of functional differentiation and integration which are involved in the method. All in all this subject is not such an easy ride. Mosel's book, described as an introduction, is aimed at graduate students and research workers in particle physics. It assumes a background knowledge of quantum mechanics, both non-relativistic and relativistic. After three chapters on the path integral formulation of non-relativistic quantum mechanics there are eight chapters on scalar and spinor field theory, followed

  14. Homing by path integration when a locomotion trajectory crosses itself.

    PubMed

    Yamamoto, Naohide; Meléndez, Jayleen A; Menzies, Derek T

    2014-01-01

    Path integration is a process with which navigators derive their current position and orientation by integrating self-motion signals along a locomotion trajectory. It has been suggested that path integration becomes disproportionately erroneous when the trajectory crosses itself. However, there is a possibility that this previous finding was confounded by effects of the length of a traveled path and the amount of turns experienced along the path, two factors that are known to affect path integration performance. The present study was designed to investigate whether the crossover of a locomotion trajectory truly increases errors of path integration. In an experiment, blindfolded human navigators were guided along four paths that varied in their lengths and turns, and attempted to walk directly back to the beginning of the paths. Only one of the four paths contained a crossover. Results showed that errors yielded from the path containing the crossover were not always larger than those observed in other paths, and the errors were attributed solely to the effects of longer path lengths or greater degrees of turns. These results demonstrated that path crossover does not always cause significant disruption in path integration processes. Implications of the present findings for models of path integration are discussed.

  15. Combining path integration and remembered landmarks when navigating without vision.

    PubMed

    Kalia, Amy A; Schrater, Paul R; Legge, Gordon E

    2013-01-01

    This study investigated the interaction between remembered landmark and path integration strategies for estimating current location when walking in an environment without vision. We asked whether observers navigating without vision only rely on path integration information to judge their location, or whether remembered landmarks also influence judgments. Participants estimated their location in a hallway after viewing a target (remembered landmark cue) and then walking blindfolded to the same or a conflicting location (path integration cue). We found that participants averaged remembered landmark and path integration information when they judged that both sources provided congruent information about location, which resulted in more precise estimates compared to estimates made with only path integration. In conclusion, humans integrate remembered landmarks and path integration in a gated fashion, dependent on the congruency of the information. Humans can flexibly combine information about remembered landmarks with path integration cues while navigating without visual information.

  16. Path integral for multi-field inflation

    NASA Astrophysics Data System (ADS)

    Gong, Jinn-Ouk; Seo, Min-Seok; Shiu, Gary

    2016-07-01

    We develop the path integral formalism for studying cosmological perturbations in multi-field inflation, which is particularly well suited to study quantum theories with gauge symmetries such as diffeomorphism invariance. We formulate the gauge fixing conditions based on the Poisson brackets of the constraints, from which we derive two convenient gauges that are appropriate for multi-field inflation. We then adopt the in-in formalism to derive the most general expression for the power spectrum of the curvature perturbation including the corrections from the interactions of the curvature mode with other light degrees of freedom. We also discuss the contributions of the interactions to the bispectrum.

  17. Path integral quantization of generalized quantum electrodynamics

    SciTech Connect

    Bufalo, R.; Pimentel, B. M.; Zambrano, G. E. R.

    2011-02-15

    In this paper, a complete covariant quantization of generalized electrodynamics is shown through the path integral approach. To this goal, we first studied the Hamiltonian structure of the system following Dirac's methodology and, then, we followed the Faddeev-Senjanovic procedure to obtain the transition amplitude. The complete propagators (Schwinger-Dyson-Fradkin equations) of the correct gauge fixation and the generalized Ward-Fradkin-Takahashi identities are also obtained. Afterwards, an explicit calculation of one-loop approximations of all Green's functions and a discussion about the obtained results are presented.

  18. Bosonization in the path integral formulation

    NASA Astrophysics Data System (ADS)

    Fujikawa, Kazuo; Suzuki, Hiroshi

    2015-03-01

    We establish the direct d =2 on-shell bosonization ψL(x+)=ei ξ (x+) and ψR†(x-)=ei ξ (x-) in path integral formulation by deriving the off-shell relations ψL(x )ψR†(x )=exp [i ξ (x )] and ψR(x )ψL†(x )=exp [-i ξ (x )] . Similarly, the on-shell bosonization of the bosonic commuting spinor, ϕL(x+)=i e-i ξ (x+)∂+e-i χ (x+) , ϕR†(x-)=e-i ξ (x-)-i χ (x-) and ϕR(x-)=i ei ξ (x-)∂-e+i χ (x-) , ϕL†(x+)=ei ξ (x+)+i χ (x+) , is established in path integral formulation by deriving the off-shell relations ϕL(x )ϕR†(x )=i e-i ξ (x )∂+e-i χ (x ) and ϕR(x )ϕL†(x )=i ei ξ (x )∂-ei χ (x ) .

  19. Path Integral Monte Carlo Methods for Fermions

    NASA Astrophysics Data System (ADS)

    Ethan, Ethan; Dubois, Jonathan; Ceperley, David

    2014-03-01

    In general, Quantum Monte Carlo methods suffer from a sign problem when simulating fermionic systems. This causes the efficiency of a simulation to decrease exponentially with the number of particles and inverse temperature. To circumvent this issue, a nodal constraint is often implemented, restricting the Monte Carlo procedure from sampling paths that cause the many-body density matrix to change sign. Unfortunately, this high-dimensional nodal surface is not a priori known unless the system is exactly solvable, resulting in uncontrolled errors. We will discuss two possible routes to extend the applicability of finite-temperatue path integral Monte Carlo. First we extend the regime where signful simulations are possible through a novel permutation sampling scheme. Afterwards, we discuss a method to variationally improve the nodal surface by minimizing a free energy during simulation. Applications of these methods will include both free and interacting electron gases, concluding with discussion concerning extension to inhomogeneous systems. Support from DOE DE-FG52-09NA29456, DE-AC52-07NA27344, LLNL LDRD 10- ERD-058, and the Lawrence Scholar program.

  20. Building a cognitive map by assembling multiple path integration systems.

    PubMed

    Wang, Ranxiao Frances

    2016-06-01

    Path integration and cognitive mapping are two of the most important mechanisms for navigation. Path integration is a primitive navigation system which computes a homing vector based on an animal's self-motion estimation, while cognitive map is an advanced spatial representation containing richer spatial information about the environment that is persistent and can be used to guide flexible navigation to multiple locations. Most theories of navigation conceptualize them as two distinctive, independent mechanisms, although the path integration system may provide useful information for the integration of cognitive maps. This paper demonstrates a fundamentally different scenario, where a cognitive map is constructed in three simple steps by assembling multiple path integrators and extending their basic features. The fact that a collection of path integration systems can be turned into a cognitive map suggests the possibility that cognitive maps may have evolved directly from the path integration system.

  1. The path integral picture of quantum systems

    NASA Astrophysics Data System (ADS)

    Ceperley, David

    2011-03-01

    The imaginary time path integral ``formalism'' was introduced in 1953 by Feynman to understand the superfluid transition in liquid helium. The equilibrium properties of quantum many body systems is isomorphic to the classical statistical mechanics of cross-linking polymer-like objects. With the Markov Chain Monte Carlo method, invented by Metropolis et al., also in 1953, a potential way of calculating properties of correlated quantum systems was in place. But calculations for many-body quantum systems did not become routine until computers and algorithms had become sufficiently powerful three decades later. Once such simulations could happen, it was realized that simulations provided a deeper insight into boson superfluids, in particular the relation of bose condensation to the polymer end-to-end distance, and the superfluid density to the polymer ``winding number.'' Some recent developments and applications to supersolids, and helium droplets will be given. Finally, limitations of the methodology e.g. to fermion systems are discussed.

  2. Complexified Path Integrals, Exact Saddles, and Supersymmetry

    NASA Astrophysics Data System (ADS)

    Behtash, Alireza; Dunne, Gerald V.; Schäfer, Thomas; Sulejmanpasic, Tin; Ünsal, Mithat

    2016-01-01

    In the context of two illustrative examples from supersymmetric quantum mechanics we show that the semiclassical analysis of the path integral requires complexification of the configuration space and action, and the inclusion of complex saddle points, even when the parameters in the action are real. We find new exact complex saddles, and show that without their contribution the semiclassical expansion is in conflict with basic properties such as the positive semidefiniteness of the spectrum, as well as constraints of supersymmetry. Generic saddles are not only complex, but also possibly multivalued and even singular. This is in contrast to instanton solutions, which are real, smooth, and single valued. The multivaluedness of the action can be interpreted as a hidden topological angle, quantized in units of π in supersymmetric theories. The general ideas also apply to nonsupersymmetric theories.

  3. Multiloop string vertices from the path integral

    NASA Astrophysics Data System (ADS)

    Bochicchio, M.; Lerda, A.

    1989-02-01

    We derive the multiloop vertices for the bosonic string using path integral methods and establish a precise equivalence between the functional approach to string perturbation theory and the operator formalism on Riemann surfaces recently developed by various authors. One of us (A.L.) would like to thank P. Di Vecchia and S. Sciuto for helpful discussions and INFN, Sezione di Torino, for the kind hospitality extended to him during the completion of this work. The work of M.B. was partially supported by the National Science Foundation under Grant NSF-PHY85-07627. The work of A.L. was partially supported by the US Department of Energy under grant DE-AC02-76ER03069.

  4. Complexified Path Integrals, Exact Saddles, and Supersymmetry.

    PubMed

    Behtash, Alireza; Dunne, Gerald V; Schäfer, Thomas; Sulejmanpasic, Tin; Ünsal, Mithat

    2016-01-01

    In the context of two illustrative examples from supersymmetric quantum mechanics we show that the semiclassical analysis of the path integral requires complexification of the configuration space and action, and the inclusion of complex saddle points, even when the parameters in the action are real. We find new exact complex saddles, and show that without their contribution the semiclassical expansion is in conflict with basic properties such as the positive semidefiniteness of the spectrum, as well as constraints of supersymmetry. Generic saddles are not only complex, but also possibly multivalued and even singular. This is in contrast to instanton solutions, which are real, smooth, and single valued. The multivaluedness of the action can be interpreted as a hidden topological angle, quantized in units of π in supersymmetric theories. The general ideas also apply to nonsupersymmetric theories. PMID:26799010

  5. How do insects use path integration for their navigation?

    PubMed

    Collett, M; Collett, T S

    2000-09-01

    We combine experimental findings on ants and bees, and build on earlier models, to give an account of how these insects navigate using path integration, and how path integration interacts with other modes of navigation. At the core of path integration is an accumulator. This is set to an initial state at the nest and is updated as the insect moves so that it always reports the insect's current position relative to the nest. Navigation that uses path integration requires, in addition, a way of storing states of the accumulator at significant places for subsequent recall as goals, and a means of computing the direction to such goals. We discuss three models of how path integration might be used for this process, which we call vector navigation. Vector navigation is the principal means of navigating over unfamiliar terrain, or when landmarks are unavailable. Under other conditions, insects often navigate by landmarks, and ignore the output of the vector navigation system. Landmark navigation does not interfere with the updating of the accumulator. There is an interesting symmetry in the use of landmarks and path integration. In the short term, vector navigation can be independent of landmarks, and landmark navigation needs no assistance from path integration. In the longer term, visual landmarks help keep path vector navigation calibrated, and the learning of visual landmarks is guided by path integration.

  6. Path-integral simulation of solids.

    PubMed

    Herrero, C P; Ramírez, R

    2014-06-11

    The path-integral formulation of the statistical mechanics of quantum many-body systems is described, with the purpose of introducing practical techniques for the simulation of solids. Monte Carlo and molecular dynamics methods for distinguishable quantum particles are presented, with particular attention to the isothermal-isobaric ensemble. Applications of these computational techniques to different types of solids are reviewed, including noble-gas solids (helium and heavier elements), group-IV materials (diamond and elemental semiconductors), and molecular solids (with emphasis on hydrogen and ice). Structural, vibrational, and thermodynamic properties of these materials are discussed. Applications also include point defects in solids (structure and diffusion), as well as nuclear quantum effects in solid surfaces and adsorbates. Different phenomena are discussed, as solid-to-solid and orientational phase transitions, rates of quantum processes, classical-to-quantum crossover, and various finite-temperature anharmonic effects (thermal expansion, isotopic effects, electron-phonon interactions). Nuclear quantum effects are most remarkable in the presence of light atoms, so that especial emphasis is laid on solids containing hydrogen as a constituent element or as an impurity.

  7. Mining Relational Paths in Integrated Biomedical Data

    PubMed Central

    He, Bing; Tang, Jie; Ding, Ying; Wang, Huijun; Sun, Yuyin; Shin, Jae Hong; Chen, Bin; Moorthy, Ganesh; Qiu, Judy; Desai, Pankaj; Wild, David J.

    2011-01-01

    Much life science and biology research requires an understanding of complex relationships between biological entities (genes, compounds, pathways, diseases, and so on). There is a wealth of data on such relationships in publicly available datasets and publications, but these sources are overlapped and distributed so that finding pertinent relational data is increasingly difficult. Whilst most public datasets have associated tools for searching, there is a lack of searching methods that can cross data sources and that in particular search not only based on the biological entities themselves but also on the relationships between them. In this paper, we demonstrate how graph-theoretic algorithms for mining relational paths can be used together with a previous integrative data resource we developed called Chem2Bio2RDF to extract new biological insights about the relationships between such entities. In particular, we use these methods to investigate the genetic basis of side-effects of thiazolinedione drugs, and in particular make a hypothesis for the recently discovered cardiac side-effects of Rosiglitazone (Avandia) and a prediction for Pioglitazone which is backed up by recent clinical studies. PMID:22162991

  8. Path-integral simulation of solids.

    PubMed

    Herrero, C P; Ramírez, R

    2014-06-11

    The path-integral formulation of the statistical mechanics of quantum many-body systems is described, with the purpose of introducing practical techniques for the simulation of solids. Monte Carlo and molecular dynamics methods for distinguishable quantum particles are presented, with particular attention to the isothermal-isobaric ensemble. Applications of these computational techniques to different types of solids are reviewed, including noble-gas solids (helium and heavier elements), group-IV materials (diamond and elemental semiconductors), and molecular solids (with emphasis on hydrogen and ice). Structural, vibrational, and thermodynamic properties of these materials are discussed. Applications also include point defects in solids (structure and diffusion), as well as nuclear quantum effects in solid surfaces and adsorbates. Different phenomena are discussed, as solid-to-solid and orientational phase transitions, rates of quantum processes, classical-to-quantum crossover, and various finite-temperature anharmonic effects (thermal expansion, isotopic effects, electron-phonon interactions). Nuclear quantum effects are most remarkable in the presence of light atoms, so that especial emphasis is laid on solids containing hydrogen as a constituent element or as an impurity. PMID:24810944

  9. Differential neural network configuration during human path integration.

    PubMed

    Arnold, Aiden E G F; Burles, Ford; Bray, Signe; Levy, Richard M; Iaria, Giuseppe

    2014-01-01

    Path integration is a fundamental skill for navigation in both humans and animals. Despite recent advances in unraveling the neural basis of path integration in animal models, relatively little is known about how path integration operates at a neural level in humans. Previous attempts to characterize the neural mechanisms used by humans to visually path integrate have suggested a central role of the hippocampus in allowing accurate performance, broadly resembling results from animal data. However, in recent years both the central role of the hippocampus and the perspective that animals and humans share similar neural mechanisms for path integration has come into question. The present study uses a data driven analysis to investigate the neural systems engaged during visual path integration in humans, allowing for an unbiased estimate of neural activity across the entire brain. Our results suggest that humans employ common task control, attention and spatial working memory systems across a frontoparietal network during path integration. However, individuals differed in how these systems are configured into functional networks. High performing individuals were found to more broadly express spatial working memory systems in prefrontal cortex, while low performing individuals engaged an allocentric memory system based primarily in the medial occipito-temporal region. These findings suggest that visual path integration in humans over short distances can operate through a spatial working memory system engaging primarily the prefrontal cortex and that the differential configuration of memory systems recruited by task control networks may help explain individual biases in spatial learning strategies.

  10. Differential neural network configuration during human path integration

    PubMed Central

    Arnold, Aiden E. G. F; Burles, Ford; Bray, Signe; Levy, Richard M.; Iaria, Giuseppe

    2014-01-01

    Path integration is a fundamental skill for navigation in both humans and animals. Despite recent advances in unraveling the neural basis of path integration in animal models, relatively little is known about how path integration operates at a neural level in humans. Previous attempts to characterize the neural mechanisms used by humans to visually path integrate have suggested a central role of the hippocampus in allowing accurate performance, broadly resembling results from animal data. However, in recent years both the central role of the hippocampus and the perspective that animals and humans share similar neural mechanisms for path integration has come into question. The present study uses a data driven analysis to investigate the neural systems engaged during visual path integration in humans, allowing for an unbiased estimate of neural activity across the entire brain. Our results suggest that humans employ common task control, attention and spatial working memory systems across a frontoparietal network during path integration. However, individuals differed in how these systems are configured into functional networks. High performing individuals were found to more broadly express spatial working memory systems in prefrontal cortex, while low performing individuals engaged an allocentric memory system based primarily in the medial occipito-temporal region. These findings suggest that visual path integration in humans over short distances can operate through a spatial working memory system engaging primarily the prefrontal cortex and that the differential configuration of memory systems recruited by task control networks may help explain individual biases in spatial learning strategies. PMID:24808849

  11. Yang-Mills theory and fermionic path integrals

    NASA Astrophysics Data System (ADS)

    Fujikawa, Kazuo

    2016-01-01

    The Yang-Mills gauge field theory, which was proposed 60 years ago, is extremely successful in describing the basic interactions of fundamental particles. The Yang-Mills theory in the course of its developments also stimulated many important field theoretical machinery. In this brief review I discuss the path integral techniques, in particular, the fermionic path integrals which were developed together with the successful applications of quantized Yang-Mills field theory. I start with the Faddeev-Popov path integral formula with emphasis on the treatment of fermionic ghosts as an application of Grassmann numbers. I then discuss the ordinary fermionic path integrals and the general treatment of quantum anomalies. The contents of this review are mostly pedagogical except for a recent analysis of path integral bosonization.

  12. Yang-Mills Theory and Fermionic Path Integrals

    NASA Astrophysics Data System (ADS)

    Fujikawa, Kazuo

    The Yang-Mills gauge field theory, which was proposed 60 years ago, is extremely successful in describing the basic interactions of fundamental particles. The Yang-Mills theory in the course of its developments also stimulated many important field theoretical machinery. In my talk I discuss the path integral techniques, in particular, the fermionic path integrals which were developed together with the successful applications of quantized Yang-Mills field theory. I start with the Faddeev-Popov path integral formula with emphasis on the treatment of fermionic ghosts as an application of Grassmann numbers. I then discuss the ordinary fermionic path integrals and the general treatment of quantum anomalies. The contents of this talk are mostly pedagogical except for a recent analysis of path integral bosonization.

  13. Universal conditions for exact path integration in neural systems.

    PubMed

    Issa, John B; Zhang, Kechen

    2012-04-24

    Animals are capable of navigation even in the absence of prominent landmark cues. This behavioral demonstration of path integration is supported by the discovery of place cells and other neurons that show path-invariant response properties even in the dark. That is, under suitable conditions, the activity of these neurons depends primarily on the spatial location of the animal regardless of which trajectory it followed to reach that position. Although many models of path integration have been proposed, no known single theoretical framework can formally accommodate their diverse computational mechanisms. Here we derive a set of necessary and sufficient conditions for a general class of systems that performs exact path integration. These conditions include multiplicative modulation by velocity inputs and a path-invariance condition that limits the structure of connections in the underlying neural network. In particular, for a linear system to satisfy the path-invariance condition, the effective synaptic weight matrices under different velocities must commute. Our theory subsumes several existing exact path integration models as special cases. We use entorhinal grid cells as an example to demonstrate that our framework can provide useful guidance for finding unexpected solutions to the path integration problem. This framework may help constrain future experimental and modeling studies pertaining to a broad class of neural integration systems.

  14. Integrating Physically Disabled Students into Physical Education.

    ERIC Educational Resources Information Center

    Cooney, D.; And Others

    The manual provides guidelines and suggestions for integrating physically disabled students into physical education classes. An introductory section reviews the process of and rationale for integration. A section on students with special needs emphasizes that although physically disabled students may differ in some ways, they have the same needs…

  15. A note on the path integral representation for Majorana fermions

    NASA Astrophysics Data System (ADS)

    Greco, Andrés

    2016-04-01

    Majorana fermions are currently of huge interest in the context of nanoscience and condensed matter physics. Different to usual fermions, Majorana fermions have the property that the particle is its own anti-particle thus, they must be described by real fields. Mathematically, this property makes nontrivial the quantization of the problem due, for instance, to the absence of a Wick-like theorem. In view of the present interest on the subject, it is important to develop different theoretical approaches in order to study problems where Majorana fermions are involved. In this note we show that Majorana fermions can be studied in the context of field theories for constrained systems. Using the Faddeev-Jackiw formalism for quantum field theories with constraints, we derived the path integral representation for Majorana fermions. In order to show the validity of the path integral we apply it to an exactly solvable problem. This application also shows that it is rather simple to perform systematic calculations on the basis of the present framework.

  16. Integrative Physical Oncology

    PubMed Central

    Hatzikirou, Haralampos; Chauviere, Arnaud; Bauer, Amy L.; Leier, André; Lewis, Michael T.; Macklin, Paul; Marquez-Lago, Tatiana T.; Bearer, Elaine L.; Cristini, Vittorio

    2013-01-01

    Cancer is arguably the ultimate complex biological system. Solid tumors are micro-structured soft matter that evolves as a consequence of spatio-temporal events at the intracellular (e.g., signaling pathways, macromolecular trafficking), intercellular (e.g., cell-cell adhesion/communication), and tissue (e.g., cell-extracellular matrix interactions, mechanical forces) scales. To gain insight, tumor and developmental biologists have gathered a wealth of molecular, cellular and genetic data, including immunohistochemical measurements of cell type-specific division and death rates, lineage tracing, and gain-of-function/loss-of-function mutational analyses. These data are empirically extrapolated to a diagnosis/prognosis of tissue-scale behavior, e.g., for clinical decision. Integrative Physical Oncology (IPO) is the science that develops physically consistent mathematical approaches to address the significant challenge of bridging the nano (nm)-micro (μm) to macro (mm, cm) scales with respect to tumor development and progression. In the current literature, such approaches are referred to as multiscale modeling. In the present review, we attempt to assess recent modeling approaches on each separate scale and critically evaluate the current “hybrid-multiscale” models used to investigate tumor growth in the context of brain and breast cancers. Finally, we provide our perspective on the further development and the impact of Integrative Physical Oncology. PMID:21853537

  17. The path integral formulation of climate dynamics.

    PubMed

    Navarra, Antonio; Tribbia, Joe; Conti, Giovanni

    2013-01-01

    The chaotic nature of the atmospheric dynamics has stimulated the applications of methods and ideas derived from statistical dynamics. For instance, ensemble systems are used to make weather predictions recently extensive, which are designed to sample the phase space around the initial condition. Such an approach has been shown to improve substantially the usefulness of the forecasts since it allows forecasters to issue probabilistic forecasts. These works have modified the dominant paradigm of the interpretation of the evolution of atmospheric flows (and oceanic motions to some extent) attributing more importance to the probability distribution of the variables of interest rather than to a single representation. The ensemble experiments can be considered as crude attempts to estimate the evolution of the probability distribution of the climate variables, which turn out to be the only physical quantity relevant to practice. However, little work has been done on a direct modeling of the probability evolution itself. In this paper it is shown that it is possible to write the evolution of the probability distribution as a functional integral of the same kind introduced by Feynman in quantum mechanics, using some of the methods and results developed in statistical physics. The approach allows obtaining a formal solution to the Fokker-Planck equation corresponding to the Langevin-like equation of motion with noise. The method is very general and provides a framework generalizable to red noise, as well as to delaying differential equations, and even field equations, i.e., partial differential equations with noise, for example, general circulation models with noise. These concepts will be applied to an example taken from a simple ENSO model.

  18. The path integral formulation of climate dynamics.

    PubMed

    Navarra, Antonio; Tribbia, Joe; Conti, Giovanni

    2013-01-01

    The chaotic nature of the atmospheric dynamics has stimulated the applications of methods and ideas derived from statistical dynamics. For instance, ensemble systems are used to make weather predictions recently extensive, which are designed to sample the phase space around the initial condition. Such an approach has been shown to improve substantially the usefulness of the forecasts since it allows forecasters to issue probabilistic forecasts. These works have modified the dominant paradigm of the interpretation of the evolution of atmospheric flows (and oceanic motions to some extent) attributing more importance to the probability distribution of the variables of interest rather than to a single representation. The ensemble experiments can be considered as crude attempts to estimate the evolution of the probability distribution of the climate variables, which turn out to be the only physical quantity relevant to practice. However, little work has been done on a direct modeling of the probability evolution itself. In this paper it is shown that it is possible to write the evolution of the probability distribution as a functional integral of the same kind introduced by Feynman in quantum mechanics, using some of the methods and results developed in statistical physics. The approach allows obtaining a formal solution to the Fokker-Planck equation corresponding to the Langevin-like equation of motion with noise. The method is very general and provides a framework generalizable to red noise, as well as to delaying differential equations, and even field equations, i.e., partial differential equations with noise, for example, general circulation models with noise. These concepts will be applied to an example taken from a simple ENSO model. PMID:23840577

  19. Feynman path integrals for the inverse quartic oscillator

    SciTech Connect

    Mazzucchi, S.

    2008-09-15

    The Feynman path integral representation for the weak solution of the Schroedinger equation with an inverse quartic oscillator potential is given in terms of a well defined infinite dimensional oscillatory integral. An analytically continued Wiener integral representation for the solution is provided and an explicit description of the quantum dynamics associated with a nonessentially self-adjoint Hamiltonian is given.

  20. Path integral for (2+1)-dimensional Shape Dynamics

    NASA Astrophysics Data System (ADS)

    González, A.; Ocampo, H.

    2015-03-01

    We studied the path integral quantization for the Shape Dynamics formulation of General Relativity in the 2+1 torus universe. We show that the Shape Dynamics path integral on the reduced phase space is equivalent with the previous results obtained for the ADM 2+1 gravity and we found that the Shape Dynamics Hamiltonian allows us to establish a straightforward relation between reduced systems in the (τ, V)-form and the τ-form through the York time gauge fixing.

  1. Sensory feedback in a bump attractor model of path integration.

    PubMed

    Poll, Daniel B; Nguyen, Khanh; Kilpatrick, Zachary P

    2016-04-01

    Mammalian spatial navigation systems utilize several different sensory information channels. This information is converted into a neural code that represents the animal's current position in space by engaging place cell, grid cell, and head direction cell networks. In particular, sensory landmark (allothetic) cues can be utilized in concert with an animal's knowledge of its own velocity (idiothetic) cues to generate a more accurate representation of position than path integration provides on its own (Battaglia et al. The Journal of Neuroscience 24(19):4541-4550 (2004)). We develop a computational model that merges path integration with feedback from external sensory cues that provide a reliable representation of spatial position along an annular track. Starting with a continuous bump attractor model, we explore the impact of synaptic spatial asymmetry and heterogeneity, which disrupt the position code of the path integration process. We use asymptotic analysis to reduce the bump attractor model to a single scalar equation whose potential represents the impact of asymmetry and heterogeneity. Such imperfections cause errors to build up when the network performs path integration, but these errors can be corrected by an external control signal representing the effects of sensory cues. We demonstrate that there is an optimal strength and decay rate of the control signal when cues appear either periodically or randomly. A similar analysis is performed when errors in path integration arise from dynamic noise fluctuations. Again, there is an optimal strength and decay of discrete control that minimizes the path integration error.

  2. Egocentric path integration models and their application to desert arthropods.

    PubMed

    Merkle, Tobias; Rost, Martin; Alt, Wolfgang

    2006-06-01

    Path integration enables desert arthropods to find back to their nest on the shortest track from any position. To perform path integration successfully, speeds and turning angles along the preceding outbound path have to be measured continuously and combined to determine an internal global vector leading back home at any time. A number of experiments have given an idea how arthropods might use allothetic or idiothetic signals to perceive their orientation and moving speed. We systematically review the four possible model descriptions of mathematically precise path integration, whereby we favour and elaborate the hitherto not used variant of egocentric cartesian coordinates. Its simple and intuitive structure is demonstrated in comparison to the other models. Measuring two speeds, the forward moving speed and the angular turning rate, and implementing them into a linear system of differential equations provides the necessary information during outbound route, reorientation process and return path. In addition, we propose several possible types of systematic errors that can cause deviations from the correct homeward course. Deviations have been observed for several species of desert arthropods in different experiments, but their origin is still under debate. Using our egocentric path integration model we propose simple error indices depending on path geometry that will allow future experiments to rule out or corroborate certain error types.

  3. Improving the convergence of closed and open path integral molecular dynamics via higher order Trotter factorization schemes

    NASA Astrophysics Data System (ADS)

    Pérez, Alejandro; Tuckerman, Mark E.

    2011-08-01

    Higher order factorization schemes are developed for path integral molecular dynamics in order to improve the convergence of estimators for physical observables as a function of the Trotter number. The methods are based on the Takahashi-Imada and Susuki decompositions of the Boltzmann operator. The methods introduced improve the averages of the estimators by using the classical forces needed to carry out the dynamics to construct a posteriori weighting factors for standard path integral molecular dynamics. The new approaches are straightforward to implement in existing path integral codes and carry no significant overhead. The Suzuki higher order factorization was also used to improve the end-to-end distance estimator in open path integral molecular dynamics. The new schemes are tested in various model systems, including an ab initio path integral molecular dynamics calculation on the hydrogen molecule and a quantum water model. The proposed algorithms have potential utility for reducing the cost of path integral molecular dynamics calculations of bulk systems.

  4. The perturbative approach to path integrals: A succinct mathematical treatment

    NASA Astrophysics Data System (ADS)

    Nguyen, Timothy

    2016-09-01

    We study finite-dimensional integrals in a way that elucidates the mathematical meaning behind the formal manipulations of path integrals occurring in quantum field theory. This involves a proper understanding of how Wick's theorem allows one to evaluate integrals perturbatively, i.e., as a series expansion in a formal parameter irrespective of convergence properties. We establish invariance properties of such a Wick expansion under coordinate changes and the action of a Lie group of symmetries, and we use this to study essential features of path integral manipulations, including coordinate changes, Ward identities, Schwinger-Dyson equations, Faddeev-Popov gauge-fixing, and eliminating fields by their equation of motion. We also discuss the asymptotic nature of the Wick expansion and the implications this has for defining path integrals perturbatively and nonperturbatively.

  5. Medial Temporal Lobe Roles in Human Path Integration

    PubMed Central

    Yamamoto, Naohide; Philbeck, John W.; Woods, Adam J.; Gajewski, Daniel A.; Arthur, Joeanna C.; Potolicchio, Samuel J.; Levy, Lucien; Caputy, Anthony J.

    2014-01-01

    Path integration is a process in which observers derive their location by integrating self-motion signals along their locomotion trajectory. Although the medial temporal lobe (MTL) is thought to take part in path integration, the scope of its role for path integration remains unclear. To address this issue, we administered a variety of tasks involving path integration and other related processes to a group of neurosurgical patients whose MTL was unilaterally resected as therapy for epilepsy. These patients were unimpaired relative to neurologically intact controls in many tasks that required integration of various kinds of sensory self-motion information. However, the same patients (especially those who had lesions in the right hemisphere) walked farther than the controls when attempting to walk without vision to a previewed target. Importantly, this task was unique in our test battery in that it allowed participants to form a mental representation of the target location and anticipate their upcoming walking trajectory before they began moving. Thus, these results put forth a new idea that the role of MTL structures for human path integration may stem from their participation in predicting the consequences of one's locomotor actions. The strengths of this new theoretical viewpoint are discussed. PMID:24802000

  6. Quantum Calisthenics: Gaussians, The Path Integral and Guided Numerical Approximations

    SciTech Connect

    Weinstein, Marvin; /SLAC

    2009-02-12

    It is apparent to anyone who thinks about it that, to a large degree, the basic concepts of Newtonian physics are quite intuitive, but quantum mechanics is not. My purpose in this talk is to introduce you to a new, much more intuitive way to understand how quantum mechanics works. I begin with an incredibly easy way to derive the time evolution of a Gaussian wave-packet for the case free and harmonic motion without any need to know the eigenstates of the Hamiltonian. This discussion is completely analytic and I will later use it to relate the solution for the behavior of the Gaussian packet to the Feynman path-integral and stationary phase approximation. It will be clear that using the information about the evolution of the Gaussian in this way goes far beyond what the stationary phase approximation tells us. Next, I introduce the concept of the bucket brigade approach to dealing with problems that cannot be handled totally analytically. This approach combines the intuition obtained in the initial discussion, as well as the intuition obtained from the path-integral, with simple numerical tools. My goal is to show that, for any specific process, there is a simple Hilbert space interpretation of the stationary phase approximation. I will then argue that, from the point of view of numerical approximations, the trajectory obtained from my generalization of the stationary phase approximation specifies that subspace of the full Hilbert space that is needed to compute the time evolution of the particular state under the full Hamiltonian. The prescription I will give is totally non-perturbative and we will see, by the grace of Maple animations computed for the case of the anharmonic oscillator Hamiltonian, that this approach allows surprisingly accurate computations to be performed with very little work. I think of this approach to the path-integral as defining what I call a guided numerical approximation scheme. After the discussion of the anharmonic oscillator I will

  7. Low level constraints on dynamic contour path integration.

    PubMed

    Hall, Sophie; Bourke, Patrick; Guo, Kun

    2014-01-01

    Contour integration is a fundamental visual process. The constraints on integrating discrete contour elements and the associated neural mechanisms have typically been investigated using static contour paths. However, in our dynamic natural environment objects and scenes vary over space and time. With the aim of investigating the parameters affecting spatiotemporal contour path integration, we measured human contrast detection performance of a briefly presented foveal target embedded in dynamic collinear stimulus sequences (comprising five short 'predictor' bars appearing consecutively towards the fovea, followed by the 'target' bar) in four experiments. The data showed that participants' target detection performance was relatively unchanged when individual contour elements were separated by up to 2° spatial gap or 200 ms temporal gap. Randomising the luminance contrast or colour of the predictors, on the other hand, had similar detrimental effect on grouping dynamic contour path and subsequent target detection performance. Randomising the orientation of the predictors reduced target detection performance greater than introducing misalignment relative to the contour path. The results suggest that the visual system integrates dynamic path elements to bias target detection even when the continuity of path is disrupted in terms of spatial (2°), temporal (200 ms), colour (over 10 colours) and luminance (-25% to 25%) information. We discuss how the findings can be largely reconciled within the functioning of V1 horizontal connections.

  8. Canonical formulation and path integral for local vacuum energy sequestering

    NASA Astrophysics Data System (ADS)

    Bufalo, R.; KlusoÅ, J.; Oksanen, M.

    2016-08-01

    We establish the Hamiltonian analysis and the canonical path integral for a local formulation of vacuum energy sequestering. In particular, by considering the state of the Universe as a superposition of vacuum states corresponding to different values of the cosmological and gravitational constants, the path integral is extended to include integrations over the cosmological and gravitational constants. The result is an extension of the Ng-van Dam form of the path integral of unimodular gravity. It is argued to imply a relation between the fraction of the most likely values of the gravitational and cosmological constants and the average values of the energy density and pressure of matter over spacetime. Finally, we construct and analyze a Becchi-Rouet-Stora-Tyutin-exact formulation of the theory, which can be considered as a topological field theory.

  9. A whole-path importance-sampling scheme for Feynman path integral calculations of absolute partition functions and free energies.

    PubMed

    Mielke, Steven L; Truhlar, Donald G

    2016-01-21

    Using Feynman path integrals, a molecular partition function can be written as a double integral with the inner integral involving all closed paths centered at a given molecular configuration, and the outer integral involving all possible molecular configurations. In previous work employing Monte Carlo methods to evaluate such partition functions, we presented schemes for importance sampling and stratification in the molecular configurations that constitute the path centroids, but we relied on free-particle paths for sampling the path integrals. At low temperatures, the path sampling is expensive because the paths can travel far from the centroid configuration. We now present a scheme for importance sampling of whole Feynman paths based on harmonic information from an instantaneous normal mode calculation at the centroid configuration, which we refer to as harmonically guided whole-path importance sampling (WPIS). We obtain paths conforming to our chosen importance function by rejection sampling from a distribution of free-particle paths. Sample calculations on CH4 demonstrate that at a temperature of 200 K, about 99.9% of the free-particle paths can be rejected without integration, and at 300 K, about 98% can be rejected. We also show that it is typically possible to reduce the overhead associated with the WPIS scheme by sampling the paths using a significantly lower-order path discretization than that which is needed to converge the partition function.

  10. A whole-path importance-sampling scheme for Feynman path integral calculations of absolute partition functions and free energies.

    PubMed

    Mielke, Steven L; Truhlar, Donald G

    2016-01-21

    Using Feynman path integrals, a molecular partition function can be written as a double integral with the inner integral involving all closed paths centered at a given molecular configuration, and the outer integral involving all possible molecular configurations. In previous work employing Monte Carlo methods to evaluate such partition functions, we presented schemes for importance sampling and stratification in the molecular configurations that constitute the path centroids, but we relied on free-particle paths for sampling the path integrals. At low temperatures, the path sampling is expensive because the paths can travel far from the centroid configuration. We now present a scheme for importance sampling of whole Feynman paths based on harmonic information from an instantaneous normal mode calculation at the centroid configuration, which we refer to as harmonically guided whole-path importance sampling (WPIS). We obtain paths conforming to our chosen importance function by rejection sampling from a distribution of free-particle paths. Sample calculations on CH4 demonstrate that at a temperature of 200 K, about 99.9% of the free-particle paths can be rejected without integration, and at 300 K, about 98% can be rejected. We also show that it is typically possible to reduce the overhead associated with the WPIS scheme by sampling the paths using a significantly lower-order path discretization than that which is needed to converge the partition function. PMID:26801023

  11. Integrating Physical Education, Math, and Physics

    ERIC Educational Resources Information Center

    Hatch, Greg M.; Smith, Darla R.

    2004-01-01

    The primary goal of education is to help students gain the knowledge and skills necessary to solve the problems that occur in real-life situations. One of the most touted methods for achieving this goal is through curriculum integration. Physical education students can benefit from an integrated curriculum. NASPE's (National Association tar Sport…

  12. Path integral hybrid Monte Carlo algorithm for correlated Bose fluids.

    PubMed

    Miura, Shinichi; Tanaka, Junji

    2004-02-01

    Path integral hybrid Monte Carlo (PIHMC) algorithm for strongly correlated Bose fluids has been developed. This is an extended version of our previous method [S. Miura and S. Okazaki, Chem. Phys. Lett. 308, 115 (1999)] applied to a model system consisting of noninteracting bosons. Our PIHMC method for the correlated Bose fluids is constituted of two trial moves to sample path-variables describing system coordinates along imaginary time and a permutation of particle labels giving a boundary condition with respect to imaginary time. The path-variables for a given permutation are generated by a hybrid Monte Carlo method based on path integral molecular dynamics techniques. Equations of motion for the path-variables are formulated on the basis of a collective coordinate representation of the path, staging variables, to enhance the sampling efficiency. The permutation sampling to satisfy Bose-Einstein statistics is performed using the multilevel Metropolis method developed by Ceperley and Pollock [Phys. Rev. Lett. 56, 351 (1986)]. Our PIHMC method has successfully been applied to liquid helium-4 at a state point where the system is in a superfluid phase. Parameters determining the sampling efficiency are optimized in such a way that correlation among successive PIHMC steps is minimized. PMID:15268354

  13. hiPathDB: a human-integrated pathway database with facile visualization

    PubMed Central

    Yu, Namhee; Seo, Jihae; Rho, Kyoohyoung; Jang, Yeongjun; Park, Jinah; Kim, Wan Kyu; Lee, Sanghyuk

    2012-01-01

    One of the biggest challenges in the study of biological regulatory networks is the systematic organization and integration of complex interactions taking place within various biological pathways. Currently, the information of the biological pathways is dispersed in multiple databases in various formats. hiPathDB is an integrated pathway database that combines the curated human pathway data of NCI-Nature PID, Reactome, BioCarta and KEGG. In total, it includes 1661 pathways consisting of 8976 distinct physical entities. hiPathDB provides two different types of integration. The pathway-level integration, conceptually a simple collection of individual pathways, was achieved by devising an elaborate model that takes distinct features of four databases into account and subsequently reformatting all pathways in accordance with our model. The entity-level integration creates a single unified pathway that encompasses all pathways by merging common components. Even though the detailed molecular-level information such as complex formation or post-translational modifications tends to be lost, such integration makes it possible to investigate signaling network over the entire pathways and allows identification of pathway cross-talks. Another strong merit of hiPathDB is the built-in pathway visualization module that supports explorative studies of complex networks in an interactive fashion. The layout algorithm is optimized for virtually automatic visualization of the pathways. hiPathDB is available at http://hiPathDB.kobic.re.kr. PMID:22123737

  14. Linear Path Integration Deficits in Patients with Abnormal Vestibular Afference

    PubMed Central

    Arthur, Joeanna C.; Kortte, Kathleen B.; Shelhamer, Mark; Schubert, Michael C.

    2014-01-01

    Effective navigation requires the ability to keep track of one’s location and maintain orientation during linear and angular displacements. Path integration is the process of updating the representation of body position by integrating internally-generated self-motion signals over time (e.g., walking in the dark). One major source of input to path integration is vestibular afference. We tested patients with reduced vestibular function (unilateral vestibular hypofunction, UVH), patients with aberrant vestibular function (benign paroxysmal positional vertigo, BPPV), and healthy participants (controls) on two linear path integration tasks: experimenter-guided walking and target-directed walking. The experimenter-guided walking task revealed a systematic underestimation of self-motion signals in UVH patients compared to the other groups. However, we did not find any difference in the distance walked between the UVH group and the control group for the target-directed walking task. Results from neuropsychological testing and clinical balance measures suggest that the errors in experimenter-guided walking were not attributable to cognitive and/or balance impairments. We conclude that impairment in linear path integration in UVH patients stem from deficits in self-motion perception. Importantly, our results also suggest that patients with a UVH deficit do not lose their ability to walk accurately without vision to a memorized target location. PMID:22726251

  15. Path Integral Understanding in the Context of the Electromagnetic Theory

    NASA Astrophysics Data System (ADS)

    Gonzalez, Maria D.

    2006-12-01

    Introductory electromagnetic courses at the University of Juarez are in general identified by the use of a traditional instruction. The path integral is a fundamental mathematical knowledge to understand the properties of conservative fields such that the electric field. Many students in these courses do not develop the necessary scientific skills and mathematical formalism to understand the fact that the potential difference does not depend on the path followed from one point to another one inside an electric field. It is fundamental to probe the student understanding difficulties to apply the concept of path integral in an electromagnetic context. The use of the software CABRI could become an important didactic choice during the development of the potential difference concept. It was necessary the recollection of data related to the student procedural difficulties in the use of the designed CABRI activities. Sponsor: member Sergio Flores

  16. Piloting and Path Integration within and across Boundaries

    ERIC Educational Resources Information Center

    Mou, Weimin; Wang, Lin

    2015-01-01

    Three experiments investigated whether navigation is less efficient across boundaries than within boundaries. In an immersive virtual environment, participants learned objects' locations in a large room or a small room. Participants then pointed to the objects' original locations after physically walking a circuitous path without vision.…

  17. Path Integral for Dirac oscillator with generalized uncertainty principle

    SciTech Connect

    Benzair, H.; Boudjedaa, T.; Merad, M.

    2012-12-15

    The propagator for Dirac oscillator in (1+1) dimension, with deformed commutation relation of the Heisenberg principle, is calculated using path integral in quadri-momentum representation. As the mass is related to momentum, we then adapt the space-time transformation method to evaluate quantum corrections and this latter is dependent from the point discretization interval.

  18. Quantum tunneling splittings from path-integral molecular dynamics

    NASA Astrophysics Data System (ADS)

    Mátyus, Edit; Wales, David J.; Althorpe, Stuart C.

    2016-03-01

    We illustrate how path-integral molecular dynamics can be used to calculate ground-state tunnelling splittings in molecules or clusters. The method obtains the splittings from ratios of density matrix elements between the degenerate wells connected by the tunnelling. We propose a simple thermodynamic integration scheme for evaluating these elements. Numerical tests on fully dimensional malonaldehyde yield tunnelling splittings in good overall agreement with the results of diffusion Monte Carlo calculations.

  19. Computational Physics as a Path for Physics Education

    NASA Astrophysics Data System (ADS)

    Landau, Rubin H.

    2008-04-01

    Evidence and arguments will be presented that modifications in the undergraduate physics curriculum are necessary to maintain the long-term relevance of physics. Suggested will a balance of analytic, experimental, computational, and communication skills, that in many cases will require an increased inclusion of computation and its associated skill set into the undergraduate physics curriculum. The general arguments will be followed by a detailed enumeration of suggested subjects and student learning outcomes, many of which have already been adopted or advocated by the computational science community, and which permit high performance computing and communication. Several alternative models for how these computational topics can be incorporated into the undergraduate curriculum will be discussed. This includes enhanced topics in the standard existing courses, as well as stand-alone courses. Applications and demonstrations will be presented throughout the talk, as well as prototype video-based materials and electronic books.

  20. Theory of extreme correlations using canonical Fermions and path integrals

    SciTech Connect

    Shastry, B. Sriram

    2014-04-15

    The  t–J  model is studied using a novel and rigorous mapping of the Gutzwiller projected electrons, in terms of canonical electrons. The mapping has considerable similarity to the Dyson–Maleev transformation relating spin operators to canonical Bosons. This representation gives rise to a non Hermitian quantum theory, characterized by minimal redundancies. A path integral representation of the canonical theory is given. Using it, the salient results of the extremely correlated Fermi liquid (ECFL) theory, including the previously found Schwinger equations of motion, are easily rederived. Further, a transparent physical interpretation of the previously introduced auxiliary Greens function and the ‘caparison factor’, is obtained. The low energy electron spectral function in this theory, with a strong intrinsic asymmetry, is summarized in terms of a few expansion coefficients. These include an important emergent energy scale Δ{sub 0} that shrinks to zero on approaching the insulating state, thereby making it difficult to access the underlying very low energy Fermi liquid behavior. The scaled low frequency ECFL spectral function, related simply to the Fano line shape, has a peculiar energy dependence unlike that of a Lorentzian. The resulting energy dispersion obtained by maximization is a hybrid of a massive and a massless Dirac spectrum E{sub Q}{sup ∗}∼γQ−√(Γ{sub 0}{sup 2}+Q{sup 2}), where the vanishing of Q, a momentum type variable, locates the kink minimum. Therefore the quasiparticle velocity interpolates between (γ∓1) over a width Γ{sub 0} on the two sides of Q=0, implying a kink there that strongly resembles a prominent low energy feature seen in angle resolved photoemission spectra (ARPES) of cuprate materials. We also propose novel ways of analyzing the ARPES data to isolate the predicted asymmetry between particle and hole excitations. -- Highlights: •Spectral function of the Extremely Correlated Fermi Liquid theory at low energy.

  1. Path integrals and large deviations in stochastic hybrid systems

    NASA Astrophysics Data System (ADS)

    Bressloff, Paul C.; Newby, Jay M.

    2014-04-01

    We construct a path-integral representation of solutions to a stochastic hybrid system, consisting of one or more continuous variables evolving according to a piecewise-deterministic dynamics. The differential equations for the continuous variables are coupled to a set of discrete variables that satisfy a continuous-time Markov process, which means that the differential equations are only valid between jumps in the discrete variables. Examples of stochastic hybrid systems arise in biophysical models of stochastic ion channels, motor-driven intracellular transport, gene networks, and stochastic neural networks. We use the path-integral representation to derive a large deviation action principle for a stochastic hybrid system. Minimizing the associated action functional with respect to the set of all trajectories emanating from a metastable state (assuming that such a minimization scheme exists) then determines the most probable paths of escape. Moreover, evaluating the action functional along a most probable path generates the so-called quasipotential used in the calculation of mean first passage times. We illustrate the theory by considering the optimal paths of escape from a metastable state in a bistable neural network.

  2. Path-integrated Lagrangian measures from the velocity gradient tensor

    NASA Astrophysics Data System (ADS)

    Pérez-Muñuzuri, V.; Huhn, F.

    2013-11-01

    Spatial maps of the finite-time Lyapunov exponent (FTLE) have been used extensively to study LCS in two-dimensional dynamical systems, in particular with application to transport in unsteady fluid flows. We use the time-periodic double-gyre model to compare spatial fields of FTLE and the path-integrated Eulerian Okubo-Weiss parameter (OW). Both fields correlate strongly, and by solving the dynamics of the deformation gradient tensor, a theoretical relationship between both magnitudes has been obtained. While for long integration times more and more FTLE ridges appear that do not seem to coincide with the stable manifold, ridges in the field of path-integrated OW represent fewer additional structures.

  3. Tackling higher derivative ghosts with the Euclidean path integral

    SciTech Connect

    Fontanini, Michele; Trodden, Mark

    2011-05-15

    An alternative to the effective field theory approach to treat ghosts in higher derivative theories is to attempt to integrate them out via the Euclidean path integral formalism. It has been suggested that this method could provide a consistent framework within which we might tolerate the ghost degrees of freedom that plague, among other theories, the higher derivative gravity models that have been proposed to explain cosmic acceleration. We consider the extension of this idea to treating a class of terms with order six derivatives, and find that for a general term the Euclidean path integral approach works in the most trivial background, Minkowski. Moreover we see that even in de Sitter background, despite some difficulties, it is possible to define a probability distribution for tensorial perturbations of the metric.

  4. Integrating Physically Handicapped Pupils.

    ERIC Educational Resources Information Center

    Hodgson, Ann

    1984-01-01

    Intended for regular class teachers working with mainstreamed physically handicapped pupils, the article offers guidelines regarding school organization, conditions directly affecting the pupil, and classroom considerations. A brief review of the major conditions (such as allergies, cerebral palsy, and muscular dystrophy) is presented. (CL)

  5. Integrating the Physically Handicapped Child.

    ERIC Educational Resources Information Center

    Bleck, Eugene E.

    1979-01-01

    The problems of integrating the physically handicapped child are discussed including descriptions of major handicapping conditions, a discussion of the development of mainstreaming programs, suggestions for successful programs, and comments on the financial implications of mainstreaming. (MM)

  6. Path integral Liouville dynamics for thermal equilibrium systems

    SciTech Connect

    Liu, Jian

    2014-06-14

    We show a new imaginary time path integral based method—path integral Liouville dynamics (PILD), which can be derived from the equilibrium Liouville dynamics [J. Liu and W. H. Miller, J. Chem. Phys. 134, 104101 (2011)] in the Wigner phase space. Numerical tests of PILD with the simple (white noise) Langevin thermostat have been made for two strongly anharmonic model problems. Since implementation of PILD does not request any specific form of the potential energy surface, the results suggest that PILD offers a potentially useful approach for general condensed phase molecular systems to have the two important properties: conserves the quantum canonical distribution and recovers exact thermal correlation functions (of even nonlinear operators, i.e., nonlinear functions of position or momentum operators) in the classical, high temperature, and harmonic limits.

  7. A Discrete History of the Lorentzian Path Integral

    NASA Astrophysics Data System (ADS)

    Loll, Renate

    In these lecture notes, I describe the motivation behind a recent formulation of a non-perturbative gravitational path integral for Lorentzian (instead of the usual Euclidean) space-times, and give a pedagogical introduction to its main features. At the regularized, discrete level this approach solves the problems of (i) having a well-defined Wick rotation, (ii) possessing a coordinate-invariant cutoff, and (iii) leading to convergent sums over geometries. Although little is known as yet about the existence and nature of an underlying continuum theory of quantum gravity in four dimensions, there are already a number of beautiful results in d=2 and d=3 where continuum limits have been found. They include an explicit example of the inequivalence of the Euclidean and Lorentzian path integrals, a non-perturbative mechanism for the cancellation of the conformal factor, and the discovery that causality can act as an effective regulator of quantum geometry.

  8. Gauge Invariance of Parametrized Systems and Path Integral Quantization

    NASA Astrophysics Data System (ADS)

    de Cicco, Hernán; Simeone, Claudio

    Gauge invariance of systems whose Hamilton-Jacobi equation is separable is improved by adding surface terms to the action functional. The general form of these terms is given for some complete solutions of the Hamilton-Jacobi equation. The procedure is applied to the relativistic particle and toy universes, which are quantized by imposing canonical gauge conditions in the path integral; in the case of empty models, we first quantize the parametrized system called "ideal clock," and then we examine the possibility of obtaining the amplitude for the minisuperspaces by matching them with the ideal clock. The relation existing between the geometrical properties of the constraint surface and the variables identifying the quantum states in the path integral is discussed.

  9. Theory of extreme correlations using canonical Fermions and path integrals

    NASA Astrophysics Data System (ADS)

    Shastry, B. Sriram

    2014-04-01

    The t-J model is studied using a novel and rigorous mapping of the Gutzwiller projected electrons, in terms of canonical electrons. The mapping has considerable similarity to the Dyson-Maleev transformation relating spin operators to canonical Bosons. This representation gives rise to a non Hermitian quantum theory, characterized by minimal redundancies. A path integral representation of the canonical theory is given. Using it, the salient results of the extremely correlated Fermi liquid (ECFL) theory, including the previously found Schwinger equations of motion, are easily rederived. Further, a transparent physical interpretation of the previously introduced auxiliary Greens function and the ‘caparison factor’, is obtained. The low energy electron spectral function in this theory, with a strong intrinsic asymmetry, is summarized in terms of a few expansion coefficients. These include an important emergent energy scale Δ0 that shrinks to zero on approaching the insulating state, thereby making it difficult to access the underlying very low energy Fermi liquid behavior. The scaled low frequency ECFL spectral function, related simply to the Fano line shape, has a peculiar energy dependence unlike that of a Lorentzian. The resulting energy dispersion obtained by maximization is a hybrid of a massive and a massless Dirac spectrum EQ∗˜γ Q-√{Γ02+Q2}, where the vanishing of Q, a momentum type variable, locates the kink minimum. Therefore the quasiparticle velocity interpolates between (γ∓1) over a width Γ0 on the two sides of Q=0, implying a kink there that strongly resembles a prominent low energy feature seen in angle resolved photoemission spectra (ARPES) of cuprate materials. We also propose novel ways of analyzing the ARPES data to isolate the predicted asymmetry between particle and hole excitations.

  10. Path-integral formulation of scattering theory: Central potentials

    SciTech Connect

    Gerry, C.C.; Singh, V.A.

    1980-05-15

    We consider central-potential scattering and determine a path-integral representation for the S matrix in polar coordinates. This is obtained by transforming to polar coordinates a Cartesian form of the nonrelativistic S matrix given by Campbell et al., and implementing an idea of Faddeev to obtain the appropriate asymptotic conditions. Our results are applied to scattering in an inverse-square potential to determine the correct phase shifts as well as the S matrix.

  11. Asymptotics of Selberg-like integrals by lattice path counting

    SciTech Connect

    Novaes, Marcel

    2011-04-15

    We obtain explicit expressions for positive integer moments of the probability density of eigenvalues of the Jacobi and Laguerre random matrix ensembles, in the asymptotic regime of large dimension. These densities are closely related to the Selberg and Selberg-like multidimensional integrals. Our method of solution is combinatorial: it consists in the enumeration of certain classes of lattice paths associated to the solution of recurrence relations.

  12. Physics Integration KErnels (PIKE)

    2014-07-31

    Pike is a software library for coupling and solving multiphysics applications. It provides basic interfaces and utilities for performing code-to-code coupling. It provides simple “black-box” Picard iteration methods for solving the coupled system of equations including Jacobi and Gauss-Seidel solvers. Pike was developed originally to couple neutronics and thermal fluids codes to simulate a light water nuclear reactor for the Consortium for Simulation of Light-water Reactors (CASL) DOE Energy Innovation Hub. The Pike library containsmore » no physics and just provides interfaces and utilities for coupling codes. It will be released open source under a BSD license as part of the Trilinos solver framework (trilinos.org) which is also BSD. This code provides capabilities similar to other open source multiphysics coupling libraries such as LIME, AMP, and MOOSE.« less

  13. Physics Integration KErnels (PIKE)

    SciTech Connect

    Pawlowski, Roger

    2014-07-31

    Pike is a software library for coupling and solving multiphysics applications. It provides basic interfaces and utilities for performing code-to-code coupling. It provides simple “black-box” Picard iteration methods for solving the coupled system of equations including Jacobi and Gauss-Seidel solvers. Pike was developed originally to couple neutronics and thermal fluids codes to simulate a light water nuclear reactor for the Consortium for Simulation of Light-water Reactors (CASL) DOE Energy Innovation Hub. The Pike library contains no physics and just provides interfaces and utilities for coupling codes. It will be released open source under a BSD license as part of the Trilinos solver framework (trilinos.org) which is also BSD. This code provides capabilities similar to other open source multiphysics coupling libraries such as LIME, AMP, and MOOSE.

  14. Path integral approach to the quantum fidelity amplitude

    PubMed Central

    2016-01-01

    The Loschmidt echo is a measure of quantum irreversibility and is determined by the fidelity amplitude of an imperfect time-reversal protocol. Fidelity amplitude plays an important role both in the foundations of quantum mechanics and in its applications, such as time-resolved electronic spectroscopy. We derive an exact path integral formula for the fidelity amplitude and use it to obtain a series of increasingly accurate semiclassical approximations by truncating an exact expansion of the path integral exponent. While the zeroth-order expansion results in a remarkably simple, yet non-trivial approximation for the fidelity amplitude, the first-order expansion yields an alternative derivation of the so-called ‘dephasing representation,’ circumventing the use of a semiclassical propagator as in the original derivation. We also obtain an approximate expression for fidelity based on the second-order expansion, which resolves several shortcomings of the dephasing representation. The rigorous derivation from the path integral permits the identification of sufficient conditions under which various approximations obtained become exact. PMID:27140973

  15. Path integral approach to the quantum fidelity amplitude.

    PubMed

    Vaníček, Jiří; Cohen, Doron

    2016-06-13

    The Loschmidt echo is a measure of quantum irreversibility and is determined by the fidelity amplitude of an imperfect time-reversal protocol. Fidelity amplitude plays an important role both in the foundations of quantum mechanics and in its applications, such as time-resolved electronic spectroscopy. We derive an exact path integral formula for the fidelity amplitude and use it to obtain a series of increasingly accurate semiclassical approximations by truncating an exact expansion of the path integral exponent. While the zeroth-order expansion results in a remarkably simple, yet non-trivial approximation for the fidelity amplitude, the first-order expansion yields an alternative derivation of the so-called 'dephasing representation,' circumventing the use of a semiclassical propagator as in the original derivation. We also obtain an approximate expression for fidelity based on the second-order expansion, which resolves several shortcomings of the dephasing representation. The rigorous derivation from the path integral permits the identification of sufficient conditions under which various approximations obtained become exact.

  16. Path integral approach to the quantum fidelity amplitude.

    PubMed

    Vaníček, Jiří; Cohen, Doron

    2016-06-13

    The Loschmidt echo is a measure of quantum irreversibility and is determined by the fidelity amplitude of an imperfect time-reversal protocol. Fidelity amplitude plays an important role both in the foundations of quantum mechanics and in its applications, such as time-resolved electronic spectroscopy. We derive an exact path integral formula for the fidelity amplitude and use it to obtain a series of increasingly accurate semiclassical approximations by truncating an exact expansion of the path integral exponent. While the zeroth-order expansion results in a remarkably simple, yet non-trivial approximation for the fidelity amplitude, the first-order expansion yields an alternative derivation of the so-called 'dephasing representation,' circumventing the use of a semiclassical propagator as in the original derivation. We also obtain an approximate expression for fidelity based on the second-order expansion, which resolves several shortcomings of the dephasing representation. The rigorous derivation from the path integral permits the identification of sufficient conditions under which various approximations obtained become exact. PMID:27140973

  17. A review of path-independent integrals in elastic-plastic fracture mechanics, task 4

    NASA Technical Reports Server (NTRS)

    Kim, K. S.

    1985-01-01

    The path independent (P-I) integrals in elastic plastic fracture mechanics which have been proposed in recent years to overcome the limitations imposed on the J integral are reviewed. The P-I integrals considered herein are the J integral by Rice, the thermoelastic P-I integrals by Wilson and Yu and by Gurtin, the J* integral by Blackburn, the J sub theta integral by Ainsworth et al., the J integral by Kishimoto et al., and the delta T sub p and delta T* sub p integrals by Atluri et al. The theoretical foundation of these P-I integrals is examined with emphasis on whether or not path independence is maintained in the presence of nonproportional loading and unloading in the plastic regime, thermal gradients, and material inhomogeneities. The similarities, differences, salient features, and limitations of these P-I integrals are discussed. Comments are also made with regard to the physical meaning, the possibility of experimental measurement, and computational aspects.

  18. The asymptotic evaluation of a class of path integrals. II

    NASA Astrophysics Data System (ADS)

    Luttinger, J. M.

    1983-08-01

    The asymptotic behavior of a class of Wiener-like path integrals (functions of the ``local time'') is determined. These integrals are of interest in themselves and also arise very naturally in the theory of disordered systems. We show that by making use of a Grassman algebra (i.e., a set of anticommuting variables), the earlier treatment of this problem can be greatly simplified. In particular, the previous use of ``replica trick'' (which involves a difficult to justify analytic continuation in the number of field components) is thus avoided.

  19. Physical Layer Security Using Two-Path Successive Relaying

    PubMed Central

    Liau, Qian Yu; Leow, Chee Yen; Ding, Zhiguo

    2016-01-01

    Relaying is one of the useful techniques to enhance wireless physical-layer security. Existing literature shows that employing full-duplex relay instead of conventional half-duplex relay improves secrecy capacity and secrecy outage probability, but this is at the price of sophisticated implementation. As an alternative, two-path successive relaying has been proposed to emulate operation of full-duplex relay by scheduling a pair of half-duplex relays to assist the source transmission alternately. However, the performance of two-path successive relaying in secrecy communication remains unexplored. This paper proposes a secrecy two-path successive relaying protocol for a scenario with one source, one destination and two half-duplex relays. The relays operate alternately in a time division mode to forward messages continuously from source to destination in the presence of an eavesdropper. Analytical results reveal that the use of two half-duplex relays in the proposed scheme contributes towards a quadratically lower probability of interception compared to full-duplex relaying. Numerical simulations show that the proposed protocol achieves the ergodic achievable secrecy rate of full-duplex relaying while delivering the lowest probability of interception and secrecy outage probability compared to the existing half duplex relaying, full duplex relaying and full duplex jamming schemes. PMID:27294924

  20. Physical Layer Security Using Two-Path Successive Relaying.

    PubMed

    Liau, Qian Yu; Leow, Chee Yen; Ding, Zhiguo

    2016-06-09

    Relaying is one of the useful techniques to enhance wireless physical-layer security. Existing literature shows that employing full-duplex relay instead of conventional half-duplex relay improves secrecy capacity and secrecy outage probability, but this is at the price of sophisticated implementation. As an alternative, two-path successive relaying has been proposed to emulate operation of full-duplex relay by scheduling a pair of half-duplex relays to assist the source transmission alternately. However, the performance of two-path successive relaying in secrecy communication remains unexplored. This paper proposes a secrecy two-path successive relaying protocol for a scenario with one source, one destination and two half-duplex relays. The relays operate alternately in a time division mode to forward messages continuously from source to destination in the presence of an eavesdropper. Analytical results reveal that the use of two half-duplex relays in the proposed scheme contributes towards a quadratically lower probability of interception compared to full-duplex relaying. Numerical simulations show that the proposed protocol achieves the ergodic achievable secrecy rate of full-duplex relaying while delivering the lowest probability of interception and secrecy outage probability compared to the existing half duplex relaying, full duplex relaying and full duplex jamming schemes.

  1. Physical Layer Security Using Two-Path Successive Relaying.

    PubMed

    Liau, Qian Yu; Leow, Chee Yen; Ding, Zhiguo

    2016-01-01

    Relaying is one of the useful techniques to enhance wireless physical-layer security. Existing literature shows that employing full-duplex relay instead of conventional half-duplex relay improves secrecy capacity and secrecy outage probability, but this is at the price of sophisticated implementation. As an alternative, two-path successive relaying has been proposed to emulate operation of full-duplex relay by scheduling a pair of half-duplex relays to assist the source transmission alternately. However, the performance of two-path successive relaying in secrecy communication remains unexplored. This paper proposes a secrecy two-path successive relaying protocol for a scenario with one source, one destination and two half-duplex relays. The relays operate alternately in a time division mode to forward messages continuously from source to destination in the presence of an eavesdropper. Analytical results reveal that the use of two half-duplex relays in the proposed scheme contributes towards a quadratically lower probability of interception compared to full-duplex relaying. Numerical simulations show that the proposed protocol achieves the ergodic achievable secrecy rate of full-duplex relaying while delivering the lowest probability of interception and secrecy outage probability compared to the existing half duplex relaying, full duplex relaying and full duplex jamming schemes. PMID:27294924

  2. Multi-instantons and exact results IV: Path integral formalism

    SciTech Connect

    Jentschura, Ulrich D.; Zinn-Justin, Jean

    2011-08-15

    Highlights: > O(N) anharmonic oscillators are considered in the path integral formalism. > Higher-order corrections to instantons are obtained using Feynman diagram calculations. > Generalized Bender-Wu formulas are confirmed. > The O(N) functional determinant describing the zero modes leads to higher-order terms. > Surprising cancellations are observed for the sextic oscillator. - Abstract: This is the fourth paper in a series devoted to the large-order properties of anharmonic oscillators. We attempt to draw a connection of anharmonic oscillators to field theory, by investigating the partition function in the path integral representation around both the Gaussian saddle point, which determines the perturbative expansion of the eigenvalues, as well as the nontrivial instanton saddle point. The value of the classical action at the saddle point is the instanton action which determines the large-order properties of perturbation theory by a dispersion relation. In order to treat the perturbations about the instanton, one has to take into account the continuous symmetries broken by the instanton solution because they lead to zero-modes of the fluctuation operator of the instanton configuration. The problem is solved by changing variables in the path integral, taking the instanton parameters as integration variables (collective coordinates). The functional determinant (Faddeev-Popov determinant) of the change of variables implies nontrivial modifications of the one-loop and higher-loop corrections about the instanton configuration. These are evaluated and compared to exact WKB calculations. A specific cancellation mechanism for the first perturbation about the instanton, which has been conjectured for the sextic oscillator based on a nonperturbative generalized Bohr-Sommerfeld quantization condition, is verified by an analytic Feynman diagram calculation.

  3. Direct path integral estimators for isotope fractionation ratios

    SciTech Connect

    Cheng, Bingqing; Ceriotti, Michele

    2014-12-28

    Fractionation of isotopes among distinct molecules or phases is a quantum effect which is often exploited to obtain insights on reaction mechanisms, biochemical, geochemical, and atmospheric phenomena. Accurate evaluation of isotope ratios in atomistic simulations is challenging, because one needs to perform a thermodynamic integration with respect to the isotope mass, along with time-consuming path integral calculations. By re-formulating the problem as a particle exchange in the ring polymer partition function, we derive new estimators giving direct access to the differential partitioning of isotopes, which can simplify the calculations by avoiding thermodynamic integration. We demonstrate the efficiency of these estimators by applying them to investigate the isotope fractionation ratios in the gas-phase Zundel cation, and in a few simple hydrocarbons.

  4. Neural dynamics for landmark orientation and angular path integration.

    PubMed

    Seelig, Johannes D; Jayaraman, Vivek

    2015-05-14

    Many animals navigate using a combination of visual landmarks and path integration. In mammalian brains, head direction cells integrate these two streams of information by representing an animal's heading relative to landmarks, yet maintaining their directional tuning in darkness based on self-motion cues. Here we use two-photon calcium imaging in head-fixed Drosophila melanogaster walking on a ball in a virtual reality arena to demonstrate that landmark-based orientation and angular path integration are combined in the population responses of neurons whose dendrites tile the ellipsoid body, a toroidal structure in the centre of the fly brain. The neural population encodes the fly's azimuth relative to its environment, tracking visual landmarks when available and relying on self-motion cues in darkness. When both visual and self-motion cues are absent, a representation of the animal's orientation is maintained in this network through persistent activity, a potential substrate for short-term memory. Several features of the population dynamics of these neurons and their circular anatomical arrangement are suggestive of ring attractors, network structures that have been proposed to support the function of navigational brain circuits. PMID:25971509

  5. Neural dynamics for landmark orientation and angular path integration

    PubMed Central

    Seelig, Johannes D.; Jayaraman, Vivek

    2015-01-01

    Summary Many animals navigate using a combination of visual landmarks and path integration. In mammalian brains, head direction cells integrate these two streams of information by representing an animal's heading relative to landmarks, yet maintaining their directional tuning in darkness based on self-motion cues. Here we use two-photon calcium imaging in head-fixed flies walking on a ball in a virtual reality arena to demonstrate that landmark-based orientation and angular path integration are combined in the population responses of neurons whose dendrites tile the ellipsoid body — a toroidal structure in the center of the fly brain. The population encodes the fly's azimuth relative to its environment, tracking visual landmarks when available and relying on self-motion cues in darkness. When both visual and self-motion cues are absent, a representation of the animal's orientation is maintained in this network through persistent activity — a potential substrate for short-term memory. Several features of the population dynamics of these neurons and their circular anatomical arrangement are suggestive of ring attractors — network structures proposed to support the function of navigational brain circuits. PMID:25971509

  6. Quantum corrections from a path integral over reparametrizations

    SciTech Connect

    Makeenko, Yuri; Olesen, Poul

    2010-08-15

    We study the path integral over reparametrizations that has been proposed as an ansatz for the Wilson loops in the large-N QCD and reproduces the area law in the classical limit of large loops. We show that a semiclassical expansion for a rectangular loop captures the Luescher term associated with d=26 dimensions and propose a modification of the ansatz that reproduces the Luescher term in other dimensions, which is observed in lattice QCD. We repeat the calculation for an outstretched ellipse advocating the emergence of an analog of the Luescher term and verify this result by a direct computation of the determinant of the Laplace operator and the conformal anomaly.

  7. Path Integral Solubility of Two-Dimensional Models

    SciTech Connect

    Das, Ashok K.; Mathur, Vishnu S.

    1985-07-01

    We apply the technique of Fujikawa to solve for simple two-dimensional models by looking at the nontrivial transformation properties of the fermion measure in the path-integral formalism. We obtain the most general solution for the massless Thirring model and point out how the one-parameter solution reduces to that of Johnson and Sommerfield in a particular limit. We present the most general solution for the massive vector model indicating how it reduces to the solutions of Brown and Sommerfield for different values of the parameter. The solution of a gradient-coupling model is also discussed.

  8. Path-integral approach to the Wigner-Kirkwood expansion.

    PubMed

    Jizba, Petr; Zatloukal, Václav

    2014-01-01

    We study the high-temperature behavior of quantum-mechanical path integrals. Starting from the Feynman-Kac formula, we derive a functional representation of the Wigner-Kirkwood perturbation expansion for quantum Boltzmann densities. As shown by its applications to different potentials, the presented expansion turns out to be quite efficient in generating analytic form of the higher-order expansion coefficients. To put some flesh on the bare bones, we apply the expansion to obtain basic thermodynamic functions of the one-dimensional anharmonic oscillator. Further salient issues, such as generalization to the Bloch density matrix and comparison with the more customary world-line formulation, are discussed. PMID:24580200

  9. Integrating the physically handicapped child.

    PubMed

    Bleck, E E

    1979-03-01

    This paper will serve several purposes: (1) to provide information on the incidence of physically handicapped children (exclusive of the blind and deaf) who are likely to be integrated into schools for normal non-physically impaired children, (2) to describe briefly the major handicapping conditions and their educational implications, (3) to comment on why integration has come about and why it promises to enrich the lives of normal children, (4) to suggest how physicians, physical therapists, and occupational therapists might help to make schools programs successful, (5) to comment briefly on financial implications of this program and to suggest ways in which the complexity of the medical management might be simplified, (6) to provide factual knowledge about the handicapped child and his potential to teachers who are already on the firing line to "improve" the academic achievement of the alleged normal child. PMID:155177

  10. Path integrals for electronic densities, reactivity indices, and localization functions in quantum systems.

    PubMed

    Putz, Mihai V

    2009-11-10

    The density matrix theory, the ancestor of density functional theory, provides the immediate framework for Path Integral (PI) development, allowing the canonical density be extended for the many-electronic systems through the density functional closure relationship. Yet, the use of path integral formalism for electronic density prescription presents several advantages: assures the inner quantum mechanical description of the system by parameterized paths; averages the quantum fluctuations; behaves as the propagator for time-space evolution of quantum information; resembles Schrödinger equation; allows quantum statistical description of the system through partition function computing. In this framework, four levels of path integral formalism were presented: the Feynman quantum mechanical, the semiclassical, the Feynman-Kleinert effective classical, and the Fokker-Planck non-equilibrium ones. In each case the density matrix or/and the canonical density were rigorously defined and presented. The practical specializations for quantum free and harmonic motions, for statistical high and low temperature limits, the smearing justification for the Bohr's quantum stability postulate with the paradigmatic Hydrogen atomic excursion, along the quantum chemical calculation of semiclassical electronegativity and hardness, of chemical action and Mulliken electronegativity, as well as by the Markovian generalizations of Becke-Edgecombe electronic focalization functions - all advocate for the reliability of assuming PI formalism of quantum mechanics as a versatile one, suited for analytically and/or computationally modeling of a variety of fundamental physical and chemical reactivity concepts characterizing the (density driving) many-electronic systems.

  11. Path Integrals for Electronic Densities, Reactivity Indices, and Localization Functions in Quantum Systems

    PubMed Central

    Putz, Mihai V.

    2009-01-01

    The density matrix theory, the ancestor of density functional theory, provides the immediate framework for Path Integral (PI) development, allowing the canonical density be extended for the many-electronic systems through the density functional closure relationship. Yet, the use of path integral formalism for electronic density prescription presents several advantages: assures the inner quantum mechanical description of the system by parameterized paths; averages the quantum fluctuations; behaves as the propagator for time-space evolution of quantum information; resembles Schrödinger equation; allows quantum statistical description of the system through partition function computing. In this framework, four levels of path integral formalism were presented: the Feynman quantum mechanical, the semiclassical, the Feynman-Kleinert effective classical, and the Fokker-Planck non-equilibrium ones. In each case the density matrix or/and the canonical density were rigorously defined and presented. The practical specializations for quantum free and harmonic motions, for statistical high and low temperature limits, the smearing justification for the Bohr’s quantum stability postulate with the paradigmatic Hydrogen atomic excursion, along the quantum chemical calculation of semiclassical electronegativity and hardness, of chemical action and Mulliken electronegativity, as well as by the Markovian generalizations of Becke-Edgecombe electronic focalization functions – all advocate for the reliability of assuming PI formalism of quantum mechanics as a versatile one, suited for analytically and/or computationally modeling of a variety of fundamental physical and chemical reactivity concepts characterizing the (density driving) many-electronic systems. PMID:20087467

  12. Path-Integration Computation of the Transport Properties of Nanoparticles

    NASA Astrophysics Data System (ADS)

    Douglas, Jack

    2014-03-01

    There is need for effective computational methods for calculating the transport properties of polymers and complex-shaped particle aggregates arising in materials science and biology as a foundation for rational material design and the design of well-defined measurements assessing the environmental impact of nanoparticles. We focus on the problem of calculating basic solution transport properties (translational diffusion coefficient, intrinsic viscosity) of isolated particles having essentially any geometry using a novel computational method involving path integration developed by Mansfield and Douglas. The basic concepts behind the method are described and the method is validated in cases where exact analytic, or at least highly accurate numerical estimates, are known for comparison. After defining and validating our method, some applications of the program are given to some non-trivial problems illustrating the use of the program for charactering such as nanoparticles with grafted DNA brush layers, DNA orgami, carbon nanotubes, etc. The path-integration method is evidently a powerful tool for computing basic transport properties of complex-shaped objects and should find wide application in polymer science, nanotechnological applications and biology.

  13. Path integral Monte Carlo on a lattice. II. Bound states

    NASA Astrophysics Data System (ADS)

    O'Callaghan, Mark; Miller, Bruce N.

    2016-07-01

    The equilibrium properties of a single quantum particle (qp) interacting with a classical gas for a wide range of temperatures that explore the system's behavior in the classical as well as in the quantum regime is investigated. Both the qp and the atoms are restricted to sites on a one-dimensional lattice. A path integral formalism developed within the context of the canonical ensemble is utilized, where the qp is represented by a closed, variable-step random walk on the lattice. Monte Carlo methods are employed to determine the system's properties. To test the usefulness of the path integral formalism, the Metropolis algorithm is employed to determine the equilibrium properties of the qp in the context of a square well potential, forcing the qp to occupy bound states. We consider a one-dimensional square well potential where all atoms on the lattice are occupied with one atom with an on-site potential except for a contiguous set of sites of various lengths centered at the middle of the lattice. Comparison of the potential energy, the energy fluctuations, and the correlation function are made between the results of the Monte Carlo simulations and the numerical calculations.

  14. Path integral Monte Carlo on a lattice. II. Bound states.

    PubMed

    O'Callaghan, Mark; Miller, Bruce N

    2016-07-01

    The equilibrium properties of a single quantum particle (qp) interacting with a classical gas for a wide range of temperatures that explore the system's behavior in the classical as well as in the quantum regime is investigated. Both the qp and the atoms are restricted to sites on a one-dimensional lattice. A path integral formalism developed within the context of the canonical ensemble is utilized, where the qp is represented by a closed, variable-step random walk on the lattice. Monte Carlo methods are employed to determine the system's properties. To test the usefulness of the path integral formalism, the Metropolis algorithm is employed to determine the equilibrium properties of the qp in the context of a square well potential, forcing the qp to occupy bound states. We consider a one-dimensional square well potential where all atoms on the lattice are occupied with one atom with an on-site potential except for a contiguous set of sites of various lengths centered at the middle of the lattice. Comparison of the potential energy, the energy fluctuations, and the correlation function are made between the results of the Monte Carlo simulations and the numerical calculations. PMID:27575090

  15. Physical integration: a causal account for consciousness.

    PubMed

    Manzotti, Riccardo; Chella, Antonio

    2014-06-01

    The issue of integration in neural networks is intimately connected with that of consciousness. In this paper, integration as an effective level of physical organization is contrasted with a methodological integrative approach. Understanding how consciousness arises out of neural processes requires a model of integration in just causal physical terms. Based on a set of feasible criteria (physical grounding, causal efficacy, no circularity and scaling), a causal account of physical integration for consciousness centered on joint causation is outlined.

  16. Potential theory, path integrals and the Laplacian of the indicator

    NASA Astrophysics Data System (ADS)

    Lange, Rutger-Jan

    2012-11-01

    This paper links the field of potential theory — i.e. the Dirichlet and Neumann problems for the heat and Laplace equation — to that of the Feynman path integral, by postulating the following seemingly ill-defined potential: V(x):=∓ {{σ^2}}/2nabla_x^2{1_{{xin D}}} where the volatility is the reciprocal of the mass (i.e. m = 1/ σ 2) and ħ = 1. The Laplacian of the indicator can be interpreted using the theory of distributions: it is the d-dimensional analogue of the Dirac δ'-function, which can formally be defined as partial_x^2{1_{x>0 }} . We show, first, that the path integral's perturbation series (or Born series) matches the classical single and double boundary layer series of potential theory, thereby connecting two hitherto unrelated fields. Second, we show that the perturbation series is valid for all domains D that allow Green's theorem (i.e. with a finite number of corners, edges and cusps), thereby expanding the classical applicability of boundary layers. Third, we show that the minus (plus) in the potential holds for the Dirichlet (Neumann) boundary condition; showing for the first time a particularly close connection between these two classical problems. Fourth, we demonstrate that the perturbation series of the path integral converges as follows:

    mode of convergence absorbed propagator reflected propagator convex domain alternating monotone
  17. PhytoPath: an integrative resource for plant pathogen genomics

    PubMed Central

    Pedro, Helder; Maheswari, Uma; Urban, Martin; Irvine, Alistair George; Cuzick, Alayne; McDowall, Mark D.; Staines, Daniel M.; Kulesha, Eugene; Hammond-Kosack, Kim Elizabeth; Kersey, Paul Julian

    2016-01-01

    PhytoPath (www.phytopathdb.org) is a resource for genomic and phenotypic data from plant pathogen species, that integrates phenotypic data for genes from PHI-base, an expertly curated catalog of genes with experimentally verified pathogenicity, with the Ensembl tools for data visualization and analysis. The resource is focused on fungi, protists (oomycetes) and bacterial plant pathogens that have genomes that have been sequenced and annotated. Genes with associated PHI-base data can be easily identified across all plant pathogen species using a BioMart-based query tool and visualized in their genomic context on the Ensembl genome browser. The PhytoPath resource contains data for 135 genomic sequences from 87 plant pathogen species, and 1364 genes curated for their role in pathogenicity and as targets for chemical intervention. Support for community annotation of gene models is provided using the WebApollo online gene editor, and we are working with interested communities to improve reference annotation for selected species. PMID:26476449

  18. PhytoPath: an integrative resource for plant pathogen genomics.

    PubMed

    Pedro, Helder; Maheswari, Uma; Urban, Martin; Irvine, Alistair George; Cuzick, Alayne; McDowall, Mark D; Staines, Daniel M; Kulesha, Eugene; Hammond-Kosack, Kim Elizabeth; Kersey, Paul Julian

    2016-01-01

    PhytoPath (www.phytopathdb.org) is a resource for genomic and phenotypic data from plant pathogen species, that integrates phenotypic data for genes from PHI-base, an expertly curated catalog of genes with experimentally verified pathogenicity, with the Ensembl tools for data visualization and analysis. The resource is focused on fungi, protists (oomycetes) and bacterial plant pathogens that have genomes that have been sequenced and annotated. Genes with associated PHI-base data can be easily identified across all plant pathogen species using a BioMart-based query tool and visualized in their genomic context on the Ensembl genome browser. The PhytoPath resource contains data for 135 genomic sequences from 87 plant pathogen species, and 1364 genes curated for their role in pathogenicity and as targets for chemical intervention. Support for community annotation of gene models is provided using the WebApollo online gene editor, and we are working with interested communities to improve reference annotation for selected species.

  19. Path To Ignition: US Indirect Target Physics (LIRPP Vol. 12)

    NASA Astrophysics Data System (ADS)

    Cray, M.; Campbell, E. M.

    2016-10-01

    The United States ICF Program has been pursuing an aggressive research program in preparation for an ignition demonstration on the National Ignition Facility. Los Alamos and Livermore laboratories have collaborated on resolving indirect drive target physics issues on the Nova laser at Livermore National Laboratory. This combined with detailed modeling of laser heated indirectly driven targets likely to achieve ignition, has provided the basis for planning for the NIF. A detailed understanding of target physics, laser performance, and target fabrication is required for developing robust ignition targets. We have developed large-scale computational models to simulate complex physics which occurs in an indirectly driven target. For ignition, detailed understanding of hohlraum and implosion physics is required in order to control competing processes at the few percent level. From crucial experiments performed by Los Alamos and Livermore on the Nova laser, a comprehensive indirect drive database has been assembled. Time integrated and time dependent measurements of radiation drive and symmetry coupled with a detailed set of plasma instability measurements have confirmed our ability to predict hohlraum energetics. Implosion physics campaigns are focused on underdstanding detailed capsule hydrodynamics and instability growth. Target fabrication technology is also an active area of research at Los Alamos, Livermore, and General Atomics for NIF. NIF targets require developing technology in cryogenics and manufacturing in such areas as beryllium shell manufacture. Descriptions of our NIF target designs, experimental results, and fabrication technology supporting NIF target performance predictions will be given.

  20. Quantum-classical interactions through the path integral

    NASA Astrophysics Data System (ADS)

    Metaxas, Dimitrios

    2007-03-01

    I consider the case of two interacting scalar fields, ϕ and ψ, and use the path integral formalism in order to treat the first classically and the second quantum-mechanically. I derive the Feynman rules and the resulting equation of motion for the classical field which should be an improvement of the usual semiclassical procedure. As an application I use this method in order to enforce Gauss’s law as a classical equation in a non-Abelian gauge theory. I argue that the theory is renormalizable and equivalent to the usual Yang-Mills theory as far as the gauge field terms are concerned. There are additional terms in the effective action that depend on the Lagrange multiplier field λ that is used to enforce the constraint. These terms and their relation to the confining properties of the theory are discussed.

    1. Path integral approach to electron scattering in classical electromagnetic potential

      NASA Astrophysics Data System (ADS)

      Chuang, Xu; Feng, Feng; Ying-Jun, Li

      2016-05-01

      As is known to all, the electron scattering in classical electromagnetic potential is one of the most widespread applications of quantum theory. Nevertheless, many discussions about electron scattering are based upon single-particle Schrodinger equation or Dirac equation in quantum mechanics rather than the method of quantum field theory. In this paper, by using the path integral approach of quantum field theory, we perturbatively evaluate the scattering amplitude up to the second order for the electron scattering by the classical electromagnetic potential. The results we derive are convenient to apply to all sorts of potential forms. Furthermore, by means of the obtained results, we give explicit calculations for the one-dimensional electric potential. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374360, 11405266, and 11505285) and the National Basic Research Program of China (Grant No. 2013CBA01504).

    2. Hippocampal “Time Cells”: Time versus Path Integration

      PubMed Central

      Kraus, Benjamin J.; Robinson, Robert J.; White, John A.; Eichenbaum, Howard; Hasselmo, Michael E.

      2014-01-01

      SUMMARY Recent studies have reported the existence of hippocampal “time cells,” neurons that fire at particular moments during periods when behavior and location are relatively constant. However, an alternative explanation of apparent time coding is that hippocampal neurons “path integrate” to encode the distance an animal has traveled. Here, we examined hippocampal neuronal firing patterns as rats ran in place on a treadmill, thus “clamping” behavior and location, while we varied the treadmill speed to distinguish time elapsed from distance traveled. Hippocampal neurons were strongly influenced by time and distance, and less so by minor variations in location. Furthermore, the activity of different neurons reflected integration over time and distance to varying extents, with most neurons strongly influenced by both factors and some significantly influenced by only time or distance. Thus, hippocampal neuronal networks captured both the organization of time and distance in a situation where these dimensions dominated an ongoing experience. PMID:23707613

    3. Path integrals of spin- J systems in the holomorphic representation

      NASA Astrophysics Data System (ADS)

      Vieira, V. R.; Sacramento, P. D.

      1995-02-01

      A path integral expression for the matrix element and the diagonal representative of the spin- J evolution operator or Boltzmann factor is obtained using Bloch coherent states in the holomorphic representation, yielding the appropriate boundary conditions. Quantum Dyson-Schwinger equations of motion are derived and used as criteria to select the appropriate action. In the case of the diagonal representative the equations of motion satisfy the commutation relations of the spin operators and are the classical limit of the Dyson-Schwinger equations, if we redefine the Lagrangian together with the integration measure. It is shown that in the case of a spin in a time-independent magnetic field the saddle-point approximation for both representatives gives the exact results. We present analytical algorithms to obtain the exponential factor and the prefactor in the saddle-point expansion, without an ad hoc reduction to an effective one-dimensional problem, but keeping instead a 2 × 2 matrix structure. We apply our results to several models.

    4. Age differences in virtual environment and real world path integration

      PubMed Central

      Adamo, Diane E.; Briceño, Emily M.; Sindone, Joseph A.; Alexander, Neil B.; Moffat, Scott D.

      2012-01-01

      Accurate path integration (PI) requires the integration of visual, proprioceptive, and vestibular self-motion cues and age effects associated with alterations in processing information from these systems may contribute to declines in PI abilities. The present study investigated age-related differences in PI in conditions that varied as a function of available sources of sensory information. Twenty-two healthy, young (23.8 ± 3.0 years) and 16 older (70.1 ± 6.4 years) adults participated in distance reproduction and triangle completion tasks (TCTs) performed in a virtual environment (VE) and two “real world” conditions: guided walking and wheelchair propulsion. For walking and wheelchair propulsion conditions, participants wore a blindfold and wore noise-blocking headphones and were guided through the workspace by the experimenter. For the VE condition, participants viewed self-motion information on a computer monitor and used a joystick to navigate through the environment. For TCTs, older compared to younger individuals showed greater errors in rotation estimations performed in the wheelchair condition, and for rotation and distance estimations in the VE condition. Distance reproduction tasks (DRTs), in contrast, did not show any age effects. These findings demonstrate that age differences in PI vary as a function of the available sources of information and by the complexity of outbound pathway. PMID:23055969

    5. Imaginary time path integral Monte Carlo route to rate coefficients for nonadiabatic barrier crossing

      NASA Technical Reports Server (NTRS)

      Wolynes, Peter G.

      1987-01-01

      Nonadiabatic transitions are central to many areas of chemical and condensed matter physics, ranging from biological electron transfer to the optical properties of one-dimensional conductors. Here, a path integral Monte Carlo method is used to simulate such transitions, based on the observation that nonadiabatic rate coefficients are often dominated by saddle point trajectories that correspond to an imaginary time. Simple analytic theories can be used to continue these imaginary time correlation functions to determine rate coefficients. The advantages and drawbacks of this approach are discussed.

    6. Seismic Imaging, One-Way Wave Equations, Pseudodifferential Operators, Path Integrals, and all that Jazz

      NASA Astrophysics Data System (ADS)

      Artoun, Ojenie; David-Rus, Diana; Emmett, Matthew; Fishman, Lou; Fital, Sandra; Hogan, Chad; Lim, Jisun; Lushi, Enkeleida; Marinov, Vesselin

      2006-05-01

      In this report we summarize an extension of Fourier analysis for the solution of the wave equation with a non-constant coefficient corresponding to an inhomogeneous medium. The underlying physics of the problem is exploited to link pseudodifferential operators and phase space path integrals to obtain a marching algorithm that incorporates the backward scattering into the evolution of the wave. This allows us to successfully apply single-sweep, one-way marching methods in inherently two-way environments, which was not achieved before through other methods for this problem.

    7. 77 FR 33486 - Certain Integrated Circuit Packages Provided With Multiple Heat-Conducting Paths and Products...

      Federal Register 2010, 2011, 2012, 2013, 2014

      2012-06-06

      ... COMMISSION Certain Integrated Circuit Packages Provided With Multiple Heat- Conducting Paths and Products... With Multiple Heat-Conducting Paths and Products Containing Same, DN 2899; the Commission is soliciting... multiple heat-conducting paths and products containing same. The complaint names as respondents...

    8. Kinetic paths, time scale, and underlying landscapes: A path integral framework to study global natures of nonequilibrium systems and networks

      NASA Astrophysics Data System (ADS)

      Wang, Jin; Zhang, Kun; Wang, Erkwang

      2010-09-01

      We developed a general framework to quantify three key ingredients for dynamics of nonequilibrium systems through path integrals in length space. First, we identify dominant kinetic paths as the ones with optimal weights, leading to effective reduction of dimensionality or degrees of freedom from exponential to polynomial so large systems can be treated. Second, we uncover the underlying nonequilibrium potential landscapes from the explorations of the state space through kinetic paths. We apply our framework to a specific example of nonequilibrium network system: lambda phage genetic switch. Two distinct basins of attractions emerge. The dominant kinetic paths from one basin to another are irreversible and do not follow the usual steepest descent or gradient path along the landscape. It reflects the fact that the dynamics of nonequilibrium systems is not just determined by potential gradient but also the residual curl flux force, suggesting experiments to test theoretical predictions. Third, we have calculated dynamic transition time scales from one basin to another critical for stability of the system through instantons. Theoretical predictions are in good agreements with wild type and mutant experiments. We further uncover the correlations between the kinetic transition time scales and the underlying landscape topography: the barrier heights along the dominant paths. We found that both the dominant paths and the landscape are relatively robust against the influences of external environmental perturbations and the system tends to dissipate less with less fluctuations. Our general framework can be applied to other nonequilibrium systems.

    9. Kinetic paths, time scale, and underlying landscapes: a path integral framework to study global natures of nonequilibrium systems and networks.

      PubMed

      Wang, Jin; Zhang, Kun; Wang, Erkwang

      2010-09-28

      We developed a general framework to quantify three key ingredients for dynamics of nonequilibrium systems through path integrals in length space. First, we identify dominant kinetic paths as the ones with optimal weights, leading to effective reduction of dimensionality or degrees of freedom from exponential to polynomial so large systems can be treated. Second, we uncover the underlying nonequilibrium potential landscapes from the explorations of the state space through kinetic paths. We apply our framework to a specific example of nonequilibrium network system: lambda phage genetic switch. Two distinct basins of attractions emerge. The dominant kinetic paths from one basin to another are irreversible and do not follow the usual steepest descent or gradient path along the landscape. It reflects the fact that the dynamics of nonequilibrium systems is not just determined by potential gradient but also the residual curl flux force, suggesting experiments to test theoretical predictions. Third, we have calculated dynamic transition time scales from one basin to another critical for stability of the system through instantons. Theoretical predictions are in good agreements with wild type and mutant experiments. We further uncover the correlations between the kinetic transition time scales and the underlying landscape topography: the barrier heights along the dominant paths. We found that both the dominant paths and the landscape are relatively robust against the influences of external environmental perturbations and the system tends to dissipate less with less fluctuations. Our general framework can be applied to other nonequilibrium systems.

    10. The retrosplenial cortex is necessary for path integration in the dark.

      PubMed

      Elduayen, Coralie; Save, Etienne

      2014-10-01

      An increasing amount of data indicates that the retrosplenial cortex (RSC) plays a role in navigation and spatial memory. Moreover, it has been suggested that the RSC integrates mnemonic spatial features of the environment with self-motion information therefore enabling accurate path integration in darkness. This hypothesis rests on data obtained from animals trained in spatial memory tasks involving the conjoint use of allothetic and idiothetic information [8]. We examined the contribution of the RSC when animals are submitted to a path integration task with minimal memory requirement in light and dark. We found that RSC-lesioned rats exhibited a path integration deficit in the dark but not in the light. This suggests that the RSC is important for path integration and incorporates visuospatial information to maintain path integration accuracy.

    11. Path integrals, matter waves, and the double slit

      NASA Astrophysics Data System (ADS)

      Jones, Eric R.; Bach, Roger A.; Batelaan, Herman

      2015-11-01

      Basic explanations of the double slit diffraction phenomenon include a description of waves that emanate from two slits and interfere. The locations of the interference minima and maxima are determined by the phase difference of the waves. An optical wave, which has a wavelength λ and propagates a distance L, accumulates a phase of 2π L/λ . A matter wave, also having wavelength λ that propagates the same distance L, accumulates a phase of π L/λ , which is a factor of two different from the optical case. Nevertheless, in most situations, the phase difference, {{Δ }}\\varphi , for interfering matter waves that propagate distances that differ by {{Δ }}L, is approximately 2π {{Δ }}L/λ , which is the same value computed in the optical case. The difference between the matter and optical case hinders conceptual explanations of diffraction from two slits based on the matter-optics analogy. In the following article we provide a path integral description for matter waves with a focus on conceptual explanation. A thought experiment is provided to illustrate the validity range of the approximation {{Δ }}\\varphi ≈ 2π {{Δ }}L/λ .

    12. Quantum Thermal Bath for Path Integral Molecular Dynamics Simulation.

      PubMed

      Brieuc, Fabien; Dammak, Hichem; Hayoun, Marc

      2016-03-01

      The quantum thermal bath (QTB) method has been recently developed to account for the quantum nature of the nuclei by using standard molecular dynamics (MD) simulation. QTB-MD is an efficient but approximate method when dealing with strongly anharmonic systems, while path integral molecular dynamics (PIMD) gives exact results but in a huge amount of computation time. The QTB and PIMD methods have been combined in order to improve the PIMD convergence or correct the failures of the QTB-MD technique. Therefore, a new power spectral density of the random force within the QTB has been developed. A modified centroid-virial estimator of the kinetic energy, especially adapted to QTB-PIMD, has also been proposed. The method is applied to selected systems: a one-dimensional double-well system, a ferroelectric phase transition, and the position distribution of an hydrogen atom in a fuel cell material. The advantage of the QTB-PIMD method is its ability to give exact results with a more reasonable computation time for strongly anharmonic systems.

    13. Path integral regularization of pure Yang-Mills theory

      SciTech Connect

      Jacquot, J. L.

      2009-07-15

      In enlarging the field content of pure Yang-Mills theory to a cutoff dependent matrix valued complex scalar field, we construct a vectorial operator, which is by definition invariant with respect to the gauge transformation of the Yang-Mills field and with respect to a Stueckelberg type gauge transformation of the scalar field. This invariant operator converges to the original Yang-Mills field as the cutoff goes to infinity. With the help of cutoff functions, we construct with this invariant a regularized action for the pure Yang-Mills theory. In order to be able to define both the gauge and scalar fields kinetic terms, other invariant terms are added to the action. Since the scalar fields flat measure is invariant under the Stueckelberg type gauge transformation, we obtain a regularized gauge-invariant path integral for pure Yang-Mills theory that is mathematically well defined. Moreover, the regularized Ward-Takahashi identities describing the dynamics of the gauge fields are exactly the same as the formal Ward-Takahashi identities of the unregularized theory.

    14. A reductionist perspective on quantum statistical mechanics: Coarse-graining of path integrals.

      PubMed

      Sinitskiy, Anton V; Voth, Gregory A

      2015-09-01

      Computational modeling of the condensed phase based on classical statistical mechanics has been rapidly developing over the last few decades and has yielded important information on various systems containing up to millions of atoms. However, if a system of interest contains important quantum effects, well-developed classical techniques cannot be used. One way of treating finite temperature quantum systems at equilibrium has been based on Feynman's imaginary time path integral approach and the ensuing quantum-classical isomorphism. This isomorphism is exact only in the limit of infinitely many classical quasiparticles representing each physical quantum particle. In this work, we present a reductionist perspective on this problem based on the emerging methodology of coarse-graining. This perspective allows for the representations of one quantum particle with only two classical-like quasiparticles and their conjugate momenta. One of these coupled quasiparticles is the centroid particle of the quantum path integral quasiparticle distribution. Only this quasiparticle feels the potential energy function. The other quasiparticle directly provides the observable averages of quantum mechanical operators. The theory offers a simplified perspective on quantum statistical mechanics, revealing its most reductionist connection to classical statistical physics. By doing so, it can facilitate a simpler representation of certain quantum effects in complex molecular environments.

    15. A reductionist perspective on quantum statistical mechanics: Coarse-graining of path integrals

      SciTech Connect

      Sinitskiy, Anton V.; Voth, Gregory A.

      2015-09-07

      Computational modeling of the condensed phase based on classical statistical mechanics has been rapidly developing over the last few decades and has yielded important information on various systems containing up to millions of atoms. However, if a system of interest contains important quantum effects, well-developed classical techniques cannot be used. One way of treating finite temperature quantum systems at equilibrium has been based on Feynman’s imaginary time path integral approach and the ensuing quantum-classical isomorphism. This isomorphism is exact only in the limit of infinitely many classical quasiparticles representing each physical quantum particle. In this work, we present a reductionist perspective on this problem based on the emerging methodology of coarse-graining. This perspective allows for the representations of one quantum particle with only two classical-like quasiparticles and their conjugate momenta. One of these coupled quasiparticles is the centroid particle of the quantum path integral quasiparticle distribution. Only this quasiparticle feels the potential energy function. The other quasiparticle directly provides the observable averages of quantum mechanical operators. The theory offers a simplified perspective on quantum statistical mechanics, revealing its most reductionist connection to classical statistical physics. By doing so, it can facilitate a simpler representation of certain quantum effects in complex molecular environments.

    16. A reductionist perspective on quantum statistical mechanics: Coarse-graining of path integrals.

      PubMed

      Sinitskiy, Anton V; Voth, Gregory A

      2015-09-01

      Computational modeling of the condensed phase based on classical statistical mechanics has been rapidly developing over the last few decades and has yielded important information on various systems containing up to millions of atoms. However, if a system of interest contains important quantum effects, well-developed classical techniques cannot be used. One way of treating finite temperature quantum systems at equilibrium has been based on Feynman's imaginary time path integral approach and the ensuing quantum-classical isomorphism. This isomorphism is exact only in the limit of infinitely many classical quasiparticles representing each physical quantum particle. In this work, we present a reductionist perspective on this problem based on the emerging methodology of coarse-graining. This perspective allows for the representations of one quantum particle with only two classical-like quasiparticles and their conjugate momenta. One of these coupled quasiparticles is the centroid particle of the quantum path integral quasiparticle distribution. Only this quasiparticle feels the potential energy function. The other quasiparticle directly provides the observable averages of quantum mechanical operators. The theory offers a simplified perspective on quantum statistical mechanics, revealing its most reductionist connection to classical statistical physics. By doing so, it can facilitate a simpler representation of certain quantum effects in complex molecular environments. PMID:26342356

    17. Physics as an Integrative Theme in Oceanography.

      ERIC Educational Resources Information Center

      Myers, Richard L.

      1990-01-01

      The teaching of physics as an integral part of an undergraduate oceanography course is described. A general outline of oceanography and the corresponding physics topics is given. The objectives, organization, and difficulties of such a course are discussed. (CW)

    18. Navigational path integration by cortical neurons: origins in higher-order direction selectivity

      PubMed Central

      Page, William K.; Sato, Nobuya; Froehler, Michael T.; Vaughn, William

      2015-01-01

      Navigation relies on the neural processing of sensory cues about observer self-movement and spatial location. Neurons in macaque dorsal medial superior temporal cortex (MSTd) respond to visual and vestibular self-movement cues, potentially contributing to navigation and orientation. We moved monkeys on circular paths around a room while recording the activity of MSTd neurons. MSTd neurons show a variety of sensitivities to the monkey's heading direction, circular path through the room, and place in the room. Changing visual cues alters the relative prevalence of those response properties. Disrupting the continuity of self-movement paths through the environment disrupts path selectivity in a manner linked to the time course of single neuron responses. We hypothesize that sensory cues interact with the spatial and temporal integrative properties of MSTd neurons to derive path selectivity for navigational path integration supporting spatial orientation. PMID:25589586

    19. Path Integral Coarse-Graining Replica Exchange Method for Enhanced Sampling.

      PubMed

      Peng, Yuxing; Cao, Zhen; Zhou, Ruhong; Voth, Gregory A

      2014-09-01

      An enhanced conformational space sampling method is developed that utilizes replica exchange molecular dynamics between a set of imaginary time Feynman path integral replicas, each having an increasing degree of contraction (or coarse-graining) of the quasi-particle or "polymer beads" in the evaluation of the isomorphic ring-polymer potential energy terms. However, there is no contraction of beads in the effectively harmonic kinetic energy terms. The final replica in this procedure is the fully contracted one in which the potential energy is evaluated only at the centroid of the beads-and hence it is the classical distribution in the centroid variable-while the initial replica has the full degree (or even a heightened degree, if desired) of quantum delocalization and tunneling in the physical potential by the polymer necklace beads. The exchange between the different ring-polymer ensembles is governed by the Metropolis criteria to guarantee detailed balance. The method is applied successfully to several model systems, ranging from one-dimensional prototype rough energy landscape models having analytical solutions to the more realistic alanine dipeptide. A detailed comparison with the classical temperature-based replica exchange method shows an improved efficiency of this new method in the classical conformational space sampling due to coupling with the fictitious path integral (quantum) replicas. PMID:26588508

    20. Path-integral treatment of the Hulthén potential

      NASA Astrophysics Data System (ADS)

      Cai, J. M.; Cai, P. Y.; Inomata, A.

      1986-12-01

      An exact path-integral treatment of the s states for the Hulthén potential is presented. A procedure of the nontrivial change of variable accompanied by the local time rescaling is given in detail. The dimensional extension trick is applied to convert the radial path integral into a path integral in the SU(2) manifold. The exact energy spectrum and the normalized s-state eigenfunctions are obtained from the poles of the Green function and their residues, respectively. The Yukawa and the Coulomb limits are also discussed.

    1. The Many Faces of Integrated Physical Education.

      ERIC Educational Resources Information Center

      Placek, Judith H.; O'Sullivan, Mary

      1997-01-01

      Describes two forms of integrating physical education curriculum that are appropriate for elementary and secondary education (internal and external). Presents implications of integrated curriculum for teachers and schools, discusses implications for teacher education and physical education units, and examines the importance of subject matter…

    2. Tracking the Career Paths of Physics Teachers in Texas

      ERIC Educational Resources Information Center

      Mount, Jennifer; Marshall, Jill; Fuller, Edward

      2013-01-01

      In Texas, and some other states, there is a documented shortage of physics teachers, in terms of both number and qualifications. The shortage in Texas is due as much to teachers leaving the field (attrition) as to a lack of teachers entering. There are efforts under way to prepare more and better-qualified physics teachers who will stay in the…

    3. Physics Thematic Paths: Laboratorial Activities and Historical Scientific Instruments

      ERIC Educational Resources Information Center

      Pantano, O.; Talas, S.

      2010-01-01

      The Physics Department of Padua University keeps an important collection of historical physics instruments which alludes to the fruitful scientific activity of Padua through the centuries. This heritage led to the suggestion of setting up laboratory activities connected to the Museum collection for secondary school students. This article shows how…

    4. Integrated Physics at University Level.

      ERIC Educational Resources Information Center

      Bardeche, G.; And Others

      1980-01-01

      Updates the results of a six-year experimental course in physics whose goal was to translate the physicist's approach to science into an approach to the teaching of physics. Provides a course description and rationale and outlines the instructional procedures used. (GS)

    5. FUNdamental Integrative Training (FIT) for Physical Education

      ERIC Educational Resources Information Center

      Bukowsky, Michael; Faigenbaum, Avery D.; Myer, Gregory D.

      2014-01-01

      There is a growing need for physical education teachers to integrate different types of fitness activities into their lessons in order to provide opportunities for all students to learn and practice a variety of movement skills that will enhance their physical fitness and support free-time physical activity. An increased focus on age-appropriate…

    6. Continuum tensor network field states, path integral representations and spatial symmetries

      NASA Astrophysics Data System (ADS)

      Jennings, David; Brockt, Christoph; Haegeman, Jutho; Osborne, Tobias J.; Verstraete, Frank

      2015-06-01

      A natural way to generalize tensor network variational classes to quantum field systems is via a continuous tensor contraction. This approach is first illustrated for the class of quantum field states known as continuous matrix-product states (cMPS). As a simple example of the path-integral representation we show that the state of a dynamically evolving quantum field admits a natural representation as a cMPS. A completeness argument is also provided that shows that all states in Fock space admit a cMPS representation when the number of variational parameters tends to infinity. Beyond this, we obtain a well-behaved field limit of projected entangled-pair states (PEPS) in two dimensions that provide an abstract class of quantum field states with natural symmetries. We demonstrate how symmetries of the physical field state are encoded within the dynamics of an auxiliary field system of one dimension less. In particular, the imposition of Euclidean symmetries on the physical system requires that the auxiliary system involved in the class’ definition must be Lorentz-invariant. The physical field states automatically inherit entropy area laws from the PEPS class, and are fully described by the dissipative dynamics of a lower dimensional virtual field system. Our results lie at the intersection many-body physics, quantum field theory and quantum information theory, and facilitate future exchanges of ideas and insights between these disciplines.

    7. Four dimensional quantum gravity: The covariant path integral and quantization of the conformal factor

      SciTech Connect

      Mottola, E.

      1993-03-01

      After first reviewing the issue of vacuum energy (the cosmological constant problem) in the Einstein theory, the covariant path integral for gravity in four dimensions is constructed. The problem of vacuum energy requires determining the correct ground state of the quantum theory of gravity, and as such is an infrared problem, arising prior to and independently of the physics of the Planck scale. It is addressed in these lectures by studying the infrared fixed point of the low energy effective action of the conformal factor generated by the quantum trace anomaly in four dimensions. The infrared fixed point of this effective theory describes a conformally invariant phase of gravity with a vanishing effective cosmological term.

    8. Four dimensional quantum gravity: The covariant path integral and quantization of the conformal factor

      SciTech Connect

      Mottola, E.

      1993-01-01

      After first reviewing the issue of vacuum energy (the cosmological constant problem) in the Einstein theory, the covariant path integral for gravity in four dimensions is constructed. The problem of vacuum energy requires determining the correct ground state of the quantum theory of gravity, and as such is an infrared problem, arising prior to and independently of the physics of the Planck scale. It is addressed in these lectures by studying the infrared fixed point of the low energy effective action of the conformal factor generated by the quantum trace anomaly in four dimensions. The infrared fixed point of this effective theory describes a conformally invariant phase of gravity with a vanishing effective cosmological term.

    9. A brief view of known landmarks reorientates path integration in hamsters

      NASA Astrophysics Data System (ADS)

      Etienne, A. S.; Boulens, V.; Maurer, R.; Rowe, T.; Siegrist, C.

      In darkness, hamsters commute between their nest and a feeding site through path integration only, and therefore show cumulative errors in the return direction to the nest. We examined whether a brief presentation of familiar room cues could reset the path integrator. The hamsters could see the room cues either during, or at the end of, the outward journey to the food place, in a conflict situation where motion cues and visual information were set at variance. In both conditions, the animals used mainly visual information to return home. Thus, hamsters can determine their azimuth, and possibly their location, through a visual fix, and can reset their path integrator through the fix. This allows them to update their position during further locomotion in the dark and thus to compute a correct homing vector with respect to a visually induced reference frame. Taking episodic positional fixes may greatly enhance the functional value of path integration.

    10. Path Integral Calculation of GREEN’S Function for SCHRÖDINGER Equation in Unitary Gauge

      NASA Astrophysics Data System (ADS)

      Rozansky, L.

      Green’s function of Schrödinger equation is represented as a time-reparametrization invariant path integral. Unitary gauge fixing enables us to get the WKB preexponential factor without calculating determinants of operators containing derivatives.

    11. Comment of Fujikawa's path-integral derivation of the chiral anomaly

      SciTech Connect

      Einhorn, M.B.; Jones, D.R.T.

      1984-01-15

      It is shown that the path-integral derivation of the axial anomaly, when generalized correctly to the case of parity-violating gauge theories, gives the same result as the use of standard gauge-invariant regulators.

    12. Deciphering the hippocampal polyglot: the hippocampus as a path integration system.

      PubMed

      McNaughton, B L; Barnes, C A; Gerrard, J L; Gothard, K; Jung, M W; Knierim, J J; Kudrimoti, H; Qin, Y; Skaggs, W E; Suster, M; Weaver, K L

      1996-01-01

      Hippocampal 'place' cells and the head-direction cells of the dorsal presubiculum and related neocortical and thalamic areas appear to be part of a preconfigured network that generates an abstract internal representation of two-dimensional space whose metric is self-motion. It appears that viewpoint-specific visual information (e.g. landmarks) becomes secondarily bound to this structure by associative learning. These associations between landmarks and the preconfigured path integrator serve to set the origin for path integration and to correct for cumulative error. In the absence of familiar landmarks, or in darkness without a prior spatial reference, the system appears to adopt an initial reference for path integration independently of external cues. A hypothesis of how the path integration system may operate at the neuronal level is proposed. PMID:8576689

    13. A simple and accurate algorithm for path integral molecular dynamics with the Langevin thermostat.

      PubMed

      Liu, Jian; Li, Dezhang; Liu, Xinzijian

      2016-07-14

      We introduce a novel simple algorithm for thermostatting path integral molecular dynamics (PIMD) with the Langevin equation. The staging transformation of path integral beads is employed for demonstration. The optimum friction coefficients for the staging modes in the free particle limit are used for all systems. In comparison to the path integral Langevin equation thermostat, the new algorithm exploits a different order of splitting for the phase space propagator associated to the Langevin equation. While the error analysis is made for both algorithms, they are also employed in the PIMD simulations of three realistic systems (the H2O molecule, liquid para-hydrogen, and liquid water) for comparison. It is shown that the new thermostat increases the time interval of PIMD by a factor of 4-6 or more for achieving the same accuracy. In addition, the supplementary material shows the error analysis made for the algorithms when the normal-mode transformation of path integral beads is used.

    14. A simple and accurate algorithm for path integral molecular dynamics with the Langevin thermostat

      NASA Astrophysics Data System (ADS)

      Liu, Jian; Li, Dezhang; Liu, Xinzijian

      2016-07-01

      We introduce a novel simple algorithm for thermostatting path integral molecular dynamics (PIMD) with the Langevin equation. The staging transformation of path integral beads is employed for demonstration. The optimum friction coefficients for the staging modes in the free particle limit are used for all systems. In comparison to the path integral Langevin equation thermostat, the new algorithm exploits a different order of splitting for the phase space propagator associated to the Langevin equation. While the error analysis is made for both algorithms, they are also employed in the PIMD simulations of three realistic systems (the H2O molecule, liquid para-hydrogen, and liquid water) for comparison. It is shown that the new thermostat increases the time interval of PIMD by a factor of 4-6 or more for achieving the same accuracy. In addition, the supplementary material shows the error analysis made for the algorithms when the normal-mode transformation of path integral beads is used.

    15. Which way and how far? Tracking of translation and rotation information for human path integration.

      PubMed

      Chrastil, Elizabeth R; Sherrill, Katherine R; Hasselmo, Michael E; Stern, Chantal E

      2016-10-01

      Path integration, the constant updating of the navigator's knowledge of position and orientation during movement, requires both visuospatial knowledge and memory. This study aimed to develop a systems-level understanding of human path integration by examining the basic building blocks of path integration in humans. To achieve this goal, we used functional imaging to examine the neural mechanisms that support the tracking and memory of translational and rotational components of human path integration. Critically, and in contrast to previous studies, we examined movement in translation and rotation tasks with no defined end-point or goal. Navigators accumulated translational and rotational information during virtual self-motion. Activity in hippocampus, retrosplenial cortex (RSC), and parahippocampal cortex (PHC) increased during both translation and rotation encoding, suggesting that these regions track self-motion information during path integration. These results address current questions regarding distance coding in the human brain. By implementing a modified delayed match to sample paradigm, we also examined the encoding and maintenance of path integration signals in working memory. Hippocampus, PHC, and RSC were recruited during successful encoding and maintenance of path integration information, with RSC selective for tasks that required processing heading rotation changes. These data indicate distinct working memory mechanisms for translation and rotation, which are essential for updating neural representations of current location. The results provide evidence that hippocampus, PHC, and RSC flexibly track task-relevant translation and rotation signals for path integration and could form the hub of a more distributed network supporting spatial navigation. Hum Brain Mapp 37:3636-3655, 2016. © 2016 Wiley Periodicals, Inc.

    16. Which way and how far? Tracking of translation and rotation information for human path integration.

      PubMed

      Chrastil, Elizabeth R; Sherrill, Katherine R; Hasselmo, Michael E; Stern, Chantal E

      2016-10-01

      Path integration, the constant updating of the navigator's knowledge of position and orientation during movement, requires both visuospatial knowledge and memory. This study aimed to develop a systems-level understanding of human path integration by examining the basic building blocks of path integration in humans. To achieve this goal, we used functional imaging to examine the neural mechanisms that support the tracking and memory of translational and rotational components of human path integration. Critically, and in contrast to previous studies, we examined movement in translation and rotation tasks with no defined end-point or goal. Navigators accumulated translational and rotational information during virtual self-motion. Activity in hippocampus, retrosplenial cortex (RSC), and parahippocampal cortex (PHC) increased during both translation and rotation encoding, suggesting that these regions track self-motion information during path integration. These results address current questions regarding distance coding in the human brain. By implementing a modified delayed match to sample paradigm, we also examined the encoding and maintenance of path integration signals in working memory. Hippocampus, PHC, and RSC were recruited during successful encoding and maintenance of path integration information, with RSC selective for tasks that required processing heading rotation changes. These data indicate distinct working memory mechanisms for translation and rotation, which are essential for updating neural representations of current location. The results provide evidence that hippocampus, PHC, and RSC flexibly track task-relevant translation and rotation signals for path integration and could form the hub of a more distributed network supporting spatial navigation. Hum Brain Mapp 37:3636-3655, 2016. © 2016 Wiley Periodicals, Inc. PMID:27238897

    17. Equivalence of the Path Integral for Fermions in Cartesian and Spherical Coordinates

      NASA Astrophysics Data System (ADS)

      Briggs, Andrew; Camblong, Horacio E.; Ordóñez, Carlos R.

      2013-06-01

      The path integral calculation for the free energy of a spin-1/2 Dirac-fermion gas is performed in spherical polar coordinates for a flat space-time geometry. Its equivalence with the Cartesian-coordinate representation is explicitly established. This evaluation involves a relevant limiting case of the fermionic path integral in a Schwarzschild background, whose near-horizon limit has been shown to be related to black hole thermodynamics.

    18. Path integral and boson-fermion expansion in many-fermion systems: Lipkin model

      SciTech Connect

      Kaneko, K. )

      1989-11-01

      In a previous paper, a quantum-mechanical formulation involving both mean fields and independent-particle fields in many-fermion systems was proposed using the path-integral technique. Then the semiclassical calculation of the energy spectra was performed, and the quantization rule was derived by applying a stationary phase approximation on the path integral. In this paper, a boson-fermion expansion is derived from our formulation using Dirac quantization. As an illustration, the Lipkin model is utilized.

    19. Physically Important Integrals Without Calculus

      ERIC Educational Resources Information Center

      Reif, F.; Larkin, Jill H.

      1976-01-01

      Develops a geometric solution to be used with spatial integrals needed for finding electric and magnetic fields. The method is used in the calculation of the electric fields due to a uniformly charged plane, line and sphere. (CP)

    20. Environmental stability modulates the role of path integration in human navigation.

      PubMed

      Zhao, Mintao; Warren, William H

      2015-09-01

      Path integration has long been thought of as an obligatory process that automatically updates one's position and orientation during navigation. This has led to the hypotheses that path integration serves as a back-up system in case landmark navigation fails, and a reference system that detects discrepant landmarks. Three experiments tested these hypotheses in humans, using a homing task with a catch-trial paradigm. Contrary to the back-up system hypothesis, when stable landmarks unexpectedly disappeared on catch trials, participants were completely disoriented, and only then began to rely on path integration in subsequent trials (Experiment 1). Contrary to the reference system hypothesis, when stable landmarks unexpectedly shifted by 115° on catch trials, participants failed to detect the shift and were completely captured by the landmarks (Experiment 2). Conversely, when chronically unstable landmarks unexpectedly remained in place on catch trials, participants failed to notice and continued to navigate by path integration (Experiment 3). In the latter two cases, they gradually sensed the instability (or stability) of landmarks on later catch trials. These results demonstrate that path integration does not automatically serve as a back-up system, and does not function as a reference system on individual sorties, although it may contribute to monitoring environmental stability over time. Rather than being automatic, the roles of path integration and landmark navigation are thus dynamically modulated by the environmental context.

    1. Variational Perturbation Theory Path Integral Monte Carlo (VPT-PIMC): Trial Path Optimization Approach for Warm Dense Matter

      NASA Astrophysics Data System (ADS)

      Belof, Jonathan; Dubois, Jonathan

      2013-06-01

      Warm dense matter (WDM), the regime of degenerate and strongly coupled Coulomb systems, is of great interest due to it's importance in understanding astrophysical processes and high energy density laboratory experiments. Path Integral Monte Carlo (PIMC) presents a particularly attractive formalism for tackling outstanding questions in WDM, in that electron correlation can be calculated exactly, with the nuclear and electronic degrees of freedom on equal footing. Here we present an efficient means of solving the Feynman path integral numerically by variational optimization of a trial density matrix, a method originally proposed for simple potentials by Feynman and Kleinert, and we show that this formalism provides an accurate description of warm dense matter with a number of unique advantages over other PIMC approaches. An exchange interaction term is derived for the variationally optimized path, as well as a numerically efficient scheme for dealing with long-range electrostatics. Finally, we present results for the pair correlation functions and thermodynamic observables of the spin polarized electron gas, warm dense hydrogen and all-electron warm dense carbon within the presented VPT-PIMC formalism. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

    2. In Franklin's Path: Establishing Physics at the University of Pennsylvania

      NASA Astrophysics Data System (ADS)

      Halpern, Paul

      2008-04-01

      In 1751 Benjamin Franklin established the Academy of Philadelphia, the precursor of the University of Pennsylvania. Among its curricular mandates he envisioned included ``Natural and Mechanic History,'' using a popular text he suggested by No"el Antoine Pluche that encompassed optics and celestial dynamics among its subjects. This talk will trace the history of physics research and education at Penn from its establishment, to the appointment of the first designated physics professor, George Frederic Barker, in 1873, to the opening of the Randall Morgan Laboratory in 1901 under the directorship of Arthur Goodspeed, and finally to the inauguration of the David Rittenhouse Laboratory in 1954 under the university leadership of Gaylord Harnwell.

    3. The path dependency theory: analytical framework to study institutional integration. The case of France

      PubMed Central

      Trouvé, Hélène; Couturier, Yves; Etheridge, Francis; Saint-Jean, Olivier; Somme, Dominique

      2010-01-01

      Background The literature on integration indicates the need for an enhanced theorization of institutional integration. This article proposes path dependence as an analytical framework to study the systems in which integration takes place. Purpose PRISMA proposes a model for integrating health and social care services for older adults. This model was initially tested in Quebec. The PRISMA France study gave us an opportunity to analyze institutional integration in France. Methods A qualitative approach was used. Analyses were based on semi-structured interviews with actors of all levels of decision-making, observations of advisory board meetings, and administrative documents. Results Our analyses revealed the complexity and fragmentation of institutional integration. The path dependency theory, which analyzes the change capacity of institutions by taking into account their historic structures, allows analysis of this situation. The path dependency to the Bismarckian system and the incomplete reforms of gerontological policies generate the coexistence and juxtaposition of institutional systems. In such a context, no institution has sufficient ability to determine gerontology policy and build institutional integration by itself. Conclusion Using path dependence as an analytical framework helps to understand the reasons why institutional integration is critical to organizational and clinical integration, and the complex construction of institutional integration in France. PMID:20689740

    4. How Do They Get Here?: Paths into Physics Education Research

      ERIC Educational Resources Information Center

      Barthelemy, Ramon S.; Henderson, Charles; Grunert, Megan L.

      2013-01-01

      Physics education research (PER) is a relatively new and rapidly growing area of Ph.D. specialization. To sustain the field of PER, a steady pipeline of talented scholars needs to be developed and supported. One aspect of building this pipeline is understanding how students come to graduate and postdoctoral work in PER and what their career goals…

    5. Physical modeling of the feedback path in hearing aids with application to adaptive feedback cancellation

      NASA Astrophysics Data System (ADS)

      Hayes, Joanna L.; Rafaely, Boaz

      2002-05-01

      Hearing aid system modeling based on two-port network theory has been used previously to study the forward gain and the feedback path in hearing aids. The two-port modeling approach is employed in this work to develop an analytic model of the feedback path by reducing the model matrices to simplified analytic expressions. Such an analytic model can simulate the frequency response of the feedback path given the values of relatively few physical parameters such as vent dimensions. The model was extended to include variability in the feedback path due to slit leaks, for example. The analytic model was then incorporated in an adaptive feedback cancellation system, where the physical parameters of the model were adapted to match the actual feedback path and cancel the feedback signal. In the initial stage of this study, the ability of the model to match the frequency response of various measured feedback paths was studied using numerical optimization. Then, an adaptive filtering configuration based on the physical model was developed and studied using computer simulations. Results show that this new approach to adaptive feedback cancellation has the potential to improve both adaptation speed and performance robustness.

    6. Tracking the Career Paths of Physics Teachers in Texas

      NASA Astrophysics Data System (ADS)

      Mount, Jennifer; Marshall, Jill; Fuller, Edward

      2013-10-01

      In Texas, and some other states, there is a documented shortage of physics teachers, in terms of both number and qualifications. The shortage in Texas is due as much to teachers leaving the field (attrition) as to a lack of teachers entering. There are efforts under way to prepare more and better-qualified physics teachers who will stay in the field longer,2 but increasing the overall supply and retention will not necessarily address localized teacher shortages. To investigate this issue, we obtained a database cataloging every teacher who taught science in Texas public schools from 2003 to 2008, indicating the school where they taught during each of those years, the subjects they taught, and their route to certification. This allowed us to track not only teachers entering and leaving the public school system, but also migration between schools within the system. We found that migration poses a much bigger problem than attrition for some schools. We also found patterns in the movement of physics teachers in Texas that we would not necessarily have predicted and that varied substantially depending on certification.

    7. Ensemble variance in free energy calculations by thermodynamic integration: theory, optimal "Alchemical" path, and practical solutions.

      PubMed

      Blondel, Arnaud

      2004-05-01

      Thermodynamic integration is a widely used method to calculate and analyze the effect of a chemical modification on the free energy of a chemical or biochemical process, for example, the impact of an amino acid substitution on protein association. Numerical fluctuations can introduce large uncertainties, limiting the domain of application of the method. The parametric energy function describing the chemical modification in the thermodynamic integration, the "Alchemical path," determines the amplitudes of the fluctuations. In the present work, I propose a measure of the fluctuations in the thermodynamic integration and an approach to search for a parametric energy path minimizing that measure. The optimal path derived with this approach is very close to the theoretical minimum of the measure, but produces nonergodic sampling. Nevertheless, this path is used to guide the design of a practical and efficient path producing correct sampling. The convergence with this practical path is evaluated on test cases, and compares favorably with that of other methods such as power or polynomial path, soft-core van der Waals, and some other approaches presented in the literature.

    8. Path-Integration Computation of the Transport Properties of Polymers Nanoparticles and Complex Biological Structures

      NASA Astrophysics Data System (ADS)

      Douglas, Jack

      2014-03-01

      One of the things that puzzled me when I was a PhD student working under Karl Freed was the curious unity between the theoretical descriptions of excluded volume interactions in polymers, the hydrodynamic properties of polymers in solution, and the critical properties of fluid mixtures, gases and diverse other materials (magnets, superfluids,etc.) when these problems were formally expressed in terms of Wiener path integration and the interactions treated through a combination of epsilon expansion and renormalization group (RG) theory. It seemed that only the interaction labels changed from one problem to the other. What do these problems have in common? Essential clues to these interrelations became apparent when Karl Freed, myself and Shi-Qing Wang together began to study polymers interacting with hyper-surfaces of continuously variable dimension where the Feynman perturbation expansions could be performed through infinite order so that we could really understand what the RG theory was doing. It is evidently simply a particular method for resuming perturbation theory, and former ambiguities no longer existed. An integral equation extension of this type of exact calculation to ``surfaces'' of arbitrary fixed shape finally revealed the central mathematical object that links these diverse physical models- the capacity of polymer chains, whose value vanishes at the critical dimension of 4 and whose magnitude is linked to the friction coefficient of polymer chains, the virial coefficient of polymers and the 4-point function of the phi-4 field theory,...Once this central object was recognized, it then became possible solve diverse problems in material science through the calculation of capacity, and related ``virials'' properties, through Monte Carlo sampling of random walk paths. The essential ideas of this computational method are discussed and some applications given to non-trivial problems: nanotubes treated as either rigid rods or ensembles worm-like chains having

    9. Mnemonic discrimination relates to perforant path integrity: An ultra-high resolution diffusion tensor imaging study.

      PubMed

      Bennett, Ilana J; Stark, Craig E L

      2016-03-01

      Pattern separation describes the orthogonalization of similar inputs into unique, non-overlapping representations. This computational process is thought to serve memory by reducing interference and to be mediated by the dentate gyrus of the hippocampus. Using ultra-high in-plane resolution diffusion tensor imaging (hrDTI) in older adults, we previously demonstrated that integrity of the perforant path, which provides input to the dentate gyrus from entorhinal cortex, was associated with mnemonic discrimination, a behavioral outcome designed to load on pattern separation. The current hrDTI study assessed the specificity of this perforant path integrity-mnemonic discrimination relationship relative to other cognitive constructs (identified using a factor analysis) and white matter tracts (hippocampal cingulum, fornix, corpus callosum) in 112 healthy adults (20-87 years). Results revealed age-related declines in integrity of the perforant path and other medial temporal lobe (MTL) tracts (hippocampal cingulum, fornix). Controlling for global effects of brain aging, perforant path integrity related only to the factor that captured mnemonic discrimination performance. Comparable integrity-mnemonic discrimination relationships were also observed for the hippocampal cingulum and fornix. Thus, whereas perforant path integrity specifically relates to mnemonic discrimination, mnemonic discrimination may be mediated by a broader MTL network.

    10. Physics Research Integrated Development Environment (PRIDE)

      SciTech Connect

      Burton, J.; Cormell, L.

      1993-12-01

      Past efforts to implement a Software Engineering approach to High Energy Physics computing have been met with significant resistance and have been, in many cases, only marginally successful. At least a portion of the problem has been the Lick of an integrated development environment, tailored to High Energy Physics and incorporating a suite of Computer Aided Software Engineering tools. The Superconducting Super Collider Physics Research Division Computing Department is implementing pilot projects to develop just such an environment.

    11. Automatic Tool Path Generation for Robot Integrated Surface Sculpturing System

      NASA Astrophysics Data System (ADS)

      Zhu, Jiang; Suzuki, Ryo; Tanaka, Tomohisa; Saito, Yoshio

      In this paper, a surface sculpturing system based on 8-axis robot is proposed, the CAD/CAM software and tool path generation algorithm for this sculpturing system are presented. The 8-axis robot is composed of a 6-axis manipulator and a 2-axis worktable, it carves block of polystyrene foams by heated cutting tools. Multi-DOF (Degree of Freedom) robot benefits from the faster fashion than traditional RP (Rapid Prototyping) methods and more flexibility than CNC machining. With its flexibility driven from an 8-axis configuration, as well as efficient custom-developed software for rough cutting and finish cutting, this surface sculpturing system can carve sculptured surface accurately and efficiently.

    12. How do they get here?: Paths into physics education research

      NASA Astrophysics Data System (ADS)

      Barthelemy, Ramón S.; Henderson, Charles; Grunert, Megan L.

      2013-12-01

      Physics education research (PER) is a relatively new and rapidly growing area of Ph.D. specialization. To sustain the field of PER, a steady pipeline of talented scholars needs to be developed and supported. One aspect of building this pipeline is understanding how students come to graduate and postdoctoral work in PER and what their career goals are. This paper presents the first study on the experiences and career pathways of students in PER. Data were collected through open-ended interviews with 13 graduate students and postdoctoral scholars in PER. Results show that many of these PER graduate students and postdoctoral scholars were not aware of PER as undergraduates. PER graduate students that were aware of PER as undergraduates chose to study PER as they were applying to graduate schools. The graduate school experiences of the interviewees were overwhelmingly positive, with participants reporting a positive climate that was facilitated by communicative and productive relationships with their advisors. However, some participants reported concerns about the acceptance of PER within some departments, including open hostility towards the field. The majority of participants were interested in pursuing a career as a university faculty member, with more participants preferring a position at a research-intensive university. These results suggest that a further large-scale study of graduate students in PER may be able to highlight the field as being a leader in student mentoring and community development while collecting important demographic information that could show PER to have more gender diversity than other subfields of physics.

    13. Effects of stress paths on physical properties of sediments at the Nankai Trough subduction zone

      NASA Astrophysics Data System (ADS)

      Kitajima, H.; Saffer, D. M.

      2011-12-01

      Stress states are one of the most important factors governing deformation modes and fault strength. In subduction systems where tectonic stress is large, sediments are subjected to complicated stress conditions in time and space. Because direct measurements of stress are very limited, stress conditions at depths have been estimated by combining seismic reflection data with empirical relations between compressional-wave, porosity, and effective stress [Tsuji et al., 2008; Tobin and Saffer, 2009]. However, most of the empirical relations are derived from experiments conducted under isotropic conditions, and do not account for the more complicated stress states expected in active subduction-accretion complexes. In this study, we aim to derive relations between physical properties and stress states from triaxial deformation experiments on sediments. During the Integrated Ocean Drilling Program (IODP) Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) Expeditions 314, 315, 319, 322, and 333, core samples were recovered from shallow boreholes into the accretionary prism and two sites seaward of the deformation front (reference sites). We used core samples from reference sites (Sites C0011 and C0012) for this study because they represent input material for the subduction system, and have not been subjected to tectonic compression in the accretionary wedge. In our deformation tests, samples are loaded under a range of different stress paths including isotropic loading, triaxial compression, and triaxial extension by controlling axial stress (up to 100 MPa), confining pressure (up to 100 MPa), and pore pressure (0.5-28 MPa). During tests, all pressures, axial displacement, and pore volume change were monitored. Permeability, and ultrasonic velocity were also measured during the tests. Two experiments have been conducted on samples taken from the core 322-C0011B-19R-5 (Lower Shikoku Basin hemipelagic mudstone, initial porosity of 43 %). The first test was conducted

    14. A path-integral Langevin equation treatment of low-temperature doped helium clusters

      NASA Astrophysics Data System (ADS)

      Ing, Christopher; Hinsen, Konrad; Yang, Jing; Zeng, Toby; Li, Hui; Roy, Pierre-Nicholas

      2012-06-01

      We present an implementation of path integral molecular dynamics for sampling low temperature properties of doped helium clusters using Langevin dynamics. The robustness of the path integral Langevin equation and white-noise Langevin equation [M. Ceriotti, M. Parrinello, T. E. Markland, and D. E. Manolopoulos, J. Chem. Phys. 133, 124104 (2010)], 10.1063/1.3489925 sampling methods are considered for those weakly bound systems with comparison to path integral Monte Carlo (PIMC) in terms of efficiency and accuracy. Using these techniques, convergence studies are performed to confirm the systematic error reduction introduced by increasing the number of discretization steps of the path integral. We comment on the structural and energetic evolution of HeN-CO2 clusters from N = 1 to 20. To quantify the importance of both rotations and exchange in our simulations, we present a chemical potential and calculated band origin shifts as a function of cluster size utilizing PIMC sampling that includes these effects. This work also serves to showcase the implementation of path integral simulation techniques within the molecular modelling toolkit [K. Hinsen, J. Comp. Chem. 21, 79 (2000)], 10.1002/(SICI)1096-987X(20000130)21:2<79::AID-JCC1>3.0.CO;2-B, an open-source molecular simulation package.

    15. Feynman path integral application on deriving black-scholes diffusion equation for european option pricing

      NASA Astrophysics Data System (ADS)

      Utama, Briandhika; Purqon, Acep

      2016-08-01

      Path Integral is a method to transform a function from its initial condition to final condition through multiplying its initial condition with the transition probability function, known as propagator. At the early development, several studies focused to apply this method for solving problems only in Quantum Mechanics. Nevertheless, Path Integral could also apply to other subjects with some modifications in the propagator function. In this study, we investigate the application of Path Integral method in financial derivatives, stock options. Black-Scholes Model (Nobel 1997) was a beginning anchor in Option Pricing study. Though this model did not successfully predict option price perfectly, especially because its sensitivity for the major changing on market, Black-Scholes Model still is a legitimate equation in pricing an option. The derivation of Black-Scholes has a high difficulty level because it is a stochastic partial differential equation. Black-Scholes equation has a similar principle with Path Integral, where in Black-Scholes the share's initial price is transformed to its final price. The Black-Scholes propagator function then derived by introducing a modified Lagrange based on Black-Scholes equation. Furthermore, we study the correlation between path integral analytical solution and Monte-Carlo numeric solution to find the similarity between this two methods.

    16. Travel distance estimation from visual motion by leaky path integration.

      PubMed

      Lappe, Markus; Jenkin, Michael; Harris, Laurence R

      2007-06-01

      Visual motion can be a cue to travel distance when the motion signals are integrated. Distance estimates from visually simulated self-motion are imprecise, however. Previous work in our labs has given conflicting results on the imprecision: experiments by Frenz and Lappe had suggested a general underestimation of travel distance, while results from Redlick, Jenkin and Harris had shown an overestimation of travel distance. Here we describe a collaborative study that resolves the conflict by tracing it to differences in the tasks given to the subjects. With an identical set of subjects and identical visual motion simulation we show that underestimation of travel distance occurs when the task involves a judgment of distance from the starting position, and that overestimation of travel distance occurs when the task requires a judgment of the remaining distance to a particular target position. We present a leaky integrator model that explains both effects with a single mechanism. In this leaky integrator model we introduce the idea that, depending on the task, either the distance from start, or the distance to target is used as a state variable. The state variable is updated during the movement by integration over the space covered by the movement, rather than over time. In this model, travel distance mis-estimation occurs because the integration leaks and because the transformation of visual motion to travel distance involves a gain factor. Mis-estimates in both tasks can be explained with the same leak rate and gain in both conditions. Our results thus suggest that observers do not simply integrate traveled distance and then relate it to the task. Instead, the internally represented variable is either distance from the origin or distance to the goal, whichever is relevant.

    17. Cyber/Physical Security Vulnerability Assessment Integration

      SciTech Connect

      MacDonald, Douglas G.; Clements, Samuel L.; Patrick, Scott W.; Perkins, Casey J.; Muller, George; Lancaster, Mary J.; Hutton, William J.

      2013-02-28

      Securing high value and critical assets is one of the biggest challenges facing this nation and others around the world. In modern integrated systems, there are four potential modes of attack available to an adversary: • physical only attack, • cyber only attack, • physical-enabled cyber attack, • cyber-enabled physical attack. Blended attacks involve an adversary working in one domain to reduce system effectiveness in another domain. This enables the attacker to penetrate further into the overall layered defenses. Existing vulnerability assessment (VA) processes and software tools which predict facility vulnerabilities typically evaluate the physical and cyber domains separately. Vulnerabilities which result from the integration of cyber-physical control systems are not well characterized and are often overlooked by existing assessment approaches. In this paper, we modified modification of the timely detection methodology, used for decades in physical security VAs, to include cyber components. The Physical and Cyber Risk Analysis Tool (PACRAT) prototype illustrates an integrated vulnerability assessment that includes cyber-physical interdependencies. Information about facility layout, network topology, and emplaced safeguards is used to evaluate how well suited a facility is to detect, delay, and respond to attacks, to identify the pathways most vulnerable to attack, and to evaluate how often safeguards are compromised for a given threat or adversary type. We have tested the PACRAT prototype on critical infrastructure facilities and the results are promising. Future work includes extending the model to prescribe the recommended security improvements via an automated cost-benefit analysis.

    18. Computational Acoustics: Computational PDEs, Pseudodifferential Equations, Path Integrals, and All That Jazz

      NASA Astrophysics Data System (ADS)

      Fishman, Louis

      2000-11-01

      The role of mathematical modeling in the physical sciences will be briefly addressed. Examples will focus on computational acoustics, with applications to underwater sound propagation, electromagnetic modeling, optics, and seismic inversion. Direct and inverse wave propagation problems in both the time and frequency domains will be considered. Focusing on fixed-frequency (elliptic) wave propagation problems, the usual, two-way, partial differential equation formulation will be exactly reformulated, in a well-posed manner, as a one-way (marching) problem. This is advantageous for both direct and inverse considerations, as well as stochastic modeling problems. The reformulation will require the introduction of pseudodifferential operators and their accompanying phase space analysis (calculus), in addition to path integral representations for the fundamental solutions and their subsequent computational algorithms. Unlike the more traditional, purely numerical applications of, for example, finite-difference and finite-element methods, this approach, in effect, writes the exact, or, more generally, the asymptotically correct, answer as a functional integral and, subsequently, computes it directly. The overall computational philosophy is to combine analysis, asymptotics, and numerical methods to attack complicated, real-world problems. Exact and asymptotic analysis will stress the complementary nature of the direct and inverse formulations, as well as indicating the explicit structural connections between the time- and frequency-domain solutions.

    19. Path Integrals, Fourier Transforms, and Feynman's Operational Calculus

      SciTech Connect

      Ahn, Byung Moo; Johnson, G. W.

      1998-03-15

      The disentangling process is the key to Feynman's operational calculus for noncommuting operators. The main result of his heuristic calculations deals with disentangling an exponential factor. We use the Wiener and Feynman integrals to make this disentangling (or time-ordering) mathematically rigorous in the case where the analytic functions from earlier work are replaced by Fourier transforms of complex-valued measures.

    20. An integration of integrated information theory with fundamental physics.

      PubMed

      Barrett, Adam B

      2014-01-01

      To truly eliminate Cartesian ghosts from the science of consciousness, we must describe consciousness as an aspect of the physical. Integrated Information Theory states that consciousness arises from intrinsic information generated by dynamical systems; however existing formulations of this theory are not applicable to standard models of fundamental physical entities. Modern physics has shown that fields are fundamental entities, and in particular that the electromagnetic field is fundamental. Here I hypothesize that consciousness arises from information intrinsic to fundamental fields. This hypothesis unites fundamental physics with what we know empirically about the neuroscience underlying consciousness, and it bypasses the need to consider quantum effects.

    1. MPI CyberMotion Simulator: implementation of a novel motion simulator to investigate multisensory path integration in three dimensions.

      PubMed

      Barnett-Cowan, Michael; Meilinger, Tobias; Vidal, Manuel; Teufel, Harald; Bülthoff, Heinrich H

      2012-01-01

      Path integration is a process in which self-motion is integrated over time to obtain an estimate of one's current position relative to a starting point (1). Humans can do path integration based exclusively on visual (2-3), auditory (4), or inertial cues (5). However, with multiple cues present, inertial cues - particularly kinaesthetic - seem to dominate (6-7). In the absence of vision, humans tend to overestimate short distances (<5 m) and turning angles (<30°), but underestimate longer ones (5). Movement through physical space therefore does not seem to be accurately represented by the brain. Extensive work has been done on evaluating path integration in the horizontal plane, but little is known about vertical movement (see (3) for virtual movement from vision alone). One reason for this is that traditional motion simulators have a small range of motion restricted mainly to the horizontal plane. Here we take advantage of a motion simulator (8-9) with a large range of motion to assess whether path integration is similar between horizontal and vertical planes. The relative contributions of inertial and visual cues for path navigation were also assessed. 16 observers sat upright in a seat mounted to the flange of a modified KUKA anthropomorphic robot arm. Sensory information was manipulated by providing visual (optic flow, limited lifetime star field), vestibular-kinaesthetic (passive self motion with eyes closed), or visual and vestibular-kinaesthetic motion cues. Movement trajectories in the horizontal, sagittal and frontal planes consisted of two segment lengths (1st: 0.4 m, 2nd: 1 m; ±0.24 m/s(2) peak acceleration). The angle of the two segments was either 45° or 90°. Observers pointed back to their origin by moving an arrow that was superimposed on an avatar presented on the screen. Observers were more likely to underestimate angle size for movement in the horizontal plane compared to the vertical planes. In the frontal plane observers were more likely to

    2. MPI CyberMotion Simulator: implementation of a novel motion simulator to investigate multisensory path integration in three dimensions.

      PubMed

      Barnett-Cowan, Michael; Meilinger, Tobias; Vidal, Manuel; Teufel, Harald; Bülthoff, Heinrich H

      2012-05-10

      Path integration is a process in which self-motion is integrated over time to obtain an estimate of one's current position relative to a starting point (1). Humans can do path integration based exclusively on visual (2-3), auditory (4), or inertial cues (5). However, with multiple cues present, inertial cues - particularly kinaesthetic - seem to dominate (6-7). In the absence of vision, humans tend to overestimate short distances (<5 m) and turning angles (<30°), but underestimate longer ones (5). Movement through physical space therefore does not seem to be accurately represented by the brain. Extensive work has been done on evaluating path integration in the horizontal plane, but little is known about vertical movement (see (3) for virtual movement from vision alone). One reason for this is that traditional motion simulators have a small range of motion restricted mainly to the horizontal plane. Here we take advantage of a motion simulator (8-9) with a large range of motion to assess whether path integration is similar between horizontal and vertical planes. The relative contributions of inertial and visual cues for path navigation were also assessed. 16 observers sat upright in a seat mounted to the flange of a modified KUKA anthropomorphic robot arm. Sensory information was manipulated by providing visual (optic flow, limited lifetime star field), vestibular-kinaesthetic (passive self motion with eyes closed), or visual and vestibular-kinaesthetic motion cues. Movement trajectories in the horizontal, sagittal and frontal planes consisted of two segment lengths (1st: 0.4 m, 2nd: 1 m; ±0.24 m/s(2) peak acceleration). The angle of the two segments was either 45° or 90°. Observers pointed back to their origin by moving an arrow that was superimposed on an avatar presented on the screen. Observers were more likely to underestimate angle size for movement in the horizontal plane compared to the vertical planes. In the frontal plane observers were more likely to

    3. On the path integral representation of the Wigner function and the Barker-Murray ansatz

      NASA Astrophysics Data System (ADS)

      Sels, Dries; Brosens, Fons; Magnus, Wim

      2012-01-01

      The propagator of the Wigner function is constructed from the Wigner-Liouville equation as a phase space path integral over a new effective Lagrangian. In contrast to a paper by Barker and Murray (1983) [1], we show that the path integral can in general not be written as a linear superposition of classical phase space trajectories over a family of non-local forces. Instead, we adopt a saddle point expansion to show that the semiclassical Wigner function is a linear superposition of classical solutions for a different set of non-local time dependent forces. As shown by a simple example the specific form of the path integral makes the formulation ideal for Monte Carlo simulation.

    4. Path-integral Monte Carlo study of asymmetric quantum quadrupolar rotors with fourth-order propagators

      NASA Astrophysics Data System (ADS)

      Park, Sungjin; Shin, Hyeondeok; Kwon, Yongkyung

      2012-08-01

      The recently-proposed fourth-order propagator based on the multi-product expansion has been applied to path-integral Monte Carlo calculations for asymmetric quantum quadruploar rotors fixed at face-centered cubic lattice sites. The rotors are observed to undergo an orientational orderdisorder phase transition at a low temperature when the electric quadrupole-quadrupole interaction is strong enough. At intermediate interaction strength, a further decrease of temperature after the first transition to the ordered phase results in a reentrant transition back to the disordered phase. The theoretical phase diagram of these asymmetric rotors determined by using fourth-order path-integral Monte Carlo calculations is found to be in good quantitative agreement with the experimental one for solid hydrogen deuteride. This leads us to conclude that the fourth-order propagator can be effectively implemented for an accurate path-integral Monte Carlo calculation of a quantum many-body system with rotational degrees of freedom.

    5. Path integral action and Chern-Simons quantum mechanics in noncommutative plane

      NASA Astrophysics Data System (ADS)

      Gangopadhyay, Sunandan; Scholtz, Frederik G.

      2014-06-01

      In this paper, the connection between the path integral representation of propagators in the coherent state basis with additional degrees of freedom (Rohwer et al 2010 J. Phys. A: Math. Theor. 43 345302) and the one without any such degrees of freedom (Gangopadhyay and Scholtz 2009 Phys. Rev. Lett. 102 241602) is established. We further demonstrate that the path integral formalism developed in the noncommutative plane using the coherent state basis leads to a quantum mechanics involving a Chern-Simons term in momentum which is of noncommutative origin. The origin of this term from the Bopp-shift point of view is also investigated. A relativistic generalization of the action derived from the path integral framework is then proposed. Finally, we construct a map from the commutative quantum Hall system to a particle in a noncommutative plane moving in a magnetic field. The value of the noncommutative parameter from this map is then computed and is found to agree with previous results.

    6. Path integration in desert ants, Cataglyphis: how to make a homing ant run away from home.

      PubMed

      Andel, David; Wehner, Rüdiger

      2004-07-22

      Path integration is an ant's lifeline on any of its foraging journeys. It results in a homebound global vector that continually informs the animal about its position relative to its starting point. Here, we use a particular (repeated training and displacement) paradigm, in which homebound ants are made to follow a familiar landmark route repeatedly from the feeder to the nest, even after they have arrived at the nest. The results show that during the repeated landmark-guided home runs the ant's path integrator runs continually, so that the current state of the homebound vector increasingly exceeds the reference state. The dramatic result is that the homing ants run away from home. This finding implies that the ants do not rely on cartographic information about the locations of nest and feeder (e.g. that the nest is always south of the feeder), but just behave according to what the state of their egocentric path integrator tells them.

    7. Managing the physics of the economics of integrated health care.

      PubMed

      Zismer, Daniel K; Werner, Mark J

      2012-01-01

      The physics metaphor, as applied to the economics (and financial performance) of the integrated health system, seems appropriate when considered together with the nine principles of management framework provided. The nature of the integrated design enhances leaders' management potential as they consider organizational operations and strategy in the markets ahead. One question begged by this argument for the integrated design is the durability, efficiency and ultimate long-term survivability of the more "traditional" community health care delivery models, which, by design, are fragmented, internally competitive and less capital efficient. They also cannot exploit the leverage of teams, optimal access management or the pursuit of revenues made available in many forms. For those who wish to move from the traditional to the more integrated community health system designs (especially those who have not yet started the journey), the path requires: * Sufficient balance sheet capacity to fund the integration process-especially as the model requires physician practice acquisitions and electronic health record implementations * A well-prepared board13, 14 * A functional, durable and sustainable physician services enterprise design * A redesigned organizational and governance structure * Favorable internal financial incentives alignment design * Effective accountable physician leadership * Awareness that the system is not solely a funding strategy for acquired physicians, rather a fully -.. committed clinical and business model, one in which patient-centered integrated care is the core service (and not acute care hospital-based services) A willingness to create and exploit the implied and inherent potential of an integrated design and unified brand Last, it's important to remember that an integrated health system is a tool that creates a "new potential" (a physics metaphor reference, one last time). The design doesn't operate itself. Application of the management principles

    8. PathJam: a new service for integrating biological pathway information.

      PubMed

      Glez-Peña, Daniel; Reboiro-Jato, Miguel; Domínguez, Rubén; Gómez-López, Gonzalo; Pisano, David G; Fdez-Riverola, Florentino

      2010-10-28

      Biological pathways are crucial to much of the scientific research today including the study of specific biological processes related with human diseases. PathJam is a new comprehensive and freely accessible web-server application integrating scattered human pathway annotation from several public sources. The tool has been designed for both (i) being intuitive for wet-lab users providing statistical enrichment analysis of pathway annotations and (ii) giving support to the development of new integrative pathway applications. PathJam’s unique features and advantages include interactive graphs linking pathways and genes of interest, downloadable results in fully compatible formats, GSEA compatible output files and a standardized RESTful API.

    9. Path integral measure, constraints and ghosts for massive gravitons with a cosmological constant

      NASA Astrophysics Data System (ADS)

      Metaxas, Dimitrios

      2009-12-01

      For massive gravity in a de Sitter background one encounters problems of stability when the curvature is larger than the graviton mass. I analyze this situation from the path integral point of view and show that it is related to the conformal factor problem of Euclidean quantum (massless) gravity. When a constraint for massive gravity is incorporated and the proper treatment of the path integral measure is taken into account one finds that, for particular choices of the DeWitt metric on the space of metrics (in fact, the same choices as in the massless case), one obtains the opposite bound on the graviton mass.

    10. Path integral measure, constraints and ghosts for massive gravitons with a cosmological constant

      SciTech Connect

      Metaxas, Dimitrios

      2009-12-15

      For massive gravity in a de Sitter background one encounters problems of stability when the curvature is larger than the graviton mass. I analyze this situation from the path integral point of view and show that it is related to the conformal factor problem of Euclidean quantum (massless) gravity. When a constraint for massive gravity is incorporated and the proper treatment of the path integral measure is taken into account one finds that, for particular choices of the DeWitt metric on the space of metrics (in fact, the same choices as in the massless case), one obtains the opposite bound on the graviton mass.

    11. Enzymatic Kinetic Isotope Effects from Path-Integral Free Energy Perturbation Theory.

      PubMed

      Gao, J

      2016-01-01

      Path-integral free energy perturbation (PI-FEP) theory is presented to directly determine the ratio of quantum mechanical partition functions of different isotopologs in a single simulation. Furthermore, a double averaging strategy is used to carry out the practical simulation, separating the quantum mechanical path integral exactly into two separate calculations, one corresponding to a classical molecular dynamics simulation of the centroid coordinates, and another involving free-particle path-integral sampling over the classical, centroid positions. An integrated centroid path-integral free energy perturbation and umbrella sampling (PI-FEP/UM, or simply, PI-FEP) method along with bisection sampling was summarized, which provides an accurate and fast convergent method for computing kinetic isotope effects for chemical reactions in solution and in enzymes. The PI-FEP method is illustrated by a number of applications, to highlight the computational precision and accuracy, the rule of geometrical mean in kinetic isotope effects, enhanced nuclear quantum effects in enzyme catalysis, and protein dynamics on temperature dependence of kinetic isotope effects.

    12. Enzymatic Kinetic Isotope Effects from Path-Integral Free Energy Perturbation Theory.

      PubMed

      Gao, J

      2016-01-01

      Path-integral free energy perturbation (PI-FEP) theory is presented to directly determine the ratio of quantum mechanical partition functions of different isotopologs in a single simulation. Furthermore, a double averaging strategy is used to carry out the practical simulation, separating the quantum mechanical path integral exactly into two separate calculations, one corresponding to a classical molecular dynamics simulation of the centroid coordinates, and another involving free-particle path-integral sampling over the classical, centroid positions. An integrated centroid path-integral free energy perturbation and umbrella sampling (PI-FEP/UM, or simply, PI-FEP) method along with bisection sampling was summarized, which provides an accurate and fast convergent method for computing kinetic isotope effects for chemical reactions in solution and in enzymes. The PI-FEP method is illustrated by a number of applications, to highlight the computational precision and accuracy, the rule of geometrical mean in kinetic isotope effects, enhanced nuclear quantum effects in enzyme catalysis, and protein dynamics on temperature dependence of kinetic isotope effects. PMID:27498645

    13. An algorithm to find minimum free-energy paths using umbrella integration

      NASA Astrophysics Data System (ADS)

      Bohner, Matthias U.; Kästner, Johannes

      2012-07-01

      The calculation of free-energy barriers by umbrella sampling and many other methods is hampered by the necessity for an a priori choice of the reaction coordinate along which to sample. We avoid this problem by providing a method to search for saddle points on the free-energy surface in many coordinates. The necessary gradients and Hessians of the free energy are obtained by multidimensional umbrella integration. We construct the minimum free-energy path by following the gradient down to minima on the free-energy surface. The change of free energy along the path is obtained by integrating out all coordinates orthogonal to the path. While we expect the method to be applicable to large systems, we test it on the alanine dipeptide in vacuum. The minima, transition states, and free-energy barriers agree well with those obtained previously with other methods.

    14. Integrative Families and Systems Treatment: A Middle Path toward Integrating Common and Specific Factors in Evidence-Based Family Therapy

      ERIC Educational Resources Information Center

      Fraser, J. Scott; Solovey, Andrew D.; Grove, David; Lee, Mo Yee; Greene, Gilbert J.

      2012-01-01

      A moderate common factors approach is proposed as a synthesis or middle path to integrate common and specific factors in evidence-based approaches to high-risk youth and families. The debate in family therapy between common and specific factors camps is reviewed and followed by suggestions from the literature for synthesis and creative flexibility…

    15. Singular path-independent energy integrals for elastic bodies with thin elastic inclusions

      NASA Astrophysics Data System (ADS)

      Shcherbakov, V. V.

      2016-06-01

      An equilibrium problem for a two-dimensional homogeneous linear elastic body containing a thin elastic inclusion and an interfacial crack is considered. The thin inclusion is modeled within the framework of Euler-Bernoulli beam theory. An explicit formula for the first derivative of the energy functional with respect to the crack perturbation along the interface is presented. It is shown that the formulas for the derivative associated with translation and self-similar expansion of the crack are represented as path-independent integrals along smooth contour surrounding one or both crack tips. These path-independent integrals consist of regular and singular terms and are analogs of the well-known Eshelby-Cherepanov-Rice J-integral and Knowles-Sternberg M-integral.

    16. Theta rhythm of navigation: link between path integration and landmark navigation, episodic and semantic memory.

      PubMed

      Buzsáki, György

      2005-01-01

      Five key topics have been reverberating in hippocampal-entorhinal cortex (EC) research over the past five decades: episodic and semantic memory, path integration ("dead reckoning") and landmark ("map") navigation, and theta oscillation. We suggest that the systematic relations between single cell discharge and the activity of neuronal ensembles reflected in local field theta oscillations provide a useful insight into the relationship among these terms. In rats trained to run in direction-guided (1-dimensional) tasks, hippocampal cell assemblies discharge sequentially, with different assemblies active on opposite runs, i.e., place cells are unidirectional. Such tasks do not require map representation and are formally identical with learning sequentially occurring items in an episode. Hebbian plasticity, acting within the temporal window of the theta cycle, converts the travel distances into synaptic strengths between the sequentially activated and unidirectionally connected assemblies. In contrast, place representations by hippocampal neurons in 2-dimensional environments are typically omnidirectional, characteristic of a map. Generation of a map requires exploration, essentially a dead reckoning behavior. We suggest that omnidirectional navigation through the same places (junctions) during exploration gives rise to omnidirectional place cells and, consequently, maps free of temporal context. Analogously, multiple crossings of common junction(s) of episodes convert the common junction(s) into context-free or semantic memory. Theta oscillation can hence be conceived as the navigation rhythm through both physical and mnemonic space, facilitating the formation of maps and episodic/semantic memories.

    17. Accelerated path integral methods for atomistic simulations at ultra-low temperatures

      NASA Astrophysics Data System (ADS)

      Uhl, Felix; Marx, Dominik; Ceriotti, Michele

      2016-08-01

      Path integral methods provide a rigorous and systematically convergent framework to include the quantum mechanical nature of atomic nuclei in the evaluation of the equilibrium properties of molecules, liquids, or solids at finite temperature. Such nuclear quantum effects are often significant for light nuclei already at room temperature, but become crucial at cryogenic temperatures such as those provided by superfluid helium as a solvent. Unfortunately, the cost of converged path integral simulations increases significantly upon lowering the temperature so that the computational burden of simulating matter at the typical superfluid helium temperatures becomes prohibitive. Here we investigate how accelerated path integral techniques based on colored noise generalized Langevin equations, in particular the so-called path integral generalized Langevin equation thermostat (PIGLET) variant, perform in this extreme quantum regime using as an example the quasi-rigid methane molecule and its highly fluxional protonated cousin, CH5+. We show that the PIGLET technique gives a speedup of two orders of magnitude in the evaluation of structural observables and quantum kinetic energy at ultralow temperatures. Moreover, we computed the spatial spread of the quantum nuclei in CH4 to illustrate the limits of using such colored noise thermostats close to the many body quantum ground state.

    18. Integrated flight path planning system and flight control system for unmanned helicopters.

      PubMed

      Jan, Shau Shiun; Lin, Yu Hsiang

      2011-01-01

      This paper focuses on the design of an integrated navigation and guidance system for unmanned helicopters. The integrated navigation system comprises two systems: the Flight Path Planning System (FPPS) and the Flight Control System (FCS). The FPPS finds the shortest flight path by the A-Star (A*) algorithm in an adaptive manner for different flight conditions, and the FPPS can add a forbidden zone to stop the unmanned helicopter from crossing over into dangerous areas. In this paper, the FPPS computation time is reduced by the multi-resolution scheme, and the flight path quality is improved by the path smoothing methods. Meanwhile, the FCS includes the fuzzy inference systems (FISs) based on the fuzzy logic. By using expert knowledge and experience to train the FIS, the controller can operate the unmanned helicopter without dynamic models. The integrated system of the FPPS and the FCS is aimed at providing navigation and guidance to the mission destination and it is implemented by coupling the flight simulation software, X-Plane, and the computing software, MATLAB. Simulations are performed and shown in real time three-dimensional animations. Finally, the integrated system is demonstrated to work successfully in controlling the unmanned helicopter to operate in various terrains of a digital elevation model (DEM).

    19. Coherent-state path integrals in the continuum: The SU(2) case

      NASA Astrophysics Data System (ADS)

      Kordas, G.; Kalantzis, D.; Karanikas, A. I.

      2016-09-01

      We define the time-continuous spin coherent-state path integral in a way that is free from inconsistencies. The proposed definition is used to reproduce known exact results. Such a formalism opens new possibilities for applying approximations with improved accuracy and can be proven useful in a great variety of problems where spin Hamiltonians are used.

    20. Accelerated path integral methods for atomistic simulations at ultra-low temperatures.

      PubMed

      Uhl, Felix; Marx, Dominik; Ceriotti, Michele

      2016-08-01

      Path integral methods provide a rigorous and systematically convergent framework to include the quantum mechanical nature of atomic nuclei in the evaluation of the equilibrium properties of molecules, liquids, or solids at finite temperature. Such nuclear quantum effects are often significant for light nuclei already at room temperature, but become crucial at cryogenic temperatures such as those provided by superfluid helium as a solvent. Unfortunately, the cost of converged path integral simulations increases significantly upon lowering the temperature so that the computational burden of simulating matter at the typical superfluid helium temperatures becomes prohibitive. Here we investigate how accelerated path integral techniques based on colored noise generalized Langevin equations, in particular the so-called path integral generalized Langevin equation thermostat (PIGLET) variant, perform in this extreme quantum regime using as an example the quasi-rigid methane molecule and its highly fluxional protonated cousin, CH5 (+). We show that the PIGLET technique gives a speedup of two orders of magnitude in the evaluation of structural observables and quantum kinetic energy at ultralow temperatures. Moreover, we computed the spatial spread of the quantum nuclei in CH4 to illustrate the limits of using such colored noise thermostats close to the many body quantum ground state.

    1. Applications of Path Integral Langevin Dynamics to Weakly Bound Clusters and Biological Molecules

      NASA Astrophysics Data System (ADS)

      Ing, Christopher; Hinsen, Conrad; Yang, Jing; Roy, Pierre-Nicholas

      2011-06-01

      We present the use of path integral molecular dynamics (PIMD) in conjunction with the path integral Langevin equation thermostat for sampling systems that exhibit nuclear quantum effects, notably those at low temperatures or those consisting mainly of hydrogen or helium. To test this approach, the internal energy of doped helium clusters are compared with white-noise Langevin thermostatting and high precision path integral monte carlo (PIMC) simulations. We comment on the structural evolution of these clusters in the absence of rotation and exchange as a function of cluster size. To quantify the importance of both rotation and exchange in our PIMD simulation, we compute band origin shifts for (He)_N-CO_2 as a function of cluster size and compare to previously published experimental and theoretical shifts. A convergence study is presented to confirm the systematic error reduction introduced by increasing path integral beads for our implementation in the Molecular Modelling Toolkit (MMTK) software package. Applications to carbohydrates are explored at biological temperatures by calculating both equilibrium and dynamical properties using the methods presented. M. Ceriotti, M. Parrinello, and D. E. Manolopoulos, J Chem Phys 133, 124104. H. Li, N. Blinov, P.-N. Roy, and R. J. L. Roy, J Chem Phys 130, 144305.

    2. Path-dependent J-integral evaluations around an elliptical hole for large deformation theory

      NASA Astrophysics Data System (ADS)

      Unger, David J.

      2016-08-01

      An exact expression is obtained for a path-dependent J-integral for finite strains of an elliptical hole subject to remote tensile tractions under the Tresca deformation theory for a thin plate composed of non-work hardening material. Possible applications include an analytical resistance curve for the initial stage of crack propagation due to crack tip blunting.

    3. Route-segment odometry and its interactions with global path-integration.

      PubMed

      Collett, Thomas S; Collett, Matthew

      2015-06-01

      Insects such as desert ants and honeybees use visual memories to travel along familiar routes between their nest and a food-site. We trained Cataglyphis fortis foragers along a two-segment route to investigate whether they encode the lengths of route segments over which visual cues remain approximately constant. Our results support earlier studies suggesting that such route-segment odometry exists, and allows an individual to stop using a visual route memory at an appropriate point, even in the absence of any change in the visual surroundings. But we find that the behavioural effects of route-segment odometry are often complicated by interactions with guidance from the global path-integration system. If route-segment odometry and path-integration agree, they act together to produce a precise signal for search. If the endpoint of route-segment odometry arrives first, it does not trigger search but its effect can persist and cause guidance by path-integration to end early. Conversely, if ants start with their path-integration state at zero, they follow a route memory for no more than 3 m, irrespective of the route-segment length. A possible explanation for these results is that if one guidance system is made to overshoot its endpoint, it can cause the other to be cut short. PMID:25904159

    4. Deficits in landmark navigation and path integration after lesions of the interpeduncular nucleus.

      PubMed

      Clark, Benjamin J; Taube, Jeffrey S

      2009-06-01

      Experiments were designed to determine the role of the interpeduncular nucleus (IPN) in 3 forms of navigation: beacon, landmark, and path integration. In beacon navigation, animals reach goals using cues directly associated with them, whereas in landmark navigation animals use external cues to determine a direction and distance to goals. Path integration refers to the use of self-movement cues to obtain a trajectory to a goal. IPN-lesioned rats were tested in a food-carrying task in which they searched for food in an open field, and returned to a refuge after finding the food. Landmark navigation was evaluated during trials performed under lighted conditions and path integration was tested under darkened conditions, thus eliminating external cues. We report that IPN lesions increased the number of errors and reduced heading accuracy under both lighted and darkened conditions. Tests using a Morris water maze procedure indicated that IPN lesions produced moderate impairments in the landmark version of the water task, but left beacon navigation intact. These findings suggest that the IPN plays a fundamental role in landmark navigation and path integration.

    5. Teaching Basic Quantum Mechanics in Secondary School Using Concepts of Feynman Path Integrals Method

      ERIC Educational Resources Information Center

      Fanaro, Maria de los Angeles; Otero, Maria Rita; Arlego, Marcelo

      2012-01-01

      This paper discusses the teaching of basic quantum mechanics in high school. Rather than following the usual formalism, our approach is based on Feynman's path integral method. Our presentation makes use of simulation software and avoids sophisticated mathematical formalism. (Contains 3 figures.)

    6. Integrated Flight Path Planning System and Flight Control System for Unmanned Helicopters

      PubMed Central

      Jan, Shau Shiun; Lin, Yu Hsiang

      2011-01-01

      This paper focuses on the design of an integrated navigation and guidance system for unmanned helicopters. The integrated navigation system comprises two systems: the Flight Path Planning System (FPPS) and the Flight Control System (FCS). The FPPS finds the shortest flight path by the A-Star (A*) algorithm in an adaptive manner for different flight conditions, and the FPPS can add a forbidden zone to stop the unmanned helicopter from crossing over into dangerous areas. In this paper, the FPPS computation time is reduced by the multi-resolution scheme, and the flight path quality is improved by the path smoothing methods. Meanwhile, the FCS includes the fuzzy inference systems (FISs) based on the fuzzy logic. By using expert knowledge and experience to train the FIS, the controller can operate the unmanned helicopter without dynamic models. The integrated system of the FPPS and the FCS is aimed at providing navigation and guidance to the mission destination and it is implemented by coupling the flight simulation software, X-Plane, and the computing software, MATLAB. Simulations are performed and shown in real time three-dimensional animations. Finally, the integrated system is demonstrated to work successfully in controlling the unmanned helicopter to operate in various terrains of a digital elevation model (DEM). PMID:22164029

    7. Accelerated path integral methods for atomistic simulations at ultra-low temperatures.

      PubMed

      Uhl, Felix; Marx, Dominik; Ceriotti, Michele

      2016-08-01

      Path integral methods provide a rigorous and systematically convergent framework to include the quantum mechanical nature of atomic nuclei in the evaluation of the equilibrium properties of molecules, liquids, or solids at finite temperature. Such nuclear quantum effects are often significant for light nuclei already at room temperature, but become crucial at cryogenic temperatures such as those provided by superfluid helium as a solvent. Unfortunately, the cost of converged path integral simulations increases significantly upon lowering the temperature so that the computational burden of simulating matter at the typical superfluid helium temperatures becomes prohibitive. Here we investigate how accelerated path integral techniques based on colored noise generalized Langevin equations, in particular the so-called path integral generalized Langevin equation thermostat (PIGLET) variant, perform in this extreme quantum regime using as an example the quasi-rigid methane molecule and its highly fluxional protonated cousin, CH5 (+). We show that the PIGLET technique gives a speedup of two orders of magnitude in the evaluation of structural observables and quantum kinetic energy at ultralow temperatures. Moreover, we computed the spatial spread of the quantum nuclei in CH4 to illustrate the limits of using such colored noise thermostats close to the many body quantum ground state. PMID:27497533

    8. Draw Your Physics Homework? Art as a Path to Understanding in Physics Teaching

      ERIC Educational Resources Information Center

      van der Veen, Jatila

      2012-01-01

      The persistent fear of physics by learners motivated the author to take action to increase all students' interest in the subject via a new curriculum for introductory college physics that applies Greene's model of Aesthetic Education to the study of contemporary physics, utilizing symmetry as the mathematical foundation of physics as well as the…

    9. PRELIMINARY PROJECT PLAN FOR LANSCE INTEGRATED FLIGHT PATHS 11A, 11B, 12, and 13

      SciTech Connect

      D. H. BULTMAN; D. WEINACHT - AIRES CORP.

      2000-08-01

      This Preliminary Project Plan Summarizes the Technical, Cost, and Schedule baselines for an integrated approach to developing several flight paths at the Manual Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center. For example, the cost estimate is intended to serve only as a rough order of magnitude assessment of the cost that might be incurred as the flight paths are developed. Further refinement of the requirements and interfaces for each beamline will permit additional refinement and confidence in the accuracy of all three baselines (Technical, Cost, Schedule).

    10. path integral approach to closed form pricing formulas in the Heston framework.

      NASA Astrophysics Data System (ADS)

      Lemmens, Damiaan; Wouters, Michiel; Tempere, Jacques; Foulon, Sven

      2008-03-01

      We present a path integral approach for finding closed form formulas for option prices in the framework of the Heston model. The first model for determining option prices was the Black-Scholes model, which assumed that the logreturn followed a Wiener process with a given drift and constant volatility. To provide a realistic description of the market, the Black-Scholes results must be extended to include stochastic volatility. This is achieved by the Heston model, which assumes that the volatility follows a mean reverting square root process. Current applications of the Heston model are hampered by the unavailability of fast numerical methods, due to a lack of closed-form formulae. Therefore the search for closed form solutions is an essential step before the qualitatively better stochastic volatility models will be used in practice. To attain this goal we outline a simplified path integral approach yielding straightforward results for vanilla Heston options with correlation. Extensions to barrier options and other path-dependent option are discussed, and the new derivation is compared to existing results obtained from alternative path-integral approaches (Dragulescu, Kleinert).

    11. Spatial representations of place cells in darkness are supported by path integration and border information

      PubMed Central

      Zhang, Sijie; Schönfeld, Fabian; Wiskott, Laurenz; Manahan-Vaughan, Denise

      2014-01-01

      Effective spatial navigation is enabled by reliable reference cues that derive from sensory information from the external environment, as well as from internal sources such as the vestibular system. The integration of information from these sources enables dead reckoning in the form of path integration. Navigation in the dark is associated with the accumulation of errors in terms of perception of allocentric position and this may relate to error accumulation in path integration. We assessed this by recording from place cells in the dark under circumstances where spatial sensory cues were suppressed. Spatial information content, spatial coherence, place field size, and peak and infield firing rates decreased whereas sparsity increased following exploration in the dark compared to the light. Nonetheless it was observed that place field stability in darkness was sustained by border information in a subset of place cells. To examine the impact of encountering the environment’s border on navigation, we analyzed the trajectory and spiking data gathered during navigation in the dark. Our data suggest that although error accumulation in path integration drives place field drift in darkness, under circumstances where border contact is possible, this information is integrated to enable retention of spatial representations. PMID:25009477

    12. Path integration of head direction: updating a packet of neural activity at the correct speed using axonal conduction delays.

      PubMed

      Walters, Daniel; Stringer, Simon; Rolls, Edmund

      2013-01-01

      The head direction cell system is capable of accurately updating its current representation of head direction in the absence of visual input. This is known as the path integration of head direction. An important question is how the head direction cell system learns to perform accurate path integration of head direction. In this paper we propose a model of velocity path integration of head direction in which the natural time delay of axonal transmission between a linked continuous attractor network and competitive network acts as a timing mechanism to facilitate the correct speed of path integration. The model effectively learns a "look-up" table for the correct speed of path integration. In simulation, we show that the model is able to successfully learn two different speeds of path integration across two different axonal conduction delays, and without the need to alter any other model parameters. An implication of this model is that, by learning look-up tables for each speed of path integration, the model should exhibit a degree of robustness to damage. In simulations, we show that the speed of path integration is not significantly affected by degrading the network through removing a proportion of the cells that signal rotational velocity.

    13. Path-integral methods for analyzing the effects of fluctuations in stochastic hybrid neural networks.

      PubMed

      Bressloff, Paul C

      2015-01-01

      We consider applications of path-integral methods to the analysis of a stochastic hybrid model representing a network of synaptically coupled spiking neuronal populations. The state of each local population is described in terms of two stochastic variables, a continuous synaptic variable and a discrete activity variable. The synaptic variables evolve according to piecewise-deterministic dynamics describing, at the population level, synapses driven by spiking activity. The dynamical equations for the synaptic currents are only valid between jumps in spiking activity, and the latter are described by a jump Markov process whose transition rates depend on the synaptic variables. We assume a separation of time scales between fast spiking dynamics with time constant [Formula: see text] and slower synaptic dynamics with time constant τ. This naturally introduces a small positive parameter [Formula: see text], which can be used to develop various asymptotic expansions of the corresponding path-integral representation of the stochastic dynamics. First, we derive a variational principle for maximum-likelihood paths of escape from a metastable state (large deviations in the small noise limit [Formula: see text]). We then show how the path integral provides an efficient method for obtaining a diffusion approximation of the hybrid system for small ϵ. The resulting Langevin equation can be used to analyze the effects of fluctuations within the basin of attraction of a metastable state, that is, ignoring the effects of large deviations. We illustrate this by using the Langevin approximation to analyze the effects of intrinsic noise on pattern formation in a spatially structured hybrid network. In particular, we show how noise enlarges the parameter regime over which patterns occur, in an analogous fashion to PDEs. Finally, we carry out a [Formula: see text]-loop expansion of the path integral, and use this to derive corrections to voltage-based mean-field equations, analogous

    14. Functional integration of vertical flight path and speed control using energy principles

      NASA Technical Reports Server (NTRS)

      Lambregts, A. A.

      1984-01-01

      A generalized automatic flight control system was developed which integrates all longitudinal flight path and speed control functions previously provided by a pitch autopilot and autothrottle. In this design, a net thrust command is computed based on total energy demand arising from both flight path and speed targets. The elevator command is computed based on the energy distribution error between flight path and speed. The engine control is configured to produce the commanded net thrust. The design incorporates control strategies and hierarchy to deal systematically and effectively with all aircraft operational requirements, control nonlinearities, and performance limits. Consistent decoupled maneuver control is achieved for all modes and flight conditions without outer loop gain schedules, control law submodes, or control function duplication.

    15. Moving to a Soft Path for Water: Integrated Research and Management Needs

      NASA Astrophysics Data System (ADS)

      Gleick, P. H.

      2011-12-01

      Water on Earth in its three fundamental phases is integral to the functioning, dynamics, and variability of the global climatological and biological support systems. From a purely scientific point of view, understanding the complexity of the hydrological cycle is of paramount interest and central to our understanding of other planetary geological, atmospheric, chemical, and physical processes. But water is more than that: water is key to economic, social, and political issues as well, including some of the core challenges of our time such central to issues of poverty, health, environmental sustainability, conflict, and economic prosperity. The more society seeks to solve these challenges, the more obvious it becomes that we must improve more than just our understanding of the fundamental science of the hydrological cycle and its links with related global processes; we must also improve our understanding of the complex social, economic, and structural challenges facing water managers and users. We must move to a different paradigm where water is managed in a far more integrated way - what I call the "soft path for water." Central to our basic science needs are (1) an expansion of the frequency and nature of the data we collect, (2) the development of systems for managing, sharing, and analyzing those data, and (3) improvements in our ability to model and forecast the hydrological cycle together with other climatological, geophysical, and biochemical systems. These improvements would lead to a far better understanding of the local, regional, and global details of the water balance on timescales from minutes to millennia. These needs are increasingly well understood in the research community and extensive efforts in these areas are underway under the auspices of national research centers, universities, and international scientific collaborations. But it is also becoming increasingly apparent that many of the current water challenges facing society are not going to be

    16. Path-integral treatment of multi-mode vibronic coupling. II. Correlation expansion of class averages

      NASA Astrophysics Data System (ADS)

      Krempl, Stefan; Winterstetter, Manfred; Domcke, Wolfgang

      1995-04-01

      A path-integral approach to real-time quantum dynamics is presented which is suitable to treat the dynamics of vibronic coupling or spin boson models. In these models the vibrational dynamics is nonseparable as a consequence of the electronic inter-state coupling. The sum over all possible paths in electronic-state space generated by the usual Trotter procedure is expressed in terms of single-mode averages over classes of paths and statistical mode correlations. The averages for classes of a given length can be calculated iteratively from averages over shorter paths. This expansion is formally exact and finite for a finite number of modes. Usually only a limited number of terms has to be evaluated in order to obtain converged results. The scaling of the computational effort with respect to the number of time steps and the number of modes is given by a low-order power law, depending on the chosen class structure and the order of the expansion. The usual time-dependent wave-packet propagation and the full path enumeration, which exhibit an exponential scaling behavior with respect to either the number of modes or the number of time steps, can be considered as opposite limiting cases of the correlation expansion (CE) of the path integral. The convergence of the CE is tested by application to a two-state four-mode model representing S1-S2 vibronic coupling in pyrazine, for which exact references (time-dependent correlation functions) are available. The potential of the CE approximation for the treatment of multi-mode problems is demonstrated by application to an extended 24-mode vibronic-coupling model. This model is suitable to provide a microscopic description of ultrafast optical dephasing processes in large molecules.

    17. CYBER/PHYSICAL SECURITY VULNERABILITY ASSESSMENT INTEGRATION

      SciTech Connect

      MacDonald, Douglas G.; Key, Brad; Clements, Samuel L.; Hutton, William J.; Craig, Philip A.; Patrick, Scott W.; Crawford, Cary E.

      2011-07-17

      This internally funded Laboratory-Directed R&D project by the Pacific Northwest National Laboratory, in conjunction with QinetiQ North America, is intended to identify and properly assess areas of overlap (and interaction) in the vulnerability assessment process between cyber security and physical protection. Existing vulnerability analysis (VA) processes and software tools exist, and these are heavily utilized in the determination of predicted vulnerability within the physical and cyber security domains. These determinations are normally performed independently of one another, and only interact on a superficial level. Both physical and cyber security subject matter experts have come to realize that though the various interactive elements exist, they are not currently quantified in most periodic security assessments. This endeavor aims to evaluate both physical and cyber VA techniques and provide a strategic approach to integrate the interdependent relationships of each into a single VA capability. This effort will also transform the existing suite of software currently utilized in the physical protection world to more accurately quantify the risk associated with a blended attack scenario. Performance databases will be created to support the characterization of the cyber security elements, and roll them into prototype software tools. This new methodology and software capability will enable analysts to better identify and assess the overall risk during a vulnerability analysis.

    18. Two-scale large deviations for chemical reaction kinetics through second quantization path integral

      NASA Astrophysics Data System (ADS)

      Li, Tiejun; Lin, Feng

      2016-04-01

      Motivated by the study of rare events for a typical genetic switching model in systems biology, in this paper we aim to establish the general two-scale large deviations for chemical reaction systems. We build a formal approach to explicitly obtain the large deviation rate functionals for the considered two-scale processes based upon the second quantization path integral technique. We get three important types of large deviation results when the underlying two timescales are in three different regimes. This is realized by singular perturbation analysis to the rate functionals obtained by the path integral. We find that the three regimes possess the same deterministic mean-field limit but completely different chemical Langevin approximations. The obtained results are natural extensions of the classical large volume limit for chemical reactions. We also discuss its implication on the single-molecule Michaelis-Menten kinetics. Our framework and results can be applied to understand general multi-scale systems including diffusion processes.

    19. Using integrating spheres as absorption cells: path-length distribution and application of Beer's law.

      PubMed

      Hodgkinson, Jane; Masiyano, Dackson; Tatam, Ralph P

      2009-10-20

      We have modeled the path-length distribution in an integrating sphere used as a multipass optical cell for absorption measurements. The measured radiant flux as a function of analyte concentration is nonlinear as a result, deviating from that expected for a single path length. We have developed a full numerical model and introduce a new analytical relationship that describes this behavior for high reflectivity spheres. We have tested both models by measuring the optical absorption of methane at 1651 nm in a 50 mm diameter sphere, with good agreement with experimental data in the absorption range of 0-0.01 cm(-1). Our results compare well with previous work on the temporal response of integrating spheres.

    20. Efficient algorithms for semiclassical instanton calculations based on discretized path integrals

      SciTech Connect

      Kawatsu, Tsutomu E-mail: smiura@mail.kanazawa-u.ac.jp; Miura, Shinichi E-mail: smiura@mail.kanazawa-u.ac.jp

      2014-07-14

      Path integral instanton method is a promising way to calculate the tunneling splitting of energies for degenerated two state systems. In order to calculate the tunneling splitting, we need to take the zero temperature limit, or the limit of infinite imaginary time duration. In the method developed by Richardson and Althorpe [J. Chem. Phys. 134, 054109 (2011)], the limit is simply replaced by the sufficiently long imaginary time. In the present study, we have developed a new formula of the tunneling splitting based on the discretized path integrals to take the limit analytically. We have applied our new formula to model systems, and found that this approach can significantly reduce the computational cost and gain the numerical accuracy. We then developed the method combined with the electronic structure calculations to obtain the accurate interatomic potential on the fly. We present an application of our ab initio instanton method to the ammonia umbrella flip motion.

    1. The path integral for the statistical sum of the microcanonical ensemble in cosmology

      SciTech Connect

      Barvinsky, A.O.

      2011-04-01

      The path integral is calculated for the statistical sum of the microcanonical ensemble in a generic time-parametrization invariant gravitational model with the Friedman-Robertson-Walker (FRW) metric. This represents the first example of a systematic calculation of the Faddeev-Popov gauge-fixed path integral in the minisuperspace sector of quantum cosmology. The gauge fixing procedure, together with gauging out local diffeomorphisms, also handles the residual symmetries associated with the conformal Killing vector of the FRW metric and incorporates the Batalin-Vilkovisky quantization technique for gauge theories with linearly dependent generators. For a subset of saddle-point instantons, characterized by a single oscillation of the FRW scale factor, this technique is designed to obtain the one-loop statistical sum in the recently suggested model of cosmological initial conditions generated by a conformal field theory with a large number of quantum species.

    2. Path-integral and Ornstein-Zernike study of quantum fluid structures on the crystallization line

      NASA Astrophysics Data System (ADS)

      Sesé, Luis M.

      2016-03-01

      Liquid neon, liquid para-hydrogen, and the quantum hard-sphere fluid are studied with path integral Monte Carlo simulations and the Ornstein-Zernike pair equation on their respective crystallization lines. The results cover the whole sets of structures in the r-space and the k-space and, for completeness, the internal energies, pressures and isothermal compressibilities. Comparison with experiment is made wherever possible, and the possibilities of establishing k-space criteria for quantum crystallization based on the path-integral centroids are discussed. In this regard, the results show that the centroid structure factor contains two significant parameters related to its main peak features (amplitude and shape) that can be useful to characterize freezing.

    3. Path-integral and Ornstein-Zernike study of quantum fluid structures on the crystallization line.

      PubMed

      Sesé, Luis M

      2016-03-01

      Liquid neon, liquid para-hydrogen, and the quantum hard-sphere fluid are studied with path integral Monte Carlo simulations and the Ornstein-Zernike pair equation on their respective crystallization lines. The results cover the whole sets of structures in the r-space and the k-space and, for completeness, the internal energies, pressures and isothermal compressibilities. Comparison with experiment is made wherever possible, and the possibilities of establishing k-space criteria for quantum crystallization based on the path-integral centroids are discussed. In this regard, the results show that the centroid structure factor contains two significant parameters related to its main peak features (amplitude and shape) that can be useful to characterize freezing. PMID:26957169

    4. A path-independent integral for the characterization of solute concentration and flux at biofilm detachments

      USGS Publications Warehouse

      Moran, B.; Kulkarni, S.S.; Reeves, H.W.

      2007-01-01

      A path-independent (conservation) integral is developed for the characterization of solute concentration and flux in a biofilm in the vicinity of a detachment or other flux limiting boundary condition. Steady state conditions of solute diffusion are considered and biofilm kinetics are described by an uptake term which can be expressed in terms of a potential (Michaelis-Menten kinetics). An asymptotic solution for solute concentration at the tip of the detachment is obtained and shown to be analogous to that of antiplane crack problems in linear elasticity. It is shown that the amplitude of the asymptotic solution can be calculated by evaluating a path-independent integral. The special case of a semi-infinite detachment in an infinite strip is considered and the amplitude of the asymptotic field is related to the boundary conditions and problem parameters in closed form for zeroth and first order kinetics and numerically for Michaelis-Menten kinetics. ?? Springer Science+Business Media, Inc. 2007.

    5. Data assimilation using a GPU accelerated path integral Monte Carlo approach

      NASA Astrophysics Data System (ADS)

      Quinn, John C.; Abarbanel, Henry D. I.

      2011-09-01

      The answers to data assimilation questions can be expressed as path integrals over all possible state and parameter histories. We show how these path integrals can be evaluated numerically using a Markov Chain Monte Carlo method designed to run in parallel on a graphics processing unit (GPU). We demonstrate the application of the method to an example with a transmembrane voltage time series of a simulated neuron as an input, and using a Hodgkin-Huxley neuron model. By taking advantage of GPU computing, we gain a parallel speedup factor of up to about 300, compared to an equivalent serial computation on a CPU, with performance increasing as the length of the observation time used for data assimilation increases.

    6. Path integral formulation of scattering theory with application to scattering by black holes

      SciTech Connect

      Zhang, T.R.

      1985-01-01

      The computational power of Feynman path integrals was exploited. Path-integration formalism for the quantum mechanics scattering and classical wave scattering was generalized. Firstly, the standard WKB approximation was generalized to the cases where the critical points of the action functional are degenerate. Three typical semiclassical scattering features served as examples for a classification of degenerate critical points: conservation laws, rainbows, glories. Secondly, the method developed for non-relativistic quantum mechanics scattering was used in the case of classical wave scattering. Scattering by Schwarzschild black holes was chosen as an example, and WKB cross sections for scalar, vector, and tensor fields were worked out. Finally, 2s-th Bessel function behavior of WKB cross section for helicity-s polarized glory scattering in curved space time was proved.

    7. Path integral formalism for the spectral line shape in plasmas: Lyman-{alpha} with fine structure

      SciTech Connect

      Bedida, N.; Meftah, M. T.; Boland, D.; Stamm, R.

      2008-10-22

      We examine in this work the expression of the dipolar autocorrelation function for an emitter in the plasma using the path integrals formalism. The results for Lyman alpha lines with fine structure are retrieved in a compact formula. The expression of the dipolar autocorrelation function takes into account the ions dynamics and the fine structure effects. The electron's effect is represented by the impact operator {phi}{sub e} in the final formula.

    8. A 2-Micron Pulsed Integrated Path Differential Absorption Lidar Development For Atmospheric CO2 Concentration Measurements

      NASA Technical Reports Server (NTRS)

      Yu, Jirong; Petros, Mulugeta; Reithmaier, Karl; Bai, Yingxin; Trieu, Bo C.; Refaat, Tamer F.; Kavaya, Michael J.; Singh, Upendra N.

      2012-01-01

      A 2-micron pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This instrument will provide an alternate approach to measure atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement.

    9. Path integral formulation of the conformal Wess-Zumino-Witten --> Liouville reduction

      NASA Astrophysics Data System (ADS)

      O'Raifeartaigh, L.; Sreedhar, V. V.

      1998-04-01

      The quantum Wess-Zumino-Witten --> Liouville reduction is formulated using the phase space path integral method of Batalin, Fradkin, and Vilkovisky, adapted to theories on compact two dimensional manifolds. The importance of the zero modes of the Lagrange multipliers in producing the Liouville potential and the WZW anomaly, and in proving gauge invariance, is emphasised. A previous problem concerning the gauge dependence of the Virasoro centre is solved.

    10. Do familiar landmarks reset the global path integration system of desert ants?

      PubMed

      Collett, M; Collett, T S; Chameron, S; Wehner, R

      2003-03-01

      It is often suggested that animals may link landmark memories to a global coordinate system provided by path integration, thereby obtaining a map-like representation of familiar terrain. In an attempt to discover if desert ants form such associations we have performed experiments that test whether desert ants recall a long-term memory of a global path integration vector on arriving at a familiar food site. Ants from three nests were trained along L-shaped routes to a feeder. Each route was entirely within open-topped channels that obscured all natural landmarks. Conspicuous artificial landmarks were attached to the channelling that formed the latter part of the route. The homeward vectors of ants accustomed to the route were tested with the foodward route, either as in training, or with the first leg of the L shortened or extended. These ants were taken from the feeder to a test area and released, whereupon they performed a home vector. If travelling the latter part of a familiar route and arriving at a familiar food site triggers the recall of an accustomed home vector, then the home vector should be the same under both test conditions. We find instead that the home vector tended to reflect the immediately preceding outward journey. In conjunction with earlier work, these experiments led us to conclude in the case of desert ants that landmark memories do not prime the recall of long-term global path integration memories. On the other hand, landmark memories are known to be linked to local path integration vectors that guide ants along a segment of a route. Landmarks thus seem to provide procedural information telling ants what action to perform next but not the positional information that gives an ant its location relative to its nest.

    11. Phase space path-integral formulation of the above-threshold ionization

      SciTech Connect

      Milosevic, D. B.

      2013-04-15

      Atoms and molecules submitted to a strong laser field can emit electrons of high energies in the above-threshold ionization (ATI) process. This process finds a highly intuitive and also quantitative explanation in terms of Feynman's path integral and the concept of quantum orbits [P. Salieres et al., Science 292, 902 (2001)]. However, the connection with the Feynman path-integral formalism is explained only by intuition and analogy and within the so-called strong-field approximation (SFA). Using the phase space path-integral formalism we have obtained an exact result for the momentum-space matrix element of the total time-evolution operator. Applying this result to the ATI we show that the SFA and the so-called improved SFA are, respectively, the zeroth- and the first-order terms of the expansion in powers of the laser-free effective interaction of the electron with the rest of the atom (molecule). We have also presented the second-order term of this expansion which is responsible for the ATI with double scattering of the ionized electron.

    12. i-PI: A Python interface for ab initio path integral molecular dynamics simulations

      NASA Astrophysics Data System (ADS)

      Ceriotti, Michele; More, Joshua; Manolopoulos, David E.

      2014-03-01

      Recent developments in path integral methodology have significantly reduced the computational expense of including quantum mechanical effects in the nuclear motion in ab initio molecular dynamics simulations. However, the implementation of these developments requires a considerable programming effort, which has hindered their adoption. Here we describe i-PI, an interface written in Python that has been designed to minimise the effort required to bring state-of-the-art path integral techniques to an electronic structure program. While it is best suited to first principles calculations and path integral molecular dynamics, i-PI can also be used to perform classical molecular dynamics simulations, and can just as easily be interfaced with an empirical forcefield code. To give just one example of the many potential applications of the interface, we use it in conjunction with the CP2K electronic structure package to showcase the importance of nuclear quantum effects in high-pressure water. Catalogue identifier: AERN_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AERN_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 138626 No. of bytes in distributed program, including test data, etc.: 3128618 Distribution format: tar.gz Programming language: Python. Computer: Multiple architectures. Operating system: Linux, Mac OSX, Windows. RAM: Less than 256 Mb Classification: 7.7. External routines: NumPy Nature of problem: Bringing the latest developments in the modelling of nuclear quantum effects with path integral molecular dynamics to ab initio electronic structure programs with minimal implementational effort. Solution method: State-of-the-art path integral molecular dynamics techniques are implemented in a Python interface. Any electronic structure code can be patched to receive the atomic

    13. Managing the physics of the economics of integrated health care.

      PubMed

      Zismer, Daniel K; Werner, Mark J

      2012-01-01

      The physics metaphor, as applied to the economics (and financial performance) of the integrated health system, seems appropriate when considered together with the nine principles of management framework provided. The nature of the integrated design enhances leaders' management potential as they consider organizational operations and strategy in the markets ahead. One question begged by this argument for the integrated design is the durability, efficiency and ultimate long-term survivability of the more "traditional" community health care delivery models, which, by design, are fragmented, internally competitive and less capital efficient. They also cannot exploit the leverage of teams, optimal access management or the pursuit of revenues made available in many forms. For those who wish to move from the traditional to the more integrated community health system designs (especially those who have not yet started the journey), the path requires: * Sufficient balance sheet capacity to fund the integration process-especially as the model requires physician practice acquisitions and electronic health record implementations * A well-prepared board13, 14 * A functional, durable and sustainable physician services enterprise design * A redesigned organizational and governance structure * Favorable internal financial incentives alignment design * Effective accountable physician leadership * Awareness that the system is not solely a funding strategy for acquired physicians, rather a fully -.. committed clinical and business model, one in which patient-centered integrated care is the core service (and not acute care hospital-based services) A willingness to create and exploit the implied and inherent potential of an integrated design and unified brand Last, it's important to remember that an integrated health system is a tool that creates a "new potential" (a physics metaphor reference, one last time). The design doesn't operate itself. Application of the management principles

    14. Accurate path integration in continuous attractor network models of grid cells.

      PubMed

      Burak, Yoram; Fiete, Ila R

      2009-02-01

      Grid cells in the rat entorhinal cortex display strikingly regular firing responses to the animal's position in 2-D space and have been hypothesized to form the neural substrate for dead-reckoning. However, errors accumulate rapidly when velocity inputs are integrated in existing models of grid cell activity. To produce grid-cell-like responses, these models would require frequent resets triggered by external sensory cues. Such inadequacies, shared by various models, cast doubt on the dead-reckoning potential of the grid cell system. Here we focus on the question of accurate path integration, specifically in continuous attractor models of grid cell activity. We show, in contrast to previous models, that continuous attractor models can generate regular triangular grid responses, based on inputs that encode only the rat's velocity and heading direction. We consider the role of the network boundary in the integration performance of the network and show that both periodic and aperiodic networks are capable of accurate path integration, despite important differences in their attractor manifolds. We quantify the rate at which errors in the velocity integration accumulate as a function of network size and intrinsic noise within the network. With a plausible range of parameters and the inclusion of spike variability, our model networks can accurately integrate velocity inputs over a maximum of approximately 10-100 meters and approximately 1-10 minutes. These findings form a proof-of-concept that continuous attractor dynamics may underlie velocity integration in the dorsolateral medial entorhinal cortex. The simulations also generate pertinent upper bounds on the accuracy of integration that may be achieved by continuous attractor dynamics in the grid cell network. We suggest experiments to test the continuous attractor model and differentiate it from models in which single cells establish their responses independently of each other. PMID:19229307

    15. Spatial memory and path integration studied by self-driven passive linear displacement. I. Basic properties.

      PubMed

      Israël, I; Grasso, R; Georges-Francois, P; Tsuzuku, T; Berthoz, A

      1997-06-01

      According to path integration, the brain is able to compute the distance of a traveled path. In this research we applied our previously reported method for studying memory of linear distance, a crucial mechanism in path integration; our method is based on the overt reconstruction of a passive transport. Passive transport is a special case of navigation in which no active control is performed. Blindfolded subjects were first asked to travel 2 m forward, in darkness, by driving with a joystick the robot on which they were seated. The results show that all subjects but two undershot this distance, i.e., overestimated their own displacement. Then, subjects were submitted to a passive linear forward displacement along 2, 4, 6, 8, or 10 m, and had to reproduce the same distance, still blindfolded. The results show that the distance of the stimulus was accurately reproduced, as well as stimulus duration, peak velocity, and velocity profile. In this first condition, the imposed velocity profile was triangular and therefore stimulus distance and duration were correlated. In a second condition, it was shown that distance was correctly reproduced also when the information about stimulus duration was kept constant. Here, different velocity profiles were used as stimuli, and most subjects also reproduced the velocity profile. Statistical analyses indicated that distance was not reproduced as a consequence of duration, peak velocity, or velocity profile reproduction, but was uniquely correlated to stimulus distance. The previous hypothesis of a double integration of the otolith signal to provide a distance estimate can explain our results. There was a large discrepancy between the accuracy with which the subjects matched the velocity profiles and that of distance reproduction. It follows that, whereas the dynamics of passive motion are stored and available to further use, distance is independently estimated. It is concluded that vestibular and somatosensory signals excited by

    16. Spatial memory and path integration studied by self-driven passive linear displacement. I. Basic properties.

      PubMed

      Israël, I; Grasso, R; Georges-Francois, P; Tsuzuku, T; Berthoz, A

      1997-06-01

      According to path integration, the brain is able to compute the distance of a traveled path. In this research we applied our previously reported method for studying memory of linear distance, a crucial mechanism in path integration; our method is based on the overt reconstruction of a passive transport. Passive transport is a special case of navigation in which no active control is performed. Blindfolded subjects were first asked to travel 2 m forward, in darkness, by driving with a joystick the robot on which they were seated. The results show that all subjects but two undershot this distance, i.e., overestimated their own displacement. Then, subjects were submitted to a passive linear forward displacement along 2, 4, 6, 8, or 10 m, and had to reproduce the same distance, still blindfolded. The results show that the distance of the stimulus was accurately reproduced, as well as stimulus duration, peak velocity, and velocity profile. In this first condition, the imposed velocity profile was triangular and therefore stimulus distance and duration were correlated. In a second condition, it was shown that distance was correctly reproduced also when the information about stimulus duration was kept constant. Here, different velocity profiles were used as stimuli, and most subjects also reproduced the velocity profile. Statistical analyses indicated that distance was not reproduced as a consequence of duration, peak velocity, or velocity profile reproduction, but was uniquely correlated to stimulus distance. The previous hypothesis of a double integration of the otolith signal to provide a distance estimate can explain our results. There was a large discrepancy between the accuracy with which the subjects matched the velocity profiles and that of distance reproduction. It follows that, whereas the dynamics of passive motion are stored and available to further use, distance is independently estimated. It is concluded that vestibular and somatosensory signals excited by

    17. Efficient Calculation of Free Energy Differences Associated with Isotopic Substitution Using Path-Integral Molecular Dynamics.

      PubMed

      Marsalek, Ondrej; Chen, Pei-Yang; Dupuis, Romain; Benoit, Magali; Méheut, Merlin; Bačić, Zlatko; Tuckerman, Mark E

      2014-04-01

      The problem of computing free energy differences due to isotopic substitution in chemical systems is discussed. The shift in the equilibrium properties of a system upon isotopic substitution is a purely quantum mechanical effect that can be quantified using the Feynman path integral approach. In this paper, we explore two developments that lead to a highly efficient path integral scheme. First, we employ a mass switching function inspired by the work of Ceriotti and Markland [ J. Chem. Phys. 2013, 138, 014112] that is based on the inverse square root of the mass and which leads to a perfectly constant free energy derivative with respect to the switching parameter in the harmonic limit. We show that even for anharmonic systems, this scheme allows a single-point thermodynamic integration approach to be used in the construction of free energy differences. In order to improve the efficiency of the calculations even further, however, we derive a set of free energy derivative estimators based on the fourth-order scheme of Takahashi and Imada [ J. Phys. Soc. Jpn. 1984, 53, 3765]. The Takahashi-Imada procedure generates a primitive fourth-order estimator that allows the number of imaginary time slices in the path-integral approach to be reduced substantially. However, as with all primitive estimators, its convergence is plagued by numerical noise. In order to alleviate this problem, we derive a fourth-order virial estimator based on a transferring of the difference between second- and fourth-order primitive estimators, which remains relatively constant as a function of the number of configuration samples, to the second-order virial estimator. We show that this new estimator converges as smoothly as the second-order virial estimator but requires significantly fewer imaginary time points. PMID:26580362

    18. Methods for integrating moderation and mediation: a general analytical framework using moderated path analysis.

      PubMed

      Edwards, Jeffrey R; Lambert, Lisa Schurer

      2007-03-01

      Studies that combine moderation and mediation are prevalent in basic and applied psychology research. Typically, these studies are framed in terms of moderated mediation or mediated moderation, both of which involve similar analytical approaches. Unfortunately, these approaches have important shortcomings that conceal the nature of the moderated and the mediated effects under investigation. This article presents a general analytical framework for combining moderation and mediation that integrates moderated regression analysis and path analysis. This framework clarifies how moderator variables influence the paths that constitute the direct, indirect, and total effects of mediated models. The authors empirically illustrate this framework and give step-by-step instructions for estimation and interpretation. They summarize the advantages of their framework over current approaches, explain how it subsumes moderated mediation and mediated moderation, and describe how it can accommodate additional moderator and mediator variables, curvilinear relationships, and structural equation models with latent variables.

    19. From Classical to Quantum and Back: A Hamiltonian Scheme for Adaptive Multiresolution Classical/Path-Integral Simulations.

      PubMed

      Kreis, Karsten; Tuckerman, Mark E; Donadio, Davide; Kremer, Kurt; Potestio, Raffaello

      2016-07-12

      Quantum delocalization of atomic nuclei affects the physical properties of many hydrogen-rich liquids and biological systems even at room temperature. In computer simulations, quantum nuclei can be modeled via the path-integral formulation of quantum statistical mechanics, which implies a substantial increase in computational overhead. By restricting the quantum description to a small spatial region, this cost can be significantly reduced. Herein, we derive a bottom-up, rigorous, Hamiltonian-based scheme that allows molecules to change from quantum to classical and vice versa on the fly as they diffuse through the system, both reducing overhead and making quantum grand-canonical simulations possible. The method is validated via simulations of low-temperature parahydrogen. Our adaptive resolution approach paves the way to efficient quantum simulations of biomolecules, membranes, and interfaces. PMID:27214610

    20. An integrated radiation physics computer code system.

      NASA Technical Reports Server (NTRS)

      Steyn, J. J.; Harris, D. W.

      1972-01-01

      An integrated computer code system for the semi-automatic and rapid analysis of experimental and analytic problems in gamma photon and fast neutron radiation physics is presented. Such problems as the design of optimum radiation shields and radioisotope power source configurations may be studied. The system codes allow for the unfolding of complex neutron and gamma photon experimental spectra. Monte Carlo and analytic techniques are used for the theoretical prediction of radiation transport. The system includes a multichannel pulse-height analyzer scintillation and semiconductor spectrometer coupled to an on-line digital computer with appropriate peripheral equipment. The system is geometry generalized as well as self-contained with respect to material nuclear cross sections and the determination of the spectrometer response functions. Input data may be either analytic or experimental.

    1. Path integration in a three-dimensional maze: ground distance estimation keeps desert ants Cataglyphis fortis on course.

      PubMed

      Grah, Gunnar; Wehner, Rüdiger; Ronacher, Bernhard

      2005-11-01

      In this study, we investigate the ability of desert ants to gauge the ground distances of sloped sections in a three-dimensional (3D) outbound path. Ground distance estimation, as opposed to a simple measurement of walking distances, is a necessary prerequisite for precise path integration in undulating terrain. We trained ants to visit a feeder along a path that included an angular turn as well as a 'hill', resulting in an outbound path with a distinct 3D structure. We then observed the ants' return path in a test field on level ground. From the angles of the ants' return path on the test field one can infer which property of the hill segment was fed into the ants' path integration module, the actual walking distance or the ground distance. The results show clearly that it is the ground distance that Cataglyphis fortis feeds into its path integrator, and suggest that the ants are able to keep an accurate home vector also in hilly terrain.

    2. Accelerating ab initio path integral molecular dynamics with multilevel sampling of potential surface

      SciTech Connect

      Geng, Hua Y.

      2015-02-15

      A multilevel approach to sample the potential energy surface in a path integral formalism is proposed. The purpose is to reduce the required number of ab initio evaluations of energy and forces in ab initio path integral molecular dynamics (AI-PIMD) simulation, without compromising the overall accuracy. To validate the method, the internal energy and free energy of an Einstein crystal are calculated and compared with the analytical solutions. As a preliminary application, we assess the performance of the method in a realistic model—the FCC phase of dense atomic hydrogen, in which the calculated result shows that the acceleration rate is about 3 to 4-fold for a two-level implementation, and can be increased up to 10 times if extrapolation is used. With only 16 beads used for the ab initio potential sampling, this method gives a well converged internal energy. The residual error in pressure is just about 3 GPa, whereas it is about 20 GPa for a plain AI-PIMD calculation with the same number of beads. The vibrational free energy of the FCC phase of dense hydrogen at 300 K is also calculated with an AI-PIMD thermodynamic integration method, which gives a result of about 0.51 eV/proton at a density of r{sub s}=0.912.

    3. Path-integrated measurements of carbon dioxide in the urban canopy layer

      NASA Astrophysics Data System (ADS)

      Büns, Christian; Kuttler, Wilhelm

      2012-01-01

      Continuous CO 2 concentration measurements have been recorded within the city center of Essen, Germany, using a path-integrated measuring system above a typical urban area over the course of nine months (February-October 2010). Mean monthly urban CO 2 concentrations were 396 and 446 ppm in summer and winter, respectively, which were 8.5 % in average higher than at a nearby suburban measuring site. Urban-suburban differences mainly occur due to increased CO 2 emissions from traffic and industry within the urban area, as well as domestic heating in winter. Among the analyzed meteorological variables, low wind velocities increased CO 2 concentrations as well as high atmospheric stability within the urban boundary layer, respectively. The influence of wind direction reflects the heterogeneous distribution of local CO 2 sources at the recording sites, particularly industrial point sources. Other point sources in the vicinity of the urban site strongly influence the additional point measurements but show no significant effect on the measured CO 2 concentrations by the path-integrated measuring system. Within an eight-day case study, a significant positive correlation between CO 2 concentration and traffic count ( R = 0.26; p < 0.05) was found on weekdays using partial correlation analysis after excluding the influence of meteorological variables. This correlation diminishes when combined with the meteorological components, and mixing layer height shows the strongest negative correlation with measured urban CO 2 ( R = -0.59). The path-integrated system provides CO 2 concentrations on a greater temporal and spatial scale than common point measurements, which can be influenced by strong adjacent local CO 2 sources.

    4. Temperature-dependent isovector pairing gap equations using a path integral approach

      SciTech Connect

      Fellah, M.; Allal, N. H.; Belabbas, M.; Oudih, M. R.; Benhamouda, N.

      2007-10-15

      Temperature-dependent isovector neutron-proton (np) pairing gap equations have been established by means of the path integral approach. These equations generalize the BCS ones for the pairing between like particles at finite temperature. The method has been numerically tested using the one-level model. It has been shown that the gap parameter {delta}{sub np} has a behavior analogous to that of {delta}{sub nn} and {delta}{sub pp} as a function of the temperature: one notes the presence of a critical temperature. Moreover, it has been shown that the isovector pairing effects remain beyond the critical temperature that corresponds to the pairing between like particles.

    5. Option pricing formulas and nonlinear filtering: a Feynman path integral perspective

      NASA Astrophysics Data System (ADS)

      Balaji, Bhashyam

      2013-05-01

      Many areas of engineering and applied science require the solution of certain parabolic partial differential equa­ tions, such as the Fokker-Planck and Kolmogorov equations. The fundamental solution, or the Green's function, for such PDEs can be written in terms of the Feynman path integral (FPI). The partial differential equation arising in the valuing of options is the Kolmogorov backward equation that is referred to as the Black-Scholes equation. The utility of this is demonstrated and numerical examples that illustrate the high accuracy of option price calculation even when using a fairly coarse grid.

    6. Error Reduction Methods for Integrated-path Differential-absorption Lidar Measurements

      NASA Technical Reports Server (NTRS)

      Chen, Jeffrey R.; Numata, Kenji; Wu, Stewart T.

      2012-01-01

      We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".

    7. Error reduction methods for integrated-path differential-absorption lidar measurements.

      PubMed

      Chen, Jeffrey R; Numata, Kenji; Wu, Stewart T

      2012-07-01

      We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".

    8. Quantum Zeno effect with the Feynman-Mensky path-integral approach

      NASA Astrophysics Data System (ADS)

      Onofrio, Roberto; Presilla, Carlo; Tambini, Ubaldo

      1993-12-01

      A model for the quantum Zeno effect based upon an effective Schrödinger equation originated by the path-integral approach is developed and applied to a two-level system simultaneously stimulated by a resonant perturbation. It is shown that inhibition of stimulated transitions between the two levels appears as a consequence of the influence of the meter whenever measurements of energy, either continuous or pulsed, are performed at quantum level of sensitivity. The generality of this approach allows one to qualitatively understand the inhibition of spontaneous transitions as the decay of unstable particles, originally presented as a paradox of the quantum measurement theory.

    9. Path integral approach to Brownian motion driven with an ac force

      NASA Astrophysics Data System (ADS)

      Chen, L. Y.; Nash, P. L.

      2004-09-01

      Brownian motion in a periodic potential driven by an ac (oscillatory) force is investigated for the full range of damping constant from the overdamped limit to the underdamped limit. The path (functional) integral approach is advanced to produce formulas for the probability distribution function and for the current of the Brownian particle in response to an ac driving force. The negative friction Langevin dynamics technique is employed to evaluate the dc current for various parameters without invoking the overdamped or the underdamped approximation. The dc current is found to have nonlinear dependence upon the damping constant, the potential parameter, and the ac force magnitude and frequency.

    10. Path-integral calculation of the second virial coefficient including intramolecular flexibility effects

      SciTech Connect

      Garberoglio, Giovanni; Jankowski, Piotr; Szalewicz, Krzysztof; Harvey, Allan H.

      2014-07-28

      We present a path-integral Monte Carlo procedure for the fully quantum calculation of the second molecular virial coefficient accounting for intramolecular flexibility. This method is applied to molecular hydrogen (H{sub 2}) and deuterium (D{sub 2}) in the temperature range 15–2000 K, showing that the effect of molecular flexibility is not negligible. Our results are in good agreement with experimental data, as well as with virials given by recent empirical equations of state, although some discrepancies are observed for H{sub 2} between 100 and 200 K.

    11. High-order sampling schemes for path integrals and Gaussian chain simulations of polymers

      SciTech Connect

      Müser, Martin H.; Müller, Marcus

      2015-05-07

      In this work, we demonstrate that path-integral schemes, derived in the context of many-body quantum systems, benefit the simulation of Gaussian chains representing polymers. Specifically, we show how to decrease discretization corrections with little extra computation from the usual O(1/P{sup 2}) to O(1/P{sup 4}), where P is the number of beads representing the chains. As a consequence, high-order integrators necessitate much smaller P than those commonly used. Particular emphasis is placed on the questions of how to maintain this rate of convergence for open polymers and for polymers confined by a hard wall as well as how to ensure efficient sampling. The advantages of the high-order sampling schemes are illustrated by studying the surface tension of a polymer melt and the interface tension in a binary homopolymers blend.

    12. Development of a Pulsed 2-Micron Integrated Path Differential Absorption Lidar for CO2 Measurement

      NASA Technical Reports Server (NTRS)

      Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Refaat, Tamer

      2013-01-01

      Atmospheric carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and global radiation budget on Earth. Active remote sensing of CO2 is important to address several limitations that contend with passive sensors. A 2-micron double-pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This active remote sensing instrument will provide an alternate approach of measuring atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise ratio level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. Commercial, on the shelf, components are implemented for the detection system. Instrument integration will be presented in this paper as well as a background for CO2 measurement at NASA Langley research Center

    13. Advanced Car-Parrinello Techniques: Path Integrals and Nonadiabaticity in Condensed Matter Simulations

      NASA Astrophysics Data System (ADS)

      Marx, D.

      Extensions of Car-Parrinello (CP) ab initio molecular dynamics are presented for efficient treatments of nuclear quantum effects and electronically nonadiabatic processes in the realm of condensed matter simulations. Ab initio path integrals, being a combination of CP propagation of the electrons in conjunction with path integral MD sampling of the nuclei, allow to investigate quantum phenomena, such as the influence of zero-point motion and proton tunneling, in chemically complex systems. Nonadiabatic ab initio simulations rely on the coupling of the Kohn-Sham ground state, S 0, and the first excited electronic state, S 1, obtained within the restricted open-shell Kohn- Sham (ROKS) approach using Tully's surface hopping algorithm. The efficient evaluation of the nonadiabatic couplings together with an "on-the-fly" updating scheme makes possible nonadiabatic ab initio simulations of systems of similar complexity as those typically studied by ground-state CP methods. This method is thus ideally suited to study photoinduced reactions of large molecular systems, particularly in condensed phases.

    14. Interactions of the polarization and the sun compass in path integration of desert ants.

      PubMed

      Lebhardt, Fleur; Ronacher, Bernhard

      2014-08-01

      Desert ants, Cataglyphis fortis, perform large-scale foraging trips in their featureless habitat using path integration as their main navigation tool. To determine their walking direction they use primarily celestial cues, the sky's polarization pattern and the sun position. To examine the relative importance of these two celestial cues, we performed cue conflict experiments. We manipulated the polarization pattern experienced by the ants during their outbound foraging excursions, reducing it to a single electric field (e-)vector direction with a linear polarization filter. The simultaneous view of the sun created situations in which the directional information of the sun and the polarization compass disagreed. The heading directions of the homebound runs recorded on a test field with full view of the natural sky demonstrate that none of both compasses completely dominated over the other. Rather the ants seemed to compute an intermediate homing direction to which both compass systems contributed roughly equally. Direct sunlight and polarized light are detected in different regions of the ant's compound eye, suggesting two separate pathways for obtaining directional information. In the experimental paradigm applied here, these two pathways seem to feed into the path integrator with similar weights.

    15. Path-integral description of combined Hamiltonian and non-Hamiltonian dynamics in quantum dissipative systems

      NASA Astrophysics Data System (ADS)

      Barth, A. M.; Vagov, A.; Axt, V. M.

      2016-09-01

      We present a numerical path-integral iteration scheme for the low-dimensional reduced density matrix of a time-dependent quantum dissipative system. Our approach simultaneously accounts for the combined action of a microscopically modeled pure-dephasing-type coupling to a continuum of harmonic oscillators representing, e.g., phonons, and further environmental interactions inducing non-Hamiltonian dynamics in the inner system represented, e.g., by Lindblad-type dissipation or relaxation. Our formulation of the path-integral method allows for a numerically exact treatment of the coupling to the oscillator modes and moreover is general enough to provide a natural way to include Markovian processes that are sufficiently described by rate equations. We apply this new formalism to a model of a single semiconductor quantum dot which includes the coupling to longitudinal acoustic phonons for two cases: (a) external laser excitation taking into account a phenomenological radiative decay of the excited dot state and (b) a coupling of the quantum dot to a single mode of an optical cavity taking into account cavity photon losses.

    16. a Latent Variable Path Analysis Model of Secondary Physics Enrollments in New York State.

      NASA Astrophysics Data System (ADS)

      Sobolewski, Stanley John

      The Percentage of Enrollment in Physics (PEP) at the secondary level nationally has been approximately 20% for the past few decades. For a more scientifically literate citizenry as well as specialists to continue scientific research and development, it is desirable that more students enroll in physics. Some of the predictor variables for physics enrollment and physics achievement that have been identified previously includes a community's socioeconomic status, the availability of physics, the sex of the student, the curriculum, as well as teacher and student data. This study isolated and identified predictor variables for PEP of secondary schools in New York. Data gathered by the State Education Department for the 1990-1991 school year was used. The source of this data included surveys completed by teachers and administrators on student characteristics and school facilities. A data analysis similar to that done by Bryant (1974) was conducted to determine if the relationships between a set of predictor variables related to physics enrollment had changed in the past 20 years. Variables which were isolated included: community, facilities, teacher experience, number of type of science courses, school size and school science facilities. When these variables were isolated, latent variable path diagrams were proposed and verified by the Linear Structural Relations computer modeling program (LISREL). These diagrams differed from those developed by Bryant in that there were more manifest variables used which included achievement scores in the form of Regents exam results. Two criterion variables were used, percentage of students enrolled in physics (PEP) and percent of students enrolled passing the Regents physics exam (PPP). The first model treated school and community level variables as exogenous while the second model treated only the community level variables as exogenous. The goodness of fit indices for the models was 0.77 for the first model and 0.83 for the second

    17. TOWARD EFFICIENT RIPARIAN RESTORATION: INTEGRATING ECONOMIC, PHYSICAL, AND BIOLOGICAL MODELS

      EPA Science Inventory

      This paper integrates economic, biological, and physical models to determine the efficient combination and spatial allocation of conservation efforts for water quality protection and salmonid habitat enhancement in the Grande Ronde basin, Oregon. The integrated modeling system co...

    18. Dogs, Cats, and Kids: Integrating Yoga into Elementary Physical Education

      ERIC Educational Resources Information Center

      Toscano, Lisa; Clemente, Fran

      2008-01-01

      This article describes the benefits of integrating yoga into elementary physical education classes. Taught as warm-up exercises or as an entire class, yoga offers children of any age and physical ability the opportunity to experience success in physical activity. Children need to experience joy while participating in physical activity in order to…

    19. Movement and Learning: Integrating Physical Activity into the Classroom

      ERIC Educational Resources Information Center

      Reeves, Emily; Miller, Stacia; Chavez, Crystal

      2016-01-01

      We know the benefits of physical activity, and yet recess and physical education classes are being cut or scaled back to make room for meeting academic standards. Is cutting recess and physical education really benefiting academics? A look at some recent studies suggests that it is not. Integrating physical activity into the classroom may increase…

    20. Real-time Feynman path integral with Picard–Lefschetz theory and its applications to quantum tunneling

      SciTech Connect

      Tanizaki, Yuya; Koike, Takayuki

      2014-12-15

      Picard–Lefschetz theory is applied to path integrals of quantum mechanics, in order to compute real-time dynamics directly. After discussing basic properties of real-time path integrals on Lefschetz thimbles, we demonstrate its computational method in a concrete way by solving three simple examples of quantum mechanics. It is applied to quantum mechanics of a double-well potential, and quantum tunneling is discussed. We identify all of the complex saddle points of the classical action, and their properties are discussed in detail. However a big theoretical difficulty turns out to appear in rewriting the original path integral into a sum of path integrals on Lefschetz thimbles. We discuss generality of that problem and mention its importance. Real-time tunneling processes are shown to be described by those complex saddle points, and thus semi-classical description of real-time quantum tunneling becomes possible on solid ground if we could solve that problem. - Highlights: • Real-time path integral is studied based on Picard–Lefschetz theory. • Lucid demonstration is given through simple examples of quantum mechanics. • This technique is applied to quantum mechanics of the double-well potential. • Difficulty for practical applications is revealed, and we discuss its generality. • Quantum tunneling is shown to be closely related to complex classical solutions.

    1. Quantum Mechanical Single Molecule Partition Function from PathIntegral Monte Carlo Simulations

      SciTech Connect

      Chempath, Shaji; Bell, Alexis T.; Predescu, Cristian

      2006-10-01

      An algorithm for calculating the partition function of a molecule with the path integral Monte Carlo method is presented. Staged thermodynamic perturbation with respect to a reference harmonic potential is utilized to evaluate the ratio of partition functions. Parallel tempering and a new Monte Carlo estimator for the ratio of partition functions are implemented here to achieve well converged simulations that give an accuracy of 0.04 kcal/mol in the reported free energies. The method is applied to various test systems, including a catalytic system composed of 18 atoms. Absolute free energies calculated by this method lead to corrections as large as 2.6 kcal/mol at 300 K for some of the examples presented.

    2. Semiclassical Path Integral Dynamics: Photosynthetic Energy Transfer with Realistic Environment Interactions.

      PubMed

      Lee, Mi Kyung; Huo, Pengfei; Coker, David F

      2016-05-27

      This article reviews recent progress in the theoretical modeling of excitation energy transfer (EET) processes in natural light harvesting complexes. The iterative partial linearized density matrix path-integral propagation approach, which involves both forward and backward propagation of electronic degrees of freedom together with a linearized, short-time approximation for the nuclear degrees of freedom, provides an accurate and efficient way to model the nonadiabatic quantum dynamics at the heart of these EET processes. Combined with a recently developed chromophore-protein interaction model that incorporates both accurate ab initio descriptions of intracomplex vibrations and chromophore-protein interactions treated with atomistic detail, these simulation tools are beginning to unravel the detailed EET pathways and relaxation dynamics in light harvesting complexes.

    3. Path-integral Monte Carlo method for Rényi entanglement entropies.

      PubMed

      Herdman, C M; Inglis, Stephen; Roy, P-N; Melko, R G; Del Maestro, A

      2014-07-01

      We introduce a quantum Monte Carlo algorithm to measure the Rényi entanglement entropies in systems of interacting bosons in the continuum. This approach is based on a path-integral ground state method that can be applied to interacting itinerant bosons in any spatial dimension with direct relevance to experimental systems of quantum fluids. We demonstrate how it may be used to compute spatial mode entanglement, particle partitioned entanglement, and the entanglement of particles, providing insights into quantum correlations generated by fluctuations, indistinguishability, and interactions. We present proof-of-principle calculations and benchmark against an exactly soluble model of interacting bosons in one spatial dimension. As this algorithm retains the fundamental polynomial scaling of quantum Monte Carlo when applied to sign-problem-free models, future applications should allow for the study of entanglement entropy in large-scale many-body systems of interacting bosons.

    4. Semiclassical Path Integral Dynamics: Photosynthetic Energy Transfer with Realistic Environment Interactions

      NASA Astrophysics Data System (ADS)

      Lee, Mi Kyung; Huo, Pengfei; Coker, David F.

      2016-05-01

      This article reviews recent progress in the theoretical modeling of excitation energy transfer (EET) processes in natural light harvesting complexes. The iterative partial linearized density matrix path-integral propagation approach, which involves both forward and backward propagation of electronic degrees of freedom together with a linearized, short-time approximation for the nuclear degrees of freedom, provides an accurate and efficient way to model the nonadiabatic quantum dynamics at the heart of these EET processes. Combined with a recently developed chromophore-protein interaction model that incorporates both accurate ab initio descriptions of intracomplex vibrations and chromophore-protein interactions treated with atomistic detail, these simulation tools are beginning to unravel the detailed EET pathways and relaxation dynamics in light harvesting complexes.

    5. A PATH INTEGRAL FORMULATION OF THE WRIGHT-FISHER PROCESS WITH GENIC SELECTION

      PubMed Central

      SCHRAIBER, JOSHUA G.

      2014-01-01

      The Wright-Fisher process with selection is an important tool in population genetics theory. Traditional analysis of this process relies on the diffusion approximation. The diffusion approximation is usually studied in a partial differential equations framework. In this paper, I introduce a path integral formalism to study the Wright-Fisher process with selection and use that formalism to obtain a simple perturbation series to approximate the transition density. The perturbation series can be understood in terms of Feynman diagrams, which have a simple probabilistic interpretation in terms of selective events. The perturbation series proves to be an accurate approximation of the transition density for weak selection and is shown to be arbitrarily accurate for any selection coefficient. PMID:24269333

    6. Excitonic effects in two-dimensional semiconductors: Path integral Monte Carlo approach

      SciTech Connect

      Velizhanin, Kirill A.; Saxena, Avadh

      2015-11-01

      The most striking features of novel two-dimensional semiconductors (e.g., transition metal dichalcogenide monolayers or phosphorene) is a strong Coulomb interaction between charge carriers resulting in large excitonic effects. In particular, this leads to the formation of multicarrier bound states upon photoexcitation (e.g., excitons, trions, and biexcitons), which could remain stable at near-room temperatures and contribute significantly to the optical properties of such materials. In our work we have used the path integral Monte Carlo methodology to numerically study properties of multicarrier bound states in two-dimensional semiconductors. Specifically, we have accurately investigated and tabulated the dependence of single-exciton, trion, and biexciton binding energies on the strength of dielectric screening, including the limiting cases of very strong and very weak screening. Our results of this work are potentially useful in the analysis of experimental data and benchmarking of theoretical and computational models.

    7. Topics in mode conversion theory and the group theoretical foundations of path integrals

      NASA Astrophysics Data System (ADS)

      Richardson, Andrew Stephen

      discrete Beisenberg-Wey1 group to construct the symbol of a matrix. We then go on to show how the path integral arises when calculating the symbol of a function of an operator. We also show how the phase space and configuration space path integrals arise when considering reductions of the regular representation of the Heisenberg-Wey1 group to the primary representations and irreducible representations, respectively. We also show how the path integral can be interpreted as a Fourier transform on the space of measures, opening up the possibility of using tools from statistical mechanics (such as maximum entropy techniques) to analyze the path integral. We conclude with a survey of ideas for future research and describe several potential applications of this group theoretical perspective to problems in mode conversion.

    8. Proton transfer dynamics in the propionic acid dimer from path integral molecular dynamics calculations.

      PubMed

      Durlak, Piotr; Latajka, Zdzisław

      2011-09-01

      The double proton transfer process in the cyclic dimer of propionic acid in the gas phase was studied using a path integral molecular dynamics method. Structures, energies and proton trajectories were determined. Very large amplitude motions of the skeleton of a propionic acid molecule were observed during the simulations, and almost free rotation of the C(2)H(5) group around the C(α)-C bond. A double-well symmetric potential with a very small energy barrier was determined from the free energy profile for the proton motions. Infrared spectra for different isotopomers were calculated, and comparative vibrational analysis was performed. The vibrational results from CPMD appear to be in qualitative agreement with the experimental ones. PMID:21213001

    9. Torsional path integral Monte Carlo method for the quantum simulation of large molecules

      NASA Astrophysics Data System (ADS)

      Miller, Thomas F.; Clary, David C.

      2002-05-01

      A molecular application is introduced for calculating quantum statistical mechanical expectation values of large molecules at nonzero temperatures. The Torsional Path Integral Monte Carlo (TPIMC) technique applies an uncoupled winding number formalism to the torsional degrees of freedom in molecular systems. The internal energy of the molecules ethane, n-butane, n-octane, and enkephalin are calculated at standard temperature using the TPIMC technique and compared to the expectation values obtained using the harmonic oscillator approximation and a variational technique. All studied molecules exhibited significant quantum mechanical contributions to their internal energy expectation values according to the TPIMC technique. The harmonic oscillator approximation approach to calculating the internal energy performs well for the molecules presented in this study but is limited by its neglect of both anharmonicity effects and the potential coupling of intramolecular torsions.

    10. Gaussian white noise analysis and its application to Feynman path integral

      NASA Astrophysics Data System (ADS)

      Suryawan, Herry Pribawanto

      2016-02-01

      In applied science, Gaussian white noise (the time derivative of Brownian motion) is often chosen as a mathematical idealization of phenomena involving sudden and extremely large fluctuations. It is also possible to define and study Gaussian white noise in a mathematically rigorous framework. In this survey paper we review the Gaussian white noise as an object in an infinite dimensional topological vector space. A brief construction of Gaussian white noise space and Gaussian white noise distributions will be presented. Gaussian white noise analysis provides a framework which offers various generalization of concept known from finite dimensional analysis to the infinite dimensional case, among them are differential operators, Fourier transform, and distribution theory. We will also present some recent developments and results on the application of Gaussian white noise theory to Feynman's path integral approach for quantum mechanics.

    11. Time travel paradoxes, path integrals, and the many worlds interpretation of quantum mechanics

      NASA Astrophysics Data System (ADS)

      Everett, Allen

      2004-06-01

      We consider two approaches to evading paradoxes in quantum mechanics with closed timelike curves. In a model similar to Politzer’s, assuming pure states and using path integrals, we show that the problems of paradoxes and of unitarity violation are related; preserving unitarity avoids paradoxes by modifying the time evolution so that improbable events become certain. Deutsch has argued, using the density matrix, that paradoxes do not occur in the “many worlds interpretation.” We find that in this approach account must be taken of the resolution time of the device that detects objects emerging from a wormhole or other time machine. When this is done one finds that this approach is viable only if macroscopic objects traversing a wormhole interact with it so strongly that they are broken into microscopic fragments.

    12. Excitonic effects in two-dimensional semiconductors: Path integral Monte Carlo approach

      DOE PAGES

      Velizhanin, Kirill A.; Saxena, Avadh

      2015-11-01

      The most striking features of novel two-dimensional semiconductors (e.g., transition metal dichalcogenide monolayers or phosphorene) is a strong Coulomb interaction between charge carriers resulting in large excitonic effects. In particular, this leads to the formation of multicarrier bound states upon photoexcitation (e.g., excitons, trions, and biexcitons), which could remain stable at near-room temperatures and contribute significantly to the optical properties of such materials. In our work we have used the path integral Monte Carlo methodology to numerically study properties of multicarrier bound states in two-dimensional semiconductors. Specifically, we have accurately investigated and tabulated the dependence of single-exciton, trion, and biexcitonmore » binding energies on the strength of dielectric screening, including the limiting cases of very strong and very weak screening. Our results of this work are potentially useful in the analysis of experimental data and benchmarking of theoretical and computational models.« less

    13. A path integral formulation of the Wright-Fisher process with genic selection.

      PubMed

      Schraiber, Joshua G

      2014-03-01

      The Wright-Fisher process with selection is an important tool in population genetics theory. Traditional analysis of this process relies on the diffusion approximation. The diffusion approximation is usually studied in a partial differential equations framework. In this paper, I introduce a path integral formalism to study the Wright-Fisher process with selection and use that formalism to obtain a simple perturbation series to approximate the transition density. The perturbation series can be understood in terms of Feynman diagrams, which have a simple probabilistic interpretation in terms of selective events. The perturbation series proves to be an accurate approximation of the transition density for weak selection and is shown to be arbitrarily accurate for any selection coefficient. PMID:24269333

    14. WORM ALGORITHM PATH INTEGRAL MONTE CARLO APPLIED TO THE 3He-4He II SANDWICH SYSTEM

      NASA Astrophysics Data System (ADS)

      Al-Oqali, Amer; Sakhel, Asaad R.; Ghassib, Humam B.; Sakhel, Roger R.

      2012-12-01

      We present a numerical investigation of the thermal and structural properties of the 3He-4He sandwich system adsorbed on a graphite substrate using the worm algorithm path integral Monte Carlo (WAPIMC) method [M. Boninsegni, N. Prokof'ev and B. Svistunov, Phys. Rev. E74, 036701 (2006)]. For this purpose, we have modified a previously written WAPIMC code originally adapted for 4He on graphite, by including the second 3He-component. To describe the fermions, a temperature-dependent statistical potential has been used. This has proven very effective. The WAPIMC calculations have been conducted in the millikelvin temperature regime. However, because of the heavy computations involved, only 30, 40 and 50 mK have been considered for the time being. The pair correlations, Matsubara Green's function, structure factor, and density profiles have been explored at these temperatures.

    15. Excitonic effects in two-dimensional semiconductors: Path integral Monte Carlo approach

      SciTech Connect

      Velizhanin, Kirill A.; Saxena, Avadh

      2015-11-11

      The most striking features of novel two-dimensional semiconductors (e.g., transition metal dichalcogenide monolayers or phosphorene) is a strong Coulomb interaction between charge carriers resulting in large excitonic effects. In particular, this leads to the formation of multicarrier bound states upon photoexcitation (e.g., excitons, trions, and biexcitons), which could remain stable at near-room temperatures and contribute significantly to the optical properties of such materials. In our work we have used the path integral Monte Carlo methodology to numerically study properties of multicarrier bound states in two-dimensional semiconductors. Specifically, we have accurately investigated and tabulated the dependence of single-exciton, trion, and biexciton binding energies on the strength of dielectric screening, including the limiting cases of very strong and very weak screening. Our results of this work are potentially useful in the analysis of experimental data and benchmarking of theoretical and computational models.

    16. Airborne 2-Micron Double-Pulsed Integrated Path Differential Absorption Lidar for Column CO2 Measurement

      NASA Technical Reports Server (NTRS)

      Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

      2014-01-01

      Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 millijouls and up to 10 Hz repetition rate. The two laser pulses are separated by 200 microseconds and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micron IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

    17. Maintaining a cognitive map in darkness: the need to fuse boundary knowledge with path integration.

      PubMed

      Cheung, Allen; Ball, David; Milford, Michael; Wyeth, Gordon; Wiles, Janet

      2012-01-01

      Spatial navigation requires the processing of complex, disparate and often ambiguous sensory data. The neurocomputations underpinning this vital ability remain poorly understood. Controversy remains as to whether multimodal sensory information must be combined into a unified representation, consistent with Tolman's "cognitive map", or whether differential activation of independent navigation modules suffice to explain observed navigation behaviour. Here we demonstrate that key neural correlates of spatial navigation in darkness cannot be explained if the path integration system acted independently of boundary (landmark) information. In vivo recordings demonstrate that the rodent head direction (HD) system becomes unstable within three minutes without vision. In contrast, rodents maintain stable place fields and grid fields for over half an hour without vision. Using a simple HD error model, we show analytically that idiothetic path integration (iPI) alone cannot be used to maintain any stable place representation beyond two to three minutes. We then use a measure of place stability based on information theoretic principles to prove that featureless boundaries alone cannot be used to improve localization above chance level. Having shown that neither iPI nor boundaries alone are sufficient, we then address the question of whether their combination is sufficient and--we conjecture--necessary to maintain place stability for prolonged periods without vision. We addressed this question in simulations and robot experiments using a navigation model comprising of a particle filter and boundary map. The model replicates published experimental results on place field and grid field stability without vision, and makes testable predictions including place field splitting and grid field rescaling if the true arena geometry differs from the acquired boundary map. We discuss our findings in light of current theories of animal navigation and neuronal computation, and elaborate on

    18. Maintaining a Cognitive Map in Darkness: The Need to Fuse Boundary Knowledge with Path Integration

      PubMed Central

      Cheung, Allen; Ball, David; Milford, Michael; Wyeth, Gordon; Wiles, Janet

      2012-01-01

      Spatial navigation requires the processing of complex, disparate and often ambiguous sensory data. The neurocomputations underpinning this vital ability remain poorly understood. Controversy remains as to whether multimodal sensory information must be combined into a unified representation, consistent with Tolman's “cognitive map”, or whether differential activation of independent navigation modules suffice to explain observed navigation behaviour. Here we demonstrate that key neural correlates of spatial navigation in darkness cannot be explained if the path integration system acted independently of boundary (landmark) information. In vivo recordings demonstrate that the rodent head direction (HD) system becomes unstable within three minutes without vision. In contrast, rodents maintain stable place fields and grid fields for over half an hour without vision. Using a simple HD error model, we show analytically that idiothetic path integration (iPI) alone cannot be used to maintain any stable place representation beyond two to three minutes. We then use a measure of place stability based on information theoretic principles to prove that featureless boundaries alone cannot be used to improve localization above chance level. Having shown that neither iPI nor boundaries alone are sufficient, we then address the question of whether their combination is sufficient and – we conjecture – necessary to maintain place stability for prolonged periods without vision. We addressed this question in simulations and robot experiments using a navigation model comprising of a particle filter and boundary map. The model replicates published experimental results on place field and grid field stability without vision, and makes testable predictions including place field splitting and grid field rescaling if the true arena geometry differs from the acquired boundary map. We discuss our findings in light of current theories of animal navigation and neuronal computation, and

    19. Short-time asymptotics of a rigorous path integral for N = 1 supersymmetric quantum mechanics on a Riemannian manifold

      SciTech Connect

      Fine, Dana S.; Sawin, Stephen

      2014-06-15

      Following Feynman's prescription for constructing a path integral representation of the propagator of a quantum theory, a short-time approximation to the propagator for imaginary-time, N = 1 supersymmetric quantum mechanics on a compact, even-dimensional Riemannian manifold is constructed. The path integral is interpreted as the limit of products, determined by a partition of a finite time interval, of this approximate propagator. The limit under refinements of the partition is shown to converge uniformly to the heat kernel for the Laplace-de Rham operator on forms. A version of the steepest descent approximation to the path integral is obtained, and shown to give the expected short-time behavior of the supertrace of the heat kernel.

    20. A new approach to calculate charge carrier transport mobility in organic molecular crystals from imaginary time path integral simulations

      SciTech Connect

      Song, Linze; Shi, Qiang

      2015-05-07

      We present a new non-perturbative method to calculate the charge carrier mobility using the imaginary time path integral approach, which is based on the Kubo formula for the conductivity, and a saddle point approximation to perform the analytic continuation. The new method is first tested using a benchmark calculation from the numerical exact hierarchical equations of motion method. Imaginary time path integral Monte Carlo simulations are then performed to explore the temperature dependence of charge carrier delocalization and mobility in organic molecular crystals (OMCs) within the Holstein and Holstein-Peierls models. The effects of nonlocal electron-phonon interaction on mobility in different charge transport regimes are also investigated.

    1. Integrating Physical Activity into Academic Pursuits

      ERIC Educational Resources Information Center

      Gaus, Mark D.; Simpson, Cynthia G.

      2009-01-01

      Children of today may be the first generation in the United States in more than 200 years to have a life expectancy shorter than their parents. Low levels of fitness caused by physical inactivity and poor nutritional habits of many of today's youth may be a contributing factor. Combating low fitness levels with physical activity is of utmost…

    2. Evaluation of Sex Integrated Physical Education Classes.

      ERIC Educational Resources Information Center

      Sander, Erika

      Implementation of Title IX and resultant sex equity laws in secondary physical education programs occasions a need to develop new methods of evaluating and grading students enrolled in coeducational physical education classes. This document discusses problems that may occur as a result of sex equity modifications from the point of view of the…

    3. Discovering Integration through a Physical Phenomenon

      ERIC Educational Resources Information Center

      Burt, Derek; Magnes, Jenny; Schwarz, Gregory; Hartke, John

      2008-01-01

      This article outlines a method of conducting a laboratory designed to discover mathematical integration with students. The results are produced and verified in the laboratory by students. Understanding that an integral is defined by the area bounded by a function of x and the x-axis from a point a to a point b is challenging. Students often have…

    4. Integrating Condensed Matter Physics into a Liberal Arts Physics Curriculum

      NASA Astrophysics Data System (ADS)

      Collett, Jeffrey

      2008-03-01

      The emergence of nanoscale science into the popular consciousness presents an opportunity to attract and retain future condensed matter scientists. We inject nanoscale physics into recruiting activities and into the introductory and the core portions of the curriculum. Laboratory involvement and research opportunity play important roles in maintaining student engagement. We use inexpensive scanning tunneling (STM) and atomic force (AFM) microscopes to introduce students to nanoscale structure early in their college careers. Although the physics of tip-surface interactions is sophisticated, the resulting images can be interpreted intuitively. We use the STM in introductory modern physics to explore quantum tunneling and the properties of electrons at surfaces. An interdisciplinary course in nanoscience and nanotechnology course team-taught with chemists looks at nanoscale phenomena in physics, chemistry, and biology. Core quantum and statistical physics courses look at effects of quantum mechanics and quantum statistics in degenerate systems. An upper level solid-state physics course takes up traditional condensed matter topics from a structural perspective by beginning with a study of both elastic and inelastic scattering of x-rays from crystalline solids and liquid crystals. Students encounter reciprocal space concepts through the analysis of laboratory scattering data and by the development of the scattering theory. The course then examines the importance of scattering processes in band structure and in electrical and thermal conduction. A segment of the course is devoted to surface physics and nanostructures where we explore the effects of restricting particles to two-dimensional surfaces, one-dimensional wires, and zero-dimensional quantum dots.

    5. Computer Integrated Manufacturing: Physical Modelling Systems Design. A Personal View.

      ERIC Educational Resources Information Center

      Baker, Richard

      A computer-integrated manufacturing (CIM) Physical Modeling Systems Design project was undertaken in a time of rapid change in the industrial, business, technological, training, and educational areas in Australia. A specification of a manufacturing physical modeling system was drawn up. Physical modeling provides a flexibility and configurability…

    6. Effects of Partners Together in Health (PaTH) Intervention on Physical Activity and Healthy Eating Behaviors: A Pilot Study

      PubMed Central

      Yates, Bernice C.; Norman, Joseph; Meza, Jane; Krogstrand, Kaye Stanek; Harrington, Susana; Shurmur, Scott; Johnson, Matthew; Schumacher, Karen

      2014-01-01

      Background Despite proven efficacy of cardiac rehabilitation (CR) in helping patients initiate physical activity and healthy eating changes, less than 50% of CR participants maintain changes 6 months later. Objective The objective of this feasibility study was to test the Partners Together in Health (PaTH) Intervention versus usual care (UC) in improving physical activity and healthy eating behaviors in coronary artery bypass graft (CABG) surgery patients and spouses. Methods An experimental, two-group (n = 17 couples/group), repeated measures design was used. CABG patients in both groups participated in Phase II outpatient CR. Spouses in the PaTH group attended CR with the patient and were asked to make the same physical activity and healthy eating changes as patients. Spouses in the control group attended educational classes with patients. It was theorized that “two persons would be better than one” at making changes and sticking with them long-term. Physical activity behavior was measured using the Actiheart accelerometer; the activity biomarker was an exercise tolerance test. Eating behavior was measured using 3-day food records; the biomarker was the lipid profile. Data were collected at baseline (entrance in CR), 3-months (post-CR), and 6-months. Changes over time were examined using Mann-Whitney U statistics and effect sizes. Results The PaTH intervention was successful primarily in demonstrating improved trends in healthy eating behavior for patients and spouses. No differences were found between the PaTH and UC patients or spouses at 3 or 6 months in the number of minutes/week of physical activity. By 6 months, patients in both groups were, on average, below the national guidelines for PA recommendations (≥ 150 min/week at > 3 METs). Conclusions The couple-focused PaTH intervention demonstrated promise in offsetting the decline in dietary adherence typically seen 6 months after CR. PMID:24434826

    7. A reliable acoustic path: Physical properties and a source localization method

      NASA Astrophysics Data System (ADS)

      Duan, Rui; Yang, Kun-De; Ma, Yuan-Liang; Lei, Bo

      2012-12-01

      The physical properties of a reliable acoustic path (RAP) are analysed and subsequently a weighted-subspace-fitting matched field (WSF-MF) method for passive localization is presented by exploiting the properties of the RAP environment. The RAP is an important acoustic duct in the deep ocean, which occurs when the receiver is placed near the bottom where the sound velocity exceeds the maximum sound velocity in the vicinity of the surface. It is found that in the RAP environment the transmission loss is rather low and no blind zone of surveillance exists in a medium range. The ray theory is used to explain these phenomena. Furthermore, the analysis of the arrival structures shows that the source localization method based on arrival angle is feasible in this environment. However, the conventional methods suffer from the complicated and inaccurate estimation of the arrival angle. In this paper, a straightforward WSF-MF method is derived to exploit the information about the arrival angles indirectly. The method is to minimize the distance between the signal subspace and the spanned space by the array manifold in a finite range-depth space rather than the arrival-angle space. Simulations are performed to demonstrate the features of the method, and the results are explained by the arrival structures in the RAP environment.

    8. Ab initio path-integral molecular dynamics and the quantum nature of hydrogen bonds

      NASA Astrophysics Data System (ADS)

      Yexin, Feng; Ji, Chen; Xin-Zheng, Li; Enge, Wang

      2016-01-01

      The hydrogen bond (HB) is an important type of intermolecular interaction, which is generally weak, ubiquitous, and essential to life on earth. The small mass of hydrogen means that many properties of HBs are quantum mechanical in nature. In recent years, because of the development of computer simulation methods and computational power, the influence of nuclear quantum effects (NQEs) on the structural and energetic properties of some hydrogen bonded systems has been intensively studied. Here, we present a review of these studies by focussing on the explanation of the principles underlying the simulation methods, i.e., the ab initio path-integral molecular dynamics. Its extension in combination with the thermodynamic integration method for the calculation of free energies will also be introduced. We use two examples to show how this influence of NQEs in realistic systems is simulated in practice. Project supported by the National Natural Science Foundation of China (Grant Nos. 11275008, 91021007, and 10974012) and the China Postdoctoral Science Foundation (Grant No. 2014M550005).

    9. Kinetic isotope effect in malonaldehyde determined from path integral Monte Carlo simulations.

      PubMed

      Huang, Jing; Buchowiecki, Marcin; Nagy, Tibor; Vaníček, Jiří; Meuwly, Markus

      2014-01-01

      The primary H/D kinetic isotope effect on the intramolecular proton transfer in malonaldehyde is determined from quantum instanton path integral Monte Carlo simulations on a fully dimensional and validated potential energy surface for temperatures between 250 and 1500 K. Our calculations, based on thermodynamic integration with respect to the mass of the transferring particle, are significantly accelerated by the direct evaluation of the kinetic isotope effect instead of computing it as a ratio of two rate constants. At room temperature, the KIE from the present simulations is 5.2 ± 0.4. The KIE is found to vary considerably as a function of temperature and the low-T behaviour is dominated by the fact that the free energy derivative in the reactant state increases more rapidly than in the transition state. Detailed analysis of the various contributions to the quantum rate constant together with estimates for rates from conventional transition state theory and from periodic orbit theory suggest that the KIE in malonaldehyde is dominated by zero point energy effects and that tunneling plays a minor role at room temperature.

    10. Path integral studies of the rotations of methane and its heavier isotopomers in 4He nanoclusters.

      PubMed

      Markovskiy, N D; Mak, C H

      2009-08-13

      Path integral Monte Carlo simulations have been carried out to study the rotations of a methane molecule and its heavier isotopomers inside a small cluster of 4He atoms at 0.3 K in order to determine how the renormalization in the methane's rotational constant is related to the quantum statistics and superfluidity of the helium shell. By changing the mass of the hydrogens and systematically varying the moment of inertia of the methane, we were able to study the effects of its rotations on the quantum statistics of the helium atoms and their countereffects on the methane's effective rotational constant. The renormalized rotational constant depends strongly on the intrinsic moment of inertia of the methane. A heavy probe favors strong templating of the helium density as well as a large renormalization in the probe's rotational constant, but a light probe shows almost no effect on the shell density or the effective rotational constant. These results suggest that in order to fully understand the superfluidity of the helium shell, the probe must be treated as an integral part of the system. We rationalize the findings in terms of a rotational smearing effect and suggest that there is no clearly quantifiable relationship between the superfluid fraction of the shell and the renormalized rotational constant of the probe for cases where the probe molecule is either light or has weak anisotropic interactions with the helium atoms. PMID:19618956

    11. Integrated Health and Physical Education Program to Reduce Media Use and Increase Physical Activity in Youth

      ERIC Educational Resources Information Center

      Clocksin, Brian D.; Wattson, Doris L.; Williams, Daniel P.; Randsell, Lynda

      2009-01-01

      The purpose of this project was to compare an integrated health and physical education curriculum, focused on reducing media use and on increasing physical activity in middle school adolescents, to traditional and nonintegrated health and physical education curricula. Two middle schools' health and physical education classes were assigned to an…

    12. Triple-Pulsed Two-Micron Integrated Path Differential Absorption Lidar: A New Active Remote Sensing Capability with Path to Space

      NASA Technical Reports Server (NTRS)

      Singh, Upendra N.; Refaat, Tamer F.; Petros, Mulugeta; Yu, Jirong

      2015-01-01

      The two-micron wavelength is suitable for monitoring atmospheric water vapor and carbon dioxide, the two most dominant greenhouse gases. Recent advances in 2-micron laser technology paved the way for constructing state-of-the-art lidar transmitters for active remote sensing applications. In this paper, a new triple-pulsed 2-micron integrated path differential absorption lidar is presented. This lidar is capable of measuring either two species or single specie with two different weighting functions, simultaneously and independently. Development of this instrument is conducted at NASA Langley Research Center. Instrument scaling for projected future space missions will be discussed.

    13. Triple-Pulsed Two-Micron Integrated Path Differential Absorption Lidar: A New Active Remote Sensing Capability with Path to Space

      NASA Astrophysics Data System (ADS)

      Singh, Upendra N.; Refaat, Tamer F.; Petros, Mulugeta; Yu, Jirong

      2016-06-01

      The two-micron wavelength is suitable for monitoring atmospheric water vapor and carbon dioxide, the two most dominant greenhouse gases. Recent advances in 2-μm laser technology paved the way for constructing state-of-the-art lidar transmitters for active remote sensing applications. In this paper, a new triple-pulsed 2-μm integrated path differential absorption lidar is presented. This lidar is capable of measuring either two species or single specie with two different weighting functions, simultaneously and independently. Development of this instrument is conducted at NASA Langley Research Center. Instrument scaling for projected future space missions will be discussed.

    14. Homing strategies of the Australian desert ant Melophorus bagoti. II. Interaction of the path integrator with visual cue information.

      PubMed

      Narendra, Ajay

      2007-05-01

      Individually foraging ants are known to return to their nest by using path-integration and recording visual information present in the environment. The interaction between the path integrator and the information provided by the visual cues in an Australian desert ant are reported here. Ants were trained to travel in a 1-m wide and 20-m long corridor of cylinders. Homeward paths of trained ants were recorded in the presence and absence of vector information and route cues in both the familiar training field and in an unfamiliar test field. Homing ants used route cue information only in a familiar context. The route cues were not essential but served to reduce the deviation of the homing trajectory from the nest-feeder line. When displaced locally, homebound ants initially oriented towards the nest using distant cues and then headed in a direction intermediate between that dictated by the path integrator and the distant cues. If in the course of travel ants encountered the familiar path they adhered to it. If not, they travelled on average half the distance of the outbound journey and initiated a search directed towards the nest. Following the search, ants headed in a direction intermediate between that dictated by the route cues and the distant cues. In an unfamiliar context neither vector nor route cue information could steer a homing ant towards the nest. The dominance of distant cues, the importance of familiar context and the interaction between different navigation strategies are discussed here.

    15. Cyber / Physical Security Vulnerability Assessment Integration

      SciTech Connect

      MacDonald, Douglas G.; Simpkins, Bret E.

      2012-07-28

      Abstract Both physical protection and cyber security domains offer solutions for the discovery of vulnerabilities through the use of various assessment processes and software tools. Each vulnerability assessment (VA) methodology provides the ability to identify and categorize vulnerabilities, and quantifies the risks within their own areas of expertise. Neither approach fully represents the true potential security risk to a site and/or a facility, nor comprehensively assesses the overall security posture. The technical approach to solving this problem was to identify methodologies and processes that blend the physical and cyber security assessments, and develop tools to accurately quantify the unaccounted for risk. SMEs from both the physical and the cyber security domains developed the blending methodologies, and cross trained each other on the various aspects of the physical and cyber security assessment processes. A local critical infrastructure entity volunteered to host a proof of concept physical/cyber security assessment, and the lessons learned have been leveraged by this effort. The four potential modes of attack an adversary can use in approaching a target are; Physical Only Attack, Cyber Only Attack, Physical Enabled Cyber Attack, and the Cyber Enabled Physical Attack. The Physical Only and the Cyber Only pathway analysis are two of the most widely analyzed attack modes. The pathway from an off-site location to the desired target location is dissected to ensure adversarial activity can be detected and neutralized by the protection strategy, prior to completion of a predefined task. This methodology typically explores a one way attack from the public space (or common area) inward towards the target. The Physical Enabled Cyber Attack and the Cyber Enabled Physical Attack are much more intricate. Both scenarios involve beginning in one domain to affect change in the other, then backing outward to take advantage of the reduced system effectiveness, before

    16. Review of computer simulations of isotope effects on biochemical reactions: From the Bigeleisen equation to Feynman's path integral.

      PubMed

      Wong, Kin-Yiu; Xu, Yuqing; Xu, Liang

      2015-11-01

      Enzymatic reactions are integral components in many biological functions and malfunctions. The iconic structure of each reaction path for elucidating the reaction mechanism in details is the molecular structure of the rate-limiting transition state (RLTS). But RLTS is very hard to get caught or to get visualized by experimentalists. In spite of the lack of explicit molecular structure of the RLTS in experiment, we still can trace out the RLTS unique "fingerprints" by measuring the isotope effects on the reaction rate. This set of "fingerprints" is considered as a most direct probe of RLTS. By contrast, for computer simulations, oftentimes molecular structures of a number of TS can be precisely visualized on computer screen, however, theoreticians are not sure which TS is the actual rate-limiting one. As a result, this is an excellent stage setting for a perfect "marriage" between experiment and theory for determining the structure of RLTS, along with the reaction mechanism, i.e., experimentalists are responsible for "fingerprinting", whereas theoreticians are responsible for providing candidates that match the "fingerprints". In this Review, the origin of isotope effects on a chemical reaction is discussed from the perspectives of classical and quantum worlds, respectively (e.g., the origins of the inverse kinetic isotope effects and all the equilibrium isotope effects are purely from quantum). The conventional Bigeleisen equation for isotope effect calculations, as well as its refined version in the framework of Feynman's path integral and Kleinert's variational perturbation (KP) theory for systematically incorporating anharmonicity and (non-parabolic) quantum tunneling, are also presented. In addition, the outstanding interplay between theory and experiment for successfully deducing the RLTS structures and the reaction mechanisms is demonstrated by applications on biochemical reactions, namely models of bacterial squalene-to-hopene polycyclization and RNA 2'-O

    17. The roots of physics students' motivations: Fear and integrity

      NASA Astrophysics Data System (ADS)

      Van Dusen, Ben

      Too often, physics students are beset by feelings of failure and isolation rather than experiencing the creative joys of discovery that physics has to offer. This dissertation research was founded on the desire of a teacher to make physics class exciting and motivating to his students. This work explores how various aspects of learning environments interact with student motivation. This work uses qualitative and quantitative methods to explore how students are motivated to engage in physics and how they feel about themselves while engaging in physics. The collection of four studies in this dissertation culminates in a sociocultural perspective on motivation and identity. This perspective uses two extremes of how students experience physics as a lens for understanding motivation: fear and self-preservation versus integrity and self-expression. Rather than viewing motivation as a property of the student, or viewing students as inherently interested or disinterested in physics, the theoretical perspective on motivation and identity helps examine features of the learning environments that determine how students' experience themselves through physics class. This perspective highlights the importance of feeling a sense of belonging in the context of physics and the power that teachers have in shaping students' motivation through the construction of their classroom learning environments. Findings demonstrate how different ways that students experience themselves in physics class impact their performance and interest in physics. This dissertation concludes with a set of design principles that can foster integration and integrity among students in physics learning environments.

    18. PLANE-INTEGRATED OPEN-PATH FOURIER TRANSFORM INFRARED SPECTROMETRY METHODOLOGY FOR ANAEROBIC SWINE LAGOON EMISSION MEASUREMENTS

      EPA Science Inventory

      Emissions of ammonia and methane from an anaerobic lagoon at a swine animal feeding operation were evaluated five times over a period of two years. The plane-integrated (PI) open-path Fourier transform infrared spectrometry (OP-FTIR) methodology was used to transect the plume at ...

    19. Green function of the double-fractional Fokker-Planck equation: path integral and stochastic differential equations.

      PubMed

      Kleinert, H; Zatloukal, V

      2013-11-01

      The statistics of rare events, the so-called black-swan events, is governed by non-Gaussian distributions with heavy power-like tails. We calculate the Green functions of the associated Fokker-Planck equations and solve the related stochastic differential equations. We also discuss the subject in the framework of path integration.

    20. Architectural constraints are a major factor reducing path integration accuracy in the rat head direction cell system.

      PubMed

      Page, Hector J I; Walters, Daniel; Stringer, Simon M

      2015-01-01

      Head direction cells fire to signal the direction in which an animal's head is pointing. They are able to track head direction using only internally-derived information (path integration)In this simulation study we investigate the factors that affect path integration accuracy. Specifically, two major limiting factors are identified: rise time, the time after stimulation it takes for a neuron to start firing, and the presence of symmetric non-offset within-layer recurrent collateral connectivity. On the basis of the latter, the important prediction is made that head direction cell regions directly involved in path integration will not contain this type of connectivity; giving a theoretical explanation for architectural observations. Increased neuronal rise time is found to slow path integration, and the slowing effect for a given rise time is found to be more severe in the context of short conduction delays. Further work is suggested on the basis of our findings, which represent a valuable contribution to understanding of the head direction cell system.

    1. Path-integral solution for a two-dimensional model with axial-vector-current--pseudoscalar derivative interaction

      SciTech Connect

      Botelho, L.C.L.

      1985-03-15

      We study a two-dimensional quantum field model with axial-vector-current--pseudoscalar derivative interaction using path-integral methods. We construct an effective Lagrangian by performing a chiral change in the fermionic variables leading to an exact solution of the model.

    2. White Noise Path Integral Treatment of a Two-dimensional Dirac Oscillator in a Uniform Magnetic Field

      SciTech Connect

      Bastatas, Lyndon D.; Bornales, Jinky B.

      2008-06-18

      White noise path integral prescription is applied to solve the Dirac equation for a two-dimensional Dirac oscillator in a uniform magnetic field. The energy spectrum obtained agrees with the result obtained by Villalba and Maggiolo using the differential approach.

    3. Coherent-state path integral versus coarse-grained effective stochastic equation of motion: From reaction diffusion to stochastic sandpiles

      NASA Astrophysics Data System (ADS)

      Wiese, Kay Jörg

      2016-04-01

      We derive and study two different formalisms used for nonequilibrium processes: the coherent-state path integral, and an effective, coarse-grained stochastic equation of motion. We first study the coherent-state path integral and the corresponding field theory, using the annihilation process A +A →A as an example. The field theory contains counterintuitive quartic vertices. We show how they can be interpreted in terms of a first-passage problem. Reformulating the coherent-state path integral as a stochastic equation of motion, the noise generically becomes imaginary. This renders it not only difficult to interpret, but leads to convergence problems at finite times. We then show how alternatively an effective coarse-grained stochastic equation of motion with real noise can be constructed. The procedure is similar in spirit to the derivation of the mean-field approximation for the Ising model, and the ensuing construction of its effective field theory. We finally apply our findings to stochastic Manna sandpiles. We show that the coherent-state path integral is inappropriate, or at least inconvenient. As an alternative, we derive and solve its mean-field approximation, which we then use to construct a coarse-grained stochastic equation of motion with real noise.

    4. Creativity, Spirituality, and Transcendence: Paths to Integrity and Wisdom in the Mature Self. Publications in Creativity Research.

      ERIC Educational Resources Information Center

      Miller, Melvin E., Ed.; Cook-Greuter, Susanne R., Ed.

      This book contains 11 papers on creativity, spirituality, and transcendence as paths to integrity and wisdom in the mature self. The book begins with the paper "Introduction--Creativity in Adulthood: Personal Maturity and Openness to Extraordinary Sources of Inspiration" (Susanne R. Cook-Greuter, Melvin E. Miller). The next four papers, which…

    5. Derivation of the Schrodinger Equation from the Hamilton-Jacobi Equation in Feynman's Path Integral Formulation of Quantum Mechanics

      ERIC Educational Resources Information Center

      Field, J. H.

      2011-01-01

      It is shown how the time-dependent Schrodinger equation may be simply derived from the dynamical postulate of Feynman's path integral formulation of quantum mechanics and the Hamilton-Jacobi equation of classical mechanics. Schrodinger's own published derivations of quantum wave equations, the first of which was also based on the Hamilton-Jacobi…

    6. On the calculation of the static structure factor of path-integral quantum simple fluids far from exchange

      NASA Astrophysics Data System (ADS)

      Sesé, Luis M.

      This paper addresses several points of interest concerning the computation of the static structure factor of path-integral monatomic quantum fluids. First of all, the connection between the structure factor and the path-integral linear response pair radial correlation function is shown as its defining quantity by assuming a generalized Fermi's potential for the neutron- nuclei interactions, which is to be included in the general expression of the dynamic structure factor. Second, the possibilities of finding Ornstein-Zernike equations for full path-integral fluids, and also for the effective potential models of fluids derived from the path-integral formalism, are explored by working in the grand canonical ensemble. By so doing, the success and features for improvement of the weak-field approach used previously in this context of determining quantum static structure factors [SESE,L.M.,1996, Molec. Phys., 89, 1783; SESE, L.M., and LEDESMA,R., 1997, J. chem. Phys., 106, 1134] can be understood. New numerical applications are performed within this weak-field approach taking as probes the quantum hard-sphere fluid and dense fluid helium-4, the latter being described through LennardJones and Aziz-Slaman underlying interactions. The results show that the structure factors associated with the linear response and instantaneous path-integral pair radial correlation functions differ noticeably from each other with increasing quantum effects. In particular, the linear response description leads to more compressible fluids than the instantaneous one. Besides, the equality between the isothermal compressibilities fixed via the linear response and the quantum particle centre-of-gravity pair radial correlation functions does not hold beyond the situations that can be treated with the Gaussian Feynman-Hibbs effective potential picture. Comparison with experiment in the case of helium-4 (T = 4.2 K) reveals clearly that, under strong quantum conditions, an operative framework more

    7. Path ANalysis

      2007-07-14

      The PANL software determines path through an Adversary Sequence Diagram (ASD) with minimum Probability of Interruption, P(I), given the ASD information and data about site detection, delay, and response force times. To accomplish this, the software generates each path through the ASD, then applies the Estimate of Adversary Sequence Interruption (EASI) methodology for calculating P(I) to each path, and keeps track of the path with the lowest P(I). Primary use is for training purposes duringmore » courses on physical security design. During such courses PANL will be used to demonstrate to students how more complex software codes are used by the US Department of Energy to determine the most-vulnerable paths and, where security needs improvement, how such codes can help determine physical security upgrades.« less

    8. Path ANalysis

      SciTech Connect

      Snell, Mark K.

      2007-07-14

      The PANL software determines path through an Adversary Sequence Diagram (ASD) with minimum Probability of Interruption, P(I), given the ASD information and data about site detection, delay, and response force times. To accomplish this, the software generates each path through the ASD, then applies the Estimate of Adversary Sequence Interruption (EASI) methodology for calculating P(I) to each path, and keeps track of the path with the lowest P(I). Primary use is for training purposes during courses on physical security design. During such courses PANL will be used to demonstrate to students how more complex software codes are used by the US Department of Energy to determine the most-vulnerable paths and, where security needs improvement, how such codes can help determine physical security upgrades.

    9. The Atomic Relay: Integrating Physical Education and Science.

      ERIC Educational Resources Information Center

      Menelly, Daniel J.

      1997-01-01

      Presents a lesson plan for teaching abstract science concepts to gifted middle school students. The lesson integrates a physical education component into science instruction to reinforce the abstract notion that electrons emit energy in the form of visible light. (CR)

    10. On the Intramolecular Hydrogen Bond in Solution: Car-Parrinello and Path Integral Molecular Dynamics Perspective.

      PubMed

      Dopieralski, Przemyslaw; Perrin, Charles L; Latajka, Zdzislaw

      2011-11-01

      The issue of the symmetry of short, low-barrier hydrogen bonds in solution is addressed here with advanced ab initio simulations of a hydrogen maleate anion in different environments, starting with the isolated anion, going through two crystal structures (sodium and potassium salts), then to an aqueous solution, and finally in the presence of counterions. By Car-Parrinello and path integral molecular dynamics simulations, it is demonstrated that the position of the proton in the intramolecular hydrogen bond of an aqueous hydrogen maleate anion is entirely related to the solvation pattern around the oxygen atoms of the intramolecular hydrogen bond. In particular, this anion has an asymmetric hydrogen bond, with the proton always located on the oxygen atom that is less solvated, owing to the instantaneous solvation environment. Simulations of water solutions of hydrogen maleate ion with two different counterions, K(+) and Na(+), surprisingly show that the intramolecular hydrogen-bond potential in the case of the Na(+) salt is always asymmetric, regardless of the hydrogen bonds to water, whereas for the K(+) salt, the potential for H motion depends on the location of the K(+). It is proposed that repulsion by the larger and more hydrated K(+) is weaker than that by Na(+) and competitive with solvation by water. PMID:26598249

    11. Iterative quantum-classical path integral with dynamically consistent state hopping.

      PubMed

      Walters, Peter L; Makri, Nancy

      2016-01-28

      We investigate the convergence of iterative quantum-classical path integral calculations in sluggish environments strongly coupled to a quantum system. The number of classical trajectories, thus the computational cost, grows rapidly (exponentially, unless filtering techniques are employed) with the memory length included in the calculation. We argue that the choice of the (single) trajectory branch during the time preceding the memory interval can significantly affect the memory length required for convergence. At short times, the trajectory branch associated with the reactant state improves convergence by eliminating spurious memory. We also introduce an instantaneous population-based probabilistic scheme which introduces state-to-state hops in the retained pre-memory trajectory branch, and which is designed to choose primarily the trajectory branch associated with the reactant at early times, but to favor the product state more as the reaction progresses to completion. Test calculations show that the dynamically consistent state hopping scheme leads to accelerated convergence and a dramatic reduction of computational effort. PMID:26827203

    12. Bayesian Uncertainty Quantification for Bond Energies and Mobilities Using Path Integral Analysis

      PubMed Central

      Chang, Joshua C.; Fok, Pak-Wing; Chou, Tom

      2015-01-01

      Dynamic single-molecule force spectroscopy is often used to distort bonds. The resulting responses, in the form of rupture forces, work applied, and trajectories of displacements, are used to reconstruct bond potentials. Such approaches often rely on simple parameterizations of one-dimensional bond potentials, assumptions on equilibrium starting states, and/or large amounts of trajectory data. Parametric approaches typically fail at inferring complicated bond potentials with multiple minima, while piecewise estimation may not guarantee smooth results with the appropriate behavior at large distances. Existing techniques, particularly those based on work theorems, also do not address spatial variations in the diffusivity that may arise from spatially inhomogeneous coupling to other degrees of freedom in the macromolecule. To address these challenges, we develop a comprehensive empirical Bayesian approach that incorporates data and regularization terms directly into a path integral. All experimental and statistical parameters in our method are estimated directly from the data. Upon testing our method on simulated data, our regularized approach requires less data and allows simultaneous inference of both complex bond potentials and diffusivity profiles. Crucially, we show that the accuracy of the reconstructed bond potential is sensitive to the spatially varying diffusivity and accurate reconstruction can be expected only when both are simultaneously inferred. Moreover, after providing a means for self-consistently choosing regularization parameters from data, we derive posterior probability distributions, allowing for uncertainty quantification. PMID:26331254

    13. Path-integral simulation of ice VII: Pressure and temperature effects

      NASA Astrophysics Data System (ADS)

      Herrero, Carlos P.; Ramírez, Rafael

      2015-11-01

      The effects of pressure and temperature on structural and thermodynamic properties of ice VII have been studied by using path-integral molecular dynamics (PIMD) simulations. Temperatures between 25 and 450 K, as well as pressures up to 12 GPa were considered. Interatomic interactions were modeled by using the effective q-TIP4P/F potential for flexible water. We analyze the pressure dependence of the molar volume, bulk modulus, interatomic distances, kinetic energy, and atomic delocalization at various temperatures. Results of PIMD simulations are compared with those derived from a quasi-harmonic approximation (QHA) of vibrational modes, which helps to assess the importance of anharmonic effects, as well as the influence of the different modes on the properties of ice VII. The accuracy of the QHA for describing this high-pressure phase decreases for rising temperature, but this approximation becomes more reliable as pressure grows, since anharmonicity becomes less relevant. Comparisons with low-pressure cubic ice are presented.

    14. Ground return signal simulation and retrieval algorithm of spaceborne integrated path DIAL for CO2 measurements

      NASA Astrophysics Data System (ADS)

      Liu, Bing-Yi; Wang, Jun-Yang; Liu, Zhi-Shen

      2014-11-01

      Spaceborne integrated path differential absorption (IPDA) lidar is an active-detection system which is able to perform global CO2 measurement with high accuracy of 1ppmv at day and night over ground and clouds. To evaluate the detection performance of the system, simulation of the ground return signal and retrieval algorithm for CO2 concentration are presented in this paper. Ground return signals of spaceborne IPDA lidar under various ground surface reflectivity and atmospheric aerosol optical depths are simulated using given system parameters, standard atmosphere profiles and HITRAN database, which can be used as reference for determining system parameters. The simulated signals are further applied to the research on retrieval algorithm for CO2 concentration. The column-weighted dry air mixing ratio of CO2 denoted by XCO2 is obtained. As the deviations of XCO2 between the initial values for simulation and the results from retrieval algorithm are within the expected error ranges, it is proved that the simulation and retrieval algorithm are reliable.

    15. Bayesian Uncertainty Quantification for Bond Energies and Mobilities Using Path Integral Analysis

      NASA Astrophysics Data System (ADS)

      Fok, Pak-Wing; Chang, Joshua; Chou, Tom; UCLA-OSU-UD Biomath Group Collaboration

      Dynamic single-molecule force spectroscopy is often used to distort bonds. The resulting responses, in the form of rupture forces and trajectories of displacements, are used to reconstruct bond potentials. Such approaches often rely on simple parameterizations of one-dimensional bond potentials and/or large amounts of trajectory data. Parametric approaches typically fail at inferring complicated bond potentials with multiple minima, while piecewise estimation may not guarantee smooth results. Existing techniques also do not address spatial variations in the diffusivity that may arise from inhomogeneous coupling to other degrees of freedom in the macromolecule. To address these challenges, we develop an empirical Bayesian approach that incorporates data and regularization terms into a path integral. All experimental and statistical parameters in our method are estimated from the data. Upon testing our method on simulated data, our regularized approach requires less data and allows simultaneous inference of both complex bond potentials and diffusivities. We show that the accuracy of the reconstructed bond potential is sensitive to the spatially varying diffusivity and accurate reconstruction can be expected only when both are simultaneously inferred.

    16. Evaluating the B-cell density with various activation functions using White Noise Path Integral Approach

      NASA Astrophysics Data System (ADS)

      Aban, C. J. G.; Bacolod, R. O.; Confesor, M. N. P.

      2015-06-01

      A The White Noise Path Integral Approach is used in evaluating the B-cell density or the number of B-cell per unit volume for a basic type of immune system response based on the modeling done by Perelson and Wiegel. From the scaling principles of Perelson [1], the B- cell density is obtained where antigens and antibodies mutates and activation function f(|S-SA|) is defined describing the interaction between a specific antigen and a B-cell. If the activation function f(|S-SA|) is held constant, the major form of the B-cell density evaluated using white noise analysis is similar to the form of the B-cell density obtained by Perelson and Wiegel using a differential approach.A piecewise linear functionis also used to describe the activation f(|S-SA|). If f(|S-SA|) is zero, the density decreases exponentially. If f(|S-SA|) = S-SA-SB, the B- cell density increases exponentially until it reaches a certain maximum value. For f(|S-SA|) = 2SA-SB-S, the behavior of B-cell density is oscillating and remains to be in small values.

    17. Path-integral Monte Carlo simulation of the second layer of 4He adsorbed on graphite

      NASA Astrophysics Data System (ADS)

      Pierce, Marlon; Manousakis, Efstratios

      1999-02-01

      We have developed a path-integral Monte Carlo method for simulating helium films and apply it to the second layer of helium adsorbed on graphite. We use helium-helium and helium-graphite interactions that are found from potentials which realistically describe the interatomic interactions. The Monte Carlo sampling is over both particle positions and permutations of particle labels. From the particle configurations and static structure factor calculations, we find that this layer possesses, in order of increasing density, a superfluid liquid phase, a 7×7 commensurate solid phase that is registered with respect to the first layer, and an incommensurate solid phase. By applying the Maxwell construction to the dependence of the low-temperature total energy on the coverage, we are able to identify coexistence regions between the phases. From these, we deduce an effectively zero-temperature phase diagram. Our phase boundaries are in agreement with heat capacity and torsional oscillator measurements, and demonstrate that the experimentally observed disruption of the superfluid phase is caused by the growth of the commensurate phase. We further observe that the superfluid phase has a transition temperature consistent with the two-dimensional value. Promotion to the third layer occurs for densities above 0.212 atom/Å 2, in good agreement with experiment. Finally, we calculate the specific heat for each phase and obtain peaks at temperatures in general agreement with experiment.

    18. Equilibrium fractionation of H and O isotopes in water from path integral molecular dynamics

      NASA Astrophysics Data System (ADS)

      Pinilla, Carlos; Blanchard, Marc; Balan, Etienne; Ferlat, Guillaume; Vuilleumier, Rodolphe; Mauri, Francesco

      2014-06-01

      The equilibrium fractionation factor between two phases is of importance for the understanding of many planetary and environmental processes. Although thermodynamic equilibrium can be achieved between minerals at high temperature, many natural processes involve reactions between liquids or aqueous solutions and solids. For crystals, the fractionation factor α can be theoretically determined using a statistical thermodynamic approach based on the vibrational properties of the phases. These calculations are mostly performed in the harmonic approximation, using empirical or ab-initio force fields. In the case of aperiodic and dynamic systems such as liquids or solutions, similar calculations can be done using finite-size molecular clusters or snapshots obtained from molecular dynamics (MD) runs. It is however difficult to assess the effect of these approximate models on the isotopic fractionation properties. In this work we present a systematic study of the calculation of the D/H and 18O/16O equilibrium fractionation factors in water for the liquid/vapour and ice/vapour phases using several levels of theory within the simulations. Namely, we use a thermodynamic integration approach based on Path Integral MD calculations (PIMD) and an empirical potential model of water. Compared with standard MD, PIMD takes into account quantum effects in the thermodynamic modeling of systems and the exact fractionation factor for a given potential can be obtained. We compare these exact results with those of modeling strategies usually used, which involve the mapping of the quantum system on its harmonic counterpart. The results show the importance of including configurational disorder for the estimation of isotope fractionation in liquid phases. In addition, the convergence of the fractionation factor as a function of parameters such as the size of the simulated system and multiple isotope substitution is analyzed, showing that isotope fractionation is essentially a local effect in

    19. Integrating two-dimensional paths: do desert ants process distance information in the absence of celestial compass cues?

      PubMed

      Ronacher, B; Westwig, E; Wehner, R

      2006-09-01

      When performing foraging trips desert ants of the genus Cataglyphis continuously process and update a ;home vector' that enables them to return to their nest on the shortest route. This capacity of path integration requires two types of information: (i) information about the travelling directions, and (ii) odometric information about the distances travelled in a particular direction. We have investigated how these two necessary pieces of information interact within the path integration processor. The specific question is: how do the ants process distance information if there is no simultaneous input from the sky compass available. Ants were trained to forage in a ;Z'-shaped channel system, the three segments of which joined at right angles. Individual animals were transferred from the feeder to a test field where their homing paths could be observed. In the crucial tests the middle segment of the maze was covered by orange Perspex that did not transmit the UV part of the spectrum, and thus precluded the perception of polarization patterns. Changes of the ant's processing of odometric information within this channel segment directly translate into a change in homing direction on the test field. The results indicate that the odometric information about travelling distance is largely ignored for path integration if there is no simultaneous input from the sky-view-based compass. They further show that idiothetic information cannot adequately substitute for the polarization compass to infer travelling directions.

    20. An irrotation correction on pressure gradient and orthogonal-path integration for PIV-based pressure reconstruction

      NASA Astrophysics Data System (ADS)

      Wang, Zhongyi; Gao, Qi; Wang, Chengyue; Wei, Runjie; Wang, Jinjun

      2016-06-01

      Particle image velocimetry (PIV)-based pressure reconstruction has become a popular technique in experimental fluid mechanics. Noise or errors in raw velocity field would significantly affect the quality of pressure reconstruction in PIV measurement. To reduce experimental errors in pressure gradient and improve the precision of reconstructed pressure field, a minimal 2-norm criteria-based new technique called irrotation correction (IC) with orthogonal decomposition is developed. The pressure reconstruction is therefore composed of three steps: calculation of pressure gradient from time-resolved velocity fields of PIV, an irrotation correction on the pressure gradient field, and finally a simple orthogonal-path integration (OPI) for pressure. Systematic assessments of IC algorithm are performed on synthetic solid-body rotation flow, direct numerical simulations of a channel flow and an isotropic turbulent flow. The results show that IC is a robust algorithm which can significantly improve the accuracy of pressure reconstruction primarily in the low wave number domain. After irrotation correction, noisy pressure gradient field ideally becomes an irrotational field on which the pressure integration is independent of integrating paths. Therefore, an OPI algorithm is proposed to perform the pressure integration in an efficient way with very few integration paths. This makes the new technique to be a doable method on three-dimensional pressure reconstruction with acceptable computational cost.

    1. Path-integral derivation of the anomaly for the Hermitian equivalent of the complex PT-symmetric quartic Hamiltonian

      SciTech Connect

      Jones, H. F.; Rivers, R. J.; Mateo, J.

      2006-12-15

      It can be shown using operator techniques that the non-Hermitian PT-symmetric quantum mechanical Hamiltonian with a 'wrong-sign' quartic potential -gx{sup 4} is equivalent to a Hermitian Hamiltonian with a positive quartic potential together with a linear term. A naieve derivation of the same result in the path-integral approach misses this linear term. In a recent paper by Bender et al. it was pointed out that this term was in the nature of a parity anomaly and a more careful, discretized treatment of the path integral appeared to reproduce it successfully. However, on re-examination of this derivation we find that a yet more careful treatment is necessary, keeping terms that were ignored in that paper. An alternative, much simpler derivation is given using the additional potential that has been shown to appear whenever a change of variables to curvilinear coordinates is made in a functional integral.

    2. Path programmable logic: A structured design method for digital and/or mixed analog integrated circuits

      NASA Technical Reports Server (NTRS)

      Taylor, B.

      1990-01-01

      The design of Integrated Circuits has evolved past the black art practiced by a few semiconductor companies to a world wide community of users. This was basically accomplished by the development of computer aided design tools which were made available to this community. As the tools matured into different components of the design task they were accepted into the community at large. However, the next step in this evolution is being ignored by the large tool vendors hindering the continuation of this process. With system level definition and simulation through the logic specification well understood, why is the physical generation so blatantly ignored. This portion of the development is still treated as an isolated task with information being passed from the designer to the layout function. Some form of result given back but it severely lacks full definition of what has transpired. The level of integration in I.C.'s for tomorrow, whether through new processes or applications will require higher speeds, increased transistor density, and non-digital performance which can only be achieved through attention to the physical implementation.

    3. Integrative Curriculum Program for Physical Education: Classroom on the Court

      ERIC Educational Resources Information Center

      Irwin, Carol C.; Irwin, Richard L.; Hays, Brandon

      2011-01-01

      Integrative curriculum has been noted as a best practice toward effective learning. Quality physical educators struggle and search for different ways to integrate other content areas (e.g.., language arts, math, and social studies) into their daily lessons; however, due to budgetary limitations, they must find ways to do so with educationally…

    4. Integrating Computational Chemistry into the Physical Chemistry Curriculum

      ERIC Educational Resources Information Center

      Johnson, Lewis E.; Engel, Thomas

      2011-01-01

      Relatively few undergraduate physical chemistry programs integrate molecular modeling into their quantum mechanics curriculum owing to concerns about limited access to computational facilities, the cost of software, and concerns about increasing the course material. However, modeling exercises can be integrated into an undergraduate course at a…

    5. Accelerator physics analysis with an integrated toolkit

      SciTech Connect

      Holt, J.A.; Michelotti, L.; Satogata, T.

      1992-08-01

      Work is in progress on an integrated software toolkit for linear and nonlinear accelerator design, analysis, and simulation. As a first application, beamline'' and MXYZPTLK'' (differential algebra) class libraries, were used with an X Windows graphics library to build an user-friendly, interactive phase space tracker which, additionally, finds periodic orbits. This program was used to analyse a theoretical lattice which contains octupoles and decapoles to find the 20th order, stable and unstable periodic orbits and to explore the local phase space structure.

    6. Physical integrity: the missing link in biological monitoring and TMDLs.

      PubMed

      Asmus, Brenda; Magner, Joseph A; Vondracek, Bruce; Perry, Jim

      2009-12-01

      The Clean Water Act mandates that the chemical, physical, and biological integrity of our nation's waters be maintained and restored. Physical integrity has often been defined as physical habitat integrity, and as such, data collected during biological monitoring programs focus primarily on habitat quality. However, we argue that channel stability is a more appropriate measure of physical integrity and that channel stability is a foundational element of physical habitat integrity in low-gradient alluvial streams. We highlight assessment tools that could supplement stream assessments and the Total Maximum Daily Load stressor identification process: field surveys of bankfull cross-sections; longitudinal thalweg profiles; particle size distribution; and regionally calibrated, visual, stream stability assessments. Benefits of measuring channel stability include a more informed selection of reference or best attainable stream condition for an Index of Biotic Integrity, establishment of a baseline for monitoring changes in present and future condition, and indication of channel stability for investigations of chemical and biological impairments associated with sediment discontinuity and loss of habitat quality. PMID:19142740

    7. Max Delbruck Prize in Biological Physics Lecture: Single-molecule protein folding and transition paths

      NASA Astrophysics Data System (ADS)

      Eaton, William

      2012-02-01

      The transition path is the tiny fraction of an equilibrium molecular trajectory when a transition occurs by crossing the free energy barrier between two states. It is a uniquely single-molecule property, and has not yet been observed experimentally for any system in the condensed phase. The importance of the transition path in protein folding is that it contains all of the mechanistic information on how a protein folds. As a major step toward observing transition paths, we have determined the average transition-path time for a fast and a slow-folding protein from a photon-by-photon analysis of fluorescence trajectories in single-molecule FRET experiments. While the folding rate coefficients differ by 10,000-fold, surprisingly, the transition-path times differ by less than 5-fold, showing that a successful barrier crossing event takes almost the same time for a fast- and a slow-folding protein, i.e. almost the same time to fold when it actually happens.

    8. Determinants of physical activity based on the theory of planned behavior in Iranian Military Staff's Wives: a path analysis.

      PubMed

      Gholamnia Shirvani, Zeinab; Ghofranipour, Fazlollah; Gharakhanlou, Reza; Kazemnejad, Anoshirvan

      2015-01-01

      Level of physical activity as a key determinant of healthy lifestyle less than is required in individuals particularly women. Applying theories of behavioral change about complex behaviors such as physical activity leads to identify effective factors and their relations. The aim of this study was to determine predictors of physical activity behavior based on the Theory of Planned Behavior in military staff's wives in Tehran. This cross-sectional study was performed in 180 military personnel's spouses residing in organizational houses, in Tehran, Iran in 2014. The participants were randomly selected with multi-stage cluster sampling. The validity and reliability of the theory based scale evaluated before conducting the path analysis. Statistical analysis was carried out using SPSS16 and LISREL8.8. The results indicated the model explained 77% and 17% of intention and behavior variance. Subjective norms (Beta=0.83) and intention (Beta=0.37) were the strongest predictors of intention and behavior, respectively. The instrumental and affective attitude had no significant path to intention and behavior. The direct relation of perceived behavioral control to behavior was non-significant. This research demonstrated relative importance and relationships of Theory of Planned Behavior constructs in physical activity behavior of military personnel's spouses in Tehran. It is essential to consider these determinants in designing of educational interventions for promoting and maintaining physical activity behavior in this target group. PMID:25948459

    9. Determinants of physical activity based on the theory of planned behavior in Iranian Military Staff's Wives: a path analysis.

      PubMed

      Gholamnia Shirvani, Zeinab; Ghofranipour, Fazlollah; Gharakhanlou, Reza; Kazemnejad, Anoshirvan

      2014-11-30

      Level of physical activity as a key determinant of healthy lifestyle less than is required in individuals particularly women. Applying theories of behavioral change about complex behaviors such as physical activity leads to identify effective factors and their relations. The aim of this study was to determine predictors of physical activity behavior based on the Theory of Planned Behavior in military staff's wives in Tehran. This cross-sectional study was performed in 180 military personnel's spouses residing in organizational houses, in Tehran, Iran in 2014. The participants were randomly selected with multi-stage cluster sampling. The validity and reliability of the theory based scale evaluated before conducting the path analysis. Statistical analysis was carried out using SPSS16 and LISREL8.8. The results indicated the model explained 77% and 17% of intention and behavior variance. Subjective norms (Beta=0.83) and intention (Beta=0.37) were the strongest predictors of intention and behavior, respectively. The instrumental and affective attitude had no significant path to intention and behavior. The direct relation of perceived behavioral control to behavior was non-significant. This research demonstrated relative importance and relationships of Theory of Planned Behavior constructs in physical activity behavior of military personnel's spouses in Tehran. It is essential to consider these determinants in designing of educational interventions for promoting and maintaining physical activity behavior in this target group.

    10. Proton transport in triflic acid hydrates studied via path integral car-parrinello molecular dynamics.

      PubMed

      Hayes, Robin L; Paddison, Stephen J; Tuckerman, Mark E

      2009-12-31

      The mono-, di-, and tetrahydrates of trifluoromethanesulfonic acid, which contain characteristic H(3)O(+), H(5)O(2)(+), and H(9)O(4)(+) structures, provide model systems for understanding proton transport in materials with high perfluorosulfonic acid density such as perfluorosulfonic acid membranes commonly employed in hydrogen fuel cells. Ab initio molecular dynamics simulations indicate that protons in these solids are predisposed to transfer to the water most strongly bound to sulfonate groups via a Grotthuss-type mechanism, but quickly return to the most solvated defect structure either due to the lack of a nearby species to stabilize the new defect or a preference for the proton to be maximally hydrated. Path integral molecular dynamics of the mono- and dihydrate reveal significant quantum effects that facilitate proton transfer to the "presolvated" water or SO(3)(-) in the first solvation shell and increase the Zundel character of all the defects. These trends are quantified in free energy profiles for each bonding environment. Hydrogen bonding criteria for HOH-OH(2) and HOH-O(3)S are extracted from the two-dimensional potential of mean force. The quantum radial distribution function, radius of gyration, and root-mean-square displacement position correlation function show that the protonic charge is distributed over two or more water molecules. Metastable structural defects with one excess proton shared between two sulfonate groups and another Zundel or Eigen type cation defect are found for the mono- and dihydrate but not for the tetrahydrate crystal. Results for the tetrahydrate native crystal exhibit minor differences at 210 and 250 K. IR spectra are calculated for all native and stable defect structures. Graph theory techniques are used to characterize the chain lengths and ring sizes in the hydrogen bond network. Low conductivities when limited water is present may be attributable to trapping of protons between SO(3)(-) groups and the increased

    11. Comparison of the timing of hippocampal and subicular spatial signals: implications for path integration.

      PubMed

      Sharp, P E

      1999-01-01

      Cells in several portions of the hippocampal formation show location-related firing, so that the momentary rate of each cell signals the spatial location of a freely moving rat. Insight into how these signals are generated, and how they travel around the hippocampal circuitry, can be gained by examination of the exact timing of the locational signal. Here, this was investigated for both hippocampal and subicular cells. For this, several aspects of the spatial firing pattern of each cell were examined over a series of time shifts, in which spikes were paired with locations occupied by the animal in either the immediate past, present, or future. Results showed that subicular cells appear to anticipate future locations by approximately 50 to 70 msec, on average. In contrast, hippocampal cells were best correlated with positions about 30 to 40 msec in the future. However, this timing, for hippocampal cells only, was related to the average session running speed, so that the cells were correlated with future locations at slow speeds, but lagged behind (were correlated with past locations) at high speeds. These data support the idea that both subicular and hippocampal cells use a path integration mechanism to generate their spatial signal (since both can anticipate future location). For the hippocampal cells the mechanism does not, apparently, take into account speed information, however. Also, the data suggest that the subicular signal cannot be the result of simple transmission of spatial information from the hippocampus to the subiculum, since this would predict that the subicular signal should correlate with later positions than the hippocampal signal.

    12. Blip decomposition of the path integral: Exponential acceleration of real-time calculations on quantum dissipative systems

      SciTech Connect

      Makri, Nancy

      2014-10-07

      The real-time path integral representation of the reduced density matrix for a discrete system in contact with a dissipative medium is rewritten in terms of the number of blips, i.e., elementary time intervals over which the forward and backward paths are not identical. For a given set of blips, it is shown that the path sum with respect to the coordinates of all remaining time points is isomorphic to that for the wavefunction of a system subject to an external driving term and thus can be summed by an inexpensive iterative procedure. This exact decomposition reduces the number of terms by a factor that increases exponentially with propagation time. Further, under conditions (moderately high temperature and/or dissipation strength) that lead primarily to incoherent dynamics, the “fully incoherent limit” zero-blip term of the series provides a reasonable approximation to the dynamics, and the blip series converges rapidly to the exact result. Retention of only the blips required for satisfactory convergence leads to speedup of full-memory path integral calculations by many orders of magnitude.

    13. Ensuring critical event sequences in high integrity software by applying path expressions

      SciTech Connect

      Kidd, M.E.C.

      1996-07-01

      The goal of this work is to extend the use of existing path expression theory and methodologies to ensure that critical software event sequences are maintained even in the face of malevolent attacks and harsh or unstable operating environments. This will be accomplished by providing dynamic fault management measures directly to the software developer and to their varied development environments. This paper discusses the perceived problems, a brief overview of path expressions, and the author`s proposed extension areas. The authors discuss how the traditional path expression usage and implementation differs from the intended usage and implementation.

    14. Car-Parrinello and path integral molecular dynamics study of the hydrogen bond in the chloroacetic acid dimer system

      NASA Astrophysics Data System (ADS)

      Durlak, Piotr; Morrison, Carole A.; Middlemiss, Derek S.; Latajka, Zdzislaw

      2007-08-01

      We have studied the double proton transfer (DPT) reaction in the cyclic dimer of chloroacetic acid using both classical and path integral Car-Parrinello molecular dynamics. We also attempt to quantify the errors in the potential energy surface that arise from the use of a pure density functional. In the classical dynamics a clear reaction mechanism can be identified, where asynchronized DPT arises due to coupling between the O-H stretching oscillator and several low energy intermolecular vibrational modes. This mechanism is considerably altered when quantum tunneling is permitted in the simulation. The introduction of path integrals leads to considerable changes in the thermally averaged molecular geometry, leading to shorter and more centered hydrogen bond linkages.

    15. Going beyond the BCS level in the superfluid path integral: A consistent treatment of electrodynamics and thermodynamics

      NASA Astrophysics Data System (ADS)

      Anderson, Brandon M.; Boyack, Rufus; Wu, Chien-Te; Levin, K.

      2016-05-01

      In this Rapid Communication we derive the full gauge-invariant electromagnetic response beyond the BCS level using the fermionic superfluid path integral. In the process we identify and redress a failure to satisfy the compressibility sum rule; this shortcoming is associated with the conventional path-integral formulation of BCS-level electrodynamics. The approach in this paper builds on an alternative saddle point scheme. At the mean field level, this leads to the well known gauge-invariant electrodynamics of BCS theory and to the satisfaction of the compressibility sum rule. Moreover, this scheme can be readily extended to address arbitrary higher order fluctuation theories (for example, at the Gaussian level.) At any level this approach will lead to a gauge invariant and compressibility sum rule consistent treatment of electrodynamics and thermodynamics.

    16. A new approach to calculate charge carrier transport mobility in organic molecular crystals from imaginary time path integral simulations.

      PubMed

      Song, Linze; Shi, Qiang

      2015-05-01

      We present a new non-perturbative method to calculate the charge carrier mobility using the imaginary time path integral approach, which is based on the Kubo formula for the conductivity, and a saddle point approximation to perform the analytic continuation. The new method is first tested using a benchmark calculation from the numerical exact hierarchical equations of motion method. Imaginary time path integral Monte Carlo simulations are then performed to explore the temperature dependence of charge carrier delocalization and mobility in organic molecular crystals (OMCs) within the Holstein and Holstein-Peierls models. The effects of nonlocal electron-phonon interaction on mobility in different charge transport regimes are also investigated. PMID:25956086

    17. On Dirac-Coulomb problem in (2+1) dimensional space-time and path integral quantization

      SciTech Connect

      Haouat, S.; Chetouani, L.

      2012-06-15

      The problem of Dirac particle interacting with Coulomb potential in (2+1) dimensions is formulated in the framework of super-symmetric path integrals where the spin degrees of freedom are described by odd Grassmannian variables. The relative propagator is expressed through Cartesian coordinates in a Hamiltonian form by the use of an adequate transformation. The passage to the polar coordinates permitted us to calculate the fixed energy Green's function and to extract bound states and associating wave functions.

    18. Integrated Path Detection of Co2 and CH4 Using a Waveform Driven Electro-Optic Single Sideband Laser Source

      NASA Astrophysics Data System (ADS)

      Wagner, Gerd; Maxwell, Stephen; Plusquellic, David

      2016-06-01

      Integrated path concentrations of ambient levels of carbon dioxide and methane have been measured during nighttime periods at NIST, Boulder (CO, USA), using a ground-based, eyesafe laser system. In this contribution, we describe the transmitter and receiver system, demonstrate measurements of CO2 and CH4 in comparison with an in situ point sensor measurement using a commercial cavity ring-down instrument, and demonstrate a speckle noise reduction method.

    19. Challenges and Solutions for Frequency and Energy References for Spaceborne and Airborne Integrated Path Differential Absorption Lidars

      NASA Astrophysics Data System (ADS)

      Fix, Andreas; Quatrevalet, Mathieu; Witschas, Benjamin; Wirth, Martin; Büdenbender, Christian; Amediek, Axel; Ehret, Gerhard

      2016-06-01

      The stringent requirements for both the frequency stability and power reference represent a challenging task for Integrated Path Differential Absorption Lidars (IPDA) to measure greenhouse gas columns from satellite or aircraft. Currently, the German-French methane mission MERLIN (Methan Remote Lidar Mission) is prepared. At the same time CHARM-F, an aircraft installed system has been developed at DLR as an airborne demonstrator for a spaceborne greenhouse gas mission. The concepts and realization of these important sub-systems are discussed.

    20. Inclusion of trial functions in the Langevin equation path integral ground state method: Application to parahydrogen clusters and their isotopologues

      SciTech Connect

      Schmidt, Matthew; Constable, Steve; Ing, Christopher; Roy, Pierre-Nicholas

      2014-06-21

      We developed and studied the implementation of trial wavefunctions in the newly proposed Langevin equation Path Integral Ground State (LePIGS) method [S. Constable, M. Schmidt, C. Ing, T. Zeng, and P.-N. Roy, J. Phys. Chem. A 117, 7461 (2013)]. The LePIGS method is based on the Path Integral Ground State (PIGS) formalism combined with Path Integral Molecular Dynamics sampling using a Langevin equation based sampling of the canonical distribution. This LePIGS method originally incorporated a trivial trial wavefunction, ψ{sub T}, equal to unity. The present paper assesses the effectiveness of three different trial wavefunctions on three isotopes of hydrogen for cluster sizes N = 4, 8, and 13. The trial wavefunctions of interest are the unity trial wavefunction used in the original LePIGS work, a Jastrow trial wavefunction that includes correlations due to hard-core repulsions, and a normal mode trial wavefunction that includes information on the equilibrium geometry. Based on this analysis, we opt for the Jastrow wavefunction to calculate energetic and structural properties for parahydrogen, orthodeuterium, and paratritium clusters of size N = 4 − 19, 33. Energetic and structural properties are obtained and compared to earlier work based on Monte Carlo PIGS simulations to study the accuracy of the proposed approach. The new results for paratritium clusters will serve as benchmark for future studies. This paper provides a detailed, yet general method for optimizing the necessary parameters required for the study of the ground state of a large variety of systems.

    1. Path integral molecular dynamics within the grand canonical-like adaptive resolution technique: Simulation of liquid water

      SciTech Connect

      Agarwal, Animesh Delle Site, Luigi

      2015-09-07

      Quantum effects due to the spatial delocalization of light atoms are treated in molecular simulation via the path integral technique. Among several methods, Path Integral (PI) Molecular Dynamics (MD) is nowadays a powerful tool to investigate properties induced by spatial delocalization of atoms; however, computationally this technique is very demanding. The above mentioned limitation implies the restriction of PIMD applications to relatively small systems and short time scales. One of the possible solutions to overcome size and time limitation is to introduce PIMD algorithms into the Adaptive Resolution Simulation Scheme (AdResS). AdResS requires a relatively small region treated at path integral level and embeds it into a large molecular reservoir consisting of generic spherical coarse grained molecules. It was previously shown that the realization of the idea above, at a simple level, produced reasonable results for toy systems or simple/test systems like liquid parahydrogen. Encouraged by previous results, in this paper, we show the simulation of liquid water at room conditions where AdResS, in its latest and more accurate Grand-Canonical-like version (GC-AdResS), is merged with two of the most relevant PIMD techniques available in the literature. The comparison of our results with those reported in the literature and/or with those obtained from full PIMD simulations shows a highly satisfactory agreement.

    2. Integrating Physical Education and Language Arts: What Literature Do Physical Education Specialists Use, and How Are Physical Education and Language Arts Integrated?

      ERIC Educational Resources Information Center

      Schumacher, Joy

      This study investigated the literature physical education (PE) specialists used and how they integrated PE and language arts. The researcher kept a journal to record books, poems, and ideas of ways to integrate to two disciplines. She sent a survey to 10 PE teachers that asked what books they used and how they integrated language arts and PE. She…

    3. Iterative path integral calculations of non-linear spectra and entanglement dynamics

      NASA Astrophysics Data System (ADS)

      Sahrapour, Mohammad Mehdi

      We review an iterative path integral method that allows the computation of exact, long-time dynamics of small systems interacting with a dissipative bath. The method takes advantage of the finite memory of large environments at finite temperature to allow an iterative evaluation of the dynamics, thereby replacing an exponential scaling in simulation time with a linear scaling. This method is applied to calculate the dynamics of two model systems. The first consists of two-qubits interacting with a common bath. In this case we observe a variety of entanglement effects. If the qubits are initially separable, through an indirect coupling, the bath can create steady state entanglement between the qubits. This effect is due to the existence of a decoherence-free subspace as a result of the form of the qubit Hamiltonian and system-bath coupling. Entanglement created by the bath is shown to decrease with increasing temperature and system-bath coupling strength. However large system-bath coupling causes a faster increase in the entanglement. Initially entangled qubits lose their entanglement as a result of interactions with the bath, an effect that is heightened at higher temperatures. Direct coupling between the qubits is shown to slow the decay of entanglement and preserve some entanglement at long times; however at high temperatures this steady state entanglement becomes negligible. The second system we consider is vibrational degree of freedom coupled to a bath of harmonic oscillators or two-level systems. We compute four-time correlation functions which are used to calculate response functions relevant to third order infrared or seventh order Raman experiments for harmonic, Morse, and quadratic-quartic potentials. Our calculations reveal the role of potential features (anharmonicity and eigenvalue spectrum), both on short and long time scales, on the response function. Further, thermal excitation causes dramatic changes in the appearance of the response function

    4. Proton transport in triflic acid pentahydrate studied via ab initio path integral molecular dynamics.

      PubMed

      Hayes, Robin L; Paddison, Stephen J; Tuckerman, Mark E

      2011-06-16

      Trifluoromethanesulfonic acid hydrates provide a well-defined system to study proton dissociation and transport in perfluorosulfonic acid membranes, typically used as the electrolyte in hydrogen fuel cells, in the limit of minimal water. The triflic acid pentahydrate crystal (CF(3)SO(3)H·5H(2)O) is sufficiently aqueous that it contains an extended three-dimensional water network. Despite it being extended, however, long-range proton transport along the network is structurally unfavorable and would require considerable rearrangement. Nevertheless, the triflic acid pentahydrate crystal system can provide a clear picture of the preferred locations of local protonic defects in the water network, which provides insights about related structures in the disordered, low-hydration environment of perfluorosulfonic acid membranes. Ab initio molecular dynamics simulations reveal that the proton defect is most likely to transfer to the closest water that has the expected presolvation and only contains water in its first solvation shell. Unlike the tetrahydrate of triflic acid (CF(3)SO(3)H·4H(2)O), there is no evidence of the proton preferentially transferring to a water molecule bridging two of the sulfonate groups. However, this could be an artifact of the crystal structure since the only such water molecule is separated from the proton by long O-O distances. Hydrogen bonding criteria, using the two-dimensional potential of mean force, are extracted. Radial distribution functions, free energy profiles, radii of gyration, and the root-mean-square displacement computed from ab initio path integral molecular dynamics simulations reveal that quantum effects do significantly extend the size of the protonic defect and increase the frequency of proton transfer events by nearly 15%. The calculated IR spectra confirm that the dominant protonic defect mostly exists as an Eigen cation but contains some Zundel ion characteristics. Chain lengths and ring sizes determined from the

    5. Integrated information theory: from consciousness to its physical substrate.

      PubMed

      Tononi, Giulio; Boly, Melanie; Massimini, Marcello; Koch, Christof

      2016-07-01

      In this Opinion article, we discuss how integrated information theory accounts for several aspects of the relationship between consciousness and the brain. Integrated information theory starts from the essential properties of phenomenal experience, from which it derives the requirements for the physical substrate of consciousness. It argues that the physical substrate of consciousness must be a maximum of intrinsic cause-effect power and provides a means to determine, in principle, the quality and quantity of experience. The theory leads to some counterintuitive predictions and can be used to develop new tools for assessing consciousness in non-communicative patients.

    6. Physical Activity and Health Perception in Aging: Do Body Mass and Satisfaction Matter? A Three-Path Mediated Link.

      PubMed

      Condello, Giancarlo; Capranica, Laura; Stager, Joel; Forte, Roberta; Falbo, Simone; Di Baldassarre, Angela; Segura-Garcia, Cristina; Pesce, Caterina

      2016-01-01

      Although ageing people could benefit from healthy diet and physical activity to maintain health and quality of life, further understandings of the diet- and physical activity-related mechanisms that may cause changes in health and quality of life perception are necessary. The purpose of the study was to investigate the effect of eating attitudes, body mass and image satisfaction, and exercise dependence in the relationship between physical activity and health and quality of life perception in older individuals. Hundred and seventy-nine late middle-aged, (55-64 yrs), young-old (65-74 yrs), and old (75-84 yrs) senior athletes (n = 56), physically active (n = 58) or sedentary adults (n = 65) were submitted to anthropometric evaluations (body mass, height) and self-reported questionnaires: Body Image Dimensional Assessment, Exercise Dependence Scale, Eating Attitude Test, and Short Form Health Survey (Physical Component Summary [PCS] and Mental Component Summary [MCS] of and health and quality of life perception). Senior athletes, physically active, and sedentary participants subgroups differed (P<0.05) from each other in body mass index (BMI) and several components of body image and exercise dependence. Senior athletes showed, compared to their sedentary counterparts, further differences (P<0.05) in eating attitudes and in both PCS and MCS. Mediation analysis showed that the relationship between physical activity habit and MCS, but not PCS, was indirectly explained by a serial mediation chain composed of objective BMI and subjective body image (dis)satisfaction. Findings confirm the relevant role of physically active life habits for older individuals to perceive good physical and mental health. The novelty of the three-path mediated link between physical activity level and mental health perception suggests that the beneficial effect of a physically active lifestyle on weight control can positively impinge on the cognitive-emotional dimension of mental health by

    7. Physical Activity and Health Perception in Aging: Do Body Mass and Satisfaction Matter? A Three-Path Mediated Link

      PubMed Central

      Capranica, Laura; Stager, Joel; Forte, Roberta; Falbo, Simone; Di Baldassarre, Angela; Segura-Garcia, Cristina; Pesce, Caterina

      2016-01-01

      Although ageing people could benefit from healthy diet and physical activity to maintain health and quality of life, further understandings of the diet- and physical activity-related mechanisms that may cause changes in health and quality of life perception are necessary. The purpose of the study was to investigate the effect of eating attitudes, body mass and image satisfaction, and exercise dependence in the relationship between physical activity and health and quality of life perception in older individuals. Hundred and seventy-nine late middle-aged, (55–64 yrs), young-old (65–74 yrs), and old (75–84 yrs) senior athletes (n = 56), physically active (n = 58) or sedentary adults (n = 65) were submitted to anthropometric evaluations (body mass, height) and self-reported questionnaires: Body Image Dimensional Assessment, Exercise Dependence Scale, Eating Attitude Test, and Short Form Health Survey (Physical Component Summary [PCS] and Mental Component Summary [MCS] of and health and quality of life perception). Senior athletes, physically active, and sedentary participants subgroups differed (P<0.05) from each other in body mass index (BMI) and several components of body image and exercise dependence. Senior athletes showed, compared to their sedentary counterparts, further differences (P<0.05) in eating attitudes and in both PCS and MCS. Mediation analysis showed that the relationship between physical activity habit and MCS, but not PCS, was indirectly explained by a serial mediation chain composed of objective BMI and subjective body image (dis)satisfaction. Findings confirm the relevant role of physically active life habits for older individuals to perceive good physical and mental health. The novelty of the three-path mediated link between physical activity level and mental health perception suggests that the beneficial effect of a physically active lifestyle on weight control can positively impinge on the cognitive-emotional dimension of mental health by

    8. Physical Activity and Health Perception in Aging: Do Body Mass and Satisfaction Matter? A Three-Path Mediated Link.

      PubMed

      Condello, Giancarlo; Capranica, Laura; Stager, Joel; Forte, Roberta; Falbo, Simone; Di Baldassarre, Angela; Segura-Garcia, Cristina; Pesce, Caterina

      2016-01-01

      Although ageing people could benefit from healthy diet and physical activity to maintain health and quality of life, further understandings of the diet- and physical activity-related mechanisms that may cause changes in health and quality of life perception are necessary. The purpose of the study was to investigate the effect of eating attitudes, body mass and image satisfaction, and exercise dependence in the relationship between physical activity and health and quality of life perception in older individuals. Hundred and seventy-nine late middle-aged, (55-64 yrs), young-old (65-74 yrs), and old (75-84 yrs) senior athletes (n = 56), physically active (n = 58) or sedentary adults (n = 65) were submitted to anthropometric evaluations (body mass, height) and self-reported questionnaires: Body Image Dimensional Assessment, Exercise Dependence Scale, Eating Attitude Test, and Short Form Health Survey (Physical Component Summary [PCS] and Mental Component Summary [MCS] of and health and quality of life perception). Senior athletes, physically active, and sedentary participants subgroups differed (P<0.05) from each other in body mass index (BMI) and several components of body image and exercise dependence. Senior athletes showed, compared to their sedentary counterparts, further differences (P<0.05) in eating attitudes and in both PCS and MCS. Mediation analysis showed that the relationship between physical activity habit and MCS, but not PCS, was indirectly explained by a serial mediation chain composed of objective BMI and subjective body image (dis)satisfaction. Findings confirm the relevant role of physically active life habits for older individuals to perceive good physical and mental health. The novelty of the three-path mediated link between physical activity level and mental health perception suggests that the beneficial effect of a physically active lifestyle on weight control can positively impinge on the cognitive-emotional dimension of mental health by

    9. Testing a Longitudinal Integrated Self-Efficacy and Self-Determination Theory Model for Physical Activity Post-Cardiac Rehabilitation.

      PubMed

      Sweet, Shane N; Fortier, Michelle S; Strachan, Shaelyn M; Blanchard, Chris M; Boulay, Pierre

      2014-01-13

      Self-determination theory and self-efficacy theory are prominent theories in the physical activity literature, and studies have begun integrating their concepts. Sweet, Fortier, Strachan and Blanchard (2012) have integrated these two theories in a cross-sectional study. Therefore, this study sought to test a longitudinal integrated model to predict physical activity at the end of a 4-month cardiac rehabilitation program based on theory, research and Sweet et al.'s cross-sectional model. Participants from two cardiac rehabilitation programs (N=109) answered validated self-report questionnaires at baseline, two and four months. Data were analyzed using Amos to assess the path analysis and model fit. Prior to integration, perceived competence and self-efficacy were combined, and labeled as confidence. After controlling for 2-month physical activity and cardiac rehabilitation site, no motivational variables significantly predicted residual change in 4-month physical activity. Although confidence at two months did not predict residual change in 4-month physical activity, it had a strong positive relationship with 2-month physical activity (β=0.30, P<0.001). The overall model retained good fit indices. In conclusion, results diverged from theoretical predictions of physical activity, but self-determination and self-efficacy theory were still partially supported. Because the model had good fit, this study demonstrated that theoretical integration is feasible. PMID:26973926

    10. Testing a Longitudinal Integrated Self-Efficacy and Self-Determination Theory Model for Physical Activity Post-Cardiac Rehabilitation.

      PubMed

      Sweet, Shane N; Fortier, Michelle S; Strachan, Shaelyn M; Blanchard, Chris M; Boulay, Pierre

      2014-01-13

      Self-determination theory and self-efficacy theory are prominent theories in the physical activity literature, and studies have begun integrating their concepts. Sweet, Fortier, Strachan and Blanchard (2012) have integrated these two theories in a cross-sectional study. Therefore, this study sought to test a longitudinal integrated model to predict physical activity at the end of a 4-month cardiac rehabilitation program based on theory, research and Sweet et al.'s cross-sectional model. Participants from two cardiac rehabilitation programs (N=109) answered validated self-report questionnaires at baseline, two and four months. Data were analyzed using Amos to assess the path analysis and model fit. Prior to integration, perceived competence and self-efficacy were combined, and labeled as confidence. After controlling for 2-month physical activity and cardiac rehabilitation site, no motivational variables significantly predicted residual change in 4-month physical activity. Although confidence at two months did not predict residual change in 4-month physical activity, it had a strong positive relationship with 2-month physical activity (β=0.30, P<0.001). The overall model retained good fit indices. In conclusion, results diverged from theoretical predictions of physical activity, but self-determination and self-efficacy theory were still partially supported. Because the model had good fit, this study demonstrated that theoretical integration is feasible.

    11. Testing a Longitudinal Integrated Self-Efficacy and Self-Determination Theory Model for Physical Activity Post-Cardiac Rehabilitation

      PubMed Central

      Sweet, Shane N.; Fortier, Michelle S.; Strachan, Shaelyn M.; Blanchard, Chris M.; Boulay, Pierre

      2014-01-01

      Self-determination theory and self-efficacy theory are prominent theories in the physical activity literature, and studies have begun integrating their concepts. Sweet, Fortier, Strachan and Blanchard (2012) have integrated these two theories in a cross-sectional study. Therefore, this study sought to test a longitudinal integrated model to predict physical activity at the end of a 4-month cardiac rehabilitation program based on theory, research and Sweet et al.’s cross-sectional model. Participants from two cardiac rehabilitation programs (N=109) answered validated self-report questionnaires at baseline, two and four months. Data were analyzed using Amos to assess the path analysis and model fit. Prior to integration, perceived competence and self-efficacy were combined, and labeled as confidence. After controlling for 2-month physical activity and cardiac rehabilitation site, no motivational variables significantly predicted residual change in 4-month physical activity. Although confidence at two months did not predict residual change in 4-month physical activity, it had a strong positive relationship with 2-month physical activity (β=0.30, P<0.001). The overall model retained good fit indices. In conclusion, results diverged from theoretical predictions of physical activity, but self-determination and self-efficacy theory were still partially supported. Because the model had good fit, this study demonstrated that theoretical integration is feasible. PMID:26973926

    12. Conceptual Integration of Chemical Equilibrium by Prospective Physical Sciences Teachers

      ERIC Educational Resources Information Center

      Ganaras, Kostas; Dumon, Alain; Larcher, Claudine

      2008-01-01

      This article describes an empirical study concerning the mastering of the chemical equilibrium concept by prospective physical sciences teachers. The main objective was to check whether the concept of chemical equilibrium had become an integrating and unifying concept for them, that is to say an operational and functional knowledge to explain and…

    13. Understanding Student Use of Differentials in Physics Integration Problems

      ERIC Educational Resources Information Center

      Hu, Dehui; Rebello, N. Sanjay

      2013-01-01

      This study focuses on students' use of the mathematical concept of differentials in physics problem solving. For instance, in electrostatics, students need to set up an integral to find the electric field due to a charged bar, an activity that involves the application of mathematical differentials (e.g., "dr," "dq"). In…

    14. Integrating Physical Activity Data Technologies into Elementary School Classrooms

      ERIC Educational Resources Information Center

      Lee, Victor R.; Thomas, Jonathan M.

      2011-01-01

      This paper describes an iteration of a design-based research project that involved integrating commercial physical activity data (PAD) sensors, such as heart rate monitors and pedometers, as technologies that could be used in two fifth grade classrooms. By working in partnership with two participating teachers and seeking out immediate resources…

    15. Systematic perturbation calculation of integrals with applications to physics.

      PubMed

      Amore, Paolo; Aranda, Alfredo; Sáenz, Ricardo; Fernández, Francisco M

      2005-01-01

      In this paper we generalize and improve a method for calculating the period of a classical oscillator and other integrals of physical interest, which was recently developed by some of the authors. We derive analytical expressions that prove to be more accurate than those commonly found in the literature, and test the convergence of the series produced by the approach.

    16. Milkweed Seed Dispersal: A Means for Integrating Biology and Physics.

      ERIC Educational Resources Information Center

      Bisbee, Gregory D.; Kaiser, Cheryl A.

      1997-01-01

      Describes an activity that integrates biology and physics concepts by experimenting with the seed dispersal of common milkweed or similar wind-dispersed seeds. Student teams collect seeds and measure several parameters, review principles of trajectory motion, perform experiments, and graph data. Students examine the ideas of…

    17. TOWARD EFFICIENT RIPARIAN RESTORATION: INTEGRATING ECONOMIC, PHYSICAL, AND BIOLOGICAL MODELS

      EPA Science Inventory

      This paper integrates economic, biological, and physical models to explore the efficient combination and spatial allocation of conservation efforts to protect water quality and increase salmonid populations in the Grande Ronde basin, Oregon. We focus on the effects of shade on wa...

    18. Path integrated optical remote sensing technique to estimate ammonia and methane gas emissions from CAFOs

      Technology Transfer Automated Retrieval System (TEKTRAN)

      The U.S. EPA recently demonstrated the open-path optical remote sensing technology to identify hot spots and estimate mass flux of fugitive gases from closed landfill. The objective of this research is to validate this technology for estimating ammonia and methane emission from concentrated animal f...

    19. Qualitative Evaluation of the Project P.A.T.H.S.: An Integration of Findings Based on Program Implementers

      PubMed Central

      Shek, Daniel T. L.

      2012-01-01

      An integration of the qualitative evaluation findings collected from program implementers conducting the Project P.A.T.H.S. (Positive Adolescent Training through Holistic Social Programmes) in different years (n = 177 participants in 36 focus groups) was carried out. General qualitative data analyses utilizing intra and interrater reliability techniques were performed. Results showed that the descriptors used to describe the program and the metaphors named by the informants that could stand for the program were generally positive in nature. Program participants also perceived the program to be beneficial to the development of the students in different psychosocial domains. The present study further supports the effectiveness of the Tier 1 Program of the Project P.A.T.H.S. in Hong Kong based on the perspective of the program implementers. PMID:22666139

    20. Path integral Monte Carlo determination of the fourth-order virial coefficient for unitary two-component Fermi gas with zero-range interactions

      NASA Astrophysics Data System (ADS)

      Yan, Yangqian; Blume, D.

      2016-05-01

      The unitary equal-mass Fermi gas with zero-range interactions constitutes a paradigmatic model system that is relevant to atomic, condensed matter, nuclear, particle, and astro physics. This work determines the fourth-order virial coefficient b4 of such a strongly-interacting Fermi gas using a customized ab inito path integral Monte Carlo (PIMC) algorithm. In contrast to earlier theoretical results, which disagreed on the sign and magnitude of b4, our b4 agrees with the experimentally determined value, thereby resolving an ongoing literature debate. Utilizing a trap regulator, our PIMC approach determines the fourth-order virial coefficient by directly sampling the partition function. An on-the-fly anti-symmetrization avoids the Thomas collapse and, combined with the use of the exact two-body zero-range propagator, establishes an efficient general means to treat small Fermi systems with zero-range interactions. We gratefully acknowledge support by the NSF.

    1. A Path Analytic Explanation of the Lower Participation Rates of Women in College Physical Science.

      ERIC Educational Resources Information Center

      Brush, Lorelei R.

      Two studies used a structural equation model to examine the relationship between gender and participation in college mathematics, physics, and chemistry courses. The intervening variables under scrutiny were ability scores, attitudes toward mathematics and mathematicians, and expectations of future performance in physical science courses. The…

    2. Physical Activity Affects Brain Integrity in HIV + Individuals

      PubMed Central

      Ortega, Mario; Baker, Laurie M.; Vaida, Florin; Paul, Robert; Basco, Brian; Ances, Beau M.

      2015-01-01

      Prior research has suggested benefits of aerobic physical activity (PA) on cognition and brain volumes in HIV uninfected (HIV−) individuals, however, few studies have explored the relationships between PA and brain integrity (cognition and structural brain volumes) in HIV-infected (HIV +) individuals. Seventy HIV + individuals underwent neuropsychological testing, structural neuroimaging, laboratory tests, and completed a PA questionnaire, recalling participation in walking, running, and jogging activities over the last year. A PA engagement score of weekly metabolic equivalent (MET) hr of activity was calculated using a compendium of PAs. HIV + individuals were classified as physically active (any energy expended above resting expenditure, n = 22) or sedentary (n = 48). Comparisons of neuropsychological performance, grouped by executive and motor domains, and brain volumes were completed between groups. Physically active and sedentary HIV + individuals had similar demographic and laboratory values, but the active group had higher education (14.0 vs. 12.6 years, p = .034). Physically active HIV + individuals performed better on executive (p = .040, unadjusted; p = .043, adjusted) but not motor function (p = .17). In addition, among the physically active group the amount of physical activity (METs) positively correlated with executive (Pearson’s r = 0.45, p = 0.035) but not motor (r = 0.21; p = .35) performance. In adjusted analyses the physically active HIV + individuals had larger putamen volumes (p = .019). A positive relationship exists between PA and brain integrity in HIV + individuals. Results from the present study emphasize the importance to conduct longitudinal interventional investigation to determine if PA improves brain integrity in HIV + individuals. PMID:26581799

    3. How physics teachers approach innovation: An empirical study for reconstructing the appropriation path in the case of special relativity

      NASA Astrophysics Data System (ADS)

      de Ambrosis, Anna; Levrini, Olivia

      2010-07-01

      This paper concerns an empirical study carried out with a group of high school physics teachers engaged in the Module on relativity of a Master course on the teaching of modern physics. The study is framed within the general research issue of how to promote innovation in school via teachers’ education and how to foster fruitful interactions between research and school practice via the construction of networks of researchers and teachers. In the paper, the problems related to innovation are addressed by focusing on the phase during which teachers analyze an innovative teaching proposal in the perspective of designing their own paths for the class work. The proposal analyzed in this study is Taylor and Wheeler’s approach for teaching special relativity. The paper aims to show that the roots of problems known in the research literature about teachers’ difficulties in coping with innovative proposals, and usually related to the implementation process, can be found and addressed already when teachers approach the proposal and try to appropriate it. The study is heuristic and has been carried out in order to trace the “appropriation path,” followed by the group of teachers, in terms of the main steps and factors triggering the progressive evolution of teachers’ attitudes and competences.

    4. Vulnerabilities, Influences and Interaction Paths: Failure Data for Integrated System Risk Analysis

      NASA Technical Reports Server (NTRS)

      Malin, Jane T.; Fleming, Land

      2006-01-01

      We describe graph-based analysis methods for identifying and analyzing cross-subsystem interaction risks from subsystem connectivity information. By discovering external and remote influences that would be otherwise unexpected, these methods can support better communication among subsystem designers at points of potential conflict and to support design of more dependable and diagnosable systems. These methods identify hazard causes that can impact vulnerable functions or entities if propagated across interaction paths from the hazard source to the vulnerable target. The analysis can also assess combined impacts of And-Or trees of disabling influences. The analysis can use ratings of hazards and vulnerabilities to calculate cumulative measures of the severity and importance. Identification of cross-subsystem hazard-vulnerability pairs and propagation paths across subsystems will increase coverage of hazard and risk analysis and can indicate risk control and protection strategies.

    5. A comparison of NH{sub 3} point monitoring and diode laser based path integrated measurements

      SciTech Connect

      Goldstein, N.; Richtsmeier, S.C.; Lee, J.; Bien, F.; Fetzer, G.J.; Groff, K.W.

      1994-12-31

      Measurements made using two different types of ammonia monitors during a two-month field study in the summer of 1994 are discussed. The first was a diode-laser based open path monitor designed for automated operation in an industrial environment. The second is a monitoring analyzer based on thermal decomposition of ammonia to NO and subsequent analysis by O{sub 3}-NO chemiluminescence. The two monitors provided consistent measurements of ammonia concentration during weeks of continuous unattended operation.

    6. Becoming physics people: Development of integrated physics identity through the Learning Assistant experience

      NASA Astrophysics Data System (ADS)

      Close, Eleanor W.; Conn, Jessica; Close, Hunter G.

      2016-06-01

      [This paper is part of the Focused Collection on Preparing and Supporting University Physics Educators.] In this study, we analyze the experience of students in the Physics Learning Assistant (LA) program at Texas State University in terms of the existing theoretical frameworks of community of practice and physics identity, and explore the implications suggested by these theories for LA program adoption and adaptation. Regression models from physics identity studies show that the physics identity construct strongly predicts intended choice of a career in physics. The goal of our current project is to understand the details of the impacts of participation in the LA experience on participants' practice and self-concept, in order to identify critical elements of LA program structure that positively influence physics identity and physics career intentions for students. Our analysis suggests that participation in the LA program impacts LAs in ways that support both stronger "physics student" identity and stronger "physics instructor" identity, and that these identities are reconciled into a coherent integrated physics identity. Increased comfort in interactions with peers, near peers, and faculty seems to be an important component of this identity development and reconciliation, suggesting that a focus on supporting community membership is useful for effective program design.

    7. Equation of state of an interacting Bose gas at finite temperature: A path-integral Monte Carlo study

      SciTech Connect

      Pilati, S.; Giorgini, S.; Sakkos, K.; Boronat, J.; Casulleras, J.

      2006-10-15

      By using exact path-integral Monte Carlo methods we calculate the equation of state of an interacting Bose gas as a function of temperature both below and above the superfluid transition. The universal character of the equation of state for dilute systems and low temperatures is investigated by modeling the interatomic interactions using different repulsive potentials corresponding to the same s-wave scattering length. The results obtained for the energy and the pressure are compared to the virial expansion for temperatures larger than the critical temperature. At very low temperatures we find agreement with the ground-state energy calculated using the diffusion Monte Carlo method.

    8. Path integral approach to closed-form option pricing formulas with applications to stochastic volatility and interest rate models

      NASA Astrophysics Data System (ADS)

      Lemmens, D.; Wouters, M.; Tempere, J.; Foulon, S.

      2008-07-01

      We present a path integral method to derive closed-form solutions for option prices in a stochastic volatility model. The method is explained in detail for the pricing of a plain vanilla option. The flexibility of our approach is demonstrated by extending the realm of closed-form option price formulas to the case where both the volatility and interest rates are stochastic. This flexibility is promising for the treatment of exotic options. Our analytical formulas are tested with numerical Monte Carlo simulations.

    9. Beyond complex Langevin equations: from simple examples to positive representation of Feynman path integrals directly in the Minkowski time

      NASA Astrophysics Data System (ADS)

      Wosiek, Jacek

      2016-04-01

      A positive representation for an arbitrary complex, gaussian weight is derived and used to construct a statistical formulation of gaussian path integrals directly in the Minkowski time. The positivity of Minkowski weights is achieved by doubling the number of real variables. The continuum limit of the new representation exists only if some of the additional couplings tend to infinity and are tuned in a specific way. The construction is then successfully applied to three quantum mechanical examples including a particle in a constant magnetic field — a simplest prototype of a Wilson line. Further generalizations are shortly discussed and an intriguing interpretation of new variables is alluded to.

    10. Directional Radiometry and Radiative Transfer: the Convoluted Path From Centuries-old Phenomenology to Physical Optics

      NASA Technical Reports Server (NTRS)

      Mishchenko, Michael I.

      2014-01-01

      This Essay traces the centuries-long history of the phenomenological disciplines of directional radiometry and radiative transfer in turbid media, discusses their fundamental weaknesses, and outlines the convoluted process of their conversion into legitimate branches of physical optics.

    11. Tool Path Design of Incremental Open-Die Disk Forging Using Physical Modeling

      NASA Astrophysics Data System (ADS)

      Lee, Sung-Uk; Yang, Dong-Yol

      A small-batch product of large-sized parts is usually manufactured using incremental open-die forging. In order to control the overall change in the shape of a part, it is essential to be able to predict the shape changes that occur during each step. This paper addresses shape changes of a material according to the forging path. Rapid prediction of metal flows for continuing incremental deformation using theoretical methods is difficult. Accordingly, instead of a theoretical approach, an experiment that tests the tendency of the metal flow for development of forming processes is required. For the sake of convenience, simulative experiments are carried out using plasticine at room temperature. In present study, the tool movement is dominant parameters to with respect to changing the shape of the workpiece.

    12. A kinetic model for voltage-gated ion channels in cell membranes based on the path integral method

      NASA Astrophysics Data System (ADS)

      Erdem, Rıza; Ekiz, Cesur

      2005-04-01

      A kinetic model of cell membrane ion channels is proposed based on the path integral method. From the Pauli-type master equations valid on a macroscopic time scale, we derive a first-order differential equation or the kinetic equation which governs temporal evolution of the channel system along the paths of extreme probability. Using known parameters for the batrachotoxin (BTX)-modified sodium channels in squid giant axon, the time dependence of the channel activation and the voltage dependence of the corresponding time constants ( τ) are examined numerically. It is found that the channel activation relaxes to the steady (or equilibrium)-state values for a given membrane potential and the corresponding time constant reaches a maximum at a certain potential and thereafter decreases in magnitude as the membrane potential increases. A qualitative comparison between these results and the results of Hodgkin-Huxley theory, path probability method and thermodynamic models as well as the cut-open axon technique is presented. Good agreement is achieved.

    13. Path integral molecular dynamics method based on a pair density matrix approximation: An algorithm for distinguishable and identical particle systems

      NASA Astrophysics Data System (ADS)

      Miura, Shinichi; Okazaki, Susumu

      2001-09-01

      In this paper, the path integral molecular dynamics (PIMD) method has been extended to employ an efficient approximation of the path action referred to as the pair density matrix approximation. Configurations of the isomorphic classical systems were dynamically sampled by introducing fictitious momenta as in the PIMD based on the standard primitive approximation. The indistinguishability of the particles was handled by a pseudopotential of particle permutation that is an extension of our previous one [J. Chem. Phys. 112, 10 116 (2000)]. As a test of our methodology for Boltzmann statistics, calculations have been performed for liquid helium-4 at 4 K. We found that the PIMD with the pair density matrix approximation dramatically reduced the computational cost to obtain the structural as well as dynamical (using the centroid molecular dynamics approximation) properties at the same level of accuracy as that with the primitive approximation. With respect to the identical particles, we performed the calculation of a bosonic triatomic cluster. Unlike the primitive approximation, the pseudopotential scheme based on the pair density matrix approximation described well the bosonic correlation among the interacting atoms. Convergence with a small number of discretization of the path achieved by this approximation enables us to construct a method of avoiding the problem of the vanishing pseudopotential encountered in the calculations by the primitive approximation.

    14. Internal limiting membrane layer visualization and vitreoretinal surgery guidance using a common-path OCT integrated microsurgical tool

      NASA Astrophysics Data System (ADS)

      Liu, Xuan; Meisne, Eric; Han, Jae-Ho; Zhang, Kang; Gehlbach, Peter; Taylor, Russell; Kang, Jin U.

      2010-02-01

      Contemporary retinal microsurgery is performed by skilled surgeons through operating microscopes, utilizing free hand techniques and manually operated micro-instruments. One technically challenging procedure is the incising and peeling of the internal limiting membrane (ILM) while minimizing damage to the underlying retina. One strategy for minimizing damage is to improve visualization of the ILM layer. Here we present a preliminary evaluation of a prototype tool that integrates an ultra high resolution Fourier domain common path Optical Coherence Tomography (OCT) with an intelligent microsurgical instrument. The tool provides OCT guided visualization of the ILM layer at the point of tissue contact by the surgical tool. We have evaluated the imaging properties of the common path OCT system. The common path OCT system used in this study has a maximum imaging depth of 1.3mm and a sensitivity of 91dB. We have achieved an experimental axial resolution of 3μm in air and this appears to be sufficient to both identify the ILM and to perform surgical maneuvers. We scanned the single mode fiber probe using an intelligent microsurgical instrument to form B-Mode images. We imaged a porcine eye with both anterior eye segment and the vitreous removed. The image obtained show distinct functional layers of retina.

    15. Integrated physics package of a chip-scale atomic clock

      NASA Astrophysics Data System (ADS)

      Li, Shao-Liang; Xu, Jing; Zhang, Zhi-Qiang; Zhao, Lu-Bing; Long, Liang; Wu, Ya-Ming

      2014-07-01

      The physics package of a chip-scale atomic clock (CSAC) has been successfully realized by integrating vertical cavity surface emitting laser (VCSEL), neutral density (ND) filter, λ/4 wave plate, 87Rb vapor cell, photodiode (PD), and magnetic coil into a cuboid metal package with a volume of about 2.8 cm3. In this physics package, the critical component, 87Rb vapor cell, is batch-fabricated based on MEMS technology and in-situ chemical reaction method. Pt heater and thermistors are integrated in the physics package. A PTFE pillar is used to support the optical elements in the physics package, in order to reduce the power dissipation. The optical absorption spectrum of 87Rb D1 line and the microwave frequency correction signal are successfully observed while connecting the package with the servo circuit system. Using the above mentioned packaging solution, a CSAC with short-term frequency stability of about 7 × 10-10 τ-1/2 has been successfully achieved, which demonstrates that this physics package would become one promising solution for the CSAC.

    16. The new AP Physics exams: Integrating qualitative and quantitative reasoning

      NASA Astrophysics Data System (ADS)

      Elby, Andrew

      2015-04-01

      When physics instructors and education researchers emphasize the importance of integrating qualitative and quantitative reasoning in problem solving, they usually mean using those types of reasoning serially and separately: first students should analyze the physical situation qualitatively/conceptually to figure out the relevant equations, then they should process those equations quantitatively to generate a solution, and finally they should use qualitative reasoning to check that answer for plausibility (Heller, Keith, & Anderson, 1992). The new AP Physics 1 and 2 exams will, of course, reward this approach to problem solving. But one kind of free response question will demand and reward a further integration of qualitative and quantitative reasoning, namely mathematical modeling and sense-making--inventing new equations to capture a physical situation and focusing on proportionalities, inverse proportionalities, and other functional relations to infer what the equation ``says'' about the physical world. In this talk, I discuss examples of these qualitative-quantitative translation questions, highlighting how they differ from both standard quantitative and standard qualitative questions. I then discuss the kinds of modeling activities that can help AP and college students develop these skills and habits of mind.

    17. Maximizing Information Diffusion in the Cyber-physical Integrated Network.

      PubMed

      Lu, Hongliang; Lv, Shaohe; Jiao, Xianlong; Wang, Xiaodong; Liu, Juan

      2015-01-01

      Nowadays, our living environment has been embedded with smart objects, such as smart sensors, smart watches and smart phones. They make cyberspace and physical space integrated by their abundant abilities of sensing, communication and computation, forming a cyber-physical integrated network. In order to maximize information diffusion in such a network, a group of objects are selected as the forwarding points. To optimize the selection, a minimum connected dominating set (CDS) strategy is adopted. However, existing approaches focus on minimizing the size of the CDS, neglecting an important factor: the weight of links. In this paper, we propose a distributed maximizing the probability of information diffusion (DMPID) algorithm in the cyber-physical integrated network. Unlike previous approaches that only consider the size of CDS selection, DMPID also considers the information spread probability that depends on the weight of links. To weaken the effects of excessively-weighted links, we also present an optimization strategy that can properly balance the two factors. The results of extensive simulation show that DMPID can nearly double the information diffusion probability, while keeping a reasonable size of selection with low overhead in different distributed networks. PMID:26569254

    18. Maximizing Information Diffusion in the Cyber-physical Integrated Network.

      PubMed

      Lu, Hongliang; Lv, Shaohe; Jiao, Xianlong; Wang, Xiaodong; Liu, Juan

      2015-11-11

      Nowadays, our living environment has been embedded with smart objects, such as smart sensors, smart watches and smart phones. They make cyberspace and physical space integrated by their abundant abilities of sensing, communication and computation, forming a cyber-physical integrated network. In order to maximize information diffusion in such a network, a group of objects are selected as the forwarding points. To optimize the selection, a minimum connected dominating set (CDS) strategy is adopted. However, existing approaches focus on minimizing the size of the CDS, neglecting an important factor: the weight of links. In this paper, we propose a distributed maximizing the probability of information diffusion (DMPID) algorithm in the cyber-physical integrated network. Unlike previous approaches that only consider the size of CDS selection, DMPID also considers the information spread probability that depends on the weight of links. To weaken the effects of excessively-weighted links, we also present an optimization strategy that can properly balance the two factors. The results of extensive simulation show that DMPID can nearly double the information diffusion probability, while keeping a reasonable size of selection with low overhead in different distributed networks.

    19. Understanding student use of differentials in physics integration problems

      NASA Astrophysics Data System (ADS)

      Hu, Dehui; Rebello, N. Sanjay

      2013-12-01

      This study focuses on students’ use of the mathematical concept of differentials in physics problem solving. For instance, in electrostatics, students need to set up an integral to find the electric field due to a charged bar, an activity that involves the application of mathematical differentials (e.g., dr, dq). In this paper we aim to explore students’ reasoning about the differential concept in physics problems. We conducted group teaching or learning interviews with 13 engineering students enrolled in a second-semester calculus-based physics course. We amalgamated two frameworks—the resources framework and the conceptual metaphor framework—to analyze students’ reasoning about differential concept. Categorizing the mathematical resources involved in students’ mathematical thinking in physics provides us deeper insights into how students use mathematics in physics. Identifying the conceptual metaphors in students’ discourse illustrates the role of concrete experiential notions in students’ construction of mathematical reasoning. These two frameworks serve different purposes, and we illustrate how they can be pieced together to provide a better understanding of students’ mathematical thinking in physics.

    20. Quantum partition functions of composite particles in a hydrogen-helium plasma via path integral Monte Carlo

      SciTech Connect

      Wendland, D.; Ballenegger, V.; Alastuey, A.

      2014-11-14

      We compute two- and three-body cluster functions that describe contributions of composite entities, like hydrogen atoms, ions H{sup −}, H{sub 2}{sup +}, and helium atoms, and also charge-charge and atom-charge interactions, to the equation of state of a hydrogen-helium mixture at low density. A cluster function has the structure of a truncated virial coefficient and behaves, at low temperatures, like a usual partition function for the composite entity. Our path integral Monte Carlo calculations use importance sampling to sample efficiently the cluster partition functions even at low temperatures where bound state contributions dominate. We also employ a new and efficient adaptive discretization scheme that allows one not only to eliminate Coulomb divergencies in discretized path integrals, but also to direct the computational effort where particles are close and thus strongly interacting. The numerical results for the two-body function agree with the analytically known quantum second virial coefficient. The three-body cluster functions are compared at low temperatures with familiar partition functions for composite entities.

    1. Intensity moments by path integral techniques for wave propagation through random media, with application to sound in the ocean

      NASA Technical Reports Server (NTRS)

      Bernstein, D. R.; Dashen, R.; Flatte, S. M.

      1983-01-01

      A theory is developed which describes intensity moments for wave propagation through random media. It is shown using the path integral technique that these moments are significantly different from those of a Rayleigh distribution in certain asymptotic regions. The path integral approach is extended to inhomogeneous, anisotropic media possessing a strong deterministic velocity profile. The behavior of the corrections to Rayleigh statistics is examined, and it is shown that the important characteristics can be attributed to a local micropath focusing function. The correction factor gamma is a micropath focusing parameter defined in terms of medium fluctuations. The value of gamma is calculated for three ocean acoustic experiments, using internal waves as the medium fluctuations. It is found that all three experiments show excellent agreement as to the relative values of the intensity moments. The full curved ray is found to yield results that are significantly different from the straight-line approximations. It is noted that these methods are applicable to a variety of experimental situations, including atmospheric optics and radio waves through plasmas.

    2. Total and correlation energy of the uniform polarized electron gas at finite temperature: Direct path integral simulations

      NASA Astrophysics Data System (ADS)

      Filinov, V. S.; Fortov, V. E.; Bonitz, M.; Moldabekov, Zh

      2015-11-01

      The uniform electron gas (UEG) at finite temperature has recently attracted substantial interest due to the experimental progress in the field of warm dense matter. To explain the experimental data accurate theoretical models for high density plasmas are needed which crucially depend on treatment of quantum effects in electron-electron interaction as well as in the interaction of electrons with uniform positive background. To comply with these requirements we have developed the new quantum path integral model of the UEG and present the results of related direct path integral Monte-Carlo (DPIMC) simulations. Contrary to the known in literature approaches treating the electron-background interaction classically our simulations take into account the quantum effects in this interaction. We have observed very good agreement with known in literature results only up to moderate densities when the ratio of the average interparticle distance to the Bohr radius is of order four (rs ≥ 4) and observe deviations for higher densities. At very high electron density (rs ≈ 1) presented in literature approaches as well as our simulations are problematic due to the strong degeneracy of electrons and increasing fermion sign problem.

    3. Idiosyncratic route-based memories in desert ants, Melophorus bagoti: how do they interact with path-integration vectors?

      PubMed

      Kohler, Martin; Wehner, Rüdiger

      2005-01-01

      Individually foraging desert ants of central Australia, Melophorus bagoti, exhibit amazingly precise mechanisms of visual landmark guidance when navigating through cluttered environments. If trained to shuttle back and forth between the nest and a feeder, they establish habitual outbound and inbound routes, which guide them idiosyncratically across the natural maze of extended arrays of grass tussocks covering their foraging areas. The route-based memories that usually differ between outbound and inbound runs are acquired already during the first runs to the nest and feeder. If the ants are displaced sideways of their habitual routes, they can enter their stereotyped routes at any place and then follow these routes with the same accuracy as if they had started at the usual point of departure. Furthermore, the accuracy of maintaining a route does not depend on whether homebound ants have been captured at the feeder shortly before starting their home run and, hence, with their home vector still fully available (full-vector ants), or whether they have been captured at the nest after they had already completed their home run (zero-vector ants). Hence, individual landmark memories can be retrieved independently of the state of the path-integration vector with which they have been associated during the acquisition phase of learning. However, the ants display their path-integration vector when displaced from the feeder to unfamiliar territory.

    4. Exchange and spin states in quantum dots under strong spatial correlations. Computer simulation by the Feynman path integral method

      SciTech Connect

      Shevkunov, S. V.

      2013-10-15

      The fundamental laws in the behavior of electrons in model quantum dots that are caused by exchange and strong Coulomb correlations are studied. The ab initio path integral method is used to numerically simulate systems of two, three, four, and six interacting identical electrons confined in a three-dimensional spherical potential well with a parabolic confining potential against the background of thermal fluctuations. The temperature dependences of spin and collective spin magnetic susceptibility are calculated for model quantum dots of various spatial sizes. A basically exact procedure is proposed for taking into account the permutation symmetry and the spin state of electrons, which makes it possible to perform numerical calculations using modern computer facilities. The conditions of applicability of a virial energy estimator and its optimum form in exchange systems are determined. A correlation estimator of kinetic energy, which is an alternative to a basic estimator, is suggested. A fundamental relation between the kinetic energy of a quantum particle and the character of its virtual diffusion in imaginary time is demonstrated. The process of natural 'pairing' of electron spins during the compression of a quantum dot and cooling of a system is numerically reproduced in terms of path integrals. The temperature dependences of the spin magnetic susceptibility of electron pairs with a characteristic maximum caused by spin pairing are obtained.

    5. Ab initio path-integral calculations of kinetic and equilibrium isotope effects on base-catalyzed RNA transphosphorylation models.

      PubMed

      Wong, Kin-Yiu; Xu, Yuqing; York, Darrin M

      2014-06-30

      Detailed understandings of the reaction mechanisms of RNA catalysis in various environments can have profound importance for many applications, ranging from the design of new biotechnologies to the unraveling of the evolutionary origin of life. An integral step in the nucleolytic RNA catalysis is self-cleavage of RNA strands by 2'-O-transphosphorylation. Key to elucidating a reaction mechanism is determining the molecular structure and bonding characteristics of transition state. A direct and powerful probe of transition state is measuring isotope effects on biochemical reactions, particularly if we can reproduce isotope effect values from quantum calculations. This article significantly extends the scope of our previous joint experimental and theoretical work in examining isotope effects on enzymatic and nonenzymatic 2'-O-transphosphorylation reaction models that mimic reactions catalyzed by RNA enzymes (ribozymes), and protein enzymes such as ribonuclease A (RNase A). Native reactions are studied, as well as reactions with thio substitutions representing chemical modifications often used in experiments to probe mechanism. Here, we report and compare results from eight levels of electronic-structure calculations for constructing the potential energy surfaces in kinetic and equilibrium isotope effects (KIE and EIE) computations, including a "gold-standard" coupled-cluster level of theory [CCSD(T)]. In addition to the widely used Bigeleisen equation for estimating KIE and EIE values, internuclear anharmonicity and quantum tunneling effects were also computed using our recently developed ab initio path-integral method, that is, automated integration-free path-integral method. The results of this work establish an important set of benchmarks that serve to guide calculations of KIE and EIE for RNA catalysis.

    6. Ab Initio Path-Integral Calculations of Kinetic and Equilibrium Isotope Effects on Base-Catalyzed RNA Transphosphorylation Models

      PubMed Central

      Wong, Kin-Yiu; Yuqing, Xu; York, Darrin M.

      2014-01-01

      Detailed understandings of the reaction mechanisms of RNA catalysis in various environments can have profound importance for many applications, ranging from the design of new biotechnologies to the unraveling of the evolutionary origin of life. An integral step in the nucleolytic RNA catalysis is self-cleavage of RNA strands by 2′-O-transphosphorylation. Key to elucidating a reaction mechanism is determining the molecular structure and bonding characteristics of transition state. A direct and powerful probe of transition state is measuring isotope effects on biochemical reactions, particularly if we can reproduce isotope effect values from quantum calculations. This paper significantly extends the scope of our previous joint experimental and theoretical work in examining isotope effects on enzymatic and non-enzymatic 2′-O-transphosphorylation reaction models that mimic reactions catalyzed by RNA enzymes (ribozymes), and protein enzymes such as ribonuclease A (RNase A). Native reactions are studied, as well as reactions with thio substitutions representing chemical modifications often used in experiments to probe mechanism. Here, we report and compare results from eight levels of electronic-structure calculations for constructing the potential energy surfaces in kinetic and equilibrium isotope effects (KIE and EIE) computations, including a “gold-standard” coupled-cluster level of theory [CCSD(T)]. In addition to the widely-used Bigeleisen equation for estimating KIE and EIE values, internuclear anharmonicity and quantum tunneling effects were also computed using our recently-developed ab initio path-integral method, i.e., automated integration-free path-integral (AIF-PI) method. The results of this work establish an important set of benchmarks that serve to guide calculations of KIE and EIE for RNA catalysis. PMID:24841935

    7. Physical Education Teachers' Subjective Theories about Integrating Information and Communication Technology (ICT) into Physical Education

      ERIC Educational Resources Information Center

      Kretschmann, Rolf

      2015-01-01

      As well as other school subjects, physical education (PE) is emerging in terms of integrating information and communication technology (ICT) into regular classes. Such innovative teaching practices that implement ICT in PE involve diverse parties that are affected by these teaching processes. Students, principals, districts, parents,…

    8. Pre-Service Physics and Chemistry Teachers' Conceptual Integration of Physics and Chemistry Concepts

      ERIC Educational Resources Information Center

      Tuysuz, Mustafa; Bektas, Oktay; Geban, Omer; Ozturk, Gokhan; Yalvac, Bugrahan

      2016-01-01

      This study examines the pre-service teachers' opinions about conceptual integration (CI) and their understanding of it. A qualitative phenomenology design was used in the study. Data was collected through in-depth semi-structured interviews comprising ten guiding questions. Three pre-service physics and three pre-service chemistry teachers…

    9. The Physics of White Dwarf Mergers and Detonations: A Path to Type Ia Supernova

      NASA Astrophysics Data System (ADS)

      Chang, Philip

      This project will investigate the double degenerate scenario for Type Ia supernova (SN Ia) and the physics of detonation initiation in white dwarfs. While the progenitors of SN Ia are not known, the detonation of a remnant from a pair of merging white dwarfs produces a mix of burnt material that is similar to the compositional makeup of SN Ia. Hence, the merger of two white dwarfs and detonation of its relaxed remnant is a promising avenue to SN Ia. Using a combination of numerical and analytic techniques, the PI and his collaborators will investigate the merger of two white dwarfs and the initiation of detonations in these remnants. In particular, the group will use a previously modified smooth particle hydrodynamics code to perform a parameter study of the mergers of two white dwarfs. The group will then determine how the properties of the resulting remnant depends on it initial conditions of the merger. In doing so, the group will map out the parameter space of white dwarf mergers, whose remnant's secular evolution that can lead to Type Ia supernova. The group will also investigate the physics of detonation initiation in WDs. In particular, the group will leverage prior work on terrestial detonations to map the controlling parameters of detonation initiation in WDs. For instance, the group will determine the physics of detonations for a given size and shape of a hotspot, i.e., if the detonation occurs due pure combustion effects or if the interaction between combustion waves and hydrodynamics waves are important. Armed with this information, the group will proceed to study if large scale turbulence can give rise the hotspots capable of initiating detonations and the physics of these initiations. The work performed by this group will be important in future dark energy survey mission such as a WFIRST descendent and in current transient all-sky surveys.

    10. ["Living with the bomb" - Carl Friedrich von Weizsäcker's path from physics to politics].

      PubMed

      Walker, Mark

      2014-01-01

      Carl Friedrich von Weizsäcker spanned a spectrum from physics to politics, with philosophy in-between. This chapter surveys the most controversial part of his career, including his work on nuclear weapons and participation in cultural propaganda during the Second World War, his subsequent active political engagement during the postwar Federal German Republic, in particular the role of nuclear weapons, and his participation in myths surrounding Hitler's Bomb".

    11. The role of neighborhood disadvantage, physical disorder, and collective efficacy in adolescent alcohol use: a multilevel path analysis.

      PubMed

      Jackson, Nicki; Denny, Simon; Sheridan, Janie; Zhao, Jinfeng; Ameratunga, Shanthi

      2016-09-01

      Research into the salient exposures which explain neighborhood variation in adolescent alcohol use remains inconclusive. The Social Disorganization Theory suggests that neighborhood-level disadvantage may reduce collective efficacy to control adolescent risky behavior. Collective perceptions of physical disorder are also implicated in this neighborhood pathway. Drawing on data from a nationally-representative survey of urban high school students in New Zealand, multilevel path analysis was used to estimate the direct and mediating effects of neighborhood disadvantage, physical disorder, and collective efficacy on current drinking, frequency of binge drinking, and typical quantity of alcohol consumed. The findings supported an indirect pathway from disadvantage to binge drinking and high typical quantities in young adolescents (<16 years), mediated by physical disorder and reduced collective efficacy. Collective efficacy was not associated with current drinking in young adolescents. An opposing indirect effect was evident among older adolescents (≥16 years), whereby collective efficacy was positively associated with drinking outcomes. Implications for future research are discussed. PMID:27521816

    12. Displaced path integral formulation for the momentum distribution of quantum particles.

      PubMed

      Lin, Lin; Morrone, Joseph A; Car, Roberto; Parrinello, Michele

      2010-09-10

      The proton momentum distribution, accessible by deep inelastic neutron scattering, is a very sensitive probe of the potential of mean force experienced by the protons in hydrogen-bonded systems. In this work we introduce a novel estimator for the end-to-end distribution of the Feynman paths, i.e., the Fourier transform of the momentum distribution. In this formulation, free particle and environmental contributions factorize. Moreover, the environmental contribution has a natural analogy to a free energy surface in statistical mechanics, facilitating the interpretation of experiments. The new formulation is not only conceptually but also computationally advantageous. We illustrate the method with applications to an empirical water model, ab initio ice, and one dimensional model systems.

    13. Displaced path integral formulation for the momentum distribution of quantum particles.

      PubMed

      Lin, Lin; Morrone, Joseph A; Car, Roberto; Parrinello, Michele

      2010-09-10

      The proton momentum distribution, accessible by deep inelastic neutron scattering, is a very sensitive probe of the potential of mean force experienced by the protons in hydrogen-bonded systems. In this work we introduce a novel estimator for the end-to-end distribution of the Feynman paths, i.e., the Fourier transform of the momentum distribution. In this formulation, free particle and environmental contributions factorize. Moreover, the environmental contribution has a natural analogy to a free energy surface in statistical mechanics, facilitating the interpretation of experiments. The new formulation is not only conceptually but also computationally advantageous. We illustrate the method with applications to an empirical water model, ab initio ice, and one dimensional model systems. PMID:20867559

    14. Circular trajectory formation during blind locomotion: a test for path integration and motor memory.

      PubMed

      Takei, Y; Grasso, R; Amorim, M A; Berthoz, A

      1997-06-01

      Eight healthy subjects were asked to walk blindfolded along circular paths of different radii after several practice trials with vision. Their task was to stop after completing two full revolutions. They always walked counter-clockwise (CCW) in (a) a control condition (CONTROL), including the instructions mentioned above, (b) with the further instruction to count backwards in twos (MENTAL), (c) with the instruction to count loudly (LOUD). The movement of two markers lying along the head naso-occipital axis was recorded by means of an ELITE system. Total walked distance (DISTANCE), total head turning angle (ANGLE) and average radius (RADIUS) of the trajectories performed were measured. All subjects were able to perform approximately circular trajectories. They consistently overshot the ideal radius independently of the condition and circle size, undershot the total angle and overshot total distance. The LOUD condition induced greater errors in the performance but only on total distance (P<0.05). A strong correlation was found between the errors in radius and total distance but not between distance and total angle. Principal components analysis suggested that radius and distance share a common source of errors while total angle produced independent errors. The results indicate that (a) circular trajectories can be generated starting from spatial and/or motor memory, without the aid of visual information; (b) the task needs some attentional control and does not involve simple automatic processing of afferent information; (c) different sensory information or different processing modes are probably involved in the estimation of the curvature and length of the walked path on the one hand, and of the total rotation angle on the other.

    15. An Integrated Simulation Module for Cyber-Physical Automation Systems.

      PubMed

      Ferracuti, Francesco; Freddi, Alessandro; Monteriù, Andrea; Prist, Mariorosario

      2016-01-01

      The integration of Wireless Sensors Networks (WSNs) into Cyber Physical Systems (CPSs) is an important research problem to solve in order to increase the performances, safety, reliability and usability of wireless automation systems. Due to the complexity of real CPSs, emulators and simulators are often used to replace the real control devices and physical connections during the development stage. The most widespread simulators are free, open source, expandable, flexible and fully integrated into mathematical modeling tools; however, the connection at a physical level and the direct interaction with the real process via the WSN are only marginally tackled; moreover, the simulated wireless sensor motes are not able to generate the analogue output typically required for control purposes. A new simulation module for the control of a wireless cyber-physical system is proposed in this paper. The module integrates the COntiki OS JAva Simulator (COOJA), a cross-level wireless sensor network simulator, and the LabVIEW system design software from National Instruments. The proposed software module has been called "GILOO" (Graphical Integration of Labview and cOOja). It allows one to develop and to debug control strategies over the WSN both using virtual or real hardware modules, such as the National Instruments Real-Time Module platform, the CompactRio, the Supervisory Control And Data Acquisition (SCADA), etc. To test the proposed solution, we decided to integrate it with one of the most popular simulators, i.e., the Contiki OS, and wireless motes, i.e., the Sky mote. As a further contribution, the Contiki Sky DAC driver and a new "Advanced Sky GUI" have been proposed and tested in the COOJA Simulator in order to provide the possibility to develop control over the WSN. To test the performances of the proposed GILOO software module, several experimental tests have been made, and interesting preliminary results are reported. The GILOO module has been applied to a smart home

    16. An Integrated Simulation Module for Cyber-Physical Automation Systems.

      PubMed

      Ferracuti, Francesco; Freddi, Alessandro; Monteriù, Andrea; Prist, Mariorosario

      2016-05-05

      The integration of Wireless Sensors Networks (WSNs) into Cyber Physical Systems (CPSs) is an important research problem to solve in order to increase the performances, safety, reliability and usability of wireless automation systems. Due to the complexity of real CPSs, emulators and simulators are often used to replace the real control devices and physical connections during the development stage. The most widespread simulators are free, open source, expandable, flexible and fully integrated into mathematical modeling tools; however, the connection at a physical level and the direct interaction with the real process via the WSN are only marginally tackled; moreover, the simulated wireless sensor motes are not able to generate the analogue output typically required for control purposes. A new simulation module for the control of a wireless cyber-physical system is proposed in this paper. The module integrates the COntiki OS JAva Simulator (COOJA), a cross-level wireless sensor network simulator, and the LabVIEW system design software from National Instruments. The proposed software module has been called "GILOO" (Graphical Integration of Labview and cOOja). It allows one to develop and to debug control strategies over the WSN both using virtual or real hardware modules, such as the National Instruments Real-Time Module platform, the CompactRio, the Supervisory Control And Data Acquisition (SCADA), etc. To test the proposed solution, we decided to integrate it with one of the most popular simulators, i.e., the Contiki OS, and wireless motes, i.e., the Sky mote. As a further contribution, the Contiki Sky DAC driver and a new "Advanced Sky GUI" have been proposed and tested in the COOJA Simulator in order to provide the possibility to develop control over the WSN. To test the performances of the proposed GILOO software module, several experimental tests have been made, and interesting preliminary results are reported. The GILOO module has been applied to a smart home

    17. The heritable path of human physical performance: from single polymorphisms to the "next generation".

      PubMed

      Santos, C G M; Pimentel-Coelho, P M; Budowle, B; de Moura-Neto, R S; Dornelas-Ribeiro, M; Pompeu, F A M S; Silva, R

      2016-06-01

      Human physical performance is a complex multifactorial trait. Historically, environmental factors (e.g., diet, training) alone have been unable to explain the basis of all prominent phenotypes for physical performance. Therefore, there has been an interest in the study of the contribution of genetic factors to the development of these phenotypes. Support for a genetic component is found with studies that shown that monozygotic twins were more similar than were dizygotic twins for many physiological traits. The evolution of molecular techniques and the ability to scan the entire human genome enabled association of several genetic polymorphisms with performance. However, some biases related to the selection of cohorts and inadequate definition of the study variables have complicated the already difficult task of studying such a large and polymorphic genome, often resulting in inconsistent results about the influence of candidate genes. This review aims to provide a critical overview of heritable genetic aspects. Novel molecular technologies, such as next-generation sequencing, are discussed and how they can contribute to improving understanding of the molecular basis for athletic performance. It is important to ensure that the large amount of data that can be generated using these tools will be used effectively by ensuring well-designed studies.

    18. Homing strategies of the Australian desert ant Melophorus bagoti. I. Proportional path-integration takes the ant half-way home.

      PubMed

      Narendra, Ajay

      2007-05-01

      Highly evolved eusocial insects such as ants return from a food source to their nest by the shortest possible distance. This form of navigation, called path-integration, involves keeping track of the distance travelled and the angles steered on the outbound journey, which then aids in the computation of the shortest return distance. In featureless terrain, ants rely on the path integrator to travel the entire distance to return to the nest, whereas in landmark-rich habitats ants are guided by visual cues and in the absence of the visual cues homing ants rely on the path integrator to travel only an initial 10-60 cm of the homebound distance. The functioning of the path integrator in a habitat of intermediate landmark density is unknown. The findings reported here show that when the outward journey is on a familiar foraging area, and the inward journey is on an unfamiliar area, the Australian route-following desert ant Melophorus bagoti relies on the path integrator and consistently travels half the distance of the outward trip. However, when both the outward and inward trips are performed in plain and featureless channels, which blocks the distinct terrestrial visual cues, ants travel the entire distance accurately. A similar half-way abbreviation of the home vector occurs when the ant's outward trip is in an L-shaped channel and the homeward trip is over an open and unfamiliar region. The ecological significance of these new findings is discussed.

    19. Photon, light ion, and heavy ion cancer radiotherapy: paths from physics and biology to clinical practice

      PubMed Central

      2015-01-01

      External beam radiotherapy has proven highly effective against a wide range of cancers, and in recent decades there have been rapid advances with traditional photon-based (X-ray) radiotherapy and the development of two particle-based techniques, proton and carbon ion radiotherapy (CIRT). There are major cost differences and both physical and biological differences among these modalities that raise important questions about relative treatment efficacy and cost-effectiveness. Randomized clinical trials (RCTs) represent the gold standard for comparing treatments, but there are significant cost and ethical barriers to their wide-spread use. Meta-analysis of non-coordinated clinical trials data is another tool that can be used to compare treatments, and while this approach has recognized limitations, it is argued that meta-analysis represents an early stage of investigation that can help inform the design of future RCTs. PMID:26734646

    20. The Regional University: Paths of Integration in the Framework of the Bologna Process

      ERIC Educational Resources Information Center

      Lazarev, G.; Martynenko, O.

      2006-01-01

      The development of international systems of education is opening the way to accomplish tasks in the sphere of higher education that are common to the world community. The Bologna Process, in the framework of which the educational systems of Europe are becoming integrated, makes it possible for Russia to make a choice of the forms of its…

    1. Making Laboratories Count -- Better Integration of Laboratories in Physics Courses

      NASA Astrophysics Data System (ADS)

      Sizemore, Jim

      2011-10-01

      The quality of K-12 education leaves something to be desired and presents higher education faculty with the challenge of instructing under-prepared students. However, by their own admission, students from many institutions inform us that laboratory sections in science classes, including physics, consist mostly of showing up, going through the motions, and getting grades that boost their overall grade. This work presents laboratories that challenge students to take their laboratory work more seriously including specific rubrics enforcing SOLVE and Bloom's Taxonomy, pre-lab preparation work, and quizzes on pre-lab preparation. Early results are encouraging revealing greater student progress with better integration of laboratory with the rest of a complete physics course.

    2. Integrating particle physical geometry into composting degradation kinetics.

      PubMed

      Wang, Yongjiang; Ai, Ping

      2016-01-01

      The study was carried out to integrate physical geometry of compost particle with degradation kinetics to model biological reactions, which revealing additional dynamic approaches. A sphere and its circumscribing cube were used to represent compost particles. An inner sphere, representing anaerobic zone, was introduced to describe variations of substrate volume without sufficient oxygen supply. Degradation of soluble substrates and hydrolysis of insoluble substrates were associated with the particle geometry. Transportation of soluble substrates produced from hydrolysis was expressed using Fick's law. Through the integration of degradation kinetics with geometry models, degradation models could describe varying volume of composting materials involving aerobic or anaerobic digestion and transportation of soluble substrates in a unit compost particle.

    3. An integrated physical and biological model for anaerobic lagoons.

      PubMed

      Wu, Binxin; Chen, Zhenbin

      2011-04-01

      A computational fluid dynamics (CFD) model that integrates physical and biological processes for anaerobic lagoons is presented. In the model development, turbulence is represented using a transition k-ω model, heat conduction and solar radiation are included in the thermal model, biological oxygen demand (BOD) reduction is characterized by first-order kinetics, and methane yield rate is expressed as a linear function of temperature. A test of the model applicability is conducted in a covered lagoon digester operated under tropical climate conditions. The commercial CFD software, ANSYS-Fluent, is employed to solve the integrated model. The simulation procedures include solving fluid flow and heat transfer, predicting local resident time based on the converged flow fields, and calculating the BOD reduction and methane production. The simulated results show that monthly methane production varies insignificantly, but the time to achieve a 99% BOD reduction in January is much longer than that in July.

    4. 77 FR 9226 - Physical Systems Integration, LLC; Supplemental Notice That Initial Market-Based Rate Filing...

      Federal Register 2010, 2011, 2012, 2013, 2014

      2012-02-16

      ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Physical Systems Integration, LLC; Supplemental Notice That Initial Market... in the above-referenced proceeding of Physical Systems Integration, LLC's application for...

    5. The polarization compass dominates over idiothetic cues in path integration of desert ants.

      PubMed

      Lebhardt, Fleur; Koch, Julja; Ronacher, Bernhard

      2012-02-01

      Desert ants, Cataglyphis, use the sky's pattern of polarized light as a compass reference for navigation. However, they do not fully exploit the complexity of this pattern, rather - as proposed previously - they assess their walking direction by means of an approximate solution based on a simplified internal template. Approximate rules are error-prone. We therefore asked whether the ants use additional cues to improve the accuracy of directional decisions, and focused on 'idiothetic' cues, i.e. cues based on information from proprioceptors. We trained ants in a channel system that was covered with a polarization filter, providing only a single e-vector direction as a directional 'celestial' cue. Then we observed their homebound runs on a test field, allowing full view of the sky. In crucial experiments, the ants were exposed to a cue conflict, in which sky compass and idiothetic information disagreed, by training them in a straight channel that provided a change in e-vector direction. The results indicated that the polarization information completely dominates over idiothetic cues. Two path segments with different e-vector orientations are combined linearly to a summed home vector. Our data provide additional evidence that Cataglyphis uses a simplified internal template to derive directional information from the sky's polarization pattern.

    6. Simulation of thermal ionization in a dense helium plasma by the Feynman path integral method

      NASA Astrophysics Data System (ADS)

      Shevkunov, S. V.

      2011-04-01

      The region of equilibrium states is studied where the quantum nature of the electron component and a strong nonideality of a plasma play a key role. The problem of negative signs in the calculation of equilibrium averages a system of indistinguishable quantum particles with a spin is solved in the macroscopic limit. It is demonstrated that the calculation can be conducted up to a numerical result. The complete set of symmetrized basis wave functions is constructed based on the Young symmetry operators. The combinatorial weight coefficients of the states corresponding to different graphs of connected Feynman paths in multiparticle systems are calculated by the method of random walk over permutation classes. The kinetic energy is calculated using a viral estimator at a finite pressure in a statistical ensemble with flexible boundaries. Based on the methods developed in the paper, the computer simulation is performed for a dense helium plasma in the temperature range from 30000 to 40000 K. The equation of state, internal energy, ionization degree, and structural characteristic of the plasma are calculated in terms of spatial correlation functions. The parameters of a pseudopotential plasma model are estimated.

    7. Simulation of thermal ionization in a dense helium plasma by the Feynman path integral method

      SciTech Connect

      Shevkunov, S. V.

      2011-04-15

      The region of equilibrium states is studied where the quantum nature of the electron component and a strong nonideality of a plasma play a key role. The problem of negative signs in the calculation of equilibrium averages a system of indistinguishable quantum particles with a spin is solved in the macroscopic limit. It is demonstrated that the calculation can be conducted up to a numerical result. The complete set of symmetrized basis wave functions is constructed based on the Young symmetry operators. The combinatorial weight coefficients of the states corresponding to different graphs of connected Feynman paths in multiparticle systems are calculated by the method of random walk over permutation classes. The kinetic energy is calculated using a viral estimator at a finite pressure in a statistical ensemble with flexible boundaries. Based on the methods developed in the paper, the computer simulation is performed for a dense helium plasma in the temperature range from 30000 to 40000 K. The equation of state, internal energy, ionization degree, and structural characteristic of the plasma are calculated in terms of spatial correlation functions. The parameters of a pseudopotential plasma model are estimated.

    8. Integrative Analysis of the Physical Transport Network into Australia.

      PubMed

      Cope, Robert C; Ross, Joshua V; Wittmann, Talia A; Prowse, Thomas A A; Cassey, Phillip

      2016-01-01

      Effective biosecurity is necessary to protect nations and their citizens from a variety of threats, including emerging infectious diseases, agricultural or environmental pests and pathogens, and illegal wildlife trade. The physical pathways by which these threats are transported internationally, predominantly shipping and air traffic, have undergone significant growth and changes in spatial distributions in recent decades. An understanding of the specific pathways and donor-traffic hotspots created by this integrated physical transport network is vital for the development of effective biosecurity strategies into the future. In this study, we analysed the physical transport network into Australia over the period 1999-2012. Seaborne and air traffic were weighted to calculate a "weighted cumulative impact" score for each source region worldwide, each year. High risk source regions, and those source regions that underwent substantial changes in risk over the study period, were determined. An overall risk ranking was calculated by integrating across all possible weighting combinations. The source regions having greatest overall physical connectedness with Australia were Singapore, which is a global transport hub, and the North Island of New Zealand, a close regional trading partner with Australia. Both those regions with large amounts of traffic across multiple vectors (e.g., Hong Kong), and those with high levels of traffic of only one type (e.g., Bali, Indonesia with respect to passenger flights), were represented among high risk source regions. These data provide a baseline model for the transport of individuals and commodities against which the effectiveness of biosecurity controls may be assessed, and are a valuable tool in the development of future biosecurity policy. PMID:26881782

    9. Integrative Analysis of the Physical Transport Network into Australia

      PubMed Central

      Cope, Robert C.; Ross, Joshua V.; Wittmann, Talia A.; Prowse, Thomas A. A.; Cassey, Phillip

      2016-01-01

      Effective biosecurity is necessary to protect nations and their citizens from a variety of threats, including emerging infectious diseases, agricultural or environmental pests and pathogens, and illegal wildlife trade. The physical pathways by which these threats are transported internationally, predominantly shipping and air traffic, have undergone significant growth and changes in spatial distributions in recent decades. An understanding of the specific pathways and donor-traffic hotspots created by this integrated physical transport network is vital for the development of effective biosecurity strategies into the future. In this study, we analysed the physical transport network into Australia over the period 1999–2012. Seaborne and air traffic were weighted to calculate a “weighted cumulative impact” score for each source region worldwide, each year. High risk source regions, and those source regions that underwent substantial changes in risk over the study period, were determined. An overall risk ranking was calculated by integrating across all possible weighting combinations. The source regions having greatest overall physical connectedness with Australia were Singapore, which is a global transport hub, and the North Island of New Zealand, a close regional trading partner with Australia. Both those regions with large amounts of traffic across multiple vectors (e.g., Hong Kong), and those with high levels of traffic of only one type (e.g., Bali, Indonesia with respect to passenger flights), were represented among high risk source regions. These data provide a baseline model for the transport of individuals and commodities against which the effectiveness of biosecurity controls may be assessed, and are a valuable tool in the development of future biosecurity policy. PMID:26881782

    10. Integrative Analysis of the Physical Transport Network into Australia.

      PubMed

      Cope, Robert C; Ross, Joshua V; Wittmann, Talia A; Prowse, Thomas A A; Cassey, Phillip

      2016-01-01

      Effective biosecurity is necessary to protect nations and their citizens from a variety of threats, including emerging infectious diseases, agricultural or environmental pests and pathogens, and illegal wildlife trade. The physical pathways by which these threats are transported internationally, predominantly shipping and air traffic, have undergone significant growth and changes in spatial distributions in recent decades. An understanding of the specific pathways and donor-traffic hotspots created by this integrated physical transport network is vital for the development of effective biosecurity strategies into the future. In this study, we analysed the physical transport network into Australia over the period 1999-2012. Seaborne and air traffic were weighted to calculate a "weighted cumulative impact" score for each source region worldwide, each year. High risk source regions, and those source regions that underwent substantial changes in risk over the study period, were determined. An overall risk ranking was calculated by integrating across all possible weighting combinations. The source regions having greatest overall physical connectedness with Australia were Singapore, which is a global transport hub, and the North Island of New Zealand, a close regional trading partner with Australia. Both those regions with large amounts of traffic across multiple vectors (e.g., Hong Kong), and those with high levels of traffic of only one type (e.g., Bali, Indonesia with respect to passenger flights), were represented among high risk source regions. These data provide a baseline model for the transport of individuals and commodities against which the effectiveness of biosecurity controls may be assessed, and are a valuable tool in the development of future biosecurity policy.

    11. Neocartilage integration in temporomandibular joint discs: physical and enzymatic methods

      PubMed Central

      Murphy, Meghan K.; Arzi, Boaz; Prouty, Shannon M.; Hu, Jerry C.; Athanasiou, Kyriacos A.

      2015-01-01

      Integration of engineered musculoskeletal tissues with adjacent native tissues presents a significant challenge to the field. Specifically, the avascularity and low cellularity of cartilage elicit the need for additional efforts in improving integration of neocartilage within native cartilage. Self-assembled neocartilage holds significant potential in replacing degenerated cartilage, though its stabilization and integration in native cartilage require further efforts. Physical and enzymatic stabilization methods were investigated in an in vitro model for temporomandibular joint (TMJ) disc degeneration. First, in phase 1, suture, glue and press-fit constructs were compared in TMJ disc intermediate zone defects. In phase 1, suturing enhanced interfacial shear stiffness and strength immediately; after four weeks, a 15-fold increase in stiffness and a ninefold increase in strength persisted over press-fit. Neither suture nor glue significantly altered neocartilage properties. In phase 2, the effects of the enzymatic stabilization regimen composed of lysyl oxidase, CuSO4 and hydroxylysine were investigated. A full factorial design was employed, carrying forward the best physical method from phase 1, suturing. Enzymatic stabilization significantly increased interfacial shear stiffness after eight weeks. Combined enzymatic stabilization and suturing led to a fourfold increase in shear stiffness and threefold increase in strength over press-fit. Histological analysis confirmed the presence of a collagen-rich interface. Enzymatic treatment additionally enhanced neocartilage mechanical properties, yielding a tensile modulus over 6 MPa and compressive instantaneous modulus over 1200 kPa at eight weeks. Suturing enhances stabilization of neocartilage, and enzymatic treatment enhances functional properties and integration of neocartilage in the TMJ disc. Methods developed here are applicable to other orthopaedic soft tissues, including knee meniscus and hyaline articular

    12. Development of Path Integral Monte Carlo Simulations with Localized Nodal Surfaces for Second-Row Elements.

      PubMed

      Militzer, Burkhard; Driver, Kevin P

      2015-10-23

      We extend the applicability range of fermionic path integral Monte Carlo simulations to heavier elements and lower temperatures by introducing various localized nodal surfaces. Hartree-Fock nodes yield the most accurate prediction for pressure and internal energy, which we combine with the results from density functional molecular dynamics simulations to obtain a consistent equation of state for hot, dense silicon under plasma conditions and in the regime of warm dense matter (2.3-18.6  g cm(-3), 5.0×10(5)-1.3×10(8)  K). The shock Hugoniot curve is derived and the structure of the fluid is characterized with various pair correlation functions. PMID:26551129

    13. Effects of Uncertainty in TRMM Precipitation Radar Path Integrated Attenuation on Interannual Variations of Tropical Oceanic Rainfall

      NASA Technical Reports Server (NTRS)

      Robertson, Franklin R.; Fitzjarrald, Dan E.; Kummerow, Christian D.; Arnold, James E. (Technical Monitor)

      2002-01-01

      Considerable uncertainty surrounds the issue of whether precipitation over the tropical oceans (30 deg N/S) systematically changes with interannual sea-surface temperature (SST) anomalies that accompany El Nino (warm) and La Nina (cold) events. Time series of rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM Precipitation Radar (PR) over the tropical oceans show marked differences with estimates from two TRMM Microwave Imager (TMI) passive microwave algorithms. We show that path-integrated attenuation derived from the effects of precipitation on the radar return from the ocean surface exhibits interannual variability that agrees closely with the TMI time series. Further analysis of the frequency distribution of PR (2A25 product) rain rates suggests that the algorithm incorporates the attenuation measurement in a very conservative fashion so as to optimize the instantaneous rain rates. Such an optimization appears to come at the expense of monitoring interannual climate variability.

    14. Double path integral method for obtaining the mobility of the one-dimensional charge transport in molecular chain.

      PubMed

      Yoo-Kong, Sikarin; Liewrian, Watchara

      2015-12-01

      We report on a theoretical investigation concerning the polaronic effect on the transport properties of a charge carrier in a one-dimensional molecular chain. Our technique is based on the Feynman's path integral approach. Analytical expressions for the frequency-dependent mobility and effective mass of the carrier are obtained as functions of electron-phonon coupling. The result exhibits the crossover from a nearly free particle to a heavily trapped particle. We find that the mobility depends on temperature and decreases exponentially with increasing temperature at low temperature. It exhibits large polaronic-like behaviour in the case of weak electron-phonon coupling. These results agree with the phase transition (A.S. Mishchenko et al., Phys. Rev. Lett. 114, 146401 (2015)) of transport phenomena related to polaron motion in the molecular chain. PMID:26701710

    15. Effects of Uncertainty in TRMM Precipitation Radar Path Integrated Attenuation on Interannual Variations of Tropical Oceanic Rainfall

      NASA Technical Reports Server (NTRS)

      Robertson, Franklin R.; Fitzjarrald, Dan E.; Kummerow, Christian D.

      2003-01-01

      Considerable uncertainty surrounds the issue of whether precipitation over the tropical oceans (30 deg N/S) systematically changes with interannual sea-surface temperature (SST) anomalies that accompany El Nino (warm) and La Nina (cold) events. Time series of rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) over the tropical oceans show marked differences with estimates from two TRMM Microwave Imager (TMI) passive microwave algorithms. We show that path-integrated attenuation derived from the effects of precipitation on the radar return from the ocean surface exhibits interannual variability that agrees closely with the TMI time series. Our analysis of discrepancies between the PR rainfall and attenuation suggests that uncertainty in the assumed drop size distribution and associated attenuation/reflectivity/rainfall relationships inherent in single-frequency radar methods is a serious issue for studies of interannual variability.

    16. Path-Integral Monte Carlo Study on a Droplet of a Dipolar Bose–Einstein Condensate Stabilized by Quantum Fluctuation

      NASA Astrophysics Data System (ADS)

      Saito, Hiroki

      2016-05-01

      Motivated by recent experiments [H. Kadau et al., Nature (London) 530, 194 (2016); I. Ferrier-Barbut et al., arXiv:1601.03318] and theoretical prediction (F. Wächtler and L. Santos, arXiv:1601.04501), the ground state of a dysprosium Bose-Einstein condensate with strong dipole-dipole interaction is studied by the path-integral Monte Carlo method. It is shown that quantum fluctuation can stabilize the condensate against dipolar collapse.

    17. A new post-quantization constrained propagator for rigid tops for use in path integral quantum simulations

      SciTech Connect

      Guillon, Grégoire; Zeng, Tao; Roy, Pierre-Nicholas

      2013-11-14

      In this paper, we extend the previously introduced Post-Quantization Constraints (PQC) procedure [G. Guillon, T. Zeng, and P.-N. Roy, J. Chem. Phys. 138, 184101 (2013)] to construct approximate propagators and energy estimators for different rigid body systems, namely, the spherical, symmetric, and asymmetric tops. These propagators are for use in Path Integral simulations. A thorough discussion of the underlying geometrical concepts is given. Furthermore, a detailed analysis of the convergence properties of the density as well as the energy estimators towards their exact counterparts is presented along with illustrative numerical examples. The Post-Quantization Constraints approach can yield converged results and is a practical alternative to so-called sum over states techniques, where one has to expand the propagator as a sum over a complete set of rotational stationary states [as in E. G. Noya, C. Vega, and C. McBride, J. Chem. Phys. 134, 054117 (2011)] because of its modest memory requirements.

    18. Low-temperature phases of dense hydrogen and deuterium by first-principles path-integral molecular dynamics

      NASA Astrophysics Data System (ADS)

      Torrent, Marc; Geneste, Gregory

      2012-02-01

      The low-temperature phases of dense hydrogen and deuterium have been investigated using first-principles path-integral molecular dynamics, a technique that we have recently implemented in the ABINIT code and that allows to account for the quantum fluctuations of atomic nuclei. A massively parallelized scheme is applied to produce trajectories of several tens of thousands steps using a 64-atom supercell and a Trotter number of 64. The so-called phases I, II and III are studied and compared to the structures proposed in the literature. The quantum fluctuations produce configurational disorder and are shown to systematically enhance the symmetry of the system: a continuous gain of symmetry in the angular density of probability of the molecules is found from classical particles to quantum D2 and finally to quantum H2. Particular emphasis is made on the ``broken-symmetry'' phase (phase II).

    19. Path-integral calculations of heavy atom kinetic isotope effects in condensed phase reactions using higher-order Trotter factorizations.

      PubMed

      Vardi-Kilshtain, Alexandra; Azuri, Asaf; Major, Dan Thomas

      2012-02-01

      A convenient approach to compute kinetic isotope effects (KIEs) in condensed phase chemical reactions is via path integrals (PIs). Usually, the primitive approximation is used in PI simulations, although such quantum simulations are computationally demanding. The efficiency of PI simulations may be greatly improved, if higher-order Trotter factorizations of the density matrix operator are used. In this study, we use a higher-order PI method, in conjunction with mass-perturbation, to compute heavy-atom KIE in the decarboxylation of orotic acid in explicit sulfolane solvent. The results are in good agreement with experiment and show that the mass-perturbation higher-order Trotter factorization provides a practical approach for computing condensed phase heavy-atom KIE.

    20. Integrated parasite management: path to sustainable control of fishborne trematodes in aquaculture.

      PubMed

      Clausen, Jesper H; Madsen, Henry; Van, Phan Thi; Dalsgaard, Anders; Murrell, K Darwin

      2015-01-01

      Fishborne zoonotic trematodes (FZT) are an emerging problem and there is now a consensus that, in addition to wild-caught fish, fish produced in aquaculture present a major food safety risk, especially in Southeast Asia where aquaculture is important economically. Current control programs target communities at risk through mass drug administration. However, we argue that treatment alone will not reduce the risk from eating infected fish and that sustainable effective control must adopt an integrated FZT control approach based on education, infrastructure improvements, and management practices that target critical control points in the aquaculture production cycle identified from a thorough understanding of FZT and host biology and epidemiology. We present recommendations for an integrated parasite management (IPM) program for aquaculture farms.

    1. Guided growth of horizontal nanowires: A new path to self-integrated nanosystems

      NASA Astrophysics Data System (ADS)

      Joselevich, Ernesto

      2014-03-01

      The large-scale assembly of nanowires with controlled orientation on surfaces remains one of the most critical challenges toward their integration into practical devices. We report the vapor-liquid-solid growth of perfectly aligned, millimeter-long, horizontal GaN and ZnO nanowires with controlled crystallographic orientations on different planes of sapphire and other substrates. The growth directions, crystallographic orientation and faceting of the nanowires vary with each surface orientation, as determined by their epitaxial relationship with the substrate, as well as by a graphoepitaxial effect that guides their growth along surface steps and grooves. Despite their interaction with the surface, these horizontally grown nanowires display few structural defects, exhibiting optical and electronic properties comparable to those of vertically grown nanowires. Guided GaN nanowires and ZnO nanowires present general similarities and a few interesting differences, which shed light into the guided growth mechanism. The controlled horizontal growth of nanowires of different materials on different substrates proves the generality of the guided growth approach. Recently, we demonstrated the feasibility of massively parallel ``self-integration'' of NWs into functional systems based on guided growth, including hundreds of sing-NW based field-effect transistors made all at once, and complex logic circuits, such as a 3-bit address decoder. These examples highlight the potential of guided growth for the large-scale integration of nanowires into practical devices.

    2. Feynman formulae and phase space Feynman path integrals for tau-quantization of some Lévy-Khintchine type Hamilton functions

      NASA Astrophysics Data System (ADS)

      Butko, Yana A.; Grothaus, Martin; Smolyanov, Oleg G.

      2016-02-01

      Evolution semigroups generated by pseudo-differential operators are considered. These operators are obtained by different (parameterized by a number τ) procedures of quantization from a certain class of functions (or symbols) defined on the phase space. This class contains Hamilton functions of particles with variable mass in magnetic and potential fields and more general symbols given by the Lévy-Khintchine formula. The considered semigroups are represented as limits of n-fold iterated integrals when n tends to infinity. Such representations are called Feynman formulae. Some of these representations are constructed with the help of another pseudo-differential operator, obtained by the same procedure of quantization; such representations are called Hamiltonian Feynman formulae. Some representations are based on integral operators with elementary kernels; these are called Lagrangian Feynman formulae. Langrangian Feynman formulae provide approximations of evolution semigroups, suitable for direct computations and numerical modeling of the corresponding dynamics. Hamiltonian Feynman formulae allow to represent the considered semigroups by means of Feynman path integrals. In the article, a family of phase space Feynman pseudomeasures corresponding to different procedures of quantization is introduced. The considered evolution semigroups are represented as phase space Feynman path integrals with respect to these Feynman pseudomeasures, i.e., different quantizations correspond to Feynman path integrals with the same integrand but with respect to different pseudomeasures. This answers Berezin's problem of distinguishing a procedure of quantization on the language of Feynman path integrals. Moreover, the obtained Lagrangian Feynman formulae allow also to calculate these phase space Feynman path integrals and to connect them with some functional integrals with respect to probability measures.

    3. A Path to Successful Energy Retrofits: Early Collaboration through Integrated Project Delivery Teams

      SciTech Connect

      Parrish, Kristen

      2012-10-31

      This document guides you through a process for the early design phases of retrofit projects to help you mitigate frustrations commonly experienced by building owners and designers. It outlines the value of forming an integrated project delivery team and developing a communication and information-sharing infrastructure that fosters collaboration. This guide does not present a complete process for designing an energy retrofit for a building. Instead, it focuses on the early design phase tasks related to developing and selecting energy efficiency measures (EEMs) that benefit from collaboration, and highlights the resulting advantages.

    4. Note: A portable Raman analyzer for microfluidic chips based on a dichroic beam splitter for integration of imaging and signal collection light paths

      SciTech Connect

      Geng, Yijia; Xu, Shuping; Xu, Weiqing; Chen, Lei; Chen, Gang; Bi, Wenbin; Cui, Haining

      2015-05-15

      An integrated and portable Raman analyzer featuring an inverted probe fixed on a motor-driving adjustable optical module was designed for the combination of a microfluidic system. It possesses a micro-imaging function. The inverted configuration is advantageous to locate and focus microfluidic channels. Different from commercial micro-imaging Raman spectrometers using manual switchable light path, this analyzer adopts a dichroic beam splitter for both imaging and signal collection light paths, which avoids movable parts and improves the integration and stability of optics. Combined with surface-enhanced Raman scattering technique, this portable Raman micro-analyzer is promising as a powerful tool for microfluidic analytics.

    5. Beyond transition state theory: accurate description of nuclear quantum effects on the rate and equilibrium constants of chemical reactions using Feynman path integrals.

      PubMed

      Vanícek, Jirí

      2011-01-01

      Nuclear tunneling and other nuclear quantum effects have been shown to play a significant role in molecules as large as enzymes even at physiological temperatures. I discuss how these quantum phenomena can be accounted for rigorously using Feynman path integrals in calculations of the equilibrium and kinetic isotope effects as well as of the temperature dependence of the rate constant. Because these calculations are extremely computationally demanding, special attention is devoted to increasing the computational efficiency by orders of magnitude by employing efficient path integral estimators.

    6. The Results of the “Positive Action for Today’s Health” (PATH) Trial for Increasing Walking and Physical Activity in Underserved African-American Communities

      PubMed Central

      Wilson, Dawn K.; Van Horn, M. Lee; Siceloff, E. Rebekah; Alia, Kassandra A.; St. George, Sara M.; Lawman, Hannah G.; Trumpeter, Nevelyn N.; Coulon, Sandra M.; Griffin, Sarah F.; Wandersman, Abraham; Egan, Brent; Colabianchi, Natalie; Forthofer, Melinda; Gadson, Barney

      2015-01-01

      Background The “Positive Action for Today’s Health” (PATH) trial tested an environmental intervention to increase walking in underserved communities. Methods Three matched communities were randomized to a police-patrolled walking plus social marketing, a police-patrolled walking-only, or a no-walking intervention. The 24-month intervention addressed safety and access for physical activity (PA) and utilized social marketing to enhance environmental supports for PA. African-Americans (N=434; 62 % females; aged 51±16 years) provided accelerometry and psychosocial measures at baseline and 12, 18, and 24 months. Walking attendance and trail use were obtained over 24 months. Results There were no significant differences across communities over 24 months for moderate-to-vigorous PA. Walking attendance in the social marketing community showed an increase from 40 to 400 walkers per month at 9 months and sustained ~200 walkers per month through 24 months. No change in attendance was observed in the walking-only community. Conclusions Findings support integrating social marketing strategies to increase walking in underserved African-Americans (ClinicalTrials.gov #NCT01025726). PMID:25385203

    7. Physical incorporation of particles in a porous media: a path to a smart wood

      NASA Astrophysics Data System (ADS)

      Zerriaa, Azza; El Ganaoui, Mohammed; Gerardin, Christine; Tazibt, Abdel; Gabsi, Slimane

      2016-05-01

      The aim of this work is to develop a functional wood incorporating, in its surface, physical and chemical properties that meet society demand. For instance: fire resistance, magnetic electrical conduction (metal-wood particles), antibacterial reaction (copper-wood), anti-pollution (zeolite-wood), dry coloring, reflective effects (minerals-wood). As part of the research on wooden materials, the technique of "JAZOLTHOP1" driving micrometric particles before combining them and moving in supersonic speeds was used in the framework of enriching a wooden substrate. Various tests were conducted on two wooden materials (fir and ash tree) submitted to four typologies of particles (steel shot, garnet, corundum and glass beads). The surfaces of the test samples were machined beforehand for a use of conventional smooth quality, thus defining a reference surface before incorporation. The enriched samples were characterized by using two optical techniques; firstly a surface technique through macroscopy Leica 110X ZP, then a volume technique through tomography2. Subsequently, volume simulations (wood-inclusions) were implemented to study the thermal transfer. The obtained results showcase the existence of certain set conditions to reach the critical fluency of incorporation and to localize the enrichment on a parallel plan to the sample surface. The results show also the influence of particles concentration and the kind of the chosen wood on the final composite matrix/particle media. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui http:// http:// http:// http:// http:// http://Nunzihttp://

    8. Physical incorporation of particles in a porous media: a path to a smart wood

      NASA Astrophysics Data System (ADS)

      Zerriaa, Azza; El Ganaoui, Mohammed; Gerardin, Christine; Tazibt, Abdel; Gabsi, Slimane

      2016-05-01

      The aim of this work is to develop a functional wood incorporating, in its surface, physical and chemical properties that meet society demand. For instance: fire resistance, magnetic electrical conduction (metal-wood particles), antibacterial reaction (copper-wood), anti-pollution (zeolite-wood), dry coloring, reflective effects (minerals-wood). As part of the research on wooden materials, the technique of "JAZOLTHOP1" driving micrometric particles before combining them and moving in supersonic speeds was used in the framework of enriching a wooden substrate. Various tests were conducted on two wooden materials (fir and ash tree) submitted to four typologies of particles (steel shot, garnet, corundum and glass beads). The surfaces of the test samples were machined beforehand for a use of conventional smooth quality, thus defining a reference surface before incorporation. The enriched samples were characterized by using two optical techniques; firstly a surface technique through macroscopy Leica 110X ZP, then a volume technique through tomography2. Subsequently, volume simulations (wood-inclusions) were implemented to study the thermal transfer. The obtained results showcase the existence of certain set conditions to reach the critical fluency of incorporation and to localize the enrichment on a parallel plan to the sample surface. The results show also the influence of particles concentration and the kind of the chosen wood on the final composite matrix/particle media. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui http:// http:// http:// http:// http:// http://Nunzihttp://

    9. Source Apportionment of the Anthropogenic Increment to Ozone, Formaldehyde, and Nitrogen Dioxide by the Path-Integral Method in a 3D Model.

      PubMed

      Dunker, Alan M; Koo, Bonyoung; Yarwood, Greg

      2015-06-01

      The anthropogenic increment of a species is the difference in concentration between a base-case simulation with all emissions included and a background simulation without the anthropogenic emissions. The Path-Integral Method (PIM) is a new technique that can determine the contributions of individual anthropogenic sources to this increment. The PIM was applied to a simulation of O3 formation in July 2030 in the U.S., using the Comprehensive Air Quality Model with Extensions and assuming advanced controls on light-duty vehicles (LDVs) and other sources. The PIM determines the source contributions by integrating first-order sensitivity coefficients over a range of emissions, a path, from the background case to the base case. There are many potential paths, with each representing a specific emission-control strategy leading to zero anthropogenic emissions, i.e., controlling all sources together versus controlling some source(s) preferentially are different paths. Three paths were considered, and the O3, formaldehyde, and NO2 anthropogenic increments were apportioned to five source categories. At rural and urban sites in the eastern U.S. and for all three paths, point sources typically have the largest contribution to the O3 and NO2 anthropogenic increments, and either LDVs or area sources, the smallest. Results for formaldehyde are more complex. PMID:25938820

    10. Integrated physical, genetic and genome map of chickpea (Cicer arietinum L.).

      PubMed

      Varshney, Rajeev K; Mir, Reyazul Rouf; Bhatia, Sabhyata; Thudi, Mahendar; Hu, Yuqin; Azam, Sarwar; Zhang, Yong; Jaganathan, Deepa; You, Frank M; Gao, Jinliang; Riera-Lizarazu, Oscar; Luo, Ming-Cheng

      2014-03-01

      Physical map of chickpea was developed for the reference chickpea genotype (ICC 4958) using bacterial artificial chromosome (BAC) libraries targeting 71,094 clones (~12× coverage). High information content fingerprinting (HICF) of these clones gave high-quality fingerprinting data for 67,483 clones, and 1,174 contigs comprising 46,112 clones and 3,256 singletons were defined. In brief, 574 Mb genome size was assembled in 1,174 contigs with an average of 0.49 Mb per contig and 3,256 singletons represent 407 Mb genome. The physical map was linked with two genetic maps with the help of 245 BAC-end sequence (BES)-derived simple sequence repeat (SSR) markers. This allowed locating some of the BACs in the vicinity of some important quantitative trait loci (QTLs) for drought tolerance and reistance to Fusarium wilt and Ascochyta blight. In addition, fingerprinted contig (FPC) assembly was also integrated with the draft genome sequence of chickpea. As a result, ~965 BACs including 163 minimum tilling path (MTP) clones could be mapped on eight pseudo-molecules of chickpea forming 491 hypothetical contigs representing 54,013,992 bp (~54 Mb) of the draft genome. Comprehensive analysis of markers in abiotic and biotic stress tolerance QTL regions led to identification of 654, 306 and 23 genes in drought tolerance "QTL-hotspot" region, Ascochyta blight resistance QTL region and Fusarium wilt resistance QTL region, respectively. Integrated physical, genetic and genome map should provide a foundation for cloning and isolation of QTLs/genes for molecular dissection of traits as well as markers for molecular breeding for chickpea improvement.

    11. Using Multiple Instrument Measurements To Assess Integrated Water Vapor Path From A Multispectral Microwave Radiometer

      NASA Astrophysics Data System (ADS)

      Fallon, J.; Han, Z. T.; Gross, B.; Moshary, F.

      2013-12-01

      Microwave Radiometers are mounted on satellites and the ground to collect climatological data. While they provide very useful information about temperature, RH, and water vapor, radiometers should periodically be cross-referenced with other instruments to gauge the veracity of the data. Data available from the closest ground-based GPS receivers and sun photometers was plotted alongside, and used to analyze, data from City College's Microwave Radiometer. Observing all of the data together in a graph allows one to see some of the general advantages and disadvantages of each instrument. The GPS-MET seems to be accurate continuously, while AERONET data is not even available during the night and while there is cloud cover. Lastly, the microwave radiometer collects data continuously, but at certain times the data are about five times higher than the expected values, based on the values given by GPS-MET and AERONET. A good explanation for those spikes is rainfall. For times when it is not raining, the microwave radiometer at City College is sufficiently close to the integrated water vapor data collected by City College's sun photometer and data from Union, New Jersey and East Moriches, New York, as proven by statistical tools.

    12. Ecosystem services and integrated water resource management: different paths to the same end?

      PubMed

      Cook, Brian R; Spray, Christopher J

      2012-10-30

      The two concepts that presently dominate water resource research and management are the Global Water Partnership's (GWP, 2000) interpretation of Integrated Water Resource Management (IWRM) and Ecosystem Services (ES) as interpreted by the Millennium Ecosystem Assessment (MA, 2005). Both concepts are subject to mounting criticism, with a significant number of critiques focusing on both their conceptual and methodological incompatibility with management and governance, what has come to be known as the 'implementation gap'. Emergent within the ES and IWRM literatures, then, are two parallel debates concerning the gap between conceptualisation and implementation. Our purpose for writing this review is to argue: 1) that IWRM and ES have evolved into nearly identical concepts, 2) that they face the same critical challenge of implementation, and 3) that, if those interested in water research and management are to have a positive impact on the sustainable utilisation of dwindling water resources, they must break the tendency to jump from concept to concept and confront the challenges that arise with implementation.

    13. Omics integrating physical techniques: aged Piedmontese meat analysis.

      PubMed

      Lana, Alessandro; Longo, Valentina; Dalmasso, Alessandra; D'Alessandro, Angelo; Bottero, Maria Teresa; Zolla, Lello

      2015-04-01

      Piedmontese meat tenderness becomes higher by extending the ageing period after slaughter up to 44 days. Classical physical analysis only partially explain this evidence, so in order to discover the reason of the potential beneficial effects of prolonged ageing, we performed omic analysis in the Longissimus thoracis muscle by examining main biochemical changes through mass spectrometry-based metabolomics and proteomics. We observed a progressive decline in myofibrillar structural integrity (underpinning meat tenderness) and impaired energy metabolism. Markers of autophagic responses (e.g. serine and glutathione metabolism) and nitrogen metabolism (urea cycle intermediates) accumulated until the end of the assayed period. Key metabolites such as glutamate, a mediator of the appreciated umami taste of the meat, were found to constantly accumulate until day 44. Finally, statistical analyses revealed that glutamate, serine and arginine could serve as good predictors of ultimate meat quality parameters, even though further studies are mandatory.

    14. A Critical Path for Data Integration in the U.S. Earth Sciences

      NASA Astrophysics Data System (ADS)

      Gallagher, K. T.; Allison, M. L.

      2011-12-01

      Development efforts for the U.S. Geoscience Information Network (US GIN) have crystallized around the Community for Data Integration (CDI) at the USGS, and the 50-state AASG State Geothermal Data project. The next step in developing a USGS-AASG community is to bring these two efforts into closer alignment through greater participation in CDI activities by geoinformatics practitioners from state geological surveys, and implementation of test bed activities by the USGIN partners. Test bed activities in the geological survey community will define a scope and provide a foundation to promote the use of specifications developed by the larger geoinformatics community. Adoption of some of these specifications as 'standards' by USGS and AASG for use by those organizations will lend authority and motivate wider adoption. The arc from use case to test bed to production deployments to agreement on 'standard' specifications for data discovery and access must be propelled by active interest from the user communities who have a stake in the outcome. The specifications developed will benefit the organizations involved in development, testing and deployment, which motivates participation -- a model that has worked successfully for standards organizations such as OGC, ISO and OASIS. The governance structure to support such a community process should promote grass root nucleation of interest groups that are the core of development efforts. Some mechanism for community agreement on priorities is desirable because geological survey agencies will need to allocate resources to support development. Loosely knit organizations such as ESIP and the current CDI provide models for this kind of structure. Because many geological surveys have data archive and dissemination functions as part of their portfolio, some support for the system can be built into the operating expenses and overhead. Sharing of resources and reuse of components can reduce the cost. Wide adoption of similar software

    15. Calculation for path-domain independent J integral with elasto-viscoplastic consistent tangent operator concept-based boundary element methods

      NASA Astrophysics Data System (ADS)

      Yong, Liu; Qichao, Hong; Lihua, Liang

      1999-05-01

      This paper presents an elasto-viscoplastic consistent tangent operator (CTO) based boundary element formulation, and application for calculation of path-domain independent J integrals (extension of the classical J integrals) in nonlinear crack analysis. When viscoplastic deformation happens, the effective stresses around the crack tip in the nonlinear region is allowed to exceed the loading surface, and the pure plastic theory is not suitable for this situation. The concept of consistency employed in the solution of increment viscoplastic problem, plays a crucial role in preserving the quadratic rate asymptotic convergence of iteractive schemes based on Newton's method. Therefore, this paper investigates the viscoplastic crack problem, and presents an implicit viscoplastic algorithm using the CTO concept in a boundary element framework for path-domain independent J integrals. Applications are presented with two numerical examples for viscoplastic crack problems and J integrals.

    16. A New Integral Transform for Solving Physical Problems

      NASA Astrophysics Data System (ADS)

      Vastola, John; Efthimiou, Costas

      2015-04-01

      Finding a good integral representation of the reciprocal gamma function is a problem that arises naturally from a certain method of evaluating infinite sums. After finding one representation, and observing that its form is suggestive of an integral transform, we naively define one, and go on to explore its properties. While our transform as we initially define it turns out to be problematic, we demonstrate how to redefine it so that important properties (reminiscent of the Laplace and Fourier transforms) are preserved. Of particular interest is that we may transform any entire function, and that the values of the transform at the nonnegative integers correspond to the function's Taylor coefficients. We may also transform large classes of continuous and meromorphic functions. Interestingly, the aforementioned relationship between a function's transform and a function's Taylor series can be exploited to calculate analytic ``approximations'' to transformable functions. Other topics, like defining the transform for real and complex arguments, and the geometry of transformed functions, are considered. Applications to ordinary and partial differential equations, and related physical problems (from classical mechanics, electrodynamics, and quantum mechanics, among others) are discussed.

    17. Fostering Scientific Thinking by Prospective Teachers in a Course That Integrates Physics and Literacy Learning

      ERIC Educational Resources Information Center

      van Zee, Emily H.; Jansen, Henri; Winograd, Kenneth; Crowl, Michele; Devitt, Adam

      2013-01-01

      We designed a physics course for prospective elementary and middle school teachers to foster aspects of scientific thinking recommended in reform documents. Because the elementary school curriculum focuses heavily on literacy, we also explicitly integrated physics and literacy learning in this course. By integrating physics and literacy learning,…

    18. A derivation of centroid molecular dynamics and other approximate time evolution methods for path integral centroid variables

      NASA Astrophysics Data System (ADS)

      Jang, Seogjoo; Voth, Gregory A.

      1999-08-01

      Several methods to approximately evolve path integral centroid variables in real time are presented in this paper, the first of which, the centroid molecular dynamics (CMD) method, is recast into the new formalism of the preceding paper and thereby derived. The approximations involved in the CMD method are thus fully characterized by mathematical derivations. Additional new approaches are also presented: centroid Hamiltonian dynamics (CHD), linearized quantum dynamics (LQD), and a perturbative correction of the LQD method (PT-LQD). The CHD method is shown to be a variation of the CMD method which conserves the approximate time dependent centroid Hamiltonian. The LQD method amounts to a linear approximation for the quantum Liouville equation, while the PT-LQD method includes a perturbative correction to the LQD method. All of these approaches are then tested for the equilibrium position correlation functions of three different one-dimensional nondissipative model systems, and it is shown that certain quantum effects are accounted for by all of them, while others, such as the long time coherence characteristic of low-dimensional nondissipative systems, are not. The CMD method is found to be consistently better than the LQD method, while the PT-LQD method improves the latter and is better than the CMD method in most cases. The CHD method gives results complementary to those of the CMD method.

    19. Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. III. Exact stochastic path integral evaluation

      SciTech Connect

      Moix, Jeremy M.; Ma, Jian; Cao, Jianshu

      2015-03-07

      A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters.

    20. Polymer extension under flow: A path integral evaluation of the free energy change using the Jarzynski relation

      NASA Astrophysics Data System (ADS)

      Ghosal, Aishani; Cherayil, Binny J.

      2016-06-01

      The Jarzynski relation (and its variants) has provided a route to the experimental evaluation of equilibrium free energy changes based on measurements conducted under arbitrary non-equilibrium conditions. Schroeder and co-workers [Soft Matter 10, 2178 (2014) and J. Chem. Phys. 141, 174903 (2014)] have recently exploited this fact to determine the elastic properties of model DNA from simulations and experiments of chain extension under elongational flow, bypassing the need to make these measurements mechanically using sophisticated optical trapping techniques. In this paper, motivated by these observations, we investigate chain elasticity analytically, using the Jarzynski relation and a finitely extensible nonlinear elastic-type Rouse model within a path integral formalism to calculate (essentially exactly) both the flow-induced free energy change between chain conformations of definite average end-to-end distance, as well as the force-extension curve that follows from it. This curve, based on a new analytic expression, matches the trends in the corresponding curve obtained from a model of chain stretching developed by Marko and Siggia [Macromolecules 28, 8759 (1995)], which itself is in very satisfactory agreement with the numerical and experimental data from the work of Schroeder et al.

    1. Effect of a force-free end on the mechanical property of a biopolymer — A path integral approach

      NASA Astrophysics Data System (ADS)

      Zhou, Zicong; Joós, Béla

      2016-08-01

      We study the effect of a force-free end on the mechanical property of a stretched biopolymer. The system can be divided into two parts. The first part consists of the segment counted from the fixed point (i.e., the origin) to the forced point in the biopolymer, with arclength L f . The second part consists of the segment counted from the forced point to the force-free end with arclength ΔL. We apply the path integral technique to find the relationship between these two parts. At finite temperature and without any constraint at the end, we show exactly that if we focus on the quantities related to the first part, then we can ignore the second part completely. Monte Carlo simulation confirms this conclusion. In contrast, the effect for the quantities related to the second part is dependent on what we want to observe. A force-free end has little effect on the relative extension, but it affects seriously the value of the end-to-end distance if ΔL is comparable to L f . Project supported by the MOST and the NSERC (Canada).

    2. NMR signal for particles diffusing under potentials: From path integrals and numerical methods to a model of diffusion anisotropy

      NASA Astrophysics Data System (ADS)

      Yolcu, Cem; Memiç, Muhammet; Şimşek, Kadir; Westin, Carl-Fredrik; Özarslan, Evren

      2016-05-01

      We study the influence of diffusion on NMR experiments when the molecules undergo random motion under the influence of a force field and place special emphasis on parabolic (Hookean) potentials. To this end, the problem is studied using path integral methods. Explicit relationships are derived for commonly employed gradient waveforms involving pulsed and oscillating gradients. The Bloch-Torrey equation, describing the temporal evolution of magnetization, is modified by incorporating potentials. A general solution to this equation is obtained for the case of parabolic potential by adopting the multiple correlation function (MCF) formalism, which has been used in the past to quantify the effects of restricted diffusion. Both analytical and MCF results were found to be in agreement with random walk simulations. A multidimensional formulation of the problem is introduced that leads to a new characterization of diffusion anisotropy. Unlike the case of traditional methods that employ a diffusion tensor, anisotropy originates from the tensorial force constant, and bulk diffusivity is retained in the formulation. Our findings suggest that some features of the NMR signal that have traditionally been attributed to restricted diffusion are accommodated by the Hookean model. Under certain conditions, the formalism can be envisioned to provide a viable approximation to the mathematically more challenging restricted diffusion problems.

    3. Finite temperature path integral Monte Carlo simulations of structural and dynamical properties of Ar(N)-CO2 clusters.

      PubMed

      Wang, Lecheng; Xie, Daiqian

      2012-08-21

      We report finite temperature quantum mechanical simulations of structural and dynamical properties of Ar(N)-CO(2) clusters using a path integral Monte Carlo algorithm. The simulations are based on a newly developed analytical Ar-CO(2) interaction potential obtained by fitting ab initio results to an anisotropic two-dimensional Morse/Long-range function. The calculated distributions of argon atoms around the CO(2) molecule in Ar(N)-CO(2) clusters with different sizes are consistent to the previous studies of the configurations of the clusters. A first-order perturbation theory is used to quantitatively predict the CO(2) vibrational frequency shift in different clusters. The first-solvation shell is completed at N = 17. Interestingly, our simulations for larger Ar(N)-CO(2) clusters showed several different structures of the argon shell around the doped CO(2) molecule. The observed two distinct peaks (2338.8 and 2344.5 cm(-1)) in the υ(3) band of CO(2) may be due to the different arrangements of argon atoms around the dopant molecule.

    4. Functional correlates of the lateral and medial entorhinal cortex: objects, path integration and local–global reference frames

      PubMed Central

      Knierim, James J.; Neunuebel, Joshua P.; Deshmukh, Sachin S.

      2014-01-01

      The hippocampus receives its major cortical input from the medial entorhinal cortex (MEC) and the lateral entorhinal cortex (LEC). It is commonly believed that the MEC provides spatial input to the hippocampus, whereas the LEC provides non-spatial input. We review new data which suggest that this simple dichotomy between ‘where’ versus ‘what’ needs revision. We propose a refinement of this model, which is more complex than the simple spatial–non-spatial dichotomy. MEC is proposed to be involved in path integration computations based on a global frame of reference, primarily using internally generated, self-motion cues and external input about environmental boundaries and scenes; it provides the hippocampus with a coordinate system that underlies the spatial context of an experience. LEC is proposed to process information about individual items and locations based on a local frame of reference, primarily using external sensory input; it provides the hippocampus with information about the content of an experience. PMID:24366146

    5. An analysis of quantum effects on the thermodynamic properties of cryogenic hydrogen using the path integral method.

      PubMed

      Nagashima, H; Tsuda, S; Tsuboi, N; Koshi, M; Hayashi, K A; Tokumasu, T

      2014-04-01

      In this paper, we describe the analysis of the thermodynamic properties of cryogenic hydrogen using classical molecular dynamics (MD) and path integral MD (PIMD) method to understand the effects of the quantum nature of hydrogen molecules. We performed constant NVE MD simulations across a wide density-temperature region to establish an equation of state (EOS). Moreover, the quantum effect on the difference of molecular mechanism of pressure-volume-temperature relationship was addressed. The EOS was derived based on the classical mechanism idea only using the MD simulation results. Simulation results were compared with each MD method and experimental data. As a result, it was confirmed that although the EOS on the basis of classical MD cannot reproduce the experimental data of saturation property of hydrogen in the high-density region, the EOS on the basis of PIMD well reproduces those thermodynamic properties of hydrogen. Moreover, it was clarified that taking quantum effects into account makes the repulsion force larger and the potential well shallower. Because of this mechanism, the intermolecular interaction of hydrogen molecules diminishes and the virial pressure increases.

    6. Path integral Monte Carlo study of hydrogen tunneling effect on dielectric properties of molecular crystal 5-Bromo-9-hydroxyphenalenone

      NASA Astrophysics Data System (ADS)

      Otaki, Hiroki; Ando, Koji

      2015-01-01

      The dielectric properties of proton(H)-deuteron(D) mixed crystals of the hydrogen-bonded material 5-Bromo-9-hydroxyphenalenone are studied using a novel path integral Monte Carlo (PIMC) method that takes account of the dipole induction effect depending on the relative proton configurations in the surrounding molecules. The induced dipole is evaluated using the fragment molecular orbital method with electron correlation included by second-order Møller-Plesset perturbation theory and long-range corrected density functional theory. The results show a greater influence of Csbnd H ⋯O intermolecular weak hydrogen bonding on the induction than for results evaluated with the Hartree-Fock method. The induction correction is incorporated into the PIMC simulations with a model Hamiltonian that consists of long-range dipolar interactions and a transverse term describing proton tunneling. The relationship between the calculated phase transition temperature and H/D mixing ratio is consistent with the experimental phase diagram, indicating that the balance between the proton tunneling and the collective ordering is appropriately described.

    7. Polymer extension under flow: A path integral evaluation of the free energy change using the Jarzynski relation.

      PubMed

      Ghosal, Aishani; Cherayil, Binny J

      2016-06-01

      The Jarzynski relation (and its variants) has provided a route to the experimental evaluation of equilibrium free energy changes based on measurements conducted under arbitrary non-equilibrium conditions. Schroeder and co-workers [Soft Matter 10, 2178 (2014) and J. Chem. Phys. 141, 174903 (2014)] have recently exploited this fact to determine the elastic properties of model DNA from simulations and experiments of chain extension under elongational flow, bypassing the need to make these measurements mechanically using sophisticated optical trapping techniques. In this paper, motivated by these observations, we investigate chain elasticity analytically, using the Jarzynski relation and a finitely extensible nonlinear elastic-type Rouse model within a path integral formalism to calculate (essentially exactly) both the flow-induced free energy change between chain conformations of definite average end-to-end distance, as well as the force-extension curve that follows from it. This curve, based on a new analytic expression, matches the trends in the corresponding curve obtained from a model of chain stretching developed by Marko and Siggia [Macromolecules 28, 8759 (1995)], which itself is in very satisfactory agreement with the numerical and experimental data from the work of Schroeder et al. PMID:27276965

    8. Airborne Measurements of CO2 Column Absorption and Range Using a Pulsed Direct-Detection Integrated Path Differential Absorption Lidar

      NASA Technical Reports Server (NTRS)

      Abshire, James B.; Riris, Haris; Weaver, Clark J.; Mao, Jianping; Allan, Graham R.; Hasselbrack, William E.; Browell, Edward V.

      2013-01-01

      We report on airborne CO2 column absorption measurements made in 2009 with a pulsed direct-detection lidar operating at 1572.33 nm and utilizing the integrated path differential absorption technique. We demonstrated these at different altitudes from an aircraft in July and August in flights over four locations in the central and eastern United States. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. The lidar measurement statistics were also calculated for each flight as a function of altitude. The optical depth varied nearly linearly with altitude, consistent with calculations based on atmospheric models. The scatter in the optical depth measurements varied with aircraft altitude as expected, and the median measurement precisions for the column varied from 0.9 to 1.2 ppm. The altitude range with the lowest scatter was 810 km, and the majority of measurements for the column within it had precisions between 0.2 and 0.9 ppm.

    9. Is there a stable commensurate solid phase in the second 4He layer on graphite? - path integral Monte Carlo study

      NASA Astrophysics Data System (ADS)

      Ahn, Jeonghwan; Lee, Hoonkyung; Kwon, Yongkyung

      2015-03-01

      Existence of a stable commensurate structure in the second 4He layer on graphite has been a subject of intensive experimental and theoretical studies because of its implication in the possible realization of two-dimensional supersolidity. Earlier path-integral Monte Carlo (PIMC) calculations of Pierce and Manousakis predicted a stable C4/7 commensurate structure above the first-layer 4He atoms fixed at triangular lattice sites, but Corboz et al. later showed that no commensurate phase was stable when quantum dynamics of the first-layer 4He atoms was incorporated in the PIMC calculations. On the other hand, recent heat capacity measurements of Nakamura et al. provided a strong evidence for a commensurate solid in the second 4He layer over an extended density range. Motivated by this, we have performed new PIMC calculations for the second helium layer on graphite. Unlike previous PIMC calculations where a laterally-averaged one-dimensional substrate potential was used, we here employ an anisotropic 4He-graphite potential described by a sum of the 4He-C pair potentials. With this fully-corrugated substrate potential we make more accurate description of quantum dynamics of the first-layer 4He atoms and analyze its effects on the phase diagram of the second layer.

    10. Effect of the shape on the spin state and exchange in quantum dots. Feynman path integral analysis

      SciTech Connect

      Shevkunov, S. V.

      2015-05-15

      The ab initio computer simulation of the mixed quantum states of 1–5-nm model ellipsoid quantum dots with “soft” walls containing two and three quantum-indistinguishable nonrelativistic electrons has been performed by the path integral method. The calculation has been carried out beyond the single-electron and mean-field approximations with the fundamentally exact inclusion of Coulomb and exchange correlations of all orders and the spin variable. Distributions over the eigenfunctions of the spin-squared operator, as well as the equilibrium spin numbers, have been obtained depending on the shape of a quantum dot and the temperature. The complete set of basis functions symmetrized in permutations according to the spin of the system has been obtained by application of the Young symmetry operators. The dependence of the energy on the shape of the quantum dot corresponds to the negative sign of the surface tension at its boundary. The calculation indicates that the spin magnetic susceptibility in the system of two electrons decreases strongly for spherical quantum dots (“pairing” of spins) and the temperature dependences have a pronounced maximum whose position depends on the shape of the quantum dot. For three electrons in an oblate quantum dot, the inversion of the energy levels of spin states is observed and affects the spin magnetic susceptibility. The results indicate a strong dependence of the energy of collective spin states of electrons on the detailed inclusion of exchange and Coulomb spatial correlations.

    11. Integrated Path Differential Absorption Lidar Optimizations Based on Pre-Analyzed Atmospheric Data for ASCENDS Mission Applications

      NASA Technical Reports Server (NTRS)

      Pliutau, Denis; Prasad, Narasimha S.

      2012-01-01

      In this paper a modeling method based on data reductions is investigated which includes pre analyzed MERRA atmospheric fields for quantitative estimates of uncertainties introduced in the integrated path differential absorption methods for the sensing of various molecules including CO2. This approach represents the extension of our existing lidar modeling framework previously developed and allows effective on- and offline wavelength optimizations and weighting function analysis to minimize the interference effects such as those due to temperature sensitivity and water vapor absorption. The new simulation methodology is different from the previous implementation in that it allows analysis of atmospheric effects over annual spans and the entire Earth coverage which was achieved due to the data reduction methods employed. The effectiveness of the proposed simulation approach is demonstrated with application to the mixing ratio retrievals for the future ASCENDS mission. Independent analysis of multiple accuracy limiting factors including the temperature, water vapor interferences, and selected system parameters is further used to identify favorable spectral regions as well as wavelength combinations facilitating the reduction in total errors in the retrieved XCO2 values.

    12. Path Integral Simulation of the H/D Kinetic Isotope Effect in Monoamine Oxidase B Catalyzed Decomposition of Dopamine.

      PubMed

      Mavri, Janez; Matute, Ricardo A; Chu, Zhen T; Vianello, Robert

      2016-04-14

      Brain monoamines regulate many centrally mediated body functions, and can cause adverse symptoms when they are out of balance. A starting point to address challenges raised by the increasing burden of brain diseases is to understand, at atomistic level, the catalytic mechanism of an essential amine metabolic enzyme-monoamine oxidase B (MAO B). Recently, we demonstrated that the rate-limiting step of MAO B catalyzed conversion of amines into imines represents the hydride anion transfer from the substrate α-CH2 group to the N5 atom of the flavin cofactor moiety. In this article we simulated for MAO B catalyzed dopamine decomposition the effects of nuclear tunneling by the calculation of the H/D kinetic isotope effect. We applied path integral quantization of the nuclear motion for the methylene group and the N5 atom of the flavin moiety in conjunction with the QM/MM treatment on the empirical valence bond (EVB) level for the rest of the enzyme. The calculated H/D kinetic isotope effect of 12.8 ± 0.3 is in a reasonable agreement with the available experimental data for closely related biogenic amines, which gives strong support for the proposed hydride mechanism. The results are discussed in the context of tunneling in enzyme centers and advent of deuterated drugs into clinical practice. PMID:27010708

    13. Accurate path integral molecular dynamics simulation of ab-initio water at near-zero added cost

      NASA Astrophysics Data System (ADS)

      Elton, Daniel; Fritz, Michelle; Soler, José; Fernandez-Serra, Marivi

      It is now established that nuclear quantum motion plays an important role in determining water's structure and dynamics. These effects are important to consider when evaluating DFT functionals and attempting to develop better ones for water. The standard way of treating nuclear quantum effects, path integral molecular dynamics (PIMD), multiplies the number of energy/force calculations by the number of beads, which is typically 32. Here we introduce a method whereby PIMD can be incorporated into a DFT molecular dynamics simulation at virtually zero cost. The method is based on the cluster (many body) expansion of the energy. We first subtract the DFT monomer energies, using a custom DFT-based monomer potential energy surface. The evolution of the PIMD beads is then performed using only the more-accurate Partridge-Schwenke monomer energy surface. The DFT calculations are done using the centroid positions. Various bead thermostats can be employed to speed up the sampling of the quantum ensemble. The method bears some resemblance to multiple timestep algorithms and other schemes used to speed up PIMD with classical force fields. We show that our method correctly captures some of key effects of nuclear quantum motion on both the structure and dynamics of water. We acknowledge support from DOE Award No. DE-FG02-09ER16052 (D.E.) and DOE Early Career Award No. DE-SC0003871 (M.V.F.S.).

    14. NMR signal for particles diffusing under potentials: From path integrals and numerical methods to a model of diffusion anisotropy.

      PubMed

      Yolcu, Cem; Memiç, Muhammet; Şimşek, Kadir; Westin, Carl-Fredrik; Özarslan, Evren

      2016-05-01

      We study the influence of diffusion on NMR experiments when the molecules undergo random motion under the influence of a force field and place special emphasis on parabolic (Hookean) potentials. To this end, the problem is studied using path integral methods. Explicit relationships are derived for commonly employed gradient waveforms involving pulsed and oscillating gradients. The Bloch-Torrey equation, describing the temporal evolution of magnetization, is modified by incorporating potentials. A general solution to this equation is obtained for the case of parabolic potential by adopting the multiple correlation function (MCF) formalism, which has been used in the past to quantify the effects of restricted diffusion. Both analytical and MCF results were found to be in agreement with random walk simulations. A multidimensional formulation of the problem is introduced that leads to a new characterization of diffusion anisotropy. Unlike the case of traditional methods that employ a diffusion tensor, anisotropy originates from the tensorial force constant, and bulk diffusivity is retained in the formulation. Our findings suggest that some features of the NMR signal that have traditionally been attributed to restricted diffusion are accommodated by the Hookean model. Under certain conditions, the formalism can be envisioned to provide a viable approximation to the mathematically more challenging restricted diffusion problems. PMID:27300946

    15. An integrated genetic, physical, and transcriptional map of chromosome 13

      SciTech Connect

      Scheffer, H.; Kooy, R.F.; Wijngaard, A.

      1994-09-01

      In this study a genetic map containing 20 markers and typed in 40 CEPH families is presented. It includes 7 thusfar untyped microsatellite markers, 7 that have previously been mapped on a subset of 8 CEPH families, one reference marker, D13S71, and three telomeric VNTR markers. Also, 4 intragenic RB1 markers were typed. The markers have an average heterozygosity of 73% (80%, excluding the three RFLPs). The total sex average length of the map is 140 cM. The mean female to male ratio is 1.54. For the non-telomeric part of the chromosome between the markers D13S221 in 13q12 and D13S173 in 13q33-q34, this ratio is 1.99. This ratio is reversed in the telomeric part of the chromosome between D13S173 and D13S234 in distal 13q34, where it is 0.47. A high new mutation frequency of 1% was detected in the (CTTT(T)){sub n} repeat in intron 20 of the RB1 gene. The map has been integrated with 7 microsatellite markers and 2 RFLP markers from CEPH database version 7.0, resulting in a map with 32 markers (28 loci) of chromosome 13q. In addition, a deletion hybrid breakpoint map ordering 50 markers in 18 intervals is constructed. It includes 32 microsatellite markers, 4 genes, 5 STSs, and 9 ESTs. Each of 18 intervals contains at least one microsatellite marker included in the extended genetic map. These data allow a correlation between the genetic and physical map of chromosome 13. New ESTs are currently being identified and localized at this integrated map.

    16. Path integral Monte Carlo simulations of H2 adsorbed to lithium-doped benzene: A model for hydrogen storage materials

      NASA Astrophysics Data System (ADS)

      Lindoy, Lachlan P.; Kolmann, Stephen J.; D'Arcy, Jordan H.; Crittenden, Deborah L.; Jordan, Meredith J. T.

      2015-11-01

      Finite temperature quantum and anharmonic effects are studied in H2-Li+-benzene, a model hydrogen storage material, using path integral Monte Carlo (PIMC) simulations on an interpolated potential energy surface refined over the eight intermolecular degrees of freedom based upon M05-2X/6-311+G(2df,p) density functional theory calculations. Rigid-body PIMC simulations are performed at temperatures ranging from 77 K to 150 K, producing both quantum and classical probability density histograms describing the adsorbed H2. Quantum effects broaden the histograms with respect to their classical analogues and increase the expectation values of the radial and angular polar coordinates describing the location of the center-of-mass of the H2 molecule. The rigid-body PIMC simulations also provide estimates of the change in internal energy, ΔUads, and enthalpy, ΔHads, for H2 adsorption onto Li+-benzene, as a function of temperature. These estimates indicate that quantum effects are important even at room temperature and classical results should be interpreted with caution. Our results also show that anharmonicity is more important in the calculation of U and H than coupling—coupling between the intermolecular degrees of freedom becomes less important as temperature increases whereas anharmonicity becomes more important. The most anharmonic motions in H2-Li+-benzene are the "helicopter" and "ferris wheel" H2 rotations. Treating these motions as one-dimensional free and hindered rotors, respectively, provides simple corrections to standard harmonic oscillator, rigid rotor thermochemical expressions for internal energy and enthalpy that encapsulate the majority of the anharmonicity. At 150 K, our best rigid-body PIMC estimates for ΔUads and ΔHads are -13.3 ± 0.1 and -14.5 ± 0.1 kJ mol-1, respectively.

    17. Path integral Monte Carlo simulations of H2 adsorbed to lithium-doped benzene: A model for hydrogen storage materials.

      PubMed

      Lindoy, Lachlan P; Kolmann, Stephen J; D'Arcy, Jordan H; Crittenden, Deborah L; Jordan, Meredith J T

      2015-11-21

      Finite temperature quantum and anharmonic effects are studied in H2-Li(+)-benzene, a model hydrogen storage material, using path integral Monte Carlo (PIMC) simulations on an interpolated potential energy surface refined over the eight intermolecular degrees of freedom based upon M05-2X/6-311+G(2df,p) density functional theory calculations. Rigid-body PIMC simulations are performed at temperatures ranging from 77 K to 150 K, producing both quantum and classical probability density histograms describing the adsorbed H2. Quantum effects broaden the histograms with respect to their classical analogues and increase the expectation values of the radial and angular polar coordinates describing the location of the center-of-mass of the H2 molecule. The rigid-body PIMC simulations also provide estimates of the change in internal energy, ΔUads, and enthalpy, ΔHads, for H2 adsorption onto Li(+)-benzene, as a function of temperature. These estimates indicate that quantum effects are important even at room temperature and classical results should be interpreted with caution. Our results also show that anharmonicity is more important in the calculation of U and H than coupling-coupling between the intermolecular degrees of freedom becomes less important as temperature increases whereas anharmonicity becomes more important. The most anharmonic motions in H2-Li(+)-benzene are the "helicopter" and "ferris wheel" H2 rotations. Treating these motions as one-dimensional free and hindered rotors, respectively, provides simple corrections to standard harmonic oscillator, rigid rotor thermochemical expressions for internal energy and enthalpy that encapsulate the majority of the anharmonicity. At 150 K, our best rigid-body PIMC estimates for ΔUads and ΔHads are -13.3 ± 0.1 and -14.5 ± 0.1 kJ mol(-1), respectively.

    18. Equilibrium magnesium isotope fractionation between aqueous Mg2+ and carbonate minerals: Insights from path integral molecular dynamics

      NASA Astrophysics Data System (ADS)

      Pinilla, Carlos; Blanchard, Marc; Balan, Etienne; Natarajan, Suresh K.; Vuilleumier, Rodolphe; Mauri, Francesco

      2015-08-01

      The theoretical determination of the isotopic fractionation between an aqueous solution and a mineral is of utmost importance in Earth sciences. While for crystals, it is well established that equilibrium isotopic fractionation factors can be calculated using a statistical thermodynamic approach based on the vibrational properties, several theoretical methods are currently used to model ions in aqueous solution. In this work, we present a systematic study to determine the reduced partition function ratio (β-factor) of aqueous Mg2+ using several levels of theory within the simulations. In particular, using an empirical force field, we compare and discuss the performance of the exact results obtained from path integral molecular dynamics (PIMD) simulations, with respect to the more traditional methods based on vibrational properties and the cluster approximation. The results show the importance of including configurational disorder for the estimation of the equilibrium isotope fractionation factor. We also show that using the vibrational frequencies computed from snapshots taken from equilibrated classical molecular dynamics represents a good approximation for the study of aqueous ions. Based on these conclusions, the β-factor of aqueous Mg2+ have been estimated from a Car-Parrinello molecular dynamics (CPMD) simulation with an ab initio force field, and combined with the β-factors of carbonate minerals (magnesite, dolomite, calcite and aragonite). Mg β-factor of Mg-bearing aragonite, calculated here for the first time, displays a lower value than the three other carbonate minerals. This is explained by a strong distortion of the cationic site leading to a decrease of the coordination number during Ca-Mg substitution. Overall, the equilibrium magnesium isotope fractionation factors between aqueous Mg2+ and carbonate minerals that derive from this methodological study support the previous theoretical results obtained from embedded cluster models.

    19. A path integral molecular dynamics study of the hyperfine coupling constants of the muoniated and hydrogenated acetone radicals

      NASA Astrophysics Data System (ADS)

      Oba, Yuki; Kawatsu, Tsutomu; Tachikawa, Masanori

      2016-08-01

      The on-the-fly ab initio density functional path integral molecular dynamics (PIMD) simulations, which can account for both the nuclear quantum effect and thermal effect, were carried out to evaluate the structures and "reduced" isotropic hyperfine coupling constants (HFCCs) for muoniated and hydrogenated acetone radicals (2-muoxy-2-propyl and 2-hydoxy-2-propyl) in vacuo. The reduced HFCC value from a simple geometry optimization calculation without both the nuclear quantum effect and thermal effect is -8.18 MHz, and that by standard ab initio molecular dynamics simulation with only the thermal effect and without the nuclear quantum effect is 0.33 MHz at 300 K, where these two methods cannot distinguish the difference between muoniated and hydrogenated acetone radicals. In contrast, the reduced HFCC value of the muoniated acetone radical by our PIMD simulation is 32.1 MHz, which is about 8 times larger than that for the hydrogenated radical of 3.97 MHz with the same level of calculation. We have found that the HFCC values are highly correlated with the local molecular structures; especially, the Mu—O bond length in the muoniated acetone radical is elongated due to the large nuclear quantum effect of the muon, which makes the expectation value of the HFCC larger. Although our PIMD result calculated in vacuo is about 4 times larger than the measured experimental value in aqueous solvent, the ratio of these HFCC values between muoniated and hydrogenated acetone radicals in vacuo is in reasonable agreement with the ratio of the experimental values in aqueous solvent (8.56 MHz and 0.9 MHz); the explicit presence of solvent molecules has a major effect on decreasing the reduced muon HFCC of in vacuo calculations for the quantitative reproduction.

    20. Path integral Monte Carlo simulations of H2 adsorbed to lithium-doped benzene: A model for hydrogen storage materials.

      PubMed

      Lindoy, Lachlan P; Kolmann, Stephen J; D'Arcy, Jordan H; Crittenden, Deborah L; Jordan, Meredith J T

      2015-11-21

      Finite temperature quantum and anharmonic effects are studied in H2-Li(+)-benzene, a model hydrogen storage material, using path integral Monte Carlo (PIMC) simulations on an interpolated potential energy surface refined over the eight intermolecular degrees of freedom based upon M05-2X/6-311+G(2df,p) density functional theory calculations. Rigid-body PIMC simulations are performed at temperatures ranging from 77 K to 150 K, producing both quantum and classical probability density histograms describing the adsorbed H2. Quantum effects broaden the histograms with respect to their classical analogues and increase the expectation values of the radial and angular polar coordinates describing the location of the center-of-mass of the H2 molecule. The rigid-body PIMC simulations also provide estimates of the change in internal energy, ΔUads, and enthalpy, ΔHads, for H2 adsorption onto Li(+)-benzene, as a function of temperature. These estimates indicate that quantum effects are important even at room temperature and classical results should be interpreted with caution. Our results also show that anharmonicity is more important in the calculation of U and H than coupling-coupling between the intermolecular degrees of freedom becomes less important as temperature increases whereas anharmonicity becomes more important. The most anharmonic motions in H2-Li(+)-benzene are the "helicopter" and "ferris wheel" H2 rotations. Treating these motions as one-dimensional free and hindered rotors, respectively, provides simple corrections to standard harmonic oscillator, rigid rotor thermochemical expressions for internal energy and enthalpy that encapsulate the majority of the anharmonicity. At 150 K, our best rigid-body PIMC estimates for ΔUads and ΔHads are -13.3 ± 0.1 and -14.5 ± 0.1 kJ mol(-1), respectively. PMID:26590532

    1. Physical approach to analytic simulation of Fresnel integrals

      NASA Astrophysics Data System (ADS)

      Anokhov, Sergey

      2007-01-01

      Fresnel integrals continue to find new applications in various areas of human activity, including technology and music. However, performing calculations with them is often hindered by a mathematical peculiarity of these integrals, which is the rapidly oscillating functions of the basic variable. This circumstance complicates the numerical calculations when these integrals need additional integral transformation: convolution, Fourier transform, etc. The suggested solution of the problem consists of replacement of the complex Fresnel integral by a single rational function that simulates this integral in the entire area of its existence with an accuracy up to 10-6. The advantages of the suggested approach are confirmed by the concrete example.

    2. Determinants of Physical Activity Based on the Theory of Planned Behavior in Iranian Military Staff’s Wives: A Path Analysis

      PubMed Central

      Shirvani, Zeinab Gholamnia; Ghofranipour, Fazlollah; Gharakhanlou, Reza; Kazemnejad, Anoshirvan

      2015-01-01

      Level of physical activity as a key determinant of healthy lifestyle less than is required in individuals particularly women. Applying theories of behavioral change about complex behaviors such as physical activity leads to identify effective factors and their relations. The aim of this study was to determine predictors of physical activity behavior based on the Theory of Planned Behavior in military staff’s wives in Tehran. This cross-sectional study was performed in 180 military personnel’s spouses residing in organizational houses, in Tehran, Iran in 2014. The participants were randomly selected with multi-stage cluster sampling. The validity and reliability of the theory based scale evaluated before conducting the path analysis. Statistical analysis was carried out using SPSS16 and LISREL8.8. The results indicated the model explained 77% and 17% of intention and behavior variance. Subjective norms (Beta=0.83) and intention (Beta=0.37) were the strongest predictors of intention and behavior, respectively. The instrumental and affective attitude had no significant path to intention and behavior. The direct relation of perceived behavioral control to behavior was non-significant. This research demonstrated relative importance and relationships of Theory of Planned Behavior constructs in physical activity behavior of military personnel’s spouses in Tehran. It is essential to consider these determinants in designing of educational interventions for promoting and maintaining physical activity behavior in this target group. PMID:25948459

    3. Double-pulse 2-μm integrated path differential absorption lidar airborne validation for atmospheric carbon dioxide measurement.

      PubMed

      Refaat, Tamer F; Singh, Upendra N; Yu, Jirong; Petros, Mulugeta; Remus, Ruben; Ismail, Syed

      2016-05-20

      Field experiments were conducted to test and evaluate the initial atmospheric carbon dioxide (CO2) measurement capability of airborne, high-energy, double-pulsed, 2-μm integrated path differential absorption (IPDA) lidar. This IPDA was designed, integrated, and operated at the NASA Langley Research Center on-board the NASA B-200 aircraft. The IPDA was tuned to the CO2 strong absorption line at 2050.9670 nm, which is the optimum for lower tropospheric weighted column measurements. Flights were conducted over land and ocean under different conditions. The first validation experiments of the IPDA for atmospheric CO2 remote sensing, focusing on low surface reflectivity oceanic surface returns during full day background conditions, are presented. In these experiments, the IPDA measurements were validated by comparison to airborne flask air-sampling measurements conducted by the NOAA Earth System Research Laboratory. IPDA performance modeling was conducted to evaluate measurement sensitivity and bias errors. The IPDA signals and their variation with altitude compare well with predicted model results. In addition, off-off-line testing was conducted, with fixed instrument settings, to evaluate the IPDA systematic and random errors. Analysis shows an altitude-independent differential optical depth offset of 0.0769. Optical depth measurement uncertainty of 0.0918 compares well with the predicted value of 0.0761. IPDA CO2 column measurement compares well with model-driven, near-simultaneous air-sampling measurements from the NOAA aircraft at different altitudes. With a 10-s shot average, CO2 differential optical depth measurement of 1.0054±0.0103 was retrieved from a 6-km altitude and a 4-GHz on-line operation. As compared to CO2 weighted-average column dry-air volume mixing ratio of 404.08 ppm, derived from air sampling, IPDA measurement resulted in a value of 405.22±4.15  ppm with 1.02% uncertainty and

    4. Double-pulse 2-μm integrated path differential absorption lidar airborne validation for atmospheric carbon dioxide measurement.

      PubMed

      Refaat, Tamer F; Singh, Upendra N; Yu, Jirong; Petros, Mulugeta; Remus, Ruben; Ismail, Syed

      2016-05-20

      Field experiments were conducted to test and evaluate the initial atmospheric carbon dioxide (CO2) measurement capability of airborne, high-energy, double-pulsed, 2-μm integrated path differential absorption (IPDA) lidar. This IPDA was designed, integrated, and operated at the NASA Langley Research Center on-board the NASA B-200 aircraft. The IPDA was tuned to the CO2 strong absorption line at 2050.9670 nm, which is the optimum for lower tropospheric weighted column measurements. Flights were conducted over land and ocean under different conditions. The first validation experiments of the IPDA for atmospheric CO2 remote sensing, focusing on low surface reflectivity oceanic surface returns during full day background conditions, are presented. In these experiments, the IPDA measurements were validated by comparison to airborne flask air-sampling measurements conducted by the NOAA Earth System Research Laboratory. IPDA performance modeling was conducted to evaluate measurement sensitivity and bias errors. The IPDA signals and their variation with altitude compare well with predicted model results. In addition, off-off-line testing was conducted, with fixed instrument settings, to evaluate the IPDA systematic and random errors. Analysis shows an altitude-independent differential optical depth offset of 0.0769. Optical depth measurement uncertainty of 0.0918 compares well with the predicted value of 0.0761. IPDA CO2 column measurement compares well with model-driven, near-simultaneous air-sampling measurements from the NOAA aircraft at different altitudes. With a 10-s shot average, CO2 differential optical depth measurement of 1.0054±0.0103 was retrieved from a 6-km altitude and a 4-GHz on-line operation. As compared to CO2 weighted-average column dry-air volume mixing ratio of 404.08 ppm, derived from air sampling, IPDA measurement resulted in a value of 405.22±4.15  ppm with 1.02% uncertainty and

    5. Integrating Global Games in the Elementary Physical Education Curriculum

      ERIC Educational Resources Information Center

      Gross, Michael K.; Buchanan, Alice M.

      2011-01-01

      Global education units are great motivators for activity in elementary physical education because they can bring freshness and excitement to a physical education program. Additionally, children are provided with the opportunity to learn just how much physical education interacts with the other academic subjects that they study. This article…

    6. Automated integration of genomic physical mapping data via parallel simulated annealing

      SciTech Connect

      Slezak, T.

      1994-06-01

      The Human Genome Center at the Lawrence Livermore National Laboratory (LLNL) is nearing closure on a high-resolution physical map of human chromosome 19. We have build automated tools to assemble 15,000 fingerprinted cosmid clones into 800 contigs with minimal spanning paths identified. These islands are being ordered, oriented, and spanned by a variety of other techniques including: Fluorescence Insitu Hybridization (FISH) at 3 levels of resolution, ECO restriction fragment mapping across all contigs, and a multitude of different hybridization and PCR techniques to link cosmid, YAC, AC, PAC, and Pl clones. The FISH data provide us with partial order and distance data as well as orientation. We made the observation that map builders need a much rougher presentation of data than do map readers; the former wish to see raw data since these can expose errors or interesting biology. We further noted that by ignoring our length and distance data we could simplify our problem into one that could be readily attacked with optimization techniques. The data integration problem could then be seen as an M x N ordering of our N cosmid clones which ``intersect`` M larger objects by defining ``intersection`` to mean either contig/map membership or hybridization results. Clearly, the goal of making an integrated map is now to rearrange the N cosmid clone ``columns`` such that the number of gaps on the object ``rows`` are minimized. Our FISH partially-ordered cosmid clones provide us with a set of constraints that cannot be violated by the rearrangement process. We solved the optimization problem via simulated annealing performed on a network of 40+ Unix machines in parallel, using a server/client model built on explicit socket calls. For current maps we can create a map in about 4 hours on the parallel net versus 4+ days on a single workstation. Our biologists are now using this software on a daily basis to guide their efforts toward final closure.

    7. Car-Parrinello and path integral molecular dynamics study of the hydrogen bonds in 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene

      NASA Astrophysics Data System (ADS)

      Durlak, Piotr; Latajka, Zdzisław

      2010-10-01

      Theoretical studies of the structure and proton motion in the intramolecular O-H…O hydrogen bonds in 2-acetyl-1,8-dihydroxy-3,6-dimethylnapthlane were carried out at the DFT and molecular dynamics levels. Geometry optimization at the PBE1PBE/6-311++G(2d,2p) level demonstrate the existence of two tautomers on the potential energy surface. Dynamics of proton motion in intramolecular hydrogen bonds was investigated in vacuo at 100 K using Car-Parrinello and path integral molecular dynamics. For the strong intramolecular hydrogen bond very large delocalization of bridging proton is noted, especially in the path integral simulation where quantum effects are taken into account. No tautomerism was found for this intramolecular hydrogen bond.

    8. A Car-Parrinello and path integral molecular dynamics study of the intramolecular lithium bond in the lithium 2-pyridyl-N-oxide acetate.

      PubMed

      Durlak, Piotr; Latajka, Zdzisław; Berski, Sławomir

      2009-07-14

      Lithium bonding in lithium 2-pyridyl-N-oxide acetate has been investigated using classic Car-Parrinello molecular dynamics (CPMD) and the path integral approach [path integrals molecular dynamics (PIMD)]. The simulations have been performed in 300 K. Structures, energies, and lithium trajectories have been determined. The CPMD results show that the lithium atom is generally equidistant between heavy atoms in the (O...Li...O) bridge. Applying quantum effects through the PIMD leads to similar conclusion. The theoretical lithium 2-pyridyl-N-oxide acetate infrared spectrum has also been determined using the CPMD calculations. This shows very good agreement with available experimental results and reproduces well the broad low-frequency band observed experimentally. In order to gain deeper understanding of the nature of the lithium bonding topological analysis of the electron localization function has been applied.

    9. A Car-Parrinello and path integral molecular dynamics study of the intramolecular lithium bond in the lithium 2-pyridyl-N-oxide acetate

      NASA Astrophysics Data System (ADS)

      Durlak, Piotr; Latajka, Zdzisław; Berski, Sławomir

      2009-07-01

      Lithium bonding in lithium 2-pyridyl-N-oxide acetate has been investigated using classic Car-Parrinello molecular dynamics (CPMD) and the path integral approach [path integrals molecular dynamics (PIMD)]. The simulations have been performed in 300 K. Structures, energies, and lithium trajectories have been determined. The CPMD results show that the lithium atom is generally equidistant between heavy atoms in the (O⋯Li⋯O) bridge. Applying quantum effects through the PIMD leads to similar conclusion. The theoretical lithium 2-pyridyl-N-oxide acetate infrared spectrum has also been determined using the CPMD calculations. This shows very good agreement with available experimental results and reproduces well the broad low-frequency band observed experimentally. In order to gain deeper understanding of the nature of the lithium bonding topological analysis of the electron localization function has been applied.

    10. Student Modeling of Physical Phenomena as They Derive Integral Formulae: One Way To Reduce Proof Phobia.

      ERIC Educational Resources Information Center

      Dancis, Jerome

      2001-01-01

      Students in a freshmen calculus course should become fluent in modeling physical phenomena represented by integrals, in particular geometric formulas for volumes and arc length and physical formulas for work. Describes how to train students to became fluent in such modeling and derivation of standard integral formulas. Indicates that these lessons…

    11. Path Finder

      SciTech Connect

      Rigdon, J. Brian; Smith, Marcus Daniel; Mulder, Samuel A

      2014-01-07

      PathFinder is a graph search program, traversing a directed cyclic graph to find pathways between labeled nodes. Searches for paths through ordered sequences of labels are termed signatures. Determining the presence of signatures within one or more graphs is the primary function of Path Finder. Path Finder can work in either batch mode or interactively with an analyst. Results are limited to Path Finder whether or not a given signature is present in the graph(s).

    12. Improved methods for Feynman path integral calculations and their application to calculate converged vibrational-rotational partition functions, free energies, enthalpies, entropies, and heat capacities for methane.

      PubMed

      Mielke, Steven L; Truhlar, Donald G

      2015-01-28

      We present an improved version of our "path-by-path" enhanced same path extrapolation scheme for Feynman path integral (FPI) calculations that permits rapid convergence with discretization errors ranging from O(P(-6)) to O(P(-12)), where P is the number of path discretization points. We also present two extensions of our importance sampling and stratified sampling schemes for calculating vibrational-rotational partition functions by the FPI method. The first is the use of importance functions for dihedral angles between sets of generalized Jacobi coordinate vectors. The second is an extension of our stratification scheme to allow some strata to be defined based only on coordinate information while other strata are defined based on both the geometry and the energy of the centroid of the Feynman path. These enhanced methods are applied to calculate converged partition functions by FPI methods, and these results are compared to ones obtained earlier by vibrational configuration interaction (VCI) calculations, both calculations being for the Jordan-Gilbert potential energy surface. The earlier VCI calculations are found to agree well (within ∼1.5%) with the new benchmarks. The FPI partition functions presented here are estimated to be converged to within a 2σ statistical uncertainty of between 0.04% and 0.07% for the given potential energy surface for temperatures in the range 300-3000 K and are the most accurately converged partition functions for a given potential energy surface for any molecule with five or more atoms. We also tabulate free energies, enthalpies, entropies, and heat capacities.

    13. Improved methods for Feynman path integral calculations and their application to calculate converged vibrational-rotational partition functions, free energies, enthalpies, entropies, and heat capacities for methane.

      PubMed

      Mielke, Steven L; Truhlar, Donald G

      2015-01-28

      We present an improved version of our "path-by-path" enhanced same path extrapolation scheme for Feynman path integral (FPI) calculations that permits rapid convergence with discretization errors ranging from O(P(-6)) to O(P(-12)), where P is the number of path discretization points. We also present two extensions of our importance sampling and stratified sampling schemes for calculating vibrational-rotational partition functions by the FPI method. The first is the use of importance functions for dihedral angles between sets of generalized Jacobi coordinate vectors. The second is an extension of our stratification scheme to allow some strata to be defined based only on coordinate information while other strata are defined based on both the geometry and the energy of the centroid of the Feynman path. These enhanced methods are applied to calculate converged partition functions by FPI methods, and these results are compared to ones obtained earlier by vibrational configuration interaction (VCI) calculations, both calculations being for the Jordan-Gilbert potential energy surface. The earlier VCI calculations are found to agree well (within ∼1.5%) with the new benchmarks. The FPI partition functions presented here are estimated to be converged to within a 2σ statistical uncertainty of between 0.04% and 0.07% for the given potential energy surface for temperatures in the range 300-3000 K and are the most accurately converged partition functions for a given potential energy surface for any molecule with five or more atoms. We also tabulate free energies, enthalpies, entropies, and heat capacities. PMID:25637967

    14. Quantum mechanics in space-time: The Feynman path amplitude description of physical optics, de Broglie matter waves and quark and neutrino flavour oscillations

      SciTech Connect

      Field, J.H. . E-mail: john.field@cern.ch

      2006-03-15

      Feynman's laws of quantum dynamics are concisely stated, discussed in comparison with other formulations of quantum mechanics and applied to selected problems in the physical optics of photons and massive particles as well as flavour oscillations. The classical wave theory of light is derived from these laws for the case in which temporal variation of path amplitudes may be neglected, whereas specific experiments, sensitive to the temporal properties of path amplitudes, are suggested. The reflection coefficient of light from the surface of a transparent medium is found to be markedly different to that predicted by the classical Fresnel formula. Except for neutrino oscillations, good agreement is otherwise found with previous calculations of spatially dependent quantum interference effects.

    15. Integrating Children's Books and Literacy into the Physical Education Curriculum

      ERIC Educational Resources Information Center

      Fingon, Joan C.

      2011-01-01

      Since the onset of No Child Left Behind (NCLB, 2002) schools have been focusing on raising test scores in reading and mathematics, while at the same time feeling pressured to reduce subjects such as physical education and health. It seems for many educators finding time in the school day for students' physical activity has become increasingly…

    16. 2-Micron Triple-Pulse Integrated Path Differential Absorption Lidar Development for Simultaneous Airborne Column Measurements of Carbon Dioxide and Water Vapor in the Atmosphere

      NASA Technical Reports Server (NTRS)

      Singh, Upendra N.; Petros, Mulugeta; Refaat, Tamer F.; Yu, Jirong

      2016-01-01

      For more than 15 years, NASA Langley Research Center (LaRC) has contributed in developing several 2-micron carbon dioxide active remote sensors using the DIAL technique. Currently, an airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar is under development at NASA LaRC. This paper focuses on the advancement of the 2-micron triple-pulse IPDA lidar development. Updates on the state-of-the-art triple-pulse laser transmitter will be presented including the status of wavelength control, packaging and lidar integration. In addition, receiver development updates will also be presented, including telescope integration, detection systems and data acquisition electronics. Future plan for IPDA lidar system for ground integration, testing and flight validation will be presented.

    17. The Relative Effectiveness of Integrated Reading Study Strategy and Conceptual Physics Approach

      ERIC Educational Resources Information Center

      Taslidere, Erdal; Eryilmaz, Ali

      2012-01-01

      The primary purpose of this study was to investigate the combined and partial effects of the Integrated Reading/Study Strategy and Conceptual Physics Approach on ninth grade private high school students' achievement in and attitudes toward optics. The Integrated Reading/Study Strategy is a new strategy which was developed by integrating previously…

    18. Ray-tracing studies and path-integrated gains of ELF unducted whistler mode waves in the earth's magnetosphere

      NASA Technical Reports Server (NTRS)

      Huang, C. Y.; Goertz, C. K.

      1983-01-01

      Gyroresonance and Landau resonance interactions between unducted low-frequency whistler waves and trapped electrons in the earth's plasmasphere have been studied. Ray paths for waves launched near the plasmapause have been traced. In agreement with recent findings by Thorne et al. (1979), waves have been found which return through the equatorial zone with field-aligned wave normal angles. However, when the growth along the ray path is calculated for such waves, assuming an electron distribution function of the form E exp -n sin exp m alpha, it is found that for all the waves considered, the local growth rate becomes negative before plasmapause reflection, limiting the total gain to small values. Most waves reach zero gain before reflection. This is the result of Landau damping at oblique propagation angles, which necessarily occurs before reflection can take place. It is concluded that the concept of cyclic ray paths does not provide an explanation for the generation of unguided plasmaspheric hiss.

    19. Path planning for everday robotics with SANDROS

      SciTech Connect

      Watterberg, P.; Xavier, P.; Hwang, Y.

      1997-02-01

      We discuss the integration of the SANDROS path planner into a general robot simulation and control package with the inclusion of a fast geometry engine for distance calculations. This creates a single system that allows the path to be computed, simulated, and then executed on the physical robot. The architecture and usage procedures are presented. Also, we present examples of its usage in typical environments found in our organization. The resulting system is as easy to use as the general simulation system (which is in common use here) and is fast enough (example problems are solved in seconds) to be used interactively on an everyday basis.

    20. Improved methods for Feynman path integral calculations and their application to calculate converged vibrational–rotational partition functions, free energies, enthalpies, entropies, and heat capacities for methane

      SciTech Connect

      Mielke, Steven L. E-mail: truhlar@umn.edu; Truhlar, Donald G. E-mail: truhlar@umn.edu

      2015-01-28

      We present an improved version of our “path-by-path” enhanced same path extrapolation scheme for Feynman path integral (FPI) calculations that permits rapid convergence with discretization errors ranging from O(P{sup −6}) to O(P{sup −12}), where P is the number of path discretization points. We also present two extensions of our importance sampling and stratified sampling schemes for calculating vibrational–rotational partition functions by the FPI method. The first is the use of importance functions for dihedral angles between sets of generalized Jacobi coordinate vectors. The second is an extension of our stratification scheme to allow some strata to be defined based only on coordinate information while other strata are defined based on both the geometry and the energy of the centroid of the Feynman path. These enhanced methods are applied to calculate converged partition functions by FPI methods, and these results are compared to ones obtained earlier by vibrational configuration interaction (VCI) calculations, both calculations being for the Jordan–Gilbert potential energy surface. The earlier VCI calculations are found to agree well (within ∼1.5%) with the new benchmarks. The FPI partition functions presented here are estimated to be converged to within a 2σ statistical uncertainty of between 0.04% and 0.07% for the given potential energy surface for temperatures in the range 300–3000 K and are the most accurately converged partition functions for a given potential energy surface for any molecule with five or more atoms. We also tabulate free energies, enthalpies, entropies, and heat capacities.

    1. An Integrated Architecture for On-Board Aircraft Engine Performance Trend Monitoring and Gas Path Fault Diagnostics

      NASA Technical Reports Server (NTRS)

      Simon, Donald L.

      2010-01-01

      Aircraft engine performance trend monitoring and gas path fault diagnostics are closely related technologies that assist operators in managing the health of their gas turbine engine assets. Trend monitoring is the process of monitoring the gradual performance change that an aircraft engine will naturally incur over time due to turbomachinery deterioration, while gas path diagnostics is the process of detecting and isolating the occurrence of any faults impacting engine flow-path performance. Today, performance trend monitoring and gas path fault diagnostic functions are performed by a combination of on-board and off-board strategies. On-board engine control computers contain logic that monitors for anomalous engine operation in real-time. Off-board ground stations are used to conduct fleet-wide engine trend monitoring and fault diagnostics based on data collected from each engine each flight. Continuing advances in avionics are enabling the migration of portions of the ground-based functionality on-board, giving rise to more sophisticated on-board engine health management capabilities. This paper reviews the conventional engine performance trend monitoring and gas path fault diagnostic architecture commonly applied today, and presents a proposed enhanced on-board architecture for future applications. The enhanced architecture gains real-time access to an expanded quantity of engine parameters, and provides advanced on-board model-based estimation capabilities. The benefits of the enhanced architecture include the real-time continuous monitoring of engine health, the early diagnosis of fault conditions, and the estimation of unmeasured engine performance parameters. A future vision to advance the enhanced architecture is also presented and discussed

    2. A Path Analysis to Identify the Psychosocial Factors Influencing Physical Activity and Bone Health in Middle-School Girls

      PubMed Central

      Sharma, Shreela V.; Hoelscher, Deanna M.; Kelder, Steven H.; Diamond, Pamela M.; Day, R. Sue; Hergenroeder, Albert C.

      2011-01-01

      Background The purpose of this study was to identify pathways used by psychosocial factors to influence physical activity and bone health in middle-school girls. Methods Baseline data from the Incorporating More Physical Activity and Calcium in Teens (IMPACT) study collected in 2001 to 2003 were used. IMPACT was a 1 1/2 years nutrition and physical activity intervention study designed to improve bone density in 717 middle-school girls in Texas. Structural Equations Modeling was used to examine the interrelationships and identify the direct and indirect pathways used by various psychosocial and environmental factors to influence physical activity and bone health. Results Results show that physical activity self-efficacy and social support (friend, family engagement, and encouragement in physical activity) had a significant direct and indirect influence on physical activity with participation in sports teams as the mediator. Participation in sports teams had a direct effect on both physical activity (β= 0.20, P < .05) and bone health and (β=0.13, P < .05). Conclusion The current study identified several direct and indirect pathways that psychosocial factors use to influence physical activity and bone health among adolescent girls. These findings are critical for the development of effective interventions for promoting bone health in this population. PMID:19953837

    3. CHARM-F: An airborne integral path differential absorption lidar for simultaneous measurements of carbon dioxide and methane columns

      NASA Astrophysics Data System (ADS)

      Amediek, A.; Büdenbender, H.-C.; Ehret, G.; Fix, A.; Kiemle, C.; Quatrevalet, M.; Wirth, M.; Hoffmann, D.; Löhring, J.; Klein, V.

      2012-04-01

      CHARM-F (CO2 and CH4 Atmospheric Remote Monitoring - Flugzeug) is DLR's airborne Integral Path Differential Absorption (IPDA) lidar for simultaneous measurements of the column-weighted average dry-air mixing ratios of atmospheric carbon dioxide and methane, designed to be flown on DLR's new High-Altitude, LOng-range research aircraft, HALO. It is meant to serve as a demonstrator of the use of spaceborne active optical instruments in inferring atmospheric CO2 and CH4 surface fluxes from total column measurements by inverse modeling. As it will be shown, this is enabled by HALO's high flight altitude and its range of 8000 km, which will make it possible to produce real-world data at truly regional scales with a viewing geometry and vertical weighting function similar to those enabled by a space platform. In addition, CHARM-F has the potential to be used as a validation tool not only for active but also passive spaceborne instruments utilizing scattered solar radiation for remote sensing of greenhouse gases. Building on the expertise from CHARM, a helicopter-borne methane IPDA lidar for pipeline monitoring developed in collaboration with E.ON, and WALES, DLR's water vapour differential absorption lidar, CHARM-F relies on a double-pulse transmitter architecture producing nanosecond pulses which allows for a precise ranging and a clean separation of atmospheric influences from the ground returns leading to an unambiguously defined column. One pulse is tuned to an absorption line of the trace gas under consideration, the other to a nearby wavelength with much less absorption. The close temporal separation of 250 μs within each pulse pair ensures that nearly the same spot on ground is illuminated. The ratio of both return signals is then a direct function of the column-weighted average dry-air mixing ratio. The two laser systems, one for each trace gas, use highly efficient and robust Nd:YAG lasers to pump an optical parametric oscillator (OPO) level which converts the

    4. How Physics Teachers Approach Innovation: An Empirical Study for Reconstructing the Appropriation Path in the Case of Special Relativity

      ERIC Educational Resources Information Center

      De Ambrosis, Anna; Levrini, Olivia

      2010-01-01

      This paper concerns an empirical study carried out with a group of high school physics teachers engaged in the Module on relativity of a Master course on the teaching of modern physics. The study is framed within the general research issue of how to promote innovation in school via teachers' education and how to foster fruitful interactions…

    5. An Integration of Chemistry, Biology, and Physics: The Interdisciplinary Laboratory.

      ERIC Educational Resources Information Center

      Van Hecke, Gerald R.; Karukstis, Kerry K.; Haskell, Richard C.; McFadden, Catherine S.; Wettack, F. Sheldon

      2002-01-01

      Reports on a first-year laboratory sequence known as the Interdisciplinary Laboratory (ID Lab) introduced at Harvey Mudd College. The course seeks to illustrate commonality of investigative methods and laboratory techniques in biology, chemistry, and physics and introduce discipline-specific principles. Provides details of the experiments…

    6. Use of Picture Cards in Integrated Physical Education Classes

      ERIC Educational Resources Information Center

      Waugh, Leslie; Bowers, Tiffany; French, Ron

      2007-01-01

      With the implementation of the inclusion concept in public school classes, the ability of the general physical educator to effectively teach all of his or her students has been tested. This is particularly true with some students who have a receptive language disability (e.g., deaf, traumatic brain injury), an expressive language disability (e.g.,…

    7. An Integrated, Statistical Molecular Approach to the Physical Chemistry Curriculum

      ERIC Educational Resources Information Center

      Cartier, Stephen F.

      2009-01-01

      As an alternative to the "thermodynamics first" or "quantum first" approaches to the physical chemistry curriculum, the statistical definition of entropy and the Boltzmann distribution are introduced in the first days of the course and the entire two-semester curriculum is then developed from these concepts. Once the tools of statistical mechanics…

    8. Integrated Hydrologic Validation to Improve Physical Precipitation Retrievals for GPM

      NASA Astrophysics Data System (ADS)

      Peters-Lidard, C. D.; Harrison, K. W.; Tian, Y.; Kumar, S.

      2011-12-01

      One of the five scientific objectives for GPM is to "Improve hydrological modeling and prediction", including advancing prediction skill for high-impact hazards such as floods, droughts, landslides and landfalling hurricanes. Given the focus on land hydrology, and the range of hydrologic regimes targeted by GPM, it follows that a hydrologically-oriented ground validation program that covers these regimes from both the physical retrieval and the hydrological prediction perspectives is required for the successful application of GPM to land hydrology. In order to investigate the robustness of both hydrologic model predictions and physical precipitation retrievals, this talk will present recent evaluations of skill in land surface hydrologic models forced with TRMM-era multisensor products, with and without land data assimilation. In addition to LSM skill, we will also demonstrate how physical precipitation retrievals can be supported by land surface emissivity and temperature estimates obtained by coupling microwave emission models (e.g., the Joint Center for Satellite Data Assimilation Community Radiative Transfer Model CRTM and the European Center for Medium-Range Weather Forecasting's Community Microwave Emission Model CMEM) to the land surface models in the Land Information System (LIS; http://lis.gsfc.nasa.gov). Evaluation at multiple frequencies, with and without land data assimilation, demonstrates the critical impact of certain real-time ancillary data (e.g., snow cover) on the microwave background states required for physical retrievals.

    9. How to Integrate Tai Ji Quan into Physical Education Programs

      ERIC Educational Resources Information Center

      Lu, Chunlei

      2008-01-01

      Tai ji quan, also known as "tai chi," is an ancient Chinese exercise characterized by soft, slow, and meditative movements. It consists of a set of continuous, evenly paced, carefully choreographed, but natural, body shifts. "Tai ji" is an ancient Chinese philosophy, while "tai ji quan" refers to a type of physical activity based on tai ji…

    10. Integrating Microcomputers and Microelectronics into the Physics Curriculum.

      ERIC Educational Resources Information Center

      Gale, Douglas S.

      1980-01-01

      Describes an interdisciplinary microcomputer and microelectronics program offered jointly by the Physics and Computer Science Departments of East Texas State University. The program operates on both the graduate and undergraduate level. Content as well as structure of the program are discussed. (Author/DS)

    11. Integrating Animations, Narratives and Textual Information for Improving Physics Learning

      ERIC Educational Resources Information Center

      Adegoke, Benson Adesina

      2010-01-01

      Introduction: This article examined the effect of multimedia instruction on students' learning outcomes (achievement and interest) in secondary school physics. Method: The sample comprised of 517 (294 boys and 223 girls) students who came from 12 senior secondary schools in Ibadan Educational Zone 1, Oyo State, Nigeria. Their ages ranged between…

    12. Jack O'Lanterns and integrating spheres: Halloween physics

      NASA Astrophysics Data System (ADS)

      Whitehead, Lorne A.; Mossman, Michele A.

      2006-06-01

      Although photometry, the measurement of the intensity and distribution of visible light, is important in many areas, most undergraduate physics courses do not include this topic. We present a simple introduction to key concepts in photometry, and as a fun example, we investigate the optics of a Jack O'Lantern.

    13. Rainsticks: Integrating Culture, Folklore, and the Physics of Sound

      ERIC Educational Resources Information Center

      Moseley, Christine; Fies, Carmen

      2007-01-01

      The purpose of this activity is for students to build a rainstick out of materials in their own environment and imitate the sound of rain while investigating the physical principles of sound. Students will be able to relate the sound produced by an instrument to the type and quantity of materials used in its construction.

    14. A physically based model for dielectric charging in an integrated optical MEMS wavelength selective switch.

      SciTech Connect

      Nielson, Gregory N.; Barbastathis, George

      2005-07-01

      A physical parameter based model for dielectric charge accumulation is proposed and used to predict the displacement versus applied voltage and pull-in response of an electrostatic MEMS wavelength selective integrated optical switch.

    15. Structure and Dynamics of the Instantaneous Water/Vapor Interface Revisited by Path-Integral and Ab Initio Molecular Dynamics Simulations.

      PubMed

      Kessler, Jan; Elgabarty, Hossam; Spura, Thomas; Karhan, Kristof; Partovi-Azar, Pouya; Hassanali, Ali A; Kühne, Thomas D

      2015-08-01

      The structure and dynamics of the water/vapor interface is revisited by means of path-integral and second-generation Car-Parrinello ab initio molecular dynamics simulations in conjunction with an instantaneous surface definition [Willard, A. P.; Chandler, D. J. Phys. Chem. B 2010, 114, 1954]. In agreement with previous studies, we find that one of the OH bonds of the water molecules in the topmost layer is pointing out of the water into the vapor phase, while the orientation of the underlying layer is reversed. Therebetween, an additional water layer is detected, where the molecules are aligned parallel to the instantaneous water surface.

    16. Options for integrated beam experiments for inertial fusion energy and high-energy density physics research

      NASA Astrophysics Data System (ADS)

      Leitner, M. A.; Celata, C. M.; Lee, E. P.; Logan, B. G.; Waldron, W. L.; Yu, S. S.; Barnard, J. J.

      2005-05-01

      The Heavy Ion Fusion Virtual National Laboratory (HIF-VNL), a collaboration among LBNL, LLNL, and PPPL, is presently focused on separate smaller-scale scientific experiments addressing key issues of future Inertial Fusion Energy (IFE) and High-Energy-Density-Physics (HEDP) drivers: the injection, transport, and focusing of intense heavy ion beams at currents from 25 to 600 mA. As a next major step in the HIF-VNL program, we aim for a fully integrated beam physics experiment, which allows integrated source-to-target physics research with a high-current heavy ion beam of IFE-relevant brightness with the goal of optimizing target focusing. This paper describes two rather different options for such an integrated experiment, the Integrated Beam Experiment (IBX) and the Neutralized Drift Compression Experiment (NDCX). Both proposals put emphasis on the unique capability for integrated injection, acceleration, compression, and focusing of a high-current, space-charge-dominated heavy ion beam.

    17. Mixed signal custom integrated circuit development for physics instrumentation

      SciTech Connect

      Britton, C.L. Jr.; Bryan, W.L.; Emery, M.S.

      1998-10-01

      The Monolithic Systems Development Group at the Oak Ridge National Laboratory has been greatly involved in custom mixed-mode integrated circuit development for the PHENIX detector at the Relativistic Heavy Ion collider (RHIC) at Brookhaven National Laboratory and position-sensitive germanium spectrometer front-ends for the Naval Research Laboratory (NRL). This paper will outline the work done for both PHENIX and the Naval Research Laboratory in the area of full-custom, mixed-signal CMOS integrated electronics. This paper presents the architectures chosen for the various PHENIX detectors which include position-sensitive silicon, capacitive pixel, and phototube detectors, and performance results for the subsystems as well as a system description of the NRL germanium strip system and its performance. The performance of the custom preamplifiers, discriminators, analog memories, analog-digital converters, and control circuitry for all systems will be presented.

    18. Combined Monte Carlo and path-integral method for simulated library of time-resolved reflectance curves from layered tissue models

      NASA Astrophysics Data System (ADS)

      Wilson, Robert H.; Vishwanath, Karthik; Mycek, Mary-Ann

      2009-02-01

      Monte Carlo (MC) simulations are considered the "gold standard" for mathematical description of photon transport in tissue, but they can require large computation times. Therefore, it is important to develop simple and efficient methods for accelerating MC simulations, especially when a large "library" of related simulations is needed. A semi-analytical method involving MC simulations and a path-integral (PI) based scaling technique generated time-resolved reflectance curves from layered tissue models. First, a zero-absorption MC simulation was run for a tissue model with fixed scattering properties in each layer. Then, a closed-form expression for the average classical path of a photon in tissue was used to determine the percentage of time that the photon spent in each layer, to create a weighted Beer-Lambert factor to scale the time-resolved reflectance of the simulated zero-absorption tissue model. This method is a unique alternative to other scaling techniques in that it does not require the path length or number of collisions of each photon to be stored during the initial simulation. Effects of various layer thicknesses and absorption and scattering coefficients on the accuracy of the method will be discussed.

    19. Fast-cycling superconducting synchrotrons and possible path to the future of US experimental high-energy particle physics

      SciTech Connect

      Piekarz, Henryk; /Fermilab

      2008-02-01

      The authors outline primary physics motivation, present proposed new arrangement for Fermilab accelerator complex, and then discuss possible long-range application of fast-cycling superconducting synchrotrons at Fermilab.

    20. Becoming Physics People: Development of Integrated Physics Identity through the Learning Assistant Experience

      ERIC Educational Resources Information Center

      Close, Eleanor W.; Conn, Jessica; Close, Hunter G.

      2016-01-01

      In this study, we analyze the experience of students in the Physics Learning Assistant (LA) program at Texas State University in terms of the existing theoretical frameworks of "community of practice" and "physics identity," and explore the implications suggested by these theories for LA program adoption and adaptation.…