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Sample records for point particle limit

  1. Collisions of unequal mass black holes and the point particle limit

    SciTech Connect

    Sperhake, Ulrich; Cardoso, Vitor; Ott, Christian D.; Schnetter, Erik; Witek, Helvi

    2011-10-15

    Numerical relativity has seen incredible progress in the last years, and is being applied with success to a variety of physical phenomena, from gravitational wave research and relativistic astrophysics to cosmology and high-energy physics. Here we probe the limits of current numerical setups, by studying collisions of unequal mass, nonrotating black holes of mass ratios up to 1 ratio 100 and making contact with a classical calculation in general relativity: the infall of a pointlike particle into a massive black hole. Our results agree well with the predictions coming from linearized calculations of the infall of pointlike particles into nonrotating black holes. In particular, in the limit that one hole is much smaller than the other, and the infall starts from an infinite initial separation, we recover the point-particle limit. Thus, numerical relativity is able to bridge the gap between fully nonlinear dynamics and linearized approximations, which may have important applications. Finally, we also comment on the 'spurious' radiation content in the initial data and the linearized predictions.

  2. Point-particle limit and the far-zone quadrupole formula in general relativity

    SciTech Connect

    Futamase, T.

    1985-11-15

    Strong internal gravity is incorporated in a divergent-free post-Newtonian approximation scheme by introducing a body-zone limit. When incorporated into the notion of sequences of solutions, this provides the first rigorous point-particle limit in general relativity. The scheme is applied to construct an asymptotic approximation to a binary system composed of two rotating neutron stars. The lowest-order calculation is carried out in the near and far zones, giving Newton's equations of motion and the far-zone quadrupole formula. The quadrupole moment of the system is expressed in terms of a mass integral over each compact star. The same mass appears in Newton's equations of motion. The mass is indeed the Arnowitt-Deser-Misner mass the compact star would have if it were isolated. Thus the equivalence principle for strong gravity is confirmed, even for gravitational radiation: gravitational potential energy radiates the same amount of gravitational waves as any other form of energy does.

  3. Limits on light weakly interacting massive particles from the CDEX-1 experiment with a p -type point-contact germanium detector at the China Jinping Underground Laboratory

    NASA Astrophysics Data System (ADS)

    Yue, Q.; Zhao, W.; Kang, K. J.; Cheng, J. P.; Li, Y. J.; Lin, S. T.; Chang, J. P.; Chen, N.; Chen, Q. H.; Chen, Y. H.; Chuang, Y. C.; Deng, Z.; Du, Q.; Gong, H.; Hao, X. Q.; He, H. J.; He, Q. J.; Huang, H. X.; Huang, T. R.; Jiang, H.; Li, H. B.; Li, J. M.; Li, J.; Li, J.; Li, X.; Li, X. Y.; Li, Y. L.; Liao, H. Y.; Lin, F. K.; Liu, S. K.; Lü, L. C.; Ma, H.; Mao, S. J.; Qin, J. Q.; Ren, J.; Ren, J.; Ruan, X. C.; Shen, M. B.; Singh, L.; Singh, M. K.; Soma, A. K.; Su, J.; Tang, C. J.; Tseng, C. H.; Wang, J. M.; Wang, L.; Wang, Q.; Wong, H. T.; Wu, S. Y.; Wu, Y. C.; Wu, Y. C.; Xianyu, Z. Z.; Xiao, R. Q.; Xing, H. Y.; Xu, F. Z.; Xu, Y.; Xu, X. J.; Xue, T.; Yang, L. T.; Yang, S. W.; Yi, N.; Yu, C. X.; Yu, H.; Yu, X. Z.; Zeng, X. H.; Zeng, Z.; Zhang, L.; Zhang, Y. H.; Zhao, M. G.; Zhou, Z. Y.; Zhu, J. J.; Zhu, W. B.; Zhu, X. Z.; Zhu, Z. H.; CDEX Collaboration

    2014-11-01

    We report results of a search for light dark matter weakly interacting massive particles (WIMPs) with CDEX-1 experiment at the China Jinping Underground Laboratory, based on 53.9 kg-days of data from a p -type point-contact germanium detector enclosed by a NaI(Tl) crystal scintillator as anti-Compton detector. The event rate and spectrum above the analysis threshold of 475 eVee are consistent with the understood background model. Part of the allowed regions for WIMP-nucleus coherent elastic scattering at WIMP mass of 6-20 GeV are probed and excluded. Independent of interaction channels, this result contradicts the interpretation that the anomalous excesses of the CoGeNT experiment are induced by dark matter, since identical detector techniques are used in both experiments.

  4. Salt deposition at particle contact points

    NASA Astrophysics Data System (ADS)

    Nie, Xiaodong; Evitts, Richard W.; Besant, Robert W.; Kennell, Glyn F.

    2015-09-01

    Caking may occur when granular potash fertilizer with a moisture content greater than 0.25 % (w/w) undergoes drying. Since cake strength is proportional to the mass of crystal deposited per unit volume near contact points (and other factors) the modelling of mass deposition near contact points is important. The Young-Laplace equation for the air-salt-solution interface is used to determine the geometry of a 2-D planar saline film between two cubic potash particles. A 2-D theoretical model is developed and applied for ion diffusion and deposition near the contact point during drying. The numerical predictions of ion diffusion in an initially saturated salt illustrate the transient spatial distribution of new KCl deposits along the solid surfaces near the contact line. These results indicate the average salt deposition commences at the air-liquid-solid intersection, where the liquid film is thinnest, and moves toward the particle contact point with increasing area averaged KCl deposits, causing the formation of crystal deposits and bridges near contact points. It is concluded that the average salt deposit height increases inversely with distance from the contact point and decreases with initial contact angle of the contact region, but the deposition is nearly independent of the evaporation or drying rate near each contact region. Caking strength depends on, among other parameters, the amount of salt deposition near contact points.

  5. Diffusion-Limited Aggregation with Polygon Particles

    NASA Astrophysics Data System (ADS)

    Deng, Li; Wang, Yan-Ting; Ou-Yang, Zhong-Can

    2012-12-01

    Diffusion-limited aggregation (DLA) assumes that particles perform pure random walk at a finite temperature and aggregate when they come close enough and stick together. Although it is well known that DLA in two dimensions results in a ramified fractal structure, how the particle shape influences the formed morphology is still unclear. In this work, we perform the off-lattice two-dimensional DLA simulations with different particle shapes of triangle, quadrangle, pentagon, hexagon, and octagon, respectively, and compare with the results for circular particles. Our results indicate that different particle shapes only change the local structure, but have no effects on the global structure of the formed fractal cluster. The local compactness decreases as the number of polygon edges increases.

  6. Preliminary particle scoop limiter measurements in PDX

    SciTech Connect

    Jacobsen, R.

    1981-08-01

    A plasma edge particle scoop limiter has been installed on the equator of the Princeton Divertor Experiment (PDX), a large tokamak. The scoop limiter is unique in that it is designed such that the plasma plugs the entrance throat thereby impeding the return flow of neutralized gas to the discharge. Neutral gas pressures of the order of 50 microns were measured inside the scoop. The pressure dependence on electron density in the scrapeoff plasma at the throat entrance was stronger than linear.

  7. Diffusion-limited deposition of dipolar particles.

    PubMed

    de los Santos, F; Tavares, J M; Tasinkevych, M; Telo da Gama, M M

    2004-06-01

    Deposits of dipolar particles are investigated by means of extensive Monte Carlo simulations. We found that the effect of the interactions is described by an initial, nonuniversal, scaling regime characterized by orientationally ordered deposits. In the dipolar regime, the order and geometry of the clusters depend on the strength of the interactions and the magnetic properties are tunable by controlling the growth conditions. At later stages, the growth is dominated by thermal effects and the diffusion-limited universal regime obtains, at finite temperatures. At low temperatures the crossover size increases exponentially as T decreases and at T=0 only the dipolar regime is observed. PMID:15244567

  8. Quantum limited particle sensing in optical tweezers

    SciTech Connect

    Tay, J.W.; Hsu, Magnus T. L.; Bowen, Warwick P.

    2009-12-15

    Particle sensing in optical tweezers systems provides information on the position, velocity, and force of the specimen particles. The conventional quadrant detection scheme is applied ubiquitously in optical tweezers experiments to quantify these parameters. In this paper, we show that quadrant detection is nonoptimal for particle sensing in optical tweezers and propose an alternative optimal particle sensing scheme based on spatial homodyne detection. A formalism for particle sensing in terms of transverse spatial modes is developed and numerical simulations of the efficacies of both quadrant and spatial homodyne detection are shown. We demonstrate that 1 order of magnitude improvement in particle sensing sensitivity can be achieved using spatial homodyne over quadrant detection.

  9. Bounded limit for the Monte Carlo point-flux-estimator

    SciTech Connect

    Grimesey, R.A.

    1981-01-01

    In a Monte Carlo random walk the kernel K(R,E) is used as an expected value estimator at every collision for the collided flux phi/sub c/ r vector,E) at the detector point. A limiting value for the kernel is derived from a diffusion approximation for the probability current at a radius R/sub 1/ from the detector point. The variance of the collided flux at the detector point is thus bounded using this asymptotic form for K(R,E). The bounded point flux estimator is derived. (WHK)

  10. Fundamental concepts and limitations in precision pointing and tracking problems

    NASA Astrophysics Data System (ADS)

    Johnson, Carroll D.; Masten, Michael K.

    1993-10-01

    In this paper, we first describe the generic pointing and tracking problems in a general dynamical system/state-space context. Then, we analyze the information-theoretical aspects of the various uncertain signals in those problems, and establish some fundamental performance limitations those uncertainties induce, using various results and principles of modern control theory. It is shown that the introduction of 'waveform models' for uncertain signals, leading to an extended-state formulation of pointing and tracking problems, is the most effective rational means of coping with those fundamental limitations.

  11. Continuum Limit of Total Variation on Point Clouds

    NASA Astrophysics Data System (ADS)

    García Trillos, Nicolás; Slepčev, Dejan

    2016-04-01

    We consider point clouds obtained as random samples of a measure on a Euclidean domain. A graph representing the point cloud is obtained by assigning weights to edges based on the distance between the points they connect. Our goal is to develop mathematical tools needed to study the consistency, as the number of available data points increases, of graph-based machine learning algorithms for tasks such as clustering. In particular, we study when the cut capacity, and more generally total variation, on these graphs is a good approximation of the perimeter (total variation) in the continuum setting. We address this question in the setting of Γ-convergence. We obtain almost optimal conditions on the scaling, as the number of points increases, of the size of the neighborhood over which the points are connected by an edge for the Γ-convergence to hold. Taking of the limit is enabled by a transportation based metric which allows us to suitably compare functionals defined on different point clouds.

  12. Two-point particle tracking microrheology of nematic complex fluids.

    PubMed

    Gómez-González, Manuel; Del Álamo, Juan C

    2016-06-29

    Many biological and technological complex fluids exhibit tight microstructural alignment that confers them nematic mechanical properties. Among these we count liquid crystals and biopolymer networks, which are often available in microscopic amounts. However, current microrheological methods cannot measure the directional viscoelastic coefficients that appear in the constitutive relation of nematic complex fluids. This article presents directional two-point particle-tracking microrheology (D2PTM) - a novel microrheology technique to determine these coefficients. We establish the theoretical foundation for D2PTM by analyzing the motion of a probing microscopic particle embedded in a nematic complex fluid, and the mutual hydrodynamic interactions between pairs of distant particles. From this analysis, we generalize the formulation of two-point particle tracking microrheology for nematic complex fluids, and demonstrate that the new formulation provides sufficient information to fully characterize the anisotropic viscoelastic coefficients of such materials. We test D2PTM by simulating the Brownian motion of particles in nematic viscoelastic fluids with prescribed directional frequency-dependent shear moduli, showing that D2PTM accurately recovers the prescribed shear moduli. Furthermore, we experimentally validate D2PTM by applying it to a lyotropic nematic liquid crystal, and demonstrate that this new microrheology method provides results in agreement with dynamic light scattering measurements. Lastly, we illustrate the experimental application of the new technique to characterize nematic F-actin solutions. These experiments constitute the first microrheological measurement of the directional viscoelastic coefficients of an anisotropic soft material. PMID:27270816

  13. Microscale Simulations of Shock Interaction with Large Assembly of Particles for Developing Point-Particle Models

    NASA Astrophysics Data System (ADS)

    Thakur, Siddharth; Neal, Chris; Mehta, Yash; Sridharan, Prashanth; Jackson, Tom; Balachandar, S.; University of Florida Team

    2015-06-01

    Micrsoscale simulations are being conducted for developing point-particle models that are needed for macroscale simulations of explosive dispersal of particles. These particle models are required to compute instantaneous force and heat transfer between particles and surroundings. A strategy for a sequence of microscale simulations has been devised for systematic development of hybrid surrogate models that are applicable at conditions representative of explosive dispersal. The microscale simulations examine particle force dependence on: Mach number, Reynolds number, and volume fraction (particle arrangements such as cubic, face-centered cubic, body-centered cubic and random). Future plans include investigation of sequences of fully-resolved microscale simulations consisting of an array of particles subjected to more realistic time-dependent flows that progressively better approximate the problem of explosive dispersal. Additionally, effects of particle shape, size, and number as well as the transient particle deformation dependence on parameters including: (a) particle material, (b) medium material, (c) multiple particles, (d) incoming shock pressure and speed, (e) medium to particle impedance ratio, (f) particle shape and orientation to shock, etc. are being investigated.

  14. Accuracy limit of rigid 3-point water models.

    PubMed

    Izadi, Saeed; Onufriev, Alexey V

    2016-08-21

    Classical 3-point rigid water models are most widely used due to their computational efficiency. Recently, we introduced a new approach to constructing classical rigid water models [S. Izadi et al., J. Phys. Chem. Lett. 5, 3863 (2014)], which permits a virtually exhaustive search for globally optimal model parameters in the sub-space that is most relevant to the electrostatic properties of the water molecule in liquid phase. Here we apply the approach to develop a 3-point Optimal Point Charge (OPC3) water model. OPC3 is significantly more accurate than the commonly used water models of same class (TIP3P and SPCE) in reproducing a comprehensive set of liquid bulk properties, over a wide range of temperatures. Beyond bulk properties, we show that OPC3 predicts the intrinsic charge hydration asymmetry (CHA) of water - a characteristic dependence of hydration free energy on the sign of the solute charge - in very close agreement with experiment. Two other recent 3-point rigid water models, TIP3PFB and H2ODC, each developed by its own, completely different optimization method, approach the global accuracy optimum represented by OPC3 in both the parameter space and accuracy of bulk properties. Thus, we argue that an accuracy limit of practical 3-point rigid non-polarizable models has effectively been reached; remaining accuracy issues are discussed. PMID:27544113

  15. Influence of particle size on diffusion-limited aggregation.

    PubMed

    Tan, Z J; Zou, X W; Zhang, W B; Jin, Z Z

    1999-11-01

    The influence of particle size on diffusion-limited aggregation (DLA) has been investigated by computer simulations. For DLA clusters consisting of two kinds of particles with different sizes, when large particles are in the minority, the patterns of clusters appear asymmetrical and nonuniform, and their fractal dimensions D(f) increase compared with one-component DLA. With increasing size of large particles, D(f) increases. This increase can be attributed to two reasons: one is that large particles become new growth centers; the other is the big masses of large particles. As the concentration ratio x(n) of large particles increases, D(f) will reach a maximum value D(f(m)) and then decrease. When x(n) exceeds a certain value, the morphology and D(f) of the two-component DLA clusters are similar to those of one-component DLA clusters. PMID:11970534

  16. The dynamics of point particles around black holes

    NASA Astrophysics Data System (ADS)

    Vega, Michael Francis Ian G., II

    A point particle moving in a curved spacetime gives rise to fields that in turn affect its motion. One conveniently thinks of this interplay as the response of the particle to its self-force. To date, models of point particle motion in the vicinity of black holes have ignored parts of this self-force because it is such a challenge to calculate. This work is part of a larger effort to develop systematic tools for the efficient calculation of such self-forces. This development is made with the aim of accurately simulating the inspiraling motion of compact objects onto supermassive black holes (also known as extreme-mass-ratio binary inspirals, or EMRIs), and of obtaining good predictions of the gravitational waves they emit. EMRIs are the main targets for the proposed space-based gravitational wave detector, the Laser Interferometer Space Antenna (LISA). For the mission to succeed, accurate templates of the gravitational waves it will pick up are necessary. This work is an attempt to address this need. The main contribution of this dissertation is the design and testing of a novel method for simultaneously calculating self-forces and radiation fluxes due point particle sources using (3+1) codes. Concrete calculations of self-forces for particles in strong-field gravity have only previously been done through mode sum approaches, which, while having been critical to the development of the subject, appears inconvenient for the eventual goal of using a calculated self-force to update particle trajectories. The new method avoids a mode decomposition entirely, and instead properly replaces the distributional source of the curved spacetime wave equation by an effective regular source. The resulting regular solution of the wave equation, under appropriate boundary conditions, results in the physical retarded field when evaluated in the wavezone, while its gradient at the location of the particle gives the full self-force. This prescription is founded on the possibility of

  17. The Observed squeezed limit of cosmological three-point functions

    NASA Astrophysics Data System (ADS)

    Pajer, Enrico; Schmidt, Fabian; Zaldarriaga, Matias

    2013-10-01

    The squeezed limit of the three-point function of cosmological perturbations is a powerful discriminant of different models of the early Universe. We present a conceptually simple and complete framework to relate any primordial bispectrum in this limit to late time observables, such as the cosmic microwave background (CMB) temperature bispectrum and the scale-dependent halo bias. We employ a series of convenient coordinate transformations to capture the leading nonlinear effects of cosmological perturbation theory on these observables. This makes crucial use of Fermi normal coordinates and their conformal generalization, which we introduce here and discuss in detail. As an example, we apply our formalism to standard slow-roll single-field inflation. We show explicitly that Maldacena’s results for the squeezed limits of the scalar bispectrum [proportional to (ns-1) in comoving gauge] and the tensor-scalar-scalar bispectrum lead to no deviations from a Gaussian universe, except for projection effects. In particular, the primordial contributions to the squeezed CMB bispectrum and scale dependent halo bias vanish, and there are no primordial “fossil” correlations between long-wavelength tensor perturbations and small-scale perturbations. The contributions to observed correlations are then only due to projection effects such as gravitational lensing and redshift perturbations.

  18. Shock interaction with a deformable particle: Direct numerical simulation and point-particle modeling

    NASA Astrophysics Data System (ADS)

    Ling, Y.; Haselbacher, A.; Balachandar, S.; Najjar, F. M.; Stewart, D. S.

    2013-01-01

    The interaction of shock waves with deformable particles is an important fundamental problem. In some applications, e.g., the detonation of explosives loaded with metal particles, the pressure behind the shock wave can be significantly larger than the yield strength of the particle material. This means that particles can deform severely during their interaction with the shock wave. The experimental and theoretical studies of shock interaction with deformable particles (SIDP) are extremely challenging because of its highly transient nature. As a result, no accurate model exists yet that can be used in simulations. The objective of this paper is to develop a simple point-particle model that accurately captures the unsteady force and heat-transfer in SIDP. In the development of this model, we build on earlier models by Ling et al. (Int. J. Multiphase Flow 37, 1026-1044 (2011)) for the unsteady force and heat-transfer contributions for rigid particles. Insights gained from direct numerical simulations (DNS) guide the extension of these models to deforming particles. Results obtained with the extended model for the interaction of a deforming particle with a shock wave and a Chapman-Jouguet detonation wave compare well with DNS results and therefore offer significant improvements over standard models.

  19. Multi-point Observations and Modeling of Particle Injections

    NASA Astrophysics Data System (ADS)

    Henderson, M. G.; Morley, S.; Reeves, G. D.; Larsen, B.; Skoug, R. M.; Funsten, H. O.; Spence, H. E.

    2014-12-01

    Dispersionless and dispersed particle injections associated with substorms have been studied for many years based on observations acquired primarily at geosynchronous orbit. A general picture that has emerged is that particles are energized and rapidly transported/organized behind an "injection boundary" that penetrates closer to Earth in some magnetic local time sector (e.g. the so-called double-spiral injection boundary model). While this picture provides a very good description of injections at geosynchronous orbit, with the recent launchof the Van Allen Probes mission, we are now able to explore the evolution of injection signatures well inside of geosynchronous orbit at multiple locations as well. Here we report initial results of injection boundary modeling based on simultaneous multi-point measurements at both geosynchronous orbit (from the LANL/GEO spacecraft) and inside (from Van Allen Probes spacecraft). It is shown that many of the complex dispersion features observed in Van Allen Probes particle data are reproduced by the injection boundary model.

  20. A Diffusion Limit for a Test Particle in a Random Distribution of Scatterers

    NASA Astrophysics Data System (ADS)

    Basile, G.; Nota, A.; Pulvirenti, M.

    2014-06-01

    We consider a point particle moving in a random distribution of obstacles described by a potential barrier. We show that, in a weak-coupling regime, under a diffusion limit suggested by the potential itself, the probability distribution of the particle converges to the solution of the heat equation. The diffusion coefficient is given by the Green-Kubo formula associated to the generator of the diffusion process dictated by the linear Landau equation.

  1. Energy straggling eliminated as a limitation to charge resolution of transmission detectors. [used for particle identification

    NASA Technical Reports Server (NTRS)

    Tarle, G.; Ahlen, S. P.; Price, P. B.

    1981-01-01

    It is pointed out that detectors of the energy loss of penetrating charged particles are widely used for particle identification. These measurements are hampered, however, by fluctuations in the amount of energy deposited within the detector. It is shown that this limitation can be overcome with a new nuclear track detector, CR-39(DOP), and that the charge resolution of this detector exceeds that of any other, including semiconductor diodes.

  2. Stochastic dynamics of coupled active particles in an overdamped limit

    NASA Astrophysics Data System (ADS)

    Ann, Minjung; Lee, Kong-Ju-Bock; Park, Pyeong Jun

    2015-10-01

    We introduce a model for Brownian dynamics of coupled active particles in an overdamped limit. Our system consists of several identical active particles and one passive particle. Each active particle is elastically coupled to the passive particle and there is no direct coupling among the active particles. We investigate the dynamics of the system with respect to the number of active particles, viscous friction, and coupling between the active and passive particles. For this purpose, we consider an intracellular transport process as an application of our model and perform a Brownian dynamics simulation using realistic parameters for processive molecular motors such as kinesin-1. We determine an adequate energy conversion function for molecular motors and study the dynamics of intracellular transport by multiple motors. The results show that the average velocity of the coupled system is not affected by the number of active motors and that the stall force increases linearly as the number of motors increases. Our results are consistent with well-known experimental observations. We also examine the effects of coupling between the motors and the cargo, as well as of the spatial distribution of the motors around the cargo. Our model might provide a physical explanation of the cooperation among active motors in the cellular transport processes.

  3. Advantages and Limitations of the RICH Technique for Particle Identification

    SciTech Connect

    Ratcliff, Blair N.; /SLAC

    2011-11-07

    The ring imaging Cherenkov (RICH) technique for hadronic particle identification (PID) is described. The advantages and limitations of RICH PID counters are compared with those of other classic PID techniques, such as threshold Cherenkov counters, ionization loss (dE/dx) in tracking devices, and time of flight (TOF) detectors.

  4. Nucleation of mesospheric cloud particles: Sensitivities and limits

    NASA Astrophysics Data System (ADS)

    Wilms, Henrike; Rapp, Markus; Kirsch, Annekatrin

    2016-03-01

    Nucleation of mesospheric ice particles is thought to occur via heterogeneous nucleation on meteor smoke particles. However, several factors determining the nucleation rate are poorly known. To study the effect of uncertainties in the nucleation rate on cloud properties, we use the Community Aerosol and Radiation Model for Atmospheres and systematically vary the nucleation rate over ±10 orders of magnitude. In one set of simulations, the background state of the atmosphere is described by climatological conditions. In a second set, gravity wave-perturbed profiles from the Kühlungsborn Mechanistic general Circulation Model (KMCM) are used with typical temperature (vertical wind) perturbations at the mesopause on the order of 9 K (0.45 m/s). The resulting noctilucent cloud (NLC) characteristics are compared to lidar and satellite measurements. Realistic NLCs compared to the lidar measurements can only be modeled if the nucleation rate is reduced by up to 3 orders of magnitude compared to standard assumptions. For the same cases, the simulated NLCs compare best to the satellite measurements if the nucleation rate is reduced by 2 orders of magnitude or more. Dynamical processes at the mesopause strongly influence the NLC development. In a gravity wave-perturbed atmosphere, the ice particles have only limited time for nucleation and growth. The growth time is limited by the vertical wind, because the vertical wind determines the residence time of the ice particles in the supersaturated region. Since the vertical wind amplitudes reach 1.5 m/s in KMCM (compared to a mean upwelling of ˜4 cm/s in the climatology), the ice particles remain significantly smaller in a gravity wave-perturbed atmosphere than in climatological background conditions.

  5. Influence of neighboring reactive particles on diffusion-limited reactions

    NASA Astrophysics Data System (ADS)

    Eun, Changsun; Kekenes-Huskey, Peter M.; McCammon, J. Andrew

    2013-07-01

    Competition between reactive species is commonplace in typical chemical reactions. Specifically the primary reaction between a substrate and its target enzyme may be altered when interactions with secondary species in the system are substantial. We explore this competition phenomenon for diffusion-limited reactions in the presence of neighboring particles through numerical solution of the diffusion equation. As a general model for globular proteins and small molecules, we consider spherical representations of the reactants and neighboring particles; these neighbors vary in local density, size, distribution, and relative distance from the primary target reaction, as well as their surface reactivity. Modulations of these model variables permit inquiry into the influence of excluded volume and competition on the primary reaction due to the presence of neighboring particles. We find that the surface reactivity effect is long-ranged and a strong determinant of reaction kinetics, whereas the excluded volume effect is relatively short-ranged and less influential in comparison. As a consequence, the effect of the excluded volume is only modestly dependent on the neighbor distribution and is approximately additive; this additivity permits a linear approximation to the many-body effect on the reaction kinetics. In contrast, the surface reactivity effect is non-additive, and thus it may require higher-order approximations to describe the reaction kinetics. Our model study has broad implications in the general understanding of competition and local crowding on diffusion-limited chemical reactions.

  6. Limitation of point source pesticide pollution: results of bioremediation system.

    PubMed

    Spanoghe, P; Maes, A; Steurbaut, W

    2004-01-01

    Groundwater and surface water is at risk of contamination from the use of some agricultural pesticides. In many circumstances pesticide contamination of water resources is more likely to result from point sources than from diffuse sources following approved application to crops in the field. Such point sources include areas on farms where pesticides are handled, filled into sprayers or where sprayers are washed down. To overcome this way of contamination different kind of bio-remediation systems are nowadays in development. In Flanders, Belgium two pilot plants of bioremediation systems for the in situ retention and/or degradation of pesticides were installed. Both systems were based on the Phytobac concept, a watertight excavation filled with straw, peat, compost and soil. The channel was made in the bottom from plastic foil. All kinds of spray rests were captured by the phytobacs. This study focuses on what level pesticides leach, bio-degrade or are retained by the filling of the phytobac. The soil-properties of the filling were investigated. Pesticide tracers were added for monitoring to both phytobacs. Soil and water samples were taken during one year. Pesticides are retained at least for one month by the filling of the phytobac. Almost no pesticide leached out. In winter hardly any pesticide degradation was observed in the filling of the phytobac. In summer no detectable pesticides were still left in the phytobacs. PMID:15756863

  7. Theoretical limit in the magnetization reversal of stoner particles.

    PubMed

    Wang, X R; Sun, Z Z

    2007-02-16

    Magnetization reversal of uniaxial Stoner particles under the Slonczewski spin-transfer torques of polarized electric currents is investigated. Based on the modified Landau-Lifshitz-Gilbert equation of magnetization dynamics, the theoretical limit of critical currents required to reverse a magnetization with an arbitrary polarized current is obtained. Under a constant polarization degree and constant current amplitude, the optimal current pulse for the fastest magnetization reversal is derived. These results can be used as benchmarks to evaluate different reversal strategies besides other possible usages. PMID:17359053

  8. Strategies for setting occupational exposure limits for particles.

    PubMed Central

    Greim, H A; Ziegler-Skylakakis, K

    1997-01-01

    To set occupational exposure limits (OELs) for aerosol particles, dusts, or chemicals, one has to evaluate whether mechanistic considerations permit identification of a no observed effect level (NOEL). In the case of carcinogenic effects, this can be assumed if no genotoxicity is involved, and exposure is considered safe if it does not exceed the NOEL. If tumor induction is associated with genotoxicity, any exposure is considered to be of risk, although a NOEL may be identified in the animal or human exposure studies. This must also be assumed when no information on the carcinogenic mechanism, including genotoxicity, is available. Aerosol particles, especially fibrous dusts, which include man-made mineral fiber(s) (MMMF), present a challenge for toxicological evaluation. Many MMMF that have been investigated have induced tumors in animals and genotoxicity in vitro. Since these effects have been associated with long-thin fiber geometry and high durability in vivo, all fibers meeting such criteria are considered carcinogenic unless the opposite has been demonstrated. This approach is practicable. Investigations on fiber tumorigenicity/genotoxicity should include information on dose response, pathobiochemistry, particle clearance, and persistence of the material in the target organ. Such information will introduce quantitative aspects into the qualitative approach that has so far been used to classify fibrous dusts as carcinogens. The rationales for classifying the potential carcinogenicity of MMMF and for setting OELs used by the different European committees and regulatory agencies are described. PMID:9400750

  9. Cosmological limits on axions and axion-like particles

    NASA Astrophysics Data System (ADS)

    Cadamuro, Davide

    2012-10-01

    The axion is a pseudo-Nambu-Goldstone boson. It appears after the spontaneous breaking of the Peccei-Quinn symmetry, which was proposed to solve the strong-CP problem. Other pseudo-Nambu-Goldstone bosons, postulated in some extensions of the standard model of particle physics, are called axion-like particles (ALPs) if they share certain characteristics with the axion, in particular a coupling to two photons. Thus far, axion and ALP searches have been unsuccessful, indicating that their couplings have to be extremely weak. However, axions and ALPs could be responsible for some observable effects in astrophysics and cosmology, which can also be exploited to constrain the parameter space of these particles. We focus on limits coming from cosmology, which is an optimal field for studying axions and ALPs. In particular, we first investigate the possibility of a primordial population of axions and ALPs arising during the earliest epochs of the universe. The importance of this analysis lies on the fact that axions and ALPs are ideal dark matter candidates because of their faint interactions and their peculiar production mechanisms. Finally, we consider the consequences of the decay of such a population on specific cosmological observables, namely the photon spectrum of galaxies, the cosmic microwave background, the effective number of neutrino species, and the abundance of primordial elements. Our bounds constitute the most stringent probes of early decays and exclude a part of the ALP parameter space that is otherwise very difficult to test experimentally.

  10. Optical multi-point measurements of the acoustic particle velocity with frequency modulated Doppler global velocimetry.

    PubMed

    Fischer, Andreas; König, Jörg; Haufe, Daniel; Schlüssler, Raimund; Büttner, Lars; Czarske, Jürgen

    2013-08-01

    To reduce the noise of machines such as aircraft engines, the development and propagation of sound has to be investigated. Since the applicability of microphones is limited due to their intrusiveness, contactless measurement techniques are required. For this reason, the present study describes an optical method based on the Doppler effect and its application for acoustic particle velocity (APV) measurements. While former APV measurements with Doppler techniques are point measurements, the applied system is capable of simultaneous measurements at multiple points. In its current state, the system provides linear array measurements of one component of the APV demonstrated by multi-tone experiments with tones up to 17 kHz for the first time. PMID:23927110

  11. New Dirac equation from the view point of particle

    SciTech Connect

    Ozaydin, Fatih; Altintas, Azmi Ali; Susam, Lidya Amon; Arik, Metin; Yarman, Tolga

    2012-09-06

    According to the classical approach, especially the Lorentz Invariant Dirac Equation, when particles are bound to each other, the interaction term appears as a quantity belonging to the 'field'. In this work, as a totally new approach, we propose to alter the rest masses of the particles due to their interaction, as much as their respective contributions to the static binding energy. Thus we re-write and solve the Dirac Equation for the hydrogen atom, and amazingly, obtain practically the same numerical results for the ground states, as those obtained from the Dirac Equation.

  12. Semiclassical limit for Dirac particles interacting with a gravitational field

    NASA Astrophysics Data System (ADS)

    Silenko, Alexander J.; Teryaev, Oleg V.

    2005-03-01

    The behavior of a spin-1/2 particle in a weak static gravitational field is considered. The Dirac Hamiltonian is diagonalized by the Foldy-Wouthuysen transformation providing also the simple form for the momentum and spin polarization operators. The operator equations of momentum and spin motion are derived for a first time. Their semiclassical limit is analyzed. The dipole spin-gravity coupling in the previously found (another) Hamiltonian does not lead to any observable effects. The general agreement between the quantum and classical approaches is established, contrary to several recent claims. The expression for the gravitational Stern-Gerlach force is derived. The helicity evolution in the gravitational field and corresponding accelerated frame coincides, being the manifestation of the equivalence principle.

  13. Evidence for equilibrium gels of valence-limited particles.

    PubMed

    Dudukovic, Nikola A; Zukoski, Charles F

    2014-10-21

    We explore the formation and structure of gels produced from solutions of the aromatic dipeptide derivative molecule fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF) in dimethyl sulfoxide (DMSO). Mixing these solutions with water results in the self-assembly of Fmoc-FF molecules into space-filling fibrous networks, exhibiting mechanical properties characteristic of gels. Using confocal fluorescence microscopy, we observe the gel transition in situ and find that, upon the addition of water, the solution undergoes a rapid transition to a non-equilibrium state forming ∼ 2 μm spheres, followed by the formation of fibers 5-10 nm in diameter, nucleating at a sphere surface and expanding into the solution as the remaining spheres dissolve, extending the network. The gel aging process is associated with the network becoming increasingly uniform through apparent redissolution/reaggregation of the Fmoc-FF molecules, corresponding to the observed increase in the elastic modulus to a plateau value. We demonstrate that this increase in uniformity and elastic modulus can be expedited by controlling the temperature of the system, as well as that these gels are thermally reversible, further indicating that the system is in equilibrium in its fibrous network state. X-ray scattering information suggests that the packing of the molecules within a fiber is based on π-π stacking of β-sheets, consistent with models proposed in the literature for similar systems, implying that each particle (molecule) possesses a limited number of interaction sites. These observations provide experimental evidence that these low molecular weight gelator molecules can be considered valence-limited "patchy" particles, which associate at low enough temperature to form equilibrium gels. PMID:25155031

  14. Estimating the contribution of point sources to atmospheric metals using single-particle mass spectrometry

    NASA Astrophysics Data System (ADS)

    Snyder, David C.; Schauer, James J.; Gross, Deborah S.; Turner, Jay R.

    Single-particle mass spectra were collected using an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) during December of 2003 and February of 2004 at an industrially impacted location in East St. Louis, IL. Hourly integrated peak areas for twenty ions were evaluated for their suitability in representing metals/metalloids, particularly those reported in the US EPA Toxic Release Inventory (TRI). Of the initial twenty ions examined, six (Al, As, Cu, Hg, Ti, and V) were found to be unsuitable due to strong isobaric interferences with commonly observed organic fragments, and one (Be) was found to have no significant signal. The usability of three ions (Co, Cr, and Mn) was limited due to suspected isobaric interferences based on temporal comparisons with commonly observed organic fragments. The identity of the remaining ions (Sb, Ba, Cd, Ca, Fe, Ni, Pb, K, Se, and Zn) was substantiated by comparing their signals with the integrated hourly signals of one or more isotope ions. When compared with one-in-six day integrated elemental data as determined by X-ray fluorescence spectroscopy (XRF), the daily integrated ATOFMS signal for several metal ions revealed a semi-quantitative relationship between ATOFMS peak area and XRF concentrations, although in some cases comparison of these measurements were poor at low elemental concentrations/ion signals due to isobaric interferences. A method of estimating the impact of local point sources was developed using hourly integrated ATOFMS peak areas, and this method attributed as much as 85% of the concentration of individual metals observed at the study site to local point sources. Hourly surface wind data were used in conjunction with TRI facility emissions data to reveal likely point sources impacting metal concentrations at the study site and to illustrate the utility of using single-particle mass spectral data to characterize atmospheric metals and identify point sources.

  15. A covariance analysis tool for assessing fundamental limits of SIM pointing performance

    NASA Astrophysics Data System (ADS)

    Bayard, David S.; Kang, Bryan H.

    2007-09-01

    This paper presents a performance analysis of the instrument pointing control system for NASA's Space Interferometer Mission (SIM). SIM has a complex pointing system that uses a fast steering mirror in combination with a multirate control architecture to blend feedforward information with feedback information. A pointing covariance analysis tool (PCAT) is developed specifically to analyze systems with such complexity. The development of PCAT as a mathematical tool for covariance analysis is outlined in the paper. PCAT is then applied to studying performance of SIM's science pointing system. The analysis reveals and clearly delineates a fundamental limit that exists for SIM pointing performance. The limit is especially stringent for dim star targets. Discussion of the nature of the performance limit is provided, and methods are suggested to potentially improve pointing performance.

  16. A Covariance Analysis Tool for Assessing Fundamental Limits of SIM Pointing Performance

    NASA Technical Reports Server (NTRS)

    Bayard, David S.; Kang, Bryan H.

    2007-01-01

    This paper presents a performance analysis of the instrument pointing control system for NASA's Space Interferometer Mission (SIM). SIM has a complex pointing system that uses a fast steering mirror in combination with a multirate control architecture to blend feed forward information with feedback information. A pointing covariance analysis tool (PCAT) is developed specifically to analyze systems with such complexity. The development of PCAT as a mathematical tool for covariance analysis is outlined in the paper. PCAT is then applied to studying performance of SIM's science pointing system. The analysis reveals and clearly delineates a fundamental limit that exists for SIM pointing performance. The limit is especially stringent for dim star targets. Discussion of the nature of the performance limit is provided, and methods are suggested to potentially improve pointing performance.

  17. Lieb-Thirring inequality for a model of particles with point interactions

    SciTech Connect

    Frank, Rupert L.; Seiringer, Robert

    2012-09-15

    We consider a model of quantum-mechanical particles interacting via point interactions of infinite scattering length. In the case of fermions we prove a Lieb-Thirring inequality for the energy, i.e., we show that the energy is bounded from below by a constant times the integral of the particle density to the power (5/3).

  18. Heat and particle transport in a one-dimensional hard-point gas model with on-site potential

    SciTech Connect

    Wang, Lei

    2015-05-15

    Heat and particle transport in a one-dimensional hard-point gas of elastically colliding particles are studied. In the nonequal mass case, due to the presence of on-site potential, the heat conduction of the model obeys the Fourier law and all the transport coefficients asymptotically approach constants in the thermodynamic limit. The thermoelectric figure of merit ZT increases slowly with the system length L and is proportional to the height of the potential barriers H in high H regime. These findings may serve as a guide for future theoretical and experimental studies.

  19. Diffusion-limited retention of porous particles at density interfaces

    PubMed Central

    Kindler, Kolja; Khalili, Arzhang; Stocker, Roman

    2010-01-01

    Downward carbon flux in the ocean is largely governed by particle settling. Most marine particles settle at low Reynolds numbers and are highly porous, yet the fluid dynamics of this regime have remained unexplored. We present results of an experimental investigation of porous particles settling through a density interface at Reynolds numbers between 0.1 and 1. We tracked 100 to 500 μm hydrogel spheres with 95.5% porosity and negligible permeability. We found that a small negative initial excess density relative to the lower (denser) fluid layer, a common scenario in the ocean, results in long retention times of particles at the interface. We hypothesized that the retention time was determined by the diffusive exchange of the stratifying agent between interstitial and ambient fluid, which increases excess density of particles that have stalled at the interface, enabling their settling to resume. This hypothesis was confirmed by observations, which revealed a quadratic dependence of retention time on particle size, consistent with diffusive exchange. These results demonstrate that porosity can control retention times and therefore accumulation of particles at density interfaces, a mechanism that could underpin the formation of particle layers frequently observed at pycnoclines in the ocean. We estimate retention times of 3 min to 3.3 d for the characteristic size range of marine particles. This enhancement in retention time can affect carbon transformation through increased microbial colonization and utilization of particles and release of dissolved organics. The observed size dependence of the retention time could further contribute to improve quantifications of vertical carbon flux. PMID:21135242

  20. Object detection and tracking with active camera on motion vectors of feature points and particle filter.

    PubMed

    Chen, Yong; Zhang, Rong-Hua; Shang, Lei; Hu, Eric

    2013-06-01

    A method based on motion vectors of feature points and particle filter has been proposed and developed for an active∕moving camera for object detection and tracking purposes. The object is detected by histogram of motion vectors first, and then, on the basis of particle filter algorithm, the weighing factors are obtained via color information. In addition, re-sampling strategy and surf feature points are used to remedy the drawback of particle degeneration. Experimental results demonstrate the practicability and accuracy of the new method and are presented in the paper. PMID:23822380

  1. Accurate calculation of Stokes drag for point-particle tracking in two-way coupled flows

    NASA Astrophysics Data System (ADS)

    Horwitz, J. A. K.; Mani, A.

    2016-08-01

    In this work, we propose and test a method for calculating Stokes drag applicable to particle-laden fluid flows where two-way momentum coupling is important. In the point-particle formulation, particle dynamics are coupled to fluid dynamics via a source term that appears in the respective momentum equations. When the particle Reynolds number is small and the particle diameter is smaller than the fluid scales, it is common to approximate the momentum coupling source term as the Stokes drag. The Stokes drag force depends on the difference between the undisturbed fluid velocity evaluated at the particle location, and the particle velocity. However, owing to two-way coupling, the fluid velocity is modified in the neighborhood of a particle, relative to its undisturbed value. This causes the computed Stokes drag force to be underestimated in two-way coupled point-particle simulations. We develop estimates for the drag force error as function of the particle size relative to the grid size. Because the disturbance field created by the particle contaminates the surrounding fluid, correctly calculating the drag force cannot be done solely by direct interpolation of the fluid velocity. Instead, we develop a correction method that calculates the undisturbed fluid velocity from the computed disturbed velocity field by adding an estimate of the velocity disturbance created by the particle. The correction scheme is tested for a particle settling in an otherwise quiescent fluid and is found to reduce the error in computed settling velocity by an order of magnitude compared with common interpolation schemes.

  2. Limiter

    DOEpatents

    Cohen, S.A.; Hosea, J.C.; Timberlake, J.R.

    1984-10-19

    A limiter with a specially contoured front face is provided. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution. This limiter shape accommodates the various power scrape-off distances lambda p, which depend on the parallel velocity, V/sub parallel/, of the impacting particles.

  3. Liquidus slopes of impurities in ITS-90 fixed points from the mercury point to the copper point in the low concentration limit

    NASA Astrophysics Data System (ADS)

    Pearce, Jonathan V.; Gisby, John A.; Steur, Peter P. M.

    2016-08-01

    A knowledge of the effect of impurities at the level of parts per million on the freezing temperature of very pure metals is essential for realisation of ITS-90 fixed points. New information has become available for use with the thermodynamic modelling software MTDATA, permitting calculation of liquidus slopes, in the low concentration limit, of a wider range of binary alloy systems than was previously possible. In total, calculated values for 536 binary systems are given. In addition, new experimental determinations of phase diagrams, in the low impurity concentration limit, have recently appeared. All available data have been combined to provide a comprehensive set of liquidus slopes for impurities in ITS-90 metal fixed points. In total, liquidus slopes for 838 systems are tabulated for the fixed points Hg, Ga, In, Sn, Zn, Al, Ag, Au, and Cu. It is shown that the value of the liquidus slope as a function of impurity element atomic number can be approximated using a simple formula, and good qualitative agreement with the existing data is observed for the fixed points Al, Ag, Au and Cu, but curiously the formula is not applicable to the fixed points Hg, Ga, In, Sn, and Zn. Some discussion is made concerning the influence of oxygen on the liquidus slopes, and some calculations using MTDATA are discussed. The BIPM’s consultative committee for thermometry has long recognised that the sum of individual estimates method is the ideal approach for assessing uncertainties due to impurities, but the community has been largely powerless to use the model due to lack of data. Here, not only is data provided, but a simple model is given to enable known thermophysical data to be used directly to estimate impurity effects for a large fraction of the ITS-90 fixed points.

  4. Limitation of electrostatic charging of dust particles in a plasma

    NASA Technical Reports Server (NTRS)

    Goertz, C. K.; Ip, W.-H.

    1984-01-01

    It is shown that in a dusty plasma consisting of a plasma (density n and temperature T) and dust grains (density N and radius a) the charge on a grain is not given by its free-space value. Instead, the charge is reduced by a factor 1 + x. Except for the optically thin E and G rings, this factor is large. Usually electromagnetic forces on dust particles in Saturn's ring system are too small to produce observable effects. The current carried by dust particles moving relative to the plasma with a speed w is to a good approximation given by j = NQw. Thus, magnetic perturbations by the F ring should be much smaller than previously estimated.

  5. Radiation reaction and renormalization in classical electrodynamics of a point particle in any dimension

    NASA Astrophysics Data System (ADS)

    Kazinski, P. O.; Lyakhovich, S. L.; Sharapov, A. A.

    2002-07-01

    The effective equations of motion for a point charged particle taking into account the radiation reaction are considered in various space-time dimensions. The divergences stemming from the pointness of the particle are studied and an effective renormalization procedure is proposed encompassing uniformly the cases of all even dimensions. It is shown that in any dimension the classical electrodynamics is a renormalizable theory if not multiplicatively beyond d=4. For the cases of three and six dimensions the covariant analogues of the Lorentz-Dirac equation are explicitly derived.

  6. Integration of GPS Precise Point Positioning and MEMS-Based INS Using Unscented Particle Filter

    PubMed Central

    Abd Rabbou, Mahmoud; El-Rabbany, Ahmed

    2015-01-01

    Integration of Global Positioning System (GPS) and Inertial Navigation System (INS) integrated system involves nonlinear motion state and measurement models. However, the extended Kalman filter (EKF) is commonly used as the estimation filter, which might lead to solution divergence. This is usually encountered during GPS outages, when low-cost micro-electro-mechanical sensors (MEMS) inertial sensors are used. To enhance the navigation system performance, alternatives to the standard EKF should be considered. Particle filtering (PF) is commonly considered as a nonlinear estimation technique to accommodate severe MEMS inertial sensor biases and noise behavior. However, the computation burden of PF limits its use. In this study, an improved version of PF, the unscented particle filter (UPF), is utilized, which combines the unscented Kalman filter (UKF) and PF for the integration of GPS precise point positioning and MEMS-based inertial systems. The proposed filter is examined and compared with traditional estimation filters, namely EKF, UKF and PF. Tightly coupled mechanization is adopted, which is developed in the raw GPS and INS measurement domain. Un-differenced ionosphere-free linear combinations of pseudorange and carrier-phase measurements are used for PPP. The performance of the UPF is analyzed using a real test scenario in downtown Kingston, Ontario. It is shown that the use of UPF reduces the number of samples needed to produce an accurate solution, in comparison with the traditional PF, which in turn reduces the processing time. In addition, UPF enhances the positioning accuracy by up to 15% during GPS outages, in comparison with EKF. However, all filters produce comparable results when the GPS measurement updates are available. PMID:25815446

  7. Integration of GPS precise point positioning and MEMS-based INS using unscented particle filter.

    PubMed

    Abd Rabbou, Mahmoud; El-Rabbany, Ahmed

    2015-01-01

    Integration of Global Positioning System (GPS) and Inertial Navigation System (INS) integrated system involves nonlinear motion state and measurement models. However, the extended Kalman filter (EKF) is commonly used as the estimation filter, which might lead to solution divergence. This is usually encountered during GPS outages, when low-cost micro-electro-mechanical sensors (MEMS) inertial sensors are used. To enhance the navigation system performance, alternatives to the standard EKF should be considered. Particle filtering (PF) is commonly considered as a nonlinear estimation technique to accommodate severe MEMS inertial sensor biases and noise behavior. However, the computation burden of PF limits its use. In this study, an improved version of PF, the unscented particle filter (UPF), is utilized, which combines the unscented Kalman filter (UKF) and PF for the integration of GPS precise point positioning and MEMS-based inertial systems. The proposed filter is examined and compared with traditional estimation filters, namely EKF, UKF and PF. Tightly coupled mechanization is adopted, which is developed in the raw GPS and INS measurement domain. Un-differenced ionosphere-free linear combinations of pseudorange and carrier-phase measurements are used for PPP. The performance of the UPF is analyzed using a real test scenario in downtown Kingston, Ontario. It is shown that the use of UPF reduces the number of samples needed to produce an accurate solution, in comparison with the traditional PF, which in turn reduces the processing time. In addition, UPF enhances the positioning accuracy by up to 15% during GPS outages, in comparison with EKF. However, all filters produce comparable results when the GPS measurement updates are available. PMID:25815446

  8. The pedagogical value of the four-dimensional picture: I. Relativistic mechanics of point particles

    NASA Astrophysics Data System (ADS)

    Kosyakov, B. P.

    2014-03-01

    In this paper we outline two subjects of relativistic mechanics: (i) the set of allowable world lines, and (ii) the origin of the relativistic law of dynamics governing point particles. We show that: (i) allowable world lines in the classical theory of particles and fields are quite simple geometric objects as opposed to their associated three-dimensional trajectories; and (ii) Newton’s second law requires neither modification nor generalization, it should only be smoothly embedded in the four-dimensional geometry of Minkowski spacetime to yield the dynamical law for relativistic particles.

  9. The point of no return: A fundamental limit on the ability to control thought and action.

    PubMed

    Logan, Gordon D

    2015-01-01

    Bartlett (1958. Thinking. New York: Basic Books) described the point of no return as a point of irrevocable commitment to action, which was preceded by a period of gradually increasing commitment. As such, the point of no return reflects a fundamental limit on the ability to control thought and action. I review the literature on the point of no return, taking three perspectives. First, I consider the point of no return from the perspective of the controlled act, as a locus in the architecture and anatomy of the underlying processes. I review experiments from the stop-signal paradigm that suggest that the point of no return is located late in the response system. Then I consider the point of no return from the perspective of the act of control that tries to change the controlled act before it becomes irrevocable. From this perspective, the point of no return is a point in time that provides enough "lead time" for the act of control to take effect. I review experiments that measure the response time to the stop signal as the lead time required for response inhibition in the stop-signal paradigm. Finally, I consider the point of no return in hierarchically controlled tasks, in which there may be many points of no return at different levels of the hierarchy. I review experiments on skilled typing that suggest different points of no return for the commands that determine what is typed and the countermands that inhibit typing, with increasing commitment to action the lower the level in the hierarchy. I end by considering the point of no return in perception and thought as well as action. PMID:25633089

  10. Limiter

    DOEpatents

    Cohen, Samuel A.; Hosea, Joel C.; Timberlake, John R.

    1986-01-01

    A limiter with a specially contoured front face accommodates the various power scrape-off distances .lambda..sub.p, which depend on the parallel velocity, V.sub..parallel., of the impacting particles. The front face of the limiter (the plasma-side face) is flat with a central indentation. In addition, the limiter shape is cylindrically symmetric so that the limiter can be rotated for greater heat distribution.

  11. Limits on spin-independent couplings of WIMP dark matter with a p-type point-contact germanium detector.

    PubMed

    Li, H B; Liao, H Y; Lin, S T; Liu, S K; Singh, L; Singh, M K; Soma, A K; Wong, H T; Wu, Y C; Zhao, W; Asryan, G; Chuang, Y C; Deniz, M; Fang, J M; Hsu, C L; Huang, T R; Kiran Kumar, G; Lee, S C; Li, J; Li, J M; Li, Y J; Li, Y L; Lin, C W; Lin, F K; Liu, Y F; Ma, H; Ruan, X C; Shen, Y T; Singh, V; Tang, C J; Tseng, C H; Xu, Y; Yang, S W; Yu, C X; Yue, Q; Zeng, Z; Zeyrek, M; Zhou, Z Y

    2013-06-28

    We report new limits on a spin-independent weakly interacting massive particle (WIMP)-nucleon interaction cross section using 39.5 kg days of data taken with a p-type point-contact germanium detector of 840 g fiducial mass at the Kuo-Sheng Reactor Neutrino Laboratory. Crucial to this study is the understanding of the selection procedures and, in particular, the bulk-surface events differentiation at the sub-keV range. The signal-retaining and background-rejecting efficiencies were measured with calibration gamma sources and a novel n-type point-contact germanium detector. Part of the parameter space in the cross section versus WIMP-mass implied by various experiments is probed and excluded. PMID:23848861

  12. Hand-Grip Strength Cut-Points to Screen Older Persons at Risk for Mobility Limitation

    PubMed Central

    Sallinen, Janne; Stenholm, Sari; Rantanen, Taina; Heliövaara, Markku; Sainio, Päivi; Koskinen, Seppo

    2010-01-01

    Objectives To determine optimal hand-grip strength cut-points for increased likelihood for mobility limitation among older people and to study whether these cut-points differ according to body mass index (BMI). Design and setting Cross-sectional analysis of data collected in the Finnish population-based Health 2000 Survey. Participants and measurements 1 084 men and 1 562 women aged 55 years and older with complete data on anthropometry, hand-grip strength and self-reported mobility. Mobility limitation was defined as difficulties in walking 0.5-km or climbing stairs. Receiver Operating Characteristics analysis was used to estimate hand-grip strength cut-points for increased likelihood for mobility limitation. Results The overall hand-grip strength cut-points for increased likelihood for mobility limitation were 37 kg (sensitivity 62% and specificity 76%) for men and 21 kg (67% and 73%) for women. Hand-grip strength by BMI interaction on mobility limitation was significant among men (p = 0.022), while no such interaction was observed among women (p = 0.156). Among men, most optimal cut-offs were 33 kg (73% and 79%) for normal-weight men, 39 kg (67% and 71%) for overweight men and 40 kg (57% and 68%) for obese men. Among women, BMI-specific hand-grip strength cut-off values did not markedly increase accuracy over the overall cut-off value. Conclusion Hand-grip strength test is a useful tool to identify persons with increased risk for mobility limitation. Among men, the hand-grip strength cut-points for mobility increased along with BMI, while among women only one hand-grip strength threshold was identified. PMID:20863331

  13. 78 FR 19434 - Effluent Limitations Guidelines and Standards for the Construction and Development Point Source...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-01

    ...EPA is proposing changes to the effluent limitations guidelines and standards for the Construction and Development point source category. EPA is proposing these changes pursuant to a settlement agreement to resolve litigation. This proposed rule would withdraw the numeric discharge standards, which are currently stayed, and change several of the non-numeric provisions of the existing...

  14. 75 FR 68305 - Proposed Rule Staying Numeric Limitation for the Construction and Development Point Source Category

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-05

    ... AGENCY 40 CFR Part 450 Proposed Rule Staying Numeric Limitation for the Construction and Development... requirements for the Construction and Development Point Source Category. This action is necessary so that EPA... regulated by this action, you should carefully examine the applicability criteria in 40 CFR 450.10 (74...

  15. Calculation of a velocity distribution from particle trajectory end-points.

    USGS Publications Warehouse

    Rasmussen, Lowell A.

    1983-01-01

    The longitudinal component of the velocity of a particle at or near a glacier surface is considered, its position as a function of time being termed its trajectory. Functional relationships are derived for obtaining the trajectory from the spatial distribution of velocity and for obtaining the velocity distribution from the trajectory. It is established that the trajectory end-points impose only an integral condition on the velocity distribution and that no individual point on the velocity distribution can be determined if only the end-points are known.-from Author

  16. Thermal runaway limit of tubular reactors, defined at the inflection point of the temperature profile

    SciTech Connect

    Bashir, S.; Chovan, T.; Masri, B.J.; Mukherjee, A.; Pant, A.; Sen, S.; Vijayaragharvan, P. . Dept. of Chemical Engineering); Berty, J.M. )

    1992-09-01

    The predicted maximum temperature difference between reacting fluid and wall to avoid thermal runaways can be exceeded in production reactors. This has been known for some time but the explanation has been lacking. The reason for this deviation was found in that the traditional approximation of the sensitivity criterion by [Delta]T [le] RT[sup 2]/E is correct for a limiting value at the inflection point but not at the hot spot, where it can be much higher. The exact expression for the limiting value at the inflection point is the total temperature derivative of the rate, and this is proven in this paper mathematically. The total temperature derivative of a rate can be measured in a few, well-designed recycle reactor experiments. Results were checked by computer simulation of tubular reactors. Matching to those predicted from CSTR or recycle reactor (RR) measurements was excellent. The proposed interpretation explains why previously predicted limits could be exceeded in practice.

  17. Measuring the isoelectric point of the edges of clay mineral particles: the case of montmorillonite.

    PubMed

    Pecini, Eliana M; Avena, Marcelo J

    2013-12-01

    The isoelectric point (IEP) of the edge surface of a montmorillonite sample was determined by using electrophoretic mobility measurements. This parameter, which is fundamental for the understanding of the charging behavior of clay mineral surfaces, was never measured so far because of the presence of permanent negative charges within the montmorillonite structure, charges that mask the electrokinetic behavior of the edges. The strategy was to block or neutralize the structural charges with two different cations, methylene blue (MB(+)) and tetraethylenepentaminecopper(II) ([Cu(tetren)](2+)), so that the charging behavior of the particles becomes that of the edge surfaces. Adsorption isotherms of MB(+) and [Cu(tetren)](2+) at different ionic strengths (NaCl) were performed to establish the uptakes that neutralize the cation exchange capacity (CEC, 0.96 meq g(-1)) of the sample. At high adsorptive concentrations, there was a superequivalent adsorption of MB(+) (adsorption exceeding the CEC) and an equivalent adsorption of [Cu(tetren)](2+) (adsorption reaching the CEC). In both cases, structural charges were neutralized at uptakes very close to the CEC. Zeta potential (ζ) vs pH data at different ionic strengths of montmorillonite with adsorbed MB(+) allowed to estimate an upper limit of the edge's IEP, 5.3 ± 0.2. The same kind of data obtained with adsorbed [Cu(tetren)](2+) provided a lower limit of the IEP, 4.0 ± 0.2. These values are in agreement with previously informed IEP and point of zero charge of pyrophyllite, which is structurally analogous to montmorillonite but carries no permanent charges. The importance of knowing the IEP of the edge surface of clay minerals is discussed. This value characterizes the intrinsic reactivity of edges, that is, the protonating capacity of edge groups in absence of any electric field generated by structural charges. It also allows us to correct relative edge charge vs pH curves obtained by potentiometric titrations and to

  18. Landauer limit of energy dissipation in a magnetostrictive particle.

    PubMed

    Roy, Kuntal

    2014-12-10

    According to Landauer's principle, a minimum amount of energy proportional to temperature must be dissipated during the erasure of a classical bit of information compensating the entropy loss, thereby linking the information and thermodynamics. Here, we show that the Landauer limit of energy dissipation is achievable in a shape-anisotropic single-domain magnetostrictive nanomagnet having two mutually anti-parallel degenerate magnetization states that store a bit of information. We model the magnetization dynamics using the stochastic Landau-Lifshitz-Gilbert equation in the presence of thermal fluctuations and show that on average the Landauer bound is satisfied, i.e. it is in accordance with the generalized Landauer's principle for small systems with stochastic fluctuations. PMID:25379608

  19. PDEs on moving surfaces via the closest point method and a modified grid based particle method

    NASA Astrophysics Data System (ADS)

    Petras, A.; Ruuth, S. J.

    2016-05-01

    Partial differential equations (PDEs) on surfaces arise in a wide range of applications. The closest point method (Ruuth and Merriman (2008) [20]) is a recent embedding method that has been used to solve a variety of PDEs on smooth surfaces using a closest point representation of the surface and standard Cartesian grid methods in the embedding space. The original closest point method (CPM) was designed for problems posed on static surfaces, however the solution of PDEs on moving surfaces is of considerable interest as well. Here we propose solving PDEs on moving surfaces using a combination of the CPM and a modification of the grid based particle method (Leung and Zhao (2009) [12]). The grid based particle method (GBPM) represents and tracks surfaces using meshless particles and an Eulerian reference grid. Our modification of the GBPM introduces a reconstruction step into the original method to ensure that all the grid points within a computational tube surrounding the surface are active. We present a number of examples to illustrate the numerical convergence properties of our combined method. Experiments for advection-diffusion equations that are strongly coupled to the velocity of the surface are also presented.

  20. Sound Radiation from Moving Point-Like Charged Particles in Plasmas

    SciTech Connect

    Guio, P.; Miloch, W. J.; Pecseli, H. L.; Trulsen, J.

    2008-10-15

    The electrostatic potential and plasma density variations around a point-like charged object in a plasma flow are studied. These objects can represent small charged dust particles, for instance. The radiation patterns can be interpreted as the result of sound waves being radiated by the obstacle. For large electron to ion temperature ratios we find that radiation patterns develop for the sub-as well as the supersonic case. The results are illustrated by numerical simulations using a hybrid Particle In Cell (PIC) code, where the electrons are treated as an isothermal massless fluid, giving a nonlinear Poisson equation. The analytical results are in good agreement with the numerical simulations.

  1. A Northern Sky Survey for Point-like Sources of EeV Neutral Particles with the Telescope Array Experiment

    NASA Astrophysics Data System (ADS)

    Abbasi, R. U.; Abe, M.; Abu-Zayyad, T.; Allen, M.; Anderson, R.; Azuma, R.; Barcikowski, E.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Cady, R.; Chae, M. J.; Cheon, B. G.; Chiba, J.; Chikawa, M.; Cho, W. R.; Fujii, T.; Fukushima, M.; Goto, T.; Hanlon, W.; Hayashi, Y.; Hayashida, N.; Hibino, K.; Honda, K.; Ikeda, D.; Inoue, N.; Ishii, T.; Ishimori, R.; Ito, H.; Ivanov, D.; Jui, C. C. H.; Kadota, K.; Kakimoto, F.; Kalashev, O.; Kasahara, K.; Kawai, H.; Kawakami, S.; Kawana, S.; Kawata, K.; Kido, E.; Kim, H. B.; Kim, J. H.; Kim, J. H.; Kitamura, S.; Kitamura, Y.; Kuzmin, V.; Kwon, Y. J.; Lan, J.; Lim, S. I.; Lundquist, J. P.; Machida, K.; Martens, K.; Matsuda, T.; Matsuyama, T.; Matthews, J. N.; Minamino, M.; Mukai, K.; Myers, I.; Nagasawa, K.; Nagataki, S.; Nakamura, T.; Nonaka, T.; Nozato, A.; Ogio, S.; Ogura, J.; Ohnishi, M.; Ohoka, H.; Oki, K.; Okuda, T.; Ono, M.; Oshima, A.; Ozawa, S.; Park, I. H.; Pshirkov, M. S.; Rodriguez, D. C.; Rubtsov, G.; Ryu, D.; Sagawa, H.; Sakurai, N.; Sampson, A. L.; Scott, L. M.; Shah, P. D.; Shibata, F.; Shibata, T.; Shimodaira, H.; Shin, B. K.; Smith, J. D.; Sokolsky, P.; Springer, R. W.; Stokes, B. T.; Stratton, S. R.; Stroman, T. A.; Suzawa, T.; Takamura, M.; Takeda, M.; Takeishi, R.; Taketa, A.; Takita, M.; Tameda, Y.; Tanaka, H.; Tanaka, K.; Tanaka, M.; Thomas, S. B.; Thomson, G. B.; Tinyakov, P.; Tkachev, I.; Tokuno, H.; Tomida, T.; Troitsky, S.; Tsunesada, Y.; Tsutsumi, K.; Uchihori, Y.; Udo, S.; Urban, F.; Vasiloff, G.; Wong, T.; Yamane, R.; Yamaoka, H.; Yamazaki, K.; Yang, J.; Yashiro, K.; Yoneda, Y.; Yoshida, S.; Yoshii, H.; Zollinger, R.; Zundel, Z.

    2015-05-01

    We report on the search for steady point-like sources of neutral particles around 1018 eV between 2008 and 2013 May with the scintillator SD of the Telescope Array experiment. We found overall no significant point-like excess above 0.5 EeV in the northern sky. Subsequently, we also searched for coincidence with the Fermi bright Galactic sources. No significant coincidence was found within the statistical uncertainty. Hence, we set an upper limit on the neutron flux that corresponds to an averaged flux of 0.07 km-2 yr-1 for E\\gt 1 EeV in the northern sky at the 95% confidence level. This is the most stringent flux upper limit in a northern sky survey assuming point-like sources. The upper limit at the 95% confidence level on the neutron flux from Cygnus X-3 is also set to 0.2 km-2 yr-1 for E\\gt 0.5 EeV. This is an order of magnitude lower than previous flux measurements.

  2. Plant responses, climate pivot points, and trade-offs in water-limited ecosystems

    USGS Publications Warehouse

    Munson, Seth M.

    2013-01-01

    Plant species in dryland ecosystems are limited by water availability and may be vulnerable to increases in aridity. Methods are needed to monitor and assess the rate of change in plant abundance and composition in relation to climate, understand the potential for degradation in dryland ecosystems, and forecast future changes in plant species assemblages. I employ nearly a century of vegetation monitoring data from three North American deserts to demonstrate an approach to determine plant species responses to climate and critical points over a range of climatic conditions at which plant species shift from increases to decreases in abundance (climate pivot points). I assess these metrics from a site to regional scale and highlight how these indicators of plant performance can be modified by the physical and biotic environment. For example, shrubs were more responsive to drought and high temperatures on shallow soils with limited capacity to store water and fine-textured soils with slow percolation rates, whereas perennial grasses were more responsive to precipitation in sparse shrublands than in relatively dense grasslands and shrublands, where competition for water is likely more intense. The responses and associated climate pivot points of plant species aligned with their lifespan and structural characteristics, and the relationship between responses and climate pivot points provides evidence of the trade-off between the capacity of a plant species to increase in abundance when water is available and its drought resistance.

  3. Propagator, sewing rules, and vacuum amplitude for the Polyakov point particles with ghosts

    SciTech Connect

    Giannakis, I.; Ordonez, C.R.; Rubin, M.A.; Zucchini, R.

    1989-01-01

    The authors apply techniques developed for strings to the case of the spinless point particle. The Polyakov path integral with ghosts is used to obtain the propagator and one-loop vacuum amplitude. The propagator is shown to correspond to the Green's function for the BRST field theory in Siegel gauge. The reparametrization invariance of the Polyakov path integral is shown to lead automatically to the correct trace log result for the one-loop diagram, despite the fact that naive sewing of the ends of a propagator would give an incorrect answer. This type of failure of naive sewing is identical to that found in the string case. The present treatment provides, in the simplified context of the point particle, a pedagogical introduction to Polyakov path integral methods with and without ghosts.

  4. Nordstroem gravity coupled to point particles in (1+1) dimensions

    SciTech Connect

    Boozer, A. D.

    2010-03-15

    We consider a (1+1)-dimensional model of general relativity that is based on a geometric theory of gravity due to Nordstroem. We show that the theory is formally equivalent to scalar field theory in flat spacetime, and we exploit this equivalence to solve the initial value problem for the system for the case of point particle sources. We illustrate our results by obtaining several example solutions to the model.

  5. Mapping out spin and particle conductances in a quantum point contact.

    PubMed

    Krinner, Sebastian; Lebrat, Martin; Husmann, Dominik; Grenier, Charles; Brantut, Jean-Philippe; Esslinger, Tilman

    2016-07-19

    We study particle and spin transport in a single-mode quantum point contact, using a charge neutral, quantum degenerate Fermi gas with tunable, attractive interactions. This yields the spin and particle conductance of the point contact as a function of chemical potential or confinement. The measurements cover a regime from weak attraction, where quantized conductance is observed, to the resonantly interacting superfluid. Spin conductance exhibits a broad maximum when varying the chemical potential at moderate interactions, which signals the emergence of Cooper pairing. In contrast, the particle conductance is unexpectedly enhanced even before the gas is expected to turn into a superfluid, continuously rising from the plateau at [Formula: see text] for weak interactions to plateau-like features at nonuniversal values as high as [Formula: see text] for intermediate interactions. For strong interactions, the particle conductance plateaus disappear and the spin conductance gets suppressed, confirming the spin-insulating character of a superfluid. Our observations document the breakdown of universal conductance quantization as many-body correlations appear. The observed anomalous quantization challenges a Fermi liquid description of the normal phase, shedding new light on the nature of the strongly attractive Fermi gas. PMID:27357668

  6. KINETIC MODELING OF PARTICLE ACCELERATION IN A SOLAR NULL-POINT RECONNECTION REGION

    SciTech Connect

    Baumann, G.; Haugbolle, T.; Nordlund, A.

    2013-07-10

    The primary focus of this paper is on the particle acceleration mechanism in solar coronal three-dimensional reconnection null-point regions. Starting from a potential field extrapolation of a Solar and Heliospheric Observatory (SOHO) magnetogram taken on 2002 November 16, we first performed magnetohydrodynamics (MHD) simulations with horizontal motions observed by SOHO applied to the photospheric boundary of the computational box. After a build-up of electric current in the fan plane of the null point, a sub-section of the evolved MHD data was used as initial and boundary conditions for a kinetic particle-in-cell model of the plasma. We find that sub-relativistic electron acceleration is mainly driven by a systematic electric field in the current sheet. A non-thermal population of electrons with a power-law distribution in energy forms in the simulated pre-flare phase, featuring a power-law index of about -1.78. This work provides a first step toward bridging the gap between macroscopic scales on the order of hundreds of Mm and kinetic scales on the order of centimeter in the solar corona, and explains how to achieve such a cross-scale coupling by utilizing either physical modifications or (equivalent) modifications of the constants of nature. With their exceptionally high resolution-up to 135 billion particles and 3.5 billion grid cells of size 17.5 km-these simulations offer a new opportunity to study particle acceleration in solar-like settings.

  7. Mapping out spin and particle conductances in a quantum point contact

    PubMed Central

    Krinner, Sebastian; Lebrat, Martin; Husmann, Dominik; Grenier, Charles; Brantut, Jean-Philippe; Esslinger, Tilman

    2016-01-01

    We study particle and spin transport in a single-mode quantum point contact, using a charge neutral, quantum degenerate Fermi gas with tunable, attractive interactions. This yields the spin and particle conductance of the point contact as a function of chemical potential or confinement. The measurements cover a regime from weak attraction, where quantized conductance is observed, to the resonantly interacting superfluid. Spin conductance exhibits a broad maximum when varying the chemical potential at moderate interactions, which signals the emergence of Cooper pairing. In contrast, the particle conductance is unexpectedly enhanced even before the gas is expected to turn into a superfluid, continuously rising from the plateau at 1/h for weak interactions to plateau-like features at nonuniversal values as high as 4/h for intermediate interactions. For strong interactions, the particle conductance plateaus disappear and the spin conductance gets suppressed, confirming the spin-insulating character of a superfluid. Our observations document the breakdown of universal conductance quantization as many-body correlations appear. The observed anomalous quantization challenges a Fermi liquid description of the normal phase, shedding new light on the nature of the strongly attractive Fermi gas. PMID:27357668

  8. Electrostatics in dissipative particle dynamics using Ewald sums with point charges.

    PubMed

    Terrón-Mejía, Ketzasmin A; López-Rendón, Roberto; Goicochea, Armando Gama

    2016-10-26

    A proper treatment of electrostatic interactions is crucial for the accurate calculation of forces in computer simulations. Electrostatic interactions are typically modeled using Ewald-based methods, which have become some of the cornerstones upon which many other methods for the numerical computation of electrostatic interactions are based. However, their use with charge distributions rather than point charges requires the inclusion of ansatz for the solutions of the Poisson equation, since there is no exact solution known for smeared out charges. The interest in incorporating electrostatic interactions at the scales of length and time that are relevant for the study the physics of soft condensed matter has increased considerably. Using mesoscale simulation techniques, such as dissipative particle dynamics (DPD), allows us to reach longer time scales in numerical simulations, without abandoning the particulate description of the problem. The main problem with incorporating electrostatics into DPD simulations is that DPD particles are soft and those particles with opposite charge can form artificial clusters of ions. Here we show that one can incorporate the electrostatic interactions through Ewald sums with point charges in DPD if larger values of coarse-graining degree are used, where DPD is truly mesoscopic. Using point charges with larger excluded volume interactions, the artificial formation of ionic pairs with point charges can be avoided and one obtains correct predictions. We establish ranges of parameters useful for detecting boundaries where artificial formation of ionic pairs occurs. Lastly, using point charges we predict the scaling properties of polyelectrolytes in solvents of varying quality, and obtain predictions that are in agreement with calculations that use other methods and with recent experimental results. PMID:27541198

  9. Probing surface characteristics of diffusion-limited-aggregation clusters with particles of variable size

    NASA Astrophysics Data System (ADS)

    Menshutin, A. Yu.; Shchur, L. N.; Vinokur, V. M.

    2007-01-01

    We develop a technique for probing the harmonic measure of a diffusion-limited-aggregation (DLA) cluster surface with variable-size particles and generate 1000 clusters with 50×106 particles using an original off-lattice killing-free algorithm. Taking, in sequence, the limit of the vanishing size of the probing particles and then sending the growing cluster size to infinity, we achieve unprecedented accuracy in determining the fractal dimension D=1.7100(2) crucial to the characterization of the geometric properties of DLA clusters.

  10. Particle in Cell Simulations of the Pulsar Y-Point -- Nature of the Accelerating Electric Field

    NASA Astrophysics Data System (ADS)

    Belyaev, Mikhail

    2016-06-01

    Over the last decade, satellite observations have yielded a wealth of data on pulsed high-energy emission from pulsars. Several different models have been advanced to fit this data, all of which “paint” the emitting region onto a different portion of the magnetosphere.In the last few years, particle in cell simulations of pulsar magnetospheres have reached the point where they are able to self-consistently model particle acceleration and dissipation. One of the key findings of these simulations is that the region of the current sheet in and around the Y-point provides the highest rate of dissipation of Poynting flux (Belyaev 2015a). On the basis of this physical evidence, it is quite plausible that this region should be associated with the pulsed high energy emission from pulsars. We present high resolution PIC simulations of an axisymmetric pulsar magnetosphere, which are run using PICsar (Belyaev 2015b). These simulations focus on the particle dynamics and electric fields in and around the Y-point region. We run two types of simulations -- first, a force-free magnetosphere and second, a magnetosphere with a gap between the return current layer and the outflowing plasma in the polar wind zone. The latter setup is motivated by studies of pair production with general relativity (Philippov et al. 2015, Belyaev & Parfrey (in preparation)). In both cases, we find that the Y-point and the current sheet in its direct vicinity act like an “electric particle filter” outwardly accelerating particles of one sign of charge while returning the other sign of charge back to the pulsar. We argue that this is a natural behavior of the plasma as it tries to adjust to a solution that is as close to force-free as possible. As a consequence, a large E dot J develops in the vicinity of the Y-point leading to dissipation of Poynting flux. Our work is relevant for explaining the plasma physical mechanisms underlying pulsed high energy emission from pulsars.

  11. First direct limits on lightly ionizing particles with electric charge less than e/6.

    PubMed

    Agnese, R; Anderson, A J; Balakishiyeva, D; Basu Thakur, R; Bauer, D A; Billard, J; Borgland, A; Bowles, M A; Brandt, D; Brink, P L; Bunker, R; Cabrera, B; Caldwell, D O; Cerdeno, D G; Chagani, H; Chen, Y; Cooley, J; Cornell, B; Crewdson, C H; Cushman, P; Daal, M; Di Stefano, P C F; Doughty, T; Esteban, L; Fallows, S; Figueroa-Feliciano, E; Godfrey, G L; Golwala, S R; Hall, J; Harris, H R; Hertel, S A; Hofer, T; Holmgren, D; Hsu, L; Huber, M E; Jastram, A; Kamaev, O; Kara, B; Kelsey, M H; Kennedy, A; Kiveni, M; Koch, K; Leder, A; Loer, B; Lopez Asamar, E; Mahapatra, R; Mandic, V; Martinez, C; McCarthy, K A; Mirabolfathi, N; Moffatt, R A; Moore, D C; Nelson, H; Nelson, R H; Ogburn, R W; Page, K; Page, W A; Partridge, R; Pepin, M; Phipps, A; Prasad, K; Pyle, M; Qiu, H; Rau, W; Redl, P; Reisetter, A; Ricci, Y; Rogers, H E; Saab, T; Sadoulet, B; Sander, J; Schneck, K; Schnee, R W; Scorza, S; Serfass, B; Shank, B; Speller, D; Upadhyayula, S; Villano, A N; Welliver, B; Wright, D H; Yellin, S; Yen, J J; Young, B A; Zhang, J

    2015-03-20

    While the standard model of particle physics does not include free particles with fractional charge, experimental searches have not ruled out their existence. We report results from the Cryogenic Dark Matter Search (CDMS II) experiment that give the first direct-detection limits for cosmogenically produced relativistic particles with electric charge lower than e/6. A search for tracks in the six stacked detectors of each of two of the CDMS II towers finds no candidates, thereby excluding new parameter space for particles with electric charges between e/6 and e/200. PMID:25839256

  12. First Direct Limits on Lightly Ionizing Particles with Electric Charge Less than e/6

    DOE PAGESBeta

    Agnese, R.; Anderson, A. J.; Balakishiyeva, D.; Basu Thakur, R.; Bauer, D. A.; Billard, J.; Borgland, A.; Bowles, M. A.; Brandt, D.; Brink, P. L.; et al

    2015-03-18

    While the Standard Model of particle physics does not include free particles with fractional charge, experimental searches have not ruled out their existence. We report results from the Cryogenic Dark Matter Search (CDMS II) experiment that give the first direct-detection limits for cosmogenically- produced relativistic particles with electric charge lower than e/6. A search for tracks in the six stacked detectors of each of two of the CDMS II towers found no candidates, thereby excluding new parameter space for particles with electric charges between e/6 and e/200.

  13. Magnetic particle hyperthermia—biophysical limitations of a visionary tumour therapy

    NASA Astrophysics Data System (ADS)

    Hergt, Rudolf; Dutz, Silvio

    2007-04-01

    Loss processes being relevant for magnetic particle hyperthermia are analysed with respect to specific loss power under the condition of a limitation of the alternating magnetic field amplitude and frequency. Extrapolations to the maximum specific loss power of magnetic nanoparticles are discussed and conclusions are drawn with respect to the minimum particle concentration being necessary for hyperthermia or thermoablation under intra-tumoural or systemic particle supply. As a result, much efforts are necessary to render magnetic particle hyperthermia a valuable tumour therapy keeping at least part of the promises found in literature.

  14. Straight-line motion of classical point particles in a three-dimensional lattice

    NASA Astrophysics Data System (ADS)

    De Luca, R.

    2016-07-01

    By means of the usual definition of inner product and of the Gauss condition on the sum of squares of three integers in number theory, it can be seen that there exist specific directions in continuous space in which a classical point particle moving in a three-dimensional lattice cannot propagate. When representing all directions for which propagation is possible as points on a unitary sphere, the forbidden directions appear as vacancies on this sphere. By means of a stereographic projection of the allowed direction, it is argued that propagation is not allowed for specific sets of points on the stereographic plane. The present work can be considered as an interdisciplinary lecture for advanced high-school students or to first-year college students.

  15. Two-particle correlations in high-energy collisions and the gluon four-point function

    SciTech Connect

    Dumitru, Adrian; Jalilian-Marian, Jamal

    2010-05-01

    We derive the rapidity evolution equation for the gluon four-point function in the dilute regime and at small x from the JIMWLK functional equation. We show that beyond leading order in N{sub c} the mean field (Gaussian) approximation where the four-point function is factorized into a product of two-point functions is violated. We calculate these factorization breaking terms and show that they contribute at leading order in N{sub c} to correlations of two produced gluons as a function of their relative rapidity and azimuthal angle, for generic (rather than back-to-back) angles. Such two-particle correlations have been studied experimentally at the BNL-RHIC collider and could be scrutinized also for pp (and, in the future, also AA) collisions at the CERN-LHC accelerator.

  16. Fixed points of the SRG evolution and the on-shell limit of the nuclear force

    NASA Astrophysics Data System (ADS)

    Arriola, E. Ruiz; Szpigel, S.; Timóteo, V. S.

    2016-08-01

    We study the infrared limit of the similarity renormalization group (SRG) using a simple toy model for the nuclear force aiming to investigate the fixed points of the SRG evolution with both the Wilson and the Wegner generators. We show how a fully diagonal interaction at the similarity cutoff λ → 0 may be obtained from the eigenvalues of the Hamiltonian and quantify the diagonalness by means of operator norms. While the fixed points for both generators are equivalent when no bound-states are allowed by the interaction, the differences arising from the presence of the Deuteron bound-state can be disentangled very clearly by analyzing the evolved interactions in the infrared limit λ → 0 on a finite momentum grid. Another issue we investigate is the location on the diagonal of the Hamiltonian in momentum-space where the SRG evolution places the Deuteron bound-state eigenvalue once it reaches the fixed point. This finite momentum grid setup provides an alternative derivation of the celebrated trace identities, as a by product. The different effects due to either the Wilson or the Wegner generators on the binding energies of A = 2 , 3 , 4 systems are investigated and related to the occurrence of a Tjon-line which emerges as the minimum of an avoided crossing between Eα = 4Et - 3Ed and Eα = 2Et. All infrared features of the flow equations are illustrated using the toy model for the two-nucleon S-waves.

  17. Rapid torque-limited line-of-sight pointing of SCOLE (Spacecraft Control Laboratory Experiment) configuration

    NASA Technical Reports Server (NTRS)

    Lin, J. G.

    1986-01-01

    The design concept of a control for rapid torque-limited slewing of a rigid-mast version of the NASA SCOLE configuration is presented and demonstrated by means of numerical simulation. The time-optimal control problem for the system is decomposed into separate single-axis problems, expanding analytically the implicit nonlinear transcendental expression for the SCOLE line-of-sight error, and the final Euler attitude angles and slew angles are determined. The simulation results are presented in tables and graphs, and it is found that bang-bang or bang-pause-bang slew maneuvers with control moment applied to the Shuttle and control force applied to the reflector, and with a 5-deg/s slew-rate limit, produce the best pointing accuracy and the shortest slew times, although the specified line-of-sight error of 0.02 deg cannot be achieved using such open-loop single-axis maneuvers.

  18. Preliminary limits on the flux of muon neutrinos from extraterrestrial point sources

    SciTech Connect

    Bionta, R.M.; Blewitt, G.; Bratton, C.B.; Casper, D.; Cortez, B.G.; Chrysicopoulou, P.; Claus, R.; Dye, S.T.; Errede, S.; Foster, G.W.

    1985-07-03

    We present the arrival directions of 117 upward-going muon events collected with the IMB proton lifetime detector during 317 days of live detector operation. The rate of upward-going muons observed in our detector was found to be consistent with the rate expected from atmospheric neutrino production. The upper limit on the total flux of extraterrestrial neutrinos >1 GeV is <0.06 neutrinos/cm/sup 2/-sec. Using our data and a Monte Carlo simulation of high energy muon production in the earth surrounding the detector, we place limits on the flux of neutrinos from a point source in the Vela X-2 system of <0.009 neutrinos/cm/sup 2/-sec with E > 1 GeV. 6 refs., 5 figs.

  19. Evaluation of parameters for particles acceleration by the zero-point field of quantum electrodynamics

    NASA Technical Reports Server (NTRS)

    Rueda, A.

    1985-01-01

    That particles may be accelerated by vacuum effects in quantum field theory has been repeatedly proposed in the last few years. A natural upshot of this is a mechanism for cosmic rays (CR) primaries acceleration. A mechanism for acceleration by the zero-point field (ZPE) when the ZPE is taken in a realistic sense (in opposition to a virtual field) was considered. Originally the idea was developed within a semiclassical context. The classical Einstein-Hopf model (EHM) was used to show that free isolated electromagnrtically interacting particles performed a random walk in phase space and more importantly in momentum space when submitted to the perennial action of the so called classical electromagnrtic ZPE.

  20. Gravitational radiation by point particle eccentric binary systems in the linearised characteristic formulation of general relativity

    NASA Astrophysics Data System (ADS)

    Cedeño Montaña, C. E.; de Araujo, J. C. N.

    2016-04-01

    We study a binary system composed of point particles of unequal masses in eccentric orbits in the linear regime of the characteristic formulation of general relativity, generalising a previous study found in the literature in which a system of equal masses in circular orbits is considered. We also show that the boundary conditions on the time-like world tubes generated by the orbits of the particles can be extended beyond circular orbits. Concerning the power lost by the emission of gravitational waves, it is directly obtained from the Bondi's News function. It is worth stressing that our results are completely consistent, because we obtain the same result for the power derived by Peters and Mathews, in a different approach, in their seminal paper of 1963. In addition, the present study constitutes a powerful tool to construct extraction schemes in the characteristic formalism to obtain the gravitational radiation produced by binary systems during the inspiralling phase.

  1. A point-of-care PCR test for HIV-1 detection in resource-limited settings.

    PubMed

    Jangam, Sujit R; Agarwal, Abhishek K; Sur, Kunal; Kelso, David M

    2013-04-15

    A low-cost, fully integrated sample-to-answer, quantitative PCR (qPCR) system that can be used for detection of HIV-1 proviral DNA in infants at the point-of-care in resource-limited settings has been developed and tested. The system is based on a novel DNA extraction method, which uses a glass fiber membrane, a disposable assay card that includes on-board reagent storage, provisions for thermal cycling and fluorescence detection, and a battery-operated portable analyzer. The system is capable of automated PCR mix assembly using a novel reagent delivery system and performing qPCR. HIV-1 and internal control targets are detected using two spectrally separated fluorophores, FAM and Quasar 670. In this report, a proof-of-concept of the platform is demonstrated. Initial results with whole blood demonstrate that the test is capable of detecting HIV-1 in blood samples containing greater than 5000 copies of HIV-1. In resource-limited settings, a point-of-care HIV-1 qPCR test would greatly increase the number of test results that reach the infants caregivers, allowing them to pursue anti-retroviral therapy. PMID:23202333

  2. Mode confinement in photonic quasicrystal point-defect cavities for particle accelerators

    NASA Astrophysics Data System (ADS)

    Di Gennaro, E.; Savo, S.; Andreone, A.; Galdi, V.; Castaldi, G.; Pierro, V.; Masullo, M. Rosaria

    2008-10-01

    In this letter, we present a study of the confinement properties of point-defect resonators in finite-size photonic-bandgap structures composed of aperiodic arrangements of dielectric rods, with special emphasis on their use for the design of cavities for particle accelerators. Specifically, for representative geometries, we study the properties of the fundamental mode (as a function of the filling fraction, structure size, and losses) via two-dimensional and three-dimensional full-wave numerical simulations, as well as microwave measurements at room temperature. Results indicate that for reduced-size structures, aperiodic geometries exhibit superior confinement properties by comparison with periodic ones.

  3. Statistical mechanics of two-dimensional point vortices: relaxation equations and strong mixing limit

    NASA Astrophysics Data System (ADS)

    Chavanis, Pierre-Henri

    2014-04-01

    We complement the literature on the statistical mechanics of point vortices in two-dimensional hydrodynamics. Using a maximum entropy principle, we determine the multi-species Boltzmann-Poisson equation and establish a form of Virial theorem. Using a maximum entropy production principle (MEPP), we derive a set of relaxation equations towards statistical equilibrium. These relaxation equations can be used as a numerical algorithm to compute the maximum entropy state. We mention the analogies with the Fokker-Planck equations derived by Debye and Hückel for electrolytes. We then consider the limit of strong mixing (or low energy). To leading order, the relationship between the vorticity and the stream function at equilibrium is linear and the maximization of the entropy becomes equivalent to the minimization of the enstrophy. This expansion is similar to the Debye-Hückel approximation for electrolytes, except that the temperature is negative instead of positive so that the effective interaction between like-sign vortices is attractive instead of repulsive. This leads to an organization at large scales presenting geometry-induced phase transitions, instead of Debye shielding. We compare the results obtained with point vortices to those obtained in the context of the statistical mechanics of continuous vorticity fields described by the Miller-Robert-Sommeria (MRS) theory. At linear order, we get the same results but differences appear at the next order. In particular, the MRS theory predicts a transition between sinh and tanh-like ω - ψ relationships depending on the sign of Ku - 3 (where Ku is the Kurtosis) while there is no such transition for point vortices which always show a sinh-like ω - ψ relationship. We derive the form of the relaxation equations in the strong mixing limit and show that the enstrophy plays the role of a Lyapunov functional.

  4. Point and column aerosol radiative closure during ACE 1: Effects of particle shape and size

    NASA Astrophysics Data System (ADS)

    Fridlind, A. M.; Jacobson, M. Z.

    2003-02-01

    We used data collected during the First Aerosol Characterization Experiment (ACE 1) to study point and column aerosol radiative closure over the remote ocean. To test point closure, total and hemispheric backscattering coefficients calculated with a Mie single-scattering model were compared with measurements made by ship and aircraft at three wavelengths (400, 550, and 700 nm). On the ship, assuming spherical particles, calculated total scattering was usually within 10% of measurements (closure obtained in >80% of the cases) but calculated backscattering was usually 15-25% lower than measurements (closure obtained in <50% of the cases). When a model for particle nonsphericity was applied to the dried sea spray, assuming the particles to be ideal cubes or irregular convex and concave crystals resulted in overestimation of backscattering. However, when nonsphericity parameters were fit to the measurements, calculated backscattering was also usually within 10% of measurements (closure obtained in >80% of the cases). On the aircraft, however, calculated scattering and backscattering were usually lower than measurements by 20-45% regardless of assumed particle shape (closure obtained in <50% of the cases), likely owing to differences in the aerosol inlet penetration efficiencies to each instrument or unidentified uncertainties in the measured number size distributions or scattering coefficients. To test column closure, aerosol extinction profiles calculated from in situ observations (below 5.5 km) and satellite observations (above 5.5 km) were vertically integrated, and the resulting aerosol optical depth was compared with measurements made on the ship during two clear-sky days at three wavelengths (500, 778, and 862 nm). Calculated spectral optical depths were usually within 25% of measurements (closure obtained at one or more wavelengths on both days), and agreement at longer wavelengths was improved when satellite measurements were spectrally scaled using in situ

  5. Diffusion Rate Limitations in Actin-Based Propulsion of Hard and Deformable Particles

    PubMed Central

    Dickinson, Richard B.; Purich, Daniel L.

    2006-01-01

    The mechanism by which actin polymerization propels intracellular vesicles and invasive microorganisms remains an open question. Several recent quantitative studies have examined propulsion of biomimetic particles such as polystyrene microspheres, phospholipid vesicles, and oil droplets. In addition to allowing quantitative measurement of parameters such as the dependence of particle speed on its size, these systems have also revealed characteristic behaviors such a saltatory motion of hard particles and oscillatory deformation of soft particles. Such measurements and observations provide tests for proposed mechanisms of actin-based motility. In the actoclampin filament end-tracking motor model, particle-surface-bound filament end-tracking proteins are involved in load-insensitive processive insertion of actin subunits onto elongating filament plus-ends that are persistently tethered to the surface. In contrast, the tethered-ratchet model assumes working filaments are untethered and the free-ended filaments grow as thermal ratchets in a load-sensitive manner. This article presents a model for the diffusion and consumption of actin monomers during actin-based particle propulsion to predict the monomer concentration field around motile particles. The results suggest that the various behaviors of biomimetic particles, including dynamic saltatory motion of hard particles and oscillatory vesicle deformations, can be quantitatively and self-consistently explained by load-insensitive, diffusion-limited elongation of (+)-end-tethered actin filaments, consistent with predictions of the actoclampin filament-end tracking mechanism. PMID:16731556

  6. Unitarity limits on the mass and radius of dark matter particles

    NASA Technical Reports Server (NTRS)

    Griest, Kim; Kamionkowski, Marc

    1989-01-01

    Using partial wave unitarity and the observed density of the Universe, it is show that a stable elementary particle which was once in thermal equilibrium cannot have a mass greater than 340 TeV. An extended object which was once in thermal equilibrium cannot have a radius less than 7.5 x 10(exp -7) fm. A lower limit to the relic abundance of such particles is also found.

  7. 40 CFR 414.91 - Toxic pollutant effluent limitations and standards for direct discharge point sources that use...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... and standards for direct discharge point sources that use end-of-pipe biological treatment. 414.91... Use End-of-Pipe Biological Treatment § 414.91 Toxic pollutant effluent limitations and standards for direct discharge point sources that use end-of-pipe biological treatment. (a) Any point source subject...

  8. 40 CFR 414.91 - Toxic pollutant effluent limitations and standards for direct discharge point sources that use...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... and standards for direct discharge point sources that use end-of-pipe biological treatment. 414.91... Use End-of-Pipe Biological Treatment § 414.91 Toxic pollutant effluent limitations and standards for direct discharge point sources that use end-of-pipe biological treatment. (a) Any point source subject...

  9. 40 CFR 414.91 - Toxic pollutant effluent limitations and standards for direct discharge point sources that use...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... and standards for direct discharge point sources that use end-of-pipe biological treatment. 414.91... Use End-of-Pipe Biological Treatment § 414.91 Toxic pollutant effluent limitations and standards for direct discharge point sources that use end-of-pipe biological treatment. (a) Any point source subject...

  10. 40 CFR 414.91 - Toxic pollutant effluent limitations and standards for direct discharge point sources that use...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... and standards for direct discharge point sources that use end-of-pipe biological treatment. 414.91... Use End-of-Pipe Biological Treatment § 414.91 Toxic pollutant effluent limitations and standards for direct discharge point sources that use end-of-pipe biological treatment. (a) Any point source subject...

  11. 40 CFR 414.91 - Toxic pollutant effluent limitations and standards for direct discharge point sources that use...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... and standards for direct discharge point sources that use end-of-pipe biological treatment. 414.91... Use End-of-Pipe Biological Treatment § 414.91 Toxic pollutant effluent limitations and standards for direct discharge point sources that use end-of-pipe biological treatment. (a) Any point source subject...

  12. Reassessment of data used in setting exposure limits for hot particles

    SciTech Connect

    Baum, J.W.; Kaurin, D.G.

    1991-05-01

    A critical review and a reassessment of data reviewed in NCRP Report 106 on effects of hot particles'' on the skin of pigs, monkeys, and humans were made. Our analysis of the data of Forbes and Mikhail on effects from activated UC{sub 2} particles, ranging in diameter from 144 {mu}m to 328 {mu}m, led to the formulation of a new model for prediction of both the threshold for acute ulceration and for ulcer diameter. A dose of 27 Gy at a depth of 1.33 mm in tissue in this model will result in an acute ulcer with a diameter determined by the radius over which this dose (at 1.33-mm depth) extends. Application of the model to the Forbes-Mikhail data yielded a threshold'' (5% probability) of 6 {times} 10{sup 9} beta particles from a point source on skin of mixed fission product beta particles, or about 10{sup 10} beta particles from Sr--Y-90, since few of the Sr-90 beta particles reach this depth. The data of Hopewell et al. for their 1 mm Sr-Y-90 exposures were also analyzed with the above model and yielded a predicted threshold of 2 {times} 10{sup 10} Sr-Y-90 beta particles for a point source on skin. Dosimetry values were employed in this latter analysis that are 3.3 times higher than previously reported for this source. An alternate interpretation of the Forbes and Mikhail data, derived from linear plots of the data, is that the threshold depends strongly on particle size with the smaller particles yielding a much lower threshold and smaller minimum size ulcer. Additional animal exposures are planned to distinguish between the above explanations. 17 refs., 3 figs., 3 tabs.

  13. Limiting diffusion current at rotating disk electrode with dense particle layer

    NASA Astrophysics Data System (ADS)

    Weroński, P.; Nosek, M.; Batys, P.

    2013-09-01

    Exploiting the concept of diffusion permeability of multilayer gel membrane and porous multilayer we have derived a simple analytical equation for the limiting diffusion current at rotating disk electrode (RDE) covered by a thin layer with variable tortuosity and porosity, under the assumption of negligible convection in the porous film. The variation of limiting diffusion current with the porosity and tortuosity of the film can be described in terms of the equivalent thickness of stagnant solution layer, i.e., the average ratio of squared tortuosity to porosity. In case of monolayer of monodisperse spherical particles, the equivalent layer thickness is an algebraic function of the surface coverage. Thus, by means of cyclic voltammetry of RDE with a deposited particle monolayer we can determine the monolayer surface coverage. The effect of particle layer adsorbed on the surface of RDE increases non-linearly with surface coverage. We have tested our theoretical results experimentally by means of cyclic voltammetry measurements of limiting diffusion current at the glassy carbon RDE covered with a monolayer of 3 μm silica particles. The theoretical and experimental results are in a good agreement at the surface coverage higher than 0.7. This result suggests that convection in a monolayer of 3 μm monodisperse spherical particles is negligibly small, in the context of the coverage determination, in the range of very dense particle layers.

  14. Limits on deeply penetrating particles in the 10(17) eV cosmic ray flux

    NASA Technical Reports Server (NTRS)

    Baltrusaitis, R. M.; Gerhardy, J. W.; Mizumoto, Y.; Cassiday, G. L.; Cooper, R.; Elbert, J. W.; Loh, P. R.; Sokolsky, P.; Sommers, P.; Steck, D.

    1985-01-01

    Deeply penetrating particles in the 10 to the 17th power eV cosmic ray flux were investigated. No such events were found in 8.2 x 10 to the 6th power sec of running time. Limits were set on the following: quark-matter in the primary cosmic ray flux; long-lived, weakly interacting particles produced in p-air collisions; the astrophysical neutrino flux. In particular, the neutrino flux limit at 10 to the 17th power eV implies that z, the red shift of maximum activity is 10 in the model of Hill and Schramm.

  15. The chaotic four-body problem in Newtonian gravity I: Identical point-particles

    NASA Astrophysics Data System (ADS)

    Leigh, Nathan W. C.; Stone, Nicholas C.; Geller, Aaron M.; Shara, Michael M.; Muddu, Harsha; Solano-Oropeza, Diana; Thomas, Yancey

    2016-08-01

    In this paper, we study the chaotic four-body problem in Newtonian gravity. Assuming point particles and total encounter energies ≤ 0, the problem has three possible outcomes. We describe each outcome as a series of discrete transformations in energy space, using the diagrams first presented in Leigh & Geller (2012; see the Appendix). Furthermore, we develop a formalism for calculating probabilities for these outcomes to occur, expressed using the density of escape configurations per unit energy, and based on the Monaghan description originally developed for the three-body problem. We compare this analytic formalism to results from a series of binary-binary encounters with identical point particles, simulated using the FEWBODY code. Each of our three encounter outcomes produces a unique velocity distribution for the escaping star(s). Thus, these distributions can potentially be used to constrain the origins of dynamically-formed populations, via a direct comparison between the predicted and observed velocity distributions. Finally, we show that, for encounters that form stable triples, the simulated single star escape velocity distributions are the same as for the three-body problem. This is also the case for the other two encounter outcomes, but only at low virial ratios. This suggests that single and binary stars processed via single-binary and binary-binary encounters in dense star clusters should have a unique velocity distribution relative to the underlying Maxwellian distribution (provided the relaxation time is sufficiently long), which can be calculated analytically.

  16. Analysis of ultrasonically rotating droplet using moving particle semi-implicit and distributed point source methods

    NASA Astrophysics Data System (ADS)

    Wada, Yuji; Yuge, Kohei; Tanaka, Hiroki; Nakamura, Kentaro

    2016-07-01

    Numerical analysis of the rotation of an ultrasonically levitated droplet with a free surface boundary is discussed. The ultrasonically levitated droplet is often reported to rotate owing to the surface tangential component of acoustic radiation force. To observe the torque from an acoustic wave and clarify the mechanism underlying the phenomena, it is effective to take advantage of numerical simulation using the distributed point source method (DPSM) and moving particle semi-implicit (MPS) method, both of which do not require a calculation grid or mesh. In this paper, the numerical treatment of the viscoacoustic torque, which emerges from the viscous boundary layer and governs the acoustical droplet rotation, is discussed. The Reynolds stress traction force is calculated from the DPSM result using the idea of effective normal particle velocity through the boundary layer and input to the MPS surface particles. A droplet levitated in an acoustic chamber is simulated using the proposed calculation method. The droplet is vertically supported by a plane standing wave from an ultrasonic driver and subjected to a rotating sound field excited by two acoustic sources on the side wall with different phases. The rotation of the droplet is successfully reproduced numerically and its acceleration is discussed and compared with those in the literature.

  17. Advances in addressing technical challenges of point-of-care diagnostics in resource-limited settings

    PubMed Central

    Wang, ShuQi; Lifson, Mark A.; Inci, Fatih; Liang, Li-Guo; Sheng, Ye-Feng; Demirci, Utkan

    2016-01-01

    The striking prevalence of HIV, TB and malaria, as well as outbreaks of emerging infectious diseases, such as influenza A (H7N9), Ebola and MERS, poses great challenges for patient care in resource-limited settings (RLS). However, advanced diagnostic technologies cannot be implemented in RLS largely due to economic constraints. Simple and inexpensive point-of-care (POC) diagnostics, which rely less on environmental context and operator training, have thus been extensively studied to achieve early diagnosis and treatment monitoring in non-laboratory settings. Despite great input from material science, biomedical engineering and nanotechnology for developing POC diagnostics, significant technical challenges are yet to be overcome. Summarized here are the technical challenges associated with POC diagnostics from a RLS perspective and the latest advances in addressing these challenges are reviewed. PMID:26777725

  18. Advances in addressing technical challenges of point-of-care diagnostics in resource-limited settings.

    PubMed

    Wang, ShuQi; Lifson, Mark A; Inci, Fatih; Liang, Li-Guo; Sheng, Ye-Feng; Demirci, Utkan

    2016-04-01

    The striking prevalence of HIV, TB and malaria, as well as outbreaks of emerging infectious diseases, such as influenza A (H7N9), Ebola and MERS, poses great challenges for patient care in resource-limited settings (RLS). However, advanced diagnostic technologies cannot be implemented in RLS largely due to economic constraints. Simple and inexpensive point-of-care (POC) diagnostics, which rely less on environmental context and operator training, have thus been extensively studied to achieve early diagnosis and treatment monitoring in non-laboratory settings. Despite great input from material science, biomedical engineering and nanotechnology for developing POC diagnostics, significant technical challenges are yet to be overcome. Summarized here are the technical challenges associated with POC diagnostics from a RLS perspective and the latest advances in addressing these challenges are reviewed. PMID:26777725

  19. Positions of equilibrium points for dust particles in the circular restricted three-body problem with radiation

    NASA Astrophysics Data System (ADS)

    Pástor, P.

    2014-11-01

    For a body with negligible mass moving in the gravitational field of a star with one planet in a circular orbit (the circular restricted three-body problem), five equilibrium points exist and are known as the Lagrangian points. The positions of the Lagrangian points are not valid for dust particles because in the derivation of the Lagrangian points it is assumed that no other forces besides the gravitation act on the body with negligible mass. Here, we determined positions of the equilibrium points for the dust particles in the circular restricted three-body problem with radiation. The equilibrium points are located on curves connecting the Lagrangian points in the circular restricted three-body problem. The equilibrium points for Jupiter are distributed in large interval of heliocentric distances due to its large mass. The equilibrium points for the Earth explain a cloud of dust particles trailing the Earth observed with the Spitzer Space Telescope. The dust particles moving in the equilibrium points are distributed in interplanetary space according to their properties.

  20. VIV of a Flexible Cylinder: Three-dimensional Response Reconstruction from Limited Localized Measurement Points

    NASA Astrophysics Data System (ADS)

    Seyed-Aghazadeh, Banafsheh; Modarres-Sadeghi, Yahya

    2015-11-01

    Vortex-induced vibration (VIV) of a low mass ratio flexible cylinder (m*<1), is studied experimentally. The flexible tension-dominated cylinder was held fixed at both ends and was immersed in the uniform incoming flow. Dynamic response of the system was studied in the reduced velocity range of U* = 2.9 - 14.5 and the Reynolds number range of Re = 315 - 1580. Continuous response of the cylinder was reconstructed from limited number of measurement points based on modal expansion theorem modified using Modal Assurance Criterion (MAC). This reconstruction technique made it possible to properly reconstruct a continuous response along the length of the cylinder, even when the measurement points were localized in a small region of the cylinder. Mono- and multi-frequency excitation responses as well as transition from low mode numbers to higher ones were studied. Also, flow forces acting on the cylinder were calculated and they showed a consistent relation between the regions where the cylinder was being excited by the flow (CLv>0) and the counterclockwise figure-eight trajectories of oscillations in which the phase difference between the inline and crossflow directions were in the range of φxy =[ 0 π].

  1. Feasibility of HIV point-of-care tests for resource-limited settings: challenges and solutions.

    PubMed

    Stevens, Wendy; Gous, Natasha; Ford, Nathan; Scott, Lesley E

    2014-01-01

    Improved access to anti-retroviral therapy increases the need for affordable monitoring using assays such as CD4 and/or viral load in resource-limited settings. Barriers to accessing treatment, high rates of loss to initiation and poor retention in care are prompting the need to find alternatives to conventional centralized laboratory testing in certain countries. Strong advocacy has led to a rapidly expanding repertoire of point-of-care tests for HIV. point-of-care testing is not without its challenges: poor regulatory control, lack of guidelines, absence of quality monitoring and lack of industry standards for connectivity, to name a few. The management of HIV increasingly requires a multidisciplinary testing approach involving hematology, chemistry, and tests associated with the management of non-communicable diseases, thus added expertise is needed. This is further complicated by additional human resource requirements and the need for continuous training, a sustainable supply chain, and reimbursement strategies. It is clear that to ensure appropriate national implementation either in a tiered laboratory model or a total decentralized model, clear country-specific assessments need to be conducted. PMID:25197773

  2. Scaling Limits of a Tagged Particle in the Exclusion Process with Variable Diffusion Coefficient

    NASA Astrophysics Data System (ADS)

    Gonçalves, Patrícia; Jara, Milton

    2008-09-01

    We prove a law of large numbers and a central limit theorem for a tagged particle in a symmetric simple exclusion process in ℤ with variable diffusion coefficient. The scaling limits are obtained from a similar result for the current through -1/2 for a zero-range process with bond disorder. For the CLT, we prove convergence to a fractional Brownian motion of Hurst exponent 1/4.

  3. String limit of the isotropic Heisenberg chain in the four-particle sector

    SciTech Connect

    Antipov, A. G. Komarov, I. V.

    2008-05-15

    The quantum method of variable separation is applied to the spectral problem of the isotropic Heisenberg model. The Baxter difference equation is resolved by means of a special quasiclassical asymptotic expansion. States are identified by multiplicities of limiting values of the Bethe parameters. The string limit of the four-particle sector is investigated. String solutions are singled out and classified. It is shown that only a minor fraction of solutions demonstrate string behavior.

  4. Oklahoma Retailers’ Perspectives on Mutual Benefit Exchange to Limit Point-of-Sale Tobacco Advertisements

    PubMed Central

    Chan, Andie; Douglas, Malinda Reddish; Ling, Pamela M.

    2015-01-01

    Businesses changing their practices in ways that support tobacco control efforts recently have gained interest, as demonstrated by CVS Health’s voluntary policy to end tobacco sales. Point of sale (POS) advertisements are associated with youth smoking initiation, increased tobacco consumption, and reduced quit attempts among smokers. There is interest in encouraging retailers to limit tobacco POS advertisements voluntarily. This qualitative exploratory study describes Oklahoma tobacco retailers’ perspectives on a mutual benefit exchange approach, and preferred message and messenger qualities that would entice them to take voluntary action to limit tobacco POS advertisements. This study found mutual benefit exchange could be a viable option along with education and law as strategies to create behavior change among tobacco retailers. Many retailers stated that they would be willing to remove non-contractual POS advertisements for a six-month commitment period when presented with mutual exchange benefit, tailored message, and appropriate messenger. Mutual benefit exchange, as a behavior change strategy to encourage voluntary removal of POS tobacco advertisements, was acceptable to retailers, could enhance local tobacco control in states with preemption, and may contribute to setting the foundation for broader legislative efforts. PMID:25767197

  5. Oklahoma Retailers' Perspectives on Mutual Benefit Exchange to Limit Point-of-Sale Tobacco Advertisements.

    PubMed

    Chan, Andie; Douglas, Malinda Reddish; Ling, Pamela M

    2015-09-01

    Businesses changing their practices in ways that support tobacco control efforts recently have gained interest, as demonstrated by CVS Health's voluntary policy to end tobacco sales. Point-of-sale (POS) advertisements are associated with youth smoking initiation, increased tobacco consumption, and reduced quit attempts among smokers. There is interest in encouraging retailers to limit tobacco POS advertisements voluntarily. This qualitative exploratory study describes Oklahoma tobacco retailers' perspectives on a mutual benefit exchange approach, and preferred message and messenger qualities that would entice them to take voluntary action to limit tobacco POS advertisements. This study found that mutual benefit exchange could be a viable option along with education and law as strategies to create behavior change among tobacco retailers. Many retailers stated that they would be willing to remove noncontractual POS advertisements for a 6-month commitment period when presented with mutual exchange benefit, tailored message, and appropriate messenger. Mutual benefit exchange, as a behavior change strategy to encourage voluntary removal of POS tobacco advertisements, was acceptable to retailers, could enhance local tobacco control in states with preemption, and may contribute to setting the foundation for broader legislative efforts. PMID:25767197

  6. The (not so) squeezed limit of the primordial 3-point function

    SciTech Connect

    Creminelli, Paolo; Musso, Marcello; D'Amico, Guido; Noreña, Jorge E-mail: gda2@nyu.edu E-mail: jorge.norena@icc.ub.edu

    2011-11-01

    We prove that, in a generic single-field model, the consistency relation for the 3-point function in the squeezed limit receives corrections that vanish quadratically in the ratio of the momenta, i.e. as (k{sub L}/k{sub S}){sup 2}. This implies that a detection of a bispectrum signal going as 1/k{sub L}{sup 2} in the squeezed limit, that is suppressed only by one power of k{sub L} compared with the local shape, would rule out all single-field models. The absence of this kind of terms in the bispectrum holds also for multifield models, but only if all the fields have a mass much smaller than H. The detection of any scale dependence of the bias, for scales much larger than the size of the haloes, would disprove all single-field models. We comment on the regime of squeezing that can be probed by realistic surveys.

  7. Focal Image Plane Detection Based on Central Coordinate Point Spectral Value in Off-Axis Digital Particle Holography

    NASA Astrophysics Data System (ADS)

    Qiu, Peizhen; Deng, Lijun; Lu, Wenhui

    2015-12-01

    A method to detect the focal image plane from a single off-axis digital particle hologram is proposed. This method utilizes the central coordinate point spectral value of the reconstructed particle image as focusing criterion to detect the focal image plane. It is found that the central coordinate point spectral values come into maximum when the reconstruction distance is equal to the actual distance that was used in experiment of hologram acquisition. Numerical simulations are given to validate the feasibility and effectiveness of the proposed method. The proposed method is a potential and better option for studying three dimensional particles by using digital holography.

  8. Gaussian mixture sigma-point particle filter for optical indoor navigation system

    NASA Astrophysics Data System (ADS)

    Zhang, Weizhi; Gu, Wenjun; Chen, Chunyi; Chowdhury, M. I. S.; Kavehrad, Mohsen

    2013-12-01

    With the fast growing and popularization of smart computing devices, there is a rise in demand for accurate and reliable indoor positioning. Recently, systems using visible light communications (VLC) technology have been considered as candidates for indoor positioning applications. A number of researchers have reported that VLC-based positioning systems could achieve position estimation accuracy in the order of centimeter. This paper proposes an Indoors navigation environment, based on visible light communications (VLC) technology. Light-emitting-diodes (LEDs), which are essentially semiconductor devices, can be easily modulated and used as transmitters within the proposed system. Positioning is realized by collecting received-signal-strength (RSS) information on the receiver side, following which least square estimation is performed to obtain the receiver position. To enable tracking of user's trajectory and reduce the effect of wild values in raw measurements, different filters are employed. In this paper, by computer simulations we have shown that Gaussian mixture Sigma-point particle filter (GM-SPPF) outperforms other filters such as basic Kalman filter and sequential importance-resampling particle filter (SIR-PF), at a reasonable computational cost.

  9. Self-limiting trajectories of a particle moving deterministically in a random medium

    NASA Astrophysics Data System (ADS)

    Webb, B. Z.; Cohen, E. G. D.

    2015-12-01

    We study the motion of a particle moving on a two-dimensional honeycomb lattice, whose sites are randomly occupied by either right or left rotators. These rotators deterministically scatter the particle to the right or left, additionally changing orientation from left to right or from right to left after scattering the particle. In the model we consider, the scatterers are each initially oriented to the right with probability p\\in [0,1]. The initial configuration of scatterers, which forms the medium through which the particle moves, is set up so that the scatterer’s orientations are independent and identically distributed. For p\\in (0,1), we show that as the particle moves through the lattice, it creates a number of reflecting structures. These structures ultimately limit the particle’s motion, causing it to have a periodic trajectory. As p approaches either 0 or 1, and the medium becomes increasingly homogenous, the particle’s dynamics undergoes a discontinuous transition from this self-limiting, periodic motion to a self-avoiding motion, where the particle’s trajectory, away from its initial position, is a self-avoiding walk. In a generalization of this model, we also show the same periodic behavior exists if the model’s initial configuration of scatterers are independently but not identically distributed. However, if these orientations are not chosen independently, we demonstrate that this can drastically change the particle’s motion causing it to have a nonperiodic behavior.

  10. Calculation of the limiting parameters for oxide ceramic particles during HVOF spraying

    SciTech Connect

    Kadyrov, V.; Evdokimenko, Y.; Kisel, V.; Kadyrov, E.

    1994-12-31

    The authors analyze numerically gas-dynamical schemes peculiar for HVOF spraying equipment and present methods to calculate velocity and thermal state of sprayed particles which allow one to find the limiting values of these parameters and to define the applicability limitations of modern HVOF spraying apparatus. The method includes gas dynamical calculations of gas flow in accelerating channel (AC) and calculations of sprayed particle motion and its thermal state (temperature and melted mass fraction). The calculations were performed for particles of aluminum oxide and zirconium oxide with the size distributions of 10--80 {micro}m. Three different jet schemes were considered: with supersonic AC, with subsonic AC, and with combined gas dynamical path having functionally separated regions of heating and acceleration. Analysis of the results obtained at limiting parameters of jet operation suggests that energetic potentialities of HVOF method are not utilized completely. Although accelerated to a high speed the ceramic oxide particles have a thermal state which is far from optimal. It is possible to significantly increase the powder temperature and fraction of melted material by using new configuration solutions without essential constructive complications. The authors propose one of the possible solutions to optimize gas dynamical path. The results obtained for heating and acceleration in such a path suggest that the utilized approach is correct and allows one to predict the creation of a new family of more efficient HVOF torches and an expanded applicability of HVOF method.

  11. Feedback localization of freely diffusing fluorescent particles near the optical shot-noise limit

    NASA Astrophysics Data System (ADS)

    Berglund, Andrew J.; McHale, Kevin; Mabuchi, Hideo

    2007-01-01

    We report near-optimal tracking of freely diffusing fluorescent particles in a quasi-two-dimensional geometry via photon counting and real-time feedback. We present a quantitative statistical model of our feedback network and find excellent agreement with the experiment. We monitor the motion of a single fluorescent particle with a sensitivity of 15 nm/sqrt Hz while collecting fewer than 5000 fluorescence photons/s. Fluorescent microspheres (diffusion coefficient 1.3 μm2/s) are tracked with a root-mean-square tracking error of 170 nm, within a factor of 2 of the theoretical limit set by photon counting shot noise.

  12. Melting and solidification point of fcc-metal nanoparticles with respect to particle size: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Shibuta, Yasushi; Suzuki, Toshio

    2010-10-01

    The phase transition between liquid droplets and solid nanoparticles of face-centered cubic (fcc) metals is investigated by the molecular dynamics simulation. Depression of both the melting and solidification points is negatively correlated with the inverse of particle radius. Polycrystalline nanoparticles are obtained by cooling and the polycrystalline structure causes a fluctuation in the trend of the melting point with respect to particle size. It was found that the Gibbs-Thomson coefficient is proportional to the melting point among various body-centered cubic (bcc) and fcc metals in the same matter, even though different interatomic potentials are employed between bcc and fcc metals.

  13. 40 CFR 414.101 - Toxic pollutant effluent limitations and standards for direct discharge point sources that do not...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... and standards for direct discharge point sources that do not use end-of-pipe biological treatment. 414... That Do Not Use End-of-Pipe Biological Treatment § 414.101 Toxic pollutant effluent limitations and standards for direct discharge point sources that do not use end-of-pipe biological treatment. (a)Any...

  14. 40 CFR 414.101 - Toxic pollutant effluent limitations and standards for direct discharge point sources that do not...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... and standards for direct discharge point sources that do not use end-of-pipe biological treatment. 414... That Do Not Use End-of-Pipe Biological Treatment § 414.101 Toxic pollutant effluent limitations and standards for direct discharge point sources that do not use end-of-pipe biological treatment. (a)Any...

  15. 40 CFR 414.101 - Toxic pollutant effluent limitations and standards for direct discharge point sources that do not...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... and standards for direct discharge point sources that do not use end-of-pipe biological treatment. 414... That Do Not Use End-of-Pipe Biological Treatment § 414.101 Toxic pollutant effluent limitations and standards for direct discharge point sources that do not use end-of-pipe biological treatment. (a)Any...

  16. 40 CFR 414.101 - Toxic pollutant effluent limitations and standards for direct discharge point sources that do not...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... and standards for direct discharge point sources that do not use end-of-pipe biological treatment. 414... That Do Not Use End-of-Pipe Biological Treatment § 414.101 Toxic pollutant effluent limitations and standards for direct discharge point sources that do not use end-of-pipe biological treatment. (a)Any...

  17. 40 CFR 414.101 - Toxic pollutant effluent limitations and standards for direct discharge point sources that do not...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... and standards for direct discharge point sources that do not use end-of-pipe biological treatment. 414... That Do Not Use End-of-Pipe Biological Treatment § 414.101 Toxic pollutant effluent limitations and standards for direct discharge point sources that do not use end-of-pipe biological treatment. (a)Any...

  18. Particle velocity and sediment transport at the limit of deposition in sewers.

    PubMed

    Ota, J J; Perrusquía, G S

    2013-01-01

    This paper focuses on the sediment particle while it is transported at the limit of deposition in storm sewers, i.e. as bed load at the limit of concentration that leads to sediment deposition. Although many empirical sediment transport equations are known in the literature, there is only limited knowledge concerning particle velocity. Sediment particle and sphere velocity measurements were carried out in two pipe channels and these results led to the development of a semi-theoretical equation for sediment transport at the limit of deposition in sewers. Even in the transport process without deposition, sediment movement is slower than water velocity and depends on the angle of repose of sediment with a diameter d on the roughness k of the pipe channel. Instead of classical dimensionless bed shear stress ψ, a modified dimensionless bed shear stress ψ (d/k)(2/3) was suggested, based on the angle of repose and this parameter was proved to be significant for quantifying the transport capacity. The main purpose of this article is to emphasize the importance of careful observation of experiments. Not only number of tests, but physical understanding are essential for better empirical equations. PMID:23416585

  19. The polar cusp from a particle point of view: A statistical study based on Viking data

    SciTech Connect

    Aparicio, B.; Thelin, B.; Lundin, R. )

    1991-08-01

    The authors present results from the particle measurements made on board the Viking satellite. For the period of interest the Viking orbits covered at high latitudes the whole dayside sector. Data from the Viking V-3 particle experiment acquired during the Polar Region Outer Magnetospheric International Study period have been used to study the extension of the cusp and cleft in magnetic local time and invariant latitude, and furthermore, their dependence on solar wind and interplanetary magnetic field parameters. The study is limited to the MLT range from 0900 to 1500 and to invariant latitudes (ILAT) from 74{degree} to 82{degree}. This region is divided into bins of size. The authors concentrated on the region where magnetosheath solar wind plasma penetrates more directly into the magnetosphere and is measured at Viking altitudes. This region is called the cusp proper, to be distinguished from a broader region denoted the cleft, where more energetic particles are observed. Statistically, they find the cusp proper to extend from invariant latitudes of 75{degree} to 82{degree} and magnetic local times from 0930 to 1400 MLT. The width in ILAT is found to be on average {approx}2{degree} and in MLT {approx}2 hours. It is shown that a clear correlation exists between the densities in the cusp proper calculated from the Viking V-3 experiment in the cusp proper and those in the solar wind calculated from IMP 8 measurements. It is also shown that the position of the cusp proper in MLT depends on the sense of the By component of the interplanetary magnetic field (IMF By), giving a well-defined displacement of the region of maximum occurrence toward earlier MLTs for IMF By < 0 and a less defined displacement toward later MLTs for IMF By > 0.

  20. Particle acceleration and turbulence in cosmic Ray shocks: possible pathways beyond the Bohm limit

    NASA Astrophysics Data System (ADS)

    Malkov, M. A.; Diamond, P. H.

    2007-08-01

    Diffusive shock acceleration is discussed in terms of its potential to accelerate cosmic rays (CR) to 1018 eV (beyond the ``knee,'' as observations suggest) and in terms of the related observational signatures (spectral features). One idea to reach this energy is to resonantly generate a turbulent magnetic field via accelerated particles much in excess of the background field. We identify difficulties with this scenario and suggest two separate mechanisms that can work in concert with one another leading to a significant acceleration enhancement. The first mechanism is based on a nonlinear modification of the flow ahead of the shock supported by particles already accelerated to some specific (knee) momentum. The particles gain energy by bouncing off converging magnetic irregularities frozen into the flow in the shock precursor and not so much by re-crossing the shock itself. The acceleration rate is determined by the gradient of the flow velocity and turns out to be formally independent of the particle mean free path. The velocity gradient is set by the knee-particles. The acceleration rate of particles above the knee does not decrease with energy, unlike in the linear acceleration regime. The knee (spectrum steepening) forms because particles above it are effectively confined to the shock only if they are within limited domains in the momentum space, while other particles fall into ``loss-islands'', similar to the ``loss-cone'' of magnetic traps. This also maintains the steep velocity gradient and high acceleration rate. The second mechanism is based on the generation of Alfven waves at the gyroradius scale at the background field level, with a subsequent transfer to longer scales via interaction with strong acoustic turbulence in the shock precursor. The acoustic turbulence in turn, may be generated by Drury instability or by parametric instability of the Alfven (A) waves.

  1. Collective scattering and oscillation modes of optically bound point particles trapped in a single mode waveguide field.

    PubMed

    Holzmann, Daniela; Ritsch, Helmut

    2015-12-14

    Collective coherent scattering of laser light induces strong light forces between polarizable point particles. These dipole forces are strongly enhanced in magnitude and distance within the field of an optical waveguide so that at low temperature the particles self-order in strongly bound regular patterns. The stationary configurations typically exhibit super-radiant scattering with strong particle and light confinement. Here we study collective excitations of such self-consistent crystalline particle-light structures as function of particle number and pump strength. Multiple scattering and absorption modify the collective particle-field eigenfrequencies and create eigenmodes of surprisingly complex nature. For larger arrays this often leads to dynamical instabilities and disintegration of the structures even if additional damping is present. PMID:26698971

  2. Model of alpha particle diffusion in the outer limiter shadow of TFTR

    SciTech Connect

    Wang, S. |; Zweben, S.J.

    1996-05-01

    A new code, Monte Carlo Collisional Stochastic Orbit Retracing (MCCSOR), has been developed to model the alpha particle loss signal as measured by the outer midplane scintillator detector in TFTR. The shadowing effects due to the outer limiters and the detector itself have been included, along with a pitch angle scattering and stochastic ripple diffusion. Shadowing by the outer limiters has a strong effect on both the magnitude and pitch angle distribution of the calculated loss. There is at least qualitative agreement between the calculated results and the experimental data.

  3. Evaluation of the Strength of Railway Ballast Using Point Load Test for Various Size Fractions and Particle Shapes

    NASA Astrophysics Data System (ADS)

    Koohmishi, Mehdi; Palassi, Massoud

    2016-07-01

    The ballast layer is one of the most important components of the railway track superstructure in which angular aggregates of high strength rocks are used. Ballast degradation is one of the main sources of railway problems in which the ballast aggregates are gradually degraded due to the abrasion of the sharp corners of the angular particles and splitting each individual particle into two or several small pieces under loading. In this paper, the effects of rock type, aggregate size and particle shape on the strength of the single ballast particles are investigated. For this purpose, point load test is carried out on ballast aggregates of four rock types including basalt, marl, dolomite and trachyte. According to the obtained results, as the size of the aggregates increases, the point load strength index decreases. The influence of size on the strength is more noticeable for ballasts obtained from higher strength rocks. It is also found that the shape of ballast particles has no major effect on its strength. Furthermore, our findings show that the failure pattern for ballasts of higher strength is so that each particle commonly splits into three pieces; while the dominant failure pattern for ballast particles with less strength is breaking the particle into two pieces.

  4. CHARGE-EXCHANGE LIMITS ON LOW-ENERGY {alpha}-PARTICLE FLUXES IN SOLAR FLARES

    SciTech Connect

    Hudson, H. S.; Fletcher, L.; MacKinnon, A. L.; Woods, T. N.

    2012-06-20

    This paper reports on a search for flare emission via charge-exchange radiation in the wings of the Ly{alpha} line of He II at 304 A, as originally suggested for hydrogen by Orrall and Zirker. Via this mechanism a primary {alpha} particle that penetrates into the neutral chromosphere can pick up an atomic electron and emit in the He II bound-bound spectrum before it stops. The Extreme-ultraviolet Variability Experiment on board the Solar Dynamics Observatory gives us our first chance to search for this effect systematically. The Orrall-Zirker mechanism has great importance for flare physics because of the essential roles that particle acceleration plays; this mechanism is one of the few proposed that would allow remote sensing of primary accelerated particles below a few MeV nucleon{sup -1}. We study 10 events in total, including the {gamma}-ray events SOL2010-06-12 (M2.0) and SOL2011-02-24 (M3.5) (the latter a limb flare), seven X-class flares, and one prominent M-class event that produced solar energetic particles. The absence of charge-exchange line wings may point to a need for more complete theoretical work. Some of the events do have broadband signatures, which could correspond to continua from other origins, but these do not have the spectral signatures expected from the Orrall-Zirker mechanism.

  5. Secondary nitrogen limitation in a subtropical lake impacted by non-point source agricultural pollution.

    PubMed

    Havens, K E

    1995-01-01

    A 20-year history of nutrient limitation was quantified for Lake Okeechobee, a nutrient-impacted lake in Florida, USA. Limiting status (nitrogen versus phosphorus) was estimated from deviations between trophic state index (TSI) parameters, calculated from routine monitoring data. The lake is presently nitrogen-limited. However, historical trends in the TSI deviations indicate that contemporary nitrogen limitation is a secondary, unnatural condition that has arisen due to excessive phosphorus loading. Prior to 1980, there was evidence of lake-wide limitation by phosphorus, rather than nitrogen. The finding of secondary nitrogen limitation in Lake Okeechobee has important management implications. Phosphorus loads are presently being reduced in order to reduce in-lake concentrations and create phosphorus-limited conditions (nitrogen limitation is undersirable because it has favored bloom-forming cyanobacteria). The present results indicate that this long-term management goal is ecologically sound; it is consistent with the concept of restoration of the lake. PMID:15091513

  6. Multi-Scale Simulation of Atomization with small drops represented by Lagrangian Point-Particle Model

    NASA Astrophysics Data System (ADS)

    Ling, Yue; Zaleski, Stéphane; Institut Jean Le Rond d'Alembert Team

    2014-11-01

    Numerical simulation is conducted to investigate the drop formation and evolution in gas-assisted atomization. The atomizer consists of two parallel planar jets: the fast gas jet and the slow liquid jet. Due to the shear between gas and liquid streams, the liquid-gas interface is unstable, and this eventually leads to full atomization. A fundamental challenge in atomization simulations is the existence of multiple length scales involved. In order to accurately capture both the gas-liquid interface instability and the drop dynamics, a multi-scale multiphase flow simulation strategy is proposed. In the present model, the gas-liquid interface is resolved by the Volume-of-Fluid (VOF) method, while the small drops are represented by Lagrangian point-particle (LPP) models. Particular attention is paid on validating the coupling and conversion between LPP and VOF. The present model is validated by comparing with direct numerical simulation (DNS) results and also experimental data. The simulation results show complex coupling between the interface instability and the turbulent gas jet, which in turn influence the formation and evolution of the drops formed in atomization. ANR-11-MONU-0011.

  7. Inverse dependency of particle residence times in ponds to the concentration of phosphate, the limiting nutrient.

    PubMed

    Roberts, Kimberly A; Santschi, Peter H

    2004-01-01

    234Th, a commonly used short-lived particle-reactive tracer in marine systems, was measured in three different holding pond series at the Rocky Flats Environmental Technology Site (RFETS), Colorado, along with its parent nuclide 238U, to determine steady-state residence times of particle-reactive actinides such as Pu, and of particles. Series B ponds, which received industrial effluent that includes ortho-phosphate (PO4) and actinides, differed from series A and C ponds, which did not. This difference was also evident in the calculated particle residence times, which were <1 day for the ponds B4 and B5, where PO4 concentrations were higher (1.4 and 1.8 mg/l), and 3 and 3.4 days for ponds A3 and C2, respectively, where ortho-phosphate concentrations were lower (<0.1 mg/l). Particle residence times thus showed an inverse relationship with the concentration of ortho-phosphate, the limiting nutrient in fresh water systems. The same relationship to the concentration of ortho-phosphate or any of the other nutrient elements was not evident for the residence times of dissolved 234Th, which ranged between 0.1 and 2 days. This can be attributed to higher concentrations of dissolved and particulate ligands with greater binding potential for actinides such as four-valent Th and Pu in ponds with higher ortho-phosphate concentrations. Regardless of actual ortho-phosphate concentration, however, at water residence (holding) times of 1 month in these ponds, particles and associated actinides would be expected to be completely removed from the pond water to sediments. PMID:15261419

  8. The Mean-Field Limit for Solid Particles in a Navier-Stokes Flow

    NASA Astrophysics Data System (ADS)

    Desvillettes, Laurent; Golse, François; Ricci, Valeria

    2008-06-01

    We propose a mathematical derivation of Brinkman's force for a cloud of particles immersed in an incompressible viscous fluid. Specifically, we consider the Stokes or steady Navier-Stokes equations in a bounded domain Ω⊂ℝ3 for the velocity field u of an incompressible fluid with kinematic viscosity ν and density 1. Brinkman's force consists of a source term 6 π ν j where j is the current density of the particles, and of a friction term 6 π ν ρ u where ρ is the number density of particles. These additional terms in the motion equation for the fluid are obtained from the Stokes or steady Navier-Stokes equations set in Ω minus the disjoint union of N balls of radius ɛ=1/ N in the large N limit with no-slip boundary condition. The number density ρ and current density j are obtained from the limiting phase space empirical measure 1/Nsum_{1le kle N}δ_{xk,vk} , where x k is the center of the k-th ball and v k its instantaneous velocity. This can be seen as a generalization of Allaire's result in [Arch. Ration. Mech. Anal. 113:209-259, [1991

  9. Collinearity constraints for on-shell massless particle three-point functions, and implications for allowed-forbidden n +1 -point functions

    NASA Astrophysics Data System (ADS)

    Adler, Stephen L.

    2016-03-01

    A simple collinearity argument implies that the massless particle three-point function of helicities h1,h2,h3 with corresponding real-valued four-momenta k1,k2,k3 taken as all incoming or all outgoing (i.e., k1+k2+k3=0 ) vanishes by helicity conservation unless h1+h2+h3=0 . When any one particle with four-momentum k is off mass shell, this constraint no longer applies; a forbidden amplitude with h1+h2+h3≠0 on shell can be nonzero off shell, but it vanishes proportionally to k2 as k approaches mass shell. When an on-shell forbidden amplitude is coupled to an allowed n -point amplitude to form an n +1 -point function, this k2 factor in the forbidden amplitude cancels the k2 in the propagator, leading to an n +1 -point function that has no pole at k2=0 . We relate our results for real-valued four-momenta to the corresponding selection rules that have been derived in the on-shell literature for complexified four-momenta.

  10. Gravitational dynamics of an infinite shuffled lattice: Particle coarse-graining, nonlinear clustering, and the continuum limit.

    PubMed

    Baertschiger, T; Joyce, M; Gabrielli, A; Sylos Labini, F

    2007-07-01

    We study the evolution under their self-gravity of particles evolving from infinite "shuffled lattice" initial conditions. We focus here specifically on the comparison between the evolution of such a system and that of "daughter" coarse-grained particle distributions. These are sparser (i.e., lower density) particle distributions, defined by a simple coarse-graining procedure, which share the same large-scale mass fluctuations. We consider both the case that such coarse-grainings are performed (i) on the initial conditions, and (ii) at a finite time with a specific additional prescription. In numerical simulations we observe that, to a first approximation, these coarse-grainings represent well the evolution of the two-point correlation properties over a significant range of scales. We note, in particular, that the form of the two-point correlation function in the original system, when it is evolving in the asymptotic "self-similar" regime, may be reproduced well in a daughter coarse-grained system in which the dynamics are still dominated by two-body (nearest neighbor) interactions. This provides a simple physical description of the origin of the form of part of the asymptotic nonlinear correlation function. Using analytical results on the early time evolution of these systems, however, we show that small observed differences between the evolved system and its coarse-grainings at the initial time will in fact diverge as the ratio of the coarse-graining scale to the original interparticle distance increases. The second coarse-graining studied, performed at a finite time in a specified manner, circumvents this problem. It also makes it more physically transparent why gravitational dynamics from these initial conditions tends toward a self-similar evolution. We finally discuss the precise definition of a limit in which a continuum (specifically Vlasov-type) description of the observed linear and nonlinear evolution should be applicable. This requires the introduction

  11. Characterizing the size distribution of particles in urban stormwater by use of fixed-point sample-collection methods

    USGS Publications Warehouse

    Selbig, William R.; Bannerman, Roger T.

    2011-01-01

    The U.S Geological Survey, in cooperation with the Wisconsin Department of Natural Resources (WDNR) and in collaboration with the Root River Municipal Stormwater Permit Group monitored eight urban source areas representing six types of source areas in or near Madison, Wis. in an effort to improve characterization of particle-size distributions in urban stormwater by use of fixed-point sample collection methods. The types of source areas were parking lot, feeder street, collector street, arterial street, rooftop, and mixed use. This information can then be used by environmental managers and engineers when selecting the most appropriate control devices for the removal of solids from urban stormwater. Mixed-use and parking-lot study areas had the lowest median particle sizes (42 and 54 (u or mu)m, respectively), followed by the collector street study area (70 (u or mu)m). Both arterial street and institutional roof study areas had similar median particle sizes of approximately 95 (u or mu)m. Finally, the feeder street study area showed the largest median particle size of nearly 200 (u or mu)m. Median particle sizes measured as part of this study were somewhat comparable to those reported in previous studies from similar source areas. The majority of particle mass in four out of six source areas was silt and clay particles that are less than 32 (u or mu)m in size. Distributions of particles ranging from 500 (u or mu)m were highly variable both within and between source areas. Results of this study suggest substantial variability in data can inhibit the development of a single particle-size distribution that is representative of stormwater runoff generated from a single source area or land use. Continued development of improved sample collection methods, such as the depth-integrated sample arm, may reduce variability in particle-size distributions by mitigating the effect of sediment bias inherent with a fixed-point sampler.

  12. Nuclear Gamma-Ray Spectroscopy at the Limit of Particle Spectroscopy

    SciTech Connect

    Dr. Norbert Pietralla

    2006-03-29

    The research project ''Nuclear Gamma-Ray Spectroscopy at the Limit of Particle Stability'' with sponsor ID ''DE-FG02-04ER41334'' started late-summer 2004 and aims at the investigation of highly excited low-spin states of selected key-nuclei in the vicinity of the particle separation threshold by means of high-resolution gamma-ray spectroscopy in electromagnetic excitation reactions. This work addresses nuclear structures with excitation energies close to the binding energy or highly excited off-yrast states in accordance with the NSAC milestones. In 2005 the program was extended towards additional use of virtual photons and theoretical description of the low-lying collective excitations in the well deformed nuclei.

  13. Quantum heat engine in the relativistic limit: the case of a Dirac particle.

    PubMed

    Muñoz, Enrique; Peña, Francisco J

    2012-12-01

    We studied the efficiency of two different schemes for a quantum heat engine, by considering a single Dirac particle trapped in an infinite one-dimensional potential well as the "working substance." The first scheme is a cycle, composed of two adiabatic and two isoenergetic reversible trajectories in configuration space. The trajectories are driven by a quasistatic deformation of the potential well due to an external applied force. The second scheme is a variant of the former, where isoenergetic trajectories are replaced by isothermal ones, along which the system is in contact with macroscopic thermostats. This second scheme constitutes a quantum analog of the classical Carnot cycle. Our expressions, as obtained from the Dirac single-particle spectrum, converge in the nonrelativistic limit to some of the existing results in the literature for the Schrödinger spectrum. PMID:23367894

  14. Phase transition in diffusion limited aggregation with patchy particles in two dimensions

    NASA Astrophysics Data System (ADS)

    Kartha, Moses J.; Sayeed, Ahmed

    2016-08-01

    The influence of patchy interactions on diffusion-limited aggregation (DLA) has been investigated by computer simulations. In this model, the adsorption of the particle is irreversible, but the adsorption occurs only when the 'sticky patch' makes contact with the sticky patch of a previously adsorbed particle. As we vary the patch size, growth rate of the cluster decreases, and below a well-defined critical patch size, pc the steady state growth rate goes to zero. The system reaches an absorbing phase producing a non-equilibrium continuous phase transition. The order parameter close to the critical value of the patch size shows a power law behavior ρ (∞) ∼(p -pc) β, where β = 0.2840. We have found that the value of the critical exponent convincingly shows that this transition in patchy DLA belongs to the directed percolation universality class.

  15. Quantifying the kinetic limitations of atmospheric gas-to-particle conversion

    NASA Astrophysics Data System (ADS)

    Booth, A.; Murphy, B.; Riipinen, I.; Percival, C.; Topping, D. O.

    2013-12-01

    Atmospheric aerosol particles, from anthropogenic and biogenic sources, remain a major uncertainty in the Earth system: they impact the climate by directly scattering and absorbing solar radiation, as well as regulating the properties of clouds. On regional scales, aerosols are among the main pollutants deteriorating air quality, their impacts on both poorly quantified. Reducing these uncertainties requires accurate knowledge on the composition, concentrations and size distributions of these particles as they reside in the atmosphere. Unfortunately, there are currently huge uncertainties in many fundamental parameters that are required to predict their environmental impacts. This is largely down to the fact that a significant fraction of atmospheric aerosol particles are comprised of organic material (20-90% of particle mass), containing potentially thousands of compounds with largely uncertain properties It is becoming increasingly evident that aerosols exist as metastable amorphous states, rather than simple liquid/solid mixtures. Empirical evidence suggests that particles can form glass like substances. As the glass transition temperature is approached, an increase in viscosity leads to a reduced rate of molecular diffusion and an arrested non-equilibrium structure. Partitioning between the gas and condensed phase is kinetically limited in such amorphous states. Traditional organic aerosol models do not account for this, they assume that 1) the aerosol phase is a well-mixed non-viscous liquid; 2) the aerosol phase instantaneously equilibrates with the gas phase constituents. This adds significant uncertainty to predictions of gas/particle mass transfer as mixing timescales are ultimately governed by the diffusion coefficients of the aerosol constituents in the aerosol, which, on the other hand, are connected to the viscosity of the particulate matter. For typical aerosol sizes, the characteristic time for mixing could increase from a few milliseconds to hours or

  16. Holographic interpretation of 1-point toroidal block in the semiclassical limit

    NASA Astrophysics Data System (ADS)

    Alkalaev, K. B.; Belavin, V. A.

    2016-06-01

    We propose the holographic interpretation of the 1-point conformal block on a torus in the semiclassical regime. To this end we consider the linearized version of the block and find its coefficients by means of the perturbation procedure around natural seed configuration corresponding to the zero-point block. From the AdS/CFT perspective the linearized block is given by the geodesic length of the tadpole graph embedded into the thermal AdS plus the holomorphic part of the thermal AdS action.

  17. 77 FR 112 - Effluent Limitations Guidelines and Standards for the Construction and Development Point Source...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-03

    ... Section 450.10 of the December 1, 2009 final rule (74 FR 62995) and the definition of ``storm water... Development Point Source Category (hereafter referred to as the ``C&D rule'') on December 1, 2009 (74 FR 62995... Elimination System (NPDES) stormwater regulations (55 FR 47990) on November 16, 1990. The Phase I...

  18. Interaction of fission products and SiC in TRISO fuel particles: a limiting HTGR design parameter

    SciTech Connect

    Stansfield, O.M.; Homan, F.J.; Simon, W.A.; Turner, R.F.

    1983-09-01

    The fuel particle system for the steam cycle cogeneration HTGR being developed in the US consists of 20% enriched UC/sub 0/./sub 3/O/sub 1/./sub 7/ and ThO/sub 2/ kernels with TRISO coatings. The reaction of fission products with the SiC coating is the limiting thermochemical coating failure mechanism affecting performance. The attack of the SiC by palladium (Pd) is considered the controlling reaction with systems of either oxide or carbide fuels. The lanthanides, such as cerium, neodymium, and praseodymium, also attack SiC in carbide fuel particles. In reactor design, the time-temperature relationships at local points in the core are used to calculate the depth of SiC-Pd reaction. The depth of penetration into the SiC during service varies with core power density, power distribution, outlet gas temperature, and fuel residence time. These parameters are adjusted in specifying the core design to avoid SiC coating failure.

  19. The Point of Departure of a Particle Sliding on a Curved Surface

    ERIC Educational Resources Information Center

    Aghamohammadi, Amir

    2012-01-01

    A particle is thrown tangentially on a surface. It is shown that for some surfaces and for special initial velocities the thrown particle immediately leaves the surface, and for special conditions it never leaves the surface. The conditions for leaving the surface are investigated. The problem is studied for a surface with the cross-section y =…

  20. Optical atmospheric scattering and absorption limitations on offset pointing from Earth Observatory Satellite /EOS/ sensors

    NASA Technical Reports Server (NTRS)

    Egan, W. G.; Fischbein, W. L.

    1975-01-01

    The Braslau-Dave atmospheric model which calculates the upward monochromatic light fluxes leaving the top of the atmosphere as a function of viewing angle, sun angle, and ground reflectance was employed to study the effect of atmospheric scattering and attenuation on universal apparent contrast for two EOS remote sensors operated at very large offset or pointing angles: the Thematic Mapper (TM) and the High Resolution Pointable Imager (HRPI). The TM offset off nadir could be plus or minus 20 degrees with an 11 degree scan angle and the HRPI pointing angle off nadir could be plus or minus 45 degrees with a 3 degree scan angle. The reduction of universal apparent contrast of EOS imagery is studied as a function of sun elevation angle, atmospheric aerosol loading, radiation wavelength and sensor look angles.

  1. 78 FR 34431 - Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-07

    ... the development of BCT limitations in July 9, 1986 (51 FR 24974). Section 304(a)(4) designates the... grease as an additional conventional pollutant on July 30, 1979 (44 FR 44501; 40 CFR 401.16). 3. Best... standards that apply to all non-domestic dischargers. See 52 FR 1586 (January 14, 1987). 6....

  2. 75 FR 68215 - Direct Final Rule Staying Numeric Limitation for the Construction and Development Point Source...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-05

    ....10 (74 FR 62995) and the definition of ``storm water discharges associated with industrial activity.... Instructions: Direct your comments to Docket ID No. EPA-HQ-OW-2010- 0884. EPA's policy is that all comments... Federal Register (74 FR 62995) effluent limitations guidelines and new source performance standards...

  3. 78 FR 41907 - Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-12

    ... days. DATES: Comments. The public-comment period for the proposed rule published June 7, 2013, (78 FR.../courier. Please refer to the proposal (78 FR 34432) for the addresses and detailed instructions. Docket... AGENCY 40 CFR Part 423 RIN 2040-AF14 Effluent Limitations Guidelines and Standards for the Steam...

  4. A critical reassessment of particle Dark Matter limits from dwarf satellites

    NASA Astrophysics Data System (ADS)

    Ullio, Piero; Valli, Mauro

    2016-07-01

    Dwarf satellite galaxies are ideal laboratories for identifying particle Dark Matter signals. When setting limits on particle Dark Matter properties from null searches, it becomes however crucial the level at which the Dark Matter density profile within these systems is constrained by observations. In the limit in which the spherical Jeans equation is assumed to be valid for a given tracer stellar population, we study the solution of this equation having the Dark Matter mass profile as an output rather than as a trial parametric input. Within our new formulation, we address to what level dwarf spheroidal galaxies feature a reliable mass estimator. We assess then possible extrapolation of the density profiles in the inner regions and—keeping explicit the dependence on the orbital anisotropy profile of the tracer population—we derive general trends on the line-of-sight integral of the density profile squared, a quantity commonly dubbed J-factor and crucial to estimate fluxes from prompt Dark Matter pair annihilations. Taking Ursa Minor as a study case among Milky Way satellites, we perform Bayesian inference using the available kinematical data for this galaxy. Contrary to all previous studies, we avoid marginalization over quantities poorly constrained by observations or by theoretical arguments. We find minimal J-factors to be about 2 to 4 times smaller than commonly quoted estimates, approximately relaxing by the same amount the limit on Dark Matter pair annihilation cross section from gamma-ray surveys of Ursa Minor. At the same time, if one goes back to a fixed trial parametric form for the density, e.g. using a NFW or Burkert profile, we show that the minimal J can hardly be reduced by more than a factor of 1.5.

  5. Evaluation of design parameters for TRISO-coated fuel particles to establish manufacturing critical limits using PARFUME

    DOE PAGESBeta

    Skerjanc, William F.; Maki, John T.; Collin, Blaise P.; Petti, David A.

    2015-12-02

    The success of modular high temperature gas-cooled reactors is highly dependent on the performance of the tristructural-isotopic (TRISO) coated fuel particle and the quality to which it can be manufactured. During irradiation, TRISO-coated fuel particles act as a pressure vessel to contain fission gas and mitigate the diffusion of fission products to the coolant boundary. The fuel specifications place limits on key attributes to minimize fuel particle failure under irradiation and postulated accident conditions. PARFUME (an integrated mechanistic coated particle fuel performance code developed at the Idaho National Laboratory) was used to calculate fuel particle failure probabilities. By systematically varyingmore » key TRISO-coated particle attributes, failure probability functions were developed to understand how each attribute contributes to fuel particle failure. Critical manufacturing limits were calculated for the key attributes of a low enriched TRISO-coated nuclear fuel particle with a kernel diameter of 425 μm. As a result, these critical manufacturing limits identify ranges beyond where an increase in fuel particle failure probability is expected to occur.« less

  6. Evaluation of design parameters for TRISO-coated fuel particles to establish manufacturing critical limits using PARFUME

    SciTech Connect

    Skerjanc, William F.; Maki, John T.; Collin, Blaise P.; Petti, David A.

    2015-12-02

    The success of modular high temperature gas-cooled reactors is highly dependent on the performance of the tristructural-isotopic (TRISO) coated fuel particle and the quality to which it can be manufactured. During irradiation, TRISO-coated fuel particles act as a pressure vessel to contain fission gas and mitigate the diffusion of fission products to the coolant boundary. The fuel specifications place limits on key attributes to minimize fuel particle failure under irradiation and postulated accident conditions. PARFUME (an integrated mechanistic coated particle fuel performance code developed at the Idaho National Laboratory) was used to calculate fuel particle failure probabilities. By systematically varying key TRISO-coated particle attributes, failure probability functions were developed to understand how each attribute contributes to fuel particle failure. Critical manufacturing limits were calculated for the key attributes of a low enriched TRISO-coated nuclear fuel particle with a kernel diameter of 425 μm. As a result, these critical manufacturing limits identify ranges beyond where an increase in fuel particle failure probability is expected to occur.

  7. Evaluation of design parameters for TRISO-coated fuel particles to establish manufacturing critical limits using PARFUME

    NASA Astrophysics Data System (ADS)

    Skerjanc, William F.; Maki, John T.; Collin, Blaise P.; Petti, David A.

    2016-02-01

    The success of modular high temperature gas-cooled reactors is highly dependent on the performance of the tristructural-isotopic (TRISO) coated fuel particle and the quality to which it can be manufactured. During irradiation, TRISO-coated fuel particles act as a pressure vessel to contain fission gas and mitigate the diffusion of fission products to the coolant boundary. The fuel specifications place limits on key attributes to minimize fuel particle failure under irradiation and postulated accident conditions. PARFUME (an integrated mechanistic coated particle fuel performance code developed at the Idaho National Laboratory) was used to calculate fuel particle failure probabilities. By systematically varying key TRISO-coated particle attributes, failure probability functions were developed to understand how each attribute contributes to fuel particle failure. Critical manufacturing limits were calculated for the key attributes of a low enriched TRISO-coated nuclear fuel particle with a kernel diameter of 425 μm. These critical manufacturing limits identify ranges beyond where an increase in fuel particle failure probability is expected to occur.

  8. Detectability limitations with 3-D point reconstruction algorithms using digital radiography

    SciTech Connect

    Lindgren, Erik

    2015-03-31

    The estimated impact of pores in clusters on component fatigue will be highly conservative when based on 2-D rather than 3-D pore positions. To 3-D position and size defects using digital radiography and 3-D point reconstruction algorithms in general require a lower inspection time and in some cases work better with planar geometries than X-ray computed tomography. However, the increase in prior assumptions about the object and the defects will increase the intrinsic uncertainty in the resulting nondestructive evaluation output. In this paper this uncertainty arising when detecting pore defect clusters with point reconstruction algorithms is quantified using simulations. The simulation model is compared to and mapped to experimental data. The main issue with the uncertainty is the possible masking (detectability zero) of smaller defects around some other slightly larger defect. In addition, the uncertainty is explored in connection to the expected effects on the component fatigue life and for different amount of prior object-defect assumptions made.

  9. Physical constraints, fundamental limits, and optimal locus of operating points for an inverted pendulum based actuated dynamic walker.

    PubMed

    Patnaik, Lalit; Umanand, Loganathan

    2015-12-01

    The inverted pendulum is a popular model for describing bipedal dynamic walking. The operating point of the walker can be specified by the combination of initial mid-stance velocity (v0) and step angle (φm) chosen for a given walk. In this paper, using basic mechanics, a framework of physical constraints that limit the choice of operating points is proposed. The constraint lines thus obtained delimit the allowable region of operation of the walker in the v0-φm plane. A given average forward velocity vx,avg can be achieved by several combinations of v0 and φm. Only one of these combinations results in the minimum mechanical power consumption and can be considered the optimum operating point for the given vx,avg. This paper proposes a method for obtaining this optimal operating point based on tangency of the power and velocity contours. Putting together all such operating points for various vx,avg, a family of optimum operating points, called the optimal locus, is obtained. For the energy loss and internal energy models chosen, the optimal locus obtained has a largely constant step angle with increasing speed but tapers off at non-dimensional speeds close to unity. PMID:26502096

  10. A Bayesian approach for suppression of limited angular sampling artifacts in single particle 3D reconstruction.

    PubMed

    Moriya, Toshio; Acar, Erman; Cheng, R Holland; Ruotsalainen, Ulla

    2015-09-01

    In the single particle reconstruction, the initial 3D structure often suffers from the limited angular sampling artifact. Selecting 2D class averages of particle images generally improves the accuracy and efficiency of the reference-free 3D angle estimation, but causes an insufficient angular sampling to fill the information of the target object in the 3D frequency space. Similarly, the initial 3D structure by the random-conical tilt reconstruction has the well-known "missing cone" artifact. Here, we attempted to solve the limited angular sampling problem by sequentially applying maximum a posteriori estimate with expectation maximization algorithm (sMAP-EM). Using both simulated and experimental cryo-electron microscope images, the sMAP-EM was compared to the direct Fourier method on the basis of reconstruction error and resolution. To establish selection criteria of the final regularization weight for the sMAP-EM, the effects of noise level and sampling sparseness on the reconstructions were examined with evenly distributed sampling simulations. The frequency information filled in the missing cone of the conical tilt sampling simulations was assessed by developing new quantitative measurements. All the results of visual and numerical evaluations showed the sMAP-EM performed better than the direct Fourier method, regardless of the sampling method, noise level, and sampling sparseness. Furthermore, the frequency domain analysis demonstrated that the sMAP-EM can fill the meaningful information in the unmeasured angular space without detailed a priori knowledge of the objects. The current research demonstrated that the sMAP-EM has a high potential to facilitate the determination of 3D protein structures at near atomic-resolution. PMID:26193484

  11. Dynamics of charged particle motion in the vicinity of three dimensional magnetic null points: Energization and chaos

    SciTech Connect

    Gascoyne, Andrew

    2015-03-15

    Using a full orbit test particle approach, we analyse the motion of a single proton in the vicinity of magnetic null point configurations which are solutions to the kinematic, steady state, resistive magnetohydrodynamics equations. We consider two magnetic configurations, namely, the sheared and torsional spine reconnection regimes [E. R. Priest and D. I. Pontin, Phys. Plasmas 16, 122101 (2009); P. Wyper and R. Jain, Phys. Plasmas 17, 092902 (2010)]; each produce an associated electric field and thus the possibility of accelerating charged particles to high energy levels, i.e., > MeV, as observed in solar flares [R. P. Lin, Space Sci. Rev. 124, 233 (2006)]. The particle's energy gain is strongly dependent on the location of injection and is characterised by the angle of approach β, with optimum angle of approach β{sub opt} as the value of β which produces the maximum energy gain. We examine the topological features of each regime and analyse the effect on the energy gain of the proton. We also calculate the complete Lyapunov spectrum for the considered dynamical systems in order to correctly quantify the chaotic nature of the particle orbits. We find that the sheared model is a good candidate for the acceleration of particles, and for increased shear, we expect a larger population to be accelerated to higher energy levels. In the strong electric field regime (E{sub 0}=1500 V/m), the torsional model produces chaotic particle orbits quantified by the calculation of multiple positive Lyapunov exponents in the spectrum, whereas the sheared model produces chaotic orbits only in the neighbourhood of the null point.

  12. Fixed points and limit cycles in the population dynamics of lysogenic viruses and their hosts.

    PubMed

    Wang, Zhenyu; Goldenfeld, Nigel

    2010-07-01

    Starting with stochastic rate equations for the fundamental interactions between microbes and their viruses, we derive a mean-field theory for the population dynamics of microbe-virus systems, including the effects of lysogeny. In the absence of lysogeny, our model is a generalization of that proposed phenomenologically by Weitz and Dushoff. In the presence of lysogeny, we analyze the possible states of the system, identifying a limit cycle, which we interpret physically. To test the robustness of our mean-field calculations to demographic fluctuations, we have compared our results with stochastic simulations using the Gillespie algorithm. Finally, we estimate the range of parameters that delineate the various steady states of our model. PMID:20866659

  13. Fixed points and limit cycles in the population dynamics of lysogenic viruses and their hosts

    NASA Astrophysics Data System (ADS)

    Wang, Zhenyu; Goldenfeld, Nigel

    2010-07-01

    Starting with stochastic rate equations for the fundamental interactions between microbes and their viruses, we derive a mean-field theory for the population dynamics of microbe-virus systems, including the effects of lysogeny. In the absence of lysogeny, our model is a generalization of that proposed phenomenologically by Weitz and Dushoff. In the presence of lysogeny, we analyze the possible states of the system, identifying a limit cycle, which we interpret physically. To test the robustness of our mean-field calculations to demographic fluctuations, we have compared our results with stochastic simulations using the Gillespie algorithm. Finally, we estimate the range of parameters that delineate the various steady states of our model.

  14. Multi-point Observations and Modeling of Particle Injections During Substorms

    NASA Astrophysics Data System (ADS)

    Henderson, M. G.; Woodroffe, J. R.; Jordanova, V.; Harris, C.

    2015-12-01

    Dispersionless and dispersed particle injections associated with substorms have been studied for many years based on observations acquired primarily at geosynchronous orbit. A general picture that has emerged is that particles are energized and rapidly transported/organized behind an "injection boundary" that penetrates closer to Earth in some magnetic local time sector (e.g. the so-called double-spiral injection boundary model). While this picture provides a very good description of injections at geosynchronous orbit, with the launch of the Van Allen Probes mission, we are now able to explore the evolution of injection signatures well inside of geosynchronous orbit at multiple locations as well. We find that the injection boundary model also appears to reproduce a number of complicated types of dispersion patterns observed in the Van Allen Probes particle data. The dispersion patterns are found to depend dramatically on orbital configuration and timing of onset relative to the phasing of the spacecraft in their orbits. In addition to observational results, we present results of simulated dispersion patterns obtained from the injection boundary model using guiding center particle tracing in two different field configurations: 1) a simplistic dipole magnetic field with Volland-Stern electric field, and 2) RAM/SCB running in the Space Weather Modeling Framework.

  15. Improved limits on scattering of weakly interacting massive particles from reanalysis of 2013 LUX data

    DOE PAGESBeta

    Akerib, D. S.

    2016-04-20

    Here, we present constraints on weakly interacting massive particles (WIMP)-nucleus scattering from the 2013 data of the Large Underground Xenon dark matter experiment, including 1.4 × 104 kg day of search exposure. This new analysis incorporates several advances: single-photon calibration at the scintillation wavelength, improved event-reconstruction algorithms, a revised background model including events originating on the detector walls in an enlarged fiducial volume, and new calibrations from decays of an injected tritium β source and from kinematically constrained nuclear recoils down to 1.1 keV. Sensitivity, especially to low-mass WIMPs, is enhanced compared to our previous results which modeled the signalmore » only above a 3 keV minimum energy. Under standard dark matter halo assumptions and in the mass range above 4 GeV c–2, these new results give the most stringent direct limits on the spin-independent WIMP-nucleon cross section. The 90% C.L. upper limit has a minimum of 0.6 zb at 33 GeV c–2 WIMP mass.« less

  16. Improved Limits on Scattering of Weakly Interacting Massive Particles from Reanalysis of 2013 LUX Data

    NASA Astrophysics Data System (ADS)

    Akerib, D. S.; Araújo, H. M.; Bai, X.; Bailey, A. J.; Balajthy, J.; Beltrame, P.; Bernard, E. P.; Bernstein, A.; Biesiadzinski, T. P.; Boulton, E. M.; Bradley, A.; Bramante, R.; Cahn, S. B.; Carmona-Benitez, M. C.; Chan, C.; Chapman, J. J.; Chiller, A. A.; Chiller, C.; Currie, A.; Cutter, J. E.; Davison, T. J. R.; de Viveiros, L.; Dobi, A.; Dobson, J. E. Y.; Druszkiewicz, E.; Edwards, B. N.; Faham, C. H.; Fiorucci, S.; Gaitskell, R. J.; Gehman, V. M.; Ghag, C.; Gibson, K. R.; Gilchriese, M. G. D.; Hall, C. R.; Hanhardt, M.; Haselschwardt, S. J.; Hertel, S. A.; Hogan, D. P.; Horn, M.; Huang, D. Q.; Ignarra, C. M.; Ihm, M.; Jacobsen, R. G.; Ji, W.; Kazkaz, K.; Khaitan, D.; Knoche, R.; Larsen, N. A.; Lee, C.; Lenardo, B. G.; Lesko, K. T.; Lindote, A.; Lopes, M. I.; Malling, D. C.; Manalaysay, A.; Mannino, R. L.; Marzioni, M. F.; McKinsey, D. N.; Mei, D.-M.; Mock, J.; Moongweluwan, M.; Morad, J. A.; Murphy, A. St. J.; Nehrkorn, C.; Nelson, H. N.; Neves, F.; O'Sullivan, K.; Oliver-Mallory, K. C.; Ott, R. A.; Palladino, K. J.; Pangilinan, M.; Pease, E. K.; Phelps, P.; Reichhart, L.; Rhyne, C.; Shaw, S.; Shutt, T. A.; Silva, C.; Solovov, V. N.; Sorensen, P.; Stephenson, S.; Sumner, T. J.; Szydagis, M.; Taylor, D. J.; Taylor, W.; Tennyson, B. P.; Terman, P. A.; Tiedt, D. R.; To, W. H.; Tripathi, M.; Tvrznikova, L.; Uvarov, S.; Verbus, J. R.; Webb, R. C.; White, J. T.; Whitis, T. J.; Witherell, M. S.; Wolfs, F. L. H.; Yazdani, K.; Young, S. K.; Zhang, C.; LUX Collaboration

    2016-04-01

    We present constraints on weakly interacting massive particles (WIMP)-nucleus scattering from the 2013 data of the Large Underground Xenon dark matter experiment, including 1.4 ×104 kg day of search exposure. This new analysis incorporates several advances: single-photon calibration at the scintillation wavelength, improved event-reconstruction algorithms, a revised background model including events originating on the detector walls in an enlarged fiducial volume, and new calibrations from decays of an injected tritium β source and from kinematically constrained nuclear recoils down to 1.1 keV. Sensitivity, especially to low-mass WIMPs, is enhanced compared to our previous results which modeled the signal only above a 3 keV minimum energy. Under standard dark matter halo assumptions and in the mass range above 4 GeV c-2 , these new results give the most stringent direct limits on the spin-independent WIMP-nucleon cross section. The 90% C.L. upper limit has a minimum of 0.6 zb at 33 GeV c-2 WIMP mass.

  17. Improved Limits on Scattering of Weakly Interacting Massive Particles from Reanalysis of 2013 LUX Data.

    PubMed

    Akerib, D S; Araújo, H M; Bai, X; Bailey, A J; Balajthy, J; Beltrame, P; Bernard, E P; Bernstein, A; Biesiadzinski, T P; Boulton, E M; Bradley, A; Bramante, R; Cahn, S B; Carmona-Benitez, M C; Chan, C; Chapman, J J; Chiller, A A; Chiller, C; Currie, A; Cutter, J E; Davison, T J R; de Viveiros, L; Dobi, A; Dobson, J E Y; Druszkiewicz, E; Edwards, B N; Faham, C H; Fiorucci, S; Gaitskell, R J; Gehman, V M; Ghag, C; Gibson, K R; Gilchriese, M G D; Hall, C R; Hanhardt, M; Haselschwardt, S J; Hertel, S A; Hogan, D P; Horn, M; Huang, D Q; Ignarra, C M; Ihm, M; Jacobsen, R G; Ji, W; Kazkaz, K; Khaitan, D; Knoche, R; Larsen, N A; Lee, C; Lenardo, B G; Lesko, K T; Lindote, A; Lopes, M I; Malling, D C; Manalaysay, A; Mannino, R L; Marzioni, M F; McKinsey, D N; Mei, D-M; Mock, J; Moongweluwan, M; Morad, J A; Murphy, A St J; Nehrkorn, C; Nelson, H N; Neves, F; O'Sullivan, K; Oliver-Mallory, K C; Ott, R A; Palladino, K J; Pangilinan, M; Pease, E K; Phelps, P; Reichhart, L; Rhyne, C; Shaw, S; Shutt, T A; Silva, C; Solovov, V N; Sorensen, P; Stephenson, S; Sumner, T J; Szydagis, M; Taylor, D J; Taylor, W; Tennyson, B P; Terman, P A; Tiedt, D R; To, W H; Tripathi, M; Tvrznikova, L; Uvarov, S; Verbus, J R; Webb, R C; White, J T; Whitis, T J; Witherell, M S; Wolfs, F L H; Yazdani, K; Young, S K; Zhang, C

    2016-04-22

    We present constraints on weakly interacting massive particles (WIMP)-nucleus scattering from the 2013 data of the Large Underground Xenon dark matter experiment, including 1.4×10^{4}  kg day of search exposure. This new analysis incorporates several advances: single-photon calibration at the scintillation wavelength, improved event-reconstruction algorithms, a revised background model including events originating on the detector walls in an enlarged fiducial volume, and new calibrations from decays of an injected tritium β source and from kinematically constrained nuclear recoils down to 1.1 keV. Sensitivity, especially to low-mass WIMPs, is enhanced compared to our previous results which modeled the signal only above a 3 keV minimum energy. Under standard dark matter halo assumptions and in the mass range above 4  GeV c^{-2}, these new results give the most stringent direct limits on the spin-independent WIMP-nucleon cross section. The 90% C.L. upper limit has a minimum of 0.6 zb at 33  GeV c^{-2} WIMP mass. PMID:27152785

  18. Behavior of the particle transport coefficients near the density limit in MTX

    SciTech Connect

    Marinak, M.M.

    1993-04-01

    The perturbed particle transport coefficients were determined for a range of plasma conditions in the Alcator C tokamak, a component of the Microwave Tokamak Experiment (MTX), from analysis of density perturbations created in gas modulation experiments. Density measurements from a 15 chord far-infrared interferometer were sufficiently detailed to allow radial profiles of the transport coefficients to be resolved. Gas modulation experiments were carried out on plasmas over a range of relatively low currents and a wide variety of line-averaged densities, including values near the Greenwald density limit. With this technique the perturbed diffusion coefficient D and the perturbed convection velocity V can be determined simultaneously. Measured profiles of D rise toward the outside of the plasma column in a manner generally similar to those determined previously for {chi}{sub e,HP} from sawtooth heat pulse propagation. Values of D are typically smaller than those of {chi}{sub e,HP} given for the same line-averaged densities by a factor of 2-5. Diffusion coefficients from a series of discharges at constant current showed little variation with density through most of the saturated ohmic confinement regime. At the Greenwald density limit threshold a dramatic increase occurred in both the perturbed convective and diffusive transport coefficients in the outer region of the plasma. The increases were most pronounced at the outermost range of the radii where coefficients were determined (r/a = 0.8), but were apparent over a region which extended well into the plasma interior. Density profiles maintained a similar shape near the density limit, congruous with the similar behavior of the transport coefficients. No dramatic deterioration was evident in the global energy confinement.

  19. Explaining Melting and Evaporation below Boiling Point. Can Software Help with Particle Ideas?

    ERIC Educational Resources Information Center

    Papageorgiou, George; Johnson, Philip; Fotiades, Fotis

    2008-01-01

    This paper reports the findings of a study exploring the use of a software package to help pupils understand particulate explanations for melting and evaporation below boiling point. Two matched classes in a primary school in Greece (ages 11-12, n = 16 and 19) were involved in a short intervention of six one hour lessons. Covering the same…

  20. Nanoparticle size detection limits by single particle ICP-MS for 40 elements.

    PubMed

    Lee, Sungyun; Bi, Xiangyu; Reed, Robert B; Ranville, James F; Herckes, Pierre; Westerhoff, Paul

    2014-09-01

    The quantification and characterization of natural, engineered, and incidental nano- to micro-size particles are beneficial to assessing a nanomaterial's performance in manufacturing, their fate and transport in the environment, and their potential risk to human health. Single particle inductively coupled plasma mass spectrometry (spICP-MS) can sensitively quantify the amount and size distribution of metallic nanoparticles suspended in aqueous matrices. To accurately obtain the nanoparticle size distribution, it is critical to have knowledge of the size detection limit (denoted as Dmin) using spICP-MS for a wide range of elements (other than a few available assessed ones) that have been or will be synthesized into engineered nanoparticles. Herein is described a method to estimate the size detection limit using spICP-MS and then apply it to nanoparticles composed of 40 different elements. The calculated Dmin values correspond well for a few of the elements with their detectable sizes that are available in the literature. Assuming each nanoparticle sample is composed of one element, Dmin values vary substantially among the 40 elements: Ta, U, Ir, Rh, Th, Ce, and Hf showed the lowest Dmin values, ≤10 nm; Bi, W, In, Pb, Pt, Ag, Au, Tl, Pd, Y, Ru, Cd, and Sb had Dmin in the range of 11-20 nm; Dmin values of Co, Sr, Sn, Zr, Ba, Te, Mo, Ni, V, Cu, Cr, Mg, Zn, Fe, Al, Li, and Ti were located at 21-80 nm; and Se, Ca, and Si showed high Dmin values, greater than 200 nm. A range of parameters that influence the Dmin, such as instrument sensitivity, nanoparticle density, and background noise, is demonstrated. It is observed that, when the background noise is low, the instrument sensitivity and nanoparticle density dominate the Dmin significantly. Approaches for reducing the Dmin, e.g., collision cell technology (CCT) and analyte isotope selection, are also discussed. To validate the Dmin estimation approach, size distributions for three engineered nanoparticle samples were

  1. Analysis of the ideal phase-Doppler System: Limitations imposed by the single-particle constraint

    SciTech Connect

    Edwards, C.F.; Marx, K.D.

    1991-06-01

    This paper explores the effects of particles statistics on the ability of a phase-Doppler system (or any single-particle diagnostic) to make accurate measurements of complex particle flows. This is accomplished by analyzing the response of an ideal phase-Doppler system to a postulated particle flux. The ideal system defined here senses particles of all sizes and velocities with perfect accuracy, but is subject to one constraint: in order for a measurement to be considered valid there must be only one particle in the probe volume at a time. A consequence of this constraint is that the measured flux of particles is similar to the true flux, but reduced by passage through two stages of filters. The first rejects particles for insufficient spacing and is controlled by a spatial Poisson process, while the second rejects particles for excessive residence time and is driven by a temporal Poisson process. The key filter parameters are the expected values of the number of particles in the probe volume and the number of particles entering the probe region during the residence time of a previous particle. Only if these values are kept below order 10{sup {minus}2} can the measured joint distribution function, flux rate, and derived quantities, be assumed to reflect the true nature of the flow. 8 refs., 30 figs., 2 tabs.

  2. Non-Gaussian particle number fluctuations in vicinity of the critical point for van der Waals equation of state

    NASA Astrophysics Data System (ADS)

    Vovchenko, V.; Poberezhnyuk, R. V.; Anchishkin, D. V.; Gorenstein, M. I.

    2016-01-01

    The non-Gaussian measures of the particle number fluctuations—skewness Sσ and kurtosis κ {σ }2—are calculated in a vicinity of the critical point (CP). This point corresponds to the end point of the first-order liquid-gas phase transition. The gaseous phase is characterized by the positive values of skewness while the liquid phase has negative skew. The kurtosis appears to be significantly negative at the critical density and supercritical temperatures. The skewness and kurtosis diverge at the CP. The classical van der Waals (VDW) equation of state in the grand canonical ensemble formulation is used in our studies. Neglecting effects of the quantum statistics we succeed to obtain the analytical expressions for the rich structures of the skewness and kurtosis in a wide region around the CP. These results have universal form, i.e., they do not depend on particular values of the VDW parameters a and b. The strongly intensive measures of particle number and energy fluctuations are also considered and show singular behavior in the vicinity of the CP.

  3. Quantum phase transition in trigonal triple quantum dots: The case of quantum dots deviated from particle-hole symmetric point

    NASA Astrophysics Data System (ADS)

    Kim, Song-Hyok; Kang, Chol-Jin; Kim, Yon-Il; Kim, Kwang-Hyon

    2015-05-01

    We consider a triple quantum dot system in a triangular geometry with one of the dots connected to metallic leads. We investigate quantum phase transition between local moment phase and Kondo screened strong coupling phase in triple quantum dots where energy levels of dots are deviated from the particle-hole symmetric point. The effect of on-site energy of dots on quantum phase transition between local moment phase and Kondo screened strong coupling phase in triple quantum dots is studied based on the analytical arguments and the numerical renormalization group method. The results show that the critical value of tunnel coupling between side dots decreases when the energy level of embedded dot rises up from the symmetric point to the Fermi level and the critical value increases when the energy levels of two side dots rise up. The study of the influence of on-site-energy changes on the quantum phase transitions in triple quantum dots has the importance for clarifying the mechanism of Kondo screening in triple quantum dots where energy levels of dots are deviated from the particle-hole symmetric point.

  4. Glass-transition properties of Yukawa potentials: from charged point particles to hard spheres.

    PubMed

    Yazdi, Anoosheh; Ivlev, Alexei; Khrapak, Sergey; Thomas, Hubertus; Morfill, Gregor E; Löwen, Hartmut; Wysocki, Adam; Sperl, Matthias

    2014-06-01

    The glass transition is investigated in three dimensions for single and double Yukawa potentials for the full range of control parameters. For vanishing screening parameter, the limit of the one-component plasma is obtained; for large screening parameters and high coupling strengths, the glass-transition properties cross over to the hard-sphere system. Between the two limits, the entire transition diagram can be described by analytical functions. Unlike other potentials, the glass-transition and melting lines for Yukawa potentials are found to follow shifted but otherwise identical curves in control-parameter space. PMID:25019902

  5. SIMULATIONS OF PARTICLE ACCELERATION BEYOND THE CLASSICAL SYNCHROTRON BURNOFF LIMIT IN MAGNETIC RECONNECTION: AN EXPLANATION OF THE CRAB FLARES

    SciTech Connect

    Cerutti, B.; Werner, G. R.; Uzdensky, D. A.; Begelman, M. C. E-mail: greg.werner@colorado.edu E-mail: mitch@jila.colorado.edu

    2013-06-20

    It is generally accepted that astrophysical sources cannot emit synchrotron radiation above 160 MeV in their rest frame. This limit is given by the balance between the accelerating electric force and the radiation reaction force acting on the electrons. The discovery of synchrotron gamma-ray flares in the Crab Nebula, well above this limit, challenges this classical picture of particle acceleration. To overcome this limit, particles must accelerate in a region of high electric field and low magnetic field. This is possible only with a non-ideal magnetohydrodynamic process, like magnetic reconnection. We present the first numerical evidence of particle acceleration beyond the synchrotron burnoff limit, using a set of two-dimensional particle-in-cell simulations of ultra-relativistic pair plasma reconnection. We use a new code, Zeltron, that includes self-consistently the radiation reaction force in the equation of motion of the particles. We demonstrate that the most energetic particles move back and forth across the reconnection layer, following relativistic Speiser orbits. These particles then radiate >160 MeV synchrotron radiation rapidly, within a fraction of a full gyration, after they exit the layer. Our analysis shows that the high-energy synchrotron flux is highly variable in time because of the strong anisotropy and inhomogeneity of the energetic particles. We discover a robust positive correlation between the flux and the cut-off energy of the emitted radiation, mimicking the effect of relativistic Doppler amplification. A strong guide field quenches the emission of >160 MeV synchrotron radiation. Our results are consistent with the observed properties of the Crab flares, supporting the reconnection scenario.

  6. Simulations of Particle Acceleration beyond the Classical Synchrotron Burnoff Limit in Magnetic Reconnection: An Explanation of the Crab Flares

    NASA Astrophysics Data System (ADS)

    Cerutti, B.; Werner, G. R.; Uzdensky, D. A.; Begelman, M. C.

    2013-06-01

    It is generally accepted that astrophysical sources cannot emit synchrotron radiation above 160 MeV in their rest frame. This limit is given by the balance between the accelerating electric force and the radiation reaction force acting on the electrons. The discovery of synchrotron gamma-ray flares in the Crab Nebula, well above this limit, challenges this classical picture of particle acceleration. To overcome this limit, particles must accelerate in a region of high electric field and low magnetic field. This is possible only with a non-ideal magnetohydrodynamic process, like magnetic reconnection. We present the first numerical evidence of particle acceleration beyond the synchrotron burnoff limit, using a set of two-dimensional particle-in-cell simulations of ultra-relativistic pair plasma reconnection. We use a new code, Zeltron, that includes self-consistently the radiation reaction force in the equation of motion of the particles. We demonstrate that the most energetic particles move back and forth across the reconnection layer, following relativistic Speiser orbits. These particles then radiate >160 MeV synchrotron radiation rapidly, within a fraction of a full gyration, after they exit the layer. Our analysis shows that the high-energy synchrotron flux is highly variable in time because of the strong anisotropy and inhomogeneity of the energetic particles. We discover a robust positive correlation between the flux and the cut-off energy of the emitted radiation, mimicking the effect of relativistic Doppler amplification. A strong guide field quenches the emission of >160 MeV synchrotron radiation. Our results are consistent with the observed properties of the Crab flares, supporting the reconnection scenario.

  7. Revisiting the SN1987A gamma-ray limit on ultralight axion-like particles

    SciTech Connect

    Payez, Alexandre; Ringwald, Andreas; Evoli, Carmelo; Mirizzi, Alessandro; Fischer, Tobias; Giannotti, Maurizio E-mail: carmelo.evoli@desy.de E-mail: mgiannotti@barry.edu E-mail: andreas.ringwald@desy.de

    2015-02-01

    We revise the bound from the supernova SN1987A on the coupling of ultralight axion-like particles (ALPs) to photons. In a core-collapse supernova, ALPs would be emitted via the Primakoff process, and eventually convert into gamma rays in the magnetic field of the Milky Way. The lack of a gamma-ray signal in the GRS instrument of the SMM satellite in coincidence with the observation of the neutrinos emitted from SN1987A therefore provides a strong bound on their coupling to photons. Due to the large uncertainty associated with the current bound, we revise this argument, based on state-of-the-art physical inputs both for the supernova models and for the Milky-Way magnetic field. Furthermore, we provide major amendments, such as the consistent treatment of nucleon-degeneracy effects and of the reduction of the nuclear masses in the hot and dense nuclear medium of the supernova. With these improvements, we obtain a new upper limit on the photon-ALP coupling: g{sub aγ} ∼< 5.3 × 10{sup -12} GeV{sup -1}, for m{sub a} ∼< 4.4 × 10{sup -10} eV, and we also give its dependence at larger ALP masses m{sub a}. Moreover, we discuss how much the Fermi-LAT satellite experiment could improve this bound, should a close-enough supernova explode in the near future.

  8. Comparison of dust charging between orbital-motion-limited theory and particle-in-cell simulations

    SciTech Connect

    Delzanno, Gian Luca Tang, Xian-Zhu

    2015-11-15

    The Orbital-Motion-Limited (OML) theory has been modified to predict the dust charge and the results were contrasted with the Whipple approximation [X. Z. Tang and G. L. Delzanno, Phys. Plasmas 21, 123708 (2014)]. To further establish its regime of applicability, in this paper, the OML predictions (for a non-electron-emitting, spherical dust grain at rest in a collisionless, unmagnetized plasma) are compared with particle-in-cell simulations that retain the absorption radius effect. It is found that for large dust grain radius r{sub d} relative to the plasma Debye length λ{sub D}, the revised OML theory remains a very good approximation as, for the parameters considered (r{sub d}/λ{sub D} ≤ 10, equal electron and ion temperatures), it yields the dust charge to within 20% accuracy. This is a substantial improvement over the Whipple approximation. The dust collected currents and energy fluxes, which remain the same in the revised and standard OML theories, are accurate to within 15%–30%.

  9. Point particle binary system with components of different masses in the linear regime of the characteristic formulation of general relativity

    NASA Astrophysics Data System (ADS)

    Cedeño M, C. E.; de Araujo, J. C. N.

    2016-05-01

    A study of binary systems composed of two point particles with different masses in the linear regime of the characteristic formulation of general relativity with a Minkowski background is provided. The present paper generalizes a previous study by Bishop et al. The boundary conditions at the world tubes generated by the particles's orbits are explored, where the metric variables are decomposed in spin-weighted spherical harmonics. The power lost by the emission of gravitational waves is computed using the Bondi News function. The power found is the well-known result obtained by Peters and Mathews using a different approach. This agreement validates the approach considered here. Several multipole term contributions to the gravitational radiation field are also shown.

  10. Estimating the Collision Rate of Inertial Particles in a Turbulent Flow: Limitations of the "Ghost Collision" Approximation

    NASA Astrophysics Data System (ADS)

    Voßkuhle, Michel; Pumir, Alain; Lévêque, Emmanuel

    2011-12-01

    Most studies of collisions in turbulent flows are based on the "ghost collision" approximation, whereby one follows a number of particles, and simply counts the number of times the distance between two particles becomes less than the sum of their radii; particles are kept in the flow after they collided. We discuss here the limitations of this approximation, and demonstrate, using a simple model flow, that it leads to overestimates of the real collision rate by as much as ~ 30% at small Stokes numbers.

  11. Investigation of point and extended defects in electron irradiated silicon—Dependence on the particle energy

    SciTech Connect

    Radu, R.; Pintilie, I.; Nistor, L. C.; Fretwurst, E.; Lindstroem, G.; Makarenko, L. F.

    2015-04-28

    This work is focusing on generation, time evolution, and impact on the electrical performance of silicon diodes impaired by radiation induced active defects. n-type silicon diodes had been irradiated with electrons ranging from 1.5 MeV to 27 MeV. It is shown that the formation of small clusters starts already after irradiation with high fluence of 1.5 MeV electrons. An increase of the introduction rates of both point defects and small clusters with increasing energy is seen, showing saturation for electron energies above ∼15 MeV. The changes in the leakage current at low irradiation fluence-values proved to be determined by the change in the configuration of the tri-vacancy (V{sub 3}). Similar to V{sub 3}, other cluster related defects are showing bistability indicating that they might be associated with larger vacancy clusters. The change of the space charge density with irradiation and with annealing time after irradiation is fully described by accounting for the radiation induced trapping centers. High resolution electron microscopy investigations correlated with the annealing experiments revealed changes in the spatial structure of the defects. Furthermore, it is shown that while the generation of point defects is well described by the classical Non Ionizing Energy Loss (NIEL), the formation of small defect clusters is better described by the “effective NIEL” using results from molecular dynamics simulations.

  12. Two-point one-dimensional δ-{\\delta }^{\\prime } interactions: non-abelian addition law and decoupling limit

    NASA Astrophysics Data System (ADS)

    Gadella, M.; Mateos-Guilarte, J.; Muñoz-Castañeda, J. M.; Nieto, L. M.

    2016-01-01

    In this contribution to the study of one-dimensional point potentials, we prove that if we take the limit q\\to 0 on a potential of the type {v}0δ (y)+2{v}1{δ }\\prime (y)+{w}0δ (y-q)+2{w}1{δ }\\prime (y-q), we obtain a new point potential of the type {u}0δ (y)+2{u}1{δ }\\prime (y), when u 0 and u 1 are related to v 0, v 1, w 0 and w 1 by a law with the structure of a group. This is the Borel subgroup of {{SL}}2({{R}}). We also obtain the non-abelian addition law from the scattering data. The spectra of the Hamiltonian in the decoupling cases emerging in the study are also described in full. It is shown that for the {v}1=+/- 1, {w}1=+/- 1 values of the {δ }\\prime couplings the singular Kurasov matrices become equivalent to Dirichlet at one side of the point interaction and Robin boundary conditions at the other side.

  13. 40 CFR Table 5 to Part 455 - BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That Do Not Use End-of-Pipe Biological Treatment 5... Limitations for Priority Pollutants for Direct Discharge Point Sources That Do Not Use End-of-Pipe...

  14. 40 CFR Table 4 to Part 455 - BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 30 2011-07-01 2011-07-01 false BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That use End-of-Pipe Biological Treatment 4 Table 4... Limitations for Priority Pollutants for Direct Discharge Point Sources That use End-of-Pipe...

  15. 40 CFR Table 5 to Part 455 - BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 30 2011-07-01 2011-07-01 false BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That Do Not Use End-of-Pipe Biological Treatment 5... Limitations for Priority Pollutants for Direct Discharge Point Sources That Do Not Use End-of-Pipe...

  16. 40 CFR Table 4 to Part 455 - BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That use End-of-Pipe Biological Treatment 4 Table 4... Limitations for Priority Pollutants for Direct Discharge Point Sources That use End-of-Pipe...

  17. Observation of oxide particles below the apparent oxygen solubility limit in tantalum

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1973-01-01

    The apparent solubility of oxygen in polycrystalline tantalum as determined by the X-ray diffraction lattice parameter technique is about 1.63 atomic percent at 820 C. However, oxide particles were identified in samples containing as low as 0.5 atomic percent of oxygen. These oxide particles were present at the grain boundaries and within the grains. The number of oxide particles increased with increasing oxygen concentration in tantalum. The presence of oxide particles suggests that the true solubility of oxygen in the polycrystalline tantalum metal is probably significantly lower than that reported in the literature.

  18. Observation of oxide particles below the apparent oxygen solubility limit in tantalum

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1974-01-01

    The apparent solubility of oxygen in polycrystalline tantalum as determined by the X-ray diffraction lattice parameter technique is about 1.63 at. pct at 820 C. However, oxide particles were identified in samples containing as low as 0.5 at. pct oxygen. These particles were present at the grain boundaries and within the grains. The number of oxide particles increased with increasing oxygen concentration in tantalum. The presence of oxide particles suggests that the true solubility in the polycrystalline tantalum metal is probably lower than that reported in the literature.

  19. Prompt particle acceleration around moving X-point magnetic field during impulsive phase of solar flares

    NASA Technical Reports Server (NTRS)

    Sakai, Jun-Ichi

    1992-01-01

    We present a model for high-energy solar flares to explain prompt proton and electron acceleration, which occurs around moving X-point magnetic field during the implosion phase of the current sheet. We derive the electromagnetic fields during the strong implosion phase of the current sheets, which is driven by the converging flow derived from the magnetohydrodynamic equations. It is shown that both protons and electrons can be promptly (within 1 second) accelerated to approximately 70 MeV and approximately 200 MeV, respectively. This acceleration mechanism can be applicable for the impulsive phase of the gradual gamma ray and proton flares (gradual GR/P flare), which have been called two-ribbon flares.

  20. Near-Infrared and Optical Limits for the Central X-Ray Point Source in the Cassiopeia A Supernova Remnant

    NASA Astrophysics Data System (ADS)

    Fesen, R. A.; Pavlov, G. G.; Sanwal, D.

    2006-01-01

    We set new near-infrared and optical magnitude limits for the central X-ray point source (XPS) in the Cassiopeia A supernova remnant based on HST images. Near-infrared images of the center of Cas A taken with the NICMOS 2 camera in combination with the F110W and F160W filters (~J and H bands) have magnitude limits >=26.2 and >=24.6, respectively. These images reveal no sources within a 1.2" radius (corresponding to a 99% confidence limit) of the Chandra XPS position. The NICMOS data, taken together with broadband optical magnitude limits (R~28 mag) obtained from a deep STIS CCD exposure taken with a clear filter (50CCD), indicate that the XPS luminosities are very low in the optical/NIR bands (e.g., LH<3×1029 ergs s-1) with no optical, J-, or H-band counterpart to the XPS easily detectable by HST. The closest detected object lies 1.8" from the XPS's nominal coordinates, with magnitudes R=25.7, mF110W=21.9, and mF160W=20.6, and is a foreground, late-type star as suggested by Kaplan, Kulkarni, and Murray. We discuss the nature of the Cas A central compact object on the basis of these near-infrared and optical flux limits. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with programs GO-8692 and GO-9798.

  1. Gravitational radiation from the radial infall of highly relativistic point particles into Kerr black holes

    NASA Astrophysics Data System (ADS)

    Cardoso, Vitor; Lemos, José P.

    2003-04-01

    In this paper, we consider the gravitational radiation generated by the collision of highly relativistic particles with rotating Kerr black holes. We use the Sasaki-Nakamura formalism to compute the waveform, energy spectra, and total energy radiated during this process. We show that the gravitational spectrum for high-energy collisions has definite characteristic universal features, which are independent of the spin of the colliding objects. We also discuss the possible connections between these results and black-hole black-hole collisions at the speed of light. Our results show that during the high-speed collision of a nonrotating hole with a rotating one, at most 35% of the total energy can get converted into gravitational waves. This 35% efficiency occurs only in the most optimistic situation, that of a zero impact parameter collision, along the equatorial plane, with an almost extreme Kerr black hole. In the general situation, the total gravitational energy radiated is expected to be much less, especially if the impact parameter increases. Thus, if one is able to produce black holes at the CERN Large Hadron Collider, at most 35% of the partons’ energy should be emitted during the so-called balding phase. This energy will be missing, since we do not have gravitational wave detectors able to measure such amplitudes. The collision at the speed of light between one rotating black hole and a nonrotating one or two rotating black holes turns out to be the most efficient gravitational wave generator in the Universe.

  2. Limitations on analysis of small particles with an electron probe: pollution studies

    USGS Publications Warehouse

    Heidel, R.H.; Desborough, G.A.

    1975-01-01

    Recent literature concerning the size and composition of airborne lead particles in automobile exhaust emissions determined by electron microprobe analysis reports 14 distinct lead compounds. Particle sizes reported were from 0.2 ??m to 2 ??m in the diameter. The determination of chemical formulae for compounds requires quantitative elemental data for individual particles. It was also assumed that the lead bearing particles analysed were solid (specifically non porous or non fluffy) compounds which occurred as discrete (non aggregate) particles. Intensity data obtained in the laboratory from the excited volume in a 1 ??m diameter sphere of solid lead chloride indicate insufficient precision and sensitivity to obtain chemical formulae as reported in the literature for exhaust emission products.

  3. Transient resonances in the inspirals of point particles into black holes.

    PubMed

    Flanagan, Eanna E; Hinderer, Tanja

    2012-08-17

    We show that transient resonances occur in the two-body problem in general relativity for spinning black holes in close proximity to one another when one black hole is much more massive than the other. These resonances occur when the ratio of polar and radial orbital frequencies, which is slowly evolving under the influence of gravitational radiation reaction, passes through a low order rational number. At such points, the adiabatic approximation to the orbital evolution breaks down, and there is a brief but order unity correction to the inspiral rate. The resonances cause a perturbation to orbital phase of order a few tens of cycles for mass ratios ∼10(-6), make orbits more sensitive to changes in initial data (though not quite chaotic), and are genuine nonperturbative effects that are not seen at any order in a standard post-Newtonian expansion. Our results apply to an important potential source of gravitational waves, the gradual inspiral of white dwarfs, neutron stars, or black holes into much more massive black holes. Resonances' effects will increase the computational challenge of accurately modeling these sources. PMID:23006355

  4. Space Weather Measurements Despite Resource Limitations: A Conceptual Overview of Novel Energetic Particle Instruments at a Geostationary Orbit

    NASA Astrophysics Data System (ADS)

    Burward-Hoy, J.

    2006-12-01

    Solar energetic particle events, cosmic rays, and relativistic electrons in the outer edge of the radiation belts produce single event upsets in the electronics and spacecraft charging on a host satellite located at a geostationary orbit. In order to determine the space weather environment for the host, particle instruments capable of measuring both electrons and protons in a wide energy range, with a large angular coverage but finite angular resolution are necessary. In order to adhere to resource limitations, including weight and power consumption and whether or not a host platform is spinning or three-axis stabilized, energetic particle instruments must be designed accordingly. I will present a conceptual overview of novel LANL instruments, specifically two-element collimated telescopes with solid-state sensors, and describe how the requirements for accurate space weather determination are met despite the resource limitations.

  5. Potential of mean force of association of large hydrophobic particles: toward the nanoscale limit.

    PubMed

    Makowski, Mariusz; Czaplewski, Cezary; Liwo, Adam; Scheraga, Harold A

    2010-01-21

    The potentials of mean force (PMFs) were determined, in both water with the TIP3P water model and in vacuo, for systems involving formation of nonpolar dimers composed of bicyclooctane, adamantane (both an all-atom model and a sphere with the radius of 3.4 A representing adamantane), and fullerene, respectively. A series of umbrella-sampling molecular dynamics simulations with the AMBER force field were carried out for each pair under both environmental conditions. The PMFs were calculated by using the weighted histogram analysis method. The results were compared with our previously determined PMF for neopentane. The shape of the PMFs for dimers of all four nonpolar molecules is characteristic of hydrophobic interactions with contact and solvent-separated minima and desolvation maxima. The positions of all these minima and maxima change with the size of the nonpolar molecule; for larger molecules they shift toward larger distances. Comparison of the PMFs of the bicyclooctane, adamantane, and fullerene dimers in water and in vacuo shows that hydrophobic interactions in each dimer are different from that for the dimer of neopentane. Interactions in the bicyclooctane, adamantane, and fullerene dimers are stronger in vacuo than in water. These dimers cannot be treated as classical, spherical, hydrophobic objects. The solvent contribution to the PMF was also computed by subtracting the PMF determined in vacuo from that in explicit solvent. The solvent contribution to the PMFs of bicyclooctane, adamantane, and fullerene is positive, as opposed to that of neopentane. The water molecules in the first solvation sphere of both adamantane and neopentane dimers are more ordered as compared to bulk water, with their dipole moments pointing away from the surface of the dimers. The average number of hydrogen bonds per water molecule in the first hydration shell of adamantane is smaller compared to that in bulk water, but this shell is thicker for all-atom adamantane than for

  6. Kinetic Study of Radiation-Reaction-Limited Particle Acceleration During the Relaxation of Force-Free Equilibria

    NASA Astrophysics Data System (ADS)

    Yuan, Yajie; Nalewajko, Krzysztof; Blandford, Roger D.; East, William E.; Zrake, Jonathan

    2016-01-01

    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 short time scales. This might be due to prodigal dissipation in a highly magnetized outflow. In order to understand the generic behavior of relativistic plasma with high magnetization, we consider a class of prototypical force-free equilibria which are shown to be unstable to ideal modes (East et al 2015 PRL 115, 095002). Kinetic simulations are carried out to follow the evolution of the instability and to study the basic mechanisms of particle acceleration, especially in the radiation-reaction-limited regime. We find that the instability naturally produces current layers and these are sites for efficient particle acceleration. Detailed calculations of the gamma ray spectrum, the evolution of the particle distribution function and the dynamical consequences of radiation reaction will be presented.

  7. A microfluidic platform with digital readout and ultra-low detection limit for quantitative point-of-care diagnostics.

    PubMed

    Li, Ying; Xuan, Jie; Song, Yujun; Wang, Ping; Qin, Lidong

    2015-08-21

    Quantitative assays are of great importance for point-of-care (POC) diagnostics because they can offer accurate information on the analytes. However, current POC devices often require an accessory instrument to give quantitative readouts for protein biomarkers, especially for those at very low concentration levels. Here, we report a microfluidic platform, the digital volumetric bar-chart chip (DV-chip), for quantitative POC diagnostics with ultra-low detection limits that are readable with the naked eye. Requiring no calibration, the DV-chip presents a digital ink bar chart (representing multiple bits composed of 0 and 1) for the target biomarker based on direct competition between O2 generated by the experimental and control samples. The bar chart clearly and accurately defines target concentration, allowing identification of disease status. For the standard PtNP solutions, the detection limit of the platform is approximately 0.1 pM and the dynamic range covers four orders of magnitude from 0.1 to 1000 pM. CEA samples with concentrations of 1 ng mL(-1) and 1.5 ng mL(-1) could be differentiated by the device. We also performed the ELISA assay for B-type natriuretic peptide (BNP) in 20 plasma samples from heart failure patients and the obtained on-chip data were in agreement with the clinical results. In addition, BNP was detectable at concentrations of less than 5 pM, which is three orders of magnitude lower than the detection limit of the previously reported readerless digital methods. By the integration of gas competition, volumetric bar chart, and digital readout, the DV-chip possesses merits of portability, visible readout, and ultra-low detection limit, which should offer a powerful platform for quantitative POC diagnostics in clinical settings and personalized detection. PMID:26170154

  8. Recurrent hamstring muscle injury: applying the limited evidence in the professional football setting with a seven-point programme.

    PubMed

    Brukner, Peter; Nealon, Andrew; Morgan, Christopher; Burgess, Darren; Dunn, Andrew

    2014-06-01

    Recurrent hamstring injuries are a major problem in sports such as football. The aim of this paper was to use a clinical example to describe a treatment strategy for the management of recurrent hamstring injuries and examine the evidence for each intervention. A professional footballer sustained five hamstring injuries in a relatively short period of time. The injury was managed successfully with a seven-point programme-biomechanical assessment and correction, neurodynamics, core stability, eccentric strengthening, an overload running programme, injection therapies and stretching/relaxation. The evidence for each of these treatment options is reviewed. It is impossible to be definite about which aspects of the programme contributed to a successful outcome. Only limited evidence is available in most cases; therefore, decisions regarding the use of different treatment modalities must be made by using a combination of clinical experience and research evidence. PMID:23322894

  9. Recurrent hamstring muscle injury: applying the limited evidence in the professional football setting with a seven-point programme

    PubMed Central

    Brukner, Peter; Nealon, Andrew; Morgan, Christopher; Burgess, Darren; Dunn, Andrew

    2014-01-01

    Recurrent hamstring injuries are a major problem in sports such as football. The aim of this paper was to use a clinical example to describe a treatment strategy for the management of recurrent hamstring injuries and examine the evidence for each intervention. A professional footballer sustained five hamstring injuries in a relatively short period of time. The injury was managed successfully with a seven-point programme—biomechanical assessment and correction, neurodynamics, core stability, eccentric strengthening, an overload running programme, injection therapies and stretching/relaxation. The evidence for each of these treatment options is reviewed. It is impossible to be definite about which aspects of the programme contributed to a successful outcome. Only limited evidence is available in most cases; therefore, decisions regarding the use of different treatment modalities must be made by using a combination of clinical experience and research evidence. PMID:23322894

  10. Limitations on the use of laser velocimeter signals for particle sizing

    NASA Technical Reports Server (NTRS)

    Orloff, K. L.; Myer, F. C.; Mikasa, M. F.; Phillips, J. R.

    1976-01-01

    The paper discusses the complex relationship existing between the diameter of a particle, its index of refraction, and the output signal of a fringe-type laser velocimeter, and describes a special purpose laser velocimeter for aerosol sizing that determines aerosol size distributions on the basis of Farmer's (1973) relationship between visibility and particle size. In experiments with particles of known size, this relationship is in qualitative agreement with the experimentally observed results, the main differences being that (1) the visibility does not assume a minimum value of zero, as predicted, and (2) the visibility value above which there is no ambiguity in the corresponding fringe spacing is higher than that predicted.

  11. Lidar observations of Arctic polar stratospheric clouds, 1988 - Signature of small, solid particles above the frost point

    NASA Technical Reports Server (NTRS)

    Poole, L. R.; Osborn, M. T.; Hunt, W. H.

    1988-01-01

    The paper presents recent (January 1988) Arctic airborne lidar data which suggest that Type I polar stratospheric clouds (PSCs) are composed of small solid particles with radii on the order of 0.5 micron. PSCs were observed remotely in the 21-24 km altitude range north of Greenland during a round-trip flight from Andenes, Norway on January 29, 1988, aboard the NASA Wallops Flight Facility P-3 Orion aircraft. Synoptic analyses at the 30-mb level show local temperatures of 191-193 K, which are well above the estimated frost point temperature of 185 K; this suggests that the PSCs were probably of the binary HNO3-H2O (Type I) class.

  12. Dynamic analysis of ultrasonically levitated droplet with moving particle semi-implicit and distributed point source method

    NASA Astrophysics Data System (ADS)

    Wada, Yuji; Yuge, Kohei; Nakamura, Ryohei; Tanaka, Hiroki; Nakamura, Kentaro

    2015-07-01

    Numerical analysis of an ultrasonically levitated droplet with a free surface boundary is discussed. The droplet is known to change its shape from sphere to spheroid when it is suspended in a standing wave owing to the acoustic radiation force. However, few studies on numerical simulation have been reported in association with this phenomenon including fluid dynamics inside the droplet. In this paper, coupled analysis using the distributed point source method (DPSM) and the moving particle semi-implicit (MPS) method, both of which do not require grids or meshes to handle the moving boundary with ease, is suggested. A droplet levitated in a plane standing wave field between a piston-vibrating ultrasonic transducer and a reflector is simulated with the DPSM-MPS coupled method. The dynamic change in the spheroidal shape of the droplet is successfully reproduced numerically, and the gravitational center and the change in the spheroidal aspect ratio are discussed and compared with the previous literature.

  13. LIMITS ON ALPHA PARTICLE TEMPERATURE ANISOTROPY AND DIFFERENTIAL FLOW FROM KINETIC INSTABILITIES: SOLAR WIND OBSERVATIONS

    SciTech Connect

    Bourouaine, Sofiane; Verscharen, Daniel; Chandran, Benjamin D. G.; Maruca, Bennett A.; Kasper, Justin C.

    2013-11-01

    Previous studies have shown that the observed temperature anisotropies of protons and alpha particles in the solar wind are constrained by theoretical thresholds for pressure and anisotropy driven instabilities such as the Alfvén/ion-cyclotron (A/IC) and fast-magnetosonic/whistler (FM/W) instabilities. In this Letter, we use a long period of in situ measurements provided by the Wind spacecraft's Faraday cups to investigate the combined constraint on the alpha proton differential flow velocity and the alpha particle temperature anisotropy due to A/IC and FM/W instabilities. We show that the majority of the data are constrained to lie within the region of parameter space in which A/IC and FM/W waves are either stable or have extremely low growth rates. In the minority of observed cases in which the growth rate of the A/IC (FM/W) instability is comparatively large, we find relatively higher values of T {sub α}/T {sub p} (T {sub ∥α}/T {sub ∥p}) when the alpha proton differential flow velocity is small, where T {sub α} and T {sub p} (T {sub ∥α} and T {sub ∥p}) are the perpendicular (parallel) temperatures of alpha particles and protons. We conjecture that this observed feature might arise from preferential alpha particle heating which can drive the alpha particles beyond the instability thresholds.

  14. Pushing the limit: investigation of hydrodynamic forces on a trapped particle kicked by a laser pulse.

    PubMed

    Villadsen, Naja; Andreasen, Daniel Ø; Hagelskjær, Jesper; Thøgersen, Jan; Imparato, Alberto; Keiding, Søren Rud

    2015-05-18

    We introduce a new optical technique where a train of short optical pulses is utilized to disturb a trapped microscopic particle. Using fast (250 kHz) and accurate (nm) detection of the position of the particle, accurately synchronized to the repetition rate of the laser pulses, we can coherently superimpose the displacement caused by each individual laser pulse. Thereby we are able to both bypass the influence from the Brownian motion of the trapped particle and to simultaneously increase the ability to localize its average trajectory by √n, where n is the number of repetitive pulses. In the results presented here we utilize a train of 1200 pulses to kick a 5 μm polystyrene sphere and obtain a spatial resolution corresponding to 0.09 nm and a time resolution of 4 μs. The magnitude of the optical force pushing the particle corresponds to ∼ 10(4)g and enables an investigation of both the hydrodynamical drag and the inertial effects caused by the particle and the surrounding liquid. Our results enables a more accurate testing of the existing extended models for the hydrodynamic drag and we discuss the observed agreement between experiments and theory. PMID:26074567

  15. Three dimensional indoor positioning based on visible light with Gaussian mixture sigma-point particle filter technique

    NASA Astrophysics Data System (ADS)

    Gu, Wenjun; Zhang, Weizhi; Wang, Jin; Amini Kashani, M. R.; Kavehrad, Mohsen

    2015-01-01

    Over the past decade, location based services (LBS) have found their wide applications in indoor environments, such as large shopping malls, hospitals, warehouses, airports, etc. Current technologies provide wide choices of available solutions, which include Radio-frequency identification (RFID), Ultra wideband (UWB), wireless local area network (WLAN) and Bluetooth. With the rapid development of light-emitting-diodes (LED) technology, visible light communications (VLC) also bring a practical approach to LBS. As visible light has a better immunity against multipath effect than radio waves, higher positioning accuracy is achieved. LEDs are utilized both for illumination and positioning purpose to realize relatively lower infrastructure cost. In this paper, an indoor positioning system using VLC is proposed, with LEDs as transmitters and photo diodes as receivers. The algorithm for estimation is based on received-signalstrength (RSS) information collected from photo diodes and trilateration technique. By appropriately making use of the characteristics of receiver movements and the property of trilateration, estimation on three-dimensional (3-D) coordinates is attained. Filtering technique is applied to enable tracking capability of the algorithm, and a higher accuracy is reached compare to raw estimates. Gaussian mixture Sigma-point particle filter (GM-SPPF) is proposed for this 3-D system, which introduces the notion of Gaussian Mixture Model (GMM). The number of particles in the filter is reduced by approximating the probability distribution with Gaussian components.

  16. The Use of Positron Emission Particle Tracking (PEPT) to Study the Movement of Inclusions in Low-Melting-Point Alloy Castings

    NASA Astrophysics Data System (ADS)

    Griffiths, W. D.; Beshay, Y.; Caden, A. J.; Fan, X.; Gargiuli, J.; Leadbeater, T. W.; Parker, D. J.

    2012-04-01

    Positron emission particle tracking (PEPT) employs a radioactive particle that decays by emission of positrons. These positrons collide with local electrons to produce γ-rays emitted at 180 deg to each other; detection of these γ-ray pairs allows the location of the radioactive particle to be identified within a few millimeters. This technique has been tested to determine its applicability to the study of inclusions in cast metals. To use particles representative of inclusion sizes in castings, both alumina particles and particles of an ion exchange resin were employed. These were within a size range of approximately 60 to 100 μm, made radioactive by adsorption and ion exchange techniques, respectively. The radioactive particles, of activity 100 to 1000 μCi, were introduced into tube-shaped castings made from the low-melting-point alloys Field's metal and Lensalloy-136, cast into an acrylic mold. The technique allowed the particle track to be determined from the point of initial introduction to the final resting place of the particle, with increasing reproducibility being obtained as the reproducibility as the casting technique was improved. Experiments in which filters were placed in to the running system showed that the removal of the particles by the filters varied according to the filter pore size.

  17. Diffusion limited aggregation of particles with different sizes: Fractal dimension change by anisotropic growth

    NASA Astrophysics Data System (ADS)

    Braga, F. L.; Mattos, O. A.; Amorin, V. S.; Souza, A. B.

    2015-07-01

    Clusters formation models have been extensively studied in literature, and one of the main task of this research area is the analysis of the particle aggregation processes. Some work support that the main characteristics of this processes are strictly correlated to the cluster morphology, for example in DLA. It is expected that in the DLA clusters formation with particles containing different sizes the modification of the aggregation processes can be responsible for changes in the DLA morphology. The present article is going to analyze the formation of DLA clusters of particles with different sizes and show that the aggregates obtained by this approach generate an angle selection mechanism on dendritic growth that influences the shielding effect of the DLA edge and affect the fractal dimension of the clusters.

  18. Fundamental limitations to the spatial resolution and flow volume that can be mapped using holographic particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Coupland, Jeremy M.; Lobera Salazar, Julia; Halliwell, Neil A.

    2000-08-01

    We have recently proposed a variant of holographic particle image velocimetry (HPIV) to measure three-component measurements of fluid velocity throughout an extended flow volume. In essence the technique uses double exposure holography to record the positions of seeding particles at two, close spaced constants in time. Analysis of the resulting record is achieved by computing the auto (or cross) correlation of the complex amplitude distributions transmitted by a sampling aperture placed within a real, reconstruction of the holographic image. IN the case of sparsely seeded flows, it is straightforward to show that the field transmitted by the aperture is dominated by the particle images reconstructed close to the aperture itself and the measurement is therefore attributed to the instantaneous flow velocity at the centre of the aperture. As the seeding concentration is increased, however, a significant contribution of the transmitted field is due to light scattered from more distant particles. If significant velocity gradients exist, the contribution due to distant particles is largely un- correlated and the local particle displacement can be extracted even if the field is dominated by this component. If a significant proportion of the scattered light that passes from the aperture is collected from areas in the flow with similar velocity (for example from stagnant regions or light scattered from the flow vessel) then spurious peaks can occur in the correlation signal. This paper examines the limitations on the flow volume that can be mapped at a given seeding concentration and hence the fundamental limits on the number of velocity measurements that can be retrieved from a single recording.

  19. Youden Index and Optimal Cut-Point Estimated from Observations Affected by a Lower Limit of Detection

    PubMed Central

    Ruopp, Marcus D.; Perkins, Neil J.; Whitcomb, Brian W.; Schisterman, Enrique F.

    2008-01-01

    Summary The receiver operating characteristic (ROC) curve is used to evaluate a biomarker’s ability for classifying disease status. The Youden Index (J), the maximum potential effectiveness of a biomarker, is a common summary measure of the ROC curve. In biomarker development, levels may be unquantifiable below a limit of detection (LOD) and missing from the overall dataset. Disregarding these observations may negatively bias the ROC curve and thus J. Several correction methods have been suggested for mean estimation and testing; however, little has been written about the ROC curve or its summary measures. We adapt non-parametric (empirical) and semi-parametric (ROC-GLM [generalized linear model]) methods and propose parametric methods (maximum likelihood (ML)) to estimate J and the optimal cut-point (c*) for a biomarker affected by a LOD. We develop unbiased estimators of J and c* via ML for normally and gamma distributed biomarkers. Alpha level confidence intervals are proposed using delta and bootstrap methods for the ML, semi-parametric, and non-parametric approaches respectively. Simulation studies are conducted over a range of distributional scenarios and sample sizes evaluating estimators’ bias, root-mean square error, and coverage probability; the average bias was less than one percent for ML and GLM methods across scenarios and decreases with increased sample size. An example using polychlorinated biphenyl levels to classify women with and without endometriosis illustrates the potential benefits of these methods. We address the limitations and usefulness of each method in order to give researchers guidance in constructing appropriate estimates of biomarkers’ true discriminating capabilities. PMID:18435502

  20. Estimating Limit Reference Points for Western Pacific Leatherback Turtles (Dermochelys coriacea) in the U.S. West Coast EEZ.

    PubMed

    Curtis, K Alexandra; Moore, Jeffrey E; Benson, Scott R

    2015-01-01

    Biological limit reference points (LRPs) for fisheries catch represent upper bounds that avoid undesirable population states. LRPs can support consistent management evaluation among species and regions, and can advance ecosystem-based fisheries management. For transboundary species, LRPs prorated by local abundance can inform local management decisions when international coordination is lacking. We estimated LRPs for western Pacific leatherbacks in the U.S. West Coast Exclusive Economic Zone (WCEEZ) using three approaches with different types of information on local abundance. For the current application, the best-informed LRP used a local abundance estimate derived from nest counts, vital rate information, satellite tag data, and fishery observer data, and was calculated with a Potential Biological Removal estimator. Management strategy evaluation was used to set tuning parameters of the LRP estimators to satisfy risk tolerances for falling below population thresholds, and to evaluate sensitivity of population outcomes to bias in key inputs. We estimated local LRPs consistent with three hypothetical management objectives: allowing the population to rebuild to its maximum net productivity level (4.7 turtles per five years), limiting delay of population rebuilding (0.8 turtles per five years), or only preventing further decline (7.7 turtles per five years). These LRPs pertain to all human-caused removals and represent the WCEEZ contribution to meeting population management objectives within a broader international cooperative framework. We present multi-year estimates, because at low LRP values, annual assessments are prone to substantial error that can lead to volatile and costly management without providing further conservation benefit. The novel approach and the performance criteria used here are not a direct expression of the "jeopardy" standard of the U.S. Endangered Species Act, but they provide useful assessment information and could help guide international

  1. Evaluation of generic medical information accessed via mobile phones at the point of care in resource-limited settings

    PubMed Central

    Goldbach, Hayley; Chang, Aileen Y; Kyer, Andrea; Ketshogileng, Dineo; Taylor, Lynne; Chandra, Amit; Dacso, Matthew; Kung, Shiang-Ju; Rijken, Taatske; Fontelo, Paul; Littman-Quinn, Ryan; Seymour, Anne K; Kovarik, Carrie L

    2014-01-01

    Objective Many mobile phone resources have been developed to increase access to health education in the developing world, yet few studies have compared these resources or quantified their performance in a resource-limited setting. This study aims to compare the performance of resident physicians in answering clinical scenarios using PubMed abstracts accessed via the PubMed for Handhelds (PubMed4Hh) website versus medical/drug reference applications (Medical Apps) accessed via software on the mobile phone. Methods A two-arm comparative study with crossover design was conducted. Subjects, who were resident physicians at the University of Botswana, completed eight scenarios, each with multi-part questions. The primary outcome was a grade for each question. The primary independent variable was the intervention arm and other independent variables included residency and question. Results Within each question type there were significant differences in ‘percentage correct’ between Medical Apps and PubMed4Hh for three of the six types of questions: drug-related, diagnosis/definitions, and treatment/management. Within each of these question types, Medical Apps had a higher percentage of fully correct responses than PubMed4Hh (63% vs 13%, 33% vs 12%, and 41% vs 13%, respectively). PubMed4Hh performed better for epidemiologic questions. Conclusions While mobile access to primary literature remains important and serves an information niche, mobile applications with condensed content may be more appropriate for point-of-care information needs. Further research is required to examine the specific information needs of clinicians in resource-limited settings and to evaluate the appropriateness of current resources in bridging location- and context-specific information gaps. PMID:23535665

  2. Estimating Limit Reference Points for Western Pacific Leatherback Turtles (Dermochelys coriacea) in the U.S. West Coast EEZ

    PubMed Central

    Curtis, K. Alexandra; Moore, Jeffrey E.; Benson, Scott R.

    2015-01-01

    Biological limit reference points (LRPs) for fisheries catch represent upper bounds that avoid undesirable population states. LRPs can support consistent management evaluation among species and regions, and can advance ecosystem-based fisheries management. For transboundary species, LRPs prorated by local abundance can inform local management decisions when international coordination is lacking. We estimated LRPs for western Pacific leatherbacks in the U.S. West Coast Exclusive Economic Zone (WCEEZ) using three approaches with different types of information on local abundance. For the current application, the best-informed LRP used a local abundance estimate derived from nest counts, vital rate information, satellite tag data, and fishery observer data, and was calculated with a Potential Biological Removal estimator. Management strategy evaluation was used to set tuning parameters of the LRP estimators to satisfy risk tolerances for falling below population thresholds, and to evaluate sensitivity of population outcomes to bias in key inputs. We estimated local LRPs consistent with three hypothetical management objectives: allowing the population to rebuild to its maximum net productivity level (4.7 turtles per five years), limiting delay of population rebuilding (0.8 turtles per five years), or only preventing further decline (7.7 turtles per five years). These LRPs pertain to all human-caused removals and represent the WCEEZ contribution to meeting population management objectives within a broader international cooperative framework. We present multi-year estimates, because at low LRP values, annual assessments are prone to substantial error that can lead to volatile and costly management without providing further conservation benefit. The novel approach and the performance criteria used here are not a direct expression of the “jeopardy” standard of the U.S. Endangered Species Act, but they provide useful assessment information and could help guide

  3. A search for acoplanar pairs of leptons or jets in Z0 decays. Mass limits on supersymmetric particles

    NASA Astrophysics Data System (ADS)

    Akrawy, M. Z.; Alexander, G.; Allison, J.; Allport, P. P.; Anderson, K. J.; Armitage, J. C.; Arnison, G. T. J.; Ashton, P.; Azuelos, G.; Baines, J. T. M.; Ball, A. H.; Banks, J.; Barker, G. J.; Barlow, R. J.; Batley, J. R.; Bavaria, G.; Beck, F.; Bell, K. W.; Bella, G.; Bethke, S.; Biebel, O.; Bloodworth, I. J.; Bock, P.; Breuker, H.; Brown, R. M.; Brun, R.; Buijs, A.; Burckhart, H. J.; Capiluppi, P.; Carnegie, R. K.; Carter, A. A.; Carter, J. R.; Chang, C. Y.; Charlton, D. G.; Chrin, J. T. M.; Cohen, I.; Conboy, J. E.; Couch, M.; Coupland, M.; Cuffiani, M.; Dado, S.; Dallavalle, G. M.; Davies, O. W.; Deninno, M. M.; Dieckmann, A.; Dittmar, M.; Dixit, M. S.; Duchesneau, D.; Duchovni, E.; Duerdoth, I. P.; Dumas, D.; El Mamouni, H.; Elcombe, P. A.; Estabrooks, P. G.; Etzion, E.; Fabbri, F.; Farthouat, P.; Fischer, H. M.; Fong, D. G.; French, M. T.; Fukunaga, C.; Gandois, B.; Ganel, O.; Gary, J. W.; Geddes, N. I.; Gee, C. N. P.; Geich-Gimbel, C.; Gensler, S. W.; Gentit, F. X.; Giacomelli, G.; Gibson, W. R.; Gillies, J. D.; Goldberg, J.; Goodrick, M. J.; Gorn, W.; Granite, D.; Gross, E.; Grosse-Wiesmann, P.; Grunhaus, J.; Hagedorn, H.; Hagemann, J.; Hansroul, M.; Hargrove, C. K.; Hart, J.; Hattersley, P. M.; Hatzifotiadou, D.; Hauschild, M.; Hawkes, C. M.; Heflin, E.; Heintze, J.; Hemingway, R. J.; Heuer, R. D.; Hill, J. C.; Hillier, S. J.; Hinde, P. S.; Ho, C.; Hobbs, J. D.; Hobson, P. R.; Hochman, D.; Holl, B.; Homer, R. J.; Hou, S. R.; Howarth, C. P.; Hughes-Jones, R. E.; Igo-Kemenes, P.; Imori, M.; Imrie, D. C.; Jawahery, A.; Jeffreys, P. W.; Jeremie, H.; Jimack, M.; Jin, E.; Jobes, M.; Jones, R. W. L.; Jovanovic, P.; Karlen, D.; Kawagoe, K.; Kawamoto, T.; Kellogg, R. G.; Kennedy, B. W.; Kleinwort, C.; Klem, D. E.; Knop, G.; Kobayashi, T.; Köpke, L.; Kokott, T. P.; Koshiba, M.; Kowalewski, R.; Kreutzmann, H.; von Krogh, J.; Kroll, J.; Kyberd, P.; Lafferty, G. D.; Lamarche, F.; Larson, W. J.; Lasota, M. M. B.; Layter, J. G.; Le Du, P.; Leblanc, P.; Lellouch, D.; Lennert, P.; Lessard, L.; Levinson, L.; Lloyd, S. L.; Loebinger, F. K.; Lorah, J. M.; Lorazo, B.; Losty, M. J.; Ludwig, J.; Lupu, N.; Ma, J.; MacBeth, A. A.; Mannelli, M.; Marcellini, S.; Maringer, G.; Martin, J. P.; Mashimo, T.; Mättig, P.; Maur, U.; McMahon, T. J.; McPherson, A. C.; Meijers, F.; Menszner, D.; Merritt, F. S.; Mes, H.; Michelini, A.; Middleton, R. P.; Mikenberg, G.; Miller, D. J.; Milstene, C.; Minowa, M.; Mohr, W.; Montanari, A.; Mori, T.; Moss, M. W.; Muller, A.; Murphy, P. G.; Murray, W. J.; Nellen, B.; Nguyen, H. H.; Nozaki, M.; O'Dowd, A. J. P.; O'Neale, S. W.; O'Neill, B.; Oakham, F. G.; Odorici, F.; Ogg, M.; Oh, H.; Oreglia, M. J.; Orito, S.; Patrick, G. N.; Pawley, S. J.; Perez, A.; Pilcher, J. E.; Pinfold, J. L.; Plane, D. E.; Poli, B.; Possoz, A.; Pouladdej, A.; Pritchard, T. W.; Quast, G.; Raab, J.; Redmond, M. W.; Rees, D. L.; Regimbald, M.; Riles, K.; Roach, C. M.; Roehner, F.; Rollnik, A.; Roney, J. M.; Rossi, A. M.; Routenburg, P.; Runge, K.; Runolfsson, O.; Sanghera, S.; Sansum, R. A.; Sasaki, M.; Saunders, B. J.; Schaile, A. D.; Schaile, O.; Schappert, W.; Scharff-Hansen, P.; von der Schmitt, H.; Schreiber, S.; Schwarz, J.; Shapira, A.; Shen, B. C.; Sherwood, P.; Simon, A.; Siroli, G. P.; Skuja, A.; Smith, A. M.; Smith, T. J.; Snow, G. A.; Spreadbury, E. J.; Springer, R. W.; Sproston, M.; Stephens, K.; Steuerer, J.; Stier, H. E.; Ströhmer, R.; Strom, D.; Takeda, H.; Takeshita, T.; Tsukamoto, T.; Turner, M. F.; Tysarczyk, G.; van den Plas, D.; Vandalen, G. J.; Virtue, C. J.; Wagner, A.; Wahl, C.; Wang, H.; Ward, C. P.; Ward, D. R.; Waterhouse, J.; Watkins, P. M.; Watson, A. T.; Watson, N. K.; Weber, M.; Weisz, S.; Wermes, N.; Weymann, M.; Wilson, G. W.; Wilson, J. A.; Wingerter, I.; Winterer, V.-H.; Wood, N. C.; Wotton, S.; Wuensch, B.; Wyatt, T. R.; Yaari, R.; Yamashita, H.; Yang, Y.; Yekutieli, G.; Zeuner, W.; Zorn, G. T.; Zylberajch, S.

    1990-04-01

    We have searched for Z0 decays into acoplanar pairs of leptons or jets. The data were recorded with the OPAL detector during an energy scan around the Z0 peak and correspond to about 17000 produced Z0,s. We have determined model independent limits on branching ratios for the Z0 to decay into pairs of heavy particles with subsequent decays leading to the above topologies. In the context of supersymmetric models, mass bounds close to the kinematic limit were obtained for the scalar leptons, e~, g~m, g~t, and for the chargino, X~+/-.

  4. Terrestrial and Solar Limits on Long-Lived Particles in a Dark Sector

    SciTech Connect

    Schuster, Philip; Toro, Natalia; Yavin, Itay; /CCPP, New York U.

    2010-08-26

    Dark matter charged under a new gauge sector, as motivated by recent data, suggests a rich GeV-scale 'dark sector' weakly coupled to the Standard Model by gauge kinetic mixing. The new gauge bosons can decay to Standard Model leptons, but this mode is suppressed if decays into lighter 'dark sector' particles are kinematically allowed. These particles in turn typically have macroscopic decay lifetimes that are constrained by two classes of experiments, which we discuss. Lifetimes of 10 cm {approx}< c{tau} {approx}< 10{sup 8} cm are constrained by existing terrestrial beam-dump experiments. If, in addition, dark matter captured in the Sun (or Earth) annihilates into these particles, lifetimes up to {approx} 10{sup 15} cm are constrained by solar observations. These bounds span fourteen orders of magnitude in lifetime, but they are not exhaustive. Accordingly, we identify promising new directions for experiments including searches for displaced di-muons in B-factories, studies at high-energy and -intensity proton beam dumps, precision gamma-ray and electronic measurements of the Sun, and milli-charge searches re-analyzed in this new context.

  5. Terrestrial and solar limits on long-lived particles in a dark sector

    NASA Astrophysics Data System (ADS)

    Schuster, Philip; Toro, Natalia; Yavin, Itay

    2010-01-01

    Dark matter charged under a new gauge sector, as motivated by recent data, suggests a rich GeV-scale “dark sector” weakly coupled to the standard model by gauge kinetic mixing. The new gauge bosons can decay to standard model leptons, but this mode is suppressed if decays into lighter “dark sector” particles are kinematically allowed. These particles in turn typically have macroscopic decay lifetimes that are constrained by two classes of experiments, which we discuss. Lifetimes of 10cm≲cτ≲108cm are constrained by existing terrestrial beam-dump experiments. If, in addition, dark matter captured in the Sun (or Earth) annihilates into these particles, lifetimes up to ˜1015cm are constrained by solar observations. These bounds span 14 orders of magnitude in lifetime, but they are not exhaustive. Accordingly, we identify promising new directions for experiments including searches for displaced di-muons in B factories, studies at high-energy and -intensity proton beam dumps, precision gamma-ray and electronic measurements of the Sun, and milli-charge searches reanalyzed in this new context.

  6. Students' Understanding of Limiting Behavior at a Point for Functions from [Set of Real Numbers][superscript 2] to [Set of Real Numbers

    ERIC Educational Resources Information Center

    Mamona-Downs, Joanna K.; Megalou, Foteini J.

    2013-01-01

    The aim of this paper is to examine students' understanding of the limiting behavior of a function from [set of real numbers][superscript 2] to [set of real numbers] at a point "P." This understanding depends on which definition is used for a limit. Several definitions are considered; two of these concern the notion of a neighborhood of "P", while…

  7. SAMBA HIV semiquantitative test, a new point-of-care viral-load-monitoring assay for resource-limited settings.

    PubMed

    Ritchie, Allyson V; Ushiro-Lumb, Ines; Edemaga, Daniel; Joshi, Hrishikesh A; De Ruiter, Annemiek; Szumilin, Elisabeth; Jendrulek, Isabelle; McGuire, Megan; Goel, Neha; Sharma, Pia I; Allain, Jean-Pierre; Lee, Helen H

    2014-09-01

    Routine viral-load (VL) testing of HIV-infected individuals on antiretroviral therapy (ART) is used to monitor treatment efficacy. However, due to logistical challenges, implementation of VL has been difficult in resource-limited settings. The aim of this study was to evaluate the performance of the SAMBA semi-Q (simple amplification-based assay semiquantitative test for HIV-1) in London, Malawi, and Uganda. The SAMBA semi-Q can distinguish between patients with VLs above and below 1,000 copies/ml. The SAMBA semi-Q was validated with diluted clinical samples and blinded plasma samples collected from HIV-1-positive individuals. SAMBA semi-Q results were compared with results from the Roche COBAS AmpliPrep/COBAS TaqMan HIV-1 test, v2.0. Testing of 96 2- to 10-fold dilutions of four samples containing HIV-1 subtype C as well as 488 samples from patients in the United Kingdom, Malawi, and Uganda yielded an overall accuracy for the SAMBA semi-Q of 99% (95% confidence interval [CI], 93.8 to 99.9%) and 96.9% (95% CI 94.9 to 98.3%), respectively, compared to to the Roche test. Analysis of VL data from patients in Malawi and Uganda showed that the SAMBA cutoff of 1,000 copies/ml appropriately distinguished treated from untreated individuals. Furthermore, analysis of the viral loads of 232 patients on ART in Malawi and Uganda revealed similar patterns for virological control, defined as either <1,000 copies/ml (SAMBA cutoff) or <5,000 copies/ml (WHO 2010 criterion; WHO, Antiretroviral Therapy for HIV Infection in Adults and Adolescents: Recommendations for a Public Health Approach, 2010). This study suggests that the SAMBA semi-Q has adequate concurrency with the gold standard measurements for viral load. This test can allow VL monitoring of patients on ART at the point of care in resource-limited settings. PMID:25031444

  8. Design of a Novel Low Cost Point of Care Tampon (POCkeT) Colposcope for Use in Resource Limited Settings

    PubMed Central

    Lam, Christopher T.; Krieger, Marlee S.; Gallagher, Jennifer E.; Asma, Betsy; Muasher, Lisa C.; Schmitt, John W.; Ramanujam, Nimmi

    2015-01-01

    Introduction Current guidelines by WHO for cervical cancer screening in low- and middle-income countries involves visual inspection with acetic acid (VIA) of the cervix, followed by treatment during the same visit or a subsequent visit with cryotherapy if a suspicious lesion is found. Implementation of these guidelines is hampered by a lack of: trained health workers, reliable technology, and access to screening facilities. A low cost ultra-portable Point of Care Tampon based digital colposcope (POCkeT Colposcope) for use at the community level setting, which has the unique form factor of a tampon, can be inserted into the vagina to capture images of the cervix, which are on par with that of a state of the art colposcope, at a fraction of the cost. A repository of images to be compiled that can be used to empower front line workers to become more effective through virtual dynamic training. By task shifting to the community setting, this technology could potentially provide significantly greater cervical screening access to where the most vulnerable women live. The POCkeT Colposcope’s concentric LED ring provides comparable white and green field illumination at a fraction of the electrical power required in commercial colposcopes. Evaluation with standard optical imaging targets to assess the POCkeT Colposcope against the state of the art digital colposcope and other VIAM technologies. Results Our POCkeT Colposcope has comparable resolving power, color reproduction accuracy, minimal lens distortion, and illumination when compared to commercially available colposcopes. In vitro and pilot in vivo imaging results are promising with our POCkeT Colposcope capturing comparable quality images to commercial systems. Conclusion The POCkeT Colposcope is capable of capturing images suitable for cervical lesion analysis. Our portable low cost system could potentially increase access to cervical cancer screening in limited resource settings through task shifting to community

  9. Functional renormalization-group approaches, one-particle (irreducible) reducible with respect to local Green’s functions, with dynamical mean-field theory as a starting point

    SciTech Connect

    Katanin, A. A.

    2015-06-15

    We consider formulations of the functional renormalization-group (fRG) flow for correlated electronic systems with the dynamical mean-field theory as a starting point. We classify the corresponding renormalization-group schemes into those neglecting one-particle irreducible six-point vertices (with respect to the local Green’s functions) and neglecting one-particle reducible six-point vertices. The former class is represented by the recently introduced DMF{sup 2}RG approach [31], but also by the scale-dependent generalization of the one-particle irreducible representation (with respect to local Green’s functions, 1PI-LGF) of the generating functional [20]. The second class is represented by the fRG flow within the dual fermion approach [16, 32]. We compare formulations of the fRG approach in each of these cases and suggest their further application to study 2D systems within the Hubbard model.

  10. Orientational kinetics of dipolar particles in a Maxwell fluid matrix: inertialess limit for the rotary microrheology.

    PubMed

    Raikher, Yu L; Rusakov, V V

    2005-12-01

    We study magnetic response of an assembly of ferroparticles suspended in a viscoelastic matrix which is modeled by a Maxwell fluid with a unique stress relaxation time. The problem refers to the magnetic microrheology approach where deformational properties of a complex fluid are tested with the aid of embedded nanoparticle probes set to motion by an external ac magnetic field. A possibility is considered to simplify the description of the orientational kinetics of the system at the expense of neglecting inertia effects in particle rotary motion. It is shown that in this aspect a Maxwell matrix differs essentially from the Newtonian one. In the latter the inertialess approximation for the particles of the approximately 10nm size is valid practically unboundedly. For a viscoelastic matrix the inertialess approximation means an important restriction on the value of the stress relaxation time. Assuming weak nonequilibrium, the magneto-orientational relaxation times are found and low-frequency magnetic spectra of a viscoelastic suspension are determined in the presence of a constant (magnetizing) field. PMID:16485946

  11. On the non-relativistic limit of a spin- {1}/{2} particle in a classical gravitational field

    NASA Astrophysics Data System (ADS)

    Bäuerle, G. G. A.; Twelker, H. F.

    1985-04-01

    An external gravitational field modifies the description of a spin- {1}/{2} particle in various ways. For instance, the inner product of Dirac wave functions, and the equal-time anti-commutation relations and the canonical energy-momentum tensor of the quantized Dirac field are modified. This has the following consequences. The Dirac-Hamiltonian (2.29) of a spin- {1}/{2} particle in a time-dependent gravitational field is not Hermitian. Furthermore, the Euler-Lagrange equation and the Heisenberg equation for the quantized Dirac field are not consistent. We obviate these deficiencies by the introduction of the η-field as the fundamental variable instead of the Dirac field. At the same time, the non-relativistic limit is most conveniently discussed in the η-description. For this purpose, we introduce a modification of the Foldy-Wouthuysen transformation.

  12. Limits of PowerPoint's Power: Enhancing Students' Self-Efficacy and Attitudes but Not Their Behavior

    ERIC Educational Resources Information Center

    Susskind, Joshua E.

    2008-01-01

    The effects of accompanying lectures with computer-mediated PowerPoint presentations or PowerPoint generated overheads on students' self-efficacy, attitudes, course performance, and class-related behaviors were examined. Two Introduction to Developmental Psychology sections were initially taught with lectures accompanied by either overheads or…

  13. X-ray microanalysis in the environmental scanning electron microscope (ESEM): Small size particles analysis limits

    NASA Astrophysics Data System (ADS)

    Khouchaf, L.; Verstraete, J.

    2002-07-01

    In this work we will present a study of the effects of some parameters such as pressure and data acquisition duration in EDS microanalysis results. The chamber pressure has been increased from 1Torr (133Pa) to 15 Torr (1995 Pa). Measurements with times of measurement varying between 180 seconds and 1800 seconds were carried out. Small size particles of iron and silicon are analyzed. The results show that at 1Torr (133Pa), the primary electron beam can move if the time of measurement is long, which introduces some mistakes in the microananlysis results. Moreover an increase in the chamber pressure induces an amplification of the skirt beam phenomena up to 160 microns. This fact adds some noise coming from the environment around the analyzed particle. We showed that, the displacement of the electron beam during measurement caused a decrease in the iron concentration versus the time of measurment which reachs approximately 15% when the time of measurement is 1800seconds. Dans cette étude nous présenterons les effets de certains paramètres tels que la durée d'acquisition et la pression dans la chambre du microscope électronique à balayage environnemental sur les résultats de la microanalyse X. La pression dans la chambre a été augmentée de 1 Torr (133 Pa) à 15 Torr (1995 Pa). Des mesures avec des durées d'acquisition entre 180 secondes et 1800 secondes ont été effectuées. Des particules de fer et de silicium de petites tailles sont analysées. Les résultats ont montré qu'à 1 Torr (133 Pa), le faisceau d'électrons primaire peut fluctuer si la durée d'acquisition est longue, ce qui induit quelques erreurs dans les résultats obtenus. Une augmentation de la pression dans la chambre induit une amplification des phénomènes de diffusion du faisceau d'électrons jusqu'à 160 microns. Ce fait, ajoute un certain bruit venant de l'environnement autour de la particule analysée. Nous avons ensuite montré que le déplacement du faisceau d'électrons pendant

  14. Exponential Scaling Limit of the Single-Particle Anderson Model Via Adaptive Feedback Scaling

    NASA Astrophysics Data System (ADS)

    Chulaevsky, Victor

    2016-02-01

    We propose a twofold extension of the Germinet-Klein bootstrap multi-scale analysis (BMSA) for the Anderson models on graphs. First, we show, with the help of a single scaling algorithm, that power-law decay bounds at some initial scale imply an asymptotically exponential decay of eigenfunctions (EFs) and of EF correlators (EFCs), even on graphs (of polynomial growth) which do not fulfill the uniform scalability condition required for the existing BMSA techniques. We also show that the exponential scaling limit of the EFs and EFCs holds true for a class of marginal distributions of the random potential with regularity lower than Hölder continuity of any positive order.

  15. Transcutaneous CO(2) plateau as set-point for respiratory drive during upper airway flow-limitation.

    PubMed

    Rimpilä, Ville; Saaresranta, Tarja; Huhtala, Heini; Virkki, Arho; Salminen, Aaro V; Polo, Olli

    2014-01-15

    Upper airway flow-limitation is often but not always associated with prolonged gradually increasing respiratory effort. We investigated the changes in transcutaneous carbon dioxide tension (tcCO(2)) during episodes of upper airway flow limitation during sleep with or without respiratory effort response. Seventy-seven episodes of progressive flow-limitation were analyzed in 36 patients with sleep-disordered breathing. TcCO(2) and arterial oxyhaemoglobin saturation (SaO2) were measured during steady breathing and during episodes of flow-limitation with and without effort response. After lights-off tcCO(2) increased and leveled-off at plateau, when breathing stabilized. During flow-limitation tcCO(2) increased at rate of 4.0kPa/h. Flow-limitation with increasing respiratory effort associated with tcCO(2) increase above the plateau (terminating at 105.2%, p<0.001), whereas flow-limitation without effort response associated with tcCO(2) increase starting below the plateau (95.8%, p<0.001). We conclude that the nocturnal tcCO(2) plateau indicates the level above which the increasing respiratory effort is triggered as response to upper airway flow-limitation. We propose that flow-limitation below the tcCO(2) plateau is an event related to stabilization of sleep and breathing. PMID:24200642

  16. Assessing the limits of hidden Markov model analysis for multi-state particle tracks in living systems

    NASA Astrophysics Data System (ADS)

    Young, Dylan

    Particle tracking offers significant insight into the molecular mechanics that govern the behavior of living cells. The analysis of molecular trajectories that transition between different motive states, such as diffusive, driven and tethered modes, is of considerable importance, with even single trajectories containing significant amounts of information about a molecule's environment and its interactions with cellular structures such as the cell cytoskeleton, membrane or extracellular matrix. Hidden Markov models (HMM) have been widely adopted to perform the segmentation of such complex tracks, however robust methods for failure detection are required when HMMs are applied to individual particle tracks and limited data sets. Here, we show that extensive analysis of hidden Markov model outputs using data derived from multi-state Brownian dynamics simulations can be used for both the optimization of likelihood models, and also to generate custom failure tests based on a modified Bayesian Information Criterion. In the first instance, these failure tests can be applied to assess the quality of the HMM results. In addition, they provide critical information for the successful design of particle tracking experiments where trajectories containing multiple mobile states are expected.

  17. Particle production and aeolian transport from a ``supply-limited'' source area in the Chihuahuan desert, New Mexico, United States

    NASA Astrophysics Data System (ADS)

    Gillette, Dale A.; Chen, Weinan

    2001-03-01

    Wind erosion mechanisms were investigated for the "scrape site" at the Jornada Experimental Range near Las Cruces, New Mexico, in the Chihuahuan desert. The scrape site was denuded of vegetation and scraped flat in 1991. We adopted the site in 1994 because it offered an opportunity to study wind erosion mechanisms for a large area of unprotected sandy and crusted soil in an otherwise natural setting and over a period of several years. We installed and operated the following instrumentation for a period of 35 months: three meteorological towers, each 2 m in height, with wind speed sensors at 0.2, 0.5, 1.0, and 2.0 m above ground; air temperature at 0.2 and 2 m height; rain gauge; seven sets of particle collectors at 0.1, 0.5, and 1.0 m heights; and three fast-response particle mass flux sensors at 0.02, 0.1, 0.2, and 0.5 m heights; all along a transect crossing the site and parallel to the predominant southwesterly wind direction. The minimum threshold friction velocity for the scrape site with a thin layer of loose material was 25 cm s-1. This minimum threshold velocity increased to as high as 100 cm s-1 depending on the degree of particle depletion and the site's status which varied between supply unlimited just after a high wind episode and supply limited which was more typical for the rest of the time. The dominant mechanism producing fresh sediment for transport was sandblasting of the surface crust. The measurements showed that supply and availability of loose, fine particles on the surface is a strong control of rates of erosion rather than wind energy alone.

  18. Two-flavor lattice QCD with a finite density of heavy quarks: heavy-dense limit and "particle-hole" symmetry

    NASA Astrophysics Data System (ADS)

    Rindlisbacher, Tobias; de Forcrand, Philippe

    2016-02-01

    We investigate the properties of the half-filling point in lattice QCD (LQCD), in particular the disappearance of the sign problem and the emergence of an apparent particle-hole symmetry, and try to understand where these properties come from by studying the heavy-dense fermion determinant and the corresponding strong-coupling partition function (which can be integrated analytically). We then add in a first step an effective Polyakov loop gauge action (which reproduces the leading terms in the character expansion of the Wilson gauge action) to the heavy-dense partition function and try to analyze how some of the properties of the half-filling point change when leaving the strong coupling limit. In a second step, we take also the leading nearest-neighbor fermion hopping terms into account (including gauge interactions in the fundamental representation) and mention how the method could be improved further to incorporate the full set of nearest-neighbor fermion hoppings. Using our mean-field method, we also obtain an approximate ( μ, T) phase diagram for heavy-dense LQCD at finite inverse gauge coupling β. Finally, we propose a simple criterion to identify the chemical potential beyond which lattice artifacts become dominant.

  19. REVISED BIG BANG NUCLEOSYNTHESIS WITH LONG-LIVED, NEGATIVELY CHARGED MASSIVE PARTICLES: UPDATED RECOMBINATION RATES, PRIMORDIAL {sup 9}Be NUCLEOSYNTHESIS, AND IMPACT OF NEW {sup 6}Li LIMITS

    SciTech Connect

    Kusakabe, Motohiko; Kim, K. S.; Cheoun, Myung-Ki; Kajino, Toshitaka; Kino, Yasushi; Mathews, Grant J. E-mail: kyungsik@kau.ac.kr E-mail: kajino@nao.ac.jp E-mail: gmathews@nd.edu

    2014-09-01

    We extensively reanalyze the effects of a long-lived, negatively charged massive particle, X {sup –}, on big bang nucleosynthesis (BBN). The BBN model with an X {sup –} particle was originally motivated by the discrepancy between the {sup 6,} {sup 7}Li abundances predicted in the standard BBN model and those inferred from observations of metal-poor stars. In this model, {sup 7}Be is destroyed via the recombination with an X {sup –} particle followed by radiative proton capture. We calculate precise rates for the radiative recombinations of {sup 7}Be, {sup 7}Li, {sup 9}Be, and {sup 4}He with X {sup –}. In nonresonant rates, we take into account respective partial waves of scattering states and respective bound states. The finite sizes of nuclear charge distributions cause deviations in wave functions from those of point-charge nuclei. For a heavy X {sup –} mass, m{sub X} ≳ 100 GeV, the d-wave → 2P transition is most important for {sup 7}Li and {sup 7,} {sup 9}Be, unlike recombination with electrons. Our new nonresonant rate of the {sup 7}Be recombination for m{sub X} = 1000 GeV is more than six times larger than the existing rate. Moreover, we suggest a new important reaction for {sup 9}Be production: the recombination of {sup 7}Li and X {sup –} followed by deuteron capture. We derive binding energies of X nuclei along with reaction rates and Q values. We then calculate BBN and find that the amount of {sup 7}Be destruction depends significantly on the charge distribution of {sup 7}Be. Finally, updated constraints on the initial abundance and the lifetime of the X {sup –} are derived in the context of revised upper limits to the primordial {sup 6}Li abundance. Parameter regions for the solution to the {sup 7}Li problem and the primordial {sup 9}Be abundances are revised.

  20. Revised Big Bang Nucleosynthesis with Long-lived, Negatively Charged Massive Particles: Updated Recombination Rates, Primordial 9Be Nucleosynthesis, and Impact of New 6Li Limits

    NASA Astrophysics Data System (ADS)

    Kusakabe, Motohiko; Kim, K. S.; Cheoun, Myung-Ki; Kajino, Toshitaka; Kino, Yasushi; Mathews, Grant. J.

    2014-09-01

    We extensively reanalyze the effects of a long-lived, negatively charged massive particle, X -, on big bang nucleosynthesis (BBN). The BBN model with an X - particle was originally motivated by the discrepancy between the 6, 7Li abundances predicted in the standard BBN model and those inferred from observations of metal-poor stars. In this model, 7Be is destroyed via the recombination with an X - particle followed by radiative proton capture. We calculate precise rates for the radiative recombinations of 7Be, 7Li, 9Be, and 4He with X -. In nonresonant rates, we take into account respective partial waves of scattering states and respective bound states. The finite sizes of nuclear charge distributions cause deviations in wave functions from those of point-charge nuclei. For a heavy X - mass, mX >~ 100 GeV, the d-wave → 2P transition is most important for 7Li and 7, 9Be, unlike recombination with electrons. Our new nonresonant rate of the 7Be recombination for mX = 1000 GeV is more than six times larger than the existing rate. Moreover, we suggest a new important reaction for 9Be production: the recombination of 7Li and X - followed by deuteron capture. We derive binding energies of X nuclei along with reaction rates and Q values. We then calculate BBN and find that the amount of 7Be destruction depends significantly on the charge distribution of 7Be. Finally, updated constraints on the initial abundance and the lifetime of the X - are derived in the context of revised upper limits to the primordial 6Li abundance. Parameter regions for the solution to the 7Li problem and the primordial 9Be abundances are revised.

  1. Polarization of intersecting particles

    NASA Astrophysics Data System (ADS)

    Paley, A. V.; Radchik, A. V.; Smith, G. B.; Vagov, A. V.

    1994-06-01

    An exact expression for the polarizability of intersecting circular cylinders has been derived covering all degrees of intersection and arbitrary complex dielectric constants for the particle material. This enables a comparison between the induced dipole moment on two particles of almost identical shape; a cardioid and a particular pair of overlapping cylinders. The absorption spectra in the small particle limit are extremely sensitive to the detailed shape of the surfaces near the point of intersection.

  2. 40 CFR Table 4 to Part 455 - BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 31 2013-07-01 2013-07-01 false BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That use End-of-Pipe Biological Treatment 4 Table 4... Biological Treatment Pollutant Daily maximum shall not exceed Monthly average shall not exceed...

  3. 40 CFR Table 5 to Part 455 - BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 31 2012-07-01 2012-07-01 false BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That Do Not Use End-of-Pipe Biological Treatment 5... Biological Treatment Pollutant Daily maximum shall not exceed Monthly average shall not exceed...

  4. 40 CFR Table 5 to Part 455 - BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 30 2014-07-01 2014-07-01 false BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That Do Not Use End-of-Pipe Biological Treatment 5... Biological Treatment Pollutant Daily maximum shall not exceed Monthly average shall not exceed...

  5. 40 CFR Table 4 to Part 455 - BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 31 2012-07-01 2012-07-01 false BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That use End-of-Pipe Biological Treatment 4 Table 4... Biological Treatment Pollutant Daily maximum shall not exceed Monthly average shall not exceed...

  6. 40 CFR Table 5 to Part 455 - BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 31 2013-07-01 2013-07-01 false BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That Do Not Use End-of-Pipe Biological Treatment 5... Biological Treatment Pollutant Daily maximum shall not exceed Monthly average shall not exceed...

  7. 40 CFR Table 4 to Part 455 - BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 30 2014-07-01 2014-07-01 false BAT and NSPS Effluent Limitations for Priority Pollutants for Direct Discharge Point Sources That use End-of-Pipe Biological Treatment 4 Table 4... Biological Treatment Pollutant Daily maximum shall not exceed Monthly average shall not exceed...

  8. Kinetic Study of Radiation-reaction-limited Particle Acceleration During the Relaxation of Unstable Force-free Equilibria

    NASA Astrophysics Data System (ADS)

    Yuan, Yajie; Nalewajko, Krzysztof; Zrake, Jonathan; East, William E.; Blandford, Roger D.

    2016-09-01

    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 focus 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.

  9. On the limit of existence of Borromean binding in three-particle systems with screened Coulomb interactions

    NASA Astrophysics Data System (ADS)

    Pawlak, Mariusz; Bylicki, Mirosław; Mukherjee, Prasanta K.

    2014-05-01

    Molecular-type systems, (m1)±(m2)±(m3)∓, consisting of three particles of masses mi and of unit electric charges with the Coulomb interactions weakened by the Debye screening are considered. Existence and range of Borromean binding in symmetric systems (of masses m1 = m2) is investigated with respect to the masses of their constituents. It is shown that such systems can exist in Borromean ground states if the mass ratio q = m3/m1 is less or equal to 1.668. This improves considerably the lower bound to the limit of existence of the Borromean binding of symmetric systems suggested by Pont and Serra (2009 Phys. Rev. A 79 032508) as q ⩽ 1. Qualitative meaning of the improvement is that the Borromean binding occurs not only for systems where two identical particles are heavier than the third one but it is also possible for systems of the opposite mass relation. The range of screening parameter in which a system is Borromean known as a Borromean window is also determined for μ+μ+e-, π+π+μ-, π+μ-μ- and e+e-e-.

  10. Conserved and narrow temperature limits in alpine insects: Thermal tolerance and supercooling points of the ice-crawlers, Grylloblatta (Insecta: Grylloblattodea: Grylloblattidae).

    PubMed

    Schoville, Sean D; Slatyer, Rachel A; Bergdahl, James C; Valdez, Glenda A

    2015-07-01

    For many terrestrial species, habitat associations and range size are dependent on physiological limits, which in turn may influence large-scale patterns of species diversity. The temperature range experienced by individuals is considered to shape the breadth of the thermal niche, with species occupying temporally and/or geographically stable climates tolerating a narrow temperature range. High-elevation environments experience large temperature fluctuations, with frequent periods below 0 °C, but Grylloblatta (Grylloblattodea: Grylloblattidae) occupy climatically stable microhabitats within this region. Here we test critical thermal limits and supercooling points for five Grylloblatta populations from across a large geographic area, to examine whether the stable microhabitats of this group are associated with a narrow thermal niche and assess their capacity to tolerate cold conditions. Thermal limits are highly conserved in Grylloblatta, despite substantial genetic divergence among populations spanning 1500 m elevation and being separated by over 500 km. Further, Grylloblatta show exceptionally narrow thermal limits compared to other insect taxa with little capacity to improve cold tolerance via plasticity. In contrast, upper thermal limits were significantly depressed by cold acclimation. Grylloblatta maintain coordinated movement until they freeze, and they die upon freezing. Convergence of the critical thermal minima, supercooling point and lower lethal limits point to adaptation to a cold but, importantly, constant thermal environment. These physiological data provide an explanation for the high endemism and patchy distribution of Grylloblatta, which relies on subterranean retreats to accommodate narrow thermal limits. These retreats are currently buffered from temperature fluctuations by snow cover, and a declining snowpack thus places Grylloblatta at risk of exposure to temperatures beyond its tolerance capacity. PMID:25956197

  11. First Direct Limits on Lightly Ionizing Particles with Electric Charge Less than e/6

    SciTech Connect

    Agnese, R.; Anderson, A. J.; Balakishiyeva, D.; Basu Thakur, R.; Bauer, D. A.; Billard, J.; Borgland, A.; Bowles, M. A.; Brandt, D.; Brink, P. L.; Bunker, R.; Cabrera, B.; Caldwell, D. O.; Cerdeno, D. G.; Chagani, H.; Chen, Y.; Cooley, J.; Cornell, B.; Crewdson, C. H.; Cushman, P.; Daal, M.; Di Stefano, P. C. F.; Doughty, T.; Esteban, L.; Fallows, S.; Figueroa-Feliciano, E.; Godfrey, G. L.; Golwala, S. R.; Hall, J.; Harris, H. R.; Hertel, S. A.; Hofer, T.; Holmgren, D.; Hsu, L.; Huber, M. E.; Jastram, A.; Kamaev, O.; Kara, B.; Kelsey, M. H.; Kennedy, A.; Kiveni, M.; Koch, K.; Leder, A.; Loer, B.; Lopez Asamar, E.; Mahapatra, R.; Mandic, V.; Martinez, C.; McCarthy, K. A.; Mirabolfathi, N.; Moffatt, R. A.; Moore, D. C.; Nelson, H.; Nelson, R. H.; Ogburn, R. W.; Page, K.; Page, W. A.; Partridge, R.; Pepin, M.; Phipps, A.; Prasad, K.; Pyle, M.; Qiu, H.; Rau, W.; Redl, P.; Reisetter, A.; Ricci, Y.; Rogers, H. E.; Saab, T.; Sadoulet, B.; Sander, J.; Schneck, K.; Schnee, R. W.; Scorza, S.; Serfass, B.; Shank, B.; Speller, D.; Upadhyayula, S.; Villano, A. N.; Welliver, B.; Wright, D. H.; Yellin, S.; Yen, J. J.; Young, B. A.; Zhang, J.

    2015-03-18

    While the Standard Model of particle physics does not include free particles with fractional charge, experimental searches have not ruled out their existence. We report results from the Cryogenic Dark Matter Search (CDMS II) experiment that give the first direct-detection limits for cosmogenically- produced relativistic particles with electric charge lower than e/6. A search for tracks in the six stacked detectors of each of two of the CDMS II towers found no candidates, thereby excluding new parameter space for particles with electric charges between e/6 and e/200.

  12. Determination of char combustion kinetics parameters: Comparison of point detector and imaging-based particle-sizing pyrometry

    NASA Astrophysics Data System (ADS)

    Schiemann, Martin; Geier, Manfred; Shaddix, Christopher R.; Vorobiev, Nikita; Scherer, Viktor

    2014-07-01

    In this study, the char burnout characteristics of two German coals (a lignite and a high-volatile bituminous coal) were investigated using two different experimental configurations and optical techniques in two distinct laboratories for measurement of temperature and size of burning particles. The optical diagnostic hardware is quite different in the two systems, but both perform two-color pyrometry and optical sizing measurements on individual particles burning in isolation from each other in high-temperature laminar flows to characterize the char consumption kinetics. The performance of the specialized systems is compared for two different combustion atmospheres (with 6.6 and 12 vol.% O2) and gas temperatures between 1700 and 1800 K. The measured particle temperatures and diameters are converted to char burning rate parameters for several residence times during the course of the particles' burnout. The results confirm that comparable results are obtained with the two configurations, although higher levels of variability in the measured data were observed in the imaging-based pyrometer setup. Corresponding uncertainties in kinetics parameters were larger, and appear to be more sensitive to systematic measurement errors when lower oxygen contents are used in the experiments. Consequently, burnout experiments in environments with sufficiently high O2 contents may be used to measure reliable char burning kinetics rates. Based on simulation results for the two coals, O2 concentrations in the range 10%-30% are recommended for kinetic rate measurements on 100 μm particles.

  13. Broadband Ultrahigh-Resolution Spectroscopy of Particle-Induced X Rays: Extending the Limits of Nondestructive Analysis

    NASA Astrophysics Data System (ADS)

    Palosaari, M. R. J.; Käyhkö, M.; Kinnunen, K. M.; Laitinen, M.; Julin, J.; Malm, J.; Sajavaara, T.; Doriese, W. B.; Fowler, J.; Reintsema, C.; Swetz, D.; Schmidt, D.; Ullom, J. N.; Maasilta, I. J.

    2016-08-01

    Nondestructive analysis (NDA) based on x-ray emission is widely used, for example, in the semiconductor and concrete industries. Here, we demonstrate significant quantitative and qualitative improvements in broadband x-ray NDA by combining particle-induced emission with detection based on superconducting microcalorimeter arrays. We show that the technique offers great promise in the elemental analysis of thin-film and bulk samples, especially in the difficult cases where tens of different elements with nearly overlapping emission lines have to be identified down to trace concentrations. We demonstrate the efficiency and resolving capabilities by spectroscopy of several complex multielement samples in the energy range 1-10 keV, some of which have a trace amount of impurities not detectable with standard silicon drift detectors. The ability to distinguish the chemical environment of an element is also demonstrated by measuring the intensity differences and chemical shifts of the characteristics x-ray peaks of titanium compounds. In particular, we report measurements of the K α /K β intensity ratio of thin films of TiN and measurements of Ti K α satellite peak intensities in various Ti thin-film compounds. We also assess the detection limits of the technique, comment on detection limits possible in the future, and discuss possible applications.

  14. Measurement of the forward charged particle pseudorapidity density in pp collisions at TeV using a displaced interaction point. TOTEM Collaboration

    NASA Astrophysics Data System (ADS)

    Antchev, G.; Aspell, P.; Atanassov, I.; Avati, V.; Baechler, J.; Berardi, V.; Berretti, M.; Bossini, E.; Bottigli, U.; Bozzo, M.; Brücken, E.; Buzzo, A.; Cafagna, F. S.; Catanesi, M. G.; Covault, C.; Csanád, M.; Csörgő, T.; Deile, M.; Doubek, M.; Eggert, K.; Eremin, V.; Ferro, F.; Fiergolski, A.; Garcia, F.; Georgiev, V.; Giani, S.; Grzanka, L.; Hammerbauer, J.; Heino, J.; Hilden, T.; Karev, A.; Kašpar, J.; Kopal, J.; Kundrát, V.; Lami, S.; Latino, G.; Lauhakangas, R.; Leszko, T.; Lippmaa, E.; Lippmaa, J.; Lokajíček, M. V.; Losurdo, L.; Lo Vetere, M.; Lucas Rodríguez, F.; Macrí, M.; Mäki, T.; Mercadante, A.; Minafra, N.; Minutoli, S.; Nemes, F.; Niewiadomski, H.; Oliveri, E.; Oljemark, F.; Orava, R.; Oriunno, M.; Österberg, K.; Palazzi, P.; Peroutka, Z.; Procházka, J.; Quinto, M.; Radermacher, E.; Radicioni, E.; Ravotti, F.; Robutti, E.; Ropelewski, L.; Ruggiero, G.; Saarikko, H.; Scribano, A.; Smajek, J.; Snoeys, W.; Sodzawiczny, T.; Sziklai, J.; Taylor, C.; Turini, N.; Vacek, V.; Welti, J.; Whitmore, J.; Wyszkowski, P.; Zielinski, K.

    2015-03-01

    The pseudorapidity density of charged particles dN/d is measured by the TOTEM experiment in proton-proton collisions at TeV within the range and . Data were collected in a low intensity LHC run with collisions occurring at a distance of 11.25 m from the nominal interaction point. The data sample is expected to include 96-97 % of the inelastic proton-proton interactions. The measurement reported here considers charged particles with MeV/c, produced in inelastic interactions with at least one charged particle in or . The dN/d has been found to decrease with , from 5.11 0.73 at to 1.81 0.56 at 6.925. Several Monte Carlo generators are compared to the data and are found to be within the systematic uncertainty of the measurement.

  15. Trapped fast particle destabilization of internal kink mode for the locally flattened q-profile with an inflection point

    NASA Astrophysics Data System (ADS)

    Wang, Xian-Qu; Zhang, Rui-Bin; Meng, Guo

    2016-07-01

    The destabilization of ideal internal kink modes by trapped fast particles in tokamak plasmas with a "shoulder"-like equilibrium current is investigated. It is found that energetic particle branch of the mode is unstable with the driving of fast-particle precession drifts and corresponds to a precessional fishbone. The mode with a low stability threshold is also more easily excited than the conventional precessional fishbone. This is different from earlier studies for the same equilibrium in which the magnetohydrodynamic (MHD) branch of the mode is stable. Furthermore, the stability and characteristic frequency of the mode are analyzed by solving the dispersion relation and comparing with the conventional fishbone. The results suggest that an equilibrium with a locally flattened q-profile, may be modified by localized current drive (or bootstrap current, etc.), is prone to the onset of the precessional fishbone branch of the mode.

  16. Quantum motion of a point particle in the presence of the Aharonov-Bohm potential in curved space

    NASA Astrophysics Data System (ADS)

    Silva, Edilberto O.; Ulhoa, Sérgio C.; Andrade, Fabiano M.; Filgueiras, Cleverson; Amorim, R. G. G.

    2015-11-01

    The nonrelativistic quantum dynamics of a spinless charged particle in the presence of the Aharonov-Bohm potential in curved space is considered. We chose the surface as being a cone defined by a line element in polar coordinates. The geometry of this line element establishes that the motion of the particle can occur on the surface of a cone or an anti-cone. As a consequence of the nontrivial topology of the cone and also because of two-dimensional confinement, the geometric potential should be taken into account. At first, we establish the conditions for the particle describing a circular path in such a context. Because of the presence of the geometric potential, which contains a singular term, we use the self-adjoint extension method in order to describe the dynamics in all space including the singularity. Expressions are obtained for the bound state energies and wave functions.

  17. Artifact free reconstruction with the system matrix approach by overscanning the field-free-point trajectory in magnetic particle imaging

    NASA Astrophysics Data System (ADS)

    Weber, A.; Werner, F.; Weizenecker, J.; Buzug, T. M.; Knopp, T.

    2016-01-01

    Magnetic particle imaging is a tracer-based imaging method that utilizes the non-linear magnetization response of iron-oxide for determining their spatial distribution. The method is based on a sampling scheme where a sensitive spot is moved along a trajectory that captured a predefined field-of-view (FOV). However, particles outside the FOV also contribute to the measurement signal due to their rotation and the non-sharpness of the sensitive spot. In the present work we investigate artifacts that are induced by particles not covered by the FOV and show that the artifacts can be mitigated by using a system matrix that covers not only the region of interest but also a certain area around the FOV. The findings are especially relevant when using a multi-patch acquisition scheme where the boundaries of neighboring patches have to be handled.

  18. Rheumatic heart disease screening by "point-of-care" echocardiography: an acceptable alternative in resource limited settings?

    PubMed

    Saxena, Anita

    2015-07-01

    Rheumatic heart disease (RHD) is estimated to affect over 20 million people worldwide, the vast majority being in developing countries. Screening for RHD has been recommended by World Health Organization (WHO) since 2004. Conventionally, auscultation has been used for diagnosing RHD. Auscultation has its limitations and may not detect mild cases. With the evolution of portable echocardiographic systems, mass screening for subclinical RHD has become possible. Portable echo has the advantage of rapid access and hence screening in schools or communities is possible. Its cost is lower than that of standard echo equipment. A large number of studies have reported echocardiographic screening for RHD over the last decade or so. A 3-10 fold increase in prevalence of RHD has been detected by using portable echo when compared with conventional method of auscultation. More recently, a small, compact, easy to carry in a pocket, hand held system has been introduced which is much cheaper than the conventional portable system. A few previous reports have shown the feasibility of using hand held echo system for diagnosis of various cardiac diseases. A recently published article has shown that the hand held system can be used to screen for RHD. It is more sensitive than the conventional auscultation for RHD. Authors of this report have concluded that screening with the hand held device may be a more cost effective strategy for screening for RHD in resource limited settings, since it is much cheaper than the portable echocardiography equipment. PMID:26835377

  19. Searches for New Physics, involving Top Quarks, Dark Matter and the Higgs Bosons, at the ATLAS, CDF and Fermi-LAT Particle Experiments, and a description of a new limit re-interpretation tool, Basis-Limits

    NASA Astrophysics Data System (ADS)

    Rao, Kanury Kanishka

    Searches for new physics are presented in the lepton + jets channel at the CDF and ATLAS experiments. At CDF, we search for exotic quarks that couple to dark matter, new particle resonances in top-quark pairs, a Z' boson decaying quarks, and a two-Higgs doublet model. At ATLAS, we search for fourth generation down-type quarks, new particle resonances in top-quark pairs, and a multi-Higgs boson cascade. A novel methodology, Basis-limits, which allows for re-interpretation of experimental limits is presented. Basis-limits is used to extend ATLAS limits on fourth generation quarks to set limits on a new vector-like quark for all its decay modes. Finally, a spatial analysis of the gamma-ray excess, seen by the Fermi-LAT experiment, is performed. We find the location of the excess to be consistent with a dark matter halo at the Galactic center as the source.

  20. Assessment of a three-point restraint system with a pre-tensioned lap belt and an inflatable, force-limited shoulder belt.

    PubMed

    Kent, Richard; Lopez-Valdes, Francisco J; Dennis, Nate J; Lessley, David; Forman, Jason; Higuchi, Kazuo; Tanji, Hiromasa; Ato, Tadayuki; Kameyoshi, Hikaru; Arbogast, Kristy

    2011-11-01

    This study investigates the performance of a 3-point restraint system incorporating an inflatable shoulder belt with a nominal 2.5-kN load limiter and a non-inflatable lap belt with a pretensioner (the "Airbelt"). Frontal impacts with PMHS in a rear seat environment are presented and the Airbelt system is contrasted with an earlier 3-point system with inflatable lap and shoulder belts but no load-limiter or pretensioners, which was evaluated with human volunteers in the 1970s but not fully reported in the open literature (the "Inflataband"). Key differences between the systems include downward pelvic motion and torso recline with the Inflataband, while the pelvis moved almost horizontally and the torso pitched forward with the Airbelt. One result of these kinematic differences was an overall more biomechanically favorable restraint loading but greater maximum forward head excursion with the Airbelt. The Airbelt is shown to generate generally lower head, neck, and thoracic injury metrics and PMHS trauma than other, non-inflatable rear-seat restraint concepts (viz., a standard 3-point belt and a pre-tensioned shoulder belt with a progressive load limiter). Further study is needed to evaluate the Airbelt system for different size occupants (e.g., children), non-frontal impact vectors, and for out-of-position occupants and to allow the results with this particular system to be generalized to a broader range of Airbelt designs. PMID:22869308

  1. Development document for effluent limitations guidelines and standards for the porcelain enameling. Point source category. Final report

    SciTech Connect

    Not Available

    1982-11-01

    EPA has subcategorized the porcelain enameling industry based on the basis material coated. The subcategories are defined as porcelain enameling on: steel, cast iron, aluminum and copper. No limitations are established for porcelain enameling on precious metals (gold, silver and platinum group metals) because they are believed to be very small sources and virtually all would be excluded from regulation by the small indirect discharger exemption. The study included the identification of raw waste and treated effluent characteristics, including: (1) the sources and volume of water used, the processes employed, and the sources of pollutants and wastewaters in the plant, and (2) the constituents of wastewaters. Such analysis enabled EPA to determine the presence and concentration of toxic pollutants in wastewater discharges.

  2. Model-independent analysis of dark matter points to a particle mass at the keV scale

    NASA Astrophysics Data System (ADS)

    de Vega, H. J.; Sanchez, N. G.

    2010-05-01

    We present a model-independent analysis of dark matter (DM) decoupling both ultrarelativistically (UR) and non-relativistically (NR) based on the DM phase-space density . We derive explicit formulae for the DM particle mass m and for the number of ultrarelativistic degrees of freedom gd at decoupling. We find that for DM particles decoupling UR both at local thermal equilibrium (LTE) and out of LTE, m turns out to be in the keV scale. For example, for DM Majorana fermions decoupling at LTE the resulting mass is m ~= 0.85 keV. For DM particles decoupling NR, results in the keV scale (Td is the decoupling temperature) and the value of m is consistent with the keV scale. In all cases, DM turns out to be cold DM (CDM). In addition, lower and upper bounds on the DM annihilation cross-section for NR decoupling are derived. We evaluate the free-streaming (Jeans) wavelength and Jeans mass: they are independent of the type of DM except for the DM self-gravity dynamics. The free-streaming wavelength today turns to be in the kpc range. These results are based on our theoretical analysis, on astronomical observations of dwarf spheroidal satellite galaxies in the Milky Way and on N-body numerical simulations. We analyse and discuss the results for from analytic approximate formulae for both linear fluctuations and the (non-linear) spherical model and from N-body simulations results. In this way we obtain upper bounds for the DM particle mass, which are all below the 100-keV range.

  3. Methane and CO2 fluxes of moving point sources - Beyond or within the limits of eddy covariance measurements

    NASA Astrophysics Data System (ADS)

    Felber, Raphael; Neftel, Albrecht; Münger, Andreas; Ammann, Christof

    2014-05-01

    The eddy covariance (EC) technique has been extensively used for CO2 and energy exchange measurements over different ecosystems. For some years, it has been also becoming widely used to investigate CH4 and N2O exchange over ecosystems including grazing systems. EC measurements represent a spatially integrated flux over an upwind area (footprint). Whereas for extended homogenous areas EC measurements work well, the animals in a grazing system are a challenge as they represent moving point sources that create inhomogeneous conditions in space and time. The main issues which have to be taken into account when applying EC flux measurements over a grazed system are: i) In the presence of animals the high time resolution concentration measurements show large spikes in the signal. These spikes may be filtered/reduced by standard quality control software in order to avoid wrong measurements. ii) Data on the position of the animals relative to the flux footprint is needed to quantify the contribution of the grazing animals to the measured flux. For one grazing season we investigated the ability of EC flux measurements to reliably quantify the contribution of the grazing animals to the CH4 and CO2 exchange over pasture systems. For this purpose, a field experiment with a herd of twenty dairy cows in a full-day rotational grazing system was carried out on the Swiss central plateau. Net CH4 and CO2 exchange of the pasture system was measured continuously by the eddy covariance technique (Sonic Anemometer HS-50, Gill Instruments Ltd; FGGA, Los Gatos Research Inc.). To quantify the contribution of the animals to the net flux, the position of the individual cows was recorded using GPS (5 s time resolution) on each animal. An existing footprint calculation tool (ART footprint tool) was adapted and CH4 emissions of the cows were calculated. CH4 emissions from cows could be used as a tracer to investigate the quality of the evaluation of the EC data, since the background exchange of

  4. Rigorous Derivation of Nonlinear Scalar Conservation Laws from Follow-the-Leader Type Models via Many Particle Limit

    NASA Astrophysics Data System (ADS)

    Di Francesco, M.; Rosini, M. D.

    2015-09-01

    We prove that the unique entropy solution to a scalar nonlinear conservation law with strictly monotone velocity and nonnegative initial condition can be rigorously obtained as the large particle limit of a microscopic follow-the-leader type model, which is interpreted as the discrete Lagrangian approximation of the nonlinear scalar conservation law. More precisely, we prove that the empirical measure (respectively the discretised density) obtained from the follow-the-leader system converges in the 1-Wasserstein topology (respectively in ) to the unique Kružkov entropy solution of the conservation law. The initial data are taken in , nonnegative, and with compact support, hence we are able to handle densities with a vacuum. Our result holds for a reasonably general class of velocity maps (including all the relevant examples in the applications, for example in the Lighthill-Whitham-Richards model for traffic flow) with a possible degenerate slope near the vacuum state. The proof of the result is based on discrete estimates and on a discrete version of the one-sided Oleinik-type condition. In particular, we prove that the regularizing effect for nonlinear scalar conservation laws is intrinsic to the discrete model.

  5. Efficient gradient field generation providing a multi-dimensional arbitrary shifted field-free point for magnetic particle imaging

    NASA Astrophysics Data System (ADS)

    Kaethner, Christian; Ahlborg, Mandy; Knopp, Tobias; Sattel, Timo F.; Buzug, Thorsten M.

    2014-01-01

    Magnetic Particle Imaging (MPI) is a tomographic imaging modality capable to visualize tracers using magnetic fields. A high magnetic gradient strength is mandatory, to achieve a reasonable image quality. Therefore, a power optimization of the coil configuration is essential. In order to realize a multi-dimensional efficient gradient field generator, the following improvements compared to conventionally used Maxwell coil configurations are proposed: (i) curved rectangular coils, (ii) interleaved coils, and (iii) multi-layered coils. Combining these adaptions results in total power reduction of three orders of magnitude, which is an essential step for the feasibility of building full-body human MPI scanners.

  6. Efficient gradient field generation providing a multi-dimensional arbitrary shifted field-free point for magnetic particle imaging

    SciTech Connect

    Kaethner, Christian Ahlborg, Mandy; Buzug, Thorsten M.; Knopp, Tobias; Sattel, Timo F.

    2014-01-28

    Magnetic Particle Imaging (MPI) is a tomographic imaging modality capable to visualize tracers using magnetic fields. A high magnetic gradient strength is mandatory, to achieve a reasonable image quality. Therefore, a power optimization of the coil configuration is essential. In order to realize a multi-dimensional efficient gradient field generator, the following improvements compared to conventionally used Maxwell coil configurations are proposed: (i) curved rectangular coils, (ii) interleaved coils, and (iii) multi-layered coils. Combining these adaptions results in total power reduction of three orders of magnitude, which is an essential step for the feasibility of building full-body human MPI scanners.

  7. Quantitative determination of minerals and anthropogenic particles in some Polish peat occurrences using a novel SEM point-counting method.

    PubMed

    Smieja-Król, Beata; Fiałkiewicz-Kozieł, Barbara

    2014-04-01

    A method is proposed for determining the mineral composition of peat using scanning electron microscope. In an illustrative example, five groups of particles occurring in amounts of >0.05% are distinguished in peat from Puścizna Mała bog in the Carpathian foreland, Poland. These are spheroidal aluminosilicate particles (SAP), feldspars, nondescript aluminosilicates (mainly clays), silica (quartz and opaline silica), and Fe(hydro)oxides. Two more site-specific groups (barite and ZnS) are distinguished in highly polluted fens (Bagno Bruch and Bagno Mikołeska) near a zinc smelter in Upper Silesia. At Bagno Bruch, peat contents of predominantly authigenic ZnS microspheroids range up to 1.1%. SAP originating from coal-burning power stations account for maximum concentrations of <21-39% of the inorganic fraction in the studied mires. SAP concentrations vary with depth, and mean spheroid diameters with distance from emission sources. A distinct feature of SAP is their common enrichment in Ti what questions the use of Ti as a proxy for soil dust in fly ash polluted bogs. As amounts of anthropogenic magnetic spherules, less abundant than SAP in all mires, relate to water table level position, they are unsuitable as tracers of air pollution. The proposed method is recommended for application with peats having ash contents > ~4%. PMID:24442577

  8. Relation between absorbed dose, charged particle equilibrium and nuclear transformations: a non-equilibrium thermodynamics point of view.

    PubMed

    Alvarez-Romero, J T

    2006-01-01

    We present a discussion to show that the absorbed dose D is a time-dependent function. This time dependence is demonstrated based on the concepts of charged particle equilibrium and on radiation equilibrium within the context of thermodynamic non-equilibrium. In the latter, the time dependence is due to changes of the rest mass energy of the nuclei and elementary particles involved in the terms summation operator Q and Q that appear in the definitions of energy imparted epsilon and energy deposit epsilon(i), respectively. In fact, nothing is said about the averaging operation of the non-stochastic quantity mean energy imparted epsilon, which is used in the definition of D according to ICRU 60. It is shown in this research that the averaging operation necessary to define the epsilon employed to get D cannot be performed with an equilibrium statistical operator rho(r) as could be expected. Rather, the operation has to be defined with a time-dependent non-equilibrium statistical operator rho(r, t); therefore, D is a time-dependent function D(r,t). PMID:16731692

  9. Self-Organizing Hierarchical Particle Swarm Optimization with Time-Varying Acceleration Coefficients for Economic Dispatch with Valve Point Effects and Multifuel Options

    NASA Astrophysics Data System (ADS)

    Polprasert, Jirawadee; Ongsakul, Weerakorn; Dieu, Vo Ngoc

    2011-06-01

    This paper proposes a self-organizing hierarchical particle swarm optimization (SPSO) with time-varying acceleration coefficients (TVAC) for solving economic dispatch (ED) problem with non-smooth functions including multiple fuel options (MFO) and valve-point loading effects (VPLE). The proposed SPSO with TVAC is the new approach optimizer and good performance for solving ED problems. It can handle the premature convergence of the problem by re-initialization of velocity whenever particles are stagnated in the search space. To properly control both local and global explorations of the swarm during the optimization process, the performance of TVAC is included. The proposed method is tested in different ED problems with non-smooth cost functions and the obtained results are compared to those from many other methods in the literature. The results have revealed that the proposed SPSO with TVAC is effective in finding higher quality solutions for non-smooth ED problems than many other methods.

  10. Limits on Spin-independent Couplings of Light Dark Matter WIMPs with a p-type Point-contact Germanium Detector

    NASA Astrophysics Data System (ADS)

    Lin, S. T.; Wong, H. T.

    New limits on spin-independent WIMP-nucleon coupling using 39.5 kg-days of data taken with a p-type point-contact germanium detector with fiducial mass of 840 g at the Kuo-Sheng Reactor Neutrino Laboratory (KSNL) is presented. Charactering and understanding the anomalous surface behaviour is of particular significance to this study. The slow rise-time of surface events is identified via software pulse shape analysis techniques. In addition, the signal-retaining and background-rejecting efficiencies are implied to clarify the actual bulk and surface events in the mixed regime at sub-keV range. Both efficiencies are evaluated with calibration sources and a novel n-type point-contact germanium detector. Efficiencies-corrected background spectra from the low-background facility at KSNL are derived. Part of the parameter space in cross-section versus WIMP-mass is probed and excluded.

  11. Data that describe at-a-point temporal variations in the transport rate and particle-size distribution of bedload; East Fork River, Wyoming, and Fall River, Colorado

    USGS Publications Warehouse

    Gomez, Basil; Emmett, W.W.

    1990-01-01

    Data from the East Fork River, Wyoming, and the Fall River, Colorado, that document at-a-point temporal variations in the transport rate and particle-size distribution of bedload, associated with the downstream migration of dunes, are presented. Bedload sampling was undertaken, using a 76.2 x 76.2 mm Helley-Smith sampler, on three separate occasions at each site in June 1988. In each instance, the sampling time was 30 seconds and the sampling intervals 5 minutes. The sampling period ranged from 4.92 to 8.25 hours. Water stage did not vary appreciably during any of the sampling periods. (USGS)

  12. Precise Three-Dimensional Scan-Free Multiple-Particle Tracking over Large Axial Ranges with Tetrapod Point Spread Functions.

    PubMed

    Shechtman, Yoav; Weiss, Lucien E; Backer, Adam S; Sahl, Steffen J; Moerner, W E

    2015-06-10

    We employ a novel framework for information-optimal microscopy to design a family of point spread functions (PSFs), the Tetrapod PSFs, which enable high-precision localization of nanoscale emitters in three dimensions over customizable axial (z) ranges of up to 20 μm with a high numerical aperture objective lens. To illustrate, we perform flow profiling in a microfluidic channel and show scan-free tracking of single quantum-dot-labeled phospholipid molecules on the surface of living, thick mammalian cells. PMID:25939423

  13. Multi-point observations of energetic particle injection deep into the inner magnetosphere: Implications for the ring current and radiation belts

    NASA Astrophysics Data System (ADS)

    Reeves, G. D.; Larsen, B.; Friedel, R. H. W.; Henderson, M. G.; Skoug, R. M.; Funsten, H. O.; Claudepierre, S. G.; Fennell, J.; Tu, W.; Cunningham, G.; Spence, H. E.

    2014-12-01

    For thirty years, the "injection boundary" model of substorm injections has provided a framework for studies of the impulsive transport of energetic electrons and ions into the inner magnetosphere. New, multi-satellite observations of substorm injections show signatures that require revision and rethinking of the classical picture. Recent observations by the LANL-GEO and GOES energetic particle instruments provide unprecedented coverage at geosynchronous orbit while the Van Allen Probes satellites provide simultaneous multi-point measurements inside geosynchronous orbit. With these satellites we can observe injections at three different radial distances and up to ten different local times - simultaneously. These observations reveal a complex and varied set of dynamics that have important implications for the development of the radiation belts and ring current. In this study we look specifically at the radial penetration of energetic particle injections in storms and substorms. Radial alignments of satellites confirm and extend the CRRES/LANL-GEO observations of relatively slow inward propagation of the injection region inside geosynchronous orbit [1]. At the same time, synoptic Van Allen Probes observations show frequent storm-time "injection" of energetic (~50-500 keV) electrons to very low L-shells (L < 3) that have not previously been reported. The radial distribution of electrons and ions injected during storms and substorms have profound implications for the generation of waves, for the availability of a radiation belt "seed population", and for the radial distribution of ring current ions. In this paper we will use multi-point satellite observations to understand the processes that inject energetic particles into the inner magnetosphere, the Earthward propagation of these injections, the conditions that control variation in Earthward extent of energetic particle injections, and how particles can be injected deep inside the plasmasphere and even through the

  14. Open-source point-of-care electronic medical records for use in resource-limited settings: systematic review and questionnaire surveys

    PubMed Central

    Bru, Juan; Berger, Christopher A

    2012-01-01

    Background Point-of-care electronic medical records (EMRs) are a key tool to manage chronic illness. Several EMRs have been developed for use in treating HIV and tuberculosis, but their applicability to primary care, technical requirements and clinical functionalities are largely unknown. Objectives This study aimed to address the needs of clinicians from resource-limited settings without reliable internet access who are considering adopting an open-source EMR. Study eligibility criteria Open-source point-of-care EMRs suitable for use in areas without reliable internet access. Study appraisal and synthesis methods The authors conducted a comprehensive search of all open-source EMRs suitable for sites without reliable internet access. The authors surveyed clinician users and technical implementers from a single site and technical developers of each software product. The authors evaluated availability, cost and technical requirements. Results The hardware and software for all six systems is easily available, but they vary considerably in proprietary components, installation requirements and customisability. Limitations This study relied solely on self-report from informants who developed and who actively use the included products. Conclusions and implications of key findings Clinical functionalities vary greatly among the systems, and none of the systems yet meet minimum requirements for effective implementation in a primary care resource-limited setting. The safe prescribing of medications is a particular concern with current tools. The dearth of fully functional EMR systems indicates a need for a greater emphasis by global funding agencies to move beyond disease-specific EMR systems and develop a universal open-source health informatics platform. PMID:22763661

  15. The LDCE Particle Impact Experiment as flown on STS-46. [limited duration space environment candidate materials exposure (LDCE)

    NASA Technical Reports Server (NTRS)

    Maag, Carl R.; Tanner, William G.; Borg, Janet; Bibring, Jean-Pierre; Alexander, W. Merle; Maag, Andrew J.

    1992-01-01

    Many materials and techniques have been developed by the authors to sample the flux of particles in Low Earth Orbit (LEO). Though regular in-site sampling of the flux in LEO the materials and techniques have produced data which compliment the data now being amassed by the Long Duration Exposure Facility (LDEF) research activities. Orbital debris models have not been able to describe the flux of particles with d sub p less than or = 0.05 cm, because of the lack of data. Even though LDEF will provide a much needed baseline flux measurement, the continuous monitoring of micron and sub-micron size particles must be carried out. A flight experiment was conducted on the Space Shuttle as part of the LDCE payload to develop an understanding of the Spatial Density (concentration) as a function of size (mass) for particle sizes 1 x 10(exp 6) cm and larger. In addition to the enumeration of particle impacts, it is the intent of the experiment that hypervelocity particles be captured and returned intact. Measurements will be performed post flight to determine the flux density, diameters, and subsequent effects on various optical, thermal control and structural materials. In addition to these principal measurements, the Particle Impact Experiment (PIE) also provides a structure and sample holders for the exposure of passive material samples to the space environment, e.g., thermal cycling, and atomic oxygen, etc. The experiment will measure the optical property changes of mirrors and will provide the fluence of the ambient atomic oxygen environment to other payload experimenters. In order to augment the amount of material returned in a form which can be analyzed, the survivability of the experiment as well as the captured particles will be assessed. Using Sandia National Laboratory's hydrodynamic computer code CTH, hypervelocity impacts on the materials which comprise the experiments have been investigated and the progress of these studies are reported.

  16. Point of no return in diving emperor penguins: is the timing of the decision to return limited by the number of strokes?

    PubMed

    Shiomi, Kozue; Sato, Katsufumi; Ponganis, Paul J

    2012-01-01

    At some point in a dive, breath-hold divers must decide to return to the surface to breathe. The issue of when to end a dive has been discussed intensively in terms of foraging ecology and behavioral physiology, using dive duration as a temporal parameter. Inevitably, however, a time lag exists between the decision of animals to start returning to the surface and the end of the dive, especially in deep dives. In the present study, we examined the decision time in emperor penguins under two different conditions: during foraging trips at sea and during dives at an artificial isolated dive hole. It was found that there was an upper limit for the decision-to-return time irrespective of dive depth in birds diving at sea. However, in a large proportion of dives at the isolated dive hole, the decision-to-return time exceeded the upper limit at sea. This difference between the decision times in dives at sea versus the isolated dive hole was accounted for by a difference in stroke rate. The stroke rates were much lower in dives at the isolated hole and were inversely correlated with the upper limit of decision times in individual birds. Unlike the decision time to start returning, the cumulative number of strokes at the decision time fell within a similar range in the two experiments. This finding suggests that the number of strokes, but not elapsed time, constrained the decision of emperor penguins to return to the surface. While the decision to return and to end a dive may be determined by a variety of ecological, behavioral and physiological factors, the upper limit to that decision time may be related to cumulative muscle workload. PMID:22162861

  17. Are Treponema pallidum Specific Rapid and Point-of-Care Tests for Syphilis Accurate Enough for Screening in Resource Limited Settings? Evidence from a Meta-Analysis

    PubMed Central

    Jafari, Yalda; Peeling, Rosanna W.; Shivkumar, Sushmita; Claessens, Christiane; Joseph, Lawrence; Pai, Nitika Pant

    2013-01-01

    Background Rapid and point-of-care (POC) tests for syphilis are an invaluable screening tool, yet inadequate evaluation of their diagnostic accuracy against best reference standards limits their widespread global uptake. To fill this gap, a systematic review and meta-analysis was conducted to evaluate the sensitivity and specificity of rapid and POC tests in blood and serum samples against Treponema pallidum (TP) specific reference standards. Methods Five electronic databases (1980–2012) were searched, data was extracted from 33 articles, and Bayesian hierarchical models were fit. Results In serum samples, against a TP specific reference standard point estimates with 95% credible intervals (CrI) for the sensitivities of popular tests were: i) Determine, 90.04% (80.45, 95.21), ii) SD Bioline, 87.06% (75.67, 94.50), iii) VisiTect, 85.13% (72.83, 92.57), and iv) Syphicheck, 74.48% (56.85, 88.44), while specificities were: i) Syphicheck, 99.14% (96.37, 100), ii) Visitect, 96.45% (91.92, 99.29), iii) SD Bioline, 95.85% (89.89, 99.53), and iv) Determine, 94.15% (89.26, 97.66). In whole blood samples, sensitivities were: i) Determine, 86.32% (77.26, 91.70), ii) SD Bioline, 84.50% (78.81, 92.61), iii) Syphicheck, 74.47% (63.94, 82.13), and iv) VisiTect, 74.26% (53.62, 83.68), while specificities were: i) Syphicheck, 99.58% (98.91, 99.96), ii) VisiTect, 99.43% (98.22, 99.98), iii) SD Bioline, 97.95%(92.54, 99.33), and iv) Determine, 95.85% (92.42, 97.74). Conclusions Rapid and POC treponemal tests reported sensitivity and specificity estimates comparable to laboratory-based treponemal tests. In resource limited settings, where access to screening is limited and where risk of patients lost to follow up is high, the introduction of these tests has already been shown to improve access to screening and treatment to prevent stillbirths and neonatal mortality due to congenital syphilis. Based on the evidence, it is concluded that rapid and POC tests are useful in resource

  18. Benchmark calculations of the complete configuration-interaction limit of Born-Oppenheimer diagonal corrections to the saddle points of isotopomers of the H + H2 reaction.

    PubMed

    Mielke, Steven L; Schwenke, David W; Peterson, Kirk A

    2005-06-01

    We present a detailed ab initio study of the effect that the Born-Oppenheimer diagonal correction (BODC) has on the saddle-point properties of the H3 system and its isotopomers. Benchmark values are presented that are estimated to be within 0.1 cm(-1) of the complete configuration-interaction limit. We consider the basis set and correlation treatment requirements for accurate BODC calculations, and both are observed to be more favorable than for the Born-Oppenheimer energies. The BODC raises the H + H2 barrier height by 0.1532 kcal/mol and slightly narrows the barrier--with the imaginary frequency increasing by approximately 2%. PMID:15974674

  19. Benchmark calculations of the complete configuration-interaction limit of Born-Oppenheimer diagonal corrections to the saddle points of isotopomers of the H +H2 reaction

    NASA Astrophysics Data System (ADS)

    Mielke, Steven L.; Schwenke, David W.; Peterson, Kirk A.

    2005-06-01

    We present a detailed ab initio study of the effect that the Born-Oppenheimer diagonal correction (BODC) has on the saddle-point properties of the H3 system and its isotopomers. Benchmark values are presented that are estimated to be within 0.1cm-1 of the complete configuration-interaction limit. We consider the basis set and correlation treatment requirements for accurate BODC calculations, and both are observed to be more favorable than for the Born-Oppenheimer energies. The BODC raises the H+H2 barrier height by 0.1532kcal/mol and slightly narrows the barrier—with the imaginary frequency increasing by ˜2%.

  20. The Clinical and Economic Impact of Point-of-Care CD4 Testing in Mozambique and Other Resource-Limited Settings: A Cost-Effectiveness Analysis

    PubMed Central

    Hyle, Emily P.; Jani, Ilesh V.; Lehe, Jonathan; Su, Amanda E.; Wood, Robin; Quevedo, Jorge; Losina, Elena; Bassett, Ingrid V.; Pei, Pamela P.; Paltiel, A. David; Resch, Stephen; Freedberg, Kenneth A.; Peter, Trevor; Walensky, Rochelle P.

    2014-01-01

    Background Point-of-care CD4 tests at HIV diagnosis could improve linkage to care in resource-limited settings. Our objective is to evaluate the clinical and economic impact of point-of-care CD4 tests compared to laboratory-based tests in Mozambique. Methods and Findings We use a validated model of HIV testing, linkage, and treatment (CEPAC-International) to examine two strategies of immunological staging in Mozambique: (1) laboratory-based CD4 testing (LAB-CD4) and (2) point-of-care CD4 testing (POC-CD4). Model outcomes include 5-y survival, life expectancy, lifetime costs, and incremental cost-effectiveness ratios (ICERs). Input parameters include linkage to care (LAB-CD4, 34%; POC-CD4, 61%), probability of correctly detecting antiretroviral therapy (ART) eligibility (sensitivity: LAB-CD4, 100%; POC-CD4, 90%) or ART ineligibility (specificity: LAB-CD4, 100%; POC-CD4, 85%), and test cost (LAB-CD4, US$10; POC-CD4, US$24). In sensitivity analyses, we vary POC-CD4-specific parameters, as well as cohort and setting parameters to reflect a range of scenarios in sub-Saharan Africa. We consider ICERs less than three times the per capita gross domestic product in Mozambique (US$570) to be cost-effective, and ICERs less than one times the per capita gross domestic product in Mozambique to be very cost-effective. Projected 5-y survival in HIV-infected persons with LAB-CD4 is 60.9% (95% CI, 60.9%–61.0%), increasing to 65.0% (95% CI, 64.9%–65.1%) with POC-CD4. Discounted life expectancy and per person lifetime costs with LAB-CD4 are 9.6 y (95% CI, 9.6–9.6 y) and US$2,440 (95% CI, US$2,440–US$2,450) and increase with POC-CD4 to 10.3 y (95% CI, 10.3–10.3 y) and US$2,800 (95% CI, US$2,790–US$2,800); the ICER of POC-CD4 compared to LAB-CD4 is US$500/year of life saved (YLS) (95% CI, US$480–US$520/YLS). POC-CD4 improves clinical outcomes and remains near the very cost-effective threshold in sensitivity analyses, even if point-of-care CD4 tests have lower sensitivity

  1. A numerical study of the Rayleigh wave particle motions excited by a point source and Poisson's ratio for lateral inhomogeneous half-spaces

    NASA Astrophysics Data System (ADS)

    Yu, Wenfu; Liu, Zhengping

    2015-12-01

    In this paper, the dependence of Rayleigh wave particle motions excited by a point source on the lateral inhomogeneous Poisson's ratio of propagation half-spaces is studied based on the theoretical analysis and wave field numerical simulation method. First, two types of time signals named single frequency harmonic and broadband Ricker wavelet are used respectively as a point source in the simulation of homogenous half-spaces. The results show that in the far-field region absolutely dominated by Rayleigh waves, or where body waves are well removed either by muting or polarization filtering, the ellipticity of particle motion can be approximated to be a simple inverse linear and frequency-independent relation with Poisson's ratio of rocks and soils, which has a linear correlation coefficient of over 0.9775 with the exact analytic solutions derived from theoretical formula for a homogeneous half-space. Then, two types of lateral inhomogeneous models, a vertical rock interface and a local heterogeneous body with various Poisson's ratios, are simulated. The results show that a local inhomogeneity can cause a local and wavelength-dependent ellipticity anomaly. The ellipticity is still in inverse proportion of Poisson's ratio but distorted with a high nonlinearity for the lateral inhomogeneous. The interferences of converted body waves are also studied, and the results suggest that the ellipticity estimation of Rayleigh waves suffers little from the body waves converted by the scattering of lateral inhomogeneity. The study shows that the dependency of Rayleigh wave ellipticity on Poisson's ratio is potentially beneficial for Poisson's ratio estimation, which is based on the inverse linear approximation for a homogeneous region within several half-wavelengths, and in surveys for space geometry and elastic properties of the lateral inhomogeneity, which are based on the frequency-dependent and inverse proportional properties that are all of the main goals of geophysical

  2. Aerosol- and updraft-limited regimes of cloud droplet formation: influence of particle number, size and hygroscopicity on the activation of cloud condensation nuclei (CCN)

    NASA Astrophysics Data System (ADS)

    Reutter, P.; Su, H.; Trentmann, J.; Simmel, M.; Rose, D.; Gunthe, S. S.; Wernli, H.; Andreae, M. O.; Pöschl, U.

    2009-09-01

    We have investigated the formation of cloud droplets under pyro-convective conditions using a cloud parcel model with detailed spectral microphysics and with the κ-Köhler model approach for efficient and realistic description of the cloud condensation nucleus (CCN) activity of aerosol particles. Assuming a typical biomass burning aerosol size distribution (accumulation mode centred at 120 nm), we have calculated initial cloud droplet number concentrations (NCD) for a wide range of updraft velocities (w=0.25-20 m s-1) and aerosol particle number concentrations (NCN=200-105 cm-3) at the cloud base. Depending on the ratio between updraft velocity and particle number concentration (w/NCN), we found three distinctly different regimes of CCN activation and cloud droplet formation: (1) An aerosol-limited regime that is characterized by high w/NCN ratios (>≈10-3 m s-1 cm3), high maximum values of water vapour supersaturation (Smax>≈0.5%), and high activated fractions of aerosol particles (NCN/NCN>≈90%). In this regime NCD is directly proportional to NCN and practically independent of w. (2) An updraft-limited regime that is characterized by low w/NCN ratios (<≈10-4 m s-1 cm3), low maximum values of water vapour supersaturation (Smax<≈0.2%), and low activated fractions of aerosol particles (NCD/NCN<≈20%). In this regime NCD is directly proportional to w and practically independent of NCN. (3) An aerosol- and updraft-sensitive regime (transitional regime), which is characterized by parameter values in between the two other regimes and covers most of the conditions relevant for pyro-convection. In this regime NCD depends non-linearly on both NCN and w. In sensitivity studies we have tested the influence of aerosol particle size distribution and hygroscopicity on NCD. Within the range of effective hygroscopicity parameters that is characteristic for continental atmospheric aerosols (κ≈0.05-0.6), we found that NCD depends rather weakly on the actual value of κ

  3. External control strategies for self-propelled particles: Optimizing navigational efficiency in the presence of limited resources.

    PubMed

    Haeufle, Daniel F B; Bäuerle, Tobias; Steiner, Jakob; Bremicker, Lena; Schmitt, Syn; Bechinger, Clemens

    2016-07-01

    We experimentally and numerically study the dependence of different navigation strategies regarding the effectivity of an active particle to reach a predefined target area. As the only control parameter, we vary the particle's propulsion velocity depending on its position and orientation relative to the target site. By introducing different figures of merit, e.g., the time to target or the total consumed propulsion energy, we are able to quantify and compare the efficiency of different strategies. Our results suggest that each strategy to navigate towards a target has its strengths and weaknesses, and none of them outperforms the other in all regards. Accordingly, the choice of an ideal navigation strategy will strongly depend on the specific conditions and the figure of merit which should be optimized. PMID:27575189

  4. External control strategies for self-propelled particles: Optimizing navigational efficiency in the presence of limited resources

    NASA Astrophysics Data System (ADS)

    Haeufle, Daniel F. B.; Bäuerle, Tobias; Steiner, Jakob; Bremicker, Lena; Schmitt, Syn; Bechinger, Clemens

    2016-07-01

    We experimentally and numerically study the dependence of different navigation strategies regarding the effectivity of an active particle to reach a predefined target area. As the only control parameter, we vary the particle's propulsion velocity depending on its position and orientation relative to the target site. By introducing different figures of merit, e.g., the time to target or the total consumed propulsion energy, we are able to quantify and compare the efficiency of different strategies. Our results suggest that each strategy to navigate towards a target has its strengths and weaknesses, and none of them outperforms the other in all regards. Accordingly, the choice of an ideal navigation strategy will strongly depend on the specific conditions and the figure of merit which should be optimized.

  5. Designs for testing group-based interventions with limited numbers of social units: The dynamic wait-listed and regression point displacement designs

    PubMed Central

    Wyman, Peter A.; Brown, C. Hendricks

    2015-01-01

    The dynamic wait-listed design (DWLD) and regression point displacement design (RPDD) address several challenges in evaluating group-based interventions when there is a limited number of groups. Both DWLD and RPDD utilize efficiencies that increase statistical power and can enhance balance between community needs and research priorities. The DWLD blocks on more time units than traditional wait-listed designs, thereby increasing the proportion of a study period during which intervention and control conditions can be compared, and can also improve logistics of implementing intervention across multiple sites and strengthen fidelity. We discuss DWLDs in the larger context of roll-out randomized designs and compare it with its cousin the Stepped Wedge design. The RPDD uses archival data on the population of settings from which intervention unit(s) are selected to create expected posttest scores for units receiving intervention, to which actual posttest scores are compared. High pretest-posttest correlations give the RPDD statistical power for assessing intervention impact even when one or a few settings receive intervention. RPDD works best when archival data are available over a number of years prior to and following intervention. If intervention units were not randomly selected, propensity scores can be used to control for nonrandom selection factors. Examples are provided of the DWLD and RPDD used to evaluate, respectively, suicide prevention training (QPR) in 32 schools and a violence prevention program (CeaseFire) in 2 Chicago police districts over a 10-year period. How DWLD and RPDD address common threats to internal and external validity, as well as their limitations, are discussed. PMID:25481512

  6. DETERMINATION OF THE POINT-SPREAD FUNCTION FOR THE FERMI LARGE AREA TELESCOPE FROM ON-ORBIT DATA AND LIMITS ON PAIR HALOS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Ackermann, M.; Ajello, M.; Allafort, A.; Bechtol, K.; Bloom, E. D.; Borgland, A. W.; Bottacini, E.; Buehler, R.; Asano, K.; Atwood, W. B.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Ballet, J.; Bastieri, D.; Bonamente, E.; Brandt, T. J.; Brigida, M.; Bruel, P. E-mail: mar0@uw.edu [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS and others

    2013-03-01

    The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to detect photons with energies from Almost-Equal-To 20 MeV to >300 GeV. The pre-launch response functions of the LAT were determined through extensive Monte Carlo simulations and beam tests. The point-spread function (PSF) characterizing the angular distribution of reconstructed photons as a function of energy and geometry in the detector is determined here from two years of on-orbit data by examining the distributions of {gamma} rays from pulsars and active galactic nuclei (AGNs). Above 3 GeV, the PSF is found to be broader than the pre-launch PSF. We checked for dependence of the PSF on the class of {gamma}-ray source and observation epoch and found none. We also investigated several possible spatial models for pair-halo emission around BL Lac AGNs. We found no evidence for a component with spatial extension larger than the PSF and set upper limits on the amplitude of halo emission in stacked images of low- and high-redshift BL Lac AGNs and the TeV blazars 1ES0229+200 and 1ES0347-121.

  7. Quantifying Upper Particle-size Limits of Salmonid Spawning Gravel: Analysis of Fall-run Chinook Salmon of the Sacramento River

    NASA Astrophysics Data System (ADS)

    Wooster, J. K.; Riebe, C. S.; Ligon, F. K.

    2008-12-01

    Reversing the decline of historically prolific runs of Chinook salmon (Oncorhynchus tshawytscha) remains a high priority of river restoration along the US Pacific Coast. One routinely implemented strategy is gravel injection, to supplement spawning habitat which has been depleted by gravel mining and bed coarsening below dams. Gravel augmentation is generally designed around a qualitatively assessed "preferred" median particle size. Implementation sites are not always ecologically ideal, because there often is little quantitative basis for determining where added gravel would be most suitable. Although gravel augmentation may increase spawning habitat, a more mechanistic design basis could reduce costs, improve efficiency, and make results more predictable. One key to developing better designs is a better method for characterizing existing spawning gravel deposits. Here we propose a series of mechanistically oriented hypotheses about the spawning suitability of natural gravels. One hypothesis is that there is an upper size limit on particles that can be moved by salmon. We expect that this limit depends on salmon size, water velocity and the size (and embeddedness) of surrounding rocks. Another hypothesis is that spawning success is related to percent coverage by immovable particles. A corollary hypothesis is that redds become irregular (and less productive) as percent coverage by immovable particles increases. Another related hypothesis is that redd-building success should approach zero at an upper threshold of coverage by immovable particles. We explored our hypotheses for fall-run Chinook in the Sacramento River. We collected grain size data, constructed facies maps of the bed, and delineated boundaries of spawning use at the peak of spawning, prior to the run's recent population decline. Our observations suggest that particles with intermediate axes diameters bigger than about 130 mm are not generally movable by fall run Chinook. Moreover we observed no

  8. Deleterious effects of sunscreen titanium dioxide nanoparticles on DNA: efforts to limit DNA damage by particle surface modification

    NASA Astrophysics Data System (ADS)

    Serpone, Nick; Salinaro, Angela; Emeline, A.

    2001-06-01

    Sunlight can have deleterious effects on humans: causes sunburns and is the principal cause of skin cancers. Usage of TiO2 (and ZnO) in sunscreen lotions, widely used as UVA/UVB blockers, and intended to prevent sunburns and to protect consumers from skin cancers (carcinomas and melanomas) is examined. Although used to mineralize many undesired organic pollutants, TiO2 is considered to be a safe physical sunscreen agent because it reflects and scatters both UVB (290-320 nm) and UVA (320-400 nm) sunlight; however, it also absorbs substantial UV radiation which, in aqueous media, yields hydroxyl radial ((DOT)OH) species. These species cause substantial damage to DNA (J. Photochem.Photobio.A:Chem.,111(1997)205). Most importantly, sunlight-illuminated sunscreen TiO2 particles catalyze DNA damage both in vitro and in human cells (FEBS Letters, 418 (1997)87). These results raise concerns on the overall effects of sunscreens and raise the question on the suitability of photoactive TiO2 as a sunscreen component without further studies. The photocatalytically active nature of these metal oxides necessitates some changes since even the TiO2 specimens currently used in suncreams cause significant DNA strand breaks.

  9. Stereo ENA Imaging of the Ring Current and Multi-point Measurements of Suprathermal Particles and Magnetic Fields by TRIO-CINEMA

    NASA Astrophysics Data System (ADS)

    Lin, R. P.; Sample, J. G.; Immel, T. J.; Lee, D.; Horbury, T. S.; Jin, H.; SEON, J.; Wang, L.; Roelof, E. C.; Lee, E.; Parks, G. K.; Vo, H.

    2012-12-01

    The TRIO (Triplet Ionospheric Observatory) - CINEMA (Cubesat for Ions, Neutrals, Electrons, & Magnetic fields) mission consists of three identical 3-u cubesats to provide high sensitivity, high cadence, stereo measurements of Energetic Neutral Atoms (ENAs) from the Earth's ring current with ~1 keV FWHM energy resolution from ~4 to ~200 keV, as well as multi-point in situ measurements of magnetic fields and suprathermal electrons (~2 -200 keV) and ions (~ 4 -200 keV) in the auroral and ring current precipitation regions in low Earth orbit (LEO). A new Suprathermal Electron, Ion, Neutral (STEIN) instrument, using a 32-pixel silicon semiconductor detector with an electrostatic deflection system to separate ENAs from ions and from electrons below 30 keV, will sweep over most of the sky every 15 s as the spacecraft spins at 4 rpm. In addition, inboard and outboard (on an extendable 1m boom) miniature magnetoresistive sensor magnetometers will provide high cadence 3-axis magnetic field measurements. An S-band transmitter will be used to provide ~8 kbps orbit-average data downlink to the ~11m diameter antenna of the Berkeley Ground Station.The first CINEMA (funded by NSF) is scheduled for launch on August 14, 2012 into a 65 deg. inclination LEO. Two more identical CINEMAs are being developed by Kyung Hee University (KHU) in Korea under the World Class University (WCU) program, for launch in November 2012 into a Sun-synchronous LEO to form TRIO-CINEMA. A fourth CINEMA is being developed for a 2013 launch into LEO. This LEO constellation of nanosatellites will provide unique measurements highly complementary to NASA's RBSP and THEMIS missions. Furthermore, CINEMA's development of miniature particle and magnetic field sensors, and cubesat-size spinning spacecraft may be important for future constellation space missions. Initial results from the first CINEMA will be presented if available.

  10. A Canonical Ensemble Approach to the Fermion/Boson Random Point Processes and Its Applications

    NASA Astrophysics Data System (ADS)

    Tamura, H.; Ito, K. R.

    2006-04-01

    We introduce the boson and the fermion point processes from the elementary quantum mechanical point of view. That is, we consider quantum statistical mechanics of the canonical ensemble for a fixed number of particles which obey Bose-Einstein, Fermi-Dirac statistics, respectively, in a finite volume. Focusing on the distribution of positions of the particles, we have point processes of the fixed number of points in a bounded domain. By taking the thermodynamic limit such that the particle density converges to a finite value, the boson/fermion processes are obtained. This argument is a realization of the equivalence of ensembles, since resulting processes are considered to describe a grand canonical ensemble of points. Random point processes corresponding to para-particles of order two are discussed as an application of the formulation. Statistics of a system of composite particles at zero temperature are also considered as a model of determinantal random point processes.

  11. Constructing Amplitudes from Their Soft Limits

    SciTech Connect

    Boucher-Veronneau, Camille; Larkoski, Andrew J.; /SLAC

    2011-12-09

    The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an (n-1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which 'soft' particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedure and relate it to Britto-Cachazo-Feng-Witten recursion. We show that all tree-level amplitudes in gauge theory and gravity up through seven points can be constructed in this way, as well as certain classes of NMHV gauge-theory amplitudes with any number of external legs. This provides us with a systematic procedure for constructing amplitudes solely from their soft limits.

  12. U{sup BF}(5) to SU{sup BF}(3) shape phase transition in odd nuclei for j=1/2, 3/2, and 5/2 orbits: The role of the odd particle at the critical point

    SciTech Connect

    Alonso, C. E.; Arias, J. M.; Fortunato, L.; Vitturi, A.

    2009-01-15

    We investigate the phase transition in odd nuclei within the Interacting Boson Fermion Model in correspondence with the transition from spherical to stable axially deformed shape. The odd particle is assumed to be moving in the single-particle orbitals with angular momenta j=1/2,3/2,5/2 with a boson-fermion Hamiltonian that leads to the occurrence of the SU{sup BF}(3) boson-fermion symmetry when the boson part approaches the SU(3) condition. Both energy spectra and electromagnetic transitions show characteristic patterns similar to those displayed by the even nuclei at the corresponding critical point. The role of the additional particle in characterizing the properties of the critical points in finite quantal systems is investigated by resorting to the formalism based on the intrinsic frame.

  13. TH-A-19A-07: The Effect of Particle Tracking Step Size Limit On Monte Carlo- Computed LET Spectrum of Therapeutic Proton Beams

    SciTech Connect

    Guan, F; Bronk, L; Kerr, M; Titt, U; Taleei, R; Mirkovic, D; Zhu, X; Grosshans, D; Mohan, R

    2014-06-15

    Purpose: To investigate the effect of charged particle tracking step size limit in the determination of the LET spectrum of therapeutic proton beams using Monte Carlo simulations. Methods: The LET spectra at different depths in a water phantom from a 79.7 MeV spot-scanning proton beam were calculated using Geant4. Five different tracking step limits 0.5 mm, 0.1 mm, 0.05 mm, 0.01 mm and 1 μm were adopted. The field size was set to 10×10 cm{sup 2} on the isocenter plane. A 40×40×6 cm{sup 3} water phantom was modelled as the irradiation target. The voxel size was set to 1×1×0.5 mm{sup 3} to obtain high resolution results. The LET spectra were scored ranging from 0.01 keV/μm to 10{sup 4}keV/μm in the logarithm scale. In addition, the proton energy spectra at different depths were also scored. Results: The LET spectra calculated using different step size limits were compared at four depths along the Bragg curve. At any depths, the spread of the LET spectra increases with the decrease of step size limit. In the dose buildup region (z = 1.9 cm) and in the region proximal to the Bragg peak (z = 3.95 cm), the frequency mean LET does not vary with decreasing step size limit. At Bragg peak (z = 4.75 cm) and in the distal edge (z = 4.85 cm), frequency mean LET decreases with decreasing step size limit. The energy spectrum at any specified depths does not vary with the step size limit. Conclusion: The calculated LET has a spectral distribution rather than a single value at any depths along the Bragg curve and the spread of the computed spectrum depends on the tracking step limit. Incorporating the LET spectrum distribution into the robust IMPT optimization plan may provide more accurate biological dose distribution than using the dose- or fluence-averaged LET. NIH Program Project Grant P01CA021239.

  14. Scattering by Atmospheric Particles: From Aerosols to Clouds with the Point-Spread Function ... using Water, Milk, Plastic Cups, and a Laser Pointer

    NASA Astrophysics Data System (ADS)

    Davis, A. B.

    2015-12-01

    Planetary atmospheres are made primarily of molecules, and their optical properties are well known. They scatter sunlight across the spectrum, but far more potently at shorter wavelengths. Consequently, they redden the Sun as it sets and, at the same time, endow the daytime sky with its characteristic blue hue. There are also microscopic atmospheric particulates that are equally omnipresent because small enough (up to ~10s of microns) to remain lofted for long periods of time. However, in contrast with molecules of the major gases, their concentrations are highly variable in space and time. Their optical properties are also far more interesting. These airborne particles are either solid---hence the word "aerosols"---or liquid, most notably in the form of cloud droplets. Needless to say that both aerosols and clouds have major impacts on the balance of the Earth's climate system. Harder to understand, but nonetheless true, is that their climate impacts are much harder to assess by Earth system modelers than those of greenhouse gases such as CO2. That makes them prime targets of study by multiple approaches, including ground- and space-based remote sensing. To characterize aerosols and clouds quantitatively by optical remote sensing methods, either passive (sunlight-based) or active (laser-based), we need predictive capability for the signals recorded by sensors, whether ground-based, airborne, or carried by satellites. This in turn draws on the physical theory of "radiative transfer" that describes how the light propagates and scatters in the molecular-and-particulate atmosphere. This is a challenge for remote sensing scientists. I will show why by simulating with simple means the point spread function or "PSF" of scattering particulate atmospheres with varying opacity, thus covering tabletop analogs of the pristine air, the background aerosol, all the way to optically thick cloudy airmasses. I will also show PSF measurements of real clouds over New Mexico and

  15. A Stringent Limit on the Warm Dark Matter Particle Masses from the Abundance of z = 6 Galaxies in the Hubble Frontier Fields

    NASA Astrophysics Data System (ADS)

    Menci, N.; Grazian, A.; Castellano, M.; Sanchez, N. G.

    2016-07-01

    We show that the recently measured UV luminosity functions of ultra-faint lensed galaxies at z ≈ 6 in the Hubble Frontier Fields provide an unprecedented probe for the mass m X of the warm dark matter (WDM) candidates independent of baryonic physics. Comparing the measured abundance of the faintest galaxies with the maximum number density of dark matter halos in WDM cosmologies sets a robust limit of m X ≥ 2.9 keV for the mass of thermal relic WDM particles at a 1σ confidence level, m X ≥ 2.4 keV at 2σ, and m X ≥ 2.1 keV at 3σ. These constraints are independent of the baryonic physics involved in galaxy formation and constitute the tightest constraints on WDM particle mass derived to date. We discuss the impact of our results on the production mechanism of sterile neutrinos. In particular, if sterile neutrinos are responsible for the 3.5 keV line reported in observations of X-ray clusters, our results firmly rule out the Dodelson–Widrow production mechanism and yield m sterile ≳ 6.1 keV for sterile neutrinos produced via the Shi–Fuller mechanism.

  16. An overview on limitations of TiO2-based particles for photocatalytic degradation of organic pollutants and the corresponding countermeasures.

    PubMed

    Dong, Haoran; Zeng, Guangming; Tang, Lin; Fan, Changzheng; Zhang, Chang; He, Xiaoxiao; He, Yan

    2015-08-01

    The pollutants classified as "persistent organic pollutants (POPs)", are being subject to high concern among the scientific community due to their persistence in the environment. TiO2-based photocatalytic process has shown a great potential as a low-cost, environmentally friendly and sustainable treatment technology to remove POPs in sewage to overcome the shortcomings of the conventional technologies. However, this technology suffers from some main technical barriers that impede its commercialization, i.e., the inefficient exploitation of visible light, low adsorption capacity for hydrophobic contaminants, uniform distribution in aqueous suspension and post-recovery of the TiO2 particles after water treatment. To improve the photocatalytic efficiency of TiO2, many studies have been carried out with the aim of eliminating the limitations mentioned above. This review summarizes the recently developed countermeasures for improving the performance of TiO2-based photocatalytic degradation of organic pollutants with respect to the visible-light photocatalytic activity, adsorption capacity, stability and separability. The performance of various TiO2-based photocatalytic processes for POPs degradation and the underlying mechanisms were summarized and discussed. The future research needs for TiO2-based technology are suggested accordingly. This review will significantly improve our understanding of the process of photocatalytic degradation of POPs by TiO2-based particles and provide useful information to scientists and engineers who work in this field. PMID:25980914

  17. Particle therapy

    SciTech Connect

    Raju, M.R.

    1993-09-01

    Particle therapy has a long history. The experimentation with particles for their therapeutic application got started soon after they were produced in the laboratory. Physicists played a major role in proposing the potential applications in radiotherapy as well as in the development of particle therapy. A brief review of the current status of particle radiotherapy with some historical perspective is presented and specific contributions made by physicists will be pointed out wherever appropriate. The rationale of using particles in cancer treatment is to reduce the treatment volume to the target volume by using precise dose distributions in three dimensions by using particles such as protons and to improve the differential effects on tumors compared to normal tissues by using high-LET radiations such as neutrons. Pions and heavy ions combine the above two characteristics.

  18. Supplemental development document for effluent-limitations guidelines and standards for the leather tanning and finishing. Point source category. Final report

    SciTech Connect

    Gile, R.R.

    1988-02-01

    EPA amended 40 CFR Part 425 which limits effluent discharges to waters of the U.S. and the introduction of pollutants into publicly owned treatment works (POTW) by existing and new sources engaged in leather tanning and finishing. EPA agreed to promulgate these amendments in a settlement agreement with the Tanners' Council of America, Inc. The agreement settles a dispute between the Council and EPA that was the subject of a petition for judicial review of the final leather tanning and finishing regulation promulgated by EPA on November 23, 1982 (47 FR 52848). The document describes the technical development of these amendments which include: (1) a new analytical method for the determination of the presence of sulfide in wastewater for use in the Hair Save or Pulp, Non-Chrome Tan, Retan-Wet Finish Subcategory; (2) clarification of procedural requirements for POTW to follow in determining whether sulfide pretreatment standards are applicable; (3) revisions to certain of the effluent limitations guidelines for best practicable control technology currently available (BPT) and new source performance standards (NSPS).

  19. Intratumoral spread of wild-type adenovirus is limited after local injection of human xenograft tumors: virus persists and spreads systemically at late time points.

    PubMed

    Sauthoff, Harald; Hu, Jing; Maca, Cielo; Goldman, Michael; Heitner, Sheila; Yee, Herman; Pipiya, Teona; Rom, William N; Hay, John G

    2003-03-20

    Oncolytic replicating adenoviruses are a promising new modality for the treatment of cancer. Despite the assumed biologic advantage of continued viral replication and spread from infected to uninfected cancer cells, early clinical trials demonstrate that the efficacy of current vectors is limited. In xenograft tumor models using immune-incompetent mice, wild-type adenovirus is also rarely able to eradicate established tumors. This suggests that innate immune mechanisms may clear the virus or that barriers within the tumor prevent viral spread. The aim of this study was to evaluate the kinetics of viral distribution and spread after intratumoral injection of virus in a human tumor xenograft model. After intratumoral injection of wild-type virus, high levels of titratable virus persisted within the xenograft tumors for at least 8 weeks. Virus distribution within the tumors as determined by immunohistochemistry was patchy, and virus-infected cells appeared to be flanked by tumor necrosis and connective tissue. The close proximity of virus-infected cells to the tumor-supporting structure, which is of murine origin, was clearly demonstrated using a DNA probe that specifically hybridizes to the B1 murine DNA repeat. Importantly, although virus was cleared from the circulation 6 hr after intratumoral injection, after 4 weeks systemic spread of virus was detected. In addition, vessels of infected tumors were surrounded by necrosis and an advancing rim of virus-infected tumor cells, suggesting reinfection of the xenograft tumor through the vasculature. These data suggest that human adenoviral spread within tumor xenografts is impaired by murine tumor-supporting structures. In addition, there is evidence for continued viral replication within the tumor, with subsequent systemic dissemination and reinfection of tumors via the tumor vasculature. Despite the limitations of immune-incompetent models, an understanding of the interactions between the virus and the tumor

  20. Point-Force Energy Coupling

    NASA Astrophysics Data System (ADS)

    Burton, Tristan; Squires, Kyle

    2005-11-01

    Fully resolved simulations of particle-laden turbulent flows are computationally expensive even with a single particle. Therefore, simulations of flows with realistic numbers of particles typically treat the disperse phase as point-particles and models are used to account for the interaction between the phases. The particle trajectories are determined using a Lagrangian particle equation of motion that accounts for the fluid forces. The effect of the particulate phase on the fluid is included using point-force momentum coupling, where the opposite of the force applied to each particle by the fluid is distributed back to fluid grid points in a local region. In this work, we perform direct numerical simulation (DNS) of a particle moving at a prescribed constant or time-dependent velocity through a stationary fluid, and use the resulting force history in a corresponding point-force simulation to study point-force energy coupling. The energy input from the moving particle and the fluid dissipation in the DNS are compared to corresponding quantities in the unresolved calculation. A range of particle Reynolds numbers and ratios of the particle diameter to the unresolved grid spacing are considered to determine the conditions under which point-force momentum coupling provides accurate energy coupling.

  1. Single-Particle Tracking Shows that a Point Mutation in the Carnivore Parvovirus Capsid Switches Binding between Host-Specific Transferrin Receptors.

    PubMed

    Lee, Donald W; Allison, Andrew B; Bacon, Kaitlyn B; Parrish, Colin R; Daniel, Susan

    2016-05-01

    Determining how viruses infect new hosts via receptor-binding mechanisms is important for understanding virus emergence. We studied the binding kinetics of canine parvovirus (CPV) variants isolated from raccoons-a newly recognized CPV host-to different carnivore transferrin receptors (TfRs) using single-particle tracking. Our data suggest that CPV may utilize adhesion-strengthening mechanisms during TfR binding and that a single mutation in the viral capsid at VP2 position 300 can profoundly alter receptor binding and infectivity. PMID:26889026

  2. Current limiters

    SciTech Connect

    Loescher, D.H.; Noren, K.

    1996-09-01

    The current that flows between the electrical test equipment and the nuclear explosive must be limited to safe levels during electrical tests conducted on nuclear explosives at the DOE Pantex facility. The safest way to limit the current is to use batteries that can provide only acceptably low current into a short circuit; unfortunately this is not always possible. When it is not possible, current limiters, along with other design features, are used to limit the current. Three types of current limiters, the fuse blower, the resistor limiter, and the MOSFET-pass-transistor limiters, are used extensively in Pantex test equipment. Detailed failure mode and effects analyses were conducted on these limiters. Two other types of limiters were also analyzed. It was found that there is no best type of limiter that should be used in all applications. The fuse blower has advantages when many circuits must be monitored, a low insertion voltage drop is important, and size and weight must be kept low. However, this limiter has many failure modes that can lead to the loss of over current protection. The resistor limiter is simple and inexpensive, but is normally usable only on circuits for which the nominal current is less than a few tens of milliamperes. The MOSFET limiter can be used on high current circuits, but it has a number of single point failure modes that can lead to a loss of protective action. Because bad component placement or poor wire routing can defeat any limiter, placement and routing must be designed carefully and documented thoroughly.

  3. Kinetic interfaces of patchy particles

    NASA Astrophysics Data System (ADS)

    Araújo, N. A. M.; Dias, C. S.; Telo da Gama, M. M.

    2015-05-01

    We study the irreversible adsorption of patchy particles on substrates in the limit of advective mass transport. Recent numerical results show that the interface roughening depends strongly on the particle attributes, such as, patch-patch correlations, bond flexibility and strength of the interactions, uncovering new absorbing phase transitions. Here, we revisit these results and discuss in detail the transitions. In particular, we present new evidence that the tricritical point, observed in systems of particles with flexible patches, is in the tricritical directed percolation universality class. A scaling analysis of the time evolution of the correlation length for the aggregation of patchy particles with distinct bonding energies confirms that the critical regime is in the Kardar-Parisi-Zhang with quenched disorder universality class.

  4. Kinetic interfaces of patchy particles.

    PubMed

    Araújo, N A M; Dias, C S; Telo da Gama, M M

    2015-05-20

    We study the irreversible adsorption of patchy particles on substrates in the limit of advective mass transport. Recent numerical results show that the interface roughening depends strongly on the particle attributes, such as, patch-patch correlations, bond flexibility and strength of the interactions, uncovering new absorbing phase transitions. Here, we revisit these results and discuss in detail the transitions. In particular, we present new evidence that the tricritical point, observed in systems of particles with flexible patches, is in the tricritical directed percolation universality class. A scaling analysis of the time evolution of the correlation length for the aggregation of patchy particles with distinct bonding energies confirms that the critical regime is in the Kardar-Parisi-Zhang with quenched disorder universality class. PMID:25923051

  5. Non-Abelian monopole in the parameter space of point-like interactions

    NASA Astrophysics Data System (ADS)

    Ohya, Satoshi

    2014-12-01

    We study non-Abelian geometric phase in N = 2 supersymmetric quantum mechanics for a free particle on a circle with two point-like interactions at antipodal points. We show that non-Abelian Berry's connection is that of SU(2) magnetic monopole discovered by Moody, Shapere and Wilczek in the context of adiabatic decoupling limit of diatomic molecule.

  6. On Limits

    NASA Technical Reports Server (NTRS)

    Holzmann, Gerard J.

    2008-01-01

    In the last 3 decades or so, the size of systems we have been able to verify formally with automated tools has increased dramatically. At each point in this development, we encountered a different set of limits -- many of which we were eventually able to overcome. Today, we may have reached some limits that may be much harder to conquer. The problem I will discuss is the following: given a hypothetical machine with infinite memory that is seamlessly shared among infinitely many CPUs (or CPU cores), what is the largest problem size that we could solve?

  7. Splitting the Cartesian point

    SciTech Connect

    Blodwell, J.F.

    1987-10-01

    It is argued that the point structure of space and time must be constructed from the primitive extensional character of space and time. A procedure for doing this is laid down and applied to one-dimensional and two-dimensional systems of abstract extensions. Topological and metrical properties of the constructed point systems, which differ nontrivially from the usual R and R/sup 2/ models, are examined. Briefly, constructed points are associated with directions and the Cartesian point is split. In one-dimension each point splits into a point pair compatible with the linear ordering. An application to one-dimensional particle motion is given, with the result that natural topological assumptions force the number of left point, right point transitions to remain locally finite in a continuous motion. In general, Cartesian points are seen to correspond to certain filters on a suitable Boolean algebra. Constructed points correspond to ultrafilters. Thus, point construction gives a natural refinement of the Cartesian systems.

  8. Particle blender

    DOEpatents

    Willey, Melvin G.

    1981-01-01

    An infinite blender that achieves a homogeneous mixture of fuel microspheres is provided. Blending is accomplished by directing respective groups of desired particles onto the apex of a stationary coaxial cone. The particles progress downward over the cone surface and deposit in a space at the base of the cone that is described by a flexible band provided with a wide portion traversing and in continuous contact with the circumference of the cone base and extending upwardly therefrom. The band, being attached to the cone at a narrow inner end thereof, causes the cone to rotate on its arbor when the band is subsequently pulled onto a take-up spool. As a point at the end of the wide portion of the band passes the point where it is tangent to the cone, the blended particles are released into a delivery tube leading directly into a mold, and a plate mounted on the lower portion of the cone and positioned between the end of the wide portion of the band and the cone assures release of the particles only at the tangent point.

  9. Sustainment of Fine Particle Cloud by Means of Time-Averaged Particle Driving Force in Plasmas

    SciTech Connect

    Gohda, Takuma; Iizuka, Satoru

    2008-09-07

    We have succeeded in sustaining fine particle cloud by using a time-averaged particle driving (TAPD) method in the RF discharge plasma. The particles feel only time-averaged force when the period of pulses applied to those point-electrodes is shorter than the particle response time. The particles are transported to a middle point between two point-electrodes.

  10. Particle Accelerators Test Cosmological Theory.

    ERIC Educational Resources Information Center

    Schramm, David N.; Steigman, Gary

    1988-01-01

    Discusses the symbiotic relationship of cosmology and elementary-particle physics. Presents a brief overview of particle physics. Explains how cosmological considerations set limits on the number of types of elementary particles. (RT)

  11. Oil point pressure of Indian almond kernels

    NASA Astrophysics Data System (ADS)

    Aregbesola, O.; Olatunde, G.; Esuola, S.; Owolarafe, O.

    2012-07-01

    The effect of preprocessing conditions such as moisture content, heating temperature, heating time and particle size on oil point pressure of Indian almond kernel was investigated. Results showed that oil point pressure was significantly (P < 0.05) affected by above mentioned parameters. It was also observed that oil point pressure reduced with increase in heating temperature and heating time for both coarse and fine particles. Furthermore, an increase in moisture content resulted in increased oil point pressure for coarse particles while there was a reduction in oil point pressure with increase in moisture content for fine particles.

  12. Tipping Point

    MedlinePlus Videos and Cool Tools

    ... Tipping Point by CPSC Blogger September 22 appliance child Childproofing CPSC danger death electrical fall furniture head ... TV falls with about the same force as child falling from the third story of a building. ...

  13. Triple Point Topological Metals

    NASA Astrophysics Data System (ADS)

    Zhu, Ziming; Winkler, Georg W.; Wu, QuanSheng; Li, Ju; Soluyanov, Alexey A.

    2016-07-01

    Topologically protected fermionic quasiparticles appear in metals, where band degeneracies occur at the Fermi level, dictated by the band structure topology. While in some metals these quasiparticles are direct analogues of elementary fermionic particles of the relativistic quantum field theory, other metals can have symmetries that give rise to quasiparticles, fundamentally different from those known in high-energy physics. Here, we report on a new type of topological quasiparticles—triple point fermions—realized in metals with symmorphic crystal structure, which host crossings of three bands in the vicinity of the Fermi level protected by point group symmetries. We find two topologically different types of triple point fermions, both distinct from any other topological quasiparticles reported to date. We provide examples of existing materials that host triple point fermions of both types and discuss a variety of physical phenomena associated with these quasiparticles, such as the occurrence of topological surface Fermi arcs, transport anomalies, and topological Lifshitz transitions.

  14. Astrophysical data on 5 eV to 1 keV radiation from the radiative decay of fundamental particles - Current limits and prospects for improvement

    NASA Technical Reports Server (NTRS)

    Bowyer, Stuart; Malina, Roger F.

    1986-01-01

    Line emission from the decay of fundamental particles, integrated over cosmological distances, can give rise to detectable spectral features in the diffuse astronomical background between 5 eV and 1 keV. Spectroscopic observations may allow these features to be separated from line emission from the numerous local sources of radiation. The current observational status and existing evidence for such features are reviewed. No definitive detections of nongalactic line features have been made. Several local sources of background mask the features at many wavelengths and confuse the interpretation of the data. No systematic spectral observations have been carried out to date. Upcoming experiments which can be expected to provide significantly better constraints on the presence of spectral features in the diffuse background from 5 eV to 1 keV are reviewed.

  15. Visualization of charged particle traversals in cells

    SciTech Connect

    Metting, N.F.; Braby, L.A.

    1997-12-31

    This research addresses the early events that occur in the cell, and particularly in the cell nucleus, after passage of a charged particle. The authors present an assay system which locates the path of a charged particle through the cell nucleus, and speculate that this will be a valuable tool to define a start point for cell signaling of DNA repair processes, as well as signaling of cell-cycle checkpoint proteins. This study of the biological effects of low doses of high LET particles stems from the need to understand molecular mechanisms of long term health effects originating from the heavy particle component of galactic cosmic rays, a major concern in extended space missions. In the deep-space environment each target cell would be traversed only once a month, on average, by a heavy charged particle (1); therefore it was important to use very low particle fluences for subsequent analysis and understanding of resulting measurements. The Single-Cell/Single-particle Irradiator at PNNL was used to deliver particles from an electrostatic accelerator, and thus eliminate most of the experimental variability in the exposure of cells to high LET radiation. The number of tracks through each cell can be specified, rather than the random number obtained with conventional irradiation. Irradiation can be limited to a specified portion of the cell, and the variation in stopping power of the particles as they enter the cell can be minimized.

  16. The QCD Phase Diagram: Large Nc, Quarkyonic Matter and the Triple Point

    SciTech Connect

    McLerran L.

    2010-01-31

    I discuss the phase diagram of QCD in the large N_c limit. Quarkyonic Matter is described. The properties of QCD matter as measured in the abundance of produced particles are shown to be consistent with this phase diagram. A possible triple point of Hadronic Mater, Deconfined Matter and Quarkyonic matter is shown to explain various behaviors of ratios of particles abundances seen in CERN fixed target experiments.

  17. Implicit frictional-contact model for soft particle systems

    NASA Astrophysics Data System (ADS)

    Nezamabadi, Saeid; Radjai, Farhang; Averseng, Julien; Delenne, Jean-Yves

    2015-10-01

    We introduce a novel numerical approach for the simulation of soft particles interacting via frictional contacts. This approach is based on an implicit formulation of the Material Point Method, allowing for large particle deformations, combined with the Contact Dynamics method for the treatment of unilateral frictional contacts between particles. This approach is both precise due to the treatment of contacts with no regularization and artificial damping parameters, and robust due to implicit time integration of both bulk degrees of freedom and relative contact velocities at the nodes representing the contact points. By construction, our algorithm is capable of handling arbitrary particle shapes and deformations. We illustrate this approach by two simple 2D examples: a Hertz contact and a rolling particle on an inclined plane. We also investigate the compaction of a packing of circular particles up to a solid fraction well above the jamming limit of hard particles. We find that, for the same level of deformation, the solid fraction in a packing of frictional particles is above that of a packing of frictionless particles as a result of larger particle shape change.

  18. Ergodic Distribution of Trapped Charged Particles in Coulomb Field

    NASA Astrophysics Data System (ADS)

    Krasovsky, Victor L.

    2016-03-01

    Spatially limited motion of electrons after instantaneous appearance of an external positive point-like charge is considered. The trapped particle distribution function averaged over periods of the motion is determined. Contribution of the electrons to the total perturbation of plasma density is calculated. It is shown that the trapped particle contribution dominates at small distances from the charge, whereas it is negligible at large distances. The developed approach and expressions for the trapped particle number density are applicable to studies of nonlinear screening of charged bodies in collisionless plasmas.

  19. Some Annihilating Particle Systems.

    NASA Astrophysics Data System (ADS)

    Balding, David

    Available from UMI in association with The British Library. Requires signed TDF. Systems of annihilating and coalescing particles on both infinite and periodic one-dimensional state spaces are studied. These systems have various applications in the physical sciences, in particular they are useful as simple models of diffusion-limited reactions. A unified approach to computing properties of the systems using duality methods is presented and it is shown that many results in the scientific literature, derived using diverse techniques, are readily obtained in this general framework. The transition distributions of the processes with arbitrary initial configurations are characterized in terms of two-particle annihilation processes. Further, a concise expression for the distribution of the cardinality of the processes with finite initial configurations is given and particular cases of interest from the applications perspective are described in detail. Asymptotic site occupancies, previously known for certain classes of initial configurations, are derived for all spatially stationary configurations. The asymptotic spatial structure is described for many cases by showing convergence to point processes whose properties are given.

  20. Implementing molecular dynamics on hybrid high performance computers - Particle-particle particle-mesh

    NASA Astrophysics Data System (ADS)

    Brown, W. Michael; Kohlmeyer, Axel; Plimpton, Steven J.; Tharrington, Arnold N.

    2012-03-01

    The use of accelerators such as graphics processing units (GPUs) has become popular in scientific computing applications due to their low cost, impressive floating-point capabilities, high memory bandwidth, and low electrical power requirements. Hybrid high-performance computers, machines with nodes containing more than one type of floating-point processor (e.g. CPU and GPU), are now becoming more prevalent due to these advantages. In this paper, we present a continuation of previous work implementing algorithms for using accelerators into the LAMMPS molecular dynamics software for distributed memory parallel hybrid machines. In our previous work, we focused on acceleration for short-range models with an approach intended to harness the processing power of both the accelerator and (multi-core) CPUs. To augment the existing implementations, we present an efficient implementation of long-range electrostatic force calculation for molecular dynamics. Specifically, we present an implementation of the particle-particle particle-mesh method based on the work by Harvey and De Fabritiis. We present benchmark results on the Keeneland InfiniBand GPU cluster. We provide a performance comparison of the same kernels compiled with both CUDA and OpenCL. We discuss limitations to parallel efficiency and future directions for improving performance on hybrid or heterogeneous computers.

  1. Implementing Molecular Dynamics on Hybrid High Performance Computers - Particle-Particle Particle-Mesh

    SciTech Connect

    Brown, W Michael; Kohlmeyer, Axel; Plimpton, Steven J; Tharrington, Arnold N

    2012-01-01

    The use of accelerators such as graphics processing units (GPUs) has become popular in scientific computing applications due to their low cost, impressive floating-point capabilities, high memory bandwidth, and low electrical power requirements. Hybrid high-performance computers, machines with nodes containing more than one type of floating-point processor (e.g. CPU and GPU), are now becoming more prevalent due to these advantages. In this paper, we present a continuation of previous work implementing algorithms for using accelerators into the LAMMPS molecular dynamics software for distributed memory parallel hybrid machines. In our previous work, we focused on acceleration for short-range models with an approach intended to harness the processing power of both the accelerator and (multi-core) CPUs. To augment the existing implementations, we present an efficient implementation of long-range electrostatic force calculation for molecular dynamics. Specifically, we present an implementation of the particle-particle particle-mesh method based on the work by Harvey and De Fabritiis. We present benchmark results on the Keeneland InfiniBand GPU cluster. We provide a performance comparison of the same kernels compiled with both CUDA and OpenCL. We discuss limitations to parallel efficiency and future directions for improving performance on hybrid or heterogeneous computers.

  2. Magnetic particle-scanning for ultrasensitive immunodetection on-chip.

    PubMed

    Cornaglia, Matteo; Trouillon, Raphaël; Tekin, H Cumhur; Lehnert, Thomas; Gijs, Martin A M

    2014-08-19

    We describe the concept of magnetic particle-scanning for on-chip detection of biomolecules: a magnetic particle, carrying a low number of antigens (Ag's) (down to a single molecule), is transported by hydrodynamic forces and is subjected to successive stochastic reorientations in an engineered magnetic energy landscape. The latter consists of a pattern of substrate-bound small magnetic particles that are functionalized with antibodies (Ab's). Subsequationuent counting of the captured Ag-carrying particles provides the detection signal. The magnetic particle-scanning principle is investigated in a custom-built magneto-microfluidic chip and theoretically described by a random walk-based model, in which the trajectory of the contact point between an Ag-carrying particle and the small magnetic particle pattern is described by stochastic moves over the surface of the mobile particle, until this point coincides with the position of an Ag, resulting in the binding of the particle. This model explains the particular behavior of previously reported experimental dose-response curves obtained for two different ligand-receptor systems (biotin/streptavidin and TNF-α) over a wide range of concentrations. Our model shows that magnetic particle-scanning results in a very high probability of immunocomplex formation for very low Ag concentrations, leading to an extremely low limit of detection, down to the single molecule-per-particle level. When compared to other types of magnetic particle-based surface coverage assays, our strategy was found to offer a wider dynamic range (>8 orders of magnitude), as the system does not saturate for concentrations as high as 10(11) Ag molecules in a 5 μL drop. Furthermore, by emphasizing the importance of maximizing the encounter probability between the Ag and the Ab to improve sensitivity, our model also contributes to explaining the behavior of other particle-based heterogeneous immunoassays. PMID:25072276

  3. Abnormal behaviors detection using particle motion model

    NASA Astrophysics Data System (ADS)

    Chen, Yutao; Zhang, Hong; Cheng, Feiyang; Yuan, Ding; You, Yuhu

    2015-03-01

    Human abnormal behaviors detection is one of the most challenging tasks in the video surveillance for the public security control. Interaction Energy Potential model is an effective and competitive method published recently to detect abnormal behaviors, but their model of abnormal behaviors is not accurate enough, so it has some limitations. In order to solve this problem, we propose a novel Particle Motion model. Firstly, we extract the foreground to improve the accuracy of interest points detection since the complex background usually degrade the effectiveness of interest points detection largely. Secondly, we detect the interest points using the graphics features. Here, the movement of each human target can be represented by the movements of detected interest points of the target. Then, we track these interest points in videos to record their positions and velocities. In this way, the velocity angles, position angles and distance between each two points can be calculated. Finally, we proposed a Particle Motion model to calculate the eigenvalue of each frame. An adaptive threshold method is proposed to detect abnormal behaviors. Experimental results on the BEHAVE dataset and online videos show that our method could detect fight and robbery events effectively and has a promising performance.

  4. Compound nucleus decay: Comparison between saddle point and scission point barriers

    SciTech Connect

    Santos, T. J.; Carlson, B. V.

    2014-11-11

    One of the principal characteristics of nuclear multifragmentation is the emission of complex fragments of intermediate mass. An extension of the statistical multifragmentation model has been developed, in which the process can be interpreted as the near simultaneous limit of a series of sequential binary decays. In this extension, intermediate mass fragment emissions are described by expressions almost identical to those of light particle emission. At lower temperatures, similar expressions have been shown to furnish a good description of very light intermediate mass fragment emission but not of the emission of heavier fragments, which seems to be determined by the transition density at the saddle-point rather than at the scission point. Here, we wish to compare these different formulations of intermediate fragmment emission and analyze the extent to which they remain distinguishable at high excitation energy.

  5. Radiation from charges in the continuum limit

    SciTech Connect

    Ianconescu, Reuven

    2013-06-15

    It is known that an accelerating charge radiates according to Larmor formula. On the other hand, any DC current following a curvilinear path, consists of accelerating charges, but in such case the radiated power is 0. The scope of this paper is to analyze and quantify how a system of charges goes from a radiating state to a non radiating state when the charges distribution goes to the continuum limit. Understanding this is important from the theoretical point of view and the results of this work are applicable to particle accelerator, cyclotron and other high energy devices.

  6. Load management strategy for Particle-In-Cell simulations in high energy particle acceleration

    NASA Astrophysics Data System (ADS)

    Beck, A.; Frederiksen, J. T.; Dérouillat, J.

    2016-09-01

    In the wake of the intense effort made for the experimental CILEX project, numerical simulation campaigns have been carried out in order to finalize the design of the facility and to identify optimal laser and plasma parameters. These simulations bring, of course, important insight into the fundamental physics at play. As a by-product, they also characterize the quality of our theoretical and numerical models. In this paper, we compare the results given by different codes and point out algorithmic limitations both in terms of physical accuracy and computational performances. These limitations are illustrated in the context of electron laser wakefield acceleration (LWFA). The main limitation we identify in state-of-the-art Particle-In-Cell (PIC) codes is computational load imbalance. We propose an innovative algorithm to deal with this specific issue as well as milestones towards a modern, accurate high-performance PIC code for high energy particle acceleration.

  7. Beaming of Particles and Synchrotron Radiation in Relativistic Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Kagan, Daniel; Nakar, Ehud; Piran, Tsvi

    2016-08-01

    Relativistic reconnection has been invoked as a mechanism for particle acceleration in numerous astrophysical systems. According to idealized analytical models, reconnection produces a bulk relativistic outflow emerging from the reconnection sites (X-points). The resulting radiation is therefore highly beamed. Using two-dimensional particle-in-cell simulations, we investigate particle and radiation beaming, finding a very different picture. Instead of having a relativistic average bulk motion with an isotropic electron velocity distribution in its rest frame, we find that the bulk motion of the particles in X-points is similar to their Lorentz factor γ, and the particles are beamed within ˜ 5/γ . On the way from the X-point to the magnetic islands, particles turn in the magnetic field, forming a fan confined to the current sheet. Once they reach the islands they isotropize after completing a full Larmor gyration and their radiation is no longer strongly beamed. The radiation pattern at a given frequency depends on where the corresponding emitting electrons radiate their energy. Lower-energy particles that cool slowly spend most of their time in the islands and their radiation is not highly beamed. Only particles that quickly cool at the edge of the X-points generate a highly beamed fan-like radiation pattern. The radiation emerging from these fast cooling particles is above the burn-off limit (˜100 MeV in the overall rest frame of the reconnecting plasma). This has significant implications for models of gamma-ray bursts and active galactic nuclei that invoke beaming in that frame at much lower energies.

  8. Beaming of Particles and Synchrotron Radiation in Relativistic Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Kagan, Daniel; Nakar, Ehud; Piran, Tsvi

    2016-08-01

    Relativistic reconnection has been invoked as a mechanism for particle acceleration in numerous astrophysical systems. According to idealized analytical models, reconnection produces a bulk relativistic outflow emerging from the reconnection sites (X-points). The resulting radiation is therefore highly beamed. Using two-dimensional particle-in-cell simulations, we investigate particle and radiation beaming, finding a very different picture. Instead of having a relativistic average bulk motion with an isotropic electron velocity distribution in its rest frame, we find that the bulk motion of the particles in X-points is similar to their Lorentz factor γ, and the particles are beamed within ∼ 5/γ . On the way from the X-point to the magnetic islands, particles turn in the magnetic field, forming a fan confined to the current sheet. Once they reach the islands they isotropize after completing a full Larmor gyration and their radiation is no longer strongly beamed. The radiation pattern at a given frequency depends on where the corresponding emitting electrons radiate their energy. Lower-energy particles that cool slowly spend most of their time in the islands and their radiation is not highly beamed. Only particles that quickly cool at the edge of the X-points generate a highly beamed fan-like radiation pattern. The radiation emerging from these fast cooling particles is above the burn-off limit (∼100 MeV in the overall rest frame of the reconnecting plasma). This has significant implications for models of gamma-ray bursts and active galactic nuclei that invoke beaming in that frame at much lower energies.

  9. An upper limit on the neutrino rest mass.

    NASA Technical Reports Server (NTRS)

    Cowsik, R.; Mcclelland, J.

    1972-01-01

    It is pointed out that the measurement of the deceleration parameter by Sandage (1972) implies an upper limit of a few tens of electron volts on the sum of the masses of all the possible light, stable particles that interact only weakly. In the discussion of the problem, it is assumed that the universe is expanding from an initially hot and condensed state as envisaged in the 'big-bang' theories.

  10. Pumped limiter development on ISX

    SciTech Connect

    Mioduszewski, P.K.; Edmonds, P.H.; Sheffield, J.

    1981-01-01

    Pumped limiter configurations are being suggested for FED and INTOR for helium ash exhaust and fuel particle control. The goal of the pump limiter studies in ISX is the selection of the most promising concept and its evaluation in the ISX-C device under the following conditions: (1) quasi steady state operation (less than or equal to 30s), (2) high edge power densities, and (3) particle control by means of mechanical devices. We are considering various options, including particle scraper and ballistic particle collection concepts as well as the current FED design. In ISX-B we will test a full-size pump limiter and directly compare the heat removal and particle control capabilities with a bundle divertor. In ISX-C the steady state operation characteristics of pump limiters will be explored.

  11. Extended Automatic Pointing Assistive Program--A Pointing Assistance Program to Help People with Developmental Disabilities Improve Their Pointing Efficiency

    ERIC Educational Resources Information Center

    Shih, Ching-Hsiang; Li, Chia-Chun; Shih, Ching-Tien; Lin, Kun-Tsan; Lo, Ching-Shui

    2010-01-01

    The latest research adopted software technology to improve pointing performance is through an Automatic Pointing Assistive Program (APAP). However, APAP has some limitations. This study evaluated whether two children with developmental disabilities would be able to improve their pointing performance through an Extended Automatic Pointing Assistive…

  12. Initial ALT-I pump limiter studies on TEXOR

    SciTech Connect

    Pontau, A.E.; Guthrie, S.E.; Malinowski, M.E.; Ver Berkmoes, A.A.; Whitley, J.B.; McDonald, J.M.; Watson, R.D.; Gauster, W.B.; Campbell, G.A.; Goebel, D.M.

    1984-05-01

    The ALT-I pump limiter has been used to control the fueling and recycling characteristics of TEXTOR during stable, reproducible tokamak discharges. The module has been operated in three modes: (1) Normal Limiter, with no particle collection, (2) Particle Scoop, with a maximum approx. 2 x 10/sup -3/ torr pressure rise in the 700 liter unpumped collection chamber, and (3) Pump Limiter, with up to approx. 10,000 1/s pumping speed and particle removal rates of up to 6 x 10/sup 20//s. In a comparison of operation in modes (1) and (3) using identical gas fueling programs, the total core electron number decreased by as much as 50%. The effective TEXTOR particle confinement time, tau/sub p/* = tau/sub p//(1-R), was decreased by a similar ratio. Within the throat region, during typical operation, electron densities and temperatures were 6 x 10/sup 11/ to 2 x 10/sup 12//cm/sup 3/ and 15 to 30 eV. These conditions are representative of an operating regime in which there is high reionization of neutrals, but no change in incoming plasma parameters in the throat region. Energetic particles near the deflector plate were observed. During a gradual insertion of TiC-coated ALT-I beyond the stainless steel TEXTOR main limiters, the density of Ti in the plasma increased to a level similar to those of Cr and Fe. The gas injection fueling efficiency while puffing hydrogen directly into the plasma at the pump limiter tangency point was measured to be > 0.9. These results are discussed in conjunction with measurements of particle flows within ALT-I and other plasma diagnostics to characterize pump limiter operation on TEXTOR.

  13. One-dimensional gravity in infinite point distributions.

    PubMed

    Gabrielli, A; Joyce, M; Sicard, F

    2009-10-01

    The dynamics of infinite asymptotically uniform distributions of purely self-gravitating particles in one spatial dimension provides a simple and interesting toy model for the analogous three dimensional problem treated in cosmology. In this paper we focus on a limitation of such models as they have been treated so far in the literature: the force, as it has been specified, is well defined in infinite point distributions only if there is a centre of symmetry (i.e., the definition requires explicitly the breaking of statistical translational invariance). The problem arises because naive background subtraction (due to expansion, or by "Jeans swindle" for the static case), applied as in three dimensions, leaves an unregulated contribution to the force due to surface mass fluctuations. Following a discussion by Kiessling of the Jeans swindle in three dimensions, we show that the problem may be resolved by defining the force in infinite point distributions as the limit of an exponentially screened pair interaction. We show explicitly that this prescription gives a well defined (finite) force acting on particles in a class of perturbed infinite lattices, which are the point processes relevant to cosmological N -body simulations. For identical particles the dynamics of the simplest toy model (without expansion) is equivalent to that of an infinite set of points with inverted harmonic oscillator potentials which bounce elastically when they collide. We discuss and compare with previous results in the literature and present new results for the specific case of this simplest (static) model starting from "shuffled lattice" initial conditions. These show qualitative properties of the evolution (notably its "self-similarity") like those in the analogous simulations in three dimensions, which in turn resemble those in the expanding universe. PMID:19905274

  14. On the Newtonian limit of metric f( R) gravity

    NASA Astrophysics Data System (ADS)

    Schellstede, Gerold Oltman

    2016-09-01

    The quasi-Newtonian limit for arbitrary gravitational theories of the f( R) class is considered. It is shown that only a subclass of these theories have such a limit. The approximate field equation and equations of motion are calculated and discussed. Moreover, the general solutions of the approximate field equation is investigated where especially solutions for point particles are focused. We found that the approximate field equation is in general of fourth-order with a source term which depends not only on the mass density but also on its Laplaceian.

  15. On limit and limit setting.

    PubMed

    Gorney, J E

    1994-01-01

    This article investigates the role of limit and limit setting within the psychoanalytic situation. Limit is understood to be a boundary between self and others, established as an interactional dimension of experience. Disorders of limit are here understood within the context of Winnicott's conception of the "anti-social tendency." Limit setting is proposed as a necessary and authentic response to the patient's acting out via holding and empathic responsiveness, viewed here as a form of boundary delineation. It is proposed that the patient attempts to repair his or her boundary problem through a seeking of secure limits within the analyst. The setting of secure and appropriate limits must arise from a working through of the analyst's own countertransference response to the patient. It is critical that this response be evoked by, and arise from, the immediate therapeutic interaction so that the patient can experience limit setting as simultaneously personal and authentic. PMID:7972580

  16. Particle separation

    DOEpatents

    Moosmuller, Hans; Chakrabarty, Rajan K.; Arnott, W. Patrick

    2011-04-26

    Embodiments of a method for selecting particles, such as based on their morphology, is disclosed. In a particular example, the particles are charged and acquire different amounts of charge, or have different charge distributions, based on their morphology. The particles are then sorted based on their flow properties. In a specific example, the particles are sorted using a differential mobility analyzer, which sorts particles, at least in part, based on their electrical mobility. Given a population of particles with similar electrical mobilities, the disclosed process can be used to sort particles based on the net charge carried by the particle, and thus, given the relationship between charge and morphology, separate the particles based on their morphology.

  17. Particle separation

    NASA Technical Reports Server (NTRS)

    Moosmuller, Hans (Inventor); Chakrabarty, Rajan K. (Inventor); Arnott, W. Patrick (Inventor)

    2011-01-01

    Embodiments of a method for selecting particles, such as based on their morphology, is disclosed. In a particular example, the particles are charged and acquire different amounts of charge, or have different charge distributions, based on their morphology. The particles are then sorted based on their flow properties. In a specific example, the particles are sorted using a differential mobility analyzer, which sorts particles, at least in part, based on their electrical mobility. Given a population of particles with similar electrical mobilities, the disclosed process can be used to sort particles based on the net charge carried by the particle, and thus, given the relationship between charge and morphology, separate the particles based on their morphology.

  18. Traveling wave magnetic particle imaging.

    PubMed

    Vogel, Patrick; Ruckert, Martin A; Klauer, Peter; Kullmann, Walter H; Jakob, Peter M; Behr, Volker C

    2014-02-01

    Most 3-D magnetic particle imaging (MPI) scanners currently use permanent magnets to create the strong gradient field required for high resolution MPI. However, using permanent magnets limits the field of view (FOV) due to the large amount of energy required to move the field free point (FFP) from the center of the scanner. To address this issue, an alternative approach called "Traveling Wave MPI" is here presented. This approach employs a novel gradient system, the dynamic linear gradient array, to cover a large FOV while dynamically creating a strong magnetic gradient. The proposed design also enables the use of a so-called line-scanning mode, which simplifies the FFP trajectory to a linear path through the 3-D volume. This results in simplified mathematics, which facilitates the image reconstruction. PMID:24132006

  19. Particle behavior in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Wolf, R. A.; Spiro, R. W.

    1985-01-01

    The Rice Convection Model deals with large-scale processes in the earth's inner and middle magnetosphere, including coupling to the ionosphere. Starting from appropriate initial and boundary conditions, the model computes the following physical parameters: ionospheric electric fields and currents; magnetospheric particle distributions, electric fields, and electric currents; and magnetic-field-aligned (Birkeland) currents connecting the two regions. This paper evaluates work on the model, with emphasis on the assumptions made, the basic equations, and the numerical methods. The theoretical basis of the model is compared and contrasted with standard magnetohydrodynamics. The limitations imposed by the major assumptions are discussed. Model inputs and boundary conditions are listed, and the methods of specifying them discussed. Some physical conclusions and insights that have been gained from the model are listed and described very briefly. References are given to published discussions of the major points of physics.

  20. Noise, Bifurcations, and Modeling of Interacting Particle Systems

    PubMed Central

    Mier-y-Teran-Romero, Luis; Forgoston, Eric; Schwartz, Ira B.

    2011-01-01

    We consider the stochastic patterns of a system of communicating, or coupled, self-propelled particles in the presence of noise and communication time delay. For sufficiently large environmental noise, there exists a transition between a translating state and a rotating state with stationary center of mass. Time delayed communication creates a bifurcation pattern dependent on the coupling amplitude between particles. Using a mean field model in the large number limit, we show how the complete bifurcation unfolds in the presence of communication delay and coupling amplitude. Relative to the center of mass, the patterns can then be described as transitions between translation, rotation about a stationary point, or a rotating swarm, where the center of mass undergoes a Hopf bifurcation from steady state to a limit cycle. Examples of some of the stochastic patterns will be given for large numbers of particles. PMID:22124204

  1. An automatic, stagnation point based algorithm for the delineation of Wellhead Protection Areas

    NASA Astrophysics Data System (ADS)

    Tosco, Tiziana; Sethi, Rajandrea; di Molfetta, Antonio

    2008-07-01

    Time-related capture areas are usually delineated using the backward particle tracking method, releasing circles of equally spaced particles around each well. In this way, an accurate delineation often requires both a very high number of particles and a manual capture zone encirclement. The aim of this work was to propose an Automatic Protection Area (APA) delineation algorithm, which can be coupled with any model of flow and particle tracking. The computational time is here reduced, thanks to the use of a limited number of nonequally spaced particles. The particle starting positions are determined coupling forward particle tracking from the stagnation point, and backward particle tracking from the pumping well. The pathlines are postprocessed for a completely automatic delineation of closed perimeters of time-related capture zones. The APA algorithm was tested for a two-dimensional geometry, in homogeneous and nonhomogeneous aquifers, steady state flow conditions, single and multiple wells. Results show that the APA algorithm is robust and able to automatically and accurately reconstruct protection areas with a very small number of particles, also in complex scenarios.

  2. Charged particle beam current monitoring tutorial

    SciTech Connect

    Webber, R.C.

    1994-10-01

    A tutorial presentation is made on topics related to the measurement of charged particle beam currents. The fundamental physics of electricity and magnetism pertinent to the problem is reviewed. The physics is presented with a stress on its interpretation from an electrical circuit theory point of view. The operation of devices including video pulse current transformers, direct current transformers, and gigahertz bandwidth wall current style transformers is described. Design examples are given for each of these types of devices. Sensitivity, frequency response, and physical environment are typical parameters which influence the design of these instruments in any particular application. Practical engineering considerations, potential pitfalls, and performance limitations are discussed.

  3. Collisions of spinning massive particles in a Schwarzschild background

    NASA Astrophysics Data System (ADS)

    Armaza, Cristóbal; Banados, Máximo; Koch, Benjamin

    2016-05-01

    It is known that the center-of-mass energy of the collision of two massive particles following geodesics around a black hole presents a maximum. The maximum energy increases when the black hole is endowed with spin, and for a maximally rotating hole this energy blows up, offering, in principle, a unique probe of fundamental physics. This work extends the latter studies by considering that the colliding particles possess intrinsic angular momentum (spin), described by the Hanson-Regge-Hojman theory of spinning particles. By analyzing planar trajectories of spinning particles around non-rotating black holes, a significant increase of the invariant collision energy is found. Radial turning points, causality constraints, and limitations of the theory are discussed.

  4. Gravity and Zero Point Energy

    NASA Astrophysics Data System (ADS)

    Massie, U. W.

    When Planck introduced the 1/2 hv term to his 1911 black body equation he showed that there is a residual energy remaining at zero degree K after all thermal energy ceased. Other investigators, including Lamb, Casimir, and Dirac added to this information. Today zero point energy (ZPE) is accepted as an established condition. The purpose of this paper is to demonstrate that the density of the ZPE is given by the gravity constant (G) and the characteristics of its particles are revealed by the cosmic microwave background (CMB). Eddies of ZPE particles created by flow around mass bodies reduce the pressure normal to the eddy flow and are responsible for the force of gravity. Helium atoms resonate with ZPE particles at low temperature to produce superfluid helium. High velocity micro vortices of ZPE particles about a basic particle or particles are responsible for electromagnetic forces. The speed of light is the speed of the wave front in the ZPE and its value is a function of the temperature and density of the ZPE.

  5. FY 1999 cold demonstration of the Multi-Point Injection (MPI) process for stabilizing contaminated sludge in buried horizontal tanks with limited access at the Oak Ridge National Laboratory

    SciTech Connect

    Kauschinger, J.L.; Lewis, B.E.; Spence, R.D.

    2000-01-01

    A major problem faced by the U.S. Department of Energy is the remediation of buried tank waste. Exhumation of the sludge is currently the preferred remediation method. However, exhumation does not typically remove all the contaminated material from the tank. The best management practices for in-tank treatment of wastes require an integrated approach to develop appropriate treatment agents that can be safely delivered and uniformly mixed with the sludge. Ground Environmental Services, Inc., has developed and demonstrated a remotely controlled, high-velocity, jet-delivery system, which is termed Multi-Point-Injection (MPI{trademark}). This robust jet-delivery system has been used to create homogeneous monoliths containing shallow-buried miscellaneous waste in trenches [fiscal year (FY) 1995] and surrogate sludge in a cylindrical test tank (FY 1998). During the FY 1998 demonstration, the MPI process was able to successfully form a 32-ton uniform monolith in about 8 min. Analytical data indicated that 10 tons of a zeolite-type physical surrogate were uniformly mixed within the 40-inch-thick monolith without lifting the MPI jetting tools off the tank floor. Over 1,000 lb of cohesive surrogates, with consistencies of Gunite and Associated Tanks (GAATs) TH-4 and Hanford tank sludges, were easily mixed into the monolith without exceeding a core temperature of 100 F during curing.

  6. Tipping point leadership.

    PubMed

    Kim, W Chan; Mauborgne, Renée

    2003-04-01

    When William Bratton was appointed police commissioner of New York City in 1994, turf wars over jurisdiction and funding were rife and crime was out of control. Yet in less than two years, and without an increase in his budget, Bratton turned New York into the safest large city in the nation. And the NYPD was only the latest of five law-enforcement agencies Bratton had turned around. In each case, he succeeded in record time despite limited resources, a demotivated staff, opposition from powerful vested interests, and an organization wedded to the status quo. Bratton's turnarounds demonstrate what the authors call tipping point leadership. The theory of tipping points hinges on the insight that in any organization, fundamental changes can occur quickly when the beliefs and energies of a critical mass of people create an epidemic movement toward an idea. Bratton begins by overcoming the cognitive hurdles that block organizations from recognizing the need for change. He does this by putting managers face-to-face with operational problems. Next, he manages around limitations on funds, staff, or equipment by concentrating resources on the areas that are most in need of change and that have the biggest payoffs. He meanwhile solves the motivation problem by singling out key influencers--people with disproportionate power due to their connections or persuasive abilities. Finally, he closes off resistance from powerful opponents. Not every CEO has the personality to be a Bill Bratton, but his successes are due to much more than his personality. He relies on a remarkably consistent method that any manager looking to turn around an organization can use to overcome the forces of inertia and reach the tipping point. PMID:12687920

  7. The Point of No Return

    PubMed Central

    Logan, Gordon D.

    2015-01-01

    Bartlett (1958) described the point of no return as a point of irrevocable commitment to action, which was preceded by a period of gradually increasing commitment. As such, the point of no return reflects a fundamental limit on the ability to control thought and action. I review the literature on the point of no return, taking three perspectives. First, I consider the point of no return from the perspective of the controlled act, as a locus in the architecture and anatomy of the underlying processes. I review experiments from the stop-signal paradigm that suggest that the point of no return is located late in the response system. Then I consider the point of no return from the perspective of the act of control that tries to change the controlled act before it becomes irrevocable. From this perspective, the point of no return is a point in time that provides enough “lead time” for the act of control to take effect. I review experiments that measure the response time to the stop signal as the lead time required for response inhibition in the stop-signal paradigm. Finally, I consider the point of no return in hierarchically controlled tasks, in which there may be many points of no return at different levels of the hierarchy. I review experiments on skilled typing that suggest different points of no return for the commands that determine what is typed and the countermands that inhibit typing, with increasing commitment to action the lower the level in the hierarchy. I end by considering the point of no return in perception and thought as well as action. PMID:25633089

  8. The limits of prevention.

    PubMed Central

    McGinnis, J M

    1985-01-01

    Recent years have been marked by unprecedented accomplishments in preventing disease and reducing mortality. More gains can be expected, but there are limits. The forces shaping the nature and potential of prevention programs can be characterized as points falling along a spectrum ranging from the purely scientific to the purely social. This paper focuses on four elements of that spectrum, discussing some of the limitations to prevention that are presented by biological, technical, ethical, and economic factors. The author concludes with an essentially optimistic perspective on the prospects, special opportunities, and imperatives inherent in each of the categories of limitations discussed. PMID:3923530

  9. Interlaced Particle Systems and Tilings of the Aztec Diamond

    NASA Astrophysics Data System (ADS)

    Fleming, Benjamin J.; Forrester, Peter J.

    2011-02-01

    Motivated by the problem of domino tilings of the Aztec diamond, a weighted particle system is defined on N lines, with line j containing j particles. The particles are restricted to lattice points from 0 to N, and particles on successive lines are subject to an interlacing constraint. It is shown that this particle system is exactly solvable, to the extent that not only can the partition function be computed exactly, but so too can the marginal distributions. These results in turn are used to give new derivations within the particle picture of a number of known fundamental properties of the tiling problem, for example that the number of distinct configurations is 2 N( N+1)/2, and that there is a limit to the GUE minor process, which we show at the level of the joint PDFs. It is shown too that the study of tilings of the half Aztec diamond—not known from earlier literature—also leads to an interlaced particle system, now with successive lines 2 n-1 and 2 n ( n=1,…, N/2-1) having n particles. Its exact solution allows for an analysis of the half Aztec diamond tilings analogous to that given for the Aztec diamond tilings.

  10. Colloidal Recycling: Reconfiguration of Random Aggregates into Patchy Particles.

    PubMed

    Meester, Vera; Verweij, Ruben W; van der Wel, Casper; Kraft, Daniela J

    2016-04-26

    The key ingredients to the successful bottom-up construction of complex materials are believed to be colloids with anisotropic shapes and directional, or patchy, interactions. We present an approach for creating such anisotropic patchy particles based on reconfiguring randomly shaped aggregates of colloidal spheres. While colloidal aggregates are often undesirable in colloidal dispersions due to their random shapes, we exploit them as a starting point to synthesize patchy particles. By a deliberate destabilization of the colloidal particles, diffusion-limited aggregation is induced which partitions the particles into randomly shaped aggregates with controlled size distribution. We achieve a reconfiguration of the aggregates into uniform structures by swelling the polymer spheres with an apolar solvent. The swelling lowers the attractive van der Waals forces, lubricates the contact area between the spheres, and drives the reorganization through minimization of the interfacial energy of the swollen polymer network. This reorganization process yields patchy particles whose patch arrangement is uniform for up to five patches. For particles with more patches, we find that the patch orientation depends on the degree of phase separation between the spheres and the monomer. This enables the synthesis of patchy particles with unprecedented patch arrangements. We demonstrate the broad applicability of this recycling strategy for making patchy particles as well as clusters of spheres by varying the swelling ratio, swelling solvent, surfactant concentration, and swelling time. PMID:27014995

  11. The role of ions in the self-healing behavior of soft particle suspensions

    NASA Astrophysics Data System (ADS)

    Scotti, Andrea; Gasser, Urs; Herman, Emily S.; Pelaez-Fernandez, Miguel; Han, Jun; Menzel, Andreas; Lyon, L. Andrew; Fernández-Nieves, Alberto

    2016-05-01

    Impurities in crystals generally cause point defects and can even suppress crystallization. This general rule, however, does not apply to colloidal crystals formed by soft microgel particles [Iyer ASJ, Lyon LA (2009) Angew Chem Int Ed 48:4562–4566], as, in this case, the larger particles are able to shrink and join the crystal formed by a majority of smaller particles. Using small-angle X-ray scattering, we find the limit in large-particle concentration for this spontaneous deswelling to persist. We rationalize our data in the context of those counterions that are bound to the microgel particles as a result of the electrostatic attraction exerted by the fixed charges residing on the particle periphery. These bound counterions do not contribute to the suspension osmotic pressure in dilute conditions, as they can be seen as internal degrees of freedom associated with each microgel particle. In contrast, at sufficiently high particle concentrations, the counterion cloud of each particle overlaps with that of its neighbors, allowing these ions to freely explore the space outside the particles. We confirm this scenario by directly measuring the osmotic pressure of the suspension. Because these counterions are then no longer bound, they create an osmotic pressure difference between the inside and outside of the microgels, which, if larger than the microgel bulk modulus, can cause deswelling, explaining why large, soft microgel particles feel the squeeze when suspended with a majority of smaller particles. We perform small-angle neutron scattering measurements to further confirm this remarkable behavior.

  12. Alpha Particle

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Term that is sometimes used to describe a helium nucleus, a positively charged particle that consists of two protons and two neutrons, bound together. Alpha particles, which were discovered by Ernest Rutherford (1871-1937) in 1898, are emitted by atomic nuclei that are undergoing alpha radioactivity. During this process, an unstable heavy nucleus spontaneously emits an alpha particle and transmut...

  13. Particle generator

    DOEpatents

    Hess, Wayne P.; Joly, Alan G.; Gerrity, Daniel P.; Beck, Kenneth M.; Sushko, Peter V.; Shlyuger, Alexander L.

    2005-06-28

    Energy tunable solid state sources of neutral particles are described. In a disclosed embodiment, a halogen particle source includes a solid halide sample, a photon source positioned to deliver photons to a surface of the halide, and a collimating means positioned to accept a spatially defined plume of hyperthermal halogen particles emitted from the sample surface.

  14. Limiting SUSY compressed spectra scenarios

    NASA Astrophysics Data System (ADS)

    Nelson, Andy; Tanedo, Philip; Whiteson, Daniel

    2016-06-01

    Typical searches for supersymmetry cannot test models in which the two lightest particles have a small ("compressed") mass splitting, due to the small momentum of the particles produced in the decay of the second-to-lightest particle. However, data sets with large missing transverse momentum (ETmiss) can generically search for invisible particle production and therefore provide constraints on such models. We apply data from the ATLAS monojet (jet+ETmiss ) and vector-boson-fusion (forward jets and ETmiss ) searches to such models. In all cases, experimental limits are at least five times weaker than theoretical predictions.

  15. The Effect of Particle Properties on Hot Particle Spot Fire Ignition

    NASA Astrophysics Data System (ADS)

    Zak, Casey David

    The ignition of natural combustible material by hot metal particles is an important fire ignition pathway by which wildland and wildland-urban-interface spot fires are started. There are numerous cases reported of wild fires started by clashing power-lines or from sparks generated by machines or engines. Similarly there are many cases reported of fires caused by grinding, welding and cutting sparks. Up to this point, research on hot particle spot fire ignition has largely focused on particle generation and transport. A small number of studies have examined what occurs after a hot particle contacts a natural fuel bed, but until recently the process remained poorly understood. This work describes an investigation of the effect of particle size, temperature and thermal properties on the ability of hot particles to cause flaming ignition of cellulosic fuel beds. Both experimental and theoretical approaches are used, with a focus on understanding the physics underlying the ignition process. For the experimental study, spheres of stainless steel, aluminum, brass and copper are heated in a tube furnace and dropped onto a powdered cellulose fuel bed; the occurrence of flaming ignition or lack thereof is visually observed and recorded. This procedure is repeated a large number of times for each metal type, varying particle diameter from 2 to 11 mm and particle temperature between 575 and 1100°C. The results of these experiments are statistically analyzed to find approximate ignition boundaries and identify boundary trends with respect to the particle parameters of interest. Schlieren images recorded during the ignition experiments are also used to more accurately describe the ignition process. Based on these images, a simple theoretical model of hot particle spot fire ignition is developed and used to explore the experimental trends further. The model under-predicts the minimum ignition temperatures required for small spheres, but agrees qualitatively with the experimental

  16. PLT rotating pumped limiter

    SciTech Connect

    Cohen, S.A.; Budny, R.V.; Corso, V.; Boychuck, J.; Grisham, L.; Heifetz, D.; Hosea, J.; Luyber, S.; Loprest, P.; Manos, D.

    1984-07-01

    A limiter with a specially contoured front face and the ability to rotate during tokamak discharges has been installed in a PLT pump duct. These features have been selected to handle the unique particle removal and heat load requirements of ICRF heating and lower-hybrid current-drive experiments. The limiter has been conditioned and commissioned in an ion-beam test stand by irradiation with 1 MW power, 200 ms duration beams of 40 keV hydrogen ions. Operation in PLT during ohmic discharges has proven the ability of the limiter to reduce localized heating caused by energetic electron bombardment and to remove about 2% of the ions lost to the PLT walls and limiters.

  17. Particle Detectors

    NASA Astrophysics Data System (ADS)

    Grupen, Claus; Shwartz, Boris

    2011-09-01

    Preface to the first edition; Preface to the second edition; Introduction; 1. Interactions of particles and radiation with matter; 2. Characteristic properties of detectors; 3. Units of radiation measurements and radiation sources; 4. Accelerators; 5. Main physical phenomena used for particle detection and basic counter types; 6. Historical track detectors; 7. Track detectors; 8. Calorimetry; 9. Particle identification; 10. Neutrino detectors; 11. Momentum measurement and muon detection; 12. Ageing and radiation effects; 13. Example of a general-purpose detector: Belle; 14. Electronics; 15. Data analysis; 16. Applications of particle detectors outside particle physics; 17. Glossary; 18. Solutions; 19. Resumé; Appendixes; Index.

  18. Limits on nonlinear electrodynamics

    NASA Astrophysics Data System (ADS)

    Fouché, M.; Battesti, R.; Rizzo, C.

    2016-05-01

    In this paper we set a framework in which experiments whose goal is to test QED predictions can be used in a more general way to test nonlinear electrodynamics (NLED) which contains low-energy QED as a special case. We review some of these experiments and we establish limits on the different free parameters by generalizing QED predictions in the framework of NLED. We finally discuss the implications of these limits on bound systems and isolated charged particles for which QED has been widely and successfully tested.

  19. Quantum limits of thermometry

    SciTech Connect

    Stace, Thomas M.

    2010-07-15

    The precision of typical thermometers consisting of N particles scales as {approx}1/{radical}(N). For high-precision thermometry and thermometric standards, this presents an important theoretical noise floor. Here it is demonstrated that thermometry may be mapped onto the problem of phase estimation, and using techniques from optimal phase estimation, it follows that the scaling of the precision of a thermometer may in principle be improved to {approx}1/N, representing a Heisenberg limit to thermometry.

  20. Quantitative wave-particle duality

    NASA Astrophysics Data System (ADS)

    Qureshi, Tabish

    2016-07-01

    The complementary wave and particle character of quantum objects (or quantons) was pointed out by Niels Bohr. This wave-particle duality, in the context of the two-slit experiment, is here described not just as two extreme cases of wave and particle characteristics, but in terms of quantitative measures of these characteristics, known to follow a duality relation. A very simple and intuitive derivation of a closely related duality relation is presented, which should be understandable to the introductory student.

  1. Theory of point contact spectroscopy in correlated materials

    PubMed Central

    Lee, Wei-Cheng; Park, Wan Kyu; Arham, Hamood Z.; Greene, Laura H.; Phillips, Philip

    2015-01-01

    We developed a microscopic theory for the point-contact conductance between a metallic electrode and a strongly correlated material using the nonequilibrium Schwinger-Kadanoff-Baym-Keldysh formalism. We explicitly show that, in the classical limit, contact size shorter than the scattering length of the system, the microscopic model can be reduced to an effective model with transfer matrix elements that conserve in-plane momentum. We found that the conductance dI/dV is proportional to the effective density of states, that is, the integrated single-particle spectral function A(ω = eV) over the whole Brillouin zone. From this conclusion, we are able to establish the conditions under which a non-Fermi liquid metal exhibits a zero-bias peak in the conductance. This finding is discussed in the context of recent point-contact spectroscopy on the iron pnictides and chalcogenides, which has exhibited a zero-bias conductance peak. PMID:25561532

  2. Management of particles detected on the Dounreay site.

    PubMed

    Goss, O E; Liddiard, M

    2007-09-01

    Much effort is involved in finding and retrieving historic particles from the environs surrounding the Dounreay nuclear site. Historic particles are also present on the site itself, and these are dealt with as part of the ongoing contaminated land management regime. UKAEA operates systems of routine monitoring on outside surface areas in order to limit exposure to the workforce under the Ionising Radiation Regulations 1999. Contaminated material is removed when found, and this material undergoes separation and analysis routinely and where suspected to contain a particle. Information regarding on-site particles has been built up as a result of this. The distribution of on-site particles provides details of the likely dispersion pathways, and it is apparent that some interaction occurs between the on-site and off-site particle transport mechanisms. The strategy for dealing with contaminated land at Dounreay is to manage contamination in situ during the decommissioning phase, where the risk of doing so is acceptable. Particles present a very low risk to Dounreay site workers but it is considered ALARP (as low as reasonably practicable) to detect and remove these particles. The particles are a legacy issue arising from historic practices, which would not meet today's safety standards. A continuing programme to detect, remove and record their presence will be required during the site closure process. This will be necessary to meet current regulations and the likely criteria for releasing the site for future re-use. The final solution for the particles will not be known until the Best Practicable Environmental Options study is completed and further development of the site end-point work has been reported. It is unlikely that there will be a full removal of particles from the total environment, so some form of long term monitoring programme may be required plus a high standard of record keeping. PMID:17768322

  3. The Physical Principles of Particle Detectors.

    ERIC Educational Resources Information Center

    Jones, Goronwy Tudor

    1991-01-01

    Describes the use of a particle detector, an instrument that records the passage of particles through it, to determine the mass of a particle by measuring the particles momentum, speed, and kinetic energy. An appendix discusses the limits on the impact parameter. (MDH)

  4. Particle astrophysics

    NASA Astrophysics Data System (ADS)

    Sadoulet, Bernard; Cronin, James; Aprile, Elena; Barish, Barry C.; Beier, Eugene W.; Brandenberger, Robert; Cabrera, Blas; Caldwell, David; Cassiday, George; Cline, David B.

    The following scientific areas are reviewed: (1) cosmology and particle physics (particle physics and the early universe, dark matter, and other relics); (2) stellar physics and particles (solar neutrinos, supernovae, and unconventional particle physics); (3) high energy gamma ray and neutrino astronomy; (4) cosmic rays (space and ground observations). Highest scientific priorities for the next decade include implementation of the current program, new initiatives, and longer-term programs. Essential technological developments, such as cryogenic detectors of particles, new solar neutrino techniques, and new extensive air shower detectors, are discussed. Also a certain number of institutional issues (the funding of particle astrophysics, recommended funding mechanisms, recommended facilities, international collaborations, and education and technology) which will become critical in the coming decade are presented.

  5. Particle astrophysics

    NASA Technical Reports Server (NTRS)

    Sadoulet, Bernard; Cronin, James; Aprile, Elena; Barish, Barry C.; Beier, Eugene W.; Brandenberger, Robert; Cabrera, Blas; Caldwell, David; Cassiday, George; Cline, David B.

    1991-01-01

    The following scientific areas are reviewed: (1) cosmology and particle physics (particle physics and the early universe, dark matter, and other relics); (2) stellar physics and particles (solar neutrinos, supernovae, and unconventional particle physics); (3) high energy gamma ray and neutrino astronomy; (4) cosmic rays (space and ground observations). Highest scientific priorities for the next decade include implementation of the current program, new initiatives, and longer-term programs. Essential technological developments, such as cryogenic detectors of particles, new solar neutrino techniques, and new extensive air shower detectors, are discussed. Also a certain number of institutional issues (the funding of particle astrophysics, recommended funding mechanisms, recommended facilities, international collaborations, and education and technology) which will become critical in the coming decade are presented.

  6. Development of Point Doppler Velocimetry for Flow Field Investigations

    NASA Technical Reports Server (NTRS)

    Cavone, Angelo A.; Meyers, James F.; Lee, Joseph W.

    2006-01-01

    A Point Doppler Velocimeter (pDv) has been developed using a vapor-limited iodine cell as the sensing medium. The iodine cell is utilized to directly measure the Doppler shift frequency of laser light scattered from submicron particles suspended within a fluid flow. The measured Doppler shift can then be used to compute the velocity of the particles, and hence the fluid. Since this approach does not require resolution of scattered light from individual particles, the potential exists to obtain temporally continuous signals that could be uniformly sampled in the manner as a hot wire anemometer. This leads to the possibility of obtaining flow turbulence power spectra without the limitations of fringe-type laser velocimetry. The development program consisted of a methodical investigation of the technology coupled with the solution of practical engineering problems to produce a usable measurement system. The paper outlines this development along with the evaluation of the resulting system as compared to primary standards and other measurement technologies.

  7. Magnetic particles

    NASA Technical Reports Server (NTRS)

    Chang, Manchium (Inventor); Colvin, Michael S. (Inventor)

    1989-01-01

    Magnetic polymer particles are formed by swelling porous, polymer particles and impregnating the particles with an aqueous solution of precursor magnetic metal salt such as an equimolar mixture of ferrous chloride and ferric chloride. On addition of a basic reagent such as dilute sodium hydroxide, the metal salts are converted to crystals of magnetite which are uniformly contained througout the pores of the polymer particle. The magnetite content can be increased and neutral buoyancy achieved by repetition of the impregnaton and neutralization steps to adjust the magnetite content to a desired level.

  8. Marginal Stability Dynamics for Energetic Particles

    NASA Astrophysics Data System (ADS)

    Berk, Herbert

    2009-11-01

    Marginal stability in plasmas characteristically sets a stiff limit to the range of that can be achieved. Below this limit, the system is governed by classical. Near marginal stability, however, plasmas may be subject to rapid processes, resulting in a system that hovers near marginality. This scenario emerged from nonlinear studies of energetic particle relaxation and may be to more general plasma transport. We describe results from several such which include. [1] Avalanches---Near marginal stability, an important point is whether an instability driven by resonant particles where the distribution function has ``free energy'' will cause global radial diffusion. For that,modes need to overlap. This process can be continuous or bursty, the latter having been recently observed in NSTX and DIII-D. [2] Frequency chirping---Recent simulations by Vann showed that marginal stability can be sustained when there is only one unstable linear mode, due to the mechanism of spontaneous frequency sweeping. Although a single mode near stability should not cause dramatic relaxation, nevertheless in the Vann simulations, the achievement of marginal stability induced a continual chirping of that had removed energy from the bulk of the region where the external beam to deposit free energy. The distribution was then found to hover near stability. This mechanism may apply to the n=0 GAM where frequency sweeping might be a mechanism for extracting energy from alpha particles in a burning plasma, thereby reducing the stored alpha particle pressure. One way to implement this is to have the n=0 geodesic acoustic modes (GAM) be preferentially excited, since energy rather than momentum (leading to spatial diffusion) is then primarily extracted from alpha particles.

  9. HVOF particle flow field characteristics

    SciTech Connect

    Swank, W.D.; Fincke, J.R.; Haggard, D.C.; Irons, G.; Bullock, R.

    1994-12-31

    The effect of varying fuel/oxygen mixture ratio and combustion chamber pressure on the sprayed particle temperature and velocity in the supersonic, high pressure HVOF process is examined. Particle temperature is shown to correlate to the fuel/oxygen mixture and particle velocity is a function of combustion chamber pressure. inconel 718 coatings were fabricated at the same conditions as the particle measurements. High particle velocities resulted in high micro hardness. Deposition efficiency is a function of both particle temperature and velocity. The optimal deposition efficiency occurs at an average particle temperature which is below the melting point of Inconel 718 and the lowest velocity investigated. Oxide content is a function of substrate temperature and not entrained air or excess combustion oxygen.

  10. Visualization of instationary flows by particle traces

    NASA Astrophysics Data System (ADS)

    Raasch, S.

    An abstract on a study which represents a model of atmospheric flow output by computer movies is presented. The structure and evolution of the flow is visualized by starting weightless particles at the locations of the model grid points at distinct, equally spaced times. These particles are then only advected by the flow. In order to avoid useless accumulation of particles, they can be provided with a limited lifetime. Scalar quantities can be shown in addition to using color shaded contours as background information. A movie with several examples of atmospheric flows, for example convection in the atmospheric boundary layer, slope winds, land seabreeze and Kelvin-Helmholtz waves is presented. The simulations are performed by two dimensional and three dimensional nonhydrostatic, finite difference models. Graphics are produced by using the UNIRAS software and the graphic output is in form of CGM metafiles. The single frames are stored on an ABEKAS real time video disc and then transferred to a BETACAM-SP tape recorder. The graphic software is suitable to produce 2 dimensional pictures, for example only cross sections of three dimensional simulations can be made. To produce a movie of typically 90 seconds duration, the graphic software and the particle model need about 10 hours CPU time on a CCD CYBER 990 and the CGM metafile has a size of about 1.4 GByte.

  11. Particle control studies on Tore Supra

    SciTech Connect

    Mioduszewski, P.

    1987-01-01

    The report consists of viewgraphs. The goal of the particle control program at Tore Supra is to study plasma performance with strong pellet fueling and corresponding particle exhaust in a limiter tokamak. (WRF)

  12. Particle preconcentrator

    DOEpatents

    Linker, K.L.; Conrad, F.J.; Custer, C.A.; Rhykerd, C.L. Jr.

    1998-12-29

    An apparatus and method are disclosed for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents. 3 figs.

  13. Particle preconcentrator

    SciTech Connect

    Linker, K.L.; Conrad, F.J.; Custer, C.A.; Rhykerd, C.L. Jr

    2000-07-11

    An apparatus and method are disclosed for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a previous screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents.

  14. Particle preconcentrator

    SciTech Connect

    Linker, Kevin L.; Conrad, Frank J.; Custer, Chad A.; Rhykerd, Jr., Charles L.

    1998-01-01

    An apparatus and method for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents.

  15. Particle preconcentrator

    SciTech Connect

    Linker, Kevin L.; Conrad, Frank J.; Custer, Chad A.; Rhykerd, Jr., Charles L.

    2005-09-20

    An apparatus and method for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents.

  16. Particle preconcentrator

    SciTech Connect

    Linker, Kevin L.; Conrad, Frank J.; Custer, Chad A.; Rhykerd, Jr., Charles L.

    2000-01-01

    An apparatus and method for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents.

  17. Role of surface gauging in extended particle interactions: The case for spin

    NASA Astrophysics Data System (ADS)

    Mazilu, Nicolae; Ghizdovat, Vlad; Agop, Maricel

    2016-05-01

    The matter, being extended in space, should be first characterized by a surface of separation from the empty space. This surface cannot be neatly, i.e. purely geometrically, defined. When it comes to extended particles, which thereby are to be considered the fundamental structural units of the matter, the physical evidence points out that they are not even stable: they are in a continuous transformation; and so is their limit of separation from space. The present work describes a concept of extended particle with special emphasis on this limit of separation. It turns out that the properties of inertia, as classically understood, are intrinsically related to the spin properties of quantum origin. Thus, an extended particle model cannot be but "holographic" when it comes to imbedding it in a physical structure. The spin properties turn out to be essential, inasmuch as they decide the forces of interaction issuing from particles.

  18. Yukawa particles in a confining potential

    SciTech Connect

    Girotto, Matheus Levin, Yan; Santos, Alexandre P. dos; Colla, Thiago

    2014-07-07

    We study the density distribution of repulsive Yukawa particles confined by an external potential. In the weak coupling limit, we show that the mean-field theory is able to accurately account for the particle distribution. In the strong coupling limit, the correlations between the particles become important and the mean-field theory fails. For strongly correlated systems, we construct a density functional theory which provides an excellent description of the particle distribution, without any adjustable parameters.

  19. Family Limitation

    PubMed Central

    Smith, Robert

    1966-01-01

    Dr Robert Smith surveys the history of birth control and sounds a warning for the future of mankind, if the population explosion is allowed to continue unchecked. He stresses the importance of the role of the general practitioner in the limitation of births. Sir Theodore Fox describes the work of the Family Planning Association and stresses that, increasingly, this is a specialist service covering all aspects of fertility. He also feels that the general practitioner has a role in family planning. PMID:5954261

  20. Particle plasmons: Why shape matters

    NASA Astrophysics Data System (ADS)

    Barnes, William L.

    2016-08-01

    Simple analytic expressions for the polarizability of metallic nanoparticles are in wide use in the field of plasmonics, but their origins are not obvious. In this article, expressions for the polarizability of a particle are derived in the quasistatic limit in a manner that allows the physical origin of the terms to be clearly seen. The discussion is tutorial in nature, with particular attention given to the role of particle shape since this is a controlling factor in particle plasmon resonances.

  1. Beyond diffusion-limited aggregation kinetics in microparticle suspensions.

    PubMed

    Erb, Randall M; Krebs, Melissa D; Alsberg, Eben; Samanta, Bappaditya; Rotello, Vincent M; Yellen, Benjamin B

    2009-11-01

    Aggregation in nondiffusion limited colloidal particle suspensions follows a temporal power-law dependence that is consistent with classical diffusion limited cluster aggregation models; however, the dynamic scaling exponents observed in these systems are not adequately described by diffusion limited cluster aggregation models, which expect these scaling exponents to be constant over all experimental conditions. We show here that the dynamic scaling exponents for 10 microm particles increase with the particle concentration and the particle-particle free energy of interaction. We provide a semiquantitative explanation for the scaling behavior in terms of the long-ranged particle-particle interaction potential. PMID:20364980

  2. Floating Point Control Library

    Energy Science and Technology Software Center (ESTSC)

    2007-08-02

    Floating Point Control is a Library that allows for the manipulation of floating point unit exception masking funtions control exceptions in both the Streaming "Single Instruction, Multiple Data" Extension 2 (SSE2) unit and the floating point unit simultaneously. FPC also provides macros to set floating point rounding and precision control.

  3. Myofascial trigger point pain.

    PubMed

    Jaeger, Bernadette

    2013-01-01

    Myofascial trigger point pain is an extremely prevalent cause of persistent pain disorders in all parts of the body, not just the head, neck, and face. Features include deep aching pain in any structure, referred from focally tender points in taut bands of skeletal muscle (the trigger points). Diagnosis depends on accurate palpation with 2-4 kg/cm2 of pressure for 10 to 20 seconds over the suspected trigger point to allow the referred pain pattern to develop. In the head and neck region, cervical muscle trigger points (key trigger points) often incite and perpetuate trigger points (satellite trigger points) and referred pain from masticatory muscles. Management requires identification and control of as many perpetuating factors as possible (posture, body mechanics, psychological stress or depression, poor sleep or nutrition). Trigger point therapies such as spray and stretch or trigger point injections are best used as adjunctive therapy. PMID:24864393

  4. Internal one-particle density matrix for Bose-Einstein condensates with finite number of particles in a harmonic potential

    SciTech Connect

    Yamada, Taiichi; Funaki, Yasuro; Horiuchi, Hisashi; Roepke, Gerd; Schuck, Peter; Tohsaki, Akihiro

    2009-05-15

    Investigations on the internal one-particle density matrix in the case of Bose-Einstein condensates with a finite number (N) of particles in a harmonic potential are performed. We solve the eigenvalue problem of the Pethick-Pitaevskii-type internal density matrix and find a fragmented condensate. On the contrary the condensate Jacobi-type internal density matrix gives complete condensation into a single state. The internal one-particle density matrix is, therefore, shown to be different in general for different choices of the internal coordinate system. We propose two physically motivated criteria for the choice of the adequate coordinate systems that give us a unique answer for the internal one-particle density matrix. One criterion is that in the infinite particle number limit (N={infinity}) the internal one-particle density matrix should have the same eigenvalues and eigenfunctions as those of the corresponding ideal Bose-Einstein condensate in the laboratory frame. The other criterion is that the coordinate of the internal one-particle density matrix should be orthogonal to the remaining (N-2) internal coordinates, though the (N-2) coordinates, in general, do not need to be mutually orthogonal. This second criterion is shown to imply the first criterion. It is shown that the internal Jacobi coordinate system satisfies these two criteria while the internal coordinate system adopted by Pethick and Pitaevskii for the construction of the internal one-particle density matrix does not. It is demonstrated that these two criteria uniquely determine the internal one-particle density matrix that is identical to that calculated with the Jacobi coordinates. The relevance of this work concerning {alpha}-particle condensates in nuclei, as well as bosonic atoms in traps, is pointed out.

  5. Accelerators for charged particle therapy: PAMELA and related issues

    NASA Astrophysics Data System (ADS)

    Peach, Ken

    2014-05-01

    Cancer is a dreadful disease that will affect one in three people at some point in their life; radiotherapy is used in more than half of all cancer treatment, and contributes about 40% to the successful treatment of cancer. Charged Particle Therapy uses protons and other light ions to deliver the lethal dose to the tumor while being relatively sparing of healthy tissue and, because of the finite range of the particles, is able to avoid giving any dose to vital organs. While there are adequate technologies currently available to deliver the required energies and fluxes, the two main technologies (cyclotrons and synchrotrons) have limitations. PAMELA (the Particle Accelerator for MEdicaLApplications) uses the newly-developed non-scaling Fixed Field Alternating Gradient accelerator concepts to deliver therapeutically relevant beams. The status of the development of the PAMELA conceptual design is discussed.

  6. Deliquescence and efflorescence of small particles: Unifying perspectives from nucleation theory

    SciTech Connect

    McGraw,R.; Lewis, E.

    2009-02-23

    We examine size dependent deliquescence/efflorescence phase transformation for particles down to several nanometers in size. A thin layer criterion (TLC) is introduced to define a deliquescence relative humidity (DRH) for small particles. The usual bulk deliquescence conditions are recovered in the limit of large dry particle size. Nano-size particles are shown to deliquesce to metastable states via a nucleation process at relative humidity just below the DRH. The nucleation barrier is located at a critical solution layer thickness and vanishes at the DRH defined by the TLC. Methods from nucleation theory form the basis for the analysis and yield new insights into the theory, facilitate the interpretation of measurements, and point to unification of deliquescence and efflorescence processes for particles in the nano regime. Methods include thermodynamic area constructions, Legendre transforms relating the binary free-energy surfaces for deliquescence and efflorescence processes, and application of nucleation theorems.

  7. Particle physics and cosmology

    SciTech Connect

    Kolb, E.W.

    1986-10-01

    This series of lectures is about the role of particle physics in physical processes that occurred in the very early stages of the bug gang. Of particular interest is the role of particle physics in determining the evolution of the early Universe, and the effect of particle physics on the present structure of the Universe. The use of the big bang as a laboratory for placing limits on new particle physics theories will also be discussed. Section 1 reviews the standard cosmology, including primordial nucleosynthesis. Section 2 reviews the decoupling of weakly interacting particles in the early Universe, and discusses neutrino cosmology and the resulting limits that may be placed on the mass and lifetime of massive neutrinos. Section 3 discusses the evolution of the vacuum through phase transitions in the early Universe and the formation of topological defects in the transitions. Section 4 covers recent work on the generation of the baryon asymmetry by baryon-number violating reactions in Grand Unified Theories, and mentions some recent work on baryon number violation effects at the electroweak transition. Section 5 is devoted to theories of cosmic inflation. Finally, Section 6 is a discussion of the role of extra spatial dimensions in the evolution of the early Universe. 78 refs., 32 figs., 6 tabs.

  8. Suppression of Fermi acceleration in composite particles

    NASA Astrophysics Data System (ADS)

    Siqueira, Kellen Manoela; de Aguiar, Marcus Aloizio Martinez

    2016-09-01

    We study the motion of a composite particle in a one-dimensional billiard with a moving wall. The particle is modeled by two point masses coupled by a harmonic spring. We show that the energy gained by the composite particle is greatly reduced with respect to a single point particle. We show that the amount of energy transferred to the system at each collision with the walls is independent of the spring constant. However, the presence of the spring is responsible for the energy suppression because it diminishes the number of collisions by storing part of the system's energy and reducing the velocity of the particle's center of mass.

  9. The boiling point of stratospheric aerosols.

    NASA Technical Reports Server (NTRS)

    Rosen, J. M.

    1971-01-01

    A photoelectric particle counter was used for the measurement of aerosol boiling points. The operational principle involves raising the temperature of the aerosol by vigorously heating a portion of the intake tube. At or above the boiling point, the particles disintegrate rather quickly, and a noticeable effect on the size distribution and concentration is observed. Stratospheric aerosols appear to have the same volatility as a solution of 75% sulfuric acid. Chemical analysis of the aerosols indicates that there are other substances present, but that the sulfate radical is apparently the major constituent.

  10. Optimal diffusion coefficient estimation in single-particle tracking

    PubMed Central

    Michalet, Xavier; Berglund, Andrew J.

    2016-01-01

    Single-particle tracking is increasingly used to extract quantitative parameters on single molecules and their environment, while advances in spatial and temporal resolution of tracking techniques inspire new questions and avenues of investigation. Correspondingly, sophisticated analytical methods are constantly developed to obtain more refined information from measured trajectories. Here we point out some fundamental limitations of these approaches due to the finite length of trajectories, the presence of localization error, and motion blur, focusing on the simplest motion regime of free diffusion in an isotropic medium (Brownian motion). We show that two recently proposed algorithms approach the theoretical limit of diffusion coefficient uncertainty. We discuss the practical performance of the algorithms as well as some important implications of these results for single-particle tracking. PMID:23005136

  11. Magnetic particles

    NASA Technical Reports Server (NTRS)

    Chang, Manchium (Inventor); Colvin, Michael S. (Inventor); Rembaum, Alan (Inventor); Richards, Gil F. (Inventor)

    1987-01-01

    Metal oxide containing polymers and particularly styrene, acrylic or protein polymers containing fine, magnetic iron oxide particles are formed by combining a NO.sub.2 -substituted polymer with an acid such as hydrochloric acid in the presence of metal, particularly iron particles. The iron is oxidized to fine, black Fe.sub.3 O.sub.4 particles which deposit selectively on the polymer particles. Nitrated polymers are formed by reacting functionally substituted, nitrated organic compounds such as trinitrobenzene sulfonate or dinitrofluoro benzene with a functionally coreactive polymer such as an amine modified acrylic polymer or a protein. Other transition metals such as cobalt can also be incorporated into polymers using this method.

  12. Elementary Particles

    ERIC Educational Resources Information Center

    Parham, R.

    1974-01-01

    Presents the text of a speech given to a conference of physics teachers in which the full spectrum of elementary particles is given, along with their classification. Also includes some teaching materials available on this topic. (PEB)

  13. Elementary particles

    NASA Astrophysics Data System (ADS)

    Fritzsch, Harald; Heusch, Karin

    Introduction -- Electrons and atomic nuclei -- Quantum properties of atoms and particles -- The knives of Democritus -- Quarks inside atomic nuclei -- Quantum electrodynamics -- Quantum chromodynamics -- Mesons, baryons, and quarks -- Electroweak interactions -- Grand unification -- Conclusion.

  14. Optimal Limited Contingency Planning

    NASA Technical Reports Server (NTRS)

    Meuleau, Nicolas; Smith, David E.

    2003-01-01

    For a given problem, the optimal Markov policy over a finite horizon is a conditional plan containing a potentially large number of branches. However, there are applications where it is desirable to strictly limit the number of decision points and branches in a plan. This raises the question of how one goes about finding optimal plans containing only a limited number of branches. In this paper, we present an any-time algorithm for optimal k-contingency planning. It is the first optimal algorithm for limited contingency planning that is not an explicit enumeration of possible contingent plans. By modelling the problem as a partially observable Markov decision process, it implements the Bellman optimality principle and prunes the solution space. We present experimental results of applying this algorithm to some simple test cases.

  15. Updates on Force Limiting Improvements

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; Scharton, Terry

    2013-01-01

    The following conventional force limiting methods currently practiced in deriving force limiting specifications assume one-dimensional translation source and load apparent masses: Simple TDOF model; Semi-empirical force limits; Apparent mass, etc.; Impedance method. Uncorrelated motion of the mounting points for components mounted on panels and correlated, but out-of-phase, motions of the support structures are important and should be considered in deriving force limiting specifications. In this presentation "rock-n-roll" motions of the components supported by panels, which leads to a more realistic force limiting specifications are discussed.

  16. Auroral particles

    NASA Technical Reports Server (NTRS)

    Evans, David S.

    1987-01-01

    The problems concerning the aurora posed prior to the war are now either solved in principle or were restated in a more fundamental form. The pre-war hypothesis concerning the nature of the auroral particles and their energies was fully confirmed, with the exception that helium and oxygen ions were identified as participating in the auroral particle precipitation in addition to the protons. The nature of the near-Earth energization processes affecting auroral particles was clarified. Charged particle trajectories in various electric field geometries were modeled. The physical problems have now moved from determining the nature and geometry of the electric fields, which accelerate charged particles near the Earth, to accounting for the existence of these electric fields as a natural consequence of the solar wind's interaction with Earth. Ultimately the reward in continuing the work in auroral and magnetospheric particle dynamics will be a deeper understanding of the subtleties of classical electricity and magnetism as applied to situations not blessed with well-defined and invariant geometries.

  17. Two-point derivative dispersion relations

    NASA Astrophysics Data System (ADS)

    Ferreira, Erasmo; Sesma, Javier

    2013-03-01

    A new derivation is given for the representation, under certain conditions, of the integral dispersion relations of scattering theory through local forms. The resulting expressions have been obtained through an independent procedure to construct the real part and consist of new mathematical structures of double infinite summations of derivatives. In this new form the derivatives are calculated at the generic value of the energy E and separately at the reference point E = m that is the lower limit of the integration. This new form may be more interesting in certain circumstances and directly shows the origin of the difficulties in convergence that were present in the old truncated forms called standard-derivative dispersion relations (DDR). For all cases in which the reductions of the double to single sums were obtained in our previous work, leading to explicit demonstration of convergence, these new expressions are seen to be identical to the previous ones. We present, as a glossary, the most simplified explicit results for the DDR's in the cases of imaginary amplitudes of forms (E/m)λ[ln (E/m)]n that cover the cases of practical interest in particle physics phenomenology at high energies. We explicitly study the expressions for the cases with λ negative odd integers, that require identification of cancelation of singularities, and provide the corresponding final results.

  18. Comet Dust: The Diversity of "Primitive" Particles and Implications

    NASA Technical Reports Server (NTRS)

    Wooden, Diane H.; Ishii, Hope A.; Bradley, John P.; Zolensky, Michael E.

    2016-01-01

    Comet dust is primitive and shows significant diversity. Our knowledge of the properties of primitive particles has expanded significantly through microscale investigations of cosmic dust samples ( IDP's(Interplanetary Dust Particles) and AMM's (Antarctic Micrometeorites)) and of comet dust samples (Stardust and Rosetta's COSIMA), as well as through remote sensing (spectroscopy and imaging) via Spitzer and via spacecraft encounters with 103P/Hartley 2 and 67P/Churyumov-Gerasimenko. Microscale investigations show that comet dust and cosmic dust are particles of unequilibrated materials, including aggregates of materials unequilibrated at submicron scales. We call unequilibrated materials "primitive" and we deduce they were incorporated into ice-rich (H2O-, CO2-, and CO-ice) parent bodies that remained cold, i.e., into comets, because of the lack of aqueous or thermal alteration since particle aggregation; yet some Stardust olivines suggest mild thermal metamorphism. Primitive particles exhibit a diverse range of: structure and typology; size and size distribution of constituents; concentration and form of carbonaceous and organic matter; D-, N-, and O- isotopic enhancements over solar; Mg-, Fe-contents of the silicate minerals; the compositions and concentrations of sulfides, and of less abundant mineral species such as chondrules, CAIs and carbonates. The uniformity within a group of samples points to: aerodynamic sorting of particles and/or particle constituents; the inclusion of a limited range of oxygen fugacities; the inclusion or exclusion of chondrules; a selection of organics. The properties of primitive particles imply there were disk processes that resulted in different comets having particular selections of primitive materials. The diversity of primitive particles has implications for the diversity of materials in the protoplanetary disk present at the time and in the region where the comets formed.

  19. Shape phase transitions and critical points

    SciTech Connect

    Alonso, C. E.; Arias, J. M.; Fortunato, L.; Vitturi, A.

    2009-05-04

    We investigate different aspects connected with shape phase transitions in nuclei and the possible occurrence of dynamical symmetries at the critical points. We discuss in particular the behaviour of the neighbour odd nuclei at the vicinity of the critical points in the even nuclei. We consider both the case of the transition from the vibrational behaviour to the gamma-unstable deformation (characterized within the collective Bohr hamiltonian by the E(5) critical point symmetry) and the case of the transition from the vibrational behaviour to the stable axial deformation (characterized by the X(5) symmetry). The odd particle is assumed to be moving in the three single particle orbitals j = 1/2,3/2,5/2, a set of orbitals that is known to lead to possible supersymmetric cases. The coupling of the odd particle to the Bohr hamiltonian does lead in fact in the former case at the critical point to the E(5/12) boson-fermion dynamical symmetry. An alternative approach to the two shape transitions is based on the Interacting Boson Fermion Model. In this case suitably parametrized boson-fermion hamiltonians can describe the evolution of the odd system along the shape transitions. At the critical points both energy spectra and electromagnetic transitions were found to display characteristic patterns similar to those displayed by the even nuclei at the corresponding critical point. The behaviour of the odd nuclei can therefore be seen as necessary complementary signatures of the occurrence of the phase transitions.

  20. Limits on extra dimensions and new particle production in the exclusive photon and missing energy signature in pp collisions at square root [s]=1.8 TeV.

    PubMed

    Acosta, D; Affolder, T; Akimoto, H; Albrow, M G; Ambrose, D; Amidei, D; Anikeev, K; Antos, J; Apollinari, G; Arisawa, T; Artikov, A; Asakawa, T; Ashmanskas, W; Azfar, F; Azzi-Bacchetta, P; Bacchetta, N; Bachacou, H; Badgett, W; Bailey, S; de Barbaro, P; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Barone, M; Bauer, G; Bedeschi, F; Behari, S; Belforte, S; Bell, W H; Bellettini, G; Bellinger, J; Benjamin, D; Bensinger, J; Beretvas, A; Berryhill, J; Bhatti, A; Binkley, M; Bisello, D; Bishai, M; Blair, R E; Blocker, C; Bloom, K; Blumenfeld, B; Blusk, S R; Bocci, A; Bodek, A; Bolla, G; Bonushkin, Y; Bortoletto, D; Boudreau, J; Brandl, A; Bromberg, C; Brozovic, M; Brubaker, E; Bruner, N; Budagov, J; Budd, H S; Burkett, K; Busetto, G; Byrum, K L; Cabrera, S; Calafiura, P; Campbell, M; Carithers, W; Carlson, J; Carlsmith, D; Caskey, W; Castro, A; Cauz, D; Cerri, A; Chan, A W; Chang, P S; Chang, P T; Chapman, J; Chen, C; Chen, Y C; Cheng, M-T; Chertok, M; Chiarelli, G; Chirikov-Zorin, I; Chlachidze, G; Chlebana, F; Christofek, L; Chu, M L; Chung, J Y; Chung, W-H; Chung, Y S; Ciobanu, C I; Clark, A G; Coca, M; Colijn, A P; Connolly, A; Convery, M; Conway, J; Cordelli, M; Cranshaw, J; Culbertson, R; Dagenhart, D; D'Auria, S; DeJongh, F; Dell'Agnello, S; Dell'Orso, M; Demers, S; Demortier, L; Deninno, M; Derwent, P F; Devlin, T; Dittmann, J R; Dominguez, A; Donati, S; D'Onofrio, M; Dorigo, T; Dunietz, I; Eddy, N; Einsweiler, K; Engels, E; Erbacher, R; Errede, D; Errede, S; Fan, Q; Fang, H-C; Feild, R G; Fernandez, J P; Ferretti, C; Field, R D; Fiori, I; Flaugher, B; Flores-Castillo, L R; Foster, G W; Franklin, M; Freeman, J; Friedman, J; Frisch, H J; Fukui, Y; Furic, I; Galeotti, S; Gallas, A; Gallinaro, M; Gao, T; Garcia-Sciveres, M; Garfinkel, A F; Gatti, P; Gay, C; Gerdes, D W; Gerstein, E; Giannetti, P; Giolo, K; Giordani, M; Giromini, P; Glagolev, V; Glenzinski, D; Gold, M; Goldstein, J; Gomez, G; Gorelov, I; Goshaw, A T; Gotra, Y; Goulianos, K; Green, C; Grim, G; Grosso-Pilcher, C; Guenther, M; Guillian, G; Guimaraes da Costa, J; Haas, R M; Haber, C; Hahn, S R; Hall, C; Handa, T; Handler, R; Happacher, F; Hara, K; Hardman, A D; Harris, R M; Hartmann, F; Hatakeyama, K; Hauser, J; Heinrich, J; Heiss, A; Herndon, M; Hill, C; Hocker, A; Hoffman, K D; Hollebeek, R; Holloway, L; Huffman, B T; Hughes, R; Huston, J; Huth, J; Ikeda, H; Incandela, J; Introzzi, G; Ivanov, A; Iwai, J; Iwata, Y; James, E; Jones, M; Joshi, U; Kambara, H; Kamon, T; Kaneko, T; Karagoz Unel, M; Karr, K; Kartal, S; Kasha, H; Kato, Y; Keaffaber, T A; Kelley, K; Kelly, M; Kennedy, R D; Kephart, R; Khazins, D; Kikuchi, T; Kilminster, B; Kim, B J; Kim, D H; Kim, H S; Kim, M J; Kim, S B; Kim, S H; Kim, Y K; Kirby, M; Kirk, M; Kirsch, L; Klimenko, S; Koehn, P; Kondo, K; Konigsberg, J; Korn, A; Korytov, A; Kovacs, E; Kroll, J; Kruse, M; Krutelyov, V; Kuhlmann, S E; Kurino, K; Kuwabara, T; Laasanen, A T; Lai, N; Lami, S; Lammel, S; Lancaster, J; Lancaster, M; Lander, R; Lath, A; Latino, G; LeCompte, T; Le, Y; Lee, K; Lee, S W; Leone, S; Lewis, J D; Lindgren, M; Liss, T M; Liu, J B; Liu, T; Liu, Y C; Litvintsev, D O; Lobban, O; Lockyer, N S; Loken, J; Loreti, M; Lucchesi, D; Lukens, P; Lusin, S; Lyons, L; Lys, J; Madrak, R; Maeshima, K; Maksimovic, P; Malferrari, L; Mangano, M; Manca, G; Mariotti, M; Martignon, G; Martin, M; Martin, A; Martin, V; Matthews, J A J; Mazzanti, P; McFarland, K S; McIntyre, P; Menguzzato, M; Menzione, A; Merkel, P; Mesropian, C; Meyer, A; Miao, T; Miller, R; Miller, J S; Minato, H; Miscetti, S; Mishina, M; Mitselmakher, G; Miyazaki, Y; Moggi, N; Moore, E; Moore, R; Morita, Y; Moulik, T; Mulhearn, M; Mukherjee, A; Muller, T; Munar, A; Murat, P; Murgia, S; Nachtman, J; Nagaslaev, V; Nahn, S; Nakada, H; Nakano, I; Napora, R; Nelson, C; Nelson, T; Neu, C; Neuberger, D; Newman-Holmes, C; Ngan, C-Y P; Nigmanov, T; Niu, H; Nodulman, L; Nomerotski, A; Oh, S H; Oh, Y D; Ohmoto, T; Ohsugi, T; Oishi, R; Okusawa, T; Olsen, J; Onyisi, P U E; Orejudos, W; Pagliarone, C; Palmonari, F; Paoletti, R; Papadimitriou, V; Partos, D; Patrick, J; Pauletta, G; Paulini, M; Pauly, T; Paus, C; Pellett, D; Pescara, L; Phillips, T J; Piacentino, G; Piedra, J; Pitts, K T; Pompos, A; Pondrom, L; Pope, G; Pratt, T; Prokoshin, F; Proudfoot, J; Ptohos, F; Pukhov, O; Punzi, G; Rademacker, J; Rakitine, A; Ratnikov, F; Reher, D; Reichold, A; Renton, P; Ribon, A; Riegler, W; Rimondi, F; Ristori, L; Riveline, M; Robertson, W J; Rodrigo, T; Rolli, S; Rosenson, L; Roser, R; Rossin, R; Rott, C; Roy, A; Ruiz, A; Safonov, A; St Denis, R; Sakumoto, W K; Saltzberg, D; Sanchez, C; Sansoni, A; Santi, L; Sato, H; Savard, P; Savoy-Navarro, A; Schlabach, P; Schmidt, E E; Schmidt, M P; Schmitt, M; Scodellaro, L; Scott, A; Scribano, A; Sedov, A; Seidel, S; Seiya, Y; Semenov, A; Semeria, F; Shah, T; Shapiro, M D; Shepard, P F; Shibayama, T; Shimojima, M; Shochet, M

    2002-12-31

    The exclusive gammaE(T) signal has a small standard model cross section and is thus a channel sensitive to new physics. This signature is predicted by models with a superlight gravitino or with large extra spatial dimensions. We search for such signals at the Collider Detector at Fermilab, using 87 pb(-1) of data at square root [s]=1.8 TeV, and extract 95% C.L. limits on these processes. A limit of 221 GeV is set on the scale |F|(1/2) in supersymmetric models. For 4, 6, and 8 extra dimensions, model-dependent limits on the fundamental mass scale M(D) of 0.55, 0.58, and 0.60 TeV, respectively, are found. We also specify a "pseudo-model-independent" method of comparing the results to theoretical predictions. PMID:12513133

  1. Point-to-Point Multicast Communications Protocol

    NASA Technical Reports Server (NTRS)

    Byrd, Gregory T.; Nakano, Russell; Delagi, Bruce A.

    1987-01-01

    This paper describes a protocol to support point-to-point interprocessor communications with multicast. Dynamic, cut-through routing with local flow control is used to provide a high-throughput, low-latency communications path between processors. In addition multicast transmissions are available, in which copies of a packet are sent to multiple destinations using common resources as much as possible. Special packet terminators and selective buffering are introduced to avoid a deadlock during multicasts. A simulated implementation of the protocol is also described.

  2. Temperature dependence of particle-particle interactions in electrorheological fluids

    NASA Astrophysics Data System (ADS)

    Gonon, P.; Foulc, J.-N.

    2000-04-01

    We report on the temperature dependence of particle-particle interactions in electrorheological (ER) fluids for the temperature range 20-100 °C. The attraction force between polyamide spheres immersed in silicone oil is measured as a function of temperature. The force-temperature characteristic shows a broad maximum around 40 °C, corresponding to an increase of about 30% compared to the force measured at room temperature. In view of these results we proposed that the temperature dependence of the shear stress in ER fluids is directly related to the variation of the local particle-particle attraction forces. Data are discussed in light of models which were proposed in the literature to describe particle-particle interactions. At high electric fields "conduction models" could explain the observed temperature dependence through the variations of the oil breakdown field with temperature. However, limitations of such models are also clearly evidenced by data obtained at low electric fields.

  3. Practical limitations of ITS-90 from the mercury triple point to the silver freeze point

    SciTech Connect

    Tavener, J. P.; Tavener, S. J.; Tavener, I. F.; Davies, N.

    2013-09-11

    The NPL published a forward to the ITS-90 text as follows:- 'The purpose of the ITS is to define procedures by which certain specified practical thermometers of the required quality can be calibrated in such a way that the values of temperature obtained from them can be precise and reproducible, while at the same time closely approximating the corresponding thermodynamic values.' [1]. The paper investigates the properties of thirty four lots of 6N pure metal used to make cells conforming to ITS-90 from mercury through silver over a period of twenty years. Three hundred individual cells are analysed by the impurities listed and supplied with each lot, melt and freeze curve slopes are also summarised for each lot and depressions calculated. These are then compared to the slopes and depressions suggested in the Supplementary Information for the ITS-90 and in CCT/2000-13 'Optimal Realizations'. Results are summarised, tabulated and discussed. Three lots of the thirty four were found to produce cells outside 6N expectations; however the remaining thirty one lots no matter how well or badly the accompanying certification was presented produced cells that conformed to 6N expectations as suggested in Supplementary Information to ITS-90 and CCT/2000-13.

  4. Quantum particle-number fluctuations in a two-component Bose gas in a double-well potential

    SciTech Connect

    Zin, Pawel; Oles, Bartlomiej; Sacha, Krzysztof

    2011-09-15

    A two-component Bose gas in a double-well potential with repulsive interactions may undergo a phase separation transition if the interspecies interactions outweigh the intraspecies ones. We analyze the transition in the strong interaction limit within the two-mode approximation. Numbers of particles in each potential well are equal and constant. However, at the transition point, the ground state of the system reveals huge fluctuations of numbers of particles belonging to the different gas components; that is, the probability for observation of any mixture of particles in each potential well becomes uniform.

  5. Carbon particles

    DOEpatents

    Hunt, Arlon J.

    1984-01-01

    A method and apparatus whereby small carbon particles are made by pyrolysis of a mixture of acetylene carried in argon. The mixture is injected through a nozzle into a heated tube. A small amount of air is added to the mixture. In order to prevent carbon build-up at the nozzle, the nozzle tip is externally cooled. The tube is also elongated sufficiently to assure efficient pyrolysis at the desired flow rates. A key feature of the method is that the acetylene and argon, for example, are premixed in a dilute ratio, and such mixture is injected while cool to minimize the agglomeration of the particles, which produces carbon particles with desired optical properties for use as a solar radiant heat absorber.

  6. Particle Sizer

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Microspheres are tiny plastic beads that represent the first commercial products manufactured in orbit. An example of how they are used is a new aerodynamic particle sizer designated APS 33B produced by TSI Incorporated. TSI purchased the microspheres from the National Bureau of Standards which certified their exact size and the company uses them in calibration of the APS 33B* instrument, latest in a line of TSI systems for generating counting and weighing minute particles of submicron size. Instruments are used for evaluating air pollution control devices, quantifying environments, meteorological research, testing filters, inhalation, toxicology and other areas where generation or analysis of small airborne particles is required. * The APS 33B is no longer being manufactured. An improved version, APS 3320, is now being manufactured. 2/28/97

  7. Point by Point: Adding up Motivation

    ERIC Educational Resources Information Center

    Marchionda, Denise

    2010-01-01

    Students often view their course grades as a mysterious equation of teacher-given grades, teacher-given grace, and some other ethereal components based on luck. However, giving students the power to earn points based on numerous daily/weekly assignments and attendance makes the grading process objective and personal, freeing the instructor to…

  8. Electrokinetic particle-electrode interactions at high frequencies

    NASA Astrophysics Data System (ADS)

    Yariv, Ehud; Schnitzer, Ory

    2013-01-01

    We provide a macroscale description of electrokinetic particle-electrode interactions at high frequencies, where chemical reactions at the electrodes are negligible. Using a thin-double-layer approximation, our starting point is the set of macroscale equations governing the “bounded” configuration comprising of a particle suspended between two electrodes, wherein the electrodes are governed by a capacitive charging condition and the imposed voltage is expressed as an integral constraint. In the large-cell limit the bounded model is transformed into an effectively equivalent “unbounded” model describing the interaction between the particle and a single electrode, where the imposed-voltage condition is manifested in a uniform field at infinity together with a Robin-type condition applying at the electrode. This condition, together with the standard no-flux condition applying at the particle surface, leads to a linear problem governing the electric potential in the fluid domain in which the dimensionless frequency ω of the applied voltage appears as a governing parameter. In the high-frequency limit ω≫1 the flow is dominated by electro-osmotic slip at the particle surface, the contribution of electrode electro-osmosis being O(ω-2) small. That simplification allows for a convenient analytical investigation of the prevailing case where the clearance between the particle and the adjacent electrode is small. Use of tangent-sphere coordinates allows to calculate the electric and flows fields as integral Hankel transforms. At large distances from the particle, along the electrode, both fields decay with the fourth power of distance.

  9. Trajectory dependent particle response for anisotropic mono domain particles in magnetic particle imaging

    NASA Astrophysics Data System (ADS)

    Graeser, M.; Bente, K.; Neumann, A.; Buzug, T. M.

    2016-02-01

    In magnetic particle imaging, scanners use different spatial sampling techniques to cover the field of view (FOV). As spatial encoding is realized by a selective low field region (a field-free-point, or field-free-line), this region has to be moved through the FOV on specific sampling trajectories. To achieve these trajectories complex time dependent magnetic fields are necessary. Due to the superposition of the selection field and the homogeneous time dependent fields, particles at different spatial positions experience different field sequences. As a result, the dynamic behaviour of those particles can be strongly spatially dependent. So far, simulation studies that determined the trajectory quality have used the Langevin function to model the particle response. This however, neglects the dynamic relaxation of the particles, which is highly affected by magnetic anisotropy. More sophisticated models based on stochastic differential equations that include these effects were only used for one dimensional excitation. In this work, a model based on stochastic differential equations is applied to two-dimensional trajectory field sequences, and the effects of these field sequences on the particle response are investigated. The results show that the signal of anisotropic particles is not based on particle parameters such as size and shape alone, but is also determined by the field sequence that a particle ensemble experiences at its spatial position. It is concluded, that the particle parameters can be optimized in terms of the used trajectory.

  10. Black hole formation from pointlike particles in three-dimensional anti-de Sitter space

    NASA Astrophysics Data System (ADS)

    Lindgren, E. J.

    2016-07-01

    We study collisions of many point-like particles in three-dimensional anti-de Sitter space, generalizing the known result with two particles. We show how to construct exact solutions corresponding to the formation of either a black hole or a conical singularity from the collision of an arbitrary number of massless particles falling in radially from the boundary. We find that when going away from the case of equal energies and discrete rotational symmetry, this is not a trivial generalization of the two-particle case, but requires that the excised wedges corresponding to the particles must be chosen in a very precise way for a consistent solution. We also explicitly take the limit when the number of particles goes to infinity and obtain thin shell solutions that in general break rotational invariance, corresponding to an instantaneous and inhomogeneous perturbation at the boundary. We also compute the stress–energy tensor of the shell using the junction formalism for null shells and obtain agreement with the point particle picture.

  11. Plasma Particle Lofting

    NASA Astrophysics Data System (ADS)

    Heijmans, Lucas; Nijdam, Sander

    2015-09-01

    In plasma particle lofting, macroscopic particles are picked up from a surface by an electric force. This force originates from a plasma that charges both the surface and any particle on it, leading to an electric force that pushes particles off the surface. This process has been suggested as a novel cleaning technique in modern high-tech applications, because it has intrinsic advantages over more traditional methods. Its development is, however, limited by a lack of knowledge of the underlying physics. Although the lofting has been demonstrated before, there are neither numerical nor experimental quantitative measures of it. Especially determining the charge deposited by a plasma on a particle on a surface proves difficult. We have developed a novel experimental method using a ``probe force.'' This allows us to, for the first time, quantitatively measure the plasma lofting force. By applying this method to different plasma conditions we can identify the important plasma parameters, allowing us to tailor a plasma for specific cleaning applications. Additionally, the quantitative result can help in the development of new models for the electron and ion currents through a plasma sheath.

  12. Particles causing lung disease.

    PubMed Central

    Kilburn, K H

    1984-01-01

    The lung has a limited number of patterns of reaction to inhaled particles. The disease observed depends upon the location: conducting airways, terminal bronchioles and alveoli, and upon the nature of inflammation induced: acute, subacute or chronic. Many different agents cause narrowing of conducting airways (asthma) and some of these cause permanent distortion or obliteration of airways as well. Terminal bronchioles appear to be particularly susceptible to particles which cause goblet cell metaplasia, mucous plugging and ultimately peribronchiolar fibrosis. Cancer is the last outcome at the bronchial level and appears to depend upon continuous exposure to or retention of an agent in the airway and failure of the affected cells to be exfoliated which may be due to squamous metaplasia. Alveoli are populated by endothelial cells, Type I or pavement epithelial cells and metabolically active cuboidal Type II cells that produce the lungs specific surfactant, dipalmytol lecithin. Disturbances of surfactant lead to edema in distal lung while laryngeal edema due to anaphylaxis or fumes may produce asphyxia. Physical retention of indigestible particles or retention by immune memory responses may provoke hyaline membranes, stimulate alveolar lipoproteinosis and finally fibrosis. This later exuberant deposition of connective tissue has been best studied in the occupational pneumoconioses especially silicosis and asbestosis. In contrast emphysema a catabolic response, appears frequently to result from leakage or release of lysosomal proteases into the lung during processing of cigarette smoke particles. The insidious and probably most important human lung disease due to particles is bronchiolar obstruction and obliteration, producing progressive impairment of air flow. The responsible particle is the complex combination of poorly digestive lipids and complex carbohydrates with active chemicals which we call cigarette smoke. More research is needed to perfect, correct and

  13. Is the wash-off process of road-deposited sediment source limited or transport limited?

    PubMed

    Zhao, Hongtao; Chen, Xuefei; Hao, Shaonan; Jiang, Yan; Zhao, Jiang; Zou, Changliang; Xie, Wenxia

    2016-09-01

    An in-depth understanding of the road-deposited sediments (RDS) wash-off process is essential to estimation of urban surface runoff pollution load and to designing methods to minimize the adverse impacts on the receiving waters. There are two debatable RDS wash-off views: source limited and transport limited. The RDS build-up and wash-off process was characterized to explore what determines the wash-off process to be source limited or transport limited based on twelve RDS sampling activities on an urban road in Beijing. The results showed that two natural rain events (2.0mm and 23.2mm) reduced the total RDS mass by 30%-40%, and that finer particles (<105μm) contributed 60%-80% of the wash-off load. Both single- and multi-rain events caused the RDS particle grain size to become coarser, while dry days made the RDS particle grain size finer. These findings indicated that the bulk RDS particles wash-off tends to be transport limited, but that finer particles tend to be source limited. To further explore and confirm the results of the field experiment, a total of 40 simulated rain events were designed to observe the RDS wash-off with different particle size fractions. The finer particles have a higher wash-off percentage (Fw) than the coarser particles, and the Fw values provide a good view to characterize the wash-off process. The key conclusions drawn from the combined field and simulated experiments data are: (i) Finer and coarser particle wash-off processes tend to be source limited and transport limited, respectively. (ii) The source and transport limited processes occur during the initial period (the first flush) and later periods, respectively. (iii) The smaller and larger rain events tend to be transport limited and source limited, respectively. Overall, the wash-off process is generally a combination of source and transport limited processes. PMID:27135567

  14. 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.

  15. Particle astrophysics

    SciTech Connect

    Sadoulet, B. |

    1992-12-31

    In the last few years, particle astrophysics has emerged as a new field at the frontier between high energy astrophysics, cosmology, and particle physics. Two spectacular achievements of this new field in the last decade have been the establishment of neutrino astronomy with the detection of solar neutrinos by two independent experiments and the spectacular observation of the neutrinos from the supernova SN1987A. In addition, the field has produced tantalizing hints of new physics beyond the standard models of astrophysics and particle physics, generating enthusiastic attempts to confirm these potential effects. This new field involves some two hundred experimentalists and a similar number of theorists, most of them coming from particle and nuclear physics, and as scientist will see, their effort is to a large extent complementary to accelerator based high energy physics. This review attempts, at the beginning of this workshop, to capture the excitement of this new field. Summary talks will describe in more detail some of the topics discussed in the study groups.

  16. Small particle melting of pure metals

    NASA Technical Reports Server (NTRS)

    Allen, G. L.; Bayles, R. A.; Gile, W. W.; Jesser, W. A.

    1986-01-01

    Submicron-sized crystallites of lead, tin, indium and bismuth were melted in situ in the modified specimen chamber of a Siemens transmission e lectron microscope. Melting point and size determinations were made directly from the dark field images of the crystallites. Particles exhibited melting points that decreased with decreasing particle size. A near-linear relationship was observed for the melting point as a function of the reciprocal of the radius. Thermodynamnic expressions based on the significant contributions of the surface energy to the free energy of the system also suggest a linear relation. Other factors, such as shape and surface contamination, were also observed to affect the size-dependent melting of particles. Crystallites of extended platelet shape did not exhibit a significant depression in melting point. Elevated residual gas pressures were found to lessen the melting point depression of spherical particles.

  17. Classifying and assembling two-dimensional X-ray laser diffraction patterns of a single particle to reconstruct the three-dimensional diffraction intensity function: resolution limit due to the quantum noise

    PubMed Central

    Tokuhisa, Atsushi; Taka, Junichiro; Kono, Hidetoshi; Go, Nobuhiro

    2012-01-01

    A new two-step algorithm is developed for reconstructing the three-dimensional diffraction intensity of a globular biological macromolecule from many experimentally measured quantum-noise-limited two-dimensional X-ray laser diffraction patterns, each for an unknown orientation. The first step is classification of the two-dimensional patterns into groups according to the similarity of direction of the incident X-rays with respect to the molecule and an averaging within each group to reduce the noise. The second step is detection of common intersecting circles between the signal-enhanced two-dimensional patterns to identify their mutual location in the three-dimensional wavenumber space. The newly developed algorithm enables one to detect a signal for classification in noisy experimental photon-count data with as low as ∼0.1 photons per effective pixel. The wavenumber of such a limiting pixel determines the attainable structural resolution. From this fact, the resolution limit due to the quantum noise attainable by this new method of analysis as well as two important experimental parameters, the number of two-dimensional patterns to be measured (the load for the detector) and the number of pairs of two-dimensional patterns to be analysed (the load for the computer), are derived as a function of the incident X-ray intensity and quantities characterizing the target molecule. PMID:22514069

  18. Entropic force in black hole binaries and its Newtonian limits

    NASA Astrophysics Data System (ADS)

    van Putten, Maurice H. P. M.

    2012-03-01

    We give an exact solution for the static force between two black holes at the turning points in their binary motion. The results are derived by Gibbs’ principle and the Bekenstein-Hawking entropy applied to the apparent horizon surfaces in time-symmetric initial data. New power laws are derived for the entropy jump in mergers, while Newton’s law is shown to derive from a new adiabatic variational principle for the Hilbert action in the presence of apparent horizon surfaces. In this approach, entropy is strictly monotonic such that gravity is attractive for all separations including mergers, and the Bekenstein entropy bound is satisfied also at arbitrarily large separations, where gravity reduces to Newton’s law. The latter is generalized to point particles in the Newtonian limit by application of Gibbs’ principle to world-lines crossing light cones.

  19. Particle Detectors Subatomic Bomb Squad

    SciTech Connect

    Lincoln, Don

    2014-08-29

    The manner in which particle physicists investigate collisions in particle accelerators is a puzzling process. Using vaguely-defined “detectors,” scientists are able to somehow reconstruct the collisions and convert that information into physics measurements. In this video, Fermilab’s Dr. Don Lincoln sheds light on this mysterious technique. In a surprising analogy, he draws a parallel between experimental particle physics and bomb squad investigators and uses an explosive example to illustrate his points. Be sure to watch this video… it’s totally the bomb.

  20. Rapid detection of Ebola virus with a reagent-free, point-of-care biosensor

    DOE PAGESBeta

    Baca, Justin T.; Severns, Virginia; Lovato, Debbie; Branch, Darren W.; Larson, Richard S.

    2015-04-14

    Surface acoustic wave (SAW) sensors can rapidly detect Ebola antigens at the point-of-care without the need for added reagents, sample processing, or specialized personnel. This preliminary study demonstrates SAW biosensor detection of the Ebola virus in a concentration-dependent manner. The detection limit with this methodology is below the average level of viremia detected on the first day of symptoms by PCR. We observe a log-linear sensor response for highly fragmented Ebola viral particles, with a detection limit corresponding to 1.9 × 10⁴ PFU/mL prior to virus inactivation. We predict greatly improved sensitivity for intact, infectious Ebola virus. This point-of-care methodologymore » has the potential to detect Ebola viremia prior to symptom onset, greatly enabling infection control and rapid treatment. This biosensor platform is powered by disposable AA batteries and can be rapidly adapted to detect other emerging diseases in austere conditions.« less

  1. Rapid detection of Ebola virus with a reagent-free, point-of-care biosensor

    SciTech Connect

    Baca, Justin T.; Severns, Virginia; Lovato, Debbie; Branch, Darren W.; Larson, Richard S.

    2015-04-14

    Surface acoustic wave (SAW) sensors can rapidly detect Ebola antigens at the point-of-care without the need for added reagents, sample processing, or specialized personnel. This preliminary study demonstrates SAW biosensor detection of the Ebola virus in a concentration-dependent manner. The detection limit with this methodology is below the average level of viremia detected on the first day of symptoms by PCR. We observe a log-linear sensor response for highly fragmented Ebola viral particles, with a detection limit corresponding to 1.9 × 10⁴ PFU/mL prior to virus inactivation. We predict greatly improved sensitivity for intact, infectious Ebola virus. This point-of-care methodology has the potential to detect Ebola viremia prior to symptom onset, greatly enabling infection control and rapid treatment. This biosensor platform is powered by disposable AA batteries and can be rapidly adapted to detect other emerging diseases in austere conditions.

  2. Quasi-Static Hydrodynamic Limits

    NASA Astrophysics Data System (ADS)

    De Masi, Anna; Olla, Stefano

    2015-12-01

    We consider hydrodynamic limits of interacting particles systems with open boundaries, where the exterior parameters change in a time scale slower than the typical relaxation time scale. The limit deterministic profiles evolve quasi-statically. These limits define rigorously the thermodynamic quasi static transformations also for transitions between non-equilibrium stationary states. We study first the case of the symmetric simple exclusion, where duality can be used, and then we use relative entropy methods to extend to other models like zero range systems. Finally we consider a chain of anharmonic oscillators in contact with a thermal Langevin bath with a temperature gradient and a slowly varying tension applied to one end.

  3. Acoustic particle acceleration sensors

    SciTech Connect

    Franklin, J.B.; Barry, P.J.

    1996-04-01

    A crossed dipole array provides a directional receiving capability in a relatively small sensor package and is therefore very attractive for many applications in acoustics. Particle velocity measurements on two axes perpendicular to each other are required to provide the dipole signals. These can be obtained directly using particle velocity sensors or via simple transfer functions using acceleration and displacement sensors. Also, the derivative of the acoustic pressure with respect to space provides a signal proportional to the particle acceleration and gives rise to the pressure gradient sensor. Each of these sensors has strengths and drawbacks depending on the frequency regime of interest, the noise background, and whether a point or a line configuration of dipole sensors is desired. In this paper, the performance of acceleration sensors is addressed using a sensor concept developed at DREA. These sensors exploit bending stresses in a cantilever beam of piezoelectric material to obtain wide bandwidth and high sensitivity. Models which predict the acceleration sensitivity, pressure sensitivity, and natural frequency for this type of sensor are described. Experimental results obtained using several different versions of these sensors are presented and compared with theory. The predicted performance of acceleration sensors are compared with that of pressure gradient arrays and particle velocity sensors. {copyright} {ital 1996 American Institute of Physics.}

  4. Beauty is Attractive: Moduli Trapping at Enhanced Symmetry Points

    SciTech Connect

    Kofman, L

    2004-02-27

    We study quantum effects on moduli dynamics arising from the production of particles which are light at points of enhanced symmetry in moduli space. The resulting forces trap the moduli at these points. Moduli trapping occurs in time-dependent quantum field theory, as well as in systems of moving D-branes, where it leads the branes to combine into stacks. Trapping also occurs in the presence of gravity, though the range over which the moduli can roll is limited by Hubble friction. We observe that a scalar field trapped on a steep potential can induce a stage of acceleration of the universe, which we call trapped inflation. Moduli trapping ameliorates the cosmological moduli problem and may affect vacuum selection. In particular, rolling moduli are most powerfully attracted to the points of greatest symmetry. Given suitable assumptions about the dynamics of the very early universe, this effect might help to explain why among the plethora of possible vacuum states of string theory, we appear to live in one with a large number of (spontaneously broken) symmetries.

  5. RELATIVISTIC RECONNECTION: AN EFFICIENT SOURCE OF NON-THERMAL PARTICLES

    SciTech Connect

    Sironi, Lorenzo; Spitkovsky, Anatoly E-mail: anatoly@astro.princeton.edu

    2014-03-01

    In magnetized astrophysical outflows, the dissipation of field energy into particle energy via magnetic reconnection is often invoked to explain the observed non-thermal signatures. By means of two- and three-dimensional particle-in-cell simulations, we investigate anti-parallel reconnection in magnetically dominated electron-positron plasmas. Our simulations extend to unprecedentedly long temporal and spatial scales, so we can capture the asymptotic state of the system beyond the initial transients, and without any artificial limitation by the boundary conditions. At late times, the reconnection layer is organized into a chain of large magnetic islands connected by thin X-lines. The plasmoid instability further fragments each X-line into a series of smaller islands, separated by X-points. At the X-points, the particles become unmagnetized and they get accelerated along the reconnection electric field. We provide definitive evidence that the late-time particle spectrum integrated over the whole reconnection region is a power law whose slope is harder than –2 for magnetizations σ ≳ 10. Efficient particle acceleration to non-thermal energies is a generic by-product of the long-term evolution of relativistic reconnection in both two and three dimensions. In three dimensions, the drift-kink mode corrugates the reconnection layer at early times, but the long-term evolution is controlled by the plasmoid instability which facilitates efficient particle acceleration, analogous to the two-dimensional physics. Our findings have important implications for the generation of hard photon spectra in pulsar winds and relativistic astrophysical jets.

  6. Particle acceleration

    NASA Technical Reports Server (NTRS)

    Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.; Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.; Ellison, D.

    1986-01-01

    Data is compiled from Solar Maximum Mission and Hinothori satellites, particle detectors in several satellites, ground based instruments, and balloon flights in order to answer fundamental questions relating to: (1) the requirements for the coronal magnetic field structure in the vicinity of the energization source; (2) the height (above the photosphere) of the energization source; (3) the time of energization; (4) transistion between coronal heating and flares; (5) evidence for purely thermal, purely nonthermal and hybrid type flares; (6) the time characteristics of the energization source; (7) whether every flare accelerates protons; (8) the location of the interaction site of the ions and relativistic electrons; (9) the energy spectra for ions and relativistic electrons; (10) the relationship between particles at the Sun and interplanetary space; (11) evidence for more than one acceleration mechanism; (12) whether there is single mechanism that will accelerate particles to all energies and also heat the plasma; and (13) how fast the existing mechanisms accelerate electrons up to several MeV and ions to 1 GeV.

  7. Nickel Curie Point Engine

    ERIC Educational Resources Information Center

    Chiaverina, Chris; Lisensky, George

    2014-01-01

    Ferromagnetic materials such as nickel, iron, or cobalt lose the electron alignment that makes them attracted to a magnet when sufficient thermal energy is added. The temperature at which this change occurs is called the "Curie temperature," or "Curie point." Nickel has a Curie point of 627 K, so a candle flame is a sufficient…

  8. Torsade de pointes.

    PubMed

    Munro, P T; Graham, C A

    2002-09-01

    A case is described of torsade de pointes in a 41 year old woman with pre-existing QTc prolongation, potentially exacerbated by treatment with sotalol. Previous cardiac investigations had been normal and after a second episode of ventricular fibrillation the patient was referred for electrophysiological studies. The authors review the physiology, causes, and treatment of QTc prolongation and torsade de pointes. PMID:12205024

  9. Model Breaking Points Conceptualized

    ERIC Educational Resources Information Center

    Vig, Rozy; Murray, Eileen; Star, Jon R.

    2014-01-01

    Current curriculum initiatives (e.g., National Governors Association Center for Best Practices and Council of Chief State School Officers 2010) advocate that models be used in the mathematics classroom. However, despite their apparent promise, there comes a point when models break, a point in the mathematical problem space where the model cannot,…

  10. PDT - PARTICLE DISPLACEMENT TRACKING SOFTWARE

    NASA Technical Reports Server (NTRS)

    Wernet, M. P.

    1994-01-01

    Particle Imaging Velocimetry (PIV) is a quantitative velocity measurement technique for measuring instantaneous planar cross sections of a flow field. The technique offers very high precision (1%) directionally resolved velocity vector estimates, but its use has been limited by high equipment costs and complexity of operation. Particle Displacement Tracking (PDT) is an all-electronic PIV data acquisition and reduction procedure which is simple, fast, and easily implemented. The procedure uses a low power, continuous wave laser and a Charged Coupled Device (CCD) camera to electronically record the particle images. A frame grabber board in a PC is used for data acquisition and reduction processing. PDT eliminates the need for photographic processing, system costs are moderately low, and reduced data are available within seconds of acquisition. The technique results in velocity estimate accuracies on the order of 5%. The software is fully menu-driven from the acquisition to the reduction and analysis of the data. Options are available to acquire a single image or 5- or 25-field series of images separated in time by multiples of 1/60 second. The user may process each image, specifying its boundaries to remove unwanted glare from the periphery and adjusting its background level to clearly resolve the particle images. Data reduction routines determine the particle image centroids and create time history files. PDT then identifies the velocity vectors which describe the particle movement in the flow field. Graphical data analysis routines are included which allow the user to graph the time history files and display the velocity vector maps, interpolated velocity vector grids, iso-velocity vector contours, and flow streamlines. The PDT data processing software is written in FORTRAN 77 and the data acquisition routine is written in C-Language for 80386-based IBM PC compatibles running MS-DOS v3.0 or higher. Machine requirements include 4 MB RAM (3 MB Extended), a single or

  11. Multispectral Image Feature Points

    PubMed Central

    Aguilera, Cristhian; Barrera, Fernando; Lumbreras, Felipe; Sappa, Angel D.; Toledo, Ricardo

    2012-01-01

    This paper presents a novel feature point descriptor for the multispectral image case Far-Infrared and Visible Spectrum images. It allows matching interest points on images of the same scene but acquired in different spectral bands. Initially, points of interest are detected on both images through a SIFT-like based scale space representation. Then, these points are characterized using an Edge Oriented Histogram (EOH) descriptor. Finally, points of interest from multispectral images are matched by finding nearest couples using the information from the descriptor. The provided experimental results and comparisons with similar methods show both the validity of the proposed approach as well as the improvements it offers with respect to the current state-of-the-art.

  12. Instabilities in the Mean Field Limit

    NASA Astrophysics Data System (ADS)

    Han-Kwan, Daniel; Nguyen, Toan T.

    2016-03-01

    Consider a system of N particles interacting through Newton's second law with Coulomb interaction potential in one spatial dimension or a {C}^2 smooth potential in any dimension. We prove that in the mean field limit N → + ∞, the N particles system displays instabilities in times of order log N, for some configurations approximately distributed according to unstable homogeneous equilibria.

  13. Effective reaction rates for transport of particles to heterogeneous reactive (or porous) surfaces under shear

    NASA Astrophysics Data System (ADS)

    Shah, Preyas; Shaqfeh, Eric S. G.

    2015-11-01

    Mass transfer to heterogeneous reactive (or porous) surfaces is common in applications like heterogeneous catalysis, and biological porous media transport like drug delivery. This is modeled as advection-diffusion in a shear flow to an inert surface with first order reactive patches. We study transport of point particles using boundary element simulations. We show that the heterogeneous surface can be replaced with a uniform-flux boundary condition related to the Sherwood number (S), aka, the dimensionless flux to the reactive region. In the dilute limit of reactive regions, large-scale interaction between the reactive patches is important. In the dilute limit of inert regions, [S] grows as the reciprocal of the inert area fraction. Based on the method of resistances and numerical results, we provide correlations for [S] for general reactive surfaces and flow conditions. We model finite sized particles as general spheroids, specifically for biological applications. We do Brownian Dynamics simulations to account for hydrodynamic and steric interactions with the flow field and the domain geometry, and compare to the point particle results. We observe that anisotropic particles gave a higher pore transport flux compared to spherical particles at all flow conditions.

  14. Broken flavor symmetries in high energy particle phenomenology

    SciTech Connect

    Antaramian, A.

    1995-02-22

    Over the past couple of decades, the Standard Model of high energy particle physics has clearly established itself as an invaluable tool in the analysis of high energy particle phenomenon. However, from a field theorists point of view, there are many dissatisfying aspects to the model. One of these, is the large number of free parameters in the theory arising from the Yukawa couplings of the Higgs doublet. In this thesis, we examine various issues relating to the Yukawa coupeng structure of high energy particle field theories. We begin by examining extensions to the Standard Model of particle physics which contain additional scalar fields. By appealing to the flavor structure observed in the fermion mass and Kobayashi-Maskawa matrices, we propose a reasonable phenomenological parameterization of the new Yukawa couplings based on the concept of approximate flavor symmetries. It is shown that such a parameterization eliminates the need for discrete symmetries which limit the allowed couplings of the new scalars. New scalar particles which can mediate exotic flavor changing reactions can have masses as low as the weak scale. Next, we turn to the issue of neutrino mass matrices, where we examine a particular texture which leads to matter independent neutrino oscillation results for solar neutrinos. We, then, examine the basis for extremely strict limits placed on flavor changing interactions which also break lepton- and/or baryon-number. These limits are derived from cosmological considerations. Finally, we embark on an extended analysis of proton decay in supersymmetric SO(10) grand unified theories. In such theories, the dominant decay diagrams involve the Yukawa couplings of a heavy triplet superfield. We argue that past calculations of proton decay which were based on the minimal supersymmetric SU(5) model require reexamination because the Yukawa couplings of that theory are known to be wrong.

  15. The role of ions in the self-healing behavior of soft particle suspensions.

    PubMed

    Scotti, Andrea; Gasser, Urs; Herman, Emily S; Pelaez-Fernandez, Miguel; Han, Jun; Menzel, Andreas; Lyon, L Andrew; Fernández-Nieves, Alberto

    2016-05-17

    Impurities in crystals generally cause point defects and can even suppress crystallization. This general rule, however, does not apply to colloidal crystals formed by soft microgel particles [Iyer ASJ, Lyon LA (2009) Angew Chem Int Ed 48:4562-4566], as, in this case, the larger particles are able to shrink and join the crystal formed by a majority of smaller particles. Using small-angle X-ray scattering, we find the limit in large-particle concentration for this spontaneous deswelling to persist. We rationalize our data in the context of those counterions that are bound to the microgel particles as a result of the electrostatic attraction exerted by the fixed charges residing on the particle periphery. These bound counterions do not contribute to the suspension osmotic pressure in dilute conditions, as they can be seen as internal degrees of freedom associated with each microgel particle. In contrast, at sufficiently high particle concentrations, the counterion cloud of each particle overlaps with that of its neighbors, allowing these ions to freely explore the space outside the particles. We confirm this scenario by directly measuring the osmotic pressure of the suspension. Because these counterions are then no longer bound, they create an osmotic pressure difference between the inside and outside of the microgels, which, if larger than the microgel bulk modulus, can cause deswelling, explaining why large, soft microgel particles feel the squeeze when suspended with a majority of smaller particles. We perform small-angle neutron scattering measurements to further confirm this remarkable behavior. PMID:27125854

  16. Point Source Location Sensitivity Analysis

    NASA Astrophysics Data System (ADS)

    Cox, J. Allen

    1986-11-01

    This paper presents the results of an analysis of point source location accuracy and sensitivity as a function of focal plane geometry, optical blur spot, and location algorithm. Five specific blur spots are treated: gaussian, diffraction-limited circular aperture with and without central obscuration (obscured and clear bessinc, respectively), diffraction-limited rectangular aperture, and a pill box distribution. For each blur spot, location accuracies are calculated for square, rectangular, and hexagonal detector shapes of equal area. The rectangular detectors are arranged on a hexagonal lattice. The two location algorithms consist of standard and generalized centroid techniques. Hexagonal detector arrays are shown to give the best performance under a wide range of conditions.

  17. Catalytic behaviors of enzymes attached to nanoparticles: the effect of particle mobility.

    PubMed

    Jia, Hongfei; Zhu, Guangyu; Wang, Ping

    2003-11-20

    Nanoparticles provide an ideal remedy to the usually contradictory issues encountered in the optimization of immobilized enzymes: minimum diffusional limitation, maximum surface area per unit mass, and high effective enzyme loading. In addition to the promising performance features, the unique solution behaviors of the nanoparticles also point to a transitional region between the heterogeneous (with immobilized enzymes) and homogeneous (with soluble free enzymes) catalysis. The particle mobility, which is related to particle size and solution viscosity through Stokes-Einstein equation, may impact the reaction kinetics according to the collision theory. The mobility-activity relationship was examined through experimental studies and theoretical modeling in the present work. Polystyrene particles with diameters ranging from 110-1000 nm were prepared. A model enzyme, alpha-chymotrypsin, was covalently attached to the nanoparticles up to 6.6 wt%. The collision theory model was found feasible in correlating the catalytic activities of particles to particle size and solution viscosity. Changes in the size of particles and the viscosity of reaction media, which all affect the mobility of the enzyme catalyst, evidently altered the intrinsic activity of the particle-attached enzyme. Compared to K(M), k(cat) appeared to be less sensitive to particle size and viscosity. PMID:14574697

  18. Generation and accretion of electrons in complex plasmas with cylindrical particles

    SciTech Connect

    Sodha, Mahendra Singh; Misra, Shikha; Mishra, S. K.

    2009-12-15

    This paper presents an analytical model for the physical understanding of the charging of cylindrical dust particles in an open complex plasma system. Two different mechanisms, viz., thermionic emission and photoelectric emission have been considered for the electron generation from the charged cylindrical dust particles; the corresponding expressions for the rate of emission of electrons and their mean energy have been derived. A simple approach has been adopted to derive the expression for the rate of electron accretion to the dust particle. Further a new expression for the mean energy associated with the accreted electrons due to cylindrical dust particle has been derived and presented. An interesting comparison of results obtained in the case of spherical and cylindrical dust particles has also been made. Using these expressions, a formalism has been developed for the electronic processes in an illuminated dust cloud with cylindrical particles, on the basis of charge neutrality condition and number and energy balance of electrons; the charge carried by the cylindrical dust particles, electron temperature, and electron density corresponding to a given situation have been determined. The limitation of the applicability of the theory, viz., that the mean free path of an electron for accretion by dust particles be less than the dimension of the dust cloud has been pointed out.

  19. Triple point of Yukawa systems

    NASA Astrophysics Data System (ADS)

    Hamaguchi, S.; Farouki, R. T.; Dubin, D. H. E.

    1997-10-01

    The molecular dynamics simulations of Yukawa (i.e., screened-Coulomb) systems that were applied to the regime of weak screening in an earlier study [S. Hamaguchi, R. T. Farouki, and D. H. E. Dubin, J. Chem. Phys. 105, 7641 (1996)] are extended to the strong screening regime. Transition temperatures at the fluid-solid phase boundary and the solid-solid phase boundary are obtained as functions of the screening parameter κ=a/λD (i.e., the ratio of the Wigner-Seitz radius a to the Debye length λD). The resulting phase diagram also covers the triple point-the intersection of the fluid-solid and solid-solid phase boundaries-at κ=4.28 and Γ=5.6×103, where Γ is the ratio of the Coulomb potential energy to the kinetic energy per particle (i.e., Γ=Q2/4πɛ0akT, where Q is the charge of each Yukawa particle and T is the system temperature). Yukawa systems serve as models for plasmas and colloidal suspensions of charged particulates.

  20. Experimental Investigation of Particle Deagglomeration using Turbulence

    NASA Astrophysics Data System (ADS)

    Köksoy, Çaǧatay; Ertunç, Özgür; Hüttner, Sebastian; Wachtel, Herbert; Delgado, Antonio

    2011-12-01

    The effect of turbulence on powder aerosol deagglomeration was investigated. Two impinging jets were used to generate turbulence. Lactose particles, whose fully dispersed fine particle fraction (FPF) - number percentage of the particles whose diameter smaller than 5 μm- is above 90 %, were applied as aerosol powder. The particle size distribution after the dispersion unit were measured by using phase Doppler anemometer (PDA) and turbulence level were quantified at the impingement point of two jets with laser Doppler anemometer. As the turbulence level increases turbulent time and length scales decrease, and the ratio of fine particle fraction (FPF) increases from 36% to 86%.

  1. Particles causing lung disease

    SciTech Connect

    Kilburn, K.H.

    1984-04-01

    The lung has a limited number of patterns of reaction to inhaled particles. The disease observed depends upon the location: conducting airways, terminal bronchioles and alveoli, and upon the nature of inflammation induced: acute, subacute or chronic. Many different agents cause narrowing of conducting airways (asthma) and some of these cause permanent distortion or obliteration of airways as well. Terminal bronchioles appear to be particularly susceptible to particles which cause goblet cell metaplasia, mucous plugging and ultimately peribronchiolar fibrosis. Cancer is the last outcome at the bronchial level and appears to depend upon continuous exposure to or retention of an agent in the airway and failure of the affected cells to be exfoliated which may be due to squamous metaplasia. Alveoli are populated by endothelial cells, Type I or pavement epithelial cells and metabolically active cuboidal Type II cells that produce the lungs specific surfactant, dipalmytol lecithin. Disturbances of surfactant lead to edema in distal lung while laryngeal edema due to anaphylaxis or fumes may produce asphyxia. Physical retention of indigestible particles or retention by immune memory responses may provoke hyaline membranes, stimulate alveolar lipoproteinosis and finally fibrosis. This later exuberant deposition of connective tissue has been best studied in the occupational pneumoconioses especially silicosis and asbestosis. In contrast emphysema a catabolic response appears frequently to result from leakage or release of lysosomal proteases into the lung during processing of cigarette smoke particles. 164 references, 1 figure, 2 tables.

  2. CFD development for macro particle simulations

    NASA Astrophysics Data System (ADS)

    Zhao, Xiang; Glenn, Chance; Xiao, Zhigang; Zhang, Sijun

    2014-05-01

    Numerous industrial operations involve fluid-particle systems, in which both phases display very complex behaviour. Some examples include fluidisation technology in catalytic reactors, pneumatic transportation of grain or powder materials, carbon nanotube alignment in the nano-devices and circuit integration and so on. In this paper, a macro particle method is developed to model the fluid-particle flows. The macro particle is formed by a collection of micro-sized particles so that the number of macro particles to be tracked is much less than the number of smaller particles. Unlike the calculations of instantaneous point variables of fluid phase with moving discrete boundaries of the smaller particles with direct numerical simulation, the boundary of each macro particle is just dealt with the blocked-off approach. On the other hand, the flow fields based on the present method is solved by original Navier-Stokes, rather than the modified ones based on the locally averaged theorem. The flow fields are solved on the length scale of computational cells, while the resolutions of solid particles are the size of macro particle, which is determined as needed in specific applications. The macro particle method is validated by several selected cases, which demonstrate that the macro particle method could accurately resolve fluid-particle systems in an efficient, robust and flexible fashion.

  3. Strike Point Control on EAST Using an Isoflux Control Method

    NASA Astrophysics Data System (ADS)

    Xing, Zhe; Xiao, Bingjia; Luo, Zhengping; L. Walker, M.; A. Humphreys, D.

    2015-09-01

    For the advanced tokamak, the particle deposition and thermal load on the divertor is a big challenge. By moving the strike points on divertor target plates, the position of particle deposition and thermal load can be shifted. We could adjust the Poloidal Field (PF) coil current to achieve the strike point position feedback control. Using isoflux control method, the strike point position can be controlled by controlling the X point position. On the basis of experimental data, we establish relational expressions between X point position and strike point position. Benchmark experiments are carried out to validate the correctness and robustness of the control methods. The strike point position is successfully controlled following our command in the EAST operation. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2012GB105000 and 2014GB103000)

  4. Arctic climate tipping points.

    PubMed

    Lenton, Timothy M

    2012-02-01

    There is widespread concern that anthropogenic global warming will trigger Arctic climate tipping points. The Arctic has a long history of natural, abrupt climate changes, which together with current observations and model projections, can help us to identify which parts of the Arctic climate system might pass future tipping points. Here the climate tipping points are defined, noting that not all of them involve bifurcations leading to irreversible change. Past abrupt climate changes in the Arctic are briefly reviewed. Then, the current behaviour of a range of Arctic systems is summarised. Looking ahead, a range of potential tipping phenomena are described. This leads to a revised and expanded list of potential Arctic climate tipping elements, whose likelihood is assessed, in terms of how much warming will be required to tip them. Finally, the available responses are considered, especially the prospects for avoiding Arctic climate tipping points. PMID:22270703

  5. Point tenderness - abdomen

    MedlinePlus

    ... medlineplus.gov/ency/article/003273.htm Point tenderness - abdomen To use the sharing features on this page, ... over a certain part of the belly area (abdomen). Considerations The abdomen is an area of the ...

  6. Review of Particle Physics

    NASA Astrophysics Data System (ADS)

    Olive, K. A.; Particle Data Group

    2014-08-01

    The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 3,283 new measurements from 899 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as heavy neutrinos, supersymmetric and technicolor particles, axions, dark photons, etc. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as Supersymmetry, Extra Dimensions, Particle Detectors, Probability, and Statistics. Among the 112 reviews are many that are new or heavily revised including those on: Dark Energy, Higgs Boson Physics, Electroweak Model, Neutrino Cross Section Measurements, Monte Carlo Neutrino Generators, Top Quark, Dark Matter, Dynamical Electroweak Symmetry Breaking, Accelerator Physics of Colliders, High-Energy Collider Parameters, Big Bang Nucleosynthesis, Astrophysical Constants and Cosmological Parameters. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: http://pdg.lbl.gov. Contents Abstract, Contributors, Highlights and Table of ContentsAcrobat PDF (4.4 MB) IntroductionAcrobat PDF (595 KB) Particle Physics Summary Tables Gauge and Higgs bosonsAcrobat PDF (204 KB) LeptonsAcrobat PDF (167 KB) QuarksAcrobat PDF (115 KB) MesonsAcrobat PDF (976 KB) BaryonsAcrobat PDF (384 KB) Searches (Supersymmetry, Compositeness, etc.)Acrobat PDF (120 KB) Tests of conservation lawsAcrobat PDF (383 KB) Reviews, Tables, and Plots Detailed contents for this sectionAcrobat PDF (73 KB) Constants, Units, Atomic and Nuclear PropertiesAcrobat PDF (395 KB) Standard Model and Related TopicsAcrobat PDF (8.37 MB) Astrophysics and CosmologyAcrobat PDF (3.79 MB) Experimental Methods and CollidersAcrobat PDF (3.82 MB) Mathematical Tools of Statistics, Monte Carlo, Group Theory Acrobat

  7. Nickel Curie point engine

    NASA Astrophysics Data System (ADS)

    Chiaverina, Chris; Lisensky, George

    2014-04-01

    Ferromagnetic materials such as nickel, iron, or cobalt lose the electron alignment that makes them attracted to a magnet when sufficient thermal energy is added. The temperature at which this change occurs is called the "Curie temperature," or "Curie point." Nickel has a Curie point of 627 K, so a candle flame is a sufficient heat source. A simple but elegant device illustrates this phenomenon beautifully.

  8. Oxidation Numbers and Their Limitations.

    ERIC Educational Resources Information Center

    Woolf, A. A.

    1988-01-01

    Reviews a method for determining oxidation numbers in covalent compounds and balancing mixed organic-inorganic or purely organic systems. Points out ambiguities presented when adjacent atoms have small or zero electronegativity differences. Presents other limitations that arise when using electronegativity values. (CW)

  9. Particle Physics

    NASA Astrophysics Data System (ADS)

    Cooper, Necia Grant; West, Geoffrey B.

    1988-06-01

    Preface; Introduction; Part I. Theoretical Framework: 1. Scale and dimension - From animals to quarks Geoffrey B. West; 2. Particle physics and the standard model Stuart Raby, Richard C. Slansky and Geoffrey B. West; QCD on a Cray: the masses of elementary particles Gerald Guralnik, Tony Warnock and Charles Zemach; Lecture Notes - From simple field theories to the standard model; 3. Toward a unified theory: an essay on the role of supergravity in the search for unification Richard C. Slansky; 4. Supersymmetry at 100 GeV Stuart Raby; 5. The family problem T. Goldman and Michael Martin Nieto; Part II. Experimental Developments: 6. Experiments to test unification schemes Gary H. Sanders; 7. The march toward higher energies S. Peter Rosen; LAMPF II and the High-Intensity Frontier Henry A. Thiessen; The SSC - An engineering challenge Mahlon T. Wilson; 8. Science underground - the search for rare events L. M. Simmons, Jr; Part III. Personal Perspectives: 9. Quarks and quirks among friends Peter A. Carruthers, Stuart Raby, Richard C. Slansky, Geoffrey B. West and George Zweig; Index.

  10. Bloch points are sticky

    NASA Astrophysics Data System (ADS)

    Tchernyshyov, Oleg; Kim, Se Kwon

    2014-03-01

    Bloch points are zero-dimensional topological defects in three-dimensional ferromagnets. A representative magnetic configuration is a hedgehog with magnetization pointing away from a center. The singular nature of a Bloch point's core leads to interesting and observable consequences. A simple argument based on dimensional analysis shows that a magnetic lattice creates a periodic potential that can pin a Bloch point even if the lattice has no defects. The pinning force is of the order of the micromagnetic exchange constant, a few piconewtons in a typical ferromagnet. A domain wall in a cylindrical ferromagnetic wire with the diameter of a few tens of nanometers may contain a Bloch point. Such a domain wall will have a sizable depinning field, tens of oersteds. A Bloch point moving through an atomic lattice should emit electromagnetic waves at the frequency of a few hundred gigahertz. Research supported in part by the U.S. National Science Foundation under Grants No. DMR-0520491 and No. DMR-1104753.

  11. Particle Pollution

    MedlinePlus

    ... EPA Air Quality Index (AQI) tells you when air pollution is likely to reach levels that could be ... high, take steps to limit the amount of air you breathe in while you're outside. ... pollution levels are usually lower. Choose easier outdoor activities ( ...

  12. Magnetic guidance of charged particles

    NASA Astrophysics Data System (ADS)

    Dubbers, Dirk

    2015-09-01

    Many experiments and devices in physics use static magnetic fields to guide charged particles from a source onto a detector, and we ask the innocent question: What is the distribution of particle intensity over the detector surface? One should think that the solution to this seemingly simple problem is well known. We show that, even for uniform guide fields, this is not the case, and we present analytical point spread functions (PSF) for magnetic transport that deviate strongly from previous results. The "magnetic" PSF shows unexpected singularities, which were recently also observed experimentally, and which make detector response very sensitive to minute changes of position, field amplitude, or particle energy. In the field of low-energy particle physics, these singularities may become a source of error in modern high precision experiments, or may be used for instrument tests.

  13. FINE PARTICLE EMISSIONS INFORMATION SYSTEM REFERENCE MANUAL

    EPA Science Inventory

    The report is a basic reference manual on the Fine Particle Emissions Information System (FPEIS), a computerized database on primary fine particle emissions to the atmosphere from stationary point sources. The FPEIS is a component of the Environmental Assessment Data Systems (EAD...

  14. Particle acceleration by Majumdar-Papapetrou di-hole

    NASA Astrophysics Data System (ADS)

    Patil, Mandar; Joshi, Pankaj S.

    2014-10-01

    We explore the multi-black hole spacetimes from the perspective of the ultra-high energy particle collisions. Such a discussion is limited to the spacetimes containing a single black hole so far. We deal with the Majumdar-Papapetrou solution representing a system consisting of two identical black holes in the equilibrium. In order to identify the conditions suitable for the process of high energy collisions, we consider particles confined to move on the equatorial plane towards the axis of symmetry with the zero angular momentum. We consider collision between the particles moving in opposite directions at the location midway between the black holes on the axis. We show that the center of mass energy of collision between the particles increases with the decrease in the separation between the black holes and shows divergence in the limit where the separation goes to zero. We estimate the size of the region close to the central point on the equatorial plane where it would be possible to have high energy collisions and show that this region has a reasonably large spatial extent. We further explore the process of high energy collisions with the general geodesics with arbitrary angular momentum on the equatorial plane away from the central point. Although in this paper we deal with theMajumdar-Papapetrou spacetime which serves as a toy example representing multiple black holes, we speculate on the possibility that the ultra-high energy collisions would also occur in the more general setting like colliding black holes, when distance between the black holes is extremely small, which can in principle be verified in the numerical relativity simulations.

  15. Dispersal pathways for particle-associated pollutants

    SciTech Connect

    Young, R.A.: Swift, D.J.P; Clarke, T.L.; Harvey, G.R.; Betzer, P.R.

    1985-08-02

    Particle-associated pollutants (totaling 10/sup 7/ metric tons per year) are introduced into the New York Bight by ocean dumping, estuarine discharge, sewage outfalls, eoliam transport, and shipping waste and spillage. Oceanic and estuarine circulation processes dilute and transport the particles by a natural dispersal system that also tends to be highly distributive; particle-associated pollutants apparently seek the same sinks in the Hudson River shelf valley and intracoastal wetlands, regardless of their point of introduction. 27 references, 5 figures.

  16. Single Particle Difraction at FLASH

    SciTech Connect

    Bogan, M.; Boutet, S.; Starodub, Dmitri; Decorwin-Martin, Philippe; Chapman, H.; Bajt, S.; Schulz, J.; Hajdu, Janos; Seibert, M.M.; Iwan, Bianca; Timneanu, Nicusor; Marchesini, Stefano; Barty, Anton; Benner, W.Henry; Frank, Matthias; Hau-Riege, Stefan P.; Woods, Bruce; Rohner, Urs; /Tofwerk AG, Thun

    2010-06-11

    Single-pulse coherent diffraction patterns have been collected from randomly injected single particles with a soft X-ray free-electron laser (FEL). The intense focused FEL pulse gives a high-resolution low-noise coherent diffraction pattern of the object before that object turns into a plasma and explodes. A diffraction pattern of a single particle will only be recorded when the particle arrival into the FEL interaction region coincides with FEL pulse arrival and detector integration. The properties of the experimental apparatus coinciding with these three events set the data acquisition rate. For our single particle FLASH diffraction imaging experiments: (1) an aerodynamic lens stack prepared a particle beam that consisted of particles moving at 150-200 m/s positioned randomly in space and time, (2) the 10 fs long FEL pulses were delivered at a fixed rate, and (3) the detector was set to integrate and readout once every two seconds. The effect of these experimental parameters on the rate of data acquisition using randomly injected particles will be discussed. Overall, the ultrashort FEL pulses do not set the limit of the data acquisition, more important is the effective interaction time of the particle crossing the FEL focus, the pulse sequence structure and the detector readout rate. Example diffraction patterns of randomly injected ellipsoidal iron oxide nanoparticles in different orientations are presented. This is the first single particle diffraction data set of identical particles in different orientations collected on a shot-to-shot basis. This data set will be used to test algorithms for recovering 3D structure from single particle diffraction.

  17. Relativistic point interactions: Approximation by smooth potentials

    NASA Astrophysics Data System (ADS)

    Hughes, Rhonda J.

    1997-06-01

    We show that the four-parameter family of one-dimensional relativistic point interactions studied by Benvegnu and Dąbrowski may be approximated in the strong resolvent sense by smooth, local, short-range perturbations of the Dirac Hamiltonian. In addition, we prove that the nonrelativistic limits correspond to the Schrödinger point interactions studied extensively by the author and Paul Chernoff.

  18. Thermodynamic Limit in Statistical Physics

    NASA Astrophysics Data System (ADS)

    Kuzemsky, A. L.

    2014-03-01

    The thermodynamic limit in statistical thermodynamics of many-particle systems is an important but often overlooked issue in the various applied studies of condensed matter physics. To settle this issue, we review tersely the past and present disposition of thermodynamic limiting procedure in the structure of the contemporary statistical mechanics and our current understanding of this problem. We pick out the ingenious approach by Bogoliubov, who developed a general formalism for establishing the limiting distribution functions in the form of formal series in powers of the density. In that study, he outlined the method of justification of the thermodynamic limit when he derived the generalized Boltzmann equations. To enrich and to weave our discussion, we take this opportunity to give a brief survey of the closely related problems, such as the equipartition of energy and the equivalence and nonequivalence of statistical ensembles. The validity of the equipartition of energy permits one to decide what are the boundaries of applicability of statistical mechanics. The major aim of this work is to provide a better qualitative understanding of the physical significance of the thermodynamic limit in modern statistical physics of the infinite and "small" many-particle systems.

  19. Particle dynamics and particle-cell interaction in microfluidic systems

    NASA Astrophysics Data System (ADS)

    Stamm, Matthew T.

    Particle-laden flow in a microchannel resulting in aggregation of microparticles was investigated to determine the dependence of the cluster growth rate on the following parameters: suspension void fraction, shear strain rate, and channel-height to particle-diameter ratio. The growth rate of an average cluster was found to increase linearly with suspension void fraction, and to obey a power-law relationships with shear strain rate as S 0.9 and channel-height to particle-diameter ratio as (h/d )--3.5. Ceramic liposomal nanoparticles and silica microparticles were functionalized with antibodies that act as targeting ligands. The bio-functionality and physical integrity of the cerasomes were characterized. Surface functionalization allows cerasomes to deliver drugs with selectivity and specificity that is not possible using standard liposomes. The functionalized particle-target cell binding process was characterized using BT-20 breast cancer cells. Two microfluidic systems were used; one with both species in suspension, the other with cells immobilized inside a microchannel and particle suspension as the mobile phase. Effects of incubation time, particle concentration, and shear strain rate on particle-cell binding were investigated. With both species in suspension, the particle-cell binding process was found to be reasonably well-described by a first-order model. Particle desorption and cellular loss of binding affinity in time were found to be negligible; cell-particle-cell interaction was identified as the limiting mechanism in particle-cell binding. Findings suggest that separation of a bound particle from a cell may be detrimental to cellular binding affinity. Cell-particle-cell interactions were prevented by immobilizing cells inside a microchannel. The initial stage of particle-cell binding was investigated and was again found to be reasonably well-described by a first-order model. For both systems, the time constant was found to be inversely proportional to

  20. Nonlinear Burn Control and Operating Point Optimization in ITER

    NASA Astrophysics Data System (ADS)

    Boyer, Mark; Schuster, Eugenio

    2013-10-01

    Control of the fusion power through regulation of the plasma density and temperature will be essential for achieving and maintaining desired operating points in fusion reactors and burning plasma experiments like ITER. In this work, a volume averaged model for the evolution of the density of energy, deuterium and tritium fuel ions, alpha-particles, and impurity ions is used to synthesize a multi-input multi-output nonlinear feedback controller for stabilizing and modulating the burn condition. Adaptive control techniques are used to account for uncertainty in model parameters, including particle confinement times and recycling rates. The control approach makes use of the different possible methods for altering the fusion power, including adjusting the temperature through auxiliary heating, modulating the density and isotopic mix through fueling, and altering the impurity density through impurity injection. Furthermore, a model-based optimization scheme is proposed to drive the system as close as possible to desired fusion power and temperature references. Constraints are considered in the optimization scheme to ensure that, for example, density and beta limits are avoided, and that optimal operation is achieved even when actuators reach saturation. Supported by the NSF CAREER award program (ECCS-0645086).

  1. Particle bed reactor modeling

    NASA Technical Reports Server (NTRS)

    Sapyta, Joe; Reid, Hank; Walton, Lew

    1993-01-01

    The topics are presented in viewgraph form and include the following: particle bed reactor (PBR) core cross section; PBR bleed cycle; fuel and moderator flow paths; PBR modeling requirements; characteristics of PBR and nuclear thermal propulsion (NTP) modeling; challenges for PBR and NTP modeling; thermal hydraulic computer codes; capabilities for PBR/reactor application; thermal/hydralic codes; limitations; physical correlations; comparison of predicted friction factor and experimental data; frit pressure drop testing; cold frit mask factor; decay heat flow rate; startup transient simulation; and philosophy of systems modeling.

  2. ATLAS solar pointing operations

    NASA Technical Reports Server (NTRS)

    Tyler, C. A.; Zimmerman, C. J.

    1994-01-01

    The ATLAS-series of Spacelab missions are comprised of a diverse group of scientific instruments including instruments for studying the sun and how the sun's energy changes across an eleven-year solar cycle. The ATLAS solar instruments are located on one or more pallets in the Orbiter payload bay and use the Orbiter as a pointing platform for their examinations of the sun. One of the ATLAS instruments contained a sun sensor which allowed scientists and engineers on the ground to see the pointing error of the sun with respect to the instrument and correct for the error based upon the information coming from the ATLAS 1 and ATLAS 2 missions with particular attention given to identifying the sources of pointing discrepancies of the solar instruments and to describe the crew and ground controller procedures that were developed to correct for these discrepancies. The Orbiter pointing behavior from the ATLAS 1 and ATLAS 2 flights presented in this paper can be applied to future flights which use the Orbiter as a pointing platform.

  3. SOFIA pointing history

    NASA Astrophysics Data System (ADS)

    Kärcher, Hans J.; Kunz, Nans; Temi, Pasquale; Krabbe, Alfred; Wagner, Jörg; Süß, Martin

    2014-07-01

    The original pointing accuracy requirement of the Stratospheric Observatory for Infrared Astronomy SOFIA was defined at the beginning of the program in the late 1980s as very challenging 0.2 arcsec rms. The early science flights of the observatory started in December 2010 and the observatory has reached in the mean time nearly 0.7 arcsec rms, which is sufficient for most of the SOFIA science instruments. NASA and DLR, the owners of SOFIA, are planning now a future 4 year program to bring the pointing down to the ultimate 0.2 arcsec rms. This may be the right time to recall the history of the pointing requirement and its verification and the possibility of its achievement via early computer models and wind tunnel tests, later computer aided end-to-end simulations up to the first commissioning flights some years ago. The paper recollects the tools used in the different project phases for the verification of the pointing performance, explains the achievements and may give hints for the planning of the upcoming final pointing improvement phase.

  4. Modeling particle loss in ventilation ducts

    SciTech Connect

    Sippola, Mark R.; Nazaroff, William W.

    2003-04-01

    Empirical equations were developed and applied to predict losses of 0.01-100 {micro}m airborne particles making a single pass through 120 different ventilation duct runs typical of those found in mid-sized office buildings. For all duct runs, losses were negligible for submicron particles and nearly complete for particles larger than 50 {micro}m. The 50th percentile cut-point diameters were 15 {micro}m in supply runs and 25 {micro}m in return runs. Losses in supply duct runs were higher than in return duct runs, mostly because internal insulation was present in portions of supply duct runs, but absent from return duct runs. Single-pass equations for particle loss in duct runs were combined with models for predicting ventilation system filtration efficiency and particle deposition to indoor surfaces to evaluate the fates of particles of indoor and outdoor origin in an archetypal mechanically ventilated building. Results suggest that duct losses are a minor influence for determining indoor concentrations for most particle sizes. Losses in ducts were of a comparable magnitude to indoor surface losses for most particle sizes. For outdoor air drawn into an unfiltered ventilation system, most particles smaller than 1 {micro}m are exhausted from the building. Large particles deposit within the building, mostly in supply ducts or on indoor surfaces. When filters are present, most particles are either filtered or exhausted. The fates of particles generated indoors follow similar trends as outdoor particles drawn into the building.

  5. Compton scattering off elementary spin (3/2) particles

    SciTech Connect

    Delgado-Acosta, E. G.; Napsuciale, M.

    2009-09-01

    We calculate Compton scattering off an elementary spin (3/2) particle in a recently proposed framework for the description of high spin fields based on the projection onto eigensubspaces of the Casimir operators of the Poincare group. We also calculate this process in the conventional Rarita-Schwinger formalism. Both formalisms yield the correct Thomson limit but the predictions for the angular distribution and total cross section differ beyond this point. We point out that the average squared amplitudes in the forward direction for Compton scattering off targets with spin s=0, (1/2), 1 are energy independent and have the common value 4e{sup 4}. As a consequence, in the rest frame of the particle the differential cross section for Compton scattering in the forward direction is energy independent and coincides with the classical squared radius. We show that these properties are also satisfied by a spin (3/2) target in the Poincare projector formalism but not by the Rarita-Schwinger spin (3/2) particle.

  6. Particle Motion Analysis Reveals Nanoscale Bond Characteristics and Enhances Dynamic Range for Biosensing.

    PubMed

    Visser, Emiel W A; van IJzendoorn, Leo J; Prins, Menno W J

    2016-03-22

    Biofunctionalized colloidal particles are widely used as labels in bioanalytical assays, lab-on-chip devices, biophysical research, and in studies on live biological systems. With detection resolution going down to the level of single particles and single molecules, understanding the nature of the interaction of the particles with surfaces and substrates becomes of paramount importance. Here, we present a comprehensive study of motion patterns of colloidal particles maintained in close proximity to a substrate by short molecular tethers (40 nm). The motion of the particles (500-1000 nm) was optically tracked with a very high localization accuracy (below 3 nm). A surprisingly large variation in motion patterns was observed, which can be attributed to properties of the particle-molecule-substrate system, namely the bond number, the nature of the bond, particle protrusions, and substrate nonuniformities. Experimentally observed motion patterns were compared to numerical Monte Carlo simulations, revealing a close correspondence between the observed motion patterns and properties of the molecular system. Particles bound via single tethers show distinct disc-, ring-, and bell-shaped motion patterns, where the ring- and bell-shaped patterns are caused by protrusions on the particle in the direct vicinity of the molecular attachment point. Double and triple tethered particles exhibit stripe-shaped and triangular-shaped motion patterns, respectively. The developed motion pattern analysis allows for discrimination between particles bound by different bond types, which opens the possibility to improve the limit of detection and the dynamic range of bioanalytical assays, with a projected increase of dynamic range by nearly 2 orders of magnitude. PMID:26913834

  7. Predictive model for diffusion-limited aggregation kinetics of nanocolloids under high concentration.

    PubMed

    Lattuada, Marco

    2012-01-12

    Smoluchowski's equation for the rate of aggregation of colloidal particles under diffusion-limited conditions has set the basis for the interpretation of kinetics of aggregation phenomena. Nevertheless, its use is limited to sufficiently dilute conditions. In this work we propose a correction to Smoluchowski's equation by using a result derived by Richards ( J. Phys. Chem. 1986 , 85 , 3520 ) within the framework of trapping theory. This corrected aggregation kernel, which accounts for concentration dependence effects, has been implemented in a population-balance equations scheme and used to model the aggregation kinetics of colloidal particles undergoing diffusion-limited aggregation under concentrated conditions (up to a particle volume fraction of 30%). The predictions of population balance calculations have been validated by means of Brownian dynamic simulations. It was found that the corrected kernel can very well reproduce the results from Brownian dynamic simulations for all concentration values investigated, and is also able to accurately predict the time required by a suspension to reach the gel point. On the other hand, classical Smoluchowski's theory substantially underpredicts the rate of aggregation as well as the onset of gelation, with deviations becoming progressively more severe as the particle volume fraction increases. PMID:22148884

  8. ) Composites Containing Nanoparticles and Larger Particles

    NASA Astrophysics Data System (ADS)

    Ghanaraja, S.; Nath, S. K.; Ray, S.

    2014-07-01

    The composites reinforced with nanoparticles result in improved strength and ductility while those containing coarser particles of micron size have limited ductility. The present study investigates the outcome of mechanical properties in a composite reinforced simultaneously with coarse and fine particles. High energy milling of manganese dioxide particles with excess of aluminum powder ensures that nanoparticles generated, either of MnO2 or alumina, are mostly separate and surrounded by aluminum particles. The milled powder when added to aluminum alloy melt, the excess aluminum particles will melt leaving behind separate oxide nanoparticles without significant agglomeration. Different amounts of milled powder mix have been stirred into molten aluminum alloy where nanoparticles of MnO2 react with melt to form alumina. The resulting slurry is cast into composites, which also contains coarser (nearly micron size) alumina particles formed by internal oxidation of the melt during processing. The microstructure of the composites shows good distribution of both the size categories of particles without significant clustering. The oxide particles are primarily γ-alumina in a matrix of aluminum-magnesium-manganese alloy containing some iron picked up from the stirrer. These composites fail during tensile test by ductile fracture due to debonding of coarser particles. The presence of nanoparticles along with coarser particles in a composite improves both strength and ductility considerably, presumably due to delay in debonding of coarser particles to higher stress because of reduced mismatch in extension caused by increased strain hardening in presence of nanoparticles in the matrix. The composites containing only coarser oxide particles show limited strength and ductility attributed to early debonding of particles at a relatively lower stress due to larger mismatch in extension between matrix and larger particles. Higher addition of powder mix beyond a limit, however

  9. Point-by-point near-field optical energy deposition around plasmonic nanospheres in absorbing media.

    PubMed

    Harrison, R K; Ben-Yakar, Adela

    2015-08-01

    Here we investigate the effects of absorbing media on plasmon-enhanced near-field optical energy deposition. We find that increasing absorption by the medium results in increased particle scattering at the expense of particle absorption, and that much of this increased particle scattering is absorbed by the medium close to the particle surface. We present an analytical method for evaluating the spatial distribution of near-field enhanced absorption surrounding plasmonic metal nanospheres in absorbing media using a new point-by-point method. We propose criteria to define relevant near-field boundaries and calculate the properties of the local absorption enhancement, which redistributes absorption to the near-field and decays asymptotically as a function of the distance from the particle to background levels. Using this method, we performed a large-scale parametric study to understand the effect of particle size and wavelength on the near-field absorption for gold nanoparticles in aqueous media and silicon, and identified conditions that are relevant to enhanced local infrared absorption in silicon. The presented approach provides insight into the local energy transfer around plasmonic nanoparticles for predicting near-field effects for advanced concepts in optical sensing, thin-film solar cells, nonlinear imaging, and photochemical applications. PMID:26367296

  10. A Lagrangian stochastic model for the trajectories of particle pairs and its application to the prediction of concentration variance within plant canopies

    NASA Astrophysics Data System (ADS)

    Reynolds, A. M.

    A simple Lagrangian stochastic model for the trajectories of particle pairs in high Reynolds-number turbulent flows is presented. In this model, the velocities of particle pairs are initially correlated but subsequently each particle moves independently. The independent single-particle trajectories are simulated using Thomson's model [J. Fluid Mech. 180, 529-556, 1987]. This two-particle model exactly satisfies the well-mixed condition for Gaussian turbulence when length scales, characterizing the two-point Eulerian velocity correlation function, vanish. Temperature variances, due to heat released as a passive scalar from an elevated plane source, within a model plant canopy (Coppin et al. Boundary Layer Meteorol. 35, 167-191, 1986) are shown to be well predicted by the model. It is suggested that for strongly inhomogeneous flows, the two-point Eulerian velocity function is of secondary importance in determining the simulated trajectories of particle pairs compared to the importance of ensuring satisfaction of the two-to-one constraint (Borgas and Sawford. J. Fluid Mech. 279, 69-99, 1994); i.e ensuring that one-particle statistics obtained from the two-particle model are the same as those obtained from the corresponding one-particle model. Limitations of this modelling approach are discussed.

  11. Low participation ratio vibrational modes in a limit-periodic structure

    NASA Astrophysics Data System (ADS)

    Marcoux, Catherine; Socolar, Joshua E. S.

    Motivated by the demonstration that patterned colloidal particles may form a limit-periodic phase, we study the nature of vibrational modes in a toy model based on the Taylor-Socolar tiling. We consider a triangular lattice of identical point masses with nearest neighbors connected by springs of two different strengths, where the pattern of spring constants reflects the limit-periodic structure of the tiling. Using calculations of the phonon spectra for crystalline approximants to the limit-periodic structure, we identify several hierarchies of modes shared by the full limit-periodic system that have arbitrarily low participation ratios. We present a heuristic explanation of the existence of such modes, which are robust in the presence of vacancies and small amounts of disorder in the spring constants. Supported by the NSF Research Triangle MRSEC (DMR-1121107).

  12. Particle correlations in saturated QCD matter

    SciTech Connect

    Baier, Rudolf; Kovner, Alex; Nardi, Marzia; Wiedemann, Urs Achim

    2005-11-01

    We study quantitatively angular correlations in the two-particle spectrum produced by an energetic probe scattering off a dense hadronic target with sizable saturation momentum. To this end, two-parton inclusive cross sections for arbitrary projectiles with small color charge density are derived in the eikonal formalism. Our results are the following: For large momenta of the observed particles, the perturbative limit with characteristic back-to-back correlation is recovered. As the trigger momenta get closer to the saturation scale Q{sub s}, the angular distribution broadens. When the momenta are significantly smaller than Q{sub s}, the azimuthal distribution is broad but still peaked back-to-back. However, in a narrow momentum range (0.5 divide 1.5)Q{sub s}, we observe that the azimuthal correlation splits into a double peak with maxima displaced away from 180 deg. We argue that it is the soft multiple scattering physics that is responsible for the appearance of this shift in the angle of maximal correlation. We also point out that when the physical size of the projectile is particularly small, the double peak structure persists in a significantly wider range of final state momenta.

  13. Microgravity nucleation and particle coagulation experiments support

    NASA Technical Reports Server (NTRS)

    Lilleleht, L. U.; Ferguson, F. T.; Stephens, J. R.

    1992-01-01

    Modifications to the nucleation apparatus suggested by our first microgravity flight campaign are complete. These included a complete 'repackaging' of the equipment into three racks along with an improved vapor spout shutter mechanism and additional thermocouples for gas temperature measurements. The 'repackaged' apparatus was used in two KC-135 campaigns: one during the week of June 3, 1991 consisting of two flights with Mg and two with Zn, and another series consisting of three flights with Zn during the week of September 23, 1991. Our effort then was focused on the analysis of these data, including further development of the mathematical models to generate the values of temperature and supersaturation at the observed points of nucleation. The efforts to apply Hale's Scaled Nucleation Theory to our experimental data have met with only limited success, most likely due to still inadequate temperature field determination. Work on the development of a preliminary particle collector system designed to capture particles from the region of nucleation and condensation, as well as from other parts of the chamber, are discussed.

  14. Extending particle tracking capability with Delaunay triangulation.

    PubMed

    Chen, Kejia; Anthony, Stephen M; Granick, Steve

    2014-04-29

    Particle tracking, the analysis of individual moving elements in time series of microscopic images, enables burgeoning new applications, but there is need to better resolve conformation and dynamics. Here we describe the advantages of Delaunay triangulation to extend the capabilities of particle tracking in three areas: (1) discriminating irregularly shaped objects, which allows one to track items other than point features; (2) combining time and space to better connect missing frames in trajectories; and (3) identifying shape backbone. To demonstrate the method, specific examples are given, involving analyzing the time-dependent molecular conformations of actin filaments and λ-DNA. The main limitation of this method, shared by all other clustering techniques, is the difficulty to separate objects when they are very close. This can be mitigated by inspecting locally to remove edges that are longer than their neighbors and also edges that link two objects, using methods described here, so that the combination of Delaunay triangulation with edge removal can be robustly applied to processing large data sets. As common software packages, both commercial and open source, can construct Delaunay triangulation on command, the methods described in this paper are both computationally efficient and easy to implement. PMID:24734998

  15. Detection of biological particles by the use of circular dichroism measurements improved by scattering theory

    NASA Astrophysics Data System (ADS)

    Rosen, David L.; Pendleton, J. David

    1995-09-01

    Light scattered from optically active spheres was theoretically analyzed for biodetection. The circularly polarized signal of near-forward scattering from circularly dichroic spheres was calculated. Both remote and point biodetection were considered. The analysis included the effect of a circular aperture and beam block at the detector. If the incident light is linearly polarized, a false signal would limit the sensitivity of the biodetector. If the incident light is randomly polarized, shot noise would limit the sensitivity. Suggested improvements to current techniques include a beam block, precise angular measurements, randomly polarized light, index-matching fluid, and larger apertures for large particles.

  16. A holographic critical point

    SciTech Connect

    DeWolfe, Oliver; Rosen, Christopher; Gubser, Steven S.

    2011-04-15

    We numerically construct a family of five-dimensional black holes exhibiting a line of first-order phase transitions terminating at a critical point at finite chemical potential and temperature. These black holes are constructed so that the equation of state and baryon susceptibilities approximately match QCD lattice data at vanishing chemical potential. The critical end point in the particular model we consider has temperature 143 MeV and chemical potential 783 MeV. Critical exponents are calculated, with results that are consistent with mean-field scaling relations.

  17. Precision Pointing System Development

    SciTech Connect

    BUGOS, ROBERT M.

    2003-03-01

    The development of precision pointing systems has been underway in Sandia's Electronic Systems Center for over thirty years. Important areas of emphasis are synthetic aperture radars and optical reconnaissance systems. Most applications are in the aerospace arena, with host vehicles including rockets, satellites, and manned and unmanned aircraft. Systems have been used on defense-related missions throughout the world. Presently in development are pointing systems with accuracy goals in the nanoradian regime. Future activity will include efforts to dramatically reduce system size and weight through measures such as the incorporation of advanced materials and MEMS inertial sensors.

  18. Microfabricated particle focusing device

    DOEpatents

    Ravula, Surendra K.; Arrington, Christian L.; Sigman, Jennifer K.; Branch, Darren W.; Brener, Igal; Clem, Paul G.; James, Conrad D.; Hill, Martyn; Boltryk, Rosemary June

    2013-04-23

    A microfabricated particle focusing device comprises an acoustic portion to preconcentrate particles over large spatial dimensions into particle streams and a dielectrophoretic portion for finer particle focusing into single-file columns. The device can be used for high throughput assays for which it is necessary to isolate and investigate small bundles of particles and single particles.

  19. MountPointAttributes

    Energy Science and Technology Software Center (ESTSC)

    2001-06-16

    MountPointAttributes is a software component that provides client code with a technique to raise the local namespace of a file to a global namespace. Its abstractions and mechanisms allow the client code to gather global properties of a file and to use them in devising an effective storage access strategy on this file.

  20. GLAS Spacecraft Pointing Study

    NASA Technical Reports Server (NTRS)

    Born, George H.; Gold, Kenn; Ondrey, Michael; Kubitschek, Dan; Axelrad, Penina; Komjathy, Attila

    1998-01-01

    Science requirements for the GLAS mission demand that the laser altimeter be pointed to within 50 m of the location of the previous repeat ground track. The satellite will be flown in a repeat orbit of 182 days. Operationally, the required pointing information will be determined on the ground using the nominal ground track, to which pointing is desired, and the current propagated orbit of the satellite as inputs to the roll computation algorithm developed by CCAR. The roll profile will be used to generate a set of fit coefficients which can be uploaded on a daily basis and used by the on-board attitude control system. In addition, an algorithm has been developed for computation of the associated command quaternions which will be necessary when pointing at targets of opportunity. It may be desirable in the future to perform the roll calculation in an autonomous real-time mode on-board the spacecraft. GPS can provide near real-time tracking of the satellite, and the nominal ground track can be stored in the on-board computer. It will be necessary to choose the spacing of this nominal ground track to meet storage requirements in the on-board environment. Several methods for generating the roll profile from a sparse reference ground track are presented.

  1. ACCESS Pointing Control System

    NASA Technical Reports Server (NTRS)

    Brugarolas, Paul; Alexander, James; Trauger, John; Moody, Dwight; Egerman, Robert; Vallone, Phillip; Elias, Jason; Hejal, Reem; Camelo, Vanessa; Bronowicki, Allen; O'Connor, David; Partrick, Richard; Orzechowski, Pawel; Spitter, Connie; Lillie, Chuck

    2010-01-01

    ACCESS (Actively-Corrected Coronograph for Exoplanet System Studies) was one of four medium-class exoplanet concepts selected for the NASA Astrophysics Strategic Mission Concept Study (ASMCS) program in 2008/2009. The ACCESS study evaluated four major coronograph concepts under a common space observatory. This paper describes the high precision pointing control system (PCS) baselined for this observatory.

  2. EndPoints 2000

    Energy Science and Technology Software Center (ESTSC)

    2009-08-13

    The application leads the user through a logical framework to determine the minimum effort and cost necessary to reach the desired end state for each space, system, and facility. Endpoints are used to plan the project work, track and manage the determination, management, verification, and closure of D&D endpoints, consistent with DOE End Point guidance documents.

  3. EcoTipping Points

    ERIC Educational Resources Information Center

    Marten, Gerald G.; Matthews, Catherine E.

    2009-01-01

    Contrary to what we often hear and teach, there is good news to be found on the environmental front. Environmental success stories show us not only that sustainability is possible, but also how people have made it happen. We can make these stories and their lessons accessible to students with help from the EcoTipping Points Project, which has…

  4. Optical Pointing Sensor

    NASA Technical Reports Server (NTRS)

    Shields, Joel F.; Metz, Brandon C.

    2010-01-01

    The optical pointing sensor provides a means of directly measuring the relative positions of JPL s Formation Control Testbed (FCT) vehicles without communication. This innovation is a steerable infrared (IR) rangefinder that gives measurements in terms of range and bearing to a passive retroreflector.

  5. The Lagrange Points

    ERIC Educational Resources Information Center

    Lovell, M.S.

    2007-01-01

    This paper presents a derivation of all five Lagrange points by methods accessible to sixth-form students, and provides a further opportunity to match Newtonian gravity with centripetal force. The predictive powers of good scientific theories are also discussed with regard to the philosophy of science. Methods for calculating the positions of the…

  6. Noncommutative Point Sources

    SciTech Connect

    Stern, A.

    2008-02-15

    We construct a perturbative solution to classical noncommutative gauge theory on R{sup 3} minus the origin using the Groenewald-Moyal star product. The result describes a noncommutative point charge. Applying it to the quantum mechanics of the noncommutative hydrogen atom gives shifts in the 1S hyperfine splitting which are first order in the noncommutativity parameter.

  7. Points and Practices

    ERIC Educational Resources Information Center

    Ahmed, Syed Jamil; Heddon, Dee; Mackey, Sally

    2007-01-01

    This collection of three articles represents the "Points and Practices" section of this month's issue of "Research in Drama Education." The first article, "'Fitting the Bill' for 'Helping Them.' A Response to 'Integrated Popular Theatre Approach in Africa' and 'Commissioned Theatre Projects on Human Rights in Pakistan,'" by Syed Jamil Ahmed,…

  8. Point and Shoot Astronomy

    NASA Astrophysics Data System (ADS)

    Hoot, John E.

    2011-05-01

    A new generation of point and shoot digital cameras, when combined with open source firmware enhancements can operate as astrographs. This paper explores the research and astro-photographic opportunities and capabilities offered by this pairing of mass production optics and open source functional extensions that retail for as little as $200.

  9. Identifying the Real Seed Population for Shock Accelerated Energetic Particles: Recent Observational Progress

    NASA Astrophysics Data System (ADS)

    Mason, G. M.; Mazur, J. E.; Desai, M. I.; Dwyer, J. R.

    2002-12-01

    Gradual solar energetic particle events, traveling interplanetary shocks, and corotating interaction regions are examples of shock acceleration of particles in the heliosphere. Although shock acceleration of particles has long been the subject of theoretical investigation, nevertheless key energetic particle properties such as intensity and spectral index are only roughly correlated with predictions of the theories. This may be due to limitations of the theories, but it may also be due to a lack of understanding of properties of the seed population. Recent measurements have shown that trace elements in the thermal plasma (e.g. singly ionized He, and 3He) often show dramatic enhancements in the energetic particle population. Although the observational picture is far from complete, it appears that the injection threshold in these events is about 1.5-2 times the solar wind speed. In this range, multiple particle sources are present, including solar wind suprathermals, pick up ions, and remnant material from prior shocks and impulsive events. Thus, the enhancements are not due to properties of the shock acceleration, but rather are primarily due to the properties of the seed population. This points to new opportunities for theoretical and experimental investigations to quantitatively model shock accelerated particle populations using realistic seed populations.

  10. Collision of two general geodesic particles around a Kerr black hole

    SciTech Connect

    Harada, Tomohiro; Kimura, Masashi

    2011-04-15

    We obtain an explicit expression for the center-of-mass (CM) energy of two colliding general geodesic massive and massless particles at any spacetime point around a Kerr black hole. Applying this, we show that the CM energy can be arbitrarily high only in the limit to the horizon and then derive a formula for the CM energy of two general geodesic particles colliding near the horizon in terms of the conserved quantities of each particle and the polar angle. We present the necessary and sufficient condition for the CM energy to be arbitrarily high in terms of the conserved quantities of each particle. To have an arbitrarily high CM energy, the angular momentum of either of the two particles must be fine-tuned to the critical value L{sub i}={Omega}{sub H}{sup -1}E{sub i}, where {Omega}{sub H} is the angular velocity of the horizon and E{sub i} and L{sub i} are the energy and angular momentum of particle i(=1,2), respectively. We show that, in the direct collision scenario, the collision with an arbitrarily high CM energy can occur near the horizon of maximally rotating black holes not only at the equator but also on a belt centered at the equator. This belt lies between latitudes {+-}acos({radical}(3)-1){approx_equal}{+-}42.94 deg. This is also true in the scenario through the collision of a last stable orbit particle.

  11. Correction for solute/solvent interaction extends accurate freezing point depression theory to high concentration range.

    PubMed

    Fullerton, G D; Keener, C R; Cameron, I L

    1994-12-01

    The authors describe empirical corrections to ideally dilute expressions for freezing point depression of aqueous solutions to arrive at new expressions accurate up to three molal concentration. The method assumes non-ideality is due primarily to solute/solvent interactions such that the correct free water mass Mwc is the mass of water in solution Mw minus I.M(s) where M(s) is the mass of solute and I an empirical solute/solvent interaction coefficient. The interaction coefficient is easily derived from the constant in the linear regression fit to the experimental plot of Mw/M(s) as a function of 1/delta T (inverse freezing point depression). The I-value, when substituted into the new thermodynamic expressions derived from the assumption of equivalent activity of water in solution and ice, provides accurate predictions of freezing point depression (+/- 0.05 degrees C) up to 2.5 molal concentration for all the test molecules evaluated; glucose, sucrose, glycerol and ethylene glycol. The concentration limit is the approximate monolayer water coverage limit for the solutes which suggests that direct solute/solute interactions are negligible below this limit. This is contrary to the view of many authors due to the common practice of including hydration forces (a soft potential added to the hard core atomic potential) in the interaction potential between solute particles. When this is recognized the two viewpoints are in fundamental agreement. PMID:7699200

  12. Statistical Physics of Particles

    NASA Astrophysics Data System (ADS)

    Kardar, Mehran

    2006-06-01

    Statistical physics has its origins in attempts to describe the thermal properties of matter in terms of its constituent particles, and has played a fundamental role in the development of quantum mechanics. Based on lectures for a course in statistical mechanics taught by Professor Kardar at Massachusetts Institute of Technology, this textbook introduces the central concepts and tools of statistical physics. It contains a chapter on probability and related issues such as the central limit theorem and information theory, and covers interacting particles, with an extensive description of the van der Waals equation and its derivation by mean field approximation. It also contains an integrated set of problems, with solutions to selected problems at the end of the book. It will be invaluable for graduate and advanced undergraduate courses in statistical physics. A complete set of solutions is available to lecturers on a password protected website at www.cambridge.org/9780521873420. Based on lecture notes from a course on Statistical Mechanics taught by the author at MIT Contains 89 exercises, with solutions to selected problems Contains chapters on probability and interacting particles Ideal for graduate courses in Statistical Mechanics

  13. New particles and interactions

    SciTech Connect

    Gilman, F.J.; Grannis, P.D.

    1984-04-01

    The Working Group on New Particles and Interactions met as a whole at the beginning and at the end of the Workshop. However, much of what was accomplished was done in five subgroups. These were devoted to: (1) new quarks and leptons; (2) technicolor; (3) supersymmetry; (4) rare decays and CP; and (5) substructure of quarks and leptons. Other aspects of new particles, e.g., Higgs, W', Z', fell to the Electroweak Working Group to consider. The central question of this Workshop of comparing anti pp (with L = 10/sup 32//cm/sup 2/-sec) with pp (with L = 10/sup 33//cm/sup 2/-sec) colliders carried through to all these subgroups. In addition there were several other aspects of hadron colliders which were considered: what does an increase in ..sqrt..s gain in cross section and resultant sensitivity to new physics versus an increase in luminosity; will polarized beams or the use of asymmetries be essential in finding new interactions; where and at what level do rate limitations due to triggering or detection systems play a role; and how and where will the detection of particles with short, but detectable, lifetimes be important. 25 references.

  14. Active particles on curved surfaces

    NASA Astrophysics Data System (ADS)

    Fily, Yaouen; Baskaran, Aparna; Hagan, Michael

    Active systems have proved to be very sensitive to the geometry of their environment. This is often achieved by spending significant time at the boundary, probing its shape by gliding along it. I will discuss coarse graining the microscopic dynamics of self-propelled particles on a general curved surface to predict the way the density profile on the surface depends on its geometry. Beyond confined active particles, this formalism is a natural starting point to study objects that cannot leave the boundary at all, such as cells crawling on a curved substrate, animals running on uneven ground, or active colloids trapped at an interface.

  15. Superbackscattering from single dielectric particles

    NASA Astrophysics Data System (ADS)

    Liberal, Iñigo; Ederra, Iñigo; Gonzalo, Ramón; Ziolkowski, Richard W.

    2015-07-01

    We demonstrate that superbackscattering responses can be excited in subwavelength dielectric particles with simple geometries. The superbackscattering response arises from the simultaneous, coherent excitation of electric dipole and magnetic quadrupole resonances. Its signature is a superdirective scattering pattern simultaneously pointing towards both the forward and backward directions. The practical implementation of this effect with Tellurium particles operating in the thermal infrared is also addressed. The examples presented reveal that spherical resonators outperform array-based superbackscatterers in terms of the backscattering peak, compact size, robustness against losses and isotropic response.

  16. Generation of Particles and Seeding

    NASA Technical Reports Server (NTRS)

    Meyers, James F.

    1994-01-01

    One of the most important elements in laser velocimetry, yet the most neglected, is the small particle embedded in the flow field that scatters the light necessary to make velocity measurements. The characteristics of this small particle are often ignored in the effort to obtain data. This seems strange since it is the primary cause of measurement error. If the particle is too large, it will not follow the flow resulting in an inaccurate representation of the fluid velocity. If the particle is too small, it will not scatter sufficient light to provide the signal-to-noise necessary to minimize measurement uncertainty in the signal processing electronics. This lecture will attempt to remove the confusion in choosing a seeding method by assessing many of the techniques currently used. It will outline their characteristics and typical limitations imposed by various applications. The lecture will then focus on the ramifications of these methods on measurement accuracy.

  17. The MAGIC Meteoric Smoke Particle Sampler - Description and Results

    NASA Astrophysics Data System (ADS)

    Hedin, J.

    2013-12-01

    Between a few to several hundred tons of meteoric material enters the Earth's atmosphere each day, and much of this material ablates in the 70 -130 km region of the atmosphere. Already in the early 1960's it was suggested that meteoroid ablation products could recondense and form solid nanometer-scale smoke particles in the altitude range of the mesosphere and lower thermosphere (MLT). These so-called meteoric smoke particles (MSPs) are then subject to further coagulation, sedimentation, and transport by the mesospheric meridional circulation which in turn determines the latitudinal and seasonal variation of the MSP distribution. MSPs have been suggested to be important for a variety of atmospheric phenomena: 1. they are the most likely candidate for the nuclei of mesospheric ice particles (NLC and PMSE); 2. they provide surface area on which heterogeneous chemical reactions take place and may influence, for example, the water vapor distribution and Ox/HOx chemistry in the mesosphere; 3. they act as ultimate sink in mesospheric metal chemistry by scavenging various gas-phase products of meteoric ablation; 4. they can significantly influence the ionospheric D-region charge balance by scavenging free electrons and positive ions; and 5. they may be involved in the formation of NAT particles in polar stratospheric clouds and the destruction of ozone. Given the above points, it is obvious that there is a large scientific interest in the properties and global distribution of MSPs. Basic information about MSP properties is today available from optical occultation measurements (AIM/SOFIE) and, more indirectly, from in-situ measurements of the charged particle population. In order to understand the role of meteoric smoke particles in the mesosphere and their impact on that environment their presence must be certified and their physical characterization (number density, size distribution, shape, composition etc.) determined. A way to obtain maximum information about particle

  18. Effects of Inter-Particle Collisions and Two-Way Coupling on Particle Deposition Velocity in a Turbulent Channel Flow

    NASA Astrophysics Data System (ADS)

    Nasr, Hojjat; Ahmadi, Goodarz; McLaughlin, John

    2010-11-01

    This study was concerned with the effect of particle-particle collisions and two-way coupling on the particle deposition velocity in a turbulent channel flow. The time history of the instantaneous turbulent velocity vector was generated by the two-way coupled direct numerical simulation (DNS) of the Navier-Stokes equation via a pseudospectral method. The particle equation of motion included the Stokes drag, the Saffman lift, and the gravitational forces. The effect of particles on the flow was included in the analysis via a feedback force that acted on the fluid on the computational grid points. Several simulations for different particle relaxation times and particle mass loading were performed, and the effects of the inter-particle collisions and two-way coupling on the particle deposition velocity, fluid and particle fluctuating velocities, particle normal mean velocity, and particle concentration were determined. It was found that when particle-particle collisions were included in the computation, the particle deposition velocity increased. When the particle collision was neglected but the particle-fluid two-way coupling was accounted for, the particle deposition velocity decreased slightly. For the four-way coupling case, when both inter-particle collisions and two-way coupling effects were taken into account, the particle deposition velocity increased. Comparisons of the present simulation results with the available experimental data and earlier numerical results are also presented.

  19. ALT-I pump limiter experiments

    SciTech Connect

    Goebel, D.M.; Conn, R.W.; Campbell, G.A.; Leung, W.K.; Dippel, K.H.; Finken, K.H.; Wolf, G.H.; Thomas, G.J.; Pontau, A.E.; Hsu, W.

    1987-09-01

    Results from the ALT-I pump limiter experiments in TEXTOR are presented. ALT-I has demonstrated control of the plasma density in a high recycling tokamak by pumping up to 15% of the core efflux. The closed pump limiter designs with restricted entrance geometries to reduce the backflow of neutral gas to the plasma remove over 50% of the ion flux incident on the collection slot. Up to 80% of the entrance ion flux is removed when the edge electron temperature is less than 10 eV and plasma-neutral gas interactions are minimized inside the limiter. Results from a 3-D Monte Carlo neutral gas transport code agree closely with these experimental results. The compound curvature of the head is found to distribute the heat over the surface as predicted in the original designs. Impurity removal experiments demonstrate that significant helium exhaust can be achieved with a pump limiter. During ohmic heating in TEXTOR, the energy and particle confinement times are proportional to the line averaged core density. With ICRH auxiliary heating, tau/sub E/ follow L-mode scaling independent of particle removal by the pump limiter. Pump limiter operation does not directly modify the SOL plasma density and electron temperature, but controls the core plasma density by changing the global recycling at the boundary. The global particle confinement, the particle flux to the limiter, and the edge electron temperature follow the changes in the core density and auxiliary heating power. 25 refs.

  20. Physical Investigations of Small Particles: (I) Aerosol Particle Charging and Flux Enhancement and (II) Whispering Gallery Mode Sensing

    NASA Astrophysics Data System (ADS)

    Lopez-Yglesias, Xerxes

    Part I: Particles are a key feature of planetary atmospheres. On Earth they represent the greatest source of uncertainty in the global energy budget. This uncertainty can be addressed by making more measurement, by improving the theoretical analysis of measurements, and by better modeling basic particle nucleation and initial particle growth within an atmosphere. This work will focus on the latter two methods of improvement. Uncertainty in measurements is largely due to particle charging. Accurate descriptions of particle charging are challenging because one deals with particles in a gas as opposed to a vacuum, so different length scales come into play. Previous studies have considered the effects of transition between the continuum and kinetic regime and the effects of two and three body interactions within the kinetic regime. These studies, however, use questionable assumptions about the charging process which resulted in skewed observations, and bias in the proposed dynamics of aerosol particles. These assumptions affect both the ions and particles in the system. Ions are assumed to be point monopoles that have a single characteristic speed rather than follow a distribution. Particles are assumed to be perfect conductors that have up to five elementary charges on them. The effects of three body interaction, ion-molecule-particle, are also overestimated. By revising this theory so that the basic physical attributes of both ions and particles and their interactions are better represented, we are able to make more accurate predictions of particle charging in both the kinetic and continuum regimes. The same revised theory that was used above to model ion charging can also be applied to the flux of neutral vapor phase molecules to a particle or initial cluster. Using these results we can model the vapor flux to a neutral or charged particle due to diffusion and electromagnetic interactions. In many classical theories currently applied to these models, the finite size

  1. Dissolution and coarsening of polydisperse, polymorph drug particles liberated from a disintegrating finished dosage form: Theoretical considerations.

    PubMed

    Horkovics-Kovats, Stefan

    2016-08-25

    In order to improve the bioavailability of substances with limited water-solubility, they are often formulated as nanoparticles. Nanoparticles show enhanced dissolution properties when compared to large particles. In this paper a dissolution theory is presented that comprehensively describes the dissolution properties of both large- and nanoparticles. It comprises non-sink conditions and arbitrary shaped isometrically dissolving particles, considering particle-size-independent dissolution layer thickness and several polymorphic drug forms. The known root-laws of dissolution kinetics happen to be special cases that depend on particle-size in relation to the diffusion layer thickness i.e. whether the particles are much larger, comparable, or much smaller than the diffusion layer thickness. The presented theory explains the improved dissolution properties of nanoparticles, such as their increased solubility, almost immediate dissolution, and the dissolution kinetics which is independent from hydrodynamic conditions. For polydisperse, polymorphic particles of arbitrary shapes that are liberated from a disintegrating finished dosage form, the Ostwald ripening (coarsening of particles and transition of metastable polymorphic forms into a more stable crystalline form) is described as water mediated mass transport. The presented theory points to certain limitations of the Ostwald-Freundlich equation for nanoparticles and provides their better characterization. This way it may contribute to a more specifically targeted development of finished dosage forms and may help to reduce the bias of toxicological and environmental assessments especially for drugs that are formed as nanoparticles. PMID:27155254

  2. Solar Energetic Particle Variations

    NASA Technical Reports Server (NTRS)

    Reames, D. V.

    2003-01-01

    In the largest solar energetic-particle (SEP) events, acceleration occurs at shock waves driven out from the Sun by coronal mass ejections (CMEs). In fact, the highest proton intensities directly measured near Earth at energies up to approximately 1 GeV occur at the time of passage of shocks, which arrive about a day after the CMEs leave the Sun. CME-driven shocks expanding across magnetic fields can fill over half of the heliosphere with SEPs. Proton-generated Alfven waves trap particles near the shock for efficient acceleration but also throttle the intensities at Earth to the streaming limit early in the events. At high energies, particles begin to leak from the shock and the spectrum rolls downward to form an energy-spectral 'knee' that can vary in energy from approximately 1 MeV to approximately 1 GeV in different events. All of these factors affect the radiation dose as a function of depth and latitude in the Earth's atmosphere and the risk to astronauts and equipment in space. SEP ionization of the polar atmosphere produces nitrates that precipitate to become trapped in the polar ice. Observations of nitrate deposits in ice cores reveal individual large SEP events and extend back approximately 400 years. Unlike sunspots, SEP events follow the approximately 80-100-year Gleissberg cycle rather faithfully and are now at a minimum in that cycle. The largest SEP event in the last 400 years appears to be related to the flare observed by Carrington in 1859, but the probability of SEP events with such large fluences falls off sharply because of the streaming limit.

  3. Quantum states for Heisenberg limited interferometry

    NASA Astrophysics Data System (ADS)

    Uys, Hermann; Meystre, Pierre

    2007-06-01

    An important aspect of quantum metrology is the engineering of quantum states with which to achieve Heisenberg limited measurement precision. In this limit the measurement uncertainty is inversely proportional to the number of interfering particles, N, a 1/√N improvement over the standad quantum limit. We have used numerical global optimization strategies to systematically search for quantum interferometer input states that achieve Heisenberg limited uncertainty in estimates of the interferometer phase shift. We compare the performance of candidates so obtained with that of non-classical states already known to yield Heisenberg limited uncertainty.

  4. Quantum states for Heisenberg-limited interferometry

    NASA Astrophysics Data System (ADS)

    Uys, H.; Meystre, P.

    2007-07-01

    The phase sensitivity of interferometers is limited by the so-called Heisenberg limit, which states that the optimum phase sensitivity is inversely proportional to the number of interfering particles N , a 1/N improvement over the standard quantum limit. We have used simulated annealing, a global optimization strategy, to systematically search for quantum interferometer input states that approach the Heisenberg-limited uncertainty in estimates of the interferometer phase shift. We compare the performance of these states to that of other nonclassical states already known to yield Heisenberg-limited uncertainty.

  5. Non-thermal fixed points and solitons in a one-dimensional Bose gas

    NASA Astrophysics Data System (ADS)

    Schmidt, Maximilian; Erne, Sebastian; Nowak, Boris; Sexty, Dénes; Gasenzer, Thomas

    2012-07-01

    Single-particle momentum spectra for a dynamically evolving one-dimensional Bose gas are analysed in the semi-classical wave limit. Representing one of the simplest correlation functions, these provide information on a possible universal scaling behaviour. Motivated by the previously discovered connection between (quasi-) topological field configurations, strong wave turbulence and non-thermal fixed points of quantum field dynamics, soliton formation is studied with respect to the appearance of transient power-law spectra. A random-soliton model is developed for describing the spectra analytically, and the analogies and differences between the emerging power laws and those found in a field theory approach to strong wave turbulence are discussed. The results open a new perspective on solitary wave dynamics from the point of view of critical phenomena far from thermal equilibrium and the possibility of studying this dynamics by experiment without the need for detecting solitons in situ.

  6. Particle-hole and particle-particle correlations in neodymium isotopes

    NASA Astrophysics Data System (ADS)

    Ponomarev, V. Yu.; Pignanelli, M.; Blasi, N.; Bontempi, A.; Bordewijk, J. A.; De Leo, R.; Graw, G.; Harakeh, M. N.; Hofer, D.; Hofstee, M. A.; Micheletti, S.; Perrino, R.; van der Werf, S. Y.

    Excited states in 140, 142, 144, 146Nd nuclei, up to an excitation energy of about 5 MeV, were investigated by (p,t) experiments performed with a good energy resolution. These data, together with proton and deuteron scattering data from a previous experiment, are compared with Quasi-Particle Phonon Model evaluations, in which the competition between particle-hole and particle-particle residual interactions is considered. The B(Eλ) distributions are satisfactorily reproduced. The 146, 148Nd(p,t) reaction data are well accounted for, while difficulties are found in reproducing those for 142, 144Nd(p,t). Limitations and improvements of the model are discussed.

  7. Proximal Point Methods Revisited

    NASA Astrophysics Data System (ADS)

    Boikanyo, Oganeditse A.; Moroşanu, Gheorghe

    2011-09-01

    The proximal point methods have been widely used in the last decades to approximate the solutions of nonlinear equations associated with monotone operators. Inspired by the iterative procedure defined by B. Martinet (1970), R.T. Rockafellar introduced in 1976 the so-called proximal point algorithm (PPA) for a general maximal monotone operator. The sequence generated by this iterative method is weakly convergent under appropriate conditions, but not necessarily strongly convergent, as proved by O. Güler (1991). This fact explains the introduction of different modified versions of the PPA which generate strongly convergent sequences under appropriate conditions, including the contraction-PPA defined by H.K. Xu in 2002. Here we discuss Xu's modified PPA as well as some of its generalizations. Special attention is paid to the computational errors, in particular the original Rockafellar summability assumption is replaced by the condition that the error sequence converges to zero strongly.

  8. Particle size distribution effects in an irradiated turbulent gas-particle mixture

    NASA Astrophysics Data System (ADS)

    Rahmani, Mona; Geraci, Gianluca; Iaccarino, Gianluca; Mani, Ali

    2015-11-01

    The effects of particle size distribution on thermodynamic and hydrodynamic behavior of solid particle solar receivers, that involve a turbulent mixture of gas and particles in a radiation environment, are investigated, using DNS with point particles. The turbulent flow is seeded with monodisperse and polydisperse particles, where the mass loading and total frontal area of particles are matched between the two systems. The results show that the variability of the Stokes number for polydisperse particles can significantly influence the particle clustering, and consequently the thermal performance of the system. In all cases studied, the preferential concentration is less pronounced for polydisperse as opposed to monodisperse particles. This reduced preferential concentration results in less heating of the particles, but more efficient energy release to the gas phase. Due to their different clustering patterns, polydisperse particles influence the Taylor scale of the flow in the turbulent gas phase. Polydispersity also implies variable thermodynamic and hydrodynamic properties of the particles. Our results show that the thermal behavior of the system with polydisperse particles is set by the integral measures for particle and gas momentum and thermal relaxation times.

  9. Limitations on quantum key repeaters.

    PubMed

    Bäuml, Stefan; Christandl, Matthias; Horodecki, Karol; Winter, Andreas

    2015-01-01

    A major application of quantum communication is the distribution of entangled particles for use in quantum key distribution. Owing to noise in the communication line, quantum key distribution is, in practice, limited to a distance of a few hundred kilometres, and can only be extended to longer distances by use of a quantum repeater, a device that performs entanglement distillation and quantum teleportation. The existence of noisy entangled states that are undistillable but nevertheless useful for quantum key distribution raises the question of the feasibility of a quantum key repeater, which would work beyond the limits of entanglement distillation, hence possibly tolerating higher noise levels than existing protocols. Here we exhibit fundamental limits on such a device in the form of bounds on the rate at which it may extract secure key. As a consequence, we give examples of states suitable for quantum key distribution but unsuitable for the most general quantum key repeater protocol. PMID:25903096

  10. Steering a robot with vanishing points

    SciTech Connect

    Schuster, R.; Ansari, N.; Bani-Hashemi, A.R.

    1993-08-01

    The paper analyzes the use of vanishing points for steering a robot. Parallel lines in the environment of the robot are used to compute vanishing points which serve as a reference for guiding the robot. To accomplish the steering task, three subtasks are performed: detection of straight lines, computation of vanishing points, and robot steering using vanishing points. Straight lines are detected by employing a high precision edge detector and a line-fitting algorithm. The cross product method introduced by Magee and Aggarwal is modified to make the detection of vanishing points appropriate for an indoor environment. Properties of vanishing points under camera rotation and translation are derived. Using these properties, the location of the vanishing points can serve as a reference for steering the robot. A model of the robot environment is defined, summarizing the minimum number of constraints necessary for the method to work. Finally, the limitations as well as the advantage of using vanishing points in robot navigation are discussed.

  11. Particle-laden tubeless siphon

    NASA Astrophysics Data System (ADS)

    Joseph, Daniel; Wang, Jing

    2003-11-01

    A tubeless siphon was created by sucking a 1% aqueous Polyox(Polyox is a registered trademark of Union Carbide.) solution laden with particles from a beaker into a cylinder by a moving piston. The piston speed and particle concentration were varied. At very high rates of withdrawal, all the fluid could be removed before the siphon broke. In this case, the beaker was completely cleaned without a trace of liquid. The addition of small concentrations of small, nearly neutrally buoyant particles greatly enhanced the pulling power of the liquid, reducing the threshold speed of withdrawal at which the beaker was completely cleaned. At speeds of withdrawal smaller than the threshold not all of the fluid-particle mixture is pulled out of the beaker. The amount pulled out first increases, then decreases as the particle concentration is increased. We present an argument, based on viscoelastic potential flow, that the enhancement of the effective extensional stress is due to the reversal of the sign of the normal stresses at stagnation points on the particles.

  12. Acceleration technologies for charged particles: an introduction

    NASA Astrophysics Data System (ADS)

    Carter, Richard G.

    2011-01-01

    Particle accelerators have many important uses in scientific experiments, in industry and in medicine. This paper reviews the variety of technologies which are used to accelerate charged particles to high energies. It aims to show how the capabilities and limitations of these technologies are related to underlying physical principles. The paper emphasises the way in which different technologies are used together to convey energy from the electrical supply to the accelerated particles.

  13. Global Modeling of Nebulae with Particle Growth, Drift, and Evaporation Fronts. I. Methodology and Typical Results

    NASA Astrophysics Data System (ADS)

    Estrada, Paul R.; Cuzzi, Jeffrey N.; Morgan, Demitri A.

    2016-02-01

    We model particle growth in a turbulent, viscously evolving protoplanetary nebula, incorporating sticking, bouncing, fragmentation, and mass transfer at high speeds. We treat small particles using a moments method and large particles using a traditional histogram binning, including a probability distribution function of collisional velocities. The fragmentation strength of the particles depends on their composition (icy aggregates are stronger than silicate aggregates). The particle opacity, which controls the nebula thermal structure, evolves as particles grow and mass redistributes. While growing, particles drift radially due to nebula headwind drag. Particles of different compositions evaporate at “evaporation fronts” (EFs) where the midplane temperature exceeds their respective evaporation temperatures. We track the vapor and solid phases of each component, accounting for advection and radial and vertical diffusion. We present characteristic results in evolutions lasting 2 × 105 years. In general, (1) mass is transferred from the outer to the inner nebula in significant amounts, creating radial concentrations of solids at EFs; (2) particle sizes are limited by a combination of fragmentation, bouncing, and drift; (3) “lucky” large particles never represent a significant amount of mass; and (4) restricted radial zones just outside each EF become compositionally enriched in the associated volatiles. We point out implications for millimeter to submillimeter SEDs and the inference of nebula mass, radial banding, the role of opacity on new mechanisms for generating turbulence, the enrichment of meteorites in heavy oxygen isotopes, variable and nonsolar redox conditions, the primary accretion of silicate and icy planetesimals, and the makeup of Jupiter’s core.

  14. At the Tipping Point

    SciTech Connect

    Wiley, H. S.

    2011-02-28

    There comes a time in every field of science when things suddenly change. While it might not be immediately apparent that things are different, a tipping point has occurred. Biology is now at such a point. The reason is the introduction of high-throughput genomics-based technologies. I am not talking about the consequences of the sequencing of the human genome (and every other genome within reach). The change is due to new technologies that generate an enormous amount of data about the molecular composition of cells. These include proteomics, transcriptional profiling by sequencing, and the ability to globally measure microRNAs and post-translational modifications of proteins. These mountains of digital data can be mapped to a common frame of reference: the organism’s genome. With the new high-throughput technologies, we can generate tens of thousands of data points from each sample. Data are now measured in terabytes and the time necessary to analyze data can now require years. Obviously, we can’t wait to interpret the data fully before the next experiment. In fact, we might never be able to even look at all of it, much less understand it. This volume of data requires sophisticated computational and statistical methods for its analysis and is forcing biologists to approach data interpretation as a collaborative venture.

  15. Non-Gimbaled Antenna Pointing

    NASA Technical Reports Server (NTRS)

    Vigil, Jeannine S.

    1997-01-01

    The small satellite community has been interested in accessing fixed ground stations for means of space-to-ground transmissions, although a problem arises from the limited global coverage. There is a growing interest for using the Space Network (SN) or Tracking and Data Relay Satellites (TDRS) as the primary support for communications because of the coverage it provides. This thesis will address the potential for satellite access of the Space Network with a non-gimbaled antenna configuration and low-power, coded transmission. The non-gimbaled antenna and the TDRS satellites, TDRS-East, TDRS-West, and TDRS-Zone of Exclusion, were configured in an orbital analysis software package called Satellite Tool Kit to emulate the three-dimensional position of the satellites. The access potential, which is the average number of contacts per day and the average time per contact, were obtained through simulations run over a 30-day period to gain all the possible orientations. The orbital altitude was varied from 600 km through 1200 km with the results being a function of orbital inclination angles varying from 20 deg through 100 deg and pointing half-angles of I0 deg through 40 deg. To compare the validity of the simulations, Jet Propulsion Laboratory granted the use of the TOPEX satellite. The TOPEX satellite was configured to emulate a spin-stabilized antenna with its communications antenna stowed in the zenith-pointing direction. This mimicked the antenna pointing spin-stabilized satellite in the simulations. To make valid comparisons, the TOPEX orbital parameters were entered into Satellite Tool Kit and simulated over five test times provided by Jet Propulsion Laboratory.

  16. Two-Point Functions on Deformed Spacetime

    NASA Astrophysics Data System (ADS)

    Trampetić, Josip; You, Jiangyang

    2014-05-01

    We present a review of the one-loop photon (Π) and neutrino (Σ) two-point functions in a covariant and deformed U(1) gauge-theory on the 4-dimensional noncommutative spaces, determined by a constant antisymmetric tensor θ^{μν}, and by a parameter-space (κ_f,κ_g), respectively. For the general fermion-photon S_f(κ_f) and photon self-interaction S_g(κ_g) the closed form results reveal two-point functions with all kind of pathological terms: the UV divergence, the quadratic UV/IR mixing terms as well as a logarithmic IR divergent term of the type ln(μ^2(θ p)^2). In addition, the photon-loop produces new tensor structures satisfying transversality condition by themselves. We show that the photon two-point function in the 4-dimensional Euclidean spacetime can be reduced to two finite terms by imposing a specific full rank of θ^{μν} and setting deformation parameters (κ_f,κ_g)=(0,3). In this case the neutrino two-point function vanishes. Thus for a specific point (0,3) in the parameter-space (κ_f,κ_g), a covariant θ-exact approach is able to produce a divergence-free result for the one-loop quantum corrections, having also both well-defined commutative limit and point-like limit of an extended object.

  17. Particle Diffusion in an Inhomogeneous Medium

    ERIC Educational Resources Information Center

    Bringuier, E.

    2011-01-01

    This paper is an elementary introduction to particle diffusion in a medium where the coefficient of diffusion varies with position. The introduction is aimed at third-year university courses. We start from a simple model of particles hopping on a discrete lattice, in one or more dimensions, and then take the continuous-space limit so as to obtain…

  18. A point matching algorithm based on reference point pair

    NASA Astrophysics Data System (ADS)

    Zou, Huanxin; Zhu, Youqing; Zhou, Shilin; Lei, Lin

    2016-03-01

    Outliers and occlusions are important degradation in the real application of point matching. In this paper, a novel point matching algorithm based on the reference point pairs is proposed. In each iteration, it firstly eliminates the dubious matches to obtain the relatively accurate matching points (reference point pairs), and then calculates the shape contexts of the removed points with reference to them. After re-matching the removed points, the reference point pairs are combined to achieve better correspondences. Experiments on synthetic data validate the advantages of our method in comparison with some classical methods.

  19. 49 CFR 172.315 - Limited quantities.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... and outer package quantity limits in § 173.27(f) of this subchapter. (1) Marking description. The top... the square-on-point must be at least 2 mm and the minimum dimension of each side must be 100 mm unless...) Marking Description. The top and bottom portions of the square-on-point and the border forming the...

  20. 14 CFR 158.9 - Limitations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... PASSENGER FACILITY CHARGES (PFC'S) General § 158.9 Limitations. (a) No public agency may impose a PFC on any... Department of Transportation for which PFC's may not be imposed under this section; (3) Who is a nonrevenue... a point or points in the U.S. to collect a PFC from a passenger....