Science.gov

Sample records for state space transitions

  1. Multiple transition states and roaming in ion-molecule reactions: A phase space perspective

    NASA Astrophysics Data System (ADS)

    Mauguière, Frédéric A. L.; Collins, Peter; Ezra, Gregory S.; Farantos, Stavros C.; Wiggins, Stephen

    2014-01-01

    We provide a dynamical interpretation of the recently identified ‘roaming' mechanism for molecular dissociation reactions in terms of geometrical structures in phase space. These are NHIMs (Normally Hyperbolic Invariant Manifolds) and their stable/unstable manifolds that define transition states for ion-molecule association or dissociation reactions. The associated dividing surfaces rigorously define a roaming region of phase space, in which both reactive and non reactive trajectories can be trapped for arbitrarily long times.

  2. The Jastrow antisymmetric geminal power in Hilbert space: Theory, benchmarking, and application to a novel transition state

    SciTech Connect

    Neuscamman, Eric

    2013-11-21

    The Jastrow-modified antisymmetric geminal power (JAGP) ansatz in Hilbert space successfully overcomes two key failings of other pairing theories, namely, a lack of inter-pair correlations and a lack of multiple resonance structures, while maintaining a polynomially scaling cost, variational energies, and size consistency. Here, we present efficient quantum Monte Carlo algorithms that evaluate and optimize the JAGP energy for a cost that scales as the fifth power of the system size. We demonstrate the JAGP’s ability to describe both static and dynamic correlation by applying it to bond stretching in H{sub 2}O, C{sub 2}, and N{sub 2} as well as to a novel, multi-reference transition state of ethene. JAGP’s accuracy in these systems outperforms even the most sophisticated single-reference methods and approaches that of exponentially scaling active space methods.

  3. The Jastrow antisymmetric geminal power in Hilbert space: Theory, benchmarking, and application to a novel transition state

    NASA Astrophysics Data System (ADS)

    Neuscamman, Eric

    2013-11-01

    The Jastrow-modified antisymmetric geminal power (JAGP) ansatz in Hilbert space successfully overcomes two key failings of other pairing theories, namely, a lack of inter-pair correlations and a lack of multiple resonance structures, while maintaining a polynomially scaling cost, variational energies, and size consistency. Here, we present efficient quantum Monte Carlo algorithms that evaluate and optimize the JAGP energy for a cost that scales as the fifth power of the system size. We demonstrate the JAGP's ability to describe both static and dynamic correlation by applying it to bond stretching in H2O, C2, and N2 as well as to a novel, multi-reference transition state of ethene. JAGP's accuracy in these systems outperforms even the most sophisticated single-reference methods and approaches that of exponentially scaling active space methods.

  4. Quantum phase transition in space

    SciTech Connect

    Damski, Bogdan; Zurek, Wojciech H

    2008-01-01

    A quantum phase transition between the symmetric (polar) phase and the phase with broken symmetry can be induced in a ferromagnetic spin-1 Bose-Einstein condensate in space (rather than in time). We consider such a phase transition and show that the transition region in the vicinity of the critical point exhibits scalings that reflect a compromise between the rate at which the transition is imposed (i.e., the gradient of the control parameter) and the scaling of the divergent healing length in the critical region. Our results suggest a method for the direct measurement of the scaling exponent {nu}.

  5. 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.

  6. 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.

  7. Primordial equation of state transitions

    NASA Astrophysics Data System (ADS)

    Aravind, Aditya; Lorshbough, Dustin; Paban, Sonia

    2016-06-01

    We revisit the physics of transitions from a general equation of state parameter to the final stage of slow-roll inflation. We show that it is unlikely for the modes comprising the cosmic microwave background to contain imprints from a preinflationary equation of state transition and still be consistent with observations. We accomplish this by considering observational consistency bounds on the amplitude of excitations resulting from such a transition. As a result, the physics which initially led to inflation likely cannot be probed with observations of the cosmic microwave background. Furthermore, we show that it is unlikely that equation of state transitions may explain the observed low multipole power suppression anomaly.

  8. 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.

  9. 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.

  10. Spectroscopic characterization of isomerization transition states.

    PubMed

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

    2015-12-11

    Transition state theory is central to our understanding of chemical reaction dynamics. We demonstrate 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, ω(eff). The method is applied to the cis-trans conformational change in the S1 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. PMID:26659051

  11. Spectroscopic characterization of isomerization transition states

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Transition state theory is central to our understanding of chemical reaction dynamics. We demonstrate 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 S1 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.

  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. PMID:15220139

  13. Space-time formulation of quantum transitions

    NASA Astrophysics Data System (ADS)

    Petrosky, T.; Ordonez, G.; Prigogine, I.

    2001-12-01

    In a previous paper we have studied dressed excited states in the Friedrichs model, which describes a two-level atom interacting with radiation. In our approach, excited states are distributions (or generalized functions) in the Liouville space. These states decay in a strictly exponential way. In contrast, the states one may construct in the Hilbert space of wave functions always present deviations from exponential decay. We have considered the momentum representation, which is applicable to global quantities (trace, energy transfer). Here we study the space-time description of local quantities associated with dressed unstable states, such as, the intensity of the photon field. In this situation the excited states become factorized in Gamow states. To go from local quantities to global quantities, we have to proceed to an integration over space, which is far from trivial. There are various elements that appear in the space-time evolution of the system: the unstable cloud that surrounds the bare atom, the emitted real photons and the ``Zeno photons,'' which are associated with deviations from exponential decay. We consider a Hilbert space approximation to our dressed excited state. This approximation leads already to decay close to exponential in the field surrounding the atom, and to a line shape different from the Lorentzian line shape. Our results are compared with numerical simulations. We show that the time evolution of an unstable state satisfies a Boltzmann-like H theorem. This is applied to emission and absorption as well as scattering. The existence of a microscopic H theorem is not astonishing. The excited states are ``nonequilibrium'' states and their time evolution leads to the emission of photons, which distributes the energy of the unstable state among the field modes.

  14. 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. PMID:25340992

  15. State Transitions in Semiarid Landscapes

    NASA Astrophysics Data System (ADS)

    Phillips, J. D.

    2012-04-01

    The U.S. Department of Agriculture has developed a large number of state-and-transition models (STM) to predict and interpret changes in vegetation communities in drylands of the southwestern U.S. These are represented as box-and-arrow models indicating potential changes in response to various combinations of management practices and environmental forcings. Analysis of the 320 STMs developed for areas within the state of Texas reveals two important aspects of environmental change in semiarid environments. First, the STMs are highly local—they are specific to very particular combinations of landform, soil, and climate. This is consistent with the perfect landscape concept in geomorphology, which emphasizes the irreducible importance of geographically and historically contingent local factors in addition to universal laws or principles in determining the state or condition of landscapes. Second, analysis of the STMs using algebraic graph theory shows that a majority of them have structures that tend to amplify effects of change and disturbances. In many cases the STMs represent a form of self-organization characterized by the potential of divergent behavior rather than convergence toward a dominant pattern or outcome. These results indicate that geomorphic, hydrologic, and ecological responses to climate and land use change are likely to be highly variable and idiosyncratic, both within and between semiarid landscapes of Texas.

  16. Transitioning NASA Space Operations to Commercial Services

    NASA Technical Reports Server (NTRS)

    Gilbert, Charlene E.

    1998-01-01

    Major considerations associated with "Transitioning NASA Space Operations to Commercial Services" are presented in viewgraph form. Specific topics include: 1) Government use of commercial frequencies vs. commercial use of commercial frequencies for government use; 2) Commercial use of government frequencies; 3) Government vs commercial: Access techniques, data formats, and modulation and coding; 4) Government need for multiple sources: backup and competition; 5) Government in perceived competition with commercial service providers if TDRSS is used for commercial purposes; and 6) Coordination required among plans for CSOC, NSCP, and satellite industry.

  17. Periodic-orbit formula for quantum reactions through transition states

    SciTech Connect

    Schubert, Roman; Goussev, Arseni; Wiggins, Stephen; Waalkens, Holger

    2010-07-15

    Transition state theory forms the basis of computing reaction rates in chemical and other systems. Recently, it has been shown how transition state theory can rigorously be realized in phase space by using an explicit algorithm. The quantization has been demonstrated to lead to an efficient procedure to compute cumulative reaction probabilities and the associated Gamov-Siegert resonances. In this paper, these results are used to express the cumulative reaction probability as an absolutely convergent sum over periodic orbits contained in the transition state.

  18. 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.

  19. 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.

  20. Quasi-classical models of transition state absorption or emission

    NASA Astrophysics Data System (ADS)

    Lee, Soo-Y.; Pollard, W. Thomas; Mathies, Richard A.

    1989-11-01

    By making a short-time approximation to the correlation function in the quantum result for transition state absorption (or emission) we obtain the Lorentzian and reflection results as integrals of simple configuration space functions. These and the time-integrated quantum results are used to derive and unify the following descriptions of transition-state absorption: (a) the classical model of Bersohn and Zewail, (b) the time-dependent wave mechanical description by Agrawal, Mohan and Sathyamurthy, (c) the classical trajectory approach by Polanyi and coworkers and (d) the time-independent quantum-mechanical description by Engel, Bacic, Schinke and Shapiro.

  1. 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...

  2. Radiative transitions of heavy quarkonium states

    SciTech Connect

    De Fazio, Fulvia

    2009-03-01

    We study radiative decays of heavy QQ states, both for Q=c and Q=b, using an effective Lagrangian approach which exploits spin symmetry for such states. We use existing data on radiative quarkonium transitions to predict some unmeasured decay rates. We also discuss how these modes can be useful to understand the structure of X(3872)

  3. Soil, resilience, and state and transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    State and transition models are based on the assumption that less resilient systems are more susceptible to state changes. The objective of this paper is to show how two different types of soil properties contribute to resilience through their direct and indirect effects on ecosystem processes, and ...

  4. 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

  5. Successfully Transitioning Science Research to Space Weather Applications

    NASA Technical Reports Server (NTRS)

    Spann, James

    2012-01-01

    The awareness of potentially significant impacts of space weather on spaceand ground ]based technological systems has generated a strong desire in many sectors of government and industry to effectively transform knowledge and understanding of the variable space environment into useful tools and applications for use by those entities responsible for systems that may be vulnerable to space weather impacts. Essentially, effectively transitioning science knowledge to useful applications relevant to space weather has become important. 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.

  6. United States space transportation survey

    NASA Technical Reports Server (NTRS)

    Branscome, Darrel R.

    1989-01-01

    Different developmental paths for the U.S. space transportation fleet are discussed. Development of a purely cargo, unmanned space shuttle, using many components of the present manned space shuttle system, is presented. Future manned spacecraft solutions are discussed. Launch vehicle programs for unmanned missions are described. The Titan solid rocket motor upgrade is identified as the biggest improvement in this area. A return to a better balance between manned and unmanned launch systems for space transportation is predicted. The Titan, Delta, Scout, and Pegasus families of rockets are described. The need to upgrade this fleet in meeting the space challenges of the future is stressed.

  7. 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. PMID:26008760

  8. See Your State From Space!

    USGS Publications Warehouse

    U.S. Geological Survey

    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.

  9. 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.

  10. Perimenopause as a neurological transition state.

    PubMed

    Brinton, Roberta D; Yao, Jia; Yin, Fei; Mack, Wendy J; Cadenas, Enrique

    2015-07-01

    Perimenopause is a midlife transition state experienced by women that occurs in the context of a fully functioning neurological system and results in reproductive senescence. Although primarily viewed as a reproductive transition, the symptoms of perimenopause are largely neurological in nature. Neurological symptoms that emerge during perimenopause are indicative of disruption in multiple estrogen-regulated systems (including thermoregulation, sleep, circadian rhythms and sensory processing) and affect multiple domains of cognitive function. Estrogen is a master regulator that functions through a network of estrogen receptors to ensure that the brain effectively responds at rapid, intermediate and long timescales to regulate energy metabolism in the brain via coordinated signalling and transcriptional pathways. The estrogen receptor network becomes uncoupled from the bioenergetic system during the perimenopausal transition and, as a corollary, a hypometabolic state associated with neurological dysfunction can develop. For some women, this hypometabolic state might increase the risk of developing neurodegenerative diseases later in life. The perimenopausal transition might also represent a window of opportunity to prevent age-related neurological diseases. This Review considers the importance of neurological symptoms in perimenopause in the context of their relationship to the network of estrogen receptors that control metabolism in the brain. PMID:26007613

  11. Order of the transition versus space dimension in a family of cellular automata

    NASA Astrophysics Data System (ADS)

    Bidaux, Roger; Boccara, Nini; Chaté, Hugues

    1989-03-01

    A mean-field theory of (probabilistic) cellular automata is developed and used to select a typical local rule whose mean-field analysis predicts first-order phase transitions. The corresponding automaton is then studied numerically on regular lattices for space dimensions d between 1 and 4. At odds with usual beliefs on two-state automata with one absorbing phase, first-order transitions are indeed exhibited as soon as d>1, with closer quantitative agreement with mean-field predictions for high space dimensions. For d=1, the transition is continuous, but with critical exponents different from those of directed percolation.

  12. 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.

  13. 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…

  14. 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. PMID:22844438

  15. 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

  16. QM/MM Analysis of Transition States and Transition State Analogues in Metalloenzymes.

    PubMed

    Roston, D; Cui, Q

    2016-01-01

    Enzymology is approaching an era where many problems can benefit from computational studies. While ample challenges remain in quantitatively predicting behavior for many enzyme systems, the insights that often come from computations are an important asset for the enzymology community. Here we provide a primer for enzymologists on the types of calculations that are most useful for mechanistic problems in enzymology. In particular, we emphasize the integration of models that range from small active-site motifs to fully solvated enzyme systems for cross-validation and dissection of specific contributions from the enzyme environment. We then use a case study of the enzyme alkaline phosphatase to illustrate specific application of the methods. The case study involves examination of the binding modes of putative transition state analogues (tungstate and vanadate) to the enzyme. The computations predict covalent binding of these ions to the enzymatic nucleophile and that they adopt the trigonal bipyramidal geometry of the expected transition state. By comparing these structures with transition states found through free energy simulations, we assess the degree to which the transition state analogues mimic the true transition states. Technical issues worth treating with care as well as several remaining challenges to quantitative analysis of metalloenzymes are also highlighted during the discussion. PMID:27498640

  17. 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.

  18. Quadratic Stochastic Operators with Countable State Space

    NASA Astrophysics Data System (ADS)

    Ganikhodjaev, Nasir

    2016-03-01

    In this paper, we provide the classes of Poisson and Geometric quadratic stochastic operators with countable state space, study the dynamics of these operators and discuss their application to economics.

  19. 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.

  20. 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.

  1. Spin state transitions in cobaltites: spectroscopic perspective

    NASA Astrophysics Data System (ADS)

    Hao Tjeng, Liu

    2010-03-01

    The class of cobalt-oxide based materials has attracted increasing interest in the last decade. A key aspect of the cobaltites that distinguishes them clearly from the Cu, Ni, and Mn oxides is the spin state degree of freedom of the Co3+ and Co4+ ions: the ions can be low spin, high spin, and perhaps even intermediate spin. This aspect comes on top of the orbital and charge degrees of freedom that already make the Cu, Ni, Mn systems so exciting. It is, however, also precisely this aspect that causes considerable debate in the literature. In this presentation we would like to show how synchrotron based soft-x-ray spectroscopies can successfully resolve the local electronic structure of the Co ions and thus contribute to a better understanding of the physical properties of the cobaltites. In particular, we will address the issue of spin state transitions, metal insulator transitions and the newly proposed spin-blockade phenomenon in several layered cobalt materials. --- Work done in collaboration with Z. Hu, M.W. Haverkort, C.F. Chang, H. Wu, T. Burnus, Y.Y. Chin, N. Hollmann, C. Schussler- Langeheine, M. Benomar, T. Lorenz, D.I. Khomskii (Univ. Cologne), A. Tanaka (Univ. Hiroshima), S.N. Barilo (NAS, Minsk), J. Cezar, N.B. Brookes (ESRF-Grenoble), H.H. Hsieh, H.J. Lin, C.T. Chen (NSRRC-Hsinchu). Supported by the DFG through SFB 608.

  2. Spectral presheaves as quantum state spaces.

    PubMed

    Döring, Andreas

    2015-08-01

    For each quantum system described by an operator algebra [Formula: see text] of physical quantities, we provide a (generalized) state space, notwithstanding the Kochen-Specker theorem. This quantum state space is the spectral presheaf [Formula: see text]. We formulate the time evolution of quantum systems in terms of Hamiltonian flows on this generalized space and explain how the structure of the spectral presheaf [Formula: see text] geometrically mirrors the double role played by self-adjoint operators in quantum theory, as quantum random variables and as generators of time evolution. PMID:26124247

  3. 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.

  4. 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.

  5. Universal transition state scaling relations for (de)hydrogenation over transition metals.

    PubMed

    Wang, S; Petzold, V; Tripkovic, V; Kleis, J; Howalt, J G; Skúlason, E; Fernández, E M; Hvolbæk, B; Jones, G; Toftelund, A; Falsig, H; Björketun, M; Studt, F; Abild-Pedersen, F; Rossmeisl, J; Nørskov, J K; Bligaard, T

    2011-12-14

    We analyse the transition state energies for 249 hydrogenation/dehydrogenation reactions of atoms and simple molecules over close-packed and stepped surfaces and nanoparticles of transition metals using Density Functional Theory. Linear energy scaling relations are observed for the transition state structures leading to transition state scaling relations for all the investigated reactions. With a suitable choice of reference systems the transition state scaling relations form a universality class that can be approximated with one single linear relation describing the entire range of reactions over all types of surfaces and nanoclusters. PMID:21996683

  6. Transitioning Space Weather Models Into Operations: The Basic Building Blocks

    NASA Astrophysics Data System (ADS)

    Araujo-Pradere, Eduardo A.

    2009-10-01

    New and improved space weather models that provide real-time or near-real time operational awareness to the long list of customers that the NOAA Space Weather Prediction Center (SWPC) serves are critically needed. Recognizing this, SWPC recently established a Developmental Testbed Center (DTC [see Kumar, 2009]) at which models will be vetted for operational use. What characteristics should models have if they are to survive this transition? The difficulties around the implementation of real-time models are many. From the stability of the data input (frequently coming from third parties) to the elevated information technology (IT) security atmosphere present everywhere, scientists and developers are confronting a series of challenges in the implementation of their models. Quinn et al. [2009] noted that “the transition challenges are numerous and require ongoing interaction between model developers and users.” However, the 2006 Report of the Assessment Committee for the National Space Weather Program (NSWP; see http://www.nswp.gov/nswp_acreport0706.pdf) found that “there is an absence of suitable connection[s] for ‘academia-to-operations’ knowledge transfer and for the transition of research to operations in general.”

  7. 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.

  8. "Show me your impact": evaluating transitional justice in contested spaces.

    PubMed

    Duggan, Colleen

    2012-02-01

    This paper discusses some of the most significant challenges and opportunities for evaluating the effects of programs in support of transitional justice - the field that addresses how post-conflict or post authoritarian societies deal with legacies of wide spread human rights violations. The discussion is empirically grounded in a case study that assesses the efforts of the International Development Research Centre (IDRC) and one of its Guatemalan partners to evaluate the effects of a museum exposition that is attempting to recast historic memory and challenge racist attitudes in post-conflict Guatemala. The paper argues that despite the increasing trend to fund transitional justice programs, many international aid donors are stuck in traditional and arguably orthodox paradigms of program evaluation. This is having a negative effect not only upon the administration of aid but also upon how transitional justice research is perceived and valued by local populations. The case study experience indicates that there is no perfect evaluation model or approach for evaluating transitional justice programming - only choices to be made by commissioners of evaluation, evaluators, and those being evaluated. These are profoundly influenced by the extreme politics and moral values that define transitional justice settings as contested spaces in which calls to remember the tragic past must be balanced with aspirations to re-build a hopeful future. PMID:21190735

  9. Space-based Search for Transiting Exoplanets Orbiting Bright Stars

    NASA Astrophysics Data System (ADS)

    Tsvetanov, Zlatan

    At the current stage of research transiting planets hold the key to advancing our knowledge of exoplanets as they are the only targets that allow determination of many of the key plane-tary parameters. Because the employed techniques are differential (either photometry or spec-troscopy) and the planet is significantly fainter the host star the dominant limitation is simply the number of photons. This puts a very high premium on transiting planets with bright parent stars. The ExoPlanet Task Force recognized the high value of planets transiting bright stars and identified the need to perform a wide area space-based transit survey. In this presentation I will describe a program that addresses the ExoPTF recommendation by using the output of one of the instruments on the currently operating space mission STEREO. STEREO is the third mission in NASA's Solar Terrestrial Probes program. It uses two nearly identical spacecrafts -one on an Earth-leading orbit and one on an Earth-trailing orbit -each equipped with a suit of five small telescopes to provide a stereoscopic view of the coronal mass ejections (CME) as they propagate away from the Sun. As each of these telescopes observes a portion of the heliospehre, they also image the star field in the background. For the purposes of this study we will consider only the images obtained by the HI-1 instruments. Other instruments, although showing the stellar background as well, do not have the data output suitable for a search for transiting exoplanets. This project described here has the potential of delivering a number of very high value targets for follow-up studies with a wide range of facilities, both ground-based and space-based. It will provide a complete survey of all bright stars (<10m) for 18% of the sky. The photometric data series have the sensitivity to detect all transiting hot-Jupiters and other gas giants with periods up to ˜20 days and even some Neptune size planets orbiting bright and/or late type stars. On

  10. 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

  11. 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.

  12. 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

  13. Fractal Complexity in Spontaneous EEG Metastable-State Transitions: New Vistas on Integrated Neural Dynamics

    PubMed Central

    Allegrini, Paolo; Paradisi, Paolo; Menicucci, Danilo; Gemignani, Angelo

    2010-01-01

    Resting-state EEG signals undergo rapid transition processes (RTPs) that glue otherwise stationary epochs. We study the fractal properties of RTPs in space and time, supporting the hypothesis that the brain works at a critical state. We discuss how the global intermittent dynamics of collective excitations is linked to mentation, namely non-constrained non-task-oriented mental activity. PMID:21423370

  14. Recrossings and transition-state theory.

    PubMed

    Pritchard, Huw O

    2005-02-24

    When classical trajectory calculations are run on the two isomerization reactions NCCN <==> NCNC and CH3CN right harpoon over left harpoon CH3NC over a long period of time, up to ca. 0.2 micros each, one finds many more recrossings than actual reactive events. In these calculations a "recrossing" is defined as passage over the potential barrier separating the two species followed by return to the original side within 0.2 ps. For the C2N2 case there are about twice as many crossings of the barrier as there are genuine reactive events, and for CH3CN, there are about 10 times as many. Long-term mean residence times, tau(infinity)CN and tau(infinity)NC, in reactant and product wells are compared with the corresponding mean first passage times, tau1(CN) and tau1(NC), the latter found by terminating the trajectories at the first crossing of the barrier. For the NCCN <==> NCNC reaction, except at the lowest energies, the mean residence times are exactly twice the mean first passage times, implying that the transition-state theory transmission coefficient, as traditionally defined, should be kappa = 0.5. PMID:16833457

  15. 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.

  16. Electric dipole transitions between Gamow-Teller and spin-dipole states

    SciTech Connect

    Suzuki, T.; Sagawa, H.; Van Giai, N.

    1998-01-01

    We study electric dipole transitions between Gamow-Teller (GT) and spin-dipole (SD) states. SD and GT excitations are calculated within the Hartree-Fock+Tamm-Dancoff approximation for {sup 48}Sc and {sup 90}Nb. The electric dipole transitions are found to be rather selective, and strong E1 transitions occur to some specific spin-dipole states. Calculated E1 transition strengths between GT and SD states are compared with the analytic sum rules within one-particle{endash}one-hole (1p-1h) configuration space and within both 1p-1h and 2p-2h model space. Possible implications for charge-exchange reactions may help to understand the quenching problem of spin excitations. {copyright} {ital 1998} {ital The American Physical Society}

  17. Unified transition path and universal transition state for ZB to RS or WZ to RS high pressure phase transition

    NASA Astrophysics Data System (ADS)

    Miao, Maosheng

    2005-07-01

    We show that the previously proposed transition paths for high pressure phase transitions for semiconductor from zinc blende (ZB) to rocksalt (RS) and from wurtzite (WZ) to rocksalt can be unified and can be extended to transitions from various tetrahedrally bonded polytypes to rocksalt [1]. Our first principle pseudopotential calculations with density functional and constrained relaxation methods on SiC showed that the ZB to RS transition has the lowest transition barrier. Our calculations on ZB to RS transition path for other semiconductors including II-VI, III-V and group IV semiconductors, show that the position and the geometry of the transition state, the state that correspond to the transition barrier, are universal and do not depend on the chemical components of the system [2]. We also extended the Landau phase transition model to a ZB to RS transition by using a cosine function of the atom displacement as order parameter. The model shows that the position of the transition state does not depend on the coupling between the atom displacement and the strains of the lattice, which is the key point that the transition state is independent of the chemical components. [1] M. S. Miao and Walter R. L. Lambrecht, Phys. Rev. B 68, 092103 (2003). [2] M. S. Miao and Walter R. L. Lambrecht, Phys. Rev. Lett., accepted

  18. 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. PMID:26590549

  19. Smooth transitions from the Schwarzschild vacuum to de Sitter space

    SciTech Connect

    Conboy, Steven; Lake, Kayll

    2005-06-15

    We provide an infinity of spacetimes which contain part of both the Schwarzschild vacuum and de Sitter space. The transition, which occurs below the Schwarzschild event horizon, involves only boundary surfaces (no surface layers). An explicit example is given in which the weak and strong energy conditions are satisfied everywhere (except in the de Sitter section) and the dominant energy condition is violated only in the vicinity of the boundary to the Schwarzschild section. The singularity is avoided by way of a change in topology in accord with a theorem due to Borde.

  20. Frequency domain state-space system identification

    NASA Technical Reports Server (NTRS)

    Chen, Chung-Wen; Juang, Jer-Nan; Lee, Gordon

    1992-01-01

    An algorithm for identifying state-space models from frequency response data of linear systems is presented. A matrix-fraction description of the transfer function is employed to curve-fit the frequency response data, using the least-squares method. The parameters of the matrix-fraction representation are then used to construct the Markov parameters of the system. Finally, state-space models are obtained through the Eigensystem Realization Algorithm using Markov parameters. The main advantage of this approach is that the curve-fitting and the Markov parameter construction are linear problems which avoid the difficulties of nonlinear optimization of other approaches. Another advantage is that it avoids windowing distortions associated with other frequency domain methods.

  1. Two-photon transitions to excited states in atomic hydrogen

    SciTech Connect

    Quattropani, A.; Bassani, F.; Carillo, S.

    1982-06-01

    Resonant two-photon transition rates from the ground state of atomic hydrogen to ns excited states have been computed as a function of photon frequencies in the length and velocity gauges in order to test the accuracy of the calculation and to discuss the rate of convergence over the intermediate states. The dramatic structure of the transition rates produced by intermediate-state resonances is exhibited. A two-photon transparency is found in correspondence to each resonance.

  2. 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.…

  3. State-space formulations for flutter analysis

    NASA Technical Reports Server (NTRS)

    Weiss, S. J.; Tseng, K.; Morino, L.

    1976-01-01

    Various methods are presented and assessed for approximating the aerodynamic forces so that the State Space formulation and off-the-imaginary axis analysis are retained. The advantages of retaining these features are considerable, not only in simplifying the flutter analysis, but especially for more advanced applications such as optimal design of active control in which the flutter is merely a constraint to the optimization problem.

  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. 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.

  7. 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). PMID:9730016

  8. Markov chain evaluation of acute postoperative pain transition states.

    PubMed

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

    2016-03-01

    Previous investigations on acute postoperative pain dynamicity have focused on daily pain assessments, and so were unable to examine intraday variations in acute pain intensity. We analyzed 476,108 postoperative acute pain intensity ratings, which were clinically documented on postoperative days 1 to 7 from 8346 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 0 to state 0. 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 0 from the current state. An 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 0 (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 using Markov chains is 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

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

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 16 2014-07-01 2014-07-01 false State program submittals and... PROGRAMS (CONTINUED) STATE OPERATING PERMIT PROGRAMS § 70.4 State program submittals and transition. (a... Administrator for approval a proposed part 70 program, under State law or under an interstate compact,...

  10. 40 CFR 70.4 - State program submittals and transition.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 16 2012-07-01 2012-07-01 false State program submittals and... PROGRAMS (CONTINUED) STATE OPERATING PERMIT PROGRAMS § 70.4 State program submittals and transition. (a... Administrator for approval a proposed part 70 program, under State law or under an interstate compact,...

  11. 40 CFR 70.4 - State program submittals and transition.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 16 2013-07-01 2013-07-01 false State program submittals and... PROGRAMS (CONTINUED) STATE OPERATING PERMIT PROGRAMS § 70.4 State program submittals and transition. (a... Administrator for approval a proposed part 70 program, under State law or under an interstate compact,...

  12. The folding transition state theory in simple model systems

    NASA Astrophysics Data System (ADS)

    Niewieczerzał, Szymon; Cieplak, Marek

    2008-06-01

    We present the results of an exact analysis of several model free energy landscapes of a protein to clarify the notion of the transition state and the physical meaning of the phi values determined in protein engineering experiments. We argue that a proper search strategy for the transition state in more realistic models should involve identification of a common part of various methods. Two of the models considered involve explicit conformations instead of just points on the free energy axis. These models are minimalistic as they are endowed only with five or 36 states to enumerate folding paths and to identify the transition state easily. Even though they display much of the two-state behavior, the phi values are found not to correspond to the conformation of the transition state.

  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 State Structure of RNA Depurination by Saporin L3.

    PubMed

    Yuan, Hongling; Stratton, Christopher F; Schramm, Vern L

    2016-05-20

    Saporin L3 from the leaves of the common soapwort is a catalyst for hydrolytic depurination of adenine from RNA. Saporin L3 is a type 1 ribosome inactivating protein (RIP) composed only of a catalytic domain. Other RIPs have been used in immunotoxin cancer therapy, but off-target effects have limited their development. In the current study, we use transition state theory to understand the chemical mechanism and transition state structure of saporin L3. In favorable cases, transition state structures guide the design of transition state analogues as inhibitors. Kinetic isotope effects (KIEs) were determined for an A14C mutant of saporin L3. To permit KIE measurements, small stem-loop RNAs that contain an AGGG tetraloop structure were enzymatically synthesized with the single adenylate bearing specific isotopic substitutions. KIEs were measured and corrected for forward commitment to obtain intrinsic values. A model of the transition state structure for depurination of stem-loop RNA (5'-GGGAGGGCCC-3') by saporin L3 was determined by matching KIE values predicted via quantum chemical calculations to a family of intrinsic KIEs. This model indicates saporin L3 displays a late transition state with the N-ribosidic bond to the adenine nearly cleaved, and the attacking water nucleophile weakly bonded to the ribosyl anomeric carbon. The transition state retains partial ribocation character, a feature common to most N-ribosyl transferases. However, the transition state geometry for saporin L3 is distinct from ricin A-chain, the only other RIP whose transition state is known. PMID:26886255

  15. Momentum space imaging of the FFLO state

    NASA Astrophysics Data System (ADS)

    Akbari, Alireza; Thalmeier, Peter

    2016-06-01

    In a magnetic field superconductors (SC) with small orbital effect exhibit the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) phase above the Pauli limiting field. It is characterized by Cooper pairs with finite center of mass momentum and is stabilized by the gain in Zeeman energy of depaired electrons in the imbalanced Fermi gas. The ground state is a coherent superposition of paired and depaired states. This concept, although central to the FFLO state lacks a direct experimental confirmation. We propose that STM quasiparticle interference (QPI) can give a direct momentum space image of the depaired states in the FFLO wave function. For a proof of principle we investigate a 2D single orbital tight binding model with a SC s-wave order parameter. Using the equilibrium values of pair momentum and SC gap we calculate the spectral function of quasiparticles and associated QPI spectrum as function of magnetic field. We show that the characteristic depaired Fermi surface parts appear as a fingerprint in the QPI spectrum of the FFLO phase and we demonstrate its evolution with field strength. Its observation in STM experiments would constitute a direct proof for FFLO ground state wave function.

  16. Morse bifurcations of transition states in bimolecular reactions

    NASA Astrophysics Data System (ADS)

    MacKay, R. S.; Strub, D. C.

    2015-12-01

    The transition states and dividing surfaces used to find rate constants for bimolecular reactions are shown to undergo Morse bifurcations, in which they change diffeomorphism class, and to exist for a large range of energies, not just immediately above the critical energy for first connection between reactants and products. Specifically, we consider capture between two molecules and the associated transition states for the case of non-zero angular momentum and general attitudes. The capture between an atom and a diatom, and then a general molecule are presented, providing concrete examples of Morse bifurcations of transition states and dividing surfaces.

  17. 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.

  18. Theory of Interface States at Silicon / Transition - - Silicide Interfaces.

    NASA Astrophysics Data System (ADS)

    Lim, Hunhwa

    The Si/NiSi(,2)(111) interface is of both fundamental and techno- logical interest: From the fundamental point of view, it is the best characterized of all semiconductor/metal interfaces, with two well-determined geometries (A and B) involving nearly perfect bonding. (This is because Si and NiSi(,2) have nearly the same lattice spacing.) Consequently, a theoretical treatment of this system makes sense--as it would not for messier systems--and one can have some confidence that the theoretical predictions are relevant to experimental observa- tions. From the technological point of view, Si/NiSi(,2) is representative of the class of semiconductor/metal interfaces that are currently of greatest interest in regard to electronic devices--Si/transition -metal-silicide interfaces. The calculations of this dissertation are for the intrinsic interface states of Si/NiSi(,2)-A geometry. These calculations also provide a foundation for later studies of defects at this interface, and for studies of other related systems, such as CoSi(,2). The calculations employ empirical tight-binding Hamiltonians for both Si and NiSi(,2) (with the parameters fitted to prior calculations of the bulk band structures, which appear to be in agreement with the available experimental data on bulk Si and NiSi(,2)). They also employ Green's function techniques--in particular, the subspace Hamiltonian technique. Our principal results are the following: (1) Interface state disper- sion curves are predicted along the symmetry lines (')(GAMMA)(')M, (')M(')K and (')K(')(GAMMA) of the surface Brillouin zone. (2) A prominent band of interface states is found which disperses downward from an energy within the Si band gap to an energy below the Si valence band edge E(,(upsilon)) as the planar wavevector (')k increases from (')(GAMMA) ((')k = 0) to (')M or (')K (symmetry points at boundary of the surface Brillouin zone). This band of inter- face states should be observable. It produces a peak in the surface

  19. 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

  20. 45 CFR 150.221 - Transition to State enforcement.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Determining Whether States Are Failing To Substantially Enforce HIPAA Requirements § 150.221 Transition to... enacted and implemented legislation to enforce HIPAA requirements and also determines that it...

  1. 45 CFR 150.221 - Transition to State enforcement.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Determining Whether States Are Failing To Substantially Enforce HIPAA Requirements § 150.221 Transition to... enacted and implemented legislation to enforce HIPAA requirements and also determines that it...

  2. 45 CFR 150.221 - Transition to State enforcement.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Determining Whether States Are Failing To Substantially Enforce HIPAA Requirements § 150.221 Transition to... enacted and implemented legislation to enforce HIPAA requirements and also determines that it...

  3. 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...

  4. Transition state theory and the dynamics of hard disks

    NASA Astrophysics Data System (ADS)

    Barnett-Jones, M.; Dickinson, P. A.; Godfrey, M. J.; Grundy, T.; Moore, M. A.

    2013-11-01

    The dynamics of two- and five-disk systems confined in a square has been studied using molecular dynamics simulations and compared with the predictions of transition state theory. We determine the partition functions Z and Z‡ of transition state theory using a procedure first used by Salsburg and Wood for the pressure. Our simulations show this procedure and transition state theory are in excellent agreement with the simulations. A generalization of the transition state theory to the case of a large number of disks N is made and shown to be in full agreement with simulations of disks moving in a narrow channel. The same procedure for hard spheres in three dimensions leads to the Vogel-Fulcher-Tammann formula for their alpha relaxation time.

  5. 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.

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

    PubMed

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

    2016-04-21

    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. PMID:27389209

  7. 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.

  8. Edge States in Transitional Pipe Flow

    NASA Astrophysics Data System (ADS)

    Schneider, Tobias M.; Eckhardt, Bruno

    2006-11-01

    We study the boundary of the laminar region near the onset of turbulence. Approaching the boundary from the laminar side, the lifetime of perturbations increases, diverges when the boundary is reached, and varies chaotically for larger amplitudes. In the chaotic region, lifetimes vary sensitively with amplitude, consistent with the strange saddle picture of the turbulence proposed earlier. The trajectory on the edge between the laminar and chaotic regions is asymptotic to a single well defined state, essentially independent of the type of perturbation. The edge then becomes the stable manifold of this structure. In the case of a model shear flow, the edge states are simple or period doubled or chaotic trajectories. In the case of pipe flow the edge state seems to remain close to a state with simple vortical structure. Edge of Chaos in a Parallel Shear Flow, Joseph D. Skufca, James A. Yorke, and Bruno Eckhardt, Phys. Rev. Lett. 96, 174101 (2006)

  9. 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.

  10. Mental health work with Gulf War evacuees: the use of a transitional therapeutic space.

    PubMed

    Benyakar, M; Kretsch, R; Baruch, E

    1994-01-01

    This paper describes the intervention of a mental health team formed during the Persian Gulf War to provide assistance to people evacuated from their homes after they were seriously damaged or destroyed by Iraqi Scud missiles. The intervention was based on the view that a crisis upsets the person's emotional equilibrium, resulting in a new and alien emotional state, which is frightening to the person involved by virtue of its strangeness. The disturbance may result in the development of a frozen, rigid unadaptive internal state, i.e. trauma. The mental health team used the interaction between external and internal realities, within a transitional space which enabled the development of a potential space. PMID:7928296

  11. 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.

  12. Polymorphic phase transitions in systems evolving in a two-dimensional discrete space.

    PubMed

    Gadomski, A

    1999-08-01

    Polymorphic phase transitions in systems evolving in a two-dimensional discrete space have been studied. The driving force of the transitions appears to be a difference between two main energetic contributions: one, related to the thermal activation of the process, and another, being of quantum nature. The former (high temperature limit) is naturally assigned to the expansion (melting) part of the transition, while the latter (low temperature limit) has much in common with the contraction (solidification) part. Between the two main physical states distinguished, there exists a certain state, corresponding to a discontinuity point (pole) in the morphological phase diagram, represented by the well-known Bose-Einstein (Planck) formula, in which the system blows up. This point is related to an expected situation in which the contour of the object under investigation stands for the Brownian or purely diffusional path, with the fractal dimension dw=2, and the situation can be interpreted as some emergence of an intermediate "tetratic" phase. This, in turn, recalls a certain analogy to the equilibrium (order-disorder) phase transition of Kosterlitz-Thouless type, characteristic of, e.g., rough vs rigid interfaces in a two-dimensional space, with some disappearance of interface correlation length at dw=2. Otherwise, the contours of the objects are equivalent to fractional Brownian paths either in superlinear or "turbulent" (dw<2; the expansion case), or sublinear, viz., anomalously slow (dw>2; the contraction case) regimes, respectively. It is hoped that the description offered will serve to reflect properly the main subtleties of the dynamics of the polymorphic transitions in complex "soft-matter" systems, like formation of lipid mesomorphs or diffusional patterns, with nonzero line tension effect. PMID:11969883

  13. 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.

  14. Precritical State Transition Dynamics in the Attractor Landscape of a Molecular Interaction Network Underlying Colorectal Tumorigenesis

    PubMed Central

    Cho, Kwang-Hyun

    2015-01-01

    From the perspective of systems science, tumorigenesis can be hypothesized as a critical transition (an abrupt shift from one state to another) between proliferative and apoptotic attractors on the state space of a molecular interaction network, for which an attractor is defined as a stable state to which all initial states ultimately converge, and the region of convergence is called the basin of attraction. Before the critical transition, a cellular state might transit between the basin of attraction for an apoptotic attractor and that for a proliferative attractor due to the noise induced by the inherent stochasticity in molecular interactions. Such a flickering state transition (state transition between the basins of attraction for alternative attractors from the impact of noise) would become more frequent as the cellular state approaches near the boundary of the basin of attraction, which can increase the variation in the estimate of the respective basin size. To investigate this for colorectal tumorigenesis, we have constructed a stochastic Boolean network model of the molecular interaction network that contains an important set of proteins known to be involved in cancer. In particular, we considered 100 representative sequences of 20 gene mutations that drive colorectal tumorigenesis. We investigated the appearance of cancerous cells by examining the basin size of apoptotic, quiescent, and proliferative attractors along with the sequential accumulation of gene mutations during colorectal tumorigenesis. We introduced a measure to detect the flickering state transition as the variation in the estimate of the basin sizes for three-phenotype attractors from the impact of noise. Interestingly, we found that this measure abruptly increases before a cell becomes cancerous during colorectal tumorigenesis in most of the gene mutation sequences under a certain level of stochastic noise. This suggests that a frequent flickering state transition can be a precritical

  15. 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.

  16. Space and time renormalization in phase transition dynamics

    DOE PAGESBeta

    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 investigatingmore » an exact solution of the transverse field quantum Ising chain in the thermodynamic limit.« less

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

    PubMed Central

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

    2015-01-01

    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. PMID:26254328

  18. 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. PMID:26254328

  19. 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.

  20. 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.

  1. 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.

  2. Transition State Analysis of Thymidine Hydrolysis by Human Thymidine Phosphorylase*

    PubMed Central

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

    2010-01-01

    Human thymidine phosphorylase (hTP) is responsible for thymidine (dT) homeostasis and its action promotes angiogenesis. In the absence of phosphate, hTP catalyzes a slow hydrolytic depyrimidination of dT yielding thymine and 2-deoxyribose (dRib). Its transition state was characterized using multiple kinetic isotope effect (KIE) measurements. Isotopically enriched thymidines were synthesized enzymatically from glucose or (deoxy)ribose and intrinsic KIEs were used to interpret the transition state structure. KIEs from [1′-14C]-, [1-15N]-, [1′-3H]-, [2′R-3H]-, [2′S-3H]-, [4′-3H]-, [5′-3H]dTs provided values of 1.033 ± 0.002, 1.004 ± 0.002, 1.325 ± 0.003, 1.101 ± 0.004, 1.087 ± 0.005, 1.040 ± 0.003, and 1.033 ± 0.003, respectively. Transition state analysis revealed a stepwise mechanism with a 2-deoxyribocation formed early and a higher energetic barrier for nucleophilic attack of a water molecule on the high energy intermediate. An equilibrium exists between the deoxyribocation and reactants prior to the irreversible nucleophilic attack by water. The results establish activation of the thymine leaving group without requirement for phosphate. A transition state constrained to match the intrinsic KIEs was found using density functional theory. An active site histidine (His116) is implicated as the catalytic base for activation of the water nucleophile at the rate-limiting transition state. The distance between the water nucleophile and the anomeric carbon (rC-O) is predicted to be 2.3 Å at the transition state. The transition state model predicts that deoxyribose adopts a mild 3′-endo confirmation during nucleophilic capture. These results differ from the concerted bimolecular mechanism reported for the arsenolytic reaction PMID:20804144

  3. Exploring the Conformational Transitions of Biomolecular Systems Using a Simple Two-State Anisotropic Network Model

    PubMed Central

    Jo, Sunhwan; Bahar, Ivet; Roux, Benoît

    2014-01-01

    Biomolecular conformational transitions are essential to biological functions. Most experimental methods report on the long-lived functional states of biomolecules, but information about the transition pathways between these stable states is generally scarce. Such transitions involve short-lived conformational states that are difficult to detect experimentally. For this reason, computational methods are needed to produce plausible hypothetical transition pathways that can then be probed experimentally. Here we propose a simple and computationally efficient method, called ANMPathway, for constructing a physically reasonable pathway between two endpoints of a conformational transition. We adopt a coarse-grained representation of the protein and construct a two-state potential by combining two elastic network models (ENMs) representative of the experimental structures resolved for the endpoints. The two-state potential has a cusp hypersurface in the configuration space where the energies from both the ENMs are equal. We first search for the minimum energy structure on the cusp hypersurface and then treat it as the transition state. The continuous pathway is subsequently constructed by following the steepest descent energy minimization trajectories starting from the transition state on each side of the cusp hypersurface. Application to several systems of broad biological interest such as adenylate kinase, ATP-driven calcium pump SERCA, leucine transporter and glutamate transporter shows that ANMPathway yields results in good agreement with those from other similar methods and with data obtained from all-atom molecular dynamics simulations, in support of the utility of this simple and efficient approach. Notably the method provides experimentally testable predictions, including the formation of non-native contacts during the transition which we were able to detect in two of the systems we studied. An open-access web server has been created to deliver ANMPathway results

  4. A Markovian state-space framework for integrating flexibility into space system design decisions

    NASA Astrophysics Data System (ADS)

    Lafleur, Jarret M.

    The past decades have seen the state of the art in aerospace system design progress from a scope of simple optimization to one including robustness, with the objective of permitting a single system to perform well even in off-nominal future environments. Integrating flexibility, or the capability to easily modify a system after it has been fielded in response to changing environments, into system design represents a further step forward. One challenge in accomplishing this rests in that the decision-maker must consider not only the present system design decision, but also sequential future design and operation decisions. Despite extensive interest in the topic, the state of the art in designing flexibility into aerospace systems, and particularly space systems, tends to be limited to analyses that are qualitative, deterministic, single-objective, and/or limited to consider a single future time period. To address these gaps, this thesis develops a stochastic, multi-objective, and multi-period framework for integrating flexibility into space system design decisions. Central to the framework are five steps. First, system configuration options are identified and costs of switching from one configuration to another are compiled into a cost transition matrix. Second, probabilities that demand on the system will transition from one mission to another are compiled into a mission demand Markov chain. Third, one performance matrix for each design objective is populated to describe how well the identified system configurations perform in each of the identified mission demand environments. The fourth step employs multi-period decision analysis techniques, including Markov decision processes from the field of operations research, to find efficient paths and policies a decision-maker may follow. The final step examines the implications of these paths and policies for the primary goal of informing initial system selection. Overall, this thesis unifies state-centric concepts of

  5. Kinetic transitions in diffusion-reaction space. II. Geometrical effects

    NASA Astrophysics Data System (ADS)

    Kozak, John J.

    1999-02-01

    We extend the stochastic master equation approach described earlier [J. J. Kozak and R. Davidson, J. Chem. Phys. 101, 6101 (1994)] to examine the influence on reaction efficiency of multipolar correlations between a fixed target molecule and a diffusing coreactant, the latter constrained to move on the surface of a host medium (e.g., a colloidal catalyst or molecular organizate) modeled as a Cartesian shell [Euler characteristic, χ=2]. Our most comprehensive results are for processes involving ion pairs, and we find that there exists a transition between two qualitatively different types of behavior in diffusion-reaction space, viz., a regime where the coreactant's motion is totally correlated with respect to the target ion, and a regime where the coreactant's motion is effectively uncorrelated. This behavior emerges both in the situation where correlations between the ion pair are strictly confined to the surface of the host medium or where correlations can be propagated through the host medium. The effects of system size are also examined and comparisons with diffusion-reaction processes taking place on surfaces characterized by Euler characteristic χ=0 are made. In all cases studied, the most dramatic effects on the reaction efficiency are uncovered in the regime where the Onsager (thermalization) length is comparable to the mean displacement of the coreactant, a conclusion consistent with results reported in earlier work.

  6. Strain glass state as the boundary of two phase transitions.

    PubMed

    Zhou, Zhijian; Cui, Jian; Ren, Xiaobing

    2015-01-01

    A strain glass state was found to be located between B2-B19' (cubic to monoclinic) phase transition and B2-R (cubic to rhombohedral) phase transition in Ti49Ni51 alloys after aging process. After a short time aging, strong strain glass transition was observed, because the size of the precipitates is small, which means the strain field induced by the precipitates is isotropic and point-defect-like, and the distribution of the precipitates is random. After a long time aging, the average size of the precipitates increases. The strong strain field induced by the precipitates around them forces the symmetry of the matrix materials to conform to the symmetry of the crystalline structure of the precipitates, which results in the new phase transition. The experiment shows that there exists no well-defined boundary in the evolution from the strain glass transition to the new phase transition. Due to its generality, this glass mediated phase transition divergence scheme can be applied to other proper material systems to induce a more important new phase transition path, which can be useful in the field of phase transition engineering. PMID:26307500

  7. Strain glass state as the boundary of two phase transitions

    NASA Astrophysics Data System (ADS)

    Zhou, Zhijian; Cui, Jian; Ren, Xiaobing

    2015-08-01

    A strain glass state was found to be located between B2-B19’ (cubic to monoclinic) phase transition and B2-R (cubic to rhombohedral) phase transition in Ti49Ni51 alloys after aging process. After a short time aging, strong strain glass transition was observed, because the size of the precipitates is small, which means the strain field induced by the precipitates is isotropic and point-defect-like, and the distribution of the precipitates is random. After a long time aging, the average size of the precipitates increases. The strong strain field induced by the precipitates around them forces the symmetry of the matrix materials to conform to the symmetry of the crystalline structure of the precipitates, which results in the new phase transition. The experiment shows that there exists no well-defined boundary in the evolution from the strain glass transition to the new phase transition. Due to its generality, this glass mediated phase transition divergence scheme can be applied to other proper material systems to induce a more important new phase transition path, which can be useful in the field of phase transition engineering.

  8. 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

  9. 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

  10. Resilience-based application of state-and-transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We recommend that several conceptual modifications be incorporated into the state-and-transition model (STM) framework to: 1) explicitly link this framework to the concept of ecological resilience, 2) direct management attention away from thresholds and toward the maintenance of state resilience, an...

  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. PMID:26613942

  12. 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.

  13. Glycosidase inhibition: assessing mimicry of the transition state

    PubMed Central

    2010-01-01

    Glycoside hydrolases, the enzymes responsible for hydrolysis of the glycosidic bond in di-, oligo- and polysaccharides, and glycoconjugates, are ubiquitous in Nature and fundamental to existence. The extreme stability of the glycosidic bond has meant these enzymes have evolved into highly proficient catalysts, with an estimated 1017 fold rate enhancement over the uncatalysed reaction. Such rate enhancements mean that enzymes bind the substrate at the transition state with extraordinary affinity; the dissociation constant for the transition state is predicted to be 10–22 M. Inhibition of glycoside hydrolases has widespread application in the treatment of viral infections, such as influenza and HIV, lysosomal storage disorders, cancer and diabetes. If inhibitors are designed to mimic the transition state, it should be possible to harness some of the transition state affinity, resulting in highly potent and specific drugs. Here we examine a number of glycosidase inhibitors which have been developed over the past half century, either by Nature or synthetically by man. A number of criteria have been proposed to ascertain which of these inhibitors are true transition state mimics, but these features have only be critically investigated in a very few cases. PMID:20066263

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

    DOE PAGESBeta

    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 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

  15. 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…

  16. 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.

  17. 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.

  18. Analysis of slow transitions between nonequilibrium steady states

    NASA Astrophysics Data System (ADS)

    Mandal, Dibyendu; Jarzynski, Christopher

    2016-06-01

    Transitions between nonequilibrium steady states obey a generalized Clausius inequality, which becomes an equality in the quasistatic limit. For slow but finite transitions, we show that the behavior of the system is described by a response matrix whose elements are given by a far-from-equilibrium Green–Kubo formula, involving the decay of correlations evaluated in the nonequilibrium steady state. This result leads to a fluctuation-dissipation relation between the mean and variance of the nonadiabatic entropy production, Δ {{s}\\text{na}} . Furthermore, our results extend—to nonequilibrium steady states—the thermodynamic metric structure introduced by Sivak and Crooks for analyzing minimal-dissipation protocols for transitions between equilibrium states.

  19. 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

  20. 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.

  1. 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).

  2. 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.

  3. 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).

  4. 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.

  5. Transition paths of Met-enkephalin from Markov state modeling of a molecular dynamics trajectory.

    PubMed

    Banerjee, Rahul; Cukier, Robert I

    2014-03-20

    Conformational states and their interconversion pathways of the zwitterionic form of the pentapeptide Met-enkephalin (MetEnk) are identified. An explicit solvent molecular dynamics (MD) trajectory is used to construct a Markov state model (MSM) based on dihedral space clustering of the trajectory, and transition path theory (TPT) is applied to identify pathways between open and closed conformers. In the MD trajectory, only four of the eight backbone dihedrals exhibit bistable behavior. Defining a conformer as the string XXXX with X = "+" or "-" denoting, respectively, positive or negative values of a given dihedral angle and obtaining the populations of these conformers shows that only four conformers are highly populated, implying a strong correlation among these dihedrals. Clustering in dihedral space to construct the MSM finds the same four bistable dihedral angles. These state populations are very similar to those found directly from the MD trajectory. TPT is used to obtain pathways, parametrized by committor values, in dihedral state space that are followed in transitioning from closed to open states. Pathway costs are estimated by introducing a kinetics-based procedure that orders pathways from least (shortest) to greater cost paths. The least costly pathways in dihedral space are found to only involve the same XXXX set of dihedral angles, and the conformers accessed in the closed to open transition pathways are identified. For these major pathways, a correlation between reaction path progress (committors) and the end-to-end distance is identified. A dihedral space principal component analysis of the MD trajectory shows that the first three modes capture most of the overall fluctuation, and pick out the same four dihedrals having essentially all the weight in those modes. A MSM based on root-mean-square backbone clustering was also carried out, with good agreement found with dihedral clustering for the static information, but with results that differ

  6. Leading the Transition from Classrooms to Learning Spaces

    ERIC Educational Resources Information Center

    Oblinger, Diana

    2005-01-01

    A number of factors are prompting higher education's interest in learning spaces: the need to renovate existing space or accommodate additional students, pedagogical advances, a better understanding of learners, and, in some cases, curricular reform. Moving from classrooms to learning spaces involves a conceptual shift as well as a commitment to…

  7. Catching Up on State Transitions in Cygnus X-1

    NASA Technical Reports Server (NTRS)

    Boeck, Moritz; Hanke, Manfred; Wilms, Joern; Pirner, Stefan; Grinberg, Victoria; Markoff, Sera; Pottschmidt, Katja; Nowak, Michael A.; Pooley, Guy

    2008-01-01

    In 2005 February we observed Cygnus X-1 over a period of 10 days quasi-continuously with the Rossi X-ray Timing Explorer and the Ryle telescope. We present the results of the spectral and timing analysis on a timescale of 90 min and show that the behavior of Cyg X-1 is similar to that found during our years long monitoring campaign. As a highlight we present evidence for a full transition from the hard to the soft state that happened during less than three hours. The observation provided a more complete picture of a state transition than before, especially concerning the evolution of the time lags, due to unique transition coverage and analysis with high time resolution.

  8. 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.

  9. The State-of-the-art in Space Robotics

    NASA Astrophysics Data System (ADS)

    da Fonseca, Ijar M.; Pontuschka, Maurício N.

    2015-10-01

    This paper deals with the space robotics and associate space applications. An overview of the space era and the robotic space probes is presented to contextualize the space robotics in the space exploration scenario. Concepts, classification and key-questions associated with robotics for space applications are presented and discussed. Safety-critical aspects of the space robotics are discussed as well the human limitation to operate in the hostile space environment and long time duration missions. The paper also focuses on the state-of-the- art of robotics for the International Space Station EVA operations, for the planetary exploration such as the ongoing Mars exploration, Hayabusa rendezvous and landing in asteroids and the robotic probe Rosetta landed in a comet recently. The paper also includes a discussion of the applications of new concepts like the robonauts, the space tugs applications and robots for future planetary exploration.

  10. 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.

  11. Cosmic evolution from phase transition of three-dimensional flat space.

    PubMed

    Bagchi, Arjun; Detournay, Stephane; Grumiller, Daniel; Simón, Joan

    2013-11-01

    Flat space cosmology spacetimes are exact time-dependent solutions of three-dimensional gravity theories, such as Einstein gravity or topologically massive gravity. We exhibit a novel kind of phase transition between these cosmological spacetimes and the Minkowski vacuum. At sufficiently high temperature, (rotating) hot flat space tunnels into a universe described by flat space cosmology. PMID:24237503

  12. Storing excitons in transition-metal dichalcogenides using dark states

    NASA Astrophysics Data System (ADS)

    Gunlycke, Daniel; Tseng, Frank; Simsek, Ergun

    Monolayer transition-metal dichalcogenides exhibit strongly bound excitons confined to two dimensions. One challenge in exploiting these excitons is that they have a finite life time and collapse through electron-hole recombination. We propose that the exciton life time could be extended by transitioning the exciton population into dark states. The symmetry of these dark states require the electron and hole to be spatially separated, which not only causes these states to be optically inactive but also inhibits electron-hole recombination. Based on an atomistic model we call the Triangular Lattice Exciton (3ALE) model, we derive transition matrix elements and approximate selection rules showing that excitons could be transitioned into and out of dark states using a pulsed infrared laser. For illustration, we also present exciton population scenarios based on different recombination decay constants. Longer exciton lifetimes could make these materials candidates for applications in energy management and quantum information processing. This work was supported by the Office of Naval Research, directly and through the Naval Research Laboratory.

  13. 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 ...

  14. Absorbing-state phase transitions with extremal dynamics

    NASA Astrophysics Data System (ADS)

    Dickman, Ronald; Garcia, Guilherme J. M.

    2005-06-01

    Extremal dynamics represents a path to self-organized criticality in which the order parameter is tuned to a value of zero. The order parameter is associated with a phase transition to an absorbing state. Given a process that exhibits a phase transition to an absorbing state, we define an “extremal absorbing” process, providing the link to the associated extremal (nonabsorbing) process. Stationary properties of the latter correspond to those at the absorbing-state phase transition in the former. Studying the absorbing version of an extremal dynamics model allows to determine certain critical exponents that are not otherwise accessible. In the case of the Bak-Sneppen (BS) model, the absorbing version is closely related to the “ f -avalanche” introduced by Paczuski, Maslov, and Bak [Phys. Rev. E 53, 414 (1996)], or, in spreading simulations to the “BS branching process” also studied by these authors. The corresponding nonextremal process belongs to the directed percolation universality class. We revisit the absorbing BS model, obtaining refined estimates for the threshold and critical exponents in one dimension. We also study an extremal version of the usual contact process, using mean-field theory and simulation. The extremal condition slows the spread of activity and modifies the critical behavior radically, defining an “extremal directed percolation” universality class of absorbing-state phase transitions. Asymmetric updating is a relevant perturbation for this class, even though it is irrelevant for the corresponding nonextremal class.

  15. 40 CFR 70.4 - State program submittals and transition.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 15 2010-07-01 2010-07-01 false State program submittals and transition. 70.4 Section 70.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR..., including authority to carry out each of the following: (i) Issue permits and assure compliance with...

  16. 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...

  17. Spatially-explicit representation of state-and-transition models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The broad-scale assessment of natural resource conditions (e.g., rangeland health, restoration needs) requires knowledge of their spatial distribution. We argue that creating a database that links state-and-transition models (STMs) to spatial units is a valuable management tool for structuring groun...

  18. State Accountability in the Transition to Common Core. Updated

    ERIC Educational Resources Information Center

    Sears, Victoria

    2014-01-01

    The Common Core is at a critical juncture. While many surveys show that support for the standards themselves remains strong, implementation has not been without major challenges. "State Accountability in the Transition to Common Core," a new policy brief from the Thomas B. Fordham Institute, provides cautionary advice about what key…

  19. 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

  20. State-space size considerations for disease-progression models.

    PubMed

    Regnier, Eva D; Shechter, Steven M

    2013-09-30

    Markov models of disease progression are widely used to model transitions in patients' health state over time. Usually, patients' health status may be classified according to a set of ordered health states. Modelers lump together similar health states into a finite and usually small, number of health states that form the basis of a Markov chain disease-progression model. This increases the number of observations used to estimate each parameter in the transition probability matrix. However, lumping together observably distinct health states also obscures distinctions among them and may reduce the predictive power of the model. Moreover, as we demonstrate, precision in estimating the model parameters does not necessarily improve as the number of states in the model declines. This paper explores the tradeoff between lumping error introduced by grouping distinct health states and sampling error that arises when there are insufficient patient data to precisely estimate the transition probability matrix. PMID:23609629

  1. Specificity in Transition State Binding: The Pauling Model Revisited

    PubMed Central

    Amyes, Tina L.; Richard, John P.

    2013-01-01

    Linus Pauling proposed that the large rate accelerations for enzymes are due to the high specificity of the protein catalyst for binding the reaction transition state. The observation that stable analogs of the transition states for enzymatic reactions often act as tight-binding binding inhibitors provided early support for this simple and elegant proposal. We review experimental results which 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 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-CoA:3-oxoacid coenzyme A transferase (SCOT) and the nonreacting portions of CoA are responsible for a rate increase of 3 × 1012-fold, which is close to the estimated total 5 × 1013-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 a ca. 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 state complex compared

  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. 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

    2015-12-01

    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 primarily

  4. Using Brain Imaging to Track Problem Solving in a Complex State Space

    PubMed Central

    Anderson, John R.; Fincham, Jon M.; Schneider, Darryl W.; Yang, Jian

    2011-01-01

    This paper describes how behavioral and imaging data can be combined with a Hidden Markov Model (HMM) to track participants’ trajectories through a complex state space. Participants completed a problem-solving variant of a memory game that involved 625 distinct states, 24 operators, and an astronomical number of paths through the state space. Three sources of information were used for classification purposes. First, an Imperfect Memory Model was used to estimate transition probabilities for the HMM. Second, behavioral data provided information about the timing of different events. Third, multivoxel pattern analysis of the imaging data was used to identify features of the operators. By combining the three sources of information, an HMM algorithm was able to efficiently identify the most probable path that participants took through the state space, achieving over 80% accuracy. These results support the approach as a general methodology for tracking mental states that occur during individual problem-solving episodes. PMID:22209783

  5. 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.

  6. State transitions in geomorphic responses to environmental change

    NASA Astrophysics Data System (ADS)

    Phillips, Jonathan D.

    2014-01-01

    The fundamental geomorphic responses to environmental change are qualitative changes in system states. This study is concerned with the complexity of state transition models (STM), and synchronization. The latter includes literal and inferential synchronization, the extent to which observations or relationships at one time period can be applied to others. Complexity concerns the extent to which STM structure may tend to amplify effects of change. Three metrics-spectral radius, Laplacian spectral radius, and algebraic connectivity-were applied to several generic geomorphic STMs, and to three real-world examples: the San Antonio River delta, soil transitions in a coastal plain agricultural landscape, and high-latitude thermokarst systems. While the Laplacian spectral radius was of limited use, spectral radius and algebraic complexity provide significant, independent information. The former is more sensitive to the intensity of cycles within the transition graph structure, and to the overall complexity of the STM. Spectral radius is an effective general index of graph complexity, and especially the likelihood of amplification and intensification of changes in environmental boundary conditions, or of the propagation of local disturbances within the system. The spectral radius analyses here illustrate that more information does not necessarily decrease uncertainty, as increased information often results in the expansion of state transition networks from simpler linear sequential and cyclic to more complex structures. Algebraic connectivity applied to landscape-scale STMs provides a measure of the likelihood of complex response, with synchronization inversely related to complex response.

  7. 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.

  8. Isotopic mapping of transition-state structural features associated with enzymic catalysis of methyl transfer

    SciTech Connect

    Rodgers, J.; Femec, D.A.; Schowen, R.L.

    1982-06-16

    For comparison of the molecular structures of nonenzymic and enzymic sulfur-to-oxygen transmethylation transition states by the use of kinetic isotope effects, a series of isotopic maps is produced. In these, contours of constant isotope effect are displayed vs. the Pauling bond orders B/sub CS/ and B/sub CO/, for the carbon-sulfur and carbon-oxygen bonds, respectively, taken as independent variables to describe the transition states. Maps are calculated by the BEBOVIB approach for k(CH/sub 3/)/k(CD/sub 3/), k(/sup 12/CH/sub 3/)/k(/sup 13/CH/sub 3/), k(/sup 16/O)/k(/sup 18/O), and k(/sup 32/S)/k(/sup 34/S), with two models for the reaction coordinate, two force-field assumptions, and four temperatures. Nonenzymic isotope effects and isotope effects for catechol-O-methyltransferase action are then used to construct figures on the CH/sub 3//CD/sub 3/ and /sup 12/CH/sub 3///sup 13/CH/sub 3/ maps which correspond to allowed spaces of transition-states structures. Superposition of the figures yields the spaces of transition-state structures simultaneously consistent with both hydrogen and carbon isotope effects. It is concluded that the enzyme compresses the S/sub N/2 transition state and that the compression of the C-O and C-S bonds may well be of the order of 0.15 A per bond and could conceivably be more than twice as large.

  9. 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

  10. State Directors of Special Education Transition Programs: State Definitions, and Real and Ideal Teacher Competencies.

    ERIC Educational Resources Information Center

    Beard, John; And Others

    This study surveys states' mandates, definitions, and components of transition programs that assist disabled students in successfully moving to the community environment. Among the 60 state-level directors of special education surveyed, 34 state and 4 territorial directors responded to the questionnaire comprised of 8 questions, and nominated 230…

  11. Adaptive importance sampling of random walks on continuous state spaces

    SciTech Connect

    Baggerly, K.; Cox, D.; Picard, R.

    1998-11-01

    The authors consider adaptive importance sampling for a random walk with scoring in a general state space. Conditions under which exponential convergence occurs to the zero-variance solution are reviewed. These results generalize previous work for finite, discrete state spaces in Kollman (1993) and in Kollman, Baggerly, Cox, and Picard (1996). This paper is intended for nonstatisticians and includes considerable explanatory material.

  12. Driving transitions between quantized flow states in an atomtronic circuit

    NASA Astrophysics Data System (ADS)

    Eckel, Stephen

    Superfluidity, or flow without resistance, is a macroscopic quantum effect that is present in a multitude of systems, including liquid helium, superconductors, and ultra-cold atomic gases. In superconductors, flow without resistance has led to the development of a number of useful devices. Here, I will present our work studying a superfluid analog to the rf-superconducting interference device (SQUID). Our atomtronic analog is formed in a ring-shaped Bose-Einstein condensate (BEC) of sodium atoms. Ring condensates are unique in that they can support persistent currents that are quantized. We drive transitions between persistent current states using a rotating perturbation, or weak link. Here, rotation acts as the analog to magnetic field in superconductors. In our system, a current (as viewed in the frame co-rotating with the perturbation) develops to oppose any change in rotation. If the rotation rate is sufficiently large, the critical current of the superfluid is exceeded in the weak link region, causing a transition to a state of larger persistent current. The strength of the perturbation tunes the critical rotation rates. Like the rf-SQUID, the transitions show hysteresis - rotation rates that increase the quantized current are different from those that decrease the current. The size of the hysteresis loop allows us to explore the microscopic mechanisms responsible for the transitions. In a more recent experiment, we have observed the time it takes for the first persistent current state to decay in the presence of a stationary perturbation. The measured timescales depend strongly on temperature, but in a way that suggests that other physical effects, like quantum coherence, could also play a role in the transitions between current states.

  13. 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.

  14. 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.

  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. PMID:19518178

  16. Transitional flow in thin tubes for space station freedom radiator

    NASA Technical Reports Server (NTRS)

    Loney, Patrick; Ibrahim, Mounir

    1995-01-01

    A two dimensional finite volume method is used to predict the film coefficients in the transitional flow region (laminar or turbulent) for the radiator panel tubes. The code used to perform this analysis is CAST (Computer Aided Simulation of Turbulent Flows). The information gathered from this code is then used to augment a Sinda85 model that predicts overall performance of the radiator. A final comparison is drawn between the results generated with a Sinda85 model using the Sinda85 provided transition region heat transfer correlations and the Sinda85 model using the CAST generated data.

  17. Federal and state benefits for transition age youth.

    PubMed

    Altman, Stephanie; O'Connor, Sarah; Anapolsky, Ellyce; Sexton, Laura

    2014-01-01

    While all children face challenges as they become adults, children with chronic medical conditions or disabilities face unique barriers in their transition to adulthood. Children, especially those who are low income and have special needs, are eligible for a range of supports including income supports, health care coverage, vocational and educational supports. These supports are critical to sound health because they ensure access to necessary medical services, while also offsetting the social determinants that negatively affect health. Unfortunately, as children transition into adulthood, eligibility for these benefits can change abruptly or even end entirely. If medical providers have a better understanding of five transition key dates, they can positively impact their patients' health by ensuring continuous coverage through the transition to adulthood. The key dates are as follows: (1) transition services for students with an Individualized Education Program (IEP) must begin by age 16 (in some states such as Illinois, these services must be in place by age 14 1/2); (2) at age 18, eligibility for income supports may change; (3) at age 19, eligibility for Medicaid may change; (4) at graduation, eligibility for educational supports will end unless steps are taken to extend those benefits until age 22; and (5) when individuals prepare to enter the workforce, they will become eligible for vocational rehabilitation services. With an understanding of these key transition dates and how to partner with social services and advocacy organizations on behalf of their patients, medical providers can help to ensure that transition-age patients retain the holistic social services and supports they need to protect their health. PMID:24919940

  18. A transition in brain state during propofol-induced unconsciousness.

    PubMed

    Mukamel, Eran A; Pirondini, Elvira; Babadi, Behtash; Wong, Kin Foon Kevin; Pierce, Eric T; Harrell, P Grace; Walsh, John L; Salazar-Gomez, Andres F; Cash, Sydney S; Eskandar, Emad N; Weiner, Veronica S; Brown, Emery N; Purdon, Patrick L

    2014-01-15

    Rhythmic oscillations shape cortical dynamics during active behavior, sleep, and general anesthesia. Cross-frequency phase-amplitude coupling is a prominent feature of cortical oscillations, but its role in organizing conscious and unconscious brain states is poorly understood. Using high-density EEG and intracranial electrocorticography during gradual induction of propofol general anesthesia in humans, we discovered a rapid drug-induced transition between distinct states with opposite phase-amplitude coupling and different cortical source distributions. One state occurs during unconsciousness and may be similar to sleep slow oscillations. A second state occurs at the loss or recovery of consciousness and resembles an enhanced slow cortical potential. These results provide objective electrophysiological landmarks of distinct unconscious brain states, and could be used to help improve EEG-based monitoring for general anesthesia. PMID:24431442

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

    NASA Astrophysics Data System (ADS)

    Minaev, Y. A.

    2015-03-01

    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 TS0 (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 TSf of any metal, which value lies in the range of (0.55…0.86) TS0. 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.

  20. 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.

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

    PubMed

    Meyer, Robert E

    2015-01-01

    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

  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. PMID:27367395

  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. Transition state geometry in radical hydrogen atom abstraction

    NASA Astrophysics Data System (ADS)

    Denisov, Evgenii T.; Shestakov, Alexander F.; Denisova, Taisa G.

    2012-12-01

    The interatomic distances in the transition states of radical hydrogen atom abstraction reactions X•+HY → XH+Y• determined by quantum chemical calculations are systematized and generalized. It is shown that depending on the reaction centre structure, these reactions can be subdivided into classes with the same X...Y interatomic distance in each class. The transition state geometries found by the methods of intersecting parabolas and intersecting Morse curves are also presented. The X...H...Y fragments are almost linear, the hydrogen atom position being determined by the reaction enthalpy. The effects of triplet repulsion, electronegativities and radii of X and Y atoms, the presence of adjoining π-bonds, and steric effects on the X...Y interatomic distances are analyzed and characterized. The bibliography includes 62 references.

  5. 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

  6. Classical codes in quantum state space

    NASA Astrophysics Data System (ADS)

    Howard, Mark

    2015-12-01

    We present a construction of Hermitian operators and quantum states labelled by strings from a finite field. The distance between these operators or states is then simply related (typically, proportional) to the Hamming distance between their corresponding strings. This allows a straightforward application of classical coding theory to find arrangements of operators or states with a given distance distribution. Using the simplex or extended Reed-Solomon code in our construction recovers the discrete Wigner function, which has important applications in quantum information theory.

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

    PubMed

    Zimmerman, Paul

    2013-07-01

    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. PMID:26583985

  8. Fish reintroductions reveal smooth transitions between lake community states.

    PubMed

    Mittelbach, Gary G; Garcia, Erica A; Taniguchi, Yoshinori

    2006-02-01

    Whether communities respond smoothly or discontinuously to changing environmental conditions has important consequences for the preservation and restoration of ecosystems. Theory shows that communities may exhibit a variety of responses to environmental change, including abrupt transitions due to the existence of alternate states. However, there have been few opportunities to look for such transitions in nature. Here, we examine the impact of a two-orders-of-magnitude decrease and then increase in planktivore abundance in Wintergreen lake (Michigan, USA), caused by the extinction and reintroduction of two dominant fish species (largemouth bass, Micropterus salmoides, and bluegill, Lepomis macrochirus). Over a 16 + yr period of slow change from high planktivory to low planktivory back to high planktivory, the zooplankton community changed smoothly and predictably between states. In years of low planktivory, the zooplankton assemblage was dominated by a single, large, cladoceran species, Daphnia pulicaria, whereas in years of high planktivory, D. pulicaria disappeared and was replaced by a suite of small-bodied cladocerans. We quantified the multivariate change in zooplankton community dissimilarity and found that community state smoothly tracked changes in planktivore density in both a forward and backward direction. Thus, there was little evidence of discontinuity in this system where transitions are strongly driven by planktivory. PMID:16637356

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Inherent structure versus geometric metric for state space discretization.

    PubMed

    Liu, Hanzhong; Li, Minghai; Fan, Jue; Huo, Shuanghong

    2016-05-30

    Inherent structure (IS) and geometry-based clustering methods are commonly used for analyzing molecular dynamics trajectories. ISs are obtained by minimizing the sampled conformations into local minima on potential/effective energy surface. The conformations that are minimized into the same energy basin belong to one cluster. We investigate the influence of the applications of these two methods of trajectory decomposition on our understanding of the thermodynamics and kinetics of alanine tetrapeptide. We find that at the microcluster level, the IS approach and root-mean-square deviation (RMSD)-based clustering method give totally different results. Depending on the local features of energy landscape, the conformations with close RMSDs can be minimized into different minima, while the conformations with large RMSDs could be minimized into the same basin. However, the relaxation timescales calculated based on the transition matrices built from the microclusters are similar. The discrepancy at the microcluster level leads to different macroclusters. Although the dynamic models established through both clustering methods are validated approximately Markovian, the IS approach seems to give a meaningful state space discretization at the macrocluster level in terms of conformational features and kinetics. © 2016 Wiley Periodicals, Inc. PMID:26915811

  11. Coherent States of Quantum Free Particle on the Spherical Space

    NASA Astrophysics Data System (ADS)

    Dehdashti, Shahram; Roknizadeh, Rasoul; Mahdifar, Ali; Chen, Hongsheng

    2016-01-01

    In this paper, we study the quantum free particle on the spherical space by applying da costa approach for quantum particle on the curved space. We obtain the discrete energy eigenvalues and associated normalized eigenfunctions of the free particle on the sphere. In addition, we introduce the Gazeau-Klauder coherent states of free particle on the sphere. Then, the Gaussian coherent states is defined, which is used to describe the localized particle on the spherical space. Finally, we study the relation between the f-deformed coherent states and Gazeau-Klauder ones for this system.

  12. 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.

  13. 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.

  14. Third Space Strategists: International Students Negotiating the Transition from Pathway Program to Postgraduate Coursework Degree

    ERIC Educational Resources Information Center

    Benzie, Helen

    2015-01-01

    Pathway programs exist to prepare students for progression into university degrees but the transition experience for many students may not be as smooth as is suggested by the notion of the pathway. While attending a pathway program and at the beginning of their university degree, students may be in a third space, a liminal space where they engage…

  15. 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…

  16. 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…

  17. 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.

  18. On infinite-dimensional state spaces

    SciTech Connect

    Fritz, Tobias

    2013-05-15

    It is well known that the canonical commutation relation [x, p]=i can be realized only on an infinite-dimensional Hilbert space. While any finite set of experimental data can also be explained in terms of a finite-dimensional Hilbert space by approximating the commutation relation, Occam's razor prefers the infinite-dimensional model in which [x, p]=i holds on the nose. This reasoning one will necessarily have to make in any approach which tries to detect the infinite-dimensionality. One drawback of using the canonical commutation relation for this purpose is that it has unclear operational meaning. Here, we identify an operationally well-defined context from which an analogous conclusion can be drawn: if two unitary transformations U, V on a quantum system satisfy the relation V{sup -1}U{sup 2}V=U{sup 3}, then finite-dimensionality entails the relation UV{sup -1}UV=V{sup -1}UVU; this implication strongly fails in some infinite-dimensional realizations. This is a result from combinatorial group theory for which we give a new proof. This proof adapts to the consideration of cases where the assumed relation V{sup -1}U{sup 2}V=U{sup 3} holds only up to {epsilon} and then yields a lower bound on the dimension.

  19. On infinite-dimensional state spaces

    NASA Astrophysics Data System (ADS)

    Fritz, Tobias

    2013-05-01

    It is well known that the canonical commutation relation [x, p] = i can be realized only on an infinite-dimensional Hilbert space. While any finite set of experimental data can also be explained in terms of a finite-dimensional Hilbert space by approximating the commutation relation, Occam's razor prefers the infinite-dimensional model in which [x, p] = i holds on the nose. This reasoning one will necessarily have to make in any approach which tries to detect the infinite-dimensionality. One drawback of using the canonical commutation relation for this purpose is that it has unclear operational meaning. Here, we identify an operationally well-defined context from which an analogous conclusion can be drawn: if two unitary transformations U, V on a quantum system satisfy the relation V-1U2V = U3, then finite-dimensionality entails the relation UV-1UV = V-1UVU; this implication strongly fails in some infinite-dimensional realizations. This is a result from combinatorial group theory for which we give a new proof. This proof adapts to the consideration of cases where the assumed relation V-1U2V = U3 holds only up to ɛ and then yields a lower bound on the dimension.

  20. Solid state neutron dosimeter for space applications

    NASA Astrophysics Data System (ADS)

    Entine, Gerald; Nagargar, Vivek; Sharif, Daud

    1990-08-01

    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.

  1. 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.…

  2. 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.

  3. 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.

  4. 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.

  5. 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.

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

    PubMed

    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. PMID:26551825

  7. Planar homotropenylium cation: a transition state with reversed aromaticity.

    PubMed

    Gibson, Christopher M; Havenith, Remco W A; Fowler, Patrick W; Jenneskens, Leonardus W

    2015-02-01

    In contrast to the equilibrium structure of the homoaromatic C(s) homotropenylium cation, C8H9(+) (1), which supports a pinched diatropic ring current, the C(2v) transition state (2) for inversion of the methylene bridge of 1 is antiaromatic and supports a two-lobe paratropic π current, as detected by plotting B3LYP/6-31G** ipsocentric current maps. Participation of the bridge CH bonds is crucial for the change in global character of the current in the transition state, as shown by the quenching of its paratropicity on substitution of H by F. Orbital-based arguments allow rationalization of this transition between homoaromaticity and hyper(conjugative) antiaromaticity. More generally, the hyperconjugative ring current in a family of C(2v) planar-constrained geometries of (CR2)C(N-1)H(N-1)(q) homoannulenes (R = H, F) can be switched from paratropic (antiaromatic) to diatropic (aromatic) by variation of ring size, charge, and bridge substituent. An orbital-based counting rule accounts for these systematic trends. PMID:25526524

  8. Anisotropic Magnetoresistance State Space of Permalloy Nanowires with Domain Wall Pinning Geometry

    PubMed Central

    Corte-León, Héctor; Nabaei, Vahid; Manzin, Alessandra; Fletcher, Jonathan; Krzysteczko, Patryk; Schumacher, Hans W.; Kazakova, Olga

    2014-01-01

    The domain wall-related change in the anisotropic magnetoresistance in L-shaped permalloy nanowires is measured as a function of the magnitude and orientation of the applied magnetic field. The magnetoresistance curves, compiled into so-called domain wall magnetoresistance state space maps, are used to identify highly reproducible transitions between domain states. Magnetic force microscopy and micromagnetic modelling are correlated with the transport measurements of the devices in order to identify different magnetization states. Analysis allows to determine the optimal working parameters for specific devices, such as the minimal field required to switch magnetization or the most appropriate angle for maximal separation of the pinning/depinning fields. Moreover, the complete state space maps can be used to predict evolution of nanodevices in magnetic field without a need of additional electrical measurements and for repayable initialization of magnetic sensors into a well-specified state. PMID:25116470

  9. 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.

  10. Mechanical properties of 4d transition metals in molten state

    NASA Astrophysics Data System (ADS)

    Singh, Deobrat; Sonvane, Yogesh; Thakor, P. B.

    2016-05-01

    Mechanical properties of 4d transition metals in molten state have been studied in the present study. We have calculated mechanical properties such as isothermal bulk modulus (B), modulus of rigidity (G), Young's modulus (Y) and Hardness have also been calculated from the elastic part of the Phonon dispersion curve (PDC). To describe the structural information, we have used different structure factor S(q) using Percus-Yevick hard sphere (PYHS) reference systems along with our newly constructed parameter free model potential.To see the influence of exchange and correlation effect on the above said properties of 3d liquid transition metals, we have used Sarkar et al (S)local field correction functions. Present results have been found good in agreement with available experimental data.

  11. 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.

  12. 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.

  13. Control of State Transitions in Complex and Biophysical Networks

    NASA Astrophysics Data System (ADS)

    Motter, Adilson; Wells, Daniel; Kath, William

    Noise is a fundamental part of intracellular processes. While the response of biological systems to noise has been studied extensively, there has been limited understanding of how to exploit it to induce a desired cell state. Here I will present a scalable, quantitative method based on the Freidlin-Wentzell action to predict and control noise-induced switching between different states in genetic networks that, conveniently, can also control transitions between stable states in the absence of noise. I will discuss applications of this methodology to predict control interventions that can induce lineage changes and to identify new candidate strategies for cancer therapy. This framework offers a systems approach to identifying the key factors for rationally manipulating network dynamics, and should also find use in controlling other classes of complex networks exhibiting multi-stability. Reference: D. K. Wells, W. L. Kath, and A. E. Motter, Phys. Rev. X 5, 031036 (2015). Work funded by CBC, NCI, NIGMS, and NSF.

  14. Virtual states introduced for overcoming entropic barriers in conformational space

    PubMed Central

    Higo, Junichi; Nakamura, Haruki

    2012-01-01

    Free-energy landscape is an important quantity to study large-scale motions of a biomolecular system because it maps possible pathways for the motions. When the landscape consists of thermodynamically stable states (low-energy basins), which are connected by narrow conformational pathways (i.e., bottlenecks), the narrowness slows the inter-basin round trips in conformational sampling. This results in inaccuracy of free energies for the basins. This difficulty is not cleared out even when an enhanced conformational sampling is fairly performed along a reaction coordinate. In this study, to enhance the inter-basin round trips we introduced a virtual state that covers the narrow pathways. The probability distribution function for the virtual state was controlled based on detailed balance condition for the inter-state transitions (transitions between the real-state basins and the virtual state). To mimic the free-energy landscape of a real biological system, we introduced a simple model where a wall separates two basins and a narrow hole is pierced in the wall to connect the basins. The sampling was done based on Monte Carlo (MC). We examined several hole-sizes and inter-state transition probabilities. For a small hole-size, a small inter-state transition probability produced a sampling efficiency 100 times higher than a conventional MC does. This result goes against ones intuition, because one considers generally that the sampling efficiency increases with increasing the transition probability. The present method is readily applicable to enhanced conformational sampling such as multi-canonical or adaptive umbrella sampling, and extendable to molecular dynamics.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Hatzes, Artie P.

    2014-09-01

    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.

  17. 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. PMID:25230657

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

    NASA Astrophysics Data System (ADS)

    Morimae, Tomoyuki

    2011-04-01

    In the framework of the computational tensor network [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.98.220503 98, 220503 (2007)], the quantum computation is performed in a virtual linear space called the correlation space. It was recently shown [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.050503 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 [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.050503 103, 050503 (2009)], which also works to upload, the proposed uploading method has several advantages.

  19. Solid State Molecular Reactors in Space

    NASA Astrophysics Data System (ADS)

    Maurette, M.

    2011-03-01

    Lunar minerals and impact glasses, convert the polyatomic beam of solar wind (SW) ions into a flux of small molecules (e.g., H2, N2, H2O, CO, CO2, CH4, C2H4, C2H6, HCN, metal carbides and deuterides, etc.). They thus behave as "Solid State Molecular Reactors". Moreover, ~100-200 μm size micrometeoroids (μMs) have also been exposed to the SW in the zodiacal cloud, before being captured by the Earth and recovered as Antarctic micrometeorites. They are mostly composed of a PAH-rich hydrous-carbonaceous material, which amplifies their power as molecular reactors. In particular, during the first ~200 Myr of the post-lunar period, about 75% of the μMs have been melted and/or volatilized upon atmospheric entry. The release of their volatile species triggered a cosmic volcanism around the mesopause that ruled the formation of the early Earth's atmosphere and climate. Furthermore, a fraction of the μMs that survive unmelted upon atmospheric entry did settle on the proto-oceans floors. Upon further burial in sediments their constituent PAH-rich kerogen was cracked into abiotic oil, which generated giant oil slicks that fed prebiotic chemistry. Many stars, of all ages and types, are embedded into a secondary debris-disk loaded with ion implanted μMs. Some of them are expelled to the interstellar medium (ISM) where they behave first as "dormant-invisible" molecular reactors, until they became reactivated by various processes to synthesize interstellar molecules. This short paper only focus on some highlights of this research dealing with the synthesis of important interstellar molecules, including the most abundant ones (H2 and CO) and H2O, HCN and PAHs, all involved in prebiotic chemistry.

  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. Green's function approach to edge states in transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Farmanbar, Mojtaba; Amlaki, Taher; Brocks, Geert

    2016-05-01

    The semiconducting two-dimensional transition metal dichalcogenides MX 2 show an abundance of one-dimensional metallic edges and grain boundaries. Standard techniques for calculating edge states typically model nanoribbons, and require the use of supercells. In this paper, we formulate a Green's function technique for calculating edge states of (semi-)infinite two-dimensional systems with a single well-defined edge or grain boundary. We express Green's functions in terms of Bloch matrices, constructed from the solutions of a quadratic eigenvalue equation. The technique can be applied to any localized basis representation of the Hamiltonian. Here, we use it to calculate edge states of MX 2 monolayers by means of tight-binding models. Aside from the basic zigzag and armchair edges, we study edges with a more general orientation, structurally modifed edges, and grain boundaries. A simple three-band model captures an important part of the edge electronic structures. An 11-band model comprising all valence orbitals of the M and X atoms is required to obtain all edge states with energies in the MX 2 band gap. Here, states of odd symmetry with respect to a mirror plane through the layer of M atoms have a dangling-bond character, and tend to pin the Fermi level.

  2. Two Dimensional State Transition of a Swarming Model

    NASA Astrophysics Data System (ADS)

    Chuang, Yao-Li; Marthaler, Daniel

    2005-03-01

    A rotating mill is widely seen in swarming patterns of various species, such as ants, fishes, or daphnia. Levine et al. (2000) proposed an individual based model which produces a pair of co- existing clockwise and counter-clockwise mills on top of each other while a unified rotating mill can be achieved by switching the formula of the self-propulsion to an ensemble average. Without changing its fundamental concepts, we modify the model to include a Rayleigh-type self-driving mechanism, which has a cleaner connection to its continuum limit, i.e., macroscopic description, where analysis can be more efficiently done. By varying parameter values, we find that the modified model goes through a three-stage transition from the co-existing state to the unified state. We also compare the numerical results of the model and of its continuum counterpart.

  3. Space Grant and Astronomy Education: The State of Washington's Story

    NASA Astrophysics Data System (ADS)

    Lutz, J.

    2000-12-01

    This poster summarizes projects that I have been involved in which utilize NASA Space Grant resources to improve K-12 and undergraduate education at institutions in the State of Washington. Examples I will use include the development of preservice courses for K-12 teachers, inservice workshops for K-12 teachers, minigrants for teachers, support of teacher/scientist partnerships, dissemination of NASA and other resources (curriculum, videos, etc.) to teachers, and support for undergraduate research projects, mentoring and scholarships. I will show how these projects contribute to achieving Washington state and national science standards. Space Grant funding exists in every state and can potentially be accessed by astronomers to carry out education projects that are appropriate to their institution and area of interest. Information will be provided on how to contact Space Grant offices in each state.

  4. Chemical potential driven phase transition of black holes in anti-de Sitter space

    NASA Astrophysics Data System (ADS)

    Galante, Mario; Giribet, Gaston; Goya, Andrés; Oliva, Julio

    2015-11-01

    Einstein-Maxwell theory conformally coupled to a scalar field in D dimensions may exhibit a phase transition at low temperature whose end point is an asymptotically anti-de Sitter black hole with a scalar field profile that is regular everywhere outside and on the horizon. This provides a tractable model to study the phase transition of hairy black holes in anti-de Sitter space in which the backreaction on the geometry can be solved analytically.

  5. 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).

  6. 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

  7. 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)

  8. Conformational Transition of Giant DNA in a Confined Space Surrounded by a Phospholipid Membrane

    PubMed Central

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

    2009-01-01

    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 Mg2+ 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 Mg2+. 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. PMID:19751673

  9. Observing in space and time the ephemeral nucleation of liquid-to-crystal phase transitions

    PubMed Central

    Yoo, Byung-Kuk; Kwon, Oh-Hoon; Liu, Haihua; Tang, Jau; Zewail, Ahmed H.

    2015-01-01

    The phase transition of crystalline ordering is a general phenomenon, but its evolution in space and time requires microscopic probes for visualization. Here we report direct imaging of the transformation of amorphous titanium dioxide nanofilm, from the liquid state, passing through the nucleation step and finally to the ordered crystal phase. Single-pulse transient diffraction profiles at different times provide the structural transformation and the specific degree of crystallinity (η) in the evolution process. It is found that the temporal behaviour of η exhibits unique ‘two-step' dynamics, with a robust ‘plateau' that extends over a microsecond; the rate constants vary by two orders of magnitude. Such behaviour reflects the presence of intermediate structure(s) that are the precursor of the ordered crystal state. Theoretically, we extend the well-known Johnson–Mehl–Avrami–Kolmogorov equation, which describes the isothermal process with a stretched-exponential function, but here over the range of times covering the melt-to-crystal transformation. PMID:26478194

  10. Observing in space and time the ephemeral nucleation of liquid-to-crystal phase transitions.

    PubMed

    Yoo, Byung-Kuk; Kwon, Oh-Hoon; Liu, Haihua; Tang, Jau; Zewail, Ahmed H

    2015-01-01

    The phase transition of crystalline ordering is a general phenomenon, but its evolution in space and time requires microscopic probes for visualization. Here we report direct imaging of the transformation of amorphous titanium dioxide nanofilm, from the liquid state, passing through the nucleation step and finally to the ordered crystal phase. Single-pulse transient diffraction profiles at different times provide the structural transformation and the specific degree of crystallinity (η) in the evolution process. It is found that the temporal behaviour of η exhibits unique 'two-step' dynamics, with a robust 'plateau' that extends over a microsecond; the rate constants vary by two orders of magnitude. Such behaviour reflects the presence of intermediate structure(s) that are the precursor of the ordered crystal state. Theoretically, we extend the well-known Johnson-Mehl-Avrami-Kolmogorov equation, which describes the isothermal process with a stretched-exponential function, but here over the range of times covering the melt-to-crystal transformation. PMID:26478194

  11. Observing in space and time the ephemeral nucleation of liquid-to-crystal phase transitions

    NASA Astrophysics Data System (ADS)

    Yoo, Byung-Kuk; Kwon, Oh-Hoon; Liu, Haihua; Tang, Jau; Zewail, Ahmed H.

    2015-10-01

    The phase transition of crystalline ordering is a general phenomenon, but its evolution in space and time requires microscopic probes for visualization. Here we report direct imaging of the transformation of amorphous titanium dioxide nanofilm, from the liquid state, passing through the nucleation step and finally to the ordered crystal phase. Single-pulse transient diffraction profiles at different times provide the structural transformation and the specific degree of crystallinity (η) in the evolution process. It is found that the temporal behaviour of η exhibits unique `two-step' dynamics, with a robust `plateau' that extends over a microsecond; the rate constants vary by two orders of magnitude. Such behaviour reflects the presence of intermediate structure(s) that are the precursor of the ordered crystal state. Theoretically, we extend the well-known Johnson-Mehl-Avrami-Kolmogorov equation, which describes the isothermal process with a stretched-exponential function, but here over the range of times covering the melt-to-crystal transformation.

  12. 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.

  13. Calculating helium atomic excited states in coordinate space

    NASA Astrophysics Data System (ADS)

    Hall, Shane; Siegel, P. B.

    2015-12-01

    Two coupled Schrödinger equations are used to calculate excited states of atomic helium. Using product state functions for the two-electron state, the shooting method is used to numerically determine the energies of the allowed singlet and triplet levels. The calculations agree well with the data, and the coordinate-space basis yields Schrödinger equations for helium that are familiar to students who have used similar methods for the hydrogen atom.

  14. 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.

  15. 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. PMID:20866399

  16. Bethe-Salpeter bound-state structure in Minkowski space

    NASA Astrophysics Data System (ADS)

    Gutierrez, C.; Gigante, V.; Frederico, T.; Salmè, G.; Viviani, M.; Tomio, Lauro

    2016-08-01

    The quantitative investigation of the scalar Bethe-Salpeter equation in Minkowski space, within the ladder-approximation framework, is extended to include the excited states. This study has been carried out for an interacting system composed by two massive bosons exchanging a massive scalar, by adopting (i) the Nakanishi integral representation of the Bethe-Salpeter amplitude, and (ii) the formally exact projection onto the null plane. Our analysis, on one hand, confirms the reliability of the method already applied to the ground state and, on the other one, extends the investigation from the valence distribution in momentum space to the corresponding quantity in the impact-parameter space, pointing out some relevant features, like (i) the equivalence between Minkowski and Euclidean transverse-momentum amplitudes, and (ii) the leading exponential fall-off of the valence wave function in the impact-parameter space.

  17. 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.

  18. Transition between locked and running states for dimer motion induced by periodic external driving.

    PubMed

    Hennig, D; Martens, S; Fugmann, S

    2008-07-01

    We study the motion of a dimer in a one-dimensional spatially periodic washboard potential. The tilt of the latter is time-periodically modulated by an ac field. We focus interest on the detrapping of the (static) ground state solution of the dimer caused by the ac field. Moreover, we demonstrate that slow tilt modulations not only induce a trapping-detrapping transition but drive the dimer dynamics into a regime of transient long-range running states. Most strikingly, the motion proceeds then unidirectionally, so that the dimer covers huge distances regardless of the fact that the bias force in the driven system vanishes on the average. We elucidate the underlying dynamics in phase space and associate long-lasting running states with the motion in ballistic channels occurring due to stickiness to invariant tori. PMID:18763916

  19. 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

  20. State-Space Algorithms for Estimating Spike Rate Functions

    PubMed Central

    Smith, Anne C.; Scalon, Joao D.; Wirth, Sylvia; Yanike, Marianna; Suzuki, Wendy A.; Brown, Emery N.

    2010-01-01

    The accurate characterization of spike firing rates including the determination of when changes in activity occur is a fundamental issue in the analysis of neurophysiological data. Here we describe a state-space model for estimating the spike rate function that provides a maximum likelihood estimate of the spike rate, model goodness-of-fit assessments, as well as confidence intervals for the spike rate function and any other associated quantities of interest. Using simulated spike data, we first compare the performance of the state-space approach with that of Bayesian adaptive regression splines (BARS) and a simple cubic spline smoothing algorithm. We show that the state-space model is computationally efficient and comparable with other spline approaches. Our results suggest both a theoretically sound and practical approach for estimating spike rate functions that is applicable to a wide range of neurophysiological data. PMID:19911062

  1. A MECHANISM FOR HYSTERESIS IN BLACK HOLE BINARY STATE TRANSITIONS

    SciTech Connect

    Begelman, Mitchell C.; Armitage, Philip J.

    2014-02-20

    We suggest that the hysteretic cycle of black hole state transitions arises from two established properties of accretion disks: the increase in turbulent stress in disks threaded by a net magnetic field and the ability of thick (but not thin) disks to advect such a field radially. During quiescence, magnetic field loops are generated by the magnetorotational instability at the interface between the inner hot flow and outer thin disk. Vertical flux is advected into and accumulates stochastically within the inner flow, where it stimulates the turbulence so that α ∼ 1. The transition to a geometrically thin inner disk occurs when L ∼ α{sup 2} L {sub Edd} ∼ L {sub Edd}, and the first ''thin'' disk to form is itself moderately thick, strongly magnetized, and able to advect field inward. These properties favor episodic jet production. As the accretion rate declines magnetic flux escapes, α decreases to α ∼ 0.01-0.1, and a hot inner flow is not re-established until L << L {sub Edd}. We discuss possible observational consequences of our scenario.

  2. A new vacuum state in de Sitter space

    NASA Astrophysics Data System (ADS)

    Pfautsch, Jonathan D.

    1982-11-01

    We present a new vacuum state which can be defined in a region of de Sitter space. This region corresponds to a K=-1 Robertson-Walker coordinatization of de Sitter space. The renormalized expectation value of the stress tensor for the conformally invariant massless scalar field in this vacuum is evaluated, and is found to differ from the corresponding result in the usual de Sitter-invariant vacuum by the absence of a pure radiation term. We also indicate that this can be accounted for by regarding the de Sitter-invariant vacuum as a thermal state relative to the new vacuum.

  3. Shell transitions between metastable states of Yukawa balls

    SciTech Connect

    Kaeding, S.; Melzer, A.; Block, D.; Piel, A.; Kaehlert, H.; Ludwig, P.; Bonitz, M.

    2008-07-15

    Spherical dust clusters composed of several concentric shells are experimentally investigated with particular interest on transitions between different configurations and transitions of particles between different shells. Transitions between different ground and metastable configurations are frequently observed. The experimental analysis allows us to derive the energy differences of different configurations from particles traveling between shells. The observed transitions and transition probabilities are compared to molecular dynamics simulations.

  4. 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.

  5. 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}

  6. Test of the Chevallier-Polarski-Linder parametrization for rapid dark energy equation of state transitions

    SciTech Connect

    Linden, Sebastian; Virey, Jean-Marc

    2008-07-15

    We test the robustness and flexibility of the Chevallier-Polarski-Linder (CPL) parametrization of the dark energy equation of state w(z)=w{sub 0}+w{sub a}(z/1+z) in recovering a four-parameter steplike fiducial model. We constrain the parameter space region of the underlying fiducial model where the CPL parametrization offers a reliable reconstruction. It turns out that non-negligible biases leak into the results for recent (z<2.5) rapid transitions, but that CPL yields a good reconstruction in all other cases. The presented analysis is performed with supernova Ia data as forecasted for a space mission like SNAP/JDEM, combined with future expectations for the cosmic microwave background shift parameter R and the baryonic acoustic oscillation parameter A.

  7. 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.

  8. 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.

  9. 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. PMID:24335761

  10. State transitions and decoherence in the avian compass

    NASA Astrophysics Data System (ADS)

    Poonia, Vishvendra Singh; Saha, Dipankar; Ganguly, Swaroop

    2015-05-01

    The radical pair model has been successful in explaining behavioral characteristics of the geomagnetic compass believed to underlie the navigation capability of certain avian species. In this study, the spin dynamics of the radical pair model and decoherence therein are interpreted from a microscopic state transition point of view. This helps to elucidate the interplay between the hyperfine and Zeeman interactions that enables the avian compass and clarify the distinctive effects of nuclear and environmental decoherence on it. Three regimes have been identified for the strength of the hyperfine interaction with respect to that of the geomagnetic Zeeman. It is found that the compass is likely to function in the large hyperfine interaction regime. Using a quantum information theoretic quantifier of coherence, we find that nuclear decoherence induces new structure in the spin dynamics for intermediate hyperfine interaction strength. On the other hand, environmental decoherence—modeled by two different noise models—seems to disrupt the compass action.

  11. Optimizing transition states via kernel-based machine learning.

    PubMed

    Pozun, Zachary D; Hansen, Katja; Sheppard, Daniel; Rupp, Matthias; Müller, Klaus-Robert; Henkelman, Graeme

    2012-05-01

    We present a method for optimizing transition state theory dividing surfaces with support vector machines. The resulting dividing surfaces require no a priori information or intuition about reaction mechanisms. To generate optimal dividing surfaces, we apply a cycle of machine-learning and refinement of the surface by molecular dynamics sampling. We demonstrate that the machine-learned surfaces contain the relevant low-energy saddle points. The mechanisms of reactions may be extracted from the machine-learned surfaces in order to identify unexpected chemically relevant processes. Furthermore, we show that the machine-learned surfaces significantly increase the transmission coefficient for an adatom exchange involving many coupled degrees of freedom on a (100) surface when compared to a distance-based dividing surface. PMID:22583204

  12. State transitions and decoherence in the avian compass.

    PubMed

    Poonia, Vishvendra Singh; Saha, Dipankar; Ganguly, Swaroop

    2015-05-01

    The radical pair model has been successful in explaining behavioral characteristics of the geomagnetic compass believed to underlie the navigation capability of certain avian species. In this study, the spin dynamics of the radical pair model and decoherence therein are interpreted from a microscopic state transition point of view. This helps to elucidate the interplay between the hyperfine and Zeeman interactions that enables the avian compass and clarify the distinctive effects of nuclear and environmental decoherence on it. Three regimes have been identified for the strength of the hyperfine interaction with respect to that of the geomagnetic Zeeman. It is found that the compass is likely to function in the large hyperfine interaction regime. Using a quantum information theoretic quantifier of coherence, we find that nuclear decoherence induces new structure in the spin dynamics for intermediate hyperfine interaction strength. On the other hand, environmental decoherence-modeled by two different noise models-seems to disrupt the compass action. PMID:26066201

  13. Comparison of double-ended transition state search methods

    NASA Astrophysics Data System (ADS)

    Koslover, Elena F.; Wales, David J.

    2007-10-01

    While a variety of double-ended transition state search methods have been developed, their relative performance in characterizing complex multistep pathways between structurally disparate molecular conformations remains unclear. Three such methods (doubly-nudged elastic band, a string method, and a growing string method) are compared for a series of benchmarks ranging from permutational isomerizations of the seven-atom Lennard-Jones cluster (LJ7) to highly cooperative LJ38 and LJ75 rearrangements, and the folding pathways of two peptides. A database of short paths between LJ13 local minima is used to explore the effects of parameters and suggest reasonable default values. Each double-ended method was employed within the framework of a missing connection network flow algorithm to construct more complicated multistep pathways. We find that in our implementation none of the three methods definitively outperforms the others, and that their relative effectiveness is strongly system and parameter dependent.

  14. Comparison of double-ended transition state search methods.

    PubMed

    Koslover, Elena F; Wales, David J

    2007-10-01

    While a variety of double-ended transition state search methods have been developed, their relative performance in characterizing complex multistep pathways between structurally disparate molecular conformations remains unclear. Three such methods (doubly-nudged elastic band, a string method, and a growing string method) are compared for a series of benchmarks ranging from permutational isomerizations of the seven-atom Lennard-Jones cluster (LJ(7)) to highly cooperative LJ(38) and LJ(75) rearrangements, and the folding pathways of two peptides. A database of short paths between LJ(13) local minima is used to explore the effects of parameters and suggest reasonable default values. Each double-ended method was employed within the framework of a missing connection network flow algorithm to construct more complicated multistep pathways. We find that in our implementation none of the three methods definitively outperforms the others, and that their relative effectiveness is strongly system and parameter dependent. PMID:17919006

  15. 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.

  16. Transition from ring to beam arc distributions of water ions near the Space Shuttle orbiter

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.

    1990-01-01

    The distribution function of water ions produced near the Space Shuttle by charge exchange between ionospheric oxygen ions and outgassed water molecules is studied. The transition from a ring to a beam arc distribution function is described. The number density of water ions is found to increase monotonically with decreasing distance from the Shuttle.

  17. Transition: Life-Span and Life-Space Considerations for Empowerment.

    ERIC Educational Resources Information Center

    Szymanski, Edna Mora

    1994-01-01

    This article integrates literature from counseling, rehabilitation, multicultural education, and special education to explain the importance of life-span considerations, including the preschool and early school years, and the life-space factors of family, culture, and community. Principles for transition interventions which promote empowerment are…

  18. 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…

  19. Predicting Boundary-Layer Transition on Space-Shuttle Re-Entry

    NASA Technical Reports Server (NTRS)

    Berry, Scott; Horvath, Tom; Merski, Ron; Liechty, Derek; Greene, Frank; Bibb, Karen; Buck, Greg; Hamilton, Harris; Weilmuenster, Jim; Campbell, Chuck; Bouslog, Stan; Kirk, Ben; Bourland, Garry; Cassady, Amy; Anderson, Brian; Reda, Dan; Reuther, James; Kinder, Gerry; Chao, Dennis; Hyatt, Jay; Barnwell, Maria; Wang, K. C.; Schneider, Steve

    2008-01-01

    The BLT Prediction Tool ("BLT" signifies "Boundary Layer Transition") is provided as part of the Damage Assessment Team analysis package, which is utilized for analyzing local aerothermodynamics environments of damaged or repaired space-shuttle thermal protection tiles. Such analyses are helpful in deciding whether to repair launch-induced damage before re-entering the terrestrial atmosphere.

  20. 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.

  1. 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.

  2. 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

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

    PubMed

    Zweig, C L; Kitchens, W M

    2009-07-01

    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, U.S.A., 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

  4. 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.

  5. Conformational transition in signal transduction: metastable states and transition pathways in the activation of a signaling protein.

    PubMed

    Banerjee, Rahul; Yan, Honggao; Cukier, Robert I

    2015-06-01

    Signal transduction is of vital importance to the growth and adaptation of living organisms. The key to understand mechanisms of biological signal transduction is elucidation of the conformational dynamics of its signaling proteins, as the activation of a signaling protein is fundamentally a process of conformational transition from an inactive to an active state. A predominant form of signal transduction for bacterial sensing of environmental changes in the wild or inside their hosts is a variety of two-component systems, in which the conformational transition of a response regulator (RR) from an inactive to an active state initiates responses to the environmental changes. Here, RR activation has been investigated using RR468 as a model system by extensive unbiased all-atom molecular dynamics (MD) simulations in explicit solvent, starting from snapshots along a targeted MD trajectory that covers the conformational transition. Markov state modeling, transition path theory, and geometric analyses of the wealth of the MD data have provided a comprehensive description of the RR activation. It involves a network of metastable states, with one metastable state essentially the same as the inactive state and another very similar to the active state that are connected via a small set of intermediates. Five major pathways account for >75% of the fluxes of the conformational transition from the inactive to the active-like state. The thermodynamic stability of the states and the activation barriers between states are found, to identify rate-limiting steps. The conformal transition is initiated predominantly by movements of the β3α3 loop, followed by movements of the β4α4-loop and neighboring α4 helix region, and capped by additional movements of the β3α3 loop. A number of transient hydrophobic and hydrogen bond interactions are revealed, and they may be important for the conformational transition. PMID:25945797

  6. Zero-momentum coupling induced transitions of ground states in Rashba spin-orbit coupled Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Jin, Jingjing; Zhang, Suying; Han, Wei

    2014-06-01

    We investigate the transitions of ground states induced by zero momentum (ZM) coupling in pseudospin-1/2 Rashba spin-orbit coupled Bose-Einstein condensates confined in a harmonic trap. In a weak harmonic trap, the condensate presents a plane wave (PW) state, a stripe state or a spin polarized ZM state, and the particle distribution of the stripe state is weighted equally at two points in the momentum space without ZM coupling. The presence of ZM coupling induces an imbalanced particle distribution in the momentum space, and leads to the decrease of the amplitude of the stripe state. When its strength exceeds a critical value, the system experiences the transition from stripe phase to PW phase. The boundary of these two phases is shifted and a new phase diagram spanned by the ZM coupling and the interatomic interactions is obtained. The presence of ZM coupling can also achieve the transition from ZM phase to PW phase. In a strong harmonic trap, the condensate exhibits a vortex lattice state without ZM coupling. For the positive effective Rabi frequency of ZM coupling, the condensate is driven from a vortex lattice state to a vortex-free lattice state and finally to a PW state with the increase of coupling strength. In addition, for the negative effective Rabi frequency, the condensate is driven from a vortex lattice state to a stripe state, and finally to a PW state. The stripe state found in the strong harmonic trap is different from that in previous works because of its nonzero superfluid velocity along the stripes. We also discuss the influences of the ZM coupling on the spin textures, and indicate that the spin textures are squeezed transversely by the ZM coupling.

  7. 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.

  8. Space science public outreach at Louisiana State University

    NASA Astrophysics Data System (ADS)

    Guzik, T. G.; Babin, E.; Cooney, W.; Giammanco, J.; Hartman, D.; McNeil, R.; Slovak, M.; Stacy, J. G.

    2004-01-01

    Over the last seven years the Astronomy/Astrophysics group in the Department of Physics and Astronomy of Louisiana State University has developed an extensive Space Science education and public outreach program. This program includes partners from state and parish government, the local community, museums and school districts and has directly led to the development of the Highland Road Park Observatory, in-service teacher training program, content standards aligned classroom material and new technology for the classroom. In addition, a new planetarium/space theater opening soon in downtown Baton Rouge, Louisiana will provide our group with new space science education and public outreach opportunities. In this paper, we will discuss details about some of our individual projects.

  9. 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.

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

    DOE PAGESBeta

    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 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