Science.gov

Sample records for ion-atom collisions results

  1. Multiple-electron processes in fast ion-atom collisions

    SciTech Connect

    Schlachter, A.S.

    1989-03-01

    Research in atomic physics at the Lawrence Berkeley Laboratory Super-HILAC and Bevalac accelerators on multiple-electron processes in fast ion-atom collisions is described. Experiments have studied various aspects of the charge-transfer, ionization, and excitation processes. Examples of processes in which electron correlation plays a role are resonant transfer and excitation and Auger-electron emission. Processes in which electron behavior can generally be described as uncorrelated include ionization and charge transfer in high-energy ion-atom collisions. A variety of experiments and results for energies from 1 MeV/u to 420 MeV/u are presented. 20 refs., 15 figs.

  2. Ionization Phenomena in Ion-Atom Collisions

    NASA Astrophysics Data System (ADS)

    Deveney, Edward Francis

    Two many-electron ion-atom collision systems are used to investigate atomic and molecular structure and collisional interactions. Electrons emitted from MeV/u C^{3+} projectile target -atom collisions were measured with a high-resolution position -sensitive electron spectrometer at Oak Ridge National Laboratory. The electrons are predominantly ionized by direct projectile -target interactions or autoionizing (AI) from doubly excited AI levels of the ion which were excited in the collision. The energy dependence of directly scattered target electrons, binary-encounter electrons (BEE), is investigated and compared with theory. AI levels of the projectile 1s to nl single electron excited series, (1s2snl) n = 2,3,4,....infty, including the series limit are identified uniquely using energy level calculations. Original Auger yield calculations using a code by Cowan were used to discover a 1/{n^3} scaling in intensities of Auger peaks in the aforementioned series. This is explained using scattering theory. A nonstatistical population of the terms in the (1s2s2l) configuration was identified and investigated as a function of the beam energy and for four different target atoms. Two electron excited configurations are identified and investigated. The angular distribution of a correlated transfer and excitation AI state is measured and compared to theory. The final scattered charge state distributions of Kr^ {n+}, n = 1, 2, 3, 4, 5, projectiles are measured following collisions with Kr targets in the Van de Graaff Laboratory here at The University of Connecticut. Average scattered charge states as high as 12 are observed. It appears that these electrons are ionized during the lifetime of the quasimolecular state but a complete picture of the ionization mechanism(s) is not known. Calculations using a statistical model of ionization, modified in several ways, are compared with the experimental results to see if it is possible to isolate whether or not the electrons originate

  3. Saturation Effect of Projectile Excitation in Ion-Atom Collisions

    NASA Astrophysics Data System (ADS)

    Mukoyama, Takeshi; Lin, Chii-Dong

    Calculations of projectile K-shell electron excitation cross sections for He-like ions during ion-atom collisions have been performed in the distortion approximation by the use of Herman-Skillman wave functions. The calculated results are compared with the experimental data for several targets. The excitation cross sections deviate from the first-Born approximation and show the saturation effect as a function of target atomic number. This effect can be explained as the distortion of the projectile electronic states by the target nucleus.

  4. Newly appreciated roles for electrons in ion-atom collisions

    SciTech Connect

    Sellin, I.A. . Dept. of Physics and Astronomy Oak Ridge National Lab., TN )

    1990-01-01

    Since the previous Debrecen workshop on High-Energy Ion-Atom Collisions there have been numerous experiments and substantial theoretical developments in the fields of fast ion-atom and ion- solid collisions concerned with explicating the previously largely underappreciated role of electrons as ionizing and exciting agents in such collisions. Examples to be discussed include the double electron ionization problem in He; transfer ionization by protons in He; double excitation in He; backward scattering of electrons in He; the role of electron-electron interaction in determining beta parameters for ELC; projectile K ionization by target electrons; electron spin exchange in transfer excitation; electron impact ionization in crystal channels; resonant coherent excitation in crystal channels; excitation and dielectronic recombination in crystal channels; resonant transfer and excitation; the similarity of recoil ion spectra observed in coincidence with electron capture vs. electron loss; and new research on ion-atom collisions at relativistic energies.

  5. Storage rings for investigation of ion-atom collisions

    SciTech Connect

    Schuch, R.

    1987-08-01

    In this survey, we give a brief description of synchrotron storage rings for heavy ions, and examples for their use in ion-atom collision physics. The compression of the phase space distribution of the ions by electron cooling, and the gain factors of in-ring experiments compared to single-pass experiments are explained. Some examples of a new generation of ion-atom collision experiments which may become feasible with storage rings are given. These include the studies of angular differential single- and double-electron capture cross sections, the production of slow highly charged recoil ions, and atomic collision processes using decelerated and crossed beam. 30 refs.

  6. Manipulating ion-atom collisions with coherent electromagnetic radiation.

    PubMed

    Kirchner, Tom

    2002-08-26

    Laser-assisted ion-atom collisions are considered in terms of a nonperturbative quantum mechanical description of the electronic motion. It is shown for the system He(2+) - H at 2 keV/amu that the collision dynamics depend strongly on the initial phase of the laser field and the applied wavelength. Whereas electronic transitions are caused by the concurrent action of the field and the projectile ion at relatively low frequencies, they can be separated into modified collisional capture and field ionization events in the region above the one-photon ionization threshold.

  7. Ion-Atom Cold Collisions and Atomic Clocks

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Maleki, Lute; Tjoelker, Robert L.

    1997-01-01

    Collisions between ultracold neutral atoms have for some time been the subject of investigation, initially with hydrogen and more recently with laser cooled alkali atoms. Advances in laser cooling and trapping of neutral atoms in a Magneto-Optic Trap (MOT) have made cold atoms available as the starting point for many laser cooled atomic physics investigations. The most spectacularly successful of these, the observation of Bose-Einstein Condensation (BEC) in a dilute ultra-cold spin polarized atomic vapor, has accelerated the study of cold collisions. Experimental and theoretical studies of BEC and the long range interaction between cold alkali atoms is at the boundary of atomic and low temperature physics. Such studies have been difficult and would not have been possible without the development and advancement of laser cooling and trapping of neutral atoms. By contrast, ion-atom interactions at low temperature, also very difficult to study prior to modern day laser cooling, have remained largely unexplored. But now, many laboratories worldwide have almost routine access to cold neutral atoms. The combined technologies of ion trapping, together with laser cooling of neutrals has made these studies experimentally feasible and several very important, novel applications might come out of such investigations . This paper is an investigation of ion-atom interactions in the cold and ultra-cold temperature regime. Some of the collisional ion-atom interactions present at room temperature are very much reduced in the low temperature regime. Reaction rates for charge transfer between unlike atoms, A + B(+) approaches A(+) + B, are expected to fall rapidly with temperature, approximately as T(sup 5/2). Thus, cold mixtures of atoms and ions are expected to coexist for very long times, unlike room temperature mixtures of the same ion-atom combination. Thus, it seems feasible to cool ions via collisions with laser cooled atoms. Many of the conventional collisional interactions

  8. Treatment of Ion-Atom Collisions Using a Partial-Wave Expansion of the Projectile Wavefunction

    ERIC Educational Resources Information Center

    Wong, T. G.; Foster, M.; Colgan, J.; Madison, D. H.

    2009-01-01

    We present calculations of ion-atom collisions using a partial-wave expansion of the projectile wavefunction. Most calculations of ion-atom collisions have typically used classical or plane-wave approximations for the projectile wavefunction, since partial-wave expansions are expected to require prohibitively large numbers of terms to converge…

  9. Recent Applications of the Lattice, Time-Dependent Schr dinger Equation Approach for Ion-Atom Collisions

    SciTech Connect

    Schultz, David Robert; Ovchinnikov, S. Yu.; Sternberg, J. B.; Macek, J. H.

    2011-01-01

    Contemporary computational methods, such as the lattice, time-dependent Schroedinger equation (LTDSE) approach, have opened opportunities to study ion-atom collisions at a new level of detail and to uncover unexpected phenomena. Such interactions within gaseous, plasma, and material environments are fundamental to diverse applications such as low temperature plasma processing of materials, magnetic confinement fusion, and astrophysics. Results are briefly summarized here stemming from recent use of the LTDSE approach, with particular emphasis on elucidation of unexpected vortices in the ejected electron spectrum in ion-atom collisions and for an atom subject to an electric field pulse.

  10. One and a half centered expansion for ion-atom collisions

    SciTech Connect

    Reading, J.F.; Ford, A.L.; Becker, R.L.

    1980-01-01

    Fast ion-atom collisions in which charge transfer plays a dominant role have been traditionally treated by a two center expansion (TCE): the state wavefunction is approximated by a truncated set of Hilbert states centered on the target and projectile. This method is accurate but expensive in the use of computer time. A new method which allows charge transfer through variational time independent amplitudes, and target excitation and ionization through variational time dependent amplitudes is presented. The method retains the efficiency of a single centered expansion and yet reproduces the conventional TCE results in situations where charge transfer is dominant. Comparison to experiment is made.

  11. Two-Centre Convergent Close-Coupling Approach to Ion-Atom Collisions: Current Progress

    NASA Astrophysics Data System (ADS)

    Kadyrov, Alisher; Abdurakhmanov, Ilkhom; Bailey, Jackson; Bray, Igor

    2016-09-01

    There are two versions of the convergent close-coupling (CCC) approach to ion-atom collisions: quantum-mechanical (QM-CCC) and semi-classical (SC-CCC). Recently, both implementations have been extended to include electron-transfer channels. The SC-CCC approach has been applied to study the excitation and the electron-capture processes in proton-hydrogen collisions. The integral alignment parameter A20 for polarization of Lyman- α emission and the cross sections for excitation and electron-capture into the lowest excited states have been calculated for a wide range of the proton impact energies. It has been established that for convergence of the results a very wide range of impact parameters (typically, 0-50 a.u.) is required due to extremely long tails of transition probabilities for transitions into the 2 p states at high energies. The QM-CCC approach allowed to obtain an accurate solution of proton-hydrogen scattering problem including all underlying processes, namely, direct scattering and ionisation, and electron capture into bound and continuum states of the projectile. In this presentation we give a general overview of current progress in applications of the two-centre CCC approach to ion-atom and atom-atom collisions. The work is supported by the Australian Research Council.

  12. Coordinate space translation technique for simulation of electronic process in the ion-atom collision.

    PubMed

    Wang, Feng; Hong, Xuhai; Wang, Jian; Kim, Kwang S

    2011-04-21

    Recently we developed a theoretical model of ion-atom collisions, which was made on the basis of a time-dependent density functional theory description of the electron dynamics and a classical treatment of the heavy particle motion. Taking advantage of the real-space grid method, we introduce a "coordinate space translation" technique to allow one to focus on a certain space of interest such as the region around the projectile or the target. Benchmark calculations are given for collisions between proton and oxygen over a wide range of impact energy. To extract the probability of charge transfer, the formulation of Lüdde and Dreizler [J. Phys. B 16, 3973 (1983)] has been generalized to ensemble-averaging application in the particular case of O((3)P). Charge transfer total cross sections are calculated, showing fairly good agreements between experimental data and present theoretical results.

  13. Coherence and correlations in fast ion-atom collisions

    SciTech Connect

    Burgdoerfer, J.

    1987-01-01

    This paper focusses on the description, classification and interpretation of coherent excitation of atomic or ionic systems with Coulombic two-body final state interactions. A group-theoretical approach is used to classify and interpret coherent excitation. The most significant result is that the state of excitation represented by a density operator can be mapped one to one onto expectation values of a set of operators. Examples are used to illustrate what can be learned about the collision process from investigations of coherent excitation. (JDH)

  14. Screening-Antiscreening Effect in Ion-Atom Collisions.

    NASA Astrophysics Data System (ADS)

    Hulskotter, Hans-Peter G.

    1990-01-01

    In a collision between an atomic projectile carrying one or more electrons and a target atom, one of the events that may occur is the ionization of a projectile electron. Projectile ionization, usually called electron loss, is normally attributed to the Coulomb interaction between the target nucleus and projectile electron. The effect of the target electrons can be accounted for partially by introducing a screened Coulomb interaction between the target and the projectile electron. However, the target electrons can not only act coherently as screening agents, but may also act incoherently as ionizing (antiscreening) agents. We have measured the cross sections for projectile K-shell ionization for 0.75 - 3.5 MeV/Nucleon Li^{2+ }, C^{5+}, and O^{7+} projectiles, for projectile electron loss of 100 and 380 MeV/Nucleon Au^{52+} projectiles in collisions with H_2, He, and N _2, and for 380 MeV/N Au^ {75+} projectiles in collisions with H _2 and N_2 targets. We unambiguously demonstrate that for energies where the target electrons have sufficient kinetic energy in the projectile frame to ionize the projectile electron, the electron-electron interaction can lead to a significant increase in the total ionization cross section. The largest relative increase we have been able to observe is 76%. The experimental results generally agree with plane-wave Born approximation calculations by Bates and Griffing and modified by Anholt which take into account the interaction between projectile and target electrons. We also describe the properties of a new target gas cell which has been designed and built for the use at the relativistic heavy-ion accelerator at Lawrence Berkeley Laboratory.

  15. Numerical calculation of ionization in fast ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Horbatsch, Marko; Chassid, Michal

    1996-05-01

    Numerical solutions of the time-dependent Schrödinger equation in a 1D model and in a realistic 3D setting^1,2 are analyzed to calculate excitation probabilities and differential electron emission probabilities for collisions of fast bare projectiles with hydrogen atoms. The results are tested for the expected scaling behaviour with projectile charge and collision energy. The ionization probabilities are calculated by first projecting out the bound-state contributions from the time-evolved wavefunction and then performing a discrete Fourier transform. Comparison is provided with recent experiments for helium targets using cold target recoil ion momentum spectroscopy^3. For fast (v=12 au) and highly charged projectiles (Z_p=24) bound-state excitations are dominantly produced at much larger impact parameters than b >= 3 au for which the ionization channel receives its largest contribution. ^1 M. Horbatsch, Phys. Rev. A 44, R5346 (1991) ^2 M. Chassid and M. Horbatsch, J. Phys. B 28,L621 (1995) ^3 R. Moshammer, J. Ullrich, et. al. Phys. Rev. Lett. 73, 3371 (1994).

  16. Correlated eikonal initial state in ion-atom collisions

    SciTech Connect

    Ciappina, M.F.; Otranto, S.; Garibotti, C.R.

    2002-11-01

    An approximation is developed to deal with the ionization of atoms by bare charged ions. In this method the transition amplitude describing the three-body final state is evaluated using a continuum correlated wave and that for the initial state by an analytical continuation of the {phi}{sub 2} model to complex momenta. This procedure introduces in the atomic bound state a kinematical correlation with the projectile motion. Doubly differential cross sections (DDCS's) are computed for collisions of H{sup +} and F{sup 9+} ions with He atoms. Results for the DDCS's in the forward direction are compared with experimental data and other theoretical models. We find an enhancement of the distribution for low energy electrons and that the asymmetry of the electron capture to the continuum (ECC) peak is correctly described.

  17. Forward electron production in heavy ion-atom and ion-solid collisions

    SciTech Connect

    Sellin, I.A.

    1984-01-01

    A sharp cusp in the velocity spectrum of electrons, ejected in ion-atom and ion-solid collisions, is observed when the ejected electron velocity vector v/sub e/ matches that of the emergent ion vector v/sub p/ in both speed and direction. In ion-atom collisions, the electrons originate from capture to low-lying, projectile-centered continuum states (ECC) for fast bare or nearly bare projectiles, and from loss to those low-lying continuum states (ELC) when loosely bound projectile electrons are available. Most investigators now agree that ECC cusps are strongly skewed toward lower velocities, and exhibit full widths half maxima roughly proportional to v/sub p/ (neglecting target-shell effects, which are sometimes strong). A close examination of recent ELC data shows that ELC cusps are instead nearly symmetric, with widths nearly independent on v/sub p/ in the velocity range 6 to 18 a.u., a result only recently predicted by theory. Convoy electron cusps produced in heavy ion-solid collisions at MeV/u energies exhibit approximately velocity-independent widths very similar to ELC cusp widths. While the shape of the convoy peaks is approximately independent of projectile Z, velocity, and of target material, it is found that the yields in polycrystalline targets exhibit a strong dependence on projectile Z and velocity. While attempts have been made to link convoy electron production to binary ECC or ELC processes, sometimes at the last layer, or alternatively to a solid-state wake-riding model, our measured dependences of cusp shape and yield on projectile charge state and energy are inconsistent with the predictions of available theories. 10 references, 8 figures, 1 table.

  18. Effect of electron-nuclei interaction on internuclear motions in slow ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Tolstikhina, Inga Yu.; Tolstikhin, Oleg I.

    2015-10-01

    The electron-nuclei interaction affects the internuclear motion in slow ion-atom collisions, which in turn affects theoretical results for the cross sections of various collision processes. The results are especially sensitive to the details of the internuclear dynamics in the presence of a strong isotope effect on the cross sections, as is the case, e.g., for the charge transfer in low-energy collisions of He2+ with H, D, and T. By considering this system as an example, we show that internuclear trajectories defined by the Born-Oppenheimer (BO) potential in the entrance collision channel, which effectively accounts for the electron-nuclei interaction, are in much better agreement with trajectories obtained in the ab initio electron-nuclear dynamics approach [R. Cabrera-Trujillo et al., Phys. Rev. A 83, 012715 (2011), 10.1103/PhysRevA.83.012715] than the corresponding Coulomb trajectories. We also show that the use of the BO trajectory instead of the Coulomb trajectory in the calculations of the charge-transfer cross sections within the adiabatic approach improves the agreement of the results with ab initio calculations.

  19. Spin-Orbit Interactions and Quantum Spin Dynamics in Cold Ion-Atom Collisions

    NASA Astrophysics Data System (ADS)

    Tscherbul, Timur V.; Brumer, Paul; Buchachenko, Alexei A.

    2016-09-01

    We present accurate ab initio and quantum scattering calculations on a prototypical hybrid ion-atom system Yb+ -Rb, recently suggested as a promising candidate for the experimental study of open quantum systems, quantum information processing, and quantum simulation. We identify the second-order spin-orbit (SO) interaction as the dominant source of hyperfine relaxation in cold Yb+ -Rb collisions. Our results are in good agreement with recent experimental observations [L. Ratschbacher et al., Phys. Rev. Lett. 110, 160402 (2013)] of hyperfine relaxation rates of trapped Yb+ immersed in an ultracold Rb gas. The calculated rates are 4 times smaller than is predicted by the Langevin capture theory and display a weak T-0.3 temperature dependence, indicating significant deviations from statistical behavior. Our analysis underscores the deleterious nature of the SO interaction and implies that light ion-atom combinations such as Yb+ -Li should be used to minimize hyperfine relaxation and decoherence of trapped ions in ultracold atomic gases.

  20. High charge state, ion-atom collision experiments using accel-decel

    SciTech Connect

    Bernstein, E.M.; Clark, M.W.; Tanis, J.A.; Graham, W.G.

    1987-01-01

    Recent studies of /sub 16/S/sup 13 +/ + He collisions between 2.5 and 200 MeV, which were made using the accel-decel technique with the Brookhaven National Laboratory coupled MP tandem Van de Graaff accelerators, are discussed. Cross sections were measured for single electron-capture and -loss as well as K x rays correlated to electron-capture. Other planned ion-atom collision experiments requiring accel-decel are also presented. 18 refs., 3 figs.

  1. Vortices Associated with the Wave Function of a Single Electron Emitted in Slow Ion-Atom Collisions

    NASA Astrophysics Data System (ADS)

    Schmidt, L. Ph. H.; Goihl, C.; Metz, D.; Schmidt-Böcking, H.; Dörner, R.; Ovchinnikov, S. Yu.; Macek, J. H.; Schultz, D. R.

    2014-02-01

    We present measurements and calculations of the momentum distribution of electrons emitted during the ion-atom collision 10 keV/u He2++He→He++He2++e-, which show rich structures for ion scattering angles above 2 mrad arising dominantly from two-electron states. Our calculations reveal that minima in the measured distributions are zeros in the electronic probability density resulting from vortices in the electronic current.

  2. Treatment of ion-atom collisions using a partial-wave expansion of the projectile wavefunction

    SciTech Connect

    Foster, M; Colgan, J; Wong, T G; Madison, D H

    2008-01-01

    We present calculations of ion-atom collisions using a partial-wave expansion of the projectile wavefunction. Most calculations of ion-atom collisions have typically used classical or plane-wave approximations for the projectile wavefunction, since partial-wave expansions are expected to require prohibitively large numbers of terms to converge scattering quantities. Here we show that such calculations are possible using modern high-performance computing. We demonstrate the utility of our method by examining elastic scattering of protons by hydrogen and helium atoms, problems familiar to undergraduate students of atomic scattering. Application to ionization of helium using partial-wave expansions of the projectile wavefunction, which has long been desirable in heavy-ion collision physics, is thus quite feasible.

  3. Metal vapor target for precise studies of ion-atom collisions

    SciTech Connect

    Chen, W. Vorobyev, G.; Herfurth, F.; Hillenbrand, P.-M.; Spillmann, U.; Guo, D.; Trotsenko, S.; Gumberidze, A.; Stöhlker, Th.

    2014-05-15

    Although different ion-atom collisions have been studied in various contexts, precise values of cross-sections for many atomic processes were seldom obtained. One of the main uncertainties originates from the value of target densities. In this paper, we describe a unique method to measure a target density precisely with a combination of physical vapor deposition and inductively coupled plasma optical emission spectrometry. This method is preliminarily applied to a charge transfer cross-section measurement in collisions between highly charged ions and magnesium vapor. The final relative uncertainty of the target density is less than 2.5%. This enables the precise studies of atomic processes in ion-atom collisions, even though in the trial test the deduction of precise capture cross-sections was limited by other systematic errors.

  4. Near-threshold photoionization of hydrogenlike uranium studied in ion-atom collisions via the time-reversed process.

    PubMed

    Stöhlker, T; Ma, X; Ludziejewski, T; Beyer, H F; Bosch, F; Brinzanescu, O; Dunford, R W; Eichler, J; Hagmann, S; Ichihara, A; Kozhuharov, C; Krämer, A; Liesen, D; Mokler, P H; Stachura, Z; Swiat, P; Warczak, A

    2001-02-05

    Radiative electron capture, the time-reversed photoionization process occurring in ion-atom collisions, provides presently the only access to photoionization studies for very highly charged ions. By applying the deceleration mode of the ESR storage ring, we studied this process in low-energy collisions of bare uranium ions with low- Z target atoms. This technique allows us to extend the current information about photoionization to much lower energies than those accessible for neutral heavy elements in the direct reaction channel. The results prove that for high- Z systems, higher-order multipole contributions and magnetic corrections persist even at energies close to the threshold.

  5. Wave-packet continuum-discretization approach to ion-atom collisions: Nonrearrangement scattering

    NASA Astrophysics Data System (ADS)

    Abdurakhmanov, I. B.; Kadyrov, A. S.; Bray, I.

    2016-08-01

    A general single-center close-coupling approach based on a continuum-discretization procedure is developed to calculate excitation and ionization processes in ion-atom collisions. The continuous spectrum of the target is discretized using stationary wave packets constructed from the Coulomb wave functions, the eigenstates of the target Hamiltonian. Such continuum discretization allows one to generate pseudostates with arbitrary energies and distribution. These features are ideal for detailed differential ionization studies. The approach starts from the semiclassical three-body Schrödinger equation for the scattering wave function and leads to a set of coupled differential equations for the transition probability amplitudes. To demonstrate its utility the method is applied to calculate collisions of antiprotons with atomic hydrogen. A comprehensive set of benchmark results from integrated to fully differential cross sections for antiproton-impact ionization of hydrogen in the energy range from 1 keV to 1 MeV is provided. Contrary to previous predictions, we find that at low incident energies the singly differential cross section has a maximum away from the zero emission energy. This feature could not be seen without a fine discretization of the low-energy part of the continuum.

  6. Correlated charge-changing ion-atom collisions. Progress report, February 16, 1990--February 15, 1993

    SciTech Connect

    Tanis, J.A.

    1993-02-01

    This report summarizes the progress and accomplishments in accelerator atomic physics research supported by DOE grant DE-FG02-87ER13778 from February 16, 1990 through February 15, 1993. This work involves the experimental investigation of atomic interactions in collisions of charged projectiles with neutral targets or electrons, with particular emphasis on two-electron interactions and electron-correlation effects. The processes studied are of interest both from fundamental and applied points of view. In the latter case, results are obtained which are relevant to the understanding of laboratory and astrophysical plasmas, highly-excited (Rydberg) and continuum states of atoms and ions, atomic structure effects, the interaction of ions with surfaces, and the development of heavy-ion storage-rings. The results obtained have provided the basis for several M.A. thesis projects at Western Michigan and several Ph.D. dissertation projects are currently underway. Summaries of work completed and work in progress are given below in Section II. This research has resulted in 26 papers (in print and in press), 12 invited presentations at national and international meetings, and 28 contributed presentations as detailed in Section III.

  7. Hybrid ion-atom trap for studying ultra-cold collisions

    NASA Astrophysics Data System (ADS)

    Makarov, Oleg P.; Lin, Jian; Smith, W. W.

    2003-05-01

    We built an apparatus for studying ultra-cold collisions between atoms and atomic or molecular ions. Atomic sodium vapor is produced from getters in the ultra-high vacuum chamber. The atoms are trapped in a vapor-cell magneto-optical trap (MOT) by capturing a low-velocity component of a thermal distribution into the region between two anti-Helmholtz coils. A localized cloud of cold Na atoms was successfully generated for MOT types I and II. The cooling transitions were stimulated by the red-detuned Na D2 line emission from a single-frequency stabilized ring-dye laser. The repumping frequency was generated by an electro-optical modulator (EOM) at 1.712 GHz. The loading time constant, ˜ 500 ms, was measured from the fluorescence intensity increase when the magnetic field is suddenly turned on. A linear Paul ion trap, centered on the MOT, is designed to trap Ca^+ ions, produced by electronic bombardment of neutral calcium atoms from a tube oven. A detector is provided for product ions from charge-transfer collisions or photoassociative ionization. We are testing the various components of the completed apparatus. This work is supported by NSF grant # PHY-9988215 and in part by the University of CT Research Foundation.

  8. Electron-Electron Interaction in Ion-Atom Collisions Studied by Projectile State-Resolved Auger Electron Spectroscopy.

    NASA Astrophysics Data System (ADS)

    Lee, Do-Hyung

    1990-01-01

    This dissertation addresses the problem of dynamic electron-electron interactions in fast ion-atom collisions using projectile Auger electron spectroscopy. The study was carried out by measuring high-resolution projectile KLL Auger electron spectra as a function of projectile energy for the various collision systems of 0.25-2 MeV/u O^{q+} and F^ {q+} incident on H_2 and He targets. The electrons were detected in the beam direction, where the kinematic broadening is minimized. A zero-degree tandem electron spectrometer system was developed and showed the versatility of zero-degree measurements of collisionally-produced atomic states. The zero-degree binary encounter electrons (BEe), quasifree target electrons ionized by the projectiles in head-on collisions, were observed as a strong background in the KLL Auger electron spectrum. They were studied by treating the target ionization as 180^circ Rutherford elastic scattering in the projectile frame, and resulted in a validity test of the impulse approximation (IA) and a way to determine the spectrometer efficiency. An anomalous q-dependence, in which the zero-degree BEe yields increase with decreasing projectile charge state (q), was observed. State-resolved KLL Auger cross sections were determined by using the BEe normalization and thus the cross sections of the electron -electron interactions such as resonant transfer-excitation (RTE), electron-electron excitation (eeE), and electron -electron ionization (eeI) were determined. Projectile 2l capture with 1s to 2p excitation by the captured target electron was observed as an RTE process with Li-like and He-like projectiles and the measured RTEA (RTE followed by Auger decay) cross sections showed good agreement with an RTE-IA treatment and RTE alignment theory. Projectile 1s to 2p excitation by a target electron was observed an an eeE process with Li-like projectiles. Projectile 1s ionization by a target electron was observed as an eeI process with Be-like projectiles

  9. Single ionization in highly charged ion-atom collisions at low to intermediate velocities

    NASA Astrophysics Data System (ADS)

    Abdallah, Mohammad Abdallah

    1998-11-01

    Single electron ejection from neutral targets (He and Ne) by the impact of low to highly charged ions (p, He+,/ Ne+,/ He2+,/ C6+,/ O8+, and Ne10+) at low to intermediate impact velocities is studied. A novel technique of electron momentum imaging is implemented. In this technique two-dimensional electron momentum distributions are produced in coincidence with recoil ions and projectile ions. In first generation experiments we studied the ejected electron momentum distributions without analyzing recoil ions momentum. This series of experiments revealed a charge-state dependence and velocity dependence that are contradictory to a dominant saddle point ionization mechanism at intermediate velocities. It showed a possibility of an agreement with a saddle centered distributions for low charge states at low collision velocities. To pursue the problem in more detail, we developed a second generation spectrometer which allowed us to fully determine the recoil ions momentum. This allowed us to determine the collision plane, energy loss (Q-value), and impact parameter for every collision that resulted in a single (target) electron ejection. This series of experiments revealed for the first time very marked structure in electron spectra that were impossible to observe in other experiments. These structures indicate the quasi-molecular nature of the collision process even at velocities comparable to the electron 'classical' orbital velocity. For the collisions of p, He+, and He2+ with He, a π-orbital shape of the electron momentum distribution is observed. This indicates the importance of the rotational coupling 2p/sigma/to2p/pi in the initial promotion of the ground state electron. This is followed by further promotions to the continuum. This agrees with the 'classical' description implied by the saddle-point ionization mechanism picture.

  10. State selective Rydberg charge transfer and ionization in low energy ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Perumal, A. N.; Tripathi, D. N.

    1998-10-01

    The Classical Trajectory Monte Carlo (CTMC) simulation method with a core modified interaction potential has been used to study the single charge transfer in Na +and Ar + ions colliding with a variety of state selected Na Rydberg atom targets ( n=24, 28, 33, 40 and l=2) in the reduced velocity region v=0.2-2.0. The experimentally observed structures in the total capture cross section versus reduced velocity curves are reproduced by CTMC method. The n-distribution of final capture state has got two peaks viz. first one at nf= ni and the second one at a higher nf depending on the initial angular momentum in the velocity regime 0.4-0.6. These structures have been explained in terms of quasimolecular-ion formation and a classical model proposed by Roy et al. (B.N. Roy, D.N. Tripathi, D.K. Rai, Phys. Rev. A 5 (1972) 1252). The CTMC ionization cross section results are benchmarked with the recent experimental measurement of Makarov et al. (O.P. Makarov, D.M. Homan, O.P. Sorokina, K.B. MacAdam, in: F. Aumayr, G. Betz, H.P. Winter (Eds.), Proceedings of the 20th International Conference on the Physics of Electronics and Atomic Collisions, Vienna, 1997, p. FR052) for Na +-Na(24 d).

  11. Organic surfaces excited by low-energy ions: atomic collisions, molecular desorption and buckminsterfullerenes.

    PubMed

    Delcorte, Arnaud

    2005-10-07

    This article reviews the recent progress in the understanding of kiloelectronvolt particle interactions with organic solids, including atomic displacements in a light organic medium, vibrational excitation and desorption of fragments and entire molecules. This new insight is the result of a combination of theoretical and experimental approaches, essentially molecular dynamics (MD) simulations and secondary ion mass spectrometry (SIMS). Classical MD simulations provide us with a detailed microscopic view of the processes occurring in the bombarded target, from the collision cascade specifics to the scenarios of molecular emission. Time-of-flight SIMS measures the mass and energy distributions of sputtered ionized fragments and molecular species, a precious source of information concerning their formation, desorption, ionization and delayed unimolecular dissociation in the gas phase. The mechanisms of energy transfer and sputtering are compared for bulk molecular solids, organic overlayers on metal and large molecules embedded in a low-molecular weight matrix. These comparisons help understand some of the beneficial effects of metal substrates and matrices for the analysis of molecules by SIMS. In parallel, I briefly describe the distinct ionization channels of molecules sputtered from organic solids and overlayers. The specific processes induced by polyatomic projectile bombardment, especially fullerenes, are discussed on the basis of new measurements and calculations. Finally, the perspective addresses the state-of-the-art and potential developments in the fields of surface modification and analysis of organic materials by kiloelectronvolt ion beams.

  12. Multiple ionization and capture in relativistic heavy-ion atom collisions

    SciTech Connect

    Meyerhof, W.E.; Anholt, R.; Xu, Xiang-Yuan; Gould, H.; Feinberg, B.; McDonald, R.J.; Wegner, H.E.; Thieberger, P.

    1987-02-01

    We show that in relativistic heavy-ion collisions the independent electron model can be used to predict cross sections for multiple inner-shell ionization and capture in a single collision. Charge distributions of 82- to 200-MeV/amu Xe and 105- to 955-MeV/amu U ion beams emerging from thin solid targets were used to obtain single- and multiple-electron stripping and capture cross sections. The probabilities of stripping electrons from the K, L, or M shells were calculated using the semiclassical approximation and Dirac hydrogenic wavefunctions. For capture, a simplified model for electron capture was uded. The data generally agree with theory.

  13. Time-Dependent Lattice Methods for Ion-Atom Collisions in Cartesian and Cylindrical Coordinate Systems

    SciTech Connect

    Pindzola, Michael S; Schultz, David Robert

    2008-01-01

    Time-dependent lattice methods in both Cartesian and cylindrical coordinates are applied to calculate excitation cross sections for p+H collisions at 40 keV incident energy. The time-dependent Schroedinger equation is solved using a previously formulated Cartesian coordinate single-channel method on a full 3D lattice and a newly formulated cylindrical coordinate multichannel method on a set of coupled 2D lattices. Cartesian coordinate single-channel and cylindrical coordinate five-channel calculations are found to be in reasonable agreement for excitation cross sections from the 1s ground state to the 2s, 2p, 3s, 3p, and 3d excited states. For extension of the time-dependent lattice method to handle the two electron dynamics found in p+He collisions, the cylindrical coordinate multichannel method appears promising due to the reduced dimensionality of its lattice.

  14. Improved atomic model for charge transfer in multielectron ion-atom collisions at intermediate energies

    NASA Astrophysics Data System (ADS)

    Lin, C. D.; Tunnell, L. N.

    1980-07-01

    Electron capture to the K shell of projectiles from the K and other subshells of multielectron target atoms is studied in the intermediate energy region using the single-active-electron approximation and the two-state, two-center atomic eigenfunction expansion method. It is concluded that the theoretical capture cross section is not sensitive to the atomic models used at high collision energies where the projectile velocity v is near or greater than the orbital velocity ve of the active electron. For vcollision systems are obtained and compared with experimental data when available to illustrate the reliability of the present model.

  15. Classical-quantum correspondence for ionization in fast ion-atom collisions

    SciTech Connect

    Burgdoerfer, J. |; Reinhold, C.O.

    1994-10-01

    We analyze the interplay between classical and quantum dynamics in ionization of atoms by fast charged particles The convergence to the classical limit is studied as a function of the momentum transferred to the electron during the collision, the impact parameter. the energy and angle of the emitted electron, and the initial state of the target. One goal is to assess the validity of exact classical (CTMC) methods and approximate classical models such as the Thomson model. Applications to data for electron ejection at large angles are presented. The connection between collisional ionization by charged particles and ionization by half-cycle pulses is discussed.

  16. Charge transfer reactions in multiply charged ion-atom collisions. [in interstellar clouds

    NASA Technical Reports Server (NTRS)

    Steigman, G.

    1975-01-01

    Charge-transfer reactions in collisions between highly charged ions and neutral atoms of hydrogen and/or helium may be rapid at thermal energies. If these reactions are rapid, they will suppress highly charged ions in H I regions and guarantee that the observed absorption features from such ions cannot originate in the interstellar gas. A discussion of such charge-transfer reactions is presented and compared with the available experimental data. The possible implications of these reactions for observations of the interstellar medium, H II regions, and planetary nebulae are outlined.

  17. Energy and angular distributions of detached electrons in a solvable model of ion-atom collisions

    SciTech Connect

    Macek, J.H.; Ovchinnikov, S.Y. |; Solovev, E.A.

    1999-08-01

    Electron energy and angular distributions are computed for a model of atom{endash}negative-ion collisions. In this model, electron-atom interactions are represented by zero-range potentials in an approximation where two identical atoms move along straight-line classical trajectories in head-on collisions. Analytic expressions for the ionization amplitudes are interpreted in terms of Sturmian eigenvalues and eigenfunctions. At high velocity, the computed distributions exhibit direct excitation and continuum capture cusps in addition to the binary encounter ridge. At low velocities, a single feature corresponding to an electron distribution centered midway between the target and projectile emerges. For initial conditions corresponding to gerade symmetry a single broad peak appears, while for ungerade symmetry there is a node at the midpoint so that the peak splits into two parts. It is confirmed that the advanced adiabatic approximation gives an accurate description of the ungerade distribution at low and intermediate velocities. {copyright} {ital 1999} {ital The American Physical Society}

  18. Energy and angular distributions of detached electrons in a solvable model of ion-atom collisions

    SciTech Connect

    Macek, J.H.; Ovchinnikov, S.Y. Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 ); Solovev, E.A. )

    1999-08-01

    Electron energy and angular distributions are computed for a model of atom[endash]negative-ion collisions. In this model, electron-atom interactions are represented by zero-range potentials in an approximation where two identical atoms move along straight-line classical trajectories in head-on collisions. Analytic expressions for the ionization amplitudes are interpreted in terms of Sturmian eigenvalues and eigenfunctions. At high velocity, the computed distributions exhibit direct excitation and continuum capture cusps in addition to the binary encounter ridge. At low velocities, a single feature corresponding to an electron distribution centered midway between the target and projectile emerges. For initial conditions corresponding to gerade symmetry a single broad peak appears, while for ungerade symmetry there is a node at the midpoint so that the peak splits into two parts. It is confirmed that the advanced adiabatic approximation gives an accurate description of the ungerade distribution at low and intermediate velocities. [copyright] [ital 1999] [ital The American Physical Society

  19. Quantum fluid density functional theory of time-dependent phenomena: Ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Deb, B. M.; Chattaraj, P. K.

    1988-07-01

    Using a recently proposed kinetic energy density functional and an amalgamation of density functional theory with quantum fluid dynamics, a time-dependent Kohn-Sham-type equation in three-dimensional space, which is a new non-linear Schrödinger equation, has been derived. The equation is also derived through the stochastic interpretation of quantum mechanics. A molecular "thermodynamic" viewpoint is suggested in terms of space-time-dependent quantities. Numerical solution of the above equation yields the time-dependent charge density, current density, effective potential and chemical potential. Perspective plots of these quantities for the proton-neon 25 keV head-on collision are presented.

  20. The Role of High-Energy Ion-Atom/Molecule Collisions in Radiotherapy

    NASA Astrophysics Data System (ADS)

    Belkić, Dževad

    2014-12-01

    The need for ions in radiotherapy stems from the most favorable localization of the largest energy deposition, precisely at the tumor site with small energy losses away from the target. Such a dose conformity to the target is due to heavy masses of ions that scatter predominantly in the forward direction and lose maximal energy mainly near the end of their path in the vicinity of the Bragg peak. The heavy masses of nuclei preclude noticeable multiple scattering of the primary ion beam. This occurrence is responsible for only about 30% of ion efficiency in killing tumor cells. However, ionization of targets by fast ions yields electrons that might be of sufficient energy to produce further radiation damage. These δ-electrons, alongside radicals produced by ion-water collisions, can accomplish the remaining 70% of tumor cell eradication. Electrons achieve this chiefly through multiple scattering due to their small mass. Therefore, energy depositions by both heavy (nuclei) and light (electrons) particles as well as highly reactive radicals need to be simultaneously transported in Monte Carlo simulations. This threefold transport of particles is yet to be developed for the existing Monte Carlo codes. Critical to accomplishing this key goal is the availability of accurate cross section databases. To this end, the leading continuum distorted wave methodologies are poised to play a pivotal role in predicting energy losses of ions in tissue as discussed in this work.

  1. Measurements of scattering processes in negative ion: Atom collisions. Technical progress report, 1 September 1991--31 December 1994

    SciTech Connect

    Kvale, T.J.

    1994-09-27

    This report describes the progress made on the research objectives during the past three years of the grant. This research project is designed to study various scattering processes which occur in H{sup {minus}} collisions with atomic (specifically, noble gas and atomic hydrogen) targets in the intermediate energy region. These processes include: elastic scattering, single- and double-electron detachment, and target excitation/ionization. For the elastic and target inelastic processes where H{sup {minus}} is scattered intact, the experimental technique of Ion Energy-Loss Spectroscopy (IELS) will be employed to identify the final target state(s). In most of the above processes, cross sections are unknown both experimentally and theoretically. The measurements will provide total cross sections (TCS) initially, and once the angular positioning apparatus is installed, will provide angular differential cross sections (ADCS).

  2. Many-electron aspects of molecular promotion in ion-atom collisions - Production of core-excited states of Li in Li/+/-He collisions

    NASA Technical Reports Server (NTRS)

    Elston, S. B.; Vane, C. R.; Schumann, S.

    1979-01-01

    Production of core-excited autoionizing states of neutral Li having configurations of the form 1snln(prime)l(prime) has been observed over the impact-energy range from 10-50 keV. Although the results for production of all such states is remarkably consistent with a quasi-molecular-excitation model proposed by Stolterfoht and Leithaeuser (1976), production of individual lines in the observed spectra exhibits collision-velocity dependencies indicative of considerably more complex processes, including processes which appear to be inherently two-electron in nature. Excitation functions are presented for (1s2s/2/)/2/S, 1s(2s2p/3/P)/2/P, 1s(2s2p/1/P)/2/P, and (1s2p/2/)/2/D core-excited state of Li and for total core excitation.

  3. Fraunhofer-type diffraction patterns of matter-wave scattering of projectiles: Electron transfer in energetic ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Agueny, Hicham

    2015-07-01

    We present results for single and double electron captures in intermediate energies H+ and 2H+ projectiles colliding with a helium target. The processes under investigations are treated using a nonperturbative semiclassical approach in combination with Eikonal approximation to calculate the scattering differential cross sections. The latter reveals pronounced minima and maxima in the scattering angles, in excellent agreement with the recent experimental data. It turns out that the present structure depends strongly on the projectile energy and shows only slight variations with different capture channels. The observed structure demonstrates the analogy of atomic de Broglie's matter-wave scattering with λd B=1.3 -3.2 ×10-3 a.u. and Fraunhofer-type diffraction of light waves.

  4. JPL Ultrastable Trapped Ion Atomic Frequency Standards.

    PubMed

    Burt, Eric A; Yi, Lin; Tucker, Blake; Hamell, Robert; Tjoelker, Robert L

    2016-07-01

    Recently, room temperature trapped ion atomic clock development at the Jet Propulsion Laboratory (JPL) has focused on three directions: 1) ultrastable atomic clocks, usually for terrestrial applications emphasizing ultimate stability performance and autonomous timekeeping; 2) new atomic clock technology for space flight applications that require strict adherence to size, weight, and power requirements; and 3) miniature clocks. In this paper, we concentrate on the first direction and present a design and the initial results from a new ultrastable clock referred to as L10 that achieves a short-term stability of 4.5 ×10(-14)/τ(1/2) and an initial measurement of no significant drift with an uncertainty of 2.4 ×10(-16) /day over a two-week period.

  5. New results for ultraperipheral heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Szczurek, Antoni; Kłusek-Gawenda, Mariola; Lebiedowicz, Piotr; Schäfer, Wolfgang

    2017-03-01

    We discuss diphoton semi(exclusive) production in ultraperipheral PbPb collisions at energy of √{sN N }=5.5 TeV (LHC). The nuclear calculations are based on equivalent photon approximation in the impact parameter space. The cross sections for elementary γγ → γγ subprocess are calculated including three different mechanisms: box diagrams with leptons and quarks in the loops, a VDM-Regge contribution with virtual intermediate hadronic excitations of the photons and the two-gluon exchange contribution (formally three-loops). We got relatively high cross sections in PbPb collisions. This opens a possibility to study the γγ → γγ (quasi)elastic scattering at the LHC. We find that the cross section for elastic γγ scattering could be measured in the lead-lead collisions for the diphoton invariant mass up to Wγγ ≈ 15 - 20 GeV. We identify region(s) of phase space where the two-gluon exchange contribution becomes important ingredient compared to box and nonperturbative VDM-Regge mechanisms. We discuss also first results concerning production of two e+e- pairs in UPCs of heavy ions. We considered only double scattering mechanism.

  6. Sixteenth International Conference on the physics of electronic and atomic collisions

    SciTech Connect

    Dalgarno, A.; Freund, R.S.; Lubell, M.S.; Lucatorto, T.B.

    1989-01-01

    This report contains abstracts of papers on the following topics: photons, electron-atom collisions; electron-molecule collisions; electron-ion collisions; collisions involving exotic species; ion- atom collisions, ion-molecule or atom-molecule collisions; atom-atom collisions; ion-ion collisions; collisions involving rydberg atoms; field assisted collisions; collisions involving clusters and collisions involving condensed matter.

  7. Scaling Cross Sections for Ion-atom Impact Ionization

    SciTech Connect

    Igor D. Kaganovich; Edward Startsev; Ronald C. Davidson

    2003-06-06

    The values of ion-atom ionization cross sections are frequently needed for many applications that utilize the propagation of fast ions through matter. When experimental data and theoretical calculations are not available, approximate formulas are frequently used. This paper briefly summarizes the most important theoretical results and approaches to cross section calculations in order to place the discussion in historical perspective and offer a concise introduction to the topic. Based on experimental data and theoretical predictions, a new fit for ionization cross sections is proposed. The range of validity and accuracy of several frequently used approximations (classical trajectory, the Born approximation, and so forth) are discussed using, as examples, the ionization cross sections of hydrogen and helium atoms by various fully stripped ions.

  8. Direct recoil oxygen ion fractions resulting from Ar + collisions

    NASA Astrophysics Data System (ADS)

    Chen, Jie-Nan; Rabalais, J. Wayne

    1986-03-01

    Direct recoil of oxygen from oxidized and hydroxylated magnesium surfaces as a result of 6 keV Ar + collisions produces O -, O +, and O species. The total ion fraction at a recoil angle of 22° is ~33.5%, of which O - is 23.7% and O + is 9.8% for the oxidized surface. The O -/O + intensity ratio is extremely sensitive to the amount of hydrogen present, with the O + yield dropping to ~1% on the hydroxylated surface. These results are considered within a model for electronic transitions in ion/surface collisions which considers Auger and resonant transitions along the ion trajectory and electron promotions in the quasi-diatomic molecule of the close encounter.

  9. Light flavor results in p-Pb collisions with ALICE

    NASA Astrophysics Data System (ADS)

    Ortiz, Antonio

    2016-12-01

    Particle ratios provide insight into the hadrochemistry of the event and the mechanisms for particle production. In Pb-Pb collisions the relative multi-strange baryon yields exhibit an enhancement with respect to pp collisions, whereas the short-lived K*0 resonance is suppressed in the most central events due to re-scattering of its decay daughter particles. Measurements in p-Pb allow us to investigate the development of these effects as a function of the system size. We report comprehensive results on light-flavor hadron production measured with the ALICE detector in p-Pb collisions at √{sNN} = 5.02 TeV, covering a wide range of particle species which includes long-lived hadrons, resonances and multi-strange baryons. The measurements include the transverse momentum spectra and the ratios of spectra among different species, and extend over a very large transverse momentum region, from ≈ 100 MeV / c to ≈ 20 GeV / c, depending on the particle species.

  10. Effects of Ion Atomic Number on Single-Event Gate Rupture (SEGR) Susceptibility of Power MOSFETs

    NASA Technical Reports Server (NTRS)

    Lauenstein, Jean-Marie; Goldsman, Neil; Liu, Sandra; Titus, Jeffrey L.; Ladbury, Raymond L.; Kim, Hak S.; Phan, Anthony M.; LaBel, Kenneth A.; Zafrani, Max; Sherman, Phillip

    2012-01-01

    The relative importance of heavy-ion interaction with the oxide, charge ionized in the epilayer, and charge ionized in the drain substrate, on the bias for SEGR failure in vertical power MOSFETs is experimentally investigated. The results indicate that both the charge ionized in the epilayer and the ion atomic number are important parameters of SEGR failure. Implications on SEGR hardness assurance are discussed.

  11. Compact, Highly Stable Ion Atomic Clock

    NASA Technical Reports Server (NTRS)

    Prestage, John

    2008-01-01

    A mercury-ion clock now at the breadboard stage of development (see figure) has a stability comparable to that of a hydrogen-maser clock: In tests, the clock exhibited an Allan deviation of between 2 x 10(exp -13) and 3 x 10(exp -13) at a measurement time of 1 second, averaging to about 10(exp -15) at 1 day. However, the clock occupies a volume of only about 2 liters . about a hundredth of the volume of a hydrogen-maser clock. The ion-handling parts of the apparatus are housed in a sealed vacuum tube, wherein only a getter pump is used to maintain the vacuum. Hence, this apparatus is a prototype of a generation of small, potentially portable high-precision clocks for diverse ground- and space-based navigation and radio science applications. Furthermore, this new ion-clock technology is about 100 times more stable and precise than the rubidium atomic clocks currently in use in the NAV STAR GPS Earth-orbiting satellites. In this clock, mercury ions are shuttled between a quadrupole and a 16-pole linear radio-frequency trap. In the quadrupole trap, the ions are tightly confined and optical state selection from a Hg-202 radio-frequency-discharge ultraviolet lamp is carried out. In the 16-pole trap, the ions are more loosely confined and atomic transitions resonant at frequency of about 40.507 GHz are interrogated by use of a microwave beam at that frequency. The trapping of ions effectively eliminates the frequency pulling caused by wall collisions inherent to gas-cell clocks. The shuttling of the ions between the two traps enables separation of the state-selection process from the clock microwave- resonance process, so that each of these processes can be optimized independently of the other. The basic ion-shuttling, two-trap scheme as described thus far is not new: it has been the basis of designs of prior larger clocks. The novelty of the present development lies in major redesigns of its physics package (the ion traps and the vacuum and optical subsystems) to effect

  12. Selected experimental results from heavy-ion collisions at LHC

    DOE PAGES

    Singh, Ranbir; Kumar, Lokesh; Netrakanti, Pawan Kumar; ...

    2013-01-01

    We reviewmore » a subset of experimental results from the heavy-ion collisions at the Large Hadron Collider (LHC) facility at CERN. Excellent consistency is observed across all the experiments at the LHC (at center of mass energysNN=2.76 TeV) for the measurements such as charged particle multiplicity density, azimuthal anisotropy coefficients, and nuclear modification factor of charged hadrons. Comparison to similar measurements from the Relativistic Heavy Ion Collider (RHIC) at lower energy (sNN=200 GeV) suggests that the system formed at LHC has a higher energy density and larger system size and lives for a longer time. These measurements are compared to model calculations to obtain physical insights on the properties of matter created at the RHIC and LHC.« less

  13. Discrepant Results in a 2-D Marble Collision

    NASA Astrophysics Data System (ADS)

    Kalajian, Peter

    2013-03-01

    Video analysis of 2-D collisions is an excellent way to investigate conservation of linear momentum. The often-desired experimental design goal is to minimize the momentum loss in order to demonstrate the conservation law. An air table with colliding pucks is an ideal medium for this experiment, but such equipment is beyond the budget of many schools. Substituting marbles on a table for air pucks introduces angular momentum and sliding friction so that simple video analysis will demonstrate that linear momentum is not conserved.1,2 Nevertheless, these labs offer students insights into the real-world application of physics. During a recent classroom trial, an unexpected result forced my students to think creatively and critically about what happened in the experiment.

  14. Recent theoretical results on electron-polyatomic molecule collisions

    SciTech Connect

    McCurdy, C.W.

    1994-03-01

    Until recently, the principal barrier to the accurate theoretical description of electronic collisions with polyatomic molecules was the computational problem of scattering by a nonlocal, arbitrarily asymmetric potential. Effective numerical techniques capable of solving this variety of potential scattering problem for electronic collisions have now matured, and the first applications of methods for treating many-body aspects of collisions of electrons with polyatomic molecules have begun to appear in the literature. The past two years have seen the appearance of a large collection of calculations on electron-polyatomic collisions which compare favorably with experimental determinations. In addition to the dramatic developments in methods which explicitly exploit the methods of quantum chemistry to treat the effects of electron correlation, polarization, etc., parameter-free model potential methods for electronically elastic collisions have also evolved markedly in recent years. Progress in both electronically elastic and inelastic processes is reviewed briefly.

  15. Next Generation JPL Ultra-Stable Trapped Ion Atomic Clocks

    NASA Technical Reports Server (NTRS)

    Burt, Eric; Tucker, Blake; Larsen, Kameron; Hamell, Robert; Tjoelker, Robert

    2013-01-01

    Over the past decade, trapped ion atomic clock development at the Jet Propulsion Laboratory (JPL) has focused on two directions: 1) new atomic clock technology for space flight applications that require strict adherence to size, weight, and power requirements, and 2) ultra-stable atomic clocks, usually for terrestrial applications emphasizing ultimate performance. In this paper we present a new ultra-stable trapped ion clock designed, built, and tested in the second category. The first new standard, L10, will be delivered to the Naval Research Laboratory for use in characterizing DoD space clocks.

  16. Discrepant Results in a 2-D Marble Collision

    ERIC Educational Resources Information Center

    Kalajian, Peter

    2013-01-01

    Video analysis of 2-D collisions is an excellent way to investigate conservation of linear momentum. The often-desired experimental design goal is to minimize the momentum loss in order to demonstrate the conservation law. An air table with colliding pucks is an ideal medium for this experiment, but such equipment is beyond the budget of many…

  17. Characterization of acoustic emissions resulting from particle collision with a stationary bubble.

    PubMed

    Zhang, Wen; Spencer, Steven J; Coghill, Peter

    2013-05-01

    The present work characterizes the acoustic emissions resulting from the collision of a particle driven under gravity with a captive bubble. Conventional methods to investigate the bubble particle collision interaction model measure a descriptive parameter known as the collision time. During such a collision, particle impact may cause a strong deformation and a following oscillation of the bubble-particle interface generates detectable passive acoustic emissions (AE). Experiments and models presented show that the AE frequency monotonically decreases with the particle radius and is independent of the impact velocity, whereas the AE amplitude has a more complicated relationship with impact parameters.

  18. Fast computation of high energy elastic collision scattering angle for electric propulsion plume simulation

    NASA Astrophysics Data System (ADS)

    Araki, Samuel J.

    2016-11-01

    In the plumes of Hall thrusters and ion thrusters, high energy ions experience elastic collisions with slow neutral atoms. These collisions involve a process of momentum exchange, altering the initial velocity vectors of the collision pair. In addition to the momentum exchange process, ions and atoms can exchange electrons, resulting in slow charge-exchange ions and fast atoms. In these simulations, it is particularly important to accurately perform computations of ion-atom elastic collisions in determining the plume current profile and assessing the integration of spacecraft components. The existing models are currently capable of accurate calculation but are not fast enough such that the calculation can be a bottleneck of plume simulations. This study investigates methods to accelerate an ion-atom elastic collision calculation that includes both momentum- and charge-exchange processes. The scattering angles are pre-computed through a classical approach with ab initio spin-orbit free potential and are stored in a two-dimensional array as functions of impact parameter and energy. When performing a collision calculation for an ion-atom pair, the scattering angle is computed by a table lookup and multiple linear interpolations, given the relative energy and randomly determined impact parameter. In order to further accelerate the calculations, the number of collision calculations is reduced by properly defining two cut-off cross-sections for the elastic scattering. In the MCC method, the target atom needs to be sampled; however, it is confirmed that initial target atom velocity does not play a significant role in typical electric propulsion plume simulations such that the sampling process is unnecessary. With these implementations, the computational run-time to perform a collision calculation is reduced significantly compared to previous methods, while retaining the accuracy of the high fidelity models.

  19. Experimental results from CERN on reaction mechanisms in high energy heavy ion collisions

    SciTech Connect

    Sorensen, S.P. Tennessee Univ., Knoxville, TN . Dept. of Physics)

    1990-01-01

    Three main experimental results from CERN concerning reaction mechanisms in high energy heavy ion collisions are discussed: (1) the striking validity of the single particle picture, (2) the nuclear stopping power and (3) the attained energy densities.

  20. Path Integral Approach to Atomic Collisions

    NASA Astrophysics Data System (ADS)

    Harris, Allison

    2016-09-01

    The Path Integral technique is an alternative formulation of quantum mechanics that is based on a Lagrangian approach. In its exact form, it is completely equivalent to the Hamiltonian-based Schrödinger equation approach. Developed by Feynman in the 1940's, following inspiration from Dirac, the path integral approach has been widely used in high energy physics, quantum field theory, and statistical mechanics. However, only in limited cases has the path integral approach been applied to quantum mechanical few-body scattering. We present a theoretical and computational development of the path integral method for use in the study of atomic collisions. Preliminary results are presented for some simple systems. Ultimately, this approach will be applied to few-body ion-atom collisions. Work supported by NSF grant PHY-1505217.

  1. PHENIX results on reconstructed jets in p + p and Cu + Au collisions

    NASA Astrophysics Data System (ADS)

    Timilsina, Arbin

    2016-12-01

    Measurements of jet production rates in p+p and Cu+Au collisions at √{sNN} = 200 GeV with the PHENIX detector are reported. Jets are reconstructed using the anti-kt algorithm with R = 0.2 from charged particles and electromagnetic clusters. The jet spectra are unfolded to correct for detector effects and underlying event background, and the resulting jet spectra are reported for the transverse momentum range 12 collision centrality. The results indicated that jets are suppressed by approximately a factor of two in the most central collisions.

  2. Insight into collision zone dynamics from topography: numerical modelling results and observations

    NASA Astrophysics Data System (ADS)

    Bottrill, A. D.; van Hunen, J.; Allen, M. B.

    2012-07-01

    Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) deepening in the area of the back arc-basin after initial collision. This collisional mantle dynamic basin (CMDB) is caused by slab steepening drawing material away from the base of the overriding plate. Also during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate causes the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene-Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. This uplift and subsidence pattern correlates well with our modelled topography changes.

  3. Insight into collision zone dynamics from topography: numerical modelling results and observations

    NASA Astrophysics Data System (ADS)

    Bottrill, A. D.; van Hunen, J.; Allen, M. B.

    2012-11-01

    Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) basin on the overriding plate after initial collision. This "collisional mantle dynamic basin" (CMDB) is caused by slab steepening drawing, material away from the base of the overriding plate. Also, during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate cause the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene-Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. Our modelled topography changes fit well with this observed uplift and subsidence.

  4. Design of a versatile pressure control system for gas targets in ion-atom collision studies

    NASA Astrophysics Data System (ADS)

    Fuelling, S.; Bruch, R.

    1993-06-01

    In this work, a unique gas target pressure control system is described which has been developed to measure state selective absolute EUV cross sections subsequent to electron and ion impact on gaseous targets. This system can be used in any type of gas phase experiment using positively or negatively charged and neutral particle beams interacting with atomic and molecular targets.

  5. Influence of Earth crust composition on continental collision style in Precambrian conditions: Results of supercomputer modelling

    NASA Astrophysics Data System (ADS)

    Zavyalov, Sergey; Zakharov, Vladimir

    2016-04-01

    A number of issues concerning Precambrian geodynamics still remain unsolved because of uncertainity of many physical (thermal regime, lithosphere thickness, crust thickness, etc.) and chemical (mantle composition, crust composition) parameters, which differed considerably comparing to the present day values. In this work, we show results of numerical supercomputations based on petrological and thermomechanical 2D model, which simulates the process of collision between two continental plates, each 80-160 km thick, with various convergence rates ranging from 5 to 15 cm/year. In the model, the upper mantle temperature is 150-200 ⁰C higher than the modern value, while the continental crust radiogenic heat production is higher than the present value by the factor of 1.5. These settings correspond to Archean conditions. The present study investigates the dependence of collision style on various continental crust parameters, especially on crust composition. The 3 following archetypal settings of continental crust composition are examined: 1) completely felsic continental crust; 2) basic lower crust and felsic upper crust; 3) basic upper crust and felsic lower crust (hereinafter referred to as inverted crust). Modeling results show that collision with completely felsic crust is unlikely. In the case of basic lower crust, a continental subduction and subsequent continental rocks exhumation can take place. Therefore, formation of ultra-high pressure metamorphic rocks is possible. Continental subduction also occurs in the case of inverted continental crust. However, in the latter case, the exhumation of felsic rocks is blocked by upper basic layer and their subsequent interaction depends on their volume ratio. Thus, if the total inverted crust thickness is about 15 km and the thicknesses of the two layers are equal, felsic rocks cannot be exhumed. If the total thickness is 30 to 40 km and that of the felsic layer is 20 to 25 km, it breaks through the basic layer leading to

  6. New results on fully corrected dijet asymmetry in Pb + Pb collisions with ATLAS

    SciTech Connect

    Perepelitsa, Dennis V.

    2016-12-01

    The phenomenon of events containing highly asymmetric dijet pairs is one of the most striking results in heavy ion physics, providing the first direct observation of in-medium jet energy loss at the Large Hadron Collider. Detailed measurements of a centrality-dependent dijet imbalance in 2.76 TeV Pb+Pb collisions using data collected by the ATLAS detector in the 2011 LHC heavy ion run are presented. The new analysis provides a measurement, fully corrected for detector effects to the particle level, of the centrality- and leading jet transverse momentum-(pT-) dependence of the dijet pT balance distribution, compared to an analogous measurement in pp collisions at the same center-of-mass energy.

  7. New results on fully corrected dijet asymmetry in Pb + Pb collisions with ATLAS

    NASA Astrophysics Data System (ADS)

    Perepelitsa, Dennis V.

    2016-12-01

    The phenomenon of events containing highly asymmetric dijet pairs is one of the most striking results in heavy ion physics, providing the first direct observation of in-medium jet energy loss at the Large Hadron Collider. Detailed measurements of a centrality-dependent dijet imbalance in 2.76 TeV Pb + Pb collisions using data collected by the ATLAS detector in the 2011 LHC heavy ion run are presented. The new analysis provides a measurement, fully corrected for detector effects to the particle level, of the centrality- and leading jet transverse momentum-(pT-) dependence of the dijet pT balance distribution, compared to an analogous measurement in pp collisions at the same center-of-mass energy.

  8. Coulomb path'' interference in low energy He sup + + He collisions

    SciTech Connect

    Swenson, J.K. ); Burgdoerfer, J. ); Meyer, F.W.; Havener, C.C.; Gregory, D.C.; Stolterfoht, N. )

    1990-01-01

    A new interference mechanism, analogous to classic'' double-slit electron scattering, has been identified in low energy ion-atom collisions. This Coulomb path'' interference results from the existence of two trajectories, indistinguishable with respect to laboratory energy and emission angle, along which ejected autoionizing electrons may be scattered by the attractive Coulomb potential of the slowly receding spectator ion. We present a simple semi-classical model for this effect in which we account for the path dependence of the amplitude of the ejected electron following decay of the autoionizing state. Calculated model lineshapes are found to be in excellent agreement with strong angular dependence of the interference structure observed in the He target 2s{sup 2} {sup 1}S autoionizing lineshape measured near 0{degree} following 10 keV He{sup +} + He collisions.

  9. How Usability Testing Resulted in Improvements to Ground Collision Software for General Aviation: Improved Ground Collision Avoidance System (IGCAS)

    NASA Technical Reports Server (NTRS)

    Lamarr, Michael; Chinske, Chris; Williams, Ethan; Law, Cameron; Skoog, Mark; Sorokowski, Paul

    2016-01-01

    The NASA improved Ground Collision Avoidance System (iGCAS) team conducted an onsite usability study at Experimental Aircraft Association (EAA) Air Venture in Oshkosh, Wisconsin from July 19 through July 26, 2015. EAA Air Venture had approximately 550,000 attendees from which the sample pool of pilots were selected. The objectives of this study were to assess the overall appropriateness and acceptability of iGCAS as a warning system for General Aviation aircraft, usability of the iGCAS displays and audio cues, test terrain avoidance characteristics, performance, functionality, pilot response time, and correlate terrain avoidance performance and pilot response time data.

  10. NA49 Results on Single Particle and Correlation Measurements in Central PB+PB Collisions

    SciTech Connect

    Wang, F.

    1998-12-01

    Single-particle spectra and two-particle correlation functions measured by the NA49 collaboration in central Pb+Pb collisions at 158 GeV/nucleon are presented. These measurements are used to study the kinetic and chemical freeze-out conditions in heavy ion collisions. We conclude that large baryon stopping, high baryon density and strong transverse radial flow are achieved in central Pb+Pb collisions at the SPS.

  11. Spin dynamics and entanglement growth with trapped ions, atoms & molecules

    NASA Astrophysics Data System (ADS)

    Schachenmayer, Johannes; Lanyon, Ben; Roos, Christian; Daley, Andrew; Zhu, Bihui; Rey, Ana Maria

    2014-03-01

    Trapped ions and systems of cold atoms or molecules in optical lattices offer controlled environments to experimentally study non-equilibrium dynamics of many-body quantum spin-models with interactions of varying range. Theoretically calculating dynamics of observables for these experiments is a major challenge both analytically and numerically. In 1D, the growth behavior of the entanglement entropy between different blocks of a many-body state determines whether the evolution of the system can be efficiently simulated on a classical computer or not. In return, the study of entanglement growth can guide experiments to regimes where a quantum simulator can outperform a numerical simulation. Here we present results on the entanglement growth behavior in 1D strings of ions after a quench, and show how the growth depends on the range of the interactions. Furthermore we report on progress on methods for higher dimensional systems. These can be used to model Ramsey-dynamics for current experiments with alkaline earth atoms or polar molecules in optical lattices, or for systems with Rydberg atoms.

  12. Biomechanics of neck injuries resulting from rear-end vehicle collisions.

    PubMed

    Erbulut, Deniz U

    2014-01-01

    It has been claimed that 85% of the neck injuries caused by car accidents are the result of rear-end collisions. This type of injury is called a whiplash injury, and its mechanisms are not completely understood due to the limited ability to diagnose them using X-ray or MRI. Biomechanical studies including research on injury mechanisms, injury criteria, neck kinematics and injury epidemiology were reviewed to investigate the details of whiplash injuries. Many different injury mechanisms has been studied and identified such as hyperextension of the neck, facet joint impingement, spine column pressure, and muscle strains. Possible injury criterions have been reported as The Neck Injury Criterion (NIC), Nij criterion, IV-NIC criterio, Nkm criterion, NDC criterion.

  13. Preliminary results of characteristic seismic anisotropy beneath Sunda-Banda subduction-collision zone

    SciTech Connect

    Wiyono, Samsul H.; Nugraha, Andri Dian

    2015-04-24

    Determining of seismic anisotropy allowed us for understanding the deformation processes that occured in the past and present. In this study, we performed shear wave splitting to characterize seismic anisotropy beneath Sunda-Banda subduction-collision zone. For about 1,610 XKS waveforms from INATEWS-BMKG networks have been analyzed. From its measurements showed that fast polarization direction is consistent with trench-perpendicular orientation but several stations presented different orientation. We also compared between fast polarization direction with absolute plate motion in the no net rotation and hotspot frame. Its result showed that both absolute plate motion frame had strong correlation with fast polarization direction. Strong correlation between the fast polarization direction and the absolute plate motion can be interpreted as the possibility of dominant anisotropy is in the asthenosphere.

  14. First Results on Angular Distributions of Thermal Dileptons in Nuclear Collisions

    SciTech Connect

    Arnaldi, R.; Colla, A.; Cortese, P.; Ferretti, A.; Oppedisano, C.; Scomparin, E.; Banicz, K.; Damjanovic, S.; Castor, J.; Devaux, A.; Fargeix, J.; Force, P.; Manso, F.; Chaurand, B.; Cicalo, C.; Falco, A. de; Floris, M.; Masoni, A.; Puddu, G.; Serci, S.

    2009-06-05

    The NA60 experiment at the CERN Super Proton Synchrotron has studied dimuon production in 158A GeV In-In collisions. The strong excess of pairs above the known sources found in the complete mass region 0.2results on the associated angular distributions. Using the Collins-Soper reference frame, the structure function parameters {lambda}, {mu}, and {nu} are measured to be zero, and the projected distributions in polar and azimuth angles are found to be uniform. The absence of any polarization is consistent with the interpretation of the excess dimuons as thermal radiation from a randomized system.

  15. Strangeness production in Au+Au collisions at the AGS: recent results from E917.

    SciTech Connect

    Chang, W.-C.; Back, B. B.; Betts, R. R.; Britt, H. C.; Chang, W. C.; Gillitzer, A.; Henning, W. F.; Hofman, D. J.; Holzman, B.; Nanal, V.; Wuosmaa, A. H.

    1999-03-30

    Strangeness production in Au+Au collisions has been measured via the yields of K{sup +} , K{sup {minus}} at 6, 8 AGeV and of {bar {Lambda}} at 10.8 AGeV beam kinetic energy in experiment E917. By varying the collision centrally and beam energy, a systematic search for indications of new phenomena and in-medium effects under high baryon density is undertaken.

  16. Exit charge state dependence of convoy electron production in heavy-ion solid collisions

    SciTech Connect

    Huelskoetter, H.P.; Burgdoerfer, J.; Sellin, I.A.

    1986-01-01

    The dependence of the yield of convoy electrons emitted near the forward direction in collisions involving fast ions and thin solid targets on the emergent projectile charge state is presented and described in terms of primary electron loss events in the solid. The data include a large array of projectiles, projectile energies and charge states, as well as targets ranging in thickness from the non-equilibrium well into the equilibrium thickness region. The description presented is consistent with other experimental and theoretical results indicating that the convoy electron production is closely linked to the ELC process observed in binary ion-atom collisions, with the dominant contribution to the convoy yield stemming from excited states of the projectiles. 22 refs., 3 figs.

  17. Theoretical investigation of the electron capture and loss processes in the collisions of He2+ + Ne.

    PubMed

    Hong, Xuhai; Wang, Feng; Jiao, Yalong; Su, Wenyong; Wang, Jianguo; Gou, Bingcong

    2013-08-28

    Based on the time-dependent density functional theory, a method is developed to study ion-atom collision dynamics, which self-consistently couples the quantum mechanical description of electron dynamics with the classical treatment of the ion motion. Employing real-time and real-space method, the coordinate space translation technique is introduced to allow one to focus on the region of target or projectile depending on the actual concerned process. The benchmark calculations are performed for the collisions of He(2+) + Ne, and the time evolution of electron density distribution is monitored, which provides interesting details of the interaction dynamics between the electrons and ion cores. The cross sections of single and many electron capture and loss have been calculated in the energy range of 1-1000 keV/amu, and the results show a good agreement with the available experiments over a wide range of impact energies.

  18. Vibrationally inelastic collisions of H+D2: a comparison of quantum mechanical, quasiclassical, and experimental results.

    PubMed

    Jambrina, P G; Aldegunde, J; Castillo, J F; Aoiz, F J; Sáez Rábanos, V

    2009-01-21

    A detailed comparison of quantum mechanical (QM) and quasiclassical trajectory (QCT) integral and differential cross sections (DCSs) as well as opacity functions is presented in this work for the vibrationally inelastic collisions of H+D(2)(v=0,j=0)-->H+D(2)(v(')=3,j(')) at 1.72 eV collision energy. These results are also compared with the experimental differential cross sections by Greaves et al. [Nature (London) 454, 88 (2008)]. The agreement between QCT and QM results is fairly good but some differences are appreciable, and it is shown that the experimental results are in a somewhat better agreement with the calculated QM DCS. The present results and their analysis confirm that the vibrational excitation takes place by elongation of the D-D bond in a "tug-of-war" mechanism, where the incoming H atom and one of the D atoms compete for the formation of a bond with the other D atom, as proposed by Greaves et al. It is also found that these collisions may give rise to the formation of short-lived collision complexes (tau(coll)=35-50 fs) that can be traced back to the presence of relatively deep wells in the potential surface when the original D-D bond is stretched. The analysis of the trajectories into v(')=3 reveals that most of them cross at least twice the reaction barrier via a recrossing mechanism.

  19. Results from Cu+Au collisions at 200 GeV in PHENIX Experiment

    SciTech Connect

    Berdnikov, Ya. A.; Kotov, D. O.; Safonov, A. S.; Ivanishchev, D. A.; Riabov, V. G.; Riabov, Yu. G.; Samsonov, V. M.

    2016-01-22

    Collisions of asymmetric nuclei (Cu+Au) differ essentially from the case of symmetric nuclei (Cu+Cu, Au+Au) collisions in the geometry of overlap region. This leads to a number of consequences, which provide more absolute and accurate information about fundamental properties of matter under extreme conditions. Nuclear modification factors for π-mesons in Cu+Au interactions at 200 GeV were measured in PHENIX Experiment at RHIC. New experimental data on measurement of flows of different order (v{sub 1}, v{sub 2}) for light hadrons in Cu+Au interactions at 200 GeV will be discussed in this paper.

  20. Monitoring hazardous near-Earth-object debris at 1 au using interplanetary magnetic signatures resulting from meteoroid-asteroid collisions

    NASA Astrophysics Data System (ADS)

    Lai, H.; Russell, C.; Wei, H.; Connors, M.; Delzanno, G.

    2014-07-01

    While telescopic observations can determine accurately the orbits of potentially hazardous NEOs, they do not resolve the debris trail that accompanies these objects. The density of impactors increases with decreasing size, and these smaller objects upon impact can release material from the parent object and at times may completely disrupt it. This material leaves the region in which the collision occurred with momentum gained or lost in the collision and may move out of the original safe orbit into one that is hazardous to Earth. Thus we are at greater risk of a hazardous collision than our telescopic observations lead us to believe. Because material in these debris trails suffers disruptive collisions with the numerous but much smaller solar system meteoroid populations, and because this material becomes ionized and interacts with the solar wind, we can use magnetometers in space to monitor the amount and size distribution of potentially hazardous objects near 1 au. We have applied this to materials accompanying asteroid 138175 in its orbit around the Sun. Statistical results reveal that those materials are of tens of meters in diameter and have significant dispersion about the asteroid's orbit. A temporal study from 1970s to present shows that the lifetime of those co-orbiting materials are decades, which can be explained by their orbital resonance with Earth and Venus.

  1. Femtosecond laser field induced modifications of electron-transfer processes in Ne{sup +}-He collisions

    SciTech Connect

    Lu Zhenzhong; Chen Deying; Fan Rongwei; Xia Yuanqin

    2012-01-02

    We demonstrate the presence of femtosecond laser induced charge transfer in Ne{sup +}-He collisions. Electron transfer in ion-atom collisions is considerably modified when the collision is embedded in a strong laser field with the laser intensity of {approx}10{sup 15} W/cm{sup 2}. The observed anisotropy of the He{sup +} angular distribution confirms the prediction of early work that the capture probability varies significantly with the laser polarization angle.

  2. Collision tectonics

    SciTech Connect

    Coward, M.P.; Ries, A.C.

    1985-01-01

    The motions of lithospheric plates have produced most existing mountain ranges, but structures produced as a result of, and following the collision of continental plates need to be distinguished from those produced before by subduction. If subduction is normally only stopped when collision occurs, then most geologically ancient fold belts must be collisional, so it is essential to recognize and understand the effects of the collision process. This book consists of papers that review collision tectonics, covering tectonics, structure, geochemistry, paleomagnetism, metamorphism, and magmatism.

  3. Theory of inelastic ion-atom scattering at low and intermediate energies

    NASA Technical Reports Server (NTRS)

    Schmid, G. B.; Garcia, J. D.

    1977-01-01

    Ab initio calculations are presented of inelastic energy loss and ionization phenomena associated with Ar(+)-Ar collisions at small distances of closest approach and for laboratory collision energies ranging from several keV to several hundred keV. Outer-shell excitations are handled statistically; inner-shell excitations are calculated from the viewpoint of quasidiabatic molecular orbital promotion. Auger electron yield, average state of ionization, and average inelastic energy loss are calculated per collision as a function of distance of closest approach of the collision partners for several laboratory collision energies. Average charge-state probabilities per collision partner are calculated as a function of the average inelastic energy loss per atom. It is shown that the structure in the data is due to the underlying structure in the inner-shell independent-electron quasimolecular promotion probabilities.

  4. Nucleus-nucleus collisions at 60 to 200 GeV/nucleon: Results from the WA80 experiment at CERN

    SciTech Connect

    Plasil, F.; Awes, T.C.; Baktash, C.; Ferguson, R.L.; Lee, I.Y.; Saini, S.; Tincknell, M.L.; Young, G.R. ); Obenshain, F.E.; Sorensen, S.P. Tennessee Univ., Knoxville, TN ); Albrecht, R.; Bock, R.; Claesson, G.; Gutbrod, H.H.; Kolb, B.W.; Lund, I.; Schmidt, H.R.; Siemiarczuk, T. (Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germa

    1990-05-01

    Results from {sup 16}O- and {sup 32}S-induced reactions obtained by the WA80 collaboration at the CERN SPS are presented with reference to global event characteristics such as collision geometry, the degree of nuclear stopping, and the energy density attained. Transverse momentum spectra of neutral pions and of direct photons are also presented. At an accuracy within 15{percent} limits, all observed photons are accounted for by known hadronic decays. 13 refs., 8 figs., 1 tab.

  5. Results (and future prospects) of the CMS experiment in photon-induced interactions in p-Pb collisions

    NASA Astrophysics Data System (ADS)

    Bylinkin, Alexander

    2017-03-01

    Exclusive vector meson photoproduction is studied in ultra-peripheral pPb collisions at √{sN N }=5.02 TeV with the CMS experiment at the LHC. The cross sections are measured as a function of the photon-proton centre-of-mass energy, extending the energy range explored by H1 and ZEUS Experiments at HERA. In addition, the differential cross sections (dσ/d|t|), where | t | ≈pT2 is the squared transverse momentum of produced vector mesons, are measured and the slope parameters are obtained. The results are compared to previous measurements and to theoretical predictions. Finally, prospect for further measurements of vector meson production that can be performed using the 2016 pPb collision data at 8 TeV to be collected at the end of the year are presented.

  6. From subduction to collision: results of French POP2 program on Taiwan-Philippine festoon

    SciTech Connect

    Blanchet, R.; Stephan, J.F.; Rangin, C.; Baladad, D.; Bouysse, Ph.; Chen, M.P.; Chotin, P.; Collot, J.Y.; Daniel, J.; Drouhot, J.M.; Marsset, B.; Pelletier, B.; Richard, M.; Tardy, M.

    1986-07-01

    A sea-beam, seismic, magnetic, and gravimetric survey was conducted with the R/V Jean-Charcot in three key regions off the Taiwan-Philippine festoon in the western Pacific: (1) Ryukyu active margin and its junction with Taiwan; (2) northern part of the Manila Trench and its junction with the Taiwan tectonic prism; and (3) southern termination of Manila Trench in front of Mindoro Island. Transitions between active subduction along the Manila Trench and collision of Taiwan and Mindoro, and relations between active subduction and extension in the Okinawa-Ryukyu and the northeastern Taiwan systems are particularly studied.

  7. Occupant and Crash Characteristics in Thoracic and Lumbar Spine Injuries Resulting From Motor Vehicle Collisions

    PubMed Central

    Rao, Raj D.; Berry, Chirag; Yoganandan, Narayan; Agarwal, Arnav

    2016-01-01

    Background context Motor vehicle collisions (MVC) are a leading cause of thoracic and lumbar (T and L) spine injuries. Mechanisms of injury in vehicular crashes that result in thoracic and lumbar fractures and the spectrum of injury in these occupants have not been extensively studied in the literature. Purpose The objective was to investigate the patterns of T and L spine injury following MVC; correlate these patterns with restraint use, crash characteristics and demographic variables; and study the associations of these injuries with general injury morbidity and fatality. Study design/Setting Retrospective study of a prospectively gathered database. Patient sample Six hundred and thirty-one occupants with T and L (T1-L5) spine injuries from 4572 occupants included in the Crash Injury Research and Engineering Network (CIREN) database between 1996 and 2011. Outcome measures No clinical outcome measures were evaluated in this study. Methods The CIREN database includes moderate to severely injured occupants from MVC involving vehicles manufactured recently. Demographic, injury and crash data from each patient was analyzed for correlations between pattern of T and L spine injury, associated extra-spinal injuries and overall injury severity score (ISS), type and use of seat belts, and other crash characteristics. T and L spine injury pattern was categorized using a modified Denis classification, to include extension injuries as a separate entity. Results T and L spine injuries were identified in 631 of 4572 vehicle occupants, of whom 299 sustained major injuries (including 21 extension injuries) and 332 sustained minor injuries. Flexion-distraction injuries were more prevalent in children and young adults, and extension injuries in older adults (mean age 65.7 years). Occupants with extension injuries had a mean BMI of 36.0 and a fatality rate of 23.8%, much higher than the fatality rate for the entire cohort (10.9%). The most frequent extra-spinal injuries (Abbreviated

  8. Latest results of charged hadron flow measurements in CuAu collisions at RHIC-PHENIX

    NASA Astrophysics Data System (ADS)

    Nakagomi, Hiroshi

    2016-08-01

    Measurements of azimuthal anisotropic flow vn for inclusive charged hadrons and identified particles at mid rapidity in Cu+Au collisions at √sNN = 200GeV are presented. The data were recorded by the PHENIX experiment at Relativistic Heavy Ion Collider(RHIC). Directed, elliptic and triangular flow as a function of transverse momentum pT are measured with respect to event planes. The inclusive charged hadron vi shows the negative value at high pT. The v2 and v3 are compared to those in Au+Au and Cu+Cu collisions. We find the v 2 and v3 follow an empirical scaling with 1/(ɛnN1/3 part). We also compare the v2 and v3 to hydrodynamical predictions. The identified particles v2 and v3 show a mass ordering in low pT region and baryon and meson splitting in high pT region. However the identified hadron v1 only shows mass ordering in mid pT region.

  9. Small UAV Automatic Ground Collision Avoidance System Design Considerations and Flight Test Results

    NASA Technical Reports Server (NTRS)

    Sorokowski, Paul; Skoog, Mark; Burrows, Scott; Thomas, SaraKatie

    2015-01-01

    The National Aeronautics and Space Administration (NASA) Armstrong Flight Research Center Small Unmanned Aerial Vehicle (SUAV) Automatic Ground Collision Avoidance System (Auto GCAS) project demonstrated several important collision avoidance technologies. First, the SUAV Auto GCAS design included capabilities to take advantage of terrain avoidance maneuvers flying turns to either side as well as straight over terrain. Second, the design also included innovative digital elevation model (DEM) scanning methods. The combination of multi-trajectory options and new scanning methods demonstrated the ability to reduce the nuisance potential of the SUAV while maintaining robust terrain avoidance. Third, the Auto GCAS algorithms were hosted on the processor inside a smartphone, providing a lightweight hardware configuration for use in either the ground control station or on board the test aircraft. Finally, compression of DEM data for the entire Earth and successful hosting of that data on the smartphone was demonstrated. The SUAV Auto GCAS project demonstrated that together these methods and technologies have the potential to dramatically reduce the number of controlled flight into terrain mishaps across a wide range of aviation platforms with similar capabilities including UAVs, general aviation aircraft, helicopters, and model aircraft.

  10. New paleomagnetic results from Ladakh, Western Himalaya support multi-stage collision scenario between India and Eurasia.

    NASA Astrophysics Data System (ADS)

    Bailey, E.; Tikoo, S. M.; Jagoutz, O. E.; Royden, L.; Weiss, B. P.

    2014-12-01

    The Kohistan-Ladakh arc (KLA) separates India from Eurasia in the western Himalaya. Two conflicting hypotheses have been developed concerning the collision between India, the KLA, and Eurasia. In the classical model, the KLA is thought to have collided with Eurasia in the Cretaceous (~85-110 Ma), and, subsequently, India collided with Eurasia and the KLA at ~50 Ma along the Indus-Tsangpo suture. Alternatively, it has been proposed that India first collided with the KLA at ~50 Ma, and, subsequently, India and the KLA collided with Eurasia at ~40 Ma along the Shyok-Tsangpo suture zone. These different collision scenarios make distinct predictions for the absolute timing of the India-Eurasia collision. In the classical hypothesis, the KLA should have been located at ~20°N after collision with Eurasia, whereas the alternative model predicts that the KLA remained far removed form Eurasia, therefore south of ~20°N in the Paleo-Tethys until 50 Ma. We conducted a paleomagnetic study to test these two conflicting hypotheses by determining the paleolatitude of formation for a ~67-52 Ma sequence of the Khardung volcanics--a unit located in the Shyok-Nubra valley and overlying the KLA. Samples were collected at four sites. During stepwise thermal demagnetization, samples from all four sites contained co-directional high-temperature (HT) magnetization components persisting to the magnetite Curie temperature of 580°C or greater. A baked contact test at one site suggests that these HT magnetizations predate dike intrusion and bedding tilt, indicating that the HT components likely reflect primary magnetization. The average of the HT site mean directions implies a paleolatitude of 5°N. Our results preclude the possibility that the KLA collided with Eurasia at ~ 20°N in the Cretaceous. Instead, they support the hypothesis that the KLA initially collided with India at ~ 50 Ma in the equatorial region of the Tethyan ocean.

  11. PHENIX results on fluctuations and Bose-Einstein correlations in Au + Au collisions from the RHIC Beam Energy Scan

    NASA Astrophysics Data System (ADS)

    Garg, Prakhar

    2016-12-01

    The RHIC Beam Energy Scan focuses on mapping the QCD phase diagram and pinpointing the location of a possible critical end point. Bose-Einstein correlations and event-by-event fluctuations of conserved quantities, measured as a function of centrality and collision energy, are promising tools in these studies. Recent lattice QCD and statistical thermal model calculations predict that higher-order cumulants of the fluctuations are sensitive indicators of the phase transition. Products of these cumulants can be used to extract the freeze-out parameters [A. Bazavov et al., Phys. Rev. Lett. 109, 192302 (2012)] and to locate the critical point [M. A. Stephanov, K. Rajagopal and E. V. Shuryak, Phys. Rev. D 60, 114028 (1999)]. Two-pion interferometry measurements are predicted to be sensitive to potential softening of the equation of state and prolonged emission duration close to the critical point [S. Pratt, Phys. Rev. Lett. 53, 1219 (1984)]. We present recent PHENIX results on fluctuations of net-charge using high-order cumulants and their products in Au+Au collisions at √{sNN} = 7.7- 200 GeV, and measurement of two-pion correlation functions and emission-source radii in Cu+Cu and Au+Au collisions at several beam energies. The extracted source radii are compared to previous measurements at RHIC and LHC in order to study energy dependence of the specific quantities sensitive to expansion velocity and emission duration. Implications for the search of a critical point and baryon chemical potentials at various collision energies are discussed.

  12. Three-body Coulomb problem probed by mapping the Bethe surface in ionizing ion-atom collisions.

    PubMed

    Moshammer, R; Perumal, A; Schulz, M; Rodríguez, V D; Kollmus, H; Mann, R; Hagmann, S; Ullrich, J

    2001-11-26

    The three-body Coulomb problem has been explored in kinematically complete experiments on single ionization of helium by 100 MeV/u C(6+) and 3.6 MeV/u Au(53+) impact. Low-energy electron emission ( E(e)<150 eV) as a function of the projectile deflection theta(p) (momentum transfer), i.e., the Bethe surface [15], has been mapped with Delta theta(p)+/-25 nanoradian resolution at extremely large perturbations ( 3.6 MeV/u Au(53+)) where single ionization occurs at impact parameters of typically 10 times the He K-shell radius. The experimental data are not in agreement with state-of-the-art continuum distorted wave-eikonal initial state theory.

  13. Collisions of slow polyatomic ions with surfaces: the scattering method and results.

    PubMed

    Herman, Zdenek

    2003-12-01

    Surface-induced dissociation (SID) and reactions following impact of well-defined ion beams of polyatomic cations C2H5OH+, CH4+, and CH5+ (and its deuterated variants) at several incident angles and energies with self-assembled monolayers (SAM), carbon surfaces, and hydrocarbon covered stainless steel were investigated by the scattering method. Energy transfer and partitioning of the incident projectile energy into internal excitation of the projectile, translational energy of products, and energy transferred into the surface were deduced from the mass spectra and the translational energy and angular distributions of the product ions. Conversion of ion impact energy into internal energy of the recoiling ions peaked at about 17% of the incident energy for the perfluoro-hydrocarbon SAM, and at about 6% for the other surfaces investigated. Ion survival probability is about 30-50 times higher for closed-shell ions than for open-shell radical cations (e.g., 12% for CD5+ versus 0.3% for CD4+, at the incident angle of 60 degrees with respect to the surface normal). Contour velocity plots for inelastic scattering of CD5+ from hydrocarbon-coated and hydrocarbon-free highly oriented pyrolytic graphite (HOPG) surfaces gave effective masses of the surface involved in the scattering event, approximately matching that of an ethyl group (or two methyl groups) and four to five carbon atoms, respectively. Internal energy effects in impacting ions on SID were investigated by comparing collision energy resolved mass spectra (CERMS) of methane ions generated in a low pressure Nier-type electron impact source versus those generated in a Colutron source in which ions undergo many collisions prior to extraction and are essentially vibrationally relaxed. This comparison supports the hypothesis that internal energy of incident projectile ions is fully available to drive their dissociation following surface impact.

  14. Origin, evolution, and imaging of vortices in proton-hydrogen collisions

    NASA Astrophysics Data System (ADS)

    Schultz, D. R.; Macek, J. H.; Sternberg, J. B.; Ovchinnikov, S. Yu; Lee, T.-G.

    2009-11-01

    Using a novel computational approach, we have elucidated the origin of unexpected vortices in the electronic wavefunction during ion-atom collisions. It is shown how they could be observed in experiments and how they play a new and wide ranging role in angular momentum transfer and other atomic processes.

  15. Recent results from the STAR experiment on vector meson production in ultra peripheral AuAu collisions at RHIC

    NASA Astrophysics Data System (ADS)

    Adamczyk, Leszek

    2017-03-01

    In 2010, the STAR Collaboration collected a large sample of low-multiplicity triggers for ultraperipheral collision studies. We present preliminary results involving photonuclear interactions in ultraperipheral relativistic heavy-ion collisions (UPCs), based on an analysis of photoproduced pion pairs, from ρ0, ω and direct ππ pair production. The relative amplitudes of the three components have been measured, along with the phase angle between the ρ0 and ω0 components. The ρ0 squared momentum transfer (t) spectrum exhibits a spectrum with both coherent and incoherent production. The coherent component shows two characteristic diffraction minima, with positions that are sensitive to the hadronic radius of the gold nucleus. Using a two-year (2010 and 2011) dataset, we explore higher mass final states, and observe a ππ state roughly compatible with the ρ3(1690). Preliminary results for the J/ψ production cross section as a function of rapidity and transverse momentum pT are also presented; the dominant component at low pT demonstrates the coherent production of J/ψ of the entire Au nucleus, and a significant component at higher pT indicates incoherent production of individual nucleons within the nucleus. Future RHIC runs with polarized protons will provide the opportunity to measure J/ψ production in ultra-peripheral pp and pAu collisions. The STAR Roman Pot system will allow measurement of the final state protons. A non-zero transverse asymmetry of the produced J/ψ's would be the first measure of the nucleon helicity-flip Generalized Parton Distributions (GPD)-E for gluons, which is connected with the orbital angular momentum of gluons in the nucleon.

  16. PHENIX results on low-mass dileptons in Au + Au collisions with the Hadron Blind Detector

    NASA Astrophysics Data System (ADS)

    Makek, M.

    2016-12-01

    We present e+e- continuum measurement in Au+Au collisions at √{sNN} = 200 GeV from the RHIC 2010 run with the Hadron Blind Detector upgrade of PHENIX. The measurement reaches a high purity of the electron sample of ≥ 95% at all centralities and provides an excellent qualitative and quantitative understanding of the background. The e+e- invariant yields show an enhancement in the low-mass region (mee = 0.30 - 0.76 GeV /c2) compared to the expectations from hadronic sources, but not as large as the one previously reported by PHENIX. The observed excess is well reproduced by models incorporating the broadening of the ρ meson due to scattering off baryons in the hot hadronic gas. The measured invariant yields in the intermediate-mass region (mee = 1.2 - 2.8 GeV /c2) leave room for additional sources when compared to the cocktail dominated by the semileptonic decays of heavy flavor mesons.

  17. Geology of the d'Entrecasteaux-New Hebrides arc collision zone: results from a deep submersible survey

    USGS Publications Warehouse

    Collot, J.-Y.; Lallemand, S.; Pelletier, B.; Bissen, J.-P.; Glacon, G.; Fisher, M.A.; Greene, H. Gary; Boulin, J.; Daniel, J.; Monzier, M.

    1992-01-01

    During the SUBPSO1 cruise, seven submersible dives were conducted between water depths of 5350 and 900 m over the collision zone between the New Hebrides island arc and the d'Entrecasteaux Zone (DEZ). The DEZ, a topographic high on the Australian plate, encompasses the North d'Entrecasteaux Ridge (NDR) and the Bougainville guyot, both of which collide with the island-are slope. In this report we use diving observations and samples, as well as dredging results, to analyse the geology of the Bougainville guyot and the outer arc slope in the DEZ-arc collision zone, and to decipher the mechanisms of scamount subduction. These data indicate that the Bougainville guyot is a middle Eocene island arc volcano capped with reef limestones that appear to have been deposited during the Late Oligocene to Early Miocene and in Miocene-Pliocene times. This guyot possibly emerged during the Middle and Late Miocene, and started to sink in the New Hebrides trench after the Pliocene. The rocks of the New Hebrides arc slope, in the collision zone, consist primarily of Pliocene-Recent volcaniclastic rocks derived from the arc, and underlying fractured island-arc volcanic basement, possibly of Late Miocene age. However, highly sheared, Upper Oligocene to Lower Miocene nannofossil ooze and chalk are exposed at the toe of the arc slope against the northern flank of the NDR. Based on a comparison with cores collected at DSDP Site 286, the ooze and chalk can be interpreted as sediments accreted from the downgoing plate. East of the Bougainville guyot an antiform that developed in the arc slope as a consequence of the collision reveals a 500-m-thick wedge of strongly tectonized rocks, possibly accreted from the guyot or an already subducted seamount. The wedge that is overlain by less deformed volcaniclastic island-arc rocks and sediments includes imbricated layers of Late Oligocene to Early Miocene reef and micritic limestones. This wedge, which develops against the leading flank of the guyot

  18. Initial results of a full kinetic simulation of RF H{sup −} source including Coulomb collision process

    SciTech Connect

    Mochizuki, S.; Shibata, T.; Nishida, K.; Hatayama, A.; Mattei, S.; Lettry, J.

    2015-04-08

    In order to evaluate Electron Energy Distribution Function (EEDF) more correctly for radio frequency inductively coupled plasma (RF-ICP) in hydrogen negative ion sources, the Electromagnetic Particle-In-Cell (EM-PIC) simulation code has been improved by taking into account electron-electron Coulomb collision. Binary collision model is employed to model Coulomb collision process and we have successfully modeled it. The preliminary calculation including Coulomb collision has been done and it is shown that Coulomb collision doesn’t have significant effects under the condition: electron density n{sub e} ∼ 10{sup 18} m{sup −3} and high gas pressure p{sub H{sub 2}} = 3 Pa, while it is necessary to include Coulomb collision under high electron density and low gas pressure conditions.

  19. From subduction to collision: Results from seismic profiling, gravity modeling, and earthquake finite fault inversions in Taiwan region

    NASA Astrophysics Data System (ADS)

    Chi, Wu-Cheng

    This study used (1) 132-channel reflection profiles, forward gravity modeling, and (2) finite source inversions of earthquakes to analyze crustal evolution from Subduction to collision in the region of Taiwan. Reflection and gravity data in the offshore region shows that the accretionary prism in the Subduction zone is mainly sedimentary; however, due to tectonic wedging in the initial collision zone, high-density basement materials are incorporated into the rear of the accretionary prism and may extend northward to compose a portion of high-density rocks that underly southeastern Taiwan. Further to the north in the mature collision zone was the site of the 1999, Chi-Chi, Taiwan earthquake. For this earthquake and its large aftershocks, we inverted strong motion data for finite source processes to study the deep fault structures. The mainshock ruptured on a shallow eastward-dipping fault possibly rooted in the proposed decollement of thin-skin deformation model. Several aftershocks either nucleated in or ruptured the basement indicating active deformation below the decollement, suggesting basement-involved deformation. Interpreting finite-source results requires a thorough understanding of the uncertainty in the parameters. Further more, near-realtime applications of finite-source inversions for estimation of near-fault strong ground motion requires well constrained fault orientation and hypocentral parameters. With this in mind, we tested a wide range of hypocenters and focal mechanisms, and the corresponding fits of the synthetics to the observed waveforms when studying the aftershock source parameters. As a result, we obtained optimal waveform fits and determined how the errors reported in hypocenters and focal mechanisms affected the inverted waveforms and the sensitivity of the waveform fits. For example, if the hypocenter was within 5 km of the optimal hypocenter and the focal mechanism was within 20 degrees of optimal strike, dip, and rake, the waveform fits

  20. Ion-Atom/Argon—Calculation of ionization cross sections by fast ion impact for neutral target atoms ranging from hydrogen to argon

    NASA Astrophysics Data System (ADS)

    McSherry, D. M.; O'Rourke, S. F. C.; Crothers, D. S. F.

    2003-10-01

    A FORTRAN 90 program is presented which calculates the total cross sections, and the electron energy spectra of the singly and doubly differential cross sections for the single target ionization of neutral atoms ranging from hydrogen up to and including argon. The code is applicable for the case of both high and low Z projectile impact in fast ion-atom collisions. The theoretical models provided for the program user are based on two quantum mechanical approximations which have proved to be very successful in the study of ionization in ion-atom collisions. These are the continuum-distorted-wave (CDW) and continuum-distorted-wave eikonal-initial-state (CDW-EIS) approximations. The codes presented here extend previously published codes for single ionization of target hydrogen [Crothers and McCartney, Comput. Phys. Commun. 72 (1992) 288], target helium [Nesbitt, O'Rourke and Crothers, Comput. Phys. Commun. 114 (1998) 385] and target atoms ranging from lithium to neon [O'Rourke, McSherry and Crothers, Comput. Phys. Commun. 131 (2000) 129]. Cross sections for all of these target atoms may be obtained as limiting cases from the present code. Program summaryTitle of program: ARGON Catalogue identifier: ADSE Program summary URL:http://cpc.cs.qub.ac.uk/cpc/summaries/ADSE Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: none Computer for which the program is designed and others on which it is operable: Computers: Four by 200 MHz Pro Pentium Linux server, DEC Alpha 21164; Four by 400 MHz Pentium 2 Xeon 450 Linux server, IBM SP2 and SUN Enterprise 3500 Installations: Queen's University, Belfast Operating systems under which the program has been tested: Red-hat Linux 5.2, Digital UNIX Version 4.0d, AIX, Solaris SunOS 5.7 Compilers: PGI workstations, DEC CAMPUS Programming language used: FORTRAN 90 with MPI directives No. of bits in a word: 64, except on Linux servers 32 Number of processors used: any number Has the

  1. Studies of Strangeness Production in proton-Nucleus Collision: preliminary results from E910 at BNL-AGS

    NASA Astrophysics Data System (ADS)

    Yang, Xihong

    1996-10-01

    Strange particle production has been viewed as an interesting probe of Heavy-Ion physics because it has the signature of QGP formation. Using the EOS TPC and downstream drift chambers for tracking and using TOF and Cerenkov counters for particle identification, experiment E910 provides a facility with large acceptance and high resolution for exclusive measurements of proton-nucleus collisions at AGS energy. Production of Λ in both 12.5 GeV/c and 18 GeV/c p+A (A = Au, Cu) from '96 run data has been analyzed. The initial reconstruction results of the Λ invariant mass distribution shows a mass resolution of 2.5MeV/c^2. The Λ yield for different beam energies and target masses has been analyzed and compared with the p+p data and E859 data. The transverse mass and rapidity distributions are also discussed here.

  2. Estimation of the Risks of Collision or Strike to Freshwater Aquatic Organisms Resulting from Operation of Instream Hydrokinetic Turbines

    SciTech Connect

    Schweizer, Peter E; Cada, Glenn F; Bevelhimer, Mark S

    2010-05-01

    Hydrokinetic energy technologies have been proposed as renewable, environmentally preferable alternatives to fossil fuels for generation of electricity. Hydrokinetic technologies harness the energy of water in motion, either from waves, tides or from river currents. For energy capture from free-flowing rivers, arrays of rotating devices are most commonly proposed. The placement of hydrokinetic devices in large rivers is expected to increase the underwater structural complexity of river landscapes. Moore and Gregory (1988) found that structural complexity increased local fish populations because fish and other aquatic biota are attracted to structural complexity that provides microhabitats with steep flow velocity gradients (Liao 2007). However, hydrokinetic devices have mechanical parts, blades, wings or bars that move through the water column, posing a potential strike or collision risk to fish and other aquatic biota. Furthermore, in a setting with arrays of hydrokinetic turbines the cumulative effects of multiple encounters may increase the risk of strike. Submerged structures associated with a hydrokinetic (HK) project present a collision risk to aquatic organisms and diving birds (Cada et al. 2007). Collision is physical contact between a device or its pressure field and an organism that may result in an injury to that organism (Wilson et al. 2007). Collisions can occur between animals and fixed submerged structures, mooring equipment, horizontal or vertical axis turbine rotors, and structures that, by their individual design or in combination, may form traps. This report defines strike as a special case of collision where a moving part, such as a rotor blade of a HK turbine intercepts the path of an organism of interest, resulting in physical contact with the organism. The severity of a strike incidence may range from minor physical contact with no adverse effects to the organism to severe strike resulting in injury or death of the organism. Harmful effects

  3. Inelastic transitions in slow heavy-particle atomic collisions

    SciTech Connect

    Krstic, P. S.; Reinhold, C. O.; Burgdo''rfer, J.

    2001-05-01

    It is a generally held belief that inelastic transition probabilities and cross sections in slow, nearly adiabatic atomic collisions decrease exponentially with the inverse of the collision velocity v [i.e., {sigma}{proportional_to}exp(-const/v)]. This notion is supported by the Landau-Zener approximation and the hidden crossings approximation. We revisit the adiabatic limit of ion-atom collisions and show that for very slow collisions radial transitions are dominated by the topology of the branch points of the radial velocity rather than the branch points of the energy eigensurface. This can lead to a dominant power-law dependence of inelastic cross sections, {sigma}{proportional_to}v{sup n}. We illustrate the interplay between different contributions to the transition probabilities in a one-dimensional collision system for which the exact probabilities can be obtained from a direct numerical solution of the time-dependent Scho''dinger equation.

  4. First results on bilepton production based on LHC collision data and predictions for run II

    NASA Astrophysics Data System (ADS)

    Nepomuceno, A. A.; Eccard, F. L.; Meirose, B.

    2016-09-01

    The LHC potential for discovering doubly charged vector bileptons is investigated considering the measurable process p p →μ+μ+μ-μ-X . The study is performed assuming different bilepton and leptoquark masses. The process cross section is calculated at leading order using the Calchep package. Combining the calculation with the latest ATLAS experiment results at a center-of-mass energy of 7 TeV, bounds on bilepton masses based on LHC data are derived for the first time. The results exclude bilepton masses in the range of 250 GeV to 500 GeV at 95% C.L., depending on the leptoquark mass. Moreover, minimal LHC integrated luminosities needed for discovering and for setting limits on bilepton masses are obtained for 13 TeV center-of-mass energy. Simulated events are passed through a fast parametric detector simulation using the Delphes package.

  5. Collision Cross Sections for 20 Protonated Amino Acids: Fourier Transform Ion Cyclotron Resonance and Ion Mobility Results

    NASA Astrophysics Data System (ADS)

    Anupriya; Jones, Chad A.; Dearden, David V.

    2016-08-01

    We report relative dephasing cross sections for the 20 biogenic protonated amino acids measured using the cross sectional areas by Fourier transform ion cyclotron resonance (CRAFTI) technique at 1.9 keV in the laboratory reference frame, as well as momentum transfer cross sections for the same ions computed from Boltzmann-weighted structures determined using molecular mechanics. Cross sections generally increase with increasing molecular weight. Cross sections for aliphatic and aromatic protonated amino acids are larger than the average trend, suggesting these side chains do not fold efficiently. Sulfur-containing protonated amino acids have smaller than average cross sections, reflecting the mass of the S atom. Protonated amino acids that can internally hydrogen-bond have smaller than average cross sections, reflecting more extensive folding. The CRAFTI measurements correlate well with results from drift ion mobility (IMS) and traveling wave ion mobility (TWIMS) spectrometric measurements; CRAFTI results correlate with IMS values approximately as well as IMS and TWIMS values from independent measurements correlate with each other. Both CRAFTI and IMS results correlate well with the computed momentum transfer cross sections, suggesting both techniques provide accurate molecular structural information. Absolute values obtained using the various methods differ significantly; in the case of CRAFTI, this may be due to errors in measurements of collision gas pressure, measurement of excitation voltage, and/or dependence of cross sections on kinetic energy.

  6. Collision Cross Sections for 20 Protonated Amino Acids: Fourier Transform Ion Cyclotron Resonance and Ion Mobility Results.

    PubMed

    Anupriya; Jones, Chad A; Dearden, David V

    2016-08-01

    We report relative dephasing cross sections for the 20 biogenic protonated amino acids measured using the cross sectional areas by Fourier transform ion cyclotron resonance (CRAFTI) technique at 1.9 keV in the laboratory reference frame, as well as momentum transfer cross sections for the same ions computed from Boltzmann-weighted structures determined using molecular mechanics. Cross sections generally increase with increasing molecular weight. Cross sections for aliphatic and aromatic protonated amino acids are larger than the average trend, suggesting these side chains do not fold efficiently. Sulfur-containing protonated amino acids have smaller than average cross sections, reflecting the mass of the S atom. Protonated amino acids that can internally hydrogen-bond have smaller than average cross sections, reflecting more extensive folding. The CRAFTI measurements correlate well with results from drift ion mobility (IMS) and traveling wave ion mobility (TWIMS) spectrometric measurements; CRAFTI results correlate with IMS values approximately as well as IMS and TWIMS values from independent measurements correlate with each other. Both CRAFTI and IMS results correlate well with the computed momentum transfer cross sections, suggesting both techniques provide accurate molecular structural information. Absolute values obtained using the various methods differ significantly; in the case of CRAFTI, this may be due to errors in measurements of collision gas pressure, measurement of excitation voltage, and/or dependence of cross sections on kinetic energy. Graphical Abstract ᅟ.

  7. Probability of satellite collision

    NASA Technical Reports Server (NTRS)

    Mccarter, J. W.

    1972-01-01

    A method is presented for computing the probability of a collision between a particular artificial earth satellite and any one of the total population of earth satellites. The collision hazard incurred by the proposed modular Space Station is assessed using the technique presented. The results of a parametric study to determine what type of satellite orbits produce the greatest contribution to the total collision probability are presented. Collision probability for the Space Station is given as a function of Space Station altitude and inclination. Collision probability was also parameterized over miss distance and mission duration.

  8. Irreversible kinetics on a one-dimensional lattice: Comparison of exact result with a point-process nucleation-growth-collision model

    NASA Astrophysics Data System (ADS)

    Fletcher, S.

    1983-02-01

    In this paper we discuss irreversible kinetics on a one-dimensional lattice. We compare the expectation value of the coverage of the lattice, as a function of time, with that predicted by a point-process nucleation-growth-collision model. We conclude that the nucleation-growth-collision model is only applicable to lattice kinetics when the spreading rate of clusters is much greater than their nucleation rate. Although the kinetics of coverage of a one-dimensional lattice are known exactly, the complete solution turns out to be rather complex. In order to facilitate comparison with the point-process nucleation and growth model, we calculate an approximation to the lattice kinetics which is valid when the collision rate of clusters is very fast. The result is complementary to an earlier approximation of McQuarrie, McTague and Reiss, which described the case when the collision rate of clusters was comparable with the spreading rate. We also consider an integral geometrical approach to discreteness effects in lattice models. The general approach which we suggest is to calculate coefficients of variation of the numbers of lattice sites covered by various geometric shapes as a measure of "discreteness". This method uses some mathematical results of Kendall et al.

  9. Relationship Between Motor Vehicle Collisions and Results of Perimetry, Useful Field of View, and Driving Simulation in Drivers With Glaucoma

    PubMed Central

    Tatham, Andrew J.; Boer, Erwin R.; Gracitelli, Carolina P. B.; Rosen, Peter N.; Medeiros, Felipe A.

    2015-01-01

    Purpose: To examine the relationship between Motor Vehicle Collisions (MVCs) in drivers with glaucoma and standard automated perimetry (SAP), Useful Field of View (UFOV), and driving simulator assessment of divided attention. Methods: A cross-sectional study of 153 drivers from the Diagnostic Innovations in Glaucoma Study. All subjects had SAP and divided attention was assessed using UFOV and driving simulation using low-, medium-, and high-contrast peripheral stimuli presented during curve negotiation and car following tasks. Self-reported history of MVCs and average mileage driven were recorded. Results: Eighteen of 153 subjects (11.8%) reported a MVC. There was no difference in visual acuity but the MVC group was older, drove fewer miles, and had worse binocular SAP sensitivity, contrast sensitivity, and ability to divide attention (UFOV and driving simulation). Low contrast driving simulator tasks were the best discriminators of MVC (AUC 0.80 for curve negotiation versus 0.69 for binocular SAP and 0.59 for UFOV). Adjusting for confounding factors, longer reaction times to driving simulator divided attention tasks provided additional value compared with SAP and UFOV, with a 1 standard deviation (SD) increase in reaction time (approximately 0.75 s) associated with almost two-fold increased odds of MVC. Conclusions: Reaction times to low contrast divided attention tasks during driving simulation were significantly associated with history of MVC, performing better than conventional perimetric tests and UFOV. Translational Relevance: The association between conventional tests of visual function and MVCs in drivers with glaucoma is weak, however, tests of divided attention, particularly using driving simulation, may improve risk assessment. PMID:26046007

  10. Early Cretaceous paleomagnetic and geochronologic results from the Tethyan Himalaya: Insights into the Neotethyan paleogeography and the India–Asia collision

    PubMed Central

    Ma, Yiming; Yang, Tianshui; Bian, Weiwei; Jin, Jingjie; Zhang, Shihong; Wu, Huaichun; Li, Haiyan

    2016-01-01

    To better understand the Neotethyan paleogeography, a paleomagnetic and geochronological study has been performed on the Early Cretaceous Sangxiu Formation lava flows, which were dated from ~135.1 Ma to ~124.4 Ma, in the Tethyan Himalaya. The tilt-corrected site-mean characteristic remanent magnetization (ChRM) direction for 26 sites is Ds = 296.1°, Is = −65.7°, ks = 51.7, α95 = 4.0°, corresponding to a paleopole at 5.9°S, 308.0°E with A95 = 6.1°. Positive fold and reversal tests prove that the ChRM directions are prefolding primary magnetizations. These results, together with reliable Cretaceous-Paleocene paleomagnetic data observed from the Tethyan Himalaya and the Lhasa terrane, as well as the paleolatitude evolution indicated by the apparent polar wander paths (APWPs) of India, reveal that the Tethyan Himalaya was a part of Greater India during the Early Cretaceous (135.1–124.4 Ma) when the Neotethyan Ocean was up to ~6900 km, it rifted from India sometime after ~130 Ma, and that the India-Asia collision should be a dual-collision process including the first Tethyan Himalaya-Lhasa terrane collision at ~54.9 Ma and the final India-Tethyan Himalaya collision at ~36.7 Ma. PMID:26883692

  11. Isospin Effects in Heavy-Ion Collisions: Some Results From CHIMERA Experiments At LNS And Perspectives With Radioactive Beams

    SciTech Connect

    Cardella, G.; De Filippo, E.; Pagano, A.; Papa, M.; Pirrone, S.; Verde, G.; Amorini, F.; Cavallaro, S.; Lombardo, I.; Porto, F.; Rizzo, F.; Russotto, P.; Anzalone, A.; Maiolino, C.; Arena, N.; Geraci, E.; Grassi, L.; Lo Nigro, S.; Politi, G.; Auditore, L.

    2009-05-04

    CHIMERA is a 4{pi} multidetector for charged particles available at Laboratori Nazionali del Sud (INFN-LNS). A new method to measure the time scale of the emission of nuclear fragments is described, together with some applications in the field of the isospin dynamics of heavy-ion collisions. Competition between fusion-like and binary reactions near the energy threshold for nuclear multifragmentation is discussed. Opportunities are pointed out to use the detector at low and intermediate energies using the kinematical-coincidence method.

  12. PHENIX results on collectivity tests in high-multiplicity p + p and p + Au collisions at √{sNN} = 200 GeV

    NASA Astrophysics Data System (ADS)

    Nakagawa, Itaru

    2016-12-01

    The observation of possible collective effects in high-multiplicity p+p and p+Pb collisions at the LHC and in d+Au and 3He+Au collisions at RHIC challenge our understanding of the ingredients necessary for quark-gluon plasma formation. For further investigation of these effects, the PHENIX collaboration has taken high statistics data in p+p and p+Au and p+Al collisions in 2015. For these data sets, high-multiplicity triggers were implemented using the forward silicon detector (FVTX) and the beam-beam counter (BBC) covering pseudo-rapidity 1.0 < | η | < 3.0 and 3.1 < | η | < 3.9, respectively. The multi-hundred million high-multiplicity event samples recorded enable highly differential analysis to look for collective effects. We report results on large pseudo-rapidity separation correlations to elucidate if the so-called ridge phenomena exists in certain p+p event classes at RHIC. The flow coefficients from azimuthal anisotropies in p+Au are extracted and compared with theoretical expectations in various models, including viscous hydrodynamics where the elliptic flow strength is expected to be substantially smaller than in d+Au and 3He+Au at the same energy due to the smaller initial spatial eccentricity.

  13. Ultra-precise single-ion atomic mass measurements on deuterium and helium-3

    NASA Astrophysics Data System (ADS)

    Zafonte, S. L.; Van Dyck, R. S., Jr.

    2015-04-01

    The former University of Washington Penning Trap Mass Spectrometer (UW-PTMS), now located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, was used in the decade before the move to determine new values for the deuteron atomic mass, M (2H+) = 2.013 553 212 745(40) u, and the deuterium atomic mass, M (2H) = 2.014 101 778 052(40) u, both of which are now more than an order-of-magnitude more accurate than the previous best 1994-MIT measurements of these quantities. The new value for the deuteron’s mass can then be used with the accepted 2010-CODATA proton mass and the most recent 1999-measurement of the 2.2 MeV gamma-ray binding energy of the deuteron to refine the neutron’s mass to mn = 1.008 664 916 018(435) u which has about half the uncertainty relative to the value computed using that previous 1994-MIT deuterium measurement. As a result, further improvements of mn must now come from a more accurate determination of the wavelength of this gamma ray. In this same period of time, this spectrometer has also been used to determine new values for the helion atomic mass, M (3He2+) = 3.014 932 246 668(43) u, and the neutral helium-3 atomic mass, M (3He) = 3.016 029 321 675(43) u, which are both about 60 times more accurate than the 2006-SMILETRAP measurements, but disagree with the 4.4-times less-accurate 2015-Florida-State measurements by 0.76 nu. It is expected that these helium-3 results will be used in the future 3H/3He mass ratio (to be determined by the Heidelberg, Germany version of the old UW-PTMS) in order to generate a more accurate value for the tritium atomic mass.

  14. Arc-arc Collision Structure in the Southernmost Part of the Kuril Trench Region -Results from Integrated Analyses of the 1998-2000 Hokkaido Transect Seismic Data-

    NASA Astrophysics Data System (ADS)

    Iwasaki, Takaya; Tsumura, Noriko; Ito, Tanio; Sato, Hiroshi; Kurashimo, Eiji; Hirata, Naoshi; Arita, Kazunori; Noda, Katsuya; Fujiwara, Akira; Abe, Susumu; Kikkuchi, Shunsuke; Suzuki, Kazuko

    2015-04-01

    -10 km) are interpreted to be fragments of Cretaceous subduction/arc complexes or deformation interfaces branched from the HMT. The refraction/wide-angle reflection analysis revealed a series of eastward dipping interfaces at depths of 15-30 km east of the HMT, some of which show a very large Vp contrast exceeding 0.5-1.0 km/s. The subducted NE Japan arc meets the Kuril arc 20-40 km east of the HMT at a depth of 20-30 km. The above mentioned high Vp contrasts may result from the mixture of the upper crustal (low Vp) materials of the NE Japan arc and lower crustal (high Vp) materials of the Kuril arc. Seismic reflection image in the southern HCZ reprocessed by almost the same techniques confirms a clear crustal delamination, where the upper 23-km crust is thrust up along the HMT while the lower part of the crust descends down to the subducted PAC plate. At the moment, the results in the northern HCZ do not provide positive evidence on shallow crustal delamination as found in the case of the southern HCZ, suggesting regional difference in collision style along the HMT.

  15. [Electron transfer, ionization, and excitation in atomic collisions]. Final technical report, June 15, 1986--June 14, 1998

    SciTech Connect

    1998-12-31

    The research on theoretical atomic collisions that was funded at The Pennsylvania State University`s Wilkes-Barre Campus by DOE from 1986 to 1998 was carried out by Winger from 1986 to 1989 and by Winter and Alston from 1989 to 1998. The fundamental processes of electron transfer, ionization, and excitation in ion-ion, ion-atom, and, more recently, ion-molecule collisions were addressed. These collision processes were treated in the context of simple one-electron, quasi-one-electron, or two-electron systems in order to provide unambiguous results and reveal more clearly the collisional mechanisms. Winter`s work generally focused on the intermediate projectile-energy range corresponding to proton energies from about ten to a few hundred keV. In this velocity-matching energy range, the electron-transfer cross section reaches a peak, and many states, including electron-transfer and ionization states, contribute to the overall electron-cloud distribution and transition probabilities; a large number of states are coupled, and therefore perturbative approaches are generally inappropriate. These coupled-state calculations were sometimes also extended to higher energies to join with perturbative results. Alston concentrated on intermediate-energy asymmetric collision systems, for which coupling with the projectile is weaker, but many target states are included, and on high energies (MeV energies). Thus, while perturbation theory for electron transfer is valid, it is not adequate to first order. The studies by Winter and Alston described were often done in parallel. Alston also developed formal perturbative approaches not tied to any particular system. Materials studied included He{sup +}, Li{sup 2+}, Be{sup 3+}, B{sup 4+}, C{sup 5+}, and the H{sup +} + Na system.

  16. Puck collisions

    NASA Astrophysics Data System (ADS)

    Hauge, E. H.

    2012-09-01

    Collisions between two ice hockey pucks sliding on frictionless ice are studied, with both inelasticity and frictional contact between the colliding surfaces of the two pucks taken into account. The latter couples translational and rotational motion. The full solution depends on the sign and magnitude of the initial mismatch between the surface velocities at the point of contact. The initial state defines two physically distinct regimes for the friction coefficient. To illustrate the complexities, we discuss at length the typical situation (well known from curling) when puck number 1 is initially at rest, and is hit by puck number 2 with an arbitrary impact parameter, velocity and angular velocity. We find that the total outgoing angle between the pucks exceeds \\frac{1}{2}\\pi if and only if the collision leads to a net increase in the translational part of the kinetic energy. The conditions for this to happen are scrutinized, and the results are presented both analytically and numerically by a set of representative curves. This paper is written with an ambitious undergraduate, and her teacher, in mind.

  17. Finite strain calculations of continental deformation. I - Method and general results for convergent zones. II - Comparison with the India-Asia collision zone

    NASA Technical Reports Server (NTRS)

    Houseman, G.; England, P.

    1986-01-01

    The present investigation has the objective to perform numerical experiments on a rheologically simple continuum model for the continental lithosphere. It is attempted to obtain a better understanding of the dynamics of continental deformation. Calculations are presented of crustal thickness distributions, stress, strain, strain rate fields, latitudinal displacements, and finite rotations, taking into account as basis a model for continental collision which treats the litoshphere as a thin viscous layer subject to indenting boundary conditions. The results of this paper support the conclusions of England and McKenzie (1982) regarding the role of gravity in governing the deformation of a thin viscous layer subject to indenting boundary conditions. The results of the experiments are compared with observations of topography, stress and strain rate fields, and palaeomagnetic latitudinal displacements in Asia.

  18. Photon-photon collisions

    SciTech Connect

    Burke, D.L.

    1982-10-01

    Studies of photon-photon collisions are reviewed with particular emphasis on new results reported to this conference. These include results on light meson spectroscopy and deep inelastic e..gamma.. scattering. Considerable work has now been accumulated on resonance production by ..gamma gamma.. collisions. Preliminary high statistics studies of the photon structure function F/sub 2//sup ..gamma../(x,Q/sup 2/) are given and comments are made on the problems that remain to be solved.

  19. CARS spectroscopy of the NaH2 collision complex: the nature of the Na(32 P)H2 exciplex — ab initio calculations and experimental results

    NASA Astrophysics Data System (ADS)

    de Vivie-Riedle, R.; Hering, P.; Kompa, K. L.

    1990-12-01

    CARS (Coherent Anti-Stokes Raman Scattering) has been used to analyze the rovibronic state distribution of H2 after collision with Na(32 P). New lines, which do not correspond to H2 lines are observed in the CARS spectrum. The experiments point to the formation of a complex of Na(32 P)H2 in A 2 B 2 symmetry. Ab initio calculations of the A 2 B 2 potential were performed. On this surface the vibrational spectra of the exciplex are evaluated. The observed lines can be attributed to vibrational transitions in the complex, in which combinational modes are involved. The connection of experimental and theoretical results indicates that a collisionally stabilized exciplex molecule is formed during the quenching process.

  20. Electron removal from H0(n) in fast collisions with multiply charged ions

    NASA Astrophysics Data System (ADS)

    Kim, H. J.; Meyer, F. W.

    1982-09-01

    The cross sections for electron removal from highly excited (n=9-24) hydrogen atoms in fast collisions with multiply charged (q=1-5) N, O, and Ar ions were investigated in an ion-atom crossed-beams experiment. The ion-atom collisions occurred inside a deflector where a moderate electrostatic field of up to 1.8 kV/cm was applied. The range of collision velocity (vc) investigated is vc=1.0v1-2.0v1, where v1=2.2×108 cm/s is the Bohr velocity. The electron-removal cross section was found to be independent of ion species for a given q and vc, to increase as q2 for a given vc, and to decrease as v-2c for a given q. These q and vc dependences of the experimental cross section are in accord with classical Coulomb ionization theories. The experimental n dependence of the cross section differs significantly from the theoretically predicted dependence, but the difference can be accounted for if we assume the presence of the external electric field in the collision volume reduces the ionization energy.

  1. Asteroidal collision probabilities

    NASA Astrophysics Data System (ADS)

    Bottke, W. F.; Greenberg, R.

    1993-05-01

    Several past calculations of collision probabilities between pairs of bodies on independent orbits have yielded inconsistent results. We review the methodologies and identify their various problems. Greenberg's (1982) collision probability formalism (now with a corrected symmetry assumption) is equivalent to Wetherill's (1967) approach, except that it includes a way to avoid singularities near apsides. That method shows that the procedure by Namiki and Binzel (1991) was accurate for those cases where singularities did not arise.

  2. Infrared absorption by molecular gases as a probe of nanoporous silica xerogel and molecule-surface collisions: Low-pressure results

    NASA Astrophysics Data System (ADS)

    Vander Auwera, J.; Ngo, N. H.; El Hamzaoui, H.; Capoen, B.; Bouazaoui, M.; Ausset, P.; Boulet, C.; Hartmann, J.-M.

    2013-10-01

    Transmission spectra of gases confined (but not adsorbed) within the pores of a 1.4-cm-thick silica xerogel sample have been recorded between 2.5 and 5 μm using a high-resolution Fourier transform spectrometer. This was done for pure CO, CO2, N2O, H2O, and CH4 at room temperature and pressures of a few hectopascals. Least-squares fits of measured absorption lines provide the optical-path lengths within the confined (LC) and free (LF) gas inside the absorption cell and the half width at half maximum ΓC of the lines of the confined gases. The values of LC and LF retrieved using numerous transitions of all studied species are very consistent. Furthermore, LC is in satisfactory agreement with values obtained from independent measurements, thus showing that reliable information on the open porosity volume can be retrieved from an optical experiment. The values of ΓC, here resulting from collisions of the molecules with the inner surfaces of the xerogel pores, are practically independent of the line for each gas and inversely proportional to the square root of the probed-molecule molar mass. This is a strong indication that, for the studied transitions, a single collision of a molecule with a pore surface is sufficient to change its rotational state. A previously proposed simple model, used for the prediction of the line shape, leads to satisfactory agreement with the observations. It also enables a determination of the average pore size, bringing information complementary to that obtained from nitrogen adsorption porosimetry.

  3. Auto Body and Collision Damage Repairer (Branch 1). Apprenticeship Training Standards = Reparateur de carrossiers et de dommages resultant d'une collision (categorie 1). Normes de formation en apprentissage.

    ERIC Educational Resources Information Center

    Ontario Ministry of Skills Development, Toronto.

    This manual presents training standards for auto body and collision damage repairers (branch 1) and is intended to be used by apprentice/trainees, instructors, and companies in Ontario, Canada as a blueprint for training or as a prerequisite for accreditation/certification. The training standards identify skills required for this occupation and…

  4. Collision Dynamics of Decimeter Bodies

    NASA Astrophysics Data System (ADS)

    Deckers, Johannes; Teiser, J.

    2013-10-01

    The collision dynamics of decimeter bodies are important for the early phase of planet formation. Planets form by accretion of km-sized objects, the so called planetesimals. These planetesimals evolve from small grains, but their formation process is not yet understood entirely. Two groups of models try to explain the formation process. Decimeter bodies and their collision behavior play a vital role in both groups. The threshold between bouncing and fragmentation is especially interesting for coagulation models, as decimeter bodies are the direct precursors to meter sized bodies. But the collision dynamics are also relevant for the models, which describe planetesimal formation by gravitational collapse in dense regions of the protoplanetary disk. We will present preliminary results of our collision experiments. Previous experiments on mutual collisions of decimeter dust agglomerates showed that the threshold between bouncing and fragmentation lies at a collision velocity of 16.2 cm/s, which corresponds to a specific kinetic energy of 5 mJ/kg. We expand these experiments to investigate the conditions for “catastrophic disruption” of decimeter dust bodies. Here, “catastrophic disruption” means that the largest fragment of a collision partner has only half the mass of the original body. Furthermore, we extend the parameter range to ice aggregates. We will present first experimental results of collisions of ice aggregates in the decimeter range. In these first experiments we will analyze the threshold conditions for solid ice. We will investigate the collision dynamics for both central and non-central collisions.

  5. Launch Collision Probability

    NASA Technical Reports Server (NTRS)

    Bollenbacher, Gary; Guptill, James D.

    1999-01-01

    This report analyzes the probability of a launch vehicle colliding with one of the nearly 10,000 tracked objects orbiting the Earth, given that an object on a near-collision course with the launch vehicle has been identified. Knowledge of the probability of collision throughout the launch window can be used to avoid launching at times when the probability of collision is unacceptably high. The analysis in this report assumes that the positions of the orbiting objects and the launch vehicle can be predicted as a function of time and therefore that any tracked object which comes close to the launch vehicle can be identified. The analysis further assumes that the position uncertainty of the launch vehicle and the approaching space object can be described with position covariance matrices. With these and some additional simplifying assumptions, a closed-form solution is developed using two approaches. The solution shows that the probability of collision is a function of position uncertainties, the size of the two potentially colliding objects, and the nominal separation distance at the point of closest approach. ne impact of the simplifying assumptions on the accuracy of the final result is assessed and the application of the results to the Cassini mission, launched in October 1997, is described. Other factors that affect the probability of collision are also discussed. Finally, the report offers alternative approaches that can be used to evaluate the probability of collision.

  6. Crustal structure and seismicity associated with seamount subduction: A synthesis of results from the Tonga-Kermadec Trench - Louisville Ridge collision zone

    NASA Astrophysics Data System (ADS)

    Bassett, D.; Watts, A. B.; Paulatto, M.; Stratford, W. R.; Peirce, C.; Grevemeyer, I.

    2013-12-01

    The Tonga-Kermadec plate boundary is the most linear, fastest converging and most seismically active subduction zone on Earth. The margin is intersected at ~26° S by the Louisville Ridge seamount chain. Crustal structure of both the overthrusting Indo-Australian and subducting Pacific plate are sufficiently uniform north and south of the contemporary collision zone to make this an ideal location to study the mechanics and seismological consequences of seamount subduction. We present here a synthesis and interpretation of structural observations from the Louisville collision zone made during three marine geophysical surveys onboard R/V Sonne in 2004, 2007-2008 and 2011. The Louisville collision zone is characterized by a 3000 m reduction in trench depth and a 15° anticlockwise rotation of the trench axis. Swath bathymetry data reveal a pronounced forearc high (~ 2000 m relative to adjacent regions), which is correlated with a free-air gravity and magnetic anomaly high (50 mGal and 200 nT peaks respectively). Morphological characteristics are accompanied by a 40 % reduction in seismicity compared to regions immediately to the north and south. Forward modeling of active source seismic travel-times constrain the subducting Pacific plate to ~30 km depth and suggests that it is ~6 km thick and has Vp 6.2-6.8 km/sec. The overthrusting Indo-Australian plate has Vp 4.5-6.8 km/sec and a Moho depth of 15 km. The mantle wedge has Vp ~8.0 km/sec. Beneath the forearc high, seismic wave-speeds within the upper-plate are 0.3-0.5 km/sec slower than regions to the north and south and a up to 3 km thick volume of anomalously low Vp (<4.5 km/sec at > 10 km depth) is inferred to overlie the subduction interface. This latter observation is interpreted as subducting and underplated volcaniclastic sediments, which reach up to 1-2 km in thickness within the flanking flexural moats of the Louisville Ridge. The projected width of the ridge and flanking moats are well correlated with the

  7. Combined results of searches for the standard model Higgs boson in pp collisions at sqrt(s) = 7 TeV

    SciTech Connect

    Chatrchyan, Serguei; et al.

    2012-03-01

    Combined results are reported from searches for the standard model Higgs boson in proton-proton collisions at sqrt(s)=7 TeV in five Higgs boson decay modes: gamma pair, b-quark pair, tau lepton pair, W pair, and Z pair. The explored Higgs boson mass range is 110-600 GeV. The analysed data correspond to an integrated luminosity of 4.6-4.8 inverse femtobarns. The expected excluded mass range in the absence of the standard model Higgs boson is 118-543 GeV at 95% CL. The observed results exclude the standard model Higgs boson in the mass range 127-600 GeV at 95% CL, and in the mass range 129-525 GeV at 99% CL. An excess of events above the expected standard model background is observed at the low end of the explored mass range making the observed limits weaker than expected in the absence of a signal. The largest excess, with a local significance of 3.1 sigma, is observed for a Higgs boson mass hypothesis of 124 GeV. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-600 (110-145) GeV is estimated to be 1.5 sigma (2.1 sigma). More data are required to ascertain the origin of this excess.

  8. [The specific features of a lethal injury to the driver and the passenger of a scooter resulting from the collision with a car moving in the same direction].

    PubMed

    Fetisov, V A; Smirenin, S A; Khabova, Z S

    2014-01-01

    Forensic medical diagnostics of the injuries inflicted to the drivers and the passengers of bicycles (scooters, mopeds, quadrocycles, etc.) remains a serious challenge for the specialists involved in forensic medical and combined medico-autotechnical expertises. The present article is an overview of materials pertinent to the analysis of this form of traffic injuries. The approach to the analysis is exemplified by the case of repeated panel expertise with the purpose of elucidation of the mechanisms and the sequence of events leading to a combined blunt injury in the driver and the passenger of a scooter resulting from the collision with a car moving at a high speed in the same direction. Both victims presented with a whiplash injury to the brain stem region responsible for their immediate death at the scene of the accident. The results of the expertise allowed to differentiate between the driver and the passenger in terms of the extent of the injury. The authors emphasize the necessity of and good prospects for further traffic injury research bearing in mind a great variety of the aforementioned means of transportation.

  9. Stress-related psychological symptoms contribute to axial pain persistence after motor vehicle collision: path analysis results from a prospective longitudinal study.

    PubMed

    Feinberg, Rose K; Hu, JunMei; Weaver, Mark A; Fillingim, Roger B; Swor, Robert A; Peak, David A; Jones, Jeffrey S; Rathlev, Niels K; Lee, David C; Domeier, Robert M; Hendry, Phyllis L; Liberzon, Israel; McLean, Samuel A

    2017-04-01

    Posttraumatic stress disorder (PTSD) symptoms and pain after traumatic events such as motor vehicle collision (MVC) have been proposed to be mutually promoting. We performed a prospective multicenter study that enrolled 948 individuals who presented to the emergency department within 24 hours of MVC and were discharged home after evaluation. Follow-up evaluations were completed 6 weeks, 6 months, and 1 year after MVC. Path analysis results supported the hypothesis that axial pain after MVC consistently promotes the maintenance of hyperarousal and intrusive symptoms, from the early weeks after injury through 1 year. In addition, path analysis results supported the hypothesis that one or more PTSD symptom clusters had an influence on axial pain outcomes throughout the year after MVC, with hyperarousal symptoms most influencing axial pain persistence in the initial months after MVC. The influence of hyperarousal symptoms on pain persistence was only present among individuals with genetic vulnerability to stress-induced pain, suggesting specific mechanisms by which hyperarousal symptoms may lead to hyperalgesia and allodynia. Further studies are needed to better understand the specific mechanisms by which pain and PTSD symptoms enhance one another after trauma, and how such mechanisms vary among specific patient subgroups, to better inform the development of secondary preventive interventions.

  10. Preliminary result of teleseismic double-difference relocation of earthquakes in the Molucca collision zone with a 3D velocity model

    SciTech Connect

    Shiddiqi, Hasbi Ash E-mail: h.a.shiddiqi@gmail.com; Widiyantoro, Sri; Nugraha, Andri Dian; Ramdhan, Mohamad; Wandono,; Sutiyono,; Handayani, Titi; Nugroho, Hendro

    2015-04-24

    We have relocated hypocenters of earthquakes occurring in the Molucca collision zone and surrounding region taken from the BMKG catalog using teleseismic double-difference relocation algorithm (teletomoDD). We used P-wave arrival times of local, regional, and teleseismic events recorded at 304 recording stations. Over 7,000 earthquakes were recorded by the BMKG seismographicnetworkin the study region from April, 2009 toJune, 2014. We used a 3D regional-global nested velocity modelresulting fromprevious global tomographystudy. In this study, the3D seismic velocity model was appliedto theIndonesian region, whilethe1D seismicvelocity model (ak135)wasused for regions outside of Indonesia. Our relocation results show a better improvement in travel-time RMS residuals comparedto those of the BMKG catalog.Ourresultsalso show that relocation shifts were dominated intheeast-west direction, whichmaybeinfluenced by theexistingvelocity anomaly related to the reversed V-shaped slabbeneaththestudy region. Our eventrelocation results refine the geometry of slabs beneath the Halmahera and Sangihe arcs.

  11. Preliminary result of teleseismic double-difference relocation of earthquakes in the Molucca collision zone with a 3D velocity model

    NASA Astrophysics Data System (ADS)

    Shiddiqi, Hasbi Ash; Widiyantoro, Sri; Nugraha, Andri Dian; Ramdhan, Mohamad; Wandono, Sutiyono, Handayani, Titi; Nugroho, Hendro

    2015-04-01

    We have relocated hypocenters of earthquakes occurring in the Molucca collision zone and surrounding region taken from the BMKG catalog using teleseismic double-difference relocation algorithm (teletomoDD). We used P-wave arrival times of local, regional, and teleseismic events recorded at 304 recording stations. Over 7,000 earthquakes were recorded by the BMKG seismographicnetworkin the study region from April, 2009 toJune, 2014. We used a 3D regional-global nested velocity modelresulting fromprevious global tomographystudy. In this study, the3D seismic velocity model was appliedto theIndonesian region, whilethe1D seismicvelocity model (ak135)wasused for regions outside of Indonesia. Our relocation results show a better improvement in travel-time RMS residuals comparedto those of the BMKG catalog.Ourresultsalso show that relocation shifts were dominated intheeast-west direction, whichmaybeinfluenced by theexistingvelocity anomaly related to the reversed V-shaped slabbeneaththestudy region. Our eventrelocation results refine the geometry of slabs beneath the Halmahera and Sangihe arcs.

  12. Photonic, Electronic and Atomic Collisions

    NASA Astrophysics Data System (ADS)

    Fainstein, Pablo D.; Lima, Marco Aurelio P.; Miraglia, Jorge E.; Montenegro, Eduardo C.; Rivarola, Roberto D.

    2006-11-01

    -coincidence technique / T. Kaneyasu, T. Azuma and K. Okuno. Recent developments in proton-transfer-reaction mass spectrometry / A. Wisthaler ... [et al.]. Interferences in electron emission from H[symbol] induced by fast ions / N. Stolterfoht. Atomic realization of the young single electron interference process in individual autoionization collisions / R. O. Barrachina and M. Šitnik. Multiple ionization processes related to irradiation of biological tissue / M. E. Galassi ... [et al.]. Atom-diatom collisions at cold and ultra-cold temperatures / F. D. Colavecchia, G. A. Parker and R. T. Pack. Interactions of ions with hydrogen atoms / A. Luca, G. Borodi and D. Gerlich. Analysis of all structures in the elastic and charge transfer cross sections for proton-hydrogen collisions in the range of 10[symbol]-10øeV / P. S. Krstić ... [et al.]. Ab-initio ion-atom collision calculations for many-electron systems / J. Anton and B. Fricke. Fully differential studies on single ionization of helium by slow proton impact / A. Hasan ... [et al.]. Dipole polarization effects on highly-charged-ion-atom electron capture / C. C. Havener ... [et al.]. Proton-, antiproton-, and photon-he collisions in the context of ultra fast processes / T. Morishita ... [et al.]. Impact parameter dependent charge exchange studies with channeled heavy ions / D. Dauvergne ... [et al.]. Crystal assisted atomic physics experiments using heavy ions / K. Komaki -- Collisions involving clusters and surfaces. Structure and dynamics of Van der Waal complexes: from triatomic to medium size clusters / G. Delgado Barrio ... [et al.]. Evaporation, fission and multifragmentation processes of multicharged C[symbol] ions versus excitation energies / S. Martin ... [et al.]. Fragmentation of collisionally excited fullerenes / M. Alcami, S. Diaz-Tendero and F. Martín. Lifetimes of C[symbol] and C[symbol] dianions in a storage ring / S. Tomita ... [et al.]. Clusters and clusters of clusters in collisions / B. Manil ... [et al

  13. Legal update. Definition of accident--accidental death and dismemberment--alcohol-related automobile collision--foreseeability of death as result of driving while intoxicated.

    PubMed

    2011-01-01

    LaAsmar v. Phelps Dodge Corp. Life, Accidental Death & Dismemberment & Dependent Life Ins. Plan, 605 F3d 789, 2010 WL 1794437(10th Cir. 2010). A death caused by an alcohol-related automobile collision qualifies as an "accident" that would require payment of accidental death and dismemberment plan benefits.

  14. Geochemical Interpretation of Collision Volcanism

    NASA Astrophysics Data System (ADS)

    Pearce, Julian

    2014-05-01

    Collision volcanism can be defined as volcanism that takes place during an orogeny from the moment that continental subduction starts to the end of orogenic collapse. Its importance in the Geological Record is greatly underestimated as collision volcanics are easily misinterpreted as being of volcanic arc, extensional or mantle plume origin. There are many types of collision volcanic province: continent-island arc collision (e.g. Banda arc); continent-active margin collision (e.g. Tibet, Turkey-Iran); continent-rear-arc collision (e.g. Bolivia); continent-continent collision (e.g. Tuscany); and island arc-island arc collision (e.g. Taiwan). Superimposed on this variability is the fact that every orogeny is different in detail. Nonetheless, there is a general theme of cyclicity on different time scales. This starts with syn-collision volcanism resulting from the subduction of an ocean-continent transition and continental lithosphere, and continues through post-collision volcanism. The latter can be subdivided into orogenic volcanism, which is related to thickened crust, and post-orogenic, which is related to orogenic collapse. Typically, but not always, collision volcanism is preceded by normal arc volcanism and followed by normal intraplate volcanism. Identification and interpretation of collision volcanism in the Geologic Record is greatly facilitated if a dated stratigraphic sequence is present so that the petrogenic evolution can be traced. In any case, the basis of fingerprinting collision terranes is to use geochemical proxies for mantle and subduction fluxes, slab temperatures, and depths and degrees of melting. For example, syn-collision volcanism is characterized by a high subduction flux relative to mantle flux because of the high input flux of fusible sediment and crust coupled with limited mantle flow, and because of high slab temperatures resulting from the decrease in subduction rate. The resulting geochemical patterns are similar regardless of

  15. Atomic cluster collisions

    NASA Astrophysics Data System (ADS)

    Korol, Andrey V.; Solov'yov, Andrey

    2013-01-01

    Atomic cluster collisions are a field of rapidly emerging research interest by both experimentalists and theorists. The international symposium on atomic cluster collisions (ISSAC) is the premier forum to present cutting-edge research in this field. It was established in 2003 and the most recent conference was held in Berlin, Germany in July of 2011. This Topical Issue presents original research results from some of the participants, who attended this conference. This issues specifically focuses on two research areas, namely Clusters and Fullerenes in External Fields and Nanoscale Insights in Radiation Biodamage.

  16. Photon-photon collisions

    SciTech Connect

    Brodsky, S.J.

    1988-07-01

    Highlights of the VIIIth International Workshop on Photon-Photon Collisions are reviewed. New experimental and theoretical results were reported in virtually every area of ..gamma gamma.. physics, particularly in exotic resonance production and tests of quantum chromodynamics where asymptotic freedom and factorization theorems provide predictions for both inclusive and exclusive ..gamma gamma.. reactions at high momentum transfer. 73 refs., 12 figs.

  17. Incidence and pattern of traumatic spinal fractures and associated spinal cord injury resulting from motor vehicle collisions in China over 11 years: An observational study.

    PubMed

    Wang, Hongwei; Liu, Xinwei; Zhao, Yiwen; Ou, Lan; Zhou, Yue; Li, Changqing; Liu, Jun; Chen, Yu; Yu, Hailong; Wang, Qi; Han, Jianda; Xiang, Liangbi

    2016-10-01

    To investigate the incidence and pattern of traumatic spinal fractures (TSFs) and associated spinal cord injury (SCI) resulting from motor vehicle collisions (MVCs).This was a cross-sectional study. We retrospectively reviewed 698 patients with TSFs resulting from MVCs admitted to our university-affiliated hospitals from 2001 to 2011. The incidence and pattern were summarized with respect to different age groups, fracture levels, and the role of patients.There were 464 males (66.5%) and 234 females (33.5%) aged 40.5 ± 13.8 years old. The most common roles of patients in MVCs were car drivers (189, 27.1%), pedestrians hurt by a car (155, 22.2%), and car passengers (145, 20.8%). The most common fracture levels were L1 (n = 198, 19.2%) and T12 (n = 116, 11.3%), followed by C2 (n = 86, 8.3%). A total of 298 (42.7%) patients suffered a spinal cord injury. The frequencies of SCIs decreased from 53.1% to 24.6% with increasing age. The patients in the 20 to 39 age group (45.3% of all patients) had the largest sex ratio (2.4) and highest frequency of complete SCIs (19.3%) and complications (3.2%). Motorcycle drivers had the youngest mean age (35.7 ± 10.2), largest sex ratio (10.4), and highest frequency of SCIs (56.0%) and complications (4.4%). Motorcycle passengers had the highest frequency of complete SCI (22.7%) and ASOIs (45.5%) and the largest mean injury severity scoring (ISS) (18.9 ± 9.6). The most common fracture levels of motorcycle drivers were C3-C7, while that of others were T11-L2.The most common role of patients who sustained TSFs were car drivers who were 20 to 39 years old. Motorcycle drivers had the highest frequency of SCIs and complications. Motorcycle passengers had the highest frequency of complete SCIs and ASOIs and the largest ISS. Therefore, we should pay more attention to MVC patients, especially car drivers and motorcycle drivers and passengers.

  18. Incidence and pattern of traumatic spinal fractures and associated spinal cord injury resulting from motor vehicle collisions in China over 11 years

    PubMed Central

    Wang, Hongwei; Liu, Xinwei; Zhao, Yiwen; Ou, Lan; Zhou, Yue; Li, Changqing; Liu, Jun; Chen, Yu; Yu, Hailong; Wang, Qi; Han, Jianda; Xiang, Liangbi

    2016-01-01

    Abstract To investigate the incidence and pattern of traumatic spinal fractures (TSFs) and associated spinal cord injury (SCI) resulting from motor vehicle collisions (MVCs). This was a cross-sectional study. We retrospectively reviewed 698 patients with TSFs resulting from MVCs admitted to our university-affiliated hospitals from 2001 to 2011. The incidence and pattern were summarized with respect to different age groups, fracture levels, and the role of patients. There were 464 males (66.5%) and 234 females (33.5%) aged 40.5 ± 13.8 years old. The most common roles of patients in MVCs were car drivers (189, 27.1%), pedestrians hurt by a car (155, 22.2%), and car passengers (145, 20.8%). The most common fracture levels were L1 (n = 198, 19.2%) and T12 (n = 116, 11.3%), followed by C2 (n = 86, 8.3%). A total of 298 (42.7%) patients suffered a spinal cord injury. The frequencies of SCIs decreased from 53.1% to 24.6% with increasing age. The patients in the 20 to 39 age group (45.3% of all patients) had the largest sex ratio (2.4) and highest frequency of complete SCIs (19.3%) and complications (3.2%). Motorcycle drivers had the youngest mean age (35.7 ± 10.2), largest sex ratio (10.4), and highest frequency of SCIs (56.0%) and complications (4.4%). Motorcycle passengers had the highest frequency of complete SCI (22.7%) and ASOIs (45.5%) and the largest mean injury severity scoring (ISS) (18.9 ± 9.6). The most common fracture levels of motorcycle drivers were C3–C7, while that of others were T11–L2. The most common role of patients who sustained TSFs were car drivers who were 20 to 39 years old. Motorcycle drivers had the highest frequency of SCIs and complications. Motorcycle passengers had the highest frequency of complete SCIs and ASOIs and the largest ISS. Therefore, we should pay more attention to MVC patients, especially car drivers and motorcycle drivers and passengers. PMID:27787384

  19. PHENIX results on centrality dependence of yields and correlations in d plus Au collisions at root s(NN)=200 GeV

    SciTech Connect

    Sakaguchi, T.

    2016-12-01

    PHENIX has measured the transverse momentum (pT) spectra and two particle angular correlations for high pT particles in d+Au collisions at psNN=200 GeV using the RHIC Year-2008 run data. The azimuthal angle correlations for two particles with a large rapidity gap exhibit a ridge-like structure. Using the pi-0s reconstructed in the EMCal, we have successfully extended the pT reach of the correlation up to 8 GeV/c. We find that the azimuthal anisotropy of hadrons found at low pT persists up to 6 GeV/c with a significant centrality and pT dependence, similar to what was observed in A+A collisions.

  20. Electron transfer, ionization, and excitation in atomic collisions. Progress report, June 15, 1992--June 14, 1995

    SciTech Connect

    Winter, T.G.; Alston, S.G.

    1995-08-01

    The research program of Winter and Alston addresses the fundamental processes of electron transfer, ionization, and excitation in ion-atom, ion-ion, and ion-molecule collisions. Attention is focussed on one- and two-electron systems and, more recently, quasi-one-electron systems whose electron-target-core interaction can be accurately modeled by one-electron potentials. The basic computational approaches can then be taken with few, if any, approximations, and the underlying collisional mechanisms can be more clearly revealed. Winter has focussed on intermediate collision energies (e.g., proton energies for p-He{sup +} collisions on the order of 100 kilo-electron volts), in which many electron states are strongly coupled during the collision and a coupled-state approach, such as a coupled-Sturmian-pseudostate approach, is appropriate. Alston has concentrated on higher collision energies (million electron-volt energies), or asymmetric collision systems, for which the coupling of the projectile is weaker with, however, many more target states being coupled together so that high-order perturbation theory is essential. Several calculations by Winter and Alston are described, as set forth in the original proposal.

  1. Collisions of Vortex Filament Pairs

    NASA Astrophysics Data System (ADS)

    Banica, Valeria; Faou, Erwan; Miot, Evelyne

    2014-12-01

    We consider the problem of collisions of vortex filaments for a model introduced by Klein et al. (J Fluid Mech 288:201-248, 1995) and Zakharov (Sov Phys Usp 31(7):672-674, 1988, Lect. Notes Phys 536:369-385, 1999) to describe the interaction of almost parallel vortex filaments in three-dimensional fluids. Since the results of Crow (AIAA J 8:2172-2179, 1970) examples of collisions are searched as perturbations of antiparallel translating pairs of filaments, with initial perturbations related to the unstable mode of the linearized problem; most results are numerical calculations. In this article, we first consider a related model for the evolution of pairs of filaments, and we display another type of initial perturbation leading to collision in finite time. Moreover, we give numerical evidence that it also leads to collision through the initial model. We finally study the self-similar solutions of the model.

  2. The case for synchrotron radiation studies of two-electron ions, atoms, and molecules at the ALS

    NASA Astrophysics Data System (ADS)

    Lubell, M. S.

    1995-05-01

    The theoretical description of two-electron systems has remained one of the most vexing problems in atomic physics since Bohr first introduced the concept of the quantized atom in 1913. Despite the diversity in approach, a degree of orthodoxy developed over the course of many years for characterizing and clasifying the discrete spectrum of two-electron states and for describing the features of the near-threshold double continuum. The last four years have seen this orthodoxy challenged both theoretically and experimentally. As a result, a strong need exists for additional experimental investigations of two-electron systems. We will first examine the long-held orthodox views and the recent challenges to them. We will then review the details and status of a new program at the Advanced Light Source (ALS) of Lawrence Berkeley Laboratory that has been developed by the NAU8 Collaboration to address this need.

  3. Collision-Induced Absorption by H2 Pairs in the Second Overtone Band at 298 and 77.5 K: Comparison between Experimental and Theoretical Results

    NASA Technical Reports Server (NTRS)

    Brodbeck, C.; Bouanich, J.-P.; van-Thanh, Nguyen; Fu, Y.; Borysow, A.

    1999-01-01

    The collision-induced spectra of hydrogen in the region of the second overtone at 0.8 microns have been recorded at temperatures of 298 and 77.5 K and for gas densities ranging from 100 to 800 amagats. The spectral profile defined by the absorption coefficient per squared density varies significantly with the density, so that the binary absorption coefficient has been determined by extrapolations to zero density of the measured profiles. Our extrapolated measurements and our recent ab initio quantum calculation are in relatively good agreement with one another. Taking into account the very weak absorption of the second overtone band, the agreement is, however, not as good as it has become (our) standard for strong bands.

  4. Determination of the 1s2{\\ell }2{{\\ell }}^{\\prime } state production ratios {{}^{4}P}^{o}/{}^{2}P, {}^{2}D/{}^{2}P and {{}^{2}P}_{+}/{{}^{2}P}_{-} from fast (1{s}^{2},1s2s\\,{}^{3}S) mixed-state He-like ion beams in collisions with H2 targets

    NASA Astrophysics Data System (ADS)

    Benis, E. P.; Zouros, T. J. M.

    2016-12-01

    New results are presented on the ratio {R}m={σ }{T2p}( {}4P)/{σ }{T2p}({}2P) concerning the production cross sections of Li-like 1s2s2p quartet and doublet P states formed in energetic ion-atom collisions by single 2p electron transfer to the metastable 1s2s {}3S component of the He-like ion beam. Spin statistics predict a value of R m = 2 independent of the collision system in disagreement with most reported measurements of {R}m≃ 1{--}9. A new experimental approach is presented for the evaluation of R m having some practical advantages over earlier approaches. It also allows for the determination of the separate contributions of ground- and metastable-state beam components to the measured spectra. Applying our technique to zero-degree Auger projectile spectra from 4.5 MeV {{{B}}}3+ (Benis et al 2002 Phys. Rev. A 65 064701) and 25.3 MeV {{{F}}}7+ (Zamkov et al 2002 Phys. Rev. A 65 062706) mixed state (1{s}2 {}1S,1s2s {}3S) He-like ion collisions with H2 targets, we report new values of {R}m=3.5+/- 0.4 for boron and {R}m=1.8+/- 0.3 for fluorine. In addition, the ratios of {}2D/{}2P and {{}2P}+/{{}2P}- populations from either the metastable and/or ground state beam component, also relevant to this analysis, are evaluated and compared to previously reported results for carbon collisions on helium (Strohschein et al 2008 Phys. Rev. A 77 022706) including a critical comparison to theory.

  5. Chronic Widespread Pain after Motor Vehicle Collision Typically Occurs via Immediate Development and Non-Recovery: Results of an Emergency Department-Based Cohort Study

    PubMed Central

    JunMei, Hu; Andrey V, Bortsov; Lauren, Ballina; Danielle C, Orrey; Robert A, Swor; David, Peak; Jeffrey, Jones; Niels, Rathlev; David C, Lee; Robert, Domeier; Phyllis, Hendry; Blair A, Parry; Samuel A, McLean

    2016-01-01

    Motor vehicle collision (MVC) can trigger chronic widespread pain (CWP) development in vulnerable individuals. Whether such CWP typically develops via the evolution of pain from regional to widespread or via the early development of widespread pain with non-recovery is currently unknown. We evaluated the trajectory of CWP development (American College of Rheumatology criteria) among 948 European-American individuals who presented to the emergency department (ED) for care in the early aftermath of MVC. Pain extent was assessed in the ED and 6 weeks, 6 months, and 1 year after MVC on 100%, 91%, 89%, and 91% of participants, respectively. Individuals who reported prior CWP at the time of ED evaluation (n = 53) were excluded. Trajectory modeling identified a two-group solution as optimal, with the Bayes Factor value (138) indicating strong model selection. Linear solution plots supported a non-recovery model. While the number of body regions with pain in the non-CWP group steadily declined, the number of body regions with pain in the CWP trajectory group (192/895, 22%) remained relatively constant over time. These data support the hypothesis that individuals who develop CWP after MVC develop widespread pain in the early aftermath of MVC which does not remit. PMID:26808013

  6. Results.

    ERIC Educational Resources Information Center

    Zemsky, Robert; Shaman, Susan; Shapiro, Daniel B.

    2001-01-01

    Describes the Collegiate Results Instrument (CRI), which measures a range of collegiate outcomes for alumni 6 years after graduation. The CRI was designed to target alumni from institutions across market segments and assess their values, abilities, work skills, occupations, and pursuit of lifelong learning. (EV)

  7. Collision Repair Campaign

    EPA Pesticide Factsheets

    The Collision Repair Campaign targets meaningful risk reduction in the Collision Repair source category to reduce air toxic emissions in their communities. The Campaign also helps shops to work towards early compliance with the Auto Body Rule.

  8. Radiative double electron capture in collisions of fully-stripped fluorine ions with thin carbon foils

    NASA Astrophysics Data System (ADS)

    Elkafrawy, Tamer Mohammad Samy

    Radiative double electron capture (RDEC) is a one-step process in ion-atom collisions occurring when two target electrons are captured to a bound state of the projectile simultaneously with the emission of a single photon. The emitted photon has approximately double the energy of the photon emitted due to radiative electron capture (REC), which occurs when a target electron is captured to a projectile bound state with simultaneous emission of a photon. REC and RDEC can be treated as time-reversed photoionization (PI) and double photoionization (DPI), respectively, if loosely-bound target electrons are captured. This concept can be formulated with the principle of detailed balance, in which the processes of our interest can be described in terms of their time-reversed ones. Fully-stripped ions were used as projectiles in the performed RDEC experiments, providing a recipient system free of electron-related Coulomb fields. This allows the target electrons to be transferred without interaction with any of the projectile electrons, enabling accurate investigation of the electron-electron interaction in the vicinity of electromagnetic field. In this dissertation, RDEC was investigated during the collision of fully-stripped fluorine ions with a thin carbon foil and the results are compared with the recent experimental and theoretical studies. In the current work, x rays associated with projectile charge-changing by single and double electron capture and no charge change by F9+ ions were observed and compared with recent work for O8+ ions and with theory. Both the F 9+ and O8+ ions had energies in the ˜MeV/u range. REC, in turn, was investigated as a means to compare with the theoretical predictions of the RDEC/REC cross section ratio. The most significant background processes including various mechanisms of x-ray emission that may interfere with the energy region of interest are addressed in detail. This enables isolation of the contributions of REC and RDEC from the

  9. Maxillofacial injuries in moose-motor vehicle collisions versus other high-speed motor vehicle collisions

    PubMed Central

    Kim, Sharon; Harrop, A Robertson

    2005-01-01

    BACKGROUND: Anecdotal experience has suggested that there is a higher frequency of maxillofacial injuries among motor vehicle collisions involving moose. OBJECTIVES: A retrospective cohort study design was used to investigate the incidence of various injuries resulting from moose-motor vehicle collisions versus other high-speed motor vehicle collisions. METHODS: A chart review was conducted among patients presenting to a Canadian regional trauma centre during the five-year period from 1996 to 2000. RESULTS: Fifty-seven moose-motor vehicle collisions were identified; 121 high-speed collisions were randomly selected as a control group. Demographic, collision and injury data were collected from these charts and statistically analyzed. The general demographic features of the two groups were similar. Moose collisions were typically frontal impact resulting in windshield damage. The overall injury severity was similar in both groups. Likewise, the frequency of intracranial, spinal, thoracic and extremity injuries was similar for both groups. The group involved in collisions with moose, however, was 1.8 times more likely then controls to sustain a maxillofacial injury (P=0.004) and four times more likely to sustain a maxillofacial fracture (P=0.006). CONCLUSIONS: Occupants of motor vehicles colliding with moose are more likely to sustain maxillofacial injuries than those involved in other types of motor vehicle collisions. It is speculated that this distribution of injuries relates to the mechanism of collision with these large mammals with a high centre of gravity. PMID:24227930

  10. A problem of collision avoidance

    NASA Technical Reports Server (NTRS)

    Vincent, T. L.; Cliff, E. M.; Grantham, W. J.; Peng, W. Y.

    1972-01-01

    Collision avoidance between two vehicles of constant speed with limited turning radii, moving in a horizontal plane is investigated. Collision avoidance is viewed as a game by assuming that the operator of one vehicle has perfect knowledge of the state of the other, whereas the operator of the second vehicle is unaware of any impending danger. The situation envisioned is that of an encounter between a commercial aircraft and a small light aircraft. This worse case situation is examined to determine the conditions under which the commercial aircraft should execute a collision avoidance maneuver. Three different zones of vulnerability are defined and the boundaries, or barriers, between these zones are determined for a typical aircraft encounter. A discussion of the methods used to obtain the results as well as some of the salient features associated with the resultant barriers is included.

  11. Restricted Collision List method for faster Direct Simulation Monte-Carlo (DSMC) collisions

    SciTech Connect

    Macrossan, Michael N.

    2016-08-15

    The ‘Restricted Collision List’ (RCL) method for speeding up the calculation of DSMC Variable Soft Sphere collisions, with Borgnakke–Larsen (BL) energy exchange, is presented. The method cuts down considerably on the number of random collision parameters which must be calculated (deflection and azimuthal angles, and the BL energy exchange factors). A relatively short list of these parameters is generated and the parameters required in any cell are selected from this list. The list is regenerated at intervals approximately equal to the smallest mean collision time in the flow, and the chance of any particle re-using the same collision parameters in two successive collisions is negligible. The results using this method are indistinguishable from those obtained with standard DSMC. The CPU time saving depends on how much of a DSMC calculation is devoted to collisions and how much is devoted to other tasks, such as moving particles and calculating particle interactions with flow boundaries. For 1-dimensional calculations of flow in a tube, the new method saves 20% of the CPU time per collision for VSS scattering with no energy exchange. With RCL applied to rotational energy exchange, the CPU saving can be greater; for small values of the rotational collision number, for which most collisions involve some rotational energy exchange, the CPU may be reduced by 50% or more.

  12. Restricted Collision List method for faster Direct Simulation Monte-Carlo (DSMC) collisions

    NASA Astrophysics Data System (ADS)

    Macrossan, Michael N.

    2016-08-01

    The 'Restricted Collision List' (RCL) method for speeding up the calculation of DSMC Variable Soft Sphere collisions, with Borgnakke-Larsen (BL) energy exchange, is presented. The method cuts down considerably on the number of random collision parameters which must be calculated (deflection and azimuthal angles, and the BL energy exchange factors). A relatively short list of these parameters is generated and the parameters required in any cell are selected from this list. The list is regenerated at intervals approximately equal to the smallest mean collision time in the flow, and the chance of any particle re-using the same collision parameters in two successive collisions is negligible. The results using this method are indistinguishable from those obtained with standard DSMC. The CPU time saving depends on how much of a DSMC calculation is devoted to collisions and how much is devoted to other tasks, such as moving particles and calculating particle interactions with flow boundaries. For 1-dimensional calculations of flow in a tube, the new method saves 20% of the CPU time per collision for VSS scattering with no energy exchange. With RCL applied to rotational energy exchange, the CPU saving can be greater; for small values of the rotational collision number, for which most collisions involve some rotational energy exchange, the CPU may be reduced by 50% or more.

  13. A framework of boundary collision data aggregation into neighbourhoods.

    PubMed

    Cui, Ge; Wang, Xin; Kwon, Dae-Won

    2015-10-01

    A large portion of the total number of motor collisions can be boundary collisions; therefore, exaggerated or underestimated numbers for boundary collisions aggregated into neighbourhoods may hamper road safety analyses and management. In this paper, we propose a systematic framework for boundary collision aggregation. First, an entropy-based histogram thresholding method is utilized to determine the boundary zone size and identify boundary collisions. Next, the collision density probability distribution is then established, based on the collisions in each neighbourhood. Last, an effective boundary collision aggregation method, called the collision density ratio (CDR), is used to aggregate boundary collisions into neighbourhoods. The proposed framework is applied to collision data in the City of Edmonton for a case study. The experimental results show that the proposed entropy-based histogram thresholding method can identify boundary collision with the high precision and recall, and the proposed CDR method is more effective than the existing methods, the half-to-half ratio method and the one-to-one ratio method, to aggregate boundary collisions into neighbourhoods.

  14. Final results of the searches for neutral Higgs bosons in e+e- collisions at /sqrt(s) up to 209 GeV

    NASA Astrophysics Data System (ADS)

    ALEPH Collaboration; Heister, A.; Schael, S.; Barate, R.; Brunelière, R.; De Bonis, I.; Decamp, D.; Goy, C.; Jezequel, S.; Lees, J.-P.; Martin, F.; Merle, E.; Minard, M.-N.; Pietrzyk, B.; Trocmé, B.; Boix, G.; Bravo, S.; Casado, M. P.; Chmeissani, M.; Crespo, J. M.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, Ll.; Graugés, E.; Lopez, J.; Martinez, M.; Merino, G.; Miquel, R.; Mir, Ll. 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.; Quyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Abbaneo, D.; Azzurri, P.; Barklow, T.; Buchmüller, O.; Cattaneo, M.; Cerutti, F.; Clerbaux, B.; 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.; Maley, P.; Mato, P.; Moutoussi, A.; Ranjard, F.; Rolandi, L.; Schlatter, D.; Sguazzoni, G.; Tejessy, W.; Teubert, F.; Valassi, A.; Videau, I.; Ward, J. J.; Badaud, F.; Dessagne, S.; Falvard, A.; Fayolle, D.; Gay, P.; Jousset, J.; Michel, B.; Monteil, S.; Pallin, D.; Pascolo, J. M.; Perret, P.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Nilsson, B. S.; Wäänänen, A.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Vayaki, A.; Zachariadou, K.; Blondel, A.; Brient, J.-C.; Machefert, F.; Rougé, A.; Swynghedauw, M.; Tanaka, R.; Videau, H.; Ciulli, V.; Focardi, E.; Parrini, G.; 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.; Spagnolo, P.; Kennedy, J.; Lynch, J. G.; Negus, P.; O'Shea, V.; Smith, D.; Thompson, A. S.; Wasserbaech, S.; Cavanaugh, R.; Dhamotharan, S.; Geweniger, C.; Hanke, P.; Hepp, V.; Kluge, E. E.; Leibenguth, G.; Putzer, A.; Stenzel, H.; Tittel, K.; Werner, S.; Wunsch, M.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Davies, G.; Dornan, P. J.; Girone, M.; Hill, R. D.; Marinelli, N.; Nowell, J.; Przysiezniak, H.; Rutherford, S. A.; Sedgbeer, J. K.; Thompson, J. C.; 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.; Lemaitre, V.; Blumenschein, U.; Hölldorfer, F.; Jakobs, K.; Kayser, F.; Kleinknecht, K.; Müller, A.-S.; Quast, G.; Renk, B.; 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.; Ragusa, F.; David, A.; Dietl, H.; Ganis, G.; Hüttmann, K.; Lütjens, G.; Mannert, C.; Männer, W.; Moser, H.-G.; Settles, R.; Wolf, G.; Boucrot, J.; Callot, O.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph.; Jacholkowska, A.; Loomis, C.; Serin, L.; Veillet, J.-J.; de Vivie de Régie, J.-B.; Yuan, C.; Bagliesi, G.; Boccali, T.; Foà, L.; Giammanco, A.; Giassi, A.; Ligabue, F.; Messineo, A.; Palla, F.; Sanguinetti, G.; Sciabà, A.; Tenchini, R.; Venturi, A.; Verdini, P. G.; Awunor, O.; Blair, G. A.; Coles, J.; Cowan, G.; Garcia-Bellido, A.; Green, M. G.; Jones, L. T.; Medcalf, T.; Misiejuk, A.; Strong, J. A.; Teixeira-Dias, P.; Clifft, R. W.; Edgecock, T. R.; Norton, P. R.; Tomalin, I. R.; Bloch-Devaux, B.; Boumediene, D.; Colas, P.; Fabbro, B.; Lancon, 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.; 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.; Ngac, A.; Prange, G.; Sieler, U.; Borean, C.; Giannini, G.; He, H.; Putz, J.; Rothberg, J.; Armstrong, S. R.; Berkelman, K.; Cranmer, K.; Ferguson, D. P. S.; Gao, Y.; González, S.; Hayes, O. J.; Hu, H.; Jin, S.; Kile, J.; McNamara, P. A.; Nielsen, J.; Pan, Y. B.; von Wimmersperg-Toeller, J. H.; Wiedenmann, W.; Wu, J.; Wu, S. L.; Wu, X.; Zobernig, G.; Dissertori, G.

    2002-02-01

    The final results of the ALEPH search for the Standart Model Higgs boson at LEP, with data collected in the year 2000 at center-of-mass energies up to 209 GeV, are presented. The changes with respect to the preceding publication are described and a complete study of systematic effects is reported. The findings of this final analysis confirm the preliminary results published in November 2000 shortly after the closing down of the LEP collider: a significant excess of events is observed, consistent with the production of a 115 GeV/c2 Standard Model Higgs boson. The final results of the searches for the neutral Higgs bosons od the MSSM are also reported, in terms of limits on mh, mA and /tanβ. Limits are also set on mh in the case of invisible decays.

  15. Cold ion-atom chemistry driven by spontaneous radiative relaxation: a case study for the formation of the YbCa+ molecular ion

    NASA Astrophysics Data System (ADS)

    Zygelman, B.; Lucic, Zelimir; Hudson, Eric R.

    2014-01-01

    Using both quantum and semi-classical methods, we calculate the rates for radiative association and charge transfer in cold collisions of Yb+ with Ca. We demonstrate the fidelity of the local optical potential method in predictions for the total radiative relaxation rates. We find a large variation in the isotope dependence of the cross sections at ultra-cold gas temperatures. However, at cold temperatures, 1 mK < T < 1 K, the effective spontaneous radiative rates for the different isotopes share a common value of about 1.5 × 10-15 cm3 s-1. It is about five orders of magnitude smaller than the chemical reaction rate measured in Rellergert et al (2011 Phys. Rev. Lett. 107 243201).

  16. Basins in ARC-continental collisions

    USGS Publications Warehouse

    Draut, Amy E.; Clift, Peter D.; Busby, Cathy; Azor, Antonio

    2012-01-01

    Arc-continent collisions occur commonly in the plate-tectonic cycle and result in rapidly formed and rapidly collapsing orogens, often spanning just 5-15 My. Growth of continental masses through arc-continent collision is widely thought to be a major process governing the structural and geochemical evolution of the continental crust over geologic time. Collisions of intra-oceanic arcs with passive continental margins (a situation in which the arc, on the upper plate, faces the continent) involve a substantially different geometry than collisions of intra-oceanic arcs with active continental margins (a situation requiring more than one convergence zone and in which the arc, on the lower plate, backs into the continent), with variable preservation potential for basins in each case. Substantial differences also occur between trench and forearc evolution in tectonically erosive versus tectonically accreting margins, both before and after collision. We examine the evolution of trenches, trench-slope basins, forearc basins, intra-arc basins, and backarc basins during arc-continent collision. The preservation potential of trench-slope basins is low; in collision they are rapidly uplifted and eroded, and at erosive margins they are progressively destroyed by subduction erosion. Post-collisional preservation of trench sediment and trench-slope basins is biased toward margins that were tectonically accreting for a substantial length of time before collision. Forearc basins in erosive margins are usually floored by strong lithosphere and may survive collision with a passive margin, sometimes continuing sedimentation throughout collision and orogeny. The low flexural rigidity of intra-arc basins makes them deep and, if preserved, potentially long records of arc and collisional tectonism. Backarc basins, in contrast, are typically subducted and their sediment either lost or preserved only as fragments in melange sequences. A substantial proportion of the sediment derived from

  17. High velocity collisions of nanoparticles

    NASA Astrophysics Data System (ADS)

    Johnson, Donald F.; Mattson, William D.

    2017-01-01

    Nanoparticles (NPs) are a unique class of material with highly functionalizable surfaces and exciting applications. With a large surface-to-volume ratio and potentially high surface tension, shocked nanoparticles might display unique materials behavior. Using density functional theory, we have simulated high-velocity NP collisions under a variety of conditions. NPs composed of diamond-C, cubic-BN, and diamond-Si were considered with particle sizes up to 3.5 nm diameter. Additional simulations involved NPs that were destabilized by incorporating internal strain. The initial spherical NP structures were carved out of bulk crystals while the NPs with internal strain were constructed as a dense core (compressive strain) encompassed by a thin shell (tensile strain). Both on-axis and off-axis collisions were simulated at 10 km/s relative velocity. The amount of internal strain was artificially increased by creating a dense inner core with bond lengths compressed up to 8%. Collision dynamics, shock propagation, and fragmentation will be analyzed, but the simulation are ongoing and results are not finalized. The effect of material properties, internal strain, and collision velocity will be discussed.

  18. Impact Collision Ion Scattering Spectroscopy Applied to the Determination of Atomic Surface Structure

    NASA Astrophysics Data System (ADS)

    Daley, Richard Stephen

    1990-08-01

    The technique of impact collision ion scattering spectroscopy (ICISS) was used to investigate the atomic structure and low energy ion scattering dynamics from various surfaces. A new formalism for calculating the three-dimensional cross section for an ion to scatter sequentially and classically from two atoms has been developed. This method can be used to assist in the interpretation of ICISS data in terms of quantitative surface-structure models. Shadowing and blocking effects for energetic ions scattering from more than one atom are shown to be special cases of rainbow scattering. Even at keV energies and above, the cross section at the critical angle for scattering must be evaluated by quantum or semi-classical means to avoid the singularity in the classically calculated cross sections. In an ICISS investigation of the Ag(110) surface, a surface flux peak analysis demonstrated that the surface was not a complete monolayer, but rather contained 10-15% random vacancies. Subsurface Li^+ scattering results confirmed the oscillatory relaxation of the first two atomic layers of the surface, with Delta_{12} = -7.5% and Delta_{23} = 4.0%. Modeling of the neutralization mechanism for the He^+ scattering gave a best fit time-dependent Auger neutralization time constant of 0.84 +/- 0.08 fs. A neutralization study of 5 keV He^+ ions scattered from Au adatoms on the Si(111)- sqrt{3} x sqrt {3}-Au surface showed the He^+ ICISS data contained false shadowing features that were actually the result of local neutralization effects. Good agreement was obtained for a radially dependent ion-atom neutralization theory with rate R = Aexp (-ar) , where A and a are 15.5 fs^{ -1} and 1.94 A^{-1} , respectively. A detailed examination of the Si(111)- sqrt{3} x sqrt{3 })-Ag surface was also made. The 5 keV Li ^+ ICISS data gave evidence for Ag island formation at single monolayer coverages of silver, while the LEED, AES and LEIS data showed that at relatively high coverages of Ag (35 ML

  19. Ball Collision Experiments

    ERIC Educational Resources Information Center

    Cross, R.

    2015-01-01

    Experiments are described on collisions between two billiard balls and between a bat and a ball. The experiments are designed to extend a student's understanding of collision events and could be used either as a classroom demonstration or for a student project.

  20. Elastic and Inelastic Collisions

    ERIC Educational Resources Information Center

    Gluck, Paul

    2010-01-01

    There have been two articles in this journal that described a pair of collision carts used to demonstrate vividly the difference between elastic and inelastic collisions. One cart had a series of washers that were mounted rigidly on a rigid wooden framework, the other had washers mounted on rubber bands stretched across a framework. The rigidly…

  1. Bubble collision with gravitation

    SciTech Connect

    Hwang, Dong-il; Lee, Bum-Hoon; Lee, Wonwoo; Yeom, Dong-han E-mail: bhl@sogang.ac.kr E-mail: innocent.yeom@gmail.com

    2012-07-01

    In this paper, we study vacuum bubble collisions with various potentials including gravitation, assuming spherical, planar, and hyperbolic symmetry. We use numerical calculations from double-null formalism. Spherical symmetry can mimic the formation of a black hole via multiple bubble collisions. Planar and especially hyperbolic symmetry describes two bubble collisions. We study both cases, when two true vacuum regions have the same field value or different field values, by varying tensions. For the latter case, we also test symmetric and asymmetric bubble collisions, and see details of causal structures. If the colliding energy is sufficient, then the vacuum can be destabilized, and it is also demonstrated. This double-null formalism can be a complementary approach in the context of bubble collisions.

  2. Collision lifetimes of polyatomic molecules at low temperatures: Benzene–benzene vs benzene–rare gas atom collisions

    SciTech Connect

    Cui, Jie; Krems, Roman V.; Li, Zhiying

    2014-10-28

    We use classical trajectory calculations to study the effects of the interaction strength and the geometry of rigid polyatomic molecules on the formation of long-lived collision complexes at low collision energies. We first compare the results of the calculations for collisions of benzene molecules with rare gas atoms He, Ne, Ar, Kr, and Xe. The comparison illustrates that the mean lifetimes of the collision complexes increase monotonically with the strength of the atom–molecule interaction. We then compare the results of the atom–benzene calculations with those for benzene–benzene collisions. The comparison illustrates that the mean lifetimes of the benzene–benzene collision complexes are significantly reduced due to non-ergodic effects prohibiting the molecules from sampling the entire configuration space. We find that the thermally averaged lifetimes of the benzene–benzene collisions are much shorter than those for Xe with benzene and similar to those for Ne with benzene.

  3. Collision lifetimes of polyatomic molecules at low temperatures: Benzene-benzene vs benzene-rare gas atom collisions

    NASA Astrophysics Data System (ADS)

    Cui, Jie; Li, Zhiying; Krems, Roman V.

    2014-10-01

    We use classical trajectory calculations to study the effects of the interaction strength and the geometry of rigid polyatomic molecules on the formation of long-lived collision complexes at low collision energies. We first compare the results of the calculations for collisions of benzene molecules with rare gas atoms He, Ne, Ar, Kr, and Xe. The comparison illustrates that the mean lifetimes of the collision complexes increase monotonically with the strength of the atom-molecule interaction. We then compare the results of the atom-benzene calculations with those for benzene-benzene collisions. The comparison illustrates that the mean lifetimes of the benzene-benzene collision complexes are significantly reduced due to non-ergodic effects prohibiting the molecules from sampling the entire configuration space. We find that the thermally averaged lifetimes of the benzene-benzene collisions are much shorter than those for Xe with benzene and similar to those for Ne with benzene.

  4. Collision lifetimes of polyatomic molecules at low temperatures: benzene-benzene vs benzene-rare gas atom collisions.

    PubMed

    Cui, Jie; Li, Zhiying; Krems, Roman V

    2014-10-28

    We use classical trajectory calculations to study the effects of the interaction strength and the geometry of rigid polyatomic molecules on the formation of long-lived collision complexes at low collision energies. We first compare the results of the calculations for collisions of benzene molecules with rare gas atoms He, Ne, Ar, Kr, and Xe. The comparison illustrates that the mean lifetimes of the collision complexes increase monotonically with the strength of the atom-molecule interaction. We then compare the results of the atom-benzene calculations with those for benzene-benzene collisions. The comparison illustrates that the mean lifetimes of the benzene-benzene collision complexes are significantly reduced due to non-ergodic effects prohibiting the molecules from sampling the entire configuration space. We find that the thermally averaged lifetimes of the benzene-benzene collisions are much shorter than those for Xe with benzene and similar to those for Ne with benzene.

  5. Holographic heavy ion collisions with baryon charge

    NASA Astrophysics Data System (ADS)

    Casalderrey-Solana, Jorge; Mateos, David; van der Schee, Wilke; Triana, Miquel

    2016-09-01

    We numerically simulate collisions of charged shockwaves in Einstein-Maxwell theory in anti-de Sitter space as a toy model of heavy ion collisions with non-zero baryon charge. The stress tensor and the baryon current become well described by charged hydrodynamics at roughly the same time. The effect of the charge density on generic observables is typically no larger than 15%. We find significant stopping of the baryon charge and compare our results with those in heavy ion collision experiments.

  6. Injuries in Near-Side Collisions

    PubMed Central

    Augenstein, J.; Perdeck, E.; Bowen, J.; Stratton, J.; Singer, M.; Horton, T.; Rao, A.; Digges, K.; Malliaris, A.; Steps, J.

    1999-01-01

    This paper examines crash characteristics and the resulting injuries to occupants whose seat position is on the side of impact in a vehicle exposed to a side collision. The databases of the 1988–96 NASS/CDS and the 1995–98 William Lehman Injury Research Center (WLIRC) are examined in this study. The subset of cases analyzed is those in which there is a vehicle-to-vehicle near-side collision, occupant compartment damage and no subsequent collision or rollover. The WLIRC data contains highly detailed occupant injury data not available in NASS.

  7. Antioscillons from bubble collisions at finite temperature

    NASA Astrophysics Data System (ADS)

    Mersini-Houghton, Laura

    2014-04-01

    We study the role of the topology of bubbles at finite temperatures plays on collisions and the existence of new field configurations. We show that in the case of false vacuum decay at finite temperature, the cylindrical symmetry of bubbles admits a new exotic field with negative energies, the antiperiodic "twisted" field. New field configurations arise generically, not only at finite temperatures but whenever a cluster of bubbles resulting from collisions form nontrivial topologies. The interaction of both configurations induces instabilites on the bubble. Collisions of bubbles occupied by the new fields can lead to the emergence of new structures, named antioscillons.

  8. Reactive collisions of atoms with diatomic molecules

    NASA Astrophysics Data System (ADS)

    Wolniewicz, L.; Hinze, Juergen; Alijah, Alexander

    1993-08-01

    The theory of the reactive collision of an atom with a diatomic molecule is formulated in 'democratic' hyperspherical coordinates. An adiabatic ansatz is used to separate the distance coordinate from the angular coordinates. The angular eigenvalue problem is solved, using the hyperspherical harmonics as basis functions, while the R-matrix propagation method is used to integrate the resulting coupled equations along the distance coordinate. As an example, reactive collision probabilities for H + H2 are computed, using the Porter-Karplus surface. The symmetry requirements, when dealing with three identical Fermions in the collision, are considered explicitly.

  9. Comparison of argon K-Xray production crossections by H{sup +} and H{sup +}{sub 2} bombardment

    SciTech Connect

    Fou, C.M.

    1994-12-31

    The Argon K X-ray production crossections by isotachic H{sup +} and H{sub 2}{sup +} bombardment were measured. The purpose was to examine how the molecular structure of the target affects the investigation of molecular effect in ion-atom collision process usually done with solid targets. Using Argon gas as target, the author had truly atomic ion atom, molecular ion-atom collisions instead of atomic ion-molecule, molecular ion-molecule collisions. Comparison of results on KCl target under the same experimental conditions will be made also.

  10. Molecular vibrational states during a collision

    NASA Technical Reports Server (NTRS)

    Recamier, Jose A.; Jauregui, Rocio

    1995-01-01

    Alternative algebraic techniques to approximate a given Hamiltonian by a harmonic oscillator are described both for time-independent and time-dependent systems. We apply them to the description of a one dimensional atom-diatom collision. From the resulting evolution operator, we evaluate vibrational transition probabilities as well as other time-dependent properties. As expected, the ground vibrational state becomes a squeezed state during the collision.

  11. Two-Dimensional Distributed Velocity Collision Avoidance

    DTIC Science & Technology

    2014-02-11

    a mechanism for congestion control. The TCP is useful for applications that need reliability and correctness such as web pages or databases. The...a curved turn, and for the protection of hardware assets via a buffer region. If the bot radius is too low, then the bots will always scrape or...both the KVO and non-KVO scenarios. Figure 12 shows the results in terms of scrapes , collisions, and runs completed with no collisions, and Figure 13

  12. COLLIDE: Collisions into Dust Experiment

    NASA Technical Reports Server (NTRS)

    Colwell, Joshua E.

    1999-01-01

    The Collisions Into Dust Experiment (COLLIDE) was completed and flew on STS-90 in April and May of 1998. After the experiment was returned to Earth, the data and experiment were analyzed. Some anomalies occurred during the flight which prevented a complete set of data from being obtained. However, the experiment did meet its criteria for scientific success and returned surprising results on the outcomes of very low energy collisions into powder. The attached publication, "Low Velocity Microgravity Impact Experiments into Simulated Regolith," describes in detail the scientific background, engineering, and scientific results of COLLIDE. Our scientific conclusions, along with a summary of the anomalies which occurred during flight, are contained in that publication. We offer it as our final report on this grant.

  13. Icy Collisions - Planet Building beyond the snowline

    NASA Astrophysics Data System (ADS)

    Gaertner, Sabrina; Hill, Catherine; Heisselmann, Daniel; Blum, Juergen; Fraser, Helen

    2015-11-01

    Collisions of small icy and dust particles beyond the “snow-line” are a key step in planet formation. Whilst the physical forces that underpin the aggregation of the smallest grains (van der Waals) and the largest planetessimals (gravity) are well understood, the processes involving mm - cm sized particles remain a mystery.In a unique set of experiments, we investigated low velocity collisions of dust and icy particles in this size range under microgravity conditions - utilizing parabolic flight (e.g. Salter 2009, Hill 2015 (a) & (b)). Experiments were performed at cryogenic temperatures (below 140 K) for icy aggregates and ambient as well as cryogenic temperatures (80 - 220 K) for dust aggregates.The kinetic analysis of the observed collisions of different aggregate types in different shapes and sizes revealed astonishing results - as the collisional properties of all investigated particles differ strongly from the usual assumptions in models of planet formation.Here, we present a summary of the results on the collisions of icy particles as well as first results on the collisions of dust aggregates. Focus will be on the coefficient of restitution, which measures the loss of translational energy in bouncing collisions and is a key parameter in models of planet formation.

  14. Mean field and collisions in hot nuclei

    SciTech Connect

    K /umlt o/hler, H.S.

    1989-06-01

    Collisions between heavy nuclei produce nuclear matter of high density and excitation. Brueckner methods are used to calculate the momentum and temperature dependent mean field for nucleons propagating through nuclear matter during these collisions. The mean field is complex and the imaginary part is related to the ''two-body'' collision, while the real part relates to ''one-body'' collisions. A potential model for the N-N interactions is avoided by calculating the Reaction matrix directly from the T-matrix (i.e., N-N phase shifts) using a version of Brueckner theory previously published by the author. Results are presented for nuclear matter at normal and twice normal density and for temperatures up to 50 MeV. 23 refs., 7 figs.

  15. Oscillating collision of the granular chain on static wall

    NASA Astrophysics Data System (ADS)

    Ma, Liang; Huang, Decai; Chen, Weizhong; Jiao, Tengfei; Sun, Min; Hu, Fenglan; Su, Jiaye

    2017-02-01

    Collision of the granular chain on static wall is investigated by discrete element method. Collision time and traveling time are proposed on the basis of the characteristics of the collision of a single grain with a wall and the propagation of interaction force wave in a granular chain to explain the collision process. Simulation results show that an oscillating collision force is generated when the force waves successively arrive at the wall. For the collision of a mono-dispersed chain, the simulation data are in good agreement with the predicted relationship between the maximum chain length of nmax and the first maximum collision force FA. Rigid wall and soft wall are defined as nmax = 1 and nmax ≥ 2, respectively. Two similar processes of oscillating collisions occur when a light or a heavy impure grain is introduced. In these processes, two maximum collision forces, namely, FA and FB, are observed, respectively. The simulation results about the influence of the mass and position of light impure grain on the collision force FB further confirm our theoretical predictions.

  16. Strategies of locomotor collision avoidance.

    PubMed

    Basili, Patrizia; Sağlam, Murat; Kruse, Thibault; Huber, Markus; Kirsch, Alexandra; Glasauer, Stefan

    2013-03-01

    Collision avoidance during locomotion can be achieved by a variety of strategies. While in some situations only a single trajectory will successfully avoid impact, in many cases several different strategies are possible. Locomotor experiments in the presence of static boundary conditions have suggested that the choice of an appropriate trajectory is based on a maximum-smoothness strategy. Here we analyzed locomotor trajectories of subjects avoiding collision with another human crossing their path orthogonally. In such a case, changing walking direction while keeping speed or keeping walking direction while changing speed would be two extremes of solving the problem. Our participants clearly favored changing their walking speed while keeping the path on a straight line between start and goal. To interpret this result, we calculated the costs of the chosen trajectories in terms of a smoothness-maximization criterion and simulated the trajectories with a computational model. Data analysis together with model simulation showed that the experimentally chosen trajectory to avoid collision with a moving human is not the optimally smooth solution. However, even though the trajectory is not globally smooth, it was still locally smooth. Modeling further confirmed that, in presence of the moving human, there is always a trajectory that would be smoother but would deviate from the straight line. We therefore conclude that the maximum smoothness strategy previously suggested for static environments no longer holds for locomotor path planning and execution in dynamically changing environments such as the one tested here.

  17. Collision prediction software for radiotherapy treatments

    SciTech Connect

    Padilla, Laura; Pearson, Erik A.; Pelizzari, Charles A.

    2015-11-15

    Purpose: This work presents a method of collision predictions for external beam radiotherapy using surface imaging. The present methodology focuses on collision prediction during treatment simulation to evaluate the clearance of a patient’s treatment position and allow for its modification if necessary. Methods: A Kinect camera (Microsoft, Redmond, WA) is used to scan the patient and immobilization devices in the treatment position at the simulator. The surface is reconstructed using the SKANECT software (Occipital, Inc., San Francisco, CA). The treatment isocenter is marked using simulated orthogonal lasers projected on the surface scan. The point cloud of this surface is then shifted to isocenter and converted from Cartesian to cylindrical coordinates. A slab models the treatment couch. A cylinder with a radius equal to the normal distance from isocenter to the collimator plate, and a height defined by the collimator diameter is used to estimate collisions. Points within the cylinder clear through a full gantry rotation with the treatment couch at 0° , while points outside of it collide. The angles of collision are reported. This methodology was experimentally verified using a mannequin positioned in an alpha cradle with both arms up. A planning CT scan of the mannequin was performed, two isocenters were marked in PINNACLE, and this information was exported to AlignRT (VisionRT, London, UK)—a surface imaging system for patient positioning. This was used to ensure accurate positioning of the mannequin in the treatment room, when available. Collision calculations were performed for the two treatment isocenters and the results compared to the collisions detected the room. The accuracy of the Kinect-Skanect surface was evaluated by comparing it to the external surface of the planning CT scan. Results: Experimental verification results showed that the predicted angles of collision matched those recorded in the room within 0.5°, in most cases (largest deviation

  18. Turbulent collision statistics of cloud droplets at low dissipation rates

    NASA Astrophysics Data System (ADS)

    Banerjee, Sandipan

    Collisions of sedimenting droplets in a turbulent flow is of great importance in cloud physics. Collision efficiency and collision enhancement over gravitational collision by air turbulence govern the growth of the cloud droplets leading to warm rain initiation and precipitation dynamics. In this thesis we present direct numerical simulation (DNS) results for collision statistics of droplets in turbulent flows of low dissipation rates (in the range of 3 cm2/s3-100 cm2/s3) relevant to strato-cumulus clouds. First, we revisit the case of gravitational collision in still fluid to validate the details of the collision detection algorithm used in our code. We compare the collision statistics with either new analytical predictions regarding the percentages of different collision types, or results from published papers. The effect of initial conditions on the collision statistics and statistical uncertainties are analyzed both analytically and through the simulation data. Second, we consider the case of weak turbulence (as in strato-cumulus clouds). In this case the particle motion is mainly driven by gravity. The standard deviation (or the uncertainty) of the average collision statistics is examined analytically in terms of time correlation function of the data. We then report new DNS results of collision statistics in a turbulent flow, showing how air turbulence increases the geometric colli- sion statistics and the collision efficiency. We find that the collision-rate enhancement due to turbulence depends nonlinearly on the flow dissipation rate. This result calls for a more careful parameterization of the collision statistics in strato-cumulus clouds. Due to the low flow dissipation rate in stratocumulus clouds, a related challenge is low droplet Stokes number. Here the Stokes number is the ratio of droplet inertial response time to the flow Kolmogorov time. A very low Stokes number implies that the numerical integration time step is now governed by the droplet

  19. Microscope collision protection apparatus

    DOEpatents

    DeNure, Charles R.

    2001-10-23

    A microscope collision protection apparatus for a remote control microscope which protects the optical and associated components from damage in the event of an uncontrolled collision with a specimen, regardless of the specimen size or shape. In a preferred embodiment, the apparatus includes a counterbalanced slide for mounting the microscope's optical components. This slide replaces the rigid mounts on conventional upright microscopes with a precision ball bearing slide. As the specimen contacts an optical component, the contacting force will move the slide and the optical components mounted thereon. This movement will protect the optical and associated components from damage as the movement causes a limit switch to be actuated, thereby stopping all motors responsible for the collision.

  20. Hydrodynamic evolution and jet energy loss in Cu + Cu collisions

    SciTech Connect

    Schenke, Bjoern; Jeon, Sangyong; Gale, Charles

    2011-04-15

    We present results from a hybrid description of Cu + Cu collisions using (3 + 1)-dimensional hydrodynamics (music) for the bulk evolution and a Monte Carlo simulation (martini) for the evolution of high-momentum partons in the hydrodynamical background. We explore the limits of this description by going to small system sizes and determine the dependence on different fractions of wounded nucleon and binary collisions scaling of the initial energy density. We find that Cu + Cu collisions are well described by the hybrid description at least up to 20% central collisions.

  1. Rapidity dependence in holographic heavy ion collisions

    DOE PAGES

    Wilke van der Schee; Schenke, Bjorn

    2015-12-11

    We present an attempt to closely mimic the initial stage of heavy ion collisions within holography, assuming a decoupling of longitudinal and transverse dynamics in the very early stage. We subsequently evolve the obtained initial state using state-of-the-art hydrodynamic simulations and compare results with experimental data. We present results for charged hadron pseudorapidity spectra and directed and elliptic flow as functions of pseudorapidity for √sNN = 200GeV Au-Au and 2.76TeV Pb-Pb collisions. As a result, the directed flow interestingly turns out to be quite sensitive to the viscosity. The results can explain qualitative features of the collisions, but the rapiditymore » spectra in our current model is narrower than the experimental data.« less

  2. Rapidity dependence in holographic heavy ion collisions

    SciTech Connect

    Wilke van der Schee; Schenke, Bjorn

    2015-12-11

    We present an attempt to closely mimic the initial stage of heavy ion collisions within holography, assuming a decoupling of longitudinal and transverse dynamics in the very early stage. We subsequently evolve the obtained initial state using state-of-the-art hydrodynamic simulations and compare results with experimental data. We present results for charged hadron pseudorapidity spectra and directed and elliptic flow as functions of pseudorapidity for √sNN = 200GeV Au-Au and 2.76TeV Pb-Pb collisions. As a result, the directed flow interestingly turns out to be quite sensitive to the viscosity. The results can explain qualitative features of the collisions, but the rapidity spectra in our current model is narrower than the experimental data.

  3. Interparticle collision mechanism in turbulence.

    PubMed

    Choi, Jung-Il; Park, Yongnam; Kwon, Ohjoon; Lee, Changhoon

    2016-01-01

    Direct numerical simulations of particle-laden homogeneous isotropic turbulence are performed to investigate interparticle collisions in a wide range of Stokes numbers. Dynamics of the particles are described by Stokes drag including particle-particle interactions via hard-sphere collisions, while fluid turbulence is solved using a pseudospectral method. Particular emphasis is placed on interparticle-collision-based conditional statistics of rotation and dissipation rates of the fluid experienced by heavy particles, which provide essential information on the collision process. We also investigate the collision statistics of collision time interval and angle. Based on a Lamb vortex model for a vortex structure, we claim that collision events occur in the edge region for vortical structures in the intermediate-Stokes-number regime, suggesting that the sling effect enhances collision as well as clustering.

  4. New Caledonia a classic example of an arc continent collision

    NASA Astrophysics Data System (ADS)

    Aitchison, J.

    2011-12-01

    The SW Pacific island of New Caledonia presents a classic example of an arc-continent collision. This event occurred in the Late Eocene when elements of an intra-oceanic island arc system, the Loyalty-D'Entrecasteaux arc, which stretched SSE from near Papua New Guinea east of New Caledonia to offshore New Zealand, collided with micro-continental fragments that had rifted off eastern Gondwana (Australia) in the late Cretaceous. Intervening Late Cretaceous to Paleogene oceanic crust of the South Loyalty Basin was eliminated through eastward subduction beneath this west-facing intra-oceanic island arc. As with many arc-continent collisions elsewhere collision was accompanied by ophiolite emplacement. The erosional remnants of which are extensive in New Caledonia. Collision led to subduction flip, followed by extensive rollback in front of the newly established east-facing Vitiaz arc. Post-collisional magmatism occurred after slab break-off and is represented by small-scale granitoid intrusions. Additional important features of New Caledonia include the presence of a regionally extensive UHP metamorphic terrain consisting of blueschists and eclogites that formed during the subduction process and were rapidly exhumed as a result of the collision Not only was collision and associated orogeny short-lived this collision system has not been overprinted by any major subsequent collision. New Caledonia thus provides an exceptional location for the study of processes related to arc-continent collision in general.

  5. High energy hadron-hadron collisions

    SciTech Connect

    Chou, T.T.

    1990-11-01

    Results of a study on high energy collision with the geometrical model are summarized in three parts: (i) the elastic hadron-hadron collision, (ii) the inelastic hadron-hadron collision, and (iii) the e{sup +}e{sup {minus}} annihilation. For elastic collisions, a simple expression for the proton matter distribution is proposed which fits well the elastic {bar p}p scattering from ISR to S{bar p}pS energies within the geometrical model. The proton form factor is of the dipole form with an energy-dependent range parameter. The {bar p}p elastic differential cross section at Tevatron energies obtained by extrapolation is in good agreement with experiments. For multiparticle emission processes a unified physical picture for hadron-hadron and e{sup +}e{sup {minus}} collisions was proposed. A number of predictions were made, including the one that KNO-scaling does not obtain for e{sup +}e{sup {minus}} two-jet events. An extension of the considerations within the geometrical model led to a theory of the momentum distributions of the outgoing particles which are found in good agreement with current experimental data. Extrapolations of results to higher energies have been made. The cluster size of hadrons produced in e{sup +}e{sup {minus}} annihilation is found to increase slowly with energy.

  6. Neutrino-atom collisions

    NASA Astrophysics Data System (ADS)

    Kouzakov, Konstantin A.; Studenikin, Alexander I.

    2016-05-01

    Neutrino-atom scattering provides a sensitive tool for probing nonstandard interactions of massive neutrinos in laboratory measurements. The ionization channel of this collision process plays an important role in experiments searching for neutrino magnetic moments. We discuss some theoretical aspects of atomic ionization by massive neutrinos. We also outline possible manifestations of neutrino electromagnetic properties in coherent elastic neutrino-nucleus scattering.

  7. Rotation as an origin of high energy particle collisions

    NASA Astrophysics Data System (ADS)

    Zaslavskii, O. B.

    2016-01-01

    We consider collision of two particles in rotating spacetimes without horizons. If the metric coefficient responsible for rotation of spacetime is big enough, the energy of collisions in the center of mass frame can be as large as one likes. This can happen in the ergoregion only. The results are model-independent and apply both to relativistic stars and wormholes.

  8. Crabbed Waist Collisions in DAFNE and Super-B Design

    SciTech Connect

    Raimondi, P.; Alesini, D.; Biagini, M.E.; Biscari, C.; Boni, R.; Boscolo, M.; Bossi, F.; Buonomo, B.; Clozza, A.; Delle Monache, G.O.; Demma, T.; Di Pasquale, E.; Di Pirro, G.; Drago, A.; Gallo, A.; Ghigo, A.; Guiducci, S.; Ligi, C.; Marcellini, F.; Mazzitelli, Giovanni; Milardi, C.; /Frascati /Orsay, LAL /CERN /Rome III U. /Rome U. /Novosibirsk, IYF /KEK, Tsukuba /INFN, Pisa /INFN, Cosenza /SLAC /Frascati

    2011-11-02

    The new idea of increasing the luminosity of a collider with crab waist collisions and first experimental results from the DA{Phi}NE {Phi}-Factory at LNF, Frascati, using this concept are presented. Consequences for the design of future factories will be discussed. An outlook to the performance reach with crab waist collisions is given, with emphasis on future B Factories.

  9. A Search for Collision Orbits in the Free-Fall Three-Body Problem. I. Numerical Procedure

    NASA Astrophysics Data System (ADS)

    Tanikawa, Kiyotaka; Umehara, Hiroaki; Abe, Hiroshi

    1995-12-01

    A numerical procedure is devised to find binary collision orbits in the free-fall three-body problem. Applying this procedure, families of binary collision orbits are found and a sequence of triple collision orbits are positioned. A property of sets of binary collision orbits which is convenient to search triple collision orbits is found. Important numerical results are formulated and summarized in the final section.

  10. Fixed Target Collisions at STAR

    NASA Astrophysics Data System (ADS)

    Meehan, Kathryn C.

    2016-12-01

    The RHIC Beam Energy Scan (BES) program was proposed to look for the turn-off of signatures of the quark gluon plasma (QGP), search for a possible QCD critical point, and study the nature of the phase transition between hadronic and partonic matter. Previous results have been used to claim that the onset of deconfinement occurs at a center-of-mass energy of 7 GeV. Data from lower energies are needed to test if this onset occurs. The goal of the STAR Fixed-Target Program is to extend the collision energy range in BES II to energies that are likely below the onset of deconfinement. Currently, STAR has inserted a gold target into the beam pipe and conducted test runs at center-of-mass energies of 3.9 and 4.5 GeV. Tests have been done with both Au and Al beams. First physics results from a Coulomb potential analysis of Au + Au fixed-target collisions are presented and are found to be consistent with results from previous experiments. Furthermore, the Coulomb potential, which is sensitive to the Z of the projectile and degree of baryonic stopping, will be compared to published results from the AGS.

  11. meson production in Au+Au collisions at in STAR

    NASA Astrophysics Data System (ADS)

    Zhou, Long; STAR collaboration

    2017-01-01

    In this article, we report the measurements of the nuclear modification factor (R AA) and elliptic flow (v 2) for in Au+Au collisions at from the STAR experiment. These results are compared with the results of other open charm mesons to study the hadronization mechanism of the charm quarks and disentangle the transport properties of quark-gluon plasma and hadronic phase [1]. We found that the nuclear modification factor for D s are systematically higher than unity and D 0 R AA. The ratio of D s /D 0 for 10-40% central Au+Au collisions is also higher than that in p+p collisions as predicted by PYTHIA. The D s /D 0 ratio is also compared to that in Pb+Pb collisions at measured by the ALICE experiment. Our results indicate an enhancement of D s meson production in Au+Au collisions.

  12. Characteristics of Unequal Size Drop Collisions

    NASA Astrophysics Data System (ADS)

    Kim, Jungyong; Longmire, Ellen; Kim, Man Sik

    2009-11-01

    Pairs of water/glycerin drops were injected into silicone oil and traveled on downward trajectories before colliding. Unequal size drop collisions with drop size ratios (Ds/DL) of 0.7 and 0.5 were investigated. Simultaneous dual-field PIV measurements were obtained to characterize coalescence and rebounding behavior. The initial injection angle and tube height were adjusted to access appropriate impact parameters. In the current study, the collision angle of the large drop was, in general, shallower than that of the small drop, and a range of velocity ratios and impact parameters was examined. Coalescence occurs above We* = 11 similar to collision outcomes for equal size drops. As drop size ratio decreases, the intervening film deforms more. If the velocity ratio uL/us < 1, the interface remains deformed at coalescence, but if uL/us > 1, the interface flattens before coalescence. The rupture location varies due to the asymmetry of the drops. As collision offset increases (B > 0), the film rupture time is shortened and mixing of the fluid within the drops is enhanced after coalescence. These results will be compared with the behavior observed previously for equal size drop collisions.

  13. Modelling of a collision between two smartphones

    NASA Astrophysics Data System (ADS)

    de Jesus, V. L. B.; Sasaki, D. G. G.

    2016-09-01

    In the predominant approach in physics textbooks, the collision between particles is treated as a black box, where no physical quantity can be measured. This approach becomes even more evident in experimental classes where collisions are the simplest and most common way of applying the theorem of conservation of linear momentum in the asymptotic behavior. In this paper we develop and analyse an experiment on collisions using only two smartphones. The experimental setup is amazingly simple; the two devices are aligned on a horizontal table of lacquered wood, in order to slide more easily. At the edge of one of them a piece of common sponge is glued using double-sided tape. By using a free smartphone application, the values generated by the accelerometer of the two devices in full motion are measured and tabulated. Through numerical iteration, the speed graphs of the smartphones before, during, and after the collision are obtained. The main conclusions were: (i) the demonstration of the feasibility of using smartphones as an alternative to air tracks and electronic sensors employed in a teaching lab, (ii) the possibility of investigating the collision itself, its characteristics and effects; this is the great advantage of the use of smartphones over traditional experiments, (iii) the compatibility of the results with the impulse-momentum theorem, within the margin of uncertainty.

  14. Collisions of solid ice in planetesimal formation

    NASA Astrophysics Data System (ADS)

    Deckers, J.; Teiser, J.

    2016-03-01

    We present collision experiments of centimetre projectiles on to decimetre targets, both made up of solid ice, at velocities of 15-45 m s-1 at an average temperature of {T_{avg}}=255.8 ± 0.7 K. In these collisions, the centimetre body gets disrupted and part of it sticks to the target. This behaviour can be observed up to an upper threshold, that depends on the projectile size, beyond which there is no mass transfer. In collisions of small particles, as produced by the disruption of the centimetre projectiles, we also find mass transfer to the target. In this way, the larger body can gain mass, although the efficiency of the initial mass transfer is rather low. These collision results can be applied to planetesimal formation near the snowline, where evaporation and condensation is expected to produce solid ice. In free fall collisions at velocities up to about 7 m s-1, we investigated the threshold to fragmentation and coefficient of restitution of centimetre ice spheres.

  15. Reactive Collision Avoidance Algorithm

    NASA Technical Reports Server (NTRS)

    Scharf, Daniel; Acikmese, Behcet; Ploen, Scott; Hadaegh, Fred

    2010-01-01

    The reactive collision avoidance (RCA) algorithm allows a spacecraft to find a fuel-optimal trajectory for avoiding an arbitrary number of colliding spacecraft in real time while accounting for acceleration limits. In addition to spacecraft, the technology can be used for vehicles that can accelerate in any direction, such as helicopters and submersibles. In contrast to existing, passive algorithms that simultaneously design trajectories for a cluster of vehicles working to achieve a common goal, RCA is implemented onboard spacecraft only when an imminent collision is detected, and then plans a collision avoidance maneuver for only that host vehicle, thus preventing a collision in an off-nominal situation for which passive algorithms cannot. An example scenario for such a situation might be when a spacecraft in the cluster is approaching another one, but enters safe mode and begins to drift. Functionally, the RCA detects colliding spacecraft, plans an evasion trajectory by solving the Evasion Trajectory Problem (ETP), and then recovers after the collision is avoided. A direct optimization approach was used to develop the algorithm so it can run in real time. In this innovation, a parameterized class of avoidance trajectories is specified, and then the optimal trajectory is found by searching over the parameters. The class of trajectories is selected as bang-off-bang as motivated by optimal control theory. That is, an avoiding spacecraft first applies full acceleration in a constant direction, then coasts, and finally applies full acceleration to stop. The parameter optimization problem can be solved offline and stored as a look-up table of values. Using a look-up table allows the algorithm to run in real time. Given a colliding spacecraft, the properties of the collision geometry serve as indices of the look-up table that gives the optimal trajectory. For multiple colliding spacecraft, the set of trajectories that avoid all spacecraft is rapidly searched on

  16. Electromagnetically induced absorption via incoherent collisions

    SciTech Connect

    Yang Xihua; Sheng Jiteng; Xiao Min

    2011-10-15

    We conduct theoretical studies on electromagnetically induced absorption via incoherent collisions in an inhomogeneously broadened ladder-type three-level system with the density-matrix approach. The effects of the collision-induced coherence decay rates as well as the probe laser field intensity on the probe field absorption are examined. It is shown that with the increase of the collisional decay rates in a moderate range, a narrow dip due to electromagnetically induced transparency superimposed on the Doppler-broadened absorption background can be turned into a narrow peak under the conditions that the probe field intensity is not very weak as compared to the pump field, which results from the enhancement of constructive interference and suppression of destructive interference between one-photon and multiphoton transition pathways. The physical origin of the collision-assisted electromagnetically induced absorption is analyzed with a power-series solution of the density-matrix equations.

  17. Coefficient of restitution for a superelastic collision

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2017-03-01

    A simple experiment is described where the tip of a metal ruler is used to strike a 50 g mass. Since the ruler is very flexible, the impact duration is much longer than usual, giving the impression that the ruler simply pushes the mass forward at low speed over a long distance. The tip of the ruler remains in contact with the mass throughout the impact. However, the impact is best described as a long duration collision with a coefficient of restitution (COR) greater than zero, despite the fact that the relative speed during and at the end of the collision is zero. If the mass rests on a table and if the ruler strikes the table before striking the mass, then the ruler bends and stores elastic energy. The result is a superelastic collision where the COR is greater than unity.

  18. Neutrino quantum kinetic equations: The collision term

    DOE PAGES

    Blaschke, Daniel N.; Cirigliano, Vincenzo

    2016-08-01

    We derive the collision term relevant for neutrino quantum kinetic equations in the early universe and compact astrophysical objects, displaying its full matrix structure in both flavor and spin degrees of freedom. We include in our analysis neutrino-neutrino processes, scattering and annihilation with electrons and positrons, and neutrino scattering off nucleons (the latter in the low-density limit). After presenting the general structure of the collision terms, we take two instructive limiting cases. The one-flavor limit highlights the structure in helicity space and allows for a straightforward interpretation of the off-diagonal entries in terms of the product of scattering amplitudes ofmore » the two helicity states. As a result, the isotropic limit is relevant for studies of the early universe: in this case the terms involving spin coherence vanish and the collision term can be expressed in terms of two-dimensional integrals, suitable for computational implementation.« less

  19. Active Collision Avoidance for Planetary Landers

    NASA Technical Reports Server (NTRS)

    Rickman, Doug; Hannan, Mike; Srinivasan, Karthik

    2014-01-01

    Present day robotic missions to other planets require precise, a priori knowledge of the terrain to pre-determine a landing spot that is safe. Landing sites can be miles from the mission objective, or, mission objectives may be tailored to suit landing sites. Future robotic exploration missions should be capable of autonomously identifying a safe landing target within a specified target area selected by mission requirements. Such autonomous landing sites must (1) 'see' the surface, (2) identify a target, and (3) land the vehicle. Recent advances in radar technology have resulted in small, lightweight, low power radars that are used for collision avoidance and cruise control systems in automobiles. Such radar systems can be adapted for use as active hazard avoidance systems for planetary landers. The focus of this CIF proposal is to leverage earlier work on collision avoidance systems for MSFC's Mighty Eagle lander and evaluate the use of automotive radar systems for collision avoidance in planetary landers.

  20. Neutrino quantum kinetic equations: The collision term

    SciTech Connect

    Blaschke, Daniel N.; Cirigliano, Vincenzo

    2016-08-01

    We derive the collision term relevant for neutrino quantum kinetic equations in the early universe and compact astrophysical objects, displaying its full matrix structure in both flavor and spin degrees of freedom. We include in our analysis neutrino-neutrino processes, scattering and annihilation with electrons and positrons, and neutrino scattering off nucleons (the latter in the low-density limit). After presenting the general structure of the collision terms, we take two instructive limiting cases. The one-flavor limit highlights the structure in helicity space and allows for a straightforward interpretation of the off-diagonal entries in terms of the product of scattering amplitudes of the two helicity states. As a result, the isotropic limit is relevant for studies of the early universe: in this case the terms involving spin coherence vanish and the collision term can be expressed in terms of two-dimensional integrals, suitable for computational implementation.

  1. Tracking improves performance of biological collision avoidance models.

    PubMed

    Pant, Vivek; Higgins, Charles M

    2012-07-01

    Collision avoidance models derived from the study of insect brains do not perform universally well in practical collision scenarios, although the insects themselves may perform well in similar situations. In this article, we present a detailed simulation analysis of two well-known collision avoidance models and illustrate their limitations. In doing so, we present a novel continuous-time implementation of a neuronally based collision avoidance model. We then show that visual tracking can improve performance of these models by allowing an relative computation of the distance between the obstacle and the observer. We compare the results of simulations of the two models with and without tracking to show how tracking improves the ability of the model to detect an imminent collision. We present an implementation of one of these models processing imagery from a camera to show how it performs in real-world scenarios. These results suggest that insects may track looming objects with their gaze.

  2. Cognitive demands of collision avoidance in simulated ship control.

    PubMed

    Hockey, G Robert J; Healey, Alex; Crawshaw, Martin; Wastell, David G; Sauer, Jürgen

    2003-01-01

    The study examines the cognitive demands of collision avoidance under a range of maritime scenarios. Operators used a PC-based radar simulator to navigate set courses over 100 6-min trials varying in collision threat and traffic density. Corrective maneuvers were made through the application of standard navigation rules and by using two decision aids (target acquisition and test maneuver). Results showed widespread effects of collision threat in terms of decision aid use, subjective workload, and secondary task performance. Most notably, demand increased markedly over the course of emergency trials, in which collision threat resulted from rule violation by target vessels. The findings are discussed in terms of the comparison between predictable demands (requiring standard course changes) and those involving uncertainty about the others' intentions (involving more intensive monitoring and forced delays in corrective action). The study has relevance for the design of collision avoidance systems, specifically for the use of ecological displays.

  3. Interaction of Radiation with Matter: Atomic Collision Processes Occurring in the Presence of Radiation Fields

    DTIC Science & Technology

    1988-09-15

    Degenerate Four -Wave Mixing,* Saturation Spectroscopy,’ Dressed Atom,’ Photon Echo: Bloch Equations’, Collision Kernel; Collisions; Optical Noise, 20...information regarding high resolution laser spectroscopy. The initial problem which was studied involved the four -wave mixing signals generated in Na vapor...in four -wave mixing. If the ground and excited state collision rates for a two-level atom differ, collisions result in non-conservation of population

  4. Holographic collisions in non-conformal theories

    NASA Astrophysics Data System (ADS)

    Attems, Maximilian; Casalderrey-Solana, Jorge; Mateos, David; Santos-Oliván, Daniel; Sopuerta, Carlos F.; Triana, Miquel; Zilhão, Miguel

    2017-01-01

    We numerically simulate gravitational shock wave collisions in a holographic model dual to a non-conformal four-dimensional gauge theory. We find two novel effects associated to the non-zero bulk viscosity of the resulting plasma. First, the hydrodynamization time increases. Second, if the bulk viscosity is large enough then the plasma becomes well described by hydrodynamics before the energy density and the average pressure begin to obey the equilibrium equation of state. We discuss implications for the quark-gluon plasma created in heavy ion collision experiments.

  5. Energy behavior on side structure in event of ship collision subjected to external parameters.

    PubMed

    Prabowo, Aditya Rio; Bae, Dong Myung; Sohn, Jung Min; Cao, Bo

    2016-11-01

    The safety of ships in regards to collisions and groundings, as well as the navigational and structural aspects of ships, has been improved and developed up to this day by technical, administrative and nautical parties. The damage resulting from collisions could be reduced through several techniques such as designing appropriate hull structures, ensuring tightness of cargo tanks as well as observation and review on structural behaviors, whilst accounting for all involved parameters. The position during a collision can be influenced by the collisions' location and angle as these parts are included in the external dynamics of ship collisions. In this paper, the results of several collision analyses using the finite element method were used and reviewed regarding the effect of location and angle on energy characteristic. Firstly, the capabilities of the structure and its ability to resist destruction in a collision process were presented and comparisons were made to other collision cases. Three types of collisions were identified based on the relative location of contact points to each other. From the results, it was found that the estimation of internal energy by the damaged ships differed in range from 12%-24%. In the second stage, the results showed that a collision between 30 to 60 degrees produced higher level energy than a collision in the perpendicular position. Furthermore, it was concluded that striking and struck objects in collision contributed to energy and damage shape.

  6. Operational Collision Avoidance

    NASA Technical Reports Server (NTRS)

    Guit, Bill

    2015-01-01

    This presentation will describe the early days of the EOS Aqua and Aura operational collision avoidance process. It will highlight EOS debris avoidance maneuvers, EOS high interest event statistic and A-Train systematic conjunctions and conclude with future challenges. This is related to earlier e-DAA (tracking number 21692) that an abstract was submitted to a different conference. Eric Moyer, ESMO Deputy Project Manager has reviewed and approved this presentation on May 6, 2015

  7. Kuang's Semi-Classical Formalism for Electron Capture Cross-Sections in Ion-Ion Collisions at Approximately to MeV/amu: Application to ENA Modeling

    NASA Technical Reports Server (NTRS)

    Barghouty, A. F.

    2012-01-01

    Recent discovery by STEREO A/B of energetic neutral hydrogen is spurring an interest and need for reliable estimates of electron capture cross sections at few MeVs per nucleon as well as for multi-electron ions. Required accuracy in such estimates necessitates detailed and involved quantum-mechanical calculations or expensive numerical simulations. For ENA modeling and similar purposes, a semi-classical approach offers a middle-ground approach. Kuang's semiclassical formalism to calculate electron-capture cross sections for single and multi-electron ions is an elegant and efficient method, but has so far been applied to limited and specific laboratory measurements and at somewhat lower energies. Our goals are to test and extend Kuang s method to all ion-atom and ion-ion collisions relevant to ENA modeling, including multi-electron ions and for K-shell to K-shell transitions.

  8. Affordable MMW aircraft collision avoidance system

    NASA Astrophysics Data System (ADS)

    Almsted, Larry D.; Becker, Robert C.; Zelenka, Richard E.

    1997-06-01

    Collision avoidance is of concern to all aircraft, requiring the detection and identification of hazardous terrain or obstacles in sufficient time for clearance maneuvers. The collision avoidance requirement is even more demanding for helicopters, as their unique capabilities result in extensive operations at low-altitude, near to terrain and other hazardous obstacles. TO augment the pilot's visual collision avoidance abilities, some aircraft are equipped with 'enhanced-vision' systems or terrain collision warning systems. Enhanced-vision systems are typically very large and costly systems that are not very covert and are also difficult to install in a helicopter. The display is typically raw images from infrared or radar sensors, and can require a high degree of pilot interpretation and attention. Terrain collision warning system that rely on stored terrain maps are often of low resolution and accuracy and do not represent hazards to the aircraft placed after map sampling. Such hazards could include aircraft parked on runway, man- made towers or buildings and hills. In this paper, a low cost dual-function scanning pencil-beam, millimeter-wave radar forward sensor is used to determine whether an aircraft's flight path is clear of obstructions. Due to the limited space and weight budget in helicopters, the system is a dual function system that is substituted in place of the existing radar altimeter. The system combines a 35 GHz forward looking obstacle avoidance radar and a 4.3 GHz radar altimeter. The forward looking 35 GHz 3D radar's returns are used to construct a terrain and obstruction database surrounding an aircraft, which is presented to the pilot as a synthetic perspective display. The 35 GHz forward looking radar and the associated display was evaluated in a joint NASA Honeywell flight test program in 1996. The tests were conducted on a NASA/Army test helicopter. The test program clearly demonstrated the systems potential usefulness for collision avoidance.

  9. Fan Affinity Laws from a Collision Model

    ERIC Educational Resources Information Center

    Bhattacharjee, Shayak

    2012-01-01

    The performance of a fan is usually estimated using hydrodynamical considerations. The calculations are long and involved and the results are expressed in terms of three affinity laws. In this paper we use kinetic theory to attack this problem. A hard sphere collision model is used, and subsequently a correction to account for the flow behaviour…

  10. Super high energy heavy ion collisions

    SciTech Connect

    Geist, W.M.

    1987-12-01

    Basic theoretical ideas on a phase transition to a plasma of free quarks and gluons in heavy ion collisions are outlined. First results from experiments with oxygen beams at 14.5 GeV/c/N (BNL), 60 and 200 GeV/c/N (CERN) are discussed. 30 refs., 9 figs.

  11. High energy nucleus-nucleus collisions

    NASA Technical Reports Server (NTRS)

    Wosiek, B.

    1986-01-01

    Experimental results on high energy nucleus-nucleus interactions are presented. The data are discussed within the framework of standard super-position models and from the point-of-view of the possible formation of new states of matter in heavy ion collisions.

  12. Collision of Bose Condensate Dark Matter structures

    SciTech Connect

    Guzman, F. S.

    2008-12-04

    The status of the scalar field or Bose condensate dark matter model is presented. Results about the solitonic behavior in collision of structures is presented as a possible explanation to the recent-possibly-solitonic behavior in the bullet cluster merger. Some estimates about the possibility to simulate the bullet cluster under the Bose Condensate dark matter model are indicated.

  13. A gyrokinetic collision operator for magnetized Lorentz plasmas

    SciTech Connect

    Liu Chang; Ma Chenhao; Yu Xiongjie; Qin, Hong

    2011-03-15

    A gyrocenter collision operator for magnetized Lorentz plasmas is derived using the Fokker-Plank method. The gyrocenter collision operator consists of drift and diffusion terms in the gyrocenter coordinates, including the diffusion of the gyrocenter, which does not exist for the collision operator in the particle phase space coordinates. The gyrocenter collision operator also depends on the transverse electric field explicitly, which is crucial for the correct treatment of collisional effects and transport in the gyrocenter coordinates. The gyrocenter collision operator derived is applied to calculate the particle and heat transport fluxes in a magnetized Lorentz plasma with an electric field. The particle and heat transport fluxes calculated from our gyrocenter collision operator agree exactly with the classical Braginskii's result [S. I. Braginskii, Reviews of Plasma Physics (Consultants Bureau, New York, 1965), Vol. 1, p. 205: P. Helander and D. J. Sigmar, Collisional Transport in Magnetized Plasmas (Cambridge University, Cambridge, 2002), p. 65], which validates the correctness of our collision operator. To calculate the transport fluxes correctly, it is necessary to apply the pullback transformation associated with gyrocenter coordinate transformation in the presence of collisions, which also serves as a practical algorithm for evaluating collisional particle and heat transport fluxes in the gyrocenter coordinates.

  14. Toward a Physical Characterization of Raindrop Collision Outcome Regimes

    NASA Technical Reports Server (NTRS)

    Testik, F. Y.; Barros, Ana P.; Bilven, Francis L.

    2011-01-01

    A comprehensive raindrop collision outcome regime diagram that delineates the physical conditions associated with the outcome regimes (i.e., bounce, coalescence, and different breakup types) of binary raindrop collisions is proposed. The proposed diagram builds on a theoretical regime diagram defined in the phase space of collision Weber numbers We and the drop diameter ratio p by including critical angle of impact considerations. In this study, the theoretical regime diagram is first evaluated against a comprehensive dataset for drop collision experiments representative of raindrop collisions in nature. Subsequently, the theoretical regime diagram is modified to explicitly describe the dominant regimes of raindrop interactions in (We, p) by delineating the physical conditions necessary for the occurrence of distinct types of collision-induced breakup (neck/filament, sheet, disk, and crown breakups) based on critical angle of impact consideration. Crown breakup is a subtype of disk breakup for lower collision kinetic energy that presents distinctive morphology. Finally, the experimental results are analyzed in the context of the comprehensive collision regime diagram, and conditional probabilities that can be used in the parameterization of breakup kernels in stochastic models of raindrop dynamics are provided.

  15. A comparative collision-based analysis of human gait.

    PubMed

    Lee, David V; Comanescu, Tudor N; Butcher, Michael T; Bertram, John E A

    2013-11-22

    This study compares human walking and running, and places them within the context of other mammalian gaits. We use a collision-based approach to analyse the fundamental dynamics of the centre of mass (CoM) according to three angles derived from the instantaneous force and velocity vectors. These dimensionless angles permit comparisons across gait, species and size. The collision angle Φ, which is equivalent to the dimensionless mechanical cost of transport CoTmech, is found to be three times greater during running than walking of humans. This threefold difference is consistent with previous studies of walking versus trotting of quadrupeds, albeit tends to be greater in the gaits of humans and hopping bipeds than in quadrupeds. Plotting the collision angle Φ together with the angles of the CoM force vector Θ and velocity vector Λ results in the functional grouping of bipedal and quadrupedal gaits according to their CoM dynamics-walking, galloping and ambling are distinguished as separate gaits that employ collision reduction, whereas trotting, running and hopping employ little collision reduction and represent more of a continuum that is influenced by dimensionless speed. Comparable with quadrupedal mammals, collision fraction (the ratio of actual to potential collision) is 0.51 during walking and 0.89 during running, indicating substantial collision reduction during walking, but not running, of humans.

  16. Simulating Collisions for Hydrokinetic Turbines

    SciTech Connect

    Richmond, Marshall C.; Romero Gomez, Pedro DJ; Rakowski, Cynthia L.

    2013-10-01

    Evaluations of blade-strike on an axial-flow Marine Hydrokinetic turbine were conducted using a conventional methodology as well as an alternative modeling approach proposed in the present document. The proposed methodology integrates the following components into a Computa- tional Fluid Dynamics (CFD) model: (i) advanced eddy-resolving flow simulations, (ii) ambient turbulence based on field data, (iii) moving turbine blades in highly transient flows, and (iv) Lagrangian particles to mimic the potential fish pathways. The sensitivity of blade-strike prob- ability to the following conditions was also evaluated: (i) to the turbulent environment, (ii) to fish size and (iii) to mean stream flow velocity. The proposed methodology provided fraction of collisions and offered the capability of analyzing the causal relationships between the flow envi- ronment and resulting strikes on rotating blades. Overall, the conventional methodology largely overestimates the probability of strike, and lacks the ability to produce potential fish and aquatic biota trajectories as they interact with the rotating turbine. By using a set of experimental corre- lations of exposure-response of living fish colliding on moving blades, the occurrence, frequency and intensity of the particle collisions was next used to calculate the survival rate of fish crossing the MHK turbine. This step indicated survival rates always greater than 98%. Although the proposed CFD framework is computationally more expensive, it provides the advantage of evaluating multiple mechanisms of stress and injury of hydrokinetic turbine devices on fish.

  17. Molecular collisions coming into focus.

    PubMed

    Onvlee, Jolijn; Vogels, Sjoerd N; von Zastrow, Alexander; Parker, David H; van de Meerakker, Sebastiaan Y T

    2014-08-14

    The Stark deceleration method exploits the concepts of charged particle accelerator physics to produce beams of neutral polar molecules with an almost perfect quantum state purity, a tunable velocity and a narrow velocity distribution. These monochromatic molecular beams offer interesting perspectives for precise studies of molecular scattering processes, in particular when used in conjunction with state-of-the-art laser-based detection techniques such as velocity map imaging. Here, we describe crossed beam scattering experiments in which the Stark deceleration method is combined with the velocity map imaging technique. The narrow velocity spread of Stark-decelerated molecular beams results in scattering images with unprecedented velocity and angular resolution. We demonstrate this by resolving quantum diffraction oscillations in state-to-state inelastic differential scattering cross sections for collisions between NO radicals and rare gas atoms. We describe the future prospects of this "best-of-two-worlds" combination, ranging from scattering studies at low collision energies to bimolecular scattering using two decelerators, and discuss the challenges that lie ahead to achieve these goals.

  18. Catching Collisions in the LHC

    SciTech Connect

    Fruguiele, Claudia; Hirschauer, Jim

    2015-06-16

    Now that the Large Hadron Collider has officially turned back on for its second run, within every proton collision could emerge the next new discovery in particle physics. Learn how the detectors on the Compact Muon Solenoid, or CMS, experiment capture and track particles as they are expelled from a collision. Talking us through these collisions are Claudia Fruguiele and Jim Hirschauer of Fermi National Accelerator Laboratory, the largest U.S. institution collaborating on the LHC.

  19. Catching Collisions in the LHC

    ScienceCinema

    Fruguiele, Claudia; Hirschauer, Jim

    2016-07-12

    Now that the Large Hadron Collider has officially turned back on for its second run, within every proton collision could emerge the next new discovery in particle physics. Learn how the detectors on the Compact Muon Solenoid, or CMS, experiment capture and track particles as they are expelled from a collision. Talking us through these collisions are Claudia Fruguiele and Jim Hirschauer of Fermi National Accelerator Laboratory, the largest U.S. institution collaborating on the LHC.

  20. Strangeness production in AA and pp collisions

    NASA Astrophysics Data System (ADS)

    Castorina, Paolo; Satz, Helmut

    2016-07-01

    Boost-invariant hadron production in high-energy collisions occurs in causally disconnected regions of finite space-time size. As a result, globally conserved quantum numbers (charge, strangeness, baryon number) are conserved locally in spatially restricted correlation clusters. Their size is determined by two time scales: the equilibration time specifying the formation of a quark-gluon plasma, and the hadronization time, specifying the onset of confinement. The expected values for these scales provide the theoretical basis for the suppression observed for strangeness production in elementary interactions ( pp , e^+e^- below LHC energies. In contrast, the space-time superposition of individual collisions in high-energy heavy-ion interactions leads to higher energy densities, resulting in much later hadronization and hence much larger hadronization volumes. This largely removes the causality constraints and results in an ideal hadronic resonance gas in full chemical equilibrium. In the present paper, we determine the collision energies needed for that; we also estimate when pp collisions reach comparable hadronization volumes and thus determine when strangeness suppression should disappear there as well.

  1. Sensor management for collision alert in orbital object tracking

    NASA Astrophysics Data System (ADS)

    Xu, Peiran; Chen, Huimin; Charalampidis, D.; Shen, Dan; Chen, Genshe; Blasch, Erik; Pham, Khanh

    2011-06-01

    Given the increasingly dense environment in both low-earth orbit (LEO) and geostationary orbit (GEO), a sudden change in the trajectory of any existing resident space object (RSO) may cause potential collision damage to space assets. With a constellation of electro-optical/infrared (EO/IR) sensor platforms and ground radar surveillance systems, it is important to design optimal estimation algorithms for updating nonlinear object states and allocating sensing resources to effectively avoid collisions among many RSOs. Previous work on RSO collision avoidance often assumes that the maneuver onset time or maneuver motion of the space object is random and the sensor management approach is designed to achieve efficient average coverage of the RSOs. Few attempts have included the inference of an object's intent in the response to an RSO's orbital change. We propose a game theoretic model for sensor selection and assume the worst case intentional collision of an object's orbital change. The intentional collision results from maximal exposure of an RSO's path. The resulting sensor management scheme achieves robust and realistic collision assessment, alerts the impending collisions, and identifies early RSO orbital change with lethal maneuvers. We also consider information sharing among distributed sensors for collision alert and an object's intent identification when an orbital change has been declared. We compare our scheme with the conventional (non-game based) sensor management (SM) scheme using a LEO-to-LEO space surveillance scenario where both the observers and the unannounced and unplanned objects have complete information on the constellation of vulnerable assets. We demonstrate that, with adequate information sharing, the distributed SM method can achieve the performance close to that of centralized SM in identifying unannounced objects and making early warnings to the RSO for potential collision to ensure a proper selection of collision avoidance action.

  2. Electron-impact excitation of Sc II: collision strengths and effective collision strengths for fine-structure transitions

    NASA Astrophysics Data System (ADS)

    Grieve, M. F. R.; Ramsbottom, C. A.

    2012-08-01

    Accurate fine-structure atomic data for the Fe-peak elements are essential for interpreting astronomical spectra. There is a severe paucity of data available for Sc II, highlighted by the fact that no collision strengths are readily available for this ion. We present electron-impact excitation collision strengths and Maxwellian averaged effective collision strengths for Sc II. The collision strengths were calculated for all 3916 transitions amongst 89 jj levels (arising from the 3d4s, 3d2, 4s2, 3d4p, 4s4p, 3d5s, 3d4d, 3d5p, 4p2 and 3d4f configurations), resulting in a 944 coupled channel problem. The R-matrix package RMATRXII was utilized, along with the transformation code FINE and the external region code PSTGF, to calculate the collision strengths for a range of incident electron energies in the 0 to 8.3 Rydberg region. Maxwellian averaged effective collision strengths were then produced for 27 temperatures lying within the astrophysically significant range of 30 to 105 K. The collision strengths and effective collision strengths were produced for two different target models. The purpose was to systematically examine the effect of including open 3p correlation terms into the configuration interaction expansion for the wavefunction. The first model consisted of all 36 CI terms that could be generated with the 3p core closed. The second model incorporated an additional six configurations which allowed for single-electron excitations from within the 3p core. Comparisons are made between the two models and the results of Bautista et al., obtained by private communication. It is concluded that the first model produced the most reliable set of collision and effective collision strengths for use in astrophysical and plasma applications.

  3. Chemical activation through super energy transfer collisions.

    PubMed

    Smith, Jonathan M; Nikow, Matthew; Ma, Jianqiang; Wilhelm, Michael J; Han, Yong-Chang; Sharma, Amit R; Bowman, Joel M; Dai, Hai-Lung

    2014-02-05

    Can a molecule be efficiently activated with a large amount of energy in a single collision with a fast atom? If so, this type of collision will greatly affect molecular reactivity and equilibrium in systems where abundant hot atoms exist. Conventional expectation of molecular energy transfer (ET) is that the probability decreases exponentially with the amount of energy transferred, hence the probability of what we label "super energy transfer" is negligible. We show, however, that in collisions between an atom and a molecule for which chemical reactions may occur, such as those between a translationally hot H atom and an ambient acetylene (HCCH) or sulfur dioxide, ET of chemically significant amounts of energy commences with surprisingly high efficiency through chemical complex formation. Time-resolved infrared emission observations are supported by quasi-classical trajectory calculations on a global ab initio potential energy surface. Results show that ∼10% of collisions between H atoms moving with ∼60 kcal/mol energy and HCCH result in transfer of up to 70% of this energy to activate internal degrees of freedom.

  4. Real-time collision avoidance in space: the GETEX experiment

    NASA Astrophysics Data System (ADS)

    Freund, Eckhard; Rossmann, Juergen; Schluse, Michael

    2000-10-01

    Intelligent autonomous robotic systems require efficient safety components to assure system reliability during the entire operation. Especially if commanded over long distances, the robotic system must be able to guarantee the planning of safe and collision free movements independently. Therefore the IRF developed a new collision avoidance methodology satisfying the needs of autonomous safety systems considering the dynamics of the robots to protect. To do this, the collision avoidance system cyclically calculates the actual collision danger of the robots with respect to all static and dynamic obstacles in the environment. If a robot gets in collision danger the methodology immediately starts an evasive action to avoid the collision and guides the robot around the obstacle to its target position. This evasive action is calculated in real-time in a mathematically exact way by solving a quadratic convex optimization problem. The secondary conditions of this optimization problem include the potential collision danger of the robots kinematic chain including all temporarily attached grippers and objects and the dynamic constraints of the robots. The result of the optimization procedure are joint accelerations to apply to prevent the robot from colliding and to guide it to its target position. This methodology has been tested very successfully during the Japanese/German space robot project GETEX in April 1999. During the mission, the collision avoidance system successfully protected the free flying Japanese robot ERA on board the satellite ETS-VII at all times. The experiments showed, that the developed system is fully capable of ensuring the safety of such autonomous robotic systems by actively preventing collisions and generating evasive actions in cases of collision danger.

  5. Geocoding police collision report data from California: a comprehensive approach

    PubMed Central

    2009-01-01

    Background Collision geocoding is the process of assigning geographic descriptors, usually latitude and longitude coordinates, to a traffic collision record. On California police reports, relative collision location is recorded using a highway postmile marker or a street intersection. The objective of this study was to create a geocoded database of all police-reported, fatal and severe injury collisions in the California Statewide Integrated Traffic Records System (SWITRS) for years 1997-2006 for use by public agencies. Results Geocoding was completed with a multi-step process. First, pre-processing was performed using a scripting language to clean and standardize street name information. A state highway network with postmile values was then created using a custom tool written in Visual Basic for Applications (VBA) in ArcGIS software. Custom VBA functionality was also used to incorporate the offset direction and distance. Intersection and address geocoding was performed using ArcGIS, StreetMap Pro 2003 digital street network, and Google Earth Pro. A total of 142,007 fatal and severe injury collisions were identified in SWITRS. The geocoding match rate was 99.8% for postmile-coded collisions and 86% for intersection-coded collisions. The overall match rate was 91%. Conclusions The availability of geocoded collision data will be beneficial to clinicians, researchers, policymakers, and practitioners in the fields of traffic safety and public health. Potential uses of the data include studies of collision clustering on the highway system, examinations of the associations between collision occurrence and a variety of variables on environmental and social characteristics, including housing and personal demographics, alcohol outlets, schools, and parks. The ability to build maps may be useful in research planning and conduct and in the delivery of information to both technical and non-technical audiences. PMID:20040106

  6. Heavy-quark dynamics in heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Song, T.; Berrehrah, H.; Bratkovskaya, E. L.; Cabrera, D.; Cassing, W.; Tolos, T.; Torres-Rincon, J. M.

    2017-01-01

    The dynamics of partons and hadrons in ultra-relativistic nucleus-nucleus collisions are analyzed within the Parton-Hadron-String Dynamics (PHSD) transport approach, which is based on a dynamical quasiparticle model (DQPM) for the partonic phase including a dynamical hadronization scheme while reproducing lattice QCD results in thermodynamic equilibrium for the equation-of-state as well as transport coefficients like shear and bulk viscosities, the electric conductivity or the charm diffusion coefficient of the hot QCD medium. In this contribution, we report on recent results on the charm dynamics and elliptic flow in Au+Au collisions at RHIC and Pb+Pb collisions at the LHC.

  7. Test of Sigmund scaling for low collision energies

    NASA Technical Reports Server (NTRS)

    Vedder, M.

    1982-01-01

    A scaling law that describes the most probable vibrorotational excitation in ion-molecule collisions has recently been extended by Sigmund (1981) to cover polyatomic targets. The predictions of this scaling law are examined for collisions of Cl(-) and K(+) with the targets O2, N2, CO, CO2, and CH4 in the energy range 50-200 eV. The experimental results do not all scale according to the theory. The study does demonstrate the usefulness of the scaling variables when examining the most probable vibrorotational excitation in ion-molecule collisions. A collection of isoelectronic scattering results is presented.

  8. Simulations of collision of ice particles

    NASA Astrophysics Data System (ADS)

    Zamankhan, Piroz

    2010-06-01

    The objective of this paper is to develop a realistic model for ice-structure interaction. To this end, the experiments made by Bridges et al. [Bridges FG, Hatzes A, Liu DNC. Structure, stability and evolution of Saturn's rings. Nature 1984;309:333-5] in order to measure the coefficient of restitution for ice particles are thoroughly analyzed. One particularly troublesome aspect of the aforementioned experiments is fracture of the ice particles during a collision. In the present effort, the collisional properties of the ice particles are investigated using a Finite Element approach. It is found that a major challenge in modeling collision of the ice balls is the prediction of the onset of fracture and crack propagation in them. In simulations of a block of ice collision to a structure, it is crucial that fracture is determined correctly, as it will influence the collisional properties of the ice particles. The results of the simulation, considering fracture criterion implemented into the Finite Element Model [Zamankhan P, Bordbar M-H. Complex flow dynamics in dense granular flows. Part I: experimentation. J Appl Mech (T-ASME) 2006;73:648-57; Zamankhan P, Huang J. Complex flow dynamics in dense granular flows. Part II: simulations. J Appl Mech (T-ASME) 2007;74:691-702] together with a material model for the ice, imply that most of the kinetic energy dissipation occurs as a result of fracturing at the contact surface of the ice particles. The results obtained in the present study suggest that constitutive models such as those proposed by Brilliantov et al. [Brilliantov NV, Spahn F, Hertzsch JM, Poschel T. Model for collisions in granular gases. Phys Rev E;1996;53:5382-92] for collisions of ice particles are highly questionable.

  9. Elliptic Flow in Au+Au Collisions at √sNN = 130 GeV

    NASA Astrophysics Data System (ADS)

    Ackermann, K. H.; Adams, N.; Adler, C.; Ahammed, Z.; Ahmad, S.; Allgower, C.; Amsbaugh, J.; Anderson, M.; Anderssen, E.; Arnesen, H.; Arnold, L.; Averichev, G. S.; Baldwin, A.; Balewski, J.; Barannikova, O.; Barnby, L. S.; Baudot, J.; Beddo, M.; Bekele, S.; Belaga, V. V.; Bellwied, R.; Bennett, S.; Bercovitz, J.; Berger, J.; Betts, W.; Bichsel, H.; Bieser, F.; Bland, L. C.; Bloomer, M.; Blyth, C. O.; Boehm, J.; Bonner, B. E.; Bonnet, D.; Bossingham, R.; Botlo, M.; Boucham, A.; Bouillo, N.; Bouvier, S.; Bradley, K.; Brady, F. P.; Braithwaite, E. S.; Braithwaite, W.; Brandin, A.; Brown, R. L.; Brugalette, G.; Byrd, C.; Caines, H.; Calderón de La Barca Sánchez, M.; Cardenas, A.; Carr, L.; Carroll, J.; Castillo, J.; Caylor, B.; Cebra, D.; Chatopadhyay, S.; Chen, M. L.; Chen, W.; Chen, Y.; Chernenko, S. P.; Cherney, M.; Chikanian, A.; Choi, B.; Chrin, J.; Christie, W.; Coffin, J. P.; Conin, L.; Consiglio, C.; Cormier, T. M.; Cramer, J. G.; Crawford, H. J.; Danilov, V. I.; Dayton, D.; Demello, M.; Deng, W. S.; Derevschikov, A. A.; Dialinas, M.; Diaz, H.; Deyoung, P. A.; Didenko, L.; Dimassimo, D.; Dioguardi, J.; Dominik, W.; Drancourt, C.; Draper, J. E.; Dunin, V. B.; Dunlop, J. C.; Eckardt, V.; Edwards, W. R.; Efimov, L. G.; Eggert, T.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Etkin, A.; Fachini, P.; Feliciano, C.; Ferenc, D.; Ferguson, M. I.; Fessler, H.; Finch, E.; Fine, V.; Fisyak, Y.; Flierl, D.; Flores, I.; Foley, K. J.; Fritz, D.; Gagunashvili, N.; Gans, J.; Gazdzicki, M.; Germain, M.; Geurts, F.; Ghazikhanian, V.; Gojak, C.; Grabski, J.; Grachov, O.; Grau, M.; Greiner, D.; Greiner, L.; Grigoriev, V.; Grosnick, D.; Gross, J.; Guilloux, G.; Gushin, E.; Hall, J.; Hallman, T. J.; Hardtke, D.; Harper, G.; Harris, J. W.; He, P.; Heffner, M.; Heppelmann, S.; Herston, T.; Hill, D.; Hippolyte, B.; Hirsch, A.; Hjort, E.; Hoffmann, G. W.; Horsley, M.; Howe, M.; Huang, H. Z.; Humanic, T. J.; Hümmler, H.; Hunt, W.; Hunter, J.; Igo, G. J.; Ishihara, A.; Ivanshin, Yu. I.; Jacobs, P.; Jacobs, W. W.; Jacobson, S.; Jared, R.; Jensen, P.; Johnson, I.; Jones, P. G.; Judd, E.; Kaneta, M.; Kaplan, M.; Keane, D.; Kenney, V. P.; Khodinov, A.; Klay, J.; Klein, S. R.; Klyachko, A.; Koehler, G.; Konstantinov, A. S.; Kormilitsyne, V.; Kotchenda, L.; Kotov, I.; Kovalenko, A. D.; Kramer, M.; Kravtsov, P.; Krueger, K.; Krupien, T.; Kuczewski, P.; Kuhn, C.; Kunde, G. J.; Kunz, C. L.; Kutuev, R. Kh.; Kuznetsov, A. A.; Lakehal-Ayat, L.; Lamas-Valverde, J.; Lamont, M. A.; Landgraf, J. M.; Lange, S.; Lansdell, C. P.; Lasiuk, B.; Laue, F.; Lebedev, A.; Lecompte, T.; Leonhardt, W. J.; Leontiev, V. M.; Leszczynski, P.; Levine, M. J.; Li, Q.; Li, Q.; Li, Z.; Liaw, C.-J.; Lin, J.; Lindenbaum, S. J.; Lindenstruth, V.; Lindstrom, P. J.; Lisa, M. A.; Liu, H.; Ljubicic, T.; Llope, W. J.; Locurto, G.; Long, H.; Longacre, R. S.; Lopez-Noriega, M.; Lopiano, D.; Love, W. A.; Lutz, J. R.; Lynn, D.; Madansky, L.; Maier, R.; Majka, R.; Maliszewski, A.; Margetis, S.; Marks, K.; Marstaller, R.; Martin, L.; Marx, J.; Matis, H. S.; Matulenko, Yu. A.; Matyushevski, E. A.; McParland, C.; McShane, T. S.; Meier, J.; Melnick, Yu.; Meschanin, A.; Middlekamp, P.; Mikhalin, N.; Miller, B.; Milosevich, Z.; Minaev, N. G.; Minor, B.; Mitchell, J.; Mogavero, E.; Moiseenko, V. A.; Moltz, D.; Moore, C. F.; Morozov, V.; Morse, R.; de Moura, M. M.; Munhoz, M. G.; Mutchler, G. S.; Nelson, J. M.; Nevski, P.; Ngo, T.; Nguyen, M.; Nguyen, T.; Nikitin, V. A.; Nogach, L. V.; Noggle, T.; Norman, B.; Nurushev, S. B.; Nussbaum, T.; Nystrand, J.; Odyniec, G.; Ogawa, A.; Ogilvie, C. A.; Olchanski, K.; Oldenburg, M.; Olson, D.; Ososkov, G. A.; Ott, G.; Padrazo, D.; Paic, G.; Pandey, S. U.; Panebratsev, Y.; Panitkin, S. Y.; Pavlinov, A. I.; Pawlak, T.; Pentia, M.; Perevotchikov, V.; Peryt, W.; Petrov, V. A.; Pinganaud, W.; Pirogov, S.; Platner, E.; Pluta, J.; Polk, I.; Porile, N.; Porter, J.; Poskanzer, A. M.; Potrebenikova, E.; Prindle, D.; Pruneau, C.; Puskar-Pasewicz, J.; Rai, G.; Rasson, J.; Ravel, O.; Ray, R. L.; Razin, S. V.; Reichhold, D.; Reid, J.; Renfordt, R. E.; Retiere, F.; Ridiger, A.; Riso, J.; Ritter, H. G.; Roberts, J. B.; Roehrich, D.; Rogachevski, O. V.; Romero, J. L.; Roy, C.; Russ, D.; Rykov, V.; Sakrejda, I.; Sanchez, R.; Sandler, Z.; Sandweiss, J.; Sappenfield, P.; Saulys, A. C.; Savin, I.; Schambach, J.; Scharenberg, R. P.; Scheblien, J.; Scheetz, R.; Schlueter, R.; Schmitz, N.; Schroeder, L. S.; Schulz, M.; Schüttauf, A.; Sedlmeir, J.; Seger, J.; Seliverstov, D.; Seyboth, J.; Seyboth, P.; Seymour, R.; Shakaliev, E. I.; Shestermanov, K. E.; Shi, Y.; Shimanskii, S. S.; Shuman, D.; Shvetcov, V. S.; Skoro, G.; Smirnov, N.; Smykov, L. P.; Snellings, R.; Solberg, K.; Sowinski, J.; Spinka, H. M.; Srivastava, B.; Stephenson, E. J.; Stock, R.; Stolpovsky, A.; Stone, N.; Stone, R.; Strikhanov, M.; Stringfellow, B.; Stroebele, H.; Struck, C.; Suaide, A. A.; Sugarbaker, E.; Suire, C.; Symons, T. J.; Takahashi, J.; Tang, A. H.; Tarchini, A.; Tarzian, J.; Thomas, J. H.; Tikhomirov, V.; Szanto de Toledo, A.; Tonse, S.; Trainor, T.; Trentalange, S.; Tokarev, M.; Tonjes, M. B.; Trofimov, V.; Tsai, O.; Turner, K.; Ullrich, T.; Underwood, D. G.; Vakula, I.; van Buren, G.; Vandermolen, A. M.; Vanyashin, A.; Vasilevski, I. M.; Vasiliev, A. N.; Vigdor, S. E.; Visser, G.; Voloshin, S. A.; Vu, C.; Wang, F.; Ward, H.; Weerasundara, D.; Weidenbach, R.; Wells, R.; Wells, R.; Wenaus, T.; Westfall, G. D.; Whitfield, J. P.; Whitten, C.; Wieman, H.; Willson, R.; Wilson, K.; Wirth, J.; Wisdom, J.; Wissink, S. W.; Witt, R.; Wolf, J.; Wood, L.; Xu, N.; Xu, Z.; Yakutin, A. E.; Yamamoto, E.; Yang, J.; Yepes, P.; Yokosawa, A.; Yurevich, V. I.; Zanevski, Y. V.; Zhang, J.; Zhang, W. M.; Zhu, J.; Zimmerman, D.; Zoulkarneev, R.; Zubarev, A. N.

    2001-01-01

    Elliptic flow from nuclear collisions is a hadronic observable sensitive to the early stages of system evolution. We report first results on elliptic flow of charged particles at midrapidity in Au+Au collisions at sNN = 130 GeV using the STAR Time Projection Chamber at the Relativistic Heavy Ion Collider. The elliptic flow signal, v2, averaged over transverse momentum, reaches values of about 6% for relatively peripheral collisions and decreases for the more central collisions. This can be interpreted as the observation of a higher degree of thermalization than at lower collision energies. Pseudorapidity and transverse momentum dependence of elliptic flow are also presented.

  10. Meson interferometry in relativistic heavy ion collisions

    SciTech Connect

    Not Available

    1993-05-01

    This report contains discussions on the following topics: Recent HBT results form CERN experiment NA44; interferometry results from E802/E859/E866; recent results on two particle correlations from E814; source sizes from CERN data; intermittency and interferometry; Bose-Einstein correlations in 200A GeV S+Au collisions; HBT correlations at STAR; HBT interferometry with PHENIX; HBT calculations from ARC; three pion correlations; and pion correlations in proton-induced reactions.

  11. High-Velocity Collisions of Nanoparticles

    NASA Astrophysics Data System (ADS)

    Johnson, Donald; Mattson, William

    Nanoparticles (NPs) are interesting materials with exciting applications due to their large surface-to-volume ratio and functionalizable surfaces. The large surface area and potentially high surface tension might result in unique materials behavior when subject to shock loading. Using density functional theory, we have simulated high-velocity NP collisions producing high-pressure, high-temperature, and extreme shock conditions. NPs composed of diamond-C, cubic-BN, and diamond-Si were considered with particle sizes up to 3.5 nm diameter. Some simulations involved NPs that were destabilized by incorporating internal strain. Normal, spherical NPs were carved out of bulk crystals and structurally optimized while the NPs with internal strain were constructed as a dense core (compressive strain) encompassed by a thin shell (tensile strain). Both on-axis and off-axis collisions were simulated at various speeds. Collision dynamics, shock propagation, and fragmentation will be presented and analyzed. The effect of material properties, internal strain, and collision velocity on the final temperature of the fragments will be discussed.

  12. Kinetic effects on geodesic acoustic mode from combined collisions and impurities

    SciTech Connect

    Yang, Shangchuan; Xie, Jinlin Liu, Wandong

    2015-04-15

    The dispersion relation for geodesic acoustic mode (GAM) is derived by applying a gyrokinetic model that accounts for the effects from both collisions and impurities. Based on the dispersion relation, an analysis is performed for the non-monotonic behavior of GAM damping versus the characteristic collision rate at various impurity levels. As the effective charge increases, the maximum damping rate is found to shift towards lower collision rates, nearer to the parameter range of a typical tokamak edge plasma. The relative strengths of ion-ion and impurity-induced collision effects, which are illustrated by numerical calculations, are found to be comparable. Impurity-induced collisions help decrease the frequency of GAM, while their effects on the damping rate are non-monotonic, resulting in a weaker total damping in the high collision regime. The results presented suggest considering collision effects as well as impurity effects in GAM analysis.

  13. Dirac R-matrix collision strengths and effective collision strengths for transitions of Ni xvii

    NASA Astrophysics Data System (ADS)

    Hudson, C. E.; Norrington, P. H.; Ramsbottom, C. A.; Scott, M. P.

    2012-01-01

    Context. Electron impact excitation collision strengths are required for the analysis and interpretation of stellar observations. Aims: This calculation aims to provide fine structure effective collision strengths for the Ni xvii ion using a method which includes contributions from resonances. Methods: A fully relativistic R-matrix calculation has been performed using the DARC code. In the structure part of our calculation 141 fine-structure levels are employed and 37 of these are used in the scattering calculation. Results: Collision strengths have been determined for 666 fine-structure transitions arising from the 37 lowest j-levels involving configurations 3s2, 3p2, 3d2, 3s3p, 3s3d, 3p3d and 3s4s. The effective collision strengths for these transitions have been calculated for electron temperatures (Te) in the range log 10Te(K) = 4.5 - 8.0. Effective collision strengths are tabulated for transitions between the first ten fine structure levels, arising from the 3s2, 3s3p and 3p2 configurations. The remaining transitions are available at the CDS as well as via the author's website. Tables 2 and 5 are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/537/A12

  14. Experimental observation of the collision of three vortex rings

    NASA Astrophysics Data System (ADS)

    Hernández, R. H.; Monsalve, E.

    2015-06-01

    We investigate for the first time the motion, interaction and simultaneous collision between three initially stable vortex rings arranged symmetrically, making an angle of 120 degrees between their straight path lines. We report results with laminar vortex rings in air and water obtained through measurements of the ring velocity field with a hot-wire anemometer, both in free flight and during the entire collision. In the air experiment, our flow visualizations allowed us to identify two main collision stages. A first ring-dominated stage where the rings slowdown progressively, increasing their diameter rapidly, followed by secondary vortex structures resulting after the rings make contact. Local portions of the vortex tubes of opposite circulation are coupled together thus creating local arm-like vortex structures moving radially in outward directions, rapidly dissipating kinetic energy. From a similar water experiment, we provide detailed shadowgraph visualizations of both the ring bubble and the full size collision, showing clearly the final expanding vortex structure. It is accurately resolved that the physical contact between vortex ring tubes gives rise to three symmetric expanding vortex arms but also the vortex reconnection of the top and lower vortex tubes. The central collision zone was found to have the lowest kinetic energy during the entire collision and therefore it can be identified as a safe zone. The preserved collision symmetries leading to the weak kinematic activity in the safe zone is the first step into the development of an intermittent hydrodynamic trap for small and lightweight particles.

  15. Sensor-Based Collision Avoidance: Theory and Experiments

    NASA Technical Reports Server (NTRS)

    Seraji, Homayoun; Steele, Robert; Ivlev, Robert

    1996-01-01

    A new on-line control strategy for sensor-based collision avoidance of manipulators and supporting experimental results are presented in this article. This control strategy is based on nullification of virtual forces applied to the end-effector by a hypothetical spring-plus-damper attached to the object's surface. In the proposed approach, the real-time arm control software continuously monitors the object distance measured by the arm-mounted proximity sensors. When this distance is less than a preset threshold, the collision avoidance control action is initiated to inhibit motion toward the object and thus prevent collision. This is accomplished by employing an outer feedback loop to perturb the end-effector nominal motion trajectory in real-time based on the sensory data. The perturbation is generated by a proportional-plus-integral (PI) collision avoidance controller acting on the difference between the sensed distance and the preset threshold. This approach is computationally very fast, requires minimal modification to the existing manipulator positioning system, and provides the manipulator with an on-line collision avoidance capability to react autonomously and intelligently. A dexterous RRC robotic arm is instrumented with infrared proximity sensors and is operated under the proposed collision avoidance strategy. Experimental results are presented to demonstrate end-effector collision avoidance both with an approaching object and while reaching inside a constricted opening.

  16. Human performance models and rear-end collision avoidance algorithms.

    PubMed

    Brown, T L; Lee, J D; McGehee, D V

    2001-01-01

    Collision warning systems offer a promising approach to mitigate rear-end collisions, but substantial uncertainty exists regarding the joint performance of the driver and the collision warning algorithms. A simple deterministic model of driver performance was used to examine kinematics-based and perceptual-based rear-end collision avoidance algorithms over a range of collision situations, algorithm parameters, and assumptions regarding driver performance. The results show that the assumptions concerning driver reaction times have important consequences for algorithm performance, with underestimates dramatically undermining the safety benefit of the warning. Additionally, under some circumstances, when drivers rely on the warning algorithms, larger headways can result in more severe collisions. This reflects the nonlinear interaction among the collision situation, the algorithm, and driver response that should not be attributed to the complexities of driver behavior but to the kinematics of the situation. Comparisons made with experimental data demonstrate that a simple human performance model can capture important elements of system performance and complement expensive human-in-the-loop experiments. Actual or potential applications of this research include selection of an appropriate algorithm, more accurate specification of algorithm parameters, and guidance for future experiments.

  17. Spin Changing Collisions of Hydrogen

    NASA Technical Reports Server (NTRS)

    Zygelman, Bernard

    2006-01-01

    We discuss spin changing collisions of hydrogen atoms. Employing a fully quantal theory we calculate and present new collision data. We discuss the respective roles of spin exchange and long range magnetic interactions in collisonal redistribution of sub-level populations. The calculated atomic data is needed for accurate modeling of 21 cm line emission/absorption by primordial hydrogen in the early universe.

  18. Electron Collisions with Hydrogen Fluoride

    NASA Astrophysics Data System (ADS)

    Itikawa, Yukikazu

    2017-03-01

    Cross section data are reviewed for electron collisions with hydrogen fluoride. Collision processes considered are total scattering, elastic scattering, excitations of rotational, vibrational, and electronic states, ionization, and dissociative electron attachment. After a survey of the literature, recommended values of the cross sections are determined, as far as possible.

  19. Collision in space

    NASA Technical Reports Server (NTRS)

    Ellis, S. R.

    2000-01-01

    On June 25, 1997, the Russian supply spacecraft Progress 234 collided with the Mir space station, rupturing Mir's pressure hull, throwing it into an uncontrolled attitude drift, and nearly forcing evacuation of the station. Like many high-profile accidents, this collision was the consequence of a chain of events leading to the final piloting errors that were its immediate cause. The discussion in this article does not resolve the relative contributions of the actions and decisions in this chain. Neither does it suggest corrective measures, many of which are straightforward and have already been implemented by the National Aeronautics and Space Administration (NASA) and the Russian Space Agency. Rather, its purpose is to identify the human factors that played a pervasive role in the incident. Workplace stress, fatigue, and sleep deprivation were identified by NASA as contributory factors in the Mir-Progress collision (Culbertson, 1997; NASA, forthcoming), but other contributing factors, such as requiring crew to perform difficult tasks for which their training is not current, could potentially become important factors in future situations.

  20. Collision in space.

    PubMed

    Ellis, S R

    2000-01-01

    On June 25, 1997, the Russian supply spacecraft Progress 234 collided with the Mir space station, rupturing Mir's pressure hull, throwing it into an uncontrolled attitude drift, and nearly forcing evacuation of the station. Like many high-profile accidents, this collision was the consequence of a chain of events leading to the final piloting errors that were its immediate cause. The discussion in this article does not resolve the relative contributions of the actions and decisions in this chain. Neither does it suggest corrective measures, many of which are straightforward and have already been implemented by the National Aeronautics and Space Administration (NASA) and the Russian Space Agency. Rather, its purpose is to identify the human factors that played a pervasive role in the incident. Workplace stress, fatigue, and sleep deprivation were identified by NASA as contributory factors in the Mir-Progress collision (Culbertson, 1997; NASA, forthcoming), but other contributing factors, such as requiring crew to perform difficult tasks for which their training is not current, could potentially become important factors in future situations.

  1. Continuum modeling of catastrophic collisions

    NASA Technical Reports Server (NTRS)

    Ryan, Eileen V.; Aspaug, Erik; Melosh, H. J.

    1991-01-01

    A two dimensional hydrocode based on 2-D SALE was modified to include strength effects and fragmentation equations for fracture resulting from tensile stress in one dimension. Output from this code includes a complete fragmentation summary for each cell of the modeled object: fragment size (mass) distribution, vector velocities of particles, peak values of pressure and tensile stress, and peak strain rates associated with fragmentation. Contour plots showing pressure and temperature at given times within the object are also produced. By invoking axial symmetry, three dimensional events can be modeled such as zero impact parameter collisions between asteroids. The code was tested against the one dimensional model and the analytical solution for a linearly increasing tensile stress under constant strain rate.

  2. Real-Time Collision Avoidance for Dexterous 7-DOF Arms

    NASA Technical Reports Server (NTRS)

    Bon, Bruce; Seraji, Homayoun

    1996-01-01

    A new approach to real-time collison avoidance for dexterous 7-DOF arms and supportive simulation and experimental results are presented. The collision avoidance problem is formulated and solved as a force control problem.

  3. Heavy-particle collisions and quantum optics: The parabolic noncrossing model

    SciTech Connect

    Nesbitt, B.S.; Crothers, D.S.; ORourke, S.F.; Berman, P.R.

    1997-08-01

    The problem of deriving analytic formulas for transition probabilities in two-level systems is studied. The two-level systems are described by a pair of first-order differential equations coupled by a time-dependent potential. One such model is given by da{sub m}/dt={minus}i{beta}f(t)a{sub n}e{sup ({minus}1){sup n}i{alpha}t} (m,n=1,2; m{ne}/n), which describes certain types of ion-atom collisions and some quantum-optics two-level problems. It will be shown that the correct approach in solving the coupled equations is to adopt a Zwaan-Stueckelberg phase-integral analysis of the four-transition-point problem based on the parabolic noncrossing model of Crothers [J. Phys. B {bold 9}, 635 (1976)]. Alternatively, one may obtain an approximation by employing adiabatic perturbation theory, but such an approach can at best provide only weak-coupling solutions and can never guarantee unitarity in the probability amplitudes. The advantage of the phase-integral method is that it produces a strong-coupling approximation by embracing the appropriate asymptotic expansions for cylinder functions of large order and argument [D. S. F. Crothers, J. Phys. A {bold 5}, 1680 (1972)] and it also ensures analyticity, unitarity, and symmetry. {copyright} {ital 1997} {ital The American Physical Society}

  4. Division B Commission 14 Working Group: Collision Processes

    NASA Astrophysics Data System (ADS)

    Peach, Gillian; Dimitrijevic, Milan S.; Barklem, Paul S.

    2016-04-01

    Since our last report (Peach & Dimitrijević 2012), a large number of new publications on the results of research in atomic and molecular collision processes and spectral line broadening have been published. Due to the limited space available, we have only included work of importance for astrophysics. Additional relevant papers, not included in this report, can be found in the databases at the web addresses provided in Section 6. Elastic and inelastic collisions between electrons, atoms, ions, and molecules are included, as well as charge transfer in collisions between heavy particles which can be very important.

  5. Universal strangeness production in hadronic and nuclear collisions

    NASA Astrophysics Data System (ADS)

    Castorina, P.; Plumari, S.; Satz, H.

    2016-07-01

    We show that strangeness suppression in hadronic and nuclear collisions is fully determined by the initial energy density of the collision. The suppression factor γs(s), with s denoting the collision energy, can be expressed as a universal function of the initial energy density ɛ0(s), and the resulting pattern is in excellent agreement with data from p-p, p-Pb, Cu-Cu, Au-Au and Pb-Pb data over a wide range of energies and for different centralities.

  6. A space-based concept for a collision warning sensor

    NASA Technical Reports Server (NTRS)

    Talent, David L.; Vilas, Faith

    1990-01-01

    This paper describes a concept for a space-based collision warning sensor experiment, the Debris Collision Warning Sensor (DCWS) experiment, in which the sensor will rely on passive sensing of debris in optical and IR passband. The DCWS experiment will be carried out under various conditions of solar phase angle and pass geometry; debris from 1.5 m to 1 mm diam will be observable. The mission characteristics include inclination in the 55-60 deg range and an altitude of about 500 km. The results of the DCWS experiment will be used to generate collision warning scenarios for the Space Station Freedom.

  7. Determination of electron-nucleus collisions geometry with forward neutrons

    DOE PAGES

    Zheng, L.; Aschenauer, E.; Lee, J. H.

    2014-12-29

    There are a large number of physics programs one can explore in electron-nucleus collisions at a future electron-ion collider. Collision geometry is very important in these studies, while the measurement for an event-by-event geometric control is rarely discussed in the prior deep-inelastic scattering experiments off a nucleus. This paper seeks to provide some detailed studies on the potential of tagging collision geometries through forward neutron multiplicity measurements with a zero degree calorimeter. As a result, this type of geometry handle, if achieved, can be extremely beneficial in constraining nuclear effects for the electron-nucleus program at an electron-ion collider.

  8. The nature of mutations induced by replication–transcription collisions.

    PubMed

    Sankar, T Sabari; Wastuwidyaningtyas, Brigitta D; Dong, Yuexin; Lewis, Sarah A; Wang, Jue D

    2016-07-07

    The DNA replication and transcription machineries share a common DNA template and thus can collide with each other co-directionally or head-on. Replication–transcription collisions can cause replication fork arrest, premature transcription termination, DNA breaks, and recombination intermediates threatening genome integrity. Collisions may also trigger mutations, which are major contributors to genetic disease and evolution. However, the nature and mechanisms of collision-induced mutagenesis remain poorly understood. Here we reveal the genetic consequences of replication–transcription collisions in actively dividing bacteria to be two classes of mutations: duplications/deletions and base substitutions in promoters. Both signatures are highly deleterious but are distinct from the previously well-characterized base substitutions in the coding sequence. Duplications/deletions are probably caused by replication stalling events that are triggered by collisions; their distribution patterns are consistent with where the fork first encounters a transcription complex upon entering a transcription unit. Promoter substitutions result mostly from head-on collisions and frequently occur at a nucleotide that is conserved in promoters recognized by the major σ factor in bacteria. This substitution is generated via adenine deamination on the template strand in the promoter open complex, as a consequence of head-on replication perturbing transcription initiation. We conclude that replication–transcription collisions induce distinct mutation signatures by antagonizing replication and transcription, not only in coding sequences but also in gene regulatory elements.

  9. The Nature of Mutations Induced by Replication-Transcription Collisions

    PubMed Central

    Sankar, T. Sabari; Wastuwidyaningtyas, Brigitta D.; Dong, Yuexin; Lewis, Sarah A.; Wang, Jue D.

    2016-01-01

    Summary The DNA replication and transcription machineries share a common DNA template and thus can collide with each other co-directionally or head-on1,2. Replication-transcription collisions can cause replication fork arrest, premature transcription termination, DNA breaks, and recombination intermediates threatening genome integrity1–10. Collisions may also trigger mutations, which are major contributors of genetic disease and evolution5,7,11. However, the nature and mechanisms of collision-induced mutagenesis remain poorly understood. Here we reveal the genetic consequence of replication-transcription collisions in actively dividing bacteria to be two classes of mutations: duplications/deletions and base substitutions in promoters. Both signatures are highly deleterious but are distinct from the well-characterized base substitutions in coding sequence. Duplications/deletions are likely caused by replication stalling events that are triggered by collisions; their distribution patterns are consistent with where the fork first encounters a transcription complex upon entering a transcription unit. Promoter substitutions result mostly from head-on collisions and frequently occur at a nucleotide conserved in promoters recognized by the major sigma factor in bacteria. This substitution is generated via adenine deamination on the template strand in the promoter open complex, as a consequence of head-on replication perturbing transcription initiation. We conclude that replication-transcription collisions induce distinct mutation signatures by antagonizing replication and transcription, not only in coding sequences but also in gene regulatory elements. PMID:27362223

  10. Azimuthal anisotropy in U+U collisions at STAR

    SciTech Connect

    Wang, Hui; Sorensen, Paul

    2014-10-06

    The azimuthal anisotropy of particle production is commonly used in high-energy nuclear collisions to study the early evolution of the expanding system. The prolate shape of uranium nuclei makes it possible to study how the geometry of the colliding nuclei affects final state anisotropies. It also provides a unique opportunity to understand how entropy is produced in heavy ion collisions. In this paper, the two- and four- particle cumulant v2 (v2{2} and v2{4}) from U+U collisions at √sNN = 193 GeV and Au+Au collisions at √sNN = 200 GeV for inclusive charged hadrons will be presented. The STAR Zero Degree Calorimeters are used to select very central collisions. Differences were observed between the multiplicity dependence of v2{2} for most central Au+Au and U+U collisions. The multiplicity dependence of v2{2} in central collisions were compared to Monte Carlo Glauber model predictions and it was seen that this model cannot explain the present results. (auth)

  11. Azimuthal anisotropy in U+U collisions at STAR

    DOE PAGES

    Wang, Hui; Sorensen, Paul

    2014-10-06

    The azimuthal anisotropy of particle production is commonly used in high-energy nuclear collisions to study the early evolution of the expanding system. The prolate shape of uranium nuclei makes it possible to study how the geometry of the colliding nuclei affects final state anisotropies. It also provides a unique opportunity to understand how entropy is produced in heavy ion collisions. In this paper, the two- and four- particle cumulant v2 (v2{2} and v2{4}) from U+U collisions at √sNN = 193 GeV and Au+Au collisions at √sNN = 200 GeV for inclusive charged hadrons will be presented. The STAR Zero Degreemore » Calorimeters are used to select very central collisions. Differences were observed between the multiplicity dependence of v2{2} for most central Au+Au and U+U collisions. The multiplicity dependence of v2{2} in central collisions were compared to Monte Carlo Glauber model predictions and it was seen that this model cannot explain the present results. (auth)« less

  12. Molecular Dissociation Induced by Electron Collisions

    NASA Astrophysics Data System (ADS)

    Wolf, Andreas

    2009-05-01

    Free electrons can efficiently break molecules or molecular ions in low-energy collisions by the processes of dissociative recombination or attachment. These processes make slow electrons efficient chemical agents in many environments. For dissociative recombination, in particular, studies of the underlying reaction paths and mechanisms have become possible on a uniquely elementary level in recent years both for theory and experiment. On the experimental side, collisions can be prepared at resolved collision energies down to the meV (10 Kelvin) level, increasingly gaining control also over the initial molecular quantum level, and individual events are detected and kinematically analyzed by fast-beam coincidence fragment imaging. Experiments are reported from the ion cooler ring TSR in Heidelberg. Stored beams of molecular ions cooled in their external and internal degrees of freedom are collinearly merged with intense and cold electron beams from cryogenic GaAs photocathodes, recently shown to yield fast cooling of the center-of-mass motion also for heavy and correspondingly slow molecular ion beams. To reconstruct the molecular fragmentation events multiparticle imaging can now be used systematically with collision energies set a wide range, especially aiming at specific electron capture resonances. Thus, for CF^+ it is found that the electronic state of the C fragment (^3P or ^1D) switches resonantly when the collision energy is changed by only a small fraction. As a new powerful tool, an energy-sensitive multi-strip surface-barrier detector (EMU) has been set up to measure with near-unity efficiency the masses of all fragments together with their hit positions in high-multiplicity events. Among many uses, this device allows internal molecular excitations to be derived for individual chemical channels in polyatomic fragmentation. New results will be presented in particular on the breakup of the hydronium ion (D3O^+).

  13. Femtoscopy in Relativistic Heavy Ion Collisions

    SciTech Connect

    Lisa, M; Pratt, S; Soltz, R A; Wiedemann, U

    2005-07-29

    Analyses of two-particle correlations have provided the chief means for determining spatio-temporal characteristics of relativistic heavy ion collisions. We discuss the theoretical formalism behind these studies and the experimental methods used in carrying them out. Recent results from RHIC are put into context in a systematic review of correlation measurements performed over the past two decades. The current understanding of these results are discussed in terms of model comparisons and overall trends.

  14. Collisions of Planetesimals and Formation of Planets

    NASA Astrophysics Data System (ADS)

    Dvorak, Rudolf; Maindl, Thomas I.; Süli, Áron; Schäfer, Christoph M.; Speith, Roland; Burger, Christoph

    2016-01-01

    We present preliminary results of models of terrestrial planet formation using on the one hand classical numerical integration of hundreds of small bodies on CPUs and on the other hand-for comparison-the results of our GPU code with thousands of small bodies which then merge to larger ones. To be able to determine the outcome of collision events we use our smooth particle hydrodynamics (SPH) code which tracks how water is lost during such events.

  15. Bulk viscosity of multiparticle collision dynamics fluids.

    PubMed

    Theers, Mario; Winkler, Roland G

    2015-03-01

    We determine the viscosity parameters of the multiparticle collision dynamics (MPC) approach, a particle-based mesoscale hydrodynamic simulation method for fluids. We perform analytical calculations and verify our results by simulations. The stochastic rotation dynamics and the Andersen thermostat variant of MPC are considered, both with and without angular momentum conservation. As an important result, we find a nonzero bulk viscosity for every MPC version. The explicit calculation shows that the bulk viscosity is determined solely by the collisional interactions of MPC.

  16. Systematics of Global Observables in Cu+Cu and Au+Au Collisions at RHIC Energies

    SciTech Connect

    Nouicer, Rachid

    2006-07-11

    Charged particles produced in Cu+Cu collisions at {radical}(s{sub NN}) = 200 and 62.4 GeV have been measured in the PHOBOS experiment at RHIC. The comparison of the results for Cu+Cu and Au+Au for the most central collisions at the same energy reveals that the particle density per nucleon participant pair and the extended longitudinal scaling behavior are similar in both systems. This implies that for the most central events in symmetric nucleus-nucleus collisions the particle density per nucleon participant pair does not depend on the size of the two colliding nuclei but only on the collision energy. Also the extended longitudinal scaling seems independent of the colliding energy and species for central collisions. In addition, there is an overall factorization of dNch/d{eta} shapes as a function of collision centraliry between Au+Au and Cu+Cu collisions at the same energy.

  17. Effect of velocity-changing collisions on the output of a gas laser.

    NASA Technical Reports Server (NTRS)

    Borenstein, M.; Lamb, W. E., Jr.

    1972-01-01

    A theoretical model for the pressure dependence of the intensity of a gas laser is presented in which only velocity-changing collisions with foreign-gas atoms are included. This is a special case where the phase shifts are the same for the two atomic-laser levels or are so small that deflections are the dominant effect of collisions. A collision model for hard-sphere repulsive interactions is derived and the collision parameters, persistence of velocity and collision frequency, are assumed to be independent of velocity. The collision theory is applied to a third-order expansion of the polarization in powers of the cavity electric field (weak-signal theory). The resulting expression for the intensity shows strong pressure dependence. The collisions reduce the amount of saturation and the laser intensity increases with pressure in a characteristic fashion.

  18. Burnup calculation by the method of first-flight collision probabilities using average chords prior to the first collision

    NASA Astrophysics Data System (ADS)

    Karpushkin, T. Yu.

    2012-12-01

    A technique to calculate the burnup of materials of cells and fuel assemblies using the matrices of first-flight neutron collision probabilities rebuilt at a given burnup step is presented. A method to rebuild and correct first collision probability matrices using average chords prior to the first neutron collision, which are calculated with the help of geometric modules of constructed stochastic neutron trajectories, is described. Results of calculation of the infinite multiplication factor for elementary cells with a modified material composition compared to the reference one as well as calculation of material burnup in the cells and fuel assemblies of a VVER-1000 are presented.

  19. An Approach Toward Understanding Wildlife-Vehicle Collisions

    NASA Astrophysics Data System (ADS)

    Litvaitis, John A.; Tash, Jeffrey P.

    2008-10-01

    Among the most conspicuous environmental effects of roads are vehicle-related mortalities of wildlife. Research to understand the factors that contribute to wildlife-vehicle collisions can be partitioned into several major themes, including (i) characteristics associated with roadkill hot spots, (ii) identification of road-density thresholds that limit wildlife populations, and (iii) species-specific models of vehicle collision rates that incorporate information on roads (e.g., proximity, width, and traffic volume) and animal movements. We suggest that collision models offer substantial opportunities to understand the effects of roads on a diverse suite of species. We conducted simulations using collision models and information on Blanding’s turtles ( Emydoidea blandingii), bobcats ( Lynx rufus), and moose ( Alces alces), species endemic to the northeastern United States that are of particular concern relative to collisions with vehicles. Results revealed important species-specific differences, with traffic volume and rate of movement by candidate species having the greatest influence on collision rates. We recommend that future efforts to reduce wildlife-vehicle collisions be more proactive and suggest the following protocol. For species that pose hazards to drivers (e.g., ungulates), identify collision hot spots and implement suitable mitigation to redirect animal movements (e.g., underpasses, fencing, and habitat modification), reduce populations of problematic game species via hunting, or modify driver behavior (e.g., dynamic signage that warns drivers when animals are near roads). Next, identify those species that are likely to experience additive (as opposed to compensatory) mortality from vehicle collisions and rank them according to vulnerability to extirpation. Then combine information on the distribution of at-risk species with information on existing road networks to identify areas where immediate actions are warranted.

  20. Comparison of measured and calculated collision efficiencies at low temperatures

    NASA Astrophysics Data System (ADS)

    Nagare, B.; Marcolli, C.; Stetzer, O.; Lohmann, U.

    2015-12-01

    Interactions of atmospheric aerosols with clouds influence cloud properties and modify the aerosol life cycle. Aerosol particles act as cloud condensation nuclei and ice nucleating particles or become incorporated into cloud droplets by scavenging. For an accurate description of aerosol scavenging and ice nucleation in contact mode, collision efficiency between droplets and aerosol particles needs to be known. This study derives the collision rate from experimental contact freezing data obtained with the ETH CoLlision Ice Nucleation CHamber (CLINCH). Freely falling 80 μm diameter water droplets are exposed to an aerosol consisting of 200 and 400 nm diameter silver iodide particles of concentrations from 500 to 5000 and 500 to 2000 cm-3, respectively, which act as ice nucleating particles in contact mode. The experimental data used to derive collision efficiency are in a temperature range of 238-245 K, where each collision of silver iodide particles with droplets can be assumed to result in the freezing of the droplet. An upper and lower limit of collision efficiency is also estimated for 800 nm diameter kaolinite particles. The chamber is kept at ice saturation at a temperature range of 236 to 261 K, leading to the slow evaporation of water droplets giving rise to thermophoresis and diffusiophoresis. Droplets and particles bear charges inducing electrophoresis. The experimentally derived collision efficiency values of 0.13, 0.07 and 0.047-0.11 for 200, 400 and 800 nm particles are around 1 order of magnitude higher than theoretical formulations which include Brownian diffusion, impaction, interception, thermophoretic, diffusiophoretic and electric forces. This discrepancy is most probably due to uncertainties and inaccuracies in the description of thermophoretic and diffusiophoretic processes acting together. This is, to the authors' knowledge, the first data set of collision efficiencies acquired below 273 K. More such experiments with different droplet and

  1. Collision avoidance sensor skin

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The objective was to totally eliminate the possibility of a robot (or any mechanism for that matter) inducing a collision in space operations. We were particularly concerned that human beings were safe under all circumstances. This was apparently accomplished, and it is shown that GSFC has a system that is ready for space qualification and flight. However, it soon became apparent that much more could be accomplished with this technology. Payloads could be made invulnerable to collision avoidance and the blind spots behind them eliminated. This could be accomplished by a simple, non-imaging set of 'Capaciflector' sensors on each payload. It also is evident that this system could be used to align and dock the system with a wide margin of safety. Throughout, lighting problems could be ignored, and unexpected events and modeling errors taken in stride. At the same time, computational requirements would be reduced. This can be done in a simple, rugged, reliable manner that will not disturb the form factor of space systems. It will be practical for space applications. The lab experiments indicate we are well on the way to accomplishing this. Still, the research trail goes deeper. It now appears that the sensors can be extended to end effectors to provide precontact information and make robot docking (or any docking connection) very smooth, with minimal loads impacted back into the mating structures. This type of ability would be a major step forward in basic control techniques in space. There are, however, baseline and restructuring issues to be tackled. The payloads must get power and signals to them from the robot or from the astronaut servicing tool. This requires a standard electromechanical interface. Any of several could be used. The GSFC prototype shown in this presentation is a good one. Sensors with their attendant electronics must be added to the payloads, end effectors, and robot arms and integrated into the system.

  2. Patterns of bird-window collisions inform mitigation on a university campus.

    PubMed

    Ocampo-Peñuela, Natalia; Winton, R Scott; Wu, Charlene J; Zambello, Erika; Wittig, Thomas W; Cagle, Nicolette L

    2016-01-01

    Bird-window collisions cause an estimated one billion bird deaths annually in the United States. Building characteristics and surrounding habitat affect collision frequency. Given the importance of collisions as an anthropogenic threat to birds, mitigation is essential. Patterned glass and UV-reflective films have been proven to prevent collisions. At Duke University's West campus in Durham, North Carolina, we set out to identify the buildings and building characteristics associated with the highest frequencies of collisions in order to propose a mitigation strategy. We surveyed six buildings, stratified by size, and measured architectural characteristics and surrounding area variables. During 21 consecutive days in spring and fall 2014, and spring 2015, we conducted carcass surveys to document collisions. In addition, we also collected ad hoc collision data year-round and recorded the data using the app iNaturalist. Consistent with previous studies, we found a positive relationship between glass area and collisions. Fitzpatrick, the building with the most window area, caused the most collisions. Schwartz and the Perk, the two small buildings with small window areas, had the lowest collision frequencies. Penn, the only building with bird deterrent pattern, caused just two collisions, despite being almost completely made out of glass. Unlike many research projects, our data collection led to mitigation action. A resolution supported by the student government, including news stories in the local media, resulted in the application of a bird deterrent film to the building with the most collisions: Fitzpatrick. We present our collision data and mitigation result to inspire other researchers and organizations to prevent bird-window collisions.

  3. Patterns of bird-window collisions inform mitigation on a university campus

    PubMed Central

    Winton, R. Scott; Wu, Charlene J.; Zambello, Erika; Wittig, Thomas W.; Cagle, Nicolette L.

    2016-01-01

    Bird-window collisions cause an estimated one billion bird deaths annually in the United States. Building characteristics and surrounding habitat affect collision frequency. Given the importance of collisions as an anthropogenic threat to birds, mitigation is essential. Patterned glass and UV-reflective films have been proven to prevent collisions. At Duke University’s West campus in Durham, North Carolina, we set out to identify the buildings and building characteristics associated with the highest frequencies of collisions in order to propose a mitigation strategy. We surveyed six buildings, stratified by size, and measured architectural characteristics and surrounding area variables. During 21 consecutive days in spring and fall 2014, and spring 2015, we conducted carcass surveys to document collisions. In addition, we also collected ad hoc collision data year-round and recorded the data using the app iNaturalist. Consistent with previous studies, we found a positive relationship between glass area and collisions. Fitzpatrick, the building with the most window area, caused the most collisions. Schwartz and the Perk, the two small buildings with small window areas, had the lowest collision frequencies. Penn, the only building with bird deterrent pattern, caused just two collisions, despite being almost completely made out of glass. Unlike many research projects, our data collection led to mitigation action. A resolution supported by the student government, including news stories in the local media, resulted in the application of a bird deterrent film to the building with the most collisions: Fitzpatrick. We present our collision data and mitigation result to inspire other researchers and organizations to prevent bird-window collisions. PMID:26855877

  4. Geometrical methods in heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Taliotis, Anastasios

    -shock wave. We show in explicit detail that in the boundary theory the proton is completely stopped by strong-coupling interactions with the nucleus, in agreement with our LO, NLO and NNLO results. In all the previous calculations, the incident nuclei are assumed to have a constant Tmunu on the transverse plane. Improving the earlier works in the literature, we then assume that the two nuclei have a non-trivial transverse profile and collide wit an impact parameter b. The nuclear matter is modeled by two shock waves corresponding to a non-zero five dimensional bulk Stress-Energy Tensor JMN . An analytic formula for Tmunu at small tau is derived and is used in order to calculate the energy density, the momentum anisotropy and the spatial eccentricity of the medium produced in the collision. The results agree qualitatively with the results obtained in the context of perturbation theory and by using hydrodynamic simulations.

  5. Collisions in the Oort Cloud

    SciTech Connect

    Stern, S.A.

    1988-03-01

    The present assessment of the consequentiality of physical collisions between Oort Cloud objects by a first-generation model indicates that natural power-law population structures produce significant numbers of collisions between each comet and smaller objects over the age of the solar system. These collisions are held to constitute a feedback mechanism for small debris production. The impacts yield extensive comet surface evolution in the cloud, in conditions where the number of small orbiting objects conforms to the standard power-law populations. 16 references.

  6. A collision tumor of esophagus.

    PubMed

    Yao, Bin; Guan, Shanghui; Huang, Xiaochen; Su, Peng; Song, Qingxu; Cheng, Yufeng

    2015-01-01

    The collision tumor is defined by Meyer as that arisen from the accidental meeting and eventual intermingling of two independent neoplasms, which is quite rare. Most of them occur in the junction of different epithelial types of tissue such as oral cavity, esophagogastric junction, anorectaljunction and cervix, while collision tumors occurring in the liver, gallbladder, pancreatic, urinary bladder also have been reported. Here we present a case of 55-year-old Chinese man diagnosed as a collision tumor composed of leiomyosarcoma and squamous cell carcinoma (SqCC) in the lower third part of esophagus with 6 years survival after surgery and radiotherapy.

  7. Control of Ultracold Collisions with Frequency-Chirped Light

    SciTech Connect

    Wright, M.J.; Gould, P.L.; Gensemer, S.D.; Vala, J.; Kosloff, R.

    2005-08-05

    We report on ultracold atomic collision experiments utilizing frequency-chirped laser light. A rapid chirp below the atomic resonance results in adiabatic excitation to an attractive molecular potential over a wide range of internuclear separation. This leads to a transient inelastic collision rate which is large compared to that obtained with fixed-frequency excitation. The combination of high efficiency and temporal control demonstrates the benefit of applying the techniques of coherent control to the ultracold domain.

  8. High p{sub T} jet production in pp collisions

    SciTech Connect

    Eskola, K.J.; Wang, X.N.

    1995-07-01

    Production rates of large p{sub T} jets in pp collisions at RHIC and LHC energies are studied using the next-to-leading order calculation of S. D. Ellis, Z. Zunszt and D. Soper. The computed inclusive one-jet cross sections are compared against the CERN and Fermilab jet data from p{bar p} and pp collisions. The dependence of the results on the choice of the parton distributions and renormalization/factorization scales is investigated.

  9. A virtual simulator designed for collision prevention in proton therapy

    SciTech Connect

    Jung, Hyunuk; Kum, Oyeon; Han, Youngyih Park, Hee Chul; Kim, Jin Sung; Choi, Doo Ho

    2015-10-15

    Purpose: In proton therapy, collisions between the patient and nozzle potentially occur because of the large nozzle structure and efforts to minimize the air gap. Thus, software was developed to predict such collisions between the nozzle and patient using treatment virtual simulation. Methods: Three-dimensional (3D) modeling of a gantry inner-floor, nozzle, and robotic-couch was performed using SolidWorks based on the manufacturer’s machine data. To obtain patient body information, a 3D-scanner was utilized right before CT scanning. Using the acquired images, a 3D-image of the patient’s body contour was reconstructed. The accuracy of the image was confirmed against the CT image of a humanoid phantom. The machine components and the virtual patient were combined on the treatment-room coordinate system, resulting in a virtual simulator. The simulator simulated the motion of its components such as rotation and translation of the gantry, nozzle, and couch in real scale. A collision, if any, was examined both in static and dynamic modes. The static mode assessed collisions only at fixed positions of the machine’s components, while the dynamic mode operated any time a component was in motion. A collision was identified if any voxels of two components, e.g., the nozzle and the patient or couch, overlapped when calculating volume locations. The event and collision point were visualized, and collision volumes were reported. Results: All components were successfully assembled, and the motions were accurately controlled. The 3D-shape of the phantom agreed with CT images within a deviation of 2 mm. Collision situations were simulated within minutes, and the results were displayed and reported. Conclusions: The developed software will be useful in improving patient safety and clinical efficiency of proton therapy.

  10. Thinking Problems of the Present Collision Warning Work by Analyzing the Intersection Between Cosmos 2251 and Iridium 33

    NASA Astrophysics Data System (ADS)

    Wang, R. L.; Liu, W.; Yan, R. D.; Gong, J. C.

    2013-08-01

    After Cosmos 2251 and Iridium 33 collision breakup event, the institutions at home and abroad began the collision warning analysis for the event. This paper compared the results from the different research units and discussed the problems of the current collision warning work, then gave the suggestions of further study.

  11. Theoretical studies of molecular collisions

    NASA Technical Reports Server (NTRS)

    Kouri, Donald J.

    1991-01-01

    The following subject areas are covered: (1) total integral reactive cross sections and vibrationally resolved reaction probabilities for F + H2 = HF + H; (2) a theoretical study of inelastic O + N2 collisions; (3) body frame close coupling wave packet approach to gas phase atom-rigit rotor inelastic collisions; (4) wave packet study of gas phase atom-rigit motor scattering; (5) the application of optical potentials for reactive scattering; (6) time dependent, three dimensional body frame quantal wave packet treatment of the H + H2 exchange reaction; (7) a time dependent wave packet approach to atom-diatom reactive collision probabilities; (8) time dependent wave packet for the complete determination of s-matrix elements for reactive molecular collisions in three dimensions; (9) a comparison of three time dependent wave packet methods for calculating electron-atom elastic scattering cross sections; and (10) a numerically exact full wave packet approach to molecule-surface scattering.

  12. Continental collisions and seismic signature

    NASA Astrophysics Data System (ADS)

    Meissner, R.; Wever, Th.; Sadowiak, P.

    1991-04-01

    Reflection seismics in compressional belts has revealed the structure of crustal shortening and thickening processes, showing complex patterns of indentation and interfingering of colliding crusts and subcrustal lithospheres. Generally, in the upper crust large zones of detachments develop, often showing duplexes and 'crocodile' structures. The lower crust from zones of active collision (e.g. Alps, Pyrenees) is characterized by strongly dipping reflections. The base of the crust with the Moho must be continuously equilibrating after orogenic collapse as areas of former continental collision exhibit flat Mohos and subhorizontal reflections. The depth to the Moho increases during collision and decreases after the onset of post-orogenic extension, until finally the crustal root disappears completely together with the erosion of the mountains. Processes, active during continental collisions and orogenic collapse, create distinct structures which are imaged by reflection seismic profiling. Examples are shown and discussed.

  13. Milky Way's Head On Collision

    NASA Video Gallery

    This animation depicts the collision between our Milky Way galaxy and the Andromeda galaxy. Hubble Space Telescope observations indicate that the two galaxies, pulled together by their mutual gravi...

  14. The roads ahead: collision risks, trends, and safety of drivers.

    PubMed

    Straus, Sandy Helene; Gu, Xiaojun

    2009-06-01

    The propensity of fatal traffic collisions transcends driver age and reinforces the need to evaluate, among other factors, the impact of roadway lighting and other features of driver vision, perception, and performance. Collisions may result from a driver's inability to notice delineation, recognize warnings, and other possible road safety controls during various lighting conditions. Hence we compare the relative accident involvement ratio (RAIR) of collisions of millions of drivers from two U.S. States over an 11-year period, 1991-2001. We associate collision trends through RAIR with bathtub curves that are commonly identified with product failure and reliability engineering. Hence we observe the need for improved and automated driver's license testing techniques and applications, especially as these relate to the visual and cognitive abilities of drivers of all ages. Our findings may ultimately improve motorist safety, save lives, and benefit numerous other states, countries, and agencies, including, but not limited to, aviation, commercial vehicles, maritime, and rail sectors, among others.

  15. Jets in heavy ion collisions at the LHC

    NASA Astrophysics Data System (ADS)

    Roland, Christof

    2015-11-01

    In this document I present a brief review of the concepts of jet physics employed in heavy ion physics. Fast partons originating from scatterings with large momentum transfer are produced at very short time-scales and subsequently propagate through the strongly interacting medium produced in the collisions of heavy nuclei. They feature the only experimental handle available to directly study the interaction of a well defined probe and the medium. Consequently they are ideally suited to investigate the nature of the medium produced in these collisions and the mechanism of interaction between the medium and the partons. The experimental methods necessary to reconstruct jets originating from fragmenting partons in the environment of high particle multiplicity heavy ion collisions will be discussed. Physics observables suited to investigate the parton medium interaction will be introduced and a summary of recent results on jet physics in heavy ion collisions is presented.

  16. Airborne Collision Avoidance System X

    DTIC Science & Technology

    2015-06-01

    avoidance system on behalf of the Federal Aviation Adminis- tration (FAA). The current Traffic Alert and Collision Avoidance System II (TCAS II...which are used on board an aircraft. The tables provide a cost for each action—no alert , a traffic advisory alerting pilots about nearby aircraft, or a...suitabil- ity than does TCAS II; studies show that ACAS X reduces mid-air collision risk by 59% and unnecessary disruptive alerts by 25% when

  17. Do speed cameras reduce collisions?

    PubMed

    Skubic, Jeffrey; Johnson, Steven B; Salvino, Chris; Vanhoy, Steven; Hu, Chengcheng

    2013-01-01

    We investigated the effects of speed cameras along a 26 mile segment in metropolitan Phoenix, Arizona. Motor vehicle collisions were retrospectively identified according to three time periods - before cameras were placed, while cameras were in place and after cameras were removed. A 14 mile segment in the same area without cameras was used for control purposes. Five cofounding variables were eliminated. In this study, the placement or removal of interstate highway speed cameras did not independently affect the incidence of motor vehicle collisions.

  18. Collision of Dual Aggregates (CODA): Experimental observations of low-velocity collisions

    NASA Astrophysics Data System (ADS)

    Jorges, Jeffery; Dove, Adrienne; Colwell, Josh E.

    2016-10-01

    Low-velocity collisions are one of the driving factors that determine the particle size distribution and particle size evolution in planetary ring systems and in the early stages of planet formation. Collisions of sub-micron to decimeter-sized objects may result in particle growth by accretion, rebounding, or erosive processes that result in the production of additional smaller particles. Numerical simulations of these systems are limited by a need to understand these collisional parameters over a range of conditions. We present the results of a sequence of laboratory experiments designed to explore collisions over a range of parameter space . We are able to observe low-velocity collisions by conducting experiments in vacuum chambers in our 0.8-sec drop tower apparatus. Initial experiments utilize a variety of impacting spheres, including glass, Teflon, aluminum, stainless steel, and brass. These spheres are either used in their natural state or are "mantled" - coated with a few-mm thick layer of a cohesive powder. A high-speed, high-resolution video camera is used to record the motion of the colliding bodies. We track the particles to determine impactor speeds before and after collision, the impact parameter, and the collisional outcome. In the case of the mantled impactors, we can assess how much rotation is generated by the collision and estimate how much powder is released (i.e. how much mass is lost) due to the collision. We also determine how the coefficient of restitution varies as a function of material type, morphology, and impact velocity. With impact velocities ranging from about 20-100 cm/s we observe that mantling of particles significantly reduces their coefficients of restitution, but we see basically no dependence of the coefficient of restitution on the impact velocity, impact parameter, or system mass. The results of this study will contribute to a better empirical model of collisional outcomes that will be refined with numerical simulation of the

  19. Factors associated with single-vehicle and multi-vehicle road traffic collision injuries in Ireland.

    PubMed

    Donnelly-Swift, Erica; Kelly, Alan

    2016-12-01

    Generalised linear regression models were used to identify factors associated with fatal/serious road traffic collision injuries for single- and multi-vehicle collisions. Single-vehicle collisions and multi-vehicle collisions occurring during the hours of darkness or on a wet road surface had reduced likelihood of a fatal/serious injury. Single-vehicle 'driver with passengers' collisions occurring at junctions or on a hill/gradient were less likely to result in a fatal/serious injury. Multi-vehicle rear-end/angle collisions had reduced likelihood of a fatal/serious injury. Single-vehicle 'driver only' collisions and multi-vehicle collisions occurring on a public/bank holiday or on a hill/gradient were more likely to result in a fatal/serious injury. Single-vehicle collisions involving male drivers had increased likelihood of a fatal/serious injury and single-vehicle 'driver with passengers' collisions involving drivers under the age of 25 years also had increased likelihood of a fatal/serious injury. Findings can enlighten decision-makers to circumstances leading to fatal/serious injuries.

  20. A simple collision model for small bubbles

    NASA Astrophysics Data System (ADS)

    Heitkam, Sascha; Sommer, Anna-Elisabeth; Drenckhan, Wiebke; Fröhlich, Jochen

    2017-03-01

    In this work, a model for the interaction force between a small bubble and a wall or another bubble is presented. The formulation is especially designed for Lagrangian calculations of bubble or soft sphere trajectories, with or without resolution of the continuous fluid. The force only relies on position and velocity of the bubble. The model does not include any empirical parameter that would have to be calibrated. Therefore, this force model is easy to implement. The formulation of the force is explicit, which means low computational effort. The collision of a small bubble with an inclined top wall is investigated numerically and experimentally. The computational results achieved with the new collision model show good agreement with the experiment.

  1. Anomalons, honey, and glue in nuclear collisions

    SciTech Connect

    Gyulassy, M.

    1982-12-01

    In these lectures, selected topics in nuclear collisions in the energy range 10/sup -1/ to 10/sup 3/ GeV per nucleon are discussed. The evidence for anomalous projectile fragments with short mean free paths is presented. Theoretical speculations on novel topological nuclear excitation and on quark-nuclear complexes in connection with anomalons are discussed. Recent tests for pion field instabilities are presented. Then evidence for collective nuclear flow phenomena are reviewed. Global event analysis and cascade simulations are presented. We address the question of whether nuclear flow is like viscous honey. Finally, the criteria for the production of a quark-gluon plasma are discussed. Nuclear stopping power and longitudinal growth at high energies are considered. Results from cosmic ray data show that nuclear collision at TeV per nucleon energies are likely to product a plasma.

  2. Theory of Electron-Ion Collisions

    SciTech Connect

    Griffin, Donald C

    2009-10-02

    Collisions of electrons with atoms and ions play a crucial role in the modeling and diagnostics of fusion plasmas. In the edge and divertor regions of magnetically confined plasmas, data for the collisions of electrons with neutral atoms and low charge-state ions are of particular importance, while in the inner region, data on highly ionized species are needed. Since experimental measurements for these collisional processes remain very limited, data for such processes depend primarily on the results of theoretical calculations. Over the period of the present grant (January 2006 - August 2009), we have made additional improvements in our parallel scattering programs, generated data of direct fusion interest and made these data available on The Controlled Fusion Atomic Data Center Web site at Oak Ridge National Laboratory. In addition, we have employed these data to do collsional-radiative modeling studies in support of a variety of experiments with magnetically confined fusion plasmas.

  3. US Coast Guard collision at sea.

    PubMed

    McCaughey, B G

    1985-01-01

    The collision between the USCGC Cuyahoga and the motor vessel Santa Cruz II resulted in psychological distress among the Coast Guard crewmen. The US Navy Special Psychiatric Rapid Intervention Team (SPRINT) was activated to provide mental health services to the Coast Guard survivors and others who had been affected by the disaster. The psychiatric records of the 18 survivors were examined and summarized, and combined with anecdotal comments made by SPRINT members. The most prominent psychological reactions among the survivors were shock, anger, sadness, and guilt. Spouses of the survivors dealt with bereavement and strove to understand their husbands' reactions. Variables identified by the SPRINT as being important to their success were communication with and support from the training center command, assurances of confidentiality to the survivors, and commencement of their work almost immediately following the collision.

  4. Benchmark Calculations of Atomic Collision Processes

    NASA Astrophysics Data System (ADS)

    Bartschat, Klaus

    2012-02-01

    The rapid development of computational resources has resulted in enormous improvements in the accuracy of numerical calculations of atomic collision processes. This talk will concentrate on recent advances in the computational treatment of charged-particle and intense short-pulse laser interactions with atoms, ions, and small molecules. Examples include electron collisions with heavy complex targets that are of significant importance in many modelling applications in plasma and astrophysics, fundamental studies of highly correlated 4-body Coulomb processes such as simultaneous ionization with excitation, and the accurate solution of the time-dependent Schr"odinger equation in the presence of intense femto/attosecond laser fields, which paves the way for quantum dynamic imaging and coherent control.

  5. Hybrid Long-Range Collision Avoidance for Crowd Simulation.

    PubMed

    Golas, Abhinav; Narain, Rahul; Curtis, Sean; Lin, Ming C

    2014-07-01

    Local collision avoidance algorithms in crowd simulation often ignore agents beyond a neighborhood of a certain size. This cutoff can result in sharp changes in trajectory when large groups of agents enter or exit these neighborhoods. In this work, we exploit the insight that exact collision avoidance is not necessary between agents at such large distances, and propose a novel algorithm for extending existing collision avoidance algorithms to perform approximate, long-range collision avoidance. Our formulation performs long-range collision avoidance for distant agent groups to efficiently compute trajectories that are smoother than those obtained with state-of-the-art techniques and at faster rates. Comparison to real-world data demonstrates that crowds simulated with our algorithm exhibit an improved speed sensitivity to density similar to human crowds. Another issue often sidestepped in existing work is that discrete and continuum collision avoidance algorithms have different regions of applicability. For example, low-density crowds cannot be modeled as a continuum, while high-density crowds can be expensive to model using discrete methods. We formulate a hybrid technique for crowd simulation which can accurately and efficiently simulate crowds at any density with seamless transitions between continuum and discrete representations. Our approach blends results from continuum and discrete algorithms, based on local density and velocity variance. In addition to being robust across a variety of group scenarios, it is also highly efficient, running at interactive rates for thousands of agents on portable systems.

  6. Hybrid Long-Range Collision Avoidance for Crowd Simulation.

    PubMed

    Golas, Abhinav; Narain, Rahul; Curtis, Sean; Lin, Ming C

    2013-09-26

    Local collision avoidance algorithms in crowd simulation often ignore agents beyond a neighborhood of a certain size. This cutoff can result in sharp changes in trajectory when large groups of agents enter or exit these neighborhoods. In this work, we exploit the insight that exact collision avoidance is not necessary between agents at such large distances, and propose a novel algorithm for extending existing collision avoidance algorithms to perform approximate, long-range collision avoidance. Our formulation performs long-range collision avoidance for distant agent groups to efficiently compute trajectories that are smoother than those obtained with state-of-the-art techniques and at faster rates. Another issue often sidestepped in existing work is that discrete and continuum collision avoidance algorithms have different regions of applicability. For example, low-density crowds cannot be modeled as a continuum, while high-density crowds can be expensive to model using discrete methods. We formulate a hybrid technique for crowd simulation which can accurately and efficiently simulate crowds at any density with seamless transitions between continuum and discrete representations. Our approach blends results from continuum and discrete algorithms, based on local density and velocity variance. In addition to being robust across a variety of group scenarios, it is also highly efficient, running at interactive rates for thousands of agents on portable systems.

  7. Binary droplet collision at high Weber number

    NASA Astrophysics Data System (ADS)

    Pan, Kuo-Long; Chou, Ping-Chung; Tseng, Yu-Jen

    2009-09-01

    By using the techniques developed for generating high-speed droplets, we have systematically investigated binary droplet collision when the Weber number (We) was increased from the range usually tested in previous studies on the order of 10 to a much larger value of about 5100 for water (a droplet at 23 m/s with a diameter of 0.7 mm). Various liquids were also used to explore the effects of viscosity and surface tension. Specifically, beyond the well-known regimes at moderate We’s, which exhibited coalescence, separation, and separation followed by satellite droplets, we found different behaviors showing a fingering lamella, separation after fingering, breakup of outer fingers, and prompt splattering into multiple secondary droplets as We was increased. The critical Weber numbers that mark the boundaries between these impact regimes are identified. The specific impact behaviors, such as fingering and prompt splattering or splashing, share essential similarity with those also observed in droplet-surface impacts, whereas substantial variations in the transition boundaries may result from the disparity of the boundary conditions at impacts. To compare the outcomes of both types of collisions, a simple model based on energy conservation was carried out to predict the maximum diameter of an expanding liquid disk for a binary droplet collision. The results oppose the dominance of viscous drag, as proposed by previous studies, as the main deceleration force to effect a Rayleigh-Taylor instability and ensuing periphery fingers, which may further lead to the formations of satellite droplets.

  8. Simulating the universe(s) III: observables for the full bubble collision spacetime

    SciTech Connect

    Johnson, Matthew C.; Wainwright, Carroll L.; Aguirre, Anthony; Peiris, Hiranya V.

    2016-07-14

    This is the third paper in a series establishing a quantitative relation between inflationary scalar field potential landscapes and the relic perturbations left by the collision between bubbles produced during eternal inflation. We introduce a new method for computing cosmological observables from numerical relativity simulations of bubble collisions in one space and one time dimension. This method tiles comoving hypersurfaces with locally-perturbed Friedmann-Robertson-Walker coordinate patches. The method extends previous work, which was limited to the spacetime region just inside the future light cone of the collision, and allows us to explore the full bubble-collision spacetime. We validate our new methods against previous work, and present a full set of predictions for the comoving curvature perturbation and local negative spatial curvature produced by identical and non-identical bubble collisions, in single scalar field models of eternal inflation. In both collision types, there is a non-zero contribution to the spatial curvature and cosmic microwave background quadrupole. Some collisions between non-identical bubbles excite wall modes, giving extra structure to the predicted temperature anisotropies. We comment on the implications of our results for future observational searches. For non-identical bubble collisions, we also find that the surfaces of constant field can readjust in the presence of a collision to produce spatially infinite sections that become nearly homogeneous deep into the region affected by the collision. Contrary to previous assumptions, this is true even in the bubble into which the domain wall is accelerating.

  9. Simulating the universe(s) III: observables for the full bubble collision spacetime

    NASA Astrophysics Data System (ADS)

    Johnson, Matthew C.; Wainwright, Carroll L.; Aguirre, Anthony; Peiris, Hiranya V.

    2016-07-01

    This is the third paper in a series establishing a quantitative relation between inflationary scalar field potential landscapes and the relic perturbations left by the collision between bubbles produced during eternal inflation. We introduce a new method for computing cosmological observables from numerical relativity simulations of bubble collisions in one space and one time dimension. This method tiles comoving hypersurfaces with locally-perturbed Friedmann-Robertson-Walker coordinate patches. The method extends previous work, which was limited to the spacetime region just inside the future light cone of the collision, and allows us to explore the full bubble-collision spacetime. We validate our new methods against previous work, and present a full set of predictions for the comoving curvature perturbation and local negative spatial curvature produced by identical and non-identical bubble collisions, in single scalar field models of eternal inflation. In both collision types, there is a non-zero contribution to the spatial curvature and cosmic microwave background quadrupole. Some collisions between non-identical bubbles excite wall modes, giving extra structure to the predicted temperature anisotropies. We comment on the implications of our results for future observational searches. For non-identical bubble collisions, we also find that the surfaces of constant field can readjust in the presence of a collision to produce spatially infinite sections that become nearly homogeneous deep into the region affected by the collision. Contrary to previous assumptions, this is true even in the bubble into which the domain wall is accelerating.

  10. Simulation of Droplets Collisions Using Two-Phase Entropic Lattice Boltzmann Method

    NASA Astrophysics Data System (ADS)

    Mazloomi Moqaddam, A.; Chikatamarla, S. S.; Karlin, I. V.

    2015-12-01

    The recently introduced entropic lattice Boltzmann model for multiphase flows (Mazloomi et al. in Phys Rev Lett 114:174502, 2015) is used to simulate binary droplet collisions. The entropy-based stabilization, together with a new polynomial equation of state, enhances performance of the model and allow us to simulate droplet collision for various Weber and Reynolds numbers and large liquid to vapor density ratio. Different types of droplet collision outcomes, namely coalescence, stretching separation and reflexive separation are recovered in a range of impact parameter for two equal sized droplets. The results demonstrated the essential role played by the surface tension, kinematic viscosity, impact parameter and relative velocity in the droplet collision dynamics leading to coalescence or separation collision outcomes. Comparison between numerical results and experiments in both coalescence and separation collisions demonstrate viability of the presented model.

  11. Considering the collision probability of Active Debris Removal missions

    NASA Astrophysics Data System (ADS)

    Lidtke, Aleksander A.; Lewis, Hugh G.; Armellin, Roberto; Urrutxua, Hodei

    2017-02-01

    Active Debris Removal (ADR) methods are being developed due to a growing concern about the congestion on-orbit and sustainability of spaceflight. This study examined the probability of an on-orbit collision between an ADR target, whilst being de-orbited, and all the objects in the public catalogue published by the US Strategic Command. Such a collision could have significant effects because the target is likely to be located in a densely populated orbital regime and thus follow-on collisions could take place. Six impulsive and three low-thrust example ADR mission trajectories were screened for conjunctions. Extremely close conjunctions were found to result in as much as 99% of the total accumulated collision probability. The need to avoid those conjunctions is highlighted, which raises concerns about ADR methods that do not support collision avoidance. Shortening the removal missions, at an expense of more ΔV and so cost, will also lower their collision probability by reducing the number of conjunctions that they will experience.

  12. Recommended Screening Practices for Launch Collision Aviodance

    NASA Technical Reports Server (NTRS)

    Beaver, Brian A.; Hametz, Mark E.; Ollivierre, Jarmaine C.; Newman, Lauri K.; Hejduk, Matthew D.

    2015-01-01

    The objective of this document is to assess the value of launch collision avoidance (COLA) practices and provide recommendations regarding its implementation for NASA robotic missions. The scope of this effort is limited to launch COLA screens against catalog objects that are either spacecraft or debris. No modifications to manned safety COLA practices are considered in this effort. An assessment of the value of launch COLA can be broken down into two fundamental questions: 1) Does collision during launch represent a significant risk to either the payload being launched or the space environment? 2) Can launch collision mitigation be performed in a manner that provides meaningful risk reduction at an acceptable level of operational impact? While it has been possible to piece together partial answers to these questions for some time, the first attempt to comprehensively address them is documented in reference (a), Launch COLA Operations: an Examination of Data Products, Procedures, and Thresholds, Revision A. This report is the product of an extensive study that addressed fundamental technical questions surrounding launch collision avoidance analysis and practice. The results provided in reference (a) will be cited throughout this document as these two questions are addressed. The premise of this assessment is that in order to conclude that launch COLA is a value-added activity, the answer to both of these questions must be affirmative. A "no" answer to either of these questions points toward the conclusion that launch COLA provides little or no risk mitigation benefit. The remainder of this assessment will focus on addressing these two questions.

  13. Heavy-ion collisions at the LHC

    NASA Astrophysics Data System (ADS)

    Roland, G.; Šafařík, K.; Steinberg, P.

    2014-07-01

    A new era in the study of high-energy nuclear collisions began when the CERN Large Hadron Collider (LHC) provided the first collisions of lead nuclei in late 2010. In the first three years of operation the ALICE, ATLAS and CMS experiments each collected Pb-Pb data samples of more than 50 μb at √{sNN}=2.76 TeV, exceeding the previously studied collision energies by more than an order of magnitude. These data have provided new insights into the properties of QCD matter under extreme conditions, with extensive measurements of soft particle production and newly accessible hard probes of the hot and dense medium. In this review, we provide a comprehensive overview of the results obtained in heavy-ion collisions at the LHC so far, with particular emphasis on the complementary nature of the observations by the three experiments. In particular, the combination of ALICE’s strengths at hadron identification, the strengths of ATLAS and CMS to make precise measurements of high pT probes, and the resourceful measurements of collective flow by all of the experiments have provided a rich and diverse dataset in only a few years. While the basic paradigm established at RHIC - that of a hot, dense medium that flows with a viscosity to shear-entropy ratio near the predicted lower bound, and which degrades the energy of probes, such as jets, heavy-flavours and J/ψ - is confirmed at the LHC, the new data suggest many new avenues for extracting its properties in detail.

  14. Half collision resonance phenomena in molecules

    SciTech Connect

    Maximo Garcia-Sucre ); Raseev, G. ); Ross, S.C. )

    1991-01-01

    The Escuela Latinoamericana de Fisica (ELAF) is a series of meeting s that for 28 years has played an important role in research-level teaching of physics in Latin America. This book contains the proceedings of ELAF 90 which was held at the Instituto Venezolano de Investigaciones Cientificas (IVIC) in Caracas, Venezuela from July 23 to August 3, 1990, as part of the commemoration of the 30th anniversary of IVIC. In contrast to previous ELAF's that were of general scope, ELAF 90 centered on a particular subject matter: Half Collisional Resonance Phenomena in Molecules, Experimental and Theoretical Approaches. The term Half Collision'' refers to the fragmentation of a molecular system following is excitation by light. The lack of an incident fragmentation of a molecular system following is excitation by light. The lack of an incident particle (other than the photon) in the fragmentation process is what leads to the term. The purpose of this volume is to present current results in the experimental and theoretical study of half collisions and also to include pedagogical papers at an introductory or intermediate level. The contributions are grouped into several sections; light sources; ionization; dissociation-experimental; dissociation-theory; competition between ionization and dissociation; and particle-molecule collisions.

  15. Initial data for black hole collisions

    NASA Astrophysics Data System (ADS)

    Rauber, J. D.

    A problem of considerable interest in relativistic astrophysics is to determine the gravitational radiation produced by collisions of compact objects, such as black holes. Such collisions may occur, for example, in the nuclei of galaxies. This problem requires that one solve the Einstein equation without limiting approximations, for example, as a Cauchy problem. Therefore, one must first construct the initial data. The extrinsic curvature on an initial spacelike hypersurface of two black holes with asisymmetric parallel spins is derived in terms of an analytic infinite series. Other two body configurations are also considered. The extrinsic curvature is constructed so that the resulting spacetime will have the topology of two Einstein-Rosen bridges; a physical equivalence of the top and bottom sheets of the initial hypersurface is also built in. It is shown that one may a priori specify the spins of the two black holes. The extrinsic curvature, so constructed, is not derivable from a potential. An appropriate numerical problem for the conformal factor is posed and examined in the above configurations. Efforts at using multi-grid differencing schemes for solving the differential equations are discussed. In order to time evolve ablack hole interaction or collision, the extrinsic curvature and conformal factor must be completely specified on an initial slice of spacetime.

  16. Initial Data for Black Hole Collisions

    NASA Astrophysics Data System (ADS)

    Rauber, Joel David

    A problem of considerable interest in relativistic astrophysics is to determine the gravitational radiation produced by collisions of compact objects, such as black holes. Such collisions may occur, for example, in the nuclei of galaxies. This problem requires that one solve the Einstein equation without limiting approximations, for example, as a Cauchy problem. Therefore, one must first construct the initial data. The extrinsic curvature on an initial spacelike hypersurface of two black holes with axisymmetric parallel spins is derived in terms of an analytic infinite series. Other two body configurations are also considered. The extrinsic curvature is constructed so that the resulting spacetime will have the topology of two Einstein-Rosen bridges; a physical equivalence of the top and bottom sheets of the initial hypersurface is also built in. It is shown that one may a priori specify the spins of the two black holes. The extrinsic curvature, so constructed, is not derivable from a potential. An appropriate numerical problem for the conformal factor is posed and examined in the above configurations. Efforts at using multi-grid differencing schemes for solving the differential equations are discussed. In order to time evolve a black hole interaction or collision, the extrinsic curvature and conformal factor must be completely specified on an initial slice of spacetime.

  17. Radar sensors for intersection collision avoidance

    NASA Astrophysics Data System (ADS)

    Jocoy, Edward H.; Phoel, Wayne G.

    1997-02-01

    On-vehicle sensors for collision avoidance and intelligent cruise control are receiving considerably attention as part of Intelligent Transportation Systems. Most of these sensors are radars and `look' in the direction of the vehicle's headway, that is, in the direction ahead of the vehicle. Calspan SRL Corporation is investigating the use of on- vehicle radar for Intersection Collision Avoidance (ICA). Four crash scenarios are considered and the goal is to design, develop and install a collision warning system in a test vehicle, and conduct both test track and in-traffic experiments. Current efforts include simulations to examine ICA geometry-dependent design parameters and the design of an on-vehicle radar and tracker for threat detection. This paper discusses some of the simulation and radar design efforts. In addition, an available headway radar was modified to scan the wide angles (+/- 90 degree(s)) associated with ICA scenarios. Preliminary proof-of-principal tests are underway as a risk reduction effort. Some initial target detection results are presented.

  18. TURBULENCE-INDUCED RELATIVE VELOCITY OF DUST PARTICLES. IV. THE COLLISION KERNEL

    SciTech Connect

    Pan, Liubin; Padoan, Paolo E-mail: ppadoan@icc.ub.edu

    2014-12-20

    Motivated by its importance for modeling dust particle growth in protoplanetary disks, we study turbulence-induced collision statistics of inertial particles as a function of the particle friction time, τ{sub p}. We show that turbulent clustering significantly enhances the collision rate for particles of similar sizes with τ{sub p} corresponding to the inertial range of the flow. If the friction time, τ{sub p,} {sub h}, of the larger particle is in the inertial range, the collision kernel per unit cross section increases with increasing friction time, τ{sub p,} {sub l}, of the smaller particle and reaches the maximum at τ{sub p,} {sub l} = τ{sub p,} {sub h}, where the clustering effect peaks. This feature is not captured by the commonly used kernel formula, which neglects the effect of clustering. We argue that turbulent clustering helps alleviate the bouncing barrier problem for planetesimal formation. We also investigate the collision velocity statistics using a collision-rate weighting factor to account for higher collision frequency for particle pairs with larger relative velocity. For τ{sub p,} {sub h} in the inertial range, the rms relative velocity with collision-rate weighting is found to be invariant with τ{sub p,} {sub l} and scales with τ{sub p,} {sub h} roughly as ∝ τ{sub p,h}{sup 1/2}. The weighting factor favors collisions with larger relative velocity, and including it leads to more destructive and less sticking collisions. We compare two collision kernel formulations based on spherical and cylindrical geometries. The two formulations give consistent results for the collision rate and the collision-rate weighted statistics, except that the spherical formulation predicts more head-on collisions than the cylindrical formulation.

  19. Collision zone magmatism aids continental crustal growth

    NASA Astrophysics Data System (ADS)

    Savov, Ivan; Meliksetian, Khachatur; Ralf, Halama; Gevorg, Navasardian; Chuck, Connor; Massimo, D'Antonio; Samuele, Agostini; Osamu, Ishizuka; Sergei, Karapetian; Arkadi, Karakhanian

    2014-05-01

    .51282, respectively). These isotopic signatures are much more similar to those typical of intra-oceanic subduction zones than those typical of continental crust, likely due to the very young age of the rocks. In contrast, trace element abundances reveal many similarities to average CC, such as Nb-Ta and Ti troughs and Pb peaks. The range of d11B isotope ratios (-8.7 to +2.1 per mil) signifies magmas originating from moderately metasomatised (arc preconditioned) mantle sources. Our combined results reveal that the collision-related mantle melting is capable of generating large volumes of plutons and volcanic rocks that resemble (although not perfectly) the composition of the average CC. We will attempt to use the new combined datasets in order to quantify the importance of the collision zone magmatism for continental crustal growth. [1] Lee et al. (2007) EPSL 263, 370-387; [2] Niu et al. (2013) Earth-Science Reviews 127, 96-110; [3] Connor et al., (2012) J.Applied Volcanology, 1:3, 1-19.

  20. Non-Evaporative Cooling via Inelastic Collisions in an Optical Trap

    DTIC Science & Technology

    2013-02-28

    first-order Zeeman effect rather than second-order Zeeman effect for cooling, resulting in easier experimental apparatus design. The use of two atoms...the second-order Zeeman effect . This energy is supplied by the atoms’ kinetic energy in the collision. After the spin-exchange collisions have been...population, but have reduced kinetic energy. In effect , the spin-exchange collisions transfer kinetic energy to Zeeman energy that is subsequently

  1. Impulsive model for reactive collisions

    NASA Technical Reports Server (NTRS)

    Marron, M. T.; Bernstein, R. B.

    1972-01-01

    A simple classical mechanical model of the reactive scattering of a structureless atom A and a quasi-diatomic BC is developed which takes full advantage of energy, linear and angular momentum conservation relations but introduces a minimum of further assumptions. These are as follows: (1) the vibrational degree of freedom of the reactant (BC) and product (AB) molecules is suppressed, so the change in vibrational energy is simply a parameter; (2) straight-line trajectories are assumed outside of a reaction shell; (3) within this zone, momentum transfer occurs impulsively (essentially instantaneously) following mass transfer; (4) the impulse, which may be either positive or negative, is directed along the BC axis, which may, however, assume all orientations with respect to the incident relative velocity. The model yields differential and total cross sections and product rotational energy distributions for a given collision exoergicity Q, or for any known distribution over Q. Numerical results are presented for several prototype reactions whose dynamics have been well-studied.

  2. Automatic Collision Avoidance Technology (ACAT)

    NASA Technical Reports Server (NTRS)

    Swihart, Donald E.; Skoog, Mark A.

    2007-01-01

    This document represents two views of the Automatic Collision Avoidance Technology (ACAT). One viewgraph presentation reviews the development and system design of Automatic Collision Avoidance Technology (ACAT). Two types of ACAT exist: Automatic Ground Collision Avoidance (AGCAS) and Automatic Air Collision Avoidance (AACAS). The AGCAS Uses Digital Terrain Elevation Data (DTED) for mapping functions, and uses Navigation data to place aircraft on map. It then scans DTED in front of and around aircraft and uses future aircraft trajectory (5g) to provide automatic flyup maneuver when required. The AACAS uses data link to determine position and closing rate. It contains several canned maneuvers to avoid collision. Automatic maneuvers can occur at last instant and both aircraft maneuver when using data link. The system can use sensor in place of data link. The second viewgraph presentation reviews the development of a flight test and an evaluation of the test. A review of the operation and comparison of the AGCAS and a pilot's performance are given. The same review is given for the AACAS is given.

  3. Coastal river plumes: Collisions and coalescence

    NASA Astrophysics Data System (ADS)

    Warrick, Jonathan A.; Farnsworth, Katherine L.

    2017-02-01

    Plumes of buoyant river water spread in the ocean from river mouths, and these plumes influence water quality, sediment dispersal, primary productivity, and circulation along the world's coasts. Most investigations of river plumes have focused on large rivers in a coastal region, for which the physical spreading of the plume is assumed to be independent from the influence of other buoyant plumes. Here we provide new understanding of the spreading patterns of multiple plumes interacting along simplified coastal settings by investigating: (i) the relative likelihood of plume-to-plume interactions at different settings using geophysical scaling, (ii) the diversity of plume frontal collision types and the effects of these collisions on spreading patterns of plume waters using a two-dimensional hydrodynamic model, and (iii) the fundamental differences in plume spreading patterns between coasts with single and multiple rivers using a three-dimensional hydrodynamic model. Geophysical scaling suggests that coastal margins with numerous small rivers (watershed areas < 10,000 km2), such as found along most active geologic coastal margins, were much more likely to have river plumes that collide and interact than coastal settings with large rivers (watershed areas > 100,000 km2). When two plume fronts meet, several types of collision attributes were found, including refection, subduction and occlusion. We found that the relative differences in pre-collision plume densities and thicknesses strongly influenced the resulting collision types. The three-dimensional spreading of buoyant plumes was found to be influenced by the presence of additional rivers for all modeled scenarios, including those with and without Coriolis and wind. Combined, these results suggest that plume-to-plume interactions are common phenomena for coastal regions offshore of the world's smaller rivers and for coastal settings with multiple river mouths in close proximity, and that the spreading and fate of

  4. Coastal river plumes: Collisions and coalescence

    USGS Publications Warehouse

    Warrick, Jonathan; Farnsworth, Katherine L

    2017-01-01

    Plumes of buoyant river water spread in the ocean from river mouths, and these plumes influence water quality, sediment dispersal, primary productivity, and circulation along the world’s coasts. Most investigations of river plumes have focused on large rivers in a coastal region, for which the physical spreading of the plume is assumed to be independent from the influence of other buoyant plumes. Here we provide new understanding of the spreading patterns of multiple plumes interacting along simplified coastal settings by investigating: (i) the relative likelihood of plume-to-plume interactions at different settings using geophysical scaling, (ii) the diversity of plume frontal collision types and the effects of these collisions on spreading patterns of plume waters using a two-dimensional hydrodynamic model, and (iii) the fundamental differences in plume spreading patterns between coasts with single and multiple rivers using a three-dimensional hydrodynamic model. Geophysical scaling suggests that coastal margins with numerous small rivers (watershed areas < 10,000 km2), such as found along most active geologic coastal margins, were much more likely to have river plumes that collide and interact than coastal settings with large rivers (watershed areas > 100,000 km2). When two plume fronts meet, several types of collision attributes were found, including refection, subduction and occlusion. We found that the relative differences in pre-collision plume densities and thicknesses strongly influenced the resulting collision types. The three-dimensional spreading of buoyant plumes was found to be influenced by the presence of additional rivers for all modeled scenarios, including those with and without Coriolis and wind. Combined, these results suggest that plume-to-plume interactions are common phenomena for coastal regions offshore of the world’s smaller rivers and for coastal settings with multiple river mouths in close proximity, and that the spreading and

  5. Semiholography for heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Ayan; Preis, Florian

    2017-03-01

    The formation of QGP in heavy ion collisions gives us a great opportunity for learning about nonperturbative dynamics of QCD. Semiholography provides a new consistent framework to combine perturbative and non-perturbative effects in a coherent way and can be applied to obtain an effective description for heavy ion collisions. In particular, it allows us to include nonperturbative effects in existing glasma effective theory and QCD kinetic theory for the weakly coupled saturated degrees of freedom liberated by the collisions in the initial stages in a consistent manner. We argue why the full framework should be able to confront experiments with only a few phenomenological parameters and present feasibility tests for the necessary numerical computations. Furthermore, we discuss that semiholography leads to a new description of collective flow in the form of a generalised non-Newtonian fluid. We discuss some open questions which we hope to answer in the near future.

  6. POLARIZED PROTON COLLISIONS AT RHIC.

    SciTech Connect

    BAI, M.; AHRENS, L.; ALEKSEEV, I.G.; ALESSI, J.; ET AL.

    2005-05-16

    The Relativistic Heavy Ion Collider provides not only collisions of ions but also collisions of polarized protons. In a circular accelerator, the polarization of polarized proton beam can be partially or fully lost when a spin depolarizing resonance is encountered. To preserve the beam polarization during acceleration, two full Siberian snakes were employed in RHIC. In 2002, polarized proton beams were first accelerated to 100 GeV and collided in RHIC. Beams were brought into collisions with longitudinal polarization at the experiments STAR and PHENIX by using spin rotators. Optimizing polarization transmission efficiency and improving luminosity performance are significant challenges. Currently, the luminosity lifetime in RHIC is limited by the beam-beam effect. The current state of RHIC polarized proton program, including its dedicated physics run in 2005 and efforts to optimize luminosity production in beam-beam limited conditions are reported.

  7. Elliptic flow in Au+Au collisions at square root(S)NN = 130 GeV.

    PubMed

    Ackermann, K H; Adams, N; Adler, C; Ahammed, Z; Ahmad, S; Allgower, C; Amsbaugh, J; Anderson, M; Anderssen, E; Arnesen, H; Arnold, L; Averichev, G S; Baldwin, A; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Beddo, M; Bekele, S; Belaga, V V; Bellwied, R; Bennett, S; Bercovitz, J; Berger, J; Betts, W; Bichsel, H; Bieser, F; Bland, L C; Bloomer, M; Blyth, C O; Boehm, J; Bonner, B E; Bonnet, D; Bossingham, R; Botlo, M; Boucham, A; Bouillo, N; Bouvier, S; Bradley, K; Brady, F P; Braithwaite, E S; Braithwaite, W; Brandin, A; Brown, R L; Brugalette, G; Byrd, C; Caines, H; Calderón de la Barca Sánchez, M; Cardenas, A; Carr, L; Carroll, J; Castillo, J; Caylor, B; Cebra, D; Chatopadhyay, S; Chen, M L; Chen, W; Chen, Y; Chernenko, S P; Cherney, M; Chikanian, A; Choi, B; Chrin, J; Christie, W; Coffin, J P; Conin, L; Consiglio, C; Cormier, T M; Cramer, J G; Crawford, H J; Danilov, V I; Dayton, D; DeMello, M; Deng, W S; Derevschikov, A A; Dialinas, M; Diaz, H; DeYoung, P A; Didenko, L; Dimassimo, D; Dioguardi, J; Dominik, W; Drancourt, C; Draper, J E; Dunin, V B; Dunlop, J C; Eckardt, V; Edwards, W R; Efimov, L G; Eggert, T; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Etkin, A; Fachini, P; Feliciano, C; Ferenc, D; Ferguson, M I; Fessler, H; Finch, E; Fine, V; Fisyak, Y; Flierl, D; Flores, I; Foley, K J; Fritz, D; Gagunashvili, N; Gans, J; Gazdzicki, M; Germain, M; Geurts, F; Ghazikhanian, V; Gojak, C; Grabski, J; Grachov, O; Grau, M; Greiner, D; Greiner, L; Grigoriev, V; Grosnick, D; Gross, J; Guilloux, G; Gushin, E; Hall, J; Hallman, T J; Hardtke, D; Harper, G; Harris, J W; He, P; Heffner, M; Heppelmann, S; Herston, T; Hill, D; Hippolyte, B; Hirsch, A; Hjort, E; Hoffmann, G W; Horsley, M; Howe, M; Huang, H Z; Humanic, T J; Hümmler, H; Hunt, W; Hunter, J; Igo, G J; Ishihara, A; Ivanshin, Y I; Jacobs, P; Jacobs, W W; Jacobson, S; Jared, R; Jensen, P; Johnson, I; Jones, P G; Judd, E; Kaneta, M; Kaplan, M; Keane, D; Kenney, V P; Khodinov, A; Klay, J; Klein, S R; Klyachko, A; Koehler, G; Konstantinov, A S; Kormilitsyne, V; Kotchenda, L; Kotov, I; Kovalenko, A D; Kramer, M; Kravtsov, P; Krueger, K; Krupien, T; Kuczewski, P; Kuhn, C; Kunde, G J; Kunz, C L; Kutuev, R K; Kuznetsov, A A; Lakehal-Ayat, L; Lamas-Valverde, J; Lamont, M A; Landgraf, J M; Lange, S; Lansdell, C P; Lasiuk, B; Laue, F; Lebedev, A; LeCompte, T; Leonhardt, W J; Leontiev, V M; Leszczynski, P; LeVine, M J; Li, Q; Li, Q; Li, Z; Liaw, C J; Lin, J; Lindenbaum, S J; Lindenstruth, V; Lindstrom, P J; Lisa, M A; Liu, H; Ljubicic, T; Llope, W J; LoCurto, G; Long, H; Longacre, R S; Lopez-Noriega, M; Lopiano, D; Love, W A; Lutz, J R; Lynn, D; Madansky, L; Maier, R; Majka, R; Maliszewski, A; Margetis, S; Marks, K; Marstaller, R; Martin, L; Marx, J; Matis, H S; Matulenko, Y A; Matyushevski, E A; McParland, C; McShane, T S; Meier, J; Melnick, Y; Meschanin, A; Middlekamp, P; Mikhalin, N; Miller, B; Milosevich, Z; Minaev, N G; Minor, B; Mitchell, J; Mogavero, E; Moiseenko, V A; Moltz, D; Moore, C F; Morozov, V; Morse, R; de Moura, M M; Munhoz, M G; Mutchler, G S; Nelson, J M; Nevski, P; Ngo, T; Nguyen, M; Nguyen, T; Nikitin, V A; Nogach, L V; Noggle, T; Norman, B; Nurushev, S B; Nussbaum, T; Nystrand, J; Odyniec, G; Ogawa, A; Ogilvie, C A; Olchanski, K; Oldenburg, M; Olson, D; Ososkov, G A; Ott, G; Padrazo, D; Paic, G; Pandey, S U; Panebratsev, Y; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Pentia, M; Perevotchikov, V; Peryt, W; Petrov, V A; Pinganaud, W; Pirogov, S; Platner, E; Pluta, J; Polk, I; Porile, N; Porter, J; Poskanzer, A M; Potrebenikova, E; Prindle, D; Pruneau, C; Puskar-Pasewicz, J; Rai, G; Rasson, J; Ravel, O; Ray, R L; Razin, S V; Reichhold, D; Reid, J; Renfordt, R E; Retiere, F; Ridiger, A; Riso, J; Ritter, H G; Roberts, J B; Roehrich, D; Rogachevski, O V; Romero, J L; Roy, C; Russ, D; Rykov, V; Sakrejda, I; Sanchez, R; Sandler, Z; Sandweiss, J; Sappenfield, P; Saulys, A C; Savin, I; Schambach, J; Scharenberg, R P; Scheblien, J; Scheetz, R; Schlueter, R; Schmitz, N; Schroeder, L S; Schulz, M; Schüttauf, A; Sedlmeir, J; Seger, J; Seliverstov, D; Seyboth, J; Seyboth, P; Seymour, R; Shakaliev, E I; Shestermanov, K E; Shi, Y; Shimanskii, S S; Shuman, D; Shvetcov, V S; Skoro, G; Smirnov, N; Smykov, L P; Snellings, R; Solberg, K; Sowinski, J; Spinka, H M; Srivastava, B; Stephenson, E J; Stock, R; Stolpovsky, A; Stone, N; Stone, R; Strikhanov, M; Stringfellow, B; Stroebele, H; Struck, C; Suaide, A A; Sugarbaker, E; Suire, C; Symons, T J; Takahashi, J; Tang, A H; Tarchini, A; Tarzian, J; Thomas, J H; Tikhomirov, V; Szanto De Toledo, A; Tonse, S; Trainor, T; Trentalange, S; Tokarev, M; Tonjes, M B; Trofimov, V; Tsai, O; Turner, K; Ullrich, T; Underwood, D G; Vakula, I; Van Buren, G; VanderMolen, A M; Vanyashin, A; Vasilevski, I M; Vasiliev, A N; Vigdor, S E; Visser, G; Voloshin, S A; Vu, C; Wang, F; Ward, H; Weerasundara, D; Weidenbach, R; Wells, R; Wells, R; Wenaus, T; Westfall, G D; Whitfield, J P; Whitten, C; Wieman, H; Willson, R; Wilson, K; Wirth, J; Wisdom, J; Wissink, S W; Witt, R; Wolf, J; Wood, L; Xu, N; Xu, Z; Yakutin, A E; Yamamoto, E; Yang, J; Yepes, P; Yokosawa, A; Yurevich, V I; Zanevski, Y V; Zhang, J; Zhang, W M; Zhu, J; Zimmerman, D; Zoulkarneev, R; Zubarev, A N

    2001-01-15

    Elliptic flow from nuclear collisions is a hadronic observable sensitive to the early stages of system evolution. We report first results on elliptic flow of charged particles at midrapidity in Au+Au collisions at square root(S)NN = 130 GeV using the STAR Time Projection Chamber at the Relativistic Heavy Ion Collider. The elliptic flow signal, v2, averaged over transverse momentum, reaches values of about 6% for relatively peripheral collisions and decreases for the more central collisions. This can be interpreted as the observation of a higher degree of thermalization than at lower collision energies. Pseudorapidity and transverse momentum dependence of elliptic flow are also presented.

  8. Protein folding dynamics: the diffusion-collision model and experimental data.

    PubMed Central

    Karplus, M.; Weaver, D. L.

    1994-01-01

    The diffusion-collision model of protein folding is assessed. A description is given of the qualitative aspects and quantitative results of the diffusion-collision model and their relation to available experimental data. We consider alternative mechanisms for folding and point out their relationship to the diffusion-collision model. We show that the diffusion-collision model is supported by a growing body of experimental and theoretical evidence, and we outline future directions for developing the model and its applications. PMID:8003983

  9. Oblique collision of dust acoustic solitons in a strongly coupled dusty plasma

    SciTech Connect

    Boruah, A.; Sharma, S. K. Bailung, H.; Nakamura, Y.

    2015-09-15

    The oblique collision between two equal amplitude dust acoustic solitons is observed in a strongly coupled dusty plasma. The solitons are subjected to oblique interaction at different colliding angles. We observe a resonance structure during oblique collision at a critical colliding angle which is described by the idea of three wave resonance interaction modeled by Kadomtsev-Petviashvili equation. After collision, the solitons preserve their identity. The amplitude of the resultant wave formed during interaction is measured for different collision angles as well as for different colliding soliton amplitudes. At resonance, the maximum amplitude of the new soliton formed is nearly 3.7 times the initial soliton amplitude.

  10. Waveguide properties of the asymmetric collision between two bright spatial solitons in Kerr media.

    PubMed

    Martínez, D Ramírez; Otero, M M Méndez; Carrasco, M L Arroyo; Castillo, M D Iturbe

    2012-11-19

    In this work, we numerically characterize the waveguide properties of the asymmetric collision between two bright spatial solitons in a nonlinear Kerr media. The results demonstrate that the energy carried by a probe beam guided by one soliton can be transferred after the collision to the waveguide created by the other soliton depending on the initial separation between the solitons, the angle of their collision, and in some cases, the particular soliton that initially guides the probe beam. The observed behavior is equivalent to that obtained for the symmetrical collision when there is an initial relative phase between the solitons.

  11. Collisions of Small Drops in a Turbulent Flow. Part II: Effects of Flow Accelerations.

    NASA Astrophysics Data System (ADS)

    Pinsky, M. B.; Khain, A. P.

    2004-08-01

    The effects of Lagrangian acceleration on collision efficiency and collision kernels of small cloud droplets in a turbulent flow are investigated using the results of the recent laboratory experiments by La Porta et al., conducted under high Reλ flow of pronounced intermittency. The effect of Lagrangian accelerations on drop collisions has been found to be significant, namely, for drop pairs, containing a drop collector exceeding 10 μm in radius, collision efficiency, and collision kernels increase by up to 25% and 40%, respectively, at dissipation rates of 200 cm2 s-3 typical of weak cumulus clouds. In well-developed deep cumulus clouds, the increase attains the factor of 2.5 and 5, respectively, at typical dissipation rates of 1000 cm2 s-3. The effect of Lagrangian accelerations is mainly caused by the increase in the collision efficiency that is highly sensitive even to weak variations of interdrop relative velocity. The increase in the swept volume is responsible only for a fraction of the overall increase in the collision kernel.The effect of intermittency of a turbulent flow manifests itself in two aspects: (i) an increase in variance of Lagrangian accelerations with an increase in Reλ, and (ii) the formation of a specific shape of the probability distribution function (PDF) characterized by a sharp maximum and elongated tail. The increase in variance of Lagrangian accelerations leads to an increase in the collision rate between droplets. The effect of the PDF shape on the collision rate is studied by comparing the magnitudes of collision efficiencies (and kernels) obtained in case of the non-Gaussian PDF with those obtained using the Gaussian PDF of the same acceleration variation. The utilization of the Gaussian PDF leads to a slight (about 10% 15%) overestimation of the values of the collision efficiency and collision kernel. Thus, the effect of intermittency on drop collisions related to high values of PDF flatness has been found to be insignificant

  12. Conservative bin-to-bin fractional collisions

    NASA Astrophysics Data System (ADS)

    Martin, Robert

    2016-11-01

    Particle methods such as direct simulation Monte Carlo (DSMC) and particle-in-cell (PIC) are commonly used to model rarefied kinetic flows for engineering applications because of their ability to efficiently capture non-equilibrium behavior. The primary drawback to these methods relates to the poor convergence properties due to the stochastic nature of the methods which typically rely heavily on high degrees of non-equilibrium and time averaging to compensate for poor signal to noise ratios. For standard implementations, each computational particle represents many physical particles which further exacerbate statistical noise problems for flow with large species density variation such as encountered in flow expansions and chemical reactions. The stochastic weighted particle method (SWPM) introduced by Rjasanow and Wagner overcome this difficulty by allowing the ratio of real to computational particles to vary on a per particle basis throughout the flow. The DSMC procedure must also be slightly modified to properly sample the Boltzmann collision integral accounting for the variable particle weights and to avoid the creation of additional particles with negative weight. In this work, the SWPM with necessary modification to incorporate the variable hard sphere (VHS) collision cross section model commonly used in engineering applications is first incorporated into an existing engineering code, the Thermophysics Universal Research Framework. The results and computational efficiency are compared to a few simple test cases using a standard validated implementation of the DSMC method along with the adapted SWPM/VHS collision using an octree based conservative phase space reconstruction. The SWPM method is then further extended to combine the collision and phase space reconstruction into a single step which avoids the need to create additional computational particles only to destroy them again during the particle merge. This is particularly helpful when oversampling the

  13. ACAT Ground Collision Avoidance Flight Tests Over

    NASA Video Gallery

    NASA's Dryden Flight Research Center has concluded flight tests of an Automatic Ground Collision Avoidance System (Auto GCAS) under the joint U.S. Air Force/NASA F-16D Automatic Collision Avoidance...

  14. Outreach Materials for the Collision Repair Campaign

    EPA Pesticide Factsheets

    The Collision Repair Campaign offers outreach materials to help collision repair shops reduce toxic air exposure. Materials include a DVD, poster, training video, and materials in Spanish (materiales del outreach en español).

  15. Dissipative heavy-ion collisions

    SciTech Connect

    Feldmeier, H.T.

    1985-01-01

    This report is a compilation of lecture notes of a series of lectures held at Argonne National Laboratory in October and November 1984. The lectures are a discussion of dissipative phenomena as observed in collisions of atomic nuclei. The model is based on a system which has initially zero temperature and the initial energy is kinetic and binding energy. Collisions excite the nuclei, and outgoing fragments or the compound system deexcite before they are detected. Brownian motion is used to introduce the concept of dissipation. The master equation and the Fokker-Planck equation are derived. 73 refs., 59 figs. (WRF)

  16. Do Speed Cameras Reduce Collisions?

    PubMed Central

    Skubic, Jeffrey; Johnson, Steven B.; Salvino, Chris; Vanhoy, Steven; Hu, Chengcheng

    2013-01-01

    We investigated the effects of speed cameras along a 26 mile segment in metropolitan Phoenix, Arizona. Motor vehicle collisions were retrospectively identified according to three time periods – before cameras were placed, while cameras were in place and after cameras were removed. A 14 mile segment in the same area without cameras was used for control purposes. Five cofounding variables were eliminated. In this study, the placement or removal of interstate highway speed cameras did not independently affect the incidence of motor vehicle collisions. PMID:24406979

  17. Signature of anisotropic bubble collisions

    SciTech Connect

    Salem, Michael P.

    2010-09-15

    Our universe may have formed via bubble nucleation in an eternally inflating background. Furthermore, the background may have a compact dimension--the modulus of which tunnels out of a metastable minimum during bubble nucleation--which subsequently grows to become one of our three large spatial dimensions. When in this scenario our bubble universe collides with other ones like it, the collision geometry is constrained by the reduced symmetry of the tunneling instanton. While the regions affected by such bubble collisions still appear (to leading order) as disks in an observer's sky, the centers of these disks all lie on a single great circle, providing a distinct signature of anisotropic bubble nucleation.

  18. Multidimensional intermittency in hadronic collisions

    NASA Astrophysics Data System (ADS)

    Pan, Jicai; Hwa, Rudolph C.

    1992-12-01

    The study of intermittency in high-energy hadronic collisions by the Monte Carlo code ecco is extended to three-dimensional phase space. Strong intermittency is found in agreement with the data. Fluctuation in the impact parameter is responsible for the intermittency in lnpT, and the transverse-momentum conservation leads to negative intermittency slopes in the azimuthal angle φ. The Ochs-Wosiek plots are linear in all dimensions having universal slopes. An exponent ν=1.448 emerges to characterize multiparticle production in pp collisions. The properties of G moments are also examined, and the fractal dimensions determined.

  19. Multidimensional intermittency in hadronic collisions

    NASA Astrophysics Data System (ADS)

    Pan, J.; Hwa, R. C.

    1992-06-01

    The study of intermittency in high-energy hadronic collisions by the Monte Carlo code ECCO is extended to 3-dimensional phase space. Strong intermittency is found in agreement with the data. Fluctuation in the impact parameter is responsible for the intermittency in 1np(sub T), and the transverse-momentum conservation leads to negative intermittency slopes in the azimuthal angle (phi). The Ochs-Wosiek plots are linear in all dimensions having universal slopes. An exponent nu = 1.448 emerges to characterize multiparticle production in pp collisions. The properties of G moments are also examined, and the fractal dimensions determined.

  20. Investigation of droplet collisions for solutions with different solids content

    NASA Astrophysics Data System (ADS)

    Kuschel, Matthias; Sommerfeld, Martin

    2013-02-01

    The collision behaviour of droplets and the collision outcome are investigated for high viscous polymer solutions. For that purpose, two droplet chains produced by piezoelectric droplet generators are directed towards each other at a certain angle so that individual droplet pairs collide. For recording the collision event, one double-image and one high-speed CCD camera were used. One camera is positioned perpendicular to the collision plane recording the outcome of the collision, and the second camera is aligned parallel to the collision plane to assure that the droplet chains are exactly in one plane. A new approach for tracking droplets in combination with an extended particle tracking velocimetry algorithm has been developed. Time-resolved series of pictures were used to analyse the dynamics of droplet collisions. The three different water soluble substances were saccharose and 1-Ethenyl-2-pyrrolidone (PVP) with different molecular weights (K17, K30). The solvent was demineralised water. The solids contents ranged from 20 to 60 %, 5 to 25 % and 5 to 35 %, yielding dynamic viscosities in the range of 2-60 mPa s. Results were collected for different pairs of impact angles and Weber numbers in order to establish common collision maps for characterising the outcomes. Here, relative velocities between 0.5 and 4 m/s and impact parameters in the interval from 0 to 1 for equal-sized droplets (Δ = 1) have been investigated. Additionally, satellite formation will be discussed exemplarily for K30. A comparison with common models of different authors (Ashgriz and Poo in J Fluid Mech 221:183-204, 1990; Estrade et al. in Int J Heat Fluid Flow 20:486-491, 1999) mainly derived for low viscous droplets revealed that the upper limit of their validity is given by an Ohnesorge number of Oh = 0.115 and a capillary number of Ca = 0.577. For higher values of these non-dimensional parameters and hence higher dynamic viscosities, these models are unable to predict correctly the

  1. Measurement of the low-energy Na+-Na total collision rate in an ion-neutral hybrid trap

    NASA Astrophysics Data System (ADS)

    Goodman, D. S.; Wells, J. E.; Kwolek, J. M.; Blümel, R.; Narducci, F. A.; Smith, W. W.

    2015-01-01

    We present measurements of the total elastic and resonant charge-exchange ion-atom collision rate coefficient kia of cold sodium (Na) with optically dark low-energy Na+ ions in a hybrid ion-neutral trap. To determine kia, we measured the trap loading and loss rates from both a Na magneto-optical trap (MOT) and a linear radio-frequency quadrupole Paul trap. We found the total rate coefficient to be 7.4 ±1.9 ×10-8 cm3/s for the type-I Na MOT immersed within an ≈140 -K ion cloud and 1.10 ±0.25 ×10-7 cm3/s for the type-II Na MOT within an ≈1070 -K ion cloud. Our measurements show excellent agreement with previously reported theoretical fully quantal ab initio calculations. In the process of determining the total rate coefficient, we demonstrate that a MOT can be used to probe an optically dark ion cloud's spatial distribution within a hybrid trap.

  2. Dynamics of electronically inelastic collisions from 3D Doppler measurements

    SciTech Connect

    Suits, A.G.; de Pujo, P.; Sublemontier, O.; Visticot, J.; Berlande, J.; Cuvellier, J.; Gustavsson, T.; Mestdagh, J.; Meynadier, P. ); Lee, Y.T. )

    1991-11-25

    Flux-velocity contour maps were obtained for the inelastic collision process Ba({sup 1}{ital P}{sub 1})+O{sub 2}N{sub 2}{r arrow}Ba({sup 3}{ital P}{sub 2})+O{sub 2}N{sub 2} from Doppler scans of scattered Ba({sup 3}{ital P}{sub 2}) taken over a range of probe laser directions in a crossed-beam experiment. Collision with O{sub 2} resulted in sharply forward scattered Ba({sup 3}{ital P}{sub 2}), with efficient conversion of inital electronic energy into O{sub 2} internal energy and little momentum transfer. Collision with N{sub 2} was dominated by wide-angle scattering with most of the available electronic energy appearing in product translation. The results suggest the importance of large-impact-parameter collisions and a near-resonant energy transfer in the case of O{sub 2}, while for N{sub 2} close collisions dominate despite the presence of an analogous near-resonant channel. The results represent the first direct experimental demonstration of a near-resonant quenching process.

  3. DETECTION OF LOW-VELOCITY COLLISIONS IN SATURN'S F RING

    SciTech Connect

    Attree, N. O.; Murray, C. D.; Cooper, N. J.; Williams, G. A.

    2012-08-20

    Jets of material extending several hundred kilometers from Saturn's F ring are thought to be caused by collisions at speeds of several tens of ms{sup -1} between {approx}10 km diameter objects such as S/2004 S 6 and the core of the ring. The subsequent effects of Keplerian shear give rise to the multi-stranded nature of the F ring. Observations of the ring by the Imaging Science Subsystem experiment on the Cassini spacecraft have provided evidence that some smaller protrusions from the ring's core are the result of low-velocity collisions with nearby objects. We refer to these protrusions as 'mini-jets' and one such feature has been observed for {approx}7.5 hr as its length changed from {approx}75 km to {approx}250 km while it simultaneously appeared to collapse into the core. Orbit determinations suggest that such mini-jets consist of ring material displaced by a {approx}1 ms{sup -1} collision with a nearby moonlet, resulting in paths relative to the core that are due to a combination of Keplerian shear and epicyclic motion. Detections of mini-jets in the Cassini images suggest that it may now be possible to understand most small-scale F ring structure as the result of such collisions. A study of these mini-jets will therefore put constraints on the properties of the colliding population as well as improve our understanding of low-velocity collisions between icy objects.

  4. Centrality dependence of high-p(T) hadron suppression in Au+Au collisions at sqrt[s(NN)]=130 GeV.

    PubMed

    Adler, C; Ahammed, Z; Allgower, C; Amonett, J; Anderson, B D; Anderson, M; Averichev, G S; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Bekele, S; Belaga, V V; Bellwied, R; Berger, J; Bichsel, H; Billmeier, A; Bland, L C; Blyth, C O; Bonner, B E; Boucham, A; Brandin, A; Bravar, A; Cadman, R V; Caines, H; Calderón de la Barca Sánchez, M; Cardenas, A; Carroll, J; Castillo, J; Castro, M; Cebra, D; Chaloupka, P; Chattopadhyay, S; Chen, Y; Chernenko, S P; Cherney, M; Chikanian, A; Choi, B; Christie, W; Coffin, J P; Cormier, T M; Cramer, J G; Crawford, H J; Deng, W S; Derevschikov, A A; Didenko, L; Dietel, T; Draper, J E; Dunin, V B; Dunlop, J C; Eckardt, V; Efimov, L G; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Fachini, P; Faine, V; Faivre, J; Filimonov, K; Finch, E; Fisyak, Y; Flierl, D; Foley, K J; Fu, J; Gagliardi, C A; Gagunashvili, N; Gans, J; Gaudichet, L; Germain, M; Geurts, F; Ghazikhanian, V; Grachov, O; Grigoriev, V; Guedon, M; Gushin, E; Hallman, T J; Hardtke, D; Harris, J W; Henry, T W; Heppelmann, S; Herston, T; Hippolyte, B; Hirsch, A; Hjort, E; Hoffmann, G W; Horsley, M; Huang, H Z; Humanic, T J; Igo, G; Ishihara, A; Ivanshin, Yu I; Jacobs, P; Jacobs, W W; Janik, M; Johnson, I; Jones, P G; Judd, E G; Kaneta, M; Kaplan, M; Keane, D; Kiryluk, J; Kisiel, A; Klay, J; Klein, S R; Klyachko, A; Konstantinov, A S; Kopytine, M; Kotchenda, L; Kovalenko, A D; Kramer, M; Kravtsov, P; Krueger, K; Kuhn, C; Kulikov, A I; Kunde, G J; Kunz, C L; Kutuev, R Kh; Kuznetsov, A A; Lakehal-Ayat, L; Lamont, M A C; Landgraf, J M; Lange, S; Lansdell, C P; Lasiuk, B; Laue, F; Lauret, J; Lebedev, A; Lednický, R; Leontiev, V M; LeVine, M J; Li, Q; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, L; Liu, Z; Liu, Q J; Ljubicic, T; Llope, W J; LoCurto, G; Long, H; Longacre, R S; Lopez-Noriega, M; Love, W A; Ludlam, T; Lynn, D; Ma, J; Majka, R; Margetis, S; Markert, C; Martin, L; Marx, J; Matis, H S; Matulenko, Yu A; McShane, T S; Meissner, F; Melnick, Yu; Meschanin, A; Messer, M; Miller, M L; Milosevich, Z; Minaev, N G; Mitchell, J; Moiseenko, V A; Moore, C F; Morozov, V; de Moura, M M; Munhoz, M G; Nelson, J M; Nevski, P; Nikitin, V A; Nogach, L V; Norman, B; Nurushev, S B; Odyniec, G; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Paic, G; Pandey, S U; Panebratsev, Y; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Perevoztchikov, V; Peryt, W; Petrov, V A; Planinic, M; Pluta, J; Porile, N; Porter, J; Poskanzer, A M; Potrebenikova, E; Prindle, D; Pruneau, C; Putschke, J; Rai, G; Rakness, G; Ravel, O; Ray, R L; Razin, S V; Reichhold, D; Reid, J G; Renault, G; Retiere, F; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevski, O V; Romero, J L; Rose, A; Roy, C; Rykov, V; Sakrejda, I; Salur, S; Sandweiss, J; Saulys, A C; Savin, I; Schambach, J; Scharenberg, R P; Schmitz, N; Schroeder, L S; Schüttauf, A; Schweda, K; Seger, J; Seliverstov, D; Seyboth, P; Shahaliev, E; Shestermanov, K E; Shimanskii, S S; Shvetcov, V S; Skoro, G; Smirnov, N; Snellings, R; Sorensen, P; Sowinski, J; Spinka, H M; Srivastava, B; Stephenson, E J; Stock, R; Stolpovsky, A; Strikhanov, M; Stringfellow, B; Struck, C; Suaide, A A P; Sugarbaker, E; Suire, C; Sumbera, M; Surrow, B; Symons, T J M; Szanto de Toledo, A; Szarwas, P; Tai, A; Takahashi, J; Tang, A H; Thomas, J H; Thompson, M; Tikhomirov, V; Tokarev, M; Tonjes, M B; Trainor, T A; Trentalange, S; Tribble, R E; Trofimov, V; Tsai, O; Ullrich, T; Underwood, D G; Van Buren, G; VanderMolen, A M; Vasilevski, I M; Vasiliev, A N; Vigdor, S E; Voloshin, S A; Wang, F; Ward, H; Watson, J W; Wells, R; Westfall, G D; Whitten, C; Wieman, H; Willson, R; Wissink, S W; Witt, R; Wood, J; Xu, N; Xu, Z; Yakutin, A E; Yamamoto, E; Yang, J; Yepes, P; Yurevich, V I; Zanevski, Y V; Zborovský, I; Zhang, H; Zhang, W M; Zoulkarneev, R; Zubarev, A N

    2002-11-11

    Inclusive transverse momentum distributions of charged hadrons within 0.2collisions at sqrt[s(NN)]=130 GeV. Hadron yields are suppressed at high p(T) in central collisions relative to peripheral collisions and to a nucleon-nucleon reference scaled for collision geometry. Peripheral collisions are not suppressed relative to the nucleon-nucleon reference. The suppression varies continuously at intermediate centralities. The results indicate significant nuclear medium effects on high-p(T) hadron production in heavy-ion collisions at high energy.

  5. Photon and dilepton production in high energy heavy ion collisions

    SciTech Connect

    Sakaguchi, Takao

    2015-05-07

    The recent results on direct photons and dileptons in high energy heavy ion collisions, obtained particularly at RHIC and LHC are reviewed. The results are new not only in terms of the probes, but also in terms of the precision. We shall discuss the physics learned from the results.

  6. 46 CFR 171.085 - Collision bulkhead.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Collision bulkhead. 171.085 Section 171.085 Shipping... PERTAINING TO VESSELS CARRYING PASSENGERS Additional Subdivision Requirements § 171.085 Collision bulkhead... portion of the collision bulkhead that is below the bulkhead deck must be watertight. (c) Each portion...

  7. 46 CFR 179.210 - Collision bulkhead.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Collision bulkhead. 179.210 Section 179.210 Shipping....210 Collision bulkhead. (a) A vessel of more than 19.8 meters (65 feet) in length must have a collision bulkhead. (b) A vessel of not more than 19.8 meters (65 feet) in length must have a...

  8. 46 CFR 174.340 - Collision bulkhead.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Collision bulkhead. 174.340 Section 174.340 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY SPECIAL RULES... Collision bulkhead. Each hopper dredge must have a collision bulkhead that is located not less than...

  9. 46 CFR 171.085 - Collision bulkhead.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Collision bulkhead. 171.085 Section 171.085 Shipping... PERTAINING TO VESSELS CARRYING PASSENGERS Additional Subdivision Requirements § 171.085 Collision bulkhead... portion of the collision bulkhead that is below the bulkhead deck must be watertight. (c) Each portion...

  10. 46 CFR 171.085 - Collision bulkhead.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Collision bulkhead. 171.085 Section 171.085 Shipping... PERTAINING TO VESSELS CARRYING PASSENGERS Additional Subdivision Requirements § 171.085 Collision bulkhead... portion of the collision bulkhead that is below the bulkhead deck must be watertight. (c) Each portion...

  11. 46 CFR 174.340 - Collision bulkhead.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Collision bulkhead. 174.340 Section 174.340 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY SPECIAL RULES... Collision bulkhead. Each hopper dredge must have a collision bulkhead that is located not less than...

  12. 46 CFR 174.340 - Collision bulkhead.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Collision bulkhead. 174.340 Section 174.340 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY SPECIAL RULES... Collision bulkhead. Each hopper dredge must have a collision bulkhead that is located not less than...

  13. 46 CFR 174.190 - Collision bulkhead.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Collision bulkhead. 174.190 Section 174.190 Shipping... PERTAINING TO SPECIFIC VESSEL TYPES Special Rules Pertaining to Offshore Supply Vessels § 174.190 Collision bulkhead. (a) Each OSV must have a collision bulkhead in compliance with §§ 171.085(c)(1), (d), (e)(2),...

  14. 46 CFR 174.190 - Collision bulkhead.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Collision bulkhead. 174.190 Section 174.190 Shipping... PERTAINING TO SPECIFIC VESSEL TYPES Special Rules Pertaining to Offshore Supply Vessels § 174.190 Collision bulkhead. (a) Each OSV must have a collision bulkhead in compliance with §§ 171.085(c)(1), (d), (e)(2),...

  15. 46 CFR 179.310 - Collision bulkheads.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Collision bulkheads. 179.310 Section 179.310 Shipping...) SUBDIVISION, DAMAGE STABILITY, AND WATERTIGHT INTEGRITY Watertight Integrity Requirements § 179.310 Collision bulkheads. (a) Each collision bulkhead required by § 179.210, must be constructed in accordance with §...

  16. 46 CFR 179.310 - Collision bulkheads.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Collision bulkheads. 179.310 Section 179.310 Shipping...) SUBDIVISION, DAMAGE STABILITY, AND WATERTIGHT INTEGRITY Watertight Integrity Requirements § 179.310 Collision bulkheads. (a) Each collision bulkhead required by § 179.210, must be constructed in accordance with §...

  17. 46 CFR 179.210 - Collision bulkhead.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Collision bulkhead. 179.210 Section 179.210 Shipping....210 Collision bulkhead. (a) A vessel of more than 19.8 meters (65 feet) in length must have a collision bulkhead. (b) A vessel of not more than 19.8 meters (65 feet) in length must have a...

  18. 46 CFR 179.210 - Collision bulkhead.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Collision bulkhead. 179.210 Section 179.210 Shipping....210 Collision bulkhead. (a) A vessel of more than 19.8 meters (65 feet) in length must have a collision bulkhead. (b) A vessel of not more than 19.8 meters (65 feet) in length must have a...

  19. 46 CFR 174.190 - Collision bulkhead.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Collision bulkhead. 174.190 Section 174.190 Shipping... PERTAINING TO SPECIFIC VESSEL TYPES Special Rules Pertaining to Offshore Supply Vessels § 174.190 Collision bulkhead. (a) Each OSV must have a collision bulkhead in compliance with §§ 171.085(c)(1), (d), (e)(2),...

  20. 46 CFR 179.310 - Collision bulkheads.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Collision bulkheads. 179.310 Section 179.310 Shipping...) SUBDIVISION, DAMAGE STABILITY, AND WATERTIGHT INTEGRITY Watertight Integrity Requirements § 179.310 Collision bulkheads. (a) Each collision bulkhead required by § 179.210, must be constructed in accordance with §...

  1. 46 CFR 174.340 - Collision bulkhead.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Collision bulkhead. 174.340 Section 174.340 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY SPECIAL RULES... Collision bulkhead. Each hopper dredge must have a collision bulkhead that is located not less than...

  2. 46 CFR 174.340 - Collision bulkhead.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Collision bulkhead. 174.340 Section 174.340 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY SPECIAL RULES... Collision bulkhead. Each hopper dredge must have a collision bulkhead that is located not less than...

  3. 46 CFR 174.190 - Collision bulkhead.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Collision bulkhead. 174.190 Section 174.190 Shipping... PERTAINING TO SPECIFIC VESSEL TYPES Special Rules Pertaining to Offshore Supply Vessels § 174.190 Collision bulkhead. (a) Each OSV must have a collision bulkhead in compliance with §§ 171.085(c)(1), (d), (e)(2),...

  4. 46 CFR 179.210 - Collision bulkhead.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Collision bulkhead. 179.210 Section 179.210 Shipping....210 Collision bulkhead. (a) A vessel of more than 19.8 meters (65 feet) in length must have a collision bulkhead. (b) A vessel of not more than 19.8 meters (65 feet) in length must have a...

  5. 46 CFR 171.085 - Collision bulkhead.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Collision bulkhead. 171.085 Section 171.085 Shipping... PERTAINING TO VESSELS CARRYING PASSENGERS Additional Subdivision Requirements § 171.085 Collision bulkhead... portion of the collision bulkhead that is below the bulkhead deck must be watertight. (c) Each portion...

  6. 46 CFR 179.210 - Collision bulkhead.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Collision bulkhead. 179.210 Section 179.210 Shipping....210 Collision bulkhead. (a) A vessel of more than 19.8 meters (65 feet) in length must have a collision bulkhead. (b) A vessel of not more than 19.8 meters (65 feet) in length must have a...

  7. 46 CFR 171.085 - Collision bulkhead.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Collision bulkhead. 171.085 Section 171.085 Shipping... PERTAINING TO VESSELS CARRYING PASSENGERS Additional Subdivision Requirements § 171.085 Collision bulkhead... portion of the collision bulkhead that is below the bulkhead deck must be watertight. (c) Each portion...

  8. 46 CFR 179.310 - Collision bulkheads.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Collision bulkheads. 179.310 Section 179.310 Shipping...) SUBDIVISION, DAMAGE STABILITY, AND WATERTIGHT INTEGRITY Watertight Integrity Requirements § 179.310 Collision bulkheads. (a) Each collision bulkhead required by § 179.210, must be constructed in accordance with §...

  9. 46 CFR 174.190 - Collision bulkhead.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Collision bulkhead. 174.190 Section 174.190 Shipping... PERTAINING TO SPECIFIC VESSEL TYPES Special Rules Pertaining to Offshore Supply Vessels § 174.190 Collision bulkhead. (a) Each OSV must have a collision bulkhead in compliance with §§ 171.085(c)(1), (d), (e)(2),...

  10. Environmental Characteristics Associated With Pedestrian–Motor Vehicle Collisions in Denver, Colorado

    PubMed Central

    Sebert Kuhlmann, Anne K.; Thomas, Deborah; R. Sain, Stephan

    2009-01-01

    Objectives. We examined patterns of pedestrian–motor vehicle collisions and associated environmental characteristics in Denver, Colorado. Methods. We integrated publicly available data on motor vehicle collisions, liquor licenses, land use, and sociodemographic characteristics to analyze spatial patterns and other characteristics of collisions involving pedestrians. We developed both linear and spatially weighted regression models of these collisions. Results. Spatial analysis revealed global clustering of pedestrian–motor vehicle collisions with concentrations in downtown, in a contiguous neighborhood, and along major arterial streets. Walking to work, population density, and liquor license outlet density all contributed significantly to both linear and spatial models of collisions involving pedestrians and were each significantly associated with these collisions. Conclusions. These models, constructed with data from Denver, identified conditions that likely contribute to patterns of pedestrian–motor vehicle collisions. Should these models be verified elsewhere, they will have implications for future research directions, public policy to enhance pedestrian safety, and public health programs aimed at decreasing unintentional injury from pedestrian–motor vehicle collisions and promoting walking as a routine physical activity. PMID:19608966

  11. Diffractive Higgs boson photoproduction in ultraperipheral collisions at LHC

    SciTech Connect

    Gay Ducati, M. B.; Silveira, G. G.

    2010-10-01

    A new production mechanism for the standard model Higgs boson in ultraperipheral collisions at the LHC, which allows central exclusive diffractive production by double pomeron exchange in photon-proton processes, is presented. The Higgs boson is centrally produced by gluon fusion with two large rapidity gaps emerging in the final state, being the main experimental signature for this process. As already studied for Pomeron-Pomeron and two-photon processes, the Higgs boson photoproduction is studied within this new mechanism in proton-proton (pp) and proton-nucleus (pA) collisions, where each system has a different dynamics to be taken into account. As a result, this mechanism predicts a production cross section for pp collisions of about 1.8 fb, which is similar to that obtained in Pomeron-Pomeron processes. Besides, in pPb collisions the cross sections have increased to about 0.6 pb, being comparable with the results of two-photon processes in pAu collisions. Therefore, as the rapidity gap survival probability is an open question in high-energy physics, an analysis for different values of this probability shows how competitive the mechanisms are in the LHC kinematical regime.

  12. Mixing Diagnostics in Confined, High-Speed Droplet Collisions

    NASA Astrophysics Data System (ADS)

    Carroll, Brian; Hidrovo, Carlos

    2012-11-01

    Fast mixing remains a major challenge in droplet-based microfluidics. The low Reynolds number operating regime of most mixing devices signifies orderly flows that are devoid of any inertial characteristics. To increase droplet mixing rates, a novel technique is under development that uses a high Reynolds number gaseous phase for droplet generation and transport and promotes mixing through binary droplet collisions at velocities near 1m/s. Limitations in existing mixing diagnostic methodologies has persuaded cultivation of a new technique for measuring droplet collision mixing in confined microchannels. The technique employs single fluorophore laser-induced fluorescence, custom image processing, and meaningful statistical analysis for monitoring and quantifying mixing in high-speed droplet collisions. Mixing progress is revealed through two statistics that separate the roles of convective rearrangement and molecular diffusion during the mixing process. The end result is a viewing window into the rich dynamics of droplet collisions with spatial and temporal resolutions of 1 μm and 25 μs, respectively. Experimental results obtained across a decade of Reynolds and Peclet numbers reveal a direct link between droplet mixing time and the collision convective timescale. This work provides valuable insight into the emerging field of two-phase gas-liquid microfluidics and opens the door to fundamental research possibilities not offered by traditional oil-based architectures.

  13. Comparing Fragmentation Functions in Pb-Pb Collisions using JEWEL

    NASA Astrophysics Data System (ADS)

    Davis, Harrison

    2016-09-01

    Collisions between lead nuclei at relativistic speeds create a hot, dense state of deconfined quark matter called the quark gluon plasma (QGP). Due to its extreme density, temperature, and abundance of color charge, the QGP gives us a unique opportunity to study strong interactions and test the limits of QCD. Collisions between nuclei produce jets, clusters of particles hadronized from an energetic parton. Jets produced in heavy ion collisions must travel through the energetic and dense QGP, which changes the structure and momenta of the jets, a phenomenon known as jet quenching. By analyzing the changes in hadron fragmentation and momenta, we probe the properties and structure of the QGP. To analyze the jet fragmentation, we simulated lead-lead collisions with JEWEL, a modification to the Monte-Carlo (MC) generator PYTHIA6, and compared the results with ATLAS data at 2.76 TeV and 5 TeV. These comparisons between the ATLAS data and the MC simulation are important for understanding jet quenching in heavy ion collisions. This poster gives an overview of the results of the simulation and how they compare with ATLAS data on fragmentation.

  14. The risk of pedestrian collisions with peripheral visual field loss

    PubMed Central

    Peli, Eli; Apfelbaum, Henry; Berson, Eliot L.; Goldstein, Robert B.

    2016-01-01

    Patients with peripheral field loss complain of colliding with other pedestrians in open-space environments such as shopping malls. Field expansion devices (e.g., prisms) can create artificial peripheral islands of vision. We investigated the visual angle at which these islands can be most effective for avoiding pedestrian collisions, by modeling the collision risk density as a function of bearing angle of pedestrians relative to the patient. Pedestrians at all possible locations were assumed to be moving in all directions with equal probability within a reasonable range of walking speeds. The risk density was found to be highly anisotropic. It peaked at ≈45° eccentricity. Increasing pedestrian speed range shifted the risk to higher eccentricities. The risk density is independent of time to collision. The model results were compared to the binocular residual peripheral island locations of 42 patients with forms of retinitis pigmentosa. The natural residual island prevalence also peaked nasally at about 45° but temporally at about 75°. This asymmetry resulted in a complementary coverage of the binocular field of view. Natural residual binocular island eccentricities seem well matched to the collision-risk density function, optimizing detection of other walking pedestrians (nasally) and of faster hazards (temporally). Field expansion prism devices will be most effective if they can create artificial peripheral islands at about 45° eccentricities. The collision risk and residual island findings raise interesting questions about normal visual development. PMID:27919101

  15. Warning Drivers about Impending Collisions using Vibrotactile Flow.

    PubMed

    Ahtamad, Mujthaba; Spence, Charles; Ho, Cristy; Gray, Rob

    2015-11-24

    Vibrotactile collision warning signals that create a sensation of motion across a driver's body result in faster brake reaction times (BRTs) to potential collision events. To date, however, such warnings have only simulated linear motion. We extended this research by exploring the effectiveness of collision warnings that incorporate vibrotactile patterns or "vibrotactile flow". In Experiment 1, expanding and contracting vibrotactile flow warnings were compared with a static warning (all tactors activated simultaneously) and a no warning condition in a car following scenario. Both vibrotactile flow warnings produced significantly faster BRTs than the static and no warning conditions. However, there was no directional effect. That is, there was no significant difference between contracting and expanding signals. Warnings that utilise vibrotactile flow therefore appear to provide an effective means of informing drivers about potential collision events. However, unlike comparable warnings utilizing linear motion, their effectiveness does not seem to depend on the precise relationship between the warning and collision events. Experiment 2 demonstrated that a tactile warning incorporating linear motion produced significantly faster BRTs than an expanding vibrotactile flow warning. Taken together, these results suggest that vibrotactile warnings that simulate linear motion may be more effective than vibrotactile flow warnings.

  16. Collision avoidance between two walkers: role-dependent strategies.

    PubMed

    Olivier, Anne-Hélène; Marin, Antoine; Crétual, Armel; Berthoz, Alain; Pettré, Julien

    2013-09-01

    This paper studies strategies for collision avoidance between two persons walking along crossing trajectories. It has been previously demonstrated that walkers are able to anticipate the risk of future collision and to react accordingly. The avoidance task has been described as a mutual control of the future distance of closest approach, MPD (i.e., Mininum Predicted Distance). In this paper, we studied the role of each walker in the task of controlling MPD. A specific question was: does the walker giving way (2nd at the crossing) and the one passing first set similar and coordinated strategies? To answer this question, we inspected the effect of motion adaptations on the future distance of closest approach. This analysis is relevant in the case of collision avoidance because subtle anticipatory behaviors or large last moment adaptations can finally yield the same result upon the final crossing distance. Results showed that collision avoidance is performed collaboratively and the crossing order impacts both the contribution and the strategies used: the participant giving way contributes more than the one passing first to avoid the collision. Both walkers reorient their path but the participant giving way also adapts his speed. Future work is planned to investigate the influence of crossing angle and TTC on adaptations as well as new types of interactions, such as intercepting or meeting tasks.

  17. Sequential binary collision ionization mechanisms

    NASA Astrophysics Data System (ADS)

    van Boeyen, R. W.; Watanabe, N.; Doering, J. P.; Moore, J. H.; Coplan, M. A.; Cooper, J. W.

    2004-03-01

    Fully differential cross sections for the electron-impact ionization of the magnesium 3s orbital have been measured in a high-momentum-transfer regime wherein the ionization mechanisms can be accurately described by simple binary collision models. Measurements where performed at incident-electron energies from 400 to 3000 eV, ejected-electron energies of 62 eV, scattering angle of 20 °, and momentum transfers of 2 to 5 a.u. In the out-of-plane geometry of the experiment the cross section is observed far off the Bethe ridge. Both first- and second-order processes can be clearly distinguished as previously observed by Murray et al [Ref. 1] and Schulz et al [Ref. 2]. Owing to the relatively large momentum of the ejected electron, the second order processes can be modeled as sequential binary collisions involving a binary elastic collision between the incident electron and ionic core and a binary knock-out collision between the incident electron and target electron. At low incident-electron energies the cross section for both first and second order processes are comparable, while at high incident energies second-order processes dominate. *Supported by NSF under grant PHY-99-87870. [1] A. J. Murray, M. B. J. Woolf, and F. H. Read J. Phys. B 25, 3021 (1992). [2] M. Schulz, R. Moshammer, D. Fischer, H. Kollmus, D. H. Madison. S. Jones and J. Ullrich, Nature 422, 48 (2003).

  18. Duration of an Elastic Collision

    ERIC Educational Resources Information Center

    de Izarra, Charles

    2012-01-01

    With a pedagogical goal, this paper deals with a study of the duration of an elastic collision of an inflatable spherical ball on a planar surface suitable for undergraduate studies. First, the force generated by the deformed spherical ball is obtained under assumptions that are discussed. The study of the motion of the spherical ball colliding…

  19. Quarkonium production in hadronic collisions

    SciTech Connect

    Gavai, R.; Schuler, G.A.; Sridhar, K.

    1995-07-01

    We summarize the theoretical description of charmonium and bottonium production in hadronic collisions and compare it to the available data from hadron-nucleon interactions. With the parameters of the theory established by these data, we obtain predictions for quarkonium production at RHIC and LHC energies.

  20. Probing GPDs in ultraperipheral collisions

    SciTech Connect

    Ivanov, D.Yu.; Pire, B.; Szymanowski, L.; Wagner, J.

    2015-04-10

    Ultraperipheral collisions in hadron colliders give new opportunities to investigate the hadron structure through exclusive photoproduction processes. We describe the possibility of measuring the Generalized Parton Distributions in the Timelike Compton Scattering process and in the production of heavy vector meson.

  1. Influence of quantum diffraction and shielding on electron-ion collision in two-component semiclassical plasmas

    SciTech Connect

    Hong, Woo-Pyo; Jung, Young-Dae

    2015-01-15

    The influence of quantum diffraction and shielding on the electron-ion collision process is investigated in two-component semiclassical plasmas. The eikonal method and micropotential taking into account the quantum diffraction and shielding are used to obtain the eikonal scattering phase shift and the eikonal collision cross section as functions of the collision energy, density parameter, Debye length, electron de Broglie wavelength, and the impact parameter. The result shows that the quantum diffraction and shielding effects suppress the eikonal scattering phase shift as well as the differential eikonal collision cross section, especially, in small-impact parameter regions. It is also shown that the quantum shielding effect on the eikonal collision cross section is more important in low-collision energies. In addition, it is found that the eikonal collision cross section increases with an increase in the density parameter. The variations of the eikonal cross section due to the quantum diffraction and shielding effects are also discussed.

  2. H- - H Collision Induced Radiative Transitions

    NASA Astrophysics Data System (ADS)

    Dadonova, A. V.; Devdariani, A. Z.

    2012-12-01

    Exchange interaction leads to the formation of gerade and ungerade states of temporary molecules (quasimolecules) formed during the H- +H slow collisions. The work deals with the radiation produced by optical transitions between those states. The main characteristics involved in the description of optical transitions in quasimolecules, i.e., energy terms, an optical dipole transition moments, have been calculated in the frame of zero-range potentials model. The main feature of calculations is that the results can be expressed analytically in closed forms via the Lambert W function.

  3. Dynamical phase trajectories for relativistic nuclear collisions

    SciTech Connect

    Arsene, I. C.; Bravina, L. V.; Cassing, W.; Ivanov, Yu. B.; Russkikh, V. N.; Larionov, A.; Randrup, J.; Toneev, V. D.; Zeeb, G.; Zschiesche, D.

    2007-03-15

    Central collisions of gold nuclei are simulated by several existing models and the central net baryon density {rho} and the energy density {epsilon} are extracted at successive times for beam kinetic energies of 5-40 GeV/nucleon. The resulting trajectories in the ({rho},{epsilon}) phase plane are discussed from the perspective of experimentally exploring the expected first-order hadronization phase transition with the planned FAIR at GSI or in a low-energy campaign at the Relativistic Heavy Ion Collider.

  4. Global Λ polarization in high energy collisions

    NASA Astrophysics Data System (ADS)

    Xie, Yilong; Wang, Dujuan; Csernai, László P.

    2017-03-01

    With a Yang-Mills flux-tube initial state and a high-resolution (3+1)D particle-in-cell relativistic (PICR) hydrodynamics simulation, we calculate the Λ polarization for different energies. The origination of polarization in high energy collisions is discussed, and we find linear impact parameter dependence of the global Λ polarization. Furthermore, the global Λ polarization in our model decreases very quickly in the low energy domain, and the decline curve fits well the recent results of Beam Energy Scan (BES) program launched by the STAR Collaboration at the Relativistic Heavy Ion Collider (RHIC). The time evolution of polarization is also discussed.

  5. Collision Avoidance for Airport Traffic Concept Evaluation

    NASA Technical Reports Server (NTRS)

    Jones, Denise R.; Prinzel, Lawrence J., III; Otero, Sharon D.; Barker, Glover D.

    2009-01-01

    An initial Collision Avoidance for Airport Traffic (CAAT) concept for the Terminal Maneuvering Area (TMA) was evaluated in a simulation study at the National Aeronautics and Space Administration (NASA) Langley Research Center. CAAT is being designed to enhance surface situation awareness and provide cockpit alerts of potential conflicts during runway, taxi, and low altitude air-to-air operations. The purpose of the study was to evaluate the initial concept for an aircraft-based method of conflict detection and resolution (CD&R) in the TMA focusing on conflict detection algorithms and alerting display concepts. This paper gives an overview of the CD&R concept, simulation study, and test results.

  6. Collision Avoidance for Airport Traffic Simulation Evaluation

    NASA Technical Reports Server (NTRS)

    Jones, Denise R.; Prinzel, Lawrence J., III; Shelton, Kevin J.; Bailey, Randall E.; Otero, Sharon D.; Barker, Glover D.

    2010-01-01

    A Collision Avoidance for Airport Traffic (CAAT) concept for the airport Terminal Maneuvering Area (TMA) was evaluated in a simulation study at the National Aeronautics and Space Administration (NASA) Langley Research Center. CAAT is being designed to enhance surface situation awareness and provide cockpit alerts of potential conflicts during runway, taxi, and low altitude air-to-air operations. The purpose of the study was to evaluate pilot reaction to conflict events in the TMA near the airport, different alert timings for various scenarios, alerting display concepts, and directive alerting concepts. This paper gives an overview of the conflict detection and resolution (CD&R) concept, simulation study, and test results

  7. Experimental overview on flow observables in heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Mohapatra, Soumya

    2016-12-01

    This paper summarizes the experimental results on flow phenomena that were presented at Quark matter 2015, with a focus on new flow observables and correlations in small systems. The results presented include event-shape selected pT spectra and vn measurements, correlations between flow harmonics of different orders, study of factorization breakdown in two-particle correlations, and principal component analysis of two-particle correlations. Recent developments in investigation of collective effects in small collisions systems, namely, p+A, d+A and 3He + A as well as in pp collisions are also presented.

  8. Causality constraints on hadron production in high energy collisions

    NASA Astrophysics Data System (ADS)

    Castorina, Paolo; Satz, Helmut

    2014-04-01

    For hadron production in high energy collisions, causality requirements lead to the counterpart of the cosmological horizon problem: the production occurs in a number of causally disconnected regions of finite space-time size. As a result, globally conserved quantum numbers (charge, strangeness, baryon number) must be conserved locally in spatially restricted correlation clusters. This provides a theoretical basis for the observed suppression of strangeness production in elementary interactions (pp, e+e-). In contrast, the space-time superposition of many collisions in heavy ion interactions largely removes these causality constraints, resulting in an ideal hadronic resonance gas in full equilibrium.

  9. Vibrationally resolved charge transfer for proton collisions with CO and H collisions with CO{sup +}

    SciTech Connect

    Lin, C. Y.; Stancil, P. C.; Li, Y.; Gu, J. P.; Liebermann, H. P.; Buenker, R. J.; Kimura, M.

    2007-07-15

    Electron capture by protons following collisions with carbon monoxide, and the reverse process, is studied with a quantal molecular-orbital coupled-channel method utilizing the infinite order sudden approximation for collision energies between 0.5 and 1000 eV/u. The potential surfaces and couplings, computed with the multireference single- and double-excitation method for a range of H{sup +}-CO orientation angles and C-O separations, are adopted in the scattering calculations. Results including vibrationally resolved and orientation-angle-dependent cross sections are presented for a range of CO and CO{sup +} vibrational levels. Comparison with experiment is made where possible and the relevance of the reaction in astrophysics and atmospheric physics is discussed.

  10. Transport coefficients of multi-particle collision algorithms with velocity-dependent collision rules.

    PubMed

    Ihle, Thomas

    2008-06-11

    Detailed calculations of the transport coefficients of a recently introduced particle-based model for fluid dynamics with a non-ideal equation of state are presented. Excluded volume interactions are modeled by means of biased stochastic multi-particle collisions which depend on the local velocities and densities. Momentum and energy are exactly conserved locally. A general scheme to derive transport coefficients for such biased, velocity-dependent collision rules is developed. Analytic expressions for the self-diffusion coefficient and the shear viscosity are obtained, and very good agreement is found with numerical results at small and large mean free paths. The viscosity turns out to be proportional to the square root of temperature, as in a real gas. In addition, the theoretical framework is applied to a two-component version of the model, and expressions for the viscosity and the difference in diffusion of the two species are given.

  11. Pion and photon production in heavy ion collisions

    SciTech Connect

    Gabor,D.

    2008-03-16

    Measurement of neutral pions and direct photons are closely connected experimentally, on the other hand they probe quite different aspects of relativistic heavy ion collisions. In this short review of the {pi}{sup 0} results from the PHENIX experiment at RHIC our focus is on the {phi}-integrated nuclear modification factor, its energy and system size dependence, and the impact of these results on parton energy loss models. We also discuss the current status of high p{sub T} and thermal direct photon measurements both in p+p and Au+Au collisions. Recognizing the advantages of measuring not only the 'signal', but also all the 'references' needed for proper interpretation in the same experiments (with same or similar systematics) we argue that RHIC should regularly include d+A and even d+d collisions into its system size and energy scan.

  12. Conservative deterministic spectral Boltzmann solver near the grazing collisions limit

    NASA Astrophysics Data System (ADS)

    Haack, Jeffrey R.; Gamba, Irene M.

    2012-11-01

    We present new results building on the conservative deterministic spectral method for the space homogeneous Boltzmann equation developed by Gamba and Tharkabhushaman. This approach is a two-step process that acts on the weak form of the Boltzmann equation, and uses the machinery of the Fourier transform to reformulate the collisional integral into a weighted convolution in Fourier space. A constrained optimization problem is solved to preserve the mass, momentum, and energy of the resulting distribution. Within this framework we have extended the formulation to the case of more general case of collision operators with anisotropic scattering mechanisms, which requires a new formulation of the convolution weights. We also derive the grazing collisions limit for the method, and show that it is consistent with the Fokker-Planck-Landau equations as the grazing collisions parameter goes to zero.

  13. Overview of recent ALICE results

    NASA Astrophysics Data System (ADS)

    Lakomov, Igor

    2016-10-01

    ALICE is one of the four largest LHC experiments. It is dedicated to the study of the properties of the deconfined state of matter formed at large energy densities in heavy-ion collisions — the Quark-Gluon Plasma. The ALICE Collaboration also participated in the pp and p-Pb data-taking periods at the LHC. An overview of recent ALICE results is presented for three collision systems: pp, p-Pb and Pb-Pb.

  14. Exposure assessment in auto collision repair shops.

    PubMed

    Bejan, Anca; Brosseau, Lisa M; Parker, David L

    2011-07-01

    Workers in auto collision shops are exposed to a variety of chemical and physical hazards. Previous studies have focused on measuring levels of isocyanates, but little is known about exposures to dust, noise, and solvents. In preparation for an intervention effectiveness study in small collision repair businesses, sampling was conducted on 3 consecutive days in four representative businesses with three to seven employees. Full-shift and task-specific exposures were measured for dust and solvents (for operations other than painting and spray gun cleaning). Full-shift personal exposures and tool-specific noise levels were also evaluated. Samples of banded earplugs were distributed to employees and feedback was collected after 1 week of wear time. Dust and solvent exposures did not exceed the OSHA PELs. Noise exposure doses were below the OSHA PEL; however, 4 of the 18 measurements were in excess of the ACGIH® threshold limit value. The majority of tools generated noise levels above 85 dBA. Air guns, wrenches, cutoff wheels, and air drills generated noise levels with the 5th percentile above 90 dBA. Mean noise levels generated by hammers, grinders, and ratchets were also above 95 dBA. Three pairs of banded earplugs had the best reviews in terms of comfort of use. This study was conducted during a time when all shops reported relatively low production levels. Noise exposure results suggest that it is likely that technicians' 8-hr time-weighted average exposures may be in excess of 85 dBA during periods of higher production, but exposures to dust and solvents are unlikely to approach OSHA exposure limits. These pilot test results will be useful when developing recommendations and technical assistance materials for health and safety interventions in auto collision repair businesses.

  15. Development of a variable speed limit strategy to reduce secondary collision risks during inclement weathers.

    PubMed

    Li, Zhibin; Li, Ye; Liu, Pan; Wang, Wei; Xu, Chengcheng

    2014-11-01

    Inclement weather reduces traveler's sight distance and increases vehicle's stopping distance. Once a collision occurred during inclement weather and resulted in a slow traffic, approaching vehicles may not have adequate time to make emergency responses to the hazardous traffic, resulting in increased potentials of secondary collisions. The primary objective of this study is to develop a control strategy of variable speed limits (VSL) to reduce the risks of secondary collisions during inclement weathers. By analyzing the occurrence condition of secondary collision, the VSL strategy is proposed to dynamically adjust the speed limits according to the current traffic and weather conditions. A car-following model is modified to simulate the vehicle maneuvers with the VSL control. Two surrogate safety measures, based on the time-to-collision notion, are used to evaluate the control effects of VSL. Five weather scenarios are evaluated in simulation. The results show that the VSL strategy effectively reduces the risks of secondary collisions in various weather types. The time exposed time-to-collision (TET) is reduced by 41.45%-50.74%, and the time integrated time-to-collision (TIT) is reduced by 38.19%-41.19%. The safety effects are compared to those with a previous VSL strategy. The results show that in most cases our strategy outperforms the previous one. We also evaluate how driver's compliance to speed limit affects the effectiveness of VSL control.

  16. Debate on the current understanding of high-energy heavy-ion collisions

    SciTech Connect

    Becattini, Francesco; Busza, Wit; Foka, Panagiota; Gazdzicki, Marek; Hippolyte, Boris; Pajares, Carlos; Philipsen, Owe; Snellings, Raimond

    2011-05-23

    We present a debate on the picture of high-energy heavy-ion collisions. Based on conventional wisdom the different stages of the collision and properties of the medium are described. The panel is asked to discuss plausible results which will either verify or unambiguously falsify the outlined picture or some aspects of it.

  17. Collective effects in light-heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Schenke, Björn; Venugopalan, Raju

    2014-11-01

    We present results for the azimuthal anisotropy of charged hadron distributions in A+A, p+A, d+A, and 3He+A collisions within the IP-Glasma+MUSIC model. Obtained anisotropies are due to the fluid dynamic response of the system to the fluctuating initial geometry of the interaction region. While the elliptic and triangular anisotropies in peripheral Pb+Pb collisions at √{ s} = 2.76 TeV are well described by the model, the same quantities in √{ s} = 5.02 TeV p+Pb collisions underestimate the experimental data. This disagreement can be due to neglected initial state correlations or the lack of a detailed description of the fluctuating spatial structure of the proton, or both. We further present predictions for azimuthal anisotropies in p+Au, d+Au, and 3He+Au collisions at √{ s} = 200 GeV. For d+Au and 3He+Au collisions we expect the detailed substructure of the nucleon to become less important.

  18. Ship collision risk assessment for the Singapore Strait.

    PubMed

    Qu, Xiaobo; Meng, Qiang; Suyi, Li

    2011-11-01

    The Singapore Strait is considered as the bottleneck and chokepoint of the shipping routes connecting the Indian and the Pacific Ocean. Therefore, the ship collision risk assessment is of significant importance for ships passing through the narrow, shallow, and busy waterway. In this paper, three ship collision risk indices are initially proposed to quantitatively assess the ship collision risks in the Strait: index of speed dispersion, degree of acceleration and deceleration, and number of fuzzy ship domain overlaps. These three risk indices for the Singapore Strait are estimated by using the real-time ship locations and sailing speeds provide by Lloyd's MIU automatic identification system (AIS). Based on estimation of these three risk indices, it can be concluded that Legs 4W, 5W, 11E, and 12E are the most risky legs in the Strait. Therefore, the ship collision risk reduction solutions should be prioritized being implemented in these four legs. This study also finds that around 25% of the vessels sail with a speed in excess of the speed limit, which results in higher potentials of ship collision. Analysis indicates that the safety level would be significantly improved if all the vessels follow the passage guidelines.

  19. Surface impacts and collisions of particle-laden nanodrops

    NASA Astrophysics Data System (ADS)

    Koplik, Joel

    2015-08-01

    The surface impact and collisions of particle-laden nanodrops are studied using molecular dynamics computer simulations. The drops are composed of Lennard-Jones dimers and the particles are rigid spherical sections of a cubic lattice, with radii about 11 nm and 0.6 nm, respectively. Uniform suspensions of 21% and 42% particle concentrations and particle-coated drops are studied, and their behavior is compared to that of pure fluid drops of the same size. The relative velocities studied span the transition to splashing, and both wetting/miscible and non-wetting/immiscible cases are considered. Impacts normal to the surface and head-on collisions are studied and compared. In surface impact, the behavior of low-density suspensions and liquid marble drops is qualitatively similar to that of pure liquid, while the concentrated drops are solid-like on impact. Collisions produce a splash only at velocities significantly higher than in impact, but the resulting drop morphology shows a similar dependence on solid concentration as in impact. In all cases, the collision or impact produces a strong local enhancement in the kinetic energy density and temperature but not in the particle or potential energy densities. Mixing of the two colliding species is not enhanced by collisions, unless the velocity is so high as to cause drop disintegration.

  20. Modeling Vehicle Collision Angle in Traffic Crashes Based on Three-Dimensional Laser Scanning Data

    PubMed Central

    Lyu, Nengchao; Huang, Gang; Wu, Chaozhong; Duan, Zhicheng; Li, Pingfan

    2017-01-01

    In road traffic accidents, the analysis of a vehicle’s collision angle plays a key role in identifying a traffic accident’s form and cause. However, because accurate estimation of vehicle collision angle involves many factors, it is difficult to accurately determine it in cases in which less physical evidence is available and there is a lack of monitoring. This paper establishes the mathematical relation model between collision angle, deformation, and normal vector in the collision region according to the equations of particle deformation and force in Hooke’s law of classical mechanics. At the same time, the surface reconstruction method suitable for a normal vector solution is studied. Finally, the estimation model of vehicle collision angle is presented. In order to verify the correctness of the model, verification of multi-angle collision experiments and sensitivity analysis of laser scanning precision for the angle have been carried out using three-dimensional (3D) data obtained by a 3D laser scanner in the collision deformation zone. Under the conditions with which the model has been defined, validation results show that the collision angle is a result of the weighted synthesis of the normal vector of the collision point and the weight value is the deformation of the collision point corresponding to normal vectors. These conclusions prove the applicability of the model. The collision angle model proposed in this paper can be used as the theoretical basis for traffic accident identification and cause analysis. It can also be used as a theoretical reference for the study of the impact deformation of elastic materials. PMID:28264517

  1. Modeling Vehicle Collision Angle in Traffic Crashes Based on Three-Dimensional Laser Scanning Data.

    PubMed

    Lyu, Nengchao; Huang, Gang; Wu, Chaozhong; Duan, Zhicheng; Li, Pingfan

    2017-02-28

    In road traffic accidents, the analysis of a vehicle's collision angle plays a key role in identifying a traffic accident's form and cause. However, because accurate estimation of vehicle collision angle involves many factors, it is difficult to accurately determine it in cases in which less physical evidence is available and there is a lack of monitoring. This paper establishes the mathematical relation model between collision angle, deformation, and normal vector in the collision region according to the equations of particle deformation and force in Hooke's law of classical mechanics. At the same time, the surface reconstruction method suitable for a normal vector solution is studied. Finally, the estimation model of vehicle collision angle is presented. In order to verify the correctness of the model, verification of multi-angle collision experiments and sensitivity analysis of laser scanning precision for the angle have been carried out using three-dimensional (3D) data obtained by a 3D laser scanner in the collision deformation zone. Under the conditions with which the model has been defined, validation results show that the collision angle is a result of the weighted synthesis of the normal vector of the collision point and the weight value is the deformation of the collision point corresponding to normal vectors. These conclusions prove the applicability of the model. The collision angle model proposed in this paper can be used as the theoretical basis for traffic accident identification and cause analysis. It can also be used as a theoretical reference for the study of the impact deformation of elastic materials.

  2. Radiative Association in Li+ + H- collisions

    NASA Astrophysics Data System (ADS)

    Dickinson, A. S.; Gadéa, F. X.

    Radiative association is one of the ways of forming LiH in low density environments. Its formation in collisions of Li(2p) +H(1s) has been shown to be about five orders of magnitude faster than for Li(2s) + H(1s) [1]. We investigate LiH formation in Li+ + H- collisions, considering association on both the C and D Σ states as about 96% of the mutual neutralization is to these states at low energy [2]. A quantal description of the process [3] has been used. The potentials are from ref. [4] and the dipole moments from ref. [5]. Similar results were obtained from both the C and D states. At 1000 K the total radiative association rate coefficient from the D state is 9.2× 10-15 cm3/s, compared to 2.1 × 10-20 cm3/s in Li(2s) + H(1s) collisions [6]. British Council support is gratefully acknowledged. {[1]} Gianturco F.A., Gori Giorgi P., 1996, Phys. Rev. A 54, 4073 {[2]} Croft H., Dickinson A.S., Gadéa F. X., 1999, MNRAS 304, 327 {[3]} Babb J.F., Kirby K.P., 1998, in The Molecular Astrophysics of Stars and Galaxies, Clarendon Press, Oxford, p. 11 {[4]} Gadéa F. X., Boutalib A., 1993, J. Phys. B 26, 61 {[5]} Berriche H., Gadéa F. X., 1995, Chem. Phys. Letts. 247 85 {[6]} Stancil P. C., Dalgarno A., 1997, ApJ 479, 543

  3. Collision-induced dissociation (CID) of peptides and proteins.

    PubMed

    Wells, J Mitchell; McLuckey, Scott A

    2005-01-01

    The most commonly used activation method in the tandem mass spectrometry (MS) of peptides and proteins is energetic collisions with a neutral target gas. The overall process of collisional activation followed by fragmentation of the ion is commonly referred to as collision-induced dissociation (CID). The structural information that results from CID of a peptide or protein ion is highly dependent on the conditions used to effect CID. These include, for example, the relative translational energy of the ion and target, the nature of the target, the number of collisions that is likely to take place, and the observation window of the apparatus. This chapter summarizes the key experimental parameters in the CID of peptide and protein ions, as well as the conditions that tend to prevail in the most commonly employed tandem mass spectrometers.

  4. A neuro-collision avoidance strategy for robot manipulators

    NASA Technical Reports Server (NTRS)

    Onema, Joel P.; Maclaunchlan, Robert A.

    1992-01-01

    The area of collision avoidance and path planning in robotics has received much attention in the research community. Our study centers on a combination of an artificial neural network paradigm with a motion planning strategy that insures safe motion of the Articulated Two-Link Arm with Scissor Hand System relative to an object. Whenever an obstacle is encountered, the arm attempts to slide along the obstacle surface, thereby avoiding collision by means of the local tangent strategy and its artificial neural network implementation. This combination compensates the inverse kinematics of a robot manipulator. Simulation results indicate that a neuro-collision avoidance strategy can be achieved by means of a learning local tangent method.

  5. Heavy quarkonium photoproduction in ultrarelativistic heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Yu, Gong-Ming; Cai, Yang-Bing; Li, Yun-De; Wang, Jian-Song

    2017-01-01

    Based on the factorization formalism of nonrelativistic quantum chromodynamics (NRQCD), we calculate the production cross section for the charmonium [J /ψ , ψ (2 S ) , χc J, ηc, and hc] and the bottomonium [Υ (n S ) , χb J, ηb, and hb] produced by the hard photoproduction processes and fragmentation processes in relativistic heavy ion collisions. It is shown that the existing experimental data on heavy quarkonium production at the Large Hadron Collider (LHC) can be described in the framework of the NRQCD formalism, and the phenomenological values of matrix elements for color-singlet and color-octet components give the main contribution. The numerical results of photoproduction processes and fragmentation processes for the heavy quarkonium production become prominent in p -p collisions and Pb-Pb collisions at LHC energies.

  6. Potential energy curves and collision integrals of air components

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Stallcop, James R.; Levin, Eugene; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Collision integrals are fundamental quantities required to determine the transport properties of the environment surrounding aerospace vehicles in the upper atmosphere. These collision integrals can be determined as a function of temperature from the potential energy curves describing the atomic and molecular collisions. Ab initio calculations provide a practical method of computing the required interaction potentials. In this work we will discuss recent advances with an emphasis on the accuracy that is obtainable. Results for interactions, e.g. N+N, N+O, O+O, and H+N2 will be reviewed and their application to the determination of transport properties, such as diffusion and viscosity coefficients, will be examined.

  7. Depolarizing collisions with hydrogen: Neutral and singly ionized alkaline earths

    SciTech Connect

    Manso Sainz, Rafael; Ramos, Andrés Asensio; Bueno, Javier Trujillo; Aguado, Alfredo

    2014-06-20

    Depolarizing collisions are elastic or quasielastic collisions that equalize the populations and destroy the coherence between the magnetic sublevels of atomic levels. In astrophysical plasmas, the main depolarizing collider is neutral hydrogen. We consider depolarizing rates on the lowest levels of neutral and singly ionized alkali earths Mg I, Sr I, Ba I, Mg II, Ca II, and Ba II, due to collisions with H°. We compute ab initio potential curves of the atom-H° system and solve the quantum mechanical dynamics. From the scattering amplitudes, we calculate the depolarizing rates for Maxwellian distributions of colliders at temperatures T ≤ 10,000 K. A comparative analysis of our results and previous calculations in the literature is completed. We discuss the effect of these rates on the formation of scattering polarization patterns of resonant lines of alkali earths in the solar atmosphere, and their effect on Hanle effect diagnostics of solar magnetic fields.

  8. Modeling of a hollow-cone liquid spray including droplet collisions

    NASA Astrophysics Data System (ADS)

    Asheim, J. P.; Kirwan, J. E.; Peters, J. E.

    1987-01-01

    A spray model is used to determine the characteristics of a hollow-cone water spray injected from a pressure jet swirl atomizer into uniform air flow traveling through a vertical wind tunnel. The model simulates droplets stochastically and accounts for 'drop-drop' effects by permitting droplet collisions which result in coalescence or breakup. This investigation's objectives are to study the model's droplet tracking capabilities with special emphasis placed on the effects of droplet collisions. It is concluded that the collision model's results for droplet velocities agree well with experimental measurements but that droplet trajectory angles are overpredicted. Droplet sizes which are underpredicted by the model when collisions are neglected are still underpredicted when collisions are included although some improvement is noted.

  9. Dynamics of skyrmion collisions in 3+1 dimensions

    NASA Astrophysics Data System (ADS)

    Allder, A. E.; Koonin, S. E.; Seki, R.; Sommermann, H. M.

    1987-12-01

    We calculate classical skyrmion collisions in 3+1 dimensions. Numerical integration of Hamilton's equations for the chiral fields is based on a staggered leap-frog method. We study collisions of defensive hedgehog solitons at various impact parameters for center-of-mass energies of 157, 432, and 885 MeV. Internal excitations of the skyrmions and meson emission are observed. The time evolution of the pion field and momentum and baryon densities is shown, as are deflection functions and inelasticities. Some results for skyrmion-antiskyrmion annihilation are presented.

  10. Quantal nucleon diffusion: Central collisions of symmetric nuclei

    NASA Astrophysics Data System (ADS)

    Ayik, S.; Yilmaz, O.; Yilmaz, B.; Umar, A. S.

    2016-10-01

    The quantal diffusion mechanism of nucleon exchange is studied in the central collisions of several symmetric heavy ions in the framework of the stochastic mean-field (SMF) approach. Since, at bombarding energies below the fusion barrier, dinuclear structure is maintained, it is possible to describe nucleon exchange as a diffusion process familiar from deep-inelastic collisions. Quantal diffusion coefficients, including memory effects, for proton and neutron exchanges are extracted microscopically employing the SMF approach. The quantal calculations of neutron and proton variances are compared with the semiclassical results.

  11. Numerically Solvable Model for Resonant Collisions of Electronswith Diatomic Molecules

    SciTech Connect

    Houfek, Karel; Rescigno, T.N.; McCurdy, C.W.

    2006-01-27

    We describe a simple model for electron-molecule collisions that has one nuclear and one electronic degree of freedom and that can be solved to arbitrarily high precision, without making the Born-Oppenheimer approximation, by employing a combination of the exterior complex scaling method and a finite-element implementation of the discrete variable representation. We compare exact cross sections for vibrational excitation and dissociative attachment with results obtained using the local complex potential approximation as commonly applied in the ''boomerang'' model, and suggest how this two-dimensional model can be used to test the underpinnings of contemporary nonlocal approximations to resonant collisions.

  12. Initial conditions in AA and pA collisions

    NASA Astrophysics Data System (ADS)

    Lappi, Tuomas

    2017-03-01

    A full understanding of the spacetime evolution of the QCD matter created in a heavy ion collision requires understanding the properties of the initial stages. In the weak coupling picture these are dominated by classical gluon fields, whose properties can also be studied via the scattering of dilute probes off a high energy hadron or nucleus. A particular challenge is understanding small systems, where LHC data is also showing signs of collective behavior. We discuss some recent results of on the initial matter production and thermalization in heavy ion collisions, in particular in the gluon saturation framework.

  13. Theia's Collision With The Early Earth - Dry Or Wet Moon?

    NASA Astrophysics Data System (ADS)

    Dvorak, R.; Loibnegger, B.; Burger, C.; Maindl, T. I.; Schäfer, C.

    2016-04-01

    Our study exist of three separated parts concerning the formation of the Moon due to a catastrophic collision of a Mars-sized body - often referred to as Theia - with the early Earth. The first one deals with planet-formation in the early Solar System, the second one with the dynamical evolution of the planets Venus, Earth, Mars, Jupiter, and Saturn and an additional planet (Theia) between Earth and Mars, and the third one with the proposed giant collision itself and its outcome concerning masses and water contents of the resulting bodies (or fragments), computed via Smoothed Particle Hydrodynamics (SPH) simulations.

  14. Airborne Collision Detection and Avoidance for Small UAS Sense and Avoid Systems

    NASA Astrophysics Data System (ADS)

    Sahawneh, Laith Rasmi

    collision risk using the uncorrelated encounter model (UEM) developed by MIT Lincoln Laboratory. We evaluate the proposed approach using Monte Carlo simulations and compare the performance with linearly extrapolated collision detection logic. For the path planning and collision avoidance part, we present multiple reactive path planning algorithms. We first propose a collision avoidance algorithm based on a simulated chain that responds to a virtual force field produced by encountering intruders. The key feature of the proposed approach is to model the future motion of both the intruder and the ownship using a chain of waypoints that are equally spaced in time. This timing information is used to continuously re-plan paths that minimize the probability of collision. Second, we present an innovative collision avoidance logic using an ownship centered coordinate system. The technique builds a graph in the local-level frame and uses the Dijkstra's algorithm to find the least cost path. An advantage of this approach is that collision avoidance is inherently a local phenomenon and can be more naturally represented in the local coordinates than the global coordinates. Finally, we propose a two step path planner for ground-based SAA systems. In the first step, an initial suboptimal path is generated using A* search. In the second step, using the A* solution as an initial condition, a chain of unit masses connected by springs and dampers evolves in a simulated force field. The chain is described by a set of ordinary differential equations that is driven by virtual forces to find the steady-state equilibrium. The simulation results show that the proposed approach produces collision-free plans while minimizing the path length. To move towards a deployable system, we apply collision detection and avoidance techniques to a variety of simulation and sensor modalities including camera, radar and ADS-B along with suitable tracking schemes. Keywords: unmanned aircraft system, small UAS

  15. A rear-end collision risk assessment model based on drivers' collision avoidance process under influences of cell phone use and gender-A driving simulator based study.

    PubMed

    Li, Xiaomeng; Yan, Xuedong; Wu, Jiawei; Radwan, Essam; Zhang, Yuting

    2016-12-01

    Driver's collision avoidance performance has a direct link to the collision risk and crash severity. Previous studies demonstrated that the distracted driving, such as using a cell phone while driving, disrupted the driver's performance on road. This study aimed to investigate the manner and extent to which cell phone use and driver's gender affected driving performance and collision risk in a rear-end collision avoidance process. Forty-two licensed drivers completed the driving simulation experiment in three phone use conditions: no phone use, hands-free, and hand-held, in which the drivers drove in a car-following situation with potential rear-end collision risks caused by the leading vehicle's sudden deceleration. Based on the experiment data, a rear-end collision risk assessment model was developed to assess the influence of cell phone use and driver's gender. The cell phone use and driver's gender were found to be significant factors that affected the braking performances in the rear-end collision avoidance process, including the brake reaction time, the deceleration adjusting time and the maximum deceleration rate. The minimum headway distance between the leading vehicle and the simulator during the rear-end collision avoidance process was the final output variable, which could be used to measure the rear-end collision risk and judge whether a collision occurred. The results showed that although cell phone use drivers took some compensatory behaviors in the collision avoidance process to reduce the mental workload, the collision risk in cell phone use conditions was still higher than that without the phone use. More importantly, the results proved that the hands-free condition did not eliminate the safety problem associated with distracted driving because it impaired the driving performance in the same way as much as the use of hand-held phones. In addition, the gender effect indicated that although female drivers had longer reaction time than male drivers in

  16. Soliton collisions in the discrete nonlinear Schrödinger equation.

    PubMed

    Papacharalampous, I E; Kevrekidis, P G; Malomed, B A; Frantzeskakis, D J

    2003-10-01

    We report analytical and numerical results for on-site and intersite collisions between solitons in the discrete nonlinear Schrödinger model. A semianalytical variational approximation correctly predicts gross features of the collision, viz., merger or bounce. We systematically examine the dependence of the collision outcome on initial velocity and amplitude of the solitons, as well as on the phase shift between them, and location of the collision point relative to the lattice; in some cases, the dependences are very intricate. In particular, merger of the solitons into a single one, and bounce after multiple collisions are found. Situations with a complicated system of alternating transmission and merger windows are identified too. The merger is often followed by symmetry breaking (SB), when the single soliton moves to the left or to the right, which implies momentum nonconservation. Two different types of the SB are identified, deterministic and spontaneous. The former one is accounted for by the location of the collision point relative to the lattice, and/or the phase shift between the solitons; the momentum generated during the collision due to the phase shift is calculated in an analytical approximation, its dependence on the solitons' velocities comparing well with numerical results. The spontaneous SB is explained by the modulational instability of a quasiflat plateau temporarily formed in the course of the collision.

  17. SU-F-BRB-05: Collision Avoidance Mapping Using Consumer 3D Camera

    SciTech Connect

    Cardan, R; Popple, R

    2015-06-15

    Purpose: To develop a fast and economical method of scanning a patient’s full body contour for use in collision avoidance mapping without the use of ionizing radiation. Methods: Two consumer level 3D cameras used in electronic gaming were placed in a CT simulator room to scan a phantom patient set up in a high collision probability position. A registration pattern and computer vision algorithms were used to transform the scan into the appropriate coordinate systems. The cameras were then used to scan the surface of a gantry in the treatment vault. Each scan was converted into a polygon mesh for collision testing in a general purpose polygon interference algorithm. All clinically relevant transforms were applied to the gantry and patient support to create a map of all possible collisions. The map was then tested for accuracy by physically testing the collisions with the phantom in the vault. Results: The scanning fidelity of both the gantry and patient was sufficient to produce a collision prediction accuracy of 97.1% with 64620 geometry states tested in 11.5 s. The total scanning time including computation, transformation, and generation was 22.3 seconds. Conclusion: Our results demonstrate an economical system to generate collision avoidance maps. Future work includes testing the speed of the framework in real-time collision avoidance scenarios. Research partially supported by a grant from Varian Medical Systems.

  18. Injuries from motor-vehicle collisions with moose--Maine, 2000-2004.

    PubMed

    2006-12-01

    Moose are among the largest mammals in North America. Standing up to 7.5 feet at the shoulder and weighing up to 1,600 lbs, they are the largest members of the deer family. Maine's moose population (approximately 29,000) is the biggest in the United States outside of Alaska. During a collision with a motor vehicle, a moose usually is struck in the legs, causing its body to roll onto the hood of the vehicle, often collapsing the windshield and roof. As a result, motor-vehicle collisions involving moose are capable of causing substantial injury to vehicle occupants. To assess motor-vehicle collisions with moose in Maine and evaluate risk factors for injuries from these types of collisions, the Maine Department of Health and Human Services studied collision reports from 2000--2004. The results of that study indicated that collision rates varied by county but had clear patterns by season and time of day. Variables associated with risk for injury were posted speed limit, type of vehicle, and sex and age of the driver. Measures to reduce collisions with moose should focus on improving driver education programs and developing better engineering controls (e.g., removing roadside vegetation to improve visibility for drivers). In addition, herd management (i.e., decreasing moose population size through hunting) is currently being used in areas of Maine with high numbers of collisions, although studies are needed to assess its effectiveness.

  19. Collision risk investigation for an operational spacecraft caused by space debris

    NASA Astrophysics Data System (ADS)

    Zhang, Binbin; Wang, Zhaokui; Zhang, Yulin

    2017-04-01

    The collision probability between an operational spacecraft and a population of space debris is investigated. By dividing the 3-dimensional operational space of the spacecraft into several space volume cells (SVC) and proposing a boundary selection method to calculate the collision probability in each SVC, the distribution of the collision risk, as functions of the time, the orbital height, the declination, the impact elevation, the collision velocity, etc., can be obtained. Thus, the collision risk could be carefully evaluated over a time span for the general orbital configurations of the spacecraft and the space debris. As an application, the collision risk for the Tiangong-2 space laboratory caused by the cataloged space debris is discussed and evaluated. Results show that most of the collision threat comes from the front left and front right in Tiangong-2's local, quasi-horizontal plane. And the collision probability will also accumulate when Tiangong-2 moves to the largest declinations (about {±} 42°). As a result, the manned space activities should be avoided at those declinations.

  20. Characteristics of officer-involved vehicle collisions in California

    PubMed Central

    Wolfe, Scott E.; Rojek, Jeff; Alpert, Geoff; Tiesman, Hope; James, Stephen

    2016-01-01

    Purpose The purpose of this paper is to examine the situational and individual officer characteristics of officer-involved vehicle collisions that result in fatality, injury, and non-injury outcomes. Design/methodology/approach Data on 35,840 vehicle collisions involving law enforcement officers in California occurring between January 2000 and December 2009 are examined. A descriptive analysis of collision characteristics is presented. Findings There were 39 officers killed by collisions over this study period and 7,684 officers who received some type injury. Incidents involving officers on motorcycles represented 39 percent of officer fatalities and 39 percent of severe injuries. In the case of fatalities, 33 percent of officers were reported as wearing seatbelts, 38 percent were not wearing a seatbelt, and seatbelt use was not stated in 29 percent of car fatalities. Research limitations/implications The findings only represent one state and the analysis is based on an estimated 86 percent of collisions that occurred during the study period due to missing data. Nonetheless, the results are based on a robust sample and address key limitations in the existing literature. Practical implications During the study period in California the estimated financial impact of collisions reached into the hundreds of millions of dollars when considering related fatality, injury, and vehicle damage costs combined. These impacts highlight the need for the law enforcement community to give greater attention to this issue. Originality/value At the time of this writing there was no published independent research that compares the situational and officer characteristics across fatality, injury, and non-injury outcomes in these events. The findings reported here will help inform emerging interest in this issue within the law enforcement, academic, and policy-making communities. PMID:26877704

  1. Physics of Nuclear Collisions at High Energy

    SciTech Connect

    Hwa, Rudolph C.

    2012-05-01

    A wide range of problems has been investigated in the research program during the period of this grant. Although the major effort has been in the subject of heavy-ion collisions, we have also studied problems in biological and other physical systems. The method of analysis used in reducing complex data in multiparticle production to simple descriptions can also be applied to the study of complex systems of very different nature. Phase transition is an important phenomenon in many areas of physics, and for heavy-ion collisions we study the fluctuations of multiplicities at the critical point. Human brain activities as revealed in EEG also involve fluctuations in time series, and we have found that our experience enables us to find the appropriate quantification of the fluctuations in ways that can differentiate stroke and normal subjects. The main topic that characterizes the research at Oregon in heavy-ion collisions is the recombination model for the treatment of the hadronization process. We have avoided the hydrodynamical model partly because there is already a large community engaged in it, but more significantly we have found the assumption of rapid thermalization unconvincing. Recent results in studying LHC physics lead us to provide more evidence that shower partons are very important even at low p_T, but are ignored by hydro. It is not easy to work in an environment where the conventional wisdom regards our approach as being incorrect because it does not adhere to the standard paradigm. But that is just what a vibrant research community needs: unconventional approach may find evidences that can challenge the orthodoxy. An example is the usual belief that elliptic flow in fluid dynamics gives rise to azimuthal anisotropy. We claim that it is only sufficient but not necessary. With more data from LHC and more independent thinkers working on the subject what is sufficient as a theory may turn out to be incorrect in reality. Another area of investigation that

  2. Studies of Fluctuation Processes in Nuclear Collisions

    SciTech Connect

    Ayik, Sakir

    2016-04-14

    The standard one-body transport approaches have been extensively applied to investigate heavy-ion collision dynamics at low and intermediate energies. At low energies the approach is the mean-field description of the time-dependent Hartree-Fock (TDHF) theory. At intermediate energies the approach is extended by including a collision term, and its application has been carried out mostly in the semi-classical framework of the Boltzmann-Uhling-Uhlenbeck (BUU) model. The standard transport models provide a good understanding of the average properties of the collision dynamics in terms of the effective interactions in both low and intermediate energies. However, the standard models are inadequate for describing the fluctuation dynamics of collective motion at low energies and disassembling of the nuclear system into fragments at intermediate energies resulting from the growth of density fluctuations in the spinodal region. Our tasks have been to improve the standard transport approaches by incorporating fluctuation mechanisms into the description. There are mainly two different mechanisms for fluctuations: (i) Collisional fluctuations generated by binary nucleon collisions, which provide the dominant mechanism at intermediate energies, and (ii) One-body mechanism or mean-field fluctuations, which is the dominant mechanism at low energies. In the first part of our project, the PI extended the standard transport model at intermediate energies by incorporating collisional mechanism according to the “Generalized Langevin Description” of Mori formalism. The PI and his collaborators carried out a number of applications for describing dynamical mechanism of nuclear multi fragmentations, and nuclear collective response in the semi-classical framework of the approach, which is known as the Boltzmann-Langevin model. In the second part of the project, we considered dynamical description at low energies. Because of the effective Pauli blocking, the collisional dissipation and

  3. HUBBLE REVEALS STELLAR FIREWORKS ACCOMPANYING GALAXY COLLISION

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This Hubble Space Telescope image provides a detailed look at a brilliant 'fireworks show' at the center of a collision between two galaxies. Hubble has uncovered over 1,000 bright, young star clusters bursting to life as a result of the head-on wreck. [Left] A ground-based telescopic view of the Antennae galaxies (known formally as NGC 4038/4039) - so named because a pair of long tails of luminous matter, formed by the gravitational tidal forces of their encounter, resembles an insect's antennae. The galaxies are located 63 million light-years away in the southern constellation Corvus. [Right] The respective cores of the twin galaxies are the orange blobs, left and right of image center, crisscrossed by filaments of dark dust. A wide band of chaotic dust, called the overlap region, stretches between the cores of the two galaxies. The sweeping spiral- like patterns, traced by bright blue star clusters, shows the result of a firestorm of star birth activity which was triggered by the collision. This natural-color image is a composite of four separately filtered images taken with the Wide Field Planetary Camera 2 (WFPC2), on January 20, 1996. Resolution is 15 light-years per pixel (picture element). Credit: Brad Whitmore (STScI), and NASA

  4. Newton's cradle versus nonbinary collisions.

    PubMed

    Sekimoto, Ken

    2010-03-26

    Newton's cradle is a classical example of a one-dimensional impact problem. In the early 1980s the naive perception of its behavior was corrected: For example, the impact of a particle does not exactly cause the release of the farthest particle of the target particle train, if the target particles have been just in contact with their own neighbors. It is also known that the naive picture would be correct if the whole process consisted of purely binary collisions. Our systematic study of particle systems with truncated power-law repulsive force shows that the quasibinary collision is recovered in the limit of hard core repulsion, or a very large exponent. In contrast, a discontinuous steplike repulsive force mimicking a hard contact, or a very small exponent, leads to a completely different process: the impacting cluster and the targeted cluster act, respectively, as if they were nondeformable blocks.

  5. Quark fragmentation in e/sup +/e/sup -/ collisions

    SciTech Connect

    Oddone, P.

    1984-12-01

    This brief review of new results in quark and gluon fragmentation observed in e/sup +/e/sup -/ collisions concentrates mostly on PEP results and, within PEP, mostly on TPC results. The new PETRA results have been reported at this conference by M. Davier. It is restricted to results on light quark fragmentation since the results on heavy quark fragmentation have been reported by J. Chapman.

  6. Central collisions of heavy ions

    SciTech Connect

    Fung, Sun-yiu.

    1992-10-01

    This report describes the activities of the Heavy Ion Physics Group at the University of California, Riverside from October 1, 1991 to September 30, 1992. During this period, the program focused on particle production at AGS energies, and correlation studies at the Bevalac in nucleus-nucleus central collisions. As part of the PHENIX collaboration, contributions were made to the Preliminary Conceptual Design Report (pCDR), and work on a RHIC silicon microstrip detector R D project was performed.

  7. QCD studies in ep collisions

    SciTech Connect

    Smith, W.H.

    1997-06-01

    These lectures describe QCD physics studies over the period 1992--1996 from data taken with collisions of 27 GeV electrons and positrons with 820 GeV protons at the HERA collider at DESY by the two general-purpose detectors H1 and ZEUS. The focus of these lectures is on structure functions and jet production in deep inelastic scattering, photoproduction, and diffraction. The topics covered start with a general introduction to HERA and ep scattering. Structure functions are discussed. This includes the parton model, scaling violation, and the extraction of F{sub 2}, which is used to determine the gluon momentum distribution. Both low and high Q{sup 2} regimes are discussed. The low Q{sup 2} transition from perturbative QCD to soft hadronic physics is examined. Jet production in deep inelastic scattering to measure {alpha}{sub s}, and in photoproduction to study resolved and direct photoproduction, is also presented. This is followed by a discussion of diffraction that begins with a general introduction to diffraction in hadronic collisions and its relation to ep collisions, and moves on to deep inelastic scattering, where the structure of diffractive exchange is studied, and in photoproduction, where dijet production provides insights into the structure of the Pomeron. 95 refs., 39 figs.

  8. Numerical Geodynamic Experiments of Continental Collision: Past and Present

    NASA Astrophysics Data System (ADS)

    Gray, Robert

    Research explores deep continental lithosphere (i.e., the continental lower crust and mantle lithosphere) deformation during continental collision. I found that depending on the composition/rheology of the crust and the amount of radiogenic heat production in the crust, three dominant modes of mantle lithosphere deformation evolve under Neoarchean-like conditions: (1) a pure-shear thickening style; (2) an imbrication style; (3) and a "flat-subduction" style. The imbrication and the flat-subduction styles result in the emplacement of "plate-like" mantle lithosphere at depths between 200 km and 325 km. The imbrication style behavior shifts to the "flat-subduction" style behavior after a crustal inversion event. I investigated mature Phanerozoic-style collision and found that it is sensitive to mantle lithosphere density, mantle lithosphere yield stress, lower-crustal strength and to the presence of phase change-related density changes in the lower crust. The early stages of collision are accommodated by subduction of lower crust and mantle lithosphere along a discrete shear zone beneath the overriding plate. Next, the subducting lower crust and mantle lithosphere retreat from the collision zone, permitting the sub-lithospheric mantle to upwell and intrude the overriding plate. Next, the lower crust and mantle lithosphere of the overriding plate delaminate from the overlying crust. This process produces plateau-like uplift. These modeling results are interpreted in the context of available geological and geophysical observables for the Himalayan-Tibetan orogen. I quantitatively investigated the effects that sediment deposition may have on continental lithosphere deformation during collision. In the absence of sedimentation, the early stages of collision are accommodated by subduction of lower crust and mantle lithosphere beneath the overriding plate. Next, the subducting lower crust and mantle lithosphere retreat from the collision zone. This permits the sub

  9. Tilting Uranus without a Collision

    NASA Astrophysics Data System (ADS)

    Rogoszinski, Zeeve; Hamilton, Douglas P.

    2016-10-01

    The most accepted hypothesis for the origin of Uranus' 98° obliquity is a giant collision during the late stages of planetary accretion. This model requires a single Earth mass object striking Uranus at high latitudes; such events occur with a probability of about 10%. Alternatively, Uranus' obliquity may have arisen from a sequence of smaller impactors which lead to a uniform distribution of obliquities. Here we explore a third model for tilting Uranus using secular spin-orbit resonance theory. We investigate early Solar System configurations in which a secular resonance between Uranus' axial precession frequency and another planet's orbital node precession frequency might occur.Thommes et al. (1999) hypothesized that Uranus and Neptune initially formed between Jupiter and Saturn, and were then kicked outward. In our scenario, Neptune leaves first while Uranus remains behind. As an exterior Neptune slowly migrates outward, it picks up both Uranus and Saturn in spin-orbit resonances (Ward and Hamilton 2004; Hamilton and Ward 2004). Only a distant Neptune has a nodal frequency slow enough to resonate with Uranus' axial precession.This scenario, with diverging orbits, results in resonance capture. As Neptune migrates outward its nodal precession slows. While in resonance, Uranus and Saturn each tilt a bit further, slowing their axial precession rates to continually match Neptune's nodal precession rate. Tilting Uranus to high obliquities takes a few 100 Myrs. This timescale may be too long to hold Uranus captive between Jupiter and Saturn, and we are investigating how to reduce it. We also find that resonance capture is rare if Uranus' initial obliquity is greater than about 10°, as the probability of capture decreases as the planet's initial obliquity increases. We will refine this estimate by quantifying capture statistics, and running accretion simulations to test the likelihood of a low early obliquity. Our preliminary findings show that most assumptions about

  10. Modeling and Simulation of an UAS Collision Avoidance Systems

    NASA Technical Reports Server (NTRS)

    Oliveros, Edgardo V.; Murray, A. Jennifer

    2010-01-01

    This paper describes a Modeling and Simulation of an Unmanned Aircraft Systems (UAS) Collision Avoidance System, capable of representing different types of scenarios for UAS collision avoidance. Commercial and military piloted aircraft currently utilize various systems for collision avoidance such as Traffic Alert and Collision A voidance System (TCAS), Automatic Dependent Surveillance-Broadcast (ADS-B), Radar and ElectroOptical and Infrared Sensors (EO-IR). The integration of information from these systems is done by the pilot in the aircraft to determine the best course of action. In order to operate optimally in the National Airspace System (NAS) UAS have to work in a similar or equivalent manner to a piloted aircraft by applying the principle of "detect-see and avoid" (DSA) to other air traffic. Hence, we have taken these existing sensor technologies into consideration in order to meet the challenge of researching the modeling and simulation of an approximated DSA system. A Schematic Model for a UAS Collision Avoidance System (CAS) has been developed ina closed loop block diagram for that purpose. We have found that the most suitable software to carry out this task is the Satellite Tool Kit (STK) from Analytical Graphics Inc. (AGI). We have used the Aircraft Mission Modeler (AMM) for modeling and simulation of a scenario where a UAS is placed on a possible collision path with an initial intruder and then with a second intruder, but is able to avoid them by executing a right tum maneuver and then climbing. Radars have also been modeled with specific characteristics for the UAS and both intruders. The software provides analytical, graphical user interfaces and data controlling tools which allow the operator to simulate different conditions. Extensive simulations have been carried out which returned excellent results.

  11. Collision rates for electron excitation of Mg V lines

    NASA Astrophysics Data System (ADS)

    Tayal, S. S.; Sossah, A. M.

    2015-02-01

    Aims: Transition probabilities and electron impact excitation collision strengths and rates for astrophysically important lines in Mg V are reported. The 86 fine-structure levels of the 2s22p4, 2s2p5, 2p6, 2s22p33s, 2s22p33p and 2s22p33d configurations are included in our calculations. The effective collision strengths are presented as a function of electron temperature for solar and other astrophysical applications. Methods: The collision strengths have been calculated using the B-splineBreit-Pauli R-matrixmethod for all fine-structure transitions among the 86 levels. The one-body mass, Darwin and spin-orbit relativistic effects are included in the Breit-Pauli Hamiltonian in the scattering calculations. The one-body and two-body relativistic operators are included in the multiconfiguration Hartree-Fock calculations of transition probabilities. Several sets of non-orthogonal spectroscopic and correlation radial orbitals are used to obtain accurate description of Mg V 86 levels and to represent the scattering functions. Results: The calculated excitation energies are in very good agreement with experiment and represents an improvement over the previous calculations. The present collision strengths show good agreement with the previously available R-matrix and distorted-wave calculations. The oscillator strengths for E1 transitions normally compare very well with previous calculations. The thermally averaged collision strengths are obtained by integrating total resonant and non-resonant collision strengths over a Maxwellian distribution of electron energies and these are presented over the temperature range log 10Te = 3.2-6.0 K. Tables 1-4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/574/A87

  12. Ion momentum and energy transfer rates for charge exchange collisions

    NASA Technical Reports Server (NTRS)

    Horwitz, J.; Banks, P. M.

    1973-01-01

    The rates of momentum and energy transfer have been obtained for charge exchange collisions between ion and neutral gases having arbitrary Maxwellian temperatures and bulk transport velocities. The results are directly applicable to the F-region of the ionosphere where 0+ - 0 charge is the dominant mechanism affecting ion momentum and energy transfer.

  13. Astroblaster--A Fascinating Game of Multi-Ball Collisions

    ERIC Educational Resources Information Center

    Kires, Marian

    2009-01-01

    Multi-ball collisions inside the Astroblaster toy are explained from the conservation of momentum point of view. The important role of the coefficient of restitution is demonstrated in ideal and real cases. Real experimental results with the simple toy can be compared with a computer model represented by an interactive Java applet. (Contains 1…

  14. Simple Expalanation of a Well-Known Collision Experiment.

    ERIC Educational Resources Information Center

    Herrmann, F.; Schmalzle, P.

    1981-01-01

    Explains that the result of collision experiments with a linear arrangement of several identical elastic balls cannot be predicted solely from the conservation laws and energy and momentum. Indicates that the system of balls must be capable of dispersion-free energy propagation. (Author/JN)

  15. Influence of quantum conservation laws on particle production in hadron collisions

    NASA Astrophysics Data System (ADS)

    Janik, Małgorzata Anna; Graczykowski, Łukasz Kamil; Kisiel, Adam

    2016-12-01

    Conservation laws strongly influence production of particles in high-energy particle collisions. Effects connected to these mechanisms were studied in details using correlation techniques in e+e- collisions. At the time, models were tuned to correctly reproduce the measurements. Similar studies for hadron-hadron collisions have never been performed, until recent ALICE measurements. ALICE has reported on studies of untriggered two-particle angular correlations of identified particles (π, K, and p) measured in pp collisions at center-of-mass energy of √{ s} = 7 TeV. Those preliminary results confirm that also in hadron-hadron collisions, at much higher energies, conservation laws strongly influence the shape of the correlation functions for different particle types and must be taken into account while analysing the data. Moreover, they show that the contemporary models (PYTHIA, PHOJET) no longer reproduce the experimental data well.

  16. Renormalization screening and collision-induced quantum interference in dense plasmas

    SciTech Connect

    Jung, Young-Dae; Rasheed, A.; Jamil, M.

    2014-07-15

    The influence of renormalization screening and collision-induced quantum interference in electron-electron collisions is investigated in partially ionized dense hydrogen plasmas. The effective interaction potential with the total spin-states of the collision system is considered to obtain the differential electron-electron scattering cross section. The results show that the renormalization plasma screening effect suppresses the electron-electron scattering cross section, including the quantum interference effect, especially, except for the forward and backward scattering directions. It is also shown that the renormalization plasma screening effect on the scattering cross section decreases with increasing collision energy. However, the renormalization screening effect is found to be important for the forward directions in the scattering cross section neglecting the quantum interference effect. The variations of the renormalization screening and collision-induced quantum interference effects are also discussed.

  17. Hydrodynamic fluctuations in thermostatted multiparticle collision dynamics.

    PubMed

    Híjar, Humberto; Sutmann, Godehard

    2011-04-01

    In this work we study the behavior of mesoscopic fluctuations of a fluid simulated by Multiparticle Collision Dynamics when this is applied together with a local thermostatting procedure that constrains the strength of temperature fluctuations. We consider procedures in which the thermostat interacts with the fluid at every simulation step as well as cases in which the thermostat is applied only at regular time intervals. Due to the application of the thermostat temperature fluctuations are forced to relax to equilibrium faster than they do in the nonthermostatted, constant-energy case. Depending on the interval of application of the thermostat, it is demonstrated that the thermodynamic state changes gradually from isothermal to adiabatic conditions. In order to exhibit this effect we compute from simulations diverse correlation functions of the hydrodynamic fluctuating fields. These correlation functions are compared with those predicted by a linearized hydrodynamic theory of a simple fluid in which a thermostat is applied locally. We find a good agreement between the model and the numerical results, which confirms that hydrodynamic fluctuations in Multiparticle Collision Dynamics in the presence of the thermostat have the properties expected for spontaneous fluctuations in fluids in contact with a heat reservoir.

  18. Octree Bin-to-Bin Fractional-NTC Collisions

    DTIC Science & Technology

    2015-09-17

    Problem Particle Methods VDF to Delta Function Set Collisions between Discrete Velocities But Poorly Resolved Tail (Tail Critical to Inelastic... Delta Function Set Collisions between Discrete Velocities But Poorly Resolved Tail (Tail Critical to Inelastic Collisions) Variable Weights Permit Extra...Continuous Distribution Discretized VDF Yields Vlasov But Collision Integral Still a Problem Particle Methods VDF to Delta Function Set Collisions

  19. Fraction of space debris collisions that are catastrophic

    SciTech Connect

    Canavan, G.H.

    1996-08-01

    Analytic calculations estimate the fraction of catalog collisions that are catastrophic by a modification of collision rates. Most catalog collisions are catastrophic. Impactors of 60 kg or larger participate in about half of the catastrophic collisions. Analytic estimates give accurate values for catastrophic collisions, which are complicated numerically.

  20. Analyzing Collisions in Terms of Newton's Laws

    NASA Astrophysics Data System (ADS)

    Roeder, John L.

    2003-02-01

    Although the principle of momentum conservation is a consequence of Newton's second and third laws of motion, as recognized by Newton himself, this principle is typically applied in analyzing collisions as if it is a separate concept of its own. This year I sought to integrate my treatment of collisions with my coverage of Newton's laws by asking students to calculate the effect on the motion of two particles due to the forces they exerted for a specified time interval on each other. For example, "A 50-kg crate slides across the ice at 3 m/s and collides with a 25-kg crate at rest. During the collision process the 50-kg crate exerts a 500 N time-averaged force on the 25 kg for 0.1 s. What are the accelerations of the crates during the collision, and what are their velocities after the collision? What are the momenta of the crates before and after collision?"

  1. A Collective Collision Operator for DSMC

    SciTech Connect

    GALLIS,MICHAIL A.; TORCZYNSKI,JOHN R.

    2000-06-21

    A new scheme to simulate elastic collisions in particle simulation codes is presented. The new scheme aims at simulating the collisions in the highly collisional regime, in which particle simulation techniques typically become computationally expensive.The new scheme is based on the concept of a grid-based collision field. According to this scheme, the particles perform a single collision with the background grid during a time step. The properties of the background field are calculated from the moments of the distribution function accumulated on the grid. The collision operator is based on the Langevin equation. Based on comparisons with other methods, it is found that the Langevin method overestimates the collision frequency for dilute gases.

  2. Surrogate safety measure for evaluating rear-end collision risk related to kinematic waves near freeway recurrent bottlenecks.

    PubMed

    Li, Zhibin; Ahn, Seongchae; Chung, Koohong; Ragland, David R; Wang, Wei; Yu, Jeong Whon

    2014-03-01

    This study presents a surrogate safety measure for evaluating the rear-end collision risk related to kinematic waves near freeway recurrent bottlenecks using aggregated traffic data from ordinary loop detectors. The attributes of kinematic waves that accompany rear-end collisions and the traffic conditions at detector stations spanning the collision locations were examined to develop the rear-end collision risk index (RCRI). Together with RCRI, standard deviations in occupancy were used to develop a logistic regression model for estimating rear-end collision likelihood near freeway recurrent bottlenecks in real-time. The parameters in the logistic regression models were calibrated using collision data gathered from the 6-mile study site between 2006 and 2007. Findings indicated that an additional unit increase in RCRI results in increasing the odds of rear-end collision by 21.1%, a unit increase in standard deviation of upstream occupancy increases the odds by 19.5%, and a unit increase in standard deviation of downstream occupancy increases the odds by 18.7%. The likelihood of rear-end collisions is highest when the traffic approaching from upstream is near capacity state while downstream traffic is highly congested. The paper also reports on the findings from comparing the predicted number of rear-end collisions at the study site using the proposed model with the observed traffic collision data from 2008. The proposed model's true positive rates were higher than those of existing real-time crash prediction models.

  3. Results from MAC

    SciTech Connect

    Chadwick, G.B.

    1983-05-01

    The MAC detector has been exposed at PEP to 40 pb/sup -1/ luminosity of e/sup +/e/sup -/ collisions. The detector is described and recent results of a continuing analysis of hadronic cross section, lepton pair charge asymmetry, Bhabha process, two photon final state and radiative ..mu.. pairs are given. New results on flavor tagging of hadronic events with an inclusive ..mu.., and some searches for new particles are presented.

  4. Flight Tests Validate Collision-Avoidance System

    NASA Video Gallery

    Flights tests of a smartphone-assisted automatic ground collision avoidance system at NASA's Dryden Flight Research Center consistently commanded evasive maneuvers when it sensed that the unmanned ...

  5. Integrated Collision Avoidance System for Air Vehicle

    NASA Technical Reports Server (NTRS)

    Lin, Ching-Fang (Inventor)

    2013-01-01

    Collision with ground/water/terrain and midair obstacles is one of the common causes of severe aircraft accidents. The various data from the coremicro AHRS/INS/GPS Integration Unit, terrain data base, and object detection sensors are processed to produce collision warning audio/visual messages and collision detection and avoidance of terrain and obstacles through generation of guidance commands in a closed-loop system. The vision sensors provide more information for the Integrated System, such as, terrain recognition and ranging of terrain and obstacles, which plays an important role to the improvement of the Integrated Collision Avoidance System.

  6. Origin of collision-induced molecular orientation.

    PubMed

    Brouard, M; Hornung, B; Aoiz, F J

    2013-11-01

    Collision-induced rotational angular momentum orientation is a fundamental property of molecular scattering, which is sensitive to the balance between attractive and repulsive forces at play during collision. Here, we quantify a new mechanism leading to orientation, which is purely quantum mechanical in origin. Although the new mechanism is quite general, and will operate more widely in atomic and molecular scattering, it is observed here for impulsive hard shell collisions, for which the orientation vanishes classically. The quantum mechanism can thus be studied in isolation from other processes. The orientation is proposed to originate from the nonlocal nature of the quantum mechanical collision encounter.

  7. Telerobotics with whole arm collision avoidance

    SciTech Connect

    Wilhelmsen, K.; Strenn, S.

    1993-09-01

    The complexity of teleorbotic operations in a cluttered environment is exacerbated by the need to present collision information to the operator in an understandable fashion. In addition to preventing movements which will cause collisions, a system providing some form of virtual force reflection (VFR) is desirable. With this goal in mind, Lawrence Livermore National Laboratory (LLNL) has installed a kinematically master/slave system and developed a whole arm collision avoidance system which interacts directly with the telerobotic controller. LLNL has also provided a structure to allow for automated upgrades of workcell models and provide collision avoidance even in a dynamically changing workcell.

  8. Lightcurve signatures for non-catastrophic asteroid collisions

    NASA Astrophysics Data System (ADS)

    McLoughlin, E.; Fitzsimmons, A.; McLoughlin, A.

    2014-07-01

    Current all-sky surveys such as Pan-STARRS 1 and the Catalina Sky Survey are now discovering objects with orbits similar to main-belt asteroids but surrounded by extended material. Some may represent catastrophic collisions resulting in significant disruption of the target asteroids (Snodgrass et al. 2010, Jewitt et al. 2010, Stevenson and Jewitt 2012, Moreno et al. 2012). The 2010 event at asteroid (596) Scheila is accepted as being due to the impact of a small asteroid on a larger body, resulting in a non-catastrophic cratering event (Jewitt et al. 2011, Ishiguro et al. 2011, Hsieh et al. 2012). Given a nominal size distribution, small collisions should dominate the catastrophic impact rate (Bottke et al. 2005, Denneau et al. 2014). A search for such events has been reported by Cikota et al. (2014). We have performed a series of analytical calculations to model the psf brightness increase resulting from a sub-catastrophic collision onto a main-belt asteroid. We used the cratering scaling laws as derived by Holsapple and Housen (2012) combined with a range of strength and other physical parameters as indicated by observation and laboratory experiments. Target radii from 1 km to 100 km represented the known main-asteroid-belt population, and impactor sizes from 1 m to 100 m ensured we are in the non-catastrophic regime. At present, we include realistic debris size and velocity distributions, together with gravitational fallback onto the target asteroid, but not radiation pressure on the grains. We find a C-type impactor radius of ≃25 m produces results consistent with the reported observations for (596) Scheila. In terms of general impacts, we find that almost all collisions involving an impactor with radius r ≥ 10m would result in a brightness increase of ≥ 1 magnitude visible 24 hours after the collision. However a combination of debris fallback and expansion of debris beyond the seeing disk rapidly reduces the photometric signature. Within 1 week of a

  9. EPOSHQ-a new approach to describe charmed mesons in pp, pA and AA collisions

    NASA Astrophysics Data System (ADS)

    Aichelin, J.; Guiot, B.; Ozvenschuck, V.; Nahrgang, M.; Gossiaux, P. B.; Werner, K.

    2016-12-01

    We present first results of a new approach, EPOSHQ, which combines the EPOS3 event generator with the heavy quarks physics. In this approach light and heavy quarks are simultaneously created in the elementary collisions. The heavy quarks interact by elastic and radiative collisions with the plasma constituents, given by the EPOS3 approach, employing the full Boltzmann collision integral. This approach will allow for the description of correlations between light and heavy mesons.

  10. Collinear Collision Chemistry: 1. A Simple Model for Inelastic and Reactive Collision Dynamics

    ERIC Educational Resources Information Center

    Mahan, Bruce H.

    1974-01-01

    Discusses a model for the collinear collision of an atom with a diatomic molecule on a simple potential surface. Indicates that the model can provide a framework for thinking about molecular collisions and reveal many factors which affect the dynamics of reactive and inelastic collisions. (CC)

  11. Effectiveness of light-reflecting devices: A systematic reanalysis of animal-vehicle collision data.

    PubMed

    Brieger, Falko; Hagen, Robert; Vetter, Daniela; Dormann, Carsten F; Storch, Ilse

    2016-12-01

    Every year, approximately 500 human fatalities occur due to animal-vehicle collisions in the United States and Europe. Especially heavy-bodied animals affect road safety. For more than 50 years, light-reflecting devices such as wildlife warning reflectors have been employed to alert animals to traffic when crossing roads during twilight and night. Numerous studies addressed the effectiveness of light-reflecting devices in reducing collisions with animals in past decades, but yielded contradictory results. In this study, we conducted a systematic literature review to investigate whether light-reflecting devices contribute to an effective prevention of animal-vehicle collisions. We reviewed 53 references and reanalyzed original data of animal-vehicle collisions with meta-analytical methods. We calculated an effect size based on the annual number of animal-vehicle collisions per kilometer of road to compare segments with and without the installation of light-reflecting devices for 185 roads in Europe and North America. Our results indicate that light-reflecting devices did not significantly reduce the number of animal-vehicle collisions. However, we observed considerable differences of effect sizes with respect to study duration, study design, and country. Our results suggest that length of the road segment studied, study duration, study design and public attitude (preconception) to the functioning of devices may affect whether the documented number of animal-vehicle collisions in- or decrease and might in turn influence whether results obtained were published.

  12. Dynamics of droplet collision and flame-front motion

    NASA Astrophysics Data System (ADS)

    Pan, Kuo-Long

    Three physical phenomena were experimentally and computationally investigated in this research, namely the dynamics of head-on droplet-droplet collision, head-on droplet-film collision, and laminar premixed flames, with emphasis on the transition between bouncing and merging of the liquid surfaces for the droplet collision studies, and on the susceptibility to exhibit hydrodynamic instability for the flame dynamics. All three problems share the common feature of having an active deformable interface separating two flow regions of disparate densities, and as such can be computationally described using the adopted immersed boundary technique. Experimentally, the droplets (˜300 mum diameter) were generated using the ink jet printing technique, and imaged using stroboscopy for the droplet-droplet collision events and high-speed cine-photography for the droplet-film collision events. For the study of droplet-droplet collision, the instant of merging was experimentally determined and then used as an input in the computational simulation of the entire collision event. The simulation identified the differences between collision and merging at small and large Weber numbers, and satisfactorily described the dynamics of the inter-droplet gap including the role of the van der Waals force in effecting surface rupture. For the study of droplet-film collision, extensive experimental mapping showed that the collision dynamics is primarily affected by the droplet Weber number (We) and the film thickness scaled by the droplet radius (H), that while droplet absorption by the film is facilitated with increasing droplet Weber number, the boundary of transition is punctuated by an absorption peninsula, in the We-H space, within which absorption is further facilitated for smaller Weber numbers. Results from computation simulation revealed the essential dependence of the collision dynamics on the restraining nature of the solid surface, the energy exchange between the droplet and the

  13. Analysis and Consequences of the Iridium 33-Cosmos 2251 Collision

    NASA Technical Reports Server (NTRS)

    Anz-Meador, P. D.; Liou, Jer-Chi

    2010-01-01

    The collision of Iridium 33 and Cosmos 2251, on 10 February 2009, was the first known unintentional hypervelocity collision in space of intact satellites. Iridium 33 was an active commercial telecommunications satellite, while Cosmos 2251 was a derelict communication satellite of the Strela-2M class. The collision occurred at a relative velocity of 11.6 km/s at an altitude of approximately 790 km over the Great Siberian Plain and near the northern apex of Cosmos 2251 s orbit. This paper describes the physical and orbital characteristics of the relevant spacecraft classes and reports upon our analysis of the resulting debris clouds size, mass, area-to-mass ratio, and relative velocity/directionality distributions. We compare these distributions to those predicted by the NASA breakup model and notable recent fragmentation events; in particular, we compare the area-to-mass ratio distribution for each spacecraft to that exhibited by the FY-1C debris cloud for the purpose of assessing the relative contribution of modern aerospace materials to debris clouds resulting from energetic collisions. In addition, we examine the long-term consequences of this event for the low Earth orbit (LEO) environment. Finally, we discuss "lessons learned", which may be incorporated into NASA s environmental models.

  14. Kinetic study of wall collisions in a coaxial Hall discharge.

    PubMed

    Meezan, Nathan B; Cappelli, Mark A

    2002-09-01

    Coaxial Hall discharges (also known as Hall thrusters, stationary plasma thrusters, and closed-drift accelerators) are cross-field plasma sources under development for space propulsion applications. The importance of the electron-wall interaction to the Hall discharge operation is studied the through analysis of experimental data and simulation of the electron energy distribution function (EEDF) inside the discharge channel. Experimental time-average plasma property data from a laboratory Hall discharge are used to calculate the electron conductivity and to estimate the rate of wall-loss collisions. The electron Boltzmann equation is then solved in the local field limit, using the experimental results as inputs. The equation takes into account ionization and wall collisions, including secondary electrons produced at the wall. Local electron balances are used to calculate the sheath potential at the insulator walls. Results show an EEDF depleted at high energy due to electron loss to the walls. The calculated EEDFs agree well with experimental electron temperature data when the experimentally determined effective collision frequency is used for electron momentum transport. The electron wall-loss and wall-return frequencies are extremely low compared to those predicted by a Maxwellian of equal average energy. The very low frequency of wall collisions suggests that secondary electrons do not contribute to cross-field transport. This conclusion holds despite significant experimental uncertainty.

  15. Radar-based collision avoidance for unmanned surface vehicles

    NASA Astrophysics Data System (ADS)

    Zhuang, Jia-yuan; Zhang, Lei; Zhao, Shi-qi; Cao, Jian; Wang, Bo; Sun, Han-bing

    2016-12-01

    Unmanned surface vehicles (USVs) have become a focus of research because of their extensive applications. To ensure safety and reliability and to perform complex tasks autonomously, USVs are required to possess accurate perception of the environment and effective collision avoidance capabilities. To achieve these, investigation into realtime marine radar target detection and autonomous collision avoidance technologies is required, aiming at solving the problems of noise jamming, uneven brightness, target loss, and blind areas in marine radar images. These technologies should also satisfy the requirements of real-time and reliability related to high navigation speeds of USVs. Therefore, this study developed an embedded collision avoidance system based on the marine radar, investigated a highly real-time target detection method which contains adaptive smoothing algorithm and robust segmentation algorithm, developed a stable and reliable dynamic local environment model to ensure the safety of USV navigation, and constructed a collision avoidance algorithm based on velocity obstacle (V-obstacle) which adjusts the USV's heading and speed in real-time. Sea trials results in multi-obstacle avoidance firstly demonstrate the effectiveness and efficiency of the proposed avoidance system, and then verify its great adaptability and relative stability when a USV sailing in a real and complex marine environment. The obtained results will improve the intelligent level of USV and guarantee the safety of USV independent sailing.

  16. Effective collision strengths for transitions in Fe XV.

    NASA Astrophysics Data System (ADS)

    Aggarwal, K. M.; Keenan, F. P.; Msezane, A. Z.

    2003-10-01

    Collision strengths for transitions among the energetically lowest 53 fine-structure levels belonging to the (1s22s22p6) 3{l}2, 3{l}3{l}', 3s4{l} and 3p4s configurations of Fe XV are computed, over an electron energy range below 160 Ryd, using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (\\cite{Norrington03}). Effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron energies, have also been calculated. These results of effective collision strengths are tabulated for all 1378 inelastic transitions over a wide temperature range of 105 to 107 K. Comparisons are also made with other R-matrix calculations and the accuracy of the results is assessed. Table 4 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/410/349

  17. Midair collisions - The accidents, the systems, and the Realpolitik

    NASA Technical Reports Server (NTRS)

    Wiener, E. L.

    1980-01-01

    Two midair collisions occurring in 1978 are described, and the air traffic control system and procedures in use at the time, human factors implications and political consequences of the accidents are examined. The first collision occurred in Memphis and involved a Falcon jet and a Cessna 150 in a situation in which the controllers handling each aircraft were not aware of the presence of the other aircraft until it was too late. The second occurred in San Diego four months later, when a Boeing 727 on a visual approach struck a Cessna 172 from the rear. Following the San Diego collision there arose a great deal of investigative activity, resulting in suggestions for tighter control on visual flight rules aircraft and the expansion of positive control airspace. These issues then led to a political battle involving general aviation, the FAA and the Congress. It is argued, however, that the collisions were in fact system-induced errors resulting from an air traffic control system which emphasizes airspace allocation and politics rather than the various human factors problems facing pilots and controllers.

  18. Atomistic Simulation of Collision Cascades in Zircon

    SciTech Connect

    Devanathan, Ram; Corrales, Louis R.; Weber, William J.; Chartier, Alain; Meis, Constantin

    2006-09-01

    Defect production in energetic collision cascades in zircon has been studied by molecular dynamics simulation using a partial charge model combined with the Ziegler-Biersack-Littmark potential. Energy dissipation, defect accumulation, Si-O-Si polymerization, and Zr coordination number were examined for 10 keV and 30 keV U recoils simulated in the constant NVE ensemble. For both energies an amorphous core was produced with features similar to that of melt quenched zircon. Disordered Si ions in this core were polymerized with an average degree of polymerization of 1.5, while disordered Zr ions showed a coordination number of about 6 in agreement with EXAFS results. These results suggest that nano-scale phase separation into silica- and zirconia-rich regions occurs in the amorphous core.

  19. Collision-induced gas phase dissociation rates

    NASA Technical Reports Server (NTRS)

    Hansen, C. Frederick

    1990-01-01

    The Landau-Zener theory of reactive cross sections was applied to diatomic molecules dissociating from a ladder of vibrational states. The result predicts a dissociation rate that is quite well duplicated by an Arrhenius function having a preexponential temperature dependence of about T(sub -1/2), at least for inert collision partners. This relation fits experimental data reasonably well. The theory is then used to calculate the effect of vibrational nonequilibrium on dissociation rate. For Morse oscillators, the results are about the same as given by Hammerling, Kivel, and Teare in their analytic approximation for harmonic oscillators, though at very high temperature a correction for the partition function limit is included. The empirical correction for vibration nonequilibrium proposed by Park, which is a convenient algorithm for CFD calculations, is modified to prevent a drastic underestimation of dissociation rates that occurs with this method when vibrational temperature is much smaller than the kinetic temperature of the gas.

  20. Collisions of planetesimals and formation of planets

    NASA Astrophysics Data System (ADS)

    Dvorak, Rudolf; Maindl, Thomas I.; Süli, Áron; Schäfer, Christoph; Speith, Roland; Burger, Christoph

    2015-02-01

    The outcome of numerical simulations of the formation of planets depends a lot on the choice of the initial distribution of planetesimals and planetary embryos after the disappearance of gas in the protoplanetary disk. We take into account that some of these planetesimals of sizes in the order of the mass of the Moon already contain water; the quantity depends on the distance from the Sun --- too close and the bodies are dry, but starting from a distance of about 2 AU they can contain substantial amounts of water. We show preliminary results of terrestrial planet formation using on one side classical numerical integrations of hundreds of small bodies on CPUs and on the other side --- for comparison reasons --- the results of our GPU code with thousands of small bodies which then merge to larger ones. To be able to determine the outcome of collisions we use our SPH code which shows how water is lost during such events.

  1. Open heavy-flavour measurements in p-Pb and Pb-Pb collisions with ALICE at the LHC

    NASA Astrophysics Data System (ADS)

    Terrevoli, Cristina; ALICE Collaboration

    2017-01-01

    Heavy flavours are sensitive probes of the hot and dense QCD medium formed in high-energy heavy-ion collisions. Measurements of their production in p-Pb collisions are crucial for the interpretation of heavy-ion results, by investigating the cold nuclear matter effects. The open heavy-flavour production studied with ALICE at the LHC in p-Pb collisions at and in Pb-Pb collisions at are presented. Emphasis is given to the recent measurements of D0 production cross section down to p T=0, the nuclear modification factor of heavy-flavour hadron decay electrons in p-Pb collisions, the nuclear modification factor of D-meson, and heavy-flavour hadron decay electron elliptic flow in Pb-Pb collisions, as a function of centrality.

  2. An introductory analysis of satellite collision probabilities

    NASA Astrophysics Data System (ADS)

    Carlton-Wippern, Kitt C.

    This paper addresses a probailistic approach in assessing the probabilities of a satellite collision occurring due to relative trajectory analyses and probability density functions representing the satellites' position/momentum vectors. The paper is divided into 2 parts: Static and Dynamic Collision Probabilities. In the Static Collision Probability section, the basic phenomenon under study is: given the mean positions and associated position probability density functions for the two objects, calculate the probability that the two objects collide (defined as being within some distance of each other). The paper presents the classic Laplace problem of the probability of arrival, using standard uniform distribution functions. This problem is then extrapolated to show how 'arrival' can be classified as 'collision', how the arrival space geometries map to collision space geometries and how arbitrary position density functions can then be included and integrated into the analysis. In the Dynamic Collision Probability section, the nature of collisions based upon both trajectory and energy considerations is discussed, and that energy states alone cannot be used to completely describe whether or not a collision occurs. This fact invalidates some earlier work on the subject and demonstrates why Liouville's theorem cannot be used in general to describe the constant density of the position/momentum space in which a collision may occur. Future position probability density functions are then shown to be the convolution of the current position and momentum density functions (linear analysis), and the paper further demonstrates the dependency of the future position density functions on time. Strategies for assessing the collision probabilities for two point masses with uncertainties in position and momentum at some given time, and thes integrated with some arbitrary impact volume schema, are then discussed. This presentation concludes with the formulation of a high level design

  3. Inclusive production of π0-mesons in π p, Kp and γ p collisions at energies around 100 GeV

    NASA Astrophysics Data System (ADS)

    Apsimon, R. J.; Atkinson, M.; Baake, M.; Bagdasarian, L. S.; Barberis, D.; Brodbeck, T. J.; Brook, N.; Charity, T.; Clegg, A. B.; Coyle, P.; Danaher, S.; Danagulian, S.; Davenport, M.; Dickinson, B.; Diekmann, B.; Donnachie, A.; Doyle, A. T.; Eades, J.; Ellison, R. J.; Flower, P. S.; Foster, J. M.; Galbraith, W.; Galumian, P. I.; Gapp, C.; Gebert, F.; Hallewell, G.; Heinloth, K.; Henderson, R. C. W.; Hickman, M. T.; Hoeger, C.; Holzkamp, A.; Holzkamp, S.; Hughes-Jones, R. E.; Ibbotson, M.; Jakob, H. P.; Joseph, D.; Keemer, N. R.; Kingler, J.; Koersgen, G.; Kolya, S. D.; Lafferty, G. D.; McCann, H.; McClatchey, R.; McManus, C.; Mercer, D.; Morris, J. A. G.; Morris, J. V.; Newton, D.; O'Connor, A.; Oedingen, R.; Oganesian, A. G.; Ottewell, P. J.; Paterson, C. N.; Paul, E.; Reid, D.; Rotscheidt, H.; Sharp, P. H.; Soeldner-Rembold, S.; Thacker, N. A.; Thompson, L.; Thompson, R. J.; Waterhouse, J.; Weigend, A. S.; Wilson, G. W.

    1991-09-01

    Measurements are reported of inclusive production of π0-mesons in the beam fragmentation region in γ p, π p and Kp collisions. Results include the ratio of π0 production in Kp and π p collisions, showing reduced production from fragmentation of the K-meson, and the ratio of π0 production in photon and hadron collisions which shows agreement with modified Vector Meson Dominance at low P T , and departures at higher P T signalling the onset of direct photon reactions. The pattern of departure from Feynman scaling at high P T points to a contribution of hard parton-parton collisions in both γ p and π p collisions.

  4. Collision Broadening Of Line Spectrum In Sonoluminescence

    SciTech Connect

    Li Chaohui; An Yu

    2008-06-24

    The direct measurement of temperature inside a sonoluminescing bubble as it is at its flashing phase is almost impossible due to the smallness of the bubble and the short duration of the flashing. One may estimate the temperature through fitting the continuum spectrum of sonoluminescence by the black body radiation formula, or fitting the shape of atomic or molecular line spectrum (the different temperature, density and pressure result in the different shape of the line spectrum due to the effect of collision broadening). However, the temperature changes in a huge range at short duration as the bubble flashes, therefore, the observed spectra are some kind of average one, so are those fitted results. To evaluate the instantaneous temperature more accurately, we simulate the processes of the bubble motion and the thermodynamics inside the bubble, in which atomic or molecular line spectra with the collision broadening effect and the continuum spectra contributed from the processes of electron-atom bremsstrahlung, electron-ion bremsstrahlung and recombination radiation and radiative attachment of electrons to atoms and molecules are taken into account in calculating the light emission. If both the calculated continuum spectra and the shape of line spectra can well represent the experimental data, we may deduce that the calculation of the temperature, density and pressure is reliable and we indirectly evaluate those quantities inside the bubble. In the present calculation, the line spectra of OH radical at about 310 nm mixing the electron transition with the vibration and rotational bands are considered. The calculation qualitatively consists with the observation, and we expect that with the more precise bubble dynamics model instead of the uniform model employed in the present calculation we may improve the quantitative result.

  5. Stellar Collisions and the Interior Structure of Blue Stragglers

    NASA Astrophysics Data System (ADS)

    Lombardi, James C., Jr.; Warren, Jessica S.; Rasio, Frederic A.; Sills, Alison; Warren, Aaron R.

    2002-04-01

    Collisions of main-sequence stars occur frequently in dense star clusters. In open and globular clusters, these collisions produce merger remnants that may be observed as blue stragglers. Detailed theoretical models of this process require lengthy hydrodynamic computations in three dimensions. However, a less computationally expensive approach, which we present here, is to approximate the merger process (including shock heating, hydrodynamic mixing, mass ejection, and angular momentum transfer) with simple algorithms based on conservation laws and a basic qualitative understanding of the hydrodynamics. These algorithms have been fine-tuned through comparisons with the results of our previous hydrodynamic simulations. We find that the thermodynamic and chemical composition profiles of our simple models agree very well with those from recent SPH (smoothed particle hydrodynamics) calculations of stellar collisions, and the subsequent stellar evolution of our simple models also matches closely that of the more accurate hydrodynamic models. Our algorithms have been implemented in an easy-to-use software package, which we are making publicly available.4 This software could be used in combination with realistic dynamical simulations of star clusters that must take into account stellar collisions.

  6. Analyzing Benzene and Cyclohexane Emulsion Droplet Collisions on Ultramicroelectrodes.

    PubMed

    Li, Yan; Deng, Haiqiang; Dick, Jeffrey E; Bard, Allen J

    2015-11-03

    We report the collisions of single emulsion oil droplets with extremely low dielectric constants (e.g., benzene, ε of 2.27, or cyclohexane, ε of 2.02) as studied via emulsion droplet reactor (EDR) on an ultramicroelectrode (UME). By applying appropriate potentials to the UME, we observed the electrochemical effects of single-collision signals from the bulk electrolysis of single emulsion droplets. Different hydrophobic redox species (ferrocene, decamethyl-ferrocene, or metalloporphyrin) were trapped in a mixed benzene (or cyclohexane) oil-in-water emulsion using an ionic liquid as the supporting electrolyte and emulsifier. The emulsions were prepared using ultrasonic processing. Spike-like responses were observed in each i-t response due to the complete electrolysis of all of the above-mentioned redox species within the droplet. On the basis of these single-particle collision results, the collision frequency, size distribution, i-t decay behavior of the emulsion droplets, and possible mechanisms are analyzed and discussed. This work demonstrated that bulk electrolysis can be achieved in a few seconds in these attoliter reactors, suggesting many applications, such as analysis and electrosynthesis in low dielectric constant solvents, which have a much broader potential window.

  7. Linking magmatism with collision in an accretionary orogen

    PubMed Central

    Li, Shan; Chung, Sun-Lin; Wilde, Simon A.; Wang, Tao; Xiao, Wen-Jiao; Guo, Qian-Qian

    2016-01-01

    A compilation of U-Pb age, geochemical and isotopic data for granitoid plutons in the southern Central Asian Orogenic Belt (CAOB), enables evaluation of the interaction between magmatism and orogenesis in the context of Paleo-Asian oceanic closure and continental amalgamation. These constraints, in conjunction with other geological evidence, indicate that following consumption of the ocean, collision-related calc-alkaline granitoid and mafic magmatism occurred from 255 ± 2 Ma to 251 ± 2 Ma along the Solonker-Xar Moron suture zone. The linear or belt distribution of end-Permian magmatism is interpreted to have taken place in a setting of final orogenic contraction and weak crustal thickening, probably as a result of slab break-off. Crustal anatexis slightly post-dated the early phase of collision, producing adakite-like granitoids with some S-type granites during the Early-Middle Triassic (ca. 251–245 Ma). Between 235 and 220 Ma, the local tectonic regime switched from compression to extension, most likely caused by regional lithospheric extension and orogenic collapse. Collision-related magmatism from the southern CAOB is thus a prime example of the minor, yet tell-tale linking of magmatism with orogenic contraction and collision in an archipelago-type accretionary orogen. PMID:27167207

  8. Collision between chemically driven self-propelled drops

    NASA Astrophysics Data System (ADS)

    Yabunaka, Shunsuke; Yoshinaga, Natsuhiko

    2016-11-01

    We consider analytically and numerically head-on collision between two self-propelled drops. Each drop is driven by chemical reactions that produce or consume the concentration isotropically. The isotropic distribution of the concentration field is destabilized by motion of the drop which is itself made by Marangoni flow from concentration-dependent surface tension. This symmetry-breaking self-propulsion is distinct from other self-propulsion mechanisms due to the intrinsic polarity such as squirmers and self-phoretic motion; there is a bifurcation point below which the drop is stationary and above which it moves spontaneously. When two drops moving along the same axis with opposite direction, the interactions arise both from hydrodynamics and concentration overlap. We found that two drops exhibit either elastic collision or fusion depending on the distance from the bifurcation point controlled, for instance, by viscosity. The elastic collision results from the balance between dissipation and energy injection by chemical reactions. We derive the reduced equations for the collision between two drops and analyze the contributions from the two interactions. The concentration-mediated interaction is found to dominate the hydrodynamic interaction.

  9. A Computational Study of Systemic Hydration in Vocal Fold Collision

    PubMed Central

    Bhattacharya, Pinaki; Siegmund, Thomas

    2013-01-01

    Mechanical stresses develop within vocal fold (VF) soft tissues, due to phonation-associated vibration and collision. These stresses in turn affect the hydration of VF tissue and thus influence voice health. In this paper, high-fidelty numerical computations are described taking into account fully three-dimensional geometry, realistic tissue and air properties, and high-amplitude vibration and collision. A segregated solver approach is employed, using sophisticated commercial solvers for both the VF tissue and glottal airflow domains. The tissue viscoelastic properties were derived from a biphasic formulation. Two cases were considered, whereby the tissue viscoelastic properties corresponded to two different volume fractions of the fluid phase of the VF tissue. For each case, hydrostatic stresses occurring as a result of vibration and collision were investigated. Assuming the VF tissue to be poroelastic, interstitial fluid movement within VF tissue was estimated from the hydrostatic stress gradient. Computed measures of overall VF dynamics (peak air-flow velocity, magnitude of VF deformation, frequency of vibration and contact pressure) were well within the range of experimentally observed values. The VF motion leading to mechanical stresses within the VFs and their effect on the interstitial fluid flux is detailed. It is found that average deformation and vibration of VFs tends to increase the state of hydration of the VF tissue whereas VF collision works to reduce hydration. PMID:23531170

  10. Linking magmatism with collision in an accretionary orogen.

    PubMed

    Li, Shan; Chung, Sun-Lin; Wilde, Simon A; Wang, Tao; Xiao, Wen-Jiao; Guo, Qian-Qian

    2016-05-11

    A compilation of U-Pb age, geochemical and isotopic data for granitoid plutons in the southern Central Asian Orogenic Belt (CAOB), enables evaluation of the interaction between magmatism and orogenesis in the context of Paleo-Asian oceanic closure and continental amalgamation. These constraints, in conjunction with other geological evidence, indicate that following consumption of the ocean, collision-related calc-alkaline granitoid and mafic magmatism occurred from 255 ± 2 Ma to 251 ± 2 Ma along the Solonker-Xar Moron suture zone. The linear or belt distribution of end-Permian magmatism is interpreted to have taken place in a setting of final orogenic contraction and weak crustal thickening, probably as a result of slab break-off. Crustal anatexis slightly post-dated the early phase of collision, producing adakite-like granitoids with some S-type granites during the Early-Middle Triassic (ca. 251-245 Ma). Between 235 and 220 Ma, the local tectonic regime switched from compression to extension, most likely caused by regional lithospheric extension and orogenic collapse. Collision-related magmatism from the southern CAOB is thus a prime example of the minor, yet tell-tale linking of magmatism with orogenic contraction and collision in an archipelago-type accretionary orogen.

  11. Formation of Cluster Complexes by Cluster-Cluster-Collisions

    NASA Astrophysics Data System (ADS)

    Ichihashi, Masahiko; Odaka, Hideho

    2015-03-01

    Multi-element clusters are interested in their chemical and physical properties, and it is expected that they are utilized as catalysts, for example. Their properties critically depend on the size, composition and atomic ordering, and it should be important to adjust the above parameters for their functionality. One of the ways to form a multi-element cluster is to employ a low-energy collision between clusters. Here, we show characteristic results obtained in the collision between a neutral Ar cluster and a size-selected Co cluster ion. Low-energy collision experiment was accomplished by using a newly developed merging-beam apparatus. Cobalt cluster ions were produced by laser ablation, and mass-selected. On the other hand, argon clusters were prepared by the supersonic expansion of Ar gas. Both cluster beams were merged together in an ion guide, and ionic cluster complexes were mass-analyzed. In the collision of Co2+ and ArN, Co2Arn+ (n = 1 - 30) were observed, and the total intensity of Co2Arn+ (n >= 1) is inversely proportional to the relative velocity between Co2+ and ArN. This suggests that the charge-induced dipole interaction between Co2+ and a neutral Ar cluster is dominant in the formation of the cluster complex, Co2+Arn.

  12. An overheight vehicle bridge collision monitoring system using piezoelectric transducers

    NASA Astrophysics Data System (ADS)

    Song, G.; Olmi, C.; Gu, H.

    2007-04-01

    With increasing traffic volume follows an increase in the number of overheight truck collisions with highway bridges. The detection of collision impact and evaluation of the impact level is a critical issue in the maintenance of a concrete bridge. In this paper, an overheight collision detection and evaluation system is developed for concrete bridge girders using piezoelectric transducers. An electric circuit is designed to detect the impact and to activate a digital camera to take photos of the offending truck. Impact tests and a health monitoring test were conducted on a model concrete bridge girder by using three piezoelectric transducers embedded before casting. From the experimental data of the impact test, it can be seen that there is a linear relation between the output of sensor energy and the impact energy. The health monitoring results show that the proposed damage index indicates the level of damage inside the model concrete bridge girder. The proposed overheight truck-bridge collision detection and evaluation system has the potential to be applied to the safety monitoring of highway bridges.

  13. Observation of sequential Υ suppression in PbPb collisions.

    PubMed

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Pierro, G A; Ross, I; Savin, A; Smith, W H; Swanson, J

    2012-11-30

    The suppression of the individual Υ(nS) states in PbPb collisions with respect to their yields in pp data has been measured. The PbPb and pp data sets used in the analysis correspond to integrated luminosities of 150 μb(-1) and 230 nb(-1), respectively, collected in 2011 by the CMS experiment at the LHC, at a center-of-mass energy per nucleon pair of 2.76 TeV. The Υ(nS) yields are measured from the dimuon invariant mass spectra. The suppression of the Υ(nS) yields in PbPb relative to the yields in pp, scaled by the number of nucleon-nucleon collisions, R(AA), is measured as a function of the collision centrality. Integrated over centrality, the R(AA) values are 0.56±0.08(stat)±0.07(syst), 0.12±0.04(stat)±0.02(syst), and lower than 0.10 (at 95% confidence level), for the Υ(1S), Υ(2S), and Υ(3S) states, respectively. The results demonstrate the sequential suppression of the Υ(nS) states in PbPb collisions at LHC energies.

  14. A computational study of systemic hydration in vocal fold collision.

    PubMed

    Bhattacharya, Pinaki; Siegmund, Thomas

    2014-01-01

    Mechanical stresses develop within vocal fold (VF) soft tissues due to phonation-associated vibration and collision. These stresses in turn affect the hydration of VF tissue and thus influence voice health. In this paper, high-fidelity numerical computations are described, taking into account fully 3D geometry, realistic tissue and air properties, and high-amplitude vibration and collision. A segregated solver approach is employed, using sophisticated commercial solvers for both the VF tissue and glottal airflow domains. The tissue viscoelastic properties were derived from a biphasic formulation. Two cases were considered, whereby the tissue viscoelastic properties corresponded to two different volume fractions of the fluid phase of the VF tissue. For each case, hydrostatic stresses occurring as a result of vibration and collision were investigated. Assuming the VF tissue to be poroelastic, interstitial fluid movement within VF tissue was estimated from the hydrostatic stress gradient. Computed measures of overall VF dynamics (peak airflow velocity, magnitude of VF deformation, frequency of vibration and contact pressure) were well within the range of experimentally observed values. The VF motion leading to mechanical stresses within the VFs and their effect on the interstitial fluid flux is detailed. It is found that average deformation and vibration of VFs tend to increase the state of hydration of the VF tissue, whereas VF collision works to reduce hydration.

  15. Observation of Sequential Υ Suppression in PbPb Collisions

    NASA Astrophysics Data System (ADS)

    Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Aguilo, E.; Bergauer, T.; Dragicevic, M.; Erö, J.; Fabjan, C.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hammer, J.; Hörmann, N.; Hrubec, J.; Jeitler, M.; Kiesenhofer, W.; Knünz, V.; Krammer, M.; Krätschmer, I.; Liko, D.; Mikulec, I.; Pernicka, M.; Rahbaran, B.; Rohringer, C.; Rohringer, H.; Schöfbeck, R.; Strauss, J.; Taurok, A.; Waltenberger, W.; Walzel, G.; Widl, E.; Wulz, C.-E.; Mossolov, V.; Shumeiko, N.; Suarez Gonzalez, J.; Bansal, S.; Cornelis, T.; De Wolf, E. A.; Janssen, X.; Luyckx, S.; Mucibello, L.; Ochesanu, S.; Roland, B.; Rougny, R.; Selvaggi, M.; Staykova, Z.; Van Haevermaet, H.; Van Mechelen, P.; Van Remortel, N.; Van Spilbeeck, A.; Blekman, F.; Blyweert, S.; D'Hondt, J.; Gonzalez Suarez, R.; Kalogeropoulos, A.; Maes, M.; Olbrechts, A.; Van Doninck, W.; Van Mulders, P.; Van Onsem, G. P.; Villella, I.; Clerbaux, B.; De Lentdecker, G.; Dero, V.; Gay, A. P. R.; Hreus, T.; Léonard, A.; Marage, P. E.; Reis, T.; Thomas, L.; Vander Velde, C.; Vanlaer, P.; Wang, J.; Adler, V.; Beernaert, K.; Cimmino, A.; Costantini, S.; Garcia, G.; Grunewald, M.; Klein, B.; Lellouch, J.; Marinov, A.; Mccartin, J.; Ocampo Rios, A. A.; Ryckbosch, D.; Strobbe, N.; Thyssen, F.; Tytgat, M.; Verwilligen, P.; Walsh, S.; Yazgan, E.; Zaganidis, N.; Basegmez, S.; Bruno, G.; Castello, R.; Ceard, L.; Delaere, C.; du Pree, T.; Favart, D.; Forthomme, L.; Giammanco, A.; Hollar, J.; Lemaitre, V.; Liao, J.; Militaru, O.; Nuttens, C.; Pagano, D.; Pin, A.; Piotrzkowski, K.; Schul, N.; Vizan Garcia, J. M.; Beliy, N.; Caebergs, T.; Daubie, E.; Hammad, G. H.; Alves, G. A.; Correa Martins Junior, M.; De Jesus Damiao, D.; Martins, T.; Pol, M. E.; Souza, M. H. G.; Aldá Júnior, W. L.; Carvalho, W.; Custódio, A.; Da Costa, E. M.; De Oliveira Martins, C.; De Souza, S. Fonseca; Matos Figueiredo, D.; Mundim, L.; Nogima, H.; Oguri, V.; Prado Da Silva, W. L.; Santoro, A.; Soares Jorge, L.; Sznajder, A.; Anjos, T. S.; Bernardes, C. A.; Dias, F. A.; Fernandez Perez Tomei, T. R.; Gregores, E. M.; Lagana, C.; Marinho, F.; Mercadante, P. G.; Novaes, S. F.; Padula, Sandra S.; Genchev, V.; Iaydjiev, P.; Piperov, S.; Rodozov, M.; Stoykova, S.; Sultanov, G.; Tcholakov, V.; Trayanov, R.; Vutova, M.; Dimitrov, A.; Hadjiiska, R.; Kozhuharov, V.; Litov, L.; Pavlov, B.; Petkov, P.; Bian, J. G.; Chen, G. M.; Chen, H. S.; Jiang, C. H.; Liang, D.; Liang, S.; Meng, X.; Tao, J.; Wang, J.; Wang, X.; Wang, Z.; Xiao, H.; Xu, M.; Zang, J.; Zhang, Z.; Asawatangtrakuldee, C.; Ban, Y.; Guo, S.; Guo, Y.; Li, W.; Liu, S.; Mao, Y.; Qian, S. J.; Teng, H.; Wang, D.; Zhang, L.; Zhu, B.; Zou, W.; Avila, C.; Gomez, J. P.; Gomez Moreno, B.; Osorio Oliveros, A. F.; Sanabria, J. C.; Godinovic, N.; Lelas, D.; Plestina, R.; Polic, D.; Puljak, I.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Duric, S.; Kadija, K.; Luetic, J.; Morovic, S.; Attikis, A.; Galanti, M.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Finger, M.; Finger, M., Jr.; Assran, Y.; Elgammal, S.; Ellithi Kamel, A.; Khalil, S.; Mahmoud, M. A.; Radi, A.; Kadastik, M.; Müntel, M.; Raidal, M.; Rebane, L.; Tiko, A.; Eerola, P.; Fedi, G.; Voutilainen, M.; Härkönen, J.; Heikkinen, A.; Karimäki, V.; Kinnunen, R.; Kortelainen, M. J.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Peltola, T.; Tuominen, E.; Tuominiemi, J.; Tuovinen, E.; Ungaro, D.; Wendland, L.; Banzuzi, K.; Karjalainen, A.; Korpela, A.; Tuuva, T.; Besancon, M.; Choudhury, S.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. L.; Ferri, F.; Ganjour, S.; Givernaud, A.; Gras, P.; Hamel de Monchenault, G.; Jarry, P.; Locci, E.; Malcles, J.; Millischer, L.; Nayak, A.; Rander, J.; Rosowsky, A.; Shreyber, I.; Titov, M.; Baffioni, S.; Beaudette, F.; Benhabib, L.; Bianchini, L.; Bluj, M.; Broutin, C.; Busson, P.; Charlot, C.; Daci, N.; Dahms, T.; Dobrzynski, L.; Granier de Cassagnac, R.; Haguenauer, M.; Miné, P.; Mironov, C.; Naranjo, I. N.; Nguyen, M.; Ochando, C.; Paganini, P.; Sabes, D.; Salerno, R.; Sirois, Y.; Veelken, C.; Zabi, A.; Agram, J.-L.; Andrea, J.; Bloch, D.; Bodin, D.; Brom, J.-M.; Cardaci, M.; Chabert, E. C.; Collard, C.; Conte, E.; Drouhin, F.; Ferro, C.; Fontaine, J.-C.; Gelé, D.; Goerlach, U.; Juillot, P.; Le Bihan, A.-C.; Van Hove, P.; Fassi, F.; Mercier, D.; Beauceron, S.; Beaupere, N.; Bondu, O.; Boudoul, G.; Chasserat, J.; Chierici, R.; Contardo, D.; Depasse, P.; El Mamouni, H.; Fay, J.; Gascon, S.; Gouzevitch, M.; Ille, B.; Kurca, T.; Lethuillier, M.; Mirabito, L.; Perries, S.; Sordini, V.; Tschudi, Y.; Verdier, P.; Viret, S.; Tsamalaidze, Z.; Anagnostou, G.; Beranek, S.; Edelhoff, M.; Feld, L.; Heracleous, N.; Hindrichs, O.; Jussen, R.; Klein, K.; Merz, J.; Ostapchuk, A.; Perieanu, A.

    2012-11-01

    The suppression of the individual Υ(nS) states in PbPb collisions with respect to their yields in pp data has been measured. The PbPb and pp data sets used in the analysis correspond to integrated luminosities of 150μb-1 and 230nb-1, respectively, collected in 2011 by the CMS experiment at the LHC, at a center-of-mass energy per nucleon pair of 2.76 TeV. The Υ(nS) yields are measured from the dimuon invariant mass spectra. The suppression of the Υ(nS) yields in PbPb relative to the yields in pp, scaled by the number of nucleon-nucleon collisions, RAA, is measured as a function of the collision centrality. Integrated over centrality, the RAA values are 0.56±0.08(stat)±0.07(syst), 0.12±0.04(stat)±0.02(syst), and lower than 0.10 (at 95% confidence level), for the Υ(1S), Υ(2S), and Υ(3S) states, respectively. The results demonstrate the sequential suppression of the Υ(nS) states in PbPb collisions at LHC energies.

  16. Collision and Break-off : Numerical models and surface observables

    NASA Astrophysics Data System (ADS)

    Bottrill, Andrew; van Hunen, Jeroen; Allen, Mark

    2013-04-01

    results in this area indicate the stress experienced by the overriding lithosphere changes through the collision and slab break-off process. This change is stress affects the topography, but also offers another observable for understanding collision zones. We relate our numerical model to Arabia-Eurasia collision which is thought to have begun around 35 Ma (Allen and Armstrong, 2008; Vincent et al., 2007). The post collision basin predicted by our numerical model can be associated with the Miocene carbonate deposits of the Qom formation (Morley et al., 2009). These Miocene carbonate deposits are found at approximately 200-300km from the suture zone and are stratigraphically "sandwiched" between terrestrial clastic sedimentary formations. The position of these deposits shows that they are intimately related with the collision process, and that this area of the overriding plate has dipped below sea level for about 10 Myrs during the Early Miocene. Another geographic area that offers possibility for observation of topography change produced during continental collision is the Italian Apennines. Here, slab detachment is proposed to have started around 30 Ma and a tear propagated north to south along Italy (Wortel, 2000). Van der Meulen et al., (1998) observed a period of basin formation followed by uplift using the sedimentary record. Migrating depocentres were interpreted as evidence of a slab tear propagating north to south. These depocentres are located on the overriding plate with the maximum observed depression around 100 km from the suture (Ascione et al., 2012). These observed depocentres could be analogous to the depressions observed in our numerical models. Allen, M. B. and Armstrong, H. A.: Arabia-Eurasia collision and the forcing of mid-Cenozoic global cooling, Palaeogeography, Palaeoclimatology, Palaeoecology, 265(1-2), 52-58, doi:10.1016/j.palaeo.2008.04.021, 2008. Andrews, E. R. and Billen, M. I.: Rheologic controls on the dynamics of slab detachment

  17. A conservative spectral method for the Boltzmann equation with anisotropic scattering and the grazing collisions limit

    SciTech Connect

    Gamba, Irene M.; Haack, Jeffrey R.

    2014-08-01

    We present the formulation of a conservative spectral method for the Boltzmann collision operator with anisotropic scattering cross-sections. The method is an extension of the conservative spectral method of Gamba and Tharkabhushanam [17,18], which uses the weak form of the collision operator to represent the collisional term as a weighted convolution in Fourier space. The method is tested by computing the collision operator with a suitably cut-off angular cross section and comparing the results with the solution of the Landau equation. We analytically study the convergence rate of the Fourier transformed Boltzmann collision operator in the grazing collisions limit to the Fourier transformed Landau collision operator under the assumption of some regularity and decay conditions of the solution to the Boltzmann equation. Our results show that the angular singularity which corresponds to the Rutherford scattering cross section is the critical singularity for which a grazing collision limit exists for the Boltzmann operator. Additionally, we numerically study the differences between homogeneous solutions of the Boltzmann equation with the Rutherford scattering cross section and an artificial cross section, which give convergence to solutions of the Landau equation at different asymptotic rates. We numerically show the rate of the approximation as well as the consequences for the rate of entropy decay for homogeneous solutions of the Boltzmann equation and Landau equation.

  18. Motor-vehicle collisions involving child pedestrians at intersection and mid-block locations.

    PubMed

    Bennet, Scott A; Yiannakoulias, Nikolaos

    2015-05-01

    We study motor-vehicle collisions involving child pedestrians walking to school in Hamilton, Ontario, Canada to understand and contrast collision risks at mid-block and intersection locations. We use a matched case-control study design and apply it to intersection and mid-block locations instead of people. Cases are intersections/mid-blocks where collisions occurred and controls are locations where collisions did not occur. We match cases to controls on geography, socio-economic status and year. We use conditional logistic regression to predict the log-odds of collision risk at intersections and mid-blocks as a function of various environmental measures while controlling for volume of child pedestrian activity. Our results suggest that child pedestrian injuries at intersections are associated with intersection control type, traffic volume, and land use characteristics. In contrast, mid-block child pedestrian collisions are not associated with small scale environmental features. The results of this study suggest that some factors associated with the risk of collision differ across location types. These findings may be useful in the planning of safer walking journeys to school.

  19. Amplitude modulation of alpha-band rhythm caused by mimic collision: MEG study.

    PubMed

    Yokosawa, Koichi; Watanabe, Tatsuya; Kikuzawa, Daichi; Aoyama, Gakuto; Takahashi, Makoto; Kuriki, Shinya

    2013-01-01

    Detection of a collision risk and avoiding the collision are important for survival. We have been investigating neural responses when humans anticipate a collision or intend to take evasive action by applying collision-simulating images in a predictable manner. Collision-simulating images and control images were presented in random order to 9 healthy male volunteers. A cue signal was also given visually two seconds before each stimulus to enable each participant to anticipate the upcoming stimulus. Magnetoencephalograms (MEG) were recorded with a 76-ch helmet system. The amplitude of alpha band (8-13 Hz) rhythm when anticipating the upcoming collision-simulating image was significantly smaller than that when anticipating control images even just after the cue signal. This result demonstrates that anticipating a negative (dangerous) event induced event-related desynchronization (ERD) of alpha band activity, probably caused by attention. The results suggest the feasibility of detecting endogenous brain activities by monitoring alpha band rhythm and its possible applications to engineering systems, such as an automatic collision evasion system for automobiles.

  20. Mechanical Energy Changes in Perfectly Inelastic Collisions

    ERIC Educational Resources Information Center

    Mungan, Carl E.

    2013-01-01

    Suppose a block of mass "m"[subscript 1] traveling at speed "v"[subscript 1] makes a one-dimensional perfectly inelastic collision with another block of mass "m"[subscript 2]. What else does one need to know to calculate the fraction of the mechanical energy that is dissipated in the collision? (Contains 1 figure.)

  1. Oblique and Head-On Elastic Collisions

    ERIC Educational Resources Information Center

    Ng, Chiu-king

    2008-01-01

    When a moving ball collides elastically with an identical, initially stationary ball, the incident ball will either come to rest (head-on collision; see Fig. 1) or will acquire a velocity that is perpendicular to that acquired by the target ball (oblique collision; see Fig. 2). These two possible outcomes are related in an interesting way, which…

  2. Positron collisions with alkali-metal atoms

    NASA Technical Reports Server (NTRS)

    Gien, T. T.

    1990-01-01

    The total cross sections for positron and electron collisions with potassium, sodium, lithium and rubidium are calculated, employing the modified Glauber approximation. The Modified Glauber cross sections for positron collision with potassium and sodium at low intermediate energies are found to agree reasonably well with existing experimental data.

  3. Cultural Collisions in L2 Academic Writing.

    ERIC Educational Resources Information Center

    Steinman, Linda

    2003-01-01

    Reviews research on writing and culture, focusing on the collisions of cultures when discourse practices second language writers are expected to reproduce clash with what they know, believe, and value in their first language writing. Describes collisions of culture in writing regarding voice, organization, reader/writer responsibility, topic, and…

  4. Variation of transverse momentum in hadronic collisions

    NASA Technical Reports Server (NTRS)

    Saint Amand, J.; Uritam, R. A.

    1975-01-01

    The paper presents a detailed parameterization of the transverse momentum in hadronic collisions on multiplicity and on beam momentum. Hadronic collisions are considered at energies below the ultra-high energy domain, on the basis of an uncertainty relation and a naive eikonal model with an impact-parameter-dependent multiplicity.

  5. Energy coupling in catastrophic collisions

    NASA Technical Reports Server (NTRS)

    Holsapple, K. A.; Choe, K. Y.

    1991-01-01

    The prediction of events leading to the catastrophic collisions and disruption of solar system bodies is fraught with the same difficulties as are other theories of impact events; since one simply cannot perform experiments in the regime of interest. In the catastrophic collisions of asteroids that regime involves bodies of a few tons to hundred of kilometers in diameter, and velocities of several kilometers pre second. For hundred kilometer bodies, gravitational stresses dominate material fracture strengths, but those gravitational stresses are essentially absent for laboratory experiments. Only numerical simulations using hydrocodes can in principle analyze the true problems, but they have their own major uncertainties about the correctness of the physical models and properties. The question of the measure of the impactor and its energy coupling is investigated using numerical code calculations. The material model was that of a generic silicate rock, including high pressure melt and vapor phases, and includes material nonlinearity and dissipation via a Mie-Gruniesen model. A series of calculations with various size ratios and impact velocities are reported.

  6. A Comparison of Catastrophic On-Orbit Collisions

    NASA Astrophysics Data System (ADS)

    Stansbery, G.; Matney, M.; Liou, J.; Whitlock, D.

    Orbital debris environment models, such as NASA's LEGEND model, show that accidental collisions between satellites will begin to be the dominant cause for future debris population growth within the foreseeable future. The collisional breakup models employed are obviously a critical component of the environment models. The Chinese Anti-Satellite (ASAT) test which destroyed the Fengyun-1C weather satellite provided a rare, but not unique, chance to compare the breakup models against an actual on-orbit collision. Measurements from the U.S. Space Surveillance Network (SSN), for debris larger than 10-cm, and from Haystack, for debris larger than 1-cm, show that the number of fragments created from Fengyun significantly exceeds model predictions using the NASA Standard Collision Breakup Model. However, it may not be appropriate to alter the model to match this one, individual case. At least three other on-orbit collisions have occurred which have produced significant numbers of debris fragments. In September 1985, the U.S. conducted an ASAT test against the Solwind P-78 spacecraft at an altitude of approximately 525 km. A year later, in September 1986, the Delta 180 payload was struck by its Delta II rocket body in a planned collision at 220 km altitude. And, in February 2008, the USA-193 satellite was destroyed by a ship launched missile in order to eliminate risk to humans on the ground from an on-board tank of frozen hydrazine. Although no Haystack data was available in 1985-6 and very few debris pieces were cataloged from Delta 180 due to its low altitude, measurements were collected sensors in the days after each test. This paper will examine the available data from each test and compare and contrast the results with model predictions and with the results from the more recent Fengyun ASAT test.

  7. Approaches to Evaluating Probability of Collision Uncertainty

    NASA Technical Reports Server (NTRS)

    Hejduk, Matthew D.; Johnson, Lauren C.

    2016-01-01

    While the two-dimensional probability of collision (Pc) calculation has served as the main input to conjunction analysis risk assessment for over a decade, it has done this mostly as a point estimate, with relatively little effort made to produce confidence intervals on the Pc value based on the uncertainties in the inputs. The present effort seeks to try to carry these uncertainties through the calculation in order to generate a probability density of Pc results rather than a single average value. Methods for assessing uncertainty in the primary and secondary objects' physical sizes and state estimate covariances, as well as a resampling approach to reveal the natural variability in the calculation, are presented; and an initial proposal for operationally-useful display and interpretation of these data for a particular conjunction is given.

  8. Elastic and inelastic collisions of swarms

    NASA Astrophysics Data System (ADS)

    Armbruster, Dieter; Martin, Stephan; Thatcher, Andrea

    2017-04-01

    Scattering interactions of swarms in potentials that are generated by an attraction-repulsion model are studied. In free space, swarms in this model form a well-defined steady state describing the translation of a stable formation of the particles whose shape depends on the interaction potential. Thus, the collision between a swarm and a boundary or between two swarms can be treated as (quasi)-particle scattering. Such scattering experiments result in internal excitations of the swarm or in bound states, respectively. In addition, varying a parameter linked to the relative importance of damping and potential forces drives transitions between elastic and inelastic scattering of the particles. By tracking the swarm's center of mass, a refraction rule is derived via simulations relating the incoming and outgoing directions of a swarm hitting the wall. Iterating the map derived from the refraction law allows us to predict and understand the dynamics and bifurcations of swarms in square boxes and in channels.

  9. Adiabatic theory for anisotropic cold molecule collisions

    SciTech Connect

    Pawlak, Mariusz; Shagam, Yuval; Narevicius, Edvardas; Moiseyev, Nimrod

    2015-08-21

    We developed an adiabatic theory for cold anisotropic collisions between slow atoms and cold molecules. It enables us to investigate the importance of the couplings between the projection states of the rotational motion of the atom about the molecular axis of the diatom. We tested our theory using the recent results from the Penning ionization reaction experiment {sup 4}He(1s2s {sup 3}S) + HD(1s{sup 2}) → {sup 4}He(1s{sup 2}) + HD{sup +}(1s) + e{sup −} [Lavert-Ofir et al., Nat. Chem. 6, 332 (2014)] and demonstrated that the couplings have strong effect on positions of shape resonances. The theory we derived provides cross sections which are in a very good agreement with the experimental findings.

  10. A clinically feasible method for the detection of potential collision in proton therapy

    SciTech Connect

    Zou Wei; Lin Haibo; Plastaras, John P.; Wang Huanshu; Bui, Viet; Vapiwala, Neha; McDonough, James; Tochner, Zelig; Both, Stefan

    2012-11-15

    Purpose: Potential collision between the patient/couch and the gantry could delay the start of the treatment and reduce clinical efficiency. The ability to accurately detect possible collisions during the treatment planning phase is desired. Such collision detection should account for the specific proton gantry design, the treatment beam configuration, couch orientation, and the patient specific geometry. In this paper the authors developed an approach to detect possible patient-machine collisions using patient treatment plan data. Methods: The geometry of the machine and the patient was reconstructed relative to the isocenter of the proton treatment room. The surface contour of the gantry was first captured from the proton computer aided design and reconstructed to account for specific gantry rotation, snout position, collimator rotation, and range compensator dimensions based on the patient treatment plan data. The patient body and couch contours were captured from the patient's CT DICOM structure file. They were reconstructed relative to the isocenter taking into account treatment couch rotation. For potential collision that occurs at body portions where no CT images exist, scout images are used to construct the body contour. A software program was developed using a ray casting algorithm that was applied to detect collisions by determining if any of the patient and couch contour points fall into the spatial polygons formed by the proton gantry surfaces. Results: Twenty-four patient plans with or without potential collisions were retrospectively identified and analyzed using the collision detection software. In addition, five collision cases were artificially generated using an anthropomorphic phantom. The program successfully detected the collisions in all cases. The calculation time for each case was within 20 s. The software program was implemented in the authors' clinic to detect patient-gantry or gantry-couch collisions in the treatment planning phase

  11. From many body wee partons dynamics to perfect fluid: a standard model for heavy ion collisions

    SciTech Connect

    Venugopalan, R.

    2010-07-22

    We discuss a standard model of heavy ion collisions that has emerged both from experimental results of the RHIC program and associated theoretical developments. We comment briefly on the impact of early results of the LHC program on this picture. We consider how this standard model of heavy ion collisions could be solidified or falsified in future experiments at RHIC, the LHC and a future Electro-Ion Collider.

  12. An optimal control strategy for collision avoidance of mobile robots in non-stationary environments

    NASA Technical Reports Server (NTRS)

    Kyriakopoulos, K. J.; Saridis, G. N.

    1991-01-01

    An optimal control formulation of the problem of collision avoidance of mobile robots in environments containing moving obstacles is presented. Collision avoidance is guaranteed if the minimum distance between the robot and the objects is nonzero. A nominal trajectory is assumed to be known from off-line planning. The main idea is to change the velocity along the nominal trajectory so that collisions are avoided. Furthermore, time consistency with the nominal plan is desirable. A numerical solution of the optimization problem is obtained. Simulation results verify the value of the proposed strategy.

  13. Simulations of ion velocity distribution functions taking into account both elastic and charge exchange collisions

    NASA Astrophysics Data System (ADS)

    Wang, Huihui; Sukhomlinov, Vladimir S.; Kaganovich, Igor D.; Mustafaev, Alexander S.

    2017-02-01

    Based on accurate representation of the He+-He angular differential scattering cross sections consisting of both elastic and charge exchange collisions, we performed detailed numerical simulations of the ion velocity distribution functions (IVDF) by Monte Carlo collision method (MCC). The results of simulations are validated by comparison with the experimental data of the ion mobility and the transverse diffusion. The IVDF simulation study shows that due to significant effect of scattering in elastic collisions IVDF cannot be separated into product of two independent IVDFs in the transverse and parallel to the electric field directions.

  14. Charmonium production in ultra-peripheral heavy ion collisions with two-photon processes

    NASA Astrophysics Data System (ADS)

    Yu, Gong-Ming; Yu, Yue-Chao; Li, Yun-De; Wang, Jian-Song

    2017-04-01

    We calculate the production of large-pT charmonium and narrow resonance state (exotic charmonium) in proton-proton, proton-nucleus, and nucleus-nucleus collisions with the semi-coherent two-photon interactions at Relativistic Heavy Ion Collider (RHIC), Large Hadron Collider (LHC), and Future Circular Collider (FCC) energies. Using the large quasi-real photon fluxes, we present the γγ → H differential cross section for charmonium and narrow resonance state production at large transverse momentum in ultra-peripheral heavy ion collisions. The numerical results demonstrate that the experimental study of ultra-peripheral collisions is feasible at RHIC, LHC, and FCC energies.

  15. Neutron skin and centrality classification in high-energy heavy-ion collisions at the LHC

    NASA Astrophysics Data System (ADS)

    Paukkunen, Hannu

    2015-05-01

    The concept of centrality in high-energy nuclear collisions has recently become a subject of an active debate. In particular, the experimental methods to determine the centrality that have given reasonable results for many observables in high-energy lead-lead collisions at the LHC have led to surprising behavior in the case of proton-lead collisions. In this letter, we discuss the possibility to calibrate the experimental determination of centrality by asymmetries caused by mutually different spatial distributions of protons and neutrons inside the nuclei - a well-known phenomenon in nuclear physics known as the neutron-skin effect.

  16. Potential Energy Curves and Collisions Integrals of Air Components. 2; Interactions Involving Ionized Atoms

    NASA Technical Reports Server (NTRS)

    Stallcop, James R.; Partridge, Harry; Levin, Eugene; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Collision integrals are fundamental quantities required to determine the transport properties of the environment surrounding aerospace vehicles in the upper atmosphere. These collision integrals can be determined as a function of temperature from the potential energy curves describing the atomic and molecular collisions. Ab initio calculations provide a practical method of computing the required interaction potentials. In this work we will discuss recent advances in scattering calculations with an emphasis on the accuracy that is obtainable. Results for interactions of the atoms and ionized atoms of nitrogen and oxygen will be reviewed and their application to the determination of transport properties, such as diffusion and viscosity coefficients, will be examined.

  17. Evaluation of human behavior in collision avoidance: a study inside immersive virtual reality.

    PubMed

    Ouellette, Michel; Chagnon, Miguel; Faubert, Jocelyn

    2009-04-01

    During our daily displacements, we should consider the individuals advancing toward us in order to avoid a possible collision with our congeneric. We developed an experimental design in a virtual immersion room, which allows us to evaluate human capacities for avoiding collisions with other people. In addition, the design allows participants to interact naturally inside this immersive virtual reality setup when a pedestrian is moving toward them, creating a possible risk of collision. Results suggest that the performance is associated with visual and motor capacities and could be adjusted by cognitive social perception.

  18. Collision frequency of artificial satellites - The creation of a debris belt

    NASA Technical Reports Server (NTRS)

    Kessler, D. J.; Cour-Palais, B. G.

    1978-01-01

    The probability of satellite collisions increases with the number of satellites. In the present paper, possible time scales for the growth of a debris belt from collision fragments are determined, and possible consequences of continued unrestrained launch activities are examined. Use is made of techniques formerly developed for studying the evolution (growth) of the asteroid belt. A model describing the flux from the known earth-orbiting satellites is developed, and the results from this model are extrapolated in time to predict the collision frequency between satellites. Hypervelocity impact phenomena are then examined to predict the debris flux resulting from collisions. The results are applied to design requirements for three types of future space missions.

  19. Numerical thermalization in particle-in-cell simulations with Monte-Carlo collisions

    NASA Astrophysics Data System (ADS)

    Lai, P. Y.; Lin, T. Y.; Lin-Liu, Y. R.; Chen, S. H.

    2014-12-01

    Numerical thermalization in collisional one-dimensional (1D) electrostatic (ES) particle-in-cell (PIC) simulations was investigated. Two collision models, the pitch-angle scattering of electrons by the stationary ion background and large-angle collisions between the electrons and the neutral background, were included in the PIC simulation using Monte-Carlo methods. The numerical results show that the thermalization times in both models were considerably reduced by the additional Monte-Carlo collisions as demonstrated by comparisons with Turner's previous simulation results based on a head-on collision model [M. M. Turner, Phys. Plasmas 13, 033506 (2006)]. However, the breakdown of Dawson's scaling law in the collisional 1D ES PIC simulation is more complicated than that was observed by Turner, and the revised scaling law of the numerical thermalization time with numerical parameters are derived on the basis of the simulation results obtained in this study.

  20. COLLISIONS OF POROUS CLUSTERS: A GRANULAR-MECHANICS STUDY OF COMPACTION AND FRAGMENTATION

    SciTech Connect

    Ringl, Christian; Urbassek, Herbert M.; Bringa, Eduardo M.; Bertoldi, Dalia S.

    2012-06-20

    The collision of granular clusters can result in a number of complex outcomes from sticking to partial or full destruction of the clusters. These outcomes will contribute to the size distribution of dust aggregates, changing their optical properties and their capability to contribute to solid-state astrochemistry. We study the collision of two clusters of equal size, formed by approximately 7000 sub-{mu}m grains each, with a mass and velocity range that is difficult to sample in experiments. We obtain the outcome of the collision: compaction, fragmentation, and size distribution of ejecta, and type of outcome, as a function of velocity and impact parameter. We compare our results to other models and simulations, at both atomistic and continuum scales, and find some agreement together with some discrepancies. We also study collision-induced compaction as a function of cluster size, up to sizes of N = 250, 000, and find that for large clusters considerably higher compactions result at higher velocities.

  1. Numerical thermalization in particle-in-cell simulations with Monte-Carlo collisions

    SciTech Connect

    Lai, P. Y.; Lin, T. Y.; Lin-Liu, Y. R.; Chen, S. H.

    2014-12-15

    Numerical thermalization in collisional one-dimensional (1D) electrostatic (ES) particle-in-cell (PIC) simulations was investigated. Two collision models, the pitch-angle scattering of electrons by the stationary ion background and large-angle collisions between the electrons and the neutral background, were included in the PIC simulation using Monte-Carlo methods. The numerical results show that the thermalization times in both models were considerably reduced by the additional Monte-Carlo collisions as demonstrated by comparisons with Turner's previous simulation results based on a head-on collision model [M. M. Turner, Phys. Plasmas 13, 033506 (2006)]. However, the breakdown of Dawson's scaling law in the collisional 1D ES PIC simulation is more complicated than that was observed by Turner, and the revised scaling law of the numerical thermalization time with numerical parameters are derived on the basis of the simulation results obtained in this study.

  2. Collision integrals for charged-charged interaction in two-temperature non-equilibrium plasma

    SciTech Connect

    Ghorui, S.; Das, A. K.

    2013-09-15

    Choice of an appropriate form of shielding distance in the estimation of collision integrals under screened coulomb potential for two-temperature non-equilibrium plasma is addressed. Simple expressions for collision integrals for charged-charged interactions are derived. It is shown that while some of the formalisms used earlier completely ignore the presence of ions, the others incorporating it may result in negative collision integrals for the interactions involving particles at higher charged states. The parametric regimes of concern and impact of different formalisms on the computed transport properties are investigated with specific reference to nitrogen plasma. A revised definition of the shielding distance is proposed, which incorporates both electrons and ions, avoids the problem of negative collision integrals in all practical regimes of interest and results in calculated property values in close agreement with experimentally observed results.

  3. Numerical modelling of overtaking collisions of dust acoustic waves in plasmas

    NASA Astrophysics Data System (ADS)

    Gao, Dong-Ning; Zhang, Heng; Zhang, Jie; Li, Zhong-Zheng; Duan, Wen-Shan

    2016-10-01

    The overtaking collision between two single and unidirectional dust acoustic waves in dusty plasmas consisting of Boltzmann electrons and ions, and negative dust grains has been investigated by PIC simulation method. The well-known physical phenomenon is that the larger soliton moves faster, approaches the smaller one and after the overtaking collision both resume their original shape and speed with different phase shifts. The merging amplitude of two solitons and phase shifts of solitons after collision are given. These PIC results are compared with the overtaking collision of two-soliton solution (TSS) of KdV equaiton obtained by Hirota bilinear method. Comparisons between two indicates that if the amplitude of fast soliton is large enough or the amplitude of slow soliton is small enough, the simulation results are consistent with the interaction of Hirota results.

  4. Influence of driver nationality on the risk of causing vehicle collisions in Spain

    PubMed Central

    Lardelli, C; Luna, D; Jimenez, M; Bueno, C; Garcia, M; Galvez, V

    2002-01-01

    Study objective: To estimate the association between driver nationality and the risk of causing a collision between vehicles in motion. Design: Retrospective, matched by collision, case-control study. Setting: Collisions that occurred in Spain during the period from 1990 to 1999 were studied. Participants: Responsible (case) and non-responsible (control) drivers identified in the databases of the Dirección General de Tráfico (General Traffic Directorate) who were involved in a collisions between two or more four wheeled vehicles in motion, in which only one of the drivers had committed a traffic violation. Main results: Crude odds ratios (ORs) for the effect of driver nationality on the risk of causing a collision were significantly higher for foreign drivers than for Spanish drivers, and ranged from a minimum of 1.19 (95% CI 1.09 to 1.29) for Portuguese drivers to a maximum of 2.06 (1.88 to 2.27) for British drivers. Corresponding adjusted ORs were slightly lower, but were still significantly higher than 1 for all nationalities except Italian, Belgian, and American (USA). Adjusted ORs were usually higher for collisions that occurred in urban areas than on open roads. Conclusions: Authorities responsible for traffic safety, and drivers in general, should consider foreign drivers in Spain at particularly high risk for causing collisions, especially in urban areas. PMID:11964439

  5. Stochastic collision and aggregation analysis of kaolinite in water through experiments and the spheropolygon theory.

    PubMed

    Tang, Fiona H M; Alonso-Marroquin, Fernando; Maggi, Federico

    2014-04-15

    An approach based on spheropolygons (i.e., the Minkowski sum of a polygon with N vertices and a disk with spheroradius r) is presented to describe the shape of kaolinite aggregates in water and to investigate interparticle collision dynamics. Spheropolygons generated against images of kaolinite aggregates achieved an error between 0.5% and 20% as compared to at least 32% of equivalent spheres. These spheropolygons were used to investigate the probability of collision (Pr[C]) and aggregation (Pr[A]) under the action of gravitational, viscous, contact (visco-elastic), electrostatic and van der Waals forces. In ortho-axial (i.e., frontal) collision, Pr[A] of equivalent spheres was always 1, however, stochastic analysis of collision among spheropolygons showed that Pr[A] decreased asymptotically with N increasing, and decreased further in peri-axial (i.e., tangential) collision. Trajectory analysis showed that not all collisions occurring within the attraction zone of the double layer resulted in aggregation, neither all those occurring outside it led to relative departure. Rather, the relative motion on surface asperities affected the intensity of contact and attractive forces to an extent to substantially control a collision outcome in either instances. Spheropolygons revealed therefore how external shape can influence particle aggregation, and suggested that this is equally important to contact and double layer forces in determining the probability of particle aggregation.

  6. Role of collisions in erosion of regolith during a lunar landing

    NASA Astrophysics Data System (ADS)

    Berger, Kyle J.; Anand, Anshu; Metzger, Philip T.; Hrenya, Christine M.

    2013-02-01

    The supersonic gas plume of a landing rocket entrains lunar regolith, which is the layer of loose solids covering the lunar surface. This ejection is problematic due to scouring and dust impregnation of surrounding hardware, reduction in visibility for the crew, and spoofing of the landing sensors. To date, model predictions of erosion and ejection dynamics have been based largely on single-trajectory models in which the role of interparticle collisions is ignored. In the present work, the parameters affecting the erosion rate of monodisperse solids are investigated using the discrete element method (DEM). The drag and lift forces exerted by the rocket exhaust are incorporated via one-way coupling. The results demonstrate that interparticle collisions are frequent in the region immediately above the regolith surface; as many as 20% of particles are engaged in a collision at a given time. These collisions play an important role both in the erosion dynamics and in the final trajectories of particles. In addition, a direct assessment of the influence of collisions on the erosion rate is accomplished via a comparison between a “collisionless” DEM model and the original DEM model. This comparison shows that the erosion dynamics change drastically when collisions are considered and that the erosion rate is dependent on the collision parameters (coefficient of restitution and coefficient of friction). Physical explanations for these trends are provided.

  7. Development of collision avoidance system for useful UAV applications using image sensors with laser transmitter

    NASA Astrophysics Data System (ADS)

    Cheong, M. K.; Bahiki, M. R.; Azrad, S.

    2016-10-01

    The main goal of this study is to demonstrate the approach of achieving collision avoidance on Quadrotor Unmanned Aerial Vehicle (QUAV) using image sensors with colour- based tracking method. A pair of high definition (HD) stereo cameras were chosen as the stereo vision sensor to obtain depth data from flat object surfaces. Laser transmitter was utilized to project high contrast tracking spot for depth calculation using common triangulation. Stereo vision algorithm was developed to acquire the distance from tracked point to QUAV and the control algorithm was designed to manipulate QUAV's response based on depth calculated. Attitude and position controller were designed using the non-linear model with the help of Optitrack motion tracking system. A number of collision avoidance flight tests were carried out to validate the performance of the stereo vision and control algorithm based on image sensors. In the results, the UAV was able to hover with fairly good accuracy in both static and dynamic collision avoidance for short range collision avoidance. Collision avoidance performance of the UAV was better with obstacle of dull surfaces in comparison to shiny surfaces. The minimum collision avoidance distance achievable was 0.4 m. The approach was suitable to be applied in short range collision avoidance.

  8. Role of collisions in erosion of regolith during a lunar landing.

    PubMed

    Berger, Kyle J; Anand, Anshu; Metzger, Philip T; Hrenya, Christine M

    2013-02-01

    The supersonic gas plume of a landing rocket entrains lunar regolith, which is the layer of loose solids covering the lunar surface. This ejection is problematic due to scouring and dust impregnation of surrounding hardware, reduction in visibility for the crew, and spoofing of the landing sensors. To date, model predictions of erosion and ejection dynamics have been based largely on single-trajectory models in which the role of interparticle collisions is ignored. In the present work, the parameters affecting the erosion rate of monodisperse solids are investigated using the discrete element method (DEM). The drag and lift forces exerted by the rocket exhaust are incorporated via one-way coupling. The results demonstrate that interparticle collisions are frequent in the region immediately above the regolith surface; as many as 20% of particles are engaged in a collision at a given time. These collisions play an important role both in the erosion dynamics and in the final trajectories of particles. In addition, a direct assessment of the influence of collisions on the erosion rate is accomplished via a comparison between a "collisionless" DEM model and the original DEM model. This comparison shows that the erosion dynamics change drastically when collisions are considered and that the erosion rate is dependent on the collision parameters (coefficient of restitution and coefficient of friction). Physical explanations for these trends are provided.

  9. Azimuthal anisotophy in U + U and Au + Au collisions at RHIC

    SciTech Connect

    Adamczyk, L.

    2015-11-24

    Collisions between prolate uranium nuclei are used to study how particle production and azimuthal anisotropies depend on initial geometry in heavy-ion collisions. We report the two- and four-particle cumulants, v2{2} and v2{4}, for charged hadrons from U+U collisions at √SNN = 193 GeV and Au+Au collisions at √SNN = 200 GeV. Nearly fully overlapping collisions are selected based on the energy deposited by spectators in zero degree calorimeters (ZDCs). Within this sample, the observed dependence of v2{2} on multiplicity demonstrates that ZDC information combined with multiplicity can preferentially select different overlap configurations in U+U collisions. As a result, we also show that v2 vs multiplicity can be better described by models, such as gluon saturation or quark participant models, that eliminate the dependence of the multiplicity on the number of binary nucleon-nucleon collisions.

  10. Azimuthal anisotophy in U + U and Au + Au collisions at RHIC

    DOE PAGES

    Adamczyk, L.

    2015-11-24

    Collisions between prolate uranium nuclei are used to study how particle production and azimuthal anisotropies depend on initial geometry in heavy-ion collisions. We report the two- and four-particle cumulants, v2{2} and v2{4}, for charged hadrons from U+U collisions at √SNN = 193 GeV and Au+Au collisions at √SNN = 200 GeV. Nearly fully overlapping collisions are selected based on the energy deposited by spectators in zero degree calorimeters (ZDCs). Within this sample, the observed dependence of v2{2} on multiplicity demonstrates that ZDC information combined with multiplicity can preferentially select different overlap configurations in U+U collisions. As a result, we alsomore » show that v2 vs multiplicity can be better described by models, such as gluon saturation or quark participant models, that eliminate the dependence of the multiplicity on the number of binary nucleon-nucleon collisions.« less

  11. Excitation Mechanisms in Moderate-Energy Na+-He and K+-He Collisions

    NASA Astrophysics Data System (ADS)

    Kita, Shigetomo; Hattori, Takehito; Shimakura, Noriyuki

    2015-01-01

    Excitation mechanisms in Na+-He and K+-He collisions were studied at laboratory collision energies of 1000 ≤ Elab ≤ 1500 eV by differential scattering spectroscopy. Extensive measurements were performed at Elab = 1500 eV. Double differential cross sections σ(Θ)k were measured over a wide range of center-of-mass scattering angles, 7.3 ≤ Θ ≤ 173°, by detecting all the scattered particles (Na+, Na, K+, K, He+, and He), where the subscript k denotes the number of exit channels in the reactions. At the collision energy of Elab = 1500 eV, one- and two-electron excitations were observed appreciably for the Na+-He collisions, while only one-electron excitations were observed in the K+-He collisions. The analyses of the experimental results for these collision systems indicate that the electronic transitions in the Na+-He and K+-He collisions take place at the internuclear distances of R < RC = 0.63 × 10-10 m [potential height V(R) > 49 eV] and R < RC = 0.80 × 10-10 m [V(R) > 36 eV], respectively. For these asymmetric systems, at Elab= 1500 eV, the electronic transition probabilities around the threshold angles are so small that the integral excitation cross sections have small values of Sex < 1.2 × 10-21 m2.

  12. Change of Collision Efficiency with Distance in Bacterial Transport Experiements

    SciTech Connect

    Dong, Hailiang; Scheibe, Timothy D.; Johnson, William P.; Monkman, Crystal; Fuller, Mark E.

    2006-05-01

    Previous bacterial transport studies have shown decreased bacterial adhesion with transport distance, largely based on laboratory core experiments. An inferred effect of microbial population variability is invoked to interpret experimental data, but there lacks direct measurement at field-scale, especially in correlation of transport distance with change of bacterial surface properties. This study was undertaken to determine change of collision efficiency with transport distance, taking advantage of the bacterial transport experiment in Oyster, VA in the summer of 2001. Upon injection of an adhesion deficient strain, Comamonas sp. DA001 into a up-gradient well, bacterial samples were taken from multi-level samplers along the flow path, and were injected into cores of 40 cm in length and 7.5 cm in diameter packed with homogenized sediment from the same site, South Oyster focus area (SOFA). Bacterial suspension samples were also measured for bacterial electrophoretic mobility distribution. Using filtration theory, collision efficiency, the probability of bacterial attachment to the grain surfaces upon collision and a quantitative measure of bacterial adhesion, was determined using CXTFIT model fitted attachment rate, measured grain size (10th percentile), porosity, flow velocity, and collector efficiency. Collision efficiency was also determined based on the fraction of retention in the cores. Contrary to previous results and interpretation of field-scale breakthrough curves, our experimentally determined collision efficiency increases with transport distance in the core experiments, which correlates with increasingly negative surface charge of the injected bacteria. Therefore we conclude that the apparent decrease in adhesion with transport distance in the field is strongly controlled by field-scale heterogeneity in physical and chemical aquifer properties and not by microbial population heterogeneity.

  13. The Mindanao collision zone: a soft collision event within a continuous Neogene strike-slip setting

    NASA Astrophysics Data System (ADS)

    Pubellier, M.; Quebral, R.; Rangin, C.; Deffontaines, B.; Muller, C.; Butterlin, J.; Manzano, J.

    Two volcanic belts are presently juxtaposed on Mindanao Island in the southern Philippines. Southward, the collision is still active in the Molucca Sea which is commonly regarded as a region of doubly verging subduction, plunging eastward below the Halmahera arc and westward below the Sangihe arc. In the Molluca Sea, tectonic features related to the incipient collision appear only in the very thick sediments of the basin, and the morphology of the parallel Halmahera, Talaud and Sangihe ridges is closely controlled by recent N-S strike-slip faults. Among these faults, the Philippine Fault is a neotectonic feature crosscutting the Agusan-Davao Basin which seals tectonic events not younger than Eocene. In addition, the Central Cordillera shows strong similarities with the Pacific Cordillera for both stratigraphy and tectonic evolution, and several indications favour a Eurasian margin affinity for the Daguma Range (Southern and Eastern Kudarat Plateau that may be part of the Sangihe arc, as inferred for the Zamboanga Peninsula and the Northern Arm of Sulawesi. Thus the island of Mindanao can be divided into two composite terranes, the western one (northward extension of the Sangihe arc) being restricted to the Kudarat Plateau and the Zamboanga Peninsula. The apparent continuation of the Sangihe arc into the Central Cordillera of Mindanao is thus the result of post collision tectonics. The portion of the suture where the collision is completed curves westward north of the southern peninsula and extends beneath the sediments of the Cotabato Basin or the volcanic plateaus of the Lanao-Misamis-Bukidnon Highlands. In the northern part, the contact is linear and suggests, together with the absence of compressional deformation, a docking of the eastern oceanic terrane (Philippine Mobile Belt-Halmahera arc) against the western continental terrane (Zamboanga-Daguma) in a strike-slip environment. Prior to Early Pliocene, the eastern and the western terranes were subject to

  14. The Collision Origin of Cohen's Stream

    NASA Astrophysics Data System (ADS)

    Tamanaha, C.

    1994-12-01

    High spacial and spectral resolution H I observations of the high-velocity cloud in Cetus called ``Cohen's Stream'' reveal 21 cm features at velocities of -280, -120, -37, and -3 km s(-1) . These new observations show in detail that the high- and very-high-velocity gas are anticorrelated in position on the sky. These observations cover only a small portion of H I clouds involved, but the anticorrelation persists on the larger scales mapped by Cohen (1981, 1982). The obvious explanation is that the high-velocity gas is the remnant of a collision between the very-high-velocity gas and a low-velocity cloud. A simple mass and momentum conserving simulation demonstrates the elegance of this model. The asymmetric velocity distribution of the individual pixels composing the remnant is a natural consequence of the different sizes of the parent clouds. Reasonable column density fluctuations added to the simulated parent clouds result in a remnant whose velocity distribution is much broader than observed. Some form of damping or momentum redistribution is needed to reduce the large velocity dispersion. The redistribution of momentum by the enhanced magnetic field in the compressed postshock gas appears to be the most promising damping mechanism. The magnetic tension in the field lines accelerates slower moving components while decelerating the faster moving ones. Recently shocked remnants are expected to have strong asymmetries in their velocity distributions. Older remnants will have more symmetric distributions, owing to the longer time over which the enhanced magnetic field has been allowed to damp the disparate velocities produced in the collision. This research has been supported in part by NSF grant FD91-23362 to Carl Heiles.

  15. Latest Electroweak Results from CDF

    SciTech Connect

    Lancaster, Mark

    2010-05-01

    The latest results in electroweak physics from proton anti-proton collisions at the Fermilab Tevatron recorded by the CDF detector are presented. The results provide constraints on parton distribution functions, the mass of the Higgs boson and beyond the Standard Model physics.

  16. Bose-Einstein correlations in pp and PbPb collisions with ALICE at the LHC

    ScienceCinema

    None

    2016-07-12

    We report on the results of identical pion femtoscopy at the LHC. The Bose-Einstein correlation analysis was performed on the large-statistics ALICE p+p at sqrt{s}= 0.9 TeV and 7 TeV datasets collected during 2010 LHC running and the first Pb+Pb dataset at sqrt{s_NN}= 2.76 TeV. Detailed pion femtoscopy studies in heavy-ion collisions have shown that emission region sizes ("HBT radii") decrease with increasing pair momentum, which is understood as a manifestation of the collective behavior of matter. 3D radii were also found to universally scale with event multiplicity. In p+p collisions at 7 TeV one measures multiplicities which are comparable with those registered in peripheral AuAu and CuCu collisions at RHIC, so direct comparisons and tests of scaling laws are now possible. We show the results of double-differential 3D pion HBT analysis, as a function of multiplicity and pair momentum. The results for two collision energies are compared to results obtained in the heavy-ion collisions at similar multiplicity and p+p collisions at lower energy. We identify the relevant scaling variables for the femtoscopic radii and discuss the similarities and differences to results from heavy-ions. The observed trends give insight into the soft particle production mechanism in p+p collisions and suggest that a self-interacting collective system may be created in sufficiently high multiplicity events. First results for the central Pb+Pb collisions are also shown. A significant increase of the reaction zone volume and lifetime in comparison to RHIC is observed. Signatures of collective hydrodynamics-like behavior of the system are also apparent, and are compared to model predictions.

  17. Bose-Einstein correlations in pp and PbPb collisions with ALICE at the LHC

    SciTech Connect

    2011-02-15

    We report on the results of identical pion femtoscopy at the LHC. The Bose-Einstein correlation analysis was performed on the large-statistics ALICE p+p at sqrt{s}= 0.9 TeV and 7 TeV datasets collected during 2010 LHC running and the first Pb+Pb dataset at sqrt{s_NN}= 2.76 TeV. Detailed pion femtoscopy studies in heavy-ion collisions have shown that emission region sizes ("HBT radii") decrease with increasing pair momentum, which is understood as a manifestation of the collective behavior of matter. 3D radii were also found to universally scale with event multiplicity. In p+p collisions at 7 TeV one measures multiplicities which are comparable with those registered in peripheral AuAu and CuCu collisions at RHIC, so direct comparisons and tests of scaling laws are now possible. We show the results of double-differential 3D pion HBT analysis, as a function of multiplicity and pair momentum. The results for two collision energies are compared to results obtained in the heavy-ion collisions at similar multiplicity and p+p collisions at lower energy. We identify the relevant scaling variables for the femtoscopic radii and discuss the similarities and differences to results from heavy-ions. The observed trends give insight into the soft particle production mechanism in p+p collisions and suggest that a self-interacting collective system may be created in sufficiently high multiplicity events. First results for the central Pb+Pb collisions are also shown. A significant increase of the reaction zone volume and lifetime in comparison to RHIC is observed. Signatures of collective hydrodynamics-like behavior of the system are also apparent, and are compared to model predictions.

  18. Heavy ion collisions and cosmology

    NASA Astrophysics Data System (ADS)

    Floerchinger, Stefan

    2016-12-01

    There are interesting parallels between the physics of heavy ion collisions and cosmology. Both systems are out-of-equilibrium and relativistic fluid dynamics plays an important role for their theoretical description. From a comparison one can draw interesting conclusions for both sides. For heavy ion physics it could be rewarding to attempt a theoretical description of fluid perturbations similar to cosmological perturbation theory. In the context of late time cosmology, it could be interesting to study dissipative properties such as shear and bulk viscosity and corresponding relaxation times in more detail. Knowledge and experience from heavy ion physics could help to constrain the microscopic properties of dark matter from observational knowledge of the cosmological fluid properties.

  19. Efficient ALL vs. ALL collision risk analyses

    NASA Astrophysics Data System (ADS)

    Escobar, D.; Paskowitz, M.; Agueda, A.; Garcia, G.; Molina, M.

    2011-09-01

    In recent years, the space debris has gained a lot of attention due to the increasing amount of uncontrolled man-made objects orbiting the Earth. This population poses a significant and constantly growing thread to operational satellites. In order to face this thread in an independent manner, ESA has launched an initiative for the development of a European SSA System where GMV is participating via several activities. Apart from those activities financed by ESA, GMV has developed closeap, a tool for efficient conjunction assessment and collision probability prediction. ESÁs NAPEOS has been selected as computational engine and numerical propagator to be used in the tool, which can be considered as an add-on to the standard NAPEOS package. closeap makes use of the same orbit computation, conjunction assessment and collision risk algorithms implemented in CRASS, but at the same time both systems are completely independent. Moreover, the implementation in closeap has been validated against CRASS with excellent results. This paper describes the performance improvements implemented in closeap at algorithm level to ensure that the most time demanding scenarios (e.g., all catalogued objects are analysed against each other - all vs. all scenarios -) can be analysed in a reasonable amount of time with commercial-off-the-shelf hardware. However, the amount of space debris increases steadily due to the human activities. Thus, the number of objects involved in a full collision assessment is expected to increase notably and, consequently, the computational cost, which scales as the square of the number of objects, will increase as well. Additionally, orbit propagation algorithms that are computationally expensive might be needed to predict more accurately the trajectories of the space debris. In order to cope with such computational needs, the next natural step in the development of collision assessment tools is the use of parallelization techniques. In this paper we investigate

  20. Why more male pedestrians die in vehicle-pedestrian collisions than females: a decompositional analysis

    PubMed Central

    Zhu, Motao; Zhao, Songzhu; Coben, Jeffrey H.; Smith, Gordon S.

    2013-01-01

    Objective Pedestrians account for a third of the 1.2 million traffic fatalities annually worldwide, and males are overrepresented. We examined the factors that contribute to this male-female discrepancy: walking exposure (kilometers walked per person-year), vehicle-pedestrian collision risk (number of collisions per kilometers walked), and vehicle-pedestrian collision case fatality rate (number of deaths per collision). Design The decomposition method quantifies the relative contributions of individual factors to death rate ratios among groups. The male-female ratio of pedestrian death rates can be expressed as the product of three component ratios: walking exposure, collision risk, and case fatality rate. Data sources included the 2008–2009 U.S. Fatality Analysis Reporting System, General Estimates System, National Household Travel Survey, and population estimates. Setting U.S. Participants Pedestrians age 5 and older. Main outcome measures death rate per person-year, kilometers walked per person-year, collisions per kilometers walked, and deaths per collision by sex. Results The pedestrian death rate per person-year for males was 2.3 times that for females. This ratio of male to female rates can be expressed as the product of three component ratios: 0.995 for walking exposure, 1.191 for collision risk, and 1.976 for case fatality rate. The relative contributions of these components were 1%, 20% and 79%, respectively. Conclusions The majority of the male-female discrepancy in 2008–2009 pedestrian deaths in the U.S. is attributed to a higher fatality per collision rate among male pedestrians. PMID:23197672