Sample records for accelerated search kinetics

  1. Accelerated Profile HMM Searches

    PubMed Central

    Eddy, Sean R.

    2011-01-01

    Profile hidden Markov models (profile HMMs) and probabilistic inference methods have made important contributions to the theory of sequence database homology search. However, practical use of profile HMM methods has been hindered by the computational expense of existing software implementations. Here I describe an acceleration heuristic for profile HMMs, the “multiple segment Viterbi” (MSV) algorithm. The MSV algorithm computes an optimal sum of multiple ungapped local alignment segments using a striped vector-parallel approach previously described for fast Smith/Waterman alignment. MSV scores follow the same statistical distribution as gapped optimal local alignment scores, allowing rapid evaluation of significance of an MSV score and thus facilitating its use as a heuristic filter. I also describe a 20-fold acceleration of the standard profile HMM Forward/Backward algorithms using a method I call “sparse rescaling”. These methods are assembled in a pipeline in which high-scoring MSV hits are passed on for reanalysis with the full HMM Forward/Backward algorithm. This accelerated pipeline is implemented in the freely available HMMER3 software package. Performance benchmarks show that the use of the heuristic MSV filter sacrifices negligible sensitivity compared to unaccelerated profile HMM searches. HMMER3 is substantially more sensitive and 100- to 1000-fold faster than HMMER2. HMMER3 is now about as fast as BLAST for protein searches. PMID:22039361

  2. A Simple "Boxed Molecular Kinetics" Approach To Accelerate Rare Events in the Stochastic Kinetic Master Equation.

    PubMed

    Shannon, Robin; Glowacki, David R

    2018-02-15

    The chemical master equation is a powerful theoretical tool for analyzing the kinetics of complex multiwell potential energy surfaces in a wide range of different domains of chemical kinetics spanning combustion, atmospheric chemistry, gas-surface chemistry, solution phase chemistry, and biochemistry. There are two well-established methodologies for solving the chemical master equation: a stochastic "kinetic Monte Carlo" approach and a matrix-based approach. In principle, the results yielded by both approaches are identical; the decision of which approach is better suited to a particular study depends on the details of the specific system under investigation. In this Article, we present a rigorous method for accelerating stochastic approaches by several orders of magnitude, along with a method for unbiasing the accelerated results to recover the "true" value. The approach we take in this paper is inspired by the so-called "boxed molecular dynamics" (BXD) method, which has previously only been applied to accelerate rare events in molecular dynamics simulations. Here we extend BXD to design a simple algorithmic strategy for accelerating rare events in stochastic kinetic simulations. Tests on a number of systems show that the results obtained using the BXD rare event strategy are in good agreement with unbiased results. To carry out these tests, we have implemented a kinetic Monte Carlo approach in MESMER, which is a cross-platform, open-source, and freely available master equation solver.

  3. Joint kinematics and kinetics of overground accelerated running versus running on an accelerated treadmill

    PubMed Central

    Van Caekenberghe, Ine; Segers, Veerle; Aerts, Peter; Willems, Patrick; De Clercq, Dirk

    2013-01-01

    Literature shows that running on an accelerated motorized treadmill is mechanically different from accelerated running overground. Overground, the subject has to enlarge the net anterior–posterior force impulse proportional to acceleration in order to overcome linear whole body inertia, whereas on a treadmill, this force impulse remains zero, regardless of belt acceleration. Therefore, it can be expected that changes in kinematics and joint kinetics of the human body also are proportional to acceleration overground, whereas no changes according to belt acceleration are expected on a treadmill. This study documents kinematics and joint kinetics of accelerated running overground and running on an accelerated motorized treadmill belt for 10 young healthy subjects. When accelerating overground, ground reaction forces are characterized by less braking and more propulsion, generating a more forward-oriented ground reaction force vector and a more forwardly inclined body compared with steady-state running. This change in body orientation as such is partly responsible for the changed force direction. Besides this, more pronounced hip and knee flexion at initial contact, a larger hip extension velocity, smaller knee flexion velocity and smaller initial plantarflexion velocity are associated with less braking. A larger knee extension and plantarflexion velocity result in larger propulsion. Altogether, during stance, joint moments are not significantly influenced by acceleration overground. Therefore, we suggest that the overall behaviour of the musculoskeletal system (in terms of kinematics and joint moments) during acceleration at a certain speed remains essentially identical to steady-state running at the same speed, yet acting in a different orientation. However, because acceleration implies extra mechanical work to increase the running speed, muscular effort done (in terms of power output) must be larger. This is confirmed by larger joint power generation at the level

  4. Study of strength kinetics of sand concrete system of accelerated hardening

    NASA Astrophysics Data System (ADS)

    Sharanova, A. V.; Lenkova, D. A.; Panfilova, A. D.

    2018-04-01

    Methods of calorimetric analysis are used to study the dynamics of the hydration processes of concretes with different accelerator contents. The efficiency of the isothermal calorimetry method is shown for study of strength kinetics of concrete mixtures of accelerated hardening, promising for additive technologies in civil engineering.

  5. Explicit integration with GPU acceleration for large kinetic networks

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brock, Benjamin; Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830; Belt, Andrew

    2015-12-01

    We demonstrate the first implementation of recently-developed fast explicit kinetic integration algorithms on modern graphics processing unit (GPU) accelerators. Taking as a generic test case a Type Ia supernova explosion with an extremely stiff thermonuclear network having 150 isotopic species and 1604 reactions coupled to hydrodynamics using operator splitting, we demonstrate the capability to solve of order 100 realistic kinetic networks in parallel in the same time that standard implicit methods can solve a single such network on a CPU. This orders-of-magnitude decrease in computation time for solving systems of realistic kinetic networks implies that important coupled, multiphysics problems inmore » various scientific and technical fields that were intractable, or could be simulated only with highly schematic kinetic networks, are now computationally feasible.« less

  6. Explicit integration with GPU acceleration for large kinetic networks

    DOE PAGES

    Brock, Benjamin; Belt, Andrew; Billings, Jay Jay; ...

    2015-09-15

    In this study, we demonstrate the first implementation of recently-developed fast explicit kinetic integration algorithms on modern graphics processing unit (GPU) accelerators. Taking as a generic test case a Type Ia supernova explosion with an extremely stiff thermonuclear network having 150 isotopic species and 1604 reactions coupled to hydrodynamics using operator splitting, we demonstrate the capability to solve of order 100 realistic kinetic networks in parallel in the same time that standard implicit methods can solve a single such network on a CPU. In addition, this orders-of-magnitude decrease in computation time for solving systems of realistic kinetic networks implies thatmore » important coupled, multiphysics problems in various scientific and technical fields that were intractable, or could be simulated only with highly schematic kinetic networks, are now computationally feasible.« less

  7. Microdroplet fusion mass spectrometry: accelerated kinetics of acid-induced chlorophyll demetallation

    PubMed Central

    Lee, Jae Kyoo; Nam, Hong Gil; Zare, Richard N.

    2017-01-01

    Kinetics of acid-induced chlorophyll demetallation was recorded in microdroplets by fusing a stream of microdroplets containing 40 μM chlorophyll a or b dissolved in methanol with a stream of aqueous microdroplets containing 35 mM hydrochloric acid (pH = 1·46). The kinetics of the demetallation of chlorophyll in the fused microdroplets (14 ± 6 μm diameter; 84 ± 18 m s−1 velocity) was recorded by controlling the traveling distance of the fused microdroplets between the fusion region and the inlet of a mass spectrometer. The rate of acid-induced chlorophyll demetallation was about 960 ± 120 times faster in the charged microdroplets compared with that reported in bulk solution. If no voltage was applied to the sprayed microdroplets, then the acceleration factor was about 580 ± 90, suggesting that the applied voltage is not a major factor determining the acceleration. Chlorophyll a was more rapidly demetallated than chlorophyll b by a factor of ~26 in bulk solution and ~5 in charged microdroplets. The demetallation kinetics was second order in the H+ concentration, but the acceleration factor of microdroplets compared with bulk solution appeared to be unchanged in going from pH = 1·3 to 7·0. The water:methanol ratio of the fused microdroplets was varied from 7:3 to 3:7 causing an increase in the reaction rate of chlorophyll a demetallation by 20%. This observation demonstrates that the solvent composition, which has different evaporation rates, does not significantly affect the acceleration. We believe that a major portion of the acceleration can be attributed to confinement effects involving surface reactions rather than either to evaporation of solvents or to the introduction of charges to the microdroplets. PMID:29233214

  8. Microdroplet fusion mass spectrometry: accelerated kinetics of acid-induced chlorophyll demetallation.

    PubMed

    Lee, Jae Kyoo; Nam, Hong Gil; Zare, Richard N

    2017-01-01

    Kinetics of acid-induced chlorophyll demetallation was recorded in microdroplets by fusing a stream of microdroplets containing 40 µM chlorophyll a or b dissolved in methanol with a stream of aqueous microdroplets containing 35 mM hydrochloric acid (pH = 1·46). The kinetics of the demetallation of chlorophyll in the fused microdroplets (14 ± 6 µm diameter; 84 ± 18 m s-1 velocity) was recorded by controlling the traveling distance of the fused microdroplets between the fusion region and the inlet of a mass spectrometer. The rate of acid-induced chlorophyll demetallation was about 960 ± 120 times faster in the charged microdroplets compared with that reported in bulk solution. If no voltage was applied to the sprayed microdroplets, then the acceleration factor was about 580 ± 90, suggesting that the applied voltage is not a major factor determining the acceleration. Chlorophyll a was more rapidly demetallated than chlorophyll b by a factor of ~26 in bulk solution and ~5 in charged microdroplets. The demetallation kinetics was second order in the H+ concentration, but the acceleration factor of microdroplets compared with bulk solution appeared to be unchanged in going from pH = 1·3 to 7·0. The water:methanol ratio of the fused microdroplets was varied from 7:3 to 3:7 causing an increase in the reaction rate of chlorophyll a demetallation by 20%. This observation demonstrates that the solvent composition, which has different evaporation rates, does not significantly affect the acceleration. We believe that a major portion of the acceleration can be attributed to confinement effects involving surface reactions rather than either to evaporation of solvents or to the introduction of charges to the microdroplets.

  9. Tyrosinase kinetics: failure of acceleration in oxidation of ring-blocked monohydric phenol substrate.

    PubMed

    Naish-Byfield, S; Riley, P A

    1998-04-01

    When 2,5,6-trimethyl-4-hydroxyanisole is used as substrate for mushroom tyrosinase the oxidation rate is slow and the kinetics do not exhibit an initial acceleration (lag period), in contrast to the kinetics of oxidation of the parent compound, 4-hydroxyanisole. This finding is interpreted as evidence that the acceleration of oxidation of 4-hydroxyanisole is indirectly contingent on a reductive nucleophile addition to the orthoquinone product of the monohydric phenol, which is prevented by ring methylation. Such a view is consistent with the proposal that the lag-phase characteristic of the kinetics of monohydric phenol oxidation by tyrosinase is due to the activation of previously inactive enzyme by electron donation from an orthodiphenol substrate formed from the orthoquinone oxidation product.

  10. Improving GPU-accelerated adaptive IDW interpolation algorithm using fast kNN search.

    PubMed

    Mei, Gang; Xu, Nengxiong; Xu, Liangliang

    2016-01-01

    This paper presents an efficient parallel Adaptive Inverse Distance Weighting (AIDW) interpolation algorithm on modern Graphics Processing Unit (GPU). The presented algorithm is an improvement of our previous GPU-accelerated AIDW algorithm by adopting fast k-nearest neighbors (kNN) search. In AIDW, it needs to find several nearest neighboring data points for each interpolated point to adaptively determine the power parameter; and then the desired prediction value of the interpolated point is obtained by weighted interpolating using the power parameter. In this work, we develop a fast kNN search approach based on the space-partitioning data structure, even grid, to improve the previous GPU-accelerated AIDW algorithm. The improved algorithm is composed of the stages of kNN search and weighted interpolating. To evaluate the performance of the improved algorithm, we perform five groups of experimental tests. The experimental results indicate: (1) the improved algorithm can achieve a speedup of up to 1017 over the corresponding serial algorithm; (2) the improved algorithm is at least two times faster than our previous GPU-accelerated AIDW algorithm; and (3) the utilization of fast kNN search can significantly improve the computational efficiency of the entire GPU-accelerated AIDW algorithm.

  11. The kinetic activation-relaxation technique: an off-lattice, self-learning kinetic Monte Carlo algorithm with on-the-fly event search

    NASA Astrophysics Data System (ADS)

    Mousseau, Nomand

    2012-02-01

    While kinetic Monte Carlo algorithm has been proposed almost 40 years ago, its application in materials science has been mostly limited to lattice-based motion due to the difficulties associated with identifying new events and building usable catalogs when atoms moved into off-lattice position. Here, I present the kinetic activation-relaxation technique (kinetic ART) is an off-lattice, self-learning kinetic Monte Carlo algorithm with on-the-fly event search [1]. It combines ART nouveau [2], a very efficient unbiased open-ended activated method for finding transition states, with a topological classification [3] that allows a discrete cataloguing of local environments in complex systems, including disordered materials. In kinetic ART, local topologies are first identified for all atoms in a system. ART nouveau event searches are then launched for new topologies, building an extensive catalog of barriers and events. Next, all low energy events are fully reconstructed and relaxed, allowing to take complete account of elastic effects in the system's kinetics. Using standard kinetic Monte Carlo, the clock is brought forward and an event is then selected and applied before a new search for topologies is launched. In addition to presenting the various elements of the algorithm, I will discuss three recent applications to ion-bombarded silicon, defect diffusion in Fe and structural relaxation in amorphous silicon.[4pt] This work was done in collaboration with Laurent Karim B'eland, Peter Brommer, Fedwa El-Mellouhi, Jean-Francois Joly and Laurent Lewis.[4pt] [1] F. El-Mellouhi, N. Mousseau and L.J. Lewis, Phys. Rev. B. 78, 153202 (2008); L.K. B'eland et al., Phys. Rev. E 84, 046704 (2011).[2] G.T. Barkema and N. Mousseau, Phys. Rev. Lett. 77, 4358 (1996); E. Machado-Charry et al., J. Chem Phys. 135, 034102, (2011).[3] B.D. McKay, Congressus Numerantium 30, 45 (1981).

  12. GPU-accelerated atmospheric chemical kinetics in the ECHAM/MESSy (EMAC) Earth system model (version 2.52)

    NASA Astrophysics Data System (ADS)

    Alvanos, Michail; Christoudias, Theodoros

    2017-10-01

    This paper presents an application of GPU accelerators in Earth system modeling. We focus on atmospheric chemical kinetics, one of the most computationally intensive tasks in climate-chemistry model simulations. We developed a software package that automatically generates CUDA kernels to numerically integrate atmospheric chemical kinetics in the global climate model ECHAM/MESSy Atmospheric Chemistry (EMAC), used to study climate change and air quality scenarios. A source-to-source compiler outputs a CUDA-compatible kernel by parsing the FORTRAN code generated by the Kinetic PreProcessor (KPP) general analysis tool. All Rosenbrock methods that are available in the KPP numerical library are supported.Performance evaluation, using Fermi and Pascal CUDA-enabled GPU accelerators, shows achieved speed-ups of 4. 5 × and 20. 4 × , respectively, of the kernel execution time. A node-to-node real-world production performance comparison shows a 1. 75 × speed-up over the non-accelerated application using the KPP three-stage Rosenbrock solver. We provide a detailed description of the code optimizations used to improve the performance including memory optimizations, control code simplification, and reduction of idle time. The accuracy and correctness of the accelerated implementation are evaluated by comparing to the CPU-only code of the application. The median relative difference is found to be less than 0.000000001 % when comparing the output of the accelerated kernel the CPU-only code.The approach followed, including the computational workload division, and the developed GPU solver code can potentially be used as the basis for hardware acceleration of numerous geoscientific models that rely on KPP for atmospheric chemical kinetics applications.

  13. Accelerated hydrolysis of substituted cellulose for potential biofuel production: kinetic study and modeling.

    PubMed

    Mu, Bingnan; Xu, Helan; Yang, Yiqi

    2015-11-01

    In this work, kinetics of substitution accelerated cellulose hydrolysis with multiple reaction stages was investigated to lay foundation for mechanism study and molecular design of substituting compounds. High-efficiency hydrolysis of cellulose is critical for cellulose-based bioethanol production. It is known that, substitution could substantially decrease activation energy and increase reaction rate of acidic hydrolysis of glycosidic bonds in cellulose. However, reaction kinetics and mechanism of the accelerated hydrolysis were not fully revealed. In this research, it was proved that substitution therefore accelerated hydrolysis only occurred in amorphous regions of cellulose fibers, and was a process with multiple reaction stages. With molar ratio of substitution less than 1%, the overall hydrolysis rate could be increased for around 10 times. We also quantified the relationship between the hydrolysis rate of individual reaction stage and its major influences, including molar ratio of substitution, activation energy of acidic hydrolysis, pH and temperature. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Kinetic Modeling of Next-Generation High-Energy, High-Intensity Laser-Ion Accelerators

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Albright, Brian James; Yin, Lin; Stark, David James

    One of the long-standing problems in the community is the question of how we can model “next-generation” laser-ion acceleration in a computationally tractable way. A new particle tracking capability in the LANL VPIC kinetic plasma modeling code has enabled us to solve this long-standing problem

  15. Kinetic Modeling of Radiative Turbulence in Relativistic Astrophysical Plasmas: Particle Acceleration and High-Energy Flares

    NASA Astrophysics Data System (ADS)

    Uzdensky, Dmitri

    Relativistic astrophysical plasma environments routinely produce intense high-energy emission, which is often observed to be nonthermal and rapidly flaring. The recently discovered gamma-ray (> 100 MeV) flares in Crab Pulsar Wind Nebula (PWN) provide a quintessential illustration of this, but other notable examples include relativistic active galactic nuclei (AGN) jets, including blazars, and Gamma-ray Bursts (GRBs). Understanding the processes responsible for the very efficient and rapid relativistic particle acceleration and subsequent emission that occurs in these sources poses a strong challenge to modern high-energy astrophysics, especially in light of the necessity to overcome radiation reaction during the acceleration process. Magnetic reconnection and collisionless shocks have been invoked as possible mechanisms. However, the inferred extreme particle acceleration requires the presence of coherent electric-field structures. How such large-scale accelerating structures (such as reconnecting current sheets) can spontaneously arise in turbulent astrophysical environments still remains a mystery. The proposed project will conduct a first-principles computational and theoretical study of kinetic turbulence in relativistic collisionless plasmas with a special focus on nonthermal particle acceleration and radiation emission. The main computational tool employed in this study will be the relativistic radiative particle-in-cell (PIC) code Zeltron, developed by the team members at the Univ. of Colorado. This code has a unique capability to self-consistently include the synchrotron and inverse-Compton radiation reaction force on the relativistic particles, while simultaneously computing the resulting observable radiative signatures. This proposal envisions performing massively parallel, large-scale three-dimensional simulations of driven and decaying kinetic turbulence in physical regimes relevant to real astrophysical systems (such as the Crab PWN), including the

  16. Using Equation-Free Computation to Accelerate Network-Free Stochastic Simulation of Chemical Kinetics.

    PubMed

    Lin, Yen Ting; Chylek, Lily A; Lemons, Nathan W; Hlavacek, William S

    2018-06-21

    The chemical kinetics of many complex systems can be concisely represented by reaction rules, which can be used to generate reaction events via a kinetic Monte Carlo method that has been termed network-free simulation. Here, we demonstrate accelerated network-free simulation through a novel approach to equation-free computation. In this process, variables are introduced that approximately capture system state. Derivatives of these variables are estimated using short bursts of exact stochastic simulation and finite differencing. The variables are then projected forward in time via a numerical integration scheme, after which a new exact stochastic simulation is initialized and the whole process repeats. The projection step increases efficiency by bypassing the firing of numerous individual reaction events. As we show, the projected variables may be defined as populations of building blocks of chemical species. The maximal number of connected molecules included in these building blocks determines the degree of approximation. Equation-free acceleration of network-free simulation is found to be both accurate and efficient.

  17. A MiniBooNE Accelerator-Produced (sub)-GeV Dark Matter Search

    NASA Astrophysics Data System (ADS)

    Thornton, Remington; MiniBooNE-DM Collaboration

    2016-09-01

    Cosmological observations indicate that our universe contains dark matter (DM), yet we have no measurements of its microscopic properties. Whereas the gravitational interaction of DM is well understood, its interaction with the Standard Model is not. Direct detection experiments search for a nuclear recoil interaction produced by a DM relic particle and have a low-mass sensitivity edge of order 1 GeV. To detect DM with mass below 1 GeV, either the sensitivity of the experiments needs to be improved or use of accelerators producing boosted low-mass DM are needed. Using neutrino detectors to search for low-mass DM is logical due to the similarity of the DM and ν signatures in the detector. The MiniBooNE experiment, located at Fermilab on the Booster Neutrino Beamline, ran for 10 years in ν and ν modes and is already well understood, making it desirable to search for accelerator-produced boosted low-mass DM. A search for DM produced by 8 GeV protons hitting a steel beam-dump has finished, collecting 1 . 86 ×1020 POT . Final analysis containing 90% confidence limits and a model independent fit will be presented.

  18. Kinetic Simulations of Plasma Energization and Particle Acceleration in Interacting Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Du, S.; Guo, F.; Zank, G. P.; Li, X.; Stanier, A.

    2017-12-01

    The interaction between magnetic flux ropes has been suggested as a process that leads to efficient plasma energization and particle acceleration (e.g., Drake et al. 2013; Zank et al. 2014). However, the underlying plasma dynamics and acceleration mechanisms are subject to examination of numerical simulations. As a first step of this effort, we carry out 2D fully kinetic simulations using the VPIC code to study the plasma energization and particle acceleration during coalescence of two magnetic flux ropes. Our analysis shows that the reconnection electric field and compression effect are important in plasma energization. The results may help understand the energization process associated with magnetic flux ropes frequently observed in the solar wind near the heliospheric current sheet.

  19. Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Yongfeng; Jiang, Chao; Bai, Xianming

    2017-01-01

    This report presents an accelerated kinetic Monte Carlo (KMC) method to compute the diffusivity of hydrogen in hcp metals and alloys, considering both thermally activated hopping and quantum tunneling. The acceleration is achieved by replacing regular KMC jumps in trapping energy basins formed by neighboring tetrahedral interstitial sites, with analytical solutions for basin exiting time and probability. Parameterized by density functional theory (DFT) calculations, the accelerated KMC method is shown to be capable of efficiently calculating hydrogen diffusivity in α-Zr and Zircaloy, without altering the kinetics of long-range diffusion. Above room temperature, hydrogen diffusion in α-Zr and Zircaloy is dominated by thermal hopping, with negligible contribution from quantum tunneling. The diffusivity predicted by this DFT + KMC approach agrees well with that from previous independent experiments and theories, without using any data fitting. The diffusivity along is found to be slightly higher than that along , with the anisotropy saturated at about 1.20 at high temperatures, resolving contradictory results in previous experiments. Demonstrated using hydrogen diffusion in α-Zr, the same method can be extended for on-lattice diffusion in hcp metals, or systems with similar trapping basins.

  20. Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

    PubMed Central

    Zhang, Yongfeng; Jiang, Chao; Bai, Xianming

    2017-01-01

    This report presents an accelerated kinetic Monte Carlo (KMC) method to compute the diffusivity of hydrogen in hcp metals and alloys, considering both thermally activated hopping and quantum tunneling. The acceleration is achieved by replacing regular KMC jumps in trapping energy basins formed by neighboring tetrahedral interstitial sites, with analytical solutions for basin exiting time and probability. Parameterized by density functional theory (DFT) calculations, the accelerated KMC method is shown to be capable of efficiently calculating hydrogen diffusivity in α-Zr and Zircaloy, without altering the kinetics of long-range diffusion. Above room temperature, hydrogen diffusion in α-Zr and Zircaloy is dominated by thermal hopping, with negligible contribution from quantum tunneling. The diffusivity predicted by this DFT + KMC approach agrees well with that from previous independent experiments and theories, without using any data fitting. The diffusivity along is found to be slightly higher than that along , with the anisotropy saturated at about 1.20 at high temperatures, resolving contradictory results in previous experiments. Demonstrated using hydrogen diffusion in α-Zr, the same method can be extended for on-lattice diffusion in hcp metals, or systems with similar trapping basins. PMID:28106154

  1. Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

    DOE PAGES

    Zhang, Yongfeng; Jiang, Chao; Bai, Xianming

    2017-01-20

    Here, this report presents an accelerated kinetic Monte Carlo (KMC) method to compute the diffusivity of hydrogen in hcp metals and alloys, considering both thermally activated hopping and quantum tunneling. The acceleration is achieved by replacing regular KMC jumps in trapping energy basins formed by neighboring tetrahedral interstitial sites, with analytical solutions for basin exiting time and probability. Parameterized by density functional theory (DFT) calculations, the accelerated KMC method is shown to be capable of efficiently calculating hydrogen diffusivity in α-Zr and Zircaloy, without altering the kinetics of long-range diffusion. Above room temperature, hydrogen diffusion in α-Zr and Zircaloy ismore » dominated by thermal hopping, with negligible contribution from quantum tunneling. The diffusivity predicted by this DFT + KMC approach agrees well with that from previous independent experiments and theories, without using any data fitting. The diffusivity along < c > is found to be slightly higher than that along < a >, with the anisotropy saturated at about 1.20 at high temperatures, resolving contradictory results in previous experiments. Demonstrated using hydrogen diffusion in α-Zr, the same method can be extended for on-lattice diffusion in hcp metals, or systems with similar trapping basins.« less

  2. Comparison of the Effects of Wave-Particle Interactions and the Kinetic Suprathermal Electron Population on the Acceleration of the Solar Wind

    NASA Technical Reports Server (NTRS)

    Tam, S. W. Y.; Chang, T.

    2002-01-01

    Kinetic effects due to wave-particle interactions and suprathermal electrons have been suggested in the literature as possible solar wind acceleration mechanisms. Ion cyclotron resonant heating, in particular, has been associated with some qualitative features observed in the solar wind. In terms of solar wind acceleration, however, it is interesting to compare the kinetic effects of suprathermal electrons with those due to the wave-particle interactions. The combined effects of the two acceleration mechanisms on the fast solar wind have been studied by Tam and Chang (1999a,b). In this study. we investigate the role of the suprathermal electron population in the acceleration of the solar wind. Our model follows the global kinetic evolution of the fast solar wind under the influence of ion cyclotron resonant heating, while taking into account Coulomb collisions, and the ambipolar electric field that is consistent with the particle distributions themselves. The kinetic effects due to the suprathermal electrons, which we define to be the tail of the electron distributions, can be included in the model as an option. By comparing the results with and without the inclusion of the suprathermal electron effects, we determine the relative importance of suprathermal electrons and wave-particle interactions in driving the solar wind. We find that although suprathermal electrons enhance the ambipolar electric potential in the solar wind considerably, their overall influence as an acceleration mechanism is relatively insignificant in a wave-driven solar wind.

  3. Kinetic Modeling of Accelerated Stability Testing Enabled by Second Harmonic Generation Microscopy.

    PubMed

    Song, Zhengtian; Sarkar, Sreya; Vogt, Andrew D; Danzer, Gerald D; Smith, Casey J; Gualtieri, Ellen J; Simpson, Garth J

    2018-04-03

    The low limits of detection afforded by second harmonic generation (SHG) microscopy coupled with image analysis algorithms enabled quantitative modeling of the temperature-dependent crystallization of active pharmaceutical ingredients (APIs) within amorphous solid dispersions (ASDs). ASDs, in which an API is maintained in an amorphous state within a polymer matrix, are finding increasing use to address solubility limitations of small-molecule APIs. Extensive stability testing is typically performed for ASD characterization, the time frame for which is often dictated by the earliest detectable onset of crystal formation. Here a study of accelerated stability testing on ritonavir, a human immunodeficiency virus (HIV) protease inhibitor, has been conducted. Under the condition for accelerated stability testing at 50 °C/75%RH and 40 °C/75%RH, ritonavir crystallization kinetics from amorphous solid dispersions were monitored by SHG microscopy. SHG microscopy coupled by image analysis yielded limits of detection for ritonavir crystals as low as 10 ppm, which is about 2 orders of magnitude lower than other methods currently available for crystallinity detection in ASDs. The four decade dynamic range of SHG microscopy enabled quantitative modeling with an established (JMAK) kinetic model. From the SHG images, nucleation and crystal growth rates were independently determined.

  4. Estimating the kinetic parameters of activated sludge storage using weighted non-linear least-squares and accelerating genetic algorithm.

    PubMed

    Fang, Fang; Ni, Bing-Jie; Yu, Han-Qing

    2009-06-01

    In this study, weighted non-linear least-squares analysis and accelerating genetic algorithm are integrated to estimate the kinetic parameters of substrate consumption and storage product formation of activated sludge. A storage product formation equation is developed and used to construct the objective function for the determination of its production kinetics. The weighted least-squares analysis is employed to calculate the differences in the storage product concentration between the model predictions and the experimental data as the sum of squared weighted errors. The kinetic parameters for the substrate consumption and the storage product formation are estimated to be the maximum heterotrophic growth rate of 0.121/h, the yield coefficient of 0.44 mg CODX/mg CODS (COD, chemical oxygen demand) and the substrate half saturation constant of 16.9 mg/L, respectively, by minimizing the objective function using a real-coding-based accelerating genetic algorithm. Also, the fraction of substrate electrons diverted to the storage product formation is estimated to be 0.43 mg CODSTO/mg CODS. The validity of our approach is confirmed by the results of independent tests and the kinetic parameter values reported in literature, suggesting that this approach could be useful to evaluate the product formation kinetics of mixed cultures like activated sludge. More importantly, as this integrated approach could estimate the kinetic parameters rapidly and accurately, it could be applied to other biological processes.

  5. Temporal acceleration of spatially distributed kinetic Monte Carlo simulations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chatterjee, Abhijit; Vlachos, Dionisios G.

    The computational intensity of kinetic Monte Carlo (KMC) simulation is a major impediment in simulating large length and time scales. In recent work, an approximate method for KMC simulation of spatially uniform systems, termed the binomial {tau}-leap method, was introduced [A. Chatterjee, D.G. Vlachos, M.A. Katsoulakis, Binomial distribution based {tau}-leap accelerated stochastic simulation, J. Chem. Phys. 122 (2005) 024112], where molecular bundles instead of individual processes are executed over coarse-grained time increments. This temporal coarse-graining can lead to significant computational savings but its generalization to spatially lattice KMC simulation has not been realized yet. Here we extend the binomial {tau}-leapmore » method to lattice KMC simulations by combining it with spatially adaptive coarse-graining. Absolute stability and computational speed-up analyses for spatial systems along with simulations provide insights into the conditions where accuracy and substantial acceleration of the new spatio-temporal coarse-graining method are ensured. Model systems demonstrate that the r-time increment criterion of Chatterjee et al. obeys the absolute stability limit for values of r up to near 1.« less

  6. Acceleration of saddle-point searches with machine learning.

    PubMed

    Peterson, Andrew A

    2016-08-21

    In atomistic simulations, the location of the saddle point on the potential-energy surface (PES) gives important information on transitions between local minima, for example, via transition-state theory. However, the search for saddle points often involves hundreds or thousands of ab initio force calls, which are typically all done at full accuracy. This results in the vast majority of the computational effort being spent calculating the electronic structure of states not important to the researcher, and very little time performing the calculation of the saddle point state itself. In this work, we describe how machine learning (ML) can reduce the number of intermediate ab initio calculations needed to locate saddle points. Since machine-learning models can learn from, and thus mimic, atomistic simulations, the saddle-point search can be conducted rapidly in the machine-learning representation. The saddle-point prediction can then be verified by an ab initio calculation; if it is incorrect, this strategically has identified regions of the PES where the machine-learning representation has insufficient training data. When these training data are used to improve the machine-learning model, the estimates greatly improve. This approach can be systematized, and in two simple example problems we demonstrate a dramatic reduction in the number of ab initio force calls. We expect that this approach and future refinements will greatly accelerate searches for saddle points, as well as other searches on the potential energy surface, as machine-learning methods see greater adoption by the atomistics community.

  7. Acceleration of saddle-point searches with machine learning

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Peterson, Andrew A., E-mail: andrew-peterson@brown.edu

    In atomistic simulations, the location of the saddle point on the potential-energy surface (PES) gives important information on transitions between local minima, for example, via transition-state theory. However, the search for saddle points often involves hundreds or thousands of ab initio force calls, which are typically all done at full accuracy. This results in the vast majority of the computational effort being spent calculating the electronic structure of states not important to the researcher, and very little time performing the calculation of the saddle point state itself. In this work, we describe how machine learning (ML) can reduce the numbermore » of intermediate ab initio calculations needed to locate saddle points. Since machine-learning models can learn from, and thus mimic, atomistic simulations, the saddle-point search can be conducted rapidly in the machine-learning representation. The saddle-point prediction can then be verified by an ab initio calculation; if it is incorrect, this strategically has identified regions of the PES where the machine-learning representation has insufficient training data. When these training data are used to improve the machine-learning model, the estimates greatly improve. This approach can be systematized, and in two simple example problems we demonstrate a dramatic reduction in the number of ab initio force calls. We expect that this approach and future refinements will greatly accelerate searches for saddle points, as well as other searches on the potential energy surface, as machine-learning methods see greater adoption by the atomistics community.« less

  8. The solution of the point kinetics equations via converged accelerated Taylor series (CATS)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ganapol, B.; Picca, P.; Previti, A.

    This paper deals with finding accurate solutions of the point kinetics equations including non-linear feedback, in a fast, efficient and straightforward way. A truncated Taylor series is coupled to continuous analytical continuation to provide the recurrence relations to solve the ordinary differential equations of point kinetics. Non-linear (Wynn-epsilon) and linear (Romberg) convergence accelerations are employed to provide highly accurate results for the evaluation of Taylor series expansions and extrapolated values of neutron and precursor densities at desired edits. The proposed Converged Accelerated Taylor Series, or CATS, algorithm automatically performs successive mesh refinements until the desired accuracy is obtained, making usemore » of the intermediate results for converged initial values at each interval. Numerical performance is evaluated using case studies available from the literature. Nearly perfect agreement is found with the literature results generally considered most accurate. Benchmark quality results are reported for several cases of interest including step, ramp, zigzag and sinusoidal prescribed insertions and insertions with adiabatic Doppler feedback. A larger than usual (9) number of digits is included to encourage honest benchmarking. The benchmark is then applied to the enhanced piecewise constant algorithm (EPCA) currently being developed by the second author. (authors)« less

  9. Advances in Sprint Acceleration Profiling for Field-Based Team-Sport Athletes: Utility, Reliability, Validity and Limitations.

    PubMed

    Simperingham, Kim D; Cronin, John B; Ross, Angus

    2016-11-01

    Advanced testing technologies enable insight into the kinematic and kinetic determinants of sprint acceleration performance, which is particularly important for field-based team-sport athletes. Establishing the reliability and validity of the data, particularly from the acceleration phase, is important for determining the utility of the respective technologies. The aim of this systematic review was to explain the utility, reliability, validity and limitations of (1) radar and laser technology, and (2) non-motorised treadmill (NMT) and torque treadmill (TT) technology for providing kinematic and kinetic measures of sprint acceleration performance. A comprehensive search of the CINAHL Plus, MEDLINE (EBSCO), PubMed, SPORTDiscus, and Web of Science databases was conducted using search terms that included radar, laser, non-motorised treadmill, torque treadmill, sprint, acceleration, kinetic, kinematic, force, and power. Studies examining the kinematics or kinetics of short (≤10 s), maximal-effort sprint acceleration in adults or children, which included an assessment of reliability or validity of the advanced technologies of interest, were included in this systematic review. Absolute reliability, relative reliability and validity data were extracted from the selected articles and tabulated. The level of acceptance of reliability was a coefficient of variation (CV) ≤10 % and an intraclass correlation coefficient (ICC) or correlation coefficient (r) ≥0.70. A total of 34 studies met the inclusion criteria and were included in the qualitative analysis. Generally acceptable validity (r = 0.87-0.99; absolute bias 3-7 %), intraday reliability (CV ≤9.5 %; ICC/r ≥0.84) and interday reliability (ICC ≥0.72) were reported for data from radar and laser. However, low intraday reliability was reported for the theoretical maximum horizontal force (ICC 0.64) within adolescent athletes, and low validity was reported for velocity during the initial 5 m of a sprint

  10. Mechanism of Facilitated Diffusion during a DNA Search in Crowded Environments.

    PubMed

    Krepel, Dana; Gomez, David; Klumpp, Stefan; Levy, Yaakov

    2016-11-03

    The key feature explaining the rapid recognition of a DNA target site by its protein lies in the combination of one- and three-dimensional (1D and 3D) diffusion, which allows efficient scanning of the many alternative sites. This facilitated diffusion mechanism is expected to be affected by cellular conditions, particularly crowding, given that up to 40% of the total cellular volume may by occupied by macromolecules. Using coarse-grained molecular dynamics and Monte Carlo simulations, we show that the crowding particles can enhance facilitated diffusion and accelerate search kinetics. This effect originates from a trade-off between 3D and 1D diffusion. The 3D diffusion coefficient is lower under crowded conditions, but it has little influence because the excluded volume effect of molecular crowding restricts its use. Largely prevented from using 3D diffusion, the searching protein dramatically increases its use of the hopping search mode, which results in a higher linear diffusion coefficient. The coefficient of linear diffusion also increases under crowded conditions as a result of increased collisions between the crowding particles and the searching protein. Overall, less 3D diffusion coupled with an increase in the use of the hopping and speed of 1D diffusion results in faster search kinetics under crowded conditions. Our study shows that the search kinetics and mechanism are modulated not only by the crowding occupancy but also by the properties of the crowding particles and the salt concentration.

  11. Fast parallel tandem mass spectral library searching using GPU hardware acceleration

    PubMed Central

    Baumgardner, Lydia Ashleigh; Shanmugam, Avinash Kumar; Lam, Henry; Eng, Jimmy K.; Martin, Daniel B.

    2011-01-01

    Mass spectrometry-based proteomics is a maturing discipline of biologic research that is experiencing substantial growth. Instrumentation has steadily improved over time with the advent of faster and more sensitive instruments collecting ever larger data files. Consequently, the computational process of matching a peptide fragmentation pattern to its sequence, traditionally accomplished by sequence database searching and more recently also by spectral library searching, has become a bottleneck in many mass spectrometry experiments. In both of these methods, the main rate limiting step is the comparison of an acquired spectrum with all potential matches from a spectral library or sequence database. This is a highly parallelizable process because the core computational element can be represented as a simple but arithmetically intense multiplication of two vectors. In this paper we present a proof of concept project taking advantage of the massively parallel computing available on graphics processing units (GPUs) to distribute and accelerate the process of spectral assignment using spectral library searching. This program, which we have named FastPaSS (for Fast Parallelized Spectral Searching) is implemented in CUDA (Compute Unified Device Architecture) from NVIDIA which allows direct access to the processors in an NVIDIA GPU. Our efforts demonstrate the feasibility of GPU computing for spectral assignment, through implementation of the validated spectral searching algorithm SpectraST in the CUDA environment. PMID:21545112

  12. Fast parallel tandem mass spectral library searching using GPU hardware acceleration.

    PubMed

    Baumgardner, Lydia Ashleigh; Shanmugam, Avinash Kumar; Lam, Henry; Eng, Jimmy K; Martin, Daniel B

    2011-06-03

    Mass spectrometry-based proteomics is a maturing discipline of biologic research that is experiencing substantial growth. Instrumentation has steadily improved over time with the advent of faster and more sensitive instruments collecting ever larger data files. Consequently, the computational process of matching a peptide fragmentation pattern to its sequence, traditionally accomplished by sequence database searching and more recently also by spectral library searching, has become a bottleneck in many mass spectrometry experiments. In both of these methods, the main rate-limiting step is the comparison of an acquired spectrum with all potential matches from a spectral library or sequence database. This is a highly parallelizable process because the core computational element can be represented as a simple but arithmetically intense multiplication of two vectors. In this paper, we present a proof of concept project taking advantage of the massively parallel computing available on graphics processing units (GPUs) to distribute and accelerate the process of spectral assignment using spectral library searching. This program, which we have named FastPaSS (for Fast Parallelized Spectral Searching), is implemented in CUDA (Compute Unified Device Architecture) from NVIDIA, which allows direct access to the processors in an NVIDIA GPU. Our efforts demonstrate the feasibility of GPU computing for spectral assignment, through implementation of the validated spectral searching algorithm SpectraST in the CUDA environment.

  13. Effective closed form mathematical approach to determine kinetic constants of NR vulcanized with sulphur and accelerators at different concentrations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Milani, Gabriele, E-mail: milani@stru.polimi.it, E-mail: gabriele.milani@polimi.it; Hanel, Thomas; Donetti, Raffaella

    2015-03-10

    The basic reaction scheme due to Han and co-workers for NR vulcanized with sulphur is adopted and modified taking into account the single contributions of the different accelerators, focusing in particular on some experimental data ad hoc obtained at Pirelli’s laboratories, where NR was vulcanized at different temperatures (from 150 to 180 °C) and concentrations of sulphur, using TBBS and DPG in the mixture as co-agents. Typically, the chain reactions are initiated by the formation of macro-compounds that are responsible of the formation of the unmatured crosslinked polymer. This first reaction depends on the reciprocal concentrations of all components andmore » their chemical nature. In presence of two accelerators, it was considered that the reactions between each single accelerator and the NR raw material occur in parallel, making the reasonable assumption that there are no mutual reactions between the two accelerators. From the kinetic scheme adopted, a closed form solution was found for the crosslink density, with the only limitation that the induction period is excluded from computations. Even kinetic constants are evaluated in closed form, avoiding a numerically demanding least-squares best fitting on rheometer experimental data. Two series of experiments available, relying into rheometer curves at different temperatures and different concentrations of sulphur and accelerator, are utilized to evaluate the fitting capabilities of the mathematical model. Very good agreement between numerical output and experimental data is experienced in all cases analysed.« less

  14. GPU-Acceleration of Sequence Homology Searches with Database Subsequence Clustering.

    PubMed

    Suzuki, Shuji; Kakuta, Masanori; Ishida, Takashi; Akiyama, Yutaka

    2016-01-01

    Sequence homology searches are used in various fields and require large amounts of computation time, especially for metagenomic analysis, owing to the large number of queries and the database size. To accelerate computing analyses, graphics processing units (GPUs) are widely used as a low-cost, high-performance computing platform. Therefore, we mapped the time-consuming steps involved in GHOSTZ, which is a state-of-the-art homology search algorithm for protein sequences, onto a GPU and implemented it as GHOSTZ-GPU. In addition, we optimized memory access for GPU calculations and for communication between the CPU and GPU. As per results of the evaluation test involving metagenomic data, GHOSTZ-GPU with 12 CPU threads and 1 GPU was approximately 3.0- to 4.1-fold faster than GHOSTZ with 12 CPU threads. Moreover, GHOSTZ-GPU with 12 CPU threads and 3 GPUs was approximately 5.8- to 7.7-fold faster than GHOSTZ with 12 CPU threads.

  15. GPU-Acceleration of Sequence Homology Searches with Database Subsequence Clustering

    PubMed Central

    Suzuki, Shuji; Kakuta, Masanori; Ishida, Takashi; Akiyama, Yutaka

    2016-01-01

    Sequence homology searches are used in various fields and require large amounts of computation time, especially for metagenomic analysis, owing to the large number of queries and the database size. To accelerate computing analyses, graphics processing units (GPUs) are widely used as a low-cost, high-performance computing platform. Therefore, we mapped the time-consuming steps involved in GHOSTZ, which is a state-of-the-art homology search algorithm for protein sequences, onto a GPU and implemented it as GHOSTZ-GPU. In addition, we optimized memory access for GPU calculations and for communication between the CPU and GPU. As per results of the evaluation test involving metagenomic data, GHOSTZ-GPU with 12 CPU threads and 1 GPU was approximately 3.0- to 4.1-fold faster than GHOSTZ with 12 CPU threads. Moreover, GHOSTZ-GPU with 12 CPU threads and 3 GPUs was approximately 5.8- to 7.7-fold faster than GHOSTZ with 12 CPU threads. PMID:27482905

  16. Accelerated search for materials with targeted properties by adaptive design

    PubMed Central

    Xue, Dezhen; Balachandran, Prasanna V.; Hogden, John; Theiler, James; Xue, Deqing; Lookman, Turab

    2016-01-01

    Finding new materials with targeted properties has traditionally been guided by intuition, and trial and error. With increasing chemical complexity, the combinatorial possibilities are too large for an Edisonian approach to be practical. Here we show how an adaptive design strategy, tightly coupled with experiments, can accelerate the discovery process by sequentially identifying the next experiments or calculations, to effectively navigate the complex search space. Our strategy uses inference and global optimization to balance the trade-off between exploitation and exploration of the search space. We demonstrate this by finding very low thermal hysteresis (ΔT) NiTi-based shape memory alloys, with Ti50.0Ni46.7Cu0.8Fe2.3Pd0.2 possessing the smallest ΔT (1.84 K). We synthesize and characterize 36 predicted compositions (9 feedback loops) from a potential space of ∼800,000 compositions. Of these, 14 had smaller ΔT than any of the 22 in the original data set. PMID:27079901

  17. Localized saddle-point search and application to temperature-accelerated dynamics

    NASA Astrophysics Data System (ADS)

    Shim, Yunsic; Callahan, Nathan B.; Amar, Jacques G.

    2013-03-01

    We present a method for speeding up temperature-accelerated dynamics (TAD) simulations by carrying out a localized saddle-point (LSAD) search. In this method, instead of using the entire system to determine the energy barriers of activated processes, the calculation is localized by only including a small chunk of atoms around the atoms directly involved in the transition. Using this method, we have obtained N-independent scaling for the computational cost of the saddle-point search as a function of system size N. The error arising from localization is analyzed using a variety of model systems, including a variety of activated processes on Ag(100) and Cu(100) surfaces, as well as multiatom moves in Cu radiation damage and metal heteroepitaxial growth. Our results show significantly improved performance of TAD with the LSAD method, for the case of Ag/Ag(100) annealing and Cu/Cu(100) growth, while maintaining a negligibly small error in energy barriers.

  18. The Research and Test of Fast Radio Burst Real-time Search Algorithm Based on GPU Acceleration

    NASA Astrophysics Data System (ADS)

    Wang, J.; Chen, M. Z.; Pei, X.; Wang, Z. Q.

    2017-03-01

    In order to satisfy the research needs of Nanshan 25 m radio telescope of Xinjiang Astronomical Observatory (XAO) and study the key technology of the planned QiTai radio Telescope (QTT), the receiver group of XAO studied the GPU (Graphics Processing Unit) based real-time FRB searching algorithm which developed from the original FRB searching algorithm based on CPU (Central Processing Unit), and built the FRB real-time searching system. The comparison of the GPU system and the CPU system shows that: on the basis of ensuring the accuracy of the search, the speed of the GPU accelerated algorithm is improved by 35-45 times compared with the CPU algorithm.

  19. Accelerating Smith-Waterman Algorithm for Biological Database Search on CUDA-Compatible GPUs

    NASA Astrophysics Data System (ADS)

    Munekawa, Yuma; Ino, Fumihiko; Hagihara, Kenichi

    This paper presents a fast method capable of accelerating the Smith-Waterman algorithm for biological database search on a cluster of graphics processing units (GPUs). Our method is implemented using compute unified device architecture (CUDA), which is available on the nVIDIA GPU. As compared with previous methods, our method has four major contributions. (1) The method efficiently uses on-chip shared memory to reduce the data amount being transferred between off-chip video memory and processing elements in the GPU. (2) It also reduces the number of data fetches by applying a data reuse technique to query and database sequences. (3) A pipelined method is also implemented to overlap GPU execution with database access. (4) Finally, a master/worker paradigm is employed to accelerate hundreds of database searches on a cluster system. In experiments, the peak performance on a GeForce GTX 280 card reaches 8.32 giga cell updates per second (GCUPS). We also find that our method reduces the amount of data fetches to 1/140, achieving approximately three times higher performance than a previous CUDA-based method. Our 32-node cluster version is approximately 28 times faster than a single GPU version. Furthermore, the effective performance reaches 75.6 giga instructions per second (GIPS) using 32 GeForce 8800 GTX cards.

  20. Intra-dialytic training accelerates oxygen uptake kinetics in hemodialysis patients.

    PubMed

    Reboredo, Maycon M; Neder, J Alberto; Pinheiro, Bruno V; Henrique, Diane Mn; Lovisi, Julio Cm; Paula, Rogério B

    2015-07-01

    End-stage renal disease is associated with several hemodynamic and peripheral muscle abnormalities that could slow the rate of change in oxygen uptake ([Formula: see text]O2) at the onset and at the end of exercise. This study was performed to determine whether an intra-dialytic aerobic training program would speed [Formula: see text]O2 kinetics at the transition to and from moderate and high-intensity exercise. This study was a randomized controlled trial. Twenty-four patients with end-stage renal disease (14 females; 47.0 ± 11.9 years) were randomly assigned to either 12-week cycle ergometer-based training at moderate exertion or a similar control period. At initial and final evaluations, patients underwent 6 min moderate and high-intensity tests to exercise intolerance (Tlim). Training improved Tlim by ∼90% (median (inter-quartile range) = 232 (59) s to 445 (451) s, p < 0.05); in contrast, Tlim decreased by ∼30% in controls (291 (134) s to 202 (131) s). [Formula: see text]O2 kinetics at the onset of moderate-intensity exercise were significantly accelerated with training leading to lower oxygen (O2) deficit (mean ± standard deviation (SD) = 3.2 ± 1.3 l vs 2.3 ± 1.2 l). Similar positive effects were found at the high-intensity test either at the onset of, or recovery from, exercise (p < 0.05). "Excess" [Formula: see text]O2 at the high-intensity test was also lessened with training. Changes in Tlim correlated with faster [Formula: see text]O2 kinetics and lower "excess" [Formula: see text]O2 (Spearman's ρ = -0.56 and -0.75, respectively; p < 0.01). A symptom-targeted intra-dialytic training program improved sub-maximal aerobic metabolism and endurance exercise capacity. [Formula: see text]O2 kinetics are valuable in providing relatively effort-independent information on the efficacy of exercise interventions in this patient population. © The European Society of Cardiology 2014 Reprints and permissions

  1. Algorithmic developments of the kinetic activation-relaxation technique: Accessing long-time kinetics of larger and more complex systems

    NASA Astrophysics Data System (ADS)

    Trochet, Mickaël; Sauvé-Lacoursière, Alecsandre; Mousseau, Normand

    2017-10-01

    In spite of the considerable computer speed increase of the last decades, long-time atomic simulations remain a challenge and most molecular dynamical simulations are limited to 1 μ s at the very best in condensed matter and materials science. There is a need, therefore, for accelerated methods that can bridge the gap between the full dynamical description of molecular dynamics and experimentally relevant time scales. This is the goal of the kinetic Activation-Relaxation Technique (k-ART), an off-lattice kinetic Monte-Carlo method with on-the-fly catalog building capabilities based on the topological tool NAUTY and the open-ended search method Activation-Relaxation Technique (ART nouveau) that has been applied with success to the study of long-time kinetics of complex materials, including grain boundaries, alloys, and amorphous materials. We present a number of recent algorithmic additions, including the use of local force calculation, two-level parallelization, improved topological description, and biased sampling and show how they perform on two applications linked to defect diffusion and relaxation after ion bombardement in Si.

  2. Allosteric activation via kinetic control: Potassium accelerates a conformational change in IMP dehydrogenase†

    PubMed Central

    Riera, Thomas V.; Zheng, Lianqing; Josephine, Helen R.; Min, Donghong; Yang, Wei; Hedstrom, Lizbeth

    2011-01-01

    Allosteric activators are generally believed to shift the equilibrium distribution of enzyme conformations to favor a catalytically productive structure; the kinetics of conformational exchange is seldom addressed. Several observations suggested that the usual allosteric mechanism might not apply to the activation of IMP dehydrogenase (IMPDH) by monovalent cations. Therefore we investigated the mechanism of K+ activation in IMPDH by delineating the kinetic mechanism in the absence of monovalent cations. Surprisingly, the K+-dependence of kcat derives from the rate of flap closure, which increases by ≥65-fold in the presence of K+. We performed both alchemical free energy simulations and potential of mean force calculations using the orthogonal space random walk strategy to computationally analyze how K+ accelerates this conformational change. The simulations recapitulate the preference of IMPDH for K+, validating the computational models. When K+ is replaced with a dummy ion, the residues of the K+ binding site relax into ordered secondary structure, creating a barrier to conformational exchange. K+ mobilizes these residues by providing alternate interactions for the main chain carbonyls. Potential of mean force calculations indicate that K+ changes the shape of the energy well, shrinking the reaction coordinate by shifting the closed conformation toward the open state. This work suggests that allosteric regulation can be under kinetic as well as thermodynamic control. PMID:21870820

  3. Ion acceleration and heating by kinetic Alfvén waves associated with magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Liang, Ji; Lin, Yu; Johnson, Jay R.; Wang, Zheng-Xiong; Wang, Xueyi

    2017-10-01

    Our previous study on the generation and signatures of kinetic Alfvén waves (KAWs) associated with magnetic reconnection in a current sheet revealed that KAWs are a common feature during reconnection [Liang et al. J. Geophys. Res.: Space Phys. 121, 6526 (2016)]. In this paper, ion acceleration and heating by the KAWs generated during magnetic reconnection are investigated with a three-dimensional (3-D) hybrid model. It is found that in the outflow region, a fraction of inflow ions are accelerated by the KAWs generated in the leading bulge region of reconnection, and their parallel velocities gradually increase up to slightly super-Alfvénic. As a result of wave-particle interactions, an accelerated ion beam forms in the direction of the anti-parallel magnetic field, in addition to the core ion population, leading to the development of non-Maxwellian velocity distributions, which include a trapped population with parallel velocities consistent with the wave speed. The ions are heated in both parallel and perpendicular directions. In the parallel direction, the heating results from nonlinear Landau resonance of trapped ions. In the perpendicular direction, however, evidence of stochastic heating by the KAWs is found during the acceleration stage, with an increase of magnetic moment μ. The coherence in the perpendicular ion temperature T⊥ and the perpendicular electric and magnetic fields of KAWs also provides evidence for perpendicular heating by KAWs. The parallel and perpendicular heating of the accelerated beam occur simultaneously, leading to the development of temperature anisotropy with T⊥>T∥ . The heating rate agrees with the damping rate of the KAWs, and the heating is dominated by the accelerated ion beam. In the later stage, with the increase of the fraction of the accelerated ions, interaction between the accelerated beam and the core population also contributes to the ion heating, ultimately leading to overlap of the beams and an overall

  4. Ion acceleration and heating by kinetic Alfvén waves associated with magnetic reconnection

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liang, Ji; Lin, Yu; Johnson, Jay R.

    In a previous study on the generation and signatures of kinetic Alfv en waves (KAWs) associated with magnetic reconnection in a current sheet revealed that KAWs are a common feature during reconnection [Liang et al. J. Geophys. Res.: Space Phys. 121, 6526 (2016)]. In this paper, ion acceleration and heating by the KAWs generated during magnetic reconnection are investigated with a three-dimensional (3-D) hybrid model. It is found that in the outflow region, a fraction of inflow ions are accelerated by the KAWs generated in the leading bulge region of reconnection, and their parallel velocities gradually increase up to slightly super-Alfv enic. As a result of waveparticle interactions, an accelerated ion beam forms in the direction of the anti-parallel magnetic field, in addition to the core ion population, leading to the development of non-Maxwellian velocity distributions, which include a trapped population with parallel velocities consistent with the wave speed. We then heat ions in both parallel and perpendicular directions. In the parallel direction, the heating results from nonlinear Landau resonance of trapped ions. In the perpendicular direction, however, evidence of stochastic heating by the KAWs is found during the acceleration stage, with an increase of magnetic moment μ. The coherence in the T more » $$\\perp$$ ion temperature and the perpendicular electric and magnetic fields of KAWs also provides evidence for perpendicular heating by KAWs. The parallel and perpendicular heating of the accelerated beam occur simultaneously, leading to the development of temperature anisotropy with the perpendicular temperature T $$\\perp$$>T $$\\parallel$$ temperature. The heating rate agrees with the damping rate of the KAWs, and the heating is dominated by the accelerated ion beam. In the later stage, with the increase of the fraction of the accelerated ions, interaction between the accelerated beam and the core population also contributes to the ion heating

  5. Ion acceleration and heating by kinetic Alfvén waves associated with magnetic reconnection

    DOE PAGES

    Liang, Ji; Lin, Yu; Johnson, Jay R.; ...

    2017-09-19

    In a previous study on the generation and signatures of kinetic Alfv en waves (KAWs) associated with magnetic reconnection in a current sheet revealed that KAWs are a common feature during reconnection [Liang et al. J. Geophys. Res.: Space Phys. 121, 6526 (2016)]. In this paper, ion acceleration and heating by the KAWs generated during magnetic reconnection are investigated with a three-dimensional (3-D) hybrid model. It is found that in the outflow region, a fraction of inflow ions are accelerated by the KAWs generated in the leading bulge region of reconnection, and their parallel velocities gradually increase up to slightly super-Alfv enic. As a result of waveparticle interactions, an accelerated ion beam forms in the direction of the anti-parallel magnetic field, in addition to the core ion population, leading to the development of non-Maxwellian velocity distributions, which include a trapped population with parallel velocities consistent with the wave speed. We then heat ions in both parallel and perpendicular directions. In the parallel direction, the heating results from nonlinear Landau resonance of trapped ions. In the perpendicular direction, however, evidence of stochastic heating by the KAWs is found during the acceleration stage, with an increase of magnetic moment μ. The coherence in the T more » $$\\perp$$ ion temperature and the perpendicular electric and magnetic fields of KAWs also provides evidence for perpendicular heating by KAWs. The parallel and perpendicular heating of the accelerated beam occur simultaneously, leading to the development of temperature anisotropy with the perpendicular temperature T $$\\perp$$>T $$\\parallel$$ temperature. The heating rate agrees with the damping rate of the KAWs, and the heating is dominated by the accelerated ion beam. In the later stage, with the increase of the fraction of the accelerated ions, interaction between the accelerated beam and the core population also contributes to the ion heating

  6. Chemical Kinetics Database

    National Institute of Standards and Technology Data Gateway

    SRD 17 NIST Chemical Kinetics Database (Web, free access)   The NIST Chemical Kinetics Database includes essentially all reported kinetics results for thermal gas-phase chemical reactions. The database is designed to be searched for kinetics data based on the specific reactants involved, for reactions resulting in specified products, for all the reactions of a particular species, or for various combinations of these. In addition, the bibliography can be searched by author name or combination of names. The database contains in excess of 38,000 separate reaction records for over 11,700 distinct reactant pairs. These data have been abstracted from over 12,000 papers with literature coverage through early 2000.

  7. Visual search accelerates during adolescence.

    PubMed

    Burggraaf, Rudolf; van der Geest, Jos N; Frens, Maarten A; Hooge, Ignace T C

    2018-05-01

    We studied changes in visual-search performance and behavior during adolescence. Search performance was analyzed in terms of reaction time and response accuracy. Search behavior was analyzed in terms of the objects fixated and the duration of these fixations. A large group of adolescents (N = 140; age: 12-19 years; 47% female, 53% male) participated in a visual-search experiment in which their eye movements were recorded with an eye tracker. The experiment consisted of 144 trials (50% with a target present), and participants had to decide whether a target was present. Each trial showed a search display with 36 Gabor patches placed on a hexagonal grid. The target was a vertically oriented element with a high spatial frequency. Nontargets differed from the target in spatial frequency, orientation, or both. Search performance and behavior changed during adolescence; with increasing age, fixation duration and reaction time decreased. Response accuracy, number of fixations, and selection of elements to fixate upon did not change with age. Thus, the speed of foveal discrimination increases with age, while the efficiency of peripheral selection does not change. We conclude that the way visual information is gathered does not change during adolescence, but the processing of visual information becomes faster.

  8. Accelerating moderately stiff chemical kinetics in reactive-flow simulations using GPUs

    NASA Astrophysics Data System (ADS)

    Niemeyer, Kyle E.; Sung, Chih-Jen

    2014-01-01

    The chemical kinetics ODEs arising from operator-split reactive-flow simulations were solved on GPUs using explicit integration algorithms. Nonstiff chemical kinetics of a hydrogen oxidation mechanism (9 species and 38 irreversible reactions) were computed using the explicit fifth-order Runge-Kutta-Cash-Karp method, and the GPU-accelerated version performed faster than single- and six-core CPU versions by factors of 126 and 25, respectively, for 524,288 ODEs. Moderately stiff kinetics, represented with mechanisms for hydrogen/carbon-monoxide (13 species and 54 irreversible reactions) and methane (53 species and 634 irreversible reactions) oxidation, were computed using the stabilized explicit second-order Runge-Kutta-Chebyshev (RKC) algorithm. The GPU-based RKC implementation demonstrated an increase in performance of nearly 59 and 10 times, for problem sizes consisting of 262,144 ODEs and larger, than the single- and six-core CPU-based RKC algorithms using the hydrogen/carbon-monoxide mechanism. With the methane mechanism, RKC-GPU performed more than 65 and 11 times faster, for problem sizes consisting of 131,072 ODEs and larger, than the single- and six-core RKC-CPU versions, and up to 57 times faster than the six-core CPU-based implicit VODE algorithm on 65,536 ODEs. In the presence of more severe stiffness, such as ethylene oxidation (111 species and 1566 irreversible reactions), RKC-GPU performed more than 17 times faster than RKC-CPU on six cores for 32,768 ODEs and larger, and at best 4.5 times faster than VODE on six CPU cores for 65,536 ODEs. With a larger time step size, RKC-GPU performed at best 2.5 times slower than six-core VODE for 8192 ODEs and larger. Therefore, the need for developing new strategies for integrating stiff chemistry on GPUs was discussed.

  9. Hydrogen-Bond Driven Loop-Closure Kinetics in Unfolded Polypeptide Chains

    PubMed Central

    Daidone, Isabella; Neuweiler, Hannes; Doose, Sören; Sauer, Markus; Smith, Jeremy C.

    2010-01-01

    Characterization of the length dependence of end-to-end loop-closure kinetics in unfolded polypeptide chains provides an understanding of early steps in protein folding. Here, loop-closure in poly-glycine-serine peptides is investigated by combining single-molecule fluorescence spectroscopy with molecular dynamics simulation. For chains containing more than 10 peptide bonds loop-closing rate constants on the 20–100 nanosecond time range exhibit a power-law length dependence. However, this scaling breaks down for shorter peptides, which exhibit slower kinetics arising from a perturbation induced by the dye reporter system used in the experimental setup. The loop-closure kinetics in the longer peptides is found to be determined by the formation of intra-peptide hydrogen bonds and transient β-sheet structure, that accelerate the search for contacts among residues distant in sequence relative to the case of a polypeptide chain in which hydrogen bonds cannot form. Hydrogen-bond-driven polypeptide-chain collapse in unfolded peptides under physiological conditions found here is not only consistent with hierarchical models of protein folding, that highlights the importance of secondary structure formation early in the folding process, but is also shown to speed up the search for productive folding events. PMID:20098498

  10. GPU-accelerated low-latency real-time searches for gravitational waves from compact binary coalescence

    NASA Astrophysics Data System (ADS)

    Liu, Yuan; Du, Zhihui; Chung, Shin Kee; Hooper, Shaun; Blair, David; Wen, Linqing

    2012-12-01

    We present a graphics processing unit (GPU)-accelerated time-domain low-latency algorithm to search for gravitational waves (GWs) from coalescing binaries of compact objects based on the summed parallel infinite impulse response (SPIIR) filtering technique. The aim is to facilitate fast detection of GWs with a minimum delay to allow prompt electromagnetic follow-up observations. To maximize the GPU acceleration, we apply an efficient batched parallel computing model that significantly reduces the number of synchronizations in SPIIR and optimizes the usage of the memory and hardware resource. Our code is tested on the CUDA ‘Fermi’ architecture in a GTX 480 graphics card and its performance is compared with a single core of Intel Core i7 920 (2.67 GHz). A 58-fold speedup is achieved while giving results in close agreement with the CPU implementation. Our result indicates that it is possible to conduct a full search for GWs from compact binary coalescence in real time with only one desktop computer equipped with a Fermi GPU card for the initial LIGO detectors which in the past required more than 100 CPUs.

  11. Accelerated procedure to solve kinetic equation for neutral atoms in a hot plasma

    NASA Astrophysics Data System (ADS)

    Tokar, Mikhail Z.

    2017-12-01

    The recombination of plasma charged components, electrons and ions of hydrogen isotopes, on the wall of a fusion reactor is a source of neutral molecules and atoms, recycling back into the plasma volume. Here neutral species participate, in particular, in charge-exchange (c-x) collisions with the plasma ions and, as a result, atoms of high energies with chaotically directed velocities are generated. Some fraction of these hot atoms hit the wall. Statistical Monte Carlo methods normally used to model c-x atoms are too time consuming for reasonably small level of accident errors and extensive parameter studies are problematic. By applying pass method to evaluate integrals from functions, including the ion velocity distribution, an iteration approach to solve one-dimensional kinetic equation [1], being alternative to Monte Carlo procedure, has been tremendously accelerated, at least by a factor of 30-50 [2]. Here this approach is developed further to solve the 2-D kinetic equation, applied to model the transport of c-x atoms in the vicinity of an opening in the wall, e.g., the entrance of the duct guiding to a diagnostic installation. This is necessary to determine firmly the energy spectrum of c-x atoms penetrating into the duct and to assess the erosion of the installation there. The results of kinetic modeling are compared with those obtained with the diffusion description for c-x atoms, being strictly relevant under plasma conditions of low temperature and high density, where the mean free path length between c-x collisions is much smaller than that till the atom ionization by electrons. It is demonstrated that the previous calculations [3], done with the diffusion approximation for c-x atoms, overestimate the erosion rate of Mo mirrors in a reactor by a factor of 3 compared to the result of the present kinetic study.

  12. Kinetic Simulations of Particle Acceleration at Shocks

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Caprioli, Damiano; Guo, Fan

    2015-07-16

    Collisionless shocks are mediated by collective electromagnetic interactions and are sources of non-thermal particles and emission. The full particle-in-cell approach and a hybrid approach are sketched, simulations of collisionless shocks are shown using a multicolor presentation. Results for SN 1006, a case involving ion acceleration and B field amplification where the shock is parallel, are shown. Electron acceleration takes place in planetary bow shocks and galaxy clusters. It is concluded that acceleration at shocks can be efficient: >15%; CRs amplify B field via streaming instability; ion DSA is efficient at parallel, strong shocks; ions are injected via reflection and shockmore » drift acceleration; and electron DSA is efficient at oblique shocks.« less

  13. Inverse modeling approach for evaluation of kinetic parameters of a biofilm reactor using tabu search.

    PubMed

    Kumar, B Shiva; Venkateswarlu, Ch

    2014-08-01

    The complex nature of biological reactions in biofilm reactors often poses difficulties in analyzing such reactors experimentally. Mathematical models could be very useful for their design and analysis. However, application of biofilm reactor models to practical problems proves somewhat ineffective due to the lack of knowledge of accurate kinetic models and uncertainty in model parameters. In this work, we propose an inverse modeling approach based on tabu search (TS) to estimate the parameters of kinetic and film thickness models. TS is used to estimate these parameters as a consequence of the validation of the mathematical models of the process with the aid of measured data obtained from an experimental fixed-bed anaerobic biofilm reactor involving the treatment of pharmaceutical industry wastewater. The results evaluated for different modeling configurations of varying degrees of complexity illustrate the effectiveness of TS for accurate estimation of kinetic and film thickness model parameters of the biofilm process. The results show that the two-dimensional mathematical model with Edward kinetics (with its optimum parameters as mu(max)rho(s)/Y = 24.57, Ks = 1.352 and Ki = 102.36) and three-parameter film thickness expression (with its estimated parameters as a = 0.289 x 10(-5), b = 1.55 x 10(-4) and c = 15.2 x 10(-6)) better describes the biofilm reactor treating the industry wastewater.

  14. Effects of dimensionality and laser polarization on kinetic simulations of laser-ion acceleration in the transparency regime

    NASA Astrophysics Data System (ADS)

    Stark, David; Yin, Lin; Albright, Brian; Guo, Fan

    2017-10-01

    The often cost-prohibitive nature of three-dimensional (3D) kinetic simulations of laser-plasma interactions has resulted in heavy use of two-dimensional (2D) simulations to extract physics. However, depending on whether the polarization is modeled as 2D-S or 2D-P (laser polarization in and out of the simulation plane, respectively), different results arise. In laser-ion acceleration in the transparency regime, VPIC particle-in-cell simulations show that 2D-S and 2D-P capture different physics that appears in 3D simulations. The electron momentum distribution is virtually two-dimensional in 2D-P, unlike the more isotropic distributions in 2D-S and 3D, leading to greater heating in the simulation plane. As a result, target expansion time scales and density thresholds for the onset of relativistic transparency differ dramatically between 2D-S and 2D-P. The artificial electron heating in 2D-P exaggerates the effectiveness of target-normal sheath acceleration (TNSA) into its dominant acceleration mechanism, whereas 2D-S and 3D both have populations accelerated preferentially during transparency to higher energies than those of TNSA. Funded by the LANL Directed Research and Development Program.

  15. An integrated fingerprinting and kinetic approach to accelerated shelf-life testing of chemical changes in thermally treated carrot puree.

    PubMed

    Kebede, Biniam T; Grauwet, Tara; Magpusao, Johannes; Palmers, Stijn; Michiels, Chris; Hendrickx, Marc; Loey, Ann Van

    2015-07-15

    To have a better understanding of chemical reactions during shelf-life, an integrated analytical and engineering toolbox: "fingerprinting-kinetics" was used. As a case study, a thermally sterilised carrot puree was selected. Sterilised purees were stored at four storage temperatures as a function of time. Fingerprinting enabled selection of volatiles clearly changing during shelf-life. Only these volatiles were identified and studied further. Next, kinetic modelling was performed to investigate the suitability of these volatiles as quality indices (markers) for accelerated shelf-life testing (ASLT). Fingerprinting enabled selection of terpenoids, phenylpropanoids, fatty acid derivatives, Strecker aldehydes and sulphur compounds as volatiles clearly changing during shelf-life. The amount of Strecker aldehydes increased during storage, whereas the rest of the volatiles decreased. Out of the volatiles, based on the applied kinetic modelling, myristicin, α-terpinolene, β-pinene, α-terpineol and octanal were identified as potential markers for ASLT. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Kinetic effects on the transition to relativistic self-induced transparency in laser-driven ion acceleration

    NASA Astrophysics Data System (ADS)

    Siminos, Evangelos; Svedung Wettervik, Benjamin; Grech, Mickael; Fülöp, Tünde

    2016-10-01

    We study kinetic effects responsible for the transition to relativistic self-induced transparency in the interaction of a circularly-polarized laser-pulse with an overdense plasma and their relation to hole-boring and ion acceleration. It is shown, using particle-in-cell simulations and an analysis of separatrices in single-particle phase-space, that this transition is mediated by the complex interplay of fast electron dynamics and ion motion at the initial stage of the interaction. It thus depends on the ion charge-to-mass ratio and can be controlled by varying the laser temporal profile. Moreover, we find a new regime in which a transition from relativistic transparency to hole-boring occurs dynamically during the course of the interaction. It is shown that, for a fixed laser intensity, this dynamic transition regime allows optimal ion acceleration in terms of both energy and energy spread. This work was supported by the Knut and Alice Wallenberg Foundation (pliona project) and the European Research Council (ERC-2014-CoG Grant 647121).

  17. Accelerated damage visualization using binary search with fixed pitch-catch distance laser ultrasonic scanning

    NASA Astrophysics Data System (ADS)

    Park, Byeongjin; Sohn, Hoon

    2017-07-01

    Laser ultrasonic scanning, especially full-field wave propagation imaging, is attractive for damage visualization thanks to its noncontact nature, sensitivity to local damage, and high spatial resolution. However, its practicality is limited because scanning at a high spatial resolution demands a prohibitively long scanning time. Inspired by binary search, an accelerated damage visualization technique is developed to visualize damage with a reduced scanning time. The pitch-catch distance between the excitation point and the sensing point is also fixed during scanning to maintain a high signal-to-noise ratio (SNR) of measured ultrasonic responses. The approximate damage boundary is identified by examining the interactions between ultrasonic waves and damage observed at the scanning points that are sparsely selected by a binary search algorithm. Here, a time-domain laser ultrasonic response is transformed into a spatial ultrasonic domain response using a basis pursuit approach so that the interactions between ultrasonic waves and damage, such as reflections and transmissions, can be better identified in the spatial ultrasonic domain. Then, the area inside the identified damage boundary is visualized as damage. The performance of the proposed damage visualization technique is validated excusing a numerical simulation performed on an aluminum plate with a notch and experiments performed on an aluminum plate with a crack and a wind turbine blade with delamination. The proposed damage visualization technique accelerates the damage visualization process in three aspects: (1) the number of measurements that is necessary for damage visualization is dramatically reduced by a binary search algorithm; (2) the number of averaging that is necessary to achieve a high SNR is reduced by maintaining the wave propagation distance short; and (3) with the proposed technique, the same damage can be identified with a lower spatial resolution than the spatial resolution required by full

  18. Electron beam accelerator with magnetic pulse compression and accelerator switching

    DOEpatents

    Birx, Daniel L.; Reginato, Louis L.

    1988-01-01

    An electron beam accelerator comprising an electron beam generator-injector to produce a focused beam of .gtoreq.0.1 MeV energy electrons; a plurality of substantially identical, aligned accelerator modules to sequentially receive and increase the kinetic energies of the beam electrons by about 0.1-1 MeV per module. Each accelerator module includes a pulse-forming network that delivers a voltage pulse to the module of substantially .gtoreq.0.1-1 MeV maximum energy over a time duration of .ltoreq.1 .mu.sec.

  19. Electron beam accelerator with magnetic pulse compression and accelerator switching

    DOEpatents

    Birx, Daniel L.; Reginato, Louis L.

    1987-01-01

    An electron beam accelerator comprising an electron beam generator-injector to produce a focused beam of .gtoreq.0.1 MeV energy electrons; a plurality of substantially identical, aligned accelerator modules to sequentially receive and increase the kinetic energies of the beam electrons by about 0.1-1 MeV per module. Each accelerator module includes a pulse-forming network that delivers a voltage pulse to the module of substantially 0.1-1 MeV maximum energy over a time duration of .ltoreq.1 .mu.sec.

  20. Accelerated Cure Project for Multiple Sclerosis

    MedlinePlus

    ... main content Accelerating research toward a cure for multiple sclerosis Toggle navigation Search form Search Connect Volunteer Donate ... is to accelerate efforts toward a cure for multiple sclerosis by rapidly advancing research that determines its causes ...

  1. Efficient Synthesis of MCu (M = Pd, Pt, and Au) Aerogels with Accelerated Gelation Kinetics and their High Electrocatalytic Activity.

    PubMed

    Zhu, Chengzhou; Shi, Qiurong; Fu, Shaofang; Song, Junhua; Xia, Haibing; Du, Dan; Lin, Yuehe

    2016-10-01

    To accelerate hydrogel formation and further simplify the synthetic procedure, a series of MCu (M = Pd, Pt, and Au) bimetallic aerogels is synthesized from the in situ reduction of metal precursors through enhancement of the gelation kinetics at elevated temperature. Moreover, the resultant PdCu aerogel with ultrathin nanowire networks exhibits excellent electrocatalytic performance toward ethanol oxidation, holding promise in fuel-cell applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Electron beam accelerator with magnetic pulse compression and accelerator switching

    DOEpatents

    Birx, D.L.; Reginato, L.L.

    1984-03-22

    An electron beam accelerator is described comprising an electron beam generator-injector to produce a focused beam of greater than or equal to .1 MeV energy electrons; a plurality of substantially identical, aligned accelerator modules to sequentially receive and increase the kinetic energies of the beam electron by about .1-1 MeV per module. Each accelerator module includes a pulse-forming network that delivers a voltage pulse to the module of substantially .1-1 MeV maximum energy over a time duration of less than or equal to 1 ..mu..sec.

  3. Enhanced Sampling Methods for the Computation of Conformational Kinetics in Macromolecules

    NASA Astrophysics Data System (ADS)

    Grazioli, Gianmarc

    Calculating the kinetics of conformational changes in macromolecules, such as proteins and nucleic acids, is still very much an open problem in theoretical chemistry and computational biophysics. If it were feasible to run large sets of molecular dynamics trajectories that begin in one configuration and terminate when reaching another configuration of interest, calculating kinetics from molecular dynamics simulations would be simple, but in practice, configuration spaces encompassing all possible configurations for even the simplest of macromolecules are far too vast for such a brute force approach. In fact, many problems related to searches of configuration spaces, such as protein structure prediction, are considered to be NP-hard. Two approaches to addressing this problem are to either develop methods for enhanced sampling of trajectories that confine the search to productive trajectories without loss of temporal information, or coarse-grained methodologies that recast the problem in reduced spaces that can be exhaustively searched. This thesis will begin with a description of work carried out in the vein of the second approach, where a Smoluchowski diffusion equation model was developed that accurately reproduces the rate vs. force relationship observed in the mechano-catalytic disulphide bond cleavage observed in thioredoxin-catalyzed reduction of disulphide bonds. Next, three different novel enhanced sampling methods developed in the vein of the first approach will be described, which can be employed either separately or in conjunction with each other to autonomously define a set of energetically relevant subspaces in configuration space, accelerate trajectories between the interfaces dividing the subspaces while preserving the distribution of unassisted transition times between subspaces, and approximate time correlation functions from the kinetic data collected from the transitions between interfaces.

  4. Self-adaptive enhanced sampling in the energy and trajectory spaces: accelerated thermodynamics and kinetic calculations.

    PubMed

    Gao, Yi Qin

    2008-04-07

    Here, we introduce a simple self-adaptive computational method to enhance the sampling in energy, configuration, and trajectory spaces. The method makes use of two strategies. It first uses a non-Boltzmann distribution method to enhance the sampling in the phase space, in particular, in the configuration space. The application of this method leads to a broad energy distribution in a large energy range and a quickly converged sampling of molecular configurations. In the second stage of simulations, the configuration space of the system is divided into a number of small regions according to preselected collective coordinates. An enhanced sampling of reactive transition paths is then performed in a self-adaptive fashion to accelerate kinetics calculations.

  5. Accelerated Bayesian model-selection and parameter-estimation in continuous gravitational-wave searches with pulsar-timing arrays

    NASA Astrophysics Data System (ADS)

    Taylor, Stephen; Ellis, Justin; Gair, Jonathan

    2014-11-01

    We describe several new techniques which accelerate Bayesian searches for continuous gravitational-wave emission from supermassive black-hole binaries using pulsar-timing arrays. These techniques mitigate the problematic increase of search dimensionality with the size of the pulsar array which arises from having to include an extra parameter per pulsar as the array is expanded. This extra parameter corresponds to searching over the phase of the gravitational wave as it propagates past each pulsar so that we can coherently include the pulsar term in our search strategies. Our techniques make the analysis tractable with powerful evidence-evaluation packages like MultiNest. We find good agreement of our techniques with the parameter-estimation and Bayes factor evaluation performed with full signal templates and conclude that these techniques make excellent first-cut tools for detection and characterization of continuous gravitational-wave signals with pulsar-timing arrays. Crucially, at low to moderate signal-to-noise ratios the factor by which the analysis is sped up can be ≳100 , permitting rigorous programs of systematic injection and recovery of signals to establish robust detection criteria within a Bayesian formalism.

  6. Electron acceleration and kinetic energy tailoring via ultrafast terahertz fields.

    PubMed

    Greig, S R; Elezzabi, A Y

    2014-11-17

    We propose a mechanism for tuning the kinetic energy of surface plasmon generated electron pulses through control of the time delay between a pair of externally applied terahertz pulses. Varying the time delay results in translation, compression, and broadening of the kinetic energy spectrum of the generated electron pulse. We also observe that the electrons' kinetic energy dependence on the carrier envelope phase of the surface plasmon is preserved under the influence of a terahertz electric field.

  7. Potential role of DNA methylation as a facilitator of target search processes for transcription factors through interplay with methyl-CpG-binding proteins

    PubMed Central

    Kemme, Catherine A.; Marquez, Rolando; Luu, Ross H.

    2017-01-01

    Abstract Eukaryotic genomes contain numerous non-functional high-affinity sequences for transcription factors. These sequences potentially serve as natural decoys that sequester transcription factors. We have previously shown that the presence of sequences similar to the target sequence could substantially impede association of the transcription factor Egr-1 with its targets. In this study, using a stopped-flow fluorescence method, we examined the kinetic impact of DNA methylation of decoys on the search process of the Egr-1 zinc-finger protein. We analyzed its association with an unmethylated target site on fluorescence-labeled DNA in the presence of competitor DNA duplexes, including Egr-1 decoys. DNA methylation of decoys alone did not affect target search kinetics. In the presence of the MeCP2 methyl-CpG-binding domain (MBD), however, DNA methylation of decoys substantially (∼10-30-fold) accelerated the target search process of the Egr-1 zinc-finger protein. This acceleration did not occur when the target was also methylated. These results suggest that when decoys are methylated, MBD proteins can block them and thereby allow Egr-1 to avoid sequestration in non-functional locations. This effect may occur in vivo for DNA methylation outside CpG islands (CGIs) and could facilitate localization of some transcription factors within regulatory CGIs, where DNA methylation is rare. PMID:28486614

  8. Accelerated defect visualization of microelectronic systems using binary search with fixed pitch-catch distance laser ultrasonic scanning

    NASA Astrophysics Data System (ADS)

    Park, Byeongjin; Sohn, Hoon

    2018-04-01

    The practicality of laser ultrasonic scanning is limited because scanning at a high spatial resolution demands a prohibitively long scanning time. Inspired by binary search, an accelerated defect visualization technique is developed to visualize defect with a reduced scanning time. The pitch-catch distance between the excitation point and the sensing point is also fixed during scanning to maintain a high signal-to-noise ratio of measured ultrasonic responses. The approximate defect boundary is identified by examining the interactions between ultrasonic waves and defect observed at the scanning points that are sparsely selected by a binary search algorithm. Here, a time-domain laser ultrasonic response is transformed into a spatial ultrasonic domain response using a basis pursuit approach so that the interactions between ultrasonic waves and defect can be better identified in the spatial ultrasonic domain. Then, the area inside the identified defect boundary is visualized as defect. The performance of the proposed defect visualization technique is validated through an experiment on a semiconductor chip. The proposed defect visualization technique accelerates the defect visualization process in three aspects: (1) The number of measurements that is necessary for defect visualization is dramatically reduced by a binary search algorithm; (2) The number of averaging that is necessary to achieve a high signal-to-noise ratio is reduced by maintaining the wave propagation distance short; and (3) With the proposed technique, defect can be identified with a lower spatial resolution than the spatial resolution required by full-field wave propagation imaging.

  9. A new class of accelerated kinetic Monte Carlo algorithms

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bulatov, V V; Oppelstrup, T; Athenes, M

    2011-11-30

    have been subsequently proposed in [refs] but applied in a different context. The most serious deficiency of the earlier methods is that size of the trapping cluster size is fixed and often too small to bring substantial simulation speedup. Furthermore, the overhead associated with solving for the probability distribution on the trapping cluster sometimes makes such simulations less efficient than the standard KMC. Here we report on a general and exact accelerated kinetic Monte Carlo algorithm generally applicable to arbitrary Markov models1. Two different implementations are attempted both based on incremental expansion of trapping sub-set of Markov states: (1) numerical solution of the Master Equation with absorbing states and (2) incremental graph reduction followed by randomization. Of the two implementations, the 2nd one performs better allowing, for the first time, to overcome trapping basins spanning several million Markov states. The new method is used for simulations of anomalous diffusion on a 2D substrate and of the kinetics of diffusive 1st order phase transformations in binary alloys. Depending on temperature and (alloy) super-saturation conditions, speedups of 3 to 7 orders of magnitude are demonstrated, with no compromise of simulation accuracy.« less

  10. Acceleration and sensitivity analysis of lattice kinetic Monte Carlo simulations using parallel processing and rate constant rescaling

    NASA Astrophysics Data System (ADS)

    Núñez, M.; Robie, T.; Vlachos, D. G.

    2017-10-01

    Kinetic Monte Carlo (KMC) simulation provides insights into catalytic reactions unobtainable with either experiments or mean-field microkinetic models. Sensitivity analysis of KMC models assesses the robustness of the predictions to parametric perturbations and identifies rate determining steps in a chemical reaction network. Stiffness in the chemical reaction network, a ubiquitous feature, demands lengthy run times for KMC models and renders efficient sensitivity analysis based on the likelihood ratio method unusable. We address the challenge of efficiently conducting KMC simulations and performing accurate sensitivity analysis in systems with unknown time scales by employing two acceleration techniques: rate constant rescaling and parallel processing. We develop statistical criteria that ensure sufficient sampling of non-equilibrium steady state conditions. Our approach provides the twofold benefit of accelerating the simulation itself and enabling likelihood ratio sensitivity analysis, which provides further speedup relative to finite difference sensitivity analysis. As a result, the likelihood ratio method can be applied to real chemistry. We apply our methodology to the water-gas shift reaction on Pt(111).

  11. Searches for magnetic monopoles with IceCube

    NASA Astrophysics Data System (ADS)

    Pollmann, Anna

    2018-01-01

    Particles that carry a magnetic monopole charge are proposed by various theories which go beyond the Standard Model of particle physics. The expected mass of magnetic monopoles varies depending on the theory describing its origin, generally the monopole mass far exceeds those which can be created at accelerators. Magnetic monopoles gain kinetic energy in large scale galactic magnetic fields and, depending on their mass, can obtain relativistic velocities. IceCube is a high energy neutrino detector using the clear ice at the South Pole as a detection medium. As monopoles pass through this ice they produce optical light by a variety of mechanisms. With increasing velocity, they produce light by catalysis of baryon decay, luminescence in the ice associated with electronic excitations, indirect and direct Cherenkov light from the monopole track, and Cherenkov light from cascades induced by pair creation and photonuclear reactions. By searching for this light, current best limits for the monopole flux over a broad range of velocities was achieved using the IceCube detector. A review of these magnetic monopole searches is presented.

  12. On-the-fly transition search and applications to temperature-accelerated dynamics

    NASA Astrophysics Data System (ADS)

    Shim, Yunsic; Amar, Jacques

    2015-03-01

    Temperature-accelerated dynamics (TAD) is a powerful method to study non-equilibrium processes and has been providing surprising insights for a variety of systems. While serial TAD simulations have been limited by the roughly N3 increase in the computational cost as a function of the number of atoms N in the system, recently we have shown that by carrying out parallel TAD simulations which combine spatial decomposition with our semi-rigorous synchronous sublattice algorithm, significantly improved scaling is possible. However, in this approach the size of activated events is limited by the processor size while the dynamics is not exact. Here we discuss progress in improving the scaling of serial TAD by combining the use of on-the-fly transition searching with our previously developed localized saddle-point method. We demonstrate improved performance for the cases of Ag/Ag(100) annealing and Cu/Cu(100) growth. Supported by NSF DMR-1410840.

  13. Application of Chemical Kinetics to Deterioration of Foods.

    ERIC Educational Resources Information Center

    Labuza, T. P.

    1984-01-01

    Possible modes of food deterioration (such as microbial decay, nonenzymatic browning, senescence, lipid oxidation) are reviewed. A basic mathematical approach to the kinetics of food deterioration, kinetic approach to accelerating shelf-life deterioration, and shelf-life predictions are discussed. (JN)

  14. Accurate acceleration of kinetic Monte Carlo simulations through the modification of rate constants.

    PubMed

    Chatterjee, Abhijit; Voter, Arthur F

    2010-05-21

    We present a novel computational algorithm called the accelerated superbasin kinetic Monte Carlo (AS-KMC) method that enables a more efficient study of rare-event dynamics than the standard KMC method while maintaining control over the error. In AS-KMC, the rate constants for processes that are observed many times are lowered during the course of a simulation. As a result, rare processes are observed more frequently than in KMC and the time progresses faster. We first derive error estimates for AS-KMC when the rate constants are modified. These error estimates are next employed to develop a procedure for lowering process rates with control over the maximum error. Finally, numerical calculations are performed to demonstrate that the AS-KMC method captures the correct dynamics, while providing significant CPU savings over KMC in most cases. We show that the AS-KMC method can be employed with any KMC model, even when no time scale separation is present (although in such cases no computational speed-up is observed), without requiring the knowledge of various time scales present in the system.

  15. Potential role of DNA methylation as a facilitator of target search processes for transcription factors through interplay with methyl-CpG-binding proteins.

    PubMed

    Kemme, Catherine A; Marquez, Rolando; Luu, Ross H; Iwahara, Junji

    2017-07-27

    Eukaryotic genomes contain numerous non-functional high-affinity sequences for transcription factors. These sequences potentially serve as natural decoys that sequester transcription factors. We have previously shown that the presence of sequences similar to the target sequence could substantially impede association of the transcription factor Egr-1 with its targets. In this study, using a stopped-flow fluorescence method, we examined the kinetic impact of DNA methylation of decoys on the search process of the Egr-1 zinc-finger protein. We analyzed its association with an unmethylated target site on fluorescence-labeled DNA in the presence of competitor DNA duplexes, including Egr-1 decoys. DNA methylation of decoys alone did not affect target search kinetics. In the presence of the MeCP2 methyl-CpG-binding domain (MBD), however, DNA methylation of decoys substantially (∼10-30-fold) accelerated the target search process of the Egr-1 zinc-finger protein. This acceleration did not occur when the target was also methylated. These results suggest that when decoys are methylated, MBD proteins can block them and thereby allow Egr-1 to avoid sequestration in non-functional locations. This effect may occur in vivo for DNA methylation outside CpG islands (CGIs) and could facilitate localization of some transcription factors within regulatory CGIs, where DNA methylation is rare. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  16. BRENDA in 2013: integrated reactions, kinetic data, enzyme function data, improved disease classification: new options and contents in BRENDA.

    PubMed

    Schomburg, Ida; Chang, Antje; Placzek, Sandra; Söhngen, Carola; Rother, Michael; Lang, Maren; Munaretto, Cornelia; Ulas, Susanne; Stelzer, Michael; Grote, Andreas; Scheer, Maurice; Schomburg, Dietmar

    2013-01-01

    The BRENDA (BRaunschweig ENzyme DAtabase) enzyme portal (http://www.brenda-enzymes.org) is the main information system of functional biochemical and molecular enzyme data and provides access to seven interconnected databases. BRENDA contains 2.7 million manually annotated data on enzyme occurrence, function, kinetics and molecular properties. Each entry is connected to a reference and the source organism. Enzyme ligands are stored with their structures and can be accessed via their names, synonyms or via a structure search. FRENDA (Full Reference ENzyme DAta) and AMENDA (Automatic Mining of ENzyme DAta) are based on text mining methods and represent a complete survey of PubMed abstracts with information on enzymes in different organisms, tissues or organelles. The supplemental database DRENDA provides more than 910 000 new EC number-disease relations in more than 510 000 references from automatic search and a classification of enzyme-disease-related information. KENDA (Kinetic ENzyme DAta), a new amendment extracts and displays kinetic values from PubMed abstracts. The integration of the EnzymeDetector offers an automatic comparison, evaluation and prediction of enzyme function annotations for prokaryotic genomes. The biochemical reaction database BKM-react contains non-redundant enzyme-catalysed and spontaneous reactions and was developed to facilitate and accelerate the construction of biochemical models.

  17. Particle Acceleration and Heating Processes at the Dayside Magnetopause

    NASA Astrophysics Data System (ADS)

    Berchem, J.; Lapenta, G.; Richard, R. L.; El-Alaoui, M.; Walker, R. J.; Schriver, D.

    2017-12-01

    It is well established that electrons and ions are accelerated and heated during magnetic reconnection at the dayside magnetopause. However, a detailed description of the actual physical mechanisms driving these processes and where they are operating is still incomplete. Many basic mechanisms are known to accelerate particles, including resonant wave-particle interactions as well as stochastic, Fermi, and betatron acceleration. In addition, acceleration and heating processes can occur over different scales. We have carried out kinetic simulations to investigate the mechanisms by which electrons and ions are accelerated and heated at the dayside magnetopause. The simulation model uses the results of global magnetohydrodynamic (MHD) simulations to set the initial state and the evolving boundary conditions of fully kinetic implicit particle-in-cell (iPic3D) simulations for different solar wind and interplanetary magnetic field conditions. This approach allows us to include large domains both in space and energy. In particular, some of these regional simulations include both the magnetopause and bow shock in the kinetic domain, encompassing range of particle energies from a few eV in the solar wind to keV in the magnetospheric boundary layer. We analyze the results of the iPic3D simulations by discussing wave spectra and particle velocity distribution functions observed in the different regions of the simulation domain, as well as using large-scale kinetic (LSK) computations to follow particles' time histories. We discuss the relevance of our results by comparing them with local observations by the MMS spacecraft.

  18. Accelerated Simulation of Kinetic Transport Using Variational Principles and Sparsity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Caflisch, Russel

    This project is centered on the development and application of techniques of sparsity and compressed sensing for variational principles, PDEs and physics problems, in particular for kinetic transport. This included derivation of sparse modes for elliptic and parabolic problems coming from variational principles. The research results of this project are on methods for sparsity in differential equations and their applications and on application of sparsity ideas to kinetic transport of plasmas.

  19. Pulsed electromagnetic gas acceleration

    NASA Technical Reports Server (NTRS)

    Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

    1971-01-01

    Experimental data were combined with one-dimensional conservation relations to yield information on the energy deposition ratio in a parallel-plate accelerator, where the downstream flow was confined to a constant area channel. Approximately 70% of the total input power was detected in the exhaust flow, of which only about 20% appeared as directed kinetic energy, thus implying that a downstream expansion to convert chamber enthalpy into kinetic energy must be an important aspect of conventional high power MPD arcs. Spectroscopic experiments on a quasi-steady MPD argon accelerator verified the presence of A(III) and the absence of A(I), and indicated an azimuthal structure in the jet related to the mass injection locations. Measurements of pressure in the arc chamber and impact pressure in the exhaust jet using a piezocrystal backed by a Plexiglas rod were in good agreement with the electromagnetic thrust model.

  20. Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators

    DOE PAGES

    O’Shea, B. D.; Andonian, G.; Barber, S. K.; ...

    2016-09-14

    There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m –1) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m –1 using a dielectric wakefield accelerator of 15 cmmore » length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m –1. As a result, both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons.« less

  1. Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators

    PubMed Central

    O'Shea, B. D.; Andonian, G.; Barber, S. K.; Fitzmorris, K. L.; Hakimi, S.; Harrison, J.; Hoang, P. D.; Hogan, M. J.; Naranjo, B.; Williams, O. B.; Yakimenko, V.; Rosenzweig, J. B.

    2016-01-01

    There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m−1) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m−1 using a dielectric wakefield accelerator of 15 cm length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m−1. Both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons. PMID:27624348

  2. Assessment of mean-field microkinetic models for CO methanation on stepped metal surfaces using accelerated kinetic Monte Carlo

    NASA Astrophysics Data System (ADS)

    Andersen, Mie; Plaisance, Craig P.; Reuter, Karsten

    2017-10-01

    First-principles screening studies aimed at predicting the catalytic activity of transition metal (TM) catalysts have traditionally been based on mean-field (MF) microkinetic models, which neglect the effect of spatial correlations in the adsorbate layer. Here we critically assess the accuracy of such models for the specific case of CO methanation over stepped metals by comparing to spatially resolved kinetic Monte Carlo (kMC) simulations. We find that the typical low diffusion barriers offered by metal surfaces can be significantly increased at step sites, which results in persisting correlations in the adsorbate layer. As a consequence, MF models may overestimate the catalytic activity of TM catalysts by several orders of magnitude. The potential higher accuracy of kMC models comes at a higher computational cost, which can be especially challenging for surface reactions on metals due to a large disparity in the time scales of different processes. In order to overcome this issue, we implement and test a recently developed algorithm for achieving temporal acceleration of kMC simulations. While the algorithm overall performs quite well, we identify some challenging cases which may lead to a breakdown of acceleration algorithms and discuss possible directions for future algorithm development.

  3. Disclosure of the oscillations in kinetics of the reactor pressure vessel steel damage at fast neutron intensity decreasing

    NASA Astrophysics Data System (ADS)

    Krasikov, E.; Nikolaenko, V.

    2017-01-01

    Fast neutron intensity influence on reactor materials radiation damage is a critically important question in the problem of the correct use of the accelerated irradiation tests data for substantiation of the materials workability in real irradiation conditions that is low neutron intensity. Investigations of the fast neutron intensity (flux) influence on radiation damage and experimental data scattering reveal the existence of non-monotonous sections in kinetics of the reactor pressure vessels (RPV) steel damage. Discovery of the oscillations as indicator of the self-organization processes presence give reasons for new ways searching on reactor pressure vessel (RPV) steel radiation stability increasing and attempt of the self-restoring metal elaboration. Revealing of the wavelike process in the form of non monotonous parts of the kinetics of radiation embrittlement testifies that periodic transformation of the structure take place. This fact actualizes the problem of more precise definition of the RPV materials radiation embrittlement mechanisms and gives reasons for search of the ways to manage the radiation stability (nanostructuring and so on to stimulate the radiation defects annihilation), development of the means for creating of more stableness self recovering smart materials.

  4. An improved hybrid of particle swarm optimization and the gravitational search algorithm to produce a kinetic parameter estimation of aspartate biochemical pathways.

    PubMed

    Ismail, Ahmad Muhaimin; Mohamad, Mohd Saberi; Abdul Majid, Hairudin; Abas, Khairul Hamimah; Deris, Safaai; Zaki, Nazar; Mohd Hashim, Siti Zaiton; Ibrahim, Zuwairie; Remli, Muhammad Akmal

    2017-12-01

    Mathematical modelling is fundamental to understand the dynamic behavior and regulation of the biochemical metabolisms and pathways that are found in biological systems. Pathways are used to describe complex processes that involve many parameters. It is important to have an accurate and complete set of parameters that describe the characteristics of a given model. However, measuring these parameters is typically difficult and even impossible in some cases. Furthermore, the experimental data are often incomplete and also suffer from experimental noise. These shortcomings make it challenging to identify the best-fit parameters that can represent the actual biological processes involved in biological systems. Computational approaches are required to estimate these parameters. The estimation is converted into multimodal optimization problems that require a global optimization algorithm that can avoid local solutions. These local solutions can lead to a bad fit when calibrating with a model. Although the model itself can potentially match a set of experimental data, a high-performance estimation algorithm is required to improve the quality of the solutions. This paper describes an improved hybrid of particle swarm optimization and the gravitational search algorithm (IPSOGSA) to improve the efficiency of a global optimum (the best set of kinetic parameter values) search. The findings suggest that the proposed algorithm is capable of narrowing down the search space by exploiting the feasible solution areas. Hence, the proposed algorithm is able to achieve a near-optimal set of parameters at a fast convergence speed. The proposed algorithm was tested and evaluated based on two aspartate pathways that were obtained from the BioModels Database. The results show that the proposed algorithm outperformed other standard optimization algorithms in terms of accuracy and near-optimal kinetic parameter estimation. Nevertheless, the proposed algorithm is only expected to work well in

  5. Study of muon-induced neutron production using accelerator muon beam at CERN

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nakajima, Y.; Lin, C. J.; Ochoa-Ricoux, J. P.

    2015-08-17

    Cosmogenic muon-induced neutrons are one of the most problematic backgrounds for various underground experiments for rare event searches. In order to accurately understand such backgrounds, experimental data with high-statistics and well-controlled systematics is essential. We performed a test experiment to measure muon-induced neutron production yield and energy spectrum using a high-energy accelerator muon beam at CERN. We successfully observed neutrons from 160 GeV/c muon interaction on lead, and measured kinetic energy distributions for various production angles. Works towards evaluation of absolute neutron production yield is underway. This work also demonstrates that the setup is feasible for a future large-scale experimentmore » for more comprehensive study of muon-induced neutron production.« less

  6. Influence of quasi-specific sites on kinetics of target DNA search by a sequence-specific DNA-binding protein.

    PubMed

    Kemme, Catherine A; Esadze, Alexandre; Iwahara, Junji

    2015-11-10

    Functions of transcription factors require formation of specific complexes at particular sites in cis-regulatory elements of genes. However, chromosomal DNA contains numerous sites that are similar to the target sequences recognized by transcription factors. The influence of such "quasi-specific" sites on functions of the transcription factors is not well understood at present by experimental means. In this work, using fluorescence methods, we have investigated the influence of quasi-specific DNA sites on the efficiency of target location by the zinc finger DNA-binding domain of the inducible transcription factor Egr-1, which recognizes a 9 bp sequence. By stopped-flow assays, we measured the kinetics of Egr-1's association with a target site on 143 bp DNA in the presence of various competitor DNAs, including nonspecific and quasi-specific sites. The presence of quasi-specific sites on competitor DNA significantly decelerated the target association by the Egr-1 protein. The impact of the quasi-specific sites depended strongly on their affinity, their concentration, and the degree of their binding to the protein. To quantitatively describe the kinetic impact of the quasi-specific sites, we derived an analytical form of the apparent kinetic rate constant for the target association and used it for fitting to the experimental data. Our kinetic data with calf thymus DNA as a competitor suggested that there are millions of high-affinity quasi-specific sites for Egr-1 among the 3 billion bp of genomic DNA. This study quantitatively demonstrates that naturally abundant quasi-specific sites on DNA can considerably impede the target search processes of sequence-specific DNA-binding proteins.

  7. Influence of Quasi-Specific Sites on Kinetics of Target DNA Search by a Sequence-Specific DNA-Binding Protein

    PubMed Central

    2015-01-01

    Functions of transcription factors require formation of specific complexes at particular sites in cis-regulatory elements of genes. However, chromosomal DNA contains numerous sites that are similar to the target sequences recognized by transcription factors. The influence of such “quasi-specific” sites on functions of the transcription factors is not well understood at present by experimental means. In this work, using fluorescence methods, we have investigated the influence of quasi-specific DNA sites on the efficiency of target location by the zinc finger DNA-binding domain of the inducible transcription factor Egr-1, which recognizes a 9 bp sequence. By stopped-flow assays, we measured the kinetics of Egr-1’s association with a target site on 143 bp DNA in the presence of various competitor DNAs, including nonspecific and quasi-specific sites. The presence of quasi-specific sites on competitor DNA significantly decelerated the target association by the Egr-1 protein. The impact of the quasi-specific sites depended strongly on their affinity, their concentration, and the degree of their binding to the protein. To quantitatively describe the kinetic impact of the quasi-specific sites, we derived an analytical form of the apparent kinetic rate constant for the target association and used it for fitting to the experimental data. Our kinetic data with calf thymus DNA as a competitor suggested that there are millions of high-affinity quasi-specific sites for Egr-1 among the 3 billion bp of genomic DNA. This study quantitatively demonstrates that naturally abundant quasi-specific sites on DNA can considerably impede the target search processes of sequence-specific DNA-binding proteins. PMID:26502071

  8. Dusty-Plasma Particle Accelerator

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2005-01-01

    A dusty-plasma apparatus is being investigated as means of accelerating nanometer- and micrometer-sized particles. Applications for the dusty-plasma particle accelerators fall into two classes: Simulation of a variety of rapidly moving dust particles and micrometeoroids in outer-space environments that include micrometeoroid streams, comet tails, planetary rings, and nebulae and Deposition or implantation of nanoparticles on substrates for diverse industrial purposes that could include hardening, increasing thermal insulation, altering optical properties, and/or increasing permittivities of substrate materials. Relative to prior apparatuses used for similar applications, dusty-plasma particle accelerators offer such potential advantages as smaller size, lower cost, less complexity, and increased particle flux densities. A dusty-plasma particle accelerator exploits the fact that an isolated particle immersed in plasma acquires a net electric charge that depends on the relative mobilities of electrons and ions. Typically, a particle that is immersed in a low-temperature, partially ionized gas, wherein the average kinetic energy of electrons exceeds that of ions, causes the particle to become negatively charged. The particle can then be accelerated by applying an appropriate electric field. A dusty-plasma particle accelerator (see figure) includes a plasma source such as a radio-frequency induction discharge apparatus containing (1) a shallow cup with a biasable electrode to hold the particles to be accelerated and (2) a holder for the substrate on which the particles are to impinge. Depending on the specific design, a pair of electrostatic-acceleration grids between the substrate and discharge plasma can be used to both collimate and further accelerate particles exiting the particle holder. Once exposed to the discharge plasma, the particles in the cup quickly acquire a negative charge. Application of a negative voltage pulse to the biasable electrode results in the

  9. Kinetic and finite ion mass effects on the transition to relativistic self-induced transparency in laser-driven ion acceleration

    NASA Astrophysics Data System (ADS)

    Siminos, E.; Grech, M.; Svedung Wettervik, B.; Fülöp, T.

    2017-12-01

    We study kinetic effects responsible for the transition to relativistic self-induced transparency in the interaction of a circularly-polarized laser-pulse with an overdense plasma and their relation to hole-boring (HB) and ion acceleration. It is demonstrated using particle-in-cell simulations and an analysis of separatrices in single-electron phase-space, that ion motion can suppress fast electron escape to the vacuum, which would otherwise lead to transition to the relativistic transparency regime. A simple analytical estimate shows that for large laser pulse amplitude a 0 the time scale over which ion motion becomes important is much shorter than usually anticipated. As a result of enhanced ion mobility, the threshold density above which HB occurs decreases with the charge-to-mass ratio. Moreover, the transition threshold is seen to depend on the laser temporal profile, due to the effect that the latter has on electron heating. Finally, we report a new regime in which a transition from relativistic transparency to HB occurs dynamically during the course of the interaction. It is shown that, for a fixed laser intensity, this dynamic transition regime allows optimal ion acceleration in terms of both energy and energy spread.

  10. Theory of bimolecular reactions in a solution with linear traps: Application to the problem of target search on DNA.

    PubMed

    Turkin, Alexander; van Oijen, Antoine M; Turkin, Anatoliy A

    2015-01-01

    One-dimensional sliding along DNA as a means to accelerate protein target search is a well-known phenomenon occurring in various biological systems. Using a biomimetic approach, we have recently demonstrated the practical use of DNA-sliding peptides to speed up bimolecular reactions more than an order of magnitude by allowing the reactants to associate not only in the solution by three-dimensional (3D) diffusion, but also on DNA via one-dimensional (1D) diffusion [A. Turkin et al., Chem. Sci. (2015)]. Here we present a mean-field kinetic model of a bimolecular reaction in a solution with linear extended sinks (e.g., DNA) that can intermittently trap molecules present in a solution. The model consists of chemical rate equations for mean concentrations of reacting species. Our model demonstrates that addition of linear traps to the solution can significantly accelerate reactant association. We show that at optimum concentrations of linear traps the 1D reaction pathway dominates in the kinetics of the bimolecular reaction; i.e., these 1D traps function as an assembly line of the reaction product. Moreover, we show that the association reaction on linear sinks between trapped reactants exhibits a nonclassical third-order behavior. Predictions of the model agree well with our experimental observations. Our model provides a general description of bimolecular reactions that are controlled by a combined 3D+1D mechanism and can be used to quantitatively describe both naturally occurring as well as biomimetic biochemical systems that reduce the dimensionality of search.

  11. Efficient search, mapping, and optimization of multi-protein genetic systems in diverse bacteria

    PubMed Central

    Farasat, Iman; Kushwaha, Manish; Collens, Jason; Easterbrook, Michael; Guido, Matthew; Salis, Howard M

    2014-01-01

    Developing predictive models of multi-protein genetic systems to understand and optimize their behavior remains a combinatorial challenge, particularly when measurement throughput is limited. We developed a computational approach to build predictive models and identify optimal sequences and expression levels, while circumventing combinatorial explosion. Maximally informative genetic system variants were first designed by the RBS Library Calculator, an algorithm to design sequences for efficiently searching a multi-protein expression space across a > 10,000-fold range with tailored search parameters and well-predicted translation rates. We validated the algorithm's predictions by characterizing 646 genetic system variants, encoded in plasmids and genomes, expressed in six gram-positive and gram-negative bacterial hosts. We then combined the search algorithm with system-level kinetic modeling, requiring the construction and characterization of 73 variants to build a sequence-expression-activity map (SEAMAP) for a biosynthesis pathway. Using model predictions, we designed and characterized 47 additional pathway variants to navigate its activity space, find optimal expression regions with desired activity response curves, and relieve rate-limiting steps in metabolism. Creating sequence-expression-activity maps accelerates the optimization of many protein systems and allows previous measurements to quantitatively inform future designs. PMID:24952589

  12. Large-scale particle acceleration by magnetic reconnection during solar flares

    NASA Astrophysics Data System (ADS)

    Li, X.; Guo, F.; Li, H.; Li, G.; Li, S.

    2017-12-01

    Magnetic reconnection that triggers explosive magnetic energy release has been widely invoked to explain the large-scale particle acceleration during solar flares. While great efforts have been spent in studying the acceleration mechanism in small-scale kinetic simulations, there have been rare studies that make predictions to acceleration in the large scale comparable to the flare reconnection region. Here we present a new arrangement to study this problem. We solve the large-scale energetic-particle transport equation in the fluid velocity and magnetic fields from high-Lundquist-number MHD simulations of reconnection layers. This approach is based on examining the dominant acceleration mechanism and pitch-angle scattering in kinetic simulations. Due to the fluid compression in reconnection outflows and merging magnetic islands, particles are accelerated to high energies and develop power-law energy distributions. We find that the acceleration efficiency and power-law index depend critically on upstream plasma beta and the magnitude of guide field (the magnetic field component perpendicular to the reconnecting component) as they influence the compressibility of the reconnection layer. We also find that the accelerated high-energy particles are mostly concentrated in large magnetic islands, making the islands a source of energetic particles and high-energy emissions. These findings may provide explanations for acceleration process in large-scale magnetic reconnection during solar flares and the temporal and spatial emission properties observed in different flare events.

  13. A prospectus on kinetic heliophysics

    NASA Astrophysics Data System (ADS)

    Howes, Gregory G.

    2017-05-01

    Under the low density and high temperature conditions typical of heliospheric plasmas, the macroscopic evolution of the heliosphere is strongly affected by the kinetic plasma physics governing fundamental microphysical mechanisms. Kinetic turbulence, collisionless magnetic reconnection, particle acceleration, and kinetic instabilities are four poorly understood, grand-challenge problems that lie at the new frontier of kinetic heliophysics. The increasing availability of high cadence and high phase-space resolution measurements of particle velocity distributions by current and upcoming spacecraft missions and of massively parallel nonlinear kinetic simulations of weakly collisional heliospheric plasmas provides the opportunity to transform our understanding of these kinetic mechanisms through the full utilization of the information contained in the particle velocity distributions. Several major considerations for future investigations of kinetic heliophysics are examined. Turbulent dissipation followed by particle heating is highlighted as an inherently two-step process in weakly collisional plasmas, distinct from the more familiar case in fluid theory. Concerted efforts must be made to tackle the big-data challenge of visualizing the high-dimensional (3D-3V) phase space of kinetic plasma theory through physics-based reductions. Furthermore, the development of innovative analysis methods that utilize full velocity-space measurements, such as the field-particle correlation technique, will enable us to gain deeper insight into these four grand-challenge problems of kinetic heliophysics. A systems approach to tackle the multi-scale problem of heliophysics through a rigorous connection between the kinetic physics at microscales and the self-consistent evolution of the heliosphere at macroscales will propel the field of kinetic heliophysics into the future.

  14. A prospectus on kinetic heliophysics

    PubMed Central

    2017-01-01

    Under the low density and high temperature conditions typical of heliospheric plasmas, the macroscopic evolution of the heliosphere is strongly affected by the kinetic plasma physics governing fundamental microphysical mechanisms. Kinetic turbulence, collisionless magnetic reconnection, particle acceleration, and kinetic instabilities are four poorly understood, grand-challenge problems that lie at the new frontier of kinetic heliophysics. The increasing availability of high cadence and high phase-space resolution measurements of particle velocity distributions by current and upcoming spacecraft missions and of massively parallel nonlinear kinetic simulations of weakly collisional heliospheric plasmas provides the opportunity to transform our understanding of these kinetic mechanisms through the full utilization of the information contained in the particle velocity distributions. Several major considerations for future investigations of kinetic heliophysics are examined. Turbulent dissipation followed by particle heating is highlighted as an inherently two-step process in weakly collisional plasmas, distinct from the more familiar case in fluid theory. Concerted efforts must be made to tackle the big-data challenge of visualizing the high-dimensional (3D-3V) phase space of kinetic plasma theory through physics-based reductions. Furthermore, the development of innovative analysis methods that utilize full velocity-space measurements, such as the field-particle correlation technique, will enable us to gain deeper insight into these four grand-challenge problems of kinetic heliophysics. A systems approach to tackle the multi-scale problem of heliophysics through a rigorous connection between the kinetic physics at microscales and the self-consistent evolution of the heliosphere at macroscales will propel the field of kinetic heliophysics into the future. PMID:29104421

  15. Pulsed electron accelerator for radiation technologies in the enviromental applications

    NASA Astrophysics Data System (ADS)

    Korenev, Sergey

    1997-05-01

    The project of pulsed electron accelerator for radiation technologies in the environmental applications is considered. An accelerator consists of high voltage generator with vacuum insulation and vacuum diode with plasma cathode on the basis discharge on the surface of dielectric of large dimensions. The main parameters of electron accelerators are following: kinetic energy 0.2 - 2.0 MeV, electron beam current 1 - 30 kA and pulse duration 1- 5 microseconds. The main applications of accelerator for decomposition of wastewaters are considered.

  16. Comparison of test particle acceleration in torsional spine and fan reconnection regimes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hosseinpour, M., E-mail: hosseinpour@tabrizu.ac.ir; Mehdizade, M.; Mohammadi, M. A.

    2014-10-15

    Magnetic reconnection is a common phenomenon taking place in astrophysical and space plasmas, especially in solar flares which are rich sources of highly energetic particles. Torsional spine and fan reconnections are important mechanisms proposed for steady-state three-dimensional null-point reconnection. By using the magnetic and electric fields for these regimes, we numerically investigate the features of test particle acceleration in both regimes with input parameters for the solar corona. By comparison, torsional spine reconnection is found to be more efficient than torsional fan reconnection in an acceleration of a proton to a high kinetic energy. A proton can gain as highmore » as 100 MeV of relativistic kinetic energy within only a few milliseconds. Moreover, in torsional spine reconnection, an accelerated particle can escape either along the spine axis or on the fan plane depending on its injection position. However, in torsional fan reconnection, the particle is only allowed to accelerate along the spine axis. In addition, in both regimes, the particle's trajectory and final kinetic energy depend on the injection position but adopting either spatially uniform or non-uniform localized plasma resistivity does not much influence the features of trajectory.« less

  17. Constraining Secluded Dark Matter models with the public data from the 79-string IceCube search for dark matter in the Sun

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ardid, M.; Felis, I.; Martínez-Mora, J.A.

    The 79-string IceCube search for dark matter in the Sun public data is used to test Secluded Dark Matter models. No significant excess over background is observed and constraints on the parameters of the models are derived. Moreover, the search is also used to constrain the dark photon model in the region of the parameter space with dark photon masses between 0.22 and ∼ 1 GeV and a kinetic mixing parameter ε ∼ 10{sup −9}, which remains unconstrained. These are the first constraints of dark photons from neutrino telescopes. It is expected that neutrino telescopes will be efficient tools tomore » test dark photons by means of different searches in the Sun, Earth and Galactic Center, which could complement constraints from direct detection, accelerators, astrophysics and indirect detection with other messengers, such as gamma rays or antiparticles.« less

  18. Acceleration of the chemistry solver for modeling DI engine combustion using dynamic adaptive chemistry (DAC) schemes

    NASA Astrophysics Data System (ADS)

    Shi, Yu; Liang, Long; Ge, Hai-Wen; Reitz, Rolf D.

    2010-03-01

    Acceleration of the chemistry solver for engine combustion is of much interest due to the fact that in practical engine simulations extensive computational time is spent solving the fuel oxidation and emission formation chemistry. A dynamic adaptive chemistry (DAC) scheme based on a directed relation graph error propagation (DRGEP) method has been applied to study homogeneous charge compression ignition (HCCI) engine combustion with detailed chemistry (over 500 species) previously using an R-value-based breadth-first search (RBFS) algorithm, which significantly reduced computational times (by as much as 30-fold). The present paper extends the use of this on-the-fly kinetic mechanism reduction scheme to model combustion in direct-injection (DI) engines. It was found that the DAC scheme becomes less efficient when applied to DI engine simulations using a kinetic mechanism of relatively small size and the accuracy of the original DAC scheme decreases for conventional non-premixed combustion engine. The present study also focuses on determination of search-initiating species, involvement of the NOx chemistry, selection of a proper error tolerance, as well as treatment of the interaction of chemical heat release and the fuel spray. Both the DAC schemes were integrated into the ERC KIVA-3v2 code, and simulations were conducted to compare the two schemes. In general, the present DAC scheme has better efficiency and similar accuracy compared to the previous DAC scheme. The efficiency depends on the size of the chemical kinetics mechanism used and the engine operating conditions. For cases using a small n-heptane kinetic mechanism of 34 species, 30% of the computational time is saved, and 50% for a larger n-heptane kinetic mechanism of 61 species. The paper also demonstrates that by combining the present DAC scheme with an adaptive multi-grid chemistry (AMC) solver, it is feasible to simulate a direct-injection engine using a detailed n-heptane mechanism with 543 species

  19. Homology search with binary and trinary scoring matrices.

    PubMed

    Smith, Scott F

    2006-01-01

    Protein homology search can be accelerated with the use of bit-parallel algorithms in conjunction with constraints on the values contained in the scoring matrices. Trinary scoring matrices (containing only the values -1, 0, and 1) allow for significant acceleration without significant reduction in the receiver operating characteristic (ROC) score of a Smith-Waterman search. Binary scoring matrices (containing the values 0 and 1) result in some reduction in ROC score, but result in even more acceleration. Binary scoring matrices and five-bit saturating scores can be used for fast prefilters to the Smith-Waterman algorithm.

  20. Kinetic energy and the equivalence principle

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Carlip, S.

    1998-05-01

    According to the general theory of relativity, kinetic energy contributes to gravitational mass. Surprisingly, the observational evidence for this prediction does not seem to be discussed in the literature. I reanalyze existing experimental data to test the equivalence principle for the kinetic energy of atomic electrons, and show that fairly strong limits on possible violations can be obtained. I discuss the relationship of this result to the occasional claim that {open_quotes}light falls with twice the acceleration of ordinary matter.{close_quotes} {copyright} {ital 1998 American Association of Physics Teachers.}

  1. Critical analysis of industrial electron accelerators

    NASA Astrophysics Data System (ADS)

    Korenev, S.

    2004-09-01

    The critical analysis of electron linacs for industrial applications (degradation of PTFE, curing of composites, modification of materials, sterlization and others) is considered in this report. Main physical requirements for industrial electron accelerators consist in the variations of beam parameters, such as kinetic energy and beam power. Questions for regulation of these beam parameters are considered. The level of absorbed dose in the irradiated product and throughput determines the main parameters of electron accelerator. The type of ideal electron linac for industrial applications is discussed.

  2. Following atomistic kinetics on experimental timescales with the kinetic Activation–Relaxation Technique

    DOE PAGES

    Mousseau, Normand; Béland, Laurent Karim; Brommer, Peter; ...

    2014-12-24

    The properties of materials, even at the atomic level, evolve on macroscopic time scales. Following this evolution through simulation has been a challenge for many years. For lattice-based activated diffusion, kinetic Monte Carlo has turned out to be an almost perfect solution. Various accelerated molecular dynamical schemes, for their part, have allowed the study on long time scale of relatively simple systems. There is still a desire and need, however, for methods able to handle complex materials such as alloys and disordered systems. In this paper, we review the kinetic Activation–Relaxation Technique (k-ART), one of a handful of off-lattice kineticmore » Monte Carlo methods, with on-the-fly cataloging, that have been proposed in the last few years.« less

  3. Effects of fatigue on kinematics and kinetics during overground running: a systematic review.

    PubMed

    Winter, Sara; Gordon, Susan; Watt, Kerrianne

    2017-06-01

    Understanding kinematic and kinetic changes with fatigue during running is important to assess changes that may influence performance and injury. The aim of this systematic review was to identify, critique and summarize literature about the effects of fatigue on kinematics and kinetics during a fatiguing overground run and present the reported influence on performance and injury. An electronic search was conducted of MEDLINE, SPORTDiscus, CINAHL and PubMed databases. Two reviewers assessed articles for inclusion, and evaluated the quality of articles included using a modified version of the Downs and Black Quality Index. A total of twelve articles were identified for review. The mean quality assessment score was seven out of a possible 12. Kinematic and kinetic changes reported to affect performance included decreased speed, step or stride frequency and length, increased trunk flexion, lower leg position at heel strike, mediolateral acceleration, changes in hip and knee ranges, and decreased stride regularity, heel lift, maximum knee rotation and backward ankle velocity. Alterations reported to increase risk of injury included decreased step frequency, increased upper body rotation and lower leg position at heel strike, and decreased knee flexion during stance. Reduced risk of injury has been linked to decreased step length and hip ranges, and increased trunk flexion. This review found limited evidence regarding changes in kinematic and kinetic during a fatiguing run in relation to performance and injury. Higher quality studies are warranted, with a larger sample of homogenous runners, and type of run carefully selected to provide quality information for runners, coaches and clinicians.

  4. Kinetic Sprint Asymmetries on a non-motorised Treadmill in Rugby Union Athletes.

    PubMed

    Brown, Scott R; Cross, Matt R; Girard, Olivier; Brocherie, Franck; Samozino, Pierre; Morin, Jean-Benoît

    2017-11-01

    The purpose of this study was to present a potential link between sprint kinetic (vertical [F V ] and horizontal force [F H ]) asymmetries and athletic performance during acceleration and maximal velocity (v max ) sprinting. Thirty un-injured male rugby athletes performed 8-s sprints on a non-motorised treadmill. Kinetic data were divided into 'strong' and 'weak' legs based on individually averaged peak values observed during sprinting and were analysed to evaluate asymmetry. Large differences were found between the strong and weak legs in F H during acceleration (4.3 vs. 3.5 N·kg -1 ) and v max (3.7 vs. 2.8 N·kg -1 ) sprinting (both ES=1.2), but not in F V (21.8 vs. 20.8 N·kg -1 , ES=- 0.6 for acceleration; 23.9 vs. 22.8 N·kg -1 , ES=- 0.5 for v max , respectively). Group mean asymmetry was lower in F V compared to F H during acceleration (1.6 vs. 6.8%) and v max (1.6 vs. 8.2%). The range of asymmetry was much lower in F V (0.03-4.3%) compared to F H (0.2-28%). In un-injured rugby athletes, the magnitude and range of asymmetry scores in F H , occurring during acceleration and v max phases, where much greater than those found in F V . These findings highlight the potential for some un-injured athletes to possess kinetic asymmetries known as crucial components for acceleration performance in sprinting. © Georg Thieme Verlag KG Stuttgart · New York.

  5. A Theory for Self-consistent Acceleration of Energetic Charged Particles by Dynamic Small-scale Flux Ropes

    NASA Astrophysics Data System (ADS)

    le Roux, J. A.; Zank, G. P.; Khabarova, O.; Webb, G. M.

    2016-12-01

    Simulations of charged particle acceleration in turbulent plasma regions with numerous small-scale contracting and merging (reconnecting) magnetic islands/flux ropes emphasize the key role of temporary particle trapping in these structures for efficient acceleration that can result in power-law spectra. In response, a comprehensive kinetic transport theory framework was developed by Zank et al. and le Roux et al. to capture the essential physics of energetic particle acceleration in solar wind regions containing numerous dynamic small-scale flux ropes. Examples of test particle solutions exhibiting hard power-law spectra for energetic particles were presented in recent publications by both Zank et al. and le Roux et al.. However, the considerable pressure in the accelerated particles suggests the need for expanding the kinetic transport theory to enable a self-consistent description of energy exchange between energetic particles and small-scale flux ropes. We plan to present the equations of an expanded kinetic transport theory framework that will enable such a self-consistent description.

  6. Accelerating object detection via a visual-feature-directed search cascade: algorithm and field programmable gate array implementation

    NASA Astrophysics Data System (ADS)

    Kyrkou, Christos; Theocharides, Theocharis

    2016-07-01

    Object detection is a major step in several computer vision applications and a requirement for most smart camera systems. Recent advances in hardware acceleration for real-time object detection feature extensive use of reconfigurable hardware [field programmable gate arrays (FPGAs)], and relevant research has produced quite fascinating results, in both the accuracy of the detection algorithms as well as the performance in terms of frames per second (fps) for use in embedded smart camera systems. Detecting objects in images, however, is a daunting task and often involves hardware-inefficient steps, both in terms of the datapath design and in terms of input/output and memory access patterns. We present how a visual-feature-directed search cascade composed of motion detection, depth computation, and edge detection, can have a significant impact in reducing the data that needs to be examined by the classification engine for the presence of an object of interest. Experimental results on a Spartan 6 FPGA platform for face detection indicate data search reduction of up to 95%, which results in the system being able to process up to 50 1024×768 pixels images per second with a significantly reduced number of false positives.

  7. Diagnosis of Acceleration, Reconnection, Turbulence, and Heating

    NASA Astrophysics Data System (ADS)

    Dufor, Mikal T.; Jemiolo, Andrew J.; Keesee, Amy; Cassak, Paul; Tu, Weichao; Scime, Earl E.

    2017-10-01

    The DARTH (Diagnosis of Acceleration, Reconnection, Turbulence, and Heating) experiment is an intermediate-scale, experimental facility designed to study magnetic reconnection at and below the kinetic scale of ions and electrons. The experiment will have non-perturbative diagnostics with high temporal and three-dimensional spatial resolution, giving it the capability to investigate kinetic-scale physics. Of specific scientific interest are particle acceleration, plasma heating, turbulence and energy dissipation during reconnection. Here we will describe the magnetic field system and the two plasma guns used to create flux ropes that then merge through magnetic reconnection. We will also describe the key diagnostic systems: laser induced fluorescence (LIF) for ion vdf measurements, a 300 GHz microwave scattering system for sub-mm wavelength fluctuation measurements and a Thomson scattering laser for electron vdf measurements. The vacuum chamber is designed to provide unparalleled access for these particle diagnostics. The scientific goals of DARTH are to examine particle acceleration and heating during, the role of three-dimensional instabilities during reconnection, how reconnection ceases, and the role of impurities and asymmetries in reconnection. This work was supported by the by the O'Brien Energy Research Fund.

  8. Electron acceleration via magnetic island coalescence

    NASA Astrophysics Data System (ADS)

    Shinohara, I.; Yumura, T.; Tanaka, K. G.; Fujimoto, M.

    2009-06-01

    Electron acceleration via fast magnetic island coalescence that happens as quick magnetic reconnection triggering (QMRT) proceeds has been studied. We have carried out a three-dimensional full kinetic simulation of the Harris current sheet with a large enough simulation run for two magnetic islands coalescence. Due to the strong inductive electric field associated with the non-linear evolution of the lower-hybrid-drift instability and the magnetic island coalescence process observed in the non-linear stage of the collisionless tearing mode, electrons are significantly accelerated at around the neutral sheet and the subsequent X-line. The accelerated meandering electrons generated by the non-linear evolution of the lower-hybrid-drift instability are resulted in QMRT, and QMRT leads to fast magnetic island coalescence. As a whole, the reconnection triggering and its transition to large-scale structure work as an effective electron accelerator.

  9. The High Time Resolution Universe Pulsar Survey - XII. Galactic plane acceleration search and the discovery of 60 pulsars

    NASA Astrophysics Data System (ADS)

    Ng, C.; Champion, D. J.; Bailes, M.; Barr, E. D.; Bates, S. D.; Bhat, N. D. R.; Burgay, M.; Burke-Spolaor, S.; Flynn, C. M. L.; Jameson, A.; Johnston, S.; Keith, M. J.; Kramer, M.; Levin, L.; Petroff, E.; Possenti, A.; Stappers, B. W.; van Straten, W.; Tiburzi, C.; Eatough, R. P.; Lyne, A. G.

    2015-07-01

    We present initial results from the low-latitude Galactic plane region of the High Time Resolution Universe pulsar survey conducted at the Parkes 64-m radio telescope. We discuss the computational challenges arising from the processing of the terabyte-sized survey data. Two new radio interference mitigation techniques are introduced, as well as a partially coherent segmented acceleration search algorithm which aims to increase our chances of discovering highly relativistic short-orbit binary systems, covering a parameter space including potential pulsar-black hole binaries. We show that under a constant acceleration approximation, a ratio of data length over orbital period of ≈0.1 results in the highest effectiveness for this search algorithm. From the 50 per cent of data processed thus far, we have redetected 435 previously known pulsars and discovered a further 60 pulsars, two of which are fast-spinning pulsars with periods less than 30 ms. PSR J1101-6424 is a millisecond pulsar whose heavy white dwarf (WD) companion and short spin period of 5.1 ms indicate a rare example of full-recycling via Case A Roche lobe overflow. PSR J1757-27 appears to be an isolated recycled pulsar with a relatively long spin period of 17 ms. In addition, PSR J1244-6359 is a mildly recycled binary system with a heavy WD companion, PSR J1755-25 has a significant orbital eccentricity of 0.09 and PSR J1759-24 is likely to be a long-orbit eclipsing binary with orbital period of the order of tens of years. Comparison of our newly discovered pulsar sample to the known population suggests that they belong to an older population. Furthermore, we demonstrate that our current pulsar detection yield is as expected from population synthesis.

  10. Effects of Current Guides Destruction at Ultra-fast Acceleration of Macrobodies

    NASA Astrophysics Data System (ADS)

    Kataev, V. N.; Boriskin, A. S.; Golosov, S. N.; Demidov, V. A.; Klimashov, M. V.; Korolev, P. V.; Makartsev, G. F.; Pikar, A. S.; Russkov, A. S.; Shapovalov, E. V.; Shibitov, Yu. M.

    2006-08-01

    The paper is devoted to discussion of current guides destruction effects in different accelerators: thermal-electric and electro-magnetic rail accelerator at macrobodies acceleration value of 108-109 m/s2. Experimental results with thermal-electric accelerators powering from megajoule capacitor battery and helical magneto-cumulative generator MCG-100 at currents up to 3.5 MA are analyzed. The process of rails destruction at railgun at pressure magnetic field excess over the limit of metal fluidity is presented. Methods of efficiency coefficient increase of capacitive storage energy transmission to kinetic energy of accelerating body are discussed.

  11. How proteins bind to DNA: target discrimination and dynamic sequence search by the telomeric protein TRF1

    PubMed Central

    2017-01-01

    Abstract Target search as performed by DNA-binding proteins is a complex process, in which multiple factors contribute to both thermodynamic discrimination of the target sequence from overwhelmingly abundant off-target sites and kinetic acceleration of dynamic sequence interrogation. TRF1, the protein that binds to telomeric tandem repeats, faces an intriguing variant of the search problem where target sites are clustered within short fragments of chromosomal DNA. In this study, we use extensive (>0.5 ms in total) MD simulations to study the dynamical aspects of sequence-specific binding of TRF1 at both telomeric and non-cognate DNA. For the first time, we describe the spontaneous formation of a sequence-specific native protein–DNA complex in atomistic detail, and study the mechanism by which proteins avoid off-target binding while retaining high affinity for target sites. Our calculated free energy landscapes reproduce the thermodynamics of sequence-specific binding, while statistical approaches allow for a comprehensive description of intermediate stages of complex formation. PMID:28633355

  12. Search by mariner 10 for electrons and protons accelerated in association with venus.

    PubMed

    Simpson, J A; Eraker, J H; Lamport, J E; Walpole, P H

    1974-03-29

    The University of Chicago instrumnents on board the Mariner 10 spacecraft bound for Mercury have measured energy spectra and fluxes of electrons from 0.18 to 30 million electron volts and protons from 0.5 to 68 million electron volts along the plasma wake and in the bow shock regions associated with Venus. Unusually quiet solar conditions and improved instrumentation made it possible to search for much lower fluxes of protons and electrons in similar energy regions as compared to earlier Mariner missions to Venus-that is, lower by a factor of 10(2) for protons and 10(3) for electrons. We found no evidence for electrons or protons either in the form of increases of intensity or energy spectral changes in the vicinity of the planet, nor any evidence of bursts of radiation in or near the observed bow shock where bursts of electrons might have been expected in analogy with the bow shock at the earth. The importance of these null results for determining the necessary and sufficient conditions for particle acceleration is discussed with respect to magnetometer evidence that Venus does not have a magnetosphere.

  13. Intermittent search strategies

    NASA Astrophysics Data System (ADS)

    Bénichou, O.; Loverdo, C.; Moreau, M.; Voituriez, R.

    2011-01-01

    This review examines intermittent target search strategies, which combine phases of slow motion, allowing the searcher to detect the target, and phases of fast motion during which targets cannot be detected. It is first shown that intermittent search strategies are actually widely observed at various scales. At the macroscopic scale, this is, for example, the case of animals looking for food; at the microscopic scale, intermittent transport patterns are involved in a reaction pathway of DNA-binding proteins as well as in intracellular transport. Second, generic stochastic models are introduced, which show that intermittent strategies are efficient strategies that enable the minimization of search time. This suggests that the intrinsic efficiency of intermittent search strategies could justify their frequent observation in nature. Last, beyond these modeling aspects, it is proposed that intermittent strategies could also be used in a broader context to design and accelerate search processes.

  14. Maximum proton kinetic energy and patient-generated neutron fluence considerations in proton beam arc delivery radiation therapy.

    PubMed

    Sengbusch, E; Pérez-Andújar, A; DeLuca, P M; Mackie, T R

    2009-02-01

    Several compact proton accelerator systems for use in proton therapy have recently been proposed. Of paramount importance to the development of such an accelerator system is the maximum kinetic energy of protons, immediately prior to entry into the patient, that must be reached by the treatment system. The commonly used value for the maximum kinetic energy required for a medical proton accelerator is 250 MeV, but it has not been demonstrated that this energy is indeed necessary to treat all or most patients eligible for proton therapy. This article quantifies the maximum kinetic energy of protons, immediately prior to entry into the patient, necessary to treat a given percentage of patients with rotational proton therapy, and examines the impact of this energy threshold on the cost and feasibility of a compact, gantry-mounted proton accelerator treatment system. One hundred randomized treatment plans from patients treated with IMRT were analyzed. The maximum radiological pathlength from the surface of the patient to the distal edge of the treatment volume was obtained for 180 degrees continuous arc proton therapy and for 180 degrees split arc proton therapy (two 90 degrees arcs) using CT# profiles from the Pinnacle (Philips Medical Systems, Madison, WI) treatment planning system. In each case, the maximum kinetic energy of protons, immediately prior to entry into the patient, that would be necessary to treat the patient was calculated using proton range tables for various media. In addition, Monte Carlo simulations were performed to quantify neutron production in a water phantom representing a patient as a function of the maximum proton kinetic energy achievable by a proton treatment system. Protons with a kinetic energy of 240 MeV, immediately prior to entry into the patient, were needed to treat 100% of patients in this study. However, it was shown that 90% of patients could be treated at 198 MeV, and 95% of patients could be treated at 207 MeV. Decreasing the

  15. Applications of High Intensity Proton Accelerators

    NASA Astrophysics Data System (ADS)

    Raja, Rajendran; Mishra, Shekhar

    2010-06-01

    Superconducting radiofrequency linac development at Fermilab / S. D. Holmes -- Rare muon decay experiments / Y. Kuno -- Rare kaon decays / D. Bryman -- Muon collider / R. B. Palmer -- Neutrino factories / S. Geer -- ADS and its potential / J.-P. Revol -- ADS history in the USA / R. L. Sheffield and E. J. Pitcher -- Accelerator driven transmutation of waste: high power accelerator for the European ADS demonstrator / J. L. Biarrotte and T. Junquera -- Myrrha, technology development for the realisation of ADS in EU: current status & prospects for realisation / R. Fernandez ... [et al.] -- High intensity proton beam production with cyclotrons / J. Grillenberger and M. Seidel -- FFAG for high intensity proton accelerator / Y. Mori -- Kaon yields for 2 to 8 GeV proton beams / K. K. Gudima, N. V. Mokhov and S. I. Striganov -- Pion yield studies for proton driver beams of 2-8 GeV kinetic energy for stopped muon and low-energy muon decay experiments / S. I. Striganov -- J-Parc accelerator status and future plans / H. Kobayashi -- Simulation and verification of DPA in materials / N. V. Mokhov, I. L. Rakhno and S. I. Striganov -- Performance and operational experience of the CNGS facility / E. Gschwendtner -- Particle physics enabled with super-conducting RF technology - summary of working group 1 / D. Jaffe and R. Tschirhart -- Proton beam requirements for a neutrino factory and muon collider / M. S. Zisman -- Proton bunching options / R. B. Palmer -- CW SRF H linac as a proton driver for muon colliders and neutrino factories / M. Popovic, C. M. Ankenbrandt and R. P. Johnson -- Rapid cycling synchrotron option for Project X / W. Chou -- Linac-based proton driver for a neutrino factory / R. Garoby ... [et al.] -- Pion production for neutrino factories and muon colliders / N. V. Mokhov ... [et al.] -- Proton bunch compression strategies / V. Lebedev -- Accelerator test facility for muon collider and neutrino factory R&D / V. Shiltsev -- The superconducting RF linac for muon

  16. Generating relevant kinetic Monte Carlo catalogs using temperature accelerated dynamics with control over the accuracy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chatterjee, Abhijit; Voter, Arthur

    2009-01-01

    We develop a variation of the temperature accelerated dynamics (TAD) method, called the p-TAD method, that efficiently generates an on-the-fly kinetic Monte Carlo (KMC) process catalog with control over the accuracy of the catalog. It is assumed that transition state theory is valid. The p-TAD method guarantees that processes relevant at the timescales of interest to the simulation are present in the catalog with a chosen confidence. A confidence measure associated with the process catalog is derived. The dynamics is then studied using the process catalog with the KMC method. Effective accuracy of a p-TAD calculation is derived when amore » KMC catalog is reused for conditions different from those the catalog was originally generated for. Different KMC catalog generation strategies that exploit the features of the p-TAD method and ensure higher accuracy and/or computational efficiency are presented. The accuracy and the computational requirements of the p-TAD method are assessed. Comparisons to the original TAD method are made. As an example, we study dynamics in sub-monolayer Ag/Cu(110) at the time scale of seconds using the p-TAD method. It is demonstrated that the p-TAD method overcomes several challenges plaguing the conventional KMC method.« less

  17. Coulomb-driven energy boost of heavy ions for laser-plasma acceleration.

    PubMed

    Braenzel, J; Andreev, A A; Platonov, K; Klingsporn, M; Ehrentraut, L; Sandner, W; Schnürer, M

    2015-03-27

    An unprecedented increase of kinetic energy of laser accelerated heavy ions is demonstrated. Ultrathin gold foils have been irradiated by an ultrashort laser pulse at a peak intensity of 8×10^{19}  W/  cm^{2}. Highly charged gold ions with kinetic energies up to >200  MeV and a bandwidth limited energy distribution have been reached by using 1.3 J laser energy on target. 1D and 2D particle in cell simulations show how a spatial dependence on the ion's ionization leads to an enhancement of the accelerating electrical field. Our theoretical model considers a spatial distribution of the ionization inside the thin target, leading to a field enhancement for the heavy ions by Coulomb explosion. It is capable of explaining the energy boost of highly charged ions, enabling a higher efficiency for the laser-driven heavy ion acceleration.

  18. Chemical Enhancements in Shock-Accelerated Particles: Ab initio Simulations.

    PubMed

    Caprioli, Damiano; Yi, Dennis T; Spitkovsky, Anatoly

    2017-10-27

    We study the thermalization, injection, and acceleration of ions with different mass/charge ratios, A/Z, in nonrelativistic collisionless shocks via hybrid (kinetic ions-fluid electrons) simulations. In general, ions thermalize to a postshock temperature proportional to A. When diffusive shock acceleration is efficient, ions develop a nonthermal tail whose extent scales with Z and whose normalization is enhanced as (A/Z)^{2} so that incompletely ionized heavy ions are preferentially accelerated. We discuss how these findings can explain observed heavy-ion enhancements in Galactic cosmic rays.

  19. Numerical investigation on the effects of acceleration reversal times in Rayleigh-Taylor Instability with multiple reversals

    NASA Astrophysics Data System (ADS)

    Farley, Zachary; Aslangil, Denis; Banerjee, Arindam; Lawrie, Andrew G. W.

    2017-11-01

    An implicit large eddy simulation (ILES) code, MOBILE, is used to explore the growth rate of the mixing layer width of the acceleration-driven Rayleigh-Taylor instability (RTI) under variable acceleration histories. The sets of computations performed consist of a series of accel-decel-accel (ADA) cases in addition to baseline constant acceleration and accel-decel (AD) cases. The ADA cases are a series of varied times for the second acceleration reversal (t2) and show drastic differences in the growth rates. Upon the deceleration phase, the kinetic energy of the flow is shifted into internal wavelike patterns. These waves are evidenced by the examined differences in growth rate in the second acceleration phase for the set of ADA cases. Here, we investigate global parameters that include mixing width, growth rates and the anisotropy tensor for the kinetic energy to better understand the behavior of the growth during the re-acceleration period. Authors acknowledge financial support from DOE-SSAA (DE-NA0003195) and NSF CAREER (#1453056) awards.

  20. Acceleration of Crystal Growth of Amorphous Griseofulvin by Low-Concentration Poly(ethylene oxide): Aspects of Crystallization Kinetics and Molecular Mobility.

    PubMed

    Shi, Qin; Zhang, Chen; Su, Yuan; Zhang, Jie; Zhou, Dongshan; Cai, Ting

    2017-07-03

    This study aims to investigate the crystallization behavior and molecular dynamics of amorphous griseofulvin (GSF) in the presence of low-concentration poly(ethylene oxide) (PEO). We observe that the addition of 3% w/w PEO remarkably increases the crystal growth rate of GSF by two orders of magnitude in both the supercooled liquid and glassy states. The liquid dynamics of amorphous GSF in the presence and absence of PEO are characterized by dielectric spectroscopy. With an increase of the PEO content, the α-relaxation times of the systems decrease, indicating the increase of global molecular mobility. The couplings between molecular mobility and crystallization kinetics of GSF systems show strong time-dependences below T g . The overlapping of α-relaxation times of GSF in presence and absence of PEO as a function of T g /T suggest the "plasticization" effect of PEO additives. However, the crystallization kinetics of amorphous GSF containing low-concentration PEO do not overlap with those of pure GSF on a T g /T scale. The remarkable accelerating effect of crystal growth of amorphous GSF by low-concentration PEO can be partially attributed to the increase of global mobility. The high segmental mobility of PEO is expected to strongly affect the crystal growth rates of GSF. These findings are relevant for understanding and predicting the physical stability of amorphous pharmaceutical solid dispersions.

  1. AIR-MRF: Accelerated iterative reconstruction for magnetic resonance fingerprinting.

    PubMed

    Cline, Christopher C; Chen, Xiao; Mailhe, Boris; Wang, Qiu; Pfeuffer, Josef; Nittka, Mathias; Griswold, Mark A; Speier, Peter; Nadar, Mariappan S

    2017-09-01

    Existing approaches for reconstruction of multiparametric maps with magnetic resonance fingerprinting (MRF) are currently limited by their estimation accuracy and reconstruction time. We aimed to address these issues with a novel combination of iterative reconstruction, fingerprint compression, additional regularization, and accelerated dictionary search methods. The pipeline described here, accelerated iterative reconstruction for magnetic resonance fingerprinting (AIR-MRF), was evaluated with simulations as well as phantom and in vivo scans. We found that the AIR-MRF pipeline provided reduced parameter estimation errors compared to non-iterative and other iterative methods, particularly at shorter sequence lengths. Accelerated dictionary search methods incorporated into the iterative pipeline reduced the reconstruction time at little cost of quality. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. Recent results of studies of acceleration of compact toroids

    NASA Astrophysics Data System (ADS)

    Hammer, J. H.; Hartmen, C. W.; Eddleman, J.

    1984-03-01

    The observed gross stability and self-contained structure of compact toroids (CT's) give rise to the possibility, unique among magnetically confined plasmas, of translating CT's from their point of origin over distances many times their own length. This feature has led us to consider magnetic acceleration of CT's to directed kinetic energies much greater than their stored magnetic and thermal energies. A CT accelerator falls in the very broad gap between traditional particle accelerators at one extreme, which are limited in the number of particles per bunch by electrostatic repulsive forces, and mass accelerators such as rail guns at the other extreme, which accelerate many particles but are forced by the stress limitations of solids to far smaller accelerations. A typical CT has about a Coulomb of particles, weighs 10 micrograms and can be accelerated by magnetic forces of several tons, leading to an acceleration on the order of 10(11) gravities.

  3. Nonlinear friction dynamics on polymer surface under accelerated movement

    NASA Astrophysics Data System (ADS)

    Aita, Yuuki; Asanuma, Natsumi; Takahashi, Akira; Mayama, Hiroyuki; Nonomura, Yoshimune

    2017-04-01

    Nonlinear phenomena on the soft material surface are one of the most exciting topics of chemical physics. However, only a few reports exist on the friction phenomena under accelerated movement, because friction between two solid surfaces is considered a linear phenomenon in many cases. We aim to investigate how nonlinear accelerated motion affects friction on solid surfaces. In the present study, we evaluate the frictional forces between two polytetrafluoroethylene (PTFE) resins using an advanced friction evaluation system. On PTFE surfaces, the normalized delay time δ, which is the time lag in the response of the friction force to the accelerated movement, is observed in the pre-sliding friction process. Under high-velocity conditions, kinetic friction increases with velocity. Based on these experimental results, we propose a two-phase nonlinear model including a pre-sliding process (from the beginning of sliding of a contact probe to the establishment of static friction) and a kinetic friction process. The present model consists of several factors including velocity, acceleration, stiffness, viscosity, and vertical force. The findings reflecting the viscoelastic properties of soft material is useful for various fields such as in the fabrication of clothes, cosmetics, automotive materials, and virtual reality systems as well as for understanding friction phenomena on soft material surfaces.

  4. Abrupt acceleration of a 'cold' ultrarelativistic wind from the Crab pulsar.

    PubMed

    Aharonian, F A; Bogovalov, S V; Khangulyan, D

    2012-02-15

    Pulsars are thought to eject electron-positron winds that energize the surrounding environment, with the formation of a pulsar wind nebula. The pulsar wind originates close to the light cylinder, the surface at which the pulsar co-rotation velocity equals the speed of light, and carries away much of the rotational energy lost by the pulsar. Initially the wind is dominated by electromagnetic energy (Poynting flux) but later this is converted to the kinetic energy of bulk motion. It is unclear exactly where this takes place and to what speed the wind is accelerated. Although some preferred models imply a gradual acceleration over the entire distance from the magnetosphere to the point at which the wind terminates, a rapid acceleration close to the light cylinder cannot be excluded. Here we report that the recent observations of pulsed, very high-energy γ-ray emission from the Crab pulsar are explained by the presence of a cold (in the sense of the low energy of the electrons in the frame of the moving plasma) ultrarelativistic wind dominated by kinetic energy. The conversion of the Poynting flux to kinetic energy should take place abruptly in the narrow cylindrical zone of radius between 20 and 50 light-cylinder radii centred on the axis of rotation of the pulsar, and should accelerate the wind to a Lorentz factor of (0.5-1.0) × 10(6). Although the ultrarelativistic nature of the wind does support the general model of pulsars, the requirement of the very high acceleration of the wind in a narrow zone not far from the light cylinder challenges current models.

  5. The crystal acceleration effect for cold neutrons

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Braginetz, Yu. P., E-mail: aiver@pnpi.spb.ru; Berdnikov, Ya. A.; Fedorov, V. V., E-mail: vfedorov@pnpi.spb.ru

    A new mechanism of neutron acceleration is discussed and studied experimentally in detail for cold neutrons passing through the accelerated perfect crystal with the energies close to the Bragg one. The effect arises due to the following reason. The crystal refraction index (neutron-crystal interaction potential) for neutron in the vicinity of the Bragg resonance sharply depends on the parameter of deviation from the exact Bragg condition, i.e. on the crystal-neutron relative velocity. Therefore the neutrons enter into accelerated crystal with one neutron-crystal interaction potential and exit with the other. Neutron kinetic energy cannot vary inside the crystal due to itsmore » homogeneity. So after passage through such a crystal neutrons will be accelerated or decelerated because of the different energy change at the entrance and exit crystal boundaries.« less

  6. Turbulent Kinetic Energy in the Energy Balance of a Solar Flare

    NASA Astrophysics Data System (ADS)

    Kontar, E. P.; Perez, J. E.; Harra, L. K.; Kuznetsov, A. A.; Emslie, A. G.; Jeffrey, N. L. S.; Bian, N. H.; Dennis, B. R.

    2017-04-01

    The energy released in solar flares derives from a reconfiguration of magnetic fields to a lower energy state, and is manifested in several forms, including bulk kinetic energy of the coronal mass ejection, acceleration of electrons and ions, and enhanced thermal energy that is ultimately radiated away across the electromagnetic spectrum from optical to x rays. Using an unprecedented set of coordinated observations, from a suite of instruments, we here report on a hitherto largely overlooked energy component—the kinetic energy associated with small-scale turbulent mass motions. We show that the spatial location of, and timing of the peak in, turbulent kinetic energy together provide persuasive evidence that turbulent energy may play a key role in the transfer of energy in solar flares. Although the kinetic energy of turbulent motions accounts, at any given time, for only ˜(0.5 - 1 )% of the energy released, its relatively rapid (˜1 - 10 s ) energization and dissipation causes the associated throughput of energy (i.e., power) to rival that of major components of the released energy in solar flares, and thus presumably in other astrophysical acceleration sites.

  7. Turbulent Kinetic Energy in the Energy Balance of a Solar Flare.

    PubMed

    Kontar, E P; Perez, J E; Harra, L K; Kuznetsov, A A; Emslie, A G; Jeffrey, N L S; Bian, N H; Dennis, B R

    2017-04-14

    The energy released in solar flares derives from a reconfiguration of magnetic fields to a lower energy state, and is manifested in several forms, including bulk kinetic energy of the coronal mass ejection, acceleration of electrons and ions, and enhanced thermal energy that is ultimately radiated away across the electromagnetic spectrum from optical to x rays. Using an unprecedented set of coordinated observations, from a suite of instruments, we here report on a hitherto largely overlooked energy component-the kinetic energy associated with small-scale turbulent mass motions. We show that the spatial location of, and timing of the peak in, turbulent kinetic energy together provide persuasive evidence that turbulent energy may play a key role in the transfer of energy in solar flares. Although the kinetic energy of turbulent motions accounts, at any given time, for only ∼(0.5-1)% of the energy released, its relatively rapid (∼1-10  s) energization and dissipation causes the associated throughput of energy (i.e., power) to rival that of major components of the released energy in solar flares, and thus presumably in other astrophysical acceleration sites.

  8. On the equilibrium between proton kappa distribution and compressible kinetic Alfvenic fluctuations

    NASA Astrophysics Data System (ADS)

    Yoon, P. H.

    2017-12-01

    Protons with a quasi inverse power law energetic population featuring the property f v-α, with α close to 5, are pervasively observed in the heliosphere. While many theoretical attempts have been made in order to describe such a feature, the so-called pump acceleration mechanism put forth by Fisk & Gloeckler is one of the most prominent theories. Their mechanism involves the low-frequency compressional fluctuations accelerating the protons. This presentation aims to reformulate the problem from the perspective of the steady state solution of the self-consistent plasma kinetic theory involving compressible kinetic Alfvenic fluctuations. By considering the steady state proton particle kinetic equation and quasi-linear wave kinetic for the kinetic Alfvenic turbulence we seek to obtain concomitant solutions for both proton velocity distribution function and the spectral intensity for kinetic Alfvenic fluctuation. It is found that the kappa distribution for the protons is a legitimate, if not unique, solution. The steady state spectrum of kinetic Alfvenic fluctuation is also obtained. The present investigation demonstrates that the kappa distribution for the protons featuring energetic tail population characterized by f v-2κ-2, where κ is the parameter for kappa distribution, may represent the background population of the protons in the heliosphere. However, it is speculated that in order to uniquely determine the value of κ, which must be close to 1.5 for asymptotic behavior of f v-5, one must have an additional constraint that involves the balance of nonlinear mode coupling terms in the wave kinetic equation.

  9. SW#db: GPU-Accelerated Exact Sequence Similarity Database Search.

    PubMed

    Korpar, Matija; Šošić, Martin; Blažeka, Dino; Šikić, Mile

    2015-01-01

    In recent years we have witnessed a growth in sequencing yield, the number of samples sequenced, and as a result-the growth of publicly maintained sequence databases. The increase of data present all around has put high requirements on protein similarity search algorithms with two ever-opposite goals: how to keep the running times acceptable while maintaining a high-enough level of sensitivity. The most time consuming step of similarity search are the local alignments between query and database sequences. This step is usually performed using exact local alignment algorithms such as Smith-Waterman. Due to its quadratic time complexity, alignments of a query to the whole database are usually too slow. Therefore, the majority of the protein similarity search methods prior to doing the exact local alignment apply heuristics to reduce the number of possible candidate sequences in the database. However, there is still a need for the alignment of a query sequence to a reduced database. In this paper we present the SW#db tool and a library for fast exact similarity search. Although its running times, as a standalone tool, are comparable to the running times of BLAST, it is primarily intended to be used for exact local alignment phase in which the database of sequences has already been reduced. It uses both GPU and CPU parallelization and was 4-5 times faster than SSEARCH, 6-25 times faster than CUDASW++ and more than 20 times faster than SSW at the time of writing, using multiple queries on Swiss-prot and Uniref90 databases.

  10. Searching for Single Pulses Using Heimdall

    NASA Astrophysics Data System (ADS)

    Walsh, Gregory; Lynch, Ryan

    2018-01-01

    In radio pulsar surveys, the interstellar medium causes a frequency dependent dispersive delay of a pulsed signal across the observing band. If not corrected, this delay substantially lowers S/N and makes most pulses undetectable. The delay is proportional to an unknown dispersion measure (DM), which must be searched over with many trial values. A number of new, GPU-accelerated codes are now available to optimize this dedispersion task, and to search for transient pulsed radio emission. We report on the use of Heimdall, one such GPU-accelerated tree dedispersion utility, to search for transient radio sources in a Green Bank Telescope survey of the Cygnus Region and North Galactic Plane. The survey is carried out at central frequency of 820 MHz with a goal of finding Fast Radio Bursts, Rotating Radio Transients, young pulsars, and millisecond pulsars. We describe the the survey, data processing pipeline, and follow-up of candidate sources.

  11. The kinetics and mechanism of nanoconfined molten salt reactions: trimerization of potassium and rubidium dicyanamide.

    PubMed

    Yancey, Benjamin; Vyazovkin, Sergey

    2015-04-21

    This study highlights the effect of the aggregate state of a reactant on the reaction kinetics under the conditions of nanoconfinement. Our previous work (Phys. Chem. Chem. Phys., 2014, 16, 11409) has demonstrated considerable deceleration of the solid state trimerization of sodium dicyanamide in organically modified silica nanopores. In the present study we use FTIR, NMR, pXRD, TGA and DSC to analyze the kinetics and mechanism of the liquid state trimerization of potassium and rubidium dicyanamide under similar conditions of nanoconfinement. It is found that nanoconfinement accelerates dramatically the kinetics of the liquid state trimerization, whereas it does not appear to affect the reaction mechanism. Kinetic analysis indicates that the acceleration is associated with an increase in the preexponential factor. Although nanoconfinement has the opposite effects on the respective kinetics of solid and liquid state trimerization, both effects are linked to a change in the preexponential factor. The results obtained are consistent with our hypothesis that the effects differ because nanoconfinement may promote disordering of the solid and ordering of the liquid reaction media.

  12. Exploring the mechanical basis for acceleration: pelvic limb locomotor function during accelerations in racing greyhounds (Canis familiaris)

    PubMed Central

    Williams, S. B.; Usherwood, J. R.; Jespers, K.; Channon, A. J.; Wilson, A. M.

    2009-01-01

    Summary Animals in their natural environments are confronted with a regular need to perform rapid accelerations (for example when escaping from predators or chasing prey). Such acceleration requires net positive mechanical work to be performed on the centre of mass by skeletal muscle. Here we determined how pelvic limb joints contribute to the mechanical work and power that are required for acceleration in galloping quadrupeds. In addition, we considered what, if any, biomechanical strategies exist to enable effective acceleration to be achieved. Simultaneous kinematic and kinetic data were collected for racing greyhounds undergoing a range of low to high accelerations. From these data, joint moments and joint powers were calculated for individual hindlimb joints. In addition, the mean effective mechanical advantage (EMA) of the limb and the `gear ratio' of each joint throughout stance were calculated. Greatest increases in joint work and power with acceleration appeared at the hip and hock joints, particularly in the lead limb. Largest increases in absolute positive joint work occurred at the hip, consistent with the hypothesis that quadrupeds power locomotion by torque about the hip. In addition, hindlimb EMA decreased substantially with increased acceleration – a potential strategy to increase stance time and thus ground impulses for a given peak force. This mechanism may also increase the mechanical advantage for applying the horizontal forces necessary for acceleration. PMID:19181903

  13. Effects of dimensionality on kinetic simulations of laser-ion acceleration in the transparency regime

    NASA Astrophysics Data System (ADS)

    Stark, D. J.; Yin, L.; Albright, B. J.; Guo, F.

    2017-05-01

    A particle-in-cell study of laser-ion acceleration mechanisms in the transparency regime illustrates how two-dimensional (2D) S and P simulations (laser polarization in and out of the simulation plane, respectively) capture different physics characterizing these systems, visible in their entirety often in cost-prohibitive three-dimensional (3D) simulations. The electron momentum anisotropy induced in the target by a laser pulse is dramatically different in the two 2D cases, manifested in differences in target expansion timescales, electric field strengths, and density thresholds for the onset of relativistically induced transparency. In particular, 2D-P simulations exhibit dramatically greater electron heating in the simulation plane, whereas 2D-S ones show a much more isotropic energy distribution, similar to 3D. An ion trajectory analysis allows one to isolate the fields responsible for ion acceleration and to characterize the acceleration regimes in time and space. The artificial longitudinal electron heating in 2D-P exaggerates the effectiveness of target-normal sheath acceleration into its dominant acceleration mechanism throughout the laser-plasma interaction, whereas 2D-S and 3D both have sizable populations accelerated preferentially during transparency.

  14. Effects of dimensionality on kinetic simulations of laser-ion acceleration in the transparency regime

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Stark, David James; Yin, Lin; Albright, Brian James

    2017-05-03

    A particle-in-cell study of laser-ion acceleration mechanisms in the transparency regime illustrates how two-dimensional (2D) S and P simulations (laser polarization in and out of the simulation plane, respectively) capture different physics characterizing these systems, visible in their entirety in often cost-prohibitive three-dimensional (3D) simulations. The electron momentum anisotropy induced in the target by the laser pulse is dramatically different in the two 2D cases, manifested in differences in target expansion timescales, electric field strengths, and density thresholds for the onset of relativistically induced transparency. In particular, 2D-P simulations exhibit dramatically greater electron heating in the simulation plane, whereas 2D-Smore » ones show a much more isotropic energy distribution, similar to 3D. An ion trajectory analysis allows one to isolate the fields responsible for ion acceleration and to characterize the acceleration regimes in time and space. The artificial longitudinal electron heating in 2D-P exaggerates the effectiveness of target-normal sheath acceleration into its dominant acceleration mechanism throughout the laser-plasma interaction, whereas 2D-S and 3D both have sizable populations accelerated preferentially during transparency.« less

  15. Overview of Accelerator Applications for Security and Defense

    DOE PAGES

    Antolak, Arlyn J.

    2015-01-01

    Particle accelerators play a key role in a broad set of defense and security applications including war-fighter and asset protection, cargo inspection, nonproliferation, materials characterization and stockpile stewardship. Accelerators can replace the high activity radioactive sources that pose a security threat for developing a radiological dispersal device and be used to produce isotopes for medical, industrial, and re-search purposes. Lastly, we present an overview of current and emerging accelerator technologies relevant to addressing the needs of defense and security.

  16. Search predicts and changes patience in intertemporal choice

    PubMed Central

    Johnson, Eric J.

    2017-01-01

    Intertemporal choice impacts many important outcomes, such as decisions about health, education, wealth, and the environment. However, the psychological processes underlying decisions involving outcomes at different points in time remain unclear, limiting opportunities to intervene and improve people’s patience. This research examines information-search strategies used during intertemporal choice and their impact on decisions. In experiment 1, we demonstrate that search strategies vary substantially across individuals. We subsequently identify two distinct search strategies across individuals. Comparative searchers, who compare features across options, discount future options less and are more susceptible to acceleration versus delay framing than integrative searchers, who integrate the features of an option. Experiment 2 manipulates search using an unobtrusive method to establish a causal relationship between strategy and choice, randomly assigning participants to conditions promoting either comparative or integrative search. Again, comparative search promotes greater patience than integrative search. Additionally, when participants adopt a comparative search strategy, they also exhibit greater effects of acceleration versus delay framing. Although most participants reported that the manipulation did not change their behavior, promoting comparative search decreased discounting of future rewards substantially and speeded patient choices. These findings highlight the central role that heterogeneity in psychological processes plays in shaping intertemporal choice. Importantly, these results indicate that theories that ignore variability in search strategies may be inadvertently aggregating over different subpopulations that use very different processes. The findings also inform interventions in choice architecture to increase patience and improve consumer welfare. PMID:29078303

  17. Acceleration Modes and Transitions in Pulsed Plasma Accelerators

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Greve, Christine M.

    2018-01-01

    accelerators was developed by Cheng, et al. The Coaxial High ENerGy (CHENG) thruster operated on the 10-microseconds timescales of pulsed plasma thrusters, but claimed high thrust density, high efficiency and low electrode erosion rates, which are more consistent with the deflagration mode of acceleration. Separate work on gas-fed pulsed plasma thrusters (PPTs) by Ziemer, et al. identified two separate regimes of performance. The regime at higher mass bits (termed Mode I in that work) possessed relatively constant thrust efficiency (ratio of jet kinetic energy to input electrical energy) as a function of mass bit. In the second regime at very low mass bits (termed Mode II), the efficiency increased with decreasing mass bit. Work by Poehlmann et al. and by Sitaraman and Raja sought to understand the performance of the CHENG thruster and the Mode I / Mode II performance in PPTs by modeling the acceleration using the Hugoniot Relation, with the detonation and deflagration modes representing two distinct sets of solutions to the relevant conservation laws. These works studied the proposal that, depending upon the values of the various controllable parameters, the accelerator would operate in either the detonation or deflagration mode. In the present work, we propose a variation on the explanation for the differences in performance between the various pulsed plasma accelerators. Instead of treating the accelerator as if it were only operating in one mode or the other during a pulse, we model the initial stage of the discharge in all cases as an accelerating current sheet (detonation mode). If the current sheet reaches the exit of the accelerator before the discharge is completed, the acceleration mode transitions to the deflagration mode type found in the quasi-steady MPD thrusters. This modeling method is used to demonstrate that standard gas-fed pulsed plasma accelerators, the CHENG thruster, and the quasi-steady MPD accelerator are variations of the same device, with the overall

  18. The significance of intergranular diffusion to the mechanisms and kinetics of porphyroblast crystallization

    NASA Astrophysics Data System (ADS)

    Carlson, William D.

    1989-09-01

    The spatial disposition, compositional zoning profiles, and size distributions of garnet crystals in 11 specimens of pelitic schist from the Picuris Range of New Mexico (USA) demonstrate that the kinetics of intergranular diffusion controlled the nucleation and growth mechanisms of porphyroblasts in these rocks. An ordered disposition of garnet centers and a significant correlation between crystal radius and near-neighbor distances manifest suppressed nucleation of new crystals in diffusionally depleted zones surrounding pre-existing crystals. Compositional zoning profiles require diffusionally controlled growth, the rate of which increases exponentially as temperature increases with time; an acceleration factor for growth rate can be estimated from a comparison of compositional profiles for crystals of different sizes in each specimen. Crystal size distributions are interpreted as the result of nucleation rates that accelerate exponentially with increasing temperature early in the crystallization process, but decline in the later stages because of suppression effects in the vicinity of earlier-formed nuclei. Simulations of porphyroblast crystallization, based upon thermally accelerated diffusionally influenced nucleation kinetics and diffusionally controlled growth kinetics, quantitatively replicate textural relations in the rocks. The simulations employ only two variable parameters, which are evaluated by fitting of crystal size distributions. Both have physical significance. The first is an acceleration factor for nucleation, with a magnitude reflecting the prograde increase during the nucleation interval of the chemical affinity for the reaction in undepleted regions of the rock. The second is a measure of the relative sizes of the porphyroblast and the diffusionally depleted zone surrounding it. Crystal size distributions for the Picuris Range garnets correspond very closely to those in the literature from a variety of other localities for garnet and other

  19. Rarefaction acceleration of ultrarelativistic magnetized jets in gamma-ray burst sources

    NASA Astrophysics Data System (ADS)

    Komissarov, Serguei S.; Vlahakis, Nektarios; Königl, Arieh

    2010-09-01

    When a magnetically dominated superfast-magnetosonic long/soft gamma-ray burst (GRB) jet leaves the progenitor star, the external pressure support will drop and the jet may enter the regime of ballistic expansion, during which additional magnetic acceleration becomes ineffective. However, recent numerical simulations by Tchekhovskoy et al. have suggested that the transition to this regime is accompanied by a spurt of acceleration. We confirm this finding numerically and attribute the acceleration to a sideways expansion of the jet, associated with a strong magnetosonic rarefaction wave that is driven into the jet when it loses pressure support, which induces a conversion of magnetic energy into kinetic energy of bulk motion. This mechanism, which we dub rarefaction acceleration, can only operate in a relativistic outflow because in this case the total energy can still be dominated by the magnetic component even in the superfast-magnetosonic regime. We analyse this process using the equations of relativistic magnetohydrodynamics and demonstrate that it is more efficient at converting internal energy into kinetic energy when the flow is magnetized than in a purely hydrodynamic outflow, as was found numerically by Mizuno et al. We show that, just as in the case of the magnetic acceleration of a collimating jet that is confined by an external pressure distribution - the collimation-acceleration mechanism - the rarefaction-acceleration process in a magnetized jet is a consequence of the fact that the separation between neighbouring magnetic flux surfaces increases faster than their cylindrical radius. However, whereas in the case of effective collimation-acceleration the product of the jet opening angle and its Lorentz factor does not exceed ~1, the addition of the rarefaction-acceleration mechanism makes it possible for this product to become >>1, in agreement with the inference from late-time panchromatic breaks in the afterglow light curves of long/soft GRBs.

  20. Effect of cellulose nanocrystals on crystallization kinetics of polycaprolactone

    NASA Astrophysics Data System (ADS)

    Migler, Kalman; Roy, Debjani; Kotula, Anthony; Natarajan, Bharath; Gilman, Jeffrey; Fox, Douglas

    The development of biocompatible polymer composites that enhance mechanical properties while maintaining thermoplastic processability is a longstanding goal in sustainable materials. Here we compatibilize a crystallizable polymer and a nano-fiber via surface modification and study the properties and crystallization kinetics of the resulting composite. First we demonstrate that polycaprolactone (PCL) and cellulose nanocrystals (CNCs) can be well-compatibilized by replacing the Na+ of sulfated cellulose nanocrystals (Na-CNCs) with tertiary butyl ammonium cations and then melt mixing via twin-screw extrusion. Transmission electron microscope and high temperature melt rheology show that the modified CNCs were dispersed in the polymer matrix. We find the crystallization kinetics are substantially affected by the CNC as indicated by the simultaneous measures of modulus and conformational states; higher loadings of CNCs accelerated the kinetics. We further correlate the crystallization kinetics, mechanical properties and stability.

  1. Microsecond kinetics in model single- and double-stranded amylose polymers.

    PubMed

    Sattelle, Benedict M; Almond, Andrew

    2014-05-07

    Amylose, a component of starch with increasing biotechnological significance, is a linear glucose polysaccharide that self-organizes into single- and double-helical assemblies. Starch granule packing, gelation and inclusion-complex formation result from finely balanced macromolecular kinetics that have eluded precise experimental quantification. Here, graphics processing unit (GPU) accelerated multi-microsecond aqueous simulations are employed to explore conformational kinetics in model single- and double-stranded amylose. The all-atom dynamics concur with prior X-ray and NMR data while surprising and previously overlooked microsecond helix-coil, glycosidic linkage and pyranose ring exchange are hypothesized. In a dodecasaccharide, single-helical collapse was correlated with linkages and rings transitioning from their expected syn and (4)C1 chair conformers. The associated microsecond exchange rates were dependent on proximity to the termini and chain length (comparing hexa- and trisaccharides), while kinetic features of dodecasaccharide linkage and ring flexing are proposed to be a good model for polymers. Similar length double-helices were stable on microsecond timescales but the parallel configuration was sturdier than the antiparallel equivalent. In both, tertiary organization restricted local chain dynamics, implying that simulations of single amylose strands cannot be extrapolated to dimers. Unbiased multi-microsecond simulations of amylose are proposed as a valuable route to probing macromolecular kinetics in water, assessing the impact of chemical modifications on helical stability and accelerating the development of new biotechnologies.

  2. Assessment of two-dimensional induced accelerations from measured kinematic and kinetic data.

    PubMed

    Hof, A L; Otten, E

    2005-11-01

    A simple algorithm is presented to calculate the induced accelerations of body segments in human walking for the sagittal plane. The method essentially consists of setting up 2x4 force equations, 4 moment equations, 2x3 joint constraint equations and two constraints related to the foot-ground interaction. Data needed for the equations are, next to masses and moments of inertia, the positions of ankle, knee and hip. This set of equations is put in the form of an 18x18 matrix or 20x20 matrix, the solution of which can be found by inversion. By applying input vectors related to gravity, to centripetal accelerations or to muscle moments, the 'induced' accelerations and reaction forces related to these inputs can be found separately. The method was tested for walking in one subject. Good agreement was found with published results obtained by much more complicated three-dimensional forward dynamic models.

  3. Investigation of kinetic friction using an iPhone

    NASA Astrophysics Data System (ADS)

    Baldock, Clive; Johnson, Roger

    2016-11-01

    The iPhone is particularly suitable for mechanics experiments using the in-built acceleration sensor or accelerometer in-conjunction with the on-board data collection facility and a downloadable so-called ‘app’. In this work the iPhone has been used to investigate the acceleration due to gravity and determine the coefficient of kinetic friction, μ k of the iPhone as an object sliding down an inclined plane. This method is more accurate than that usually employed in the laboratory where the ‘fits and starts’ of the block sliding down the inclined plane potentially invalidate the required assumption that the velocity is constant. In its simplest form the measurement of acceleration is required to be undertaken for only 2 angles.

  4. Core-Shell PdPb@Pd Aerogels with Multiply-Twinned Intermetallic Nanostructures: Facile Synthesis with Accelerated Gelation Kinetics and Their Enhanced Electrocatalytic Properties

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhu, Chengzhou; Shi, Qiurong; Fu, Shaofang

    2018-04-04

    Delicately engineering the well-defined noble metal aerogels with favorable structural and compositional features is of vital importance for wide applications. Here, we reported one-pot and facile method for synthesizing core-shell PdPb@Pd hydrogels/aerogels with multiply-twinned grains and ordered intermetallic phase using sodium hypophosphite as a multifunctional reducing agent. Due to the accelerated gelation kinetics induced by increased reaction temperature and specific function of sodium hypophosphite, the formation of hydrogels can be completed within 4 hrs, far faster than the previous reports. Owe to their unique porous structure and favorable geometric and electronic effects, the optimized PdPb@Pd aerogels exhibit enhanced electrochemical performancemore » towards ethylene glycol oxidation with a mass activity of 5.8 times higher than Pd black.« less

  5. Core–shell PdPb@Pd aerogels with multiply-twinned intermetallic nanostructures: facile synthesis with accelerated gelation kinetics and their enhanced electrocatalytic properties

    DOE PAGES

    Zhu, Chengzhou; Shi, Qiurong; Fu, Shaofang; ...

    2018-04-04

    Delicately engineering well-defined noble metal aerogels with favorable structural and compositional features is of vital importance for wide applications. Here, we reported a one-pot and facile method for synthesizing core–shell PdPb@Pd hydrogels/aerogels with multiply-twinned grains and an ordered intermetallic phase using sodium hypophosphite as a multifunctional reducing agent. Due to the accelerated gelation kinetics induced by increased reaction temperature and the specific function of sodium hypophosphite, the formation of hydrogels can be completed within 4 h. As a result, owing to their unique porous structure and favorable geometric and electronic effects, the optimized PdPb@Pd aerogels exhibit enhanced electrochemical performance towardsmore » ethylene glycol oxidation with a mass activity of 5.8 times higher than Pd black.« less

  6. Core–shell PdPb@Pd aerogels with multiply-twinned intermetallic nanostructures: facile synthesis with accelerated gelation kinetics and their enhanced electrocatalytic properties

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhu, Chengzhou; Shi, Qiurong; Fu, Shaofang

    Delicately engineering well-defined noble metal aerogels with favorable structural and compositional features is of vital importance for wide applications. Here, we reported a one-pot and facile method for synthesizing core–shell PdPb@Pd hydrogels/aerogels with multiply-twinned grains and an ordered intermetallic phase using sodium hypophosphite as a multifunctional reducing agent. Due to the accelerated gelation kinetics induced by increased reaction temperature and the specific function of sodium hypophosphite, the formation of hydrogels can be completed within 4 h. As a result, owing to their unique porous structure and favorable geometric and electronic effects, the optimized PdPb@Pd aerogels exhibit enhanced electrochemical performance towardsmore » ethylene glycol oxidation with a mass activity of 5.8 times higher than Pd black.« less

  7. Motivation and short-term memory in visual search: Attention's accelerator revisited.

    PubMed

    Schneider, Daniel; Bonmassar, Claudia; Hickey, Clayton

    2018-05-01

    A cue indicating the possibility of cash reward will cause participants to perform memory-based visual search more efficiently. A recent study has suggested that this performance benefit might reflect the use of multiple memory systems: when needed, participants may maintain the to-be-remembered object in both long-term and short-term visual memory, with this redundancy benefitting target identification during search (Reinhart, McClenahan & Woodman, 2016). Here we test this compelling hypothesis. We had participants complete a memory-based visual search task involving a reward cue that either preceded presentation of the to-be-remembered target (pre-cue) or followed it (retro-cue). Following earlier work, we tracked memory representation using two components of the event-related potential (ERP): the contralateral delay activity (CDA), reflecting short-term visual memory, and the anterior P170, reflecting long-term storage. We additionally tracked attentional preparation and deployment in the contingent negative variation (CNV) and N2pc, respectively. Results show that only the reward pre-cue impacted our ERP indices of memory. However, both types of cue elicited a robust CNV, reflecting an influence on task preparation, both had equivalent impact on deployment of attention to the target, as indexed in the N2pc, and both had equivalent impact on visual search behavior. Reward prospect thus has an influence on memory-guided visual search, but this does not appear to be necessarily mediated by a change in the visual memory representations indexed by CDA. Our results demonstrate that the impact of motivation on search is not a simple product of improved memory for target templates. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Direct acceleration in intense laser fields used for bunch amplification of relativistic electrons

    NASA Astrophysics Data System (ADS)

    Braenzel, J.; Andreev, A. A.; Ehrentraut, L.; Schnürer, M.

    2017-05-01

    A method, how electrons can be directly accelerated in intense laser fields, is investigated experimentally and discussed with numerical and analytical simulation. When ultrathin foil targets are exposed with peak laser intensities of 1x1020 W/cm2 , slow electrons ( keV kinetic energy), that are emitted from the ultrathin foil target along laser propagation direction, are post-accelerated in the transmitted laser field. They received significant higher kinetic energies (MeV), when this interaction was limited in duration and an enhanced number of fast electrons were detected. The decoupling of the light field from the electron interaction we realized with a second separator foil, blocking the transmitted laser light at a particular distance and allowing the fast electrons to pass. Variation of the propagation distance in the laser field results in different energy gains for the electrons. This finding is explained with electron acceleration in the electromagnetic field of a light pulse and confirms a concept being discussed for some time. In the experiments the effect manifests in an electron number amplification of about 3 times around a peak at 1 MeV electron energy. Measurements confirmed that the overall number in the whole bunch is enhanced to about 109 electrons covering kinetic energies between 0.5 to 5 MeV. The method holds promise for ultrashort electron bunch generation at MeV energies for direct application, e.g. ultra-fast electron diffraction, or for injection into post accelerator stages for different purposes.

  9. Kinetic scale structure of low-frequency waves and fluctuations

    NASA Astrophysics Data System (ADS)

    Lopez Herrera, R. A.; Figueroa-Vinas, A.; Araneda, J. A.; Yoon, P. H.

    2017-12-01

    The dissipation of solar wind turbulence at kinetic scales is believed to be important for heating the corona and accelerating the wind. Linear Vlasov kinetic theory is a useful tool in identifying various wave modes, including kinetic Alfvén, fast magnetosonic/whistler, ion-acoustic (or kinetic slow mode), and their possible roles in the dissipation. However, kinetic mode structure near the vicinity of ion cyclotron modes is not clearly understood. The present poster aims to further elucidate the structure of these low-frequency waves by introducing discrete particle effects through hybrid simulations and Klimontovich formalism of spontaneous emission theory. The theory and simulation of spontaneously emitted low-frequency fluctuations are employed to identify and distinguish the detailed mode structures associated with ion Bernstein versus quasi modes. The spontaneous emission theory and simulation also confirm the findings of Vlasov theory in that the kinetic Alfvén wave can be defined over a wide range of frequencies, including the proton cyclotron frequency and its harmonics, especially for high beta plasmas. This implies that these low-frequency modes may play predominant roles even in the fully kinetic description of kinetic scale turbulence and dissipation despite the fact that cyclotron harmonic and Bernstein modes may also play important roles in wave-particle interactions.

  10. Search predicts and changes patience in intertemporal choice.

    PubMed

    Reeck, Crystal; Wall, Daniel; Johnson, Eric J

    2017-11-07

    Intertemporal choice impacts many important outcomes, such as decisions about health, education, wealth, and the environment. However, the psychological processes underlying decisions involving outcomes at different points in time remain unclear, limiting opportunities to intervene and improve people's patience. This research examines information-search strategies used during intertemporal choice and their impact on decisions. In experiment 1, we demonstrate that search strategies vary substantially across individuals. We subsequently identify two distinct search strategies across individuals. Comparative searchers, who compare features across options, discount future options less and are more susceptible to acceleration versus delay framing than integrative searchers, who integrate the features of an option. Experiment 2 manipulates search using an unobtrusive method to establish a causal relationship between strategy and choice, randomly assigning participants to conditions promoting either comparative or integrative search. Again, comparative search promotes greater patience than integrative search. Additionally, when participants adopt a comparative search strategy, they also exhibit greater effects of acceleration versus delay framing. Although most participants reported that the manipulation did not change their behavior, promoting comparative search decreased discounting of future rewards substantially and speeded patient choices. These findings highlight the central role that heterogeneity in psychological processes plays in shaping intertemporal choice. Importantly, these results indicate that theories that ignore variability in search strategies may be inadvertently aggregating over different subpopulations that use very different processes. The findings also inform interventions in choice architecture to increase patience and improve consumer welfare. Copyright © 2017 the Author(s). Published by PNAS.

  11. Improvement of Space Shuttle Main Engine Low Frequency Acceleration Measurements

    NASA Technical Reports Server (NTRS)

    Stec, Robert C.

    1999-01-01

    The noise floor of low frequency acceleration data acquired on the Space Shuttle Main Engines is higher than desirable. Difficulties of acquiring high quality acceleration data on this engine are discussed. The approach presented in this paper for reducing the acceleration noise floor focuses on a search for an accelerometer more capable of measuring low frequency accelerations. An overview is given of the current measurement system used to acquire engine vibratory data. The severity of vibration, temperature, and moisture environments are considered. Vibratory measurements from both laboratory and rocket engine tests are presented.

  12. Astrophysical particle acceleration mechanisms in colliding magnetized laser-produced plasmas

    DOE PAGES

    Fox, W.; Park, J.; Deng, W.; ...

    2017-08-11

    Significant particle energization is observed to occur in numerous astrophysical environments, and in the standard models, this acceleration occurs alongside energy conversion processes including collisionless shocks or magnetic reconnection. Recent platforms for laboratory experiments using magnetized laser-produced plasmas have opened opportunities to study these particle acceleration processes in the laboratory. Through fully kinetic particle-in-cell simulations, we investigate acceleration mechanisms in experiments with colliding magnetized laser-produced plasmas, with geometry and parameters matched to recent high-Mach number reconnection experiments with externally controlled magnetic fields. 2-D simulations demonstrate significant particle acceleration with three phases of energization: first, a “direct” Fermi acceleration driven bymore » approaching magnetized plumes; second, x-line acceleration during magnetic reconnection of anti-parallel fields; and finally, an additional Fermi energization of particles trapped in contracting and relaxing magnetic islands produced by reconnection. Furthermore, the relative effectiveness of these mechanisms depends on plasma and magnetic field parameters of the experiments.« less

  13. Automated Transition State Theory Calculations for High-Throughput Kinetics.

    PubMed

    Bhoorasingh, Pierre L; Slakman, Belinda L; Seyedzadeh Khanshan, Fariba; Cain, Jason Y; West, Richard H

    2017-09-21

    A scarcity of known chemical kinetic parameters leads to the use of many reaction rate estimates, which are not always sufficiently accurate, in the construction of detailed kinetic models. To reduce the reliance on these estimates and improve the accuracy of predictive kinetic models, we have developed a high-throughput, fully automated, reaction rate calculation method, AutoTST. The algorithm integrates automated saddle-point geometry search methods and a canonical transition state theory kinetics calculator. The automatically calculated reaction rates compare favorably to existing estimated rates. Comparison against high level theoretical calculations show the new automated method performs better than rate estimates when the estimate is made by a poor analogy. The method will improve by accounting for internal rotor contributions and by improving methods to determine molecular symmetry.

  14. Combining Diffusive Shock Acceleration with Acceleration by Contracting and Reconnecting Small-scale Flux Ropes at Heliospheric Shocks

    NASA Astrophysics Data System (ADS)

    le Roux, J. A.; Zank, G. P.; Webb, G. M.; Khabarova, O. V.

    2016-08-01

    Computational and observational evidence is accruing that heliospheric shocks, as emitters of vorticity, can produce downstream magnetic flux ropes and filaments. This led Zank et al. to investigate a new paradigm whereby energetic particle acceleration near shocks is a combination of diffusive shock acceleration (DSA) with downstream acceleration by many small-scale contracting and reconnecting (merging) flux ropes. Using a model where flux-rope acceleration involves a first-order Fermi mechanism due to the mean compression of numerous contracting flux ropes, Zank et al. provide theoretical support for observations that power-law spectra of energetic particles downstream of heliospheric shocks can be harder than predicted by DSA theory and that energetic particle intensities should peak behind shocks instead of at shocks as predicted by DSA theory. In this paper, a more extended formalism of kinetic transport theory developed by le Roux et al. is used to further explore this paradigm. We describe how second-order Fermi acceleration, related to the variance in the electromagnetic fields produced by downstream small-scale flux-rope dynamics, modifies the standard DSA model. The results show that (I) this approach can qualitatively reproduce observations of particle intensities peaking behind the shock, thus providing further support for the new paradigm, and (II) stochastic acceleration by compressible flux ropes tends to be more efficient than incompressible flux ropes behind shocks in modifying the DSA spectrum of energetic particles.

  15. Oxidative desulfurization: kinetic modelling.

    PubMed

    Dhir, S; Uppaluri, R; Purkait, M K

    2009-01-30

    Increasing environmental legislations coupled with enhanced production of petroleum products demand, the deployment of novel technologies to remove organic sulfur efficiently. This work represents the kinetic modeling of ODS using H(2)O(2) over tungsten-containing layered double hydroxide (LDH) using the experimental data provided by Hulea et al. [V. Hulea, A.L. Maciuca, F. Fajula, E. Dumitriu, Catalytic oxidation of thiophenes and thioethers with hydrogen peroxide in the presence of W-containing layered double hydroxides, Appl. Catal. A: Gen. 313 (2) (2006) 200-207]. The kinetic modeling approach in this work initially targets the scope of the generation of a superstructure of micro-kinetic reaction schemes and models assuming Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms. Subsequently, the screening and selection of above models is initially based on profile-based elimination of incompetent schemes followed by non-linear regression search performed using the Levenberg-Marquardt algorithm (LMA) for the chosen models. The above analysis inferred that Eley-Rideal mechanism describes the kinetic behavior of ODS process using tungsten-containing LDH, with adsorption of reactant and intermediate product only taking place on the catalyst surface. Finally, an economic index is presented that scopes the economic aspects of the novel catalytic technology with the parameters obtained during regression analysis to conclude that the cost factor for the catalyst is 0.0062-0.04759 US $ per barrel.

  16. Particle acceleration at a reconnecting magnetic separator

    NASA Astrophysics Data System (ADS)

    Threlfall, J.; Neukirch, T.; Parnell, C. E.; Eradat Oskoui, S.

    2015-02-01

    Context. While the exact acceleration mechanism of energetic particles during solar flares is (as yet) unknown, magnetic reconnection plays a key role both in the release of stored magnetic energy of the solar corona and the magnetic restructuring during a flare. Recent work has shown that special field lines, called separators, are common sites of reconnection in 3D numerical experiments. To date, 3D separator reconnection sites have received little attention as particle accelerators. Aims: We investigate the effectiveness of separator reconnection as a particle acceleration mechanism for electrons and protons. Methods: We study the particle acceleration using a relativistic guiding-centre particle code in a time-dependent kinematic model of magnetic reconnection at a separator. Results: The effect upon particle behaviour of initial position, pitch angle, and initial kinetic energy are examined in detail, both for specific (single) particle examples and for large distributions of initial conditions. The separator reconnection model contains several free parameters, and we study the effect of changing these parameters upon particle acceleration, in particular in view of the final particle energy ranges that agree with observed energy spectra.

  17. Comparisons of time explicit hybrid kinetic-fluid code Architect for Plasma Wakefield Acceleration with a full PIC code

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Massimo, F., E-mail: francesco.massimo@ensta-paristech.fr; Dipartimento SBAI, Università di Roma “La Sapienza“, Via A. Scarpa 14, 00161 Roma; Atzeni, S.

    Architect, a time explicit hybrid code designed to perform quick simulations for electron driven plasma wakefield acceleration, is described. In order to obtain beam quality acceptable for applications, control of the beam-plasma-dynamics is necessary. Particle in Cell (PIC) codes represent the state-of-the-art technique to investigate the underlying physics and possible experimental scenarios; however PIC codes demand the necessity of heavy computational resources. Architect code substantially reduces the need for computational resources by using a hybrid approach: relativistic electron bunches are treated kinetically as in a PIC code and the background plasma as a fluid. Cylindrical symmetry is assumed for themore » solution of the electromagnetic fields and fluid equations. In this paper both the underlying algorithms as well as a comparison with a fully three dimensional particle in cell code are reported. The comparison highlights the good agreement between the two models up to the weakly non-linear regimes. In highly non-linear regimes the two models only disagree in a localized region, where the plasma electrons expelled by the bunch close up at the end of the first plasma oscillation.« less

  18. A global reaction route mapping-based kinetic Monte Carlo algorithm.

    PubMed

    Mitchell, Izaac; Irle, Stephan; Page, Alister J

    2016-07-14

    We propose a new on-the-fly kinetic Monte Carlo (KMC) method that is based on exhaustive potential energy surface searching carried out with the global reaction route mapping (GRRM) algorithm. Starting from any given equilibrium state, this GRRM-KMC algorithm performs a one-step GRRM search to identify all surrounding transition states. Intrinsic reaction coordinate pathways are then calculated to identify potential subsequent equilibrium states. Harmonic transition state theory is used to calculate rate constants for all potential pathways, before a standard KMC accept/reject selection is performed. The selected pathway is then used to propagate the system forward in time, which is calculated on the basis of 1st order kinetics. The GRRM-KMC algorithm is validated here in two challenging contexts: intramolecular proton transfer in malonaldehyde and surface carbon diffusion on an iron nanoparticle. We demonstrate that in both cases the GRRM-KMC method is capable of reproducing the 1st order kinetics observed during independent quantum chemical molecular dynamics simulations using the density-functional tight-binding potential.

  19. A global reaction route mapping-based kinetic Monte Carlo algorithm

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mitchell, Izaac; Page, Alister J., E-mail: sirle@chem.nagoya-u.ac.jp, E-mail: alister.page@newcastle.edu.au; Irle, Stephan, E-mail: sirle@chem.nagoya-u.ac.jp, E-mail: alister.page@newcastle.edu.au

    2016-07-14

    We propose a new on-the-fly kinetic Monte Carlo (KMC) method that is based on exhaustive potential energy surface searching carried out with the global reaction route mapping (GRRM) algorithm. Starting from any given equilibrium state, this GRRM-KMC algorithm performs a one-step GRRM search to identify all surrounding transition states. Intrinsic reaction coordinate pathways are then calculated to identify potential subsequent equilibrium states. Harmonic transition state theory is used to calculate rate constants for all potential pathways, before a standard KMC accept/reject selection is performed. The selected pathway is then used to propagate the system forward in time, which is calculatedmore » on the basis of 1st order kinetics. The GRRM-KMC algorithm is validated here in two challenging contexts: intramolecular proton transfer in malonaldehyde and surface carbon diffusion on an iron nanoparticle. We demonstrate that in both cases the GRRM-KMC method is capable of reproducing the 1st order kinetics observed during independent quantum chemical molecular dynamics simulations using the density-functional tight-binding potential.« less

  20. A global reaction route mapping-based kinetic Monte Carlo algorithm

    NASA Astrophysics Data System (ADS)

    Mitchell, Izaac; Irle, Stephan; Page, Alister J.

    2016-07-01

    We propose a new on-the-fly kinetic Monte Carlo (KMC) method that is based on exhaustive potential energy surface searching carried out with the global reaction route mapping (GRRM) algorithm. Starting from any given equilibrium state, this GRRM-KMC algorithm performs a one-step GRRM search to identify all surrounding transition states. Intrinsic reaction coordinate pathways are then calculated to identify potential subsequent equilibrium states. Harmonic transition state theory is used to calculate rate constants for all potential pathways, before a standard KMC accept/reject selection is performed. The selected pathway is then used to propagate the system forward in time, which is calculated on the basis of 1st order kinetics. The GRRM-KMC algorithm is validated here in two challenging contexts: intramolecular proton transfer in malonaldehyde and surface carbon diffusion on an iron nanoparticle. We demonstrate that in both cases the GRRM-KMC method is capable of reproducing the 1st order kinetics observed during independent quantum chemical molecular dynamics simulations using the density-functional tight-binding potential.

  1. First-order particle acceleration in magnetically driven flows

    DOE PAGES

    Beresnyak, Andrey; Li, Hui

    2016-03-02

    In this study, we demonstrate that particles are regularly accelerated while experiencing curvature drift in flows driven by magnetic tension. Some examples of such flows include spontaneous turbulent reconnection and decaying magnetohydrodynamic turbulence, where a magnetic field relaxes to a lower-energy configuration and transfers part of its energy to kinetic motions of the fluid. We show that this energy transfer, which normally causes turbulent cascade and heating of the fluid, also results in a first-order acceleration of non-thermal particles. Since it is generic, this acceleration mechanism is likely to play a role in the production of non-thermal particle distribution inmore » magnetically dominant environments such as the solar chromosphere, pulsar magnetospheres, jets from supermassive black holes, and γ-ray bursts.« less

  2. Kinetic Scale Structure of Low-frequency Waves and Fluctuations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    López, Rodrigo A.; Yoon, Peter H.; Viñas, Adolfo F.

    The dissipation of solar wind turbulence at kinetic scales is believed to be important for the heating of the corona and for accelerating the wind. The linear Vlasov kinetic theory is a useful tool for identifying various wave modes, including kinetic Alfvén, fast magnetosonic/whistler, and ion-acoustic (or kinetic slow), and their possible roles in the dissipation. However, the kinetic mode structure in the vicinity of ion-cyclotron modes is not clearly understood. The present paper aims to further elucidate the structure of these low-frequency waves by introducing discrete particle effects through hybrid simulations and Klimontovich formalism of spontaneous emission theory. Themore » theory and simulation of spontaneously emitted low-frequency fluctuations are employed to identify and distinguish the detailed mode structures associated with ion-Bernstein modes versus quasi-modes. The spontaneous emission theory and simulation also confirm the findings of the Vlasov theory in that the kinetic Alfvén waves can be defined over a wide range of frequencies, including the proton cyclotron frequency and its harmonics, especially for high-beta plasmas. This implies that these low-frequency modes may play predominant roles even in the fully kinetic description of kinetic scale turbulence and dissipation despite the fact that cyclotron harmonic and Bernstein modes may also play important roles in wave–particle interactions.« less

  3. Transiently disordered tails accelerate folding of globular proteins.

    PubMed

    Mallik, Saurav; Ray, Tanaya; Kundu, Sudip

    2017-07-01

    Numerous biological proteins exhibit intrinsic disorder at their termini, which are associated with multifarious functional roles. Here, we show the surprising result that an increased percentage of terminal short transiently disordered regions with enhanced flexibility (TstDREF) is associated with accelerated folding rates of globular proteins. Evolutionary conservation of predicted disorder at TstDREFs and drastic alteration of folding rates upon point-mutations suggest critical regulatory role(s) of TstDREFs in shaping the folding kinetics. TstDREFs are associated with long-range intramolecular interactions and the percentage of native secondary structural elements physically contacted by TstDREFs exhibit another surprising positive correlation with folding kinetics. These results allow us to infer probable molecular mechanisms behind the TstDREF-mediated regulation of folding kinetics that challenge protein biochemists to assess by direct experimental testing. © 2017 Federation of European Biochemical Societies.

  4. Kinetics model of bainitic transformation with stress

    NASA Astrophysics Data System (ADS)

    Zhou, Mingxing; Xu, Guang; Hu, Haijiang; Yuan, Qing; Tian, Junyu

    2018-01-01

    Thermal simulations were conducted on a Gleeble 3800 simulator. The main purpose is to investigate the effects of stress on the kinetics of bainitic transformation in a Fe-C-Mn-Si advanced high strength bainitic steel. Previous studies on modeling the kinetics of stress affected bainitic transformation only considered the stress below the yield strength of prior austenite. In the present study, the stress above the yield strength of prior austenite is taken into account. A new kinetics model of bainitic transformation dependent on the stress (including the stresses below and above the yield strength of prior austenite) and the transformation temperature is proposed. The new model presents a good agreement with experimental results. In addition, it is found that the acceleration degree of stress on bainitic transformation increases with the stress whether its magnitude is below or above the yield strength of austenite, but the increasing rate gradually slows down when the stress is above the yield strength of austenite.

  5. Repopulation Kinetics and the Linear-Quadratic Model

    NASA Astrophysics Data System (ADS)

    O'Rourke, S. F. C.; McAneney, H.; Starrett, C.; O'Sullivan, J. M.

    2009-08-01

    The standard Linear-Quadratic (LQ) survival model for radiotherapy is used to investigate different schedules of radiation treatment planning for advanced head and neck cancer. We explore how these treament protocols may be affected by different tumour repopulation kinetics between treatments. The laws for tumour cell repopulation include the logistic and Gompertz models and this extends the work of Wheldon et al. [1], which was concerned with the case of exponential repopulation between treatments. Treatment schedules investigated include standarized and accelerated fractionation. Calculations based on the present work show, that even with growth laws scaled to ensure that the repopulation kinetics for advanced head and neck cancer are comparable, considerable variation in the survival fraction to orders of magnitude emerged. Calculations show that application of the Gompertz model results in a significantly poorer prognosis for tumour eradication. Gaps in treatment also highlight the differences in the LQ model with the effect of repopulation kinetics included.

  6. The Particle-in-Cell and Kinetic Simulation Software Center

    NASA Astrophysics Data System (ADS)

    Mori, W. B.; Decyk, V. K.; Tableman, A.; Fonseca, R. A.; Tsung, F. S.; Hu, Q.; Winjum, B. J.; An, W.; Dalichaouch, T. N.; Davidson, A.; Hildebrand, L.; Joglekar, A.; May, J.; Miller, K.; Touati, M.; Xu, X. L.

    2017-10-01

    The UCLA Particle-in-Cell and Kinetic Simulation Software Center (PICKSC) aims to support an international community of PIC and plasma kinetic software developers, users, and educators; to increase the use of this software for accelerating the rate of scientific discovery; and to be a repository of knowledge and history for PIC. We discuss progress towards making available and documenting illustrative open-source software programs and distinct production programs; developing and comparing different PIC algorithms; coordinating the development of resources for the educational use of kinetic software; and the outcomes of our first sponsored OSIRIS users workshop. We also welcome input and discussion from anyone interested in using or developing kinetic software, in obtaining access to our codes, in collaborating, in sharing their own software, or in commenting on how PICKSC can better serve the DPP community. Supported by NSF under Grant ACI-1339893 and by the UCLA Institute for Digital Research and Education.

  7. Multienzyme kinetics and sequential metabolism.

    PubMed

    Wienkers, Larry C; Rock, Brooke

    2014-01-01

    Enzymes are the catalysts of biological systems and are extremely efficient. A typical enzyme accelerates the rate of a reaction by factors of at least a million compared to the rate of the same reaction in the absence of the enzyme. In contrast to traditional catalytic enzymes, the family of cytochrome P450 (CYP) enzymes are catalytically promiscuous, and thus they possess remarkable versatility in substrates. The great diversity of reactions catalyzed by CYP enzymes appears to be based on two unique properties of these heme proteins, the ability of their iron to exist under multiple oxidation states with different reactivities and a flexible active site that can accommodate a wide variety of substrates. Herein is a discussion of two distinct types of kinetics observed with CYP enzymes. The first example is of CYP complex kinetic profiles when multiple CYP enzymes form the sample product. The second is sequential metabolism, in other words, the formation of multiple products from one CYP enzyme. Given the degree of CYP enzyme promiscuity, it is hardly surprising that there is also a high degree of complex kinetic profiles generated during the catalytic cycle.

  8. Transfer Learning to Accelerate Interface Structure Searches

    NASA Astrophysics Data System (ADS)

    Oda, Hiromi; Kiyohara, Shin; Tsuda, Koji; Mizoguchi, Teruyasu

    2017-12-01

    Interfaces have atomic structures that are significantly different from those in the bulk, and play crucial roles in material properties. The central structures at the interfaces that provide properties have been extensively investigated. However, determination of even one interface structure requires searching for the stable configuration among many thousands of candidates. Here, a powerful combination of machine learning techniques based on kriging and transfer learning (TL) is proposed as a method for unveiling the interface structures. Using the kriging+TL method, thirty-three grain boundaries were systematically determined from 1,650,660 candidates in only 462 calculations, representing an increase in efficiency over conventional all-candidate calculation methods, by a factor of approximately 3,600.

  9. CUDASW++ 3.0: accelerating Smith-Waterman protein database search by coupling CPU and GPU SIMD instructions.

    PubMed

    Liu, Yongchao; Wirawan, Adrianto; Schmidt, Bertil

    2013-04-04

    The maximal sensitivity for local alignments makes the Smith-Waterman algorithm a popular choice for protein sequence database search based on pairwise alignment. However, the algorithm is compute-intensive due to a quadratic time complexity. Corresponding runtimes are further compounded by the rapid growth of sequence databases. We present CUDASW++ 3.0, a fast Smith-Waterman protein database search algorithm, which couples CPU and GPU SIMD instructions and carries out concurrent CPU and GPU computations. For the CPU computation, this algorithm employs SSE-based vector execution units as accelerators. For the GPU computation, we have investigated for the first time a GPU SIMD parallelization, which employs CUDA PTX SIMD video instructions to gain more data parallelism beyond the SIMT execution model. Moreover, sequence alignment workloads are automatically distributed over CPUs and GPUs based on their respective compute capabilities. Evaluation on the Swiss-Prot database shows that CUDASW++ 3.0 gains a performance improvement over CUDASW++ 2.0 up to 2.9 and 3.2, with a maximum performance of 119.0 and 185.6 GCUPS, on a single-GPU GeForce GTX 680 and a dual-GPU GeForce GTX 690 graphics card, respectively. In addition, our algorithm has demonstrated significant speedups over other top-performing tools: SWIPE and BLAST+. CUDASW++ 3.0 is written in CUDA C++ and PTX assembly languages, targeting GPUs based on the Kepler architecture. This algorithm obtains significant speedups over its predecessor: CUDASW++ 2.0, by benefiting from the use of CPU and GPU SIMD instructions as well as the concurrent execution on CPUs and GPUs. The source code and the simulated data are available at http://cudasw.sourceforge.net.

  10. An accelerated calendar and cycle life study of Li-ion cells.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bloom, I.; Cole, B. W.; Sohn, J. J.

    2001-10-15

    The accelerated calendar and cycle life of lithium-ion cells was studied. Useful cell life was strongly affected by temperature, time, state-of-charge (SOC) and change in state-of-charge ({Delta}SOC). In calendar life experiments, useful cell life was strongly affected by temperature and time. Temperature accelerated cell performance degradation. The rates of area specific impedance (ASI) increase and power fade followed simple laws based on a power of time and Arrhenius kinetics. The data have been modeled using these two concepts and the calculated data agree well with the experimental values. The calendar life ASI increase and power fade data follow (time){sup 1/2}more » kinetics. This behavior may be due to solid electrolyte interface layer growth. From the cycle life experiments, the ASI increase data follow (time){sup 1/2} kinetics also, but there is an apparent change in overall power fade mechanism when going from 3 to 6% {Delta}SOC. Here, the power of time drops to below 1/2, which indicates that the power fade mechanism is more complex than layer growth.« less

  11. Kinetic approach to degradation mechanisms in polymer solar cells and their accurate lifetime predictions

    NASA Astrophysics Data System (ADS)

    Arshad, Muhammad Azeem; Maaroufi, AbdelKrim

    2018-07-01

    A beginning has been made in the present study regarding the accurate lifetime predictions of polymer solar cells. Certain reservations about the conventionally employed temperature accelerated lifetime measurements test for its unworthiness of predicting reliable lifetimes of polymer solar cells are brought into light. Critical issues concerning the accelerated lifetime testing include, assuming reaction mechanism instead of determining it, and relying solely on the temperature acceleration of a single property of material. An advanced approach comprising a set of theoretical models to estimate the accurate lifetimes of polymer solar cells is therefore suggested in order to suitably alternate the accelerated lifetime testing. This approach takes into account systematic kinetic modeling of various possible polymer degradation mechanisms under natural weathering conditions. The proposed kinetic approach is substantiated by its applications on experimental aging data-sets of polymer solar materials/solar cells including, P3HT polymer film, bulk heterojunction (MDMO-PPV:PCBM) and dye-sensitized solar cells. Based on the suggested approach, an efficacious lifetime determination formula for polymer solar cells is derived and tested on dye-sensitized solar cells. Some important merits of the proposed method are also pointed out and its prospective applications are discussed.

  12. Method of and apparatus for accelerating a projectile

    DOEpatents

    Goldstein, Yeshayahu S. A.; Tidman, Derek A.

    1986-01-01

    A projectile is accelerated along a confined path by supplying a pulsed high pressure, high velocity plasma jet to the rear of the projectile as the projectile traverses the path. The jet enters the confined path at a non-zero angle relative to the projectile path. The pulse is derived from a dielectric capillary tube having an interior wall from which plasma forming material is ablated in response to a discharge voltage. The projectile can be accelerated in response to the kinetic energy in the plasma jet or in response to a pressure increase of gases in the confined path resulting from the heat added to the gases by the plasma.

  13. Search for dark photons using data from CRESST-II Phase 2

    NASA Astrophysics Data System (ADS)

    Gütlein, A.; Angloher, G.; Bento, A.; Bucci, C.; Canonica, L.; Defay, X.; Erb, A.; Feilitzsch, F. v.; Ferreiro Iachellini, N.; Gorla, P.; Hauff, D.; Jochum, J.; Kiefer, M.; Kluck, H.; Kraus, H.; Lanfranchi, J.-C.; Loebell, J.; Mancuso, M.; Münster, A.; Pagliarone, C.; Petricca, F.; Potzel, W.; Pröbst, F.; Puig, R.; Reindl, F.; Schäffner, K.; Schieck, J.; Schönert, S.; Seidel, W.; Stahlberg, M.; Stodolsky, L.; Strandhagen, C.; Strauss, R.; Tanzke, A.; Trinh Thi, H. H.; Türkoǧlu, C.; Uffinger, M.; Ulrich, A.; Usherov, I.; Wawoczny, S.; Willers, M.; Wüstrich, M.; Zöller, A.

    2017-09-01

    Understanding the nature and origin of dark matter is one of the most important challenges for modern particle physics. During the previous decade the sensitivities of direct dark matter searches have improved by several orders of magnitude. These experiments focus their work mainly on the search for dark-matter particles interacting with nuclei (e.g. Weakly Interacting Massive Particles, WIMPs). However, there exists a large variety of different candidates for dark-matter particles. One of these candidates, the so-called dark photon, is a long-lived vector boson with a kinetic mixing to the standard-model photon. In this work we present the preliminary results of our search for dark photons. Using data from the direct dark matter search CRESST-II Phase 2 we can improve the existing constraints for the kinetic mixing for dark-photon masses between 0.3 and 0.5 keV/c2. In addition, we also present projected sensitivities for the next phases of the CRESST-III experiment showing great potential to improve the sensitivity for dark-photon masses below 1 keV.

  14. COMBINING DIFFUSIVE SHOCK ACCELERATION WITH ACCELERATION BY CONTRACTING AND RECONNECTING SMALL-SCALE FLUX ROPES AT HELIOSPHERIC SHOCKS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Le Roux, J. A.; Zank, G. P.; Webb, G. M.

    2016-08-10

    Computational and observational evidence is accruing that heliospheric shocks, as emitters of vorticity, can produce downstream magnetic flux ropes and filaments. This led Zank et al. to investigate a new paradigm whereby energetic particle acceleration near shocks is a combination of diffusive shock acceleration (DSA) with downstream acceleration by many small-scale contracting and reconnecting (merging) flux ropes. Using a model where flux-rope acceleration involves a first-order Fermi mechanism due to the mean compression of numerous contracting flux ropes, Zank et al. provide theoretical support for observations that power-law spectra of energetic particles downstream of heliospheric shocks can be harder thanmore » predicted by DSA theory and that energetic particle intensities should peak behind shocks instead of at shocks as predicted by DSA theory. In this paper, a more extended formalism of kinetic transport theory developed by le Roux et al. is used to further explore this paradigm. We describe how second-order Fermi acceleration, related to the variance in the electromagnetic fields produced by downstream small-scale flux-rope dynamics, modifies the standard DSA model. The results show that (i) this approach can qualitatively reproduce observations of particle intensities peaking behind the shock, thus providing further support for the new paradigm, and (ii) stochastic acceleration by compressible flux ropes tends to be more efficient than incompressible flux ropes behind shocks in modifying the DSA spectrum of energetic particles.« less

  15. Use of induced acceleration to quantify the (de)stabilization effect of external and internal forces on postural responses.

    PubMed

    van Asseldonk, Edwin H F; Carpenter, Mark G; van der Helm, Frans C T; van der Kooij, Herman

    2007-12-01

    Due to the mechanical coupling between the body segments, it is impossible to see with the naked eye the causes of body movements and understand the interaction between movements of different body parts. The goal of this paper is to investigate the use of induced acceleration analysis to reveal the causes of body movements. We derive the analytical equations to calculate induced accelerations and evaluate its potential to study human postural responses to support-surface translations. We measured the kinematic and kinetic responses of a subject to sudden forward and backward translations of a moving platform. The kinematic and kinetics served as input to the induced acceleration analyses. The induced accelerations showed explicitly that the platform acceleration and deceleration contributed to the destabilization and restabilization of standing balance, respectively. Furthermore, the joint torques, coriolis and centrifugal forces caused by swinging of the arms, contributed positively to stabilization of the Center of Mass. It is concluded that induced acceleration analyses is a valuable tool in understanding balance responses to different kinds of perturbations and may help to identify the causes of movement in different pathologies.

  16. A New Paradigm for Flare Particle Acceleration

    NASA Astrophysics Data System (ADS)

    Guidoni, Silvina E.; Karpen, Judith T.; DeVore, C. Richard

    2017-08-01

    The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission and its spectra in solar flares is not well understood. Here, we propose a first-principle-based model of particle acceleration that produces energy spectra that closely resemble those derived from hard X-ray observations. Our mechanism uses contracting magnetic islands formed during fast reconnection in solar flares to accelerate electrons, as first proposed by Drake et al. (2006) for kinetic-scale plasmoids. We apply these ideas to MHD-scale islands formed during fast reconnection in a simulated eruptive flare. A simple analytic model based on the particles’ adiabatic invariants is used to calculate the energy gain of particles orbiting field lines in our ultrahigh-resolution, 2.5D, MHD numerical simulation of a solar eruption (flare + coronal mass ejection). Then, we analytically model electrons visiting multiple contracting islands to account for the observed high-energy flare emission. Our acceleration mechanism inherently produces sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each macroscopic island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare current sheet is a promising candidate for electron acceleration in solar eruptions. This work was supported in part by the NASA LWS and H-SR programs..

  17. Polarization controlled kinetics and composition of trivalent chromium coatings on aluminum.

    PubMed

    Dardona, Sameh; Chen, Lei; Kryzman, Michael; Goberman, Daniel; Jaworowski, Mark

    2011-08-15

    Combined in situ spectroscopic ellipsometry and electrochemistry have been employed to monitor, in real-time, the formation of trivalent Cr conversion coatings on polished Al substrates at applied sample potentials. It is found that the formation kinetics and chemical composition of the film can be controlled by adjusting the anodic and cathodic reactions. The growth kinetics are accelerated at more positive anodic potentials or more negative cathodic potentials. At more negative potentials, the percentage of chromium in the coating is found to increase, while the zirconium percentage decreases.

  18. Diffuse Galactic gamma rays from shock-accelerated cosmic rays.

    PubMed

    Dermer, Charles D

    2012-08-31

    A shock-accelerated particle flux is proportional to p(-s), where p is the particle momentum, follows from simple theoretical considerations of cosmic-ray acceleration at nonrelativistic shocks followed by rigidity-dependent escape into the Galactic halo. A flux of shock-accelerated cosmic-ray protons with s≈2.8 provides an adequate fit to the Fermi Large Area Telescope γ-ray emission spectra of high-latitude and molecular cloud gas when uncertainties in nuclear production models are considered. A break in the spectrum of cosmic-ray protons claimed by Neronov, Semikoz, and Taylor [Phys. Rev. Lett. 108, 051105 (2012)] when fitting the γ-ray spectra of high-latitude molecular clouds is a consequence of using a cosmic-ray proton flux described by a power law in kinetic energy.

  19. Accelerating atomic structure search with cluster regularization

    NASA Astrophysics Data System (ADS)

    Sørensen, K. H.; Jørgensen, M. S.; Bruix, A.; Hammer, B.

    2018-06-01

    We present a method for accelerating the global structure optimization of atomic compounds. The method is demonstrated to speed up the finding of the anatase TiO2(001)-(1 × 4) surface reconstruction within a density functional tight-binding theory framework using an evolutionary algorithm. As a key element of the method, we use unsupervised machine learning techniques to categorize atoms present in a diverse set of partially disordered surface structures into clusters of atoms having similar local atomic environments. Analysis of more than 1000 different structures shows that the total energy of the structures correlates with the summed distances of the atomic environments to their respective cluster centers in feature space, where the sum runs over all atoms in each structure. Our method is formulated as a gradient based minimization of this summed cluster distance for a given structure and alternates with a standard gradient based energy minimization. While the latter minimization ensures local relaxation within a given energy basin, the former enables escapes from meta-stable basins and hence increases the overall performance of the global optimization.

  20. Current Fragmentation and Particle Acceleration in Solar Flares

    NASA Astrophysics Data System (ADS)

    Cargill, P. J.; Vlahos, L.; Baumann, G.; Drake, J. F.; Nordlund, Å.

    2012-11-01

    Particle acceleration in solar flares remains an outstanding problem in plasma physics and space science. While the observed particle energies and timescales can perhaps be understood in terms of acceleration at a simple current sheet or turbulence site, the vast number of accelerated particles, and the fraction of flare energy in them, defies any simple explanation. The nature of energy storage and dissipation in the global coronal magnetic field is essential for understanding flare acceleration. Scenarios where the coronal field is stressed by complex photospheric motions lead to the formation of multiple current sheets, rather than the single monolithic current sheet proposed by some. The currents sheets in turn can fragment into multiple, smaller dissipation sites. MHD, kinetic and cellular automata models are used to demonstrate this feature. Particle acceleration in this environment thus involves interaction with many distributed accelerators. A series of examples demonstrate how acceleration works in such an environment. As required, acceleration is fast, and relativistic energies are readily attained. It is also shown that accelerated particles do indeed interact with multiple acceleration sites. Test particle models also demonstrate that a large number of particles can be accelerated, with a significant fraction of the flare energy associated with them. However, in the absence of feedback, and with limited numerical resolution, these results need to be viewed with caution. Particle in cell models can incorporate feedback and in one scenario suggest that acceleration can be limited by the energetic particles reaching the condition for firehose marginal stability. Contemporary issues such as footpoint particle acceleration are also discussed. It is also noted that the idea of a "standard flare model" is ill-conceived when the entire distribution of flare energies is considered.

  1. Kinetic Simulations of Type II Radio Burst Emission Processes

    NASA Astrophysics Data System (ADS)

    Ganse, U.; Spanier, F. A.; Vainio, R. O.

    2011-12-01

    The fundamental emission process of Type II Radio Bursts has been under discussion for many decades. While analytic deliberations point to three wave interaction as the source for fundamental and harmonic radio emissions, sparse in-situ observational data and high computational demands for kinetic simulations have not allowed for a definite conclusion to be reached. A popular model puts the radio emission into the foreshock region of a coronal mass ejection's shock front, where shock drift acceleration can create eletrcon beam populations in the otherwise quiescent foreshock plasma. Beam-driven instabilities are then assumed to create waves, forming the starting point of three wave interaction processes. Using our kinetic particle-in-cell code, we have studied a number of emission scenarios based on electron beam populations in a CME foreshock, with focus on wave-interaction microphysics on kinetic scales. The self-consistent, fully kinetic simulations with completely physical mass-ratio show fundamental and harmonic emission of transverse electromagnetic waves and allow for detailled statistical analysis of all contributing wavemodes and their couplings.

  2. Core–shell PdPb@Pd aerogels with multiply-twinned intermetallic nanostructures: facile synthesis with accelerated gelation kinetics and their enhanced electrocatalytic properties

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhu, Chengzhou; Shi, Qiurong; Fu, Shaofang

    Delicately engineering the well-defined noble metal aerogels with favorable structural and compositional features is of vital importance for wide applications. Here, we reported one-pot and facile method for synthesizing core-shell PdPb@Pd hydrogels/aerogels with multiply-twinned grains and ordered intermetallic phase using sodium hypophosphite as a multifunctional reducing agent. Due to the accelerated gelation kinetics induced by increased reaction temperature and specific function of sodium hypophosphite, the formation of hydrogels can be completed within 4 hrs, far faster than the previous reports. Owe to their unique porous structure and favorable geometric and electronic effects, the optimized PdPb@Pd aerogels exhibit enhanced electrochemical performancemore » towards ethylene glycol oxidation with a mass activity of 5.8 times higher than Pd black.Core–shell PdPb@Pd aerogels with multiply-twinned grains and an ordered intermetallic phase was synthesized, which exhibited good electrocatalytic activity towards ethanol oxidation.« less

  3. A Kinetic-MHD Theory for the Self-Consistent Energy Exchange Between Energetic Particles and Active Small-scale Flux Ropes

    NASA Astrophysics Data System (ADS)

    le Roux, J. A.

    2017-12-01

    We developed previously a focused transport kinetic theory formalism with Fokker-plank coefficients (and its Parker transport limit) to model large-scale energetic particle transport and acceleration in solar wind regions with multiple contracting and merging small-scale flux ropes on MHD (inertial) scales (Zank et al. 2014; le Roux et al. 2015). The theory unifies the main acceleration mechanisms identified in particle simulations for particles temporarily trapped in such active flux rope structures, such as acceleration by the parallel electric field in reconnection regions between merging flux ropes, curvature drift acceleration in incompressible/compressible contracting and merging flux ropes, and betatron acceleration (e.g., Dahlin et al 2016). Initial analytical solutions of the Parker transport equation in the test particle limit showed that the energetic particle pressure from efficient flux-rope energization can potentially be high in turbulent solar wind regions containing active flux-rope structures. This requires taking into account the back reaction of energetic particles on flux ropes to more accurately determine the efficiency of energetic particles acceleration by small-scale flux ropes. To accomplish this goal we developed recently an extension of the kinetic theory to a kinetic-MHD level. We will present the extended theory showing the focused transport equation to be coupled to a solar wind MHD transport equation for small-scale flux-rope energy density extracted from a recently published nearly incompressible theory for solar wind MHD turbulence with a plasma beta of 1 (Zank et al. 2017). In the flux-rope transport equation appears new expressions for the damping/growth rates of flux-rope energy derived from assuming energy conservation in the interaction between energetic particles and small-scale flux ropes for all the main flux-rope acceleration mechanisms, whereas previous expressions for average particle acceleration rates have been

  4. EDITORIAL: Laser and plasma accelerators Laser and plasma accelerators

    NASA Astrophysics Data System (ADS)

    Bingham, Robert

    2009-02-01

    as photon deceleration and acceleration and is the result of a modulational instability. Simulations reported by Trines et al using a photon-in-cell code or wave kinetic code agree extremely well with experimental observation. Ion acceleration is actively studied; for example the papers by Robinson, Macchi, Marita and Tripathi all discuss different types of acceleration mechanisms from direct laser acceleration, Coulombic explosion and double layers. Ion acceleration is an exciting development that may have great promise in oncology. The surprising application is in muon acceleration, demonstrated by Peano et al who show that counterpropagating laser beams with variable frequencies drive a beat structure with variable phase velocity, leading to particle trapping and acceleration with possible application to a future muon collider and neutrino factory. Laser and plasma accelerators remain one of the exciting areas of plasma physics with applications in many areas of science ranging from laser fusion, novel high-brightness radiation sources, particle physics and medicine. The guest editor would like to thank all authors and referees for their invaluable contributions to this special issue.

  5. The Kinetic Chain Revisited: New Concepts on Throwing Mechanics and Injury.

    PubMed

    Chu, Samuel K; Jayabalan, Prakash; Kibler, W Ben; Press, Joel

    2016-03-01

    The overhead throwing motion is a complex activity that is achieved through activation of the kinetic chain. The kinetic chain refers to the linkage of multiple segments of the body that allows for transfer of forces and motion. The lower extremities and core provide a base of support, generating energy that is transferred eventually through the throwing arm and hand, resulting in release of the ball. The kinetic chain requires optimal anatomy, physiology, and mechanics and is involved in all 6 phases of overhead throwing: windup, stride, arm cocking, acceleration, deceleration, and follow-through. Breaks or deficits in the kinetic chain can lead to injury or decreased performance. Through an understanding of the mechanics and pathomechanics seen in each phase of throwing, the clinician can better evaluate and screen for potential kinetic chain deficits in the overhead throwing athlete. The purpose of this article is to review the biomechanics of the overhead throwing motion, the role of the kinetic chain in throwing, and the clinical evaluation and management of abnormal throwing mechanics and related injuries. Copyright © 2016 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

  6. Accelerating Information Retrieval from Profile Hidden Markov Model Databases.

    PubMed

    Tamimi, Ahmad; Ashhab, Yaqoub; Tamimi, Hashem

    2016-01-01

    Profile Hidden Markov Model (Profile-HMM) is an efficient statistical approach to represent protein families. Currently, several databases maintain valuable protein sequence information as profile-HMMs. There is an increasing interest to improve the efficiency of searching Profile-HMM databases to detect sequence-profile or profile-profile homology. However, most efforts to enhance searching efficiency have been focusing on improving the alignment algorithms. Although the performance of these algorithms is fairly acceptable, the growing size of these databases, as well as the increasing demand for using batch query searching approach, are strong motivations that call for further enhancement of information retrieval from profile-HMM databases. This work presents a heuristic method to accelerate the current profile-HMM homology searching approaches. The method works by cluster-based remodeling of the database to reduce the search space, rather than focusing on the alignment algorithms. Using different clustering techniques, 4284 TIGRFAMs profiles were clustered based on their similarities. A representative for each cluster was assigned. To enhance sensitivity, we proposed an extended step that allows overlapping among clusters. A validation benchmark of 6000 randomly selected protein sequences was used to query the clustered profiles. To evaluate the efficiency of our approach, speed and recall values were measured and compared with the sequential search approach. Using hierarchical, k-means, and connected component clustering techniques followed by the extended overlapping step, we obtained an average reduction in time of 41%, and an average recall of 96%. Our results demonstrate that representation of profile-HMMs using a clustering-based approach can significantly accelerate data retrieval from profile-HMM databases.

  7. Nonthermally dominated electron acceleration during magnetic reconnection in a low- β plasma

    DOE PAGES

    Li, Xiaocan; Guo, Fan; Li, Hui; ...

    2015-09-24

    By means of fully kinetic simulations, we investigate electron acceleration during magnetic reconnection in a nonrelativistic proton–electron plasma with conditions similar to solar corona and flares. We demonstrate that reconnection leads to a nonthermally dominated electron acceleration with a power-law energy distribution in the nonrelativistic low-β regime but not in the high-β regime, where β is the ratio of the plasma thermal pressure and the magnetic pressure. The accelerated electrons contain most of the dissipated magnetic energy in the low-β regime. A guiding-center current description is used to reveal the role of electron drift motions during the bulk nonthermal energization.more » We find that the main acceleration mechanism is a Fermi-type acceleration accomplished by the particle curvature drift motion along the electric field induced by the reconnection outflows. Although the acceleration mechanism is similar for different plasma β, low-β reconnection drives fast acceleration on Alfvénic timescales and develops power laws out of thermal distribution. Thus, the nonthermally dominated acceleration resulting from magnetic reconnection in low-β plasma may have strong implications for the highly efficient electron acceleration in solar flares and other astrophysical systems.« less

  8. On Solar Wind Origin and Acceleration: Measurements from ACE

    NASA Astrophysics Data System (ADS)

    Stakhiv, Mark; Lepri, Susan T.; Landi, Enrico; Tracy, Patrick; Zurbuchen, Thomas H.

    2016-10-01

    The origin and acceleration of the solar wind are still debated. In this paper, we search for signatures of the source region and acceleration mechanism of the solar wind in the plasma properties measured in situ by the Advanced Composition Explorer spacecraft. Using the elemental abundances as a proxy for the source region and the differential velocity and ion temperature ratios as a proxy for the acceleration mechanism, we are able to identify signatures pointing toward possible source regions and acceleration mechanisms. We find that the fast solar wind in the ecliptic plane is the same as that observed from the polar regions and is consistent with wave acceleration and coronal-hole origin. We also find that the slow wind is composed of two components: one similar to the fast solar wind (with slower velocity) and the other likely originating from closed magnetic loops. Both components of the slow solar wind show signatures of wave acceleration. From these findings, we draw a scenario that envisions two types of wind, with different source regions and release mechanisms, but the same wave acceleration mechanism.

  9. rfpipe: Radio interferometric transient search pipeline

    NASA Astrophysics Data System (ADS)

    Law, Casey J.

    2017-10-01

    rfpipe supports Python-based analysis of radio interferometric data (especially from the Very Large Array) and searches for fast radio transients. This extends on the rtpipe library (ascl:1706.002) with new approaches to parallelization, acceleration, and more portable data products. rfpipe can run in standalone mode or be in a cluster environment.

  10. Electrical Engineering in Los Alamos Neutron Science Center Accelerator

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Silva, Michael James

    The field of electrical engineering plays a significant role in particle accelerator design and operations. Los Alamos National Laboratories LANSCE facility utilizes the electrical energy concepts of power distribution, plasma generation, radio frequency energy, electrostatic acceleration, signals and diagnostics. The culmination of these fields produces a machine of incredible potential with uses such as isotope production, neutron spallation, neutron imaging and particle analysis. The key isotope produced in LANSCE isotope production facility is Strontium-82 which is utilized for medical uses such as cancer treatment and positron emission tomography also known as PET scans. Neutron spallation is one of the verymore » few methods used to produce neutrons for scientific research the other methods are natural decay of transuranic elements from nuclear reactors. Accelerator produce neutrons by accelerating charged particles into neutron dense elements such as tungsten imparting a neutral particle with kinetic energy, this has the benefit of producing a large number of neutrons as well as minimizing the waste generated. Utilizing the accelerator scientist can gain an understanding of how various particles behave and interact with matter to better understand the natural laws of physics and the universe around us.« less

  11. Magnetic Reconnection and Particle Acceleration in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Neukirch, Thomas

    Reconnection plays a major role for the magnetic activity of the solar atmosphere, for example solar flares. An interesting open problem is how magnetic reconnection acts to redistribute the stored magnetic energy released during an eruption into other energy forms, e.g. gener-ating bulk flows, plasma heating and non-thermal energetic particles. In particular, finding a theoretical explanation for the observed acceleration of a large number of charged particles to high energies during solar flares is presently one of the most challenging problems in solar physics. One difficulty is the vast difference between the microscopic (kinetic) and the macro-scopic (MHD) scales involved. Whereas the phenomena observed to occur on large scales are reasonably well explained by the so-called standard model, this does not seem to be the case for the small-scale (kinetic) aspects of flares. Over the past years, observations, in particular by RHESSI, have provided evidence that a naive interpretation of the data in terms of the standard solar flare/thick target model is problematic. As a consequence, the role played by magnetic reconnection in the particle acceleration process during solar flares may have to be reconsidered.

  12. Insights into accelerated liposomal release of topotecan in plasma monitored by a non-invasive fluorescence spectroscopic method

    PubMed Central

    Fugit, Kyle D.; Jyoti, Amar; Upreti, Meenakshi; Anderson, Bradley D.

    2014-01-01

    A non-invasive fluorescence method was developed to monitor liposomal release kinetics of the anticancer agent topotecan (TPT) in physiological fluids and subsequently used to explore the cause of accelerated release in plasma. Analyses of fluorescence excitation spectra confirmed that unencapsulated TPT exhibits a red shift in its spectrum as pH is increased. This property was used to monitor TPT release from actively loaded liposomal formulations having a low intravesicular pH. Mathematical release models were developed to extract reliable rate constants for TPT release in aqueous solutions monitored by fluorescence and release kinetics obtained by HPLC. Using the fluorescence method, accelerated TPT release was observed in plasma as previously reported in the literature. Simulations to estimate the intravesicular pH were conducted to demonstrate that accelerated release correlated with alterations in the low intravesicular pH. This was attributed to the presence of ammonia in plasma samples rather than proteins and other plasma components generally believed to alter release kinetics in physiological samples. These findings shed light on the critical role that ammonia may play in contributing to the preclinical/clinical variability and performance seen with actively-loaded liposomal formulations of TPT and other weakly-basic anticancer agents. PMID:25456833

  13. Kinetic study on UV-absorber photodegradation under different conditions

    NASA Astrophysics Data System (ADS)

    Bubev, Emil; Georgiev, Anton; Machkova, Maria

    2016-09-01

    The photodegradation kinetics of two benzophenone derivative UV-absorbers (UVAs)-BP-4 (benzophenone-4) and 4-HBP (4-hydroxybenzophenone), as additives in polyvinyl acetate (PVAc) films, were studied. Solution-processed PVAc films were irradiated in different environments in order to study oxygen and atmospheric humidity influence on UVA photodegradation. Photodegradation was traced by absorption intensity loss via UV-vis spectroscopy. Both UVAs exhibited excellent photostability in an inert atmosphere. Rate constants showed that BP-4 has better permanence in absence of oxygen. Both film types experienced rapid absorption loss, when irradiated in an oxygen containing atmosphere. UVA degradation was treated as a two-stage process. The photodegradation kinetics in the first stage agreed with the adopted complex rate law, but the second stage was best described by pseudo-first order kinetics. BP-4 exhibited better stability. Oxygen was established as the main accelerating factor for photodegradation of benzophenone derivatives UV-absorbers in thin PVAc films.

  14. Faster heart rate and muscular oxygen uptake kinetics in type 2 diabetes patients following endurance training.

    PubMed

    Koschate, Jessica; Drescher, Uwe; Brinkmann, Christian; Baum, Klaus; Schiffer, Thorsten; Latsch, Joachim; Brixius, Klara; Hoffmann, Uwe

    2016-11-01

    Cardiorespiratory kinetics were analyzed in type 2 diabetes patients before and after a 12-week endurance exercise-training intervention. It was hypothesized that muscular oxygen uptake and heart rate (HR) kinetics would be faster after the training intervention and that this would be detectable using a standardized work rate protocol with pseudo-random binary sequences. The cardiorespiratory kinetics of 13 male sedentary, middle-aged, overweight type 2 diabetes patients (age, 60 ± 8 years; body mass index, 33 ± 4 kg·m -2 ) were tested before and after the 12-week exercise intervention. Subjects performed endurance training 3 times a week on nonconsecutive days. Pseudo-random binary sequences exercise protocols in combination with time series analysis were used to estimate kinetics. Greater maxima in cross-correlation functions (CCF max ) represent faster kinetics of the respective parameter. CCF max of muscular oxygen uptake (pre-training: 0.31 ± 0.03; post-training: 0.37 ± 0.1, P = 0.024) and CCF max of HR (pre-training: 0.25 ± 0.04; post-training: 0.29 ± 0.06, P = 0.007) as well as peak oxygen uptake (pre-training: 24.4 ± 4.7 mL·kg -1 ·min -1 ; post-training: 29.3 ± 6.5 mL·kg -1 ·min -1 , P = 0.004) increased significantly over the course of the exercise intervention. In conclusion, kinetic responses to changing work rates in the moderate-intensity range are similar to metabolic demands occurring in everyday habitual activities. Moderate endurance training accelerated the kinetic responses of HR and muscular oxygen uptake. Furthermore, the applicability of the used method to detect these accelerations was demonstrated.

  15. Consequences of wave-particle interactions on chaotic acceleration

    NASA Technical Reports Server (NTRS)

    Schriver, David; Ashour-Abdalla, Maha

    1991-01-01

    The recent model of Ashour-Abdalla et al. (1991) has proposed that the earth's plasma sheet can be formed by chaotic acceleration in a magnetotail-like field configuration. The ion velocity distributions created by chaotic acceleration have unstable features and represent robust free energy sources for kinetic plasma waves that can modify the original distributions. In the plasma sheet boundary layer, field-aligned ion beamlets are formed which drive a host of instabilities creating a broadbanded noise spectrum and cause thermal spreading of the beamlets. In addition, there is strong heating of any cold background plasma that may be present. In the central plasma sheet, ion antiloss cone distributions are created which are unstable to very low frequency waves that saturate by filling the antiloss cone.

  16. GPU-accelerated computational tool for studying the effectiveness of asteroid disruption techniques

    NASA Astrophysics Data System (ADS)

    Zimmerman, Ben J.; Wie, Bong

    2016-10-01

    This paper presents the development of a new Graphics Processing Unit (GPU) accelerated computational tool for asteroid disruption techniques. Numerical simulations are completed using the high-order spectral difference (SD) method. Due to the compact nature of the SD method, it is well suited for implementation with the GPU architecture, hence solutions are generated at orders of magnitude faster than the Central Processing Unit (CPU) counterpart. A multiphase model integrated with the SD method is introduced, and several asteroid disruption simulations are conducted, including kinetic-energy impactors, multi-kinetic energy impactor systems, and nuclear options. Results illustrate the benefits of using multi-kinetic energy impactor systems when compared to a single impactor system. In addition, the effectiveness of nuclear options is observed.

  17. Quasi-linear heating and acceleration in bi-Maxwellian plasmas

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hellinger, Petr; Passot, Thierry; Sulem, Pierre-Louis

    2013-12-15

    Quasi-linear acceleration and heating rates are derived for drifting bi-Maxwellian distribution functions in a general nonrelativistic case for arbitrary wave vectors, propagation angles, and growth/damping rates. The heating rates in a proton-electron plasma due to ion-cyclotron/kinetic Alfvén and mirror waves for a wide range of wavelengths, directions of propagation, and growth or damping rates are explicitly computed.

  18. Electron acceleration by wave turbulence in a magnetized plasma

    NASA Astrophysics Data System (ADS)

    Rigby, A.; Cruz, F.; Albertazzi, B.; Bamford, R.; Bell, A. R.; Cross, J. E.; Fraschetti, F.; Graham, P.; Hara, Y.; Kozlowski, P. M.; Kuramitsu, Y.; Lamb, D. Q.; Lebedev, S.; Marques, J. R.; Miniati, F.; Morita, T.; Oliver, M.; Reville, B.; Sakawa, Y.; Sarkar, S.; Spindloe, C.; Trines, R.; Tzeferacos, P.; Silva, L. O.; Bingham, R.; Koenig, M.; Gregori, G.

    2018-05-01

    Astrophysical shocks are commonly revealed by the non-thermal emission of energetic electrons accelerated in situ1-3. Strong shocks are expected to accelerate particles to very high energies4-6; however, they require a source of particles with velocities fast enough to permit multiple shock crossings. While the resulting diffusive shock acceleration4 process can account for observations, the kinetic physics regulating the continuous injection of non-thermal particles is not well understood. Indeed, this injection problem is particularly acute for electrons, which rely on high-frequency plasma fluctuations to raise them above the thermal pool7,8. Here we show, using laboratory laser-produced shock experiments, that, in the presence of a strong magnetic field, significant electron pre-heating is achieved. We demonstrate that the key mechanism in producing these energetic electrons is through the generation of lower-hybrid turbulence via shock-reflected ions. Our experimental results are analogous to many astrophysical systems, including the interaction of a comet with the solar wind9, a setting where electron acceleration via lower-hybrid waves is possible.

  19. A mass filter based on an accelerating traveling wave.

    PubMed

    Wiedenbeck, Michael; Kasemset, Bodin; Kasper, Manfred

    2008-01-01

    We describe a novel mass filtering concept based on the acceleration of a pulsed ion beam through a stack of electrostatic plates. A precisely controlled traveling wave generated within such an ion guide will induce a mass-selective ion acceleration, with mass separation ultimately accomplished via a simple energy-filtering system. Crucial for successful filtering is that the velocity with which the traveling wave passes through the ion guide must be dynamically controlled in order to accommodate the acceleration of the target ion species. Mass selection is determined by the velocity and acceleration with which the wave traverses the ion guide, whereby the target species will acquire a higher kinetic energy than all other lighter as well as heaver species. Finite element simulations of this design demonstrate that for small masses a mass resolution M/DeltaM approximately 1000 can be achieved within an electrode stack containing as few as 20 plates. Some of the possible advantages and drawbacks which distinguish this concept from established mass spectrometric technologies are discussed.

  20. Being Careful with PASCO's Kinetic Friction Experiment: Uncovering Pre-Sliding Displacement?

    ERIC Educational Resources Information Center

    Lawlor, T. M.

    2008-01-01

    The widely used PASCO laboratory equipment is an excellent way to introduce students to many topics in physics. In one case, PASCO's equipment may be too good! Various experiments exist for calculating the kinetic coefficient of friction by measuring the acceleration of a sliding object under some constant force. With ever more accurate equipment,…

  1. An new MHD/kinetic model for exploring energetic particle production in macro-scale systems

    NASA Astrophysics Data System (ADS)

    Drake, J. F.; Swisdak, M.; Dahlin, J. T.

    2017-12-01

    A novel MHD/kinetic model is being developed to explore magneticreconnection and particle energization in macro-scale systems such asthe solar corona and the outer heliosphere. The model blends the MHDdescription with a macro-particle description. The rationale for thismodel is based on the recent discovery that energetic particleproduction during magnetic reconnection is controlled by Fermireflection and Betatron acceleration and not parallel electricfields. Since the former mechanisms are not dependent on kineticscales such as the Debye length and the electron and ion inertialscales, a model that sheds these scales is sufficient for describingparticle acceleration in macro-systems. Our MHD/kinetic model includesmacroparticles laid out on an MHD grid that are evolved with the MHDfields. Crucially, the feedback of the energetic component on the MHDfluid is included in the dynamics. Thus, energy of the total system,the MHD fluid plus the energetic component, is conserved. The systemhas no kinetic scales and therefore can be implemented to modelenergetic particle production in macro-systems with none of theconstraints associated with a PIC model. Tests of the new model insimple geometries will be presented and potential applications will bediscussed.

  2. Electron heating and acceleration during magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Dahlin, Joel

    2017-10-01

    Magnetic reconnection is thought to be an important driver of energetic particles in a variety of astrophysical phenomena such as solar flares and magnetospheric storms. However, the observed fraction of energy imparted to a nonthermal component can vary widely in different regimes. We use kinetic particle-in-cell (PIC) simulations to demonstrate the important role of the non-reversing (guide) field in controlling the efficiency of electron acceleration in collisionless reconnection. In reconnection where the guide field is smaller than the reconnecting component, the dominant electron accelerator is a Fermi-type mechanism that preferentially energizes the most energetic particles. In strong guide field reconnection, the field-line contraction that drives the Fermi mechanism becomes weak. Instead, parallel electric fields are primarily responsible for driving electron heating but are ineffective in driving the energetic component of the spectrum. Three-dimensional simulations reveal that the stochastic magnetic field that develops during 3D guide field reconnection plays a vital role in particle acceleration and transport. The reconnection outflows that drive Fermi acceleration also expel accelerating particles from energization regions. In 2D reconnection, electrons are trapped in island cores and acceleration ceases, whereas in 3D the stochastic magnetic field enables energetic electrons to leak out of islands and freely sample regions of energy release. A finite guide field is required to break initial 2D symmetry and facilitate escape from island structures. We show that reconnection with a guide field comparable to the reconnecting field generates the greatest number of energetic electrons, a regime where both (a) the Fermi mechanism is an efficient driver and (b) energetic electrons may freely access acceleration sites. These results have important implications for electron acceleration in solar flares and reconnection-driven dissipation in turbulence.

  3. Determination of in vivo regulation kinetics of small non-coding RNA in bacteria

    NASA Astrophysics Data System (ADS)

    Fei, Jingyi

    Small RNAs (sRNAs) play important roles in regulating gene expression through a variety of mechanisms. As one of the most common strategies, sRNA induced target messenger RNA (mRNA) includes two major steps: target search by base-pairing interactions with the and downstream execution by modulating translation or the stability of the mRNA. Here we describe a new imaging and analysis platform based on super-resolution fluorescence microscopy, which enabled the first in vivo kinetic measurement of sRNA-mediated gene regulation. Specifically, this platform was used to investigate a sugar-phosphate stress-induced bacterial sRNA that induces the degradation of target mRNAs. The data reveal that the sRNA binds to a primary target mRNA in a reversible and dynamic fashion, and that formation of the sRNA-mRNA complexes is the rate-limiting step, dictating the overall efficiency of regulation in vivo; whereas the downstream co-degradation of sRNA-mRNA complex can kinetically compete with the fast complex disassembly. Examination of a secondary target of this sRNA indicated that differences in the target search kinetics contribute to setting the regulation priority among different target mRNAs. This super-resolution imaging and analysis approach provides a conceptual framework that can be generalized to other sRNA systems and other target search processes.

  4. Impact of Harness Attachment Point on Kinetics and Kinematics During Sled Towing.

    PubMed

    Bentley, Ian; Atkins, Steve J; Edmundson, Christopher J; Metcalfe, John; Sinclair, Jonathan K

    2016-03-01

    Resisted sprint training is performed in a horizontal direction and involves similar muscles, velocities, and ranges of motion (ROM) to those of normal sprinting. Generally, sleds are attached to the athletes through a lead (3 m) and harness; the most common attachment points are the shoulder or waist. At present, it is not known how the different harness point's impact on the kinematics and kinetics associated with sled towing (ST). The aim of the current investigation was to examine the kinetics and kinematics of shoulder and waist harness attachment points in relation to the acceleration phase of ST. Fourteen trained men completed normal and ST trials, loaded at 10% reduction of sprint velocity. Sagittal plane kinematics from the trunk, hip, knee, and ankle were measured, together with stance phase kinetics (third footstrike). Kinetic and kinematic parameters were compared between harness attachments using one-way repeated-measures analysis of variance. The results indicated that various kinetic differences were present between the normal and ST conditions. Significantly greater net horizontal mean force, net horizontal impulses, propulsive mean force, and propulsive impulses were measured (p < 0.05). Interestingly, the waist harness also led to greater net horizontal impulse when compared with the shoulder attachment (p < 0.001). In kinematic terms, ST conditions significantly increased peak flexion in hip, knee, and ankle joints compared with the normal trials (p < 0.05). Results highlighted that the shoulder harness had a greater impact on trunk and knee joint kinematics when compared with the waist harness (p < 0.05). In summary, waist harnesses seem to be the most suitable attachment point for the acceleration phase of sprinting. Sled towing with these attachments resulted in fewer kinematic alterations and greater net horizontal impulse when compared with the shoulder harness. Future research is necessary in order to explore the long-term adaptations of

  5. COBRA: a Bayesian approach to pulsar searching

    NASA Astrophysics Data System (ADS)

    Lentati, L.; Champion, D. J.; Kramer, M.; Barr, E.; Torne, P.

    2018-02-01

    We introduce COBRA, a GPU-accelerated Bayesian analysis package for performing pulsar searching, that uses candidates from traditional search techniques to set the prior used for the periodicity of the source, and performs a blind search in all remaining parameters. COBRA incorporates models for both isolated and accelerated systems, as well as both Keplerian and relativistic binaries, and exploits pulse phase information to combine search epochs coherently, over time, frequency or across multiple telescopes. We demonstrate the efficacy of our approach in a series of simulations that challenge typical search techniques, including highly aliased signals, and relativistic binary systems. In the most extreme case, we simulate an 8 h observation containing 24 orbits of a pulsar in a binary with a 30 M⊙ companion. Even in this scenario we show that we can build up from an initial low-significance candidate, to fully recovering the signal. We also apply the method to survey data of three pulsars from the globular cluster 47Tuc: PSRs J0024-7204D, J0023-7203J and J0024-7204R. This final pulsar is in a 1.6 h binary, the shortest of any pulsar in 47Tuc, and additionally shows significant scintillation. By allowing the amplitude of the source to vary as a function of time, however, we show that we are able to obtain optimal combinations of such noisy data. We also demonstrate the ability of COBRA to perform high-precision pulsar timing directly on the single pulse survey data, and obtain a 95 per cent upper limit on the eccentricity of PSR J0024-7204R of εb < 0.0007.

  6. Searching for Heavy Photons with Detached Verices in the Heavy Photon Search Experiment

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Szumila-Vance, Holly

    The Jefferson Lab Heavy Photon Search (HPS) experiment is searching for a hypothetical massive particle called the heavy photon which could mediate a dark electromagnetic-type force. If heavy photons kinetically mix with Standard Model photons, they may be radiated by electrons scattering from a heavy nucleus and then decay to e+e- pairs. HPS uniquely searches for heavy photons that either decay at the target or a measurable distance after. The experiment utilizes a silicon vertex tracker (SVT) for momentum and vertex reconstruction, together with an electromagnetic calorimeter for measuring particle energies and triggering events. The HPS experiment took its firstmore » data during the spring 2015 engineering run using a 1 GeV electron beam incident on a tungsten target and its second data in the spring of 2016 at a beam energy of 2.3 GeV. The 2015 run obtained two days of production data that was used for the first physics results. The analysis of the data was conducted as a blinded analysis by tuning cuts on 10% of the data. This dissertation discusses the displaced vertex search for heavy photons in the 2015 engineering run. It describes the theoretical motivation for looking for heavy photons and provides an overview of the HPS experimental design and performance. The performance details of the experiment are primarily derived from the 2015 engineering run with some discussion from the higher energy running in 2016. This dissertation further discusses the cuts used to optimize the displaced vertex search and the results of the search. The displaced vertex search did not set a limit on the heavy photon but did validate the methodology for conducting the search. Finally, we used the full data set to make projections and guide future analyses.« less

  7. Internal loop photo-biodegradation reactor used for accelerated quinoline degradation and mineralization.

    PubMed

    Chang, Ling; Zhang, Yongming; Gan, Lu; Xu, Hua; Yan, Ning; Liu, Rui; Rittmann, Bruce E

    2014-07-01

    Biofilm biodegradation was coupled with ultra-violet photolysis using the internal loop photobiodegradation reactor for degradation of quinoline. Three protocols-photolysis alone (P), biodegradation alone (B), and intimately coupled photolysis and biodegradation (P&B)-were used for degradation of quinoline in batch and continuous-flow experiments. For a 1,000 mg/L initial quinoline concentration, the volumetric removal rate for quinoline was 38 % higher with P&B than with B in batch experiments, and the P&B kinetics were the sum of kinetics from the P and B experiments. Continuous-flow experiments with an influent quinoline concentration of 1,000 mg/L also gave significantly greater quinoline removal in P&B, and the quinoline-removal kinetics for P&B were approximately equal to the sum of the removal kinetics for P and B. P&B similarly increased the rate and extent of quinoline mineralization, for which the kinetics for P&B were nearly equal to the sum of kinetics for P and B. These findings support that the rate-limiting step for mineralization was transformation of quinoline, which was accelerated by the simultaneous action of photolysis and biodegradation.

  8. Choose Wisely: Static or Kinetic Friction--The Power of Dimensionless Plots

    ERIC Educational Resources Information Center

    Ludwigsen, Daniel; Svinarich, Kathryn

    2009-01-01

    Consider a problem of sliding blocks, one stacked atop the other, resting on a frictionless table. If the bottom block is pulled horizontally, nature makes a choice: if the applied force is small, static friction between the blocks accelerates the blocks together, but with a large force the blocks slide apart. In that case, kinetic friction still…

  9. IceCube's Search for Neutrinos from Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-07-01

    In a cubic kilometer of volume of ice under Antarctica, an observatory called IceCube is taking measurements that may help us to determine what causes the ultra-high-energy cosmic rays (UHECRs) we occasionally observe from Earth. A recent study reports on its latest results.Atomic BaseballsCosmic rays are high-energy radiation primarily composed of protons and atomic nuclei. When these charged and extremely energetic particles impact the Earths atmosphere on their journey through space, they generate showers of secondary particles that we then detect.A UHECR is any cosmic-ray particle with a kinetic energy exceeding 1018 eV and some have been detected with energies of more than 1020 eV! In practical terms, this is an atomic nucleus with the same kinetic energy as a baseball pitched at 60mph. These unbelievably energetic particlesare quite rare, but weve observed them for decades. Yet in spite of this, the source of UHECRs is unknown.Illustration of a gamma-ray burst in a star-forming region. Could these phenomena accelerate UHECRs to their enormous energies? [NASA/Swift/Mary Pat Hrybyk-Keith and John Jones]Gamma-Ray Burst FireballsOne proposed source that could accelerate particles to these energies is a gamma-ray burst (GRB). In some models for GRBs, the explosion is envisioned as a relativistically expanding fireball of electrons, photons and protons. Internal shock fronts accelerate electrons and protons within the fireball, generating UHECRs, gamma rays, and neutrinos in the process.Because the charged cosmic-ray particles can be easily deflected as they travel, its difficult to identify where they came from. Neutrinos and photons, on the other hand, both travel largely undeflected through the universe. As a result, if we detect high-energy neutrinos that are correlated with gamma-ray photons from a GRB, this would providestrong support for GRBfireball models for UHECR production.Heading Under the IceThe IceCube Laboratory in Antarctica. Beneath the Antarctic

  10. ON SOLAR WIND ORIGIN AND ACCELERATION: MEASUREMENTS FROM ACE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Stakhiv, Mark; Lepri, Susan T.; Landi, Enrico

    The origin and acceleration of the solar wind are still debated. In this paper, we search for signatures of the source region and acceleration mechanism of the solar wind in the plasma properties measured in situ by the Advanced Composition Explorer spacecraft. Using the elemental abundances as a proxy for the source region and the differential velocity and ion temperature ratios as a proxy for the acceleration mechanism, we are able to identify signatures pointing toward possible source regions and acceleration mechanisms. We find that the fast solar wind in the ecliptic plane is the same as that observed frommore » the polar regions and is consistent with wave acceleration and coronal-hole origin. We also find that the slow wind is composed of two components: one similar to the fast solar wind (with slower velocity) and the other likely originating from closed magnetic loops. Both components of the slow solar wind show signatures of wave acceleration. From these findings, we draw a scenario that envisions two types of wind, with different source regions and release mechanisms, but the same wave acceleration mechanism.« less

  11. Particle Acceleration and Fractional Transport in Turbulent Reconnection

    NASA Astrophysics Data System (ADS)

    Isliker, Heinz; Pisokas, Theophilos; Vlahos, Loukas; Anastasiadis, Anastasios

    2017-11-01

    We consider a large-scale environment of turbulent reconnection that is fragmented into a number of randomly distributed unstable current sheets (UCSs), and we statistically analyze the acceleration of particles within this environment. We address two important cases of acceleration mechanisms when particles interact with the UCS: (a) electric field acceleration and (b) acceleration by reflection at contracting islands. Electrons and ions are accelerated very efficiently, attaining an energy distribution of power-law shape with an index 1-2, depending on the acceleration mechanism. The transport coefficients in energy space are estimated from test-particle simulation data, and we show that the classical Fokker-Planck (FP) equation fails to reproduce the simulation results when the transport coefficients are inserted into it and it is solved numerically. The cause for this failure is that the particles perform Levy flights in energy space, while the distributions of the energy increments exhibit power-law tails. We then use the fractional transport equation (FTE) derived by Isliker et al., whose parameters and the order of the fractional derivatives are inferred from the simulation data, and solving the FTE numerically, we show that the FTE successfully reproduces the kinetic energy distribution of the test particles. We discuss in detail the analysis of the simulation data and the criteria that allow one to judge the appropriateness of either an FTE or a classical FP equation as a transport model.

  12. Particle Acceleration and Fractional Transport in Turbulent Reconnection

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Isliker, Heinz; Pisokas, Theophilos; Vlahos, Loukas

    We consider a large-scale environment of turbulent reconnection that is fragmented into a number of randomly distributed unstable current sheets (UCSs), and we statistically analyze the acceleration of particles within this environment. We address two important cases of acceleration mechanisms when particles interact with the UCS: (a) electric field acceleration and (b) acceleration by reflection at contracting islands. Electrons and ions are accelerated very efficiently, attaining an energy distribution of power-law shape with an index 1–2, depending on the acceleration mechanism. The transport coefficients in energy space are estimated from test-particle simulation data, and we show that the classical Fokker–Planckmore » (FP) equation fails to reproduce the simulation results when the transport coefficients are inserted into it and it is solved numerically. The cause for this failure is that the particles perform Levy flights in energy space, while the distributions of the energy increments exhibit power-law tails. We then use the fractional transport equation (FTE) derived by Isliker et al., whose parameters and the order of the fractional derivatives are inferred from the simulation data, and solving the FTE numerically, we show that the FTE successfully reproduces the kinetic energy distribution of the test particles. We discuss in detail the analysis of the simulation data and the criteria that allow one to judge the appropriateness of either an FTE or a classical FP equation as a transport model.« less

  13. Accelerated Peer-Review Journal Usage Technique for Undergraduates

    ERIC Educational Resources Information Center

    Wallace, J. D.

    2008-01-01

    The internet has given undergraduate students ever-increasing access to academic journals via search engines and online databases. However, students typically do not have the ability to use these journals effectively. This often poses a dilemma for instructors. The accelerated peer-review journal usage (APJU) technique provides a way for…

  14. Demonstrations that the Solar Wind Is Not Accelerated by Waves

    NASA Technical Reports Server (NTRS)

    Roberts, Aaron

    2008-01-01

    The present work uses both observations and theoretical considerations to show that hydromagnetic waves cannot produce the acceleration of the fast solar wind and the related heating of the open solar corona. Waves do exist, and can play a role in the differential heating and acceleration of minor ions, but their amplitudes are not sufficient to power the wind, as demonstrated by extrapolation of magnetic spectra from Helios and Ulysses observations. Dissipation mechanisms invoked to circumvent this conclusion cannot be effective for a variety of reasons. In particular, turbulence does not play a strong role in the corona as shown by both observations of coronal striations and theoretical considerations of line-tying to a nonturbulent photosphere, nonlocality of interactions, and the nature of the kinetic dissipation. In the absence of wave heating and acceleration, the chromosphere and transition region become the natural source of open coronal energization. We suggest a variant of the 'velocity filtration' approach in which the emergence and complex churning of the magnetic flux in the chromosphere and transition region continuously and ubiquitously produces the nonthermal distributions required. These particles are then released by magnetic carpet reconnection at a wide range of scales and produce the wind as described in kinetic approaches. Since the carpet reconnection is not the main source of the energization of the plasma, there is no expectation of an observable release of energy in nanoflares.

  15. Tempest: Accelerated MS/MS database search software for heterogeneous computing platforms

    PubMed Central

    Adamo, Mark E.; Gerber, Scott A.

    2017-01-01

    MS/MS database search algorithms derive a set of candidate peptide sequences from in-silico digest of a protein sequence database, and compute theoretical fragmentation patterns to match these candidates against observed MS/MS spectra. The original Tempest publication described these operations mapped to a CPU-GPU model, in which the CPU generates peptide candidates that are asynchronously sent to a discrete GPU to be scored against experimental spectra in parallel (Milloy et al., 2012). The current version of Tempest expands this model, incorporating OpenCL to offer seamless parallelization across multicore CPUs, GPUs, integrated graphics chips, and general-purpose coprocessors. Three protocols describe how to configure and run a Tempest search, including discussion of how to leverage Tempest's unique feature set to produce optimal results. PMID:27603022

  16. Nonlinear theory of diffusive acceleration of particles by shock waves

    NASA Astrophysics Data System (ADS)

    Malkov, M. A.; Drury, L. O'C.

    2001-04-01

    Among the various acceleration mechanisms which have been suggested as responsible for the nonthermal particle spectra and associated radiation observed in many astrophysical and space physics environments, diffusive shock acceleration appears to be the most successful. We review the current theoretical understanding of this process, from the basic ideas of how a shock energizes a few reactionless particles to the advanced nonlinear approaches treating the shock and accelerated particles as a symbiotic self-organizing system. By means of direct solution of the nonlinear problem we set the limit to the test-particle approximation and demonstrate the fundamental role of nonlinearity in shocks of astrophysical size and lifetime. We study the bifurcation of this system, proceeding from the hydrodynamic to kinetic description under a realistic condition of Bohm diffusivity. We emphasize the importance of collective plasma phenomena for the global flow structure and acceleration efficiency by considering the injection process, an initial stage of acceleration and, the related aspects of the physics of collisionless shocks. We calculate the injection rate for different shock parameters and different species. This, together with differential acceleration resulting from nonlinear large-scale modification, determines the chemical composition of accelerated particles. The review concentrates on theoretical and analytical aspects but our strategic goal is to link the fundamental theoretical ideas with the rapidly growing wealth of observational data.

  17. Kinetics of the head-neck complex in low-speed rear impact.

    PubMed

    Stemper, Brian D; Yoganandan, Naryan; Pintar, Frank A

    2003-01-01

    A comprehensive characterization of the biomechanics of the cervical spine in rear impact will lead to an understanding of the mechanisms of whiplash injury. Cervical kinematics have been experimentally described using human volunteers, full-body cadaver specimens, and isolated and intact head-neck specimens. However, forces and moments at the cervico-thoracic junction have not been clearly delineated. An experimental investigation was performed using ten intact head-neck complexes to delineate the loading at the base of the cervical spine and angular acceleration of the head in whiplash. A pendulum-minisled apparatus was used to simulate whiplash acceleration of the thorax at four impact severities. Lower neck loads were measured using a six-axis load cell attached between the minisled and head-neck specimens, and head angular motion was measured with an angular rate sensor attached to the lateral side of the head. Shear and axial force, extension moment, and head angular acceleration increased with impact severity. Shear force was significantly larger than axial force (p < 0.0001). Shear force reached its maximum value at 46 msec. Maximum extension moment occurred between 7 and 22 msec after maximum shear force. Maximum angular acceleration of the head occurred 2 to 18 msec later. Maximum axial force occurred last (106 msec). All four kinetic components reached maximum values during cervical S-curvature, with maximum shear force and extension moment occurring before the attainment of maximum S-curvature. Results of the present investigation indicate that shear force and extension moment at the cervico-thoracic junction drive the non-physiologic cervical S-curvature responsible for whiplash injury and underscore the importance of understanding cervical kinematics and the underlying kinetics.

  18. SABIO-RK: an updated resource for manually curated biochemical reaction kinetics

    PubMed Central

    Rey, Maja; Weidemann, Andreas; Kania, Renate; Müller, Wolfgang

    2018-01-01

    Abstract SABIO-RK (http://sabiork.h-its.org/) is a manually curated database containing data about biochemical reactions and their reaction kinetics. The data are primarily extracted from scientific literature and stored in a relational database. The content comprises both naturally occurring and alternatively measured biochemical reactions and is not restricted to any organism class. The data are made available to the public by a web-based search interface and by web services for programmatic access. In this update we describe major improvements and extensions of SABIO-RK since our last publication in the database issue of Nucleic Acid Research (2012). (i) The website has been completely revised and (ii) allows now also free text search for kinetics data. (iii) Additional interlinkages with other databases in our field have been established; this enables users to gain directly comprehensive knowledge about the properties of enzymes and kinetics beyond SABIO-RK. (iv) Vice versa, direct access to SABIO-RK data has been implemented in several systems biology tools and workflows. (v) On request of our experimental users, the data can be exported now additionally in spreadsheet formats. (vi) The newly established SABIO-RK Curation Service allows to respond to specific data requirements. PMID:29092055

  19. Stochastic acceleration of electrons from multiple uncorrelated plasma waves

    NASA Astrophysics Data System (ADS)

    Gee, David; Michel, Pierre; Wurtele, Jonathan

    2017-10-01

    One-dimensional theory puts a strict limit on the maximum energy attainable by an electron trapped and accelerated by an electron plasma wave (EPW). However, experimental measurements of hot electron distributions accelerated by stimulated Raman scattering (SRS) in ICF experiments typically show a thermal distribution with temperatures of the order of the kinetic energy of the resonant EPW's (Thot mvp2 , where vp is the phase velocity of the EPW's driven by SRS) and no clear cutoff at high energies. In this project, we are investigating conditions under which electrons can be stochastically accelerated by multiple uncorrelated EPW's, such as those generated by incoherent laser speckles in large laser spots like the ones used on NIF ( mm-size), and reproduce distributions similar to those observed in experiments. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  20. Nonlocal Models of Cosmic Acceleration

    NASA Astrophysics Data System (ADS)

    Woodard, R. P.

    2014-02-01

    I review a class of nonlocally modified gravity models which were proposed to explain the current phase of cosmic acceleration without dark energy. Among the topics considered are deriving causal and conserved field equations, adjusting the model to make it support a given expansion history, why these models do not require an elaborate screening mechanism to evade solar system tests, degrees of freedom and kinetic stability, and the negative verdict of structure formation. Although these simple models are not consistent with data on the growth of cosmic structures many of their features are likely to carry over to more complicated models which are in better agreement with the data.

  1. Tempest: Accelerated MS/MS Database Search Software for Heterogeneous Computing Platforms.

    PubMed

    Adamo, Mark E; Gerber, Scott A

    2016-09-07

    MS/MS database search algorithms derive a set of candidate peptide sequences from in silico digest of a protein sequence database, and compute theoretical fragmentation patterns to match these candidates against observed MS/MS spectra. The original Tempest publication described these operations mapped to a CPU-GPU model, in which the CPU (central processing unit) generates peptide candidates that are asynchronously sent to a discrete GPU (graphics processing unit) to be scored against experimental spectra in parallel. The current version of Tempest expands this model, incorporating OpenCL to offer seamless parallelization across multicore CPUs, GPUs, integrated graphics chips, and general-purpose coprocessors. Three protocols describe how to configure and run a Tempest search, including discussion of how to leverage Tempest's unique feature set to produce optimal results. © 2016 by John Wiley & Sons, Inc. Copyright © 2016 John Wiley & Sons, Inc.

  2. Fast Kinetics of Calcium Signaling and Sensor Design

    PubMed Central

    Tang, Shen; Reddish, Florence; Zhuo, You; Yang, Jenny J.

    2015-01-01

    Fast calcium signaling is regulated by numerous calcium channels exhibiting high spatiotemporal profiles which are currently measured by fluorescent calcium sensors. There is still a strong need to improve the kinetics of genetically encoded calcium indicators (sensors) to capture calcium dynamics in the millisecond time frame. In this review, we summarize several major fast calcium signaling pathways and discuss the recent developments and application of genetically encoded calcium indicators to detect these pathways. A new class of genetically encoded calcium indicators designed with site-directed mutagenesis on the surface of beta-barrel fluorescent proteins to form a pentagonal bipyramidal-like calcium binding domain dramatically accelerates calcium binding kinetics. Furthermore, novel genetically encoded calcium indicators with significantly increased fluorescent lifetime change are advantageous in deep-field imaging with high light-scattering and notable morphology change. PMID:26151819

  3. Formation of electrostatic structures by wakefield acceleration in ultrarelativistic plasma flows: Electron acceleration to cosmic ray energies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dieckmann, M.E.; Shukla, P.K.; Eliasson, B.

    2006-06-15

    The ever increasing performance of supercomputers is now enabling kinetic simulations of extreme astrophysical and laser produced plasmas. Three-dimensional particle-in-cell (PIC) simulations of relativistic shocks have revealed highly filamented spatial structures and their ability to accelerate particles to ultrarelativistic speeds. However, these PIC simulations have not yet revealed mechanisms that could produce particles with tera-electron volt energies and beyond. In this work, PIC simulations in one dimension (1D) of the foreshock region of an internal shock in a gamma ray burst are performed to address this issue. The large spatiotemporal range accessible to a 1D simulation enables the self-consistent evolutionmore » of proton phase space structures that can accelerate particles to giga-electron volt energies in the jet frame of reference, and to tens of tera-electron volt in the Earth's frame of reference. One potential source of ultrahigh energy cosmic rays may thus be the thermalization of relativistically moving plasma.« less

  4. Accelerating Families of Fuzzy K-Means Algorithms for Vector Quantization Codebook Design

    PubMed Central

    Mata, Edson; Bandeira, Silvio; de Mattos Neto, Paulo; Lopes, Waslon; Madeiro, Francisco

    2016-01-01

    The performance of signal processing systems based on vector quantization depends on codebook design. In the image compression scenario, the quality of the reconstructed images depends on the codebooks used. In this paper, alternatives are proposed for accelerating families of fuzzy K-means algorithms for codebook design. The acceleration is obtained by reducing the number of iterations of the algorithms and applying efficient nearest neighbor search techniques. Simulation results concerning image vector quantization have shown that the acceleration obtained so far does not decrease the quality of the reconstructed images. Codebook design time savings up to about 40% are obtained by the accelerated versions with respect to the original versions of the algorithms. PMID:27886061

  5. Accelerating Families of Fuzzy K-Means Algorithms for Vector Quantization Codebook Design.

    PubMed

    Mata, Edson; Bandeira, Silvio; de Mattos Neto, Paulo; Lopes, Waslon; Madeiro, Francisco

    2016-11-23

    The performance of signal processing systems based on vector quantization depends on codebook design. In the image compression scenario, the quality of the reconstructed images depends on the codebooks used. In this paper, alternatives are proposed for accelerating families of fuzzy K-means algorithms for codebook design. The acceleration is obtained by reducing the number of iterations of the algorithms and applying efficient nearest neighbor search techniques. Simulation results concerning image vector quantization have shown that the acceleration obtained so far does not decrease the quality of the reconstructed images. Codebook design time savings up to about 40% are obtained by the accelerated versions with respect to the original versions of the algorithms.

  6. Kinetic Contributions to Gating by Interactions Unique to N-methyl-d-aspartate (NMDA) Receptors*

    PubMed Central

    Borschel, William F.; Cummings, Kirstie A.; Tindell, LeeAnn K.; Popescu, Gabriela K.

    2015-01-01

    Among glutamate-gated channels, NMDA receptors produce currents that subside with unusually slow kinetics, and this feature is essential to the physiology of central excitatory synapses. Relative to the homologous AMPA and kainate receptors, NMDA receptors have additional intersubunit contacts in the ligand binding domain that occur at both conserved and non-conserved sites. We examined GluN1/GluN2A single-channel currents with kinetic analyses and modeling to probe these class-specific intersubunit interactions for their role in glutamate binding and receptor gating. We found that substitutions that eliminate such interactions at non-conserved sites reduced stationary gating, accelerated deactivation, and imparted sensitivity to aniracetam, an AMPA receptor-selective positive modulator. Abolishing unique contacts at conserved sites also reduced stationary gating and accelerated deactivation. These results show that contacts specific to NMDA receptors, which brace the heterodimer interface within the ligand binding domain, stabilize actively gating receptor conformations and result in longer bursts and slower deactivations. They support the view that the strength of the heterodimer interface modulates gating in both NMDA and non-NMDA receptors and that unique interactions at this interface are responsible in part for basic differences between the kinetics of NMDA and non-NMDA currents at glutamatergic synapses. PMID:26370091

  7. Steady-state kinetic modeling constrains cellular resting states and dynamic behavior.

    PubMed

    Purvis, Jeremy E; Radhakrishnan, Ravi; Diamond, Scott L

    2009-03-01

    A defining characteristic of living cells is the ability to respond dynamically to external stimuli while maintaining homeostasis under resting conditions. Capturing both of these features in a single kinetic model is difficult because the model must be able to reproduce both behaviors using the same set of molecular components. Here, we show how combining small, well-defined steady-state networks provides an efficient means of constructing large-scale kinetic models that exhibit realistic resting and dynamic behaviors. By requiring each kinetic module to be homeostatic (at steady state under resting conditions), the method proceeds by (i) computing steady-state solutions to a system of ordinary differential equations for each module, (ii) applying principal component analysis to each set of solutions to capture the steady-state solution space of each module network, and (iii) combining optimal search directions from all modules to form a global steady-state space that is searched for accurate simulation of the time-dependent behavior of the whole system upon perturbation. Importantly, this stepwise approach retains the nonlinear rate expressions that govern each reaction in the system and enforces constraints on the range of allowable concentration states for the full-scale model. These constraints not only reduce the computational cost of fitting experimental time-series data but can also provide insight into limitations on system concentrations and architecture. To demonstrate application of the method, we show how small kinetic perturbations in a modular model of platelet P2Y(1) signaling can cause widespread compensatory effects on cellular resting states.

  8. From the Kinetic Energy Recovery System to the Thermo-Hydraulic Hybrid Motor Vehicle

    NASA Astrophysics Data System (ADS)

    Cristescu, Corneliu; Drumea, Petrin; Guta, Dragos; Dumitrescu, Catalin

    2011-12-01

    The paper presents some theoretical and experimental results obtained by the Hydraulics and Pneumatics Research Institute INOE 2000-IHP with its partners, regarding the creating of one hydraulic system able to recovering the kinetic energy of the motor vehicles, in the braking phases, and use this recovered energy in the starting and accelerating phases. Also, in the article is presented a testing stand, which was especially designed for testing the hydraulic system for recovery the kinetic energy. Through mounting of the kinetic energy recovering hydraulic system, on one motor vehicle, this vehicle became a thermo-hydraulic hybrid vehicle. Therefore, the dynamic behavior was analyzed for the whole hybrid motor vehicle, which includes the energy recovery system. The theoretical and experimental results demonstrate the possible performances of the hybrid vehicle and that the kinetic energy recovery hydraulic systems are good means to increase energy efficiency of the road motor vehicles and to decrease of the fuel consumption.

  9. The Talent Search Model: Implications for Secondary School Reform.

    ERIC Educational Resources Information Center

    VanTassel-Baska, Joyce

    1985-01-01

    The Midwest Talent Search Project is an effort to identify and provide an appropriate accelerated curriculum for gifted secondary school students in the midwest. Many aspects of the project are discussed here, including testing, programming, benefits, and implications for curriculum reform. (Author/MCG)

  10. ACCELERATION OF THERMAL PROTONS BY GENERIC PHENOMENOLOGICAL MECHANISMS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Petrosian, Vahé; Kang, Byungwoo, E-mail: vahep@stanford.edu, E-mail: redcrux8@stanford.edu

    2015-11-01

    We investigate heating and acceleration of protons from a thermal gas with a generic diffusion and acceleration model, and subject to Coulomb scattering and energy loss, as was done by Petrosian and East for electrons. As protons gain energy their loss to electrons becomes important. Thus, we need to solve the coupled proton–electron kinetic equation. We numerically solve the coupled Fokker–Planck equations and compute the time evolution of the spectra of both particles. We show that this can lead to a quasi-thermal component plus a high-energy nonthermal tail. We determine the evolution of the nonthermal tail and the quasi-thermal component.more » The results may be used to explore the possibility of inverse bremsstrahlung radiation as a source of hard X-ray emissions from hot sources such as solar flares, accretion disk coronas, and the intracluster medium of galaxy clusters. We find that the emergence of nonthermal protons is accompanied by excessive heating of the entire plasma, unless the turbulence needed for scattering and acceleration is steeper than Kolmogorov and the acceleration parameters, the duration of the acceleration, and/or the initial distributions are significantly fine-tuned. These results severely constrain the feasibility of the nonthermal inverse bremsstrahlung process producing hard X-ray emissions. However, the nonthermal tail may be the seed particles for further re-acceleration to relativistic energies, say by a shock. In the Appendix we present some tests of the integrity of the algorithm used and present a new formula for the energy loss rate due to inelastic proton–proton interactions.« less

  11. Timescales for detecting a significant acceleration in sea level rise

    PubMed Central

    Haigh, Ivan D.; Wahl, Thomas; Rohling, Eelco J.; Price, René M.; Pattiaratchi, Charitha B.; Calafat, Francisco M.; Dangendorf, Sönke

    2014-01-01

    There is observational evidence that global sea level is rising and there is concern that the rate of rise will increase, significantly threatening coastal communities. However, considerable debate remains as to whether the rate of sea level rise is currently increasing and, if so, by how much. Here we provide new insights into sea level accelerations by applying the main methods that have been used previously to search for accelerations in historical data, to identify the timings (with uncertainties) at which accelerations might first be recognized in a statistically significant manner (if not apparent already) in sea level records that we have artificially extended to 2100. We find that the most important approach to earliest possible detection of a significant sea level acceleration lies in improved understanding (and subsequent removal) of interannual to multidecadal variability in sea level records. PMID:24728012

  12. Serendipity in dark photon searches

    NASA Astrophysics Data System (ADS)

    Ilten, Philip; Soreq, Yotam; Williams, Mike; Xue, Wei

    2018-06-01

    Searches for dark photons provide serendipitous discovery potential for other types of vector particles. We develop a framework for recasting dark photon searches to obtain constraints on more general theories, which includes a data-driven method for determining hadronic decay rates. We demonstrate our approach by deriving constraints on a vector that couples to the B-L current, a leptophobic B boson that couples directly to baryon number and to leptons via B- γ kinetic mixing, and on a vector that mediates a protophobic force. Our approach can easily be generalized to any massive gauge boson with vector couplings to the Standard Model fermions, and software to perform any such recasting is provided at https://gitlab.com/philten/darkcast .

  13. Design of Spacecraft Missions to Test Kinetic Impact for Asteroid Deflection

    NASA Technical Reports Server (NTRS)

    Barbee, Brent W.; Hernandez, Sonia

    2012-01-01

    Earth has previously been struck with devastating force by near-Earth asteroids (NEAs) and will be struck again. Telescopic search programs aim to provide advance warning of such an impact, but no techniques or systems have yet been tested for deflecting an incoming NEA. To begin addressing this problem, we have analyzed the more than 8000 currently known NEAs to identify those that offer opportunities for safe and meaningful near-term tests of the proposed kinetic impact asteroid deflection technique. In this paper we present our methodology and results, including complete mission designs for the best kinetic impactor test mission opportunities.

  14. Interdisciplinary glossary — particle accelerators and medicine

    NASA Astrophysics Data System (ADS)

    Dmitrieva, V. V.; Dyubkov, V. S.; Nikitaev, V. G.; Ulin, S. E.

    2016-02-01

    A general concept of a new interdisciplinary glossary, which includes particle accelerator terminology used in medicine, as well as relevant medical concepts, is presented. Its structure and usage rules are described. An example, illustrating the quickly searching technique of relevant information in this Glossary, is considered. A website address, where one can get an access to the Glossary, is specified. Glossary can be refined and supplemented.

  15. Heavy Ion Acceleration at J-PARC

    NASA Astrophysics Data System (ADS)

    SATO, Susumu

    2018-02-01

    J-PARC, the Japan Proton Accelerator Research Complex, is an accelerator, which provides a high-intensity proton beam. Recently as a very attractive project, the acceleration of heavy ions produced by supplementary ion sources, called J-PARC-HI, is seriously contemplated by domestic as well as international communities. The planned facility would accelerate heavy ions up to U92+ with a beam energy 20 AGeV ( of 6.2 AGeV). The highlight of the J-PARC-HI project is its very high beam rate up to 1011 Hz, which will enable the study of very rare events. Taking advantage of this high intensity, J-PARC-HI will carry out frontier studies of new and rare observables in this energy region: (i) nuclear medium modification of chiral property of vector mesons through low-mass di-lepton signal, (ii) QCD critical pointcharacterization through event-by-event fluctuation signals of particle production, (iii) systematic measurements related to the equation of state through collective flow signal or two-particle momentum correlation signal, or (iv) the search of hyper nuclei with multi strangeness including or exceeding S = 3. The current plan of J-PARC-HI aims to carrying out the first experimental measurements in 2025.

  16. The kinetics of the 2π+2π photodimerisation reactions of single-crystalline derivatives of trans-cinnamic acid: A study by infrared microspectroscopy

    NASA Astrophysics Data System (ADS)

    Jenkins, Samantha L.; Almond, Matthew J.; Atkinson, Samantha D. M.; Drew, Michael G. B.; Hollins, Peter; Mortimore, Joanne L.; Tobin, Mark J.

    2006-04-01

    The kinetics of the photodimerisation reactions of the 2- and 4-β-halogeno-derivatives of trans-cinnamic acid (where the halogen is fluorine, chlorine or bromine) have been investigated by infrared microspectroscopy. It is found that none of the reactions proceed to 100% yield. This is in line with a reaction mechanism developed by Wernick and his co-workers that postulates the formation of isolated monomers within the solid, which cannot react. β-4-Bromo and β-4-chloro- trans-cinnamic acids show approximately first order kinetics, although in both cases the reaction accelerates somewhat as it proceeds. First order kinetics is explained in terms of a reaction between one excited- and one ground-state monomer molecule, while the acceleration of the reaction implies that it is promoted as defects are formed within the crystal. By contrast β-2-chloro- trans-cinnamic acid shows a strongly accelerating reaction which models closely to the contracting cube equation. β-2-Fluoro- and β-4-fluoro- trans-cinnamic acids show a close match to first order kinetics. The 4-fluoro-derivative, however, shows a reaction that proceeds via a structural intermediate. The difference in behaviour between the 2-fluoro- and 4-fluoro-derivative may be due to different C-H⋯F hydrogen bonds observed within these single-crystalline starting materials.

  17. Shape transitions in strained islands: kinetics versus energetics

    NASA Astrophysics Data System (ADS)

    Shim, Yunsic; Kryukov, Yevgen; Amar, Jacques

    2011-03-01

    Recently, it has been argued that the shape transition from compact to ramified islands observed experimentally in submonolayer Cu/Ni(100) growth is not due to kinetics but can be understood in terms of energetic arguments. In order to determine the responsible mechanisms we have carried out temperature-accelerated dynamics (TAD) simulations as well as energetics calculations. Surprisingly, our results indicate that the strain-energy contribution to the dependence of island-energy on shape is relatively weak. In contrast, our TAD simulations indicate that unexpected concerted motions occurring at step edges may be responsible. The energy barriers for these concerted motions are significantly lower than for Cu/Cu(100) and Ni/Ni(100), decrease with increasing island size, and appear to saturate for islands larger than 300 - 400 atoms. These results suggest that the shape transition is of kinetic origin but is strongly mediated by strain. Supported by NSF-DMR 0907399.

  18. Are supernova remnants quasi-parallel or quasi-perpendicular accelerators

    NASA Technical Reports Server (NTRS)

    Spangler, S. R.; Leckband, J. A.; Cairns, I. H.

    1989-01-01

    Observations of shock waves in the solar system which show a pronounced difference in the plasma wave and particle environment depending on whether the shock is propagating along or perpendicular to the interplanetary magnetic field are discussed. Theories for particle acceleration developed for quasi-parallel and quasi-perpendicular shocks, when extended to the interstellar medium suggest that the relativistic electrons in radio supernova remnants are accelerated by either the Q parallel or Q perpendicular mechanisms. A model for the galactic magnetic field and published maps of supernova remnants were used to search for a dependence of structure on the angle Phi. Results show no tendency for the remnants as a whole to favor the relationship expected for either mechanism, although individual sources resemble model remnants of one or the other acceleration process.

  19. The role of three-dimensional transport in driving enhanced electron acceleration during magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Dahlin, J. T.; Drake, J. F.; Swisdak, M.

    2017-09-01

    Magnetic reconnection is an important driver of energetic particles in many astrophysical phenomena. Using kinetic particle-in-cell simulations, we explore the impact of three-dimensional reconnection dynamics on the efficiency of particle acceleration. In two-dimensional systems, Alfvénic outflows expel energetic electrons into flux ropes where they become trapped and disconnected from acceleration regions. However, in three-dimensional systems these flux ropes develop an axial structure that enables particles to leak out and return to acceleration regions. This requires a finite guide field so that particles may move quickly along the flux rope axis. We show that greatest energetic electron production occurs when the guide field is of the same order as the reconnecting component: large enough to facilitate strong transport, but not so large as to throttle the dominant Fermi mechanism responsible for efficient electron acceleration. This suggests a natural explanation for the envelope of electron acceleration during the impulsive phase of eruptive flares.

  20. The role of three-dimensional transport in driving enhanced electron acceleration during magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Swisdak, M.; Dahlin, J. T.; Drake, J. F.

    2017-12-01

    Magnetic reconnection is an important driver of energetic particles in many space and astrophysical phenomena. Using kinetic particle-in-cell simulations, we explore the effects that the dynamics in three-dimensions has on reconnection and the efficiency of particle acceleration. In two-dimensional systems, Alfvenic outflows expel energetic electrons into flux ropes where they become trapped and disconnected from acceleration regions. However, in three-dimensional systems these flux ropes develop axial structure that enables particles to leak out and return to acceleration regions. This requires a finite guide field so that particles may move quickly along the flux rope axis. The greatest energetic electron production occurs when the guide field is of the same order as the reconnecting component: large enough to facilitate strong transport, but not so large as to throttle the dominant Fermi mechanism responsible for efficient electron acceleration.

  1. Cosmic ray sources, acceleration and propagation

    NASA Technical Reports Server (NTRS)

    Ptuskin, V. S.

    1986-01-01

    A review is given of selected papers on the theory of cosmic ray (CR) propagation and acceleration. The high isotropy and a comparatively large age of galactic CR are explained by the effective interaction of relativistic particles with random and regular electromagnetic fields in interstellar medium. The kinetic theory of CR propagation in the Galaxy is formulated similarly to the elaborate theory of CR propagation in heliosphere. The substantial difference between these theories is explained by the necessity to take into account in some cases the collective effects due to a rather high density of relativisitc particles. In particular, the kinetic CR stream instability and the hydrodynamic Parker instability is studied. The interaction of relativistic particles with an ensemble of given weak random magnetic fields is calculated by perturbation theory. The theory of CR transfer is considered to be basically completed for this case. The main problem consists in poor information about the structure of the regular and the random galactic magnetic fields. An account is given of CR transfer in a turbulent medium.

  2. Attrition and success rates of accelerated students in nursing courses: a systematic review.

    PubMed

    Doggrell, Sheila Anne; Schaffer, Sally

    2016-01-01

    There is a comprehensive literature on the academic outcomes (attrition and success) of students in traditional/baccalaureate nursing programs, but much less is known about the academic outcomes of students in accelerated nursing programs. The aim of this systematic review is to report on the attrition and success rates (either internal examination or NCLEX-RN) of accelerated students, compared to traditional students. For the systematic review, the databases (Pubmed, Cinahl and PsychINFO) and Google Scholar were searched using the search terms 'accelerated' or 'accreditation for prior learning', 'fast-track' or 'top up' and 'nursing' with 'attrition' or 'retention' or 'withdrawal' or 'success' from 1994 to January 2016. All relevant articles were included, regardless of quality. The findings of 19 studies of attrition rates and/or success rates for accelerated students are reported. For international accelerated students, there were only three studies, which are heterogeneous, and have major limitations. One of three studies has lower attrition rates, and one has shown higher success rates, than traditional students. In contrast, another study has shown high attrition and low success for international accelerated students. For graduate accelerated students, most of the studies are high quality, and showed that they have rates similar or better than traditional students. Thus, five of six studies have shown similar or lower attrition rates. Four of these studies with graduate accelerated students and an additional seven studies of success rates only, have shown similar or better success rates, than traditional students. There are only three studies of non-university graduate accelerated students, and these had weaknesses, but were consistent in reporting higher attrition rates than traditional students. The paucity and weakness of information available makes it unclear as to the attrition and/or success of international accelerated students in nursing programs. The

  3. Generation of attosecond electron packets via conical surface plasmon electron acceleration

    PubMed Central

    Greig, S. R.; Elezzabi, A. Y.

    2016-01-01

    We present a method for the generation of high kinetic energy attosecond electron packets via magnetostatic and aperture filtering of conical surface plasmon (SP) accelerated electrons. The conical SP waves are excited by coupling an ultrafast radially polarized laser beam to a conical silica lens coated with an Ag film. Electromagnetic and particle tracking models are employed to characterize the ultrafast electron packets. PMID:26764129

  4. Kinetic Adaptations of Myosins for their Diverse Cellular Functions

    PubMed Central

    Heissler, Sarah M.; Sellers, James R.

    2016-01-01

    Members of the myosin superfamily are involved in all aspects of eukaryotic life. Their function ranges from the transport of organelles and cargos to the generation of membrane tension, and the contraction of muscle. The diversity of physiological functions is remarkable, given that all enzymatically active myosins follow a conserved mechanoenzymatic cycle in which the hydrolysis of ATP to ADP and inorganic phosphate is coupled to either actin-based transport or tethering of actin to defined cellular compartments. Kinetic capacities and limitations of a myosin are determined by the extent to with actin can accelerate the hydrolysis of ATP and the release of the hydrolysis products and are indispensably linked to its physiological tasks. This review focuses on kinetic competencies that – together with structural adaptations – result in myosins with unique mechanoenzymatic properties targeted to their diverse cellular function. PMID:26929436

  5. Slow domain reconfiguration causes power-law kinetics in a two-state enzyme.

    PubMed

    Grossman-Haham, Iris; Rosenblum, Gabriel; Namani, Trishool; Hofmann, Hagen

    2018-01-16

    Protein dynamics are typically captured well by rate equations that predict exponential decays for two-state reactions. Here, we describe a remarkable exception. The electron-transfer enzyme quiescin sulfhydryl oxidase (QSOX), a natural fusion of two functionally distinct domains, switches between open- and closed-domain arrangements with apparent power-law kinetics. Using single-molecule FRET experiments on time scales from nanoseconds to milliseconds, we show that the unusual open-close kinetics results from slow sampling of an ensemble of disordered domain orientations. While substrate accelerates the kinetics, thus suggesting a substrate-induced switch to an alternative free energy landscape of the enzyme, the power-law behavior is also preserved upon electron load. Our results show that the slow sampling of open conformers is caused by a variety of interdomain interactions that imply a rugged free energy landscape, thus providing a generic mechanism for dynamic disorder in multidomain enzymes.

  6. [Statocyst regulation of the heart and statokinetic reflexes in the crab, Hemigrapsus sanguineus, during linear acceleration].

    PubMed

    Kuntsova, M Ia; Sveshnikov, V G; Timofeeva, E V

    1978-01-01

    In experiments on the shore crab H. sanguineus studies have been made of the effect of variable longitudinal acceleration during swinging (for 15--30 min) upon cardiac activity and gravitational reflexes. High sensitivity of gravitational receptors of the canal statocyst to the effect of acceleration was demonstrated. Removal of the statocysts increases the frequency and amplitude of cardiac contractions as revealed by ECG recording. Changes in stato-kinetic coordinations cause both the disorder of overturning reactions and the disorder of reciprocal inhibition in antagonistic muscles of the dactylopodite. Statocyst regulation of skeletal muscles and heart is presumably realised via contralateral inhibitory canal which is sensitive to linear accelerations.

  7. 160-fold acceleration of the Smith-Waterman algorithm using a field programmable gate array (FPGA)

    PubMed Central

    Li, Isaac TS; Shum, Warren; Truong, Kevin

    2007-01-01

    Background To infer homology and subsequently gene function, the Smith-Waterman (SW) algorithm is used to find the optimal local alignment between two sequences. When searching sequence databases that may contain hundreds of millions of sequences, this algorithm becomes computationally expensive. Results In this paper, we focused on accelerating the Smith-Waterman algorithm by using FPGA-based hardware that implemented a module for computing the score of a single cell of the SW matrix. Then using a grid of this module, the entire SW matrix was computed at the speed of field propagation through the FPGA circuit. These modifications dramatically accelerated the algorithm's computation time by up to 160 folds compared to a pure software implementation running on the same FPGA with an Altera Nios II softprocessor. Conclusion This design of FPGA accelerated hardware offers a new promising direction to seeking computation improvement of genomic database searching. PMID:17555593

  8. 160-fold acceleration of the Smith-Waterman algorithm using a field programmable gate array (FPGA).

    PubMed

    Li, Isaac T S; Shum, Warren; Truong, Kevin

    2007-06-07

    To infer homology and subsequently gene function, the Smith-Waterman (SW) algorithm is used to find the optimal local alignment between two sequences. When searching sequence databases that may contain hundreds of millions of sequences, this algorithm becomes computationally expensive. In this paper, we focused on accelerating the Smith-Waterman algorithm by using FPGA-based hardware that implemented a module for computing the score of a single cell of the SW matrix. Then using a grid of this module, the entire SW matrix was computed at the speed of field propagation through the FPGA circuit. These modifications dramatically accelerated the algorithm's computation time by up to 160 folds compared to a pure software implementation running on the same FPGA with an Altera Nios II softprocessor. This design of FPGA accelerated hardware offers a new promising direction to seeking computation improvement of genomic database searching.

  9. A hole accelerator for InGaN/GaN light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Zhang, Zi-Hui; Liu, Wei; Tan, Swee Tiam; Ji, Yun; Wang, Liancheng; Zhu, Binbin; Zhang, Yiping; Lu, Shunpeng; Zhang, Xueliang; Hasanov, Namig; Sun, Xiao Wei; Demir, Hilmi Volkan

    2014-10-01

    The quantum efficiency of InGaN/GaN light-emitting diodes (LEDs) has been significantly limited by the insufficient hole injection, and this is caused by the inefficient p-type doping and the low hole mobility. The low hole mobility makes the holes less energetic, which hinders the hole injection into the multiple quantum wells (MQWs) especially when a p-type AlGaN electron blocking layer (EBL) is adopted. In this work, we report a hole accelerator to accelerate the holes so that the holes can obtain adequate kinetic energy, travel across the p-type EBL, and then enter the MQWs more efficiently and smoothly. In addition to the numerical study, the effectiveness of the hole accelerator is experimentally shown through achieving improved optical output power and reduced efficiency droop for the proposed InGaN/GaN LED.

  10. On the relationships between Michaelis–Menten kinetics, reverse Michaelis–Menten kinetics, Equilibrium Chemistry Approximation kinetics and quadratic kinetics

    DOE PAGES

    Tang, J. Y.

    2015-09-03

    The Michaelis–Menten kinetics and the reverse Michaelis–Menten kinetics are two popular mathematical formulations used in many land biogeochemical models to describe how microbes and plants would respond to changes in substrate abundance. However, the criteria of when to use which of the two are often ambiguous. Here I show that these two kinetics are special approximations to the Equilibrium Chemistry Approximation kinetics, which is the first order approximation to the quadratic kinetics that solves the equation of enzyme-substrate complex exactly for a single enzyme single substrate biogeochemical reaction with the law of mass action and the assumption of quasi-steady-state formore » the enzyme-substrate complex and that the product genesis from enzyme-substrate complex is much slower than the equilibration between enzyme-substrate complexes, substrates and enzymes. In particular, I showed that the derivation of the Michaelis–Menten kinetics does not consider the mass balance constraint of the substrate, and the reverse Michaelis–Menten kinetics does not consider the mass balance constraint of the enzyme, whereas both of these constraints are taken into account in the Equilibrium Chemistry Approximation kinetics. By benchmarking against predictions from the quadratic kinetics for a wide range of substrate and enzyme concentrations, the Michaelis–Menten kinetics was found to persistently under-predict the normalized sensitivity ∂ ln v / ∂ ln k 2 + of the reaction velocity v with respect to the maximum product genesis rate k 2 +, persistently over-predict the normalized sensitivity ∂ ln v / ∂ ln k 1 + of v with respect to the intrinsic substrate affinity k 1 +, persistently over-predict the normalized sensitivity ∂ ln v / ∂ ln [ E ] T of v with respect the total enzyme concentration [ E ] T and persistently under-predict the normalized sensitivity ∂ ln v / ∂ ln [ S ] T of v with respect to the total substrate concentration [ S ] T

  11. Electron Heating and Acceleration in a Reconnecting Magnetotail

    NASA Astrophysics Data System (ADS)

    El-Alaoui, M.; Zhou, M.; Lapenta, G.; Berchem, J.; Richard, R. L.; Schriver, D.; Walker, R. J.

    2017-12-01

    Electron heating and acceleration in the magnetotail have been investigated intensively. A major site for this process is the reconnection region. However, where and how the electrons are accelerated in a realistic three-dimensional X-line geometry is not fully understood. In this study, we employed a three-dimensional implicit particle-in-cell (iPIC3D) simulation and large-scale kinetic (LSK) simulation to address these problems. We modeled a magnetotail reconnection event observed by THEMIS in an iPIC3D simulation with initial and boundary conditions given by a global magnetohydrodynamic (MHD) simulation of Earth's magnetosphere. The iPIC3D simulation system includes the region of fast outflow emanating from the reconnection site that drives dipolarization fronts. We found that current sheet electrons exhibit elongated (cigar-shaped) velocity distributions with a higher parallel temperature. Using LSK we then followed millions of test electrons using the electromagnetic fields from iPIC3D. We found that magnetotail reconnection can generate power law spectra around the near-Earth X-line. A significant number of electrons with energies higher than 50 keV are produced. We identified several acceleration mechanisms at different locations that were responsible for energizing these electrons: non-adiabatic cross-tail drift, betatron and Fermi acceleration. Relative contributions to the energy gain of these high energy electrons from the different mechanisms will be discussed.

  12. Taboo search by successive confinement: Surveying a potential energy surface

    NASA Astrophysics Data System (ADS)

    Chekmarev, Sergei F.

    2001-09-01

    A taboo search for minima on a potential energy surface (PES) is performed by means of confinement molecular dynamics: the molecular dynamics trajectory of the system is successively confined to various basins on the PES that have not been sampled yet. The approach is illustrated for a 13-atom Lennard-Jones cluster. It is shown that the taboo search radically accelerates the process of surveying the PES, with the probability of finding a new minimum defined by a propagating Fermi-like distribution.

  13. SigrafW: An Easy-to-Use Program for Fitting Enzyme Kinetic Data

    ERIC Educational Resources Information Center

    Leone, Francisco Assis; Baranauskas, Jose Augusto; Furriel, Rosa Prazeres Melo; Borin, Ivana Aparecida

    2005-01-01

    SigrafW is Windows-compatible software developed using the Microsoft[R] Visual Basic Studio program that uses the simplified Hill equation for fitting kinetic data from allosteric and Michaelian enzymes. SigrafW uses a modified Fibonacci search to calculate maximal velocity (V), the Hill coefficient (n), and the enzyme-substrate apparent…

  14. Utilization of rotor kinetic energy storage for hybrid vehicles

    DOEpatents

    Hsu, John S [Oak Ridge, TN

    2011-05-03

    A power system for a motor vehicle having an internal combustion engine, the power system comprises an electric machine (12) further comprising a first excitation source (47), a permanent magnet rotor (28) and a magnetic coupling rotor (26) spaced from the permanent magnet rotor and at least one second excitation source (43), the magnetic coupling rotor (26) also including a flywheel having an inertial mass to store kinetic energy during an initial acceleration to an operating speed; and wherein the first excitation source is electrically connected to the second excitation source for power cycling such that the flywheel rotor (26) exerts torque on the permanent magnet rotor (28) to assist braking and acceleration of the permanent magnet rotor (28) and consequently, the vehicle. An axial gap machine and a radial gap machine are disclosed and methods of the invention are also disclosed.

  15. Impact Accelerations of Barefoot and Shod Running.

    PubMed

    Thompson, M; Seegmiller, J; McGowan, C P

    2016-05-01

    During the ground contact phase of running, the body's mass is rapidly decelerated resulting in forces that propagate through the musculoskeletal system. The repetitive attenuation of these impact forces is thought to contribute to overuse injuries. Modern running shoes are designed to reduce impact forces, with the goal to minimize running related overuse injuries. Additionally, the fore/mid foot strike pattern that is adopted by most individuals when running barefoot may reduce impact force transmission. The aim of the present study was to compare the effects of the barefoot running form (fore/mid foot strike & decreased stride length) and running shoes on running kinetics and impact accelerations. 10 healthy, physically active, heel strike runners ran in 3 conditions: shod, barefoot and barefoot while heel striking, during which 3-dimensional motion analysis, ground reaction force and accelerometer data were collected. Shod running was associated with increased ground reaction force and impact peak magnitudes, but decreased impact accelerations, suggesting that the midsole of running shoes helps to attenuate impact forces. Barefoot running exhibited a similar decrease in impact accelerations, as well as decreased impact peak magnitude, which appears to be due to a decrease in stride length and/or a more plantarflexed position at ground contact. © Georg Thieme Verlag KG Stuttgart · New York.

  16. MMS Observations of Protons and Heavy Ions Acceleration at Plasma Jet Fronts

    NASA Astrophysics Data System (ADS)

    Catapano, F.; Retino, A.; Zimbardo, G.; Cozzani, G.; Breuillard, H.; Le Contel, O.; Alexandrova, A.; Mirioni, L.; Cohen, I. J.; Turner, D. L.; Perri, S.; Greco, A.; Mauk, B.; Torbert, R. B.; Russell, C. T.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Ergun, R.; Giles, B. L.; Fuselier, S. A.; Moore, T. E.; Burch, J.

    2017-12-01

    Plasma jet fronts in the Earth's magnetotail are kinetic-scale boundaries separating hot fast plasma jets, generally attributed to reconnection outflows, from colder ambient plasma. Jet fronts are typically associated with a sharp increase of the vertical component of the magnetic field Bz, an increase of the plasma temperature and a drop of plasma density. Spacecraft observations and numerical simulations indicate that jet fronts are sites of major ion acceleration. The exact acceleration mechanisms as well as the dependence of such mechanisms on ion composition are not fully understood, yet. Recent high-resolution measurements of ion distribution functions in the magnetotail allow for the first time to study the acceleration mechanisms in detail. Here, we show several examples of jet fronts and discuss ion acceleration therein. We show fronts that propagate in the mid-tail magnetotail both as isolated laminar boundaries and as multiple boundaries embedded in strong magnetic fluctuations and turbulence. We also show fronts in the near-Earth jet braking region, where they interact with the dipolar magnetic field and are significantly decelerated/diverted. Finally, we study the acceleration of different ion species (H+, He++, O+) at different types of fronts and we discuss possible different acceleration mechanisms and how they depend on the ion species.

  17. Common origin of kinetic scale turbulence and the electron halo in the solar wind – Connection to nanoflares

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Che, Haihong; Goddard Space Flight Center, NASA, Greenbelt, MD, 20771

    2016-03-25

    We summarize our recent studies on the origin of solar wind kinetic scale turbulence and electron halo in the electron velocity distribution function. Increasing observations of nanoflares and microscopic type III radio bursts strongly suggest that nanoflares and accelerated electron beams are common in the corona. Based on particle-in-cell simulations, we show that both the core-halo feature and kinetic scale turbulence observed in the solar wind can be produced by the nonlinear evolution of electron two-stream instability driven by nanoflare accelerated electron beams. The energy exchange between waves and particles reaches equilibrium in the inner corona and the key featuresmore » of the turbulence and velocity distribution are preserved as the solar wind escapes into interplanetary space along open magnetic field lines. Observational tests of the model and future theoretical work are discussed.« less

  18. Parametric Quantum Search Algorithm as Quantum Walk: A Quantum Simulation

    NASA Astrophysics Data System (ADS)

    Ellinas, Demosthenes; Konstandakis, Christos

    2016-02-01

    Parametric quantum search algorithm (PQSA) is a form of quantum search that results by relaxing the unitarity of the original algorithm. PQSA can naturally be cast in the form of quantum walk, by means of the formalism of oracle algebra. This is due to the fact that the completely positive trace preserving search map used by PQSA, admits a unitarization (unitary dilation) a la quantum walk, at the expense of introducing auxiliary quantum coin-qubit space. The ensuing QW describes a process of spiral motion, chosen to be driven by two unitary Kraus generators, generating planar rotations of Bloch vector around an axis. The quadratic acceleration of quantum search translates into an equivalent quadratic saving of the number of coin qubits in the QW analogue. The associated to QW model Hamiltonian operator is obtained and is shown to represent a multi-particle long-range interacting quantum system that simulates parametric search. Finally, the relation of PQSA-QW simulator to the QW search algorithm is elucidated.

  19. Drosophila QVR/SSS modulates the activation and C-type inactivation kinetics of Shaker K+ channels

    PubMed Central

    Dean, Terry; Xu, Rong; Joiner, William; Sehgal, Amita; Hoshi, Toshinori

    2011-01-01

    The quiver/sleepless (qvr/sss) gene encodes a small, glycosylphosphatidylinositol-anchored protein that plays a critical role in the regulation of sleep in Drosophila. Loss-of-function mutations in qvr/sss severely suppress sleep and effect multiple changes in in situ Shaker K+ currents, including decreased magnitude, slower time-to-peak, and cumulative inactivation. Recently, we demonstrated that SLEEPLESS (SSS) protein modulates Shaker channel activity, possibly through a direct interaction at the plasma membrane. We show here that SSS accelerates the activation of heterologously expressed Shaker channels with no effect on deactivation or fast N-type inactivation. Furthermore, this SSS-induced acceleration is sensitive to the pharmacological disruption of lipid rafts and sufficiently accounts for the slower time-to-peak of in situ Shaker currents seen in qvr/sss mutants. We also find that SSS decreases the rate of C-type inactivation of heterologously expressed Shaker channels, providing a potential mechanism for the cumulative inactivation phenotype induced by qvr/sss loss of function mutations. Kinetic modeling based on the in vitro results suggests that the SSS-dependent regulation of channel kinetics accounts for nearly 40% of the decrease in Shaker current magnitude in flies lacking SSS. Sleep duration in qvr/sss null mutants is restored to normal by a qvr/sss transgene that fully rescues the Shaker kinetic phenotypes but only partially rescues the decrease in current magnitude. Together, these results suggest that the role of SSS in the regulation of sleep in Drosophila correlates more strongly with the effects of SSS on Shaker kinetics than current magnitude. PMID:21813698

  20. Drosophila QVR/SSS modulates the activation and C-type inactivation kinetics of Shaker K(+) channels.

    PubMed

    Dean, Terry; Xu, Rong; Joiner, William; Sehgal, Amita; Hoshi, Toshinori

    2011-08-03

    The quiver/sleepless (qvr/sss) gene encodes a small, glycosylphosphatidylinositol-anchored protein that plays a critical role in the regulation of sleep in Drosophila. Loss-of-function mutations in qvr/sss severely suppress sleep and effect multiple changes in in situ Shaker K(+) currents, including decreased magnitude, slower time-to-peak, and cumulative inactivation. Recently, we demonstrated that SLEEPLESS (SSS) protein modulates Shaker channel activity, possibly through a direct interaction at the plasma membrane. We show here that SSS accelerates the activation of heterologously expressed Shaker channels with no effect on deactivation or fast N-type inactivation. Furthermore, this SSS-induced acceleration is sensitive to the pharmacological disruption of lipid rafts and sufficiently accounts for the slower time-to-peak of in situ Shaker currents seen in qvr/sss mutants. We also find that SSS decreases the rate of C-type inactivation of heterologously expressed Shaker channels, providing a potential mechanism for the cumulative inactivation phenotype induced by qvr/sss loss-of-function mutations. Kinetic modeling based on the in vitro results suggests that the SSS-dependent regulation of channel kinetics accounts for nearly 40% of the decrease in Shaker current magnitude in flies lacking SSS. Sleep duration in qvr/sss-null mutants is restored to normal by a qvr/sss transgene that fully rescues the Shaker kinetic phenotypes but only partially rescues the decrease in current magnitude. Together, these results suggest that the role of SSS in the regulation of sleep in Drosophila correlates more strongly with the effects of SSS on Shaker kinetics than current magnitude.

  1. A Hybrid Method for Accelerated Simulation of Coulomb Collisions in a Plasma

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Caflisch, R; Wang, C; Dimarco, G

    2007-10-09

    If the collisional time scale for Coulomb collisions is comparable to the characteristic time scales for a plasma, then simulation of Coulomb collisions may be important for computation of kinetic plasma dynamics. This can be a computational bottleneck because of the large number of simulated particles and collisions (or phase-space resolution requirements in continuum algorithms), as well as the wide range of collision rates over the velocity distribution function. This paper considers Monte Carlo simulation of Coulomb collisions using the binary collision models of Takizuka & Abe and Nanbu. It presents a hybrid method for accelerating the computation of Coulombmore » collisions. The hybrid method represents the velocity distribution function as a combination of a thermal component (a Maxwellian distribution) and a kinetic component (a set of discrete particles). Collisions between particles from the thermal component preserve the Maxwellian; collisions between particles from the kinetic component are performed using the method of or Nanbu. Collisions between the kinetic and thermal components are performed by sampling a particle from the thermal component and selecting a particle from the kinetic component. Particles are also transferred between the two components according to thermalization and dethermalization probabilities, which are functions of phase space.« less

  2. A kinetic model of plasma turbulence

    NASA Astrophysics Data System (ADS)

    Servidio, S.; Valentini, F.; Perrone, D.; Greco, A.; Califano, F.; Matthaeus, W. H.; Veltri, P.

    2015-01-01

    A Hybrid Vlasov-Maxwell (HVM) model is presented and recent results about the link between kinetic effects and turbulence are reviewed. Using five-dimensional (2D in space and 3D in the velocity space) simulations of plasma turbulence, it is found that kinetic effects (or non-fluid effects) manifest through the deformation of the proton velocity distribution function (DF), with patterns of non-Maxwellian features being concentrated near regions of strong magnetic gradients. The direction of the proper temperature anisotropy, calculated in the main reference frame of the distribution itself, has a finite probability of being along or across the ambient magnetic field, in general agreement with the classical definition of anisotropy T ⊥/T ∥ (where subscripts refer to the magnetic field direction). Adopting the latter conventional definition, by varying the global plasma beta (β) and fluctuation level, simulations explore distinct regions of the space given by T ⊥/T ∥ and β∥, recovering solar wind observations. Moreover, as in the solar wind, HVM simulations suggest that proton anisotropy is not only associated with magnetic intermittent events, but also with gradient-type structures in the flow and in the density. The role of alpha particles is reviewed using multi-ion kinetic simulations, revealing a similarity between proton and helium non-Maxwellian effects. The techniques presented here are applied to 1D spacecraft-like analysis, establishing a link between non-fluid phenomena and solar wind magnetic discontinuities. Finally, the dimensionality of turbulence is investigated, for the first time, via 6D HVM simulations (3D in both spaces). These preliminary results provide support for several previously reported studies based on 2.5D simulations, confirming several basic conclusions. This connection between kinetic features and turbulence open a new path on the study of processes such as heating, particle acceleration, and temperature

  3. Particle acceleration and plasma dynamics during magnetic reconnection in the magnetically dominated regime

    DOE PAGES

    Guo, Fan; Liu, Yi -Hsin; Daughton, William; ...

    2015-06-17

    Magnetic reconnection is thought to be the driver for many explosive phenomena in the universe. The energy release and particle acceleration during reconnection have been proposed as a mechanism for producing high-energy emissions and cosmic rays. We carry out two- and three-dimensional (3D) kinetic simulations to investigate relativistic magnetic reconnection and the associated particle acceleration. The simulations focus on electron–positron plasmas starting with a magnetically dominated, force-free current sheet (σ ≡ B 2 / (4πn em ec 2) >> 1). For this limit, we demonstrate that relativistic reconnection is highly efficient at accelerating particles through a first-order Fermi process accomplishedmore » by the curvature drift of particles along the electric field induced by the relativistic flows. This mechanism gives rise to the formation of hard power-law spectra f α (γ - 1) -p and approaches p = 1 for sufficiently large σ and system size. Eventually most of the available magnetic free energy is converted into nonthermal particle kinetic energy. An analytic model is presented to explain the key results and predict a general condition for the formation of power-law distributions. The development of reconnection in these regimes leads to relativistic inflow and outflow speeds and enhanced reconnection rates relative to nonrelativistic regimes. In the 3D simulation, the interplay between secondary kink and tearing instabilities leads to strong magnetic turbulence, but does not significantly change the energy conversion, reconnection rate, or particle acceleration. This paper suggests that relativistic reconnection sites are strong sources of nonthermal particles, which may have important implications for a variety of high-energy astrophysical problems.« less

  4. Experimental Evidence of Kinetic Effects in Indirect-Drive Inertial Confinement Fusion Hohlraums

    NASA Astrophysics Data System (ADS)

    Shan, L. Q.; Cai, H. B.; Zhang, W. S.; Tang, Q.; Zhang, F.; Song, Z. F.; Bi, B.; Ge, F. J.; Chen, J. B.; Liu, D. X.; Wang, W. W.; Yang, Z. H.; Qi, W.; Tian, C.; Yuan, Z. Q.; Zhang, B.; Yang, L.; Jiao, J. L.; Cui, B.; Zhou, W. M.; Cao, L. F.; Zhou, C. T.; Gu, Y. Q.; Zhang, B. H.; Zhu, S. P.; He, X. T.

    2018-05-01

    We present the first experimental evidence supported by simulations of kinetic effects launched in the interpenetration layer between the laser-driven hohlraum plasma bubbles and the corona plasma of the compressed pellet at the Shenguang-III prototype laser facility. Solid plastic capsules were coated with carbon-deuterium layers; as the implosion neutron yield is quenched, DD fusion yield from the corona plasma provides a direct measure of the kinetic effects inside the hohlraum. An anomalous large energy spread of the DD neutron signal (˜282 keV ) and anomalous scaling of the neutron yield with the thickness of the carbon-deuterium layers cannot be explained by the hydrodynamic mechanisms. Instead, these results can be attributed to kinetic shocks that arise in the hohlraum-wall-ablator interpenetration region, which result in efficient acceleration of the deuterons (˜28.8 J , 0.45% of the total input laser energy). These studies provide novel insight into the interactions and dynamics of a vacuum hohlraum and near-vacuum hohlraum.

  5. Power Supplies for High Energy Particle Accelerators

    NASA Astrophysics Data System (ADS)

    Dey, Pranab Kumar

    2016-06-01

    The on-going research and the development projects with Large Hadron Collider at CERN, Geneva, Switzerland has generated enormous enthusiasm and interest amongst all to know about the ultimate findings on `God's Particle'. This paper has made an attempt to unfold the power supply requirements and the methodology adopted to provide the stringent demand of such high energy particle accelerators during the initial stages of the search for the ultimate particles. An attempt has also been made to highlight the present status on the requirement of power supplies in some high energy accelerators with a view that, precautionary measures can be drawn during design and development from earlier experience which will be of help for the proposed third generation synchrotron to be installed in India at a huge cost.

  6. Possible acceleration of cosmic rays in a rotating system: Uehling-Uhlenbeck model

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kwang-Hua, Chu Rainer, E-mail: 1559877413@qq.com

    2016-11-15

    We illustrate the possible acceleration of cosmic rays passing through a kind of amplification channel (via diffusion modes of propagating plane-wave fronts) induced by a rotating system. Our analysis is mainly based on the quantum discrete kinetic model (considering a discrete Uehling-Uhlenbeck collision term), which has been used to study the propagation of plane (e.g., acoustic) waves in a system of rotating gases.

  7. SigrafW: An easy-to-use program for fitting enzyme kinetic data.

    PubMed

    Leone, Francisco Assis; Baranauskas, José Augusto; Furriel, Rosa Prazeres Melo; Borin, Ivana Aparecida

    2005-11-01

    SigrafW is Windows-compatible software developed using the Microsoft® Visual Basic Studio program that uses the simplified Hill equation for fitting kinetic data from allosteric and Michaelian enzymes. SigrafW uses a modified Fibonacci search to calculate maximal velocity (V), the Hill coefficient (n), and the enzyme-substrate apparent dissociation constant (K). The estimation of V, K, and the sum of the squares of residuals is performed using a Wilkinson nonlinear regression at any Hill coefficient (n). In contrast to many currently available kinetic analysis programs, SigrafW shows several advantages for the determination of kinetic parameters of both hyperbolic and nonhyperbolic saturation curves. No initial estimates of the kinetic parameters are required, a measure of the goodness-of-the-fit for each calculation performed is provided, the nonlinear regression used for calculations eliminates the statistical bias inherent in linear transformations, and the software can be used for enzyme kinetic simulations either for educational or research purposes. Persons interested in receiving a free copy of the software should contact Dr. F. A. Leone. Copyright © 2005 International Union of Biochemistry and Molecular Biology, Inc.

  8. Accelerator mass spectrometry for measurement of long-lived radioisotopes.

    PubMed

    Elmore, D; Phillips, F M

    1987-05-01

    Particle accelerators, such as those built for research in nuclear physics, can also be used together with magnetic and electrostatic mass analyzers to measure rare isotopes at very low abundance ratios. All molecular ions can be eliminated when accelerated to energies of millions of electron volts. Some atomic isobars can be eliminated with the use of negative ions; others can be separated at high energies by measuring their rate of energy loss in a detector. The long-lived radioisotopes (10)Be, (14)C,(26)A1, 36Cl, and (129)1 can now be measured in small natural samples having isotopic abundances in the range 10(-12) to 10(- 5) and as few as 10(5) atoms. In the past few years, research applications of accelerator mass spectrometry have been concentrated in the earth sciences (climatology, cosmochemistry, environmental chemistry, geochronology, glaciology, hydrology, igneous petrogenesis, minerals exploration, sedimentology, and volcanology), in anthropology and archeology (radiocarbon dating), and in physics (searches for exotic particles and measurement of halflives). In addition, accelerator mass spectrometry may become an important tool for the materials and biological sciences.

  9. Accelerator Mass Spectrometry for Measurement of Long-Lived Radioisotopes

    NASA Astrophysics Data System (ADS)

    Elmore, David; Phillips, Fred M.

    1987-05-01

    Particle accelerators, such as those built for research in nuclear physics, can also be used together with magnetic and electrostatic mass analyzers to measure rare isotopes at very low abundance ratios. All molecular ions can be eliminated when accelerated to energies of millions of electron volts. Some atomic isobars can be eliminated with the use of negative ions; others can be separated at high energies by measuring their rate of energy loss in a detector. The long-lived radioisotopes 10Be, 14C, 26Al, 36Cl, and 129I can now be measured in small natural samples having isotopic abundances in the range 10-12 to 10-15 and as few as 105 atoms. In the past few years, research applications of accelerator mass spectrometry have been concentrated in the earth sciences (climatology, cosmochemistry, environmental chemistry, geochronology, glaciology, hydrology, igneous petrogenesis, minerals exploration, sedimentology, and volcanology), in anthropology and archeology (radiocarbon dating), and in physics (searches for exotic particles and measurement of half-lives). In addition, accelerator mass spectrometry may become an important tool for the materials and biological sciences.

  10. On the relationships between the Michaelis–Menten kinetics, reverse Michaelis–Menten kinetics, equilibrium chemistry approximation kinetics, and quadratic kinetics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tang, J. Y.

    The Michaelis–Menten kinetics and the reverse Michaelis–Menten kinetics are two popular mathematical formulations used in many land biogeochemical models to describe how microbes and plants would respond to changes in substrate abundance. However, the criteria of when to use either of the two are often ambiguous. Here I show that these two kinetics are special approximations to the equilibrium chemistry approximation (ECA) kinetics, which is the first-order approximation to the quadratic kinetics that solves the equation of an enzyme–substrate complex exactly for a single-enzyme and single-substrate biogeochemical reaction with the law of mass action and the assumption of a quasi-steadymore » state for the enzyme–substrate complex and that the product genesis from enzyme–substrate complex is much slower than the equilibration between enzyme–substrate complexes, substrates, and enzymes. In particular, I show that the derivation of the Michaelis–Menten kinetics does not consider the mass balance constraint of the substrate, and the reverse Michaelis–Menten kinetics does not consider the mass balance constraint of the enzyme, whereas both of these constraints are taken into account in deriving the equilibrium chemistry approximation kinetics. By benchmarking against predictions from the quadratic kinetics for a wide range of substrate and enzyme concentrations, the Michaelis–Menten kinetics was found to persistently underpredict the normalized sensitivity ∂ ln v / ∂ ln k 2 + of the reaction velocity v with respect to the maximum product genesis rate k 2 +, persistently overpredict the normalized sensitivity ∂ ln v / ∂ ln k 1 + of v with respect to the intrinsic substrate affinity k 1 +, persistently overpredict the normalized sensitivity ∂ ln v / ∂ ln [ E] T of v with respect the total enzyme concentration [ E] T, and persistently underpredict the normalized sensitivity ∂ ln v / ∂ ln [ S] T of v with respect to the total substrate

  11. On the relationships between the Michaelis–Menten kinetics, reverse Michaelis–Menten kinetics, equilibrium chemistry approximation kinetics, and quadratic kinetics

    DOE PAGES

    Tang, J. Y.

    2015-12-01

    The Michaelis–Menten kinetics and the reverse Michaelis–Menten kinetics are two popular mathematical formulations used in many land biogeochemical models to describe how microbes and plants would respond to changes in substrate abundance. However, the criteria of when to use either of the two are often ambiguous. Here I show that these two kinetics are special approximations to the equilibrium chemistry approximation (ECA) kinetics, which is the first-order approximation to the quadratic kinetics that solves the equation of an enzyme–substrate complex exactly for a single-enzyme and single-substrate biogeochemical reaction with the law of mass action and the assumption of a quasi-steadymore » state for the enzyme–substrate complex and that the product genesis from enzyme–substrate complex is much slower than the equilibration between enzyme–substrate complexes, substrates, and enzymes. In particular, I show that the derivation of the Michaelis–Menten kinetics does not consider the mass balance constraint of the substrate, and the reverse Michaelis–Menten kinetics does not consider the mass balance constraint of the enzyme, whereas both of these constraints are taken into account in deriving the equilibrium chemistry approximation kinetics. By benchmarking against predictions from the quadratic kinetics for a wide range of substrate and enzyme concentrations, the Michaelis–Menten kinetics was found to persistently underpredict the normalized sensitivity ∂ ln v / ∂ ln k 2 + of the reaction velocity v with respect to the maximum product genesis rate k 2 +, persistently overpredict the normalized sensitivity ∂ ln v / ∂ ln k 1 + of v with respect to the intrinsic substrate affinity k 1 +, persistently overpredict the normalized sensitivity ∂ ln v / ∂ ln [ E] T of v with respect the total enzyme concentration [ E] T, and persistently underpredict the normalized sensitivity ∂ ln v / ∂ ln [ S] T of v with respect to the total substrate

  12. Mass spectrometry with accelerators.

    PubMed

    Litherland, A E; Zhao, X-L; Kieser, W E

    2011-01-01

    As one in a series of articles on Canadian contributions to mass spectrometry, this review begins with an outline of the history of accelerator mass spectrometry (AMS), noting roles played by researchers at three Canadian AMS laboratories. After a description of the unique features of AMS, three examples, (14)C, (10)Be, and (129)I are given to illustrate the methods. The capabilities of mass spectrometry have been extended by the addition of atomic isobar selection, molecular isobar attenuation, further ion acceleration, followed by ion detection and ion identification at essentially zero dark current or ion flux. This has been accomplished by exploiting the techniques and accelerators of atomic and nuclear physics. In 1939, the first principles of AMS were established using a cyclotron. In 1977 the selection of isobars in the ion source was established when it was shown that the (14)N(-) ion was very unstable, or extremely difficult to create, making a tandem electrostatic accelerator highly suitable for assisting the mass spectrometric measurement of the rare long-lived radioactive isotope (14)C in the environment. This observation, together with the large attenuation of the molecular isobars (13)CH(-) and (12)CH 2(-) during tandem acceleration and the observed very low background contamination from the ion source, was found to facilitate the mass spectrometry of (14)C to at least a level of (14)C/C ~ 6 × 10(-16), the equivalent of a radiocarbon age of 60,000 years. Tandem Accelerator Mass Spectrometry, or AMS, has now made possible the accurate radiocarbon dating of milligram-sized carbon samples by ion counting as well as dating and tracing with many other long-lived radioactive isotopes such as (10)Be, (26)Al, (36)Cl, and (129)I. The difficulty of obtaining large anion currents with low electron affinities and the difficulties of isobar separation, especially for the heavier mass ions, has prompted the use of molecular anions and the search for alternative

  13. The accelerated characterization of viscoelastic composite materials. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Griffith, W. I.; Morris, D. H.; Brinson, H. F.

    1980-01-01

    Necessary fundamentals relative to composite materials and viscoelasticity are reviewed. The accelerated characterization techniques of time temperature superposition and time temperature stress superposition are described. An experimental procedure for applying the latter to composites is given along with results obtained on a particular T300/934 graphite/epoxy. The accelerated characterization predictions are found in good agreement with actual long term tests. A postcuring phenomenon is discussed that necessitates thermal conditioning of the specimen prior to testing. A closely related phenomenon of physical aging is described as well as the effect of each on the glass transition temperature and strength. Creep rupture results are provided for a variety of geometries and temperatures for T300/934 graphite/epoxy. The results are found to compare reasonably with a modified kinetic rate theory.

  14. Acceleration modules in linear induction accelerators

    NASA Astrophysics Data System (ADS)

    Wang, Shao-Heng; Deng, Jian-Jun

    2014-05-01

    The Linear Induction Accelerator (LIA) is a unique type of accelerator that is capable of accelerating kilo-Ampere charged particle current to tens of MeV energy. The present development of LIA in MHz bursting mode and the successful application into a synchrotron have broadened LIA's usage scope. Although the transformer model is widely used to explain the acceleration mechanism of LIAs, it is not appropriate to consider the induction electric field as the field which accelerates charged particles for many modern LIAs. We have examined the transition of the magnetic cores' functions during the LIA acceleration modules' evolution, distinguished transformer type and transmission line type LIA acceleration modules, and re-considered several related issues based on transmission line type LIA acceleration module. This clarified understanding should help in the further development and design of LIA acceleration modules.

  15. Darwin's bee-trap: The kinetics of Catasetum, a new world orchid.

    PubMed

    Nicholson, Charles C; Bales, James W; Palmer-Fortune, Joyce E; Nicholson, Robert G

    2008-01-01

    The orchid genera Catasetum employs a hair-trigger activated, pollen release mechanism, which forcibly attaches pollen sacs onto foraging insects in the New World tropics. This remarkable adaptation was studied extensively by Charles Darwin and he termed this rapid response "sensitiveness." Using high speed video cameras with a frame speed of 1000 fps, this rapid release was filmed and from the subsequent footage, velocity, speed, acceleration, force and kinetic energy were computed.

  16. A survey of kinetic data of compounds containing flourine

    NASA Technical Reports Server (NTRS)

    Brewer, D. A.

    1976-01-01

    Chlorofluoromethanes may have a significant effect on the level of ozone in the atmosphere. However, the role of fluroine-containing compounds has not been examined fully. A tabulation of a search of the chemical kinetic literature published between 1953 and July 1975, is presented. The data are then evaluated with respect to acceptability and importance to the overall reaction balance in the atmosphere. Possible future research to elucidate important reaction processes is discussed.

  17. Accelerated Aging of Lead-Free Propellant

    NASA Technical Reports Server (NTRS)

    Furrow, Keith W.; Jervey, David D.

    2000-01-01

    Following higher than expected 2-NDPA depletion rates in a lead-free doublebase formulation (RPD-422), an accelerated aging study was conducted to verify the depletion rates. A test plan was prepared to compare the aging characteristics of lead-free propellant and NOSIH-AA2. The study was also designed to determine which lead-free ballistic modifiers accelerated 2-NDPA depletion. The increased depletion rate occurred in propellants containing monobasic copper salicylate. Four lead-free propellants were then formulated to improved aging characteristics over previous lead-free propellant formulations. The new formulations reduced or replaced the monobasic copper salicylate. The new formulations had improved aging characteristics. Their burn rates, however, were unacceptable for use in a 2.75 inch rocket. To compare aging characteristics, stabilizer depletion rates of RPD-422, AA2, M28, and RLC 470/6A were measured or taken from the literature. The data were fit to a kinetic model. The model contained first and zero order terms which allowed the stabilizer concentration to go to zero. In the model, only the concentration of the primary stabilizer was considered. Derivatives beyond the first nitrated or nitroso derivative of 2-NPDA were not considered. The rate constants were fit to the Arrhenius equation and extrapolated to lower temperatures. The time to complete stabilizer depletion was estimated using the kinetic model. The four propellants were compared and the RPD-422 depleted faster at 45 C than both A22 and M28. These types of predictions depend on the validity of the model and on confidence in the Arrhenius relationship holding at lower temperatures. At 45 C, the zero order portion of the model dominates the depletion rate.

  18. E258K HCM-causing mutation in cardiac MyBP-C reduces contractile force and accelerates twitch kinetics by disrupting the cMyBP-C and myosin S2 interaction.

    PubMed

    De Lange, Willem J; Grimes, Adrian C; Hegge, Laura F; Spring, Alexander M; Brost, Taylor M; Ralphe, J Carter

    2013-09-01

    Mutations in cardiac myosin binding protein C (cMyBP-C) are prevalent causes of hypertrophic cardiomyopathy (HCM). Although HCM-causing truncation mutations in cMyBP-C are well studied, the growing number of disease-related cMyBP-C missense mutations remain poorly understood. Our objective was to define the primary contractile effect and molecular disease mechanisms of the prevalent cMyBP-C E258K HCM-causing mutation in nonremodeled murine engineered cardiac tissue (mECT). Wild-type and human E258K cMyBP-C were expressed in mECT lacking endogenous mouse cMyBP-C through adenoviral-mediated gene transfer. Expression of E258K cMyBP-C did not affect cardiac cell survival and was appropriately incorporated into the cardiac sarcomere. Functionally, expression of E258K cMyBP-C caused accelerated contractile kinetics and severely compromised twitch force amplitude in mECT. Yeast two-hybrid analysis revealed that E258K cMyBP-C abolished interaction between the N terminal of cMyBP-C and myosin heavy chain sub-fragment 2 (S2). Furthermore, this mutation increased the affinity between the N terminal of cMyBP-C and actin. Assessment of phosphorylation of three serine residues in cMyBP-C showed that aberrant phosphorylation of cMyBP-C is unlikely to be responsible for altering these interactions. We show that the E258K mutation in cMyBP-C abolishes interaction between N-terminal cMyBP-C and myosin S2 by directly disrupting the cMyBP-C-S2 interface, independent of cMyBP-C phosphorylation. Similar to cMyBP-C ablation or phosphorylation, abolition of this inhibitory interaction accelerates contractile kinetics. Additionally, the E258K mutation impaired force production of mECT, which suggests that in addition to the loss of physiological function, this mutation disrupts contractility possibly by tethering the thick and thin filament or acting as an internal load.

  19. Study the oxidation kinetics of uranium using XRD and Rietveld method

    NASA Astrophysics Data System (ADS)

    Zhang, Yanzhi; Guan, Weijun; Wang, Qinguo; Wang, Xiaolin; Lai, Xinchun; Shuai, Maobing

    2010-03-01

    The surface oxidation of uranium metal has been studied by X-ray diffraction (XRD) and Rietveld method in the range of 50~300°C in air. The oxidation processes are analyzed by XRD to determine the extent of surface oxidation and the oxide structure. The dynamics expression for the formation of UO2 was derived. At the beginning, the dynamic expression was nonlinear, but switched to linear subsequently for uranium in air and humid oxygen. That is, the growth kinetics of UO2 can be divided into two stages: nonlinear portion and linear portion. Using the kinetic data of linear portion, the activation energy of reaction between uranium and air was calculated about 46.0 kJ/mol. However the content of oxide as a function of time was linear in humid helium ambience. Contrast the dynamics results, it prove that the absence of oxygen would accelerate the corrosion rate of uranium in the humid gas. We can find that the XRD and Rietveld method are a useful convenient method to estimate the kinetics and thermodynamics of solid-gas reaction.

  20. Defining Nitrogen Kinetics for Air Break in Prebreath

    NASA Technical Reports Server (NTRS)

    Conkin, Johnny

    2010-01-01

    Actual tissue nitrogen (N2) kinetics are complex; the uptake and elimination is often approximated with a single half-time compartment in statistical descriptions of denitrogenation [prebreathe(PB)] protocols. Air breaks during PB complicate N2 kinetics. A comparison of symmetrical versus asymmetrical N2 kinetics was performed using the time to onset of hypobaric decompression sickness (DCS) as a surrogate for actual venous N2 tension. METHODS: Published results of 12 tests involving 179 hypobaric exposures in altitude chambers after PB, with and without airbreaks, provide the complex protocols from which to model N2 kinetics. DCS survival time for combined control and airbreaks were described with an accelerated log logistic model where N2 uptake and elimination before, during, and after the airbreak was computed with a simple exponential function or a function that changed half-time depending on ambient N2 partial pressure. P1N2-P2 = (Delta)P defined decompression dose for each altitude exposure, where P2 was the test altitude and P1N2 was computed N2 pressure at the beginning of the altitude exposure. RESULTS: The log likelihood (LL) without decompression dose (null model) was -155.6, and improved (best-fit) to -97.2 when dose was defined with a 240 min half-time for both N2 elimination and uptake during the PB. The description of DCS survival time was less precise with asymmetrical N2 kinetics, for example, LL was -98.9 with 240 min half-time elimination and 120 min half-time uptake. CONCLUSION: The statistical regression described survival time mechanistically linked to symmetrical N2 kinetics during PBs that also included airbreaks. The results are data-specific, and additional data may change the conclusion. The regression is useful to compute additional PB time to compensate for an airbreak in PB within the narrow range of tested conditions.

  1. Defining Nitrogen Kinetics for Air Break in Prebreathe

    NASA Technical Reports Server (NTRS)

    Conkin, Johnny

    2009-01-01

    Actual tissue nitrogen (N2) kinetics are complex; the uptake and elimination is often approximated with a single half-time compartment in statistical descriptions of denitrogenation [prebreathe (PB)] protocols. Air breaks during PB complicate N2 kinetics. A comparison of symmetrical versus asymmetrical N2 kinetics was performed using the time to onset of hypobaric decompression sickness (DCS) as a surrogate for actual venous N2 tension. Published results of 12 tests involving 179 hypobaric exposures in altitude chambers after PB, with and without air breaks, provide the complex protocols from which to model N2 kinetics. DCS survival time for combined control and air breaks were described with an accelerated log logistic model where N2 uptake and elimination before, during, and after the air break was computed with a simple exponential function or a function that changed half-time depending on ambient N2 partial pressure. P1N2-P2 = delta P defined DCS dose for each altitude exposure, where P2 was the test altitude and P1N2 was computed N2 pressure at the beginning of the altitude exposure. The log likelihood (LL) without DCS dose (null model) was -155.6, and improved (best-fit) to -97.2 when dose was defined with a 240 min half-time for both N2 elimination and uptake during the PB. The description of DCS survival time was less precise with asymmetrical N2 kinetics, for example, LL was -98.9 with 240 min half-time elimination and 120 min half-time uptake. The statistical regression described survival time mechanistically linked to symmetrical N2 kinetics during PBs that also included air breaks. The results are data-specific, and additional data may change the conclusion. The regression is useful to compute additional PB time to compensate for an air break in PB within the narrow range of tested conditions.

  2. Effect of ketamine, pentobarbital, and morphine on Tc-99m-DISIDA hepatobiliary kinetics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Durakovic, A.; Dubois, A.

    1985-05-01

    The purpose of this study was to evaluate hapatobiliary kinetics of Tc-99m-DISIDA in dogs after administration of anesthetic sedative or narcotic agents. Four groups of six male Beagle dogs were studied as a non-treated control group and after parenteral administration of ketamine (30 mg/kg IM), pentobarbital (25 mg/kg IV) or morphine (1 mg/kg IV). Each animal was injected with 4 mCi Tc-99m-DISIDA and hepatobiliary scintigraphic studies were obtained using a gamma camera with parallel hole multipurpose collimator and an A/sup 3/ MDS computer. The authors determined; peak activity of Tc-99m-DISIDA in the liver, visualization and peak activity of gallbladder, andmore » intestinal visualization of Tc-99m-DISIDA. Total bilirubin, LDH, SGOT and SGPT were not modified significantly after any drug compared to control. The results showed that two commonly used anesthetics and sedatives (ketamine and pentobarbital) have dramatic and opposite effects on extrahepatic biliary kinetics. Furthermore, ketamine, but not pentobarbital, significantly accelerates intrahepatic biliary kinetics. Finally, as expected, morphine delayed extrahepatic biliary kinetics. Thus, studies of biliary kinetics should be interpreted with caution when measurements are made after administration of anesthetic, sedative or narcotic agents.« less

  3. Mechanistic study of manganese-substituted glycerol dehydrogenase using a kinetic and thermodynamic analysis.

    PubMed

    Fang, Baishan; Niu, Jin; Ren, Hong; Guo, Yingxia; Wang, Shizhen

    2014-01-01

    Mechanistic insights regarding the activity enhancement of dehydrogenase by metal ion substitution were investigated by a simple method using a kinetic and thermodynamic analysis. By profiling the binding energy of both the substrate and product, the metal ion's role in catalysis enhancement was revealed. Glycerol dehydrogenase (GDH) from Klebsiella pneumoniae sp., which demonstrated an improvement in activity by the substitution of a zinc ion with a manganese ion, was used as a model for the mechanistic study of metal ion substitution. A kinetic model based on an ordered Bi-Bi mechanism was proposed considering the noncompetitive product inhibition of dihydroxyacetone (DHA) and the competitive product inhibition of NADH. By obtaining preliminary kinetic parameters of substrate and product inhibition, the number of estimated parameters was reduced from 10 to 4 for a nonlinear regression-based kinetic parameter estimation. The simulated values of time-concentration curves fit the experimental values well, with an average relative error of 11.5% and 12.7% for Mn-GDH and GDH, respectively. A comparison of the binding energy of enzyme ternary complex for Mn-GDH and GDH derived from kinetic parameters indicated that metal ion substitution accelerated the release of dioxyacetone. The metal ion's role in catalysis enhancement was explicated.

  4. tICA-Metadynamics: Accelerating Metadynamics by Using Kinetically Selected Collective Variables.

    PubMed

    M Sultan, Mohammad; Pande, Vijay S

    2017-06-13

    Metadynamics is a powerful enhanced molecular dynamics sampling method that accelerates simulations by adding history-dependent multidimensional Gaussians along selective collective variables (CVs). In practice, choosing a small number of slow CVs remains challenging due to the inherent high dimensionality of biophysical systems. Here we show that time-structure based independent component analysis (tICA), a recent advance in Markov state model literature, can be used to identify a set of variationally optimal slow coordinates for use as CVs for Metadynamics. We show that linear and nonlinear tICA-Metadynamics can complement existing MD studies by explicitly sampling the system's slowest modes and can even drive transitions along the slowest modes even when no such transitions are observed in unbiased simulations.

  5. Electron and Ion Acceleration Associated with Magnetotail Reconnection

    NASA Astrophysics Data System (ADS)

    Liang, Haoming

    This dissertation is dedicated to understanding electron and ion acceleration associated with magnetotail reconnection during substorms by using numerical simulations. Electron dynamics were investigated by using the UCLA global magnetohydrodynamic (MHD) model and large scale kinetic (LSK) simulations. The neutral line configurations and magnetotail flows modify the amounts of the adiabatic and non-adiabatic acceleration that electrons undergo. This causes marked differences in the temperature anisotropy for different substorms. In particular, one substorm event analyzed shows T⊥ > T∥ (T⊥ / T ∥ ≈ 2.3)at -10RE while another shows T ∥ > T⊥ (T ⊥ / T∥ ≈ 0.8), where T⊥ and T∥ (second order moments of the distribution functions) are defined with respect to the magnetic field. These differences determine the subsequent acceleration of the energetic electrons in the inner magnetosphere. Whether the acceleration is mostly parallel or perpendicular is determined by the location of dayside reconnection. A 2.5D implicit Particle-in-Cell simulation was used to study the effects produced by oxygen ions on magnetotail reconnection, and the associated acceleration of protons and oxygen ions. The inertia of oxygen ions reduces the reconnection rate and slows down the earthward propagation of dipolarization fronts (DFs). An ambipolar electric field in the oxygen diffusion region contributes to the smaller reconnection rate. This change in the reconnection rate affects the ion acceleration. In particular 67% of protons and 58% of oxygen ions were accelerated in the exhaust (between the X-point and the DF) in a simulation corresponding to a magnetic storm in which there was a 50% concentration of oxygen ions. In addition, 42% of lobe oxygen-ions are accelerated locally by the Hall electric field, far away from the X-point without entering the exhaust. Protons at the same locations experience Ex B drift. This finding extends previous knowledge that oxygen and

  6. In vitro evaluation of flow patterns and turbulent kinetic energy in trans-catheter aortic valve prostheses.

    PubMed

    Giese, Daniel; Weiss, Kilian; Baeßler, Bettina; Madershahian, Navid; Choi, Yeong-Hoon; Maintz, David; Bunck, Alexander C

    2018-02-01

    The objective of the current work was to evaluate flow and turbulent kinetic energy in different transcatheter aortic valve implants using highly undersampled time-resolved multi-point 3-directional phase-contrast measurements (4D Flow MRI) in an in vitro setup. A pulsatile flow setup was used with a compliant tubing mimicking a stiff left ventricular outflow tract and ascending aorta. Five different implants were measured using a highly undersampled multi-point 4D Flow MRI sequence. Velocities and turbulent kinetic energy values were analysed and compared. Strong variations of turbulent kinetic energy distributions between the valves were observed. Maximum turbulent kinetic energy values ranged from 100 to over 500 J/m 3 while through-plane velocities were similar between all valves. Highly accelerated 4D Flow MRI for the measurement of velocities and turbulent kinetic energy values allowed for the assessment of hemodynamic parameters in five different implant models. The presented setup, measurement protocol and analysis methods provides an efficient approach to compare different valve implants and could aid future novel valve designs.

  7. Minimizing Head Acceleration in Soccer: A Review of the Literature.

    PubMed

    Caccese, Jaclyn B; Kaminski, Thomas W

    2016-11-01

    Physicians and healthcare professionals are often asked for recommendations on how to keep athletes safe during contact sports such as soccer. With an increase in concussion awareness and concern about repetitive subconcussion, many parents and athletes are interested in mitigating head acceleration in soccer, so we conducted a literature review on factors that affect head acceleration in soccer. We searched electronic databases and reference lists to find studies using the keywords 'soccer' OR 'football' AND 'head acceleration'. Because of a lack of current research in soccer heading biomechanics, this review was limited to 18 original research studies. Low head-neck segment mass predisposes athletes to high head acceleration, but head-neck-torso alignment during heading and follow-through after contact can be used to decrease head acceleration. Additionally, improvements in symmetric neck flexor and extensor strength and neuromuscular neck stiffness can decrease head acceleration. Head-to-head impacts and unanticipated ball contacts result in the highest head acceleration. Ball contacts at high velocity may also be dangerous. The risk of concussive impacts may be lessened through the use of headgear, but headgear may also cause athletes to play more recklessly because they feel a sense of increased security. Young, but physically capable, athletes should be taught proper heading technique in a controlled setting, using a carefully planned progression of the skill.

  8. Simulations of Magnetic Reconnection - Kinetic Mechanisms Underlying the Fluid Description of Ions

    NASA Technical Reports Server (NTRS)

    Aunai, icolas; Belmont, Gerard; Smets, Roch

    2012-01-01

    Because of its ability to transfer the energy stored in magnetic field together with the breaking of the flux freezing constraint, magnetic reconnection is considered as one of the most important phenomena in plasma physics. When it happens in a collision less environment such as the terrestrial magnetosphere, it should a priori be modelled with in the framework of kinetic physics. The evidence of kinetic features has incidentally for a long time, been shown by researchers with the help of both numerical simulations and satellite observations. However, most of our understanding of the process comes from the more intuitive fluid interpretation with simple closure hypothesis which do not include kinetic effects. To what extent are these two separate descriptions of the same phenomenon related? What is the role of kinetic effects in the averaged/fluid dynamics of reconnection? This thesis addresses these questions for the proton population in the particular case of anti parallel merging with the help of 2D Hybrid simulations. We show that one can not assume, as is usually done, that the acceleration of the proton flow is only due to the Laplace force. Our results show, for symmetric and asymmetric connection, the importance of the pressure force, opposed to the electric one on the separatrices, in the decoupling region. In the symmetric case, we emphasize the kinetic origin of this force by analyzing the proton distribution functions and explain their structure by studying the underlying particle dynamics. Protons, as individual particles, are shown to bounce in the electric potential well created by the Hall effect. The spatial divergence of this well results in a mixing in phase space responsible for the observed structure of the pressure tensor. A detailed energy budget analysis confirms the role of the pressure force for the acceleration; but, contrary to what is sometimes assumed, it also reveals that the major part of the incoming Poynting flux is transferred to

  9. Kinetic analysis of thermal stability of human low density lipoproteins: a model for LDL fusion in atherogenesis.

    PubMed

    Lu, Mengxiao; Gantz, Donald L; Herscovitz, Haya; Gursky, Olga

    2012-10-01

    Fusion of modified LDL in the arterial wall promotes atherogenesis. Earlier we showed that thermal denaturation mimics LDL remodeling and fusion, and revealed kinetic origin of LDL stability. Here we report the first quantitative analysis of LDL thermal stability. Turbidity data show sigmoidal kinetics of LDL heat denaturation, which is unique among lipoproteins, suggesting that fusion is preceded by other structural changes. High activation energy of denaturation, E(a) = 100 ± 8 kcal/mol, indicates disruption of extensive packing interactions in LDL. Size-exclusion chromatography, nondenaturing gel electrophoresis, and negative-stain electron microscopy suggest that LDL dimerization is an early step in thermally induced fusion. Monoclonal antibody binding suggests possible involvement of apoB N-terminal domain in early stages of LDL fusion. LDL fusion accelerates at pH < 7, which may contribute to LDL retention in acidic atherosclerotic lesions. Fusion also accelerates upon increasing LDL concentration in near-physiologic range, which likely contributes to atherogenesis. Thermal stability of LDL decreases with increasing particle size, indicating that the pro-atherogenic properties of small dense LDL do not result from their enhanced fusion. Our work provides the first kinetic approach to measuring LDL stability and suggests that lipid-lowering therapies that reduce LDL concentration but increase the particle size may have opposite effects on LDL fusion.

  10. Acceleration mechanisms for energetic particles in the earth's magnetosphere

    NASA Technical Reports Server (NTRS)

    Schiferl, S.; Fan, C. Y.; Hsieh, K. C.; Erickson, K. N.; Gloeckler, G.

    1982-01-01

    By analyzing data on energetic particle fluxes measured simultaneously with detector systems on several earth satellites, signatures of different acceleration mechanisms for these particles were searched for. One of the samples is an event observed on ATS-6 and IMP-7. IMP-7 was in the dusk quarter at 38 earth radii while ATS-6 was located at local midnight at a distance of 6.6 earth radii. Although the flux variations as observed on the two spacecraft both showed 1.5 min periodicity, there was a 40-second time lag with IMP-7 behind. The results indicate that the particles are accelerated by magnetic field line annihilation, with the x-point located at about 10 earth radii.

  11. Electron transfer kinetics on natural crystals of MoS2 and graphite.

    PubMed

    Velický, Matěj; Bissett, Mark A; Toth, Peter S; Patten, Hollie V; Worrall, Stephen D; Rodgers, Andrew N J; Hill, Ernie W; Kinloch, Ian A; Novoselov, Konstantin S; Georgiou, Thanasis; Britnell, Liam; Dryfe, Robert A W

    2015-07-21

    Here, we evaluate the electrochemical performance of sparsely studied natural crystals of molybdenite and graphite, which have increasingly been used for fabrication of next generation monolayer molybdenum disulphide and graphene energy storage devices. Heterogeneous electron transfer kinetics of several redox mediators, including Fe(CN)6(3-/4-), Ru(NH3)6(3+/2+) and IrCl6(2-/3-) are determined using voltammetry in a micro-droplet cell. The kinetics on both materials are studied as a function of surface defectiveness, surface ageing, applied potential and illumination. We find that the basal planes of both natural MoS2 and graphite show significant electroactivity, but a large decrease in electron transfer kinetics is observed on atmosphere-aged surfaces in comparison to in situ freshly cleaved surfaces of both materials. This is attributed to surface oxidation and adsorption of airborne contaminants at the surface exposed to an ambient environment. In contrast to semimetallic graphite, the electrode kinetics on semiconducting MoS2 are strongly dependent on the surface illumination and applied potential. Furthermore, while visibly present defects/cracks do not significantly affect the response of graphite, the kinetics on MoS2 systematically accelerate with small increase in disorder. These findings have direct implications for use of MoS2 and graphene/graphite as electrode materials in electrochemistry-related applications.

  12. Plasma Radiation and Acceleration Effectiveness of CME-driven Shocks

    NASA Astrophysics Data System (ADS)

    Gopalswamy, N.; Schmidt, J. M.

    2008-05-01

    CME-driven shocks are effective radio radiation generators and accelerators for Solar Energetic Particles (SEPs). We present simulated 3 D time-dependent radio maps of second order plasma radiation generated by CME- driven shocks. The CME with its shock is simulated with the 3 D BATS-R-US CME model developed at the University of Michigan. The radiation is simulated using a kinetic plasma model that includes shock drift acceleration of electrons and stochastic growth theory of Langmuir waves. We find that in a realistic 3 D environment of magnetic field and solar wind outflow of the Sun the CME-driven shock shows a detailed spatial structure of the density, which is responsible for the fine structure of type II radio bursts. We also show realistic 3 D reconstructions of the magnetic cloud field of the CME, which is accelerated outward by magnetic buoyancy forces in the diverging magnetic field of the Sun. The CME-driven shock is reconstructed by tomography using the maximum jump in the gradient of the entropy. In the vicinity of the shock we determine the Alfven speed of the plasma. This speed profile controls how steep the shock can grow and how stable the shock remains while propagating away from the Sun. Only a steep shock can provide for an effective particle acceleration.

  13. Plasma radiation and acceleration effectiveness of CME-driven shocks

    NASA Astrophysics Data System (ADS)

    Schmidt, Joachim

    CME-driven shocks are effective radio radiation generators and accelerators for Solar Energetic Particles (SEPs). We present simulated 3 D time-dependent radio maps of second order plasma radiation generated by CME-driven shocks. The CME with its shock is simulated with the 3 D BATS-R-US CME model developed at the University of Michigan. The radiation is simulated using a kinetic plasma model that includes shock drift acceleration of electrons and stochastic growth theory of Langmuir waves. We find that in a realistic 3 D environment of magnetic field and solar wind outflow of the Sun the CME-driven shock shows a detailed spatial structure of the density, which is responsible for the fine structure of type II radio bursts. We also show realistic 3 D reconstructions of the magnetic cloud field of the CME, which is accelerated outward by magnetic buoyancy forces in the diverging magnetic field of the Sun. The CME-driven shock is reconstructed by tomography using the maximum jump in the gradient of the entropy. In the vicinity of the shock we determine the Alfven speed of the plasma. This speed profile controls how steep the shock can grow and how stable the shock remains while propagating away from the Sun. Only a steep shock can provide for an effective particle acceleration.

  14. Kinetic Monte Carlo simulations of scintillation processes in NaI(Tl)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kerisit, Sebastien N.; Wang, Zhiguo; Williams, Richard

    2014-04-26

    Developing a comprehensive understanding of the processes that govern the scintillation behavior of inorganic scintillators provides a pathway to optimize current scintillators and allows for the science-driven search for new scintillator materials. Recent experimental data on the excitation density dependence of the light yield of inorganic scintillators presents an opportunity to incorporate parameterized interactions between excitations in scintillation models and thus enable more realistic simulations of the nonproportionality of inorganic scintillators. Therefore, a kinetic Monte Carlo (KMC) model of elementary scintillation processes in NaI(Tl) is developed in this work to simulate the kinetics of scintillation for a range of temperaturesmore » and Tl concentrations as well as the scintillation efficiency as a function of excitation density. The ability of the KMC model to reproduce available experimental data allows for elucidating the elementary processes that give rise to the kinetics and efficiency of scintillation observed experimentally for a range of conditions.« less

  15. Kinetic Monte Carlo Simulations of Scintillation Processes in NaI(Tl)

    NASA Astrophysics Data System (ADS)

    Kerisit, Sebastien; Wang, Zhiguo; Williams, Richard T.; Grim, Joel Q.; Gao, Fei

    2014-04-01

    Developing a comprehensive understanding of the processes that govern the scintillation behavior of inorganic scintillators provides a pathway to optimize current scintillators and allows for the science-driven search for new scintillator materials. Recent experimental data on the excitation density dependence of the light yield of inorganic scintillators presents an opportunity to incorporate parameterized interactions between excitations in scintillation models and thus enable more realistic simulations of the nonproportionality of inorganic scintillators. Therefore, a kinetic Monte Carlo (KMC) model of elementary scintillation processes in NaI(Tl) is developed in this paper to simulate the kinetics of scintillation for a range of temperatures and Tl concentrations as well as the scintillation efficiency as a function of excitation density. The ability of the KMC model to reproduce available experimental data allows for elucidating the elementary processes that give rise to the kinetics and efficiency of scintillation observed experimentally for a range of conditions.

  16. Prolonged electron accelerations at a high-Mach-number, quasi-perpendicular shock

    NASA Astrophysics Data System (ADS)

    Matsumoto, Y.; Amano, T.; Kato, T.; Hoshino, M.

    2016-12-01

    Weibel turbulence is essentially the key to prolonged acceleration processes which can produce relativistic particles with energies more than 1000 times the initial kinetic energy. We present how such relativistic electrons are produced during traveling in the 3D shock structure.

  17. Injection of externally produced kinetic electrons into a self-guided laser wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Pollock, Bradley; Ralph, Joseph; Albert, Felicie; Shaw, Jessica; Clayton, Christopher; Marsh, Ken; Joshi, Chan; Mori, Warren; Kesler, Leigh; Mills, Sarah; Severson, Brian; Rigby, Alexandra; Glenzer, Siegfried

    2012-10-01

    A two-stage laser wakefield accelerator is being developed at the Lawrence Livermore National Laboratory using the Callisto laser system. The first stage is a high density (˜10^19 cm-3), 5 mm He gas jet plasma which is driven by 30 TW of 800 nm laser light focused to an a0˜ 2. The <100 MeV electrons produced in this stage are deflected by a 0.5 T dipole magnet onto the axis of the second stage, which is a low density (˜10^18 cm-3), 15 mm He gas cell driven by 200 TW of 800 nm light also focused to an a0˜ 2; no additional electrons are trapped in this stage. Electrons injected into the second stage can then be further accelerated to higher energy without increasing the energy spread. Measurements of the transmitted laser profile and spectrum from the second stage indicate that the laser pulse is self-guided throughout the gas cell and that a strong wake is driven. These results compare well with particle-in-cell (PIC) simulations performed with the code OSIRIS. This work was performed under the auspices of the United States Department of Energy by the Lawrence Livermore National Laboratory under contract No. DE-AC52-07NA-27344.

  18. Kinetics and mechanism of imazosulfuron hydrolysis.

    PubMed

    Morrica, P; Barbato, F; Della Iacovo, R; Seccia, S; Ungaro, F

    2001-08-01

    Knowledge of the kinetics and pathways of hydrolytic degradation is crucial to the prediction of the fate and transport mechanism of chemicals. This work first describes the kinetics of the chemical hydrolysis of imazosulfuron, a new sulfonylurea herbicide, and evaluates the results to propose a degradation pathway. The hydrolysis of imazosulfuron has been studied in aqueous buffers both within the pH range 1.9-12.3 at ambient temperature (thermostated at 25 +/- 2 degrees C) and at pH 3.6 within the temperature range of 15-55 degrees C. The hydrolysis rate of imazosulfuron was characterized by a first-order kinetics, pH- and temperature-dependent, and accelerated by acidic conditions and higher temperatures. The calculated half-lives at pH 4.5 and 5.9 were 36.5 and 578 days, respectively. At pH 6.6, 7.4, 9.2, and 12.3 no significant change in imazosulfuron concentration was observed after 150 days. Half-lives were much lower at pH <4 (= imazosulfuron pK(a)), at which they ranged from 3.3 to 6.3 days. Moreover, a change in temperature from 15 to 25 degrees C in acidic conditions (pH 3.6) decreased the half-life of imazosulfuron by a factor of approximately 4.0; in any case, a 3-5-fold increase in the rate of hydrolysis was found for each 10 degrees C increase in temperature. In acidic conditions the only hydrolysis products were the two molecules resulting from the cleavage of the sulfonylurea bridge.

  19. Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH). Part 1

    NASA Technical Reports Server (NTRS)

    Micheletti, David A.; Baughman, Jack A.; Nelson, Gordon L.; Simmons, Gloyd A.

    1997-01-01

    This report documents the activities, results, conclusions and recommendations of the Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH) Project in which the use of magnetohydrodynamics (MHD) technology is investigated for its applicability to augment hypersonic wind tunnels. The long range objective of this investigation is to advance the development of ground test facilities to support the development of hypervelocity flight vehicles. The MHD accelerator adds kinetic energy directly to the wind tunnel working fluid, thereby increasing its Mach number to hypervelocity levels. Several techniques for MHD augmentation, as well as other physical characteristics of the process are studied to enhance the overall performance of hypersonic wind tunnel design. Specific recommendations are presented to improve the effectiveness of ground test facilities. The work contained herein builds on nearly four decades of research and experimentation by the aeronautics ground test and evaluation community, both foreign and domestic.

  20. Magnetohydrodynamics Accelerator Research into Advanced Hypersonics (MARIAH). Part 2

    NASA Technical Reports Server (NTRS)

    Baughman, Jack A.; Micheletti, David A.; Nelson, Gordon L.; Simmons, Gloyd A.

    1997-01-01

    This report documents the activities, results, conclusions and recommendations of the Magnetohydrodynamics Accelerator Research Into Advanced Hypersonics (MARIAH) Project in which the use of magnetohydrodynamics (MHD) technology is investigated for its applicability to augment hypersonic wind tunnels. The long range objective of this investigation is to advance the development of ground test facilities to support the development of hypervelocity flight vehicles. The MHD accelerator adds kinetic energy directly to the wind tunnel working fluid, thereby increasing its Mach number to hypervelocity levels. Several techniques for MHD augmentation, as well as other physical characteristics of the process are studied to enhance the overall performance of hypersonic wind tunnel design. Specific recommendations are presented to improve the effectiveness of ground test facilities. The work contained herein builds on nearly four decades of research and experimentation by the aeronautics ground test and evaluation community, both foreign and domestic.

  1. Semantic search during divergent thinking.

    PubMed

    Hass, Richard W

    2017-09-01

    Divergent thinking, as a method of examining creative cognition, has not been adequately analyzed in the context of modern cognitive theories. This article casts divergent thinking responding in the context of theories of memory search. First, it was argued that divergent thinking tasks are similar to semantic fluency tasks, but are more constrained, and less well structured. Next, response time distributions from 54 participants were analyzed for temporal and semantic clustering. Participants responded to two prompts from the alternative uses test: uses for a brick and uses for a bottle, for two minutes each. Participants' cumulative response curves were negatively accelerating, in line with theories of search of associative memory. However, results of analyses of semantic and temporal clustering suggested that clustering is less evident in alternative uses responding compared to semantic fluency tasks. This suggests either that divergent thinking responding does not involve an exhaustive search through a clustered memory trace, but rather that the process is more exploratory, yielding fewer overall responses that tend to drift away from close associates of the divergent thinking prompt. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Kinetic study of olive oil degradation monitored by fourier transform infrared spectrometry. Application to oil characterization.

    PubMed

    Román Falcó, Iván P; Grané Teruel, Nuria; Prats Moya, Soledad; Martín Carratalá, M Luisa

    2012-11-28

    A new approach for the determination of kinetic parameters of the cis/trans isomerization during the oxidation process of 24 virgin olive oils belonging to 8 different varieties is presented. The accelerated process of degradation at 100 °C was monitored by recording the Fourier transform infrared spectra. The parameters obtained confirm pseudo-first-order kinetics for the degradation of cis and the appearance of trans double bonds. The kinetic approach affords the induction time and the rate coefficient; these parameters are related to the fatty acid profile of the fresh olive oils. The data obtained were used to compare the oil stability of the samples with the help of multivariate statistical techniques. Fatty acid allowed a classification of the samples in five groups, one of them constituted by the cultivars with higher stability. Meanwhile, the kinetic parameters showed greater ability for the characterization of olive oils, allowing the classification in seven groups.

  3. Multi-gigaelectronvolt acceleration of positrons in a self-loaded plasma wakefield.

    PubMed

    Corde, S; Adli, E; Allen, J M; An, W; Clarke, C I; Clayton, C E; Delahaye, J P; Frederico, J; Gessner, S; Green, S Z; Hogan, M J; Joshi, C; Lipkowitz, N; Litos, M; Lu, W; Marsh, K A; Mori, W B; Schmeltz, M; Vafaei-Najafabadi, N; Walz, D; Yakimenko, V; Yocky, G

    2015-08-27

    Electrical breakdown sets a limit on the kinetic energy that particles in a conventional radio-frequency accelerator can reach. New accelerator concepts must be developed to achieve higher energies and to make future particle colliders more compact and affordable. The plasma wakefield accelerator (PWFA) embodies one such concept, in which the electric field of a plasma wake excited by a bunch of charged particles (such as electrons) is used to accelerate a trailing bunch of particles. To apply plasma acceleration to electron-positron colliders, it is imperative that both the electrons and their antimatter counterpart, the positrons, are efficiently accelerated at high fields using plasmas. Although substantial progress has recently been reported on high-field, high-efficiency acceleration of electrons in a PWFA powered by an electron bunch, such an electron-driven wake is unsuitable for the acceleration and focusing of a positron bunch. Here we demonstrate a new regime of PWFAs where particles in the front of a single positron bunch transfer their energy to a substantial number of those in the rear of the same bunch by exciting a wakefield in the plasma. In the process, the accelerating field is altered--'self-loaded'--so that about a billion positrons gain five gigaelectronvolts of energy with a narrow energy spread over a distance of just 1.3 metres. They extract about 30 per cent of the wake's energy and form a spectrally distinct bunch with a root-mean-square energy spread as low as 1.8 per cent. This ability to transfer energy efficiently from the front to the rear within a single positron bunch makes the PWFA scheme very attractive as an energy booster to an electron-positron collider.

  4. Memory-induced acceleration and slowdown of barrier crossing

    NASA Astrophysics Data System (ADS)

    Kappler, Julian; Daldrop, Jan O.; Brünig, Florian N.; Boehle, Moritz D.; Netz, Roland R.

    2018-01-01

    We study the mean first-passage time τMFP for the barrier crossing of a single massive particle with non-Markovian memory by Langevin simulations in one dimension. In the Markovian limit of short memory time τΓ, the expected Kramers turnover between the overdamped (high-friction) and the inertial (low-friction) limits is recovered. Compared to the Markovian case, we find barrier crossing to be accelerated for intermediate memory time, while for long memory time, barrier crossing is slowed down and τMFP increases with τΓ as a power law τM F P˜τΓ2. Both effects are derived from an asymptotic propagator analysis: while barrier crossing acceleration at intermediate memory can be understood as an effective particle mass reduction, slowing down for long memory is caused by the slow kinetics of energy diffusion. A simple and globally accurate heuristic formula for τMFP in terms of all relevant time scales of the system is presented and used to establish a scaling diagram featuring the Markovian overdamped and the Markovian inertial regimes, as well as the non-Markovian intermediate memory time regime where barrier crossing is accelerated and the non-Markovian long memory time regime where barrier crossing is slowed down.

  5. Accelerator-based Neutrino Physics at Fermilab

    NASA Astrophysics Data System (ADS)

    Dukes, Edmond

    2008-10-01

    The discovery of neutrino mass has excited great interest in elucidating the properties of neutrinos and their role in nature. Experiments around the world take advantage of solar, atmospheric, reactor, and accelerator sources of neutrinos. Accelerator-based sources are particularly convenient since their parameters can be tuned to optimize the measurement in question. At Fermilab an extensive neutrino program includes the MiniBooNE, SciBooNE, and MINOS experiments. Two major new experiments, MINERvA and NOvA, are being constructed, plans for a high-intensity neutrino source to DUSEL are underway, and an R&D effort towards a large liquid argon detector is being pursued. The NOvA experiment intends to search for electron neutrino appearance using a massive surface detector 811 km from Fermilab. In addition to measuring the last unknown mixing angle, theta(13), NOvA has the possibility of seeing matter-antimatter asymmetries in neutrinos and resolving the ordering of the neutrino mass states.

  6. Accelerator system and method of accelerating particles

    NASA Technical Reports Server (NTRS)

    Wirz, Richard E. (Inventor)

    2010-01-01

    An accelerator system and method that utilize dust as the primary mass flux for generating thrust are provided. The accelerator system can include an accelerator capable of operating in a self-neutralizing mode and having a discharge chamber and at least one ionizer capable of charging dust particles. The system can also include a dust particle feeder that is capable of introducing the dust particles into the accelerator. By applying a pulsed positive and negative charge voltage to the accelerator, the charged dust particles can be accelerated thereby generating thrust and neutralizing the accelerator system.

  7. The HMMER Web Server for Protein Sequence Similarity Search.

    PubMed

    Prakash, Ananth; Jeffryes, Matt; Bateman, Alex; Finn, Robert D

    2017-12-08

    Protein sequence similarity search is one of the most commonly used bioinformatics methods for identifying evolutionarily related proteins. In general, sequences that are evolutionarily related share some degree of similarity, and sequence-search algorithms use this principle to identify homologs. The requirement for a fast and sensitive sequence search method led to the development of the HMMER software, which in the latest version (v3.1) uses a combination of sophisticated acceleration heuristics and mathematical and computational optimizations to enable the use of profile hidden Markov models (HMMs) for sequence analysis. The HMMER Web server provides a common platform by linking the HMMER algorithms to databases, thereby enabling the search for homologs, as well as providing sequence and functional annotation by linking external databases. This unit describes three basic protocols and two alternate protocols that explain how to use the HMMER Web server using various input formats and user defined parameters. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

  8. Actin assembly factors regulate the gelation kinetics and architecture of F-actin networks.

    PubMed

    Falzone, Tobias T; Oakes, Patrick W; Sees, Jennifer; Kovar, David R; Gardel, Margaret L

    2013-04-16

    Dynamic regulation of the actin cytoskeleton is required for diverse cellular processes. Proteins regulating the assembly kinetics of the cytoskeletal biopolymer F-actin are known to impact the architecture of actin cytoskeletal networks in vivo, but the underlying mechanisms are not well understood. Here, we demonstrate that changes to actin assembly kinetics with physiologically relevant proteins profilin and formin (mDia1 and Cdc12) have dramatic consequences on the architecture and gelation kinetics of otherwise biochemically identical cross-linked F-actin networks. Reduced F-actin nucleation rates promote the formation of a sparse network of thick bundles, whereas increased nucleation rates result in a denser network of thinner bundles. Changes to F-actin elongation rates also have marked consequences. At low elongation rates, gelation ceases and a solution of rigid bundles is formed. By contrast, rapid filament elongation accelerates dynamic arrest and promotes gelation with minimal F-actin density. These results are consistent with a recently developed model of how kinetic constraints regulate network architecture and underscore how molecular control of polymer assembly is exploited to modulate cytoskeletal architecture and material properties. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  9. Predicting the dissolution kinetics of silicate glasses using machine learning

    NASA Astrophysics Data System (ADS)

    Anoop Krishnan, N. M.; Mangalathu, Sujith; Smedskjaer, Morten M.; Tandia, Adama; Burton, Henry; Bauchy, Mathieu

    2018-05-01

    Predicting the dissolution rates of silicate glasses in aqueous conditions is a complex task as the underlying mechanism(s) remain poorly understood and the dissolution kinetics can depend on a large number of intrinsic and extrinsic factors. Here, we assess the potential of data-driven models based on machine learning to predict the dissolution rates of various aluminosilicate glasses exposed to a wide range of solution pH values, from acidic to caustic conditions. Four classes of machine learning methods are investigated, namely, linear regression, support vector machine regression, random forest, and artificial neural network. We observe that, although linear methods all fail to describe the dissolution kinetics, the artificial neural network approach offers excellent predictions, thanks to its inherent ability to handle non-linear data. Overall, we suggest that a more extensive use of machine learning approaches could significantly accelerate the design of novel glasses with tailored properties.

  10. Kinetic models in industrial biotechnology - Improving cell factory performance.

    PubMed

    Almquist, Joachim; Cvijovic, Marija; Hatzimanikatis, Vassily; Nielsen, Jens; Jirstrand, Mats

    2014-07-01

    An increasing number of industrial bioprocesses capitalize on living cells by using them as cell factories that convert sugars into chemicals. These processes range from the production of bulk chemicals in yeasts and bacteria to the synthesis of therapeutic proteins in mammalian cell lines. One of the tools in the continuous search for improved performance of such production systems is the development and application of mathematical models. To be of value for industrial biotechnology, mathematical models should be able to assist in the rational design of cell factory properties or in the production processes in which they are utilized. Kinetic models are particularly suitable towards this end because they are capable of representing the complex biochemistry of cells in a more complete way compared to most other types of models. They can, at least in principle, be used to in detail understand, predict, and evaluate the effects of adding, removing, or modifying molecular components of a cell factory and for supporting the design of the bioreactor or fermentation process. However, several challenges still remain before kinetic modeling will reach the degree of maturity required for routine application in industry. Here we review the current status of kinetic cell factory modeling. Emphasis is on modeling methodology concepts, including model network structure, kinetic rate expressions, parameter estimation, optimization methods, identifiability analysis, model reduction, and model validation, but several applications of kinetic models for the improvement of cell factories are also discussed. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  11. Update of KDBI: Kinetic Data of Bio-molecular Interaction database

    PubMed Central

    Kumar, Pankaj; Han, B. C.; Shi, Z.; Jia, J.; Wang, Y. P.; Zhang, Y. T.; Liang, L.; Liu, Q. F.; Ji, Z. L.; Chen, Y. Z.

    2009-01-01

    Knowledge of the kinetics of biomolecular interactions is important for facilitating the study of cellular processes and underlying molecular events, and is essential for quantitative study and simulation of biological systems. Kinetic Data of Bio-molecular Interaction database (KDBI) has been developed to provide information about experimentally determined kinetic data of protein–protein, protein–nucleic acid, protein–ligand, nucleic acid–ligand binding or reaction events described in the literature. To accommodate increasing demand for studying and simulating biological systems, numerous improvements and updates have been made to KDBI, including new ways to access data by pathway and molecule names, data file in System Biology Markup Language format, more efficient search engine, access to published parameter sets of simulation models of 63 pathways, and 2.3-fold increase of data (19 263 entries of 10 532 distinctive biomolecular binding and 11 954 interaction events, involving 2635 proteins/protein complexes, 847 nucleic acids, 1603 small molecules and 45 multi-step processes). KDBI is publically available at http://bidd.nus.edu.sg/group/kdbi/kdbi.asp. PMID:18971255

  12. Proton acceleration by irradiation of isolated spheres with an intense laser pulse

    DOE PAGES

    Ostermayr, Tobias M.; Haffa, D.; Hilz, P.; ...

    2016-09-26

    We report on experiments irradiating isolated plastic spheres with a peak laser intensity of 2–3 × 10 20 W cm –2. With a laser focal spot size of 10 μm full width half maximum (FWHM) the sphere diameter was varied between 520 nm and 19.3 μm. Maximum proton energies of ~ 25 MeV are achieved for targets matching the focal spot size of 10 μm in diameter or being slightly smaller. For smaller spheres the kinetic energy distributions of protons become nonmonotonic, indicating a change in the accelerating mechanism from ambipolar expansion towards a regime dominated by effects caused bymore » Coulomb repulsion of ions. The energy conversion efficiency from laser energy to proton kinetic energy is optimized when the target diameter matches the laser focal spot size with efficiencies reaching the percent level. The change of proton acceleration efficiency with target size can be attributed to the reduced cross-sectional overlap of subfocus targets with the laser. Reported experimental observations are in line with 3D3V particle in cell simulations. In conclusion, they make use of well-defined targets and point out pathways for future applications and experiments.« less

  13. Proton acceleration by irradiation of isolated spheres with an intense laser pulse

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ostermayr, Tobias M.; Haffa, D.; Hilz, P.

    We report on experiments irradiating isolated plastic spheres with a peak laser intensity of 2–3 × 10 20 W cm –2. With a laser focal spot size of 10 μm full width half maximum (FWHM) the sphere diameter was varied between 520 nm and 19.3 μm. Maximum proton energies of ~ 25 MeV are achieved for targets matching the focal spot size of 10 μm in diameter or being slightly smaller. For smaller spheres the kinetic energy distributions of protons become nonmonotonic, indicating a change in the accelerating mechanism from ambipolar expansion towards a regime dominated by effects caused bymore » Coulomb repulsion of ions. The energy conversion efficiency from laser energy to proton kinetic energy is optimized when the target diameter matches the laser focal spot size with efficiencies reaching the percent level. The change of proton acceleration efficiency with target size can be attributed to the reduced cross-sectional overlap of subfocus targets with the laser. Reported experimental observations are in line with 3D3V particle in cell simulations. In conclusion, they make use of well-defined targets and point out pathways for future applications and experiments.« less

  14. Adaptive and accelerated tracking-learning-detection

    NASA Astrophysics Data System (ADS)

    Guo, Pengyu; Li, Xin; Ding, Shaowen; Tian, Zunhua; Zhang, Xiaohu

    2013-08-01

    An improved online long-term visual tracking algorithm, named adaptive and accelerated TLD (AA-TLD) based on Tracking-Learning-Detection (TLD) which is a novel tracking framework has been introduced in this paper. The improvement focuses on two aspects, one is adaption, which makes the algorithm not dependent on the pre-defined scanning grids by online generating scale space, and the other is efficiency, which uses not only algorithm-level acceleration like scale prediction that employs auto-regression and moving average (ARMA) model to learn the object motion to lessen the detector's searching range and the fixed number of positive and negative samples that ensures a constant retrieving time, but also CPU and GPU parallel technology to achieve hardware acceleration. In addition, in order to obtain a better effect, some TLD's details are redesigned, which uses a weight including both normalized correlation coefficient and scale size to integrate results, and adjusts distance metric thresholds online. A contrastive experiment on success rate, center location error and execution time, is carried out to show a performance and efficiency upgrade over state-of-the-art TLD with partial TLD datasets and Shenzhou IX return capsule image sequences. The algorithm can be used in the field of video surveillance to meet the need of real-time video tracking.

  15. Accelerating execution of the integrated TIGER series Monte Carlo radiation transport codes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Smith, L.M.; Hochstedler, R.D.

    1997-02-01

    Execution of the integrated TIGER series (ITS) of coupled electron/photon Monte Carlo radiation transport codes has been accelerated by modifying the FORTRAN source code for more efficient computation. Each member code of ITS was benchmarked and profiled with a specific test case that directed the acceleration effort toward the most computationally intensive subroutines. Techniques for accelerating these subroutines included replacing linear search algorithms with binary versions, replacing the pseudo-random number generator, reducing program memory allocation, and proofing the input files for geometrical redundancies. All techniques produced identical or statistically similar results to the original code. Final benchmark timing of themore » accelerated code resulted in speed-up factors of 2.00 for TIGER (the one-dimensional slab geometry code), 1.74 for CYLTRAN (the two-dimensional cylindrical geometry code), and 1.90 for ACCEPT (the arbitrary three-dimensional geometry code).« less

  16. Multiensemble Markov models of molecular thermodynamics and kinetics.

    PubMed

    Wu, Hao; Paul, Fabian; Wehmeyer, Christoph; Noé, Frank

    2016-06-07

    We introduce the general transition-based reweighting analysis method (TRAM), a statistically optimal approach to integrate both unbiased and biased molecular dynamics simulations, such as umbrella sampling or replica exchange. TRAM estimates a multiensemble Markov model (MEMM) with full thermodynamic and kinetic information at all ensembles. The approach combines the benefits of Markov state models-clustering of high-dimensional spaces and modeling of complex many-state systems-with those of the multistate Bennett acceptance ratio of exploiting biased or high-temperature ensembles to accelerate rare-event sampling. TRAM does not depend on any rate model in addition to the widely used Markov state model approximation, but uses only fundamental relations such as detailed balance and binless reweighting of configurations between ensembles. Previous methods, including the multistate Bennett acceptance ratio, discrete TRAM, and Markov state models are special cases and can be derived from the TRAM equations. TRAM is demonstrated by efficiently computing MEMMs in cases where other estimators break down, including the full thermodynamics and rare-event kinetics from high-dimensional simulation data of an all-atom protein-ligand binding model.

  17. Multiensemble Markov models of molecular thermodynamics and kinetics

    PubMed Central

    Wu, Hao; Paul, Fabian; Noé, Frank

    2016-01-01

    We introduce the general transition-based reweighting analysis method (TRAM), a statistically optimal approach to integrate both unbiased and biased molecular dynamics simulations, such as umbrella sampling or replica exchange. TRAM estimates a multiensemble Markov model (MEMM) with full thermodynamic and kinetic information at all ensembles. The approach combines the benefits of Markov state models—clustering of high-dimensional spaces and modeling of complex many-state systems—with those of the multistate Bennett acceptance ratio of exploiting biased or high-temperature ensembles to accelerate rare-event sampling. TRAM does not depend on any rate model in addition to the widely used Markov state model approximation, but uses only fundamental relations such as detailed balance and binless reweighting of configurations between ensembles. Previous methods, including the multistate Bennett acceptance ratio, discrete TRAM, and Markov state models are special cases and can be derived from the TRAM equations. TRAM is demonstrated by efficiently computing MEMMs in cases where other estimators break down, including the full thermodynamics and rare-event kinetics from high-dimensional simulation data of an all-atom protein–ligand binding model. PMID:27226302

  18. Observational and Theoretical Challenges to Wave or Turbulence Accelerations of the Fast Solar Wind

    NASA Technical Reports Server (NTRS)

    Roberts, D. Aaron

    2008-01-01

    We use both observations and theoretical considerations to show that hydromagnetic waves or turbulence cannot produce the acceleration of the fast solar wind and the related heating of the open solar corona. Waves do exist as shown by Hinode and other observations, and can play a role in the differential heating and acceleration of minor ions but their amplitudes are not sufficient to power the wind, as demonstrated by extrapolation of magnetic spectra from Helios and Ulysses observations. Dissipation mechanisms invoked to circumvent this conclusion cannot be effective for a variety of reasons. In particular, turbulence does not play a strong role in the corona as shown by both eclipse observations of coronal striations and theoretical considerations of line-tying to a nonturbulent photosphere, nonlocality of interactions, and the nature of kinetic dissipation. In the absence of wave heating and acceleration, the chromosphere and transition region become the natural source of open coronal energization. We suggest a variant of the velocity filtration approach in which the emergence and complex churning of the magnetic flux in the chromosphere and transition region continuously and ubiquitously produces the nonthermal distributions required. These particles are then released by magnetic carpet reconnection at a wide range of scales and produce the wind as described in kinetic approaches. Since the carpet reconnection is not the main source of the energization of the plasma, there is no expectation of an observable release of energy in nanoflares.

  19. EIDOSCOPE: particle acceleration at plasma boundaries

    NASA Astrophysics Data System (ADS)

    Vaivads, A.; Andersson, G.; Bale, S. D.; Cully, C. M.; De Keyser, J.; Fujimoto, M.; Grahn, S.; Haaland, S.; Ji, H.; Khotyaintsev, Yu. V.; Lazarian, A.; Lavraud, B.; Mann, I. R.; Nakamura, R.; Nakamura, T. K. M.; Narita, Y.; Retinò, A.; Sahraoui, F.; Schekochihin, A.; Schwartz, S. J.; Shinohara, I.; Sorriso-Valvo, L.

    2012-04-01

    We describe the mission concept of how ESA can make a major contribution to the Japanese Canadian multi-spacecraft mission SCOPE by adding one cost-effective spacecraft EIDO (Electron and Ion Dynamics Observatory), which has a comprehensive and optimized plasma payload to address the physics of particle acceleration. The combined mission EIDOSCOPE will distinguish amongst and quantify the governing processes of particle acceleration at several important plasma boundaries and their associated boundary layers: collisionless shocks, plasma jet fronts, thin current sheets and turbulent boundary layers. Particle acceleration and associated cross-scale coupling is one of the key outstanding topics to be addressed in the Plasma Universe. The very important science questions that only the combined EIDOSCOPE mission will be able to tackle are: 1) Quantitatively, what are the processes and efficiencies with which both electrons and ions are selectively injected and subsequently accelerated by collisionless shocks? 2) How does small-scale electron and ion acceleration at jet fronts due to kinetic processes couple simultaneously to large scale acceleration due to fluid (MHD) mechanisms? 3) How does multi-scale coupling govern acceleration mechanisms at electron, ion and fluid scales in thin current sheets? 4) How do particle acceleration processes inside turbulent boundary layers depend on turbulence properties at ion/electron scales? EIDO particle instruments are capable of resolving full 3D particle distribution functions in both thermal and suprathermal regimes and at high enough temporal resolution to resolve the relevant scales even in very dynamic plasma processes. The EIDO spin axis is designed to be sun-pointing, allowing EIDO to carry out the most sensitive electric field measurements ever accomplished in the outer magnetosphere. Combined with a nearby SCOPE Far Daughter satellite, EIDO will form a second pair (in addition to SCOPE Mother-Near Daughter) of closely

  20. Kinematic and kinetic comparisons between American and Korean professional baseball pitchers.

    PubMed

    Escamilla, Rafael; Fleisig, Glen; Barrentine, Steven; Andrews, James; Moorman, Claude

    2002-07-01

    The purpose of this study was to quantify and compare kinematic, temporal, and kinetic characteristics of American and Korean professional pitchers in order to investigate differences in pitching mechanics, performance, and injury risks among two different cultures and populations of baseball pitchers. Eleven American and eight Korean healthy professional baseball pitchers threw multiple fastball pitches off an indoor throwing mound positioned at regulation distance from home plate. A Motion Analysis three-dimensional automatic digitizing system was used to collect 200 Hz video data from four electronically synchronized cameras. Twenty kinematic, six temporal, and 11 kinetic variables were analyzed at lead foot contact, during the arm cocking and arm acceleration phases, at ball release, and during the arm deceleration phase. A radar gun was used to quantify ball velocity. At lead foot contact, the American pitchers had significantly greater horizontal abduction of the throwing shoulder, while Korean pitchers exhibited significantly greater abduction and external rotation of the throwing shoulder. During arm cocking, the American pitchers displayed significantly greater maximum shoulder external rotation and maximum pelvis angular velocity. At the instant of ball release, the American pitchers had significantly greater forward trunk tilt and ball velocity and significantly less knee flexion, which help explain why the American pitchers had 10% greater ball velocity compared to the Korean pitchers. The American pitchers had significantly greater maximum shoulder internal rotation torque and maximum elbow varus torque during arm cocking, significantly greater elbow flexion torque during arm acceleration, and significantly greater shoulder and elbow proximal forces during arm deceleration. While greater shoulder and elbow forces and torques generated in the American pitchers helped generate greater ball velocity for the American group, these greater kinetics may

  1. Asymptotic domination of cold relativistic MHD winds by kinetic energy flux

    NASA Technical Reports Server (NTRS)

    Begelman, Mitchell C.; Li, Zhi-Yun

    1994-01-01

    We study the conditions which lead to the conversion of most Poynting flux into kinetic energy flux in cold, relativistic hydromagnetic winds. It is shown that plasma acceleration along a precisely radial flow is extremely inefficient due to the near cancellation of the toroidal magnetic pressure and tension forces. However, if the flux tubes in a flow diverge even slightly faster than radially, the fast magnetosonic point moves inward from infinity to a few times the light cylinder radius. Once the flow becomes supermagnetosonic, further divergence of the flux tubes beyond the fast point can accelerate the flow via the 'magnetic nozzle' effect, thereby further converting Poynting flux to kinetic energy flux. We show that the Grad-Shafranov equation admits a generic family of kinetic energy-dominated asymptotic wind solutions with finite total magnetic flux. The Poynting flux in these solutions vanishes logarithmically with distance. The way in which the flux surfaces are nested within the flow depends only on the ratio of angular velocity to poliodal 4-velocity as a function of magnetic flux. Radial variations in flow structure can be expressed in terms of a pressure boundary condition on the outermost flux surface, provided that no external toriodal field surrounds the flow. For a special case, we show explicitly how the flux surfaces merge gradually to their asymptotes. For flows confined by an external medium of pressure decreasing to zero at infinity we show that, depending on how fast the ambient pressure declines, the final flow state could be either a collimated jet or a wind that fills the entire space. We discuss the astrophysical implications of our results for jets from active galactic nuclei and for free pulsar winds such as that believed to power the Crab Nebula.

  2. Search for Hidden Particles: a new experiment proposal

    NASA Astrophysics Data System (ADS)

    De Lellis, G.

    2015-08-01

    Searches for new physics with accelerators are being performed at the LHC, looking for high massive particles coupled to matter with ordinary strength. We propose a new experiment meant to search for very weakly coupled particles in the few GeV mass domain. The existence of such particles, foreseen in different models beyond the Standard Model, is largely unexplored from the experimental point of view. A beam dump facility, built at CERN in the north area, using 400 GeV protons is a copious factory of charmed hadrons and it could be used to probe the existence of such particles. The beam dump is also an ideal source of tau neutrinos, the less known particle in the Standard Model. In particular, tau anti-neutrinos have not been observed so far. We therefore propose an experiment to search for hidden particles and study tau neutrino physics at the same time.

  3. Searches for Periodic Neutrino Emission from Binary Systems with 22 and 40 Strings of IceCube

    NASA Technical Reports Server (NTRS)

    Abassi, R.; Abdou, Y.; Abu-Zayyad, T.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Allen, M. M.; Altmann, D.; Andeen, K.; hide

    2011-01-01

    Recent observations of GeV /TeV photon emission from several X-ray binaries have sparked a renewed interest in these objects as galactic particle accelerators. In spite of the available multi-wavelength data, their acceleration mechanisms are not determined, and the nature of the accelerated particles (hadrons or leptons) is unknown. While much evidence favors leptonic emission, it is very likely that a hadronic component is also accelerated in the jets of these binary systems. The observation of neutrino emission would be clear evidence for the presence of a hadronic component in the outflow of these sources. In this paper we look for periodic neutrino emission from binary systems. Such modulation, observed in the photon flux, would be caused by the geometry of these systems. The results of two searches are presented that differ in the treatment of the spectral shape and phase of the emission. The 'generic' search allows parameters to vary freely and best fit values, in a 'model-dependent' search, predictions are used to constrain these parameters. We use the IceCube data taken from May 31, 2007 to April 5, 2008 with its 22-string configuration, and from April 5, 2008 and May 20, 2009 with its 40-string configuration. For the generic search and the 40 string sample, we find that the most significant source in the catalog of 7 binary stars is Cygnus X-3 with a 1.8% probability after trials (2.10" sigma one-sided) of being produced by statistical fluctuations of the background. The model-dependent method tested a range of system geometries - the inclination and the massive star's disk size - for LS I+61 deg 303, no significant excess was found.

  4. A Fast, Minimalist Search Tool for Remote Sensing Data

    NASA Astrophysics Data System (ADS)

    Lynnes, C. S.; Macharrie, P. G.; Elkins, M.; Joshi, T.; Fenichel, L. H.

    2005-12-01

    We present a tool that emphasizes speed and simplicity in searching remotely sensed Earth Science data. The tool, nicknamed "Mirador" (Spanish for a scenic overlook), provides only four freetext search form fields, for Keywords, Location, Data Start and Data Stop. This contrasts with many current Earth Science search tools that offer highly structured interfaces in order to ensure precise, non-zero results. The disadvantages of the structured approach lie in its complexity and resultant learning curve, as well as the time it takes to formulate and execute the search, thus discouraging iterative discovery. On the other hand, the success of the basic Google search interface shows that many users are willing to forgo high search precision if the search process is fast enough to enable rapid iteration. Therefore, we employ several methods to increase the speed of search formulation and execution. Search formulation is expedited by the minimalist search form, with only one required field. Also, a gazetteer enables the use of geographic terms as shorthand for latitude/longitude coordinates. The search execution is accelerated by initially presenting dataset results (returned from a Google Mini appliance) with an estimated number of "hits" for each dataset based on the user's space-time constraints. The more costly file-level search is executed against a PostGres database only when the user "drills down", and then covering only the fraction of the time period needed to return the next page of results. The simplicity of the search form makes the tool easy to learn and use, and the speed of the searches enables an iterative form of data discovery.

  5. Cosmology with nonminimal kinetic coupling and a Higgs-like potential

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Matsumoto, Jiro; Sushkov, Sergey V., E-mail: jmatsumoto@kpfu.ru, E-mail: sergey_sushkov@mail.ru

    2015-11-01

    We consider cosmological dynamics in the theory of gravity with the scalar field possessing the nonminimal kinetic coupling to curvature given as κG{sup μν}φ{sub ,μ}φ{sub ,ν}, and the Higgs-like potential . Using the dynamical system method, we analyze stationary points, their stability, and all possible asymptotical regimes of the model under consideration. We show that the Higgs field with the kinetic coupling provides an existence of accelerated regimes of the Universe evolution. There are three possible cosmological scenarios with acceleration: (i) The late-time de Sitter epoch when the Hubble parameter tends to the constant value, as t → ∞, while the scalarmore » field tends to zero, 0φ(t)→ , so that the Higgs potential reaches its local maximum . (ii) The Big Rip when H(t)∼(t{sub *}−t){sup −1} → ∞ and φ(t)∼(t{sub *}−t){sup −2} → ∞ as t →  t{sub *}. (iii) The Little Rip when H(t)∼ t{sup 1/2} → ∞ and φ(t)∼ t{sup 1/4} → ∞ as t → ∞. Also, we derive modified slow-roll conditions for the Higgs field and demonstrate that they lead to the Little Rip scenario.« less

  6. Accelerated carbonation using municipal solid waste incinerator bottom ash and cold-rolling wastewater: Performance evaluation and reaction kinetics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chang, E-E; Pan, Shu-Yuan; Yang, Liuhanzi

    2015-09-15

    Highlights: • Carbonation was performed using CO{sub 2}, wastewater and bottom ash in a slurry reactor. • A maximum capture capacity of 102 g CO{sub 2} per kg BA was achieved at mild conditions. • A maximum carbonation conversion of MSWI-BA was predicted to be 95% by RSM. • The CO{sub 2} emission from Bali incinerator could be expected to reduce by 6480 ton/y. • The process energy consumption per ton CO{sub 2} captured was estimated to be 180 kW h. - Abstract: Accelerated carbonation of alkaline wastes including municipal solid waste incinerator bottom ash (MSWI-BA) and the cold-rolling wastewatermore » (CRW) was investigated for carbon dioxide (CO{sub 2}) fixation under different operating conditions, i.e., reaction time, CO{sub 2} concentration, liquid-to-solid ratio, particle size, and CO{sub 2} flow rate. The MSWI-BA before and after carbonation process were analyzed by the thermogravimetry and differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The MSWI-BA exhibits a high carbonation conversion of 90.7%, corresponding to a CO{sub 2} fixation capacity of 102 g per kg of ash. Meanwhile, the carbonation kinetics was evaluated by the shrinking core model. In addition, the effect of different operating parameters on carbonation conversion of MSWI-BA was statistically evaluated by response surface methodology (RSM) using experimental data to predict the maximum carbonation conversion. Furthermore, the amount of CO{sub 2} reduction and energy consumption for operating the proposed process in refuse incinerator were estimated. Capsule abstract: CO{sub 2} fixation process by alkaline wastes including bottom ash and cold-rolling wastewater was developed, which should be a viable method due to high conversion.« less

  7. Resampling to accelerate cross-correlation searches for continuous gravitational waves from binary systems

    NASA Astrophysics Data System (ADS)

    Meadors, Grant David; Krishnan, Badri; Papa, Maria Alessandra; Whelan, John T.; Zhang, Yuanhao

    2018-02-01

    Continuous-wave (CW) gravitational waves (GWs) call for computationally-intensive methods. Low signal-to-noise ratio signals need templated searches with long coherent integration times and thus fine parameter-space resolution. Longer integration increases sensitivity. Low-mass x-ray binaries (LMXBs) such as Scorpius X-1 (Sco X-1) may emit accretion-driven CWs at strains reachable by current ground-based observatories. Binary orbital parameters induce phase modulation. This paper describes how resampling corrects binary and detector motion, yielding source-frame time series used for cross-correlation. Compared to the previous, detector-frame, templated cross-correlation method, used for Sco X-1 on data from the first Advanced LIGO observing run (O1), resampling is about 20 × faster in the costliest, most-sensitive frequency bands. Speed-up factors depend on integration time and search setup. The speed could be reinvested into longer integration with a forecast sensitivity gain, 20 to 125 Hz median, of approximately 51%, or from 20 to 250 Hz, 11%, given the same per-band cost and setup. This paper's timing model enables future setup optimization. Resampling scales well with longer integration, and at 10 × unoptimized cost could reach respectively 2.83 × and 2.75 × median sensitivities, limited by spin-wandering. Then an O1 search could yield a marginalized-polarization upper limit reaching torque-balance at 100 Hz. Frequencies from 40 to 140 Hz might be probed in equal observing time with 2 × improved detectors.

  8. Accelerating oxygen reduction on Pt monolayer via substrate compression

    NASA Astrophysics Data System (ADS)

    Zhang, Xilin; Chen, Yue; Yang, Zongxian; Lu, Zhansheng

    2017-11-01

    Many methods have been proposed to accelerate the oxygen reduction and save the dosage of Pt. Here, we report a promising way in fulfilling these purposes by applying substrate strain on the supported Pt monolayer. The compressive strain would modify the geometric and electronic structures of tungsten carbide (WC) substrate, changing the interaction nature between substrate and Pt monolayer and resulting in a downward shift of the d-band center of surface Pt atoms. The activity of Pt monolayer on the compressed WC is further evaluated from the kinetics of the dissociation and protonation of O2. The dissociation barrier of O2 is increased and the hydrogenation barrier of O atom is decreased, indicating that the recovery of the catalytically active sites is accelerated and the deactivation by oxygen poison is alleviated. The present study provides an effective way in tuning the activity of Pt-based catalysts by applying the substrate strain.

  9. Search for neutrino emission from microquasars with the ANTARES telescope

    NASA Astrophysics Data System (ADS)

    Galatà, S.

    2012-12-01

    Neutrino telescopes are nowadays exploring a new window of observation on the high energy universe and may shed light on the longstanding problem regarding the origin of cosmic rays. The ANTARES neutrino telescope is located underwater 40 km offshore from the Southern coast of France, on a plateau at 2475 m depth. Since 2007 it observes the high energy (>100 GeV) neutrino sky looking for cosmic neutrino sources. Among the candidate neutrino emitters are microquasars, i.e. galactic X-ray binaries exhibiting relativistic jets, which may accelerate hadrons thus producing neutrinos, under certain conditions. These sources are also variable in time and undergo X-ray or gamma ray outburst that can be related to the acceleration of relativistic particles witnessed by their radio emission. These events can provide a trigger to the neutrino search, with the advantage of drastically reducing the atmospheric neutrino background. A search for neutrino emission from microquasar during outbursts is presented based on the data collected by ANTARES between 2007 and 2010. Upper limits are shown and compared with the predictions.

  10. Accelerated behavioural development changes fine-scale search behaviour and spatial memory in honey bees (Apis mellifera L.).

    PubMed

    Ushitani, Tomokazu; Perry, Clint J; Cheng, Ken; Barron, Andrew B

    2016-02-01

    Normally, worker honey bees (Apis mellifera) begin foraging when more than 2 weeks old as adults, but if individual bees or the colony is stressed, bees often begin foraging precociously. Here, we examined whether bees that accelerated their behavioural development to begin foraging precociously differed from normal-aged foragers in cognitive performance. We used a social manipulation to generate precocious foragers from small experimental colonies and tested their performance in a free-flight visual reversal learning task, and a test of spatial memory. To assess spatial memory, bees were trained to learn the location of a small sucrose feeder within an array of three landmarks. In tests, the feeder and one landmark were removed and the search behaviour of the bees was recorded. Performance of precocious and normal-aged foragers did not differ in a visual reversal learning task, but the two groups showed a clear difference in spatial memory. Flight behaviour suggested normal-aged foragers were better able to infer the position of the removed landmark and feeder relative to the remaining landmarks than precocious foragers. Previous studies have documented the cognitive decline of old foragers, but this is the first suggestion of a cognitive deficit in young foragers. These data imply that worker honey bees continue their cognitive development during the adult stage. These findings may also help to explain why precocious foragers perform quite poorly as foragers and have a higher than normal loss rate. © 2016. Published by The Company of Biologists Ltd.

  11. Experiments assigned to determine the acceleration of 8000kN shear laboratory model elements

    NASA Astrophysics Data System (ADS)

    Budiul Berghian, A.; Vasiu, T.; Abrudean, C.

    2017-01-01

    In this paper presents an experimental kinetics study by measuring accelerations using a bi-axial accelerometer constructed in the basis of a miniature integrated circuit, included in the class of micro-electrical and mechanical systems - MMA6261Q on the experimental installation reduced to the 1:5 dividing rule by comparison with the shear existent in exploitation, conceived and projected at the Faculty of Engineering in Hunedoara.

  12. Searching for light dark matter with the SLAC millicharge experiment.

    PubMed

    Diamond, M; Schuster, P

    2013-11-27

    New sub-GeV gauge forces ("dark photons") that kinetically mix with the photon provide a promising scenario for MeV-GeV dark matter and are the subject of a program of searches at fixed-target and collider facilities around the world. In such models, dark photons produced in collisions may decay invisibly into dark-matter states, thereby evading current searches. We reexamine results of the SLAC mQ electron beam dump experiment designed to search for millicharged particles and find that it was strongly sensitive to any secondary beam of dark matter produced by electron-nucleus collisions in the target. The constraints are competitive for dark photon masses in the ~1-30 MeV range, covering part of the parameter space that can reconcile the apparent (g-2)(μ) anomaly. Simple adjustments to the original SLAC search for millicharges may extend sensitivity to cover a sizable portion of the remaining (g-2)(μ) anomaly-motivated region. The mQ sensitivity is therefore complementary to ongoing searches for visible decays of dark photons. Compared to existing direct-detection searches, mQ sensitivity to electron-dark-matter scattering cross sections is more than an order of magnitude better for a significant range of masses and couplings in simple models.

  13. Dynamics of particles accelerated by head-on collisions of two magnetized plasma shocks

    NASA Astrophysics Data System (ADS)

    Takeuchi, Satoshi

    2018-02-01

    A kinetic model of the head-on collision of two magnetized plasma shocks is analyzed theoretically and in numerical calculations. When two plasmas with anti-parallel magnetic fields collide, they generate magnetic reconnection and form a motional electric field at the front of the collision region. This field accelerates the particles sandwiched between both shock fronts to extremely high energy. As they accelerate, the particles are bent by the transverse magnetic field crossing the magnetic neutral sheet, and their energy gains are reduced. In the numerical calculations, the dynamics of many test particles were modeled through the relativistic equations of motion. The attainable energy gain was obtained by multiplying three parameters: the propagation speed of the shock, the magnitude of the magnetic field, and the acceleration time of the test particle. This mechanism for generating high-energy particles is applicable over a wide range of spatial scales, from laboratory to interstellar plasmas.

  14. Parallelization of combinatorial search when solving knapsack optimization problem on computing systems based on multicore processors

    NASA Astrophysics Data System (ADS)

    Rahman, P. A.

    2018-05-01

    This scientific paper deals with the model of the knapsack optimization problem and method of its solving based on directed combinatorial search in the boolean space. The offered by the author specialized mathematical model of decomposition of the search-zone to the separate search-spheres and the algorithm of distribution of the search-spheres to the different cores of the multi-core processor are also discussed. The paper also provides an example of decomposition of the search-zone to the several search-spheres and distribution of the search-spheres to the different cores of the quad-core processor. Finally, an offered by the author formula for estimation of the theoretical maximum of the computational acceleration, which can be achieved due to the parallelization of the search-zone to the search-spheres on the unlimited number of the processor cores, is also given.

  15. Microscopy as a statistical, Rényi-Ulam, half-lie game: a new heuristic search strategy to accelerate imaging.

    PubMed

    Drumm, Daniel W; Greentree, Andrew D

    2017-11-07

    Finding a fluorescent target in a biological environment is a common and pressing microscopy problem. This task is formally analogous to the canonical search problem. In ideal (noise-free, truthful) search problems, the well-known binary search is optimal. The case of half-lies, where one of two responses to a search query may be deceptive, introduces a richer, Rényi-Ulam problem and is particularly relevant to practical microscopy. We analyse microscopy in the contexts of Rényi-Ulam games and half-lies, developing a new family of heuristics. We show the cost of insisting on verification by positive result in search algorithms; for the zero-half-lie case bisectioning with verification incurs a 50% penalty in the average number of queries required. The optimal partitioning of search spaces directly following verification in the presence of random half-lies is determined. Trisectioning with verification is shown to be the most efficient heuristic of the family in a majority of cases.

  16. Kinetic compensation effect in logistic distributed activation energy model for lignocellulosic biomass pyrolysis.

    PubMed

    Xu, Di; Chai, Meiyun; Dong, Zhujun; Rahman, Md Maksudur; Yu, Xi; Cai, Junmeng

    2018-06-04

    The kinetic compensation effect in the logistic distributed activation energy model (DAEM) for lignocellulosic biomass pyrolysis was investigated. The sum of square error (SSE) surface tool was used to analyze two theoretically simulated logistic DAEM processes for cellulose and xylan pyrolysis. The logistic DAEM coupled with the pattern search method for parameter estimation was used to analyze the experimental data of cellulose pyrolysis. The results showed that many parameter sets of the logistic DAEM could fit the data at different heating rates very well for both simulated and experimental processes, and a perfect linear relationship between the logarithm of the frequency factor and the mean value of the activation energy distribution was found. The parameters of the logistic DAEM can be estimated by coupling the optimization method and isoconversional kinetic methods. The results would be helpful for chemical kinetic analysis using DAEM. Copyright © 2018 Elsevier Ltd. All rights reserved.

  17. An electron fixed target experiment to search for a new vector boson A' decaying to e +e -

    DOE PAGES

    Rouven Essig; Schuster, Philip; Toro, Natalia; ...

    2011-02-02

    We describe an experiment to search for a new vector boson A' with weak coupling alpha' > 6 x 10 –8 α to electrons (α' = e 2/4π) in the mass range 65 MeV < m A' < 550 MeV. New vector bosons with such small couplings arise naturally from a small kinetic mixing of the "dark photon" A' with the photon -- one of the very few ways in which new forces can couple to the Standard Model -- and have received considerable attention as an explanation of various dark matter related anomalies. A' bosons are produced by radiationmore » off an electron beam, and could appear as narrow resonances with small production cross-section in the trident e +e - spectrum. We summarize the experimental approach described in a proposal submitted to Jefferson Laboratory's PAC35, PR-10-009. This experiment, the A' Experiment (APEX), uses the electron beam of the Continuous Electron Beam Accelerator Facility at Jefferson Laboratory (CEBAF) at energies of ~1-4 GeV incident on 0.5-10% radiation length Tungsten wire mesh targets, and measures the resulting e+e- pairs to search for the A' using the High Resolution Spectrometer and the septum magnet in Hall A. With a ~1 month run, APEX will achieve very good sensitivity because the statistics of e+e- pairs will be ~10,000 times larger in the explored mass range than any previous search for the A' boson. These statistics and the excellent mass resolution of the spectrometers allow sensitivity to α'/α one to three orders of magnitude below current limits, in a region of parameter space of great theoretical and phenomenological interest. Similar experiments could also be performed at other facilities, such as the Mainz Microtron.« less

  18. The Effect of Polymer Char on Nitridation Kinetics of Silicon

    NASA Technical Reports Server (NTRS)

    Chan, Rickmond C.; Bhatt, Ramakrishna T.

    1994-01-01

    Effects of polymer char on nitridation kinetics of attrition milled silicon powder have been investigated from 1200 to 1350 C. Results indicate that at and above 1250 C, the silicon compacts containing 3.5 wt percent polymer char were fully converted to Si3N4 after 24 hr exposure in nitrogen. In contrast, the silicon compacts without polymer char could not be fully converted to Si3N4 at 1350 C under similar exposure conditions. At 1250 and 1350 C, the silicon compacts with polymer char showed faster nitridation kinetics than those without the polymer char. As the polymer char content is increased, the amount of SiC in the nitrided material is also increased. By adding small amounts (approx. 2.5 wt percent) of NiO, the silicon compacts containing polymer char can be completely nitrided at 1200 C. The probable mechanism for the accelerated nitridation of silicon containing polymer char is discussed.

  19. Actin Assembly Factors Regulate the Gelation Kinetics and Architecture of F-actin Networks

    PubMed Central

    Falzone, Tobias T.; Oakes, Patrick W.; Sees, Jennifer; Kovar, David R.; Gardel, Margaret L.

    2013-01-01

    Dynamic regulation of the actin cytoskeleton is required for diverse cellular processes. Proteins regulating the assembly kinetics of the cytoskeletal biopolymer F-actin are known to impact the architecture of actin cytoskeletal networks in vivo, but the underlying mechanisms are not well understood. Here, we demonstrate that changes to actin assembly kinetics with physiologically relevant proteins profilin and formin (mDia1 and Cdc12) have dramatic consequences on the architecture and gelation kinetics of otherwise biochemically identical cross-linked F-actin networks. Reduced F-actin nucleation rates promote the formation of a sparse network of thick bundles, whereas increased nucleation rates result in a denser network of thinner bundles. Changes to F-actin elongation rates also have marked consequences. At low elongation rates, gelation ceases and a solution of rigid bundles is formed. By contrast, rapid filament elongation accelerates dynamic arrest and promotes gelation with minimal F-actin density. These results are consistent with a recently developed model of how kinetic constraints regulate network architecture and underscore how molecular control of polymer assembly is exploited to modulate cytoskeletal architecture and material properties. PMID:23601318

  20. Kinetic features revealed by top-hat electrostatic analysers: numerical simulations and instrument response results

    NASA Astrophysics Data System (ADS)

    De Marco, Rossana; Marcucci, Maria Federica; Brienza, Daniele; Bruno, Roberto; Consolini, Giuseppe; Perrone, Denise; Valentini, Franceso; Servidio, Sergio; Stabile, Sara; Pezzi, Oreste; Sorriso-Valvo, Luca; Lavraud, Benoit; De Keyser, Johan; Retinò, Alessandro; Fazakerley, Andrew; Wicks, Robert; Vaivads, Andris; Salatti, Mario; Veltri, Pierliugi

    2017-04-01

    Turbulence Heating ObserveR (THOR) is the first mission devoted to study energization, acceleration and heating of turbulent space plasmas, and designed to perform field and particle measurements at kinetic scales in different near-Earth regions and in the solar wind. Solar Orbiter (SolO), together with Solar Probe Plus, will provide the first comprehensive remote and in situ measurements which are critical to establish the fundamental physical links between the Sun's dynamic atmosphere and the turbulent solar wind. The fundamental process of turbulent dissipation is mediated by physical mechanism that occur at a variety of temporal and spatial scales, and most efficiently at the kinetics scales. Hybrid Vlasov-Maxwell simulations of solar-wind turbulence show that kinetic effects manifest as particle beams, production of temperature anisotropies and ring-like modulations, preferential heating of heavy ions. We use a numerical code able to reproduce the response of a typical electrostatic analyzer of top-hat type starting from velocity distribution functions (VDFs) generated by Hybrid Vlasov-Maxwell (HVM) numerical simulations. Here, we show how optimized particle measurements by top-hat analysers can capture the kinetic features injected by turbulence in the VDFs.

  1. C IV BROAD ABSORPTION LINE ACCELERATION IN SLOAN DIGITAL SKY SURVEY QUASARS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Grier, C. J.; Brandt, W. N.; Trump, J. R.

    2016-06-20

    We present results from the largest systematic investigation of broad absorption line (BAL) acceleration to date. We use spectra of 140 quasars from three Sloan Digital Sky Survey programs to search for global velocity offsets in BALs over timescales of ≈2.5–5.5 years in the quasar rest frame. We carefully select acceleration candidates by requiring monolithic velocity shifts over the entire BAL trough, avoiding BALs with velocity shifts that might be caused by profile variability. The C iv BALs of two quasars show velocity shifts consistent with the expected signatures of BAL acceleration, and the BAL of one quasar shows amore » velocity-shift signature of deceleration. In our two acceleration candidates, we see evidence that the magnitude of the acceleration is not constant over time; the magnitudes of the change in acceleration for both acceleration candidates are difficult to produce with a standard disk-wind model or via geometric projection effects. We measure upper limits to acceleration and deceleration for 76 additional BAL troughs and find that the majority of BALs are stable to within about 3% of their mean velocities. The lack of widespread acceleration/deceleration could indicate that the gas producing most BALs is located at large radii from the central black hole and/or is not currently strongly interacting with ambient material within the host galaxy along our line of sight.« less

  2. Towards the reliable calculation of residence time for off-lattice kinetic Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Alexander, Kathleen C.; Schuh, Christopher A.

    2016-08-01

    Kinetic Monte Carlo (KMC) methods have the potential to extend the accessible timescales of off-lattice atomistic simulations beyond the limits of molecular dynamics by making use of transition state theory and parallelization. However, it is a challenge to identify a complete catalog of events accessible to an off-lattice system in order to accurately calculate the residence time for KMC. Here we describe possible approaches to some of the key steps needed to address this problem. These include methods to compare and distinguish individual kinetic events, to deterministically search an energy landscape, and to define local atomic environments. When applied to the ground state  ∑5(2 1 0) grain boundary in copper, these methods achieve a converged residence time, accounting for the full set of kinetically relevant events for this off-lattice system, with calculable uncertainty.

  3. A measurement of hadron production cross sections for the simulation of accelerator neutrino beams and a search for muon-neutrino to electron-neutrino oscillations in the Δm 2 about equals 1-eV 2 region

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schmitz, David W.

    2008-01-01

    A measurement of hadron production cross-sections for the simulation of accelerator neutrino beams and a search for muon neutrino to electron neutrino oscillations in the Δm 2 ~ 1 eV 2} region. This dissertation presents measurements from two different high energy physics experiments with a very strong connection: the Hadron Production (HARP) experiment located at CERN in Geneva, Switzerland, and the Mini Booster Neutrino Experiment (Mini-BooNE) located at Fermilab in Batavia, Illinois.

  4. Current-driven plasma acceleration versus current-driven energy dissipation. I - Wave stability theory

    NASA Technical Reports Server (NTRS)

    Kelly, A. J.; Jahn, R. G.; Choueiri, E. Y.

    1990-01-01

    The dominant unstable electrostatic wave modes of an electromagnetically accelerated plasma are investigated. The study is the first part of a three-phase program aimed at characterizing the current-driven turbulent dissipation degrading the efficiency of Lorentz force plasma accelerators such as the MPD thruster. The analysis uses a kinetic theory that includes magnetic and thermal effects as well as those of an electron current transverse to the magnetic field and collisions, thus combining all the features of previous models. Analytical and numerical solutions allow a detailed description of threshold criteria, finite growth behavior, destabilization mechanisms and maximized-growth characteristics of the dominant unstable modes. The lower hybrid current-driven instability is implicated as dominant and was found to preserve its character in the collisional plasma regime.

  5. The effect of cosmic-ray acceleration on supernova blast wave dynamics

    NASA Astrophysics Data System (ADS)

    Pais, M.; Pfrommer, C.; Ehlert, K.; Pakmor, R.

    2018-05-01

    Non-relativistic shocks accelerate ions to highly relativistic energies provided that the orientation of the magnetic field is closely aligned with the shock normal (quasi-parallel shock configuration). In contrast, quasi-perpendicular shocks do not efficiently accelerate ions. We model this obliquity-dependent acceleration process in a spherically expanding blast wave setup with the moving-mesh code AREPO for different magnetic field morphologies, ranging from homogeneous to turbulent configurations. A Sedov-Taylor explosion in a homogeneous magnetic field generates an oblate ellipsoidal shock surface due to the slower propagating blast wave in the direction of the magnetic field. This is because of the efficient cosmic ray (CR) production in the quasi-parallel polar cap regions, which softens the equation of state and increases the compressibility of the post-shock gas. We find that the solution remains self-similar because the ellipticity of the propagating blast wave stays constant in time. This enables us to derive an effective ratio of specific heats for a composite of thermal gas and CRs as a function of the maximum acceleration efficiency. We finally discuss the behavior of supernova remnants expanding into a turbulent magnetic field with varying coherence lengths. For a maximum CR acceleration efficiency of about 15 per cent at quasi-parallel shocks (as suggested by kinetic plasma simulations), we find an average efficiency of about 5 per cent, independent of the assumed magnetic coherence length.

  6. Current driven instabilities of an electromagnetically accelerated plasma

    NASA Technical Reports Server (NTRS)

    Chouetri, E. Y.; Kelly, A. J.; Jahn, R. G.

    1988-01-01

    A plasma instability that strongly influences the efficiency and lifetime of electromagnetic plasma accelerators was quantitatively measured. Experimental measurements of dispersion relations (wave phase velocities), spatial growth rates, and stability boundaries are reported. The measured critical wave parameters are in excellent agreement with theoretical instability boundary predictions. The instability is current driven and affects a wide spectrum of longitudinal (electrostatic) oscillations. Current driven instabilities, which are intrinsic to the high-current-carrying magnetized plasma of the magnetoplasmadynmic (MPD) accelerator, were investigated with a kinetic theoretical model based on first principles. Analytical limits of the appropriate dispersion relation yield unstable ion acoustic waves for T(i)/T(e) much less than 1 and electron acoustic waves for T(i)/T(e) much greater than 1. The resulting set of nonlinear equations for the case of T(i)/T(e) = 1, of most interest to the MPD thruster Plasma Wave Experiment, was numerically solved to yield a multiparameter set of stability boundaries. Under certain conditions, marginally stable waves traveling almost perpendicular to the magnetic field would travel at a velocity equal to that of the electron current. Such waves were termed current waves. Unstable current waves near the upper stability boundary were observed experimentally and are in accordance with theoretical predictions. This provides unambiguous proof of the existence of such instabilites in electromagnetic plasma accelerators.

  7. Influence of surfactants on gas-hydrate formation' kinetics in water-oil emulsion

    NASA Astrophysics Data System (ADS)

    Zemenkov, Yu D.; Shirshova, A. V.; Arinstein, E. A.; Shuvaev, A. N.

    2018-05-01

    The kinetics of gas hydrate formation of propane in a water-oil emulsion is experimentally studied when three types of surfactants (SAA (surface acting agent)) - anionic type emulsifiers - are added to the aqueous phase. It is shown that all three types of surfactants decelerate the growth of the gas-hydrate in the emulsion and can be considered as anti-agglutinating and kinetic low-dose inhibitors. The most effective inhibitor of hydrate formation in water-oil emulsion of SV-102 surfactant was revealed. For comparison, experimental studies of gas-hydrate formation under the same conditions for bulk water have been carried out. It is shown that in bulk water, all the surfactants investigated act as promoters (accelerators) of hydrate formation. A qualitative explanation of the action mechanisms of emulsifiers in the process of gas-hydrate formation in water-oil emulsion is given.

  8. Peptide kinetics from picoseconds to microseconds using boxed molecular dynamics: Power law rate coefficients in cyclisation reactions

    NASA Astrophysics Data System (ADS)

    Shalashilin, Dmitrii V.; Beddard, Godfrey S.; Paci, Emanuele; Glowacki, David R.

    2012-10-01

    Molecular dynamics (MD) methods are increasingly widespread, but simulation of rare events in complex molecular systems remains a challenge. We recently introduced the boxed molecular dynamics (BXD) method, which accelerates rare events, and simultaneously provides both kinetic and thermodynamic information. We illustrate how the BXD method may be used to obtain high-resolution kinetic data from explicit MD simulations, spanning picoseconds to microseconds. The method is applied to investigate the loop formation dynamics and kinetics of cyclisation for a range of polypeptides, and recovers a power law dependence of the instantaneous rate coefficient over six orders of magnitude in time, in good agreement with experimental observations. Analysis of our BXD results shows that this power law behaviour arises when there is a broad and nearly uniform spectrum of reaction rate coefficients. For the systems investigated in this work, where the free energy surfaces have relatively small barriers, the kinetics is very sensitive to the initial conditions: strongly non-equilibrium conditions give rise to power law kinetics, while equilibrium initial conditions result in a rate coefficient with only a weak dependence on time. These results suggest that BXD may offer us a powerful and general algorithm for describing kinetics and thermodynamics in chemical and biochemical systems.

  9. Evolutionary optimization methods for accelerator design

    NASA Astrophysics Data System (ADS)

    Poklonskiy, Alexey A.

    Many problems from the fields of accelerator physics and beam theory can be formulated as optimization problems and, as such, solved using optimization methods. Despite growing efficiency of the optimization methods, the adoption of modern optimization techniques in these fields is rather limited. Evolutionary Algorithms (EAs) form a relatively new and actively developed optimization methods family. They possess many attractive features such as: ease of the implementation, modest requirements on the objective function, a good tolerance to noise, robustness, and the ability to perform a global search efficiently. In this work we study the application of EAs to problems from accelerator physics and beam theory. We review the most commonly used methods of unconstrained optimization and describe the GATool, evolutionary algorithm and the software package, used in this work, in detail. Then we use a set of test problems to assess its performance in terms of computational resources, quality of the obtained result, and the tradeoff between them. We justify the choice of GATool as a heuristic method to generate cutoff values for the COSY-GO rigorous global optimization package for the COSY Infinity scientific computing package. We design the model of their mutual interaction and demonstrate that the quality of the result obtained by GATool increases as the information about the search domain is refined, which supports the usefulness of this model. We Giscuss GATool's performance on the problems suffering from static and dynamic noise and study useful strategies of GATool parameter tuning for these and other difficult problems. We review the challenges of constrained optimization with EAs and methods commonly used to overcome them. We describe REPA, a new constrained optimization method based on repairing, in exquisite detail, including the properties of its two repairing techniques: REFIND and REPROPT. We assess REPROPT's performance on the standard constrained

  10. Characterization and Accelerated Ageing of UHMWPE Used in Orthopedic Prosthesis by Peroxide

    PubMed Central

    Rocha, Magda; Mansur, Alexandra; Mansur, Herman

    2009-01-01

    Ultra-high molecular weight polyethylene (UHMWPE) has been the most commonly used bearing material in total joint arthroplasty. Wear and oxidation fatigue resistance of UHMWPE are regarded as two important mechanical properties to extend the longevity of knee prostheses. Though accelerated in vitro protocols have been developed to test the relative oxidation resistance of various types of UHMWPE, its mechanism is not accurately understood yet. Thus, in the present study an accelerated ageing of UHMWPE in hydrogen peroxide solution was performed and relative oxidation was extensively characterized by Fourier Transformed Infrared Spectroscopy (FTIR) spectroscopy and the morphological changes were analyzed by Scanning Electron Microscopy (SEM). Different chemical groups of UHMWPE associated with the degradation reaction were monitored for over 120 days in order to evaluate the possible oxidation mechanism(s) which may have occurred. The results have provided strong evidence that the oxidation mechanism is rather complex, and two stages with their own particular first-order kinetics reaction patterns have been clearly identified. Furthermore, hydrogen peroxide has proven to be an efficient oxidative medium to accelerate ageing of UHMWPE.

  11. SymDex: increasing the efficiency of chemical fingerprint similarity searches for comparing large chemical libraries by using query set indexing.

    PubMed

    Tai, David; Fang, Jianwen

    2012-08-27

    The large sizes of today's chemical databases require efficient algorithms to perform similarity searches. It can be very time consuming to compare two large chemical databases. This paper seeks to build upon existing research efforts by describing a novel strategy for accelerating existing search algorithms for comparing large chemical collections. The quest for efficiency has focused on developing better indexing algorithms by creating heuristics for searching individual chemical against a chemical library by detecting and eliminating needless similarity calculations. For comparing two chemical collections, these algorithms simply execute searches for each chemical in the query set sequentially. The strategy presented in this paper achieves a speedup upon these algorithms by indexing the set of all query chemicals so redundant calculations that arise in the case of sequential searches are eliminated. We implement this novel algorithm by developing a similarity search program called Symmetric inDexing or SymDex. SymDex shows over a 232% maximum speedup compared to the state-of-the-art single query search algorithm over real data for various fingerprint lengths. Considerable speedup is even seen for batch searches where query set sizes are relatively small compared to typical database sizes. To the best of our knowledge, SymDex is the first search algorithm designed specifically for comparing chemical libraries. It can be adapted to most, if not all, existing indexing algorithms and shows potential for accelerating future similarity search algorithms for comparing chemical databases.

  12. Search for Stable Strange Quark Matter in Lunar Soil

    NASA Astrophysics Data System (ADS)

    Han, K.; Ashenfelter, J.; Chikanian, A.; Emmet, W.; Finch, L. E.; Heinz, A.; Madsen, J.; Majka, R. D.; Monreal, B.; Sandweiss, J.

    2009-08-01

    We report results from a search for strangelets (small chunks of strange quark matter) in lunar soil using the Yale WNSL accelerator as a mass spectrometer. We have searched over a range in mass from A=42 to A=70amu for nuclear charges 5, 6, 8, 9, and 11. No strangelets were found in the experiment. For strangelets with nuclear charge 8, a concentration in lunar soil higher than 10-16 is excluded at the 95% confidence level. The implied limit on the strangelet flux in cosmic rays is the most sensitive to date for the covered range and is relevant to both recent theoretical flux predictions and a strangelet candidate event found by the AMS-01 experiment.

  13. Electrostatically Accelerated Encounter and Folding for Facile Recognition of Intrinsically Disordered Proteins

    PubMed Central

    Ganguly, Debabani; Zhang, Weihong; Chen, Jianhan

    2013-01-01

    Achieving facile specific recognition is essential for intrinsically disordered proteins (IDPs) that are involved in cellular signaling and regulation. Consideration of the physical time scales of protein folding and diffusion-limited protein-protein encounter has suggested that the frequent requirement of protein folding for specific IDP recognition could lead to kinetic bottlenecks. How IDPs overcome such potential kinetic bottlenecks to viably function in signaling and regulation in general is poorly understood. Our recent computational and experimental study of cell-cycle regulator p27 (Ganguly et al., J. Mol. Biol. (2012)) demonstrated that long-range electrostatic forces exerted on enriched charges of IDPs could accelerate protein-protein encounter via “electrostatic steering” and at the same time promote “folding-competent” encounter topologies to enhance the efficiency of IDP folding upon encounter. Here, we further investigated the coupled binding and folding mechanisms and the roles of electrostatic forces in the formation of three IDP complexes with more complex folded topologies. The surface electrostatic potentials of these complexes lack prominent features like those observed for the p27/Cdk2/cyclin A complex to directly suggest the ability of electrostatic forces to facilitate folding upon encounter. Nonetheless, similar electrostatically accelerated encounter and folding mechanisms were consistently predicted for all three complexes using topology-based coarse-grained simulations. Together with our previous analysis of charge distributions in known IDP complexes, our results support a prevalent role of electrostatic interactions in promoting efficient coupled binding and folding for facile specific recognition. These results also suggest that there is likely a co-evolution of IDP folded topology, charge characteristics, and coupled binding and folding mechanisms, driven at least partially by the need to achieve fast association kinetics for

  14. DIFFUSIVE PARTICLE ACCELERATION IN SHOCKED, VISCOUS ACCRETION DISKS: GREEN'S FUNCTION ENERGY DISTRIBUTION

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Becker, Peter A.; Das, Santabrata; Le, Truong, E-mail: pbecker@gmu.edu, E-mail: sbdas@iitg.ernet.in, E-mail: truong.le@nhrec.org

    2011-12-10

    The acceleration of relativistic particles in a viscous accretion disk containing a standing shock is investigated as a possible explanation for the energetic outflows observed around radio-loud black holes. The energy/space distribution of the accelerated particles is computed by solving a transport equation that includes the effects of first-order Fermi acceleration, bulk advection, spatial diffusion, and particle escape. The velocity profile of the accreting gas is described using a model for shocked viscous disks recently developed by the authors, and the corresponding Green's function distribution for the accelerated particles in the disk and the outflow is obtained using a classicalmore » method based on eigenfunction analysis. The accretion-driven, diffusive shock acceleration scenario explored here is conceptually similar to the standard model for the acceleration of cosmic rays at supernova-driven shocks. However, in the disk application, the distribution of the accelerated particles is much harder than would be expected for a plane-parallel shock with the same compression ratio. Hence the disk environment plays a key role in enhancing the efficiency of the shock acceleration process. The presence of the shock helps to stabilize the disk by reducing the Bernoulli parameter, while channeling the excess binding energy into the escaping relativistic particles. In applications to M87 and Sgr A*, we find that the kinetic power in the jet is {approx}0.01 M-dot c{sup 2}, and the outflowing relativistic particles have a mean energy {approx}300 times larger than that of the thermal gas in the disk at the shock radius. Our results suggest that a standing shock may be an essential ingredient in accretion onto underfed black holes, helping to resolve the long-standing problem of the stability of advection-dominated accretion disks.« less

  15. Kinetic analysis of thermal stability of human low density lipoproteins: a model for LDL fusion in atherogenesis[S

    PubMed Central

    Lu, Mengxiao; Gantz, Donald L.; Herscovitz, Haya; Gursky, Olga

    2012-01-01

    Fusion of modified LDL in the arterial wall promotes atherogenesis. Earlier we showed that thermal denaturation mimics LDL remodeling and fusion, and revealed kinetic origin of LDL stability. Here we report the first quantitative analysis of LDL thermal stability. Turbidity data show sigmoidal kinetics of LDL heat denaturation, which is unique among lipoproteins, suggesting that fusion is preceded by other structural changes. High activation energy of denaturation, Ea = 100 ± 8 kcal/mol, indicates disruption of extensive packing interactions in LDL. Size-exclusion chromatography, nondenaturing gel electrophoresis, and negative-stain electron microscopy suggest that LDL dimerization is an early step in thermally induced fusion. Monoclonal antibody binding suggests possible involvement of apoB N-terminal domain in early stages of LDL fusion. LDL fusion accelerates at pH < 7, which may contribute to LDL retention in acidic atherosclerotic lesions. Fusion also accelerates upon increasing LDL concentration in near-physiologic range, which likely contributes to atherogenesis. Thermal stability of LDL decreases with increasing particle size, indicating that the pro-atherogenic properties of small dense LDL do not result from their enhanced fusion. Our work provides the first kinetic approach to measuring LDL stability and suggests that lipid-lowering therapies that reduce LDL concentration but increase the particle size may have opposite effects on LDL fusion. PMID:22855737

  16. Accelerated Biodegradation of Cement by Sulfur-Oxidizing Bacteria as a Bioassay for Evaluating Immobilization of Low-Level Radioactive Waste

    PubMed Central

    Aviam, Orli; Bar-Nes, Gabi; Zeiri, Yehuda; Sivan, Alex

    2004-01-01

    Disposal of low-level radioactive waste by immobilization in cement is being evaluated worldwide. The stability of cement in the environment may be impaired by sulfur-oxidizing bacteria that corrode the cement by producing sulfuric acid. Since this process is so slow that it is not possible to perform studies of the degradation kinetics and to test cement mixtures with increased durability, procedures that accelerate the biodegradation are required. Semicontinuous cultures of Halothiobacillus neapolitanus and Thiomonas intermedia containing thiosulfate as the sole energy source were employed to accelerate the biodegradation of cement samples. This resulted in a weight loss of up to 16% after 39 days, compared with a weight loss of 0.8% in noninoculated controls. Scanning electron microscopy of the degraded cement samples revealed deep cracks, which could be associated with the formation of low-density corrosion products in the interior of the cement. Accelerated biodegradation was also evident from the leaching rates of Ca2+ and Si2+, the major constituents of the cement matrix, and Ca exhibited the highest rate (up to 20 times greater than the control rate) due to the reaction between free lime and the biogenic sulfuric acid. Leaching of Sr2+ and Cs+, which were added to the cement to simulate immobilization of the corresponding radioisotopes, was also monitored. In contrast to the linear leaching kinetics of calcium, silicon, and strontium, the leaching pattern of cesium produced a saturation curve similar to the control curve. Presumably, the leaching of cesium is governed by the diffusion process, whereas the leaching kinetics of the other three ions seems to governed by dissolution of the cement. PMID:15466547

  17. Multi-species first-principles simulations of particle acceleration at shocks

    NASA Astrophysics Data System (ADS)

    Caprioli, Damiano

    Astrophysical shocks are known to be prominent sources of non-thermal particles and emission. In particular, strong shocks at supernova remnant blast waves are thought to accelerate Galactic cosmic rays (CRs) up to about 10^17eV via diffusive shock acceleration (DSA). The chemical composition of Galactic CRs, now measured with great accuracy by payloads and satellites, is reminiscent of that of the typical interstellar medium, although with some significant deviations. Observations reveal: 1) an electron/proton ratio of about 1% at about 10 GeV, (2) a general enhancement of the refractory elements relative to the volatile ones, (3) among the volatile elements, an enhancement of the heavier elements relative to the lighter ones, and (4) a discrepant hardening of CR nuclei heavier than hydrogen. Such peculiar trends contain precious information about the dependence of the acceleration process on the particle mass/charge ratio, a trend that has no theoretical counterpart in the DSA theory, yet. Building on our recent successes in modeling electron and proton DSA at non-relativistic astrophysical shocks via first-principles kinetic simulations, we will perform multispecies particle-in-cells simulations of such systems also including nuclei heavier than hydrogen, in order to investigate thermalization, injection, and acceleration of species with different mass/charge ratio. We will also analyze how the simulation outputs compare with the observed CR abundances, in order to build a model for DSA that accounts for the relative acceleration efficiency of energetic electrons, protons, and heavier ions. Finally, we will assess the possible contribution of accelerated heavy ions, especially helium, to the generation of magnetic turbulence via CR-driven instabilities - crucial to foster rapid particle energgization- and to the hadronic gamma-ray emission from young supernova remnants.

  18. Programming and Runtime Support to Blaze FPGA Accelerator Deployment at Datacenter Scale.

    PubMed

    Huang, Muhuan; Wu, Di; Yu, Cody Hao; Fang, Zhenman; Interlandi, Matteo; Condie, Tyson; Cong, Jason

    2016-10-01

    With the end of CPU core scaling due to dark silicon limitations, customized accelerators on FPGAs have gained increased attention in modern datacenters due to their lower power, high performance and energy efficiency. Evidenced by Microsoft's FPGA deployment in its Bing search engine and Intel's 16.7 billion acquisition of Altera, integrating FPGAs into datacenters is considered one of the most promising approaches to sustain future datacenter growth. However, it is quite challenging for existing big data computing systems-like Apache Spark and Hadoop-to access the performance and energy benefits of FPGA accelerators. In this paper we design and implement Blaze to provide programming and runtime support for enabling easy and efficient deployments of FPGA accelerators in datacenters. In particular, Blaze abstracts FPGA accelerators as a service (FaaS) and provides a set of clean programming APIs for big data processing applications to easily utilize those accelerators. Our Blaze runtime implements an FaaS framework to efficiently share FPGA accelerators among multiple heterogeneous threads on a single node, and extends Hadoop YARN with accelerator-centric scheduling to efficiently share them among multiple computing tasks in the cluster. Experimental results using four representative big data applications demonstrate that Blaze greatly reduces the programming efforts to access FPGA accelerators in systems like Apache Spark and YARN, and improves the system throughput by 1.7 × to 3× (and energy efficiency by 1.5× to 2.7×) compared to a conventional CPU-only cluster.

  19. Monoenergetic acceleration of a target foil by circularly polarized laser pulse in RPA regime without thermal heating

    NASA Astrophysics Data System (ADS)

    Khudik, V.; Yi, S. A.; Siemon, C.; Shvets, G.

    2012-12-01

    A kinetic model of the monoenergetic acceleration of a target foil irradiated by the circularly polarized laser pulse is developed. The target moves without thermal heating with constant acceleration which is provided by chirping the frequency of the laser pulse and correspondingly increasing its intensity. In the accelerated reference frame, bulk plasma in the target is neutral and its parameters are stationary: cold ions are immobile while nonrelativistic electrons bounce back and forth inside the potential well formed by ponderomotive and electrostatic potentials. It is shown that a positive charge left behind of the moving target in the ion tail and a negative charge in front of the target in the electron sheath form a capacitor whose constant electric field accelerates the ions of the target. The charge separation is maintained by the radiation pressure pushing electrons forward. The scalings of the target thickness and electromagnetic radiation with the electron temperature are found.

  20. Increased photoelectron transmission in High-pressure photoelectron spectrometers using "swift acceleration"

    NASA Astrophysics Data System (ADS)

    Edwards, Mårten O. M.; Karlsson, Patrik G.; Eriksson, Susanna K.; Hahlin, Maria; Siegbahn, Hans; Rensmo, Håkan; Kahk, Juhan M.; Villar-Garcia, Ignacio J.; Payne, David J.; Åhlund, John

    2015-06-01

    A new operation mode of a HPXPS (high-pressure X-ray photoelectron spectroscopy) analyzer is evaluated on a HPXPS system fitted with an Al Kα X-ray source. A variety of metal foil samples (gold, silver and copper) were measured in different sample gas environments (N2 and H2O), and a front aperture diameter of 0.8 mm. The new design concept is based upon "swiftly" accelerating the photoelectrons to kinetic energies of several keV after they pass the analyzer front aperture. Compared to the standard mode, in which the front section between the two first apertures is field-free, this gives a wider angular collection and a lower tendency for electron losses in collisions with gas molecules within the analyzer. With the swift-acceleration mode we attain, depending on the experimental conditions, up to about 3 times higher peak intensities in vacuum and about 10 to 20 times higher peak intensities in the 6-9 mbar regime, depending on kinetic energy. These experimental findings agree well with simulated transmission functions for the analyzer. The new mode of operation enables faster data acquisition than the standard mode of operation, particularly valuable in a home laboratory environment. Further demonstrations of performance are highlighted by measurements of the valence band structure in dye-sensitized solar cell photoelectrodes under a 2 mbar H2O atmosphere, a molecularly modified surface of interest in photoelectrochemical devices.

  1. The Xenon1T Dark Matter Search Experiment

    NASA Astrophysics Data System (ADS)

    Aprile, Elena

    The worldwide race towards direct dark matter detection in the form of Weakly Interacting Massive Particles (WIMPs) has been dramatically accelerated by the remarkable progress and evolution of liquid xenon time projection chambers (LXeTPCs). With a realistic discovery potential, Xenon100 has already reached a sensitivity of 7 × 10-45 cm2, and continues to accrue data at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy towards its ultimate sensitivity reach at the σ SI ˜ 2 × 10-45 cm2 level for the spin-independent WIMP-nucleon cross-section. To fully explore the favoured parameter space for WIMP dark matter in search of a first robust and statistically significant discovery, or to confirm any hint of a signal from Xenon100, the next phase of the Xenon program will be a detector at the ton scale - Xenon1T. The Xenon1T detector, based on 2.2 ton of LXe viewed by low radioactivity photomultiplier tubes and housed in a water Cherenkov muon veto at LNGS, is presented. With an experimental aim of probing WIMP interaction cross-sections above of order σ SI ˜ 2 × 10-47 cm2 within 2 years of operation, Xenon1T will provide the sensitivity to probe a particularly favourable region of electroweak physics on a timescale compatible with complementary ground and satellite based indirect searches and with accelerator dark matter searches at the LHC. Indeed, for a σ SI ˜ 10-45 cm2 and 100 GeV/c2 WIMP mass, Xenon1T could detect of order 100 events in this exposure, providing statistics for placing significant constraints on the WIMP mass.

  2. Shape transitions in strained Cu islands on Ni(100): kinetics versus energetics

    NASA Astrophysics Data System (ADS)

    Shim, Yunsic; Amar, Jacques

    2012-02-01

    We examine the shape transition from compact to ramified islands observed in submonolayer Cu/Ni(100) growth. Recently, it has been argued that this transition is not due to a growth instability but can be understood in terms of energetic arguments. In order to determine the responsible mechanisms we have carried out energetics calculations as well as temperature-accelerated dynamics (TAD) and kinetic Monte Carlo (KMC) simulations. Our results indicate that the shape transition cannot be explained by equilibrium arguments, but is instead due to kinetic effects which are mediated by strain. In particular, by calculating the relevant line-tension and strain energies, we find that the equilibrium critical island-width is at least four orders of magnitude larger than the experimentally observed arm-width. In contrast, our TAD simulations indicate that unexpected concerted motions occurring at step edges are responsible. The energy barriers for these concerted motions decrease with increasing island size and appear to saturate for islands larger than 300 - 400 atoms. By including these strain-induced kinetic processes in our KMC simulations of island-growth, we have been able to explain both the temperature- and coverage-dependence of the island morphology.

  3. Ion acceleration by Alfvén waves on auroral field lines

    NASA Astrophysics Data System (ADS)

    Bingham, Robert; Eliasson, Bengt; Tito Mendonça, José; Stenflo, Lennart

    2013-05-01

    Observations of ion acceleration along auroral field lines at the boundary of the plasma sheet and tail lobe of the Earth show that the energy of the ions increases with decreasing density. The observations can be explained by ion acceleration through Landau resonance with kinetic Alfvén waves (KAWs) such that kA·vi = ωA, where kA is the wave vector, vi is the ion resonance velocity and ωA is the Alfvén wave frequency. The ion resonance velocities are proportional to the Alfvén velocity which increases with decreasing density. This is in agreement with the data if the process is occurring at the plasma sheet tail lobe boundary. A quasi-linear theory of ion acceleration by KAWs is presented. These ions propagate both down towards and away from the Earth. The paths of the Freja and Polar satellites indicate that the acceleration takes place between the two satellites, between 1Re and 5Re. The downward propagating ions develop a horseshoe-type of distribution which has a positive slope in the perpendicular direction. This type of distribution can produce intense lower hybrid wave activity, which is also observed. Finally, the filamentation of shear Alfvén waves is considered. It may be responsible for large-scale density striations. In memory of Padma Kant Shukla, a great scientist and a good friend.

  4. Accelerated in vitro release testing of implantable PLGA microsphere/PVA hydrogel composite coatings

    PubMed Central

    Shen, Jie; Burgess, Diane J.

    2011-01-01

    Dexamethasone loaded poly(lactic-co-glycolic acid) (PLGA) microsphere/PVA hydrogel composites have been investigated as an outer drug-eluting coating for implantable devices such as glucose sensors to counter negative tissue responses to implants. The objective of this study was to develop a discriminatory, accelerated in vitro release testing method for this drug-eluting coating using United States Pharmacopeia (USP) apparatus 4. Polymer degradation and drug release kinetics were investigated under “real-time” and accelerated conditions (i.e. extreme pH, hydro-alcoholic solutions and elevated temperatures). Compared to “real-time” conditions, the initial burst and lag phases were similar using hydro-alcoholic solutions and extreme pH conditions, while the secondary apparent zero-order release phase was slightly accelerated. Elevated temperatures resulted in a significant acceleration of dexamethasone release. The accelerated release data were able to predict “real-time” release when applying the Arrhenius equation. Microsphere batches with faster and slower release profiles were investigated under “real-time” and elevated temperature (60°C) conditions to determine the discriminatory ability of the method. The results demonstrated both the feasibility and the discriminatory ability of this USP apparatus 4 method for in vitro release testing of drug loaded PLGA microsphere/PVA hydrogel composites. This method may be appropriate for similar drug/device combination products and drug delivery systems. PMID:22016033

  5. Accelerated in vitro release testing of implantable PLGA microsphere/PVA hydrogel composite coatings.

    PubMed

    Shen, Jie; Burgess, Diane J

    2012-01-17

    Dexamethasone loaded poly(lactic-co-glycolic acid) (PLGA) microsphere/PVA hydrogel composites have been investigated as an outer drug-eluting coating for implantable devices such as glucose sensors to counter negative tissue responses to implants. The objective of this study was to develop a discriminatory, accelerated in vitro release testing method for this drug-eluting coating using United States Pharmacopeia (USP) apparatus 4. Polymer degradation and drug release kinetics were investigated under "real-time" and accelerated conditions (i.e. extreme pH, hydro-alcoholic solutions and elevated temperatures). Compared to "real-time" conditions, the initial burst and lag phases were similar using hydro-alcoholic solutions and extreme pH conditions, while the secondary apparent zero-order release phase was slightly accelerated. Elevated temperatures resulted in a significant acceleration of dexamethasone release. The accelerated release data were able to predict "real-time" release when applying the Arrhenius equation. Microsphere batches with faster and slower release profiles were investigated under "real-time" and elevated temperature (60°C) conditions to determine the discriminatory ability of the method. The results demonstrated both the feasibility and the discriminatory ability of this USP apparatus 4 method for in vitro release testing of drug loaded PLGA microsphere/PVA hydrogel composites. This method may be appropriate for similar drug/device combination products and drug delivery systems. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Kinetic study of an enzymic cycling system coupled to an enzymic step: determination of alkaline phosphatase activity.

    PubMed Central

    Valero, E; Varón, R; García-Carmona, F

    1995-01-01

    A kinetic study is made of a system consisting of a specific enzymic cycling assay coupled to an enzymic reaction. A kinetic analysis of this system is presented, and the accumulation of chromophore involved in the cycle is seen to be parabolic, i.e. the rate of the reaction increases continuously with constant acceleration. The system is illustrated by the measurement of alkaline phosphatase activity using beta-NADP+ as substrate. The enzymes alcohol dehydrogenase and diaphorase are used to cycle beta-NAD+ in the presence of ethanol and p-Iodonitrotetrazolium Violet. During each turn of the cycle, one molecule of the tetrazolium salt is reduced to an intensely coloured formazan. A simple procedure for evaluating the kinetic parameters involved in the system and for optimizing this cycling assay is described. The method is applicable to the measurement of any enzyme, and its amplification capacity as well as the simplicity of determining kinetic parameters enable it to be employed in enzyme immunoassays to increase the magnitude of the measured response. PMID:7619054

  7. The radial velocity search for extrasolar planets

    NASA Technical Reports Server (NTRS)

    Mcmillan, Robert S.

    1991-01-01

    Radial velocity measurements are being made to search for planets orbiting stars other than the Sun. The reflex acceleration induced on stars by planets can be sensed by measuring the small, slow changes in the line-of-site velocities of stars. To detect these planetary perturbations, the data series must be made on a uniform instrumental scale for as long as it takes a planet to orbit its star. A spectrometer of extreme stability and unprecedented sensitivity to changes in stellar radial velocities was operated.

  8. Synchrotron Study on Crystallization Kinetics of Milk Fat under Shear Flow

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mazzanti, G.; Marangoni, A; Idziak, S

    A detailed synchrotron X-ray diffraction study on the kinetics of crystallization of anhydrous milk fat (AMF) and milk fat triacylglycerols (MFT) was done in a Couette cell at 17 C, 17.5 C and 20 C under shear rates between 0 and 2880 s-1. We observed shear-induced acceleration of the transition from phase ? to ?? and the presence of crystalline orientation, but no effect of shear on the onset time of phase ? was observed. A two stage regime was observed for the growth of phase ??. The first stage follows a series-parallel system of differential equations describing the conversionmore » between liquid and crystalline phases. The second stage follows a diffusion-controlled regime. These mechanisms are consistent with the crystalline orientation, the growth of the crystalline domains and the observed displacement of the diffraction peak positions. The absence of the polar lipids explains the faster kinetics of MFT.« less

  9. Interband and intraband electron kinetics in non-thermal warm dense gold

    NASA Astrophysics Data System (ADS)

    Brennan Brown, Shaughnessy; Chen, Zhijiang; Curry, Chandra; Hering, Philippe; Hoffmann, Matthias C.; Ng, Andrew; Reid, Matthew; Tsui, Ying Y.; Glenzer, Siegfried H.

    2015-11-01

    Single-state warm dense matter may be produced via isochoric heating of thin metal foils using ultrafast high-power lasers. Previous experiments have confirmed that electron temperatures exceed ion temperatures during the initial picoseconds following excitation; however, electron kinetics in non-thermal states preceding establishment of a well-defined electron thermal distribution remain little understood. X-ray and optical probing techniques provide necessary resolution to investigate these electronic properties. Here, we will present a study of electron kinetics in warm dense gold produced by irradiating free-standing 30 nm Au foils with a 400 nm FWHM, 45 fs Ti:Sapphire laser system at SLAC National Accelerator Laboratory. The temporal evolutions of AC conductivity for 400 nm and 800 nm laser pulses are simultaneously determined with sub-100 fs resolution, providing insight into the 5 d-6 s/ p interband and 6 s / p intraband transitions respectively. Our results suggest that Auger decay and three-body recombination play important roles in electron thermalization of warm dense gold.

  10. Relativistic cosmic-ray spectra in the fully nonlinear theory of shock acceleration

    NASA Technical Reports Server (NTRS)

    Ellison, D. C.; Eichler, D.

    1985-01-01

    The non-linear theory of shock acceleration was generalized to include wave dynamics. In the limit of rapid wave damping, it is found that a finite wave velocity tempers the acceleration of high Mach number shocks and limits the maximum compression ratio even when energy loss is important. For a given spectrum, the efficiency of relativistic particle production is essentially independent of v sub Ph. For the three families shown, the percentage of kinetic energy flux going into relativistic particles is (1) 72 percent, (2) 44 percent, and (3) 26 percent (this includes the energy loss at the upper energy cutoff). Even small v sub ph, typical of the HISM, produce quasi-universal spectra that depend only weakly on the acoustic Mach number. These spectra should be close enough to e(-2) to satisfy cosmic ray source requirements.

  11. Resonance Search for a Heavy Photon in the 2015 Engineering Run Data of the Heavy Photon Search Experiment

    NASA Astrophysics Data System (ADS)

    Moreno, Omar; Heavy Photon Search Collaboration

    2017-01-01

    The Heavy Photon Search (HPS) experiment at Jefferson Lab is searching for a new U(1) vector boson (``heavy photon'',``dark photon'' or A') in the mass range of 20-500 MeV/c2. An A' in this mass range is theoretically favorable and may also mediate dark matter interactions. The A' couples to the ordinary photon through kinetic mixing, which induces their coupling to electric charge. Since heavy photons couple to electrons, they can be produced through a process analogous to bremsstrahlung, subsequently decaying to an e+e- , which can be observed as a narrow resonance above the dominant QED trident background. For suitably small couplings, heavy photons travel detectable distances before decaying, providing a second signature. Using the CEBAF electron beam at Jefferson Lab incident on a thin tungsten target, along with a compact, large acceptance forward spectrometer consisting of a silicon vertex tracker and lead tungstate electromagnetic calorimeter, HPS is accessing unexplored regions in the mass-coupling phase space. The HPS engineering run took place in spring of 2015 using a 1.056 GeV, 50 nA beam and collected 1165 nb-1 (7.29 mC) of data. This talk will present the results of a resonance search for a heavy photon using the engineering run data.

  12. Adhesion and debonding kinetics of photovoltaic encapsulation in moist environments: Adhesion and debonding kinetics of photovoltaic encapsulation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Novoa, Fernando D.; Miller, David C.; Dauskardt, Reinhold H.

    Debonding of photovoltaic (PV) encapsulation in moist environments is frequently reported but presently not well understood or quantified. Temperature cycling, moisture, and mechanical loads often cause loss of encapsulation adhesion and interfacial debonding, initially facilitating back-reflectance and reduced electrical current, but ultimately leading to internal corrosion and loss of module functionality. To investigate the effects of temperature (T) and relative humidity (RH) on the kinetics of encapsulation debonding, we developed a mechanics-based technique to measure encapsulation debond energy and debond growth rates in a chamber of controlled environment. The debond energy decreased from 2.15 to 1.75 kJ m-2 in poly(ethylene-co-vinylmore » acetate) (EVA) and from 0.67 to 0.52 kJ m-2 in polyvinyl butyral when T increased from 25 to 50 degrees C and 20 to 40 degrees C, respectively. The debond growth rates of EVA increased up to 1000-fold with small increases of T (10 degrees C) and RH (15%). To elucidate the mechanisms of environmental debonding, we developed a fracture-kinetics model, where the viscoelastic relaxation processes at the debonding-tip are used to predict debond growth. The model and techniques constitute the fundamental basis for developing accelerated aging tests and long-term reliability predictions for PV encapsulation.« less

  13. Great moments in kinetic theory: 150 years of Maxwell’s (other) equations

    NASA Astrophysics Data System (ADS)

    Robson, Robert E.; Mehrling, Timon J.; Osterhoff, Jens

    2017-11-01

    In 1867, just two years after laying the foundations of electromagnetism, J. Clerk Maxwell presented a fundamental paper on kinetic gas theory, in which he described the evolution of the gas in terms of certain ‘moments’ of its velocity distribution function. This inspired Ludwig Boltzmann to formulate his famous kinetic equation, from which followed the H-theorem and the connection with entropy. On the occasion of the 150th anniversary of publication of Maxwell's paper, we review the Maxwell-Boltzmann formalism and discuss how its generality and adaptability enable it to play a key role in describing the behaviour of a variety of systems of current interest, in both gaseous and condensed matter, and in modern-day physics and technologies which Maxwell and Boltzmann could not possibly have foreseen. In particular, we illustrate the relevance and applicability of Maxwell's formalism to the dynamic field of plasma-wakefield acceleration.

  14. Simulated maximum likelihood method for estimating kinetic rates in gene expression.

    PubMed

    Tian, Tianhai; Xu, Songlin; Gao, Junbin; Burrage, Kevin

    2007-01-01

    Kinetic rate in gene expression is a key measurement of the stability of gene products and gives important information for the reconstruction of genetic regulatory networks. Recent developments in experimental technologies have made it possible to measure the numbers of transcripts and protein molecules in single cells. Although estimation methods based on deterministic models have been proposed aimed at evaluating kinetic rates from experimental observations, these methods cannot tackle noise in gene expression that may arise from discrete processes of gene expression, small numbers of mRNA transcript, fluctuations in the activity of transcriptional factors and variability in the experimental environment. In this paper, we develop effective methods for estimating kinetic rates in genetic regulatory networks. The simulated maximum likelihood method is used to evaluate parameters in stochastic models described by either stochastic differential equations or discrete biochemical reactions. Different types of non-parametric density functions are used to measure the transitional probability of experimental observations. For stochastic models described by biochemical reactions, we propose to use the simulated frequency distribution to evaluate the transitional density based on the discrete nature of stochastic simulations. The genetic optimization algorithm is used as an efficient tool to search for optimal reaction rates. Numerical results indicate that the proposed methods can give robust estimations of kinetic rates with good accuracy.

  15. Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria

    DOE PAGES

    Yuan, Yajie; Nalewajko, Krzysztof; Zrake, Jonathan; ...

    2016-09-07

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focusmore » on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The "flares" are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model. Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. As a result, higher magnetization studies are promising and will be carried out in the future.« less

  16. KINETIC STUDY OF RADIATION-REACTION-LIMITED PARTICLE ACCELERATION DURING THE RELAXATION OF UNSTABLE FORCE-FREE EQUILIBRIA

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yuan, Yajie; Nalewajko, Krzysztof; Zrake, Jonathan

    2016-09-10

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focusmore » on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The “flares” are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model. Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. Higher magnetization studies are promising and will be carried out in the future.« less

  17. Efficient protein structure search using indexing methods

    PubMed Central

    2013-01-01

    Understanding functions of proteins is one of the most important challenges in many studies of biological processes. The function of a protein can be predicted by analyzing the functions of structurally similar proteins, thus finding structurally similar proteins accurately and efficiently from a large set of proteins is crucial. A protein structure can be represented as a vector by 3D-Zernike Descriptor (3DZD) which compactly represents the surface shape of the protein tertiary structure. This simplified representation accelerates the searching process. However, computing the similarity of two protein structures is still computationally expensive, thus it is hard to efficiently process many simultaneous requests of structurally similar protein search. This paper proposes indexing techniques which substantially reduce the search time to find structurally similar proteins. In particular, we first exploit two indexing techniques, i.e., iDistance and iKernel, on the 3DZDs. After that, we extend the techniques to further improve the search speed for protein structures. The extended indexing techniques build and utilize an reduced index constructed from the first few attributes of 3DZDs of protein structures. To retrieve top-k similar structures, top-10 × k similar structures are first found using the reduced index, and top-k structures are selected among them. We also modify the indexing techniques to support θ-based nearest neighbor search, which returns data points less than θ to the query point. The results show that both iDistance and iKernel significantly enhance the searching speed. In top-k nearest neighbor search, the searching time is reduced 69.6%, 77%, 77.4% and 87.9%, respectively using iDistance, iKernel, the extended iDistance, and the extended iKernel. In θ-based nearest neighbor serach, the searching time is reduced 80%, 81%, 95.6% and 95.6% using iDistance, iKernel, the extended iDistance, and the extended iKernel, respectively. PMID:23691543

  18. Efficient protein structure search using indexing methods.

    PubMed

    Kim, Sungchul; Sael, Lee; Yu, Hwanjo

    2013-01-01

    Understanding functions of proteins is one of the most important challenges in many studies of biological processes. The function of a protein can be predicted by analyzing the functions of structurally similar proteins, thus finding structurally similar proteins accurately and efficiently from a large set of proteins is crucial. A protein structure can be represented as a vector by 3D-Zernike Descriptor (3DZD) which compactly represents the surface shape of the protein tertiary structure. This simplified representation accelerates the searching process. However, computing the similarity of two protein structures is still computationally expensive, thus it is hard to efficiently process many simultaneous requests of structurally similar protein search. This paper proposes indexing techniques which substantially reduce the search time to find structurally similar proteins. In particular, we first exploit two indexing techniques, i.e., iDistance and iKernel, on the 3DZDs. After that, we extend the techniques to further improve the search speed for protein structures. The extended indexing techniques build and utilize an reduced index constructed from the first few attributes of 3DZDs of protein structures. To retrieve top-k similar structures, top-10 × k similar structures are first found using the reduced index, and top-k structures are selected among them. We also modify the indexing techniques to support θ-based nearest neighbor search, which returns data points less than θ to the query point. The results show that both iDistance and iKernel significantly enhance the searching speed. In top-k nearest neighbor search, the searching time is reduced 69.6%, 77%, 77.4% and 87.9%, respectively using iDistance, iKernel, the extended iDistance, and the extended iKernel. In θ-based nearest neighbor serach, the searching time is reduced 80%, 81%, 95.6% and 95.6% using iDistance, iKernel, the extended iDistance, and the extended iKernel, respectively.

  19. First muon acceleration using a radio-frequency accelerator

    NASA Astrophysics Data System (ADS)

    Bae, S.; Choi, H.; Choi, S.; Fukao, Y.; Futatsukawa, K.; Hasegawa, K.; Iijima, T.; Iinuma, H.; Ishida, K.; Kawamura, N.; Kim, B.; Kitamura, R.; Ko, H. S.; Kondo, Y.; Li, S.; Mibe, T.; Miyake, Y.; Morishita, T.; Nakazawa, Y.; Otani, M.; Razuvaev, G. P.; Saito, N.; Shimomura, K.; Sue, Y.; Won, E.; Yamazaki, T.

    2018-05-01

    Muons have been accelerated by using a radio-frequency accelerator for the first time. Negative muonium atoms (Mu- ), which are bound states of positive muons (μ+) and two electrons, are generated from μ+'s through the electron capture process in an aluminum degrader. The generated Mu- 's are initially electrostatically accelerated and injected into a radio-frequency quadrupole linac (RFQ). In the RFQ, the Mu- 's are accelerated to 89 keV. The accelerated Mu- 's are identified by momentum measurement and time of flight. This compact muon linac opens the door to various muon accelerator applications including particle physics measurements and the construction of a transmission muon microscope.

  20. Modification of 1,2,4,5-tetrazine with cationic rhenium(I) polypyridine units to afford phosphorogenic bioorthogonal probes with enhanced reaction kinetics.

    PubMed

    Choi, Alex Wing-Tat; Tso, Karson Ka-Shun; Yim, Vicki Man-Wai; Liu, Hua-Wei; Lo, Kenneth Kam-Wing

    2015-02-25

    New phosphorogenic bioorthogonal probes derived from mononuclear and binuclear rhenium(I) polypyridine complexes containing a 1,2,4,5-tetrazine moiety were designed; these complexes displayed substantial dienophile-induced emission enhancement, and accelerated reaction kinetics and could target a protein conjugate in living cells.

  1. GPU Accelerated Chemical Similarity Calculation for Compound Library Comparison

    PubMed Central

    Ma, Chao; Wang, Lirong; Xie, Xiang-Qun

    2012-01-01

    Chemical similarity calculation plays an important role in compound library design, virtual screening, and “lead” optimization. In this manuscript, we present a novel GPU-accelerated algorithm for all-vs-all Tanimoto matrix calculation and nearest neighbor search. By taking advantage of multi-core GPU architecture and CUDA parallel programming technology, the algorithm is up to 39 times superior to the existing commercial software that runs on CPUs. Because of the utilization of intrinsic GPU instructions, this approach is nearly 10 times faster than existing GPU-accelerated sparse vector algorithm, when Unity fingerprints are used for Tanimoto calculation. The GPU program that implements this new method takes about 20 minutes to complete the calculation of Tanimoto coefficients between 32M PubChem compounds and 10K Active Probes compounds, i.e., 324G Tanimoto coefficients, on a 128-CUDA-core GPU. PMID:21692447

  2. Particle Identification on an FPGA Accelerated Compute Platform for the LHCb Upgrade

    NASA Astrophysics Data System (ADS)

    Fäerber, Christian; Schwemmer, Rainer; Machen, Jonathan; Neufeld, Niko

    2017-07-01

    The current LHCb readout system will be upgraded in 2018 to a “triggerless” readout of the entire detector at the Large Hadron Collider collision rate of 40 MHz. The corresponding bandwidth from the detector down to the foreseen dedicated computing farm (event filter farm), which acts as the trigger, has to be increased by a factor of almost 100 from currently 500 Gb/s up to 40 Tb/s. The event filter farm will preanalyze the data and will select the events on an event by event basis. This will reduce the bandwidth down to a manageable size to write the interesting physics data to tape. The design of such a system is a challenging task, and the reason why different new technologies are considered and have to be investigated for the different parts of the system. For the usage in the event building farm or in the event filter farm (trigger), an experimental field programmable gate array (FPGA) accelerated computing platform is considered and, therefore, tested. FPGA compute accelerators are used more and more in standard servers such as for Microsoft Bing search or Baidu search. The platform we use hosts a general Intel CPU and a high-performance FPGA linked via the high-speed Intel QuickPath Interconnect. An accelerator is implemented on the FPGA. It is very likely that these platforms, which are built, in general, for high-performance computing, are also very interesting for the high-energy physics community. First, the performance results of smaller test cases performed at the beginning are presented. Afterward, a part of the existing LHCb RICH particle identification is tested and is ported to the experimental FPGA accelerated platform. We have compared the performance of the LHCb RICH particle identification running on a normal CPU with the performance of the same algorithm, which is running on the Xeon-FPGA compute accelerator platform.

  3. PARTICLE ACCELERATOR

    DOEpatents

    Teng, L.C.

    1960-01-19

    ABS>A combination of two accelerators, a cyclotron and a ring-shaped accelerator which has a portion disposed tangentially to the cyclotron, is described. Means are provided to transfer particles from the cyclotron to the ring accelerator including a magnetic deflector within the cyclotron, a magnetic shield between the ring accelerator and the cyclotron, and a magnetic inflector within the ring accelerator.

  4. Using the Fast Fourier Transform to Accelerate the Computational Search for RNA Conformational Switches

    PubMed Central

    Senter, Evan; Sheikh, Saad; Dotu, Ivan; Ponty, Yann; Clote, Peter

    2012-01-01

    Using complex roots of unity and the Fast Fourier Transform, we design a new thermodynamics-based algorithm, FFTbor, that computes the Boltzmann probability that secondary structures differ by base pairs from an arbitrary initial structure of a given RNA sequence. The algorithm, which runs in quartic time and quadratic space , is used to determine the correlation between kinetic folding speed and the ruggedness of the energy landscape, and to predict the location of riboswitch expression platform candidates. A web server is available at http://bioinformatics.bc.edu/clotelab/FFTbor/. PMID:23284639

  5. Development and evaluation of accelerated drug release testing methods for a matrix-type intravaginal ring.

    PubMed

    Externbrink, Anna; Eggenreich, Karin; Eder, Simone; Mohr, Stefan; Nickisch, Klaus; Klein, Sandra

    2017-01-01

    Accelerated drug release testing is a valuable quality control tool for long-acting non-oral extended release formulations. Currently, several intravaginal ring candidates designed for the long-term delivery of steroids or anti-infective drugs are being in the developing pipeline. The present article addresses the demand for accelerated drug release methods for these formulations. We describe the development and evaluation of accelerated release methods for a steroid releasing matrix-type intravaginal ring. The drug release properties of the formulation were evaluated under real-time and accelerated test conditions. Under real-time test conditions drug release from the intravaginal ring was strongly affected by the steroid solubility in the release medium. Under sufficient sink conditions that were provided in release media containing surfactants drug release was Fickian diffusion driven. Both temperature and hydro-organic dissolution media were successfully employed to accelerate drug release from the formulation. Drug release could be further increased by combining the temperature effect with the application of a hydro-organic release medium. The formulation continued to exhibit a diffusion controlled release kinetic under the investigated accelerated conditions. Moreover, the accelerated methods were able to differentiate between different prototypes of the intravaginal ring that exhibited different release profiles under real-time test conditions. Overall, the results of the present study indicate that both temperature and hydro-organic release media are valid parameters for accelerating drug release from the intravaginal ring. Variation of either a single or both parameters yielded release profiles that correlated well with real-time release. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Primakoff Prize Talk: The Search for Dark Sectors

    NASA Astrophysics Data System (ADS)

    Essig, Rouven

    2015-04-01

    Dark sectors, consisting of new, light, weakly-coupled particles that do not interact with the known strong, weak, or electromagnetic forces, are a particularly interesting possibility for new physics. Nature may contain numerous dark sectors, each with their own beautiful structure, distinct particles, and forces. Examples of dark sector particles include dark photons, axions, axion-like particles, and dark matter. In many cases, the exploration of dark sectors can proceed with existing facilities and comparatively modest experiments. This talk summarizes the physics motivation for dark sectors and the exciting opportunities for experimental exploration. Particular emphasis will be given to the search for dark photons, the mediators of a broken dark U(1) gauge theory that kinetically mixes with the Standard Model hypercharge, with masses in the MeV-to-GeV range. Experimental searches include low-energy e+e- colliders, new and old high-intensity fixed-target experiments, and high-energy colliders. The talk will highlight the APEX and HPS experiments at Jefferson Lab, which are pioneering, low-cost experiments to search for dark photons in fixed target electroproduction. Over the next few years, they have the potential for a transformative discovery.

  7. Programming and Runtime Support to Blaze FPGA Accelerator Deployment at Datacenter Scale

    PubMed Central

    Huang, Muhuan; Wu, Di; Yu, Cody Hao; Fang, Zhenman; Interlandi, Matteo; Condie, Tyson; Cong, Jason

    2017-01-01

    With the end of CPU core scaling due to dark silicon limitations, customized accelerators on FPGAs have gained increased attention in modern datacenters due to their lower power, high performance and energy efficiency. Evidenced by Microsoft’s FPGA deployment in its Bing search engine and Intel’s 16.7 billion acquisition of Altera, integrating FPGAs into datacenters is considered one of the most promising approaches to sustain future datacenter growth. However, it is quite challenging for existing big data computing systems—like Apache Spark and Hadoop—to access the performance and energy benefits of FPGA accelerators. In this paper we design and implement Blaze to provide programming and runtime support for enabling easy and efficient deployments of FPGA accelerators in datacenters. In particular, Blaze abstracts FPGA accelerators as a service (FaaS) and provides a set of clean programming APIs for big data processing applications to easily utilize those accelerators. Our Blaze runtime implements an FaaS framework to efficiently share FPGA accelerators among multiple heterogeneous threads on a single node, and extends Hadoop YARN with accelerator-centric scheduling to efficiently share them among multiple computing tasks in the cluster. Experimental results using four representative big data applications demonstrate that Blaze greatly reduces the programming efforts to access FPGA accelerators in systems like Apache Spark and YARN, and improves the system throughput by 1.7 × to 3× (and energy efficiency by 1.5× to 2.7×) compared to a conventional CPU-only cluster. PMID:28317049

  8. Accelerated Reader and Its Effect on Fifth-Grade Students' Reading Comprehension

    ERIC Educational Resources Information Center

    Nichols, Jan Shelton

    2013-01-01

    Schools in the United States have been using the Accelerated Reader (AR) program since the mid-1980s. A search of the literature related to the effectiveness of the AR program revealed that many of the studies were conducted more than a decade ago, and a large number of those studies failed to utilize a control group to provide comparative data.…

  9. One-calibrant kinetic calibration for on-site water sampling with solid-phase microextraction.

    PubMed

    Ouyang, Gangfeng; Cui, Shufen; Qin, Zhipei; Pawliszyn, Janusz

    2009-07-15

    The existing solid-phase microextraction (SPME) kinetic calibration technique, using the desorption of the preloaded standards to calibrate the extraction of the analytes, requires that the physicochemical properties of the standard should be similar to those of the analyte, which limited the application of the technique. In this study, a new method, termed the one-calibrant kinetic calibration technique, which can use the desorption of a single standard to calibrate all extracted analytes, was proposed. The theoretical considerations were validated by passive water sampling in laboratory and rapid water sampling in the field. To mimic the variety of the environment, such as temperature, turbulence, and the concentration of the analytes, the flow-through system for the generation of standard aqueous polycyclic aromatic hydrocarbons (PAHs) solution was modified. The experimental results of the passive samplings in the flow-through system illustrated that the effect of the environmental variables was successfully compensated with the kinetic calibration technique, and all extracted analytes can be calibrated through the desorption of a single calibrant. On-site water sampling with rotated SPME fibers also illustrated the feasibility of the new technique for rapid on-site sampling of hydrophobic organic pollutants in water. This technique will accelerate the application of the kinetic calibration method and also will be useful for other microextraction techniques.

  10. Search for Hidden Particles (SHiP): a new experiment proposal

    NASA Astrophysics Data System (ADS)

    De Lellis, G.

    2015-06-01

    Searches for new physics with accelerators are being performed at the LHC, looking for high massive particles coupled to matter with ordinary strength. We propose a new experimental facility meant to search for very weakly coupled particles in the few GeV mass domain. The existence of such particles, foreseen in different theoretical models beyond the Standard Model, is largely unexplored from the experimental point of view. A beam dump facility, built at CERN in the north area, using 400 GeV protons is a copious factory of charmed hadrons and could be used to probe the existence of such particles. The beam dump is also an ideal source of tau neutrinos, the less known particle in the Standard Model. In particular, tau anti-neutrinos have not been observed so far. We therefore propose an experiment to search for hidden particles and study tau neutrino physics at the same time.

  11. Kinetics of drug decomposition. Part XXXVI. Stability of 10-(1'-methyl-4'-piperazinylpropyl)-phenothiazine derivatives on the grounds of kinetics of thermal degradation and Hammett equation.

    PubMed

    Pawelczyk, E; Marciniec, B; Matlak, B

    1975-01-01

    Thermal degradation of aqueous and buffered solutions of perazine, prochlorperazine, trifluoperazine, thioproperazine, thiethylperazine and butaperazine salts was examined by kinetic method using an accelerated testing of pharmaceutical preparations. The order, rate constants and activation parameters (Q100, E, delta H not equal to, delta S not equal to, delta G not equal to ) of the reaction given were discussed. The predicted stability of the examined derivatives was compared on the grounds of a calculated time t10% and K293 kappa. A dependence between the stability and kind of substituent in the C2 positions was discussed in terms of the Hammett equation.

  12. Defocusing beam line design for an irradiation facility at the TAEA SANAEM Proton Accelerator Facility

    NASA Astrophysics Data System (ADS)

    Gencer, A.; Demirköz, B.; Efthymiopoulos, I.; Yiğitoğlu, M.

    2016-07-01

    Electronic components must be tested to ensure reliable performance in high radiation environments such as Hi-Limu LHC and space. We propose a defocusing beam line to perform proton irradiation tests in Turkey. The Turkish Atomic Energy Authority SANAEM Proton Accelerator Facility was inaugurated in May 2012 for radioisotope production. The facility has also an R&D room for research purposes. The accelerator produces protons with 30 MeV kinetic energy and the beam current is variable between 10 μA and 1.2 mA. The beam kinetic energy is suitable for irradiation tests, however the beam current is high and therefore the flux must be lowered. We plan to build a defocusing beam line (DBL) in order to enlarge the beam size, reduce the flux to match the required specifications for the irradiation tests. Current design includes the beam transport and the final focusing magnets to blow up the beam. Scattering foils and a collimator is placed for the reduction of the beam flux. The DBL is designed to provide fluxes between 107 p /cm2 / s and 109 p /cm2 / s for performing irradiation tests in an area of 15.4 cm × 21.5 cm. The facility will be the first irradiation facility of its kind in Turkey.

  13. Self-optimized construction of transition rate matrices from accelerated atomistic simulations with Bayesian uncertainty quantification

    NASA Astrophysics Data System (ADS)

    Swinburne, Thomas D.; Perez, Danny

    2018-05-01

    A massively parallel method to build large transition rate matrices from temperature-accelerated molecular dynamics trajectories is presented. Bayesian Markov model analysis is used to estimate the expected residence time in the known state space, providing crucial uncertainty quantification for higher-scale simulation schemes such as kinetic Monte Carlo or cluster dynamics. The estimators are additionally used to optimize where exploration is performed and the degree of temperature acceleration on the fly, giving an autonomous, optimal procedure to explore the state space of complex systems. The method is tested against exactly solvable models and used to explore the dynamics of C15 interstitial defects in iron. Our uncertainty quantification scheme allows for accurate modeling of the evolution of these defects over timescales of several seconds.

  14. Acceleration through passive destabilization: protein folding in a weak hydrophobic environment

    NASA Astrophysics Data System (ADS)

    Jewett, Andrew; Baumketner, Andrij; Shea, Joan-Emma

    2004-03-01

    The GroEL chaperonin is a biomolecule which assists the folding of an extremely diverse range of proteins in Eubacteria. Some proteins undergo many rounds of ATP-regulated binding and dissociation from GroEL/ES before folding. It has been proposed that transient stress from ATP-regulated binding and release from GroEL/ES frees frustrated proteins from misfolded conformations. However recent evidence suggests that chaperonin-accelerated protein folding can take place entirely within a mutated GroEL+ES cavity that is unable to open and release the protein. Using molecular dynamics, we demonstrate that static confinement within a weakly hydrophobic (attractive) cavity (similar to the interior of the cavity formed by the GroEL+ES complex) is sufficient to significantly accelerate the folding of a highly frustrated protein-like heteropolymer. Our frustrated molecule benifits kinetically from a static hydrophobic environment that destabilizes misfolded conformations. This may shed light on the mechanisms used by other chaperones which do not depend on ATP.

  15. A cellular automata model for traffic flow based on kinetics theory, vehicles capabilities and driver reactions

    NASA Astrophysics Data System (ADS)

    Guzmán, H. A.; Lárraga, M. E.; Alvarez-Icaza, L.; Carvajal, J.

    2018-02-01

    In this paper, a reliable cellular automata model oriented to faithfully reproduce deceleration and acceleration according to realistic reactions of drivers, when vehicles with different deceleration capabilities are considered is presented. The model focuses on describing complex traffic phenomena by coding in its rules the basic mechanisms of drivers behavior, vehicles capabilities and kinetics, while preserving simplicity. In particular, vehiclés kinetics is based on uniform accelerated motion, rather than in impulsive accelerated motion as in most existing CA models. Thus, the proposed model calculates in an analytic way three safe preserving distances to determine the best action a follower vehicle can take under a worst case scenario. Besides, the prediction analysis guarantees that under the proper assumptions, collision between vehicles may not happen at any future time. Simulations results indicate that all interactions of heterogeneous vehicles (i.e., car-truck, truck-car, car-car and truck-truck) are properly reproduced by the model. In addition, the model overcomes one of the major limitations of CA models for traffic modeling: the inability to perform smooth approach to slower or stopped vehicles. Moreover, the model is also capable of reproducing most empirical findings including the backward speed of the downstream front of the traffic jam, and different congested traffic patterns induced by a system with open boundary conditions with an on-ramp. Like most CA models, integer values are used to make the model run faster, which makes the proposed model suitable for real time traffic simulation of large networks.

  16. Correlation between X-ray flux and rotational acceleration in Vela X-1

    NASA Technical Reports Server (NTRS)

    Deeter, J. E.; Boynton, P. E.; Shibazaki, N.; Hayakawa, S.; Nagase, F.

    1989-01-01

    The results of a search for correlations between X-ray flux and angular acceleration for the accreting binary pulsar Vela X-1 are presented. Results are based on data obtained with the Hakucho satellite during the interval 1982 to 1984. In undertaking this correlation analysis, it was necessary to modify the usual statistical method to deal with conditions imposed by generally unavoidable satellite observing constraints, most notably a mismatch in sampling between the two variables. The results are suggestive of a correlation between flux and the absolute value of the angular acceleration, at a significance level of 96 percent. The implications of the methods and results for future observations and analysis are discussed.

  17. Nonlinear Monte Carlo model of superdiffusive shock acceleration with magnetic field amplification

    NASA Astrophysics Data System (ADS)

    Bykov, Andrei M.; Ellison, Donald C.; Osipov, Sergei M.

    2017-03-01

    Fast collisionless shocks in cosmic plasmas convert their kinetic energy flow into the hot downstream thermal plasma with a substantial fraction of energy going into a broad spectrum of superthermal charged particles and magnetic fluctuations. The superthermal particles can penetrate into the shock upstream region producing an extended shock precursor. The cold upstream plasma flow is decelerated by the force provided by the superthermal particle pressure gradient. In high Mach number collisionless shocks, efficient particle acceleration is likely coupled with turbulent magnetic field amplification (MFA) generated by the anisotropic distribution of accelerated particles. This anisotropy is determined by fast particle transport, making the problem strongly nonlinear and multiscale. Here, we present a nonlinear Monte Carlo model of collisionless shock structure with superdiffusive propagation of high-energy Fermi accelerated particles coupled to particle acceleration and MFA, which affords a consistent description of strong shocks. A distinctive feature of the Monte Carlo technique is that it includes the full angular anisotropy of the particle distribution at all precursor positions. The model reveals that the superdiffusive transport of energetic particles (i.e., Lévy-walk propagation) generates a strong quadruple anisotropy in the precursor particle distribution. The resultant pressure anisotropy of the high-energy particles produces a nonresonant mirror-type instability that amplifies compressible wave modes with wavelengths longer than the gyroradii of the highest-energy protons produced by the shock.

  18. Combined experimental and numerical kinetic characterization of NR vulcanized with sulphur, N terbutyl, 2 benzothiazylsulphenamide and N,N diphenyl guanidine

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Milani, G., E-mail: gabriele.milani@polimi.it; Hanel, T.; Donetti, R.

    2016-06-08

    The paper presents the final results of a comprehensive experimental and numerical analysis aimed at deeply investigating the behavior of Natural Rubber (NR) vulcanized with sulphur in presence of different accelerators during standard rheometer tests. NR in presence of sulphur and two different accelerators (DPG and TBBS) in various concentrations is investigated, changing the curing temperature in the range 150-180°C and obtaining rheometer curves with a step of 10°C. Sulphur-TBBS concentrations considered are 1-1, 1-3, 3-3 and 3-1, with DPG at 1-4 phr respectively. A total of 48 experimental rheometer curves is so obtained. To fit experimental data, the generalmore » reaction scheme proposed by Han and co-workers for vulcanized sulphur NR is re-adapted and suitably modified taking into account the single contributions of the different accelerators. Chain reactions initiated by the formation of macro-compounds responsible for the formation of the unmatured crosslinked polymer are accounted for. In presence of two accelerators, reactions are assumed to proceed in parallel, making the practically effective hypothesis that there is no interaction between the two accelerators. From the simplified kinetic scheme adopted, a closed form solution is found for the crosslink density, with the only limitation that the induction period is excluded from computations. For each experimented case on the same blend, reaction kinetic constants provided by the model are utilized to deduce their trend in the Arrhenius space, also outside the temperature range inspected. Rather close linearity is found in the majority of the cases. A comparative analysis is carefully conducted among the constants at the different concentrations of S, TBBS and DPG investigated, allowing a prediction of curing behavior at any vulcanization temperature and with concentrations not experimentally tested, without the need of addition costly experimentation.« less

  19. Combined experimental and numerical kinetic characterization of NR vulcanized with sulphur, N terbutyl, 2 benzothiazylsulphenamide and N,N diphenyl guanidine

    NASA Astrophysics Data System (ADS)

    Milani, G.; Hanel, T.; Donetti, R.; Milani, F.

    2016-06-01

    The paper presents the final results of a comprehensive experimental and numerical analysis aimed at deeply investigating the behavior of Natural Rubber (NR) vulcanized with sulphur in presence of different accelerators during standard rheometer tests. NR in presence of sulphur and two different accelerators (DPG and TBBS) in various concentrations is investigated, changing the curing temperature in the range 150-180°C and obtaining rheometer curves with a step of 10°C. Sulphur-TBBS concentrations considered are 1-1, 1-3, 3-3 and 3-1, with DPG at 1-4 phr respectively. A total of 48 experimental rheometer curves is so obtained. To fit experimental data, the general reaction scheme proposed by Han and co-workers for vulcanized sulphur NR is re-adapted and suitably modified taking into account the single contributions of the different accelerators. Chain reactions initiated by the formation of macro-compounds responsible for the formation of the unmatured crosslinked polymer are accounted for. In presence of two accelerators, reactions are assumed to proceed in parallel, making the practically effective hypothesis that there is no interaction between the two accelerators. From the simplified kinetic scheme adopted, a closed form solution is found for the crosslink density, with the only limitation that the induction period is excluded from computations. For each experimented case on the same blend, reaction kinetic constants provided by the model are utilized to deduce their trend in the Arrhenius space, also outside the temperature range inspected. Rather close linearity is found in the majority of the cases. A comparative analysis is carefully conducted among the constants at the different concentrations of S, TBBS and DPG investigated, allowing a prediction of curing behavior at any vulcanization temperature and with concentrations not experimentally tested, without the need of addition costly experimentation.

  20. Algorithm for Search and Recovery of the Vertex of Decay in the Hypernuclear Experiment NIS-GIBS at Dubna Nuclotron

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Korotkova, Anna M.; Lukstins, Juris

    2010-01-05

    Search of the decay vertex is an important part of the hypernuclear experiment, carried out of the Dubna nuclotron accelerator. The decay vertex is reconstructed from data from two sets of proportional chambers. The distribution of the vertex of decay of the hypernucleus allows to measure the lifetime of the hypernuclei. Algorithm for searches and automatically calculates the decay vertex has been written.

  1. The CHASE laboratory search for chameleon dark energy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Steffen, Jason H.; /Fermilab

    2010-11-01

    A scalar field is a favorite candidate for the particle responsible for dark energy. However, few theoretical means exist that can simultaneously explain the observed acceleration of the Universe and evade tests of gravity. The chameleon mechanism, whereby the properties of a particle depend upon the local environment, is one possible avenue. We present the results of the Chameleon Afterglow Search (CHASE) experiment, a laboratory probe for chameleon dark energy. CHASE marks a significant improvement other searches for chameleons both in terms of its sensitivity to the photon/chameleon coupling as well as its sensitivity to the classes of chameleon darkmore » energy models and standard power-law models. Since chameleon dark energy is virtually indistinguishable from a cosmological constant, CHASE tests dark energy models in a manner not accessible to astronomical surveys.« less

  2. MAGNETIC-ISLAND CONTRACTION AND PARTICLE ACCELERATION IN SIMULATED ERUPTIVE SOLAR FLARES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Guidoni, S. E.; DeVore, C. R.; Karpen, J. T.

    The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gainsmore » in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magnetohydrodynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions.« less

  3. Magnetic-Island Contraction and Particle Acceleration in Simulated Eruptive Solar Flares

    NASA Technical Reports Server (NTRS)

    Guidoni, S. E.; Devore, C. R.; Karpen, J. T.; Lynch, B. J.

    2016-01-01

    The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gains in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magneto hydro dynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions.

  4. Search for Dark Photons Produced in 13 TeV pp Collisions.

    PubMed

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Blusk, S; Bocci, V; Boettcher, T; Bondar, A; Bondar, N; Bordyuzhin, I; Borghi, S; Borisyak, M; Borsato, M; Bossu, F; Boubdir, M; Bowcock, T J V; Bowen, E; Bozzi, C; Braun, S; Britton, T; Brodzicka, J; Brundu, D; Buchanan, E; Burr, C; Bursche, A; Buytaert, J; Byczynski, W; Cadeddu, S; Cai, H; Calabrese, R; Calladine, R; Calvi, M; Calvo Gomez, M; Camboni, A; Campana, P; Campora Perez, D H; Capriotti, L; Carbone, A; Carboni, G; Cardinale, R; Cardini, A; Carniti, P; Carson, L; Carvalho Akiba, K; Casse, G; Cassina, L; Cattaneo, M; Cavallero, G; Cenci, R; Chamont, D; Chapman, M G; Charles, M; Charpentier, Ph; Chatzikonstantinidis, G; Chefdeville, M; Chen, S; Cheung, S F; Chitic, S-G; Chobanova, V; Chrzaszcz, M; Chubykin, A; Ciambrone, P; Cid Vidal, X; Ciezarek, G; Clarke, P E L; Clemencic, M; Cliff, H V; Closier, J; Cogan, J; Cogneras, E; Cogoni, V; Cojocariu, L; Collins, P; Colombo, T; Comerma-Montells, A; Contu, A; Cook, A; Coombs, G; Coquereau, S; Corti, G; Corvo, M; Costa Sobral, C M; Couturier, B; Cowan, G A; Craik, D C; Crocombe, A; Cruz Torres, M; Currie, R; D'Ambrosio, C; Da Cunha Marinho, F; Dall'Occo, E; Dalseno, J; Davis, A; De Aguiar Francisco, O; De Capua, S; De Cian, M; De Miranda, J M; De Paula, L; De Serio, M; De Simone, P; Dean, C T; Decamp, D; Del Buono, L; Dembinski, H-P; Demmer, M; Dendek, A; Derkach, D; Deschamps, O; Dettori, F; Dey, B; Di Canto, A; Di Nezza, P; Dijkstra, H; Dordei, F; Dorigo, M; Dosil Suárez, A; Douglas, L; Dovbnya, A; Dreimanis, K; Dufour, L; Dujany, G; Durante, P; Dzhelyadin, R; Dziewiecki, M; Dziurda, A; Dzyuba, A; Easo, S; Ebert, M; Egede, U; Egorychev, V; Eidelman, S; Eisenhardt, S; Eitschberger, U; Ekelhof, R; Eklund, L; Ely, S; Esen, S; Evans, H M; Evans, T; Falabella, A; Farley, N; Farry, S; Fazzini, D; Federici, L; Ferguson, D; Fernandez, G; Fernandez Declara, P; Fernandez Prieto, A; Ferrari, F; Ferreira Rodrigues, F; Ferro-Luzzi, M; Filippov, S; Fini, R A; Fiorini, M; Firlej, M; Fitzpatrick, C; Fiutowski, T; Fleuret, F; Fohl, K; Fontana, M; 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Morris, A B; Mountain, R; Muheim, F; Mulder, M; Müller, D; Müller, J; Müller, K; Müller, V; Naik, P; Nakada, T; Nandakumar, R; Nandi, A; Nasteva, I; Needham, M; Neri, N; Neubert, S; Neufeld, N; Neuner, M; Nguyen, T D; Nguyen-Mau, C; Nieswand, S; Niet, R; Nikitin, N; Nikodem, T; Nogay, A; O'Hanlon, D P; Oblakowska-Mucha, A; Obraztsov, V; Ogilvy, S; Oldeman, R; Onderwater, C J G; Ossowska, A; Otalora Goicochea, J M; Owen, P; Oyanguren, A; Pais, P R; Palano, A; Palutan, M; Papanestis, A; Pappagallo, M; Pappalardo, L L; Parker, W; Parkes, C; Passaleva, G; Pastore, A; Patel, M; Patrignani, C; Pearce, A; Pellegrino, A; Penso, G; Pepe Altarelli, M; Perazzini, S; Perret, P; Pescatore, L; Petridis, K; Petrolini, A; Petrov, A; Petruzzo, M; Picatoste Olloqui, E; Pietrzyk, B; Pikies, M; Pinci, D; Pisani, F; Pistone, A; Piucci, A; Placinta, V; Playfer, S; Plo Casasus, M; Polci, F; Poli Lener, M; Poluektov, A; Polyakov, I; Polycarpo, E; Pomery, G J; Ponce, S; Popov, A; Popov, D; Poslavskii, S; Potterat, C; Price, E; Prisciandaro, J; Prouve, C; Pugatch, V; Puig Navarro, A; Pullen, H; Punzi, G; Qian, W; Quagliani, R; Quintana, B; Rachwal, B; Rademacker, J H; Rama, M; Ramos Pernas, M; Rangel, M S; Raniuk, I; Ratnikov, F; Raven, G; Ravonel Salzgeber, M; Reboud, M; Redi, F; Reichert, S; Dos Reis, A C; Remon Alepuz, C; Renaudin, V; Ricciardi, S; Richards, S; Rihl, M; Rinnert, K; Rives Molina, V; Robbe, P; Robert, A; Rodrigues, A B; Rodrigues, E; Rodriguez Lopez, J A; Rogozhnikov, A; Roiser, S; Rollings, A; Romanovskiy, V; Romero Vidal, A; Ronayne, J W; Rotondo, M; Rudolph, M S; Ruf, T; Ruiz Valls, P; Ruiz Vidal, J; Saborido Silva, J J; Sadykhov, E; Sagidova, N; Saitta, B; Salustino Guimaraes, V; Sanchez Mayordomo, C; Sanmartin Sedes, B; Santacesaria, R; Santamarina Rios, C; Santimaria, M; Santovetti, E; Sarpis, G; Sarti, A; Satriano, C; Satta, A; Saunders, D M; Savrina, D; Schael, S; Schellenberg, M; Schiller, M; Schindler, H; Schmelling, M; Schmelzer, T; Schmidt, B; Schneider, O; Schopper, A; Schreiner, H F; Schubiger, M; Schune, M-H; Schwemmer, R; Sciascia, B; Sciubba, A; Semennikov, A; Sepulveda, E S; Sergi, A; Serra, N; Serrano, J; Sestini, L; Seyfert, P; Shapkin, M; Shapoval, I; Shcheglov, Y; Shears, T; Shekhtman, L; Shevchenko, V; Siddi, B G; Silva Coutinho, R; Silva de Oliveira, L; Simi, G; Simone, S; Sirendi, M; Skidmore, N; Skwarnicki, T; Smith, E; Smith, I T; Smith, J; Smith, M; Soares Lavra, L; Sokoloff, M D; Soler, F J P; Souza De Paula, B; Spaan, B; Spradlin, P; Sridharan, S; Stagni, F; Stahl, M; Stahl, S; Stefko, P; Stefkova, S; Steinkamp, O; Stemmle, S; Stenyakin, O; Stepanova, M; Stevens, H; Stone, S; Storaci, B; Stracka, S; Stramaglia, M E; Straticiuc, M; Straumann, U; Sun, J; Sun, L; Sutcliffe, W; Swientek, K; Syropoulos, V; Szumlak, T; Szymanski, M; T'Jampens, S; Tayduganov, A; Tekampe, T; Tellarini, G; Teubert, F; Thomas, E; van Tilburg, J; Tilley, M J; Tisserand, V; Tobin, M; Tolk, S; Tomassetti, L; Tonelli, D; Toriello, F; Tourinho Jadallah Aoude, R; Tournefier, E; Traill, M; Tran, M T; Tresch, M; Trisovic, A; Tsaregorodtsev, A; Tsopelas, P; Tully, A; Tuning, N; Ukleja, A; Usachov, A; Ustyuzhanin, A; Uwer, U; Vacca, C; Vagner, A; Vagnoni, V; Valassi, A; Valat, S; Valenti, G; Vazquez Gomez, R; Vazquez Regueiro, P; Vecchi, S; van Veghel, M; Velthuis, J J; Veltri, M; Veneziano, G; Venkateswaran, A; Verlage, T A; Vernet, M; Vesterinen, M; Viana Barbosa, J V; Viaud, B; Vieira, D; Vieites Diaz, M; Viemann, H; Vilasis-Cardona, X; Vitti, M; Volkov, V; Vollhardt, A; Voneki, B; Vorobyev, A; Vorobyev, V; Voß, C; de Vries, J A; Vázquez Sierra, C; Waldi, R; Wallace, C; Wallace, R; Walsh, J; Wang, J; Ward, D R; Wark, H M; Watson, N K; Websdale, D; Weiden, A; Weisser, C; Whitehead, M; Wicht, J; Wilkinson, G; Wilkinson, M; Williams, M; Williams, M P; Williams, M; Williams, T; Wilson, F F; Wimberley, J; Winn, M; Wishahi, J; Wislicki, W; Witek, M; Wormser, G; Wotton, S A; Wraight, K; Wyllie, K; Xie, Y; Xu, M; Xu, Z; Yang, Z; Yang, Z; Yao, Y; Yin, H; Yu, J; Yuan, X; Yushchenko, O; Zarebski, K A; Zavertyaev, M; Zhang, L; Zhang, Y; Zhelezov, A; Zheng, Y; Zhu, X; Zhukov, V; Zonneveld, J B; Zucchelli, S

    2018-02-09

    Searches are performed for both promptlike and long-lived dark photons, A^{'}, produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using A^{'}→μ^{+}μ^{-} decays and a data sample corresponding to an integrated luminosity of 1.6  fb^{-1} collected with the LHCb detector. The promptlike A^{'} search covers the mass range from near the dimuon threshold up to 70 GeV, while the long-lived A^{'} search is restricted to the low-mass region 214kinetic-mixing strength. The constraints placed on promptlike dark photons are the most stringent to date for the mass range 10.6search for long-lived dark photons is the first to achieve sensitivity using a displaced-vertex signature.

  5. Search for Dark Photons Produced in 13 TeV p p Collisions

    NASA Astrophysics Data System (ADS)

    Aaij, R.; Adeva, B.; Adinolfi, M.; Ajaltouni, Z.; Akar, S.; Albrecht, J.; Alessio, F.; Alexander, M.; Alfonso Albero, A.; Ali, S.; Alkhazov, G.; Alvarez Cartelle, P.; Alves, A. A.; Amato, S.; Amerio, S.; Amhis, Y.; An, L.; Anderlini, L.; Andreassi, G.; Andreotti, M.; Andrews, J. E.; Appleby, R. B.; Archilli, F.; d'Argent, P.; Arnau Romeu, J.; Artamonov, A.; Artuso, M.; Aslanides, E.; Atzeni, M.; Auriemma, G.; Baalouch, M.; Babuschkin, I.; Bachmann, S.; Back, J. J.; Badalov, A.; Baesso, C.; Baker, S.; Balagura, V.; Baldini, W.; Baranov, A.; Barlow, R. J.; Barschel, C.; Barsuk, S.; Barter, W.; Baryshnikov, F.; Batozskaya, V.; Battista, V.; Bay, A.; Beaucourt, L.; Beddow, J.; Bedeschi, F.; Bediaga, I.; Beiter, A.; Bel, L. J.; Beliy, N.; Bellee, V.; Belloli, N.; Belous, K.; Belyaev, I.; Ben-Haim, E.; Bencivenni, G.; Benson, S.; Beranek, S.; Berezhnoy, A.; Bernet, R.; Berninghoff, D.; Bertholet, E.; Bertolin, A.; Betancourt, C.; Betti, F.; Bettler, M.-O.; van Beuzekom, M.; Bezshyiko, Ia.; Bifani, S.; Billoir, P.; Birnkraut, A.; Bizzeti, A.; Bjørn, M.; Blake, T.; Blanc, F.; Blusk, S.; Bocci, V.; Boettcher, T.; Bondar, A.; Bondar, N.; Bordyuzhin, I.; Borghi, S.; Borisyak, M.; Borsato, M.; Bossu, F.; Boubdir, M.; Bowcock, T. J. V.; Bowen, E.; Bozzi, C.; Braun, S.; Britton, T.; Brodzicka, J.; Brundu, D.; Buchanan, E.; Burr, C.; Bursche, A.; Buytaert, J.; Byczynski, W.; Cadeddu, S.; Cai, H.; Calabrese, R.; Calladine, R.; Calvi, M.; Calvo Gomez, M.; Camboni, A.; Campana, P.; Campora Perez, D. H.; Capriotti, L.; Carbone, A.; Carboni, G.; Cardinale, R.; Cardini, A.; Carniti, P.; Carson, L.; Carvalho Akiba, K.; Casse, G.; Cassina, L.; Cattaneo, M.; Cavallero, G.; Cenci, R.; Chamont, D.; Chapman, M. G.; Charles, M.; Charpentier, Ph.; Chatzikonstantinidis, G.; Chefdeville, M.; Chen, S.; Cheung, S. F.; Chitic, S.-G.; Chobanova, V.; Chrzaszcz, M.; Chubykin, A.; Ciambrone, P.; Cid Vidal, X.; Ciezarek, G.; Clarke, P. E. L.; Clemencic, M.; Cliff, H. V.; Closier, J.; Cogan, J.; Cogneras, E.; Cogoni, V.; Cojocariu, L.; Collins, P.; Colombo, T.; Comerma-Montells, A.; Contu, A.; Cook, A.; Coombs, G.; Coquereau, S.; Corti, G.; Corvo, M.; Costa Sobral, C. M.; Couturier, B.; Cowan, G. A.; Craik, D. C.; Crocombe, A.; Cruz Torres, M.; Currie, R.; D'Ambrosio, C.; Da Cunha Marinho, F.; Dall'Occo, E.; Dalseno, J.; Davis, A.; De Aguiar Francisco, O.; De Capua, S.; De Cian, M.; De Miranda, J. M.; De Paula, L.; De Serio, M.; De Simone, P.; Dean, C. T.; Decamp, D.; Del Buono, L.; Dembinski, H.-P.; Demmer, M.; Dendek, A.; Derkach, D.; Deschamps, O.; Dettori, F.; Dey, B.; Di Canto, A.; Di Nezza, P.; Dijkstra, H.; Dordei, F.; Dorigo, M.; Dosil Suárez, A.; Douglas, L.; Dovbnya, A.; Dreimanis, K.; Dufour, L.; Dujany, G.; Durante, P.; Dzhelyadin, R.; Dziewiecki, M.; Dziurda, A.; Dzyuba, A.; Easo, S.; Ebert, M.; Egede, U.; Egorychev, V.; Eidelman, S.; Eisenhardt, S.; Eitschberger, U.; Ekelhof, R.; Eklund, L.; Ely, S.; Esen, S.; Evans, H. M.; Evans, T.; Falabella, A.; Farley, N.; Farry, S.; Fazzini, D.; Federici, L.; Ferguson, D.; Fernandez, G.; Fernandez Declara, P.; Fernandez Prieto, A.; Ferrari, F.; Ferreira Rodrigues, F.; Ferro-Luzzi, M.; Filippov, S.; Fini, R. A.; Fiorini, M.; Firlej, M.; Fitzpatrick, C.; Fiutowski, T.; Fleuret, F.; Fohl, K.; Fontana, M.; Fontanelli, F.; Forshaw, D. C.; Forty, R.; Franco Lima, V.; Frank, M.; Frei, C.; Fu, J.; Funk, W.; Furfaro, E.; Färber, C.; Gabriel, E.; Gallas Torreira, A.; Galli, D.; Gallorini, S.; Gambetta, S.; Gandelman, M.; Gandini, P.; Gao, Y.; Garcia Martin, L. M.; García Pardiñas, J.; Garra Tico, J.; Garrido, L.; Garsed, P. J.; Gascon, D.; Gaspar, C.; Gavardi, L.; Gazzoni, G.; Gerick, D.; Gersabeck, E.; Gersabeck, M.; Gershon, T.; Ghez, Ph.; Gianı, S.; Gibson, V.; Girard, O. G.; Giubega, L.; Gizdov, K.; Gligorov, V. V.; Golubkov, D.; Golutvin, A.; Gomes, A.; Gorelov, I. V.; Gotti, C.; Govorkova, E.; Grabowski, J. P.; Graciani Diaz, R.; Granado Cardoso, L. A.; Graugés, E.; Graverini, E.; Graziani, G.; Grecu, A.; Greim, R.; Griffith, P.; Grillo, L.; Gruber, L.; Gruberg Cazon, B. R.; Grünberg, O.; Gushchin, E.; Guz, Yu.; Gys, T.; Göbel, C.; Hadavizadeh, T.; Hadjivasiliou, C.; Haefeli, G.; Haen, C.; Haines, S. C.; Hamilton, B.; Han, X.; Hancock, T. H.; Hansmann-Menzemer, S.; Harnew, N.; Harnew, S. T.; Hasse, C.; Hatch, M.; He, J.; Hecker, M.; Heinicke, K.; Heister, A.; Hennessy, K.; Henrard, P.; Henry, L.; van Herwijnen, E.; Heß, M.; Hicheur, A.; Hill, D.; Hombach, C.; Hopchev, P. H.; Hu, W.; Huard, Z. C.; Hulsbergen, W.; Humair, T.; Hushchyn, M.; Hutchcroft, D.; Ibis, P.; Idzik, M.; Ilten, P.; Jacobsson, R.; Jalocha, J.; Jans, E.; Jawahery, A.; Jiang, F.; John, M.; Johnson, D.; Jones, C. R.; Joram, C.; Jost, B.; Jurik, N.; Kandybei, S.; Karacson, M.; Kariuki, J. M.; Karodia, S.; Kazeev, N.; Kecke, M.; Keizer, F.; Kelsey, M.; Kenzie, M.; Ketel, T.; Khairullin, E.; Khanji, B.; Khurewathanakul, C.; Kirn, T.; Klaver, S.; Klimaszewski, K.; Klimkovich, T.; Koliiev, S.; Kolpin, M.; Kopecna, R.; Koppenburg, P.; Kosmyntseva, A.; Kotriakhova, S.; Kozeiha, M.; Kravchuk, L.; Kreps, M.; Kress, F.; Krokovny, P.; Kruse, F.; Krzemien, W.; Kucewicz, W.; Kucharczyk, M.; Kudryavtsev, V.; Kuonen, A. K.; Kvaratskheliya, T.; Lacarrere, D.; Lafferty, G.; Lai, A.; Lanfranchi, G.; Langenbruch, C.; Latham, T.; Lazzeroni, C.; Le Gac, R.; Leflat, A.; Lefrançois, J.; Lefèvre, R.; Lemaitre, F.; Lemos Cid, E.; Leroy, O.; Lesiak, T.; Leverington, B.; Li, P.-R.; Li, T.; Li, Y.; Li, Z.; Likhomanenko, T.; Lindner, R.; Lionetto, F.; Lisovskyi, V.; Liu, X.; Loh, D.; Loi, A.; Longstaff, I.; Lopes, J. H.; Lucchesi, D.; Lucio Martinez, M.; Luo, H.; Lupato, A.; Luppi, E.; Lupton, O.; Lusiani, A.; Lyu, X.; Machefert, F.; Maciuc, F.; Macko, V.; Mackowiak, P.; Maddrell-Mander, S.; Maev, O.; Maguire, K.; Maisuzenko, D.; Majewski, M. W.; Malde, S.; Malecki, B.; Malinin, A.; Maltsev, T.; Manca, G.; Mancinelli, G.; Marangotto, D.; Maratas, J.; Marchand, J. F.; Marconi, U.; Marin Benito, C.; Marinangeli, M.; Marino, P.; Marks, J.; Martellotti, G.; Martin, M.; Martinelli, M.; Martinez Santos, D.; Martinez Vidal, F.; Massacrier, L. M.; Massafferri, A.; Matev, R.; Mathad, A.; Mathe, Z.; Matteuzzi, C.; Mauri, A.; Maurice, E.; Maurin, B.; Mazurov, A.; McCann, M.; McNab, A.; McNulty, R.; Mead, J. V.; Meadows, B.; Meaux, C.; Meier, F.; Meinert, N.; Melnychuk, D.; Merk, M.; Merli, A.; Michielin, E.; Milanes, D. A.; Millard, E.; Minard, M.-N.; Minzoni, L.; Mitzel, D. S.; Mogini, A.; Molina Rodriguez, J.; Mombächer, T.; Monroy, I. A.; Monteil, S.; Morandin, M.; Morello, M. J.; Morgunova, O.; Moron, J.; Morris, A. B.; Mountain, R.; Muheim, F.; Mulder, M.; Müller, D.; Müller, J.; Müller, K.; Müller, V.; Naik, P.; Nakada, T.; Nandakumar, R.; Nandi, A.; Nasteva, I.; Needham, M.; Neri, N.; Neubert, S.; Neufeld, N.; Neuner, M.; Nguyen, T. D.; Nguyen-Mau, C.; Nieswand, S.; Niet, R.; Nikitin, N.; Nikodem, T.; Nogay, A.; O'Hanlon, D. P.; Oblakowska-Mucha, A.; Obraztsov, V.; Ogilvy, S.; Oldeman, R.; Onderwater, C. J. G.; Ossowska, A.; Otalora Goicochea, J. M.; Owen, P.; Oyanguren, A.; Pais, P. R.; Palano, A.; Palutan, M.; Papanestis, A.; Pappagallo, M.; Pappalardo, L. L.; Parker, W.; Parkes, C.; Passaleva, G.; Pastore, A.; Patel, M.; Patrignani, C.; Pearce, A.; Pellegrino, A.; Penso, G.; Pepe Altarelli, M.; Perazzini, S.; Perret, P.; Pescatore, L.; Petridis, K.; Petrolini, A.; Petrov, A.; Petruzzo, M.; Picatoste Olloqui, E.; Pietrzyk, B.; Pikies, M.; Pinci, D.; Pisani, F.; Pistone, A.; Piucci, A.; Placinta, V.; Playfer, S.; Plo Casasus, M.; Polci, F.; Poli Lener, M.; Poluektov, A.; Polyakov, I.; Polycarpo, E.; Pomery, G. J.; Ponce, S.; Popov, A.; Popov, D.; Poslavskii, S.; Potterat, C.; Price, E.; Prisciandaro, J.; Prouve, C.; Pugatch, V.; Puig Navarro, A.; Pullen, H.; Punzi, G.; Qian, W.; Quagliani, R.; Quintana, B.; Rachwal, B.; Rademacker, J. H.; Rama, M.; Ramos Pernas, M.; Rangel, M. S.; Raniuk, I.; Ratnikov, F.; Raven, G.; Ravonel Salzgeber, M.; Reboud, M.; Redi, F.; Reichert, S.; dos Reis, A. C.; Remon Alepuz, C.; Renaudin, V.; Ricciardi, S.; Richards, S.; Rihl, M.; Rinnert, K.; Rives Molina, V.; Robbe, P.; Robert, A.; Rodrigues, A. B.; Rodrigues, E.; Rodriguez Lopez, J. A.; Rogozhnikov, A.; Roiser, S.; Rollings, A.; Romanovskiy, V.; Romero Vidal, A.; Ronayne, J. W.; Rotondo, M.; Rudolph, M. S.; Ruf, T.; Ruiz Valls, P.; Ruiz Vidal, J.; Saborido Silva, J. J.; Sadykhov, E.; Sagidova, N.; Saitta, B.; Salustino Guimaraes, V.; Sanchez Mayordomo, C.; Sanmartin Sedes, B.; Santacesaria, R.; Santamarina Rios, C.; Santimaria, M.; Santovetti, E.; Sarpis, G.; Sarti, A.; Satriano, C.; Satta, A.; Saunders, D. M.; Savrina, D.; Schael, S.; Schellenberg, M.; Schiller, M.; Schindler, H.; Schmelling, M.; Schmelzer, T.; Schmidt, B.; Schneider, O.; Schopper, A.; Schreiner, H. F.; Schubiger, M.; Schune, M.-H.; Schwemmer, R.; Sciascia, B.; Sciubba, A.; Semennikov, A.; Sepulveda, E. S.; Sergi, A.; Serra, N.; Serrano, J.; Sestini, L.; Seyfert, P.; Shapkin, M.; Shapoval, I.; Shcheglov, Y.; Shears, T.; Shekhtman, L.; Shevchenko, V.; Siddi, B. G.; Silva Coutinho, R.; Silva de Oliveira, L.; Simi, G.; Simone, S.; Sirendi, M.; Skidmore, N.; Skwarnicki, T.; Smith, E.; Smith, I. T.; Smith, J.; Smith, M.; Soares Lavra, l.; Sokoloff, M. D.; Soler, F. J. P.; Souza De Paula, B.; Spaan, B.; Spradlin, P.; Sridharan, S.; Stagni, F.; Stahl, M.; Stahl, S.; Stefko, P.; Stefkova, S.; Steinkamp, O.; Stemmle, S.; Stenyakin, O.; Stepanova, M.; Stevens, H.; Stone, S.; Storaci, B.; Stracka, S.; Stramaglia, M. E.; Straticiuc, M.; Straumann, U.; Sun, J.; Sun, L.; Sutcliffe, W.; Swientek, K.; Syropoulos, V.; Szumlak, T.; Szymanski, M.; T'Jampens, S.; Tayduganov, A.; Tekampe, T.; Tellarini, G.; Teubert, F.; Thomas, E.; van Tilburg, J.; Tilley, M. J.; Tisserand, V.; Tobin, M.; Tolk, S.; Tomassetti, L.; Tonelli, D.; Toriello, F.; Tourinho Jadallah Aoude, R.; Tournefier, E.; Traill, M.; Tran, M. T.; Tresch, M.; Trisovic, A.; Tsaregorodtsev, A.; Tsopelas, P.; Tully, A.; Tuning, N.; Ukleja, A.; Usachov, A.; Ustyuzhanin, A.; Uwer, U.; Vacca, C.; Vagner, A.; Vagnoni, V.; Valassi, A.; Valat, S.; Valenti, G.; Vazquez Gomez, R.; Vazquez Regueiro, P.; Vecchi, S.; van Veghel, M.; Velthuis, J. J.; Veltri, M.; Veneziano, G.; Venkateswaran, A.; Verlage, T. A.; Vernet, M.; Vesterinen, M.; Viana Barbosa, J. V.; Viaud, B.; Vieira, D.; Vieites Diaz, M.; Viemann, H.; Vilasis-Cardona, X.; Vitti, M.; Volkov, V.; Vollhardt, A.; Voneki, B.; Vorobyev, A.; Vorobyev, V.; Voß, C.; de Vries, J. A.; Vázquez Sierra, C.; Waldi, R.; Wallace, C.; Wallace, R.; Walsh, J.; Wang, J.; Ward, D. R.; Wark, H. M.; Watson, N. K.; Websdale, D.; Weiden, A.; Weisser, C.; Whitehead, M.; Wicht, J.; Wilkinson, G.; Wilkinson, M.; Williams, M.; Williams, M. P.; Williams, M.; Williams, T.; Wilson, F. F.; Wimberley, J.; Winn, M.; Wishahi, J.; Wislicki, W.; Witek, M.; Wormser, G.; Wotton, S. A.; Wraight, K.; Wyllie, K.; Xie, Y.; Xu, M.; Xu, Z.; Yang, Z.; Yang, Z.; Yao, Y.; Yin, H.; Yu, J.; Yuan, X.; Yushchenko, O.; Zarebski, K. A.; Zavertyaev, M.; Zhang, L.; Zhang, Y.; Zhelezov, A.; Zheng, Y.; Zhu, X.; Zhukov, V.; Zonneveld, J. B.; Zucchelli, S.; LHCb Collaboration

    2018-02-01

    Searches are performed for both promptlike and long-lived dark photons, A', produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using A'→μ+μ- decays and a data sample corresponding to an integrated luminosity of 1.6 fb-1 collected with the LHCb detector. The promptlike A' search covers the mass range from near the dimuon threshold up to 70 GeV, while the long-lived A' search is restricted to the low-mass region 214 kinetic-mixing strength. The constraints placed on promptlike dark photons are the most stringent to date for the mass range 10.6 search for long-lived dark photons is the first to achieve sensitivity using a displaced-vertex signature.

  6. Reverse Stability Kinetics of Meat Pigment Oxidation in Aqueous Extract from Fresh Beef.

    PubMed

    Frelka, John C; Phinney, David M; Wick, Macdonald P; Heldman, Dennis R

    2017-12-01

    The use of kinetic models is an evolving approach to describing quality changes in foods during processes, including storage. Previous studies indicate that the oxidation rate of myoglobin is accelerated under frozen storage conditions, a phenomenon termed reverse stability. The goal of this study was to develop a model for meat pigment oxidation to incorporate the phenomenon of reverse stability. In this investigation, the model system was an aqueous extract from beef which was stored under a range of temperatures, both unfrozen and frozen. The kinetic analysis showed that in unfrozen solutions, the temperature dependence of oxidation rate followed Arrhenius kinetics. However, under in frozen solutions the rate of oxidation increased with decreasing temperature until reaching a local maximum around -20 °C. The addition of NaCl to the model system increased oxidation rates at all temperatures, even above the initial freezing temperature. This observation suggests that this reaction is dependent on the ionic strength of the solution as well as temperature. The mechanism of this deviant kinetic behavior is not fully understood, but this study shows that the interplay of temperature and composition on the rate of oxidation of meat pigments is complicated and may involve multiple mechanisms. A better understanding of the kinetics of quality loss in a meat system allows for a re-examination of the current recommendations for frozen storage. The deviant kinetic behavior observed in this study indicates that the relationship between quality loss and temperature in a frozen food is not as simple as once thought. Product-specific recommendations could be implemented in the future that would allow for a decrease in energy consumption without a significant loss of quality. © 2017 Institute of Food Technologists®.

  7. ACL reconstruction with hamstring tendon autograft and accelerated brace-free rehabilitation: a systematic review of clinical outcomes

    PubMed Central

    van Melick, Nicky; van Mourik, Jan B A; Reijman, Max; van Rhijn, Lodewijk W

    2018-01-01

    Objective To investigate the clinical outcomes after hamstring tendon autograft ACL reconstruction (ACLR) with accelerated, brace-free rehabilitation. Design Systematic review according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Data sources Embase, MEDLINE Ovid, Web of Science, Cochrane CENTRAL and Google scholar from 1 January 1974 to 31 January 2017. Eligibility criteria for selecting studies Study designs reporting outcomes in adults after arthroscopic, primary ACLR with hamstring autograft and accelerated, brace-free rehabilitation. Results Twenty-four studies were included in the review. The clinical outcomes after hamstring tendon autograft ACLR with accelerated brace-free rehabilitation were the following: (1) early start of open kinetic exercises at 4 weeks in a limited range of motion (ROM, 90°−45°) and progressive concentric and eccentric exercises from 12 weeks did not alter outcomes, (2) gender and age did not influence clinical outcomes, (3) anatomical reconstructions showed better results than non-anatomical reconstructions, (4) there was no difference between single-bundle and double-bundle reconstructions, (5) femoral and tibial tunnel widening occurred, (6) hamstring tendons regenerated after harvest and (7) biological knowledge did not support return to sports at 4–6 months. Conclusions After hamstring tendon autograft ACLR with accelerated brace-free rehabilitation, clinical outcome is similar after single-bundle and double-bundle ACLR. Early start of open kinetic exercises at 4 weeks in a limited ROM (90°−45°) and progressive concentric and eccentric exercises from 12 weeks postsurgery do not alter clinical outcome. Further research should focus on achievement of best balance between graft loading and graft healing in the various rehabilitation phases after ACLR as well as on validated, criterion-based assessments for safe return to sports. Level of evidence Level 2b; therapeutic outcome studies

  8. Efficacy of low-level laser therapy in accelerating tooth movement, preventing relapse and managing acute pain during orthodontic treatment in humans: a systematic review.

    PubMed

    Sonesson, Mikael; De Geer, Emelie; Subraian, Jaqueline; Petrén, Sofia

    2016-07-07

    Recently low-level laser therapy (LLLT) has been proposed to improve orthodontic treatment. The aims of this systematic review were to investigate the scientific evidence to support applications of LLLT: (a) to accelerate tooth movement, (b) to prevent orthodontic relapse and (c) to modulate acute pain, during treatment with fixed appliances in children and young adults. To ensure a systematic literature approach, this systematic review was conducted to Goodman's four step model. Three databases were searched (Medline, Cochrane Controlled Clinical Trials Register and Scitation), using predetermined search terms. The quality of evidence was rated according to the GRADE system. The search identified 244 articles, 16 of which fulfilled the inclusion criteria: three on acceleration of tooth movement by LLLT and 13 on LLLT modulation of acute pain. No study on LLLT for prevention of relapse was identified. The selected studies reported promising results for LLLT; elevated acceleration of tooth movement and lower pain scores, than controls. With respect to method, there were wide variations in type of laser techniques. The quality of evidence supporting LLLT to accelerate orthodontic tooth movement is very low and low with respect to modulate acute pain. No studies met the inclusion criteria for evaluating LLLT to limit relapse. The results highlight the need for high quality research, with consistency in study design, to determine whether LLLT can enhance fixed appliance treatment in children and young adults.

  9. Covariant Uniform Acceleration

    NASA Astrophysics Data System (ADS)

    Friedman, Yaakov; Scarr, Tzvi

    2013-04-01

    We derive a 4D covariant Relativistic Dynamics Equation. This equation canonically extends the 3D relativistic dynamics equation , where F is the 3D force and p = m0γv is the 3D relativistic momentum. The standard 4D equation is only partially covariant. To achieve full Lorentz covariance, we replace the four-force F by a rank 2 antisymmetric tensor acting on the four-velocity. By taking this tensor to be constant, we obtain a covariant definition of uniformly accelerated motion. This solves a problem of Einstein and Planck. We compute explicit solutions for uniformly accelerated motion. The solutions are divided into four Lorentz-invariant types: null, linear, rotational, and general. For null acceleration, the worldline is cubic in the time. Linear acceleration covariantly extends 1D hyperbolic motion, while rotational acceleration covariantly extends pure rotational motion. We use Generalized Fermi-Walker transport to construct a uniformly accelerated family of inertial frames which are instantaneously comoving to a uniformly accelerated observer. We explain the connection between our approach and that of Mashhoon. We show that our solutions of uniformly accelerated motion have constant acceleration in the comoving frame. Assuming the Weak Hypothesis of Locality, we obtain local spacetime transformations from a uniformly accelerated frame K' to an inertial frame K. The spacetime transformations between two uniformly accelerated frames with the same acceleration are Lorentz. We compute the metric at an arbitrary point of a uniformly accelerated frame. We obtain velocity and acceleration transformations from a uniformly accelerated system K' to an inertial frame K. We introduce the 4D velocity, an adaptation of Horwitz and Piron s notion of "off-shell." We derive the general formula for the time dilation between accelerated clocks. We obtain a formula for the angular velocity of a uniformly accelerated object. Every rest point of K' is uniformly accelerated, and

  10. Analyzing radial acceleration with a smartphone acceleration sensor

    NASA Astrophysics Data System (ADS)

    Vogt, Patrik; Kuhn, Jochen

    2013-03-01

    This paper continues the sequence of experiments using the acceleration sensor of smartphones (for description of the function and the use of the acceleration sensor, see Ref. 1) within this column, in this case for analyzing the radial acceleration.

  11. Kinetic isotope effects and how to describe them

    PubMed Central

    Karandashev, Konstantin; Xu, Zhen-Hao; Meuwly, Markus; Vaníček, Jiří; Richardson, Jeremy O.

    2017-01-01

    We review several methods for computing kinetic isotope effects in chemical reactions including semiclassical and quantum instanton theory. These methods describe both the quantization of vibrational modes as well as tunneling and are applied to the ⋅H + H2 and ⋅H + CH4 reactions. The absolute rate constants computed with the semiclassical instanton method both using on-the-fly electronic structure calculations and fitted potential-energy surfaces are also compared directly with exact quantum dynamics results. The error inherent in the instanton approximation is found to be relatively small and similar in magnitude to that introduced by using fitted surfaces. The kinetic isotope effect computed by the quantum instanton is even more accurate, and although it is computationally more expensive, the efficiency can be improved by path-integral acceleration techniques. We also test a simple approach for designing potential-energy surfaces for the example of proton transfer in malonaldehyde. The tunneling splittings are computed, and although they are found to deviate from experimental results, the ratio of the splitting to that of an isotopically substituted form is in much better agreement. We discuss the strengths and limitations of the potential-energy surface and based on our findings suggest ways in which it can be improved. PMID:29282447

  12. Stochastic acceleration of electrons. I - Effects of collisions in solar flares

    NASA Technical Reports Server (NTRS)

    Hamilton, Russell J.; Petrosian, Vahe

    1992-01-01

    Stochastic acceleration of thermal electrons to nonrelativistic energies is studied under solar flare conditions. We show that, in turbulent regions, electron-whistler wave interactions can result in the acceleration of electrons in times comparable to or shorter than the Coulomb collision time. The kinetic equation describing the evolution of the electron energy distribution including stochastic acceleration by whistlers and energy loss via Coulomb interactions is solved for an initial thermal electron energy spectrum. In general, the shape of the resulting electron distributions are characterized by the energy E(c) where systematic energy gain by turbulence equals energy loss due to Coulomb collisions. For energies less than E(c), the spectra are steep (quasi-thermal) whereas above E(c), the spectra are power laws. We find that hard X-ray spectra computed using the electron distributions obtained from our numerical simulations are able to explain the complex spectral shapes and variations observed in impulsive hard X-ray bursts. In particular, we show that the gradual steepening observed by Lin et al. (1981) could be due to a systematic increase in the density of the plasma (due to evaporation) and the increasing importance of collisions instead of the appearance of a superhot thermal component.

  13. OpenFOAM Modeling of Particle Heating and Acceleration in Cold Spraying

    NASA Astrophysics Data System (ADS)

    Leitz, K.-H.; O'Sullivan, M.; Plankensteiner, A.; Kestler, H.; Sigl, L. S.

    2018-01-01

    In cold spraying, a powder material is accelerated and heated in the gas flow of a supersonic nozzle to velocities and temperatures that are sufficient to obtain cohesion of the particles to a substrate. The deposition efficiency of the particles is significantly determined by their velocity and temperature. Particle velocity correlates with the amount of kinetic energy that is converted to plastic deformation and thermal heating. The initial particle temperature significantly influences the mechanical properties of the particle. Velocity and temperature of the particles have nonlinear dependence on the pressure and temperature of the gas at the nozzle entrance. In this contribution, a simulation model based on the reactingParcelFoam solver of OpenFOAM is presented and applied for an analysis of particle velocity and temperature in the cold spray nozzle. The model combines a compressible description of the gas flow in the nozzle with a Lagrangian particle tracking. The predictions of the simulation model are verified based on an analytical description of the gas flow, the particle acceleration and heating in the nozzle. Based on experimental data, the drag model according to Plessis and Masliyah is identified to be best suited for OpenFOAM modeling particle heating and acceleration in cold spraying.

  14. Negative ion kinetics in RF glow discharges

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gottscho, R.A.; Gacbe, C.E.

    1986-04-01

    Using temporally and spatially resolved laser spectroscopy, the authors have determined the identities, approximate concentrations, effects on the local field, and kinetics of formation and loss of negative ions in RF discharges. CI/sup -/ and BCI/sub 3//sup -/ are the dominant negative ions found in low-frequency discharges through CI/sub 2/ and BCI/sub 3/, respectively. The electron affinity for CI is measured to be 3.6118 +- 0.0005 eV. Negative ion kinetics are strongly affected by application of the RF field. Formation of negative ions by attachment of slow electrons in RF discharges is governed by the extent and duration of electronmore » energy relaxation. Similarly, destruction of negative ions by collisional detachment and field extraction is dependent upon ion energy modulation. Thus, at low frequency, the anion density peaks at the beginning of the anodic and cathodic half-cycles after electrons have attached but before detachment and extraction have had time to occur. At higher frequencies, electrons have insufficient time to attach before they are reheated and the instantaneous anion density in the sheath is greatly reduced. When the negative ion density is comparable to the positive ion density, the plasma potential is observed to lie below the anode potential, double layers form between sheath and plasma, and anions and electrons are accelerated by large sheath fields to electrode surfaces.« less

  15. Fundamental electrode kinetics

    NASA Technical Reports Server (NTRS)

    Elder, J. P.

    1968-01-01

    Report presents the fundamentals of electrode kinetics and the methods used in evaluating the characteristic parameters of rapid-charge transfer processes at electrode-electrolyte interfaces. The concept of electrode kinetics is outlined, followed by the principles underlying the experimental techniques for the investigation of electrode kinetics.

  16. Body mass index kinetics around adiposity rebound in Anorexia nervosa: A case-control study.

    PubMed

    Neveu, Rémi; Neveu, Dorine; Carrier, Edouard; Ourrad, Nadia; Perroud, Alain; Nicolas, Alain

    2016-10-01

    Anorexia nervosa (AN) is associated with parameters involved in body mass index (BMI) regulation. Contrary to obesity, BMI kinetics around the adiposity rebound is not documented in AN. This study aimed at investigating which characteristics of BMI kinetics around the adiposity rebound are associated with AN. Multicentre case-control study with 101 inpatient women with AN onset after 10 years of age, and 101 healthy women, all free of overweight history and matched for age, level of education and fathers' socio-professional status. Age at adiposity rebound, pre- and post-adiposity rebound BMI velocities and accelerations (change in velocity over time) were estimated with linear mixed models using data recorded between 2 and 10 years of age. Patients had an earlier adiposity rebound (mean (standard deviation (SD)): 5.3 (1.3) vs 5.7 (1.1) years), a larger BMI at adiposity rebound (mean (SD): 15.3 [1] vs 14.9 (0.9) kg/m 2 ) and 29% lower BMI acceleration after adiposity rebound than controls. After adjustment, only BMI at adiposity rebound and BMI acceleration after adiposity rebound were associated with a higher risk of AN (Odds ratio [95% confidence interval]: 2.15 [1.41-3.46] for an increase of 1 kg/m 2 and 2.44 [1.56-4.02] for an increase of 0.1 kg/(m 2 *years 2 ) respectively). These two factors were not correlated in patients (r = 0.007, p = 0.96). A flattened evolution of BMI after adiposity rebound and higher BMI at adiposity rebound were associated with AN. Further prospective study is needed to confirm these findings. Copyright © 2016 European Society for Clinical Nutrition and Metabolism. Published by Elsevier Ltd. All rights reserved.

  17. Sarcomeric protein modification during adrenergic stress enhances cross-bridge kinetics and cardiac output

    PubMed Central

    Gresham, Kenneth S.; Mamidi, Ranganath; Li, Jiayang; Kwak, Hyerin

    2017-01-01

    Molecular adaptations to chronic neurohormonal stress, including sarcomeric protein cleavage and phosphorylation, provide a mechanism to increase ventricular contractility and enhance cardiac output, yet the link between sarcomeric protein modifications and changes in myocardial function remains unclear. To examine the effects of neurohormonal stress on posttranslational modifications of sarcomeric proteins, mice were administered combined α- and β-adrenergic receptor agonists (isoproterenol and phenylephrine, IPE) for 14 days using implantable osmotic pumps. In addition to significant cardiac hypertrophy and increased maximal ventricular pressure, IPE treatment accelerated pressure development and relaxation (74% increase in dP/dtmax and 14% decrease in τ), resulting in a 52% increase in cardiac output compared with saline (SAL)-treated mice. Accelerated pressure development was maintained when accounting for changes in heart rate and preload, suggesting that myocardial adaptations contribute to enhanced ventricular contractility. Ventricular myocardium isolated from IPE-treated mice displayed a significant reduction in troponin I (TnI) and myosin-binding protein C (MyBP-C) expression and a concomitant increase in the phosphorylation levels of the remaining TnI and MyBP-C protein compared with myocardium isolated from saline-treated control mice. Skinned myocardium isolated from IPE-treated mice displayed a significant acceleration in the rate of cross-bridge (XB) detachment (46% increase) and an enhanced magnitude of XB recruitment (43% increase) at submaximal Ca2+ activation compared with SAL-treated mice but unaltered myofilament Ca2+ sensitivity of force generation. These findings demonstrate that sarcomeric protein modifications during neurohormonal stress are molecular adaptations that enhance in vivo ventricular contractility through accelerated XB kinetics to increase cardiac output. NEW & NOTEWORTHY Posttranslational modifications to sarcomeric

  18. Sarcomeric protein modification during adrenergic stress enhances cross-bridge kinetics and cardiac output.

    PubMed

    Gresham, Kenneth S; Mamidi, Ranganath; Li, Jiayang; Kwak, Hyerin; Stelzer, Julian E

    2017-03-01

    Molecular adaptations to chronic neurohormonal stress, including sarcomeric protein cleavage and phosphorylation, provide a mechanism to increase ventricular contractility and enhance cardiac output, yet the link between sarcomeric protein modifications and changes in myocardial function remains unclear. To examine the effects of neurohormonal stress on posttranslational modifications of sarcomeric proteins, mice were administered combined α- and β-adrenergic receptor agonists (isoproterenol and phenylephrine, IPE) for 14 days using implantable osmotic pumps. In addition to significant cardiac hypertrophy and increased maximal ventricular pressure, IPE treatment accelerated pressure development and relaxation (74% increase in dP/d t max and 14% decrease in τ), resulting in a 52% increase in cardiac output compared with saline (SAL)-treated mice. Accelerated pressure development was maintained when accounting for changes in heart rate and preload, suggesting that myocardial adaptations contribute to enhanced ventricular contractility. Ventricular myocardium isolated from IPE-treated mice displayed a significant reduction in troponin I (TnI) and myosin-binding protein C (MyBP-C) expression and a concomitant increase in the phosphorylation levels of the remaining TnI and MyBP-C protein compared with myocardium isolated from saline-treated control mice. Skinned myocardium isolated from IPE-treated mice displayed a significant acceleration in the rate of cross-bridge (XB) detachment (46% increase) and an enhanced magnitude of XB recruitment (43% increase) at submaximal Ca 2+ activation compared with SAL-treated mice but unaltered myofilament Ca 2+ sensitivity of force generation. These findings demonstrate that sarcomeric protein modifications during neurohormonal stress are molecular adaptations that enhance in vivo ventricular contractility through accelerated XB kinetics to increase cardiac output. NEW & NOTEWORTHY Posttranslational modifications to sarcomeric

  19. Community Petascale Project for Accelerator Science and Simulation: Advancing Computational Science for Future Accelerators and Accelerator Technologies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Spentzouris, P.; /Fermilab; Cary, J.

    The design and performance optimization of particle accelerators are essential for the success of the DOE scientific program in the next decade. Particle accelerators are very complex systems whose accurate description involves a large number of degrees of freedom and requires the inclusion of many physics processes. Building on the success of the SciDAC-1 Accelerator Science and Technology project, the SciDAC-2 Community Petascale Project for Accelerator Science and Simulation (ComPASS) is developing a comprehensive set of interoperable components for beam dynamics, electromagnetics, electron cooling, and laser/plasma acceleration modelling. ComPASS is providing accelerator scientists the tools required to enable the necessarymore » accelerator simulation paradigm shift from high-fidelity single physics process modeling (covered under SciDAC1) to high-fidelity multiphysics modeling. Our computational frameworks have been used to model the behavior of a large number of accelerators and accelerator R&D experiments, assisting both their design and performance optimization. As parallel computational applications, the ComPASS codes have been shown to make effective use of thousands of processors. ComPASS is in the first year of executing its plan to develop the next-generation HPC accelerator modeling tools. ComPASS aims to develop an integrated simulation environment that will utilize existing and new accelerator physics modules with petascale capabilities, by employing modern computing and solver technologies. The ComPASS vision is to deliver to accelerator scientists a virtual accelerator and virtual prototyping modeling environment, with the necessary multiphysics, multiscale capabilities. The plan for this development includes delivering accelerator modeling applications appropriate for each stage of the ComPASS software evolution. Such applications are already being used to address challenging problems in accelerator design and optimization. The Com

  20. Accelerator mass spectrometry in biomedical research

    NASA Astrophysics Data System (ADS)

    Vogel, J. S.; Turteltaub, K. W.

    1994-06-01

    Biological effects occur in natural systems at chemical concentrations of parts per billion (1:10 9) or less. Affected biomolecules may be separable in only milligram or microgram quantities. Quantification at attomole sensitivity is needed to study these interactions. AMS measures isotope concentrations to parts per 10 13-15 on milligram-sized samples and is ideal for quantifying long-lived radioisotopic labels for tracing biochemical pathways in natural systems. 14C-AMS has now been coupled to a variety of organic separation and definition technologies. Our primary research investigates pharmacokinetics and genotoxicities of toxins and drugs at very low doses. Human subjects research using AMS includes nutrition, toxicity and elemental balance studies. 3H, 41Ca and 26Al are also traced by AMS for fundamental biochemical kinetic research. Expansion of biomedical AMS awaits further development of biochemical and accelerator technologies designed specifically for these applications.

  1. Effect of polypyrrole embedment on non-isothermal crystallization kinetics of poly (vinylidene fluoride-co-hexafluoropropylene)

    NASA Astrophysics Data System (ADS)

    Biswas, Swarup; Bhattacharya, S.

    2017-05-01

    Polypyrrole (PPy)/Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) blend is synthesized by in situ polymerization of pyrrole. FTIR confirms the formation of Polypyrrole (PPy) within PVDF-HFP matrices. Weight percentages of different components within composites are estimated by TGA. Detailed study of nucleation and kinetics at its melt condition under non-isothermal environment is done by the DSC measurement. The presence of PPy within the PVDF-HFP matrices accelerated the nucleation rate of the polymer.

  2. Dynamic Kinetic Resolution of Allylic Sulfoxides by Rh-Catalyzed Hydrogenation: A Combined Theoretical and Experimental Mechanistic Study

    PubMed Central

    Dornan, Peter K.; Kou, Kevin G. M.; Houk, K. N.; Dong, Vy M.

    2014-01-01

    A dynamic kinetic resolution (DKR) of allylic sulfoxides has been demonstrated by combining the Mislow [2,3]-sigmatropic rearrangement with catalytic asymmetric hydrogenation. The efficiency of our DKR was optimized by using low pressures of hydrogen gas to decrease the rate of hydrogenation relative to the rate of sigmatropic rearrangement. Kinetic studies reveal that the rhodium complex acts as a dual-role catalyst and accelerates the substrate racemization while catalyzing olefin hydrogenation. Scrambling experiments and theoretical modeling support a novel mode of sulfoxide racemization which occurs via a rhodium π-allyl intermediate in polar solvents. In non-polar solvents, however, the substrate racemization is primarily uncatalyzed. Computational studies suggest that the sulfoxide binds to rhodium via O–coordination throughout the catalytic cycle for hydrogenation. PMID:24350903

  3. Accelerators, Beams And Physical Review Special Topics - Accelerators And Beams

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Siemann, R.H.; /SLAC

    Accelerator science and technology have evolved as accelerators became larger and important to a broad range of science. Physical Review Special Topics - Accelerators and Beams was established to serve the accelerator community as a timely, widely circulated, international journal covering the full breadth of accelerators and beams. The history of the journal and the innovations associated with it are reviewed.

  4. Commnity Petascale Project for Accelerator Science And Simulation: Advancing Computational Science for Future Accelerators And Accelerator Technologies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Spentzouris, Panagiotis; /Fermilab; Cary, John

    The design and performance optimization of particle accelerators are essential for the success of the DOE scientific program in the next decade. Particle accelerators are very complex systems whose accurate description involves a large number of degrees of freedom and requires the inclusion of many physics processes. Building on the success of the SciDAC-1 Accelerator Science and Technology project, the SciDAC-2 Community Petascale Project for Accelerator Science and Simulation (ComPASS) is developing a comprehensive set of interoperable components for beam dynamics, electromagnetics, electron cooling, and laser/plasma acceleration modelling. ComPASS is providing accelerator scientists the tools required to enable the necessarymore » accelerator simulation paradigm shift from high-fidelity single physics process modeling (covered under SciDAC1) to high-fidelity multiphysics modeling. Our computational frameworks have been used to model the behavior of a large number of accelerators and accelerator R&D experiments, assisting both their design and performance optimization. As parallel computational applications, the ComPASS codes have been shown to make effective use of thousands of processors.« less

  5. Electron kinetic effects in atmosphere breakdown by an intense electromagnetic pulse.

    PubMed

    Solovyev, A A; Terekhin, V A; Tikhonchuk, V T; Altgilbers, L L

    1999-12-01

    A physical model is proposed for description of electron kinetics driven by a powerful electromagnetic pulse in the Earth's atmosphere. The model is based on a numerical solution to the Boltzmann kinetic equation for two groups of electrons. Slow electrons (with energies below a few keV) are described in a two-term approximation assuming a weak anisotropy of the electron distribution function. Fast electrons (with energies above a few keV) are described by a modified macroparticle method, taking into account the electron acceleration in the electric field, energy losses in the continuous deceleration approximation, and the multiple pitch angle scattering. The model is applied to a problem of the electric discharge in a nitrogen, which is preionized by an external gamma-ray source. It is shown that the runaway electrons have an important effect on the energy distribution of free electrons, and on the avalanche ionization rate. This mechanism might explain the observation of multiple lightning discharges observed in the Ivy-Mike thermonuclear test in the early 1950's.

  6. Search for CP Violation in Hyperon Decay: $$\\Xi^- / \\bar{\\Xi}^+$$ and $$\\Lambda / \\bar{\\Lambda}$$ (in French)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Leros, Nicolas

    2001-06-01

    The HyperCP(EB71) experiment, performed at the Fermi National Accelerator Laboratory in the United States, provides a primary search for direct OP violation in the decays ofmore » $$\\Xi^-/\\bar{\\Xi}^+$$ and $$\\Lambda/ \\bar{\\Lambda}$$ hyperons....« less

  7. Mechanisms responsible for the acceleration of pulmonary V̇O2 on-kinetics in humans after prolonged endurance training.

    PubMed

    Zoladz, Jerzy A; Grassi, Bruno; Majerczak, Joanna; Szkutnik, Zbigniew; Korostyński, Michal; Grandys, Marcin; Jarmuszkiewicz, Wieslawa; Korzeniewski, Bernard

    2014-11-01

    The effect of prolonged endurance training on the pulmonary V̇O2 on- and off-kinetics in humans, in relation to muscle mitochondria biogenesis, is investigated. Eleven untrained physically active men (means±SD: age 22.4±1.5 years, V̇O2peak 3,187±479 ml/min) performed endurance cycling training (4 sessions per week) lasting 20 wk. Training shortened τp of the pulmonary V̇O2 on-kinetics during moderate-intensity cycling by ∼19% from 28.3±5.2 to 23.0±4.0 s (P=0.005). τp of the pulmonary V̇O2 off-kinetics decreased by ∼11% from 33.7±7.2 to 30.0±6.6 (P=0.02). Training increased (in vastus lateralis muscle) mitochondrial DNA copy number in relation to nuclear DNA (mtDNA/nDNA) (+53%) (P=0.014), maximal citrate synthase (CS) activity (+38%), and CS protein content (+38%) (P=0.004), whereas maximal cytochrome c oxidase (COX) activity after training tended to be only slightly (+5%) elevated (P=0.08). By applying to the experimental data, our computer model of oxidative phosphorylation (OXPHOS) and using metabolic control analysis, we argue that COX activity is a much better measure of OXPHOS intensity than CS activity. According to the model, in the present study a training-induced increase in OXPHOS activity accounted for about 0-10% of the decrease in τp of muscle and pulmonary V̇O2 for the on-transient, whereas the remaining 90-100% is caused by an increase in each-step parallel activation of OXPHOS. Copyright © 2014 the American Physiological Society.

  8. Opportunities for future supernova studies of cosmic acceleration.

    PubMed

    Weller, J; Albrecht, A

    2001-03-05

    We investigate the potential of a future supernova data set, as might be obtained by the proposed SNAP satellite, to discriminate among different "dark energy" theories that describe an accelerating Universe. We find that many such models can be distinguished with a fit to the effective pressure-to-density ratio w of this energy. More models can be distinguished when the effective slope dw/dz of a changing w is also fit, but only if our knowledge of the current mass density Omega(m) is improved. We investigate the use of "fitting functions" to interpret luminosity distance data from supernova searches.

  9. Electrostatic/magnetic ion acceleration through a slowly diverging magnetic nozzle between a ring anode and an on-axis hollow cathode

    NASA Astrophysics Data System (ADS)

    Sasoh, A.; Mizutani, K.; Iwakawa, A.

    2017-06-01

    Ion acceleration through a slowly diverging magnetic nozzle between a ring anode and a hollow cathode set on the axis of symmetry has been realized. Xenon was supplied as the propellant gas from an annular slit along the inner surface of the ring anode so that it was ionized near the anode, and the applied electric potential was efficiently transformed to an ion kinetic energy. As an electrostatic thruster, within the examined operation conditions, the thrust, F, almost scaled with the propellant mass flow rate; the discharge current, Jd, increased with the discharge voltage, Vd. An important characteristic was that the thrust also exhibited electromagnetic acceleration performance, i.e., the so-called "swirl acceleration," in which F ≅JdB Ra /√{2 }, where B and Ra were a magnetic field and an anode inner radius, respectively. Such a unique thruster performance combining both electrostatic and electromagnetic accelerations is expected to be useful as another option for in-space electric propulsion in its broad functional diversity.

  10. Kinetic Atom.

    ERIC Educational Resources Information Center

    Wilson, David B.

    1981-01-01

    Surveys the research of scientists like Joule, Kelvin, Maxwell, Clausius, and Boltzmann as it comments on the basic conceptual issues involved in the development of a more precise kinetic theory and the idea of a kinetic atom. (Author/SK)

  11. Pyroclast acceleration and energy partitioning in fake explosive eruptions

    NASA Astrophysics Data System (ADS)

    Gaudin, Damien; Taddeucci, Jacopo; Scheu, Bettina; Valentine, Greg; Capponi, Antonio; Kueppers, Ulrich; Graettiger, Allison; Sonder, Ingo

    2014-05-01

    acceleration processes (and related kinetic energy) can be used to brings new constraints on the energy partition and general pyroclasts ejection mechanisms during eruptions.

  12. Acceleration and Precipitation of Electrons during Substorm Dipolarization Events

    NASA Astrophysics Data System (ADS)

    Ashour-Abdalla, Maha; Richard, Robert; Donovan, Eric; Zhou, Meng; Goldstein, Mevlyn; El-Alaoui, Mostafa; Schriver, David; Walker, Raymond

    Observations and modeling have established that during geomagnetically disturbed times the Earth’s magnetotail goes through large scale changes that result in enhanced electron precipitation into the ionosphere and earthward propagating dipolarization fronts that contain highly energized plasma. Such events originate near reconnection regions in the magnetotail at about 20-30 R_E down tail. As the dipolarization fronts propagate earthward, strong acceleration of both ions and electrons occurs due to a combination of non-adiabatic and adiabatic (betatron and Fermi) acceleration, with particle energies reaching up to 100 keV within the dipolarization front. One consequence of the plasma transport that occurs during these events is direct electron precipitation into the ionosphere, which form auroral precipitation. Using global kinetic simulations along with spacecraft and ground-based data, causes of electron precipitation are determined during well-documented, disturbed events. It is found that precipitation of keV electrons in the pre-midnight sector at latitudes around 70(°) occur due to two distinct physical processes: (1) higher latitude (≥72(°) ) precipitation due to electrons that undergo relatively rapid non-adiabatic pitch angle scattering into the loss cone just earthward of the reconnection region at around 20 R_E downtail, and (2) lower latitude (≤72(°) ) precipitation due to electrons that are more gradually accelerated primarily parallel to the geomagnetic field during its bounce motion by Fermi acceleration and enter the loss cone much closer to the Earth at 10-15 R_E, somewhat tailward of the dipolarization front. As the dipolarization fronts propagate earthward, the electron precipitation shifts to lower latitudes and occurs over a wider region in the auroral ionosphere. Our results show a direct connection between electron acceleration in the magnetotail and electron precipitation in the ionosphere during disturbed times. The electron

  13. Spectrum-to-Spectrum Searching Using a Proteome-wide Spectral Library*

    PubMed Central

    Yen, Chia-Yu; Houel, Stephane; Ahn, Natalie G.; Old, William M.

    2011-01-01

    The unambiguous assignment of tandem mass spectra (MS/MS) to peptide sequences remains a key unsolved problem in proteomics. Spectral library search strategies have emerged as a promising alternative for peptide identification, in which MS/MS spectra are directly compared against a reference library of confidently assigned spectra. Two problems relate to library size. First, reference spectral libraries are limited to rediscovery of previously identified peptides and are not applicable to new peptides, because of their incomplete coverage of the human proteome. Second, problems arise when searching a spectral library the size of the entire human proteome. We observed that traditional dot product scoring methods do not scale well with spectral library size, showing reduction in sensitivity when library size is increased. We show that this problem can be addressed by optimizing scoring metrics for spectrum-to-spectrum searches with large spectral libraries. MS/MS spectra for the 1.3 million predicted tryptic peptides in the human proteome are simulated using a kinetic fragmentation model (MassAnalyzer version2.1) to create a proteome-wide simulated spectral library. Searches of the simulated library increase MS/MS assignments by 24% compared with Mascot, when using probabilistic and rank based scoring methods. The proteome-wide coverage of the simulated library leads to 11% increase in unique peptide assignments, compared with parallel searches of a reference spectral library. Further improvement is attained when reference spectra and simulated spectra are combined into a hybrid spectral library, yielding 52% increased MS/MS assignments compared with Mascot searches. Our study demonstrates the advantages of using probabilistic and rank based scores to improve performance of spectrum-to-spectrum search strategies. PMID:21532008

  14. The Heavy Photon Search beamline and its performance

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Baltzell, N.; Egiyan, H.; Ehrhart, M.

    The Heavy Photon Search (HPS) is an experiment to search for a hidden sector photon, aka a heavy photon or dark photon, in fixed target electroproduction at the Thomas Jefferson National Accelerator Facility (JLab). The HPS experiment searches for the emore » $^+$e$^-$ decay of the heavy photon with bump hunt and detached vertex strategies using a compact, large acceptance forward spectrometer, consisting of a silicon microstrip detector (SVT) for tracking and vertexing, and a PbWO$$_4$$ electromagnetic calorimeter for energy measurement and fast triggering. To achieve large acceptance and good vertexing resolution, the first layer of silicon detectors is placed just 10 cm downstream of the target with the sensor edges only 500 $$\\mu$$m above and below the beam. Placing the SVT in such close proximity to the beam puts stringent requirements on the beam profile and beam position stability. As part of an approved engineering run, HPS took data in 2015 and 2016 at 1.05 GeV and 2.3 GeV beam energies, respectively. This study describes the beam line and its performance during that data taking.« less

  15. The Heavy Photon Search beamline and its performance

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Baltzell, N.; Egiyan, H.; Ehrhart, M.

    The Heavy Photon Search (HPS) is an experiment to search for a hidden sector photon, aka a heavy photon or dark photon, in fixed target electroproduction at the Thomas Jefferson National Accelerator Facility (JLab). The HPS experiment searches for the e+e- decay of the heavy photon with bump hunt and detached vertex strategies using a compact, large acceptance forward spectrometer, consisting of a silicon microstrip detector (SVT) for tracking and vertexing, and a PbWO 4 electromagnetic calorimeter for energy measurement and fast triggering. To achieve large acceptance and good vertexing resolution, the first layer of silicon detectors is placed justmore » 10 cm downstream of the target with the sensor edges only 500 μm above and below the beam. Placing the SVT in such close proximity to the beam puts stringent requirements on the beam profile and beam position stability. As part of an approved engineering run, HPS took data in 2015 and 2016 at 1.05 GeV and 2.3 GeV beam energies, respectively. This paper describes the beam line and its performance during that data taking.« less

  16. The Heavy Photon Search beamline and its performance

    DOE PAGES

    Baltzell, N.; Egiyan, H.; Ehrhart, M.; ...

    2017-07-01

    The Heavy Photon Search (HPS) is an experiment to search for a hidden sector photon, aka a heavy photon or dark photon, in fixed target electroproduction at the Thomas Jefferson National Accelerator Facility (JLab). The HPS experiment searches for the emore » $^+$e$^-$ decay of the heavy photon with bump hunt and detached vertex strategies using a compact, large acceptance forward spectrometer, consisting of a silicon microstrip detector (SVT) for tracking and vertexing, and a PbWO$$_4$$ electromagnetic calorimeter for energy measurement and fast triggering. To achieve large acceptance and good vertexing resolution, the first layer of silicon detectors is placed just 10 cm downstream of the target with the sensor edges only 500 $$\\mu$$m above and below the beam. Placing the SVT in such close proximity to the beam puts stringent requirements on the beam profile and beam position stability. As part of an approved engineering run, HPS took data in 2015 and 2016 at 1.05 GeV and 2.3 GeV beam energies, respectively. This study describes the beam line and its performance during that data taking.« less

  17. Particle acceleration in a complex solar active region modelled by a Cellular automata model

    NASA Astrophysics Data System (ADS)

    Dauphin, C.; Vilmer, N.; Anastasiadis, A.

    2004-12-01

    The models of cellular automat allowed to reproduce successfully several statistical properties of the solar flares. We use a cellular automat model based on the concept of self-organised critical system to model the evolution of the magnetic energy released in an eruptive active area. Each burst of magnetic energy released is assimilated to a process of magnetic reconnection. We will thus generate several current layers (RCS) where the particles are accelerated by a direct electric field. We calculate the energy gain of the particles (ions and electrons) for various types of magnetic configuration. We calculate the distribution function of the kinetic energy of the particles after their interactions with a given number of RCS for each type of configurations. We show that the relative efficiency of the acceleration of the electrons and the ions depends on the selected configuration.

  18. Kinetic energy partition method applied to ground state helium-like atoms.

    PubMed

    Chen, Yu-Hsin; Chao, Sheng D

    2017-03-28

    We have used the recently developed kinetic energy partition (KEP) method to solve the quantum eigenvalue problems for helium-like atoms and obtain precise ground state energies and wave-functions. The key to treating properly the electron-electron (repulsive) Coulomb potential energies for the KEP method to be applied is to introduce a "negative mass" term into the partitioned kinetic energy. A Hartree-like product wave-function from the subsystem wave-functions is used to form the initial trial function, and the variational search for the optimized adiabatic parameters leads to a precise ground state energy. This new approach sheds new light on the all-important problem of solving many-electron Schrödinger equations and hopefully opens a new way to predictive quantum chemistry. The results presented here give very promising evidence that an effective one-electron model can be used to represent a many-electron system, in the spirit of density functional theory.

  19. Privacy-preserving search for chemical compound databases.

    PubMed

    Shimizu, Kana; Nuida, Koji; Arai, Hiromi; Mitsunari, Shigeo; Attrapadung, Nuttapong; Hamada, Michiaki; Tsuda, Koji; Hirokawa, Takatsugu; Sakuma, Jun; Hanaoka, Goichiro; Asai, Kiyoshi

    2015-01-01

    Searching for similar compounds in a database is the most important process for in-silico drug screening. Since a query compound is an important starting point for the new drug, a query holder, who is afraid of the query being monitored by the database server, usually downloads all the records in the database and uses them in a closed network. However, a serious dilemma arises when the database holder also wants to output no information except for the search results, and such a dilemma prevents the use of many important data resources. In order to overcome this dilemma, we developed a novel cryptographic protocol that enables database searching while keeping both the query holder's privacy and database holder's privacy. Generally, the application of cryptographic techniques to practical problems is difficult because versatile techniques are computationally expensive while computationally inexpensive techniques can perform only trivial computation tasks. In this study, our protocol is successfully built only from an additive-homomorphic cryptosystem, which allows only addition performed on encrypted values but is computationally efficient compared with versatile techniques such as general purpose multi-party computation. In an experiment searching ChEMBL, which consists of more than 1,200,000 compounds, the proposed method was 36,900 times faster in CPU time and 12,000 times as efficient in communication size compared with general purpose multi-party computation. We proposed a novel privacy-preserving protocol for searching chemical compound databases. The proposed method, easily scaling for large-scale databases, may help to accelerate drug discovery research by making full use of unused but valuable data that includes sensitive information.

  20. Privacy-preserving search for chemical compound databases

    PubMed Central

    2015-01-01

    Background Searching for similar compounds in a database is the most important process for in-silico drug screening. Since a query compound is an important starting point for the new drug, a query holder, who is afraid of the query being monitored by the database server, usually downloads all the records in the database and uses them in a closed network. However, a serious dilemma arises when the database holder also wants to output no information except for the search results, and such a dilemma prevents the use of many important data resources. Results In order to overcome this dilemma, we developed a novel cryptographic protocol that enables database searching while keeping both the query holder's privacy and database holder's privacy. Generally, the application of cryptographic techniques to practical problems is difficult because versatile techniques are computationally expensive while computationally inexpensive techniques can perform only trivial computation tasks. In this study, our protocol is successfully built only from an additive-homomorphic cryptosystem, which allows only addition performed on encrypted values but is computationally efficient compared with versatile techniques such as general purpose multi-party computation. In an experiment searching ChEMBL, which consists of more than 1,200,000 compounds, the proposed method was 36,900 times faster in CPU time and 12,000 times as efficient in communication size compared with general purpose multi-party computation. Conclusion We proposed a novel privacy-preserving protocol for searching chemical compound databases. The proposed method, easily scaling for large-scale databases, may help to accelerate drug discovery research by making full use of unused but valuable data that includes sensitive information. PMID:26678650

  1. Fermilab | Tevatron | Accelerator

    Science.gov Websites

    Leading accelerator technology Accelerator complex Illinois Accelerator Research Center Fermilab temperature. They were used to transfer particles from one part of the Fermilab accelerator complex to another center ring of Fermilab's accelerator complex. Before the Tevatron shut down, it had three primary

  2. Experimental Investigation on the Mechanism of Chelation-Assisted, Copper(II) Acetate-Accelerated Azide-Alkyne Cycloaddition

    PubMed Central

    Kuang, Gui-Chao; Guha, Pampa M.; Brotherton, Wendy S.; Simmons, J. Tyler; Stankee, Lisa A.; Nguyen, Brian T.; Clark, Ronald J.; Zhu, Lei

    2011-01-01

    A mechanistic model is formulated to account for the high reactivity of chelating azides (organic azides capable of chelation-assisted metal coordination at the alkylated azido nitrogen position) and copper(II) acetate (Cu(OAc)2) in copper(II)-mediated azide-alkyne cycloaddition (AAC) reactions. Fluorescence and 1H NMR assays are developed for monitoring the reaction progress in two different solvents – methanol and acetonitrile. Solvent kinetic isotopic effect and pre-mixing experiments give credence to the proposed different induction reactions for converting copper(II) to catalytic copper(I) species in methanol (methanol oxidation) and acetonitrile (alkyne oxidative homocoupling), respectively. The kinetic orders of individual components in a chelation-assisted, copper(II)-accelerated AAC reaction are determined in both methanol and acetonitrile. Key conclusions resulting from the kinetic studies include (1) the interaction between copper ion (either in +1 or +2 oxidation state) and a chelating azide occurs in a fast, pre-equilibrium step prior to the formation of the in-cycle copper(I)-acetylide, (2) alkyne deprotonation is involved in several kinetically significant steps, and (3) consistent with prior experimental and computational results by other groups, two copper centers are involved in the catalysis. The X-ray crystal structures of chelating azides with Cu(OAc)2 suggest a mechanistic synergy between alkyne oxidative homocoupling and copper(II)-accelerated AAC reactions, in which both a bimetallic catalytic pathway and a base are involved. The different roles of the two copper centers (a Lewis acid to enhance the electrophilicity of the azido group and a two-electron reducing agent in oxidative metallacycle formation, respectively) in the proposed catalytic cycle suggest that a mixed valency (+2 and +1) dinuclear copper species be a highly efficient catalyst. This proposition is supported by the higher activity of the partially reduced Cu(OAc)2 in

  3. Optimum tuned mass damper design using harmony search with comparison of classical methods

    NASA Astrophysics Data System (ADS)

    Nigdeli, Sinan Melih; Bekdaş, Gebrail; Sayin, Baris

    2017-07-01

    As known, tuned mass dampers (TMDs) are added to mechanical systems in order to obtain a good vibration damping. The main aim is to reduce the maximum amplitude at the resonance state. In this study, a metaheuristic algorithm called harmony search employed for the optimum design of TMDs. As the optimization objective, the transfer function of the acceleration of the system with respect to ground acceleration was minimized. The numerical trails were conducted for 4 single degree of freedom systems and the results were compared with classical methods. As a conclusion, the proposed method is feasible and more effective than the other documented methods.

  4. Altered redox state of monocytes from cryopyrin-associated periodic syndromes causes accelerated IL-1β secretion

    PubMed Central

    Tassi, Sara; Carta, Sonia; Delfino, Laura; Caorsi, Roberta; Martini, Alberto; Gattorno, Marco; Rubartelli, Anna

    2010-01-01

    In healthy monocytes, Toll-like receptor (TLR) engagement induces production of reactive oxygen species (ROS), followed by an antioxidant response involved in IL-1β processing and secretion. Markers of the antioxidant response include intracellular thioredoxin and extracellular release of reduced cysteine. Cryopyrin-associated periodic syndromes (CAPS) are autoinflammatory diseases in which Nod-like receptor family pyrin domain–containing 3 (NLRP3) gene mutations lead to increased IL-1β secretion. We show in a large cohort of patients that IL-1β secretion by CAPS monocytes is much faster than that by healthy monocytes. This accelerated kinetics is caused by alterations in the basal redox state, as well as in the redox response to TLR triggering displayed by CAPS monocytes. Indeed, unstimulated CAPS monocytes are under a mild oxidative stress, with elevated levels of both ROS and antioxidants. The redox response to LPS is quickened, with early generation of the reducing conditions favoring IL-1β processing and secretion, and then rapidly exhausted. Therefore, secretion of IL-1β is accelerated, but reaches a plateau much earlier than in healthy controls. Pharmacologic inhibition of the redox response hinders IL-1β release, confirming the functional link between redox impairment and altered kinetics of secretion. Monocytes from patients with juvenile idiopathic arthritis display normal kinetics of redox response and IL-1β secretion, excluding a role of chronic inflammation in the alterations observed in CAPS. We conclude that preexisting redox alterations distinct from CAPS monocytes anticipate the pathogen-associated molecular pattern molecule–induced generation of the reducing environment favorable to inflammasome activation and IL-1β secretion. PMID:20445104

  5. Altered redox state of monocytes from cryopyrin-associated periodic syndromes causes accelerated IL-1beta secretion.

    PubMed

    Tassi, Sara; Carta, Sonia; Delfino, Laura; Caorsi, Roberta; Martini, Alberto; Gattorno, Marco; Rubartelli, Anna

    2010-05-25

    In healthy monocytes, Toll-like receptor (TLR) engagement induces production of reactive oxygen species (ROS), followed by an antioxidant response involved in IL-1beta processing and secretion. Markers of the antioxidant response include intracellular thioredoxin and extracellular release of reduced cysteine. Cryopyrin-associated periodic syndromes (CAPS) are autoinflammatory diseases in which Nod-like receptor family pyrin domain-containing 3 (NLRP3) gene mutations lead to increased IL-1beta secretion. We show in a large cohort of patients that IL-1beta secretion by CAPS monocytes is much faster than that by healthy monocytes. This accelerated kinetics is caused by alterations in the basal redox state, as well as in the redox response to TLR triggering displayed by CAPS monocytes. Indeed, unstimulated CAPS monocytes are under a mild oxidative stress, with elevated levels of both ROS and antioxidants. The redox response to LPS is quickened, with early generation of the reducing conditions favoring IL-1beta processing and secretion, and then rapidly exhausted. Therefore, secretion of IL-1beta is accelerated, but reaches a plateau much earlier than in healthy controls. Pharmacologic inhibition of the redox response hinders IL-1beta release, confirming the functional link between redox impairment and altered kinetics of secretion. Monocytes from patients with juvenile idiopathic arthritis display normal kinetics of redox response and IL-1beta secretion, excluding a role of chronic inflammation in the alterations observed in CAPS. We conclude that preexisting redox alterations distinct from CAPS monocytes anticipate the pathogen-associated molecular pattern molecule-induced generation of the reducing environment favorable to inflammasome activation and IL-1beta secretion.

  6. Drying kinetics and characteristics of dried gambir leaves using solar heating and silica gel dessicant

    NASA Astrophysics Data System (ADS)

    Hasibuan, R.; Hidayati, J.; Sundari, R.; Wicaksono, A. S.

    2018-02-01

    A drying combination of solar heating and silica gel dessicant has been applied to dry gambir leaves. The solar energy is captured by a collector to heat the air and the hot air is used to dry gambir leaves in a drying chamber. An exhaust fan in drying chamber assists to draw water molecules from gambir leaves accelerated by silica gel dessicant. This study has investigated the drying kinetics and drying characteristics of gambir leaves drying. In drying operation the air velocity is tuned by a PWM (pulse width modulation) controller to adjust minimum and maximum level, which is based on the rotation speed of the exhaust fan. The results show that the air velocity influenced the drying kinetics and drying characteristics of gambir leaves using solar-dessicant drying at 40 cm distance between exhaust fan and silica gel dessicant.

  7. Non-Kinetic Losses Caused by Electrochemical Carbon Corrosion in PEM Fuel Cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Park, Seh Kyu; Shao, Yuyan; Viswanathan, Vilayanur V.

    2012-05-01

    This paper presented non-kinetic losses in PEM fuel cells under an accelerated stress test of catalyst support. The cathode with carbon-supported Pt catalyst was prepared and characterized with potential hold at 1.2 V vs. SHE in PEM fuel cells. Irreversible losses caused by carbon corrosion were evaluated using a variety of electrochemical characterizations including cyclic voltammetry, linear sweep voltammetry, electrochemical impedance spectroscopy, and polarization technique. Ohmic losses at the cathode with potential hold were determined using its capacitive responses. Concentration losses in PEM fuel cells were analyzed in terms of Tafel behavior and thin film/flooded-agglomerate dynamics.

  8. Piezoelectric particle accelerator

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kemp, Mark A.; Jongewaard, Erik N.; Haase, Andrew A.

    2017-08-29

    A particle accelerator is provided that includes a piezoelectric accelerator element, where the piezoelectric accelerator element includes a hollow cylindrical shape, and an input transducer, where the input transducer is disposed to provide an input signal to the piezoelectric accelerator element, where the input signal induces a mechanical excitation of the piezoelectric accelerator element, where the mechanical excitation is capable of generating a piezoelectric electric field proximal to an axis of the cylindrical shape, where the piezoelectric accelerator is configured to accelerate a charged particle longitudinally along the axis of the cylindrical shape according to the piezoelectric electric field.

  9. Wave-Particle Interactions and Particle Acceleration in Turbulent Plasmas: Hybrid Simulations

    NASA Astrophysics Data System (ADS)

    Kucharek, Harald; Pogorelov, Nikolai; Mueller, Hans; Gamayunov, Konstantin; Farrugia, Charles

    2015-04-01

    Wave-particle interactions and acceleration processes are present in all key regions inside and outside of the heliosphere. Spacecraft observations measure ion distributions and accelerated ion populations, which are the result of one or several processes. For instance STEREO measures energetic particles associated with interplanetary discontinuities and in the solar wind. Voyager and IBEX provide unique data of energetic particles from the termination shock and the inner and outer heliopause. The range of plasma conditions covered by observations is enormous. However, the physical processes causing particle acceleration and wave-particle interaction and determining the particle distributions are still unknown. Currently two mechanisms, the so-called pumping mechanism (Fisk and Gloeckler, 2010) and merging/contracting island (Fermo, Drake & Swisdak, 2010) are discussed as promising models. In order to determine these individual processes, numerical models or theoretical considerations are needed. Hybrid simulations, which include all kinetic processes self-consistently on the ion level, are a very proven, powerful tool to investigate wave-particle interaction, turbulence, and phase-space evolution of pickup and solar wind ions. In the framework of this study we performed 3D multi-species hybrid simulations for an ion/ion beam instability to study the temporal evolution of ion distributions, their stability, and the influence of self-generated waves. We investigated the energization of ions downstream of interplanetary discontinuities and shocks and downstream of the termination shock, the turbulence, and growth rate of instabilities and compared the results with theoretical predictions. The simulations show that ions can be accelerated downstream of collisionless shocks by trapping of charged particles in coherent wave fronts.

  10. Crystallization kinetics of cocoa butter in the presence of sorbitan esters.

    PubMed

    Sonwai, Sopark; Podchong, Pawitchaya; Rousseau, Dérick

    2017-01-01

    Cocoa butter crystallization in the presence of sorbitan mono- and triesters or canola oil was investigated. Solid-state surfactant esters accelerated early-stage cocoa butter solidification while suppressing later growth. Sorbitan tristearate showed the strongest effect, followed by sorbitan monostearate and sorbitan monopalmitate. Liquid-state surfactants suppressed cocoa butter crystallization at all time points, with sorbitan trioleate showing a stronger effect than sorbitan monooleate, which behaved in a similar fashion to canola oil. Via DSC, the palmitic and stearic-based surfactants only associated with cocoa butter's high-melting fraction, with the oleic acid-based surfactants and canola oil showing little influence. All sorbitan esters had little effect on polymorphism, whereas canola oil accelerated the form II-to-III-to-IV transition. The palmitic and stearic-based surfactants greatly reduced cocoa butter crystal size whereas the oleic acid-based surfactants and canola showed no notable effect. Overall, sorbitan esters impacted cocoa butter crystallization kinetics, though this depended on surfactant structure and concentration. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Computing Principal Eigenvectors of Large Web Graphs: Algorithms and Accelerations Related to PageRank and HITS

    ERIC Educational Resources Information Center

    Nagasinghe, Iranga

    2010-01-01

    This thesis investigates and develops a few acceleration techniques for the search engine algorithms used in PageRank and HITS computations. PageRank and HITS methods are two highly successful applications of modern Linear Algebra in computer science and engineering. They constitute the essential technologies accounted for the immense growth and…

  12. Extending the Search for Muon Neutrinos Coincident with Gamma-Ray Bursts in IceCube Data

    NASA Astrophysics Data System (ADS)

    Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Samarai, I. Al; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, G.; Archinger, M.; Argüelles, C.; Auffenberg, J.; Axani, S.; Bai, X.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson, D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Bohm, C.; Börner, M.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Braun, J.; Brayeur, L.; Bretz, H.-P.; Bron, S.; Burgman, A.; Carver, T.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Clark, K.; Classen, L.; Coenders, S.; Collin, G. H.; Conrad, J. M.; Cowen, D. F.; Cross, R.; Day, M.; de André, J. P. A. M.; De Clercq, C.; del Pino Rosendo, E.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; di Lorenzo, V.; Dujmovic, H.; Dumm, J. P.; Dunkman, M.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Eller, P.; Euler, S.; Evenson, P. A.; Fahey, S.; Fazely, A. R.; Feintzeig, J.; Felde, J.; Filimonov, K.; Finley, C.; Flis, S.; Fösig, C.-C.; Franckowiak, A.; Friedman, E.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Ghorbani, K.; Giang, W.; Gladstone, L.; Glauch, T.; Glüsenkamp, T.; Goldschmidt, A.; Gonzalez, J. G.; Grant, D.; Griffith, Z.; Haack, C.; Hallgren, A.; Halzen, F.; Hansen, E.; Hansmann, T.; Hanson, K.; Hebecker, D.; Heereman, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Hoshina, K.; Huang, F.; Huber, M.; Hultqvist, K.; In, S.; Ishihara, A.; Jacobi, E.; Japaridze, G. S.; Jeong, M.; Jero, K.; Jones, B. J. P.; Kang, W.; Kappes, A.; Karg, T.; Karle, A.; Katz, U.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kheirandish, A.; Kim, J.; Kim, M.; Kintscher, T.; Kiryluk, J.; Kittler, T.; Klein, S. R.; Kohnen, G.; Koirala, R.; Kolanoski, H.; Konietz, R.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Krings, K.; Kroll, M.; Krückl, G.; Krüger, C.; Kunnen, J.; Kunwar, S.; Kurahashi, N.; Kuwabara, T.; Kyriacou, A.; Labare, M.; Lanfranchi, J. L.; Larson, M. J.; Lauber, F.; Lennarz, D.; Lesiak-Bzdak, M.; Leuermann, M.; Lu, L.; Lünemann, J.; Madsen, J.; Maggi, G.; Mahn, K. B. M.; Mancina, S.; Mandelartz, M.; Maruyama, R.; Mase, K.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meier, M.; Menne, T.; Merino, G.; Meures, T.; Miarecki, S.; Micallef, J.; Momenté, G.; Montaruli, T.; Moulai, M.; Nahnhauer, R.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke Pollmann, A.; Olivas, A.; O'Murchadha, A.; Palczewski, T.; Pandya, H.; Pankova, D. V.; Peiffer, P.; Penek, Ö.; Pepper, J. A.; Pérez de los Heros, C.; Pieloth, D.; Pinat, E.; Price, P. B.; Przybylski, G. T.; Quinnan, M.; Raab, C.; Rädel, L.; Rameez, M.; Rawlins, K.; Reimann, R.; Relethford, B.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Riedel, B.; Robertson, S.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk, D.; Sabbatini, L.; Sanchez Herrera, S. E.; Sandrock, A.; Sandroos, J.; Sarkar, S.; Satalecka, K.; Schlunder, P.; Schmidt, T.; Schoenen, S.; Schöneberg, S.; Schumacher, L.; Seckel, D.; Seunarine, S.; Soldin, D.; Song, M.; Spiczak, G. M.; Spiering, C.; Stachurska, J.; Stanev, T.; Stasik, A.; Stettner, J.; Steuer, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Ström, R.; Strotjohann, N. L.; Sullivan, G. W.; Sutherland, M.; Taavola, H.; Taboada, I.; Tatar, J.; Tenholt, F.; Ter-Antonyan, S.; Terliuk, A.; Tešić, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Toscano, S.; Tosi, D.; Tselengidou, M.; Tung, C. F.; Turcati, A.; Unger, E.; Usner, M.; Vandenbroucke, J.; van Eijndhoven, N.; Vanheule, S.; van Rossem, M.; van Santen, J.; Vehring, M.; Voge, M.; Vogel, E.; Vraeghe, M.; Walck, C.; Wallace, A.; Wallraff, M.; Wandkowsky, N.; Waza, A.; Weaver, Ch.; Weiss, M. J.; Wendt, C.; Westerhoff, S.; Whelan, B. J.; Wickmann, S.; Wiebe, K.; Wiebusch, C. H.; Wille, L.; Williams, D. R.; Wills, L.; Wolf, M.; Wood, T. R.; Woolsey, E.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zoll, M.; IceCube Collaboration

    2017-07-01

    We present an all-sky search for muon neutrinos produced during the prompt γ-ray emission of 1172 gamma-ray bursts (GRBs) with the IceCube Neutrino Observatory. The detection of these neutrinos would constitute evidence for ultra-high-energy cosmic-ray (UHECR) production in GRBs, as interactions between accelerated protons and the prompt γ-ray field would yield charged pions, which decay to neutrinos. A previously reported search for muon neutrino tracks from northern hemisphere GRBs has been extended to include three additional years of IceCube data. A search for such tracks from southern hemisphere GRBs in five years of IceCube data has been introduced to enhance our sensitivity to the highest energy neutrinos. No significant correlation between neutrino events and observed GRBs is seen in the new data. Combining this result with previous muon neutrino track searches and a search for cascade signature events from all neutrino flavors, we obtain new constraints for single-zone fireball models of GRB neutrino and UHECR production.

  13. Characterising the acceleration phase of blast wave formation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fox, T. E., E-mail: tef503@york.ac.uk; Pasley, J.; Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX

    2014-10-15

    Intensely heated, localised regions in uniform fluids will rapidly expand and generate an outwardly propagating blast wave. The Sedov-Taylor self-similar solution for such blast waves has long been studied and applied to a variety of scenarios. A characteristic time for their formation has also long been identified using dimensional analysis, which by its very nature, can offer several interpretations. We propose that, rather than simply being a characteristic time, it may be interpreted as the definitive time taken for a blast wave resulting from an intense explosion in a uniform media to contain its maximum kinetic energy. A scaling relationmore » for this measure of the acceleration phase, preceding the establishment of the blast wave, is presented and confirmed using a 1D planar hydrodynamic model.« less

  14. A computational atomistic study of the relaxation of ion-bombarded c-Si on experimental time-scales: an application of the kinetic Activation Relaxation Technique

    NASA Astrophysics Data System (ADS)

    Béland, Laurent Karim; Mousseau, Normand

    2012-02-01

    The kinetic activation relaxation technique (kinetic ART) method, an off-lattice, self-learning kinetic Monte Carlo (KMC) algorithm with on-the-fly event search,ootnotetextL. K. B'eland, P. Brommer, F. El-Mellouhi, J.-F. Joly and N. Mousseau, Phys. Rev. E 84, 046704 (2011). is used to study the relaxation of c-Si after Si^- bombardment at 3 keV. We describe the evolution of the damaged areas at room-temperature and above for periods of the order of seconds, treating long-range elastic deformations exactly. We assess the stability of the nanoscale structures formed by the damage cascade and the mechanisms that govern post-implantation annealing.

  15. The Heavy Photon Search test detector

    DOE PAGES

    Battaglieri, M.; Boyarinov, S.; Bueltmann, S.; ...

    2014-12-17

    The Heavy Photon Search (HPS), an experiment to search for a hidden sector photon in fixed target electroproduction, is preparing for installation at the Thomas Jefferson National Accelerator Facility (JLab) in the Fall of 2014. As the first stage of this project, the HPS Test Run apparatus was constructed and operated in 2012 to demonstrate the experiment's technical feasibility and to confirm that the trigger rates and occupancies are as expected. This paper describes the HPS Test Run apparatus and readout electronics and its performance. In this setting, a heavy photon can be identified as a narrow peak in themore » e⁺e⁻invariant mass spectrum above the trident background or as a narrow invariant mass peak with a decay vertex displaced from the production target, so charged particle tracking and vertexing are needed for its detection. In the HPS Test Run, charged particles are measured with a compact forward silicon microstrip tracker inside a dipole magnet. Electromagnetic showers are detected in a PbW0 4 crystal calorimeter situated behind the magnet, and are used to trigger the experiment and identify electrons and positrons. Both detectors are placed close to the beam line and split top-bottom. This arrangement provides sensitivity to low-mass heavy photons, allows clear passage of the unscattered beam, and avoids the spray of degraded electrons coming from the target. The discrimination between prompt and displaced e⁺e⁻ pairs requires the first layer of silicon sensors be placed only 10 cm downstream of the target. The expected signal is small, and the trident background huge, so the experiment requires very large statistics. In addition, the HPS Test Run utilizes high-rate readout and data acquisition electronics and a fast trigger to exploit the essentially 100% duty cycle of the CEBAF accelerator at JLab.« less

  16. Source-to-accelerator quadrupole matching section for a compact linear accelerator

    NASA Astrophysics Data System (ADS)

    Seidl, P. A.; Persaud, A.; Ghiorso, W.; Ji, Q.; Waldron, W. L.; Lal, A.; Vinayakumar, K. B.; Schenkel, T.

    2018-05-01

    Recently, we presented a new approach for a compact radio-frequency (RF) accelerator structure and demonstrated the functionality of the individual components: acceleration units and focusing elements. In this paper, we combine these units to form a working accelerator structure: a matching section between the ion source extraction grids and the RF-acceleration unit and electrostatic focusing quadrupoles between successive acceleration units. The matching section consists of six electrostatic quadrupoles (ESQs) fabricated using 3D-printing techniques. The matching section enables us to capture more beam current and to match the beam envelope to conditions for stable transport in an acceleration lattice. We present data from an integrated accelerator consisting of the source, matching section, and an ESQ doublet sandwiched between two RF-acceleration units.

  17. Search for Light Dark Matter Produced in a Proton Beam Dump

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thornton, Remington Tyler

    Cosmological observations indicate that our universe contains dark matter (DM), yet we have no measurements of its microscopic properties. Whereas the gravitational interaction of DM is well understood, its interaction with the Standard Model is not. Direct detection experiments, the current standard, search for a nuclear recoil interaction and have a low-mass sensitivity edge of order 1 GeV. A path to detect DM with mass below 1 GeV is the use of accelerators producing boosted low-mass DM. Using neutrino detectors to search for low-mass DM is logical due to the similarity of the DM and neutrino signatures in the detector.more » The MiniBooNE experiment, located at Fermilab on the Booster Neutrino Beamline, has produced the first proton beam-dump light DM search results. Using dark matter scattering from nucleons 90% confidence limits were set over a large parameter space and, to allow tests of other theories, a model independent DM rate was extracted.« less

  18. Search for light dark matter produced in a proton beam dump

    NASA Astrophysics Data System (ADS)

    Thornton, Remington Tyler

    Cosmological observations indicate that our universe contains dark matter (DM), yet we have no measurements of its microscopic properties. Whereas the gravitational interaction of DM is well understood, its interaction with the Standard Model is not. Direct detection experiments, the current standard, search for a nuclear recoil interaction and have a low-mass sensitivity edge of order 1 GeV. A path to detect DM with mass below 1 GeV is the use of accelerators producing boosted low-mass DM. Using neutrino detectors to search for low-mass DM is logical due to the similarity of the DM and neutrino signatures in the detector. The MiniBooNE experiment, located at Fermilab on the Booster Neutrino Beamline, has produced the first proton beam-dump light DM search results. Using dark matter scattering from nucleons 90% confidence limits were set over a large parameter space and, to allow tests of other theories, a model independent DM rate was extracted.

  19. NASA's GeneLab Phase II: Federated Search and Data Discovery

    NASA Technical Reports Server (NTRS)

    Berrios, Daniel C.; Costes, Sylvain V.; Tran, Peter B.

    2017-01-01

    GeneLab is currently being developed by NASA to accelerate 'open science' biomedical research in support of the human exploration of space and the improvement of life on earth. Phase I of the four-phase GeneLab Data Systems (GLDS) project emphasized capabilities for submission, curation, search, and retrieval of genomics, transcriptomics and proteomics ('omics') data from biomedical research of space environments. The focus of development of the GLDS for Phase II has been federated data search for and retrieval of these kinds of data across other open-access systems, so that users are able to conduct biological meta-investigations using data from a variety of sources. Such meta-investigations are key to corroborating findings from many kinds of assays and translating them into systems biology knowledge and, eventually, therapeutics.

  20. NASAs GeneLab Phase II: Federated Search and Data Discovery

    NASA Technical Reports Server (NTRS)

    Berrios, Daniel C.; Costes, Sylvain; Tran, Peter

    2017-01-01

    GeneLab is currently being developed by NASA to accelerate open science biomedical research in support of the human exploration of space and the improvement of life on earth. Phase I of the four-phase GeneLab Data Systems (GLDS) project emphasized capabilities for submission, curation, search, and retrieval of genomics, transcriptomics and proteomics (omics) data from biomedical research of space environments. The focus of development of the GLDS for Phase II has been federated data search for and retrieval of these kinds of data across other open-access systems, so that users are able to conduct biological meta-investigations using data from a variety of sources. Such meta-investigations are key to corroborating findings from many kinds of assays and translating them into systems biology knowledge and, eventually, therapeutics.

  1. Experimental observation of direct particle acceleration by stimulated emission of radiation.

    PubMed

    Banna, Samer; Berezovsky, Valery; Schächter, Levi

    2006-09-29

    We report the first experimental evidence for direct particle acceleration by stimulated emission of radiation. In the framework of this proof-of-principle experiment, a 45 MeV electron macrobunch was modulated by a high-power CO2 laser and then injected into an excited CO2 gas mixture. The emerging microbunches experienced a 0.15% relative change in the kinetic energy, in a less than 40 cm long interaction region. According to our experimental results, a fraction of these electrons have gained more than 200 keV each, implying that such an electron has undergone an order of magnitude of 2 x 10(6) collisions of the second kind.

  2. DNA hybridization kinetics: zippering, internal displacement and sequence dependence.

    PubMed

    Ouldridge, Thomas E; Sulc, Petr; Romano, Flavio; Doye, Jonathan P K; Louis, Ard A

    2013-10-01

    Although the thermodynamics of DNA hybridization is generally well established, the kinetics of this classic transition is less well understood. Providing such understanding has new urgency because DNA nanotechnology often depends critically on binding rates. Here, we explore DNA oligomer hybridization kinetics using a coarse-grained model. Strand association proceeds through a complex set of intermediate states, with successful binding events initiated by a few metastable base-pairing interactions, followed by zippering of the remaining bonds. But despite reasonably strong interstrand interactions, initial contacts frequently dissociate because typical configurations in which they form differ from typical states of similar enthalpy in the double-stranded equilibrium ensemble. Initial contacts must be stabilized by two or three base pairs before full zippering is likely, resulting in negative effective activation enthalpies. Non-Arrhenius behavior arises because the number of base pairs required for nucleation increases with temperature. In addition, we observe two alternative pathways-pseudoknot and inchworm internal displacement-through which misaligned duplexes can rearrange to form duplexes. These pathways accelerate hybridization. Our results explain why experimentally observed association rates of GC-rich oligomers are higher than rates of AT- rich equivalents, and more generally demonstrate how association rates can be modulated by sequence choice.

  3. Merging for Particle-Mesh Complex Particle Kinetic Modeling of the Multiple Plasma Beams

    NASA Technical Reports Server (NTRS)

    Lipatov, Alexander S.

    2011-01-01

    We suggest a merging procedure for the Particle-Mesh Complex Particle Kinetic (PMCPK) method in case of inter-penetrating flow (multiple plasma beams). We examine the standard particle-in-cell (PIC) and the PMCPK methods in the case of particle acceleration by shock surfing for a wide range of the control numerical parameters. The plasma dynamics is described by a hybrid (particle-ion-fluid-electron) model. Note that one may need a mesh if modeling with the computation of an electromagnetic field. Our calculations use specified, time-independent electromagnetic fields for the shock, rather than self-consistently generated fields. While a particle-mesh method is a well-verified approach, the CPK method seems to be a good approach for multiscale modeling that includes multiple regions with various particle/fluid plasma behavior. However, the CPK method is still in need of a verification for studying the basic plasma phenomena: particle heating and acceleration by collisionless shocks, magnetic field reconnection, beam dynamics, etc.

  4. Can Accelerators Accelerate Learning?

    NASA Astrophysics Data System (ADS)

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-01

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ) [1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  5. High-Throughput Study of Diffusion and Phase Transformation Kinetics of Magnesium-Based Systems for Automotive Cast Magnesium Alloys

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Luo, Alan A; Zhao, Ji-Cheng; Riggi, Adrienne

    The objective of the proposed study is to establish a scientific foundation on kinetic modeling of diffusion, phase precipitation, and casting/solidification, in order to accelerate the design and optimization of cast magnesium (Mg) alloys for weight reduction of U.S. automotive fleet. The team has performed the following tasks: 1) study diffusion kinetics of various Mg-containing binary systems using high-throughput diffusion multiples to establish reliable diffusivity and mobility databases for the Mg-aluminum (Al)-zinc (Zn)-tin (Sn)-calcium (Ca)-strontium (Sr)-manganese (Mn) systems; 2) study the precipitation kinetics (nucleation, growth and coarsening) using both innovative dual-anneal diffusion multiples and cast model alloys to provide largemore » amounts of kinetic data (including interfacial energy) and microstructure atlases to enable implementation of the Kampmann-Wagner numerical model to simulate phase transformation kinetics of non-spherical/non-cuboidal precipitates in Mg alloys; 3) implement a micromodel to take into account back diffusion in the solid phase in order to predict microstructure and microsegregation in multicomponent Mg alloys during dendritic solidification especially under high pressure die-casting (HPDC) conditions; and, 4) widely disseminate the data, knowledge and information using the Materials Genome Initiative infrastructure (http://www.mgidata.org) as well as publications and digital data sharing to enable researchers to identify new pathways/routes to better cast Mg alloys.« less

  6. Longitudinal instabilities of the experimentally generated laser accelerated ion beam relevant to fast ignition

    NASA Astrophysics Data System (ADS)

    Khoshbinfar, S.

    2017-11-01

    The advent of laser-assisted ion acceleration technology promises an alternative candidate to conventional accelerator drivers used in inertial confinement fusion. The experimental generation of quasi-monoenergetic heavier ion species i.e. carbon and aluminum, applicable to fast ignition studies has been recently reported. The propagation of these energetic ions may impact on the proper ignition phase through growing of micro-instabilities of beam-plasma system. The growth of flow-aligned instabilities is much more important for heavier ions transport in the dense plasma. Here, we have presented a general non-relativistic one-dimensional dispersion relation of cold fluid model as well as corresponding kinetic theory of incident ion beam with atomic number, Zb enters into a fast ignition DT plasma. The longitudinal instabilities of some selected average energies of experimentally generated C6+ (EC=50, 100 and 200 MeV with δE/E ∼ 10 %) and Al11+ (EAl=150 and 300 MeV with δE/E ∼25%) quasi-monoenergetic beams were examined and beam-plasma system stable configuration have been then derived. It has been shown that in the kinetic theory framework, carbon and aluminum ions may be completely stabilized by the combination of beam to plasma density ratio (αb) and plasma temperature (Tp) of ignition phase parameters. Moreover, in complete stabilization, αb parameter of aluminum beam is an order of magnitude lower than carbon.

  7. Timing and searching millisecond pulsars in globular clusters

    NASA Astrophysics Data System (ADS)

    D'Amico, Nichi; Possenti, Andrea; Manchester, Dick; Johnston, Simon; Kramer, Michael; Sarkissian, John; Lyne, Andrew; Burgay, Marta; Corongiu, Alessandro; Camilo, Fernando; Bailes, Matthew

    2009-10-01

    Timing the dozen pulsars discovered in P303 is ensuring high quality results: (a) the peculiarities (in position or projected acceleration) of all the 5 millisecond pulsars in NGC6752 suggested the presence of non thermal dynamics in the core, perhaps due to black-holes of intermediate mass; (b) the eclipsing pulsar in NGC6397 is a stereotype for studying the late evolution of exotic binaries. We propose to continue our timing project focusing mostly on NGC6752 at 20cm (in order to measure additional parameters useful to constrain the existence of a black-hole) and NGC6397 at 10cm (for studying the eclipse region and the orbital secular evolution). We also request time for performing pilot observations for a new deeper than ever search for millisecond pulsars in a subset of suitable clusters. This revamped search (as well as the requested timing observations) will exploit the new back-ends (APSR and DFB4) now available at Parkes.

  8. Timing and searching millisecond pulsars in globular clusters

    NASA Astrophysics Data System (ADS)

    D'Amico, Nichi; Possenti, Andrea; Manchester, Dick; Johnston, Simon; Kramer, Michael; Sarkissian, John; Lyne, Andrew; Burgay, Marta; Corongiu, Alessandro; Camilo, Fernando; Bailes, Matthew; van Straten, Willem

    2010-04-01

    Timing the dozen pulsars discovered in P303 is ensuring high quality results: (a) the peculiarities (in position or projected acceleration) of all the 5 millisecond pulsars in NGC6752 suggested the presence of non thermal dynamics in the core, perhaps due to black-holes of intermediate mass; (b) the eclipsing pulsar in NGC6397 is a stereotype for studying the late evolution of exotic binaries. We propose to continue our timing project focusing mostly on NGC6752 at 20cm (in order to measure additional parameters useful to constrain the existence of a black-hole) and NGC6397 at 10cm (for studying the eclipse region and the orbital secular evolution). We also request time for performing observations for a new deeper than ever search for millisecond pulsars in a subset of suitable clusters. This revamped search (as well as the requested timing observations) will exploit the new back-ends (APSR and DFB4) now available at Parkes.

  9. Reaction mechanism of the acidic hydrolysis of highly twisted amides: Rate acceleration caused by the twist of the amide bond.

    PubMed

    Mujika, Jon I; Formoso, Elena; Mercero, Jose M; Lopez, Xabier

    2006-08-03

    We present an ab initio study of the acid hydrolysis of a highly twisted amide and a planar amide analogue. The aim of these studies is to investigate the effect that the twist of the amide bond has on the reaction barriers and mechanism of acid hydrolysis. Concerted and stepwise mechanisms were investigated using density functional theory and polarizable continuum model calculations. Remarkable differences were observed between the mechanism of twisted and planar amide, due mainly to the preference for N-protonation of the former and O-protonation of the latter. In addition, we were also able to determine that the hydrolytic mechanism of the twisted amide will be pH dependent. Thus, there is a preference for a stepwise mechanism with formation of an intermediate in the acid hydrolysis, whereas the neutral hydrolysis undergoes a concerted-type mechanism. There is a nice agreement between the characterized intermediate and available X-ray data and a good agreement with the kinetically estimated rate acceleration of hydrolysis with respect to analogous undistorted amide compounds. This work, along with previous ab initio calculations, describes a complex and rich chemistry for the hydrolysis of highly twisted amides as a function of pH. The theoretical data provided will allow for a better understanding of the available kinetic data of the rate acceleration of amides upon twisting and the relation of the observed rate acceleration with intrinsic differential reactivity upon loss of amide bond resonance.

  10. Massive Thermal Acceleration of the Emergence of Primordial Chemistry, the Incidence of Spontaneous Mutation, and the Evolution of Enzymes*

    PubMed Central

    Wolfenden, Richard

    2014-01-01

    Kelvin considered it unlikely that sufficient time had elapsed on the earth for life to have reached its present level of complexity. In the warm surroundings in which life first appeared, however, elevated temperatures would have reduced the kinetic barriers to reaction. Recent experiments disclose the profound extent to which very slow reactions are accelerated by elevated temperatures, collapsing the time that would have been required for early events in primordial chemistry before the advent of enzymes. If a primitive enzyme, like model catalysts and most modern enzymes, accelerated a reaction by lowering its enthalpy of activation, then the rate enhancement that it produced would have increased automatically as the environment cooled, quite apart from any improvements in catalytic activity that arose from mutation and natural selection. The chemical events responsible for spontaneous mutation are also highly sensitive to temperature, furnishing an independent mechanism for accelerating evolution. PMID:25210030

  11. Accelerations in Flight

    NASA Technical Reports Server (NTRS)

    Doolittle, J H

    1925-01-01

    This work on accelerometry was done at McCook Field for the purpose of continuing the work done by other investigators and obtaining the accelerations which occur when a high-speed pursuit airplane is subjected to the more common maneuvers. The accelerations obtained in suddenly pulling out of a dive with well-balanced elevators are shown to be within 3 or 4 per cent of the theoretically possible accelerations. The maximum acceleration which a pilot can withstand depends upon the length of time the acceleration is continued. It is shown that he experiences no difficulty under the instantaneous accelerations as high as 7.8 G., but when under accelerations in excess of 4.5 G., continued for several seconds, he quickly loses his faculties.

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

    PubMed

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

    2014-01-07

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

  13. VisSearch: A Collaborative Web Searching Environment

    ERIC Educational Resources Information Center

    Lee, Young-Jin

    2005-01-01

    VisSearch is a collaborative Web searching environment intended for sharing Web search results among people with similar interests, such as college students taking the same course. It facilitates students' Web searches by visualizing various Web searching processes. It also collects the visualized Web search results and applies an association rule…

  14. CUDAMPF: a multi-tiered parallel framework for accelerating protein sequence search in HMMER on CUDA-enabled GPU.

    PubMed

    Jiang, Hanyu; Ganesan, Narayan

    2016-02-27

    HMMER software suite is widely used for analysis of homologous protein and nucleotide sequences with high sensitivity. The latest version of hmmsearch in HMMER 3.x, utilizes heuristic-pipeline which consists of MSV/SSV (Multiple/Single ungapped Segment Viterbi) stage, P7Viterbi stage and the Forward scoring stage to accelerate homology detection. Since the latest version is highly optimized for performance on modern multi-core CPUs with SSE capabilities, only a few acceleration attempts report speedup. However, the most compute intensive tasks within the pipeline (viz., MSV/SSV and P7Viterbi stages) still stand to benefit from the computational capabilities of massively parallel processors. A Multi-Tiered Parallel Framework (CUDAMPF) implemented on CUDA-enabled GPUs presented here, offers a finer-grained parallelism for MSV/SSV and Viterbi algorithms. We couple SIMT (Single Instruction Multiple Threads) mechanism with SIMD (Single Instructions Multiple Data) video instructions with warp-synchronism to achieve high-throughput processing and eliminate thread idling. We also propose a hardware-aware optimal allocation scheme of scarce resources like on-chip memory and caches in order to boost performance and scalability of CUDAMPF. In addition, runtime compilation via NVRTC available with CUDA 7.0 is incorporated into the presented framework that not only helps unroll innermost loop to yield upto 2 to 3-fold speedup than static compilation but also enables dynamic loading and switching of kernels depending on the query model size, in order to achieve optimal performance. CUDAMPF is designed as a hardware-aware parallel framework for accelerating computational hotspots within the hmmsearch pipeline as well as other sequence alignment applications. It achieves significant speedup by exploiting hierarchical parallelism on single GPU and takes full advantage of limited resources based on their own performance features. In addition to exceeding performance of other

  15. Kinetic and Mechanism Study of Vanadium Acid Leaching from Black Shale Using Microwave Heating Method

    NASA Astrophysics Data System (ADS)

    Wang, Jing-peng; Zhang, Yi-min; Huang, Jing; Liu, Tao

    2018-04-01

    The leaching kinetics of the vanadium leaching process were investigated by the comparison of microwave heating and conventional heating methods. Microwave heating with CaF2 had a synergistic effect and improved the vanadium leaching efficiency. In contrast to conventional heating leaching, microwave heating accelerated the vanadium leaching rate by approximately 1-3% and by approximately 15% when CaF2 was also used. The kinetics analysis showed that the calculated activation energy decreased in the microwave heating method in the presence and absence of CaF2. The control procedure of leaching also changed from a chemical reaction control step to a mixed chemical diffusion control step upon the addition of CaF2. Microwave heating was shown to be suitable for leaching systems with diffusion or mixed chemical diffusion control steps when the target mineral does not have a microwave absorbing ability.

  16. Kinetic and Mechanism Study of Vanadium Acid Leaching from Black Shale Using Microwave Heating Method

    NASA Astrophysics Data System (ADS)

    Wang, Jing-peng; Zhang, Yi-min; Huang, Jing; Liu, Tao

    2018-06-01

    The leaching kinetics of the vanadium leaching process were investigated by the comparison of microwave heating and conventional heating methods. Microwave heating with CaF2 had a synergistic effect and improved the vanadium leaching efficiency. In contrast to conventional heating leaching, microwave heating accelerated the vanadium leaching rate by approximately 1-3% and by approximately 15% when CaF2 was also used. The kinetics analysis showed that the calculated activation energy decreased in the microwave heating method in the presence and absence of CaF2. The control procedure of leaching also changed from a chemical reaction control step to a mixed chemical diffusion control step upon the addition of CaF2. Microwave heating was shown to be suitable for leaching systems with diffusion or mixed chemical diffusion control steps when the target mineral does not have a microwave absorbing ability.

  17. Pressure-strain energy redistribution in compressible turbulence: return-to-isotropy versus kinetic-potential energy equipartition

    NASA Astrophysics Data System (ADS)

    Lee, Kurnchul; Venugopal, Vishnu; Girimaji, Sharath S.

    2016-08-01

    Return-to-isotropy and kinetic-potential energy equipartition are two fundamental pressure-moderated energy redistributive processes in anisotropic compressible turbulence. Pressure-strain correlation tensor redistributes energy among various Reynolds stress components and pressure-dilatation is responsible for energy reallocation between dilatational kinetic and potential energies. The competition and interplay between these pressure-based processes are investigated in this study. Direct numerical simulations (DNS) of low turbulent Mach number dilatational turbulence are performed employing the hybrid thermal Lattice Boltzman method (HTLBM). It is found that a tendency towards equipartition precedes proclivity for isotropization. An evolution towards equipartition has a collateral but critical effect on return-to-isotropy. The preferential transfer of energy from strong (rather than weak) Reynolds stress components to potential energy accelerates the isotropization of dilatational fluctuations. Understanding of these pressure-based redistributive processes is critical for developing insight into the character of compressible turbulence.

  18. Electron acceleration in the Solar corona - 3D PiC code simulations of guide field reconnection

    NASA Astrophysics Data System (ADS)

    Alejandro Munoz Sepulveda, Patricio

    2017-04-01

    The efficient electron acceleration in the solar corona detected by means of hard X-ray emission is still not well understood. Magnetic reconnection through current sheets is one of the proposed production mechanisms of non-thermal electrons in solar flares. Previous works in this direction were based mostly on test particle calculations or 2D fully-kinetic PiC simulations. We have now studied the consequences of self-generated current-aligned instabilities on the electron acceleration mechanisms by 3D magnetic reconnection. For this sake, we carried out 3D Particle-in-Cell (PiC) code numerical simulations of force free reconnecting current sheets, appropriate for the description of the solar coronal plasmas. We find an efficient electron energization, evidenced by the formation of a non-thermal power-law tail with a hard spectral index smaller than -2 in the electron energy distribution function. We discuss and compare the influence of the parallel electric field versus the curvature and gradient drifts in the guiding-center approximation on the overall acceleration, and their dependence on different plasma parameters.

  19. A kinetic equation with kinetic entropy functions for scalar conservation laws

    NASA Technical Reports Server (NTRS)

    Perthame, Benoit; Tadmor, Eitan

    1990-01-01

    A nonlinear kinetic equation is constructed and proved to be well-adapted to describe general multidimensional scalar conservation laws. In particular, it is proved to be well-posed uniformly in epsilon - the microscopic scale. It is also shown that the proposed kinetic equation is equipped with a family of kinetic entropy functions - analogous to Boltzmann's microscopic H-function, such that they recover Krushkov-type entropy inequality on the macroscopic scale. Finally, it is proved by both - BV compactness arguments in the one-dimensional case, that the local density of kinetic particles admits a continuum limit, as it converges strongly with epsilon below 0 to the unique entropy solution of the corresponding conservation law.

  20. Curved-line search algorithm for ab initio atomic structure relaxation

    NASA Astrophysics Data System (ADS)

    Chen, Zhanghui; Li, Jingbo; Li, Shushen; Wang, Lin-Wang

    2017-09-01

    Ab initio atomic relaxations often take large numbers of steps and long times to converge, especially when the initial atomic configurations are far from the local minimum or there are curved and narrow valleys in the multidimensional potentials. An atomic relaxation method based on on-the-flight force learning and a corresponding curved-line search algorithm is presented to accelerate this process. Results demonstrate the superior performance of this method for metal and magnetic clusters when compared with the conventional conjugate-gradient method.

  1. Accelerated cognitive aging following severe traumatic brain injury: A review.

    PubMed

    Wood, Rodger Ll

    2017-01-01

    The primary objective of this review was to examine relevant clinical and experimental literatures for information on the long-term cognitive impact of serious traumatic brain injury (TBI) with regard to the process of cognitive aging. Online journal databases were queried for studies pertaining to cognitive aging in neurologically healthy populations, as well as the late cognitive effects of serious TBI. Additional studies were identified through searching bibliographies of related publications and using Google search engine. Problems of cognition exhibited by young adults after TBI resemble many cognitive weaknesses of attention deficit and poor working memory that are usually seen in an elderly population who have no neurological history. The current state of the literature provides support for the argument that TBI can result in diminished cognitive reserve which may accelerate the normal process of cognitive decline, leading to premature aging, potentially increasing the risk of dementia.

  2. Thermal decomposition of wood: kinetics and degradation mechanisms.

    PubMed

    Poletto, Matheus; Zattera, Ademir J; Santana, Ruth M C

    2012-12-01

    The influence of wood components and cellulose crystallinity on the kinetic degradation of different wood species has been investigated using thermogravimetry. Four wood species were studied: Pinus elliottii (PIE), Eucalyptus grandis (EUG), Mezilaurus itauba (ITA) and Dipteryx odorata (DIP). Thermogravimetric results showed that higher extractive contents in the wood accelerate the degradation process and promote an increase in the conversion values at low temperatures. Alternatively, the results indicated that the cellulose crystallinity inhibits wood degradation; organized cellulose regions slow the degradation process because the well-packed cellulose chains impede heat diffusion, which improves the wood's thermal stability. The wood degradation mechanism occurs by diffusion processes when the conversion values are below 0.4. When the conversion values are above 0.5, the degradation is a result of random nucleation with one nucleus in each particle. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Acceleration of the direct reconstruction of linear parametric images using nested algorithms.

    PubMed

    Wang, Guobao; Qi, Jinyi

    2010-03-07

    Parametric imaging using dynamic positron emission tomography (PET) provides important information for biological research and clinical diagnosis. Indirect and direct methods have been developed for reconstructing linear parametric images from dynamic PET data. Indirect methods are relatively simple and easy to implement because the image reconstruction and kinetic modeling are performed in two separate steps. Direct methods estimate parametric images directly from raw PET data and are statistically more efficient. However, the convergence rate of direct algorithms can be slow due to the coupling between the reconstruction and kinetic modeling. Here we present two fast gradient-type algorithms for direct reconstruction of linear parametric images. The new algorithms decouple the reconstruction and linear parametric modeling at each iteration by employing the principle of optimization transfer. Convergence speed is accelerated by running more sub-iterations of linear parametric estimation because the computation cost of the linear parametric modeling is much less than that of the image reconstruction. Computer simulation studies demonstrated that the new algorithms converge much faster than the traditional expectation maximization (EM) and the preconditioned conjugate gradient algorithms for dynamic PET.

  4. Ir4+-Doped NiFe LDH to expedite hydrogen evolution kinetics as a Pt-like electrocatalyst for water splitting.

    PubMed

    Chen, Qian-Qian; Hou, Chun-Chao; Wang, Chuan-Jun; Yang, Xiao; Shi, Rui; Chen, Yong

    2018-06-06

    NiFe-layered double hydroxide (NiFe LDH) is a state-of-the-art oxygen evolution reaction (OER) electrocatalyst, yet it suffers from rather poor catalytic activity for the hydrogen evolution reaction (HER) due to its extremely sluggish water dissociation kinetics, severely restricting its application in overall water splitting. Herein, we report a novel strategy to expedite the HER kinetics of NiFe LDH by an Ir4+-doping strategy to accelerate the water dissociation process (Volmer step), and thus this catalyst exhibits superior and robust catalytic activity for finally oriented overall water splitting in 1 M KOH requiring only a low initial voltage of 1.41 V delivering at 20 mA cm-2 for more than 50 h.

  5. Non-Isothermal Kinetics.

    ERIC Educational Resources Information Center

    Brown, M. E.; Phillpotts, C. A. R.

    1978-01-01

    Discusses the principle of nonisothermal kinetics and some of the factors involved in such reactions, especially when considering the reliability of the kinetic parameters, compared to those of isothermal conditions. (GA)

  6. Compact Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2004-01-01

    A plasma accelerator has been conceived for both material-processing and spacecraft-propulsion applications. This accelerator generates and accelerates ions within a very small volume. Because of its compactness, this accelerator could be nearly ideal for primary or station-keeping propulsion for spacecraft having masses between 1 and 20 kg. Because this accelerator is designed to generate beams of ions having energies between 50 and 200 eV, it could also be used for surface modification or activation of thin films.

  7. Electrostatically Accelerated Coupled Binding and Folding of Intrinsically Disordered Proteins

    PubMed Central

    Ganguly, Debabani; Otieno, Steve; Waddell, Brett; Iconaru, Luigi; Kriwacki, Richard W.; Chen, Jianhan

    2012-01-01

    Intrinsically disordered proteins (IDPs) are now recognized to be prevalent in biology, and many potential functional benefits have been discussed. However, the frequent requirement of peptide folding in specific interactions of IDPs could impose a kinetic bottleneck, which could be overcome only by efficient folding upon encounter. Intriguingly, existing kinetic data suggest that specific binding of IDPs is generally no slower than that of globular proteins. Here, we exploited the cell cycle regulator p27Kip1 (p27) as a model system to understand how IDPs might achieve efficient folding upon encounter for facile recognition. Combining experiments and coarse-grained modeling, we demonstrate that long-range electrostatic interactions between enriched charges on p27 and near its binding site on cyclin A not only enhance the encounter rate (i.e., electrostatic steering), but also promote folding-competent topologies in the encounter complexes, allowing rapid subsequent formation of short-range native interactions en route to the specific complex. In contrast, nonspecific hydrophobic interactions, while hardly affecting the encounter rate, can significantly reduce the efficiency of folding upon encounter and lead to slower binding kinetics. Further analysis of charge distributions in a set of known IDP complexes reveals that, although IDP binding sites tend to be more hydrophobic compared to the rest of the target surface, their vicinities are frequently enriched with charges to complement those on IDPs. This observation suggests that electrostatically accelerated encounter and induced folding might represent a prevalent mechanism for promoting facile IDP recognition. PMID:22721951

  8. Accelerated telomere shortening and replicative senescence in human fibroblasts overexpressing mutant and wild-type lamin A

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huang Shurong; Risques, Rosa Ana; Martin, George M.

    2008-01-01

    LMNA mutations are responsible for a variety of genetic disorders, including muscular dystrophy, lipodystrophy, and certain progeroid syndromes, notably Hutchinson-Gilford Progeria. Although a number of clinical features of these disorders are suggestive of accelerated aging, it is not known whether cells derived from these patients exhibit cellular phenotypes associated with accelerated aging. We examined a series of isogenic skin fibroblast lines transfected with LMNA constructs bearing known pathogenic point mutations or deletion mutations found in progeroid syndromes. Fibroblasts overexpressing mutant lamin A exhibited accelerated rates of loss of telomeres and shortened replicative lifespans, in addition to abnormal nuclear morphology. Tomore » our surprise, these abnormalities were also observed in lines overexpressing wild-type lamin A. Copy number variants are common in human populations; those involving LMNA, whether arising meiotically or mitotically, might lead to progeroid phenotypes. In an initial pilot study of 23 progeroid cases without detectable WRN or LMNA mutations, however, no cases of altered LMNA copy number were detected. Nevertheless, our findings raise a hypothesis that changes in lamina organization may cause accelerated telomere attrition, with different kinetics for overexpession of wild-type and mutant lamin A, which leads to rapid replicative senescence and progroid phenotypes.« less

  9. QuickVina: accelerating AutoDock Vina using gradient-based heuristics for global optimization.

    PubMed

    Handoko, Stephanus Daniel; Ouyang, Xuchang; Su, Chinh Tran To; Kwoh, Chee Keong; Ong, Yew Soon

    2012-01-01

    Predicting binding between macromolecule and small molecule is a crucial phase in the field of rational drug design. AutoDock Vina, one of the most widely used docking software released in 2009, uses an empirical scoring function to evaluate the binding affinity between the molecules and employs the iterated local search global optimizer for global optimization, achieving a significantly improved speed and better accuracy of the binding mode prediction compared its predecessor, AutoDock 4. In this paper, we propose further improvement in the local search algorithm of Vina by heuristically preventing some intermediate points from undergoing local search. Our improved version of Vina-dubbed QVina-achieved a maximum acceleration of about 25 times with the average speed-up of 8.34 times compared to the original Vina when tested on a set of 231 protein-ligand complexes while maintaining the optimal scores mostly identical. Using our heuristics, larger number of different ligands can be quickly screened against a given receptor within the same time frame.

  10. Microelectromechanical acceleration-sensing apparatus

    DOEpatents

    Lee, Robb M [Albuquerque, NM; Shul, Randy J [Albuquerque, NM; Polosky, Marc A [Albuquerque, NM; Hoke, Darren A [Albuquerque, NM; Vernon, George E [Rio Rancho, NM

    2006-12-12

    An acceleration-sensing apparatus is disclosed which includes a moveable shuttle (i.e. a suspended mass) and a latch for capturing and holding the shuttle when an acceleration event is sensed above a predetermined threshold level. The acceleration-sensing apparatus provides a switch closure upon sensing the acceleration event and remains latched in place thereafter. Examples of the acceleration-sensing apparatus are provided which are responsive to an acceleration component in a single direction (i.e. a single-sided device) or to two oppositely-directed acceleration components (i.e. a dual-sided device). A two-stage acceleration-sensing apparatus is also disclosed which can sense two acceleration events separated in time. The acceleration-sensing apparatus of the present invention has applications, for example, in an automotive airbag deployment system.

  11. SHORT ACCELERATION TIMES FROM SUPERDIFFUSIVE SHOCK ACCELERATION IN THE HELIOSPHERE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Perri, S.; Zimbardo, G., E-mail: silvia.perri@fis.unical.it

    2015-12-10

    The analysis of time profiles of particles accelerated at interplanetary shocks allows particle transport properties to be inferred. The frequently observed power-law decay upstream, indeed, implies a superdiffusive particle transport when the level of magnetic field variance does not change as the time interval from the shock front increases. In this context, a superdiffusive shock acceleration (SSA) theory has been developed, allowing us to make predictions of the acceleration times. In this work we estimate for a number of interplanetary shocks, including the solar wind termination shock, the acceleration times for energetic protons in the framework of SSA and wemore » compare the results with the acceleration times predicted by standard diffusive shock acceleration. The acceleration times due to SSA are found to be much shorter than in the classical model, and also shorter than the interplanetary shock lifetimes. This decrease of the acceleration times is due to the scale-free nature of the particle displacements in the framework of superdiffusion. Indeed, very long displacements are possible, increasing the probability for particles far from the front of the shock to return, and short displacements have a high probability of occurrence, increasing the chances for particles close to the front to cross the shock many times.« less

  12. Dark gauge bosons: LHC signatures of non-abelian kinetic mixing

    DOE PAGES

    Argüelles, Carlos A.; He, Xiao-Gang; Ovanesyan, Grigory; ...

    2017-04-20

    We consider non-abelian kinetic mixing between the Standard Model and a dark sector gauge group associated with the presence of a scalar triplet. The magnitude of the resulting dark photon coupling ϵ is determined by the ratio of the triplet vacuum expectation value, constrained to by by electroweak precision tests, to the scale Λ of the effective theory. The corresponding effective operator Wilson coefficient can be while accommodating null results for dark photon searches, allowing for a distinctive LHC dark photon phenomenology. After outlining the possible LHC signatures, we illustrate by recasting current ATLAS dark photon results into the non-abelianmore » mixing context.« less

  13. Light-current-induced acceleration of degradation of methylammonium lead iodide perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Xiang, Yuren; Zhang, Fan; He, Junjie; Lian, Jiarong; Zeng, Pengju; Song, Jun; Qu, Junle

    2018-04-01

    The photo-conversion efficiency of perovskite solar cells (PSCs) has been improved considerably in recent years, but the poor stability of PSCs still prevents their commercialization. In this report, we use the rate of the integrated short-circuit current change (Drate) to investigate the performance degradation kinetics and identify the degradation of PSCs that is accelerated by the light current. The value of Drate increases by an order of magnitude from about 0.02 to 0.35 mA cm-2·min-1 after light-IV testing. The accelerated degradation progress is proven to be dominated by the hydration process and the migration of the iodine ions of the light current. The migration of the iodine ions enhances the hydration process through a chain reaction, enabling the formation of fast diffusion channels for both H2O and O2, which induce the rapid decomposition of the perovskite film and increase the density of the trap state. The X-ray photoelectron spectroscopy measurement data also indicate that the super oxygen may be formed due to the PCBM damage caused by the migration iodine ions. An understanding of the degradation acceleration mechanism would provide an insight into the effect of ion migration on the stability of PSCs.

  14. [Study on the kinetics of organo-clay removing red tide organisms].

    PubMed

    Wu, Ping; Yu, Zhi-ming

    2007-07-01

    The kinetics of red tide organisms (Heterosigma akashiwo and Scrippsiella trochoidea) coagulation with clays modified by dialkyl-polyoxyethenyl quaternary ammonium compound (DPQAC) was studied using spectrophotometer and fluorometry, and the effects of different kinds and concentrations of clays, the second component DPQAC added in clays and pH on the coagulation rate were examined. When using spectrophotometer, the coagulation kinetics of red tide organism coagulation with organo-clays is well fit for the bimolecular reaction model; while using fluorometry, it is fit for the hyperbola model much better. Moreover, the results also prove that using fluorometry can avoid the great change of permeance efficiency caused by clays' sedimentation when using spectrophotometer, which has availably avoided the influence of clays' sedimentation and reflected the essential of algal coagulation and sedimentation well and truly. The results of two studying methods show that the coagulation rate is more rapid in the system of kaolin than in that of bentonite; increasing the concentration of clays and DPQAC and increasing pH all can accelerate coagulation, and among those increasing the concentration of DPQAC is the most efficient way of increasing the removal efficiency and coagulation rate.

  15. MABE multibeam accelerator

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hasti, D.E.; Ramirez, J.J.; Coleman, P.D.

    1985-01-01

    The Megamp Accelerator and Beam Experiment (MABE) was the technology development testbed for the multiple beam, linear induction accelerator approach for Hermes III, a new 20 MeV, 0.8 MA, 40 ns accelerator being developed at Sandia for gamma-ray simulation. Experimental studies of a high-current, single-beam accelerator (8 MeV, 80 kA), and a nine-beam injector (1.4 MeV, 25 kA/beam) have been completed, and experiments on a nine-beam linear induction accelerator are in progress. A two-beam linear induction accelerator is designed and will be built as a gamma-ray simulator to be used in parallel with Hermes III. The MABE pulsed power systemmore » and accelerator for the multiple beam experiments is described. Results from these experiments and the two-beam design are discussed. 11 refs., 6 figs.« less

  16. Non-isothermal crystallization kinetics of eucalyptus lignosulfonate/polyvinyl alcohol composite.

    PubMed

    Ye, De-Zhan; Zhang, Xi; Gu, Shaojin; Zhou, Yingshan; Xu, Weilin

    2017-04-01

    The nonisothermal crystallinization kinetic was performed on Polyvinyl alcohol (PVA) mixed with eucalyptus lignosulfonate calcuim (HLS) as the biobased thermal stabilizer, which was systematically analyzed based on Jeziorny model, Ozawa equation and the Mo method. The results indicated that the entire crystallization process took place through two main stages involving the primary and secondary crystallization processes. The Mo method described nonisothermal crystallization behavior well. Based on the results of the half time for completing crystallization, k c value in Jeziorny model, F(T) value in Mo method and crystallization activation energy, it was concluded that low loading of HLS accelerated PVA crystallization process, however, the growth rate of PVA crystallization was impeded at high content of HLS. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Advances in petascale kinetic plasma simulation with VPIC and Roadrunner

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bowers, Kevin J; Albright, Brian J; Yin, Lin

    2009-01-01

    VPIC, a first-principles 3d electromagnetic charge-conserving relativistic kinetic particle-in-cell (PIC) code, was recently adapted to run on Los Alamos's Roadrunner, the first supercomputer to break a petaflop (10{sup 15} floating point operations per second) in the TOP500 supercomputer performance rankings. They give a brief overview of the modeling capabilities and optimization techniques used in VPIC and the computational characteristics of petascale supercomputers like Roadrunner. They then discuss three applications enabled by VPIC's unprecedented performance on Roadrunner: modeling laser plasma interaction in upcoming inertial confinement fusion experiments at the National Ignition Facility (NIF), modeling short pulse laser GeV ion acceleration andmore » modeling reconnection in magnetic confinement fusion experiments.« less

  18. Probing electron acceleration and x-ray emission in laser-plasma accelerators

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Thaury, C.; Ta Phuoc, K.; Corde, S.

    2013-06-15

    While laser-plasma accelerators have demonstrated a strong potential in the acceleration of electrons up to giga-electronvolt energies, few experimental tools for studying the acceleration physics have been developed. In this paper, we demonstrate a method for probing the acceleration process. A second laser beam, propagating perpendicular to the main beam, is focused on the gas jet few nanosecond before the main beam creates the accelerating plasma wave. This second beam is intense enough to ionize the gas and form a density depletion, which will locally inhibit the acceleration. The position of the density depletion is scanned along the interaction lengthmore » to probe the electron injection and acceleration, and the betatron X-ray emission. To illustrate the potential of the method, the variation of the injection position with the plasma density is studied.« less

  19. Pressure-dependent decomposition kinetics of the energetic material HMX up to 3.6 GPa.

    PubMed

    Glascoe, Elizabeth A; Zaug, Joseph M; Burnham, Alan K

    2009-12-03

    The effect of pressure on the global thermal decomposition rate of the energetic material HMX was studied. HMX was precompressed in a diamond anvil cell (DAC) and heated at various rates. The parent species population was monitored as a function of time and temperature using Fourier transform infrared (FTIR) spectroscopy. Global decomposition rates were determined by fitting the fraction reacted to the extended-Prout-Tompkins nucleation-growth model and the Friedman isoconversional method. The results of these experiments and analysis indicate that pressure accelerates the decomposition at low-to-moderate pressures (i.e., between ambient pressure and 0.1 GPa) and decelerates the decomposition at higher pressures. The decomposition acceleration is attributed to pressure-enhanced autocatalysis, whereas the deceleration at high pressures is attributed to pressure-inhibiting bond homolysis step(s), which would result in an increase in volume. These results indicate that both the beta- and delta-polymorphs of HMX are sensitive to pressure in the thermally induced decomposition kinetics.

  20. Empirical force field-based kinetic Monte Carlo simulation of precipitate evolution and growth in Al-Cu alloys

    NASA Astrophysics Data System (ADS)

    Joshi, Kaushik; Chaudhuri, Santanu

    2016-10-01

    Ability to accelerate the morphological evolution of nanoscale precipitates is a fundamental challenge for atomistic simulations. Kinetic Monte Carlo (KMC) methodology is an effective approach for accelerating the evolution of nanoscale systems that are dominated by so-called rare events. The quality and accuracy of energy landscape used in KMC calculations can be significantly improved using DFT-informed interatomic potentials. Using newly developed computational framework that uses molecular simulator LAMMPS as a library function inside KMC solver SPPARKS, we investigated formation and growth of Guiner-Preston (GP) zones in dilute Al-Cu alloys at different temperature and copper concentrations. The KMC simulations with angular dependent potential (ADP) predict formation of coherent disc-shaped monolayers of copper atoms (GPI zones) in early stage. Such monolayers are then gradually transformed into energetically favored GPII phase that has two aluminum layers sandwiched between copper layers. We analyzed the growth kinetics of KMC trajectory using Johnson-Mehl-Avrami (JMA) theory and obtained a phase transformation index close to 1.0. In the presence of grain boundaries, the KMC calculations predict the segregation of copper atoms near the grain boundaries instead of formation of GP zones. The computational framework presented in this work is based on open source potentials and MD simulator and can predict morphological changes during the evolution of the alloys in the bulk and around grain boundaries.