Science.gov

Sample records for state space transitions

  1. Quantum Transition State Theory

    NASA Astrophysics Data System (ADS)

    Waalkens, Holger

    2009-03-01

    The main idea of Wigner's transition state theory (TST) is to compute reaction rates from the flux through a dividing surface placed between reactants and products. In order not to overestimate the rate the dividing surface needs to have the no- recrossing property, i.e. reactive trajectories cross the dividing surface exactly once, and nonreactive trajectories do not cross it at all. The long standing problem of how to construct such a diving surface for multi-degree-of-freedom systems was solved only recently using ideas from dynamical systems theory. Here a normal form allows for a local decoupling of the classical dynamics which leads to the explicit construction of the phase space structures that govern the reaction dynamics through transition states. The dividing surface is spanned by a normally hyperbolic manifold which is the mathematical manifestation of the transition state as an unstable invariant subsystem of one degree of freedom less than the full system. The mere existence of a quantum version of TST is discussed controversially in the literature. The key isssue is the presence of quantum mechanical tunneling which prohibits the existence of a local theory analogous to the classical case. Various approaches have been devloped to overcome this problem by propagating quantum wavefunctions through the transition state region. These approaches have in common that they are computationally very expensive which seriously limits their applicability. In contrast the approach by Roman Schubert, Stephen Wiggins and myself is local in nature. A quantum normal form allows us to locally decouple the quantum dynamics to any desired order in Planck's constant. This yields not only the location of the scattering and resonance wavefunctions relative to the classical phase space structures, but also leads to very efficient algorithms to compute cumulative reaction probabilities and Gamov-Siegert resonances which are the quantum imprints of the transition state.

  2. Variational Transition State Theory

    SciTech Connect

    Truhlar, Donald G.

    2016-09-29

    This is the final report on a project involving the development and applications of variational transition state theory. This project involved the development of variational transition state theory for gas-phase reactions, including optimized multidimensional tunneling contributions and the application of this theory to gas-phase reactions with a special emphasis on developing reaction rate theory in directions that are important for applications to combustion. The development of variational transition state theory with optimized multidimensional tunneling as a useful computational tool for combustion kinetics involved eight objectives.

  3. Transition state in atomic physics

    NASA Astrophysics Data System (ADS)

    Jaffé, Charles; Farrelly, David; Uzer, T.

    1999-11-01

    The transition state is fundamental to modern theories of reaction dynamics: essentially, the transition state is a structure in phase space that all reactive trajectories must cross. While transition-state theory (TST) has been used mainly in chemical physics, it is possible to apply the theory to considerable advantage in any collision problem that involves some form of reaction. Of special interest are systems in which chaotic scattering or half-scattering occurs such as the ionization of Rydberg atoms in external fields. In this paper the ionization dynamics of a hydrogen atom in crossed electric and magnetic fields are shown to possess a transition state: We compute the periodic orbit dividing surface (PODS) which is found not to be a dividing surface when projected into configuration space. Although the possibility of a PODS occurring in phase space rather than configuration space has been recognized before, to our knowledge this is the first actual example: its origin is traced directly to the presence of velocity-dependent terms in the Hamiltonian. Our findings establish TST as the method of choice for understanding ionization of Rydberg atoms in the presence of velocity-dependent forces. To demonstrate this TST is used to (i) uncover a multiple-scattering mechanism for ionization and (ii) compute ionization rates. In the process we also develop a method of computing surfaces of section that uses periodic orbits to define the surface, and examine the fractal nature of the dynamics.

  4. Variational transition state theory

    SciTech Connect

    Truhlar, D.G.

    1993-12-01

    This research program involves the development of variational transition state theory (VTST) and semiclassical tunneling methods for the calculation of gas-phase reaction rates and selected applications. The applications are selected for their fundamental interest and/or their relevance to combustion.

  5. Transition States and transition state analogue interactions with enzymes.

    PubMed

    Schramm, Vern L

    2015-04-21

    Enzymatic transition states have lifetimes of a few femtoseconds (fs). Computational analysis of enzyme motions leading to transition state formation suggests that local catalytic site motions on the fs time scale provide the mechanism to locate transition states. An experimental test of protein fs motion and its relation to transition state formation can be provided by isotopically heavy proteins. Heavy enzymes have predictable mass-altered bond vibration states without altered electrostatic properties, according to the Born-Oppenheimer approximation. On-enzyme chemistry is slowed in most heavy proteins, consistent with altered protein bond frequencies slowing the search for the transition state. In other heavy enzymes, structural changes involved in reactant binding and release are also influenced. Slow protein motions associated with substrate binding and catalytic site preorganization are essential to allow the subsequent fs motions to locate the transition state and to facilitate the efficient release of products. In the catalytically competent geometry, local groups move in stochastic atomic motion on the fs time scale, within transition state-accessible conformations created by slower protein motions. The fs time scale for the transition state motions does not permit thermodynamic equilibrium between the transition state and stable enzyme states. Isotopically heavy enzymes provide a diagnostic tool for fast coupled protein motions to transition state formation and mass-dependent conformational changes. The binding of transition state analogue inhibitors is the opposite in catalytic time scale to formation of the transition state but is related by similar geometries of the enzyme-transition state and enzyme-inhibitor interactions. While enzymatic transition states have lifetimes as short as 10(-15) s, transition state analogues can bind tightly to enzymes with release rates greater than 10(3) s. Tight-binding transition state analogues stabilize the rare but

  6. Combining active-space coupled-cluster methods with moment energy corrections via the CC(P;Q) methodology, with benchmark calculations for biradical transition states

    NASA Astrophysics Data System (ADS)

    Shen, Jun; Piecuch, Piotr

    2012-04-01

    We have recently suggested the CC(P;Q) methodology that can correct energies obtained in the active-space coupled-cluster (CC) or equation-of-motion (EOM) CC calculations, which recover much of the nondynamical and some dynamical electron correlation effects, for the higher-order, mostly dynamical, correlations missing in the active-space CC/EOMCC considerations. It is shown that one can greatly improve the description of biradical transition states, both in terms of the resulting energy barriers and total energies, by combining the CC approach with singles, doubles, and active-space triples, termed CCSDt, with the CC(P;Q)-style correction due to missing triple excitations defining the CC(t;3) approximation.

  7. Combining active-space coupled-cluster methods with moment energy corrections via the CC(P;Q) methodology, with benchmark calculations for biradical transition states.

    PubMed

    Shen, Jun; Piecuch, Piotr

    2012-04-14

    We have recently suggested the CC(P;Q) methodology that can correct energies obtained in the active-space coupled-cluster (CC) or equation-of-motion (EOM) CC calculations, which recover much of the nondynamical and some dynamical electron correlation effects, for the higher-order, mostly dynamical, correlations missing in the active-space CC/EOMCC considerations. It is shown that one can greatly improve the description of biradical transition states, both in terms of the resulting energy barriers and total energies, by combining the CC approach with singles, doubles, and active-space triples, termed CCSDt, with the CC(P;Q)-style correction due to missing triple excitations defining the CC(t;3) approximation.

  8. Parametric State Space Structuring

    NASA Technical Reports Server (NTRS)

    Ciardo, Gianfranco; Tilgner, Marco

    1997-01-01

    Structured approaches based on Kronecker operators for the description and solution of the infinitesimal generator of a continuous-time Markov chains are receiving increasing interest. However, their main advantage, a substantial reduction in the memory requirements during the numerical solution, comes at a price. Methods based on the "potential state space" allocate a probability vector that might be much larger than actually needed. Methods based on the "actual state space", instead, have an additional logarithmic overhead. We present an approach that realizes the advantages of both methods with none of their disadvantages, by partitioning the local state spaces of each submodel. We apply our results to a model of software rendezvous, and show how they reduce memory requirements while, at the same time, improving the efficiency of the computation.

  9. Universal Keplerian state transition matrix

    NASA Technical Reports Server (NTRS)

    Shepperd, S. W.

    1985-01-01

    A completely general method for computing the Keplerian state transition matrix in terms of Goodyear's universal variables is presented. This includes a new scheme for solving Kepler's problem which is a necessary first step to computing the transition matrix. The Kepler problem is solved in terms of a new independent variable requiring the evaluation of only one transcendental function. Furthermore, this transcendental function may be conveniently evaluated by means of a Gaussian continued fraction.

  10. Progression of Space Transportation - Transitioning from Government to Commercial

    NASA Technical Reports Server (NTRS)

    Lueders, Kathy

    2015-01-01

    Spaceflight began as the exclusive province of government, however, starting in the 1980's the United States began to promote commercial participation in space transportation. Beginning with Executive policy and extending through legislation and regulation, NASA has embarked on facilitating the commercialization of space transportation to serve NASA needs and enable a non-NASA market place. This presentation provides background on the transition to commercial space transportation and the specific role NASA is playing in that endeavor.

  11. APL experience with space weather modeling and transition to operations

    NASA Astrophysics Data System (ADS)

    Zanetti, L. J.; Wing, S.

    2009-12-01

    In response to the growing space weather needs, the Johns Hopkins University Applied Physics Laboratory (APL) developed and delivered twenty two state of the art space weather products under the auspice of the University Partnering in Operational Support program, initiated in 1998. These products offer nowcasts and forecasts for the region spanning from the Sun to the Earth. Some of these products have been transitioned to the Air Force Weather Agency and other space weather centers. The transition process is quite different from research modeling, requiring additional staff with different sets of expertise. Recently, APL has developed a space weather web page to serve these products to the research and user community. For the initial stage, we have chosen ten of these products to be served from our website, which is presently still under construction. APL’s experience, lessons learned, and successes from developing space weather models, the transition to operations process and the webpage access will be shared and discussed

  12. On the occurrence of transition states in celestial mechanics.

    PubMed

    Jaffé, Charles; Uzer, T

    2004-05-01

    The transition state is a central concept in the study of chemical reactions. The basic idea is that state space (phase space) can be partitioned into two volumes; the first corresponding to reactants and the second to products. Chemists call the boundary between these two regions the transition state. The rate of a chemical reaction is then discussed in terms the of the flow across the transition state. These ideas can also be applied with good effect to celestial problems. This paper outlines the chemists' view of molecular dynamics and then illustrates its application to problem of transport in celestial mechanics.

  13. Spectroscopic Characterization of Isomerization Transition States

    NASA Astrophysics Data System (ADS)

    Baraban, Joshua H.; Changala, Bryan; Mellau, Georg Ch.; Stanton, John F.; Merer, Anthony; Field, Robert W.

    2016-06-01

    Transition state theory is central to our understanding of chemical reaction dynamics. We demonstrate here a method for extracting transition state energies and properties from a characteristic pattern found in frequency domain spectra of isomerizing systems. This pattern, a dip in the spacings of certain barrier-proximal vibrational levels, can be understood using the concept of effective frequency, ωeff. The method is applied to the cis-trans conformational change in the S_1 state of C2H2 and the bond-breaking HCN-HNC isomerization. In both cases, the barrier heights derived from spectroscopic data agree extremely well with previous ab initio calculations. We also show that it is possible to distinguish between vibrational modes that are actively involved in the isomerization process and those that are passive bystanders. (This work has been published in J. H. Baraban, P. B. Changala, G. Ch. Mellau, J. F. Stanton, A. J. Merer, and R. W. Field. Spectroscopic characterization of isomerization transition states. Science, 350(6266):1338--1342, 2015.)

  14. Transition state structures in solution

    SciTech Connect

    Bertran, J.; Lluch, J. M.; Gonzalez-Lafont, A.; Dillet, V.; Perez, V.

    1995-04-05

    In the present paper the location of transition state structures for reactions in solution has been studied. Continuum model calculations have been carried out on the Friedel-Crafts alkylation reaction and a proton transfer through a water molecule between two oxygen atoms in formic acid. In this model the separation between the chemical system and the solvent has been introduced. On the other hand, the discrete Monte Carlo methodology has also been used to simulate the solvent effect on dissociative electron transfer processes. In this model, the hypothesis of separability is not assumed. Finally, the validity of both approaches is discussed.

  15. Transition state structures in solution

    NASA Astrophysics Data System (ADS)

    Bertrán, J.; Lluch, J. M.; Gonzàlez-Lafont, A.; Dillet, V.; Pérez, V.

    1995-04-01

    In the present paper the location of transition state structures for reactions in solution has been studied. Continuum model calculations have been carried out on the Friedel-Crafts alkylation reaction and a proton transfer through a water molecule between two oxygen atoms in formic acid. In this model the separation between the chemical system and the solvent has been introduced. On the other hand, the discrete Monte Carlo methodology has also been used to simulate the solvent effect on dissociative electron transfer processes. In this model, the hypothesis of separability is not assumed. Finally, the validity of both approaches is discussed.

  16. Multiferroic behavior at a spin state transition

    NASA Astrophysics Data System (ADS)

    Zapf, Vivien; Chikara, Shalinee; Singleton, John; Lin, Shizeng; Batista, Cristian; Scott, Brian; Smythe, Nathan

    Traditionally, multiferroic behavior is studied in materials with coexisting long-range orders, such as ferromagnetism and ferroelectricity. Here we present multiferroic behavior at a spin-state transition (SST). SSTs, for example, the S = 1 to S = 2 transition in Mn3+ can become cooperative magneto-structural phase transitions due to structural coupling between ions. SSTs are accompanied by change in the orbital occupation and hence, strongly coupled to the lattice and charge degrees of freedom. They are a dominant functionality in metal-organic materials, persisting up to room temperature in some compounds. We demonstrate that a magnetic SST can induce ferroelectricity. We study a Mn-based metal-organic system in which a three-fold degenerate dynamic Jahn-Teller effect at high temperatures vanishes when the temperature is lowered, and the system drops into a lower spin state. Application of a magnetic field restores the high spin Jahn-Teller-active state and allows the Jahn Teller distortions to order cooperatively, creating a dielectric constant change and a net electric polarization. We use high magnetic fields at the NHMFL to study the magnetic and electric behavior of this system across a significant fraction of its T-H phase space, and compare to theoretical modeling.

  17. Transition metal catalysis in confined spaces.

    PubMed

    Leenders, Stefan H A M; Gramage-Doria, Rafael; de Bruin, Bas; Reek, Joost N H

    2015-01-21

    Transition metal catalysis plays an important role in both industry and in academia where selectivity, activity and stability are crucial parameters to control. Next to changing the structure of the ligand, introducing a confined space as a second coordination sphere around a metal catalyst has recently been shown to be a viable method to induce new selectivity and activity in transition metal catalysis. In this review we focus on supramolecular strategies to encapsulate transition metal complexes with the aim of controlling the selectivity via the second coordination sphere. As we will discuss, catalyst confinement can result in selective processes that are impossible or difficult to achieve by traditional methods. We will describe the template-ligand approach as well as the host-guest approach to arrive at such supramolecular systems and discuss how the performance of the catalyst is enhanced by confining it in a molecular container.

  18. Typology of State Types: Persistence and Transition

    DTIC Science & Technology

    2015-04-28

    developed in this paper, a more tailored policy to each type of state might be applied. Such nuances cannot be captured by broader categorizations such as...DRDC-RDDC-2014-P105 1 Typology of State Types : Persistence and Transition Peter Tikuisis Defence Research and Development Canada David...Additionally, changes in legitimacy most often led state transitions into or out of fragility. Implications of intervention policy for transitioning

  19. EXPLORING TRANSITIONS OF SPACE PLASMAS OUT OF EQUILIBRIUM

    SciTech Connect

    Livadiotis, G.; McComas, D. J.

    2010-05-01

    Space plasmas from the solar wind to planetary magnetospheres and the outer heliosphere are systems in stationary states out of equilibrium. Empirical kappa distributions, which naturally emerge from Tsallis Statistics, successfully describe these space plasmas. The Tsallis formalism offers a solid statistical foundation and provides a set of proven tools for understanding these distributions, including a consistent definition of temperature-the physical temperature, which characterizes the non-equilibrium stationary states. Here, we develop a measure of the 'thermodynamic distance' of stationary states away from equilibrium. The stationary states are labeled by the value of the entropic q-index, lying in a spectrum from q = 1 (equilibrium) to the maximum value of q, which specifies the furthest possible stationary state from equilibrium. We call this the 'q-frozen state', because as a system approaches this state, it behaves analogously to when its temperature approaches absolute zero. We also introduce a novel isothermal procedure that describes a system's transition into different stationary states by varying the q-index, and show how the variation of temperature can be realized using an 'iso-metastability' procedure, in which the system remains in a fixed stationary state. These innovations allow a generalization of the zeroth law of thermodynamics to cover stationary states out of equilibrium. By expressing the entropy in terms of the q-index, we show the detailed paths by which the transition of stationary states evolves toward equilibrium following the dynamics of a characteristic difference equation along the q-indices. This naturally exhibits certain stationary states out of equilibrium that are frequently observed in space plasmas.

  20. Exploring Transitions of Space Plasmas Out of Equilibrium

    NASA Astrophysics Data System (ADS)

    Livadiotis, G.; McComas, D. J.

    2010-05-01

    Space plasmas from the solar wind to planetary magnetospheres and the outer heliosphere are systems in stationary states out of equilibrium. Empirical kappa distributions, which naturally emerge from Tsallis Statistics, successfully describe these space plasmas. The Tsallis formalism offers a solid statistical foundation and provides a set of proven tools for understanding these distributions, including a consistent definition of temperature—the physical temperature, which characterizes the non-equilibrium stationary states. Here, we develop a measure of the "thermodynamic distance" of stationary states away from equilibrium. The stationary states are labeled by the value of the entropic q-index, lying in a spectrum from q = 1 (equilibrium) to the maximum value of q, which specifies the furthest possible stationary state from equilibrium. We call this the "q-frozen state," because as a system approaches this state, it behaves analogously to when its temperature approaches absolute zero. We also introduce a novel isothermal procedure that describes a system's transition into different stationary states by varying the q-index, and show how the variation of temperature can be realized using an "iso-metastability" procedure, in which the system remains in a fixed stationary state. These innovations allow a generalization of the zeroth law of thermodynamics to cover stationary states out of equilibrium. By expressing the entropy in terms of the q-index, we show the detailed paths by which the transition of stationary states evolves toward equilibrium following the dynamics of a characteristic difference equation along the q-indices. This naturally exhibits certain stationary states out of equilibrium that are frequently observed in space plasmas.

  1. Energy management during the space shuttle transition.

    NASA Technical Reports Server (NTRS)

    Stengel, R. F.

    1972-01-01

    An approach to calculating optimal, gliding flight paths of the type associated with the space shuttle's transition from entry to cruising flight is presented. Kinetic energy and total energy (per unit weight) replace velocity and time in the dynamic equations, reducing the dimension and complexity of the problem. The capability for treating integral and terminal penalties (as well as Mach number effects) is retained in the numerical optimization; hence, stability and control boundaries can be observed as trajectories to the desired final energy, flight path angle, and range are determined. Numerical results show that the 'jump' to the 'front-side of the L/D curve' need not be made until the end of the transition and that the dynamic model provides a conservative range estimate. Alternatives for real-time trajectory control are discussed.

  2. Energy management during the space shuttle transition

    NASA Technical Reports Server (NTRS)

    Stengel, R. F.

    1972-01-01

    An approach to calculating optimal, gliding flight paths of the type associated with the space shuttle's transition from entry to cruising flight is presented. Kinetic energy and total energy (per unit weight) replace velocity and time in the dynamic equations, reducing the dimension and complexity of the problem. The capability for treating integral and terminal penalties (as well as Mach number effects) is retained in the numerical optimization; hence, stability and control boundaries can be observed as trajectories to the desired final energy, flight path angle, and range are determined. Numerical results show that the jump to the front-side of the L/D curve need not be made until the end of the transition and that the dynamic model provides a conservative range estimate. Alternatives for real time trajectory control are discussed.

  3. Quantum phase transition induced by real-space topology

    NASA Astrophysics Data System (ADS)

    Li, C.; Zhang, G.; Lin, S.; Song, Z.

    2016-12-01

    A quantum phase transition (QPT), including both topological and symmetry breaking types, is usually induced by the change of global parameters, such as external fields or global coupling constants. In this work, we demonstrate the existence of QPT induced by the real-space topology of the system. We investigate the groundstate properties of the tight-binding model on a honeycomb lattice with the torus geometry based on exact results. It is shown that the ground state experiences a second-order QPT, exhibiting the scaling behavior, when the torus switches to a tube, which reveals the connection between quantum phase and the real-space topology of the system.

  4. Quantum phase transition induced by real-space topology

    PubMed Central

    Li, C.; Zhang, G.; Lin, S.; Song, Z.

    2016-01-01

    A quantum phase transition (QPT), including both topological and symmetry breaking types, is usually induced by the change of global parameters, such as external fields or global coupling constants. In this work, we demonstrate the existence of QPT induced by the real-space topology of the system. We investigate the groundstate properties of the tight-binding model on a honeycomb lattice with the torus geometry based on exact results. It is shown that the ground state experiences a second-order QPT, exhibiting the scaling behavior, when the torus switches to a tube, which reveals the connection between quantum phase and the real-space topology of the system. PMID:28004736

  5. Gravitational phase transitions with an exclusion constraint in position space

    NASA Astrophysics Data System (ADS)

    Chavanis, Pierre-Henri

    2014-01-01

    We discuss the statistical mechanics of a system of self-gravitating particles with an exclusion constraint in position space in a space of dimension d. The exclusion constraint puts an upper bound on the density of the system and can stabilize it against gravitational collapse. We plot the caloric curves giving the temperature as a function of the energy and investigate the nature of phase transitions as a function of the size of the system and of the dimension of space in both microcanonical and canonical ensembles. We consider stable and metastable states and emphasize the importance of the latter for systems with long-range interactions. For d ≤ 2, there is no phase transition. For d > 2, phase transitions can take place between a "gaseous" phase unaffected by the exclusion constraint and a "condensed" phase dominated by this constraint. The condensed configurations have a core-halo structure made of a "rocky core" surrounded by an "atmosphere", similar to a giant gaseous planet. For large systems there exist microcanonical and canonical first order phase transitions. For intermediate systems, only canonical first order phase transitions are present. For small systems there is no phase transition at all. As a result, the phase diagram exhibits two critical points, one in each ensemble. There also exist a region of negative specific heats and a situation of ensemble inequivalence for sufficiently large systems. We show that a statistical equilibrium state exists for any values of energy and temperature in any dimension of space. This differs from the case of the self-gravitating Fermi gas for which there is no statistical equilibrium state at low energies and low temperatures when d ≥ 4. By a proper interpretation of the parameters, our results have application for the chemotaxis of bacterial populations in biology described by a generalized Keller-Segel model including an exclusion constraint in position space. They also describe colloids at a fluid

  6. Longitudinal space charge effects near transition

    SciTech Connect

    Pozdeyev,E.; Rodriguez, J.A.; Marti, F.; York, R.C.

    2009-05-04

    Experimental and numerical studies of the longitudinal beam dynamics in the Small Isochronous Ring (SIR) at Michigan State University revealed a fast, space-charge driven instability that did not fit the model of the negative mass instability. This paper proposes a simple analytical model explaining these results. Also, the paper compares the model to result s of experimental and numerical studies of the longitudinal beam dynamics in SIR.

  7. Optimal guidance for the space shuttle transition.

    NASA Technical Reports Server (NTRS)

    Stengel, R. F.

    1972-01-01

    A guidance method for the space shuttle's transition from hypersonic entry to subsonic cruising flight is presented. The method evolves from a numerical trajectory optimization technique in which kinetic energy and total energy (per unit weight) replace velocity and time in the dynamic equations. This allows the open end-time problem to be transformed to one of fixed terminal energy. In its ultimate form, 'E-Guidance' obtains energy balance (including dynamic-pressure-rate damping) and path length control by angle-of-attack modulation and cross-range control by roll angle modulation. The guidance functions also form the basis for a pilot display of instantaneous maneuver limits and destination. Numerical results illustrate the E-Guidance concept and the optimal trajectories on which it is based.

  8. Optimal guidance for the space shuttle transition

    NASA Technical Reports Server (NTRS)

    Stengel, R. F.

    1974-01-01

    A guidance method for the space shuttle's transition from hypersonic entry to subsonic cruising flight is presented. The method evolves from a numerical trajectory optimization technique in which kinetic energy and total energy (per unit weight) replace velocity and time in the dynamic equations. This allows the open end-time problem to be transformed to one of fixed terminal energy. In its ultimate form, E-Guidance obtains energy balance (including dynamic-pressure-rate damping) and path length control by angle-of-attack modulation and cross-range control by roll angle modulation. The guidance functions also form the basis for a pilot display of instantaneous maneuver limits and destination. Numerical results illustrate the E-Guidance concept and the optimal trajectories on which it is based.

  9. Optimal guidance for the space shuttle transition

    NASA Technical Reports Server (NTRS)

    Stengel, R. F.

    1972-01-01

    A guidance method for the space shuttle's transition from hypersonic entry to subsonic cruising flight is presented. The method evolves from a numerical trajectory optimization technique in which kinetic energy and total energy (per unit weight) replace velocity and time in the dynamic equations. This allows the open end-time problem to be transformed to one of fixed terminal energy. In its ultimate form, E-Guidance obtains energy balance (including dynamic-pressure-rate damping) and path length control by angle-of-attack modulation and cross-range control by roll angle modulation. The guidance functions also form the basis for a pilot display of instantaneous maneuver limits and destination. Numerical results illustrate the E-Guidance concept and the optimal trajectories on which it is based.

  10. Challenges for Transitioning Science Research to Space Weather Applications

    NASA Technical Reports Server (NTRS)

    Spann, James

    2013-01-01

    Effectively transitioning science knowledge to useful applications relevant to space weather has become important. The effort to transition scientific knowledge to a useful application is not a research nor is it operations, but an activity that connects two. Successful transitioning must be an intentional effort with a clear goal and measureable outcome. This talk will present proven methodologies that have been demonstrated to be effective, and how in the current environment those can be applied to space weather transition efforts.

  11. Transition of unsteady flows of evaporation to steady state

    NASA Astrophysics Data System (ADS)

    d'Almeida, Amah

    2008-07-01

    We investigate the half-space problem of evaporation and condensation in the scope of discrete kinetic theory. Exact solutions are found to the boundary value problem and the initial boundary value problems of the flow in the half space for a discrete velocity model. The results are used to analyze the transition of the unsteady solutions towards steady states. To cite this article: A. d'Almeida, C. R. Mecanique 336 (2008).

  12. Wetting transition on patterned surfaces: transition states and energy barriers.

    PubMed

    Ren, Weiqing

    2014-03-18

    We study the wetting transition on microstructured hydrophobic surfaces. We use the string method [J. Chem. Phys. 2007, 126, 164103; J. Chem. Phys. 2013, 138, 134105] to accurately compute the transition states, the energy barriers, and the minimum energy paths for the wetting transition from the Cassie-Baxter state to the Wenzel state. Numerical results are obtained for the wetting of a hydrophobic surface textured with a square lattice of pillars. It is found that the wetting of the solid substrate occurs via infiltration of the liquid in a single groove, followed by lateral propagation of the liquid front. The propagation of the liquid front proceeds in a stepwise manner, and a zipping mechanism is observed during the infiltration of each layer. The minimum energy path for the wetting transition goes through a sequence of intermediate metastable states, whose wetted areas reflect the microstructure of the patterned surface. We also study the dependence of the energy barrier on the drop size and the gap between the pillars.

  13. Theory on Superconducting Transition from Pseudogap State

    NASA Astrophysics Data System (ADS)

    Yanase, Youichi; Jujo, Takanobu; Yamada, Kosaku

    2000-11-01

    The anomalous properties of High-T c cuprates are investigated both in the normal state and in the superconducting state. In particular, we pay attention to the pseudogap in the normal state and the phase transition from the pseudogap state to the superconducting state. The pseudogap phenomena observed in cuprates are naturally understood as a precursor of the strong coupling superconductivity. We have previously shown by using the self-consistent T-matrix calculation that the pseudogap is a result of the strong superconducting fluctuations which are accompanied by the strong coupling superconductivity in quasi-two dimensional systems [J. Phys. Soc. Jpn. 68 (1999) 2999]. We extend the scenario to the superconducting state. The close relation between the pseudogap state and the superconducting state is pointed out. Once the superconducting phase transition occurs, the superconducting order parameter rapidly grows rather than the result of BCS theory. With the rapid growth of the order parameter, the gap structure becomes sharp, while it is remarkably broad in the pseudogap state. The characteristic energy scale of the gap does not change. These results well explain the phase transition observed in the spectroscopic measurements. Further, we calculate the magnetic and transport properties which show the pseudogap phenomena. The comprehensive understanding of the NMR, the neutron scattering, the optical conductivity and the London penetration depth is obtained both in the pseudogap state and in the superconducting state.

  14. Operationalizing resilience using state and transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In management, restoration, and policy contexts, the notion of resilience can be confusing. Systematic development of conceptual models of ecological state change (state transition models; STMs) can help overcome semantic confusion and promote a mechanistic understanding of resilience. Drawing on ex...

  15. The Aromaticity of Pericyclic Reaction Transition States

    ERIC Educational Resources Information Center

    Rzepa, Henry S.

    2007-01-01

    An approach is presented that starts from two fundamental concepts in organic chemistry, chirality and aromaticity, and combines them into a simple rule for stating selection rules for pericyclic reactions in terms of achiral Huckel-aromatic and chiral Mobius-aromatic transition states. This is illustrated using an example that leads to apparent…

  16. Transition state ensemble optimization for reactions of arbitrary complexity

    NASA Astrophysics Data System (ADS)

    Zinovjev, Kirill; Tuñón, Iñaki

    2015-10-01

    In the present work, we use Variational Transition State Theory (VTST) to develop a practical method for transition state ensemble optimization by looking for an optimal hyperplanar dividing surface in a space of meaningful trial collective variables. These might be interatomic distances, angles, electrostatic potentials, etc. Restrained molecular dynamics simulations are used to obtain on-the-fly estimates of ensemble averages that guide the variations of the hyperplane maximizing the transmission coefficient. A central result of our work is an expression that quantitatively estimates the importance of the coordinates used for the localization of the transition state ensemble. Starting from an arbitrarily large set of trial coordinates, one can distinguish those that are indeed essential for the advance of the reaction. This facilitates the use of VTST as a practical theory to study reaction mechanisms of complex processes. The technique was applied to the reaction catalyzed by an isochorismate pyruvate lyase. This reaction involves two simultaneous chemical steps and has a shallow transition state region, making it challenging to define a good reaction coordinate. Nevertheless, the hyperplanar transition state optimized in the space of 18 geometrical coordinates provides a transmission coefficient of 0.8 and a committor histogram well-peaked about 0.5, proving the strength of the method. We have also tested the approach with the study of the NaCl dissociation in aqueous solution, a stringest test for a method based on transition state theory. We were able to find essential degrees of freedom consistent with the previous studies and to improve the transmission coefficient with respect to the value obtained using solely the NaCl distance as the reaction coordinate.

  17. Transition state for protein-DNA recognition.

    PubMed

    Ferreiro, Diego U; Sánchez, Ignacio E; de Prat Gay, Gonzalo

    2008-08-05

    We describe the formation of protein-DNA contacts in the two-state route for DNA sequence recognition by a transcriptional regulator. Surprisingly, direct sequence readout establishes in the transition state and constitutes the bottleneck of complex formation. Although a few nonspecific ionic interactions are formed at this early stage, they mainly play a stabilizing role in the final consolidated complex. The interface is fairly plastic in the transition state, likely because of a high level of hydration. The overall picture of this two-state route largely agrees with a smooth energy landscape for binding that speeds up DNA recognition. This "direct" two-state route differs from the parallel multistep pathway described for this system, which involves nonspecific contacts and at least two intermediate species that must involve substantial conformational rearrangement in either or both macromolecules.

  18. United States Space Explorations 1958

    NASA Technical Reports Server (NTRS)

    1962-01-01

    United States Space Explorations 1958. The film describes preparation and launch of five satellites and two space probes during 1958. On January 31, a Jupiter vehicle launched Explorer I into space. Data from this satellite was used to identify the van Allen radiation belts. On March 17, a Vanguard I rocket launched an Earth satellite with solar batteries. Data from the mission was used to determine that the Earth is slightly pear-shaped. On March 26, Explorer III was launched to further study the van Allen belts, micrometeoroid impacts, and internal and external temperatures. Explorer IV, launched on July 26, was intended to study radiation and temperature data. A lunar probe, ABLE I, was intended to measure radiation, magnetic fields of Earth and the Moon, density of micrometeoric matter, and internal temperatures. A four-stage rocket was used in the launch. However, a turbo-pump failed and the liquid oxygen pump stopped, resulting in a failed mission. On October 10, Pioneer I was launched by an ABLE vehicle. First and second stage velocity was less than desired and the probe did not leave Earth orbit. Attempts to attain escape velocity were unsuccessful. On December, a Jupiter boost vehicle was used to launch Juno II, with Pioneer III as the payload. Escape velocity was reached and Pioneer III left Earth's atmosphere. Failed launches, such as those of Vanguard boost vehicles and several Explorer satellites, also added to scientific knowledge. [Entire movie available on DVD from CASI as Doc ID 20070030963. Contact help@sti.nasa.gov

  19. Entanglement transitions in random definite particle states

    SciTech Connect

    Vijayaraghavan, Vikram S.; Bhosale, Udaysinh T.; Lakshminarayan, Arul

    2011-09-15

    Entanglements within qubits are studied for the subspace of definite particle states or definite number of up spins. A transition from an algebraic decay of entanglement within two qubits with the total number N of qubits to an exponential one when the number of particles is increased from two to three is studied in detail. In particular the probability that the concurrence is nonzero is calculated using statistical methods and is shown to agree with numerical simulations. Further entanglement within a block of m qubits is studied using the log-negativity measure, which indicates that a transition from algebraic to exponential decay occurs when the number of particles exceeds m. Several algebraic exponents for the decay of the log negativity are analytically calculated. The transition is shown to be possibly connected to the changes in the density of states of the reduced density matrix, which has a divergence at the zero eigenvalue when the entanglement decays algebraically.

  20. Adaptive single replica multiple state transition interface sampling

    NASA Astrophysics Data System (ADS)

    Du, Wei-Na; Bolhuis, Peter G.

    2013-07-01

    The multiple state transition path sampling method allows sampling of rare transitions between many metastable states, but has the drawback that switching between qualitatively different pathways is difficult. Combination with replica exchange transition interface sampling can in principle alleviate this problem, but requires a large number of simultaneous replicas. Here we remove these drawbacks by introducing a single replica sampling algorithm that samples only one interface at a time, while efficiently walking through the entire path space using a Wang-Landau approach or, alternatively, a fixed bias. We illustrate the method on several model systems: a particle diffusing in a simple 2D potential, isomerization in a small Lennard Jones cluster, and isomerization of the alanine dipeptide in explicit water.

  1. Transition state theory for enzyme kinetics.

    PubMed

    Truhlar, Donald G

    2015-09-15

    This article is an essay that discusses the concepts underlying the application of modern transition state theory to reactions in enzymes. Issues covered include the potential of mean force, the quantization of vibrations, the free energy of activation, and transmission coefficients to account for nonequilibrium effect, recrossing, and tunneling.

  2. Transition state theory for enzyme kinetics

    PubMed Central

    Truhlar, Donald G.

    2015-01-01

    This article is an essay that discusses the concepts underlying the application of modern transition state theory to reactions in enzymes. Issues covered include the potential of mean force, the quantization of vibrations, the free energy of activation, and transmission coefficients to account for nonequilibrium effect, recrossing, and tunneling. PMID:26008760

  3. Reversible State Transition in Nanoconfined Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Zhao, Liang; Wang, Chunlei; Liu, Jian; Wen, Binghai; Tu, Yusong; Wang, Zuowei; Fang, Haiping

    2014-02-01

    Using molecular dynamics simulations, we find a reversible transition between the dispersion and aggregation states of solute molecules in aqueous solutions confined in nanoscale geometry, which is not observed in macroscopic systems. The nanoscale confinement also leads to a significant increase of the critical aggregation concentration (CAC). A theoretical model based on Gibbs free energy calculation is developed to describe the simulation results. It indicates that the reversible state transition is attributed to the low free energy barrier (of order kBT) in between two energy minima corresponding to the dispersion and aggregation states, and the enhancement of the CAC results from the fact that at lower concentrations the number of solute molecules is not large enough to allow the formation of a stable cluster in the confined systems.

  4. A Model of Mental State Transition Network

    NASA Astrophysics Data System (ADS)

    Xiang, Hua; Jiang, Peilin; Xiao, Shuang; Ren, Fuji; Kuroiwa, Shingo

    Emotion is one of the most essential and basic attributes of human intelligence. Current AI (Artificial Intelligence) research is concentrating on physical components of emotion, rarely is it carried out from the view of psychology directly(1). Study on the model of artificial psychology is the first step in the development of human-computer interaction. As affective computing remains unpredictable, creating a reasonable mental model becomes the primary task for building a hybrid system. A pragmatic mental model is also the fundament of some key topics such as recognition and synthesis of emotions. In this paper a Mental State Transition Network Model(2) is proposed to detect human emotions. By a series of psychological experiments, we present a new way to predict coming human's emotions depending on the various current emotional states under various stimuli. Besides, people in different genders and characters are taken into consideration in our investigation. According to the psychological experiments data derived from 200 questionnaires, a Mental State Transition Network Model for describing the transitions in distribution among the emotions and relationships between internal mental situations and external are concluded. Further more the coefficients of the mental transition network model were achieved. Comparing seven relative evaluating experiments, an average precision rate of 0.843 is achieved using a set of samples for the proposed model.

  5. Entangled states and superradiant phase transitions

    SciTech Connect

    Aparicio Alcalde, M.; Cardenas, A. H.; Svaiter, N. F.; Bezerra, V. B.

    2010-03-15

    The full Dicke model is composed of a single bosonic mode and an ensemble of N identical two-level atoms. In the model, the coupling between the bosonic mode and the atoms generates resonant and nonresonant processes. We also consider a dipole-dipole interaction between the atoms, which is able to generate entangled states in the atomic system. By assuming thermal equilibrium with a reservoir at temperature {beta}{sup -1}, the transition from fluorescent to superradiant phase and the quantum phase transition are investigated. It is shown that the critical behavior of the full Dicke model is not modified by the introduction of the dipole-dipole interaction.

  6. See Your State From Space!

    USGS Publications Warehouse

    ,

    2008-01-01

    Each of the 50 States in the United States is beautiful in its own way. That beauty can be seen from a unique perspective using satellite images taken from high above the Earth. These State images were created from multiple satellite images stitched together into one seamless image for each State. Names of major cities, administrative boundaries, and State flags have been added.

  7. Transition State Analog Inhibitors for Esterases.

    DTIC Science & Technology

    1983-06-02

    advanced about 1970, it has led to the synthesis of powerful reversible Inhibitors for a number of enzymes. More recently, transition state analog theory...to inactivate It. Organophosphate anticholinesterases are a classic example; many of the more recent examples allow the enzyme to generate a strong...could be utilized to explore such mechanistic questions. A second more practical goal was to prepare anticholinesterases of novel structure and

  8. State-transition diagrams for biologists.

    PubMed

    Bersini, Hugues; Klatzmann, David; Six, Adrien; Thomas-Vaslin, Véronique

    2012-01-01

    It is clearly in the tradition of biologists to conceptualize the dynamical evolution of biological systems in terms of state-transitions of biological objects. This paper is mainly concerned with (but obviously not limited too) the immunological branch of biology and shows how the adoption of UML (Unified Modeling Language) state-transition diagrams can ease the modeling, the understanding, the coding, the manipulation or the documentation of population-based immune software model generally defined as a set of ordinary differential equations (ODE), describing the evolution in time of populations of various biological objects. Moreover, that same UML adoption naturally entails a far from negligible representational economy since one graphical item of the diagram might have to be repeated in various places of the mathematical model. First, the main graphical elements of the UML state-transition diagram and how they can be mapped onto a corresponding ODE mathematical model are presented. Then, two already published immune models of thymocyte behavior and time evolution in the thymus, the first one originally conceived as an ODE population-based model whereas the second one as an agent-based one, are refactored and expressed in a state-transition form so as to make them much easier to understand and their respective code easier to access, to modify and run. As an illustrative proof, for any immunologist, it should be possible to understand faithfully enough what the two software models are supposed to reproduce and how they execute with no need to plunge into the Java or Fortran lines.

  9. State-Transition Diagrams for Biologists

    PubMed Central

    Bersini, Hugues; Klatzmann, David; Six, Adrien; Thomas-Vaslin, Véronique

    2012-01-01

    It is clearly in the tradition of biologists to conceptualize the dynamical evolution of biological systems in terms of state-transitions of biological objects. This paper is mainly concerned with (but obviously not limited too) the immunological branch of biology and shows how the adoption of UML (Unified Modeling Language) state-transition diagrams can ease the modeling, the understanding, the coding, the manipulation or the documentation of population-based immune software model generally defined as a set of ordinary differential equations (ODE), describing the evolution in time of populations of various biological objects. Moreover, that same UML adoption naturally entails a far from negligible representational economy since one graphical item of the diagram might have to be repeated in various places of the mathematical model. First, the main graphical elements of the UML state-transition diagram and how they can be mapped onto a corresponding ODE mathematical model are presented. Then, two already published immune models of thymocyte behavior and time evolution in the thymus, the first one originally conceived as an ODE population-based model whereas the second one as an agent-based one, are refactored and expressed in a state-transition form so as to make them much easier to understand and their respective code easier to access, to modify and run. As an illustrative proof, for any immunologist, it should be possible to understand faithfully enough what the two software models are supposed to reproduce and how they execute with no need to plunge into the Java or Fortran lines. PMID:22844438

  10. Transition to the space shuttle operations era

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The tasks involved in the Space Shuttle Development Program are discussed. The ten major characteristics of an operational Shuttle are described, as well as the changes occurring in Shuttle processing, on-line operations, operations engineering, and support operations. A summary is given of tasks and goals that are being pursued in the effort to create a cost effective and efficient system.

  11. Symmetry calculation for molecules and transition states.

    PubMed

    Vandewiele, Nick M; Van de Vijver, Ruben; Van Geem, Kevin M; Reyniers, Marie-Françoise; Marin, Guy B

    2015-01-30

    The symmetry of molecules and transition states of elementary reactions is an essential property with important implications for computational chemistry. The automated identification of symmetry by computers is a very useful tool for many applications, but often relies on the availability of three-dimensional coordinates of the atoms in the molecule and hence becomes less useful when these coordinates are a priori unavailable. This article presents a new algorithm that identifies symmetry of molecules and transition states based on an augmented graph representation of the corresponding structures, in which both topology and the presence of stereocenters are accounted for. The automorphism group order of the graph associated with the molecule or transition state is used as a starting point. A novel concept of label-stereoisomers, that is, stereoisomers that arise after labeling homomorph substituents in the original molecule so that they become distinguishable, is introduced and used to obtain the symmetry number. The algorithm is characterized by its generic nature and avoids the use of heuristic rules that would limit the applicability. The calculated symmetry numbers are in agreement with expected values for a large and diverse set of structures, ranging from asymmetric, small molecules such as fluorochlorobromomethane to highly symmetric structures found in drug discovery assays. The new algorithm opens up new possibilities for the fast screening of the degree of symmetry of large sets of molecules.

  12. Coherent states in the fermionic Fock space

    NASA Astrophysics Data System (ADS)

    Oeckl, Robert

    2015-01-01

    We construct the coherent states in the sense of Gilmore and Perelomov for the fermionic Fock space. Our treatment is from the outset adapted to the infinite-dimensional case. The fermionic Fock space becomes in this way a reproducing kernel Hilbert space of continuous holomorphic functions.

  13. Transitioning research to application in the area of space weather at ESA

    NASA Astrophysics Data System (ADS)

    Hilgers, Alain; Glover, Alexi; Daly, Eamonn; Luntama, Juha-Pekka

    This presentation gives an overview of the past and current ESA space weather research ac-tivities and discusses the approaches used or foreseen for transitioning research products into application. Since its establishment ESA has supported and coordinated space weather re-search through its various programmes. The scientific programme has especially contributed to the investigation of key scientific aspects of space weather phenomena while the technology and research programmes targeted the effects of space environments on space systems. In 1998 ESA has started consultations among member states and performed studies to identify the requirements for a future European wide space weather application programme encompassing monitoring and forecasting services to support and protect the operation of space and ground based systems. As a by-product, structural developments were made including the establish-ment of a network of space weather service prototypes (SWENET). In 2008 the council of ESA decided to initiate a Space Situational Awareness (SSA) programme including space weather as one of the pillars together with space surveillance and near-Earth objects elements. Since the Space Weather element is planned to primarily rely on relevant existing assets it will provide a framework for transitioning several research assets of ESA and its member states to operational components of the overall system. Other paths will be considered for other assets which are not directly relevant to the SSA programme or which are still in a early research stage.

  14. State-Space Formulation for Circuit Analysis

    ERIC Educational Resources Information Center

    Martinez-Marin, T.

    2010-01-01

    This paper presents a new state-space approach for temporal analysis of electrical circuits. The method systematically obtains the state-space formulation of nondegenerate linear networks without using concepts of topology. It employs nodal/mesh systematic analysis to reduce the number of undesired variables. This approach helps students to…

  15. PAMELA Space Mission: The Transition Radiation Detector

    NASA Astrophysics Data System (ADS)

    Ambriola, M.; Bellotti, R.; Cafagna, F.; Circella, M.; De Marzo, C.; Giglietto, N.; Marangelli, B.; Mirizzi, N.; Romita, M.; Spinelli, P.

    2003-07-01

    PAMELA telescope is a satellite-b orne magnetic spectrometer built to fulfill the primary scientific objectives of detecting antiparticles (antiprotons and positrons) in the cosmic rays, and to measure spectra of particles in cosmic rays. The PAMELA telescope is currently under integration and is composed of: a silicon tracker housed in a permanent magnet, a time of flight and an anticoincidence system both made of plastic scintillators, a silicon imaging calorimeter, a neutron detector and a Transition Radiation Detector (TRD). The TRD detector is composed of 9 sensitive layers of straw tubes working in proportional mode for a total of 1024 channels. Each layer is interleaved with a radiator plane made of carbon fibers. The TRD detector characteristics will be described along with its performance studied exposing the detector to particle beams of electrons, pions, muons and protons of different momenta at both CERN-PS and CERN-SPS facilities.

  16. Projective loop quantum gravity. I. State space

    NASA Astrophysics Data System (ADS)

    Lanéry, Suzanne; Thiemann, Thomas

    2016-12-01

    Instead of formulating the state space of a quantum field theory over one big Hilbert space, it has been proposed by Kijowski to describe quantum states as projective families of density matrices over a collection of smaller, simpler Hilbert spaces. Beside the physical motivations for this approach, it could help designing a quantum state space holding the states we need. In a latter work by Okolów, the description of a theory of Abelian connections within this framework was developed, an important insight being to use building blocks labeled by combinations of edges and surfaces. The present work generalizes this construction to an arbitrary gauge group G (in particular, G is neither assumed to be Abelian nor compact). This involves refining the definition of the label set, as well as deriving explicit formulas to relate the Hilbert spaces attached to different labels. If the gauge group happens to be compact, we also have at our disposal the well-established Ashtekar-Lewandowski Hilbert space, which is defined as an inductive limit using building blocks labeled by edges only. We then show that the quantum state space presented here can be thought as a natural extension of the space of density matrices over this Hilbert space. In addition, it is manifest from the classical counterparts of both formalisms that the projective approach allows for a more balanced treatment of the holonomy and flux variables, so it might pave the way for the development of more satisfactory coherent states.

  17. State Transitions in Chlamydomonas reinhardtii. The Role of the Mehler Reaction in State 2-to-State 1 Transition1

    PubMed Central

    Forti, Giorgio; Caldiroli, Giovanni

    2005-01-01

    The light intensity-dependent transition to state 1 of dark-adapted anaerobic state 2 Chlamydomonas reinhardtii cells is stimulated by oxygen and by other electron acceptors for photosystem I, such as oxaloacetate and methylviologen. This suggests that the transition to state 1 requires the oxidation of the intersystem chain by photosystem I photochemistry. On the other hand, the mere oxidation in the dark of the chain—by addition of O2—leads only to a slow and incomplete transition. The light-driven stimulation by O2 of the state 1 transition is saturated at an O2 concentration of 15 to 20 μm, definitely higher than that of respiration. We suggest that this may represent the affinity for oxygen of the Mehler reaction, a conclusion that is confirmed by the observations that mitochondrial respiration is apparently not involved in modulating state 2-to-state 1 transition. The catalysis of the state 2-to-state 1 transition upon illumination of anaerobically adapted algae might represent, therefore, a relevant physiological role of this process in C. reinhardtii. PMID:15591440

  18. Identifying the order of a quantum phase transition by means of Wehrl entropy in phase space.

    PubMed

    Castaños, Octavio; Calixto, Manuel; Pérez-Bernal, Francisco; Romera, Elvira

    2015-11-01

    We propose a method to identify the order of a quantum phase transition by using area measures of the ground state in phase space. We illustrate our proposal by analyzing the well known example of the quantum cusp and four different paradigmatic boson models: Dicke, Lipkin-Meshkov-Glick, interacting boson model, and vibron model.

  19. Identifying the order of a quantum phase transition by means of Wehrl entropy in phase space

    NASA Astrophysics Data System (ADS)

    Castaños, Octavio; Calixto, Manuel; Pérez-Bernal, Francisco; Romera, Elvira

    2015-11-01

    We propose a method to identify the order of a quantum phase transition by using area measures of the ground state in phase space. We illustrate our proposal by analyzing the well known example of the quantum cusp and four different paradigmatic boson models: Dicke, Lipkin-Meshkov-Glick, interacting boson model, and vibron model.

  20. Cell Fate Decision as High-Dimensional Critical State Transition

    PubMed Central

    Zhou, Joseph; Castaño, Ivan G.; Leong-Quong, Rebecca Y. Y.; Chang, Hannah; Trachana, Kalliopi; Giuliani, Alessandro; Huang, Sui

    2016-01-01

    Cell fate choice and commitment of multipotent progenitor cells to a differentiated lineage requires broad changes of their gene expression profile. But how progenitor cells overcome the stability of their gene expression configuration (attractor) to exit the attractor in one direction remains elusive. Here we show that commitment of blood progenitor cells to the erythroid or myeloid lineage is preceded by the destabilization of their high-dimensional attractor state, such that differentiating cells undergo a critical state transition. Single-cell resolution analysis of gene expression in populations of differentiating cells affords a new quantitative index for predicting critical transitions in a high-dimensional state space based on decrease of correlation between cells and concomitant increase of correlation between genes as cells approach a tipping point. The detection of “rebellious cells” that enter the fate opposite to the one intended corroborates the model of preceding destabilization of a progenitor attractor. Thus, early warning signals associated with critical transitions can be detected in statistical ensembles of high-dimensional systems, offering a formal theory-based approach for analyzing single-cell molecular profiles that goes beyond current computational pattern recognition, does not require knowledge of specific pathways, and could be used to predict impending major shifts in development and disease. PMID:28027308

  1. The Applied Meteorology Unit: Nineteen Years Successfully Transitioning Research Into Operations for America's Space Program

    NASA Technical Reports Server (NTRS)

    Madura, John T.; Bauman, William H., III; Merceret, Francis J.; Roeder, William P.; Brody, Frank C.; Hagemeyer, Bartlett C.

    2011-01-01

    The Applied Meteorology Unit (AMU) provides technology development and transition services to improve operational weather support to America's space program . The AMU was founded in 1991 and operates under a triagency Memorandum of Understanding (MOU) between the National Aeronautics and Space Administration (NASA), the United States Air Force (USAF) and the National Weather Service (NWS) (Ernst and Merceret, 1995). It is colocated with the 45th Weather Squadron (45WS) at Cape Canaveral Air Force Station (CCAFS) and funded by the Space Shuttle Program . Its primary customers are the 45WS, the Spaceflight Meteorology Group (SMG) operated for NASA by the NWS at the Johnson Space Center (JSC) in Houston, TX, and the NWS forecast office in Melbourne, FL (MLB). The gap between research and operations is well known. All too frequently, the process of transitioning research to operations fails for various reasons. The mission of the AMU is in essence to bridge this gap for America's space program.

  2. United States Space Explorations 1958

    NASA Technical Reports Server (NTRS)

    1962-01-01

    The film describes preparation and launch of five satellites and two space probes during 1958. On January 31, a Jupiter vehicle launched Explorer I into space. Data from this satellite was used to identify the van Allen radiation belts. On March 17, a Vanguard I rocket launched an Earth satellite with solar batteries. Data from the mission was used to determine that the Earth is slightly pear-shaped. On March 26, Explorer III was launched to further study the van Allen belts, micrometeoroid impacts, and internal and external temperatures. Explorer IV, launched on July 26, was intended to study radiation and temperature data. A lunar probe, ABLE I, was intended to measure radiation, magnetic fields of Earth and the Moon, density of micrometeoric matter, and internal temperatures. A four-stage rocket was used in the launch. However, a turbo-pump failed and the liquid oxygen pump stopped, resulting in a failed mission. On October 10, Pioneer I was launched by an ABLE vehicle. First and second stage velocity was less than desired and the probe did not leave Earth orbit. Attempts to attain escape velocity were unsuccessful. On December, a Jupiter boost vehicle was used to launch Juno II, with Pioneer III as the payload. Escape velocity was reached and Pioneer III left Earth's atmosphere. Failed launches, such as those of Vanguard boost vehicles and several Explorer satellites, also added to scientific knowledge.

  3. Wetting reversal at gelation transition freezes thermodynamically unstable states.

    PubMed

    Hirayama, Shinya; Sano, Masahito

    2013-07-23

    The contact angle of a drop of gelling solution on a flat, solid surface was monitored as the hot solution was allowed to cool. When a solvent with a high cohesive energy and a wettable solid surface was used, a wetting solution turned into a dewetting solid at the gelation transition. The density profiles in gel as probed by confocal Raman microscopy reveal that the adsorption of both gelator and solvent shifts at the transition and the solvent is severely depleted from the interfacial region. Thus, the wetting reversal is accompanied by the interfacial desolvation. As a result of the adsorption shift during the gelation process in progress, a locally concentrated region of the gelator is frozen in space far away from the surface. This is a thermodynamically unstable state but can be realized reproducibly. The profile analysis also shows that the effect of the surface extends out to a few hundred micrometers, 2 orders of magnitude larger than the bulk correlation length.

  4. Contractive Maps in Locally Transitive Relational Metric Spaces

    PubMed Central

    2014-01-01

    Some fixed point results are given for a class of Meir-Keeler contractive maps acting on metric spaces endowed with locally transitive relations. Technical connections with the related statements due to Berzig et al. (2014) are also being discussed. PMID:24737960

  5. Transition From NASA Space Communication Systems to Commerical Communication Products

    NASA Technical Reports Server (NTRS)

    Ghazvinian, Farzad; Lindsey, William C.

    1994-01-01

    Transitioning from twenty-five years of space communication system architecting, engineering and development to creating and marketing of commercial communication system hardware and software products is no simple task for small, high-tech system engineering companies whose major source of revenue has been the U.S. Government. Yet, many small businesses are faced with this onerous and perplexing task. The purpose of this talk/paper is to present one small business (LinCom) approach to taking advantage of the systems engineering expertise and knowledge captured in physical neural networks and simulation software by supporting numerous National Aeronautics and Space Administration (NASA) and the Department of Defense (DoD) projects, e.g., Space Shuttle, TDRSS, Space Station, DCSC, Milstar, etc. The innovative ingredients needed for a systems house to transition to a wireless communication system products house that supports personal communication services and networks (PCS and PCN) development in a global economy will be discussed. Efficient methods for using past government sponsored space system research and development to transition to VLSI communication chip set products will be presented along with notions of how synergy between government and industry can be maintained to benefit both parties.

  6. Human DNMT1 transition state structure.

    PubMed

    Du, Quan; Wang, Zhen; Schramm, Vern L

    2016-03-15

    Human DNA methyltransferase 1 (DNMT1) maintains the epigenetic state of DNA by replicating CpG methylation signatures from parent to daughter strands, producing heritable methylation patterns through cell divisions. The proposed catalytic mechanism of DNMT1 involves nucleophilic attack of Cys(1226) to cytosine (Cyt) C6, methyl transfer from S-adenosyl-l-methionine (SAM) to Cyt C5, and proton abstraction from C5 to form methylated CpG in DNA. Here, we report the subangstrom geometric and electrostatic structure of the major transition state (TS) of the reaction catalyzed by human DNMT1. Experimental kinetic isotope effects were used to guide quantum mechanical calculations to solve the TS structure. Methyl transfer occurs after Cys(1226) attack to Cyt C6, and the methyl transfer step is chemically rate-limiting for DNMT1. Electrostatic potential maps were compared for the TS and ground states, providing the electronic basis for interactions between the protein and reactants at the TS. Understanding the TS of DNMT1 demonstrates the possibility of using similar analysis to gain subangstrom geometric insight into the complex reactions of epigenetic modifications.

  7. Human DNMT1 transition state structure

    PubMed Central

    Du, Quan; Wang, Zhen; Schramm, Vern L.

    2016-01-01

    Human DNA methyltransferase 1 (DNMT1) maintains the epigenetic state of DNA by replicating CpG methylation signatures from parent to daughter strands, producing heritable methylation patterns through cell divisions. The proposed catalytic mechanism of DNMT1 involves nucleophilic attack of Cys1226 to cytosine (Cyt) C6, methyl transfer from S-adenosyl-l-methionine (SAM) to Cyt C5, and proton abstraction from C5 to form methylated CpG in DNA. Here, we report the subangstrom geometric and electrostatic structure of the major transition state (TS) of the reaction catalyzed by human DNMT1. Experimental kinetic isotope effects were used to guide quantum mechanical calculations to solve the TS structure. Methyl transfer occurs after Cys1226 attack to Cyt C6, and the methyl transfer step is chemically rate-limiting for DNMT1. Electrostatic potential maps were compared for the TS and ground states, providing the electronic basis for interactions between the protein and reactants at the TS. Understanding the TS of DNMT1 demonstrates the possibility of using similar analysis to gain subangstrom geometric insight into the complex reactions of epigenetic modifications. PMID:26929335

  8. State space forecasting and noise reduction

    SciTech Connect

    Eubank, S.; Casdagli, M.; Farmer, J.D.; Gibson, J.

    1990-01-01

    We discuss the effects of nonlinearity and noise on the problem of finding states and dynamics. We point out problems which arise in the construction of state space models for scalar time series. We describe solutions for the case when error due to noise dominates parameter estimation error and outline a framework for the general case.

  9. Transit Imaging and Spectroscopy with the James Webb Space Telescope

    NASA Technical Reports Server (NTRS)

    Clampin, Mark

    2008-01-01

    The James Webb Space Telescope (JWST) is a large aperture (6.5 meter), cryogenic space telescope with a suite of near and mid-infrared instruments covering the wavelength range of 0.6 microns to 28 microns. JWST's primary science goal is to detect and characterize the first galaxies. It will also study the assembly of galaxies, star formation, and the formation of evolution of planetary systems. Recent progress in hardware development for the observatory will be presented, including a discussion of the status of JWST's optical system and Beryllium mirror fabrication, progress with sunshield prototypes, and recent changes in the integration and test configuration. We also review the expected scientific performance of the observatory for observations of exosolar planets by means of transit imaging and spectroscopy. We will review the capabilities of each science instrument, and discuss the performance of each mode, with reference to current transiting systems.

  10. International Space Station: Transitional Platform for Moon and Mars

    NASA Technical Reports Server (NTRS)

    Greeniesen, Michael C.

    2006-01-01

    Humans on the path to Mars are employing the Space Station to better understand the Life Sciences issues during long duration space flight. In this phase the problems, for example, of bone loss, skeletal muscle atrophy and radiation will be prioritized for countermeasure development. This presentation will feature NASA's critical path to the Moon and Mars as the initial blueprint for addressing these Human Life Sciences challenges necessary to accomplish a successful Mars transit, surface exploration and return to Earth. A Moon base will be the test bed for resolving the engineering obstacles for later establishment of the Mars Crew Habitat. Current engineering concept scenarios for Moon and Mars bases plus Mars transit vehicles will receive the final focus.

  11. How Accurate Are Transition States from Simulations of Enzymatic Reactions?

    PubMed Central

    2015-01-01

    The rate expression of traditional transition state theory (TST) assumes no recrossing of the transition state (TS) and thermal quasi-equilibrium between the ground state and the TS. Currently, it is not well understood to what extent these assumptions influence the nature of the activated complex obtained in traditional TST-based simulations of processes in the condensed phase in general and in enzymes in particular. Here we scrutinize these assumptions by characterizing the TSs for hydride transfer catalyzed by the enzyme Escherichia coli dihydrofolate reductase obtained using various simulation approaches. Specifically, we compare the TSs obtained with common TST-based methods and a dynamics-based method. Using a recently developed accurate hybrid quantum mechanics/molecular mechanics potential, we find that the TST-based and dynamics-based methods give considerably different TS ensembles. This discrepancy, which could be due equilibrium solvation effects and the nature of the reaction coordinate employed and its motion, raises major questions about how to interpret the TSs determined by common simulation methods. We conclude that further investigation is needed to characterize the impact of various TST assumptions on the TS phase-space ensemble and on the reaction kinetics. PMID:24860275

  12. Estimation of State Transition Probabilities: A Neural Network Model

    NASA Astrophysics Data System (ADS)

    Saito, Hiroshi; Takiyama, Ken; Okada, Masato

    2015-12-01

    Humans and animals can predict future states on the basis of acquired knowledge. This prediction of the state transition is important for choosing the best action, and the prediction is only possible if the state transition probability has already been learned. However, how our brains learn the state transition probability is unknown. Here, we propose a simple algorithm for estimating the state transition probability by utilizing the state prediction error. We analytically and numerically confirmed that our algorithm is able to learn the probability completely with an appropriate learning rate. Furthermore, our learning rule reproduced experimentally reported psychometric functions and neural activities in the lateral intraparietal area in a decision-making task. Thus, our algorithm might describe the manner in which our brains learn state transition probabilities and predict future states.

  13. Coherent states in projected Hilbert spaces

    NASA Astrophysics Data System (ADS)

    Drummond, P. D.; Reid, M. D.

    2016-12-01

    Coherent states in a projected Hilbert space have many useful properties. When there are conserved quantities, a representation of the entire Hilbert space is not necessary. The same issue arises when conditional observations are made with postselected measurement results. In these cases, only a part of the Hilbert space needs to be represented, and one can define this restriction by way of a projection operator. Here coherent state bases and normally ordered phase-space representations are introduced for treating such projected Hilbert spaces, including existence theorems and dynamical equations. These techniques are very useful in studying novel optical or microwave integrated photonic quantum technologies, such as boson sampling or Josephson quantum computers. In these cases, states become strongly restricted due to inputs, nonlinearities, or conditional measurements. This paper focuses on coherent phase states, which have especially simple properties. Practical applications are reported on calculating recurrences in anharmonic oscillators, the effects of arbitrary phase noise on Schrödinger cat fringe visibility, and on boson sampling interferometry for large numbers of modes.

  14. State space control of frequency standards

    NASA Astrophysics Data System (ADS)

    Koppang, Paul A.

    2016-06-01

    Discrete time control systems are widely used in time and frequency applications. Control systems can be designed to reduce phase and frequency offsets to a given reference either more or less aggressively depending on overall system needs. There are many methods available to aid in designing control systems, including techniques based on state space system models. Several state space control design methods will be shown. The control concepts covered in this paper are pole placement, minimum control effort, and linear quadratic Gaussian. The effects of steering limits on system performance will also be discussed.

  15. Transitions among the diverse oscillation quenching states induced by the interplay of direct and indirect coupling

    NASA Astrophysics Data System (ADS)

    Ghosh, Debarati; Banerjee, Tanmoy

    2014-12-01

    We report the transitions among different oscillation quenching states induced by the interplay of diffusive (direct) coupling and environmental (indirect) coupling in coupled identical oscillators. This coupling scheme was introduced by Resmi et al. [Phys. Rev. E 84, 046212 (2011), 10.1103/PhysRevE.84.046212] as a general scheme to induce amplitude death (AD) in nonlinear oscillators. Using a detailed bifurcation analysis we show that, in addition to AD, which actually occurs only in a small region of parameter space, this coupling scheme can induce other oscillation quenching states, namely oscillation death (OD) and a novel nontrvial AD (NAD) state, which is a nonzero bistable homogeneous steady state; more importantly, this coupling scheme mediates a transition from the AD state to the OD state and a new transition from the AD state to the NAD state. We identify diverse routes to the NAD state and map all the transition scenarios in the parameter space for periodic oscillators. Finally, we present the first experimental evidence of oscillation quenching states and their transitions induced by the interplay of direct and indirect coupling.

  16. The transition to the metallic state in low density hydrogen.

    PubMed

    McMinis, Jeremy; Morales, Miguel A; Ceperley, David M; Kim, Jeongnim

    2015-11-21

    Solid atomic hydrogen is one of the simplest systems to undergo a metal-insulator transition. Near the transition, the electronic degrees of freedom become strongly correlated and their description provides a difficult challenge for theoretical methods. As a result, the order and density of the phase transition are still subject to debate. In this work, we use diffusion quantum Monte Carlo to benchmark the transition between paramagnetic and anti-ferromagnetic body centered cubic atomic hydrogen in its ground state. We locate the density of the transition by computing the equation of state for these two phases and identify the phase transition order by computing the band gap near the phase transition. These benchmark results show that the phase transition is continuous and occurs at a Wigner-Seitz radius of rs = 2.27(3) a0. We compare our results to previously reported density functional theory, Hedin's GW approximation, and dynamical mean field theory results.

  17. Interplanetary Transit Simulations Using the International Space Station

    NASA Technical Reports Server (NTRS)

    Charles, John B.; Arya, M.; Kundrot, C. E.

    2010-01-01

    We evaluated the space life sciences utility of the International Space Station (ISS) to simulate the outbound transit portion of missions to Mars and Near Earth Asteroids (NEA) to investigate biomedical and psychological aspects of such transits, to develop and test space operation procedures compatible with communication delays and outages, and to demonstrate and validate technologies and countermeasures. Two major categories of space life sciences activities can capitalize on ISS capabilities. The first includes studies that require ISS (or a comparable facility), typically for access to prolonged weightlessness. The second includes studies that do not strictly require ISS but can exploit it to maximize their scientific return more efficiently and productively than in ground-based simulations. For these studies, ISS offers a high fidelity analog for fundamental factors on future missions, such as crew composition, mission control personnel, operational tasks and workload, real-world risk, and isolation, and can mimic the effects of distance and limited accessibility. In addition to conducting Mars- and NEA-transit simulations on 6-month ISS increments, extending the current ISS increment duration from 6 months to 9 or even 12 months will provide opportunities for enhanced and focused research relevant to long duration Mars and NEA missions. Increasing the crew duration may pose little additional risk to crewmembers beyond that currently accepted on 6-month increments, but additional medical monitoring capabilities will be required beyond those currently used for ISS operations. Finally, while presenting major logistical challenges, such a simulation followed by a post-landing simulation of Mars exploration could provide quantitative evidence of capabilities in an actual mission. Thus, the use of ISS to simulate aspects of Mars and NEA missions seems practical. If it were to be implemented without major disruption of on-going ISS activities, then planning should

  18. State Space Grids: Analyzing Dynamics across Development

    ERIC Educational Resources Information Center

    Hollenstein, Tom

    2007-01-01

    Developmentalists are generally interested in systems perspectives and this is reflected in the theoretical models of the past decade. However, the methodological tools to test these models are either nonexistent or difficult for many researchers to use. This article reviews the state space grid (SSG) method for analyzing synchronized event…

  19. The Variable Transition State in Polar Additions to Pi Bonds

    ERIC Educational Resources Information Center

    Weiss, Hilton M.

    2010-01-01

    A vast majority of polar additions of Bronsted acids to alkynes involve a termolecular transition state. With strong acids, considerable positive charge is developed on carbon and Markovnikov addition predominates. In less acidic solutions, however, the reaction is much slower and the transition state more closely resembles the olefinic product.…

  20. Path Flow Estimation Using Time Varying Coefficient State Space Model

    NASA Astrophysics Data System (ADS)

    Jou, Yow-Jen; Lan, Chien-Lun

    2009-08-01

    The dynamic path flow information is very crucial in the field of transportation operation and management, i.e., dynamic traffic assignment, scheduling plan, and signal timing. Time-dependent path information, which is important in many aspects, is nearly impossible to be obtained. Consequently, researchers have been seeking estimation methods for deriving valuable path flow information from less expensive traffic data, primarily link traffic counts of surveillance systems. This investigation considers a path flow estimation problem involving the time varying coefficient state space model, Gibbs sampler, and Kalman filter. Numerical examples with part of a real network of the Taipei Mass Rapid Transit with real O-D matrices is demonstrated to address the accuracy of proposed model. Results of this study show that this time-varying coefficient state space model is very effective in the estimation of path flow compared to time-invariant model.

  1. Analytical expressions for partial wave two-body Coulomb transition matrices at ground-state energy

    NASA Astrophysics Data System (ADS)

    Kharchenko, V. F.

    2016-11-01

    Leaning upon the Fock method of the stereographic projection of the three-dimensional momentum space onto the four-dimensional unit sphere the possibility of the analytical solving of the Lippmann-Schwinger integral equation for the partial wave two-body Coulomb transition matrix at the ground bound state energy has been studied. In this case new expressions for the partial p-, d- and f-wave two-body Coulomb transition matrices have been obtained in the simple analytical form. The developed approach can also be extended to determine analytically the partial wave Coulomb transition matrices at the energies of excited bound states.

  2. From 3-geometry transition amplitudes to graviton states

    NASA Astrophysics Data System (ADS)

    Mattei, Federico; Rovelli, Carlo; Speziale, Simone; Testa, Massimo

    2006-04-01

    In various background independent approaches, quantum gravity is defined in terms of a field propagation kernel: a sum over paths interpreted as a transition amplitude between 3-geometries, expected to project quantum states of the geometry on the solutions of the Wheeler-deWitt equation. We study the relation between this formalism and conventional quantum field theory methods. We consider the propagation kernel of 4d Lorentzian general relativity in the temporal gauge, defined by a conventional formal Feynman path integral, gauge fixed à la Faddeev-Popov. If space is compact, this turns out to depend only on the initial and final 3-geometries, while in the asymptotically flat case it depends also on the asymptotic proper time. We compute the explicit form of this kernel at first order around flat space, and show that it projects on the solutions of all quantum constraints, including the Wheeler-DeWitt equation, and yields the correct vacuum and n-graviton states. We also illustrate how the Newtonian interaction is coded into the propagation kernel, a key open issue in the spinfoam approach.

  3. Space Surveillance: United States, Russia, and China

    NASA Astrophysics Data System (ADS)

    Seidelmann, P. K.

    2012-06-01

    With the launch of Sputnik, the United States and Russia began the process of tracking artificial satellites. This led to developments for observations, orbit determination, and catalog maintenance. The two countries followed somewhat different approaches to the same problem based on the available hardware and theoretical developments. As more sophisticated hardware and theories have been developed, progress has been made. However, new problems have developed because of debris, collision possibilities, and reentering objects. In addition, the range of spacecraft has increased to include geosynchronous orbits. In more recent times the European Space Agency (ESA) and China have become involved in various aspects of Space Surveillance. In 1994, the first meeting between United States and Russian experts in the field of space surveillance was held. Since then, seven more US Russia Space Surveillance Workshops have been held, with the addition of participants from ESA. Terry Alfriend has been the US Technical Chairman for many of these workshops. In 2009 a US China Space Surveillance Technical Interchange was held in Shanghai, China, and Terry was the US Technical Chairman.

  4. A flexible transition state searching method for atmospheric reaction systems

    NASA Astrophysics Data System (ADS)

    Lin, Xiao-Xiao; Liu, Yi-Rong; Huang, Teng; Chen, Jiao; Jiang, Shuai; Huang, Wei

    2015-04-01

    The precise and rapid exploration of transition states (TSs) is a major challenge when studying atmospheric reactions due to their complexity. In this work, a Monte Carlo Transition State Search Method (MCTSSM), which integrates Monte Carlo sampling technique with transition state optimization methods using an efficient computer script, has been developed for transition state searches. The efficiency and the potential application in atmospheric reactions of this method have been demonstrated by three types of test suits related to the reactions of atmospheric volatile organic compounds (VOCs): (1) OH addition, (2) OH hydrogen-abstraction, and (3) the other reactive group (e.g. Cl, O3, NO3), especially for the reaction of β-pinene-sCI (stabilized Criegee Intermediates) with water. It was shown that the application of this method with effective restricted parameters has greatly simplified the time-consuming and tedious manual search procedure for transition state (TS) of the bimolecular reaction systems.

  5. A Flexible Transition State Searching Method for Atmospheric Reaction Systems

    SciTech Connect

    Lin, Xiao-Xiao; Liu, Yi-Rong; Huang, Teng; Chen, Jiao; Jiang, Shuai; Huang, Wei

    2015-04-01

    The precise and rapid exploration of transition states (TSs) is a major challenge when studying atmospheric reactions due to their complexity. In this work, a Monte Carlo Transition State Search Method (MCTSSM), which integrates Monte Carlo sampling technique with transition state optimization methods using an efficient computer script, has been developed for transition state searches. The efficiency and the potential application in atmospheric reactions of this method have been demonstrated by three types of test suits related to the reactions of atmospheric volatile organic compounds (VOCs): (1) OH addition, (2) OH hydrogen-abstraction, and (3) the other reactive group (e.g. Cl, O3, NO3), especially for the reaction of β-pinene-sCI (stabilized Criegee Intermediates) with water. It was shown that the application of this method with effective restricted parameters has greatly simplified the time-consuming and tedious manual search procedure for transition state (TS) of the bimolecular reaction systems.

  6. Markov Chain evaluation of acute postoperative pain transition states

    PubMed Central

    Tighe, Patrick J.; Bzdega, Matthew; Fillingim, Roger B.; Rashidi, Parisa; Aytug, Haldun

    2016-01-01

    Prior investigations on acute postoperative pain dynamicity have focused on daily pain assessments, and so were unable to examine intra-day variations in acute pain intensity. We analyzed 476,108 postoperative acute pain intensity ratings clinically documented on postoperative days 1 to 7 from 8,346 surgical patients using Markov Chain modeling to describe how patients are likely to transition from one pain state to another in a probabilistic fashion. The Markov Chain was found to be irreducible and positive recurrent, with no absorbing states. Transition probabilities ranged from 0.0031 for the transition from state 10 to state 1, to 0.69 for the transition from state zero to state zero. The greatest density of transitions was noted in the diagonal region of the transition matrix, suggesting that patients were generally most likely to transition to the same pain state as their current state. There were also slightly increased probability densities in transitioning to a state of asleep or zero from the current state. Examination of the number of steps required to traverse from a particular first pain score to a target state suggested that overall, fewer steps were required to reach a state of zero (range 6.1–8.8 steps) or asleep (range 9.1–11) than were required to reach a mild pain intensity state. Our results suggest that Markov Chains are a feasible method for describing probabilistic postoperative pain trajectories, pointing toward the possibility of using Markov decision processes to model sequential interactions between pain intensity ratings and postoperative analgesic interventions. PMID:26588689

  7. Transition pathways between solid and liquid state in suspensions.

    PubMed

    Heymann, Lutz; Aksel, Nuri

    2007-02-01

    Suspensions containing rigid monodisperse spherical particles in a Newtonian carrier liquid are investigated experimentally, providing evidence for solid and liquid states in a transient shear rate from rest. Between these two states a transition takes place; the transition pathways from solid to liquid and from liquid to solid being different. The dynamics of the transition are shown, with the material in this regime reacting as a highly nonlinear system. This involves inverting the input to output and vice versa and comparing them. A key feature of the transition regime is a material instability caused by the collapse of the particle network structure.

  8. Space Shuttle Boundary Layer Transition Flight Experiment Ground Testing Overview

    NASA Technical Reports Server (NTRS)

    Berger, Karen T.; Anderson, Brian P.; Campbell, Charles H.

    2014-01-01

    In support of the Boundary Layer Transition (BLT) Flight Experiment (FE) Project in which a manufactured protuberance tile was installed on the port wing of Space Shuttle Orbiter Discovery for STS-119, STS- 128, STS-131 and STS-133 as well as Space Shuttle Orbiter Endeavour for STS-134, a significant ground test campaign was completed. The primary goals of the test campaign were to provide ground test data to support the planning and safety certification efforts required to fly the flight experiment as well as validation for the collected flight data. These test included Arcjet testing of the tile protuberance, aerothermal testing to determine the boundary layer transition behavior and resultant surface heating and planar laser induced fluorescence (PLIF) testing in order to gain a better understanding of the flow field characteristics associated with the flight experiment. This paper provides an overview of the BLT FE Project ground testing. High-level overviews of the facilities, models, test techniques and data are presented, along with a summary of the insights gained from each test.

  9. Improving Upon String Methods for Transition State Discovery.

    PubMed

    Chaffey-Millar, Hugh; Nikodem, Astrid; Matveev, Alexei V; Krüger, Sven; Rösch, Notker

    2012-02-14

    Transition state discovery via application of string methods has been researched on two fronts. The first front involves development of a new string method, named the Searching String method, while the second one aims at estimating transition states from a discretized reaction path. The Searching String method has been benchmarked against a number of previously existing string methods and the Nudged Elastic Band method. The developed methods have led to a reduction in the number of gradient calls required to optimize a transition state, as compared to existing methods. The Searching String method reported here places new beads on a reaction pathway at the midpoint between existing beads, such that the resolution of the path discretization in the region containing the transition state grows exponentially with the number of beads. This approach leads to favorable convergence behavior and generates more accurate estimates of transition states from which convergence to the final transition states occurs more readily. Several techniques for generating improved estimates of transition states from a converged string or nudged elastic band have been developed and benchmarked on 13 chemical test cases. Optimization approaches for string methods, and pitfalls therein, are discussed.

  10. A State Charter School Law in Transition

    ERIC Educational Resources Information Center

    Fox, Robert A.; Buchanan, Nina K.

    2006-01-01

    State-by-state comparison of charter school laws is complicated by the wide variation in terminology and by the idiosyncratic impact that interpretation and implementation by mid-level administrators has on the actual way in which charter school laws work. In this regard, each state is different and true comparison can best be accomplished by…

  11. Modeling volatility using state space models.

    PubMed

    Timmer, J; Weigend, A S

    1997-08-01

    In time series problems, noise can be divided into two categories: dynamic noise which drives the process, and observational noise which is added in the measurement process, but does not influence future values of the system. In this framework, we show that empirical volatilities (the squared relative returns of prices) exhibit a significant amount of observational noise. To model and predict their time evolution adequately, we estimate state space models that explicitly include observational noise. We obtain relaxation times for shocks in the logarithm of volatility ranging from three weeks (for foreign exchange) to three to five months (for stock indices). In most cases, a two-dimensional hidden state is required to yield residuals that are consistent with white noise. We compare these results with ordinary autoregressive models (without a hidden state) and find that autoregressive models underestimate the relaxation times by about two orders of magnitude since they do not distinguish between observational and dynamic noise. This new interpretation of the dynamics of volatility in terms of relaxators in a state space model carries over to stochastic volatility models and to GARCH models, and is useful for several problems in finance, including risk management and the pricing of derivative securities. Data sets used: Olsen & Associates high frequency DEM/USD foreign exchange rates (8 years). Nikkei 225 index (40 years). Dow Jones Industrial Average (25 years).

  12. Linear canonical transformations of coherent and squeezed states in the Wigner phase space. II - Quantitative analysis

    NASA Technical Reports Server (NTRS)

    Han, D.; Kim, Y. S.; Noz, Marilyn E.

    1989-01-01

    It is possible to calculate expectation values and transition probabilities from the Wigner phase-space distribution function. Based on the canonical transformation properties of the Wigner function, an algorithm is developed for calculating these quantities in quantum optics for coherent and squeezed states. It is shown that the expectation value of a dynamical variable can be written in terms of its vacuum expectation value of the canonically transformed variable. Parallel-axis theorems are established for the photon number and its variant. It is also shown that the transition probability between two squeezed states can be reduced to that of the transition from one squeezed state to vacuum.

  13. The State of Space Propulsion Research

    NASA Technical Reports Server (NTRS)

    Sackheim, R. L.; Cole, J. W.; Litchford, R. J.

    2006-01-01

    The current state of space propulsion research is assessed from both a historical perspective, spanning the decades since Apollo, and a forward-looking perspective, as defined by the enabling technologies required for a meaningful and sustainable human and robotic exploration program over the forthcoming decades. Previous research and technology investment approaches are examined and a course of action suggested for obtaining a more balanced portfolio of basic and applied research. The central recommendation is the establishment of a robust national Space Propulsion Research Initiative that would run parallel with systems development and include basic research activities. The basic framework and technical approach for this proposed initiative are defined and a potential implementation approach is recommended.

  14. Transition voltages of vacuum-spaced and molecular junctions with Ag and Pt electrodes

    SciTech Connect

    Wu, Kunlin; Bai, Meilin; Hou, Shimin; Sanvito, Stefano

    2014-07-07

    The transition voltage of vacuum-spaced and molecular junctions constructed with Ag and Pt electrodes is investigated by non-equilibrium Green's function formalism combined with density functional theory. Our calculations show that, similarly to the case of Au-vacuum-Au previously studied, the transition voltages of Ag and Pt metal-vacuum-metal junctions with atomic protrusions on the electrode surface are determined by the local density of states of the p-type atomic orbitals of the protrusion. Since the energy position of the Pt 6p atomic orbitals is higher than that of the 5p/6p of Ag and Au, the transition voltage of Pt-vacuum-Pt junctions is larger than that of both Ag-vacuum-Ag and Au-vacuum-Au junctions. When one moves to analyzing asymmetric molecular junctions constructed with biphenyl thiol as central molecule, then the transition voltage is found to depend on the specific bonding site for the sulfur atom in the thiol group. In particular agreement with experiments, where the largest transition voltage is found for Ag and the smallest for Pt, is obtained when one assumes S binding at the hollow-bridge site on the Ag/Au(111) surface and at the adatom site on the Pt(111) one. This demonstrates the critical role played by the linker-electrode binding geometry in determining the transition voltage of devices made of conjugated thiol molecules.

  15. Grassland-shrubland state transitions in arid lands: Competition matters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background/Question/Methods: State transition from grassland to shrubland is synonymous with desertification in many dryland systems. The classic desertification model emphasizes abiotic feedbacks that modify the physical environment in ways that promote shrub proliferation and impede grass survival...

  16. Transition radiation detectors: state of art and new developments

    NASA Astrophysics Data System (ADS)

    Mazziotta, M. N.; Brigida, M.; Favuzzi, C.; Fusco, P.; Gargano, F.; Giglietto, N.; Giordano, F.; Loparco, F.; Marangelli, B.; Mirizzi, N.; Rainò, S.; Spinelli, P.

    2005-08-01

    Transition radiation (TR) is emitted whenever a fast particle (γ > 1000) crosses the boundaries of a periodic structure. Since the prediction of this effect, many studies and tests have been accomplished to understand both the features of this radiation and the eventual practical applications. Nowadays. the main application of TR is particle identification in accelerator physics and astrophysics. Particle identification is one of the most challenging aspect of the experiments performed in these fields. In fact the experimental problems arisen in the recent accelerator physics pose stringent constraints on the detectors due to the high rates, severe background conditions, event final state complexity. On the other hand, the cosmic ray physics requires in some cases simple but refined and reliable devices to be used in outer space or otherwise huge and stable apparata for surface and underground laboratories. After a brief presentation of the TR phenomenon produced by ultrarelativistic particles and relative detectors, the state of the art of this particle identification technique relative to the more recent TRDs will be discussed.

  17. Avoiding traps in trajectory space: Metadynamics enhanced transition path sampling

    NASA Astrophysics Data System (ADS)

    Borrero, E. E.; Dellago, C.

    2016-10-01

    We propose a transition path sampling (TPS) scheme designed to enhance sampling in systems with multiple reaction channels. In this method, based on a combination of the metadynamics algorithm with the TPS shooting move, a history dependent bias drives the simulation towards unexplored reaction channels. The bias, constructed as a superposition of repulsive Gaussian potentials deposited on the trajectories harvested in the course of the simulation, acts only during the initial stage of the trajectory generation, but leaves the dynamics along the trajectories unaffected such that the sampled pathways are true dynamical trajectories. Simulations carried out for two test systems indicate that the new approach effortlessly switches between distinct reaction channels even if they are separated by high barriers in trajectory space.

  18. The transition radiation detector of the PAMELA space mission

    NASA Astrophysics Data System (ADS)

    Ambriola, M.; Bellotti, R.; Cafagna, F.; Circella, M.; de Marzo, C.; Giglietto, N.; Marangelli, B.; Mirizzi, N.; Romita, M.; Spinelli, P.

    2004-04-01

    PAMELA space mission objective is to flight a satellite-borne magnetic spectrometer built to fulfill the primary scientific goals of detecting antiparticles (antiprotons and positrons) and to measure spectra of particles in cosmic rays. The PAMELA telescope is composed of: a silicon tracker housed in a permanent magnet, a time-of-flight and an anticoincidence system both made of plastic scintillators, a silicon imaging calorimeter, a neutron detector and a Transition Radiation Detector (TRD). The TRD is composed of nine sensitive layers of straw tubes working in proportional mode for a total of 1024 channels. Each layer is interleaved with a radiator plane made of carbon fibers. The TRD characteristics will be described along with its performances studied at both CERN-PS and CERN-SPS facilities, using electrons, pions, muons and protons of different momenta.

  19. η' transition form factor from space- and timelike experimental data

    NASA Astrophysics Data System (ADS)

    Escribano, R.; Gonzàlez-Solís, S.; Masjuan, P.; Sanchez-Puertas, P.

    2016-09-01

    The η' transition form factor is reanalyzed in view of the recent first observation by BESIII of the Dalitz decay η'→γ e+e- in both space- and timelike regions at low and intermediate energies using the Padé approximants method. The present analysis provides a suitable parametrization for reproducing the measured form factor in the whole energy region and allows one to extract the corresponding low-energy parameters together with a prediction of their values at the origin, related to Γη'→γ γ , and the asymptotic limit. The η - η' mixing is reassessed within a mixing scheme compatible with the large-Nc chiral perturbation theory at next-to-leading order, with particular attention to the Okubo-Zweig-Iizuka-rule-violating parameters. The J /ψ , Z →η(')γ decays are also considered and predictions are reported.

  20. Simultaneous transitions in cuprate momentum-space topology and electronic symmetry breaking.

    PubMed

    Fujita, K; Kim, Chung Koo; Lee, Inhee; Lee, Jinho; Hamidian, M H; Firmo, I A; Mukhopadhyay, S; Eisaki, H; Uchida, S; Lawler, M J; Kim, E-A; Davis, J C

    2014-05-09

    The existence of electronic symmetry breaking in the underdoped cuprates and its disappearance with increased hole density p are now widely reported. However, the relation between this transition and the momentum-space (k-space) electronic structure underpinning the superconductivity has not yet been established. Here, we visualize the Q = 0 (intra-unit-cell) and Q ≠ 0 (density-wave) broken-symmetry states, simultaneously with the coherent k-space topology, for Bi₂Sr₂CaCu₂O(8+δ) samples spanning the phase diagram 0.06 ≤ p ≤ 0.23. We show that the electronic symmetry-breaking tendencies weaken with increasing p and disappear close to a critical doping p(c) = 0.19. Concomitantly, the coherent k-space topology undergoes an abrupt transition, from arcs to closed contours, at the same p(c). These data reveal that the k-space topology transformation in cuprates is linked intimately with the disappearance of the electronic symmetry breaking at a concealed critical point.

  1. Enhancing pairwise state-transition weights: A new weighting scheme in simulated tempering that can minimize transition time between a pair of conformational states

    NASA Astrophysics Data System (ADS)

    Qiao, Qin; Zhang, Hou-Dao; Huang, Xuhui

    2016-04-01

    Simulated tempering (ST) is a widely used enhancing sampling method for Molecular Dynamics simulations. As one expanded ensemble method, ST is a combination of canonical ensembles at different temperatures and the acceptance probability of cross-temperature transitions is determined by both the temperature difference and the weights of each temperature. One popular way to obtain the weights is to adopt the free energy of each canonical ensemble, which achieves uniform sampling among temperature space. However, this uniform distribution in temperature space may not be optimal since high temperatures do not always speed up the conformational transitions of interest, as anti-Arrhenius kinetics are prevalent in protein and RNA folding. Here, we propose a new method: Enhancing Pairwise State-transition Weights (EPSW), to obtain the optimal weights by minimizing the round-trip time for transitions among different metastable states at the temperature of interest in ST. The novelty of the EPSW algorithm lies in explicitly considering the kinetics of conformation transitions when optimizing the weights of different temperatures. We further demonstrate the power of EPSW in three different systems: a simple two-temperature model, a two-dimensional model for protein folding with anti-Arrhenius kinetics, and the alanine dipeptide. The results from these three systems showed that the new algorithm can substantially accelerate the transitions between conformational states of interest in the ST expanded ensemble and further facilitate the convergence of thermodynamics compared to the widely used free energy weights. We anticipate that this algorithm is particularly useful for studying functional conformational changes of biological systems where the initial and final states are often known from structural biology experiments.

  2. The photon-plasmon transitions and diagnostics of the space plasma turbulence

    NASA Astrophysics Data System (ADS)

    Glushkov, Alexander; Glushkov, Alexander; Khetselius, Olga

    We present a new approach to treating the space plasma turbulence, based on using to make diagnostic data regarding the photon-plasmon transitions. The theoretical definition of characteristics for these transitions is caried out within consistent theoretical approach, based on the Gell-Mann and Low formalism (energy approach in QED theory).We apply it to calculation of such transitions (Ps) with emission of photon and Langmuir quanta. It is well known that the hfs states of positronium Ps Ps differ in spin S, life time t and mode of annihilation. As a rule, probabilities of the cascade radiation transitions are more than the annihilation probability. The ortho-Ps atom has a metastable state 23s1 and probability of two-photon radiation transition from this state into 13s1 state (1.8•10(-3) 1/s) is significantly less than probability of the three-photon annihilation directly from 23s1level 8.9•10(5) s(-1), i.e. it is usually supposed that the ortho-Ps annihilates from 23s1state. Another situation may take place in plasma, where it is arisen the competition process of destruction of the metastable level - the photonplasmon transition 23s1-13s1with emission of photon and Langmuir quanta. In this paper we carried out the calculation of the probability of the Ps photon-plasmon transition and propose tu use it for diagnostics of the space plasma (dusty one etc.).Standard S-matrix calculation with using an expression for tensor of dielectric permeability of the isotropic space plasma and dispersion relationships for transverse and Langmuir waves [3] allows getting the corresponding probability P(ph-pl). Numerical value of P(ph-pl) is 5.2•10(6)•UL(s-1), where UL is density of the Langmuir waves energy. Our value is correlated with estimate, available in literature [3]: P(phpl)= 6•10(6)•UL (s-1). Comparison of the obtained probability with the life time t(3) allows getting the condition of predominance of the photon-plasmon transition over three

  3. Presence of state transitions in the cryptophyte alga Guillardia theta.

    PubMed

    Cheregi, Otilia; Kotabová, Eva; Prášil, Ondřej; Schröder, Wolfgang P; Kaňa, Radek; Funk, Christiane

    2015-10-01

    Plants and algae have developed various regulatory mechanisms for optimal delivery of excitation energy to the photosystems even during fluctuating light conditions; these include state transitions as well as non-photochemical quenching. The former process maintains the balance by redistributing antennae excitation between the photosystems, meanwhile the latter by dissipating excessive excitation inside the antennae. In the present study, these mechanisms have been analysed in the cryptophyte alga Guillardia theta. Photoprotective non-photochemical quenching was observed in cultures only after they had entered the stationary growth phase. These cells displayed a diminished overall photosynthetic efficiency, measured as CO2 assimilation rate and electron transport rate. However, in the logarithmic growth phase G. theta cells redistributed excitation energy via a mechanism similar to state transitions. These state transitions were triggered by blue light absorbed by the membrane integrated chlorophyll a/c antennae, and green light absorbed by the lumenal biliproteins was ineffective. It is proposed that state transitions in G. theta are induced by small re-arrangements of the intrinsic antennae proteins, resulting in their coupling/uncoupling to the photosystems in state 1 or state 2, respectively. G. theta therefore represents a chromalveolate algae able to perform state transitions.

  4. Interplanetary Transit Simulations Using the International Space Station

    NASA Technical Reports Server (NTRS)

    Charles, J. B.; Arya, Maneesh

    2010-01-01

    It has been suggested that the International Space Station (ISS) be utilized to simulate the transit portion of long-duration missions to Mars and near-Earth asteroids (NEA). The ISS offers a unique environment for such simulations, providing researchers with a high-fidelity platform to study, enhance, and validate technologies and countermeasures for these long-duration missions. From a space life sciences perspective, two major categories of human research activities have been identified that will harness the various capabilities of the ISS during the proposed simulations. The first category includes studies that require the use of the ISS, typically because of the need for prolonged weightlessness. The ISS is currently the only available platform capable of providing researchers with access to a weightless environment over an extended duration. In addition, the ISS offers high fidelity for other fundamental space environmental factors, such as isolation, distance, and accessibility. The second category includes studies that do not require use of the ISS in the strictest sense, but can exploit its use to maximize their scientific return more efficiently and productively than in ground-based simulations. In addition to conducting Mars and NEA simulations on the ISS, increasing the current increment duration on the ISS from 6 months to a longer duration will provide opportunities for enhanced and focused research relevant to long-duration Mars and NEA missions. Although it is currently believed that increasing the ISS crew increment duration to 9 or even 12 months will pose little additional risk to crewmembers, additional medical monitoring capabilities may be required beyond those currently used for the ISS operations. The use of the ISS to simulate aspects of Mars and NEA missions seems practical, and it is recommended that planning begin soon, in close consultation with all international partners.

  5. State Machine Modeling of the Space Launch System Solid Rocket Boosters

    NASA Technical Reports Server (NTRS)

    Harris, Joshua A.; Patterson-Hine, Ann

    2013-01-01

    The Space Launch System is a Shuttle-derived heavy-lift vehicle currently in development to serve as NASA's premiere launch vehicle for space exploration. The Space Launch System is a multistage rocket with two Solid Rocket Boosters and multiple payloads, including the Multi-Purpose Crew Vehicle. Planned Space Launch System destinations include near-Earth asteroids, the Moon, Mars, and Lagrange points. The Space Launch System is a complex system with many subsystems, requiring considerable systems engineering and integration. To this end, state machine analysis offers a method to support engineering and operational e orts, identify and avert undesirable or potentially hazardous system states, and evaluate system requirements. Finite State Machines model a system as a finite number of states, with transitions between states controlled by state-based and event-based logic. State machines are a useful tool for understanding complex system behaviors and evaluating "what-if" scenarios. This work contributes to a state machine model of the Space Launch System developed at NASA Ames Research Center. The Space Launch System Solid Rocket Booster avionics and ignition subsystems are modeled using MATLAB/Stateflow software. This model is integrated into a larger model of Space Launch System avionics used for verification and validation of Space Launch System operating procedures and design requirements. This includes testing both nominal and o -nominal system states and command sequences.

  6. Thermal effects and space-charge limited transition in crossed-field devices

    SciTech Connect

    Marini, Samuel; Rizzato, Felipe B.; Pakter, Renato

    2014-08-15

    A fully kinetic model for the electron flow in a crossed field device is derived and used to determine the system stationary states. It is found that for low injection temperatures, there is a simultaneous presence of distinct stationary solutions and an abrupt transition between accelerating and space-charge limited regimes. On the other hand, for high injection temperatures, there is only a single stationary solution branch and the change between the regimes becomes continuous. For intermediate temperatures, it is then identified a critical point that separates the abrupt and continuous behaviors. It is also investigated how intrinsic space-charge oscillations may drive stationary states unstable in certain parameter regimes. The results are verified with N-particle self-consistent simulations.

  7. Performance and state-space analyses of systems using Petri nets

    NASA Technical Reports Server (NTRS)

    Watson, James Francis, III

    1992-01-01

    The goal of any modeling methodology is to develop a mathematical description of a system that is accurate in its representation and also permits analysis of structural and/or performance properties. Inherently, trade-offs exist between the level detail in the model and the ease with which analysis can be performed. Petri nets (PN's), a highly graphical modeling methodology for Discrete Event Dynamic Systems, permit representation of shared resources, finite capacities, conflict, synchronization, concurrency, and timing between state changes. By restricting the state transition time delays to the family of exponential density functions, Markov chain analysis of performance problems is possible. One major drawback of PN's is the tendency for the state-space to grow rapidly (exponential complexity) compared to increases in the PN constructs. It is the state space, or the Markov chain obtained from it, that is needed in the solution of many problems. The theory of state-space size estimation for PN's is introduced. The problem of state-space size estimation is defined, its complexities are examined, and estimation algorithms are developed. Both top-down and bottom-up approaches are pursued, and the advantages and disadvantages of each are described. Additionally, the author's research in non-exponential transition modeling for PN's is discussed. An algorithm for approximating non-exponential transitions is developed. Since only basic PN constructs are used in the approximation, theory already developed for PN's remains applicable. Comparison to results from entropy theory show the transition performance is close to the theoretic optimum. Inclusion of non-exponential transition approximations improves performance results at the expense of increased state-space size. The state-space size estimation theory provides insight and algorithms for evaluating this trade-off.

  8. The transition to the metallic state in low density hydrogen

    SciTech Connect

    McMinis, Jeremy; Morales, Miguel A.; Ceperley, David M.; Kim, Jeongnim

    2015-11-21

    Solid atomic hydrogen is one of the simplest systems to undergo a metal-insulator transition. Near the transition, the electronic degrees of freedom become strongly correlated and their description provides a difficult challenge for theoretical methods. As a result, the order and density of the phase transition are still subject to debate. In this work, we use diffusion quantum Monte Carlo to benchmark the transition between paramagnetic and anti-ferromagnetic body centered cubic atomic hydrogen in its ground state. We locate the density of the transition by computing the equation of state for these two phases and identify the phase transition order by computing the band gap near the phase transition. These benchmark results show that the phase transition is continuous and occurs at a Wigner-Seitz radius of r{sub s} = 2.27(3) a{sub 0}. We compare our results to previously reported density functional theory, Hedin’s GW approximation, and dynamical mean field theory results.

  9. The transition to the metallic state in low density hydrogen

    SciTech Connect

    McMinis, Jeremy; Morales, Miguel A.; Ceperley, David M.; Kim, Jeongnim

    2015-11-18

    Solid atomic hydrogen is one of the simplest systems to undergo a metal-insulator transition. Near the transition, the electronic degrees of freedom become strongly correlated and their description provides a difficult challenge for theoretical methods. As a result, the order and density of the phase transition are still subject to debate. In this work we use diffusion quantum Monte Carlo to benchmark the transition between the paramagnetic and anti-ferromagnetic phases of ground state body centered cubic atomic hydrogen. We locate the density of the transition by computing the equation of state for these two phases and identify the phase transition order by computing the band gap near the phase transition. These benchmark results show that the phase transition is continuous and occurs at a Wigner-Seitz radius of rs = 2.27(3)a0. As a result, we compare our results to previously reported density functional theory, Hedin s GW approximation, and dynamical mean field theory results.

  10. New York State's Transition to Stability: The Demographic Outlook.

    ERIC Educational Resources Information Center

    Morrison, Peter A.

    The paper highlights economic and social problems that current population trends in New York State are likely to create. Major features of population change in New York are: (1) transition from steady growth to near stability; (2) an end to metropolitan growth statewide and the onset of decline in four of the state's ten Standard Metropolitan…

  11. State-to-State Mode Specificity: Energy Sequestration and Flow Gated by Transition State.

    PubMed

    Zhao, Bin; Sun, Zhigang; Guo, Hua

    2015-12-23

    Energy flow and sequestration at the state-to-state level are investigated for a prototypical four-atom reaction, H2 + OH → H + H2O, using a transition-state wave packet (TSWP) method. The product state distribution is found to depend strongly on the reactant vibrational excitation, indicating mode specificity at the state-to-state level. From a local-mode perspective, it is shown that the vibrational excitation of the H2O product derives from two different sources, one attributable to the energy flow along the reaction coordinate into the newly formed OH bond and the other due to the sequestration of the vibrational energy in the OH spectator moiety during the reaction. The analysis provided a unified interpretation of some seemingly contradicting experimental observations. It is further shown that the transfer of vibrational energy from the OH reactant to H2O product is gated by the transition state, accomplished coherently by multiple TSWPs with the corresponding OH vibrational excitation.

  12. Space and time renormalization in phase transition dynamics

    DOE PAGES

    Francuz, Anna; Dziarmaga, Jacek; Gardas, Bartłomiej; ...

    2016-02-18

    Here, when a system is driven across a quantum critical point at a constant rate, its evolution must become nonadiabatic as the relaxation time τ diverges at the critical point. According to the Kibble-Zurek mechanism (KZM), the emerging post-transition excited state is characterized by a finite correlation length ξˆ set at the time tˆ=τˆ when the critical slowing down makes it impossible for the system to relax to the equilibrium defined by changing parameters. This observation naturally suggests a dynamical scaling similar to renormalization familiar from the equilibrium critical phenomena. We provide evidence for such KZM-inspired spatiotemporal scaling by investigatingmore » an exact solution of the transverse field quantum Ising chain in the thermodynamic limit.« less

  13. Space and time renormalization in phase transition dynamics

    SciTech Connect

    Francuz, Anna; Dziarmaga, Jacek; Gardas, Bartłomiej; Zurek, Wojciech H.

    2016-02-18

    Here, when a system is driven across a quantum critical point at a constant rate, its evolution must become nonadiabatic as the relaxation time τ diverges at the critical point. According to the Kibble-Zurek mechanism (KZM), the emerging post-transition excited state is characterized by a finite correlation length ξˆ set at the time tˆ=τˆ when the critical slowing down makes it impossible for the system to relax to the equilibrium defined by changing parameters. This observation naturally suggests a dynamical scaling similar to renormalization familiar from the equilibrium critical phenomena. We provide evidence for such KZM-inspired spatiotemporal scaling by investigating an exact solution of the transverse field quantum Ising chain in the thermodynamic limit.

  14. Variation in Event-Related Potentials by State Transitions

    PubMed Central

    Higashi, Hiroshi; Minami, Tetsuto; Nakauchi, Shigeki

    2017-01-01

    The probability of an event's occurrence affects event-related potentials (ERPs) on electroencephalograms. The relation between probability and potentials has been discussed by using a quantity called surprise that represents the self-information that humans receive from the event. Previous studies have estimated surprise based on the probability distribution in a stationary state. Our hypothesis is that state transitions also play an important role in the estimation of surprise. In this study, we compare the effects of surprise on the ERPs based on two models that generate an event sequence: a model of a stationary state and a model with state transitions. To compare these effects, we generate the event sequences with Markov chains to avoid a situation that the state transition probability converges with the stationary probability by the accumulation of the event observations. Our trial-by-trial model-based analysis showed that the stationary probability better explains the P3b component and the state transition probability better explains the P3a component. The effect on P3a suggests that the internal model, which is constantly and automatically generated by the human brain to estimate the probability distribution of the events, approximates the model with state transitions because Bayesian surprise, which represents the degree of updating of the internal model, is highly reflected in P3a. The global effect reflected in P3b, however, may not be related to the internal model because P3b depends on the stationary probability distribution. The results suggest that an internal model can represent state transitions and the global effect is generated by a different mechanism than the one for forming the internal model. PMID:28289380

  15. Variation in Event-Related Potentials by State Transitions.

    PubMed

    Higashi, Hiroshi; Minami, Tetsuto; Nakauchi, Shigeki

    2017-01-01

    The probability of an event's occurrence affects event-related potentials (ERPs) on electroencephalograms. The relation between probability and potentials has been discussed by using a quantity called surprise that represents the self-information that humans receive from the event. Previous studies have estimated surprise based on the probability distribution in a stationary state. Our hypothesis is that state transitions also play an important role in the estimation of surprise. In this study, we compare the effects of surprise on the ERPs based on two models that generate an event sequence: a model of a stationary state and a model with state transitions. To compare these effects, we generate the event sequences with Markov chains to avoid a situation that the state transition probability converges with the stationary probability by the accumulation of the event observations. Our trial-by-trial model-based analysis showed that the stationary probability better explains the P3b component and the state transition probability better explains the P3a component. The effect on P3a suggests that the internal model, which is constantly and automatically generated by the human brain to estimate the probability distribution of the events, approximates the model with state transitions because Bayesian surprise, which represents the degree of updating of the internal model, is highly reflected in P3a. The global effect reflected in P3b, however, may not be related to the internal model because P3b depends on the stationary probability distribution. The results suggest that an internal model can represent state transitions and the global effect is generated by a different mechanism than the one for forming the internal model.

  16. Solid state neutron dosimeter for space applications

    SciTech Connect

    Nagarkar, V.; Entine, G.; Stoppel, P.; Cirignano, L. ); Swinehart, P. )

    1992-08-01

    One of the most important contributions to the radiation exposure of astronauts engaged in space flight is the significant flux of high energy neutrons arising from both primary and secondary sources of ionizing radiation. Under NASA sponsorship, the authors are developing a solid state neutron sensor capable of being incorporated into a very compact, flight instrument to provide high quality real time measurement of this important radiation flux. The dosimeter uses a special, high neutron sensitivity, PIN diode that is insensitive t the other forms of ionizing radiation. The dosimeter will have the ability to measure and record neutron dose over a range of 50 microgray to tens of milligrays (5 millirads to several rads) over a flight of up to 30 days. the performance characteristics of the PIN diode with a detailed description of the overall dosimeter is presented. in this paper.

  17. The transition to the metallic state in low density hydrogen

    DOE PAGES

    McMinis, Jeremy; Morales, Miguel A.; Ceperley, David M.; ...

    2015-11-18

    Solid atomic hydrogen is one of the simplest systems to undergo a metal-insulator transition. Near the transition, the electronic degrees of freedom become strongly correlated and their description provides a difficult challenge for theoretical methods. As a result, the order and density of the phase transition are still subject to debate. In this work we use diffusion quantum Monte Carlo to benchmark the transition between the paramagnetic and anti-ferromagnetic phases of ground state body centered cubic atomic hydrogen. We locate the density of the transition by computing the equation of state for these two phases and identify the phase transitionmore » order by computing the band gap near the phase transition. These benchmark results show that the phase transition is continuous and occurs at a Wigner-Seitz radius of rs = 2.27(3)a0. As a result, we compare our results to previously reported density functional theory, Hedin s GW approximation, and dynamical mean field theory results.« less

  18. Reshaping the College Transition: Early College Readiness Assessments and Transition Curricula in Four States. A State Policy Report

    ERIC Educational Resources Information Center

    Barnett, Elisabeth A.; Fay, Maggie P.; Trimble, Madeline Joy; Pheatt, Lara

    2013-01-01

    Based largely on interviews with stakeholders in California, New York, Tennessee, and West Virginia, this report describes how these states have established initiatives related to early college readiness assessments and transition curricula. It then compares the development of these interventions across states and identifies factors that have…

  19. Topological Lifshitz transitions

    NASA Astrophysics Data System (ADS)

    Volovik, G. E.

    2017-01-01

    Different types of Lifshitz transitions are governed by topology in momentum space. They involve the topological transitions with the change of topology of Fermi surfaces, Weyl and Dirac points, nodal lines, and also the transitions between the fully gapped states.

  20. United States/Russia Space Cooperation Documentary

    NASA Technical Reports Server (NTRS)

    1993-01-01

    This video documents the initiative to develop a multinational, permanent space research laboratory. Historical background on the U.S. and Soviet manned space flight program as well as joint efforts such as the Apollo-Soyuz link up is shown. The current initiative will begin with collaborative missions involving NASA's space shuttle and Russia's Mir space station, and culminate in a permanently manned space station involving the U.S., Russia, Japan, Canada, and ESA. Shown are computer simulations of the proposed space station. Commentary is provided by the NASA administrator, former astronauts, cosmonauts, and Russian and American space experts.

  1. Exploring the phase space of multiple states in highly turbulent Taylor-Couette flow

    NASA Astrophysics Data System (ADS)

    van der Veen, Roeland C. A.; Huisman, Sander G.; Dung, On-Yu; Tang, Ho L.; Sun, Chao; Lohse, Detlef

    2016-06-01

    We investigate the existence of multiple turbulent states in highly turbulent Taylor-Couette flow in the range of Ta =1011 to 9 ×1012 by measuring the global torques and the local velocities while probing the phase space spanned by the rotation rates of the inner and outer cylinders. The multiple states are found to be very robust and are expected to persist beyond Ta =1013 . The rotation ratio is the parameter that most strongly controls the transitions between the flow states; the transitional values only weakly depend on the Taylor number. However, complex paths in the phase space are necessary to unlock the full region of multiple states. By mapping the flow structures for various rotation ratios in a Taylor-Couette setup with an equal radius ratio but a larger aspect ratio than before, multiple states are again observed. Here they are characterized by even richer roll structure phenomena, including an antisymmetrical roll state.

  2. NASA's Space Launch Transitions: From Design to Production

    NASA Technical Reports Server (NTRS)

    Askins, Bruce; Robinson, Kimberly

    2016-01-01

    NASA's Space Launch System (SLS) successfully completed its Critical Design Review (CDR) in 2015, a major milestone on the journey to an unprecedented era of exploration for humanity. CDR formally marked the program's transition from design to production phase just four years after the program's inception and the first such milestone for a human launch vehicle in 40 years. While challenges typical of a complex development program lie ahead, CDR evaluators concluded that the design is technically and programmatically sound and ready to press forward to Design Certification Review (DCR) and readiness for launch of Exploration Mission 1 (EM-1) in the 2018 timeframe. SLS is prudently based on existing propulsion systems, infrastructure and knowledge with a clear, evolutionary path as required by mission needs. In its initial configuration, designated Block I, SLS will a minimum of 70 metric tons (t) of payload to low Earth orbit (LEO). It can evolve to a 130 t payload capacity by upgrading its engines, boosters, and upper stage, dramatically increasing the mass and volume of human and robotic exploration while decreasing mission risk, increasing safety, and simplifying ground and mission operations. CDR was the central programmatic accomplishment among many technical accomplishments that will be described in this paper. The government/industry SLS team successfully test fired a flight-like five-segment solid rocket motor, as well as seven hotfire development tests of the RS-25 core stage engine. The majority of the major test article and flight barrels, rings, and domes for the core stage liquid oxygen, liquid hydrogen, engine section, intertank, and forward skirt were manufactured at NASA's Michoud Assembly Facility. Renovations to the B-2 test stand for stage green run testing were completed at NASA Stennis Space Center. Core stage test stands are rising at NASA Marshall Space Flight Center. The modified Pegasus barge for core stage transportation from manufacturing

  3. NASA's Space Launch System Transitions From Design To Production

    NASA Technical Reports Server (NTRS)

    Askins, Bruce R.; Robinson, Kimberly F.

    2016-01-01

    NASA's Space Launch System (SLS) successfully completed its Critical Design Review (CDR) in 2015, a major milestone on the journey to an unprecedented era of exploration for humanity. CDR formally marked the program's transition from design to production phase just four years after the program's inception and the first such milestone for a human launch vehicle in 40 years. While challenges typical of a complex development program lie ahead, CDR evaluators concluded that the design is technically and programmatically sound and ready to press forward to Design Certification Review (DCR) and readiness for launch of Exploration Mission 1 (EM-1) in the 2018 timeframe. SLS is prudently based on existing propulsion systems, infrastructure and knowledge with a clear, evolutionary path as required by mission needs. In its initial configuration, designated Block 1, SLS will a minimum of 70 metric tons (t) (154,324 pounds) of payload to low Earth orbit (LEO). It will evolve to a 130 t (286,601 pound) payload capacity by upgrading its engines, boosters, and upper stage, dramatically increasing the mass and volume of human and robotic exploration while decreasing mission risk, increasing safety, and simplifying ground and mission operations. CDR was the central programmatic accomplishment among many technical accomplishments that will be described in this paper. The government/industry SLS team successfully test-fired a flight-like five-segment solid rocket motor, as well as seven hotfire development tests of the RS-25 core stage engine. The majority of the major test article and flight barrels, rings, and domes for the core stage liquid oxygen, liquid hydrogen, engine section, intertank, and forward skirt were manufactured at NASA's Michoud Assembly Facility in New Orleans, Louisiana. Renovations to the B-2 test stand for stage green run testing were completed at NASA's Stennis Space Center (SSC), near Bay St. Louis, Mississippi. Core stage test stands are reaching completion

  4. Elasticity of the transition state for oligonucleotide hybridization

    PubMed Central

    Whitley, Kevin D.; Comstock, Matthew J.; Chemla, Yann R.

    2017-01-01

    Despite its fundamental importance in cellular processes and abundant use in biotechnology, we lack a detailed understanding of the kinetics of nucleic acid hybridization. In particular, the identity of the transition state, which determines the kinetics of the two-state reaction, remains poorly characterized. Here, we used optical tweezers with single-molecule fluorescence to observe directly the binding and unbinding of short oligonucleotides (7–12 nt) to a complementary strand held under constant force. Binding and unbinding rate constants measured across a wide range of forces (1.5–20 pN) deviate from the exponential force dependence expected from Bell's equation. Using a generalized force dependence model, we determined the elastic behavior of the transition state, which we find to be similar to that of the pure single-stranded state. Our results indicate that the transition state for hybridization is visited before the strands form any significant amount of native base pairs. Such a transition state supports a model in which the rate-limiting step of the hybridization reaction is the alignment of the two strands prior to base pairing. PMID:27903889

  5. OptZyme: Computational Enzyme Redesign Using Transition State Analogues

    PubMed Central

    Grisewood, Matthew J.; Gifford, Nathanael P.; Pantazes, Robert J.; Li, Ye; Cirino, Patrick C.; Janik, Michael J.; Maranas, Costas D.

    2013-01-01

    OptZyme is a new computational procedure for designing improved enzymatic activity (i.e., kcat or kcat/KM) with a novel substrate. The key concept is to use transition state analogue compounds, which are known for many reactions, as proxies for the typically unknown transition state structures. Mutations that minimize the interaction energy of the enzyme with its transition state analogue, rather than with its substrate, are identified that lower the transition state formation energy barrier. Using Escherichia coli β-glucuronidase as a benchmark system, we confirm that KM correlates (R2 = 0.960) with the computed interaction energy between the enzyme and the para-nitrophenyl- β, D-glucuronide substrate, kcat/KM correlates (R2 = 0.864) with the interaction energy of the transition state analogue, 1,5-glucarolactone, and kcat correlates (R2 = 0.854) with a weighted combination of interaction energies with the substrate and transition state analogue. OptZyme is subsequently used to identify mutants with improved KM, kcat, and kcat/KM for a new substrate, para-nitrophenyl- β, D-galactoside. Differences between the three libraries reveal structural differences that underpin improving KM, kcat, or kcat/KM. Mutants predicted to enhance the activity for para-nitrophenyl- β, D-galactoside directly or indirectly create hydrogen bonds with the altered sugar ring conformation or its substituents, namely H162S, L361G, W549R, and N550S. PMID:24116038

  6. A new perspective on transition states: χ1 separatrix

    NASA Astrophysics Data System (ADS)

    Ledbetter, Paul J.; Clementi, Cecilia

    2011-07-01

    We present a new definition of the transition state for chemical reactions, named the χ1 separatrix. In contrast to previous transition state definitions which depend on the choice of reaction coordinates, the χ1 separatrix is defined by choosing a time scale for observation and is connected to exact rate constants in the high friction limit. We demonstrate that this separatrix appears in the isomerization of alanine dipeptide as a stationary population in quasi-equilibrium, without assuming a particular coordinate system or reactant and product surfaces.

  7. Markov-chain model of classified atomistic transition states for discrete kinetic Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Numazawa, Satoshi; Smith, Roger

    2011-10-01

    Classical harmonic transition state theory is considered and applied in discrete lattice cells with hierarchical transition levels. The scheme is then used to determine transitions that can be applied in a lattice-based kinetic Monte Carlo (KMC) atomistic simulation model. The model results in an effective reduction of KMC simulation steps by utilizing a classification scheme of transition levels for thermally activated atomistic diffusion processes. Thermally activated atomistic movements are considered as local transition events constrained in potential energy wells over certain local time periods. These processes are represented by Markov chains of multidimensional Boolean valued functions in three-dimensional lattice space. The events inhibited by the barriers under a certain level are regarded as thermal fluctuations of the canonical ensemble and accepted freely. Consequently, the fluctuating system evolution process is implemented as a Markov chain of equivalence class objects. It is shown that the process can be characterized by the acceptance of metastable local transitions. The method is applied to a problem of Au and Ag cluster growth on a rippled surface. The simulation predicts the existence of a morphology-dependent transition time limit from a local metastable to stable state for subsequent cluster growth by accretion. Excellent agreement with observed experimental results is obtained.

  8. Markov-chain model of classified atomistic transition states for discrete kinetic Monte Carlo simulations.

    PubMed

    Numazawa, Satoshi; Smith, Roger

    2011-10-01

    Classical harmonic transition state theory is considered and applied in discrete lattice cells with hierarchical transition levels. The scheme is then used to determine transitions that can be applied in a lattice-based kinetic Monte Carlo (KMC) atomistic simulation model. The model results in an effective reduction of KMC simulation steps by utilizing a classification scheme of transition levels for thermally activated atomistic diffusion processes. Thermally activated atomistic movements are considered as local transition events constrained in potential energy wells over certain local time periods. These processes are represented by Markov chains of multidimensional Boolean valued functions in three-dimensional lattice space. The events inhibited by the barriers under a certain level are regarded as thermal fluctuations of the canonical ensemble and accepted freely. Consequently, the fluctuating system evolution process is implemented as a Markov chain of equivalence class objects. It is shown that the process can be characterized by the acceptance of metastable local transitions. The method is applied to a problem of Au and Ag cluster growth on a rippled surface. The simulation predicts the existence of a morphology-dependent transition time limit from a local metastable to stable state for subsequent cluster growth by accretion. Excellent agreement with observed experimental results is obtained.

  9. Columbus State University Global Observation and Outreach for the 2012 Transit of Venus

    NASA Astrophysics Data System (ADS)

    Perry, Matthew; McCarty, C.; Bartow, M.; Hood, J. C.; Lodder, K.; Johnson, M.; Cruzen, S. T.; Williams, R. N.

    2013-01-01

    Faculty, staff and students from Columbus State University’s (CSU’s) Coca-Cola Space Science Center presented a webcast of the 2012 Transit of Venus from three continents to a global audience of 1.4 million unique viewers. Team members imaged the transit with telescopes using white-light, hydrogen-alpha, and calcium filters, from Alice Springs, Australia; the Gobi Desert, Mongolia; Bryce Canyon, UT; and Columbus, GA. Images were webcast live during the transit in partnership with NASA’s Sun-Earth Day program, and Science Center staff members were featured on NASA TV. Local members of the public were brought in for a series of outreach initiatives, in both Georgia and Australia, before and during the transit. The data recorded from the various locations have been archived for use in demonstrating principles such as the historical measurement of the astronomical unit.

  10. Transitioning From Space Physics Research to Space Weather Application at The Johns Hopkins University Applied Physics Laboratory (JHU/APL)

    NASA Astrophysics Data System (ADS)

    Meng, C. I.

    2003-12-01

    The ability to monitor and predict our near-Earth space environment ("space weather") lags its sister discipline of terrestrial weather studies by years, in both observational and forecast capabilities. However, with current rapid progress in space physics research, and with current and near-future space environment sensors on research and operational satellites, the space weather operational community can reach new levels of maturity. A rapid transition of scientific research results into prototype operational products is especially important. This paper addresses the concept of rapid transition and presents examples carried out recently by scientists at JHU/APL, such as: OVATION (Oval Variation, Assessment, Tracking, Intensity and Online Nowcasting), and real-time geomagnetic activity nowcasting using observations from limited ground magnetometer stations. Several potential future application projects will be discussed as well; these space-environment products are designed to coincide with operationally significant events, such as communication outages or space object tracking.

  11. Steady-state plasma transition in the Venus ionosheath

    NASA Technical Reports Server (NTRS)

    Perez-De-tejada, H.; Intriligator, D. S.; Strangeway, R. J.

    1991-01-01

    The results of an extended analysis of the plasma and electric field data of the Pioneer Venus Orbiter (PVO) are presented. The persistent presence of a plasma transition embedded in the flanks of the Venus ionosheath between the bow shock and the ionopause is reported. This transition is identified by the repeated presence of characteristic bursts in the 30 kHz channel of the electric field detector of the PVO. The observed electric field signals coincide with the onset of different plasma conditions in the inner ionosheath where more rarified plasma fluxes are measured. The repeated identification of this intermediate ionosheath transition in the PVO data indicates that it is present as a steady state feature of the Venus plasma environment. The distribution of PVO orbits in which the transition is observed suggests that it is more favorably detected in the vicinity of and downstream from the terminator.

  12. Europe/United States space activities

    NASA Technical Reports Server (NTRS)

    Bainum, P. M. (Editor); Von Bun, F. (Editor)

    1985-01-01

    Among the topics discussed are: the Olympus satellite program; trends in the Italian space technology; and ESA Space Station planning. Consideration is also given to cooperative international programs, including the Eurostar platform, the Tethered Satellite System, and the SPAS system; space science and applications programs; and the development of next generation space propulsion systems. Among the specific propulsion technologies discussed are: LOX/LR2 engines; the Ariane 5 solid propellant booster; and propulsion systems for earth-to-orbit vehicles.

  13. Global Infrared Observations of Roughness Induced Transition on the Space Shuttle Orbiter

    NASA Technical Reports Server (NTRS)

    Horvath, Thomas J.; Zalameda, Joseph N.; Wood, William A.; Berry, Scott A.; Schwartz, Richard J.; Dantowitz, Ronald F.; Spisz, Thomas S.; Taylor, Jeff C.

    2012-01-01

    High resolution infrared observations made from a mobile ground based optical system captured the laminar-to-turbulent boundary layer transition process as it occurred during Space Shuttle Endeavour's return to earth following its final mission in 2011. The STS-134 imagery was part of a larger effort to demonstrate an emerging and reliable non-intrusive global thermal measurement capability and to complement a series of boundary layer transition flight experiments that were flown on the Shuttle. The STS-134 observations are believed to be the first time that the development and movement of a hypersonic boundary layer transition front has been witnessed in flight over the entire vehicle surface and in particular, at unprecedented spatial resolution. Additionally, benchmark surface temperature maps of the Orbiter lower surface collected over multiple flights and spanning a Mach range of 18 to 6 are now available and represent an opportunity for collaborative comparison with computational techniques focused on hypersonic transition and turbulence modeling. The synergy of the global temperature maps with the companion in-situ thermocouple measurements serve as an example of the effective leveraging of resources to achieve a common goal of advancing our understanding of the complex nature of high Mach number transition. It is shown that quantitative imaging can open the door to a multitude of national and international opportunities for partnership associated with flight-testing and subsequent validation of numerical simulation techniques. The quantitative imaging applications highlighted in this paper offer unique and complementary flight measurement alternatives and suggest collaborative instrumentation opportunities to advance the state of the art in transition prediction and maximize the return on investment in terms of developmental flight tests for future vehicle designs.

  14. Topological properties of flat electroencephalography's state space

    NASA Astrophysics Data System (ADS)

    Ken, Tan Lit; Ahmad, Tahir bin; Mohd, Mohd Sham bin; Ngien, Su Kong; Suwa, Tohru; Meng, Ong Sie

    2016-02-01

    Neuroinverse problem are often associated with complex neuronal activity. It involves locating problematic cell which is highly challenging. While epileptic foci localization is possible with the aid of EEG signals, it relies greatly on the ability to extract hidden information or pattern within EEG signals. Flat EEG being an enhancement of EEG is a way of viewing electroencephalograph on the real plane. In the perspective of dynamical systems, Flat EEG is equivalent to epileptic seizure hence, making it a great platform to study epileptic seizure. Throughout the years, various mathematical tools have been applied on Flat EEG to extract hidden information that is hardly noticeable by traditional visual inspection. While these tools have given worthy results, the journey towards understanding seizure process completely is yet to be succeeded. Since the underlying structure of Flat EEG is dynamic and is deemed to contain wealthy information regarding brainstorm, it would certainly be appealing to explore in depth its structures. To better understand the complex seizure process, this paper studies the event of epileptic seizure via Flat EEG in a more general framework by means of topology, particularly, on the state space where the event of Flat EEG lies.

  15. Granger causality for state-space models

    NASA Astrophysics Data System (ADS)

    Barnett, Lionel; Seth, Anil K.

    2015-04-01

    Granger causality has long been a prominent method for inferring causal interactions between stochastic variables for a broad range of complex physical systems. However, it has been recognized that a moving average (MA) component in the data presents a serious confound to Granger causal analysis, as routinely performed via autoregressive (AR) modeling. We solve this problem by demonstrating that Granger causality may be calculated simply and efficiently from the parameters of a state-space (SS) model. Since SS models are equivalent to autoregressive moving average models, Granger causality estimated in this fashion is not degraded by the presence of a MA component. This is of particular significance when the data has been filtered, downsampled, observed with noise, or is a subprocess of a higher dimensional process, since all of these operations—commonplace in application domains as diverse as climate science, econometrics, and the neurosciences—induce a MA component. We show how Granger causality, conditional and unconditional, in both time and frequency domains, may be calculated directly from SS model parameters via solution of a discrete algebraic Riccati equation. Numerical simulations demonstrate that Granger causality estimators thus derived have greater statistical power and smaller bias than AR estimators. We also discuss how the SS approach facilitates relaxation of the assumptions of linearity, stationarity, and homoscedasticity underlying current AR methods, thus opening up potentially significant new areas of research in Granger causal analysis.

  16. Granger causality for state-space models.

    PubMed

    Barnett, Lionel; Seth, Anil K

    2015-04-01

    Granger causality has long been a prominent method for inferring causal interactions between stochastic variables for a broad range of complex physical systems. However, it has been recognized that a moving average (MA) component in the data presents a serious confound to Granger causal analysis, as routinely performed via autoregressive (AR) modeling. We solve this problem by demonstrating that Granger causality may be calculated simply and efficiently from the parameters of a state-space (SS) model. Since SS models are equivalent to autoregressive moving average models, Granger causality estimated in this fashion is not degraded by the presence of a MA component. This is of particular significance when the data has been filtered, downsampled, observed with noise, or is a subprocess of a higher dimensional process, since all of these operations-commonplace in application domains as diverse as climate science, econometrics, and the neurosciences-induce a MA component. We show how Granger causality, conditional and unconditional, in both time and frequency domains, may be calculated directly from SS model parameters via solution of a discrete algebraic Riccati equation. Numerical simulations demonstrate that Granger causality estimators thus derived have greater statistical power and smaller bias than AR estimators. We also discuss how the SS approach facilitates relaxation of the assumptions of linearity, stationarity, and homoscedasticity underlying current AR methods, thus opening up potentially significant new areas of research in Granger causal analysis.

  17. Metal-insulator transition near a superconducting state

    NASA Astrophysics Data System (ADS)

    Kaveh, M.; Mott, N. F.

    1992-03-01

    We show that when the metal-insulation transition occurs near a superconducting state it results in a different critical behavior from that of amorphous metals or uncompensated doped semiconductors. This difference results from the enhancement of the effective electron-electron interaction caused by fluctuations to the superconducting state. This explains the recent experiments of Micklitz and co-workers on amorphous superconducting mixtures Ga-Ar and Bi-Kr.

  18. Current status of the state-and-transition framework

    Technology Transfer Automated Retrieval System (TEKTRAN)

    State-and-transition models (STM) have been widely adopted as a tool for explaining plant community dynamics and response to disturbance within rangeland ecosystems. Our understanding of the STM concepts has advanced substantially since they were introduced by Westoby et al. (1989) and modified by ...

  19. Practical guidance for developing state-and-transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    State-and-transition models (STMs) are synthetic descriptions of the dynamics of vegetation and surface soils occurring within specific ecological sites. STMs consist of a diagram and narratives that describe the dynamics and its causes. STMs are developed using a broad array of evidence including h...

  20. Theoretical analysis of droplet transition from Cassie to Wenzel state

    NASA Astrophysics Data System (ADS)

    Liu, Tian-Qing; Yan-Jie, Li; Xiang-Qin, Li; Wei, Sun

    2015-11-01

    Whether droplets transit from the Cassie to the Wenzel state (C-W) on a textured surface is the touchstone that the superhydrophobicity of the surface is still maintained. However, the C-W transition mechanism, especially the spontaneous transition of small droplets, is still not very clear to date. The interface free energy gradient of a small droplet is firstly proposed and derived as the driving force for its C-W evolution in this study based on the energy and gradient analysis. Then the physical and mathematical model of the C-W transition is found after the C-W driving force or transition pressure, the resistance, and the parameters of the meniscus beneath the droplet are formulated. The results show that the micro/nano structural parameters significantly affect the C-W driving force and resistance. The smaller the pillar diameter and pitch, the minor the C-W transition pressure, and the larger the resistance. Consequently, the C-W transition is difficult to be completed for the droplets on nano-textured surfaces. Meanwhile if the posts are too short, the front of the curved liquid-air interface below the droplet will touch the structural substrate easily even though the three phase contact line (TPCL) has not depinned. When the posts are high enough, the TPCL beneath the drop must move firstly before the meniscus can reach the substrate. As a result, the droplet on a textured surface with short pillars is easy to complete its C-W evolution. On the other hand, the smaller the droplet, the easier the C-W shift, since the transition pressure becomes larger, which well explains why an evaporating drop will collapse spontaneously from composite to Wenzel state. Besides, both intrinsic and advancing contact angles affect the C-W transition as well. The greater the two angles, the harder the C-W transition. In the end, the C-W transition parameters and the critical conditions measured in literatures are calculated and compared, and the calculations accord well with

  1. Transition state-finding strategies for use with the growing string method.

    PubMed

    Goodrow, Anthony; Bell, Alexis T; Head-Gordon, Martin

    2009-06-28

    Efficient identification of transition states is important for understanding reaction mechanisms. Most transition state search algorithms require long computational times and a good estimate of the transition state structure in order to converge, particularly for complex reaction systems. The growing string method (GSM) [B. Peters et al., J. Chem. Phys. 120, 7877 (2004)] does not require an initial guess of the transition state; however, the calculation is still computationally intensive due to repeated calls to the quantum mechanics code. Recent modifications to the GSM [A. Goodrow et al., J. Chem. Phys. 129, 174109 (2008)] have reduced the total computational time for converging to a transition state by a factor of 2 to 3. In this work, three transition state-finding strategies have been developed to complement the speedup of the modified-GSM: (1) a hybrid strategy, (2) an energy-weighted strategy, and (3) a substring strategy. The hybrid strategy initiates the string calculation at a low level of theory (HF/STO-3G), which is then refined at a higher level of theory (B3LYP/6-31G(*)). The energy-weighted strategy spaces points along the reaction pathway based on the energy at those points, leading to a higher density of points where the energy is highest and finer resolution of the transition state. The substring strategy is similar to the hybrid strategy, but only a portion of the low-level string is refined using a higher level of theory. These three strategies have been used with the modified-GSM and are compared in three reactions: alanine dipeptide isomerization, H-abstraction in methanol oxidation on VO(x)/SiO(2) catalysts, and C-H bond activation in the oxidative carbonylation of toluene to p-toluic acid on Rh(CO)(2)(TFA)(3) catalysts. In each of these examples, the substring strategy was proved most effective by obtaining a better estimate of the transition state structure and reducing the total computational time by a factor of 2 to 3 compared to the

  2. Transition state-finding strategies for use with the growing string method

    NASA Astrophysics Data System (ADS)

    Goodrow, Anthony; Bell, Alexis T.; Head-Gordon, Martin

    2009-06-01

    Efficient identification of transition states is important for understanding reaction mechanisms. Most transition state search algorithms require long computational times and a good estimate of the transition state structure in order to converge, particularly for complex reaction systems. The growing string method (GSM) [B. Peters et al., J. Chem. Phys. 120, 7877 (2004)] does not require an initial guess of the transition state; however, the calculation is still computationally intensive due to repeated calls to the quantum mechanics code. Recent modifications to the GSM [A. Goodrow et al., J. Chem. Phys. 129, 174109 (2008)] have reduced the total computational time for converging to a transition state by a factor of 2 to 3. In this work, three transition state-finding strategies have been developed to complement the speedup of the modified-GSM: (1) a hybrid strategy, (2) an energy-weighted strategy, and (3) a substring strategy. The hybrid strategy initiates the string calculation at a low level of theory (HF/STO-3G), which is then refined at a higher level of theory (B3LYP/6-31G∗). The energy-weighted strategy spaces points along the reaction pathway based on the energy at those points, leading to a higher density of points where the energy is highest and finer resolution of the transition state. The substring strategy is similar to the hybrid strategy, but only a portion of the low-level string is refined using a higher level of theory. These three strategies have been used with the modified-GSM and are compared in three reactions: alanine dipeptide isomerization, H-abstraction in methanol oxidation on VOx/SiO2 catalysts, and C-H bond activation in the oxidative carbonylation of toluene to p-toluic acid on Rh(CO)2(TFA)3 catalysts. In each of these examples, the substring strategy was proved most effective by obtaining a better estimate of the transition state structure and reducing the total computational time by a factor of 2 to 3 compared to the modified

  3. Theoretical calculations on electronic transitions for H/sub 3/, including Rydberg and transition state spectra

    SciTech Connect

    Petsalakis, I.D.; Theodorakopoulos, G.; Wright, J.S.

    1988-12-01

    MRD-CI calculations have been carried out on the ground and excited electronic states of H/sub 3/ for D/sub 3//sub h/, D/sub infinity//sub h/, C/sub infinity//sub v/, and C/sub 2//sub v/ geometries. Dipole transition moments between the various electronic states have been also obtained at the different geometries calculated. The present work provides accurate theoretical information relevant to the transition state spectroscopy of H+H/sub 2/ along a collinear path and also along a perpendicular path. In addition, the present work is the first all-electron configuration interaction treatment of the Rydberg states of H/sub 3/, and the results are in excellent agreement with the observed spectra.

  4. Destination state screening of active spaces in spin dynamics simulations

    NASA Astrophysics Data System (ADS)

    Krzystyniak, M.; Edwards, Luke J.; Kuprov, Ilya

    2011-06-01

    We propose a novel avenue for state space reduction in time domain Liouville space spin dynamics simulations, using detectability as a selection criterion - only those states that evolve into or affect other detectable states are kept in the simulation. This basis reduction procedure (referred to as destination state screening) is formally exact and can be applied on top of the existing state space restriction techniques. As demonstrated below, in many cases this results in further reduction of matrix dimension, leading to considerable acceleration of many spin dynamics simulation types. Destination state screening is implemented in the latest version of the Spinach library (http://spindynamics.org).

  5. Valuation of financial models with non-linear state spaces

    NASA Astrophysics Data System (ADS)

    Webber, Nick

    2001-02-01

    A common assumption in valuation models for derivative securities is that the underlying state variables take values in a linear state space. We discuss numerical implementation issues in an interest rate model with a simple non-linear state space, formulating and comparing Monte Carlo, finite difference and lattice numerical solution methods. We conclude that, at least in low dimensional spaces, non-linear interest rate models may be viable.

  6. Space science in the United States

    NASA Technical Reports Server (NTRS)

    Alexander, Joseph K.; Mcdonald, Frank B.

    1988-01-01

    Despite the hiatus in spacecraft launches after the Space Shuttle Challenger accident in 1986, the U.S. space program continues to generate research data on the basis of the productive operation of 18 scientific spacecraft. Attention is presently given to NASA's planned missions for the 1990s in such fields as astronomy and astrophysics (the Hubble Space Telescope, the Extreme UV Explorer), solar system exploration (the Magellan Venus orbiter, the Galileo Jupiter orbiter), space physics (the Tethered Satellite System, the Combined Release and Radiation Effects Satellite), earth science (the Upper Atmospheric Research Satellite), and microgravity sciences (the International Microgravity Observatory).

  7. The structure of enumerated spin glass state spaces

    NASA Astrophysics Data System (ADS)

    Schubert, Sven; Hoffmann, Karl Heinz

    2006-02-01

    We enumerate the low energy part of the state space of an Ising spin glass using an efficient branch-and-bound algorithm. A coarse graining algorithm (NB-clustering) is employed to condense the inherent information to a system size which is treatable in computer simulations. The reduced state space still incorporates all ingredients necessary to simulate aging effects. We investigate its structure in detail and find that certain assumptions made in heuristical state space models which have been presented in the past to reproduce aging phenomena in spin glass experiments are indeed compatible with the data from the observed state spaces.

  8. State transitions of actin cortices in vitro and in vivo

    NASA Astrophysics Data System (ADS)

    Tan, Tzer Han; Keren, Kinneret; Mackintosh, Fred; Schmidt, Christoph; Fakhri, Nikta

    Most animal cells are enveloped by a thin layer of actin cortex which governs the cell mechanics. A functional cortex must be rigid to provide mechanical support while being flexible to allow for rapid restructuring events such as cell division. To satisfy these requirements, the actin cortex is highly dynamic with fast actin turnover and myosin-driven contractility. The regulatory mechanism responsible for the transition between a mechanically stable state and a restructuring state is not well understood. Here, we develop a technique to map the dynamics of reconstituted actin cortices in emulsion droplets using IR fluorescent single-walled carbon nanotubes (SWNTs). By increasing crosslinker concentration, we find that a homogeneous cortex transitions to an intermediate state with broken rotational symmetry and a globally contractile state which further breaks translational symmetry. We apply this new dynamic mapping technique to cortices of live starfish oocytes in various developmental stages. To identify the regulatory mechanism for steady state transitions, we subject the oocytes to actin and myosin disrupting drugs.

  9. Raman transitions between hyperfine clock states in a magnetic trap

    NASA Astrophysics Data System (ADS)

    Naber, J. B.; Torralbo-Campo, L.; Hubert, T.; Spreeuw, R. J. C.

    2016-07-01

    We present our experimental investigation of an optical Raman transition between the magnetic clock states of 87Rb in an atom chip magnetic trap. The transfer of atomic population is induced by a pair of diode lasers which couple the two clock states off-resonantly to an intermediate state manifold. This transition is subject to destructive interference of two excitation paths, which leads to a reduction of the effective two-photon Rabi frequency. Furthermore, we find that the transition frequency is highly sensitive to the intensity ratio of the diode lasers. Our results are well described in terms of light shifts in the multilevel structure of 87Rb. The differential light shifts vanish at an optimal intensity ratio, which we observe as a narrowing of the transition linewidth. We also observe the temporal dynamics of the population transfer and find good agreement with a model based on the system's master equation and a Gaussian laser beam profile. Finally, we identify several sources of decoherence in our system, and discuss possible improvements.

  10. How to upload a physical quantum state into correlation space

    SciTech Connect

    Morimae, Tomoyuki

    2011-04-15

    In the framework of the computational tensor network [Phys. Rev. Lett. 98, 220503 (2007)], the quantum computation is performed in a virtual linear space called the correlation space. It was recently shown [Phys. Rev. Lett. 103, 050503 (2009)] that a state in a correlation space can be downloaded to the real physical space. In this paper, conversely, we study how to upload a state from a real physical space to the correlation space. After showing the impossibility of cloning a state between a real physical space and the correlation space, we propose a simple teleportation-like method of uploading. This method also enables the Gottesman-Chuang gate teleportation trick and entanglement swapping in the virtual-real hybrid setting. Furthermore, compared with the inverse of the downloading method by Cai et al. [Phys. Rev. Lett. 103, 050503 (2009)], which also works to upload, the proposed uploading method has several advantages.

  11. On the correspondence between polymer-modified turbulence states and transitional states in Newtonian flows

    NASA Astrophysics Data System (ADS)

    Dubief, Yves; White, Christopher

    2010-11-01

    Polymer addition is known to reduce drag in wall-bounded flows up to an asymptotic state called maximum drag reduction (MDR). The definition of MDR is still largely empirical and its uniqueness is a matter of debate. Using direct numerical simulations, a correspondence is first established between MDR and a specific state of transition in boundary layer flow. A model is derived as a function of the flow topology of the transitional Newtonian flow and the FENE-P model. The model is then extended to natural convection where heat transfer reduction (HTR) and augmentation (HTA) are observed as a function of polymer length. Yet, HTR and HTA are topologically equivalent and again correspond to a transitional state of Rayleigh Benard convection flow. This suggests that polymer-modified turbulence may be predictable as a function of the polymer solution's properties and transitional states of the corresponding Newtonian flow.

  12. PULSAR STATE SWITCHING FROM MARKOV TRANSITIONS AND STOCHASTIC RESONANCE

    SciTech Connect

    Cordes, J. M.

    2013-09-20

    Markov processes are shown to be consistent with metastable states seen in pulsar phenomena, including intensity nulling, pulse-shape mode changes, subpulse drift rates, spin-down rates, and X-ray emission, based on the typically broad and monotonic distributions of state lifetimes. Markovianity implies a nonlinear magnetospheric system in which state changes occur stochastically, corresponding to transitions between local minima in an effective potential. State durations (though not transition times) are thus largely decoupled from the characteristic timescales of various magnetospheric processes. Dyadic states are common but some objects show at least four states with some transitions forbidden. Another case is the long-term intermittent pulsar B1931+24 that has binary radio-emission and torque states with wide, but non-monotonic duration distributions. It also shows a quasi-period of 38 ± 5 days in a 13 yr time sequence, suggesting stochastic resonance in a Markov system with a forcing function that could be strictly periodic or quasi-periodic. Nonlinear phenomena are associated with time-dependent activity in the acceleration region near each magnetic polar cap. The polar-cap diode is altered by feedback from the outer magnetosphere and by return currents from the equatorial region outside the light cylinder that may also cause the neutron star to episodically charge and discharge. Orbital perturbations of a disk or current sheet provide a natural periodicity for the forcing function in the stochastic-resonance interpretation of B1931+24. Disk dynamics may introduce additional timescales in observed phenomena. Future work can test the Markov interpretation, identify which pulsar types have a propensity for state changes, and clarify the role of selection effects.

  13. The morphological state space revisited: what do phylogenetic patterns in homoplasy tell us about the number of possible character states?

    PubMed Central

    Hoyal Cuthill, Jennifer F.

    2015-01-01

    Biological variety and major evolutionary transitions suggest that the space of possible morphologies may have varied among lineages and through time. However, most models of phylogenetic character evolution assume that the potential state space is finite. Here, I explore what the morphological state space might be like, by analysing trends in homoplasy (repeated derivation of the same character state). Analyses of ten published character matrices are compared against computer simulations with different state space models: infinite states, finite states, ordered states and an ‘inertial' model, simulating phylogenetic constraints. Of these, only the infinite states model results in evolution without homoplasy, a prediction which is not generally met by real phylogenies. Many authors have interpreted the ubiquity of homoplasy as evidence that the number of evolutionary alternatives is finite. However, homoplasy is also predicted by phylogenetic constraints on the morphological distance that can be traversed between ancestor and descendent. Phylogenetic rarefaction (sub-sampling) shows that finite and inertial state spaces do produce contrasting trends in the distribution of homoplasy. Two clades show trends characteristic of phylogenetic inertia, with decreasing homoplasy (increasing consistency index) as we sub-sample more distantly related taxa. One clade shows increasing homoplasy, suggesting exhaustion of finite states. Different clades may, therefore, show different patterns of character evolution. However, when parsimony uninformative characters are excluded (which may occur without documentation in cladistic studies), it may no longer be possible to distinguish inertial and finite state spaces. Interestingly, inertial models predict that homoplasy should be clustered among comparatively close relatives (parallel evolution), whereas finite state models do not. If morphological evolution is often inertial in nature, then homoplasy (false homology) may

  14. The morphological state space revisited: what do phylogenetic patterns in homoplasy tell us about the number of possible character states?

    PubMed

    Hoyal Cuthill, Jennifer F

    2015-12-06

    Biological variety and major evolutionary transitions suggest that the space of possible morphologies may have varied among lineages and through time. However, most models of phylogenetic character evolution assume that the potential state space is finite. Here, I explore what the morphological state space might be like, by analysing trends in homoplasy (repeated derivation of the same character state). Analyses of ten published character matrices are compared against computer simulations with different state space models: infinite states, finite states, ordered states and an 'inertial' model, simulating phylogenetic constraints. Of these, only the infinite states model results in evolution without homoplasy, a prediction which is not generally met by real phylogenies. Many authors have interpreted the ubiquity of homoplasy as evidence that the number of evolutionary alternatives is finite. However, homoplasy is also predicted by phylogenetic constraints on the morphological distance that can be traversed between ancestor and descendent. Phylogenetic rarefaction (sub-sampling) shows that finite and inertial state spaces do produce contrasting trends in the distribution of homoplasy. Two clades show trends characteristic of phylogenetic inertia, with decreasing homoplasy (increasing consistency index) as we sub-sample more distantly related taxa. One clade shows increasing homoplasy, suggesting exhaustion of finite states. Different clades may, therefore, show different patterns of character evolution. However, when parsimony uninformative characters are excluded (which may occur without documentation in cladistic studies), it may no longer be possible to distinguish inertial and finite state spaces. Interestingly, inertial models predict that homoplasy should be clustered among comparatively close relatives (parallel evolution), whereas finite state models do not. If morphological evolution is often inertial in nature, then homoplasy (false homology) may primarily

  15. Absorbing-state phase transitions on percolating lattices.

    PubMed

    Lee, Man Young; Vojta, Thomas

    2009-04-01

    We study nonequilibrium phase transitions of reaction-diffusion systems defined on randomly diluted lattices, focusing on the transition across the lattice percolation threshold. To develop a theory for this transition, we combine classical percolation theory with the properties of the supercritical nonequilibrium system on a finite-size cluster. In the case of the contact process, the interplay between geometric criticality due to percolation and dynamical fluctuations of the nonequilibrium system leads to a different universality class. The critical point is characterized by ultraslow activated dynamical scaling and accompanied by strong Griffiths singularities. To confirm the universality of this exotic scaling scenario we also study the generalized contact process with several (symmetric) absorbing states and we support our theory by extensive Monte Carlo simulations.

  16. United State space programs - Present and planned

    NASA Technical Reports Server (NTRS)

    Frosch, R. A.

    1978-01-01

    The U.S. space program is considered with reference to the benefits derived by the public. Missions are divided into three categories: the use of near-earth space for remote sensing, communications, and other purposes directly beneficial to human welfare; the scientific exploration of the solar system and observation of the universe as part of the continuing effort to understand the place of earth and man in the cosmos; and the investigation of the sun-earth relationships which are basic to the terrestrial biosphere. Individual projects are described, and it is suggested that the future of space technology in 1978 is comparable to the future of aviation in 1924.

  17. The United States space observation policy

    NASA Technical Reports Server (NTRS)

    Chevrel, M.

    1980-01-01

    The steps pursued since 1978 to establish an operational civil space remote sensing system are outlined. The role of the National Oceanographic and Atmospheric Agency is defined, and the problems still remaining are discussed.

  18. Phenomena of solid state grain boundaries phase transition in technology

    SciTech Connect

    Minaev, Y. A.

    2015-03-30

    The results of study the phenomenon, discovered by author (1971), of the phase transition of grain boundary by the formation of two-dimensional liquid or quasi-liquid films have been done. The described phenomena of the first order phase transition (two-dimensional melting) at temperatures 0.6 – 0.9 T{sub S0} (of the solid state melting point) is a fundamental property of solid crystalline materials, which has allowed to revise radically scientific representations about a solid state of substance. Using the mathematical tools of the film thermodynamics it has been obtained the generalized equation of Clausius - Clapeyron type for two-dimensional phase transition. The generalized equation has been used for calculating grain boundary phase transition temperature T{sub Sf} of any metal, which value lies in the range of (0.55…0.86) T{sub S0}. Based on these works conclusions the develop strategies for effective forming of coatings (by thermo-chemical processing) on surface layers of functional alloys and hard metals have been made. The short overview of the results of some graded alloys characterization has been done.

  19. Priorities in national space strategies and governance of the member states of the European Space Agency

    NASA Astrophysics Data System (ADS)

    Adriaensen, Maarten; Giannopapa, Christina; Sagath, Daniel; Papastefanou, Anastasia

    2015-12-01

    The European Space Agency (ESA) has twenty Member States with a variety of strategic priorities and governance structures regarding their space activities. A number of countries engage in space activities exclusively though ESA, while others have also their own national space programme. Some consider ESA as their prime space agency and others have additionally their own national agency with respective programmes. The main objective of this paper is to provide an up-to date overview and a holistic assessment of strategic priorities and the national space governance structures in 20 ESA Member States. This analysis and assessment has been conducted by analysing the Member States public documents, information provided at ESA workshop on this topic and though unstructured interviews. The paper is structured to include two main elements: priorities and trends in national space strategies and space governance in ESA Member States. The first part of this paper focuses on the content and analysis of the national space strategies and indicates the main priorities and trends in Member States. The priorities are categorised with regards to technology domains, the role of space in the areas of sustainability and the motivators that boost engagement in space. These vary from one Member State to another and include with different levels of engagement in technology domains amongst others: science and exploration, navigation, Earth observation, human space flight, launchers, telecommunications, and integrated applications. Member States allocate a different role of space as enabling tool adding to the advancement of sustainability areas including: security, resources, environment and climate change, transport and communication, energy, and knowledge and education. The motivators motivating reasoning which enhances or hinders space engagement also differs. The motivators identified are industrial competitiveness, job creation, technology development and transfer, social benefits

  20. Optimal Control of Transitions between Nonequilibrium Steady States

    PubMed Central

    Zulkowski, Patrick R.; Sivak, David A.; DeWeese, Michael R.

    2013-01-01

    Biological systems fundamentally exist out of equilibrium in order to preserve organized structures and processes. Many changing cellular conditions can be represented as transitions between nonequilibrium steady states, and organisms have an interest in optimizing such transitions. Using the Hatano-Sasa Y-value, we extend a recently developed geometrical framework for determining optimal protocols so that it can be applied to systems driven from nonequilibrium steady states. We calculate and numerically verify optimal protocols for a colloidal particle dragged through solution by a translating optical trap with two controllable parameters. We offer experimental predictions, specifically that optimal protocols are significantly less costly than naive ones. Optimal protocols similar to these may ultimately point to design principles for biological energy transduction systems and guide the design of artificial molecular machines. PMID:24386112

  1. Physiologic Measures of Animal Stress during Transitional States of Consciousness.

    PubMed

    Meyer, Robert E

    2015-08-07

    Determination of the humaneness of methods used to produce unconsciousness in animals, whether for anesthesia, euthanasia, humane slaughter, or depopulation, relies on our ability to assess stress, pain, and consciousness within the contexts of method and application. Determining the subjective experience of animals during transitional states of consciousness, however, can be quite difficult; further, loss of consciousness with different agents or methods may occur at substantially different rates. Stress and distress may manifest behaviorally (e.g., overt escape behaviors, approach-avoidance preferences [aversion]) or physiologically (e.g., movement, vocalization, changes in electroencephalographic activity, heart rate, sympathetic nervous system [SNS] activity, hypothalamic-pituitary axis [HPA] activity), such that a one-size-fits-all approach cannot be easily applied to evaluate methods or determine specific species applications. The purpose of this review is to discuss methods of evaluating stress in animals using physiologic methods, with emphasis on the transition between the conscious and unconscious states.

  2. Absorbing State Phase Transition with Competing Quantum and Classical Fluctuations.

    PubMed

    Marcuzzi, Matteo; Buchhold, Michael; Diehl, Sebastian; Lesanovsky, Igor

    2016-06-17

    Stochastic processes with absorbing states feature examples of nonequilibrium universal phenomena. While the classical regime has been thoroughly investigated in the past, relatively little is known about the behavior of these nonequilibrium systems in the presence of quantum fluctuations. Here, we theoretically address such a scenario in an open quantum spin model which, in its classical limit, undergoes a directed percolation phase transition. By mapping the problem to a nonequilibrium field theory, we show that the introduction of quantum fluctuations stemming from coherent, rather than statistical, spin flips alters the nature of the transition such that it becomes first order. In the intermediate regime, where classical and quantum dynamics compete on equal terms, we highlight the presence of a bicritical point with universal features different from the directed percolation class in a low dimension. We finally propose how this physics could be explored within gases of interacting atoms excited to Rydberg states.

  3. Absorbing State Phase Transition with Competing Quantum and Classical Fluctuations

    NASA Astrophysics Data System (ADS)

    Marcuzzi, Matteo; Buchhold, Michael; Diehl, Sebastian; Lesanovsky, Igor

    2016-06-01

    Stochastic processes with absorbing states feature examples of nonequilibrium universal phenomena. While the classical regime has been thoroughly investigated in the past, relatively little is known about the behavior of these nonequilibrium systems in the presence of quantum fluctuations. Here, we theoretically address such a scenario in an open quantum spin model which, in its classical limit, undergoes a directed percolation phase transition. By mapping the problem to a nonequilibrium field theory, we show that the introduction of quantum fluctuations stemming from coherent, rather than statistical, spin flips alters the nature of the transition such that it becomes first order. In the intermediate regime, where classical and quantum dynamics compete on equal terms, we highlight the presence of a bicritical point with universal features different from the directed percolation class in a low dimension. We finally propose how this physics could be explored within gases of interacting atoms excited to Rydberg states.

  4. IRIDIUM (R): A Lockheed transition to commercial space

    NASA Technical Reports Server (NTRS)

    Tadano, Thomas N.

    1995-01-01

    At Lockheed Missiles & Space Company, the IRIDIUM commercial space program is dramatically revolutionizing spacecraft development and manufacturing processes to reduce cost while maintaining quality and reliability. This report includes the following sections: an overview of the IRIDIUM system, the Lockheed IRIDIUM project and challenges; cycle-time reduction through production reorganization; and design for manufacturing and quality.

  5. Information content in cortical spike trains during brain state transitions.

    PubMed

    Arnold, Maria M; Szczepanski, Janusz; Montejo, Noelia; Amigó, José M; Wajnryb, Eligiusz; Sanchez-Vives, Maria V

    2013-02-01

    Even in the absence of external stimuli there is ongoing activity in the cerebral cortex as a result of recurrent connectivity. This paper attempts to characterize one aspect of this ongoing activity by examining how the information content carried by specific neurons varies as a function of brain state. We recorded from rats chronically implanted with tetrodes in the primary visual cortex during awake and sleep periods. Electro-encephalogram and spike trains were recorded during 30-min periods, and 2-4 neuronal spikes were isolated per tetrode off-line. All the activity included in the analysis was spontaneous, being recorded from the visual cortex in the absence of visual stimuli. The brain state was determined through a combination of behavior evaluation, electroencephalogram and electromyogram analysis. Information in the spike trains was determined by using Lempel-Ziv Complexity. Complexity was used to estimate the entropy of neural discharges and thus the information content (Amigóet al. Neural Comput., 2004, 16: 717-736). The information content in spike trains (range 4-70 bits s(-1) ) was evaluated during different brain states and particularly during the transition periods. Transitions toward states of deeper sleep coincided with a decrease of information, while transitions to the awake state resulted in an increase in information. Changes in both directions were of the same magnitude, about 30%. Information in spike trains showed a high temporal correlation between neurons, reinforcing the idea of the impact of the brain state in the information content of spike trains.

  6. Biosynthetic consequences of multiple sequential post-transition-state bifurcations.

    PubMed

    Hong, Young Joo; Tantillo, Dean J

    2014-02-01

    Selectivity in chemical reactions that form complex molecular architectures from simpler precursors is usually rationalized by comparing competing transition-state structures that lead to different possible products. Herein we describe a system for which a single transition-state structure leads to the formation of many isomeric products via pathways that feature multiple sequential bifurcations. The reaction network described connects the pimar-15-en-8-yl cation to miltiradiene, a tricyclic diterpene natural product, and isomers via cyclizations and/or rearrangements. The results suggest that the selectivity of the reaction is controlled by (post-transition-state) dynamic effects, that is, how the carbocation structure changes in response to the distribution of energy in its vibrational modes. The inherent dynamical effects revealed herein (characterized through quasiclassical direct dynamics calculations using density functional theory) have implications not only for the general principles of selectivity prediction in systems with complex potential energy surfaces, but also for the mechanisms of terpene synthase enzymes and their evolution. These findings redefine the challenges faced by nature in controlling the biosynthesis of complex natural products.

  7. Reliable Transition State Searches Integrated with the Growing String Method.

    PubMed

    Zimmerman, Paul

    2013-07-09

    The growing string method (GSM) is highly useful for locating reaction paths connecting two molecular intermediates. GSM has often been used in a two-step procedure to locate exact transition states (TS), where GSM creates a quality initial structure for a local TS search. This procedure and others like it, however, do not always converge to the desired transition state because the local search is sensitive to the quality of the initial guess. This article describes an integrated technique for simultaneous reaction path and exact transition state search. This is achieved by implementing an eigenvector following optimization algorithm in internal coordinates with Hessian update techniques. After partial convergence of the string, an exact saddle point search begins under the constraint that the maximized eigenmode of the TS node Hessian has significant overlap with the string tangent near the TS. Subsequent optimization maintains connectivity of the string to the TS as well as locks in the TS direction, all but eliminating the possibility that the local search leads to the wrong TS. To verify the robustness of this approach, reaction paths and TSs are found for a benchmark set of more than 100 elementary reactions.

  8. Enhancement of canonical sampling by virtual-state transitions.

    PubMed

    Higo, Junichi; Kasahara, Kota; Dasgupta, Bhaskar; Nakamura, Haruki

    2017-01-28

    A novel method was developed to enhance canonical sampling. A system is divided into virtually introduced sub-states, called "virtual states," which does not exist in reality. The configuration sampling is achieved by a standard canonical sampling method, the Metropolis Monte Carlo method, and confined in a virtual state for a while. In contrast, inter-virtual state motions are controlled by transition probabilities, which can be set arbitrarily. A simple recursive equation was introduced to determine the inter-virtual state transition probabilities, by which the sampling is enhanced considerably. We named this method "virtual-system coupled canonical Monte Carlo (VcMC) sampling." A simple method was proposed to reconstruct a canonical distribution function at a certain temperature from the resultant VcMC sampling data. Two systems, a one-dimensional double-well potential and a three-dimensional ligand-receptor binding/unbinding model, were examined. VcMC produced an accurate canonical distribution much more quickly than a conventional canonical Monte Carlo simulation does.

  9. Enhancement of canonical sampling by virtual-state transitions

    NASA Astrophysics Data System (ADS)

    Higo, Junichi; Kasahara, Kota; Dasgupta, Bhaskar; Nakamura, Haruki

    2017-01-01

    A novel method was developed to enhance canonical sampling. A system is divided into virtually introduced sub-states, called "virtual states," which does not exist in reality. The configuration sampling is achieved by a standard canonical sampling method, the Metropolis Monte Carlo method, and confined in a virtual state for a while. In contrast, inter-virtual state motions are controlled by transition probabilities, which can be set arbitrarily. A simple recursive equation was introduced to determine the inter-virtual state transition probabilities, by which the sampling is enhanced considerably. We named this method "virtual-system coupled canonical Monte Carlo (VcMC) sampling." A simple method was proposed to reconstruct a canonical distribution function at a certain temperature from the resultant VcMC sampling data. Two systems, a one-dimensional double-well potential and a three-dimensional ligand-receptor binding/unbinding model, were examined. VcMC produced an accurate canonical distribution much more quickly than a conventional canonical Monte Carlo simulation does.

  10. Excited-state quantum phase transition in the Rabi model

    NASA Astrophysics Data System (ADS)

    Puebla, Ricardo; Hwang, Myung-Joong; Plenio, Martin B.

    2016-08-01

    The Rabi model, a two-level atom coupled to a harmonic oscillator, can undergo a second-order quantum phase transition (QPT) [M.-J. Hwang et al., Phys. Rev. Lett. 115, 180404 (2015), 10.1103/PhysRevLett.115.180404]. Here we show that the Rabi QPT accompanies critical behavior in the higher-energy excited states, i.e., the excited-state QPT (ESQPT). We derive analytic expressions for the semiclassical density of states, which show a logarithmic divergence at a critical energy eigenvalue in the broken symmetry (superradiant) phase. Moreover, we find that the logarithmic singularities in the density of states lead to singularities in the relevant observables in the system such as photon number and atomic polarization. We corroborate our analytical semiclassical prediction of the ESQPT in the Rabi model with its numerically exact quantum mechanical solution.

  11. Crossing the dividing surface of transition state theory. III. Once and only once. Selecting reactive trajectories

    SciTech Connect

    Lorquet, J. C.

    2015-09-14

    The purpose of the present work is to determine initial conditions that generate reacting, recrossing-free trajectories that cross the conventional dividing surface of transition state theory (i.e., the plane in configuration space passing through a saddle point of the potential energy surface and perpendicular to the reaction coordinate) without ever returning to it. Local analytical equations of motion valid in the neighborhood of this planar surface have been derived as an expansion in Poisson brackets. We show that the mere presence of a saddle point implies that reactivity criteria can be quite simply formulated in terms of elements of this series, irrespective of the shape of the potential energy function. Some of these elements are demonstrated to be equal to a sum of squares and thus to be necessarily positive, which has a profound impact on the dynamics. The method is then applied to a three-dimensional model describing an atom-diatom interaction. A particular relation between initial conditions is shown to generate a bundle of reactive trajectories that form reactive cylinders (or conduits) in phase space. This relation considerably reduces the phase space volume of initial conditions that generate recrossing-free trajectories. Loci in phase space of reactive initial conditions are presented. Reactivity is influenced by symmetry, as shown by a comparative study of collinear and bent transition states. Finally, it is argued that the rules that have been derived to generate reactive trajectories in classical mechanics are also useful to build up a reactive wave packet.

  12. Combining transition state theory with quasiclassical trajectory calculations. III. Applications to the three-dimensional H + H 2(ν) reaction

    NASA Astrophysics Data System (ADS)

    Frost, Robert J.; Smith, Ian W. M.

    1987-11-01

    A new method is described of using quasiclassical trajectories to study the dynamics of elementary reactions in three dimensions. Trajectories are initiated in the phase space of suitably chosen transition state and run forwards and backwards in time from the same starting point to simulate a complete collision. The transition state for a given vibrational level ν is determined by first finding pods (periodic orbiting dividing surfaces) on fixed-angle potential energy surfaces for which the action over one cycle of the pods motion is (ν + 1/2) h. The complete transition is then defined by joining these pods together. Methods are described for pseudo-randomly sampling the phase space of these transition states. Results for collisions of H + H 2(ν) with ν = 0-5 and 9 on the accurate Liu-Siegbahn-Truhlar-Horowitz surface are presented and compared with the results of conventional quasiclassical trajectory studies that have already been reported in the literature. Absolute values of rate constants are obtained using the adiabatic reactive sudden version of the transition state theory. Comparisons of our combined method with conventional techniques are encouraging and there is a considerable saving in computer time resulting from the elimination of trajectories which do not reach the strong interaction zone. Only slight differences are found when the energy of the transition state bending motion is set equal to its zero-point quantum value rather than selected from a classical Boltzmann distribution.

  13. California's Transition to the Common Core State Standards: The State's Role in Local Capacity Building

    ERIC Educational Resources Information Center

    Warren, Paul; Murphy, Patrick

    2014-01-01

    The Common Core State Standards (CCSS) and the Local Control Funding Formula are introducing major changes to California's K-12 system. Implementation of new curricula and instruction is under way at the district level, but California started its transition relatively late and it has taken a more decentralized approach than most other states.…

  14. Specificity in transition state binding: the Pauling model revisited.

    PubMed

    Amyes, Tina L; Richard, John P

    2013-03-26

    Linus Pauling proposed that the large rate accelerations for enzymes are caused by the high specificity of the protein catalyst for binding the reaction transition state. The observation that stable analogues of the transition states for enzymatic reactions often act as tight-binding inhibitors provided early support for this simple and elegant proposal. We review experimental results that support the proposal that Pauling's model provides a satisfactory explanation for the rate accelerations for many heterolytic enzymatic reactions through high-energy reaction intermediates, such as proton transfer and decarboxylation. Specificity in transition state binding is obtained when the total intrinsic binding energy of the substrate is significantly larger than the binding energy observed at the Michaelis complex. The results of recent studies that aimed to characterize the specificity in binding of the enolate oxygen at the transition state for the 1,3-isomerization reaction catalyzed by ketosteroid isomerase are reviewed. Interactions between pig heart succinyl-coenzyme A:3-oxoacid coenzyme A transferase (SCOT) and the nonreacting portions of coenzyme A (CoA) are responsible for a rate increase of 3 × 10(12)-fold, which is close to the estimated total 5 × 10(13)-fold enzymatic rate acceleration. Studies that partition the interactions between SCOT and CoA into their contributing parts are reviewed. Interactions of the protein with the substrate phosphodianion group provide an ~12 kcal/mol stabilization of the transition state for the reactions catalyzed by triosephosphate isomerase, orotidine 5'-monophosphate decarboxylase, and α-glycerol phosphate dehydrogenase. The interactions of these enzymes with the substrate piece phosphite dianion provide a 6-8 kcal/mol stabilization of the transition state for reaction of the appropriate truncated substrate. Enzyme activation by phosphite dianion reflects the higher dianion affinity for binding to the enzyme-transition

  15. MOST Space-based Photometry of the Transiting Exoplanet System HD 209458: Transit Timing to Search for Additional Planets

    NASA Astrophysics Data System (ADS)

    Miller-Ricci, Eliza; Rowe, Jason F.; Sasselov, Dimitar; Matthews, Jaymie M.; Guenther, David B.; Kuschnig, Rainer; Moffat, Anthony F. J.; Rucinski, Slavek M.; Walker, Gordon A. H.; Weiss, Werner W.

    2008-07-01

    We report on the measurement of transit times for the HD 209458 planetary system from photometry obtained with the MOST (Microvariability and Oscillations of Stars) space telescope. Deviations from a constant orbital period can indicate the presence of additional planets in the system that are yet undetected, potentially with masses approaching an Earth mass. The MOST data sets of HD 209458 from 2004 and 2005 represent unprecedented time coverage with nearly continuous observations spanning 14 and 43 days and monitoring three transits and 12 consecutive transits, respectively. The transit times that we obtain show no variations on three scales: (1) no long-term change in P since before 2004 at 25 ms level, (2) no trend in transit timings during the 2005 run, and (3) no individual transit timing deviations above 80 s level. Together with previously published transit times from Agol & Steffen, this allows us to place limits on the presence of additional close-in planets in the system, in some cases down to below an Earth mass. This result, along with previous radial velocity work, now eliminates the possibility that a perturbing planet could be responsible for the additional heat source needed to explain HD 209458b's anomalous low density.

  16. A United States regulator's perspective on the ongoing chlorofluorocarbon transition.

    PubMed

    Meyer, R J

    1999-12-01

    The Food and Drug Administration (FDA) put in place a general ban on the use of chlorofluorocarbons for the products it regulates (medical devices, drugs, and foods) in 1978, exempting those products where chlorofluorocarbon use was determined to be essential for the public health. In the intervening years, as the international commitment to a full transition away from all chlorofluorocarbon use took shape under the Montreal Protocol, the FDA has worked with industry to facilitate the development and testing of alternative technologies and products for inhalation drug products. As these alternative products begin to move from testing through the approval process and into marketing, the FDA is working collaboratively with the Environmental Protection Agency, other governmental agencies, and nongovernmental stakeholders to develop a transition policy for the United States. The transition policy for metered dose inhalers must be one that achieves the dual aims of first protecting the patients who rely on these vital medical products, while also achieving the public health need of protecting the ozone layer. As a part of developing such a transition strategy, the FDA published an advance notice of proposed rulemaking (ANPRM) in March 1997. The ANPRM proposed mechanisms by which the FDA could determine when chlorofluorocarbon use in a drug product could no longer be considered essential. The ANPRM resulted in a large amount of valuable public debate and input. The FDA is now working to incorporate the knowledge gained from these public comments as it continues the rule-making process.

  17. Lagrangian Descriptors of Thermalized Transition States on Time-Varying Energy Surfaces

    NASA Astrophysics Data System (ADS)

    Craven, Galen T.; Hernandez, Rigoberto

    2015-10-01

    Thermalized chemical reactions driven under dynamical load are characteristic of activated dynamics for arbitrary nonautonomous systems. Recent generalizations of transition state theory to obtain formally exact rates have required the construction of a time-dependent transition state trajectory. Here, we show that Lagrangian descriptors can be used to obtain this structure directly. By developing a phase space separatrix that is void of recrossings, these constructs allow for the principal criterion in the implementation of modern rate theories to be satisfied. Thus, the reactive flux over a time-varying barrier can be determined without ambiguity in chemical reactions. The generality of the formalism suggests that this approach is applicable to any activated system subjected to arbitrary driving and thermal fluctuations.

  18. Wannier function analysis of charge states in transition metal oxides

    NASA Astrophysics Data System (ADS)

    Quan, Yundi; Pickett, Warren

    2015-03-01

    The charge (or oxidation) state of a cation has been a crucial concept in analyzing the electronic and magnetic properties of oxides as well as interpreting ``charge ordering'' metal-insulator transitions. In recent years a few methods have been proposed for the objective identification of charge states, beyond the conventional (and occasionally subjective) use of projected densities of states, weighted band structures (fatbands), and Born effective charges. In the past two decades Wannier functions (WFs) and particularly maximally localized WFs (MLWFs), have become an indispensable tool for several different purposes in electronic structure studies. These developments have motivated us to explore the charge state picture from the perspective of MLWFs. We will illustrate with a few transition metal oxide examples such as AgO and YNiO3 that the shape, extent, and location of the charge centers of the MLWFs provide insights into how cation-oxygen hybridization determines chemical bonding, charge distribution, and ``charge ordering.'' DOE DE-FG02-04ER46111.

  19. Mechanical induction of transitions into mesenchymal and amoeboid states

    NASA Astrophysics Data System (ADS)

    Liphardt, Jan

    One of the fundamental mysteries of biology lies in the ability of cells to convert from one phenotype to another in response to external control inputs. We have been studying the Epithelial-to-Mesenchymal Transition (EMT), which allows organized assemblies of epithelial cells to scatter into lone mesenchymal cells. EMT is critical for normal development and wound healing, and may be important for cancer metastasis. I'll present recent data on disorganizing mammary epithelial structures. We have used CRISPR to insert fluorescent tags directly into eight EMT-related genes (such as E-cadherin and Vimentin), which allows us to monitor the dynamics of the transition in real time, subject only to delays imposed by fluorophore folding/maturation times. With this information, we can begin to order events in time (temporal resolution 30 minutes), starting with external signal inputs and proceeding through a secession of intracellular changes of gene expression on the path to the mesenchymal state.

  20. Symmetry for the nonadiabatic transition in Floquet states

    SciTech Connect

    Hijii, Keigo; Miyashita, Seiji

    2010-01-15

    The frequency of the Rabi oscillation driven by a periodic external field varies with the parameters of the external field, e.g., frequency and amplitude, and it becomes zero at some points of the parameters, which is called coherent destruction of tunneling. This phenomenon is understood as a degeneracy of the Floquet quasienergies as a function of the parameters. We prove that the time-reversal symmetry of the external field is a necessary condition of the degeneracy. We demonstrate the gap opening in the quasienergy spectrum in asymmetrically periodically driven systems. Moreover, an adiabatic transition of the Floquet states is demonstrated and analyzed in the analogy to the Landau-Zener transition.

  1. A Space for Academic Play: Student Learning Journals as Transitional Writing

    ERIC Educational Resources Information Center

    Creme, Phyllis

    2008-01-01

    This article builds on the author's previous research on student learning journals to explore how their use can give students a "space" to engage meaningfully and in their own way with their university work. Drawing on the psychoanalytical concept of transitional space and on notions of narrative, it is argued that the student learning journal can…

  2. Public Pedagogy via PostSecret: A Transitional Space Where Private and Public Coincide

    ERIC Educational Resources Information Center

    Motter, Jennifer L.

    2011-01-01

    PostSecret (www.postsecret.com) is a transitional space where the in-betweenness of public and private exists. Within this space, peer public pedagogy occurs through critical participatory democratic interactions of community participants. Integrating PostSecret into the art education curriculum can offer the potential for generative knowledge…

  3. Phase space flow of particles in squeezed states

    NASA Technical Reports Server (NTRS)

    Ceperley, Peter H.

    1994-01-01

    The manipulation of noise and uncertainty in squeezed states is governed by the wave nature of the quantum mechanical particles in these states. This paper uses a deterministic model of quantum mechanics in which real guiding waves control the flow of localized particles. This model will be used to examine the phase space flow of particles in typical squeezed states.

  4. Challenges for Transitioning Science Knowledge to an Operational Environment for Space Weather

    NASA Technical Reports Server (NTRS)

    Spann, James

    2012-01-01

    Effectively transitioning science knowledge to an operational environment relevant to space weather is critical to meet the civilian and defense needs, especially considering how technologies are advancing and present evolving susceptibilities to space weather impacts. The effort to transition scientific knowledge to a useful application is not a research task nor is an operational activity, but an effort that bridges the two. Successful transitioning must be an intentional effort that has a clear goal for all parties and measureable outcome and deliverable. This talk will present proven methodologies that have been demonstrated to be effective for terrestrial weather and disaster relief efforts, and how those methodologies can be applied to space weather transition efforts.

  5. Simulation of space charge effects and transition crossing in the Fermilab Booster

    SciTech Connect

    Lucas, P.; MacLachlan, J.

    1987-03-01

    The longitudinal phase space program ESME, modified for space charge and wall impedance effects, has been used to simulate transition crossing in the Fermilab Booster. The simulations yield results in reasonable quantitative agreement with measured parameters. They further indicate that a transition jump scheme currently under construction will significantly reduce emittance growth, while attempts to alter machine impedance are less obviously beneficial. In addition to presenting results, this paper points out a serious difficulty, related to statistical fluctuations, in the space charge calculation. False indications of emittance growth can appear if care is not taken to minimize this problem.

  6. Noise-induced transitions in state-dependent dichotomous processes.

    PubMed

    Laio, Francesco; Ridolfi, Luca; D'Odorico, Paolo

    2008-09-01

    In a number of stochastic systems the random forcing is represented as a dichotomous Markov noise. A common characteristic of these models is that the noise is usually supposed to be independent of the state of the forced dynamical system. However, there are several situations in which positive or negative feedback exist between the system and the random driver. This paper investigates a class of systems characterized by feedback between dichotomous Markov noise and the system's dynamics. The effect of the feedback is accounted for through a state dependency in the transition rates of the dichotomous noise. We study noise-induced transitions in these systems, with special attention to the delicate problem of correctly defining the deterministic counterpart of the stochastic system. We find that (i) if in the absence of any feedback the dynamical system has a single deterministic stable point, the deterministic dynamics remain monostable when a negative feedback is introduced, while they may become bistable in the presence of a positive feedback. (ii) Noise may induce bistability in the presence of a null or negative feedback. (iii) Bistable deterministic dynamics, induced by the positive feedback, may be destroyed by the noise, which tends to stabilize the system around a new intermediate stable state between those of the deterministic dynamics.

  7. The transition of ground-based space environmental effects testing to the space environment

    NASA Technical Reports Server (NTRS)

    Zaat, Stephen V.; Schaefer, Glen A.; Wallace, John F.

    1991-01-01

    The goal of the space flight program at the Center for Commercial Development of Space (CCDS)--Materials for Space Structures is to provide environmentally stable structural materials to support the continued humanization and commercialization of the space frontier. Information on environmental stability will be obtained through space exposure, evaluation, documentation, and subsequent return to the supplier of the candidate material for internal investigation. This program provides engineering and scientific service to space systems development firms and also exposes CCDS development candidate materials to space environments representative of in-flight conditions. The maintenance of a technological edge in space for NASA suggests the immediate search for space materials that maintain their structural integrity and remain environmentally stable. The materials being considered for long-lived space structures are complex, high strength/weight ratio composites. In order for these new candidate materials to qualify for use in space structures, they must undergo strenuous testing to determine their reliability and stability when subjected to the space environment. Ultraviolet radiation, atomic oxygen, debris/micrometeoroids, charged particles radiation, and thermal fatigue all influence the design of space structural materials. The investigation of these environmental interactions is the key purpose of this center. Some of the topics discussed with respect to the above information include: the Space Transportation System, mission planning, spaceborne experiments, and space flight payloads.

  8. Deep Space Habitat Concept of Operations for Transit Mission Phases

    NASA Technical Reports Server (NTRS)

    Hoffman, Stephen J.

    2011-01-01

    The National Aeronautics and Space Administration (NASA) has begun evaluating various mission and system components of possible implementations of what the U.S. Human Spaceflight Plans Committee (also known as the Augustine Committee) has named the flexible path (Anon., 2009). As human spaceflight missions expand further into deep space, the duration of these missions increases to the point where a dedicated crew habitat element appears necessary. There are several destinations included in this flexible path a near Earth asteroid (NEA) mission, a Phobos/Deimos (Ph/D) mission, and a Mars surface exploration mission that all include at least a portion of the total mission in which the crew spends significant periods of time (measured in months) in the deep space environment and are thus candidates for a dedicated habitat element. As one facet of a number of studies being conducted by the Human Spaceflight Architecture Team (HAT) a workshop was conducted to consider how best to define and quantify habitable volume for these future deep space missions. One conclusion reached during this workshop was the need for a description of the scope and scale of these missions and the intended uses of a habitat element. A group was set up to prepare a concept of operations document to address this need. This document describes a concept of operations for a habitat element used for these deep space missions. Although it may eventually be determined that there is significant overlap with this concept of operations and that of a habitat destined for use on planetary surfaces, such as the Moon and Mars, no such presumption is made in this document.

  9. Solid state neutron dosimeter for space applications

    NASA Technical Reports Server (NTRS)

    Entine, Gerald; Nagargar, Vivek; Sharif, Daud

    1990-01-01

    Personnel engaged in space flight are exposed to significant flux of high energy neutrons arising from both primary and secondary sources of ionizing radiation. Presently, there exist no compact neutron sensor capable of being integrated in a flight instrument to provide real time measurement of this radiation flux. A proposal was made to construct such an instrument using special PIN silicon diode which has the property of being insensitive to the other forms of ionizing radiation. Studies were performed to determine the design and construction of a better reading system to allow the PIN diode to be read with high precision. The physics of the device was studied, especially with respect to those factors which affect the sensitivity and reproducibility of the neutron response. This information was then used to develop methods to achieve high sensitivity at low neutron doses. The feasibility was shown of enhancing the PIN diode sensitivity to make possible the measurement of the low doses of neutrons encountered in space flights. The new PIN diode will make possible the development of a very compact, accurate, personal neutron dosimeter.

  10. Transition-state structures for enzymatic and alkaline phosphotriester hydrolysis

    SciTech Connect

    Caldwell, S.R.; Raushel, F.M. ); Weiss, P.M.; Cleland, W.W. )

    1991-07-30

    The primary and secondary {sup 18}O isotope effects for the alkaline (KOH) and enzymatic (phosphotriesterase) hydrolysis of two phosphotriesters, O,O-diethyl p-nitrophenyl phosphate (I) and O,O-diethyl O-(4-carbamoylphenyl) phosphate (II), are consistent with an associative mechanism with significant changes in bond order to both the phosphoryl and phenolic leaving group oxygens in the transition state. The synthesis of ({sup 15}N, phosphoryl-{sup 18}O)-,({sup 15}N, phenolic-{sup 18}O)-, and ({sup 15}N)-O,O-diethyl p-nitrophenyl phosphate and O,O-diethyl O-(4-carbamoylphenyl)phosphate is described. The primary and secondary {sup 18}O isotope effects for the alkaline hydrolysis of compound I are 1.0060 and 1.0063 {plus minus} 0.0001, whereas for compound II they are 1.027{plus minus}0.002 and 1.025 {plus minus} 0.002, respectively. These isotope effects are consistent with the rate-limiting addition of hydroxide and provide evidence for a S{sub N}2-like transition state with the absence of a stable phosphorane intermediate. For the enzymatic hydrolysis of compound I, the primary and secondary {sup 18}O isotope effects are very small, 1.0020 and 1.0021{plus minus}0.0004, respectively, and indicate that the chemical step in the enzymatic mechanism is not rate-limiting. The {sup 18}O isotope effects for the enzymatic hydrolysis of compound II are 1.036{plus minus}0.001 and 1.0181{plus minus}0.0007, respectively, and are comparable in magnitude to the isotope effects for alkaline hydrolysis, suggesting that the chemical step is rate-limiting. The relative magnitude of the primary {sup 18}O isotope effects for the alkaline and enzymatic hydrolysis of compound II reflect a transition state that is more progressed for the enzymatic reaction.

  11. Transition-state structures for enzymatic and alkaline phosphotriester hydrolysis.

    PubMed

    Caldwell, S R; Raushel, F M; Weiss, P M; Cleland, W W

    1991-07-30

    The primary and secondary 18O isotope effects for the alkaline (KOH) and enzymatic (phosphotriesterase) hydrolysis of two phosphotriesters, O,O-diethyl p-nitrophenyl phosphate (I) and O,O-diethyl O-(4-carbamoylphenyl) phosphate (II), are consistent with an associative mechanism with significant changes in bond order to both the phosphoryl and phenolic leaving group oxygens in the transition state. The synthesis of [15N, phosphoryl-18O]-, [15N, phenolic-18O]-, and [15N]-O,O-diethyl p-nitrophenyl phosphate and O,O-diethyl O-(4-carbamoylphenyl)phosphate is described. The primary and secondary 18O isotope effects for the alkaline hydrolysis of compound I are 1.0060 and 1.0063 +/- 0.0001, whereas for compound II they are 1.027 +/- 0.002 and 1.025 +/- 0.002, respectively. These isotope effects are consistent with the rate-limiting addition of hydroxide and provide evidence for a SN2-like transition state with the absence of a stable phosphorane intermediate. For the enzymatic hydrolysis of compound I, the primary and secondary 18O isotope effects are very small, 1.0020 and 1.0021 +/- 0.0004, respectively, and indicate that the chemical step in the enzymatic mechanism is not rate-limiting. The 18O isotope effects for the enzymatic hydrolysis of compound II are 1.036 +/- 0.001 and 1.0181 +/- 0.0007, respectively, and are comparable in magnitude to the isotope effects for alkaline hydrolysis, suggesting that the chemical step is rate-limiting. The relative magnitude of the primary 18O isotope effects for the alkaline and enzymatic hydrolysis of compound II reflect a transition state that is more progressed for the enzymatic reaction.

  12. Transition state and ground state properties of the helix–coil transition in peptides deduced from high-pressure studies

    PubMed Central

    Neumaier, Sabine; Büttner, Maren; Bachmann, Annett; Kiefhaber, Thomas

    2013-01-01

    Volume changes associated with protein folding reactions contain valuable information about the folding mechanism and the nature of the transition state. However, meaningful interpretation of such data requires that overall volume changes be deconvoluted into individual contributions from different structural components. Here we focus on one type of structural element, the α-helix, and measure triplet–triplet energy transfer at high pressure to determine volume changes associated with the helix–coil transition. Our results reveal that the volume of a 21-amino-acid alanine-based peptide shrinks upon helix formation. Thus, helices, in contrast with native proteins, become more stable with increasing pressure, explaining the frequently observed helical structures in pressure-unfolded proteins. Both helix folding and unfolding become slower with increasing pressure. The volume changes associated with the addition of a single helical residue to a preexisting helix were obtained by comparing the experimental results with Monte Carlo simulations based on a kinetic linear Ising model. The reaction volume for adding a single residue to a helix is small and negative (−0.23 cm3 per mol = −0.38 Å3 per molecule) implying that intrahelical hydrogen bonds have a smaller volume than peptide-water hydrogen bonds. In contrast, the transition state has a larger volume than either the helical or the coil state, with activation volumes of 2.2 cm3/mol (3.7 Å3 per molecule) for adding and 2.4 cm3/mol (4.0 Å3 per molecule) for removing one residue. Thus, addition or removal of a helical residue proceeds through a transitory high-energy state with a large volume, possibly due to the presence of unsatisfied hydrogen bonds, although steric effects may also contribute. PMID:24324160

  13. E2 transitions between excited single-phonon states: Role of ground-state correlations

    NASA Astrophysics Data System (ADS)

    Kamerdzhiev, S. P.; Voitenkov, D. A.

    2016-11-01

    The probabilities for E2 transitions between low-lying excited 3- and 5- single-phonon states in the 208Pb and 132Sn magic nuclei are estimated on the basis of the theory of finite Fermi systems. The approach used involves a new type of ground-state correlations, that which originates from integration of three (rather than two, as in the random-phase approximation) single-particle Green's functions. These correlations are shown to make a significant contribution to the probabilities for the aforementioned transitions.

  14. Design and Implementation of the Boundary Layer Transition Flight Experiment on Space Shuttle Discovery

    NASA Technical Reports Server (NTRS)

    Spanos, Theodoros A.; Micklos, Ann

    2010-01-01

    In an effort to better the understanding of high speed aerodynamics, a series of flight experiments were installed on Space Shuttle Discovery during the STS-119 and STS-128 missions. This experiment, known as the Boundary Layer Transition Flight Experiment (BLTFE), provided the technical community with actual entry flight data from a known height protuberance at Mach numbers at and above Mach 15. Any such data above Mach 15 is irreproducible in a laboratory setting. Years of effort have been invested in obtaining this valuable data, and many obstacles had to be overcome in order to ensure the success of implementing an Orbiter modification. Many Space Shuttle systems were involved in the installation of appropriate components that revealed 'concurrent engineering' was a key integration tool. This allowed the coordination of all various parts and pieces which had to be sequenced appropriately and installed at the right time. Several issues encountered include Orbiter configuration and access, design requirements versus current layout, implementing the modification versus typical processing timelines, and optimizing the engineering design cycles and changes. Open lines of communication within the entire modification team were essential to project success as the team was spread out across the United States, from NASA Kennedy Space Center in Florida, to NASA Johnson Space Center in Texas, to Boeing Huntington Beach, California among others. The forum permits the discussion of processing concerns from the design phase to the implementation phase, which eventually saw the successful flights and data acquisition on STS-119 in March 2009 and on STS-128 in September 2009.

  15. 19 CFR 123.42 - Truck shipments transiting the United States.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Truck shipments transiting the United States. 123...; DEPARTMENT OF THE TREASURY CBP RELATIONS WITH CANADA AND MEXICO United States and Canada In-Transit Truck Procedures § 123.42 Truck shipments transiting the United States. (a) Manifest required. Trucks...

  16. 19 CFR 123.42 - Truck shipments transiting the United States.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 1 2014-04-01 2014-04-01 false Truck shipments transiting the United States. 123...; DEPARTMENT OF THE TREASURY CBP RELATIONS WITH CANADA AND MEXICO United States and Canada In-Transit Truck Procedures § 123.42 Truck shipments transiting the United States. (a) Manifest required. Trucks...

  17. 19 CFR 123.42 - Truck shipments transiting the United States.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 1 2013-04-01 2013-04-01 false Truck shipments transiting the United States. 123...; DEPARTMENT OF THE TREASURY CBP RELATIONS WITH CANADA AND MEXICO United States and Canada In-Transit Truck Procedures § 123.42 Truck shipments transiting the United States. (a) Manifest required. Trucks...

  18. 19 CFR 123.42 - Truck shipments transiting the United States.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Truck shipments transiting the United States. 123...; DEPARTMENT OF THE TREASURY CBP RELATIONS WITH CANADA AND MEXICO United States and Canada In-Transit Truck Procedures § 123.42 Truck shipments transiting the United States. (a) Manifest required. Trucks...

  19. 19 CFR 123.42 - Truck shipments transiting the United States.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Truck shipments transiting the United States. 123...; DEPARTMENT OF THE TREASURY CUSTOMS RELATIONS WITH CANADA AND MEXICO United States and Canada In-Transit Truck Procedures § 123.42 Truck shipments transiting the United States. (a) Manifest required. Trucks...

  20. Detecting critical state before phase transition of complex systems by hidden Markov model

    NASA Astrophysics Data System (ADS)

    Liu, Rui; Chen, Pei; Li, Yongjun; Chen, Luonan

    Identifying the critical state or pre-transition state just before the occurrence of a phase transition is a challenging task, because the state of the system may show little apparent change before this critical transition during the gradual parameter variations. Such dynamics of phase transition is generally composed of three stages, i.e., before-transition state, pre-transition state, and after-transition state, which can be considered as three different Markov processes. Thus, based on this dynamical feature, we present a novel computational method, i.e., hidden Markov model (HMM), to detect the switching point of the two Markov processes from the before-transition state (a stationary Markov process) to the pre-transition state (a time-varying Markov process), thereby identifying the pre-transition state or early-warning signals of the phase transition. To validate the effectiveness, we apply this method to detect the signals of the imminent phase transitions of complex systems based on the simulated datasets, and further identify the pre-transition states as well as their critical modules for three real datasets, i.e., the acute lung injury triggered by phosgene inhalation, MCF-7 human breast cancer caused by heregulin, and HCV-induced dysplasia and hepatocellular carcinoma.

  1. The Physics of Imaging with Remote Sensors : Photon State Space & Radiative Transfer

    NASA Technical Reports Server (NTRS)

    Davis, Anthony B.

    2012-01-01

    Standard (mono-pixel/steady-source) retrieval methodology is reaching its fundamental limit with access to multi-angle/multi-spectral photo- polarimetry. Next... Two emerging new classes of retrieval algorithm worth nurturing: multi-pixel time-domain Wave-radiometry transition regimes, and more... Cross-fertilization with bio-medical imaging. Physics-based remote sensing: - What is "photon state space?" - What is "radiative transfer?" - Is "the end" in sight? Two wide-open frontiers! center dot Examples (with variations.

  2. Metal-insulator transitions of bulk and domain-wall states in pyrochlore iridates

    NASA Astrophysics Data System (ADS)

    Ueda, Kentaro

    A family of pyrochlore iridates R2Ir2O7 offers an ideal platform to explore intriguing phases such as topological Mott insulator and Weyl semimetal. Here we report transport and spectroscopic studies on the metal-insulator transition (MIT) induced by the modulations of effective electron correlation and magnetic structures, which is finely tuned by external pressure, chemical substitutions (R = Nd1-x Prx and SmyNd1-y) , and magnetic field. A reentrant insulator-metal-insulator transition is observed near the paramagnetic insulator-metal phase boundary reminiscent of a first-order Mott transition for R = SmyNd1-y compounds (y~0.8). The metallic states on the magnetic domain walls (DWs), which are observed for R = Nd in real space as well as in transport properties, is simultaneously turned into the insulating one. These findings imply that the DW electronic state is intimately linked to the bulk states. For the mixed R = Nd1-x Prx compounds, the divergent behavior of resistivity with antiferromagnetic order is significantly suppressed by applying a magnetic field along [001] direction. It is attributed to the phase transition from the antiferromagnetic insulating state to the novel Weyl (semi-)metal state accompanied by the change of magnetic structure. The present study combined with experiment and theory suggests that there are abundant exotic phases with physical parameters such as electron correlation and Ir-5 d magnetic order pattern. Work performed in collaboration with J. Fujioka, B.-J. Yang, C. Terakura, N. Nagaosa, Y. Tokura (University of Tokyo, RIKEN CEMS), J. Shiogai, A. Tsukazaki, S. Nakamura, S. Awaji (Tohoku University). 1This work was supported by JSPS FIRST Program and Grant-in-Aid for Scientific Research (Grants No. 80609488 and No. 24224009).

  3. Thylakoid membrane remodeling during state transitions in Arabidopsis.

    PubMed

    Chuartzman, Silvia G; Nevo, Reinat; Shimoni, Eyal; Charuvi, Dana; Kiss, Vladimir; Ohad, Itzhak; Brumfeld, Vlad; Reich, Ziv

    2008-04-01

    Adaptability of oxygenic photosynthetic organisms to fluctuations in light spectral composition and intensity is conferred by state transitions, short-term regulatory processes that enable the photosynthetic apparatus to rapidly adjust to variations in light quality. In green algae and higher plants, these processes are accompanied by reversible structural rearrangements in the thylakoid membranes. We studied these structural changes in the thylakoid membranes of Arabidopsis thaliana chloroplasts using atomic force microscopy, scanning and transmission electron microscopy, and confocal imaging. Based on our results and on the recently determined three-dimensional structure of higher-plant thylakoids trapped in one of the two major light-adapted states, we propose a model for the transitions in membrane architecture. The model suggests that reorganization of the membranes involves fission and fusion events that occur at the interface between the appressed (granal) and nonappressed (stroma lamellar) domains of the thylakoid membranes. Vertical and lateral displacements of the grana layers presumably follow these localized events, eventually leading to macroscopic rearrangements of the entire membrane network.

  4. Thylakoid Membrane Remodeling during State Transitions in Arabidopsis[W

    PubMed Central

    Chuartzman, Silvia G.; Nevo, Reinat; Shimoni, Eyal; Charuvi, Dana; Kiss, Vladimir; Ohad, Itzhak; Brumfeld, Vlad; Reich, Ziv

    2008-01-01

    Adaptability of oxygenic photosynthetic organisms to fluctuations in light spectral composition and intensity is conferred by state transitions, short-term regulatory processes that enable the photosynthetic apparatus to rapidly adjust to variations in light quality. In green algae and higher plants, these processes are accompanied by reversible structural rearrangements in the thylakoid membranes. We studied these structural changes in the thylakoid membranes of Arabidopsis thaliana chloroplasts using atomic force microscopy, scanning and transmission electron microscopy, and confocal imaging. Based on our results and on the recently determined three-dimensional structure of higher-plant thylakoids trapped in one of the two major light-adapted states, we propose a model for the transitions in membrane architecture. The model suggests that reorganization of the membranes involves fission and fusion events that occur at the interface between the appressed (granal) and nonappressed (stroma lamellar) domains of the thylakoid membranes. Vertical and lateral displacements of the grana layers presumably follow these localized events, eventually leading to macroscopic rearrangements of the entire membrane network. PMID:18398051

  5. Tracking the embryonic stem cell transition from ground state pluripotency.

    PubMed

    Kalkan, Tüzer; Olova, Nelly; Roode, Mila; Mulas, Carla; Lee, Heather J; Nett, Isabelle; Marks, Hendrik; Walker, Rachael; Stunnenberg, Hendrik G; Lilley, Kathryn S; Nichols, Jennifer; Reik, Wolf; Bertone, Paul; Smith, Austin

    2017-04-01

    Mouse embryonic stem (ES) cells are locked into self-renewal by shielding from inductive cues. Release from this ground state in minimal conditions offers a system for delineating developmental progression from naïve pluripotency. Here, we examine the initial transition process. The ES cell population behaves asynchronously. We therefore exploited a short-half-life Rex1::GFP reporter to isolate cells either side of exit from naïve status. Extinction of ES cell identity in single cells is acute. It occurs only after near-complete elimination of naïve pluripotency factors, but precedes appearance of lineage specification markers. Cells newly departed from the ES cell state display features of early post-implantation epiblast and are distinct from primed epiblast. They also exhibit a genome-wide increase in DNA methylation, intermediate between early and late epiblast. These findings are consistent with the proposition that naïve cells transition to a distinct formative phase of pluripotency preparatory to lineage priming.

  6. Transition states of magnetization reversal in ferromagnetic nanorings

    NASA Astrophysics Data System (ADS)

    Chaves-O'Flynn, Gabriel; Kent, Andrew; Stein, Daniel

    2008-03-01

    Thin ferromagnetic rings are of interest for fundamental studies of magnetization reversal, in part, because they are a rare example of a geometry for which an analytical solution for the rate of thermally induced switching has been determined [1]. The theoretical model predicts the transition state to be either a global magnetization rotation of constant azimuthal angle or a localized fluctuation, denoted the instanton saddle. Numerically we have confirmed that for a range of values of external magnetic field and ring size the instanton saddle is energetically favored [2]. The model takes the annular width to be small compared to the mean radius of the annulus; in which case the main contribution to the magnetization energy comes from the surface magnetostatic energy. We present numerical micromagnetic calculations of the activation energy for thermally induced magnetization reversal for the two different transition states for the case when the annular width is equal in magnitude to the mean radius of the ring. Results of the total and surface magnetostatic energies are compared for different ring sizes. [1] K. Martens, D.L. Stein, A.D. Kent, PRB 73, 054413 (2006) [2] G.D. Chaves-O'Flynn, K. Xiao, D.L. Stein, A. D. Kent, arXiv:0710.2546 (2007)

  7. Physiologic Measures of Animal Stress during Transitional States of Consciousness

    PubMed Central

    Meyer, Robert E.

    2015-01-01

    Simple Summary The humaneness, and therefore suitability, of any particular agent or method used to produce unconsciousness in animals, whether for anesthesia, euthanasia, humane slaughter, or depopulation, depends on the experience of pain or distress prior to loss of consciousness. Commonly reported physiologic measures of animal stress, including physical movement and vocalization, heart rate and ECG, electroencephalographic activity, and plasma and neuronal stress markers are discussed within this context. Abstract Determination of the humaneness of methods used to produce unconsciousness in animals, whether for anesthesia, euthanasia, humane slaughter, or depopulation, relies on our ability to assess stress, pain, and consciousness within the contexts of method and application. Determining the subjective experience of animals during transitional states of consciousness, however, can be quite difficult; further, loss of consciousness with different agents or methods may occur at substantially different rates. Stress and distress may manifest behaviorally (e.g., overt escape behaviors, approach-avoidance preferences [aversion]) or physiologically (e.g., movement, vocalization, changes in electroencephalographic activity, heart rate, sympathetic nervous system [SNS] activity, hypothalamic-pituitary axis [HPA] activity), such that a one-size-fits-all approach cannot be easily applied to evaluate methods or determine specific species applications. The purpose of this review is to discuss methods of evaluating stress in animals using physiologic methods, with emphasis on the transition between the conscious and unconscious states. PMID:26479382

  8. The role of space telescopes in the characterization of transiting exoplanets.

    PubMed

    Hatzes, Artie P

    2014-09-18

    Characterization studies now have a dominant role in the field of exoplanets. Such studies include the measurement of an exoplanet's bulk density, its brightness temperature and the chemical composition of its atmosphere. The use of space telescopes has played a key part in the characterization of transiting exoplanets. These facilities offer astronomers data of exquisite precision and temporal sampling as well as access to wavelength regions of the electromagnetic spectrum that are inaccessible from the ground. Space missions such as the Hubble Space Telescope, Microvariability and Oscillations of Stars (MOST), Spitzer Space Telescope, Convection, Rotation and Planetary Transits (CoRoT), and Kepler have rapidly advanced our knowledge of the physical properties of exoplanets and have blazed a trail for a series of future space missions that will help us to understand the observed diversity of exoplanets.

  9. Phase transitions of the generalized contact process with two absorbing states.

    PubMed

    Lee, Man Young; Vojta, Thomas

    2010-06-01

    We investigate the generalized contact process with two absorbing states in one space dimension by means of large-scale Monte Carlo simulations. Treating the creation rate of active sites between inactive domains as an independent parameter leads to a rich phase diagram. In addition to the conventional active and inactive phases we find a parameter region where the simple contact process is inactive, but an infinitesimal creation rate at the boundary between inactive domains is sufficient to take the system into the active phase. Thus, the generalized contact process has two different phase transition lines. The point separating them shares some characteristics with a multicritical point. We also study in detail the critical behaviors of these transitions and their universality.

  10. Transition of multidiffusive states in a biased periodic potential

    NASA Astrophysics Data System (ADS)

    Zhang, Jia-Ming; Bao, Jing-Dong

    2017-03-01

    We study a frequency-dependent damping model of hyperdiffusion within the generalized Langevin equation. The model allows for the colored noise defined by its spectral density, assumed to be proportional to ωδ -1 at low frequencies with 0 <δ <1 (sub-Ohmic damping) or 1 <δ <2 (super-Ohmic damping), where the frequency-dependent damping is deduced from the noise by means of the fluctuation-dissipation theorem. It is shown that for super-Ohmic damping and certain parameters, the diffusive process of the particle in a titled periodic potential undergos sequentially four time regimes: thermalization, hyperdiffusion, collapse, and asymptotical restoration. For analyzing transition phenomenon of multidiffusive states, we demonstrate that the first exist time of the particle escaping from the locked state into the running state abides by an exponential distribution. The concept of an equivalent velocity trap is introduced in the present model; moreover, reformation of ballistic diffusive system is also considered as a marginal situation but does not exhibit the collapsed state of diffusion.

  11. Conformational transition of giant DNA in a confined space surrounded by a phospholipid membrane.

    PubMed

    Kato, Ayako; Shindo, Eri; Sakaue, Takahiro; Tsuji, Akihiko; Yoshikawa, Kenichi

    2009-09-16

    It has been established that a long DNA molecule exhibits a large discrete conformational change from a coiled state to a highly folded state in aqueous solution, depending on the presence of various condensing agents such as polyamines. In this study, T4 DNA labeled with fluorescent dyes was encapsulated in a cell-sized microdroplet covered with a phospholipid membrane to investigate the conformational behavior of a DNA molecule in such a confined space. Fluorescence microscopy showed that the presence of Mg(2+) induced the adsorption of DNA onto the membrane inner-surface of a droplet composed of phosphatidylethanolamine, while no adsorption was observed onto a phosphatidylcholine membrane. Under the presence of spermine (tetravalent amine), DNA had a folded conformation in the bulk solution. However, when these molecules were encapsulated in the microdroplet, DNA adsorbed onto the membrane surface accompanied by unfolding of its structure into an extended coil conformation under high concentrations of Mg(2+). In addition, DNA molecules trapped in large droplets tended not to be adsorbed on the membrane, i.e., no conformational transition occurred. A thermodynamic analysis suggests that the translational entropy loss of a DNA molecule that is accompanied by adsorption is a key factor in these phenomena under micrometer-scale confinement.

  12. State-Space Stabilizing Controllers for Descriptor Systems

    NASA Astrophysics Data System (ADS)

    Inoue, Masaki; Wada, Teruyo; Ikeda, Masao; Uezato, Eiho

    This paper considers stabilization of linear time-invariant descriptor systems by dynamic output feedback controllers. We deal with general descriptor systems including those being irregular or impulsive, and derive state-space stabilizing controllers. On the derivation process of the state-space controllers, we first consider descriptor-type controllers. We present a necessary and sufficient condition for the existence of a descriptor-type controller which makes the closed-loop descriptor system regular, impulse-free, and stable. The condition is expressed in terms of linear matrix inequalities (LMIs), and we show that coefficient matrices of any descriptor-type stabilizing controller of the same size as the given descriptor system can be represented by the solution of the LMIs. Then, we present a necessary and sufficient condition for the descriptor-type controller to be transformable to an input-output equivalent state-space controller with the dimension of the dynamic order (the rank of the coefficient matrix for the time-derivative of the descriptor variable) of the given descriptor system, that is, a state-space stabilizing controller. The transformability condition is mild and almost always satisfied by the obtained descriptor-type controller. Furthermore, even if the transformability condition is not satisfied, a slightly modified solution of the LMIs, which always exists, gives a descriptor-type controller being transformable to a state-space controller. The transformation is carried out analytically, thus the coefficient matrices of any such state-space stabilizing controller can be expressed by the solution of the LMIs. We also reveal that if we restrict the classes of descriptor systems or descriptor-type controllers such that their transfer functions are strictly proper, the descriptor-type controllers obtained by the LMI condition are always transformable to state-space controllers.

  13. America's Next Great Ship: Space Launch System Core Stage Transitioning from Design to Manufacturing

    NASA Technical Reports Server (NTRS)

    Birkenstock, Benjamin; Kauer, Roy

    2014-01-01

    The Space Launch System (SLS) Program is essential to achieving the Nation's and NASA's goal of human exploration and scientific investigation of the solar system. As a multi-element program with emphasis on safety, affordability, and sustainability, SLS is becoming America's next great ship of exploration. The SLS Core Stage includes avionics, main propulsion system, pressure vessels, thrust vector control, and structures. Boeing manufactures and assembles the SLS core stage at the Michoud Assembly Facility (MAF) in New Orleans, LA, a historical production center for Saturn V and Space Shuttle programs. As the transition from design to manufacturing progresses, the importance of a well-executed manufacturing, assembly, and operation (MA&O) plan is crucial to meeting performance objectives. Boeing employs classic techniques such as critical path analysis and facility requirements definition as well as innovative approaches such as Constraint Based Scheduling (CBS) and Cirtical Chain Project Management (CCPM) theory to provide a comprehensive suite of project management tools to manage the health of the baseline plan on both a macro (overall project) and micro level (factory areas). These tools coordinate data from multiple business systems and provide a robust network to support Material & Capacity Requirements Planning (MRP/CRP) and priorities. Coupled with these tools and a highly skilled workforce, Boeing is orchestrating the parallel buildup of five major sub assemblies throughout the factory. Boeing and NASA are transforming MAF to host state of the art processes, equipment and tooling, the most prominent of which is the Vertical Assembly Center (VAC), the largest weld tool in the world. In concert, a global supply chain is delivering a range of structural elements and component parts necessary to enable an on-time delivery of the integrated Core Stage. SLS is on plan to launch humanity into the next phase of space exploration.

  14. Coherent states on horospheric three-dimensional Lobachevsky space

    NASA Astrophysics Data System (ADS)

    Kurochkin, Yu.; Rybak, I.; Shoukavy, Dz.

    2016-08-01

    In the paper it is shown that due to separation of variables in the Laplace-Beltrami operator (Hamiltonian of a free quantum particle) in horospheric and quasi-Cartesian coordinates of three dimensional Lobachevsky space, it is possible to introduce standard ("conventional" according to Perelomov [Generalized Coherent States and Their Applications (Springer-Verlag, 1986), p. 320]) coherent states. Some problems (oscillator on horosphere, charged particle in analogy of constant uniform magnetic field) where coherent states are suitable for treating were considered.

  15. Transition in the Human Exploration of Space at NASA

    NASA Technical Reports Server (NTRS)

    Koch, Carla A.; Cabana, Robert

    2011-01-01

    NASA is taking the next step in human exploration, beyond low Earth orbit. We have been going to low Earth orbit for the past 50 years and are using this experience to work with commercial companies to perform this function. This will free NASA resources to develop the systems necessary to travel to a Near Earth Asteroid, the Moon, Lagrange Points, and eventually Mars. At KSC, we are positioning ourselves to become a multi-user launch complex and everything we are working on is bringing us closer to achieving this goal. A vibrant multi-use spaceport is to the 21st Century what the airport was to the 20th Century - an invaluable transportation hub that supports government needs while promoting economic development and commercial markets beyond Earth's atmosphere. This past year saw the end of Shuttle, but the announcements of NASA's crew module, Orion, and heavy-lift rocket, the SLS, as well as the establishment of the Commercial Crew Program. We have a busy, but very bright future ahead of us and KSC is looking forward to playing an integral part in the next era of human space exploration. The future is SLS, 21st Century Ground Systems Program, and the Commercial Crew Program; and the future is here.

  16. Vibrational states and optical transitions in hydrogen bonds

    NASA Astrophysics Data System (ADS)

    Johannsen, P. G.

    1998-03-01

    Proton energies in hydrogen bonds are mostly calculated using a double Morse potential (the DMP model). This form, however, does not reproduce the experimentally observed correlation between the proton stretching frequency and the bond length in an extended bond-length region sufficiently well. An alternative potential is proposed in the present paper. The quantum states of this non-symmetric double-well potential are calculated numerically using the Numerov (Fox-Goodwin) algorithm. It is shown that the optical spectra of hydrogen bonds in various substances can be well approximated on the basis of the transition frequencies and intensities predicted by the present model. For weakly interacting OH impurities in 0953-8984/10/10/008/img1, the overtone spectrum and line intensities are well reproduced, whereas the line broadenings and the decrease of the fundamental stretching frequencies in intermediate and strong hydrogen bonds are traced back to the influence of the reduced height of the central barrier. The model is also extrapolated to the range of symmetric hydrogen bonds, and the calculated transition frequencies are discussed with respect to most recent infra-red experiments on ice under strong compression. A possible artificial infra-red signal from strained diamond anvils is thereby noted.

  17. Estimating state-transition probabilities for unobservable states using capture-recapture/resighting data

    USGS Publications Warehouse

    Kendall, W.L.; Nichols, J.D.

    2002-01-01

    Temporary emigration was identified some time ago as causing potential problems in capture-recapture studies, and in the last five years approaches have been developed for dealing with special cases of this general problem. Temporary emigration can be viewed more generally as involving transitions to and from an unobservable state, and frequently the state itself is one of biological interest (e.g., 'nonbreeder'). Development of models that permit estimation of relevant parameters in the presence of an unobservable state requires either extra information (e.g., as supplied by Pollock's robust design) or the following classes of model constraints: reducing the order of Markovian transition probabilities, imposing a degree of determinism on transition probabilities, removing state specificity of survival probabilities, and imposing temporal constancy of parameters. The objective of the work described in this paper is to investigate estimability of model parameters under a variety of models that include an unobservable state. Beginning with a very general model and no extra information, we used numerical methods to systematically investigate the use of ancillary information and constraints to yield models that are useful for estimation. The result is a catalog of models for which estimation is possible. An example analysis of sea turtle capture-recapture data under two different models showed similar point estimates but increased precision for the model that incorporated ancillary data (the robust design) when compared to the model with deterministic transitions only. This comparison and the results of our numerical investigation of model structures lead to design suggestions for capture-recapture studies in the presence of an unobservable state.

  18. Formation of metastable excited states during sputtering of transition metals

    SciTech Connect

    Wucher, A.; Sroubek, Z.

    1997-01-01

    We propose a simple model which treats the formation of metastable excited neutral atoms during sputtering of a transition metal as a two step process. First, the energy deposited into the electronic system of the solid by electronic energy losses of all moving particles in the collision cascade is considered to lead to a locally altered equilibrium electronic state of the solid. It is found that this step is dominated by collective interaction with the conduction band electrons rather than by electron promotion in binary atom-atom collisions. Second, sputtered excited atoms are assumed to be formed by resonant neutralization of excited ions (reflecting the altered equilibrium state) while crossing the surface. It is shown that this model explains the total as well as the velocity dependent excitation probability observed in recent experiments on sputtered neutral silver atoms, which cannot be understood in terms of existing theories describing the formation of excited states in sputtering. {copyright} {ital 1996} {ital The American Physical Society}

  19. Spin-Orbital Entangled States in Transition Metal Oxides

    NASA Astrophysics Data System (ADS)

    Oleś, Andrzej M.

    The phenomenon of spin-orbital entanglement which occurs in superexchange models for transition metal oxides is introduced and explained. We present its consequences in the RVO_3 Mott insulators, with R=La,Pr,\\cdots ,Yb,Lu, and show that entanglement occurs here in excited states of the spin-orbital d^2 model and determines: (i) the temperature dependence of low-energy optical spectral weight, (ii) the phase diagram of the RVO_3 perovskites, and (iii) the dimerization observed in the magnon excitations in YVO_3. Entangled ground states occur in two other model systems: (i) the bilayer d^9 (Kugel-Khomskii) model, and (ii) the d^1 model on the triangular frustrated lattice. In such cases even the predictions concerning the magnetic exchange constants based on the mean field decoupling of spin and orbital operators are incorrect. On the example of a single hole doped to a Mott insulator with coexisting antiferromagnetic and alternating t_{2g} orbital order we show that transport is hindered by spin-orbital excitations. It is suggested that spin-orbital entanglement in Mott insulators might be controlled by doping, leading to orbital disordered states with possible new opportunities for thermoelectric applications.

  20. 31 CFR 560.406 - Transshipment or transit through the United States.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 31 Money and Finance:Treasury 3 2013-07-01 2013-07-01 false Transshipment or transit through the... SANCTIONS REGULATIONS Interpretations § 560.406 Transshipment or transit through the United States. (a) The prohibitions in § 560.201 apply to the importation into the United States, for transshipment or transit,...

  1. 31 CFR 560.406 - Transshipment or transit through the United States.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 31 Money and Finance:Treasury 3 2014-07-01 2014-07-01 false Transshipment or transit through the... SANCTIONS REGULATIONS Interpretations § 560.406 Transshipment or transit through the United States. (a) The prohibitions in § 560.201 apply to the importation into the United States, for transshipment or transit,...

  2. Near-optimal energy transitions for energy-state trajectories of hypersonic aircraft

    NASA Technical Reports Server (NTRS)

    Ardema, M. D.; Bowles, J. V.; Terjesen, E. J.; Whittaker, T.

    1992-01-01

    A problem of the instantaneous energy transition that occurs in energy-state approximation is considered. The transitions are modeled as a sequence of two load-factor bounded paths (either climb-dive or dive-climb). The boundary-layer equations associated with the energy-state dynamic model are analyzed to determine the precise location of the transition.

  3. Validating and Characterizing Transiting Exoplanets from Space with EPOXI, Kepler, and Warm Spitzer

    NASA Astrophysics Data System (ADS)

    Ballard, Sarah

    2012-01-01

    My thesis work comprises analyses of transiting exoplanets with observations from three space-based instruments. The Extrasolar Planet Observation and Characterization (EPOCh) component of the EPOXI mission repurposed the Deep Impact Spacecraft to gather photometry of six known transiting exoplanet systems. I systematically searched the EPOXI light curves for additional transiting planets, and identified one such candidate in the exoplanet system GJ 436. I gathered Warm Spitzer light curves of GJ 436 during a predicted transit of this putative planet: while I ruled out the presence of the hypothesized planet, I developed a novel reduction technique for Warm Spitzer observations and demonstrated the sensitivity of that instrument to sub-Earth-sized transiting planets. I next applied these techniques to a sample of super-Earth-sized planetary candidates identified by the Kepler mission. In the absence of radial velocity confirmation (challenging for such low-mass planets), it is nonetheless possible to make a statistical argument for the planetary nature of the candidate, if the combined likelihood of all false positive scenarios is sufficiently smaller than the planet scenario. An authentic planet will exhibit an achromatic transit depth, as measured in the optical with Kepler and near-infrared with Warm Spitzer. The eclipse from a stellar blend, in contrast, would likely vary with wavelength. I presented the discovery of the Kepler-19 system, applying Warm Spitzer observations toward validation of the transiting 2.2 REarth planet, Kepler-19b. I identified systematic variations in the transit times of Kepler-19b, which led to the first robust detection of a non-transiting planet using the transit timing variation method: Kepler-19c. Support for EPOXI was provided by NASA's Discovery Program via Agreement NNX08AB64A. This work is based on observations made with the Spitzer Space Telescope. Support for Spitzer observations is provided by NASA through an award issued

  4. Topologically insulating states in ternary transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Lin, Xianqing; Ni, Jun

    2017-01-01

    The topological and electronic properties of monolayered monoclinic transition metal dichalcogenide (TMD) alloys (1T '-M1-xNxX2 with M, N = Cr, Mo, W and X = S, Se) have been studied through calculations based on the projected Wannier functions obtained from first-principles calculations. We predict that the ternary compounds 1T '-Mo1-xCrxS2 with x up to 7/12 and all 1T '-Mo1-xWxSe2 host topologically insulating states with band gaps comparable to the pure systems. For Cr contained alloys, the mechanism of sign changing of Berry curvature is proposed to explain the trivial band topology of some configurations. The predicted topologically insulating ternary TMDs may be promising candidates for future realization of topological devices.

  5. Excited states and reduced transition probabilities in 168Os

    NASA Astrophysics Data System (ADS)

    Grahn, T.; Stolze, S.; Joss, D. T.; Page, R. D.; Sayǧı, B.; O'Donnell, D.; Akmali, M.; Andgren, K.; Bianco, L.; Cullen, D. M.; Dewald, A.; Greenlees, P. T.; Heyde, K.; Iwasaki, H.; Jakobsson, U.; Jones, P.; Judson, D. S.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Lumley, N.; Mason, P. J. R.; Möller, O.; Nomura, K.; Nyman, M.; Petts, A.; Peura, P.; Pietralla, N.; Pissulla, Th.; Rahkila, P.; Sapple, P. J.; Sarén, J.; Scholey, C.; Simpson, J.; Sorri, J.; Stevenson, P. D.; Uusitalo, J.; Watkins, H. V.; Wood, J. L.

    2016-10-01

    The level scheme of the neutron-deficient nuclide 168Os has been extended and mean lifetimes of excited states have been measured by the recoil distance Doppler-shift method using the JUROGAM γ -ray spectrometer in conjunction with the IKP Köln plunger device. The 168Osγ rays were measured in delayed coincidence with recoiling fusion-evaporation residues detected at the focal plane of the RITU gas-filled separator. The ratio of reduced transition probabilities B (E 2 ;41+→21+) /B (E 2 ;21+→01+) is measured to be 0.34(18), which is very unusual for collective band structures and cannot be reproduced by interacting boson model (IBM-2) calculations based on the SkM* energy-density functional.

  6. Detecting nonstationarity and state transitions in a time series

    NASA Astrophysics Data System (ADS)

    Gao, J. B.

    2001-06-01

    One cause of complexity in a time series may be due to nonstationarity and transience. In this paper, we analyze the nonstationarity and transience in a number of dynamical systems. We find that the nonstationarity in the metastable chaotic Lorenz system is due to nonrecurrence. The latter determines a lack of fractal structure in the signal. In 1/fα noise, we find that the associated correlation dimension are local graph dimensions calculated from sojourn points. We also design a transient Lorenz system with a slowly oscillating controlling parameter, and a transient Rossler system with a slowly linearly increasing parameter, with parameter ranges covering a sequence of chaotic dynamics with increased phase incoherence. State transitions, from periodic to chaotic, and vice versa, are identified, together with different facets of nonstationarity in each phase.

  7. Profiling base excision repair glycosylases with synthesized transition state analogs.

    PubMed

    Chu, Aurea M; Fettinger, James C; David, Sheila S

    2011-09-01

    Two base excision repair glycosylase (BER) transition state (TS) mimics, (3R,4R)-1-benzyl (hydroxymethyl) pyrrolidin-3-ol (1NBn) and (3R,4R)-(hydroxymethyl) pyrrolidin-3-ol (1N), were synthesized using an improved method. Several BER glycosylases that repair oxidized DNA bases, bacterial formamidopyrimdine glycosylase (Fpg), human OG glycosylase (hOGG1) and human Nei-like glycosylase 1 (hNEIL1) exhibit exceptionally high affinity (K(d)∼pM) with DNA duplexes containing the 1NBn and 1N nucleotide. Notably, comparison of the K(d) values of both TS mimics relative to an abasic analog (THF) in duplex contexts paired opposite C or A suggest that these DNA repair enzymes use distinctly different mechanisms for damaged base recognition and catalysis despite having overlapping substrate specificities.

  8. Co-operativity in a nanocrystalline solid-state transition.

    PubMed

    White, Sarah L; Smith, Jeremy G; Behl, Mayank; Jain, Prashant K

    2013-01-01

    Co-operativity is a remarkable phenomenon mostly seen in biology, where initial reaction events significantly alter the propensity of subsequent reaction events, giving rise to a nonlinear tightly regulated synergistic response. Here we have found unique evidence of atomic level co-operativity in an inorganic material. A thousand-atom nanocrystal (NC) of the inorganic solid cadmium selenide exhibits strong positive co-operativity in its reaction with copper ions. A NC doped with a few copper impurities becomes highly prone to be doped even further, driving an abrupt transition of the entire NC to the copper selenide phase, as manifested by a strongly sigmoidal response in optical spectroscopy and electron diffraction measurements. The examples presented here suggest that cooperative phenomena may have an important role in the solid state, especially in the nucleation of new chemical phases, crystal growth, and other materials' transformations.

  9. Co-operativity in a nanocrystalline solid-state transition

    NASA Astrophysics Data System (ADS)

    White, Sarah L.; Smith, Jeremy G.; Behl, Mayank; Jain, Prashant K.

    2013-12-01

    Co-operativity is a remarkable phenomenon mostly seen in biology, where initial reaction events significantly alter the propensity of subsequent reaction events, giving rise to a nonlinear tightly regulated synergistic response. Here we have found unique evidence of atomic level co-operativity in an inorganic material. A thousand-atom nanocrystal (NC) of the inorganic solid cadmium selenide exhibits strong positive co-operativity in its reaction with copper ions. A NC doped with a few copper impurities becomes highly prone to be doped even further, driving an abrupt transition of the entire NC to the copper selenide phase, as manifested by a strongly sigmoidal response in optical spectroscopy and electron diffraction measurements. The examples presented here suggest that cooperative phenomena may have an important role in the solid state, especially in the nucleation of new chemical phases, crystal growth, and other materials’ transformations.

  10. Ab initio transition dipole moments and potential energy curves for the low-lying electronic states of CaH

    NASA Astrophysics Data System (ADS)

    Shayesteh, Alireza; Alavi, S. Fatemeh; Rahman, Moloud; Gharib-Nezhad, Ehsan

    2017-01-01

    Ab initio potential energy curves have been calculated for the X2Σ+, A2Π, B2Σ+, 12Δ, E2Π and D2Σ+ states of CaH using the multi-reference configuration interaction method with large active space and basis sets. Transition dipole moments were calculated at Ca-H distances from 2.0 a0 to 14.0 a0, and excited state lifetimes were obtained. Our theoretical transition dipole moments can be combined with the available experimental data on the X2Σ+, A2Π and B2Σ+ states to calculate Einstein A coefficients for all rovibronic transitions of CaH appearing in solar and stellar spectra.

  11. Outline of a transition-state hydrogen-bond theory

    NASA Astrophysics Data System (ADS)

    Gilli, Paola; Bertolasi, Valerio; Pretto, Loretta; Gilli, Gastone

    2006-06-01

    Though the H-bond is well characterized as a D-H⋯:A three-center-four-electron interaction, the formulation of a general H-bond theory has turned out to be a rather formidable problem because of the extreme variability of the bonds formed (for instance, O-H⋯O energies range from 0.1 to 31 kcal mol -1). This paper surveys our previous contributions to the problem, including: (a) the H-bond chemical leitmotifs (CLs), showing that there are only four classes of strong H-bonds and one of moderately strong ones; (b) the PA/pK a equalization principle , showing that the four CLs forming strong H-bonds are actually molecular devices apt to equalize the acid-base properties (PA or p Ka) of the H-bond donor and acceptor groups; (c) the driving variable of the H-bond strength, which remains so identified as the difference Δp Ka=p KAH(D-H)-p KBH(A-H +) or, alternatively, ΔPA=PA(D -)-PA(A); and, in particular, (d) the transition-state H-bond theory (TSHBT), which interprets the H-bond as a stationary point along the complete proton transfer pathway going from D-H⋯A to D⋯H-A via the D⋯H⋯A transition state. TSHBT is verified in connection with a series of seven 1-(X-phenylazo)-2-naphthols, a class of compounds forming a strong intramolecular resonance-assisted H-bond (RAHB), which is switched from N-H⋯O to N⋯H-O by the decreasing electron-withdrawing properties of the substituent X. The system is studied in terms of: (i) variable-temperature X-ray crystallography; (ii) DFT emulation of stationary points and full PT pathways; (iii) Marcus rate-equilibrium analysis correlated with substituent LFER Hammett parameters.

  12. Ongoing Space Nuclear Systems Development in the United States

    SciTech Connect

    S. Bragg-Sitton; J. Werner; S. Johnson; Michael G. Houts; Donald T. Palac; Lee S. Mason; David I. Poston; A. Lou Qualls

    2011-10-01

    Reliable, long-life power systems are required for ambitious space exploration missions. Nuclear power and propulsion options can enable a bold, new set of missions and introduce propulsion capabilities to achieve access to science destinations that are not possible with more conventional systems. Space nuclear power options can be divided into three main categories: radioisotope power for heating or low power applications; fission power systems for non-terrestrial surface application or for spacecraft power; and fission power systems for electric propulsion or direct thermal propulsion. Each of these areas has been investigated in the United States since the 1950s, achieving various stages of development. While some nuclear systems have achieved flight deployment, others continue to be researched today. This paper will provide a brief overview of historical space nuclear programs in the U.S. and will provide a summary of the ongoing space nuclear systems research, development, and deployment in the United States.

  13. Space Sciences Education and Outreach Project of Moscow State University

    NASA Astrophysics Data System (ADS)

    Krasotkin, S.

    2006-11-01

    sergekras@mail.ru The space sciences education and outreach project was initiated at Moscow State University in order to incorporate modern space research into the curriculum popularize the basics of space physics, and enhance public interest in space exploration. On 20 January 2005 the first Russian University Satellite “Universitetskiy-Tatyana” was launched into circular polar orbit (inclination 83 deg., altitude 940-980 km). The onboard scientific complex “Tatyana“, as well as the mission control and information receiving centre, was designed and developed at Moscow State University. The scientific programme of the mission includes measurements of space radiation in different energy channels and Earth UV luminosity and lightning. The current education programme consists of basic multimedia lectures “Life of the Earth in the Solar Atmosphere” and computerized practice exercises “Space Practice” (based on the quasi-real-time data obtained from “Universitetskiy-Tatyana” satellite and other Internet resources). A multimedia lectures LIFE OF EARTH IN THE SOLAR ATMOSPHERE containing the basic information and demonstrations of heliophysics (including Sun structure and solar activity, heliosphere and geophysics, solar-terrestrial connections and solar influence on the Earth’s life) was created for upper high-school and junior university students. For the upper-university students there a dozen special computerized hands-on exercises were created based on the experimental quasi-real-time data obtained from our satellites. Students specializing in space physics from a few Russian universities are involved in scientific work. Educational materials focus on upper high school, middle university and special level for space physics students. Moscow State University is now extending its space science education programme by creating multimedia lectures on remote sensing, space factors and materials study, satellite design and development, etc. The space

  14. Multi-state succession in wetlands: a novel use of state and transition models

    USGS Publications Warehouse

    Zweig, Christa L.; Kitchens, Wiley M.

    2009-01-01

    The complexity of ecosystems and mechanisms of succession are often simplified by linear and mathematical models used to understand and predict system behavior. Such models often do not incorporate multivariate, nonlinear feedbacks in pattern and process that include multiple scales of organization inherent within real-world systems. Wetlands are ecosystems with unique, nonlinear patterns of succession due to the regular, but often inconstant, presence of water on the landscape. We develop a general, nonspatial state and transition (S and T) succession conceptual model for wetlands and apply the general framework by creating annotated succession/management models and hypotheses for use in impact analysis on a portion of an imperiled wetland. The S and T models for our study area, Water Conservation Area 3A South (WCA3), Florida, USA, included hydrologic and peat depth values from multivariate analyses and classification and regression trees. We used the freeware Vegetation Dynamics Development Tool as an exploratory application to evaluate our S and T models with different management actions (equal chance [a control condition], deeper conditions, dry conditions, and increased hydrologic range) for three communities: slough, sawgrass (Cladium jamaicense), and wet prairie. Deeper conditions and increased hydrologic range behaved similarly, with the transition of community states to deeper states, particularly for sawgrass and slough. Hydrology is the primary mechanism for multi-state transitions within our study period, and we show both an immediate and lagged effect on vegetation, depending on community state. We consider these S and T succession models as a fraction of the framework for the Everglades. They are hypotheses for use in adaptive management, represent the community response to hydrology, and illustrate which aspects of hydrologic variability are important to community structure. We intend for these models to act as a foundation for further restoration

  15. Phase transitions for random states and a semicircle law for the partial transpose

    NASA Astrophysics Data System (ADS)

    Aubrun, Guillaume; Szarek, Stanisław J.; Ye, Deping

    2012-03-01

    For a system of N identical particles in a random pure state, there is a threshold k0=k0(N)˜N/5 such that two subsystems of k particles each typically share entanglement if k>k0, and typically do not share entanglement if kspace. The analogous phase transition for the positive partial transpose (PPT) property can be described even more precisely. For example, for N qubits the two subsystems of size k are typically in a PPT state if kstate if k>k1. Since, for a given state of the entire system, the induced state of a subsystem is given by the partial trace, the above facts can be rephrased as properties of random induced states. An important step in the analysis depends on identifying the asymptotic spectral density of the partial transposes of such random induced states, a result which is interesting in its own right.

  16. The 2004 Transit of Venus as a Space Science Education Opportunity

    NASA Astrophysics Data System (ADS)

    Odenwald, S.; Mayo, L.; Vondrak, R.; Thieman, J.; Hawkins, I.; Schultz, G.

    2003-12-01

    We will present some of the programs and activities that NASA and its missions are preparing in order to support public and K12 education in space science and astronomy using the 2004 transit of Venus as a focal event. The upcoming transit of Venus on June 8 offers a unique opportunity to educate students and the general public about the scale of the solar system and the universe, as well as basic issues in comparative planetology. NASA's Sun-Earth Connection Education Forum is offering a number of programs to take advantage of this rare event. Among these are a live web cast from Spain of the entire transit, a series of radio and TV programs directed at students and the general public, a web cast describing extra-solar planet searches using the transit geometry, and archived observations produced by public observatories and student-operated solar viewers. The NASA/OSS Education Forums will also partner with science museums, planetaria and teachers across the country to bring the transit of Venus 'down to Earth'. In addition to offering enrichment activities in mathematics and space science, we also describe collaborations that have yielded unique historical resources including online archives of newspaper articles from the 1874 and 1882 transits. In addition, in collaboration with the Library of Congress Music Division, we have supported a modern re-orchestration of John Philip Sousa's Transit of Venus March which has not been performed since 1883. We anticipate that the transit of Venus will be a significant event of considerable public interest and curiosity, if the newspaper headlines from the transit seen in 1882 are any indication.

  17. Quantum imaging with N-photon states in position space.

    PubMed

    Brainis, E

    2011-11-21

    We investigate the physics of quantum imaging with N > 2 entangled photons in position space. It is shown that, in paraxial approximation, the space-time propagation of the quantum state can be described by a generalized Huygens-Fresnel principle for the N-photon wave function. The formalism allows the initial conditions to be set on multiple reference planes, which is very convenient to describe the generation of multiple photon pairs in separate thin crystals. Applications involving state shaping and spatial entanglement swapping are developed.

  18. Analysis of physiological signals using state space correlation entropy.

    PubMed

    Tripathy, Rajesh Kumar; Deb, Suman; Dandapat, Samarendra

    2017-02-01

    In this letter, the authors propose a new entropy measure for analysis of time series. This measure is termed as the state space correlation entropy (SSCE). The state space reconstruction is used to evaluate the embedding vectors of a time series. The SSCE is computed from the probability of the correlations of the embedding vectors. The performance of SSCE measure is evaluated using both synthetic and real valued signals. The experimental results reveal that, the proposed SSCE measure along with SVM classifier have sensitivity value of 91.60%, which is higher than the performance of both sample entropy and permutation entropy features for detection of shockable ventricular arrhythmia.

  19. The Transitional Space of History: Reflections on the Play of Roger Simon's Remembrance Pedagogy

    ERIC Educational Resources Information Center

    Farley, Lisa

    2014-01-01

    This paper reads Roger Simon's concept of "transactional memory" in relationship to D. W. Winnicott's theory of "transitional space" to examine the emotional dimensions of making historical significance. Drawing on a personal memory of archival study with Simon, I suggest that his attention to the ethical qualities of…

  20. Efficient computations of quantum canonical Gibbs state in phase space

    NASA Astrophysics Data System (ADS)

    Bondar, Denys I.; Campos, Andre G.; Cabrera, Renan; Rabitz, Herschel A.

    2016-06-01

    The Gibbs canonical state, as a maximum entropy density matrix, represents a quantum system in equilibrium with a thermostat. This state plays an essential role in thermodynamics and serves as the initial condition for nonequilibrium dynamical simulations. We solve a long standing problem for computing the Gibbs state Wigner function with nearly machine accuracy by solving the Bloch equation directly in the phase space. Furthermore, the algorithms are provided yielding high quality Wigner distributions for pure stationary states as well as for Thomas-Fermi and Bose-Einstein distributions. The developed numerical methods furnish a long-sought efficient computation framework for nonequilibrium quantum simulations directly in the Wigner representation.

  1. Magnetic ground state of semiconducting transition-metal trichalcogenide monolayers

    DOE PAGES

    Sivadas, Nikhil; Daniels, Matthew W.; Swendsen, Robert H.; ...

    2015-06-16

    Layered transition-metal trichalcogenides with the chemical formula ABX3 have attracted recent interest as potential candidates for two-dimensional magnets. Using first-principles calculations within density functional theory, we investigate the magnetic ground states of monolayers of Mn- and Cr-based semiconducting trichalcogenides.We show that the second and third nearest-neighbor exchange interactions (J2 and J3) between magnetic ions, which have been largely overlooked in previous theoretical studies, are crucial in determining the magnetic ground state. Specifically, we find that monolayer CrSiTe3 is an antiferromagnet with a zigzag spin texture due to significant contribution from J3, whereas CrGeTe3 is a ferromagnet with a Curie temperaturemore » of 106 K. Monolayers of Mn compounds (MnPS3 and MnPSe3) always show antiferromagnetic N eel order. We identify the physical origin of various exchange interactions, and demonstrate that strain can be an effective knob for tuning the magnetic properties. Possible magnetic ordering in the bulk is also discussed. In conclusion, our study suggests that ABX3 can be a promising platform to explore two-dimensional magnetic phenomena.« less

  2. Computing ensembles of transitions from stable states: Dynamic importance sampling.

    PubMed

    Perilla, Juan R; Beckstein, Oliver; Denning, Elizabeth J; Woolf, Thomas B

    2011-01-30

    There is an increasing dataset of solved biomolecular structures in more than one conformation and increasing evidence that large-scale conformational change is critical for biomolecular function. In this article, we present our implementation of a dynamic importance sampling (DIMS) algorithm that is directed toward improving our understanding of important intermediate states between experimentally defined starting and ending points. This complements traditional molecular dynamics methods where most of the sampling time is spent in the stable free energy wells defined by these initial and final points. As such, the algorithm creates a candidate set of transitions that provide insights for the much slower and probably most important, functionally relevant degrees of freedom. The method is implemented in the program CHARMM and is tested on six systems of growing size and complexity. These systems, the folding of Protein A and of Protein G, the conformational changes in the calcium sensor S100A6, the glucose-galactose-binding protein, maltodextrin, and lactoferrin, are also compared against other approaches that have been suggested in the literature. The results suggest good sampling on a diverse set of intermediates for all six systems with an ability to control the bias and thus to sample distributions of trajectories for the analysis of intermediate states.

  3. Magnetic ground state of semiconducting transition-metal trichalcogenide monolayers

    SciTech Connect

    Sivadas, Nikhil; Daniels, Matthew W.; Swendsen, Robert H.; Okamoto, Satoshi; Xiao, Di

    2015-06-16

    Layered transition-metal trichalcogenides with the chemical formula ABX3 have attracted recent interest as potential candidates for two-dimensional magnets. Using first-principles calculations within density functional theory, we investigate the magnetic ground states of monolayers of Mn- and Cr-based semiconducting trichalcogenides.We show that the second and third nearest-neighbor exchange interactions (J2 and J3) between magnetic ions, which have been largely overlooked in previous theoretical studies, are crucial in determining the magnetic ground state. Specifically, we find that monolayer CrSiTe3 is an antiferromagnet with a zigzag spin texture due to significant contribution from J3, whereas CrGeTe3 is a ferromagnet with a Curie temperature of 106 K. Monolayers of Mn compounds (MnPS3 and MnPSe3) always show antiferromagnetic N eel order. We identify the physical origin of various exchange interactions, and demonstrate that strain can be an effective knob for tuning the magnetic properties. Possible magnetic ordering in the bulk is also discussed. In conclusion, our study suggests that ABX3 can be a promising platform to explore two-dimensional magnetic phenomena.

  4. Experience Transitioning Models and Data at the NOAA Space Weather Prediction Center

    NASA Astrophysics Data System (ADS)

    Berger, Thomas

    2016-07-01

    The NOAA Space Weather Prediction Center has a long history of transitioning research data and models into operations and with the validation activities required. The first stage in this process involves demonstrating that the capability has sufficient value to customers to justify the cost needed to transition it and to run it continuously and reliably in operations. Once the overall value is demonstrated, a substantial effort is then required to develop the operational software from the research codes. The next stage is to implement and test the software and product generation on the operational computers. Finally, effort must be devoted to establishing long-term measures of performance, maintaining the software, and working with forecasters, customers, and researchers to improve over time the operational capabilities. This multi-stage process of identifying, transitioning, and improving operational space weather capabilities will be discussed using recent examples. Plans for future activities will also be described.

  5. Studies of transition states and radicals by negative ion photodetachment

    SciTech Connect

    Metz, R.B.

    1991-12-01

    Negative ion photodetachment is a versatile tool for the production and study of transient neutral species such as reaction intermediates and free radicals. Photodetachment of the stable XHY{sup {minus}} anion provides a direct spectroscopic probe of the transition state region of the potential energy surface for the neutral hydrogen transfer reaction X + HY {yields} XH + Y, where X and Y are halogen atoms. The technique is especially sensitive to resonances, which occur at a specific energy, but the spectra also show features due to direct scattering. We have used collinear adiabatic simulations of the photoelectron spectra to evaluate trail potential energy surfaces for the biomolecular reactions and have extended the adiabatic approach to three dimensions and used it to evaluate empirical potential energy surfaces for the I + Hl and Br + HI reactions. In addition, we have derived an empirical, collinear potential energy surface for the Br + HBr reaction that reproduces our experimental results and have extended this surface to three dimensions. Photodetachment of a negative ion can be also used to study neutral free radicals. We have studied the vibrational and electronic spectroscopy of CH{sub 2}NO{sub 2} by photoelectron spectroscopy of CH{sub 2}NO{sub 2}{sup {minus}}, determining the electron affinity of CH{sub 2}NO{sub 2}, gaining insight on the bonding of the {sup 2}B{sub 1} ground state and observing the {sup 2}A{sub 2} excited state for the first time. Negative ion photodetachment also provides a novel and versatile source of mass-selected, jet-cooled free radicals. We have studied the photodissociation of CH{sub 2}NO{sub 2} at 270, 235, and 208 nm, obtaining information on the dissociation products by measuring the kinetic energy release in the photodissociation.

  6. MOST SPACE TELESCOPE PHOTOMETRY OF THE 2010 JANUARY TRANSIT OF EXTRASOLAR PLANET HD80606b

    SciTech Connect

    Roberts, Jessica E.; Barnes, Jason W.; Rowe, Jason F.

    2013-01-01

    We present observations of the full 2010 January transit of HD80606b from the Canadian microsatellite, Microvariability and Oscillations of Stars. By employing a space-based telescope, we monitor the entire transit, thus limiting systematic errors that result from ground observations. We determine measurements for the planetary radius (R{sub p} = 0.987 {+-} 0.061 R {sub Jup}) and inclination (i = 89. Degree-Sign 283 {+-} 0.024) by constraining our fits with the observed parameters of different groups. Our measured mid-transit time of 2455210.6449 {+-} 0.0034 HJD is consistent with the 2010 Spitzer results and is 20 minutes earlier than predicted by groups who observed the 2009 June transit.

  7. MOST Space Telescope Photometry of the 2010 January Transit of Extrasolar Planet HD80606b

    NASA Astrophysics Data System (ADS)

    Roberts, Jessica E.; Barnes, Jason W.; Rowe, Jason F.; Fortney, Jonathan J.

    2013-01-01

    We present observations of the full 2010 January transit of HD80606b from the Canadian microsatellite, Microvariability and Oscillations of Stars. By employing a space-based telescope, we monitor the entire transit, thus limiting systematic errors that result from ground observations. We determine measurements for the planetary radius (Rp = 0.987 ± 0.061 R Jup) and inclination (i = 89.°283 ± 0.024) by constraining our fits with the observed parameters of different groups. Our measured mid-transit time of 2455210.6449 ± 0.0034 HJD is consistent with the 2010 Spitzer results and is 20 minutes earlier than predicted by groups who observed the 2009 June transit.

  8. Universal space-time scaling symmetry in the dynamics of bosons across a quantum phase transition

    NASA Astrophysics Data System (ADS)

    Clark, Logan W.; Feng, Lei; Chin, Cheng

    2016-11-01

    The dynamics of many-body systems spanning condensed matter, cosmology, and beyond are hypothesized to be universal when the systems cross continuous phase transitions. The universal dynamics are expected to satisfy a scaling symmetry of space and time with the crossing rate, inspired by the Kibble-Zurek mechanism. We test this symmetry based on Bose condensates in a shaken optical lattice. Shaking the lattice drives condensates across an effectively ferromagnetic quantum phase transition. After crossing the critical point, the condensates manifest delayed growth of spin fluctuations and develop antiferromagnetic spatial correlations resulting from the sub-Poisson distribution of the spacing between topological defects. The fluctuations and correlations are invariant in scaled space-time coordinates, in support of the scaling symmetry of quantum critical dynamics.

  9. Universal space-time scaling symmetry in the dynamics of bosons across a quantum phase transition.

    PubMed

    Clark, Logan W; Feng, Lei; Chin, Cheng

    2016-11-04

    The dynamics of many-body systems spanning condensed matter, cosmology, and beyond are hypothesized to be universal when the systems cross continuous phase transitions. The universal dynamics are expected to satisfy a scaling symmetry of space and time with the crossing rate, inspired by the Kibble-Zurek mechanism. We test this symmetry based on Bose condensates in a shaken optical lattice. Shaking the lattice drives condensates across an effectively ferromagnetic quantum phase transition. After crossing the critical point, the condensates manifest delayed growth of spin fluctuations and develop antiferromagnetic spatial correlations resulting from the sub-Poisson distribution of the spacing between topological defects. The fluctuations and correlations are invariant in scaled space-time coordinates, in support of the scaling symmetry of quantum critical dynamics.

  10. Tunable frequency stabilization to Zeeman sublevel transitions between an intermediate state and Rydberg states

    NASA Astrophysics Data System (ADS)

    Bao, Shanxia; Zhang, Hao; Zhou, Jian; Zhang, Linjie; Zhao, Jianming; Xiao, Liantuan; Jia, Suotang

    2017-01-01

    We demonstrate a robust method of direct laser frequency locking on the Zeeman sublevel transitions between an intermediate state and Rydberg states, with continuously tunable frequency range from  -35 MHz to  +35 MHz, which is based on electromagnetically induced transparency (EIT) spectra of nondegenerate Zeeman sublevels in a Rydberg cascade system. With a small axial magnetic field, the EIT spectrum will split into two individual sub-peaks due to the Zeeman Effect of three energy levels, including the 133Cs 6S1/2, 6P3/2 and nl Rydberg states which form the cascade system. It is shown that the coupling field, corresponding to the transitions between the Zeeman sublevels of the intermediate state and Rydberg state, can be locked arbitrarily on any one of the two EIT sub-peaks. The frequency stability of locked lasers is bounded by 0.81 MHz. The root of Allan variance of the frequency reaches a minimum of 2.06× {{10}-8} for an averaging time of 512 s.

  11. Enabling technologies for transition to utilization of space-based resources and operations

    NASA Technical Reports Server (NTRS)

    Sadin, S. R.; Litty, J. D.

    1985-01-01

    This article explores a potential scenario for the further development of space infrastructure resources and operations management. It is a scenario that transitions from the current ground-based system to an architecture that is predominantly space-based by exploiting key mission systems in an operational support role. If this view is accurate, an examination of the range of potential infrastructure elements and how they might interact in a maximally productive space-based operations complex is needed, innovative technologies beyond the current Shuttle and Space Station legacy need to be identified, and research programs pursued. Development of technologies within the areas of telerobotics, machine autonomy, human autonomy, in-space manufacturing and construction, propulsion and energy is discussed.

  12. Implementing Secondary Transition Evidence-Based Practices: A Multi-State Survey of Transition Service Providers

    ERIC Educational Resources Information Center

    Mazzotti, Valerie L.; Plotner, Anthony J.

    2016-01-01

    Inadequate transition outcomes for youth with disabilities have produced a call for enhanced transition service delivery that includes implementation of evidence-based practices (EBPs). However, research indicates transition service providers still lack the knowledge and skills to effectively implement EBPs to ensure youth with disabilities…

  13. Space Cooling in the United States: A Market Deep Dive

    SciTech Connect

    Baxter, Van D.; Sikes, Karen; Khowailed, Gannate

    2016-01-01

    The American space cooling market is experiencing stricter efficiency standards, prosperous economic conditions, a steadily recovering housing market, population migration shift to warmer climates, and declining electricity prices. These factors have yielded a climate conducive to growth in air conditioning (AC) and air source heat pump (HP) shipments in the recent past with total AC and HP shipments in 2015 accounting for 6.8 million units, showing a growth of 32 % relative to 2010. In this article, the authors investigate the impact that regulatory changes and economic changes have had on unit shipments and identify future market influencers, including the introduction of advanced HVAC technologies and transition to more environmentally friendly refrigerants.

  14. Transition from Fowler-Nordheim field emission to space charge limited current density

    NASA Astrophysics Data System (ADS)

    Feng, Y.; Verboncoeur, J. P.

    2006-07-01

    The Fowler-Nordheim law gives the current density extracted from a surface under strong fields, by treating the emission of electrons from a metal-vacuum interface in the presence of an electric field normal to the surface as a quantum mechanical tunneling process. Child's law predicts the maximum transmitted current density by considering the space charge effect. When the electric field becomes high enough, the emitted current density will be limited by Child's law. This work analyzes the transition of the transmitted current density from the Fowler-Nordheim law to Child's law space charge limit using a one-dimensional particle-in-cell code. Also studied is the response of the emission model to strong electric fields near the transition point. We find the transition without geometrical effort is smooth and much slower than reported previously [J. P. Barbour, W. W. Dolan, J. K. Trolan, E. E. Martin, and W. P. Dyke, Phys. Rev. 92, 45 (1953)]. We analyze the effects of geometric field enhancement and work function on the transition. Using our previous model for effective field enhancement [Y. Feng and J. P. Verboncoeur, Phys. Plasmas 12, 103301 (2005)], we find the geometric effect dominates, and enhancement β >10 can accelerate the approach to the space charge limit at practical electric field. A damped oscillation near the local plasma frequency is observed in the transient system response.

  15. Transition from Fowler-Nordheim field emission to space charge limited current density

    SciTech Connect

    Feng, Y.; Verboncoeur, J. P.

    2006-07-15

    The Fowler-Nordheim law gives the current density extracted from a surface under strong fields, by treating the emission of electrons from a metal-vacuum interface in the presence of an electric field normal to the surface as a quantum mechanical tunneling process. Child's law predicts the maximum transmitted current density by considering the space charge effect. When the electric field becomes high enough, the emitted current density will be limited by Child's law. This work analyzes the transition of the transmitted current density from the Fowler-Nordheim law to Child's law space charge limit using a one-dimensional particle-in-cell code. Also studied is the response of the emission model to strong electric fields near the transition point. We find the transition without geometrical effort is smooth and much slower than reported previously [J. P. Barbour, W. W. Dolan, J. K. Trolan, E. E. Martin, and W. P. Dyke, Phys. Rev. 92, 45 (1953)]. We analyze the effects of geometric field enhancement and work function on the transition. Using our previous model for effective field enhancement [Y. Feng and J. P. Verboncoeur, Phys. Plasmas 12, 103301 (2005)], we find the geometric effect dominates, and enhancement {beta}>10 can accelerate the approach to the space charge limit at practical electric field. A damped oscillation near the local plasma frequency is observed in the transient system response.

  16. State Space Identification of Linear Deterministic Rainfall-Runoff Models

    NASA Astrophysics Data System (ADS)

    Ramos, José; Mallants, Dirk; Feyen, Jan

    1995-06-01

    Rainfall-runoff models of the black box type abound in the water resources literature (i.e., transfer function, autoregressive moving average (ARMA), ARMAX, state space, etc.). The corresponding system identification algorithms for such models are known to be numerically efficient and accurate, leading in most cases to good parsimonious representations of the rainfall-runoff process. Alternatively, every model in transfer function, ARMA, and ARMAX form has an equivalent state space representation. However, state space models do not necessarily have simple system identification algorithms, unless the system matrices are restricted to some canonical form. Furthermore, state space system identification algorithms that work with the rainfall/runoff data directly (i.e., covariance free), require initial conditions and are inherently iterative and nonlinear. In this paper we present a state space system identification theory which overcomes these limitations. One advantage of such a theory is that the corresponding algorithms are highly robust to additive noise in the data. They are referred to as "subspace algorithms" due to their ability to separate the signal subspace from the noise subspace. The main advantages of the subspace algorithms are the automatic structure identification (system order), geometrical insights (notions of angle between subspaces), and the fact that they rely on robust numerical procedures (singular value decomposition). In this paper, two algorithms are presented. The first one is a two-step procedure, where the impulse response (unit hydrograph ordinates for the single-input, single-output case) are computed from the input/output data by solving a constrained deconvolution problem. These impulse response ordinates are then used as inputs for identifying the system matrices by means of a Hankel-based realization algorithm. The second approach uses the data directly to identify the system matrices, bypassing the deconvolution step. The

  17. Naval Space Surveillance System (NAVSPASUR) solid state transmitter modernization

    NASA Astrophysics Data System (ADS)

    Francoeur, A. R.

    The author describes the design of the modernized solid-state transmitter for the US Naval Space Surveillance System (NAVSPASUR) station transmitters at Jordan Lake, AL, Gila River, AZ, and Lake Kickapoo, TX. The modernized NAVSPASUR is the highest average power solid-state transmitter ever produced. With the antenna gain of the system, it produces an effective radiated average power in excess of 98 dBw. Solid-state modernization of the NAVSPASUR transmitter has produced significant cost and performance improvements, which are expected to extend the operating life of the system into the next century.

  18. Variable-cell double-ended surface walking method for fast transition state location of solid phase transitions.

    PubMed

    Zhang, Xiao-Jie; Liu, Zhi-Pan

    2015-10-13

    To identify the low energy pathway for solid-to-solid phase transition has been a great challenge in physics and material science. This work develops a new theoretical method, namely, variable-cell double-ended surface walking (VC-DESW) to locate the transition state (TS) and deduce the pathway in solid phase transition. Inherited from the DESW method ( J. Chem. Theory Comput. 2013 , 9 , 5745 ) for molecular systems, the VC-DESW method implements an efficient mechanism to couple the lattice and atom degrees of freedom. The method features with fast pseudopathway building and accurate TS location for solid phase transition systems without requiring expensive Hessian computation and iterative pathway optimization. A generalized coordinate, consisting of the lattice vectors and the scaled atomic coordinates, is designed for describing the crystal potential energy surface (PES), which is able to capture the anisotropic behavior in phase transition. By comparing with the existing method for solid phase transition in different systems, we show that the VC-DESW method can be much more efficient for finding the TS in crystal phase transition. With the combination of the recently developed unbiased stochastic surface walking pathway sampling method, the VC-DESW is further utilized to resolve the lowest energy pathway of SiO2 α-quartz to quartz-II phase transition from many likely reaction pathways. These new methods provide a powerful platform for understanding and predicting the solid phase transition mechanism and kinetics.

  19. Fourth-Order Vibrational Transition State Theory and Chemical Kinetics

    NASA Astrophysics Data System (ADS)

    Stanton, John F.; Matthews, Devin A.; Gong, Justin Z.

    2015-06-01

    Second-order vibrational perturbation theory (VPT2) is an enormously successful and well-established theory for treating anharmonic effects on the vibrational levels of semi-rigid molecules. Partially as a consequence of the fact that the theory is exact for the Morse potential (which provides an appropriate qualitative model for stretching anharmonicity), VPT2 calculations for such systems with appropriate ab initio potential functions tend to give fundamental and overtone levels that fall within a handful of wavenumbers of experimentally measured positions. As a consequence, the next non-vanishing level of perturbation theory -- VPT4 -- offers only slight improvements over VPT2 and is not practical for most calculations since it requires information about force constants up through sextic. However, VPT4 (as well as VPT2) can be used for other applications such as the next vibrational correction to rotational constants (the ``gammas'') and other spectroscopic parameters. In addition, the marriage of VPT with the semi-classical transition state theory of Miller (SCTST) has recently proven to be a powerful and accurate treatment for chemical kinetics. In this talk, VPT4-based SCTST tunneling probabilities and cumulative reaction probabilities are give for the first time for selected low-dimensional model systems. The prospects for VPT4, both practical and intrinsic, will also be discussed.

  20. Classical trajectory simulations of post-transition state dynamics

    NASA Astrophysics Data System (ADS)

    Lourderaj, Upakarasamy; Park, Kyoyeon; Hase, William L.

    Classical chemical dynamics simulations of post-transition state dynamics are reviewed. Most of the simulations involve direct dynamics for which the potential energy and gradient are obtained directly from an electronic structure theory. The chemical reaction attributes and chemical systems presented are product energy partitioning for Cl- ··· CH3Br → ClCH3 + Br- and C2H5F → C2H4 + HF dissociation, non-RRKM dynamics for cyclopropane stereomutation and the Cl- ··· CH3Cl complexes mediating the Cl- + CH3Cl SN2 nucleophilic substitution reaction, and non-IRC dynamics for the OH- + CH3F and F- + CH3OOH chemical reactions. These studies illustrate the important role of chemical dynamics simulations in understanding atomic-level reaction dynamics and interpreting experiments. They also show that widely used paradigms and model theories for interpreting reaction kinetics and dynamics are often inaccurate and are not applicable.

  1. Mantle transition zone discontinuities beneath the contiguous United States

    NASA Astrophysics Data System (ADS)

    Gao, Stephen S.; Liu, Kelly H.

    2014-08-01

    Using over 310,000 high-quality radial receiver functions recorded by the USArray and other seismic stations in the contiguous United States, the depths of the 410 km and 660 km discontinuities (d410 and d660) are mapped in over 1,000 consecutive overlapping circles with a radius of 1°. The average mantle transition zone (MTZ) thickness for both the western and central/eastern U.S. is within 3 km from the global average of 250 km, suggesting an overall normal MTZ temperature beneath both areas. The Pacific Coast Ranges and the southern Basin and Range Province are underlain by a depressed d410, indicating higher-than-normal temperature in the upper MTZ. The proposed Yellowstone and Raton hot spots are not associated with clear undulations of the MTZ discontinuities, but d410 beneath another proposed hot spot, Bermuda, is depressed significantly and d660 has a normal depth. Low-temperature regions are found in the upper MTZ associated with the subducted Juan de Fuca slab beneath the northern Rocky Mountains and in two circular areas beneath the northern Basin and Range Province and the southern Colorado Plateau. Part of the Great Plains is characterized by a depressed d660. This observation, when combined with results from seismic tomography, suggests the existence of a cold region in the lower MTZ, probably associated with subducted Farallon slab segments.

  2. Transition-state theory predicts clogging at the microscale

    PubMed Central

    Laar, T. van de; Klooster, S. ten; Schroën, K.; Sprakel, J.

    2016-01-01

    Clogging is one of the main failure mechanisms encountered in industrial processes such as membrane filtration. Our understanding of the factors that govern the build-up of fouling layers and the emergence of clogs is largely incomplete, so that prevention of clogging remains an immense and costly challenge. In this paper we use a microfluidic model combined with quantitative real-time imaging to explore the influence of pore geometry and particle interactions on suspension clogging in constrictions, two crucial factors which remain relatively unexplored. We find a distinct dependence of the clogging rate on the entrance angle to a membrane pore which we explain quantitatively by deriving a model, based on transition-state theory, which describes the effect of viscous forces on the rate with which particles accumulate at the channel walls. With the same model we can also predict the effect of the particle interaction potential on the clogging rate. In both cases we find excellent agreement between our experimental data and theory. A better understanding of these clogging mechanisms and the influence of design parameters could form a stepping stone to delay or prevent clogging by rational membrane design. PMID:27328715

  3. Traffic model with an absorbing-state phase transition

    NASA Astrophysics Data System (ADS)

    Iannini, M. L. L.; Dickman, Ronald

    2017-02-01

    We consider a modified Nagel-Schreckenberg (NS) model in which drivers do not decelerate if their speed is smaller than the headway (number of empty sites to the car ahead). (In the original NS model, such a reduction in speed occurs with probability p , independent of the headway, as long as the current speed is greater than zero.) In the modified model the free-flow state (with all vehicles traveling at the maximum speed, vmax) is absorbing for densities ρ smaller than a critical value ρc=1 /(vmax+2 ) . The phase diagram in the ρ -p plane is reentrant: for densities in the range ρc ,<<ρ <ρc , both small and large values of p favor free flow, while for intermediate values, a nonzero fraction of vehicles have speeds transition in the original model. Our results suggest an unexpected connection between traffic models and stochastic sandpiles.

  4. Transition state analogs of 5'-methylthioadenosine nucleosidase disrupt quorum sensing.

    SciTech Connect

    Gutierrez, J.; Crowder, T; Rinaldo-Matthis, A; Ho, M; Almo, S; Schramm, V

    2009-01-01

    5'-Methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) is a bacterial enzyme involved in S-adenosylmethionine-related quorum sensing pathways that induce bacterial pathogenesis factors. Transition state analogs MT-DADMe-Immucillin-A, EtT-DADMe-Immucillin-A and BuT-DADMe-Immucillin-A are slow-onset, tight-binding inhibitors of Vibrio cholerae MTAN (VcMTAN), with equilibrium dissociation constants of 73, 70 and 208 pM, respectively. Structural analysis of VcMTAN with BuT-DADMe-Immucillin-A revealed interactions contributing to the high affinity. We found that in V. cholerae cells, these compounds are potent MTAN inhibitors with IC50 values of 27, 31 and 6 nM for MT-, EtT- and BuT-DADMe-Immucillin-A, respectively; the compounds disrupt autoinducer production in a dose-dependent manner without affecting growth. MT- and BuT-DADMe-Immucillin-A also inhibited autoinducer-2 production in enterohemorrhagic Escherichia coli O157:H7 with IC{sub 50} values of 600 and 125 nM, respectively. BuT-DADMe-Immucillin-A inhibition of autoinducer-2 production in both strains persisted for several generations and caused reduction in biofilm formation. These results support MTAN's role in quorum sensing and its potential as a target for bacterial anti-infective drug design.

  5. Electronic states at transition metal dichalcogenide lateral heterointerfaces

    NASA Astrophysics Data System (ADS)

    Avalos-Ovando, Oscar; Mastrogiuseppe, Diego; Ulloa, Sergio

    Materials with different band gaps are typically used to create heterostructures that enable band sculpting, depending on different shape and boundaries of the systems. These are used in diode lasers and high-speed transistors devices. Potential material candidates for such heterostructures at the monolayer level are the family of transition-metal dichalcogenides, MX2 (with M=Mo,W and X=S,Se), especially interesting materials with strong spin-orbit coupling and valley degrees of freedom. We consider lateral interfaces between pairs of these materials, and study the effect of different boundary geometries, motivated by recent experimental reports of the growth of such interfaces with different geometries. Using an effective 3-orbital tight-binding model, we focus our attention on monolayer ribbons and triangular flakes. We analyze the formation of edge/interface states for different gap nesting materials. We study the spatial distribution and orbital character of the wave functions throughout, as well as their dependence on interface termination. Supported by NSF DMR-1508325.

  6. Mott-Hubbard transition and spin-liquid state on the pyrochlore lattice

    NASA Astrophysics Data System (ADS)

    Swain, Nyayabanta; Tiwari, Rajarshi; Majumdar, Pinaki

    2016-10-01

    The pyrochlore lattice involves corner-sharing tetrahedra and the resulting geometric frustration is believed to suppress any antiferromagnetic order for Mott insulators on this structure. There are nevertheless short-range correlations which could be vital near the Mott-Hubbard insulator-metal transition. We use a static auxiliary-field-based Monte Carlo to study this problem in real space on reasonably large lattices. The method reduces to unrestricted Hartree-Fock at zero temperature but captures the key magnetic fluctuations at finite temperature. Our results reveal that increasing interaction drives the nonmagnetic (semi) metal to a "spin disordered" metal with small local moments, at some critical coupling, and then, through a small pseudogap window, to a large moment, gapped, Mott insulating phase at a larger coupling. The spin disordered metal has a finite residual resistivity which grows with interaction strength, diverging at the upper coupling. We present the resistivity, optical conductivity, and density of states across the metal-insulator transition and for varying temperature. These results set the stage for the more complex cases of Mott transition in the pyrochlore iridates and molybdates.

  7. Quantum state space as a maximal consistent set

    NASA Astrophysics Data System (ADS)

    Tabia, Gelo Noel

    2012-02-01

    Measurement statistics in quantum theory are obtained from the Born rule and the uniqueness of the probability measure it assigns through quantum states is guaranteed by Gleason's theorem. Thus, a possible systematic way of exploring the geometry of quantum state space expresses quantum states in terms of outcome probabilities of a symmetric informationally complete measurement. This specific choice for representing quantum states is motivated by how the associated probability space provides a natural venue for characterizing the set of quantum states as a geometric construct called a maximal consistent set. We define the conditions for consistency and maximality of a set, provide some examples of maximal consistent sets and attempt to deduce the steps for building up a maximal consistent set of probability distributions equivalent to Hilbert space. In particular, we demonstrate how the reconstruction procedure works for qutrits and observe how it reveals an elegant underlying symmetry among five SIC-POVMs and a complete set of mutually unbiased bases, known in finite affine geometry as the Hesse configuration.

  8. A theoretical study of the excited states of CrH: potential energies, transition moments, and lifetimes.

    PubMed

    Ghigo, Giovanni; Roos, Björn O; Stancil, P C; Weck, P F

    2004-11-01

    Ab initio calculations of low-lying electronic states of CrH are presented, including potential energies, dipole and transition dipole moment (TDM) functions, and radiative lifetimes for X (6)Sigma(+), A (6)Sigma(+), 3 (6)Sigma(+), 1 (6)Pi, 2 (6)Pi, 3 (6)Pi, and (6)Delta. Calculation of dynamic correlation effects was performed using the multistate complete active space second-order perturbation method, based on state-averaged complete active space self-consistent-field reference wave functions obtained with seven active electrons in an active space of 16 molecular orbitals. A relativistic atomic natural orbital-type basis set from the MOLCAS library was used for Cr. Good agreement is found between the current calculations and experiment for the lowest two (6)Sigma(+) states, the only states for which spectroscopic data are available. Potential curves for the 3 (6)Sigma(+) and 2 (6)Pi states are complicated by avoided crossings with higher states of the same symmetry, thus resulting in double-well structures for these two states. The measured bandhead T(0)=27 181 cm(-1), previously assigned to a (6)Pi<--X (6)Sigma(+) transition, is close to our value of T(0)=28 434 cm(-1) for the 2 (6)Pi state. We tentatively assign the ultraviolet band found experimentally at 30 386 cm(-1) to the 3 (6)Pi<--X (6)Sigma(+) transition for which the computed value is 29 660 cm(-1). The A (6)Sigma(+)<--X (6)Sigma(+) TDM and A (6)Sigma(+) lifetimes are found to be in reasonable agreement with previous calculations.

  9. Dynamics of transitions between capillary stable states under weightlessness

    NASA Astrophysics Data System (ADS)

    Srikanth, Praveen

    The study of two phase systems with one of the phases obstructing the other is of importance in a lot of fields. Liquid droplets in airways and air bubbles in the blood stream both fall under this category of problems. Helium bubbles in hydrazine fuel lines of satellites also have been found to cause frequent thruster shutdown and also seriously affect spacecraft control. Studies have been carried out until now to look at static equilibrium topologies and stability of such two phase systems in straight, bent and laterally compressed capillaries. In this investigation we look at the dynamics of the transitions between the stable topologies identified for a straight cylindrical capillary. The break up of the interface could adversely affect system performance. OpenFOAM is used to compute transitions from a stable droplet to a plug or the reverse by suitably adding or removing the obstructing phase through inlet patches on the wall of the cylinder. The main parameters presented are the non-dimensional energy, non-dimensional transition times, non-dimensional transition volumes and the general dynamics of the transitions itself. Before computing transitions the static equilibrium topologies computed by OpenFOAM are compared with those predicted by Surface Evolver and are found to be within acceptable deviations. The grid dependence of these transitions has also been studied. Transitions are computed for contact angles in the range of 10° to 170°. Different modes of transitions are observed depending on the contact angle of the case for both the types of transitions. The transition volumes are compared to the volume of existence limits for the corresponding initial topology at a particular contact angle for both the transitions.

  10. Controllable transition from positive space charge to negative space charge in an inverted cylindrical magnetron

    NASA Astrophysics Data System (ADS)

    Rane, R.; Bandyopadhyay, M.; Ranjan, M.; Mukherjee, S.

    2016-01-01

    The combined effect of magnetic field (B), gas pressure (P), and the corresponding discharge voltage on the discharge properties of argon in inverted cylindrical magnetron has been investigated. In the experiment, anode is biased with continuous 10 ms sinusoidal half wave. It is observed that at a comparatively higher magnetic field (i.e., >200 gauss) and lower operating pressure (i.e., <1 × 10-3 mbar), the discharge extinguishes and demands a high voltage to reignite. Discharge current increases with increase in magnetic field and starts reducing at sufficiently higher magnetic field for a particular discharge voltage due to restricted electron diffusion towards the anode. It is observed that B/P ratio plays an important role in sustaining the discharge and is constant for a discharge voltage. The discharge is transformed to negative space charge regime from positive space charge regime at certain B/P ratio and this ratio varies linearly with the discharge voltage. The space charge reversal is indicated by the radial profile of the floating potential and plasma potential in between two electrodes for different magnetic fields. At a particular higher magnetic field (beyond 100 gauss), the floating potential increases gradually with the radial distance from cathode, whereas it remains almost constant at lower magnetic field.

  11. Controllable transition from positive space charge to negative space charge in an inverted cylindrical magnetron

    SciTech Connect

    Rane, R. Ranjan, M.; Mukherjee, S.; Bandyopadhyay, M.

    2016-01-15

    The combined effect of magnetic field (B), gas pressure (P), and the corresponding discharge voltage on the discharge properties of argon in inverted cylindrical magnetron has been investigated. In the experiment, anode is biased with continuous 10 ms sinusoidal half wave. It is observed that at a comparatively higher magnetic field (i.e., >200 gauss) and lower operating pressure (i.e., <1 × 10{sup −3} mbar), the discharge extinguishes and demands a high voltage to reignite. Discharge current increases with increase in magnetic field and starts reducing at sufficiently higher magnetic field for a particular discharge voltage due to restricted electron diffusion towards the anode. It is observed that B/P ratio plays an important role in sustaining the discharge and is constant for a discharge voltage. The discharge is transformed to negative space charge regime from positive space charge regime at certain B/P ratio and this ratio varies linearly with the discharge voltage. The space charge reversal is indicated by the radial profile of the floating potential and plasma potential in between two electrodes for different magnetic fields. At a particular higher magnetic field (beyond 100 gauss), the floating potential increases gradually with the radial distance from cathode, whereas it remains almost constant at lower magnetic field.

  12. Using the International Space Station (ISS) Oxygen Generation Assembly (OGA) Is Not Feasible for Mars Transit

    NASA Technical Reports Server (NTRS)

    Jones, Harry W.

    2016-01-01

    A review of two papers on improving the International Space Station (ISS) Oxygen Generation Assembly (OGA) shows that it would not save substantial mass on a Mars transit. The ISS OGA requires redesign for satisfactory operation, even for the ISS. The planned improvements of the OGA for ISS would not be sufficient to make it suitable for Mars, because Mars transit life support has significantly different requirements than ISS. The OGA for Mars should have lower mass, better reliability and maintainability, greater safety, radiation hardening, and capability for quiescent operation. NASA's methodical, disciplined systems engineering process should be used to develop the appropriate system.

  13. Evaluating transition state structures of vanadium-phosphatase protein complexes using shape analysis.

    PubMed

    Sánchez-Lombardo, Irma; Alvarez, Santiago; McLauchlan, Craig C; Crans, Debbie C

    2015-06-01

    Shape analysis of coordination complexes is well-suited to evaluate the subtle distortions in the trigonal bipyramidal (TBPY-5) geometry of vanadium coordinated in the active site of phosphatases and characterized by X-ray crystallography. Recent studies using the tau (τ) analysis support the assertion that vanadium is best described as a trigonal bipyramid, because this geometry is the ideal transition state geometry of the phosphate ester substrate hydrolysis (C.C. McLauchlan, B.J. Peters, G.R. Willsky, D.C. Crans, Coord. Chem. Rev. http://dx.doi.org/10.1016/j.ccr.2014.12.012 ; D.C. Crans, M.L. Tarlton, C.C. McLauchlan, Eur. J. Inorg. Chem. 2014, 4450-4468). Here we use continuous shape measures (CShM) analysis to investigate the structural space of the five-coordinate vanadium-phosphatase complexes associated with mechanistic transformations between the tetrahedral geometry and the five-coordinate high energy TBPY-5 geometry was discussed focusing on the protein tyrosine phosphatase 1B (PTP1B) enzyme. No evidence for square pyramidal geometries was observed in any vanadium-protein complexes. The shape analysis positioned the metal ion and the ligands in the active site reflecting the mechanism of the cleavage of the organic phosphate in a phosphatase. We identified the umbrella distortions to be directly on the reaction path between tetrahedral phosphate and the TBPY-5-types of high-energy species. The umbrella distortions of the trigonal bipyramid are therefore identified as being the most relevant types of transition state structures for the phosphoryl group transfer reactions for phosphatases and this may be related to the possibility that vanadium is an inhibitor for enzymes that support both exploded and five-coordinate transition states.

  14. Bayesian state space models for dynamic genetic network construction across multiple tissues.

    PubMed

    Liang, Yulan; Kelemen, Arpad

    2016-08-01

    Construction of gene-gene interaction networks and potential pathways is a challenging and important problem in genomic research for complex diseases while estimating the dynamic changes of the temporal correlations and non-stationarity are the keys in this process. In this paper, we develop dynamic state space models with hierarchical Bayesian settings to tackle this challenge for inferring the dynamic profiles and genetic networks associated with disease treatments. We treat both the stochastic transition matrix and the observation matrix time-variant and include temporal correlation structures in the covariance matrix estimations in the multivariate Bayesian state space models. The unevenly spaced short time courses with unseen time points are treated as hidden state variables. Hierarchical Bayesian approaches with various prior and hyper-prior models with Monte Carlo Markov Chain and Gibbs sampling algorithms are used to estimate the model parameters and the hidden state variables. We apply the proposed Hierarchical Bayesian state space models to multiple tissues (liver, skeletal muscle, and kidney) Affymetrix time course data sets following corticosteroid (CS) drug administration. Both simulation and real data analysis results show that the genomic changes over time and gene-gene interaction in response to CS treatment can be well captured by the proposed models. The proposed dynamic Hierarchical Bayesian state space modeling approaches could be expanded and applied to other large scale genomic data, such as next generation sequence (NGS) combined with real time and time varying electronic health record (EHR) for more comprehensive and robust systematic and network based analysis in order to transform big biomedical data into predictions and diagnostics for precision medicine and personalized healthcare with better decision making and patient outcomes.

  15. Evaluating Russian space nuclear reactor technology for United States applications

    SciTech Connect

    Polansky, G.F.; Schmidt, G.L.; Voss, S.S.; Reynolds, E.L.

    1994-08-01

    Space nuclear power and nuclear electric propulsion are considered important technologies for planetary exploration, as well as selected earth orbit applications. The Nuclear Electric Propulsion Space Test Program (NEPSTP) was intended to provide an early flight demonstration of these technologies at relatively low cost through extensive use of existing Russian technology. The key element of Russian technology employed in the program was the Topaz II reactor. Refocusing of the activities of the Ballistic Missile Defense Organization (BMDO), combined with budgetary pressures, forced the cancellation of the NEPSTP at the end of the 1993 fiscal year. The NEPSTP was faced with many unique flight qualification issues. In general, the launch of a spacecraft employing a nuclear reactor power system complicates many spacecraft qualification activities. However, the NEPSTP activities were further complicated because the reactor power system was a Russian design. Therefore, this program considered not only the unique flight qualification issues associated with space nuclear power, but also with differences between Russian and United States flight qualification procedures. This paper presents an overview of the NEPSTP. The program goals, the proposed mission, the spacecraft, and the Topaz II space nuclear power system are described. The subject of flight qualification is examined and the inherent difficulties of qualifying a space reactor are described. The differences between United States and Russian flight qualification procedures are explored. A plan is then described that was developed to determine an appropriate flight qualification program for the Topaz II reactor to support a possible NEPSTP launch.

  16. 31 CFR 593.413 - Transshipment or transit through the United States prohibited.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 31 Money and Finance:Treasury 3 2013-07-01 2013-07-01 false Transshipment or transit through the... LIBERIAN REGIME OF CHARLES TAYLOR SANCTIONS REGULATIONS Interpretations § 593.413 Transshipment or transit... apply to the importation into the United States, for transshipment or transit to third countries, of...

  17. 31 CFR 560.406 - Transshipment or transit through United States prohibited.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Transshipment or transit through... TRANSACTIONS REGULATIONS Interpretations § 560.406 Transshipment or transit through United States prohibited... or transit, of Iranian-origin goods or goods owned or controlled by the Government of Iran which...

  18. 31 CFR 593.413 - Transshipment or transit through the United States prohibited.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 31 Money and Finance:Treasury 3 2012-07-01 2012-07-01 false Transshipment or transit through the... LIBERIAN REGIME OF CHARLES TAYLOR SANCTIONS REGULATIONS Interpretations § 593.413 Transshipment or transit... apply to the importation into the United States, for transshipment or transit to third countries, of...

  19. 31 CFR 560.406 - Transshipment or transit through United States prohibited.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 31 Money and Finance:Treasury 3 2011-07-01 2011-07-01 false Transshipment or transit through... TRANSACTIONS REGULATIONS Interpretations § 560.406 Transshipment or transit through United States prohibited... or transit, of Iranian-origin goods or goods owned or controlled by the Government of Iran which...

  20. 31 CFR 545.404 - Transshipment or transit through the United States prohibited.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Transshipment or transit through the... (AFGHANISTAN) SANCTIONS REGULATIONS Interpretations § 545.404 Transshipment or transit through the United... the importation into the United States, for transshipment or transit, of foreign goods which...

  1. 31 CFR 593.413 - Transshipment or transit through the United States prohibited.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 31 Money and Finance:Treasury 3 2011-07-01 2011-07-01 false Transshipment or transit through the... LIBERIAN REGIME OF CHARLES TAYLOR SANCTIONS REGULATIONS Interpretations § 593.413 Transshipment or transit... apply to the importation into the United States, for transshipment or transit to third countries, of...

  2. 31 CFR 593.413 - Transshipment or transit through the United States prohibited.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 31 Money and Finance:Treasury 3 2014-07-01 2014-07-01 false Transshipment or transit through the... LIBERIAN REGIME OF CHARLES TAYLOR SANCTIONS REGULATIONS Interpretations § 593.413 Transshipment or transit... apply to the importation into the United States, for transshipment or transit to third countries, of...

  3. 31 CFR 593.413 - Transshipment or transit through the United States prohibited.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Transshipment or transit through the... LIBERIAN REGIME OF CHARLES TAYLOR SANCTIONS REGULATIONS Interpretations § 593.413 Transshipment or transit... apply to the importation into the United States, for transshipment or transit to third countries, of...

  4. 31 CFR 560.406 - Transshipment or transit through United States prohibited.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 31 Money and Finance:Treasury 3 2012-07-01 2012-07-01 false Transshipment or transit through... TRANSACTIONS REGULATIONS Interpretations § 560.406 Transshipment or transit through United States prohibited... or transit, of Iranian-origin goods or goods owned or controlled by the Government of Iran which...

  5. The Transition from State Care to Adulthood: International Examples of Best Practices

    ERIC Educational Resources Information Center

    Reid, Carrie

    2007-01-01

    The issue of outcomes for youth who transition from state care to adulthood is not unique to any one country. Youth exiting the child welfare system, or aging out, face a plethora of problems and issues associated with the transition to adulthood. For the majority of youth, the transition to adulthood represents a process that takes place over a…

  6. Prediction of magnetic substorms using a state space model

    NASA Astrophysics Data System (ADS)

    Unnikrishnan, K.

    2012-02-01

    Nonlinear dynamical models of the magnetosphere derived from observational time series data using phase space reconstruction techniques have yielded new advances in the understanding of its dynamics. Considering the solar wind-magnetosphere interaction to be a natural input-output system its dynamical features can be reconstructed on the storm time scale by using the method of time delay embedding. Here, fourteen magnetic storm intervals belonging to low/moderate and high solar activity periods are considered and a suitable state space model has designed by performing training and validation tests, for which dawn to dusk electric field (VBz) is chosen as the input, and the AL time series as the output. The percentage of the output variations that is reproduced by the model is termed as fit_model and a higher number of fit_model means a better model. The number of components m used in the state space model is varied from 1-9 and the best prediction is obtained when m=4. The fit_model values of time series used for validation are 67.96, 67.2, 72.44, and 70.89, with m=4. In the present study most of the storms considered are having Dstmax in between -100 and -300 nT, and they can be predicted well with this procedure. To reveal the prediction capability of the proposed state space model the 30 steps ahead outputs for the storm events are generated, which reasonably reproduce the observed values.

  7. Topology of the space of periodic ground states in the antiferromagnetic Ising and Potts models in selected spatial structures

    NASA Astrophysics Data System (ADS)

    Krawczyk, Małgorzata J.

    2010-05-01

    Topology of the space of periodic ground states in the antiferromagnetic Ising and Potts (3-state) models is analysed in selected spatial structures. The states are treated as graph nodes, connected by one-spin-flip transitions. The spatial structures are the triangular lattice, the Archimedean ( 3,12) lattice and the cubic Laves C15 lattice with the periodic boundary conditions. In most cases the ground states are isolated nodes, but for selected systems we obtain connected graphs. The latter means that the magnetisation can vary in time with zero energy cost. The ground states are classified according to their degree and type of neighbours.

  8. Transitioning Models and Model Output to Space Weather Operations: Challenges and Opportunities

    NASA Technical Reports Server (NTRS)

    Hesse, Michael; Berrios, David; Chulaki, Anna; Kuznetsova, Maria M.; MacNeice, Peter J.; Maddox, Mario; Rastaetter, Lutz; Taktakishvili, Aleksandre

    2009-01-01

    The transition of space weather models or of information derived from space weather models to space weather forecasting is the last step of the chain from model development to model deployment in forecasting operations. As such, it is an extremely important element of the quest to increase our national capability to forecast and mitigate space weather hazards. It involves establishing customer requirements, and analyses of available models, which are, in principle, capable of delivering the required product. Models will have to be verified and validated prior to a selection of the best performing model. Further considerations include operational hardware, and the availability of data streams to drive the model. The final steps include the education of forecasters, and the implementation on gateway hardware prior to operational use. This presentation will provide a discussion of opportunities for rapid progress from the viewpoint of the Community Coordinated Modeling Center.

  9. Bauman Moscow State Technical University Youth Space Centre: Student's Way in Space Technologies

    NASA Astrophysics Data System (ADS)

    Mayorova, Victoria; Zelentsov, Victor

    2002-01-01

    The Youth Space Center (YSC) was established in Bauman Moscow State Technical University (BMSTU) in 1989 to provide primary aerospace education for young people, stimulate youth creative research thinking, promote space science and technology achievements and develop cooperation with other youth organizations in the international aerospace community. The center is staffed by the Dr. Victoria Mayorova, BMSTU Associate Professor, the YSC director, Dr. Boris Kovalev, BMSTU Associate Professor, the YSC scientific director, 5 student consultants and many volunteers. Informally YSC is a community of space enthusiasts, an open club for BMSTU students interested in space science and technology and faculty teaching in this field. YSC educational activities are based on the concept of uninterrupted aerospace education, developed and implemented by the center. The concept includes working with young space interested people both in school and university and then assisting them in getting interesting job in Russian Space Industry. The school level educational activities of the center has got different forms, such as lecturing, summer scientific camps and even Classes from Space given by Mir space station flight crew in Mission Control Center - Moscow and done in cooperation with All- Russian Aerospace Society Soyuz (VAKO Soyuz). This helps to stimulate the young people interest to the fundamental sciences ( physics, mathematics, computer science, etc.) exploiting and developing their interest to space and thus increase the overall educational level in the country. YSC hosts annual Cosmonautics conference for high school students that provides the University with capability to select well-prepared and motivated students for its' rocket and space related departments. For the conference participants it's a good opportunity to be enrolled to the University without entrance examinations. BMSTU students can participate in such YSC activities as annual international workshop for space

  10. Pure state consciousness and its local reduction to neuronal space

    NASA Astrophysics Data System (ADS)

    Duggins, A. J.

    2013-01-01

    The single neuronal state can be represented as a vector in a complex space, spanned by an orthonormal basis of integer spike counts. In this model a scalar element of experience is associated with the instantaneous firing rate of a single sensory neuron over repeated stimulus presentations. Here the model is extended to composite neural systems that are tensor products of single neuronal vector spaces. Depiction of the mental state as a vector on this tensor product space is intended to capture the unity of consciousness. The density operator is introduced as its local reduction to the single neuron level, from which the firing rate can again be derived as the objective correlate of a subjective element. However, the relational structure of perceptual experience only emerges when the non-local mental state is considered. A metric of phenomenal proximity between neuronal elements of experience is proposed, based on the cross-correlation function of neurophysiology, but constrained by the association of theoretical extremes of correlation/anticorrelation in inseparable 2-neuron states with identical and opponent elements respectively.

  11. Effect of Protuberance Shape and Orientation on Space Shuttle Orbiter Boundary-Layer Transition

    NASA Technical Reports Server (NTRS)

    King, RUdolph A.; Berry, Scott A.; Kegerise, Michael A.

    2008-01-01

    This document describes an experimental study conducted to examine the effects of protuberances on hypersonic boundary-layer transition. The experiment was conducted in the Langley 20-Inch Mach 6 Tunnel on a series of 0.9%-scale Shuttle Orbiter models. The data were acquired to complement the existing ground-based boundary-layer transition database that was used to develop Version 1.0 of the boundary-layer transition RTF (return-to-flight) tool. The existing ground-based data were all acquired on 0.75%-scale Orbiter models using diamond-shaped ( pizza-box ) trips. The larger model scale facilitated in manufacturing higher fidelity protuberances. The end use of this experimental database will be to develop a technical basis (in the form of a boundary-layer transition correlation) to assess representative protrusion shapes, e.g., gap fillers and protrusions resulting from possible tile repair concepts. The primary objective of this study is to investigate the effects of protuberance-trip location and geometry on Shuttle Orbiter boundary-layer transition. Secondary goals are to assess the effects of gap-filler orientation and other protrusion shapes on boundary-layer transition. Global heat-transfer images using phosphor thermography of the Orbiter windward surface and the corresponding streamwise and spanwise heating distributions were used to infer the state of the boundary layer, i.e., laminar, transitional, or turbulent.

  12. Mean streamwise spacing of organized structures in transitional and developed bounded turbulent flows

    NASA Technical Reports Server (NTRS)

    Wallace, J. M.; Fleischmann, S. T.

    1984-01-01

    The mean periods of passage of organized structures detected by a wide variety of criteria in all regions of turbulent boundary layers, pipes, and channel flows over a range of two Reynolds number decades are compared to that of the transition 'spike'. When scaled with the local mean velocities and the shear layer thicknesses to form a nondimensional streamwise spacing, they fall within a fairly narrow range of TU/delta = 1.5-3.5. The streamwise spacing shows little variation across most of the shear layer for any particular data set.

  13. Space Environments and Effects Concept: Transitioning Research to Operations and Applications

    NASA Technical Reports Server (NTRS)

    Edwards, David L.; Spann, James; Burns, Howard D.; Schumacher, Dan

    2012-01-01

    The National Aeronautics and Space Administration (NASA) is embarking on a course to expand human presence beyond Low Earth Orbit (LEO) while expanding its mission to explore the solar system. Destinations such as Near Earth Asteroids (NEA), Mars and its moons, and the outer planets are but a few of the mission targets. NASA has established numerous offices specializing in specific space environments disciplines that will serve to enable these missions. To complement these existing discipline offices, a concept focusing on the development of space environment and effects application is presented. This includes space climate, space weather, and natural and induced space environments. This space environment and effects application is composed of 4 topic areas; characterization and modeling, engineering effects, prediction and operation, and mitigation and avoidance. These topic areas are briefly described below. Characterization and modeling of space environments will primarily focus on utilization during Program mission concept, planning, and design phases. Engineering effects includes materials testing and flight experiments producing data to be used in mission planning and design phases. Prediction and operation pulls data from existing sources into decision-making tools and empirical data sets to be used during the operational phase of a mission. Mitigation and avoidance will develop techniques and strategies used in the design and operations phases of the mission. The goal of this space environment and effects application is to develop decision-making tools and engineering products to support the mission phases of mission concept through operations by focusing on transitioning research to operations. Products generated by this space environments and effects application are suitable for use in anomaly investigations. This paper will outline the four topic areas, describe the need, and discuss an organizational structure for this space environments and effects

  14. Entropy, chaos, and excited-state quantum phase transitions in the Dicke model.

    PubMed

    Lóbez, C M; Relaño, A

    2016-07-01

    We study nonequilibrium processes in an isolated quantum system-the Dicke model-focusing on the role played by the transition from integrability to chaos and the presence of excited-state quantum phase transitions. We show that both diagonal and entanglement entropies are abruptly increased by the onset of chaos. Also, this increase ends in both cases just after the system crosses the critical energy of the excited-state quantum phase transition. The link between entropy production, the development of chaos, and the excited-state quantum phase transition is more clear for the entanglement entropy.

  15. Mantle Transition Zone Discontinuities beneath the Contiguous United States

    NASA Astrophysics Data System (ADS)

    Gao, S. S.; Liu, K. H.

    2014-12-01

    The depths of the 410 km (d410) and 660 km (d660) discontinuities are robust indicators of in-situ temperature in the upper and lower boundary, respectively, of the mantle transition zone (MTZ), and thus can provide critical constraints on the depth extent of major tectonic features. Using over 310,000 high-quality radial receiver functions recorded by the USArray and other seismic stations in the contiguous United States, the depths of the d410 and d660 are mapped in over 1000 consecutive overlapping circles with a radius of 1 degree. The average MTZ thickness for both the western and central/eastern US is within 3 km from the global average of 250 km, suggesting an overall normal MTZ temperature beneath both areas. The Pacific Coast Ranges and the southern Basin and Range Province are underlain by a depressed d410, indicating higher-than-normal temperature in the upper MTZ. The proposed Yellowstone and Raton hotspots are not associated with clear undulations of the MTZ discontinuities, but d410 beneath another proposed hotspot, Bermuda, is depressed significantly and d660 has a normal depth. Low-temperature regions are found in the upper MTZ associated with the subducted Juan de Fuca slab beneath the northern Rocky Mountains, and in two circular areas beneath the northern Basin and Range Province and the southern Colorado Plateau. Part of the Great Plains is characterized by a depressed d660. This observation, when combined with results from seismic tomography, suggests the existence of a cold region in the lower MTZ, probably associated with subducted Farallon slab segments.

  16. Modeling of Cancer Stem Cell State Transitions Predicts Therapeutic Response

    PubMed Central

    Sehl, Mary E.; Shimada, Miki; Landeros, Alfonso; Lange, Kenneth; Wicha, Max S.

    2015-01-01

    Cancer stem cells (CSCs) possess capacity to both self-renew and generate all cells within a tumor, and are thought to drive tumor recurrence. Targeting the stem cell niche to eradicate CSCs represents an important area of therapeutic development. The complex nature of many interacting elements of the stem cell niche, including both intracellular signals and microenvironmental growth factors and cytokines, creates a challenge in choosing which elements to target, alone or in combination. Stochastic stimulation techniques allow for the careful study of complex systems in biology and medicine and are ideal for the investigation of strategies aimed at CSC eradication. We present a mathematical model of the breast cancer stem cell (BCSC) niche to predict population dynamics during carcinogenesis and in response to treatment. Using data from cell line and mouse xenograft experiments, we estimate rates of interconversion between mesenchymal and epithelial states in BCSCs and find that EMT/MET transitions occur frequently. We examine bulk tumor growth dynamics in response to alterations in the rate of symmetric self-renewal of BCSCs and find that small changes in BCSC behavior can give rise to the Gompertzian growth pattern observed in breast tumors. Finally, we examine stochastic reaction kinetic simulations in which elements of the breast cancer stem cell niche are inhibited individually and in combination. We find that slowing self-renewal and disrupting the positive feedback loop between IL-6, Stat3 activation, and NF-κB signaling by simultaneous inhibition of IL-6 and HER2 is the most effective combination to eliminate both mesenchymal and epithelial populations of BCSCs. Predictions from our model and simulations show excellent agreement with experimental data showing the efficacy of combined HER2 and Il-6 blockade in reducing BCSC populations. Our findings will be directly examined in a planned clinical trial of combined HER2 and IL-6 targeted therapy in HER2

  17. Quantification of the Uncertainties for the Space Launch System Liftoff/Transition and Ascent Databases

    NASA Technical Reports Server (NTRS)

    Favaregh, Amber L.; Houlden, Heather P.; Pinier, Jeremy T.

    2016-01-01

    A detailed description of the uncertainty quantification process for the Space Launch System Block 1 vehicle configuration liftoff/transition and ascent 6-Degree-of-Freedom (DOF) aerodynamic databases is presented. These databases were constructed from wind tunnel test data acquired in the NASA Langley Research Center 14- by 22-Foot Subsonic Wind Tunnel and the Boeing Polysonic Wind Tunnel in St. Louis, MO, respectively. The major sources of error for these databases were experimental error and database modeling errors.

  18. Stability and Design Criteria for CICC with a Broad Transition to Normal State

    SciTech Connect

    Martovetsky, N N

    2004-08-04

    Stability in cable-in-conduit conductors (CICC) against perturbations is often associated with transient heat removal of heat generated in the normal zone. Based on this approach, stability criterion requires low current density in the strands. This criterion is often used for design of the magnets for fusion devices like ITER, KSTAR and others. We show that this criterion is not a mandatory requirement for serviceability of CICC and that CICC may work reliably at higher current densities. In conditions of limited and well defined perturbations, sufficient stability is provided not by a large amount of copper and high transient heat transfer, but by a smooth transition to the normal state and easy current redistribution. A strand parameter space in terms of I{sub c} and N-value meeting CICC requirements for stability, limited heat generation, and minimum temperature margin is proposed and discussed. The theory predictions are compared with known experimental data on CICC.

  19. Communication: transition state theory for dissipative systems without a dividing surface.

    PubMed

    Revuelta, F; Bartsch, Thomas; Benito, R M; Borondo, F

    2012-03-07

    Transition state theory is a central cornerstone in reaction dynamics. Its key step is the identification of a dividing surface that is crossed only once by all reactive trajectories. This assumption is often badly violated, especially when the reactive system is coupled to an environment. The calculations made in this way then overestimate the reaction rate and the results depend critically on the choice of the dividing surface. In this Communication, we study the phase space of a stochastically driven system close to an energetic barrier in order to identify the geometric structure unambiguously determining the reactive trajectories, which is then incorporated in a simple rate formula for reactions in condensed phase that is both independent of the dividing surface and exact.

  20. Metastability of the Nonlinear Wave Equation: Insights from Transition State Theory

    NASA Astrophysics Data System (ADS)

    Newhall, Katherine A.; Vanden-Eijnden, Eric

    2017-01-01

    This paper is concerned with the longtime dynamics of the nonlinear wave equation in one-space dimension, u_{tt} - κ^2 u_{xx} +V'(u) =0 quad xin [0,1] where κ >0 is a parameter and V(u) is a potential bounded from below and growing at least like u^2 as |u|→ ∞. Infinite energy solutions of this equation preserve a natural Gibbsian invariant measure, and when the potential is double-welled, for example when V(u) = 1/4 (1-u^2)^2 , there is a regime such that two small disjoint sets in the system's phase-space concentrate most of the mass of this measure. This suggests that the solutions to the nonlinear wave equation can be metastable over these sets, in the sense that they spend long periods of time in these sets and only rarely transition between them. Here, we quantify this phenomenon by calculating exactly via transition state theory (TST) the mean frequency at which the solutions of the nonlinear wave equation with initial conditions drawn from its invariant measure cross a dividing surface lying in between the metastable sets. We also investigate numerically how the mean TST frequency compares to the rate at which a typical solution crosses this dividing surface. These numerical results suggest that the dynamics of the nonlinear wave equation is ergodic and rapidly mixing with respect to the Gibbs invariant measure when the parameter κ in small enough. In this case, successive transitions between the two regions are roughly uncorrelated and their dynamics can be coarse-grained to jumps in a two-state Markov chain whose rate can be deduced from the mean TST frequency. This is a regime in which the dynamics of the nonlinear wave equation displays a metastable behavior that is not fundamentally different from that observed in its stochastic counterpart in which random noise and damping terms are added to the equation. For larger κ, however, the dynamics either stops being ergodic, or its mixing time becomes larger than the inverse of the TST frequency

  1. Latent state-space models for neural decoding.

    PubMed

    Aghagolzadeh, Mehdi; Truccolo, Wilson

    2014-01-01

    Ensembles of single-neurons in motor cortex can show strong low-dimensional collective dynamics. In this study, we explore an approach where neural decoding is applied to estimated low-dimensional dynamics instead of to the full recorded neuronal population. A latent state-space model (SSM) approach is used to estimate the low-dimensional neural dynamics from the measured spiking activity in population of neurons. A second state-space model representation is then used to decode kinematics, via a Kalman filter, from the estimated low-dimensional dynamics. The latent SSM-based decoding approach is illustrated on neuronal activity recorded from primary motor cortex in a monkey performing naturalistic 3-D reach and grasp movements. Our analysis show that 3-D reach decoding performance based on estimated low-dimensional dynamics is comparable to the decoding performance based on the full recorded neuronal population.

  2. Digital soil mapping as a tool for quantifying state-and-transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ecological sites and associated state-and-transition models (STMs) are rapidly becoming important land management tools in rangeland systems in the US and around the world. Descriptions of states and transitions are largely developed from expert knowledge and generally accepted species and community...

  3. Transition state analysis of the arsenolytic depyrimidination of thymidine by human thymidine phosphorylase.

    PubMed

    Schwartz, Phillip A; Vetticatt, Mathew J; Schramm, Vern L

    2011-03-01

    Human thymidine phosphorylase (hTP) is responsible for thymidine (dT) homeostasis, promotes angiogenesis, and is involved in metabolic inactivation of antiproliferative agents that inhibit thymidylate synthase. Understanding its transition state structure is on the path to design transition state analogues. Arsenolysis of dT by hTP permits kinetic isotope effect (KIE) analysis of the reaction by forming thymine and the chemically unstable 2-deoxyribose 1-arsenate. The transition state for the arsenolytic reaction was characterized using multiple KIEs and computational analysis. Transition state analysis revealed a concerted bimolecular (A(N)D(N)) mechanism. A transition state constrained to match the intrinsic KIE values was found using density functional theory (B3LYP/6-31G*). An active site histidine is implicated as the catalytic base responsible for activation of the arsenate nucleophile and stabilization of the thymine leaving group during the isotopically sensitive step. At the transition state, the deoxyribose ring exhibits significant oxocarbenium ion character with bond breaking (r(C-N) = 2.45 Å) nearly complete and minimal bond making to the attacking nucleophile (r(C-O) = 2.95 Å). The transition state model predicts a deoxyribose conformation with a 2'-endo ring geometry. Transition state structure for the slow hydrolytic reaction of hTP involves a stepwise mechanism [Schwartz, P. A., Vetticatt, M. J., and Schramm, V. L. (2010) J. Am. Chem. Soc. 132, 13425-13433], in contrast to the concerted mechanism described here for arsenolysis.

  4. State Efforts to Meet the Early Childhood Transition Requirements of IDEA. inForum

    ERIC Educational Resources Information Center

    Muller, Eve; Whaley, Kathy; Rous, Beth

    2009-01-01

    In March 2008, the National Early Childhood Transition Initiative released a document developed collaboratively over several months titled "Designing and Implementing Effective Early Childhood Transition Processes". The document was created as a resource for improving state and local performance on the State Performance Plans (SPP) and…

  5. Attention control learning in the decision space using state estimation

    NASA Astrophysics Data System (ADS)

    Gharaee, Zahra; Fatehi, Alireza; Mirian, Maryam S.; Nili Ahmadabadi, Majid

    2016-05-01

    The main goal of this paper is modelling attention while using it in efficient path planning of mobile robots. The key challenge in concurrently aiming these two goals is how to make an optimal, or near-optimal, decision in spite of time and processing power limitations, which inherently exist in a typical multi-sensor real-world robotic application. To efficiently recognise the environment under these two limitations, attention of an intelligent agent is controlled by employing the reinforcement learning framework. We propose an estimation method using estimated mixture-of-experts task and attention learning in perceptual space. An agent learns how to employ its sensory resources, and when to stop observing, by estimating its perceptual space. In this paper, static estimation of the state space in a learning task problem, which is examined in the WebotsTM simulator, is performed. Simulation results show that a robot learns how to achieve an optimal policy with a controlled cost by estimating the state space instead of continually updating sensory information.

  6. Semiclassical approximations in phase space with coherent states

    NASA Astrophysics Data System (ADS)

    Baranger, M.; de Aguiar, M. A. M.; Keck, F.; Korsch, H. J.; Schellhaaß, B.

    2001-09-01

    We present a complete derivation of the semiclassical limit of the coherent-state propagator in one dimension, starting from path integrals in phase space. We show that the arbitrariness in the path integral representation, which follows from the overcompleteness of the coherent states, results in many different semiclassical limits. We explicitly derive two possible semiclassical formulae for the propagator, we suggest a third one, and we discuss their relationships. We also derive an initial-value representation for the semiclassical propagator, based on an initial Gaussian wavepacket. It turns out to be related to, but different from, Heller's thawed Gaussian approximation. It is very different from the Herman-Kluk formula, which is not a correct semiclassical limit. We point out errors in two derivations of the latter. Finally we show how the semiclassical coherent-state propagators lead to WKB-type quantization rules and to approximations for the Husimi distributions of stationary states.

  7. Migration transition in small Northern and Eastern Caribbean states.

    PubMed

    Mcelroy, J L; De Albuquerque, K

    1988-01-01

    1 area of intra-Caribbean migration that has been overlooked is the "migration transition"--the transformation of rapidly modernizing societies from net labor exporters to net labor importers. This article assembles 8 case studies to 1) briefly present a spectrum of migration experiences in the Caribbean, 2) uncover some transitions under way, 3) pinpoint the forces that underlie the migration transition, and 4) point out some of the more important policy implications of labor migration reversals. The 8 island societies sampled for illustration purposes include 1) the Bahamas and the US Virgin Islands as post-migration transition societies (Zelinsky's advanced society), 2) the British Virgin Islands and the Cayman Islands as undergoing transition (Zelinsky's late transitional society), and 3) Anguilla, St. Kitts-Nevis, Turks and Caicos, and Montserrat as premigration transition societies (Zelinsky's early transitional society). Population data for the islands were derived primarily from the West Indian censuses and government statistics. These 8 historical sketches reveal certain commonalities. All are at various stages in a long-term economic restructuring to displace traditional staple crops with more income elastic, high value export services. In such societies, population growth and progress along the migration transition is an increasing function of this kind of successful export substitution. In addition, along the migration and economic transitions, such insular economies exhibit a relatively large public sector (20-30% of all activity), declining unemployment, increasing fiscal autonomy, and are committed to a development strategy remarkably similar to the "successful" model of the Bahamas and the US Virgin Islands. Cursory evidence suggests that, because of intersectoral competition for land and labor, there is an inverse relationship between farm effort/manufacturing employment and tourism intensity. This review suggests that small islands undergoing

  8. Solid-state Terahertz Sources for Space Applications

    NASA Technical Reports Server (NTRS)

    Maiwald, Frank; Pearson, John C.; Ward, John S.; Schlecht, Erich; Chattopadhyay, Goutam; Gill, John J.; Ferber, R.; Tsang, Raymond; Lin, Robert H.; Peralta, Alejandro; Finamore, B.; Chun, William W.; Baker, John J.; Dengler, Robert J.; Javadi, Hamid H.; Siegel, Peter H.; Mehdi, Imran

    2004-01-01

    This paper discusses the construction of solid-state frequency multiplier chains utilized far teraherz receiver applications such as the Herschel Space Observatory . Emphasis will he placed on the specific requirements to be met and challenges that were encountered. The availability of high power amplifiers at 100 GHz makes it possible to cascade frequency doublers and triplers with sufficient RF power to pump heterodyne receivers at THz frequencies. The environmental and mechanical constraints will be addressed as well as reliability issues.

  9. Advanced Solid State Lighting for AES Deep Space Hab Project

    NASA Technical Reports Server (NTRS)

    Holbert, Eirik

    2015-01-01

    The advanced Solid State Lighting (SSL) assemblies augmented 2nd generation modules under development for the Advanced Exploration Systems Deep Space Habitat in using color therapy to synchronize crew circadian rhythms. Current RGB LED technology does not produce sufficient brightness to adequately address general lighting in addition to color therapy. The intent is to address both through a mix of white and RGB LEDs designing for fully addressable alertness/relaxation levels as well as more dramatic circadian shifts.

  10. 2-D Signal Generation Using State-Space Formulation.

    DTIC Science & Technology

    1985-12-01

    published that have established nonoptical .~ -~ Iimage processing as a viable area of research. A large portion of this research emphasizes the linear...research and the study of time-discrete linear systems. This thesis develops the discrete model of Roesser [Ref. 5] for linear image processing which... THESIS 2-D SIGNAL GENERATION USING STATE-SPACE FORMULATION - • by (.) Evangelos Theofilou December 1985 • Thesis Advisor: Sydney R. Parker Approved

  11. News and Views: Transit events and resources; HST to use transit to probe venusian atmosphere; Now, the space weather forecast; Astronomy writing prize

    NASA Astrophysics Data System (ADS)

    2012-06-01

    TRANSIT Early risers in the UK have the opportunity to see the final stages of the last transit of Venus for more than a century. TRANSIT Researchers interested in the atmosphere of Venus will be using the Hubble Space Telescope and the Moon to examine sunlight passing through the atmosphere during the transit of Venus this month. The technique is the same as that used to determine atmospheric constituents of transiting exoplanets. The Met Office is expanding its services to include operational space-weather forecasts for the UK, working with the research community to expand existing climate models. Further collaborative work will apply the enhanced model to extrasolar planets. The ESO and the STFC are organizing a Europe-wide competition for the very best in astronomy journalism in print, online or broadcast. The winner gets a trip to ESO's Very Large Telescope in Chile.

  12. Combining transition state theory with quasiclassical trajectory calculations: application to the nitrogen exchange reaction N+N 2( v)

    NASA Astrophysics Data System (ADS)

    Frost, Robert J.; Smith, Ian W. M.

    1987-10-01

    The dynamics of collisions between N atoms and vibrationally excited N 2( v⩽ 15) have been studied using a new method in which quasiclassical trajectories are initiated at suitably chosen transition states. The transition state for a particular vibrational level v is determined by first finding PODSs (periodic orbiting dividing surfaces) on fixed-angle potential energy surfaces for which the action over one cycle of the PODS motion is ( v+ 1/2) h. The complete transition state is defined by joining these PODSs together and its phase space is sampled pseudorandomly to select starting points for quasiclassical trajectories. The results of the calculations are compared with those from conventional quasiclassical trajectory calculations on the same LEPS potential energy surface, using the adiabatic reactive sudden version of transition state theory to estimate absolute rate constants from our results. The agreement is good and the combined method brings about a great saving in computing time by eliminating trajectories which do not reach the strong interaction zone.

  13. Identification and characterization of the unfolding transition state of chymotrypsin inhibitor 2 by molecular dynamics simulations.

    PubMed

    Li, A; Daggett, V

    1996-03-29

    Temperature-induced unfolding of chymotrypsin inhibitor 2 (CI2) in water has been investigated using molecular dynamics simulations. One simulation (2.2 ns) has been analyzed in detail and three additional simulations (each > or = 1 ns) were performed to check the generality of the results. Concurrent loss of secondary and tertiary structure during unfolding was observed in all the simulations. For each simulation, the major transition state of unfolding was identified based on conformational analysis of protein structures along the unfolding trajectory. The transition state has a considerably weakened hydrophobic core and disrupted secondary structure. Nevertheless, the overall structure of the transition state is closer to the native state than to the unfolded state. The disruption of the hydrophobic core appears to be rate limiting. However, other energy barriers have to be overcome before reaching the major transition state. A method is described to quantitatively compare the structure of the simulated transition state with that characterized by protein engineering experiments. Good agreement with the experimental data is obtained for all four transition state models (the correlation coefficient R = 0.80 to 0.93) and the average over all four models gives the best correlation (R = 0.94). These simulations provide the first comprehensive atomic-level view of what the unfolding transition state of C12 may look like.

  14. The Ebb and Flow of Filipino First-Time Fatherhood Transition Space: A Grounded Theory Study.

    PubMed

    Villamor, Neil Jupiter E; de Guzman, Allan B; Matienzo, Evangeline T

    2016-11-01

    Fatherhood, as a developmental process, is both a human experience and a text that needs to be read. For developing nations like the Philippines, little is known about the process undergone by first-time fathers on their transition to fatherhood, and how nurses can play a significant role in assisting them. This grounded theory study purported to conceptualize the multifaceted process of transition from the lens of Filipino first-time fathers' lived experiences. A total of 20 first-time fathers from Metro Manila, Philippines, were purposively selected to take part in an individual, semistructured, and in-depth interview. The Glaserian (classical) method of analysis was specifically used, and field texts were inductively analyzed using a repertory grid. Member checking and correspondence were done to validate the findings of the study. Six surfacing stages emerged relative to the process of transition. Interestingly, The B.R.I.D.G.E. Theory of First-Time Fatherhood Transition Space describes how these fathers progress from the beholding, reorganizing, inhibiting, delivering, grasping, and embracing phases toward successful transition. This emerged theoretical model can be used in framing health care programs where the needs of fathers during this period are met and addressed. Finally, it can also be used in guiding nurses in their provision of a more empathetic care for first-time fathers.

  15. 14 CFR § 1217.106 - Articles brought into the United States by NASA from space.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... NASA from space. § 1217.106 Section § 1217.106 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION DUTY-FREE ENTRY OF SPACE ARTICLES § 1217.106 Articles brought into the United States by NASA from... territory of the United States by NASA from space shall not be considered an importation, and...

  16. 14 CFR 1217.106 - Articles brought into the United States by NASA from space.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... NASA from space. 1217.106 Section 1217.106 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION DUTY-FREE ENTRY OF SPACE ARTICLES § 1217.106 Articles brought into the United States by NASA from... territory of the United States by NASA from space shall not be considered an importation, and...

  17. 14 CFR 1217.106 - Articles brought into the United States by NASA from space.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... NASA from space. 1217.106 Section 1217.106 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION DUTY-FREE ENTRY OF SPACE ARTICLES § 1217.106 Articles brought into the United States by NASA from... territory of the United States by NASA from space shall not be considered an importation, and...

  18. 14 CFR 1217.106 - Articles brought into the United States by NASA from space.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... NASA from space. 1217.106 Section 1217.106 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION DUTY-FREE ENTRY OF SPACE ARTICLES § 1217.106 Articles brought into the United States by NASA from... territory of the United States by NASA from space shall not be considered an importation, and...

  19. Derivation of a true (t → 0+) quantum transition-state theory. I. Uniqueness and equivalence to ring-polymer molecular dynamics transition-state-theory.

    PubMed

    Hele, Timothy J H; Althorpe, Stuart C

    2013-02-28

    Surprisingly, there exists a quantum flux-side time-correlation function which has a non-zero t → 0+ limit and thus yields a rigorous quantum generalization of classical transition-state theory (TST). In this Part I of two articles, we introduce the new time-correlation function and derive its t → 0+ limit. The new ingredient is a generalized Kubo transform which allows the flux and side dividing surfaces to be the same function of path-integral space. Choosing this function to be a single point gives a t → 0+ limit which is identical to an expression introduced on heuristic grounds by Wigner in 1932; however, this expression does not give positive-definite quantum statistics, causing it to fail while still in the shallow-tunnelling regime. Positive-definite quantum statistics is obtained only if the dividing surface is invariant to imaginary-time translation, in which case the t → 0+ limit is identical to ring-polymer molecular dynamics (RPMD) TST. The RPMD-TST rate is not a strict upper bound to the exact quantum rate, but is a good approximation to one if real-time coherence effects are small. Part II will show that the RPMD-TST rate is equal to the exact quantum rate in the absence of recrossing.

  20. Space Cooling in the United States: A Market Deep Dive

    DOE PAGES

    Baxter, Van D.; Sikes, Karen; Khowailed, Gannate

    2016-01-01

    The American space cooling market is experiencing stricter efficiency standards, prosperous economic conditions, a steadily recovering housing market, population migration shift to warmer climates, and declining electricity prices. These factors have yielded a climate conducive to growth in air conditioning (AC) and air source heat pump (HP) shipments in the recent past with total AC and HP shipments in 2015 accounting for 6.8 million units, showing a growth of 32 % relative to 2010. In this article, the authors investigate the impact that regulatory changes and economic changes have had on unit shipments and identify future market influencers, including themore » introduction of advanced HVAC technologies and transition to more environmentally friendly refrigerants.« less

  1. Transition probabilities for non self-adjoint Hamiltonians in infinite dimensional Hilbert spaces

    SciTech Connect

    Bagarello, F.

    2015-11-15

    In a recent paper we have introduced several possible inequivalent descriptions of the dynamics and of the transition probabilities of a quantum system when its Hamiltonian is not self-adjoint. Our analysis was carried out in finite dimensional Hilbert spaces. This is useful, but quite restrictive since many physically relevant quantum systems live in infinite dimensional Hilbert spaces. In this paper we consider this situation, and we discuss some applications to well known models, introduced in the literature in recent years: the extended harmonic oscillator, the Swanson model and a generalized version of the Landau levels Hamiltonian. Not surprisingly we will find new interesting features not previously found in finite dimensional Hilbert spaces, useful for a deeper comprehension of this kind of physical systems.

  2. Space Monitoring Data Center at Moscow State University

    NASA Astrophysics Data System (ADS)

    Kalegaev, Vladimir; Bobrovnikov, Sergey; Barinova, Vera; Myagkova, Irina; Shugay, Yulia; Barinov, Oleg; Dolenko, Sergey; Mukhametdinova, Ludmila; Shiroky, Vladimir

    Space monitoring data center of Moscow State University provides operational information on radiation state of the near-Earth space. Internet portal http://swx.sinp.msu.ru/ gives access to the actual data characterizing the level of solar activity, geomagnetic and radiation conditions in the magnetosphere and heliosphere in the real time mode. Operational data coming from space missions (ACE, GOES, ELECTRO-L1, Meteor-M1) at L1, LEO and GEO and from the Earth’s surface are used to represent geomagnetic and radiation state of near-Earth environment. On-line database of measurements is also maintained to allow quick comparison between current conditions and conditions experienced in the past. The models of space environment working in autonomous mode are used to generalize the information obtained from observations on the whole magnetosphere. Interactive applications and operational forecasting services are created on the base of these models. They automatically generate alerts on particle fluxes enhancements above the threshold values, both for SEP and relativistic electrons using data from LEO orbits. Special forecasting services give short-term forecast of SEP penetration to the Earth magnetosphere at low altitudes, as well as relativistic electron fluxes at GEO. Velocities of recurrent high speed solar wind streams on the Earth orbit are predicted with advance time of 3-4 days on the basis of automatic estimation of the coronal hole areas detected on the images of the Sun received from the SDO satellite. By means of neural network approach, Dst and Kp indices online forecasting 0.5-1.5 hours ahead, depending on solar wind and the interplanetary magnetic field, measured by ACE satellite, is carried out. Visualization system allows representing experimental and modeling data in 2D and 3D.

  3. Solar Pumped High Power Solid State Laser for Space Applications

    NASA Technical Reports Server (NTRS)

    Fork, Richard L.; Laycock, Rustin L.; Green, Jason J. A.; Walker, Wesley W.; Cole, Spencer T.; Frederick, Kevin B.; Phillips, Dane J.

    2004-01-01

    Highly coherent laser light provides a nearly optimal means of transmitting power in space. The simplest most direct means of converting sunlight to coherent laser light is a solar pumped laser oscillator. A key need for broadly useful space solar power is a robust solid state laser oscillator capable of operating efficiently in near Earth space at output powers in the multi hundred kilowatt range. The principal challenges in realizing such solar pumped laser oscillators are: (1) the need to remove heat from the solid state laser material without introducing unacceptable thermal shock, thermal lensing, or thermal stress induced birefringence to a degree that improves on current removal rates by several orders of magnitude and (2) to introduce sunlight at an effective concentration (kW/sq cm of laser cross sectional area) that is several orders of magnitude higher than currently available while tolerating a pointing error of the spacecraft of several degrees. We discuss strategies for addressing these challenges. The need to remove the high densities of heat, e.g., 30 kW/cu cm, while keeping the thermal shock, thermal lensing and thermal stress induced birefringence loss sufficiently low is addressed in terms of a novel use of diamond integrated with the laser material, such as Ti:sapphire in a manner such that the waste heat is removed from the laser medium in an axial direction and in the diamond in a radial direction. We discuss means for concentrating sunlight to an effective areal density of the order of 30 kW/sq cm. The method integrates conventional imaging optics, non-imaging optics and nonlinear optics. In effect we use a method that combines some of the methods of optical pumping solid state materials and optical fiber, but also address laser media having areas sufficiently large, e.g., 1 cm diameter to handle the multi-hundred kilowatt level powers needed for space solar power.

  4. Employment Outcomes of Transition-Aged Adults with Autism Spectrum Disorders: A State of the States Report

    ERIC Educational Resources Information Center

    Burgess, Sloane; Cimera, Robert E.

    2014-01-01

    The primary purpose of this study was to evaluate the employment outcomes of transition-aged adults with autism spectrum disorders (ASD) served by vocational rehabilitation services (VR) over the last 10 years by state. A secondary purpose was to compare employment outcomes of individuals with ASD to those of the overall transition-aged population…

  5. Attractor states and quantum instabilities in de Sitter space

    SciTech Connect

    Anderson, P. R.; Eaker, W.; Habib, S.; Molina-Paris, Carmen; Mottola, E.

    2001-01-01

    The asymptotic behavior of the energy-momentum tensor for a free quantized scalar field with mass m and curvature coupling {zeta} in de Sitter space is investigated. It is shown that for an arbitrary, homogeneous and isotropic, fourth order adiabatic state for which the two-point function is infrared finite, approaches the Bunch-Davies de Sitter invariant value at late times if m{sup 2} + {zeta}R > 0. In the case m = {zeta} = 0, the energy-momentum tensor approaches the de Sitter invariant Allen-Folacci value for such a state. For m{sup 2} + {zeta}R = 0, but m and {zeta} not separately zero it is shown that at late times grows linearly in terms of cosmic time leading to an instability of de Sitter space. The asymptotic behavior is again independent of the state of the field. For m{sup 2} + {zeta}R < 0, it is shown that, for most values of m and {zeta}, grows exponentially in terms of cosmic time at late times in a state dependent manner.

  6. Distortional binding of transition state analogs to human purine nucleoside phosphorylase probed by magic angle spinning solid-state NMR

    PubMed Central

    Vetticatt, Mathew J.; Itin, Boris; Evans, Gary B.; Schramm, Vern L.

    2013-01-01

    Transition state analogs mimic the geometry and electronics of the transition state of enzymatic reactions. These molecules bind to the active site of the enzyme much tighter than substrate and are powerful noncovalent inhibitors. Immucillin-H (ImmH) and 4′-deaza-1′-aza-2′-deoxy-9-methylene Immucillin-H (DADMe-ImmH) are picomolar inhibitors of human purine nucleoside phosphorylase (hPNP). Although both molecules are electronically similar to the oxocarbenium-like dissociative hPNP transition state, DADMe-ImmH is more potent than ImmH. DADMe-ImmH captures more of the transition state binding energy by virtue of being a closer geometric match to the hPNP transition state than ImmH. A consequence of these similarities is that the active site of hPNP exerts greater distortional forces on ImmH than on DADMe-ImmH to “achieve” the hPNP transition state geometry. By using magic angle spinning solid-state NMR to investigate stable isotope-labeled ImmH and DADMe-ImmH, we have explored the difference in distortional binding of these two inhibitors to hPNP. High-precision determinations of internuclear distances from NMR recoupling techniques, rotational echo double resonance, and rotational resonance, have provided unprecedented atomistic insight into the geometric changes that occur upon binding of transition state analogs. We conclude that hPNP stabilizes conformations of these chemically distinct analogs having distances between the cation and leaving groups resembling those of the known transition state. PMID:24043827

  7. Continuity of states between the cholesteric → line hexatic transition and the condensation transition in DNA solutions

    SciTech Connect

    Yasar, Selcuk; Podgornik, Rudolf; Valle-Orero, Jessica; Johnson, Mark R.; Parsegian, V. Adrian

    2014-11-05

    A new method of finely temperature-tuning osmotic pressure allows one to identify the cholesteric → line hexatic transition of oriented or unoriented long-fragment DNA bundles in monovalent salt solutions as first order, with a small but finite volume discontinuity. This transition is similar to the osmotic pressure-induced expanded → condensed DNA transition in polyvalent salt solutions at small enough polyvalent salt concentrations. Therefore there exists a continuity of states between the two. This finding with the corresponding empirical equation of state, effectively relates the phase diagram of DNA solutions for monovalent salts to that for polyvalent salts and sheds some light on the complicated interactions between DNA molecules at high densities.

  8. Continuity of states between the cholesteric → line hexatic transition and the condensation transition in DNA solutions

    DOE PAGES

    Yasar, Selcuk; Podgornik, Rudolf; Valle-Orero, Jessica; ...

    2014-11-05

    A new method of finely temperature-tuning osmotic pressure allows one to identify the cholesteric → line hexatic transition of oriented or unoriented long-fragment DNA bundles in monovalent salt solutions as first order, with a small but finite volume discontinuity. This transition is similar to the osmotic pressure-induced expanded → condensed DNA transition in polyvalent salt solutions at small enough polyvalent salt concentrations. Therefore there exists a continuity of states between the two. This finding with the corresponding empirical equation of state, effectively relates the phase diagram of DNA solutions for monovalent salts to that for polyvalent salts and sheds somemore » light on the complicated interactions between DNA molecules at high densities.« less

  9. Hybrid phase transition into an absorbing state: Percolation and avalanches

    NASA Astrophysics Data System (ADS)

    Lee, Deokjae; Choi, S.; Stippinger, M.; Kertész, J.; Kahng, B.

    2016-04-01

    Interdependent networks are more fragile under random attacks than simplex networks, because interlayer dependencies lead to cascading failures and finally to a sudden collapse. This is a hybrid phase transition (HPT), meaning that at the transition point the order parameter has a jump but there are also critical phenomena related to it. Here we study these phenomena on the Erdős-Rényi and the two-dimensional interdependent networks and show that the hybrid percolation transition exhibits two kinds of critical behaviors: divergence of the fluctuations of the order parameter and power-law size distribution of finite avalanches at a transition point. At the transition point global or "infinite" avalanches occur, while the finite ones have a power law size distribution; thus the avalanche statistics also has the nature of a HPT. The exponent βm of the order parameter is 1 /2 under general conditions, while the value of the exponent γm characterizing the fluctuations of the order parameter depends on the system. The critical behavior of the finite avalanches can be described by another set of exponents, βa and γa. These two critical behaviors are coupled by a scaling law: 1 -βm=γa .

  10. Hybrid phase transition into an absorbing state: Percolation and avalanches.

    PubMed

    Lee, Deokjae; Choi, S; Stippinger, M; Kertész, J; Kahng, B

    2016-04-01

    Interdependent networks are more fragile under random attacks than simplex networks, because interlayer dependencies lead to cascading failures and finally to a sudden collapse. This is a hybrid phase transition (HPT), meaning that at the transition point the order parameter has a jump but there are also critical phenomena related to it. Here we study these phenomena on the Erdős-Rényi and the two-dimensional interdependent networks and show that the hybrid percolation transition exhibits two kinds of critical behaviors: divergence of the fluctuations of the order parameter and power-law size distribution of finite avalanches at a transition point. At the transition point global or "infinite" avalanches occur, while the finite ones have a power law size distribution; thus the avalanche statistics also has the nature of a HPT. The exponent β_{m} of the order parameter is 1/2 under general conditions, while the value of the exponent γ_{m} characterizing the fluctuations of the order parameter depends on the system. The critical behavior of the finite avalanches can be described by another set of exponents, β_{a} and γ_{a}. These two critical behaviors are coupled by a scaling law: 1-β_{m}=γ_{a}.

  11. Dynamical transitions in large systems of mean field-coupled Landau-Stuart oscillators: Extensive chaos and cluster states

    SciTech Connect

    Ku, Wai Lim; Girvan, Michelle; Ott, Edward

    2015-12-15

    In this paper, we study dynamical systems in which a large number N of identical Landau-Stuart oscillators are globally coupled via a mean-field. Previously, it has been observed that this type of system can exhibit a variety of different dynamical behaviors. These behaviors include time periodic cluster states in which each oscillator is in one of a small number of groups for which all oscillators in each group have the same state which is different from group to group, as well as a behavior in which all oscillators have different states and the macroscopic dynamics of the mean field is chaotic. We argue that this second type of behavior is “extensive” in the sense that the chaotic attractor in the full phase space of the system has a fractal dimension that scales linearly with N and that the number of positive Lyapunov exponents of the attractor also scales linearly with N. An important focus of this paper is the transition between cluster states and extensive chaos as the system is subjected to slow adiabatic parameter change. We observe discontinuous transitions between the cluster states (which correspond to low dimensional dynamics) and the extensively chaotic states. Furthermore, examining the cluster state, as the system approaches the discontinuous transition to extensive chaos, we find that the oscillator population distribution between the clusters continually evolves so that the cluster state is always marginally stable. This behavior is used to reveal the mechanism of the discontinuous transition. We also apply the Kaplan-Yorke formula to study the fractal structure of the extensively chaotic attractors.

  12. 45 CFR 150.221 - Transition to State enforcement.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... ACCESS CMS ENFORCEMENT IN GROUP AND INDIVIDUAL INSURANCE MARKETS CMS Enforcement Processes for... State enforcement. (a) If CMS determines that a State for which it has assumed enforcement authority has... appropriate to return enforcement authority to the State, CMS will enter into discussions with State...

  13. 45 CFR 150.221 - Transition to State enforcement.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... ACCESS CMS ENFORCEMENT IN GROUP AND INDIVIDUAL INSURANCE MARKETS CMS Enforcement Processes for... State enforcement. (a) If CMS determines that a State for which it has assumed enforcement authority has... appropriate to return enforcement authority to the State, CMS will enter into discussions with State...

  14. 45 CFR 150.221 - Transition to State enforcement.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... ACCESS CMS ENFORCEMENT IN GROUP AND INDIVIDUAL INSURANCE MARKETS CMS Enforcement Processes for... State enforcement. (a) If CMS determines that a State for which it has assumed enforcement authority has... appropriate to return enforcement authority to the State, CMS will enter into discussions with State...

  15. 45 CFR 150.221 - Transition to State enforcement.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... ACCESS CMS ENFORCEMENT IN GROUP AND INDIVIDUAL INSURANCE MARKETS CMS Enforcement Processes for... State enforcement. (a) If CMS determines that a State for which it has assumed enforcement authority has... appropriate to return enforcement authority to the State, CMS will enter into discussions with State...

  16. 45 CFR 150.221 - Transition to State enforcement.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... ACCESS CMS ENFORCEMENT IN GROUP AND INDIVIDUAL INSURANCE MARKETS CMS Enforcement Processes for... State enforcement. (a) If CMS determines that a State for which it has assumed enforcement authority has... appropriate to return enforcement authority to the State, CMS will enter into discussions with State...

  17. Transition of vegetation states positively affects harvester ants in the Great Basin, United States

    USGS Publications Warehouse

    Holbrook, Joseph D.; Pilliod, David; Arkle, Robert; Rachlow, Janet L.; Vierling, Kerri T.; Wiest, Michelle M.

    2016-01-01

    Invasions by non-native plants can alter ecosystems such that new ecological states are reached, but less is known about how these transitions influence animal populations. Sagebrush (Artemisia tridentata) ecosystems are experiencing state changes because of fire and invasion by exotic annual grasses. Our goal was to study the effects of these state changes on the Owyhee and western harvester ants (Pogonomyrmex salinusOlsen and P. occidentalis Cresson, respectively). We sampled 358 1-ha plots across the northern Great Basin, which captured unburned and burned conditions across 1 −≥31 years postfire. Our results indicated an immediate and consistent change in vegetation states from shrubland to grassland between 1 and 31 years postfire. Harvester ant occupancy was unrelated to time since fire, whereas we observed a positive effect of fire on nest density. Similarly, we discovered that fire and invasion by exotic annuals were weak predictors of harvester ant occupancy but strong predictors of nest density. Occupancy of harvester ants was more likely in areas with finer-textured soils, low precipitation, abundant native forbs, and low shrub cover. Nest density was higher in arid locations that recently burned and exhibited abundant exotic annual and perennial (exotic and native) grasses. Finally, we discovered that burned areas that received postfire restoration had minimal influence on harvester ant occupancy or nest density compared with burned and untreated areas. These results suggest that fire-induced state changes from native shrublands to grasslands dominated by non-native grasses have a positive effect on density of harvester ants (but not occupancy), and that postfire restoration does not appear to positively or negatively affect harvester ants. Although wildfire and invasion by exotic annual grasses may negatively affect other species, harvester ants may indeed be one of the few winners among a myriad of losers linked to vegetation state changes within

  18. Utilizing a Russian space nuclear reactor for a United States space mission: Systems integration issues

    SciTech Connect

    Reynolds, E.; Schaefer, E.; Polansky, G.; Lacy, J.; Bocharov, A.

    1993-09-30

    The Nuclear Electric Propulsion Space Test Program (NEPSTP) has developed a cooperative relationship with several institutes of the former Soviet Union to evaluate Russian space hardware on a US spacecraft One component is the Topaz II Nuclear Power System; a built and flight qualified nuclear reactor that has yet to be tested in space. The access to the Topaz II reactor provides the NEPSTP with a rare opportunity; to conduct an early flight demonstration of nuclear electric propulsion at a relatively low cost. This opportunity, however, is not without challenges. Topaz II was designed to be compatible with Russian spacecraft and launch vehicles. It was manufactured and flight qualified by Russian techniques and standards and conforms to safety requirements of the former Soviet Union, not the United States. As it is desired to make minimal modifications to the Topaz II, integrating the reactor system with a United States spacecraft and launch vehicle presents an engineering challenge. This paper documents the lessons teamed regarding the integration of reactor based spacecraft and also some insight about integrating Russian hardware. It examines the planned integration flow along with specific reactor requirements that affect the spacecraft integration including American-Russian space system compatibility.

  19. Model of EF4-induced ribosomal state transitions and mRNA translocation

    NASA Astrophysics Data System (ADS)

    Xie, Ping

    2014-08-01

    EF4, a highly conserved protein present in bacteria, mitochondria and chloroplasts, can bind to both the posttranslocation and pretranslocation ribosomal complexes. When binding to the posttranslocation state, it catalyzes backward translocation to a pretranslocation state. When binding to the pretranslocation state, it catalyzes transition to another pretranslocation state that is similar and possibly identical to that resulting from the posttranslocation state bound by EF4, and competes with EF-G to regulate the elongation cycle. However, the molecular mechanism on how EF4 induces state transitions and mRNA translocation remains unclear. Here, we present both the model for state transitions induced by EF4 binding to the posttranslocation state and that by EF4 binding to the pretranslocation state, based on which we study the kinetics of EF4-induced state transitions and mRNA translocation, giving quantitative explanations of the available experimental data. Moreover, we present some predicted results on state transitions and mRNA translocation induced by EF4 binding to the pretranslocation state complexed with the mRNA containing a duplex region.

  20. The Applied Meteorology Unit: Nineteen Years Successfully Transitioning Research into Operations for America's Space Program

    NASA Technical Reports Server (NTRS)

    Madura, John T.; Bauman, William H.; Merceret, Francis J.; Roeder, William P.; Brody, Frank C.; Hagemeyer, Bartlett C.

    2010-01-01

    The Applied Meteorology Unit (AMU) provides technology transition and technique development to improve operational weather support to the Space Shuttle and the entire American space program. The AMU is funded and managed by NASA and operated by a contractor that provides five meteorologists with a diverse mix of advanced degrees, operational experience, and associated skills including data processing, statistics, and the development of graphical user interfaces. The AMU's primary customers are the U.S. Air Force 45th Weather Squadron at Patrick Air Force Base, the National Weather Service Spaceflight Meteorology Group at NASA Johnson Space Center, and the National Weather Service Melbourne FL Forecast Office. The AMU has transitioned research into operations for nineteen years and worked on a wide range of topics, including new forecasting techniques for lightning probability, synoptic peak winds,.convective winds, and summer severe weather; satellite tools to predict anvil cloud trajectories and evaluate camera line of sight for Space Shuttle launch; optimized radar scan strategies; evaluated and implemented local numerical models; evaluated weather sensors; and many more. The AMU has completed 113 projects with 5 more scheduled to be completed by the end of 2010. During this rich history, the AMU and its customers have learned many lessons on how to effectively transition research into operations. Some of these lessons learned include collocating with the operational customer and periodically visiting geographically separated customers, operator submitted projects, consensus tasking process, use of operator primary advocates for each project, customer AMU liaisons with experience in both operations and research, flexibility in adapting the project plan based on lessons learned during the project, and incorporating training and other transition assistance into the project plans. Operator involvement has been critical to the AMU's remarkable success and many awards

  1. On Volterra quadratic stochastic operators with continual state space

    SciTech Connect

    Ganikhodjaev, Nasir; Hamzah, Nur Zatul Akmar

    2015-05-15

    Let (X,F) be a measurable space, and S(X,F) be the set of all probability measures on (X,F) where X is a state space and F is σ - algebraon X. We consider a nonlinear transformation (quadratic stochastic operator) defined by (Vλ)(A) = ∫{sub X}∫{sub X}P(x,y,A)dλ(x)dλ(y), where P(x, y, A) is regarded as a function of two variables x and y with fixed A ∈ F . A quadratic stochastic operator V is called a regular, if for any initial measure the strong limit lim{sub n→∞} V{sup n }(λ) is exists. In this paper, we construct a family of quadratic stochastic operators defined on the segment X = [0,1] with Borel σ - algebra F on X , prove their regularity and show that the limit measure is a Dirac measure.

  2. Vibrational energy transfer near a dissociative adsorption transition state: State-to-state study of HCl collisions at Au(111)

    NASA Astrophysics Data System (ADS)

    Geweke, Jan; Shirhatti, Pranav R.; Rahinov, Igor; Bartels, Christof; Wodtke, Alec M.

    2016-08-01

    In this work we seek to examine the nature of collisional energy transfer between HCl and Au(111) for nonreactive scattering events that sample geometries near the transition state for dissociative adsorption by varying both the vibrational and translational energy of the incident HCl molecules in the range near the dissociation barrier. Specifically, we report absolute vibrational excitation probabilities for HCl(v = 0 → 1) and HCl(v = 1 → 2) scattering from clean Au(111) as a function of surface temperature and incidence translational energy. The HCl(v = 2 → 3) channel could not be observed—presumably due to the onset of dissociation. The excitation probabilities can be decomposed into adiabatic and nonadiabatic contributions. We find that both contributions strongly increase with incidence vibrational state by a factor of 24 and 9, respectively. This suggests that V-T as well as V-EHP coupling can be enhanced near the transition state for dissociative adsorption at a metal surface. We also show that previously reported HCl(v = 0 → 1) excitation probabilities [Q. Ran et al., Phys. Rev. Lett. 98, 237601 (2007)]—50 times smaller than those reported here—were influenced by erroneous assignment of spectroscopic lines used in the data analysis.

  3. Vibrational energy transfer near a dissociative adsorption transition state: State-to-state study of HCl collisions at Au(111).

    PubMed

    Geweke, Jan; Shirhatti, Pranav R; Rahinov, Igor; Bartels, Christof; Wodtke, Alec M

    2016-08-07

    In this work we seek to examine the nature of collisional energy transfer between HCl and Au(111) for nonreactive scattering events that sample geometries near the transition state for dissociative adsorption by varying both the vibrational and translational energy of the incident HCl molecules in the range near the dissociation barrier. Specifically, we report absolute vibrational excitation probabilities for HCl(v = 0 → 1) and HCl(v = 1 → 2) scattering from clean Au(111) as a function of surface temperature and incidence translational energy. The HCl(v = 2 → 3) channel could not be observed-presumably due to the onset of dissociation. The excitation probabilities can be decomposed into adiabatic and nonadiabatic contributions. We find that both contributions strongly increase with incidence vibrational state by a factor of 24 and 9, respectively. This suggests that V-T as well as V-EHP coupling can be enhanced near the transition state for dissociative adsorption at a metal surface. We also show that previously reported HCl(v = 0 → 1) excitation probabilities [Q. Ran et al., Phys. Rev. Lett. 98, 237601 (2007)]-50 times smaller than those reported here-were influenced by erroneous assignment of spectroscopic lines used in the data analysis.

  4. Space Environments and Spacecraft Effects Concept: Transitioning Research to Operations and Applications

    NASA Technical Reports Server (NTRS)

    Edwards, D. L.; Burns, H. D.; Clinton, R. G.; Schumacher, D.; Spann, J. F.

    2012-01-01

    support function also includes working in coordination with the program in anomaly resolution and generation of lesson learned documentation. The goal of this space environment and spacecraft effects organization is to develop decision-making tools and engineering products to support the mission phases of mission concept through operations by focusing on transitioning research to application. Products generated by this space environments and spacecraft effects organization are suitable for use in anomaly investigations. This paper will describe the organizational structure for this space environments and spacecraft effects organization, and outline the scope of conceptual TWG's and their relationship to the functional areas.

  5. A hierarchical state space approach to affective dynamics

    PubMed Central

    Lodewyckx, Tom; Tuerlinckx, Francis; Kuppens, Peter; Allen, Nicholas; Sheeber, Lisa

    2010-01-01

    Linear dynamical system theory is a broad theoretical framework that has been applied in various research areas such as engineering, econometrics and recently in psychology. It quantifies the relations between observed inputs and outputs that are connected through a set of latent state variables. State space models are used to investigate the dynamical properties of these latent quantities. These models are especially of interest in the study of emotion dynamics, with the system representing the evolving emotion components of an individual. However, for simultaneous modeling of individual and population differences, a hierarchical extension of the basic state space model is necessary. Therefore, we introduce a Bayesian hierarchical model with random effects for the system parameters. Further, we apply our model to data that were collected using the Oregon adolescent interaction task: 66 normal and 67 depressed adolescents engaged in a conflict interaction with their parents and second-to-second physiological and behavioral measures were obtained. System parameters in normal and depressed adolescents were compared, which led to interesting discussions in the light of findings in recent literature on the links between cardiovascular processes, emotion dynamics and depression. We illustrate that our approach is flexible and general: The model can be applied to any time series for multiple systems (where a system can represent any entity) and moreover, one is free to focus on whatever component of the versatile model. PMID:21516216

  6. Office of Biological and Physical Research: Overview Transitioning to the Vision for Space Exploration

    NASA Technical Reports Server (NTRS)

    Crouch, Roger

    2004-01-01

    Viewgraphs on NASA's transition to its vision for space exploration is presented. The topics include: 1) Strategic Directives Guiding the Human Support Technology Program; 2) Progressive Capabilities; 3) A Journey to Inspire, Innovate, and Discover; 4) Risk Mitigation Status Technology Readiness Level (TRL) and Countermeasures Readiness Level (CRL); 5) Biological And Physical Research Enterprise Aligning With The Vision For U.S. Space Exploration; 6) Critical Path Roadmap Reference Missions; 7) Rating Risks; 8) Current Critical Path Roadmap (Draft) Rating Risks: Human Health; 9) Current Critical Path Roadmap (Draft) Rating Risks: System Performance/Efficiency; 10) Biological And Physical Research Enterprise Efforts to Align With Vision For U.S. Space Exploration; 11) Aligning with the Vision: Exploration Research Areas of Emphasis; 12) Code U Efforts To Align With The Vision For U.S. Space Exploration; 13) Types of Critical Path Roadmap Risks; and 14) ISS Human Support Systems Research, Development, and Demonstration. A summary discussing the vision for U.S. space exploration is also provided.

  7. Transition-state inhibitors of purine salvage and other prospective enzyme targets in malaria.

    PubMed

    Ducati, Rodrigo G; Namanja-Magliano, Hilda A; Schramm, Vern L

    2013-07-01

    Malaria is a leading cause of human death within the tropics. The gradual generation of drug resistance imposes an urgent need for the development of new and selective antimalarial agents. Kinetic isotope effects coupled to computational chemistry have provided the relevant details on geometry and charge of enzymatic transition states to facilitate the design of transition-state analogs. These features have been reproduced into chemically stable mimics through synthetic chemistry, generating inhibitors with dissociation constants in the pico- to femto-molar range. Transition-state analogs are expected to contribute to the control of malaria.

  8. State space representations of distributed fluid line dynamics

    NASA Technical Reports Server (NTRS)

    Yao, H.; Goodson, R. E.; Leonard, R. G.

    1974-01-01

    The purpose of this paper is to demonstrate the convenience of using a systematic straight forward procedure to obtain meaningful dynamic information for a class of complex distributed parameter fluid line networks. System transients in the time domain are determined by means of state space techniques. Digital computer implementation yields a simple but consistent way of obtaining overall system time solutions. A step-by-step analysis procedure flow chart is shown in Appendix I which illustrates the basic approach for modeling, approximating and selecting digital techniques for simulating the dynamic response of fluid line systems.

  9. 40 CFR 70.4 - State program submittals and transition.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... determines that it is necessary to require a change to an approved State program, the required revisions to the program shall be submitted within 12 months of the final changes to part 70 or within such other... specified in the State program. If the State program allows sources to make changes subject to post...

  10. Identification of biochemical association of phycobilisome with photosystems in cyanobacterial state transition.

    PubMed

    Zhao, Jiaohong; Chen, Liping; Gao, Fudan; Wang, Quanxi; Qiu, Zijian; Ma, Weimin

    2014-10-01

    State transition is a short-term balance mechanism of energy distribution between photosystem II (PSII) and PSI. Although light-induced state transition in cyanobacteria has been suggested to depend completely on the phycobilisome (PBS) movement between PSII and PSI, the biochemical evidence has not been clearly shown. In this study, we locked the association of PBS with PSII or PSI using glycinebetaine when cells attain State 1 or 2 by exposure to light of blue or green, respectively. Subsequently, the PBS-reaction centers were resolved by blue native polyacrylamide gel electrophoresis and two-dimensional electrophoresis, and then identified by western blot analysis. The results showed that in wild-type (WT) Synechocystis sp. strain PCC 6803, the PBS core always co-migrates with the PSII dimer during light-induced State 1-State 2 transition, but its rod leaves the PSII dimer in State 2 regardless of its co-migration in State 1. In the light-induced State 2, the co-migration of PBS rod with PSI trimer was observed in WT, but not in ΔndhB (M55), a State-2-transition-deficient mutant. This study first provided the biochemical evidence for the association of PBS with photosystems during cyanobacterial state transition.

  11. A nonlinear state-space approach to hysteresis identification

    NASA Astrophysics Data System (ADS)

    Noël, J. P.; Esfahani, A. F.; Kerschen, G.; Schoukens, J.

    2017-02-01

    Most studies tackling hysteresis identification in the technical literature follow white-box approaches, i.e. they rely on the assumption that measured data obey a specific hysteretic model. Such an assumption may be a hard requirement to handle in real applications, since hysteresis is a highly individualistic nonlinear behaviour. The present paper adopts a black-box approach based on nonlinear state-space models to identify hysteresis dynamics. This approach is shown to provide a general framework to hysteresis identification, featuring flexibility and parsimony of representation. Nonlinear model terms are constructed as a multivariate polynomial in the state variables, and parameter estimation is performed by minimising weighted least-squares cost functions. Technical issues, including the selection of the model order and the polynomial degree, are discussed, and model validation is achieved in both broadband and sine conditions. The study is carried out numerically by exploiting synthetic data generated via the Bouc-Wen equations.

  12. Conserved prosegment residues stabilize a late-stage folding transition state of pepsin independently of ground states.

    PubMed

    Dee, Derek R; Horimoto, Yasumi; Yada, Rickey Y

    2014-01-01

    The native folding of certain zymogen-derived enzymes is completely dependent upon a prosegment domain to stabilize the folding transition state, thereby catalyzing the folding reaction. Generally little is known about how the prosegment accomplishes this task. It was previously shown that the prosegment catalyzes a late-stage folding transition between a stable misfolded state and the native state of pepsin. In this study, the contributions of specific prosegment residues to catalyzing pepsin folding were investigated by introducing individual Ala substitutions and measuring the effects on the bimolecular folding reaction between the prosegment peptide and pepsin. The effects of mutations on the free energies of the individual misfolded and native ground states and the transition state were compared using measurements of prosegment-pepsin binding and folding kinetics. Five out of the seven prosegment residues examined yielded relatively large kinetic effects and minimal ground state perturbations upon mutation, findings which indicate that these residues form strengthened and/or non-native contacts in the transition state. These five residues are semi- to strictly conserved, while only a non-conserved residue had no kinetic effect. One conserved residue was shown to form native structure in the transition state. These results indicated that the prosegment, which is only 44 residues long, has evolved a high density of contacts that preferentially stabilize the folding transition state over the ground states. It is postulated that the prosegment forms extensive non-native contacts during the process of catalyzing correct inter- and intra-domain contacts during the final stages of folding. These results have implications for understanding the folding of multi-domain proteins and for the evolution of prosegment-catalyzed folding.

  13. Momentum-space structure of surface states in a topological semimetal with a nexus point of Dirac lines

    NASA Astrophysics Data System (ADS)

    Hyart, T.; Heikkilä, T. T.

    2016-06-01

    Three-dimensional topological semimetals come in different variants, either containing Weyl points or Dirac lines. Here we describe a more complicated momentum-space topological defect where several separate Dirac lines connect with each other, forming a momentum-space equivalent of the real-space nexus considered before for helium-3. Close to the nexus the Dirac lines exhibit a transition from type I to type II lines. We consider a general model of stacked honeycomb lattices with the symmetry of Bernal (AB) stacked graphite and show that the structural mirror symmetries in such systems protect the presence of the Dirac lines, and also naturally lead to the formation of the nexus. By the bulk-boundary correspondence of topological media, the presence of Dirac lines lead to the formation of drumhead surface states at the side surfaces of the system. We calculate the surface state spectrum, and especially illustrate the effect of the nexus on these states.

  14. Spinor Field at the Phase Transition Point of Reissner-Nordström de Sitter Space

    NASA Astrophysics Data System (ADS)

    Lyu, Yan; Zhang, Li-Qing; Zheng, Wei; Pan, Qing-Chao

    2010-08-01

    The radial parts of Dirac equation between the outer black hole horizon and the cosmological horizon are solved in Reissner-Nordström de Sitter (RNdS) space when it is at the phase transition point. We use an accurate polynomial approximation to approximate the modified tortoise coordinate hat{r}_{*} in order to get the inverse function r=r(hat{r}_{*}) and the potential V(hat{r}_{*}). Then we use a quantum mechanical method to solve the wave equation numerically. We consider two cases, one is when the two horizons are lying close to each other, the other is when the two horizons are widely separated.

  15. Malthus in the Bedroom: Birth Spacing as Birth Control in Pre-Transition England.

    PubMed

    Cinnirella, Francesco; Klemp, Marc; Weisdorf, Jacob

    2017-03-09

    We use duration models on a well-known historical data set of more than 15,000 families and 60,000 births in England for the period 1540-1850 to show that the sampled families adjusted the timing of their births in accordance with the economic conditions as well as their stock of dependent children. The effects were larger among the lower socioeconomic ranks. Our findings on the existence of parity-dependent as well as parity-independent birth spacing in England are consistent with the growing evidence that marital birth control was present in pre-transitional populations.

  16. Distributed state-space generation of discrete-state stochastic models

    NASA Technical Reports Server (NTRS)

    Ciardo, Gianfranco; Gluckman, Joshua; Nicol, David

    1995-01-01

    High-level formalisms such as stochastic Petri nets can be used to model complex systems. Analysis of logical and numerical properties of these models of ten requires the generation and storage of the entire underlying state space. This imposes practical limitations on the types of systems which can be modeled. Because of the vast amount of memory consumed, we investigate distributed algorithms for the generation of state space graphs. The distributed construction allows us to take advantage of the combined memory readily available on a network of workstations. The key technical problem is to find effective methods for on-the-fly partitioning, so that the state space is evenly distributed among processors. In this paper we report on the implementation of a distributed state-space generator that may be linked to a number of existing system modeling tools. We discuss partitioning strategies in the context of Petri net models, and report on performance observed on a network of workstations, as well as on a distributed memory multi-computer.

  17. Transitional Child Care: State Experiences and Emerging Policies under the Family Support Act.

    ERIC Educational Resources Information Center

    Ebb, Nancy; And Others

    This guide is designed to provide information about transitional child care (TCC) program policies and operations and to offer recommendations to policymakers and advocates. Transitional child care is a new federal child care program that every state must implement by April 1, 1990. Established by the Family Support Act (FSA) of 1988, TCC is…

  18. Vocational Rehabilitation Transition Outcomes of Youth with Disabilities from a Midwestern State

    ERIC Educational Resources Information Center

    Awsumb, Jessica M.; Balcazar, Fabricio E.; Alvarado, Francisco

    2016-01-01

    Purpose: To examine the outcomes (rehabilitated vs. nonrehabilitated) of youth with disabilities (ages 14-22 years) participating in the transition program from a midwestern state. Method: Five years of vocational rehabilitation transition data (N = 6,252) were analyzed to determine what demographic and system-level factors were related to…

  19. Landau-Zener transition in quadratic nonlinear two-state systems

    SciTech Connect

    Ishkhanyan, A. M.

    2010-05-15

    A comprehensive theory of the Landau-Zener transition in quadratic nonlinear two-state systems is developed. A compact analytic formula involving elementary functions only is derived for the final transition probability. The formula provides a highly accurate approximation for the whole rage of the variation of the Landau-Zener parameter.

  20. Experiences of Japanese Visiting Scholars in the United States: An Exploration of Transition

    ERIC Educational Resources Information Center

    Shimmi, Yukiko

    2014-01-01

    The purpose of this study is to examine the reasons why Japanese visiting scholars visited the United States, their activities and experiences during their visits, their challenges and support for their transition, and personal and contextual factors that affected their transition in different stages. Although short-term international scholar…

  1. Cyclophilin A inhibition: targeting transition-state-bound enzyme conformations for structure-based drug design.

    PubMed

    Nagaraju, Mulpuri; McGowan, Lauren C; Hamelberg, Donald

    2013-02-25

    Human Cyclophilin A (CypA) catalyzes cis-trans isomerization of the prolyl peptide ω-bond in proteins and is involved in many subcellular processes. CypA has, therefore, been identified as a potential drug target in many diseases, and the development of potent inhibitors with high selectivity is a key objective. In computer-aided drug design, selectivity is improved by taking into account the inherent flexibility of the receptor. However, the relevant receptor conformations to focus on in order to develop highly selective inhibitors are not always obvious from available X-ray crystal structures or ensemble of conformations generated using molecular dynamics simulations. Here, we show that the conformation of the active site of CypA varies as the substrate configuration changes during catalytic turnover. We have analyzed the principal modes of the active site dynamics of CypA from molecular dynamics simulations to show that similar ensembles of enzyme conformations recognize diverse inhibitors and bind the different configurations of the peptide substrate. Small nonpeptidomimetic inhibitors with varying activity are recognized by enzyme ensembles that are similar to those that tightly bind the transition state and cis configurations of the substrate. Our results suggest that enzyme-substrate ensembles are more relevant in structure-based drug design for CypA than free enzyme. Of the vast conformational space of the free enzyme, the enzyme conformations of the tightly bound enzyme-substrate complexes are the most important for catalysis. Therefore, functionalizing lead compounds to optimize their interactions with the enzyme's conformational ensemble bound to the substrate in the cis or the transition state could lead to more potent inhibitors.

  2. Nonlinear regime-switching state-space (RSSS) models.

    PubMed

    Chow, Sy-Miin; Zhang, Guangjian

    2013-10-01

    Nonlinear dynamic factor analysis models extend standard linear dynamic factor analysis models by allowing time series processes to be nonlinear at the latent level (e.g., involving interaction between two latent processes). In practice, it is often of interest to identify the phases--namely, latent "regimes" or classes--during which a system is characterized by distinctly different dynamics. We propose a new class of models, termed nonlinear regime-switching state-space (RSSS) models, which subsumes regime-switching nonlinear dynamic factor analysis models as a special case. In nonlinear RSSS models, the change processes within regimes, represented using a state-space model, are allowed to be nonlinear. An estimation procedure obtained by combining the extended Kalman filter and the Kim filter is proposed as a way to estimate nonlinear RSSS models. We illustrate the utility of nonlinear RSSS models by fitting a nonlinear dynamic factor analysis model with regime-specific cross-regression parameters to a set of experience sampling affect data. The parallels between nonlinear RSSS models and other well-known discrete change models in the literature are discussed briefly.

  3. Review of State Policies and Programs to Support Young People Transitioning Out of Foster Care

    ERIC Educational Resources Information Center

    Dworsky, Amy; Havlicek, Judy

    2009-01-01

    This comprehensive review of policies and programs designed to support youth transitioning out of foster care spans all 50 states and the District of Columbia. As part of the review, Chapin Hall administered a web-based survey of state independent living services coordinators to collect up-to-date information about their state's policies and…

  4. Recognition of human activity characteristics based on state transitions modeling technique

    NASA Astrophysics Data System (ADS)

    Elangovan, Vinayak; Shirkhodaie, Amir

    2012-06-01

    Human Activity Discovery & Recognition (HADR) is a complex, diverse and challenging task but yet an active area of ongoing research in the Department of Defense. By detecting, tracking, and characterizing cohesive Human interactional activity patterns, potential threats can be identified which can significantly improve situation awareness, particularly, in Persistent Surveillance Systems (PSS). Understanding the nature of such dynamic activities, inevitably involves interpretation of a collection of spatiotemporally correlated activities with respect to a known context. In this paper, we present a State Transition model for recognizing the characteristics of human activities with a link to a prior contextbased ontology. Modeling the state transitions between successive evidential events determines the activities' temperament. The proposed state transition model poses six categories of state transitions including: Human state transitions of Object handling, Visibility, Entity-entity relation, Human Postures, Human Kinematics and Distance to Target. The proposed state transition model generates semantic annotations describing the human interactional activities via a technique called Casual Event State Inference (CESI). The proposed approach uses a low cost kinect depth camera for indoor and normal optical camera for outdoor monitoring activities. Experimental results are presented here to demonstrate the effectiveness and efficiency of the proposed technique.

  5. Probing the transition state for nucleic acid hybridization using phi-value analysis.

    PubMed

    Kim, Jandi; Shin, Jong-Shik

    2010-04-27

    Genetic regulation by noncoding RNA elements such as microRNA and small interfering RNA (siRNA) involves hybridization of a short single-stranded RNA with a complementary segment in a target mRNA. The physical basis of the hybridization process between the structured nucleic acids is not well understood primarily because of the lack of information about the transition-state structure. Here we use transition-state theory, inspired by phi-value analysis in protein folding studies, to provide quantitative analysis of the relationship between changes in the secondary structure stability and the activation free energy. Time course monitoring of the hybridization reaction was performed under pseudo-steady-state conditions using a single fluorophore. The phi-value analysis indicates that the native secondary structure remains intact in the transition state. The nativelike transition state was confirmed via examination of the salt dependence of the hybridization kinetics, indicating that the number of sodium ions associated with the transition state was not substantially affected by changes in the native secondary structure. These results propose that hybridization between structured nucleic acids undergoes a transition state leading to formation of a nucleation complex and then is followed by sequential displacement of preexisting base pairings involving successive small energy barriers. The proposed mechanism might provide new insight into physical processes during small RNA-mediated gene silencing, which is essential to selection of a target mRNA segment for siRNA design.

  6. Rare transitions between metastable states in the stochastic Chaffee-Infante equation.

    NASA Astrophysics Data System (ADS)

    Rolland, Joran; Bouchet, Freddy; Simonnet, Eric

    2015-04-01

    We present a numerical and theoretical study of the transitions in the Stochastic one dimensional Chaffee-Infante equation. The one dimensional Chaffee-Infante equation, also know as the Ginzburg-Landau or Allen-Cahn equation in physics, is the prototype equation for bistability in extended systems. As such, it is the perfect model equation for the test of numerical or theoretical methods intended at investigating metastability in more complex stochastic partial differential equations ; typically those arising in oceanicl fluid dynamics. Among other examples, one can think of the alternance of meander paths of the Kuroshio current near Japan, or the switching of the thermohaline circulation in the north Atlantic ocean. The reactive trajectories, the realisations of the dynamics that actually evolve from one metastable state to the other, are the central events in such studies. The novelty and originality of our approach is the combination of theoretical approaches with a novel numerical method, Adaptive Multilevel Splitting (AMS), for the computation of the full distribution of reactive trajectories and all the properties of the rare transitions. AMS is a mutation selection/selection algorithm that uses N clones dynamics of the system of interest, and only requires N|ln(α)| iterations. Meanwhile several 1/α realisations are required for a direct numerical simulation (with α the probability of observing a transition). It thus becomes a very powerful method when the noise amplitude and therefore α goes to zero. We used the algorithm to compute the properties (escape probability, mean first passage time, average duration of reactive trajectories, number of fronts etc.) of the transition in the full parameter space (L,β) (with L the size of the system and β the inverse of the noise amplitude). There is an excelent quantitative agreement with the various theoretical approaches of the study of metastability. All of them are asymptotic and therefore concern only

  7. Finite-time quantum-to-classical transition for a Schroedinger-cat state

    SciTech Connect

    Paavola, Janika; Hall, Michael J. W.; Paris, Matteo G. A.; Maniscalco, Sabrina

    2011-07-15

    The transition from quantum to classical, in the case of a quantum harmonic oscillator, is typically identified with the transition from a quantum superposition of macroscopically distinguishable states, such as the Schroedinger-cat state, into the corresponding statistical mixture. This transition is commonly characterized by the asymptotic loss of the interference term in the Wigner representation of the cat state. In this paper we show that the quantum-to-classical transition has different dynamical features depending on the measure for nonclassicality used. Measures based on an operatorial definition have well-defined physical meaning and allow a deeper understanding of the quantum-to-classical transition. Our analysis shows that, for most nonclassicality measures, the Schroedinger-cat state becomes classical after a finite time. Moreover, our results challenge the prevailing idea that more macroscopic states are more susceptible to decoherence in the sense that the transition from quantum to classical occurs faster. Since nonclassicality is a prerequisite for entanglement generation our results also bridge the gap between decoherence, which is lost only asymptotically, and entanglement, which may show a ''sudden death''. In fact, whereas the loss of coherences still remains asymptotic, we emphasize that the transition from quantum to classical can indeed occur at a finite time.

  8. Robust Light State by Quantum Phase Transition in Non-Hermitian Optical Materials

    PubMed Central

    Zhao, Han; Longhi, Stefano; Feng, Liang

    2015-01-01

    Robust light transport is the heart of optical information processing, leading to the search for robust light states by topological engineering of material properties. Here, it is shown that quantum phase transition, rather than topology, can be strategically exploited to design a novel robust light state. We consider an interface between parity-time (PT) symmetric media with different quantum phases and use complex Berry phase to reveal the associated quantum phase transition and topological nature. While the system possesses the same topological order within different quantum phases, phase transition from PT symmetry to PT breaking across the interface in the synthetic non-Hermitian metamaterial system facilitates novel interface states, which are robust against a variety of gain/loss perturbations and topological impurities and disorder. The discovery of the robust light state by quantum phase transition may promise fault-tolerant light transport in optical communications and computing. PMID:26592765

  9. An Uncharged Amine in the Transition State of the Ribosomal Peptidyl Transfer Reaction

    PubMed Central

    Kingery, David A.; Pfund, Emmanuel; Voorhees, Rebecca M.; Okuda, Kensuke; Wohlgemuth, Ingo; Kitchen, David E.; Rodnina, Marina V.; Strobel, Scott A.

    2010-01-01

    SUMMARY The ribosome has an active site comprised of RNA that catalyzes peptide bond formation. To understand how RNA promotes this reaction requires a detailed understanding of the chemical transition state. Here, we report the Brønsted coefficient of the α-amino nucleophile (βnuc) using a series of puromycin derivatives. Both 50S subunit and 70S ribosome catalyzed reactions displayed linear free-energy relationships with slopes close to zero under conditions where chemistry is rate limiting. These results indicate that at the transition state the nucleophile is neutral in the ribosome catalyzed reaction, in contrast to the substantial positive charge reported for typical uncatalyzed aminolysis reactions. This suggests that the ribosomal transition state involves deprotonation to a degree commensurate with nitrogen-carbon bond formation. Such a transition state is significantly different from that of uncatalyzed aminolysis reactions in solution. PMID:18482701

  10. Discontinuous phase transition in an annealed multi-state majority-vote model

    NASA Astrophysics Data System (ADS)

    Li, Guofeng; Chen, Hanshuang; Huang, Feng; Shen, Chuansheng

    2016-07-01

    In this paper, we generalize the original majority-vote (MV) model with noise from two states to arbitrary q states, where q is an integer no less than two. The main emphasis is paid to the comparison on the nature of phase transitions between the two-state MV (MV2) model and the three-state MV (MV3) model. By extensive Monte Carlo simulation and mean-field analysis, we find that the MV3 model undergoes a discontinuous order-disorder phase transition, in contrast to a continuous phase transition in the MV2 model. A central feature of such a discontinuous transition is a strong hysteresis behavior as noise intensity goes forward and backward. Within the hysteresis region, the disordered phase and ordered phase are coexisting.

  11. 31 CFR 592.403 - Transshipment or transit through the United States.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL... transit, of any rough diamond intended or destined for any country other than the United States,...

  12. 31 CFR 592.403 - Transshipment or transit through the United States.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL... transit, of any rough diamond intended or destined for any country other than the United States,...

  13. 31 CFR 592.403 - Transshipment or transit through the United States.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL... transit, of any rough diamond intended or destined for any country other than the United States,...

  14. 31 CFR 592.403 - Transshipment or transit through the United States.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL... transit, of any rough diamond intended or destined for any country other than the United States,...

  15. 31 CFR 592.403 - Transshipment or transit through the United States.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY ROUGH DIAMONDS CONTROL... transit, of any rough diamond intended or destined for any country other than the United States,...

  16. Determining Transition State Geometries in Liquids Using 2D-IR

    SciTech Connect

    Harris, Charles; Cahoon, James F.; Sawyer, Karma R.; Schlegel, Jacob P.; Harris, Charles B.

    2007-12-11

    Many properties of chemical reactions are determined by the transition state connecting reactant and product, yet it is difficult to directly obtain any information about these short-lived structures in liquids. We show that two-dimensional infrared (2D-IR) spectroscopy can provide direct information about transition states by tracking the transformation of vibrational modes as a molecule crossed a transition state. We successfully monitored a simple chemical reaction, the fluxional rearrangement of Fe(CO)5, in which the exchange of axial and equatorial CO ligands causes an exchange of vibrational energy between the normal modes of the molecule. This energy transfer provides direct evidence regarding the time scale, transition state, and mechanism of the reaction.

  17. Space Competition and Time Delays in Human Range Expansions. Application to the Neolithic Transition

    PubMed Central

    Isern, Neus; Fort, Joaquim; Vander Linden, Marc

    2012-01-01

    Space competition effects are well-known in many microbiological and ecological systems. Here we analyze such an effect in human populations. The Neolithic transition (change from foraging to farming) was mainly the outcome of a demographic process that spread gradually throughout Europe from the Near East. In Northern Europe, archaeological data show a slowdown on the Neolithic rate of spread that can be related to a high indigenous (Mesolithic) population density hindering the advance as a result of the space competition between the two populations. We measure this slowdown from a database of 902 Early Neolithic sites and develop a time-delayed reaction-diffusion model with space competition between Neolithic and Mesolithic populations, to predict the observed speeds. The comparison of the predicted speed with the observations and with a previous non-delayed model show that both effects, the time delay effect due to the generation lag and the space competition between populations, are crucial in order to understand the observations. PMID:23251430

  18. Evidence for a transition state model compound of in-plane vinylic SN2 reaction.

    PubMed

    Yamaguchi, Torahiko; Yamamoto, Yohsuke; Fujiwara, Yoshihisa; Tanimoto, Yoshifumi

    2005-06-23

    [reaction: see text] To isolate a transition state model compound of an in-plane vinylic S(N)2 reaction, vinyl bromide 6 bearing a newly synthesized tridentate ligand derived from 1,8-dimethoxythioxanthen-9-one (5) was prepared as a precursor. Although irradiation of 6 gave demethylated benzofuran 12, a transient broad peak which indicates formation of the desired transition state model compound was observed in the laser flash photolytic study.

  19. L-Enantiomers of Transition State Analogue Inhibitors Bound to Human Purine Nucleoside Phosphorylase

    SciTech Connect

    Rinaldo-Matthis,A.; Murkin, A.; Ramagopal, U.; Clinch, K.; Mee, S.; Evans, G.; Tyler, P.; Furneaux, R.; Almo, S.; Schramm, v.

    2008-01-01

    Human purine nucleoside phosphorylase (PNP) was crystallized with transition-state analogue inhibitors Immucillin-H and DADMe-Immucillin-H synthesized with ribosyl mimics of l-stereochemistry. The inhibitors demonstrate that major driving forces for tight binding of these analogues are the leaving group interaction and the cationic mimicry of the transition state, even though large geometric changes occur with d-Immucillins and l-Immucillins bound to human PNP.

  20. Electronic transition dipole moment and radiative lifetime calculations of sodium dimer ion-pair states.

    PubMed

    Sanli, Aydin; Beser, Bediha; Edwardson, John R; Magnier, Sylvie; Ahmed, Ergin H; Marjatta Lyyra, A

    2015-09-14

    We report here ab initio calculated electronic transition dipole moments for the sodium dimer ion pair states of (1)Σg (+) symmetry. They vary strongly as a function of internuclear distance because of the effect of the Na(+) + Na(-) ion pair potential, which also causes the formation of additional wells and shoulders in the molecular potential energy curves. We also present a computational study of the transition dipole moment matrix elements and lifetimes for these ion-pair states.

  1. 19 CFR 123.64 - Baggage in transit through the United States between ports in Canada or in Mexico.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Baggage in transit through the United States... Baggage § 123.64 Baggage in transit through the United States between ports in Canada or in Mexico. (a) Procedure. Baggage in transit from point to point in Canada or Mexico through the United States may...

  2. 19 CFR 123.64 - Baggage in transit through the United States between ports in Canada or in Mexico.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 1 2014-04-01 2014-04-01 false Baggage in transit through the United States... Baggage § 123.64 Baggage in transit through the United States between ports in Canada or in Mexico. (a) Procedure. Baggage in transit from point to point in Canada or Mexico through the United States may...

  3. 19 CFR 123.64 - Baggage in transit through the United States between ports in Canada or in Mexico.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Baggage in transit through the United States... Baggage § 123.64 Baggage in transit through the United States between ports in Canada or in Mexico. (a) Procedure. Baggage in transit from point to point in Canada or Mexico through the United States may...

  4. 19 CFR 123.64 - Baggage in transit through the United States between ports in Canada or in Mexico.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 1 2013-04-01 2013-04-01 false Baggage in transit through the United States... Baggage § 123.64 Baggage in transit through the United States between ports in Canada or in Mexico. (a) Procedure. Baggage in transit from point to point in Canada or Mexico through the United States may...

  5. Indoor-Outdoor Space; the Transitional Areas and Their Effect on Human Behavior. Exchange Bibliography No. 517.

    ERIC Educational Resources Information Center

    Bartholomew, Robert

    This brief bibliography lists publications about the transitional areas between buildings or leading into or out of buildings. These spaces are usually public spaces, at least in urban areas, that perform functions influencing human behavior, including visual separation or connection, territorial definition, and control of traffic and climatic…

  6. Ratcheted molecular-dynamics simulations identify efficiently the transition state of protein folding

    NASA Astrophysics Data System (ADS)

    Tiana, Guido; Camilloni, Carlo

    2012-12-01

    The atomistic characterization of the transition state (TS) is a fundamental step to improve the understanding of the folding mechanism and the function of proteins. From a computational point of view, the identification of the conformations that build out the transition state is particularly cumbersome, mainly because of the large computational cost of generating a statistically sound set of folding trajectories. Here we show that a biasing algorithm, based on the physics of the ratchet-and-pawl, can be used to approximate efficiently the transition state. The basic idea is that the algorithmic ratchet exerts a force on the protein when it is climbing the free-energy barrier, while it is inactive when it is descending. The transition state can be identified as the point of the trajectory where the ratchet changes regime. Besides discussing this strategy in general terms, we test it within a protein model whose transition state can be studied independently by plain molecular dynamics simulations. Finally, we show its power in explicit-solvent simulations, obtaining and characterizing a set of transition-state conformations for Acyl-Coenzyme A-Binding Protein (ACBP) and Chymotrypsin Inhibitor 2 (CI2).

  7. TRANSITION STATE FOR THE GAS-PHASE REACTION OF URANIUM HEXAFLUORIDE WITH WATER

    SciTech Connect

    Garrison, S; James Becnel, J

    2008-03-18

    Density Functional Theory and small-core, relativistic pseudopotentials were used to look for symmetric and asymmetric transitions states of the gas-phase hydrolysis reaction of uranium hexafluoride, UF{sub 6}, with water. At the B3LYP/6-31G(d,p)/SDD level, an asymmetric transition state leading to the formation of a uranium hydroxyl fluoride, U(OH)F{sub 5}, and hydrogen fluoride was found with an energy barrier of +77.3 kJ/mol and an enthalpy of reaction of +63.0 kJ/mol (both including zero-point energy corrections). Addition of diffuse functions to all atoms except uranium led to only minor changes in the structure and relative energies of the reacting complex and transition state. However, a significant change in the product complex structure was found, significantly reducing the enthalpy of reaction to +31.9 kJ/mol. Similar structures and values were found for PBE0 and MP2 calculations with this larger basis set, supporting the B3LYP results. No symmetric transition state leading to the direct formation of uranium oxide tetrafluoride, UOF{sub 4}, was found, indicating that the reaction under ambient conditions likely includes several more steps than the mechanisms commonly mentioned. The transition state presented here appears to be the first published transition state for the important gas-phase reaction of UF{sub 6} with water.

  8. Critical space-time networks and geometric phase transitions from frustrated edge antiferromagnetism.

    PubMed

    Trugenberger, Carlo A

    2015-12-01

    Recently I proposed a simple dynamical network model for discrete space-time that self-organizes as a graph with Hausdorff dimension d(H)=4. The model has a geometric quantum phase transition with disorder parameter (d(H)-d(s)), where d(s) is the spectral dimension of the dynamical graph. Self-organization in this network model is based on a competition between a ferromagnetic Ising model for vertices and an antiferromagnetic Ising model for edges. In this paper I solve a toy version of this model defined on a bipartite graph in the mean-field approximation. I show that the geometric phase transition corresponds exactly to the antiferromagnetic transition for edges, the dimensional disorder parameter of the former being mapped to the staggered magnetization order parameter of the latter. The model has a critical point with long-range correlations between edges, where a continuum random geometry can be defined, exactly as in Kazakov's famed 2D random lattice Ising model but now in any number of dimensions.

  9. Critical space-time networks and geometric phase transitions from frustrated edge antiferromagnetism

    NASA Astrophysics Data System (ADS)

    Trugenberger, Carlo A.

    2015-12-01

    Recently I proposed a simple dynamical network model for discrete space-time that self-organizes as a graph with Hausdorff dimension dH=4 . The model has a geometric quantum phase transition with disorder parameter (dH-ds) , where ds is the spectral dimension of the dynamical graph. Self-organization in this network model is based on a competition between a ferromagnetic Ising model for vertices and an antiferromagnetic Ising model for edges. In this paper I solve a toy version of this model defined on a bipartite graph in the mean-field approximation. I show that the geometric phase transition corresponds exactly to the antiferromagnetic transition for edges, the dimensional disorder parameter of the former being mapped to the staggered magnetization order parameter of the latter. The model has a critical point with long-range correlations between edges, where a continuum random geometry can be defined, exactly as in Kazakov's famed 2D random lattice Ising model but now in any number of dimensions.

  10. MEASURING THE SOLAR RADIUS FROM SPACE DURING THE 2003 AND 2006 MERCURY TRANSITS

    SciTech Connect

    Emilio, M.; Kuhn, J. R.; Scholl, I. F.; Bush, R. I. E-mail: kuhn@ifa.hawaii.edu E-mail: rock@sun.stanford.edu

    2012-05-10

    The Michelson Doppler Imager (MDI) aboard the Solar and Heliospheric Observatory observed the transits of Mercury on 2003 May 7 and 2006 November 8. Contact times between Mercury and the solar limb have been used since the seventeenth century to derive the Sun's size but this is the first time that high-quality imagery from space, above the Earth's atmosphere, has been available. Unlike other measurements, this technique is largely independent of optical distortion. The true solar radius is still a matter of debate in the literature as measured differences of several tenths of an arcsecond (i.e., about 500 km) are apparent. This is due mainly to systematic errors from different instruments and observers since the claimed uncertainties for a single instrument are typically an order of magnitude smaller. From the MDI transit data we find the solar radius to be 960.''12 {+-} 0.''09 (696, 342 {+-} 65 km). This value is consistent between the transits and consistent between different MDI focus settings after accounting for systematic effects.

  11. Exotic topological insulator states and topological phase transitions in Sb2Se3-Bi2Se3 heterostructures.

    PubMed

    Zhang, Qianfan; Zhang, Zhiyong; Zhu, Zhiyong; Schwingenschlögl, Udo; Cui, Yi

    2012-03-27

    Topological insulator is a new state of matter attracting tremendous interest due to its gapless linear dispersion and spin momentum locking topological states located near the surface. Heterostructures, which have traditionally been powerful in controlling the electronic properties of semiconductor devices, are interesting for topological insulators. Here, we studied the spatial distribution of the topological state in Sb(2)Se(3)-Bi(2)Se(3) heterostructures by first-principle simulation and discovered that an exotic topological state exists. Surprisingly, the state migrates from the nontrivial Bi(2)Se(3) into the trivial Sb(2)Se(3) region and spreads across the entire Sb(2)Se(3) slab, extending beyond the concept of "surface" state while preserving all of the topological surface state characteristics. This unusual topological state arises from the coupling between different materials and the modification of electronic structure near Fermi energy. Our study demonstrates that heterostructures can open up opportunities for controlling the real-space distribution of the topological state and inducing quantum phase transitions between topologically trivial and nontrivial states.

  12. Transition wavelengths and fine structure for the doublet states of Be/sup +/

    SciTech Connect

    Davis, B.F.; Chung, K.T.

    1984-05-01

    Seventeen bound and core-excited states of Be/sup +/ are calculated using configuration-interaction wave functions. Relativistic and mass-polarization correction are included. The relativistic corrections considered are correction to the kinetic energy, Darwin term, contact terms, and retardation effect. The fine structure is calculated by using spin-orbit and spin-other-orbit operators. The wavelengths computed for the transitions from the core-excited states improve the agreement between theory and experiment. The lifetimes for these states are also calculated. Our calculated transition wavelengths and fine structures for the bound states agree well in most cases with the experimental data tabulated by Bashkin and Stoner.

  13. Topological quantum phase transitions and edge states in spin-orbital coupled Fermi gases.

    PubMed

    Zhou, Tao; Gao, Yi; Wang, Z D

    2014-06-11

    We study superconducting states in the presence of spin-orbital coupling and Zeeman field. It is found that a phase transition from a Fulde-Ferrell-Larkin-Ovchinnikov state to the topological superconducting state occurs upon increasing the spin-orbital coupling. The nature of this topological phase transition and its critical property are investigated numerically. Physical properties of the topological superconducting phase are also explored. Moreover, the local density of states is calculated, through which the topological feature may be tested experimentally.

  14. Shape transitions in excited states of two-electron quantum dots in a magnetic field

    NASA Astrophysics Data System (ADS)

    Nazmitdinov, R. G.; Simonović, N. S.; Plastino, A. R.; Chizhov, A. V.

    2012-10-01

    We use entanglement to study shape transitions in two-electron axially symmetric parabolic quantum dots in a perpendicular magnetic field. At a specific magnetic field value the dot attains a spherical symmetry. The transition from the axial to the spherical symmetry manifests itself as a drastic change of the entanglement of the lowest state with zero angular momentum projection. While the electrons in such a state are always localized in the plane (x - y) before the transition point, after this point they become localized in the vertical direction.

  15. Exact transition probabilities in a 6-state Landau–Zener system with path interference

    DOE PAGES

    Sinitsyn, Nikolai A.

    2015-04-23

    In this paper, we identify a nontrivial multistate Landau–Zener (LZ) model for which transition probabilities between any pair of diabatic states can be determined analytically and exactly. In the semiclassical picture, this model features the possibility of interference of different trajectories that connect the same initial and final states. Hence, transition probabilities are generally not described by the incoherent successive application of the LZ formula. Finally, we discuss reasons for integrability of this system and provide numerical tests of the suggested expression for the transition probability matrix.

  16. 40 CFR 70.4 - State program submittals and transition.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... the permitting authority may take up to 3 years from the effective date of the program to take final... program is inadequate in any other way, the State shall revise the program or its means of...

  17. Reversible Transitions between Synchronization States of the Cardiorespiratory System

    NASA Astrophysics Data System (ADS)

    Stefanovska, A.; Haken, H.; McClintock, P. V. E.; HožiČ, M.; Bajrović, F.; Ribarič, S.

    2000-11-01

    Phase synchronization between cardiac and respiratory oscillations is investigated during anesthesia in rats. Synchrograms and time evolution of synchronization indices are used to show that the system passes reversibly through a sequence of different phase-synchronized states as the anesthesia level changes, indicating that it can undergo phase transitionlike phenomena. It appears that the synchronization state may be used to characterize the depth of anesthesia.

  18. THE ROLE OF METASTABLE STATES IN POLYMER PHASE TRANSITIONS: Concepts, Principles, and Experimental Observations

    NASA Astrophysics Data System (ADS)

    Cheng, Stephen Z. D.; Keller, Andrew

    1998-08-01

    Polymer phases can be described in the same way as phases in other condensed matter using a number density operator and its correlation functions. This description requires the understanding of symmetry operations and order at different atomic and molecular levels. Statistical mechanics provides a link between the microscopic description of the structure and motion and the macroscopic thermodynamic properties. Within the limits of the laws of thermodynamics, polymers exhibit a rich variety of phase transition behaviors. By definition, a first-order phase transition describes a transformation that involves a sudden change of thermodynamic properties at its transition temperature, whereas higher-order phase transitions are classified as critical phenomena. Of special interest is the role of metastability in phase and phase transition behaviors. Although a metastable state possesses a local free energy minimum, it is not at the global equilibrium. Furthermore, metastable states can also be associated with phase sizes. Metastable behavior is also observed in phase transformations that are impeded by kinetic limitations along the pathway to thermodynamic equilibrium. This is illustrated in structural and morphological investigations of crystallization and mesophase transitions, liquid-liquid phase separation, vitrification, and gel formation, as well as combinations of transformation processes. In these cases, the metastable state often becomes the dominant state for the entire system and is observed over a range of time and size scales. This review describes the general principles of metastability in polymer phases and phase transitions and provides illustrations from current experimental works in selected areas.

  19. Primary transitions between the yrast superdeformed band and low-lying normal deformed states in {sup 194}Pb

    SciTech Connect

    Hauschild, K.; Bernstein, L.A.; Becker, J.A.

    1996-12-31

    The observation of one-step `primary` gamma-ray transitions directly linking the superdeformed (SD) states to the normal deformed (ND) low-lying states of known excitation energies (E{sub x}), spins and parities (J{sup {pi}}) is crucial to determining the E{sub x} and J{sup {pi}} of the SD states. With this knowledge one can begin to address some of the outstanding problems associated with SD nuclei, such as the identical band issue, and one can also place more stringent restrictions on theoretical calculations which predict SD states and their properties. Brinkman, et al., used the early implementation of the GAMMASPHERE spectrometer array (32 detectors) and proposed a single, candidate {gamma} ray linking the {sup 194}Pb yrast SD band to the low-lying ND states in {sup 194}Pb. Using 55 detectors in the GAMMASPHERE array Khoo, et al., observed multiple links between the yrast SD band in {sup 194}Hg and the low-lying level scheme and conclusively determined E{sub x} and J of the yrast SD states. Here the authors report on an experiment in which Gammasphere with 88 detectors was used and the E{sub x} and J{sup {pi}} values of the yrast SD states in {sup 194}Pb were uniquely determined. Twelve one-step linking transitions between the yrast SD band and low-lying states in {sup 194}Pb have been identified, including the transition proposed by Brinkman. These transitions have been placed in the level scheme of {sup 194}Pb using coincidence relationships and agreements between the energies of the primary transitions and the energy differences in level spacings. Furthermore, measurements of angular asymmetries have yielded the multipolarities of the primaries which have allowed J{sup {pi}} assignments of the {sup 194}Pb SD states to be unambiguously determined for the first time without a priori assumptions about the character of SD bands. A study performed in parallel to this work using the EUROGAM-II array reports similar, but somewhat less extensive, results.

  20. Analyzing Tabular and State-Transition Requirements Specifications in PVS

    NASA Technical Reports Server (NTRS)

    Owre, Sam; Rushby, John; Shankar, Natarajan

    1997-01-01

    We describe PVS's capabilities for representing tabular specifications of the kind advocated by Parnas and others, and show how PVS's Type Correctness Conditions (TCCs) are used to ensure certain well-formedness properties. We then show how these and other capabilities of PVS can be used to represent the AND/OR tables of Leveson and the Decision Tables of Sherry, and we demonstrate how PVS's TCCs can expose and help isolate errors in the latter. We extend this approach to represent the mode transition tables of the Software Cost Reduction (SCR) method in an attractive manner. We show how PVS can check these tables for well-formedness, and how PVS's model checking capabilities can be used to verify invariants and reachability properties of SCR requirements specifications, and inclusion relations between the behaviors of different specifications. These examples demonstrate how several capabilities of the PVS language and verification system can be used in combination to provide customized support for specific methodologies for documenting and analyzing requirements. Because they use only the standard capabilities of PVS, users can adapt and extend these customizations to suit their own needs. Those developing dedicated tools for individual methodologies may find these constructions in PVS helpful for prototyping purposes, or as a useful adjunct to a dedicated tool when the capabilities of a full theorem prover are required. The examples also illustrate the power and utility of an integrated general-purpose system such as PVS. For example, there was no need to adapt or extend the PVS model checker to make it work with SCR specifications described using the PVS TABLE construct: the model checker is applicable to any transition relation, independently of the PVS language constructs used in its definition.

  1. Conformational transitions and polymer flow in the glassy state

    NASA Astrophysics Data System (ADS)

    Bendler, John T.

    1986-01-01

    Viscoelastic response in bulk polymers reflects a strong coupling between the center-of-mass positions and the relative internal coordinates of the chain segments. In the liquid, this coupling causes a fraction of the flow stress to create an elastic strain arising from the perturbed chain dimensions. (Since the friction/elongation relation is non-linear, this can lead to coil-stretch CS at large flow rates, the main subject of this conference.) In the glass state, the lifetimes of vibrational minima are reduced next to regions of high rotational mobility within the polymer chains. Lattice strain is partly relieved by (time-dependent) conversion of internal bond states, and solid-state flow results. Non-linear stress/strain behavior also may result the glass because a drop in modulus makes it easier for rotating segments to jump over intermolecular barriers. The solid-state analog of the stretched state is the highly oriented chain conformations found in shear bands and craze fibrils. The mechanism of shear yielding is believed to involve chain alignment and reduced sliding friction in the direction of maximum stress. Similarly, craze nucleation and growth (which requires a negative hydrostatic stress) proceeds by simultaneous production of voids and cold-drawn oriented fibrils, the latter imparting load-bearing ability to the growing craze.

  2. Investigation of Space Based Solid State Coherent Lidar

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin

    2002-01-01

    This report describes the work performed over the period of October 1, 1997 through March 31, 2001. Under this contract, UAH/CAO participated in defining and designing the SPAce Readiness Coherent Lidar Experiment (SPARCLE) mission, and developed the instrument's optical subsystem. This work was performed in collaborative fashion with NASA/MSFC engineers at both UAH/CAO and NASA/MSFC facilities. Earlier work by the UAH/CAO had produced a preliminary top-level system design for the Shuttle lidar instrument meeting the proposed mission performance requirements and the Space Shuttle Hitchhiker canister volume constraints. The UAH/CAO system design efforts had concentrated on the optical and mechanical designs of the instrument. The instrument electronics were also addressed, and the major electronic components and their interfaces defined. The instrument design concept was mainly based on the state of the transmitter and local oscillator laser development at NASA Langley Research Center and Jet Propulsion Laboratory, and utilized several lidar-related technologies that were either developed or evaluated by the NASA/MSFC and UAH/CAO scientists. UAH/CAO has developed a comprehensive coherent lidar numerical model capable of analyzing the performance of different instrument and mission concepts. This model uses the instrument configuration, atmospheric conditions and current velocity estimation theory to provide prediction of instrument performance during different phases of operation. This model can also optimize the design parameters of the instrument.

  3. Rapid State Space Modeling Tool for Rectangular Wing Aeroservoelastic Studies

    NASA Technical Reports Server (NTRS)

    Suh, Peter M.; Conyers, Howard Jason; Mavris, Dimitri N.

    2015-01-01

    This report introduces a modeling and simulation tool for aeroservoelastic analysis of rectangular wings with trailing-edge control surfaces. The inputs to the code are planform design parameters such as wing span, aspect ratio, and number of control surfaces. Using this information, the generalized forces are computed using the doublet-lattice method. Using Roger's approximation, a rational function approximation is computed. The output, computed in a few seconds, is a state space aeroservoelastic model which can be used for analysis and control design. The tool is fully parameterized with default information so there is little required interaction with the model developer. All parameters can be easily modified if desired. The focus of this report is on tool presentation, verification, and validation. These processes are carried out in stages throughout the report. The rational function approximation is verified against computed generalized forces for a plate model. A model composed of finite element plates is compared to a modal analysis from commercial software and an independently conducted experimental ground vibration test analysis. Aeroservoelastic analysis is the ultimate goal of this tool, therefore, the flutter speed and frequency for a clamped plate are computed using damping-versus-velocity and frequency-versus-velocity analysis. The computational results are compared to a previously published computational analysis and wind-tunnel results for the same structure. A case study of a generic wing model with a single control surface is presented. Verification of the state space model is presented in comparison to damping-versus-velocity and frequency-versus-velocity analysis, including the analysis of the model in response to a 1-cos gust.

  4. Rapid State Space Modeling Tool for Rectangular Wing Aeroservoelastic Studies

    NASA Technical Reports Server (NTRS)

    Suh, Peter M.; Conyers, Howard J.; Mavris, Dimitri N.

    2015-01-01

    This paper introduces a modeling and simulation tool for aeroservoelastic analysis of rectangular wings with trailing-edge control surfaces. The inputs to the code are planform design parameters such as wing span, aspect ratio, and number of control surfaces. Using this information, the generalized forces are computed using the doublet-lattice method. Using Roger's approximation, a rational function approximation is computed. The output, computed in a few seconds, is a state space aeroservoelastic model which can be used for analysis and control design. The tool is fully parameterized with default information so there is little required interaction with the model developer. All parameters can be easily modified if desired. The focus of this paper is on tool presentation, verification, and validation. These processes are carried out in stages throughout the paper. The rational function approximation is verified against computed generalized forces for a plate model. A model composed of finite element plates is compared to a modal analysis from commercial software and an independently conducted experimental ground vibration test analysis. Aeroservoelastic analysis is the ultimate goal of this tool, therefore, the flutter speed and frequency for a clamped plate are computed using damping-versus-velocity and frequency-versus-velocity analysis. The computational results are compared to a previously published computational analysis and wind-tunnel results for the same structure. A case study of a generic wing model with a single control surface is presented. Verification of the state space model is presented in comparison to damping-versus-velocity and frequency-versus-velocity analysis, including the analysis of the model in response to a 1-cos gust.

  5. Rapid State Space Modeling Tool for Rectangular Wing Aeroservoelastic Studies

    NASA Technical Reports Server (NTRS)

    Suh, Peter M.; Conyers, Howard J.; Mavris, Dimitri N.

    2014-01-01

    This paper introduces a modeling and simulation tool for aeroservoelastic analysis of rectangular wings with trailing edge control surfaces. The inputs to the code are planform design parameters such as wing span, aspect ratio and number of control surfaces. A doublet lattice approach is taken to compute generalized forces. A rational function approximation is computed. The output, computed in a few seconds, is a state space aeroservoelastic model which can be used for analysis and control design. The tool is fully parameterized with default information so there is little required interaction with the model developer. Although, all parameters can be easily modified if desired.The focus of this paper is on tool presentation, verification and validation. This process is carried out in stages throughout the paper. The rational function approximation is verified against computed generalized forces for a plate model. A model composed of finite element plates is compared to a modal analysis from commercial software and an independently conducted experimental ground vibration test analysis. Aeroservoelastic analysis is the ultimate goal of this tool. Therefore the flutter speed and frequency for a clamped plate are computed using V-g and V-f analysis. The computational results are compared to a previously published computational analysis and wind tunnel results for the same structure. Finally a case study of a generic wing model with a single control surface is presented. Verification of the state space model is presented in comparison to V-g and V-f analysis. This also includes the analysis of the model in response to a 1-cos gust.

  6. A modified PATH algorithm rapidly generates transition states comparable to those found by other well established algorithms

    PubMed Central

    Chandrasekaran, Srinivas Niranj; Das, Jhuma; Dokholyan, Nikolay V.; Carter, Charles W.

    2016-01-01

    PATH rapidly computes a path and a transition state between crystal structures by minimizing the Onsager-Machlup action. It requires input parameters whose range of values can generate different transition-state structures that cannot be uniquely compared with those generated by other methods. We outline modifications to estimate these input parameters to circumvent these difficulties and validate the PATH transition states by showing consistency between transition-states derived by different algorithms for unrelated protein systems. Although functional protein conformational change trajectories are to a degree stochastic, they nonetheless pass through a well-defined transition state whose detailed structural properties can rapidly be identified using PATH. PMID:26958584

  7. CHARACTERIZING THE ATMOSPHERES OF TRANSITING PLANETS WITH A DEDICATED SPACE TELESCOPE

    SciTech Connect

    Tessenyi, M.; Tinetti, G.; Swinyard, B.; Aylward, A.; Tennyson, J.; Ollivier, M.; Beaulieu, J. P.; Coude du Foresto, V.; Encrenaz, T.; Micela, G.; Ribas, I.; Swain, M. R.; Vasisht, G.; Deroo, P.; Sozzetti, A.

    2012-02-10

    Exoplanetary science is one of the fastest evolving fields of today's astronomical research, continuously yielding unexpected and surprising results. Ground-based planet-hunting surveys, together with dedicated space missions such as Kepler and CoRoT, are delivering an ever-increasing number of exoplanets, over 690, and ESA's Gaia mission will escalate the exoplanetary census into the several thousands. The next logical step is the characterization of these new worlds. What is their nature? Why are they as they are? Use of the Hubble Space Telescope and Spitzer Space Telescope to probe the atmospheres of transiting hot, gaseous exoplanets has opened perspectives unimaginable even just 10 years ago, demonstrating that it is indeed possible with current technology to address the ambitious goal of characterizing the atmospheres of these alien worlds. However, these successful measurements have also shown the difficulty of understanding the physics and chemistry of these exotic environments when having to rely on a limited number of observations performed on a handful of objects. To progress substantially in this field, a dedicated facility for exoplanet characterization, able to observe a statistically significant number of planets over time and a broad spectral range will be essential. Additionally, the instrument design (e.g., detector performances, photometric stability) will be tailored to optimize the extraction of the astrophysical signal. In this paper, we analyze the performance and tradeoffs of a 1.2/1.4 m space telescope for exoplanet transit spectroscopy from the visible to the mid-IR. We present the signal-to-noise ratio as a function of integration time and stellar magnitude/spectral type for the acquisition of spectra of planetary atmospheres for a variety of scenarios: hot, warm, and temperate planets orbiting stars ranging in spectral type from hot F- to cooler M-dwarfs. Our results include key examples of known planets (e.g., HD 189733b, GJ 436b, GJ

  8. Characterizing the Atmospheres of Transiting Planets with a Dedicated Space Telescope

    NASA Astrophysics Data System (ADS)

    Tessenyi, M.; Ollivier, M.; Tinetti, G.; Beaulieu, J. P.; Coudé du Foresto, V.; Encrenaz, T.; Micela, G.; Swinyard, B.; Ribas, I.; Aylward, A.; Tennyson, J.; Swain, M. R.; Sozzetti, A.; Vasisht, G.; Deroo, P.

    2012-02-01

    Exoplanetary science is one of the fastest evolving fields of today's astronomical research, continuously yielding unexpected and surprising results. Ground-based planet-hunting surveys, together with dedicated space missions such as Kepler and CoRoT, are delivering an ever-increasing number of exoplanets, over 690, and ESA's Gaia mission will escalate the exoplanetary census into the several thousands. The next logical step is the characterization of these new worlds. What is their nature? Why are they as they are? Use of the Hubble Space Telescope and Spitzer Space Telescope to probe the atmospheres of transiting hot, gaseous exoplanets has opened perspectives unimaginable even just 10 years ago, demonstrating that it is indeed possible with current technology to address the ambitious goal of characterizing the atmospheres of these alien worlds. However, these successful measurements have also shown the difficulty of understanding the physics and chemistry of these exotic environments when having to rely on a limited number of observations performed on a handful of objects. To progress substantially in this field, a dedicated facility for exoplanet characterization, able to observe a statistically significant number of planets over time and a broad spectral range will be essential. Additionally, the instrument design (e.g., detector performances, photometric stability) will be tailored to optimize the extraction of the astrophysical signal. In this paper, we analyze the performance and tradeoffs of a 1.2/1.4 m space telescope for exoplanet transit spectroscopy from the visible to the mid-IR. We present the signal-to-noise ratio as a function of integration time and stellar magnitude/spectral type for the acquisition of spectra of planetary atmospheres for a variety of scenarios: hot, warm, and temperate planets orbiting stars ranging in spectral type from hot F- to cooler M-dwarfs. Our results include key examples of known planets (e.g., HD 189733b, GJ 436b, GJ

  9. Two-state transition between molten globule and unfolded states of acetylcholinesterase as monitored by electron paramagnetic resonance spectroscopy.

    PubMed Central

    Kreimer, D I; Szosenfogel, R; Goldfarb, D; Silman, I; Weiner, L

    1994-01-01

    Cys-231 of Torpedo californica acetylcholinesterase (EC 3.1.1.7) was selectively labeled with the mercury derivative of a stable nitroxyl radical. In 1.5 M guanidinium chloride, this conjugate exists in a molten globule state (MG), whereas in 5 M denaturant, it is in an unfolded state (U). The transition between the two states is reversible. In the MG, the label is highly immobilized, whereas in the U, it is almost freely rotating. The clearly distinct electron paramagnetic resonance (EPR) spectra of the two states permits the study of this transition. Upon elevating the guanidinium chloride concentration, a decrease in the EPR signal of the MG occurs concomitantly with an increase in the U signal, the total intensity of the EPR spectra remaining constant. This behavior is characteristic of a two-state transition. The thermodynamic characteristics of this transition (delta G0 and m), whether estimated directly from the EPR data or from both CD and fluorescence data analyzed by assuming a two-state scheme, are in good agreement. PMID:7991597

  10. Importance of hydrophobic cluster formation through long-range contacts in the folding transition state of two-state proteins.

    PubMed

    Selvaraj, S; Gromiha, M Michael

    2004-06-01

    Understanding the folding pathways of proteins is a challenging task. The Phi value approach provides a detailed understanding of transition-state structures of folded proteins. In this work, we have computed the hydrophobicity associated with each residue in the folded state of 16 two-state proteins and compared the Phi values of each mutant residue. We found that most of the residues with high Phi value coincide with local maximum in surrounding hydrophobicity, or have nearby residues that show such maximum in hydrophobicity, indicating the importance of hydrophobic interactions in the transition state. We have tested our approach to different structural classes of proteins, such as alpha-helical, SH3 domains of all-beta proteins, beta-sandwich, and alpha/beta proteins, and we observed a good agreement with experimental results. Further, we have proposed a hydrophobic contact network pattern to relate the Phi values with long-range contacts, which will be helpful to understand the transition-state structures of folded proteins. The present approach could be used to identify potential hydrophobic clusters that may form through long-range contacts during the transition state.

  11. Hard-disk equation of state: first-order liquid-hexatic transition in two dimensions with three simulation methods.

    PubMed

    Engel, Michael; Anderson, Joshua A; Glotzer, Sharon C; Isobe, Masaharu; Bernard, Etienne P; Krauth, Werner

    2013-04-01

    We report large-scale computer simulations of the hard-disk system at high densities in the region of the melting transition. Our simulations reproduce the equation of state, previously obtained using the event-chain Monte Carlo algorithm, with a massively parallel implementation of the local Monte Carlo method and with event-driven molecular dynamics. We analyze the relative performance of these simulation methods to sample configuration space and approach equilibrium. Our results confirm the first-order nature of the melting phase transition in hard disks. Phase coexistence is visualized for individual configurations via the orientational order parameter field. The analysis of positional order confirms the existence of the hexatic phase.

  12. Utilizing dynamic tensiometry to quantify contact angle hysteresis and wetting state transitions on nonwetting surfaces.

    PubMed

    Kleingartner, Justin A; Srinivasan, Siddarth; Mabry, Joseph M; Cohen, Robert E; McKinley, Gareth H

    2013-11-05

    Goniometric techniques traditionally quantify two parameters, the advancing and receding contact angles, that are useful for characterizing the wetting properties of a solid surface; however, dynamic tensiometry, which measures changes in the net force on a surface during the repeated immersion and emersion of a solid into a probe liquid, can provide further insight into the wetting properties of a surface. We detail a framework for analyzing tensiometric results that allows for the determination of wetting hysteresis, wetting state transitions, and characteristic topographical length scales on textured, nonwetting surfaces, in addition to the more traditional measurement of apparent advancing and receding contact angles. Fluorodecyl POSS, a low-surface-energy material, was blended with commercially available poly(methyl methacrylate) (PMMA) and then dip- or spray-coated onto glass substrates. These surfaces were probed with a variety of liquids to illustrate the effects of probe liquid surface tension, solid surface chemistry, and surface texture on the apparent contact angles and wetting hysteresis of nonwetting surfaces. Woven meshes were then used as model structured substrates to add a second, larger length scale for the surface texture. When immersed into a probe liquid, these spray-coated mesh surfaces can form a metastable, solid-liquid-air interface on the largest length scale of surface texture. The increasing hydrostatic pressure associated with progressively greater immersion depths disrupts this metastable, composite interface and forces penetration of the probe liquid into the mesh structure. This transition is marked by a sudden change in the wetting hysteresis, which can be systematically probed using spray-coated, woven meshes of varying wire radius and spacing. We also show that dynamic tensiometry can accurately and quantitatively characterize topographical length scales that are present on microtextured surfaces.

  13. Discovering the space-time dimensions of schedule padding and delay from GTFS and real-time transit data

    NASA Astrophysics Data System (ADS)

    Wessel, Nate; Widener, Michael J.

    2017-01-01

    Schedule padding is the extra time added to transit schedules to reduce the risk of delay. Where there is more random delay, there should be more schedule padding. While schedule padding is a product of transit planners, a method for detecting when and where it exists could provide valuable feedback as transit agencies continually develop their networks. By analyzing transit schedules and real-time vehicle location data at the level of stop-to-stop segments, we can locate padding in space and time and identify the places that may be most effected by stochastic delay. Such information could be used to target delay-reduction interventions such as fare prepayment or transit-only rights of way. The Toronto Transit Commission is used as a case study, and initial results suggest that highly delayed segments appear mostly in the expected, but some surprising, places.

  14. Building and Maintaining Connection: Supporting Transition in a Rural State

    ERIC Educational Resources Information Center

    Flannery, Ann; Mason, Paula; Dunagan, Janna

    2016-01-01

    Deaf and hard of hearing students at Rocky Mountain High School (RMHS), a public school in Meridian, Idaho--and other deaf and hard of hearing students throughout the state, needed skills for the workplace. The demand was critical, and administrators knew change was needed. Co-authors Janna Dunagan, who teaches deaf and hard of hearing students,…

  15. 40 CFR 70.4 - State program submittals and transition.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... comprise the permitting program, reasonably available evidence of their procedurally correct adoption... 129(e) of the Act for a period not to exceed 12 years and review such permits at least every 5 years... this part. (x) Provide an opportunity for judicial review in State court of the final permit action...

  16. Quantum phase transitions between a class of symmetry protected topological states

    SciTech Connect

    Tsui, Lokman; Jiang, Hong-Chen; Lu, Yuan-Ming; Lee, Dung-Hai

    2015-07-01

    The subject of this paper is the phase transition between symmetry protected topological states (SPTs). We consider spatial dimension d and symmetry group G so that the cohomology group, Hd+1(G,U(1)), contains at least one Z2n or Z factor. We show that the phase transition between the trivial SPT and the root states that generate the Z2n or Z groups can be induced on the boundary of a (d+1)-dimensional View the MathML source-symmetric SPT by a View the MathML source symmetry breaking field. Moreover we show these boundary phase transitions can be “transplanted” to d dimensions and realized in lattice models as a function of a tuning parameter. The price one pays is for the critical value of the tuning parameter there is an extra non-local (duality-like) symmetry. In the case where the phase transition is continuous, our theory predicts the presence of unusual (sometimes fractionalized) excitations corresponding to delocalized boundary excitations of the non-trivial SPT on one side of the transition. This theory also predicts other phase transition scenarios including first order transition and transition via an intermediate symmetry breaking phase.

  17. Synchronous transitions of up and down states in a network model based on stimulations.

    PubMed

    Xu, Xuying; Ni, Li; Wang, Rubin

    2017-01-07

    The phenomenon of spontaneous periodic up and down transitions is considered to be a significant characteristic of slow oscillations. Our previous theoretical studies have shown that the single neuron and network model can both exhibit spontaneous up and down transitions. Another characteristic of up and down dynamics is the synchronicity. So in this paper, we focused on the synchronized characteristic of up and down transitions in the network based on stimulations. Spontaneous activities showed no synchronous transitions between neurons. However, the external stimulation, mainly the stimulation frequency and the number of neurons stimulated on were related to the synchronous transitions of up and down states. The simulation results suggested that simultaneous high frequency excitation or firing of neurons in the network was responsible for the generation of synchronous transitions of up and down states. Through the observation and analysis of the findings, we have tried to explain the reason for synchronous up and down transitions and to lay the foundation for further work on the role of these synchronized transitions in cortex activity.

  18. Exotic and excited-state meson spectroscopy and radiative transitions from lattice QCD

    SciTech Connect

    Christopher Thomas

    2010-09-01

    We discuss recent progress in extracting the excited meson spectrum and radiative transition form factors using lattice QCD. We mention results in the charmonium sector, including the first lattice QCD calculation of radiative transition rates involving excited charmonium states, highlighting results for high spin and exotic states. We present recent results on a highly excited isovector meson spectrum from dynamical anisotropic lattices. Using carefully constructed operators we show how the continuum spin of extracted states can be reliably identified and confidently extract excited states, states with exotic quantum numbers and states of high spin. This spectrum includes the first spin-four state extracted from lattice QCD. We conclude with some comments on future prospects.

  19. 2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces

    NASA Astrophysics Data System (ADS)

    Orsi, Davide; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Chushkin, Yuriy; Rimoldi, Tiziano; Cristofolini, Luigi

    2015-12-01

    We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems.

  20. 2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces

    PubMed Central

    Orsi, Davide; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Chushkin, Yuriy; Rimoldi, Tiziano; Cristofolini, Luigi

    2015-01-01

    We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems. PMID:26658474

  1. Tendency to occupy a statistically dominant spatial state of the flow as a driving force for turbulent transition.

    PubMed

    Chekmarev, Sergei F

    2013-03-01

    The transition from laminar to turbulent fluid motion occurring at large Reynolds numbers is generally associated with the instability of the laminar flow. On the other hand, since the turbulent flow characteristically appears in the form of spatially localized structures (e.g., eddies) filling the flow field, a tendency to occupy such a structured state of the flow cannot be ruled out as a driving force for turbulent transition. To examine this possibility, we propose a simple analytical model that treats the flow as a collection of localized spatial structures, each of which consists of elementary cells in which the behavior of the particles (atoms or molecules) is uncorrelated. This allows us to introduce the Reynolds number, associating it with the ratio between the total phase volume for the system and that for the elementary cell. Using the principle of maximum entropy to calculate the most probable size distribution of the localized structures, we show that as the Reynolds number increases, the elementary cells group into the localized structures, which successfully explains turbulent transition and some other general properties of turbulent flows. An important feature of the present model is that a bridge between the spatial-statistical description of the flow and hydrodynamic equations is established. We show that the basic assumptions underlying the model, i.e., that the particles are indistinguishable and elementary volumes of phase space exist in which the state of the particles is uncertain, are involved in the derivation of the Navier-Stokes equation. Taking into account that the model captures essential features of turbulent flows, this suggests that the driving force for the turbulent transition is basically the same as in the present model, i.e., the tendency of the system to occupy a statistically dominant state plays a key role. The instability of the flow at high Reynolds numbers can then be a mechanism to initiate structural rearrangement of

  2. A d-person Differential Game with State Space Constraints

    SciTech Connect

    Ramasubramanian, S.

    2007-12-15

    We consider a network of d companies (insurance companies, for example) operating under a treaty to diversify risk. Internal and external borrowing are allowed to avert ruin of any member of the network. The amount borrowed to prevent ruin is viewed upon as control. Repayment of these loans entails a control cost in addition to the usual costs. Each company tries to minimize its repayment liability. This leads to a d -person differential game with state space constraints. If the companies are also in possible competition a Nash equilibrium is sought. Otherwise a utopian equilibrium is more appropriate. The corresponding systems of HJB equations and boundary conditions are derived. In the case of Nash equilibrium, the Hamiltonian can be discontinuous; there are d interlinked control problems with state constraints; each value function is a constrained viscosity solution to the appropriate discontinuous HJB equation. Uniqueness does not hold in general in this case. In the case of utopian equilibrium, each value function turns out to be the unique constrained viscosity solution to the appropriate HJB equation. Connection with Skorokhod problem is briefly discussed.

  3. The 10 Hz Frequency: A Fulcrum For Transitional Brain States

    PubMed Central

    Garcia-Rill, E.; D’Onofrio, S.; Luster, B.; Mahaffey, S.; Urbano, F. J.; Phillips, C.

    2016-01-01

    A 10 Hz rhythm is present in the occipital cortex when the eyes are closed (alpha waves), in the precentral cortex at rest (mu rhythm), in the superior and middle temporal lobe (tau rhythm), in the inferior olive (projection to cerebellar cortex), and in physiological tremor (underlying all voluntary movement). These are all considered resting rhythms in the waking brain which are “replaced” by higher frequency activity with sensorimotor stimulation. That is, the 10 Hz frequency fulcrum is replaced on the one hand by lower frequencies during sleep, or on the other hand by higher frequencies during volition and cognition. The 10 Hz frequency fulcrum is proposed as the natural frequency of the brain during quiet waking, but is replaced by higher frequencies capable of permitting more complex functions, or by lower frequencies during sleep and inactivity. At the center of the transition shifts to and from the resting rhythm is the reticular activating system, a phylogenetically preserved area of the brain essential for preconscious awareness. PMID:27547831

  4. STATE TRANSITIONS IN LOW-MASS X-RAY BINARIES

    SciTech Connect

    Bradley, Charles K.; Frank, Juhan

    2009-10-10

    We investigate the model of disk/coronal accretion into a black hole. We show that the inner regions of an accretion disk in X-ray binaries can transform from a cool standard disk to an advection-dominated flow through the known properties of Coulomb interaction in a two-temperature plasma, viscous heating, radiative processes, and thermal conduction. A hot, diffuse corona covering the disk is powered by accretion, but it exchanges mass with the underlying cold disk. If the accretion rate in the system is low enough, we show that the corona evaporates the disk away, leaving an advective flow to continue toward the hole. In the soft/hard transition commonly seen in X-ray binaries, we show that this advective flow can recondense back onto the underlying disk if the change in the system's accretion rate is slow enough due to thermal conduction. Unabsorbed spectra are produced to test against observations as well as prediction of the location of truncation radii of the accretion disk.

  5. State-and-transition models as guides for adaptive management: What are the needs?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    State and transaction models (STMs) were conceived as a means to organize information about land potential and vegetation dynamics in rangelands to be used in their management. The basic idea is to describe the plant community states that can occur on a site and the causes of transitions between the...

  6. Travel Patterns And Characteristics Of Transit Users In New York State

    SciTech Connect

    Hwang, Ho-Ling; Wilson, Daniel W.; Reuscher, Tim; Chin, Shih-Miao; Taylor, Rob D.

    2015-12-01

    This research is a detailed examination of the travel behaviors and patterns of transit users within New York State (NYS), primarily based on travel data provided by the National Household Travel Survey (NHTS) in 2009 and the associated Add-on sample households purchased by the New York State Department of Transportation (NYSDOT). Other data sources analyzed in this study include: NYS General Transit Feed Specification (GTFS) to assist in analyzing spatial relationships for access to transit and the creation of Transit Shed geographic areas of 1, 2.5, and 5 miles from transit stop locations, LandScan population database to understand transit coverage, and Census Bureau s American Community Survey (ACS) data to examine general transit patterns and trends in NYS over time. The majority of analyses performed in this research aimed at identifying transit trip locations, understanding differences in transit usage by traveler demographics, as well as producing trip/mode-specific summary statistics including travel distance, trip duration, time of trip, and travel purpose of transit trips made by NYS residents, while also analyzing regional differences and unique travel characteristics and patterns. The analysis was divided into two aggregated geographic regions: New York Metropolitan Transportation Council (NYMTC) and NYS minus NYMTC (Rest of NYS). The inclusion of NYMTC in all analysis would likely produce misleading conclusions for other regions in NYS. TRANSIT COVERAGE The NYS transit network has significant coverage in terms of transit stop locations across the state s population. Out of the 19.3 million NYS population in 2011, about 15.3 million (or 79%) resided within the 1-mile transit shed. This NYS population transit coverage increased to 16.9 million (or 88%) when a 2.5-mile transit shed was considered; and raised to 17.7 million (or 92%) when the 5-mile transit shed was applied. KEY FINDINGS Based on 2009 NHTS data, about 40% of NYMTC households used transit

  7. Continuum-continuum transitions between resonant states using the RABITT technique

    NASA Astrophysics Data System (ADS)

    Jiménez, A.; Argenti, L.; Martín, F.

    2014-04-01

    We present a study of radiative continuum-continuum transitions in helium in the presence of doubly-excited states by using the attosecond RABITT technique beyond the Single Active Electron approximation. On the one hand, transition amplitudes between correlated continuum states are calculated both by direct numerical solution of the time-dependent Schrodinger equation as well as with a two-photon perturbative model. The effect of autoionizing states on the sideband phaseshift is thus analyzed. On the other hand, we apply the soft-photon approximation to quantify the effects the IR probe intensity on the sideband non-resonant overtone components.

  8. Investigation of quantum dot passively mode-locked lasers with excited-state transition.

    PubMed

    Cheng, Hsu-Chieh; Lee, Chien-Ping

    2013-11-04

    Monolithic passively mode-locked quantum dot lasers with excited-state transition were investigated in a broad operating range without ground-state lasing. Optical and electrical characteristics of these mode locked lasers were studied in detail at different levels of injection current and absorber bias. Very different behaviors in the evolution of the hysteresis, the optical spectra and the evolution of repetition frequency were observed between our lasers and conventional quantum dot lasers with ground-state transition. Possible mechanisms behind these observed phenomena were proposed and discussed. A minimum pulse width of 3.3 ps and an externally compressed pulse width of 0.78 ps were obtained.

  9. Changing Cycle Lengths in State-Transition Models: Challenges and Solutions.

    PubMed

    Chhatwal, Jagpreet; Jayasuriya, Suren; Elbasha, Elamin H

    2016-11-01

    The choice of a cycle length in state-transition models should be determined by the frequency of clinical events and interventions. Sometimes there is need to decrease the cycle length of an existing state-transition model to reduce error in outcomes resulting from discretization of the underlying continuous-time phenomena or to increase the cycle length to gain computational efficiency. Cycle length conversion is also frequently required if a new state-transition model is built using observational data that have a different measurement interval than the model's cycle length. We show that a commonly used method of converting transition probabilities to different cycle lengths is incorrect and can provide imprecise estimates of model outcomes. We present an accurate approach that is based on finding the root of a transition probability matrix using eigendecomposition. We present underlying mathematical challenges of converting cycle length in state-transition models and provide numerical approximation methods when the eigendecomposition method fails. Several examples and analytical proofs show that our approach is more general and leads to more accurate estimates of model outcomes than the commonly used approach. MATLAB codes and a user-friendly online toolkit are made available for the implementation of the proposed methods.

  10. State Transition to High-Quality, College/Career-Ready Assessments: A Workbook for State Action on Key Policy, Legal, and Technical Issues. Updated

    ERIC Educational Resources Information Center

    Achieve, Inc., 2013

    2013-01-01

    Over the next few years, states will be transitioning to new, high-quality assessments aligned to the Common Core State Standards (CCSS) or other state college- and career-ready (CCR) standards. States are committed to making this transition in a manner that is determined and thoughtful--to help transform teaching and learning, advance CCR…

  11. Transit Observations of Venus's Atmosphere in 2012 from Terrestrial and Space Telescopes as Exoplanet Analogs

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.; Penn, M. J.; Jaeggli, S. A.; Galayda, E.; Reardon, K. P.; Widemann, T.; Tanga, P.; Ehrenreich, D.; Vidal-Madjar, A.; Nicholson, P. D.; Dantowitz, R.

    2013-06-01

    We extensively observed the 8 June 2012 transit of Venus from several sites on Earth; we provide this interim status report about this and about two subsequent ToVs observed from space. From Haleakala Obs., we observed the entire June transit over almost 7 h with a coronagraph of the Venus Twilight Experiment B filter) and with a RED Epic camera to compare with simultaneous data from ESA's Venus Express, to study the Cytherean mesosphere; from Kitt Peak, we have near-IR spectropolarimetry at 1.6 µm from the aureole and during the disk crossing that compare well with carbon dioxide spectral models; from Sac Peak/IBIS we have high-resolution imaging of the Cytherean aureole for 22 min, starting even before 1st contact; from Big Bear, we have high-resolution imaging of Venus's atmosphere and the black-drop effect through 2nd contact; and we had 8 other coronagraphs around the world. For the Sept 21 ToV as seen from Jupiter, we had 14 orbits of HST to use Jupiter's clouds as a reflecting surface to search for an 0.01% diminution in light and a differential drop that would result from Venus's atmosphere by observing in both IR/UV, for which we have 170 HST exposures. As of this writing, preliminary data reduction indicates that variations in Jovian clouds and the two periods of Jupiter's rotation will be too great to allow extraction of the transit signal. For the December 20 ToV as seen from Saturn, we had 22 hours of observing time with VIMS on Cassini, for which we are looking for a signal of the 10-hr transit in total solar irradiance and of Venus's atmosphere in IR as an exoplanet-transit analog. Our Maui & Sac Peak expedition was sponsored by National Geographic Society's Committee for Research and Exploration; HST data reduction by NASA: HST-GO-13067. Some of the funds for the carbon dioxide filter for Sac Peak provided by NASA through AAS's Small Research Grant Program. We thank Rob Ratkowski of Haleakala Amateur Astronomers; Rob Lucas, Aram Friedman, Eric

  12. Transition.

    ERIC Educational Resources Information Center

    Thompson, Sandy, Ed.; And Others

    1990-01-01

    This "feature issue" focuses on transition from school to adult life for persons with disabilities. Included are "success stories," brief program descriptions, and a list of resources. Individual articles include the following titles and authors: "Transition: An Energizing Concept" (Paul Bates); "Transition…

  13. Role of Chemical Reactivity and Transition State Modeling for Virtual Screening.

    PubMed

    Karthikeyan, Muthukumarasamy; Vyas, Renu; Tambe, Sanjeev S; Radhamohan, Deepthi; Kulkarni, Bhaskar D

    2015-01-01

    Every drug discovery research program involves synthesis of a novel and potential drug molecule utilizing atom efficient, economical and environment friendly synthetic strategies. The current work focuses on the role of the reactivity based fingerprints of compounds as filters for virtual screening using a tool ChemScore. A reactant-like (RLS) and a product- like (PLS) score can be predicted for a given compound using the binary fingerprints derived from the numerous known organic reactions which capture the molecule-molecule interactions in the form of addition, substitution, rearrangement, elimination and isomerization reactions. The reaction fingerprints were applied to large databases in biology and chemistry, namely ChEMBL, KEGG, HMDB, DSSTox, and the Drug Bank database. A large network of 1113 synthetic reactions was constructed to visualize and ascertain the reactant product mappings in the chemical reaction space. The cumulative reaction fingerprints were computed for 4000 molecules belonging to 29 therapeutic classes of compounds, and these were found capable of discriminating between the cognition disorder related and anti-allergy compounds with reasonable accuracy of 75% and AUC 0.8. In this study, the transition state based fingerprints were also developed and used effectively for virtual screening in drug related databases. The methodology presented here provides an efficient handle for the rapid scoring of molecular libraries for virtual screening.

  14. The [Formula: see text] transition form factor from space- and time-like experimental data.

    PubMed

    Escribano, R; Masjuan, P; Sanchez-Puertas, P

    The [Formula: see text] transition form factor is analyzed for the first time in both space- and time-like regions at low and intermediate energies in a model-independent approach through the use of rational approximants. The [Formula: see text] experimental data provided by the A2 Collaboration in the very low-energy region of the dielectron invariant mass distribution allows for the extraction of the most precise up-to-date slope and curvature parameters of the form factors as well as their values at zero and infinity. The impact of these new results on the mixing parameters of the [Formula: see text]-[Formula: see text] system, together with the role played by renormalization dependent effects, and on the determination of the [Formula: see text] couplings from [Formula: see text] and [Formula: see text] radiative decays is also discussed.

  15. Qualitative differences between on-orbit and transition RCS control. [for Space Shuttle

    NASA Technical Reports Server (NTRS)

    Hattis, P. D.

    1982-01-01

    Two separate reaction control system (RCS) digital autopilots (DAPs) evolved from one original Space Shuttle orbital autopilot concept. A computer overload forced this evolution. Part of the overload problem was due to unique performance requirements imposed on the RCS controller during each of several different flight regimes. The two resultant RCS DAPs yield different effector responses because they rely on different sources of sensory input and they process data differently. This paper describes the evolution of the two RCS controllers and illustrates their behavioral differences. The transition autopilot, used in orbital insertion and deorbit, is sensitive to orbiter flexure due to its feedthrough character. The on-orbit autopilot is sensitive to transient rate control degradation from large disturbances due to feed-forward rate estimation. Simulation results and flight data are used to illustrate performance differences between the two autopilots under various conditions. These include computer failures where electronic stringing and procedural reconfiguration differences affect autopilot behavior.

  16. Preliminary analysis for a Mach 8 crossflow transition experiment on the Pegasus (R) space booster

    NASA Technical Reports Server (NTRS)

    Gong, Leslie; Richards, W. Lance; Monaghan, Richard C.; Quinn, Robert D.

    1993-01-01

    A boundary-layer transition is proposed for a future flight mission of the air-launched Pegasus space booster. The flight experiment requires attaching a glove assembly to the wing of the first-stage booster. The glove design consists of a spring and hook attachment system which allows for thermal growth of a steel 4130 skin. The results from one- and two-dimensional thermal analyses of the initial design are presented. Results obtained from the thermal analysis using turbulent flow conditions showed a maximum temperature of approximately 305 C and a chordwise temperature gradient of less than 8.9 C/cm for the critical areas in the upper glove skin. The temperatures obtained from these thermal analyses are well within the required temperature limits of the glove.

  17. Automated Transition State Searches without Evaluating the Hessian.

    PubMed

    Mallikarjun Sharada, Shaama; Zimmerman, Paul M; Bell, Alexis T; Head-Gordon, Martin

    2012-12-11

    Accurate and speedy determination of transition structures (TSs) is essential for computational studies on reaction pathways, particularly when the process involves expensive electronic structure calculations. Many search algorithms require a good initial guess of the TS geometry, as well as a Hessian input that possesses a structure consistent with the desired saddle point. Among the double-ended interpolation methods for generation of the guess for the TS, the freezing string method (FSM) is proven to be far less expensive compared to its predecessor, the growing string method (GSM). In this paper, it is demonstrated that the efficiency of this technique can be improved further by replacing the conjugate gradient optimization step (FSM-CG) with a quasi-Newton line search coupled with a BFGS Hessian update (FSM-BFGS). A second crucial factor that affects the speed with which convergence to the TS is achieved is the quality and cost of the Hessian of the energy for the guessed TS. For electronic structure calculations, the cost of calculating an exact Hessian increases more rapidly with system size than the energy and gradient. Therefore, to sidestep calculation of the exact Hessian, an approximate Hessian is constructed, using the tangent direction and local curvature at the TS guess. It is demonstrated that the partitioned-rational function optimization algorithm for locating TSs with this approximate Hessian input performs at least as well as with an exact Hessian input in most test cases. The two techniques, FSM and approximate Hessian construction, therefore can significantly reduce costs associated with finding TSs.

  18. Heat Capacity Changes for Transition-State Analogue Binding and Catalysis with Human 5'-Methylthioadenosine Phosphorylase.

    PubMed

    Firestone, Ross S; Cameron, Scott A; Karp, Jerome M; Arcus, Vickery L; Schramm, Vern L

    2017-02-17

    Human 5'-methylthioadenosine phosphorylase (MTAP) catalyzes the phosphorolysis of 5'-methylthioadenosine (MTA). Its action regulates cellular MTA and links polyamine synthesis to S-adenosylmethionine (AdoMet) salvage. Transition state analogues with picomolar dissociation constants bind to MTAP in an entropically driven process at physiological temperatures, suggesting increased hydrophobic character or dynamic structure for the complexes. Inhibitor binding exhibits a negative heat capacity change (-ΔCp), and thus the changes in enthalpy and entropy upon binding are strongly temperature-dependent. The ΔCp of inhibitor binding by isothermal titration calorimetry does not follow conventional trends and is contrary to that expected from the hydrophobic effect. Thus, ligands of increasing hydrophobicity bind with increasing values of ΔCp. Crystal structures of MTAP complexed to transition-state analogues MT-DADMe-ImmA, BT-DADMe-ImmA, PrT-ImmA, and a substrate analogue, MT-tubercidin, reveal similar active site contacts and overall protein structural parameters, despite large differences in ΔCp for binding. In addition, ΔCp values are not correlated with Kd values. Temperature dependence of presteady state kinetics revealed the chemical step for the MTAP reaction to have a negative heat capacity for transition state formation (-ΔCp(‡)). A comparison of the ΔCp(‡) for MTAP presteady state chemistry and ΔCp for inhibitor binding revealed those transition-state analogues most structurally and thermodynamically similar to the transition state. Molecular dynamics simulations of MTAP apoenzyme and complexes with MT-DADMe-ImmA and MT-tubercidin show small, but increased dynamic motion in the inhibited complexes. Variable temperature CD spectroscopy studies for MTAP-inhibitor complexes indicate remarkable protein thermal stability (to Tm = 99 °C) in complexes with transition-state analogues.

  19. 19 CFR 123.64 - Baggage in transit through the United States between ports in Canada or in Mexico.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Baggage in transit through the United States... MEXICO Baggage § 123.64 Baggage in transit through the United States between ports in Canada or in Mexico. (a) Procedure. Baggage in transit from point to point in Canada or Mexico through the United...

  20. Chloroplast remodeling during state transitions in Chlamydomonas reinhardtii as revealed by noninvasive techniques in vivo

    PubMed Central

    Nagy, Gergely; Ünnep, Renáta; Zsiros, Ottó; Tokutsu, Ryutaro; Takizawa, Kenji; Porcar, Lionel; Moyet, Lucas; Petroutsos, Dimitris; Garab, Győző; Finazzi, Giovanni; Minagawa, Jun

    2014-01-01

    Plants respond to changes in light quality by regulating the absorption capacity of their photosystems. These short-term adaptations use redox-controlled, reversible phosphorylation of the light-harvesting complexes (LHCIIs) to regulate the relative absorption cross-section of the two photosystems (PSs), commonly referred to as state transitions. It is acknowledged that state transitions induce substantial reorganizations of the PSs. However, their consequences on the chloroplast structure are more controversial. Here, we investigate how state transitions affect the chloroplast structure and function using complementary approaches for the living cells of Chlamydomonas reinhardtii. Using small-angle neutron scattering, we found a strong periodicity of the thylakoids in state 1, with characteristic repeat distances of ∼200 Å, which was almost completely lost in state 2. As revealed by circular dichroism, changes in the thylakoid periodicity were paralleled by modifications in the long-range order arrangement of the photosynthetic complexes, which was reduced by ∼20% in state 2 compared with state 1, but was not abolished. Furthermore, absorption spectroscopy reveals that the enhancement of PSI antenna size during state 1 to state 2 transition (∼20%) is not commensurate to the decrease in PSII antenna size (∼70%), leading to the possibility that a large part of the phosphorylated LHCIIs do not bind to PSI, but instead form energetically quenched complexes, which were shown to be either associated with PSII supercomplexes or in a free form. Altogether these noninvasive in vivo approaches allow us to present a more likely scenario for state transitions that explains their molecular mechanism and physiological consequences. PMID:24639515

  1. James Web Space Telescope: supporting multiple ground system transitions in one year

    NASA Astrophysics Data System (ADS)

    Detter, Ryan; Fatig, Curtis; Steck, Jane

    2004-09-01

    Ideas, requirements, and concepts developed during the very early phases of the mission design often conflict with the reality of a situation once the prime contractors are awarded. This happened for the James Webb Space Telescope (JWST) as well. The high level requirement of a common real-time ground system for both the Integration and Test (I&T), as well as the Operation phase of the mission is meant to reduce the cost and time needed later in the mission development for recertification of databases, command and control systems, scripts, display pages, etc. In the case of JWST, the early Phase A flight software development needed a real-time ground system and database prior to the spacecraft prime contractor being selected. To compound the situation, the very low level requirements for the real-time ground system were not well defined. These two situations caused the initial real-time ground system to be switched out for a system that was previously used by the flight software development team. To meet the high-level requirement, a third ground system was selected based on the prime spacecraft contractor needs and JWST Project decisions. The JWST ground system team has responded to each of these changes successfully. The lessons learned from each transition have not only made each transition smoother, but have also resolved issues earlier in the mission development than what would normally occur.

  2. James Webb Space Telescope: Supporting Multiple Ground System Transitions in One Year

    NASA Technical Reports Server (NTRS)

    Detter, Ryan; Fatig, Curtis; Steck, Jane

    2004-01-01

    Ideas, requirements, and concepts developed during the very early phases of the mission design often conflict with the reality of a situation once the prime contractors are awarded. This happened for the James Webb Space Telescope (JWST) as well. The high level requirement of a common real-time ground system for both the Integration and Test (I&T), as well as the Operation phase of the mission is meant to reduce the cost and time needed later in the mission development for re-certification of databases, command and control systems, scripts, display pages, etc. In the case of JWST, the early Phase A flight software development needed a real-time ground system and database prior to the spacecraft prime contractor being selected. To compound the situation, the very low level requirements for the real-time ground system were not well defined. These two situations caused the initial real-time ground system to be switched out for a system that was previously used by the Bight software development team. To meet the high-!evel requirement, a third ground system was selected based on the prime spacecraft contractor needs and JWST Project decisions. The JWST ground system team has responded to each of these changes successfully. The lessons learned from each transition have not only made each transition smoother, but have also resolved issues earlier in the mission development than what would normally occur.

  3. United States Changing Demographics - English/Spanish Space Education

    NASA Astrophysics Data System (ADS)

    Leon, R.

    2002-01-01

    Accordingly the United States Census Bureau, the ethnic group adding the largest number of people to the national population is the Hispanic exceeding 12 percent of the population and growing by almost 60 percent between 1990 and 2000. The status of the nation's educational system with respect to Hispanic students is perhaps one of the most influential issues facing the largest economy of the world. The low income, lack of language skills, highest drop-out rate in the nation, are some of the reasons why Hispanics are less likely to receive a university degree than any other ethical group. In short, the government requires to implement compensatory programs and bilingual education to ensure global leadership. Because of ongoing immigration, Spanish persists longer among Hispanics than it did among other immigrant groups. Spanish is the fourth most spoken language in the world after Mandarin, Hindustani and English. Although not all U.S. Hispanics speak Spanish, almost all U.S. Spanish speakers are Hispanics. This paper is intended to outline the challenging implementation of a bilingual education project affiliated to NASA Johnson Space Center encouraging greater academic success of Hispanics in engineering, math and science. The prospective project covers the overall role of space activities in the development of science and technology, socioeconomic issues and international cooperation. An existent JSC project is the starting stage to keep on developing an interactive video teleconference and web-media technology and produce stimulating learning products in English and Spanish for students and teachers across the nation and around the world.

  4. Measurement-Induced State Transitions in a Superconducting Qubit: Beyond the Rotating Wave Approximation

    NASA Astrophysics Data System (ADS)

    Sank, Daniel; Chen, Zijun; Khezri, Mostafa; Kelly, J.; Barends, R.; Campbell, B.; Chen, Y.; Chiaro, B.; Dunsworth, A.; Fowler, A.; Jeffrey, E.; Lucero, E.; Megrant, A.; Mutus, J.; Neeley, M.; Neill, C.; O'Malley, P. J. J.; Quintana, C.; Roushan, P.; Vainsencher, A.; White, T.; Wenner, J.; Korotkov, Alexander N.; Martinis, John M.

    2016-11-01

    Many superconducting qubit systems use the dispersive interaction between the qubit and a coupled harmonic resonator to perform quantum state measurement. Previous works have found that such measurements can induce state transitions in the qubit if the number of photons in the resonator is too high. We investigate these transitions and find that they can push the qubit out of the two-level subspace, and that they show resonant behavior as a function of photon number. We develop a theory for these observations based on level crossings within the Jaynes-Cummings ladder, with transitions mediated by terms in the Hamiltonian that are typically ignored by the rotating wave approximation. We find that the most important of these terms comes from an unexpected broken symmetry in the qubit potential. We confirm the theory by measuring the photon occupation of the resonator when transitions occur while varying the detuning between the qubit and resonator.

  5. Phase-flip and oscillation-quenching-state transitions through environmental diffusive coupling

    NASA Astrophysics Data System (ADS)

    Sharma, Amit; Verma, Umesh Kumar; Shrimali, Manish Dev

    2016-12-01

    We study the dynamics of nonlinear oscillators coupled through environmental diffusive coupling. The interaction between the dynamical systems is maintained through its agents which, in turn, interact globally with each other in the common dynamical environment. We show that this form of coupling scheme can induce an important transition like phase-flip transition as well transitions among oscillation quenching states in identical limit-cycle oscillators. This behavior is analyzed in the parameter plane by analytical and numerical studies of specific cases of the Stuart-Landau oscillator and van der Pol oscillator. Experimental evidences of the phase-flip transition and quenching states are shown using an electronic version of the van der Pol oscillators.

  6. Slow State Transitions of Sustained Neural Oscillations by Activity-Dependent Modulation of Intrinsic Excitability

    PubMed Central

    Fröhlich, Flavio; Bazhenov, Maxim; Timofeev, Igor; Steriade, Mircea; Sejnowski, Terrence J.

    2010-01-01

    Little is known about the dynamics and mechanisms of transitions between tonic firing and bursting in cortical networks. Here, we use a computational model of a neocortical circuit with extracellular potassium dynamics to show that activity-dependent modulation of intrinsic excitability can lead to sustained oscillations with slow transitions between two distinct firing modes: fast run (tonic spiking or fast bursts with few spikes) and slow bursting. These transitions are caused by a bistability with hysteresis in a pyramidal cell model. Balanced excitation and inhibition stabilizes a network of pyramidal cells and inhibitory interneurons in the bistable region and causes sustained periodic alternations between distinct oscillatory states. During spike-wave seizures, neocortical paroxysmal activity exhibits qualitatively similar slow transitions between fast run and bursting. We therefore predict that extracellular potassium dynamics can cause alternating episodes of fast and slow oscillatory states in both normal and epileptic neocortical networks. PMID:16763023

  7. Minimal transition state charge stabilization of the oxyanion during peptide bond formation by the ribosome.

    PubMed

    Carrasco, Nicolas; Hiller, David A; Strobel, Scott A

    2011-12-06

    Peptide bond formation during ribosomal protein synthesis involves an aminolysis reaction between the aminoacyl α-amino group and the carbonyl ester of the growing peptide via a transition state with a developing negative charge, the oxyanion. Structural and molecular dynamic studies have suggested that the ribosome may stabilize the oxyanion in the transition state of peptide bond formation via a highly ordered water molecule. To biochemically investigate this mechanistic hypothesis, we estimated the energetic contribution to catalytic charge stabilization of the oxyanion using a series of transition state mimics that contain different charge distributions and hydrogen bond potential on the functional group mimicking the oxyanion. Inhibitors containing an oxyanion mimic that carried a neutral charge and a mimic that preserved the negative charge but could not form hydrogen bonds had less than a 3-fold effect on inhibitor binding affinity. These observations argue that the ribosome provides minimal transition state charge stabilization to the oxyanion during peptide bond formation via the water molecule. This is in contrast to the substantial level of oxyanion stabilization provided by serine proteases. This suggests that the oxyanion may be neutralized via a proton shuttle, resulting in an uncharged transition state.

  8. Laboratory rotational ground state transitions of NH3D+ and CF+

    NASA Astrophysics Data System (ADS)

    Stoffels, A.; Kluge, L.; Schlemmer, S.; Brünken, S.

    2016-09-01

    Aims: This paper reports accurate laboratory frequencies of the rotational ground state transitions of two astronomically relevant molecular ions, NH3D+ and CF+. Methods: Spectra in the millimetre-wave band were recorded by the method of rotational state-selective attachment of He atoms to the molecular ions stored and cooled in a cryogenic ion trap held at 4 K. The lowest rotational transition in the A state (ortho state) of NH3D+ (JK = 10-00), and the two hyperfine components of the ground state transition of CF+ (J = 1-0) were measured with a relative precision better than 10-7. Results: For both target ions, the experimental transition frequencies agree with recent observations of the same lines in different astronomical environments. In the case of NH3D+ the high-accuracy laboratory measurements lend support to its tentative identification in the interstellar medium. For CF+ the experimentally determined hyperfine splitting confirms previous quantum-chemical calculations and the intrinsic spectroscopic nature of a double-peaked line profile observed in the J = 1-0 transition towards the Horsehead photon-dominated region (PDR).

  9. Probing osmolyte participation in the unfolding transition state of a protein

    PubMed Central

    Dougan, Lorna; Genchev, Georgi Z.; Lu, Hui; Fernandez, Julio M.

    2011-01-01

    Understanding the molecular mechanisms of osmolyte protection in protein stability has proved to be challenging. In particular, little is known about the role of osmolytes in the structure of the unfolding transition state of a protein, the main determinant of its dynamics. We have developed an experimental protocol to directly probe the transition state of a protein in a range of osmolyte environments. We use an atomic force microscope in force-clamp mode to apply mechanical forces to the protein I27 and obtain force-dependent rate constants of protein unfolding. We measure the distance to the unfolding transition state, Δxu, along a 1D reaction coordinate imposed by mechanical force. We find that for the small osmolytes, ethylene glycol, propylene glycol, and glycerol, Δxu scales with the size of the molecule, whereas for larger osmolytes, sorbitol and sucrose, Δxu remains the same as that measured in water. These results are in agreement with steered molecular dynamics simulations that show that small osmolytes act as solvent bridges in the unfolding transition state structure, whereas only water molecules act as solvent bridges in large osmolyte environments. These results demonstrate that novel force protocols combined with solvent substitution can directly probe angstrom changes in unfolding transition state structure. This approach creates new opportunities to gain molecular level understanding of the action of osmolytes in biomolecular processes. PMID:21613570

  10. Hole doping effects in manganites and spin state transitions in cobaltites

    NASA Astrophysics Data System (ADS)

    Roy, Sujoy

    A systematic study of the structural, magnetic and electrical transport properties have been done to determine the effects of hole doping in some manganite (La1-xA xMnO3, A = Na and Zr) and spin state transitions in cobaltite (RBaCo2O5+delta, R = La-Ho) compounds. The manganite compounds that we investigated have rhombohedral structure. A composition dependent ferromagnetic-paramagnetic phase transition along with metal-insulator transition is observed for both Na and Zr doped LaMnO 3 compounds. The variation of the magnetic and the metal-insulator transition temperatures is due to a systematic distortion of the MnO6 octahedron and change in the tolerance factor with doping content that controls the hopping interaction. In the metallic region, a rho ˜ AT 2 behavior is observed due to the magnon excitation effect. The resistivity shows a field dependent minimum at low temperatures and is probably due to intergrain transport phenomenon. A detailed study has been carried out for the RBaCo2O 5+delta (R = La-Ho) series of compounds as function of the R site size. The appearance of ferromagnetism and spin state transition are found to be related to O-Co-O bond angle. There exist a range of R site radii within which a bond angle distortion has been observed. The R site radius has to be within this range in order to observe the spin state transition in RBaCo 2O5+delta compounds. GdBaCo2O5.45 was studied in depth to understand the dynamics of the spin transitions in cobaltites. It was found that Co 3+ has a stable intermediate spin state in the temperature range 108 ≤ T ≤ 366 K. A charge ordering effect at 241 K followed by ferromagnetic transition is observed in the intermediate spin state. At 359 K, a first order phase transition is observed due to different ionic radius of Co3+ in different spin states. Finally, irradiating GdBaCo2O 5+delta with visible red light shows a decrease in TC by 4 K and the intermediate to high spin state transition temperature increases

  11. Multiple high-level QM/MM reaction paths demonstrate transition-state stabilization in chorismate mutase: correlation of barrier height with transition-state stabilization.

    PubMed

    Claeyssens, Frederik; Ranaghan, Kara E; Manby, Frederick R; Harvey, Jeremy N; Mulholland, Adrian J

    2005-10-28

    Multiple profiles for the reaction from chorismate to prephenate in the enzyme chorismate mutase calculated with hybrid density functional combined quantum mechanics/molecular mechanics methods (B3LYP/6-31G(d)-CHARMM27) agree well with experiment, and provide direct evidence of transition-state stabilization by this important enzyme, which is at the centre of current debates about the nature of enzyme catalysis.

  12. Apparent NAC effect in chorismate mutase reflects electrostatic transition state stabilization.

    PubMed

    Strajbl, Marek; Shurki, Avital; Kato, Mitsunori; Warshel, Arieh

    2003-08-27

    The catalytic reaction of chorismate mutase (CM) has been the subject of major current attention. Nevertheless, the origin of the catalytic power of CM remains an open question. In particular, it has not been clear whether the enzyme works by providing electrostatic transition state stabilization (TSS), by applying steric strain, or by populating near attack conformation (NAC). The present work explores this issue by a systematic quantitative analysis. The overall catalytic effect is reproduced by the empirical valence bond (EVB) method. In addition, the binding free energy of the ground state and the transition state is evaluated, demonstrating that the enzyme works by TSS. Furthermore, the evaluation of the electrostatic contribution to the reduction of the activation energy establishes that the TSS results from electrostatic effects. It is also found that the apparent NAC effect is not the reason for the catalytic effect but the result of the TSS. It is concluded that in CM as in other enzymes the key catalytic effect is electrostatic TSS. However, since the charge distribution of the transition state and the reactant state is similar, the stabilization of the transition state leads to reduction in the distance between the reacting atoms in the reactant state.

  13. Double excitations and state-to-state transition dipoles in π-π∗ excited singlet states of linear polyenes: Time-dependent density-functional theory versus multiconfigurational methods

    NASA Astrophysics Data System (ADS)

    Mikhailov, Ivan A.; Tafur, Sergio; Masunov, Artëm E.

    2008-01-01

    The effect of static and dynamic electron correlation on the nature of excited states and state-to-state transition dipole moments is studied with a multideterminant wave function approach on the example of all-trans linear polyenes ( C4H6 , C6H8 , and C8H10 ). Symmetry-forbidden singlet nAg states were found to separate into three groups: purely single, mostly single, and mostly double excitations. The excited-state absorption spectrum is dominated by two bright transitions: 1Bu-2Ag and 1Bu-mAg , where mAg is the state, corresponding to two-electron excitation from the highest occupied to lowest unoccupied molecular orbital. The richness of the excited-state absorption spectra and strong mixing of the doubly excited determinants into lower- nAg states, reported previously at the complete active space self-consistent field level of theory, were found to be an artifact of the smaller active space, limited to π orbitals. When dynamic σ-π correlation is taken into account, single- and double-excited states become relatively well separated at least at the equilibrium geometry of the ground state. This electronic structure is closely reproduced within time-dependent density-functional theory (TD DFT), where double excitations appear in a second-order coupled electronic oscillator formalism and do not mix with the single excitations obtained within the linear response. An extension of TD DFT is proposed, where the Tamm-Dancoff approximation (TDA) is invoked after the linear response equations are solved (a posteriori TDA). The numerical performance of this extension is validated against multideterminant-wave-function and quadratic-response TD DFT results. It is recommended for use with a sum-over-states approach to predict the nonlinear optical properties of conjugated molecules.

  14. A Bayesian state-space formulation of dynamic occupancy models

    USGS Publications Warehouse

    Royle, J. Andrew; Kery, M.

    2007-01-01

    Species occurrence and its dynamic components, extinction and colonization probabilities, are focal quantities in biogeography and metapopulation biology, and for species conservation assessments. It has been increasingly appreciated that these parameters must be estimated separately from detection probability to avoid the biases induced by nondetection error. Hence, there is now considerable theoretical and practical interest in dynamic occupancy models that contain explicit representations of metapopulation dynamics such as extinction, colonization, and turnover as well as growth rates. We describe a hierarchical parameterization of these models that is analogous to the state-space formulation of models in time series, where the model is represented by two components, one for the partially observable occupancy process and another for the observations conditional on that process. This parameterization naturally allows estimation of all parameters of the conventional approach to occupancy models, but in addition, yields great flexibility and extensibility, e.g., to modeling heterogeneity or latent structure in model parameters. We also highlight the important distinction between population and finite sample inference; the latter yields much more precise estimates for the particular sample at hand. Finite sample estimates can easily be obtained using the state-space representation of the model but are difficult to obtain under the conventional approach of likelihood-based estimation. We use R and Win BUGS to apply the model to two examples. In a standard analysis for the European Crossbill in a large Swiss monitoring program, we fit a model with year-specific parameters. Estimates of the dynamic parameters varied greatly among years, highlighting the irruptive population dynamics of that species. In the second example, we analyze route occupancy of Cerulean Warblers in the North American Breeding Bird Survey (BBS) using a model allowing for site

  15. A Bayesian state-space formulation of dynamic occupancy models.

    PubMed

    Royle, J Andrew; Kéry, Marc

    2007-07-01

    Species occurrence and its dynamic components, extinction and colonization probabilities, are focal quantities in biogeography and metapopulation biology, and for species conservation assessments. It has been increasingly appreciated that these parameters must be estimated separately from detection probability to avoid the biases induced by non-detection error. Hence, there is now considerable theoretical and practical interest in dynamic occupancy models that contain explicit representations of metapopulation dynamics such as extinction, colonization, and turnover as well as growth rates. We describe a hierarchical parameterization of these models that is analogous to the state-space formulation of models in time series, where the model is represented by two components, one for the partially observable occupancy process and another for the observations conditional on that process. This parameterization naturally allows estimation of all parameters of the conventional approach to occupancy models, but in addition, yields great flexibility and extensibility, e.g., to modeling heterogeneity or latent structure in model parameters. We also highlight the important distinction between population and finite sample inference; the latter yields much more precise estimates for the particular sample at hand. Finite sample estimates can easily be obtained using the state-space representation of the model but are difficult to obtain under the conventional approach of likelihood-based estimation. We use R and WinBUGS to apply the model to two examples. In a standard analysis for the European Crossbill in a large Swiss monitoring program, we fit a model with year-specific parameters. Estimates of the dynamic parameters varied greatly among years, highlighting the irruptive population dynamics of that species. In the second example, we analyze route occupancy of Cerulean Warblers in the North American Breeding Bird Survey (BBS) using a model allowing for site

  16. Coherent state approach to the interacting boson model: Test of its validity in the transitional region

    SciTech Connect

    Inci, I.; Alonso, C. E.; Arias, J. M.; Fortunato, L.; Vitturi, A.

    2009-09-15

    The predictive power of the coherent state (CS) approach to the interacting boson model (IBM) is tested far from the IBM dynamical symmetry limits. The transitional region along the {gamma}-unstable path from U(5) to O(6) is considered. Excitation energy of the excited {beta} band and intraband and interband transitions obtained within the CS approach are compared with the exact results as a function of the boson number N. We find that the CS formalism provides approximations to the exact results that are correct up to the order 1/N in the transitional region, except in a narrow region close to the critical point.

  17. The 3α Process Studied Through Pair Conversion Transitions from the Hoyle State in 12C

    NASA Astrophysics Data System (ADS)

    Eriksen, T. K.; Kibédi, T.; Reed, M. W.; Stuchbery, A. E.; Akber, A.; de Vries, M.; Dowie, J.; Evitts, L. J.; Garnsworthy, A. B.; Gerathy, M.; Hota, S. S.; Lane, G. J.; Mitchell, A. J.; Palazzo, T.; Smallcombe, J.; Tornyi, T. G.

    The E0 and E2 pair transitions from the Hoyle state have been measured, with the aim of deducing the radiative width and 3α reaction rate by a new approach. The 3α process is the only way carbon is synthesised in stars and is a bottleneck in stellar nucleosynthesis. The new method, which requires the ratio of the pair transitions, is expected to reduce the uncertainty from 10 to 5%. We recently observed the E2 pair transition for the first time, confirming the feasibility of the method. However, more statistics are needed to obtain a precise value for the radiative width.

  18. Analytical results for state-to-state transition probabilities in the multistate Landau-Zener model by nonstationary perturbation theory

    SciTech Connect

    Volkov, M. V.; Ostrovsky, V. N.

    2007-02-15

    Multistate generalizations of Landau-Zener model are studied by summing entire series of perturbation theory. A technique for analysis of the series is developed. Analytical expressions for probabilities of survival at the diabatic potential curves with extreme slope are proved. Degenerate situations are considered when there are several potential curves with extreme slope. Expressions for some state-to-state transition probabilities are derived in degenerate cases.

  19. Magnetic transitions and Fe(II) spin state in mackinawite

    NASA Astrophysics Data System (ADS)

    Schroeder, C.; Wan, M.; Peiffer, S.

    2012-12-01

    (S=1) state, but not high spin (S=2). Paramagnetic substances which become magnetically ordered below a certain temperature must have unpaired electrons (S≠0). Fe(II) in mackinawite is tetrahedrally coordinated to S, and frontier molecular orbital theory modeling suggests Fe to be either in intermediate spin (S=1) or high spin (S=2) state [7]. Combined with Mössbauer isomer shifts, Fe(II) in mackinawite must therefore be in the intermediate spin (S=1) state. The absence of magnetic ordering in the freshly precipitated and filtered mackinawite sample can be explained by either extremely small particle size resulting in superparamagnetic behavior, or Fe(II) is in a low spin (S=0) state and therefore diamagnetic. In the latter case this phase cannot be mackinawite but may be cubic FeSc, the Fe equivalent of sphalerite (cubic ZnS). References: [1] Wan et al., Mineral. Mag. 75(3) (2011) 2112. [2] Wan et al., Geophysical Research Abstracts 14, EGU2012-4724-3. [3] Hellige et al., Geochim. Cosmochim. Ac. 81 (2012) 69-81. [4] Morice et al., J. inorg. nucl. Chem. 31 (1969) 3797-3802. [5] Vaughan and Ridout, J. inorg. nucl. Chem. 33 (1971) 741-746. [6] Mullet et al., Geochim. Cosmochim. Ac. 66 (2002) 829-836. [7] Luther III, personal communication.

  20. Lateral redistribution of cytochrome b6/f complexes along thylakoid membranes upon state transitions.

    PubMed Central

    Vallon, O; Bulte, L; Dainese, P; Olive, J; Bassi, R; Wollman, F A

    1991-01-01

    The cytochrome b6/f complex operates in photosynthetic electron transfer either in linear electron flow from photosystem II to photosystem I or in cyclic flow around photosystem I. Using membrane fractionation and immunocytochemistry, we show a change in lateral distribution of cytochrome b6/f complexes along the thylakoid membranes during state transitions. This change is seen in maize as well as in the green algae Chlamydomonas reinhardtii. When either of the two organisms were adapted to state II in vivo, the proportion of cytochrome b6/f complexes found in the photosystem I-enriched stroma lamellae regions was significantly larger than after adaptation to state I. A similar observation was made upon state I to state II transitions done in vitro by illuminating, in the presence of ATP, broken maize chloroplasts prepared from dark-adapted leaves. This reorganization of the electron-transfer chain is concurrent with the change in light-energy distribution between the two photosystems, which requires lateral displacement of light-harvesting complex II. That the changes in lateral distribution of both cytochrome b6/f and light-harvesting II complexes seen upon state transition in vitro similarly required addition of exogenous ATP, suggests that the change in cytochrome b6/f organization also depends on kinase activity. The increased concentration of cytochrome b6/f complexes in the vicinity of photosystem I in state II is discussed in terms of an increase in cyclic electron flow, thus favoring ATP production. Because transition to state II can be triggered in vivo by ATP depletion, we conclude that state transitions should be regarded not only as a light-adaptation mechanism but also as a rerouting of photosynthetic electron flow, enabling photosynthetic organisms to adapt to changes in the cell demand for ATP. Images PMID:1896476

  1. United States Military Space: Into the Twenty-First Century

    DTIC Science & Technology

    2002-01-01

    and spectrum crowding, orbital debris , and space traffic control. From the precedents in space arms control three major themes stand out: space...license”—a way to create incentives for the commercial sector to harden satellites against nuclear effects and to minimize orbital debris . WHAT IS...positioning system (GPS); and crowding of radio spectrum, orbital debris , and space traffic control. Table 35 Impact of Arms Control and Other

  2. One-way optical modal transition based on causality in momentum space.

    PubMed

    Yu, Sunkyu; Piao, Xianji; Yoo, KyungWan; Shin, Jonghwa; Park, Namkyoo

    2015-09-21

    The concept of parity-time (PT) symmetry has been used to identify a route toward unidirectional dynamics in optical k-space: imposing asymmetry on the flow of light. Although PT-symmetric potentials have been implemented under the requirement of V(x) = V*(-x), this precondition has only been interpreted within the mathematical framework for the symmetry of Hamiltonians and has not been directly linked to unidirectionality induced by PT symmetry. In this paper, within the context of light-matter interactions, we develop an alternative route toward unidirectionality in k-space by employing the concept of causality. We demonstrate that potentials with real and causal momentum spectra produce unidirectional transitions of optical modes inside the k-continuum, which corresponds to an exceptional point on the degree of PT symmetry. Our analysis reveals a critical link between non-Hermitian problems and spectral theory and also enables multi-dimensional designer manipulation of optical modes, in contrast to the one-dimensional approach that used a Schrödinger-like equation in previous PT-symmetric optics.

  3. Transition from ring to beam arc distributions of water ions near the space shuttle orbiter

    SciTech Connect

    Cairns, I.H. )

    1990-09-01

    The distribution function of water ions produced near the space shuttle by charge exchange between ionospheric oxygen ions and outgassed water molecules is investigated using solutions of Liouville's equation with a source term modeling the charge exchange process. A transition from ring distributions to beamlike distributions termed beam arc distributions is found with decreasing distance upstream from the orbiter. This beam arc distribution corresponds to a finite section of a ring distribution and not to a conventional beam distribution. The ratio of water ion number density to oxygen ion number density is calculated; typical values within 50 m of the shuttle are in excess of 2% with a maximum value of the order of 20% for nominal parameters, suggsting that these ions must be considered with interpreting particle data from near the space shuttle. An argument for a plasma density enhancement of the order of 10% very close to the shuttle, due to kinematic effects (corresponding to pileup of plasma) and not to plasma creation, is also presented. This kinetmatic density enhancement is insufficient, by an order of magnitude, to explain the plasma density enhancements inferred from Spacelab 2 data.

  4. Nonstationary Stochastic Dynamics Underlie Spontaneous Transitions between Active and Inactive Behavioral States

    PubMed Central

    Jun, James J.; Longtin, André

    2017-01-01

    Abstract The neural basis of spontaneous movement generation is a fascinating open question. Long-term monitoring of fish, swimming freely in a constant sensory environment, has revealed a sequence of behavioral states that alternate randomly and spontaneously between periods of activity and inactivity. We show that key dynamical features of this sequence are captured by a 1-D diffusion process evolving in a nonlinear double well energy landscape, in which a slow variable modulates the relative depth of the wells. This combination of stochasticity, nonlinearity, and nonstationary forcing correctly captures the vastly different timescales of fluctuations observed in the data (∼1 to ∼1000 s), and yields long-tailed residence time distributions (RTDs) also consistent with the data. In fact, our model provides a simple mechanism for the emergence of long-tailed distributions in spontaneous animal behavior. We interpret the stochastic variable of this dynamical model as a decision-like variable that, upon reaching a threshold, triggers the transition between states. Our main finding is thus the identification of a threshold crossing process as the mechanism governing spontaneous movement initiation and termination, and to infer the presence of underlying nonstationary agents. Another important outcome of our work is a dimensionality reduction scheme that allows similar segments of data to be grouped together. This is done by first extracting geometrical features in the dataset and then applying principal component analysis over the feature space. Our study is novel in its ability to model nonstationary behavioral data over a wide range of timescales. PMID:28374017

  5. Noise-induced precursors of state transitions in the stochastic Wilson-cowan model.

    PubMed

    Negahbani, Ehsan; Steyn-Ross, D Alistair; Steyn-Ross, Moira L; Wilson, Marcus T; Sleigh, Jamie W

    2015-01-01

    The Wilson-Cowan neural field equations describe the dynamical behavior of a 1-D continuum of excitatory and inhibitory cortical neural aggregates, using a pair of coupled integro-differential equations. Here we use bifurcation theory and small-noise linear stochastics to study the range of a phase transitions-sudden qualitative changes in the state of a dynamical system emerging from a bifurcation-accessible to the Wilson-Cowan network. Specifically, we examine saddle-node, Hopf, Turing, and Turing-Hopf instabilities. We introduce stochasticity by adding small-amplitude spatio-temporal white noise, and analyze the resulting subthreshold fluctuations using an Ornstein-Uhlenbeck linearization. This analysis predicts divergent changes in correlation and spectral characteristics of neural activity during close approach to bifurcation from below. We validate these theoretical predictions using numerical simulations. The results demonstrate the role of noise in the emergence of critically slowed precursors in both space and time, and suggest that these early-warning signals are a universal feature of a neural system close to bifurcation. In particular, these precursor signals are likely to have neurobiological significance as early warnings of impending state change in the cortex. We support this claim with an analysis of the in vitro local field potentials recorded from slices of mouse-brain tissue. We show that in the period leading up to emergence of spontaneous seizure-like events, the mouse field potentials show a characteristic spectral focusing toward lower frequencies concomitant with a growth in fluctuation variance, consistent with critical slowing near a bifurcation point. This observation of biological criticality has clear implications regarding the feasibility of seizure prediction.

  6. International Space Station as Analog of Interplanetary Transit Vehicle For Biomedical Research

    NASA Technical Reports Server (NTRS)

    Charles, John B.

    2012-01-01

    Astronaut missions lasting up to six months aboard the International Space Station (ISS) have much in common with interplanetary flights, especially the outbound, Earth-to-Mars transit portion of a Mars mission. Utilization of ISS and other appropriate platforms to prepare for crewed expeditions to planetary destinations including Mars has been the work of NASA's Human Research Program (HRP) since 2005. HRP is charged specifically to understand and reduced the risks to astronaut health and performance in space exploration missions: everything HRP does and has done is directly related to that responsibility. Two major categories of human research have capitalized on ISS capabilities. The first category centers on the biomedical aspects of long-duration exposure to spaceflight factors, including prolonged weightlessness, radiation exposure, isolation and confinement, and actual risk to life and limb. These studies contribute to astronaut safety, health and efficiency on any long-duration missions, whether in low Earth orbit (LEO) or beyond. Qualitatively, weightlessness is weightlessness, whether in LEO or en route to Mars. The HRP sponsors investigations into losses in muscle and bone integrity, cardiovascular function, sensory-motor capability, immune capacity and psychosocial health, and development and demonstration of appropriate treatments and preventative measures. The second category includes studies that are focused on planetary expeditions beyond LEO. For these, ISS offers a high fidelity analog to investigate the combined effects of spaceflight factors (described above) plus the isolation and autonomy associated with simulated increasing distance from Earth. Investigations address crew cohesion, performance and workload, and mission control performance. The behavioral health and performance and space human factors aspects of planetary missions dominate this category. Work has already begun on a new investigation in this category which will examine the

  7. Coherent states on quaternion slices and a measurable field of Hilbert spaces

    NASA Astrophysics Data System (ADS)

    Muraleetharan, B.; Thirulogasanthar, K.

    2016-12-01

    A set of reproducing kernel Hilbert spaces are obtained on Hilbert spaces over quaternion slices with the aid of coherent states. It is proved that the so obtained set forms a measurable field of Hilbert spaces and their direct integral appears again as a reproducing kernel Hilbert space for a bigger Hilbert space over the whole quaternions. Hilbert spaces over quaternion slices are identified as representation spaces for a set of irreducible unitary group representations and their direct integral is shown to be a reducible representation for the Hilbert space over the whole quaternion field.

  8. Dynamic State Transitions in the Nervous System: From Ion Channels to Neurons to Networks

    NASA Astrophysics Data System (ADS)

    Århem, Peter; Braun, Hans A.; Huber, Martin T.; Liljenström, Hans

    The following sections are included: * Introduction * Ion channels: The microscopic scale * The variety of ion channels * Channel kinetics * Neurons: The mesoscopic scale * The feedback loops between membrane potential and ion currents * Neuron models: Concepts and examples * Impulse pattern modulation by ion channel densities * Oscillatory patterns * Irregular patterns * Impulse pattern modulation by subthreshold oscillations * The cold receptor model * Deterministic patterns and noise induced state-transitions on temperature scaling * Neuronal networks: The oscopic scale * Random channel events cause network state transitions * A hippocampal neural network model * Simulating noise-induced state transitions * Functional significance of oscopic neurodynamics * Conclusions * Appendix A: Computation of the neuron models * Hippocampal neuron model * The cold receptor model * Appendix B: Neural network model * References

  9. Angular momentum dependence of variational transition states for selected association reactions

    NASA Astrophysics Data System (ADS)

    Aubanel, Eric E.; Wardlaw, David M.

    1990-03-01

    The total angular momentum dependence of variational transition states for several reactions without a potential energy barrier on the minimum energy path is illustrated. High-pressure thermal rate constants for Li ++(CH 3) 2O→Li +(CH 3) 2O and Li ++H 2O→Li +(H 2O) from 200 to 1000 K are obtained from flexible transition-state theory (FTST), with potential functions of Coriongiu, Clementi, Pretsch and Simon and of Clementi and Popkie, respectively. For Li +(H 2O) the canonically determined rate constants are 20-50% higher than the microcanonically determined ones, and for Li +(CH 3) 2O ≈ 55% higher. These differences are attributed to the strong dependence of the transition states on total angular momentum.

  10. Transition state dynamics of O( 3P) + H2S reactive scattering

    NASA Astrophysics Data System (ADS)

    Zhu, Z. Z.; McDouall, J. J. W.; Smith, D. J.; Grice, R.

    1992-01-01

    A simple model is proposed for the direct rebound dynamics of O( 3P) atoms reacting with H 2S molecules whereby an H atom is displaced at a bending angle β with respect to the direction of the OS axis of the triplet H 2SO transition state. Comparison with the recent angular distribution measurements of HSO reactive scattering by Casavecchia et al. at an initial translational energy E = 50 kJ mol -1, suggests that the bending angle lies in the range β = 60° ± 10°, where β = 0° refers to the collinear OSH configuration. Ab initio calculations indicate a more strongly bent transition state which is initially pyramidal but passes through a planar configuration before dissociating, with the bending angle decreasing from β ≈ 96° to β ≈ 80°. Excitation of both the HSH bending and asymmetric stretch modes of the transition state results in final dissociation through less strongly bent configurations.

  11. Inhibition of norovirus 3CL protease by bisulfite adducts of transition state inhibitors.

    PubMed

    Mandadapu, Sivakoteswara Rao; Gunnam, Mallikarjuna Reddy; Tiew, Kok-Chuan; Uy, Roxanne Adeline Z; Prior, Allan M; Alliston, Kevin R; Hua, Duy H; Kim, Yunjeong; Chang, Kyeong-Ok; Groutas, William C

    2013-01-01

    Noroviruses are the most common cause of acute viral gastroenteritis, accounting for >21 million cases annually in the US alone. Norovirus infections constitute an important health problem for which there are no specific antiviral therapeutics or vaccines. In this study, a series of bisulfite adducts derived from representative transition state inhibitors (dipeptidyl aldehydes and α-ketoamides) was synthesized and shown to exhibit anti-norovirus activity in a cell-based replicon system. The ED(50) of the most effective inhibitor was 60 nM. This study demonstrates for the first time the utilization of bisulfite adducts of transition state inhibitors in the inhibition of norovirus 3C-like protease in vitro and in a cell-based replicon system. The approach described herein can be extended to the synthesis of the bisulfite adducts of other classes of transition state inhibitors of serine and cysteine proteases, such as α-ketoheterocycles and α-ketoesters.

  12. Holography and quantum states in elliptic de Sitter space

    NASA Astrophysics Data System (ADS)

    Halpern, Illan F.; Neiman, Yasha

    2015-12-01

    We outline a program for interpreting the higher-spin dS/CFT model in terms of physics in the causal patch of a dS observer. The proposal is formulated in "elliptic" de Sitter space d{S}_4/{Z}_2 , obtained by identifying antipodal points in dS 4. We discuss recent evidence that the higher-spin model is especially well-suited for this, since the antipodal symmetry of bulk solutions has a simple encoding on the boundary. For context, we test some other (free and interacting) theories for the same property. Next, we analyze the notion of quantum field states in the non-time-orientable d{S}_4/{Z}_2 . We compare the physics seen by different observers, with the outcome depending on whether they share an arrow of time. Finally, we implement the marriage between higher-spin holography and observers in d{S}_4/{Z}_2 , in the limit of free bulk fields. We succeed in deriving an observer's operator algebra and Hamiltonian from the CFT, but not her S-matrix. We speculate on the extension of this to interacting higher-spin theory.

  13. A solid-state digital temperature recorder for space use

    NASA Technical Reports Server (NTRS)

    Westbrook, R. M.; Bennett, L. D.; Steinhaver, R. A.; Deboo, G. J.

    1981-01-01

    A solid-state, digital, temperature recorder has been developed for use in space experiments. The recorder is completely self-contained and includes a temperature sensor; all necessary electronics for signal conditioning, processing, storing, control and timing; and a battery power supply. No electrical interfacing with the particular spacecraft on which the unit is used is required. The recorder is small, light, and sturdy, and has no moving parts. It uses only biocompatible materials and has passed vibration and shock spaceflight qualification tests. The unit is capable of storing 2048, -10 to +45 C, 8-bit temperature measurements taken at intervals selectable by factors of 2 from 1.875 to 240 min; data can be retained for at least 6 months. The basic recorder can be simplified to accommodate a variety of applications by adding memory to allow more data to be recorded, by changing the front end to permit measurements other than temperature to be made, and by using different batteries to realize various operating periods. Stored flight data are read out from the recorder by means of a ground read-out unit.

  14. A Knowledge Discovery from POS Data using State Space Models

    NASA Astrophysics Data System (ADS)

    Sato, Tadahiko; Higuchi, Tomoyuki

    The number of competing-brands changes by new product's entry. The new product introduction is endemic among consumer packaged goods firm and is an integral component of their marketing strategy. As a new product's entry affects markets, there is a pressing need to develop market response model that can adapt to such changes. In this paper, we develop a dynamic model that capture the underlying evolution of the buying behavior associated with the new product. This extends an application of a dynamic linear model, which is used by a number of time series analyses, by allowing the observed dimension to change at some point in time. Our model copes with a problem that dynamic environments entail: changes in parameter over time and changes in the observed dimension. We formulate the model with framework of a state space model. We realize an estimation of the model using modified Kalman filter/fixed interval smoother. We find that new product's entry (1) decreases brand differentiation for existing brands, as indicated by decreasing difference between cross-price elasticities; (2) decreases commodity power for existing brands, as indicated by decreasing trend; and (3) decreases the effect of discount for existing brands, as indicated by a decrease in the magnitude of own-brand price elasticities. The proposed framework is directly applicable to other fields in which the observed dimension might be change, such as economic, bioinformatics, and so forth.

  15. PET image reconstruction: a robust state space approach.

    PubMed

    Liu, Huafeng; Tian, Yi; Shi, Pengcheng

    2005-01-01

    Statistical iterative reconstruction algorithms have shown improved image quality over conventional nonstatistical methods in PET by using accurate system response models and measurement noise models. Strictly speaking, however, PET measurements, pre-corrected for accidental coincidences, are neither Poisson nor Gaussian distributed and thus do not meet basic assumptions of these algorithms. In addition, the difficulty in determining the proper system response model also greatly affects the quality of the reconstructed images. In this paper, we explore the usage of state space principles for the estimation of activity map in tomographic PET imaging. The proposed strategy formulates the organ activity distribution through tracer kinetics models, and the photon-counting measurements through observation equations, thus makes it possible to unify the dynamic reconstruction problem and static reconstruction problem into a general framework. Further, it coherently treats the uncertainties of the statistical model of the imaging system and the noisy nature of measurement data. Since H(infinity) filter seeks minimummaximum-error estimates without any assumptions on the system and data noise statistics, it is particular suited for PET image reconstruction where the statistical properties of measurement data and the system model are very complicated. The performance of the proposed framework is evaluated using Shepp-Logan simulated phantom data and real phantom data with favorable results.

  16. Transition state geometry of driven chemical reactions on time-dependent double-well potentials.

    PubMed

    Junginger, Andrej; Craven, Galen T; Bartsch, Thomas; Revuelta, F; Borondo, F; Benito, R M; Hernandez, Rigoberto

    2016-11-09

    Reaction rates across time-dependent barriers are difficult to define and difficult to obtain using standard transition state theory approaches because of the complexity of the geometry of the dividing surface separating reactants and products. Using perturbation theory (PT) or Lagrangian descriptors (LDs), we can obtain the transition state trajectory and the associated recrossing-free dividing surface. With the latter, we are able to determine the exact reactant population decay and the corresponding rates to benchmark the PT and LD approaches. Specifically, accurate rates are obtained from a local description regarding only direct barrier crossings and to those obtained from a stability analysis of the transition state trajectory. We find that these benchmarks agree with the PT and LD approaches for obtaining recrossing-free dividing surfaces. This result holds not only for the local dynamics in the vicinity of the barrier top, but also for the global dynamics of particles that are quenched at the reactant or product wells after their sojourn over the barrier region. The double-well structure of the potential allows for long-time dynamics related to collisions with the outside walls that lead to long-time returns in the low-friction regime. This additional global dynamics introduces slow-decay pathways that do not result from the local transition across the recrossing-free dividing surface associated with the transition state trajectory, but can be addressed if that structure is augmented by the population transfer of the long-time returns.

  17. Ab initio transition state searching in complex systems: fatty acid decarboxylation in minerals.

    PubMed

    Geatches, Dawn L; Greenwell, H Christopher; Clark, Stewart J

    2011-03-31

    Because of the importance of mineral catalyzed decarboxylation reactions in both crude oil formation and, increasingly, biofuel production, we present a model study into the decarboxylation of the shortest fatty acid, propionic acid C(2)H(5)COOH, into an alkane and CO(2) catalyzed by a pyrophillite-like, phyllosilicate clay. To identify the decarboxylation pathway, we searched for a transition state between the reactant, comprised of the clay plus interlayer fatty acid, and the product, comprised of the clay plus interlayer alkane and carbon dioxide. Using linear and quadratic synchronous transit mechanisms we searched for a transition state followed by vibrational analysis to verify the intermediate found as a transition state. We employed a periodic cell, planewave, ab initio density functional theory computation to examine total energy differences, Mulliken charges, vibrational frequencies, and the frontier orbitals of the reactants, intermediates, and products. The results show that interpretation of vibrational data, Mulliken charges and Fermi-level orbital occupancies is necessary for the classification of a transition state in this type of mixed bulk surface plus interlayer species, clay-organic system.

  18. Reduced linewidth enhancement factor due to excited state transition of quantum dot lasers.

    PubMed

    Xu, Peng-Fei; Ji, Hai-Ming; Xiao, Jin-Long; Gu, Yong-Xian; Huang, Yong-Zhen; Yang, Tao

    2012-04-15

    The carrier induced refractive index change and linewidth enhancement factor α due to ground-state (GS) and excited-state (ES) transitions have been compared by measuring the optical gain spectra from an InAs/GaAs quantum dot (QD) laser structure. It is shown that the ES transition exhibits a reduced α-factor compared to the value due to the GS transition. This result can be explained by the α-factor due to the ES transition having a smaller increase from the non-resonant carriers in the combined state of the wetting layer and InGaAs strain reducing layer than the α-factor increase due to the GS transition, since the relaxation time for carriers from the combined state of the wetting layer and InGaAs strain reducing layer to the ES is shorter than to the GS. The result reported here shows another advantage of using ES QD lasers for optical communication, in addition to their higher modulation speed.

  19. Transition state for the NSD2-catalyzed methylation of histone H3 lysine 36

    PubMed Central

    Poulin, Myles B.; Schneck, Jessica L.; Matico, Rosalie E.; McDevitt, Patrick J.; Huddleston, Michael J.; Hou, Wangfang; Johnson, Neil W.; Thrall, Sara H.; Meek, Thomas D.; Schramm, Vern L.

    2016-01-01

    Nuclear receptor SET domain containing protein 2 (NSD2) catalyzes the methylation of histone H3 lysine 36 (H3K36). It is a determinant in Wolf–Hirschhorn syndrome and is overexpressed in human multiple myeloma. Despite the relevance of NSD2 to cancer, there are no potent, selective inhibitors of this enzyme reported. Here, a combination of kinetic isotope effect measurements and quantum chemical modeling was used to provide subangstrom details of the transition state structure for NSD2 enzymatic activity. Kinetic isotope effects were measured for the methylation of isolated HeLa cell nucleosomes by NSD2. NSD2 preferentially catalyzes the dimethylation of H3K36 along with a reduced preference for H3K36 monomethylation. Primary Me-14C and 36S and secondary Me-3H3, Me-2H3, 5′-14C, and 5′-3H2 kinetic isotope effects were measured for the methylation of H3K36 using specifically labeled S-adenosyl-l-methionine. The intrinsic kinetic isotope effects were used as boundary constraints for quantum mechanical calculations for the NSD2 transition state. The experimental and calculated kinetic isotope effects are consistent with an SN2 chemical mechanism with methyl transfer as the first irreversible chemical step in the reaction mechanism. The transition state is a late, asymmetric nucleophilic displacement with bond separation from the leaving group at (2.53 Å) and bond making to the attacking nucleophile (2.10 Å) advanced at the transition state. The transition state structure can be represented in a molecular electrostatic potential map to guide the design of inhibitors that mimic the transition state geometry and charge. PMID:26787850

  20. Transit timing of TrES-2: a combined analysis of ground- and space-based photometry

    NASA Astrophysics Data System (ADS)

    Raetz, St.; Maciejewski, G.; Ginski, Ch.; Mugrauer, M.; Berndt, A.; Eisenbeiss, T.; Adam, Ch.; Raetz, M.; Roell, T.; Seeliger, M.; Marka, C.; Vaňko, M.; Bukowiecki, Ł.; Errmann, R.; Kitze, M.; Ohlert, J.; Pribulla, T.; Schmidt, J. G.; Sebastian, D.; Puchalski, D.; Tetzlaff, N.; Hohle, M. M.; Schmidt, T. O. B.; Neuhäuser, R.

    2014-10-01

    Homogeneous observations and careful analysis of transit light curves can lead to the identification of transit timing variations (TTVs). TrES-2 is one of few exoplanets, which offer the matchless possibility to combine long-term ground-based observations with continuous satellite data. Our research aimed at the search for TTVs that would be indicative of perturbations from additional bodies in the system. We also wanted to refine the system parameters and the orbital elements. We obtained 44 ground-based light curves of 31 individual transit events of TrES-2. Eight 0.2-2.2-m telescopes located at six observatories in Germany, Poland and Spain were used. In addition, we analysed 18 quarters (Q0-Q17) of observational data from NASA's space telescope Kepler including 435 individual transit events and 11 publicly available ground-based light curves. Assuming different limb darkening (LD) laws we performed an analysis for all light curves and redetermined the parameters of the system. We also carried out a joint analysis of the ground- and space-based data. The long observation period of seven years (2007-2013) allowed a very precise redetermination of the transit ephemeris. For a total of 490 transit light curves of TrES-2, the time of transit mid-point was determined. The transit times support neither variations on long time-scale nor on short time-scales. The nearly continuous observations of Kepler show no statistically significant increase or decrease in the orbital inclination i and the transit duration D. Only the transit depth shows a slight increase which could be an indication of an increasing stellar activity. In general, system parameters obtained by us were found to be in agreement with previous studies but are the most precise values to date.

  1. Non-local Optical Topological Transitions and Critical States in Electromagnetic Metamaterials

    PubMed Central

    Ishii, Satoshi; Narimanov, Evgenii

    2015-01-01

    Just as the topology of the Fermi surface defines the properties of the free electrons in metals and semiconductors, the geometry of the iso-frequency surface in the phase space of the propagating electromagnetic waves, determines the optical properties of the corresponding optical materials. Furthermore, in the direct analog to the Lifshitz transition in condensed matter physics, a change in the topology of iso-frequency surface has a dramatic effect on the emission, propagation and scattering of the electromagnetic waves. Here, we uncover a new class of such optical topological transitions in metamaterials, induced by the non-locality of the electromagnetic response inherent to these composites. PMID:26670600

  2. Transition between different quantum states in a mesoscopic system: The superconducting ring

    SciTech Connect

    Horane, E.M.; Castro, J.I.; Buscaglia, G.C.; Lopez, A.

    1996-04-01

    We investigate the thermodynamic properties of a superconducting ring, both analytically and numerically, relying upon the Ginzburg-Landau theory. We find that modulated solutions for the order parameter play a role in describing the thermodynamic transitions between consecutive modes of uniform order parameter, associated with different quantum numbers. Exact expressions for these solutions are given in terms of elliptic functions. We identify the family of energy extrema which, being saddle points of the energy in the functional space of the distributions of the order parameter, represent the energy barrier to be overcome for transitions between different solutions. {copyright} {ital 1996 The American Physical Society.}

  3. 45 CFR 205.170 - State standards for office space, equipment, and facilities.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 45 Public Welfare 2 2014-10-01 2012-10-01 true State standards for office space, equipment, and... SERVICES GENERAL ADMINISTRATION-PUBLIC ASSISTANCE PROGRAMS § 205.170 State standards for office space...-A, X, XIV, or XVI(AABD) of the Social Security Act must provide that: (a) The State agency...

  4. 45 CFR 205.170 - State standards for office space, equipment, and facilities.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 45 Public Welfare 2 2011-10-01 2011-10-01 false State standards for office space, equipment, and... SERVICES GENERAL ADMINISTRATION-PUBLIC ASSISTANCE PROGRAMS § 205.170 State standards for office space...-A, X, XIV, or XVI(AABD) of the Social Security Act must provide that: (a) The State agency...

  5. 45 CFR 205.170 - State standards for office space, equipment, and facilities.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 45 Public Welfare 2 2013-10-01 2012-10-01 true State standards for office space, equipment, and... SERVICES GENERAL ADMINISTRATION-PUBLIC ASSISTANCE PROGRAMS § 205.170 State standards for office space...-A, X, XIV, or XVI(AABD) of the Social Security Act must provide that: (a) The State agency...

  6. 45 CFR 205.170 - State standards for office space, equipment, and facilities.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ..., equipment, and facilities. State plan requirements: A State plan for financial assistance under title I, IV... establish and maintain standards for office space, equipment, and facilities that will adequately and... 45 Public Welfare 2 2010-10-01 2010-10-01 false State standards for office space, equipment,...

  7. Heavy quarkonium ππ transitions and a possible bb¯qq¯ state

    NASA Astrophysics Data System (ADS)

    Guo, F.-K.; Shen, P.-N.; Chiang, H.-C.; Ping, R.-G.

    2005-11-01

    ππ transitions of heavy quarkonia, especially the ϒ(3S)→ϒ(1S)ππ decay process, are revisited. In the framework of the Chiral Unitary Theory (ChUT), the S wave ππ final state interaction (FSI) is included. It is found that when an additional intermediate state with J=1 and I=1 is introduced, not only the ππ invariant mass spectrum and the cosθπ∗ distribution in the ϒ(3S)→ϒ(1S)ππ process can simultaneously be well explained, but also a consistent description for other bottomonia ππ transitions can be obtained. As a consequence, the mass and the width of the intermediate state are predicted. From the quark content analysis, this state should be a bb¯qq¯ state.

  8. Irreversible transitions in the exchange-striction model of spin-glass state

    NASA Astrophysics Data System (ADS)

    Valkov, V. I.; Golovchan, A. V.

    2014-08-01

    Based on the assumption of a negative volume dependence of random exchange integrals, it is possible to switch to a compressible Sherrington-Kirkpatrick spin-glass model. Within the proposed model, temperature-pressure phase diagrams were calculated and pressure- and magnetic-field-induced first-order phase transitions from the initial paramagnetic and spin-glass states to the ferromagnetic state were predicted. It was shown that the application of pressure in the spin-glass state not only increases and shifts magnetic susceptibility, but also reduces the critical magnetic fields of irreversible induced phase transitions from the spin-glass to the ferromagnetic state. The obtained results are used to describe the spin-glass state in (Sm1-xGdx)0.55Sr0.45MnO3.

  9. Probing the transition state via photoelectron and photodetachment spectroscopy of H3O−

    PubMed Central

    Zhang, Dong H.; Yang, Minghui; Collins, Michael A.; Lee, Soo-Y.

    2002-01-01

    The H3O− anion has stable and metastable structures that resemble configurations in the vicinity of the transition state for the neutral reactions OH + H2 ↔ H2O + H. Photoelectron spectroscopy of this anion probes the neutral reaction dynamics in the critical transition-state region. Accurate quantum dynamics calculations of the photoelectron intensity and photodissociation product energies are shown to provide a quantitatively reliable means of interpreting such experimental observations and reveal a detailed picture of the reaction dynamics. PMID:12186977

  10. Cascade of quantum phase transitions in tunnel-coupled edge states.

    PubMed

    Yang, I; Kang, W; Baldwin, K W; Pfeiffer, L N; West, K W

    2004-02-06

    We report on the cascade of quantum phase transitions exhibited by tunnel-coupled edge states across a quantum Hall line junction. We identify a series of quantum critical points between successive strong and weak tunneling regimes in the zero-bias conductance. Scaling analysis shows that the conductance near the critical magnetic fields B(c) is a function of a single scaling argument /B-B(c)/T(-kappa), where the exponent kappa=0.42. This puzzling resemblance to a quantum Hall-insulator transition points to the importance of interedge correlation between the coupled edge states.

  11. Locating transition states on potential energy surfaces by the gentlest ascent dynamics

    NASA Astrophysics Data System (ADS)

    Bofill, Josep Maria; Quapp, Wolfgang; Caballero, Marc

    2013-09-01

    The system of ordinary differential equations for the method of the gentlest ascent dynamics (GAD) has been derived which was previously proposed [W. E and X. Zhou, Nonlinearity 24, 1831 (2011)]. For this purpose we use diverse projection operators to a given initial direction. Using simple examples we explain the two possibilities of a GAD curve: it can directly find the transition state by a gentlest ascent, or it can go the roundabout way over a turning point and then find the transition state going downhill along its ridge. An outlook to generalised formulas for higher order saddle-points is added.

  12. An Analytical State Transition Matrix for Orbits Perturbed by an Oblate Spheroid

    NASA Technical Reports Server (NTRS)

    Mueller, A. C.

    1977-01-01

    An analytical state transition matrix and its inverse, which include the short period and secular effects of the second zonal harmonic, were developed from the nonsingular PS satellite theory. The fact that the independent variable in the PS theory is not time is in no respect disadvantageous, since any explicit analytical solution must be expressed in the true or eccentric anomaly. This is shown to be the case for the simple conic matrix. The PS theory allows for a concise, accurate, and algorithmically simple state transition matrix. The improvement over the conic matrix ranges from 2 to 4 digits accuracy.

  13. Modulation of hydride formation energies in transition metal doped Mg by alteration of spin state

    NASA Astrophysics Data System (ADS)

    Ozkanlar, Abdullah; Samuels, Alex; Clark, Aurora E.

    2013-02-01

    Coupled cluster and density functional theory calculations have been used to assess the role of the transition metal spin state upon the energetic favorability of hydride formation within small, transition metal doped, magnesium clusters. The spin state is found to modulate the occupation of bonding and anti-bonding orbitals, thus having a large effect upon both geometric and energetic parameters. This chemical description provides a potential theoretical basis for unexplained experimental observations, and indicates a mechanism for using an external magnetic field to control the thermodynamics of H2 sorption and desorption in metal hydrides.

  14. Phase-space representation of quantum state vectors: The relative-state approach and the displacement-operator approach

    NASA Astrophysics Data System (ADS)

    Ban, Masashi

    1999-08-01

    Phase-space representation of quantum state vectors has been recently formulated by means of the relative-state method developed by the present author [J. Math. Phys. 39, 1744 (1998)]. It is, however, pointed out by Mo/ller that the displacement-operator method provides another basis of phase-space representation of quantum state vectors [J. Math. Phys. (to appear)]. Hence the relation between the relative-state approach and the displacement-operator approach is discussed, both of which yield equivalent phase-space representations.

  15. Development of three-dimensional state-space wake theory and application in dynamic ground effect

    NASA Astrophysics Data System (ADS)

    Yu, Ke

    In topics of rotorcraft wake analysis, state-space wake theory has a recognized reputation for advantages in real-time simulation, preliminary design and eigenvalue analysis. Developments in the past decades greatly improved range of validity and accuracy of the state-space modeling approach. This work focuses on further improvement of the state-space wake theory and applications in representing dynamic ground effect. Extended state-space model is developed to represent non-zero mass flux on rotor disk. Its instant practical application, representing ground effect with a mass source ground rotor, is evaluated in both steady and dynamic aspects. Investigations of partial ground effect simulation by state-space model are carried out in different rotor configurations. Additional work is done in improving simulation efficiency of practical application of state-space modeling.

  16. Calculation of state-to-state differential and integral cross sections for atom-diatom reactions with transition-state wave packets

    SciTech Connect

    Zhao, Bin; Sun, Zhigang E-mail: hguo@unm.edu; Guo, Hua E-mail: hguo@unm.edu

    2014-06-21

    A recently proposed transition-state wave packet method [R. Welsch, F. Huarte-Larrañaga, and U. Manthe, J. Chem. Phys. 136, 064117 (2012)] provides an efficient and intuitive framework to study reactive quantum scattering at the state-to-state level. It propagates a few transition-state wave packets, defined by the eigenfunctions of the low-rank thermal flux operator located near the transition state, into the asymptotic regions of the reactant and product arrangement channels separately using the corresponding Jacobi coordinates. The entire S-matrix can then be assembled from the corresponding flux-flux cross-correlation functions for all arrangement channels. Since the transition-state wave packets can be defined in a relatively small region, its transformation into either the reactant or product Jacobi coordinates is accurate and efficient. Furthermore, the grid/basis for the propagation, including the maximum helicity quantum number K, is much smaller than that required in conventional wave packet treatments of state-to-state reactive scattering. This approach is implemented for atom-diatom reactions using a time-dependent wave packet method and applied to the H + D{sub 2} reaction with all partial waves. Excellent agreement with benchmark integral and differential cross sections is achieved.

  17. Characterizing metastable states beyond energies and lifetimes: Dyson orbitals and transition dipole moments.

    PubMed

    Jagau, Thomas-C; Krylov, Anna I

    2016-02-07

    The theoretical description of electronic resonances is extended beyond calculations of energies and lifetimes. We present the formalism for calculating Dyson orbitals and transition dipole moments within the equation-of-motion coupled-cluster singles and doubles method for electron-attached states augmented by a complex absorbing potential (CAP-EOM-EA-CCSD). The capabilities of the new methodology are illustrated by calculations of Dyson orbitals of various transient anions. We also present calculations of transition dipole moments between transient and stable anionic states as well as between different transient states. Dyson orbitals characterize the differences between the initial neutral and final electron-attached states without invoking the mean-field approximation. By extending the molecular-orbital description to correlated many-electron wave functions, they deliver qualitative insights into the character of resonance states. Dyson orbitals and transition moments are also needed for calculating experimental observables such as spectra and cross sections. Physically meaningful results for those quantities are obtained only in the framework of non-Hermitian quantum mechanics, e.g., in the presence of a complex absorbing potential (CAP), when studying resonances. We investigate the dependence of Dyson orbitals and transition moments on the CAP strength and illustrate how Dyson orbitals help understand the properties of metastable species and how they are affected by replacing the usual scalar product by the so-called c-product.

  18. Characterizing metastable states beyond energies and lifetimes: Dyson orbitals and transition dipole moments

    SciTech Connect

    Jagau, Thomas-C.; Krylov, Anna I.

    2016-02-07

    The theoretical description of electronic resonances is extended beyond calculations of energies and lifetimes. We present the formalism for calculating Dyson orbitals and transition dipole moments within the equation-of-motion coupled-cluster singles and doubles method for electron-attached states augmented by a complex absorbing potential (CAP-EOM-EA-CCSD). The capabilities of the new methodology are illustrated by calculations of Dyson orbitals of various transient anions. We also present calculations of transition dipole moments between transient and stable anionic states as well as between different transient states. Dyson orbitals characterize the differences between the initial neutral and final electron-attached states without invoking the mean-field approximation. By extending the molecular-orbital description to correlated many-electron wave functions, they deliver qualitative insights into the character of resonance states. Dyson orbitals and transition moments are also needed for calculating experimental observables such as spectra and cross sections. Physically meaningful results for those quantities are obtained only in the framework of non-Hermitian quantum mechanics, e.g., in the presence of a complex absorbing potential (CAP), when studying resonances. We investigate the dependence of Dyson orbitals and transition moments on the CAP strength and illustrate how Dyson orbitals help understand the properties of metastable species and how they are affected by replacing the usual scalar product by the so-called c-product.

  19. Possible ground states and parallel magnetic-field-driven phase transitions of collinear antiferromagnets

    NASA Astrophysics Data System (ADS)

    Li, Hai-Feng

    2016-10-01

    Understanding the nature of all possible ground states and especially magnetic-field-driven phase transitions of antiferromagnets represents a major step towards unravelling the real nature of interesting phenomena such as superconductivity, multiferroicity or magnetoresistance in condensed-matter science. Here a consistent mean-field calculation endowed with antiferromagnetic (AFM) exchange interaction (J), easy axis anisotropy (γ), uniaxial single-ion anisotropy (D) and Zeeman coupling to a magnetic field parallel to the AFM easy axis consistently unifies the AFM state, spin-flop (SFO) and spin-flip transitions. We reveal some mathematically allowed exotic spin states and fluctuations depending on the relative coupling strength of (J, γ and D). We build the three-dimensional (J, γ and D) and two-dimensional (γ and D) phase diagrams clearly displaying the equilibrium phase conditions and discuss the origins of various magnetic states as well as their transitions in different couplings. Besides the traditional first-order type one, we unambiguously confirm an existence of a second-order type SFO transition. This study provides an integrated theoretical model for the magnetic states of collinear antiferromagnets with two interpenetrating sublattices and offers a practical approach as an alternative to the estimation of magnetic exchange parameters (J, γ and D), and the results may shed light on nontrivial magnetism-related properties of bulks, thin films and nanostructures of correlated electron systems.

  20. Design of biomimetic catalysts by molecular imprinting in synthetic polymers: the role of transition state stabilization.

    PubMed

    Wulff, Günter; Liu, Junqiu

    2012-02-21

    The impressive efficiency and selectivity of biological catalysts has engendered a long-standing effort to understand the details of enzyme action. It is widely accepted that enzymes accelerate reactions through their steric and electronic complementarity to the reactants in the rate-determining transition states. Thus, tight binding to the transition state of a reactant (rather than to the corresponding substrate) lowers the activation energy of the reaction, providing strong catalytic activity. Debates concerning the fundamentals of enzyme catalysis continue, however, and non-natural enzyme mimics offer important additional insight in this area. Molecular structures that mimic enzymes through the design of a predetermined binding site that stabilizes the transition state of a desired reaction are invaluable in this regard. Catalytic antibodies, which can be quite active when raised against stable transition state analogues of the corresponding reaction, represent particularly successful examples. Recently, synthetic chemistry has begun to match nature's ability to produce antibody-like binding sites with high affinities for the transition state. Thus, synthetic, molecularly imprinted polymers have been engineered to provide enzyme-like specificity and activity, and they now represent a powerful tool for creating highly efficient catalysts. In this Account, we review recent efforts to develop enzyme models through the concept of transition state stabilization. In particular, models for carboxypeptidase A were prepared through the molecular imprinting of synthetic polymers. On the basis of successful experiments with phosphonic esters as templates to arrange amidinium groups in the active site, the method was further improved by combining the concept of transition state stabilization with the introduction of special catalytic moieties, such as metal ions in a defined orientation in the active site. In this way, the imprinted polymers were able to provide both an