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Sample records for point particle limit

  1. Triviality of a model of particles with point interactions in the thermodynamic limit

    NASA Astrophysics Data System (ADS)

    Moser, Thomas; Seiringer, Robert

    2016-11-01

    We consider a model of fermions interacting via point interactions, defined via a certain weighted Dirichlet form. While for two particles the interaction corresponds to infinite scattering length, the presence of further particles effectively decreases the interaction strength. We show that the model becomes trivial in the thermodynamic limit, in the sense that the free energy density at any given particle density and temperature agrees with the corresponding expression for non-interacting particles.

  2. 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.

  3. STOCHASTIC POINT PROCESSES: LIMIT THEOREMS.

    DTIC Science & Technology

    A stochastic point process in R(n) is a triple (M,B,P) where M is the class of all countable sets in R(n) having no limit points, B is the smallest...converge to a mixture of Poisson processes. These results are established via a generalization of a classical limit theorem for Bernoulli trials. (Author)

  4. 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.

  5. Concave points for separating touching particles

    NASA Astrophysics Data System (ADS)

    Chaves, Deisy; Trujillo, Maria; Barraza, Juan Manuel

    2015-03-01

    Separation of touching objects/particles is a step before measuring morphological characteristics. An approach for identifying and splitting touching char particles is presented. The proposed approach is based on two processes. First, concave points are detected using a concavity measure and a list of touching point candidates is built. Second, separation lines are identified using location, length, blur and size. A decision criterion is derived for deciding whether or not to split a particle. The proposed approach is evaluated using 180 images of char particles and compared to the Watershed algorithm. The evaluation was twofold: quantifying the accuracy of identifying touching particles and measuring the separation quality. Expert criteria are used as a ground truth for qualitative evaluations. A good agreement between the visual judgement and automatic results was obtained, using the proposed approach.

  6. Point particle motion in topologically nontrivial spacetimes

    NASA Astrophysics Data System (ADS)

    Matas, Andrew; Müller, Daniel; Starkman, Glenn

    2015-07-01

    It is well known that compactifying a space can break symmetries that are present in the covering space. In this paper we study the effects of such topological symmetry breaking on point particle motion when the particle is coupled to a massless field on the space. For a torus topology where Lorentz invariance is broken but translation invariance is maintained, particles can move at a constant velocity through the space; however, nonlocal, velocity-dependent forces arise whenever the particle is accelerated. For a topology where translation invariance is broken, such as the Klein bottle, interactions with the massless field generate an effective potential as a function of position. The potential creates special stable points in the space, and prevents constant velocity motion. The latter would appear to be the generic case. This class of effects may be applicable whenever a localized object moves through a compactified bulk, such as in brane-world cosmology, or some condensed matter systems.

  7. 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.

  8. A study on the validity of the point-particle model for particle-turbulence interaction

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongzhen; Prosperetti, Andrea

    2002-11-01

    The point-particle model, widely used in simulations of particle-turbulence interaction, is justified when the particle size is smaller than or comparable to the Kolmogorov scale. The precise limits of validity of the approximation and the manner in which errors accrue when the particle size increases are not well known. In the present work, direct simulations are conducted for a single finite-size particle suspended in a decaying homogeneous turbulent flow generated with a spectral code as an intial condition. The simulations are conducted by means of the PHYSALIS method. The trajectories of finite-size and point particles are compared as the particle radius is increased above the Kolmogorov scale for different Stokes numbers.

  9. Modeling of dielectrophoretic particle motion: Point particle versus finite-sized particle.

    PubMed

    Çetin, Barbaros; Öner, S Doğan; Baranoğlu, Besim

    2017-06-01

    Dielectrophoresis (DEP) is a very popular technique for microfluidic bio-particle manipulation. For the design of a DEP-based microfluidic device, simulation of the particle trajectory within the microchannel network is crucial. There are basically two approaches: (i) point-particle approach and (ii) finite-sized particle approach. In this study, many aspects of both approaches are discussed for the simulation of direct current DEP, alternating current DEP, and traveling-wave DEP applications. Point-particle approach is implemented using Lagrangian tracking method, and finite-sized particle is implemented using boundary element method. The comparison of the point-particle approach and finite-sized particle approach is presented for different DEP applications. Moreover, the effect of particle-particle interaction is explored by simulating the motion of closely packed multiple particles for the same applications, and anomalous-DEP, which is a result of particle-wall interaction at the close vicinity of electrode surface, is illustrated. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Light Obscuration Particle Counter Fuel Contamination Limits

    DTIC Science & Technology

    2015-10-08

    contamination. Based on this work the Department of Defense Tri-Service Petroleum , Oil and Lubricants Technical Steering Committee has recommended...Lubricants, and Related Products and Field Manual No. 10-67-2, Department of the Army Manual for Petroleum Laboratory Testing and Operations...detection of free water. APPROACH The particle counter limit evaluation took place at TARDEC’s Army Petroleum Laboratory (APL) in New

  11. Matching point clouds: limits and possibilities.

    PubMed

    Rudolph, H; Quaas, S; Luthardt, R G

    2002-01-01

    In computer-aided production of fixed dental restorations, the process chain always starts with digitizing, independent of the type of further (data) processing, the material used, and the kind of restoration to be produced. The quality of the digitized data, followed by the influences of further data processing and the production parameters, decisively influence the fitting accuracy of the dental restoration to be fabricated. The accuracy with which individually measured 3D data sets in the form of point clouds can be matched for further processing in one common system of coordinates was the object of the present study. Casts of the maxilla and mandible were digitized in several partial measurements comprising two to three teeth in each case, using an optical three-coordinate measuring system. The individual segments were sequentially aligned to surfaces that were created on the basis of partial point clouds. The mean deviation between surfaces and point clouds was between 1.90 microns and 18.24 microns. The accuracy of the alignment was determined by the RMS (root mean square) error, and was on average 14.2 microns (SD 7 microns) for the maxilla and 17.2 microns (SD 9.4 microns) for the mandible. Combining a larger number of smaller segments did not improve the result, since the errors of the individual registrations are summed in sequential matching. In this study, the errors arising in matching are not negligible and can possibly negatively influence the quality (fitting accuracy) of the restoration produced on the basis of the matched data records.

  12. 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.

  13. The Motion of Point Particles in Curved Spacetime.

    PubMed

    Poisson, Eric

    2004-01-01

    This review is concerned with the motion of a point scalar charge, a point electric charge, and a point mass in a specified background spacetime. In each of the three cases the particle produces a field that behaves as outgoing radiation in the wave zone, and therefore removes energy from the particle. In the near zone the field acts on the particle and gives rise to a self-force that prevents the particle from moving on a geodesic of the background spacetime. The self-force contains both conservative and dissipative terms, and the latter are responsible for the radiation reaction. The work done by the self-force matches the energy radiated away by the particle. The field's action on the particle is difficult to calculate because of its singular nature: The field diverges at the position of the particle. But it is possible to isolate the field's singular part and show that it exerts no force on the particle - its only effect is to contribute to the particle's inertia. What remains after subtraction is a smooth field that is fully responsible for the self-force. Because this field satisfies a homogeneous wave equation, it can be thought of as a free (radiative) field that interacts with the particle; it is this interaction that gives rise to the self-force. The mathematical tools required to derive the equations of motion of a point scalar charge, a point electric charge, and a point mass in a specified background spacetime are developed here from scratch. The review begins with a discussion of the basic theory of bitensors (Section 2). It then applies the theory to the construction of convenient coordinate systems to chart a neighbourhood of the particle's word line (Section 3). It continues with a thorough discussion of Green's functions in curved spacetime (Section 4). The review concludes with a detailed derivation of each of the three equations of motion (Section 5).

  14. The Motion of Point Particles in Curved Spacetime

    NASA Astrophysics Data System (ADS)

    Poisson, Eric; Pound, Adam; Vega, Ian

    2011-09-01

    This review is concerned with the motion of a point scalar charge, a point electric charge, and a point mass in a specified background spacetime. In each of the three cases the particle produces a field that behaves as outgoing radiation in the wave zone, and therefore removes energy from the particle. In the near zone the field acts on the particle and gives rise to a self-force that prevents the particle from moving on a geodesic of the background spacetime. The self-force contains both conservative and dissipative terms, and the latter are responsible for the radiation reaction. The work done by the self-force matches the energy radiated away by the particle. The field's action on the particle is difficult to calculate because of its singular nature: the field diverges at the position of the particle. But it is possible to isolate the field's singular part and show that it exerts no force on the particle — its only effect is to contribute to the particle's inertia. What remains after subtraction is a regular field that is fully responsible for the self-force. Because this field satisfies a homogeneous wave equation, it can be thought of as a free field that interacts with the particle; it is this interaction that gives rise to the self-force. The mathematical tools required to derive the equations of motion of a point scalar charge, a point electric charge, and a point mass in a specified background spacetime are developed here from scratch. The review begins with a discussion of the basic theory of bitensors (Part I). It then applies the theory to the construction of convenient coordinate systems to chart a neighbourhood of the particle's word line (Part II). It continues with a thorough discussion of Green's functions in curved spacetime (Part III). The review presents a detailed derivation of each of the three equations of motion (Part IV). Because the notion of a point mass is problematic in general relativity, the review concludes (Part V) with an

  15. The Motion of Point Particles in Curved Spacetime.

    PubMed

    Poisson, Eric; Pound, Adam; Vega, Ian

    2011-01-01

    This review is concerned with the motion of a point scalar charge, a point electric charge, and a point mass in a specified background spacetime. In each of the three cases the particle produces a field that behaves as outgoing radiation in the wave zone, and therefore removes energy from the particle. In the near zone the field acts on the particle and gives rise to a self-force that prevents the particle from moving on a geodesic of the background spacetime. The self-force contains both conservative and dissipative terms, and the latter are responsible for the radiation reaction. The work done by the self-force matches the energy radiated away by the particle. The field's action on the particle is difficult to calculate because of its singular nature: the field diverges at the position of the particle. But it is possible to isolate the field's singular part and show that it exerts no force on the particle - its only effect is to contribute to the particle's inertia. What remains after subtraction is a regular field that is fully responsible for the self-force. Because this field satisfies a homogeneous wave equation, it can be thought of as a free field that interacts with the particle; it is this interaction that gives rise to the self-force. The mathematical tools required to derive the equations of motion of a point scalar charge, a point electric charge, and a point mass in a specified background spacetime are developed here from scratch. The review begins with a discussion of the basic theory of bitensors (Part I). It then applies the theory to the construction of convenient coordinate systems to chart a neighbourhood of the particle's word line (Part II). It continues with a thorough discussion of Green's functions in curved spacetime (Part III). The review presents a detailed derivation of each of the three equations of motion (Part IV). Because the notion of a point mass is problematic in general relativity, the review concludes (Part V) with an

  16. A point particle model of lightly bound skyrmions

    NASA Astrophysics Data System (ADS)

    Gillard, Mike; Harland, Derek; Kirk, Elliot; Maybee, Ben; Speight, Martin

    2017-04-01

    A simple model of the dynamics of lightly bound skyrmions is developed in which skyrmions are replaced by point particles, each carrying an internal orientation. The model accounts well for the static energy minimizers of baryon number 1 ≤ B ≤ 8 obtained by numerical simulation of the full field theory. For 9 ≤ B ≤ 23, a large number of static solutions of the point particle model are found, all closely resembling size B subsets of a face centred cubic lattice, with the particle orientations dictated by a simple colouring rule. Rigid body quantization of these solutions is performed, and the spin and isospin of the corresponding ground states extracted. As part of the quantization scheme, an algorithm to compute the symmetry group of an oriented point cloud, and to determine its corresponding Finkelstein-Rubinstein constraints, is devised.

  17. Bifurcations: Focal Points of Particle Adhesion in Microvascular Networks

    PubMed Central

    Prabhakarpandian, Balabhaskar; Wang, Yi; Rea-Ramsey, Angela; Sundaram, Shivshankar; Kiani, Mohammad F.; Pant, Kapil

    2011-01-01

    Objective Particle adhesion in vivo is dependent on microcirculation environment which features unique anatomical (bifurcations, tortuosity, cross-sectional changes) and physiological (complex hemodynamics) characteristics. The mechanisms behind these complex phenomena are not well understood. In this study, we used a recently developed in vitro model of microvascular networks, called Synthetic Microvascular Network, for characterizing particle adhesion patterns in the microcirculation. Methods Synthetic microvascular networks were fabricated using soft lithography processes followed by particle adhesion studies using avidin and biotin-conjugated microspheres. Particle adhesion patterns were subsequently analyzed using CFD based modeling. Results Experimental and modeling studies highlighted the complex and heterogeneous fluid flow patterns encountered by particles in microvascular networks resulting in significantly higher propensity of adhesion (>1.5X) near bifurcations compared to the branches of the microvascular networks. Conclusion Bifurcations are the focal points of particle adhesion in microvascular networks. Changing flow patterns and morphology near bifurcations are the primary factors controlling the preferential adhesion of functionalized particles in microvascular networks. Synthetic microvascular networks provide an in vitro framework for understanding particle adhesion. PMID:21418388

  18. 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, Prasanth; Jackson, Thomas; Balachandar, S.

    2017-01-01

    Micrsoscale simulations are being conducted for developing point-particle and other related models that are needed for the mesoscale and macroscale simulations of explosive dispersal of particles. These particle models are required to compute (a) instantaneous aerodynamic force on the particle and (b) instantaneous net heat transfer between the particle and the surrounding. A strategy for a sequence of microscale simulations has been devised that allows systematic development of the hybrid surrogate models that are applicable at conditions representative of the explosive dispersal application. The ongoing microscale simulations seek to examine particle force dependence on: (a) Mach number, (b) Reynolds number, and (c) volume fraction (different particle arrangements such as cubic, face-centered cubic (FCC), body-centered cubic (BCC) 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 actual problem of explosive dispersal. Additionally, effects of particle shape, size, and number in simulation as well as the transient particle deformation dependence on various 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.

  19. Particle Count Limits Recommendation for Aviation Fuel

    DTIC Science & Technology

    2015-10-05

    gravimetric measurements need to be taken to determine if poor measurement repeatability accounts for false negatives. • Photograph failed...ASTM D2276 – Particulate Contamination in Aviation Fuel by Line Sampling – gravimetric limit 1.0 mg/L (MIL-STD-3004, MIL-DTL-83133) • JP-4 and JP-5...Filtration – gravimetric limit 1.0 mg/L (MIL-STD-3004) • ASTM D3240 – Undissolved Water in Aviation Turbine Fuels – 10 PPM (MIL-STD-3004, ATP 4-43

  20. 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.

  1. Point Set Registration via Particle Filtering and Stochastic Dynamics

    PubMed Central

    Sandhu, Romeil; Dambreville, Samuel; Tannenbaum, Allen

    2013-01-01

    In this paper, we propose a particle filtering approach for the problem of registering two point sets that differ by a rigid body transformation. Typically, registration algorithms compute the transformation parameters by maximizing a metric given an estimate of the correspondence between points across the two sets of interest. This can be viewed as a posterior estimation problem, in which the corresponding distribution can naturally be estimated using a particle filter. In this work, we treat motion as a local variation in pose parameters obtained by running a few iterations of a certain local optimizer. Employing this idea, we introduce stochastic motion dynamics to widen the narrow band of convergence often found in local optimizer approaches for registration. Thus, the novelty of our method is threefold: First, we employ a particle filtering scheme to drive the point set registration process. Second, we present a local optimizer that is motivated by the correlation measure. Third, we increase the robustness of the registration performance by introducing a dynamic model of uncertainty for the transformation parameters. In contrast with other techniques, our approach requires no annealing schedule, which results in a reduction in computational complexity (with respect to particle size) as well as maintains the temporal coherency of the state (no loss of information). Also unlike some alternative approaches for point set registration, we make no geometric assumptions on the two data sets. Experimental results are provided that demonstrate the robustness of the algorithm to initialization, noise, missing structures, and/or differing point densities in each set, on several challenging 2D and 3D registration scenarios. PMID:20558877

  2. Plato's Child and the Limit-Points of Educational Theories.

    ERIC Educational Resources Information Center

    Baker, Bernadette

    2003-01-01

    Analyzes how the figure of the child has been used to authorize a series of boundaries that have been constituted the limit points of educational theories or philosophies. Concludes that the meaning-space that the child can occupy has been important to depicting Utopian and cosmological imaginings at different historical moments. (Contains 37…

  3. A phase-field point-particle model for particle-laden interfaces

    NASA Astrophysics Data System (ADS)

    Gu, Chuan; Botto, Lorenzo

    2014-11-01

    The irreversible attachment of solid particles to fluid interfaces is exploited in a variety of applications, such as froth flotation and Pickering emulsions. Critical in these applications is to predict particle transport in and near the interface, and the two-way coupling between the particles and the interface. While it is now possible to carry out particle-resolved simulations of these systems, simulating relatively large systems with many particles remains challenging. We present validation studies and preliminary results for a hybrid Eulerian-Lagrangian simulation method, in which the dynamics of the interface is fully-resolved by a phase-field approach, while the particles are treated in the ``point-particle'' approximation. With this method, which represents a compromise between the competing needs of resolving particle and interface scale phenomena, we are able to simulate the adsorption of a large number of particles in the interface of drops, and particle-interface interactions during the spinodal coarsening of a multiphase system. While this method models the adsorption phenomenon efficiently and with reasonable accuracy, it still requires understanding subtle issues related to the modelling of hydrodynamic and capillary forces for particles in contact with interface.

  4. Statistical mechanics of point particles with a gravitational interaction

    NASA Astrophysics Data System (ADS)

    Chabanol, M.-L.; Corson, F.; Pomeau, Y.

    2000-04-01

    We study the dynamics of N point particles with a gravitational interaction. The divergence of the microcanonical partition function prevents this system from reaching equilibrium. Assuming a random diffusion in phase space we deduce a scaling law involving time, which is numerically checked for 3 interacting masses in a quadratic nonsymmetrical potential. This random walk on the potential energy scale is studied in some detail and the results agree with the numerics.

  5. Shear-limited test particle diffusion in 2-dimensional plasmas

    NASA Astrophysics Data System (ADS)

    Anderegg, Francois; Driscoll, C. Fred; Dubin, Daniel H. E.

    2002-01-01

    Measurements of test-particle diffusion in pure ion plasmas show 2D enhancements over the 3D rates, limited by shear in the plasma rotation ωE(r). The diffusion is due to "long-range" ion-ion collisions in the quiescent, steady-state Mg+ plasma. For short plasma length Lp and low shear S≡r∂ωE/∂r, thermal ions bounce axially many times before shear separates them in θ, so the ions move in (r,θ) as bounce averaged "rods" of charge (i.e. 2D point vortices). Experimentally, we vary the number of bounces over the range 0.2⩽Nb⩽10,000. For long plasmas with Nb⩽1, we observe diffusion in quantitative agreement with the 3D theory of long-range E×B drift collisions. For shorter plasmas or lower shear, with Nb>1, we measure diffusion rates enhanced by up to 100×. For exceedingly small she0ar, i.e. Nb⩾1000, we observe diffusion rates consistent with the Taylor-McNamara estimates for a shear-free thermal plasma. Overall, the data shows fair agreement with Dubin's new theory of 2D diffusion in shear, which predicts an enhancement of D2D/D3D≈Nb up to the Taylor-McNamara limit.

  6. A direct comparison of fully resolved and point-particle models in particle-laden turbulent flow

    NASA Astrophysics Data System (ADS)

    Horwitz, Jeremy; Mehrabadi, Mohammad; Subramaniam, Shankar; Mani, Ali

    2016-11-01

    Point-particle methods have become a popular methodology to simulate viscous fluids laden with dispersed solid elements. Such methods may be contrasted with particle-resolved methods, whereby the boundary conditions between particles and fluid are treated exactly, while point-particle methods do not capture the boundary conditions exactly and couple the continuous and dispersed phase via point-forces. This allows point-particle methods to simulate particle-turbulence interaction at considerably lower resolution and computational cost than particle-resolved methods. However, lack of validation of point-particle methods begs the question of the predictive power of point-particle methods. In other words, can point-particle methods recover particle and fluid statistics compared with particle-resolved simulation of dynamically equivalent non-dimensional problems? We address this question in this work by examining decaying homogeneous isotropic turbulence laden with particles. For the same nominal conditions, we compare statistics predicted by a particle resolved method to those predicted by a point-particle method. We also examine the effect of the undisturbed velocity in the point-particle drag law by studying the same problem with a correction scheme. Supported by DOE and NSF.

  7. Accuracy limit of rigid 3-point water models

    NASA Astrophysics Data System (ADS)

    Izadi, Saeed; Onufriev, Alexey V.

    2016-08-01

    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.

  8. 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.

  9. Accuracy limit of rigid 3-point water models

    PubMed Central

    Izadi, Saeed

    2016-01-01

    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

  10. 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

  11. Limiting factors in acoustic separation of carbon particles in air.

    PubMed

    Karpul, David; Tapson, Jonathan; Rapson, Michael; Jongens, Adrian; Cohen, Gregory

    2010-04-01

    Particles suspended in a fluid that is exposed to an acoustic standing wave experience a time-averaged force that drives them to either the pressure nodes or anti-nodes of the wave. Several filter designs have been successfully implemented using this force to filter small particles in liquids with low flow rates and small cross-sectional areas. It has been suggested that the filtration of small solid particles out of a gas, such as carbon in air (smoke), would be a possible application of acoustic standing wave based particle separation. This study shows the limiting factors, in both power requirements and design factors, of an acoustic filter designed for filtering smoke particles across large cross-sectional areas. It is shown that while filtration is possible, the power needed is impractical. It is also shown that operating the filter within certain settling time parameters optimizes the energy usage of the filter.

  12. 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.

  13. The rotation curve of a point particle in stringy gravity

    NASA Astrophysics Data System (ADS)

    Ko, Sung Moon; Park, Jeong-Hyuck; Suh, Minwoo

    2017-06-01

    Double Field Theory suggests to view the whole massless sector of closed strings as the gravitational unity. The fundamental symmetries therein, including the O(D,D) covariance, can determine unambiguously how the Standard Model as well as a relativistic point particle should couple to the closed string massless sector. The theory also refines the notion of singularity. We consider the most general, spherically symmetric, asymptotically flat, static vacuum solution to D=4 Double Field Theory, which contains three free parameters and consequently generalizes the Schwarzschild geometry. Analyzing the circular geodesic of a point particle in string frame, we obtain the orbital velocity as a function of R/(M∞G) which is the dimensionless radial variable normalized by mass. The rotation curve generically features a maximum and thus non-Keplerian over a finite range, while becoming asymptotically Keplerian at infinity, R/(M∞G)→ ∞. The adoption of the string frame rather than Einstein frame is the consequence of the fundamental symmetry principle. Our result opens up a new scheme to solve the dark matter/energy problems by modifying General Relativity at 'short' range of R/(M∞G).

  14. Overcharging higher-dimensional black holes with point particles

    NASA Astrophysics Data System (ADS)

    Revelar, Karl Simon; Vega, Ian

    2017-09-01

    We investigate the possibility of overcharging spherically symmetric black holes in spacetime dimensions D >4 by the capture of a charged particle. We generalize Wald's classic result that extremal black holes cannot be overcharged. For nearly extremal black holes, we also generalize Hubeny's scenario by showing that overcharging is possible in a small region of parameter space. We check how D affects the overcharging parameter space and find that this appears to shrink in the large-D limit, which suggests that overcharging becomes increasingly difficult in higher dimensions.

  15. Calculated limits for particle fluxes in Jupiter's Van Allen belts

    NASA Technical Reports Server (NTRS)

    Haffner, J.

    1972-01-01

    Electron and proton fluxes in Jupiter's radiation belts are calculated, along with the envelopes of dose rates. The following assumptions are made: the particles in the Jupiter belts are influenced only by the magnetic field of the planet; the particles act correspondingly to the particles in the Earth's belts and the Earth's belts can be used as a model; the magnetic field of Jupiter is essentially a dipole; the radiation of a decimetric nature received from Jupiter is synchrotron radiation due to the electrons, and to a first approximation it is emitted isotropically; and the strength of the emission in the decimetric wavelength range gives an upper bound considering how strong the field can be and how many electrons there are. The point dose rates for tissue and 0.1 gram/cm aluminum shielding at about 3 Jupiter radii are 10000 rads/hr for electrons and 1000 rads/hr for protons.

  16. Inertial particles distribute in turbulence as Poissonian points with random intensity inducing clustering and supervoiding

    NASA Astrophysics Data System (ADS)

    Schmidt, Lukas; Fouxon, Itzhak; Holzner, Markus

    2017-07-01

    This work considers the distribution of discrete inertial particles in turbulence. We demonstrate that even for weak inertia the distribution can be strongly different from the Poisson distribution that holds for tracers. We study the cases of weak inertia or strong gravity where single-valued particle flow holds in space. In these cases, the particles distribute over a random multifractal attractor in space. This attractor is characterized by fractal dimensions describing scaling exponents of moments of number of particles inside a ball with size much smaller than the viscous scale of turbulence. Previous studies used a continuum approach to the moments which requires having a large number of particles below the viscous scale. This condition often does not hold in practice; for instance, for water droplets in clouds there is typically one droplet per viscous scale. This condition is also hard to realize in numerical simulations. In this work, we overcome this difficulty by deriving the probability pl(k ) of having k particles in a ball of small radius l for which the continuum approximation may not hold. We demonstrate that the random point process formed by positions of particles' centers in space is a Poisson point process with log-normal random intensity (the so-called log Gaussian Cox process or LGCP). This gives pl(k ) in terms of the characteristic function of a log-normal distribution from which the moments are derived. This allows finding the correlation dimension relevant for statistics of particles' collisions. The case of zero number of particles provides the statistics of the size of voids—regions without particles—that were not studied previously. The probability of voids is increased compared to a random distribution of particles because preferential concentration of inertial particles implies voids in the deserted regions. Thus voids and preferential concentration are different reflections of the same phenomena. In the limit of tracers with zero

  17. Modulation to the compressible homogenous turbulence by heavy point particles: Effect of particles' density

    NASA Astrophysics Data System (ADS)

    Xia, Zhenhua; Shi, Yipeng; Chen, Shiyi

    2015-11-01

    In this paper, two-way interactions between heavy point particles and forced compressible homogenous turbulence are simulated by using a localized artificial diffusivity scheme and an Eulerian-Lagrangian approach. The initial turbulent Mach number is around 1.0 and the Taylor Reynolds number is around 110. Seven different simulations of 106 particles with different particle densities (or Stokes number) are considered. The statistics of the compressible turbulence, such as the turbulence Mach number, kinetic energy, dilatation, and the kinetic energy spectra, from different simulations are compared with each other, and with the one-way undisturbed case. Our results show that the turbulence is suppressed if the two-way coupling backward interactions are considered, and the effect is more obvious if the density of particles is higher. The kinetic energy spectrum at larger Stokes number (higher density) exhibits a reduction at low wave numbers and an augmentation at high wave numbers, which is similar to those obtained in incompressible cases. The probability density functions of dilatation, and normal upstream Mach number of shocklets also show that the modulation to the shocklet statistics is more apparent for particles with higher density. We acknowledge the financial support provided by National Natural Science Foundation of China (Grants Nos. 11302006, and U1330107).

  18. Critical limits for the control points for halal poultry slaughter.

    PubMed

    Shahdan, Intan Azura; Regenstein, Joe Mac; Rahman, Mohammad Tariqur

    2016-12-13

    This study proposes critical limits (CL) for control points for halal slaughter (CPHS). Previously, 6 control points (CP) were determined, and CL for these 6 CPHS are suggested based on: 1) a literature survey for the CL for CP 1 (poultry breeding, rearing, and poultry feed) and CP 2 (welfare of poultry during transportation and lairage); 2) a field survey of slaughter plants in Kuantan (Malaysia) for CP 3 (immobilization), CP 4 (slaughter), CP 5 (time for full bleed-out), and CP 6 (washing and packaging); and 3) controlled experiments to refine the CL for CP 3, 4, and 5. The CL for CP 1 focused on stress reduction during rearing and use of substances that could compromise poultry meat wholesomeness. The CL for CP 2 emphasizes humane best-practices for handling poultry during lairage. The CL for CP 3 suggests a gap of 5 s between 2 shackles if only one shackler is employed and shackling times of <1 min for live chickens. In countries permitting water-bath electrical stunning of halal poultry, the stunning current needed to induce unconsciousness must be defined for the breed and bird size but not cause any chicken deaths. The CL for CP 4 mandates the recitation of the tasmiyah (the invocation), which if done for every chicken, will require ≥5 s between stunning and neck cutting. The CL for CP 4 also includes information about the slaughter knife. In CP 5 the recommended minimum time between neck cutting and scalding is 9.5 min. Finally, the CL for CP 6 emphasizes good supply chain hygiene and zero adulteration from haram species and substances.

  19. Simulation of chemical reaction via particle tracking: Diffusion-limited versus thermodynamic rate-limited regimes

    NASA Astrophysics Data System (ADS)

    Benson, David A.; Meerschaert, Mark M.

    2008-12-01

    Chemical reactions may be simulated without regard to local concentrations by applying simple probabilistic rules of particle interaction and combination. The forward reaction A + B→ C is coded by calculating the probability that any A and B particles will occupy the same volume over some time interval. This becomes a convolution of the location densities of the two particles. The backward reaction is a simple exponential decay of C particles into A and B particles. When the mixing of reactants is not a limiting process, the classical thermodynamic reaction rates are reproduced. When low mixing (as by diffusion) limits the reaction probabilities, the reaction rates drop significantly, including the rate of approach to global equilibrium. At long enough times, the law of mass action is reproduced exactly in the mean, with some irreducible deviation in the local equilibrium saturations (the equilibrium constant divided by the mass action expression) away from unity. The saturation variability is not sensitive to numerical parameters but depends strongly on how far from equilibrium the system is initiated. This is simply due to a relative paucity of particles of some species as the reaction moves far to one side or the other.

  20. 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.

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

    PubMed Central

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

    2013-01-01

    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. PMID:23901970

  2. Speed-limited particle-in-cell (SLPIC) simulation

    NASA Astrophysics Data System (ADS)

    Werner, Gregory; Cary, John; Jenkins, Thomas

    2016-10-01

    Speed-limited particle-in-cell (SLPIC) simulation is a new method for particle-based plasma simulation that allows increased timesteps in cases where the timestep is determined (e.g., in standard PIC) not by the smallest timescale of interest, but rather by an even smaller physical timescale that affects numerical stability. For example, SLPIC need not resolve the plasma frequency if plasma oscillations do not play a significant role in the simulation; in contrast, standard PIC must usually resolve the plasma frequency to avoid instability. Unlike fluid approaches, SLPIC retains a fully-kinetic description of plasma particles and includes all the same physical phenomena as PIC; in fact, if SLPIC is run with a PIC-compatible timestep, it is identical to PIC. However, unlike PIC, SLPIC can run stably with larger timesteps. SLPIC has been shown to be effective for finding steady-state solutions for 1D collisionless sheath problems, greatly speeding up computation despite a large ion/electron mass ratio. SLPIC is a relatively small modification of standard PIC, with no complexities that might degrade parallel efficiency (compared to PIC), and is similarly compatible with PIC field solvers and boundary conditions.

  3. 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

  4. Limitation of Perpetual Points for Confirming Conservation in Dynamical Systems

    NASA Astrophysics Data System (ADS)

    Jafari, Sajad; Nazarimehr, Fahimeh; Sprott, J. C.; Golpayegani, Seyed Mohammad Reza Hashemi

    2015-12-01

    Perpetual Points (PPs) have been introduced as an interesting new topic in nonlinear dynamics, and there is a hypothesis that these points can determine whether a system is dissipative or not. This paper demonstrates that this hypothesis is not true since there are counterexamples. Furthermore, we explain that it is impossible to determine dissipation of a system based only on the structure of the system and its equations.

  5. 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.

  6. The Newtonian limit of spacetimes for accelerated particles and black holes

    NASA Astrophysics Data System (ADS)

    Bičák, Jiří; Kofroň, David

    2009-01-01

    Solutions of vacuum Einstein’s field equations describing uniformly accelerated particles or black holes belong to the class of boost-rotation symmetric spacetimes. They are the only explicit solutions known which represent moving finite objects. Their Newtonian limit is analyzed using the Ehlers frame theory. Generic spacetimes with axial and boost symmetries are first studied from the Newtonian perspective. The results are then illustrated by specific examples such as C-metric, Bonnor-Swaminarayan solutions, self-accelerating “dipole particles”, and generalized boost-rotation symmetric solutions describing freely falling particles in an external field. In contrast to some previous discussions, our results are physically plausible in the sense that the Newtonian limit corresponds to the fields of classical point masses accelerated uniformly in classical mechanics. This corroborates the physical significance of the boost-rotation symmetric spacetimes.

  7. Sound reduction at a target point inside an enclosed cavity using particle dampers

    NASA Astrophysics Data System (ADS)

    Hu, Li; Shi, Yaogui; Yang, Qiliang; Song, Gangbing

    2016-12-01

    The purpose of this paper is to develop a novel structural damping approach to reduce the sound pressure at a target point inside an enclosed cavity. In this approach, particle dampers filled with either metal or nonmetal particles are used. The dissipation mechanisms of such dampers are primarily related to the friction and collision of particle-wall and particle-particle contacts. In this research, each panel contribution was first analyzed to identify the panel that contributes the most to the target point. The proposed particle dampers were then attached to this panel for sound reduction. In the numerical process, a Particle Dampers Cyclic Iterative Method (PDCIM) was proposed for extracting the damping loss factor of the particle dampers to compute the sound pressure of a target point in the cavity with the particle dampers. For further comparative studies, simulation experiments are conducted for three cases: a case with the particle dampers, a case with the empty particle containers and a case with the equivalent mass. The numerical study found that the case with the particle dampers had the best sound reduction effect. Later, model tests were carried out to validate the numerical results. Experimental test results revealed that the particle dampers are remarkably effective for reducing the sound inside the enclosed cavity.

  8. Size limit for particle-stabilized emulsion droplets under gravity.

    PubMed

    Tavacoli, J W; Katgert, G; Kim, E G; Cates, M E; Clegg, P S

    2012-06-29

    We demonstrate that emulsion droplets stabilized by interfacial particles become unstable beyond a size threshold set by gravity. This holds not only for colloids but also for supracolloidal glass beads, using which we directly observe the ejection of particles near the droplet base. The number of particles acting together in these ejection events decreases with time until a stable acornlike configuration is reached. Stability occurs when the weight of all remaining particles is less than the interfacial binding force of one particle. We also show the importance of the curvature of the droplet surface in promoting particle ejection.

  9. On Irreversibility and Radiation in Classical Electrodynamics of Point Particles

    NASA Astrophysics Data System (ADS)

    Bauer, Gernot; Deckert, Dirk-André; Dürr, Detlef; Hinrichs, Günter

    2013-09-01

    The direct interaction theory of electromagnetism, also known as Wheeler-Feynman electrodynamics, is often misinterpreted and found unappealing because of its reference to the absorber and, more importantly, to the so-called absorber condition. Here we remark that the absorber condition is indeed questionable and presumably not relevant for the explanation of irreversible radiation phenomena in our universe. What is relevant and deserves further scrutiny is the emergent effective description of a source particle in an environment. We therefore rephrase what we consider the relevant calculation by Wheeler and Feynman and comment on the status of the theory.

  10. Highly accelerated simulations of glassy dynamics using GPUs: Caveats on limited floating-point precision

    NASA Astrophysics Data System (ADS)

    Colberg, Peter H.; Höfling, Felix

    2011-05-01

    Modern graphics processing units (GPUs) provide impressive computing resources, which can be accessed conveniently through the CUDA programming interface. We describe how GPUs can be used to considerably speed up molecular dynamics (MD) simulations for system sizes ranging up to about 1 million particles. Particular emphasis is put on the numerical long-time stability in terms of energy and momentum conservation, and caveats on limited floating-point precision are issued. Strict energy conservation over 10 8 MD steps is obtained by double-single emulation of the floating-point arithmetic in accuracy-critical parts of the algorithm. For the slow dynamics of a supercooled binary Lennard-Jones mixture, we demonstrate that the use of single-floating point precision may result in quantitatively and even physically wrong results. For simulations of a Lennard-Jones fluid, the described implementation shows speedup factors of up to 80 compared to a serial implementation for the CPU, and a single GPU was found to compare with a parallelised MD simulation using 64 distributed cores.

  11. 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.

  12. Conductivity of individual particles measured by a microscopic four-point-probe method

    PubMed Central

    Sun, Ling; Wang, Jianjun; Bonaccurso, Elmar

    2013-01-01

    We introduce a technique for measuring the conductivity of individual hybrid metal, semiconducting core-shell and full-metal conducting particles by a microscopic four-point probe (μ-4PP) method. The four-point probe geometry allows for minimizing contact resistances between electrodes and particles. By using a focused ion beam we fabricate platinum nanoleads between four microelectrodes on a silicon chip and an individual particle, and determine the particle's conductivity via sensitive current and voltage measurements. Up to sixteen particles can be taken up by each chip, which allows for multiple conductivity measurements by simply multiplexing the electric contacts connected to a multimeter. Although, for demonstration, we used full Au (conducting) and Ag-coated latex particles (semiconducting) of a few micrometers in diameter, the method can be applied to other types of conducting or semiconducting particles of different diameters. PMID:23771149

  13. Stochastic electrodynamics with particle structure Part I: Zero-point induced Brownian behavior

    NASA Astrophysics Data System (ADS)

    Rueda, A.

    1993-02-01

    If ordinary views on particle structure are introduced in a simple classical particle model in replacement of the point particles of standard use in stochastic electrodynamics, it can be shown that an internal Zitterbewegung induced by the zero-point field background gives rise to a Brownian movement for the whole particle with a diffusion constant of the form D = ħ/2mD , where mD is a modeldependent mass. Since the days of Madeleung and Fuhr brownian behaviour has often been associated with quantization. We discuss this from the viewpoint of stochastic electrodynamics.

  14. Laboratory Evaluation of Light Obscuration Particle Counters used to Establish use Limits for Aviation Fuel

    DTIC Science & Technology

    2015-12-01

    5000 DISTRIBUTION A. Approved for public release: distribution unlimited. Laboratory Evaluation of Light Obscuration Particle Counters used to...To) 4. TITLE AND SUBTITLE Laboratory Evaluation of Light Obscuration Particle Counters used to Establish use Limits for Aviation Fuel 5a. CONTRACT...laboratory evaluations of automatic light obscuration particle counters to develop limits for aviation fuel cleanliness. The laboratory evaluations

  15. 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).

  16. 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.

  17. A novel scalable, robust downstream process for oncolytic rat parvovirus: isoelectric point-based elimination of empty particles.

    PubMed

    Leuchs, Barbara; Frehtman, Veronika; Riese, Markus; Müller, Marcus; Rommelaere, Jean

    2017-04-01

    The rodent protoparvovirus H-1PV, with its oncolytic and oncosuppressive properties, is a promising anticancer agent currently under testing in clinical trials. This explains the current demand for a scalable, good manufacturing practice-compatible virus purification process yielding high-grade pure infectious particles and overcoming the limitations of the current system based on density gradient centrifugation. We describe here a scalable process offering high purity and recovery. Taking advantage of the isoelectric point difference between full and empty particles, it eliminates most empty particles. Full particles have a significantly higher cationic charge than empty ones, with an isoelectric point of 5.8-6.2 versus 6.3 (as determined by isoelectric focusing and chromatofocusing). Thanks to this difference, infectious full particles can be separated from empty particles and most protein impurities by Convective interaction media(®) diethylaminoethyl (DEAE) anion exchange chromatography: applying unpurified H-1PV to the column in 0.15 M NaCl leaves, the former on the column and the latter in the flow through. The full particles are then recovered by elution with 0.25 M NaCl. The whole large-scale purification process involves filtration, single-step DEAE anion exchange chromatography, buffer exchange by cross-flow filtration, and final formulation in Visipaque/Ringer solution. It results in 98% contaminating protein removal and 96% empty particle elimination. The final infectious particle concentration reaches 3.5E10 plaque forming units (PFU)/ml, with a specific activity of 6.8E11 PFU/mg protein. Overall recovery is over 40%. The newly established method is suitable for use in commercial production.

  18. A feature point identification method for positron emission particle tracking with multiple tracers

    NASA Astrophysics Data System (ADS)

    Wiggins, Cody; Santos, Roque; Ruggles, Arthur

    2017-01-01

    A novel detection algorithm for Positron Emission Particle Tracking (PEPT) with multiple tracers based on optical feature point identification (FPI) methods is presented. This new method, the FPI method, is compared to a previous multiple PEPT method via analyses of experimental and simulated data. The FPI method outperforms the older method in cases of large particle numbers and fine time resolution. Simulated data show the FPI method to be capable of identifying 100 particles at 0.5 mm average spatial error. Detection error is seen to vary with the inverse square root of the number of lines of response (LORs) used for detection and increases as particle separation decreases.

  19. Period Doubling Bifurcation Point Detection Strategy with Nested Layer Particle Swarm Optimization

    NASA Astrophysics Data System (ADS)

    Matsushita, Haruna; Tomimura, Yusho; Kurokawa, Hiroaki; Kousaka, Takuji

    2017-06-01

    This paper proposes a bifurcation point detection strategy based on nested layer particle swarm optimization (NLPSO). The NLPSO is performed by two particle swarm optimization (PSO) algorithms with a nesting structure. The proposed method is tested in detection experiments of period doubling bifurcation points in discrete-time dynamical systems. The proposed method directly detects the parameters of period doubling bifurcation regardless of the stability of the periodic point, but require no careful initialization, exact calculation or Lyapunov exponents. Moreover, the proposed method is an effective detection technique in terms of accuracy, robustness usability, and convergence speed.

  20. [Current status and limitation of particle radiation therapy].

    PubMed

    Ogino, Takashi

    2009-11-01

    Almost 9,000 patients have been treated by particle radiation therapy as a highly advanced medical technology in Japan, and definitive evaluation of this technology might now be possible. The process of approval of medical equipment, the law of medical technologists, and the law of medicine for particle radiation therapy have also been prepared. Number of facilities is expected to increase, and time has come that the fee of this medicine would cover by social insurance. Much debate, however, has been published in English journals upon proton therapy. The National Cancer Institute has started to support clinical trials in the United States. In Japan, however, research funding is still quite small.

  1. Point-particle effective field theory III: relativistic fermions and the Dirac equation

    NASA Astrophysics Data System (ADS)

    Burgess, C. P.; Hayman, Peter; Rummel, Markus; Zalavári, László

    2017-09-01

    We formulate point-particle effective field theory (PPEFT) for relativistic spin-half fermions interacting with a massive, charged finite-sized source using a first-quantized effective field theory for the heavy compact object and a second-quantized language for the lighter fermion with which it interacts. This description shows how to determine the near-source boundary condition for the Dirac field in terms of the relevant physical properties of the source, and reduces to the standard choices in the limit of a point source. Using a first-quantized effective description is appropriate when the compact object is sufficiently heavy, and is simpler than (though equivalent to) the effective theory that treats the compact source in a second-quantized way. As an application we use the PPEFT to parameterize the leading energy shift for the bound energy levels due to finite-sized source effects in a model-independent way, allowing these effects to be fit in precision measurements. Besides capturing finite-source-size effects, the PPEFT treatment also efficiently captures how other short-distance source interactions can shift bound-state energy levels, such as due to vacuum polarization (through the Uehling potential) or strong interactions for Coulomb bound states of hadrons, or any hypothetical new short-range forces sourced by nuclei.

  2. 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.

  3. Extending the limits of direct force measurements: colloidal probes from sub-micron particles.

    PubMed

    Helfricht, Nicolas; Mark, Andreas; Dorwling-Carter, Livie; Zambelli, Tomaso; Papastavrou, Georg

    2017-07-13

    Direct force measurements by atomic force microscopy (AFM) in combination with the colloidal probe technique are widely used to determine interaction forces in colloidal systems. However, a number of limitations are still preventing a more universal applicability of this technique. Currently, one of the most significant limitations is that only particles with diameters of several micrometers can be used as probe particles. Here, we present a novel approach, based on the combination of nanofluidics and AFM (also referred to as FluidFM-technique), that allows to overcome this size limit and extend the size of suitable probe particles below diameters of 500 nanometers. Moreover, by aspiration of colloidal particles with a hollow AFM-cantilever, the immobilization process is independent of the particle's surface chemistry. Furthermore, the probe particles can be exchanged in situ. The applicability of the FluidFM-technique is demonstrated with silica particles, which are also the types of particles most often used for the preparation of colloidal probes. By comparing 'classical' colloidal probes, i.e. probes from particles irreversibly attached with glue, and various particle sizes aspirated by the FluidFM-technique, we can quantitatively evaluate the instrumental limits. Evaluation of the force profiles demonstrate that even for 500 nm silica particles the diffuse layer properties can be evaluated quantitatively. Therefore, direct force measurements on the level of particle sizes used in industrial formulations will become available in the future.

  4. Diagnostic point-of-care tests in resource-limited settings.

    PubMed

    Drain, Paul K; Hyle, Emily P; Noubary, Farzad; Freedberg, Kenneth A; Wilson, Douglas; Bishai, William R; Rodriguez, William; Bassett, Ingrid V

    2014-03-01

    The aim of diagnostic point-of-care testing is to minimise the time to obtain a test result, thereby allowing clinicians and patients to make a quick clinical decision. Because point-of-care tests are used in resource-limited settings, the benefits need to outweigh the costs. To optimise point-of-care testing in resource-limited settings, diagnostic tests need rigorous assessments focused on relevant clinical outcomes and operational costs, which differ from assessments of conventional diagnostic tests. We reviewed published studies on point-of-care testing in resource-limited settings, and found no clearly defined metric for the clinical usefulness of point-of-care testing. Therefore, we propose a framework for the assessment of point-of-care tests, and suggest and define the term test efficacy to describe the ability of a diagnostic test to support a clinical decision within its operational context. We also propose revised criteria for an ideal diagnostic point-of-care test in resource-limited settings. Through systematic assessments, comparisons between centralised testing and novel point-of-care technologies can be more formalised, and health officials can better establish which point-of-care technologies represent valuable additions to their clinical programmes. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Kinetics of Particle Adsorption in Stagnation Point Flow Studied by Optical Reflectometry

    PubMed

    Böhmer; van der Zeeuw EA; Koper

    1998-01-15

    The kinetics of adsorption of nano-sized silica particles on a polymer pretreated surface were followed in situ by using optical reflectometry in a stagnation point flow setup. Conversion of the reflectometric signal to the surface coverage could be performed using a homogeneous slab model which was verified by determining the particle density on SEM pictures taken in the stagnation point and by comparison with a model which includes the particulate nature of the layer explicitly. The effects of salt concentration on the plateau adsorbed amounts for all particle sizes can be described with an effective hard sphere concept. Although initial slopes and plateau values are in reasonable agreement with a random sequential adsorption model, this model does not accurately describe the evolution of the surface coverage as a function of time in a stagnation point flow system. Copyright 1998 Academic Press. Copyright 1998Academic Press

  6. 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

    ... Part 450 Environmental protection, Construction industry, Land development, Erosion, Sediment... AGENCY 40 CFR Part 450 Direct Final Rule Staying Numeric Limitation for the Construction and Development... monitoring requirements for the Construction and Development Point Source Category. This action is necessary...

  7. 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.

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

    PubMed

    Abd Rabbou, Mahmoud; El-Rabbany, Ahmed

    2015-03-25

    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.

  9. 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

  10. Diffusion Limit of Kinetic Equations for Multiple Species Charged Particles

    NASA Astrophysics Data System (ADS)

    Wu, Hao; Lin, Tai-Chia; Liu, Chun

    2015-02-01

    In ionic solutions, there are multi-species charged particles (ions) with different properties like mass, charge etc. Macroscopic continuum models like the Poisson-Nernst-Planck (PNP) systems have been extensively used to describe the transport and distribution of ionic species in the solvent. Starting from the kinetic theory for the ion transport, we study a Vlasov-Poisson-Fokker-Planck (VPFP) system in a bounded domain with reflection boundary conditions for charge distributions and prove that the global renormalized solutions of the VPFP system converge to the global weak solutions of the PNP system, as the small parameter related to the scaled thermal velocity and mean free path tends to zero. Our results may justify the PNP system as a macroscopic model for the transport of multi-species ions in dilute solutions.

  11. A method of limit point calculation in finite element structural analysis

    NASA Technical Reports Server (NTRS)

    Gallagher, R. H.; Mau, S. T.

    1972-01-01

    An approach is presented for the calculation of limit points for structures described by discrete coordinates, and whose governing equations derive from finite element concepts. The nonlinear load-displacement path of the imperfect structure is first traced by use of a direct iteration scheme and the determinant of the governing algebraic equations is calculated at each solution point. The limit point is then established by extrapolation and imposition of the condition of zero slope of the plot of load vs. determinant. Three problems are solved in illustration of the approach and in comparison with alternative procedures and test data.

  12. Exact many-body wave function and properties of trapped bosons in the infinite-particle limit

    NASA Astrophysics Data System (ADS)

    Cederbaum, Lorenz S.

    2017-07-01

    The emphasis of this work is on the computation of physical properties as well as of the wave function of interacting bosons in a trap potential. Many-body perturbation theory is employed to study the leading term of these quantities for finite numbers of bosons, and exact solutions are aimed at in the infinite-particle limit. As discussed before, a suitable starting point is the second-quantized Hamiltonian represented in the basis of destruction and creation operators of its own mean-field potential. This choice leads to expressions for the perturbation terms of all quantities which exhibit a very weak dependence on the particle number. Importantly, when applying ideas similar to Bogoliubov's, the Hamiltonian can be reduced in the infinite-particle limit to a much simplified form which is a priori particle-number conserving. The resulting phonon Hamiltonian is diagonalizable by a linear transformation for which an explicit eigenvalue equation is given. Physical properties can be expressed explicitly by elements of this transformation, and of particular relevance is that the particle-number-conserving wave functions of the original many-boson system can be reconstructed using recursion relations. The reconstruction of the particle-conserving wave function from the phonon Hamiltonian can also be used to assess when the infinite-particle limit is reached in practice for finite trapped condensates. Two applications are discussed in detail. For one of them, an exact solution is known which is found, in the infinite-particle limit, to exactly coincide with that of the phonon Hamiltonian. In both examples expressions for the properties are given in closed form. The physics behind the phonon Hamiltonian and its physical properties is discussed.

  13. Another limitation of DFC when stabilizing unstable fixed points of continuous chaotic systems

    NASA Astrophysics Data System (ADS)

    Chen, Mao-Yin; Han, Zheng-Zhi; Shang, Yun

    2003-05-01

    Using stability theory of delayed differential equation (DDE), we show that there exists another limitation of delayed feedback control (DFC) with arbitrary delayed time when stabilizing unstable fixed points (UFPs) of continuous chaotic systems. This limitation is called by zero real part limitation, that is, if Jacobian matrix at a UFP has a characteristic exponent with zero real part, the UFP cannot be stabilized by linear DFC with arbitrary delayed time.

  14. Combinatorics of 1-particle irreducible n-point functions via coalgebra in quantum field theory

    SciTech Connect

    Mestre, Angela

    2010-08-15

    We give a coalgebra structure on 1-vertex irreducible graphs which is that of a cocommutative coassociative graded connected coalgebra. We generalize the coproduct to the algebraic representation of graphs so as to express a bare 1-particle irreducible n-point function in terms of its loop order contributions. The algebraic representation is so that graphs can be evaluated as Feynman graphs.

  15. Limiting technologies for particle beams and high energy physics

    SciTech Connect

    Panofsky, W.K.H.

    1985-07-01

    Since 1930 the energy of accelerators had grown by an order of magnitude roughly every 7 years. Like all exponential growths, be they human population, the size of computers, or anything else, this eventually will have to come to an end. When will this happen to the growth of the energy of particle accelerators and colliders. Fortunately, as the energy of accelerators has grown the cost per unit energy has decreased almost as fast as has the increase in energy. The result is that while the energy has increased so dramatically the cost per new installation has increased only by roughly an order of magnitude since the 1930's (corrected for inflation), while the number of accelerators operating at the frontier of the field has shrunk. As is shown in the by now familiar Livingston chart this dramatic decrease in cost has been achieved largely by a succession of new technologies, in addition to the more moderate gains in efficiency due to improved design, economies of scale, etc. We are therefore facing two questions: (1) Is there good reason scientifically to maintain the exponential growth, and (2) Are there new technologies in sight which promise continued decreases in unit costs. The answer to the first question is definitely yes; the answer to the second question is maybe.

  16. Elastic collisions of classical point particles on a finite frictionless linear track with perfectly reflecting endpoints

    NASA Astrophysics Data System (ADS)

    DeLuca, R.

    2006-03-01

    Repeated elastic collisions of point particles on a finite frictionless linear track with perfectly reflecting endpoints are considered. The problem is analysed by means of an elementary linear algebra approach. It is found that, starting with a state consisting of a projectile particle in motion at constant velocity and a target particle at rest in a fixed known position, the points at which collisions occur on track, when plotted versus progressive numerals, corresponding to the collisions themselves, show periodic patterns for a rather large choice of values of the initial position x(0) and on the mass ratio r. For certain values of these parameters, however, only regular behaviour over a large number of collisions is detected.

  17. 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

  18. 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.

  19. Exact regularized point particle method for multiphase flows in the two-way coupling regime

    NASA Astrophysics Data System (ADS)

    Gualtieri, P.; Picano, F.; Sardina, G.; Casciola, C. M.

    2015-06-01

    Particulate flows have been largely studied under the simplifying assumptions of one-way coupling regime where the disperse phase do not react-back on the carrier fluid. In the context of turbulent flows, many non trivial phenomena such as small scales particles clustering or preferential spatial accumulation have been explained and understood. A more complete view of multiphase flows can be gained calling into play two-way coupling effects, i.e. by accounting for the inter-phase momentum exchange between the carrier and the suspended phase, certainly relevant at increasing mass loading. In such regime, partially investigated in the past by the so-called Particle In Cell (PIC) method, much is still to be learned about the dynamics of the disperse phase and the ensuing alteration of the carrier flow. In this paper we present a new methodology rigorously designed to capture the inter-phase momentum exchange for particles smaller than the smallest hydrodynamical scale, e.g. the Kolmogorov scale in a turbulent flow. In fact, the momentum coupling mechanism exploits the unsteady Stokes flow around a small rigid sphere where the transient disturbance produced by each particle is evaluated in a closed form. The particles are described as lumped, point masses which would lead to the appearance of singularities. A rigorous regularization procedure is conceived to extract the physically relevant interactions between particles and fluid which avoids any "ah hoc" assumption. The approach is suited for high efficiency implementation on massively parallel machines since the transient disturbance produced by the particles is strongly localized in space around the actual particle position. As will be shown, hundred thousands particles can therefore be handled at an affordable computational cost as demonstrated by a preliminary application to a particle laden turbulent shear flow.

  20. Removal of virus to protozoan sized particles in point-of-use ceramic water filters.

    PubMed

    Bielefeldt, Angela R; Kowalski, Kate; Schilling, Cherylynn; Schreier, Simon; Kohler, Amanda; Scott Summers, R

    2010-03-01

    The particle removal performance of point-of-use ceramic water filters (CWFs) was characterized in the size range of 0.02-100 microm using carboxylate-coated polystyrene fluorescent microspheres, natural particles and clay. Particles were spiked into dechlorinated tap water, and three successive water batches treated in each of six different CWFs. Particle removal generally increased with increasing size. The removal of virus-sized 0.02 and 0.1 microm spheres were highly variable between the six filters, ranging from 63 to 99.6%. For the 0.5 microm spheres removal was less variable and in the range of 95.1-99.6%, while for the 1, 2, 4.5, and 10 microm spheres removal was >99.6%. Recoating four of the CWFs with colloidal silver solution improved removal of the 0.02 microm spheres, but had no significant effects on the other particle sizes. Log removals of 1.8-3.2 were found for natural turbidity and spiked kaolin clay particles; however, particles as large as 95 microm were detected in filtered water.

  1. 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.

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

    PubMed

    Pecini, Eliana M; Avena, Marcelo J

    2013-12-03

    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

  3. Hand-grip strength cut points to screen older persons at risk for mobility limitation.

    PubMed

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

    2010-09-01

    To determine optimal hand-grip strength cut points for likelihood of mobility limitation in older people and to study whether these cut points differ according to body mass index (BMI). Cross-sectional analysis of data. Data collected in the Finnish population-based Health 2000 Survey. One thousand eighty-four men and 1,562 women aged 55 and older with complete data on anthropometry, hand-grip strength and self-reported mobility. Mobility limitation was defined as difficulty walking 0.5 km or climbing stairs. Receiver operating characteristic analysis was used to estimate hand-grip strength cut points for likelihood of mobility limitation. The overall hand-grip strength cut points for likelihood of mobility limitation were 37 kg (sensitivity 62%; specificity 76%) for men and 21 kg (sensitivity 67%; specificity 73%) for women. The effect of the interaction between hand-grip strength and BMI on mobility limitation was significant in men (P=.02), but no such interaction was observed in women (P=.16). In men, the most-optimal cutoff points were 33 kg (sensitivity 73%; specificity 79%) for normal-weight men, 39 kg (sensitivity 67%; specificity 71%) for overweight men, and 40 kg (sensitivity 57%; specificity 68%) for obese men. In women, BMI-specific hand-grip strength cutoff values was not markedly more accurate than the overall cutoff value. The hand-grip strength test is a useful tool to identify persons at risk of mobility limitation. In men, hand-grip strength cut points for mobility increased with BMI, whereas in women, only one hand-grip strength threshold was identified. © 2010, Copyright the Authors. Journal compilation © 2010, The American Geriatrics Society.

  4. Spectroscopic imaging of limiter heat and particle fluxes and the resulting impurity sources during Wendelstein 7-X startup plasmas

    SciTech Connect

    Stephey, L. Schmitz, O.; Frerichs, H.; Effenberg, F.; Wurden, G. A.; Biedermann, C.; König, R.; Kornejew, P.; Krychowiak, M.; Harris, J.; Unterberg, E. A.

    2016-11-15

    A combined IR and visible camera system [G. A. Wurden et al., “A high resolution IR/visible imaging system for the W7-X limiter,” Rev. Sci. Instrum. (these proceedings)] and a filterscope system [R. J. Colchin et al., Rev. Sci. Instrum. 74, 2068 (2003)] were implemented together to obtain spectroscopic data of limiter and first wall recycling and impurity sources during Wendelstein 7-X startup plasmas. Both systems together provided excellent temporal and spatial spectroscopic resolution of limiter 3. Narrowband interference filters in front of the camera yielded C-III and H{sub α} photon flux, and the filterscope system provided H{sub α}, H{sub β}, He-I, He-II, C-II, and visible bremsstrahlung data. The filterscopes made additional measurements of several points on the W7-X vacuum vessel to yield wall recycling fluxes. The resulting photon flux from both the visible camera and filterscopes can then be compared to an EMC3-EIRENE synthetic diagnostic [H. Frerichs et al., “Synthetic plasma edge diagnostics for EMC3-EIRENE, highlighted for Wendelstein 7-X,” Rev. Sci. Instrum. (these proceedings)] to infer both a limiter particle flux and wall particle flux, both of which will ultimately be used to infer the complete particle balance and particle confinement time τ{sub P}.

  5. 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.

  6. A second-order differential equation for a point charged particle

    NASA Astrophysics Data System (ADS)

    Torromé, Ricardo Gallego

    A model for the dynamics of a classical point charged particle interacting with higher order jet fields is introduced. In this model, the dynamics of the charged particle is described by an implicit ordinary second-order differential equation. Such equation is free of run-away and pre-accelerated solutions of Dirac’s type. The theory is Lorentz invariant, compatible with the first law of Newton and Larmor’s power radiation formula. Few implications of the new equation in the phenomenology of non-neutral plasmas is considered.

  7. Analytical calculation of four-point correlations for a simple model of cages involving numerous particles

    NASA Astrophysics Data System (ADS)

    Takeshi, Ooshida; Goto, Susumu; Matsumoto, Takeshi; Nakahara, Akio; Otsuki, Michio

    2013-12-01

    Dynamics of a one-dimensional system of Brownian particles with short-range repulsive interaction (diameter σ) is studied with a liquid-theoretical approach. The mean square displacement, the two-particle displacement correlation, and the overlap-density-based generalized susceptibility are calculated analytically by way of the Lagrangian correlation of the interparticulate space, instead of the Eulerian correlation of density that is commonly used in the standard mode-coupling theory. In regard to the mean square displacement, the linear analysis reproduces the established result on the asymptotic subdiffusive behavior of the system. A finite-time correction is given by incorporating the effect of entropic nonlinearity with a Lagrangian version of mode-coupling theory. The notorious difficulty in derivation of the mode-coupling theory concerning violation of the fluctuation-dissipation theorem is found to disappear by virtue of the Lagrangian description. The Lagrangian description also facilitates analytical calculation of four-point correlations in the space-time, such as the two-particle displacement correlation. The two-particle displacement correlation, which is asymptotically self-similar in the space-time, illustrates how the cage effect confines each particle within a short radius on one hand and creates collective motion of numerous particles on the other hand. As the time elapses, the correlation length grows unlimitedly, and the generalized susceptibility based on the overlap density converges to a finite value which is an increasing function of the density. The distribution function behind these dynamical four-point correlations and its extension to three-dimensional cases, respecting the tensorial character of the two-particle displacement correlation, are also discussed.

  8. Analytical calculation of four-point correlations for a simple model of cages involving numerous particles.

    PubMed

    Takeshi, Ooshida; Goto, Susumu; Matsumoto, Takeshi; Nakahara, Akio; Otsuki, Michio

    2013-12-01

    Dynamics of a one-dimensional system of Brownian particles with short-range repulsive interaction (diameter σ) is studied with a liquid-theoretical approach. The mean square displacement, the two-particle displacement correlation, and the overlap-density-based generalized susceptibility are calculated analytically by way of the Lagrangian correlation of the interparticulate space, instead of the Eulerian correlation of density that is commonly used in the standard mode-coupling theory. In regard to the mean square displacement, the linear analysis reproduces the established result on the asymptotic subdiffusive behavior of the system. A finite-time correction is given by incorporating the effect of entropic nonlinearity with a Lagrangian version of mode-coupling theory. The notorious difficulty in derivation of the mode-coupling theory concerning violation of the fluctuation-dissipation theorem is found to disappear by virtue of the Lagrangian description. The Lagrangian description also facilitates analytical calculation of four-point correlations in the space-time, such as the two-particle displacement correlation. The two-particle displacement correlation, which is asymptotically self-similar in the space-time, illustrates how the cage effect confines each particle within a short radius on one hand and creates collective motion of numerous particles on the other hand. As the time elapses, the correlation length grows unlimitedly, and the generalized susceptibility based on the overlap density converges to a finite value which is an increasing function of the density. The distribution function behind these dynamical four-point correlations and its extension to three-dimensional cases, respecting the tensorial character of the two-particle displacement correlation, are also discussed.

  9. 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.

  10. Pairwise Interaction Extended Point Particle (PIEP) Model for a Random Array of Spheres

    NASA Astrophysics Data System (ADS)

    Akiki, Georges; Jackson, Thomas; Balachandar, Sivaramakrishnan; CenterCompressible Multiphase Turbulence Team

    2016-11-01

    This study investigates a flow past random array of spherical particles. The understanding of the governing forces within these arrays is crucial for obtaining accurate models used in particle-laden simulations. These models have to faithfully reflect the sub-grid interactions between the particles and the continuous phase. The models being used today assumes an average force on all particles within the array based on the mean volume fraction and Reynolds number. Here, we develop a model which can compute the drag and lateral forces on each particle by accounting for the precise location of few surrounding neighbors. A pairwise interaction is assumed where the perturbation flow induced by each neighbor is considered separately, then the effect of all neighbors are linearly superposed to obtain the total perturbation. Faxén correction is used to quantify the force perturbation due to the presence of the neighbors. The single neighbor perturbations are mapped in the vicinity of a reference sphere and stored as libraries. We test the Pairwise Interaction Extended Point-Particle (PIEP) model for random arrays at two different volume fractions of ϕ = 0 . 1 and 0.21 and Reynolds number in the range 16 <= Re <= 170 . The PIEP model predictions are compared against drag and lift forces obtained from fully-resolved DNS performed using immersed boundary method. We observe the PIEP model prediction to correlate much better with the DNS results than the classical mean drag model prediction.

  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.

  12. Transition from the mechanics of material points to the mechanics of structured particles

    NASA Astrophysics Data System (ADS)

    Somsikov, V. M.

    2016-01-01

    In this paper, necessity of creation of mechanics of structured particles is discussed. The way to create this mechanics within the laws of classical mechanics with the use of energy equation is shown. The occurrence of breaking of time symmetry within the mechanics of structured particles is shown, as well as the introduction of concept of entropy in the framework of classical mechanics. The way to create the mechanics of non-equilibrium systems in the thermodynamic approach is shown. It is also shown that the use of hypothesis of holonomic constraints while deriving the canonical Lagrange equation made it impossible to describe irreversible dynamics. The difference between the mechanics of structured particles and the mechanics of material points is discussed. It is also shown that the matter is infinitely divisible according to the laws of classical mechanics.

  13. The optimum cut-off radius in Monte Carlo simulation of Yukawa potential point particles

    NASA Astrophysics Data System (ADS)

    Suwan, I.; Hussein, H.; Hussein, A.; Daragmeh, M.

    2017-06-01

    In this paper, infinite systems of point particles with Yukawa potential and periodic boundary conditions are simulated using Monte Carlo technique in three dimensions. Because of the short range nature of the Yukawa potential, cut-off radius rcut is considered in calculations (i.e, for each particle i, the effect of the other particles on it inside a sphere of radius rcut is taken into account). The cut-off radius used in Monte Carlo simulation affects the physical behavior of the system being simulated. A sequence of rcut values are used. When the change in the total potential energy becomes negligible, the optimum value of the cut-off radius is determined. This value is found to be independent of density and temperature in the NVT-ensemble case.

  14. 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.

  15. Robust upper limit of the neutron i13/2 single-particle energy

    NASA Astrophysics Data System (ADS)

    Lei, Y.; Jiang, H.

    2014-10-01

    The upper limit of the neutron i13/2 single-particle energy (ɛi13/2) is estimated in the random quasiparticle ensemble with single-particle energies. The ɛi13/2 distributions under constraints from Te134,135 and Xe136,137 spectra demonstrate that the i13/2 single-particle state can be physically mixed with the f7/2⊗3- configuration only if ɛi13/2<3 MeV. Thus, our ensemble calculation suggests a robust upper limit of 3 MeV.

  16. 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

    ...EPA is proposing a regulation that would strengthen the controls on discharges from certain steam electric power plants by revising technology-based effluent limitations guidelines and standards for the steam electric power generating point source category. Steam electric power plants alone contribute 50-60 percent of all toxic pollutants discharged to surface waters by all industrial......

  17. IONEX: A meshfree ion extraction code based on ''particle in cloud of points'' concept

    SciTech Connect

    Galkin, S. A.; Grubert, J. E.; Cluggish, B. P.; Barov, N.; Kim, J. S.

    2010-02-15

    Ion Extraction (IONEX) is an ion extraction modeling code, developed at FAR-TECH, Inc., based on the meshless particle-in-cloud-of-points concept. IONEX self-consistently solves motion equations for ions and Poisson's equation for the electrostatic field, assuming a Boltzmann distribution for the electrons. IONEX is capable of handling multiple species and is graphical user interface-driven. The two-dimensional version is benchmarked with IGUN. The basic algorithm and sample runs are presented.

  18. IONEX: a meshfree ion extraction code based on "particle in cloud of points" concept.

    PubMed

    Galkin, S A; Grubert, J E; Cluggish, B P; Barov, N; Kim, J S

    2010-02-01

    Ion Extraction (IONEX) is an ion extraction modeling code, developed at FAR-TECH, Inc., based on the meshless particle-in-cloud-of-points concept. IONEX self-consistently solves motion equations for ions and Poisson's equation for the electrostatic field, assuming a Boltzmann distribution for the electrons. IONEX is capable of handling multiple species and is graphical user interface-driven. The two-dimensional version is benchmarked with IGUN. The basic algorithm and sample runs are presented.

  19. 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.

  20. Kinetic Modeling of Particle Acceleration in a Solar Null-point Reconnection Region

    NASA Astrophysics Data System (ADS)

    Baumann, G.; Haugbølle, T.; Nordlund, Å.

    2013-07-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    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/h1/h for weak interactions to plateau-like features at nonuniversal values as high as 4/h4/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.

  2. 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

  3. Diffusion-limited attachment of large spherical particles to flexible membrane-immobilized receptors.

    PubMed

    Zhdanov, Vladimir P; Höök, Fredrik

    2015-05-01

    Relatively large (~100 nm) spherical particles, e.g., virions, vesicles, or metal nanoparticles, often interact with short (<10 nm) flexible receptors immobilized in a lipid membrane or on other biologically relevant surfaces. The attachment kinetics of such particles may be limited globally by their diffusion toward a membrane or locally by diffusion around receptors. The detachment kinetics, also, can be limited by diffusion. Focusing on local diffusion limitations and using suitable approximations, we present expressions for the corresponding rate constants and identify their dependence on particle size and receptor length. We also illustrate features likely to be observed in such kinetics for particles (e.g., vesicles) with a substantial size distribution. The results obtained are generic and can be used to interpret a variety of situations. For example, we estimate upper values of virion attachment rate constants and clarify the likely effect of vesicle size distribution on previously observed non-exponential kinetics of vesicle detachment.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    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.

  5. Single-point scratching of 6061 Al alloy reinforced by different ceramic particles

    NASA Astrophysics Data System (ADS)

    Yan, Cheng; Zhang, Liangchi

    1994-11-01

    Aluminium alloys reinforced by ceramic particles have been widely used in aerospace and automotive industries for their high stiffness and wear resistance. However, the machining of such materials is difficult and would usually cause excessive tool wear. The effect of ceramic particles on the cutting mechanisms is also unclear. The purpose of this study is to investigate the cutting mechanisms and the relationship between specific energy of scratching and depth of cut (size effect). The single-point scratch test was carried out on 6061 Al and its composites reinforced by Al2O3 and SiC ceramic particles using a pyramid indenter. The results indicated that the scratch process was composed of rubbing, ploughing, plastic cutting and reinforcement fracture. A simple model was proposed to interpret the apparent size effect. The effect of reinforcement on the specific energy was correlated to the ratio of volume fraction to particle radius. The paper found that for machining MMCs, a larger depth of cut should be used to maintain a lower machining energy, especially for those with a larger ratio of volume fraction to particle radius.

  6. A strategy to couple the material point method (MPM) and smoothed particle hydrodynamics (SPH) computational techniques

    NASA Astrophysics Data System (ADS)

    Raymond, Samuel J.; Jones, Bruce; Williams, John R.

    2016-12-01

    A strategy is introduced to allow coupling of the material point method (MPM) and smoothed particle hydrodynamics (SPH) for numerical simulations. This new strategy partitions the domain into SPH and MPM regions, particles carry all state variables and as such no special treatment is required for the transition between regions. The aim of this work is to derive and validate the coupling methodology between MPM and SPH. Such coupling allows for general boundary conditions to be used in an SPH simulation without further augmentation. Additionally, as SPH is a purely particle method, and MPM is a combination of particles and a mesh. This coupling also permits a smooth transition from particle methods to mesh methods, where further coupling to mesh methods could in future provide an effective farfield boundary treatment for the SPH method. The coupling technique is introduced and described alongside a number of simulations in 1D and 2D to validate and contextualize the potential of using these two methods in a single simulation. The strategy shown here is capable of fully coupling the two methods without any complicated algorithms to transform information from one method to another.

  7. Size limits for rounding of volcanic ash particles heated by lightning

    PubMed Central

    Vasseur, Jérémie; Llewellin, Edward W.; Genareau, Kimberly; Cimarelli, Corrado; Dingwell, Donald B.

    2017-01-01

    Abstract Volcanic ash particles can be remelted by the high temperatures induced in volcanic lightning discharges. The molten particles can round under surface tension then quench to produce glass spheres. Melting and rounding timescales for volcanic materials are strongly dependent on heating duration and peak temperature and are shorter for small particles than for large particles. Therefore, the size distribution of glass spheres recovered from ash deposits potentially record the short duration, high‐temperature conditions of volcanic lightning discharges, which are hard to measure directly. We use a 1‐D numerical solution to the heat equation to determine the timescales of heating and cooling of volcanic particles during and after rapid heating and compare these with the capillary timescale for rounding an angular particle. We define dimensionless parameters—capillary, Fourier, Stark, Biot, and Peclet numbers—to characterize the competition between heat transfer within the particle, heat transfer at the particle rim, and capillary motion, for particles of different sizes. We apply this framework to the lightning case and constrain a maximum size for ash particles susceptible to surface tension‐driven rounding, as a function of lightning temperature and duration, and ash properties. The size limit agrees well with maximum sizes of glass spheres found in volcanic ash that has been subjected to lightning or experimental discharges, demonstrating that the approach that we develop can be used to obtain a first‐order estimate of lightning conditions in volcanic plumes. PMID:28781929

  8. Size limits for rounding of volcanic ash particles heated by lightning.

    PubMed

    Wadsworth, Fabian B; Vasseur, Jérémie; Llewellin, Edward W; Genareau, Kimberly; Cimarelli, Corrado; Dingwell, Donald B

    2017-03-01

    Volcanic ash particles can be remelted by the high temperatures induced in volcanic lightning discharges. The molten particles can round under surface tension then quench to produce glass spheres. Melting and rounding timescales for volcanic materials are strongly dependent on heating duration and peak temperature and are shorter for small particles than for large particles. Therefore, the size distribution of glass spheres recovered from ash deposits potentially record the short duration, high-temperature conditions of volcanic lightning discharges, which are hard to measure directly. We use a 1-D numerical solution to the heat equation to determine the timescales of heating and cooling of volcanic particles during and after rapid heating and compare these with the capillary timescale for rounding an angular particle. We define dimensionless parameters-capillary, Fourier, Stark, Biot, and Peclet numbers-to characterize the competition between heat transfer within the particle, heat transfer at the particle rim, and capillary motion, for particles of different sizes. We apply this framework to the lightning case and constrain a maximum size for ash particles susceptible to surface tension-driven rounding, as a function of lightning temperature and duration, and ash properties. The size limit agrees well with maximum sizes of glass spheres found in volcanic ash that has been subjected to lightning or experimental discharges, demonstrating that the approach that we develop can be used to obtain a first-order estimate of lightning conditions in volcanic plumes.

  9. 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.

  10. Trapping Phenomenon Attenuates the Consequences of Tipping Points for Limit Cycles

    PubMed Central

    Medeiros, Everton S.; Caldas, Iberê L.; Baptista, Murilo S.; Feudel, Ulrike

    2017-01-01

    Nonlinear dynamical systems may be exposed to tipping points, critical thresholds at which small changes in the external inputs or in the system’s parameters abruptly shift the system to an alternative state with a contrasting dynamical behavior. While tipping in a fold bifurcation of an equilibrium is well understood, much less is known about tipping of oscillations (limit cycles) though this dynamics are the typical response of many natural systems to a periodic external forcing, like e.g. seasonal forcing in ecology and climate sciences. We provide a detailed analysis of tipping phenomena in periodically forced systems and show that, when limit cycles are considered, a transient structure, so-called channel, plays a fundamental role in the transition. Specifically, we demonstrate that trajectories crossing such channel conserve, for a characteristic time, the twisting behavior of the stable limit cycle destroyed in the fold bifurcation of cycles. As a consequence, this channel acts like a “ghost” of the limit cycle destroyed in the critical transition and instead of the expected abrupt transition we find a smooth one. This smoothness is also the reason that it is difficult to precisely determine the transition point employing the usual indicators of tipping points, like critical slowing down and flickering. PMID:28181582

  11. Trapping Phenomenon Attenuates the Consequences of Tipping Points for Limit Cycles

    NASA Astrophysics Data System (ADS)

    Medeiros, Everton S.; Caldas, Iberê L.; Baptista, Murilo S.; Feudel, Ulrike

    2017-02-01

    Nonlinear dynamical systems may be exposed to tipping points, critical thresholds at which small changes in the external inputs or in the system’s parameters abruptly shift the system to an alternative state with a contrasting dynamical behavior. While tipping in a fold bifurcation of an equilibrium is well understood, much less is known about tipping of oscillations (limit cycles) though this dynamics are the typical response of many natural systems to a periodic external forcing, like e.g. seasonal forcing in ecology and climate sciences. We provide a detailed analysis of tipping phenomena in periodically forced systems and show that, when limit cycles are considered, a transient structure, so-called channel, plays a fundamental role in the transition. Specifically, we demonstrate that trajectories crossing such channel conserve, for a characteristic time, the twisting behavior of the stable limit cycle destroyed in the fold bifurcation of cycles. As a consequence, this channel acts like a “ghost” of the limit cycle destroyed in the critical transition and instead of the expected abrupt transition we find a smooth one. This smoothness is also the reason that it is difficult to precisely determine the transition point employing the usual indicators of tipping points, like critical slowing down and flickering.

  12. Magnetic Reconnection during Collisionless, Stressed, X-point Collapse using Particle-in-cell Simulation

    NASA Astrophysics Data System (ADS)

    Tsiklauri, D.; Haruki, T.

    2008-09-01

    Dungey's (1953) work on X-point collapse is the earliest analysis done on magnetic reconnection and predates the tearing mode, Sweet-Parker and Petcheck reconnection models. X-point collapse soon fell out of favour because in the collisional (MHD) regime, for the plausible space plasma parameters, it was found to be inefficient. We however show [Tsiklauri D. and T. Haruki, Phys. of Plasmas, 14, 112905, (2007)] that in the collisionless regime, which is indeed more applicable to space plasmas, the reconnection is efficient. We study magnetic reconnection during collisionless, stressed, X-point collapse using kinetic, 2.5D, fully electromagnetic, relativistic Particle-in-Cell numerical code. Two cases of weakly and strongly stressed X-point collapse were considered. Here descriptors weakly and strongly refer to 20% and 124% unidirectional spatial compression of the X-point, respectively. We found that within about one Alfven time, 2% and 20% of the initial magnetic energy is converted into heat and accelerated particle energy in the case of weak and strong stress, respectively. In the both cases, during the peak of the reconnection, the quadruple out-of-plane magnetic field is generated. These results strongly suggest the importance of the collisionless, stressed X-point collapse as an efficient mechanism of converting magnetic energy into heat and super-thermal particle energy. In the weakly stressed case, the reconnection rate, defined as the out-of-plane electric field in the X-point normalized by the product of external magnetic field and Alfven speeds, peaks at 0.11, with its average over 1.25 Alfven times being 0.04. Electron energy distribution in the current sheet, at the high-energy end of the spectrum, shows a power-law distribution with the index varying in time, attaining a maximal value of -4.1 at the final simulation time step (1.25 Alfven times). In the strongly stressed case, magnetic reconnection peak occurs 3.4 times faster and is more efficient

  13. 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

  14. Shear-Limited Diffusion of Test Particles in Pure Ion Plasmas.

    NASA Astrophysics Data System (ADS)

    Anderegg, F.; Driscoll, C. F.; Dubin, D. H. E.

    2001-10-01

    Measurements of test-particle diffusion in pure ion plasmas show 2D enhancements over the 3D rates, limited by shear in the plasma rotation ωE (r). The diffusion is due to ``long-range'' ion-ion collisions in the quiescent, steady-state Mg^+ plasma. For short plasma length Lp and low shear ω_E^' ≡ partial ωE / partial r, thermal ions bounce axially many times before shear separates them in θ, so the ions may move in (r, θ ) as bounce averaged ``rods'' of charge (i.e. 2D point vortices). Experimentally, we vary the number of bounces over the range 0.2 <= Nb ≡ ( barv / 2 Lp ) / r ω_E^' <= 10,000. For long plasmas with Nb <= 1, we observe diffusion in quantitative agreement with the 3D theory of long-range E × B drift collisions.(F. Anderegg et al.), Phys. Rev. Lett. 78, 2128 (1997). For shorter plasmas or lower shear, with Nb > 1, we measure diffusion rates enhanced by approximately N_b. For exceedingly small shear, i.e. Nb >= 1000, we observe diffusion rates consistent with the Taylor-McNamara estimates for a shear-free plasma. Overall, the data shows fair agreement with Dubin's new theory of 2D diffusion in shear.(D.H.E. Dubin and D.Z. Jin, Phys. Lett. A 284), 112-117 (2001).

  15. Effect of particle size on colloidal zirconia rheology at the isoelectric point

    SciTech Connect

    Leong, Y.K.; Scales, P.J.; Healy, T.W.; Boger, D.V.

    1995-08-01

    This paper examines the effects of particle concentration and size on the yield stress of ZrO{sub 2} suspensions at a well-defined surface chemistry condition of the isoelectric point (IEP). At the IEP, the relationship between yield stress {tau}{sub y{sub max}} and particulate volume fraction {phi}{sub s}, and mean particle size d was evaluated to be {tau}{sub y{sub max}} = K {phi}{sub s}{sup 4.0}/d{sup 2.0}. The difference in size distribution of the various ZrO{sub 2} suspensions examined causes some degree of scatter in the data used to establish the {tau}{sub y{sub max}}, {phi}{sub s}, and d relation. The use of particle concentration n{sub t} based on the fine size fraction instead of volume fraction {phi}{sub s} provided a better correlation, because the fine particles govern the properties of the flocculated network structure.

  16. Determination of the levitation limits of dust particles within the sheath in complex plasma experiments

    SciTech Connect

    Douglass, Angela; Land, Victor; Qiao Ke; Matthews, Lorin; Hyde, Truell

    2012-01-15

    Experiments are performed in which dust particles are levitated at varying heights above the powered electrode in a radio frequency plasma discharge by changing the discharge power. The trajectories of particles dropped from the top of the discharge chamber are used to reconstruct the vertical electric force acting on the particles. The resulting data, together with the results from a self-consistent fluid model, are used to determine the lower levitation limit for dust particles in the discharge and the approximate height above the lower electrode where quasineutrality is attained, locating the sheath edge. These results are then compared with current sheath models. It is also shown that particles levitated within a few electron Debye lengths of the sheath edge are located outside the linearly increasing portion of the electric field.

  17. 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.

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

    NASA Technical Reports Server (NTRS)

    Griest, Kim; Kamionkowski, Marc

    1990-01-01

    Using partial wave unitarity and the observed density of the Universe, it is shown 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 equlibrium 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.

  19. 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.

  20. Point-ahead limitation on reciprocity tracking. [in earth-space optical link

    NASA Technical Reports Server (NTRS)

    Shapiro, J. H.

    1975-01-01

    The average power received at a spacecraft from a reciprocity-tracking transmitter is shown to be the free-space diffraction-limited result times a gain-reduction factor that is due to the point-ahead requirement. For a constant-power transmitter, the gain-reduction factor is approximately equal to the appropriate spherical-wave mutual-coherence function. For a constant-average-power transmitter, an exact expression is obtained for the gain-reduction factor.

  1. A numerical analysis on forming limits during spiral and concentric single point incremental forming

    NASA Astrophysics Data System (ADS)

    Gipiela, M. L.; Amauri, V.; Nikhare, C.; Marcondes, P. V. P.

    2017-01-01

    Sheet metal forming is one of the major manufacturing industries, which are building numerous parts for aerospace, automotive and medical industry. Due to the high demand in vehicle industry and environmental regulations on less fuel consumption on other hand, researchers are innovating new methods to build these parts with energy efficient sheet metal forming process instead of conventionally used punch and die to form the parts to achieve the lightweight parts. One of the most recognized manufacturing process in this category is Single Point Incremental Forming (SPIF). SPIF is the die-less sheet metal forming process in which the single point tool incrementally forces any single point of sheet metal at any process time to plastic deformation zone. In the present work, finite element method (FEM) is applied to analyze the forming limits of high strength low alloy steel formed by single point incremental forming (SPIF) by spiral and concentric tool path. SPIF numerical simulations were model with 24 and 29 mm cup depth, and the results were compare with Nakajima results obtained by experiments and FEM. It was found that the cup formed with Nakajima tool failed at 24 mm while cups formed by SPIF surpassed the limit for both depths with both profiles. It was also notice that the strain achieved in concentric profile are lower than that in spiral profile.

  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. Sheet-like assemblies of spherical particles with point-symmetrical patches.

    PubMed

    Mani, Ethayaraja; Sanz, Eduardo; Roy, Soumyajit; Dijkstra, Marjolein; Groenewold, Jan; Kegel, Willem K

    2012-04-14

    We report a computational study on the spontaneous self-assembly of spherical particles into two-dimensional crystals. The experimental observation of such structures stabilized by spherical objects appeared paradoxical so far. We implement patchy interactions with the patches point-symmetrically (icosahedral and cubic) arranged on the surface of the particle. In these conditions, preference for self-assembly into sheet-like structures is observed. We explain our findings in terms of the inherent symmetry of the patches and the competition between binding energy and vibrational entropy. The simulation results explain why hollow spherical shells observed in some Keplerate-type polyoxometalates (POM) appear. Our results also provide an explanation for the experimentally observed layer-by-layer growth of apoferritin--a quasi-spherical protein.

  4. 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.

  5. Stochastic electrodynamics with particle structure part II - towards a zero-point induced wave behavior

    NASA Astrophysics Data System (ADS)

    Rueda, A.

    1993-04-01

    A previously derived Brownian behavior (paper I) induced by the zero-point field is assumed to hold for a more realistic model. The statistical description of the particle in our model leads naturally to a probabilistic fluid-like description suitable for providing simple intuitive explanations for some well-publicized puzzles of classical stochastic theories like the nodes of the wave-function and the intrinsic spinning (so far nonquantized) of the particles. We confront our result with well-known recent analysis on fractal-like Brownian quantum paths and diffusion in quantum trajectories. It is shown that stochastic electrodynamics may lead to the diffusive fractal-like paths of the Schroedinger theory. A heuristic connection from this Brownian result to Schroedinger's phenomenology is also provided by the Lagrangian density of the probabilistic fluid.

  6. 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.

  7. Power and particle balance studies using an instrumented limiter system on ATF

    SciTech Connect

    Uckan, T.; Mioduszewski, P.K.; Bigelow, T.S.; Glowienka, J.C.; Hiroe, S.; Murakami, M.; Wilgen, J.B.; Wing, W.R.

    1991-06-01

    Power and particle balance studies on the Advanced Toroidal Facility (ATF) torsatron are carried out using a rail limiter system. Both top and bottom limiters are made of graphite tile arrays, and these tiles are instrumented with thermocouples and Langmuir probes for calorimetric and particle flux measurements. Initial experimental results indicate that the limiter power loss accounts for about 12% of the total and the radiation loss for about 30% of the total; the rest of the plasma heating power appears to be going to the vessel wall. The particle flux to the limiters is also about 18%. The fractions of power and particle flux to the limiters are relatively lower than in tokamaks because of the low edge safety factor, q {approximately}1 rather than q {approximately}3 as in a typical tokamak, at the natural boundary of the ATF plasma (which results from the magnetic stellarator configuration of this currentless device). Therefore, for limiters of the same size, these fractions are about a factor of q lower in ATF than in a comparable tokamak device. 11 refs., 8 figs.

  8. Determination of isoelectric points of metals and metallic alloys by adhesion of latex particles.

    PubMed

    Lefèvre, Grégory; Cerović, Ljiljana; Milonjić, Slobodan; Fédoroff, Michel; Finne, Jörgen; Jaubertie, Anne

    2009-09-15

    A set-up and a method were developed to determine the isoelectric point of metals and metallic alloys samples (stainless steels, inconel, zircaloy, aluminum and dural) by measuring the adhesion rate of negative latex particles. The concentration of polystyrene spheres with surface carboxylate groups (initially 0.5-1 mg L(-1)) in contact with metallic samples was measured as a function of pH and time by turbidimetry. The simulation of measurements by a model predicting the sticking coefficient based on DLVO theory was used for the determination of the isoelectric point from experimental results. It was found that the isoelectric points of aluminum (8.7) and dural (9.1), treated by boiling water, are close to those of hydrated aluminum oxides powders. For stainless steels, inconel and zircaloy, the values of isoelectric points were found to be between 2.4 and 3.0, far below the isoelectric points measured for metallic oxides constituting the alloy surface layer. This difference was explained by two different charging mechanisms: (1) deprotonation of hydroxyl groups on the surface of the metal oxide in suspension or as a thick layer, (2) adsorption of hydroxide ions on a metal surface covered by a thin oxide layer, as observed on hydrophobic surfaces.

  9. Electronic Zero-Point Oscillations in the Strong-Interaction Limit of Density Functional Theory.

    PubMed

    Gori-Giorgi, Paola; Vignale, Giovanni; Seidl, Michael

    2009-04-14

    The exchange-correlation energy in Kohn-Sham density functional theory can be expressed exactly in terms of the change in the expectation of the electron-electron repulsion operator when, in the many-electron Hamiltonian, this same operator is multiplied by a real parameter λ varying between 0 (Kohn-Sham system) and 1 (physical system). In this process, usually called adiabatic connection, the one-electron density is kept fixed by a suitable local one-body potential. The strong-interaction limit of density functional theory, defined as the limit λ→∞, turns out to be like the opposite noninteracting Kohn-Sham limit (λ→0) mathematically simpler than the physical (λ = 1) case and can be used to build an approximate interpolation formula between λ→0 and λ→∞ for the exchange-correlation energy. Here we extend the systematic treatment of the λ→∞ limit [Phys. Rev. A 2007, 75, 042511] to the next leading term, describing zero-point oscillations of strictly correlated electrons, with numerical examples for small spherical atoms. We also propose an improved approximate functional for the zero-point term and a revised interpolation formula for the exchange-correlation energy satisfying more exact constraints.

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

    NASA Technical Reports Server (NTRS)

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

  11. Lean-limit extinction of propane/air mixtures in the stagnation-point flow

    NASA Technical Reports Server (NTRS)

    Law, C. K.; Ishizuka, S.; Mizomoto, M.

    1981-01-01

    The extinction limits of lean propane/air mixtures in the stagnation-point flow of a flat surface were mapped as functions of the surface temperature and the mixture concentration, velocity, and temperature. The maximum flame temperatures and the flame locations were also measured. The results show that the extinction limits are extremely insensitive to the nature of the surface, which can be heated to 1000 C. On the other hand preheating the gas mixture increases the flame temperature by an almost equal amount and therefore significantly extends the extinction limits. It is also found that at extinction the maximum flame temperatures and the flame locations, which when scaled with the velocity gradient, assume almost constant values independent of the other system variables investigated.

  12. On the Scaling Limits of Determinantal Point Processes with Kernels Induced by Sturm-Liouville Operators

    NASA Astrophysics Data System (ADS)

    Bornemann, Folkmar

    2016-08-01

    By applying an idea of Borodin and Olshanski [J. Algebra 313 (2007), 40-60], we study various scaling limits of determinantal point processes with trace class projection kernels given by spectral projections of selfadjoint Sturm-Liouville operators. Instead of studying the convergence of the kernels as functions, the method directly addresses the strong convergence of the induced integral operators. We show that, for this notion of convergence, the Dyson, Airy, and Bessel kernels are universal in the bulk, soft-edge, and hard-edge scaling limits. This result allows us to give a short and unified derivation of the known formulae for the scaling limits of the classical random matrix ensembles with unitary invariance, that is, the Gaussian unitary ensemble (GUE), the Wishart or Laguerre unitary ensemble (LUE), and the MANOVA (multivariate analysis of variance) or Jacobi unitary ensemble (JUE).

  13. Limit Cycle Bifurcations Near a Piecewise Smooth Generalized Homoclinic Loop with a Saddle-Fold Point

    NASA Astrophysics Data System (ADS)

    Liang, Feng; Wang, Dechang

    In this paper, we suppose that a planar piecewise Hamiltonian system, with a straight line of separation, has a piecewise generalized homoclinic loop passing through a Saddle-Fold point, and assume that there exists a family of piecewise smooth periodic orbits near the loop. By studying the asymptotic expansion of the first order Melnikov function corresponding to the period annulus, we obtain the formulas of the first six coefficients in the expansion, based on which, we provide a lower bound for the maximal number of limit cycles bifurcated from the period annulus. As applications, two concrete systems are considered. Especially, the first one reveals that a quadratic piecewise Hamiltonian system can have five limit cycles near a generalized homoclinic loop under a quadratic piecewise smooth perturbation. Compared with the smooth case [Horozov & Iliev, 1994; Han et al., 1999], three more limit cycles are found.

  14. Experimental study of limit lean methane/air flame in a standard flammability tube using particle image velocimetry method

    SciTech Connect

    Shoshin, Yuriy; Gorecki, Grzegorz; Jarosinski, Jozef; Fodemski, Tadeusz

    2010-05-15

    Lean limit methane/air flame propagating upward in a standard 50 mm diameter and 1.8 m length tube was studied experimentally using particle image velocimetry method. Local stretch rate along the flame front was determined by measured gas velocity distributions. It was found that local stretch rate is maximum at the flame leading point, which is in agreement with earlier theoretical results. Similar to earlier observations, extinction of upward propagating limit flame was observed to start from the flame top. It is stated that the observed behavior of the extinction of the lean limit methane/air flame can not be explained in terms of the coupled effect of flame stretch and preferential diffusion. To qualitatively explain the observed extinction behavior, it is suggested that the positive strain-induced flame stretch increases local radiation heat losses from the flame front. An experimental methodology for PIV measurements in a round tube is described. (author)

  15. Triple Junction at the Triple Point Resolved on the Individual Particle Level

    NASA Astrophysics Data System (ADS)

    Chaudhuri, M.; Allahyarov, E.; Löwen, H.; Egelhaaf, S. U.; Weitz, D. A.

    2017-09-01

    At the triple point of a repulsive screened Coulomb system, a fcc crystal, a bcc crystal, and a fluid phase coexist. At their intersection, these three phases form a liquid groove, the triple junction. Using confocal microscopy, we resolve the triple junction on a single-particle level in a model system of charged PMMA colloids in a nonpolar solvent. The groove is found to be extremely deep and the incommensurate solid-solid interface to be very broad. Thermal fluctuations hence appear to dominate the solid-solid interface. This indicates a very low interfacial energy. The fcc-bcc interfacial energy is quantitatively determined based on Young's equation and, indeed, it is only about 1.3 times higher than the fcc-fluid interfacial energy close to the triple point.

  16. The angle-averaged squeezed limit of nonlinear matter N-point functions

    SciTech Connect

    Wagner, Christian; Schmidt, Fabian; Chiang, Chi-Ting; Komatsu, Eiichiro E-mail: fabians@mpa-garching.mpg.de E-mail: komatsu@mpa-garching.mpg.de

    2015-08-01

    Assuming Gaussian initial conditions, we show that in a certain, angle-averaged squeezed limit the N-point function of matter is related to the response of the matter power spectrum to a long-wavelength density perturbation, P{sup −1}d{sup nP}(k|δ{sub L})/dδ{sub L}{sup n}|{sub δ{sub L=0}}, with n=N−2. By performing N-body simulations with a homogeneous overdensity superimposed on a flat Friedmann-Robertson-Lemaȋtre-Walker (FRLW) universe using the separate universe approach, we obtain measurements of the nonlinear matter power spectrum response up to n=3, which is equivalent to measuring the fully nonlinear matter 3- to 5-point function in this squeezed limit. The sub-percent to few percent accuracy of those measurements is unprecedented. We then test the hypothesis that nonlinear N-point functions at a given time are a function of the linear power spectrum at that time, which is predicted in an Einstein-de Sitter (EdS) universe by standard perturbation theory (SPT) and its variants that are based on the ideal pressureless fluid equations. Specifically, we compare the responses computed from the separate universe simulations and simulations with a rescaled initial (linear) power spectrum amplitude. We find discrepancies of 10% at k≅ 0.2–0.5 h Mpc{sup −1} for 5- to 3-point functions at z=0. The discrepancy occurs at higher wavenumbers at z=2. Thus, theoretical predictions that are insensitive to the growth history, such as SPT and its variants assuming EdS, even when carried out to arbitrarily high order, are guaranteed to fail to describe matter N-point functions (N>2) around that scale.

  17. Universal quantum behavior of interacting fermions in one-dimensional traps: From few particles to the trap thermodynamic limit

    NASA Astrophysics Data System (ADS)

    Angelone, Adriano; Campostrini, Massimo; Vicari, Ettore

    2014-02-01

    We investigate the ground-state properties of trapped fermion systems described by the Hubbard model with an external confining potential. We discuss the universal behaviors of systems in different regimes: from few particles, i.e., in dilute regimes, to the trap thermodynamic limit. The asymptotic trap-size (TS) dependence in the dilute regime (increasing the trap size ℓ keeping the particle number N fixed) is described by a universal TS scaling controlled by the dilute fixed point associated with the metal-to-vacuum quantum transition. This scaling behavior is numerically checked by DMRG simulations of the one-dimensional (1D) Hubbard model. In particular, the particle density and its correlations show crossovers among different regimes: for strongly repulsive interactions they approach those of a spinless Fermi gas, for weak interactions those of a free Fermi gas, and for strongly attractive interactions they match those of a gas of hard-core bosonic molecules. The large-N limit keeping the ratio N /ℓ fixed corresponds to a 1D trap thermodynamic limit. We address issues related to the accuracy of the local density approximation (LDA). We show that the particle density approaches its LDA in the large-ℓ limit. When the trapped system is in the metallic phase, corrections at finite ℓ are O (ℓ-1) and oscillating around the center of the trap. They become significantly larger at the boundary of the fermion cloud, where they get suppressed as O (ℓ-1/3) only. This anomalous behavior arises from the nontrivial scaling at the metal-to-vacuum transition occurring at the boundaries of the fermion cloud.

  18. 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.

  19. Nonthermal fixed points in quantum field theory beyond the weak-coupling limit

    NASA Astrophysics Data System (ADS)

    Berges, Jürgen; Wallisch, Benjamin

    2017-02-01

    Quantum systems in extreme conditions can exhibit universal behavior far from equilibrium associated to nonthermal fixed points with a wide range of topical applications from early-Universe inflaton dynamics and heavy-ion collisions to strong quenches in ultracold quantum gases. So far, most studies have relied on a mapping of the quantum dynamics onto a classical-statistical theory that can be simulated on a computer. However, the mapping is based on a weak-coupling limit, while phenomenological applications often require moderate interaction strengths. We report on the observation of nonthermal fixed points directly in quantum field theory beyond the weak-coupling limit. For the example of a relativistic scalar O (N )-symmetric quantum field theory, we numerically solve the nonequilibrium dynamics employing a 1 /N expansion to next-to-leading order, which does not rely on a small coupling parameter. Starting from two different sets of overoccupied and of strong-field initial conditions, we find that nonthermal fixed points are not restricted to parameter ranges suitable for classical-statistical simulations but extend also to couplings of order 1. While the infrared behavior is found to be insensitive to the differences in the initial conditions, we demonstrate that transport phenomena to higher momenta depend on the presence or absence of a symmetry-breaking field expectation value.

  20. Formation of limit-periodic structures by quadrupole particles confined to a triangular lattice

    NASA Astrophysics Data System (ADS)

    Rutkowski, David M.; Marcoux, Catherine; Socolar, Joshua E. S.; Hall, Carol K.

    2017-01-01

    We have performed Monte Carlo (MC) simulations on two-dimensional systems of quadrupole particles confined to a triangular lattice in order to determine the conditions that permit the formation of a limit-periodic phase. We have found that limit-periodic structures form only when the rotations of the particles are confined to a set of six orientations aligned with the lattice directions. Related structures including striped and unidirectional rattler phases form when π /π 6 rotations or continuous rotations are allowed. Order parameters signaling the formation of the limit-periodic structure and related structures are measured as a function of temperature. Our findings on the formation of the limit-periodic structure elucidate features relevant to the experimental creation of such a structure, which is expected to have interesting vibrational and electromagnetic modes.

  1. 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.

  2. Towards encoded particles for highly multiplexed colorimetric point of care autoantibody detection.

    PubMed

    Svedberg, Gustav; Jeong, Yunjin; Na, Hunjong; Jang, Jisung; Nilsson, Peter; Kwon, Sunghoon; Gantelius, Jesper; Svahn, Helene Andersson

    2017-01-31

    Highly multiplexed point of care tests could improve diagnostic accuracy and differential diagnostic capacity in for instance emergency medicine and low resource environments. Available technology platforms for POC biomarker detection are typically simplex or low-plexed, whereas common lab-based microarray systems allow for the simultaneous detection of thousands of DNA or protein biomarkers. In this study, we demonstrate a novel suspension particle array platform that utilizes 900 μm bricks for POC amenable colorimetric biomarker detection with an encoding capacity of over two million. Due to the mm-scale size, both the lithographic codes and colorimetric signals of individual particles can be visualized using a consumer grade office flatbed scanner, with a potential for simultaneous imaging of around 19 000 particles per scan. The analytical sensitivity of the assay was determined to be 4 ng ml(-1) using an antibody model system. As a proof of concept, autoantibodies toward anoctamin 2 were detected in order to discriminate between multiple sclerosis plasma samples and healthy controls with p < 0.0001 and an inter-assay % CV of 9.44%.

  3. Point particles in 2+1 dimensions: general relativity and loop gravity descriptions

    NASA Astrophysics Data System (ADS)

    Ziprick, Jonathan

    2015-02-01

    We develop a Hamiltonian description of point particles in (2+1)-dimensions using connection and frame-field variables for general relativity. The topology of each spatial hypersurface is that of a punctured two-sphere with particles residing at the punctures. We describe this topology with a CW complex (a collection of two cells glued together along the edges), and use this to fix a gauge and reduce the Hamiltonian. The equations of motion for the fields describe a dynamical triangulation where each vertex moves according to the equation of motion for a free relativistic particle. The evolution is continuous except for when triangles collapse (i.e. the edges become parallel) causing discrete, topological changes in the underlying CW complex. We then introduce the loop gravity phase space parameterized by holonomy-flux variables on a graph (a network of one-dimensional links). By embedding a graph within the CW complex, we find a description of this system in terms of loop variables. The resulting equations of motion describe the same dynamical triangulation as the connection and frame-field variables. In this framework, the collapse of a triangle causes a discrete change in the underlying graph, giving a concrete realization of the graph-changing moves that many expect to feature in full loop quantum gravity. The main result is a dynamical model of loop gravity that agrees with general relativity and is well-suited for quantization using existing methods.

  4. 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

    2016-12-01

    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 (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) or if ejected from the cluster, which can be calculated analytically.

  5. 2015 CRC Aviation Meetings Particle Count Limits Recommendation for Aviation Fuel (Briefing Charts)

    DTIC Science & Technology

    2015-05-05

    31 AUG 2015 2. REPORT TYPE 3. DATES COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE 2015 CRC Aviation Meetings Particle Count Limits...Recommendation for Aviation Fuel 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Joel Schmitigal 5d. PROJECT NUMBER 5e...ABSTRACT None 15. SUBJECT TERMS 2015 Coordinating Research Council Aviation Meetings 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT

  6. Forming Limit Predictions for the Serrated Strain Paths in Single Point Incremental Sheet Forming

    SciTech Connect

    Eyckens, P.; He, S.; Van Houtte, P.; Bael, A. van; Duflou, J.

    2007-05-17

    The forming limits of sheets subjected to the Single Point Incremental Forming process (SPIF) is generally several times higher than those found in the Forming Limit Curve (FLC). In this paper it is shown that the non-monotonic, serrated strain paths to which the material is subjected to during the SPIF process, play a role in the high formability, compared to the monotonic loading in the traditional FLC. The deformation history of an aluminium alloy truncated cone formed with the SPIF process is retrieved through a finite element (FE) model, and discussed. Subsequently, the strain paths at three different depths in the sheet are used as input into a Marciniak-Kuczynski (MK) forming limit model. The usage of different constitutive models in this analysis shows that anisotropic hardening contributes to the delay of the onset of necking in the SPIF process. The large difference in the predicted forming limits that were obtained from the different layers indicates that an interaction between these layers should be taken into account for more accurate forming limit predictions of sheets subjected to the SPIF process.

  7. Nanoscale three-dimensional single particle tracking by light-sheet-based double-helix point spread function microscopy.

    PubMed

    Yu, Bin; Yu, Jie; Li, Weihai; Cao, Bo; Li, Heng; Chen, Danni; Niu, Hanben

    2016-01-20

    The double-helix point spread function (DH-PSF) microscopy has become an essential tool for nanoscale three-dimensional (3D) localization and tracking of single molecules in living cells. However, its localization precision is limited by fluorescent contrast in thick samples because the signal-to-noise ratio of the system is low due to the inherent low transfer function efficiency and background fluorescence. Here we combine DH-PSF microscopy with light-sheet illumination to eliminate out-of-focus background fluorescence for high-precision 3D single particle tracking. To demonstrate the capability of the method, we obtain the single fluorescent bead image with light-sheet illumination, with three-dimensional localization accuracy better than that of epi-illumination. We also show that the single fluorescent beads in agarose solution can be tracked, which demonstrates the possibility of our method for the study of dynamic processes in complex biological specimens.

  8. Temperature Measurement Challenges and Limitations for In-Flight Particles in Suspension Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Aziz, Bishoy; Gougeon, Patrick; Moreau, Christian

    2017-03-01

    Suspension plasma spraying (SPS) acquires a significant interest from the industry. The deposited coatings using this technique were proved to have unique microstructural features compared to those built by conventional plasma spraying techniques. In order to optimize this process, in-flight particle diagnostics is considered a very useful tool that helps to control various spraying parameters and permits better coating reproducibility. In that context, the temperature of in-flight particles is one of the most important key elements that helps to optimize and control the SPS process. However, the limitations and challenges associated with this process have a significant effect on the accuracy of two-color pyrometric techniques used to measure the in-flight particle temperature. In this work, the influence of several nonthermal radiation sources on the particle temperature measurement is studied. The plasma radiation scattered by in-flight particles was found to have no significant influence on temperature measurement. Moreover, the detection of the two-color signals at two different locations was found to induce a significant error on temperature measurement. Finally, the plasma radiation surrounding the in-flight particles was identified as the main source of error on the temperature measurement of in-flight particles.

  9. Temperature Measurement Challenges and Limitations for In-Flight Particles in Suspension Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Aziz, Bishoy; Gougeon, Patrick; Moreau, Christian

    2017-04-01

    Suspension plasma spraying (SPS) acquires a significant interest from the industry. The deposited coatings using this technique were proved to have unique microstructural features compared to those built by conventional plasma spraying techniques. In order to optimize this process, in-flight particle diagnostics is considered a very useful tool that helps to control various spraying parameters and permits better coating reproducibility. In that context, the temperature of in-flight particles is one of the most important key elements that helps to optimize and control the SPS process. However, the limitations and challenges associated with this process have a significant effect on the accuracy of two-color pyrometric techniques used to measure the in-flight particle temperature. In this work, the influence of several nonthermal radiation sources on the particle temperature measurement is studied. The plasma radiation scattered by in-flight particles was found to have no significant influence on temperature measurement. Moreover, the detection of the two-color signals at two different locations was found to induce a significant error on temperature measurement. Finally, the plasma radiation surrounding the in-flight particles was identified as the main source of error on the temperature measurement of in-flight particles.

  10. Emerging technologies in point-of-care molecular diagnostics for resource-limited settings.

    PubMed

    Peeling, Rosanna W; McNerney, Ruth

    2014-06-01

    Emerging molecular technologies to diagnose infectious diseases at the point at which care is delivered have the potential to save many lives in developing countries where access to laboratories is poor. Molecular tests are needed to improve the specificity of syndromic management, monitor progress towards disease elimination and screen for asymptomatic infections with the goal of interrupting disease transmission and preventing long-term sequelae. In simplifying laboratory-based molecular assays for use at point-of-care, there are inevitable compromises between cost, ease of use and test performance. Despite significant technological advances, many challenges remain for the development of molecular diagnostics for resource-limited settings. There needs to be more advocacy for these technologies to be applied to infectious diseases, increased efforts to lower the barriers to market entry through streamlined and harmonized regulatory approaches, faster policy development for adoption of new technologies and novel financing mechanisms to enable countries to scale up implementation.

  11. Limits on three-point correlations in the COBE DMR first-year anisotropy maps

    NASA Technical Reports Server (NTRS)

    Hinshaw, G.; Kogut, A.; Gorski, K. M.; Banday, A. J.; Bennett, C. L.; Lineweaver, C.; Lubin, P.; Smoot, G. F.; Wright, E. L.

    1994-01-01

    We compute the three-point temperature correlation function of the Cosmic Background Explorer (COBE) Differential Microwave Radiometer (DMR) first-year sky maps to search for non-Gaussian temperature fluctuations. The level of fluctuations seen in the computed correlation function are too large to be attributable solely to instrument noise. However the fluctuations are consistent with the level expected to result from a superposition of istrument noise and sky signal arising from a Gaussian power-law model of initial fluctuations, with a quadrupole normalized amplitude of 17 micro K and a power-law spectral index n = 1. We place limits on the amplitude of intrinsic three-point correlations with a variety of predicted functional forms.

  12. Tricritical points in a Vicsek model of self-propelled particles with bounded confidence.

    PubMed

    Romensky, Maksym; Lobaskin, Vladimir; Ihle, Thomas

    2014-12-01

    We study the orientational ordering in systems of self-propelled particles with selective interactions. To introduce the selectivity we augment the standard Vicsek model with a bounded-confidence collision rule: a given particle only aligns to neighbors who have directions quite similar to its own. Neighbors whose directions deviate more than a fixed restriction angle α are ignored. The collective dynamics of this system is studied by agent-based simulations and kinetic mean-field theory. We demonstrate that the reduction of the restriction angle leads to a critical noise amplitude decreasing monotonically with that angle, turning into a power law with exponent 3/2 for small angles. Moreover, for small system sizes we show that upon decreasing the restriction angle, the kind of the transition to polar collective motion changes from continuous to discontinuous. Thus, an apparent tricritical point with different scaling laws is identified and calculated analytically. We investigate the shifting and vanishing of this point due to the formation of density bands as the system size is increased. Agent-based simulations in small systems with large particle velocities show excellent agreement with the kinetic theory predictions. We also find that at very small interaction angles, the polar ordered phase becomes unstable with respect to the apolar phase. We derive analytical expressions for the dependence of the threshold noise on the restriction angle. We show that the mean-field kinetic theory also permits stationary nematic states below a restriction angle of 0.681π. We calculate the critical noise, at which the disordered state bifurcates to a nematic state, and find that it is always smaller than the threshold noise for the transition from disorder to polar order. The disordered-nematic transition features two tricritical points: At low and high restriction angle, the transition is discontinuous but continuous at intermediate α. We generalize our results to systems

  13. Tricritical points in a Vicsek model of self-propelled particles with bounded confidence

    NASA Astrophysics Data System (ADS)

    Romensky, Maksym; Lobaskin, Vladimir; Ihle, Thomas

    2014-12-01

    We study the orientational ordering in systems of self-propelled particles with selective interactions. To introduce the selectivity we augment the standard Vicsek model with a bounded-confidence collision rule: a given particle only aligns to neighbors who have directions quite similar to its own. Neighbors whose directions deviate more than a fixed restriction angle α are ignored. The collective dynamics of this system is studied by agent-based simulations and kinetic mean-field theory. We demonstrate that the reduction of the restriction angle leads to a critical noise amplitude decreasing monotonically with that angle, turning into a power law with exponent 3/2 for small angles. Moreover, for small system sizes we show that upon decreasing the restriction angle, the kind of the transition to polar collective motion changes from continuous to discontinuous. Thus, an apparent tricritical point with different scaling laws is identified and calculated analytically. We investigate the shifting and vanishing of this point due to the formation of density bands as the system size is increased. Agent-based simulations in small systems with large particle velocities show excellent agreement with the kinetic theory predictions. We also find that at very small interaction angles, the polar ordered phase becomes unstable with respect to the apolar phase. We derive analytical expressions for the dependence of the threshold noise on the restriction angle. We show that the mean-field kinetic theory also permits stationary nematic states below a restriction angle of 0.681 π . We calculate the critical noise, at which the disordered state bifurcates to a nematic state, and find that it is always smaller than the threshold noise for the transition from disorder to polar order. The disordered-nematic transition features two tricritical points: At low and high restriction angle, the transition is discontinuous but continuous at intermediate α . We generalize our results to

  14. 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.

  15. Extinction Limits of Nonadiabatic, Catalyst-Assisted Flames in Stagnation-Point Flow

    SciTech Connect

    Stephen B. Margolis; Timothy J. Gardner

    2001-02-01

    An idealized geometry corresponding to a premixed flame in stagnation-point flow is used to investigate the effects of catalysis on extending the extinction limits of on adiabatic stretched flames. Specifically, a surface catalytic reaction is assumed to occur on the stagnation plane, thereby augmenting combustion in the bulk gas with a exothermic surface reaction characterized by a reduced activation energy. Assuming the activation energies remain large, an asymptotic analysis of the resulting flame structure yields a formula for the extinction limit as a function of various parameters. In particular, it is demonstrated that the presence of a surface catalyst can extend the burning regime, thus counterbalancing the effects of heat loss and flame stretch that tend to shrink it. The analysis is relevant to small-volume combustors, where the increased surface-to-volume ratio can lead to extinction of the nonadiabatic flame in the absence of a catalyst.

  16. Nitrate transport and supply limitations quantified using high-frequency stream monitoring and turning point analysis

    NASA Astrophysics Data System (ADS)

    Jones, Christopher S.; Wang, Bo; Schilling, Keith E.; Chan, Kung-sik

    2017-06-01

    Agricultural landscapes often leak inorganic nitrogen to the stream network, usually in the form of nitrate-nitrite (NOx-N), degrading downstream water quality on both the local and regional scales. While the spatial distribution of nitrate sources has been delineated in many watersheds, less is known about the complicated temporal dynamics that drive stream NOx-N because traditional methods of stream grab sampling are often conducted at a low frequency. Deployment of accurate real-time, continuous measurement devices that have been developed in recent years enables high-frequency sampling that provides detailed information on the concentration-discharge relation and the timing of NOx-N delivery to streams. We aggregated 15-min interval NOx-N and discharge data over a nine-year period into daily averages and then used robust statistical methods to identify how the discharge regime within an artificially-drained agricultural watershed reflected catchment hydrology and NOx-N delivery pathways. We then quantified how transport and supply limitations varied from year-to-year and how dependence of these limitations varied with climate, especially drought. Our results show NOx-N concentrations increased linearly with discharge up to an average ;turning point; of 1.42 mm of area-normalized discharge, after which concentrations decline with increasing discharge. We estimate transport and supply limitations to govern 57 and 43 percent, respectively, of the NOx-N flux over the nine-year period. Drought effects on the NOx-N flux linger for multiple years and this is reflected in a greater tendency toward supply limitations in the three years following drought. How the turning point varies with climate may aid in prediction of NOx-N loading in future climate regimes.

  17. SAMPEX science pointing with velocity avoidance. [solar anomalous and magnetospheric particle explorer

    NASA Technical Reports Server (NTRS)

    Frakes, Joseph P.; Henretty, Debra A.; Flatley, Thomas W.; Markley, F. L.; San, Josephine K.; Lightsey, E. G.

    1992-01-01

    The Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) science pointing mode is presented with the additional constraint of velocity avoidance. This constraint has been added in light of the orbital debris and micrometeoroid fluxes that have been revealed by the Long Duration Exposure Facility (LDEF) recovered in January 1990. These fluxes are 50-100 times higher than the flux tables that were used in the September 1988 proposal to NASA for the SAMPEX mission. The SAMPEX Heavey Ion Large Telescope (HILT) sensor includes a flow-through isobutane proportional counter that is susceptible to penetration by orbital debris and micrometeoroids. Thus, keeping the HILT sensor pointed away from the velocity vector, the direction of maximum flux, will compensate for the higher than expected fluxes. Using an orbital debris model and a micrometeoroid model developed at the Johnson Space Center (JSC), and a SAMPEX dynamic simulator developed by the Guidance and Control Branch at the Goddard Space Flight Center (GSFC), an 'optimal' minimum ram angle (the angle between the HILT boresight and the velocity vector) of 90 degrees has been determined. It is optimal in the sense of minimizing the science pointing performance degradation while providing approximately an 89 percent chance of survival for the HILT sensor over a three year period.

  18. Limiting soft particle emission in e + e -, hadronic and nuclear collisions

    NASA Astrophysics Data System (ADS)

    Ochs, Wolfgang; Khoze, Valery A.; Ryskin, M. G.

    2010-07-01

    In e + e - collisions the particle spectra at low momenta reflect the properties of the underlying “soft” QCD gluon bremsstrahlung: the particle density, in the limit p→0, becomes independent of the incoming energy sqrt{s} and directly proportional to the colour factors C A , C F for primary gluons or quarks respectively. We find that experimental data from the pp and nuclear reactions reveal the same behaviour: in the limit p T→0 the invariant particle spectra become independent of the collision energy, and their intensities in e + e -, pp and nuclear reactions are compatible with the expected colour factors C F : C A : ( N part/2) C A for N part nucleons, participating in the interaction. Coherent soft gluon bremsstrahlung is, therefore, suggested to be the dominant QCD mechanism for the soft particle production in all these reactions. These “soft” particles probe the very early stage of hadron formation in the collision. Future measurements at the LHC will provide crucial tests on the contributions from possible incoherent multi-component processes.

  19. Collisions near Kerr black holes: lower limit of energy between orbiting and incoming particles

    NASA Astrophysics Data System (ADS)

    Rutkowski, Mieszko

    2017-01-01

    In our paper we investigate the lower limit of collisional energy of test particles near the Kerr black hole. In particular we examine the minimal Lorentz factor between the freely falling particles and the particles orbiting around a black hole. We consider collisions on the innermost stable circular orbit and examine near-extreme case, where collisions take place near an event horizon. By fine-tuning the particles' angular momentum, the Lorentz factor of the collision can always be minimized to a value dependent on the black hole's spin. We identified that this minimal value is always less than 2√{2}-1/√{3} and more than √{12}-1/√{6} (the limits are the values for an extreme Kerr and Schwarzschild, respectively). It implies that this kind of collisions of compact objects are expected to be highly energetic near supermassive black holes. In addition, we show that an interaction between black hole's and particle's spins has an influence on minimal Lorentz factor. This contribution is nonnegligible for near-extreme black holes. We also discuss the relation between our results and sci-fi movie Interstellar.

  20. Limits of DPUI application associated with the number of particles within actinide aerosols.

    PubMed

    Fritsch, P; Raynaud, P; Blanchin, N; Mièle, A

    2007-01-01

    Dose per unit intake (DPUI) of radionuclides is obtained using International Commission on Radiological Protection (ICRP) models. After inhalation exposure, the first model calculates the fraction of activity deposited within the different regions of the respiratory tract, assuming that the aerosol contains an infinite number of particles. Using default parameters for workers, an exposure to one annual limit of intake (ALI) corresponds to an aerosol of 239PuO2 containing approximately 1 x 10(6) particles. To reach such an exposure, very low particle number might be involved especially for compounds having a high specific activity. This study provides examples of exposures to actinide aerosols for which the number of particles is too low for a standard application of the ICRP model. These examples, which involve physical studies of aerosols collected at the workplace and interpretation of bioassay data, show that the number of particles of the aerosol can be the main limit for the application of DPUI after inhalation exposure.

  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.

  2. Analysis of the modified point-matching method in the electrostatic problem for axisymmetric particles

    NASA Astrophysics Data System (ADS)

    Farafonov, V. G.; Ustimov, V. I.; Tulegenov, A. R.

    2016-08-01

    An integral modification of the generalized point-matching method (GPMMi) in the electrostatic problem for axisymmetric particles is developed. Scalar potentials that determine electric fields are represented as expansions in terms of eigenfunctions of the Laplace operator in the spherical coordinate system. Unknown expansion coefficients are determined from infinite systems of linear algebraic equations (ISLAEs), which are obtained from the requirement of a minimum of the integrated residual in the boundary conditions on the particle surface. Matrix elements of ISLAEs and expansion coefficients of the "scattered" field at large index values are analyzed analytically and numerically. It is shown analytically that the applicability condition of the GPMMi coincides with that for the extended boundary conditions method (EBCM). As model particles, oblate pseudospheroids r( θ ) = a√ {1 - {^2}{{cos}^2}θ } ,{^2} = 1 - {b^2} {a_2} ≥ 0 with semiaxes a = 1 and b ≤ 1 are considered, which are obtained as a result of the inversion of prolate spheroids with the same semiaxes with respect to the coordinate origin. For pseudospheroids, the range of applicability of the considered methods is determined by the condition {a b} < √ 2 + 1. Numerical calculations show that, as a rule, the EBCM yields considerably more accurate results in this range, with the time consumption being substantially shorter. Beyond the EBCM range of applicability, the GPMMi approach can yield reasonable results for the calculation of the polarizability, which should be considered as approximate and which should be verified with other approaches. For oblate nonconvex pseudospheroids (i.e., at {a b} ≥slant √ 2 ), it is shown that the spheroidal model works well if pseudospheroids are replaced with ordinary "effective" oblate spheroids. Semiaxes a ef and b ef of the effective spheroids are determined from the requirement of the particle volumes, as well as from the equality of the maximal

  3. Avoidance of fisheries-induced evolution: management implications for catch selectivity and limit reference points.

    PubMed

    Hutchings, Jeffrey A

    2009-08-01

    I examined how the fitness (r) associated with early- and late-maturing genotypes varies with fishing mortality (F) and age-/size-specific probability of capture. Life-history data on Newfoundland's northern Atlantic cod (Gadus morhua) allowed for the estimation of r for individuals maturing at 4 and 7 year in the absence of fishing. Catch selectivity data associated with four types of fishing gear (trap, gillnet, handline, otter trawl) were then incorporated to examine how r varied with gear type and with F. The resulting fitness functions were then used to estimate the F above which selection would favour early (4 year) rather than delayed (7 year) maturity. This evolutionarily-sensitive threshold, F evol, identifies a limit reference point somewhat similar to those used to define overfishing (e.g., F msy, F 0.1). Over-exploitation of northern cod resulted in fishing mortalities considerably greater than those required to effect evolutionary change. Selection for early maturity is reduced by the dome-shaped selectivities characteristic of fixed gears such as handlines (the greater the leptokurtosis, the lower the probability of a selection response) and enhanced by the knife-edged selectivities of bottom trawls. Strategies to minimize genetic change are consistent with traditional management objectives (e.g., yield maximization, population increase). Compliance with harvest control rules guided by evolutionarily-sensitive limit reference points, which may be achieved by adherence to traditional reference points such as F msy and F 0.1, should be sufficient to minimize the probability of fisheries-induced evolution for commercially exploited species.

  4. 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.

  5. Avoidance of fisheries-induced evolution: management implications for catch selectivity and limit reference points

    PubMed Central

    Hutchings, Jeffrey A

    2009-01-01

    I examined how the fitness (r) associated with early- and late-maturing genotypes varies with fishing mortality (F) and age-/size-specific probability of capture. Life-history data on Newfoundland's northern Atlantic cod (Gadus morhua) allowed for the estimation of r for individuals maturing at 4 and 7 year in the absence of fishing. Catch selectivity data associated with four types of fishing gear (trap, gillnet, handline, otter trawl) were then incorporated to examine how r varied with gear type and with F. The resulting fitness functions were then used to estimate the F above which selection would favour early (4 year) rather than delayed (7 year) maturity. This evolutionarily-sensitive threshold, Fevol, identifies a limit reference point somewhat similar to those used to define overfishing (e.g., Fmsy, F0.1). Over-exploitation of northern cod resulted in fishing mortalities considerably greater than those required to effect evolutionary change. Selection for early maturity is reduced by the dome-shaped selectivities characteristic of fixed gears such as handlines (the greater the leptokurtosis, the lower the probability of a selection response) and enhanced by the knife-edged selectivities of bottom trawls. Strategies to minimize genetic change are consistent with traditional management objectives (e.g., yield maximization, population increase). Compliance with harvest control rules guided by evolutionarily-sensitive limit reference points, which may be achieved by adherence to traditional reference points such as Fmsy and F0.1, should be sufficient to minimize the probability of fisheries-induced evolution for commercially exploited species. PMID:25567884

  6. Two-Point Particle Tracking Microrheology of Nematic Lyotropic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Gomez-Gonzalez, Manuel; Del Alamo, Juan Carlos

    2016-11-01

    Biological and technological complex fluids that are usually available in microscopic amounts (e.g. liquid crystals and biopolymer networks) can exhibit microstructural order leading to nematic rheological behavior. However, current microrheological methods cannot measure their directional viscoelastic coefficients. We recently introduced a directional two-point particle-tracking microrheology (D2PTM) technique to determine these coefficients (1). Here, we experimentally validate D2PTM by applying this method to disodium cromoglycate (DSCG), a lyotropic chromonic nematic liquid crystal that has recently sparked attention due to its biocompatibility and other interesting properties. We chose DSCG because its directional viscosity coefficients have been previously characterized by dynamic light scattering and are available in the literature. Our results suggest that D2PTM measurements agree well with measurements from previous methods. Furthermore, this new technique provides additional information about the microrheological response of nematic fluids that was not accessible via previous methods.

  7. Electrical four-point probing of spherical metallic thin films coated onto micron sized polymer particles

    SciTech Connect

    Pettersen, Sigurd R. E-mail: jianying.he@ntnu.no; Stokkeland, August Emil; Zhang, Zhiliang; He, Jianying E-mail: jianying.he@ntnu.no; Kristiansen, Helge; Njagi, John; Goia, Dan V.; Redford, Keith

    2016-07-25

    Micron-sized metal-coated polymer spheres are frequently used as filler particles in conductive composites for electronic interconnects. However, the intrinsic electrical resistivity of the spherical thin films has not been attainable due to deficiency in methods that eliminate the effect of contact resistance. In this work, a four-point probing method using vacuum compatible piezo-actuated micro robots was developed to directly investigate the electric properties of individual silver-coated spheres under real-time observation in a scanning electron microscope. Poly(methyl methacrylate) spheres with a diameter of 30 μm and four different film thicknesses (270 nm, 150 nm, 100 nm, and 60 nm) were investigated. By multiplying the experimental results with geometrical correction factors obtained using finite element models, the resistivities of the thin films were estimated for the four thicknesses. These were higher than the resistivity of bulk silver.

  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. Relativistic dynamics of interacting point particles: Central position of the Wheeler-Feynman scheme

    NASA Astrophysics Data System (ADS)

    Costa de Beauregard, O.

    1985-06-01

    The Wheeler-Feynman (WF) relativistic theory of interacting point particles, generalized by acceptance of an arbitrary spacelike interaction, is shown to possess a privileged status, reminiscent of the “central force” interactions occurring in Newtonian mechanics. This scheme is shown to be isomorphic to the classical one of the statics of interacting flexible current-carrying wires obeying the Ampère-Laplace (AL) formulas: to the tension T (T 2 =const) of the wire corresponds the momentum-energy pi (pipi=-c2m2) of the particle; to the Laplace linear force density -i H×dr corresponds the Lorentz force QHij drj; to the Laplace potential ir-1 dr corresponds the WF potential Qδ(r2) dri, etc. Among the differences, there is self-action in the AL scheme and no self-action in the WF scheme. A stationary energy principle in the AL scheme is isomorphic to Fokker's stationary action principle in the WF scheme.

  10. Non-Equispaced System Matrix Acquisition for Magnetic Particle Imaging Based on Lissajous Node Points.

    PubMed

    Kaethner, Christian; Erb, Wolfgang; Ahlborg, Mandy; Szwargulski, Patryk; Knopp, Tobias; Buzug, Thorsten M

    2016-11-01

    Magnetic Particle Imaging (MPI) is an emerging technology in the field of (pre)clinical imaging. The acquisition of a particle signal is realized along specific sampling trajectories covering a defined field of view (FOV). In a system matrix (SM) based reconstruction procedure, the commonly used acquisition path in MPI is a Lissajous trajectory. Such a trajectory features an inhomogeneous coverage of the FOV, i.e. the center region is sampled less dense than the regions towards the edges of the FOV. Conventionally, the respective SM acquisition and the subsequent reconstruction do not reflect this inhomogeneous coverage. Instead, they are performed on an equispaced grid. The objective of this work is to introduce a sampling grid that inherently features the aforementioned inhomogeneity by using node points of Lissajous trajectories. Paired with a tailored polynomial interpolation of the reconstructed MPI signal, the entire image can be recovered. It is the first time that such a trajectory related non-equispaced grid is used for image reconstruction on simulated and measured MPI data and it is shown that the number of sampling positions can be reduced, while the spatial resolution remains constant.

  11. 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.

  12. 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 point...

  13. 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 to...

  14. Drift-based scrape-off particle width in X-point geometry

    NASA Astrophysics Data System (ADS)

    Reiser, D.; Eich, T.

    2017-04-01

    The Goldston heuristic estimate of the scrape-off layer width (Goldston 2012 Nucl. Fusion 52 013009) is reconsidered using a fluid description for the plasma dynamics. The basic ingredient is the inclusion of a compressible diamagnetic drift for the particle cross field transport. Instead of testing the heuristic model in a sophisticated numerical simulation including several physical mechanisms working together, the purpose of this work is to point out basic consequences for a drift-dominated cross field transport using a reduced fluid model. To evaluate the model equations and prepare them for subsequent numerical solution a specific analytical model for 2D magnetic field configurations with X-points is employed. In a first step parameter scans in high-resolution grids for isothermal plasmas are done to assess the basic formulas of the heuristic model with respect to the functional dependence of the scrape-off width on the poloidal magnetic field and plasma temperature. Particular features in the 2D-fluid calculations—especially the appearance of supersonic parallel flows and shock wave like bifurcational jumps—are discussed and can be understood partly in the framework of a reduced 1D model. The resulting semi-analytical findings might give hints for experimental proof and implementation in more elaborated fluid simulations.

  15. Self-gravitating phase transitions: Point particles, black holes and strings

    NASA Astrophysics Data System (ADS)

    Sanchez, Norma G.

    2006-04-01

    We compute the quantum string entropy S(m,j) of the microscopic string states of mass m and spin j in two physically relevant backgrounds: Kerr (rotating) black holes and de Sitter (dS) space time. We find a new formula for the quantum gravitational entropy S(M,J), as a function of the usual Bekenstein Hawking entropy Ssem(0)(M,J). We compute the quantum string emission by a black hole in de Sitter space time (bhdS). In all the following cases: (i) strings with the highest spin, and (ii) in dS space time, (iii) quantum rotating black holes, (iv) quantum dS regime, (v) late bhdS evaporation, we find a new gravitational phase transition with a common distinctive universal feature: a square root branch point singularity in any space time dimensions. This is the same behavior as for the thermal self-gravitating gas of point particles (de Vega Sanchez transition), thus describing a new universality class. To cite this article: N.G. Sanchez, C. R. Physique 7 (2006).

  16. Point-particle effective field theory II: relativistic effects and Coulomb/inverse-square competition

    NASA Astrophysics Data System (ADS)

    Burgess, C. P.; Hayman, Peter; Rummel, Markus; Williams, Matt; Zalavári, László

    2017-07-01

    We apply point-particle effective field theory (PPEFT) to compute the leading shifts due to finite-sized source effects in the Coulomb bound energy levels of a relativistic spinless charged particle. This is the analogue for spinless electrons of calculating the contribution of the charge-radius of the source to these levels, and our calculation disagrees with standard calculations in several ways. Most notably we find there are two effective interactions with the same dimension that contribute to leading order in the nuclear size, one of which captures the standard charge-radius contribution. The other effective operator is a contact interaction whose leading contribution to δE arises linearly (rather than quadratically) in the small length scale, ɛ, characterizing the finite-size effects, and is suppressed by ( Zα)5. We argue that standard calculations miss the contributions of this second operator because they err in their choice of boundary conditions at the source for the wave-function of the orbiting particle. PPEFT predicts how this boundary condition depends on the source's charge radius, as well as on the orbiting particle's mass. Its contribution turns out to be crucial if the charge radius satisfies ɛ ≲ ( Zα)2 a B , where a B is the Bohr radius, because then relativistic effects become important for the boundary condition. We show how the problem is equivalent to solving the Schrödinger equation with competing Coulomb, inverse-square and delta-function potentials, which we solve explicitly. A similar enhancement is not predicted for the hyperfine structure, due to its spin-dependence. We show how the charge-radius effectively runs due to classical renormalization effects, and why the resulting RG flow is central to predicting the size of the energy shifts (and is responsible for its being linear in the source size). We discuss how this flow is relevant to systems having much larger-than-geometric cross sections, such as those with large

  17. 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

    2016-01-01

    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.

  18. 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

  19. Superparamagnetic Particle Size Limit of Mn-Zn Ferrite Nanoparticles Synthesised Through Aqueous Method

    NASA Astrophysics Data System (ADS)

    Joseyphus, R. Justin; Narayanasamy, A.; Jeyadevan, B.; Shinoda, K.; Tohji, K.

    2006-05-01

    Mn0.67Zn0.33Fe2O4 nanoparticles with size ranging from 20 to 80 nm have been synthesized using the modified oxidation method. The Curie temperatures for all the samples are found to be within 630 ± 5 K suggesting that there is no size-dependent cation distribution. Mössbauer studies on the synthesized nanoparticles suggest that the critical particle size limit for superparamagnetism to be about 25 nm at 293 K.

  20. Superparamagnetic Particle Size Limit of Mn-Zn Ferrite Nanoparticles Synthesised Through Aqueous Method

    SciTech Connect

    Joseyphus, R. Justin; Narayanasamy, A.; Jeyadevan, B.; Shinoda, K.; Tohji, K.

    2006-05-15

    Mn0.67Zn0.33Fe2O4 nanoparticles with size ranging from 20 to 80 nm have been synthesized using the modified oxidation method. The Curie temperatures for all the samples are found to be within 630 {+-} 5 K suggesting that there is no size-dependent cation distribution. Moessbauer studies on the synthesized nanoparticles suggest that the critical particle size limit for superparamagnetism to be about 25 nm at 293 K.

  1. Composite End Points in Acute Heart Failure Research: Data Simulations Illustrate the Limitations.

    PubMed

    Brown, Paul M; Anstrom, Kevin J; Felker, G Michael; Ezekowitz, Justin A

    2016-11-01

    Composite end points are frequently used in clinical trials of investigational treatments for acute heart failure, eg, to boost statistical power and reduce the overall sample size. By incorporating multiple and varying types of clinical outcomes they provide a test for the overall efficacy of the treatment. Our objective is to compare the performance of popular composite end points in terms of statistical power and describe the uncertainty in these power estimates and issues concerning implementation. We consider several composites that incorporate outcomes of varying types (eg, time to event, categorical, and continuous). Data are simulated for 5 outcomes, and the composites are derived and compared. Power is evaluated graphically while varying the size of the treatment effects, thus describing the sensitivity of power to varying circumstances and eventualities such as opposing effects. The average z score offered the most power, although caution should be exercised when opposing effects are anticipated. Results emphasize the importance of an a priori assessment of power and scientific basis for construction, including the weighting of individual outcomes deduced from data simulations. The interpretation of a composite should be made alongside results from the individual components. The average z score offers the most power, but this should be considered in the research context and is not without its limitations. Copyright © 2016 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.

  2. Quantum limit for two-dimensional resolution of two incoherent optical point sources

    NASA Astrophysics Data System (ADS)

    Ang, Shan Zheng; Nair, Ranjith; Tsang, Mankei

    2017-06-01

    We obtain the multiple-parameter quantum Cramér-Rao bound for estimating the transverse Cartesian components of the centroid and separation of two incoherent optical point sources using an imaging system with finite spatial bandwidth. Under quite general and realistic assumptions on the point-spread function of the imaging system, and for weak source strengths, we show that the Cramér-Rao bounds for the x and y components of the separation are independent of the values of those components, which may be well below the conventional Rayleigh resolution limit. We also propose two linear-optics-based measurement methods that approach the quantum bound for the estimation of the Cartesian components of the separation once the centroid has been located. One of the methods is an interferometric scheme that approaches the quantum bound for sub-Rayleigh separations. The other method using fiber coupling can, in principle, attain the bound regardless of the distance between the two sources.

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

    PubMed

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

    2014-09-08

    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.

  4. LDPC decoder with a limited-precision FPGA-based floating-point multiplication coprocessor

    NASA Astrophysics Data System (ADS)

    Moberly, Raymond; O'Sullivan, Michael; Waheed, Khurram

    2007-09-01

    Implementing the sum-product algorithm, in an FPGA with an embedded processor, invites us to consider a tradeoff between computational precision and computational speed. The algorithm, known outside of the signal processing community as Pearl's belief propagation, is used for iterative soft-decision decoding of LDPC codes. We determined the feasibility of a coprocessor that will perform product computations. Our FPGA-based coprocessor (design) performs computer algebra with significantly less precision than the standard (e.g. integer, floating-point) operations of general purpose processors. Using synthesis, targeting a 3,168 LUT Xilinx FPGA, we show that key components of a decoder are feasible and that the full single-precision decoder could be constructed using a larger part. Soft-decision decoding by the iterative belief propagation algorithm is impacted both positively and negatively by a reduction in the precision of the computation. Reducing precision reduces the coding gain, but the limited-precision computation can operate faster. A proposed solution offers custom logic to perform computations with less precision, yet uses the floating-point format to interface with the software. Simulation results show the achievable coding gain. Synthesis results help theorize the the full capacity and performance of an FPGA-based coprocessor.

  5. Limitation of Oracle in management of vast massive points of a polygon and the solution

    NASA Astrophysics Data System (ADS)

    Liu, Ren-yi; Liu, Nan; Lu, Lizhen; Xie, Jiong

    2005-10-01

    The spatial data are processed via editing, query and other complicated analysis with spatial arithmetic operators provided by Oracle Spatial and SQL. In general, abnormal conditions will not occur in the operation with spatial arithmetic operators. In case the number of points of a polygon reaches 60000 or the number of inner rings of a polygon exceeds 200, errors may occur in the intersection overlay operation for spatial geometrical data and the connection between the system and Oracle database will be interrupted. For specific situation of GIS application in China, a polygon of a single parcel, as may occur in land resource investigation, sometimes includes 90000 points, even exceeding 120000 points, and the number of inner rings may far exceed 200. A bug is discovered by the authors in the application of spatial overlay analysis on the national city and county administrative map and national land use map at scale of 1:4000000. After a lot of tests and discuss with Oracle Corporation, the bug is finally confirmed by Oracle Corporation as a new bug (with bug ID of 3146244). To address the limitation of Oracle Spatial in processing vast massive spatial data, an algorithm of "Coordinate reduction intersection overlay" is presented after deeply analyzing the cause of the bug. The appropriate thresholds are decided depending upon the accuracy of analysis for spatial data overlay. Furthermore we have developed an extended module based on this algorithm. The correctness and validity of the solution on the algorithm have been testified by using the same spatial data in which the bug occurred for Oracle Spatial. The study results have been used in the land resource investigation and other fields in Zhejiang province of China.

  6. Integrability of particle system around a ring source as the Newtonian limit of a black ring

    NASA Astrophysics Data System (ADS)

    Igata, Takahisa; Ishihara, Hideki; Yoshino, Hirotaka

    2015-04-01

    The geodesic equation in the five-dimensional singly rotating black ring is nonintegrable, unlike the case of the Myers-Perry black hole. In the Newtonian limit of the black ring, its geodesic equation agrees with the equation of motion of a particle in the Newtonian potential due to a homogeneous ring gravitational source. In this paper, we show that the Newtonian equation of motion allows the separation of variables in the spheroidal coordinates, providing a nontrivial constant of motion quadratic in momenta. This shows that the Newtonian limit of a black ring recovers the symmetry of its geodesic system, and the geodesic chaos is caused by relativistic effects.

  7. A lower limit on the dark particle mass from dSphs

    SciTech Connect

    Angus, G.W.

    2010-03-01

    We use dwarf spheroidal galaxies as a tool to attempt to put precise lower limits on the mass of the dark matter particle, assuming it is a sterile neutrino. We begin by making cored dark halo fits to the line of sight velocity dispersions as a function of projected radius (taken from Walker et al. 2007) for six of the Milky Way's dwarf spheroidal galaxies. We test Osipkov-Merritt velocity anisotropy profiles, but find that no benefit is gained over constant velocity anisotropy. In contrast to previous attempts, we do not assume any relation between the stellar velocity dispersions and the dark matter ones, but instead we solve directly for the sterile neutrino velocity dispersion at all radii by using the equation of state for a partially degenerate neutrino gas (which ensures hydrostatic equilibrium of the sterile neutrino halo). This yields a 1:1 relation between the sterile neutrino density profile and the velocity dispersion profile, and therefore gives us an accurate estimate of the Tremaine-Gunn limit at all radii. By varying the sterile neutrino particle mass, we locate the minimum mass for all six dwarf spheroidals such that the Tremaine-Gunn limit is not exceeded at any radius (in particular at the centre). We find sizeable differences between the ranges of feasible sterile neutrino particle mass for each dwarf, but interestingly there exists a small range 270-280eV which is consistent with all dSphs at the 1-σ level.

  8. A lower limit on the dark particle mass from dSphs

    NASA Astrophysics Data System (ADS)

    Angus, G. W.

    2010-03-01

    We use dwarf spheroidal galaxies as a tool to attempt to put precise lower limits on the mass of the dark matter particle, assuming it is a sterile neutrino. We begin by making cored dark halo fits to the line of sight velocity dispersions as a function of projected radius (taken from Walker et al. 2007) for six of the Milky Way's dwarf spheroidal galaxies. We test Osipkov-Merritt velocity anisotropy profiles, but find that no benefit is gained over constant velocity anisotropy. In contrast to previous attempts, we do not assume any relation between the stellar velocity dispersions and the dark matter ones, but instead we solve directly for the sterile neutrino velocity dispersion at all radii by using the equation of state for a partially degenerate neutrino gas (which ensures hydrostatic equilibrium of the sterile neutrino halo). This yields a 1:1 relation between the sterile neutrino density profile and the velocity dispersion profile, and therefore gives us an accurate estimate of the Tremaine-Gunn limit at all radii. By varying the sterile neutrino particle mass, we locate the minimum mass for all six dwarf spheroidals such that the Tremaine-Gunn limit is not exceeded at any radius (in particular at the centre). We find sizeable differences between the ranges of feasible sterile neutrino particle mass for each dwarf, but interestingly there exists a small range 270-280eV which is consistent with all dSphs at the 1-σ level.

  9. 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

  10. 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.

  11. 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. © 2015 Society for Public Health Education.

  12. Evaluating Diagnostic Point-of-Care Tests in Resource-Limited Settings

    PubMed Central

    Drain, Paul K; Hyle, Emily P; Noubary, Farzad; Freedberg, Kenneth A; Wilson, Douglas; Bishai, William; Rodriguez, William; Bassett, Ingrid V

    2014-01-01

    Diagnostic point-of-care (POC) testing is intended to minimize the time to obtain a test result, thereby allowing clinicians and patients to make an expeditious clinical decision. As POC tests expand into resource-limited settings (RLS), the benefits must outweigh the costs. To optimize POC testing in RLS, diagnostic POC tests need rigorous evaluations focused on relevant clinical outcomes and operational costs, which differ from evaluations of conventional diagnostic tests. Here, we reviewed published studies on POC testing in RLS, and found no clearly defined metric for the clinical utility of POC testing. Therefore, we propose a framework for evaluating POC tests, and suggest and define the term “test efficacy” to describe a diagnostic test’s capacity to support a clinical decision within its operational context. We also proposed revised criteria for an ideal diagnostic POC test in resource-limited settings. Through systematic evaluations, comparisons between centralized diagnostic testing and novel POC technologies can be more formalized, and health officials can better determine which POC technologies represent valuable additions to their clinical programs. PMID:24332389

  13. 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.

  14. Microworm optode sensors limit particle diffusion to enable in vivo measurements.

    PubMed

    Ozaydin-Ince, Gozde; Dubach, J Matthew; Gleason, Karen K; Clark, Heather A

    2011-02-15

    There have been a variety of nanoparticles created for in vivo uses ranging from gene and drug delivery to tumor imaging and physiological monitoring. The use of nanoparticles to measure physiological conditions while being fluorescently addressed through the skin provides an ideal method toward minimally invasive health monitoring. Here we create unique particles that have all the necessary physical characteristics to serve as in vivo reporters, but with minimized diffusion from the point of injection. These particles, called microworms, have a cylindrical shape coated with a biocompatible porous membrane that possesses a large surface-area-to-volume ratio while maintaining a large hydrodynamic radius. We use these microworms to create fluorescent sodium sensors for use as in vivo sodium concentration detectors after subcutaneous injection. However, the microworm concept has the potential to extend to the immobilization of other types of polymers for continuous physiological detection or delivery of molecules.

  15. 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.

  16. Particle exhaust of helium plasmas with actively cooled outboard pump limiter on Tore Supra

    SciTech Connect

    Uckan, T.; Mioduszewski, P.K.; Loarer, T.; Chatelier, M.; Guilhem, D.; Lutz, T.; Nygren, R.E.; Mahdavi, M.A.

    1995-08-01

    The superconducting tokamak Tore Supra was designed for long-pulse (30-s) high input power operation. Here observations on the particle-handling characteristics of the actively cooled modular outboard pump limiter (OPL) are presented for helium discharges. The important experimental result was that a modest pumping speed (1 m{sup 3}/s) of the OPL turbomolecular pump (TMP) provided background helium exhaust. This result came about due to a well-conditioned vessel wall with helium discharges that caused no wall outgasing. The particle accountability in these helium discharges was excellent, and the well-conditioned wall did not play a significant role in the particle balance. The helium density control, 25% density drop with OPL exhaust efficiency of {approximately}1%, was possible with TMP although this may not be the case with reactive gases such as deuterium. The observed quadratic increase of the OPL neutral pressure with helium density was consistent with an improvement of the particle control with increasing plasma density.

  17. New exclusion limits on scalar and pseudoscalar axionlike particles from light shining through a wall

    NASA Astrophysics Data System (ADS)

    Ballou, R.; Deferne, G.; Finger, M.; Finger, M.; Flekova, L.; Hosek, J.; Kunc, S.; Macuchova, K.; Meissner, K. A.; Pugnat, P.; Schott, M.; Siemko, A.; Slunecka, M.; Sulc, M.; Weinsheimer, C.; Zicha, J.; Osqar Collaboration

    2015-11-01

    Physics beyond the Standard Model predicts the possible existence of new particles that can be searched at the low-energy frontier in the sub-eV range. The OSQAR photon regeneration experiment looks for "light shining through a wall" from the quantum oscillation of optical photons into "weakly interacting sub-eV particles," such as axion or axionlike particles (ALPs) in a 9 T transverse magnetic field over a length of 2 ×14.3 m . In 2014, this experiment was run with an outstanding sensitivity, using an 18.5 W continuous wave laser emitting in the green at the single wavelength of 532 nm. No regenerated photons have been detected after the wall, pushing the limits for the existence of axions and ALPs down to an unprecedented level for such type of laboratory experiment. The diphoton couplings of possible pseudoscalar and scalar ALPs can be constrained in the nearly massless limit to be less than 3.5 ×10-8 GeV-1 and 3.2 ×10-8 GeV-1 , respectively, at 95% confidence level.

  18. Characterizing the limited use of point-of-care ultrasound in Colombian emergency medicine residencies.

    PubMed

    Henwood, Patricia C; Beversluis, David; Genthon, Alissa A; Wilson, Christina N; Norwood, Brendan; Silva, Daniel; Foran, Mark; Romero, Mauricio G; Martinez, Yury B; Vargas, Luis E; Ocampo, Alejandro C; Vallejo, Carlos E; Arbelaez, Christian

    2014-02-05

    Emergency medicine (EM) is a growing specialty in Colombia with five residency programs in the country. EM leadership is interested in incorporating point-of-care (POC) ultrasound into a standardized national EM residency curriculum. This study is a nationwide survey of Colombian EM residents designed to explore the current state of POC ultrasound use within EM residencies and examine specific barriers preventing its expansion. We conducted a mix-methodology study of all available current EM residents in the five EM residencies in Colombia. The quantitative survey assessed previous ultrasound experience, current use of various applications, desire for further training, and perceived barriers to expanded use. Focus group discussions (FGDs) were conducted with current EM residents to gather additional qualitative insight into their practice patterns and perceived barriers to clinician-performed ultrasound. Sixty-nine EM residents completed the quantitative survey, a response rate of 85% of all current EM residents in Colombia; 52% of resident respondents had previously used ultrasound during their training. Of these, 58% indicated that they had performed <10 scans and 17% reported >40 scans. The most frequently used applications indicated by respondents were trauma, obstetrics, and procedures including vascular access. A quarter indicated they had previously received some ultrasound training, but almost all expressed an interest in learning more. Significant barriers included lack of trained teachers (indicated by 78% of respondents), absence of machines (57%), and limited time (41%). In FGDs, the barriers identified were inter-specialty conflicts over the control of ultrasonography, both institutionally and nationally, and program-specific curriculum decisions to include POC ultrasound. While currently limited in their access, EM residents in Colombia have a strong interest in integrating POC ultrasound into their training. Current barriers to expanded use include

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Entanglement of particles as a result of their coupling through the common background zero-point radiation field

    NASA Astrophysics Data System (ADS)

    de la Peña, L.; Valdés-Hernández, A.; Cetto, A. M.

    2010-01-01

    This paper is intended to disclose a possible physical mechanism underlying entanglement, by allowing an (otherwise classical) system of two non-interacting particles to interact with the stochastic background zero-point radiation field. The present analysis is made in the framework of linear stochastic electrodynamics (LSED), a theory that has been shown to recover the corresponding matrix formulation of quantum mechanics when applied to a one-particle (or atomic) system. We start by briefly recalling the basic elements of LSED and then extend the theory to consider the system formed of two particles. It is found that when both particles resonate to at least one common frequency of the background field, a new class of non-factorizable states emerge that correspond just to the entangled states of quantum mechanics. In the particular case of two equal particles the ensuing states are those of maximum entanglement.

  2. 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

  3. The introduction of syphilis point of care tests in resource limited settings.

    PubMed

    Marks, Michael; Mabey, David Cw

    2017-04-01

    Syphilis remains an important and preventable cause of stillbirth and neonatal mortality. About 1 million women with active syphilis become pregnant each year. Without treatment, 25% of them will deliver a stillborn baby and 33% a low birth weight baby with an increased chance of dying in the first month of life. Adverse pregnancy outcomes due to syphilis can be prevented by screening pregnant women, and treating those who test positive with a single dose of penicillin before 28 weeks' gestation. Areas covered: This manuscript covers the impact of syphilis on pregnancy outcome, the diagnosis of syphilis, with a special focus on point of care (POC) tests, and challenges to the introduction of POC tests, and their potential impact on the control and prevention of syphilis in resource limited settings. Expert commentary: POC tests for syphilis are available which meet the ASSURED criteria, and could make syphilis screening accessible to all women anywhere in the world who attend an antenatal clinic. High quality dual POC tests for HIV and syphilis could ensure that well-funded programmes for the prevention of mother to child transmission of HIV can contribute towards increased coverage of antenatal syphilis screening, and prevent more than 300,000 adverse pregnancy outcomes due to syphilis annually. Alongside investment to increase availability of syphilis POC tests, operational research is needed to understand how best to improve screening of pregnant women and to translate test availability into improved pregnancy outcomes.

  4. The six-point remainder function to all loop orders in the multi-Regge limit

    NASA Astrophysics Data System (ADS)

    Pennington, Jeffrey

    2013-01-01

    We present an all-orders formula for the six-point amplitude of planar maximally supersymmetric {N}=4 Yang-Mills theory in the leading-logarithmic approximation of multi-Regge kinematics. In the MHV helicity configuration, our results agree with an integral formula of Lipatov and Prygarin through at least 14 loops. A differential equation linking the MHV and NMHV helicity configurations has a natural action in the space of functions relevant to this problem — the single-valued harmonic polylogarithms introduced by Brown. These functions depend on a single complex variable and its conjugate, w and w * , which are quadratically related to the original kinematic variables. We investigate the all-orders formula in the near-collinear limit, which is approached as |w| → 0. Up to power-suppressed terms, the resulting expansion may be organized by powers of log |w|. The leading term of this expansion agrees with the all-orders double-leading-logarithmic approximation of Bartels, Lipatov, and Prygarin. The explicit form for the sub-leading powers of log |w| is given in terms of modified Bessel functions.

  5. Bayesian inference of whole-organ deformation dynamics from limited space-time point data.

    PubMed

    Morishita, Yoshihiro; Suzuki, Takayuki

    2014-09-21

    To understand the morphogenetic mechanisms of organ development and regeneration, it is essential to clarify the inter-hierarchical relationship between microscopic, molecular/cellular activities and organ-level tissue deformation dynamics. While the former have been studied for several decades, the latter - macroscopic geometrical information about physical tissue deformation - is often missing, especially for many vertebrates. This is mainly because live recording of detailed cell behaviors in whole tissues during vertebrate organogenesis is technically difficult. In this study, we have developed a novel method that combines snapshot lineage tracing with Bayesian statistical estimation to construct whole-organ deformation maps from landmark data on limited numbers of space-time points. Following the validation of the method using artificially generated data sets, we applied it to the analysis of tissue deformation dynamics in chick limb development. A quantitative tissue deformation map for St.23-St.24 has been constructed, and its precision has been proven by evaluating its predictive performance. Geometrical analyses of the map have revealed a spatially heterogeneous volume growth pattern that is consistent with the expression pattern of a major morphogen and anisotropic tissue deformation along an axis. Thus, our method enables deformation dynamics analysis in organogenesis using practical lineage marking techniques.

  6. A numerical analysis of contact and limit-point behavior in a class of problems of finite elastic deformation

    NASA Technical Reports Server (NTRS)

    Endo, T.; Oden, J. T.; Becker, E. B.; Miller, T.

    1984-01-01

    Finite element methods for the analysis of bifurcations, limit-point behavior, and unilateral frictionless contact of elastic bodies undergoing finite deformation are presented. Particular attention is given to the development and application of Riks-type algorithms for the analysis of limit points and exterior penalty methods for handling the unilateral constraints. Applications focus on the problem of finite axisymmetric deformations, snap-through, and inflation of thick rubber spherical shells.

  7. 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.

  8. Comment on ‘The effect of single-particle charge limits on charge distributions in dusty plasmas’

    NASA Astrophysics Data System (ADS)

    Heijmans, L. C. J.; van de Wetering, F. M. J. H.; Nijdam, S.

    2016-09-01

    It was recently suggested that the electron affinity may pose an additional upper limit on the charge of a single particle in a plasma, in addition to the electron field emission limit. Here we will, however, show that these two limits both rely on the same physical process and that the limit is only relevant for small particles, because it relies on electron tunneling. Plasma-produced particles of only several nanometres (≲ 10~\\text{nm} ) in size are actively studied, for example in the application of quantum dots and the implications of the proposed charge limit are certainly significant there. However, care must be taken to extend the results to larger particles, which are also actively studied in the field of dusty plasma physics, where typically the limit can be neglected, as we will also show.

  9. Limit cycles for the motion of finite-size particles in axisymmetric thermocapillary flows in liquid bridges

    NASA Astrophysics Data System (ADS)

    Romanò, Francesco; Kuhlmann, Hendrik C.; Ishimura, Misa; Ueno, Ichiro

    2017-09-01

    The motion of a small spherical particle of finite size in an axisymmetric thermocapillary liquid bridge is investigated numerically and experimentally. Due to the crowding of streamlines towards the free surface and the recirculating nature of the flow, advected particles visit the free surface repeatedly. The balance between centrifugal inertia and the strong short-range repulsive forces a particle experiences near the free surface leads to an attracting limit cycle for the particle motion. The existence of this limit cycle is established experimentally. It is shown that limit cycles obtained numerically by one-way-coupled simulations based on the Maxey-Riley equation and a particle-surface interaction model compare favorably with the experimental results if the thickness of the lubrication gap between the free surface and the surface of the particle is properly taken into account.

  10. Stability limits for the supercooled liquid and superheated crystal of Lennard-Jones particles

    NASA Astrophysics Data System (ADS)

    Loscar, Ernesto S.; Martin, Daniel A.; Grigera, Tomás S.

    2017-07-01

    We have studied the limits of stability in the first order liquid-solid phase transition in a Lennard-Jones system by means of the short-time relaxation method and using the bond-orientational order parameter Q6. These limits are compared with the melting line. We have paid special attention to the supercooled liquid, comparing our results with the point where the free energy cost of forming a nucleating droplet goes to zero. We also indirectly estimate the dimension associated to the critical nucleus at the spinodal, expected to be fractal according to mean field theories of nucleation.

  11. Semiclassical Theory of Inelastic Scattering of a Particle in the Near-Adiabatic Limit.

    DTIC Science & Technology

    1987-02-06

    Theory of Inelastic Scattering of a Particle in the Near-Adiabatic Limit Lit-Deh Chang and Walter Koln Department of Physic. Univesity , of California... parallel to the x-axis at a distance which we denote by wi. The procedure of Ref.(4) for obtaining R is as follows. Starting with the right-going wave (4...that this restriction is not necesary. The general features of L, and L2 are: 1. LI extends to infinity and becomes parallel to the real axis at a

  12. The effects of back-reaction on turbulence modulation in shear flows: a new exact regularized point-particle method

    NASA Astrophysics Data System (ADS)

    Gualtieri, P.; Picano, F.; Sardina, G.; Casciola, C. M.

    2011-12-01

    Particles advected by turbulent flows spread non uniformly and form small scale aggregates known as clusters where their local concentration is much higher than it is in nearby rarefaction regions. Recently it has been shown that the addition of a mean flow, through its large scale anisotropy, induces a preferential orientation of the clusters whose directionality can even increase in the smallest scales. Such finding opens new issues in presence of large mass loads, when the momentum exchange between the two phases becomes significant and the back-reaction of the particles on the carrier flow cannot be neglected. These aspects are addressed by direct numerical simulations data of particle laden homogeneous shear flows in the two-way coupling regime. Particles with Stokes number of order one induce an energy depletion of the classical inertial scales and the amplitude increase of the smallest ones where the particle back-reaction pumps energy into the turbulent eddies. We find that increased mass loads results in a broadening of the energy co-spectrum extending the range of scales driven by anisotropic production mechanisms. Such results are obtained in the context of the classical "particle in cell" method. To go beyond this approach we propose a new methodology to model particle laden two phase flows. The method is based on the exact unsteady Stokes solution around a point-particle and is intended to provide a physically consistent picture of the momentum exchange between the carrier and disperse phase.

  13. Characterizing the limited use of point-of-care ultrasound in Colombian emergency medicine residencies

    PubMed Central

    2014-01-01

    Background Emergency medicine (EM) is a growing specialty in Colombia with five residency programs in the country. EM leadership is interested in incorporating point-of-care (POC) ultrasound into a standardized national EM residency curriculum. This study is a nationwide survey of Colombian EM residents designed to explore the current state of POC ultrasound use within EM residencies and examine specific barriers preventing its expansion. Methods We conducted a mix-methodology study of all available current EM residents in the five EM residencies in Colombia. The quantitative survey assessed previous ultrasound experience, current use of various applications, desire for further training, and perceived barriers to expanded use. Focus group discussions (FGDs) were conducted with current EM residents to gather additional qualitative insight into their practice patterns and perceived barriers to clinician-performed ultrasound. Results Sixty-nine EM residents completed the quantitative survey, a response rate of 85% of all current EM residents in Colombia; 52% of resident respondents had previously used ultrasound during their training. Of these, 58% indicated that they had performed <10 scans and 17% reported >40 scans. The most frequently used applications indicated by respondents were trauma, obstetrics, and procedures including vascular access. A quarter indicated they had previously received some ultrasound training, but almost all expressed an interest in learning more. Significant barriers included lack of trained teachers (indicated by 78% of respondents), absence of machines (57%), and limited time (41%). In FGDs, the barriers identified were inter-specialty conflicts over the control of ultrasonography, both institutionally and nationally, and program-specific curriculum decisions to include POC ultrasound. Conclusion While currently limited in their access, EM residents in Colombia have a strong interest in integrating POC ultrasound into their training

  14. Point-particle effective field theory I: classical renormalization and the inverse-square potential

    NASA Astrophysics Data System (ADS)

    Burgess, C. P.; Hayman, Peter; Williams, M.; Zalavári, László

    2017-04-01

    Singular potentials (the inverse-square potential, for example) arise in many situations and their quantum treatment leads to well-known ambiguities in choosing boundary conditions for the wave-function at the position of the potential's singularity. These ambiguities are usually resolved by developing a self-adjoint extension of the original prob-lem; a non-unique procedure that leaves undetermined which extension should apply in specific physical systems. We take the guesswork out of this picture by using techniques of effective field theory to derive the required boundary conditions at the origin in terms of the effective point-particle action describing the physics of the source. In this picture ambiguities in boundary conditions boil down to the allowed choices for the source action, but casting them in terms of an action provides a physical criterion for their determination. The resulting extension is self-adjoint if the source action is real (and involves no new degrees of freedom), and not otherwise (as can also happen for reasonable systems). We show how this effective-field picture provides a simple framework for understanding well-known renormalization effects that arise in these systems, including how renormalization-group techniques can resum non-perturbative interactions that often arise, particularly for non-relativistic applications. In particular we argue why the low-energy effective theory tends to produce a universal RG flow of this type and describe how this can lead to the phenomenon of reaction catalysis, in which physical quantities (like scattering cross sections) can sometimes be surprisingly large compared to the underlying scales of the source in question. We comment in passing on the possible relevance of these observations to the phenomenon of the catalysis of baryon-number violation by scattering from magnetic monopoles.

  15. Setting limits for acceptable change in sediment particle size composition following marine aggregate dredging.

    PubMed

    Cooper, Keith M

    2012-08-01

    In the UK, Government policy requires marine aggregate extraction companies to leave the seabed in a similar physical condition after the cessation of dredging. This measure is intended to promote recovery, and the return of a similar faunal community to that which existed before dredging. Whilst the policy is sensible, and in line with the principles of sustainable development, the use of the word 'similar' is open to interpretation. There is, therefore, a need to set quantifiable limits for acceptable change in sediment composition. Using a case study site, it is shown how such limits could be defined by the range of sediment particle size composition naturally found in association with the faunal assemblages in the wider region. Whilst the approach offers a number of advantages over the present system, further testing would be required before it could be recommended for use in the regulatory context. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

  16. A fast, scalable method for the parallel evaluation of distance-limited pairwise particle interactions.

    PubMed

    Shaw, David E

    2005-10-01

    Classical molecular dynamics simulations of biological macromolecules in explicitly modeled solvent typically require the evaluation of interactions between all pairs of atoms separated by no more than some distance R, with more distant interactions handled using some less expensive method. Performing such simulations for periods on the order of a millisecond is likely to require the use of massive parallelism. The extent to which such simulations can be efficiently parallelized, however, has historically been limited by the time required for interprocessor communication. This article introduces a new method for the parallel evaluation of distance-limited pairwise particle interactions that significantly reduces the amount of data transferred between processors by comparison with traditional methods. Specifically, the amount of data transferred into and out of a given processor scales as O(R(3/2)p(-1/2)), where p is the number of processors, and with constant factors that should yield a substantial performance advantage in practice.

  17. Taking larger timesteps with speed-limited particle-in-cell simulation

    NASA Astrophysics Data System (ADS)

    Werner, Gregory; Cary, John

    2015-11-01

    Particle-in-cell (PIC) simulation is often impractical because it includes too much unnecessary physics. For example, to avoid instability in many simulations the timestep must be small enough to resolve the plasma frequency, even if plasma oscillations do not play a significant role. Other methods (e.g., MHD/fluid and hybrid approaches) allow faster simulation, but often don't include enough physics. A new method, speed-limited PIC (SLPIC) simulation, offers kinetic simulation with an arbitrary-strength approximation tied to the timestep. With a small (standard PIC) timestep, SLPIC is identical to PIC, while a larger timestep (e.g., large compared to the inverse plasma frequency) results in the relaxation of fast particles over slower timescales. SLPIC is therefore useful in situations where the particle distribution functions change slowly compared to the timestep required by PIC. For example, SLPIC can simulate collisionless sheaths with a timestep hundreds of times larger than the inverse plasma frequency. SLPIC involves relatively isolated changes of a standard PIC code and poses no extra difficulties for parallelism; complexities of PIC, such as field solvers, collisions, and boundary conditions, carry over naturally to SLPIC with little change. This work is supported by NASA.

  18. Ice slurry cooling research: Microscale study of ice particles characteristics, role of freezing point depressant, and influence on slurry fluidity

    SciTech Connect

    Hayashi, K.; Kasza, K.

    2000-05-03

    The influences of freezing-point-depressants on ice slurry characteristics in the form of ice slurry fluidity and on the microscale ice particle features are studied. The results identify microscale features of ice particles such as surface roughness that greatly influence slurry fluidity that are altered favorably by the use of a freezing point depressant. The engineering of a workable and efficient ice slurry cooling system depends very strongly on the characteristics of the individual ice particles in the slurry and, in turn, on the method of ice production. Findings from this study provide guidance on the fluidity and handleability of slurry produced by several methods currently under development and already many achieved.

  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. 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 =…

  1. 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.

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

    DOE PAGES

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

    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

  3. 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.

  4. [Distribution patterns of PAHs in soils from coking plant and the particle-size cut points of soil washing].

    PubMed

    Li, He-Lian; Chen, Jia-Jun; Wu, Wei; Piao, Xue-Song; Jiang, Lin; Shi, Zhen-Tian; Sun, Tian-Wei

    2011-04-01

    Soil particle size distribution and contaminants distribution patterns in different soil size fractions are the basis of soil treatability using soil washing method. Soil particle-size cut points are important parameters of soil washing process. According to ex situ soil washing technology, soil samples were collected in a former coking plant. The soil particle size distribution and the concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in USEPA priority list were analyzed. Tween 80 and Triton X-100 solutions were used to clean the polluted soil with different particle size. Results showed that the total concentrations of 16 PAHs ranged from 6.27 to 40.18 mg/kg dry weight in the six soil size fractions and present a bimodal distribution. The maximum individual PAH concentration mostly occurred in the 250-500 microm size fraction. The lowest individual PAH concentration was in the 50-75 microm size fraction. The removal efficiencies of PAHs in different soil size fractions depended on their initial concentrations and the characteristics of soil. The PAHs removal efficiencies in coarser size fractions were lower than that in the finer size fractions owing to their higher organic carbon content. Based on the removal efficiency of PAHs in each soil size fractions by surfactant solution and the requirements of waste volume reduction, 50 microm was determined as the particle-size cut point. Then, 82.95% volume reduction can be achieved.

  5. An expansion of general validity for the diffusive parameters of a charged particle in a zero-point field

    NASA Astrophysics Data System (ADS)

    Battezzati, M.

    2001-02-01

    The following calculations provide expressions for the drift velocity and the average diffusion coefficient, applying to diffusion in configuration space of a nonrelativistic charged particle interacting with the zero-point field of stochastic electrodynamics. The particle is assumed to evolve according to a widely popular reduced form of the Braffort-Marshall equation, which is free from runaway solutions, and supposed to be found in stationary conditions, with regard to the average values of physical quantities. The results show an interesting similarity with the equations of quantum mechanics.

  6. Application of Gauss's law space-charge limited emission model in iterative particle tracking method

    NASA Astrophysics Data System (ADS)

    Altsybeyev, V. V.; Ponomarev, V. A.

    2016-11-01

    The particle tracking method with a so-called gun iteration for modeling the space charge is discussed in the following paper. We suggest to apply the emission model based on the Gauss's law for the calculation of the space charge limited current density distribution using considered method. Based on the presented emission model we have developed a numerical algorithm for this calculations. This approach allows us to perform accurate and low time consumpting numerical simulations for different vacuum sources with the curved emitting surfaces and also in the presence of additional physical effects such as bipolar flows and backscattered electrons. The results of the simulations of the cylindrical diode and diode with elliptical emitter with the use of axysimmetric coordinates are presented. The high efficiency and accuracy of the suggested approach are confirmed by the obtained results and comparisons with the analytical solutions.

  7. Shear-induced reaction-limited aggregation kinetics of brownian particles at arbitrary concentrations.

    PubMed

    Zaccone, Alessio; Gentili, Daniele; Wu, Hua; Morbidelli, Massimo

    2010-04-07

    The aggregation of interacting brownian particles in sheared concentrated suspensions is an important issue in colloid and soft matter science per se. Also, it serves as a model to understand biochemical reactions occurring in vivo where both crowding and shear play an important role. We present an effective medium approach within the Smoluchowski equation with shear which allows one to calculate the encounter kinetics through a potential barrier under shear at arbitrary colloid concentrations. Experiments on a model colloidal system in simple shear flow support the validity of the model in the concentration range considered. By generalizing Kramers' rate theory to the presence of shear and collective hydrodynamics, our model explains the significant increase in the shear-induced reaction-limited aggregation kinetics upon increasing the colloid concentration.

  8. Application of Gauss's law space-charge limited emission model in iterative particle tracking method

    SciTech Connect

    Altsybeyev, V.V. Ponomarev, V.A.

    2016-11-01

    The particle tracking method with a so-called gun iteration for modeling the space charge is discussed in the following paper. We suggest to apply the emission model based on the Gauss's law for the calculation of the space charge limited current density distribution using considered method. Based on the presented emission model we have developed a numerical algorithm for this calculations. This approach allows us to perform accurate and low time consumpting numerical simulations for different vacuum sources with the curved emitting surfaces and also in the presence of additional physical effects such as bipolar flows and backscattered electrons. The results of the simulations of the cylindrical diode and diode with elliptical emitter with the use of axysimmetric coordinates are presented. The high efficiency and accuracy of the suggested approach are confirmed by the obtained results and comparisons with the analytical solutions.

  9. Quantum statistical imaging of particles without restriction of the diffraction limit.

    PubMed

    Cui, Jin-Ming; Sun, Fang-Wen; Chen, Xiang-Dong; Gong, Zhao-Jun; Guo, Guang-Can

    2013-04-12

    A quantum measurement method based on the quantum nature of antibunching photon emission has been developed to detect single particles without the restriction of the diffraction limit. By simultaneously counting the single-photon and two-photon signals with fluorescence microscopy, the images of nearby nitrogen-vacancy centers in diamond at a distance of 8.5±2.4  nm have been successfully reconstructed. Also their axes information was optically obtained. This quantum statistical imaging technique, with a simple experimental setup, can also be easily generalized in the measuring and distinguishing of other physical properties with any overlapping, which shows high potential in future image and study of coupled quantum systems for quantum information techniques.

  10. Well-posedness of a model of point dynamics for a limit of the Keller-Segel system

    NASA Astrophysics Data System (ADS)

    Velázquez, J. J. L.

    The purpose of this paper is to prove well-posedness for a problem that describes the dynamics of a set of points by means of a system of parabolic equations. It has been seen in Velázquez (Point dynamics in a singular limit of the Keller-Segel model. (1) motion of the concentration regions, SIAM J. Appl. Math., to appear) that the considered model is the limit of a singular perturbation problem for a system of the Keller-Segel type.

  11. 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.

  12. 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

    ... of regulated classification entities system (NAICS) code Industry Construction 236 activities... protection, Construction industry, Land development, Erosion, Sediment, Stormwater, Water pollution control... AGENCY 40 CFR Part 450 Proposed Rule Staying Numeric Limitation for the Construction and Development...

  13. 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.

  14. Avoidance model for soft particles. I. Charged spheres and rods beyond the dilute limit

    NASA Astrophysics Data System (ADS)

    Kramer, Eric M.; Herzfeld, Judith

    1999-05-01

    The avoidance model introduced by Han and Herzfeld [Mater. Res. Soc. Symp. Proc. 463, 135 (1997)] for parallel, charged spherocylinders is extended to the case of charged spherocylinders with orientational freedom. The accuracy of the theory in the dilute solution limit is checked by comparing the predicted second virial coefficient to exact values. For dilute charged spheres, the avoidance model predictions are accurate to within 17% for all values of the charge and Debye-Huckel decay length. For dilute charged spherocylinders in the long rod limit, the theory is less accurate. The second virial coefficient is overestimated by 35%-90%. However, qualitative trends in the data are captured and smaller errors are expected for shorter rods or more concentrated solutions. Isotropic-nematic phase diagrams are presented for a range of ionic strengths, rod lengths, and charges. Specific comparison is made to experimental data for colloidal suspensions of tobacco-mosaic virus (TMV) particles and the bacteriophage fd. The concentration dependence of the short range order is also discussed.

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

    SciTech Connect

    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 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.

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

    DOE PAGES

    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

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

    SciTech Connect

    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 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.

  18. STREAMING-LIMITED INTENSITIES OF SOLAR ENERGETIC PARTICLES ON THE INTENSITY PLATEAU

    SciTech Connect

    Reames, Donald V.; Ng, Chee K. E-mail: cng2@gmu.ed

    2010-11-10

    We examine the energy spectra of H, He, O, and Fe ions on the temporal intensity plateau region in large solar energetic-particle (SEP) events, where intensities may be ''streaming limited.'' Upstream of shock waves near the Sun, equilibrium may occur when outwardly streaming protons amplify resonant Alfven waves that then scatter subsequent protons sufficiently to reduce the streaming. In the largest SEP events, the so-called ground-level events (GLEs), we find proton energy spectra that are peaked near {approx}10 MeV with the energy of similar peaks decreasing for heavier ions and for smaller events. These spectra contrast sharply with spectra near the time of shock passage which rise monotonically above the plateau spectra with decreasing energy. We suggest that strong suppression of upstream ion intensities near {approx}1 MeV amu{sup -1} on the plateau occurs when those ions resonate with waves amplified earlier by streaming protons of {approx}10 MeV and above. GLEs with much lower intensities of 10-100 MeV protons on the plateau show spectra of ions that rise monotonically toward low energies with no peaking and no suppression of low-energy ions. Wave amplification by streaming protons and the pitch-angle dependence of the resonance condition are essential factors in our understanding of the limiting behavior.

  19. 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.

  20. Electrostatic limit of the T-matrix for electromagnetic scattering: Exact results for spheroidal particles

    NASA Astrophysics Data System (ADS)

    Majić, Matt R. A.; Gray, Finnian; Auguié, Baptiste; Ru, Eric C. Le

    2017-10-01

    The T-matrix, often obtained with Waterman's extended boundary condition method (EBCM), is a widely-used tool for fast calculations of electromagnetic scattering by particles. Here we investigate the quasistatic or long-wavelength limit of this approach, where it reduces to an electrostatics problem. We first present a fully electrostatic version of the EBCM/T-matrix method (dubbed ES-EBCM). Explicit expressions are then given to quantitatively express the long-wavelength limit of the EBCM matrix elements in terms of those of the ES-EBCM formalism. From this connection we deduce a number of symmetry properties of the ES-EBCM matrices. We then investigate the matrix elements of the ES-EBCM formalism in the special case of prolate spheroids. Using the general electrostatic solution in spheroidal coordinates, we derive fully analytic expressions (in the form of finite sums) for all matrix elements. Those can be used for example for studies of the convergence of the T-matrix formalism. We illustrate this by discussing the validity of the Rayleigh hypothesis, where analytical expressions highlight clearly the link with analytical continuation of series.

  1. 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.

  2. 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

    ... 40 Protection of Environment 30 2012-07-01 2012-07-01 false Toxic pollutant effluent limitations and standards for direct discharge point sources that use end-of-pipe biological treatment. 414.91 Section 414.91 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND...

  3. 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

    ... 40 Protection of Environment 29 2014-07-01 2012-07-01 true Toxic pollutant effluent limitations and standards for direct discharge point sources that do not use end-of-pipe biological treatment. 414.101 Section 414.101 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS,...

  4. 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

    ... 40 Protection of Environment 29 2014-07-01 2012-07-01 true Toxic pollutant effluent limitations and standards for direct discharge point sources that use end-of-pipe biological treatment. 414.91 Section 414.91 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND...

  5. 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

    ... 40 Protection of Environment 30 2013-07-01 2012-07-01 true Toxic pollutant effluent limitations and standards for direct discharge point sources that use end-of-pipe biological treatment. 414.91 Section 414.91 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS, PLASTICS, AND...

  6. 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

    ... 40 Protection of Environment 30 2013-07-01 2012-07-01 true Toxic pollutant effluent limitations and standards for direct discharge point sources that do not use end-of-pipe biological treatment. 414.101 Section 414.101 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS,...

  7. 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

    ... 40 Protection of Environment 30 2012-07-01 2012-07-01 false Toxic pollutant effluent limitations and standards for direct discharge point sources that do not use end-of-pipe biological treatment. 414.101 Section 414.101 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORGANIC CHEMICALS,...

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

    SciTech Connect

    Marinak, Michael Martin

    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 χe,HP from sawtooth heat pulse propagation. Values of D are typically smaller than those of χe,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.

  9. Particle-like representation for the field of a moving point charge in nonlinear electrodynamics

    NASA Astrophysics Data System (ADS)

    Gitman, D. M.; E Shabad, A.; Shishmarev, A. A.

    2017-05-01

    In a simple nonlinear model stemming from quantum electrodynamics wherein the pointlike charge has finite field-self-energy, we demonstrate that the latter can be presented as a soliton with its energy-momentum vector satisfying the standard mechanical relation characteristic of a free moving massive relativistic particle.

  10. Estimation of cirrus cloud particle fallspeeds from vertically pointing Doppler radar

    NASA Technical Reports Server (NTRS)

    Orr, Brad W.; Kropfli, Robert A.

    1993-01-01

    The First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment 2 (FIRE 2) was conducted in Coffeyville, Kansas in late 1991 to study the microphysical and radiative properties of cirrus clouds. A variety of active and passive remote sensors were employed, including an 8-mm-wavelength cloud-sensing Doppler radar developed at the Wave Propagation Laboratory (WPL). The radar, having excellent sensitivity to cloud particles (-30 dBZ at 10 km), good spatial resolution (37 m), and velocity precision (.05 ms -1), is an excellent tool for observing cirrus clouds. Having this radar directed toward the zenith for long periods of time during FIRE 2 permitted the reflectivity-weighted particle fallspeed to be related to reflectivity which allowed a separation of ice particle fallspeeds from vertical air motions. Additionally, such relationships proved useful in other multi-sensor techniques for determining vertical profiles of ice particle characteristic size and ice water content in cirrus clouds. The analysis method and the results of applying it to cirrus cloud reflectivity and velocity data collected during FIRE 2 are discussed.

  11. 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.

  12. A comparison of additional treatment processes to limit particle accumulation and microbial growth during drinking water distribution.

    PubMed

    Liu, G; Lut, M C; Verberk, J Q J C; Van Dijk, J C

    2013-05-15

    Water quality changes, particle accumulation and microbial growth occurring in pilot-scale water distribution systems fed with normally treated and additional treated groundwater were monitored over a period of almost one year. The treatment processes were ranked in the following order: nanofiltration (NF) > (better than) ultrafiltration (UF) > ion exchange (IEX) for limiting particle accumulation. A different order was found for limiting overall microbial growth: NF > IEX > UF. There were strong correlations between particle load and particle accumulation, and between nutrient load and microbial growth. It was concluded that particle accumulation can be controlled by reducing the particle load in water treatment plants; and the microbial growth can be better controlled by limiting organic nutrients rather than removing biomass in water treatment plants. The major focus of this study was on microbial growth. The results demonstrated that growth occurred in all types of treated water, including the phases of bulk water, biofilm and loose deposits. Considering the growth in different phases, similar growth in bulk water was observed for all treatments; NF strongly reduced growth both in loose deposits and in biofilm; UF promoted growth in biofilm, while strongly limiting growth in loose deposits. IEX had good efficiency in between UF and NF, limiting both growths in loose deposits and in biofilm. Significant growth was found in loose deposits, suggesting that loose deposit biomass should be taken into account for growth evaluation and/or prediction. Strong correlations were found between microbial growth and pressure drop in a membrane fouling simulator which proved that a membrane fouling simulator can be a fast growth predictor (within a week). Different results obtained by adenosine triphosphate and flow cytometry cell counts revealed that ATP can accurately describe both suspended and particle-associated biomass, and flow cytometry files of TCC measurements needs

  13. Handgrip Strength Cutoff Points to Identify Mobility Limitation in Community-dwelling Older People and Associated Factors.

    PubMed

    Vasconcelos, K S de Souza; Dias, J M Domingues; Bastone, A de Carvalho; Vieira, R Alvarenga; Andrade, A C de Souza; Perracini, M Rodrigues; Guerra, R Oliveira; Dias, R Corrêa

    2016-03-01

    Sarcopenia is defined as a progressive and generalized loss of skeletal muscle mass and strength. The specific threshold of muscle weakness that leads to mobility limitations has not been identified. To determine the best cutoff point of handgrip strength for identifying mobility limitation and to investigate the factors associated with muscle weakness and mobility limitation in community-dwelling older people. Transversal study. Cities of Belo Horizonte, Barueri and Santa Cruz in Brazil. 1374 community-dwelling older people from the Frailty study in Brazilian older people (FIBRA Study). Outcomes included muscle weakness determined according to gender-specific handgrip strength cutoff points generated by Receiver Operating Characteristic curves, mobility limitation defined as a gait speed ≤ 0.8 m/s; and a combination of both muscle weakness and mobility limitation. Associated factors included socio-demographic variables, lifestyle, anthropometrics, health conditions, use of health services and disability. The cutoff points of handgrip strength with the best balancing between sensitivity and specificity for mobility limitation were 25.8 kgf for men (sensitivity 69%, specificity 73%) and 17.4 kgf (sensitivity 60%, specificity 66%) for women. Age and disability in instrumental activities of daily living were associated with all outcomes. Women had greater odds of mobility limitation than men. Physical inactivity, body fat, diabetes, depression, sleeping disturbances, number of medications and occurrence of falls remained as significant associated factors in the final model. Handgrip strength can be a useful tool to identify mobility limitation in clinical practice. Interventions to prevent or minimize impacts of sarcopenia should stimulate physical activity and improvement of body composition in addition to the management of chronic diseases and disabilities.

  14. Overcoming the Limitations of the SIE and OME Methods in Assessing the Effects of Impurities in Temperature Fixed Points

    NASA Astrophysics Data System (ADS)

    Fahr, M.; Cundy, D. S.

    2015-08-01

    Impurities are still among the primary concerns regarding the realization of many fixed points of the International Temperature Scale (ITS-90). Several methods have been suggested to correct for these effects. The most promising strategy, with regard to the achievable uncertainty level, is the `sum of the individual estimates' (SIE) method. It involves a chemical analysis of the material and a calculation of each of the detected chemical species' effect on the phase-transition temperature of the fixed-point substance. This correction can be accurate only if all the detected impurities are completely dissolved. Given the recent evidence for insoluble impurities in metal fixed points, this strategy needs to be modified; otherwise, it may lead to an inaccurate estimation of the impurity-related effect on the fixed-point temperature. In this article, a correction method is set out that reflects the crucial distinction between soluble, insoluble, and partially soluble impurities. This `sum of the individual estimates for the dissolved species' (SIEDS) method starts from a chemical analysis but takes into account only the dissolved particles. For this purpose, different types of substances are considered as possible dissolved impurities and are discussed from a chemical point of view. For those impurities where data are insufficient, only an uncertainty estimation is possible. For this purpose, the `overall maximum estimate of the dissolved species' (OMEDS) method is derived from the SIEDS method as the new counterpart to the well-known `overall maximum estimate' (OME) method.

  15. Atomic Force Microscopy-Infrared Spectroscopy of Individual Atmospheric Aerosol Particles: Subdiffraction Limit Vibrational Spectroscopy and Morphological Analysis.

    PubMed

    Bondy, Amy L; Kirpes, Rachel M; Merzel, Rachel L; Pratt, Kerri A; Banaszak Holl, Mark M; Ault, Andrew P

    2017-09-05

    Chemical analysis of atmospheric aerosols is an analytical challenge, as aerosol particles are complex chemical mixtures that can contain hundreds to thousands of species in attoliter volumes at the most abundant sizes in the atmosphere (∼100 nm). These particles have global impacts on climate and health, but there are few methods available that combine imaging and the detailed molecular information from vibrational spectroscopy for individual particles <500 nm. Herein, we show the first application of atomic force microscopy with infrared spectroscopy (AFM-IR) to detect trace organic and inorganic species and probe intraparticle chemical variation in individual particles down to 150 nm. By detecting photothermal expansion at frequencies where particle species absorb IR photons from a tunable laser, AFM-IR can study particles smaller than the optical diffraction limit. Combining strengths of AFM (ambient pressure, height, morphology, and phase measurements) with photothermal IR spectroscopy, the potential of AFM-IR is shown for a diverse set of single-component particles, liquid-liquid phase separated particles (core-shell morphology), and ambient atmospheric particles. The spectra from atmospheric model systems (ammonium sulfate, sodium nitrate, succinic acid, and sucrose) had clearly identifiable features that correlate with absorption frequencies for infrared-active modes. Additionally, molecular information was obtained with <100 nm spatial resolution for phase separated particles with a ∼150 nm shell and 300 nm core. The subdiffraction limit capability of AFM-IR has the potential to advance understanding of particle impacts on climate and health by improving analytical capabilities to study water uptake, heterogeneous reactivity, and viscosity.

  16. 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.

  17. 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

    2014-09-02

    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

  18. 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.

  19. 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.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    Payez, Alexandre; Evoli, Carmelo; Fischer, Tobias; Giannotti, Maurizio; Mirizzi, Alessandro; Ringwald, Andreas

    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: gaγ lesssim 5.3 × 10-12 GeV-1, for ma lesssim 4.4 × 10-10 eV, and we also give its dependence at larger ALP masses ma. Moreover, we discuss how much the Fermi-LAT satellite experiment could improve this bound, should a close-enough supernova explode in the near future.

  2. 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%.

  3. Bandwidth-limited robust nonlinear sliding control of pointing and tracking maneuvers

    NASA Technical Reports Server (NTRS)

    Dwyer, Thomas A. W., III; Kim, Jinho

    1989-01-01

    It is shown how multiaxial spacecraft tracking and pointing maneuvers with known control bandwidth and given tracking error bounds can be implemented by variable-structure control in the presence of uncertain vehicle and target dynamics. It is shown how to select a nonlinear sliding surface relating attitude and rate variables, as well as a Lyapunov function in the surface variables that absorbs multiplicative model undertainties, thereby simplifying the computation of control corrections. It is then shown how a boundary layer envelope can be designed, within which the components of the surface error dynamics can be modeled as the outputs of designer-selected decoupled low-pass filters. Closed-loop stability conditions accounting for the coupling between the attitude error dynamics and the surface error dynamics are then obtained.

  4. Evaluating the six-point remainder function near the collinear limit

    NASA Astrophysics Data System (ADS)

    Papathanasiou, Georgios

    2014-10-01

    The simplicity of maximally supersymmetric Yang-Mills theory makes it an ideal theoretical laboratory for developing computational tools, which eventually find their way to QCD applications. In this contribution, we continue the investigation of a recent proposal by Basso, Sever and Vieira, for the nonperturbative description of its planar scattering amplitudes, as an expansion around collinear kinematics. The method of G. Papathanasiou, J. High Energy Phys.1311, 150 (2013), arXiv:1310.5735, for computing the integrals the latter proposal predicts for the leading term in the expansion of the six-point remainder function, is extended to one of the subleading terms. In particular, we focus on the contribution of the two-gluon bound state in the dual flux tube picture, proving its general form at any order in the coupling, and providing explicit expressions up to six loops. These are included in the ancillary file accompanying the version of this paper on the arXiv.

  5. Dose limited reliability of quantitative annular dark field scanning transmission electron microscopy for nano-particle atom-counting.

    PubMed

    De Backer, A; Martinez, G T; MacArthur, K E; Jones, L; Béché, A; Nellist, P D; Van Aert, S

    2015-04-01

    Quantitative annular dark field scanning transmission electron microscopy (ADF STEM) has become a powerful technique to characterise nano-particles on an atomic scale. Because of their limited size and beam sensitivity, the atomic structure of such particles may become extremely challenging to determine. Therefore keeping the incoming electron dose to a minimum is important. However, this may reduce the reliability of quantitative ADF STEM which will here be demonstrated for nano-particle atom-counting. Based on experimental ADF STEM images of a real industrial catalyst, we discuss the limits for counting the number of atoms in a projected atomic column with single atom sensitivity. We diagnose these limits by combining a thorough statistical method and detailed image simulations. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. 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…

  7. Evaluation of Particle Counter Technology for Detection of Fuel Contamination Detection Utilizing Fuel System Supply Point

    DTIC Science & Technology

    2014-06-19

    VA : Coordinating Research Council, Inc. Vols. 2013 Aviation Technical Committee Meetings, May 2012. 10. Dallas, A .,Block, J., Klick, P., Grove, B ...utilizing Fuel System Supply Point Joel Schmitigal U S Army Tank Automotive Research DISTRIBUTION STATEMENT A . Approved for public release; distribution...AVAILABILITY STATEMENT Distribution Statement A . Approved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT In June 2013

  8. 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…

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

    PubMed

    Patnaik, Lalit; Umanand, Loganathan

    2015-10-26

    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.

  10. 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.

  11. A practical guide to self-sustaining point-of-care ultrasound education programs in resource-limited settings.

    PubMed

    Henwood, Patricia C; Mackenzie, David C; Rempell, Joshua S; Murray, Alice F; Leo, Megan M; Dean, Anthony J; Liteplo, Andrew S; Noble, Vicki E

    2014-09-01

    The value of point-of-care ultrasound education in resource-limited settings is increasingly recognized, though little guidance exists on how to best construct a sustainable training program. Herein we offer a practical overview of core factors to consider when developing and implementing a point-of-care ultrasound education program in a resource-limited setting. Considerations include analysis of needs assessment findings, development of locally relevant curriculum, access to ultrasound machines and related technological and financial resources, quality assurance and follow-up plans, strategic partnerships, and outcomes measures. Well-planned education programs in these settings increase the potential for long-term influence on clinician skills and patient care. Copyright © 2014 American College of Emergency Physicians. Published by Mosby, Inc. All rights reserved.

  12. Effects of C(2)(n) on a vertically pointing diffraction-limited lidar.

    PubMed

    Schwiesow, R L

    1988-06-15

    Examples of different C(2)(n) profiles lead to substantially different profiles of lidar image radius in a study of the calculated performance of a diffraction-limited lidar system. The differences in image radii indicate the usefulness of a ground-based lidar for measurement of C(2)(n) profiles used to predict optical propagation phenomena. We conclude that the overall strength of the C(2)(n) profile and its general altitude dependence can be determined from inspection of the image radius profile. Approximate calculations of available and required SNRs show that a lidar with a telescope aperture of 0.5 m and a few pulses of ~1-J total transmitted energy will provide useful image radius data to an altitude of 20 km under daytime conditions. The weighting function for sensitivity of the fractional increase in image radius to changes of C(2)(n) on a logarithmic altitude scale is approximately constant with height.

  13. 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.

  14. 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.

  15. 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.

  16. Laboratory Evaluation of Light Obscuration Particle Counters used to Establish use Limits for Aviation Fuel

    DTIC Science & Technology

    2015-12-01

    August 2012 EI published the first edition of EI 1570 Handbook on electronic sensors for the detection of particulate and/or free water during...for monitoring contamination is frequently used in the hydraulics/hydraulic fluid industry . In 1999 ISO adopted ISO 11171 Hydraulic fluid power...particles/droplets identified by the particle counter. If water contamination is suspected, particle counts should be rerun with co- solvent (Resolver

  17. Quantifying intraocular scatter with near diffraction-limited double-pass point spread function

    PubMed Central

    Zhao, Junlei; Xiao, Fei; Kang, Jian; Zhao, Haoxin; Dai, Yun; Zhang, Yudong

    2016-01-01

    Measurement of the double-pass (DP) point-spread function (PSF) can provide an objective and non-invasive method for estimating intraocular scatter in the human eye. The objective scatter index (OSI), which is calculated from the DP PSF images, is commonly used to quantify intraocular scatter. In this article, we simulated the effect of higher-order ocular aberrations on OSI, and the results showed that higher-order ocular aberrations had a significant influence on OSI. Then we developed an adaptive optics DP PSF measurement system (AO-DPPMS) which was capable of correcting ocular aberrations up to eighth-order radial Zernike modes over a 6.0-mm pupil. Employing this system, we obtained DP PSF images of four subjects at the fovea. OSI values with aberrations corrected up to 2nd, 5th and 8th Zernike order were calculated respectively, from the DP PSF images of the four subjects. The experimental results were consistent with the simulation, suggesting that it is necessary to compensate for the higher-order ocular aberrations for accurate intraocular scatter estimation. PMID:27895998

  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. 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.

  20. Simulation of design-unbiased point-to-particle sampling compared to alternatives on plantation rows

    Treesearch

    Thomas B. Lynch; David Hamlin; Mark J. Ducey

    2016-01-01

    Total quantities of tree attributes can be estimated in plantations by sampling on plantation rows using several methods. At random sample points on a row, either fixed row lengths or variable row lengths with a fixed number of sample trees can be assessed. Ratio of means or mean of ratios estimators can be developed for the fixed number of trees option but are not...

  1. Searching for the QCD critical point using particle ratio fluctuations and higher moments of multiplicity distributions

    NASA Astrophysics Data System (ADS)

    Tarnowsky, Terence J.; STAR Collaboration

    2011-12-01

    Dynamical fluctuations in global conserved quantities such as baryon number, strangeness or charge may be observed near a QCD critical point. Results from new measurements of dynamical K/π, p/π and K/p ratio fluctuations are presented. The commencing of a QCD critical point search at the RHIC has extended the reach of possible measurements of dynamical K/π, p/π and K/p ratio fluctuations from Au+Au collisions to lower energies. The STAR experiment has performed a comprehensive study of the energy dependence of these dynamical fluctuations in Au+Au collisions at the energies \\sqrt{s_{NN}} = 7.7, 11.5, 39, 62.4 and 200 GeV. New results are compared to previous measurements and to theoretical predictions from several models. The measured dynamical K/π fluctuations are found to be independent of collision energy, while dynamical p/π and K/p fluctuations have a negative value that increases toward zero at top RHIC energy. Fluctuations of the higher moments of conserved quantities (net-proton and net-charge) distributions, which are predicted to be sensitive to the presence of a critical point, are also presented.

  2. Size-dependent axisymmetric vibration of functionally graded circular plates in bifurcation/limit point instability

    NASA Astrophysics Data System (ADS)

    Ashoori, A. R.; Vanini, S. A. Sadough; Salari, E.

    2017-04-01

    In the present paper, vibration behavior of size-dependent functionally graded (FG) circular microplates subjected to thermal loading are carried out in pre/post-buckling of bifurcation/limit-load instability for the first time. Two kinds of frequently used thermal loading, i.e., uniform temperature rise and heat conduction across the thickness direction are considered. Thermo-mechanical material properties of FG plate are supposed to vary smoothly and continuously throughout the thickness based on power law model. Modified couple stress theory is exploited to describe the size dependency of microplate. The nonlinear governing equations of motion and associated boundary conditions are extracted through generalized form of Hamilton's principle and von-Karman geometric nonlinearity for the vibration analysis of circular FG plates including size effects. Ritz finite element method is then employed to construct the matrix representation of governing equations which are solved by two different strategies including Newton-Raphson scheme and cylindrical arc-length method. Moreover, in the following a parametric study is accompanied to examine the effects of the several parameters such as material length scale parameter, temperature distributions, type of buckling, thickness to radius ratio, boundary conditions and power law index on the dimensionless frequency of post-buckled/snapped size-dependent FG plates in detail. It is found that the material length scale parameter and thermal loading have a significant effect on vibration characteristics of size-dependent circular FG plates.

  3. Subpixel based defocused points removal in photon-limited volumetric dataset

    NASA Astrophysics Data System (ADS)

    Muniraj, Inbarasan; Guo, Changliang; Malallah, Ra'ed; Maraka, Harsha Vardhan R.; Ryle, James P.; Sheridan, John T.

    2017-03-01

    The asymptotic property of the maximum likelihood estimator (MLE) has been utilized to reconstruct three-dimensional (3D) sectional images in the photon counting imaging (PCI) regime. At first, multiple 2D intensity images, known as Elemental images (EI), are captured. Then the geometric ray-tracing method is employed to reconstruct the 3D sectional images at various depth cues. We note that a 3D sectional image consists of both focused and defocused regions, depending on the reconstructed depth position. The defocused portion is redundant and should be removed in order to facilitate image analysis e.g., 3D object tracking, recognition, classification and navigation. In this paper, we present a subpixel level three-step based technique (i.e. involving adaptive thresholding, boundary detection and entropy based segmentation) to discard the defocused sparse-samples from the reconstructed photon-limited 3D sectional images. Simulation results are presented demonstrating the feasibility and efficiency of the proposed method.

  4. The keto-enol equilibrium in substituted acetaldehydes: focal-point analysis and ab initio limit

    NASA Astrophysics Data System (ADS)

    Balabin, Roman M.

    2011-10-01

    High-level ab initio electronic structure calculations up to the CCSD(T) theory level, including extrapolations to the complete basis set (CBS) limit, resulted in high precision energetics of the tautomeric equilibrium in 2-substituted acetaldehydes (XH2C-CHO). The CCSD(T)/CBS relative energies of the tautomers were estimated using CCSD(T)/aug-cc-pVTZ, MP3/aug-cc-pVQZ, and MP2/aug-cc-pV5Z calculations with MP2/aug-cc-pVTZ geometries. The relative enol (XHC = CHOH) stabilities (ΔE e,CCSD(T)/CBS) were found to be 5.98 ± 0.17, -1.67 ± 0.82, 7.64 ± 0.21, 8.39 ± 0.31, 2.82 ± 0.52, 10.27 ± 0.39, 9.12 ± 0.18, 5.47 ± 0.53, 7.50 ± 0.43, 10.12 ± 0.51, 8.49 ± 0.33, and 6.19 ± 0.18 kcal mol-1 for X = BeH, BH2, CH3, Cl, CN, F, H, NC, NH2, OCH3, OH, and SH, respectively. Inconsistencies between the results of complex/composite energy computations methods Gn/CBS (G2, G3, CBS-4M, and CBS-QB3) and high-level ab initio methods (CCSD(T)/CBS and MP2/CBS) were found. DFT/aug-cc-pVTZ results with B3LYP, PBE0 (PBE1PBE), TPSS, and BMK density functionals were close to the CCSD(T)/CBS levels (MAD = 1.04 kcal mol-1).

  5. Comparing point and one-dimensional neutron kinetics in the prediction of BWR limit-cycle amplitudes

    SciTech Connect

    Borkowski, J.; Robinson, G.; Baratta, A. )

    1991-01-01

    Boiling water reactor (BWR) models that are used to predict limit cycles exhibit sensitivity to the axial power profile. Because of model size limitations, point neutron kinetics are commonly used to calculate the thermal-hydraulic feedback. This type of model may employ, at best, an axial power profile that is constant in time. From simple theory, one would expect that a kinetic one-dimensional profile would follow the density wave at it traverses the heated channel and, further, that the added dimensionality would introduce stronger negative feedback and limit the amplitude of the power oscillation. The BWR model used in this analysis is intended to represent a reactor of the LaSalle type. The thermal-hydraulic model was achieved using TRAC-BF1 and steady-stated at full power for model validation purposes. Nominal full power was set to be 3,358 MW. Point kinetics and one-dimensional kinetics have been compared in terms of how BWR limit cycles are predicted. As expected, the one-dimensional calculation predicted the lower amplitude. There is still evidence, however, for radial dependence in predicting the onset and amplitude of these oscillations.

  6. 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.

  7. 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.

  8. 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.

  9. Detection of radioactive particles offshore by γ-ray spectrometry Part I: Monte Carlo assessment of detection depth limits

    NASA Astrophysics Data System (ADS)

    Maučec, M.; de Meijer, R. J.; Rigollet, C.; Hendriks, P. H. G. M.; Jones, D. G.

    2004-06-01

    A joint research project between the British Geological Survey and Nuclear Geophysics Division of the Kernfysisch Versneller Instituut, Groningen, the Netherlands, was commissioned by the United Kingdom Atomic Energy Authority to establish the efficiency of a towed seabed γ-ray spectrometer for the detection of 137Cs-containing radioactive particles offshore Dounreay, Scotland. Using the MCNP code, a comprehensive Monte Carlo feasibility study was carried out to model various combinations of geological matrices, particle burial depth and lateral displacement, source activity and detector material. To validate the sampling and absolute normalisation procedures of MCNP for geometries including multiple (natural and induced) heterogeneous sources in environmental monitoring, a benchmark experiment was conducted. The study demonstrates the ability of seabed γ-ray spectrometry to locate radioactive particles offshore and to distinguish between γ count rate increases due to particles from those due to enhanced natural radioactivity. The information presented in this study will be beneficial for estimation of the inventory of 137Cs particles and their activity distribution and for the recovery of particles from the sea floor. In this paper, the Monte Carlo assessment of the detection limits is presented. The estimation of the required towing speed and acquisition times and their application to radioactive particle detection and discrimination offshore formed a supplementary part of this study.

  10. 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

  11. Potential of mean force of association of large hydrophobic particles: towards the nanoscale limit

    PubMed Central

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

    2010-01-01

    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 Å 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 (WHAM). 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 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

  12. Hybrid fs/ps CARS for Sooting and Particle-laden Flames [PowerPoint

    SciTech Connect

    Hoffmeister, Kathryn N. Gabet; Guildenbecher, Daniel Robert; Kearney, Sean P.

    2016-01-01

    We report the application of ultrafast rotational coherent anti-Stokes Raman scattering (CARS) for temperature and relative oxygen concentration measurements in the plume emanating from a burning aluminized ammonium perchlorate propellant strand. Combustion of these metal-based propellants is a particularly hostile environment for laserbased diagnostics, with intense background luminosity, scattering and beam obstruction from hot metal particles that can be as large as several hundred microns in diameter. CARS spectra that were previously obtained using nanosecond pulsed lasers in an aluminumparticle- seeded flame are examined and are determined to be severely impacted by nonresonant background, presumably as a result of the plasma formed by particulateenhanced laser-induced breakdown. Introduction of fs/ps laser pulses enables CARS detection at reduced pulse energies, decreasing the likelihood of breakdown, while simultaneously providing time-gated elimination of any nonresonant background interference. Temperature probability densities and temperature/oxygen correlations were constructed from ensembles of several thousand single-laser-shot measurements from the fs/ps rotational CARS measurement volume positioned within 3 mm or less of the burning propellant surface. Preliminary results in canonical flames are presented using a hybrid fs/ps vibrational CARS system to demonstrate our progress towards acquiring vibrational CARS measurements for more accurate temperatures in the very high temperature propellant burns.

  13. 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.

  14. Binding affinity and adhesion force of organophosphate hydrolase enzyme with soil particles related to the isoelectric point of the enzyme.

    PubMed

    Islam, Shah Md Asraful; Yeasmin, Shabina; Islam, Md Saiful; Islam, Md Shariful

    2017-07-01

    The binding affinity of organophosphate hydrolase enzyme (OphB) with soil particles in relation to the isoelectric point (pI) was studied. Immobilization of OphB with soil particles was observed by confocal microscopy, Fourier transform infrared spectroscopy (FT-IR), and Atomic force microscopy (AFM). The calculated pI of OphB enzyme was increased from 8.69 to 8.89, 9.04 and 9.16 by the single, double and triple mutant of OphB enzyme, respectively through the replacement of negatively charged aspartate with positively charged histidine. Practically, the binding affinity was increased to 5.30%, 11.50%, and 16.80% for single, double and triple mutants, respectively. In contrast, enzyme activity of OphB did not change by the mutation of the enzyme. On the other hand, adhesion forces were gradually increased for wild type OphB enzyme (90 pN) to 96, 100 and 104 pN for single, double and triple mutants of OphB enzyme, respectively. There was an increasing trend of binding affinity and adhesion force by the increase of isoelectric point (pI) of OphB enzyme. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Point-of-care ultrasound education for non-physician clinicians in a resource-limited emergency department.

    PubMed

    Stolz, Lori A; Muruganandan, Krithika M; Bisanzo, Mark C; Sebikali, Mugisha J; Dreifuss, Bradley A; Hammerstedt, Heather S; Nelson, Sara W; Nayabale, Irene; Adhikari, Srikar; Shah, Sachita P

    2015-08-01

    To describe the outcomes and curriculum components of an educational programme to train non-physician clinicians working in a rural, Ugandan emergency department in the use of POC ultrasound. The use of point-of-care ultrasound was taught to emergency care providers through lectures, bedsides teaching and hands-on practical sessions. Lectures were tailored to care providers' knowledge base and available therapeutic means. Every ultrasound examination performed by these providers was recorded over 4.5 years. Findings of these examinations were categorised as positive, negative, indeterminate or procedural. Other radiologic studies ordered over this same time period were also recorded. A total of 22,639 patients were evaluated in the emergency department by emergency care providers, and 2185 point-of-care ultrasound examinations were performed on 1886 patients. Most commonly used were the focused assessment with sonography in trauma examination (53.3%) and echocardiography (16.4%). Point-of-care ultrasound studies were performed more frequently than radiology department-performed studies. Positive findings were documented in 46% of all examinations. We describe a novel curriculum for point-of-care ultrasound education of non-physician emergency practitioners in a resource-limited setting. These non-physician clinicians integrated ultrasound into clinical practice and utilised this imaging modality more frequently than traditional radiology department imaging with a large proportion of positive findings. © 2015 John Wiley & Sons Ltd.

  16. Simulating Biodegradation Under Mixing-limited Conditions Using Michaelis-Menten (Monod) Kinetic Expressions in a Particle Tracking Model

    NASA Astrophysics Data System (ADS)

    Ding, D.; Benson, D. A.

    2014-12-01

    Recent studies have demonstrated that the typical method of adding mass-action reaction terms to the advection-dispersion equation overestimates the field-scale reaction rates. The mismatch is usually attributed to poor mixing. A recent method, based on a purely Langragian particle tracking (PT) theoretical development, successfully reproduces the results of mixing-limited bimolecular reaction (A+B → C) from two benchmark experiments. In this numerical method, the reactants are represented by particles. The reactions are determined by a combination of two probabilities that govern whether: 1) reactant particles are collocated during a short time interval, and 2) two collocated particles favorably transform into a reaction. We extend the application of the PT method to biodegradation, which is commonly characterized by more complex Michaelis-Menten (Monod) chemical kinetics. The advantage of the PT method is that it explains the variation of reaction rate based on mixing-controlled particle collisions instead of using empirical parameters. The PT method is not only able to match the Michaelis-Menten (Monod) equation under ideal conditions, but also is able to capture the characteristics of non-ideal conditions such as imperfect mixing, disequilibrium, and limited availability of the active sites. Furthermore, for the ultimate goal of applying the Langragian PT method directly to the field scale problems, this method is implemented to the simulation of carbon tetrachloride (CT) biodegradation at the Schoolcraft, Michigan, site, where the hydraulic properties and reaction kinetics are well understood.

  17. 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.

  18. The Impact of Systematic Point-of-Care Ultrasound on Management of Patients in a Resource-Limited Setting.

    PubMed

    Stanley, Alastair; Wajanga, Bahati M K; Jaka, Hyasinta; Purcell, Rachael; Byrne, Lauren; Williams, Felicity; Rypien, Candace; Sharpe, Abigail; Laws, Patrick; Faustine, Lucas; Leeme, Tshepo; Mwabutwa, Emmanuel; Peck, Robert; Stephens, Matthew; Kaminstein, Daniel

    2017-02-08

    Although target point-of-care (POC) ultrasonography has been shown to benefit patients in resource-limited settings, it is not clear whether a systematic POC ultrasound assessment in these settings can also lead to similar changes in patient management. A predefined systematic set of POC ultrasound scans were performed on inpatients at a tertiary referral hospital in Tanzania to see if this resulted in changes to patient management. Of the 55 patients scanned, an abnormality was detected in 75% (N = 41), and a change in patient management was recommended or implemented on the basis of POC ultrasound findings in 53% (N = 29). The main impact was earlier initiation of treatment due to more rapid and accurate diagnosis. Further research is warranted to determine whether systematic POC ultrasonography would result in improved patient outcomes in resource-limited settings.

  19. Zon-Cohen singularity and negative inverse temperature in a trapped-particle limit.

    PubMed

    Nemoto, Takahiro

    2012-06-01

    We study a Brownian particle on a moving periodic potential. We focus on the statistical properties of the work done by the potential and the heat dissipated by the particle. When the period and the depth of the potential are both large, by using a boundary layer analysis, we calculate a cumulant generating function and a biased distribution function. The result allows us to understand a Zon-Cohen singularity for an extended fluctuation theorem from a viewpoint of rare trajectories characterized by a negative inverse temperature of the biased distribution function.

  20. 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.

  1. 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.

  2. Single point mutation in tick-borne encephalitis virus prM protein induces a reduction of virus particle secretion.

    PubMed

    Yoshii, Kentarou; Konno, Akihiro; Goto, Akiko; Nio, Junko; Obara, Mayumi; Ueki, Tomotaka; Hayasaka, Daisuke; Mizutani, Tetsuya; Kariwa, Hiroaki; Takashima, Ikuo

    2004-10-01

    Flaviviruses are assembled to bud into the lumen of the endoplasmic reticulum (ER) and are secreted through the vesicle transport pathway. Virus envelope proteins play important roles in this process. In this study, the effect of mutations in the envelope proteins of tick-borne encephalitis (TBE) virus on secretion of virus-like particles (VLPs), using a recombinant plasmid expression system was analysed. It was found that a single point mutation at position 63 in prM induces a reduction in secretion of VLPs. The mutation in prM did not affect the folding of the envelope proteins, and chaperone-like activity of prM was maintained. As observed by immunofluorescence microscopy, viral envelope proteins with the mutation in prM were scarce in the Golgi complex, and accumulated in the ER. Electron microscopic analysis of cells expressing the mutated prM revealed that many tubular structures were present in the lumen. The insertion of the prM mutation at aa 63 into the viral genome reduced the production of infectious virus particles. This data suggest that prM plays a crucial role in the virus budding process.

  3. 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.

  4. Numerical investigation of liver radioembolization via computational particle-hemodynamics: The role of the microcatheter distal direction and microsphere injection point and velocity.

    PubMed

    Aramburu, Jorge; Antón, Raúl; Rivas, Alejandro; Ramos, Juan Carlos; Sangro, Bruno; Bilbao, José Ignacio

    2016-11-07

    Liver radioembolization is a treatment option for patients with primary and secondary liver cancer. The procedure consists of injecting radiation-emitting microspheres via an intra-arterially placed microcatheter, enabling the deposition of the microspheres in the tumoral bed. The microcatheter location and the particle injection rate are determined during a pretreatment work-up. The purpose of this study was to numerically study the effects of the injection characteristics during the first stage of microsphere travel through the bloodstream in a patient-specific hepatic artery (i.e., the near-tip particle-hemodynamics and the segment-to-segment particle distribution). Specifically, the influence of the distal direction of an end-hole microcatheter and particle injection point and velocity were analyzed. Results showed that the procedure targeted the right lobe when injecting from two of the three injection points under study and the remaining injection point primarily targeted the left lobe. Changes in microcatheter direction and injection velocity resulted in an absolute difference in exiting particle percentage for a given liver segment of up to 20% and 30%, respectively. It can be concluded that even though microcatheter placement is presumably reproduced in the treatment session relative to the pretreatment angiography, the treatment may result in undesired segment-to-segment particle distribution and therefore undesired treatment outcomes due to modifications of any of the parameters studied, i.e., microcatheter direction and particle injection point and velocity. Copyright © 2016 Elsevier Ltd. All rights reserved.

  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, 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 Biological...

  6. 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 Biological...

  7. Determining the resolution limits of electron-beam lithography: direct measurement of the point-spread function.

    PubMed

    Manfrinato, Vitor R; Wen, Jianguo; Zhang, Lihua; Yang, Yujia; Hobbs, Richard G; Baker, Bowen; Su, Dong; Zakharov, Dmitri; Zaluzec, Nestor J; Miller, Dean J; Stach, Eric A; Berggren, Karl K

    2014-08-13

    One challenge existing since the invention of electron-beam lithography (EBL) is understanding the exposure mechanisms that limit the resolution of EBL. To overcome this challenge, we need to understand the spatial distribution of energy density deposited in the resist, that is, the point-spread function (PSF). During EBL exposure, the processes of electron scattering, phonon, photon, plasmon, and electron emission in the resist are combined, which complicates the analysis of the EBL PSF. Here, we show the measurement of delocalized energy transfer in EBL exposure by using chromatic aberration-corrected energy-filtered transmission electron microscopy (EFTEM) at the sub-10 nm scale. We have defined the role of spot size, electron scattering, secondary electrons, and volume plasmons in the lithographic PSF by performing EFTEM, momentum-resolved electron energy loss spectroscopy (EELS), sub-10 nm EBL, and Monte Carlo simulations. We expect that these results will enable alternative ways to improve the resolution limit of EBL. Furthermore, our approach to study the resolution limits of EBL may be applied to other lithographic techniques where electrons also play a key role in resist exposure, such as ion-beam-, X-ray-, and extreme-ultraviolet lithography.

  8. Upper Limits on Periodic, Pulsed Radio Emission from the X-Ray Point Source in Cassiopeia A

    NASA Astrophysics Data System (ADS)

    McLaughlin, M. A.; Cordes, J. M.; Deshpande, A. A.; Gaensler, B. M.; Hankins, T. H.; Kaspi, V. M.; Kern, J. S.

    2001-01-01

    The Chandra X-Ray Observatory recently discovered an X-ray point source near the center of Cassiopeia A, the youngest known Galactic supernova remnant. We have conducted a sensitive search for radio pulsations from this source with the Very Large Array, taking advantage of the high angular resolution of the array to resolve out the emission from the remnant itself. No convincing signatures of a dispersed, periodic source or of isolated dispersed pulses were found, whether for an isolated or a binary source. We derive upper limits of 30 and 1.3 mJy at 327 and 1435 MHz for its phase-averaged pulsed flux density. The corresponding luminosity limits are lower than those for any known radio pulsar with an age less than 104 yr. Our search sensitivities to single pulses were 25 and 1.0 Jy at 327 and 1435 MHz. For comparison, the Crab pulsar emits roughly 80 pulses per minute with flux densities greater than 100 Jy at 327 MHz and eight pulses per minute with flux densities greater than 50 Jy at 1435 MHz. These limits suggest that Cas A belongs to the growing population of young neutron stars that are radio-quiet.

  9. Laboratory Evaluation of Light Obscuration Particle Counter Contamination Limits for Aviation Fuel

    DTIC Science & Technology

    2015-11-01

    matter in aviation fuels. Specifically, free water contamination in jet fuel cannot exceed 10 parts per million (PPM) (1) and particulate matter ...free water and/or particulate matter in aviation fuel was published. In August 2012 EI published the first edition of EI 1570 Handbook on electronic...the particulate matter of fuels using light obscuration particle counters; IP 564 – Determination of the level of cleanliness of aviation turbine

  10. 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.

  11. 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.

  12. A thermodynamically consistent quasi-particle model without density-dependent infinity of the vacuum zero-point energy

    NASA Astrophysics Data System (ADS)

    Luo, Liu-jun; Cao, Jing; Yan, Yan; Sun, Wei-min; Zong, Hong-shi

    2013-11-01

    In this paper, we generalize the improved quasi-particle model proposed in Cao et al. (Phys. Lett. B 711:65, 2012) from finite temperature and zero chemical potential to the case of finite chemical potential and zero temperature, and calculate the equation of state (EOS) for (2+1) flavor Quantum Chromodynamics (QCD) at zero temperature and high density. We first calculate the partition function at finite temperature and chemical potential, then go to the limit T=0 and obtain the equation of state (EOS) for cold and dense QCD, which is important for the study of neutron stars. Furthermore, we use this EOS to calculate the quark-number density, the energy density, the quark-number susceptibility and the speed of sound at zero temperature and finite chemical potential and compare our results with the corresponding ones in the existing literature.

  13. Simulating biodegradation under mixing-limited conditions using Michaelis-Menten (Monod) kinetic expressions in a particle tracking model

    NASA Astrophysics Data System (ADS)

    Ding, Dong; Benson, David A.

    2015-02-01

    Recent studies have demonstrated that effective field-scale bioremediation reactions rates are significantly lower than batch- or lab-scale rates, when the same law of mass action is used to represent the reaction at both scales. The mismatch is usually attributed to poor mixing of reactants brought about by heterogeneity. A recent method, based on a purely Lagrangian particle tracking (PT) theoretical development, successfully reproduces the effects of mixing-limited bimolecular reaction (A + B → C) from two benchmark experiments. In this numerical method, the reactants are represented by particles, and the small-scale physics are directly translated into a combination of two probabilities that govern whether: (1) reactant particles are collocated during a short time interval, and (2) two collocated particles favorably transform into a reaction. The latter is due to thermodynamics and is independent of scale of mixing. The former directly accounts for the degree of mixing in any system. We extend the application of the PT method to biodegradation, which is commonly characterized by more complex Michaelis-Menten (Monod) chemical kinetics. The advantage of the PT method is that it explains the variation of reaction rate based on mixing-controlled particle collisions instead of using empirical parameters. The PT method not only matches the Michaelis-Menten (Monod) equation under ideal conditions, but also captures the characteristics of non-ideal conditions such as imperfect mixing, disequilibrium, and limited availability of the active sites. We show these using hypothetical systems and also successfully apply the method to a column study of carbon tetrachloride biodegradation.

  14. 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

  15. 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.

  16. From Particles and Point Clouds to Voxel Models: High Resolution Modeling of Dynamic Landscapes in Open Source GIS

    NASA Astrophysics Data System (ADS)

    Mitasova, H.; Hardin, E. J.; Kratochvilova, A.; Landa, M.

    2012-12-01

    Multitemporal data acquired by modern mapping technologies provide unique insights into processes driving land surface dynamics. These high resolution data also offer an opportunity to improve the theoretical foundations and accuracy of process-based simulations of evolving landforms. We discuss development of new generation of visualization and analytics tools for GRASS GIS designed for 3D multitemporal data from repeated lidar surveys and from landscape process simulations. We focus on data and simulation methods that are based on point sampling of continuous fields and lead to representation of evolving surfaces as series of raster map layers or voxel models. For multitemporal lidar data we present workflows that combine open source point cloud processing tools with GRASS GIS and custom python scripts to model and analyze dynamics of coastal topography (Figure 1) and we outline development of coastal analysis toolbox. The simulations focus on particle sampling method for solving continuity equations and its application for geospatial modeling of landscape processes. In addition to water and sediment transport models, already implemented in GIS, the new capabilities under development combine OpenFOAM for wind shear stress simulation with a new module for aeolian sand transport and dune evolution simulations. Comparison of observed dynamics with the results of simulations is supported by a new, integrated 2D and 3D visualization interface that provides highly interactive and intuitive access to the redesigned and enhanced visualization tools. Several case studies will be used to illustrate the presented methods and tools and demonstrate the power of workflows built with FOSS and highlight their interoperability.Figure 1. Isosurfaces representing evolution of shoreline and a z=4.5m contour between the years 1997-2011at Cape Hatteras, NC extracted from a voxel model derived from series of lidar-based DEMs.

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

    NASA Astrophysics Data System (ADS)

    Katanin, A. A.

    2015-06-01

    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 DMF2RG 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.

  18. 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.

  19. Anthropometric Cut Points for Definition of Sarcopenia Based on Incident Mobility and Physical Limitation in Older Chinese People.

    PubMed

    Woo, Jean; Leung, Jason

    2016-07-01

    The Foundation of the National Institutes for Health (FNIH) Sarcopenia Project derived cut points in appendicular lean mass (ALM) and grip strength, in relation to mobility limitation defined as a walking speed less than 0.8 m/s. Using data from the Mr and Ms Os cohort of 4,000 community-dwelling Chinese men and women aged 65 years and older and a similar data-driven approach, we examined whether the cutoff values are the same for Chinese people using baseline walking speed, incident physical limitation, and incident slow walking speed at 4 years. Physical limitation was determined by interviewer-administered questionnaire. Height, weight, body composition (using dual-energy X-ray absorptiometry), grip strength, and walking speed were measured. Cutoff values identified by Classification and Regression Tree (CART) analysis for grip strength were less than 27kg for men and less than 17kg for women. The values for ALM were less than 15.61kg in men and less than 12.42kg in women; the values for ALM/body mass index (BMI) were less than 0.72 in men and less than 0.47 in women. Using presence of physical limitation at 4 years as the outcome measure, cutoff values identified by CART analysis for grip strength were less than 27kg for men and less than 19kg for women; for ALM, less than 15.65kg for men and less than 11.26kg for women; for ALM/BMI, less than 0.69 for men and 0.52 for women. Cutoff values for grip strength were less than 28.5kg for men and less than 19kg for women; for ALM, less than 17.61kg for men and less than 10.84kg for women; for ALM/BMI, less than 0.81 for men and less than 0.53 for women. Cutoff values may differ between ethnic groups as a result of differences in body size and lifestyles. © The Author 2015. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  20. Impact of the 0.1% fuel sulfur content limit in SECA on particle and gaseous emissions from marine vessels

    NASA Astrophysics Data System (ADS)

    Zetterdahl, Maria; Moldanová, Jana; Pei, Xiangyu; Pathak, Ravi Kant; Demirdjian, Benjamin

    2016-11-01

    Emissions were measured on-board a ship in the Baltic Sea, which is a sulfur emission control area (SECA), before and after the implementation of the strict fuel sulfur content (FSC) limit of 0.1 m/m% S on the 1st of January 2015. Prior to January 2015, the ship used a heavy fuel oil (HFO) but switched to a low-sulfur residual marine fuel oil (RMB30) after the implementation of the new FSC limit. The emitted particulate matter (PM) was measured in terms of mass, number, size distribution, volatility, elemental composition, content of organics, black and elemental carbon, polycyclic aromatic hydrocarbons (PAHs), microstructure and micro-composition, along with the gaseous emissions at different operating conditions. The fuel change reduced emissions of PM mass up to 67%. The number of particles emitted remained unchanged and were dominated by nanoparticles. Furthermore, the fuel change resulted in an 80% reduction of SO2 emissions and decreased emissions of total volatile organic compounds (VOCs). The emissions of both monoaromatic and lighter polyaromatic hydrocarbon compounds increased with RMB30, while the heavy, PM-bound PAH species that belong to the carcinogenic PAH family were reduced. Emissions of BC remained similar between the two fuels. This study indicates that the use of low-sulfur residual marine fuel oil is a way to comply with the new FSC regulation and will reduce the anthropogenic load of SO2 emissions and secondary PM formed from SO2. Emissions of primary particles, however, remain unchanged and do not decrease as much as would be expected if distilled fuel was used. This applies both to the number of particles emitted and some toxic components, such as heavy metals, PAHs or elemental carbon (EC). The micro-composition analyses showed that the soot particles emitted from RMB30 combustion often do not have any trace of sulfur compared with particles from HFO combustion, which always have a sulfur content over 1%m/m. The soot sulfur content can

  1. Forced Magnetic Reconnection at an X-point: Particle-In-Cell and Ten-Moment Extended MHD Simulations

    NASA Astrophysics Data System (ADS)

    Wang, L.; Bessho, N.; Bhattacharjee, A.; Germaschewski, K.; Hakim, A.

    2013-12-01

    We will present comparative numerical studies of current sheet formation and forced magnetic reconnection at an X-point, beginning from a potential field. The problem will be simulated by the fully kinetic Particle Simulation Code (PSC) [1] and an extended ten-moment MHD code Gkeyll [2] that retains important kinetic physics, particularly, electron inertia and full electron/ion pressure tensors. Our goals are to investigate the similarities and differences between the two models, and to seek suitable parameterization of kinetic effects in the fluid models. The simulation domain is restrained in 2-D and is closed by conducting wall boundaries. The reconnection is forced by in-plane flows imposed on two opposite boundaries, where the forcing flows converge at the two boundary centers, and are slow compared to the characteristic Alfvén speed. We will compare results on the time-dependence of the reconnecting electric field (suitably normalized), as well as the structure of current sheets from PSC, Gkeyll, and an MHD code, varying ion-to-electron mass ratio and domain size. This study is carried out under the auspices of a Focus Topic in the NASA Living With a Star Targeted Research and Technology Program. [1] Fox, W., A. Bhattacharjee, and K. Germaschewski. "Magnetic reconnection in high-energy-density laser-produced plasmas." Physics of Plasmas 19 (2012): 056309. [2] Hakim, Ammar H. "Extended MHD modelling with the ten-moment equations." Journal of Fusion Energy 27.1-2 (2008): 36-43.

  2. Forced Magnetic Reconnection at an X-point: Particle-In-Cell and Ten-Moment Extended MHD Simulations

    NASA Astrophysics Data System (ADS)

    Wang, Liang; Bessho, Naoki; Bhattacharjee, Amitava; Germaschewski, Kai; Hakim, Ammar

    2013-10-01

    We will present comparative numerical studies of current sheet formation and forced magnetic reconnection at an X-point, beginning from a potential field. The problem will be simulated by the fully kinetic Particle Simulation Code (PSC) and an extended ten-moment MHD code Gkeyll that retains important kinetic physics, particularly, electron inertia and full electron/ion pressure tensors. Our goals are to investigate the similarities and differences between the two models, and to seek suitable parameterization of kinetic effects in the fluid models. The simulation domain is restrained in 2-D and is closed by conducting wall boundaries. The reconnection is forced by in-plane flows imposed on two opposite boundaries, where the forcing flows converge at the two boundary centers, and are slow compared to the characteristic Alfvén speed. We will compare results on the time-dependence of the reconnecting electric field (suitably normalized), as well as the structure of current sheets from PSC, Gkeyll, and an MHD code, varying ion-to-electron mass ratio and domain size. This study is carried out under the auspices of a Focus Topic in the NASA Living With a Star Targeted Research and Technology Program.

  3. Youden Index and optimal cut-point estimated from observations affected by a lower limit of detection.

    PubMed

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

    2008-06-01

    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. Copyright 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  4. 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

  5. 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

  6. Study of brightness and current limitations in intense charged particle beams

    NASA Astrophysics Data System (ADS)

    Reiser, M.; Guharay, S.

    1993-06-01

    Over the past several years of ONR support for our research program we have mainly studied the various schemes for intense, high-brightness H(-) beam transport and focusing in the context of its application in space defense. Detailed theoretical studies revealed that the conventional gas focusing system is not suitable as a low-energy beam transport (LEBT) system and also that there are too many unknown parameters to model accurately the behavior of partially charge-neutralized particle beams. We concluded that the electrostatic quadrupole lens system will be a good choice. We have developed a large number of simulation codes and also accessed into the existing codes in the accelerator community (e.g., PARMILA, SNOW-2D, PARMTEQ, etc.) to strengthen our analysis. During the 1992-93 contract period we focused our attention to the experimental activities on H(-) beam characterization and on the installation of a LEBT system for beam transport experiments. We have simultaneously improved our code by incorporating many practical features that we encountered during the analysis of experimental data. We have studied H(-) beams from two types of ion sources: a volume ionization type and a magnetron type source. One of the major problems in this work is to transform a highly diverging beam from the source into a highly converging one so that the output beam from the LEBT can be matched into the acceptance ellipse of an RFQ. Furthermore, the emittance budget is quite restricted.

  7. Limits on brane-world and particle dark radiation from big bang nucleosynthesis and the CMB

    NASA Astrophysics Data System (ADS)

    Sasankan, N.; Gangopadhyay, Mayukh R.; Mathews, G. J.; Kusakabe, M.

    The term dark radiation is used both to describe a noninteracting neutrino species and as a correction to the Friedmann Equation in the simplest five-dimensional (5D) RS-II brane-world cosmology. In this paper, we consider the constraints on both the meanings of dark radiation-based upon the newest results for light-element nuclear reaction rates, observed light-element abundances and the power spectrum of the Cosmic Microwave Background (CMB). Adding dark radiation during big bang nucleosynthesis (BBN) alters the Friedmann expansion rate causing the nuclear reactions to freeze out at a different temperature. This changes the final light element abundances at the end of BBN. Its influence on the CMB is to change the effective expansion rate at the surface of the last scattering. We find that the BBN constraint reduces the allowed range for both types of dark radiation at 10Mev to between ‑ 12.1% and + 6.2% of the total background energy density at 10Mev. Combining this result with fits to the CMB power spectrum, produces different results for particle versus brane-world dark radiation. In the brane-world, the range decreases from + 6.2% to ‑ 6.0%. Thus, we find that the ratio of dark radiation to the background total relativistic mass energy density ρDR/ρ is consistent with zero although there remains a very slight preference for a positive (rather than negative) contribution.

  8. Limits of preservation of samples for urine strip tests and particle counting.

    PubMed

    Kouri, Timo; Malminiemi, Outi; Penders, Joris; Pelkonen, Virpi; Vuotari, Lotta; Delanghe, Joris

    2008-01-01

    Preservation of urine samples is important for centralised laboratory services with automated instruments. A multicentre evaluation was carried out to assess preservative tubes from BD Diagnostics-Preanalytical Systems and from Greiner Bio-One for test strip reading (documented at the level of remission values), for particle counting by flow cytometers (UF-100) and for visual microscopy. Failures were expressed as percentages of originally positive samples beyond a two-fold change (+100% or -50%) from the original values. The preservative-containing BD Plus C&S plastic, BD Plus UAP and Greiner Stabilur tubes succeeded in preservation of test strip results for 6-24 h (exceptions were glucose and nitrite tests). Greiner boric acid tube showed false negative results in leukocyte, protein and ketone strip tests immediately after adding the preservative. Urine red blood cell counts (with Sysmex UF-100) were preserved for 5 h in BD Plus C&S plastic and Greiner Stabilur tubes (Greiner tubes having clearly larger preservative-related background). Bacteria or white blood cell counting succeeded in BD Plus C&S plastic tubes for 5 or 24 h, respectively, but up to 72 h in Greiner Stabilur tubes. In visual microscopy, the Greiner Stabilur tube was slightly better than the BD Plus C&S plastic tube. Urine specimens can be transported at +20 degrees C on the day of collection if preserved properly. Longer delays need careful planning with current preservatives. Flow cytometry with UF-100 is sensitive to non-dissolved preservative remnants.

  9. particles

    NASA Astrophysics Data System (ADS)

    Xia, Yu; Chen, Zhihong; Zhang, Zhengguo; Fang, Xiaoming; Liang, Guozheng

    2014-05-01

    We explore a facile and nontoxic hydrothermal route for synthesis of a Cu2ZnSnS4 nanocrystalline material by using l-cysteine as the sulfur source and ethylenediaminetetraacetic acid (EDTA) as the complexing agent. The effects of the amount of EDTA, the mole ratio of the three metal ions, and the hydrothermal temperature and time on the phase composition of the obtained product have been systematically investigated. The addition of EDTA and an excessive dose of ZnCl2 in the hydrothermal reaction system favor the generation of kesterite Cu2ZnSnS4. Pure kesterite Cu2ZnSnS4 has been synthesized at 180°C for 12 h from the reaction system containing 2 mmol of EDTA at 2:2:1 of Cu/Zn/Sn. It is confirmed by Raman spectroscopy that those binary and ternary phases are absent in the kesterite Cu2ZnSnS4 product. The kesterite Cu2ZnSnS4 material synthesized by the hydrothermal process consists of flower-like particles with 250 to 400 nm in size. It is revealed that the flower-like particles are assembled from single-crystal Cu2ZnSnS4 nanoflakes with ca. 20 nm in size. The band gap of the Cu2ZnSnS4 nanocrystalline material is estimated to be 1.55 eV. The films fabricated from the hierarchical Cu2ZnSnS4 particles exhibit fast photocurrent responses under intermittent visible-light irradiation, implying that they show potentials for use in solar cells and photocatalysis.

  10. 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.

  11. Néel-XXZ state overlaps: odd particle numbers and Lieb-Liniger scaling limit

    NASA Astrophysics Data System (ADS)

    Brockmann, M.; De Nardis, J.; Wouters, B.; Caux, J.-S.

    2014-08-01

    We specialize a recently-proposed determinant formula (Brockmann, De Nardis, Wouters and Caux 2014 J. Phys. A: Math. Theor. 47 145003) for the overlap of the zero-momentum Néel state with Bethe states of the spin-1/2 XXZ chain to the case of an odd number of downturned spins, showing that it is still of ‘Gaudin-like’ form, similar to the case of an even number of down spins. We generalize this result to the overlap of q-raised Néel states with parity-invariant Bethe states lying in a nonzero magnetization sector. The generalized determinant expression can then be used to derive the corresponding determinants and their prefactors in the scaling limit to the Lieb-Liniger (LL) Bose gas. The odd number of down spins directly translates to an odd number of bosons. We furthermore give a proof that the Néel state has no overlap with non-parity-invariant Bethe states. This is based on a determinant expression for overlaps with general Bethe states that was obtained in the context of the XXZ chain with open boundary conditions (Pozsgay 2013 arXiv:1309.4593, Kozlowski and Pozsgay 2012 J. Stat. Mech. P05021, Tsuchiya 1998 J. Math. Phys. 39 5946). The statement that overlaps with non-parity-invariant Bethe states vanish is still valid in the scaling limit to LL which means that the Bose-Einstein condensate state (De Nardis, Wouters, Brockmann and Caux 2014 Phys. Rev. A 89 033601) has zero overlap with non-parity-invariant LL Bethe states.

  12. Asymptotic-Preserving Particle-In-Cell methods for the Vlasov-Maxwell system in the quasi-neutral limit

    NASA Astrophysics Data System (ADS)

    Degond, P.; Deluzet, F.; Doyen, D.

    2017-02-01

    In this article, we design Asymptotic-Preserving Particle-In-Cell methods for the Vlasov-Maxwell system in the quasi-neutral limit, this limit being characterized by a Debye length negligible compared to the space scale of the problem. These methods are consistent discretizations of the Vlasov-Maxwell system which, in the quasi-neutral limit, remain stable and are consistent with a quasi-neutral model (in this quasi-neutral model, the electric field is computed by means of a generalized Ohm law). The derivation of Asymptotic-Preserving methods is not straightforward since the quasi-neutral model is a singular limit of the Vlasov-Maxwell model. The key step is a reformulation of the Vlasov-Maxwell system which unifies the two models in a single set of equations with a smooth transition from one to another. As demonstrated in various and demanding numerical simulations, the Asymptotic-Preserving methods are able to treat efficiently both quasi-neutral plasmas and non-neutral plasmas, making them particularly well suited for complex problems involving dense plasmas with localized non-neutral regions.

  13. 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…

  14. 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…

  15. 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.

  16. Tautomeric equilibrium and hydrogen shifts in tetrazole and triazoles: Focal-point analysis and ab initio limit

    NASA Astrophysics Data System (ADS)

    Balabin, Roman M.

    2009-10-01

    High-level ab initio electronic structure calculations, including extrapolations to the complete basis set (CBS) limit, were performed, and highly precise relative energies of five-member N-heterocycles were determined. Nitrogen-containing heterocycles studied included tautomers of tetrazole (CH2N4) and triazoles (C2H3N3). Valence focal-point analysis of 1H-tetrazole, 2H-tetrazole, 5H-tetrazole, 1H-1,2,3-triazole, 2H-1,2,3-triazole, 1H-1,2,4-triazole, and 4H-1,2,4-triazole and a number of transition state (TS) calculations were performed, using energy values determined by CCSD(T)/aug-cc-pVTZ, MP3/aug-cc-pVQZ, and MP2/aug-cc-pV5Z. An accuracy of 0.10-0.25 kcal mol-1 (35-87 cm-1) was obtained for comparison of tautomer energy differences. Relative CCSD(T)/CBS energies of 2.07, 3.98, and 6.25 kcal mol-1 for 1H-tetrazole, 1H-1,2,3-triazole, and 4H-1,2,4-triazole, respectively, were calculated. Use of electron correlation methods resulted in markedly different convergence behaviors for triazole and tetrazole tautomers. Similarly, differences in convergence were observed for TSs with respect to corresponding minima structures. It was confirmed that the MP2 method predicts an acyclic structure for 5H-tetrazole. The same was not observed for the corresponding TS geometry. Comparison with density functional theory (B3LYP) and model chemistry methods (CBS-4M and CBS-QB3) is reported.

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

    PubMed

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

    2015-01-01

    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. 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. 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 health workers.

  18. 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

  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. Systematic review shows that pathological lead points are important and frequent in intussusception and are not limited to infants.

    PubMed

    Fiegel, Henning; Gfroerer, Stefan; Rolle, Udo

    2016-11-01

    Intussusception is the most clinically relevant cause of bowel obstruction in infancy and can be idiopathic or occur as a result of pathological lead points. The incidence of these pathological lead points varies from 0.3 to 20%, and they can be mucosal, intramural or extrinsic structures. A systematic literature review was performed from 1998 to 2016 to evaluate the incidence and types of pathological lead points in paediatric intussusception, and this identified 31 epidemiological and retrospective case cohort studies, reviews and case reports. Pathological lead points were frequent in intussusceptions and not limited to infants. ©2016 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

  2. Deposition of Oral Bacteria and Polystyrene Particles to Quartz and Dental Enamel in a Parallel Plate and Stagnation Point Flow Chamber.

    PubMed

    Yang; Bos; Belder; Engel; Busscher

    1999-12-15

    The aim of this paper is to determine to what extent (i) deposition of oral bacteria and polystyrene particles, (ii) onto quartz and dental enamel with and without a salivary conditioning film, (iii) in a parallel plate (PP) and stagnation point (SP) flow chamber and at common Peclet numbers are comparable. All three bacterial strains showed different adhesion behaviors, and even Streptococcus mitis BMS, possessing a similar cell surface hydrophobicity as polystyrene particles, did not mimic polystyrene particles in its adhesion behavior, possibly as a result of the more negative zeta potentials of the polystyrene particles. The stationary endpoint adhesion of all strains, including polystyrene particles, was lower in the presence of a salivary conditioning film, while also desorption probabilities under flow were higher in the presence of a conditioning film than in its absence. Deposition onto quartz and enamel surfaces was different, but without a consistent trend valid for all strains and polystyrene particles. It is concluded that differences in experimental results exist, and the process of bacterial deposition to enamel surfaces cannot be modeled by using polystyrene particles and quartz collector surfaces. Copyright 1999 Academic Press.

  3. 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…

  4. 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…

  5. Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria

    DOE PAGES

    Yuan, Yajie; Nalewajko, Krzysztof; Zrake, Jonathan; ...

    2016-09-07

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focusmore » on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The "flares" are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model. Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. As a result, higher magnetization studies are promising and will be carried out in the future.« less

  6. Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria

    SciTech Connect

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

    2016-09-07

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We 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. As a result, higher magnetization studies are promising and will be carried out in the future.

  7. 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.

  8. Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria

    SciTech Connect

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

    2016-09-07

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We 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. As a result, higher magnetization studies are promising and will be carried out in the future.

  9. 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 finds no candidates, thereby excluding new parameter space for particles with electric charges between e / 6 and e / 200 .

  10. A comparison between a refined two-point model for the limited tokamak SOL and self-consistent plasma turbulence simulations

    NASA Astrophysics Data System (ADS)

    Wersal, C.; Ricci, P.; Loizu, J.

    2017-04-01

    A refined two-point model is derived from the drift-reduced Braginskii equations for the limited tokamak scrape-off layer (SOL) by balancing the parallel and perpendicular transport of plasma and heat and taking into account the plasma–neutral interaction. The model estimates the electron temperature drop along a field line, from a region far from the limiter to the limiter plates. Self-consistent first-principles turbulence simulations of the SOL plasma including its interaction with neutral atoms are performed with the GBS code and compared to the refined two-point model. The refined two-point model is shown to be in very good agreement with the turbulence simulation results.

  11. 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.

  12. Effects of equilibrium point displacement in limit cycle oscillation amplitude, critical frequency and prediction of critical input angular velocity in minimal brake system

    NASA Astrophysics Data System (ADS)

    Ganji, Hamed Faghanpour; Ganji, Davood Domiri

    2017-04-01

    In the present paper, brake squeal phenomenon as a noise resource in automobiles was studied. In most cases, the modeling work is carried out assuming that deformations were small; thus, equilibrium point is set zero and linearization is performed at this point. However, the equilibrium point under certain circumstances is not zero; therefore, huge errors in prediction of brake squeal may occur. In this work, large motion domains with respect to linearization importance were subjected to investigation. Nonlinear equations of motion were considered and behavior of system for COF's model was analyzed by studying amplitude and frequency of limited cycle oscillation.

  13. Quantum motion of a point particle in the presence of the Aharonov–Bohm potential in curved space

    SciTech Connect

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

    2015-11-15

    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. -- Highlights: •Motion of particle under the influence of magnetic field in curved space. •Bound state for Aharonov–Bohm problem. •Particle describing a circular path. •Determination of the self-adjoint extension parameter.

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

    PubMed

    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.

  15. 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.

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

    SciTech Connect

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

    2016-07-15

    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.

  17. 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.

  18. Waveforms produced by a scalar point particle plunging into a Schwarzschild black hole: Excitation of quasinormal modes and quasibound states

    NASA Astrophysics Data System (ADS)

    Décanini, Yves; Folacci, Antoine; Ould El Hadj, Mohamed

    2015-07-01

    With the possibility of testing massive gravity in the context of black hole physics in mind, we consider the radiation produced by a particle plunging from slightly below the innermost stable circular orbit into a Schwarzschild black hole. In order to circumvent the difficulties associated with black hole perturbation theory in massive gravity, we use a toy model in which we replace the graviton field with a massive scalar field and consider a linear coupling between the particle and this field. We compute the waveform generated by the plunging particle and study its spectral content. This permits us to highlight and interpret some important effects occurring in the plunge regime which are not present for massless fields, such as (i) the decreasing and vanishing, as the mass parameter increases, of the signal amplitude generated when the particle moves on quasicircular orbits near the innermost stable circular orbit; and (ii) in addition to the excitation of the quasinormal modes, the excitation of the quasibound states of the black hole.

  19. 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 Table 5 to Part 455 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS PESTICIDE...

  20. Generalized Ulam-Hyers Stability, Well-Posedness, and Limit Shadowing of Fixed Point Problems for α-β-Contraction Mapping in Metric Spaces

    PubMed Central

    2014-01-01

    We study the generalized Ulam-Hyers stability, the well-posedness, and the limit shadowing of the fixed point problem for new type of generalized contraction mapping, the so-called α-β-contraction mapping. Our results in this paper are generalized and unify several results in the literature as the result of Geraghty (1973) and the Banach contraction principle. PMID:24592174

  1. 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 Table 5 to Part 455 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS...

  2. 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 Table 5 to Part 455 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS PESTICIDE...

  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, 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 Table 5 to Part 455 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS...

  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 Table 5 to Part 455 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS...

  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 to Part 455 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) PESTICIDE...

  6. 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... AND STANDARDS (CONTINUED) PESTICIDE CHEMICALS Pt. 455, Table 4 Table 4 to Part 455—BAT and...

  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... AND STANDARDS (CONTINUED) PESTICIDE CHEMICALS Pt. 455, Table 4 Table 4 to Part 455—BAT and...

  8. Charged particle dynamics in multiple colliding electromagnetic waves. Survey of random walk, Lévy flights, limit circles, attractors and structurally determinate patterns

    DOE PAGES

    Bulanov, S. V.; Esirkepov, T. Zh.; Koga, J. K.; ...

    2017-03-09

    The multiple colliding laser pulse concept formulated by Bulanovet al.(Phys. Rev. Lett., vol. 104, 2010b, 220404) is beneficial for achieving an extremely high amplitude of coherent electromagnetic field. Since the topology of electric and magnetic fields of multiple colliding laser pulses oscillating in time is far from trivial and the radiation friction effects are significant in the high field limit, the dynamics of charged particles interacting with the multiple colliding laser pulses demonstrates remarkable features corresponding to random walk trajectories, limit circles, attractors, regular patterns and Lévy flights. Lastly, under extremely high intensity conditions the nonlinear dissipation mechanism stabilizes the particle motionmore » resulting in the charged particle trajectory being located within narrow regions and in the occurrence of a new class of regular patterns made by the particle ensembles.« less

  9. Reconstruction from limited single-particle diffraction data via simultaneous determination of state, orientation, intensity, and phase

    DOE PAGES

    Donatelli, Jeffrey J.; Sethian, James A.; Zwart, Peter H.

    2017-06-26

    Free-electron lasers now have the ability to collect X-ray diffraction patterns from individual molecules; however, each sample is delivered at unknown orientation and may be in one of several conformational states, each with a different molecular structure. Hit rates are often low, typically around 0.1%, limiting the number of useful images that can be collected. Determining accurate structural information requires classifying and orienting each image, accurately assembling them into a 3D diffraction intensity function, and determining missing phase information. Additionally, single particles typically scatter very few photons, leading to high image noise levels. We develop a multitiered iterative phasing algorithmmore » to reconstruct structural information from singleparticle diffraction data by simultaneously determining the states, orientations, intensities, phases, and underlying structure in a single iterative procedure. We leverage real-space constraints on the structure to help guide optimization and reconstruct underlying structure from very few images with excellent global convergence properties. We show that this approach can determine structural resolution beyond what is suggested by standard Shannon sampling arguments for ideal images and is also robust to noise.« less

  10. Multi-directional measurements of high energy particles from the Sun-Earth L1 point with STEPS

    NASA Astrophysics Data System (ADS)

    Goyal, S. K.; Shanmugam, M.; Patel, A. R.; Ladiya, T.; Tiwari, Neeraj K.; Banerjee, S. B.; Vadawale, S. V.; Janardhan, P.; Chakrabarty, D.; Srinivas, A. R.; Shukla, P.; Kumar, P.; Subramanian, K. P.; Bapat, B.; Adhyaru, P. R.

    2016-07-01

    Aditya Solar wind Particle EXperiment (ASPEX) is one of the scientific experiments onboard the Aditya-L1 mission, the first Indian solar mission planned to be launched in the year of 2019. The primary objective of the ASPEX experiment is to carry out in-situ, multi-directional measurements of solar wind ions in the energy range of 100 eV/n to 5 MeV/n. ASPEX instrument has been configured into two subsystems: Solar Wind Ion Spectrometer (SWIS) and Supra Thermal & Energetic Particle Spectrometer (STEPS). SWIS will measure the angular and energy distribution of solar wind ions in the energy range of 100 eV to 20 keV and STEPS will measure the energy spectrum of high energetic particles from six directions covering the energy range of 20 keV/n to 5 MeV/n. This paper presents the overall configuration of the STEPS subsystem with preliminary results obtained from the bread board model.

  11. 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.

  12. Driving simulator validation of driver behavior with limited safe vantage points for data collection in work zones.

    PubMed

    Bham, Ghulam H; Leu, Ming C; Vallati, Manoj; Mathur, Durga R

    2014-06-01

    This study is aimed at validating a driving simulator (DS) for the study of driver behavior in work zones. A validation study requires field data collection. For studies conducted in highway work zones, the availability of safe vantage points for data collection at critical locations can be a significant challenge. A validation framework is therefore proposed in this paper, demonstrated using a fixed-based DS that addresses the issue by using a global positioning system (GPS). The validation of the DS was conducted using objective and subjective evaluations. The objective validation was divided into qualitative and quantitative evaluations. The DS was validated by comparing the results of simulation with the field data, which were collected using a GPS along the highway and video recordings at specific locations in a work zone. The constructed work zone scenario in the DS was subjectively evaluated with 46 participants. The objective evaluation established the absolute and relative validity of the DS. The mean speeds from the DS data showed excellent agreement with the field data. The subjective evaluation indicated realistic driving experience by the participants. The use of GPS showed that continuous data collected along the highway can overcome the challenges of unavailability of safe vantage points especially at critical locations. Further, a validated DS can be used for examining driver behavior in complex situations by replicating realistic scenarios. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Wave-particle and wave-wave interactions in hot plasmas: a French historical point of view

    NASA Astrophysics Data System (ADS)

    Laval, Guy; Pesme, Denis; Adam, Jean-Claude

    2016-11-01

    The first researches on nuclear fusion for energy applications marked the entrance of hot plasmas into the laboratory. It became necessary to understand the behavior of such plasmas and to learn how to manipulate them. Theoreticians and experimentalists, building on the foundations of empirical laws, had to construct this new plasma physics from first principles and to explain the results of more and more complicated experiments. Along this line, two important topics emerged: wave-particle and wave-wave interactions. Here, their history is recalled as it has been lived by a French team from the end of the sixties to the beginning of the twenty-first century.

  14. Patient needs and point-of-care requirements for HIV load testing in resource-limited settings.

    PubMed

    Usdin, Martine; Guillerm, Martine; Calmy, Alexandra

    2010-04-15

    Medecins Sans Frontieres (MSF) is an international, independent medical nongovernmental organization. One way in which MSF acts to improve patient care is to assist in the identification and development of adapted and appropriate tools for use in resource-limited settings. One strategy to achieve this goal is through active collaborations with scientists and developers, to make some of the field needs known and to help define the medical strategy behind the implementation of new diagnostic tests. Tests used in the field need to be effective in often extreme conditions and must also deliver high-quality, reliable results that can be used in the local context. In this article, we discuss some patient and health care provider needs for human immunodeficiency virus (HIV) load measurement in resource-limited settings. This is just one of the areas in which effective, quality tools are desperately needed, not only by MSF and other international nongovernmental organizations, but also by many other health service providers. We hope that, by clearly defining the needs of patients in MSF clinics-as well as we can assess this-and by explaining why these tools are needed, how they should perform, and how their results can be integrated into a program, we will encourage the development of such tools and hasten their implementation in areas where they are so urgently needed.

  15. Complete study of suprathermal oxygen particles in Mars upper thermosphere and exosphere over the range of limiting conditions

    NASA Astrophysics Data System (ADS)

    Valeille, Arnaud; Combi, Michael; Tenishev, Valeriy; Bougher, Stephen; Nagy, Andrew

    As a part of a global effort, the dynamics of the flow of energetic particles through the Martian upper atmosphere has been studied. Being the most important reaction, the dissociative recombination (DR) of O2+ is responsible of most of the production of hot atomic oxygen deep in the thermosphere of Mars. To understand the Martian exosphere, it is then necessary to employ a global kinetic model which can include a self-consistent description of both thermosphere collisional region and exospheric collisionless domain. In this study, we have used our Direct Simulation Monte Carlo (DSMC) model in combination with the 3D Mars Thermosphere General Circulation Model (MTGCM) of Bougher et al. to describe self-consistently the region of the upper thermosphere where the exosphere is generated, the entire exosphere, and its feedback into the thermosphere generally. Along with the effect of ionization, the DSMC method allows us to provide profiles of density and temperature, atmospheric loss rates and return fluxes as functions of the Solar Zenith Angle (SZA) for all cases considered. To present a complete description of this physical problem we examined several of the most limiting cases spanning spatial and temporal domains. Along with solar activity variability, these include comparisons between the polar meridian and the equator at equinox and between the summer and winter polar meridians at perihelion and aphelion conditions, respectively. The contribution of the different physical and chemical escape processes was studied and compared for the present but also earlier Mars epochs characterized by different solar inputs (1 EUV, 3 EUV and 5 EUV) for Equinox conditions. Support for this work comes from NASA Mars Fundamental Research grant NNG05GL80G.

  16. 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%.

  17. 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.

  18. 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.

  19. Search for Point-like Sources of Ultra-high Energy Neutrinos at the Pierre Auger Observatory and Improved Limit on the Diffuse Flux of Tau Neutrinos

    NASA Astrophysics Data System (ADS)

    Pierre Auger Collaboration; Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Antiči'c, T.; Aramo, C.; Arganda, E.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Badescu, A. M.; Balzer, M.; Barber, K. B.; Barbosa, A. F.; Bardenet, R.; Barroso, S. L. C.; Baughman, B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellétoile, A.; Bellido, J. A.; BenZvi, S.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanch-Bigas, O.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Brogueira, P.; Brown, W. C.; Bruijn, R.; Buchholz, P.; Bueno, A.; Buroker, L.; Burton, R. E.; Caballero-Mora, K. S.; Caccianiga, B.; Caramete, L.; Caruso, R.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazon, L.; Cester, R.; Chauvin, J.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chirinos Diaz, J.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cook, H.; Cooper, M. J.; Coppens, J.; Cordier, A.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; De Donato, C.; de Jong, S. J.; De La Vega, G.; de Mello Junior, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; de Vries, K. D.; del Peral, L.; del Río, M.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Díaz Castro, M. L.; Diep, P. N.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; Ebr, J.; Engel, R.; Erdmann, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fliescher, S.; Fracchiolla, C. E.; Fraenkel, E. D.; Fratu, O.; Fröhlich, U.; Fuchs, B.; Gaior, R.; Gamarra, R. F.; Gambetta, S.; García, B.; Garcia Roca, S. T.; Garcia-Gamez, D.; Garcia-Pinto, D.; Gascon Bravo, A.; Gemmeke, H.; Ghia, P. L.; Giller, M.; Gitto, J.; Glass, H.; Gold, M. S.; Golup, G.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; Gookin, B.; Gorgi, A.; Gouffon, P.; Grashorn, E.; Grebe, S.; Griffith, N.; Grigat, M.; Grillo, A. F.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Herve, A. E.; Hojvat, C.; Hollon, N.; Holmes, V. C.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Ionita, F.; Italiano, A.; Jansen, S.; Jarne, C.; Jiraskova, S.; Josebachuili, M.; Kadija, K.; Kampert, K. H.; Karhan, P.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kelley, J. L.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapp, J.; Koang, D.-H.; Kotera, K.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kulbartz, J. K.; Kunka, N.; La Rosa, G.; Lachaud, C.; LaHurd, D.; Latronico, L.; Lauer, R.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Macolino, C.; Maldera, S.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, J.; Marin, V.; Maris, I. C.; Marquez Falcon, H. R.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mazur, P. O.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Mertsch, P.; Meurer, C.; Meyhandan, R.; Mi'canovi'c, S.; Micheletti, M. I.; Minaya, I. A.; Miramonti, L.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, E.; Moreno, J. C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Nhung, P. T.; Niechciol, M.; Niemietz, L.; Nierstenhoefer, N.; Nitz, D.; Nosek, D.; Nožka, L.; Oehlschläger, J.; Olinto, A.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Parente, G.; Parizot, E.; Parra, A.; Pastor, S.; Paul, T.; Pech, M.; Peķala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Petrera, S.; Petrolini, A.; Petrov, Y.; Pfendner, C.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Ponce, V. H.; Pontz, M.; Porcelli, A.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rivera, H.; Rizi, V.; Roberts, J.; Rodrigues de Carvalho, W.; Rodriguez, G.; Rodriguez Cabo, I.; Rodriguez Martino, J.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Rouillé-d'Orfeuil, B.; Roulet, E.; Rovero, A. C.; Rühle, C.; Saftoiu, A.; Salamida, F.; Salazar, H.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarkar, S.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, A.; Scholten, O.; Schoorlemmer, H.; Schovancova, J.; Schovánek, P.; Schröder, F.; Schulte, S.; Schuster, D.; Sciutto, S. J.; Scuderi, M.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Silva Lopez, H. H.; Sima, O.; 'Smiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Spinka, H.; Squartini, R.; Srivastava, Y. N.; Stanic, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Šuša, T.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Tapia, A.; Tartare, M.; Taşcău, O.; Tcaciuc, R.; Thao, N. T.; Thomas, D.; Tiffenberg, J.; Timmermans, C.; Tkaczyk, W.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Travnicek, P.; Tridapalli, D. B.; Tristram, G.; Trovato, E.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van den Berg, A. M.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Wahlberg, H.; Wahrlich, P.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Westerhoff, S.; Whelan, B. J.; Widom, A.; Wieczorek, G.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Wommer, M.; Wundheiler, B.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano Garcia, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.

    2012-08-01

    The surface detector array of the Pierre Auger Observatory can detect neutrinos with energy E ν between 1017 eV and 1020 eV from point-like sources across the sky south of +55° and north of -65° declinations. A search has been performed for highly inclined extensive air showers produced by the interaction of neutrinos of all flavors in the atmosphere (downward-going neutrinos), and by the decay of tau leptons originating from tau neutrino interactions in Earth's crust (Earth-skimming neutrinos). No candidate neutrinos have been found in data up to 2010 May 31. This corresponds to an equivalent exposure of ~3.5 years of a full surface detector array for the Earth-skimming channel and ~2 years for the downward-going channel. An improved upper limit on the diffuse flux of tau neutrinos has been derived. Upper limits on the neutrino flux from point-like sources have been derived as a function of the source declination. Assuming a differential neutrino flux k PS · E -2 ν from a point-like source, 90% confidence level upper limits for k PS at the level of ≈5 × 10-7 and 2.5 × 10-6 GeV cm-2 s-1 have been obtained over a broad range of declinations from the searches for Earth-skimming and downward-going neutrinos, respectively.

  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.

  1. Analysis of an ultrasonically rotating droplet by moving particle semi-implicit and distributed point source method in a rotational coordinate

    NASA Astrophysics Data System (ADS)

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

    2017-07-01

    Numerical analysis on the rotation of an ultrasonically levitated droplet in centrifugal coordinate is discussed. A droplet levitated in an acoustic chamber is simulated using the distributed point source method and the moving particle semi-implicit method. Centrifugal coordinate is adopted to avoid the Laplacian differential error, which causes numerical divergence or inaccuracy in the global coordinate calculation. Consequently, the duration of calculation stability has increased 30 times longer than that in a the previous paper. Moreover, the droplet radius versus rotational acceleration characteristics show a similar trend to the theoretical and experimental values in the literature.

  2. 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)

  3. Analytical and Clinical Validation of a Point-of-Care Cardiac Troponin T Test with an Improved Detection Limit.

    PubMed

    Jungbauer, Carsten; Hupf, Julian; Giannitsis, Evangelos; Frick, Johann; Slagman, Anna; Ehret, Christoph; Herbert, Nicolas; Jung, Christine; Zerback, Rainer; Bertsch, Thomas; Christ, Michael

    2017-04-01

    The point-of-care test Roche CARDIAC POC Troponin T (PoC TnT) is an improved assay which has been developed for the Roche cobas h 232 system. We performed a multicentre evaluation (four sites) to assess the analytical performance of the PoC TnT assay and to compare it with the central laboratory Elecsys® troponin T high sensitive (lab cTnT-hs) assay. The relative mean differences found in method comparisons of PoC TnT vs. lab cTnT-hs ranged from -4.1% to +6.8%. Additionally, there was good concordance between PoC TnT and lab cTnT-hs for the number of samples with troponin T values below the measuring range of 40 ng/L. Lot-to-lot differences of PoC TnT ranged from -8.6% to +4.6%. Within-series coefficients of variation (CV) resulting from 81 ten-fold measurements with patient samples were 9.3%, 11.8%, and 12.9% in the low (40 to < 200 ng/L), medium (200 to < 600 ng/L), and high (600 to 2000 ng/L) measuring range, respectively. Using the system quality control, the mean CV for between-day imprecision was 11.3%. No interference was observed by triglycerides (up to 11.4 mmol/L), bilirubin (up to 376 µmol/L), hemoglobin (up to 0.12 mmol/L), biotin (up to 30 µg/L), rheumatoid factor (up to 200 IU/mL), or with 52 standard or cardiovascular drugs at therapeutic concentrations. There was no influence on the results by varying hematocrit values in a range from 25% to 53%. However, interferences with human anti-mouse antibodies were found. No significant influence on the results was found with PoC TnT by using sample volumes between 135 to 165 µL. High troponin T concentrations up to 500 µg/L did not lead to false low results, indicating no high-concentration hook effect. No cross-reactivity was found between the PoC TnT assay and human skeletal troponin T up to 1000 µg/L (< 0.05%). Diagnostic sensitivity and specificity data of a subpopulation (23 patients) of this study are in agreement with results of another large pre-hospital study. The PoC TnT assay showed good

  4. 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

  5. Rear seat occupant safety: an investigation of a progressive force-limiting, pretensioning 3-point belt system using adult PMHS in frontal sled tests.

    PubMed

    Forman, Jason; Lopez-Valdes, Francisco; Lessley, David; Kindig, Matthew; Kent, Richard; Ridella, Stephen; Bostrom, Ola

    2009-11-01

    Rear seat adult occupant protection is receiving increased attention from the automotive safety community. Recent anthropomorphic test device (ATD) studies have suggested that it may be possible to improve kinematics and reduce injuries to rear seat occupants in frontal collisions by incorporating shoulder-belt force-limiting and pretensioning (FL+PT) technologies into rear seat 3-point belt restraints. This study seeks to further investigate the feasibility and potential kinematic benefits of a FL+PT rear seat, 3-point belt restraint system in a series of 48 kmh frontal impact sled tests (20 g, 80 ms sled acceleration pulse) performed with post mortem human surrogates (PMHS). Three PMHS were tested with a 3-point belt restraint with a progressive (two-stage) force limiting and pretensioing retractor in a sled buck representing the rear seat occupant environment of a 2004 mid-sized sedan. Instrumentation included belt tension load cells, accelerometers on the head and at multiple locations on the spine, and chestbands to measure the chest deformation contours in the transverse plane. The kinematics of the subjects were quantified using off-board, high-speed video. The results of these tests were then compared to matched PMHS tests, published in 2008, performed in the same environment with a standard (not-force limited, not pretensioning) 3-point belt restraint. The FL+PT restraint system resulted in significant (p<0.05) decreases in peak shoulder belt tension (average +/- standard deviation: 4.4 +/- 0.13 kN with the FL+PT belt, 7.8 +/- 0. 6 kN with the standard belt) and 3 ms-resultant, mid-spine acceleration (FL+PT: 34 +/- 3.8 g; standard belt: 44 +/- 1.4 g). The FL+PT tests also produced more forward torso rotation caused by decreased forward excursion of the pelvis and increased payout out of the shoulder belt by the force-limiter. These results support the previous ATD studies that suggest that it may be possible to improve the kinematics of rear seat occupants

  6. 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.

  7. Primary photochemical processes in P700-enriched photosystem I particles: Trap-limited excitation decay and primary charge separation

    SciTech Connect

    Kumazaki, Shigeichi; Kandori, Hideki; Petek, Hrvoje; Yoshihara, Keitaro ); Ikegami, Isamu )

    1994-10-06

    The energy transfer and primary charge separation in photosystem I (PS I) reaction center (RC) particles with an antenna size of 12 chlorophyll/P700 were studied by subpicosecond transient absorption spectroscopy. Upon excitation of the particles at 638 nm under the donor chlorophyll (P700)-neutral conditions, the transition from the excited state of chlorophylls to the charge-separated state of P700[sup +]A[sub 0][sup [minus

  8. Two-dimensional full particle simulation of the flow patterns in the scrape-off-layer plasma for upper- and lower-null point divertor configurations in tokamaks

    NASA Astrophysics Data System (ADS)

    Takizuka, T.; Shimizu, K.; Hayashi, N.; Hosokawa, M.; Yagi, M.

    2009-07-01

    The plasma flow in the scrape-off-layer (SOL) plays an important role in particle control in magnetic fusion reactors. The flow is expected to expel helium ashes and to retain impurities in the divertor region, if it is directed towards the divertor plate. It has been experimentally observed, however, that the flow direction is sometimes opposite; from the outer plate side to the SOL middle side in the outer SOL region of tokamaks. In order to study these SOL flow patterns by fully taking account of the kinetic effects, a full particle code, PARASOL, is applied to a tokamak plasma with the upper-null point (UN) or lower-null point (LN) divertor configuration for the downward ion ∇B drift. PARASOL simulations for the medium aspect ratio (A = 5.5) reveal the variation of the flow pattern. For the UN case with the ion ∇B drift away from the null point, the flow velocity Vpar parallel to the magnetic field is formed almost in-out symmetrically. In the inner SOL region Vpar is directed to the inner divertor plate and in the outer SOL Vpar is directed to the outer plate. The stagnation point (Vpar = 0) is located symmetrically at the bottom. On the other hand for the LN case with the ion ∇B drift towards the null point, Vpar in the outer SOL region has a backward flow pattern. The stagnation point moves below the mid-plane of the outer SOL and Vpar in the mid-plane outer SOL is directed to the inner plate. These simulation results are very similar to the experimental results. Simulations are carried out by changing the aspect ratio and by artificially cutting the electric field. It is found that the banana motion of trapped ions is very important for the formation of the flow pattern in addition to the self-consistent electric field. The trapped-ion effects can be stronger than the electric-field effects for the standard tokamaks with A < 5.

  9. Parameter identification for continuous point emission source based on Tikhonov regularization method coupled with particle swarm optimization algorithm.

    PubMed

    Ma, Denglong; Tan, Wei; Zhang, Zaoxiao; Hu, Jun

    2017-03-05

    In order to identify the parameters of hazardous gas emission source in atmosphere with less previous information and reliable probability estimation, a hybrid algorithm coupling Tikhonov regularization with particle swarm optimization (PSO) was proposed. When the source location is known, the source strength can be estimated successfully by common Tikhonov regularization method, but it is invalid when the information about both source strength and location is absent. Therefore, a hybrid method combining linear Tikhonov regularization and PSO algorithm was designed. With this method, the nonlinear inverse dispersion model was transformed to a linear form under some assumptions, and the source parameters including source strength and location were identified simultaneously by linear Tikhonov-PSO regularization method. The regularization parameters were selected by L-curve method. The estimation results with different regularization matrixes showed that the confidence interval with high-order regularization matrix is narrower than that with zero-order regularization matrix. But the estimation results of different source parameters are close to each other with different regularization matrixes. A nonlinear Tikhonov-PSO hybrid regularization was also designed with primary nonlinear dispersion model to estimate the source parameters. The comparison results of simulation and experiment case showed that the linear Tikhonov-PSO method with transformed linear inverse model has higher computation efficiency than nonlinear Tikhonov-PSO method. The confidence intervals from linear Tikhonov-PSO are more reasonable than that from nonlinear method. The estimation results from linear Tikhonov-PSO method are similar to that from single PSO algorithm, and a reasonable confidence interval with some probability levels can be additionally given by Tikhonov-PSO method. Therefore, the presented linear Tikhonov-PSO regularization method is a good potential method for hazardous emission

  10. NOTE: Detection limits for ferrimagnetic particle concentrations using magnetic resonance imaging based proton transverse relaxation rate measurements

    NASA Astrophysics Data System (ADS)

    Pardoe, H.; Chua-anusorn, W.; St. Pierre, T. G.; Dobson, J.

    2003-03-01

    A clinical magnetic resonance imaging (MRI) system was used to measure proton transverse relaxation rates (R2) in agar gels with varying concentrations of ferrimagnetic iron oxide nanoparticles in a field strength of 1.5 T. The nanoparticles were prepared by coprecipitation of ferric and ferrous ions in the presence of either dextran or polyvinyl alcohol. The method of preparation resulted in loosely packed clusters (dextran) or branched chains (polyvinyl alcohol) of particles containing of the order of 600 and 400 particles, respectively. For both methods of particle preparation, concentrations of ferrimagnetic iron in agar gel less than 0.01 mg ml-1 had no measurable effect on the value of R2 for the gel. The results indicate that MRI-based R2 measurements using 1.5 T clinical scanners are not quite sensitive enough to detect the very low concentrations of nanoparticulate biogenic magnetite reported in human brain tissue.

  11. SEARCH FOR POINT-LIKE SOURCES OF ULTRA-HIGH ENERGY NEUTRINOS AT THE PIERRE AUGER OBSERVATORY AND IMPROVED LIMIT ON THE DIFFUSE FLUX OF TAU NEUTRINOS

    SciTech Connect

    Abreu, P.; Andringa, S.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muniz, J.; Alves Batista, R.; Ambrosio, M.; Aramo, C.; Aminaei, A.; Anchordoqui, L.; Antici'c, T.; Collaboration: Pierre Auger Collaboration; and others

    2012-08-10

    The surface detector array of the Pierre Auger Observatory can detect neutrinos with energy E{sub {nu}} between 10{sup 17} eV and 10{sup 20} eV from point-like sources across the sky south of +55 Degree-Sign and north of -65 Degree-Sign declinations. A search has been performed for highly inclined extensive air showers produced by the interaction of neutrinos of all flavors in the atmosphere (downward-going neutrinos), and by the decay of tau leptons originating from tau neutrino interactions in Earth's crust (Earth-skimming neutrinos). No candidate neutrinos have been found in data up to 2010 May 31. This corresponds to an equivalent exposure of {approx}3.5 years of a full surface detector array for the Earth-skimming channel and {approx}2 years for the downward-going channel. An improved upper limit on the diffuse flux of tau neutrinos has been derived. Upper limits on the neutrino flux from point-like sources have been derived as a function of the source declination. Assuming a differential neutrino flux k{sub PS} {center_dot} E {sup -2}{sub {nu}} from a point-like source, 90% confidence level upper limits for k{sub PS} at the level of Almost-Equal-To 5 Multiplication-Sign 10{sup -7} and 2.5 Multiplication-Sign 10{sup -6} GeV cm{sup -2} s{sup -1} have been obtained over a broad range of declinations from the searches for Earth-skimming and downward-going neutrinos, respectively.

  12. Point-source idealization in classical field theories. I. Electromagnetic radiation damping of a system of two perturbed Reissner-Nordstroem singularities in the slow-motion limit

    SciTech Connect

    Kates, R.E.

    1982-05-15

    This paper calculates the leading resistive accelerations acting on a system of two slightly deformed Reissner-Nordstroem singularities due to the emission of electromagnetic radiation, using matched asymptotic expansions. The unperturbed Reissner-Nordstroem solutions are assumed to have large charge-to-mass ratios q/m and to be separated by a distance large compared to both m and q/sup 2//m. The problem is of interest primarily because of Rosenblum's use of point singularities in his calculation of the mechanical work done in small-angle gravitational scattering. Classical derivations of the electromagnetic equations of motion for a charged source were faced with the choice between indeterminate equations and divergences in the stress-energy. The use of asymptotic expansions about Reissner-Nordstroem solutions makes renormalization arguments unnecessary. The following paper compares the mechanical energy loss obtained from the present matching calculation to that predicted by the Lorentz-Dirac equation; which was derived using a point-particle assumption.

  13. Amorphous and crystalline aerosol particles interacting with water vapor: conceptual framework and experimental evidence for restructuring, phase transitions and kinetic limitations

    NASA Astrophysics Data System (ADS)

    Mikhailov, E.; Vlasenko, S.; Martin, S. T.; Koop, T.; Pöschl, U.

    2009-12-01

    Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we present a conceptual framework for the interaction of amorphous aerosol particles with water vapor, outlining characteristic features and differences in comparison to crystalline particles. We used a hygroscopicity tandem differential mobility analyzer (H-TDMA) to characterize the hydration and dehydration of crystalline ammonium sulfate, amorphous oxalic acid and amorphous levoglucosan particles (diameter ~100 nm, relative humidity 5-95% at 298 K). The experimental data and accompanying Köhler model calculations provide new insights into particle microstructure, surface adsorption, bulk absorption, phase transitions and hygroscopic growth. The results of these and related investigations lead to the following conclusions: (1) Many organic substances, including carboxylic acids, carbohydrates and proteins, tend to form amorphous rather than crystalline phases upon drying of aqueous solution droplets. Depending on viscosity and microstructure, the amorphous phases can be classified as glasses, rubbers, gels or viscous liquids. (2) Amorphous organic substances tend to absorb water vapor and undergo gradual deliquescence and hygroscopic growth at lower relative humidity than their crystalline counterparts. (3) In the course of hydration and dehydration, certain organic substances can form rubber- or gel-like structures (supramolecular networks) and undergo transitions between swollen and collapsed network structures. (4) Organic gels or (semi-)solid amorphous shells (glassy, rubbery, ultra-viscous) with low molecular diffusivity can kinetically limit the uptake and release of water and may influence the hygroscopic growth and activation of aerosol particles as cloud condensation nuclei (CCN) and ice nuclei (IN). Moreover, (semi-)solid amorphous phases may influence the uptake of gaseous photo-oxidants and the chemical transformation and aging of

  14. Particle size distributions of lead measured in battery manufacturing and secondary smelter facilities and implications in setting workplace lead exposure limits.

    PubMed

    Petito Boyce, Catherine; Sax, Sonja N; Cohen, Joel M

    2017-08-01

    Inhalation plays an important role in exposures to lead in airborne particulate matter in occupational settings, and particle size determines where and how much of airborne lead is deposited in the respiratory tract and how much is subsequently absorbed into the body. Although some occupational airborne lead particle size data have been published, limited information is available reflecting current workplace conditions in the U.S. To address this data gap, the Battery Council International (BCI) conducted workplace monitoring studies at nine lead acid battery manufacturing facilities (BMFs) and five secondary smelter facilities (SSFs) across the U.S. This article presents the results of the BCI studies focusing on the particle size distributions calculated from Personal Marple Impactor sampling data and particle deposition estimates in each of the three major respiratory tract regions derived using the Multiple-Path Particle Dosimetry model. The BCI data showed the presence of predominantly larger-sized particles in the work environments evaluated, with average mass median aerodynamic diameters (MMADs) ranging from 21-32 µm for the three BMF job categories and from 15-25 µm for the five SSF job categories tested. The BCI data also indicated that the percentage of lead mass measured at the sampled facilities in the submicron range (i.e., <1 µm, a particle size range associated with enhanced absorption of associated lead) was generally small. The estimated average percentages of lead mass in the submicron range for the tested job categories ranged from 0.8-3.3% at the BMFs and from 0.44-6.1% at the SSFs. Variability was observed in the particle size distributions across job categories and facilities, and sensitivity analyses were conducted to explore this variability. The BCI results were compared with results reported in the scientific literature. Screening-level analyses were also conducted to explore the overall degree of lead absorption potentially

  15. [The shutdown point and the output volume limit (OVL) in the present situation of healthcare in Hungary (or a little economics for practicing physicians)].

    PubMed

    Gresz, Miklós

    2008-09-07

    In the present situation of health care, financing has become so complicated that the treating doctor has to know not only his profession but also has to consider the different regulations, laws and book of rules. The work of the physician cannot be carried out only through the fact that he is a master of his art, that is healing. All healing practice, diagnostic abilities, intuition, empathy and other things are in vain: if he is not familiar with the basics of financing he can lead his institution to insolvency. This article tries to give a view of a small part of financing, the output volume limit (OVL) from another aspect. According to the basics of economy and general rules of leadership it tries to show up the practical difficulties of the output volume limit. The study enlightens that by defining the output volume limit one has to consider the shutdown point of the hospital and knowing this, the actual output volume limit should be defined in the way that it does not make the proper activity of the hospital completely impossible.

  16. 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

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

    PubMed

    Millard, Peter S; Bru, Juan; Berger, Christopher A

    2012-01-01

    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. 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. Open-source point-of-care EMRs suitable for use in areas without reliable internet access. 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. The hardware and software for all six systems is easily available, but they vary considerably in proprietary components, installation requirements and customisability. This study relied solely on self-report from informants who developed and who actively use the included products. 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.

  18. Particle-filtering-based failure prognosis via sigma-points: Application to Lithium-Ion battery State-of-Charge monitoring

    NASA Astrophysics Data System (ADS)

    Acuña, David E.; Orchard, Marcos E.

    2017-02-01

    This paper presents a novel prognostic method that allows a proper characterization of the uncertainty associated with the evolution in time of nonlinear dynamical systems. The method assumes a state-space representation of the system, as well as the availability of particle-filtering-based estimates of the state posterior density at the moment in which the prognostic algorithm is executed. Our proposal significantly improves all particle-filtering-based prognosis frameworks currently available in two main aspects. First, it provides a correction for the expression that is used for the computation of the Time-of-Failure (ToF) probability mass function in the context of online monitoring schemes. Secondly, it presents a method for improved characterization of the tails of the ToF probability mass function via sequential propagation of sigma-points and the computation of Gaussian Mixture Models (GMMs). The proposed algorithm is tested and validated using experimental data related to the problem of Lithium-Ion battery State-of-Charge prognosis.

  19. 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

  20. Setting limits for acceptable change in sediment particle size composition: testing a new approach to managing marine aggregate dredging.

    PubMed

    Cooper, Keith M

    2013-08-15

    A baseline dataset from 2005 was used to identify the spatial distribution of macrofaunal assemblages across the eastern English Channel. The range of sediment composition found in association with each assemblage was used to define limits for acceptable change at ten licensed marine aggregate extraction areas. Sediment data acquired in 2010, 4 years after the onset of dredging, were used to assess whether conditions remained within the acceptable limits. Despite the observed changes in sediment composition, the composition of sediments in and around nine extraction areas remained within pre-defined acceptable limits. At the tenth site, some of the observed changes within the licence area were judged to have gone beyond the acceptable limits. Implications of the changes are discussed, and appropriate management measures identified. The approach taken in this study offers a simple, objective and cost-effective method for assessing the significance of change, and could simplify the existing monitoring regime. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. Determining the focal spot limit of 1 MeV X-ray targets: Monte Carlo simulation of the point spread function

    NASA Astrophysics Data System (ADS)

    Wang, Jiayue; Shi, Jiaru; Huang, Wenhui; Tang, Chuanxiang

    2017-02-01

    Among all microfocus X-ray tubes, 1 MeV has remained a "gray zone" despite its universal application in radiation therapy and non-destructive testing. One challenge existing in fabricating 1 MeV microfocus X-ray tubes is beam broadening inside metal anodes, which limits the minimum focal spot size a system can obtain. In particular, a complete understanding of the intrinsic broadening process, i.e., the point-spread function (PSF) of X-ray targets is needed. In this paper, relationships between PSF and beam energy, target thickness and electron incidence angle were investigated via Monte Carlo simulation. Focal spot limits for both transmission- and reflection-type tungsten targets at 0.5, 1 and 1.5 MeV were calculated, with target thicknesses ranging from 1 μm to 2 cm. Transmission-type targets with thickness less than 5 μ m could achieve micrometer-scale spots while reflection-type targets exhibited superiority for spots larger than 100 μm . In addition, by demonstrating the spot variation at off-normal incidence, the role of unidirectional beam was explored in microfocus X-ray systems. We expect that these results can enable alternative designs to improve the focal spot limit of X-ray tubes and benefit accurate photon source modeling.

  2. Using a geographic information system to enhance patient access to point-of-care diagnostics in a limited-resource setting.

    PubMed

    Ferguson, William J; Kemp, Karen; Kost, Gerald

    2016-03-01

    Rapid and accurate diagnosis drives evidence-based care in health. Point-of-care testing (POCT) aids diagnosis by bringing advanced technologies closer to patients. Health small-world networks are constrained by natural connectivity in the interactions between geography of resources and social forces. Using a geographic information system (GIS) we can understand how populations utilize their health networks, visualize their inefficiencies, and compare alternatives. This project focuses on cardiac care resource in rural Isaan, Thailand. A health care access analysis was created using ArcGIS Network Analyst 10.1 from data representing aggregated population, roads, health resource facilities, and diagnostic technologies. The analysis quantified cardiac health care access and identified ways to improve it using both widespread and resource-limited strategies. Results indicated that having diagnostic technologies closer to populations streamlines critical care paths. GIS allowed us to compare the effectiveness of the implementation strategies and put into perspective the benefits of adopting rapid POCT within health networks. Geospatial analyses derive high impact by improving alternative diagnostic placement strategies in limited-resource settings and by revealing deficiencies in health care access pathways. Additionally, the GIS provides a platform for comparing relative costs, assessing benefits, and improving outcomes. This approach can be implemented effectively by health ministries seeking to enhance cardiac care despite limited resources.

  3. 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

  4. Sample preparation: a challenge in the development of point-of-care nucleic acid-based assays for resource-limited settings.

    PubMed

    Dineva, Magda Anastassova; MahiLum-Tapay, Lourdes; Lee, Helen

    2007-12-01

    Currently available nucleic acid testing (NAT)-based assays are complex and time-consuming, and they require expensive instrumentation and dedicated laboratory spaces for sample preparation as well as for amplification and detection of the nucleic acid target. Reagents required for these tests are also expensive and must be transported and stored refrigerated or frozen. These characteristics have limited the use of such assays for point-of-care (POC) testing, especially in resource-poor settings. Efforts to develop simple and rapid NAT-based assays have focused predominantly on the amplification and detection steps, with sample preparation and nucleic acid extraction remaining the bottleneck in the development of NAT systems suitable for POC applications or resource-limited settings. A review of NAT platforms and technologies currently under development and validation for rapid field testing revealed that, in addition to requiring expensive and complex instrumentation, many of these systems also require off-line sample preparation and reagent handling. In their current format, they are therefore not appropriate for POC testing in resource-limited settings. We evaluated several commercially available technologies and procedures for the isolation of nucleic acid with the extraction of HIV-1 RNA from human plasma as a model system. Our results indicate that solid-phase extraction with silica or glass in the presence of a chaotropic salt provides the highest extraction efficiency. However, none of the existing methods and technologies is readily adaptable to a POC system. The integration of sample preparation procedures well suited to NAT-based assays in resource-limited settings therefore remains a challenge.

  5. Cost-effectiveness of point-of-care viral load monitoring of ART in resource-limited settings: Mathematical modelling study

    PubMed Central

    ESTILL, Janne; EGGER, Matthias; BLASER, Nello; VIZCAYA, Luisa SALAZAR; GARONE, Daniela; WOOD, Robin; CAMPBELL, Jennifer; HALLETT, Timothy B.; KEISER, Olivia

    2013-01-01

    Background Monitoring of HIV viral load in patients on combination antiretroviral therapy (ART) is not generally available in resource-limited settings. We examined the cost-effectiveness of qualitative point-of-care viral load tests (POC-VL) in sub-Saharan Africa. Design Mathematical model based on longitudinal data from the Gugulethu and Khayelitsha township ART programmes in Cape Town, South Africa. Methods Cohorts of patients on ART monitored by POC-VL, CD4 cell count or clinically were simulated. Scenario A considered the more accurate detection of treatment failure with POC-VL only, Scenario B also considered the effect on HIV transmission. Scenario C further assumed that the risk of virologic failure is halved with POC-VL due to improved adherence. We estimated the change in costs per quality-adjusted life-year gained (incremental cost-effectiveness ratios, ICER) of POC-VL compared to CD4 and clinical monitoring. Results POC-VL tests with detection limits <1000 copies/ml increased costs due to unnecessary switches to second-line ART, without improving survival. Assuming POC-VL unit costs between US$5–US$20 and detection limits between 1000 and 10000 copies/ml, the ICER of POC-VL was US$4010–US$9230 compared to clinical and US$5960–US$25540 compared to CD4 monitoring. In Scenario B the corresponding ICERs were US$2450–US$5830 and US$2230–US$10380. In Scenario C the ICER ranged between US$960–US$2500 compared to clinical monitoring and between cost-saving and US$2460 compared to CD4 monitoring. Conclusions The cost-effectiveness of POC-VL for monitoring ART is improved by a higher detection limit, by taking the reduction in new HIV infections into account and when assuming that failure of first-line ART is reduced due to targeted adherence counselling. PMID:23462219

  6. Cost-effectiveness of point-of-care viral load monitoring of antiretroviral therapy in resource-limited settings: mathematical modelling study.

    PubMed

    Estill, Janne; Egger, Matthias; Blaser, Nello; Vizcaya, Luisa Salazar; Garone, Daniela; Wood, Robin; Campbell, Jennifer; Hallett, Timothy B; Keiser, Olivia

    2013-06-01

    Monitoring of HIV viral load in patients on combination antiretroviral therapy (ART) is not generally available in resource-limited settings. We examined the cost-effectiveness of qualitative point-of-care viral load tests (POC-VL) in sub-Saharan Africa. Mathematical model based on longitudinal data from the Gugulethu and Khayelitsha township ART programmes in Cape Town, South Africa. Cohorts of patients on ART monitored by POC-VL, CD4 cell count or clinically were simulated. Scenario A considered the more accurate detection of treatment failure with POC-VL only, and scenario B also considered the effect on HIV transmission. Scenario C further assumed that the risk of virologic failure is halved with POC-VL due to improved adherence. We estimated the change in costs per quality-adjusted life-year gained (incremental cost-effectiveness ratios, ICERs) of POC-VL compared with CD4 and clinical monitoring. POC-VL tests with detection limits less than 1000 copies/ml increased costs due to unnecessary switches to second-line ART, without improving survival. Assuming POC-VL unit costs between US$5 and US$20 and detection limits between 1000 and 10,000 copies/ml, the ICER of POC-VL was US$4010-US$9230 compared with clinical and US$5960-US$25540 compared with CD4 cell count monitoring. In Scenario B, the corresponding ICERs were US$2450-US$5830 and US$2230-US$10380. In Scenario C, the ICER ranged between US$960 and US$2500 compared with clinical monitoring and between cost-saving and US$2460 compared with CD4 monitoring. The cost-effectiveness of POC-VL for monitoring ART is improved by a higher detection limit, by taking the reduction in new HIV infections into account and assuming that failure of first-line ART is reduced due to targeted adherence counselling.

  7. 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

  8. 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

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

    2013-01-01

    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. Five electronic databases (1980-2012) were searched, data was extracted from 33 articles, and Bayesian hierarchical models were fit. 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). 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 limited settings with poor access to

  9. A new point mutation in the luteinising hormone receptor gene in familial and sporadic male limited precocious puberty: genotype does not always correlate with phenotype.

    PubMed Central

    Evans, B A; Bowen, D J; Smith, P J; Clayton, P E; Gregory, J W

    1996-01-01

    Genomic DNA from two families with male limited precocious puberty was examined for mutations of the LH receptor gene. In family 1, several members of the pedigree have FMPP, whereas in family 2 there is only one affected subject. A point mutation (T --> C at nucleotide 1192) resulting in substitution of threonine for methionine 398 in the second transmembrane domain of the LH receptor protein was found in both families. In addition, one member of family 1 has the mutation, but no evidence of precocious puberty. All obligate carriers within this family were shown to have the mutation, and it was not detected in 94 chromosomes from unaffected and unrelated white subjects. In family 2, the index case was the only one to have the mutation. A previously unreported neutral dimorphism (C --> T at nucleotide 1065) is also described. Images PMID:8929952

  10. Current limitations of the assessment of haemostasis in adult extracorporeal membrane oxygenation patients and the role of point-of-care testing.

    PubMed

    Venkatesh, K; Nair, P S; Hoechter, D J; Buscher, H

    2016-11-01

    Haemostatic perturbations are commonly seen in extracorporeal membrane oxygenation (ECMO) patients and remain a clinical challenge, contributing significantly to morbidity and mortality. The approach to anticoagulation monitoring and the management of bleeding varies considerably across ECMO centres. Routine laboratory tests have their limitations in terms of turnaround time and specificity of information provided. Newer point-of-care testing (POCT) for coagulation may overcome these issues, as it provides information about the entire coagulation pathway from clot initiation to lysis. It is also possible to obtain qualitative information on platelet function from these tests. Furthermore, the ability to incorporate these results into a goal-directed algorithm to manage bleeding with targeted transfusion strategies appears particularly attractive and cost effective. Further studies are required to evaluate the utility of POCT to optimise bleeding and anticoagulation management in these complex patients.

  11. 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

  12. The clinical and economic impact of point-of-care CD4 testing in mozambique and other resource-limited settings: a cost-effectiveness analysis.

    PubMed

    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

    2014-09-01

    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. 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/specificity and higher cost than published

  13. End-point limiting-dilution real-time PCR assay for evaluation of hepatitis C virus quasispecies in serum: performance under optimal and suboptimal conditions.

    PubMed

    Ramachandran, Sumathi; Xia, Guo-Liang; Ganova-Raeva, Lilia M; Nainan, Omana V; Khudyakov, Yury

    2008-08-01

    An approach for determination of hepatitis C virus (HCV) quasispecies by end-point limiting-dilution real-time PCR (EPLD-PCR) is described. It involves isolation of individual coexisting sequence variants of the hypervariable region 1 (HVR1) of the HCV genome from serum specimens using a limiting-dilution protocol. EPLD-PCR applied to an HCV outbreak study provided insights into the epidemiological relationships between incident and chronic cases. When applied to samples from a longitudinal study of infected patients, HVR1 sequences from each sampling time-point were observed to group as distinct phylogenetic clusters. Melting peak analysis conducted on EPLD-PCR products generated from these patients could be used for evaluation of HVR1 sequence heterogeneity without recourse to clonal sequencing. Further, to better understand the mechanism of single-molecule PCR, experiments were conducted under optimal and suboptimal annealing temperatures. Under all temperature conditions tested, HVR1 variants from the major phylogenetic clusters of quasispecies could be amplified, revealing that successful HVR1 quasispecies analysis is not contingent to dilution of starting cDNA preparations to a single-molecule state. It was found that EPLD-PCR conducted at suboptimal annealing temperatures generated distributions of unique-sequence variants slightly different from the distribution obtained by PCR conducted at the optimal temperature. Hence, EPLD-PCR conditions can be manipulated to access different subpopulations of HCV HVR1 quasispecies, thus, improving the range of the quasispecies detection. Although EPLD-PCR conducted at different conditions detect slightly different quasispecies populations, as was shown in this study, the resulted samples of quasispecies are completely suitable for molecular epidemiological investigation in different clinical and epidemiological settings.

  14. Multicountry Validation of SAMBA - A Novel Molecular Point-of-Care Test for HIV-1 Detection in Resource-Limited Setting.

    PubMed

    Ondiek, Johnson; Namukaya, Zikulah; Mtapuri-Zinyowera, Sekesai; Balkan, Suna; Elbireer, Ali; Ushiro Lumb, Ines; Kiyaga, Charles; Goel, Neha; Ritchie, Allyson; Ncube, Patience; Omuomu, Kenneth; Ndiege, Kenneth; Kekitiinwa, Adeodata; Mangwanya, Douglas; Fowler, Mary G; Nadala, Lou; Lee, Helen

    2017-10-01

    Early diagnosis of HIV-1 infection and the prompt initiation of antiretroviral therapy are critical to achieving a reduction in the morbidity and mortality of infected infants. The Simple AMplification-Based Assay (SAMBA) HIV-1 Qual Whole Blood Test was developed specifically for early infant diagnosis and prevention of mother-to-child transmission programs implemented at the point-of-care in resource-limited settings. We have evaluated the performance of this test run on the SAMBA I semiautomated platform with fresh whole blood specimens collected from 202 adults and 745 infants in Kenya, Uganda, and Zimbabwe. Results were compared with those obtained with the Roche COBAS AmpliPrep/COBAS TaqMan (CAP/CTM) HIV-1 assay as performed with fresh whole blood or dried blood spots of the same subjects, and discrepancies were resolved with alternative assays. The performance of the SAMBA and CAP/CTM assays evaluated at 5 laboratories in the 3 countries was similar for both adult and infant samples. The clinical sensitivity, specificity, positive predictive value, and negative predictive value for the SAMBA test were 100%, 99.2%, 98.7%, and 100%, respectively, with adult samples, and 98.5%, 99.8%, 99.7%, and 98.8%, respectively, with infant samples. Our data suggest that the SAMBA HIV-1 Qual Whole Blood Test would be effective for early diagnosis of HIV-1 infection in infants at point-of-care settings in sub-Saharan Africa.

  15. Modeling Sediment Transport Using a Lagrangian Particle Tracking Algorithm Coupled with High-Resolution Large Eddy Simulations: a Critical Analysis of Model Limits and Sensitivity

    NASA Astrophysics Data System (ADS)

    Garcia, M. H.

    2016-12-01

    Modeling Sediment Transport Using a Lagrangian Particle Tracking Algorithm Coupled with High-Resolution Large Eddy Simulations: a Critical Analysis of Model Limits and Sensitivity Som Dutta1, Paul Fischer2, Marcelo H. Garcia11Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Il, 61801 2Department of Computer Science and Department of MechSE, University of Illinois at Urbana-Champaign, Urbana, Il, 61801 Since the seminal work of Niño and Garcia [1994], one-way coupled Lagrangian particle tracking has been used extensively for modeling sediment transport. Over time, the Lagrangian particle tracking method has been coupled with Eulerian flow simulations, ranging from Reynolds Averaged Navier-Stokes (RANS) based models to Detached Eddy Simulations (DES) [Escauriaza and Sotiropoulos, 2011]. Advent of high performance computing (HPC) platforms and faster algorithms have resulted in the work of Dutta et al. [2016], where Lagrangian particle tracking was coupled with high-resolution Large Eddy Simulations (LES) to model the complex and highly non-linear phenomenon of Bulle-Effect at diversions. Despite all the advancements in using Lagrangian particle tracking, there has not been a study that looks in detail at the limits of the model in the context of sediment transport, and also analyzes the sensitivity of the various force formulation in the force balance equation of the particles. Niño and Garcia [1994] did a similar analysis, but the vertical flow velocity distribution was modeled as the log-law. The current study extends the analysis by modeling the flow using high-resolution LES at a Reynolds number comparable to experiments of Niño et al. [1994]. Dutta et al., (2016), Large Eddy Simulation (LES) of flow and bedload transport at an idealized 90-degree diversion: insight into Bulle-Effect, River Flow 2016 - Constantinescu, Garcia & Hanes (Eds), Taylor & Francis Group, London, 101-109. Escauriaza and Sotiropoulos

  16. Improvement in limit of detection in particle induced X-ray emission by means of rise time and pulse shape discrimination

    NASA Astrophysics Data System (ADS)

    Papp, Tibor; Lakatos, Tamás; Nejedly, Zdenek; Campbell, John L.

    2002-04-01

    A digital signal processor, based upon high-rate sampling of the preamplifier output, and equipped with rise time and pulse shape discrimination, has been tested in three situations. This processor provided significant improvement of particle induced X-ray emission and X-ray fluorescence detection limits over the state of the art analog processors, depending on the energy and intensity distribution of the X-ray spectra. Additionally it had a superior performance when measurements were performed in an environment of large electronic noise and in large nuclear background environment. It has also improved the reduction of several artifacts in X-ray spectra.

  17. 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.

  18. Numerical model for swirl cooling in high-heat-flux particle beam targets and the design of a swirl-flow-based plasma limiter

    NASA Astrophysics Data System (ADS)

    Milora, S. L.; Combs, S. K.; Foster, C. A.

    1984-11-01

    An unsteady, two-dimensional heat conduction code was used to study the performance of swirl-flow-based neutral particle beam targets. The model includes the effects of two-phase heat transfer and asymmetric heating of tubular elements. The calorimeter subjected to 30-s neutral beam pulses with incident heat flux intensities of greater than or equal to 5 kW/cu cm, is modeled. The numerical results indicate that local heat fluxes in excess of 7 kW/sq cm occur at the water cooled surface on the side exposed to the beam. This exceeds critical heat flux limits for uniformly heated tubes with straight flow by approximately a factor of 5. The design of a plasma limiter based on swirl flow heat transfer is presented.

  19. Resonant excitation of precursor molecules in improving the particle crystallinity, growth rate and optical limiting performance of carbon nano-onions

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Zhou, Y. S.; Park, J. B.; Wang, H.; He, X. N.; Luo, H. F.; Jiang, L.; Lu, Y. F.

    2011-04-01

    A catalyst-free and highly efficient synthetic method for growing carbon nano-onions (CNOs) in open air has been developed through the laser resonant excitation of a precursor molecule, ethylene, in a combustion process. Highly concentric CNO particles with improved crystallinity were obtained at a laser wavelength of 10.532 µm through the resonant excitation of the CH2 wagging mode of the ethylene molecules. A higher growth rate up to 2.1 g h - 1 was obtained, compared with that without a laser (1.3 g h - 1). Formation of the CNOs with ordered graphitic shells is ascribed to the decomposition of polycyclic aromatic hydrocarbons (PAHs) into C2 species. The optical limiting performances of the CNOs grown by the combustion processes were investigated. CNOs grown at 10.532 µm laser excitation demonstrated improved optical limiting properties due to the improved crystallinity.

  20. Numerical model for swirl flow cooling in high-heat-flux particle beam targets and the design of a swirl-flow-based plasma limiter

    SciTech Connect

    Milora, S.L.; Combs, S.K.; Foster, C.A.

    1984-11-01

    An unsteady, two-dimensional heat conduction code has been used to study the performance of swirl-flow-based neutral particle beam targets. The model includes the effects of two-phase heat transfer and asymmetric heating of tubular elements. The calorimeter installed in the Medium Energy Test Facility, which has been subjected to 30-s neutral beam pulses with incident heat flux intensities of greater than or equal to 5 kW/cm/sup 2/, has been modeled. The numerical results indicate that local heat fluxes in excess of 7 kW/cm/sup 2/ occur at the water-cooled surface on the side exposed to the beam. This exceeds critical heat flux limits for uniformly heated tubes wih straight flow by approximately a factor of 5. The design of a plasma limiter based on swirl flow heat transfer is presented.

  1. A quantitative framework to group nanoscale and microscale particles by hazard potency to derive occupational exposure limits: Proof of concept evaluation.

    PubMed

    Drew, Nathan M; Kuempel, Eileen D; Pei, Ying; Yang, Feng

    2017-10-01

    The large and rapidly growing number of engineered nanomaterials (ENMs) presents a challenge to assessing the potential occupational health risks. An initial database of 25 rodent studies including 1929 animals across various experimental designs and material types was constructed to identify materials that are similar with respect to their potency in eliciting neutrophilic pulmonary inflammation, a response relevant to workers. Doses were normalized across rodent species, strain, and sex as the estimated deposited particle mass dose per gram of lung. Doses associated with specific measures of pulmonary inflammation were estimated by modeling the continuous dose-response relationships using benchmark dose modeling. Hierarchical clustering was used to identify similar materials. The 18 nanoscale and microscale particles were classified into four potency groups, which varied by factors of approximately two to 100. Benchmark particles microscale TiO2 and crystalline silica were in the lowest and highest potency groups, respectively. Random forest methods were used to identify the important physicochemical predictors of pulmonary toxicity, and group assignments were correctly predicted for five of six new ENMs. Proof-of-concept was demonstrated for this framework. More comprehensive data are needed for further development and validation for use in deriving categorical occupational exposure limits. Published by Elsevier Inc.

  2. 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

  3. Deformed Carroll particle from 2 + 1 gravity

    NASA Astrophysics Data System (ADS)

    Kowalski-Glikman, Jerzy; Trześniewski, Tomasz

    2014-10-01

    We consider a point particle coupled to 2 + 1 gravity, with de Sitter gauge group SO (3 , 1). We observe that there are two contraction limits of the gauge group: one resulting in the Poincaré group, and the second with the gauge group having the form AN (2) ⋉ an (2) *. The former case was thoroughly discussed in the literature, while the latter leads to the deformed particle action with de Sitter momentum space, like in the case of κ-Poincaré particle. However, the construction forces the mass shell constraint to have the form p02 =m2, so that the effective particle action describes the deformed Carroll particle.

  4. Spin-Dependent Weakly-Interacting-Massive-Particle-Nucleon Cross Section Limits from First Data of PandaX-II Experiment

    NASA Astrophysics Data System (ADS)

    Fu, Changbo; Cui, Xiangyi; Zhou, Xiaopeng; Chen, Xun; Chen, Yunhua; Fang, Deqing; Giboni, Karl; Giuliani, Franco; Han, Ke; Huang, Xingtao; Ji, Xiangdong; Ju, Yonglin; Lei, Siao; Li, Shaoli; Liu, Huaxuan; Liu, Jianglai; Ma, Yugang; Mao, Yajun; Ren, Xiangxiang; Tan, Andi; Wang, Hongwei; Wang, Jiming; Wang, Meng; Wang, Qiuhong; Wang, Siguang; Wang, Xuming; Wang, Zhou; Wu, Shiyong; Xiao, Mengjiao; Xie, Pengwei; Yan, Binbin; Yang, Yong; Yue, Jianfeng; Zhang, Hongguang; Zhang, Tao; Zhao, Li; Zhou, Ning; PandaX-II Collaboration

    2017-02-01

    New constraints are presented on the spin-dependent weakly-interacting-massive-particle- (WIMP-)nucleon interaction from the PandaX-II experiment, using a data set corresponding to a total exposure of 3.3 ×104 kg day . Assuming a standard axial-vector spin-dependent WIMP interaction with Xe 129 and Xe 131 nuclei, the most stringent upper limits on WIMP-neutron cross sections for WIMPs with masses above 10 GeV /c2 are set in all dark matter direct detection experiments. The minimum upper limit of 4.1 ×10-41 cm2 at 90% confidence level is obtained for a WIMP mass of 40 GeV /c2 . This represents more than a factor of 2 improvement on the best available limits at this and higher masses. These improved cross-section limits provide more stringent constraints on the effective WIMP-proton and WIMP-neutron couplings.

  5. a Multi-Domain Hybrid Method for Head-On Collision of Black Holes in Particle Limit

    NASA Astrophysics Data System (ADS)

    Chakraborty, Debananda; Jung, Jae-Hun; Khanna, Gaurav

    A hybrid method is developed based on the spectral and finite-difference methods for solving the inhomogeneous Zerilli equation in time-domain. The developed hybrid method decomposes the domain into the spectral and finite-difference domains. The singular source term is located in the spectral domain while the solution in the region without the singular term is approximated by the higher-order finite-difference method. The spectral domain is also split into multi-domains and the finite-difference domain is placed as the boundary domain. Due to the global nature of the spectral method, a multi-domain method composed of the spectral domain only does not yield the proper power-law decay unless the range of the computational domain is large. The finite-difference domain helps reduce boundary effects due to the truncation of the computational domain. The multi-domain approach with the finite-difference boundary domain method reduces the computational cost significantly and also yields the proper power-law decay. Stable and accurate interface conditions between the finite-difference and spectral domains and the spectral and spectral domains are derived. For the singular source term, we use both the Gaussian model with various values of full width at half-maximum and a localized discrete δ-function. The discrete δ-function was generalized to adopt the Gauss-Lobatto collocation points of the spectral domain. The gravitational waveforms are measured. Numerical results show that the developed hybrid method accurately yields the quasi-normal modes and the power-law decay profile. The numerical results also show that the power-law decay profile is less sensitive to the shape of the regularized δ-function for the Gaussian model than expected. The Gaussian model also yields better results than the localized discrete δ-function.

  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

    DOE PAGES

    Ackermann, M.; Ajello, M.; Allafort, A.; ...

    2013-02-15

    We present the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to detect photons with energies from ≈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 γ rays from pulsars and active galactic nuclei (AGNs). Above 3 GeV, the PSF is found to be broadermore » than the pre-launch PSF. We checked for dependence of the PSF on the class of γ-ray source and observation epoch and found none. We also investigated several possible spatial models for pair-halo emission around BL Lac AGNs. Finally, 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.« less

  7. 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.

  8. Investigating the Occurrence and Environmental Significance of Methylated Arsenic Species in Atmospheric Particles by Overcoming Analytical Method Limitations.

    PubMed

    Tziaras, Thrasyvoulos; Pergantis, Spiros A; Stephanou, Euripides G

    2015-10-06

    A novel analytical method has been developed for the determination of all five arsenic species known to exist in atmospheric particulate matter (PM), i.e., the inorganic arsenite iAs(III) and arsenate iAs(V), and the methylated methylarsonate (MA), dimethylarsinate (DMA) and trimethylarsine oxide (TMAO). Although the methylated species were first detected in PM in the late 1970s, most of the recent studies focus mainly on the two inorganic As species, ignoring TMAO in particular. In the present study, an HPLC (with an anion and cation exchange column connected in series)-arsine generation-ICP-MS system provided complete separation of all five As species and limits of detection from 10 to 25 pg As mL(-1). This method was applied to analyze water extracts of the inhalable fraction of atmospheric PM (PM10, PM2.5 and PM2.1). 81 samples were collected, most during Saharan dust events, from a semirural area, and analyzed. The total water extractable arsenic ranged from 0.03 to 0.7 ng of As m(-3), values that are representative for remote areas. iAs(V) was the most abundant species followed by TMAO, DMA, iAs(III) and MA. None of the As species showed any particular trend with the presence or intensity of dust events, or seasonality, except for TMAO, which showed higher concentrations during the colder months.

  9. Spectroscopic studies of flavoproteins and non-haem iron proteins of submitochondrial particles of Torulopsis utilis modified by iron- and sulphate-limited growth in continuous culture

    PubMed Central

    Ragan, C. I.; Garland, P. B.

    1971-01-01

    1. A spectroscopic resolution has been made of the components contributing to the `iron-flavoprotein' trough extending from 450 to 520nm in the reduced-minus-oxidized difference spectrum of submitochondrial particles of Torulopsis utilis. 2. Seven components were identified other than cytochrome b, ubiquinone and succinate dehydrogenase. On the basis of the effects of iron- and sulphate-limited growth of cells on their subsequently derived electron-transport particles, and also by consideration of analytical measurements of the concentration of FMN, FAD, non-haem iron and acid-labile sulphide in the electron-transport particles in relation to the magnitude of the spectroscopic changes, it was possible to identify five of these components as follows: species 1a, the flavin of NADH dehydrogenase ferroflavoprotein; species 1b, the iron–sulphur component of NADH dehydrogenase ferroflavoprotein; species 1′, the flavin of an NADPH dehydrogenase; species 2, an iron–sulphur or ferroflavoprotein component; species 3, the flavin of l-3-glycerophosphate dehydrogenase. Two additional components were a fluorescent flavoprotein, probably lipoamide dehydrogenase, and a b-type cytochrome reducible by NADH or NADPH but not reoxidizable by the respiratory chain. 3. Species 1b and 2 were undetectable in electron-transport particles from iron- or sulphate-limited cells, but could be recovered in vivo under non-growing conditions. 4. The recovery in vivo of species 2 but not species 1b was inhibited by cycloheximide. 5. The recovery of species 1b correlates with the recovery of site 1 conservation. 6. The recovery of species 1b with species 2 correlates with the recovery of piericidin A sensitivity. 7. Evidence is presented for an NADPH dehydrogenase distinct from NADH dehydrogenase. The oxidation of NADH and NADPH by the respiratory chain is sensitive to piericidin A, and an iron–sulphur protein common to both pathways (species 2) is suggested as the piericidin A

  10. 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.

  11. 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.

  12. Particle transport in the edge plasma of the IR-T1 tokamak in the presence of limiter biasing and resonant helical field

    NASA Astrophysics Data System (ADS)

    Meshkani, S.; Ghoranneviss, M.; Lafouti, M.; Salar Elahi, A.

    2013-09-01

    Particle transport in the edge plasma of the IR-T1 tokamak in the presence of a resonant helical field (RHF) and biased limiter have been investigated and analyzed. For this purpose, a limiter biasing system was designed and constructed. The time evolution of the potential fluctuation, the electric field and the turbulent transport have been measured using two arrays of Langmuir probes in both the radial and poloidal directions. The experiments have been carried out in different regimes: as positive and negative limiter biasing, RHF and a combination of the two. The analyses have been done by the fast Fourier transport method. The results show that radial turbulent transport decreases by about 60% after applying positive biasing while it increases by about 40% after negative biasing. The effect of positive biasing on the poloidal turbulent transport displays an increase of about 55%, while negative biasing decreases the poloidal turbulent transport by about 30%. Consequently, confinement is improved and plasma density rises significantly due to applying positive biasing in IR-T1. But the results are inversed when negative biasing is applied. Also, in this work, the results of an applied RHF (with mode L = 3) are compared with biasing results and discussed.

  13. The role of point-of-care tests in antibiotic stewardship for urinary tract infections in a resource-limited setting on the Thailand-Myanmar border.

    PubMed

    Chalmers, Lauren; Cross, Jessica; Chu, Cindy S; Phyo, Aung Pyae; Trip, Margreet; Ling, Clare; Carrara, Verena; Watthanaworawit, Wanitda; Keereecharoen, Lily; Hanboonkunupakarn, Borimas; Nosten, François; McGready, Rose

    2015-10-01

    Published literature from resource-limited settings is infrequent, although urinary tract infections (UTI) are a common cause of outpatient presentation and antibiotic use. Point-of-care test (POCT) interpretation relates to antibiotic use and antibiotic resistance. We aimed to assess the diagnostic accuracy of POCT and their role in UTI antibiotic stewardship. One-year retrospective analysis in three clinics on the Thailand-Myanmar border of non-pregnant adults presenting with urinary symptoms. POCT (urine dipstick and microscopy) were compared to culture with significant growth classified as pure growth of a single organism >10(5)  CFU/ml. In 247 patients, 82.6% female, the most common symptoms were dysuria (81.2%), suprapubic pain (67.8%) and urinary frequency (53.7%). After excluding contaminated samples, UTI was diagnosed in 52.4% (97/185); 71.1% (69/97) had a significant growth on culture, and >80% of these were Escherichia coli (20.9% produced extended-spectrum β-lactamase (ESBL)). Positive urine dipstick (leucocyte esterase ≥1 and/or nitrate positive) compared against positive microscopy (white blood cell >10/HPF, bacteria ≥1/HPF, epithelial cells <5/HPF) had a higher sensitivity (99% vs. 57%) but a lower specificity (47% vs. 89%), respectively. Combined POCT resulted in the best sensitivity (98%) and specificity (81%). Nearly one in ten patients received an antimicrobial to which the organism was not fully sensitive. One rapid, cost-effective POCT was too inaccurate to be used alone by healthcare workers, impeding antibiotic stewardship in a high ESBL setting. Appropriate prescribing is improved with concurrent use and concordant results of urine dipstick and microscopy. © 2015 The Authors. Tropical Medicine & International Health Published by John Wiley & Sons Ltd.

  14. The value of point-of-care CD4+ and laboratory viral load in tailoring antiretroviral therapy monitoring strategies to resource limitations.

    PubMed

    Hyle, Emily P; Jani, Ilesh V; Rosettie, Katherine L; Wood, Robin; Osher, Benjamin; Resch, Stephen; Pei, Pamela P; Maggiore, Paolo; Freedberg, Kenneth A; Peter, Trevor; Parker, Robert A; Walensky, Rochelle P

    2017-09-24

    To examine the clinical and economic value of point-of-care CD4 (POC-CD4) or viral load monitoring compared with current practices in Mozambique, a country representative of the diverse resource limitations encountered by HIV treatment programs in sub-Saharan Africa. We use the Cost-Effectiveness of Preventing AIDS Complications-International model to examine the clinical impact, cost (2014 US$), and incremental cost-effectiveness ratio [$/year of life saved (YLS)] of ART monitoring strategies in Mozambique. We compare: monitoring for clinical disease progression [clinical ART monitoring strategy (CLIN)] vs. annual POC-CD4 in rural settings without laboratory services and biannual laboratory CD4 (LAB-CD4), biannual POC-CD4, and annual viral load in urban settings with laboratory services. We examine the impact of a range of values in sensitivity analyses, using Mozambique's 2014 per capita gross domestic product ($620) as a benchmark cost-effectiveness threshold. In rural settings, annual POC-CD4 compared to CLIN improves life expectancy by 2.8 years, reduces time on failed ART by 0.6 years, and yields an incremental cost-effectiveness ratio of $480/YLS. In urban settings, biannual POC-CD4 is more expensive and less effective than viral load. Compared to biannual LAB-CD4, viral load improves life expectancy by 0.6 years, reduces time on failed ART by 1.0 year, and is cost-effective ($440/YLS). In rural settings, annual POC-CD4 improves clinical outcomes and is cost-effective compared to CLIN. In urban settings, viral load has the greatest clinical benefit and is cost-effective compared to biannual POC-CD4 or LAB-CD4. Tailoring ART monitoring strategies to specific settings with different available resources can improve clinical outcomes while remaining economically efficient.

  15. Directional fidelity of nanoscale motors and particles is limited by the 2nd law of thermodynamics--via a universal equality.

    PubMed

    Wang, Zhisong; Hou, Ruizheng; Efremov, Artem

    2013-07-21

    Directional motion of nanoscale motors and driven particles in an isothermal environment costs a finite amount of energy despite zero work as decreed by the 2nd law, but quantifying this general limit remains difficult. Here we derive a universal equality linking directional fidelity of an arbitrary nanoscale object to the least possible energy driving it. The fidelity-energy equality depends on the environmental temperature alone; any lower energy would violate the 2nd law in a thought experiment. Real experimental proof for the equality comes from force-induced motion of biological nanomotors by three independent groups - for translational as well as rotational motion. Interestingly, the natural self-propelled motion of a biological nanomotor (F1-ATPase) known to have nearly 100% energy efficiency evidently pays the 2nd law decreed least energy cost for direction production.

  16. Momentum transfer and particle stress in polydisperse, particle-laden flow

    NASA Astrophysics Data System (ADS)

    Richter, David; Garcia, Omar; Astephen, Christopher

    2016-11-01

    Direct numerical simulations are performed in combination with two-way coupled Lagrangian point particles to study the effects of polydispersity on particle-induced modifications to momentum transfer in turbulent wall-bounded flow. Turbulent Couette flow is chosen as an idealized testbed for this purpose since total momentum flux is uniform in the wall-normal direction. Monodisperse simulations are first used to characterize momentum flux modification and particle stress as a function of particle Stokes number, and from this understanding bidisperse and continuously polydisperse mixtures of particle Stokes number are simulated. A simple model is then constructed to predict the total particle stress of these particle mixtures. While in the dilute limit particle stresses are nearly linearly additive, the entire mixture cannot simply be modeled by a single monodisperse particle with an effective Stokes number.

  17. 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

  18. Spinning black holes as particle accelerators.

    PubMed

    Jacobson, Ted; Sotiriou, Thomas P

    2010-01-15

    It has recently been pointed out that particles falling freely from rest at infinity outside a Kerr black hole can in principle collide with an arbitrarily high center of mass energy in the limiting case of maximal black hole spin. Here we aim to elucidate the mechanism for this fascinating result, and to point out its practical limitations, which imply that ultraenergetic collisions cannot occur near black holes in nature.

  19. Constructing amplitudes from their soft limits

    NASA Astrophysics Data System (ADS)

    Boucher-Veronneau, Camille; Larkoski, Andrew J.

    2011-09-01

    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.

  20. 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.

  1. 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.

  2. Optimizing the lattice design of a diffraction-limited storage ring with a rational combination of particle swarm and genetic algorithms

    NASA Astrophysics Data System (ADS)

    Jiao, Yi; Xu, Gang

    2017-02-01

    In the lattice design of a diffraction-limited storage ring (DLSR) consisting of compact multi-bend achromats (MBAs), it is challenging to simultaneously achieve an ultralow emittance and a satisfactory nonlinear performance, due to extremely large nonlinearities and limited tuning ranges of the element parameters. Nevertheless, in this paper we show that the potential of a DLSR design can be explored with a successive and iterative implementation of the multi-objective particle swarm optimization (MOPSO) and multi-objective genetic algorithm (MOGA). For the High Energy Photon Source, a planned kilometer-scale DLSR, optimizations indicate that it is feasible to attain a natural emittance of about 50 pm·rad, and simultaneously realize a sufficient ring acceptance for on-axis longitudinal injection, by using a hybrid MBA lattice. In particular, this study demonstrates that a rational combination of the MOPSO and MOGA is more effective than either of them alone, in approaching the true global optima of an explorative multi-objective problem with many optimizing variables and local optima. Supported by NSFC (11475202, 11405187) and Youth Innovation Promotion Association CAS (2015009)

  3. An integrated analytical approach using ion chromatography, PIXE and electron microscopy to point out the differences in composition of PM10 individual particles

    NASA Astrophysics Data System (ADS)

    Masiol, Mauro; Ceccato, Daniele; Squizzato, Stefania; Carturan, Sara; Pavoni, Bruno

    2013-07-01

    This study presents a part of a project aiming at characterizing the PM10 composition in the Venice area with detailed chemical analyses using various techniques. The concentrations of six major inorganic ions (Cl-, NO3-, SO42-, Na+, NH4+, Mg2+) and 19 elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Pb) were quantified using ion chromatography and PIXE, respectively. The masses of PM10 daily samples and their chemical contents were studied in relationship to micro-meteorological parameters to select a few of them characterized by very different chemical profiles. Four samples from the whole period were categorized as representative of i) clean days; ii) sea spray generation events; iii) high contribution of mineral dust and iv) heavy pollution events. Individual particle analyses of the samples were also performed by SEM-EDS microscopy. Six different classes of particles were identified (mineral particles, chlorides, sulfates, elemental and organic carbon compounds, metals and biological particles) and an estimation of their abundance yielded a significant relationship between the chemical content and composition in individual particles of PM10. Further information was also obtained on PM10 source contributions, morphology, mineralogy and mixed state of particles demonstrating the importance of combining different analytical approaches.

  4. Einstein-Vlasov system in spherical symmetry: Reduction of the equations of motion and classification of single-shell static solutions in the limit of massless particles

    NASA Astrophysics Data System (ADS)

    Gundlach, Carsten

    2016-12-01

    We express the Einstein-Vlasov system in spherical symmetry in terms of a dimensionless momentum variable z (radial over angular momentum). This regularizes the limit of massless particles, and in that limit allows us to obtain a reduced system in independent variables (t ,r ,z ) only. Similarly, in this limit the Vlasov density function f for static solutions depends on a single variable Q (energy over angular momentum). This reduction allows us to show that any given static metric that has vanishing Ricci scalar, is vacuum at the center and for r >3 M and obeys certain energy conditions uniquely determines a consistent f =k ¯(Q ) (in closed form). Vice versa, any k ¯(Q ) within a certain class uniquely determines a static metric (as the solution of a system of two first-order quasilinear ordinary differential equations). Hence the space of static spherically symmetric solutions of the Einstein-Vlasov system is locally a space of functions of one variable. For a simple two-parameter family of functions k ¯(Q ), we construct the corresponding static spherically symmetric solutions, finding that their compactness is in the interval 0.7 ≲maxr(2 M /r )≤8 /9 . This class of static solutions includes one that agrees with the approximately universal type-I critical solution recently found by Akbarian and Choptuik (AC) in numerical time evolutions. We speculate on what singles it out as the critical solution found by fine-tuning generic data to the collapse threshold, given that AC also found that all static solutions are one-parameter unstable and sit on the threshold of collapse.

  5. A Preliminary Comparison of Three Dimensional Particle Tracking and Sizing using Plenoptic Imaging and Digital In-line Holography [PowerPoint

    SciTech Connect

    Guildenbecher, Daniel Robert; Munz, Elise Dahnke; Farias, Paul Abraham; Thruow, Brian S

    2015-12-01

    Digital in-line holography and plenoptic photography are two techniques for single-shot, volumetric measurement of 3D particle fields. Here we present a preliminary comparison of the two methods by applying plenoptic imaging to experimental configurations that have been previously investigated with digital in-line holography. These experiments include the tracking of secondary droplets from the impact of a water drop on a thin film of water and tracking of pellets from a shotgun. Both plenoptic imaging and digital in-line holography successfully quantify the 3D nature of these particle fields. This includes measurement of the 3D particle position, individual particle sizes, and three-component velocity vectors. For the initial processing methods presented here, both techniques give out-of-plane positional accuracy of approximately 1-2 particle diameters. For a fixed image sensor, digital holography achieves higher effective in-plane spatial resolutions. However, collimated and coherent illumination makes holography susceptible to image distortion through index of refraction gradients, as demonstrated in the shotgun experiments. On the other hand, plenotpic imaging allows for a simpler experimental configuration. Furthermore, due to the use of diffuse, white-light illumination, plenoptic imaging is less susceptible to image distortion in the shotgun experiments. Additional work is needed to better quantify sources of uncertainty, particularly in the plenoptic experiments, as well as develop data processing methodologies optimized for the plenoptic measurement.

  6. Limited Associations between Keel Bone Damage and Bone Properties Measured with Computer Tomography, Three-Point Bending Test, and Analysis of Minerals in Swiss Laying Hens

    PubMed Central

    Gebhardt-Henrich, Sabine G.; Pfulg, Andreas; Fröhlich, Ernst K. F.; Käppeli, Susanna; Guggisberg, Dominik; Liesegang, Annette; Stoffel, Michael H.

    2017-01-01

    Keel bone damage is a wide-spread welfare problem in laying hens. It is unclear so far whether bone quality relates to keel bone damage. The goal of the present study was to detect possible associations between keel bone damage and bone properties of intact and damaged keel bones and of tibias in end-of-lay hens raised in loose housing systems. Bones were palpated and examined by peripheral quantitative computer tomography (PQCT), a three-point bending test, and analyses of bone ash. Contrary to our expectations, PQCT revealed higher cortical and trabecular contents in fractured than in intact keel bones. This might be due to structural bone repair after fractures. Density measurements of cortical and trabecular tissues of keel bones did not differ between individuals with and without fractures. In the three-point bending test of the tibias, ultimate shear strength was significantly higher in birds with intact vs. fractured keel bones. Likewise, birds with intact or slightly deviated keel bones had higher mineral and calcium contents of the keel bone than birds with fractured keel bones. Calcium content in keel bones was correlated with calcium content in tibias. Although there were some associations between bone traits related to bone strength and keel bone damage, other factors such as stochastic events related to housing such as falls and collisions seem to be at least as important for the prevalence of keel bone damage. PMID:28848740

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

    PubMed Central

    Lee, Donald W.; Allison, Andrew B.; Bacon, Kaitlyn B.

    2016-01-01

    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

  8. Specific binding of /sup 125/I-labeled human chorionic gonadotropin to gonadal tissue: comparison of limited-point saturation analyses to Scatchard analyses for determining binding capacities and factors affecting estimates of binding capacity

    SciTech Connect

    Spicer, L.J.; Ireland, J.J.

    1986-07-01

    Experiments were conducted to compare gonadotropin binding capacity calculated from limited-point saturation analyses to those obtained from Scatchard analyses, and to test the effects of membrane purity and source of gonadotropin receptors on determining the maximum percentage of radioiodinated hormone bound to receptors (maximum bindability). One- to four-point saturation analyses gave results comparable to results by Scatchard analyses when examining relative binding capacities of receptors. Crude testicular homogenates had lower estimates of maximum bindability of /sup 125/I-labeled human chorionic gonadotropin than more purified gonadotropin receptor preparations. Under similar preparation techniques, some gonadotropin receptor sources exhibited low maximum bindability.

  9. Structure of a human pre-40S particle points to a role for RACK1 in the final steps of 18S rRNA processing

    PubMed Central

    Larburu, Natacha; Montellese, Christian; O'Donohue, Marie-Françoise; Kutay, Ulrike; Gleizes, Pierre-Emmanuel; Plisson-Chastang, Célia

    2016-01-01

    Synthesis of ribosomal subunits in eukaryotes is a complex and tightly regulated process that has been mostly characterized in yeast. The discovery of a growing number of diseases linked to defects in ribosome biogenesis calls for a deeper understanding of these mechanisms and of the specificities of human ribosome maturation. We present the 19 Å resolution cryo-EM reconstruction of a cytoplasmic precursor to the human small ribosomal subunit, purified by using the tagged ribosome biogenesis factor LTV1 as bait. Compared to yeast pre-40S particles, this first three-dimensional structure of a human 40S subunit precursor shows noticeable differences with respect to the position of ribosome biogenesis factors and uncovers the early deposition of the ribosomal protein RACK1 during subunit maturation. Consistently, RACK1 is required for efficient processing of the 18S rRNA 3′-end, which might be related to its role in translation initiation. This first structural analysis of a human pre-ribosomal particle sets the grounds for high-resolution studies of conformational transitions accompanying ribosomal subunit maturation. PMID:27530427

  10. Structure of a human pre-40S particle points to a role for RACK1 in the final steps of 18S rRNA processing.

    PubMed

    Larburu, Natacha; Montellese, Christian; O'Donohue, Marie-Françoise; Kutay, Ulrike; Gleizes, Pierre-Emmanuel; Plisson-Chastang, Célia

    2016-09-30

    Synthesis of ribosomal subunits in eukaryotes is a complex and tightly regulated process that has been mostly characterized in yeast. The discovery of a growing number of diseases linked to defects in ribosome biogenesis calls for a deeper understanding of these mechanisms and of the specificities of human ribosome maturation. We present the 19 Å resolution cryo-EM reconstruction of a cytoplasmic precursor to the human small ribosomal subunit, purified by using the tagged ribosome biogenesis factor LTV1 as bait. Compared to yeast pre-40S particles, this first three-dimensional structure of a human 40S subunit precursor shows noticeable differences with respect to the position of ribosome biogenesis factors and uncovers the early deposition of the ribosomal protein RACK1 during subunit maturation. Consistently, RACK1 is required for efficient processing of the 18S rRNA 3'-end, which might be related to its role in translation initiation. This first structural analysis of a human pre-ribosomal particle sets the grounds for high-resolution studies of conformational transitions accompanying ribosomal subunit maturation. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  11. 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).

  12. Search for QCD Phase Transitions and the Critical Point Utilizing Particle Ratio Fluctuations and Transverse Momentum Correlations from the STAR Experiment

    NASA Astrophysics Data System (ADS)

    Tribedy, Prithwish

    2013-05-01

    Dynamical fluctuations of the globally conserved quantities in heavy ion collisions, such as baryon number, strangeness, charge, and isospin are suggested to carry information about the deconfinement and chiral phase transitions. The STAR experiment has performed a comprehensive study of the collision energy and charge dependence of dynamical particle ratio (K/π, p/π, and K/p) fluctuations, net-charge fluctuations, and transverse momentum correlations at mid-rapidity, as well as neutral-charge pion fluctuations at forward rapidity. The centrality, charge, and collision energy dependence from new measurements of the fluctuation observables νdyn, and r, and the energy dependence of transverse momentum correlations from s=7.7 - 200GeV Au + Au collisions are presented. These results are also compared to predictions from hadronic models.

  13. 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.

  14. Extended micro objects as dark matter particles

    NASA Astrophysics Data System (ADS)

    Belotsky, K.; Rubin, S.; Svadkovsky, I.

    2017-05-01

    Models of various forms of composite dark matter (DM) predicted by particle theory and the DM constituents formed by gravity that are not reduced to new elementary particle candidates are discussed. Main attention is paid to a gravitational origin of the DM. The influence of extended mass spectrum of primordial black holes on observational limits is considered. It is shown that non-uniformly deformed extra space can be considered as point-like masses which possess only gravitational interaction with each other and with the ordinary particles. The recently discussed six-dimensional stable wormholes could contribute to the DM. The contribution of dark atoms is also considered.

  15. Solutions for correlations along the coexistence curve and at the critical point of a kagomé lattice gas with three-particle interactions

    NASA Astrophysics Data System (ADS)

    Barry, J. H.; Muttalib, K. A.; Tanaka, T.

    2008-01-01

    We consider a two-dimensional (d=2) kagomé lattice gas model with attractive three-particle interactions around each triangular face of the kagomé lattice. Exact solutions are obtained for multiparticle correlations along the liquid and vapor branches of the coexistence curve and at criticality. The correlation solutions are also determined along the continuation of the curvilinear diameter of the coexistence region into the disordered fluid region. The method generates a linear algebraic system of correlation identities with coefficients dependent only upon the interaction parameter. Using a priori knowledge of pertinent solutions for the density and elementary triplet correlation, one finds a closed and linearly independent set of correlation identities defined upon a spatially compact nine-site cluster of the kagomé lattice. Resulting exact solution curves of the correlations are plotted and discussed as functions of the temperature and are compared with corresponding results in a traditional kagomé lattice gas having nearest-neighbor pair interactions. An example of application for the multiparticle correlations is demonstrated in cavitation theory.

  16. Anatomy-based definition of point A utilizing three-dimensional volumetric imaging approach for high-dose-rate (HDR) intracavitary brachytherapy dose prescription when treating cervical cancer using limited resources.

    PubMed

    Goyal, Manish K; Rai, D V; Kehwar, Than S; Manjhi, Jayanand; Heintz, Bret H; Shide, Kathleen L; Barker, Jerry L

    2016-07-16

    This study was designed to determine whether volumetric imaging could identify consistent alternative prescription methods to Manchester/point A when prescribing radiation dose in the treatment of cervical cancer using HDR intracavitary brachy-therapy (ICBT). One hundred and twenty-five treatment plans of 25 patients treated for carcinoma of the cervix were reviewed retrospectively. Each patient received 5 fractions of HDR ICBT following initial cisplatin-based pelvic chemoradiation, and radiation dose was originally prescribed to point A (ICRU-38). The gross tumor volume (GTV) and high-risk clinical target volume (HR-CTV) were contoured in three dimensions on the CT datasets, and inferior-superior, anterior-posterior, and left-right dimensions HR-CTV were recorded along with multiple anatomic and skeletal dimensions for each patient. The least square-best fit regression lines were plotted between one half of the HR-CTV width and pelvic cavity dimension at femoral head level and at maximum cavity dimension. The points in both plots lie reasonably close to straight lines and are well defined by straight lines with slopes of 0.15 and 0.17; intercept on y-axes of -0.08 and -0.03, point A, at the same level as defined based on applicator coordinates, is defined using this correlation, which is a function of distance between femoral heads/dimensions of maximum pelvic cavity width. Both relations, defined by straight lines, provide an estimated location of point A, which provides adequate coverage to the HR-CTV compared to the point A defined based on applicator coordinates. The point A defined based on femoral head distance would, therefore, be a reasonable surrogate to use for dose prescription because of subjective variation of cavity width dimension. Simple surrogate anatomic/skeletal landmarks can be useful for prescribing radiation dose when treating cervical cancer using intracavitary brachytherapy in limited-resource settings. Our ongoing work will continue to

  17. Growth performance and total tract nutrient digestion for Holstein heifers limit-fed diets high in distillers grains with different forage particle size

    USDA-ARS?s Scientific Manuscript database

    This study evaluated dairy heifer growth performance and total tract nutrient digestion when fed diets high in dried distillers grains with solubles (DDGS) with different forage particle size. An 8-wk randomized complete block design study was conducted utilizing twenty-two Holstein heifers (123 ±...

  18. 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.

  19. Diffusion in jammed particle packs

    NASA Astrophysics Data System (ADS)

    Bolintineanu, Dan S.; Silbert, Leonardo E.; Grest, Gary S.; Lechman, Jeremy B.

    2015-03-01

    Diffusive transport in jammed particle packs is of interest for a number of applications, as well as being a potential indicator of structural properties near the jamming point. To this end, we report stochastic simulations of equilibrium diffusion through monodisperse sphere packs near the jamming point in the limit of a perfectly insulating surrounding medium. The time dependence of various diffusion properties is resolved over several orders of magnitude. Two time regimes of expected Fickian diffusion are observed, separated by an intermediate regime of anomalous diffusion. This intermediate regime grows as the particle volume fraction approaches the critical jamming transition. The diffusion behavior is fully controlled by the extent of the contacts between neighboring particles, which in turn depend on proximity to the jamming point. In particular, the mean first passage time associated with the escape of random walkers between neighboring particles is shown to control both the time to recover Fickian diffusion and the long time diffusivity. Scaling laws are established that relate these quantities to the difference between the actual and critical jamming volume fractions. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under Contract DE- AC04-94AL85000.

  20. Quantum Change Point

    NASA Astrophysics Data System (ADS)

    Sentís, Gael; Bagan, Emilio; Calsamiglia, John; Chiribella, Giulio; Muñoz-Tapia, Ramon

    2016-10-01

    Sudden changes are ubiquitous in nature. Identifying them is crucial for a number of applications in biology, medicine, and social sciences. Here we take the problem of detecting sudden changes to the quantum domain. We consider a source that emits quantum particles in a default state, until a point where a mutation occurs that causes the source to switch to another state. The problem is then to find out where the change occurred. We determine the maximum probability of correctly identifying the change point, allowing for collective measurements on the whole sequence of particles emitted by the source. Then, we devise online strategies where the particles are measured individually and an answer is provided as soon as a new particle is received. We show that these online strategies substantially underperform the optimal quantum measurement, indicating that quantum sudden changes, although happening locally, are better detected globally.

  1. Quantum Change Point.

    PubMed

    Sentís, Gael; Bagan, Emilio; Calsamiglia, John; Chiribella, Giulio; Muñoz-Tapia, Ramon

    2016-10-07

    Sudden changes are ubiquitous in nature. Identifying them is crucial for a number of applications in biology, medicine, and social sciences. Here we take the problem of detecting sudden changes to the quantum domain. We consider a source that emits quantum particles in a default state, until a point where a mutation occurs that causes the source to switch to another state. The problem is then to find out where the change occurred. We determine the maximum probability of correctly identifying the change point, allowing for collective measurements on the whole sequence of particles emitted by the source. Then, we devise online strategies where the particles are measured individually and an answer is provided as soon as a new particle is received. We show that these online strategies substantially underperform the optimal quantum measurement, indicating that quantum sudden changes, although happening locally, are better detected globally.

  2. Pushing the performance limits of reversed-phase ultra high performance liquid chromatography with 1.3μm core-shell particles.

    PubMed

    Sanchez, A Carl; Friedlander, Gareth; Fekete, Szabolcs; Anspach, Jason; Guillarme, Dvy; Chitty, Mike; Farkas, Tivadar

    2013-10-11

    Innovative columns made with very small core-shell particles (1.0-1.4μm) were investigated over a wide experimental space using state-of-the-art ultra high performance liquid chromatography (UHPLC) instruments. Among the columns tested is one that is now commercially available and is made with 1.3μm core-shell particles consisting of non-porous cores about 0.9μm in size and porous shells <0.2μm thick. This work demonstrated that exceptionally low observed minimum plate heights of 2.2μm could be obtained using columns packed with 1.3μm particles, corresponding to a plate count of over 450,000 plates/m. It was shown that only low volume columns allow operation under optimal conditions with current top-of-the-line UHPLC instruments. It was also demonstrated that the loss in performance caused by frictional heating effects remains negligible. Finally, the practical utility of these columns was confirmed with several real-world applications requiring extreme resolving power (i.e. peptide mapping, sample typical of metabolomic studies and crude human insulin). The performance achieved was compared to that of a reference UHPLC column packed with 1.7μm fully porous particles. The column packed with 1.3μm particles gave peak capacity values that were 20-40% higher than the reference column for the same analysis time. Copyright © 2013 Elsevier B.V. All rights reserved.

  3. 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)

  4. 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)

  5. 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.

  6. Limit on the yield of single direct muons and the cross section for charmed-particle production in proton-nucleus interactions at 70 GeV

    SciTech Connect

    Bugorskii, A.P.; Volkov, A.A.; Kochetkov, V.I.; Kurbakov, V.I.; Mukhin, A.I.; Sviridov, Y.M.

    1984-09-01

    We compare the yields of direct muons in pFe interactions at 70 GeV with the expected contribution of muons from muon-pair production. We show that the contribution of these processes is (82 +- 4 +- 12)% on the average in the region 0.09< or approx. =x/sub F/< or approx. =0.6. Model-dependent restrictions on the cross section for production of charmed particles are obtained.

  7. Practical limitations of single particle ICP-MS in the determination of nanoparticle size distributions and dissolution: case of rare earth oxides.

    PubMed

    Fréchette-Viens, Laurie; Hadioui, Madjid; Wilkinson, Kevin J

    2017-01-15

    The applicability of single particle ICP-MS (SP-ICP-MS) for the analysis of nanoparticle size distributions and the determination of particle numbers was evaluated using the rare earth oxide, La2O3, as a model particle. The composition of the storage containers, as well as the ICP-MS sample introduction system were found to significantly impact SP-ICP-MS analysis. While La2O3 nanoparticles (La2O3 NP) did not appear to interact strongly with sample containers, adsorptive losses of La(3+)(over 24h) were substantial (>72%) for fluorinated ethylene propylene bottles as opposed to polypropylene (<10%). Furthermore, each part of the sample introduction system (nebulizers made of perfluoroalkoxy alkane (PFA) or glass, PFA capillary tubing, and polyvinyl chloride (PVC) peristaltic pump tubing) contributed to La(3+) adsorptive losses. On the other hand, the presence of natural organic matter in the nanoparticle suspensions led to a decreased adsorptive loss in both the sample containers and the introduction system, suggesting that SP-ICP-MS may nonetheless be appropriate for NP analysis in environmental matrices. Coupling of an ion-exchange resin to the SP-ICP-MS led to more accurate determinations of the La2O3 NP size distributions. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Anatomy-based definition of point A utilizing three-dimensional volumetric imaging approach for high-dose-rate (HDR) intracavitary brachytherapy dose prescription when treating cervical cancer using limited resources.

    PubMed

    Goyal, Manish K; Rai, D V; Kehwar, Than S; Manjhi, Jayanand; Heintz, Bret H; Shide, Kathleen L; Barker, Jerry L

    2016-11-01

    This study was designed to determine whether volumetric imaging could identify consistent alternative prescription methods to Manchester/point A when prescribing radiation dose in the treatment of cervical cancer using HDR intracavitary brachytherapy (ICBT). One hundred and twenty-five treatment plans of 25 patients treated for carcinoma of the cervix were reviewed retrospectively. Each patient received 5 fractions of HDR ICBT following initial cisplatin-based pelvic chemoradiation, and radiation dose was originally prescribed to point A (ICRU-38). The gross tumor volume (GTV) and high-risk clinical target volume (HR-CTV) were contoured in three dimensions on the CT datasets, and inferior-superior, anterior-posterior, and left-right dimensions HR-CTV were recorded along with multiple anatomic and skeletal dimensions for each patient. The least square-best fit regression lines were plotted between one half of the HR-CTV width and pelvic cavity dimension at femoral head level and at maximum cavity dimension. The points in both plots lie reasonably close to straight lines and are well defined by straight lines with slopes of 0.15 and 0.17; intercept on y-axes of -0.08 and -0.03, point A, at the same level as defined based on applicator coordinates, is defined using this correlation, which is a function of distance between femoral heads/dimensions of maximum pelvic cavity width. Both relations, defined by straight lines, provide an estimated location of point A, which provides adequate coverage to the HR-CTV compared to the point A defined based on applicator coordinates. The point A defined based on femoral head distance would, therefore, be a reasonable surrogate to use for dose prescription because of subjective variation of cavity width dimension. Simple surrogate anatomic/skeletal landmarks can be useful for prescribing radiation dose when treating cervical cancer using intracavitary brachytherapy in limited-resource settings. Our ongoing work will continue to

  9. 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?

  10. Generalized power-spectrum Larmor formula for an extended charged particle embedded in a harmonic oscillator

    NASA Astrophysics Data System (ADS)

    Marengo, Edwin A.; Khodja, Mohamed R.

    2006-09-01

    The nonrelativistic Larmor radiation formula, giving the power radiated by an accelerated charged point particle, is generalized for a spatially extended particle in the context of the classical charged harmonic oscillator. The particle is modeled as a spherically symmetric rigid charge distribution that possesses both translational and spinning degrees of freedom. The power spectrum obtained exhibits a structure that depends on the form factor of the particle, but reduces, in the limit of an infinitesimally small particle and for the charge distributions considered, to Larmor’s familiar result. It is found that for finite-duration small-enough accelerations as well as perpetual uniform accelerations the power spectrum of the spatially extended particle reduces to that of a point particle. It is also found that when the acceleration is violent or the size parameter of the particle is very large compared to the wavelength of the emitted radiation the power spectrum is highly suppressed. Possible applications are discussed.

  11. Multiplicity fluctuations near the QCD critical point

    NASA Astrophysics Data System (ADS)

    Hippert, M.; Fraga, E. S.

    2017-08-01

    Statistical moments of particle multiplicities in heavy-ion collision experiments are an important probe in the exploration of the phase diagram of strongly interacting matter and, particularly, in the search for the QCD critical end point. In order to appropriately interpret experimental measures of these moments, however, it is necessary to understand the role of experimental limitations, as well as background contributions, providing expectations on how critical behavior should be affected by them. We here present a framework for calculating moments of particle multiplicities in the presence of correlations of both critical and spurious origins. We also include effects from resonance decay and a limited acceptance window, as well as detector efficiency. Although we focus on second-order moments, for simplicity, an extension to higher-order moments is straightforward.

  12. Thermal limiting effects in optical plasmonic waveguides

    NASA Astrophysics Data System (ADS)

    Ershov, A. E.; Gerasimov, V. S.; Gavrilyuk, A. P.; Karpov, S. V.; Zakomirnyi, V. I.; Rasskazov, I. L.; Polyutov, S. P.

    2017-04-01

    We have studied thermal effects occurring during excitation of optical plasmonic waveguide (OPW) in the form of linear chain of spherical Ag nanoparticles by pulsed laser radiation. It was shown that heating and subsequent melting of the first irradiated particle in a chain can significantly deteriorate the transmission efficiency of OPW that is the crucial and limiting factor and continuous operation of OPW requires cooling devices. This effect is caused by suppression of particle's surface plasmon resonance due to reaching the melting point temperature. We have determined optimal excitation parameters which do not significantly affect the transmission efficiency of OPW.

  13. Particle-laden turbulence under radiation: toward a novel small-particle solar receiver

    NASA Astrophysics Data System (ADS)

    Frankel, Ari; Mani, Ali; Iaccarino, Gianluca

    2016-11-01

    In particle-based solar receivers, an array of mirrors focuses sunlight onto a falling curtain of particles in a duct that absorb the light and warm up. The heated particles can be stored for later energy extraction. In this work we consider a design concept in which the particles and air are in a co-flowing configuration, and as the particles are heated they conduct the energy to the surrounding air. The air-particle mixture can then be separated and the heated air used for energy extraction. To assess the viability of this energy concept we have developed a simulation capability to analyze the flow of small particles in a turbulent flow with radiation. The code combines a point-particle direct numerical simulation of the particle-air flow in the low Mach number limit with the discrete ordinates solution of the gray, quasi-steady radiative transfer equation. We will describe the individual solution components and the coupling methodology. We will then demonstrate some results from the replication of a lab-scale experiment of a laser diode array irradiating a transparent channel with a flowing air-particle mixture. This work was supported by the Predictive Science Academic Alliance Program 2 at Stanford.

  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. 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.

  16. The CELF1 RNA-Binding Protein Regulates Decay of Signal Recognition Particle mRNAs and Limits Secretion in Mouse Myoblasts

    PubMed Central

    Russo, Joseph; Lee, Jerome E.; López, Carolina M.; Anderson, John; Nguyen, Thuy-mi P.; Heck, Adam M.; Wilusz, Jeffrey

    2017-01-01

    We previously identified several mRNAs encoding components of the secretory pathway, including signal recognition particle (SRP) subunit mRNAs, among transcripts associated with the RNA-binding protein CELF1. Through immunoprecipitation of RNAs crosslinked to CELF1 in myoblasts and in vitro binding assays using recombinant CELF1, we now provide evidence that CELF1 directly binds the mRNAs encoding each of the subunits of the SRP. Furthermore, we determined the half-lives of the Srp transcripts in control and CELF1 knockdown myoblasts. Our results indicate CELF1 is a destabilizer of at least five of the six Srp transcripts and that the relative abundance of the SRP proteins is out of balance when CELF1 is depleted. CELF1 knockdown myoblasts exhibit altered secretion of a luciferase reporter protein and are impaired in their ability to migrate and close a wound, consistent with a defect in the secreted extracellular matrix. Importantly, similar defects in wound healing are observed when SRP subunit imbalance is induced by over-expression of SRP68. Our studies support the existence of an RNA regulon containing Srp mRNAs that is controlled by CELF1. One implication is that altered function of CELF1 in myotonic dystrophy may contribute to changes in the extracellular matrix of affected muscle through defects in secretion. PMID:28129347

  17. Hyperuniformity disorder length spectroscopy for extended particles

    NASA Astrophysics Data System (ADS)

    Durian, D. J.

    2017-09-01

    The concept of a hyperuniformity disorder length h was recently introduced for analyzing volume fraction fluctuations for a set of measuring windows [Chieco et al., Phys. Rev. E 96, 032909 (2017)., 10.1103/PhysRevE.96.032909]. This length permits a direct connection to the nature of disorder in the spatial configuration of the particles and provides a way to diagnose the degree of hyperuniformity in terms of the scaling of h and its value in comparison with established bounds. Here, this approach is generalized for extended particles, which are larger than the image resolution and can lie partially inside and partially outside the measuring windows. The starting point is an expression for the relative volume fraction variance in terms of four distinct volumes: that of the particle, the measuring window, the mean-squared overlap between particle and region, and the region over which particles have nonzero overlap with the measuring window. After establishing limiting behaviors for the relative variance, computational methods are developed for both continuum and pixelated particles. Exact results are presented for particles of special shape and for measuring windows of special shape, for which the equations are tractable. Comparison is made for other particle shapes, using simulated Poisson patterns. And the effects of polydispersity and image errors are discussed. For small measuring windows, both particle shape and spatial arrangement affect the form of the variance. For large regions, the variance scaling depends only on arrangement but particle shape sets the numerical proportionality. The combined understanding permit the measured variance to be translated to the spectrum of hyperuniformity lengths versus region size, as the quantifier of spatial arrangement. This program is demonstrated for a system of nonoverlapping particles at a series of increasing packing fractions as well as for an Einstein pattern of particles with several different extended shapes.

  18. 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.

  19. Escape rate of an active Brownian particle over a potential barrier

    NASA Astrophysics Data System (ADS)

    Burada, P. S.; Lindner, B.

    2012-03-01

    We study the dynamics of an active Brownian particle with a nonlinear friction function located in a spatial cubic potential. For strong but finite damping, the escape rate of the particle over the spatial potential barrier shows a nonmonotonic dependence on the noise intensity. We relate this behavior to the fact that the active particle escapes from a limit cycle rather than from a fixed point and that a certain amount of noise can stabilize the sojourn of the particle on this limit cycle.

  20. The HEL Upper Limit

    NASA Astrophysics Data System (ADS)

    Billingsley, J. P.

    2002-07-01

    A threshold particle velocity, Vf, derived by Professor E.R. Fitzgerald for the onset of atomic lattice Disintegration Phenomena (LDP) is shown to exceed and/or compare rather well with the maximum experimental Hugoniot Elastic Limit (HEL) particle (mass) velocities (UpHEL) for selected hard strong mineral/ceramic materials.

  1. Search for supersymmetric particles in e+e- collisions at /sqrt(s) up to 202 GeV and mass limit for the lightest neutralino

    NASA Astrophysics Data System (ADS)

    ALEPH Collaboration; Barate, R.; De Bonis, I.; Decamp, D.; Ghez, P.; Goy, C.; Jezequel, S.; Lees, J.-P.; Martin, F.; Merle, E.; Minard, M.-N.; Pietrzyk, B.; Bravo, S.; Casado, M. P.; Chmeissani, M.; Crespo, J. M.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, L.; Graugés, E.; Lopez, J.; Martinez, M.; Merino, G.; Miquel, R.; Mir, L. M.; Pacheco, A.; Paneque, D.; Ruiz, H.; Colaleo, A.; Creanza, D.; De Filippis, N.; de Palma, M.; Iaselli, G.; Maggi, G.; Maggi, M.; Nuzzo, S.; Ranieri, A.; Raso, G.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Tricomi, A.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Abbaneo, D.; Azzurri, P.; Barklow, T.; Boix, G.; Buchmüller, O.; Cattaneo, M.; Cerutti, F.; Clerbaux, B.; Dissertori, G.; Drevermann, H.; Forty, R. W.; Frank, M.; Gianotti, F.; Greening, T. C.; Hansen, J. B.; Harvey, J.; Hutchcroft, D. E.; Janot, P.; Jost, B.; Kado, M.; Lemaitre, V.; Maley, P.; Mato, P.; Minten, A.; Moutoussi, A.; Ranjard, F.; Rolandi, L.; Schlatter, D.; Schmitt, M.; Schneider, O.; Spagnolo, P.; Tejessy, W.; Teubert, F.; Tournefier, E.; Valassi, A.; Ward, J. J.; Wright, A. E.; Ajaltouni, Z.; Badaud, F.; Dessagne, S.; Falvard, A.; Fayolle, D.; Gay, P.; Henrard, P.; Jousset, J.; Michel, B.; Monteil, S.; Montret, J.-C.; Pallin, D.; Pascolo, J. M.; Perret, P.; Podlyski, F.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Nilsson, B. S.; Wäänänen, A.; Daskalakis, G.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Vayaki, A.; Blondel, A.; Brient, J.-C.; Machefert, F.; Rougé, A.; Swynghedauw, M.; Tanaka, R.; Videau, H.; Focardi, E.; Parrini, G.; Zachariadou, K.; Antonelli, A.; Antonelli, M.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Chiarella, V.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Passalacqua, L.; Pepe-Altarelli, M.; Chalmers, M.; Halley, A. W.; Kennedy, J.; Lynch, J. G.; Negus, P.; O'Shea, V.; Raeven, B.; Smith, D.; Teixeira-Dias, P.; Thompson, A. S.; Cavanaugh, R.; Dhamotharan, S.; Geweniger, C.; Hanke, P.; Hepp, V.; Kluge, E. E.; Leibenguth, G.; Putzer, A.; Tittel, K.; Werner, S.; Wunsch, M.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Davies, G.; Dornan, P. J.; Girone, M.; Marinelli, N.; Nowell, J.; Przysiezniak, H.; Sedgbeer, J. K.; Thompson, J. C.; Thomson, E.; White, R.; Ghete, V. M.; Girtler, P.; Kneringer, E.; Kuhn, D.; Rudolph, G.; Bouhova-Thacker, E.; Bowdery, C. K.; Clarke, D. P.; Ellis, G.; Finch, A. J.; Foster, F.; Hughes, G.; Jones, R. W. L.; Pearson, M. R.; Robertson, N. A.; Smizanska, M.; Giehl, I.; Hölldorfer, F.; Jakobs, K.; Kleinknecht, K.; Kröcker, M.; Müller, A.-S.; Nürnberger, H.-A.; Quast, G.; Renk, B.; Rohne, E.; Sander, H.-G.; Schmeling, S.; Wachsmuth, H.; Zeitnitz, C.; Ziegler, T.; Bonissent, A.; Carr, J.; Coyle, P.; Curtil, C.; Ealet, A.; Fouchez, D.; Leroy, O.; Kachelhoffer, T.; Payre, P.; Rousseau, D.; Tilquin, A.; Aleppo, M.; Gilardoni, S.; Ragusa, F.; David, A.; Dietl, H.; Ganis, G.; Heister, A.; Hüttmann, K.; Lütjens, G.; Mannert, C.; Männer, W.; Moser, H.-G.; Schael, S.; Settles, R.; Stenzel, H.; Wolf, G.; Boucrot, J.; Callot, O.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, P.; Jacholkowska, A.; Serin, L.; Veillet, J.-J.; Videau, I.; de Vivie de Régie, J.-B.; Yuan, C.; Zerwas, D.; Bagliesi, G.; Boccali, T.; Calderini, G.; Ciulli, V.; Foà, L.; Giammanco, A.; Giassi, A.; Ligabue, F.; Messineo, A.; Palla, F.; Sanguinetti, G.; Sciabà, A.; Sguazzoni, G.; Tenchini, R.; Venturi, A.; Verdini, P. G.; Blair, G. A.; Coles, J.; Cowan, G.; Green, M. G.; Jones, L. T.; Medcalf, T.; Strong, J. A.; Clifft, R. W.; Edgecock, T. R.; Norton, P. R.; Tomalin, I. R.; Bloch-Devaux, B.; Boumediene, D.; Colas, P.; Fabbro, B.; Lançon, E.; Lemaire, M.-C.; Locci, E.; Perez, P.; Rander, J.; Renardy, J.-F.; Rosowsky, A.; Seager, P.; Trabelsi, A.; Tuchming, B.; Vallage, B.; Konstantinidis, N.; Loomis, C.; Litke, A. M.; Taylor, G.; Booth, C. N.; Cartwright, S.; Combley, F.; Hodgson, P. N.; Lehto, M.; Thompson, L. F.; Affholderbach, K.; Böhrer, A.; Brandt, S.; Grupen, C.; Hess, J.; Misiejuk, A.; Prange, G.; Sieler, U.; Borean, C.; Giannini, G.; Gobbo, B.; He, H.; Putz, J.; Rothberg, J.; Wasserbaech, S.; Armstrong, S. R.; Cranmer, K.; Elmer, P.; Ferguson, D. P. S.; Gao, Y.; González, S.; Hayes, O. J.; Hu, H.; Jin, S.; Kile, J.; McNamara, P. A., III; Nielsen, J.; Orejudos, W.; Pan, Y. B.; Saadi, Y.; Scott, I. J.; von Wimmersperg-Toeller, J. H.; Walsh, J.; Wiedenmann, W.; Wu, J.; Wu, S. L.; Wu, X.; Zobernig, G.

    2001-02-01

    Searches for pair production of squarks, sleptons, charginos and neutralinos are performed with the data collected by the ALEPH detector at LEP at centre-of-mass energies from 188.6 to 201.6 GeV. No evidence for any such signals is observed in a total integrated luminosity of about 410 pb-1. The negative results of the searches are translated into exclusion domains in the space of the relevant MSSM parameters, which improve significantly on the constraints set previously. Under the assumptions of gaugino and sfermion mass unification, these results allow a 95% C.L. lower limit of 37 GeV/c2 to be set on the mass of the lightest neutralino for any /tanβ and sfermion mass. Additional constraints in the MSSM parameter space are derived from the negative results of ALEPH searches for Higgs bosons. The results are also interpreted in the framework of minimal supergravity.

  2. Detecting Contaminant Particles Acoustically

    NASA Technical Reports Server (NTRS)

    Wyett, L. M.

    1986-01-01

    Apparatus "listens" for particles in interior of complex turbomachinery. Contact microphones are attached at several points on pump housing. Acoustic transducer also attached to housing to excite entire pump with sound. Frequency of sound is slowly raised until pump resonates. Microphones detect noise of loose particles scraping against pump parts. Such as machining chips in turbopumps or other machinery without disassembly.

  3. Discretization errors in particle tracking

    NASA Astrophysics Data System (ADS)

    Carmon, G.; Mamman, N.; Feingold, M.

    2007-03-01

    High precision video tracking of microscopic particles is limited by systematic and random errors. Systematic errors are partly due to the discretization process both in position and in intensity. We study the behavior of such errors in a simple tracking algorithm designed for the case of symmetric particles. This symmetry algorithm uses interpolation to estimate the value of the intensity at arbitrary points in the image plane. We show that the discretization error is composed of two parts: (1) the error due to the discretization of the intensity, bD and (2) that due to interpolation, bI. While bD behaves asymptotically like N-1 where N is the number of intensity gray levels, bI is small when using cubic spline interpolation.

  4. SAMPEX special pointing mode

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Flatley, Thomas W.; Leoutsakos, Theodore

    1995-01-01

    A new pointing mode has been developed for the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) spacecraft. This pointing mode orients the instrument boresights perpendicular to the field lines of the Earth's magnetic field in regions of low field strength and parallel to the field lines in regions of high field strength, to allow better characterization of heavy ions trapped by the field. The new mode uses magnetometer signals and is algorithmically simpler than the previous control mode, but it requires increased momentum wheel activity. It was conceived, designed, tested, coded, uplinked to the spacecraft, and activated in less than seven months.

  5. Tipping Point

    MedlinePlus

    ... Point by CPSC Blogger September 22, 2009 appliance child Childproofing CPSC danger death electrical fall furniture head injury product safety television tipover tv Watch the video in Adobe Flash ...

  6. 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.

  7. 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.; Asano, K.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Burnett, T. H.; Busetto, G.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Charles, E.; Chaty, S.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Cillis, A. N.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Colafrancesco, S.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Palma, F.; Dermer, C. D.; do Couto e Silva, E.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fortin, P.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grandi, P.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hays, E.; Horan, D.; Hou, X.; Hughes, R. E.; Jackson, M. S.; Jogler, T.; Jóhannesson, G.; Johnson, R. P.; Johnson, A. S.; Kamae, T.; Kataoka, J.; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Lavalley, C.; Lee, S. -H.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; McConville, W.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mignani, R. P.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Nemmen, R.; Nishino, S.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Pelassa, V.; Perkins, J. S.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Poon, H.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Reyes, L. C.; Ritz, S.; Rochester, L. S.; Romoli, C.; Roth, M.; Sanchez, D. A.; Saz Parkinson, P. M.; Scargle, J. D.; Sgrò, C.; Siskind, E. J.; Snyder, A.; Spandre, G.; Spinelli, P.; Stephens, T. E.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tibolla, O.; Tinivella, M.; Tosti, G.; Troja, E.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; von Kienlin, A.; Waite, A. P.; Wallace, E.; Weltevrede, P.; Winer, B. L.; Wood, K. S.; Wood, M.; Yang, Z.; Zimmer, S.

    2013-02-15

    We present the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to detect photons with energies from ≈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 γ 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 γ-ray source and observation epoch and found none. We also investigated several possible spatial models for pair-halo emission around BL Lac AGNs. Finally, 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.

  8. Latitudinal limits to coral reef accretion: Testing the Darwin Point hypothesis at Kure Atoll, northwestern Hawaiian Islands, using new evidence from high resolution remote sensing and in situ data

    NASA Astrophysics Data System (ADS)

    Siciliano, Daria

    This dissertation focused on assessing patterns of carbonate production in a marginal reef environment as the key to understand the mechanisms that limit modern reef distribution, and those that effect the response of coral reefs to a changing environment. This investigation was carried out at Kure atoll in the Northwestern Hawaiian Islands, the northernmost atoll in the world. A less detailed comparative study was carried out throughout the 10 Northwestern Hawaiian Islands, with the goal of revisiting Grigg's (1982) Darwin Point hypothesis on the limit of coral reef formation. Patterns of carbonate metabolism and benthic diversity at Kure Atoll were obtained from analysis of high resolution IKONOS multispectral imagery; calcification rates were obtained from x-rayed slabs of coral samples and cores of the main coral reef-builders, collected in different habitats at Kure; data on habitat-specific bioerosion rates were obtained from in situ surveys of the main bioeroding taxa. These data were used to construct a habitat-specific carbonate budget for Kure Atoll. The main sources and sinks of CaCO3 at Kure Atoll were identified and their spatial extent quantified. Calcification rates vary significantly between the different habitats, with the warmer and wave-protected lagoonal patch reefs and back reef habitat exhibiting the largest growth rates. Average calcification rates were found to be one order of magnitude greater than those reported by Grigg (1982), as was the total amount of CaCO3 deposited by reef-building corals. The new habitat mapping techniques employed here show that the reef building area and amount of live coral cover in all three main geomorphic habitats of Kure Atoll is greater than previously estimated, and that the lagoonal environments of Kure Atoll contribute the greatest amount to the accretion potential of the atoll, followed by the actively accreting fore reef environment. Stable isotopic measurements indicate that the decrease in coral

  9. 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.

  10. 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.

  11. Particle-vortex symmetric liquid

    NASA Astrophysics Data System (ADS)

    Mulligan, Michael

    2017-01-01

    We introduce an effective theory with manifest particle-vortex symmetry for disordered thin films undergoing a magnetic field-tuned superconductor-insulator transition. The theory may enable one to access both the critical properties of the strong-disorder limit, which has recently been confirmed by Breznay et al. [Proc. Natl. Acad. Sci. USA 113, 280 (2016), 10.1073/pnas.1522435113] to exhibit particle-vortex symmetric electrical response, and the nearby metallic phase discovered earlier by Mason and Kapitulnik [Phys. Rev. Lett. 82, 5341 (1999), 10.1103/PhysRevLett.82.5341] in less disordered samples. Within the effective theory, the Cooper-pair and field-induced vortex degrees of freedom are simultaneously incorporated into an electrically neutral Dirac fermion minimally coupled to a (emergent) Chern-Simons gauge field. A derivation of the theory follows upon mapping the superconductor-insulator transition to the integer quantum Hall plateau transition and the subsequent use of Son's particle-hole symmetric composite Fermi liquid. Remarkably, particle-vortex symmetric response does not require the introduction of disorder; rather, it results when the Dirac fermions exhibit vanishing Hall effect. The theory predicts approximately equal (diagonal) thermopower and Nernst signal with a deviation parameterized by the measured electrical Hall response at the symmetric point.

  12. Point Processes.

    DTIC Science & Technology

    1987-05-01

    ClaSIfication , 0.1102F 2304 Point processes____________ 12. PERSONAL AUTHORIS) Serfozo, R.F. 13AL TYPE OF REPORT 13b. TIME COVERED I4. DATE OF REPORT...the Laplace functional of M is as in Lemma 1.12. Keep in mind that a typical representation of a marked point process is o V 4 =. 1 6XnZ where N = 2 6...special case, for f: A - R . is X E[f(NO)] = E[JO f(O N)dt]. 0 Keep in mind that the expectation on the left is with respect to the probability for N

  13. DMSwarm: Particles in PETSc

    NASA Astrophysics Data System (ADS)

    May, Dave A.; Knepley, Matthew G.

    2017-04-01

    Whilst specific details of particle methods are as diverse as the applications in which they are utilized within, such methods have a number of common requirements. Specifically these entail: the need to attach data (or fields) to each point; support for the advection of points within some domain; dynamic insertion and deletion of points; collection type operations to gather nearby points; and methods to interpolate and restrict data back and forth between a set of points and a background mesh. Despite the commonality of these requirements, to date, few computational libraries provide high level support for particle methods in either a sequential, or parallel (MPI) computing environment. In this presentation, we describe the recently introduced implementation DMSwarm within the Portable, Extensible Toolkit for Scientific computing (PETSc) which provides a fully parallel solution for pure particle methods (e.g. DEM, SPH, EFG) and for particle-mesh methods (e.g. PIC, FLIP, MPM, GIMP). Particle-In-Cell (PIC) methods with geodynamic simulation tools are ubiquitous. To illustrate the functionality provided by DMSwarm, we present results from viscous flow calculations using a finite element PIC method applied to study Rayleigh-Taylor instabilities using both structured and unstructured meshes. Our results are derived from standard examples provided with the PETSc source distribution and serve as an entry-point for new users to learn how to incorporate DMSwarm into their geodynamic software.

  14. Point Barrow, Alaska

    NASA Image and Video Library

    2015-09-10

    Point Barrow or Nuvuk, Alaska is the northernmost point of all territory of the United States. It also marks the limit between the Chukchi Sea to the west, and the Beaufort Sea to the east. Archaeological evidence indicates that Point Barrow was occupied about 500 CE, probably as hunting camps for whales. The image covers an area of 32 by 38 km, was acquired July 29, 2015, and is located at 71.6 degrees north, 156.45 degrees west. http://photojournal.jpl.nasa.gov/catalog/PIA19775