Science.gov

Sample records for ionizing particles interacting

  1. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, R.A.; Mendez, V.P.; Kaplan, S.N.

    1988-11-15

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation. 15 figs.

  2. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, Robert A.; Mendez, Victor P.; Kaplan, Selig N.

    1988-01-01

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation.

  3. New Results from the Search for Low-Mass Weakly Interacting Massive Particles with the CDMS Low Ionization Threshold Experiment.

    PubMed

    Agnese, R; Anderson, A J; Aramaki, T; Asai, M; Baker, W; Balakishiyeva, D; Barker, D; Basu Thakur, R; Bauer, D A; Billard, J; Borgland, A; Bowles, M A; Brink, P L; Bunker, R; Cabrera, B; Caldwell, D O; Calkins, R; Cerdeno, D G; Chagani, H; Chen, Y; Cooley, J; Cornell, B; Cushman, P; Daal, M; Di Stefano, P C F; Doughty, T; Esteban, L; Fallows, S; Figueroa-Feliciano, E; Ghaith, M; Godfrey, G L; Golwala, S R; Hall, J; Harris, H R; Hofer, T; Holmgren, D; Hsu, L; Huber, M E; Jardin, D; Jastram, A; Kamaev, O; Kara, B; Kelsey, M H; Kennedy, A; Leder, A; Loer, B; Lopez Asamar, E; Lukens, P; Mahapatra, R; Mandic, V; Mast, N; Mirabolfathi, N; Moffatt, R A; Morales Mendoza, J D; Oser, S M; Page, K; Page, W A; Partridge, R; Pepin, M; Phipps, A; Prasad, K; Pyle, M; Qiu, H; Rau, W; Redl, P; Reisetter, A; Ricci, Y; Roberts, A; Rogers, H E; Saab, T; Sadoulet, B; Sander, J; Schneck, K; Schnee, R W; Scorza, S; Serfass, B; Shank, B; Speller, D; Toback, D; Underwood, R; Upadhyayula, S; Villano, A N; Welliver, B; Wilson, J S; Wright, D H; Yellin, S; Yen, J J; Young, B A; Zhang, J

    2016-02-19

    The CDMS low ionization threshold experiment (CDMSlite) uses cryogenic germanium detectors operated at a relatively high bias voltage to amplify the phonon signal in the search for weakly interacting massive particles (WIMPs). Results are presented from the second CDMSlite run with an exposure of 70 kg day, which reached an energy threshold for electron recoils as low as 56 eV. A fiducialization cut reduces backgrounds below those previously reported by CDMSlite. New parameter space for the WIMP-nucleon spin-independent cross section is excluded for WIMP masses between 1.6 and 5.5  GeV/c^{2}. PMID:26943526

  4. New Results from the Search for Low-Mass Weakly Interacting Massive Particles with the CDMS Low Ionization Threshold Experiment

    NASA Astrophysics Data System (ADS)

    Agnese, R.; Anderson, A. J.; Aramaki, T.; Asai, M.; Baker, W.; Balakishiyeva, D.; Barker, D.; Basu Thakur, R.; Bauer, D. A.; Billard, J.; Borgland, A.; Bowles, M. A.; Brink, P. L.; Bunker, R.; Cabrera, B.; Caldwell, D. O.; Calkins, R.; Cerdeno, D. G.; Chagani, H.; Chen, Y.; Cooley, J.; Cornell, B.; Cushman, P.; Daal, M.; Di Stefano, P. C. F.; Doughty, T.; Esteban, L.; Fallows, S.; Figueroa-Feliciano, E.; Ghaith, M.; Godfrey, G. L.; Golwala, S. R.; Hall, J.; Harris, H. R.; Hofer, T.; Holmgren, D.; Hsu, L.; Huber, M. E.; Jardin, D.; Jastram, A.; Kamaev, O.; Kara, B.; Kelsey, M. H.; Kennedy, A.; Leder, A.; Loer, B.; Lopez Asamar, E.; Lukens, P.; Mahapatra, R.; Mandic, V.; Mast, N.; Mirabolfathi, N.; Moffatt, R. A.; Morales Mendoza, J. D.; Oser, S. M.; Page, K.; Page, W. A.; Partridge, R.; Pepin, M.; Phipps, A.; Prasad, K.; Pyle, M.; Qiu, H.; Rau, W.; Redl, P.; Reisetter, A.; Ricci, Y.; Roberts, A.; Rogers, H. E.; Saab, T.; Sadoulet, B.; Sander, J.; Schneck, K.; Schnee, R. W.; Scorza, S.; Serfass, B.; Shank, B.; Speller, D.; Toback, D.; Underwood, R.; Upadhyayula, S.; Villano, A. N.; Welliver, B.; Wilson, J. S.; Wright, D. H.; Yellin, S.; Yen, J. J.; Young, B. A.; Zhang, J.; SuperCDMS Collaboration

    2016-02-01

    The CDMS low ionization threshold experiment (CDMSlite) uses cryogenic germanium detectors operated at a relatively high bias voltage to amplify the phonon signal in the search for weakly interacting massive particles (WIMPs). Results are presented from the second CDMSlite run with an exposure of 70 kg day, which reached an energy threshold for electron recoils as low as 56 eV. A fiducialization cut reduces backgrounds below those previously reported by CDMSlite. New parameter space for the WIMP-nucleon spin-independent cross section is excluded for WIMP masses between 1.6 and 5.5 GeV /c2 .

  5. New results from the search for low-mass weakly interacting massive particles with the CDMS low ionization threshold experiment

    DOE PAGESBeta

    Agnese, R.

    2016-02-17

    The CDMS low ionization threshold experiment (CDMSlite) uses cryogenic germanium detectors operated at a relatively high bias voltage to amplify the phonon signal in the search for weakly interacting massive particles (WIMPs). Our results are presented from the second CDMSlite run with an exposure of 70 kg days, which reached an energy threshold for electron recoils as low as 56 eV. Furthermore, a fiducialization cut reduces backgrounds below those previously reported by CDMSlite. Lastly, new parameter space for the WIMP-nucleon spin-independent cross section is excluded forWIMP masses between 1.6 and 5.5 GeV/c2.

  6. A search for weakly interacting dark matter particles with low temperature detectors capable of simultaneously measuring ionization and heat

    NASA Astrophysics Data System (ADS)

    Sonnenschein, Andrew Harry

    1999-01-01

    The nature and extent of the mysterious ``dark matter'' has been one of the central puzzles in cosmology over the last decade. Current evidence suggests that the universe has a matter content of about 0.3 of the critical density. The theory of Big Bang nucleosynthesis allows only 20% of this matter to be made of protons and neutrons, hinting that the remaining 80% of the mass is in the form of a new elementary particle. One possibility is that this dark matter is made of the lightest neutralino suggested by supersymmetry, which should be stable and have a mass in the range 30-10000 GeV/c 2. These particles would have only weak interactions with ordinary matter, with the typical cross section for scattering on a nucleon below 10 -41 cm2. The particles would constitute a ``dark halo'' in our galaxy and could be discovered through their interactions with detectors on Earth. Since the typical interaction rate would be below 0.1 event/kg-day, the main experimental problem is to reduce the interference from environmental background radiation. The most troublesome interference comes from photons produced by the decay of radioactive elements present at trace levels in the detectors and other apparatus. One way to discriminate between signal events from WIMP- nucleus scattering and background events from photon interactions is to measure the ratio of ionization to heat deposited in a semiconductor detector. This differs by a factor of ~3 between the two cases. The Cryogenic Dark Matter Search (CDMS) experiment is based on the simultaneous measurement of ionization and phonons in germanium and silicon crystals cooled to 25 mK. This measurement allows >99% discrimination against photon interactions above 10 keV of deposited energy. We present data from two 165 g germanium detectors operated at the Stanford Underground Facility, with a total exposure equivalent to 6.4 kg-days. From this data set, we derive limits on the cross sections and masses of weakly interacting dark

  7. The collisional interaction of a beam of charged particles with a hydrogen target of arbitrary ionization level. [chromospheric heating during solar flares

    NASA Technical Reports Server (NTRS)

    Emslie, A. G.

    1978-01-01

    The classical theory of scattering under the Coulomb potential of both charged and neutral particles is used to derive formulae for the energy deposition rate and mean scattering of a beam of charged particles interacting with a cold hydrogen target of arbitrary ionization level as a function of the column density traversed by the beam. These general results hold for any form of stable injection energy spectrum, and their relevance to the existing literature on chromospheric heating during solar flares is discussed.

  8. Search for Low-Mass Weakly Interacting Massive Particles Using Voltage-Assisted Calorimetric Ionization Detection in the SuperCDMS Experiment

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    SuperCDMS is an experiment designed to directly detect weakly interacting massive particles (WIMPs), a favored candidate for dark matter ubiquitous in the Universe. In this Letter, we present WIMP-search results using a calorimetric technique we call CDMSlite, which relies on voltage-assisted Luke-Neganov amplification of the ionization energy deposited by particle interactions. The data were collected with a single 0.6 kg germanium detector running for ten live days at the Soudan Underground Laboratory. A low energy threshold of 170 eVee (electron equivalent) was obtained, which allows us to constrain new WIMP-nucleon spin-independent parameter space for WIMP masses below 6 GeV /c2.

  9. A Search for Low-Mass Weakly Interacting Massive Particles Using Voltage-Assisted Calorimetric Ionization Detection in the SuperCDMS Experiment

    SciTech Connect

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

    2014-01-27

    SuperCDMS is an experiment designed to directly detect weakly interacting massive particles (WIMPs), a favored candidate for dark matter ubiquitous in the Universe. In this Letter, we present WIMP-search results using a calorimetric technique we call CDMSlite, which relies on voltage-assisted Luke-Neganov amplification of the ionization energy deposited by particle interactions. The data were collected with a single 0.6 kg germanium detector running for ten live days at the Soudan Underground Laboratory. A low energy threshold of (electron equivalent) was obtained, which allows us to constrain new WIMP-nucleon spin-independent parameter space for WIMP masses below 6 GeV/c2.

  10. Ionization of Atoms by Slow Heavy Particles, Including Dark Matter

    NASA Astrophysics Data System (ADS)

    Roberts, B. M.; Flambaum, V. V.; Gribakin, G. F.

    2016-01-01

    Atoms and molecules can become ionized during the scattering of a slow, heavy particle off a bound electron. Such an interaction involving leptophilic weakly interacting massive particles (WIMPs) is a promising possible explanation for the anomalous 9 σ annual modulation in the DAMA dark matter direct detection experiment [R. Bernabei et al., Eur. Phys. J. C 73, 2648 (2013)]. We demonstrate the applicability of the Born approximation for such an interaction by showing its equivalence to the semiclassical adiabatic treatment of atomic ionization by slow-moving WIMPs. Conventional wisdom has it that the ionization probability for such a process should be exponentially small. We show, however, that due to nonanalytic, cusplike behavior of Coulomb functions close to the nucleus this suppression is removed, leading to an effective atomic structure enhancement. We also show that electron relativistic effects actually give the dominant contribution to such a process, enhancing the differential cross section by up to 1000 times.

  11. Ionization of Atoms by Slow Heavy Particles, Including Dark Matter.

    PubMed

    Roberts, B M; Flambaum, V V; Gribakin, G F

    2016-01-15

    Atoms and molecules can become ionized during the scattering of a slow, heavy particle off a bound electron. Such an interaction involving leptophilic weakly interacting massive particles (WIMPs) is a promising possible explanation for the anomalous 9σ annual modulation in the DAMA dark matter direct detection experiment [R. Bernabei et al., Eur. Phys. J. C 73, 2648 (2013)]. We demonstrate the applicability of the Born approximation for such an interaction by showing its equivalence to the semiclassical adiabatic treatment of atomic ionization by slow-moving WIMPs. Conventional wisdom has it that the ionization probability for such a process should be exponentially small. We show, however, that due to nonanalytic, cusplike behavior of Coulomb functions close to the nucleus this suppression is removed, leading to an effective atomic structure enhancement. We also show that electron relativistic effects actually give the dominant contribution to such a process, enhancing the differential cross section by up to 1000 times. PMID:26824537

  12. Numerical modeling of laser tunneling ionization in explicit particle-in-cell codes

    SciTech Connect

    Chen, M.; Cormier-Michel, E.; Geddes, C.G.R.; Bruhwiler, D.L.; Yu, L.L.; Esarey, E.; Schroeder, C.B.; Leemans, W.P.

    2013-03-01

    Methods for the calculation of laser tunneling ionization in explicit particle-in-cell codes used for modeling laser–plasma interactions are compared and validated against theoretical predictions. Improved accuracy is obtained by using the direct current form for the ionization rate. Multi level ionization in a single time step and energy conservation have been considered during the ionization process. The effects of grid resolution and number of macro-particles per cell are examined. Implementation of the ionization algorithm in two different particle-in-cell codes is compared for the case of ionization-based electron injection in a laser–plasma accelerator.

  13. Ionization of the atmosphere caused by energetic particles

    NASA Astrophysics Data System (ADS)

    Maik Wissing, Jan; Kallenrode, May-Britt

    Energetic particles from different sources are precipitating into the atmosphere, causing ionization and different chemical follow-ups. Focussing on low and mid-energies, this presentation will concentrate on the solar and magnetospheric particle spectrum, representing the particle forcing from the thermosphere down to the tropopause. While the precipitation of solar particles can be described in simple patterns, the magnetospheric precipitation is intensively modulated by the geomagnetic field, varying with latitude, longitude, geomagnetic disturbance, and MLT, ending up in a fluctuating auroral oval. Modeling the resulting ionization consequently is confronted with numerous challenges, ranging from sparse measurements (in-situ measuring satellites vs. global coverage), contaminated detectors, strong flux variation in space and time and finally the conversion of flux measurements into (3D) ionization profiles. This presentation will give an overview of the general setup, discuss main aspects in modeling particle precipitation and present some recent advances with the help of the Atmospheric Ionization Module OSnabrueck (AIMOS). AIMOS is based on a Geant4 Monte-Carlo Simulation for particle interactions with the atmosphere and in-situ particle measurements from the POES and GOES satellites.

  14. ALTERNATIVE IONIZATION METHODS FOR PARTICLE MASS SPECTROMETRY

    EPA Science Inventory

    The objective of this project is to enhance the capabilities of a real-time airborne particle mass spectrometer by implementing matrix-independent methods for sample ionization. The enhancements should result in improved sensitivity for trace substances and, more importantly, per...

  15. Interactive Terascale Particle Visualization

    NASA Technical Reports Server (NTRS)

    Ellsworth, David; Green, Bryan; Moran, Patrick

    2004-01-01

    This paper describes the methods used to produce an interactive visualization of a 2 TB computational fluid dynamics (CFD) data set using particle tracing (streaklines). We use the method introduced by Bruckschen et al. [2001] that pre-computes a large number of particles, stores them on disk using a space-filling curve ordering that minimizes seeks, and then retrieves and displays the particles according to the user's command. We describe how the particle computation can be performed using a PC cluster, how the algorithm can be adapted to work with a multi-block curvilinear mesh, and how the out-of-core visualization can be scaled to 296 billion particles while still achieving interactive performance on PG hardware. Compared to the earlier work, our data set size and total number of particles are an order of magnitude larger. We also describe a new compression technique that allows the lossless compression of the particles by 41% and speeds the particle retrieval by about 30%.

  16. ELEMENTARY PARTICLE INTERACTIONS

    SciTech Connect

    EFREMENKO, YURI; HANDLER, THOMAS; KAMYSHKOV, YURI; SIOPSIS, GEORGE; SPANIER, STEFAN

    2013-07-30

    The High-Energy Elementary Particle Interactions group at UT during the last three years worked on the following directions and projects: Collider-based Particle Physics; Neutrino Physics, particularly participation in “NOνA”, “Double Chooz”, and “KamLAND” neutrino experiments; and Theory, including Scattering amplitudes, Quark-gluon plasma; Holographic cosmology; Holographic superconductors; Charge density waves; Striped superconductors; and Holographic FFLO states.

  17. New Results from the Search for Low-Mass Weakly Interacting Massive Particles with the CDMS Low Ionization Threshold Experiment [WIMP-Search Results from the Second CDMSlite Run

    DOE PAGESBeta

    Agnese, R.

    2016-02-01

    The CDMS low ionization threshold experiment (CDMSlite) uses cryogenic germanium detectors operated at a relatively high bias voltage to amplify the phonon signal in the search for weakly interacting massive particles (WIMPs). Our results are presented from the second CDMSlite run with an exposure of 70 kg days, which reached an energy threshold for electron recoils as low as 56 eV. Furthermore, a fiducialization cut reduces backgrounds below those previously reported by CDMSlite. New parameter space for the WIMP-nucleon spin-independent cross section is excluded forWIMP masses between 1.6 and 5.5 GeV/c2.

  18. Ionizing particle detection based on phononic crystals

    NASA Astrophysics Data System (ADS)

    Aly, Arafa H.; Mehaney, Ahmed; Eissa, Mostafa F.

    2015-08-01

    Most conventional radiation detectors are based on electronic or photon collections. In this work, we introduce a new and novel type of ionizing particle detector based on phonon collection. Helium ion radiation treats tumors with better precision. There are nine known isotopes of helium, but only helium-3 and helium-4 are stable. Helium-4 is formed in fusion reactor technology and in enormous quantities during Big Bang nucleo-synthesis. In this study, we introduce a technique for helium-4 ion detection (sensing) based on the innovative properties of the new composite materials known as phononic crystals (PnCs). PnCs can provide an easy and cheap technique for ion detection compared with conventional methods. PnC structures commonly consist of a periodic array of two or more materials with different elastic properties. The two materials are polymethyl-methacrylate and polyethylene polymers. The calculations showed that the energies lost to target phonons are maximized at 1 keV helium-4 ion energy. There is a correlation between the total phonon energies and the transmittance of PnC structures. The maximum transmission for phonons due to the passage of helium-4 ions was found in the case of making polyethylene as a first layer in the PnC structure. Therefore, the concept of ion detection based on PnC structure is achievable.

  19. Ionizing particle detection based on phononic crystals

    SciTech Connect

    Aly, Arafa H. E-mail: arafa.hussien@science.bsu.edu.eg; Mehaney, Ahmed; Eissa, Mostafa F.

    2015-08-14

    Most conventional radiation detectors are based on electronic or photon collections. In this work, we introduce a new and novel type of ionizing particle detector based on phonon collection. Helium ion radiation treats tumors with better precision. There are nine known isotopes of helium, but only helium-3 and helium-4 are stable. Helium-4 is formed in fusion reactor technology and in enormous quantities during Big Bang nucleo-synthesis. In this study, we introduce a technique for helium-4 ion detection (sensing) based on the innovative properties of the new composite materials known as phononic crystals (PnCs). PnCs can provide an easy and cheap technique for ion detection compared with conventional methods. PnC structures commonly consist of a periodic array of two or more materials with different elastic properties. The two materials are polymethyl-methacrylate and polyethylene polymers. The calculations showed that the energies lost to target phonons are maximized at 1 keV helium-4 ion energy. There is a correlation between the total phonon energies and the transmittance of PnC structures. The maximum transmission for phonons due to the passage of helium-4 ions was found in the case of making polyethylene as a first layer in the PnC structure. Therefore, the concept of ion detection based on PnC structure is achievable.

  20. New particles and interactions

    SciTech Connect

    Gilman, F.J.; Grannis, P.D.

    1984-04-01

    The Working Group on New Particles and Interactions met as a whole at the beginning and at the end of the Workshop. However, much of what was accomplished was done in five subgroups. These were devoted to: (1) new quarks and leptons; (2) technicolor; (3) supersymmetry; (4) rare decays and CP; and (5) substructure of quarks and leptons. Other aspects of new particles, e.g., Higgs, W', Z', fell to the Electroweak Working Group to consider. The central question of this Workshop of comparing anti pp (with L = 10/sup 32//cm/sup 2/-sec) with pp (with L = 10/sup 33//cm/sup 2/-sec) colliders carried through to all these subgroups. In addition there were several other aspects of hadron colliders which were considered: what does an increase in ..sqrt..s gain in cross section and resultant sensitivity to new physics versus an increase in luminosity; will polarized beams or the use of asymmetries be essential in finding new interactions; where and at what level do rate limitations due to triggering or detection systems play a role; and how and where will the detection of particles with short, but detectable, lifetimes be important. 25 references.

  1. The Analysis of Ionization Chambers Used for Detecting Smoke Particles

    NASA Astrophysics Data System (ADS)

    Turlej, Z. (Bish).

    Ionization type cells using a radioactive source of primary ions have been used as fire detectors for many years. They have proven sufficiently sensitive to give an alarm when exposed to the relatively small concentration of smoke particles that occur during the early stages of combustion when control of a fire is still possible. In this work the charging of smoke particles in ionization chambers such as typically employed in ionization smoke detectors are investigated theoretically and experimentally. The ionization chambers investigated in this work have parallel plate and spherical electrode geometries. In the absence of smoke particles, the ionization chambers were operated at some ambient electrode current, which depends upon the ion generation rate, the electrode geometries, the potential difference between the electrodes, and the thermodynamic properties of the gas within the chamber volume. When smoke particles are introduced into the ionization chamber they act as an additional sink for the ions, so that the ion current is reduced. The smoke particles in the experiment performed in this work were transferred from the particle generator to the volume surrounding the ionization chamber and allowed to diffuse inside the ionization chamber. An Aitken nuclei counter was employed to measure the concentration of smoke particles inside the ionization chamber. The electric current flowing through the ionization chamber was recorded as a function of time and concentration of the smoke particles inside the chamber. The current loss due to the particles present inside the chamber was calculated and compared with the experimental results. It was found that at the certain level of ambient electrode current, the current loss due to the smoke particles assumes a maximum value. This optimum operating electrode current was predicted by the mathematical model employed in this work. In the light of this model experimental ionization chambers of both parallel and spherical

  2. Parameterization of ionization induced in the atmosphere by precipitating particles

    NASA Astrophysics Data System (ADS)

    Artamonov, Anton; Usoskin, Ilya; Kovaltsov, Gennady

    We present a physical model to calculate ionization induced in the atmosphere by precipitating particles. This model is based on the Bethe-Bloch equation applied for precipitating particles such as: electrons, alpha-particles and protons. The energy range of precipitating particles is up to 5MeV and 80MeV/nuc respectively. This model provides an easy implementation with a robust realization of model calculations for a wide range of incident energies of precipitating particles. This method is limited to the upper-middle atmosphere. An ionization yield function [see, Usoskin and Kovaltsov, 2006; Usoskin, Kovaltsov, Mironova, 2010] can be also used in this model, making it possible to calculate the atmospheric ionization effect of precipitating particles for the entire atmosphere, dawn to the ground.

  3. INTERACTION OF MUON BEAM WITH PLASMA DEVELOPED DURING IONIZATION COOLING

    SciTech Connect

    S. Ahmed, D. Kaplan, T. Roberts, L. Spentzouris, K. Beard

    2012-07-01

    Particle-in-cell simulations involving the interaction of muon beam (peak density 10{sup 18} m{sup 3}) with Li plasma (ionized medium) of density 10{sup 16}-10{sup 22} m{sup -3} have been performed. This study aimed to understand the effects of plasma on an incoming beam in order to explore scenario developed during the process of ionization cooling. The computer code takes into account the self-consistent electromagnetic effects of beam interacting with plasma. This study shows that the beam can pass through the plasma of densities four order of magnitude higher than its peak density. The low density plasmas are wiped out by the beam, however, the resonance is observed for densities of similar order. Study reveals the signature of plasma wakefield acceleration.

  4. Validation of Cosmic Ray Ionization Model CORIMIA applied for solar energetic particles and Anomalous Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Asenovski, S.; Velinov, P.; Mateev, L.

    2016-02-01

    Based on the electromagnetic interaction between the cosmic ray (CR) and the atmospheric neutral constituents, CORIMIA (COsmic Ray Ionization Model) gives an estimation of the dynamical ionization condition of the lower ionosphere and middle atmosphere (about 30-120 km). Galactic Cosmic Rays (GCR), modified by solar wind and later by geomagnetic and atmospheric cut offs, produce ionization in the entire atmosphere. In this paper we show the GCR ionization in periods of solar minimum and maximum. Despite the considerably lower energies than GCR, Anomalous Cosmic Rays (ACR) contribute to the ionization state mostly over the polar regions and as we present here this contribution is comparable with those of GCR. Solar energetic particles (SEP), which differ vastly from one another for different solar events, can be responsible for significant ionization over the high latitude regions. Here we compare flows of SEP caused by two of the most powerful solar proton events at February 23, 1956 and January 20, 2005.

  5. LASER DESORPTION IONIZATION OF ULTRAFINE AEROSOL PARTICLES. (R823980)

    EPA Science Inventory

    On-line analysis of ultrafine aerosol particle in the 12 to 150 nm size range is performed by
    laser desorption/ionization. Particles are size selected with a differential mobility analyzer and then
    sent into a linear time-of-flight mass spectrometer where they are ablated w...

  6. Detailed Investigations of Interactions between Ionizing Radiation and Neutral Gases

    SciTech Connect

    Landers, Allen L

    2014-03-31

    We are investigating phenomena that stem from the many body dynamics associated with ionization of an atom or molecule by photon or charged particle. Our program is funded through the Department of Energy EPSCoR Laboratory Partnership Award in collaboration with Lawrence Berkeley National Laboratory. We are using variations on the well established COLTRIMS technique to measure ions and electrons ejected during these interactions. Photoionization measurements take place at the Advanced Light Source at LBNL as part of the ALS-COLTRIMS collaboration with the groups of Reinhard Dörner at Frankfurt and Ali Belkacem at LBNL. Additional experiments on charged particle impact are conducted locally at Auburn University where we are studying the dissociative molecular dynamics following interactions with either ions or electrons over a velocity range of 1 to 12 atomic units.

  7. Particle formation and interaction

    NASA Technical Reports Server (NTRS)

    Squyres, Steven; Corso, George J.; Griffiths, Lynn D.; Mackinnon, Ian D. R.; Marshall, John R.; Nuth, Joseph A., III; Werner, Brad; Wolfe, John

    1987-01-01

    A wide variety of experiments can be conducted on the Space Station that involve the physics of small particles of planetary significance. Processes of interest include nucleation and condensation of particles from a gas, aggregation of small particles into larger ones, and low velocity collisions of particles. All of these processes could be investigated with a general purpose facility on the Space Station. The microgravity environment would be necessary to perform many experiments, as they generally require that particles be suspended for periods substantially longer than are practical at 1 g. Only experiments relevant to planetary processes will be discussed in detail here, but it is important to stress that a particle facility will be useful to a wide variety of scientific disciplines, and can be used to address many scientific problems.

  8. The electrical conductivity of weakly ionized plasma containing dust particles

    NASA Astrophysics Data System (ADS)

    Li, Hui; Wu, Jian; Yuan, Chengxun; Zhou, Zhongxiang

    2016-07-01

    The effect of charged dust particle on the electrical conductivity of weakly ionized dusty plasma is investigated. It is shown that the additional collision provided by charged dust particles can significantly alter the electrical conductivity of electron-ion plasma. The numerical results indicated that these effects are mainly determined by dust radius, density as well as the charge numbers on dust surface. The obtained results will support an enhanced understanding of the electromagnetic wave propagation processes in dusty plasma.

  9. Interaction of Burning Metal Particles

    NASA Technical Reports Server (NTRS)

    Dreizin, Edward L.; Berman, Charles H.; Hoffmann, Vern K.

    1999-01-01

    Physical characteristics of the combustion of metal particle groups have been addressed in this research. The combustion behavior and interaction effects of multiple metal particles has been studied using a microgravity environment, which presents a unique opportunity to create an "aerosol" consisting of relatively large particles, i.e., 50-300 micrometer diameter. Combustion behavior of such an aerosol could be examined using methods adopted from well-developed single particle combustion research. The experiment included fluidizing relatively large (order of 100 micrometer diameter) uniform metal particles under microgravity and igniting such an "aerosol" using a hot wire igniter. The flame propagation and details of individual particle combustion and particle interaction have been studied using a high speed movie and video-imaging with cameras coupled with microscope lenses to resolve individual particles. Interference filters were used to separate characteristic metal and metal oxide radiation bands form the thermal black body radiation. Recorded flame images were digitized and employed to understand the processes occurring in the burning aerosol. The development of individual particle flames, merging or separation, and extinguishing as well as induced particle motion have been analyzed to identify the mechanisms governing these processes. Size distribution, morphology, and elemental compositions of combustion products were characterized and used to link the observed in this project aerosol combustion phenomena with the recently expanded mechanism of single metal particle combustion.

  10. Interaction of Burning Metal Particles

    NASA Technical Reports Server (NTRS)

    Dreizin, Edward L.; Berman, Charles H.; Hoffmann, Vern K.

    1999-01-01

    Physical characteristics of the combustion of metal particle groups have been addressed in this research. The combustion behavior and interaction effects of multiple metal particles has been studied using a microgravity environment, which presents a unique opportunity to create an "aerosol" consisting of relatively large particles, i.e., 50-300 m diameter. Combustion behavior of such an aerosol could be examined using methods adopted from well-developed single particle combustion research. The experiment included fluidizing relatively large (order of 100 m diameter) uniform metal particles under microgravity and igniting such an "aerosol" using a hot wire igniter. The flame propagation and details of individual particle combustion and particle interaction have been studied using a high speed movie and video-imaging with cameras coupled with microscope lenses to resolve individual particles. Interference filters were used to separate characteristic metal and metal oxide radiation bands from the thermal black body radiation. Recorded flame images were digitized and various image processing techniques including flame position tracking, color separation, and pixel by pixel image comparison were employed to understand the processes occurring in the burning aerosol. The development of individual particle flames, merging or separation, and extinguishment as well as induced particle motion have been analyzed to identify the mechanisms governing these processes. Size distribution, morphology, and elemental compositions of combustion products were characterized and used to link the observed in this project aerosol combustion phenomena with the recently expanded mechanism of single metal particle combustion.

  11. Positrons from accelerated particle interactions

    NASA Technical Reports Server (NTRS)

    Kozlovsky, B.; Lingenfelter, R. E.; Ramaty, R.

    1987-01-01

    Positron production from the decay of radioactive nuclei produced in nuclear interactions of accelerated particles is treated in detail. Laboratory data as well as theoretical considerations are used to construct energy-dependent cross sections for the production of a large number of radioactive positron emitters resulting from proton and alpha-particle interactions with ambient cosmic matter. Using these cross sections, positron production rates are calculated for a variety of energetic particle spectra, assuming solar abundances for both the energetic particles and the ambient medium. These results can be used for the study of astrophysical sites which emit annihilation radiation. In particular, the results have been applied to solar flares, where the observed 0.511 MeV line is shown to be due to positrons resulting from accelerated particle reactions.

  12. Particle interactions in microemulsion systems

    SciTech Connect

    Brouwer, W.M.; Nieuwenhuis, E.A.; Kops-Werkhoven, M.M.

    1983-03-01

    This study obtains information about the type of interactions between microemulsion particles as a function of their composition using time averaged and dynamic light scattering and sedimentation measurements and checks the consistency of the experimental data with respect to the generalized Einstein relation. Interactions between microemulsion particles are affected by the flexibility of the soap chains. The more flexible the soap chains, the lesser the attraction forces between the particles. The lack of consistency in the interaction behavior as obtained from different experimental techniques is an important observation, which leads to the conclusion that care should be taken in the determination of the interaction behavior in microemulsion systems from one or 2 experimental techniques. 24 referernces.

  13. Ionization equilibrium in a cluster plasma with strong interparticle interaction

    SciTech Connect

    Likal'ter, A.A.

    1987-07-01

    An expansion, accurate up to the Madelung term, is derived for the drop in the ionization potential (and pressure) due to the strong Coulomb interaction. The ionization limit, separating the free and bound electron states, is determined with the help of the percolation theory. The principle of no explicit dependence of the total thermodynamic functions of the plasma on the ionization limit is employed. This has the consequence that the region of thermodynamic stability is greatly expanded compared with other models.

  14. Elementary Particles and Weak Interactions

    DOE R&D Accomplishments Database

    Lee, T. D.; Yang, C. N.

    1957-01-01

    Some general patterns of interactions between various elementary particles are reviewed and some general questions concerning the symmetry properties of these particles are studied. Topics are included on the theta-tau puzzle, experimental limits on the validity of parity conservation, some general discussions on the consequences due to possible non-invariance under P, C, and T, various possible experimental tests on invariance under P, C, and T, a two-component theory of the neutrino, a possible law of conservation of leptons and the universal Fermi interactions, and time reversal invariance and Mach's principle. (M.H.R.)

  15. Multielectron transitions resulting from interactions between target and projectile electrons in ionizing collisions

    SciTech Connect

    Manson, S.T. ); DuBois, R.D. )

    1992-12-01

    Interactions between target and projectile electrons leading to ionization of one of the collision partners and simultaneous excitation of the other are investigated for fast clothed-particle--clothed-particle collisions. For H-atom impact, the first Born approximation is used to demonstrate that the low-energy-electron emission is dominated by electron-electron rather than by electron-nucleus interaction processes. For a broad class of structured particle collision systems, the electron-electron interaction is shown to play an important, non-neglibible, role. Doubly differential cross sections for energetic H-He collisions illustrate this point.

  16. Inelastic electron interaction (attachment/ionization) with deoxyribose

    NASA Astrophysics Data System (ADS)

    Ptasińska, S.; Denifl, S.; Scheier, P.; Märk, T. D.

    2004-05-01

    We have investigated experimentally the formation of anions and cations of deoxyribose sugar (C5H10O4) via inelastic electron interaction (attachment/ionization) using a monochromatic electron beam in combination with a quadrupole mass spectrometer. The ion yields were measured as a function of the incident electron energy between about 0 and 20 eV. As in the case of other biomolecules (nucleobases and amino acids), low energy electron attachment leads to destruction of the molecule via dissociative electron attachment reactions. In contrast to the previously investigated biomolecules dehydrogenation is not the predominant reaction channel for deoxyribose; the anion with the highest dissociative electron attachment (DEA) cross section of deoxyribose is formed by the release of neutral particles equal to two water molecules. Moreover, several of the DEA reactions proceed already with "zero energy" incident electrons. In addition, the fragmentation pattern of positively charged ions of deoxyribose also indicates strong decomposition of the molecule by incident electrons. For sugar the relative amount of fragment ions compared to that of the parent cation is about an order of magnitude larger than in the case of nucleobases. We determined an ionization energy value for C5H10O4+ of 10.51±0.11 eV, which is in good agreement with ab initio calculations. For the fragment ion C5H6O2+ we obtained a threshold energy lower than the ionization energy of the parent molecular ion. All of these results have important bearing for the question of what happens in exposure of living tissue to ionizing radiation. Energy deposition into irradiated cells produces electrons as the dominant secondary species. At an early time after irradiation these electrons exist as ballistic electrons with an initial energy distribution up to several tens of electron volts. It is just this energy regime for which we find in the present study rather characteristic differences in the outcome of electron

  17. Percolation of interaction diffusing particles

    NASA Technical Reports Server (NTRS)

    Selinger, Robin Blumberg; Stanley, H. Eugene

    1990-01-01

    The connectivity properties of systems of diffusing interacting particles with the blind and myopic diffusion rules are studied. It is found that the blind rule case is equivalent to the lattice gas with J = 0 in all dimensions. The connectivity properties of blind rule diffusion are described by random site percolation due to the fact that the density on neighboring sites is uncorrelated.

  18. Asymmetric particle fluxes from drifting ionization zones in sputtering magnetrons

    NASA Astrophysics Data System (ADS)

    Panjan, Matjaž; Franz, Robert; Anders, André

    2014-04-01

    Electron and ion fluxes from direct current and high-power impulse magnetron sputtering (dcMS and HiPIMS) plasmas were measured in the plane of the target surface. Biased collector probes and a particle energy and mass analyzer showed asymmetric emission of electrons and of singly and doubly charged ions. For both HiPIMS and dcMS discharges, higher fluxes of all types of particles were observed in the direction of the electrons' E × B drift. These results are put in the context with ionization zones that drift over the magnetron's racetrack. The measured currents of time-resolving collector probes suggest that a large fraction of the ion flux originates from drifting ionization zones, while energy-resolving mass spectrometry indicates that a large fraction of the ion energy is due to acceleration by an electric field. This supports the recently proposed hypothesis that each ionization zone is associated with a negative-positive-negative space charge structure, thereby producing an electric field that accelerates ions from the location where they were formed.

  19. Dielectrophoretic particle-particle interaction under AC electrohydrodynamic flow conditions.

    PubMed

    Lee, Doh-Hyoung; Yu, Chengjie; Papazoglou, Elisabeth; Farouk, Bakhtier; Noh, Hongseok M

    2011-09-01

    We used the Maxwell stress tensor method to understand dielectrophoretic particle-particle interactions and applied the results to the interpretation of particle behaviors under alternating current (AC) electrohydrodynamic conditions such as AC electroosmosis (ACEO) and electrothermal flow (ETF). Distinct particle behaviors were observed under ACEO and ETF. Diverse particle-particle interactions observed in experiments such as particle clustering, particles keeping a certain distance from each other, chain and disc formation and their rotation, are explained based on the numerical simulation data. The improved understanding of particle behaviors in AC electrohydrodynamic flows presented here will enable researchers to design better particle manipulation strategies for lab-on-a-chip applications. PMID:21823132

  20. Impact ionization experiments with porous cosmic dust particle analogs

    NASA Astrophysics Data System (ADS)

    Sterken, Veerle; Moragas-Klostermeyer, Georg; Hillier, Jon; Fielding, Lee; Lovett, Joseph; Armes, Steven; Fechler, Nina; Srama, Ralf; Bugiel, Sebastian; Hornung, Klaus

    2016-04-01

    Impact ionization experiments have been performed since more than 40 years for calibration of cosmic dust instruments using a linear Van de Graaff dust accelerator. Such an accelerator can accelerate conductive dust particles of sizes between ca. a few tens of microns, and a micron in size to speeds up to 80 km/s depending on particle size. Many different materials have been used for instrument calibration, from iron in the earlier days to carbon, metal-coated minerals and most recently, minerals coated with conductive polymers. While different materials with different densities have been used for instrument calibration, no comparative analysis has been made yet of compact particles versus porous or fluffy particles of the same material. Porous or fluffy particles are increasingly found to be present in the solar system, e.g. dust from comet 67P Churyumov-Gerasimenko or aggregate grains from the plumes of Enceladus and recently also indications were found for low-density interstellar dust (ISD) from ISD data and trajectory simulations. These recalibrations are thus relevant for estimations of the size distributions of interplanetary and interstellar dust. In this talk we report about the calibrations being performed at the Heidelberg dust accelerator facility for investigating the influence of particle density on the impact ionization charge after impact. We use the Cassini Cosmic Dust Analyser as an impact target. We then explain the experiment set-up, the preparation of the materials and the materials used. We elaborate on the technical challenges, and finally about the current status of the research at this stage. We conclude the talk with the relevance of the study, being the potential influence of such calibrations on the estimates of the mass distributions of interstellar and interplanetary dust.

  1. Detecting weakly interacting massive particles.

    NASA Astrophysics Data System (ADS)

    Drukier, A. K.; Gelmini, G. B.

    The growing synergy between astrophysics, particle physics, and low background experiments strengthens the possibility of detecting astrophysical non-baryonic matter. The idea of direct detection is that an incident, massive weakly interacting particle could collide with a nucleus and transfer an energy that could be measured. The present low levels of background achieved by the PNL/USC Ge detector represent a new technology which yields interesting bounds on Galactic cold dark matter and on light bosons emitted from the Sun. Further improvements require the development of cryogenic detectors. The authors analyse the practicality of such detectors, their optimalization and background suppression using the "annual modulation effect".

  2. Ratio of double to single ionization of helium: The relationship between ionization by photons and by bare charged particles

    SciTech Connect

    Manson, S.T. ); McGuire, J.H. )

    1995-01-01

    It is well known that cross sections for ionization of atoms by fast charged particles and by photons are related by the Bethe-Born theory. We employ this relationship to derive a corresponding relation for the ratio [ital R] of double to single ionization including the first two terms of the Bethe expansion. For sufficiently fast charged particles, where the second term can be ignored, the ratios as a function of [Delta][ital E]---the energies transferred to the atom by the projectile---for ionization by charged particles [ital R][sub [ital z

  3. Matter and Interactions: A Particle Physics Perspective

    ERIC Educational Resources Information Center

    Organtini, Giovanni

    2011-01-01

    In classical mechanics, matter and fields are completely separated; matter interacts with fields. For particle physicists this is not the case; both matter and fields are represented by particles. Fundamental interactions are mediated by particles exchanged between matter particles. In this article we explain why particle physicists believe in…

  4. Ionization of the Earth's Upper Atmosphere in Large Energetic Particle Events

    NASA Astrophysics Data System (ADS)

    Wolff, E.; Burrows, J.; Kallenrode, M.; von Koenig, M.; Kuenzi, K. F.; Quack, M.

    2001-12-01

    Energetic charged particles ionize the upper terrestrial atmosphere. Sofar, chemical consequences of precipitating particles have been discussed for solar protons with energies up to a few hundred MeV. We present a refined model for the interaction of energetic particles with the atmosphere based on a Monte-Carlo simulation. The model includes higher energies and other particle species, such as energetic solar electrons. Results are presented for well-known solar events, such as July 14, 2000, and are extrapolated to extremely large events, such as Carrington's white light flare in 1859, which from ice cores has been identified ass the largest impulsive NO3 event in the interval 1561 -- 1994 (McCracken et al., 2001).

  5. Soft particles with anisotropic interactions

    NASA Astrophysics Data System (ADS)

    Schurtenberger, Peter

    Responsive colloids such as thermo- or pH-sensitive microgels are ideal model systems to investigate the relationship between the nature of interparticle interactions and the plethora of self-assembled structures that can form in colloidal suspensions. They allow for a variation of the form, strength and range of the interaction potential almost at will. While microgels have extensively been used as model systems to investigate various condensed matter problems such as glass formation, jamming or crystallization, they can also be used to study systems with anisotropic interactions. Here we show results from a systematic investigation of the influence of softness and anisotropy on the structural and dynamic properties of strongly interacting suspensions. We focus first on ionic microgels. Due to their large number of internal counterions they possess very large polarisabilities, and we can thus use external electrical ac fields to generate large dipolar contributions to the interparticle interaction potential. This leads to a number of new crystal phases, and we can trigger crystal-crystal phase transitions through the appropriate choice of the field strength. We then show that this approach can be extended to more complex particle shapes in an attempt to copy nature's well documented success in fabricating complex nanostructures such as virus shells via self assembly. European Research Council (ERC-339678-COMPASS).

  6. Interacting particle systems on graphs

    NASA Astrophysics Data System (ADS)

    Sood, Vishal

    In this dissertation, the dynamics of socially or biologically interacting populations are investigated. The individual members of the population are treated as particles that interact via links on a social or biological network represented as a graph. The effect of the structure of the graph on the properties of the interacting particle system is studied using statistical physics techniques. In the first chapter, the central concepts of graph theory and social and biological networks are presented. Next, interacting particle systems that are drawn from physics, mathematics and biology are discussed in the second chapter. In the third chapter, the random walk on a graph is studied. The mean time for a random walk to traverse between two arbitrary sites of a random graph is evaluated. Using an effective medium approximation it is found that the mean first-passage time between pairs of sites, as well as all moments of this first-passage time, are insensitive to the density of links in the graph. The inverse of the mean-first passage time varies non-monotonically with the density of links near the percolation transition of the random graph. Much of the behavior can be understood by simple heuristic arguments. Evolutionary dynamics, by which mutants overspread an otherwise uniform population on heterogeneous graphs, are studied in the fourth chapter. Such a process underlies' epidemic propagation, emergence of fads, social cooperation or invasion of an ecological niche by a new species. The first part of this chapter is devoted to neutral dynamics, in which the mutant genotype does not have a selective advantage over the resident genotype. The time to extinction of one of the two genotypes is derived. In the second part of this chapter, selective advantage or fitness is introduced such that the mutant genotype has a higher birth rate or a lower death rate. This selective advantage leads to a dynamical competition in which selection dominates for large populations

  7. Improved modeling of relativistic collisions and collisional ionization in particle-in-cell codes

    SciTech Connect

    Perez, F.; Gremillet, L.; Decoster, A.; Drouin, M.; Lefebvre, E.

    2012-08-15

    An improved Monte Carlo collisional scheme modeling both elastic and inelastic interactions has been implemented into the particle-in-cell code CALDER[E. Lefebvre et al., Nucl. Fusion 43, 629 (2003)]. Based on the technique proposed by Nanbu and Yonemura [J. Comput. Phys. 145, 639 (1998)] allowing to handle arbitrarily weighted macro-particles, this binary collision scheme uses a more compact and accurate relativistic formulation than the algorithm recently worked out by Sentoku and Kemp [J. Comput. Phys. 227, 6846 (2008)]. Our scheme is validated through several test cases, demonstrating, in particular, its capability of modeling the electrical resistivity and stopping power of a solid-density plasma over a broad parameter range. A relativistic collisional ionization scheme is developed within the same framework, and tested in several physical scenarios. Finally, our scheme is applied in a set of integrated particle-in-cell simulations of laser-driven fast electron transport.

  8. Test beam analysis of the effect of highly ionizing particles on the CMS Silicon Strip Tracker

    NASA Astrophysics Data System (ADS)

    De Filippis, N.; CMS Collaboration

    2004-09-01

    Highly ionizing particles (HIPs) created by nuclear interactions in the silicon sensors cause a large signal which can saturate the APV readout chip used in the CMS Silicon Tracker system. This phenomenon was studied in two different beam-tests performed at PSI and at the CERN X5 experimental areas in 2002. The probability of a HIP-like event to occur per incident pion was measured and the dependence of the APV capability to detect a MIP signal on the time required to recover from such an event is derived. From these results, the expected inefficiency of the CMS Tracker due to HIPS is inferred.

  9. Cardiovascular Risks Associated with Low Dose Ionizing Particle Radiation

    DOE PAGESBeta

    Yan, Xinhua; Sasi, Sharath P.; Gee, Hannah; Lee, JuYong; Yang, Yongyao; Mehrzad, Raman; Onufrak, Jillian; Song, Jin; Enderling, Heiko; Agarwal, Akhil; et al

    2014-10-22

    Previous epidemiologic data demonstrate that cardiovascular (CV) morbidity and mortality may occur decades after ionizing radiation exposure. With increased use of proton and carbon ion radiotherapy and concerns about space radiation exposures to astronauts on future long-duration exploration-type missions, the long-term effects and risks of low-dose charged particle irradiation on the CV system must be better appreciated. Here we report on the long-term effects of whole-body proton (1H; 0.5 Gy, 1 GeV) and iron ion (56Fe; 0.15 Gy, 1GeV/nucleon) irradiation with and without an acute myocardial ischemia (AMI) event in mice. We show that cardiac function of proton-irradiated mice initiallymore » improves at 1 month but declines by 10 months post-irradiation. In AMI-induced mice, prior proton irradiation improved cardiac function restoration and enhanced cardiac remodeling. This was associated with increased pro-survival gene expression in cardiac tissues. In contrast, cardiac function was significantly declined in 56Fe ion-irradiated mice at 1 and 3 months but recovered at 10 months. In addition, 56Fe ion-irradiation led to poorer cardiac function and more adverse remodeling in AMI-induced mice, and was associated with decreased angiogenesis and pro-survival factors in cardiac tissues at any time point examined up to 10 months. This is the first study reporting CV effects following low dose proton and iron ion irradiation during normal aging and post-AMI. Finally, understanding the biological effects of charged particle radiation qualities on the CV system is necessary both for the mitigation of space exploration CV risks and for understanding of long-term CV effects following charged particle radiotherapy.« less

  10. Cardiovascular risks associated with low dose ionizing particle radiation.

    PubMed

    Yan, Xinhua; Sasi, Sharath P; Gee, Hannah; Lee, JuYong; Yang, Yongyao; Mehrzad, Raman; Onufrak, Jillian; Song, Jin; Enderling, Heiko; Agarwal, Akhil; Rahimi, Layla; Morgan, James; Wilson, Paul F; Carrozza, Joseph; Walsh, Kenneth; Kishore, Raj; Goukassian, David A

    2014-01-01

    Previous epidemiologic data demonstrate that cardiovascular (CV) morbidity and mortality may occur decades after ionizing radiation exposure. With increased use of proton and carbon ion radiotherapy and concerns about space radiation exposures to astronauts on future long-duration exploration-type missions, the long-term effects and risks of low-dose charged particle irradiation on the CV system must be better appreciated. Here we report on the long-term effects of whole-body proton ((1)H; 0.5 Gy, 1 GeV) and iron ion ((56)Fe; 0.15 Gy, 1GeV/nucleon) irradiation with and without an acute myocardial ischemia (AMI) event in mice. We show that cardiac function of proton-irradiated mice initially improves at 1 month but declines by 10 months post-irradiation. In AMI-induced mice, prior proton irradiation improved cardiac function restoration and enhanced cardiac remodeling. This was associated with increased pro-survival gene expression in cardiac tissues. In contrast, cardiac function was significantly declined in (56)Fe ion-irradiated mice at 1 and 3 months but recovered at 10 months. In addition, (56)Fe ion-irradiation led to poorer cardiac function and more adverse remodeling in AMI-induced mice, and was associated with decreased angiogenesis and pro-survival factors in cardiac tissues at any time point examined up to 10 months. This is the first study reporting CV effects following low dose proton and iron ion irradiation during normal aging and post-AMI. Understanding the biological effects of charged particle radiation qualities on the CV system is necessary both for the mitigation of space exploration CV risks and for understanding of long-term CV effects following charged particle radiotherapy. PMID:25337914

  11. Cardiovascular Risks Associated with Low Dose Ionizing Particle Radiation

    SciTech Connect

    Yan, Xinhua; Sasi, Sharath P.; Gee, Hannah; Lee, JuYong; Yang, Yongyao; Mehrzad, Raman; Onufrak, Jillian; Song, Jin; Enderling, Heiko; Agarwal, Akhil; Rahimi, Layla; Morgan, James; Wilson, Paul F.; Carrozza, Joseph; Walsh, Kenneth; Kishore, Raj; Goukassian, David A.

    2014-10-22

    Previous epidemiologic data demonstrate that cardiovascular (CV) morbidity and mortality may occur decades after ionizing radiation exposure. With increased use of proton and carbon ion radiotherapy and concerns about space radiation exposures to astronauts on future long-duration exploration-type missions, the long-term effects and risks of low-dose charged particle irradiation on the CV system must be better appreciated. Here we report on the long-term effects of whole-body proton (1H; 0.5 Gy, 1 GeV) and iron ion (56Fe; 0.15 Gy, 1GeV/nucleon) irradiation with and without an acute myocardial ischemia (AMI) event in mice. We show that cardiac function of proton-irradiated mice initially improves at 1 month but declines by 10 months post-irradiation. In AMI-induced mice, prior proton irradiation improved cardiac function restoration and enhanced cardiac remodeling. This was associated with increased pro-survival gene expression in cardiac tissues. In contrast, cardiac function was significantly declined in 56Fe ion-irradiated mice at 1 and 3 months but recovered at 10 months. In addition, 56Fe ion-irradiation led to poorer cardiac function and more adverse remodeling in AMI-induced mice, and was associated with decreased angiogenesis and pro-survival factors in cardiac tissues at any time point examined up to 10 months. This is the first study reporting CV effects following low dose proton and iron ion irradiation during normal aging and post-AMI. Finally, understanding the biological effects of charged particle radiation qualities on the CV system is necessary both for the mitigation of space exploration CV risks and for understanding of long-term CV effects following charged particle radiotherapy.

  12. Cardiovascular Risks Associated with Low Dose Ionizing Particle Radiation

    PubMed Central

    Yan, Xinhua; Sasi, Sharath P.; Gee, Hannah; Lee, JuYong; Yang, Yongyao; Mehrzad, Raman; Onufrak, Jillian; Song, Jin; Enderling, Heiko; Agarwal, Akhil; Rahimi, Layla; Morgan, James; Wilson, Paul F.; Carrozza, Joseph; Walsh, Kenneth; Kishore, Raj; Goukassian, David A.

    2014-01-01

    Previous epidemiologic data demonstrate that cardiovascular (CV) morbidity and mortality may occur decades after ionizing radiation exposure. With increased use of proton and carbon ion radiotherapy and concerns about space radiation exposures to astronauts on future long-duration exploration-type missions, the long-term effects and risks of low-dose charged particle irradiation on the CV system must be better appreciated. Here we report on the long-term effects of whole-body proton (1H; 0.5 Gy, 1 GeV) and iron ion (56Fe; 0.15 Gy, 1GeV/nucleon) irradiation with and without an acute myocardial ischemia (AMI) event in mice. We show that cardiac function of proton-irradiated mice initially improves at 1 month but declines by 10 months post-irradiation. In AMI-induced mice, prior proton irradiation improved cardiac function restoration and enhanced cardiac remodeling. This was associated with increased pro-survival gene expression in cardiac tissues. In contrast, cardiac function was significantly declined in 56Fe ion-irradiated mice at 1 and 3 months but recovered at 10 months. In addition, 56Fe ion-irradiation led to poorer cardiac function and more adverse remodeling in AMI-induced mice, and was associated with decreased angiogenesis and pro-survival factors in cardiac tissues at any time point examined up to 10 months. This is the first study reporting CV effects following low dose proton and iron ion irradiation during normal aging and post-AMI. Understanding the biological effects of charged particle radiation qualities on the CV system is necessary both for the mitigation of space exploration CV risks and for understanding of long-term CV effects following charged particle radiotherapy. PMID:25337914

  13. Absolute negative mobility of interacting Brownian particles

    NASA Astrophysics Data System (ADS)

    Ou, Ya-li; Hu, Cai-tian; Wu, Jian-chun; Ai, Bao-quan

    2015-12-01

    Transport of interacting Brownian particles in a periodic potential is investigated in the presence of an ac force and a dc force. From Brownian dynamic simulations, we find that both the interaction between particles and the thermal fluctuations play key roles in the absolute negative mobility (the particle noisily moves backwards against a small constant bias). When no the interaction acts, there is only one region where the absolute negative mobility occurs. In the presence of the interaction, the absolute negative mobility may appear in multiple regions. The weak interaction can be helpful for the absolute negative mobility, while the strong interaction has a destructive impact on it.

  14. Ionization, Charging and Electric Field Effects on Cloud Particles in the CLOUD Experiment

    NASA Astrophysics Data System (ADS)

    Nichman, L.; Järvinen, E.; Wagner, R.; Dorsey, J.; Dias, A. M.; Ehrhart, S.; Kirkby, J.; Gallagher, M. W.; Saunders, C. P.

    2015-12-01

    Ice crystals and frozen droplets play an important role in atmospheric charging and electrification processes, particularly by collision and aggregation. The dynamics of charged particles in the atmosphere can be modulated by Galactic Cosmic Rays (GCR). High electric fields also affect the alignment of charged particles, allowing more time for interactions. The CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN has the ability to conduct ionization, charging and high electric field experiments on liquid or ice clouds created in the chamber by adiabatic pressure reductions. A pion secondary beam from the CERN Proton Synchrotron is used to ionize the molecules in the chamber, and Ar+ Corona Ion Generator for Atmospheric Research (CIGAR) is used to inject unipolar charged ions directly into the chamber. A pressurized airgun provides rapid pressure shocks inside the chamber and induces charged ice nucleation. The cloud chamber is accompanied by a variety of analysing instruments e.g. a 3View Cloud Particle Imager (3V-CPI) coupled with an induction ring, a Scattering Intensity Measurements for the Optical detection of icE (SIMONE) and a Nano-aerosol and Air Ion Spectrometer (NAIS). Using adiabatic expansion and high electric fields we can replicate the ideal conditions for adhesion, sintering and interlocking between ice crystals. Charged cloud particles produced measurable variations in the total induced current pulse on the induction ring. The most influential factors comprised initial temperature, lapse rate and charging mechanism. The ions produced in the chamber may deposit onto larger particles and form dipoles during ice nucleation and growth. The small ion concentration was monitored by the NAIS during these runs. Possible short-term aggregates or alignment of particles were observed in-situ with the SIMONE. These and future chamber measurements of charging and aggregation could shed more light on the ambient conditions and dynamics for electrification

  15. Ratio of double to single ionization of He by photon and charged particle impact

    SciTech Connect

    Manson, S.T.

    1994-12-31

    The well-known relationship between ionization of atoms by fast charged particles and by photons, the Bethe-Born theory, is applied to the ratio of double ionization to single ionization of He, a process that has been under intense recent scrutiny. It is found that for sufficiently fast charged particles, this ratio for the single differential cross sections, differential in the energy transferred to the atom, {Delta}E, is equal to the photoionization ratio at a photon energy hv = {Delta}E, and this result is unmodified even for ionization by relativistic charged particles. In addition, a relation for the ratio of total charged particle impact ionization cross sections to the photoionization ratio is derived. The results are compared with recent experimental data and various discrepancies are uncovered. Possible sources of these discrepancies are discussed.

  16. (Effects of ionizing radiation on scintillators and other particle detectors)

    SciTech Connect

    Proudfoot, J.

    1992-01-01

    It is my task to summarise the great variety of topics (covering a refreshing mix of physics, chemistry and technology) presented at this conference, which has focused on the effects of ionising radiation on scintillators and other particle detectors. One of the reasons and the central interest of many of the participants was the use of such detectors in experiments at two future large hadron colliders: the Superconducting Super Collider to be operating outside of Dallas in the United States by the turn of the decade and its European counterpart the Large Hadron Collider to be operating outside of Geneva in Switzerland on a similar time scale. These accelerators are the apple of the high energy physicist's eye.'' Their goal is to uncover the elusive Higgs particle and thereby set the cornerstone in our current knowledge of elementary particle interactions. This is the Quest, and from this lofty height the presentations rapidly moved on to the specific questions of experimental science: how such an experiment is carried out; why radiation damage is an issue; how radiation damage affects detectors; which factors affect radiation damage characteristics; which factors are not affected by radiation damage; and how better detectors may be constructed. These were the substance of this conference.

  17. Experimental and theoretical analysis of bias ionization by α-particles in a nitrogen laser

    NASA Astrophysics Data System (ADS)

    Silva, R. R.; Vieira Mendes, L. A.; Tsui, K. H.; De Simone Zanon, R. A.; de Oliveira, A. L.; Fellows, C. E.

    2011-09-01

    Nitrogen laser performance with TE configuration and wedge electrodes is analyzed with background ionization in the laser discharge channel by α particles at a low exposition rate. With the bias ionization, the laser power presents two peaks as a function of gas pressure, with one at the normal low pressure, without bias ionization, and the other at high pressure generated by bias ionization. A simple theoretical model has been developed in a trial to understand this behavior. This model was first tested in later results for a TE configuration nitrogen laser, with flat electrodes, without and with bias ionization. It has been observed that due to the competition between electrode shielding by positively charged α particles and bulk ionization by impact, the laser energy is suppressed with pressure below 50 Torr and enhanced above it.

  18. Temperature dependence of particle-particle interactions in electrorheological fluids

    NASA Astrophysics Data System (ADS)

    Gonon, P.; Foulc, J.-N.

    2000-04-01

    We report on the temperature dependence of particle-particle interactions in electrorheological (ER) fluids for the temperature range 20-100 °C. The attraction force between polyamide spheres immersed in silicone oil is measured as a function of temperature. The force-temperature characteristic shows a broad maximum around 40 °C, corresponding to an increase of about 30% compared to the force measured at room temperature. In view of these results we proposed that the temperature dependence of the shear stress in ER fluids is directly related to the variation of the local particle-particle attraction forces. Data are discussed in light of models which were proposed in the literature to describe particle-particle interactions. At high electric fields "conduction models" could explain the observed temperature dependence through the variations of the oil breakdown field with temperature. However, limitations of such models are also clearly evidenced by data obtained at low electric fields.

  19. Hydrodynamic particle interactions in sheared microflows

    NASA Astrophysics Data System (ADS)

    Marin, Alvaro; Rossi, Massimiliano; Zurita-Gotor, Mauricio; Kähler, Christian J.

    2012-11-01

    Multiphase flows in micro-confined geometries are non-trivial problems: drops and particles introduce a high degree of complexity into the otherwise linear Stokes flows. Very recently, new mechanisms of instability have been identified in simulations in shear-flows of non-Brownian particle solutions (Zurita-Gotor et al., J. Fluid Mech. 592, 2007, and Phys. Rev. Lett. 108, 2012), which might be the cause for anomalous self-diffusion measured experimentally by Zarraga and Leighton (Phys. Fluids 14, 2002). Using a 3D particle tracking technique (Astigmatism-PTV), we perform experiments in a microconfined cone-plate couette flow with a dilute suspension of non-brownian particles. The A-PTV technique permits us to track individual particles trajectories revealing particle-particle hydrodynamic interactions. Our experiments show an abnormal dispersion in the velocity field and non-homogeneous particle distribution which can be related with the swapping mechanism (JFM 592, 2007; PRL 108, 2012).

  20. Picosecond transient absorption rise time for ultrafast tagging of the interaction of ionizing radiation with scintillating crystals in high energy physics experiments

    NASA Astrophysics Data System (ADS)

    Auffray, E.; Buganov, O.; Fedorov, A.; Korjik, M.; Mechinsky, V.; Tikhomirov, A.; Vasil'ev, A.; Lecoq, P.

    2014-07-01

    Here we report the first results of a search of a signature for picosecond time stamps of the interaction between ionizing particles and transparent crystalline media. The induced absorption with sub-picosecond rise time observed in a cerium fluoride scintillation single crystal under UV excitation is directly associated with the ionization of Ce3+ atoms in CeF3 crystals, and the very fast occurrence thereof can be used to generate picosecond-precise time stamps corresponding to the interaction of ionizing particles with the crystal in high energy physics experiments.

  1. Investigation of plasma particle interactions with variable particle sizes

    NASA Astrophysics Data System (ADS)

    Dropmann, Michael; Laufer, Rene; Herdrich, Georg; Matthews, Lorin; Hyde, Truell

    2015-11-01

    In dusty plasmas, the dust particles are subjected to many forces of different origins. Both the gas and plasma directly affect the dust particles through electric fields, neutral drag, ion drag and thermophoretic forces, while the particles themselves interact with one another through a screened coulomb potential, which can be influenced by flowing ions. Recently, micron sized particles have been used as probes to analyze the electric fields in the plasma directly. A proper analysis of the resulting data requires a full understanding of the manner in which these forces couple to the dust particles. In most cases each of the forces exhibit unique characteristics, many of which are partially dependent on the particle size. In this study, five different particle sizes are used to investigate the forces resident in the sheath above the lower electrode of a GEC RF reference cell. The particles are tracked using a high-speed camera, yielding two-dimensional force maps allowing the force on the particles to be described as a polynomial series. It will be shown that the data collected can be analyzed to reveal information about the origins of the various forces. Support from the NSF and the DOE (award numbers PHY-1262031 and PHY-1414523) is gratefully acknowledged.

  2. Interaction of rotavirus particles with liposomes.

    PubMed

    Nandi, P; Charpilienne, A; Cohen, J

    1992-06-01

    We have studied the interactions of purified viral particles with liposomes as a model to understand the mechanism of entry of rotavirus into the cell. Liposomes, made from pure as well as mixed lipids, that contained encapsulated self-quenching concentrations of the fluorophore carboxyfluorescein (CF) were used. Rotavirus-liposome interactions were studied from the fluorescence dequenching of CF resulting from its release to the bulk solution. Purified infectious double-shelled virus particles induced a concentration- and temperature-dependent release of CF. The rate and extent of CF release was maximum between pH 7.3 and 7.6. The removal of outer structural proteins VP4 and VP7 from virus, which results in the formation of single-shelled particles, prevented virus interaction with liposomes. Rotavirus particles with uncleaved VP4 did not interact with liposomes, but treatment in situ of these particles with trypsin restored the interaction with the liposomes and resulted in CF dequenching. Our data support the view that rotavirus enters the cell through direct penetration of the plasma membrane. In contrast, adenovirus, the only other nonenveloped virus studied by this method, shows the optimum rate of marker release from liposomes at around pH 6 (R. Blumenthal, P. S. Seth, M. C. Willingham, and I. Pastan, Biochemistry 25:2231-2237, 1986). The interaction between rotavirus and liposomes is sensitive to specific divalent metal ions, unlike the adenovirus-liposome interaction, which is independent of them. PMID:1316453

  3. Particle dynamics and particle-cell interaction in microfluidic systems

    NASA Astrophysics Data System (ADS)

    Stamm, Matthew T.

    Particle-laden flow in a microchannel resulting in aggregation of microparticles was investigated to determine the dependence of the cluster growth rate on the following parameters: suspension void fraction, shear strain rate, and channel-height to particle-diameter ratio. The growth rate of an average cluster was found to increase linearly with suspension void fraction, and to obey a power-law relationships with shear strain rate as S 0.9 and channel-height to particle-diameter ratio as (h/d )--3.5. Ceramic liposomal nanoparticles and silica microparticles were functionalized with antibodies that act as targeting ligands. The bio-functionality and physical integrity of the cerasomes were characterized. Surface functionalization allows cerasomes to deliver drugs with selectivity and specificity that is not possible using standard liposomes. The functionalized particle-target cell binding process was characterized using BT-20 breast cancer cells. Two microfluidic systems were used; one with both species in suspension, the other with cells immobilized inside a microchannel and particle suspension as the mobile phase. Effects of incubation time, particle concentration, and shear strain rate on particle-cell binding were investigated. With both species in suspension, the particle-cell binding process was found to be reasonably well-described by a first-order model. Particle desorption and cellular loss of binding affinity in time were found to be negligible; cell-particle-cell interaction was identified as the limiting mechanism in particle-cell binding. Findings suggest that separation of a bound particle from a cell may be detrimental to cellular binding affinity. Cell-particle-cell interactions were prevented by immobilizing cells inside a microchannel. The initial stage of particle-cell binding was investigated and was again found to be reasonably well-described by a first-order model. For both systems, the time constant was found to be inversely proportional to

  4. The Particle Beam Optics Interactive Computer Laboratory

    SciTech Connect

    Gillespie, G.H.; Hill, B.W.; Brown, N.A.; Babcock, R.C.; Martono, H.; Carey, D.C. |

    1997-02-01

    The Particle Beam Optics Interactive Computer Laboratory (PBO Lab) is an educational software concept to aid students and professionals in learning about charged particle beams and particle beam optical systems. The PBO Lab is being developed as a cross-platform application and includes four key elements. The first is a graphic user interface shell that provides for a highly interactive learning session. The second is a knowledge database containing information on electric and magnetic optics transport elements. The knowledge database provides interactive tutorials on the fundamental physics of charged particle optics and on the technology used in particle optics hardware. The third element is a graphical construction kit that provides tools for students to interactively and visually construct optical beamlines. The final element is a set of charged particle optics computational engines that compute trajectories, transport beam envelopes, fit parameters to optical constraints and carry out similar calculations for the student designed beamlines. The primary computational engine is provided by the third-order TRANSPORT code. Augmenting TRANSPORT is the multiple ray tracing program TURTLE and a first-order matrix program that includes a space charge model and support for calculating single particle trajectories in the presence of the beam space charge. This paper describes progress on the development of the PBO Lab. {copyright} {ital 1997 American Institute of Physics.}

  5. The Particle Beam Optics Interactive Computer Laboratory

    NASA Astrophysics Data System (ADS)

    Gillespie, George H.; Hill, Barrey W.; Brown, Nathan A.; Babcock, R. Chris; Martono, Hendy; Carey, David C.

    1997-02-01

    The Particle Beam Optics Interactive Computer Laboratory (PBO Lab) is an educational software concept to aid students and professionals in learning about charged particle beams and particle beam optical systems. The PBO Lab is being developed as a cross-platform application and includes four key elements. The first is a graphic user interface shell that provides for a highly interactive learning session. The second is a knowledge database containing information on electric and magnetic optics transport elements. The knowledge database provides interactive tutorials on the fundamental physics of charged particle optics and on the technology used in particle optics hardware. The third element is a graphical construction kit that provides tools for students to interactively and visually construct optical beamlines. The final element is a set of charged particle optics computational engines that compute trajectories, transport beam envelopes, fit parameters to optical constraints and carry out similar calculations for the student designed beamlines. The primary computational engine is provided by the third-order TRANSPORT code. Augmenting TRANSPORT is the multiple ray tracing program TURTLE and a first-order matrix program that includes a space charge model and support for calculating single particle trajectories in the presence of the beam space charge. This paper describes progress on the development of the PBO Lab.

  6. Particle-Surface Interaction Model and Method of Determining Particle-Surface Interactions

    NASA Technical Reports Server (NTRS)

    Hughes, David W. (Inventor)

    2012-01-01

    A method and model of predicting particle-surface interactions with a surface, such as the surface of a spacecraft. The method includes the steps of: determining a trajectory path of a plurality of moving particles; predicting whether any of the moving particles will intersect a surface; predicting whether any of the particles will be captured by the surface and/or; predicting a reflected trajectory and velocity of particles reflected from the surface.

  7. Interactive methods for exploring particle simulation data

    SciTech Connect

    Co, Christopher S.; Friedman, Alex; Grote, David P.; Vay, Jean-Luc; Bethel, E. Wes; Joy, Kenneth I.

    2004-05-01

    In this work, we visualize high-dimensional particle simulation data using a suite of scatter plot-based visualizations coupled with interactive selection tools. We use traditional 2D and 3D projection scatter plots as well as a novel oriented disk rendering style to convey various information about the data. Interactive selection tools allow physicists to manually classify ''interesting'' sets of particles that are highlighted across multiple, linked views of the data. The power of our application is the ability to correspond new visual representations of the simulation data with traditional, well understood visualizations. This approach supports the interactive exploration of the high-dimensional space while promoting discovery of new particle behavior.

  8. Thermoelectricity of interacting particles: a numerical approach.

    PubMed

    Chen, Shunda; Wang, Jiao; Casati, Giulio; Benenti, Giuliano

    2015-09-01

    A method for computing the thermopower in interacting systems is proposed. This approach, which relies on Monte Carlo simulations, is illustrated first for a diatomic chain of hard-point elastically colliding particles and then in the case of a one-dimensional gas with (screened) Coulomb interparticle interaction. Numerical simulations up to N>10^{4} particles confirm the general theoretical arguments for momentum-conserving systems and show that the thermoelectric figure of merit increases linearly with the system size. PMID:26465458

  9. Identifying uranium particles using fission tracks and microsampling individual particles for analysis using thermal ionization mass spectrometry.

    PubMed

    Esaka, Fumitaka; Suzuki, Daisuke; Magara, Masaaki

    2015-03-01

    The analysis of isotope ratios in individual particles found in the environment is important to clarify the origins of the particles. In particular, the analysis of uranium particles in environmental samples from nuclear facilities is useful for detecting undeclared nuclear activities related to the production of nuclear weapons. Thermal ionization mass spectrometry (TIMS) combined with a fission track technique is an efficient method for determining the isotope ratios of individual uranium particles, but has a drawback called "particle-mixing". When some uranium particles are measured as a single particle and an average isotope ratio for the particles is obtained, it is called "particle mixing". This may lead to erroneous conclusions in terms of the particle sources that are identified. In the present study, microsampling using a scanning electron microscope was added to the fission track-TIMS procedure. The analysis of a mixture of SRM 950a and CRM U100 reference materials containing uranium particles indicated that particle mixing was almost completely avoided using the proposed technique. The performance of the proposed method was sufficient for obtaining reliable data for the sources of individual particles to be identified reliably. PMID:25680068

  10. Ionizing radiation induces heritable disruption of epithelial cell interactions

    PubMed Central

    Park, Catherine C.; Henshall-Powell, Rhonda L.; Erickson, Anna C.; Talhouk, Rabih; Parvin, Bahram; Bissell, Mina J.; Barcellos-Hoff, Mary Helen

    2003-01-01

    Ionizing radiation (IR) is a known human breast carcinogen. Although the mutagenic capacity of IR is widely acknowledged as the basis for its action as a carcinogen, we and others have shown that IR can also induce growth factors and extracellular matrix remodeling. As a consequence, we have proposed that an additional factor contributing to IR carcinogenesis is the potential disruption of critical constraints that are imposed by normal cell interactions. To test this hypothesis, we asked whether IR affected the ability of nonmalignant human mammary epithelial cells (HMEC) to undergo tissue-specific morphogenesis in culture by using confocal microscopy and imaging bioinformatics. We found that irradiated single HMEC gave rise to colonies exhibiting decreased localization of E-cadherin, β-catenin, and connexin-43, proteins necessary for the establishment of polarity and communication. Severely compromised acinar organization was manifested by the majority of irradiated HMEC progeny as quantified by image analysis. Disrupted cell–cell communication, aberrant cell–extracellular matrix interactions, and loss of tissue-specific architecture observed in the daughters of irradiated HMEC are characteristic of neoplastic progression. These data point to a heritable, nonmutational mechanism whereby IR compromises cell polarity and multicellular organization. PMID:12960393

  11. Ionizing radiation induces heritable disruption of epithelial cell interactions

    NASA Technical Reports Server (NTRS)

    Park, Catherine C.; Henshall-Powell, Rhonda L.; Erickson, Anna C.; Talhouk, Rabih; Parvin, Bahram; Bissell, Mina J.; Barcellos-Hoff, Mary Helen; Chatterjee, A. (Principal Investigator)

    2003-01-01

    Ionizing radiation (IR) is a known human breast carcinogen. Although the mutagenic capacity of IR is widely acknowledged as the basis for its action as a carcinogen, we and others have shown that IR can also induce growth factors and extracellular matrix remodeling. As a consequence, we have proposed that an additional factor contributing to IR carcinogenesis is the potential disruption of critical constraints that are imposed by normal cell interactions. To test this hypothesis, we asked whether IR affected the ability of nonmalignant human mammary epithelial cells (HMEC) to undergo tissue-specific morphogenesis in culture by using confocal microscopy and imaging bioinformatics. We found that irradiated single HMEC gave rise to colonies exhibiting decreased localization of E-cadherin, beta-catenin, and connexin-43, proteins necessary for the establishment of polarity and communication. Severely compromised acinar organization was manifested by the majority of irradiated HMEC progeny as quantified by image analysis. Disrupted cell-cell communication, aberrant cell-extracellular matrix interactions, and loss of tissue-specific architecture observed in the daughters of irradiated HMEC are characteristic of neoplastic progression. These data point to a heritable, nonmutational mechanism whereby IR compromises cell polarity and multicellular organization.

  12. Internal waves interacting with particles in suspension

    NASA Astrophysics Data System (ADS)

    Micard, Diane

    2016-04-01

    Internal waves are produced as a consequence of the dynamic balance between buoy- ancy and gravity forces when a particle of fluid is vertically displaced in a stable stratified environment. Geophysical systems such as ocean and atmosphere are naturally stratified and therefore suitable for internal waves to propagate. Furthermore, these two environ- ments stock a vast amount of particles in suspension, which present a large spectrum of physical properties (size, density, shape), and can be organic, mineral or pollutant agents. Therefore, it is reasonable to expect that internal waves will have an active effect over the dynamics of these particles. In order to study the interaction of internal waves and suspended particles, an ide- alized experimental setup has been implemented. A linear stratification is produced in a 80×40×17 cm3 tank, in which two dimensional plane waves are created thanks to the inno- vative wave generator GOAL. In addition, a particle injector has been developed to produce a vertical column of particles within the fluid, displaying the same two-dimensional sym- metry as the waves. The particle injector allows to control the volumic fraction of particles and the size of the column. The presence of internal waves passing through the column of particles allowed to observe two main effects: The column oscillates around an equilibrium position (which is observed in both, the contours an the interior of the column), and the column is displaced as a whole. The column is displaced depending on the characteristics of the column, the gradient of the density, and the intensity and frequency of the wave. When displaced, the particles within the column are sucked towards the source of waves. The direction of the displacement of the column is explained by computing the effect of the Lagrangian drift generated by the wave over the time the particles stay in the wave beam before settling.

  13. Two interacting particles in a spherical pore

    NASA Astrophysics Data System (ADS)

    Urrutia, Ignacio; Castelletti, Gabriela

    2011-02-01

    In this work we analytically evaluate, for the first time, the exact canonical partition function for two interacting spherical particles into a spherical pore. The interaction with the spherical substrate and between particles is described by an attractive square-well and a square-shoulder potential. In addition, we obtain exact expressions for both the one particle and an averaged two particle density distribution. We develop a thermodynamic approach to few-body systems by introducing a method based on thermodynamic measures [I. Urrutia, J. Chem. Phys. 134, 104503 (2010)] for nonhard interaction potentials. This analysis enables us to obtain expressions for the pressure, the surface tension, and the equivalent magnitudes for the total and Gaussian curvatures. As a by-product, we solve systems composed of two particles outside a fixed spherical obstacle. We study the low density limit for a many-body system confined to a spherical cavity and a many-body system surrounding a spherical obstacle. From this analysis we derive the exact first order dependence of the surface tension and Tolman length. Our findings show that the Tolman length goes to zero in the case of a purely hard wall spherical substrate, but contains a zero order term in density for square-well and square-shoulder wall-fluid potentials. This suggests that any nonhard wall-fluid potential should produce a non-null zero order term in the Tolman length.

  14. Wave-particle Interactions In Rotating Mirrors

    SciTech Connect

    Abraham J. Fetterman and Nathaniel J. Fisch

    2011-01-11

    Wave-particle interactions in E×B rotating plasmas feature an unusual effect: particles are diffused by waves in both potential energy and kinetic energy. This wave-particle interaction generalizes the alpha channeling effect, in which radio frequency waves are used to remove alpha particles collisionlessly at low energy. In rotating plasmas, the alpha particles may be removed at low energy through the loss cone, and the energy lost may be transferred to the radial electric field. This eliminates the need for electrodes in the mirror throat, which have presented serious technical issues in past rotating plasma devices. A particularly simple way to achieve this effect is to use a high azimuthal mode number perturbation on the magnetic field. Rotation can also be sustained by waves in plasmas without a kinetic energy source. This type of wave has been considered for plasma centrifuges used for isotope separation. Energy may also be transferred from the electric field to particles or waves, which may be useful for ion heating and energy generation.

  15. Interaction of axions with relativistic spinning particles

    NASA Astrophysics Data System (ADS)

    Popov, V. A.; Balakin, A. B.

    2016-05-01

    We consider a covariant phenomenological model, which describes an interaction between a pseudoscalar (axion) field and massive spinning particles. The model extends the Bagrmann-Michel-Telegdy approach in application to the axion electrodynamics. We present some exact solutions and discuss them in the context of experimental tests of the model and axion detection.

  16. High energy interactions of cosmic ray particles

    NASA Technical Reports Server (NTRS)

    Jones, L. W.

    1986-01-01

    The highlights of seven sessions of the Conference dealing with high energy interactions of cosmic rays are discussed. High energy cross section measurements; particle production-models of experiments; nuclei and nuclear matter; nucleus-nucleus collision; searches for magnetic monopoles; and studies of nucleon decay are covered.

  17. Treatment of Electronic Energy Level Transition and Ionization Following the Particle-Based Chemistry Model

    NASA Technical Reports Server (NTRS)

    Liechty, Derek S.; Lewis, Mark

    2010-01-01

    A new method of treating electronic energy level transitions as well as linking ionization to electronic energy levels is proposed following the particle-based chemistry model of Bird. Although the use of electronic energy levels and ionization reactions in DSMC are not new ideas, the current method of selecting what level to transition to, how to reproduce transition rates, and the linking of the electronic energy levels to ionization are, to the author s knowledge, novel concepts. The resulting equilibrium temperatures are shown to remain constant, and the electronic energy level distributions are shown to reproduce the Boltzmann distribution. The electronic energy level transition rates and ionization rates due to electron impacts are shown to reproduce theoretical and measured rates. The rates due to heavy particle impacts, while not as favorable as the electron impact rates, compare favorably to values from the literature. Thus, these new extensions to the particle-based chemistry model of Bird provide an accurate method for predicting electronic energy level transition and ionization rates in gases.

  18. Strong field ionization rates simulated with time-dependent configuration interaction and an absorbing potential

    SciTech Connect

    Krause, Pascal; Sonk, Jason A.; Schlegel, H. Bernhard

    2014-05-07

    Ionization rates of molecules have been modeled with time-dependent configuration interaction simulations using atom centered basis sets and a complex absorbing potential. The simulations agree with accurate grid-based calculations for the ionization of hydrogen atom as a function of field strength and for charge resonance enhanced ionization of H{sub 2}{sup +} as the bond is elongated. Unlike grid-based methods, the present approach can be applied to simulate electron dynamics and ionization in multi-electron polyatomic molecules. Calculations on HCl{sup +} and HCO{sup +} demonstrate that these systems also show charge resonance enhanced ionization as the bonds are stretched.

  19. Solar energetic particle interactions with the Venusian atmosphere

    NASA Astrophysics Data System (ADS)

    Plainaki, Christina; Paschalis, Pavlos; Grassi, Davide; Mavromichalaki, Helen; Andriopoulou, Maria

    2016-07-01

    In the context of planetary space weather, we estimate the ion production rates in the Venusian atmosphere due to the interactions of solar energetic particles (SEPs) with gas. The assumed concept for our estimations is based on two cases of SEP events, previously observed in near-Earth space: the event in October 1989 and the event in May 2012. For both cases, we assume that the directional properties of the flux and the interplanetary magnetic field configuration would have allowed the SEPs' arrival at Venus and their penetration to the planet's atmosphere. For the event in May 2012, we consider the solar particle properties (integrated flux and rigidity spectrum) obtained by the Neutron Monitor Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) model (Plainaki et al., 2010, 2014) applied previously for the Earth case and scaled to the distance of Venus from the Sun. For the simulation of the actual cascade in the Venusian atmosphere initiated by the incoming particle fluxes, we apply the DYASTIMA code, a Monte Carlo (MC) application based on the Geant4 software (Paschalis et al., 2014). Our predictions are afterwards compared to other estimations derived from previous studies and discussed. Finally, we discuss the differences between the nominal ionization profile due to galactic cosmic-ray-atmosphere interactions and the profile during periods of intense solar activity, and we show the importance of understanding space weather conditions on Venus in the context of future mission preparation and data interpretation.

  20. Nighttime ionization by energetic particles at Wallops Island in the altitude region 120 to 200 km

    NASA Technical Reports Server (NTRS)

    Voss, H. D.; Smith, L. G.

    1979-01-01

    Five Nike Apache rockets, each including an energetic particle spectrometer and an electron density-electron temperature experiment, have been launched from Wallops Island (L = 2.6) near midnight under varying geomagnetic conditions. On the most recent of these (5 January 1978) an additional spectrometer with a broom magnet, and a 391.4 nm photometer were flown. The data from this flight indicate that the energetic particle flux consists predominantly of protons, neutral hydrogen and possibly other energetic nuclei. The energy spectrum becomes much softer and the flux more intense with increasing Kp for 10-100 keV. The pitch angle distribution at 180 km is asymmetrical with a peak at 90 deg indicating that the majority of particles are near their mirroring altitude. Ionization rates are calculated based on the measured energy spectrum and mirror height distribution. The resulting ionization rate profile is found to be nearly constant with altitude in the region 120 to 200 km. The measured energetic particle flux and calculated ionization rate from the five flights are found to vary with magnetic activity (based on the Kp and Dst indexes) in the same way as the independently derived ionization rates deduced from the electron density profile.

  1. Hydrodynamic interaction between particles near elastic interfaces

    NASA Astrophysics Data System (ADS)

    Daddi-Moussa-Ider, Abdallah; Gekle, Stephan

    2016-07-01

    We present an analytical calculation of the hydrodynamic interaction between two spherical particles near an elastic interface such as a cell membrane. The theory predicts the frequency dependent self- and pair-mobilities accounting for the finite particle size up to the 5th order in the ratio between particle diameter and wall distance as well as between diameter and interparticle distance. We find that particle motion towards a membrane with pure bending resistance always leads to mutual repulsion similar as in the well-known case of a hard-wall. In the vicinity of a membrane with shearing resistance, however, we observe an attractive interaction in a certain parameter range which is in contrast to the behavior near a hard wall. This attraction might facilitate surface chemical reactions. Furthermore, we show that there exists a frequency range in which the pair-mobility for perpendicular motion exceeds its bulk value, leading to short-lived superdiffusive behavior. Using the analytical particle mobilities we compute collective and relative diffusion coefficients. The appropriateness of the approximations in our analytical results is demonstrated by corresponding boundary integral simulations which are in excellent agreement with the theoretical predictions.

  2. Hydrodynamic interaction between particles near elastic interfaces.

    PubMed

    Daddi-Moussa-Ider, Abdallah; Gekle, Stephan

    2016-07-01

    We present an analytical calculation of the hydrodynamic interaction between two spherical particles near an elastic interface such as a cell membrane. The theory predicts the frequency dependent self- and pair-mobilities accounting for the finite particle size up to the 5th order in the ratio between particle diameter and wall distance as well as between diameter and interparticle distance. We find that particle motion towards a membrane with pure bending resistance always leads to mutual repulsion similar as in the well-known case of a hard-wall. In the vicinity of a membrane with shearing resistance, however, we observe an attractive interaction in a certain parameter range which is in contrast to the behavior near a hard wall. This attraction might facilitate surface chemical reactions. Furthermore, we show that there exists a frequency range in which the pair-mobility for perpendicular motion exceeds its bulk value, leading to short-lived superdiffusive behavior. Using the analytical particle mobilities we compute collective and relative diffusion coefficients. The appropriateness of the approximations in our analytical results is demonstrated by corresponding boundary integral simulations which are in excellent agreement with the theoretical predictions. PMID:27394123

  3. Current models of the intensely ionizing particle environment in space

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.

    1988-01-01

    The Cosmic Ray Effects on MicroElectronics (CREME) model that is currently in use to estimate single event effect rates in spacecraft is described. The CREME model provides a description of the radiation environment in interplanetary space near the orbit of the earth that contains no major deficiencies. The accuracy of the galactic cosmic ray model is limited by the uncertainties in solar modulation. The model for solar energetic particles could be improved by making use of all the data that has been collected on solar energetic particle events. There remain major uncertainties about the environment within the earth's magnetosphere, because of the uncertainties over the charge states of the heavy ions in the anomalous component and solar flares, and because of trapped heavy ions. The present CREME model is valid only at 1 AU, but it could be extended to other parts of the heliosphere. There is considerable data on the radiation environment from 0.2 to 35 AU in the ecliptic plane. This data could be used to extend the CREME model.

  4. Search for lightly ionizing particles using CDMS-II data and fabrication of CDMS detectors with improved homogeneity in properties

    SciTech Connect

    Prasad, Kunj Bihari

    2013-12-01

    Fundamental particles are always observed to carry charges which are integral multiples of one-third charge of electron, e/3. While this is a well established experimental fact, the theoretical understanding for the charge quantization phenomenon is lacking. On the other hand, there exist numerous theoretical models that naturally allow for existence of particles with fractional electromagnetic charge. These particles, if existing, hint towards existence of physics beyond the standard model. Multiple high energy, optical, cosmological and astrophysical considerations restrict the allowable mass-charge parameter space for these fractional charges. Still, a huge unexplored region remains. The Cryogenic Dark Matter Search (CDMS-II), located at Soudan mines in northern Minnesota, employs germanium and silicon crystals to perform direct searches for a leading candidate to dark matter called Weakly Interacting Massive Particles (WIMPs). Alternately, the low detection threshold allows search for fractional electromagnetic-charged particles, or Lightly Ionizing Particles (LIPs), moving at relativistic speed. Background rejection is obtained by requiring that the magnitude and location of energy deposited in each detector be consistent with corresponding \\signatures" resulting from the passage of a fractionally charged particle. In this dissertation, the CDMS-II data is analyzed to search for LIPs, with an expected background of 0.078 0.078 events. No candidate events are observed, allowing exclusion of new parameter space for charges between e/6 and e/200.

  5. a Conduction Model Describing Particle-Particle Interaction in the Case of Surface Conducting Particles

    NASA Astrophysics Data System (ADS)

    Gonon, P.; Foulc, J.-N.; Atten, P.

    We propose an analytical conduction model describing particle-particle interactions for the case of electrorheological fluids based on surface conducting particles. The system consisting of two contacting spheres immersed in a dielectric liquid is modeled by a distributed impedances network, from which we derive analytical expressions for the potential at the spheres surface, for the electric field in the liquid phase, and finally for the interaction force. The theoretical interaction force is compared with experimental results obtained on insulating spheres coated with a thin conducting polyaniline film. A good agreement is found between the theory and experiment.

  6. Energetics of Mixed Phase Cloud Particle Interactions

    NASA Astrophysics Data System (ADS)

    Vidaurre, G.; Hallett, J.

    2005-12-01

    The ratio of the kinetic to surface energy of a crystal or a drop on impact gives a measure of the available energy for break-up and splash. Such a break-up process may influence particle collision and also particle observations at aircraft speed. The detail physical processes of the impact determines how the kinetic energy is distributed: 1) part retained by bouncing particles, 2) to create new surfaces during break-up, 3) to dislocate or melt part of the crystal, and 4) converted to thermal energy through viscous dissipation of deforming liquid or displacing air on impact. Extensive break-up of 2% of the crystal or melting of 6% is enough to explain the crystal kinetic energy losses during the encounter at aircraft speed. Ice crystals from convective and stratiform clouds and continental clouds were collected in formvar solution by continuous replicator and also were video-recorded following impact on optical flat of a Cloudscope. Particle sizes were classified in bins, the expected number of fragments being given by an exponential function for ice particles with effective diameter between 5 μm and 2500 μm, and 70% standard deviation. Regions of crystals broken into a few fragments account for 0.6% of the kinetic energy loss; in other parts severe break-up makes it impossible to measure the fracture length. Knowledge regarding ice and water interaction in Mixed-Phase clouds and also with the aircraft instruments provides basic underpinning for characterization of ice particle impact. Further, detail of the fracture process may also be of importance in relation to electrical properties of the particle after impaction or break-up. These conclusions are of major operational importance for prediction of the icing process itself, having implications for both aircraft icing and particle measurement instrumentation.

  7. Oblique propagation, wave particle interaction and particle distribution function

    NASA Astrophysics Data System (ADS)

    Osmane, Adnane; Hamza, A. M.; Meziane, Karim

    Recent results from the Cluster mission have stimulated theoretical investigations and simulations to explain ion distribution functions observed in the quasi-perp bow shock. High-time resolution observations have revealed distributions of gyrating ions that are gyrophase-bunched. When not produced at the shock, such distributions are believed to be resulting from interactions between field-aligned beams and low frequency beamdriven waves . The Conventional models used to account for such distributions assume that the waves are purely transverse, and that they propagate parallel to the ambient magnetic eld. However observations indicate that these waves are propagating obliquely with respect to the ambient magnetic eld [Meziane et al., 2001]. A theoretical investigation of the non-relativistic wave-particle interaction in a background magnetic eld with the electromagnetic wave propagating obliquely has been addressed previously, resulting in a dynamical system describing the wave interaction with a single ion in the absence of dissipation mechanisms. [Hamza et al., 2005] This dynamical system has been numerically integrated to construct the ion distribution functions by seeding the particles with di erent initial conditions. We compute the particle orbits and simulate the time evolution of the distribution functions based on Liouville's theorem of phase space density conservation. It will be shown that the trapping which is due to the oblique propagation of the wave, gives an explanation for gyrophase-bunching and unstable distributions in velocity space which could trigger instabilities such as firehose and mirror. Therefore this exercise provide insights on the particle dynamics and onset of waves away from the shock. Meziane, K., C. Mazelle, R.P. Lin, D. LeQueau, D.E. Larson, G.K. Parks, R.P. Lepping (2001), Three dimensional observations of gyrating ions distributions far upstream from the Earth's bow shock and their association with low-frequency waves, J

  8. Interaction vertex for classical spinning particles

    NASA Astrophysics Data System (ADS)

    Rempel, Trevor; Freidel, Laurent

    2016-08-01

    We consider a model of the classical spinning particle in which the coadjoint orbits of the Poincaré group are parametrized by two pairs of canonically conjugate four-vectors, one representing the standard position and momentum variables, and the other encoding the spinning degrees of freedom. This "dual phase space model" is shown to be a consistent theory of both massive and massless particles and allows for coupling to background fields such as electromagnetism. The on-shell action is derived and shown to be a sum of two terms, one associated with motion in spacetime, and the other with motion in "spin space." Interactions between spinning particles are studied, and a necessary and sufficient condition for consistency of a three-point vertex is established.

  9. (Research in elementary particles and interactions). [1992

    SciTech Connect

    Adair, R.; Sandweiss, J.; Schmidt, M.

    1992-05-01

    Research of the Yale University groups in the areas of elementary particles and their interactions are outlined. Work on the following topics is reported: development of CDF trigger system; SSC detector development; study of heavy flavors at TPL; search for composite objects produced in relativistic heavy-ion collisions; high-energy polarized lepton-nucleon scattering; rare K{sup +} decays; unpolarized high-energy muon scattering; muon anomalous magnetic moment; theoretical high-energy physics including gauge theories, symmetry breaking, string theory, and gravitation theory; study of e{sup +}e{sup {minus}} interactions with the SLD detector at SLAC; and the production and decay of particles containing charm and beauty quarks.

  10. Magnetospheric dynamics and wave-particle interactions

    NASA Technical Reports Server (NTRS)

    Scarf, F. L.; Russell, C. T.

    1976-01-01

    It has been demonstrated that two general classes of wave-particle interactions are of great importance for magnetospheric dynamics. Electromagnetic and electrostatic plasma instabilities give rise to relatively narrow-banded spontaneous emissions (e.g., ELF hiss, chorus, three-halves noise, ion cyclotron and ion-plasma-frequency turbulence) that can scatter trapped particles into the loss cone, leading to modified pitch-angle distributions, stable trapping limits, diffuse aurora, proton precipitation events, etc. The current-driven plasma instabilities give rise to impulsive ion acoustic or Buneman mode turbulence that provides very effective energy transfer (via the anomalous conductivity mechanism) at the bow shock and in regions where strong field-aligned currents are observed. We review these interactions and identify significant open questions that must be investigated during the IMS.

  11. COLLISIONLESS SHOCKS IN A PARTIALLY IONIZED MEDIUM. I. NEUTRAL RETURN FLUX AND ITS EFFECTS ON ACCELERATION OF TEST PARTICLES

    SciTech Connect

    Blasi, P.; Morlino, G.; Bandiera, R.; Amato, E.; Caprioli, D.

    2012-08-20

    A collisionless shock may be strongly modified by the presence of neutral atoms through the processes of charge exchange between ions and neutrals and ionization of the latter. These two processes lead to exchange of energy and momentum between charged and neutral particles both upstream and downstream of the shock. In particular, neutrals that suffer a charge exchange downstream with shock-heated ions generate high-velocity neutrals that have a finite probability of returning upstream. These neutrals might then deposit heat in the upstream plasma through ionization and charge exchange, thereby reducing the fluid Mach number. A consequence of this phenomenon, which we refer to as the neutral return flux, is a reduction of the shock compression factor and the formation of a shock precursor upstream. The scale length of the precursor is determined by the ionization and charge-exchange interaction lengths of fast neutrals moving toward upstream infinity. In the case of a shock propagating in the interstellar medium, the effects of ion-neutral interactions are especially important for shock velocities <3000 km s{sup -1}. Such propagation velocities are common among shocks associated with supernova remnants, the primary candidate sources for the acceleration of Galactic cosmic rays. We then investigate the effects of the return flux of neutrals on the spectrum of test particles accelerated at the shock. We find that, for shocks slower than {approx}3000 km s{sup -1}, the particle energy spectrum steepens appreciably with respect to the naive expectation for a strong shock, namely, {proportional_to}E{sup -2}.

  12. Calibration of impact ionization dust detectors with porous or fluffy dust particles

    NASA Astrophysics Data System (ADS)

    Sterken, V. J.; Moragas-Klostermeyer, G.; Hillier, J. K.; Bugiel, S.; Srama, R.; Armes, S. P.; Fielding; L. A.; Lovett, J. R.; Grün, E.

    2013-07-01

    Impact ionization instruments like the ones flying on Cassini, Galileo, Helios and Ulysses have been calibrated using compact particles made of conductive materials like iron, or of minerals (like Olivine, Orthopyroxene, Magnetite, Pyrite) coated with a thin layer of conductive material. These calibrations were performed by shooting cosmic dust analogues with hypervelocity speeds from 1 to 80 km/s onto the flight spares of these instruments, using the Van de Graaff dust accelerator facility in Heidelberg. Here, we perform first measurements with Cassini CDA of the influence of the density of these dust particles on the resulting signal by, for a given impact speed, comparing signals from micron-sized particles made of compact PPy-coated silica to those from (PPy-coated) hollow silica spheres. The degree of impact ionization depends on the ratio of the densities of the target material and the impactor material and hence, different signals may result from impacts with diffe! rent density or porosity.

  13. Interaction energy and closest approach of moving charged particles on a plasma and neutral gas background

    NASA Astrophysics Data System (ADS)

    Øien, Alf H.

    2012-02-01

    Electric interaction between two negatively charged particles of different sizes on a mixed background of positive, negative, and neutral particles is complex and has relevance both to dusty plasmas and to transports in ionized fluids in general. We consider particularly effects during interaction that particle velocity and neutrals in the background may have on the well-known “dressing” and electric shielding that is due to the charged part of the background and how the interaction energy is modified because of this. Without such effects earlier works show the interaction becomes attractive when the distance between the two particles is a bit larger than the Debye length. We use a model where one of the two interacting particles has a radius much larger than the Debye length and the other a radius shorter than the Debye length. Then, the complex interaction may be more easily determined for particle separation up to a few Debye lengths. We consider the larger particle as stationary while the smaller may move. We find quite simple analytic expressions for the dressed particle interaction energy over the whole range of speed of the incoming smaller particle, assumed coming head on the larger particle, and the whole range of neutral particle densities. We also derive a distance of closest approach of small and large particles for all such parameter values. This distance is important for excluded volume estimations for moving small charged particles in media populated by large charged particles on a background as described above, and hence, important for determining the speed of flow of the smaller particles through such media.

  14. Convective Polymer Depletion on Pair Particle Interactions

    NASA Astrophysics Data System (ADS)

    Fan, Tai-Hsi; Taniguchi, Takashi; Tuinier, Remco

    2011-11-01

    Understanding transport, reaction, aggregation, and viscoelastic properties of colloid-polymer mixture is of great importance in food, biomedical, and pharmaceutical sciences. In non-adsorbing polymer solutions, colloidal particles tend to aggregate due to the depletion-induced osmotic or entropic force. Our early development for the relative mobility of pair particles assumed that polymer reorganization around the particles is much faster than particle's diffusive time, so that the coupling of diffusive and convective effects can be neglected. Here we present a nonequilibrium two-fluid (polymer and solvent) model to resolve the convective depletion effect. The theoretical framework is based on ground state approximation and accounts for the coupling of fluid flow and polymer transport to better describe pair particle interactions. The momentum and polymer transport, chemical potential, and local viscosity and osmotic pressure are simultaneously solved by numerical approximation. This investigation is essential for predicting the demixing kinetics in the pairwise regime for colloid-polymer mixtures. This work is supported by NSF CMMI 0952646.

  15. Energetic particles and ionization in the nighttime middle and low latitude ionosphere

    NASA Technical Reports Server (NTRS)

    Voss, H. D.; Smith, L. G.

    1977-01-01

    Seven Nike Apache rockets, each equipped with an energetic particle spectrometer (12 E 80 keV) and electron-density experiments, were launched from Wallops Island, Virginia and Chilca, Peru, under varying geomagnetic conditions near midnight. At Wallops Island the energetic particle flux (E 40 keV) is found to be strongly dependent on Kp. The pitch-angle distribution is asymmetrical about a peak at 90 D signifying a predominately quasi-trapped flux and explaining the linear increase of count rate with altitute in the altitude region 120 to 200 km. The height-averaged ionization rates derived from the electron-density profiles are consistent with the rates calculated from the observed total particle flux for magnetic index Kp 3. In the region 90 to 110 km it is found that the nighttime ionization is primarily a result of Ly-beta radiation from the geocorona and interplanetary hydrogen for even very disturbed conditions. Below 90 km during rather disturbed conditions energetic electrons can be a significant ionization source. Two energetic particle precipitation zones have been identified at midlatitudes.

  16. Alfvén ionization in an MHD-gas interactions code

    NASA Astrophysics Data System (ADS)

    Wilson, A. D.; Diver, D. A.

    2016-07-01

    A numerical model of partially ionized plasmas is developed in order to capture their evolving ionization fractions as a result of Alfvén ionization (AI). The mechanism of, and the parameter regime necessary for, AI is discussed and an expression for the AI rate based on fluid parameters, from a gas-MHD model, is derived. This AI term is added to an existing MHD-gas interactions' code, and the result is a linear, 2D, two-fluid model that includes momentum transfer between charged and neutral species as well as an ionization rate that depends on the velocity fields of both fluids. The dynamics of waves propagating through such a partially ionized plasma are investigated, and it is found that AI has a significant influence on the fluid dynamics as well as both the local and global ionization fraction.

  17. Identifying Carbohydrate Ligands of a Norovirus P Particle using a Catch and Release Electrospray Ionization Mass Spectrometry Assay

    NASA Astrophysics Data System (ADS)

    Han, Ling; Kitova, Elena N.; Tan, Ming; Jiang, Xi; Klassen, John S.

    2014-01-01

    Noroviruses (NoVs), the major cause of epidemic acute gastroenteritis, recognize human histo-blood group antigens (HBGAs), which are present as free oligosaccharides in bodily fluid or glycolipids and glycoproteins on the surfaces of cells. The subviral P particle formed by the protruding (P) domain of the NoV capsid protein serves as a useful model for the study NoV-HBGA interactions. Here, we demonstrate the application of a catch-and-release electrospray ionization mass spectrometry (CaR-ESI-MS) assay for screening carbohydrate libraries against the P particle to rapidly identify NoV ligands and potential inhibitors. Carbohydrate libraries of 50 and 146 compounds, which included 18 and 24 analogs of HBGA receptors, respectively, were screened against the P particle of VA387, a member of the predominant GII.4 NoVs. Deprotonated ions corresponding to the P particle bound to carbohydrates were isolated and subjected to collision-induced dissociation to release the ligands in their deprotonated forms. The released ligands were identified by ion mobility separation followed by mass analysis. All 13 and 16 HBGA ligands with intrinsic affinities >500 M-1 were identified in the 50 and the 146 compound libraries, respectively. Furthermore, screening revealed interactions with a series of oligosaccharides with structures found in the cell wall of mycobacteria and human milk. The affinities of these newly discovered ligands are comparable to those of the HBGA receptors, as estimated from the relative abundance of released ligand ions.

  18. Baryogenesis for weakly interacting massive particles

    NASA Astrophysics Data System (ADS)

    Cui, Yanou; Sundrum, Raman

    2013-06-01

    We propose a robust, unified framework, in which the similar baryon and dark matter cosmic abundances both arise from the physics of weakly interacting massive particles (WIMPs), with the rough quantitative success of the so-called “WIMP miracle.” In particular the baryon asymmetry arises from the decay of a metastable WIMP after its thermal freeze-out at or below the weak scale. A minimal model and its embedding in R-parity violating supersymmetry are studied as examples. The new mechanism saves R-parity violating supersymmetry from the potential crisis of washing out primordial baryon asymmetry. Phenomenological implications for the LHC and precision tests are discussed.

  19. (Interaction of charged particles with matter)

    SciTech Connect

    Crawford, O.H.

    1990-12-05

    This report covers the activity of the traveler participating in a workshop entitled The 13th Werner Brandt Workshop on the Interaction of Charged Particles with Solids and conducting collaborative research with two physicists at Tokyo University. The Werner Brandt Workshops are organized by members of the traveler's group, led by Dr. R. H. Ritchie, with advice from an international committee. The traveler participated in planning for the next in the series of workshops, which will be held in or near the traveler's home base. Oak Ridge, Tennessee, in early 1992. He interacted with scientists from Japan, Spain, USSR, Israel, and other countries, initiated plans for a new collaboration with a Japanese scientist, and renewed existing collaborations, At Tokyo University, the traveler performed collaborative research with Professors Y. Yamazaki and K. Komaki on two topics of importance to the traveler's programs with the Department of Energy (DOE).

  20. Dynamics of two interacting active Janus particles

    NASA Astrophysics Data System (ADS)

    Bayati, Parvin; Najafi, Ali

    2016-04-01

    Starting from a microscopic model for a spherically symmetric active Janus particle, we study the interactions between two such active motors. The ambient fluid mediates a long range hydrodynamic interaction between two motors. This interaction has both direct and indirect hydrodynamic contributions. The direct contribution is due to the propagation of fluid flow that originated from a moving motor and affects the motion of the other motor. The indirect contribution emerges from the re-distribution of the ionic concentrations in the presence of both motors. Electric force exerted on the fluid from this ionic solution enhances the flow pattern and subsequently changes the motion of both motors. By formulating a perturbation method for very far separated motors, we derive analytic results for the translation and rotational dynamics of the motors. We show that the overall interaction at the leading order modifies the translational and rotational speeds of motors which scale as O (" separators=" [ 1 / D ] 3 ) and O (" separators=" [ 1 / D ] 4 ) with their separation, respectively. Our findings open up the way for studying the collective dynamics of synthetic micro-motors.

  1. Entropic Ratchet transport of interacting active Brownian particles

    SciTech Connect

    Ai, Bao-Quan; He, Ya-Feng; Zhong, Wei-Rong

    2014-11-21

    Directed transport of interacting active (self-propelled) Brownian particles is numerically investigated in confined geometries (entropic barriers). The self-propelled velocity can break thermodynamical equilibrium and induce the directed transport. It is found that the interaction between active particles can greatly affect the ratchet transport. For attractive particles, on increasing the interaction strength, the average velocity first decreases to its minima, then increases, and finally decreases to zero. For repulsive particles, when the interaction is very weak, there exists a critical interaction at which the average velocity is minimal, nearly tends to zero, however, for the strong interaction, the average velocity is independent of the interaction.

  2. Planckian Interacting Massive Particles as Dark Matter.

    PubMed

    Garny, Mathias; Sandora, McCullen; Sloth, Martin S

    2016-03-11

    The standard model could be self-consistent up to the Planck scale according to the present measurements of the Higgs boson mass and top quark Yukawa coupling. It is therefore possible that new physics is only coupled to the standard model through Planck suppressed higher dimensional operators. In this case the weakly interacting massive particle miracle is a mirage, and instead minimality as dictated by Occam's razor would indicate that dark matter is related to the Planck scale, where quantum gravity is anyway expected to manifest itself. Assuming within this framework that dark matter is a Planckian interacting massive particle, we show that the most natural mass larger than 0.01M_{p} is already ruled out by the absence of tensor modes in the cosmic microwave background (CMB). This also indicates that we expect tensor modes in the CMB to be observed soon for this type of minimal dark matter model. Finally, we touch upon the Kaluza-Klein graviton mode as a possible realization of this scenario within UV complete models, as well as further potential signatures and peculiar properties of this type of dark matter candidate. This paradigm therefore leads to a subtle connection between quantum gravity, the physics of primordial inflation, and the nature of dark matter. PMID:27015472

  3. Planckian Interacting Massive Particles as Dark Matter

    NASA Astrophysics Data System (ADS)

    Garny, Mathias; Sandora, McCullen; Sloth, Martin S.

    2016-03-01

    The standard model could be self-consistent up to the Planck scale according to the present measurements of the Higgs boson mass and top quark Yukawa coupling. It is therefore possible that new physics is only coupled to the standard model through Planck suppressed higher dimensional operators. In this case the weakly interacting massive particle miracle is a mirage, and instead minimality as dictated by Occam's razor would indicate that dark matter is related to the Planck scale, where quantum gravity is anyway expected to manifest itself. Assuming within this framework that dark matter is a Planckian interacting massive particle, we show that the most natural mass larger than 0.01 Mp is already ruled out by the absence of tensor modes in the cosmic microwave background (CMB). This also indicates that we expect tensor modes in the CMB to be observed soon for this type of minimal dark matter model. Finally, we touch upon the Kaluza-Klein graviton mode as a possible realization of this scenario within UV complete models, as well as further potential signatures and peculiar properties of this type of dark matter candidate. This paradigm therefore leads to a subtle connection between quantum gravity, the physics of primordial inflation, and the nature of dark matter.

  4. Critical Casimir interactions between Janus particles.

    PubMed

    Labbé-Laurent, M; Dietrich, S

    2016-08-21

    Recently there has been strong experimental and theoretical interest in studying the self-assembly and the phase behavior of patchy and Janus particles, which form colloidal suspensions. Although in this quest a variety of effective interactions have been proposed and used in order to achieve a directed assembly, the critical Casimir effect stands out as being particularly suitable in this respect because it provides both attractive and repulsive interactions as well as the potential of a sensitive temperature control of their strength. Specifically, we have calculated the critical Casimir force between a single Janus particle and a laterally homogeneous substrate as well as a substrate with a chemical step. We have used the Derjaguin approximation and compared it with results from full mean field theory. A modification of the Derjaguin approximation turns out to be generally reliable. Based on this approach we have derived the effective force and the effective potential between two Janus cylinders as well as between two Janus spheres. PMID:27444691

  5. Measurement of Few Body Interactions in Tri-Atomic Molecular Dissociation into Three Charged Particles

    NASA Astrophysics Data System (ADS)

    Mueller, Dennis; Jordon-Thaden, Brandon; Weise, Lisa; Jaecks, Duane

    2010-03-01

    Threshold ionization of atoms by electron impact remains an area of interest. Near threshold, where the total energy of the system is approximately zero, the motion of charged particles is highly correlated. Similarly, near threshold dissociation into three or more charges particles is involve highly correlated motion as the particles slowly move apart under the influence of the long-range Coulomb interaction. We will present a novel approach to gain insight into these interactions, where no simplifying approximations such as placing one of the particles near the center-of-mass, is theoretically viable. In these triple coincidence experiments, the final state momenta of all particles are measured with sub-meV resolution sufficient to resolve rovibrational levels. This allows us to determine the initial state of the tri-atomic molecular ion.

  6. 337 nm matrix-assisted laser desorption/ionization of single aerosol particles.

    PubMed

    He, L; Murray, K K

    1999-09-01

    Matrix-assisted laser desorption/ionization (MALDI) mass spectra were obtained from single particles injected directly into a time-of-flight mass spectrometer. Aerosol particles were generated at atmospheric pressure using a piezoelectric single-particle generator or a pneumatic nebulizer and introduced into the mass spectrometer through a series of narrow-bore tubes. Particles were detected by light scattering that was used to trigger a 337 nm pulsed nitrogen laser and the ions produced by laser desorption were mass separated in a two-stage reflectron time-of-flight mass spectrometer. MALDI mass spectra of single particles containing bradykinin, angiotensin II, gramicidin S, vitamin B(12) or gramicidin D were obtained at mass resolutions greater than 400 FWHM. For the piezoelectric particle generator, the efficiency of particle delivery was estimated to be approximately 0.02%, and 50 pmol of sample were consumed for each mass spectrum. For the pneumatic nebulizer, mass spectra could be obtained from single particles containing less than 100 amol of analyte, although the sample consumption for a typical mass spectrum was over 400 pmol. PMID:10491586

  7. Particle Acceleration in Shock-Shock Interaction

    NASA Astrophysics Data System (ADS)

    Nakanotani, Masaru; Matsukiyo, Shuichi; Hada, Tohru

    2015-04-01

    Collisionless shock waves play a crucial role in producing high energy particles. One of the most plausible acceleration mechanisms is the first order Fermi acceleration in which non-thermal particles statistically gain energy while scattered by MHD turbulence both upstream and downstream of a shock. Indeed, X-ray emission from energetic particles accelerated at supernova remnant shocks is often observed [e.g., Uchiyama et al., 2007]. Most of the previous studies on shock acceleration assume the presence of a single shock. In space, however, two shocks frequently come close to or even collide with each other. For instance, it is observed that a CME (coronal mass ejection) driven shock collides with the earth's bow shock [Hietala et al., 2011], or interplanetary shocks pass through the heliospheric termination shock [Lu et al., 1999]. Colliding shocks are observed also in high power laser experiments [Morita et al., 2013]. It is expected that shock-shock interactions efficiently produce high energy particles. A previous work using hybrid simulation [Cargill et al., 1986] reports efficient ion acceleration when supercritical two shocks collide. In the hybrid simulation, however, the electron dynamics cannot be resolved so that electron acceleration cannot be discussed in principle. Here, we perform one-dimensional full Particle-in-Cell (PIC) simulations to examine colliding two symmetric oblique shocks and the associated electron acceleration. In particular, the following three points are discussed in detail. 1. Energetic electrons are observed upstream of the two shocks before their collision. These energetic electrons are efficiently accelerated through multiple reflections at the two shocks (Fermi acceleration). 2. The reflected electrons excite large amplitude upstream waves. Electron beam cyclotron instability [Hasegawa, 1975] and electron fire hose instability [Li et al., 2000] appear to occur. 3. The large amplitude waves can scatters energetic electrons in

  8. Ionization states of helium in He-3-rich solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Klecker, B.; Hovestadt, D.; Moebius, E.; Scholer, M.; Gloeckler, G.; Ipavich, F. M.

    1983-01-01

    Results of a systematic study of the ionic charge state of helium in the energy range 0.6-1.0 MeV/nucleon for He-3-rich solar energetic particle events during the time period August 1978 to October 1979 are reported. The data have been obtained with the Max-Planck-Institut/University of Maryland experiment on ISEE-3. Whereas for solar energetic particle events with no enrichment of He-3 relative to He-4 surprisingly large abundances of singly ionized helium have been reported recently, He-3-rich solar energetic particle events do not show significant abundances of He-3(+). This result is consistent with current theories explaining large compositional anomalies by mass per charge dependent selective heating of the minor ion species.

  9. DNA-nuclear matrix interactions and ionizing radiation sensitivity

    SciTech Connect

    Schwartz, J.L. Chicago Univ., IL . Dept. of Radiation and Cellular Oncology); Vaughan, A.T.M. . Dept. of Radiotherapy)

    1993-01-01

    The association between inherent ionizing radiation sensitivity and DNA supercoil unwinding in mammalian cells suggests that the DNA-nuclear matrix attachment region (MAR) plays an important role in radiation response. In radioresistant cells, the MAR structure may exist in a more stable, open configuration, limiting DNA unwinding following strand break induction and maintaining DNA ends in close proximity for more rapid and accurate rejoining. In addition, the open configuration at these matrix attachment sites may serve to facilitate rapid DNA processing of breaks by providing (1) sites for repair proteins to collect and (2) energy to drive enzymatic reactions.

  10. DNA-nuclear matrix interactions and ionizing radiation sensitivity

    SciTech Connect

    Schwartz, J.L. |; Vaughan, A.T.M.

    1993-03-01

    The association between inherent ionizing radiation sensitivity and DNA supercoil unwinding in mammalian cells suggests that the DNA-nuclear matrix attachment region (MAR) plays an important role in radiation response. In radioresistant cells, the MAR structure may exist in a more stable, open configuration, limiting DNA unwinding following strand break induction and maintaining DNA ends in close proximity for more rapid and accurate rejoining. In addition, the open configuration at these matrix attachment sites may serve to facilitate rapid DNA processing of breaks by providing (1) sites for repair proteins to collect and (2) energy to drive enzymatic reactions.

  11. Particle-in-cell simulations of the critical ionization velocity effect in finite size clouds

    SciTech Connect

    Moghaddam-Taaheri, E.; Lu, G.; Nishikawa, K.I.

    1994-04-01

    The critical ionization velocity (CIV) mechanism in a finite size cloud is studied with a series of electrostatic particle-in-cell simulations. It is observed that an initial seed ionization, produced by non-CIV mechanisms, generates a cross-field ion beam which excites a modified beam-plasma instability (MBPI) with frequency in the range of the lower hybrid frequency. The excited waves accelerate electrons along the magnetic field up to the ion drift energy that exceeds the ionization energy of the neutral atoms. The heated electrons in turn enhance the ion beam by electron-neutral impact ionization, which established a positive feedback loop in maintaining the CIV process. It is also found that the efficiency of the CIV mechanism depends on the finite size of the gas cloud in the following ways: (1) Along the ambient magnetic field the finite size of the cloud, L{parallel}, restricts the growth of the fastest growing mode, with a wavelength {lambda}{sub m{parallel}}, of the MBPI. (2) Momentum coupling between the cloud and the ambient plasma via the Alfven waves occurs as a result of the finite size of the cloud in the direction perpendicular to both the ambient magnetic field and the neutral drift. (3) The transverse charge separation field across the cloud was found to result in the modulation of the beam velocity which reduces the parallel heating of electrons and increases the transverse acceleration of electrons. (4) Some energetic electrons are lost from the cloud along the magnetic field at a rate characterized by the acoustic velocity, instead of the electron thermal velocity. It is also shown that a factor of 4 increase in the ambient plasma density, increases the CIV ionization yield by almost 2 orders of magnitude at the end of a typical run. The simulation results are used to interpret various chemical release experiments in space. 68 refs., 22 figs., 4 tabs.

  12. Investigation of nonthermal particle effects on ionization dynamics in high current density ion beam transport experiments

    NASA Astrophysics Data System (ADS)

    Chung, H. K.; MacFarlane, J. J.; Wang, P.; Moses, G. A.; Bailey, J. E.; Olson, C. L.; Welch, D. R.

    1997-01-01

    Light ion inertial fusion experiments require the presence of a moderate density background gas in the transport region to provide charge and current neutralization for a high current density ion beam. In this article, we investigate the effects of nonthermal particles such as beam ions or non-Maxwellian electron distributions on the ionization dynamics of the background gas. In particular, we focus on the case of Li beams being transported in an argon gas. Nonthermal particles as well as thermal electrons are included in time-dependent collisional-radiative calculations to determine time-dependent atomic level populations and charge state distributions in a beam-produced plasma. We also briefly discuss the effects of beam ions and energetic electrons on the visible and vacuum ultraviolet (VUV) spectral regions. It is found that the mean charge state of the gas, and hence the electron density, is significantly increased by collisions with energetic particles. This higher ionization significantly impacts the VUV spectral region, where numerous resonance lines occur. On the other hand, the visible spectrum tends to be less affected because the closely spaced excited states are populated by lower energy thermal electrons.

  13. Femtosecond laser ablation particle introduction to a liquid sampling-atmospheric pressure glow discharge ionization source

    SciTech Connect

    Carado, Anthony J.; Quarles, C. Derrick; Duffin, Andrew M.; Barinaga, Charles J.; Russo, Richard E.; Marcus, R. Kenneth; Eiden, Gregory C.; Koppenaal, David W.

    2012-01-01

    This work describes the use of a compact, liquid sampling – atmospheric pressure glow discharge (LS-APGD) ionization source to ionize metal particles within a laser ablation aerosol. Mass analysis was performed with a Thermo Scientific Exactive Mass Spectrometer which utilizes an orbitrap mass analyzer capable of producing mass resolution exceeding M/ΔM > 160,000. The LS-APGD source generates a low-power plasma between the surface of an electrolytic solution flowing at several µl min-1 through a fused silica capillary and a counter electrode consisting of a stainless steel capillary employed to deliver the laser ablation particles into the plasma. Sample particles of approximately 100 nm were generated with an Applied Spectra femtosecond laser located remotely and transported through 25 meters of polyurethane tubing by means of argon carrier gas. Samples consisted of an oxygen free copper shard, a disk of solder, and a one-cent U.S. coin. Analyte signal onset was readily detectable relative to the background signal produced by the carrier gas alone. The high mass resolution capability of the orbitrap mass spectrometer was demonstrated on the solder sample with resolution exceeding 90,000 for Pb and 160,000 for Cu. In addition, results from a laser ablation depth-profiling experiment of a one cent coin revealed retention of the relative locations of the ~10 µm copper cladding and zinc rich bulk layers.

  14. Pseudopotentials of the particles interactions in complex plasmas

    SciTech Connect

    Ramazanov, T. S.; Moldabekov, Zh. A.; Dzhumagulova, K. N.; Muratov, M. M.

    2011-10-15

    This article discusses the effective interaction potentials in a complex dusty plasma. The interaction of electrons with atoms and the interaction between dusty particles are studied by the method of the dielectric response function. In the effective interaction, potential between electron and atom the quantum effects of diffraction were taken into account. On the curve of the interaction potential between dust particles under certain conditions the oscillations can be observed.

  15. Laser desorption ionization of small molecules assisted by tungsten oxide and rhenium oxide particles.

    PubMed

    Bernier, Matthew C; Wysocki, Vicki H; Dagan, Shai

    2015-07-01

    Inorganic metal oxides have shown potential as matrices for assisting in laser desorption ionization with advantages over the aromatic acids typically used. Rhenium and tungsten oxides are attractive options due to their high work functions and relative chemical inertness. In this work, it is shown that ReO3 and WO3 , in microparticle (μP) powder forms, can efficiently facilitate ionization of various types of small molecules and provide minimized background contamination at analyte concentrations below 1 ng/µL. This study shows that untreated inorganic WO3 and ReO3 particles are valid matrix options for detection of protonatable, radical, and precharged species under laser desorption ionization. Qualitatively, the WO3 μP showed improved detection of apigenin, sodiated glucose, and precharged analyte choline, while the ReO3 μP allowed better detection of protonated cocaine, quinuclidine, ametryn, and radical ions of polyaromatic hydrocarbons at detection levels as low as 50 pg/µL. For thermometer ion survival yield experiments, it was also shown that the ReO3 powder was significantly softer than α-cyano-4-hydroxycinnaminic acid. Furthermore, it provided higher intensities of cocaine and polyaromatic hydrocarbons, at laser flux values equal to those used with α-cyano-4-hydroxycinnaminic acid. PMID:26349643

  16. Charge Identification of Highly Ionizing Particles in Desensitized Nuclear Emulsion Using High Speed Read-Out System

    SciTech Connect

    Toshito, T.; Kodama, K.; Yusa, K.; Ozaki, M.; Amako, K.; Kameoka, S.; Murakami, K.; Sasaki, T.; Aoki, S.; Ban, T.; Fukuda, T.; Naganawa, N.; Nakamura, T.; Natsume, M.; Niwa, K.; Takahashi, S.; Kanazawa, M.; Kanematsu, N.; Komori, M.; Sato, S.; Asai, M.; /Nagoya U. /Aichi U. of Education /Gunma U., Maebashi /JAXA, Sagamihara /KEK, Tsukuba /Kobe U. /Chiba, Natl. Inst. Rad. Sci. /SLAC /Toho U.

    2006-05-10

    We performed an experimental study of charge identification of heavy ions from helium to carbon having energy of about 290 MeV/u using an emulsion chamber. Emulsion was desensitized by means of forced fading (refreshing) to expand a dynamic range of response to highly charged particles. For the track reconstruction and charge identification, the fully automated high speed emulsion read-out system, which was originally developed for identifying minimum ionizing particles, was used without any modification. Clear track by track charge identification up to Z=6 was demonstrated. The refreshing technique has proved to be a powerful technique to expand response of emulsion film to highly ionizing particles.

  17. Algorithm for Computing Particle/Surface Interactions

    NASA Technical Reports Server (NTRS)

    Hughes, David W.

    2009-01-01

    An algorithm has been devised for predicting the behaviors of sparsely spatially distributed particles impinging on a solid surface in a rarefied atmosphere. Under the stated conditions, prior particle-transport models in which (1) dense distributions of particles are treated as continuum fluids; or (2) sparse distributions of particles are considered to be suspended in and to diffuse through fluid streams are not valid.

  18. Lattice-Boltzmann simulation of laser interaction with weakly ionized helium plasmas

    SciTech Connect

    Li Huayu; Ki, Hyungson

    2010-07-15

    This paper presents a lattice Boltzmann method for laser interaction with weakly ionized plasmas considering electron impact ionization and three-body recombination. To simulate with physical properties of plasmas, the authors' previous work on the rescaling of variables is employed and the electromagnetic fields are calculated from the Maxwell equations by using the finite-difference time-domain method. To calculate temperature fields, energy equations are derived separately from the Boltzmann equations. In this way, we attempt to solve the full governing equations for plasma dynamics. With the developed model, the continuous-wave CO{sub 2} laser interaction with helium is simulated successfully.

  19. Chemical compositions of black carbon particle cores and coatings via soot particle aerosol mass spectrometry with photoionization and electron ionization.

    PubMed

    Canagaratna, Manjula R; Massoli, Paola; Browne, Eleanor C; Franklin, Jonathan P; Wilson, Kevin R; Onasch, Timothy B; Kirchstetter, Thomas W; Fortner, Edward C; Kolb, Charles E; Jayne, John T; Kroll, Jesse H; Worsnop, Douglas R

    2015-05-14

    Black carbon is an important constituent of atmospheric aerosol particle matter (PM) with significant effects on the global radiation budget and on human health. The soot particle aerosol mass spectrometer (SP-AMS) has been developed and deployed for real-time ambient measurements of refractory carbon particles. In the SP-AMS, black carbon or metallic particles are vaporized through absorption of 1064 nm light from a CW Nd:YAG laser. This scheme allows for continuous "soft" vaporization of both core and coating materials. The main focus of this work is to characterize the extent to which this vaporization scheme provides enhanced chemical composition information about aerosol particles. This information is difficult to extract from standard SP-AMS mass spectra because they are complicated by extensive fragmentation from the harsh 70 eV EI ionization scheme that is typically used in these instruments. Thus, in this work synchotron-generated vacuum ultraviolet (VUV) light in the 8-14 eV range is used to measure VUV-SP-AMS spectra with minimal fragmentation. VUV-SP-AMS spectra of commercially available carbon black, fullerene black, and laboratory generated flame soots were obtained. Small carbon cluster cations (C(+)-C5(+)) were found to dominate the VUV-SP-AMS spectra of all the samples, indicating that the corresponding neutral clusters are key products of the SP vaporization process. Intercomparisons of carbon cluster ratios observed in VUV-SP-AMS and SP-AMS spectra are used to confirm spectral features that could be used to distinguish between different types of refractory carbon particles. VUV-SP-AMS spectra of oxidized organic species adsorbed on absorbing cores are also examined and found to display less thermally induced decomposition and fragmentation than spectra obtained with thermal vaporization at 200 °C (the minimum temperature needed to quantitatively vaporize ambient oxidized organic aerosol with a continuously heated surface). The particle cores

  20. Numerical studies of wall-plasma interactions and ionization phenomena in an ablative pulsed plasma thruster

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Zeng, Guangshang; Tang, Haibin; Huang, Yuping; Liu, Xiangyang

    2016-07-01

    Wall-plasma interactions excited by ablation controlled arcs are very critical physical processes in pulsed plasma thrusters (PPTs). Their effects on the ionization processes of ablated vapor into discharge plasma directly determine PPT performances. To reveal the physics governing the ionization phenomena in PPT discharge, a modified model taking into account the pyrolysis effect of heated polytetrafluoroethylene propellant on the wall-plasma interactions was developed. The feasibility of the modified model was analyzed by creating a one-dimensional simulation of a rectangular ablative PPT. The wall-plasma interaction results based on this modified model were found to be more realistic than for the unmodified model; this reflects the dynamic changes of the inflow parameters during discharge in our model. Furthermore, the temporal and spatial variations of the different plasma species in the discharge chamber were numerically studied. The numerical studies showed that polytetrafluoroethylene plasma was mainly composed of monovalent ions; carbon and fluorine ions were concentrated in the upstream and downstream discharge chamber, respectively. The results based on this modified model were in good agreement with the experimental formation times of the various plasma species. A large number of short-lived and highly ionized carbon and fluorine species (divalent and trivalent ions) were created during initial discharge. These highly ionized species reached their peak density earlier than the singly ionized species.

  1. Ionized van-der-Waals systems: Structure and interactions

    SciTech Connect

    Zuelicke, L.

    1996-12-31

    Ions of molecular systems with internal interactions partly of van-der-Waals type differ significantly from their neutral parent species in binding, structure and dynamics. Theoretical knowledge is still rather scarce. The paper discusses some recent advances from theoretical work in the field concerning (i) electronic and geometric structure of triatomic rare-gas containing cations like Ar{sub 3}{sup +} and ArHCI{sup +}, in ground and excited electronic states; (ii) potential energy surfaces for the interaction of H{sup +} or H{sup -} with diatomic molecules, in ground and excited electronic states; (iii) some features of the dynamics of these systems.

  2. Direct numerical simulation of AC dielectrophoretic particle-particle interactive motions.

    PubMed

    Ai, Ye; Zeng, Zhenping; Qian, Shizhi

    2014-03-01

    Under an AC electric field, individual particles in close proximity induce spatially non-uniform electric field around each other, accordingly resulting in mutual dielectrophoretic (DEP) forces on these particles. The resulting attractive DEP particle-particle interaction could assemble individual colloidal particles or biological cells into regular patterns, which has become a promising bottom-up fabrication technique for bio-composite materials and microscopic functional structures. In this study, we developed a transient multiphysics model under the thin electric double layer (EDL) assumption, in which the fluid flow field, AC electric field and motion of finite-size particles are simultaneously solved using an Arbitrary Lagrangian-Eulerian (ALE) numerical approach. Numerical simulations show that negative DEP particle-particle interaction always tends to attract particles and form a chain parallel to the applied electric field. Particles usually accelerate at the first stage of the attractive motion due to an increase in the DEP interactive force, however, decelerate until stationary at the second stage due to a faster increase in the repulsive hydrodynamic force. Identical particles move at the same speed during the interactive motion. In contrast, smaller particles move faster than bigger particles during the attractive motion. The developed model explains the basic mechanism of AC DEP-based particle assembly technique and provides a versatile tool to design microfluidic devices for AC DEP-based particle or cell manipulation. PMID:24407661

  3. Mass spectra of organic and inorganic dust particles measured by an impact ionization mass analyzer instrument

    NASA Astrophysics Data System (ADS)

    Salter, J. G.; Sternovsky, Z.; Srama, R.; Postberg, F.; Kempf, S.; Armes, S. P.; Gruen, E.; Horanyi, M.; Drake, K.; Westphal, A.

    2009-12-01

    The composition of individual cosmic dust particles can be measured in-situ using existing techniques and instrumentations. The dust particle impacting on a solid surface with hypervelocity (> 1 km/s) is vaporized and partially ionized. The generated ions are extracted and analyzed using time-of-flight methods. Laboratory calibration measurements are possible at the dust accelerator facility in Heidelberg, Germany. The accelerator is limited to using conductive dust that was limited in the past to Fe, Al or graphite samples. In the recent years, however, dust samples of organic materials and inorganic minerals of cosmic interest were developed that are suitable for application in the accelerator. This is achieved by coating micron and submicron sized dust particles by conductive polymers. Here we present the comparison of spectra measured using organic and inorganic dust samples (polystyrene, poly-[bis(4-vinylthiophenyl)sulphide], Phyrotite). The particles were accelerated to speeds between 3 and 35 km/s. Depending on the projectile type and the impact speed, both aliphatic and aromatic molecular ions and cluster species were identified in the mass spectra with masses up to 400 Daltons. Clusters resulting from the target material (silver) and mixed clusters of target and projectile species were also observed. These fundamental studies are expected to enhance our understanding of cometary, interplanetary and interstellar dust grains, which travel at similar hyper-velocities and are known to contain both aliphatic and aromatic organic compounds.

  4. Spark bubble interaction with a suspended particle

    NASA Astrophysics Data System (ADS)

    Ohl, Siew-Wan; Wu, Di Wei; Klaseboer, Evert; Cheong Khoo, Boo

    2015-12-01

    Cavitation bubble collapse is influenced by nearby surfaces or objects. A bubble near a rigid surface will move towards the surface and collapse with a high speed jet. When a hard particle is suspended near a bubble generated by electric spark, the bubble expands and collapses moving the particle. We found that within a limit of stand-off distance, the particle is propelled away from the bubble as it collapses. At a slightly larger stand-off distance, the bubble collapse causes the particle to move towards the bubble initially before moving away. The bubble does not move the particle if it is placed far away. This conclusion is important for applications such as drug delivery in which the particle is to be propelled away from the collapsing bubble.

  5. Effect of particle interactions on thermoremanent magnetization

    NASA Astrophysics Data System (ADS)

    Newell, A. J.; Niemerg, M.; Bates, D.

    2013-12-01

    Paleomagnetism has a dizzying array of protocols for determining the strength of the Earth's magnetic field in the past from measurements of the magnetic memory in rocks. Some, such as variants of the Thellier-Thellier method, try to isolate the signal from an "ideal" fraction of magnetic minerals, discarding the contribution of "non-ideal" minerals; others, like the multi-specimen method, try to glean useful information from all of the minerals. The "ideal" remanence carriers behave like single-domain (SD) magnets with uniaxial anisotropy, and their behavior is predicted by Louis Néel's theory of thermoremanent magnetization (TRM). Non-ideal carriers are not at all well understood, but every paleointensity method relies on assumptions about their nature to either remove their signal or make use of it. One way to explore the boundary between ideal and non-ideal is to look at the behavior of SD magnets as they are brought increasingly close together, thus increasing the strength of the magnetostatic coupling between them. Magnetostatic coupling greatly increases the complexity of such a system. Instead of just two stable states, many must be found. Instead of one energy barrier, there is a network of connections between stable states over energy barriers. Instead of one rate for the relaxation of a system towards equilibrium, there are several. It is particularly difficult to find the transition states at the top of the energy barriers. We have developed software that does all of the above. A method from algebraic geometry called homotopy continuation is used to find all stable states and transition states. The software can track changes in these states with magnetic field, temperature, or other external variables. We use it to model TRM acquisition in small systems of interacting particles, and examine its behavior under various paleointensity tests.

  6. Effects of a Relativistic Electron Beam Interaction with the Upper Atmosphere: Ionization, X-Rays, and Optical Emissions

    NASA Astrophysics Data System (ADS)

    Marshall, R. A.; Nicolls, M. J.; Sanchez, E. R.; Lehtinen, N. G.; Neilson, J.

    2014-12-01

    An artificial beam of relativistic (0.5--10 MeV) electrons has been proposed as an active experiment in the ionosphere and magnetosphere, with applications to magnetic field-line tracing, studies of wave-particle interactions, and beam-atmosphere interactions. The beam-atmosphere interaction, while a scientific endeavor of its own, also provides key diagnostics for other experiments. We present results of Monte Carlo simulations of the interaction of a beam of relativistic electrons with the upper atmosphere as they are injected downwards from a notional high altitude (thermospheric / ionospheric) injection platform. The beam parameters, defined by realistic parameters of a compact linear accelerator, are used to create a distribution of thousands of electrons. Each electron is injected downwards from 300 km altitude towards the dense atmosphere, where it undergoes elastic and inelastic collisions, leading to secondary ionization, optical emissions, and X-rays via bremsstrahlung. Here we describe the Monte Carlo model and present calculations of diagnostic outputs, including optical emissions, X-ray fluxes, secondary ionization, and backscattered energetic electron fluxes. Optical emissions are propagated to the ground through the lower atmosphere, including the effects of atmospheric absorption and scattering, to estimate the brightness of the emission column for a given beam current and energy. Similarly, X-ray fluxes are propagated to hypothetical detectors on balloons and satellites, taking into account Compton scattering and photoabsorption. Secondary ionization is used to estimate the radar signal returns from various ground-based radar facilities. Finally, simulated backscattered electron fluxes are measured at the injection location. The simulation results show that for realizable accelerator parameters, each of these diagnostics should be readily detectable by appropriate instruments.

  7. Surface electrical properties of coal particles on interaction with polyelectrolytes

    SciTech Connect

    Evmenova, G.L.

    2006-07-15

    The paper presents experimental data obtained in determining an electrokinetic potential of coal particles during their interaction with coagulation and flocculation agents. It is established that flocculation agents allow decreasing electrokinetic potential of mineral particles up to the values that promote aggregation of the particles thereby enabling the control over the stability of coal dispersions.

  8. Multipole expansion in plasmas: Effective interaction potentials between compound particles

    NASA Astrophysics Data System (ADS)

    Ramazanov, T. S.; Moldabekov, Zh. A.; Gabdullin, M. T.

    2016-05-01

    In this paper, the multipole expansion method is used to determine effective interaction potentials between particles in both classical dusty plasma and dense quantum plasma. In particular, formulas for interactions of dipole-dipole and charge-dipole pairs in a classical nondegenerate plasma as well as in degenerate quantum and semiclassical plasmas were derived. The potentials describe interactions between atoms, atoms and charged particles, dust particles in the complex plasma, atoms and electrons in the degenerate plasma, and metals. Correctness of the results obtained from the multipole expansion is confirmed by their agreement with the results based on other methods of statistical physics and dielectric response function. It is shown that the method of multipole expansion can be used to derive effective interaction potentials of compound particles, if the effect of the medium on the potential of individual particles comprising compound particles is known.

  9. Forest canopy interactions with nucleation mode particles

    NASA Astrophysics Data System (ADS)

    Pryor, S. C.; Hornsby, K. E.; Novick, K. A.

    2014-07-01

    Forests play a key role in removal of particles from the atmosphere but may also significantly contribute to formation and growth of ultrafine particles. Ultrafine particle size distributions through a deciduous forest canopy indicate substantial capture of nucleation mode particles by the foliage. Concentrations decline with depth into the canopy, such that nucleation mode number concentrations at the bottom of the canopy are an average of 16% lower than those at the top. However, growth rates of nucleation mode particles (diameters 6-30 nm) are invariant with height within the canopy, which implies that the semi-volatile gases contributing to their growth are comparatively well-mixed through the canopy. Growth rates of nucleation mode particles during a meteorological drought year (2012) were substantially lower than during a meteorologically normal year with high soil water potential (2013). This may reflect suppression of actual BVOC emissions by drought and thus reduced production of condensable products (and thus particle growth) during the drought-affected vegetation season. This hypothesis is supported by evidence that growth rates during the normal year exhibit a positive correlation with emissions of biogenic volatile organic compounds (BVOC) modeled based on observed forest composition, leaf area index, temperature and PAR, but particle growth rates during the drought-affected vegetation season are not correlated with modeled BVOC emissions. These data thus provide direct evidence for the importance of canopy capture in atmospheric particle budgets and indirect evidence that drought-stress in forests may reduce BVOC emissions and limit growth of nucleation mode particles to climate-relevant sizes.

  10. Energy exchange in systems of particles with nonreciprocal interaction

    SciTech Connect

    Vaulina, O. S.; Lisina, I. I. Lisin, E. A.

    2015-10-15

    A model is proposed to describe the sources of additional kinetic energy and its redistribution in systems of particles with a nonreciprocal interaction. The proposed model is shown to explain the qualitative specific features of the dust particle dynamics in the sheath region of an RF discharge. Prominence is given to the systems of particles with a quasi-dipole–dipole interaction, which is similar to the interaction induced by the ion focusing effects that occur in experiments on a laboratory dusty plasma, and with the shadow interaction caused by thermophoretic forces and Le Sage’s forces.

  11. Energy exchange in systems of particles with nonreciprocal interaction

    NASA Astrophysics Data System (ADS)

    Vaulina, O. S.; Lisina, I. I.; Lisin, E. A.

    2015-10-01

    A model is proposed to describe the sources of additional kinetic energy and its redistribution in systems of particles with a nonreciprocal interaction. The proposed model is shown to explain the qualitative specific features of the dust particle dynamics in the sheath region of an RF discharge. Prominence is given to the systems of particles with a quasi-dipole-dipole interaction, which is similar to the interaction induced by the ion focusing effects that occur in experiments on a laboratory dusty plasma, and with the shadow interaction caused by thermophoretic forces and Le Sage's forces.

  12. Interaction of small spherical particles in confined cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Lev, B. I.; Fukuda, Jun-ichi; Tovkach, O. M.; Chernyshuk, S. B.

    2014-01-01

    The theory of the elastic interaction of spherical colloidal particles immersed into a confined cholesteric liquid crystal is proposed. The case of weak anchoring on the particle surfaces is considered. We derive a general expression for the energy of the interaction between small spherical particles (with diameter much smaller than the cholesteric pitch) suspended in a cholesteric confined by two parallel planes. The resulting form of the interaction energy has a more complex spatial pattern and energy versus distance dependence than that in nematic colloids. The absence of translational symmetry related to helical periodicity and local nematic ordering in cholesteric liquid crystals manifest themselves in the complex nature of the interaction maps.

  13. Studies of the interactions of ionizing radiations with communications materials

    SciTech Connect

    Ashley, J.C.; Williams, M.W.

    1982-01-01

    Various models were developed for calculating the energy loss per unit length, or stopping power, and the inelastic mean free path for electrons in a material. We have included both organic materials such as polyethylene and inorganic materials such as SiO/sub 2/. In each case, the calculated values of stopping power and mean free path have been compared with experimental values where available and, in the case of mean free paths for organic materials, with those predicted from our universal formula. In addition the various models for stopping power and mean free path have been compared with each other. Measurements have been made of electron attenuation lengths (approx. = electron mean free paths) as a function of incident electron energy for electrons in amorphous carbon films, as a direct check on the values predicted by our universal formula for electron mean free paths in solid organic insulators. A theory has been developed to describe charged-particle track structure in nonmetallic solids, as the track evolves in time and space. Work has continued in the field of microdosimetry with the calculation of the energy densities deposited by high-energy photons as a function of depth in traversing a SiO/sub 2/ slab sandwiched between two slabs of Si.

  14. Computation of axisymmetric and ionized hypersonic flows using particle and continuum methods

    NASA Technical Reports Server (NTRS)

    Boyd, Iain D.; Gokcen, Tahir

    1994-01-01

    Comparisons between particle and continuum simulations of hypersonic near-continuum flows are presented. The particle approach employs the direct simulation Monte Carlo (DSMC) method, and the continuum approach solves the appropriate equations of fluid flow. Both simulations have thermochemistry models for air implemented including ionization. A new axisymmetric DSMC code that is efficiently vectorized is developed for this study. In this DSMC code, particular attention is paid to matching the relaxation rates employed in the continuum approach. This investigation represents a continuum of a previous study that considered thermochemical relaxation in one-dimensional shock waves of nitrogen. Comparison of the particle and continuum methods is first made for an axisymmetric blunt-body flow of air at 7 km/s. Very good agreement is obtained for the two solutions. The two techniques also compare well for a one-dimensional shock wave in air at 10 km/s. In both applications, the results are found to be sensitive to various aspects of the chemistry model employed.

  15. Computation of axisymmetric and ionized flows using particle and continuum methods

    NASA Technical Reports Server (NTRS)

    Boyd, Iain D.; Gokcen, Tahir

    1993-01-01

    Comparisons between particle and continuum simulations of hypersonic near-continuum flows are presented. The particle approach employs the direct simulation Monte Carlo method (DSMC), and the continuum approach solves the Euler equations. Both simulations have thermochemistry models for air implemented including ionization. A new axisymmetric DSMC code which is efficiently vectorized is developed for this study. In this DSMC code, particular attention is paid to matching the relaxation rates employed in the continuum approach. This investigation represents a continuation of a previous study which considered thermochemical relaxation in one-dimensional shock waves of nitrogen. Comparison of the particle and continuum methods is first made for an axisymmetric blunt-body flow of air at 7 km/s. Very good agreement is obtained for the two solutions. The two techniques also compare well for a one-dimensional shock wave in air at 10 km/s. In both applications, the results are found to be sensitive to various aspects of the chemistry models employed.

  16. Anomalous abundances of solar energetic particles and coronal gas: Coulomb effects and First Ionization Potential (FIP) ordering

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1985-01-01

    The first ionization potential (FIP) ordering of elemental abundances in solar energetic particles and in the corona which can both be explained Coulomb effects is discussed. Solar energetic particles (SEP) and coronal gas have anomalous abundances relative to the photosphere. The anomalies are similar in both cases: which led to the conclusion that SEP acceleration is not selective, but merely preserves the source abundances. It is argued that SEP acceleration can be selective, because identical selectivity operates to determine the coronal abundances. The abundance anomalies are ordered by first ionization potential (FIP).

  17. Search for metastable heavy charged particles with large ionization energy loss in p p collisions at √{s }=13 TeV using the ATLAS experiment

    NASA Astrophysics Data System (ADS)

    Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.; Abdinov, O.; Abeloos, B.; Aben, R.; Abouzeid, O. S.; Abraham, N. L.; Abramowicz, H.; Abreu, H.; Abreu, R.; Abulaiti, Y.; Acharya, B. S.; Adamczyk, L.; Adams, D. L.; Adelman, J.; Adomeit, S.; Adye, T.; Affolder, A. A.; Agatonovic-Jovin, T.; Agricola, J.; Aguilar-Saavedra, J. A.; Ahlen, S. P.; Ahmadov, F.; Aielli, G.; Akerstedt, H.; Åkesson, T. P. A.; Akimov, A. V.; Alberghi, G. L.; Albert, J.; Albrand, S.; Alconada Verzini, M. J.; Aleksa, M.; Aleksandrov, I. N.; Alexa, C.; Alexander, G.; Alexopoulos, T.; Alhroob, M.; Aliev, M.; Alimonti, G.; Alison, J.; Alkire, S. P.; Allbrooke, B. M. M.; Allen, B. W.; Allport, P. P.; Aloisio, A.; Alonso, A.; Alonso, F.; Alpigiani, C.; Alstaty, M.; Alvarez Gonzalez, B.; Álvarez Piqueras, D.; Alviggi, M. G.; Amadio, B. T.; Amako, K.; Amaral Coutinho, Y.; Amelung, C.; Amidei, D.; Amor Dos Santos, S. P.; Amorim, A.; Amoroso, S.; Amundsen, G.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, G.; Anders, J. K.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Angelidakis, S.; Angelozzi, I.; Anger, P.; Angerami, A.; Anghinolfi, F.; Anisenkov, A. V.; Anjos, N.; Annovi, A.; Antonelli, M.; Antonov, A.; Anulli, F.; Aoki, M.; Aperio Bella, L.; Arabidze, G.; Arai, Y.; Araque, J. P.; Arce, A. T. H.; Arduh, F. A.; Arguin, J.-F.; Argyropoulos, S.; Arik, M.; Armbruster, A. J.; Armitage, L. J.; Arnaez, O.; Arnold, H.; Arratia, M.; Arslan, O.; Artamonov, A.; Artoni, G.; Artz, S.; Asai, S.; Asbah, N.; Ashkenazi, A.; Åsman, B.; Asquith, L.; Assamagan, K.; Astalos, R.; Atkinson, M.; Atlay, N. B.; Augsten, K.; Avolio, G.; Axen, B.; Ayoub, M. K.; Azuelos, G.; Baak, M. A.; Baas, A. E.; Baca, M. J.; Bachacou, H.; Bachas, K.; Backes, M.; Backhaus, M.; Bagiacchi, P.; Bagnaia, P.; Bai, Y.; Baines, J. T.; Baker, O. K.; Baldin, E. M.; Balek, P.; Balestri, T.; Balli, F.; Balunas, W. K.; Banas, E.; Banerjee, Sw.; Bannoura, A. A. E.; Barak, L.; Barberio, E. L.; Barberis, D.; Barbero, M.; Barillari, T.; Barklow, T.; Barlow, N.; Barnes, S. L.; Barnett, B. M.; Barnett, R. M.; Barnovska, Z.; Baroncelli, A.; Barone, G.; Barr, A. J.; Barranco Navarro, L.; Barreiro, F.; Barreiro Guimarães da Costa, J.; Bartoldus, R.; Barton, A. E.; Bartos, P.; Basalaev, A.; Bassalat, A.; Bates, R. L.; Batista, S. J.; Batley, J. R.; Battaglia, M.; Bauce, M.; Bauer, F.; Bawa, H. S.; Beacham, J. B.; Beattie, M. D.; Beau, T.; Beauchemin, P. H.; Bechtle, P.; Beck, H. P.; Becker, K.; Becker, M.; Beckingham, M.; Becot, C.; Beddall, A. J.; Beddall, A.; Bednyakov, V. A.; Bedognetti, M.; Bee, C. P.; Beemster, L. J.; Beermann, T. A.; Begel, M.; Behr, J. K.; Belanger-Champagne, C.; Bell, A. S.; Bella, G.; Bellagamba, L.; Bellerive, A.; Bellomo, M.; Belotskiy, K.; Beltramello, O.; Belyaev, N. L.; Benary, O.; Benchekroun, D.; Bender, M.; Bendtz, K.; Benekos, N.; Benhammou, Y.; Benhar Noccioli, E.; Benitez, J.; Benjamin, D. P.; Bensinger, J. R.; Bentvelsen, S.; Beresford, L.; Beretta, M.; Berge, D.; Bergeaas Kuutmann, E.; Berger, N.; Beringer, J.; Berlendis, S.; Bernard, N. R.; Bernius, C.; Bernlochner, F. U.; Berry, T.; Berta, P.; Bertella, C.; Bertoli, G.; Bertolucci, F.; Bertram, I. A.; Bertsche, C.; Bertsche, D.; Besjes, G. J.; Bessidskaia Bylund, O.; Bessner, M.; Besson, N.; Betancourt, C.; Bethke, S.; Bevan, A. J.; Bhimji, W.; Bianchi, R. M.; Bianchini, L.; Bianco, M.; Biebel, O.; Biedermann, D.; Bielski, R.; Biesuz, N. V.; Biglietti, M.; Bilbao de Mendizabal, J.; Bilokon, H.; Bindi, M.; Binet, S.; Bingul, A.; Bini, C.; Biondi, S.; Bjergaard, D. M.; Black, C. W.; Black, J. E.; Black, K. M.; Blackburn, D.; Blair, R. E.; Blanchard, J.-B.; Blanco, J. E.; Blazek, T.; Bloch, I.; Blocker, C.; Blum, W.; Blumenschein, U.; Blunier, S.; Bobbink, G. J.; Bobrovnikov, V. S.; Bocchetta, S. S.; Bocci, A.; Bock, C.; Boehler, M.; Boerner, D.; Bogaerts, J. A.; Bogavac, D.; Bogdanchikov, A. 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R.; Suzuki, S.; Svatos, M.; Swiatlowski, M.; Sykora, I.; Sykora, T.; Ta, D.; Taccini, C.; Tackmann, K.; Taenzer, J.; Taffard, A.; Tafirout, R.; Taiblum, N.; Takai, H.; Takashima, R.; Takeshita, T.; Takubo, Y.; Talby, M.; Talyshev, A. A.; Tan, K. G.; Tanaka, J.; Tanaka, R.; Tanaka, S.; Tannenwald, B. B.; Tapia Araya, S.; Tapprogge, S.; Tarem, S.; Tartarelli, G. F.; Tas, P.; Tasevsky, M.; Tashiro, T.; Tassi, E.; Tavares Delgado, A.; Tayalati, Y.; Taylor, A. C.; Taylor, G. N.; Taylor, P. T. E.; Taylor, W.; Teischinger, F. A.; Teixeira-Dias, P.; Temming, K. K.; Temple, D.; Ten Kate, H.; Teng, P. K.; Teoh, J. J.; Tepel, F.; Terada, S.; Terashi, K.; Terron, J.; Terzo, S.; Testa, M.; Teuscher, R. J.; Theveneaux-Pelzer, T.; Thomas, J. P.; Thomas-Wilsker, J.; Thompson, E. N.; Thompson, P. D.; Thompson, A. S.; Thomsen, L. A.; Thomson, E.; Thomson, M.; Tibbetts, M. J.; Ticse Torres, R. E.; Tikhomirov, V. O.; Tikhonov, Yu. A.; Timoshenko, S.; Tipton, P.; Tisserant, S.; Todome, K.; Todorov, T.; Todorova-Nova, S.; Tojo, J.; Tokár, S.; Tokushuku, K.; Tolley, E.; Tomlinson, L.; Tomoto, M.; Tompkins, L.; Toms, K.; Tong, B.; Torrence, E.; Torres, H.; Torró Pastor, E.; Toth, J.; Touchard, F.; Tovey, D. R.; Trefzger, T.; Tricoli, A.; Trigger, I. M.; Trincaz-Duvoid, S.; Tripiana, M. F.; Trischuk, W.; Trocmé, B.; Trofymov, A.; Troncon, C.; Trottier-McDonald, M.; Trovatelli, M.; Truong, L.; Trzebinski, M.; Trzupek, A.; Tseng, J. C.-L.; Tsiareshka, P. V.; Tsipolitis, G.; Tsirintanis, N.; Tsiskaridze, S.; Tsiskaridze, V.; Tskhadadze, E. G.; Tsui, K. M.; Tsukerman, I. I.; Tsulaia, V.; Tsuno, S.; Tsybychev, D.; Tudorache, A.; Tudorache, V.; Tuna, A. N.; Tupputi, S. A.; Turchikhin, S.; Turecek, D.; Turgeman, D.; Turra, R.; Turvey, A. J.; Tuts, P. M.; Tyndel, M.; Ucchielli, G.; Ueda, I.; Ueno, R.; Ughetto, M.; Ukegawa, F.; Unal, G.; Undrus, A.; Unel, G.; Ungaro, F. C.; Unno, Y.; Unverdorben, C.; Urban, J.; Urquijo, P.; Urrejola, P.; Usai, G.; Usanova, A.; Vacavant, L.; Vacek, V.; Vachon, B.; Valderanis, C.; Valdes Santurio, E.; Valencic, N.; Valentinetti, S.; Valero, A.; Valery, L.; Valkar, S.; Vallecorsa, S.; Valls Ferrer, J. A.; van den Wollenberg, W.; van der Deijl, P. C.; van der Geer, R.; van der Graaf, H.; van Eldik, N.; van Gemmeren, P.; van Nieuwkoop, J.; van Vulpen, I.; van Woerden, M. C.; Vanadia, M.; Vandelli, W.; Vanguri, R.; Vaniachine, A.; Vankov, P.; Vardanyan, G.; Vari, R.; Varnes, E. W.; Varol, T.; Varouchas, D.; Vartapetian, A.; Varvell, K. E.; Vasquez, J. G.; Vazeille, F.; Vazquez Schroeder, T.; Veatch, J.; Veloce, L. M.; Veloso, F.; Veneziano, S.; Ventura, A.; Venturi, M.; Venturi, N.; Venturini, A.; Vercesi, V.; Verducci, M.; Verkerke, W.; Vermeulen, J. C.; Vest, A.; Vetterli, M. C.; Viazlo, O.; Vichou, I.; Vickey, T.; Vickey Boeriu, O. E.; Viehhauser, G. H. A.; Viel, S.; Vigani, L.; Vigne, R.; Villa, M.; Villaplana Perez, M.; Vilucchi, E.; Vincter, M. G.; Vinogradov, V. B.; Vittori, C.; Vivarelli, I.; Vlachos, S.; Vlasak, M.; Vogel, M.; Vokac, P.; Volpi, G.; Volpi, M.; von der Schmitt, H.; von Toerne, E.; Vorobel, V.; Vorobev, K.; Vos, M.; Voss, R.; Vossebeld, J. H.; Vranjes, N.; Vranjes Milosavljevic, M.; Vrba, V.; Vreeswijk, M.; Vuillermet, R.; Vukotic, I.; Vykydal, Z.; Wagner, P.; Wagner, W.; Wahlberg, H.; Wahrmund, S.; Wakabayashi, J.; Walder, J.; Walker, R.; Walkowiak, W.; Wallangen, V.; Wang, C.; Wang, C.; Wang, F.; Wang, H.; Wang, H.; Wang, J.; Wang, J.; Wang, K.; Wang, R.; Wang, S. M.; Wang, T.; Wang, T.; Wang, W.; Wang, X.; Wanotayaroj, C.; Warburton, A.; Ward, C. P.; Wardrope, D. R.; Washbrook, A.; Watkins, P. M.; Watson, A. T.; Watson, M. F.; Watts, G.; Watts, S.; Waugh, B. M.; Webb, S.; Weber, M. S.; Weber, S. W.; Webster, J. S.; Weidberg, A. R.; Weinert, B.; Weingarten, J.; Weiser, C.; Weits, H.; Wells, P. S.; Wenaus, T.; Wengler, T.; Wenig, S.; Wermes, N.; Werner, M.; Werner, P.; Wessels, M.; Wetter, J.; Whalen, K.; Whallon, N. L.; Wharton, A. M.; White, A.; White, M. J.; White, R.; Whiteson, D.; Wickens, F. J.; Wiedenmann, W.; Wielers, M.; Wienemann, P.; Wiglesworth, C.; Wiik-Fuchs, L. A. M.; Wildauer, A.; Wilk, F.; Wilkens, H. G.; Williams, H. H.; Williams, S.; Willis, C.; Willocq, S.; Wilson, J. A.; Wingerter-Seez, I.; Winklmeier, F.; Winston, O. J.; Winter, B. T.; Wittgen, M.; Wittkowski, J.; Wollstadt, S. J.; Wolter, M. W.; Wolters, H.; Wosiek, B. K.; Wotschack, J.; Woudstra, M. J.; Wozniak, K. W.; Wu, M.; Wu, M.; Wu, S. L.; Wu, X.; Wu, Y.; Wyatt, T. R.; Wynne, B. M.; Xella, S.; Xu, D.; Xu, L.; Yabsley, B.; Yacoob, S.; Yakabe, R.; Yamaguchi, D.; Yamaguchi, Y.; Yamamoto, A.; Yamamoto, S.; Yamanaka, T.; Yamauchi, K.; Yamazaki, Y.; Yan, Z.; Yang, H.; Yang, H.; Yang, Y.; Yang, Z.; Yao, W.-M.; Yap, Y. C.; Yasu, Y.; Yatsenko, E.; Yau Wong, K. H.; Ye, J.; Ye, S.; Yeletskikh, I.; Yen, A. L.; Yildirim, E.; Yorita, K.; Yoshida, R.; Yoshihara, K.; Young, C.; Young, C. J. S.; Youssef, S.; Yu, D. R.; Yu, J.; Yu, J. M.; Yu, J.; Yuan, L.; Yuen, S. P. Y.; Yusuff, I.; Zabinski, B.; Zaidan, R.; Zaitsev, A. M.; Zakharchuk, N.; Zalieckas, J.; Zaman, A.; Zambito, S.; Zanello, L.; Zanzi, D.; Zeitnitz, C.; Zeman, M.; Zemla, A.; Zeng, J. C.; Zeng, Q.; Zengel, K.; Zenin, O.; Ženiš, T.; Zerwas, D.; Zhang, D.; Zhang, F.; Zhang, G.; Zhang, H.; Zhang, J.; Zhang, L.; Zhang, R.; Zhang, R.; Zhang, X.; Zhang, Z.; Zhao, X.; Zhao, Y.; Zhao, Z.; Zhemchugov, A.; Zhong, J.; Zhou, B.; Zhou, C.; Zhou, L.; Zhou, L.; Zhou, M.; Zhou, N.; Zhu, C. G.; Zhu, H.; Zhu, J.; Zhu, Y.; Zhuang, X.; Zhukov, K.; Zibell, A.; Zieminska, D.; Zimine, N. I.; Zimmermann, C.; Zimmermann, S.; Zinonos, Z.; Zinser, M.; Ziolkowski, M.; Živković, L.; Zobernig, G.; Zoccoli, A.; Zur Nedden, M.; Zurzolo, G.; Zwalinski, L.; Atlas Collaboration

    2016-06-01

    This paper presents a search for massive charged long-lived particles produced in p p collisions at √{s }=13 TeV at the LHC using the ATLAS experiment. The data set used corresponds to an integrated luminosity of 3.2 fb-1. Many extensions of the Standard Model predict the existence of massive charged long-lived particles, such as R -hadrons. These massive particles are expected to be produced with a velocity significantly below the speed of light, and therefore to have a specific ionization higher than any Standard Model particle of unit charge at high momenta. The Pixel subsystem of the ATLAS detector is used to measure the ionization energy loss of reconstructed charged particles and to search for such highly ionizing particles. The search presented here has much greater sensitivity than a similar search performed using the ATLAS detector in the √{s }=8 TeV data set, thanks to the increase in expected signal cross section due to the higher center-of-mass energy of collisions, to an upgraded detector with a new silicon layer close to the interaction point, and to analysis improvements. No significant deviation from Standard Model background expectations is observed, and lifetime-dependent upper limits on R -hadron production cross sections and masses are set. Gluino R -hadrons with lifetimes above 0.4 ns and decaying to q q ¯ plus a 100 GeV neutralino are excluded at the 95% confidence level, with lower mass limit ranging between 740 and 1590 GeV. In the case of stable R -hadrons the lower mass limit at the 95% confidence level is 1570 GeV.

  18. Laser Desorption Ionization of small molecules assisted by Tungsten oxide and Rhenium oxide particles

    PubMed Central

    Bernier, Matthew; Wysocki, Vicki; Dagan, Shai

    2015-01-01

    Inorganic metal oxides have shown potential as matrices for assisting in laser desorption ionization (LDI) with advantages over the aromatic acids typically used. Rhenium and tungsten oxides are an attractive option due to their high work functions and relative chemical inertness. In this work, it is shown that ReO3 and WO3, in microparticle (μP) powder forms, can efficiently ionize various types of small molecules and provide minimized background contamination at analyte concentrations below 1 ng/μL. This study shows that untreated inorganic WO3 and ReO3 particles are valid matrix options for detection of protonatable, radical, and precharged species under LDI. Qualitatively, the WO3 μP showed an improved detection of apigenin, sodiated glucose, and the precharged analyte choline, while the ReO3 μP allowed detection of protonated cocaine, quinuclidine, ametryn, and radical ions of polyaromatic hydrocarbons at detection levels as low as 50 pg/μL. For thermometer ion survival yield experiments, it was also shown that the ReO3 powder was significantly softer than CCA. Furthermore, it provided higher intensities of cocaine and polyaromatic hydrocarbons, at laser flux values equal to that used with CCA. PMID:26349643

  19. Energy-Dependent Ionization States of Shock-Accelerated Particles in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Reames, Donald V.; Ng, C. K.; Tylka, A. J.

    2000-01-01

    We examine the range of possible energy dependence of the ionization states of ions that are shock-accelerated from the ambient plasma of the solar corona. If acceleration begins in a region of moderate density, sufficiently low in the corona, ions above about 0.1 MeV/amu approach an equilibrium charge state that depends primarily upon their speed and only weakly on the plasma temperature. We suggest that the large variations of the charge states with energy for ions such as Si and Fe observed in the 1997 November 6 event are consistent with stripping in moderately dense coronal. plasma during shock acceleration. In the large solar-particle events studied previously, acceleration occurs sufficiently high in the corona that even Fe ions up to 600 MeV/amu are not stripped of electrons.

  20. Forest canopy interactions with nucleation mode particles

    NASA Astrophysics Data System (ADS)

    Pryor, S. C.; Hornsby, K. E.; Novick, K. A.

    2014-11-01

    Ultrafine particle size distributions through a deciduous forest canopy indicate that nucleation mode particle concentrations decline with depth into the canopy, such that number concentrations at the bottom of the canopy are an average of 16% lower than those at the top. However, growth rates of nucleation mode particles (diameters 6-30 nm) are invariant with height within the canopy, which implies that the semi-volatile gases contributing to their growth are comparatively well-mixed through the canopy. Growth rates of nucleation mode particles during a meteorological drought year (2012) were substantially lower than during a meteorologically normal year with high soil water potential (2013). This may reflect suppression of actual biogenic volatile organic compound (BVOC) emissions by drought and thus a reduction in the production of condensable products during the drought-affected vegetation season. This hypothesis is supported by evidence that growth rates during the normal year exhibit a positive correlation with emissions of BVOC modeled on observed forest composition, leaf area index, temperature and photosynthetically active radiation (PAR), but particle growth rates during the drought-affected vegetation season are not correlated with modeled BVOC emissions. These data thus provide indirect evidence that drought stress in forests may reduce BVOC emissions and limit growth of nucleation mode particles to climate-relevant sizes.

  1. Particle-particle interactions in electrorheological fluids based on surface conducting particles

    NASA Astrophysics Data System (ADS)

    Gonon, P.; Foulc, J.-N.; Atten, P.; Boissy, C.

    1999-12-01

    We develop a simple, analytical conduction model for the case of electrorheological fluids based on surface conducting particles. By modeling two contacting spheres in a dielectric liquid by a distributed impedances network we derive analytical expressions for the potential and current at the spheres surface, and for the electric field and the current in the liquid phase. The knowledge of the electric field in the dielectric liquid allows us to calculate the interparticle interaction force as a function of the applied voltage. The theoretical interaction force is compared with experimental results obtained on insulating spheres coated with a thin conducting polyaniline film. We find a good agreement between the theory and experiment. The materials properties which govern the response of the system are outlined. In this regard, the product of the liquid conductivity by the sheet resistance of the surface coating appears as a key parameter. Some applications of this model for the practical design of electrorheological fluids are given.

  2. Waves, particles, and interactions in reduced dimensions

    NASA Astrophysics Data System (ADS)

    Zhang, Yiming

    This thesis presents a set of experiments that study the interplay between the wave-particle duality of electrons and the interaction effects in systems of reduced dimensions. Both dc transport and measurements of current noise have been employed in the studies; in particular, techniques for efficiently measuring current noise have been developed specifically for these experiments. The first four experiments study current noise auto- and cross correlations in various mesoscopic devices, including quantum point contacts, single and double quantum dots, and graphene devices. In quantum point contacts, shot noise at zero magnetic field exhibits an asymmetry related to the 0.7 structure in conductance. The asymmetry in noise evolves smoothly into the symmetric signature of spin-resolved electron transmission at high field. Comparison to a phenomenological model with density-dependent level splitting yields good quantitative agreement. Additionally, a device-specific contribution to the finite-bias noise, particularly visible on conductance plateaus where shot noise vanishes, agrees with a model of bias-dependent electron heating. In a three-lead single quantum dot and a capacitively coupled double quantum dot, sign reversal of noise cross correlations have been observed in the Coulomb blockade regime, and found to be tunable by gate voltages and source-drain bias. In the limit of weak output tunneling, cross correlations in the three-lead dot are found to be proportional to the two-lead noise in excess of the Poissonian value. These results can be reproduced with master equation calculations that include multi-level transport in the single dot, and inter-dot charging energy in the double dot. Shot noise measurements in single-layer graphene devices reveal a Fano factor independent of carrier type and density, device geometry, and the presence of a p-n junction. This result contrasts with theory for ballistic graphene sheets and junctions, suggesting that the transport

  3. Significance of Wave-Particle Interaction Analyzer for direct measurement of nonlinear wave-particle interactions

    NASA Astrophysics Data System (ADS)

    Katoh, Y.; Kitahara, M.; Kojima, H.; Omura, Y.; Kasahara, S.; Hirahara, M.; Miyoshi, Y.; Seki, K.; Asamura, K.; Takashima, T.

    2012-12-01

    We study the statistical significance of the Wave Particle Interaction Analyzer (WPIA) for measurement of the energy transfer process between energetic electrons and whistler-mode chorus emissions in the Earth's inner magnetosphere. The WPIA measures a relative phase angle between the wave vector and velocity vector of each particle and computes an inner product W(t), while W(t) is equivalent to the variation of the kinetic energy of energetic electrons interacting with plasma waves. The WPIA measurements will be realized by the Software-type WPIA in the SPRINT-B/ERG satellite mission. In the present study, we evaluate the feasibility of WPIA by applying the WPIA analysis to the simulation results on whistler-mode chorus generation. We compute W(t) of a wave electric field observed at a fixed point assumed in the simulation system and a velocity vector of each energetic electron passing through the assumed point. By integrating W(t) in time, we obtain significant values of W_{int} in the kinetic energy and pitch angle ranges as expected from the evolution of chorus emissions in the simulation result. The statistical significance of the obtained W_{int} is evaluated by calculating the standard deviation σ_W of W_{int}. We show that W_{int} greater than σ_W is obtained in the velocity phase space corresponding to the wave generation and acceleration of relativistic electrons. We conduct another analysis of a distribution of energetic electrons in the wave phase space using the same dataset of the simulation results. We clarify that the deviation of the distribution in the wave phase space is found in the velocity phase space corresponding to the large W_{int} values, which is consistent with formation of nonlinear resonant currents assumed in the generation mechanism of chorus emissions. The present study suggests that the statistical significance of the WPIA can be evaluated by calculating σ_W of W_{int}, and reveals the feasibility of the WPIA, which will be on

  4. Optimization of microchannel plate multipliers for tracking minimum-ionizing particles

    SciTech Connect

    Oba, K.; Rehak, P.; Potter, D.

    1981-01-01

    The progress in development of special Microchannel Plates for particle tracking is reported. The requirements of (1) high spatial resolution; (2) high density of information; and (3) rate capability were found to be satisfied in a thick Microchannel Plate with a CsI coating operating in a focusing magnetic field. The measurements of the Microchannel Plate detection efficiency, gain and noise are presented for several detectors. The pictures of the passage and interaction of the high energy charged particles inside the detector are shown.

  5. Mean-field approach for diffusion of interacting particles.

    PubMed

    Suárez, G; Hoyuelos, M; Mártin, H

    2015-12-01

    A nonlinear Fokker-Planck equation is obtained in the continuous limit of a one-dimensional lattice with an energy landscape of wells and barriers. Interaction is possible among particles in the same energy well. A parameter γ, related to the barrier's heights, is introduced. Its value is determinant for the functional dependence of the mobility and diffusion coefficient on particle concentration, but has no influence on the equilibrium solution. A relation between the mean-field potential and the microscopic interaction energy is derived. The results are illustrated with classical particles with interactions that reproduce fermion and boson statistics. PMID:26764643

  6. Improved hydrogen ionization rate in enhanced glow discharge plasma immersion ion implantation by enlarging the interaction path using an insulating tube

    SciTech Connect

    Wang Zhuo; Zhu Ying; Li Liuhe; He Fushun; Dun Dandan; Li Fen; Lu Qiuyuan; Fu, Ricky K. Y.; Chu, Paul K.

    2011-02-15

    A small pointed hollow anode and large tabular cathode are used in enhanced glow discharge plasma immersion ion implantation (EGD-PIII). Electrons are repelled from the substrate by the electric field formed by the negative voltage pulses and concentrate in the vicinity of the anode to enhance the self-glow discharge process. To extend the application of EGD-PIII to plasma gases with low ionization rates, an insulating tube is used to increase the interaction path for electrons and neutrals in order to enhance the discharge near the anode. Results obtained from numerical simulation based on the particle-in-cell code, finite element method, and experiments show that this configuration enhances the ionization rate and subsequent ion implant fluence. The process is especially suitable for gases that have low ionization rates such as hydrogen and helium.

  7. Particle interaction measurements using laser tweezers optical trapping.

    SciTech Connect

    Koehler, Timothy P.; Brinker, C. Jeffrey; Brotherton, Christopher M.; Grillet, Anne M.; Molecke, Ryan A.

    2008-08-01

    Laser tweezers optical trapping provides a unique noninvasive capability to trap and manipulate particles in solution at the focal point of a laser beam passed through a microscope objective. Additionally, combined with image analysis, interaction forces between colloidal particles can be quantitatively measured. By looking at the displacement of particles within the laser trap due to the presence of a neighboring particle or looking at the relative diffusion of two particles held near each other by optical traps, interparticle interaction forces ranging from pico- to femto-Newtons can be measured. Understanding interaction forces is critical for predicting the behavior of particle dispersions including dispersion stability and flow rheology. Using a new analysis method proposed by Sainis, Germain, and Dufresne, we can simultaneously calculate the interparticle velocity and particle diffusivity which allows direct calculation of the interparticle potential for the particles. By applying this versatile tool, we measure difference in interactions between various phospholipid bilayers that have been coated onto silica spheres as a new type of solid supported liposome. We measure bilayer interactions of several cell membrane lipids under various environmental conditions such as pH and ionic strength and compare the results with those obtained for empty liposomes. These results provide insight into the role of bilayer fluctuations in liposome fusion, which is of fundamental interest to liposome based drug delivery schemes.

  8. Continuum modeling of hydrodynamic particle-particle interactions in microfluidic high-concentration suspensions.

    PubMed

    Ley, Mikkel W H; Bruus, Henrik

    2016-03-23

    A continuum model is established for numerical studies of hydrodynamic particle-particle interactions in microfluidic high-concentration suspensions. A suspension of microparticles placed in a microfluidic channel and influenced by an external force, is described by a continuous particle-concentration field coupled to the continuity and Navier-Stokes equation for the solution. The hydrodynamic interactions are accounted for through the concentration dependence of the suspension viscosity, of the single-particle mobility, and of the momentum transfer from the particles to the suspension. The model is applied on a magnetophoretic and an acoustophoretic system, respectively, and based on the results, we illustrate three main points: (1) for relative particle-to-fluid volume fractions greater than 0.01, the hydrodynamic interaction effects become important through a decreased particle mobility and an increased suspension viscosity. (2) At these high particle concentrations, particle-induced flow rolls occur, which can lead to significant deviations of the advective particle transport relative to that of dilute suspensions. (3) Which interaction mechanism that dominates, depends on the specific flow geometry and the specific external force acting on the particles. PMID:26948344

  9. Particle dynamics in fluids with random interactions.

    PubMed

    Shagolsem, Lenin S; Rabin, Yitzhak

    2016-05-21

    We study the dynamics of particles in a multi-component 2d Lennard-Jones (LJ) fluid in the limiting case where all the particles are different (APD). The equilibrium properties of this APD system were studied in our earlier work [L. S. Shagolsem et al., J. Chem. Phys. 142, 051104 (2015).]. We use molecular dynamics simulations to investigate the statistical properties of particle trajectories in a temperature range covering both the fluid and the solid-fluid coexistence region. We calculate the mean-square displacement as well as displacement, angle, and waiting time distributions, and compare the results with those for one-component LJ fluid. As temperature is lowered, the dynamics of the APD system becomes increasingly complex, as the intrinsic difference between the particles is amplified by neighborhood identity ordering and by the inhomogeneous character of the solid-fluid coexistence region. The ramifications of our results for the analysis of protein tracking experiments in living cells are discussed. PMID:27208955

  10. Particle dynamics in fluids with random interactions

    NASA Astrophysics Data System (ADS)

    Shagolsem, Lenin S.; Rabin, Yitzhak

    2016-05-01

    We study the dynamics of particles in a multi-component 2d Lennard-Jones (LJ) fluid in the limiting case where all the particles are different (APD). The equilibrium properties of this APD system were studied in our earlier work [L. S. Shagolsem et al., J. Chem. Phys. 142, 051104 (2015).]. We use molecular dynamics simulations to investigate the statistical properties of particle trajectories in a temperature range covering both the fluid and the solid-fluid coexistence region. We calculate the mean-square displacement as well as displacement, angle, and waiting time distributions, and compare the results with those for one-component LJ fluid. As temperature is lowered, the dynamics of the APD system becomes increasingly complex, as the intrinsic difference between the particles is amplified by neighborhood identity ordering and by the inhomogeneous character of the solid-fluid coexistence region. The ramifications of our results for the analysis of protein tracking experiments in living cells are discussed.

  11. Nuclear gamma rays from energetic particle interactions

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Kozlovsky, B.; Lingenfelter, R. E.

    1978-01-01

    Gamma ray line emission from nuclear deexcitation following energetic particle reactions is evaluated. The compiled nuclear data and the calculated gamma ray spectra and intensities can be used for the study of astrophysical sites which contain large fluxes of energetic protons and nuclei. A detailed evaluation of gamma ray line production in the interstellar medium is made.

  12. Dust particle charge screening in the dry-air plasma produced by an external ionization source

    SciTech Connect

    Derbenev, I. N.; Filippov, A. V.

    2015-08-15

    The ionic composition of the plasma produced by an external ionization source in dry air at atmospheric pressure and room temperature and the screening of the electric field of a dust particle in such a plasma have been investigated. The point sink model based on the diffusion-drift approximation has been used to solve the screening problem. We have established that the main species of ions in the plasma under consideration are O{sub 4}{sup +}, O{sub 2}{sup -}, and O{sub 4}{sup -} and that the dust particle potential distribution is described by a superposition of four exponentials with four different constants. We show that the first constant coincides with the inverse Debye length, the second is described by the inverse ambipolar diffusion length of the positive and negative plasma components in the characteristic time of their recombination, the third is determined by the conversion of negative ions, and the fourth is determined by the attachment and recombination of electrons and diatomic ions.

  13. DNA Damage by Ionizing Radiation: Tandem Double Lesions by Charged Particles

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Chaban, Galina M.; Wang, Dunyou; Dateo, Christopher E.

    2005-01-01

    Oxidative damages by ionizing radiation are the source of radiation-induced carcinogenesis, damage to the central nervous system, lowering of the immune response, as well as other radiation-induced damages to human health. Monte Carlo track simulations and kinetic modeling of radiation damages to the DNA employ available molecular and cellular data to simulate the biological effect of high and low LET radiation io the DNA. While the simulations predict single and double strand breaks and base damages, so far all complex lesions are the result of stochastic coincidence from independent processes. Tandem double lesions have not yet been taken into account. Unlike the standard double lesions that are produced by two separate attacks by charged particles or radicals, tandem double lesions are produced by one single attack. The standard double lesions dominate at the high dosage regime. On the other hand, tandem double lesions do not depend on stochastic coincidences and become important at the low dosage regime of particular interest to NASA. Tandem double lesions by hydroxyl radical attack of guanine in isolated DNA have been reported at a dosage of radiation as low as 10 Gy. The formation of two tandem base lesions was found to be linear with the applied doses, a characteristic of tandem lesions. However, tandem double lesions from attack by a charged particle have not been reported.

  14. Interactions of non-spherical particles in simple flows

    NASA Astrophysics Data System (ADS)

    Niazi, Mehdi; Brandt, Luca; Costa, Pedro; Breugem, Wim-Paul

    2015-11-01

    The behavior of particles in a flow affects the global transport and rheological properties of the mixture. In recent years much effort has been therefore devoted to the development of an efficient method for the direct numerical simulation (DNS) of the motion of spherical rigid particles immersed in an incompressible fluid. However, the literature on non-spherical particle suspensions is quite scarce despite the fact that these are more frequent. We develop a numerical algorithm to simulate finite-size spheroid particles in shear flows to gain new understanding of the flow of particle suspensions. In particular, we wish to understand the role of inertia and its effect on the flow behavior. For this purpose, DNS simulations with a direct-forcing immersed boundary method are used, with collision and lubrication models for particle-particle and particle-wall interactions. We will discuss pair interactions, relative motion and rotation, of two sedimenting spheroids and show that the interaction time increases significantly for non-spherical particles. More interestingly, we show that the particles are attracted to each other from larger lateral displacements. This has important implications for collision kernels. This work was supported by the European Research Council Grant No. ERC-2013-CoG-616186, TRITOS, and by the Swedish Research Council (VR).

  15. Improved cosmic ray ionization model for the system lower ionosphere-middle atmosphere. Determination of approximation energy interval characteristics for the particle penetration

    NASA Astrophysics Data System (ADS)

    Velinov, Peter; Mateev, Lachezar

    The effects of galactic and solar cosmic rays (CRs) in the middle atmosphere are considered in this work. We take into account the CR modulation by solar wind and the anomalous CR component also. In fact, CRs determine the electric conductivity in the middle atmosphere and influence the electric processes in it in this way. CRs introduce solar variability in the terrestrial atmosphere and ozonosphere -because they are modulated by solar wind. A new analytical approach for CR ionization by protons and nuclei with charge Z in the lower ionosphere and the middle atmosphere is developed in this paper. For this purpose, the ionization losses (dE/dh) for the energetic charged particles according to the Bohr-Bethe-Bloch formula are approximated in three different energy intervals. More accurate expressions for CR energy decrease E(h) and electron production rate profiles q(h) are derived. The obtained formulas allow comparatively easy computer programming. q(h) is determined by the solution of a 3D integral with account of geomagnetic cut-off rigidity. The integrand in q(h) gives the possibility for application of adequate numerical methods -in this case Gauss quadrature and Romberg extrapolation, for the solution of the mathematical problem. Computations for CR ionization in the middle atmosphere are made. The contributions of the different approximation energy intervals are presented. In this way the process of interaction of CR particles with the upper and middle atmosphere are described much more realistically. The full CR composition is taken into account: protons, helium (alpha-particles), light L, medium M, heavy H and very heavy VH group of nuclei. The computations are made for different geomagnetic cut-off rigidities R in the altitude interval 35-120 km. The COSPAR International Reference Atmosphere CIRA'86 is applied in the computer program for the neutral density and scale height values. The proposed improved CR ionization model will contribute to the

  16. Controlling chaos in wave-particle interactions.

    PubMed

    de Sousa, M C; Caldas, I L; Rizzato, F B; Pakter, R; Steffens, F M

    2012-07-01

    We analyze the behavior of a relativistic particle moving under the influence of a uniform magnetic field and a stationary electrostatic wave. We work with a set of pulsed waves that allows us to obtain an exact map for the system. We also use a method of control for near-integrable Hamiltonians that consists of the addition of a small and simple control term to the system. This control term creates invariant tori in phase space that prevent chaos from spreading to large regions, making the controlled dynamics more regular. We show numerically that the control term just slightly modifies the system but is able to drastically reduce chaos with a low additional cost of energy. Moreover, we discuss how the control of chaos and the consequent recovery of regular trajectories in phase space are useful to improve regular particle acceleration. PMID:23005517

  17. INTERACTIONS OF SILICA PARTICLES IN DRINKING WATER TREATMENT PROCESSES

    EPA Science Inventory

    EPA Identifier: U915331
    Title: Interactions of Silica Particles in Drinking Water Treatment Processes
    Fellow (Principal Investigator): Christina L. Clarkson
    Institution: Virginia Polytechnic Institute and State University
    EPA GRANT R...

  18. Cosmological constraints on the properties of weakly interacting massive particles

    SciTech Connect

    Steigman, G.; Turner, M.S.

    1984-10-01

    Considerations of the age and density of, as well as the evolution of structure in, the Universe lead to constraints on the masses and lifetimes of weakly interacting massive particles (WIMPs). 26 references.

  19. Dust particles interaction with plasma jet

    SciTech Connect

    Ticos, C. M.; Jepu, I.; Lungu, C. P.; Chiru, P.; Zaroschi, V.

    2009-11-10

    The flow of plasma and particularly the flow of ions play an important role in dusty plasmas. Here we present some instances in laboratory experiments where the ion flow is essential in establishing dust dynamics in strongly or weakly coupled dust particles. The formation of ion wake potential and its effect on the dynamics of dust crystals, or the ion drag force exerted on micron size dust grains are some of the phenomena observed in the presented experiments.

  20. Particle-in-cell simulations of the critical ionization velocity effect in finite size clouds

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Lu, G.; Goertz, C. K.; Nishikawa, K. - I.

    1994-01-01

    The critical ionization velocity (CIV) mechanism in a finite size cloud is studied with a series of electrostatic particle-in-cell simulations. It is observed that an initial seed ionization, produced by non-CIV mechanisms, generates a cross-field ion beam which excites a modified beam-plasma instability (MBPI) with frequency in the range of the lower hybrid frequency. The excited waves accelerate electrons along the magnetic field up to the ion drift energy that exceeds the ionization energy of the neutral atoms. The heated electrons in turn enhance the ion beam by electron-neutral impact ionization, which establishes a positive feedback loop in maintaining the CIV process. It is also found that the efficiency of the CIV mechanism depends on the finite size of the gas cloud in the following ways: (1) Along the ambient magnetic field the finite size of the cloud, L (sub parallel), restricts the growth of the fastest growing mode, with a wavelength lambda (sub m parallel), of the MBPI. The parallel electron heating at wave saturation scales approximately as (L (sub parallel)/lambda (sub m parallel)) (exp 1/2); (2) Momentum coupling between the cloud and the ambient plasma via the Alfven waves occurs as a result of the finite size of the cloud in the direction perpendicular to both the ambient magnetic field and the neutral drift. This reduces exponentially with time the relative drift between the ambient plasma and the neutrals. The timescale is inversely proportional to the Alfven velocity. (3) The transvers e charge separation field across the cloud was found to result in the modulation of the beam velocity which reduces the parallel heating of electrons and increases the transverse acceleration of electrons. (4) Some energetic electrons are lost from the cloud along the magnetic field at a rate characterized by the acoustic velocity, instead of the electron thermal velocity. The loss of energetic electrons from the cloud seems to be larger in the direction of

  1. Multireference configuration interaction calculations of the first six ionization potentials of the uranium atom

    SciTech Connect

    Bross, David H.; Parmar, Payal; Peterson, Kirk A.

    2015-11-14

    The first 6 ionization potentials (IPs) of the uranium atom have been calculated using multireference configuration interaction (MRCI+Q) with extrapolations to the complete basis set limit using new all-electron correlation consistent basis sets. The latter was carried out with the third-order Douglas-Kroll-Hess Hamiltonian. Correlation down through the 5s5p5d electrons has been taken into account, as well as contributions to the IPs due to the Lamb shift. Spin-orbit coupling contributions calculated at the 4-component Kramers restricted configuration interaction level, as well as the Gaunt term computed at the Dirac-Hartree-Fock level, were added to the best scalar relativistic results. The final ionization potentials are expected to be accurate to at least 5 kcal/mol (0.2 eV) and thus more reliable than the current experimental values of IP{sub 3} through IP{sub 6}.

  2. Fundamental Particles and Interactions. A Wall Chart of Modern Physics.

    ERIC Educational Resources Information Center

    Achor, William T.; And Others

    1988-01-01

    Discusses a wall chart, "The Standard Model of Fundamental Particles and Interactions," for use in introductory physics courses at either high school or college level. Describes the chart development process, introduction and terminology of particle physics, components of the chart, and suggestions for using the chart, booklet, and software. (YP)

  3. Effective field theory of thermal Casimir interactions between anisotropic particles.

    PubMed

    Haussman, Robert C; Deserno, Markus

    2014-06-01

    We employ an effective field theory (EFT) approach to study thermal Casimir interactions between objects bound to a fluctuating fluid surface or interface dominated by surface tension, with a focus on the effects of particle anisotropy. The EFT prescription disentangles the constraints imposed by the particles' boundaries from the calculation of the interaction free energy by constructing an equivalent point particle description. The finite-size information is captured in a derivative expansion that encodes the particles' response to external fields. The coefficients of the expansion terms correspond to generalized tensorial polarizabilities and are found by matching the results of a linear response boundary value problem computed in both the full and effective theories. We demonstrate the versatility of the EFT approach by constructing the general effective Hamiltonian for a collection of particles of arbitrary shapes. Taking advantage of the conformal symmetry of the Hamiltonian, we discuss a straightforward conformal mapping procedure to systematically determine the polarizabilities and derive a complete description for elliptical particles. We compute the pairwise interaction energies to several orders for nonidentical ellipses as well as their leading-order triplet interactions and discuss the resulting preferred pair and multibody configurations. Furthermore, we elaborate on the complications that arise with pinned particle boundary conditions and show that the powerlike corrections expected from dimensional analysis are exponentially suppressed by the leading-order interaction energies. PMID:25019720

  4. Effective field theory of thermal Casimir interactions between anisotropic particles

    NASA Astrophysics Data System (ADS)

    Haussman, Robert C.; Deserno, Markus

    2014-06-01

    We employ an effective field theory (EFT) approach to study thermal Casimir interactions between objects bound to a fluctuating fluid surface or interface dominated by surface tension, with a focus on the effects of particle anisotropy. The EFT prescription disentangles the constraints imposed by the particles' boundaries from the calculation of the interaction free energy by constructing an equivalent point particle description. The finite-size information is captured in a derivative expansion that encodes the particles' response to external fields. The coefficients of the expansion terms correspond to generalized tensorial polarizabilities and are found by matching the results of a linear response boundary value problem computed in both the full and effective theories. We demonstrate the versatility of the EFT approach by constructing the general effective Hamiltonian for a collection of particles of arbitrary shapes. Taking advantage of the conformal symmetry of the Hamiltonian, we discuss a straightforward conformal mapping procedure to systematically determine the polarizabilities and derive a complete description for elliptical particles. We compute the pairwise interaction energies to several orders for nonidentical ellipses as well as their leading-order triplet interactions and discuss the resulting preferred pair and multibody configurations. Furthermore, we elaborate on the complications that arise with pinned particle boundary conditions and show that the powerlike corrections expected from dimensional analysis are exponentially suppressed by the leading-order interaction energies.

  5. Origin of particle accumulation structures in liquid bridges: Particle-boundary-interactions versus inertia

    NASA Astrophysics Data System (ADS)

    Muldoon, Frank H.; Kuhlmann, Hendrik C.

    2016-07-01

    The formation of particle-accumulation structures in the flow in a cylindrical liquid bridge driven by the thermocapillary effect is studied with the aim of determining the physical mechanism which forms the structures. The flow is modeled using the incompressible Navier-Stokes and energy equations with the assumption of constant fluid properties except for surface tension, which is assumed to depend linearly on temperature. Different models for the motion of small non-interacting spherical particles at low concentration are employed, taking into account particle inertia due to density differences between fluid and particles and the restricted particle motion near the boundaries of the flow domain. Attention is focused on differences in formation time between particle-accumulation structures arising as a result of inertial effects only, particle-boundary-interaction effects only, and a combination of the two.

  6. Particle Interactions in DNA-laden Flows

    SciTech Connect

    Bybee, M D; Miller, G H; Trebotich, D

    2005-12-20

    Microfluidic devices are becoming state-of-the-art in many significant applications including pathogen detection, continuous monitoring, and drug delivery. Numerical algorithms which can simulate flows of complex fluids within these devices are needed for their development and optimization. A method is being developed at LLNL by Trebotich et. al. [30] for simulations of DNA-laden flows in complex microscale geometries such as packed bed reactors and pillar chips. In this method an incompressible Newtonian fluid is discretized with Cartesian grid embedded boundary methods, and the DNA is represented by a bead-rod polymer model. The fluid and polymer are coupled through a body force. In its current state, polymer-surface interactions are treated as elastic collisions between beads and surface, and polymer-polymer interactions are neglected. Implementation of polymer-polymer interactions is the main objective of this work. It is achieved by two methods: (1) a rigid constraint whereby rods elastically bounce off one another, and (2) a smooth potential acting between rods. In addition, a smooth potential is also implemented for the polymer-surface interactions. Background information will also be presented as well as related work by other researchers.

  7. Theoretical and observational analysis of individual ionizing particle effects in biological tissue

    SciTech Connect

    Nelson, A.C.

    1980-11-01

    The microstructural damage to living tissue caused by heavy ion radiation was studied. Preliminary tests on rat corneal tissue, rat cerebellar tissue grown in culture, and rat retinal tissue indicated that the best assay for heavy ion damage is the rat cornea. The corneal tissue of the living rat was exposed to beams of carbon at 474 MeV/amu, neon at 8.5 MeV/amu, argon at 8.5 MeV/amu, silicon at 530 MeV/amu, iron at 500 MeV/amu, and iron at 600 MeV/amu. X-rays were also used on corneas to compare with the heavy ion irradiated corneas. Scanning electron microscopy revealed lesions with circular symmetry on the external plasma membranes of corneal epithelium which were irradiated with heavy ions, but similar lesions were not observed on the plasma membranes of x-ray irradiated or non-irradiated control samples. These data verify the special way in which heavy ions interact with matter: each ion interacts coulombically with electrons all along its trajectory to generate a track. The dose from heavy ion radiation is not distributed homogeneously on a tissue microstructural scale but is concentrated along the individual particle track. Even along a single particle track the dose is discontinuous except at the Bragg peak when the LET is maximum. Micrographs of heavy-ion-irradiated corneas demonstrated two significant correlations with the heavy ion beam: (1) the number of plasma membrane lesions per unit area was correlated with the particle fluence, and (2) the diameter of the lesions were linearly related to the energy loss or LET of the individual particle. These observations corroborate what has already been suggested theoretically about heavy ion tracks and what has been shown experimentally. But the new data indicate that particle tracks occur in biological tissues as well, and that a single heavy ion is responsible for each membrane lesion. (ERB)

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  9. Field ionization model implemented in Particle In Cell code and applied to laser-accelerated carbon ions

    SciTech Connect

    Nuter, R.; Gremillet, L.; Lefebvre, E.; Levy, A.; Ceccotti, T.; Martin, P.

    2011-03-15

    A novel numerical modeling of field ionization in PIC (Particle In Cell) codes is presented. Based on the quasistatic approximation of the ADK (Ammosov Delone Krainov) theory and implemented through a Monte Carlo scheme, this model allows for multiple ionization processes. Two-dimensional PIC simulations are performed to analyze the cut-off energies of the laser-accelerated carbon ions measured on the UHI 10 Saclay facility. The influence of the target and the hydrocarbon pollutant composition on laser-accelerated carbon ion energies is demonstrated.

  10. Interaction between two spherical particles in a nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Fukuda, Jun-Ichi; Stark, Holger; Yoneya, Makoto; Yokoyama, Hiroshi

    2004-04-01

    We numerically investigate the interaction between two spherical particles in a nematic liquid crystal mediated by elastic distortions in the orientational order. We pay attention to the cases where two particles with equal radii R0 impose rigid normal anchoring on their surfaces and carry a pointlike topological defect referred to as a hyperbolic hedgehog. To describe the geometry of our system, we use bispherical coordinates, which prove useful in the implementation of boundary conditions at the particle surfaces and at infinity. We adopt the Landau de Gennes continuum theory in terms of a second-rank tensor order parameter Qij for the description of the orientational order of a nematic liquid crystal. We also utilize an adaptive mesh refinement scheme that has proven to be an efficient way of dealing with topological defects whose core size is much smaller than the particle size. When the two “dipoles,” composed of a particle and a hyperbolic hedgehog, are in parallel directions, the two-particle interaction potential is attractive for large interparticle distances D and proportional to D-3 as expected from the form of the dipole-dipole interaction, until the well-defined potential minimum at D≃2.46 R0 is reached. For the antiparallel configuration with no hedgehogs between the two particles, the interaction potential is repulsive and behaves as D-2 for D≲10 R0 , which is stronger than the dipole-dipole repulsion ( ˜ D-3 ) expected theoretically as an asymptotic behavior for large D .

  11. 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.

  12. Cell and Particle Interactions and Aggregation During Electrophoretic Motion

    NASA Technical Reports Server (NTRS)

    Wang, Hua; Zeng, Shulin; Loewenberg, Michael; Todd, Paul; Davis, Robert H.

    1996-01-01

    The stability and pairwise aggregation rates of small spherical particles under the collective effects of buoyancy-driven motion and electrophoretic migration are analyzed. The particles are assumed to be non-Brownian, with thin double-layers and different zeta potentials. The particle aggregation rates may be enhanced or reduced, respectively, by parallel and antiparallel alignments of the buoyancy-driven and electrophoretic velocities. For antiparallel alignments, with the buoyancy-driven relative velocity exceeding the electrophoretic relative velocity between two widely-separated particles, there is a 'collision-forbidden region' in parameter space due to hydrodynamic interactions; thus, the suspension becomes stable against aggregation.

  13. Conformal invariance in noncommutative geometry and mutually interacting Snyder particles

    NASA Astrophysics Data System (ADS)

    Pramanik, Souvik; Ghosh, Subir; Pal, Probir

    2014-11-01

    A system of relativistic Snyder particles with mutual two-body interaction that lives in a noncommutative Snyder geometry is studied. The underlying novel symplectic structure is a coupled and extended version of (single-particle) Snyder algebra. In a recent work by Casalbuoni and Gomis [Phys. Rev. D 90, 026001 (2014)], a system of interacting conventional particles (in commutative spacetime) was studied with special emphasis on its conformal invariance. Proceeding along the same lines, we have shown that our interacting Snyder particle model is also conformally invariant. Moreover, the conformal Killing vectors have been constructed. Our main emphasis is on the Hamiltonian analysis of the conformal symmetry generators. We demonstrate that the Lorentz algebra remains undeformed, but validity of the full conformal algebra requires further restrictions.

  14. Multidimensional stationary probability distribution for interacting active particles.

    PubMed

    Maggi, Claudio; Marconi, Umberto Marini Bettolo; Gnan, Nicoletta; Di Leonardo, Roberto

    2015-01-01

    We derive the stationary probability distribution for a non-equilibrium system composed by an arbitrary number of degrees of freedom that are subject to Gaussian colored noise and a conservative potential. This is based on a multidimensional version of the Unified Colored Noise Approximation. By comparing theory with numerical simulations we demonstrate that the theoretical probability density quantitatively describes the accumulation of active particles around repulsive obstacles. In particular, for two particles with repulsive interactions, the probability of close contact decreases when one of the two particle is pinned. Moreover, in the case of isotropic confining potentials, the radial density profile shows a non trivial scaling with radius. Finally we show that the theory well approximates the "pressure" generated by the active particles allowing to derive an equation of state for a system of non-interacting colored noise-driven particles. PMID:26021260

  15. Single particle density of trapped interacting quantum gases

    SciTech Connect

    Bala, Renu; Bosse, J.; Pathak, K. N.

    2015-05-15

    An expression for single particle density for trapped interacting gases has been obtained in first order of interaction using Green’s function method. Results are easily simplified for homogeneous quantum gases and are found to agree with famous results obtained by Huang-Yang-Luttinger and Lee-Yang.

  16. Renormalisation group analysis of supersymmetric particle interactions

    NASA Astrophysics Data System (ADS)

    Box, Andrew D.

    In the Minimal Supersymmetric Standard Model (MSSM), there are numerous sources of flavour-violation in addition to the usual Kobayashi-Maskawa mixing matrix of the Standard Model. We reexamine the renormalisation group equations (RGEs) with a view to investigating flavour effects in a supersymmetric theory with an arbitrary flavour structure at some high scale. To incorporate (two-loop sized) threshold effects in the one-loop RGEs, we calculate the beta-functions using a sequence of (non-supersymmetric) effective theories with heavy particles decoupled at the scale of their mass, keeping track of the fact that many couplings (such as gauge and gaugino couplings) which are equal in an exact supersymmetric theory may no longer be equal once the supersymmetry (SUSY) is broken. We find that this splitting, which is ignored in the literature, may be larger than two-loop terms that are included. In addition, gaugino couplings develop flavour structure that is absent without including decoupling effects. A program (to be incorporated into ISAJET) has been developed, which includes flavour-violating couplings of superparticles and solves the two-loop threshold RGEs subject to specified high scale inputs. The weak scale flavour structure derived in this way can be applied to the study of flavour-changing decays of SUSY particles. As an illustration, we revisit the branching ratio of the flavour-violating decay of the top squark. We find that, in the minimal supergravity (mSUGRA) class of models, previous estimates for the width of this decay have been too large by a factor 10 -- 25. However, this decay rate is sensitive to the flavour structure of the high scale boundary conditions. We analyse the consequences of introducing non-universality in the high scale soft SUSY-breaking mass matrices and find that under these conditions the partial width can be altered by a large amount.

  17. Cross sections and rate coefficients for inelastic interactions of heavy particles

    NASA Technical Reports Server (NTRS)

    Kunc, J. A.; Soon, W. H.

    1991-01-01

    The existing analytical inelastic cross-sections for direct atom-atom ionizing collisions of Firsov (1959), Fleischmann et al. (1972), and Drawin (1968) are discussed. General analytical expressions for direct ionization cross-sections in atom-atom collisions are derived. The main advantage of the present cross-sections is their generality, simplicity, and overall accuracy, which is acceptable in most applications and is better than the overall accuracy of the cross-sections of Firsov, Fleischmann et al., and Drawin. The atom-atom interaction is considered as a superposition of all the pairwise interactions between the test particle and all the electrons of the outer nl shell of the target atom. Such a picture of atom-atom collision is acceptable at low- and medium-impact energies because then the electrons of the outer shell of the target atom are most likely the ones that get ionized. At high-impact energy, the picture becomes inaccurate because of strong overlapping of the atomic shells.

  18. Dissipative Particle Dynamics interaction parameters from ab initio calculations

    NASA Astrophysics Data System (ADS)

    Sepehr, Fatemeh; Paddison, Stephen J.

    2016-02-01

    Dissipative Particle Dynamics (DPD) is a commonly employed coarse-grained method to model complex systems. Presented here is a pragmatic approach to connect atomic-scale information to the meso-scale interactions defined between the DPD particles or beads. Specifically, electronic structure calculations were utilized for the calculation of the DPD pair-wise interaction parameters. An implicit treatment of the electrostatic interactions for charged beads is introduced. The method is successfully applied to derive the parameters for a hydrated perfluorosulfonic acid ionomer with absorbed vanadium cations.

  19. Physicochemical Properties of 'Particle Brush'-Based Materials: Using Polymer Graft Modification to Tailor Particle Interactions

    NASA Astrophysics Data System (ADS)

    Schmitt, Michael D.

    The advent of surface-initiated controlled radical polymerization techniques has allowed a new class of hybrid polymer-grafted nanoparticles, known as eparticle brushes,f to be realized. By grafting polymers from the surface, interactions between particles can be tuned using the precise control over graft architecture (i.e. chain length, dispersity, particle size, and grafting density) afforded by controlled radical polymerizations. Previously, a transition from particle-like to polymer-like interactions in small particles with increasing graft length has been observed. In the limit of long graft lengths, the polymer chains impart new interactions between particles, such as entanglements. These results outline a rich, but largely unexplored parameter space. The present thesis further elucidates the extent to which polymer graft modification facilitates new interaction types between particles and the dependence of those interactions on chain conformation. Specifically, the mechanical properties, processability, phase separation, and vibrational modes of particle brushes are examined. A dependence of the mechanical properties of particle brush assemblies on particle size is accurately captured by accounting for differences in chain conformation between particles of different sizes using a simple scaling model. Further tailoring of mechanical characteristics in weak particle brush assemblies can be achieved using appropriate homopolymer additives to form two-component systems. Improved mechanical properties are accompanied by a significant enhancement in particle processability that allows application of previously unusable processing methods. Considering more complex systems, mesoscale phase separation of nanoparticles is demonstrated for the first time by blending of particle brushes with different graft polymers. Polymer graft modification is seen to not only strengthen and introduce new interactions, but also tune particle properties. Vibrational modes of

  20. Simulation of wave packet tunneling of interacting identical particles

    NASA Astrophysics Data System (ADS)

    Lozovik, Yu. E.; Filinov, A. V.; Arkhipov, A. S.

    2003-02-01

    We demonstrate a different method of simulation of nonstationary quantum processes, considering the tunneling of two interacting identical particles, represented by wave packets. The used method of quantum molecular dynamics (WMD) is based on the Wigner representation of quantum mechanics. In the context of this method ensembles of classical trajectories are used to solve quantum Wigner-Liouville equation. These classical trajectories obey Hamiltonian-like equations, where the effective potential consists of the usual classical term and the quantum term, which depends on the Wigner function and its derivatives. The quantum term is calculated using local distribution of trajectories in phase space, therefore, classical trajectories are not independent, contrary to classical molecular dynamics. The developed WMD method takes into account the influence of exchange and interaction between particles. The role of direct and exchange interactions in tunneling is analyzed. The tunneling times for interacting particles are calculated.

  1. Energetic particle acceleration at corotating interaction regions: Ulysses results

    SciTech Connect

    Desai, M.I.; Marsden, R.G.; Sanderson, T.R.; Gosling, J.T.

    1997-07-01

    We present here statistical properties of energetic ions (tilde 1 MeV) accelerated by corotating interaction regions observed at the Ulysses spacecraft. We have correlated the tilde 1 MeV proton intensity measured near the trailing edges of the interaction regions with their compression ratio. We interpret our results in terms of the plasma conditions experienced at Ulysses and identify a likely source of the low energy seed particles accelerated at the interaction regions.

  2. Two-particle and single-particle spin-dependent interactions in topological insulators

    NASA Astrophysics Data System (ADS)

    Radu, Marius; Lyanda-Geller, Yuli

    2014-03-01

    We derive single-particle and two-particle interaction Hamiltonians describing physics of two-dimensional topological insulators based on HgTe-CdTe quantum well structures by using k . p theory and extended Kane model. We include contributions from upper conduction band with orbital states of p-symmetry that bring about the terms describing lack of inversion symmetry in host semiconductors. Single-particle Hamiltonian and two-particle Hamiltonian contain important spin-dependent diagonal and off-diagonal terms. We demonstrate how these terms affect spin currents, interference effects in conductance such as weak localization and anti-localization, and contribute to spin relaxation and dephasing. The spin-dependent interaction terms couple orbital motion of one particle with evolution of spin of the other particle. Such particle-particle interactions do not conserve spin and lower the symmetry of exchange interactions, leading, e.g., to Dzyaloshinskii-Moriya exchange term. Support of Purdue Center for Topological Materials is gratefully acknowledged.

  3. Electrophoretic interactions and aggregation of colloidal biological particles

    NASA Technical Reports Server (NTRS)

    Davis, Robert H.; Nichols, Scott C.; Loewenberg, Michael; Todd, Paul

    1994-01-01

    The separation of cells or particles from solution has traditionally been accomplished with centrifuges or by sedimentation; however, many particles have specific densities close to unity, making buoyancy-driven motion slow or negligible, but most cells and particles carry surface charges, making them ideal for electrophoretic separation. Both buoyancy-driven and electrophoretic separation may be influenced by hydrodynamic interactions and aggregation of neighboring particles. Aggregation by electrophoresis was analyzed for two non-Brownian particles with different zeta potentials and thin double layers migrating through a viscous fluid. The results indicate that the initial rate of electrophoretically-driven aggregation may exceed that of buoyancy-driven aggregation, even under conditions in which buoyancy-driven relative motion of noninteracting particles is dominant.

  4. Biological effects of low doses of ionizing radiations: Particle tracks in radiobiology

    NASA Astrophysics Data System (ADS)

    Katz, Robert; Hofmann, Werner

    1982-12-01

    A radiation field is made up of a tangle of particle tracks, from the primary particle and secondary and higher generation electron interaction, well isolated at low doses and with multiple intersections in cell nuclei at high doses. Low dose effects in multicellular systems are therefore the sum of individual track structures. Until we can state with confidence the structure of a particle track in biological matter for all end-points of interest, at least as well as we can for nuclear emulsions, our knowledge of low dose effects should be regarded as uncertain and inadequate. In this context "track structure" means the response of physical and biological systems along the path of the particle, and depends on the observed end-point as well as on the identity of the particle. For mammalian cell killing and a few other biological end-points track and experimental radiosensitivity parameters allow as to construct schematic models. If we take a particle track to consist of a sequence of inactivated cells strung along the path of a particle, neither electrons nor protons leave a track in a compact mammalian cell structure. At most there is an occasional killed cell at the end of the range of a proton or an electron where the particle stops in the nucleus of a cell, with probability less than 0.3 for a proton, and less than 0.01 for an electron. The variety of potential targets whose size may be compared to the measured inactivation cross-section and the lack of a fully consistent theory of RBE make it possible to decide, from this information alone, whether cell killing is an individual (1-hit) or cooperative (many-hit) phenomenon, especilally for electrons. a siilar analysis of epidemiological data for cancer induction leads to probabilities and action cross-sections so low as to make a linear extrapolation implausible. In assigning quality factors at highest LET values we should consider that heavy ions inactive cells, so that neither mutation nor transformation can

  5. Evidence of strong projectile-target-core interaction in single ionization of neon by electron impact

    SciTech Connect

    Yan, S.; Zhang, P.; Xu, S.; Ma, X.; Zhang, S. F.; Zhu, X. L.; Feng, W. T.; Liu, H. P.

    2010-11-15

    The momentum distributions of recoil ions were measured in the single ionization of neon by electron impact at incident energies between 80 and 2300 eV. It was found that there are a noticeable number of recoil ions carrying large momenta, and the relative contributions of these ions becomes more pronounced with the further decrease of incident electron energy. These observed behaviors indicate that there is a strong projectile-target-core interaction in the single-ionization reaction. By comparing our results with those of electron-neon elastic scattering, we concluded that the elastic scattering of the projectile electron on the target core plays an important role at low and intermediate collision energies.

  6. Interaction of Strain and Nuclear Spins in Silicon: Quadrupolar Effects on Ionized Donors

    NASA Astrophysics Data System (ADS)

    Franke, David P.; Hrubesch, Florian M.; Künzl, Markus; Becker, Hans-Werner; Itoh, Kohei M.; Stutzmann, Martin; Hoehne, Felix; Dreher, Lukas; Brandt, Martin S.

    2015-07-01

    The nuclear spins of ionized donors in silicon have become an interesting quantum resource due to their very long coherence times. Their perfect isolation, however, comes at a price, since the absence of the donor electron makes the nuclear spin difficult to control. We demonstrate that the quadrupolar interaction allows us to effectively tune the nuclear magnetic resonance of ionized arsenic donors in silicon via strain and determine the two nonzero elements of the S tensor linking strain and electric field gradients in this material to S11=1.5 ×1022 V /m2 and S44=6 ×1022 V /m2 . We find a stronger benefit of dynamical decoupling on the coherence properties of transitions subject to first-order quadrupole shifts than on those subject to only second-order shifts and discuss applications of quadrupole physics including mechanical driving of magnetic resonance, cooling of mechanical resonators, and strain-mediated spin coupling.

  7. Studying bubble-particle interactions by zeta potential distribution analysis.

    PubMed

    Wu, Chendi; Wang, Louxiang; Harbottle, David; Masliyah, Jacob; Xu, Zhenghe

    2015-07-01

    Over a decade ago, Xu and Masliyah pioneered an approach to characterize the interactions between particles in dynamic environments of multicomponent systems by measuring zeta potential distributions of individual components and their mixtures. Using a Zetaphoremeter, the measured zeta potential distributions of individual components and their mixtures were used to determine the conditions of preferential attachment in multicomponent particle suspensions. The technique has been applied to study the attachment of nano-sized silica and alumina particles to sub-micron size bubbles in solutions with and without the addition of surface active agents (SDS, DAH and DF250). The degree of attachment between gas bubbles and particles is shown to be a function of the interaction energy governed by the dispersion, electrostatic double layer and hydrophobic forces. Under certain chemical conditions, the attachment of nano-particles to sub-micron size bubbles is shown to be enhanced by in-situ gas nucleation induced by hydrodynamic cavitation for the weakly interacting systems, where mixing of the two individual components results in negligible attachment. Preferential interaction in complex tertiary particle systems demonstrated strong attachment between micron-sized alumina and gas bubbles, with little attachment between micron-sized alumina and silica, possibly due to instability of the aggregates in the shear flow environment. PMID:25731913

  8. Effect of particle-particle interactions on the acoustic radiation force in an ultrasonic standing wave

    NASA Astrophysics Data System (ADS)

    Lipkens, Bart; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.

    2015-10-01

    Ultrasonic standing waves are widely used for separation applications. In MEMS applications, a half wavelength standing wave field is generated perpendicular to a laminar flow. The acoustic radiation force exerted on the particle drives the particle to the center of the MEMS channel, where concentrated particles are harvested. In macro-scale applications, the ultrasonic standing wave spans multiple wavelengths. Examples of such applications are oil/water emulsion splitting [1], and blood/lipid separation [2]. In macro-scale applications, particles are typically trapped in the standing wave, resulting in clumping or coalescence of particles/droplets. Subsequent gravitational settling results in separation of the secondary phase. An often used expression for the radiation force on a particle is that derived by Gorkov [3]. The assumptions are that the particle size is small relative to the wavelength, and therefore, only monopole and dipole scattering contributions are used to calculate the radiation force. This framework seems satisfactory for MEMS scale applications where each particle is treated separately by the standing wave, and concentrations are typically low. In macro-scale applications, particle concentration is high, and particle clumping or droplet coalescence results in particle sizes not necessarily small relative to the wavelength. Ilinskii et al. developed a framework for calculation of the acoustic radiation force valid for any size particle [4]. However, this model does not take into account particle to particle effects, which can become important as particle concentration increases. It is known that an acoustic radiation force on a particle or a droplet is determined by the local field. An acoustic radiation force expression is developed that includes the effect of particle to particle interaction. The case of two neighboring particles is considered. The approach is based on sound scattering by the particles. The acoustic field at the location of

  9. Effect of particle-particle interactions on the acoustic radiation force in an ultrasonic standing wave

    SciTech Connect

    Lipkens, Bart; Ilinskii, Yurii A. Zabolotskaya, Evgenia A.

    2015-10-28

    Ultrasonic standing waves are widely used for separation applications. In MEMS applications, a half wavelength standing wave field is generated perpendicular to a laminar flow. The acoustic radiation force exerted on the particle drives the particle to the center of the MEMS channel, where concentrated particles are harvested. In macro-scale applications, the ultrasonic standing wave spans multiple wavelengths. Examples of such applications are oil/water emulsion splitting [1], and blood/lipid separation [2]. In macro-scale applications, particles are typically trapped in the standing wave, resulting in clumping or coalescence of particles/droplets. Subsequent gravitational settling results in separation of the secondary phase. An often used expression for the radiation force on a particle is that derived by Gorkov [3]. The assumptions are that the particle size is small relative to the wavelength, and therefore, only monopole and dipole scattering contributions are used to calculate the radiation force. This framework seems satisfactory for MEMS scale applications where each particle is treated separately by the standing wave, and concentrations are typically low. In macro-scale applications, particle concentration is high, and particle clumping or droplet coalescence results in particle sizes not necessarily small relative to the wavelength. Ilinskii et al. developed a framework for calculation of the acoustic radiation force valid for any size particle [4]. However, this model does not take into account particle to particle effects, which can become important as particle concentration increases. It is known that an acoustic radiation force on a particle or a droplet is determined by the local field. An acoustic radiation force expression is developed that includes the effect of particle to particle interaction. The case of two neighboring particles is considered. The approach is based on sound scattering by the particles. The acoustic field at the location of

  10. A field-ionization neutral detector - FIND. [neutral particle mass spectrometer

    NASA Technical Reports Server (NTRS)

    Curtis, C. C.; Hsieh, K. C.; Fan, C. Y.; Swanson, L. W.

    1975-01-01

    The field ionization neutral detector FIND operates according to the following principle: Neutral atoms are attracted toward the field ionization tips since they are polarized by the electric field of the tips. The atoms are singly ionized and repelled by the positive potential of the tips toward the detector situated behind a grid at ground potential. The ions deposit in the detector their kinetic energies, typically 26 keV, corresponding to the potential difference between the ionization region and the detector. Laboratory results show that FIND can have the resolution, sensitivities and durability required to perform in situ measurements of neutral H and He fluxes in interplanetary space, cometary halos and exospheres.

  11. Particle interaction of lubricated or unlubricated binary mixtures according to their particle size and densification mechanism.

    PubMed

    Di Martino, Piera; Joiris, Etienne; Martelli, Sante

    2004-09-01

    The aim of this study is to assess an experimental approach for technological development of a direct compression formulation. A simple formula was considered composed by an active ingredient, a diluent and a lubricant. The active ingredient and diluent were selected as an example according to their typical densification mechanism: the nitrofurantoine, a fragmenting material, and the cellulose microcrystalline (Vivapur), which is a typical visco-elastic material, equally displaying good bind and disintegrant properties. For each ingredient, samples of different particle size distribution were selected. Initially, tabletability of pure materials was studied by a rotary press without magnesium stearate. Vivapur tabletability decreases with increase in particle size. The addition of magnesium stearate as lubricant decreases tabletability of Vivapur of greater particle size, while it kept unmodified that of Vivapur of lower particle size. Differences in tabletability can be related to differences in particle-particle interactions; for Vivapur of higher particle size (Vivapur 200, 102 and 101), the lower surface area develops lower surface available for bonds, while for Vivapur of lower particle size (99 and 105) the greater surface area allows high particle proximity favouring particle cohesivity. Nitrofurantoine shows great differences in compression behaviour according to its particle size distribution. Large crystals show poorer tabletability than fine crystals, further decreased by lubricant addition. The large crystals poor tabletability is due to their poor compactibility, in spite of high compressibility and plastic intrinsic deformability; in fact, in spite of the high densification tendency, the nature of the involved bonds is very weak. Nitrofurantoine samples were then mixed with Vivapurs in different proportions. Compression behaviour of binary mixes (tabletability and compressibility) was then evaluated according to diluents proportion in the mixes. The

  12. Particle-surface interactions in chemical mechanical polishing

    SciTech Connect

    Dugger, M.T.; Adkins, C.L.J.; Resnick, P.J.; Jeon, J.S.; Raghavan, S.

    1996-10-01

    Material removal in chemical mechanical polishing (CMP) occurs by a pressure accentuated chemical attack of the surface. The polishing slurry typically consists of abrasive particles and reactive chemicals that may or may not include an oxidant. Post-CMP cleaning processes must remove both the ionic contaminants and any remaining polishing slurry particles. Central to the effectiveness of a clean is the use of conditions that will minimize the binding force between the residual particles and the wafer surface. The morphology and composition of the particle, the surface from which it must be removed, and the environment surrounding the wafer will determine the magnitude of forces that hold a particle to the wafer surface. At the Sandia/SEMATECH Center for Contamination Free Manufacturing, two techniques--atomic force microscopy (AFM) and electrokinetic deposition--are being used to explore these interactions for CMP of both oxide and tungsten surfaces. A basic understanding of particle-surface interaction forces and how they are affected by the chemical/physical environment of the particle and surface is the objective of this task. Modification of the binding forces between particles and wafer surfaces may be used to maximize post-CMP cleaning effectiveness.

  13. Gas-Particle Interactions in a Microgravity Flow Cell

    NASA Technical Reports Server (NTRS)

    Louge, Michel; Jenkins, James

    1999-01-01

    We are developing a microgravity flow cell in which to study the interaction of a flowing gas with relatively massive particles that collide with each other and with the moving boundaries of the cell. The absence of gravity makes possible the independent control of the relative motion of the boundaries and the flow of the gas. The cell will permit gas-particle interactions to be studied over the entire range of flow conditions over which the mixture is not turbulent. Within this range, we shall characterize the viscous dissipation of the energy of the particle fluctuations, measure the influence of particle-phase viscosity on the pressure drop along the cell, and observe the development of localized inhomogeneities that are likely to be associated with the onset of clusters. These measurements and observations should contribute to an understanding of the essential physics of pneumatic transport.

  14. Spherical Particle Interaction with Flowing Plasma: Computational Discoveries

    NASA Astrophysics Data System (ADS)

    Hutchinson, I. H.

    2005-10-01

    The fundamental problem of the interaction of an isolated ion-absorbing sphere with a flowing collisionless plasma has been solved comprehensively for the first time, using a particle in cell code (SCEPTIC). Its results show the extent to which prior approximations affect such parameters as the particle charge, potential, ion-flux, drag, and wake structure. Several qualitatively new discoveries have been made, including: the substantial accuracy of the OML value of potential, but inaccuracy of the particle charge; reversal of the direction of asymmetry of the flux to the sphere; the rise of the ion drag force above prior analytic estimates by a factor of 2; the absence of extended oscillatory wakes, in contradiction of prior analytic predictions. These results constitute the basis for many of the dynamic parameters of dust particle interactions with the plasma and with each other.

  15. Interaction measurement of particles bound to a lipid membrane

    NASA Astrophysics Data System (ADS)

    Sarfati, Raphael; Dufresne, Eric

    2015-03-01

    The local shape and dynamics of the plasma membrane play important roles in many cellular processes. Local membrane deformations are often mediated by the adsorption of proteins (notably from the BAR family), and their subsequent self-assembly. The emerging hypothesis is that self-assembly arises from long-range interactions of individual proteins through the membrane's deformation field. We study these interactions in a model system of micron-sized colloidal particles adsorbed onto a lipid bilayer. We use fluorescent microscopy, optical tweezers and particle tracking to measure dissipative and conservative forces as a function of the separation between the particles. We find that particles are driven together with forces of order 100 fN and remain bound in a potential well with a stiffness of order 100 fN/micron.

  16. Particle-fluid interactions in rotor-generated vortex flows

    NASA Astrophysics Data System (ADS)

    Rauleder, Jürgen; Leishman, J. Gordon

    2014-03-01

    An investigation was made into the particle-laden turbulent flow produced by a rotor hovering in ground effect over a mobile sediment bed. Measurements of the two-phase flow were made using time-resolved particle image velocimetry and particle tracking velocimetry as the rotor wake and its embedded vorticity approached and interacted with the sediment bed. Mobilized particles of 45-63 μm diameter (estimated to have a particle Reynolds number of <30 and a Stokes number of about 60) were individually identified and tracked in the resulting flow, with the objective of relating any changes in the vortical flow and turbulence characteristics of the carrier flow phase to the action of the dispersed particle phase. It was observed that, in general, a two-way coupling between the flow phases was produced near the ground, and in some cases, the coupling was very significant. Specifically, it was shown that the uplifted particles altered the carrier flow near the sediment bed, leading to an earlier distortion of the external flow induced by the blade tip vortices and to the accelerated diffusion of the vorticity they contained. The uplifted particles were also seen to modify the overall turbulence field, and when sufficient particle concentrations built up, the particles began to attenuate the turbulence levels. Even in regions with lower particle concentrations, turbulence was found to be attenuated by the indirect action of the particles because of the distortions made to the tip vortices, which were otherwise a significant source of turbulence production. After the tip vortices had diffused further downstream, the uplifted particles were also found to increase the anisotropy of turbulence in the flow.

  17. Transient bimodality in interacting particle systems

    SciTech Connect

    Calderoni, P.; Pellegrinotti, A.; Presutti, E.; Vares, M.E. )

    1989-05-01

    The authors consider a system of spins which have values {plus minus} 1 and evolve according to a jump Markov process whose generator is the sum of two generators, one describing a spin-flip Glauber process, the other a Kawasaki (stirring) evolution. It was proven elsewhere that if the Kawasaki dynamics is speeded up by a factor {var epsilon}{sup {minus}2}, then, in the limit {var epsilon} {yields} 0 (continuum limit), propagation of chaos holds and the local magnetization solves a reaction-diffusion equation. They choose the parameters of the Glauber interaction so that the potential of the reaction term in the reaction-diffusion equation is a double-well potential with quartic maximum at the origin. They assume further that for each {var epsilon} the system is in a finite interval of Z with {var epsilon}{sup {minus}1} sites and periodic boundary conditions. They specify the initial measure as the product measure with 0 spin average, thus obtaining, in the continuum limit, a constant magnetic profile equal to 0, which is a stationary unstable solution to the reaction-diffusion equation. They prove that at times of the order {var epsilon}{sup {minus}1/2} propagation of chaos does not hold any more and, in the limit as {var epsilon} {yields} 0, the state becomes a nontrivial superposition of Bernoulli measures with parameters corresponding to the minima of the reaction potential. The coefficients of such a superposition depend on time (on the scale {var epsilon}{sup {minus}1/2}) and at large times (on this scale) the coefficient of the term corresponding to the initial magnetization vanishes (transient bimodality). This differs from what was observed by De Masi, Presutti, and Vares, who considered a reaction potential with quadratic maximum and no bimodal effect was seen, as predicted by Broggi, Lugiato, and Colombo.

  18. Local wave particle resonant interaction causing energetic particle prompt loss in DIII-D plasmas

    NASA Astrophysics Data System (ADS)

    Zhang, R. B.; Fu, G. Y.; White, R. B.; Wang, X. G.

    2015-11-01

    A new wave particle resonance mechanism is found explaining the first-orbit prompt neutral beam-ion losses induced by shear Alfvén Eigenmodes (AEs) in the DIII-D tokamak. Because of the large banana width, a typical trapped beam ion can only interact locally with a core localised Alfvén Eigenmode for a fraction of its orbit, i.e. part of its inner leg of the banana orbit. These trapped beam ions can experience substantial radial kick within one bounce as long as the phases of the wave seen by the particles are nearly constant during this local interaction. A wave particle resonant condition is found based on the locally averaged particle orbit frequencies over the interaction part of the particle orbit. It is further found that the frequency width of the local resonance is quite large because the interaction time is short. This implies that particles over a considerable region of phase space can interact effectively with the localised AEs and experience large radial kicks within one bounce orbit. The radial kick size is found numerically and analytically to scale linearly in AE amplitude and is about 5 cm for typical experimental parameters. These results are consistent with experimental measurement.

  19. [Effects of ionizing radiation on scintillators and other particle detectors]. Conference summary

    SciTech Connect

    Proudfoot, J.

    1992-09-01

    It is my task to summarise the great variety of topics (covering a refreshing mix of physics, chemistry and technology) presented at this conference, which has focused on the effects of ionising radiation on scintillators and other particle detectors. One of the reasons and the central interest of many of the participants was the use of such detectors in experiments at two future large hadron colliders: the Superconducting Super Collider to be operating outside of Dallas in the United States by the turn of the decade and its European counterpart the Large Hadron Collider to be operating outside of Geneva in Switzerland on a similar time scale. These accelerators are the ``apple of the high energy physicist`s eye.`` Their goal is to uncover the elusive Higgs particle and thereby set the cornerstone in our current knowledge of elementary particle interactions. This is the Quest, and from this lofty height the presentations rapidly moved on to the specific questions of experimental science: how such an experiment is carried out; why radiation damage is an issue; how radiation damage affects detectors; which factors affect radiation damage characteristics; which factors are not affected by radiation damage; and how better detectors may be constructed. These were the substance of this conference.

  20. Azimuthal structures of produced particles in heavy-ion interactions

    SciTech Connect

    Vokal, S. Orlova, G. I.; Lehocka, S.

    2009-02-15

    The angular structures of particles produced in {sup 208}Pb at 158 A GeV/c and {sup 197}Au at 11.6 A GeV/c induced interactions with Ag(Br) nuclei in emulsion detector have been investigated. Nonstatistical well-ordered ring-like structures of produced particles in azimuthal plane of a collision have been found, and their parameters have been determined.

  1. Particle-Turbulence Interaction Model for Aluminum Combustion

    NASA Astrophysics Data System (ADS)

    Sinha, Neeraj; Calhoon, William; Tomes, Jeremy

    2011-06-01

    Particle-turbulence interactions will have a substantial impact on the performance of thermobaric explosives that rely on the particle combustion for secondary heat release. Modeling these interactions from a fundamental perspective is very difficult and intractable for large-scale problems of practical interest. Alternatively, these interactions may be modeled from a macroscopic perspective that seeks to account for the probability distribution function (PDF) of variables within the modeled laminar burning rate for the particulates. Such a formulation would account for the first order effect of turbulent fluctuations on the burning rate within a computationally affordable model. This paper will describe the development of such a model for aluminum particle combustion in both the diffusion and kinetic burning regimes. This formulation is based on an assumed PDF method that may be parameterized into a database that may be deployed within a flow solver. As a result, the formulation is computational efficient and affordable for large-scale simulations.

  2. The impact of surface properties on particle-interface interactions

    NASA Astrophysics Data System (ADS)

    Wang, Anna; Kaz, David; McGorty, Ryan; Manoharan, Vinothan N.

    2013-03-01

    The propensity for particles to bind to oil-water interfaces was first noted by Ramsden and Pickering over a century ago, and has been attributed to the huge reduction in surface energy when a particle breaches an oil-water interface and straddles it at its equilibrium height. Since then materials on a variety of length scales have been fabricated using particles at interfaces, from Pickering emulsions to Janus particles. In these applications, it is simply assumed that the particle sits at its hugely energetically favourable equilibrium position. However, it was recently shown that the relaxation of particles towards their equilibrium position is logarithmic in time and could take months, much longer than typical experiments. Here we investigate how surface charge and particle 'hairiness' impact the interaction between micron-sized particles and oil-water interfaces, and explore a molecular kinetic theory model to help understand these results. We use digital holographic microscopy to track micron-sized particles as they approach an oil-water interface with a resolution of 2 nm in all three dimensions at up to thousands of frames per second.

  3. Simulation of hydrodynamically interacting particles confined by a spherical cavity

    NASA Astrophysics Data System (ADS)

    Aponte-Rivera, Christian; Zia, Roseanna N.

    2016-06-01

    We present a theoretical framework to model the behavior of a concentrated colloidal dispersion confined inside a spherical cavity. Prior attempts to model such behavior were limited to a single enclosed particle and attempts to enlarge such models to two or more particles have seen limited success owing to the challenges of accurately modeling many-body and singular hydrodynamic interactions. To overcome these difficulties, we have developed a set of hydrodynamic mobility functions that couple particle motion with hydrodynamic traction moments that, when inverted and combined with near-field resistance functions, form a complete coupling tensor that accurately captures both the far-field and near-field physics and is valid for an arbitrary number of spherical particles enclosed by a spherical cavity of arbitrary relative size a /R , where a and R are the particle and cavity size, respectively. This framework is then utilized to study the effect of spherical confinement on the self- and entrained motion of the colloids, for a range of particle-to-cavity size ratios. The self-motion of a finite-size enclosed particle is studied first, recovering prior results published in the literature: The hydrodynamic mobility of the particle is greatest at the center of the cavity and decays as (a /R ) /(1 -y2) , where y is the particle distance to the cavity center. Near the cavity wall, the no-slip surfaces couple strongly and mobility along the cavity radius vanishes as ξ ≡R -(a +y ) , where y is center-to-center distance from particle to cavity. Corresponding motion transverse to the cavity radius vanishes as [ln(1/ξ ) ] -1. The effect of confinement on entrainment of a particle in the flow created by the motion of others is also studied, where we find that confinement exerts a qualitative effect on the strength and anisotropy of entrainment of a passive particle dragged by the flow of a forced particle. As expected, entrainment strength decays with increased distance

  4. Trapping of interacting propelled colloidal particles in inhomogeneous media.

    PubMed

    Magiera, Martin P; Brendel, Lothar

    2015-07-01

    A trapping mechanism for propelled colloidal particles based on an inhomogeneous drive is presented and studied by means of computer simulations. In experiments this method can be realized using photophoretic Janus particles driven by a light source, which is partially blocked by a shading mask. This leads to an accumulation of particles in the passive part. An equation for an accumulation parameter is derived using the effective inhomogeneous diffusion constant generated by the inhomogeneous drive. The impact of particle interaction on the trapping mechanism is studied, as well as the interplay between passivity-induced trapping and the emergent self-clustering of systems containing a high density of active particles. The combination of both effects makes the clusters more controllable for applications. PMID:26274159

  5. Trapping of interacting propelled colloidal particles in inhomogeneous media

    NASA Astrophysics Data System (ADS)

    Magiera, Martin P.; Brendel, Lothar

    2015-07-01

    A trapping mechanism for propelled colloidal particles based on an inhomogeneous drive is presented and studied by means of computer simulations. In experiments this method can be realized using photophoretic Janus particles driven by a light source, which is partially blocked by a shading mask. This leads to an accumulation of particles in the passive part. An equation for an accumulation parameter is derived using the effective inhomogeneous diffusion constant generated by the inhomogeneous drive. The impact of particle interaction on the trapping mechanism is studied, as well as the interplay between passivity-induced trapping and the emergent self-clustering of systems containing a high density of active particles. The combination of both effects makes the clusters more controllable for applications.

  6. Light scattering and dynamics of interacting Brownian particles

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Tang, H. T.

    1982-01-01

    The relative motions of interacting Brownian particles in liquids may be described as radial diffusion in an effective potential of the mean force. By using a harmonic approximation for the effective potential, the intermediate scattering function may also be evaluated. For polystyrene spheres of 250 A mean radius in aqueous environment at 0.00125 g/cu cm concentration, the results for the calculated mean square displacement are in qualitative agreement with experimental data from photon correlation spectroscopy. Because of the interactions, the functions deviate considerably from the exponential forms for the free particles.

  7. Nonlinearly interacting trapped particle solitons in collisionless plasmas

    NASA Astrophysics Data System (ADS)

    Mandal, Debraj; Sharma, Devendra

    2016-02-01

    The formulation of collective waves in collisionless plasmas is complicated by the kinetic effects produced by the resonant particles, capable of responding to the smallest of the amplitude disturbance. The dispersive plasma manifests this response by generating coherent nonlinear structures associated with phase-space vortices, or holes, at very small amplitudes. The nonlinear interaction between solitary electron phase-space holes is studied in the electron acoustic regime of a collisionless plasma using Vlasov simulations. Evolution of the analytic trapped particle solitary solutions is examined, observing them propagate stably, preserve their identity across strong mutual interactions in adiabatic processes, and display close correspondence with observable processes in nature.

  8. Gas-particle interaction in detonation spraying systems

    NASA Astrophysics Data System (ADS)

    Kadyrov, E.

    1996-06-01

    A model is developed to describe dynamic interaction of particles with the carrier gas during detonation spraying. Equations of mass, energy, and momentum conservation are integrated numerically for the two-phase particle-gas flow with the Hugoniot boundary conditions at the detonation wave front. Velocity and temperature of the sprayed powder and the gas parameters are calculated self-consistently, taking into account effects of friction and cooling of the gas in the vicinity of the gun barrel and effects of particle-gas interaction on the parameters of the gas phase. Calculations are performed for tungsten carbide particles of 30 μm diam and a 1.8 m long detonation gun using a stoichiometric mixture of oxygen and propane. Distributions of gas and particle parameters along the barrel are calculated for various moments of time. Tungsten carbide particles of 30 μm reach an exit velocity of 1278 m/s and a temperature of 1950 K. Exit particle velocity is a nonmonotonic function of the loading distance, L, with a distinct maximum at L = 75 cm. The proposed model can be applied to a broad range of problems related to detonation coating technology and allows evaluation of the effectiveness of various designs and optimization of operational parameters of detonation spraying systems.

  9. Ionizing Particle Radiation as a Modulator of Endogenous Bone Marrow Cell Reprogramming: Implications for Hematological Cancers.

    PubMed

    Muralidharan, Sujatha; Sasi, Sharath P; Zuriaga, Maria A; Hirschi, Karen K; Porada, Christopher D; Coleman, Matthew A; Walsh, Kenneth X; Yan, Xinhua; Goukassian, David A

    2015-01-01

    Exposure of individuals to ionizing radiation (IR), as in the case of astronauts exploring space or radiotherapy cancer patients, increases their risk of developing secondary cancers and other health-related problems. Bone marrow (BM), the site in the body where hematopoietic stem cell (HSC) self-renewal and differentiation to mature blood cells occurs, is extremely sensitive to low-dose IR, including irradiation by high-charge and high-energy particles. Low-dose IR induces DNA damage and persistent oxidative stress in the BM hematopoietic cells. Inefficient DNA repair processes in HSC and early hematopoietic progenitors can lead to an accumulation of mutations whereas long-lasting oxidative stress can impair hematopoiesis itself, thereby causing long-term damage to hematopoietic cells in the BM niche. We report here that low-dose (1)H- and (56)Fe-IR significantly decreased the hematopoietic early and late multipotent progenitor (E- and L-MPP, respectively) cell numbers in mouse BM over a period of up to 10 months after exposure. Both (1)H- and (56)Fe-IR increased the expression of pluripotent stem cell markers Sox2, Nanog, and Oct4 in L-MPPs and 10 months post-IR exposure. We postulate that low doses of (1)H- and (56)Fe-IR may induce endogenous cellular reprogramming of BM hematopoietic progenitor cells to assume a more primitive pluripotent phenotype and that IR-induced oxidative DNA damage may lead to mutations in these BM progenitors. This could then be propagated to successive cell lineages. Persistent impairment of BM progenitor cell populations can disrupt hematopoietic homeostasis and lead to hematologic disorders, and these findings warrant further mechanistic studies into the effects of low-dose IR on the functional capacity of BM-derived hematopoietic cells including their self-renewal and pluripotency. PMID:26528440

  10. Ionizing Particle Radiation as a Modulator of Endogenous Bone Marrow Cell Reprogramming: Implications for Hematological Cancers

    PubMed Central

    Muralidharan, Sujatha; Sasi, Sharath P.; Zuriaga, Maria A.; Hirschi, Karen K.; Porada, Christopher D.; Coleman, Matthew A.; Walsh, Kenneth X.; Yan, Xinhua; Goukassian, David A.

    2015-01-01

    Exposure of individuals to ionizing radiation (IR), as in the case of astronauts exploring space or radiotherapy cancer patients, increases their risk of developing secondary cancers and other health-related problems. Bone marrow (BM), the site in the body where hematopoietic stem cell (HSC) self-renewal and differentiation to mature blood cells occurs, is extremely sensitive to low-dose IR, including irradiation by high-charge and high-energy particles. Low-dose IR induces DNA damage and persistent oxidative stress in the BM hematopoietic cells. Inefficient DNA repair processes in HSC and early hematopoietic progenitors can lead to an accumulation of mutations whereas long-lasting oxidative stress can impair hematopoiesis itself, thereby causing long-term damage to hematopoietic cells in the BM niche. We report here that low-dose 1H- and 56Fe-IR significantly decreased the hematopoietic early and late multipotent progenitor (E- and L-MPP, respectively) cell numbers in mouse BM over a period of up to 10 months after exposure. Both 1H- and 56Fe-IR increased the expression of pluripotent stem cell markers Sox2, Nanog, and Oct4 in L-MPPs and 10 months post-IR exposure. We postulate that low doses of 1H- and 56Fe-IR may induce endogenous cellular reprogramming of BM hematopoietic progenitor cells to assume a more primitive pluripotent phenotype and that IR-induced oxidative DNA damage may lead to mutations in these BM progenitors. This could then be propagated to successive cell lineages. Persistent impairment of BM progenitor cell populations can disrupt hematopoietic homeostasis and lead to hematologic disorders, and these findings warrant further mechanistic studies into the effects of low-dose IR on the functional capacity of BM-derived hematopoietic cells including their self-renewal and pluripotency. PMID:26528440

  11. Phase-space analysis for ionization processes in the laser-atom interaction using Gabor transformation

    NASA Astrophysics Data System (ADS)

    Shu, X. F.; Liu, S. B.; Song, H. Y.

    2016-04-01

    In this paper, the ionization processes during laser-atom interaction are investigated in phase-space using Gabor transformation. Based on the time-dependent Schrödinger equation (TDSE), the depletion of the whole system caused by the mask function is taken into consideration in calculating the plasma density. We obtain the momentum distribution via the Gabor transformation of the escaping portions of the time-dependent wave packet at the detector-like points on the interior boundaries from which the kinetic energies carried by the escaping portions are calculated.

  12. Interactive Learning Module Improves Resident Knowledge of Risks of Ionizing Radiation Exposure From Medical Imaging.

    PubMed

    Sheng, Alexander Y; Breaud, Alan H; Schneider, Jeffrey I; Kadom, Nadja; Mitchell, Patricia M; Linden, Judith A

    2016-01-01

    Physician awareness of the risks of ionizing radiation exposure related to medical imaging is poor. Effective educational interventions informing physicians of such risk, especially in emergency medicine (EM), are lacking. The SIEVERT (Suboptimal Ionizing Radiation Exposure Education - A Void in Emergency Medicine Residency Training) learning module was designed to improve provider knowledge of the risks of radiation exposure from medical imaging and comfort in communicating these risks to patients. The 1-hour module consists of introductory lecture, interactive discussion, and role-playing scenarios. In this pilot study, we assessed the educational effect using unmatched, anonymous preintervention and postintervention questionnaires that assessed fund of knowledge, participant self-reported imaging ordering practices in several clinical scenarios, and trainee comfort level in discussing radiation risks with patients. All 25 EM resident participants completed the preintervention questionnaire, and 22 completed the postintervention questionnaire within 4 hours after participation. Correct responses on the 14-question learning assessment increased from 6.32 (standard deviation = 2.36) preintervention to 12.23 (standard deviation = 1.85) post-intervention. Overall, 24% of residents were comfortable with discussing the risks of ionizing radiation exposure with patients preintervention, whereas 41% felt comfortable postintervention. Participants ordered fewer computed tomography scans in 2 of the 4 clinical scenarios after attending the educational intervention. There was improvement in EM residents' knowledge regarding the risks of ionizing radiation exposure from medical imaging, and increased participant self-reported comfort levels in the discussion of these risks with patients after the 1-hour SIEVERT learning module. PMID:26657346

  13. Particle-wafer interactions in semiaqueous silicon cleaning systems

    NASA Astrophysics Data System (ADS)

    Hupka, Lukasz

    During the semiconductor chip manufacturing process, a silicon wafer goes through a number of cycles in both hydrophilic and hydrophobic environments. As silicon chips become more sophisticated, the manufacturing process becomes more involved and new challenges are imposed by size reduction, increase in the aspect ratio and the formation of multilayer structures. Wafer cleaning processes emerge several times in one manufacturing cycle. By rule of thumb, it is necessary to remove wafer contamination by particles which are half of a feature size. This is an enormous challenge, keeping in mind that currently wafer structures are of nanometer size. The cleaning procedures which worked for the last 40 years are becoming ineffective and obsolete. The industry calls for more efficient cleaning procedures in terms of particle contamination removal, and at the same time less aggressive procedures to prevent damage/dissolution of the fragile and narrow wafer structures. Atomic Force Microscopy (AFM), besides being an imaging tool with nano resolution, proves to be an indispensable instrument to characterize interaction forces, lateral forces, and adhesion between micron and submicron contaminant particles and the wafer surfaces both in air and liquid. Using the AFM colloidal probe technique interaction forces were measured between a contaminant particle and a wafer surface. These measurements were done for the silica---silica hydrophilic system and for the silanated silica---silanated silica hydrophobic system. The influence of the nonaqueous component in semiconductor wafer cleaning solution on interaction forces was also investigated under both hydrophilic and hydrophobic conditions. In addition the effect of particle size on the interaction forces as well as particle removal rate under both conditions is addressed. While force/radius normalization of measured interaction forces works great for hydrophilic systems, it was found to significantly underestimate the influence

  14. Gyroresonant wave-particle interactions in a dynamic magnetosphere

    NASA Technical Reports Server (NTRS)

    Gail, W. B.; Inan, U. S.; Helliwell, R. A.; Carpenter, D. L.

    1990-01-01

    The response of the interaction mechanism to time-dependent perturbations in the magnetic field was examined using the global field compressions that occur during sudden commencements. This study was performed to assess the effect of nonequilibrium or dynamic magnetospheric processes on wave-particle interactions (WPI). It is shown that current theories of gyroresonant WPI, when modified to include a time-dependent magnetic field, can be used to predict the properties of WPI in a dynamic magnetospheric environment.

  15. Theory and modeling of particles with DNA-mediated interactions

    NASA Astrophysics Data System (ADS)

    Licata, Nicholas A.

    2008-05-01

    In recent years significant attention has been attracted to proposals which utilize DNA for nanotechnological applications. Potential applications of these ideas range from the programmable self-assembly of colloidal crystals, to biosensors and nanoparticle based drug delivery platforms. In Chapter I we introduce the system, which generically consists of colloidal particles functionalized with specially designed DNA markers. The sequence of bases on the DNA markers determines the particle type. Due to the hybridization between complementary single-stranded DNA, specific, type-dependent interactions can be introduced between particles by choosing the appropriate DNA marker sequences. In Chapter II we develop a statistical mechanical description of the aggregation and melting behavior of particles with DNA-mediated interactions. In Chapter III a model is proposed to describe the dynamical departure and diffusion of particles which form reversible key-lock connections. In Chapter IV we propose a method to self-assemble nanoparticle clusters using DNA scaffolds. A natural extension is discussed in Chapter V, the programmable self-assembly of nanoparticle clusters where the desired cluster geometry is encoded using DNA-mediated interactions. In Chapter VI we consider a nanoparticle based drug delivery platform for targeted, cell specific chemotherapy. In Chapter VII we present prospects for future research: the connection between DNA-mediated colloidal crystallization and jamming, and the inverse problem in self-assembly.

  16. The Energetic Particles in Shock-ICME Interaction Structures

    NASA Astrophysics Data System (ADS)

    Shen, C.

    2015-12-01

    Previous results show that the energetic particles intensity will decreased in the ICMEs. But, in the year of 2008, Shen et al. reported a definite case that the intensity of solar energetic particles (SEP) in the shock-MC interaction structure increase greatly. They further found that such enhancement is the main cause of the largest SEP event in solar cycle 23. The questions remained are: Did all the shock-ICME(MC) structure cause the enhancement of the SEP intensity? If not, why it only happened in some events? Is there any other mechanism which can make the energetic particle intensity in ICME enhanced? To answer these questions, the SEP signatures in all ICMEs including the shock-ICME interaction structures from 1996 to 2014 are studied detail. It is found that the SEP intensities enhanced in about half of the shock-ICME interaction events. Meanwhile, large fraction of energetic particles intensity enhanced ICMEs are interacted with shocks. To find the possible condition and physical mechanismof such enhancement, the parameters of the shock, ICME(MC) and etc. are detailed analyzed.

  17. Higgs particles interacting via a scalar Dark Matter field

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Yajnavalkya; Darewych, Jurij

    2016-07-01

    We study a system of two Higgs particles, interacting via a scalar Dark Matter mediating field. The variational method in the Hamiltonian formalism of QFT is used to derive relativistic wave equations for the two-Higgs system, using a truncated Fock-space trial state. Approximate solutions of the two-body equations are used to examine the existence of Higgs bound states.

  18. Effect of finite particle interaction time in granular systems

    SciTech Connect

    Zhang, D.Z.; Rauenzahn, R.M.

    1998-07-01

    Almost all previously published theoretical papers that propose constitutive relations for granular flows use some form of kinetic theory, which neglects effects of finite particle interaction time and multiparticle interactions. In dense systems, these effects contain essential physics and determine the evolution of the stress system in granular flows. In this paper, the authors shall demonstrate the importance of these effects and study the behavior of the granular stress in a dense system. The particle interaction time is a random variable in a granular system, and they show that its probability distribution obeys an exponential law. The temporal decay of this probability represents the destruction of contacts between particles and is related to the relaxation of the collisional stress in a granular system. By considering the balance between creation and destruction of contacts, they derive a constitutive relation for collisional stress. Depending on the form of the model chosen to approximate forces developed during particle interactions, the constitutive relation can predict either viscoelastic or viscoplastic behavior of the collisional stress. Numerical simulations are performed to verify the theoretical findings and to study further the properties of dense granular systems.

  19. Bounds on halo-particle interactions from interstellar calorimetry

    NASA Technical Reports Server (NTRS)

    Chivukula, Sekhar R.; Cohen, Andrew G.; Dimopoulos, Savas; Walker, Terry P.

    1990-01-01

    It is shown that the existence of neutral interstellar clouds constrains the interaction of any particulate dark-matter candidate with atomic hydrogen to be quite small. Even for a halo particle of mass 1 PeV (10 to the 6 GeV), it is shown that the cross section with hydrogen must be smaller than the typical atomic cross section that is expected for a positively charged particle bound to an electron. The argument presented is that if the clouds are in equilibrium, then the rate at which energy is deposited by collisions with dark-matter particles must be smaller than the rate at which the cloud can cool. This argument is used to constrain the interaction cross section of dark matter with hydrogen. Remarks are made on the general viability of charged dark matter. Comments are also made on a bound which derives from the dynamical stability of the halo.

  20. Distinct mechanisms of the inhibition of vasculogenesis by different species of ionizing particles

    PubMed Central

    Grabham, Peter; Sharma, Preety; Bigelow, Alan; Geard, Charles

    2014-01-01

    The human vasculature includes a vast network of microcapillaries networking the body and is a major target for non-carcinogenic effects of space radiation in the body. The brain microvascular system is crucial to healthy functioning of the brain and its pathology is not only a primary event in a range of neurodegenerative diseases but also an important influencing factor in many others. The vasculature is maintained by angiogenesis regenerating vessels as they are needed, this is particularly relevant if the blood–brain barrier is damaged by agents such as space radiation, thereby creating the need for angiogenic regeneration. The resulting lack of vasculature due to the inhibition of re-growth of vessels can, in turn, lead to a negative feedback loop and further pathologies. Using three-dimensional human vessel cultures with human umbilical vein and brain microvascular endothelial cells, we have developed assays that determine at what stage angiogenesis is inhibited by ionizing radiation. The relative biological effect of high linear energy transfer (LET) 1 GeV Fe ions compared with low LET 1 GeV protons is only one for developing vessels but greater than four for mature vessels. This action of low LET protons on developing vessels was surprisingly effective (50% inhibition with 40 cGy exposure) and together with the effect of high LET ions may represent a significant hazard in the space environment. The morphology of developing vessels 5 days after exposure showed significant differences that suggest distinct mechanisms of inhibition. Cells exposed to protons failed to make connections with other cells. Conversely, cells exposed to Fe ions extended cellular processes and made connections to other cells but did not develop a central lumen. The microtubule and actin cytoskeletons showed differences indicating that motility at the extending tips of endothelial cells is inhibited by protons but not Fe ions. Actin-rich protrusive structures that contain bundled and

  1. Toward a theory of the initiation of cancer by ionizing radiation: track structure analysis for electrons and alpha particles in water

    SciTech Connect

    Pagnamenta, A.; Marshall, J.H.

    1980-01-01

    Following a method of Kim differential cross sections have been constructed in analytical form for the ionization of water by electrons and alpha particles. By generalizing Wideroe's bookkeeping mmethod the number of higher order delta rays were found. (ACR)

  2. Exchange distortion and postcollision interaction for intermediate-energy electron-impact ionization of argon

    NASA Astrophysics Data System (ADS)

    Prideaux, A.; Madison, D. H.; Bartschat, K.

    2005-09-01

    Measurements of fully differential cross sections for electron impact ionization of atoms have been performed for over 30 years. However, only within the last ten years has agreement between experiment and theory been achieved for ionization of hydrogen and helium. For the heavier inert gases, reasonably good agreement between experiment and theory has only been achieved for high incident energies while serious discrepancies are common for intermediate and low incident energies. It is believed that a major source of the problem stems from an improper/inadequate treatment of exchange distortion (ED) and the effects of post-collision interactions (PCIs). In this paper, two different methods for including ED are examined—one based upon the R matrix (close-coupling) approach and one originating from the single-configuration Hartree-Fock approach. In general, these two methods predict significant, but different, ED effects. The importance of PCI is studied by including the final-state Coulomb interaction directly in the final-state wave function. This procedure guarantees that PCI effects will be included to all orders of perturbation theory. For intermediate energies, PCI is an important effect and leads to an overall improvement in the agreement between experiment and theory.

  3. Exchange distortion and postcollision interaction for intermediate-energy electron-impact ionization of argon

    SciTech Connect

    Prideaux, A.; Madison, D.H.; Bartschat, K.

    2005-09-15

    Measurements of fully differential cross sections for electron impact ionization of atoms have been performed for over 30 years. However, only within the last ten years has agreement between experiment and theory been achieved for ionization of hydrogen and helium. For the heavier inert gases, reasonably good agreement between experiment and theory has only been achieved for high incident energies while serious discrepancies are common for intermediate and low incident energies. It is believed that a major source of the problem stems from an improper/inadequate treatment of exchange distortion (ED) and the effects of post-collision interactions (PCIs). In this paper, two different methods for including ED are examined--one based upon the R matrix (close-coupling) approach and one originating from the single-configuration Hartree-Fock approach. In general, these two methods predict significant, but different, ED effects. The importance of PCI is studied by including the final-state Coulomb interaction directly in the final-state wave function. This procedure guarantees that PCI effects will be included to all orders of perturbation theory. For intermediate energies, PCI is an important effect and leads to an overall improvement in the agreement between experiment and theory.

  4. A Transition-State Interaction Shifts Nucleobase Ionization Toward Neutrality to Facilitate Small Ribozyme Catalysis

    PubMed Central

    Liberman, Joseph A.; Guo, Man; Jenkins, Jermaine L.; Krucinska, Jolanta; Chen, Yuanyuan; Carey, Paul R.; Wedekind, Joseph E.

    2012-01-01

    One mechanism by which ribozymes can accelerate biological reactions is by adopting folds that favorably perturb nucleobase ionization. Herein we used Raman crystallography to directly measure pKa values for the Ade38 N1-imino group of a hairpin ribozyme in distinct conformational states. A transition-state analogue gave a pKa value of 6.27 ± 0.05, which agrees strikingly well with values measured by pH-rate analyses. To identify the chemical attributes that contribute to the shifted pKa we determined crystal structures of hairpin ribozyme variants containing single-atom substitutions at the active site and measured their respective Ade38 N1 pKa values. This approach led to the identification of a single interaction in the transition-state conformation that elevates the base pKa >0.8 log units relative to the precatalytic state. The agreement of the microscopic and macroscopic pKa values and the accompanying structural analysis support a mechanism in which Ade38 N1(H)+ functions as a general acid in phosphodiester bond cleavage. Overall the results quantify the contribution of a single electrostatic interaction to base ionization, which has broad relevance for understanding how RNA structure can control chemical reactivity. PMID:22989273

  5. Multireference configuration interaction calculations of the first six ionization potentials of the uranium atom

    SciTech Connect

    Bross, David H.; Parmar, Payal; Peterson, Kirk A.

    2015-11-12

    The first 6 ionization potentials (IPs) of the uranium atom have been calculated using multireference configuration interaction (MRCI+Q) with extrapolations to the complete basis set (CBS) limit using new all-electron correlation consistent basis sets. The latter were carried out with the third-order Douglas-Kroll-Hess Hamiltonian. Correlation down through the 5s5p5d electrons have been taken into account, as well as contributions to the IPs due to the Lamb shift. Spin-orbit coupling contributions calculated at the 4-component Kramers restricted configuration interaction level, as well as the Gaunt term computed at the Dirac-Hartree-Fock level, were added to the best scalar relativistic results. As a result, the final ionization potentials are expected to be accurate to at least 5 kcal/mol (0.2 eV), and thus more reliable than the current experimental values of IP3 through IP6.

  6. Multireference configuration interaction calculations of the first six ionization potentials of the uranium atom

    DOE PAGESBeta

    Bross, David H.; Parmar, Payal; Peterson, Kirk A.

    2015-11-12

    The first 6 ionization potentials (IPs) of the uranium atom have been calculated using multireference configuration interaction (MRCI+Q) with extrapolations to the complete basis set (CBS) limit using new all-electron correlation consistent basis sets. The latter were carried out with the third-order Douglas-Kroll-Hess Hamiltonian. Correlation down through the 5s5p5d electrons have been taken into account, as well as contributions to the IPs due to the Lamb shift. Spin-orbit coupling contributions calculated at the 4-component Kramers restricted configuration interaction level, as well as the Gaunt term computed at the Dirac-Hartree-Fock level, were added to the best scalar relativistic results. As amore » result, the final ionization potentials are expected to be accurate to at least 5 kcal/mol (0.2 eV), and thus more reliable than the current experimental values of IP3 through IP6.« less

  7. Interaction of nanosilver particles with human lymphocyte cells

    NASA Astrophysics Data System (ADS)

    Zhornik, Alena; Baranova, Ludmila; Volotovski, Igor; Chizhik, Sergey; Drozd, Elizaveta; Sudas, Margarita; Buu Ngo, Quoc; Chau Nguyen, Hoai; Huynh, Thi Ha; Hien Dao, Trong

    2015-01-01

    The damaging effects of nanoparticles were hypothesized to be the oxidative stress caused by the formation of reactive oxygen species and initiation of inflammatory reactions. In this context a study on the effects of nanosilver particles on the formation of reactive oxygen species in human lymphocyte culture was carried out. The obtained results showed that fluorescence intensity considerably increased after cells had interacted with nanosilver particles of varying concentrations, indicating the formation of reactive oxygen species and their accumulation in lymphocyte cells. Morphological study of the lymphocyte cells under the effects of nanosilver particles showed that the change in morphology depends on the concentration and size of nanosilver particles: for a size ≤20 nm the lymphocyte cell significantly shrank with pronounced differences in the morphological structure of the cell membrane, but for a size ≥200 nm no change was observed.

  8. Density Waves in Systems of Non-Interacting Particles

    NASA Astrophysics Data System (ADS)

    Kolmes, E. J.; Geyko, V. I.; Fisch, N. J.

    2015-11-01

    Under certain conditions, systems of non-interacting particles can give rise to density waves. In general, these waves do not require any particular perturbations in the initial density or velocity distributions, but they do tend to be strongly dependent on the boundary conditions of the system; one of the simplest examples is a collection of non-interacting particles bouncing in a constant gravitational field. A wide variety of different potentials can produce density waves, which change in both shape and behavior as the potential changes. We examine the structure and origin of these waves numerically and analytically. We also analyze the sensitivity of these waves to changes in different parameters of the system, including the effects of interparticle interactions on these structures. Strong interparticle interactions tend to disrupt the structure that develops in the non-interacting-particle case. We discuss possible experimental consequences of these phenomena. This work was supported by the U.S. Defense Threat Reduction Agency, and by the NNSA SSAA Program through DOE Research Grant No. DE-FG52-08NA28553.

  9. Simultaneous Eye Tracking and Blink Detection with Interactive Particle Filters

    NASA Astrophysics Data System (ADS)

    Wu, Junwen; Trivedi, Mohan M.

    2007-12-01

    We present a system that simultaneously tracks eyes and detects eye blinks. Two interactive particle filters are used for this purpose, one for the closed eyes and the other one for the open eyes. Each particle filter is used to track the eye locations as well as the scales of the eye subjects. The set of particles that gives higher confidence is defined as the primary set and the other one is defined as the secondary set. The eye location is estimated by the primary particle filter, and whether the eye status is open or closed is also decided by the label of the primary particle filter. When a new frame comes, the secondary particle filter is reinitialized according to the estimates from the primary particle filter. We use autoregression models for describing the state transition and a classification-based model for measuring the observation. Tensor subspace analysis is used for feature extraction which is followed by a logistic regression model to give the posterior estimation. The performance is carefully evaluated from two aspects: the blink detection rate and the tracking accuracy. The blink detection rate is evaluated using videos from varying scenarios, and the tracking accuracy is given by comparing with the benchmark data obtained using the Vicon motion capturing system. The setup for obtaining benchmark data for tracking accuracy evaluation is presented and experimental results are shown. Extensive experimental evaluations validate the capability of the algorithm.

  10. Time dilation in relativistic two-particle interactions

    SciTech Connect

    Shields, B. T.; Morris, M. C.; Ware, M. R.; Su, Q.; Grobe, R.; Stefanovich, E. V.

    2010-11-15

    We study the orbits of two interacting particles described by a fully relativistic classical mechanical Hamiltonian. We use two sets of initial conditions. In the first set (dynamics 1) the system's center of mass is at rest. In the second set (dynamics 2) the center of mass evolves with velocity V. If dynamics 1 is observed from a reference frame moving with velocity -V, the principle of relativity requires that all observables must be identical to those of dynamics 2 seen from the laboratory frame. Our numerical simulations demonstrate that kinematic Lorentz space-time transformations fail to transform particle observables between the two frames. This is explained as a result of the inevitable interaction dependence of the boost generator in the instant form of relativistic dynamics. Despite general inaccuracies of the Lorentz formulas, the orbital periods are correctly predicted by the Einstein's time dilation factor for all interaction strengths.

  11. How to model the interaction of charged Janus particles

    NASA Astrophysics Data System (ADS)

    Hieronimus, Reint; Raschke, Simon; Heuer, Andreas

    2016-08-01

    We analyze the interaction of charged Janus particles including screening effects. The explicit interaction is mapped via a least square method on a variable number n of systematically generated tensors that reflect the angular dependence of the potential. For n = 2 we show that the interaction is equivalent to a model previously described by Erdmann, Kröger, and Hess (EKH). Interestingly, this mapping is for n = 2 not able to capture the subtleties of the interaction for small screening lengths. Rather, a larger number of tensors has to be used. We find that the characteristics of the Janus type interaction plays an important role for the aggregation behavior. We obtained cluster structures up to the size of 13 particles for n = 2 and 36 and screening lengths κ-1 = 0.1 and 1.0 via Monte Carlo simulations. The influence of the screening length is analyzed and the structures are compared to results for an electrostatic-type potential and for the multipole-expanded Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. We find that a dipole-like potential (EKH or dipole DLVO approximation) is not able to sufficiently reproduce the anisotropy effects of the potential. Instead, a higher order expansion has to be used to obtain cluster structures that are compatible with experimental observations. The resulting minimum-energy clusters are compared to those of sticky hard sphere systems. Janus particles with a short-range screened interaction resemble sticky hard sphere clusters for all considered particle numbers, whereas for long-range screening even very small clusters are structurally different.

  12. Chromatic patchy particles: Effects of specific interactions on liquid structure

    DOE PAGESBeta

    Vasilyev, Oleg A.; Tkachenko, Alexei V.; Klumov, Boris A.

    2015-07-13

    We study the structural and thermodynamic properties of patchy particle liquids, with a special focus on the role of “color,” i.e., specific interactions between individual patches. A possible experimental realization of such “chromatic” interactions is by decorating the particle patches with single-stranded DNA linkers. The complementarity of the linkers can promote selective bond formation between predetermined pairs of patches. By using MD simulations, we compare the local connectivity, the bond orientation order, and other structural properties of the aggregates formed by the “colored” and “colorless” systems. The analysis is done for spherical particles with two different patch arrangements (tetrahedral andmore » cubic). It is found that the aggregated (liquid) phase of the “colorless” patchy particles is better connected, denser and typically has stronger local order than the corresponding “colored” one. This, in turn, makes the colored liquid less stable thermodynamically. Specifically, we predict that in a typical case the chromatic interactions should increase the relative stability of the crystalline phase with respect to the disordered liquid, thus expanding its region in the phase diagram.« less

  13. Particle Simulations for Electron Beam-Plasma Interactions

    NASA Astrophysics Data System (ADS)

    Zhou, Guo-cheng; G, Zhou C.; Li, Yang; Cao, Jin-bin; J, Cao B.; Wang, Xue-yi; X, Wang Y.

    1998-12-01

    The computer simulations of high-frequency instabilities excited by the high density electron beam and their nonlinear effect are presented. One-dimensional electromagnetic particle simulations are performed with different values of the electron beam-to-plasma density ratio. The results show that for the high electron beam-to-background plasma density ratio, all the Langmuir waves and two electromagnetic waves with left-hand and right-hand circular polarizations (i.e., the "L-O mode" and the "R-X mode") propagating parallel to the magnetic field can be generated and the maximum values of wave electric fields are nearly the same. The electron beam and background plasma are diffused and a part of energetic background electrons are obviously accelerated by the wave-particle interactions. The heating of the beam and background plasma is mainly due to the electrostatic (Langmuir) wave-particle interactions, but the accelerations of a part of energetic background electrons may be mainly due to the electromagnetic wave-particle interactions.

  14. Chromatic patchy particles: Effects of specific interactions on liquid structure.

    PubMed

    Vasilyev, Oleg A; Klumov, Boris A; Tkachenko, Alexei V

    2015-07-01

    We study the structural and thermodynamic properties of patchy particle liquids, with a special focus on the role of "color," i.e., specific interactions between individual patches. A possible experimental realization of such "chromatic" interactions is by decorating the particle patches with single-stranded DNA linkers. The complementarity of the linkers can promote selective bond formation between predetermined pairs of patches. By using MD simulations, we compare the local connectivity, the bond orientation order, and other structural properties of the aggregates formed by the "colored" and "colorless" systems. The analysis is done for spherical particles with two different patch arrangements (tetrahedral and cubic). It is found that the aggregated (liquid) phase of the "colorless" patchy particles is better connected, denser and typically has stronger local order than the corresponding "colored" one. This, in turn, makes the colored liquid less stable thermodynamically. Specifically, we predict that in a typical case the chromatic interactions should increase the relative stability of the crystalline phase with respect to the disordered liquid, thus expanding its region in the phase diagram. PMID:26274163

  15. Chromatic patchy particles: Effects of specific interactions on liquid structure

    SciTech Connect

    Vasilyev, Oleg A.; Tkachenko, Alexei V.; Klumov, Boris A.

    2015-07-13

    We study the structural and thermodynamic properties of patchy particle liquids, with a special focus on the role of “color,” i.e., specific interactions between individual patches. A possible experimental realization of such “chromatic” interactions is by decorating the particle patches with single-stranded DNA linkers. The complementarity of the linkers can promote selective bond formation between predetermined pairs of patches. By using MD simulations, we compare the local connectivity, the bond orientation order, and other structural properties of the aggregates formed by the “colored” and “colorless” systems. The analysis is done for spherical particles with two different patch arrangements (tetrahedral and cubic). It is found that the aggregated (liquid) phase of the “colorless” patchy particles is better connected, denser and typically has stronger local order than the corresponding “colored” one. This, in turn, makes the colored liquid less stable thermodynamically. Specifically, we predict that in a typical case the chromatic interactions should increase the relative stability of the crystalline phase with respect to the disordered liquid, thus expanding its region in the phase diagram.

  16. Electrostatic interactions between charged dielectric particles in an electrolyte solution.

    PubMed

    Derbenev, Ivan N; Filippov, Anatoly V; Stace, Anthony J; Besley, Elena

    2016-08-28

    Theory is developed to address a significant problem of how two charged dielectric particles interact in the presence of a polarizable medium that is a dilute solution of a strong electrolyte. The electrostatic force is defined by characteristic parameters for the interacting particles (charge, radius, and dielectric constant) and for the medium (permittivity and Debye length), and is expressed in the form of a converging infinite series. The limiting case of weak screening and large inter-particle separation is considered, which corresponds to small (macro)ions that carry constant charge. The theory yields a solution in the limit of monopole and dipole terms that agrees exactly with existing analytical expressions, which are generally used to describe ion-ion and ion-molecular interactions in a medium. Results from the theory are compared with DLVO theory and with experimental measurements for the electrostatic force between two PMMA particles contained in a nonpolar solvent (hexadecane) with an added charge control agent. PMID:27586900

  17. Interaction forces between waterborne bacteria and activated carbon particles.

    PubMed

    Busscher, Henk J; Dijkstra, Rene J B; Langworthy, Don E; Collias, Dimitris I; Bjorkquist, David W; Mitchell, Michael D; Van der Mei, Henny C

    2008-06-01

    Activated carbons remove waterborne bacteria from potable water systems through attractive Lifshitz-van der Waals forces despite electrostatic repulsion between negatively charged cells and carbon surfaces. In this paper we quantify the interaction forces between bacteria with negatively and positively charged, mesoporous wood-based carbons, as well as with a microporous coconut carbon. To this end, we glued carbon particles to the cantilever of an atomic force microscope and measured the interaction forces upon approach and retraction of thus made tips. Waterborne Raoultella terrigena and Escherichia coli adhered weakly (1-2 nN) to different activated carbon particles, and the main difference between the activated carbons was the percentage of curves with attractive sites revealed upon traversing of a carbon particle through the bacterial EPS layer. The percentage of curves showing adhesion forces upon retraction varied between 21% and 69%, and was highest for R. terrigena with positively charged carbon (66%) and a coconut carbon (69%). Macroscopic bacterial removal by the mesoporous carbon particles increased with increasing percentages of attractive sites revealed upon traversing a carbon particle through the outer bacterial surface layer. PMID:18405910

  18. Magnetic microswimmers: Controlling particle approach through magnetic and hydrodynamic interaction

    NASA Astrophysics Data System (ADS)

    Meshkati, Farshad; Cheang, U. Kei; Kim, Minjun; Fu, Henry

    2015-11-01

    We investigate magnetic microswimmers actuated by a rotating magnetic field that may be useful for drug delivery, micro-surgery, or diagnostics in human body. For modular swimmers, assembly and disassembly requires understanding the interactions between the swimmer and other modules in the fluid. Here, we discuss possible mechanisms for a frequency-dependent attraction/repulsion between a three-bead, achiral swimmer and other magnetic particles, which represent modular assembly elements. We first investigate the hydrodynamic interaction between a swimmer and nearby particle by studying the Lagrangian trajectories in the vicinity of the swimmer. Then we show that the magnetic forces can be attractive or repulsive depending on the spatial arrangement of the swimmer and particle, with a magnitude that decreases with increasing frequency. Combining magnetic and hydrodynamic effects allows us to understand the overall behavior of magnetic particles near the swimmer. Interestingly, we find that the frequency of rotation can be used to control when the particle can closely approach the swimmer, with potential application to assembly.

  19. Diffusion and Subdiffusion of Interacting Particles on Comblike Structures

    NASA Astrophysics Data System (ADS)

    Bénichou, O.; Illien, P.; Oshanin, G.; Sarracino, A.; Voituriez, R.

    2015-11-01

    We study the dynamics of a tracer particle (TP) on a comb lattice populated by randomly moving hard-core particles in the dense limit. We first consider the case where the TP is constrained to move on the backbone of the comb only. In the limit of high density of the particles, we present exact analytical results for the cumulants of the TP position, showing a subdiffusive behavior ˜t3 /4. At longer times, a second regime is observed where standard diffusion is recovered, with a surprising nonanalytical dependence of the diffusion coefficient on the particle density. When the TP is allowed to visit the teeth of the comb, based on a mean-field-like continuous time random walk description, we unveil a rich and complex scenario with several successive subdiffusive regimes, resulting from the coupling between the geometrical constraints of the comb lattice and particle interactions. In this case, remarkably, the presence of hard-core interactions asymptotically speeds up the TP motion along the backbone of the structure.

  20. Numerical investigation of fluid-particle interactions for embolic stroke

    NASA Astrophysics Data System (ADS)

    Mukherjee, Debanjan; Padilla, Jose; Shadden, Shawn C.

    2016-04-01

    Roughly one-third of all strokes are caused by an embolus traveling to a cerebral artery and blocking blood flow in the brain. The objective of this study is to gain a detailed understanding of the dynamics of embolic particles within arteries. Patient computed tomography image is used to construct a three-dimensional model of the carotid bifurcation. An idealized carotid bifurcation model of same vessel diameters was also constructed for comparison. Blood flow velocities and embolic particle trajectories are resolved using a coupled Euler-Lagrange approach. Blood is modeled as a Newtonian fluid, discretized using the finite volume method, with physiologically appropriate inflow and outflow boundary conditions. The embolus trajectory is modeled using Lagrangian particle equations accounting for embolus interaction with blood as well as vessel wall. Both one- and two-way fluid-particle coupling are considered, the latter being implemented using momentum sources augmented to the discretized flow equations. It was observed that for small-to-moderate particle sizes (relative to vessel diameters), the estimated particle distribution ratio—with and without the inclusion of two-way fluid-particle momentum exchange—were found to be similar. The maximum observed differences in distribution ratio with and without the coupling were found to be higher for the idealized bifurcation model. Additionally, the distribution was found to be reasonably matching the volumetric flow distribution for the idealized model, while a notable deviation from volumetric flow was observed in the anatomical model. It was also observed from an analysis of particle path lines that particle interaction with helical flow, characteristic of anatomical vasculature models, could play a prominent role in transport of embolic particle. The results indicate therefore that flow helicity could be an important hemodynamic indicator for analysis of embolus particle transport. Additionally, in the presence

  1. Electrohydrodynamic interaction of spherical particles under Quincke rotation.

    PubMed

    Das, Debasish; Saintillan, David

    2013-04-01

    Weakly conducting dielectric particles suspended in a dielectric liquid of higher conductivity can undergo a transition to spontaneous sustained rotation when placed in a sufficiently strong dc electric field. This phenomenon of Quincke rotation has interesting implications for the rheology of these suspensions, whose effective viscosity can be controlled and reduced by application of an external field. While previous models based on the rotation of isolated particles have provided accurate estimates for this viscosity reduction in dilute suspensions, discrepancies have been reported in more concentrated systems where particle-particle interactions are likely significant. Motivated by this observation, we extend the classic description of Quincke rotation based on the Taylor-Melcher leaky dielectric model to account for pair electrohydrodynamic interactions between two identical spheres using the method of reflections. A coupled system of evolution equations for the dipole moments and angular velocities of the spheres is derived that accounts for electric dipole-dipole interactions and hydrodynamic rotlet interactions up to order O(R(-5)), where R is the separation distance between the spheres. A linear stability analysis of this system shows that interactions modify the value of the critical electric field for the onset of Quincke rotation: both electric and hydrodynamic interactions can either stabilize or destabilize the system depending on the orientation of the spheres, but the leading effect of interactions on the onset of rotation is hydrodynamic. We also analyze the dynamics in the nonlinear regime by performing numerical simulations of the governing equations. In the case of a pair of spheres that are fixed in space, we find that particle rotations always synchronize in magnitude at long times, though the directions of rotation of the spheres need not be the same. The steady-state angular velocity magnitude depends on the configuration of the spheres and

  2. Interactive visualization of particle beams for accelerator design

    SciTech Connect

    Wilson, Brett; Ma, Kwan-Liu; Qiang, Ji; Ryne, Robert

    2002-01-15

    We describe a hybrid data-representation and rendering technique for visualizing large-scale particle data generated from numerical modeling of beam dynamics. The basis of the technique is mixing volume rendering and point rendering according to particle density distribution, visibility, and the user's instruction. A hierarchical representation of the data is created on a parallel computer, allowing real-time partitioning into high-density areas for volume rendering, and low-density areas for point rendering. This allows the beam to be interactively visualized while preserving the fine structure usually visible only with slow point based rendering techniques.

  3. Effects of High-Energy Ionizing Particles on the Si:As Mid-Infrared Detector Array on Board the AKARI Satellite

    NASA Astrophysics Data System (ADS)

    Mouri, A.; Kaneda, H.; Ishihara, D.; Oyabu, S.; Yamagishi, M.; Mori, T.; Onaka, T.; Wada, T.; Kataza, H.

    2011-05-01

    We evaluate the effects of high-energy ionizing particles on the Si:As impurity band conduction (IBC) mid-infrared detector on board AKARI, the Japanese infrared astronomical satellite. IBC-type detectors are known to be little influenced by ionizing radiation. However, we find that the detector is significantly affected by in-orbit ionizing radiation even after spikes induced by ionizing particles are removed. The effects are described as changes mostly in the offset of detector output, but not in the gain. We conclude that the changes in the offset are caused mainly by increase in dark current. We establish a method to correct these ionizing radiation effects. The method is essential to improve the quality and to increase the sky coverage of the AKARI mid-infrared all-sky-survey map.

  4. The PHOCUS Project: Particle Interactions in the Polar Summer Mesosphere

    NASA Astrophysics Data System (ADS)

    Gumbel, J.; Hedin, J.; Khaplanov, M.

    2012-12-01

    On the morning of July 21, 2011, the PHOCUS sounding rocket was launched from Esrange, Sweden, into strong noctilucent clouds (NLC) and polar mesosphere summer echoes (PMSE) observed by the Esrange lidar and the ESRAD MST radar. The aim of the PHOCUS project (Particles, Hydrogen and Oxygen Chemistry in the Upper Summer mesosphere) is to study mesospheric particles (ice and meteoric smoke) and their interaction with their neutral and charged environment. Starting out from first ideas in 2005, PHOCUS has developed into a comprehensive venture that connects to a number of new and renewed scientific questions. Interactions of interest comprise the charging and nucleation of particles, the relationship between meteoric smoke and ice, and the influence of these particles on gas-phase chemistry. This presentation gives an overview of the campaign and scientific results. The backbone of the campaign was a sounding rocket with 18 instruments from 8 scientific groups in Sweden, Norway, Germany, Austria and the USA. Atmospheric composition and ice particle properties were probed by a set of optical instruments from Stockholm University, in collaboration with the University in Trondheim. Exciting new instrument developments concerned microwave radiometers for in situ measurements of water vapour at 183 and 558 GHz by Chalmers University of Technology. Charged particles were probed by impact detectors from the University of Colorado, the University of Tromsø and the Leibniz Institute of Atmospheric Physics (IAP), complemented by direct particle sampling from Stockholm University. The neutral and charged background state of the atmosphere was quantified by the Technical University Graz, IAP, and the Norwegian Defence Research Establishment. Important ground-based instrumentation included the Esrange lidar, the ESRAD MST radar, the SkiYMET meteor radar and EISCAT.

  5. Electrokinetic particle-electrode interactions at high frequencies

    NASA Astrophysics Data System (ADS)

    Yariv, Ehud; Schnitzer, Ory

    2013-01-01

    We provide a macroscale description of electrokinetic particle-electrode interactions at high frequencies, where chemical reactions at the electrodes are negligible. Using a thin-double-layer approximation, our starting point is the set of macroscale equations governing the “bounded” configuration comprising of a particle suspended between two electrodes, wherein the electrodes are governed by a capacitive charging condition and the imposed voltage is expressed as an integral constraint. In the large-cell limit the bounded model is transformed into an effectively equivalent “unbounded” model describing the interaction between the particle and a single electrode, where the imposed-voltage condition is manifested in a uniform field at infinity together with a Robin-type condition applying at the electrode. This condition, together with the standard no-flux condition applying at the particle surface, leads to a linear problem governing the electric potential in the fluid domain in which the dimensionless frequency ω of the applied voltage appears as a governing parameter. In the high-frequency limit ω≫1 the flow is dominated by electro-osmotic slip at the particle surface, the contribution of electrode electro-osmosis being O(ω-2) small. That simplification allows for a convenient analytical investigation of the prevailing case where the clearance between the particle and the adjacent electrode is small. Use of tangent-sphere coordinates allows to calculate the electric and flows fields as integral Hankel transforms. At large distances from the particle, along the electrode, both fields decay with the fourth power of distance.

  6. Experimental studies of wave-particle interactions in space using particle correlators: results and future developments

    NASA Astrophysics Data System (ADS)

    Gough, M.; Buckley, A.; Carozzi, T.; Beloff, N.

    The technique of particle correlation measures directly electron modulations that result from naturally occurring and actively stimulated wave-particle interactions in space plasmas. In the past this technique has been used for studies of beam-plasma interactions, caused by both natural auroral electron beams via sounding rockets and by artificially generated electron beams on Shuttle missions: TSS-1/-TSS -1R. It has also been applied to studies of how electrons become energised by waves injected from in-situ transmitters (OEDIPUS-C). All four ESA Cluster-II spacecraft launched in 2000 to study the outer magnetosphere, cusp, and bow shock were implemented with electron correlators. Here the prevalent broader band wave-particle interactions have been more difficult to extract. However, the application of new statistical algorithms has permitted these correlators to provide a novel insight into turbulence occurring and also provided an independent means whereby electron count rates can be corrected for detector saturation effects. Present work involves technical improvements to both sensor design and correlator implementation that enable many electron energy-angle combinations to be simultaneously monitored for wave-particle interactions. A b oad energy -angler range spectrograph connected to a multi-channel, multi-frequency range FPGA implemented array of correlators is scheduled to fly early 2004. Neural network techniques previously flown on TSS -1 , TSS-1R, and statistical tests developed for Cluster-II will be used on-board to select data to be transmitted.

  7. Anomalous temperature relaxation and particle transport in a strongly non-unifrom, fully in ionized Plasma in a stromg mangnetic field

    NASA Astrophysics Data System (ADS)

    Øien, Alf H.

    1995-02-01

    In classical kinetic and transport theory for a fully ionized plasma in a magnetic field, collision integrals from a uniform theory without fields are used. When the magnetic field is so strong that electrons may gyrate during electron—electron and electron—ion interactions, the form of the collision integrals will be modified. Another modification will stem from strong non-uniformities transverse to the magnetic field B. Using collision terms that explicitly incorporate these effects, we derive in particular the temperature relaxation between electrons and ions and the particle transport transverse to the magnetic field. In both cases collisions between gyrating electrons, which move along the magnetic field, and non-gyrating ions, which move in arbitrary directions at a distance transverse to B from the electrons larger than the electron Larmor radius but smaller than the Debye length, give rise to enhancement factors in the corresponding classical expressions of order In (mion/mel).

  8. Interaction with the lower ionosphere of electromagnetic pulses from lightning - Heating, attachment, and ionization

    NASA Technical Reports Server (NTRS)

    Taranenko, Y. N.; Inan, U. S.; Bell, T. F.

    1993-01-01

    A Boltzmann formulation of the electron distribution function and Maxwell's equations for the EM fields are used to simulate the interaction of lightning radiated EM pulses with the lower ionosphere. Ionization and dissociative attachment induced by the heated electrons cause significant changes in the local electron density, N(e). Due to 'slow' field changes of typical lightning EM pulses over time scales of tens of microsec, the distribution function follows the quasi-equilibrium solution of the Boltzmann equation in the altitude range of interest (70 to 100 km). The EM pulse is simulated as a planar 100 microsec long single period oscillation of a 10 kHz wave injected at 70 km. Under nighttime conditions, individual pulses of intensity 10-20 V/m (normalized to 100 km horizontal distance) produce changes in N(e) of 1-30 percent while a sequence of pulses leads to strong modification of N(e) at altitudes less than 95 km. The N(e) changes produce a 'sharpening' of the lower ionospheric boundary by causing a reduction in electron density at 75-85 km (due to attachment) and a substantial increase at 85-95 km (due to ionization) (e.g., the scale height decreases by a factor of about 2 at about 85 km for a single 20 V/m EM pulse). No substantial N(e) changes occur during daytime.

  9. Characterization of the interactions within fine particle mixtures in highly concentrated suspensions for advanced particle processing.

    PubMed

    Otsuki, Akira; Bryant, Gary

    2015-12-01

    This paper aims to summarize recent investigations into the dispersion of fine particles, and the characterization of their interactions, in concentrated suspensions. This summary will provide a better understanding of the current status of this research, and will provide useful feedback for advanced particle processing. Such processes include the fabrication of functional nanostructures and the sustainable beneficiation of complex ores. For example, there has been increasing demand for complex ore utilization due to the noticeable decrease in the accessibility of high grade and easily extractable ores. In order to maintain the sustainable use of mineral resources, the effective beneficiation of complex ores is urgently required. It can be successfully achieved only with selective particle/mineral dispersion/liberation and the assistance of mineralogical and particle characterization. PMID:26298173

  10. A mechanistic interpretation of the resonant wave-particle interaction

    NASA Astrophysics Data System (ADS)

    Chim, Chi Yung; O'Neil, Thomas M.

    2016-05-01

    This paper provides a simple mechanistic interpretation of the resonant wave-particle interaction of Landau. For the simple case of a Langmuir wave in a Vlasov plasma, the non-resonant electrons satisfy an oscillator equation that is driven resonantly by the bare electric field from the resonant electrons, and in the case of wave damping, this complex driver field is of a phase to reduce the oscillation amplitude. The wave-particle resonant interaction also occurs in waves governed by 2D E × B drift dynamics, such as a diocotron wave. In this case, the bare electric field from the resonant electrons causes E × B drift motion back in the core plasma, reducing the amplitude of the wave.