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Sample records for active state transition

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

    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

  2. Dark/light transition and vigilance states modulate jaw-closing muscle activity level in mice.

    Katayama, Keisuke; Mochizuki, Ayako; Kato, Takafumi; Ikeda, Minako; Ikawa, Yasuha; Nakamura, Shiro; Nakayama, Kiyomi; Wakabayashi, Noriyuki; Baba, Kazuyoshi; Inoue, Tomio

    2015-12-01

    Bruxism is associated with an increase in the activity of the jaw-closing muscles during sleep and wakefulness. However, the changes in jaw-closing muscle activity across states of vigilance over a 24-h period are unclear. In this study, we investigated the effects of dark/light transition and sleep/wake state on EMG activity of the masseter (jaw-closing) muscle in comparison with the activity of the upper trapezius muscle (a neck muscle) over a 24-h period in mice. The activities of the masseter and neck muscles during wakefulness were much greater than during non-REM and REM sleep. In contrast, the activities of both muscles slightly, but significantly, decreased during the transition period from dark to light. Histograms of masseter activity during wakefulness and non-REM sleep showed bimodal distributions, whereas the neck muscle showed unimodal activation in all states. These results suggest that the activities of jaw-closing and neck muscles are modulated by both sleep/wake state and dark/light transition, with the latter being to a lesser degree. Furthermore, even during non-REM sleep, jaw-closing muscles display bimodal activation, which may contribute to the occurrence of exaggerated aberrant muscle activity, such as sleep bruxism. PMID:26188127

  3. A Semi-Continuous State-Transition Probability HMM-Based Voice Activity Detector

    Othman H

    2007-01-01

    Full Text Available We introduce an efficient hidden Markov model-based voice activity detection (VAD algorithm with time-variant state-transition probabilities in the underlying Markov chain. The transition probabilities vary in an exponential charge/discharge scheme and are softly merged with state conditional likelihood into a final VAD decision. Working in the domain of ITU-T G.729 parameters, with no additional cost for feature extraction, the proposed algorithm significantly outperforms G.729 Annex B VAD while providing a balanced tradeoff between clipping and false detection errors. The performance compares very favorably with the adaptive multirate VAD, option 2 (AMR2.

  4. A Semi-Continuous State-Transition Probability HMM-Based Voice Activity Detector

    H. Othman

    2007-02-01

    Full Text Available We introduce an efficient hidden Markov model-based voice activity detection (VAD algorithm with time-variant state-transition probabilities in the underlying Markov chain. The transition probabilities vary in an exponential charge/discharge scheme and are softly merged with state conditional likelihood into a final VAD decision. Working in the domain of ITU-T G.729 parameters, with no additional cost for feature extraction, the proposed algorithm significantly outperforms G.729 Annex B VAD while providing a balanced tradeoff between clipping and false detection errors. The performance compares very favorably with the adaptive multirate VAD, option 2 (AMR2.

  5. Active to absorbing state phase transition in the presence of a fluctuating environment: feedback and universality

    We construct and analyze a simple reduced model to study the effects of the interplay between a density undergoing an active-to-absorbing state phase transition (AAPT) and a fluctuating environment in the form of a broken symmetry mode coupled to the density field in any arbitrary dimension. We show, by using perturbative renormalization group calculations, that both the effects of the environment on the density and the latter’s feedback on the environment influence the ensuing universal scaling behaviour of the AAPT at its extinction transition. Phenomenological implications of our results in the context of more realistic natural examples are discussed. (paper)

  6. Improving the activity of Trichoderma reesei cel7B through stabilizing the transition state.

    Wang, Yefei; Song, Xiangfei; Zhang, Shujun; Li, Jingwen; Shu, Zhiyu; He, Chunyan; Huang, Qingshan; Yao, Lishan

    2016-06-01

    Trichoderma reesei (Tr.) cellulases, which convert cellulose to reducing sugars, are a promising catalyst used in the lignocellulosic biofuel production. Improving Tr. cellulases activity, though very difficult, is highly desired due to the recalcitrance of lignocellulose. Meanwhile, it is preferable to enhance the cellulase's promiscuity so that substrates other than cellulose can also be hydrolyzed. In this work, an attempt is made to improve the catalytic activity of a major endogluanase Tr. Cel7B against xylan which crosslinks with cellulose in lignocellulose. By using quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations, the transition state of the xylo-oligosaccharide hydrolysis is identified. Then, mutations are introduced and their effect on the transition state stabilization is ranked based on the free energy calculations. Seven top ranked mutants are evaluated experimentally. Three mutants A208Q, A222D, and G230R show a higher activity than the wild-type Tr. Cel7B in the hydrolysis of xylan (by up to 47%) as well as filter paper (by up to 50%). The combination of the single mutants can further improve the enzyme activity. Our work demonstrates that the free energy method is effective in engineering the Tr. Cel7B activity against xylan and cellulose, and thus may also be useful for improving the activity of other Tr. cellulases. Biotechnol. Bioeng. 2016;113: 1171-1177. © 2015 Wiley Periodicals, Inc. PMID:26616246

  7. Engineering electrocatalytic activity in nanosized perovskite cobaltite through surface spin-state transition

    Zhou, Shiming; Miao, Xianbing; Zhao, Xu; Ma, Chao; Qiu, Yuhao; Hu, Zhenpeng; Zhao, Jiyin; Shi, Lei; Zeng, Jie

    2016-01-01

    The activity of electrocatalysts exhibits a strongly dependence on their electronic structures. Specifically, for perovskite oxides, Shao-Horn and co-workers have reported a correlation between the oxygen evolution reaction activity and the eg orbital occupation of transition-metal ions, which provides guidelines for the design of highly active catalysts. Here we demonstrate a facile method to engineer the eg filling of perovskite cobaltite LaCoO3 for improving the oxygen evolution reaction activity. By reducing the particle size to ∼80 nm, the eg filling of cobalt ions is successfully increased from unity to near the optimal configuration of 1.2 expected by Shao-Horn's principle. Consequently, the activity is significantly enhanced, comparable to those of recently reported cobalt oxides with eg∼1.2 configurations. This enhancement is ascribed to the emergence of spin-state transition from low-spin to high-spin states for cobalt ions at the surface of the nanoparticles, leading to more active sites with increased reactivity. PMID:27187067

  8. Engineering electrocatalytic activity in nanosized perovskite cobaltite through surface spin-state transition

    Zhou, Shiming; Miao, Xianbing; Zhao, Xu; Ma, Chao; Qiu, Yuhao; Hu, Zhenpeng; Zhao, Jiyin; Shi, Lei; Zeng, Jie

    2016-05-01

    The activity of electrocatalysts exhibits a strongly dependence on their electronic structures. Specifically, for perovskite oxides, Shao-Horn and co-workers have reported a correlation between the oxygen evolution reaction activity and the eg orbital occupation of transition-metal ions, which provides guidelines for the design of highly active catalysts. Here we demonstrate a facile method to engineer the eg filling of perovskite cobaltite LaCoO3 for improving the oxygen evolution reaction activity. By reducing the particle size to ~80 nm, the eg filling of cobalt ions is successfully increased from unity to near the optimal configuration of 1.2 expected by Shao-Horn's principle. Consequently, the activity is significantly enhanced, comparable to those of recently reported cobalt oxides with eg~1.2 configurations. This enhancement is ascribed to the emergence of spin-state transition from low-spin to high-spin states for cobalt ions at the surface of the nanoparticles, leading to more active sites with increased reactivity.

  9. Engineering electrocatalytic activity in nanosized perovskite cobaltite through surface spin-state transition.

    Zhou, Shiming; Miao, Xianbing; Zhao, Xu; Ma, Chao; Qiu, Yuhao; Hu, Zhenpeng; Zhao, Jiyin; Shi, Lei; Zeng, Jie

    2016-01-01

    The activity of electrocatalysts exhibits a strongly dependence on their electronic structures. Specifically, for perovskite oxides, Shao-Horn and co-workers have reported a correlation between the oxygen evolution reaction activity and the eg orbital occupation of transition-metal ions, which provides guidelines for the design of highly active catalysts. Here we demonstrate a facile method to engineer the eg filling of perovskite cobaltite LaCoO3 for improving the oxygen evolution reaction activity. By reducing the particle size to ∼80 nm, the eg filling of cobalt ions is successfully increased from unity to near the optimal configuration of 1.2 expected by Shao-Horn's principle. Consequently, the activity is significantly enhanced, comparable to those of recently reported cobalt oxides with eg(∼1.2) configurations. This enhancement is ascribed to the emergence of spin-state transition from low-spin to high-spin states for cobalt ions at the surface of the nanoparticles, leading to more active sites with increased reactivity. PMID:27187067

  10. State Transition Algorithm

    Zhou, Xiaojun; Gui, Weihua

    2012-01-01

    In terms of the concepts of state and state transition, a new heuristic random search algorithm named state transition algorithm is proposed. For continuous function optimization problems, four special transformation operators called rotation, translation, expansion and axesion are designed. Adjusting measures of the transformations are mainly studied to keep the balance of exploration and exploitation. Convergence analysis is also discussed about the algorithm based on random search method. In the meanwhile, to strengthen the search ability in high dimensional space, communication strategy is introduced into the basic algorithm and intermittent exchange is presented to prevent premature convergence. Finally, experiments are carried out for the algorithms. With 10 common benchmark unconstrained continuous functions used to test the performance, the results show that state transition algorithms are promising algorithms due to their good global search capability and convergence property when compared with some ...

  11. Variational transition state theory

    Truhlar, D.G. [Univ. of Minnesota, Minneapolis (United States)

    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.

  12. Active-to-absorbing-state phase transition in an evolving population with mutation

    Sarkar, Niladri

    2015-10-01

    We study the active to absorbing phase transition (AAPT) in a simple two-component model system for a species and its mutant. We uncover the nontrivial critical scaling behavior and weak dynamic scaling near the AAPT that shows the significance of mutation and highlights the connection of this model with the well-known directed percolation universality class. Our model should be a useful starting point to study how mutation may affect extinction or survival of a species.

  13. Synthesis and renin inhibitory activity of novel angiotensinogen transition state analogues modified at the P(2)-histidine position.

    Salimbeni, A; Paleari, F; Poma, D; Criscuoli, M; Scolastico, C

    1996-01-01

    With the aim of finding new renin inhibitors with improved bioavailability properties, two angiotensinogen transition state analogues 1a and 1b, containing a novel unnatural amino acid at the P(2) position, namely the (2R,3S)- and (2S,3S)-2-amino-3-(1,3-dithiolan-2-yl)-3-hydroxypropanoic acid (ADHPA), have been synthesized and tested for human renin inhibitory activity and for chemical and enzymatic stability. Only compound 1a (the S-isomer) possessed a significant activity, which was lower than that of the corresponding histidyl derivative KRI-1314, and combined with a low stability to the gut enzyme chymotrypsin. PMID:22026939

  14. Active-to-absorbing-state phase transition in the presence of fluctuating environments: weak and strong dynamic scaling.

    Sarkar, Niladri; Basu, Abhik

    2012-08-01

    We investigate the scaling properties of phase transitions between survival and extinction (active-to-absorbing-state phase transition, AAPT) in a model that by itself belongs to the directed percolation (DP) universality class, interacting with a spatiotemporally fluctuating environment having its own nontrivial dynamics. We model the environment by (i) a randomly stirred fluid, governed by the Navier-Stokes (NS) equation, and (ii) a fluctuating surface, described either by the Kardar-Parisi-Zhang (KPZ) or the Edward-Wilkinson (EW) equations. We show, by using a one-loop perturbative field theoretic setup that, depending upon the spatial scaling of the variance of the external forces that drive the environment (i.e., the NS, KPZ, or EW equations), the system may show weak or strong dynamic scaling at the critical point of active-to-absorbing-state phase transitions. In the former case AAPT displays scaling belonging to the DP universality class, whereas in the latter case the universal behavior is different. PMID:23005737

  15. Optimal Trajectories of Brain State Transitions

    Gu, Shi; Betzel, Richard F.; Cieslak, Matthew; Delio, Philip R; Grafton, Scott T; Pasqualetti, Fabio; Danielle S Bassett

    2016-01-01

    The complexity of neural dynamics stems in part from the complexity of the underlying anatomy. Yet how the organization of white matter architecture constrains how the brain transitions from one cognitive state to another remains unknown. Here we address this question from a computational perspective by defining a brain state as a pattern of activity across brain regions. Drawing on recent advances in network control theory, we model the underlying mechanisms of brain state transitions as eli...

  16. Exploring the Cross-sectional Association between Transit-Oriented Development Zoning and Active Travel and Transit Usage in the United States, 2010-2014

    Emily eThrun

    2016-06-01

    Full Text Available Background: In response to traditional zoning codes that contribute to car-dependent, sprawling, and disconnected neighborhoods, communities are reforming their land use laws to create pedestrian-friendly areas that promote physical activity. One such reform is the adoption of transit-oriented developments or districts (TODs. TODs are higher-density, compact, mixed use areas located around transit stops that are designed to encourage walking.Purpose: To identify the characteristics of communities that have adopted TODs in their land use laws and examine if communities that have included TODs in their zoning codes are more likely to have adults that commute by any form of active transportation (i.e., walking, biking, or public transportation or by using public transportation specifically.Methods: Zoning codes effective as of 2010 were obtained for a purposeful sample of the largest 3,914 municipal jurisdictions located in 473 of the most populous US counties and consolidated cities within 48 states and the District of Columbia. They were evaluated to determine whether they included TOD districts or regulations using a coding tool developed by the study team. Descriptive statistics together with t-tests and Pearson’s chi-squared independence test were used to compare characteristics of jurisdictions with and without TOD zoning. Multivariate linear regressions were used to compute the adjusted association between TOD zoning and taking public or active transportation to work.Results: Jurisdictions with TOD zoning were located more in the South and West than non-TOD jurisdictions and were more populous, higher income, more racially diverse, and younger. Jurisdictions with TOD zoning had significantly higher percentages of occupied housing with no vehicle than those without TOD zoning. TOD zoning was associated with significantly higher rates of public transportation to work (β=2.10, 95% CI=0.88, 3.32 and active transportation to work (β=2.48, 95

  17. Quantum Transition-State Theory

    Hele, Timothy J H

    2014-01-01

    This dissertation unifies one of the central methods of classical rate calculation, `Transition-State Theory' (TST), with quantum mechanics, thereby deriving a rigorous `Quantum Transition-State Theory' (QTST). The resulting QTST is identical to ring polymer molecular dynamics transition-state theory (RPMD-TST), which was previously considered a heuristic method, and whose results we thereby validate. The key step in deriving a QTST is alignment of the flux and side dividing surfaces in path-integral space to obtain a quantum flux-side time-correlation function with a non-zero $t\\to 0_+$ limit. We then prove that this produces the exact quantum rate in the absence of recrossing by the exact quantum dynamics, fulfilling the requirements of a QTST. Furthermore, strong evidence is presented that this is the only QTST with positive-definite Boltzmann statistics and therefore the pre-eminent method for computation of thermal quantum rates in direct reactions.

  18. Influence of new environmental state policy on gas industry activities in countries of economy in transition. Case of Poland

    Political and economical changes in Poland are accompanied by substantial transition of ecological policy of the state. A first sign of that policy is new law defining responsibilities of companies in minimising the environmental impacts of new investments and duties concerning waste management and disposal as well as pollutant emission reduction. These more stringent environmental rules influence force the Polish gas industry to fulfill new ecological requirements and, because of high ecological value of gas, they give it promising prospects of development. Since environmental condition improvement in Poland can not be achieved without the change in primary energy consumption structure the Gas Development Programme has been established. It assumes more than double increase in gas consumption up to 2010. Gas industry duties connected with environmental requirements have been presented and activities taken in order to meet ecological law rules have been specified for all stages of gas fuel chain from exploration to gas usage. Some measures taken to prevent environment damages have been discussed like ecological evaluation of drilling materials and wastes, elaborated strategy for water protection and Environmental Impact Assessment procedure. The problem of methane emissions from Polish gas system has also been discussed. (au)

  19. Single to Two Cluster State Transition of Primary Motor Cortex 4-posterior (MI-4p Activities in Humans

    Kazunori Nakada

    2015-11-01

    Full Text Available The human primary motor cortex has dual representation of the digits, namely, area 4 anterior (MI-4a and area 4 posterior (MI-4p. We have previously demonstrated that activation of these two functional subunits can be identified independently by functional magnetic resonance imaging (fMRI using independent component-cross correlation-sequential epoch (ICS analysis. Subsequent studies in patients with hemiparesis due to subcortical lesions and monoparesis due to peripheral nerve injury demonstrated that MI-4p represents the initiation area of activation, whereas MI-4a is the secondarily activated motor cortex requiring a “long-loop” feedback input from secondary motor systems, likely the cerebellum. A dynamic model of hand motion based on the limit cycle oscillator predicts that the specific pattern of entrainment of neural firing may occur by applying appropriate periodic stimuli. Under normal conditions, such entrainment introduces a single phase-cluster. Under pathological conditions where entrainment stimuli have insufficient strength, the phase cluster splits into two clusters. Observable physiological phenomena of this shift from single cluster to two clusters are: doubling of firing rate of output neurons; or decay in group firing density of the system due to dampening of odd harmonics components. While the former is not testable in humans, the latter can be tested by appropriately designed fMRI experiments, the quantitative index of which is believed to reflect group behavior of neurons functionally localized, e.g., firing density in the dynamic theory. Accordingly, we performed dynamic analysis of MI-4p activation in normal volunteers and paretic patients. The results clearly indicated that MI-4p exhibits a transition from a single to a two phase-cluster state which coincided with loss of MI-4a activation. The study demonstrated that motor dysfunction (hemiparesis in patients with a subcortical infarct is not simply due to afferent

  20. Transition-state theory and dynamical corrections

    Henriksen, Niels Engholm; Hansen, Flemming Yssing

    2002-01-01

    We consider conventional transition-state theory, and show how quantum dynamical correction factors can be incorporated in a simple fashion, as a natural extension of the fundamental formulation. Corrections due to tunneling and non-adiabatic dynamics are discussed, with emphasis on the latter. The...... correction factor due to non-adiabatic dynamics is considered in relation to the non-activated dissociative sticking of N-2 on Fe(111). For this process, conventional transition-state theory gives a sticking probability which is about 10 times too large (at T = 300 K). We estimate that the sticking...

  1. Modified Transition State Theory for Evaporation and Condensation

    王遵敬; 陈民; 过增元

    2002-01-01

    A modification of the transition state theory for evaporation and condensation is presented by analysing the kinetic characteristics of liquid-vapour interphase transport. In the modified transition state theory, the moving orientation of molecules is introduced into the calculation of the free volume of the activated complex. The condensation coefficients of argon at different temperatures are calculated with the modified transition state theory. The results agree well with those from molecular dynamics simulations.

  2. State Transitions in Semiarid Landscapes

    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.

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

    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

  4. Kinetics of Hydrogen Radical Reactions with Toluene Including Chemical Activation Theory Employing System-Specific Quantum RRK Theory Calibrated by Variational Transition State Theory.

    Bao, Junwei Lucas; Zheng, Jingjing; Truhlar, Donald G

    2016-03-01

    Pressure-dependent reactions are ubiquitous in combustion and atmospheric chemistry. We employ a new calibration procedure for quantum Rice-Ramsperger-Kassel (QRRK) unimolecular rate theory within a chemical activation mechanism to calculate the pressure-falloff effect of a radical association with an aromatic ring. The new theoretical framework is applied to the reaction of H with toluene, which is a prototypical reaction in the combustion chemistry of aromatic hydrocarbons present in most fuels. Both the hydrogen abstraction reactions and the hydrogen addition reactions are calculated. Our system-specific (SS) QRRK approach is adjusted with SS parameters to agree with multistructural canonical variational transition state theory with multidimensional tunneling (MS-CVT/SCT) at the high-pressure limit. The new method avoids the need for the usual empirical estimations of the QRRK parameters, and it eliminates the need for variational transition state theory calculations as a function of energy, although in this first application we do validate the falloff curves by comparing SS-QRRK results without tunneling to multistructural microcanonical variational transition state theory (MS-μVT) rate constants without tunneling. At low temperatures, the two approaches agree well with each other, but at high temperatures, SS-QRRK tends to overestimate falloff slightly. We also show that the variational effect is important in computing the energy-resolved rate constants. Multiple-structure anharmonicity, torsional-potential anharmonicity, and high-frequency-mode vibrational anharmonicity are all included in the rate computations, and torsional anharmonicity effects on the density of states are investigated. Branching fractions, which are both temperature- and pressure-dependent (and for which only limited data is available from experiment), are predicted as a function of pressure. PMID:26841076

  5. Egalitarian state-transition systems (extended version)

    Martín Sánchez, Óscar; Verdejo López, Alberto; Martí Oliet, Narciso

    2016-01-01

    We argue that considering transitions at the same level as states, as first-class citizens, is advantageous in many cases. Namely, the use of atomic propositions on transitions, as well as on states, allows temporal formulas and strategies to be more powerful, general, and meaningful. We define egalitarian structures and logics, and show how they generalize well-known state-based, event-based, and mixed ones. We present translations from egalitarian to non-egalitarian settings that, in partic...

  6. Transitions between compound states of spherical nuclei

    Wigner's statistical matrices are used to study the average reduced g widths and their dispersion for g transitions from a compound state c to another state f, with a lower excitation energy but of arbitrary complexity, for spherical nuclei. It is found that the Porter--Thomas distribution holds for the g widths for all cases of practical interest. In g transitions between compound states c and c' with E/sub g/< or =2 MeV, the most important transitions are M1 transitions involving the major many-quasiparticle components of state c and E1 transitions involving the minor components of state c. It is shown that the strength functions predicted by the various theories for M1 and E1 transitions between compound states with E/sub g/< or =2 MeV are similar. Preference is assigned to the M1-transition version because of experimental results on (n,ga) reactions with thermal and resonance neutrons

  7. Analysis of transition state theory for condensation

    2002-01-01

    By statistically analyzing the condensation process and reconsidering the transition state theory for condensation and evaporation, we first presented a completed theoretical formula of the condensation coefficient. Namely, the unknown parameters contained within the transition state theoretical calculation of the condensation coefficient are determined. The condensation coefficients calculated from this formula agree well with those from molecular dynamics simulations. With this formula, the classical expression of the condensation flux developed from the gas kinetic theory can be used to predict the condensation flux.

  8. On primordial equation of state transitions

    Aravind, Aditya; Paban, Sonia

    2016-01-01

    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 pre-inflationary 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.

  9. A Reconciliation of Collision Theory and Transition State Theory

    Yi, Y. G.

    2001-01-01

    A statistical-mechanical treatment of collision leads to a formal connection with transition-state theory, suggesting that collision theory and transition-state theory might be joined ultimately as a collision induced transition state theory.

  10. Transition of polymers from rubbery elastic state to fluid state

    Renyuan QIAN; Yansheng YU

    2009-01-01

    On increasing the temperature of a polymer,the transition of the polymer from a rubbery elastic state to a fluid state could occur. The transition temperature is termed the fluid temperature of the polymer, Tf, which has a direct relationship with the polymer molecular weight.As one of polymer parameters, Tf is as important as the glass transition temperature of a polymer, Tg. Moreover,special attention to Tf should be paid for polymer processing. In research on the transition of a polymer from a rubbery elastic state to a fluid state, the concept of Tfwould be more reasonable and more effective than the concept of T1,1 because it is neglected in the concept of T1,1in that the molecular weight of a polymer may affect the transition of the polymer. In this paper the discussion on the fluid temperature involves the characters of polymers,such as the deformation-temperature curve, the tempera-ture range of the rubbery state and the shear viscosity of polymer melt. From the viewpoint of the cohesional state of polymers, the transition of a polymer from a rubbery elastic state to a fluid state responds to destruction and construction of the cohesional entanglement network in the polymer. The relaxing network of polymer melt would be worthy to be considered as an object of study.

  11. Soil, resilience, and state and transition models

    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 ...

  12. Operationalizing resilience using state and transition models

    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...

  13. Merging transition-metal activation and aminocatalysis

    Rios, Ramon; Meazza, Marta

    2015-01-01

    In this review the principal enantioselective methodologies merging transition-metal catalysis and aminocatalysis are disclosed. 1 Introduction 2 Transition-Metal and Enamine Catalysis 3 Transition-Metal and Iminium Catalysis 4 Transition-Metal Catalysis and Organocascade (Iminium/Enamine) Activation 5 Conclusions and Perspectives

  14. Calculating state-to-state transition probabilities within TDDFT

    Rohringer, Nina; Peter, Simone; Burgdörfer, Joachim

    2005-01-01

    The determination of the elements of the S-matrix within the framework of time-dependent density-functional theory (TDDFT) has remained a widely open question. We explore two different methods to calculate state-to-state transition probabilities. The first method closely follows the extraction of the S-matrix from the time-dependent Hartree-Fock approximation. This method suffers from cross-channel correlations resulting in oscillating transition probabilities in the asymptotic channels. An a...

  15. State transition algorithm for traveling salesman problem

    Chunhua, Yang; Xiaojun, Zhou; Weihua, Gui

    2012-01-01

    Discrete version of state transition algorithm is proposed in order to solve the traveling salesman problem. Three special operators for discrete optimization problem named swap, shift and symmetry transformations are presented. Convergence analysis and time complexity of the algorithm are also considered. To make the algorithm simple and efficient, no parameter adjusting is suggested in current version. Experiments are carried out to test the performance of the strategy, and comparisons with simulated annealing and ant colony optimization have demonstrated the effectiveness of the proposed algorithm. The results also show that the discrete state transition algorithm consumes much less time and has better search ability than its counterparts, which indicates that state transition algorithm is with strong adaptability.

  16. Visualizing cell state transition using Raman spectroscopy.

    Taro Ichimura

    Full Text Available System level understanding of the cell requires detailed description of the cell state, which is often characterized by the expression levels of proteins. However, understanding the cell state requires comprehensive information of the cell, which is usually obtained from a large number of cells and their disruption. In this study, we used Raman spectroscopy, which can report changes in the cell state without introducing any label, as a non-invasive method with single cell capability. Significant differences in Raman spectra were observed at the levels of both the cytosol and nucleus in different cell-lines from mouse, indicating that Raman spectra reflect differences in the cell state. Difference in cell state was observed before and after the induction of differentiation in neuroblastoma and adipocytes, showing that Raman spectra can detect subtle changes in the cell state. Cell state transitions during embryonic stem cell (ESC differentiation were visualized when Raman spectroscopy was coupled with principal component analysis (PCA, which showed gradual transition in the cell states during differentiation. Detailed analysis showed that the diversity between cells are large in undifferentiated ESC and in mesenchymal stem cells compared with terminally differentiated cells, implying that the cell state in stem cells stochastically fluctuates during the self-renewal process. The present study strongly indicates that Raman spectral morphology, in combination with PCA, can be used to establish cells' fingerprints, which can be useful for distinguishing and identifying different cellular states.

  17. A Model of Mental State Transition Network

    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.

  18. Transition problems and play as transitory activity

    Broström, Stig

    2005-01-01

    Because too many children experience the transition to school as a culture shock, during the past decade teachers have implemented so-called transition activities in order to bridge the gap betwen pre-school and schoo. However, transition to school also calls for a development of higher mental fu...

  19. Comparison of quasi-classical, transition state theory, and quantum calculations of rate constants and activation energies for the collinear reaction X + F2 → XF + F (X = Mu, H, D, T)

    Accurate quantum total reaction probabilities for the collinear reaction X + F2 (upsilon = 0.1) → XF + F (X = Mu, H, D, T) have been used to calculate collinear rate constants and activation energies. Comparison is made with collinear quasi-classical trajectory calculations and transition state theory assuming classical motion along a separable reaction coordinate and vibrational adiabaticity. Considerable differences between the quantum and quasi-classical and transition state theory results are found only for the Mu reaction at low temperatures. 5 figures, 35 references, 6 tables

  20. Function of the chloroplast hydrogenase in the microalga Chlamydomonas: the role of hydrogenase and state transitions during photosynthetic activation in anaerobiosis.

    Bart Ghysels

    Full Text Available Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a respiration defective context, the photosynthetic electron transport chain of Chlamydomonas is remodeled by a state transition process to a conformation that favours the photoproduction of ATP at the expense of reductant synthesis. In some unicellular green algae including Chlamydomonas, anoxia also triggers the induction of a chloroplast-located, oxygen sensitive hydrogenase, which accepts electrons from reduced ferredoxin to convert protons into molecular hydrogen. Although microalgal hydrogen evolution has received much interest for its biotechnological potential, its physiological role remains unclear. By using specific Chlamydomonas mutants, we demonstrate that the state transition ability and the hydrogenase function are both critical for induction of photosynthesis in anoxia. These two processes are thus important for survival of the cells when they are transiently placed in an anaerobic environment.

  1. Function of the chloroplast hydrogenase in the microalga Chlamydomonas: the role of hydrogenase and state transitions during photosynthetic activation in anaerobiosis.

    Ghysels, Bart; Godaux, Damien; Matagne, René F; Cardol, Pierre; Franck, Fabrice

    2013-01-01

    Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a respiration defective context, the photosynthetic electron transport chain of Chlamydomonas is remodeled by a state transition process to a conformation that favours the photoproduction of ATP at the expense of reductant synthesis. In some unicellular green algae including Chlamydomonas, anoxia also triggers the induction of a chloroplast-located, oxygen sensitive hydrogenase, which accepts electrons from reduced ferredoxin to convert protons into molecular hydrogen. Although microalgal hydrogen evolution has received much interest for its biotechnological potential, its physiological role remains unclear. By using specific Chlamydomonas mutants, we demonstrate that the state transition ability and the hydrogenase function are both critical for induction of photosynthesis in anoxia. These two processes are thus important for survival of the cells when they are transiently placed in an anaerobic environment. PMID:23717558

  2. Multistate transitions and quantum oscillations of optical activity

    Blanco, Celia; 10.1103/PhysRevA.00.002100

    2012-01-01

    We consider the effects of multistate transitions on the tunneling racemization of chiral molecules. This requires going beyond simple two-state models of enantiomers and to include transitions within a multiple-level quantum-mechanical system.We derive an effective two-level description which accounts for transitions from the enantiomers to an arbitrary number of excited states as an application of the Weisskopf-Wigner approximation scheme. Modifications to the optical activity from these additional states are considered in general terms under the assumption of \\textit{CPT} invariance and then under T invariance. Some formal dynamical analogies between enantiomers and the neutral K-meson system are discussed.

  3. Quantum Phase Transitions in Matrix Product States

    We present a new general and much simpler scheme to construct various quantum phase transitions (QPTs) in spin chain systems with matrix product ground states. By use of the scheme we take into account one kind of matrix product state (MPS) QPT and provide a concrete model. We also study the properties of the concrete example and show that a kind of QPT appears, accompanied by the appearance of the discontinuity of the parity absent block physical observable, diverging correlation length only for the parity absent block operator, and other properties which are that the fixed point of the transition point is an isolated intermediate-coupling fixed point of renormalization flow and the entanglement entropy of a half-infinite chain is discontinuous

  4. Quantum phase transitions in matrix product states

    We present a new general and much simpler scheme to construct various quantum phase transitions (QPTs) in spin chain systems with matrix product ground states. By use of the scheme we take into account one kind of matrix product state (MPS) QPT and provide a concrete model. We also study the properties of the concrete example and show that a kind of QPT appears, accompanied by the appearance of the discontinuity of the parity absent block physical observable, diverging correlation length only for the parity absent block operator, and other properties which are that the fixed point of the transition point is an isolated intermediate-coupling fixed point of renormalization flow and the entanglement entropy of a half-infinite chain is discontinuous. (authors)

  5. On the Role of the Transition State Nucleus in Fission

    Although it is well-known that times. In order for fission to compete favourably with gamma-ray and neutron emission, a fixed amount of energy, equivalent to an activation energy in a chemical reaction, must be supplied to the heavy nucleus. This energy (often referred to as the fission threshold) is approximately 5 to 6 MeV for U238, and is the minimum energy required to produce the deformed transition state nucleus (zero internal excitation energy). In the process of stretching the original nucleus into the transition state nucleus (whose distortion is sometimes described as the saddle-point deformation), the increase in energy due to the short-range nuclear forces (surface tension) is greater than the decrease in energy due to the long-range Coulomb forces. However, as the particular distortion defining the transition state nucleus is approached, the decrease in Coulomb energy becomes equal to the increase in surface energy. The degree of distortion needed to produce the transition state nucleus is a function of several nuclear parameters and, hence, the saddle shape and threshold energy for fission change markedly for different nuclei. Since a large fraction of the excitation energy of the initial compound nucleus is consumed in deformation energy in passing to the fission saddle point, the transition state nucleus is thermodynamically ''cold''. Hence, for low excitation energies where the non-fission degrees of freedom favour the passage of the barrier with only a small kinetic energy, it seems reasonable to postulate that the traversal time of the saddle or the lifetime of the transition state nucleus is many orders of magnitude longer than the characteristic nuclear time. This leads to the prediction that the highly deformed transition state nucleus will have properties, including a spectrum of excited states, analogous to those of normal nuclei. Information on highly deformed transition state nuclei obtained by fission-fragment angular distribution studies

  6. Transition States at the Fission Barrier

    The current knowledge of the transition states that a nucleus traverses en route to fission is reviewed, together with the relevant theory of fission-fragment anisotropy. Theoretical progress in understanding this kind of data in terms of nuclear superfluidity is summarized. The evidence indicates that nuclear pairing effects play an important role in determining the transition state spectrum. Recent (d, pf) experimental data are noted, and their statistical analysis in terms of a pairing Hamiltonian considered in the fixed-energy ensemble appropriate for finite nuclei is presented. The results indicate that such pairing effects lead in Pu240 to an energy gap in the transition spectrum nearly twice that which occurs at the ground state shape of the same nucleus. Such a result is quite significant from the point of view of nuclear many-body physics, suggesting that the nuclear surface plays an important role in the pairing of nucleons in the finite nuclei. The significance for nuclear fission is also broad. Such a large energy gap forces reassessment of certain detailed conjectures that have been put forward concerning fission widths and mass asymmetry associated with capture resonances of specific spin and parity. The new situation suggests that the even-even and odd-odd spin-parity correlation that rules in the low energy spectra of deformed even-even nuclei does not prevail in the transition state spectrum. A possible explanation in terms of low energy mass- asymmetric and bending vibrations of the fissioning nucleus is discussed. Possible experimental studies that could support or negate the validity of this viewpoint are mentioned. (author)

  7. Phase Transitions in Model Active Systems

    Redner, Gabriel S.

    The amazing collective behaviors of active systems such as bird flocks, schools of fish, and colonies of microorganisms have long amazed scientists and laypeople alike. Understanding the physics of such systems is challenging due to their far-from-equilibrium dynamics, as well as the extreme diversity in their ingredients, relevant time- and length-scales, and emergent phenomenology. To make progress, one can categorize active systems by the symmetries of their constituent particles, as well as how activity is expressed. In this work, we examine two categories of active systems, and explore their phase behavior in detail. First, we study systems of self-propelled spherical particles moving in two dimensions. Despite the absence of an aligning interaction, this system displays complex emergent dynamics, including phase separation into a dense active solid and dilute gas. Using simulations and analytic modeling, we quantify the phase diagram and separation kinetics. We show that this nonequilibrium phase transition is analogous to an equilibrium vapor-liquid system, with binodal and spinodal curves and a critical point. We also characterize the dense active solid phase, a unique material which exhibits the structural signatures of a crystalline solid near the crystal-hexatic transition point, as well as anomalous dynamics including superdiffusive motion on intermediate timescales. We also explore the role of interparticle attraction in this system. We demonstrate that attraction drastically changes the phase diagram, which contains two distinct phase-separated regions and is reentrant as a function of propulsion speed. We interpret this complex situation with a simple kinetic model, which builds from the observed microdynamics of individual particles to a full description of the macroscopic phase behavior. We also study active nematics, liquid crystals driven out of equilibrium by energy-dissipating active stresses. The equilibrium nematic state is unstable in these

  8. Immigration Control in Transit States: The Case of Turkey

    Zeynep Sahin-Mencütek

    2012-01-01

    Transit countries exhibit many similarities with respect to state-led anti-transit and more restrictive actions toward contemporary transit migration flows. This paper examines the changes after 1990s in state concerns, behaviors, and policies regarding transit migration by taking Turkey as a case study. Which factors led to Turkey's increased attention to immigration, specifically transit migration in spite of its long history of immigration, emigration and the transit migration. Why has Tur...

  9. Transitioning Towards a Low-Carbon Hydrogen Economy in the United States: Role of Transition Management

    Jacqueline C. K. Lam; Peter Hills; Esther C. T. Wong

    2012-01-01

    This paper describes the process of transitioning to a low-carbon hydrogen economy in the United States and the role of transition management (TM) in this process. Focusing on the transition process for hydrogen-based energy and transport systems in the United States, especially California, this study outlines the key characteristics of TM that have been employed in managing the transition. Several characteristics of TM have been noted in the United States’ hydrogen transition, including: (...

  10. Stellar Transits in Active Galactic Nuclei

    Béky, Bence; Kocsis, Bence

    2013-01-01

    Supermassive black holes (SMBHs) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of stellar cusps, we find that around 106 solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or ~10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear stellar clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.

  11. A P-loop Mutation in G[alpha] Subunits Prevents Transition to the Active State: Implications for G-protein Signaling in Fungal Pathogenesis

    Bosch, Dustin E.; Willard, Francis S.; Ramanujam, Ravikrishna; Kimple, Adam J.; Willard, Melinda D.; Naqvi, Naweed I.; Siderovski, David P. (UNC); (Singapore)

    2012-10-23

    Heterotrimeric G-proteins are molecular switches integral to a panoply of different physiological responses that many organisms make to environmental cues. The switch from inactive to active G{alpha}{beta}{gamma} heterotrimer relies on nucleotide cycling by the G{alpha} subunit: exchange of GTP for GDP activates G{alpha}, whereas its intrinsic enzymatic activity catalyzes GTP hydrolysis to GDP and inorganic phosphate, thereby reverting G{alpha} to its inactive state. In several genetic studies of filamentous fungi, such as the rice blast fungus Magnaporthe oryzae, a G42R mutation in the phosphate-binding loop of G{alpha} subunits is assumed to be GTPase-deficient and thus constitutively active. Here, we demonstrate that G{alpha}(G42R) mutants are not GTPase deficient, but rather incapable of achieving the activated conformation. Two crystal structure models suggest that Arg-42 prevents a typical switch region conformational change upon G{alpha}{sub i1}(G42R) binding to GDP {center_dot} AlF{sub 4}{sup -} or GTP, but rotameric flexibility at this locus allows for unperturbed GTP hydrolysis. G{alpha}(G42R) mutants do not engage the active state-selective peptide KB-1753 nor RGS domains with high affinity, but instead favor interaction with G{beta}{gamma} and GoLoco motifs in any nucleotide state. The corresponding G{alpha}{sub q}(G48R) mutant is not constitutively active in cells and responds poorly to aluminum tetrafluoride activation. Comparative analyses of M. oryzae strains harboring either G42R or GTPase-deficient Q/L mutations in the G{alpha} subunits MagA or MagB illustrate functional differences in environmental cue processing and intracellular signaling outcomes between these two G{alpha} mutants, thus demonstrating the in vivo functional divergence of G42R and activating G-protein mutants.

  12. An absorbing phase transition from a structured active particle phase

    Lopez, Cristobal [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain); Ramos, Francisco [Departamento de Electromagnetismo y Fisica de la Materia and Instituto de Fisica Teorica y Computacional Carlos I, Facultad de Ciencias, Universidad de Granada, 18071 Granada (Spain); Hernandez-GarcIa, Emilio [Instituto Mediterraneo de Estudios Avanzados IMEDEA (CSIC-UIB), Campus de la Universidad de las Islas Baleares, E-07122 Palma de Mallorca (Spain)

    2007-02-14

    In this work we study the absorbing state phase transition of a recently introduced model for interacting particles with neighbourhood-dependent reproduction rates. The novelty of the transition is that as soon as the active phase is reached by increasing a control parameter a periodically arranged structure of particle clusters appears. A numerical study in one and two dimensions shows that the system falls into the directed percolation universality class.

  13. Absorbing-state phase transitions on percolating lattices.

    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

  14. Stellar transits in active galactic nuclei

    Béky, Bence

    2012-01-01

    Supermassive black holes (SMBH) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGN) produce a characteristic transit lightcurve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit lightcurves using the Novikov--Thorne thin accretion disk model, including general relatistic effects. Based on the expected properties of stellar cusps, we find that around 10^6 solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low mass AGNs to 1% photometric accuracy in optical, or ~ 10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Su...

  15. Savannah River Site prioritization of transition activities

    Effective management of SRS conversion from primarily a production facility to other missions (or Decontamination and Decommissioning (D ampersand D)) requires a systematic and consistent method of prioritizing the transition activities. This report discusses the design of a prioritizing method developed to achieve systematic and consistent methods of prioritizing these activities

  16. Savannah River Site prioritization of transition activities

    Finley, R.H.

    1993-11-01

    Effective management of SRS conversion from primarily a production facility to other missions (or Decontamination and Decommissioning (D&D)) requires a systematic and consistent method of prioritizing the transition activities. This report discusses the design of a prioritizing method developed to achieve systematic and consistent methods of prioritizing these activities.

  17. PULSAR STATE SWITCHING FROM MARKOV TRANSITIONS AND STOCHASTIC RESONANCE

    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

  18. Excited state quantum phase transitions in many-body systems

    Phenomena analogous to ground state quantum phase transitions have recently been noted to occur among states throughout the excitation spectra of certain many-body models. These excited state phase transitions are manifested as simultaneous singularities in the eigenvalue spectrum (including the gap or level density), order parameters, and wave function properties. In this article, the characteristics of excited state quantum phase transitions are investigated. The finite-size scaling behavior is determined at the mean-field level. It is found that excited state quantum phase transitions are universal to two-level bosonic and fermionic models with pairing interactions

  19. Urban Regional Traffic State Analysis Software System Emphasizing Pattern Transition

    Longfei Wang; Yang Li; Song Zhang; Qing Zhang

    2013-01-01

    Urban traffic state evolution analysis is very significant and constructive for traffic guidance and control. In this paper, firstly, a quantitative method for analyzing regional traffic state evolution was proposed by constructing traffic state pattern transition network to mine regional traffic state information and state pattern transition characteristics from massive data. Secondly, a GIS-based urban regional traffic state analysis soft ware system URTSAS based on the method was designed ...

  20. Microscopic model of the glass transition and the glassy state

    A microscopic model of the glass transition and the glassy state is presented. It is exactly solvable, and offers a unified view of the equilibrium and non-equilibrium aspects of the glass transition. It also provides a statistical-mechanical justification of the irreversible thermodynamic models of the glass transition proposed earlier. (author)

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

    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.…

  2. Care transition and network activation in Portugal

    Santana, Silvina; M. Viana

    2012-01-01

    Purpose To report on the use of a user-centred model and methodology to assess the quality of care transition and network activation action, in light of an ongoing home supported discharge procedure for stroke patients in Portugal. Theory In Portugal, the health care system presents weaknesses resulting from a remarkable diversity of entry points, inadequate use of scarce and expensive resources and difficult information flow between institutions and professionals. The social care network is ...

  3. The folding transition state theory in simple model systems

    Niewieczerzal, Szymon; Cieplak, Marek [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland)

    2008-06-18

    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.

  4. The folding transition state theory in simple model systems

    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.

  5. Transition States from Empirical Force Fields

    Jensen, Frank; Norrby, Per-Ola

    2003-01-01

    This is an overview of the use of empirical force fields in the study of reaction mechanisms. EVB-type methods (including RFF and MCMM) produce full reaction surfaces by mixing, in the simplest case, known force fields describing reactants and products. The SEAM method instead locates approximate...... transition structures by energy minimization along the intersection of the component force fields. The TSFF approach (including Q2MM) designs a new force field mimicking the transition structure as an energy minimum. The scope and applicability of the various methods are compared....

  6. Phase transition in Potts model with invisible states

    We study phase transition in the ferromagnetic Potts model with invisible states that are added as redundant states by mean-field calculation and Monte Carlo simulation. Invisible states affect the entropy and free energy, although they do not contribute to the internal energy. A second-order phase transition takes place at finite temperature in the standard q-state ferromagnetic Potts model on two-dimensional lattice for q=2,3, and 4. However, our present model on two-dimensional lattice undergoes a first-order phase transition with spontaneous q-fold symmetry breaking (q=2,3, and 4) due to entropy effect of invisible states. The model is fundamental for the analysis of a first-order phase transition with spontaneous discrete symmetry breaking. (author)

  7. Morse bifurcations of transition states in bimolecular reactions

    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.

  8. Decoding brain state transitions in the pedunculopontine nucleus: cooperative phasic and tonic mechanisms

    Anne ePetzold

    2015-10-01

    Full Text Available Cholinergic neurons of the pedunculopontine nucleus (PPN are most active during the waking state. Their activation is deemed to cause a switch in the global brain activity from sleep to wakefulness, while their sustained discharge may contribute to upholding the waking state and enhancing arousal. Similarly, non-cholinergic PPN neurons are responsive to brain state transitions and their activation may influence some of the same targets of cholinergic neurons, suggesting that they operate in coordination. Yet, it is not clear how the discharge of distinct classes of PPN neurons organize during brain states. Here we monitored the in vivo network activity of PPN neurons in the anesthetized rat across two distinct levels of cortical dynamics and their transitions. We identified a highly structured configuration in PPN network activity during slow-wave activity that was replaced by decorrelated activity during the activated state. During the transition, neurons were predominantly excited (phasically or tonically, but some were inhibited. Identified cholinergic neurons displayed phasic and short latency responses to sensory stimulation, whereas the majority of non-cholinergic showed tonic responses and remained at high discharge rates beyond the state transition. In vitro recordings demonstrate that cholinergic neurons exhibit fast adaptation that prevents them from discharging at high rates over prolonged time periods. Our data shows that PPN neurons have distinct but complementary roles during brain state transitions, where cholinergic neurons provide a fast and transient response to sensory events that drive state transitions, whereas non-cholinergic neurons maintain an elevated firing rate during global activation.

  9. Mixed ligand complexation of some transition metal ions in solution and solid state: Spectral characterization, antimicrobial, antioxidant, DNA cleavage activities and molecular modeling

    Shobana, Sutha; Dharmaraja, Jeyaprakash; Selvaraj, Shanmugaperumal

    2013-04-01

    Equilibrium studies of Ni(II), Cu(II) and Zn(II) mixed ligand complexes involving a primary ligand 5-fluorouracil (5-FU; A) and imidazoles viz., imidazole (him), benzimidazole (bim), histamine (hist) and L-histidine (his) as co-ligands(B) were carried out pH-metrically in aqueous medium at 310 ± 0.1 K with I = 0.15 M (NaClO4). In solution state, the stoichiometry of MABH, MAB and MAB2 species have been detected. The primary ligand(A) binds the central M(II) ions in a monodentate manner whereas him, bim, hist and his co-ligands(B) bind in mono, mono, bi and tridentate modes respectively. The calculated Δ log K, log X and log X' values indicate higher stability of the mixed ligand complexes in comparison to binary species. Stability of the mixed ligand complex equilibria follows the Irving-Williams order of stability. In vitro biological evaluations of the free ligand(A) and their metal complexes by well diffusion technique show moderate activities against common bacterial and fungal strains. Oxidative cleavage interaction of ligand(A) and their copper complexes with CT DNA is also studied by gel electrophoresis method in the presence of oxidant. In vitro antioxidant evaluations of the primary ligand(A), CuA and CuAB complexes by DPPH free radical scavenging model were carried out. In solid, the MAB type of M(II)sbnd 5-FU(A)sbnd his(B) complexes were isolated and characterized by various physico-chemical and spectral techniques. Both the magnetic susceptibility and electronic spectral analysis suggest distorted octahedral geometry. Thermal studies on the synthesized mixed ligand complexes show loss of coordinated water molecule in the first step followed by decomposition of the organic residues subsequently. XRD and SEM analysis suggest that the microcrystalline nature and homogeneous morphology of MAB complexes. Further, the 3D molecular modeling and analysis for the mixed ligand MAB complexes have also been carried out.

  10. 2014 Report: Wetland State-and-transition Model Project

    US Fish and Wildlife Service, Department of the Interior — Report from the 2014 field season of the Wetland State-and-Transition Project. Many National Wildlife Refuges in the Intermountain West and Prairie Pothole regions...

  11. Transition state theory and the dynamics of hard disks

    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.

  12. Formalization of Abstract State Transition Systems for SAT

    Marić, Filip

    2011-01-01

    We present a formalization of modern SAT solvers and their properties in a form of abstract state transition systems. SAT solving procedures are described as transition relations over states that represent the values of the solver's global variables. Several different SAT solvers are formalized, including both the classical DPLL procedure and its state-of-the-art successors. The formalization is made within the Isabelle/HOL system and the total correctness (soundness, termination, completeness) is shown for each presented system (with respect to a simple notion of satisfiability that can be manually checked). The systems are defined in a general way and cover procedures used in a wide range of modern SAT solvers. Our formalization builds up on the previous work on state transition systems for SAT, but it gives machine-verifiable proofs, somewhat more general specifications, and weaker assumptions that ensure the key correctness properties. The presented proofs of formal correctness of the transition systems c...

  13. Transition state theory demonstrated at the micron scale with out-of-equilibrium transport in a confined environment

    Vestergaard, Christian L.; Mikkelsen, Morten Bo Lindholm; Reisner, Walter;

    2016-01-01

    Transition state theory (TST) provides a simple interpretation of many thermally activated processes. It applies successfully on timescales and length scales that differ several orders of magnitude: to chemical reactions, breaking of chemical bonds, unfolding of proteins and RNA structures and...... they are observable in a microscope. Reaction rates are so slow that transitions are recorded on video. We find sharp transition states that are independent of the applied force, similar to chemical bond rupture, as well as transition states that change location on the reaction pathway with the...... strength of the applied force. The states of equilibrium and transition are separated by micrometres as compared with angstroms/nanometres for chemical bonds....

  14. Gamma transitions between compound states in spherical nuclei

    Average values of the reduced γ widths and their dispersions are investigated, basing on the Wigner statistical matrix method, for γ transitions from a compound state c into a less-energy excited state f of an arbitrary complexity in spherical nuclei. It is shown that in all the cases of practical interest the Porter-Thomas distribution is valid for the γ widths. It is found that in the γ transitions between compound states c and c' with Esub(γ) <= 2 MeV the dominating role is played by the M1 transitions due to the main multiquasiparticle states of c, and by the E1 transitions, due to small components of the state c. In framework of the existent theoretical schemes it is shown that the strength functions of the M1 and E1 transitions between the compound states with Esub(γ) <2 MeV are close. It is deduced thet the variant of the M1 transitions is preferable in view of the experimental results on the (n, γα) reactions induced by thermal and resonance neutrons

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

    McMinis, Jeremy; Morales, Miguel A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Ceperley, David M. [Department of Physics, University of Illinois, Urbana, Illinois 61801 (United States); Kim, Jeongnim [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    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.

  16. Fractal complexity in spontaneous EEG metastable-state transitions: new vistas on integrated neural dynamics

    PaoloParadisi

    2010-09-01

    Full Text Available 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.

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

    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...

  18. Vietnam: From Transitional State to Asian Tiger?

    F. Gerard Adams; Anh Le Tran

    2010-01-01

    Putting aside the legacy of its unique history, Vietnam has achieved an excellent growth record. But it is still far behind the leading East Asian economies. We consider the Vietnamese growth strategy in light of the controversies about ‘accumulation vs assimilation’ and ‘non-intervention vs governing the market’. We discuss the changes that are occurring as a result of the actions of the still large state-owned sector, and as a result of growing private domestic and FDI-led entrepren...

  19. TPmsm: Estimation of the Transition Probabilities in 3-State Models

    Artur Araújo

    2014-12-01

    Full Text Available One major goal in clinical applications of multi-state models is the estimation of transition probabilities. The usual nonparametric estimator of the transition matrix for non-homogeneous Markov processes is the Aalen-Johansen estimator (Aalen and Johansen 1978. However, two problems may arise from using this estimator: first, its standard error may be large in heavy censored scenarios; second, the estimator may be inconsistent if the process is non-Markovian. The development of the R package TPmsm has been motivated by several recent contributions that account for these estimation problems. Estimation and statistical inference for transition probabilities can be performed using TPmsm. The TPmsm package provides seven different approaches to three-state illness-death modeling. In two of these approaches the transition probabilities are estimated conditionally on current or past covariate measures. Two real data examples are included for illustration of software usage.

  20. Labour market states, mobility and entrepreneurship in transition economies

    Mark Dutz; Celine Kauffmann; Serineh Najarian; Peter Sanfey; Ruslan Yemtsov

    2001-01-01

    This paper examines the different strategies adopted by individuals in transition economies to cope with labour market restructuring. Using micro-data from seven countries at different stages of transition, we focus on “active” coping strategies, in particular mobility and entrepreneurship. Our results show that there is significant mobility across labour market states in most countries, but little inflow into entrepreneurship from unemployment or inactivity. Entrepreneurship is a high-reward...

  1. Excited states and transition metal compounds with quantum Monte Carlo

    Bande, Annika

    2007-01-01

    To the most challenging electron structure calculations belong weak interactions, excited state calculations, transition metals and properties. In this work the performance of variational (VMC) and fixed-node diffusion quantum Monte Carlo (FN-DMC) is tested for challenging electron structure problems using the quantum Monte Carlo amolqc code by Lüchow et al. The transition metal compounds under consideration are vanadium oxides. Here excitation, ionization, oxygen atom and molecule abstractio...

  2. Physical activity patterns in Greenland: A country in transition

    Dahl-Petersen, Inger; Jørgensen, Marit E; Bjerregaard, Peter

    2011-01-01

    To examine differences in physical activity patterns among Inuit in Greenland in relation to social transition. The Inuit in Greenland are an indigenous population in the circumpolar north who are experiencing rapid social transition.......To examine differences in physical activity patterns among Inuit in Greenland in relation to social transition. The Inuit in Greenland are an indigenous population in the circumpolar north who are experiencing rapid social transition....

  3. EVOLUTIONARY TRANSITIONS IN ENZYME ACTIVITY OF ANT FUNGUS GARDENS

    De Fine Licht, Henrik H; Schiøtt, Morten; Mueller, Ulrich G;

    2010-01-01

    an association with a monophyletic clade of specialized symbionts. In conjunction with the transition to specialized symbionts, the ants advanced in colony size and social complexity. Here we provide a comparative study of the functional specialization in extracellular enzyme activities in fungus gardens across...... the attine phylogeny. We show that, relative to sister clades, gardens of higher-attine ants have enhanced activity of protein-digesting enzymes, whereas gardens of leaf-cutting ants also have increased activity of starch-digesting enzymes. However, the enzyme activities of lower-attine fungus gardens...... are targeted primarily towards partial degradation of plant cell walls, reflecting a plesiomorphic state of non-domesticated fungi. The enzyme profiles of the higher-attine and leaf-cutting gardens appear particularly suited to digest fresh plant materials and to access nutrients from live cells without major...

  4. Complexity and state-transitions in social dependence networks

    Giuliano Pistolesi

    2001-01-01

    Full Text Available Computation of complexity in Social Dependence Networks is an interesting research domain to understand evolution processes and group exchange dynamics in natural and artificial intelligent Multi-Agent Systems. We perform an agent-based simulation by NET-PLEX (Conte and Pistolesi, 2000, a new software system able both to build interdependence networks tipically emerging in Multi-Agent System scenarios and to investigate complexity phenomena, i.e., unstability and state-transitions like Hopf bifurcation (Nowak and Lewenstein, 1994, and to describe social self organization phenomena emerging in these artificial social systems by means of complexity measures similar to those introduced by Hubermann and Hogg (1986. By performing analysis of complexity in these kind of artificial societies we observed interesting phenomena in emerging organizations that suggest state-transitions induced by critical configurations of parameters describing the social system similar to those observed in many studies on state-transitions in bifurcation chaos (Schuster, 1988; Ruelle, 1989.

  5. Morse bifurcations of transition states in bimolecular reactions

    MacKay, Robert S

    2015-01-01

    The transition states and dividing surfaces used to find rate constants for bimolecular reactions are shown to undergo qualitative changes, known as Morse bifurcations, 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. The reduction of the $n$-body systems representing the reactions is discussed and reviewed with comments on the difficulties associated with choosing appropriate charts and the global geometry of the reduced spaces.

  6. A quantum version of Wigner's transition state theory

    A quantum version of a recent realization of Wigner's transition state theory in phase space is presented. The theory developed builds on a quantum normal form which locally decouples the quantum dynamics near the transition state to any desired order in ℎ. This leads to an explicit algorithm to compute cumulative quantum reaction rates and the associated Gamov-Siegert resonances with high accuracy. This algorithm is very efficient since, as opposed to other approaches, it requires no quantum time propagation. This article is based on the presentation by H. Waalkens at the Fifth Workshop on Critical Stability, Erice, Sicily. (author)

  7. State transitions, hysteresis, and control parameters on DIII-D

    The theory of turbulence decorrelation by ExB velocity shear is the leading candidate to explain the changes in turbulence and transport that are seen at the plasma edge at the L to H transition. Based on this, a key question is: What are the conditions or control parameters needed to begin the formation of the Er shear layer and thus trigger the L to H transition? On the DIII-D tokamak, the authors are attacking this question both through direct tests of the various theories and by trying to gain insight into the fundamental physics by investigating the control parameters which have a major effect on the power threshold. In this paper the authors describe results of studies on oscillating discharges where the plasma transitions continuously between L and H states. By following the dynamics of the plasma state through the forward and back transitions, they can represent the evolution of various control parameter candidates as a trajectory in various parametric spaces. The shape of these control curves can illustrate the specific nonlinearities governing the L-H transition problem, and under the proper conditions may be interpreted in the context of various phase-transition based models. In particular, the hysteresis exhibited in the various curves may help to clarify causality (what are the critical parameters) and may serve as tests of the models, given sufficient experimental accuracy. At present they are looking at Te, Er and ballooning/diamagnetic parameters as possible control parameter candidates

  8. Critical Transitions in Social Network Activity

    Kuehn, Christian; Romero, Daniel

    2013-01-01

    A large variety of complex systems in ecology, climate science, biomedicine and engineering have been observed to exhibit tipping points, where the internal dynamical state of the system abruptly changes. For example, such critical transitions may result in the sudden change of ecological environments and climate conditions. Data and models suggest that some of these drastic events may be preceded by detectable early-warning signs. This view is also corroborated by abstract mathematical theory for generic bifurcations in stochastic multi-scale systems. Whether early-warnings are also present in social networks that anticipate \\textit{a-priori unknown} events in society is an open problem to which only highly speculative answers can be given at present. Here, we focus on \\textit{a-priori known} events and analyze a social network data set with a focus on classical variance and autocorrelation warning signs. We find that several a-priori known events are preceded by variance and autocorrelation growth as predic...

  9. Factorised steady states and condensation transitions in nonequilibrium systems

    M R Evans

    2005-06-01

    Systems driven out of equilibrium can often exhibit behaviour not seen in systems in thermal equilibrium – for example phase transitions in one-dimensional systems. In this talk I will review a simple model of a nonequilibrium system known as the `zero-range process' and its recent developments. The nonequilibrium stationary state of this model factorises and this property allows a detailed analysis of several `condensation' transitions wherein a finite fraction of the constituent particles condenses onto a single lattice site. I will then consider a more general class of mass transport models, encompassing continuous mass variables and discrete time updating, and present a necessary and sufficient condition for the steady state to factorise. The property of factorisation again allows an analysis of the condensation transitions which may occur.

  10. Planar Homotropenylium Cation : A Transition State with Reversed Aromaticity

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

    2015-01-01

    In contrast to the equilibrium structure of the homoaromatic C-s homotropenylium cation, C8H9+ (1), which supports a pinched diatropic ring current, the C(2)v transition state (2) for inversion of the methylene bridge of 1 is antiaromatic and supports a two-lobe paratropic pi current, as detected by

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

    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.

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

    Naber, J B; Hubert, T; Spreeuw, R J C

    2016-01-01

    We present our experimental investigation of an optical Raman transition between the magnetic clock states of $^{87}$Rb 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 multi-level structure of $^{87}$Rb. 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 decoheren...

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

    Mcelroy, J L; De Albuquerque, K

    1988-01-01

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

  14. Federal and state benefits for transition age youth.

    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

  15. Effect of ground state correlations on the charge transition densities of vibrational states

    The effect of ground state correlations on the charge transition densities of vibrational states in spherical nuclei is studied. The problem for the ground state correlations beyond RPA leads to a non-linear system of equations, which is solved numerically. The influence of the correlations on the pairing is taken into account too. The inclusion of ground state correlations beyond RPA results in an essential suppression of the charge transition density in the nuclear interior in comparison with the RPA calculations and enables one to reproduce the experimental data. 30 refs., 7 figs., 3 tabs

  16. Pion charge-exchange reactions: The analog state transitions

    The general features of pion charge-exchange reactions leading to nuclear-isobaric-analog states (IAS) and double-isobaric-analog states (DIAS), as they have emerged from studies over the past ten years, are reviewed. The energy range investigated is 20 to 550 MeV for IAS transitions and 20 to 300 MeV for DIAS transitions. These data are seen to play an important role in characterizing the pion optical potential, in determining the Δ-N interaction in nuclei, and in the study of nucleon correlations in nuclei. Recent progress achieved in understanding the role of such correlations in double-charge-exchange reactions is reviewed. 55 refs., 43 figs., 3 tabs

  17. Identification and Analysis of Transition and Metastable Markov States

    Martini, Linda; Hummer, Gerhard; Buchete, Nicolae-Viorel; Rosta, Edina

    2016-01-01

    We present a new method that enables the identification and analysis of both transition and metastable conformational states from atomistic or coarse-grained molecular dynamics (MD) trajectories. Our algorithm is presented and studied by using both analytical and actual examples from MD simulations of the helix-forming peptide Ala5, and of a larger system, the epidermal growth factor receptor (EGFR) protein. In all cases, our method identifies automatically the corresponding transition states and metastable conformations in an optimal way, with the input of a set of relevant coordinates, by capturing accurately the intrinsic slowest relaxation rate. Our approach provides a general and easy to implement analysis method that provides unique insight into the molecular mechanism and the rare but crucial rate limiting conformational pathways occurring in complex dynamical systems such as molecular trajectories.

  18. Female Employment and Timing of Births Decisions: A Multiple State Transition Model

    Bloemen, H.G.; A.S. Kalwij

    1996-01-01

    In this paper we estimate a multiple state transition model, describing transitions into maternity and labor market transitions for women.Each state is characterized by two components: the labor market state and the maternity state. This enables us to investigate to disentangle the effects of socio-economic variables on the timing of births and on labor market transitions.We find that the transition intensities into maternity are significantly higher for non-employed women than for employed w...

  19. Modeling Enzymatic Transition States by Force Field Methods

    Hansen, Mikkel Bo; Jensen, Hans Jørgen Aagaard; Jensen, Frank

    2009-01-01

    The SEAM method, which models a transition structure as a minimum on the seam of two diabatic surfaces represented by force field functions, has been used to generate 20 transition structures for the decarboxylation of orotidine by the orotidine-5'-monophosphate decarboxylase enzyme. The dependence...... by various electronic structure methods, where part of the enzyme is represented by a force field description and the effects of the solvent are represented by a continuum model. The relative energies vary by several hundreds of kJ/mol between the transition structures, and tests showed that a large part...... of this variation is due to changes in the enzyme structure at distances more than 5 Å from the active site. There are significant differences between the results obtained by pure quantum methods and those from mixed quantum and molecular mechanics methods....

  20. Nonequilibrium Critical Phenomena and Phase Transitions into Absorbing States

    Hinrichsen, Haye

    2000-01-01

    This review addresses recent developments in nonequilibrium statistical physics. Focusing on phase transitions from fluctuating phases into absorbing states, the universality class of directed percolation is investigated in detail. The survey gives a general introduction to various lattice models of directed percolation and studies their scaling properties, field-theoretic aspects, numerical techniques, as well as possible experimental realizations. In addition, several examples of absorbing-...

  1. A matlab toolbox for continuous state transition algorithm

    Zhou, Xiaojun

    2016-01-01

    State transition algorithm (STA) has been emerging as a novel stochastic method for global optimization in recent few years. To make better understanding of continuous STA, a matlab toolbox for continuous STA has been developed. Firstly, the basic principles of continuous STA are briefly described. Then, a matlab implementation of the standard continuous STA is explained, with several instances given to show how to use to the matlab toolbox to minimize an optimization problem with bound const...

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

    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

  3. Charge states of ions, and mechanisms of charge ordering transitions

    To gain insight into the mechanism of charge ordering transitions, which conventionally are pictured as a disproportionation of an ion M as 2Mn+→M(n+1)+ + M(n−1)+, we (1) review and reconsider the charge state (or oxidation number) picture itself, (2) introduce new results for the putative charge ordering compound AgNiO2 and the dual charge state insulator AgO, and (3) analyze the cationic occupations of the actual (not formal) charge, and work to reconcile the conundrums that arise. We establish that several of the clearest cases of charge ordering transitions involve no disproportion (no charge transfer between the cations, and hence no charge ordering), and that the experimental data used to support charge ordering can be accounted for within density functional-based calculations that contain no charge transfer between cations. We propose that the charge state picture retains meaning and importance, at least in many cases, if one focuses on Wannier functions rather than atomic orbitals. The challenge of modeling charge ordering transitions with model Hamiltonians isdiscussed. (paper)

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

    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

  5. Matrix Metalloproteinase Inhibition by Heterotrimeric Triple-Helical Peptide Transition State Analogs

    Bhowmick, Manishabrata; Stawikowska, Roma; Tokmina-Roszyk, Dorota; Fields, Gregg B.

    2015-01-01

    Matrix metalloproteinases (MMPs) have been implicated in numerous pathologies. An overall lack of selectivity has rendered active site targeted MMP inhibitors problematic. The present study describes MMP inhibitors that function by binding both secondary binding sites (exosites) and the active site. Heterotrimeric triple-helical peptide transition-state analog inhibitors (THPIs) were assembled utilizing click chemistry. Three different heterotrimers were constructed, allowing for the inhibito...

  6. State management in transition: Understanding water resources management in Vietnam

    Waibel, Gabi

    2010-01-01

    For many years, water resources management in Vietnam was concentrated on activities ensuring the available freshwater for agricultural production, including flood control. With the increase of water demands and the emergence of new water usages since the late 1980s, this has subsequently changed. During the past two decades, and within the context of a broad economic transition process, the water sector has undergone a series of reforms, including various attempts to integrate environmental ...

  7. Mechanical induction of transitions into mesenchymal and amoeboid states

    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.

  8. Control of transition state spectra: a variational algorithm

    We propose to control the characteristics of transition state spectra by designing the initial state of a photochemical reaction. The method proceeds by introducing parameters into the (nonstationary) initial state wave function. The parameters are determined variationally to optimize a desired feature of the spectrum. One important application of this procedure is to reduce the unstructured background in a photoabsorption spectrum. In the resulting spectra, the contrast ratio of the resonance peaks to the background is dramatically increased, allowing a spectral quantization procedure to be used to assign the peaks. The algorithm can also be used to resolve overlapping peaks and to enhance specific progressions. As a theoretical tool, the variational algorithm can be viewed as a method to analyze the resonance structure of a given potential surface. We speculate that control of spectra can also be achieved in the laboratory, and suggest one possible scheme to do so. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  9. Ground State Energies of Interacting Electrons from Projected Densities of Transitions

    Haydock, Roger

    2014-01-01

    For interacting electrons in solids, Heisenberg's equation is used to calculate the distribution in energy of transitions induced by adding an electron to an atomic-like spin orbital. This is the projected density of transitions which includes transitions between grounds states, as well as between other states differing by one electron. The energy of a ground state is then calculated as the sum of the least energies of transitions starting with the ground state of no electrons and adding one ...

  10. Critical Transitions in Social Network Activity

    Kuehn, Christian; Martens, Erik Andreas; Romero, Daniel M

    2014-01-01

    priori unknown events in society are present in social networks is an exciting open problem, to which at present only highly speculative answers can be given. Here, we instead provide a first step towards tackling a simpler question by focusing on a priori known events and analyse a social media data set...... a priori known events are preceded by variance and autocorrelation growth. Our findings thus clearly establish the necessary starting point to further investigate the relationship between abstract mathematical theory and various classes of critical transitions in social networks....... with a focus on classical variance and autocorrelation warning signs. Our results thus pertain to one absolutely fundamental question: Can the stochastic warning signs known from other areas also be detected in large-scale social media data? We answer this question affirmatively as we find that several...

  11. Steady-state organization of binary mixtures by active impurities

    Sabra, Mads Christian; Gilhøj, Henriette; Mouritsen, Ole G.

    1998-01-01

    The structural reorganization of a phase-separated binary mixture in the presence of an annealed dilution of active impurities is studied by computer-simulation techniques via a simple two-dimensional lattice-gas model. The impurities, each of which has two internal states with different affinity...... for the two species, become active by an external driving of a transition between the two impurity states, leading to an energy flow from the impurities into the binary mixture. In steady state, the drive is found to break down the phase-separated state and lead to a new finite length scale controlled...

  12. Transit and health: mode of transport, employer-sponsored public transit pass programs, and physical activity.

    Lachapelle, Ugo; Frank, Lawrence D

    2009-01-01

    Increased provision of transit service and policy incentives that favor transit use can support a physically active lifestyle. We used the smartraq travel survey in metropolitan Atlanta, Georgia (in 2001-2002) to assess whether transit and car trips were associated with meeting the recommended levels of physical activity by using walking as a means of transportation. Additionally, we assessed associations between walking and using an employer-sponsored public transit pass. We controlled for demographics, neighborhood density, presence of services near workplaces, distance from home to transit, and car availability in our sample of 4,156 completed surveys. Walking distances from origin to destination were derived by a geographical information system and categorized as: no walking, moderate walking, or meeting recommendation (walking>or=2.4 km (1.5 miles) a day, approximately>or=30 min). In a multinomial logistic regression controlling for other covariates, transit trips were associated with an odds ratio (OR) of 3.87 (confidence interval (CI) 95%, 2.93-5.11) of meeting recommendation. In a multinominal logistical regression controlling for other covariates, transit users were associated with meeting recommendation, OR 2.23 (CI 95%, 1.27-3.90). PMID:19190584

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

    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.

  14. Overlap and activity glass transitions in plaquette spin models with hierarchical dynamics

    Turner, Robert M.; Jack, Robert L.; Garrahan, Juan P.

    2015-08-01

    We consider thermodynamic and dynamic phase transitions in plaquette spin models of glasses. The thermodynamic transitions involve coupled (annealed) replicas of the model. We map these coupled-replica systems to a single replica in a magnetic field, which allows us to analyze the resulting phase transitions in detail. For the triangular plaquette model (TPM), we find for the coupled-replica system a phase transition between high- and low-overlap phases, occurring at a coupling ɛ*(T ) , which vanishes in the low-temperature limit. Using computational path sampling techniques, we show that a single TPM also displays "space-time" transitions between active and inactive dynamical phases. These first-order dynamical transitions occur at a critical counting field sc(T ) ≳0 that appears to vanish at zero temperature in a manner reminiscent of the thermodynamic overlap transition. In order to extend the ideas to three dimensions, we introduce the square pyramid model, which also displays both overlap and activity transitions. We discuss a possible common origin of these various phase transitions, based on long-lived (metastable) glassy states.

  15. An aniline dication-like transition state in the Bamberger rearrangement

    Shinichi Yamabe

    2013-06-01

    Full Text Available A Bamberger rearrangement of N-phenylhydroxylamine, Ph–N(OHH, to p-aminophenol was investigated by DFT calculations for the first time. The nitrenium ion, C6H5–NH+, suggested and seemingly established as an intermediate was calculated to be absent owing to the high nucleophilicity of the water cluster around it. First, a reaction of the monoprotonated system, Ph–N(OHH + H3O+(H2On (n = 4 and 14 was examined. However, the rate-determining transition states involving proton transfers were calculated to have much larger activation energies than the experimental one. Second, a reaction of the diprotonated system, Ph–N(OHH + (H3O+2(H2O13, was traced. An activation energy similar to the experimental one was obtained. A new mechanism of the rearrangement including the aniline dication-like transition state was proposed.

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

    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.

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

    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

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

    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. Capturing the state transitions of seizure-like events using Hidden Markov models.

    Guirgis, Mirna; Serletis, Demitre; Carlen, Peter L; Bardakjian, Berj L

    2011-01-01

    The purpose of this study was to investigate the number of states present in the progression of a seizure-like event (SLE). Of particular interest is to determine if there are more than two clearly defined states, as this would suggest that there is a distinct state preceding an SLE. Whole-intact hippocampus from C57/BL mice was used to model epileptiform activity induced by the perfusion of a low Mg(2+)/high K(+) solution while extracellular field potentials were recorded from CA3 pyramidal neurons. Hidden Markov models (HMM) were used to model the state transitions of the recorded SLEs by incorporating various features of the Hilbert transform into the training algorithm; specifically, 2- and 3-state HMMs were explored. Although the 2-state model was able to distinguish between SLE and nonSLE behavior, it provided no improvements compared to visual inspection alone. However, the 3-state model was able to capture two distinct nonSLE states that visual inspection failed to discriminate. Moreover, by developing an HMM based system a priori knowledge of the state transitions was not required making this an ideal platform for seizure prediction algorithms. PMID:22254742

  20. Experiments on the active control of transitional boundary layers

    Nelson, P. A.; Rioual, J.-L.; Fisher, M. J.

    Experimental results are presented which demonstrate that the streamwise position of the transition region of a flat plate boundary layer can be actively controlled. The means of control is through the application of suction through the surface of the plate, a progressive increase in suction rate being capable of producing transition at progressively larger distances downstream from the plate leading edge. A simple digital feedback regulator based on an integral control law is shown to be most effective in regulating the position of transition, an error signal being derived from measurements of pressure fluctuations on the surface of the plate.

  1. Public works for Poland? Active labour market policies during transition

    Puhani, Patrick A.; Steiner, Viktor

    1996-01-01

    Following the predominance of macroeconomic stabilisation policies and passive income support schemes in the first phase of transition, active labour market policies (ALMPs) have now come to play a more important role in transition economies. This paper looks at the Polish experience and provides empirical evidence on the effectiveness of ALMPs. We use the Polish Labour Force Survey of August 1994 in combination with its Supplement on the Evaluation of Labour Market Policies together with dat...

  2. Gas-phase chemistry of the yttrium-imido cation YNH{sup +} with alkenes: {Beta}-hydrogen activation by a d{sup 0} system via a multicentered transition state

    Ranatunga, D.R.A.; Hill, Y.D.; Freiser, B.S. [Purdue Univ., West Lafayette, IN (United States)

    1996-02-20

    The gas-phase chemistry of the yttrium-imido carbon cations with alkenes was studied by using Fourier transform mass spectrometry to explore the chemistry of transition metal ion complexes with low-valence metal centers. The YNH{sup +} species was synthesized by reacting Y{sup +}, generated by laser desorption, with ammonia. The dehydrogenation reaction is exothermic, yielding a lower limit for the imido bond energy of D{degree}(Y{sup +}-NH) > 101 kcal/mol. Due to the electron deficiency of the metal center upon binding to NH, the further reactivity of YNH{sup +} can only be explained by a reaction mechanism involving a multicentered transition state. YNH{sup +} reacts with ethene predominantly by dehydrogenation to produce YC{sub 2}H{sub 3}N{sup +}. Thus, instead of the metathesis reaction involving the cleavage of the 2-aza-1-metallacyclobutane intermediate, a {beta}-hydrogen transfers to the metal center and is then eliminated with a hydrogen from the remaining CH{sub 2} group to complete the reaction. All three linear butenes, 1-butene, cis-2-butene, and trans-2-butene, react very similarly with YNH{sup +}, yielding a variety of product ions with the predominant loss of NH{sub 3} resulting in the formation of YCH{sub 4}H{sub 6}{sup +}. Structural studies on this ion suggest that it is bent metallacyclopent-3-ene, not the butadiene isomer. 34 refs., 1 fig.

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

    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

  4. A molecular symmetry analysis of the electronic states and transition dipole moments for molecules with two torsional degrees of freedom

    We present a molecular symmetry analysis of electronic states and transition dipole moments for molecules which undergo large amplitude intramolecular torsions. The method is based on the correlation between the point group of the molecule at highly symmetric configurations and the molecular symmetry group. As an example, we determine the global irreducible representations of the electronic states and transition dipole moments for the quinodimethane derivative 2-[4-(cyclopenta-2,4-dien-1-ylidene)cyclohexa-2,5-dien-1-ylidene]-2H-1, 3-dioxole for which two torsional degrees of freedom can be activated upon photo-excitation and construct the resulting symmetry adapted transition dipole functions

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

    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.

  6. Bound states of quarks and gluons and hadronic transitions

    A potential which incorporates the concepts of confinement and asymptotic freedom, previously utilized in the description of the spectroscopy of mesons and baryons, is extended to the gluon sector. The mass spectroscopy of glueballs and hybrids is analyzed considering only pairwise potentials and massive constituent gluons. The mass spectrum of the color octet two-gluon system is adopted as a suitable description of the intermediate states of hadronic transitions, within the framework of the multipole expansion for quantum chromodynamics. The spin-dependent effects in the gluonium spectrum, associated with the Coulombian potential, are calculated through the inverted first Born approximation for the gluon-gluon scattering. (author). 102 refs, 1 fig, 13 tabs

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

    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.

  8. Pontine respiratory activity involved in inspiratory/expiratory phase transition

    Mörschel, Michael; Dutschmann, Mathias

    2009-01-01

    Control of the timing of the inspiratory/expiratory (IE) phase transition is a hallmark of respiratory pattern formation. In principle, sensory feedback from pulmonary stretch receptors (Breuer–Hering reflex, BHR) is seen as the major controller for the IE phase transition, while pontine-based control of IE phase transition by both the pontine Kölliker–Fuse nucleus (KF) and parabrachial complex is seen as a secondary or backup mechanism. However, previous studies have shown that the BHR can habituate in vivo. Thus, habituation reduces sensory feedback, so the role of the pons, and specifically the KF, for IE phase transition may increase dramatically. Pontine-mediated control of the IE phase transition is not completely understood. In the present review, we discuss existing models for ponto-medullary interaction that may be involved in the control of inspiratory duration and IE transition. We also present intracellular recordings of pontine respiratory units derived from an in situ intra-arterially perfused brainstem preparation of rats. With the absence of lung inflation, this preparation generates a normal respiratory pattern and many of the recorded pontine units demonstrated phasic respiratory-related activity. The analysis of changes in membrane potentials of pontine respiratory neurons has allowed us to propose a number of pontine-medullary interactions not considered before. The involvement of these putative interactions in pontine-mediated control of IE phase transitions is discussed. PMID:19651653

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

    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

  10. Transiting the Sun II: The impact of stellar activity on Lyman-$\\alpha$ transits

    Llama, J

    2015-01-01

    High-energy observations of the Sun provide an opportunity to test the limits of our ability to accurately measure properties of transiting exoplanets in the presence of stellar activity. Here we insert transits of a hot Jupiter into continuous disk integrated data of the Sun in Lyman-alpha (Ly$\\alpha$) from NASA's SDO/EVE instrument to assess the impact of stellar activity on the measured planet-to-star radius ratio $(\\textrm{R}_\\textrm{p}/\\textrm{R}_\\star)$. In 75% of our simulated light curves we measure the correct radius ratio; however, incorrect values can be measured if there is significant short term variability in the light curve. The maximum measured value of $(\\textrm{R}_\\textrm{p}/\\textrm{R}_\\star)$ is $50\\%$ larger than the input value, which is much smaller than the large Ly$\\alpha$ transit depths that have been reported in the literature, suggesting that for stars with activity levels comparable to the Sun, stellar activity alone cannot account for these deep transits. We ran simulations withou...

  11. Analysis of the chloroplast protein kinase Stt7 during state transitions.

    Sylvain Lemeille

    2009-03-01

    Full Text Available State transitions allow for the balancing of the light excitation energy between photosystem I and photosystem II and for optimal photosynthetic activity when photosynthetic organisms are subjected to changing light conditions. This process is regulated by the redox state of the plastoquinone pool through the Stt7/STN7 protein kinase required for phosphorylation of the light-harvesting complex LHCII and for the reversible displacement of the mobile LHCII between the photosystems. We show that Stt7 is associated with photosynthetic complexes including LHCII, photosystem I, and the cytochrome b6f complex. Our data reveal that Stt7 acts in catalytic amounts. We also provide evidence that Stt7 contains a transmembrane region that separates its catalytic kinase domain on the stromal side from its N-terminal end in the thylakoid lumen with two conserved Cys that are critical for its activity and state transitions. On the basis of these data, we propose that the activity of Stt7 is regulated through its transmembrane domain and that a disulfide bond between the two lumen Cys is essential for its activity. The high-light-induced reduction of this bond may occur through a transthylakoid thiol-reducing pathway driven by the ferredoxin-thioredoxin system which is also required for cytochrome b6f assembly and heme biogenesis.

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

    Metz, R.B.

    1991-12-01

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

  13. Critical behavior of absorbing phase transitions for models in the Manna class with natural initial states.

    Lee, Sang Bub

    2014-06-01

    The critical behavior of absorbing phase transitions for two typical models in the Manna universality class, the conserved Manna model and the conserved lattice gas model, both on a square lattice, was investigated using the natural initial states. Various critical exponents were estimated using the static and dynamic simulations. The exponents characterizing dynamics of active particles differ considerably from the known exponents obtained using the random initial states, whereas those associated with the steady-state quantities remain the same. The critical exponents for both models were consistent with errors of less than 1% and satisfied the known scaling relations; thus, the known violation of scaling relations for models with a conserved field was resolved using the natural initial states. The results differed by 7%∼12% from the directed percolation values. PMID:25019750

  14. Enzyme activity below the dynamical transition at 220 K.

    Daniel, R M; Smith, J. C.; Ferrand, M; Héry, S; Dunn, R; Finney, J L

    1998-01-01

    Enzyme activity requires the activation of anharmonic motions, such as jumps between potential energy wells. However, in general, the forms and time scales of the functionally important anharmonic dynamics coupled to motion along the reaction coordinate remain to be determined. In particular, the question arises whether the temperature-dependent dynamical transition from harmonic to anharmonic motion in proteins, which has been observed experimentally and using molecular dynamics simulation, ...

  15. Active State Model for Autonomous Systems

    Park, Han; Chien, Steve; Zak, Michail; James, Mark; Mackey, Ryan; Fisher, Forest

    2003-01-01

    The concept of the active state model (ASM) is an architecture for the development of advanced integrated fault-detection-and-isolation (FDI) systems for robotic land vehicles, pilotless aircraft, exploratory spacecraft, or other complex engineering systems that will be capable of autonomous operation. An FDI system based on the ASM concept would not only provide traditional diagnostic capabilities, but also integrate the FDI system under a unified framework and provide mechanism for sharing of information between FDI subsystems to fully assess the overall health of the system. The ASM concept begins with definitions borrowed from psychology, wherein a system is regarded as active when it possesses self-image, self-awareness, and an ability to make decisions itself, such that it is able to perform purposeful motions and other transitions with some degree of autonomy from the environment. For an engineering system, self-image would manifest itself as the ability to determine nominal values of sensor data by use of a mathematical model of itself, and selfawareness would manifest itself as the ability to relate sensor data to their nominal values. The ASM for such a system may start with the closed-loop control dynamics that describe the evolution of state variables. As soon as this model was supplemented with nominal values of sensor data, it would possess self-image. The ability to process the current sensor data and compare them with the nominal values would represent self-awareness. On the basis of self-image and self-awareness, the ASM provides the capability for self-identification, detection of abnormalities, and self-diagnosis.

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

    Mazzotti, Valerie L.; Plotner, Anthony J.

    2016-01-01

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

  17. Account of states with indefinite spin in calculations of intercombination collisional transitions

    States with indefinite spin are used in the second order of the perturbation theory as intermediate states for calculating electronic collisional transitions with changing spin between excited states of atoms. The rate coefficient for 41P-43D transition in helium is estimated

  18. The 10 Hz Frequency: A Fulcrum For Transitional Brain States

    Garcia-Rill, E.; D’Onofrio, S.; Luster, B.; Mahaffey, S.; Urbano, F. J.; Phillips, C.

    2016-01-01

    A 10 Hz rhythm is present in the occipital cortex when the eyes are closed (alpha waves), in the precentral cortex at rest (mu rhythm), in the superior and middle temporal lobe (tau rhythm), in the inferior olive (projection to cerebellar cortex), and in physiological tremor (underlying all voluntary movement). These are all considered resting rhythms in the waking brain which are “replaced” by higher frequency activity with sensorimotor stimulation. That is, the 10 Hz frequency fulcrum is replaced on the one hand by lower frequencies during sleep, or on the other hand by higher frequencies during volition and cognition. The 10 Hz frequency fulcrum is proposed as the natural frequency of the brain during quiet waking, but is replaced by higher frequencies capable of permitting more complex functions, or by lower frequencies during sleep and inactivity. At the center of the transition shifts to and from the resting rhythm is the reticular activating system, a phylogenetically preserved area of the brain essential for preconscious awareness.

  19. Research for the energy turnaround. Phase transitions actively shape. Contributions

    The Annual Conference 2014 of the Renewable Energy Research Association was held in Berlin on 6 and 7 November 2014. This book documents the contributions of the conference on research for the energy turnaround, phase transitions actively shape. After an introduction and two contributions to the political framework, the contributions to the economic phases of the energy transition, the phase of the current turn, the phases of social energy revolution, the stages of heat turnaround (Waermewende), and the stages of the mobility turn deal with the stages of development of the energy system. Finally, the Research Association Renewable Energy is briefly presented.

  20. Activated phosphors having matrices of yttrium-transition metal compound

    De Kalb, E.L.; Fassel, V.A.

    1975-07-01

    A method is described for preparing a phosphor composition containing a lanthanide activator element with a host matrix having a transition element as a major component. The host matrix is composed of certain rare earth phosphates or vanadates such as YPO$sub 4$ with a portion of the rare earth replaced with one or more of the transition elements. On x-ray or other electromagnetic excitation, trace lanthanide impurities or additives within the phosphor are spectrometrically determined from their characteristic luminescence. (auth)

  1. Observation of magnetic supercooling of the transition to the vortex state

    The magnetic hysteresis of an individual magnetic disc switching in and out of the vortex state has been exhaustively measured using nanomechanical torsional resonator torque magnetometry. Each individual hysteresis loop pinpoints two sharp events, a single vortex creation and an annihilation, with a bias field precision of 0.02 kA m-1. Statistical analysis of thousands of hysteresis loops reveals a dramatic difference in the sensitivity of the vortex creation and annihilation field distributions to the measurement conditions. The data sets measured at different magnetic field sweep rates demonstrate that the transition from the high-field state to the vortex state is not well modeled as a conventional thermal activation process in which it is assumed that the 'true' nucleation field is lower than any of the observed switching fields. Instead, the results are suggestive of the classic supercooling signature of a first-order phase transition, or more specifically here, its magnetic equivalent. This phenomenological evidence is consistent with a theoretical picture of the vortex nucleation process as a modified Landau first-order phase transition.

  2. Modelling transition states of a small once-through boiler

    Talonpoika, T. [Lappeenranta Univ. of Technology (Finland). Dept. of Energy Technology

    1997-12-31

    This article presents a model for the unsteady dynamic behaviour of a once-through counter flow boiler that uses an organic working fluid. The boiler is a compact waste-heat boiler without a furnace and it has a preheater, a vaporiser and a superheater. The relative lengths of the boiler parts vary with the operating conditions since they are all parts of a single tube. The boiler model is presented using a selected example case that uses toluene as the process fluid and flue gas from natural gas combustion as the heat source. The dynamic behaviour of the boiler means transition from the steady initial state towards another steady state that corresponds to the changed process conditions. The solution method chosen is to find such a pressure of the process fluid that the mass of the process fluid in the boiler equals the mass calculated using the mass flows into and out of the boiler during a time step, using the finite difference method. A special method of fast calculation of the thermal properties is used, because most of the calculation time is spent in calculating the fluid properties. The boiler is divided into elements. The values of the thermodynamic properties and mass flows are calculated in the nodes that connect the elements. Dynamic behaviour is limited to the process fluid and tube wall, and the heat source is regarded as to be steady. The elements that connect the preheater to the vaporiser and the vaporiser to the superheater are treated in a special way that takes into account a flexible change from one part to the other. The initial state of the boiler is received from a steady process model that is not a part of the boiler model. The known boundary values that may vary during the dynamic calculation were the inlet temperature and mass flow rates of both the heat source fluid and the process fluid. The dynamic boiler model is analysed for linear and step charges of the entering fluid temperatures and flow rates. The heat source side tests show that

  3. Dynamics of transitions between capillary stable states under weightlessness

    Srikanth, Praveen

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

  4. Probing an Excited-State Atomic Transition Using Hyperfine Quantum Beat Spectroscopy

    Wade, Christopher G; Keaveney, James; Adams, Charles S; Weatherill, Kevin J

    2014-01-01

    We describe a method to observe the dynamics of an excited-state transition in a room temperature atomic vapor using hyperfine quantum beats. Our experiment using cesium atoms consists of a pulsed excitation of the D2 transition, and continuous-wave driving of an excited-state transition from the 6P$_{3/2}$ state to the 7S$_{1/2}$ state. We observe quantum beats in the fluorescence from the 6P$_{3/2}$ state which are modified by the driving of the excited-state transition. The Fourier spectrum of the beat signal yields evidence of Autler-Townes splitting of the 6P$_{3/2}$, F = 5 hyperfine level and Rabi oscillations on the excited-state transition. A detailed model provides qualitative agreement with the data, giving insight to the physical processes involved.

  5. Liquid-Gas Phase Transition in Nuclear Equation of State

    Lee, S J

    1997-01-01

    A canonical ensemble model is used to describe a caloric curve of nuclear liquid-gas phase transition. Allowing a discontinuity in the freeze out density from one spinodal density to another for a given initial temperature, the nuclear liquid-gas phase transition can be described as first order. Averaging over various freeze out densities of all the possible initial temperatures for a given total reaction energy, the first order characteristics of liquid-gas phase transition is smeared out to a smooth transition. Two experiments, one at low beam energy and one at high beam energy show different caloric behaviors and are discussed.

  6. Cell-State Transitions Regulated by SLUG Are Critical for Tissue Regeneration and Tumor Initiation

    Sarah Phillips

    2014-05-01

    Full Text Available Perturbations in stem cell activity and differentiation can lead to developmental defects and cancer. We use an approach involving a quantitative model of cell-state transitions in vitro to gain insights into how SLUG/SNAI2, a key developmental transcription factor, modulates mammary epithelial stem cell activity and differentiation in vivo. In the absence of SLUG, stem cells fail to transition into basal progenitor cells, while existing basal progenitor cells undergo luminal differentiation; together, these changes result in abnormal mammary architecture and defects in tissue function. Furthermore, we show that in the absence of SLUG, mammary stem cell activity necessary for tissue regeneration and cancer initiation is lost. Mechanistically, SLUG regulates differentiation and cellular plasticity by recruiting the chromatin modifier lysine-specific demethylase 1 (LSD1 to promoters of lineage-specific genes to repress transcription. Together, these results demonstrate that SLUG plays a dual role in repressing luminal epithelial differentiation while unlocking stem cell transitions necessary for tumorigenesis.

  7. Neutrons transition densities for the $2^+-8^+$ multiplet of states in $^{90}$Zr

    Onegin, M. S.; Plavko, A. V.

    2003-01-01

    The neutron transition densities of the $2^+-8^+$ levels in $^{90}$Zr were extracted in the process of analysing ({\\bf p},p') scattering at 400 Mev. Its comparison with the proton transition densities for these levels was undertaken. The radial shapes of the experimental neutron and proton transition densities for each state were found to be different.

  8. Pseudo-transition Analysis Identifies the Key Regulators of Dynamic Metabolic Adaptations from Steady-State Data.

    Gerosa, Luca; Haverkorn van Rijsewijk, Bart R B; Christodoulou, Dimitris; Kochanowski, Karl; Schmidt, Thomas S B; Noor, Elad; Sauer, Uwe

    2015-10-28

    Hundreds of molecular-level changes within central metabolism allow a cell to adapt to the changing environment. A primary challenge in cell physiology is to identify which of these molecular-level changes are active regulatory events. Here, we introduce pseudo-transition analysis, an approach that uses multiple steady-state observations of (13)C-resolved fluxes, metabolites, and transcripts to infer which regulatory events drive metabolic adaptations following environmental transitions. Pseudo-transition analysis recapitulates known biology and identifies an unexpectedly sparse, transition-dependent regulatory landscape: typically a handful of regulatory events drive adaptation between carbon sources, with transcription mainly regulating TCA cycle flux and reactants regulating EMP pathway flux. We verify these observations using time-resolved measurements of the diauxic shift, demonstrating that some dynamic transitions can be approximated as monotonic shifts between steady-state extremes. Overall, we show that pseudo-transition analysis can explore the vast regulatory landscape of dynamic transitions using relatively few steady-state data, thereby guiding time-consuming, hypothesis-driven molecular validations. PMID:27136056

  9. Synthesis of nanosized, electrochemically active lithium transition metal phosphates

    Stark, Michael Andreas

    2011-01-01

    The increasing interest to develop new types of Li-ion batteries is motivated by the amplified need of batteries with high charge and discharge rates. Lithium transition metal phosphates are promising candidates to challenge this need. Before LiMnPO4 can be used as active material, research has to challenge two different aspects. First of all, for this material a crystallite size reduction is very important to improve the rate performance. And second, the electronic conductivity has to be imp...

  10. Possible enhancement of magnetic dipole transition strength between Gamow-Teller and isobaric analog states

    The non-energy weighted sum rule of M1 transitions between IAS and GT states is found to be significantly enhanced compared to the sum rule of parent nucleus. Mechanism of this enhancement is explained. Transition strengths between specific states in 48Sc, 90Nb and 208Bi are calculated to investigate whether the enhancement of the sum rule is reflected in these transitions. Measurement of M1 transitions between IAS and GT states is recommended to obtain more information on the spin-isospin response in medium and heavy nuclei. (orig.)

  11. NuSTAR Observations of the State Transition of Millisecond Pulsar Binary PSR J1023+0038

    Tendulkar, Shriharsh P.; Yang, Chengwei; An, Hongjun;

    2014-01-01

    . Consecutive dip separations are log-normal in distribution with a typical separation of approximately 400 s. These dips are distinct from dipping activity observed in LMXBs. We compare and contrast these dips to observations of dips and state changes in the similar transition systems PSR J1824-2452I and XSS J...

  12. The activation energy for the FCC rolling texture transition and the activation energy for cross slip

    Leffers, T.; Pedersen, O.B.

    2002-01-01

    corresponding to the stress in Cu-5%Zn during heavy rolling the theoretical activation energy for cross slip is pretty close to the activation energy for thetexture transition. It is concluded that the texture transition is governed by cross slip, and the detailed mechanism is discussed.......Already in 1968 one of the present authors determined the activation energy for the rolling-texture transition in Cu-5%Zn as a spin off of an investigation of the strain-rate dependence of the rolling texture. In the present work this determination of theactivation energy is explained and discussed...... (whereas very few details were given in the original work), and an error in the original work is corrected. The activation energy for the texture transition is compared with recent values for the activationenergy for cross slip derived from atomic-scale modelling. After adjustment to a stress level...

  13. Spin-state transition and phase separation in multi-orbital Hubbard model

    Suzuki, Ryo; Watanabe, Tsutomu; Ishihara, Sumio

    2009-01-01

    We study spin-state transition and phase separation involving this transition based on the milti-orbital Hubbard model. Multiple spin states are realized by changing the energy separation between the two orbitals and the on-site Hund coupling. By utilizing the variational Monte-Carlo simulation, we analyze the electronic and magnetic structures in hole doped and undoped states. Electronic phase separation occurs between the low-spin band insulating state and the high-spin ferromagnetic metall...

  14. 19 CFR 123.42 - Truck shipments transiting the United States.

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Truck shipments transiting the United States. 123.42 Section 123.42 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY CUSTOMS RELATIONS WITH CANADA AND MEXICO United States and Canada In-Transit Truck Procedures § 123.42 Truck...

  15. Pressure-induced phase transition to a novel spin state in striped nickelates

    Kaneshita, E.; Bishop, A. R.

    2008-01-01

    We analyze pressure effects on stripe states within a selfconsistent Hartree-Fock calculation for a model of a striped nickelates. The results show a transition induced by high pressure and predict possible new spin states. We describe characteristics in the phonon excitations at the predicted transition, based on a real-space random phase approximation.

  16. Discovering Unique, Low-Energy Transition States Using Evolutionary Molecular Memetic Computing

    Ellabaan, Mostafa M Hashim; Ong, Y.S.; Handoko, S.D.;

    2013-01-01

    In the last few decades, identification of transition states has experienced significant growth in research interests from various scientific communities. As per the transition states theory, reaction paths and landscape analysis as well as many thermodynamic properties of biochemical systems can...

  17. What can one learn from experiments about the elusive transition state?

    Chang, Iksoo; Cieplak, Marek; Banavar, Jayanth R.; Maritan, Amos

    2004-01-01

    We present the results of an exact analysis of a model energy landscape of a protein to clarify the idea of the transition state and the physical meaning of the φ values determined in protein engineering experiments. We benchmark our findings to various theoretical approaches proposed in the literature for the identification and characterization of the transition state.

  18. What one can learn from experiments about the elusive transition state?

    Chang, Iksoo; Cieplak, Marek; Banavar, Jayanth R.; Maritan, Amos

    2004-01-01

    We present the results of an exact analysis of a model energy landscape 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 benchmark our findings to various theoretical approaches proposed in the literature for the identification and characterization of the transition state.

  19. What can one learn from experiments about the elusive transition state?

    Chang, Iksoo; Cieplak, Marek; Banavar, Jayanth R.; Maritan, Amos

    2004-01-01

    We present the results of an exact analysis of a model energy landscape of a protein to clarify the idea of the transition state and the physical meaning of the φ values determined in protein engineering experiments. We benchmark our findings to various theoretical approaches proposed in the literature for the identification and characterization of the transition state. PMID:15295118

  20. On the transmission- to reprocessing-dominated spectral state transitions in Seyfert 2 galaxies

    Guainazzi, M; Iwasawa, K; Matt, G; Fiore, F

    2004-01-01

    We present Chandra and XMM-Newton observations of a small sample (11 objects) of optically-selected Seyfert~2 galaxies, for which ASCA and BeppoSAX had suggested Compton-thick obscuration of the Active Nucleus (AGN). The main goal of this study is to estimate the rate of transitions between "transmission-" and "reprocessing-dominated" states. We discover one new transition in NGC4939, with a possible additional candidate in NGC5643. This indicates a typical occurrence rate of at least ~0.02/year. These transitions could be due to large changes of the obscuring gas column density, or to a transient dimming of the AGN activity, the latter scenario being supported by detailed analysis of the best studied events. Independently of the ultimate mechanism, comparison of the observed spectral dynamics with Monte-Carlo simulations demonstrates that the obscuring gas is largely inhomogeneous, with multiple absorbing components possibly spread through the whole range of distances from the nucleus between a fraction of p...

  1. School-travel by public transit: Rethinking active transportation

    Christine Voss; Meghan Winters; Amanda Frazer; Heather McKay

    2015-01-01

    Background: Walking and cycling to school is a source of physical activity (PA). Little is known about public transit use for travel to school and whether it is a physically active alternative to car use for those who live too far to walk. Purpose: To describe school-trip characteristics, including PA, across travel modes and to assess the association between PA with walk distance. Methods: High school students (13.3 ± 0.7 years, 37% female) from Downtown Vancouver wore accelerometers (...

  2. Phase Transition of Generalized Ferromagnetic Potts Model - Effect of Invisible States -

    We investigate the nature of the phase transition of the ferromagnetic Potts model with invisible states. The ferromagnetic Potts model with invisible states can be regarded as a straightforward extension of the standard ferromagnetic Potts model. The invisible states contribute the entropy, however they do not affect the internal energy. They also do not change the symmetry which breaks at the transition temperature. The invisible states stimulate a first-order phase transition. We confirm that the first-order phase transition with spontaneous q-fold symmetry breaking for q = 2,3, and 4 takes place even on two-dimensional lattice by Monte Carlo simulation. We also find that the transition temperature decreases and the latent heat increases as the number of invisible states increases.

  3. Expanding the applicability of electrostatic potentials to the realm of transition states.

    Bhasi, Priya; Nhlabatsi, Zanele P; Sitha, Sanyasi

    2016-05-14

    Central to any reaction mechanism study, and sometimes a challenging job, is tracing a transition state in a reaction path. For the first time, electrostatic potentials (ESP) of the reactants were used as guiding tactics to predict whether there is a possibility of any transition state in a reaction surface. The main motive behind this strategy is to see whether the directionality nature of the transition state has something to do with the anisotropic natures of the ESP with their embedded directionalities. Strategically, some atmospherically important, but simple, reactions have been chosen for this study, which heretofore were believed to be barrierless. By carefully analysing the ESP maps of the reactants, regions of possible interactions were located. Using the bilinear interpolation of the 2D grids of the ESP surfaces, search co-ordinates were fine-tuned for a local gradient based approach for the search of a transition state. Out of the three reactions studied in this work, we were able to successfully locate transition states, for the first time, in two cases and the third one still proved to be barrierless. This gives a clear indication that though ESP maps can qualitatively predict the possibility of a transition state; it is not always true that there should definitely be a transition state, as some of the reaction surfaces may genuinely be barrierless. But, nevertheless this strategy definitely has credential to be tested for many more reactions, either new or already established, and may be applied to create the initial search co-ordinates for any well-established transition state search method. Moreover, we have observed that the analysis of the ESP maps of the reactants were very much useful in explaining the nature of interactions existing in those observed transition states and we hope the same can also be extended to any transition state in an electrostatically driven reaction potential energy surface. PMID:27108668

  4. Lithuanian health care in transitional state: ethical problems

    Žekas Romualdas

    2005-11-01

    Full Text Available Abstract Background Throughout the economic and political reforms in post-communist countries, significant changes have also occurred in public morality. One of the tasks of the Lithuanian health policy is to create mechanisms for strengthening the significance of ethical considerations in the decision-making processes concerning health care of individuals and groups of individuals, as well as considering the positions of physicians and the health care system itself in a general way. Thus, health care ethics could be analyzed at two levels: the micro level (the ethics of doctor-patient relationships and the macro level (the ethics of health policy-making, which can be realized by applying the principles of equal access, reasonable quality, affordable care and shared responsibilities. To date, the first level remains dominant, but the need arises for our attention to refocus now from the micro level to the patterns of managing and delivering care, managing the health care resources, and conducting business practices. Discussion In attempting to increase the efficiency of health services in Lithuania, a common strategy has been in place for the last fifteen years. Decentralization and privatization have been implemented as part of its policy to achieve greater efficiency. Although decentralization in theory is supposed to improve efficiency, in practice the reform of decentralization has still to be completely implemented in Lithuania. Debates on health policy in Lithuania also include the issue of private versus public health care. Although the approach of private health care is changing in a positive way, it is obvious that reduced access to health services is the most vulnerable aspect. In the Lithuanian Health Program adopted in July 1998, the target of equity was stressed, stating that by 2010, differences in health and health care between various socio-economic groups should be reduced by 25%. Summary The restructuring of health care system

  5. A critical assessment of theoretical methods for finding reaction pathways and transition states of surface processes

    The performance of a variety of techniques for locating transition states on potential energy surfaces is evaluated within the density functional theory framework. Diffusion of a water molecule across NaCl(001) and HCl bond breaking on the same surface are treated as general test cases; the former is an example of a low barrier diffusion process and the latter an example of a relatively high barrier covalent bond rupture event. The methods considered include the nudged elastic band (NEB), Dewar, Healy and Stewart (DHS), dimer, constrained optimization (CO), activation-relaxation technique (ART) and one-side growing string (OGS) as well as novel combinations of the DHS with growing string (DHS + GS) and DHS plus climbing image (CI-DHS). A key conclusion to come from this study is that the NEB method is relatively fast, especially when just a single (climbing) image is used. Indeed, using more images represents an unnecessary computational burden for our set of processes. The dimer method exhibits variable performance; being poor for the water diffusion processes, which have small activation energies, but much more efficient for the HCl bond breaking process which has a higher barrier. When only a poor initial guess of the transition state geometry is available, the CI-DHS scheme is one of the most efficient techniques considered. And as a means to quickly establish an approximate minimum energy pathway the DHS + GS scheme offers some potential.

  6. Fragmentation transitions in multi-state voter models

    Böhme, Gesa A

    2012-01-01

    Adaptive models of opinion formation among humans can display a fragmentation transition, where a social network breaks into disconnected components. Here, we investigate this transition in a class of models with arbitrary number of opinions. In contrast to previous work we do not assume that opinions are equidistant or arranged on a one-dimensional conceptual axis. Our investigation reveals detailed analytical results on fragmentations in a three-opinion model, which are confirmed by agent-based simulations. Furthermore, we show that in certain models the number of opinions can be reduced without affecting the fragmentation points.

  7. Universality classes of the absorbing state transition in a system with interacting static and diffusive populations.

    Argolo, C; Quintino, Yan; Siqueira, Y; Gleria, Iram; Lyra, M L

    2009-12-01

    In this work, we study the critical behavior of a one-dimensional model that mimics the propagation of an epidemic process mediated by a density of diffusive individuals which can infect a static population upon contact. We simulate the above model on linear chains to determine the critical density of the diffusive population, above which the system achieves a statistically stationary active state, as a function of two relevant parameters related to the average lifetimes of the diffusive and nondiffusive populations. A finite-size scaling analysis is employed to determine the order parameter and correlation length critical exponents. For high-recovery rates, the critical exponents are compatible with the usual directed percolation universality class. However, in the opposite regime of low-recovery rates, the diffusion is a relevant mechanism responsible for the propagation of the disease and the absorbing state phase transition is governed by a distinct set of critical exponents. PMID:20365138

  8. Classification of EGC output and Mental State Transition Networkusing Self Organizing Map

    Mera, Kazuya; Ichimura, Takumi

    2011-01-01

    Mental State Transition Network which consists of mental states connected one another is a basic concept of approximating to human psychological and mental responses. It can represent transition from an emotional state to other one with stimulus by calculating Emotion Generating Calculations method. However, this method ignores most of emotions except for an emotion which has the strongest effect although EGC can calculate the degree of 20 emotions in parallel. In this pa...

  9. Testing the transition state theory in stochastic dynamics of a genetic switch

    Ushikubo, Tomohiro; Inoue, Wataru; Yoda, Mitsumasa; Sasai, Masaki

    2006-01-01

    Stochastic dynamics of chemical reactions in a mutually repressing two-gene circuit is numerically simulated. The circuit has a rich variety of different states when the kinetic change of DNA status is slow. The stochastic switching transition between those states are compared with the theoretical estimation of the switching rate derived from the idea similar to the transition state theory. Even though the circuit is kept far from equilibrium, the method gives a consistent explanation of the ...

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

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

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

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

    2016-08-01

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

  12. Activation of the TGFβ pathway impairs endothelial to haematopoietic transition.

    Vargel, Özge; Zhang, Yang; Kosim, Kinga; Ganter, Kerstin; Foehr, Sophia; Mardenborough, Yannicka; Shvartsman, Maya; Enright, Anton J; Krijgsveld, Jeroen; Lancrin, Christophe

    2016-01-01

    The endothelial to haematopoietic transition (EHT) is a key developmental process where a drastic change of endothelial cell morphology leads to the formation of blood stem and progenitor cells during embryogenesis. As TGFβ signalling triggers a similar event during embryonic development called epithelial to mesenchymal transition (EMT), we hypothesised that TGFβ activity could play a similar role in EHT as well. We used the mouse embryonic stem cell differentiation system for in vitro recapitulation of EHT and performed gain and loss of function analyses of the TGFβ pathway. Quantitative proteomics analysis showed that TGFβ treatment during EHT increased the secretion of several proteins linked to the vascular lineage. Live cell imaging showed that TGFβ blocked the formation of round blood cells. Using gene expression profiling we demonstrated that the TGFβ signalling activation decreased haematopoietic genes expression and increased the transcription of endothelial and extracellular matrix genes as well as EMT markers. Finally we found that the expression of the transcription factor Sox17 was up-regulated upon TGFβ signalling activation and showed that its overexpression was enough to block blood cell formation. In conclusion we showed that triggering the TGFβ pathway does not enhance EHT as we hypothesised but instead impairs it. PMID:26891705

  13. Social Media Activism and State Censorship

    Poell, T.

    2015-01-01

    This chapter interrogates how activist social media communication in authoritarian contexts is shaped through the mutual articulation of social media user practices, business models, and technological architectures, as well as through the controlling efforts of states. It specifically focuses on social media protest activity and contention in China, Tunisia, and Iran, authoritarian states which have made a large effort to control online activity. The analysis shows that instead of blocking or...

  14. Quantum manifestation of systems on the macro-scale – the concept of transition state and transition amplitude wave

    Ram K Varma

    2007-06-01

    Quantum effects which have usually been associated with micro-scale phenomena can also arise on the macro-scale in situations other than the well-known macro-quantum phenomena of superconductivity and superfluidity. Such situations have been shown here to arise in processes involving inelastic scattering with bound or partially bound systems (not bound in all degrees of freedom), and the macro-quantum behaviour is associated with the state of the total system in transition in the process of scattering. Such a state is designated as a `transition-state'. It is pointed out that we have already observed such manifestations for a particular system, the charged particles in a magnetic field where interference effects involving macro-scale matter waves along the magnetic field have been reported [R K Varma et al, Phys. Rev. E65, 026503 (2002)].

  15. Possible enhancement of magnetic dipole transitions between Gamow-Teller and isobaric analog states

    A new decay scheme between Gamow-Teller (GT) resonances and isobaric analog states (IAS) by magnetic dipole transitions is studied. The sum rule of M1 transitions between IAS and GT states is found to be significantly enhanced compared to the non-energy-weighted sum rule of the parent state. Calculated enhancement factors can be as large as ∼2.5 for 48Sc and 90Nb, and 1.5 for 208Bi. Transition strengths between specific states are calculated in the Tamm-Dancoff approximation. The interest of measuring M1 transitions between IAS and GT states to obtain information on the spin-isospin response in finite nuclei is stressed. copyright 1995 The American Physical Society

  16. Semiclassical vibration-rotation transition probabilities for motion in molecular state averaged potentials.

    Stallcop, J. R.

    1971-01-01

    Collision-induced vibration-rotation transition probabilities are calculated from a semiclassical three-dimensional model, in which the collision trajectory is determined by the classical motion in the interaction potential that is averaged over the molecular rotational state, and compared with those for which the motion is governed by a spherically averaged potential. For molecules that are in highly excited rotational states, thus dominating the vibrational relaxation rate at high temperature, it is found that the transition probability for rotational state averaging is smaller than that for spherical averaging. For typical collisions, the transition cross section is decreased by a factor of about 1.5 to 2.

  17. Laser frequency stabilization to excited state transitions using electromagnetically induced transparency in a cascade system.

    Abel, R.P.; Mohapatra, A. K.; Bason, M. G.; Pritchard, J D; Weatherill, K. J.; Raitzsch, U.; Adams, C. S.

    2009-01-01

    We demonstrate laser frequency stabilization to excited state transitions using cascade electromagnetically induced transparency. Using a room temperature Rb vapor cell as a reference, we stabilize a first diode laser to the D2 transition and a second laser to a transition from the intermediate 5P3/2 state to a highly excited state with principal quantum number n = 19–70. A combined laser linewidth of 280±50 kHz over a 100 μs time period is achieved. This method may be applied generally to an...

  18. Estimation and asymptotic theory for transition probabilities in Markov Renewal Multi–state models

    Spitoni, Cristian; Verduijn, Marion; Putter, Hein

    2012-01-01

    In this paper we discuss estimation of transition probabilities for semi-Markov multi-state models. Non-parametric and semi-parametric estimators of the transition probabilities for a large class of models (forward going models) are proposed. Large sample theory is derived using the functional delta method and the use of resampling is proposed to derive confidence bands for the transition probabilities. The last part of the paper concerns the presentation of the main ideas of the R implementa...

  19. Oscillator strength, transition rates and lifetimes for n=3 states in Al-like ions

    Transition rates, oscillator strengths, and line strengths are calculated for the 3220 possible electric-dipole (E1) transitions between the 73 even-parity 3s3p2, 3s23d, 3p23d, 3d23s and 3d3 states and the 75 odd-parity 3s23p, 3p3, 3s3p3d, and 3d23p states in Al-like ions with the nuclear charges ranging from Z=15 to 100. Relativistic many-body perturbation theory (MBPT), including the Breit interaction, is used to evaluate retarded E1 matrix elements in length and velocity forms. The calculations start from a 1s22s22p6 Dirac-Fock potential. First-order MBPT is used to obtain intermediate coupling coefficients and second-order MBPT is used to calculate transition matrix elements. Contributions from negative-energy states are included in the second order E1 matrix elements to ensure gauge-independence of transition amplitudes. The transition energies used in the calculation of oscillator strengths and transition rates are from second-order MBPT. Transition rates, line strengths, and oscillator strengths are compared with critically evaluated experimental values and with results from other recent calculations. As a result, we present data for the selected transition, that includes transitions between the 10 even-parity 3s3p2, 3s23p states and the 29 odd-parity 3s23p, 3p3, and 3s3p3d states in Al-like ions. Trends of the transition rates as functions of Z are illustrates graphically for the 220 transitions. Lifetimes of the 10 possible even-parity lower levels and the 27 possible odd-parity upper levels are given for Z=15-100. (author)

  20. The Houk–List transition states for organocatalytic mechanisms revisited

    Armstrong, Alan; Boto, Roberto A.; Dingwall, Paul; Contreras-Garcia, Julia; Harvey, Matt J; Mason, Nicholas J; Rzepa, Henry S

    2014-01-01

    The ten year old Houk–List model for rationalising the origin of stereoselectivity in the organocatalysed intermolecular aldol addition is revisited, using a variety of computational techniques that have been introduced or improved since the original study. Even for such a relatively small system, the role of dispersion interactions is shown to be crucial, along with the use of basis sets where the superposition errors are low. An NCI (non-covalent interactions) analysis of the transition sta...

  1. Marketing planning: state of the art in a transitional economy

    Marjanova Jovanov, Tamara; Temjanovski, Riste; Fotov, Risto

    2014-01-01

    This paper is provoked by the distorted marketing practices of companies that operate in a transitional economy, specifically Republic of Macedonia. The analysis has two main purposes: 1. to identify the weaknesses in the marketing planning process, 2. to prove the connection of continuous formal marketing planning with business performance, i.e. profitability and market share. Data was obtained from primary and secondary research. Primary research was conducted in the food, i.e. confectioner...

  2. Study on State Transition Method Applied to Motion Planning for a Humanoid Robot

    Xuyang Wang

    2008-11-01

    Full Text Available This paper presents an approach of motion planning for a humanoid robot using a state transition method. In this method, motion planning is simplified by introducing a state-space to describe the whole motion series. And each state in the state-space corresponds to a contact state specified during the motion. The continuous motion is represented by a sequence of discrete states. The concept of the transition between two neighboring states, that is the state transition, can be realized by using some traditional path planning methods. Considering the dynamical stability of the robot, a state transition method based on search strategy is proposed. Different sets of trajectories are generated by using a variable 5th-order polynomial interpolation method. After quantifying the stabilities of these trajectories, the trajectories with the largest stability margin are selected as the final state transition trajectories. Rising motion process is exemplified to validate the method and the simulation results show the proposed method to be feasible and effective.

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

    Ishkhanyan, A. M.

    2009-01-01

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

  4. Equation of state description of the dark energy transition between quintessence and phantom regimes

    The dark energy crossing of the cosmological constant boundary (the transition between the quintessence and phantom regimes) is described in terms of the implicitly defined dark energy equation of state. The generalizations of the models explicitly constructed to exhibit the crossing provide the insight into the cancellation mechanism which makes the transition possible

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

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

    2016-01-01

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

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

    Ebb, Nancy; And Others

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

  7. Shape transition of state density for bosonic systems

    Harshal N Deota; N D Chavda; V Potbhare

    2013-12-01

    For a finite boson system, the ensemble-averaged state density has been computed with respect to the body interaction rank . The shape of such a state density changes from Gaussian to semicircle as the body rank of the interaction increases. This state density is expressed as a linear superposition of Gaussian and semicircular states. The nearest-neighbour spacing distribution (NNSD), which is one of the most important spectral properties of a system, is studied. The NNSDs are rather independent of body rank and show a Wigner distribution throughout.

  8. Transition temperature range of thermally activated nickel-titanium archwires

    Tatiana Sobottka SPINI

    2014-04-01

    Full Text Available Objectives: The shape memory resulting from the superelasticity and thermoelastic effect is the main characteristic of thermally activated NiTi archwires and is closely related to the transition temperature range (TTR. The aim of this study was to evaluate the TTR of thermally activated NiTi archwires commercially available. Material and Methods: Seven different brands of 0.019"x0.025" thermally activated nickel-titanium archwires were tested as received by differential scanning calorimetry (DSC over the temperature range from -100°C to 150°C at 10°C/min. Results: All thermally activated NiTi archwires analyzed presented stage transformation during thermal scanning with final austenitic temperature (Af ranging from 20.39°C to 45.42°C. Three brands of NiTi archwires presented Af close to the room temperature and, this way, do not present properties of shape memory and pseudoelasticity that are desirable in clinical applications. Conclusions: The thermally activated NiTi archwires present great variability in the TTR and the elastic parameters of each NiTi archwire should be provided by the manufacturers, to allow achievement of the best clinical performance possible.

  9. Evaluation of Active Transition, a Website-Delivered Physical Activity Intervention for University Students: Pilot Study

    Kwan, Matthew; Faulkner, Guy; Bray, Steven

    2013-01-01

    Background While physical activity in individuals tends to decline steadily with age, there are certain periods where this decline occurs more rapidly, such as during early adulthood. Interventions aimed at attenuating the declines in physical activity during this transition period appear warranted. Objective The purpose of the study was to test the feasibility and efficacy of a theoretically informed, website-delivered physical activity intervention aimed at students entering university. Met...

  10. Variational transition state theory. Progress report, July 1, 1981-June 30, 1982

    Further development of variational transition-state theory was carried out during this period and several applications made for many atom-molecule, bimolecular, and muonium reactions. Only qualitative results are reported

  11. Discontinuous phase transition in a multi-state majority-vote model

    Li, Guofeng; Huang, Feng; Shen, Chuansheng

    2016-01-01

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

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

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

    2016-07-01

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

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

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

    2007-12-11

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

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

    Zhao, Han; Longhi, Stefano; Feng, Liang

    2015-11-01

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

  15. Structure, bonding, and catalytic activity of monodisperse, transition-metal-substituted CeO2 nanoparticles.

    Elias, Joseph S; Risch, Marcel; Giordano, Livia; Mansour, Azzam N; Shao-Horn, Yang

    2014-12-10

    We present a simple and generalizable synthetic route toward phase-pure, monodisperse transition-metal-substituted ceria nanoparticles (M0.1Ce0.9O2-x, M = Mn, Fe, Co, Ni, Cu). The solution-based pyrolysis of a series of heterobimetallic Schiff base complexes ensures a rigorous control of the size, morphology and composition of 3 nm M0.1Ce0.9O2-x crystallites for CO oxidation catalysis and other applications. X-ray absorption spectroscopy confirms the dispersion of aliovalent (M(3+) and M(2+)) transition metal ions into the ceria matrix without the formation of any bulk transition metal oxide phases, while steady-state CO oxidation catalysis reveals an order of magnitude increase in catalytic activity with copper substitution. Density functional calculations of model slabs of these compounds confirm the stabilization of M(3+) and M(2+) in the lattice of CeO2. These results highlight the role of the host CeO2 lattice in stabilizing high oxidation states of aliovalent transition metal dopants that ordinarily would be intractable, such as Cu(3+), as well as demonstrating a rational approach to catalyst design. The current work demonstrates, for the first time, a generalizable approach for the preparation of transition-metal-substituted CeO2 for a broad range of transition metals with unparalleled synthetic control and illustrates that Cu(3+) is implicated in the mechanism for CO oxidation on CuO-CeO2 catalysts. PMID:25406101

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

    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

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

    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.

  18. Exact transition probabilities in a 6-state Landau-Zener system with path interference

    Sinitsyn, N. A.

    2015-01-01

    We identify a nontrivial multistate Landau-Zener model for which transition probabilities between any pair of diabatic states can be determined analytically and exactly. In the semiclassical picture, this model features the possibility of interference of different trajectories that connect the same initial and final states. Hence, transition probabilities are generally not described by the incoherent successive application of the Landau-Zener formula. We discuss reasons for integrability of t...

  19. Hot accretion flow with radiative cooling: state transitions in black hole X-ray binaries

    Wu, Mao-Chun; Xie, Fu-Guo; Yuan, Ye-Fei; Gan, Zhao-Ming

    2016-01-01

    We investigate state transitions in black hole X-ray binaries through different parameters by using two-dimensional axisymmetric hydrodynamical simulation method. For radiative cooling in hot accretion flow, we take into account the bremsstrahlung, synchrotron and synchrotron-self Comptonization self-consistently in the dynamics. Our main result is that the state transitions occur when the accretion rate reaches a critical value $\\dot M \\sim 3\\alpha\\ \\dot M_{\\rm Edd}$, above which cold and de...

  20. Is strong hydrogen bonding in the transition state enough to account for the observed rate acceleration in a mutant of papain?

    Zheng, Ya-Jun; Bruice, Thomas C.

    1997-01-01

    Nitriles are good inhibitors for the cysteine protease papain. However, a single amino acid mutation (Gln-19 → Glu-19) in the active site makes the mutant enzyme a good catalyst for nitrile hydrolysis. A theoretical approach was used to examine the differential transition state stabilization in the papain mutant relative to the wild-type enzyme. Based on this study, we concluded that strong hydrogen bonding in the transition state is responsible for the observed rate enhancement of 4 × 105.

  1. Transition Properties of Low Lying States in Atomic Indium

    Sahoo, B K

    2011-01-01

    We present here the results of our relativistic many-body calculations of various properties of the first six low-lying excited states of indium. The calculations were performed using the relativistic coupled-cluster method in the framework of the singles, doubles and partial triples approximation. We obtain a large lifetime ~10s for the [4p^6]5s^2 5p_{3/2} state, which had not been known earlier. Our precise results could be used to shed light on the reliability of the lifetime measurements of the excited states of atomic indium that we have considered in the present work.

  2. TRANSITION STATE FOR THE GAS-PHASE REACTION OF URANIUM HEXAFLUORIDE WITH WATER

    Garrison, S; James Becnel, J

    2008-03-18

    Density Functional Theory and small-core, relativistic pseudopotentials were used to look for symmetric and asymmetric transitions states of the gas-phase hydrolysis reaction of uranium hexafluoride, UF{sub 6}, with water. At the B3LYP/6-31G(d,p)/SDD level, an asymmetric transition state leading to the formation of a uranium hydroxyl fluoride, U(OH)F{sub 5}, and hydrogen fluoride was found with an energy barrier of +77.3 kJ/mol and an enthalpy of reaction of +63.0 kJ/mol (both including zero-point energy corrections). Addition of diffuse functions to all atoms except uranium led to only minor changes in the structure and relative energies of the reacting complex and transition state. However, a significant change in the product complex structure was found, significantly reducing the enthalpy of reaction to +31.9 kJ/mol. Similar structures and values were found for PBE0 and MP2 calculations with this larger basis set, supporting the B3LYP results. No symmetric transition state leading to the direct formation of uranium oxide tetrafluoride, UOF{sub 4}, was found, indicating that the reaction under ambient conditions likely includes several more steps than the mechanisms commonly mentioned. The transition state presented here appears to be the first published transition state for the important gas-phase reaction of UF{sub 6} with water.

  3. Transition state for the gas-phase reaction of uranium hexafluoride with water.

    Garrison, Stephen L; Becnel, James M

    2008-06-19

    Density functional theory and small-core, relativistic pseudopotentials were used to look for symmetric and asymmetric transition states of the gas-phase hydrolysis reaction of uranium hexafluoride, UF 6, with water. At the B3LYP/6-31G(d,p)/SDD level, an asymmetric transition state leading to the formation of a uranium hydroxyl fluoride, U(OH)F 5, and hydrogen fluoride was found with an energy barrier of +77.3 kJ/mol and an enthalpy of reaction of +63.0 kJ/mol (both including zero-point energy corrections). Addition of diffuse functions to all atoms except uranium led to only minor changes in the structures and relative energies of the reacting complex and transition state. However, a significant change in the structure of the product complex was found, significantly reducing the enthalpy of reaction to +31.9 kJ/mol. Similar structures and values were found for PBE0 and MP2 calculations with this larger basis set, supporting the B3LYP results. No symmetric transition state leading to the direct formation of uranium oxide tetrafluoride, UOF 4, was found, indicating that the reaction under ambient conditions likely includes several more steps than the mechanisms commonly mentioned. The transition state presented here appears to be the first published transition state for the important gas-phase reaction of UF 6 with water. PMID:18500792

  4. Transitions: the state of the automotive industry–a summary

    Emily Engel; William A. Strauss

    2007-01-01

    The United States automotive industry has been undergoing tremendous changes in recent years. Speakers at a recent Chicago Fed conference explored these changes and considered the road to the future for the auto industry.

  5. Active states and structure transformations in accreting white dwarfs

    Boneva, Daniela; Kaygorodov, Pavel

    2016-07-01

    Active states in white dwarfs are usually associated with light curve's effects that concern to the bursts, flickering or flare-up occurrences. It is common that a gas-dynamics source exists for each of these processes there. We consider the white dwarf binary stars with accretion disc around the primary. We suggest a flow transformation modeling of the mechanisms that are responsible for ability to cause some flow instability and bring the white dwarfs system to the outburst's development. The processes that cause the accretion rate to sufficiently increase are discussed. Then the transition from a quiescent to an active state is realized. We analyze a quasi-periodic variability in the luminosity of white dwarf binary stars systems. The results are supported with an observational data.

  6. Hypoxia activated EGFR signaling induces epithelial to mesenchymal transition (EMT.

    Ashish Misra

    Full Text Available Metastasis is a multi-step process which requires the conversion of polarized epithelial cells to mesenchymal cells, Epithelial-Mesenchymal Transition (EMT. EMT is essential during embryonic morphogenesis and has been implicated in the progression of primary tumors towards metastasis. Hypoxia is known to induce EMT; however the molecular mechanism is still poorly understood. Using the A431 epithelial cancer cell line, we show that cells grown under hypoxic conditions migrated faster than cells grown under normal oxygen environment. Cells grown under hypoxia showed reduced adhesion to the extracellular matrix (ECM probably due to reduced number of Vinculin patches. Growth under hypoxic conditions also led to down regulation of E-cadherin and up regulation of vimentin expression. The increased motility of cells grown under hypoxia could be due to redistribution of Rac1 to the plasma membrane as opposed to increased expression of Rac1. EGF (Epidermal Growth Factor is a known inducer of EMT and growth of A431 cells in the absence of oxygen led to increased expression of EGFR (EGF Receptor. Treatment of A431 cells with EGF led to reduced cell adhesion to ECM, increased cell motility and other EMT characteristics. Furthermore, this transition was blocked by the monoclonal antibody Cetuximab. Cetuximab also blocked the hypoxia-induced EMT suggesting that cell growth under hypoxic conditions led to activation of EGFR signaling and induction of EMT phenotype.

  7. New transition in the vortex liquid state of YBa2Cu3O7-δ

    We have carried out angular dependent magneto-transport measurements on optimally doped, untwinned YBa2Cu3O7-δ crystals irradiated with high energy heavy ions to determine the onset of vortex line tension in the vortex liquid state. The dose matching field was controlled and kept at a low level to partially preserve the first order vortex lattice melting transition. A Bose glass transition is observed below the lower critical point which then transforms into a first order phase transition near 4 T. We find that the locus of points which indicates the onset of vortex line tension overlaps with the Bose glass transition line at low fields and then deviates at higher fields, indicating a new transition line in the vortex liquid state. This new line in the vortex liquid phase is dose independent and extends beyond the upper critical point

  8. Transition probabilities of normal states determine the Jordan structure of a quantum system

    Leung, Chi-Wai; Ng, Chi-Keung; Wong, Ngai-Ching

    2015-01-01

    Let $\\Phi:\\mathfrak{S}(M_1)\\to \\mathfrak{S}(M_2)$ be a bijection (not assumed affine nor continuous) between the sets of normal states of two quantum systems, modelled on the self-adjoint parts of von Neumann algebras $M_1$ and $M_2$, respectively. This paper concerns with the situation when $\\Phi$ preserves (or partially preserves) one of the following three notions of "transition probability" on the normal state spaces: the Uhlmann transition probability $P_U$, the Raggio transition probabi...

  9. Exact transition probabilities in a 6-state Landau–Zener system with path interference

    We identify a nontrivial multistate Landau–Zener (LZ) model for which transition probabilities between any pair of diabatic states can be determined analytically and exactly. In the semiclassical picture, this model features the possibility of interference of different trajectories that connect the same initial and final states. Hence, transition probabilities are generally not described by the incoherent successive application of the LZ formula. We discuss reasons for integrability of this system and provide numerical tests of the suggested expression for the transition probability matrix. (paper)

  10. Structural Operational Semantics for Continuous State Stochastic Transition Systems

    Bacci, Giorgio; Miculan, Marino

    2015-01-01

    In this paper we show how to model syntax and semantics of stochastic processes with continuous states, respectively as algebras and coalgebras of suitable endofunctors over the category of measurable spaces Meas. Moreover, we present an SOS-like rule format, called MGSOS , representing abstract ...

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

    2010-07-01

    ... that is also responsible, in whole or in part, for the design and construction or operation of the unit... of the employees. The State need not submit complete job descriptions for every employee carrying out... shield that may be granted pursuant to § 70.6(f) shall remain in effect until the renewal permit has...

  12. The role of the transition state in polyatomic reactions: Initial state-selected reaction probabilities of the H + CH4 → H2 + CH3 reaction

    Full-dimensional calculations of initial state-selected reaction probabilities on an accurate ab initio potential energy surface (PES) have been communicated recently [R. Welsch and U. Manthe, J. Chem. Phys. 141, 051102 (2014)]. These calculations use the quantum transition state concept, the multi-layer multi-configurational time-dependent Hartree approach, and graphics processing units to speed up the potential evaluation. Here further results of these calculations and an extended analysis are presented. State-selected reaction probabilities are given for many initial ro-vibrational states. The role of the vibrational states of the activated complex is analyzed in detail. It is found that rotationally cold methane mainly reacts via the ground state of the activated complex while rotationally excited methane mostly reacts via H–H–CH3-bending excited states of the activated complex. Analyzing the different contributions to the reactivity of the vibrationally states of methane, a complex pattern is found. Comparison with initial state-selected reaction probabilities computed on the semi-empirical Jordan-Gilbert PES reveals the dependence of the results on the specific PES

  13. The slow S to M fluorescence rise in cyanobacteria is due to a state 2 to state 1 transition.

    Kaňa, Radek; Kotabová, Eva; Komárek, Ondřej; Sedivá, Barbora; Papageorgiou, George C; Govindjee; Prášil, Ondřej

    2012-08-01

    In dark-adapted plants and algae, chlorophyll a fluorescence induction peaks within 1s after irradiation due to well documented photochemical and non-photochemical processes. Here we show that the much slower fluorescence rise in cyanobacteria (the so-called "S to M rise" in tens of seconds) is due to state 2 to state 1 transition. This has been demonstrated in particular for Synechocystis PCC6803, using its RpaC(-) mutant (locked in state 1) and its wild-type cells kept in hyperosmotic suspension (locked in state 2). In both cases, the inhibition of state changes correlates with the disappearance of the S to M fluorescence rise, confirming its assignment to the state 2 to state 1 transition. The general physiological relevance of the SM rise is supported by its occurrence in several cyanobacterial strains: Synechococcus (PCC 7942, WH 5701) and diazotrophic single cell cyanobacterium (Cyanothece sp. ATCC 51142). We also show here that the SM fluorescence rise, and also the state transition changes are less prominent in filamentous diazotrophic cyanobacterium Nostoc sp. (PCC 7120) and absent in phycobilisome-less cyanobacterium Prochlorococcus marinus PCC 9511. Surprisingly, it is also absent in the phycobiliprotein rod containing Acaryochloris marina (MBIC 11017). All these results show that the S to M fluorescence rise reflects state 2 to state 1 transition in cyanobacteria with phycobilisomes formed by rods and core parts. We show that the pronounced SM fluorescence rise may reflect a protective mechanism for excess energy dissipation in those cyanobacteria (e.g. in Synechococcus PCC 7942) that are less efficient in other protective mechanisms, such as blue light induced non-photochemical quenching. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial. PMID:22402228

  14. Spectral properties of transitions between soft and hard state in GX 339-4

    Stiele, H; Muñoz-Darias, T; Belloni, T M

    2011-01-01

    We present a study of the spectral properties during state transition of GX 339-4. Data are taken from the 2010 outburst of GX 339-4, which is densely covered by Rossi X-ray Timing Explorer, providing an excellent coverage of the state transitions between the low/hard state and the high/soft state. We select all observations within a certain hardness ratio range during the soft intermediate state (SIMS). This sample was chosen in such a way to comprise all observations that show a type-B quasi-periodic oscillation (QPO). In addition, we also investigate the spectra of hard intermediate state observations. The spectra, obtained from Proportional Counter Array data in the 10 to 40 keV range, are fitted with a power law and an additional high energy cut-off if needed. We find that the spectra are significantly harder during the SIMS of the soft-to-hard transition than they are during the hard-to-soft transition. This demonstrates that during the SIMS of the soft-to-hard transition not only the luminosity and pea...

  15. Exotic and excited-state meson spectroscopy and radiative transitions from lattice QCD

    Christopher Thomas

    2010-09-01

    We discuss recent progress in extracting the excited meson spectrum and radiative transition form factors using lattice QCD. We mention results in the charmonium sector, including the first lattice QCD calculation of radiative transition rates involving excited charmonium states, highlighting results for high spin and exotic states. We present recent results on a highly excited isovector meson spectrum from dynamical anisotropic lattices. Using carefully constructed operators we show how the continuum spin of extracted states can be reliably identified and confidently extract excited states, states with exotic quantum numbers and states of high spin. This spectrum includes the first spin-four state extracted from lattice QCD. We conclude with some comments on future prospects.

  16. Transition State Structure and Inhibition of Rv0091, a 5'-Deoxyadenosine/5'-methylthioadenosine Nucleosidase from Mycobacterium tuberculosis.

    Namanja-Magliano, Hilda A; Stratton, Christopher F; Schramm, Vern L

    2016-06-17

    5'-Methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) is a bacterial enzyme that catalyzes the hydrolysis of the N-ribosidic bond in 5'-methylthioadenosine (MTA) and S-adenosylhomocysteine (SAH). MTAN activity has been linked to quorum sensing pathways, polyamine biosynthesis, and adenine salvage. Previously, the coding sequence of Rv0091 was annotated as a putative MTAN in Mycobacterium tuberculosis. Rv0091 was expressed in Escherichia coli, purified to homogeneity, and shown to be a homodimer, consistent with MTANs from other microorganisms. Substrate specificity for Rv0091 gave a preference for 5'-deoxyadenosine relative to MTA or SAH. Intrinsic kinetic isotope effects (KIEs) for the hydrolysis of [1'-(3)H], [1'-(14)C], [5'-(3)H2], [9-(15)N], and [7-(15)N]MTA were determined to be 1.207, 1.038, 0.998, 1.021, and 0.998, respectively. A model for the transition state structure of Rv0091 was determined by matching KIE values predicted via quantum chemical calculations to the intrinsic KIEs. The transition state shows a substantial loss of C1'-N9 bond order, well-developed oxocarbenium character of the ribosyl ring, and weak participation of the water nucleophile. Electrostatic potential surface maps for the Rv0091 transition state structure show similarity to DADMe-immucillin transition state analogues. DADMe-immucillin transition state analogues showed strong inhibition of Rv0091, with the most potent inhibitor (5'-hexylthio-DADMe-immucillinA) displaying a Ki value of 87 pM. PMID:27019223

  17. Travel Patterns And Characteristics Of Transit Users In New York State

    Hwang, Ho-Ling [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wilson, Daniel W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Reuscher, Tim [Macrosys, Arlington, VA (United States); Chin, Shih-Miao [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Taylor, Rob D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-12-01

    This research is a detailed examination of the travel behaviors and patterns of transit users within New York State (NYS), primarily based on travel data provided by the National Household Travel Survey (NHTS) in 2009 and the associated Add-on sample households purchased by the New York State Department of Transportation (NYSDOT). Other data sources analyzed in this study include: NYS General Transit Feed Specification (GTFS) to assist in analyzing spatial relationships for access to transit and the creation of Transit Shed geographic areas of 1, 2.5, and 5 miles from transit stop locations, LandScan population database to understand transit coverage, and Census Bureau s American Community Survey (ACS) data to examine general transit patterns and trends in NYS over time. The majority of analyses performed in this research aimed at identifying transit trip locations, understanding differences in transit usage by traveler demographics, as well as producing trip/mode-specific summary statistics including travel distance, trip duration, time of trip, and travel purpose of transit trips made by NYS residents, while also analyzing regional differences and unique travel characteristics and patterns. The analysis was divided into two aggregated geographic regions: New York Metropolitan Transportation Council (NYMTC) and NYS minus NYMTC (Rest of NYS). The inclusion of NYMTC in all analysis would likely produce misleading conclusions for other regions in NYS. TRANSIT COVERAGE The NYS transit network has significant coverage in terms of transit stop locations across the state s population. Out of the 19.3 million NYS population in 2011, about 15.3 million (or 79%) resided within the 1-mile transit shed. This NYS population transit coverage increased to 16.9 million (or 88%) when a 2.5-mile transit shed was considered; and raised to 17.7 million (or 92%) when the 5-mile transit shed was applied. KEY FINDINGS Based on 2009 NHTS data, about 40% of NYMTC households used transit

  18. Density-matrix renormalization-group study of current and activity fluctuations near nonequilibrium phase transitions.

    Gorissen, Mieke; Hooyberghs, Jef; Vanderzande, Carlo

    2009-02-01

    Cumulants of a fluctuating current can be obtained from a free-energy-like generating function, which for Markov processes equals the largest eigenvalue of a generalized generator. We determine this eigenvalue with the density-matrix renormalization group for stochastic systems. We calculate the variance of the current in the different phases, and at the phase transitions, of the totally asymmetric exclusion process. Our results can be described in the terms of a scaling ansatz that involves the dynamical exponent z . We also calculate the generating function of the dynamical activity (total number of configuration changes) near the absorbing-state transition of the contact process. Its scaling properties can be expressed in terms of known critical exponents. PMID:19391693

  19. The State and Curriculum in the Transition to Socialism: The Zimbabwean Experience.

    Jansen, Jonathan

    1991-01-01

    Uses a case study of curriculum innovation in Zimbabwe to assess existing explanations of why colonial curriculum content persists in many postcolonial states despite radical policy efforts. Argues for the primacy of conflict, history, and politics as determinants of school curriculum in Third World transition states. Contains 47 references. (SV)

  20. High spin states in transitional nuclei in the IBM + broken pair model

    For odd-A nuclei the IBFM plus broken pairs describes one and three-fermion states. The model has been applied to the description of high-spin states in the Hg, Sr-Zr and Nd-Sm regions. Calculated spectra and transition probabilities are compared with the experimental data

  1. An assessment of state-and-transition models: Perceptions following two decades of development and implementation

    State and transition models (STMs) are being developed for many areas in the United States and represent an important tool for assessing and managing public and private rangelands. Substantial resources have been invested in model development, yet minimal efforts have been made to evaluate the utili...

  2. First order phase transition of the q-state Potts model in two dimensions

    Arisue, H

    2000-01-01

    We have calculated the large-$q$ series of the energy cumulants, the magnetization cumulants and the correlation length at the first order phase transition point both in the ordered and disordered phases for the $q$-state Potts model in two dimensions. The series enables us to estimate the numerical values of the quantities more precisely by a factor of $10^2 - 10^4$ than the Monte Carlo simulations. From the large-$q$ series of the eigenvalues of the transfer matrix, we also find that the excited states form a continuum spectrum and there is no particle state at the first order phase transition point.

  3. Ground State Transitions in Vertically Coupled Four-Layer Single Electron Quantum Dots

    WANGAn-Mei; XIEWen-Fang

    2005-01-01

    We study a four-electron system in a vertically coupled four-layer quantum dot under a magnetic field by the exact diagonalization of the Hamiltonian matr/x. We find that discontinuous ground-state energy transitions are induced by an external magnetic field. We find that dot-dot distance and electron-electron interaction strongly affect the low-lying states of the coupled quantum dots. The inter-dot correlation leads to some sequences of possible disappearances of ground state transitions, which are present for uncoupled dots.

  4. Ground State Transitions in Vertically Coupled Four-Layer Single Electron Quantum Dots

    WANG An-Mei; XIE Wen-Fang

    2005-01-01

    We study a four-electron system in a vertically coupled four-layer quantum dot under a magnetic field by the exact diagonalization of the Hamiltonian matrix. We find that discontinuous ground-state energy transitions are induced by an external magnetic field. We find that dot-dot distance and electron-electron interaction strongly affect the low-lying states of the coupled quantum dots. The inter-dot correlation leads to some sequences of possible disappearances of ground state transitions, which are present for uncoupled dots.

  5. The Transition States for CO2 Capture by Substituted Ethanolamines

    Gangarapu, S.; Marcelis, A.T.M.; Alhamed, Y.A.; Zuilhof, H.

    2015-01-01

    Quantum chemical studies are used to understand the electronic and steric effects on the mechanisms of the reaction of substituted ethanolamines with CO2. SCS-MP2/6-311+G(2d,2p) calculations are used to obtain the activation energy barriers and reaction energies for both the carbamate and bicarbonat

  6. Exploring the nature of the liquid-liquid transition in silicon: a non-activated transformation.

    Lü, Y J; Zhang, X X; Chen, M; Jiang, Jian-Zhong

    2015-10-28

    In contrast to other glass formers, silicon exhibits a thermodynamic discontinuity between its liquid and amorphous solid states. Some researchers have conjectured that a first-order phase transition occurs between two forms of liquid silicon: the high-density liquid (HDL) and the low-density liquid (LDL). Despite the fact that several computer simulations have supported a liquid-liquid phase transition (LLPT) in silicon, recent work based on surface free energy calculations contradicts its existence and the authors of this work have argued that the proposed LLPT has been mistakenly interpreted [J. Chem. Phys., 2013, 138, 214504]. A similar controversy has also arisen in the case of water because of discrepancies in the calculation of its free energy surface [Nature, 2014, 510, 385; J. Chem. Phys., 2013, 138, 214504]. Current evidence supporting or not supporting the LLPT is mostly derived from the thermodynamic stability of the LDL phase. Provided that the HDL-LDL transition is a first-order transition, the formation of LDL silicon should be an activated process. Following this idea, the nature of the LLPT should be clarified by tracing the kinetic path toward LDL silicon. In this work, we focus on the transformation process from HDL to LDL phases and use the mean first passage time (MFPT) method to examine thermodynamic and dynamic trajectories. The MFPT results show that the presumed HDL-LDL transition is not characterized by a thermodynamic activated process but by a continuous dynamic transformation. LDL silicon is actually a mixture of the high-density liquid and a low-density tetrahedral network. We show that the five-membered Si-Si rings in the LDL network play a critical role in stabilizing the low-density network and suppressing the crystallization. PMID:26415631

  7. Symmetry Supporting a Transition to Zero Cosmological Constant State

    Guendelman, E I

    2007-01-01

    In a number of previous publications we demonstrated that the Two Measures Field Theory (TMT) enables to resolve the old cosmological constant (CC) problem avoiding the Weinberg's no-go CC theorem and together with this TMT agrees with all tests of the Einstein's general relativity and allows inflationary scenarios. Analysis performed in the present paper shows that there exists an intrinsic symmetry of TMT which emerges in the $\\Lambda =0$ ground state. This symmetry contains a subgroup of reflections of the metric $g_{\\mu\

  8. Transitions, cross sections and neutron binding energy in 186Re by Prompt Gamma Activation Analysis

    Lerch, A. G.; Hurst, A. M.; Firestone, R. B.; Revay, Zs.; Szentmiklosi, L.; McHale, S. R.; McClory, J. W.; Detwiler, B.; Carroll, J. J.

    2014-03-01

    The nuclide 186Re possesses an isomer with 200,000 year half-life while its ground state has a half-life of 3.718 days. It is also odd-odd and well-deformed nucleus, so should exhibit a variety of other interesting nuclear-structure phenomena. However, the available nuclear data is rather sparse; for example, the energy of the isomer is only known to within + 7 keV and, with the exception of the J?=1- ground state, every proposed level is tentative in the ENSDF. Previously, Prompt Gamma Activation Analysis (PGAA) was utilized to study natRe with 186,188Re being produced via thermal neutron capture. Recently, an enriched 185Re target was irradiated by thermal neutrons at the Budapest Research Reactor to build on those results. Prompt (primary and secondary) and delayed gamma-ray transitions were measured with a large-volume, Compton-suppressed HPGe detector. Absolute cross sections for each gamma transition were deduced and corrected for self attenuation within the sample. Fifty-two primary gamma-ray transitions were newly identified and used to determine a revised value of the neutron binding energy. DICEBOX was used to simulate the decay scheme and the total radiative thermal neutron capture cross section was found to be 97+/-3 b Supported by DTRA (Detwiler) through HDTRA1-08-1-0014.

  9. Mean transit times and the sites of synthesis and catabolism of tissue plasminogen activator and plasminogen activator inhibitor type 1 in young subjects

    Jørgensen, M; Petersen, K R; Vinberg, N; Jespersen, J; Gram, J; Tønnesen, K H

    2001-01-01

    .8 min. No net extraction of PAI-1 antigen took place in the splanchnic circulation. In conclusion, we demonstrated that active t-PA and t-PA antigen are catabolized and active PAI-1 produced in the splanchnic circulation in young healthy subjects during steady state. Furthermore, our data show that......Using an invasive technique, we studied the mean transit time, the net quantitative turnover rate, and the sites of synthesis and catabolism of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1) in healthy young volunteers in the fasting, steady state. Blood was...

  10. Generic finite size scaling for discontinuous nonequilibrium phase transitions into absorbing states.

    de Oliveira, M M; da Luz, M G E; Fiore, C E

    2015-12-01

    Based on quasistationary distribution ideas, a general finite size scaling theory is proposed for discontinuous nonequilibrium phase transitions into absorbing states. Analogously to the equilibrium case, we show that quantities such as response functions, cumulants, and equal area probability distributions all scale with the volume, thus allowing proper estimates for the thermodynamic limit. To illustrate these results, five very distinct lattice models displaying nonequilibrium transitions-to single and infinitely many absorbing states-are investigated. The innate difficulties in analyzing absorbing phase transitions are circumvented through quasistationary simulation methods. Our findings (allied to numerical studies in the literature) strongly point to a unifying discontinuous phase transition scaling behavior for equilibrium and this important class of nonequilibrium systems. PMID:26764651

  11. Prediction of monomer reactivity in radical copolymerizations from transition state quantum chemical descriptors

    Zhengde Tan

    2013-01-01

    Full Text Available In comparison with the Q-e scheme, the Revised Patterns Scheme: the U, V Version (the U-V scheme has greatly improved both its accessibility and its accuracy in interpreting and predicting the reactivity of a monomer in free-radical copolymerizations. Quantitative structure-activity relationship (QSAR models were developed to predict the reactivity parameters u and v of the U-V scheme, by applying genetic algorithm (GA and support vector machine (SVM techniques. Quantum chemical descriptors used for QSAR models were calculated from transition state species with structures C¹H3 - C²HR³• or •C¹H2 - C²H2R³ (formed from vinyl monomers C¹H²=C²HR³ + H•, using density functional theory (DFT, at the UB3LYP level of theory with 6-31G(d basis set. The optimum support vector regression (SVR model of the reactivity parameter u based on Gaussian radial basis function (RBF kernel (C = 10, ε = 10- 5 and γ = 1.0 produced root-mean-square (rms errors for the training, validation and prediction sets being 0.220, 0.326 and 0.345, respectively. The optimal SVR model for v with the RBF kernel (C = 20, ε = 10- 4 and γ = 1.2 produced rms errors for the training set of 0.123, the validation set of 0.206 and the prediction set of 0.238. The feasibility of applying the transition state quantum chemical descriptors to develop SVM models for reactivity parameters u and v in the U-V scheme has been demonstrated.

  12. GBM Monitoring of Cyg X-1 During the Recent State Transition

    Case, G L; Cherry, M L; Camero-Arranz, A; Finger, M; Jenke, P; Wilson-Hodge, C A; Chaplin, V

    2011-01-01

    Cygnus X-1 is a high-mass x-ray binary with a black hole compact object. It is normally extremely bright in hard x-rays and low energy gamma rays and resides in the canonical hard spectral state. Recently, however, Cyg X-1 made a transition to the canonical soft state, with a rise in the soft x-ray flux and a decrease in the flux in the hard x-ray and low energy gamma-ray energy bands. We have been using the Gamma-Ray Burst Monitor on Fermi to monitor the fluxes of a number of sources in the 8--1000 keV energy range, including Cyg X-1. We present light curves of Cyg X-1 showing the flux decrease in hard x-ray and low energy gamma-ray energy bands during the state transition as well as the several long flares observed in these higher energies during the soft state. We also present preliminary spectra from GBM for the pre-transition state, showing the spectral evolution to the soft state, and the post-transition state.

  13. Exact transition probabilities in the three-state Landau–Zener–Coulomb model

    We obtain the exact expression for the matrix of nonadiabatic transition probabilities in the model of three interacting states with a time-dependent Hamiltonian. Unlike other known solvable Landau–Zener-like problems, our solution is generally expressed in terms of hypergeometric functions that have relatively complex behavior, e.g. the obtained transition probabilities may show multiple oscillations as functions of parameters of the model Hamiltonian. (paper)

  14. Exact transition probabilities in the three-state Landau-Zener-Coulomb model

    Lin, Jeffmin; Sinitsyn, N. A.

    2013-01-01

    We obtain the exact expression for the matrix of nonadiabatic transition probabilities in the model of three interacting states with a time-dependent Hamiltonian. Unlike other known solvable Landau-Zener-like problems, our solution is generally expressed in terms of hypergeometric functions that have relatively complex behavior, e.g. the obtained transition probabilities may show multiple oscillations as functions of parameters of the model Hamiltonian.

  15. State Estimation for Nonlinear Discrete-Time Systems with Markov Jumps and Nonhomogeneous Transition Probabilities

    Shunyi Zhao; Zhiguo Wang; Fei Liu

    2013-01-01

    State estimation problem is addressed for a class of nonlinear discrete-time systems with Markov parameters and nonhomogeneous transition probabilities (TPs). In this paper, the optimal estimation mechanism of transition probability matrix is proposed in the minimum mean square error sense to show some critical points. Based on this mechanism, the extended Kalman filters are employed as the subfilters to obtain the subestimates with corresponding models. A novel operator which fuses the prior...

  16. Transition States in Africa : A Comparative Study: The Case of Ghana & Zambia

    Gustafsson, Oscar

    2007-01-01

    Background & Problem The author believes that there are important lessons to be learned from the states in Africa that have managed to achieve successful transitions from one-party regimes to multy-party regimes. However, Africa today displays countries that suffer from enormous problems and many of them are mired in political and economical development. A main theme of this thesis is the search for the differences, how can we explain the transitions and the outcomes of them? Purpose The ...

  17. Transition States in Africa : A Comparative Study: The Case of Ghana and Zambia

    Ekdahl, Oscar

    2007-01-01

    Abstract Background & Problem The author believes that there are important lessons to be learned from the states in Africa that have managed to achieve successful transitions from one-party regimes to multy-party regimes. However, Africa today displays countries that suffer from enormous problems and many of them are mired in political and economical development. A main theme of this thesis is the search for the differences, how can we explain the transitions and the outcomes of them? Pur...

  18. Pontine respiratory activity involved in inspiratory/expiratory phase transition

    Mörschel, Michael; Dutschmann, Mathias

    2009-01-01

    Control of the timing of the inspiratory/expiratory (IE) phase transition is a hallmark of respiratory pattern formation. In principle, sensory feedback from pulmonary stretch receptors (Breuer–Hering reflex, BHR) is seen as the major controller for the IE phase transition, while pontine-based control of IE phase transition by both the pontine Kölliker–Fuse nucleus (KF) and parabrachial complex is seen as a secondary or backup mechanism. However, previous studies have shown that the BHR can h...

  19. Equation of State of Dense Liquid Nitrogen in the Region of the Dissociative Phase Transition

    孟川民; 施尚春; 董石; 孙悦; 焦荣珍; 杨向东

    2002-01-01

    We have measured the equation of state for liquid nitrogen compressed dynamically to a pressure of 10-60 GPa by employing a two-stage light-gas gun. The data show a continuous phase transition above the shock pressure of 33 GPa, as indicated previously by shock wave experiments. A theoretical model has been derived to examine the experimental data by inducing a molecular dissociative fraction. According to theoretical and experimental data the phase transition was thought to be a molecular dissociative phase transition.

  20. M1 and E2 transitions in the ground-state configuration of atomic manganese

    Using the multiconfiguration Hartree-Fock approximation within the framework of the Breit-Pauli Hamiltonian (MCHF+BP) and the relativistic Hartree-Fock (HFR) approximation, we have calculated the forbidden transition (M1 and E2) parameters such as transition energies, logarithmic weighted oscillator strengths and transition probabilities between the fine-structure levels in the ground-state configuration of 3d54s2 for atomic manganese (Mn I, Z = 25). A discussion of these calculations for manganese using MCHF+BP and HFR methods is given here. (author)

  1. Metal–insulator transition in the quasi-one-dimensional transport of fractional quantum hall states

    We investigate edge state transmission in quantum point contacts (QPCs) in the fractional quantum-Hall regime, finding behavior reminiscent of a metal–insulator transition. The transition is suggested by an unusual behavior of the differential conductance in the fractional-quantum-Hall regime, and by the presence of a fixed point and universal scaling in the temperature dependence of the linear conductance. Noting that the 0.7 feature evolves continuously into a last fractional plateau at high magnetic fields, we suggest that this still unresolved feature may itself be viewed as a manifestation of a local, microscopic, metal–insulator transition. (fast track communication)

  2. 1 and 2 transitions in the ground-state configuration of atomic manganese

    S Kabakçi; B Karaçoban Usta; L Özdemir

    2015-10-01

    Using the multiconfiguration Hartree–Fock approximation within the framework of the Breit–Pauli Hamiltonian (MCHF+BP) and the relativistic Hartree–Fock (HFR) approximation, we have calculated the forbidden transition (1 and 2) parameters such as transition energies, logarithmic weighted oscillator strengths and transition probabilities between the fine-structure levels in the ground-state configuration of 3d5 4s2 for atomic manganese (Mn I, Z =25). A discussion of these calculations for manganese using MCHF+BP and HFR methods is given here.

  3. Scope and forms of state support to enterprises in Poland in period of transition

    Kurowski, Piotr

    2011-01-01

    In centrally planned economies state subsidies were the main instrument of supporting the economic sector. Most of them had also social functions (e.g. through subsidising the consumption of households). In the period of transition, with the withdraw all of the state from economic decisions of the enterprises, new social problems appeared. The paper analyses the process of granting state support to economic units - its scope and forms - in the 90-ties.

  4. Oscillator strength, transition rates and lifetimes for n=3 states in Al-like ions

    Safronova, U I; Safronova, M S; Sataka, M

    2002-01-01

    Transition rates, oscillator strengths, and line strengths are calculated for the 3220 possible electric-dipole (E1) transitions between the 73 even-parity 3s3p sup 2 , 3s sup 2 3d, 3p sup 2 3d, 3d sup 2 3s and 3d sup 3 states and the 75 odd-parity 3s sup 2 3p, 3p sup 3 , 3s3p3d, and 3d sup 2 3p states in Al-like ions with the nuclear charges ranging from Z=15 to 100. Relativistic many-body perturbation theory (MBPT), including the Breit interaction, is used to evaluate retarded E1 matrix elements in length and velocity forms. The calculations start from a 1s sup 2 2s sup 2 2p sup 6 Dirac-Fock potential. First-order MBPT is used to obtain intermediate coupling coefficients and second-order MBPT is used to calculate transition matrix elements. Contributions from negative-energy states are included in the second order E1 matrix elements to ensure gauge-independence of transition amplitudes. The transition energies used in the calculation of oscillator strengths and transition rates are from second-order MBPT. T...

  5. Motion, Universality of Velocities, Masses in Wave Universe. Transitive States (Resonances) - Mass Spectrum

    Chechelnitsky, A M

    2001-01-01

    Wave Universe Concept (WU Concept) opens new wide possibilities for the effective description of Elementar Objects of Matter (EOM) hierarchy, in particular, of particles, resonances mass spectrum of subatomic (and HEP) physics. The special attention to analysis and precise description of wide and important set - Transitive states (resonances) of EOM is payed. Its are obtained sufficiently precise representations for mass values, cross relations between masses of wide set objects of particle physics - metastable resonances - (fast moving) Transitive states - in terms of representations of Wave Universe Concept (WU Concept). Wide set of observed in experiments effects and connected with its resonances (including - Darmstadt effect, ABC effect,etc.) may be effectively interpreted in WU Concept and described with use of mass formula - as manifestation of rapidly moving, physically distinguished transitive states (resonances)

  6. Using dark states for exciton storage in transition-metal dichalcogenides.

    Tseng, Frank; Simsek, Ergun; Gunlycke, Daniel

    2016-01-27

    We explore the possibility of storing excitons in excitonic dark states in monolayer semiconducting transition-metal dichalcogenides. In addition to being optically inactive, these dark states require the electron and hole to be spatially separated, thus inhibiting electron/hole recombination and allowing exciton lifetimes to be extended. Based on an atomistic exciton model, we derive transition matrix elements and an approximate selection rule 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 a population analysis for different recombination decay constants. Longer exciton lifetimes could make these materials candidates for applications in energy management and quantum information processing. PMID:26704568

  7. Quantum transition state dynamics of the cyclooctatetraene unimolecular reaction on ab initio potential energy surfaces

    Tokizaki, Chihiro; Yoshida, Takahiko; Takayanagi, Toshiyuki

    2016-05-01

    The cyclooctatetraene (COT) anion has a stable D4h structure that is similar to the transition state configurations of the neutral C-C bond-alternation (D4h ↔ D8h ↔ D4h) and ring-inversion (D2d ↔ D4h ↔ D2d) unimolecular reactions. The previously measured photodetachment spectrum of COT- revealed the reaction dynamics in the vicinity of the two transition states on the neutral potential energy surface. In this work, the photodetachment spectrum is calculated quantum mechanically on ab initio-level potential energy surfaces within a three degree-of-freedom reduced-dimensionality model. Very good agreement has been obtained between theory and experiment, providing reliable interpretations for the experimental spectrum. A detailed picture of the reactive molecular dynamics of the COT unimolecular reaction in the transition state region is also discussed.

  8. A Cbx8-containing polycomb complex facilitates the transition to gene activation during ES cell differentiation.

    Catherine Creppe

    2014-12-01

    Full Text Available Polycomb proteins play an essential role in maintaining the repression of developmental genes in self-renewing embryonic stem cells. The exact mechanism allowing the derepression of polycomb target genes during cell differentiation remains unclear. Our project aimed to identify Cbx8 binding sites in differentiating mouse embryonic stem cells. Therefore, we used a genome-wide chromatin immunoprecipitation of endogenous Cbx8 coupled to direct massive parallel sequencing (ChIP-Seq. Our analysis identified 171 high confidence peaks. By crossing our data with previously published microarray analysis, we show that several differentiation genes transiently recruit Cbx8 during their early activation. Depletion of Cbx8 partially impairs the transcriptional activation of these genes. Both interaction analysis, as well as chromatin immunoprecipitation experiments support the idea that activating Cbx8 acts in the context of an intact PRC1 complex. Prolonged gene activation results in eviction of PRC1 despite persisting H3K27me3 and H2A ubiquitination. The composition of PRC1 is highly modular and changes when embryonic stem cells commit to differentiation. We further demonstrate that the exchange of Cbx7 for Cbx8 is required for the effective activation of differentiation genes. Taken together, our results establish a function for a Cbx8-containing complex in facilitating the transition from a Polycomb-repressed chromatin state to an active state. As this affects several key regulatory differentiation genes this mechanism is likely to contribute to the robust execution of differentiation programs.

  9. Burnup credit activities in the United States

    This report covers progress in burnup credit activities that have occurred in the United States of America (USA) since the International Atomic Energy Agency's (IAEA's) Advisory Group Meeting (AGM) on Burnup Credit was convened in October 1997. The Proceeding of the AGM were issued in April 1998 (IAEA-TECDOC-1013, April 1998). The three applications of the use of burnup credit that are discussed in this report are spent fuel storage, spent fuel transportation, and spent fuel disposal. (author)

  10. Jump Markov models and transition state theory: the Quasi-Stationary Distribution approach

    Di Gesù, Giacomo; Peutrec, Dorian Le; Nectoux, Boris

    2016-01-01

    We are interested in the connection between a metastable continuous state space Markov process (satisfying e.g. the Langevin or overdamped Langevin equation) and a jump Markov process in a discrete state space. More precisely, we use the notion of quasi-stationary distribution within a metastable state for the continuous state space Markov process to parametrize the exit event from the state. This approach is useful to analyze and justify methods which use the jump Markov process underlying a metastable dynamics as a support to efficiently sample the state-to-state dynamics (accelerated dynamics techniques). Moreover, it is possible by this approach to quantify the error on the exit event when the parametrization of the jump Markov model is based on the Eyring-Kramers formula. This therefore provides a mathematical framework to justify the use of transition state theory and the Eyring-Kramers formula to build kinetic Monte Carlo or Markov state models.

  11. RXTE observations and state transition in MAXI J1836-194

    Radhika, D; Seetha, S

    2014-01-01

    We present the results of analysis of the X-ray transient source MAXI J1836-194 during its outburst in August 2011. MAXI GSC detected the source on 30th August 2011, when it started rising from the quiescence. We have studied the source using the observations of RXTE. In this paper, we study the temporal and spectral evolution of the source during the outburst. Spectral analysis shows that the source exhibits state transition to Hard Intermediate state(HIMS) and decays back to a Low/Hard state. The temporal analysis indicates the presence of QPOs during the hard intermediate state. We also observe correlation between the evolution of break frequency with respect to the spectral characteristics. We conclude that this is probably the second source after H 1743-322 which exhibits transition to HIMS but does not reach soft spectral state.

  12. Solvent molecules bridge the mechanical unfolding transition state of a protein

    Dougan, Lorna; Feng, Gang; Lu, Hui; Fernandez, Julio M.

    2008-01-01

    We demonstrate a combination of single molecule force spectroscopy and solvent substitution that captures the presence of solvent molecules in the transition state structure. We measure the effect of solvent substitution on the rate of unfolding of the I27 titin module, placed under a constant stretching force. From the force dependency of the unfolding rate, we determine Δxu, the distance to the transition state. Unfolding the I27 protein in water gives a Δxu = 2.5 Å, a distance that compare...

  13. Systematic study of the single-state dominance in 2νββ decay transitions

    The single-state-dominance hypothesis (SSDH) states that the decay rates of the two-neutrino double-beta decay are governed by a virtual two-step transition connecting the initial and final ground states through the first 1+ state, 1+1, of the intermediate odd-odd nucleus, for those odd-odd nuclei where the 1+1 state is the ground state. To investigate the validity of the SSDH we have performed a systematical theoretical analysis of all known double-beta-decay transitions where the SSDH conditions are fulfilled. The calculations are based on the quasiparticle randon-phase approximation (QRPA) and the results have been obtained by using realistic single-particle bases and realistic interactions. We have studied the double β- decays of 100Mo, 110Pd, 114Cd, 116Cd and 128Te and the double electron-capture transitions in 106Cd and 136Ce. The analysis shows that the SSDH is realized either through a true dominance of the first intermediate 1+ state or by cancellations among the contributions of higher lying 1+ states of the intermediate nucleus

  14. A solid state laser system for high resolution spectroscopy of the 1S-2S transition in muonium

    This thesis describes the development and use of a solid state laser system for a precise measurement of the 1S - 2S frequency interval in muonium, the bound state of a positive muon and an electron. High resolution spectroscopy of this transition provides a clean test of bound state quantum electrodynamics (QED), free from the complications of finite nuclear size, and promises to yield an improved value for the mass of the muon. The experiment was performed using the pulsed surface muon source at the Rutherford Appleton Laboratory. Thermal muonium atoms were produced in vacuum by electron capture after stopping positive muons close to the surface of a SiO2 powder target. The 12S1/2(F = 1) → 22 S1/2(F = 1) transition was excited by Doppler-free, two-photon absorption using two counter-propagating, 244 nm laser beams. The high intensity UV light necessary to excite the muonium 1S - 2S transition was generated by frequency tripling the output of a pulsed, alexandrite ring laser in crystals of LBO and BBO. The alexandrite laser was seeded with light from a continuous wave Ti:sapphire laser operating at one-sixth of the 1S - 2S frequency interval (732 nm). A method of active cavity stabilization was developed to reduce the time jitter of the alexandrite laser output from about 20 μs to 100 ns, thereby permitting external synchronization of the laser output with the muon source. The temporal variation of the frequency (or phase) of the alexandrite output was monitored on a shot-by-shot basis using a pulsed heterodyne technique. Rapid fluctuations of the optical phase during the laser output (chirps) were compensated using an intra-cavity, electro-optic modulator. The muonium 1S - 2S transition was calibrated by stabilizing the frequency of the Ti:sapphire (seed) laser to a Doppler-free, ro-vibronic transition in thermally-excited iodine vapour. Frequency modulation, saturation spectroscopy was employed to produce derivative-like hyperfine spectra suitable for locking

  15. Calculation of state-to-state differential and integral cross sections for atom-diatom reactions with transition-state wave packets

    A recently proposed transition-state wave packet method [R. Welsch, F. Huarte-Larrañaga, and U. Manthe, J. Chem. Phys. 136, 064117 (2012)] provides an efficient and intuitive framework to study reactive quantum scattering at the state-to-state level. It propagates a few transition-state wave packets, defined by the eigenfunctions of the low-rank thermal flux operator located near the transition state, into the asymptotic regions of the reactant and product arrangement channels separately using the corresponding Jacobi coordinates. The entire S-matrix can then be assembled from the corresponding flux-flux cross-correlation functions for all arrangement channels. Since the transition-state wave packets can be defined in a relatively small region, its transformation into either the reactant or product Jacobi coordinates is accurate and efficient. Furthermore, the grid/basis for the propagation, including the maximum helicity quantum number K, is much smaller than that required in conventional wave packet treatments of state-to-state reactive scattering. This approach is implemented for atom-diatom reactions using a time-dependent wave packet method and applied to the H + D2 reaction with all partial waves. Excellent agreement with benchmark integral and differential cross sections is achieved

  16. The charge percolation mechanism and simulation of Ziegler–Natta polymerizations Part III. Oxidation states of transition metals

    BRANKA PILIC

    2006-04-01

    Full Text Available The oxidation state of the transition metal (Mt active centre is the most disputable question in the polymerization of olefins by Ziegler–Natta (ZN and metallocene complexes. In this paper the importance and the changes of the Mt active centres are presented and discussed on the basis of a charge percolation mechanism (CPM of olefin polymerization. Mt atoms can exist in different oxidation states and can be easily transformed from one to another state during activation. In all cases, the Mt atoms are present in several oxidation states, i.e., Mt+(n-1, Mt+(n to Mt+(n+1, producing an irregular charge distribution over the support surface. There is a tendency to equalize the oxidation states by a charge transfer from Mt+(n–1 (donor toMt+(n+1 (acceptor. This cannot occur since the different oxidation states are highly separated on the support. However, monomer molecules are adsorbed on the support producing clusters with stacked p-bonds, making a p-bond bridge between a donor and an acceptor. Once a bridge is formed (percolation moment, charge transfer occurs. The donor and acceptor equalize their oxidation states simultaneously with the polymerization of the monomer. The polymer chain is desorbed from the support, freeing the surface for subsequent monomer adsorption. The whole process is repeated with the oxidation-reduction of other donor-acceptor ensembles.

  17. State of the Art in Economics Education and Research in Transition Economies

    Boris Pleskovic; Anders Åslund; William Bader; Robert Campbell

    2000-01-01

    The development of the institutional capacity to create and evaluate economic policies remains a critical need—and constraint—in most transition economies if they are to complete the successful passage to fully functioning market economies. To take an active role in the transition process, economic policymakers, business leaders, government officials, and others need a thorough grounding in market-based economics. This requires strengthening economics education and providing support for quali...

  18. Ground-state shape phase transitions in nuclei: Thermodynamic analogy and finite-N effects

    We study quantum phase transitions between spherical, prolate, and oblate nuclear ground-state shapes using the interacting sd-boson model (sd-IBM) and demonstrate the analogy between the IBM results (also results of any axially symmetric quadrupole collective model) and predictions of the Landau theory of phase transitions in classical thermodynamics. A detailed comparison of the two frameworks is performed exploiting the concept of 'specific heat', introduced in four alternative ways in the quantum case. All these definitions (two of them based on spectroscopic features of the ground state, the others on a randomized version of the model) lead to similar peaked forms of the 'specific heat' at the point of the quantum phase transition. We analyze the effect of an increasing boson number on these curves and observe convergence to the singular phase-transitional behavior in the classical limit. Other observable signatures of the IBM structural phase transitions are also discussed with the aim to facilitate the location of a particular nucleus in the parameter space (extended Casten triangle) near the transitions

  19. Laboratory rotational ground state transitions of NH$_3$D$^+$ and CF$^+$

    Stoffels, Alexander; Schlemmer, Stephan; Brünken, Sandra

    2016-01-01

    Aims. This paper reports accurate laboratory frequencies of the rotational ground state transitions of two astronomically relevant molecular ions, NH3D+ and CF+. Methods. Spectra in the millimeter-wave band were recorded by the method of rotational state-selective attachment of He-atoms to the molecular ions stored and cooled in a cryogenic ion trap held at 4 K. The lowest rotational transition in the A state (ortho state) of NH$_3$D$^+$ ($J_K = 1_0 - 0_0$), and the two hyperfine components of the ground state transition of CF$^+$($J = 1 - 0$) were measured with a relative precision better than $10^{-7}$. Results. For both target ions the experimental transition frequencies agree with recent observations of the same lines in different astronomical environments. In the case of NH$_3$D$^+$ the high-accuracy laboratory measurements lend support to its tentative identification in the interstellar medium. For CF$^+$ the experimentally determined hyperfine splitting confirms previous quantum-chemical calculations a...

  20. Characterizing metastable states beyond energies and lifetimes: Dyson orbitals and transition dipole moments

    Jagau, Thomas-C.; Krylov, Anna I.

    2016-02-01

    The theoretical description of electronic resonances is extended beyond calculations of energies and lifetimes. We present the formalism for calculating Dyson orbitals and transition dipole moments within the equation-of-motion coupled-cluster singles and doubles method for electron-attached states augmented by a complex absorbing potential (CAP-EOM-EA-CCSD). The capabilities of the new methodology are illustrated by calculations of Dyson orbitals of various transient anions. We also present calculations of transition dipole moments between transient and stable anionic states as well as between different transient states. Dyson orbitals characterize the differences between the initial neutral and final electron-attached states without invoking the mean-field approximation. By extending the molecular-orbital description to correlated many-electron wave functions, they deliver qualitative insights into the character of resonance states. Dyson orbitals and transition moments are also needed for calculating experimental observables such as spectra and cross sections. Physically meaningful results for those quantities are obtained only in the framework of non-Hermitian quantum mechanics, e.g., in the presence of a complex absorbing potential (CAP), when studying resonances. We investigate the dependence of Dyson orbitals and transition moments on the CAP strength and illustrate how Dyson orbitals help understand the properties of metastable species and how they are affected by replacing the usual scalar product by the so-called c-product.

  1. Characterizing metastable states beyond energies and lifetimes: Dyson orbitals and transition dipole moments

    Jagau, Thomas-C.; Krylov, Anna I. [Department of Chemistry, University of Southern California, Los Angeles, California 90089 (United States)

    2016-02-07

    The theoretical description of electronic resonances is extended beyond calculations of energies and lifetimes. We present the formalism for calculating Dyson orbitals and transition dipole moments within the equation-of-motion coupled-cluster singles and doubles method for electron-attached states augmented by a complex absorbing potential (CAP-EOM-EA-CCSD). The capabilities of the new methodology are illustrated by calculations of Dyson orbitals of various transient anions. We also present calculations of transition dipole moments between transient and stable anionic states as well as between different transient states. Dyson orbitals characterize the differences between the initial neutral and final electron-attached states without invoking the mean-field approximation. By extending the molecular-orbital description to correlated many-electron wave functions, they deliver qualitative insights into the character of resonance states. Dyson orbitals and transition moments are also needed for calculating experimental observables such as spectra and cross sections. Physically meaningful results for those quantities are obtained only in the framework of non-Hermitian quantum mechanics, e.g., in the presence of a complex absorbing potential (CAP), when studying resonances. We investigate the dependence of Dyson orbitals and transition moments on the CAP strength and illustrate how Dyson orbitals help understand the properties of metastable species and how they are affected by replacing the usual scalar product by the so-called c-product.

  2. Characterizing metastable states beyond energies and lifetimes: Dyson orbitals and transition dipole moments

    The theoretical description of electronic resonances is extended beyond calculations of energies and lifetimes. We present the formalism for calculating Dyson orbitals and transition dipole moments within the equation-of-motion coupled-cluster singles and doubles method for electron-attached states augmented by a complex absorbing potential (CAP-EOM-EA-CCSD). The capabilities of the new methodology are illustrated by calculations of Dyson orbitals of various transient anions. We also present calculations of transition dipole moments between transient and stable anionic states as well as between different transient states. Dyson orbitals characterize the differences between the initial neutral and final electron-attached states without invoking the mean-field approximation. By extending the molecular-orbital description to correlated many-electron wave functions, they deliver qualitative insights into the character of resonance states. Dyson orbitals and transition moments are also needed for calculating experimental observables such as spectra and cross sections. Physically meaningful results for those quantities are obtained only in the framework of non-Hermitian quantum mechanics, e.g., in the presence of a complex absorbing potential (CAP), when studying resonances. We investigate the dependence of Dyson orbitals and transition moments on the CAP strength and illustrate how Dyson orbitals help understand the properties of metastable species and how they are affected by replacing the usual scalar product by the so-called c-product

  3. Adding structure to the transition process to advanced mathematical activity

    Engelbrecht, Johann

    2010-03-01

    The transition process to advanced mathematical thinking is experienced as traumatic by many students. Experiences that students had of school mathematics differ greatly to what is expected from them at university. Success in school mathematics meant application of different methods to get an answer. Students are not familiar with logical deductive reasoning, required in advanced mathematics. It is necessary to assist students in this transition process, in moving from general to mathematical thinking. In this article some structure is suggested for this transition period. This essay is an argumentative exposition supported by personal experience and international literature. This makes this study theoretical rather than empirical.

  4. Distinct large-scale turbulent-laminar states in transitional pipe flow.

    Moxey, David; Barkley, Dwight

    2010-05-01

    When fluid flows through a channel, pipe, or duct, there are two basic forms of motion: smooth laminar motion and complex turbulent motion. The discontinuous transition between these states is a fundamental problem that has been studied for more than 100 yr. What has received far less attention is the large-scale nature of the turbulent flows near transition once they are established. We have carried out extensive numerical computations in pipes of variable lengths up to 125 diameters to investigate the nature of transitional turbulence in pipe flow. We show the existence of three fundamentally different turbulent states separated by two distinct Reynolds numbers. Below Re (1) approximately equal 2,300, turbulence takes the form of familiar equilibrium (or longtime transient) puffs that are spatially localized and keep their size independent of pipe length. At Re (1) the flow makes a striking transition to a spatio-temporally intermittent flow that fills the pipe. Irregular alternation of turbulent and laminar regions is inherent and does not result from random disturbances. The fraction of turbulence increases with Re until Re (2) approximately equal 2,600 where there is a continuous transition to a state of uniform turbulence along the pipe. We relate these observations to directed percolation and argue that Re (1) marks the onset of infinite-lifetime turbulence. PMID:20404193

  5. Phosphonate analogues of carboxypeptidase A substrates are potent transition-state analogue inhibitors.

    Hanson, J E; Kaplan, A P; Bartlett, P A

    1989-07-25

    Analogues of tri- and tetrapeptide substrates of carboxypeptidase A in which the scissile peptide linkage is replaced with a phosphonate moiety (-PO2--O-) were synthesized and evaluated as inhibitors of the enzyme. The inhibitors terminated with either L-lactate or L-phenyllactate [designated (O) Ala and (O) Phe, respectively] in the P1' position. Transition-state analogy was shown for a series of 14 tri- and tetrapeptide derivatives containing the structure RCO-AlaP-(O)Ala [RCO-AP(O)A, AP indicates the phosphonic acid analogue of alanine] by the correlation of the Ki values for the inhibitors and the Km/kcat values for the corresponding amide substrates. This correlation supports a transition state for the enzymatic reaction that resembles the tetrahedral intermediate formed upon addition of water to the scissile carbonyl group. The inhibitors containing (O) Phe at the P1' position proved to be the most potent reversible inhibitors of carboxypeptidase A reported to date: the dissociation constants of ZAFP(O)F, ZAAP(O)F, and ZFAP(O)F are 4, 3, and 1 pM, respectively. Because of the high affinity of these inhibitors, their dissociation constants could not be determined by steady-state methods. Instead, the course of the association and dissociation processes was monitored for each inhibitor as its equilibrium with the enzyme was established in both the forward and reverse directions. A phosphonamidate analogue, ZAAPF, in which the peptide linkage is replaced with a -PO2-NH- moiety, was prepared and shown to hydrolyze rapidly at neutral pH (t1/2 = 20 min at pH 7.5). This inhibitor is bound an order of magnitude less tightly than the corresponding phosphonate, ZAAP(O)F, a result that contrasts with the 840-fold higher affinity of phosphonamidates for thermolysin [Bartlett, P. A., & Marlowe, C. K. (1987) Science 235, 569-571], a zinc peptidase with a similar arrangement of active-site catalytic residues. PMID:2790000

  6. Evolutionary transitions in enzyme activity of ant fungus gardens

    de Fine Licht, Henrik Hjarvard; Schiøtt, M.; Mueller, U. G.; Boomsma, J.J.

    2010-01-01

    Fungus-growing (attine) ants and their fungal symbionts passed through several evolutionary transitions during their 50 million year old evolutionary history. The basal attine lineages often shifted between two main cultivar clades, whereas the derived higher-attine lineages maintained an association with a monophyletic clade of specialized symbionts. In conjunction with the transition to specialized symbionts, the ants advanced in colony size and social complexity. Here we provide a comparat...

  7. Electron-impact fine-structure transitions in Cu XX from its ground state

    The R-matrix method is used to calculate collision strengths for electron-impact excitation of Cu XX from its ground state. Configuration interaction wavefunctions are used to represent the lowest 15 LS coupled states which are retained in the R-matrix expansion. Effective collisions strengths are calculated for transitions from the ground state to fine-structure levels of the excited states by employing a transformation of the LS coupled reactance matrices, and by assuming a Maxwellian distribution for the incident electron. This is the first detailed calculation on this ion in which the effects of exchange, channel couplings and short-range correlation effects are taken into account. (author)

  8. Self-organization of stress patterns drives state transitions in actin cortices

    Tan, Tzer Han; Abu-Shah, Enas; Li, Junang; Sharma, Abhinav; MacKintosh, Fred C; Keren, Kinneret; Schmidt, Christoph F; Fakhri, Nikta

    2016-01-01

    Biological functions rely on ordered structures and intricately controlled collective dynamics. In contrast to systems in thermodynamic equilibrium, order is typically established and sustained in stationary states by continuous dissipation of energy. Non-equilibrium dynamics is a necessary condition to make the systems highly susceptible to signals that cause transitions between different states. How cellular processes self-organize under this general principle is not fully understood. Here, we find that model actomyosin cortices, in the presence of rapid turnover, display distinct steady states, each distinguished by characteristic order and dynamics as a function of network connectivity. The different states arise from a subtle interaction between mechanical percolation of the actin network and myosin-generated stresses. Remarkably, myosin motors generate actin architectures, which in turn, force the emergence of ordered stress patterns. Reminiscent of second order phase transitions, the emergence of order...

  9. Finding possible transition states of defects in silicon-carbide and alpha-iron using the dimer method

    Energetic primary recoil atoms from ion implantation or fast neutron irradiation produce isolated point defects and clusters of both vacancies and interstitials. The migration energies and mechanisms for these defects are crucial to successful multiscale modeling of microstructural evolution during ion-implantation, thermal annealing, or under irradiation over long periods of time. The dimer method is employed to search for possible transition states of interstitials and small interstitial clusters in SiC and α-Fe. The method uses only the first derivatives of the potential energy to find saddle points without knowledge of the final state of the transition. In SiC, the possible migration pathway for the C interstitial is found to consist of the first neighbor jump via a Si site or second neighbor jump, but the relative probability for the second neighbor jump is very low. In α-Fe, the possible transition states are studied as a function of interstitial cluster size, and the lowest energy barriers correspond to defect migration along directions. However, this paper addresses whether migrating interstitial clusters can thermally change their direction, and the activation energies and corresponding mechanisms for changing the direction of these clusters are determined

  10. Continuous and discontinuous absorbing-state phase transitions on Voronoi-Delaunay random lattices

    de Oliveira, Marcelo M.; Alves, Sidiney G.; Ferreira, Silvio C.

    2016-01-01

    We study absorbing-state phase transitions (APTs) in two-dimensional Voronoi-Delaunay (VD) random lattices with quenched coordination disorder. Quenched randomness usually changes the criticality and destroys discontinuous transitions in low-dimensional nonequilibrium systems. We performed extensive simulations of the Ziff-Gulari-Barshad model, and verified that the VD disorder does not change the nature of its discontinuous transition. Our results corroborate recent findings of Barghathi and Vojta [H. Barghathi and T. Vojta, Phys. Rev. Lett. 113, 120602 (2014), 10.1103/PhysRevLett.113.120602], stating the irrelevance of topological disorder in a class of random lattices that includes VD, and raise the interesting possibility that disorder in nonequilibrium APT may, under certain conditions, be irrelevant for the phase coexistence. We also verify that the VD disorder is irrelevant for the critical behavior of models belonging to the directed percolation and Manna universality classes.

  11. Spin-state transition induced half metallicity in a cobaltate from first principles

    Ou, Xuedong; Fan, Fengren; Li, Zhengwei; Wang, Hongbo; Wu, Hua

    2016-02-01

    Half metal is a promising spintronic material. Here, we explore, using first principles calculations, a spin-state transition induced half metallicity in a layered cobaltate via a physical or chemical pressure. Our exemplary first principles study shows that the layered cobaltate Sr2CoO3F would undergo a transition, under a pressure of 5.4 GPa, from a high-spin antiferromagnetic insulator to an intermediate-spin ferromagnetic half-metal. The former phase is associated with a superexchange in a Mott insulator, and the latter one is due to a broad band formation and a kinetic energy gain of the partially occupied eg orbital. Note that the above transition could also be induced by a chemical pressure via doping in (Sr1-xCax)2CoO3F (x > 0.3). This work suggests that a cobaltate would be of a particular interest if stabilized into an intermediate-spin state.

  12. Transitions between sleep and feeding states in rat ventral striatum neurons

    Tellez, Luis A; Perez, Isaac O.; Simon, Sidney A.; Gutierrez, Ranier

    2012-01-01

    Neurons in the nucleus accumbens (NAc) have been shown to participate in several behavioral states, including feeding and sleep. However, it is not known if the same neuron participates in both states and, if so, how similar are the responses. In addition, since the NAc contains several cell types, it is not known if each type participates in the transitions associated with feeding and sleep. Such knowledge is important for understanding the interaction between two different neural networks. ...

  13. Vizualization of intermediate state near metamagnetic phase transition in ErFeO3

    Visualization of intermediate magnetic state in ErFeO3 plates during 1 order metamagnetic phase transition in magnetic field parallel to Er3+ ion Ising axis is first carried out at T=1.6 K. The range of intermediate state exsistence and domain sizes are determined. Possible mechanisms of intermediatestate thermodynamical stabilization and its visualization conditions in ErFeO3 plates are analysed

  14. Transition state theory: a generalization to nonequilibrium systems with power-law distributions

    Du, Jiulin

    2011-01-01

    Transition state theory (TST) is generalized for the nonequilibrium system with power-law distributions. The stochastic dynamics that gives rise to the power-law distributions for the reaction coordinate and momentum is modeled by the Langevin equations and corresponding Fokker-Planck equations. It is assumed that the system far away from equilibrium has not to relax to a thermal equilibrium state with Boltzmann-Gibbs distribution, but asymptotically approaches to a nonequilibrium stationary-...

  15. Localized charged states and phase separation near second order phase transition

    Kabanov, V. V.; Mamin, R. F.; Shaposhnikova, T. S.

    2008-01-01

    Localized charged states and phase segregation are described in the framework of the phenomenological Ginzburg-Landau theory of phase transitions. The Coulomb interactions determines the charge distribution and the characteristic length of the phase separated states. The phase separation with charge segregation becomes possible because of the large dielectric constant and the small density of extra charge in the range of charge localization. The phase diagram is calculated and the energy gain...

  16. Hydration of the folding transition-state ensemble of a protein

    Brun, Ludovic; Isom, Daniel G.; Velu, Priya; García-Moreno, Bertrand; Royer, Catherine

    2006-01-01

    A complete description of the mechanisms of protein folding requires knowledge of the structural and physical character of the folding transition state ensembles (TSE). A key question remains, concerning the role of hydration of the hydrophobic core in determining folding mechanisms. To address this we probed the state of hydration of the TSE of staphylococcal nuclease (SNase) by examining the fluorescence-detected pressure-jump relaxation behavior of six SNase variants in which a residue in ...

  17. An experimental survey of the transition between two-state and downhill protein folding scenarios

    Feng LIU; Du, Deguo; Fuller, Amelia A.; Davoren, Jennifer E.; Wipf, Peter; Kelly, Jeffery W.; Gruebele, Martin

    2008-01-01

    A kinetic and thermodynamic survey of 35 WW domain sequences is used in combination with a model to discern the energetic requirements for the transition from two-state folding to downhill folding. The sequences used exhibit a 600-fold range of folding rates at the temperature of maximum folding rate. Very stable proteins can achieve complete downhill folding when the temperature is lowered sufficiently below the melting temperature, and then at even lower temperatures they become two-state f...

  18. A late-time transition in the equation of state versus Lambda-CDM

    Bassett, B A; Silk, J; Ungarelli, C

    2002-01-01

    We study a model of the dark energy which exhibits a rapid change in its equation of state w(z), such as occurs in vacuum metamorphosis. We compare the model predictions with CMB, large scale structure and supernova data and show that a late-time transition is marginally preferred over standard Lambda-CDM.

  19. State-and-transition model archetypes: a global taxonomy of rangeland change

    State and transition models (STMs) synthesize science-based and local knowledge to formally represent the dynamics of rangeland and other ecosystems. Mental models or concepts of ecosystem dynamics implicitly underlie all management decisions in rangelands and thus how people influence rangeland sus...

  20. A Novel Credit Assignment to a Rule with Probabilistic State Transition

    Uemura, Wataru

    2010-01-01

    In this chapter, we have proposed a novel credit assignment method similar to profit sharing which considers the aliasing problem and the probabilistic state transition. We show that the condition to learn in a POMDP is to distribute equal rewards to rules at the same

  1. Molecular dynamics simulations from putative transition states of alpha-spectrin SH3 domain

    Periole, Xavier; Vendruscolo, Michele; Mark, Alan E.

    2007-01-01

    A series of molecular dynamics simulations in explicit solvent were started from nine structural models of the transition state of the SH3 domain of alpha-spectrin, which were generated by Lindorff Larsen et al. (Nat Struct Mol Biol 2004;11:443-449) using molecular dynamics simulations in which expe

  2. Comparison of 3D Classical Trajectory and Transition-State Theory Reaction Cross Sections

    Koeppl, G. W.; Karplus, Martin

    1970-10-01

    Although there is excellent agreement for a system such as H+H{sub 2} --> H{sub 2}+H, in which both the potential and the particle masses are symmetric, significant deviations occur for more asymmetric reactions. A detailed analysis show that the calculated differences are from the violation of two assumptions of transition-state theory.

  3. Excitonic instability at the spin-state transition in the two-band Hubbard model

    Kuneš, Jan; Augustinský, Pavel

    2014-01-01

    Roč. 89, č. 11 (2014), "115134-1"-"115134-8". ISSN 1098-0121 R&D Projects: GA ČR GA13-25251S Institutional support: RVO:68378271 Keywords : excitonic condensation * spin-state transition * dynamical mean-field theory Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  4. Trends in oxygen reduction and methanol activation on transition metal chalcogenides

    Tritsaris, Georgios; Nørskov, Jens Kehlet; Rossmeisl, Jan

    2011-01-01

    We use density functional theory calculations to study the oxygen reduction reaction and methanol activation on selenium and sulfur-containing transition metal surfaces. With ruthenium selenium as a starting point, we study the effect of the chalcogen on the activity, selectivity and stability of...... the catalyst. Ruthenium surfaces with moderate content of selenium are calculated active for the oxygen reduction reaction, and insensitive to methanol. A significant upper limit for the activity of transition metal chalcogenides is estimated....

  5. Novel states of pre-transition edge turbulence emerging from shearing mode competition

    Recent experiments have noted the coexistence of multiple shearing fields in edge turbulence, and have observed that the shearing population ratios evolve as the L-H transition is approached. A novel model including zonal flows (ZFs), geodesic acoustic modes (GAMs) and turbulence as a zero-dimensional self-consistent two predator-one prey system with multiple frequency shearings is proposed. ZF with finite frequency (i.e. GAM) can have different shearing dynamics from that with zero frequency, because of the finite shearing field autocorrelation times. Decomposing the broadband ZF spectrum into the two populations enables us to assign different shearing weights to the components of the shearing field. We define states with no ZF and GAM as an L-mode-like state, that with ZF and without GAM as an ZF-only state, with GAM and without ZF as a GAM-only state and both with ZF and GAM as the coexistence state. To resolve the origins of multiple shear coexistence, mode-competition effects are introduced. These originate from higher order perturbation of wave populations. The model exhibits a sequence of transitions between various states as the net driving flux increases. For some parameters, bistability of ZF and GAM is evident, which predicts hysteretic behaviour in the turbulence intensity field during power ramp up/down studies. The presence of noise due to ambient turbulence offers a mechanism to explain the bursts and pulsations observed in the turbulence field prior to the L-H transition.

  6. Systematic study of the single-state dominance in 2 nu beta beta decay transitions

    Civitarese, O

    1999-01-01

    The single-state-dominance hypothesis (SSDH) states that the decay rates of the two-neutrino double-beta decay are governed by a virtual two-step transition connecting the initial and final ground states through the first 1 sup + state, 1 sup + sub 1 , of the intermediate odd-odd nucleus, for those odd-odd nuclei where the 1 sup + sub 1 state is the ground state. To investigate the validity of the SSDH we have performed a systematical theoretical analysis of all known double-beta-decay transitions where the SSDH conditions are fulfilled. The calculations are based on the quasiparticle randon-phase approximation (QRPA) and the results have been obtained by using realistic single-particle bases and realistic interactions. We have studied the double beta sup - decays of sup 1 sup 0 sup 0 Mo, sup 1 sup 1 sup 0 Pd, sup 1 sup 1 sup 4 Cd, sup 1 sup 1 sup 6 Cd and sup 1 sup 2 sup 8 Te and the double electron-capture transitions in sup 1 sup 0 sup 6 Cd and sup 1 sup 3 sup 6 Ce. The analysis shows that the SSDH is real...

  7. Transitions into and out of daylight saving time compromise sleep and the rest-activity cycles

    Lönnqvist Jouko

    2008-02-01

    Full Text Available Abstract Background The aim of this study was to analyze the effects of transition out of and into daylight saving time on the rest-activity cycles and sleep. Rest-activity cycles of nine healthy participants aged 20 to 40 years were measured around transitions out of and into daylight saving time on fall 2005 and spring 2006 respectively. Rest-activity cycles were measured using wrist-worn accelerometers. The participants filled in the Morningness-Eveningness and Seasonal Pattern Assessment Questionnaires before starting the study and kept a sleep diary during the study. Results Fall transition was more disturbing for the more morning type and spring transition for the more evening type of persons. Individuals having a higher global seasonality score suffered more from the transitions. Conclusion Transitions out of and into daylight saving time enhanced night-time restlessness and thereby compromised the quality of sleep.

  8. Energy use, efficiency gains and emission abatement in transitional industrialised economies. Poland and the Baltic states

    Salay, Juergen

    1999-05-01

    This thesis is a study of how energy use and air pollution in Poland, Estonia, Latvia and Lithuania have been affected by the economic transition after 1989. It consists of six articles, which examine three different aspects of these changes. The first group of articles analyses the structure of energy use in the Baltic states (Article 1) and Poland (Articles 2 and 3) at the outset of transition. The results show that these countries had a primary energy consumption per GDP which was two to three times higher than in developed market economics because of a more energy intensive structure of the economy and higher specific energy intensities in many sectors of the economy. They also had significantly higher levels of air pollution per primary energy consumption and GDP because of a heavy reliance on fossil fuels, an energy intensive economy and an ineffective control of emissions. The deep fall in energy consumption during the first phase of transition was due to a sharp drop in industrial output and higher fuel prices. In the Baltic states, part of the fall in energy consumption was the result of shortfalls in the supply of oil and gas from Russia. The second group of articles (Articles 4 and 5) examines changes in electricity production, fuel consumption, generation efficiency and sulphur dioxide (SO{sub 2}) emissions in the Polish power industry between 1988 and 1997. The results show that SO{sub 2} emissions dropped by 45 per cent between 1988 and 1997. The drop in emissions was partly the result of a fall in economic activity and electricity production in the early 1990s. Other reasons were more important. One reason was the restructuring of the power industry, during which hard budget constraints were introduced and the price of coal was raised. Another reason for the fall in emissions was the reorganisation and stricter enforcement of environmental protection. Together, these reforms created strong incentives for power plants to switch to high-quality coal

  9. Phase transitions and dark-state physics in two-color superradiance

    Hayn, Mathias; Emary, Clive; Brandes, Tobias [Institut fuer Theoretische Physik, Technische Universitaet Berlin, D-10623 Berlin (Germany)

    2011-11-15

    We theoretically study an extension of the Dicke model, where the single-particle Hamiltonian has three energy levels in Lambda configuration (i.e., the excited state is coupled to two nondegenerate ground states via two independent quantized light fields). The corresponding many-body Hamiltonian can be diagonalized in the thermodynamic limit with the help of a generalized Holstein-Primakoff transformation. Analyzing the ground-state energy and the excitation energies, we identify one normal and two superradiant phases, separated by phase transitions of both first and second oder. A phase with both superradiant states coexisting is not stable. In addition, in the limit of two degenerate ground states a dark state emerges, which seems to be analogous to the dark state appearing in the well-known stimulated Raman adiabatic passage scheme.

  10. Contribution of cutinase serine 42 side chain to the stabilization of the oxyanion transition state.

    Nicolas, A; Egmond, M; Verrips, C T; de Vlieg, J; Longhi, S; Cambillau, C; Martinez, C

    1996-01-16

    Cutinase from the fungus Fusarium solani pisi is a lipolytic enzyme able to hydrolyze both aggregated and soluble substrates. It therefore provides a powerful tool for probing the mechanisms underlying lipid hydrolysis. Lipolytic enzymes have a catalytic machinery similar to those present in serine proteinases. It is characterized by the triad Ser, His, and Asp (Glu) residues, by an oxyanion binding site that stabilizes the transition state via hydrogen bonds with two main chain amide groups, and possibly by other determinants. It has been suggested on the basis of a covalently bond inhibitor that the cutinase oxyanion hole may consist not only of two main chain amide groups but also of the Ser42 O gamma side chain. Among the esterases and the serine and the cysteine proteases, only Streptomyces scabies esterase, subtilisin, and papain, respectively, have a side chain residue which is involved in the oxyanion hole formation. The position of the cutinase Ser42 side chain is structurally conserved in Rhizomucor miehei lipase with Ser82 O gamma, in Rhizopus delemar lipase with Thr83 O gamma 1, and in Candida antartica B lipase with Thr40 O gamma 1. To evaluate the increase in the tetrahedral intermediate stability provided by Ser42 O gamma, we mutated Ser42 into Ala. Furthermore, since the proper orientation of Ser42 O gamma is directed by Asn84, we mutated Asn84 into Ala, Leu, Asp, and Trp, respectively, to investigate the contribution of this indirect interaction to the stabilization of the oxyanion hole. The S42A mutation resulted in a drastic decrease in the activity (450-fold) without significantly perturbing the three-dimensional structure. The N84A and N84L mutations had milder kinetic effects and did not disrupt the structure of the active site, whereas the N84W and N84D mutations abolished the enzymatic activity due to drastic steric and electrostatic effects, respectively. PMID:8555209

  11. Edge states in confined active fluids

    Souslov, Anton; Vitelli, Vincenzo

    Recently, topologically protected edge modes have been proposed and realized in both mechanical and acoustic metamaterials. In one class of such metamaterials, Time-Reversal Symmetry is broken, and, to achieve this TRS breaking in mechanical and acoustic systems, an external energy input must be used. For example, motors provide a driving force that uses energy and, thus, explicitly break TRS. As a result, motors have been used as an essential component in the design of topological metamaterials. By contrast, we explore the design of topological metamaterials that use a class of far-from-equilibrium liquids, called polar active liquids, that spontaneously break TRS. We thus envision the confinement of a polar active liquid to a prescribed geometry in order to realize topological order with broken time-reversal symmetry. We address the design of the requisite geometries, for example a regular honeycomb lattice composed of annular channels, in which the active liquid may be confined. We also consider the physical character of the active liquid that, when introduced into the prescribed geometry, will spontaneously form the flow pattern of a metamaterial with topologically protected edge states. Finally, we comment on potential experimental realizations of such metamaterials.

  12. Collapse of the normal-state pseudogap at a Lifshitz transition in the Bi(2)Sr(2)CaCu(2)O(8+δ) cuprate superconductor.

    Benhabib, S; Sacuto, A; Civelli, M; Paul, I; Cazayous, M; Gallais, Y; Méasson, M-A; Zhong, R D; Schneeloch, J; Gu, G D; Colson, D; Forget, A

    2015-04-10

    We report a fine tuned doping study of strongly overdoped Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} single crystals using electronic Raman scattering. Combined with theoretical calculations, we show that the doping, at which the normal-state pseudogap closes, coincides with a Lifshitz quantum phase transition where the active holelike Fermi surface becomes electronlike. This conclusion suggests that the microscopic cause of the pseudogap is sensitive to the Fermi surface topology. Furthermore, we find that the superconducting transition temperature is unaffected by this transition, demonstrating that their origins are different on the overdoped side. PMID:25910152

  13. Variational transition state theory. Progress report, July 1, 1979-June 30, 1980

    The variational transition state theory (VTST) of chemical reaction rates has been further developed and two previously developed and one new version have been illustrated and tested by various applications to collinear and three-dimensional reactions of the type A + BC → AB + C. The first two versions considered are canonical variational theory (CVT), which is based on curves of free energy of activation as functions of location of the VTST dividing surface, and microcanonical variational theory (μVT), which is based on minimizing the reactive flux through the VTST dividing surface at each total energy. CVT is simpler but μVT is more accurate. The new theory, improved canonical variational theory (ICVT), is almost as simple as CVT but almost as accurate as μVT. This has been demonstrated by applications to H, O, F, Cl, and I reacting with H2, H reacting with F2 and Cl2, and various isotopic analogs and model systems. It was also demonstrated that VTST leads to very good agreement with accurate quantal results for several collinear reactions. Another project used VTST to explore the systematics of kinetic isotope effects for three-dimensional reactions. The predictions sometimes differ considerably from those of the conventional theory

  14. On the reaction pathways and determination of transition-state structures for retaining alpha-galactosyltransferases.

    André, Isabelle; Tvaroska, Igor; Carver, Jeremy P

    2003-04-22

    The catalytic mechanism of retaining glycosyltransferases is not yet completely understood, but one possible mechanism, by analogy with retaining glycosidases, is a double-displacement mechanism via a covalent glycosyl-enzyme intermediate (CGE). We have investigated various reaction pathways for this mechanism using non-empirical quantum mechanical methods. Because a double-displacement mechanism presumes a reaction happening in two steps, we have used predefined reaction coordinates to calculate the potential energy surface describing each step of the mechanism. By investigating several potential candidates to act as a catalytic base, this study attempts to shed some light on the unclear mechanism of the second step of the reaction. All intermediates and transition states on the reaction pathways were characterized using basis sets up to the DFT/B3LYP/6-311++G**//DFT/B3LYP/6-31G* level. Reaction pathways and structural changes were compared with the results previously obtained for inverting glycosyltransferases. The outcome of this study indicates, that among the reaction models investigated, the energetically favorable one is also the most plausible given the existing experimental data. This model requires the presence of only one catalytic acid in the active site with the UDP functioning as a general base in the second step of the reaction. This mechanism is in agreement with both kinetic data in the literature and the description of X-ray structures of retaining glycosyltransferases solved up to today. PMID:12681911

  15. Chaotic state to self-organized critical state transition of serrated flow dynamics during brittle-to-ductile transition in metallic glass

    We study serrated flow dynamics during brittle-to-ductile transition induced by tuning the sample aspect ratio in a Zr-based metallic glass. The statistical analysis reveals that the serrated flow dynamics transforms from a chaotic state characterized by Gaussian-distribution serrations corresponding to stick-slip motion of randomly generated and uncorrelated single shear band and brittle behavior, into a self-organized critical state featured by intermittent scale-free distribution of shear avalanches corresponding to a collective motion of multiple shear bands and ductile behavior. The correlation found between serrated flow dynamics and plastic deformation might shed light on the plastic deformation dynamic and mechanism in metallic glasses

  16. Chaotic state to self-organized critical state transition of serrated flow dynamics during brittle-to-ductile transition in metallic glass

    Wang, C.; Wang, W. H.; Bai, H. Y., E-mail: hybai@aphy.iphy.ac.cn [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Sun, B. A. [Centre for Advanced Structural Materials, Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon Tong, Kowloon (Hong Kong)

    2016-02-07

    We study serrated flow dynamics during brittle-to-ductile transition induced by tuning the sample aspect ratio in a Zr-based metallic glass. The statistical analysis reveals that the serrated flow dynamics transforms from a chaotic state characterized by Gaussian-distribution serrations corresponding to stick-slip motion of randomly generated and uncorrelated single shear band and brittle behavior, into a self-organized critical state featured by intermittent scale-free distribution of shear avalanches corresponding to a collective motion of multiple shear bands and ductile behavior. The correlation found between serrated flow dynamics and plastic deformation might shed light on the plastic deformation dynamic and mechanism in metallic glasses.

  17. Chaotic state to self-organized critical state transition of serrated flow dynamics during brittle-to-ductile transition in metallic glass

    Wang, C.; Sun, B. A.; Wang, W. H.; Bai, H. Y.

    2016-02-01

    We study serrated flow dynamics during brittle-to-ductile transition induced by tuning the sample aspect ratio in a Zr-based metallic glass. The statistical analysis reveals that the serrated flow dynamics transforms from a chaotic state characterized by Gaussian-distribution serrations corresponding to stick-slip motion of randomly generated and uncorrelated single shear band and brittle behavior, into a self-organized critical state featured by intermittent scale-free distribution of shear avalanches corresponding to a collective motion of multiple shear bands and ductile behavior. The correlation found between serrated flow dynamics and plastic deformation might shed light on the plastic deformation dynamic and mechanism in metallic glasses.

  18. Ab initio multi-configuration Dirac-Fock calculation of M1 visible transitions among the ground state multiplets of the W26+ ion

    The development of fusion reactors has generated a demand for improved knowledge of the atomic properties of tungsten. Using a multi-configuration Dirac-Fock (MCDF) method with a restricted active space treatment, the wavelengths and transition probabilities of the M1 and E2 transitions in the visible light region are calculated for the ground state multiplets of W26+ ions. The theoretical wavelength (388.43 nm) for the 3H5 → 3H4 magnetic dipole transition agrees quite well with the experimental value (389.41 nm). Other transitions theoretically predicted at longer wavelengths are also in good agreement with new experimental observations. The results also indicate that the core-core correlation contributions from the 4d shell are essential to determine the transition properties accurately.

  19. Ab initio multi-configuration Dirac-Fock calculation of M1 visible transitions among the ground state multiplets of the W{sup 26+} ion

    Ding Xiaobin; Murakami, Izumi; Kato, Daiji; Sakaue, Hiroyuki A [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Koike, Fumihiro [School of Medicine, Kitasato University, Sagamihara, Kanagawa 252-0374 (Japan); Dong, Chen-Zhong [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Nakamura, Nobuyuki; Komatsu, Akihiro; Sakoda, Junpei, E-mail: ding.xiaobin@LHD.nifs.ac.jp [Institute for Laser Science, The University of Electro-Comunications, Chofu, Tokyo 182-8585 (Japan)

    2011-07-28

    The development of fusion reactors has generated a demand for improved knowledge of the atomic properties of tungsten. Using a multi-configuration Dirac-Fock (MCDF) method with a restricted active space treatment, the wavelengths and transition probabilities of the M1 and E2 transitions in the visible light region are calculated for the ground state multiplets of W{sup 26+} ions. The theoretical wavelength (388.43 nm) for the {sup 3}H{sub 5} {yields} {sup 3}H{sub 4} magnetic dipole transition agrees quite well with the experimental value (389.41 nm). Other transitions theoretically predicted at longer wavelengths are also in good agreement with new experimental observations. The results also indicate that the core-core correlation contributions from the 4d shell are essential to determine the transition properties accurately.

  20. Equation of state and transition temperatures in the quark-hadron hybrid model

    Miyahara, Akihisa; Kouno, Hiroaki; Yahiro, Masanobu

    2016-01-01

    We analyze the equation of state of 2+1 flavor lattice QCD at zero baryon density by constructing the simple quark-hadron hybrid model that has both quark and hadron components simultaneously. Lattice data on the equation of state are decomposed into hadron and quark components by using the model. The transition temperature is defined by the temperature at which the hadron component is equal to the quark one in the equation of state. The transition temperature thus obtained is about 215 MeV and somewhat higher than the chiral and the deconfinement pseudocritical temperatures defined by the temperature at which the susceptibility or the derivative of the order parameter with respect to temperature becomes maximum.

  1. Monopole transitions to cluster states in $^{10}$Be and $^9$Li

    Kanada-En'yo, Yoshiko

    2016-01-01

    Isoscalar monopole transitions from the ground states to cluster states in $\\Be$ and $\\Li$ are investigated with $\\He+\\alpha$ and $\\He+t$ cluster models, respectively. In $\\Be$, significant monopole strengths to $\\He+\\alpha$ cluster resonances of $\\Be(0^+_{3,4})$ above the $\\alpha$-decay threshold are obtained, whereas those to $\\He+t$ cluster resonances in $^9$Li are not enhanced because of the large fragmentation of the strengths in the corresponding energy region. The monopole transition to $\\Be(0^+_2)$ having the molecular orbital structure is relatively weak compared with those to $\\He+\\alpha$ cluster resonances. Monopole strength distributions do not directly correspond to distributions of $\\He(0^+)+\\alpha$ and $\\He(0+)+t$ components but they reflect component of the deformed $\\He$ cluster with a specific orientation, which is originally embedded in the ground state.

  2. Forbidden Transition Probabilities of Astrophysical Interest among Low-lying States of V III

    Andrei Irimia

    2007-06-01

    Electric and magnetic multipole transitions among low-lying states of doubly ionized vanadium were computed using the multi-configuration Hartree–Fock (MCHF) method with Breit–Pauli (BP) corrections to a non-relativistic Hamiltonian. Energy levels were determined up to and including 32(1)4 b 27/2 and computed energies were found to be in good agreement with experiment and other theories. In addition to Einstein coefficients for some E2 and M1 transitions, lifetime data and selected weighted oscillator strengths are also reported.

  3. Tuning of Electron States of Transition Metal’s Catalysts Using Acceptor’s Atoms: ab initio Calculation

    R.M. Balabai

    2016-06-01

    Full Text Available Within the methods of density functional theory and ab initio pseudopotential, we have obtained the spatial distributions of the density of valence electron and the electronic energy spectrum for the small clusters from the atoms of Cu, Ni, Co, O, Si with the aim to determine the mechanisms of their high catalytic activity. Electron’s levels of catalyst guide course of chemical reaction. We explored, that the organization of electronic states of nanocatalysts on the basis of transition metals possible control by changing the spatial organization of clusters and adding electronegative atoms.

  4. Crossover of high and low spin states in transition metal complexes

    Raebiger, Hannes; Yasuhara, Hiroshi

    2012-01-01

    The stability of high vs. low spin states of transition metal complexes has been interpreted by ligand field theory, which is a perturbation theory of the electron-electron interaction. The present first principles calculation of a series of five cobalt complexes shows that the electron-electron interaction energy difference between the two states (i) exhibits the opposite trend to the total energy difference as the ligand nuclear charge varies, and (ii) is three or four orders of magnitude greater than the total energy difference. A new interpretation of the crossover of high and low spin states is given in terms of the chemical bonding.

  5. Generalization of the second law for a transition between nonequilibrium states

    The maximum work formulation of the second law of thermodynamics is generalized for a transition between nonequilibrium states. The relative entropy, the Kullback-Leibler divergence between the nonequilibrium states and the canonical distribution, determines the maximum ability to work. The difference between the final and the initial relative entropies with an effective temperature gives the maximum dissipative work for both adiabatic and isothermal processes. Our formulation reduces to both the Vaikuntanathan-Jarzynski relation and the nonequilibrium Clausius relation in certain situations. By applying our formulation to a heat engine the Carnot cycle is generalized to a circulation among nonequilibrium states.

  6. Noise-induced precursors of state transitions in the stochastic Wilson-cowan model.

    Negahbani, Ehsan; Steyn-Ross, D Alistair; Steyn-Ross, Moira L; Wilson, Marcus T; Sleigh, Jamie W

    2015-01-01

    The Wilson-Cowan neural field equations describe the dynamical behavior of a 1-D continuum of excitatory and inhibitory cortical neural aggregates, using a pair of coupled integro-differential equations. Here we use bifurcation theory and small-noise linear stochastics to study the range of a phase transitions-sudden qualitative changes in the state of a dynamical system emerging from a bifurcation-accessible to the Wilson-Cowan network. Specifically, we examine saddle-node, Hopf, Turing, and Turing-Hopf instabilities. We introduce stochasticity by adding small-amplitude spatio-temporal white noise, and analyze the resulting subthreshold fluctuations using an Ornstein-Uhlenbeck linearization. This analysis predicts divergent changes in correlation and spectral characteristics of neural activity during close approach to bifurcation from below. We validate these theoretical predictions using numerical simulations. The results demonstrate the role of noise in the emergence of critically slowed precursors in both space and time, and suggest that these early-warning signals are a universal feature of a neural system close to bifurcation. In particular, these precursor signals are likely to have neurobiological significance as early warnings of impending state change in the cortex. We support this claim with an analysis of the in vitro local field potentials recorded from slices of mouse-brain tissue. We show that in the period leading up to emergence of spontaneous seizure-like events, the mouse field potentials show a characteristic spectral focusing toward lower frequencies concomitant with a growth in fluctuation variance, consistent with critical slowing near a bifurcation point. This observation of biological criticality has clear implications regarding the feasibility of seizure prediction. PMID:25859420

  7. A College-Level Inquiry-Based Laboratory Activity on Transiting Planets

    McConnell, Nicholas J.; Medling, Anne M.; Strubbe, Linda E.; Moth, Pimol; Montgomery, Ryan M.; Raschke, Lynne M.; Hunter, Lisa; Goza, Barbara

    2010-01-01

    We have designed an inquiry-based laboratory activity on transiting extrasolar planets for an introductory college-level astronomy class. The activity was designed with the intent of simultaneously teaching science process skills and factual content about transits and light curves. In the activity, groups of two to four students each formulate a specific science question and design and carry out an investigation using a table-top model of a star and orbiting planet. Each group then presents t...

  8. Short communication: Proteins from circulating exosomes represent metabolic state in transition dairy cows.

    Crookenden, M A; Walker, C G; Peiris, H; Koh, Y; Heiser, A; Loor, J J; Moyes, K M; Murray, A; Dukkipati, V S R; Kay, J K; Meier, S; Roche, J R; Mitchell, M D

    2016-09-01

    Biomarkers that identify prepathological disease could enhance preventive management, improve animal health and productivity, and reduce costs. Circulating extracellular vesicles, particularly exosomes, are considered to be long-distance, intercellular communication systems in human medicine. Exosomes provide tissue-specific messages of functional state and can alter the cellular activity of recipient tissues through their protein and microRNA content. We hypothesized that exosomes circulating in the blood of cows during early lactation would contain proteins representative of the metabolic state of important tissues, such as liver, which play integral roles in regulating the physiology of cows postpartum. From a total of 150 cows of known metabolic phenotype, 10 cows were selected with high (n=5; high risk) and low (n=5; low risk) concentrations of nonesterified fatty acids, β-hydroxybutyrate, and liver triacylglycerol during wk 1 and 2 after calving. Exosomes were extracted from blood on the day of calving (d 0) and postcalving at wk 1 and wk 4, and their protein composition was determined by mass spectroscopy. Extracellular vesicle protein concentration and the number of exosome vesicles were not affected by risk category; however, the exosome protein cargo differed between the groups, with proteins at each time point identified as being unique to the high- and low-risk groups. The proteins α-2 macroglobulin, fibrinogen, and oncoprotein-induced transcript 3 were unique to the high-risk cows on d 0 and have been associated with metabolic syndrome and liver function in humans. Their presence may indicate a more severe inflammatory state and a greater degree of liver dysfunction in the high-risk cows than in the low-risk cows, consistent with the high-risk cows' greater plasma β-hydroxybutyrate and liver triacylglycerol concentrations. The commonly shared proteins and those unique to the low-risk category indicate a role for exosomes in immune function. The data

  9. Collective state transitions of exciton-polaritons loaded into a periodic potential

    Winkler, K.; Egorov, O. A.; Savenko, I. G.; Ma, X.; Estrecho, E.; Gao, T.; Müller, S.; Kamp, M.; Liew, T. C. H.; Ostrovskaya, E. A.; Höfling, S.; Schneider, C.

    2016-03-01

    We study the loading of a nonequilibrium, dissipative system of composite bosons—exciton polaritons—into a one-dimensional periodic lattice potential. Utilizing momentum resolved photoluminescence spectroscopy, we observe a transition between an incoherent Bose gas and a polariton condensate, which undergoes further transitions between different energy states in the band-gap spectrum of the periodic potential with increasing pumping power. We demonstrate controlled loading into distinct energy bands by modifying the size and shape of the excitation beam. The observed effects are comprehensively described in the framework of a nonequilibrium model of polariton condensation. In particular, we implement a stochastic treatment of quantum and thermal fluctuations in the system and conclude that polariton-phonon scattering is a plausible energy relaxation mechanism enabling transitions from the highly nonequilibrium polariton condensate in the gap to the ground band condensation for large pump powers.

  10. Equation of state of nuclear matter in the first order phase transition

    Maruyama, Toshiki; Chiba, Satoshi

    2009-01-01

    We investigate the properties of nuclear matter at the first-order phase transitions (FOPT) such as liquid-gas phase transition, kaon condensation, and hadron-quark phase transition. As a general feature of the FOPT of matter consisting of many species of charged particles, there appears a mixed phases with regular structures called "pasta" due to the balance of the Coulomb repulsion and the surface tension between two phases. The equation of state (EOS) of mixed phase is different from those obtained by a bulk application of Gibbs conditions or by the Maxwell construction due to the effects of the non-uniform structure. We show that the charge screening and strong surface tension make the EOS close to that of the Maxwell construction.

  11. Equation of state of nuclear matter in the first order phase transition

    We investigate the properties of nuclear matter at the first-order phase transitions (FOPT) such as liquid-gas phase transition, kaon condensation, and hadron-quark phase transition. As a general feature of the FOPT of matter consisting of many species of charged particles, there appears a mixed phases with regular structures called ''pasta'' due to the balance of the Coulomb repulsion and the surface tension between two phases. The equation of state (EOS) of mixed phase is different from those obtained by a bulk application of Gibbs conditions or by the Maxwell construction due to the effects of the non-uniform structure. We show that the charge screening and strong surface tension make the EOS close to that of the Maxwell construction.

  12. The impact of quantum dot filling on dual-band optical transitions via intermediate quantum states

    InAs/GaAs quantum dot infrared photodetectors with different doping levels were investigated to understand the effect of quantum dot filling on both intraband and interband optical transitions. The electron filling of self-assembled InAs quantum dots was varied by direct doping of quantum dots with different concentrations. Photoresponse in the near infrared and middle wavelength infrared spectral region was observed from samples with low quantum dot filling. Although undoped quantum dots were favored for interband transitions with the absence of a second optical excitation in the near infrared region, doped quantum dots were preferred to improve intraband transitions in the middle wavelength infrared region. As a result, partial filling of quantum dot was required, to the extent of maintaining a low dark current, to enhance the dual-band photoresponse through the confined electron states

  13. Transition State Models for Understanding the Origin of Chiral Induction in Asymmetric Catalysis.

    Sunoj, Raghavan B

    2016-05-17

    In asymmetric catalysis, a chiral catalyst bearing chiral center(s) is employed to impart chirality to developing stereogenic center(s). A rich and diverse set of chiral catalysts is now available in the repertoire of synthetic organic chemistry. The most recent trends point to the emergence of axially chiral catalysts based on binaphthyl motifs, in particular, BINOL-derived phosphoric acids and phosphoramidites. More fascinating ideas took shape in the form of cooperative multicatalysis wherein organo- and transition-metal catalysts are made to work in concert. At the heart of all such manifestations of asymmetric catalysis, classical or contemporary, is the stereodetermining transition state, which holds a perennial control over the stereochemical outcome of the catalytic process. Delving one step deeper, one would find that the origin of the stereoselectivity is delicately dependent on the relative stabilization of one transition state, responsible for the formation of the predominant stereoisomer, over the other transition state for the minor stereoisomer. The most frequently used working hypothesis to rationalize the experimentally observed stereoselectivity places an undue emphasis on steric factors and tends to regard the same as the origin of facial discrimination between the prochiral faces of the reacting partners. In light of the increasing number of asymmetric catalysts that rely on hydrogen bonding as well as other weak non-covalent interactions, it is important to take cognizance of the involvement of such interactions in the sterocontrolling transition states. Modern density functional theories offer a pragmatic and effective way to capture non-covalent interactions in transition states. Aided by the availability of such improved computational tools, it is quite timely that the molecular origin of stereoselectivity is subjected to more intelligible analysis. In this Account, we describe interesting molecular insights into the stereocontrolling

  14. Spectral hardening as a viable alternative to disc truncation in black hole state transitions

    Salvesen, Greg; Reis, Rubens C; Begelman, Mitchell C

    2013-01-01

    Constraining the accretion flow geometry of black hole binaries in outburst is complicated by the inability of simplified multi-colour disc models to distinguish between changes in the inner disc radius and alterations to the emergent spectrum, parameterised by the phenomenological colour correction factor, f_col. We analyse Rossi X-ray Timing Explorer observations of the low mass Galactic black hole X-ray binary, GX 339-4, taken over seven epochs when the source was experiencing a state transition. The accretion disc component is isolated using a pipeline resulting in robust detections for disc luminosities, 0.001 < L_disc / L_Edd < 0.5. Assuming that the inner disc remains situated at the innermost stable circular orbit over the course of a state transition, we measure the relative degree of change in f_col required to explain the spectral evolution of the disc component. A variable f_col that increases by a factor of ~ 2.0 - 3.5 as the source transitions from the high/soft state to the low/hard state...

  15. Cygnus X-3 transition from the ultrasoft to the hard state

    Beckmann, V; Bélanger, G; Brandt, S; Caballero-Garcia, M D; De Cesare, G; Gehrels, N; Grebenev, S; Vilhu, O; Von Kienlin, A; Courvoisier, T J -L

    2007-01-01

    Aims: The nature of Cygnus X-3 is still not understood well. This binary system might host a black hole or a neutron star. Recent observations by INTEGRAL have shown that Cygnus X-3 was again in an extremely ultrasoft state. Here we present our analysis of the transition from the ultrasoft state, dominated by blackbody radiation at soft X-rays plus non-thermal emission in the hard X-rays, to the low hard state. Methods: INTEGRAL observed Cyg X-3 six times during three weeks in late May and early June 2007. Data from IBIS/ISGRI and JEM-X1 were analysed to show the spectral transition. Results: During the ultrasoft state, the soft X-ray spectrum is well-described by an absorbed (NH = 1.5E22 1/cm**2) black body model, whereas the X-ray spectrum above 20 keV appears to be extremely low and hard (Gamma = 1.7). During the transition, the radio flux rises to a level of >1 Jy, and the soft X-ray emission drops by a factor of 3, while the hard X-ray emission rises by a factor of 14 and becomes steeper (up to Gamma = 4...

  16. Temperature induced structural transitions from native to unfolded aggregated states of tobacco etch virus protease

    Zhu, Guo-Fei; Ren, Si-Yan; Xi, Lei; Du, Lin-Fang; Zhu, Xiao-Feng

    2015-02-01

    Tobacco etch virus protease (TEVp) is widely used to remove fusion tags from recombinant proteins because of its high and unique specificity. This work describes the conformational and the thermodynamic properties in the unfolding/refolding process of TEVp3M (three-point mutant: L56V/S135G/S219V) induced by temperature. With temperature increasing from 20 to 100 °C, the CD spectra showed a transition trend from α-helix to β-sheet, and the fluorescence emission, synchronous fluorescence, ANS and RLS spectroscopy consistently revealed that the temperature-induced unfolding process behaved in a three-state manner, for there was a relatively stable intermediate state observed around 50 °C. The reversibility of thermal unfolding of TEVp3M further showed that the transition from the native to the intermediate state was reversible (below 50 °C), however the transition from the intermediate to the unfolded state was irreversible (above 60 °C). Moreover, aggregates were observed above 60 °C as revealed by SDS-PAGE, Thioflavin-T fluorescence and Congo red absorbance.

  17. Hot accretion flow with radiative cooling: state transitions in black hole X-ray binaries

    Wu, Mao-Chun; Xie, Fu-Guo; Yuan, Ye-Fei; Gan, Zhaoming

    2016-06-01

    We investigate state transitions in black hole X-ray binaries through different parameters by using two-dimensional axisymmetric hydrodynamical simulation method. For radiative cooling in hot accretion flow, we take into account the bremsstrahlung, synchrotron and synchrotron self-Comptonization self-consistently in the dynamics. Our main result is that the state transitions occur when the accretion rate reaches a critical value dot{M} ˜ 3α dot{M}_Edd, above which cold and dense clumpy/filamentary structures are formed, embedded within the hot gas. We argued this mode likely corresponds to the proposed two-phase accretion model, which may be responsible for the intermediate state of black hole X-ray binaries. When the accretion rate becomes sufficiently high, the clumpy/filamentary structures gradually merge and settle down on to the mid-plane. Eventually the accretion geometry transforms to a disc-corona configuration. In summary, our results are consistent with the truncated accretion scenario for the state transition.

  18. High-Resolution Mapping of the Folding Transition State of a WW Domain.

    Dave, Kapil; Jäger, Marcus; Nguyen, Houbi; Kelly, Jeffery W; Gruebele, Martin

    2016-04-24

    Fast-folding WW domains are among the best-characterized systems for comparing experiments and simulations of protein folding. Recent microsecond-resolution experiments and long duration (totaling milliseconds) single-trajectory modeling have shown that even mechanistic changes in folding kinetics due to mutation can now be analyzed. Thus, a comprehensive set of experimental data would be helpful to benchmark the predictions made by simulations. Here, we use T-jump relaxation in conjunction with protein engineering and report mutational Φ-values (ΦM) as indicators for folding transition-state structure of 65 side chain, 7 backbone hydrogen bond, and 6 deletion and /or insertion mutants within loop 1 of the 34-residue hPin1 WW domain. Forty-five cross-validated consensus mutants could be identified that provide structural constraints for transition-state structure within all substructures of the WW domain fold (hydrophobic core, loop 1, loop 2, β-sheet). We probe the robustness of the two hydrophobic clusters in the folding transition state, discuss how local backbone disorder in the native-state can lead to non-classical ΦM-values (ΦM > 1) in the rate-determining loop 1 substructure, and conclusively identify mutations and positions along the sequence that perturb the folding mechanism from loop 1-limited toward loop 2-limited folding. PMID:26880334

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

    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).

  20. Nuclear matter at high density: Phase transitions, multiquark states, and supernova outbursts

    Phase transition from hadronic matter to quark-gluon matter is discussed for various regimes of temperature and baryon number density. For small and medium densities, the phase transition is accurately described in the framework of the Field Correlation Method, whereas at high density predictions are less certain and leave room for the phenomenological models. We study formation of multiquark states (MQS) at zero temperature and high density. Relevant MQS components of the nuclear matter can be described using a previously developed formalism of the quark compound bags (QCB). Partialwave analysis of nucleon-nucleon scattering indicates the existence of 6QS which manifest themselves as poles of P matrix. In the framework of the QCB model, we formulate a self-consistent system of coupled equations for the nucleon and 6QS propagators in nuclear matter and the G matrix. The approach provides a link between high-density nuclear matter with the MQS components and the cumulative effect observed in reactions on the nuclei, which requires the admixture of MQS in the wave functions of nuclei kinematically. 6QS determines the natural scale of the density for a possible phase transition into theMQS phase of nuclear matter. Such a phase transition can lead to dynamic instability of newly born protoneutron stars and dramatically affect the dynamics of supernovae. Numerical simulations show that the phase transition may be a good remedy for the triggering supernova explosions in the spherically symmetric supernovamodels. A specific signature of the phase transition is an additional neutrino peak in the neutrino light curve. For a Galactic core-collapse supernova, such a peak could be resolved by the present neutrino detectors. The possibility of extracting the parameters of the phase of transition from observation of the neutrino signal is discussed also.

  1. Study of radicals, clusters and transition state species by anion photoelectron spectroscopy

    Arnold, D.W.

    1994-08-01

    Free radicals, elemental and van der Waals clusters and transition state species for bimolecular chemical reactions are investigated using anion photoelectron spectroscopy. Several low-lying electronic states of ozone have been identified via photoelectron spectroscopy of O{sub 3}{sup {minus}}. A characterization of these states is important to models for atmospheric ozone reaction kinetics. The fluoroformyloxyl radical, FCO{sub 2}, has been investigated, providing vibrational frequencies and energies for two electronic states. The technique has also been employed to make the first direct observation and characterization of the NNO{sub 2} molecule. Several electronic states are observed for this species which is believed to play a role as a reactive intermediate in the N + NO{sub 2} reaction. The experimental results for all three of these radicals are supplemented by ab initio investigations of their molecular properties. The clusters investigations include studies of elemental carbon clusters (C{sub 2}{sup {minus}} {minus} C{sub 11}{sup {minus}}), and van der Waals clusters (X{sup {minus}}(CO{sub 2}){sub n}, X = I, Br, Cl; n {le} 13 and I{sup {minus}} (N{sub 2}O){sub n=1--11}). Primarily linear clusters are observed for the smaller carbon clusters, while the spectra of the larger clusters contain contribution from cyclic anion photodetachment. Very interesting ion-solvent interactions are observed in the X{sup {minus}}(CO{sub 2})n clusters. The transition state regions for several bimolecular chemical reactions have also been investigated by photodetachment of a negative ion precursor possessing a geometry similar to that of the transition state species. These spectra show features which are assigned to motions of the unstable neutral complex existing between reactants and products.

  2. Study of radicals, clusters and transition state species by anion photoelectron spectroscopy

    Free radicals, elemental and van der Waals clusters and transition state species for bimolecular chemical reactions are investigated using anion photoelectron spectroscopy. Several low-lying electronic states of ozone have been identified via photoelectron spectroscopy of O3-. A characterization of these states is important to models for atmospheric ozone reaction kinetics. The fluoroformyloxyl radical, FCO2, has been investigated, providing vibrational frequencies and energies for two electronic states. The technique has also been employed to make the first direct observation and characterization of the NNO2 molecule. Several electronic states are observed for this species which is believed to play a role as a reactive intermediate in the N + NO2 reaction. The experimental results for all three of these radicals are supplemented by ab initio investigations of their molecular properties. The clusters investigations include studies of elemental carbon clusters (C2- - C11-), and van der Waals clusters (X-(CO2)n, X = I, Br, Cl; n ≤ 13 and I- (N2O)n=1--11). Primarily linear clusters are observed for the smaller carbon clusters, while the spectra of the larger clusters contain contribution from cyclic anion photodetachment. Very interesting ion-solvent interactions are observed in the X-(CO2)n clusters. The transition state regions for several bimolecular chemical reactions have also been investigated by photodetachment of a negative ion precursor possessing a geometry similar to that of the transition state species. These spectra show features which are assigned to motions of the unstable neutral complex existing between reactants and products

  3. Pressure controlled transition into a self-induced topological superconducting surface state

    Zhu, Zhiyong

    2014-02-07

    Ab-initio calculations show a pressure induced trivial-nontrivial-trivial topological phase transition in the normal state of 1T-TiSe2. The pressure range in which the nontrivial phase emerges overlaps with that of the superconducting ground state. Thus, topological superconductivity can be induced in protected surface states by the proximity effect of superconducting bulk states. This kind of self-induced topological surface superconductivity is promising for a realization of Majorana fermions due to the absence of lattice and chemical potential mismatches. For appropriate electron doping, the formation of the topological superconducting surface state in 1T-TiSe 2 becomes accessible to experiments as it can be controlled by pressure.

  4. Random field disorder at an absorbing state transition in one and two dimensions

    Barghathi, Hatem; Vojta, Thomas

    2016-02-01

    We investigate the behavior of nonequilibrium phase transitions under the influence of disorder that locally breaks the symmetry between two symmetrical macroscopic absorbing states. In equilibrium systems such "random-field" disorder destroys the phase transition in low dimensions by preventing spontaneous symmetry breaking. In contrast, we show here that random-field disorder fails to destroy the nonequilibrium phase transition of the one- and two-dimensional generalized contact process. Instead, it modifies the dynamics in the symmetry-broken phase. Specifically, the dynamics in the one-dimensional case is described by a Sinai walk of the domain walls between two different absorbing states. In the two-dimensional case, we map the dynamics onto that of the well studied low-temperature random-field Ising model. We also study the critical behavior of the nonequilibrium phase transition and characterize its universality class in one dimension. We support our results by large-scale Monte Carlo simulations, and we discuss the applicability of our theory to other systems.

  5. Thermodynamics and phase transitions in dense hydrogen - the role of bound state energy shifts

    In recent papers we have investigated the effects of Pauli blocking on the energy shifts in dense hydrogen. As Pauli blocking we denote effects on the shifts which result from the antisymmetry of the electronic wave functions. Here we study of the thermodynamic properties of dense hydrogen including the influence of energy shifts. Of special interest is the region where a transition from insulating behavior to metal-like conductivity has been shown experimentally. In this region, Pauli blocking effects have a deciding influence on this transition. Assuming that the system is a gas-like mixture of chemical species, the ionization equilibrium is treated by an advanced chemical approach. We calculate the Pauli and Fock shifts by perturbation theory and variational methods and construct useful interpolation formulae. Results for the ionization equilibrium are presented for temperatures between 4000 K23 cm-3 where the transition from a neutral hydrogen gas to a highly ionized plasma occurs. The results for the equation of state and the relative pressure indicate that the transition to a highly conducting state is softer than derived in earlier work. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Delay-induced state transition and resonance in periodically driven tumor model with immune surveillance

    Yang, Tao; Han, Qinglin; Zeng, Chunhua; Wang, Hua; Fu, Yunchang; Zhang, Chun

    2014-06-01

    The phenomenon of stochastic resonance (SR) in a tumor growth model under the presence of immune surveillance is investigated. Time delay and cross-correlation between multiplicative and additive noises are considered in the system. The signal-to-noise ratio (SNR) is calculated when periodic signal is introduced multiplicatively. Our results show that: (i) the time delay can accelerate the transition from the state of stable tumor to that of extinction, however the correlation between two noises can accelerate the transition from the state of extinction to that of stable tumor; (ii) the time delay and correlation between two noises can lead to a transition between SR and double SR in the curve of SNR as a function of additive noise intensity, however for the curve of SNR as a function of multiplicative noise intensity, the time delay can cause the SR phenomenon to disappear, and the cross-correlation between two noises can lead to a transition from SR to stochastic reverse-resonance. Finally, we compare the SR phenomenon for the multiplicative periodic signal with that for additive periodic signal in the tumor growth model with immune surveillance.

  7. Double excitations and state-to-state transition dipoles in π-π∗ excited singlet states of linear polyenes: Time-dependent density-functional theory versus multiconfigurational methods

    Mikhailov, Ivan A.; Tafur, Sergio; Masunov, Artëm E.

    2008-01-01

    The effect of static and dynamic electron correlation on the nature of excited states and state-to-state transition dipole moments is studied with a multideterminant wave function approach on the example of all-trans linear polyenes ( C4H6 , C6H8 , and C8H10 ). Symmetry-forbidden singlet nAg states were found to separate into three groups: purely single, mostly single, and mostly double excitations. The excited-state absorption spectrum is dominated by two bright transitions: 1Bu-2Ag and 1Bu-mAg , where mAg is the state, corresponding to two-electron excitation from the highest occupied to lowest unoccupied molecular orbital. The richness of the excited-state absorption spectra and strong mixing of the doubly excited determinants into lower- nAg states, reported previously at the complete active space self-consistent field level of theory, were found to be an artifact of the smaller active space, limited to π orbitals. When dynamic σ-π correlation is taken into account, single- and double-excited states become relatively well separated at least at the equilibrium geometry of the ground state. This electronic structure is closely reproduced within time-dependent density-functional theory (TD DFT), where double excitations appear in a second-order coupled electronic oscillator formalism and do not mix with the single excitations obtained within the linear response. An extension of TD DFT is proposed, where the Tamm-Dancoff approximation (TDA) is invoked after the linear response equations are solved (a posteriori TDA). The numerical performance of this extension is validated against multideterminant-wave-function and quadratic-response TD DFT results. It is recommended for use with a sum-over-states approach to predict the nonlinear optical properties of conjugated molecules.

  8. Supersymmetrically bounding of asymmetric states and quantum phase transitions by anti-crossing of symmetric states

    Afzal, Muhammad Imran; Lee, Yong Tak

    2016-01-01

    Von Neumann and Wigner theorized bounding of asymmetric eigenstates and anti-crossing of symmetric eigenstates. Experiments have shown that owing to anti-crossing and similar radiation rates, graphene-like resonance of inhomogeneously strained photonic eigenstates can generate pseudomagnetic field, bandgaps and Landau levels, while dissimilar rates induce non-Hermicity. Here, we showed experimentally higher-order supersymmetry and quantum phase transitions by resonance between similar one dimensional lattices. The lattices consisted of inhomgeneously strain-like phases of triangular solitons. The resonance created two dimensional inhomogeneously deformed photonic graphene. All parent eigenstates are annihilated. Where eigenstates of mildly strained solitons are annihilated with similar (power law) rates through one tail only and generated Hermitianally bounded eigenstates. The strongly strained solitons, positive defects are annihilated exponentially through both tails with dissimilar rates. Which bounded eig...

  9. Development of a True Transition State Force Field from Quantum Mechanical Calculations.

    Madarász, Ádám; Berta, Dénes; Paton, Robert S

    2016-04-12

    Transition state force fields (TSFF) treated the TS structure as an artificial minimum on the potential energy surface in the past decades. The necessary parameters were developed either manually or by the Quantum-to-molecular mechanics method (Q2MM). In contrast with these approaches, here we propose to model the TS structures as genuine saddle points at the molecular mechanics level. Different methods were tested on small model systems of general chemical reactions such as protonation, nucleophilic attack, and substitution, and the new procedure led to more accurate models than the Q2MM-type parametrization. To demonstrate the practicality of our approach, transferrable parameters have been developed for Mo-catalyzed olefin metathesis using quantum mechanical properties as reference data. Based on the proposed strategy, any force field can be extended with true transition state force field (TTSFF) parameters, and they can be readily applied in several molecular mechanics programs as well. PMID:26925858

  10. 3He- and 4He-induced nuclear fission -- A test of the transition state method

    Fission in 3H and 4He induced reactions at excitation energies between the fission barrier and 140 MeV has been investigated. Twenty-three fission excitation functions of various compound nuclei in different mass regions are shown to scale exactly according to the transition state prediction once the shell effects are accounted for. New precise measurements of excitation functions in a mass region where shell effects are very strong, allow one to test the predictions with an even higher accuracy. The fact that no deviations from the transition state method have been observed within the experimentally investigated excitation energy regime allows one to assign limits for the fission transient time. The precise measurement of fission excitation functions of neighboring isotopes enables one to experimentally estimate the first chance fission probability. Even if only first chance fission is investigated, no evidence for fission transient times larger than 30 zs can be found

  11. A mesoscopic approach on stability and phase transition between different traffic flow states

    Qian, Wei-Liang; Lin, Kai; Machado, Romuel F; Hama, Yogiro

    2015-01-01

    It is understood that congestion in traffic can be interpreted in terms of the instability of the equation of dynamic motion. The evoltuion of a traffic system from an unstable or metastable state to a globally stable state bears a strong resemblance to the phase transition in thermodynamics. In this work, we explore the underlying physics of the traffic system, by examing closely the physical properties and mathematical constraints of the phase transitons therein. By using a mesoscopic approach, one entitles the catastrophe model the same physical content as in the Landau's theory, and uncovers its close connection to the instability and phase transitions. In addition to the one-dimensional configuration space, we generalize our discussion to the higher-dimensional case, where the observed temporal oscillation in traffic flow data is attributed to the curl of a vector field. We exhibit that our model can reproduce main features of the observed fundamental diagram including the inverse-$\\lambda$ shape and the...

  12. Ground state phase transition in the Nilsson mean-field plus standard pairing model

    Guan, Xin; Xu, Haocheng; Zhang, Yu; Pan, Feng; Draayer, Jerry P.

    2016-08-01

    The ground state phase transition in Nd, Sm, and Gd isotopes is investigated by using the Nilsson mean-field plus standard pairing model based on the exact solutions obtained from the extended Heine-Stieltjes correspondence. The results of the model calculations successfully reproduce the critical phenomena observed experimentally in the odd-even mass differences, odd-even differences of two-neutron separation energy, and the α -decay and double β--decay energies of these isotopes. Since the odd-even effects are the most important signatures of pairing interactions in nuclei, the model calculations yield microscopic insight into the nature of the ground state phase transition manifested by the standard pairing interaction.

  13. State transitions redistribute rather than dissipate energy between the two photosystems in Chlamydomonas.

    Nawrocki, Wojciech J; Santabarbara, Stefano; Mosebach, Laura; Wollman, Francis-André; Rappaport, Fabrice

    2016-01-01

    Photosynthesis converts sunlight into biologically useful compounds, thus fuelling practically the entire biosphere. This process involves two photosystems acting in series powered by light harvesting complexes (LHCs) that dramatically increase the energy flux to the reaction centres. These complexes are the main targets of the regulatory processes that allow photosynthetic organisms to thrive across a broad range of light intensities. In microalgae, one mechanism for adjusting the flow of energy to the photosystems, state transitions, has a much larger amplitude than in terrestrial plants, whereas thermal dissipation of energy, the dominant regulatory mechanism in plants, only takes place after acclimation to high light. Here we show that, at variance with recent reports, microalgal state transitions do not dissipate light energy but redistribute it between the two photosystems, thereby allowing a well-balanced influx of excitation energy. PMID:27249564

  14. An alternative derivation of ring-polymer molecular dynamics transition-state theory

    Hele, Timothy J H

    2016-01-01

    In a previous article [J. Chem. Phys. 138, 084108 (2013)], we showed that the transition-state-theory ($t\\rightarrow 0_+$) limit of ring-polymer molecular dynamics rate-theory (RPMD-TST) is also the $t\\rightarrow 0_+$ limit of a new type of quantum flux-side time-correlation function, in which the dividing surfaces are invariant to imaginary-time translation; in other words, that RPMD-TST is a $t\\rightarrow 0_+$ quantum transition-state theory (QTST). Recently, Jang and Voth [J. Chem. Phys. 144, 084110 (2016)] rederived this quantum $t\\rightarrow 0_+$ limit, and claimed that it gives instead the centroid-density approximation. Here we show that the $t\\rightarrow 0_+$ limit derived by Jang and Voth is in fact RPMD-TST.

  15. Propeller driven spectral state transition in LMXB 4U 1608-52

    Chen, X; Ding, G Q; Chen, Xie; Zhang, Shuang Nan; Ding, Guo Qiang

    2006-01-01

    Spectral state transitions in neutron star LMXB systems have been widely observed yet not well understood. Here we report an abrupt spectral change in 4U 1608-52, a typical atoll source, during its decay phase of the 2004 outburst. The source is found to undergo sudden changes in its spectral hardness and other properties. The transition occurred when its luminosity is between (3.3-5.3) E36 ergs/s, assuming a distance of 3.6 kpc. Interpreting this event in terms of the propeller effect, we infer the neutron star surface magnetic field as (1.4-1.8) E8 Gauss. We also briefly discuss similarities and differences between the spectral states of neutron star and black hole binary systems.

  16. Single-step linking transition from superdeformed to spherical states in {sup 143}Eu

    Atac, A.; Axelsson, A.; Persson, J. [Uppsala Univ. (Sweden)] [and others

    1996-12-31

    A discrete {gamma}-ray transition which connects the second lowest SD state with a normally deformed one in {sup 143}Eu has been discovered. It has an energy of 3360.6 keV and carries 3.2 % of the full intensity of the SD band. It feeds into a nearly spherical state which is above the I = 35/2{sup +}, E=4947 keV level. The exact placement of the single-step link could, however, not be established due to the especially complicated level scheme in the region of interest. The angular correlation study favours a stretched dipole character for the 3360.6 keV transition. The single-step link agrees well with the previously determined two-step links, both with respect to energy and spin.

  17. An alternative derivation of ring-polymer molecular dynamics transition-state theory

    Hele, Timothy J. H.; Althorpe, Stuart C.

    2016-05-01

    In a previous article [T. J. H. Hele and S. C. Althorpe, J. Chem. Phys. 138, 084108 (2013)], we showed that the t → 0+ limit of ring-polymer molecular dynamics (RPMD) rate-theory is also the t → 0+ limit of a new type of quantum flux-side time-correlation function, in which the dividing surfaces are invariant to imaginary-time translation; in other words, that RPMD transition-state theory (RMPD-TST) is a t → 0+ quantum transition-state theory (QTST). Recently, Jang and Voth [J. Chem. Phys. 144, 084110 (2016)] rederived this quantum t → 0+ limit and claimed that it gives instead the centroid-density approximation. Here we show that the t → 0+ limit derived by Jang and Voth is in fact RPMD-TST.

  18. Search for linking transitions between the superdeformed and normal deformed states in 152Dy

    The Eurogam I γ-ray array has been used to search for the linking transitions between the superdeformed (SD) and normal deformed states in 152Dy. Triple γ-ray coincidence data were analysed by employing the technique of summation of discrete γ-rays observed in coincidence with the transitions in the lowest energy (yrast) SD band in 152Dy. Several high energy peaks have been observed in the spectrum of the summed γ-rays and these are consistent with decay paths between the two structures. Analysis of these data and of single γ-ray spectra confirm that the decay is highly fragmented and that decays occur through a quasi-continuum of states between the SD and normal deformed minima. (author). Letter-to-the-editor

  19. Search for linking transitions between the superdeformed and normal deformed states in {sup 152}Dy

    Bentley, M.A.; Beausang, C.W.; Twin, P.J.; Dagnall, P.J.; Atac, A.; Beck, F.A.; Byrski, T.; Clarke, S.; Curien, D.M.; Duchene, G.; France, G. de; Forsyth, P.D.; Herskind, B.; Haas, B.; Lisle, J.C.; Nyako, B.M.; Nyberg, J.; Paul, E.S.; Simpson, J.; Styczen, J.; Vivien, J.P.; Zuber, K. [Sch. of Sci., Staffordshire Univ., Stoke-on-Trent (United Kingdom)

    1995-04-01

    The Eurogam I {gamma}-ray array has been used to search for the linking transitions between the superdeformed (SD) and normal deformed states in {sup 152}Dy. Triple {gamma}-ray coincidence data were analysed by employing the technique of summation of discrete {gamma}-rays observed in coincidence with the transitions in the lowest energy (yrast) SD band in {sup 152}Dy. Several high energy peaks have been observed in the spectrum of the summed {gamma}-rays and these are consistent with decay paths between the two structures. Analysis of these data and of single {gamma}-ray spectra confirm that the decay is highly fragmented and that decays occur through a quasi-continuum of states between the SD and normal deformed minima. (author). Letter-to-the-editor.

  20. Spectral variability modes of GX 339-4 in a hard-to-soft state transition

    Del Santo, M.; J. Malzac; Ubertini, P.; Belloni, T.

    2006-01-01

    We report on INTEGRAL observations performed during the 2004 outburst of the bright black hole transient GX 339-4. We analysed IBIS and JEM-X public data starting on 9th August and lasting about one month. During this period GX 339-4 showed spectral state transitions. In order to seek for variability patterns, a principal component analysis (PCA) has been used.

  1. Transitions from autoionized states of Sb, Te and I in the 100-260 A region

    The spectra of antimony, tellurium and iodine were photographed in the 100-200 A region on a 2 m grazing incidence spectrograph at the Antigonish laboratory. 10, 16 and 4 transitions from the autoionized states of Sb, Te and I ions, respectively, belonging to Sb IV, V, VI; Te VI and VII, and I VI, VII and VIII have been classified. Hartree-Fock (HF) calculations were used to interpret the classifications and the line widths. (orig.)

  2. A state-and-transition approach to alpine grasslands under abandonment

    Targetti S; Staglianò N; Messeri A; Argenti G

    2010-01-01

    The abandonment of the traditional pastoral practices is acknowledged as the main causes of the shrub-encroachment in the alpine semi-natural grasslands. In this paper, we proposed a state-and-transition approach in order to organize pastoral vegetation in a simple management-oriented framework integrating ecological data. The study sites were chosen in an inner alpine territory where the abandonment of pastoral practices was more evident than in other alpine regions. Cluster and fuzzy analys...

  3. School Transition to the State-Social Management System Based on the Project Approach Application

    N. V. Nemova

    2015-01-01

    The paper looks at the opportunities for the school transition to the state-social management system based on the project approach application. The principle methods and procedures for the project initiation are observed along with the project organization and planning, recourse provision and project monitoring. According to the author, the most effective form of initiating the management modernization project simultaneously involves the two participants: the internal (school management) and ...

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

    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.

  5. Multiple Transition States and Roaming in Ion-Molecule Reactions: a Phase Space Perspective

    Mauguiere, Frederic A L; Collins, Peter; Ezra, Gregory S.; Farantos, Stavros C.; Wiggins, Stephen

    2013-01-01

    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 nonreactive trajectories can be t...

  6. Multiple Transition States and Roaming in Ion-Molecule Reactions: a Phase Space Perspective

    Mauguiere, Frederic A L; Ezra, Gregory S; Farantos, Stavros C; Wiggins, Stephen

    2013-01-01

    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 nonreactive trajectories can be trapped for arbitrarily long times.

  7. Altered Enthalpy-Entropy Compensation in Picomolar Transition State Analogues of Human Purine Nucleoside Phosphorylase†

    Edwards, Achelle A.; Mason, Jennifer M.; Clinch, Keith; Tyler, Peter C.; Evans, Gary B.; Schramm, Vern L.

    2009-01-01

    Human purine nucleoside phosphorylase (PNP) belongs to the trimeric class of PNPs and is essential for catabolism of deoxyguanosine. Genetic deficiency of PNP in humans causes a specific T-cell immune deficiency and transition state analogue inhibitors of PNP are in development for treatment of T-cell cancers and autoimmune disorders. Four generations of Immucillins have been developed, each of which contains inhibitors binding with picomolar affinity to human PNP. Full inhibition of PNP occu...

  8. Motion, Universality of Velocities, Masses in Wave Universe. Transitive States (Resonances) - Mass Spectrum

    Chechelnitsky, A. M.

    2001-01-01

    Wave Universe Concept (WU Concept) opens new wide possibilities for the effective description of Elementar Objects of Matter (EOM) hierarchy, in particular, of particles, resonances mass spectrum of subatomic (and HEP) physics. The special attention to analysis and precise description of wide and important set - Transitive states (resonances) of EOM is payed. Its are obtained sufficiently precise representations for mass values, cross relations between masses of wide set objects of particle p...

  9. Spin state transitions in RCoO3 (R = La, Pr, Nd)

    This paper presents infrared spectroscopic studies on RCoO3 (R = La, Pr and Nd) type perovskite oxides. The samples are prepared by sol-gel method and characterized by X-ray diffraction and resistivity measurements. Infrared absorption spectra recorded at various temperatures in the range 80K-350K reveal changes in the positions and intensities of Co-O stretching frequencies that confirm the reported spin state transition temperatures in these compounds. (author)

  10. Structure revision of plakotenin based on computational investigation of transition states and spectroscopic properties.

    Bihlmeier, Angela; Bourcet, Emmanuel; Arzt, Stephanie; Muller, Thierry; Bräse, Stefan; Klopper, Wim

    2012-02-01

    We show that the previously [Tetrahedron Lett.1992, 33, 2579] proposed structure of natural plakotenin must be revised. Recently, the total synthesis of plakotenin was achieved via an intramolecular Diels-Alder reaction from a (E,E,Z,E)-tetraene as linear precursor. Using density functional theory, the computation of the four possible transition states for this reaction shows that the previously proposed structure could only have been formed via an energetically high-lying transition state, which is very unlikely. Instead, we suggest that the structure of plakotenin corresponds to the product formed via the lowest transition state. A comparison of experimental and theoretical optical rotation, circular dichroism, and two-dimensional nuclear Overhauser enhancement spectra conclusively proves that the structure of plakotenin is the one that is suggested by the transition state computations. Moreover, the simulation of the nuclear Overhauser enhancement spectra suggests that it is most likely that the misassignment of the (1)H chemical shifts of two methyl groups has led to the wrong structure prediction in the 1992 work. The previously proposed structure of iso-plakotenin remains unaffected by our structure revision, but the structures of homo- and nor-plakotenin must also be revised. The present work shows how the total synthesis of a natural product, together with the theoretical determination of the barrier heights of the reactions involved, can be of great help to assign its structure. It appears that intramolecular Diels-Alder reactions can be modeled accurately by today's first-principles methods of quantum chemistry. PMID:22239598

  11. PIMC Simulations of Metal Hydrogen: Phase Transition and Equation of State

    Novoselov, Alexander; Pavlovsky, Oleg; Ulybyshev, Maxim

    2013-01-01

    The article is devoted to numerical studies of atomic (metal) hydrogen with Path Integral Monte Carlo (PIMC) technique. The research is focused on the range of temperatures and densities where quantum statistics effects are crucial for electrons and negligible for protons. In this range the equations of state are obtained as a dependence of internal energy and pressure on temperature and density. These dependences allow to detect and describe the phase transition between solid and liquid phases.

  12. Linking state-and-transition simulation and timber supply models for forest biomass production scenarios

    Jennifer K. Costanza; Robert C. Abt; Alexa J. McKerrow; Collazo, Jaime A

    2015-01-01

    We linked state-and-transition simulation models (STSMs) with an economics-based timber supply model to examine landscape dynamics in North Carolina through 2050 for three scenarios of forest biomass production. Forest biomass could be an important source of renewable energy in the future, but there is currently much uncertainty about how biomass production would impact landscapes. In the southeastern US, if forests become important sources of biomass for bioenergy, we expect increased land-u...

  13. Wigner's dynamical transition state theory in phase space: classical and quantum

    We develop Wigner's approach to a dynamical transition state theory in phase space in both the classical and quantum mechanical settings. The key to our development is the construction of a normal form for describing the dynamics in the neighbourhood of a specific type of saddle point that governs the evolution from reactants to products in high dimensional systems. In the classical case this is the standard Poincaré–Birkhoff normal form. In the quantum case we develop a normal form based on the Weyl calculus and an explicit algorithm for computing this quantum normal form. The classical normal form allows us to discover and compute the phase space structures that govern classical reaction dynamics. From this knowledge we are able to provide a direct construction of an energy dependent dividing surface in phase space having the properties that trajectories do not locally 're-cross' the surface and the directional flux across the surface is minimal. Using this, we are able to give a formula for the directional flux through the dividing surface that goes beyond the harmonic approximation. We relate this construction to the flux–flux autocorrelation function which is a standard ingredient in the expression for the reaction rate in the chemistry community. We also give a classical mechanical interpretation of the activated complex as a normally hyperbolic invariant manifold (NHIM), and further describe the structure of the NHIM. The quantum normal form provides us with an efficient algorithm to compute quantum reaction rates and we relate this algorithm to the quantum version of the flux–flux autocorrelation function formalism. The significance of the classical phase space structures for the quantum mechanics of reactions is elucidated by studying the phase space distribution of scattering states. The quantum normal form also provides an efficient way of computing Gamov–Siegert resonances. We relate these resonances to the lifetimes of the quantum activated

  14. Selective spin-state and metal-insulator transitions in GdBaCo2O5.5

    By means of ultra-high resolution synchrotron diffraction and calorimetry measurements we have studied the metal-insulator transition in GdBaCo2O5.5. The appearance of the metallic state is attributed to a sudden excitation of some electrons in the octahedra (t2g6 state) into the Co eg band (final t2g4eg2 state). In contrast, the t2g5eg1 state in the pyramids does not change at the transition. Calorimetry measurements show that the insulator-to-metal transition is first order and the entropy change estimated from the latent heat corroborates the pictured scheme

  15. The structure and energetics of the HCN-HNC transition state

    Lee, Timothy J.; Rendell, Alistair P.

    1991-01-01

    The optimum geometries and quadratic force constants of HCN, HNC and the transition state connecting them have been determined at the single- and double-excitation coupled-cluster (CCSD) and CCSD(T) levels of theory. Energy differences were evaluated using the CCSD and CCSD(T) methods in conjunction with large atomic natural orbital basis sets containing g-type basis functions on the heavy atoms and f-type functions on hydrogen. The most reliable structure obtained for the transition state has bond distances of 1.194, 1.188, and 1.389 A for r(CN), r(CH), and r(NH), respectively. Including a correction for zero-point vibrational energies, the transition state is predicted to be 44.6 + or - 1.0 kcal/mol above the HCN isomer, while HNC is predicted to be 14.4 + or - 1.0 kcal/mol above HCN. The latter value is in excellent agreement with the most recent experimental determination (14.8 + or - 2.0 kcal/mol).

  16. Superconducting detectors for photon and particle spectroscopy: Criteria for transitions to normal state

    The nonequilibrium state produced when a high energy (>1 keV) quanta interacts with a superconducting solid is the physical basis for many new detectors. The most common approaches magnetically monitor the phase of small 'grains' (SGDs) or monitor transients in the quasiparticle tunneling current in voltage-biased Josephson junctions (TJDs). While the former requires transitions to the normal state for its signal, the latter's energy resolution is degraded by excursions in the order parameter. To facilitate detector design, this article quantifies how the choices of sample material, bath temperature and field bias combine to influence the magnitude and spatial extent of the thermal excursion. Extensive tables of materials parameters are included. A wide range of inherent effects including the magnetic field dependent latent heat of the transition are discussed in the context of the limitations they produce on the operating energy range and size of proposed SGD detectors. Superheated initial conditions are not considered because the need for automatic resetting in astrophysical X-ray spectroscopy. Of the 23 elemental superconductors, we show that as SGDs only 5 have maximum grain sizes larger than 10 μm and only 3 are usable for photons with energies above 100 keV. Alpha particle detectors will be restricted by conceptually equivalent physics. Only by using inhomogeneous initial states or local, rather than global, transitions may these restrictions on bolometric detectors be lessened. (orig.)

  17. Bending crystals. Solid state photomechanical properties of transition metal complexes containing semiquinonate ligands

    Cortlandt G Pierpont

    2002-08-01

    The properties of transition metal complexes containing catecholate and radical semiquinonate ligands have often been found to be unusual and unexpected. Crystals of Rh(CO)2(3,6-DBSQ), containing the 3,6-di-tert-butyl-1,2-semiquinonate ligand, form as long thin needles that are observed to bend reversibly upon irradiation with NIR light. Crystallographic characterization reveals a stacked solid state lattice with planar molecules aligned with metal atoms atop one another. Electronic spectra recorded in the solid state and in solution show an intense band at 1600 nm that maps the energy dependence of crystal bend angle. The transition is a property of the stacked assembly, rather than of an individual complex molecule, and appears associated with an MLCT process that transfers charge from an antibonding band formed by interacting Rh $d_{z}^{2}$ orbitals to the vacant quinone * orbital. Related observations have been made on the [Co(-pyz)(3,6-DBSQ)(3,6-DBCat)] polymer. Photomechanical properties appear associated with electronic transitions that lead to a physical change in axial length of a linear polymer, coupled with a soft solid state lattice that permits axial contraction/expansion without crystal fracture.

  18. Origin of Transitions between Metallic and Insulating States in Simple Metals

    Naumov, Ivan I.; Hemley, Russell J.

    2015-04-01

    Unifying principles that underlie recently discovered transitions between metallic and insulating states in elemental solids under pressure are developed. Using group theory arguments and first-principles calculations, we show that the electronic properties of the phases involved in these transitions are controlled by symmetry principles. The valence bands in these systems are described by simple and composite band representations constructed from localized Wannier functions centered on points unoccupied by atoms, and which are not necessarily all symmetrical. The character of the Wannier functions is closely related to the degree of s -p (-d ) hybridization and reflects multicenter chemical bonding in these insulating states. The conditions under which an insulating state is allowed for structures having an integer number of atoms per primitive unit cell as well as reentrant (i.e., metal-insulator-metal) transition sequences are detailed, resulting in predictions of behavior such as phases having band-contact lines. The general principles developed are tested and applied to the alkali and alkaline earth metals, including elements where high-pressure insulating phases have been reported (e.g., Li, Na, and Ca).

  19. Transition to Democracy in Post-Soviet States: Success or Failure. Case Study Analysis.

    Ceyhun Valiyev

    2012-07-01

    Full Text Available The democratization of Post-Soviet states in past two decades is the subject of this academic study. The main question of this research is that why most of the Post-Soviet states haven’t gone through successful transition to democracy. Five countries; Azerbaijan, Belorussia, Georgia, Lithuania and Uzbekistan are the casesof this study to analyze and evaluate as empirical part of this work. I haven’t chosen the countries that have standard and equal level of success or failure. For instance, Lithuania is among those countries that have gone through quite successful process of democratization, whereas others have similar or different problems hindering the full-fledged democratization across the Post-Soviet area. Insome other cases, such as in Georgia the transition has not been fully successful but some measures of democracy are considered to be existent in state institutions and society. Several hypotheses have been developed throughout this study all arguing the preconditions that lead to democratization, then these hypotheses are checked ifthey are applicable in the cases used in this study. The conclusion is that not all these hypotheses are correct in every single case and each case study has its own characteristic causes that lead to failure or success in transition to democracy.

  20. The effects of an ionic liquid on unimolecular substitution processes: the importance of the extent of transition state solvation.

    Keaveney, Sinead T; White, Benjamin P; Haines, Ronald S; Harper, Jason B

    2016-02-16

    The reaction of bromodiphenylmethane and 3-chloropyridine, which proceeds concurrently through both unimolecular and bimolecular mechanisms, was examined in mixtures of acetonitrile and an ionic liquid. As predicted, the bimolecular rate constant (k2) gradually increased as the amount of ionic liquid in the reaction mixture increased, as a result of a minor enthalpic cost offset by a more significant entropic benefit. Addition of an ionic liquid had a substantial effect on the unimolecular rate constant (k1) of the reaction, with at least a 5-fold rate enhancement relative to acetonitrile, which was found to be due to a significant decrease in the enthalpy of activation, partially offset by the associated decrease in the entropy of activation. This is in contrast to the effects seen previously for aliphatic carbocation formation, where the entropic cost dominated reaction outcome. This change is attributed to a lessened ionic liquid-transition state interaction, as the incipient charges in the transition state were delocalized across the neighbouring π systems. By varying the mole fraction of ionic liquid in the reaction mixture the ratio between k1 and k2 could be altered, highlighting the potential to use ionic liquids to control which pathway a reaction proceeds through. PMID:26842921

  1. Vison states and confinement transitions of Z2 spin liquids on the kagome lattice

    Huh, Yejin; Punk, Matthias; Sachdev, Subir

    2011-09-01

    We present a projective symmetry group (PSG) analysis of the spinless excitations of Z2 spin liquids on the kagome lattice. In the simplest case, vortices carrying Z2 magnetic flux (“visons”) are shown to transform under the 48 element group GL(2,Z3). Alternative exchange couplings can also lead to a second case with visons transforming under 288-element group GL(2,Z3)×D3. We study the quantum phase transition in which visons condense into confining states with valence bond solid order. The critical field theories and confining states are classified using the vison PSGs.

  2. Radiative transition probabilities for all vibrational levels in the X 1Sigma(+) state of HF

    Zemke, Warren T.; Stwalley, William C.; Langhoff, Stephen R.; Valderrama, Giuseppe L.; Berry, Michael J.

    1991-01-01

    Recent analyses have led to an experimentally-based potential energy curve for the ground state of HF which includes nonadiabatic corrections and which joins smoothly to the long-range potential at an accurately determined dissociation limit. Using this potential curve and a new ab initio dipole moment function, accurate radiative transition probabilities among all vibrational levels of the ground state of HF have been calculated for selected rotational quantum numbers. Comparisons of Einstein A spontaneous emission coefficients, dipole moment absorption matrix elements, and Herman-Wallis factors for absorption bands are presented.

  3. Ground State Transitions of Four-Electron Quantum Dots in Zero Magnetic Field

    KANG Shuai; XIE Wen-Fang; LIU Yi-Ming; SHI Ting-Yun

    2008-01-01

    In this paper, we study four electrons confined in a parabolic quantum dot in the absence of magnetic field, by the exact diagonalization method. The ground-state electronic structures and orbital and spin angular momenta transitions as a function of the confined strength are investigated. We find that the confinement may cause accidental degeneracies between levels with different low-lying states and the inversion of the energy values. The present results are useful to understand the optical properties and internal electron-electron correlations of quantum dot materials.

  4. Study of intermediates from transition metal excited-state electron-transfer reactions

    Hoffman, M. Z.

    1992-07-01

    Conventional and fast-kinetics techniques of photochemistry, photophysics, radiation chemistry, and electrochemistry were used to study the intermediates involved in transition metal excited-state electron-transfer reactions. These intermediates were excited state of Ru(II) and Cr(III) photosensitizers, their reduced forms, and species formed in reactions of redox quenchers and electron-transfer agents. Of particular concern was the back electron-transfer reaction between the geminate pair formed in the redox quenching of the photosensitizers, and the dependence of its rate on solution medium and temperature in competition with transformation and cage escape processes.

  5. A physical scenario for the high and low X-ray luminosity states in the transitional pulsar PSR J1023+0038

    Campana, S; Papitto, A; Rea, N; Torres, D F; Baglio, M C; D'Avanzo, P

    2016-01-01

    PSR J1023+0038 (J1023) is a binary system hosting a neutron star and a low mass companion. J1023 is the best studied transitional pulsar, alternating a faint eclipsing millisecond radio pulsar state to a brighter X-ray active state. At variance with other Low Mass X-ray binaries, this active state reaches luminosities of only ~$10^{34}$ erg s$^{-1}$, showing strong, fast variability. In the active state, J1023 displays: i) a high state ($L_X\\sim7\\times10^{33}$ erg s$^{-1}$, 0.3-80 keV) occurring ~80% of the time and during which X-ray pulsations at the neutron star spin period are detected (pulsed fraction ~8%); ii) a low state ($L_X~10^{33}$ erg s$^{-1}$) during which pulsations are not detected (~<3%); and iii) a flaring state during which sporadic flares occur in excess of ~$10^{34}$ erg s$^{-1}$, with no pulsation too. The transition between the high and the low states is very rapid, on a ~10 s timescale. Here we put forward a plausible physical interpretation of the high and low states based on the (f...

  6. Association between body weight, physical activity and food choices among metropolitan transit workers

    Hannan Peter J; Toomey Traci L; Harnack Lisa J; French Simone A

    2007-01-01

    Abstract Background Associations between body weight, physical activity and dietary intake among a population of metropolitan transit workers are described. Methods Data were collected during October through December, 2005, as part of the baseline measures for a worksite weight gain prevention intervention in four metro transit bus garages. All garage employees were invited to complete behavioral surveys that assessed food choices and physical activity, and weight and height were directly mea...

  7. New perturbation approach for the localization transition in the dissipative two-state system

    Analysis of a dissipative two-state system at zero temperature shows that the model Hamiltonian may be exactly reduced to a modified quantum sine-Gordon model, which describes the effective interactions between the low-frequency phonons under coupling with a tunneling system. Directly considering the infrared divergence encountered in the conventional perturbation treatment, we have developed a new perturbation approach for the effective Hamiltonian, and derived the exact critical conditions for the localization transition. In the critical regime, a gap will be opened near zero momentum in the elementary excitation spectrum of the low-frequency phonons, and the corresponding ground-state wave functions is found to be a pairing quasi-particle state, analogous to the BCS superconducting state. (author). 17 refs, 2 figs

  8. State governance evolution in resource-rich transition economies: An application to Russia and Kazakhstan

    Kalyuzhnova, Yelena; Nygaard, Christian [The Centre for Euro-Asian Studies, The University of Reading, Whiteknights, PO Box, Reading RG6 6AA (United Kingdom)

    2008-06-15

    Following a decade of transition in the Former Soviet Union (FSU), governance of the oil and gas sectors has evolved to economic nationalism. In the newly independent states this has manifested itself through greater (direct) state ownership or participation in oil and gas production, at the expense of both domestic (in the case of Russia) and international oil companies, as well as legislative developments that increase the flow of oil and gas value to the state. Here we analyse some of the dynamics giving rise to economic nationalism within a model of a state capacity and the ability to implement policy and extract value. Our analysis is based on the institutional and economic functioning of the oil and gas sector. We analyse a vector of institutions and examine Production Sharing Agreements and National Oil Companies. (author)

  9. First identification of the 02+ state in 30Mg via its E0 transition

    The known 1789 keV level in 30Mg turned out to be a candidate for the 02+ state due to its long lifetime of 3.9(4) ns and the absence of a γ transition to the ground state. This triggered our search on the 02+→01+ E0 transition in 30Mg following the β decay of 30Na: β decay electrons were detected in a scintillation detector, while conversion electrons were focused onto a cooled Si(Li) detector using a Mini-Orange and detected with high resolution, which simultaneously suppresses the high background of β decay electrons. Due to the large Q value of the β decay of 30Na (17.3 MeV) the suppression of the coincident background induced by high-energy γ rays and subsequently Compton-scattered electrons turned out to be the key challenge for the success of this experiment. In order to optimise the background suppression and thus the sensitivity to weak E0 transitions, offline test measurements using an 90Y and a 152Eu source were performed together with GEANT4 simulations. Resulting from these test measurements a highly sensitive experimental setup was designed and built, consequently minimising the amount of high-Z material in the target chamber, reducing X-ray production. As a by-product from test measurements the database value of the half-life of the 02+ state in 90Zr could be corrected by more than 30 % to be t1/2=41(1) ns. Finally, in a β decay experiment at the ISOLDE facility at CERN the 02+→01+ E0 transition in 30Mg could be identified at the expected transition energy of 1788 keV proving for the first time shape coexistence at the borderline of the 'Island of Inversion'. This identification allows to determine the electric monopole strength as ρ2(E0)=26.2(7.5) x 10-3, indicating a rather weak mixing between the states in two potential minima in a simplified two-level mixing model. This result allows to extract the mixing amplitude between the two 0+ states as a=0.179(83). This experimental finding represents the first case in light nuclei where an E0

  10. Inhibition and structure of Trichomonas vaginalis purine nucleoside phosphorylase with picomolar transition state analogues.

    Rinaldo-Matthis, Agnes; Wing, Corin; Ghanem, Mahmoud; Deng, Hua; Wu, Peng; Gupta, Arti; Tyler, Peter C; Evans, Gary B; Furneaux, Richard H; Almo, Steven C; Wang, Ching C; Schramm, Vern L

    2007-01-23

    Trichomonas vaginalis is a parasitic protozoan purine auxotroph possessing a unique purine salvage pathway consisting of a bacterial type purine nucleoside phosphorylase (PNP) and a purine nucleoside kinase. Thus, T. vaginalis PNP (TvPNP) functions in the reverse direction relative to the PNPs in other organisms. Immucillin-A (ImmA) and DADMe-Immucillin-A (DADMe-ImmA) are transition state mimics of adenosine with geometric and electrostatic features that resemble early and late transition states of adenosine at the transition state stabilized by TvPNP. ImmA demonstrates slow-onset tight-binding inhibition with TvPNP, to give an equilibrium dissociation constant of 87 pM, an inhibitor release half-time of 17.2 min, and a Km/Kd ratio of 70,100. DADMe-ImmA resembles a late ribooxacarbenium ion transition state for TvPNP to give a dissociation constant of 30 pM, an inhibitor release half-time of 64 min, and a Km/Kd ratio of 203,300. The tight binding of DADMe-ImmA supports a late SN1 transition state. Despite their tight binding to TvPNP, ImmA and DADMe-ImmA are weak inhibitors of human and P. falciparum PNPs. The crystal structures of the TvPNP x ImmA x PO4 and TvPNP x DADMe-ImmA x PO4 ternary complexes differ from previous structures with substrate analogues. The tight binding with DADMe-ImmA is in part due to a 2.7 A ionic interaction between a PO4 oxygen and the N1' cation of the hydroxypyrrolidine and is weaker in the TvPNP x ImmA x PO4 structure at 3.5 A. However, the TvPNP x ImmA x PO4 structure includes hydrogen bonds between the 2'-hydroxyl and the protein that are not present in TvPNP x DADMe-ImmA x PO4. These structures explain why DADMe-ImmA binds tighter than ImmA. Immucillin-H is a 12 nM inhibitor of TvPNP but a 56 pM inhibitor of human PNP. And this difference is explained by isotope-edited difference infrared spectroscopy with [6-18O]ImmH to establish that O6 is the keto tautomer in TvPNP x ImmH x PO4, causing an unfavorable leaving-group interaction

  11. Stakeholder and Social Capital Approaches as Explanations for Relationships between SMEs and State Officials in Different Transition Economies

    Ivanova, Y

    2010-01-01

    This study targets the determination of support that small and medium enterprises (SMEs) provide to government representatives of their choice (in the form of donations, influence through their networks, information, and votes). The study tests stakeholder and social capital approaches as legitimate explanations for SMEs' relationships with state representatives in different transition economies, specifically Belarus as a state-controlled transition economy and Ukraine as a rent-seeking state...

  12. Phase transition in PT symmetric active plasmonic systems

    Mattheakis, M; Molina, M I; Tsironis, G P

    2015-01-01

    Surface plasmon polaritons (SPPs) are coherent electromagnetic surface waves trapped on an insulator-conductor interface. The SPPs decay exponentially along the propagation due to conductor losses, restricting the SPPs propagation length to few microns. Gain materials can be used to counterbalance the aforementioned losses. We provide an exact expression for the gain, in terms of the optical properties of the interface, for which the losses are eliminated. In addition, we show that systems characterized by lossless SPP propagation are related to PT symmetric systems. Furthermore, we derive an analytical critical value of the gain describing a phase transition between lossless and prohibited SPPs propagation. The regime of the aforementioned propagation can be directed by the optical properties of the system under scrutiny. Finally, we perform COMSOL simulations verifying the theoretical findings.

  13. Metallocarbene Artificial Enzymes : Extending Transition Metal Selectivity and Protein Activity

    Basauri Molina, M.

    2015-01-01

    A series of new semi-synthetic metalloprotein hybrids were created via the covalent binding of organometallic species in the active site of lipases, accordingly resulting in the first active site-directed (ASD) homogeneous artificial metalloenzymes. The use of this method promises the generation of

  14. Spectroscopic analysis of transition state energy levels - Bending-rotational spectrum and lifetime analysis of H3 quasibound states

    Zhao, Meishan; Mladenovic, Mirjana; Truhlar, Donald G.; Schwenke, David W.; Sharafeddin, Omar

    1989-11-01

    Converged quantum mechanical calculations of scattering matrices and transition probabilities are reported for the reaction of H with H2 with total angular momentum 0, 1, and 4 as functions of total energy in the range 0.85-1.15 eV on an accurate potential energy surface. The resonance structure is illustrated with Argand diagrams. State-to-state reactive collision delay times and lifetimes are presented. For J = 0, 1, and 4, the lowest-energy H3 resonance is at total energies of 0.983, 0.985, and 1.01 eV, respectively, with lifetimes of about 16-17 fs. For J = 1 and 4 there is a higher-energy resonance at 1.10-1.11 eV. For J = 1 the lifetime is about 4 fs and for J = 4 it is about 1 fs.

  15. Transitions between dynamical states of differing stability in the human brain

    Meyer-Lindenberg, Andreas; Ziemann, Ulf; Hajak, Göran; Cohen, Leonardo; Berman, Karen Faith

    2002-01-01

    What mechanisms underlie the flexible formation, adaptation, synchronization, and dissolution of large-scale neural assemblies from the 1010 densely interconnected, continuously active neurons of the human brain? Nonlinear dynamics provides a unifying perspective on self-organization. It shows that the emergence of patterns in open, nonequilibrium systems is governed by their stability in response to small disturbances and predicts macroscopic transitions between patterns of differing stabili...

  16. Radiative transition probabilities in the X2Πg state of CO2+

    Using ab initio calculated potential energy and electric dipole moment functions, absolute radiative transition probabilities between the rovibronic Renner-Teller states of the electronic ground state X2Πg of CO2+ have been evaluated. The rovibronic eigenstates were obtained (up to 6500cm-1 and J≤(13)/2 ) from variational calculations including the Renner-Teller and spin-orbit angular momentum couplings. The absolute intensities for the rovibrational states of the neutral CO2 electronic ground state, calculated by a similar approach, are found to be in excellent agreement with experimental data. For CO2+ the presented results are expected to have similar accuracy. It is found that the overtone intensities of the antisymmetric stretching mode of CO2+ are of similar magnitude as the fundamental transitions, in contrast with CO2. The theoretically generated IR-emission spectrum is compared with the limb spectrum of the Mars atmosphere, measured by the Thermal Emission Spectrometer on Mars Global Surveyor

  17. Efficient dynamical correction of the transition state theory rate estimate for a flat energy barrier

    Mökkönen, Harri; Jónsson, Hannes

    2016-01-01

    The recrossing correction to the transition state theory estimate of a thermal rate can be difficult to calculate when the energy barrier is flat. This problem arises, for example, in polymer escape if the polymer is long enough to stretch between the initial and final state energy wells while the polymer beads undergo diffusive motion back and forth over the barrier. We present an efficient method for evaluating the correction factor by constructing a sequence of hyperplanes starting at the transition state and calculating the probability that the system advances from one hyperplane to another towards the product. This is analogous to what is done in forward flux sampling except that there the hyperplane sequence starts at the initial state. The method is applied to the escape of polymers with up to 64 beads from a potential well. For high temperature, the results are compared with direct Langevin dynamics simulations as well as forward flux sampling and excellent agreement between the three rate estimates i...

  18. Magnetic properties of two-dimensional nanodots: Ground state and phase transition

    Kasperski, Maciej; Puszkarski, Henryk [Surface Physics Division, Faculty of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznan (Poland); Hoang, Danh-Tai [Asia Pacific Center for Theoretical Physics, POSTECH, San 31, Hyoja-dong, Nam-gu, Pohang, Gyeongbuk 790-784 (Korea, Republic of); Diep, H. T. [Laboratoire de Physique Théorique et Modélisation, Université de Cergy-Pontoise, CNRS, UMR 8089 2, Avenue Adolphe Chauvin, F-95302 Cergy-Pontoise Cedex (France)

    2013-12-15

    We study the effect of perpendicular single-ion anisotropy, −As{sub z}{sup 2}, on the ground-state structure and finite-temperature properties of a two-dimensional magnetic nanodot in presence of a dipolar interaction of strength D. By a simulated annealing Monte Carlo method, we show that in the ground state a vortex core perpendicular to the nanodot plane emerges already in the range of moderate anisotropy values above a certain threshold level. In the giant-anisotropy regime the vortex structure is superseded by a stripe domain structure with stripes of alternate domains perpendicular to the surface of the sample. We have also observed an intermediate stage between the vortex and stripe structures, with satellite regions of tilted nonzero perpendicular magnetization around the core. At finite temperatures, at small A, we show by Monte Carlo simulations that there is a transition from the the in-plane vortex phase to the disordered phase characterized by a peak in the specific heat and the vanishing vortex order parameter. At stronger A, we observe a discontinuous transition with a large latent heat from the in-plane vortex phase to perpendicular stripe ordering phase before a total disordering at higher temperatures. In the regime of perpendicular stripe domains, namely with giant A, there is no phase transition at finite T: the stripe domains are progressively disordered with increasing T. Finite-size effects are shown and discussed.

  19. Transition quadrupole moments of high-spin states in 170W

    Lifetimes of states in 170W have been measured by the Doppler-shift recoil-distance and Doppler-broadened line-shape (DBLS) methods using the reaction 122Sn(52Cr, 4n)170W at a bombarding energy of 230 MeV. The data were collected in the γγ-coincidence mode in order to reduce the complexities of the γ-ray spectra and to avoid some of the problems associated with side-feeding to excited states. The experimental transition quadrupole moments, Qt, cluster around a value of 6 e.b up through spin of I=24 h. This is the trend predicted by cranked Hartree-Fock-Bogoliubov (HFB) calculations and by the calculated systematics of triaxial-shape-driving forces which originate from the aligned i13/2 neutron orbitals around N=96. The interaction strength vertical stroke V vertical stroke between the g- and the s-band extracted from the data is 60±5 keV. The Qt values of several states in the negative-parity band (-, 1) also cluster around a value of 6 e.b. The El transition probabilities for the decay of states in the (π, α)=(-, 1) band to states in the ground-state band range between 10-5 to 3.5x10-4 W.u. The B(E1, I→I+1) is one order of magnitude larger than the B(E1, I→I-1). The origin of these effects can probably be understood in terms of a predominant admixture of Coriolis-coupled octupole vibrational-state wave functions in the (-, 1) band of 170W at low spin. ((orig.))

  20. Local density of states and its mesoscopic fluctuations near the transition to a superconducting state in disordered systems

    Burmistrov, I. S.; Gornyi, I. V.; Mirlin, A. D.

    2016-05-01

    We develop a theory of the local density of states (LDOS) of disordered superconductors, employing the nonlinear sigma-model formalism and the renormalization-group framework. The theory takes into account the interplay of disorder and interaction couplings in all channels, treating the systems with short-range and Coulomb interactions on equal footing. We explore two-dimensional systems that would be Anderson insulators in the absence of interaction and two- or three-dimensional systems that undergo an Anderson transition in the absence of interaction. We evaluate both the average tunneling density of states and its mesoscopic fluctuations which are related to the LDOS multifractality in normal disordered systems. The obtained average LDOS shows a pronounced depletion around the Fermi energy, both in the metallic phase (i.e., above the superconducting critical temperature Tc) and in the insulating phase near the superconductor-insulator transition (SIT). The fluctuations of the LDOS are found to be particularly strong for the case of short-range interactions, especially, in the regime when Tc is enhanced by Anderson localization. On the other hand, the long-range Coulomb repulsion reduces the mesoscopic LDOS fluctuations. However, also in a model with Coulomb interaction, the fluctuations become strong when the systems approach the SIT.

  1. Control of Steam-Turbine Regulators at Transition to an Island State

    Georgiev, Georgi

    2009-01-01

    The simple operating algorithm is presented for steam turbine regulators of type Simadin (Siemens) at emergency switching-off of the generator from system together with some, unknown in advance, load. The given situation is known as "a transition to an island state (regime)". Keeping of turbine speed and preservation of its rating value at a generator blackout when its own needs will be load only, is an easy problem. When the generator remains in its island it is necessary to solve "on-line" two additional problems: to reveal a situation "island" and to estimate the island load for translating a regulator on the new task and providing dynamic stability of transition. The algorithm was tried and entered successfully into practice on Varna TPP, CEZ GROUP (Prague), in 2008.

  2. High-spin states in the transitional odd-odd nuclei 150Eu and 152Tb

    The (7Li, 5n) and (11B, 5n) reactions have been used to study the high-spin states in the two odd-odd nuclei 150Eu and 152Tb. Three decoupled bands have been evidenced in each nucleus belonging to the same configurations [f 7/2]sub(n) [h 11/2]sub(p), [h 9/2]sub(n) [h 11/2 ]sub(p) and [i 13/2]sub(n) [h 11/2]sub(p). The latter one is well developped and improves our knowledge of this system between the spherical and deformed region. The analysis of the collective moment of inertia and transition ratios strongly suggests an increase of the deformation when the rotational frequency increases in these two transitional nuclei 150Eu and 152Tb

  3. Transition of the dark energy equation of state in an interacting holographic dark energy model

    A model of holographic dark energy with an interaction with matter fields has been investigated. Choosing the future event horizon as an IR cutoff, we have shown that the ratio of energy densities can vary with time. With the interaction between the two different constituents of the universe, we observed the evolution of the universe, from early deceleration to late time acceleration. In addition, we have found that such an interacting dark energy model can accommodate a transition of the dark energy from a normal state where wD>-1 to wD<-1 phantom regimes. Implications of interacting dark energy model for the observation of dark energy transition has been discussed

  4. Energy dependence of DCX cross section in ground state transition on 56Fe

    Differential cross section of the double charge exchange (DCX) reaction 56Fe(π+, π-)56Ni at the pion energies 10 and 60 MeV is calculated in the proton-neutron quasiparticle random phase approximation using a realistic nucleon-nucleon interaction. A detailed structure of the transition amplitude through intermediate states is discussed in some extent. It is shown that the observed resonance-like behaviour can be explained at least semi-quantitatively in terms of an ordinary NN process due to all over increase of the transition amplitudes with pion energy for each Jπ - multipolarity. The pn-QRPA seems to be a good framework for a description of structure of nuclei involved in double charge exchange processes. (author)

  5. A Latent Transition Analysis Model for Latent-State-Dependent Nonignorable Missingness.

    Sterba, Sonya K

    2016-06-01

    Psychologists often use latent transition analysis (LTA) to investigate state-to-state change in discrete latent constructs involving delinquent or risky behaviors. In this setting, latent-state-dependent nonignorable missingness is a potential concern. For some longitudinal models (e.g., growth models), a large literature has addressed extensions to accommodate nonignorable missingness. In contrast, little research has addressed how to extend the LTA to accommodate nonignorable missingness. Here we present a shared parameter LTA that can reduce bias due to latent-state-dependent nonignorable missingness: a parallel-process missing-not-at-random (MNAR-PP) LTA. The MNAR-PP LTA allows outcome process parameters to be interpreted as in the conventional LTA, which facilitates sensitivity analyses assessing changes in estimates between LTA and MNAR-PP LTA. In a sensitivity analysis for our empirical example, previous and current membership in high-delinquency states predicted adolescents' membership in missingness states that had high nonresponse probabilities for some or all items. A conventional LTA overestimated the proportion of adolescents ending up in a low-delinquency state, compared to an MNAR-PP LTA. PMID:25697371

  6. Rivastigmine hydrogen tartrate polymorphs: Solid-state characterisation of transition and polymorphic conversion via milling

    Amaro, Maria Inês; Simon, Alice; Cabral, Lúcio Mendes; de Sousa, Valéria Pereira; Healy, Anne Marie

    2015-11-01

    Rivastigmine (RHT) is an active pharmaceutical ingredient that is used for the treatment of mild to moderately severe dementia in Alzheimer's disease, and is known to present two polymorphic forms and to amorphise upon granulation. To date there is no information in the scientific or patent literature on polymorphic transition and stability. Hence, the aim of the current study was to gain a fundamental understanding of the polymorphic forms by (1) evaluating RHT thermodynamic stability (monotropy or enantiotropy) and (2) investigating the potential for polymorphic transformation upon milling. The two polymorphic and amorphous forms were characterised using X-ray powder diffractometry, thermal analyses, infra-red spectroscopy and water sorption analysis. The polymorphic transition was found to be spontaneous (ΔG0 < 0) and exothermic (ΔH0 < 0), indicative of a monotropic polymorph pair. The kinetic studies showed a fast initial polymorphic transition characterised by a heterogeneous nucleation, followed by a slow crystal growth. Ball milling can be used to promote the polymorphic transition and for the production of RHT amorphous form.

  7. Transitions to Care in the Community for Prison Releasees with HIV: a Qualitative Study of Facilitators and Challenges in Two States.

    Hammett, Theodore M; Donahue, Sara; LeRoy, Lisa; Montague, Brian T; Rosen, David L; Solomon, Liza; Costa, Michael; Wohl, David; Rich, Josiah D

    2015-08-01

    One in seven people living with HIV in the USA passes through a prison or jail each year, and almost all will return to the community. Discharge planning and transitional programs are critical but challenging elements in ensuring continuity of care, maintaining treatment outcomes achieved in prison, and preventing further viral transmission. This paper describes facilitators and challenges of in-prison care, transitional interventions, and access to and continuity of care in the community in Rhode Island and North Carolina based on qualitative data gathered as part of the mixed-methods Link Into Care Study of prisoners and releasees with HIV. We conducted 65 interviews with correctional and community-based providers and administrators and analyzed the transcripts using NVivo 10 to identify major themes. Facilitators of effective transitional systems in both states included the following: health providers affiliated with academic institutions or other entities independent of the corrections department; organizational philosophy emphasizing a patient-centered, personal, and holistic approach; strong leadership with effective "champions"; a team approach with coordination, collaboration and integration throughout the system, mutual respect and learning between corrections and health providers, staff dedicated to transitional services, and effective communication and information sharing among providers; comprehensive transitional activities and services including HIV, mental health and substance use services in prisons, timely and comprehensive discharge planning with specific linkages/appointments, supplies of medications on release, access to benefits and entitlements, case management and proactive follow-up on missed appointments; and releasees' commitment to transitional plans. These elements were generally present in both study states but their absence, which also sometimes occurred, represent ongoing challenges to success. The qualitative findings on the

  8. Antiferromagnetic–paramagnetic state transition of NiO synthesized by pulsed laser deposition

    Highlights: ► Thin films of NiO were prepared on Al substrate at different conditions. ► Antiferromagnetic to paramagnetic state transition were observed. ► The effect of substrate temperature on magnetic properties was studied. ► MWCNTs were incorporated on NiO to study their effect in the NiO magnetism. - Abstract: Thin films of nickel oxide (NiO) were deposited on Al substrates at different substrate temperatures using pulsed laser deposition (PLD). Microwave power absorption measurements at 9.4 GHz (X-band) were carried out on these PLD grown films. Multi-walled carbon nano-tubes (MWCNTs) were incorporated with NiO films and were found not to have any effect on the NiO magnetism at room temperature substrate deposition. The MWCNTs and NiO particles have been found to vary in size from 73 to 44 nm and 20 nm respectively from Raman spectroscopy study. These particle sizes are known be affected by substrate temperature during the deposition. Electron spin resonance (ESR) results demonstrated a strange antiferromagnetic to paramagnetic transition at a room temperature. This magnetic transition was attributed to the substrate temperature variations during the films growth. In addition, the angular dependence measurements were also carried out and were seen to enhance this magnetic transition from NiO films. Normally, such magnetic transitions are observed in situ with temperature variations in the ESR system. Both Raman and ESR measurements suggest the absence of detectable Magnons which act as disturbances to magnetism or electron spins.

  9. Helical edge states and topological phase transitions in phononic systems using bi-layered lattices

    Pal, Raj Kumar; Schaeffer, Marshall; Ruzzene, Massimo

    2016-02-01

    We propose a framework to realize helical edge states in phononic systems using two identical lattices with interlayer couplings between them. A methodology is presented to systematically transform a quantum mechanical lattice which exhibits edge states to a phononic lattice, thereby developing a family of lattices with edge states. Parameter spaces with topological phase boundaries in the vicinity of the transformed system are illustrated to demonstrate the robustness to mechanical imperfections. A potential realization in terms of fundamental mechanical building blocks is presented for the hexagonal and Lieb lattices. The lattices are composed of passive components and the building blocks are a set of disks and linear springs. Furthermore, by varying the spring stiffness, topological phase transitions are observed, illustrating the potential for tunability of our lattices.

  10. Suppression of spin-state transition in epitaxially strained LaCoO3

    Pinta, C.; Fuchs, D.; Merz, M.; Wissinger, M.; Arac, E.; v. Löhneysen, H.; Samartsev, A.; Nagel, P.; Schuppler, S.

    2008-11-01

    Epitaxial thin films of LaCoO3 (e-LCO) exhibit ferromagnetic order with a transition temperature TC=85K while polycrystalline thin LaCoO3 films (p-LCO) remain paramagnetic. The temperature-dependent spin-state structure for both e-LCO and p-LCO was studied by x-ray absorption spectroscopy at the CoL2,3 and OK edges. Considerable spectral redistributions over temperature are observed for p-LCO . The spectra for e-LCO , on the other hand, do not show any significant changes for temperatures between 30 and 450 K at both edges, indicating that the spin state remains constant and that the epitaxial strain inhibits any population of the low-spin (S=0) state with decreasing temperature. This observation identifies an important prerequisite for ferromagnetism in e-LCO thin films.

  11. Phase transitions in definite total spin states of two-component Fermi gases

    Yurovsky, Vladimir A

    2016-01-01

    Symmetry under permutations of indistinguishable particles, contained in each medium, is one of the fundamental symmetries. Generally, a change in symmetry affects the medium's thermodynamic properties, leading to phase transitions. Permutation symmetry can be changed since, in addition to the conventional symmetric and anti-symmetric states under permutations of bosons and fermions, mathematical group-representation theory allows for non-Abelian permutation symmetry. Such symmetry can be hidden in states with defined total spins of spinor gases, which can be formed in optical cavities. However, the thermodynamic effects of non-Abelian symmetry are unknown. The present work shows that the symmetry reveals itself in spin-independent or coordinate-independent properties of these gases, namely as non-Abelian entropy in thermodynamic properties. In weakly interacting Fermi gases, saturated and unsaturated phases appear associated with fermionic and non-Abelian symmetry under permutations of particle states, respe...

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

    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

  13. Clustering of capnogram features to track state transitions during procedural sedation.

    Mieloszyk, Rebecca J; Guo, Margaret G; Verghese, George C; Andolfatto, Gary; Heldt, Thomas; Krauss, Baruch S

    2015-08-01

    Procedural sedation has allowed many painful interventions to be conducted outside the operating room. During such procedures, it is important to maintain an appropriate level of sedation to minimize the risk of respiratory depression if patients are over-sedated and added pain or anxiety if under-sedated. However, there is currently no objective way to measure the patient's evolving level of sedation during a procedure. We investigated the use of capnography-derived features as an objective measure of sedation level. Time-based capnograms were recorded from 30 patients during sedation for cardioversion. Through causal k-means clustering of selected features, we sequentially assigned each exhalation to one of three distinct clusters, or states. Transitions between these states correlated to events during sedation (drug administration, procedure start and end, and clinical interventions). Similar clustering of capnogram recordings from 26 healthy, non-sedated subjects did not reveal distinctly separated states. PMID:26736604

  14. Irregular transition between oscillating and stationary states in multi-surface system

    A Fast Breeder Reactor (FBR) has many free surfaces in order to absorb the expansion or contraction of the liquid sodium coolant. Small size reactor vessel designs have been proposed in order to reduce the construction cost of an FBR plant. In these designs the liquid sodium velocity increases compared to conventional designs, causing undesirable surface phenomena to occur, e.g., surface waves and bubble entrainment. Surface waves induce high thermal stresses on vessel walls due to sodium's high thermal conductivity. It is anticipated that the flow rate of coolant fluctuates with large surface waves. In recent years, the Top Entry System has been proposed as a promising candidate of the demonstration fast breeder reactor (DFBR). In the primary heat transport system, the reactor vessel, the intermediate heat exchanger (IHX) vessels and the primary pump vessels are connected by inverted U-shaped pipes. Every vessel has a free surface, and the coolant flow is driven only by the surface level difference. Because of high nonlinearity of free surface behavior, surface oscillation would be induced by the interaction between free surface and coolant flow. Here, a self-induced water level oscillation was observed in a test tank connected with a larger downstream tank by a short duct. At a certain water level and tank width, irregular transition was observed, in which the oscillation and stationary states alternated irregularly. The condition under which the irregular transition occurred was investigated. The three regions, i.e., stationary, oscillating, irregular transition regions, separated clearly in the width-level map of the tank. The flow pattern transformation was measured quantitatively as regards the vector velocity of flow at a point above the outlet where the transformation occurred remarkably. The transition from oscillating to stationary state and the reverse passed by different routes of transformation

  15. Leadership for Transitions of Care: An Active Learning Innovation.

    Huber, Diane L; Joseph, M Lindell; Halbmaier, Katie Anne; Carlson, Molly; Crill, Stacy; Krieger, Kimberly; Matthys, Nicole; Mundisev, Amy

    2016-02-01

    Active learning assignments can be achieved in online discussions, resulting in creative linkages for innovation. This article describes how the teaching strategy of active learning assignment evolved into a group of student learners engaging in the development of a creative advanced clinical care scenario in an online graduate core course on leadership and management. The advanced clinical scenario that resulted from the students envisioning the assignment through the continuum of care was innovative and creative. Most importantly, the scenario stimulated vigorous conversation and excitement over the assignment, which promoted learning, pride in accomplishment, and on-the-job impact. This article serves as a model of ways to engage students in active learning for synthesis and evaluation to enable creativity and innovation. PMID:26840240

  16. Hot accretion flow with radiative cooling: state transitions in black hole X-ray binaries

    Wu, Mao-Chun; Yuan, Ye-Fei; Gan, Zhao-Ming

    2016-01-01

    We investigate state transitions in black hole X-ray binaries through different parameters by using two-dimensional axisymmetric hydrodynamical simulation method. For radiative cooling in hot accretion flow, we take into account the bremsstrahlung, synchrotron and synchrotron-self Comptonization self-consistently in the dynamics. Our main result is that the state transitions occur when the accretion rate reaches a critical value $\\dot M \\sim 3\\alpha\\ \\dot M_{\\rm Edd}$, above which cold and dense clumpy/filamentary structures are formed, embedded within the hot gas. We argued this mode likely corresponds to the proposed two-phase accretion model, which may be responsible for the intermediate state of black hole X-ray binaries. When the accretion rate becomes sufficiently high, the clumpy/filamentary structures gradually merge and settle down onto the mid-plane. Eventually the accretion geometry transforms to a disc-corona configuration. In summary our results are consistent with the truncated accretion scenari...

  17. Dynamics of Number of Packets in Transit in Free Flow State of Data Network

    We study how the dynamics of Number of Packets in Transit (NPT) is affected by the coupling of a routing type with a volume of incoming packet traffic in a data network model of packet switching type. The NPT is a network performance indicator of an aggregate type that measures in '' real time '', how many packets are in the network on their routes to their destinations. We conduct our investigation using a time-discrete simulation model that is an abstraction of the Network Layer of the ISO OSI Seven Layer Reference Model. This model focuses on packets and their routing. We consider a static routing and two different types of dynamic routings coupled with different volumes of incoming packet traffic in the network free flow state. Our study shows that the order of the values of the NPT mean value time series depends on the coupling of a routing type with a volume of incoming packet traffic and changes when the volume of incoming packet traffic increases and is closed to the critical source load values, i.e. when it is closed to the phase transition points from the network free flow state to its congested states. (authors)

  18. Cygnus X-3 transition from the ultrasoft to the hard state

    Beckmann, V.; Soldi, S.; Belanger, G.;

    2007-01-01

    , dominated by blackbody radiation at soft X- rays plus non-thermal emission in the hard X- rays, to the low hard state. Methods. INTEGRAL observed Cyg X-3 six times during three weeks in late May and early June 2007. Data from IBIS/ISGRI and JEM-X1 were analysed to show the spectral transition. Results....... During the ultrasoft state, the soft X-ray spectrum is well-described by an absorbed (NH = 1.5 x 10(22) cm(-2)) black body model, whereas the X-ray spectrum above 20 keV appears to be extremely low and hard (Gamma similar or equal to 1.7). During the transition, the radio flux rises to a level of > 1 Jy......, and the soft X-ray emission drops by a factor of similar to 3, while the hard X- ray emission rises by a factor of similar to 14 and becomes steeper (up to Gamma = 4). Conclusions. The ultrasoft state apparently precedes the emission of a jet, which is apparent in the radio and hard X-ray domain....

  19. Variational transition-state theory. Progress report, February 1981-January 1983

    During the past two years we have extended the variational transition-state theory in several ways. Especially notable is that we have developed several new methods for calculating tunneling probabilities, including two general techniques applicable to systems with small and large reaction-path curvature. We have tested these methods successfully against accurate quantal calculations, and we have applied them to real systems in three dimensions. We have also developed general algorithms for variational transition state theory calculations on polyatomic systems and we have applied these to the combustion reaction OH + H2 → H2O + H. We have developed and successfully applied a statistical-diabatic theory for state-selected rates. We made a totally ab initio prediction of an absolute chemical reaction rate, for the reaction Mu + H2 → MuH + H, using an accurate potential energy surface and ethods that we had demonstrated to be reliable by tests against accurate quantal collinear results. This prediction has now been confirmed by unpublished experiments; I believe that this is the first reliable ab initio prediction of a chemical rection rate prior to its measurement. In the rest of this technical progress report we give further details of these and other studies we have carried out in the last two years under this contract

  20. Phase transition of iron oxyhydroxides by mechanical activation

    The grinding kinetics of α-FeOOH and β-FeOOH was investigated in dependence on decreasing particle size. Samples were ground for various periods at room temperature and subsequently investigated by Moessbauer spectrometry. The Moessbauer parameters and spectra of α-FeOOH and β-FeOOH for various activation times are given. (Z.S.)

  1. Transition of radiative recombination channels from delocalized states to localized states in a GaInP alloy with partial atomic ordering: a direct optical signature of Mott transition?

    Su, Z. C.; Ning, J. Q.; Deng, Z.; Wang, X. H.; Xu, S. J.; Wang, R. X.; Lu, S. L.; Dong, J. R.; Yang, H.

    2016-03-01

    Anderson localization is a predominant phenomenon in condensed matter and materials physics. In fact, localized and delocalized states often co-exist in one material. They are separated by a boundary called the mobility edge. Mott transition may take place between these two regimes. However, it is widely recognized that an apparent demonstration of Anderson localization or Mott transition is a challenging task. In this article, we present a direct optical observation of a transition of radiative recombination dominant channels from delocalized (i.e., local extended) states to Anderson localized states in the GaInP base layer of a GaInP/GaAs single junction solar cell by the means of the variable-temperature electroluminescence (EL) technique. It is found that by increasing temperature, we can boost a remarkable transition of radiative recombination dominant channels from the delocalized states to the localized states. The delocalized states are induced by the local atomic ordering domains (InP/GaP monolayer superlattices) while the localized states are caused by random distribution of indium (gallium) content. The efficient transfer and thermal redistribution of carriers between the two kinds of electronic states was revealed to result in both a distinct EL mechanism transition and an electrical resistance evolution with temperature. Our study gives rise to a self-consistent precise picture for carrier localization and transfer in a GaInP alloy, which is an extremely technologically important energy material for fabricating high-efficiency photovoltaic devices.

  2. Transition of radiative recombination channels from delocalized states to localized states in a GaInP alloy with partial atomic ordering: a direct optical signature of Mott transition?

    Su, Z C; Ning, J Q; Deng, Z; Wang, X H; Xu, S J; Wang, R X; Lu, S L; Dong, J R; Yang, H

    2016-03-24

    Anderson localization is a predominant phenomenon in condensed matter and materials physics. In fact, localized and delocalized states often co-exist in one material. They are separated by a boundary called the mobility edge. Mott transition may take place between these two regimes. However, it is widely recognized that an apparent demonstration of Anderson localization or Mott transition is a challenging task. In this article, we present a direct optical observation of a transition of radiative recombination dominant channels from delocalized (i.e., local extended) states to Anderson localized states in the GaInP base layer of a GaInP/GaAs single junction solar cell by the means of the variable-temperature electroluminescence (EL) technique. It is found that by increasing temperature, we can boost a remarkable transition of radiative recombination dominant channels from the delocalized states to the localized states. The delocalized states are induced by the local atomic ordering domains (InP/GaP monolayer superlattices) while the localized states are caused by random distribution of indium (gallium) content. The efficient transfer and thermal redistribution of carriers between the two kinds of electronic states was revealed to result in both a distinct EL mechanism transition and an electrical resistance evolution with temperature. Our study gives rise to a self-consistent precise picture for carrier localization and transfer in a GaInP alloy, which is an extremely technologically important energy material for fabricating high-efficiency photovoltaic devices. PMID:26960547

  3. Exact solution of electric transitions and production probability of isomer state of FP

    This report describes the study done within the period of time when I was postdoctoral research worker at Japan Nuclear Cycle Development Institute. The report includes two parts as follows. 1) Exact Solution of Electric Transitions for High Energy photons. Technologies for creating high-energy γ beams have been rapidly developed. These advancements make the research using high-energy γ-rays more important. The electric transition rates for high energy γ-rays were formulated. The electric multipole fields were treated strictly in the process of calculating the electric transition rates and the nuclear states were taken as the harmonic oscillator wave functions. 2) Production of the isomeric state of 138Cs in the thermal neutron capture reaction 137Cs(n,γ)138Cs. In order to obtain precise data of the neutron capture cross section of the reaction 137Cs(n,γ)138Cs, the production probability of isomer state 138mCs was measured in this work. The 1436 keV γ-ray emitted from both of 138gCs and 138mCs was measured. A production ratio of 138mCs to (138gCs and 138mCs) was deduced from time dependence of peak counts of 1436 keV γ-ray. The probability of the production of 138mCs was obtained as 0.75±0.18 and this value revised the effective cross section upwards 9±2%. The effective cross section σ and the thermal neutron capture cross section σ0 were obtained as σ=0.29±0.02 b and σ0=0.27±0.03 b with taking into account the production of 138mCs. (author)

  4. Tropical Forest Restoration within Galapagos National Park: Application of a State-transition Model

    F. K. A. Schmiegelow

    2005-06-01

    Full Text Available Current theory on non-equilibrium communities, thresholds of irreversibility, and ecological resilience suggests the goal of ecological restoration of degraded communities is not to achieve one target, but to reestablish the temporal and spatial diversity inherent in natural ecosystems. Few restoration models, however, address ecological and management issues across the vegetation mosaic of a landscape. Because of a lack of scientific knowledge and funds, restoration practitioners focus instead on site-specific prescriptions and reactive rather than proactive approaches to restoration; this approach often dooms restoration projects to failure. We applied a state-transition model as a decision-making tool to identify and achieve short- and long-term restoration goals for a tropical, moist, evergreen forest on the island of Santa Cruz, Galapagos. The model guided the process of identifying current and desirable forest states, as well as the natural and human disturbances and management actions that caused transitions between them. This process facilitated assessment of opportunities for ecosystem restoration, expansion of the definition of restoration success for the system, and realization that, although site- or species-specific prescriptions may be available, they cannot succeed until broader landscape restoration issues are identified and addressed. The model provides a decision-making framework to allocate resources effectively to maximize these opportunities across the landscape, and to achieve long-term restoration success. Other restoration models have been limited by lack of scientific knowledge of the system. State-transition models for restoration incorporate current knowledge and funds, are adaptive, and can provide direction for restoration research and conservation management in other degraded systems.

  5. Validity Evidence for the State Mindfulness Scale for Physical Activity

    Cox, Anne E.; Ullrich-French, Sarah; French, Brian F.

    2016-01-01

    Being attentive to and aware of one's experiences in the present moment with qualities of acceptance and openness reflects the state of mindfulness. Positive associations exist between state mindfulness and state autonomous motivation for everyday activities. Though this suggests that state mindfulness links with adaptive motivational experiences,…

  6. Large discrete jumps observed in the transition between Chern states in a ferromagnetic topological insulator

    Liu, Minhao; Wang, Wudi; Richardella, Anthony R.; Kandala, Abhinav; Li, Jian; Yazdani, Ali; Samarth, Nitin; Ong, N. Phuan

    2016-01-01

    A striking prediction in topological insulators is the appearance of the quantized Hall resistance when the surface states are magnetized. The surface Dirac states become gapped everywhere on the surface, but chiral edge states remain on the edges. In an applied current, the edge states produce a quantized Hall resistance that equals the Chern number C = ±1 (in natural units), even in zero magnetic field. This quantum anomalous Hall effect was observed by Chang et al. With reversal of the magnetic field, the system is trapped in a metastable state because of magnetic anisotropy. We investigate how the system escapes the metastable state at low temperatures (10 to 200 mK). When the dissipation (measured by the longitudinal resistance) is ultralow, we find that the system escapes by making a few very rapid transitions, as detected by large jumps in the Hall and longitudinal resistances. Using the field at which the initial jump occurs to estimate the escape rate, we find that raising the temperature strongly suppresses the rate. From a detailed map of the resistance versus gate voltage and temperature, we show that dissipation strongly affects the escape rate. We compare the observations with dissipative quantum tunneling predictions. In the ultralow dissipation regime, two temperature scales (T1 ~ 70 mK and T2 ~ 145 mK) exist, between which jumps can be observed. The jumps display a spatial correlation that extends over a large fraction of the sample. PMID:27482539

  7. Large discrete jumps observed in the transition between Chern states in a ferromagnetic topological insulator.

    Liu, Minhao; Wang, Wudi; Richardella, Anthony R; Kandala, Abhinav; Li, Jian; Yazdani, Ali; Samarth, Nitin; Ong, N Phuan

    2016-07-01

    A striking prediction in topological insulators is the appearance of the quantized Hall resistance when the surface states are magnetized. The surface Dirac states become gapped everywhere on the surface, but chiral edge states remain on the edges. In an applied current, the edge states produce a quantized Hall resistance that equals the Chern number C = ±1 (in natural units), even in zero magnetic field. This quantum anomalous Hall effect was observed by Chang et al. With reversal of the magnetic field, the system is trapped in a metastable state because of magnetic anisotropy. We investigate how the system escapes the metastable state at low temperatures (10 to 200 mK). When the dissipation (measured by the longitudinal resistance) is ultralow, we find that the system escapes by making a few very rapid transitions, as detected by large jumps in the Hall and longitudinal resistances. Using the field at which the initial jump occurs to estimate the escape rate, we find that raising the temperature strongly suppresses the rate. From a detailed map of the resistance versus gate voltage and temperature, we show that dissipation strongly affects the escape rate. We compare the observations with dissipative quantum tunneling predictions. In the ultralow dissipation regime, two temperature scales (T 1 ~ 70 mK and T 2 ~ 145 mK) exist, between which jumps can be observed. The jumps display a spatial correlation that extends over a large fraction of the sample. PMID:27482539

  8. Hypothesis: could the signalling function of membrane microdomains involve a localized transition of lipids from liquid to solid state?

    Joly Etienne

    2004-01-01

    Full Text Available Abstract Background Over the past decade, it has become apparent that specialised membrane microdomains, commonly called rafts, where lipids like sphingolipids and cholesterol are arranged compactly in a liquid ordered phase are involved in cell signalling. Hypothesis The core of the hypothesis presented here is that resting cells may actively maintain their plasma membrane in liquid phase, corresponding to a metastable thermodynamic state. Following a physiological stimulus such as ligands binding to their membrane receptors, the tendency of membrane components to undergo a localised transition towards a gel state would increase, resulting in initial minute solid structures. These few membrane components having undergone a liquid to solid state transition, would then act as seeds for the specific recruitment of additional membrane components whose properties are compatible with the crystalline growth of these initial docks. Cells could therefore be using the propensity of lipids to assemble selectively to generate stable platforms of particular cellular components either for intra-cellular transport or for signal transduction. Testing the hypothesis could presumably be done via biophysical approaches such as EPR spin labelling, X-ray diffraction or FRET coupled to direct microscopic observation of cells to which very localized stimuli would be delivered. Implications Such a model of selective growth of membrane docks would provide an explanation for the existence of different types of microdomains, and for the fact that, depending on the state of the cells and on the procedures used to isolate them, membrane microdomains can vary greatly in their properties and composition. Ultimately, a thorough understanding of how and why lipid domains are assembled in biological membranes will be essential for many aspects of cell biology and medicine.

  9. Effect of stellar activity on the high precision transit light curve

    Oshagh, M.

    2015-01-01

    Full Text Available Stellar activity features such as spots and plages can create difficulties in determining planetary parameters through spectroscopic and photometric observations. The overlap of a transiting planet and a stellar spot, for instance, can produce anomalies in the transit light curve that may lead to inaccurate estimation of the transit duration, depth, and timing. Such inaccuracies can affect the precise derivation of the planet’s radius. In this talk we will present the results of a quantitative study on the effects of stellar spots on high precision transit light curves. We show that spot anomalies can lead to the estimate of a planet radius that is 4% smaller than the real value. The effects on the transit duration can also be of the order of 4%, longer or shorter. Depending on the size and distribution of spots, anomalies can also produce transit timing variations with significant amplitudes. For instance, TTVs with signal amplitudes of 200 seconds can be produced by spots as large as the largest sunspot. Finally, we examine the impact of active regions on the transit depth measurements in different wavelengths, in order to probe the impact of this effect on transmission spectroscopy measurements. We show that significant (up to 10% underestimation/overestimation of the planet-to-star radius ratio can be measured, especially in the short wavelength regime.

  10. A picomolar transition state analogue inhibitor of MTAN as a specific antibiotic for H. pylori

    Wang, Shanzhi; Haapalainen, Antti M.; Yan, Funing; Du, Quan; Tyler, Peter C.; Evans, Gary B.; Rinaldo-Matthis, Agnes; Brown, Rosemary L.; Norris, Gillian E.; Almo, Steven C.; Schramm, Vern L.

    2012-01-01

    Campylobacter and Helicobacter species express a 6-amino-6-deoxyfutalosine N-ribosylhydrolase (HpM-TAN) proposed to function in menaquinone synthesis. BuT-DADMe-ImmA is a 36 pM transition state analogue of HpM-TAN and the crystal structure of the enzyme-inhibitor complex reveals the mechanism of inhibition. BuT-DADMe-ImmA has a MIC90 value of < 8 ng/ml for H. pylori growth but does not cause growth arrest in other common clinical pathogens, thus demonstrating potential as an H. pylori-specifi...

  11. The Welfare to Work Transition in the United States: Implications for Work-Related Learning

    Fisher, James C.; Martin, Larry G.

    2000-11-01

    This paper summarizes the legislation upon which the current welfare-to-work transition in the United States is based and describes characteristics of the former welfare population from which various tiers of employment options have emerged: unsubsidized-employed workers, subsidized-employed workers, subsidized-unemployed recipients, and unsubsidized-unemployed individuals. It also discusses current program emphases, and presents a format for directions for future program development which includes academic programs, situated cognition programs, integrated literacy/occupational skills programs, and integrated literacy/soft skills training.

  12. The Urban Mortality Transition in the United States, 1800-1940

    Michael R. Haines

    2001-01-01

    In the United States in the 19th and early 20th centuries, there was a substantial mortality 'penalty' to living in urban places. This circumstance was shared with other nations. By around 1940, this penalty had been largely eliminated, and it was healthier, in many cases, to reside in the city than in the countryside. Despite the lack of systematic national data before 1933, it is possible to describe the phenomenon of the urban mortality transition. Early in the 19th century, the United Sta...

  13. Electric dipole transition rates of the bound states of the b bar b system

    We calculate the E1 decay rates of the bound states of the b bar b system in the nonsingular potential model of Gupta, Repko, and Suchyta (GRS) and compare them with the recent experimental results. We get predictions somewhat different from the original GRS results and overall these new results are in better agreement with experiment. We point out the importance of including both the relativistic corrections to the wave function and the finite-size corrections to the E1 decay rates, especially for transitions which involve a change of more than one unit in the radial quantum number

  14. Experimental and theoretical examples of the value and limitations of transition state theory

    Golden, D. M.

    1979-01-01

    Value and limitations of transition-state theory (TST) are reviewed. TST analyses of the temperature dependence of the 'direct' reactions CH3 + CH3CHO yields CH4 + CH3CO(1) and O + CH4 yields OH + CH3(2) are presented in detail, and other examples of TST usefulness are recalled. Limitations are discussed for bimolecular processes in terms of 'complex' vs. 'direct' mechanisms. The reaction OH + CO yields CO2 + H is discussed in this context. Limitations for unimolecular processes seem to arise only for simple bond fission processes, and recent advances are noted.

  15. Transition state theory description of surface self-diffusion: Comparison with classical trajectory results

    We have computed the surface self-diffusion constants on four different crystal faces [fcc(111), fcc(100), bcc(110), and bcc(211)] using classical transition state theory methods. These results can be compared directly with previous classical-trajectory results which used the same Lennard-Jones 6-12 potential and template model; the agreement is good, though dynamical effects are evident for the fcc(111) and bcc(110) surfaces. Implications are discussed for low-temperature diffusion studies, which are inaccessible to direct molecular dynamics, and the use of ab initio potentials rather than approximate pairwise potentials

  16. Transition State Theory for solvated reactions beyond recrossing-free dividing surfaces

    Revuelta, F; Garcia-Muller, P L; Hernandez, Rigoberto; Benito, R M; Borondo, F

    2016-01-01

    The accuracy of rate constants calculated using transition state theory depends crucially on the correct identification of a recrossing--free dividing surface. We show here that it is possible to define such optimal dividing surface in systems with non--Markovian friction. However, a more direct approach to rate calculation is based on invariant manifolds and avoids the use of a dividing surface altogether, Using that method we obtain an explicit expression for the rate of crossing an anharmonic potential barrier. The excellent performance of our method is illustrated with an application to a realistic model for LiNC$\\rightleftharpoons$LiCN isomerization.

  17. Study of the strength distribution of primary γ-transitions in the decay from superdeformed states in 194Hg

    The strength distribution of the primary γ rays in the decay from superdeformed (SD) states is investigated by applying the maximum likelihood method. For the 194Hg nucleus, 41 primary transitions are identified above 2600 keV. It is concluded that they represent the strongest 10% of the transitions selected stochastically from a Porter-Thomas distribution. This would support the scenario of a statistical decay of SD states via coupling to a compound state at normal deformation. However, the occurrence of several very strong 'one-step linking' transitions is found to have a very small probability. Based on the absence of strong primary transitions from SD states in adjacent nuclei, the situation in 194Hg is viewed as a very lucky incidence

  18. E1 transitions between states with n = 1 to 6 in helium-like carbon, nitrogen, oxygen, neon, silicon, and argon

    Johnson, W. R.; Savukov, I. M.; Safronova, U. I.; Dalgarno, A.

    2002-01-01

    Wavelengths and transition rates are given for E1 transitions between singlet S, P, D, and F states, between triplet S, P, and D states, and between triplet P and singlet S states in ions of astrophysical interest: helium-like carbon, nitrogen, oxygen, neon, silicon, and argon. All possible E1 transitions between states with J < 4 and n < 7 are considered. Energy levels and wave functions used in calculations of the transition rates are obtained from relativistic configuration-interaction cal...

  19. Giant Suppression of the Activation Rate in Dynamical Systems Exhibiting Chaotic Transitions

    The phenomenon of giant suppression of activation, when two or more correlated noise signals act on the system, was found a few years ago in dynamical bistable or metastable systems. When the correlation between these noise signals is strong enough and the amplitudes of the noise are chosen correctly - the life time of the metastable state may be longer than in the case of the application of only a single noise even by many orders of magnitude. In this paper, we investigate similar phenomena in systems exhibiting several chaotic transitions: Pomeau-Manneville intermittency, boundary crisis and interior crisis induced intermittency. Our goal is to show that, in these systems the application of two noise components with the proper choice of the parameters in the case of intermittency can also lengthen the mean laminar phase length or, in the case of boundary crisis, lengthen the time the trajectory spends on the pre-crisis attractor. In systems with crisis induced intermittency, we introduce a new phenomenon we called quasi-deterministic giant suppression of activation in which the lengthening of the laminar phase lengths is caused not by the action of two correlated noise signals but by a single noise term which is correlated with one of the chaotic variables of the system. (author)

  20. Recycling CO 2 ? Computational Considerations of the Activation of CO 2 with Homogeneous Transition Metal Catalysts

    Drees, Markus

    2012-08-10

    Faced with depleting fossil carbon sources, the search for alternative energy carriers and energy storage possibilities has become an important issue. Nature utilizes carbon dioxide as starting material for storing sun energy in plant hydrocarbons. A similar approach, storing energy from renewable sources in chemical bonds with CO 2 as starting material, may lead to partial recycling of CO 2 created by human industrial activities. Unfortunately, currently available routes for the transformation of CO 2 involve high temperatures and are often not selective. With the development of more sophisticated methods and better software, theoretical studies have become both increasingly widespread and useful. This concept article summarizes theoretical investigations of the current state of the feasibility of CO 2 activation with molecular transition metal catalysts, highlighting the most promising reactions of CO 2 with olefins to industrially relevant acrylic acid/acrylates, and the insertion of CO 2 into metal-element bonds, particularly for the synthesis of cyclic carbonates and polymers. Rapidly improving computational power and methods help to increase the importance and accuracy of calculations continuously and make computational chemistry a useful tool helping to solve some of the most important questions for the future. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Analytical determination of transition time between transient and steady state water infiltration

    Lassabatere, Laurent; Angulo-Jaramillo, Rafael; di Prima, Simone; Bagarello, Vincenzo; Iovino, Massimo

    2016-04-01

    The hydraulic characterization of soil hydraulic properties is a prerequisite to the modelling of flow in the vadose zone. Since many years, numerous methods were developed to determine soil hydraulic properties. Many of these methods rely on water infiltration experiments and their analysis using analytical or numerical models. At the beginning, most models were developed for water infiltration at steady state. These models had the advantage to be easy to develop from a theoretical point of view. Yet, many drawbacks remain including the need to wait for a long time, leading to time-consuming experiments, the risk to infiltrate water in large volumes of soil, leading to a response affected by soil variability, and the uncertainty regarding the attainment of steady state (i.e. constant infiltration rate). More recently, infiltration models and mathematical developments addressed the case of consecutive transient and steady states. Yet, one main problem remain. In the field, the operator is never sure about the state of water infiltration data. This paper present analytical formulations for the estimation of a transition time. We consider the model developed by Haverkamp et al. (1994) linking 1D infiltration flux to cumulative infiltration and related approximated expansions. An analytical method based on scaling is proposed to define transition time values in terms of both scaled cumulative infiltration and times. Dimensional times are then calculated for a large variety of soils and initial conditions. These time database can be considered as a relevant tool for the guidance for operators who conduct water infiltration experiments and wants to know when to stop and also for modelers who want to know how to select the data to fit transient or steady state models. Haverkamp, R., Ross, P. J., Smetten, K. R. J., Parlange, J. Y. (1994), Three-dimensional analysis of infiltration from the disc infiltrometer: 2 Physically based infiltration equation. Water Resour. Res

  2. Studies on the structure of the one-quasiparticle states in the transitional nucleus 131Ce

    The excited one-quasiparticle states of the 131Ce and their electromagnetic properties were analyzed in the framework of different model approaches: 1.) In the particle-plus-asymmetric rotor model (TARM), which describes the coupling of a particle to a stable triaxially deformed core regarding the short-range pairing force. Thereby a generalized Nilsson approach for the basing one-particle potential is applied. 2.) In the interacting boson-fermion model (IBFM), which represents an extension of the algebraic interacting boson model to nuclei of odd mass number. Hereby the following results could be obtained: Both excitation energies and the E2-transition probabilities for the positive- as negative-parity states can be generally well reproduced in both models. Thereby the numerical calculations in TARM give a triaxially deformed nuclear shape of the quantity ε=0.25 with an asymmetry parameter of γ=20deg for the positive-parity states as well as γ=25deg for the negative-parity states. The influence of the 5f7/2 orbital is proved as essential factor in the IBFM description of the negative-parity states. As by control calculations on the neighboured nuclide 125Xe could be proved, the calculations in the IBFM permit instead of the conventional U(5)-close parametrization of the bosonic core also a O(6) classification. In view on the asymmetry found in the framework of the TARM in the neighbourhood of the maximal value γ=30deg the proposed O(6) characterization for the transitional nuclei of the mass region A=130 can be founded. (orig.)

  3. Phase-Transfer Activation of Transition Metal Catalysts.

    Tuba, Robert; Xi, Zhenxing; Bazzi, Hassan S; Gladysz, John A

    2015-11-01

    With metal-based catalysts, it is quite common that a ligand (L) must first dissociate from a catalyst precursor (L'n M-L) to activate the catalyst. The resulting coordinatively unsaturated active species (L'n M) can either back react with the ligand in a k-1 step, or combine with the substrate in a k2 step. When dissociation is not rate determining and k-1 [L] is greater than or comparable to k2 [substrate], this slows the rate of reaction. By introducing a phase label onto the ligand L and providing a suitable orthogonal liquid or solid phase, dramatic rate accelerations can be achieved. This phenomenon is termed "phase-transfer activation". In this Concept, some historical antecedents are reviewed, followed by successful applications involving fluorous/organic and aqueous/organic liquid/liquid biphasic catalysis, and liquid/solid biphasic catalysis. Variants that include a chemical trap for the phase-labeled ligands are also described. PMID:26338471

  4. Association between body weight, physical activity and food choices among metropolitan transit workers

    Hannan Peter J

    2007-11-01

    Full Text Available Abstract Background Associations between body weight, physical activity and dietary intake among a population of metropolitan transit workers are described. Methods Data were collected during October through December, 2005, as part of the baseline measures for a worksite weight gain prevention intervention in four metro transit bus garages. All garage employees were invited to complete behavioral surveys that assessed food choices and physical activity, and weight and height were directly measured. Seventy-eight percent (N = 1092 of all employees participated. Results The prevalence of obesity (BMI >= 30 kg/m2 was 56%. Over half of the transit workers reported consuming fruit (55% and vegetables (59% ≥ 3/week. Reported fast food restaurant frequency was low (13% visited ≥ 3/week. Drivers reported high levels of physical activity (eg. walking 93 minutes/day. However, an objective measure of physical activity measured only 16 minutes moderate/vigorous per day. Compared to other drivers, obese drivers reported significantly less vigorous physical activity, more time sitting, and more time watching television. Healthy eating, physical activity and weight management were perceived to be difficult at the worksite, particularly among obese transit workers, and perceived social support for these behaviors was modest. However, most workers perceived weight management and increased physical activity to be personally important for their health. Conclusion Although transit workers' self-report of fruit and vegetable intake, and physical activity was high, perceived access to physical activity and healthful eating opportunities at the worksite was low. Obese workers were significantly less physically active and were more likely to report work environmental barriers to physical activity.

  5. Estimation of Time-Varying Channel State Transition Probabilities for Cognitive Radio Systems by means of Particle Swarm Optimization

    A. Akbulut; T. Adiguzel; YILMAZ, A. E.

    2012-01-01

    In this study, Particle Swarm Optimization is applied for the estimation of the channel state transition probabilities. Unlike most other studies, where the channel state transition probabilities are assumed to be known and/or constant, in this study, these values are realistically considered to be time-varying parameters, which are unknown to the secondary users of the cognitive radio systems. The results of this study demonstrate the following: without any a priori information about the cha...

  6. The Reaction Mechanism of Claisen Rearrangement Obtained by Transition State Spectroscopy and Single Direct-Dynamics Trajectory

    Takayoshi Kobayashi; Atsushi Yabushita; Shigehiko Hayashi; Izumi Iwakura; Yu Kaneko

    2013-01-01

    Chemical bond breaking and formation during chemical reactions can be observed using “transition state spectroscopy”. Comparing the measurement result of the transition state spectroscopy with the simulation result of single direct-dynamics trajectory, we have elucidated the reaction dynamics of Claisen rearrangement of allyl vinyl ether. Observed the reaction of the neat sample liquid, we have estimated the time constants of transformation from straight-chain structure to aromatic-like six-m...

  7. Study of dipion transitions among Υ(3S), Υ(2S), and Υ(1S) states

    We present measurements of decay matrix elements for hadronic transitions of the form Υ(nS)→Υ(mS)ππ, where (n,m)=(3,1),(2,1),(3,2). We reconstruct charged and neutral pion modes with the final state Upsilon decaying to either μ+μ- or e+e-. Dalitz plot distributions for the 12 decay modes are fit individually as well as jointly assuming isospin symmetry, thereby measuring the matrix elements of the decay amplitude. We observe and account for the anomaly previously noted in the dipion invariant mass distribution for the Υ(3S)→Υ(1S)ππ transition and obtain good descriptions of the dynamics of the decay using the most general decay amplitude allowed by partial conservation of the axial-vector current considerations. The fits further indicate that the Υ(2S)→Υ(1S)ππ and Υ(3S)→Υ(2S)ππ transitions also show the presence of terms in the decay amplitude that were previously ignored, although at a relatively suppressed level

  8. Electric-Field Induced Activation of Dark Excitonic States in Carbon Nanotubes.

    Uda, T; Yoshida, M; Ishii, A; Kato, Y K

    2016-04-13

    Electrical activation of optical transitions to parity-forbidden dark excitonic states in individual carbon nanotubes is reported. We examine electric-field effects on various excitonic states by simultaneously measuring photocurrent and photoluminescence. As the applied field increases, we observe an emergence of new absorption peaks in the excitation spectra. From the diameter dependence of the energy separation between the new peaks and the ground state of E11 excitons, we attribute the peaks to the dark excited states which became optically active due to the applied field. Field-induced exciton dissociation can explain the photocurrent threshold field, and the edge of the E11 continuum states has been identified by extrapolating to zero threshold. PMID:26999284

  9. The nuclear industry's transition to risk-informed regulation and operation in the United States

    This paper summarizes a study of the transition of the United States nuclear industry from a prescriptive regulatory structure to a more risk informed approach to operations and regulations. The transition occurred over a 20 yr period in which gradual changes were made in the fundamental regulations and to the approach to nuclear safety and operations. While the number of actual regulatory changes were few, they are continuing. The utilities that embraced risk informed operations made dramatic changes in the way they approached operations and outage management. Those utilities that used risk in operations showed dramatic improvement in safety based on Institute of Nuclear Power Operations (INPO) performance indicators. It was also shown that the use of risk did not negatively affect safety performance of the plants compared to standard prescriptive approaches. This was despite having greater flexibility in compliance to regulatory standards and the use of the newly instituted risk-informed reactor oversight process. Key factors affecting the successful transition to a more risk-informed approach to regulations and operations are: strong top management support and leadership both at the regulator and the utility; education and training in risk principles and probabilistic risk Assessment tools for engineers, operators and maintenance staff; a slow and steady introduction of risk initiatives in areas that can show value to both the regulator and the industry; a transparent regulatory foundation built around a safety goal policy and the development of a strong safety culture at the utility to allow for more independence in safety compliance and risk management. The experience of the United States shows positive results in both safety and economics. The INPO and NRC metrics presented show that the use of risk information in operations and regulation is marginally better with no degradation in safety when plants that have embraced risk-informed approaches are compared

  10. Transition polarizability model of induced resonance Raman optical activity

    Yamamoto, S.; Bouř, Petr

    2013-01-01

    Roč. 34, č. 25 (2013), s. 2152-2158. ISSN 0192-8651 R&D Projects: GA ČR GAP208/11/0105; GA ČR GA13-03978S; GA MŠk(CZ) LH11033 Grant ostatní: AV ČR(CZ) M200551205 Institutional support: RVO:61388963 Keywords : induced resonance Raman optical activity * europium complexes * density functional computations * light scattering Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.601, year: 2013

  11. Solid-state UV-MALDI-MS assay of transition metal dithiocarbamate fungicides.

    Ivanova, Bojidarka; Spiteller, Michael

    2014-01-01

    The determination of transition metal containing dithiocarbamate fungicides represents a challenging aspect of analytical object. They have a low stability, low solubility and stabilize versatile coordination monomers, dimers, disulfides and/or S-oxidized derivatives. Their diverse biological activities and agricultural implementation encompass plant prevention and crop protection against a variety of plants containing fungi and diseases of 400 pathogens and 70 cultures. Nonetheless, those dithiocarbamates (DTCs) are banned for agricultural use in Europe or have expiration at years 2016-2017 because of their highly toxic degradation products and/or metabolites, in particular ethylene thiourea; they found large-scale implementations in materials research and medicine. Despite the broad interdisciplinary of DTC application, due to the above reasons, they have received little attention in the rapidly growing field of analytical chemistry, and in particular, the analytical mass spectrometry. Therefore, the study reported on qualitative, quantitative and structural analysis of ten DTCs (1-10), using the matrix assisted laser desorption/ionization (UV-MALDI)-Orbitrap-mass spectrometry (MS) contributed considerably to the implementation of the method for environmental and foodstuffs monitoring. Its ultrahigh resolving power and capacity for direct solid-state analysis, at limited number of sample pretreatment steps, at concentration levels of analytes of up to femtogram per gram resulted to achievement of a highly precise analytical information for these non-trivial objects. The presented fully validated method and technique is based on the successful ionization of DTCs embedded in three novel organic salts (M1-M3). In this regard, the reported MS and the single-crystal X-ray diffraction data as well as the quantum chemical one are able to correlate the molecular structures in condense and in the gas phase. Despite the novelty of the fundamental methodological character

  12. Intra-urban human mobility and activity transition: evidence from social media check-in data.

    Lun Wu

    Full Text Available Most existing human mobility literature focuses on exterior characteristics of movements but neglects activities, the driving force that underlies human movements. In this research, we combine activity-based analysis with a movement-based approach to model the intra-urban human mobility observed from about 15 million check-in records during a yearlong period in Shanghai, China. The proposed model is activity-based and includes two parts: the transition of travel demands during a specific time period and the movement between locations. For the first part, we find the transition probability between activities varies over time, and then we construct a temporal transition probability matrix to represent the transition probability of travel demands during a time interval. For the second part, we suggest that the travel demands can be divided into two classes, locationally mandatory activity (LMA and locationally stochastic activity (LSA, according to whether the demand is associated with fixed location or not. By judging the combination of predecessor activity type and successor activity type we determine three trip patterns, each associated with a different decay parameter. To validate the model, we adopt the mechanism of an agent-based model and compare the simulated results with the observed pattern from the displacement distance distribution, the spatio-temporal distribution of activities, and the temporal distribution of travel demand transitions. The results show that the simulated patterns fit the observed data well, indicating that these findings open new directions for combining activity-based analysis with a movement-based approach using social media check-in data.

  13. Generation of multi-atom W states via Raman transition in an optical cavity

    A simple scheme is proposed to generate the W state of N λ-type neutral atoms trapped in an optical cavity via Raman transition. Conditional on no photon leakage from the cavity, the N-qubit W state can be prepared perfectly by turning on a classical coupling field for an appropriate time. Compared with the previous ones, our scheme requires neither individual laser addressing of the atoms, nor demand for controlling N atoms to go through an optical cavity simultaneously with a constant velocity. We investigate the influence of cavity decay using the quantum jump approach and show that the preparation time decreases and the success probability increases with atom number because of a collective enhancement of the coupling. (general)

  14. Observation of the transition state for pressure-induced BO₃→ BO₄ conversion in glass.

    Edwards, Trenton; Endo, Takatsugu; Walton, Jeffrey H; Sen, Sabyasachi

    2014-08-29

    A fundamental mechanistic understanding of the pressure- and/or temperature-induced facile transformation of the coordination environment of boron is important for changing the physical properties of glass. We have used in situ high-pressure (up to 2 gigapascals) boron-11 solid-state nuclear magnetic resonance spectroscopy in combination with ab initio calculations to investigate the nature of the transition state for the pressure-induced BO3→ BO4 conversion in a borosilicate glass at ambient temperature. The results indicate an anisotropic elastic deformation of the BO3 planar triangle, under isotropic stress, into a trigonal pyramid that likely serves as a precursor for the subsequent formation of a BO4 tetrahedron. PMID:25170146

  15. Absorbing phase transition in a four-state predator-prey model in one dimension

    Chatterjee, Rakesh; Mohanty, P. K.; Basu, Abhik

    2011-05-01

    The model of competition between densities of two different species, called predator and prey, is studied on a one-dimensional periodic lattice, where each site can be in one of the four states, say, empty, or occupied by a single predator, or occupied by a single prey, or by both. Along with the pairwise death of predators and growth of prey, we introduce an interaction where the predators can eat one of the neighboring prey and reproduce a new predator there instantly. The model shows a non-equilibrium phase transition into an unusual absorbing state where predators are absent and the lattice is fully occupied by prey. The critical exponents of the system are found to be different from those of the directed percolation universality class and they are robust against addition of explicit diffusion.

  16. X-ray absorption to determine the metal oxidation state of transition metal compounds

    Jiménez-Mier, J.; Olalde-Velasco, P.; Carabalí-Sandoval, G.; Herrera-Pérez, G.; Chavira, E.; Yang, W.-L.; Denlinger, J.

    2013-07-01

    We present three examples where x-ray absorption at the transition metal L2,3 edges is used to investigate the valence states of various strongly correlated (SC) and technological relevant materials. Comparison with ligand field multiplet calculations is needed to determine the metal oxidation states. The examples are CrF2, the La1-xSrxCoO3 family and YVO3. For CrF2 the results indicate a disproportionation reaction that generates Cr+, Cr2+ and Cr3+ in different proportions that can be quantified directly from the x-ray spectra. Additionally, it is shown that Co2+ is present in the catalytic La1-xSrxCoO3 perovskite family. Finally, surface effects that change the vanadium valence are also found in YVO3 nanocrystals.

  17. Probing the transition state region in catalytic CO oxidation on Ru

    Ostrom, H. [Stockholm Univ. (Sweden); Oberg, H. [Stockholm Univ. (Sweden); Xin, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); LaRue, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); Beye, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Dell' Angela, M. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Gladh, J. [Stockholm Univ. (Sweden); Ng, M. L. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Sellberg, J. A. [Stockholm Univ. (Sweden); SLAC National Accelerator Lab., Menlo Park, CA (United States); Kaya, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Mercurio, G. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Nordlund, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hantschmann, M. [Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Hieke, F. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Kuhn, D. [Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Schlotter, W. F. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Dakovski, G. L. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Turner, J. J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Minitti, M. P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Mitra, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Moeller, S. P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Fohlisch, A. [Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Univ. Potsdam, Potsdam (Germany); Wolf, M. [Fritz-Haber Institute of the Max-Planck-Society, Berlin (Germany); Wurth, W. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); DESY Photon Science, Hamburg (Germany); Persson, M. [The Univ. of Liverpool, Liverpool (United Kingdom); Norskov, J. K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); Abild-Pedersen, F. [Stanford Univ., Stanford, CA (United States); Ogasawara, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Pettersson, L. G. M. [Stockholm Univ. (Sweden); Nilsson, A. [Stockholm Univ. (Sweden); SLAC National Accelerator Lab., Menlo Park, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-02-12

    Femtosecond x-ray laser pulses are used to probe the CO oxidation reaction on ruthenium (Ru) initiated by an optical laser pulse. On a time scale of a few hundred femtoseconds, the optical laser pulse excites motions of CO and O on the surface, allowing the reactants to collide, and, with a transient close to a picosecond (ps), new electronic states appear in the O K-edge x-ray absorption spectrum. Density functional theory calculations indicate that these result from changes in the adsorption site and bond formation between CO and O with a distribution of OC–O bond lengths close to the transition state (TS). After 1 ps, 10% of the CO populate the TS region, which is consistent with predictions based on a quantum oscillator model.

  18. Absorbing phase transition in a four-state predator–prey model in one dimension

    The model of competition between densities of two different species, called predator and prey, is studied on a one-dimensional periodic lattice, where each site can be in one of the four states, say, empty, or occupied by a single predator, or occupied by a single prey, or by both. Along with the pairwise death of predators and growth of prey, we introduce an interaction where the predators can eat one of the neighboring prey and reproduce a new predator there instantly. The model shows a non-equilibrium phase transition into an unusual absorbing state where predators are absent and the lattice is fully occupied by prey. The critical exponents of the system are found to be different from those of the directed percolation universality class and they are robust against addition of explicit diffusion. (letter)

  19. Nudged-elastic band method with two climbing images: finding transition states in complex energy landscapes

    Zarkevich, Nikolai A

    2014-01-01

    The nudged-elastic band (NEB) method is modified with concomitant two climbing images (C2-NEB) to find a transition state (TS) in complex energy landscapes, such as those with serpentine minimal energy path (MEP). If a single climbing image (C1-NEB) successfully finds the TS, C2-NEB finds it with higher stability and accuracy. However, C2-NEB is suitable for more complex cases, where C1-NEB misses the TS because the MEP and NEB directions near the saddle point are different. Generally, C2-NEB not only finds the TS but guarantees that the climbing images approach it from the opposite sides along the MEP, and it estimates accuracy from the three images: the highest-energy one and its climbing neighbors. C2-NEB is suitable for fixed-cell NEB and the generalized solid-state NEB (SS-NEB).

  20. Chaotic-to-ordered state transition of cathode-sheath instabilities in DC glow discharge plasmas

    Md Nurujjaman; A N Sekar Iyengar

    2006-08-01

    Transition from chaotic to ordered state has been observed during the initial stage of a discharge in a cylindrical DC glow discharge plasma. Initially it shows a chaotic behavior but increasing the discharge voltage changes the characteristics of the discharge glow and shows a period subtraction of order 7 period → 5 period → 3 period → 1 period, i.e. the system goes to single mode through odd cycle subtraction. On further increasing the discharge voltage, the system goes through period doubling, like 1 period → 2 period → 4 period. On further increasing the voltage, the system goes to stable state through two period subtraction, like 4 period → 2 period → stable.

  1. State transitions and feedback mechanisms control hydrology in the constructed catchment ´Chicken Creeḱ

    Schaaf, Wolfgang; Gerwin, Werner; Hinz, Christoph; Zaplata, Markus

    2016-04-01

    Landscapes and ecosystems are complex systems with many feedback mechanisms acting between the various abiotic and biotic components. The knowledge about these interacting processes is mainly derived from mature ecosystems. The initial development of ecosystem complexity may involve state transitions following catastrophic shifts, disturbances or transgression of thresholds. The Chicken Creek catchment was constructed in 2005 in the mining area of Lusatia/Germany to study processes and feedback mechanisms during ecosystem evolution. The hillslope-shaped 6 ha site has defined boundary conditions and well-documented inner structures. The dominating substrate above the underlying clay layer is Pleistocene sandy material representing mainly the lower C horizon of the former landscape. Since 2005, the unrestricted, unmanaged development of the catchment was intensively monitored. During the ten years since then, we observed characteristic state transitions in catchment functioning driven by feedbacks between original substrate properties, surface structures, soil development and vegetation succession. Whereas surface runoff induced by surface crusting and infiltration dominated catchment hydrology in the first years, the impact of vegetation on hydrological pathways and groundwater levels became more and more evident during the last years. Discharge from the catchment changed from episodic events driven by precipitation and surface runoff to groundwater driven. This general picture is overlain by spatial patterns and single episodic events of external drivers. The scientific value of the Chicken Creek site with known boundary conditions and structure information could help in disentangling general feedback mechanisms between hydrologic, pedogenic, biological and geomorphological processes as well as a in gaining a more integrative view of succession and its drivers during the transition from initial, less complex systems to more mature ecosystems. Long-term time series

  2. A structural analysis of the A5/1 state transition graph

    Andreas Beckmann

    2012-10-01

    Full Text Available We describe efficient algorithms to analyze the cycle structure of the graph induced by the state transition function of the A5/1 stream cipher used in GSM mobile phones and report on the results of the implementation. The analysis is performed in five steps utilizing HPC clusters, GPGPU and external memory computation. A great reduction of this huge state transition graph of 2^64 nodes is achieved by focusing on special nodes in the first step and removing leaf nodes that can be detected with limited effort in the second step. This step does not break the overall structure of the graph and keeps at least one node on every cycle. In the third step the nodes of the reduced graph are connected by weighted edges. Since the number of nodes is still huge an efficient bitslice approach is presented that is implemented with NVIDIA's CUDA framework and executed on several GPUs concurrently. An external memory algorithm based on the STXXL library and its parallel pipelining feature further reduces the graph in the fourth step. The result is a graph containing only cycles that can be further analyzed in internal memory to count the number and size of the cycles. This full analysis which previously would take months can now be completed within a few days and allows to present structural results for the full graph for the first time. The structure of the A5/1 graph deviates notably from the theoretical results for random mappings.

  3. The peptide-receptive transition state of MHC-1 molecules: Insight from structure and molecular dynamics

    Robinson H.; Mage, M.; Dolan, M.; Wang, R.; Boyd, L.; Revilleza, M.; Natarajan, K.; Myers, N.; Hansen, T.; Margulies, D.

    2012-05-01

    MHC class I (MHC-I) proteins of the adaptive immune system require antigenic peptides for maintenance of mature conformation and immune function via specific recognition by MHC-I-restricted CD8(+) T lymphocytes. New MHC-I molecules in the endoplasmic reticulum are held by chaperones in a peptide-receptive (PR) transition state pending release by tightly binding peptides. In this study, we show, by crystallographic, docking, and molecular dynamics methods, dramatic movement of a hinged unit containing a conserved 3(10) helix that flips from an exposed 'open' position in the PR transition state to a 'closed' position with buried hydrophobic side chains in the peptide-loaded mature molecule. Crystallography of hinged unit residues 46-53 of murine H-2L(d) MHC-I H chain, complexed with mAb 64-3-7, demonstrates solvent exposure of these residues in the PR conformation. Docking and molecular dynamics predict how this segment moves to help form the A and B pockets crucial for the tight peptide binding needed for stability of the mature peptide-loaded conformation, chaperone dissociation, and Ag presentation.

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

    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

  5. Steady-state hydrodynamic instabilities of active liquid crystals: Hybrid lattice Boltzmann simulations

    Marenduzzo, D.; Orlandini, E.; Cates, M. E.; Yeomans, J. M.

    2007-09-01

    We report hybrid lattice Boltzmann (HLB) simulations of the hydrodynamics of an active nematic liquid crystal sandwiched between confining walls with various anchoring conditions. We confirm the existence of a transition between a passive phase and an active phase, in which there is spontaneous flow in the steady state. This transition is attained for sufficiently “extensile” rods, in the case of flow-aligning liquid crystals, and for sufficiently “contractile” ones for flow-tumbling materials. In a quasi-one-dimensional geometry, deep in the active phase of flow-aligning materials, our simulations give evidence of hysteresis and history-dependent steady states, as well as of spontaneous banded flow. Flow-tumbling materials, in contrast, rearrange themselves so that only the two boundary layers flow in steady state. Two-dimensional simulations, with periodic boundary conditions, show additional instabilities, with the spontaneous flow appearing as patterns made up of “convection rolls.” These results demonstrate a remarkable richness (including dependence on anchoring conditions) in the steady-state phase behavior of active materials, even in the absence of external forcing; they have no counterpart for passive nematics. Our HLB methodology, which combines lattice Boltzmann for momentum transport with a finite difference scheme for the order parameter dynamics, offers a robust and efficient method for probing the complex hydrodynamic behavior of active nematics.

  6. Steady-state hydrodynamic instabilities of active liquid crystals: hybrid lattice Boltzmann simulations.

    Marenduzzo, D; Orlandini, E; Cates, M E; Yeomans, J M

    2007-09-01

    We report hybrid lattice Boltzmann (HLB) simulations of the hydrodynamics of an active nematic liquid crystal sandwiched between confining walls with various anchoring conditions. We confirm the existence of a transition between a passive phase and an active phase, in which there is spontaneous flow in the steady state. This transition is attained for sufficiently "extensile" rods, in the case of flow-aligning liquid crystals, and for sufficiently "contractile" ones for flow-tumbling materials. In a quasi-one-dimensional geometry, deep in the active phase of flow-aligning materials, our simulations give evidence of hysteresis and history-dependent steady states, as well as of spontaneous banded flow. Flow-tumbling materials, in contrast, rearrange themselves so that only the two boundary layers flow in steady state. Two-dimensional simulations, with periodic boundary conditions, show additional instabilities, with the spontaneous flow appearing as patterns made up of "convection rolls." These results demonstrate a remarkable richness (including dependence on anchoring conditions) in the steady-state phase behavior of active materials, even in the absence of external forcing; they have no counterpart for passive nematics. Our HLB methodology, which combines lattice Boltzmann for momentum transport with a finite difference scheme for the order parameter dynamics, offers a robust and efficient method for probing the complex hydrodynamic behavior of active nematics. PMID:17930285

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

    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

  8. Social Media Activism and State Censorship

    T. Poell

    2015-01-01

    This chapter interrogates how activist social media communication in authoritarian contexts is shaped through the mutual articulation of social media user practices, business models, and technological architectures, as well as through the controlling efforts of states. It specifically focuses on soc

  9. Active-duty military service, cohabiting unions, and the transition to marriage

    2009-02-01

    Full Text Available A small but growing body of research has begun to identify the consequences of military service during the all-voluntary era. In this article, we examine the relationship between military service and the likelihood that cohabiting unions will be converted into marriages. Our paper extends previous research by making a distinction between the effects of active-duty verses reserve-duty service on the transition to marriage using data from the 1979-2004 National Longitudinal Survey of Youth (NLSY. Our findings indicate that there is a positive relationship between active-duty service and cohabitors transitioning to marriage.

  10. Measuring Acoustic Wave Transit Time in Furnace Based on Active Acoustic Source Signal

    Zhen Luo; Feng Tian; Xiao-Ping Sun

    2007-01-01

    Accurate measurement of transit time for acoustic wave between two sensors installed on two sides of a furnace is a key to implementing the temperature field measurement technique based on acoustical method. A new method for measuring transit time of acoustic wave based on active acoustic source signal is proposed in this paper, which includes the followings: the time when the acoustic source signal arrives at the two sensors is measured first; then, the difference of two arriving time arguments is computed, thereby we get the transit time of the acoustic wave between two sensors installed on the two sides of the furnace. Avoiding the restriction on acoustic source signal and background noise, the new method can get the transit time of acoustic wave with higher precision and stronger ability of resisting noise interference.

  11. Transitions between turbulent and laminar superfluid vorticity states in the outer core of a neutron star

    Peralta, C; Giacobello, M; Ooi, A

    2006-01-01

    We investigate the global transition from a turbulent state of superfluid vorticity to a laminar state, and vice versa, in the outer core of a neutron star. By solving numerically the hydrodynamic Hall-Vinen-Bekarevich-Khalatnikov equations for a rotating superfluid in a differentially rotating spherical shell, we find that the meridional counterflow driven by Ekman pumping exceeds the Donnelly-Glaberson threshold throughout most of the outer core, exciting unstable Kelvin waves which disrupt the rectilinear vortex array, creating a vortex tangle. In the turbulent state, the torque exerted on the crust oscillates, and the crust-core coupling is weaker than in the laminar state. This leads to a new scenario for the rotational glitches observed in radio pulsars: a vortex tangle is sustained in the differentially rotating outer core by the meridional counterflow, a sudden spin-up event brings the crust and core into corotation, the vortex tangle relaxes back to a rectilinear vortex array, then the crust spins do...

  12. Effects of a Transition to a Hydrogen Economy on Employment in the United States

    The U.S. Department of Energy report, Effects of a Transition to a Hydrogen Economy on Employment in the United States Report to Congress, estimates the effects on employment of a U.S. economy transformation to hydrogen between 2020 and 2050. The report includes study results on employment impacts from hydrogen market expansion in the transportation, stationary, and portable power sectors and highlights possible skill and education needs. This study is in response to Section 1820 of the Energy Policy Act of 2005 (Public Law 109-58) (EPACT). Section 1820, 'Overall Employment in a Hydrogen Economy', requires the Secretary of Energy to carry out a study of the effects of a transition to a hydrogen economy on several employment (types) in the United States. As required by Section 1820, the present report considers: (1) Replacement effects of new goods and services; (2) International competition; (3) Workforce training requirements; (4) Multiple possible fuel cycles, including usage of raw materials; (5) Rates of market penetration of technologies; (6) Regional variations based on geography; and (7) Specific recommendations of the study Both the Administration's National Energy Policy and the Department's Strategic Plan call for reducing U.S. reliance on imported oil and reducing greenhouse gas emissions. The National Energy Policy also acknowledges the need to increase energy supplies and use more energy-efficient technologies and practices. President Bush proposed in his January 2003 State of the Union Address to advance research on hydrogen so that it has the potential to play a major role in America's future energy system. Consistent with these aims, EPACT 2005 authorizes a research, development, and demonstration program for hydrogen and fuel cell technology. Projected results for the national employment impacts, projections of the job creation and job replacement underlying the total employment changes, training implications, regional employment impacts and the

  13. Effects of a Transition to a Hydrogen Economy on Employment in the United States

    Tolley, George S.; Jones, Donald W. Mintz, Marianne M.; Smith, Barton A.; Carlson, Eric; Unnasch, Stefan; Lawrence, Michael; Chmelynski, Harry

    2008-07-01

    The U.S. Department of Energy report, Effects of a Transition to a Hydrogen Economy on Employment in the United States Report to Congress, estimates the effects on employment of a U.S. economy transformation to hydrogen between 2020 and 2050. The report includes study results on employment impacts from hydrogen market expansion in the transportation, stationary, and portable power sectors and highlights possible skill and education needs. This study is in response to Section 1820 of the Energy Policy Act of 2005 (Public Law 109-58) (EPACT). Section 1820, “Overall Employment in a Hydrogen Economy,” requires the Secretary of Energy to carry out a study of the effects of a transition to a hydrogen economy on several employment [types] in the United States. As required by Section 1820, the present report considers: • Replacement effects of new goods and services • International competition • Workforce training requirements • Multiple possible fuel cycles, including usage of raw materials • Rates of market penetration of technologies • Regional variations based on geography • Specific recommendations of the study Both the Administration’s National Energy Policy and the Department’s Strategic Plan call for reducing U.S. reliance on imported oil and reducing greenhouse gas emissions. The National Energy Policy also acknowledges the need to increase energy supplies and use more energy-efficient technologies and practices. President Bush proposed in his January 2003 State of the Union Address to advance research on hydrogen so that it has the potential to play a major role in America’s future energy system. Consistent with these aims, EPACT 2005 authorizes a research, development, and demonstration program for hydrogen and fuel cell technology. Projected results for the national employment impacts, projections of the job creation and job replacement underlying the total employment changes, training implications, regional employment impacts and the

  14. State-of-the-Art Hip Surgeries for Active Adults

    STATE-OF-THE-ART HIP SURGERIES FOR ACTIVE ADULTS Thomas Jefferson University Hospital Philadelphia, PA September 24, 2008 00:00:09 ANNOUNCER: Welcome ... surgeons will demonstrate and discuss state- of-the-art surgical options for young and active older adults ...

  15. State-of-the-Art Hip Surgeries for Active Adults

    Full Text Available STATE-OF-THE-ART HIP SURGERIES FOR ACTIVE ADULTS Thomas Jefferson University Hospital Philadelphia, PA September 24, 2008 00:00:09 ANNOUNCER: Welcome ... surgeons will demonstrate and discuss state- of-the-art surgical options for young and active older adults ...

  16. Transition Planning

    Statfeld, Jenna L.

    2011-01-01

    Post-school transition is the movement of a child with disabilities from school to activities that occur after the completion of school. This paper provides information about: (1) post-school transition; (2) transition plan; (3) transition services; (4) transition planning; (5) vocational rehabilitation services; (6) services that are available…

  17. THE EUROPEAN MODEL OF STATE REGULATION OF TOURISM ACTIVITIES

    О. Davydova

    2013-01-01

    In the article the existing model of state regulation of the development of tourism. Expediency of the European model of state regulation of tourism development in Ukraine. It is noted that the European model of state regulation of tourism activities based on the coordination of marketing activities and the development of cooperation between the public and private sectors. The basic forms of public-private partnerships and the advantages of using cluster model of development of tourism, namel...

  18. Structure-composition-activity relationships in transition-metal oxide and oxyhydroxide oxygen-evolution electrocatalysts

    Trotochaud, Lena

    Solar water-splitting is a potentially transformative renewable energy technology. Slow kinetics of the oxygen evolution reaction (OER) limit the efficiency of solar-watersplitting devices, thus constituting a hurdle to widespread implementation of this technology. Catalysts must be stable under highly oxidizing conditions in aqueous electrolyte and minimally absorb light. A grand goal of OER catalysis research is the design of new materials with higher efficiencies enabled by comprehensive understanding of the fundamental chemistry behind catalyst activity. However, little progress has been made towards this goal to date. This dissertation details work addressing major challenges in the field of OER catalysis. Chapter I introduces the current state-of-the-art and challenges in the field. Chapter II highlights work using ultra-thin films as a platform for fundamental study and comparison of catalyst activity. Key results of this work are (1) the identification of a Ni0.9Fe0.1OOH catalyst displaying the highest OER activity in base to date and (2) that in base, many transition-metal oxides transform to layered oxyhydroxide materials which are the active catalysts. The latter result is critical in the context of understanding structure-activity relationships in OER catalysts. Chapter III explores the optical properties of these catalysts, using in situ spectroelectrochemistry to quantify their optical absorption. A new figure-of-merit for catalyst performance is developed which considers both optical and kinetic losses due to the catalyst and describes how these factors together affect the efficiency of composite semiconductor/catalyst photoanodes. In Chapter IV, the fundamental structure-composition-activity relationships in Ni1--xFexOOH catalysts are systematically investigated. This work shows that nearly all previous studies of Ni-based catalysts were likely affected by the presence of Fe impurities, a realization which holds significant weight for future study

  19. Thermodynamic model of the stabilization of an intermediate state in the region of the metamagnetic phase transition in erbium orthoferrite

    The possible mechanisms of the thermodynamic stabilization of an intermediate state in the first-order metamagnetic phase transition in a magnetic field parallel to the Ising c axis of the Er3+ ions in erbium orthoferrite at T = 1.6 K have been analyzed. The model is chosen using the magneto-optical experimental data on the features of this state

  20. First evidence for linking transitions between the superdeformed yrast band and the normal deformed states in Gd-149

    Finck, C; Stezowski, O; Kintz, N; Vivien, JP; Zuber, K; Nourreddine, A; Appelbe, DE; Beausang, CW; Beck, FA; Byrski, T; Courtin, S; Curien, D; de France, G; Duchene, G; Erturk, S; Gall, BJP; Haas, B; Khadiri, N; Pachoud, E; Rigollet, C; Smith, M; Theisen, C; Twin, PJ

    1999-01-01

    Double step resolved gamma-ray transitions linking the yrast superdeformed (SD) band of Gd-149 to the normal deformed (ND) level scheme have been observed using the EUROGAM phase II spectrometer. The excitation energy of the 47/2(-) SD state above the 7/2(-) ground state has thus been determined to

  1. Influence of the inert and active ion bombardment on structure of the transition metal thin films

    Blazhevich, S; Martynov, I; Neklyudov, I

    2002-01-01

    The results of the experimental research of the inert (He, Ne, Ar, Kr, Xe) and active (O, N) ion impact on the transition metal structure are presented. Thin high-purity (99.999 at.%) films of nickel, chrome and iron were used in the experiment. The bombardment was realized under room temperature at high vacuum (P<1x10 sup - sup 7 Pa) by a separated ion beam of 10-10 sup 3 keV. As a main result of the experiment, the full absence of crystal matrix changes was ascertained for all the transition metals irradiated by inert gas ions. The chemical nature of the crystal structure changes observed in transition metals being under active ion bombardment was found out too.

  2. Molecular water oxidation mechanisms followed by transition metals: state of the art.

    Sala, Xavier; Maji, Somnath; Bofill, Roger; García-Antón, Jordi; Escriche, Lluís; Llobet, Antoni

    2014-02-18

    One clean alternative to fossil fuels would be to split water using sunlight. However, to achieve this goal, researchers still need to fully understand and control several key chemical reactions. One of them is the catalytic oxidation of water to molecular oxygen, which also occurs at the oxygen evolving center of photosystem II in green plants and algae. Despite its importance for biology and renewable energy, the mechanism of this reaction is not fully understood. Transition metal water oxidation catalysts in homogeneous media offer a superb platform for researchers to investigate and extract the crucial information to describe the different steps involved in this complex reaction accurately. The mechanistic information extracted at a molecular level allows researchers to understand both the factors that govern this reaction and the ones that derail the system to cause decomposition. As a result, rugged and efficient water oxidation catalysts with potential technological applications can be developed. In this Account, we discuss the current mechanistic understanding of the water oxidation reaction catalyzed by transition metals in the homogeneous phase, based on work developed in our laboratories and complemented by research from other groups. Rather than reviewing all of the catalysts described to date, we focus systematically on the several key elements and their rationale from molecules studied in homogeneous media. We organize these catalysts based on how the crucial oxygen-oxygen bond step takes place, whether via a water nucleophilic attack or via the interaction of two M-O units, rather than based on the nuclearity of the water oxidation catalysts. Furthermore we have used DFT methodology to characterize key intermediates and transition states. The combination of both theory and experiments has allowed us to get a complete view of the water oxidation cycle for the different catalysts studied. Finally, we also describe the various deactivation pathways for

  3. 'Teaching for transitions: a review of teaching for transitions related to teaching and learning activity and research'

    O'Mahony, Catherine; Higgs, Betty; Alexander, D; Kilcommins, Shane; A. C. Ryan; Blackshields, Daniel; McCarthy, Marian; O'sullivan, Kathryn; Cronin, James

    2015-01-01

    peer-reviewed The ‘Scholarship of Teaching for Transitions’ research project aimed to provide a snapshot of existing national and international scholarship on teaching for transitions, with a particular emphasis on pedagogies for transitions. The research concentrated on the student’s journey as it relates to Higher Education, i.e. transitions in, through and out of third level.

  4. Novel Insights Into The Mode of Inhibition of Class A SHV-1 Beta-Lactamases Revealed by Boronic Acid Transition State Inhibitors

    W Ke; J Sampson; C Ori; F Prati; S Drawz; C Bethel; R Bonomo; F van den Akker

    2011-12-31

    Boronic acid transition state inhibitors (BATSIs) are potent class A and C {beta}-lactamase inactivators and are of particular interest due to their reversible nature mimicking the transition state. Here, we present structural and kinetic data describing the inhibition of the SHV-1 {beta}-lactamase, a clinically important enzyme found in Klebsiella pneumoniae, by BATSI compounds possessing the R1 side chains of ceftazidime and cefoperazone and designed variants of the latter, compounds 1 and 2. The ceftazidime and cefoperazone BATSI compounds inhibit the SHV-1 {beta}-lactamase with micromolar affinity that is considerably weaker than their inhibition of other {beta}-lactamases. The solved crystal structures of these two BATSIs in complex with SHV-1 reveal a possible reason for SHV-1's relative resistance to inhibition, as the BATSIs adopt a deacylation transition state conformation compared to the usual acylation transition state conformation when complexed to other {beta}-lactamases. Active-site comparison suggests that these conformational differences might be attributed to a subtle shift of residue A237 in SHV-1. The ceftazidime BATSI structure revealed that the carboxyl-dimethyl moiety is positioned in SHV-1's carboxyl binding pocket. In contrast, the cefoperazone BATSI has its R1 group pointing away from the active site such that its phenol moiety moves residue Y105 from the active site via end-on stacking interactions. To work toward improving the affinity of the cefoperazone BATSI, we synthesized two variants in which either one or two extra carbons were added to the phenol linker. Both variants yielded improved affinity against SHV-1, possibly as a consequence of releasing the strain of its interaction with the unusual Y105 conformation.

  5. Line Strengths of Rovibrational and Rotational Transitions in the X$^2\\Pi$ Ground State of OH

    Brooke, James S A; Western, Colin M; Sneden, Christopher; Afşar, Melike; Li, Gang; Gordon, Iouli E

    2015-01-01

    A new line list including positions and absolute intensities (in the form of Einstein $A$ values and oscillator strengths) has been produced for the OH ground X\\DP\\ state rovibrational (Meinel system) and pure rotational transitions. All possible transitions are included with v$\\primed$ and v$\\Dprimed$ up to 13, and $J$ up to between 9.5 and 59.5, depending on the band. An updated fit to determine molecular constants has been performed, which includes some new rotational data and a simultaneous fitting of all molecular constants. The absolute line intensities are based on a new dipole moment function, which is a combination of two high level ab initio calculations. The calculations show good agreement with an experimental v=1 lifetime, experimental $\\mu_\\mathrm{v}$ values, and $\\Delta$v=2 line intensity ratios from an observed spectrum. To achieve this good agreement, an alteration in the method of converting matrix elements from Hund's case (b) to (a) was made. Partitions sums have been calculated using the ...

  6. Phase transition and equation of state of paratellurite (TeO2) under high pressure

    Liu, Xun; Mashimo, Tsutomu; Kawai, Nobuaki; Sekine, Toshimori; Zeng, Zhaoyi; Zhou, Xianming

    2016-07-01

    The Hugoniot data for TeO2 single crystals were obtained for pressures up to ∼85 GPa along both the (a-axis) and (c-axis) directions using a velocity interferometer system for any reflector and inclined-mirror method combined with a powder gun or two-stage light gas gun. The Hugoniot-elastic limit of TeO2 was determined to be 3.3–4.3 GPa along the c-axes. The shock velocity (U s) versus particle velocity (U p) relation for TeO2 shows a kink around U p = 1.0 km s‑1, which suggests a phase transition completes at ∼26 ± 2 GPa. The Hugoniot relations of the low and high pressure phase are given by U s = 3.13(5) + 1.10(6)U p for U p 1.0 km s‑1, respectively. First-principles geometry optimizations based on the generalized gradient approximation after Perdew, Burke and Ernzerhof method were also performed on TeO2. It suggested that a continuous structure distortion occurs up to 22 GPa, and the lattice parameters b and c abruptly increase and decrease at 22 GPa, respectively, indicating a first-order phase transition to the cotunnite structure phase. The equation of state of the cotunnite phase TeO2 is discussed based on the experimental and simulation results.

  7. Dynamics of the charge transferred states relevant to magnetic phase transition in rubidium manganese hexacyanoferrate

    Suemoto, T., E-mail: suemoto@issp.u-tokyo.ac.j [Institute for Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi 277-8581 (Japan); Ohki, K.; Fukaya, R.; Nakajima, M. [Institute for Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi 277-8581 (Japan); Tokoro, H.; Ohkoshi, S. [Department of Chemistry, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2009-12-15

    Photoinduced charge transfer dynamics in the photomagnetic material RbMn[Fe(CN){sub 6}], which exhibits a magnetic phase transition with a large hysteresis loop (230-300 K), has been investigated by observing the CN{sup -} stretching modes, which are sensitive to the valences of the adjacent transition metal ions. Mid-infrared transient absorption measurements were performed between 2013 and 2179 cm{sup -1} to observe the transient and persistent products. The sample in the high-temperature phase was excited by 400 nm laser pulses at the ligand to metal charge transfer band near the high-temperature end of the hysteresis loop. Bleach of the Fe{sup 3+}-CN{sup -}-Mn{sup 2+} band representing a decrease of the high-temperature phase and increases of the Fe{sup 2+}-CN{sup -}-Mn{sup 3+} and Fe{sup 2+}-CN{sup -}-Mn{sup 2+} bands were observed in picosecond time region, indicating a transient production of charge transferred states.

  8. Self-induced topological transitions and edge states supported by nonlinear staggered potentials

    Hadad, Yakir; Khanikaev, Alexander B.; Alò, Andrea

    2016-04-01

    The canonical Su-Schrieffer-Heeger (SSH) array is one of the basic geometries that have spurred significant interest in topological band-gap modes. Here, we show that the judicious inclusion of third-order Kerr nonlinearities in SSH arrays opens rich physics in topological insulators, including the possibility of supporting self-induced topological transitions, as a function of the applied intensity. We highlight the emergence of a class of topological solutions in nonlinear SSH arrays localized at the array edges and with unusual properties. As opposed to their linear counterparts, these nonlinear states decay to a plateau of nonzero amplitude inside the array, highlighting the local nature of topologically nontrivial band gaps in nonlinear systems. We study the conditions under which these states can be excited and their temporal dynamics as a function of the applied excitation, paving the way to interesting directions in the physics of topological edge states with robust propagation properties based on nonlinear interactions in suitably designed periodic arrays.

  9. S-matrix decomposition, natural reaction channels, and the quantum transition state approach to reactive scattering.

    Manthe, Uwe; Ellerbrock, Roman

    2016-05-28

    A new approach for the quantum-state resolved analysis of polyatomic reactions is introduced. Based on the singular value decomposition of the S-matrix, energy-dependent natural reaction channels and natural reaction probabilities are defined. It is shown that the natural reaction probabilities are equal to the eigenvalues of the reaction probability operator [U. Manthe and W. H. Miller, J. Chem. Phys. 99, 3411 (1993)]. Consequently, the natural reaction channels can be interpreted as uniquely defined pathways through the transition state of the reaction. The analysis can efficiently be combined with reactive scattering calculations based on the propagation of thermal flux eigenstates. In contrast to a decomposition based straightforwardly on thermal flux eigenstates, it does not depend on the choice of the dividing surface separating reactants from products. The new approach is illustrated studying a prototypical example, the H + CH4 → H2 + CH3 reaction. The natural reaction probabilities and the contributions of the different vibrational states of the methyl product to the natural reaction channels are calculated and discussed. The relation between the thermal flux eigenstates and the natural reaction channels is studied in detail. PMID:27250291

  10. S-matrix decomposition, natural reaction channels, and the quantum transition state approach to reactive scattering

    Manthe, Uwe; Ellerbrock, Roman

    2016-05-01

    A new approach for the quantum-state resolved analysis of polyatomic reactions is introduced. Based on the singular value decomposition of the S-matrix, energy-dependent natural reaction channels and natural reaction probabilities are defined. It is shown that the natural reaction probabilities are equal to the eigenvalues of the reaction probability operator [U. Manthe and W. H. Miller, J. Chem. Phys. 99, 3411 (1993)]. Consequently, the natural reaction channels can be interpreted as uniquely defined pathways through the transition state of the reaction. The analysis can efficiently be combined with reactive scattering calculations based on the propagation of thermal flux eigenstates. In contrast to a decomposition based straightforwardly on thermal flux eigenstates, it does not depend on the choice of the dividing surface separating reactants from products. The new approach is illustrated studying a prototypical example, the H + CH4 → H2 + CH3 reaction. The natural reaction probabilities and the contributions of the different vibrational states of the methyl product to the natural reaction channels are calculated and discussed. The relation between the thermal flux eigenstates and the natural reaction channels is studied in detail.

  11. Phase transitions of energy and wave functions and bound states in the continuum

    Zhang, Xiao; Wei, Chaozhen; Liu, Yingming; Luo, Maokang

    2016-04-01

    This paper studies a particle subjected to an infinite potential well in the circumstance of a fractional dimensional Lévy path. To obtain analytic expression for the wave functions and energy levels, we introduce the fractional corresponding operator and a generalized de Moivre's theorem. Phase transitions of the energy and wave functions are found when the Lévy path dimension changes from integer to noninteger in nature. More importantly, we demonstrate the existence of stable bound states in the continuum in a simple potential. The results predict a phenomenon in which all bound states energy levels of the particle are continuous and the particle remains in bound states. This phenomenon can be demonstrated that this is a characteristic phenomenon of a fractional system. This phenomenon provides both an a priori criterion for theoretically describing an unknown quantum system with fractional derivatives and a sufficient condition for verifying the preparation of a fractional quantum system in experiment. Finally, we compare our results for fractional quantum systems with the existing results and explain the cause of the reported phenomenon.

  12. Theoretical direct WIMP detection rates for transitions to nuclear excited states

    Vergados, J D; Pirinen, P; Srivastava, P C; Kortelainen, M; Suhonen, J

    2015-01-01

    The recent WMAP and Planck data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Many extensions of the standard model provide dark matter candidates, in particular Weakly Interacting Massive Particles (WIMPs). Thus the direct dark matter detection is central to particle physics and cosmology. Most of the research on this issue has hitherto focused on the detection of the recoiling nucleus. In this paper we study transitions to the excited states, possible in some nuclei, which have sufficiently low lying excited states. Examples considered previously were the first excited states of $^{127}$I and $^{129}$Xe. We examine here $^{83}$Kr, which offers some kinematical advantages and is currently considered as a possible target. We find appreciable branching ratios for the inelastic scattering mediated by the spin cross sections, with an inelastic event rate of $4.4\\times 10^{-4}$kg$^{-1}$d$^{-1}$. So, the extra signature of the gamma ra...

  13. Microstructure-alone induced transition from hydrophilic to hydrophobic wetting state on silicon

    Ems, Henry; Ndao, Sidy

    2015-06-01

    Surface hydrophobicity is primarily attained through the use of low surface energy materials. Experimental attempts to turn hydrophilic surfaces to hydrophobic have consisted of coating and thin film deposition. However, in many applications low surface energy materials and coatings are not practical, though hydrophobicity is still desired. In this paper, we demonstrate the transition from hydrophilic to hydrophobic wetting states on an intrinsically hydrophilic surface (contact angle less than 45°) using only surface microstructuring. The surface microstructures consist of re-entrant microcavities which interfere with the complete wetting of the surface, causing a liquid droplet to sit on the surface in a Cassie wetting state. The microstructures were fabricated on a silicon-on-insulator (SOI) wafer through steps of photolithography, etching, and bonding. Contact angle measurements demonstrated the ability of the microfabricated surfaces to sustain large contact angles above 100°, compared to a bare silicon surface which has a contact angle of 40°. Energy-dispersive X-ray spectroscopy showed silicon to be the only chemical element on the surface, while optical observations with an inverted microscope hinted to the existence of a Cassie wetting state.

  14. Effects of home telemonitoring on transitions between frailty states and death for older adults: a randomized controlled trial

    Upatising B

    2013-03-01

    Full Text Available Benjavan Upatising,1 Gregory J Hanson,2 Young L Kim,3 Stephen S Cha,4 Yuehwern Yih,1 Paul Y Takahashi21School of Industrial Engineering, Purdue University, West Lafayette, IN, USA; 2Department of Internal Medicine, Mayo Clinic, Rochester, MN, USA; 3School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA; 4Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN, USABackground: Two primary objectives when caring for older adults are to slow the decline to a worsened frailty state and to prevent disability. Telemedicine may be one method of improving care in this population. We conducted a secondary analysis of the Tele-ERA study to evaluate the effect of home telemonitoring in reducing the rate of deterioration into a frailty state and death in older adults with comorbid health problems.Methods: This trial involved 205 adults over the age of 60 years with a high risk of hospitalization and emergency department visits. For 12 months, the intervention group received usual medical care and telemonitoring case management, and the control group received usual care alone. The primary outcome was frailty, which was based on five criteria, ie, weight loss, weakness, exhaustion, low activity, and slow gait speed. Participants were classified as frail if they met three or more criteria; prefrail if they met 1–2 criteria; and not frail if they met no criteria. Both groups were assessed for frailty at baseline, and at 6 and 12 months. Frailty transition analyses were performed using a multiple logistic regression method. Kaplan–Meier and Cox proportional hazards methods were used to evaluate each frailty criteria for mortality and to compute unadjusted hazard ratios associated with being telemonitored, respectively. A retrospective power analysis was computed.Results: During the first 6 months, 19 (25% telemonitoring participants declined in frailty status or died, compared with 17 (19% in usual care (odds ratio

  15. Mothers' Knowledge of Early Adolescents' Activities following the Middle School Transition and Pubertal Maturation

    Laird, Robert D.; Marrero, Matthew D.

    2011-01-01

    This study tested a sequential mediation model to determine whether experiences, social cognitions, or parent-adolescent interactional processes account for lower levels of mothers' knowledge of adolescents' whereabouts and activities following early adolescents' transition into middle school (MS) and pubertal development. Cross-sectional data…

  16. 25 CFR 170.152 - What transit facilities and activities are eligible for IRR Program funding?

    2010-04-01

    ... IRR Program funding? 170.152 Section 170.152 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE... funding? Transit facilities and activities eligible for IRR Program funding include, but are not limited... facilities for use in mass transportation; (f) Third-party contracts for otherwise eligible...

  17. Transition Metal–α-Amino Acid Complexes with Antibiotic Activity against Mycobacterium spp.

    Karpin, George W.; Merola, Joseph S.; Joseph O. Falkinham

    2013-01-01

    Synthetic iridium-, rhodium-, and ruthenium-amino acid complexes with hydrophobic l-amino acids have antibiotic activity against Mycobacterium spp., including Mycobacterium bovis BCG and the rapidly growing species Mycobacterium abscessus and Mycobacterium chelonae. Concentrations of transition metal-amino acid complexes demonstrating hemolysis or cytotoxicity were 10- to 25-fold higher than were the MICs.

  18. Activity Descriptors for CO2 Electroreduction to Methane on Transition-Metal Catalysts

    Peterson, Andrew; Nørskov, Jens K.

    2012-01-01

    this work, we compare trends in binding energies for the intermediates in CO2 electrochemical reduction and present an activity “volcano” based on this analysis. This analysis describes the experimentally observed variations in transition-metal catalysts, including why copper is the best-known metal...

  19. Realizing high-quality, ultralarge momentum states and ultrafast topological transitions using semiconductor hyperbolic metamaterials

    Campione, Salvatore; Luk, Ting S.; Liu, Sheng; Sinclair, Michael B.

    2015-09-01

    We employ both the effective medium approximation (EMA) and Bloch theory to compare the dispersion properties of semiconductor hyperbolic metamaterials (SHMs) at mid-infrared frequencies and metallic hyperbolic metamaterials (MHMs) at visible frequencies. This analysis reveals the conditions under which the EMA can be safely applied for both MHMs and SHMs. We find that the combination of precise nanoscale layering and the longer infrared operating wavelengths puts the SHMs well within the effective medium limit and, in contrast to MHMs, allows the attainment of very high photon momentum states. In addition, SHMs allow for new phenomena such as ultrafast creation of the hyperbolic manifold through optical pumping. In particular, we examine the possibility of achieving ultrafast topological transitions through optical pumping which can photo-dope appropriately designed quantum wells on the femtosecond time scale.

  20. CP Asymmetries in Many-Body Final States in Beauty & Charm Transitions

    Bigi, I I

    2015-01-01

    Our community has focused on two-body final states (FS) in $B$ & $D$ decays. The SM produces at least the leading source of CP violation in $B$ transitions; none has been established yet in charm decays. It is crucial to measure three- and four-body FS with accuracy and to compare with predictions based on refined theoretical tools. Correlations between different FS based on CPT invariance are often not obvious, how to apply them and where. We have to probe regional asymmetries and use refined parametrization of the CKM matrix. One uses (broken) U- & V-spin symmetries for spectroscopy. The situations with weak decays of hadrons are much more complex. The impact of strong re-scattering is large, and it connects U- \\& V-spin symmetries. Drawing diagrams often does not mean we understand the underlying dynamics. We have to probe the decays of beauty \\& charm baryons. I discuss the `strategies' more than the `tactics'.

  1. On the emergence of natural singularities and state transitions in living patterns

    Dobay, Akos

    2014-01-01

    As far as human perceptions and rational thinking are concerned, contradictions constitute a non negligible part of our reality. We often refer to these phenomena, in a more informal way, as the chicken or the egg causality dilemma. However, it is not clear whether the chicken or the egg dilemma exists only within the scope of our perceptions, or contradictions have a deeper meaning towards our understanding of reality. Here we argue that if there is an element of reality such that can be adequately described in terms of the chicken or the egg dilemma, then it might lead to a spontaneous symmetry breaking by creating an alternate entity, capable of ultimately separating the chicken from the egg. We propose a formalism to describe such mechanism and discuss how it can be applied to phenomena to describe the natural emergence of singularities and state transitions in living systems.

  2. Surface states, surface metal-insulator, and surface insulator-metal transitions

    I present an informal discussion of various cases where two-dimensional surface metal-insulator structural and charge-density-wave instabilities driven by partly filled surface states have been advocated. These include reconstructions of clean semiconductor surfaces and of W(100) and Mo(100), as well as anomalies on the hydrogen-covered surfaces H/W(110) and H/Mo(110), and possibly alkali-covered surfaces such as K/Cu(111). In addition I will also discuss the opposite type of phenomena, namely surface insulator-metal transitions, which can be argued to occur on α-Ga(001), high-temperature Ge(111), and probably Be(0001). (author). 112 refs, 1 fig

  3. An Extensible Dialogue Script for a Robot Based on Unification of State-Transition Models

    Yosuke Matsusaka

    2010-01-01

    development of communication function of the robot. Compared to previous extension-by-connection method used in behavior-based communication robot developments, the extension-by-unification method has the ability to decompose the script into components. The decomposed components can be recomposed to build a new application easily. In this paper, first we, explain a reformulation we have applied to the conventional state-transition model. Second, we explain a set of algorithms to decompose, recompose, and detect the conflict of each component. Third, we explain a dialogue engine and a script management server we have developed. The script management server has a function to propose reusable components to the developer in real time by implementing the conflict detection algorithm. The dialogue engine SEAT (Speech Event-Action Translator has flexible adapter mechanism to enable quick integration to robotic systems. We have confirmed that by the application of three robots, development efficiency has improved by 30%.

  4. Phase Transition in the Density of States of Quantum Spin Glasses

    Erdős, László, E-mail: lerdos@ist.ac.at [IST Austria (Austria); Schröder, Dominik, E-mail: schroeder.dominik@gmail.com [Ludwig-Maximilians-Universität München (Germany)

    2014-12-15

    We prove that the empirical density of states of quantum spin glasses on arbitrary graphs converges to a normal distribution as long as the maximal degree is negligible compared with the total number of edges. This extends the recent results of Keating et al. (2014) that were proved for graphs with bounded chromatic number and with symmetric coupling distribution. Furthermore, we generalise the result to arbitrary hypergraphs. We test the optimality of our condition on the maximal degree for p-uniform hypergraphs that correspond to p-spin glass Hamiltonians acting on n distinguishable spin- 1/2 particles. At the critical threshold p = n{sup 1/2} we find a sharp classical-quantum phase transition between the normal distribution and the Wigner semicircle law. The former is characteristic to classical systems with commuting variables, while the latter is a signature of noncommutative random matrix theory.

  5. Alpha-decay-induced fracturing in zircon - The transition from the crystalline to the metamict state

    Chakoumakos, Bryan C.; Murakami, Takashi; Lumpkin, Gregory R.; Ewing, Rodney C.

    1987-01-01

    Zonation due to alpha-decay damage in a natural single crystal of zircon from Sri Lanka is discussed. The zones vary in thickness on a scale from one to hundreds of microns. The uranium and thorium concentrations vary from zone to zone such that the alpha decay dose is between 0.2 x 10 to the 16th and 0.8 x 10 to the 16th alpha-events per milligram. The transition from the crystalline to the aperiodic metamict state occurs over this dose range. At doses greater than 0.8 x 10 to the 16th alpha events/mg there is no evidence for long-range order. This type of damage will accumulate in actinide-bearing, ceramic nuclear waste forms. The systematic pattern of fractures would occur in crystalline phases that are zoned with respect to actinide radionuclides.

  6. Removing External Degrees of Freedom from Transition-State Search Methods using Quaternions

    Melander, Marko; Jonsson, Hannes

    2015-01-01

    In finite systems, such as nanoparticles and gas-phase molecules, calculations of minimum energy paths (MEPs) connecting initial and final states of transitions as well as searches for saddle points are complicated by the presence of external degrees of freedom, such as overall translation and rotation. A method based on quaternion algebra for removing the external degrees of freedom is described here and applied in calculations using two commonly used methods: the nudged elastic band (NEB) method for MEPs and the DIMER method for finding the minimum mode in minimum mode following searches of first-order saddle points. With the quaternion approach, fewer images in the NEB are needed to represent MEPs accurately. In both NEB and DIMER calculations of finite systems, the number of iterations required to reach convergence is significantly reduced. The algorithms have been implemented in the Atomic Simulation Environment (ASE) open source software.

  7. Removing External Degrees of Freedom from Transition-State Search Methods using Quaternions.

    Melander, Marko; Laasonen, Kari; Jónsson, Hannes

    2015-03-10

    In finite systems, such as nanoparticles and gas-phase molecules, calculations of minimum energy paths (MEPs) connecting initial and final states of transitions as well as searches for saddle points are complicated by the presence of external degrees of freedom, such as overall translation and rotation. A method based on quaternion algebra for removing the external degrees of freedom is described here and applied in calculations using two commonly used methods: the nudged elastic band (NEB) method for MEPs and the DIMER method for finding the minimum mode in minimum mode following searches of first-order saddle points. With the quaternion approach, fewer images in the NEB are needed to represent MEPs accurately. In both NEB and DIMER calculations of finite systems, the number of iterations required to reach convergence is significantly reduced. The algorithms have been implemented in the Atomic Simulation Environment (ASE) open source software. PMID:26579757

  8. Alpha-decay-induced fracturing in zircon - The transition from the crystalline to the metamict state

    Chakoumakos, Bryan C.; Murakami, Takashi; Lumpkin, Gregory R.; Ewing, Rodney C.

    1987-06-01

    Zonation due to alpha-decay damage in a natural single crystal of zircon from Sri Lanka is discussed. The zones vary in thickness on a scale from one to hundreds of microns. The uranium and thorium concentrations vary from zone to zone such that the alpha decay dose is between 0.2 x 10 to the 16th and 0.8 x 10 to the 16th alpha-events per milligram. The transition from the crystalline to the aperiodic metamict state occurs over this dose range. At doses greater than 0.8 x 10 to the 16th alpha events/mg there is no evidence for long-range order. This type of damage will accumulate in actinide-bearing, ceramic nuclear waste forms. The systematic pattern of fractures would occur in crystalline phases that are zoned with respect to actinide radionuclides.

  9. Surface hopping, transition state theory, and decoherence. II. Thermal rate constants and detailed balance

    We investigate a simple approach to compute a non-adiabatic thermal rate constant using the fewest switches surface hopping (FSSH) dynamics. We study the effects of both decoherence (using our augmented-FSSH (A-FSSH) algorithm) and forbidden hops over a large range of parameters, including high and low friction regimes, and weak and strong electronic coupling regimes. Furthermore, when possible, we benchmark our results against exact hierarchy equations of motion results, where we usually find a maximum error of roughly a factor of two (at reasonably large temperatures). In agreement with Hammes-Schiffer and Tully, we find that a merger of transition state theory and surface hopping can be both accurate and efficient when performed correctly. We further show that detailed balance is followed approximately by A-FSSH dynamics

  10. Using state-and-transition modeling to account for imperfect detection in invasive species management

    Frid, Leonardo; Holcombe, Tracy; Morisette, Jeffrey T.; Olsson, Aaryn D.; Brigham, Lindy; Bean, Travis M.; Betancourt, Julio L.; Bryan, Katherine

    2013-01-01

    Buffelgrass, a highly competitive and flammable African bunchgrass, is spreading rapidly across both urban and natural areas in the Sonoran Desert of southern and central Arizona. Damages include increased fire risk, losses in biodiversity, and diminished revenues and quality of life. Feasibility of sustained and successful mitigation will depend heavily on rates of spread, treatment capacity, and cost–benefit analysis. We created a decision support model for the wildland–urban interface north of Tucson, AZ, using a spatial state-and-transition simulation modeling framework, the Tool for Exploratory Landscape Scenario Analyses. We addressed the issues of undetected invasions, identifying potentially suitable habitat and calibrating spread rates, while answering questions about how to allocate resources among inventory, treatment, and maintenance. Inputs to the model include a state-and-transition simulation model to describe the succession and control of buffelgrass, a habitat suitability model, management planning zones, spread vectors, estimated dispersal kernels for buffelgrass, and maps of current distribution. Our spatial simulations showed that without treatment, buffelgrass infestations that started with as little as 80 ha (198 ac) could grow to more than 6,000 ha by the year 2060. In contrast, applying unlimited management resources could limit 2060 infestation levels to approximately 50 ha. The application of sufficient resources toward inventory is important because undetected patches of buffelgrass will tend to grow exponentially. In our simulations, areas affected by buffelgrass may increase substantially over the next 50 yr, but a large, upfront investment in buffelgrass control could reduce the infested area and overall management costs.

  11. Transit times of water particles in the vadose zone across catchment states and catchments functional units

    Sprenger, Matthias; Weiler, Markus

    2014-05-01

    Understanding the water movement in the vadose zone and its associated transport of solutes are of major interest to reduce nutrient leaching, pollution transport or other risks to water quality. Soil physical models are widely used to asses such transport processes, while the site specific parameterization of these models remains challenging. Inverse modeling is a common method to adjust the soil physical parameters in a way that the observed water movement or soil water dynamics are reproduced by the simulation. We have shown that the pore water stable isotope concentration can serve as an additional fitting target to simulate the solute transport and water balance in the unsaturated zone. In the presented study, the Mualem- van Genuchten parameters for the Richards equation and diffusivity parameter for the convection-dispersion equation have been parameterized using the inverse model approach with Hydrus-1D for 46 experimental sites of different land use, topography, pedology and geology in the Attert basin in Luxembourg. With the best parameter set we simulated the transport of a conservative solute that was introduced via a pulse input at different points in time. Thus, the transit times in the upper 2 m of the soil for different catchment states could be inferred for each location. It has been shown that the time a particle needs to pass the -2 m depth plane highly varies from the systems state and the systems forcing during and after infiltration of that particle. Differences in transit times among the study sites within the Attert basin were investigated with regards to its governing factors to test the concept of functional units. The study shows the potential of pore water stable isotope concentration for residence times and transport analyses in the unsaturated zone leading to a better understanding of the time variable subsurface processes across the catchment.

  12. Transition by breaking of analyticity in the ground state of Josephson junction arrays as a static signature of the vortex jamming transition

    Nogawa, Tomoaki

    2012-05-22

    We investigate the ground state of the irrationally frustrated Josephson junction array with a controlling anisotropy parameter λ that is the ratio of the longitudinal Josephson coupling to the transverse one. We find that the ground state has one-dimensional periodicity whose reciprocal lattice vector depends on λ and is incommensurate with the substrate lattice. Approaching the isotropic point λ=1, the so-called hull function of the ground state exhibits analyticity breaking similar to the Aubry transition in the Frenkel-Kontorova model. We find a scaling law for the harmonic spectrum of the hull functions, which suggests the existence of a characteristic length scale diverging at the isotropic point. This critical behavior is directly connected to the jamming transition previously observed in the current-voltage characteristics by a numerical simulation. On top of the ground state there is a gapless continuous band of metastable states, which exhibit the same critical behavior as the ground state. © 2012 American Physical Society.

  13. Catalytic activity of non-stoichiometric mixed transition metal oxides of praseodymium with cobalt and nickel of Ln2 MO4 type

    Non- Stoichiometric mixed transition metal oxides of spinel type were synthesized by solid state reaction technique at 973, 1073, 1173 and 1273K. Characterization of oxide samples was done by XRD and FTIR methods. The surface and catalytic properties of different samples were determined and correlated. Nickel containing oxides were found a bit more catalytically active in comparison to cobalt oxide samples. Presence of oxalate ion in sample enhances surface properties but deactivate catalytic property simultaneously. Transition metal ions i.e. Ni+2, Ni+3, Co+2 and Co+3 were mainly responsible for the activity of mixed oxides where as inner transition metal ion i.e. Pr+3 ion moderates the catalytic activities of the former. (author)

  14. Girlhood, Sport and Physical Activity: The Construction of Young Femininities in the Transition to Secondary School

    Clark, Sheryl

    2010-01-01

    This thesis deals with issues of sport, gender and identity within schooling. It focuses on six physically active girls as they made the transition to secondary schools in London and considers the social and educational contexts that framed their involvement in physical activity and sport over this period. The research involved in-depth interviews with the girls, and their parents, teachers and friends, over a period of four years, beginning when the girls were in Year 5 and finishing when...

  15. An analysis of the transitions between down and up states of the cortical slow oscillation under urethane anaesthesia

    Wilson, Marcus T.; Barry, Melissa; Reynolds, John N. J.; Crump, William P.; Steyn-Ross, D Alistair; Steyn-Ross, Moira L.; Sleigh, James W.

    2009-01-01

    We study the dynamics of the transition between the low- and high-firing states of the cortical slow oscillation by using intracellular recordings of the membrane potential from cortical neurons of rats. We investigate the evidence for a bistability in assemblies of cortical neurons playing a major role in the maintenance of this oscillation. We show that the trajectory of a typical transition takes an approximately exponential form, equivalent to the response of a resistor–capacitor circuit ...

  16. A Conserved Behavioral State Barrier Impedes Transitions between Anesthetic-Induced Unconsciousness and Wakefulness: Evidence for Neural Inertia

    Friedman, Eliot B.; Sun, Yi; Moore, Jason T.; Hung, Hsiao-Tung; Meng, Qing Cheng; Perera, Priyan; Joiner, William J.; Thomas, Steven A.; Eckenhoff, Roderic G.; Sehgal, Amita; Kelz, Max B.

    2010-01-01

    One major unanswered question in neuroscience is how the brain transitions between conscious and unconscious states. General anesthetics offer a controllable means to study these transitions. Induction of anesthesia is commonly attributed to drug-induced global modulation of neuronal function, while emergence from anesthesia has been thought to occur passively, paralleling elimination of the anesthetic from its sites in the central nervous system (CNS). If this were true, then CNS anesthetic ...

  17. 19 CFR 123.64 - Baggage in transit through the United States between ports in Canada or in Mexico.

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Baggage in transit through the United States between ports in Canada or in Mexico. 123.64 Section 123.64 Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY CUSTOMS RELATIONS WITH CANADA AND MEXICO Baggage § 123.64 Baggage in transit...

  18. CMS Grid Activities in the United States

    I.Fisk; J.Amundson; 等

    2001-01-01

    The CMS groups in the USA are actively involved in several grid-elated projects,including the DoE-funded Particle Physics Data Grid(PPDG)and the NSFfunded Grid Physics Network(GriPhyN).We present developments of :the Grid data Management Pilot (GDMP) software;a Java Analysis Studio-based prototype remote analysis service for CMS data;tools for automating job submission schemes for large scale distributed simulation and reconstruction runs for CMS;modeling and development of job scheduling schemes using the MONARC toolkit;a robust execution service for distributed processors.The deployment and use of these tools at prototype Tier1 and Tier2 computing centers in the USA is described.

  19. Downscaling global land-use/land-cover projections for use in region-level state-and-transition simulation modeling

    Jason T. Sherba

    2015-06-01

    Full Text Available Global land-use/land-cover (LULC change projections and historical datasets are typically available at coarse grid resolutions and are often incompatible with modeling applications at local to regional scales. The difficulty of downscaling and reapportioning global gridded LULC change projections to regional boundaries is a barrier to the use of these datasets in a state-and-transition simulation model (STSM framework. Here we compare three downscaling techniques to transform gridded LULC transitions into spatial scales and thematic LULC classes appropriate for use in a regional STSM. For each downscaling approach, Intergovernmental Panel on Climate Change (IPCC Representative Concentration Pathway (RCP LULC projections, at the 0.5 × 0.5 cell resolution, were downscaled to seven Level III ecoregions in the Pacific Northwest, United States. RCP transition values at each cell were downscaled based on the proportional distribution between ecoregions of (1 cell area, (2 land-cover composition derived from remotely-sensed imagery, and (3 historic LULC transition values from a LULC history database. Resulting downscaled LULC transition values were aggregated according to their bounding ecoregion and “cross-walked” to relevant LULC classes. Ecoregion-level LULC transition values were applied in a STSM projecting LULC change between 2005 and 2100. While each downscaling methods had advantages and disadvantages, downscaling using the historical land-use history dataset consistently apportioned RCP LULC transitions in agreement with historical observations. Regardless of the downscaling method, some LULC projections remain improbable and require further investigation.

  20. Evaluation of activation energies in the semi-localized transition model of thermoluminescence

    Recently a semi-localized transition (SLT) kinetic model was developed for thermoluminescence (TL), which is believed to be applicable to important dosimetric materials like LiF : Mg,Ti. This model contains characteristics of both a localized transition model and a single trap model and is characterized by two distinct activation energy levels. This paper describes the simulation of several standard methods of analysis for the TL peaks calculated using the SLT model in an effort to extract the two activation energy parameters of the model. The methods of analysis are applied to both possible types of transitions within the model, namely the direct recombination of the hole-electron pairs as well as the delocalized transitions involving the conduction band. In the former case of direct recombination, the methods of analysis give consistent results for the activation energy E. In the latter case of transitions involving the conduction band, it was found that extra caution must be exercised when applying standard methods of analysis to the SLT model because of the possibility of strongly overlapping TL peaks. Specifically the peak shape methods consistently fail to yield the correct value of E, while careful application of the fractional glow, thermal cleaning and variable heating rate methods can yield the correct energy values when no retrapping is present within the localized energy levels. A possible explanation is given for the previously reported failure of the peak shape methods to yield the correct activation energies within the SLT model. The heating rate methods of analysis consistently yield the correct activation energies E with an accuracy of a few per cent