Science.gov

Sample records for ionizing particles interacting

  1. Plasma ionization through wave-particle interaction in a capacitively coupled radio-frequency discharge

    SciTech Connect

    O'Connell, D.; Gans, T.; Vender, D.; Czarnetzki, U.; Boswell, R.

    2007-03-15

    Phase resolved optical emission spectroscopy, with high temporal resolution, shows that wave-particle interactions play a fundamental role in sustaining capacitively coupled rf plasmas. The measurements are in excellent agreement with a simple particle-in-cell simulation. Excitation and ionization mechanisms are dominated by beam-like electrons, energized through the advancing and retreating electric fields of the rf sheath. The associated large-amplitude electron waves, driven by a form of two-stream instability, result in power dissipation through electron trapping and phase mixing.

  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. 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.

  4. Charged-Particle Impact Ionization of Atoms

    SciTech Connect

    Bartschat, Klaus; Guan Xiaoxu

    2008-08-08

    We have developed a hybrid method to treat charged-particle impact ionization of complex atoms and ions. The essential idea is to describe the interaction between a fast projectile and the target perturbatively, up to second order, while the initial bound state and the ejected-electron--residual-ion interaction can be handled via a convergent R-matrix with pseudo-states (close-coupling) expansion. Example results for ionization of the heavy noble gases (Ne-Xe) by positron and electron impact are presented. The general scheme for a distorted-wave treatment of ionization by heavy-particle impact is described.

  5. 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}.

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

    DOE PAGES

    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.

  7. 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 .

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

    SciTech Connect

    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.

  9. Simultaneous high resolution meausurement of phonons and ionization created by particle interactions in a 60 g germanium crystal at 25 mK

    SciTech Connect

    Shutt, T.; Wang, N.; Ellman, B.; Giraud-Heraud, Y.; Stubbs, C.; Barnes, P.D. Jr.; Cummings, A.; Da Silva, A.; Emes, J.; Haller, E.E.; Lange, A.E.; Rich, J.; Ross, R.R.; Sadoulet, B.; Smith, G.; Stockwell, W.; White, S.; Young, B.A.; Yvon, D. Department of Physics, University of California at Berkeley, Berkeley, California 94720 Department of Material Science Mineral Engineering, University of California at Berkeley, Berkeley, California 94720 Lawrence Berkeley Laboratory, 1 Cyclotron Road, Berkeley, California 94720 Department of Physics, University of California at Santa Barbara, Santa Barbara, California 93106 Department d'Astrophysique, de Physique des Particules, de Physique Nucleaire et de l'Instrumentation Associee-Service Physique des Particles Centre I'Etudes Nucleaires de Saclay, 91191 Gif-sur-Yvett

    1992-12-14

    We demonstrate simultaneous high energy resolution (rms[approx]800 eV) measurements of ionization and phonons created by particle interactions in a semiconductor crystal of macroscopic size (60 g germanium) at 25 mK. We present first studies of charge collection at biases below 1 V/cm, and find that, contrary to commonly held opinion, the full recoil energy of particle interactions is recovered as phonons when charge trapping is negligible. We also report an unanticipated correlation between charge collection and phonon energy at very low bias, and discuss this effect in terms of charge trapping.

  10. The practical use of an interactive visualization and planning tool for intervention planning in particle accelerator environments with ionizing radiation

    NASA Astrophysics Data System (ADS)

    Fabry, Thomas; Blaha, Jan; Vanherpe, Liesbeth; Braesch, Christian; Tabourot, Laurent; Feral, Bruno

    2014-04-01

    A core issue during the planning of a maintenance intervention in a facility with ionizing radiation is the minimization of the integrated equivalent dose contracted by the maintenance workers during the intervention. In this work, we explore the use of a technical-scientific software program facilitating the intervention planning in irradiated environments using sound mathematical concepts. We show how the software can be used in planning future operations using a case studies: the decommissioning of a beam dump for a linear 160 MeV H- accelerator. Interactive visualization of the facilities and radiation levels, as well as tools for interactive trajectory planning are explored, as well as automatic calculation of the expected integrated individual dose contracted during an intervention.

  11. Search for low-mass weakly interacting massive particles using voltage-assisted calorimetric ionization detection in the SuperCDMS experiment.

    PubMed

    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

    2014-01-31

    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.

  12. 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, 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.

    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 paper, 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 10 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.

  13. 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.

  14. 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.

  15. Double ionization of helium by particle impact

    NASA Technical Reports Server (NTRS)

    Jacobsen, Finn M.

    1990-01-01

    Experimental results are reviewed of the ratio, R sq., of double to single ionization of He by proton, antiproton, electron and positron impact in the energy range from 0.15 to about 10 MeV/amu. At high velocities (greater than 1 to 2 MeV/amu) values of R sq. caused by electron impact merge with those for the proton with the antiproton, electron values being up to a factor of 2 greater than that for the p, positron. At these velocities the single ionization cross sections caused by impact of any of these four particles are indistinguishable.

  16. Stellar energetic particle ionization in protoplanetary disks around T Tauri stars

    NASA Astrophysics Data System (ADS)

    Rab, Ch.; Güdel, M.; Padovani, M.; Kamp, I.; Thi, W.-F.; Woitke, P.; Aresu, G.

    2017-07-01

    Context. Anomalies in the abundance measurements of short lived radionuclides in meteorites indicate that the protosolar nebulae was irradiated by a large number of energetic particles (E ≳ 10 MeV). The particle flux of the contemporary Sun cannot explain these anomalies. However, similar to T Tauri stars the young Sun was more active and probably produced enough high energy particles to explain those anomalies. Aims: We aim to study the interaction of stellar energetic particles with the gas component of the disk (i.e. ionization of molecular hydrogen) and identify possible observational tracers of this interaction. Methods: We used a 2D radiation thermo-chemical protoplanetary disk code to model a disk representative for T Tauri stars. We used a particle energy distribution derived from solar flare observations and an enhanced stellar particle flux proposed for T Tauri stars. For this particle spectrum we calculated the stellar particle ionization rate throughout the disk with an accurate particle transport model. We studied the impact of stellar particles for models with varying X-ray and cosmic-ray ionization rates. Results: We find that stellar particle ionization has a significant impact on the abundances of the common disk ionization tracers HCO+ and N2H+, especially in models with low cosmic-ray ionization rates (e.g. 10-19 s-1 for molecular hydrogen). In contrast to cosmic rays and X-rays, stellar particles cannot reach the midplane of the disk. Therefore molecular ions residing in the disk surface layers are more affected by stellar particle ionization than molecular ions tracing the cold layers and midplane of the disk. Conclusions: Spatially resolved observations of molecular ions tracing different vertical layers of the disk allow to disentangle the contribution of stellar particle ionization from other competing ionization sources. Modelling such observations with a model like the one presented here allows to constrain the stellar particle flux in

  17. 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.

  18. 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.

  19. Elementary particle interactions

    SciTech Connect

    Bugg, W.M.; Condo, G.T.; Handler, T.; Hart, E.L.; Ward, B.F.L.; Close, F.E.; Christophorou, L.G.

    1990-10-01

    This report discusses freon bubble chamber experiments exposed to {mu}{sup +} and neutrinos, photon-proton interactions; shower counter simulations; SLD detectors at the Stanford Linear Collider, and the detectors at the Superconducting Super Collider; elementary particle interactions; physical properties of dielectric materials used in High Energy Physics detectors; and Nuclear Physics. (LSP)

  20. 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%.

  1. 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.

  2. 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

  3. STUDY OF IONIZATION POTENTIAL OF SMALL PARTICLES.

    DTIC Science & Technology

    flowing stream of helium gas and a nucleating agent. In related experiments, monodispersed sulfur hydrosols and possibly cesium particles were produced...of particle size on particle work function, the cooling process of a hot vapor in a cooler gas and the formation mechanism of monodispersed sulfur hydrosols . (Author)

  4. 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...

  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. Investigating The Ionization of The Earth's Atmosphere At Large Energetic Particle Events

    NASA Astrophysics Data System (ADS)

    Wolff, E.; Burrows, J.; Kallenrode, M.-B.; von König, M.; Künzi, K. F.; Quack, M.

    To investigate the influence of energetic particle events on the terrestrial atmosphere (e.g. due to ionization and/or hadronic interaction) a number of aspects are under consideration, such as the species of the precipitating particles, their energies, fluences as well as a repetition rate of events. In preparation of a refined model of precipitating charged particle interactions with the atmosphere, we calculate the ionization in the earth's atmosphere for well- known recent events (e.g. the Bastille Day event on July 14, 2000) of high particle fluences by using computer simulations of the earth's atmosphere and in situ measured particle intensities. The changes in atmospheric chemistry derieved from this ionization are described in the accompanying contribution of M. von König et al. (Modelling the influence of large energetic particle events on the chemical composition of the middle and upper atmosphere). Although very effective for atmospheric chemistry, these events are too rare and too short-lived to contribute significantly to the atmospheric NOx budget on a long-time basis. However, McCracken et al. (2001) suggests from nitrate depositions in ice- cores that solar particle events have occured more frequently and with a higher in- tensity in historical times, and thus may have led to a greater impact than the events discussed above. Therefore, we evaluate the influence of large historical energetic particle events, such as NOx and Ozone behaviour due to atmospheric ionization at Carrington's white light flare in 1859.

  7. 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.

  8. 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.

  9. 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.

  10. Axionlike particle assisted strongly interacting massive particle

    NASA Astrophysics Data System (ADS)

    Kamada, Ayuki; Kim, Hyungjin; Sekiguchi, Toyokazu

    2017-07-01

    We propose a new realization of strongly interacting massive particles (SIMPs) as self-interacting dark matter, where SIMPs couple to the standard model (SM) sector through an axionlike particle. Our model overcomes major obstacles accompanying the original SIMP model, such as a missing mechanism of kinetically equilibrating SIMPs with the SM plasma as well as marginal perturbativity of the chiral Lagrangian density. Remarkably, the parameter region realizing σself/mDM≃0.1 - 1 cm2/g is within the reach of future beam dump experiments such as the Search for Hidden Particles experiment.

  11. Electrospray ionizer for mass spectrometry of aerosol particles

    DOEpatents

    He, Siqin; Hogan, Chris; Li, Lin; Liu, Benjamin Y. H.; Naqwi, Amir; Romay, Francisco

    2017-09-19

    A device and method are disclosed to apply ESI-based mass spectroscopy to submicrometer and nanometer scale aerosol particles. Unipolar ionization is utilized to charge the particles in order to collect them electrostatically on the tip of a tungsten rod. Subsequently, the species composing the collected particles are dissolved by making a liquid flow over the tungsten rod. This liquid with dissolved aerosol contents is formed into highly charged droplets, which release unfragmented ions for mass spectroscopy, such as time-of-flight mass spectroscopy. The device is configured to operate in a switching mode, wherein aerosol deposition occurs while solvent delivery is turned off and vice versa.

  12. Coulomb interactions in particle beams

    SciTech Connect

    Jansen, G.H. )

    1990-01-01

    This book develops analytical and computer models for beams in which Coulomb interactions are important. The research into the different phenomena of Coulomb interactions in particle beams is stimulated by developments in the field of electron beam lithography for VLSI electronics. The standard theory of charged particle optics breaks down for intense beams in which interactions between particles are significant. This monograph is devoted to the theory of these intense beams, which are not only used in VLSI electronics but also in scanning electron microscopes. The theory is also applicable to focused ion beams, which are used in VLSI mask repair.

  13. 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.

  14. 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.

  15. 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.

  16. Ionization of multielectron atoms by fast charged particles.

    NASA Technical Reports Server (NTRS)

    Omidvar, K.; Kyle, H. L.; Sullivan, E. C.

    1972-01-01

    Using plane waves to describe the incident and scattered particles, and screened hydrogenic and Coulomb functions to describe the atomic electrons before and after ejections, we have calculated the differential and total ionization cross sections of 11 atoms and one ion by electron impact, and ionization of helium by proton impact. The effective charges of the screened hydrogenic functions are fixed by the Hartree-Fock calculations. Calculations have been carried out for the atomic s, p, and d electrons. For low atomic numbers, we find reasonable agreement with the experimental data. For intermediate atomic numbers, we expect our results to overestimate the actual cross sections, since our choice of a unit charge for the Coulomb function of the ejected electrons will overestimate the atomic dipole potential strength, and in turn the high-energy cross sections. The advantage of the method presented here is that the ionization amplitude is given in analytic form. This may allow further analysis on this amplitude, and facilitates extension of the numerical integration for the cross section to high impact energies.

  17. Ionizing Energy Depositions After Fast Neutron Interactions in Silicon

    DOE PAGES

    Bergmann, Benedikt; Pospisil, Stanislav; Caicedo, Ivan; ...

    2016-06-01

    In our study we present the ionizing energy depositions in a 300 μm thick silicon layer after fast neutron impact. With the Time-of-Flight (ToF) technique, the ionizing energy deposition spectra of recoil silicons and secondary charged particles were assigned to (quasi-)monoenergetic neutron energies in the range from 180 keV to hundreds of MeV. We also show and interpret representative measured energy spectra. By separating the ionizing energy losses of the recoil silicon from energy depositions by products of nuclear reactions, the competition of ionizing (IEL) and non-ionizing energy losses (NIEL) of a recoil silicon within the silicon lattice was investigated.more » Furthermore, the data give supplementary information to the results of a previous measurement and are compared with different theoretical predictions.« less

  18. Ionizing Energy Depositions After Fast Neutron Interactions in Silicon

    SciTech Connect

    Bergmann, Benedikt; Pospisil, Stanislav; Caicedo, Ivan; Kierstead, James; Takai, Helio; Frojdh, Erik

    2016-06-01

    In our study we present the ionizing energy depositions in a 300 μm thick silicon layer after fast neutron impact. With the Time-of-Flight (ToF) technique, the ionizing energy deposition spectra of recoil silicons and secondary charged particles were assigned to (quasi-)monoenergetic neutron energies in the range from 180 keV to hundreds of MeV. We also show and interpret representative measured energy spectra. By separating the ionizing energy losses of the recoil silicon from energy depositions by products of nuclear reactions, the competition of ionizing (IEL) and non-ionizing energy losses (NIEL) of a recoil silicon within the silicon lattice was investigated. Furthermore, the data give supplementary information to the results of a previous measurement and are compared with different theoretical predictions.

  19. Ionizing Energy Depositions After Fast Neutron Interactions in Silicon

    SciTech Connect

    Bergmann, Benedikt; Pospisil, Stanislav; Caicedo, Ivan; Kierstead, James; Takai, Helio; Frojdh, Erik

    2016-06-01

    In our study we present the ionizing energy depositions in a 300 μm thick silicon layer after fast neutron impact. With the Time-of-Flight (ToF) technique, the ionizing energy deposition spectra of recoil silicons and secondary charged particles were assigned to (quasi-)monoenergetic neutron energies in the range from 180 keV to hundreds of MeV. We also show and interpret representative measured energy spectra. By separating the ionizing energy losses of the recoil silicon from energy depositions by products of nuclear reactions, the competition of ionizing (IEL) and non-ionizing energy losses (NIEL) of a recoil silicon within the silicon lattice was investigated. Furthermore, the data give supplementary information to the results of a previous measurement and are compared with different theoretical predictions.

  20. Coulomb interactions in particle beams

    NASA Astrophysics Data System (ADS)

    Jansen, Gerrit Hermanus

    The theory of particle interactions in low and medium density, nonrelativistic, time-independent beams of identical particles, in probe forming instruments is discussed. Low and medium density and nonrelativistic refer to beam currents typically much smaller than 1 mA and beam voltages typically between 1 and 100 keV. Time-independent implies that the flow of particles is assumed to be constant. The theory is developed for electron-beam lithography pattern generators and scanning electron microscopes. It should be applicable to focused ion beam tools as well. The analytical models used are based on the ideas of Van Leeuwen and Jansen (1983). This work is extended and confronted with other theories and the results of numerical Monte Carlo simulation. The impact of particle interactions on beams in drift space is stressed. Results of an analysis to extend the model to beams in an external uniform acceleration field are presented.

  1. Ionization-cluster distributions of alpha-particles in nanometric volumes of propane: measurement and calculation.

    PubMed

    De Nardo, L; Colautti, P; Conte, V; Baek, W Y; Grosswendt, B; Tornielli, G

    2002-12-01

    The probability of the formation of ionization clusters by primary alpha-particles at 5.4 MeV in nanometric volumes of propane was studied experimentally and by Monte Carlo simulation, as a function of the distance between the center line of the particle beam and the center of the target volume. The volumes were of cylindrical shape, 3.7 mm in diameter and height. As the investigations were performed at gas pressures of 300 Pa and 350 Pa, the dimensions of the target volume were equivalent to 20.6 nm or 24.0 nm in a material of density 1.0 g/cm(3). The dependence of ionization-cluster formation on distance was studied up to values equivalent to about 70 nm. To validate the measurements, a Monte Carlo model was developed which allows the experimental arrangement and the interactions of alpha-particles and secondary electrons in the counter gas to be properly simulated. This model is supplemented by a mathematical formulation of cluster size formation in nanometric targets. The main results of our study are (i) that the mean ionization-cluster size in the delta-electron cloud of an alpha-particle track segment, decreases as a function of the distance between the center line of the alpha-particle beam and the center of the sensitive target volume to the power of 2.6, and (ii) that the mean cluster size in critical volumes and the relative variance of mean cluster size due to delta-electrons are invariant at distances greater than about 20 nm. We could imagine that the ionization-cluster formation in nanometric volumes might in future provide the physical basis for a redefinition of radiation quality.

  2. 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.)

  3. Extractive Electrospray Ionization Mass Spectrometry of Heterogeneous Particles: Implications for Applications to Complex Atmospheric Aerosol

    NASA Astrophysics Data System (ADS)

    Longin, T.; Waring-Kidd, C.; Wingen, L. M.; Lyster, K.; Anderson, C.; Kumbhani, S.; Finlayson-Pitts, B. J.

    2015-12-01

    Extractive electrospray ionization mass spectrometry (EESI-MS) is a direct, real time technique for obtaining mass spectra of gases, liquid droplets, solid particles, and aerosols with little sample processing. EESI-MS involves the interaction of charged electrospray droplets with a separate spray containing the analyte of interest, but the exact mechanism by which the solvent droplets extract analyte from the sample is unclear. Possible mechanisms include complete coalescence of the sample particle with the solvent droplet in which all of the analyte is incorporated into the solvent or a more temporary interaction such that only some of the analyte is transferred to the solvent. Previous studies of the mechanism of EESI-MS on homogeneous particles indicate that both mechanisms are possible. We studied the behavior of EESI-MS toward heterogeneous particles created by coating NaCl particles with various thicknesses of organic diacids. Our results indicate that the signal strength depends on the solubility of the organic acid in the electrospray solvent, in agreement with previous studies, and also that the outer 10-15 nm of the particles are most susceptible to extraction into the electrospray droplets. Our results combined with those of previous studies suggest that the mass spectra obtained with EESI will not necessarily reflect the overall particle composition, especially for particles that are spatially inhomogeneous, and hence caution in interpretation of the data is advised for application to complex atmospheric aerosol.

  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. 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.

  6. Light weakly interacting massive particles

    NASA Astrophysics Data System (ADS)

    Gelmini, Graciela B.

    2017-08-01

    Light weakly interacting massive particles (WIMPs) are dark matter particle candidates with weak scale interaction with the known particles, and mass in the GeV to tens of GeV range. Hints of light WIMPs have appeared in several dark matter searches in the last decade. The unprecedented possible coincidence into tantalizingly close regions of mass and cross section of four separate direct detection experimental hints and a potential indirect detection signal in gamma rays from the galactic center, aroused considerable interest in our field. Even if these hints did not so far result in a discovery, they have had a significant impact in our field. Here we review the evidence for and against light WIMPs as dark matter candidates and discuss future relevant experiments and observations.

  7. 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".

  8. 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…

  9. 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…

  10. Electrostatic interactions between Janus particles

    NASA Astrophysics Data System (ADS)

    de Graaf, Joost; Boon, Niels; Dijkstra, Marjolein; van Roij, René

    2012-09-01

    In this paper we study the electrostatic properties of "Janus" spheres with unequal charge densities on both hemispheres. We introduce a method to compare primitive-model Monte Carlo simulations of the ionic double layer with predictions of (mean-field) nonlinear Poisson-Boltzmann theory. We also derive practical Derjaguin Landau Verwey Overbeek (DLVO)-like expressions that describe the Janus-particle pair interactions by mean-field theory. Using a large set of parameters, we are able to probe the range of validity of the Poisson-Boltzmann approximation, and thus of DLVO-like theories, for such particles. For homogeneously charged spheres this range corresponds well to the range that was predicted by field-theoretical studies of homogeneously charged flat surfaces. Moreover, we find similar ranges for colloids with a Janus-type charge distribution. The techniques and parameters we introduce show promise for future studies of an even wider class of charged-patterned particles.

  11. 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

  12. 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.

  13. Cardiovascular Risks Associated with Low Dose Ionizing Particle Radiation

    DOE PAGES

    Yan, Xinhua; Sasi, Sharath P.; Gee, Hannah; ...

    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

  14. 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.

  15. In situ mass analysis of particles by surface ionization mass spectrometry

    NASA Technical Reports Server (NTRS)

    Lassiter, W. S.; Moen, A. L.

    1974-01-01

    A qualitative study of the application of surface ionization and mass spectrometry to the in situ detection and constituent analysis of atmospheric particles was conducted. The technique consists of mass analysis of ions formed as a result of impingement of a stream of particles on a hot filament where, it is presumed, surface ionization takes place. Laboratory air particles containing K, Ca, and possibly hydrocarbons were detected. Other known particles such as Al2O3, Pb(NO3)2, and Cr2O3 were analyzed by detecting the respective metal atoms making up the particles. In some cases, mass numbers indicative of compounds making up the particles were detected showing surface ionization of particles sometimes leads to chemical analysis as well as to elemental analysis. Individual particles were detected, and it was shown that the technique is sensitive to Al2O3 particles with a mass of a few nanograms.

  16. 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

  17. Intense Field-Matter Interactions: Multiple Ionization of Clusters

    SciTech Connect

    Snyder, E.M.; Buzza, S.A.; Castleman, A.W. Jr.

    1996-10-01

    We report the results for the production of highly charged atomic species (e.g., Xe{sup 20+}, Kr{sup 18+}, O{sup 5+}, and C{sup 4+}) resulting from the interaction of intense laser fields (up to {approximately}10{sup 15} W/cm{sup 2}) with atomic and multicenter molecular clusters. The processes are also investigated using ultrafast pump-probe techniques, showing distinct beating patterns for the ionization structure in the molecular system. A comparison of our results with predictions of several different theoretical models provides strong support for the ionization ignition mechanism. {copyright} {ital 1996 The American Physical Society.}

  18. 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

  19. Particle-in-cell Simulations of Raman Laser Amplification in Ionizing Plasmas

    SciTech Connect

    Daniel S. Clark; Nathaniel J. Fisch

    2003-06-27

    By using the amplifying laser pulse in a plasma-based backward Raman laser amplifier to generate the plasma by photo-ionization of a gas simultaneous with the amplification process, possible instabilities of the pumping laser pulse can be avoided. Particle-in-cell simulations are used to study this amplification mechanism, and earlier results using more elementary models of the Raman interaction are verified [D.S. Clark and N.J. Fisch, Phys. Plasmas, 9 (6): 2772-2780, 2002]. The effects (unique to amplification in ionizing plasmas and not included in previous simulations) of blue-shifting of the pump and seed laser pulses and the generation of a wake are observed not significantly to impact the amplification process. As expected theoretically, the peak output intensity is found to be limited to I {approx} 10{sup 17} W/cm{sup 2} by forward Raman scattering of the amplifying seed. The integrity of the ionization front of the seed pulse against the development of a possible transverse modulation instability is also demonstrated.

  20. Kinetic analysis of competition between aerosol particle removal and generation by ionization air purifiers.

    PubMed

    Alshawa, Ahmad; Russell, Ashley R; Nizkorodov, Sergey A

    2007-04-01

    Ionization air purifiers are increasingly used to remove aerosol particles from indoor air. However, certain ionization air purifiers also emit ozone. Reactions between the emitted ozone and unsaturated volatile organic compounds (VOC) commonly found in indoor air produce additional respirable aerosol particles in the ultrafine (<0.1 microm) and fine (<2.5 microm) size domains. A simple kinetic model is used to analyze the competition between the removal and generation of particulate matter by ionization air purifiers under conditions of a typical residential building. This model predicts that certain widely used ionization air purifiers may actually increase the mass concentration of fine and ultrafine particulates in the presence of common unsaturated VOC, such as limonene contained in many household cleaning products. This prediction is supported by an explicit observation of ultrafine particle nucleation events caused by the addition of D-limonene to a ventilated office room equipped with a common ionization air purifier.

  1. Charge cluster distribution in nanosites traversed by a single ionizing particle An experimental approach

    NASA Astrophysics Data System (ADS)

    Pszona, S.; Bantsar, A.; Kula, J.

    2008-11-01

    A method for modeling charge cluster formation by a single ionizing particle in nanoelectronic structures of few nanometres size is presented. The method is based on experimental modeling of charge formation in the equivalent gaseous nanosites irradiated by single charged particles and the subsequent scaling procedure to a needed medium. Propane irradiated by alpha particles is presented as an example.

  2. Ionization front interactions and the formation of globules

    NASA Astrophysics Data System (ADS)

    Brand, P. W. J. L.

    1981-10-01

    It is assumed that an H II region has evolved inside a molecular cloud. The interactions that result from the expanding shell of compressed molecular gas reaching the edge of the cloud are calculated, and the instability of the ionization front to the formation of globules is investigated. The rarefaction wave which is reflected from the contact discontinuity as the leading shock passes through the edge of the cloud accelerates the ionization front, and since conditions at the front satisfy Capriotti's criterion for instability, the shell breaks up. The size of the fragment so created is determined by the thickness of the compressed shell. If the shell phase of H II region evolution has proceeded significantly, then globules of up to a fraction of a solar mass may be formed in an H II region caused by a star with an ionizing luminosity of 10 to the 49th photons/sec in a molecular cloud of density 1000/cu cm. These globules may survive the ionizing flux from the star, and will be driven from the cloud by the rocket effect.

  3. Hydrodynamic particle focusing design using fluid-particle interaction.

    PubMed

    Zhou, Teng; Liu, Zhenyu; Wu, Yihui; Deng, Yongbo; Liu, Yongshun; Liu, Geng

    2013-01-01

    For passive sheathless particles focusing in microfluidics, the equilibrium positions of particles are typically controlled by micro channels with a V-shaped obstacle array (VOA). The design of the obstacles is mainly based on the distribution of flow streamlines without considering the existence of particles. We report an experimentally verified particle trajectory simulation using the arbitrary Lagrangian-Eulerian (ALE) fluid-particle interaction method. The particle trajectory which is strongly influenced by the interaction between the particle and channel wall is systematically analyzed. The numerical experiments show that the streamline is a good approximation of particle trajectory only when the particle locates on the center of the channel in depth. As the advantage of fluid-particle interaction method is achieved at a high computational cost and the streamline analysis is complex, a heuristic dimensionless design objective based on the Faxen's law is proposed to optimize the VOA devices. The optimized performance of particle focusing is verified via the experiments and ALE method.

  4. Interactions between Janus particles and membranes

    NASA Astrophysics Data System (ADS)

    Ding, Hong-Ming; Ma, Yu-Qiang

    2012-02-01

    Understanding how nanoparticles interact with cell membranes is of great importance in drug/gene delivery. In this paper, we investigate the interactions between Janus particles and membranes by using dissipative particle dynamics, and find that there exist two different modes (i.e., insertion and engulfment) in the Janus particle-membrane interactions. The initial orientation and properties of Janus particles have an important impact on the interactions. When the hydrophilic part of the particle is close to the membrane or the particle has a larger section area and higher hydrophilic coverage, the particle is more likely to be engulfed by the membrane. We also provide insights into the interactions between Janus particles and membranes containing lipid rafts, and find that a Janus particle could easily detach from a membrane after it is engulfed by the raft. The present study suggests a potential way to translocate Janus particles through membranes, which may give some significant suggestions on future nanoparticle design for drug delivery.

  5. Particle image velocimetry in viscoelastic fluids and particle interaction effects

    NASA Astrophysics Data System (ADS)

    Mirsepassi, Alireza; Rankin, Derek Dunn

    2014-01-01

    Two main assumptions in laser doppler velocimetry and particle image velocimetry (PIV) are that tracer particles are following the flow faithfully and that they are not interacting hydrodynamically or affecting the flow field. It has been shown, however, that particles in polymeric fluids even in low volumetric concentrations ( ϕ < 1 % v/v) can interact profoundly because of the viscoelastic nature of the background fluid, leading even to particle chain or string formation. The objective of this study is to determine how these interactions can affect the flow conclusions drawn from PIV measurements. We chose a highly viscoelastic and shear thinning fluid and confirmed that particle string formation does occur rapidly in a simple shear flow of this fluid. Then, we measured via PIV, the fully developed velocity profile in the mid-plane of a square channel over a wide range of particle loadings 0.005-0.2 % v/v. The measurements confirm that despite the chaining process, there is no discernible effect of particle interaction on PIV velocity measurements.

  6. Particle Production in Reflection and Transmission Mode Laser Ablation: Implications for Laserspray Ionization

    NASA Astrophysics Data System (ADS)

    Musapelo, Thabiso; Murray, Kermit K.

    2013-07-01

    Particles were ablated from laser desorption and inlet ionization matrix thin films with a UV laser in reflection and transmission geometries. Particle size distributions were measured with a combined scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS) system that measured particles in the size range from 10 nm to 20 μm. The matrixes investigated were 2,5-dihydroxybenzoic acid (DHB), α-cyano-4-hydroxycinnamic acid (CHCA), sinapic acid (SA), 2,5-dihydroxy-acetophenone (DHAP), and 2-nitrophloroglucinol (NPG). Nanoparticles with average diameters between 20 and 120 nm were observed in both transmission and reflection geometry. The particle mass distribution was significantly different in reflection and transmission geometry. In reflection geometry, approximately equal mass was distributed between particles in the 20 to 450 nm range of diameters and particles in the 450 nm to 1.5 μm diameter range. In transmission mode, the particle mass distribution was dominated by large particles in the 2 to 20 μm diameter range. Ablation of inlet ionization matrices DHAP and NPG produced particles that were 3 to 4 times smaller compared with the other matrices. The results are consistent with ion formation by nanoparticle melting and breakup or melting and breakup of the large particles through contact with heated inlet surfaces.

  7. Attractive interaction between similarly charged colloidal particles

    SciTech Connect

    Chu, X.; Wasan, D.T.

    1996-12-01

    The pair interactions between the charged colloidal particles dispersed in a solvent are studied theoretically by the integral equation method. The pair potential of the mean forces, accounting for the effective pair interaction between colloidal particles, is calculated from the solution of the Ornstein-Zernike equation with the mean spherical approximation (MSA). An attractive interaction was found between two similarly charged colloidal particles in contrast with the purely repulsive force predicted by the Debye-Huckel theory. Such an attractive interaction provides physical insight for the condensed phenomena in charged colloidal dispersions, that is, the coexistence of a condensed phase and an expanded phase (voids). At the higher concentration and charge on colloidal particles, the effective pair interaction becomes oscillatory.

  8. Construction of a fast ionization chamber for high-rate particle identification

    NASA Astrophysics Data System (ADS)

    Chae, K. Y.; Ahn, S.; Bardayan, D. W.; Chipps, K. A.; Manning, B.; Pain, S. D.; Peters, W. A.; Schmitt, K. T.; Smith, M. S.; Strauss, S. Y.

    2014-07-01

    A new gas-filled ionization chamber for high count rate particle identification has been constructed and commissioned at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). To enhance the response time of the ionization chamber, a design utilizing a tilted entrance window and tilted electrodes was adopted, which is modified from an original design by Kimura et al. [1]. A maximum counting rate of 700 , 000 particles per second has been achieved. The detector has been used for several radioactive beam measurements performed at the HRIBF.

  9. Arsenic interactions with lipid particles containing iron.

    PubMed

    Rahman, Mahbub M; Rahman, Farzana; Sansom, Lloyd; Naidu, Ravi; Schmidt, Otto

    2009-04-01

    While arsenic is toxic to all multicellular organisms, some organisms become tolerant by an unknown mechanism. We have recently uncovered an inducible tolerance mechanism in insects, which is based on a sequestration of toxins and pathogens by lipid particles. To examine whether arsenic interacts with lipid particles from mammals we compared binding of arsenic to lipid particles from insect and pig plasma after separation of lipid particles by low-density gradient centrifugation. Arsenic was found in both organisms in an area of the gradient, which corresponds to lipid-rich lipid particles. Since iron is known to affect arsenic toxicity in some organisms, we asked whether iron may be present in lipid particles. When low density cell (LDC) gradient fractions were analysed for the presence of iron we detected a peak in very low-density fractions similar to those that carried arsenic. This could indicate that arsenic interacts with lipid particles that contain iron and, if arsenic is removed from the plasma by lipid particles, that would also reduce iron-containing lipid particles at the time of arsenic emergence in the plasma. To test this assumption we measured the iron content in plasma at various time periods after the toxin ingestion. This time course revealed that iron is depleted in plasma fractions when arsenic shows a peak. Our data suggest that arsenic interacts with invertebrate and vertebrate lipid particles that are associated with proteins that may lead to detoxification by cell-free or cellular sequestration mechanisms.

  10. Particle modeling of microplasma generated by resonance enhanced multiphoton ionization

    NASA Astrophysics Data System (ADS)

    Tholeti, Siva Sashank

    Resonance-enhanced multiphoton ionization (REMPI) is a technique applied to the spectroscopy of atoms. The REMPI technique typically involves a resonant single or multiple photon absorption to an electronically excited intermediate state followed by another photon which ionizes the atom. Rayleigh scattering of REMPI plasma has given rise to a non-intrusive, time accurate measurement of electron formation and loss, which lead to many applications viz. trace species detection and micro-plasma diagnostics. It is very important to quantify the expansion process and the evolution of energy of electrons and ions. The operation scale of this process is in microns and non continuum nature of the process lead to the use of PIC/MCC scheme to compu- tationally model REMPI technique. This work attempts to understand and analyze the processes taking place during the expansion of REMPI plasma computationally using the PIC/MCC scheme. One dimensional and two dimensional approximations are considered to analyze the REMPI plasma expansion in Argon gas generated by a laser with a focal shape of a prolate ellipsoid. The expansion of the plasma is found to be very sensitive to the initial velocity distribution of the electrons. REMPI plasma expansion is shown to be ambipolar in nature, with the radial expansion more predominant than axial expansion, hence requiring the 2D model. Electron energy distribution functions(EEDFs) are found at various radial locations along with the corresponding mean energies. The deviation of the EEDFs from that of equilibrium Maxwell-Boltzmann energy distribution is presented both qualitatively and quanti- tatively, indicating the predominant processes at various instances in time.

  11. 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.

  12. 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.

  13. 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.

  14. Particle-Vortex Interaction in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Barenghi, Carlo F.

    2008-11-01

    The application of the classical Particle Image Velocimetry (PIV) technique in liquid helium has opened the way to better visualization of superfluid turbulence. To interpret the data, it is necessary to understand the interaction between micron-size tracer particles and vortex lines. This talk summarizes current understanding of this interaction resulting from theoretical and numerical calculations. In collaboration with Yuri A. Sergeev, Newcastle University.

  15. Polarization of silicon detectors by minimum ionizing particles

    NASA Astrophysics Data System (ADS)

    Dezillie, B.; Eremin, V.; Li, Z.; Verbitskaya, E.

    2000-10-01

    This work presents quantitative predictions of the properties of highly irradiated (e.g. by high-energy particles, up to an equivalent fluence of 1×10 14 n cm -2) silicon detectors operating at cryogenic temperature. It is shown that the exposure to the Minimum Ionising Particle (MIP) with counting rates of about 10 6 cm -2 s -1 can influence the electric field distribution in the detector's sensitive volume. This change in the electric field distribution and its effect on the charge collection efficiency are discussed in the frame of a model based on trapping of carriers generated by MIPs. The experiment was performed at 87 K with an infrared (1030 nm) laser to simulate MIPs.

  16. Shock Interaction with Random Spherical Particle Beds

    NASA Astrophysics Data System (ADS)

    Neal, Chris; Mehta, Yash; Salari, Kambiz; Jackson, Thomas L.; Balachandar, S. "Bala"; Thakur, Siddharth

    2016-11-01

    In this talk we present results on fully resolved simulations of shock interaction with randomly distributed bed of particles. Multiple simulations were carried out by varying the number of particles to isolate the effect of volume fraction. Major focus of these simulations was to understand 1) the effect of the shockwave and volume fraction on the forces experienced by the particles, 2) the effect of particles on the shock wave, and 3) fluid mediated particle-particle interactions. Peak drag force for particles at different volume fractions show a downward trend as the depth of the bed increased. This can be attributed to dissipation of energy as the shockwave travels through the bed of particles. One of the fascinating observations from these simulations was the fluctuations in different quantities due to presence of multiple particles and their random distribution. These are large simulations with hundreds of particles resulting in large amount of data. We present statistical analysis of the data and make relevant observations. Average pressure in the computational domain is computed to characterize the strengths of the reflected and transmitted waves. We also present flow field contour plots to support our observations. U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, under Contract No. DE-NA0002378.

  17. Cross-platform, multi-language libraries for ionization and surface interaction effects in plasmas

    NASA Astrophysics Data System (ADS)

    Stoltz, Peter; Sides, Scott; Sizemore, Nate; Veitzer, Seth; Furman, Miguel; Vay, Jean-Luc

    2006-10-01

    We are developing a library of numerical algorithms for modeling plasma effects such as ionization, secondary electron production, and ion-surface interaction. The goal is to make this library accessible to a large number of researchers by making it available on multiple computing platforms (Linux, Windows, Mac OS X) and available in multiple computing languages (Fortran, C, Python, Java). We discuss our use of the GNU autotools and the Babel utility to accomplish this cross-platform, multi-language interface. We then discuss application of this library within the WARP particle-in-cell code for modeling effects of ion-induced electrons in the High Current Experiment and within the VORPAL particle-in-cell code for modeling kinetic effects in hollow cathode discharges.

  18. MATRIX-ASSISTED LASER DESORPTION IONIZATION OF SIZE AND COMPOSITION SELECTED AEROSOL PARTICLES. (R823980)

    EPA Science Inventory

    Matrix-assisted laser desorption/ionization (MALDI) was performed on individual,
    size-selected aerosol particles in the 2-8 mu m diameter range, Monodisperse aerosol droplets
    containing matrix, analyte, and solvent were generated and entrained in a dry stream of air, The dr...

  19. Charged particle therapy: the physics of interaction.

    PubMed

    Lomax, Antony J

    2009-01-01

    Particle therapy has a long and distinguished history with more than 50,000 patients having been treated, mainly with high-energy proton therapy. Particularly, for proton therapy, there is an increasing interest in exploiting the physical characteristics of charged particles for further improving the potential of radiation therapy. In this article, we review the most important interactions of charged particles with matter and describe the basic physical principles that underlie why particle beams behave the way they do and why such a behavior could bring many benefits in radiation therapy.

  20. 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.}

  1. The Particle Beam Optics Interactive Computer Laboratory

    SciTech Connect

    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.

  2. 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.

  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. CHARGED PARTICLE MOTION IN AN EXPLOSIVELY GENERATED IONIZING SHOCK

    SciTech Connect

    Boswell, Christopher J.; O'Connor, Patrick D.

    2009-12-28

    Different aspects of the plasma generated in a gas contained in a tube due to detonation of a small explosive charge located at one end of the tube are presented. The motion of the charged particles within the plasma is monitored using Rogowski coils. Using time-resolved emission spectroscopy the temperature and species in the detonation products and compressed gas behind the shock wave are recorded. From the spectral lines of the emission profiles the temperatures and electron density were evaluated to be in the vicinity of 7,000 K and 5x10{sup 22} m{sup -3}. An ultra fast wave traveling down the guide tube ahead of the hydrodynamic shock and causing any charged particles there to move fast enough to be detected by the Rogowski coils was recorded. From the measurements the phase velocity of the wave was calculated at 525 km/s when krypton filled the tube, and 1300 km/s in the case of argon. The temperature and density measurements are consistent with the data reported in the literature for similar tests. The electrostatic pulse measurements are a new phenomena not previously observed.

  5. 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.

  6. Effect of electron impact ionization in laser-metal-cluster interactions

    NASA Astrophysics Data System (ADS)

    Liang, Zhenfeng; Zhang, Bo; Liu, Hongjie; Li, Xibo; Luo, Jiangshan; Zhou, Weimin; Cao, Leifeng; Yi, Yougen; Gu, Yuqiu

    2017-05-01

    The effects of electron impact ionization (EII) in laser-metal-cluster interactions are investigated with two-dimensional particle-in-cell simulations. For large Cu clusters (R = 10 nm) heated by moderate laser pulses (peak intensities I M = 8.8 × 1015 W cm-2), the effects of EII depend on the atom/ion density of neutral cluster or cluster plasma. In high density neutral cluster (HDNC), EII is the dominant ionization mechanism and EII efficiency reaches 55%. However, in the case of low density cluster plasma (LDCP), EII plays a minor role that only increases the mean ion charges by 5%. Moreover, when EII is considered, the energy of ions with the same charges is reduced by 60% in the HDNC case but not in the LDCP case. This is due to the fact that ions in HDNC mainly gain energy through hydrodynamic expansion while ions in LDCP obtain energy through Coulomb explosion. More importantly, it is found that EII efficiency increases when the density of cluster plasma increases and is most pronounced in the neutral cluster. The density dependence of the EII efficiency provides a control mechanism for cluster ionization products with pump-probe technology.

  7. 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.

  8. Particle-in-cell simulations of tunneling ionization effects in plasma-based accelerators

    NASA Astrophysics Data System (ADS)

    Bruhwiler, David L.; Dimitrov, D. A.; Cary, John R.; Esarey, Eric; Leemans, Wim; Giacone, Rodolfo E.

    2003-05-01

    Plasma-based accelerators can sustain accelerating gradients on the order of 100 GV/m. If the plasma is not fully ionized, fields of this magnitude will ionize neutral atoms via electron tunneling, which can completely change the dynamics of the plasma wake. Particle-in-cell simulations of a high-field plasma wakefield accelerator, using the OOPIC code [D. L. Bruhwiler et al., Phys. Rev. ST Accel. Beams 4, 101302 (2001)], which includes field-induced tunneling ionization of neutral Li gas, show that the presence of even moderate neutral gas density significantly degrades the quality of the wakefield. The tunneling ionization model in OOPIC has been validated via a detailed comparison with experimental data from the l'OASIS laboratory [W.P. Leemans et al., Phys. Rev. Lett. 89, 174802 (2002)]. The properties of a wake generated directly from a neutral gas are studied, showing that one can recover the peak fields of the fully ionized plasma simulations, if the density of the electron drive bunch is increased such that the bunch rapidly ionizes the gas.

  9. An interaction energy driven biased sampling technique: A faster route to ionization spectra in condensed phase.

    PubMed

    Bose, Samik; Ghosh, Debashree

    2017-10-05

    We introduce a computationally efficient approach for calculating spectroscopic properties, such as ionization energies (IEs) in the condensed phase. Discrete quantum mechanical/molecular mechanical (QM/MM) approaches for spectroscopic properties in a dynamic system, such as aqueous solution, need a large sample space to obtain converged estimates, especially for the cases where particle (electron) number is not conserved, such as IEs or electron affinities (EAs). We devise a biased sampling technique based on an approximate estimate of interaction energy between the solute and solvent, that accelerates the convergence and therefore, reduces the computational cost significantly. The approximate interaction energy also provides a good measure of the spectral width of the chromophores in the condensed phase. This technique has been tested and benchmarked for (i) phenol, (ii) HBDI anion (hydroxybenzylidene dimethyl imidazolinone), and (iii) thymine in water. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  10. 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.

  11. 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

  12. Microstructure and rheology of particle stabilized emulsions: Effects of particle shape and inter-particle interactions.

    PubMed

    Katepalli, Hari; John, Vijay T; Tripathi, Anubhav; Bose, Arijit

    2017-01-01

    Using fumed and spherical silica particles of similar hydrodynamic size, we investigated the effects of particle shape and inter-particle interactions on the formation, stability and rheology of bromohexadecane-in-water Pickering emulsions. The interparticle interactions were varied from repulsive to attractive by modifying the salt concentration in the aqueous phase. Optical microscope images revealed smaller droplet sizes for the fumed silica stabilized emulsions. All the emulsions remained stable for several weeks. Cryo-SEM images of the emulsion droplets showed a hexagonally packed single layer of particles at oil-water interfaces in emulsions stabilized with silica spheres, irrespective of the nature of the inter-particle interactions. Thus, entropic, excluded volume interactions dominate the fate of spherical particles at oil-water interfaces. On the other hand, closely packed layers of particles were observed at oil-water interfaces for the fumed silica stabilized emulsions for both attractive and repulsive interparticle interactions. At the high salt concentrations, attractive inter-particles interactions led to aggregation of fumed silica particles, and multiple layers of these particles were then observed on the droplet surfaces. A network of fumed silica particles was also observed between the emulsion droplets, suggesting that enthalpic interactions are responsible for the determining particle configurations at oil-water interfaces as well as in the aqueous phase. Steady shear viscosity measurements over a range of shear stresses, as well as oscillatory shear measurements at 1Hz confirm the presence of a network in fumed silica suspensions and emulsions, and the lack of such a network when spherical particles are used. The fractal structure of fumed silica leads to several contact points and particle interlocking in the water as well as on the bromohexadecane-water interfaces, with corresponding effects on the structure and rheology of the emulsions

  13. 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.

  14. 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.

  15. The Interaction of Debye-Shielded Particles

    NASA Astrophysics Data System (ADS)

    Riley, Merle E.; Buss, Richard J.

    1999-10-01

    Macroscopic particles or solid surfaces in contact with a typical low-temperature plasma immediately charge negatively and surround themselves with an electron-depleted region of positive charge. This Debye shielding effect is involved in the Debye-Huckel theory in liquids and plasma sheath formation in the gas phase. In this report, the interaction between such screened particles is found by using the same basic linearization approximation that is used in constructing the Debye shielding potential itself. The results demonstrate that a small but significant attraction exists between the particles, and, if conditions are right, this attractive force can contribute to the generation of particulate plasma crystals.

  16. The Interaction of Debye-Shielded Particles

    SciTech Connect

    Buss, Richard J.; Riley, Merle E.

    1999-04-01

    Macroscopic particles or solid surfaces in contact with a typical low-temperature plasma immediately charge negatively and surround themselves with an electron-depleted region of positive charge. This Debye shielding effect is involved in the Debye-Huckel theory in liquids and plasma sheath formation in the gas phase. In this report, the interaction between such screened particles is found by using the same basic approximation that is used in constructing the Debye shielding potential itself. The results demonstrate that a significant attraction exists between the particles, and, if conditions are right, this attractive force can contribute to the generation of particulate plasma crystals.

  17. Particle-in-Cell Simulations of Gas Ionization by Short Intense Laser Pulses

    NASA Astrophysics Data System (ADS)

    Dimitrov, Dimitre; Bruhwiler, David; Leemans, Wim; Esarey, Eric; Catravas, Palma; Toth, Csaba; Shadwick, Brad; Cary, John; Giacone, Rodolfo; Verboncoeur, John; Mardahl, Peter

    2001-10-01

    Laser wakefield accelerators (LWFA) can generate accelerating gradients orders of magnitude larger than those obtained in conventional metal structures. In many LWFA experiments, the leading edge of the short, intense laser pulse completely ionizes a background neutral gas. An important question is the effect of laser ionization on the evolution of the laser pulse. Dispersive effects can modify the length and shape of the pulse as it propagates through the gas/plasma. Pulse steepening or break-up can affect the growth of the plasma wake. We will present particle-in-cell simulations using the ADK [M.V. Ammosov et al., Sov. Phys. JETP 64, p. 1191 (1986)] tunneling ionization model in the XOOPIC [J.P. Verboncoeur et al., J. Comp. Phys. 104, p. 321 (1993)] code. These simulations will be compared with experimental LWFA results from the l'OASIS laboratory of LBNL [W.P. Leemans et al., Phys. Plasmas 8, p. 2510 (2001)].

  18. 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.

  19. Particle systems with quasihomogeneous interaction

    NASA Astrophysics Data System (ADS)

    Stoica, Cristina

    In this dissertation we analyse from a qualitative standpoint motion in a quasihomogeneous potential field: we offer a complete description of the flow associated with the two-body problem in quasihomogeneous field, obtain necessary and sufficient conditions for the block regularization of the flow and we propose an alternative model for the helium atom within the framework of a Manev-type interaction. We call a potential quasihomogeneous if it is of the form A/r α + B/rβ, where r is the distance between the two mass points, 0 < α < β are real parameters and A > 0 and B > 0 inertia factors. To obtain the full description of the flow associated with the two-body problem in quasihomogeneous fields, we use diffeomorphic transformations that lead to an equivalent analytic system and at least differentiable integral energy relation. For each level of energy, we introduce the fictional invariant collision manifold and the infinity manifolds. We offer and analyse the global flow picture and we point out the Lebesgue measure of the set of initial conditions that lead to collision for each different case with respect to α and β. The next chapter focuses on the smoothness of the flow in the neighborhood of the collision manifold. In question is the possibility of extending solutions beyond singularities maintaining good properties with respect to initial data. In this case the singularity set for the system is said to be block regularizable. It is proved that the singularity set block regularizable if and only if β = 2 - / , where n is a positive integer, n >= 2. Also, the physical interpretation of this result is pointed out, namely that block regularization is in fact the mathematical expression of constrain imposed over the classical scattering angle. The last chapter presents a model for the Helium atom within the framework of classical mechanics. The set up consists of a planar isosceles 3-body problem formed by one neutron and two electrons, whose law of motion

  20. Capillary interactions between anisotropic colloidal particles.

    PubMed

    Loudet, J C; Alsayed, A M; Zhang, J; Yodh, A G

    2005-01-14

    We report on the behavior of micron-sized prolate ellipsoids trapped at an oil-water interface. The particles experience strong, anisotropic, and long-ranged attractive capillary interactions which greatly exceed the thermal energy k(B)T. Depending on surface chemistry, the particles aggregate into open structures or chains. Using video microscopy, we extract the pair interaction potential between ellipsoids and show it exhibits a power law behavior over the length scales probed. Our observations can be explained using recent calculations, if we describe the interfacial ellipsoids as capillary quadrupoles.

  1. Search for Dark Matter Interactions using Ionization Yield in Liquid Xenon

    NASA Astrophysics Data System (ADS)

    Uvarov, Sergey

    Cosmological observations overwhelmingly support the existence of dark matter which constitutes 87% of the universe's total mass. Weakly Interacting Massive Particles (WIMPs) are a prime candidate for dark matter, and the Large Underground Xenon (LUX) experiment aims to a direct-detection of a WIMP-nucleon interaction. The LUX detector is a dual-phase xenon time-projection chamber housed 4,850 feet underground at Sanford Underground Research Facility in Lead, South Dakota. We present the ionization-only analysis of the LUX 2013 WIMP search data. In the 1.04 x 104 kg-days exposure, thirty events were observed out of the 24.8 expected from radioactive backgrounds. We employ a cut-and-count method to set a 1-sided 90% C.L. upper limit for spin-independent WIMP-nucleon cross-sections. A zero charge yield for nuclear-recoils below 0.7 keV is included upper limit calculation. This ionization-only analysis excludes an unexplored region of WIMP-nucleon cross-section for low-mass WIMPs achieving 1.56 x 10-43 cm2 WIMP-nucleon cross-section exclusion for a 5.1 GeV/ c2 WIMP.

  2. 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.

  3. Dissipative particle dynamics with attractive and repulsive particle-particle interactions

    SciTech Connect

    Paul Meakin; Moubin Liu; Hai Huang

    2006-01-01

    In molecular dynamics simulations, a combination of short-range repulsive and long-range attractive interactions allows the behavior of gases, liquids, solids, and multiphase systems to be simulated. We demonstrate that dissipative particle dynamics (DPD) simulations with similar pairwise particle-particle interactions can also be used to simulate the dynamics of multiphase fluids. In these simulations, the positive, short-range, repulsive part of the interaction potentials were represented by polynomial spline functions such as those used as smoothing functions in smoothed particle hydrodynamics, and the negative long-range part of the interaction has the same form but a different range and amplitude. If a single spline function corresponding to a purely repulsive interaction is used, the DPD fluid is a gas, and we show that the Poiseuille flow of this gas can be described accurately by the Navier-Stokes equation at low Reynolds numbers. In a two-component system in which the purely repulsive interactions between different components are substantially larger than the purely repulsive intracomponent interactions, separation into two gas phases occurs, in agreement with results obtained using DPD simulations with standard repulsive particle-particle interactions. Finally, we show that a combination of short-range repulsive interactions and long-range attractive interactions can be used to simulate the behavior of liquid drops surrounded by a gas. Similar models can be used to simulate a wide range of processes such as multiphase fluid flow through fractures and porous media with complex geometries and wetting behaviors.

  4. 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.

  5. 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.

  6. Granular segregation driven by particle interactions.

    PubMed

    Lozano, C; Zuriguel, I; Garcimartín, A; Mullin, T

    2015-05-01

    We report the results of an experimental study of particle-particle interactions in a horizontally shaken granular layer that undergoes a second order phase transition from a binary gas to a segregation liquid as the packing fraction C is increased. By focusing on the behavior of individual particles, the effect of C is studied on (1) the process of cluster formation, (2) cluster dynamics, and (3) cluster destruction. The outcomes indicate that the segregation is driven by two mechanisms: attraction between particles with the same properties and random motion with a characteristic length that is inversely proportional to C. All clusters investigated are found to be transient and the probability distribution functions of the separation times display a power law tail, indicating that the splitting probability decreases with time.

  7. From interacting particles to equilibrium statistical ensembles

    NASA Astrophysics Data System (ADS)

    Ilievski, Enej; Quinn, Eoin; Caux, Jean-Sébastien

    2017-03-01

    We argue that a particle language provides a conceptually simple framework for the description of anomalous equilibration in isolated quantum systems. We address this paradigm in the context of integrable models, which are those where particles scatter completely elastically and are stable against decay. In particular, we demonstrate that a complete description of equilibrium ensembles for interacting integrable models requires a formulation built from the mode occupation numbers of the underlying particle content, mirroring the case of noninteracting particles. This yields an intuitive physical interpretation of generalized Gibbs ensembles, and reconciles them with the microcanonical ensemble. We explain how previous attempts to identify an appropriate ensemble overlooked an essential piece of information, and provide explicit examples in the context of quantum quenches.

  8. Modeling of particle interactions in magnetorheological elastomers

    SciTech Connect

    Biller, A. M. Stolbov, O. V. Raikher, Yu. L.

    2014-09-21

    The interaction between two particles made of an isotropic linearly polarizable magnetic material and embedded in an elastomer matrix is studied. In this case, when an external field is imposed, the magnetic attraction of the particles, contrary to point dipoles, is almost wraparound. The exact solution of the magnetic problem in the linear polarization case, although existing, is not practical; to circumvent its use, an interpolation formula is proposed. One more interpolation expression is developed for the resistance of the elastic matrix to the field-induced particle displacements. Minimization of the total energy of the pair reveals its configurational bistability in a certain field range. One of the possible equilibrium states corresponds to the particles dwelling at a distance, the other—to their collapse in a tight dimer. This mesoscopic bistability causes magnetomechanical hysteresis which has important implications for the macroscopic behavior of magnetorheological elastomers.

  9. 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.

  10. Antitumor interaction of short-course endostatin and ionizing radiation.

    PubMed

    Hanna, N N; Seetharam, S; Mauceri, H J; Beckett, M A; Jaskowiak, N T; Salloum, R M; Hari, D; Dhanabal, M; Ramchandran, R; Kalluri, R; Sukhatme, V P; Kufe, D W; Weichselbaum, R R

    2000-01-01

    The purpose of this study was to evaluate whether endostatin, an antiangiogenic cleavage fragment of collagen XVIII, enhances the antitumor effects of ionizing radiation (IR). Endostatin was injected to coincide with fractionated radiotherapy. Xenografts of radioresistant SQ-20B tumor cells were established in athymic nude mice. Lewis lung carcinoma cells were injected into C57BI/6 mice. Mice bearing SQ-20B xenografts were injected intraperitoneally with 2.5 mg/kg/day of murine recombinant endostatin 5 times per week for 2 weeks 3 hours before IR treatment (50 Gy total dose). Mice bearing Lewis lung carcinoma tumors were injected intraperitoneally with endostatin (2.5 mg/kg/day) four times; the first injection was given 24 hours before the first IR dose (15 Gy) and then 3 hours before IR (15 Gy/day) for 3 consecutive days. Microvascular density was assessed on tumor tissue sections by use of CD31 immunohistochemistry and light microscopy. Endothelial cell survival analyses were employed to evaluate endostatin effects on human aortic endothelial cells and human umbilical vein endothelial cells. Endothelial cell apoptosis was examined by use of FACS analysis and DAPI microscopy. In SQ-20B xenografts, combined treatment with endostatin and IR produced tumor growth inhibition that was most pronounced at the nadir of regression (day 21). By day 35, tumors receiving combined treatment with endostatin and IR were 47% smaller than tumors treated with endostatin alone. Interactive cytotoxic treatment effects between endostatin and IR were also demonstrated in mice bearing Lewis lung carcinoma tumors. Significant tumor growth inhibition was observed in the endostatin/IR group at days 11 and 13 compared with IR alone. Histologic analyses demonstrated a reduction in microvascular density after combined treatment with endostatin and IR compared with endostatin treatment alone. Survival analyses confirmed interactive cytotoxicity between endostatin and IR in both human aortic

  11. 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.

  12. Alfvén ionization in an MHD-gas interactions code

    SciTech Connect

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

    2016-07-15

    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.

  13. (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.

  14. 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.

  15. Depinning of interacting particles in random media

    NASA Astrophysics Data System (ADS)

    Zapperi, Stefano; Andrade, José S., Jr.; Mendes Filho, Josué

    2000-06-01

    We study the overdamped motion of interacting particles in a random medium using the model introduced by Pla and Nori [Phys. Rev. Lett. 67, 919 (1991)]. We investigate the associated depinning transition by numerical integration of the equation of motion and show evidence that the model is in the same universality class of a driven elastic chain on a rough substrate. We discuss the implications of these results for flux line motion in type-II superconductors.

  16. Observations of the ionization states of energetic particles accelerated in solar flares

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.; Weiss, H.; Ipavich, F. M.; Hovestadt, D.; Klecker, B.; Scholer, M.; Fisk, L. A.; Fan, C. Y.; Ogallagher, J. J.

    1981-01-01

    The ionization states and spectra of 0.3 to 2.4 MeV/nuc He, C, O and Fe are measured in a survey of ten solar flare particle events. He(plus) is found to be present in all events, which indicates the common presence of energetic He(plus) in the source material from which solar particles are accelerated. The distribution functions of He(plus), He(plus plus) and heavier elements are represented by simple exponentials of the particle speed times its rigidity to a power n, where n is between 0 and 1, and equal e-folding values. Results are consistent with a model where ions are accelerated in the corona by multi-dimensional shocks out of a population taken from both hot and cold coronal regions.

  17. 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.

  18. Ambient gas/particle partitioning. 1. Sorption mechanisms of apolar, polar, and ionizable organic compounds.

    PubMed

    Arp, Hans Peter H; Schwarzenbach, René P; Goss, Kai-Uwe

    2008-08-01

    There remain several ambiguities in the literature regarding the dominating sorption mechanisms involved in gas/particle partitioning, particularly for polar and ionizable compounds. The various hypothetical mechanisms would depend differently on relative humidity (RH) and the presence of various aerosol components. Thus, in order to resolve these ambiguities, here we measured the RH-dependency of gas/particle partitioning constants, K(ip), for four diverse aerosol samples and a large set of chemicals covering apolar, polar, and ionizable organic compounds. In addition, we also removed the water-soluble components from two ambient particle samples to study how their presence influences sorption behavior. The measured K(ip) values collectively indicate that a dual-phase sorption mechanism is occurring, in which organic compounds partition into a RH-independent water-insoluble organic matter phase and additionally into a RH-dependent mixed-aqueous phase. All K(ip) values could be successfully fitted to a RH-dependent dual-phase sorption model. The trends in K(ip) data further support findings that the sorption behavior of ambient aerosol samples is different from raw mineral surfaces and soot.

  19. 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.

  20. Cosmological constraints on interacting light particles

    NASA Astrophysics Data System (ADS)

    Brust, Christopher; Cui, Yanou; Sigurdson, Kris

    2017-08-01

    Cosmological observations are becoming increasingly sensitive to the effects of light particles in the form of dark radiation (DR) at the time of recombination. The conventional observable of effective neutrino number, Neff, is insufficient for probing generic, interacting models of DR. In this work, we perform likelihood analyses which allow both free-streaming effective neutrinos (parametrized by Neff) and interacting effective neutrinos (parametrized by Nfld). We motivate an alternative parametrization of DR in terms of Ntot (total effective number of neutrinos) and ffs (the fraction of effective neutrinos which are free-streaming), which is less degenerate than using Neff and Nfld. Using the Planck 2015 likelihoods in conjunction with measurements of baryon acoustic oscillations (BAO), we find constraints on the total amount of beyond the Standard Model effective neutrinos (both free-streaming and interacting) of Δ Ntot < 0.39 at 2σ. In addition, we consider the possibility that this scenario alleviates the tensions between early-time and late-time cosmological observations, in particular the measurements of σ8 (the amplitude of matter power fluctuations at 8h-1 Mpc), finding a mild preference for interactions among light species. We further forecast the sensitivities of a variety of future experiments, including Advanced ACTPol (a representative CMB Stage-III experiment), CMB Stage-IV, and the Euclid satellite. This study is relevant for probing non-standard neutrino physics as well as a wide variety of new particle physics models beyond the Standard Model that involve dark radiation.

  1. Detecting halo weakly interacting massive particles with a cryogenic phonon detector

    SciTech Connect

    Wang, N.; Barnes, P.D.; Cummings, A.; Emes, J. ); Giraud-Heraud, Y. ); Haller, E.E. ); Lange, A.; Ross, R.; Sadoulet, B.; Shutt, T.; Stubbs, C. )

    1991-04-15

    If dark matter in the halo is made of weakly interacting massive particles (WIMPs), it may be detected with a cryogenic phonon detector. Such a detector must have low energy threshold, high energy resolution, and, more importantly, good background rejection capability. It has been proposed that a good background rejection ratio can be obtained by a simultaneous measurement of phonons and ionization. To test this experimentally, we have built a 60 g Ge detector and have measured simultaneous phonon and ionization signals, each with 4 keV energy resolution. We present a simple estimate of the rejection ratios, and WIMP event rates that may be achieved by such a detector.

  2. 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.

  3. A laser desorption-electron impact ionization ion trap mass spectrometer for real-time analysis of single atmospheric particles

    NASA Astrophysics Data System (ADS)

    Simpson, E. A.; Campuzano-Jost, P.; Hanna, S. J.; Robb, D. B.; Hepburn, J. H.; Blades, M. W.; Bertram, A. K.

    2009-04-01

    A novel aerosol ion trap mass spectrometer combining pulsed IR laser desorption with electron impact (EI) ionization for single particle studies is described. The strengths of this instrument include a two-step desorption and ionization process to minimize matrix effects; electron impact ionization, a universal and well-characterized ionization technique; vaporization and ionization inside the ion trap to improve sensitivity; and an ion trap mass spectrometer for MSn experiments. The instrument has been used for mass spectral identification of laboratory generated pure aerosols in the 600 nm-1.1 [mu]m geometric diameter range of a variety of aromatic and aliphatic compounds, as well as for tandem mass spectrometry studies (up to MS3) of single caffeine particles. We investigate the effect of various operational parameters on the mass spectrum and fragmentation patterns. The single particle detection limit of the instrument was found to be a 325 nm geometric diameter particle (8.7 × 107 molecules or 22 fg) for 2,4-dihydroxybenzoic acid. Lower single particle detection limits are predicted to be attainable by modifying the EI pulse. The use of laser desorption-electron impact (LD-EI) in an ion trap is a promising technique for determining the size and chemical composition of single aerosol particles in real time.

  4. 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.

  5. Information propagation for interacting-particle systems

    SciTech Connect

    Schuch, Norbert; Harrison, Sarah K.; Osborne, Tobias J.; Eisert, Jens

    2011-09-15

    We study the speed at which information propagates through systems of interacting quantum particles moving on a regular lattice and show that for a certain class of initial conditions there exists a maximum speed of sound at which information can propagate. Our argument applies equally to quantum spins, bosons such as in the Bose-Hubbard model, fermions, anyons, and general mixtures thereof, on arbitrary lattices of any dimension. It also pertains to dissipative dynamics on the lattice, and generalizes to the continuum for quantum fields. Our result can be seen as an analog of the Lieb-Robinson bound for strongly correlated models.

  6. 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.

  7. 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.

  8. DNA-nuclear matrix interactions and ionizing radiation sensitivity

    SciTech Connect

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

    1993-01-01

    The association between inherent ionizing radiation sensitivity and DNA supercoil unwinding in mammalian cells suggests that the organization of the DNA in chromosomes plays an important role in radiation responses. In this paper, a model is proposed which suggests that these DNA unwinding alterations reflect differences in the attachment of DNA to the nuclear matrix. In radioresistant cells, the MAR structure might exist in a more stable, open configuration, limiting DNA unwinding following strand break induction and influencing the rate and nature of DNA double-strand break rejoining.

  9. Evaluation of an electrostatic particle ionization technology for decreasing airborne pathogens in pigs.

    PubMed

    Alonso, Carmen; Raynor, Peter C; Davies, Peter R; Morrison, Robert B; Torremorell, Montserrat

    Influenza A virus (IAV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV) and Staphylococcus aureus are important swine pathogens capable of being transmitted via aerosols. The electrostatic particle ionization system (EPI) consists of a conductive line that emits negative ions that charge particles electrically resulting in the settling of airborne particles onto surfaces and potentially decreasing the risk of pathogen dissemination. The objectives of this study were to determine the effect of the EPI system on the quantity and viability of IAV, PRRSV, PEDV and S. aureus in experimentally generated aerosols and in aerosols generated by infected animals. Efficiency at removing airborne particles was evaluated as a function of particle size (ranging from 0.4 to 10 µm), distance from the source of ions (1, 2 and 3 m) and relative air humidity (RH 30 vs. 70 %). Aerosols were sampled with the EPI system "off" and "on." Removal efficiency was significantly greater for all pathogens when the EPI line was the closest to the source of aerosols. There was a greater reduction for larger particles ranging between 3.3 and 9 µm, which varied by pathogen. Overall airborne pathogen reduction ranged between 0.5 and 1.9 logs. Viable pathogens were detected with the EPI system "on," but there was a trend to reducing the quantity of viable PRRSV and IAV. There was not a significant effect on the pathogens removal efficiency based on the RH conditions tested. In summary, distance to the source of ions, type of pathogen and particle size influenced the removal efficiency of the EPI system. The reduction in infectious agents in the air by the EPI technology could potentially decrease the microbial exposure for pigs and people in confinement livestock facilities.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Dynamics of two interacting active Janus particles.

    PubMed

    Bayati, Parvin; Najafi, Ali

    2016-04-07

    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[1/D](3) and O[1/D](4) with their separation, respectively. Our findings open up the way for studying the collective dynamics of synthetic micro-motors.

  16. TASEP of interacting particles of arbitrary size

    NASA Astrophysics Data System (ADS)

    Narasimhan, S. L.; Baumgaertner, A.

    2017-10-01

    A mean-field description of the stationary state behaviour of interacting k-mers performing totally asymmetric exclusion processes (TASEP) on an open lattice segment is presented employing the discrete Takahashi formalism. It is shown how the maximal current and the phase diagram, including triple-points, depend on the strength of repulsive and attractive interactions. We compare the mean-field results with Monte Carlo simulation of three types interacting k-mers: monomers, dimers and trimers. (a) We find that the Takahashi estimates of the maximal current agree quantitatively with those of the Monte Carlo simulation in the absence of interaction as well as in both the the attractive and the strongly repulsive regimes. However, theory and Monte Carlo results disagree in the range of weak repulsion, where the Takahashi estimates of the maximal current show a monotonic behaviour, whereas the Monte Carlo data show a peaking behaviour. It is argued that the peaking of the maximal current is due to a correlated motion of the particles. In the limit of very strong repulsion the theory predicts a universal behavior: th maximal currents of k-mers correspond to that of non-interacting (k+1) -mers; (b) Monte Carlo estimates of the triple-points for monomers, dimers and trimers show an interesting general behaviour : (i) the phase boundaries α * and β* for entry and exit current, respectively, as function of interaction strengths show maxima for α* whereas β * exhibit minima at the same strength; (ii) in the attractive regime, however, the trend is reversed (β * > α * ). The Takahashi estimates of the triple-point for monomers show a similar trend as the Monte Carlo data except for the peaking of α * ; for dimers and trimers, however, the Takahashi estimates show an opposite trend as compared to the Monte Carlo data.

  17. Particle-fluid interactions for flow measurements

    NASA Technical Reports Server (NTRS)

    Berman, N. S.

    1973-01-01

    Study has been made of the motion of single particle and of group of particles, emphasizing solid particles in gaseous fluid. Velocities of fluid and particle are compared for several conditions of physical interest. Mean velocity and velocity fluctuations are calculated for single particle, and some consideration is given to multiparticle systems.

  18. Ionization of glycine molecules by α-particles with keV energies

    NASA Astrophysics Data System (ADS)

    Afrosimov, V. V.; Basalaev, A. A.; Kuz'michev, V. V.; Panov, M. N.; Smirnov, O. V.

    2017-04-01

    The method of "multistop" time-of-flight mass spectrometry has been used to study the mechanism of radiation damage to glycine molecules in the gas phase upon their interaction with He2+ ions with energy E p = 4 keV/amu. The relative cross sections of various elementary processes occurring in single collisions of glycine molecules with the ions were measured for the first time. A difference was found between the fragmentations of intermediate doubly charged ions formed in capture of a single electron with ionization and in two-electron capture, which is accounted for by the difference between the excitation energies of molecular ions.

  19. 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

  20. Monte Carlo approach to calculate ionization dynamics of hot solid-density plasmas within particle-in-cell simulations.

    PubMed

    Wu, D; He, X T; Yu, W; Fritzsche, S

    2017-02-01

    A physical model based on a Monte Carlo approach is proposed to calculate the ionization dynamics of hot-solid-density plasmas within particle-in-cell (PIC) simulations, and where the impact (collision) ionization (CI), electron-ion recombination (RE), and ionization potential depression (IPD) by surrounding plasmas are taken into consideration self-consistently. When compared with other models, which are applied in the literature for plasmas near thermal equilibrium, the temporal relaxation of ionization dynamics can also be simulated by the proposed model. Besides, this model is general and can be applied for both single elements and alloys with quite different compositions. The proposed model is implemented into a PIC code, with (final) ionization equilibriums sustained by competitions between CI and its inverse process (i.e., RE). Comparisons between the full model and model without IPD or RE are performed. Our results indicate that for bulk aluminium at temperature of 1 to 1000 eV, (i) the averaged ionization degree increases by including IPD; while (ii) the averaged ionization degree is significantly over estimated when the RE is neglected. A direct comparison from the PIC code is made with the existing models for the dependence of averaged ionization degree on thermal equilibrium temperatures and shows good agreements with that generated from Saha-Boltzmann model and/or FLYCHK code.

  1. Monte Carlo approach to calculate ionization dynamics of hot solid-density plasmas within particle-in-cell simulations

    NASA Astrophysics Data System (ADS)

    Wu, D.; He, X. T.; Yu, W.; Fritzsche, S.

    2017-02-01

    A physical model based on a Monte Carlo approach is proposed to calculate the ionization dynamics of hot-solid-density plasmas within particle-in-cell (PIC) simulations, and where the impact (collision) ionization (CI), electron-ion recombination (RE), and ionization potential depression (IPD) by surrounding plasmas are taken into consideration self-consistently. When compared with other models, which are applied in the literature for plasmas near thermal equilibrium, the temporal relaxation of ionization dynamics can also be simulated by the proposed model. Besides, this model is general and can be applied for both single elements and alloys with quite different compositions. The proposed model is implemented into a PIC code, with (final) ionization equilibriums sustained by competitions between CI and its inverse process (i.e., RE). Comparisons between the full model and model without IPD or RE are performed. Our results indicate that for bulk aluminium at temperature of 1 to 1000 eV, (i) the averaged ionization degree increases by including IPD; while (ii) the averaged ionization degree is significantly over estimated when the RE is neglected. A direct comparison from the PIC code is made with the existing models for the dependence of averaged ionization degree on thermal equilibrium temperatures and shows good agreements with that generated from Saha-Boltzmann model and/or FLYCHK code.

  2. Shock Particle Interaction - Fully Resolved Simulations and Modeling

    NASA Astrophysics Data System (ADS)

    Mehta, Yash; Neal, Chris; Jackson, Thomas L.; Balachandar, S. "Bala"; Thakur, Siddharth

    2016-11-01

    Currently there is a substantial lack of fully resolved data for shock interacting with multiple particles. In this talk we will fill this gap by presenting results of shock interaction with 1-D array and 3-D structured arrays of particles. Objectives of performing fully resolved simulations of shock propagation through packs of multiple particles are twofold, 1) To understand the complicated physical phenomena occurring during shock particle interaction, and 2) To translate the knowledge from microscale simulations in building next generation point-particle models for macroscale simulations that can better predict the motion (forces) and heat transfer for particles. We compare results from multiple particle simulations against the single particle simulations and make relevant observations. The drag history and flow field for multiple particle simulations are markedly different from those of single particle simluations, highlighting the effect of neighboring particles. We propose new models which capture this effect of neighboring particles. These models are called Pair-wise Interaction Extended Point Particle models (PIEP). Effect of multiple neighboring particles is broken down into pair-wise interactions, and these pair-wise interactions are superimposed to get the final model U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, under Contract No. DE-NA0002378.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Alpha Particles and X Rays Interact in Inducing DNA Damage in U2OS Cells.

    PubMed

    Sollazzo, Alice; Brzozowska, Beata; Cheng, Lei; Lundholm, Lovisa; Haghdoost, Siamak; Scherthan, Harry; Wojcik, Andrzej

    2017-10-01

    Survivors of the atomic bombings of Hiroshima and Nagasaki are monitored for health effects within the Life Span Study (LSS). The LSS results represent the most important source of data about cancer effects from ionizing radiation exposure, which forms the foundation for the radiation protection system. One uncertainty connected to deriving universal risk factors from these results is related to the problem of mixed radiation qualities. The A-bomb explosions generated a mixed beam of the sparsely ionizing gamma radiation and densely ionizing neutrons. However, until now the possible interaction of the two radiation types of inducing biological effects has not been taken into consideration. The existence of such interaction would suggest that the application of risk factors derived from the LSS to predict cancer effects after pure gamma-ray irradiation (such as in the Fukushima prefecture) leads to an overestimation of risk. To analyze the possible interaction of radiation types, a mixed-beam exposure facility was constructed where cells can be exposed to sparsely ionizing X rays and densely ionizing alpha particles. U2OS cells were used, which are stably transfected with a plasmid coding for the DNA repair gene 53BP1 coupled to a gene coding for the green fluorescent protein (GFP). The induction and repair of DNA damage, which are known to be related to cancer induction, were analyzed. The results suggest that alpha particles and X rays interact, leading to cellular and possibly cancer effects, which cannot be accurately predicted based on assuming simple additivity of the individual mixed-beam components.

  8. 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

  9. On the turbulent heating and the threshold condition in the critical ionization velocity interaction

    NASA Technical Reports Server (NTRS)

    Moebius, E.; Papadopoulos, K.; Piel, A.

    1987-01-01

    On the basis of the nonlinear treatment of the ion beam instability and the modified two-stream instability, threshold conditions for the critical ionization velocity interaction are derived. There are three different regimes of interaction: (1) additional ionization for relative velocities smaller than the critical velocity, (2) the self-sustained discharge for velocities greater than the critical velocity which indeed turns out as a sharp threshold, and (3) an explosive growth regime for velocities exceeding 1.5 times the critical velocity. Additional charge exchange collisions of ions and energy loss of electrons due to excitation do not change the basic threshold behavior but modify the value of the critical velocity.

  10. 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.

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

    PubMed

    Li, Huayu; Ki, Hyungson

    2010-07-01

    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 CO2 laser interaction with helium is simulated successfully.

  12. 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.

  13. Search for metastable heavy charged particles with large ionization energy loss in pp collisions at s=13TeV using the ATLAS experiment

    DOE PAGES

    Aaboud, M.; Aad, G.; Abbott, B.; ...

    2016-06-28

    This study presents a search for massive charged long-lived particles produced in pp collisions at √s = 13TeV 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 tomore » 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 = 8TeV 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 qq¯ 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.« less

  14. 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. G.; Bohm, C.; Boisvert, V.; Bokan, P.; Bold, T.; Boldyrev, A. S.; Bomben, M.; Bona, M.; Boonekamp, M.; Borisov, A.; Borissov, G.; Bortfeldt, J.; Bortoletto, D.; Bortolotto, V.; Bos, K.; Boscherini, D.; Bosman, M.; Bossio Sola, J. D.; Boudreau, J.; Bouffard, J.; Bouhova-Thacker, E. V.; Boumediene, D.; Bourdarios, C.; Boutle, S. K.; Boveia, A.; Boyd, J.; Boyko, I. R.; Bracinik, J.; Brandt, A.; Brandt, G.; Brandt, O.; Bratzler, U.; Brau, B.; Brau, J. E.; Braun, H. M.; Breaden Madden, W. D.; Brendlinger, K.; Brennan, A. J.; Brenner, L.; Brenner, R.; Bressler, S.; Bristow, T. M.; Britton, D.; Britzger, D.; Brochu, F. M.; Brock, I.; Brock, R.; Brooijmans, G.; Brooks, T.; Brooks, W. K.; Brosamer, J.; Brost, E.; Broughton, J. H.; Bruckman de Renstrom, P. A.; Bruncko, D.; Bruneliere, R.; Bruni, A.; Bruni, G.; Brunt, Bh; Bruschi, M.; Bruscino, N.; Bryant, P.

    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.

  15. 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.

  16. Numerical studies of wall–plasma interactions and ionization phenomena in an ablative pulsed plasma thruster

    SciTech Connect

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

    2016-07-15

    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.

  17. The importance of particle-support interaction on particle size determination by gas chemisorption.

    PubMed

    Torrente-Murciano, L

    The interaction of the metal-support and particle shape has a key role on the determination of the particle size by gas chemisorption. This paper demonstrates mathematically that, assuming metal particles with hemispherical shapes (a common assumption in this type of characterisation) can provide misleading results of up to one order of magnitude. Thus, the metal particle sizes are underestimated when the metal strongly interacts with the support and overestimated when there is a weak metal-support interaction. Additionally, we also demonstrate that although the assumption of spherical shapes always underestimates the size of particles, this error is considerably lower with regular geometries than that associated to the effect of the metal-support interaction due to their effect on the particle shape. Herein, it is demonstrated the importance of introducing the particle-support interaction factor in the chemisorption particle size determination.

  18. On the Relation of Wave-Particle Interactions, Particle Dynamics, and Suprathermal Particle Distributions

    NASA Astrophysics Data System (ADS)

    Kucharek, Harald; Galvin, Antoinette; Farrugia, Charles; Klecker, Berndt; Pogorelov, Nikolai

    2016-04-01

    Wave-particle interactions, ion acceleration, and magnetic turbulence are closely interlinked and the physical processes may occur on different scales. These scales range from the kinetic scale to the macro-scale (MHD-scale). These processes are likely universal and the same basic processes occur at the Earth's environment, at the Earth's bow shock, the solar wind, and around the heliosphere. Undoubtedly, the Earth's environment as well as the close interplanetary space are the best plasma environments to study these processes using satellite measurements. Recently, ACE, STEREO, IBEX and Voyager observations clearly showed that turbulence and wave-particle interactions and turbulence are extremely important in interplanetary space and in the heliosphere. Using data from STEREO, Wind, we have investigated the spectral properties of suprathermal ion distributions. The results show that spectral slopes are very variable and depend on the plasma properties. We have also performed 3D hybrid simulations and studied particle dynamics. These simulations show that the particle dynamics in the turbulent magnetic wave field is Levy-Flight like which leads to a kappa distribution, which is often found in various space environments. This result is very significant of future mission such as THOR and IMAP and current operating missions such as STEREO, IBEX, and MMS.

  19. Geometry of the equilibrium distribution of interacting particles

    NASA Astrophysics Data System (ADS)

    Rebesh, A. P.; Lev, B. I.

    2017-08-01

    The formations of structures in all systems of interacting particles at different temperatures and particle concentrations have the same physical nature and therefore they could be described geometrically the same way. We propose a geometric description of a thermodynamically stable distribution of interacting particles. The character and intensity of interaction between particles determine the effective geometry of the medium which is provided by the minimum of the total free energy with non-linearity. A realization of spaces with possible particle distributions of arbitrary-order symmetries (including fifth, seventh etc. orders) which cannot occur in the ordinary Euclidean space, is described.

  20. Ring particles - Collisional interactions and physical nature

    NASA Technical Reports Server (NTRS)

    Weidenschilling, S. J.; Chapman, C. R.; Davis, D. R.; Greenberg, R.

    1984-01-01

    Attention is given to the properties of, and dynamical processes affecting individual particles of Saturn's rings. Because particles tend to be gravitationally bound when located on the surfaces of larger particles, and since net tidal stresses within the particles are small, particle collisions should produce accretion in Saturn's rings. Rapid accretionary processes within the rings are counterbalanced by tidal disruption of the larger accreted aggregates, which are presently designated 'dynamic ephemeral bodies'. The coefficient of restitution is probably very low, implying that the large particles containing most of the rings' mass are in a monolayer, although the small particles responsible for most of the rings' visible cross section form a layer many particles thick. Kinematic viscosity and interparticle erosive process models should incorporate these properties.

  1. 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.

  2. 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.

  3. 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.

  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. Novel lutetium spectroscopic interactions via cw RIMS (Resonance Ionization Mass Spectrometry)

    SciTech Connect

    Fearey, B.L.; Miller, C.M.

    1989-01-01

    Novel spectroscopic interactions of argon-ion laser enhanced resonance ionization of lutetium are observed and discussed; these include line-narrowing, non-linear power dependences and anomalous optical pumping effects of the hyperfine transitions. In addition, isotopically saturation dip spectra are observed and presented, allowing for precise determination of hyperfine constants of rare isotopes. 12 refs., 2 figs.

  6. Internal bremsstrahlung of strongly interacting charged particles

    NASA Astrophysics Data System (ADS)

    Kurgalin, S. D.; Tchuvil'sky, Yu. M.; Churakova, T. A.

    2016-11-01

    A universal theoretical model intended for calculating internal-bremsstrahlung spectra is proposed. In this model, which can be applied to describing nuclear decays of various type (such as alpha decay, cluster decay, and proton emission), use is made of realistic nucleus-nucleus potentials. Theoretical internal-bremsstrahlung spectra were obtained for the alpha decay of the 214Po nucleus, as well as for the decay of the 222Ra nucleus via the emission of a 14C cluster and for the decay of the 113Cs nucleus via proton emission, and the properties of these spectra were studied. The contributions of various regions (internal, subbarrier, and external) to the internal-bremsstrahlung amplitude were analyzed in detail. It is shown that the contribution of the internal region to the amplitude for internal bremsstrahlung generated in nuclear decay via proton emission is quite large, but that this is not so for alpha decay and decay via cluster emission. Thus, a process in which strong interaction of nuclear particles affects the internal-bremsstrahlung spectrum if found.

  7. Simply split strongly interacting massive particles

    NASA Astrophysics Data System (ADS)

    Bernal, Nicolás; Chu, Xiaoyong; Pradler, Josef

    2017-06-01

    Dark matter which interacts strongly with itself, but only feebly with the Standard Model, is a possibility that has been entertained to solve apparent small-scale structure problems that are pertinent to the noninteracting cold dark matter paradigm. In this paper, we study the simple case in which the self-scattering rate today is regulated by kinematics and/or the abundance ratio, through the mass splitting of nearly degenerate pseudo-Dirac fermions χ1 and χ2 or real scalars ϕ1 and ϕ2. We calculate the relic density of these states in a scenario where self-scattering proceeds through off-diagonal couplings with a vector particle V (dark photon) and where the abundance is set through number-depleting 4-to-2 reactions in the hidden sector, or, alternatively, via freeze-in. We study the implications of the considered models and their prospect of solving astrophysical small-scale structure problems. We also show how the introduction of the (meta)stable heavier state may be probed in future dark matter searches.

  8. Internal bremsstrahlung of strongly interacting charged particles

    SciTech Connect

    Kurgalin, S. D.; Tchuvil’sky, Yu. M.; Churakova, T. A.

    2016-11-15

    A universal theoretical model intended for calculating internal-bremsstrahlung spectra is proposed. In this model, which can be applied to describing nuclear decays of various type (such as alpha decay, cluster decay, and proton emission), use is made of realistic nucleus–nucleus potentials. Theoretical internal-bremsstrahlung spectra were obtained for the alpha decay of the {sup 214}Po nucleus, as well as for the decay of the {sup 222}Ra nucleus via the emission of a {sup 14}C cluster and for the decay of the {sup 113}Cs nucleus via proton emission, and the properties of these spectra were studied. The contributions of various regions (internal, subbarrier, and external) to the internal-bremsstrahlung amplitude were analyzed in detail. It is shown that the contribution of the internal region to the amplitude for internal bremsstrahlung generated in nuclear decay via proton emission is quite large, but that this is not so for alpha decay and decay via cluster emission. Thus, a process in which strong interaction of nuclear particles affects the internal-bremsstrahlung spectrum if found.

  9. 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

  10. Nonlinear Wave-particle Interaction and Particle Trapping in Large Amplitude Dust Acoustic Waves

    SciTech Connect

    Chang, Mei-Chu; Teng, Lee-Wen; Lin, I.

    2011-11-29

    Large amplitude dust acoustic wave can be self-excited by the strong downward ion flow in a dusty plasma liquid formed by negatively charged dusts suspended in a weakly ionized low pressure discharge. In this work, we investigate experimentally the wave-particle phase space dynamics of the large amplitude dust acoustic wave by connecting the Lagrangian and Eulerian views, through directly tracking particle motion and measuring local dust density fluctuations. The microscopic pictures of wave steepening and breaking, resonant particle-wave crest trapping, and the absence of trough trapping observed in our experiment are constructed.

  11. Protective effects of dimethyl sulfoxide on labile protein interactions during electrospray ionization.

    PubMed

    Landreh, Michael; Alvelius, Gunvor; Johansson, Jan; Jörnvall, Hans

    2014-05-06

    Electrospray ionization mass spectrometry is a valuable tool to probe noncovalent interactions. However, the integrity of the interactions in the gas-phase is heavily influenced by the ionization process. Investigating oligomerization and ligand binding of transthyretin (TTR) and the chaperone domain from prosurfactant protein C, we found that dimethyl sulfoxide (DMSO) can improve the stability of the noncovalent interactions during the electrospray process, both regarding ligand binding and the protein quaternary structure. Low amounts of DMSO can reduce in-source dissociation of native protein oligomers and their interactions with hydrophobic ligands, even under destabilizing conditions. We interpret the effects of DMSO as being derived from its enrichment in the electrospray droplets during evaporation. Protection of labile interactions can arise from the decrease in ion charges to reduce the contributions from Coulomb repulsions, as well as from the cooling effect of adduct dissociation. The protective effects of DMSO on labile protein interactions are an important property given its widespread use in protein analysis by electrospray ionization mass spectrometry (ESI-MS).

  12. Lattice-Boltzmann simulations of repulsive particle-particle and particle-wall interactions: Coughing and choking

    NASA Astrophysics Data System (ADS)

    Başaǧaoǧlu, Hakan; Succi, Sauro

    2010-04-01

    We propose and numerically investigate a new particle retention mechanism for particle entrapment in creeping flows in a constricted section of a saturated rough-walled narrow flow channel. We hypothesize that particles, whose size is smaller than channel width, can be temporarily or permanently immobilized in a flow channel away from channel walls due to particle-particle and particle-wall repulsive potentials, and, consequently, the flow field is clogged temporarily (coughing) or permanently (choking). Two mathematically simplified repulsive particle-particle and particle-wall interaction potentials are incorporated into a two-dimensional colloidal lattice-Boltzmann model. These potentials are two-body Lennard-Jones 12 and screened electrostatic repulsive potentials. Numerical simulations reveal that unlike in smooth-walled flow channels, particles are entrapped away from rough-walled channel walls and subsequently clog the flow field if fluid-drag and repulsive forces on particles are in balance. Off-balance forces, however, could result in temporary clogging if repulsive forces are stronger on the advancing edge of a particle than on its trailing edge. The new conceptualization and two-particle numerical simulations successfully captured (i) temporary entrapment of two particles (coughing), (ii) temporary entrapment of one of the particles with permanent entrapment of the other particle (coughing-choking), and (iii) permanent entrapment of both particles (choking) as a function of repulsive interaction strength.

  13. Probing spin-orbit-interaction-induced electron dynamics in the carbon atom by multiphoton ionization

    NASA Astrophysics Data System (ADS)

    Rey, H. F.; van der Hart, H. W.

    2014-09-01

    We use R-matrix theory with time dependence (RMT) to investigate multiphoton ionization of ground-state atomic carbon with initial orbital magnetic quantum number ML=0 and ML=1 at a laser wavelength of 390 nm and peak intensity of 1014W/cm2. Significant differences in ionization yield and ejected-electron momentum distribution are observed between the two values for ML. We use our theoretical results to model how the spin-orbit interaction affects electron emission along the laser polarization axis. Under the assumption that an initial C atom is prepared at zero time delay with ML=0, the dynamics with respect to time delay of an ionizing probe pulse modeled by using RMT theory is found to be in good agreement with available experimental data.

  14. 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.

  15. Ionization-assisted Relativistic Electron Generation with Monoenergetic Features from Laser Thin Foil Interaction

    NASA Astrophysics Data System (ADS)

    Karpeev, Artem; Glazyrin, Igor; Kotova, Olga; Bychenkov, Valery; Fedosejevs, Robert; Rozmus, Wojciech

    2013-10-01

    The concept of ionization-induced injection into the laser pulse to produce quasi-monoenergetic bunches of electrons from ultra-thin solid dense targets is analyzed. When the laser pulse propagates through semi-transparent foil the electrons from inner atom shells remain bound during the rise time of the laser pulse and are ionized by the laser intensity near its maximum amplitude, which satisfies the best injection condition for subsequent acceleration. The 2D3V PIC code PICNIC was used for simulation of a linearly polarized laser pulse with a wavelength λ = 1 . 053 μ m normally incident onto nano-sized DLC target. We performed simulations for 3 cases: (1) 5 nm carbon foil ionized due to field ionization (FI); (2) the same, but already ionized foil, i.e. the foil in the form of a plasma slab with average charge < Z > = 3.4; (3) 42 nm carbon foil with FI. Comparison of the results obtained with different target models shows that a correct description of the interaction of a high contrast laser pulse with an ultra-thin solid dense target should include the FI effect. It was found that for the case (1) a bunch of quasimonoenergetic electrons from inner atom shells moves co-directionally with laser pulse and acquire energy ~mec2a2 / 2 .

  16. The diffusion of charged particles in the weakly ionized plasma with power-law kappa-distributions

    NASA Astrophysics Data System (ADS)

    Wang, Lan; Du, Jiulin

    2017-10-01

    We study the diffusion of charged particles in the weakly ionized plasma with the power-law κ-distributions and without the magnetic field. The electrons and ions have different κ-parameters. We obtain the expressions of both diffusion and mobility coefficients of electrons and ions respectively in the plasma. We find that these new transport coefficient formulae depend strongly on the κ-parameters in the power-law distributed plasma. When we take κ→∞, these formulae reduce to the classical forms in the weakly ionized plasma with a Maxwellian distribution.

  17. 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.

  18. Electrostatic interaction between colloidal particles trapped at an electrolyte interface.

    PubMed

    Majee, Arghya; Bier, Markus; Dietrich, S

    2014-04-28

    The electrostatic interaction between colloidal particles trapped at the interface between two immiscible electrolyte solutions is studied in the limit of small inter-particle distances. Within an appropriate model analytic expressions for the electrostatic potential as well as for the surface and line interaction energies are obtained. They demonstrate that the widely used superposition approximation, which is commonly applied to large distances between the colloidal particles, fails qualitatively at small distances, and is quantitatively unreliable even at large distances. Our results contribute to an improved description of the interaction between colloidal particles trapped at fluid interfaces.

  19. 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)

  20. Elementary Particle Interactions with CMS at LHC

    SciTech Connect

    Spanier, Stefan

    2016-07-31

    The High Energy Particle Physics group of the University of Tennessee participates in the search for new particles and forces in proton-proton collisions at the LHC with the Compact Muon Solenoid experiment. Since the discovery of the Higgs boson in 2012, the search has intensified to find new generations of particles beyond the standard model using the higher collision energies and ever increasing luminosity, either directly or via deviations from standard model predictions such as the Higgs boson decays. As part of this effort, the UTK group has expanded the search for new particles in four-muon final states, and in final states with jets, has successfully helped and continues to help to implement and operate an instrument for improved measurements of the luminosity needed for all data analyses, and has continued to conduct research of new technologies for charged particle tracking at a high-luminosity LHC.

  1. The interaction of an ionizing ligand with enzymes having a single ionizing group. Implications for the reaction of folate analogues with dihydrofolate reductase.

    PubMed

    Stone, S R; Morrison, J F

    1983-06-29

    Binding theory has been developed for the reaction of an ionizing enzyme with an ionizing ligand. Consideration has been given to the most general scheme in which all possible reactions and interconversions occur as well as to schemes in which certain interactions do not take place. Equations have been derived in terms of the variation of the apparent dissociation constant (Kiapp) as a function of pH. These equations indicate that plots of pKiapp against pH can be wave-, half-bell- or bell-shaped according to the reactions involved. A wave is obtained whenever there is formation of the enzyme-ligand complexes, ionized enzyme . ionized ligand and protonated enzyme . protonated ligand. The additional formation of singly protonated enzyme-ligand complexes does not affect the wave form of the plot, but can influence the shape of the overall curve. The formation of either ionized enzyme . ionized ligand or protonated enzyme . protonated ligand, with or without singly protonated enzyme-ligand species, gives rise to a half-bell-shaped plot. If only singly protonated enzyme-ligand complexes are formed the plots are bell-shaped, but it is not possible to deduce the ionic forms of the reactants that participate in complex formation. Depending on the reaction pathways, true values for the ionization and dissociation constants may or may not be determined.

  2. 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.

  3. Ionizing radiation induced catalysis on metal oxide particles. 1997 annual progress report

    SciTech Connect

    Fryberger, T.A.

    1997-06-01

    'This project focuses on a novel approach for destroying organics found in high-level mixed waste prevalent at DOE sites. In this project the authors propose that organics can be destroyed by utilizing reduction/oxidation (redox) chemistry resulting from electron-hole (e{sup -}/h{sup +}) pairs generated in stable, wide bandgap semiconductors via interactions with ionizing radiation ({alpha}, {beta}, {gamma}). Conceptually this process is an extension of visible and near-UV photocatalytic processes known to occur at the interfaces of narrow bandgap semiconductors in both solution and gas phases. In these processes, an electron is excited across the energy gap between the filled and empty states in the semiconductor. The excited electron does reductive chemistry and the hole (the point from which the electron was excited) does oxidative chemistry. The energy separation between the hole and the excited electron reflects the redox capability of the e{sup -}/h{sup +} pair, and is dictated by the energy of the absorbed photon and the bandgap of the material. The use of ionizing radiation has advantages in that it (1) overcomes optical transparency limitations associated with visible and near-UV illumination (y-rays penetrate much farther into a solution than UV/Vis light), and (2) permits the use of wider bandgap materials (such as ZrO{sub 2}), which possess potentially greater redox capabilities than those with narrow bandgap materials. Planned experiments are aimed at extending the body of knowledge about e{sup -}/h{sup +} pair chemistry of semiconducting metal oxide (MO) materials by examining the influence of surface structure, defects, and dopants on the photocatalytic activity of narrow bandgap materials (TiO{sub 2}), and by expanding these studies to wider bandgap materials (ZrO{sub 2}) that are virtually unexplored in terms of their e{sup -}/h{sup +} pair chemistry. Experiments are being conducted in three areas: (1) g-radiocatalysis of reactant-colloidal metal

  4. Stellar and ionized gas kinematics of the interacting Seyfert 1.9 galaxy NGC 2992

    NASA Astrophysics Data System (ADS)

    García-Lorenzo, B.; Arribas, S.; Mediavilla, E.

    2001-11-01

    Integral field spectroscopy in the central 16''x 12'' (2.4 kpc x 1.8 kpc, if H0 = 75 km s-1 Mpc-1) of the Seyfert 1.9 galaxy NGC 2992 has been obtained using the fibre system INTEGRAL. The data are mainly used to study the stellar and ionized gas kinematics. In spite of the photometric disruptions in the outer parts (r > 6 kpc) produced by the interaction with its close companion (NGC 2993), the present stellar velocity field shows regular rotation. The ionized gas presents several kinematically distinct components. Apart from the outflowing component already reported by other authors, we found an additional (high ionization) kinematic component which seems to be associated with the boundaries of the figure-of-eight-shaped emission detected in the 6 cm radio map. We locate the hidden nucleus in the apex of the biconical structure defined by the [O iii] emission, coincident with the outflow origin and with the center of the dust lane. We do not find any clear evidence of direct influence of the interaction in the kinematics of the stars or the ionized gas in the circumnuclear region of NGC 2992.

  5. Spatial Distribution of Element Abundances and Ionization States in Solar Energetic-Particle Events

    NASA Astrophysics Data System (ADS)

    Reames, Donald V.

    2017-08-01

    We have studied the spatial and temporal distribution of abundances of chemical elements in large "gradual" solar energetic-particle (SEP) events, and especially the source plasma temperatures, derived from those abundances, using measurements from the Wind and Solar TErrestrial RElations Observatory (STEREO) spacecraft, widely separated in solar longitude. A power-law relationship between abundance enhancements and mass-to-charge ratios [A/Q] of the ions can be used to determine Q-values and source plasma temperatures at remote spacecraft with instruments that were not designed for charge-state measurements. We search for possible source variations along the accelerating shock wave, finding one clear case where the accelerating shock wave appears to dispatch ions from 3.2± 0.8 MK plasma toward one spacecraft and those from 1.6± 0.2 MK plasma toward another, 116∘ away. The difference persists for three days and then fades away. Three other SEP events show less-extreme variation in source temperatures at different spacecraft, in one case observed over 222∘ in longitude. This initial study shows how the power-law relation between abundance enhancements and ion A/Q-values provides a new technique to determine Q and plasma temperatures in the seed population of SEP ions over a broad region of space using remote spacecraft with instruments that were not originally designed for measurements of ionization states.

  6. 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.

  7. Electrostatic interactions between particles through heterogeneous fluid phases.

    PubMed

    Kang, Dong Woo; Lee, Mina; Kim, Kyung Hak; Xia, Ming; Im, Sang Hyuk; Park, Bum Jun

    2017-09-27

    We investigated the electrostatic interactions between particles acting through heterogeneous fluid phases. An oil lens system floating on the surface of water was used to trap particles at different fluid-fluid interfaces. The inner particles are located at the centrosymmetrically curved oil-water interface inside the oil lens while satellite particles are located at the curved air-water interface, separated by a particular distance from the triple phase boundary. The satellite particles are likely to be captured in an energy minimum state due to electrostatic repulsions by the inner particles balanced with the gravity-induced potential energy. As the size of the oil lens decreases upon evaporation, the satellite particles escape from the gravitational confinement at a critical moment. The self-potential values of the inner particles and the satellite particles were calculated by employing an energy balance and the experimentally obtained geometric parameter values. It was found that the self-potential values of the inner particles decrease as oil evaporates over time and that the magnitude of the self-potential of the satellite particles is a hundred times larger than that of the inner particles. These results demonstrate significant effects of the thickness and shape of the nonpolar superphase on the electrostatic interactions between the particles trapped at different fluid-fluid interfaces.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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 IP3 through IP6.

  10. 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}.

  11. Characterization of the CDMS Ionization Readout

    NASA Astrophysics Data System (ADS)

    Phipps, Arran

    2007-10-01

    Current cosmological models predict that a large portion of the total mass of the universe, about eighty percent, consists of putative dark matter. Theory predicts this dark matter may be in the form of particles constantly passing through the Earth. A class of these particles may interact with ordinary matter, earning the name weakly-interacting massive particles (WIMPs). The Cryogenic Dark Matter Search (CDMS) aims to directly detect the existence of WIMPs. CDMS has designed ZIP (Z-dependent Ionization & Phonon) detectors which measure phonon production and ionization of an interaction, making it possible to determine the interacting particle. The low-energy threshold of the ZIP detectors is determined by the signal-to-noise ratio of the ionization readout. A characterization of the signal-to-noise ratio of the ionization readout, along with possible modifications for improved sensitivity will be presented.

  12. Computation of Capillary Interactions among Many Particles at Free Surface

    NASA Astrophysics Data System (ADS)

    Fujita, Masahiro; Koike, Osamu; Yamaguchi, Yukio

    2013-03-01

    We have developed a new computational method to efficiently estimate capillary interactions among many moving particles at a free surface. A novelty of the method is the immersed free surface (IFS) model that transforms the surface tension exerted on a three-phase contact line on a particle surface into the surface tension exerted on an artificially created virtual free surface in the particle. Using the IFS model along with a level set method and an immersed boundary method, we have reasonably simulated a capillary-force-induced self-assembly of particles that is common in coating-drying of particle suspension.

  13. Interactions between particles in a magnetocapillary self-assembly

    NASA Astrophysics Data System (ADS)

    Lagubeau, Guillaume; Darras, Alexis; Grosjean, Galien; Lumay, Geoffroy; Hubert, Maxime; Vandewalle, Nicolas; Grasp Team

    2014-11-01

    When particles are suspended at air-water interfaces in the presence of a vertical magnetic field, dipole-dipole repulsion competes with capillary attraction. This interaction was used recently to control self-assembling particles, as well as to create low Reynolds swimming systems. Although the equilibrium properties of the magnetocapillary interaction is understood, the dynamics was unclear. In the present report, we emphasize the rich behavior of two/three particles driven by this interaction. We propose a model for describing the motion driven by an external field, being the basis for developing swimming strategies and other elaborated collective behaviors along liquid-air interfaces.

  14. Angle-Dependent Ionization of Small Molecules by Time-Dependent Configuration Interaction and an Absorbing Potential.

    PubMed

    Krause, Pascal; Schlegel, H Bernhard

    2015-06-04

    The angle-dependence of strong field ionization of O2, N2, CO2, and CH2O has been studied theoretically using a time-dependent configuration interaction approach with a complex absorbing potential (TDCIS-CAP). Calculation of the ionization yields as a function of the direction of polarization of the laser pulse produces three-dimensional surfaces of the angle-dependent ionization probability. These three-dimensional shapes and their variation with laser intensity can be interpreted in terms of ionization from the highest occupied molecular orbital (HOMO) and lower lying orbitals, and the Dyson orbitals for the ground and excited states of the cations.

  15. 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.

  16. 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.

  17. Particle identification in a LKr ionization chamber by multiple induced current measurements using the shape analysis of the signal

    NASA Astrophysics Data System (ADS)

    Diaferia, R.; Lanni, F.; Maggi, B.; Palombo, F.; Sala, A.; Cantoni, P.; Frabetti, P. L.; Stagni, L.

    1996-01-01

    Charged particle (π/K) separation in the momentum range 0.5-0.7 GeV/c using a new method of shape analysis of the signal from a liquid krypton ionization chamber has been studied experimentally. The detector has been exposed to pions and protons at the T11 test beam at CERN PS. The shape of preamplifier output signal has been recorded by a waveform digitizer and differentiated to obtain multiple measurements of induced current inside a 2 cm gap. Results on particle separation are presented and compared with a Monte Carlo simulation.

  18. Particle identification in a LKr ionization chamber by multiple induced current measurements using the shape analysis of the signal

    NASA Astrophysics Data System (ADS)

    Cantoni, P.; Frabetti, P. L.; Stagni, L.; Diaferia, R.; Lanni, F.; Maggi, B.; Palombo, F.; Sala, A.; Manfredi, P. F.; Re, V.; Speziali, V.

    1995-02-01

    Charged particle ( {π}/{K}) separation in the momentum range 0.5-0.7 GeV/ c using a new method of shape analysis of the signal from a liquid krypton ionization chamber has been studied experimentally. The detector has been exposed to the T11 test beam at CERN PS. The shape of the preamplifier output signal has been recorded by a waveform digitizer and differentiated to obtain multiple measurements of induced current inside a 2 cm gap. Results on particle separation are presented.

  19. 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

  20. 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.

  1. Energetic charged particle interactions at icy satellites

    NASA Astrophysics Data System (ADS)

    Nordheim, T.; Hand, K. P.; Paranicas, C.; Howett, C.; Hendrix, A. R.

    2016-12-01

    Satellites embedded within planetary magnetospheres are typically exposed to bombardment by charged particles, from thermal plasma to more energetic particles at radiation belt energies. At many planetary satellites, energetic charged particles are typically unimpeded by patchy atmospheres or induced satellite magnetic fields and instead are stopped in the surface itself. Most of these primaries have ranges in porous water ice that are at most centimeters, but some of their secondary photons, emitted during the deceleration process, can reach meter depths [Paranicas et al., 2002, 2004; Johnson et al., 2004]. Examples of radiation-induced surface alteration includes sputtering, radiolysis and grain sintering, processes that are capable of significantly altering the physical properties of surface material. Thus, accurate characterization of energetic charged particle weathering at icy satellites is crucial to a more comprehensive understanding of these bodies. At Saturn's inner mid-size moons remote sensing observations by several instruments onboard the Cassini spacecraft have revealed distinct weathering patterns which have been attributed to energetic electron bombardment of the surface [Howett et al., 2011, 2012, 2014; Schenk et al., 2011; Paranicas et al., 2014]. In the Jovian system, radiolytic production of oxidants has been invoked as a potential source of energy for life which may reside in the sub-surface ocean of its satellite Europa [Johnson et al., 2003; Hand et al., 2007; Vance et al., 2016]. Here we will discuss the near-surface energetic charged particle environment of icy satellites, with particular emphasis on comparative studies between the Saturnian and Jovian systems and interpretation of remote sensing observations by instruments onboard missions such as Cassini and Galileo. In addition, we will discuss implications for surface sampling by future lander missions (e.g. the proposed Europa lander now under study).

  2. 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.

  3. 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.

  4. Magnetospheric plasma - Sources, wave-particle interactions and acceleration mechanisms.

    NASA Technical Reports Server (NTRS)

    Speiser, T. W.

    1971-01-01

    Some of the basic problems associated with magnetospheric physics are reviewed. The sources of magnetospheric plasma, with auroral particles included as a subset, are discussed. The possible ways in which the solar wind plasma can gain access to the magnetosphere are outlined. Some important consequences of wave-particle interactions are examined. Finally, the basic mechanisms which energize or accelerate particles by reconnection and convection are explained.

  5. Exactly solvable interacting two-particle quantum graphs

    NASA Astrophysics Data System (ADS)

    Bolte, Jens; Garforth, George

    2017-03-01

    We construct models of exactly solvable two-particle quantum graphs with certain non-local two-particle interactions, establishing appropriate boundary conditions via suitable self-adjoint realisations of the two-particle Laplacian. Showing compatibility with the Bethe ansatz method, we calculate quantisation conditions in the form of secular equations from which the spectra can be deduced. We compare spectral statistics of some examples to well known results in random matrix theory, analysing the chaotic properties of their classical counterparts.

  6. 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.

  7. 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.

  8. Particle interactions of polyvinylpyrrolidone-coated iron oxide particles as magnetic drug delivery agents

    NASA Astrophysics Data System (ADS)

    İşçi, Sevim; İşçi, Yavuz; Bekaroğlu, Maide Gökçe

    2017-08-01

    Iron oxide particles have been recently researched for the potential applications of targeted drug delivery due to their magnetic properties. The surfaces of the iron oxide particles must be modified to reduce the toxicity and to load the drug to the particles. Biopolymers are good surface modifiers of colloidal particles such as iron oxide particles. The degree of surface coverage of the colloidal iron oxide particles affects the stability, toxicity, magnetic properties and drug loading efficiency. In this study, the interactions of iron oxide (Fe3O4) particles and PVP were determined according to the colloidal properties. The proper concentration of PVP for the whole coverage of the iron oxide particles was found for the possible magnetic drug delivery applications by controlling the colloidal properties of the dispersions. The magnetic properties and toxicity of the fully covered bioiron oxide was also determined for possible applications.

  9. Spatiotemporal binary interaction and designer quasi-particle condensates

    NASA Astrophysics Data System (ADS)

    Ramaswamy, Radha; Pattu Sakthi, Vinayagam; Hyun Jong, Shin; Kuppuswamy, Porsezian

    2014-03-01

    We introduce a new integrable model to investigate the dynamics of two component quasi-particle condensates with spatiotemporal interaction strengths. We derive the associated Lax pair of the coupled Gross—Pitaevskii (GP) equation and construct matter wave solitons. We show that the spatiotemporal binary interaction strengths not only facilitate the stabilization of the condensates, but also enables one to fabricate condensates with desirable densities, geometries, and properties, leading to the so-called “designer quasi-particle condensates”.

  10. 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.

  11. 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.

  12. 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.

  13. Stochastic transport of interacting particles in periodically driven ratchets

    NASA Astrophysics Data System (ADS)

    Savel'Ev, Sergey; Marchesoni, Fabio; Nori, Franco

    2004-12-01

    An open system of overdamped, interacting Brownian particles diffusing on a periodic substrate potential U(x+l)=U(x) is studied in terms of an infinite set of coupled partial differential equations describing the time evolution of the relevant many-particle distribution functions. In the mean-field approximation, this hierarchy of equations can be replaced by a nonlinear integro-differential Fokker-Planck equation. This is applicable when the distance a between particles is much less than the interaction length λ , i.e., a particle interacts with many others, resulting in averaging out fluctuations. The equation obtained in the mean-field approximation is applied to an ensemble of locally (a≪λ≪l) interacting (either repelling or attracting) particles placed in an asymmetric one-dimensional substrate potential, either with an oscillating temperature (temperature rachet) or driven by an ac force (rocked ratchet). In both cases we focus on the high-frequency limit. For the temperature ratchet, we find that the net current is typically suppressed (or can even be inverted) with increasing density of the repelling particles. In contrast, the net current through a rocked ratchet can be enhanced by increasing the density of the repelling particles. In the case of attracting particles, our perturbation technique is valid up to a critical value of the particle density, above which a finite fraction of the particles starts condensing in a liquidlike state near the substrate minima. The dependence of the net transport current on the particle density and the interparticle potential is analyzed in detail for different values of the ratchet parameters.

  14. Stochastic transport of interacting particles in periodically driven ratchets.

    PubMed

    Savel'ev, Sergey; Marchesoni, Fabio; Nori, Franco

    2004-12-01

    An open system of overdamped, interacting Brownian particles diffusing on a periodic substrate potential U(x+l)=U(x) is studied in terms of an infinite set of coupled partial differential equations describing the time evolution of the relevant many-particle distribution functions. In the mean-field approximation, this hierarchy of equations can be replaced by a nonlinear integro-differential Fokker-Planck equation. This is applicable when the distance a between particles is much less than the interaction length lambda , i.e., a particle interacts with many others, resulting in averaging out fluctuations. The equation obtained in the mean-field approximation is applied to an ensemble of locally (ainteracting (either repelling or attracting) particles placed in an asymmetric one-dimensional substrate potential, either with an oscillating temperature (temperature rachet) or driven by an ac force (rocked ratchet). In both cases we focus on the high-frequency limit. For the temperature ratchet, we find that the net current is typically suppressed (or can even be inverted) with increasing density of the repelling particles. In contrast, the net current through a rocked ratchet can be enhanced by increasing the density of the repelling particles. In the case of attracting particles, our perturbation technique is valid up to a critical value of the particle density, above which a finite fraction of the particles starts condensing in a liquidlike state near the substrate minima. The dependence of the net transport current on the particle density and the interparticle potential is analyzed in detail for different values of the ratchet parameters.

  15. 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

  16. 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.

  17. 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.

  18. 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 .

  19. Interactions between two touching spherical particles in sedimentation.

    PubMed

    Sun, Ren; Chwang, Allen T

    2007-10-01

    A contact of a falling spherical particle with another fixed one in an unbounded viscous fluid is theoretically investigated based on a model of adding the contact interaction to the gravitational and hydrodynamic forces. The hydrodynamic interaction between the two particles is dealt with using an extended successive reflection method, with which the complete solution to the exterior velocity field around the two-particle system is constructed on the basis of the general expression given by Lamb, and then the hydrodynamic forces and torques on the two particles are obtained by integrating the fluid stress over each particle surface. The mechanical contact force is characterized by the standard friction theory with a criterion responsible for the transition from pure rolling to rolling with slip. Resorting to the dynamical equations of motion including the gravitational, hydrodynamic, and contact forces, the settling motion of a spherical particle in the vicinity of another fixed one is depicted using the fourth-order Runge-Kutta-Fehlberg method. Compared with the experimental results available in the literature, the theoretical prediction confirms two moving patterns at contact: pure rolling and rolling with slip, analyzes the dependence of the transition from one to another on the static friction coefficient and the contact separation distance between the particle surfaces, and accounts for a limitation of the quasisteady description of two interacting noncolloidal particles.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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.

  1. Turbulence-radiation interactions in a particle-laden flow

    NASA Astrophysics Data System (ADS)

    Frankel, Ari; Pouransari, Hadi; Iaccarino, Gianluca; Mani, Ali

    2014-11-01

    Turbulent fluctuations in a radiatively participating medium can significantly alter the mean heat transfer characteristics in a manner that current RANS models cannot accurately capture. While turbulence-radiation interaction has been studied extensively in traditional combustion systems, such interactions have not yet been studied in the context of particle-laden flows. This work is motivated by applications in particle-based solar receivers in which external radiation is primarily absorbed by a dispersed phase and conductively exchanged with the carrier fluid. Direct numerical simulations of turbulence with Lagrangian particles subject to a collimated radiation source are performed with a flux-limited diffusion approximation to radiative transfer. The dependence of the turbulence-radiation interaction statistics on the particle Stokes number will be demonstrated. Supported by PSAAP II.

  2. Simulation of Au particle interaction on graphene sheets

    NASA Astrophysics Data System (ADS)

    Mcleod, A.; Vernon, K. C.; Rider, A. E.; Ostrikov, K.

    2013-09-01

    The interaction of Au particles with few layer graphene is of interest for the formation of the next generation of sensing devices 1. In this paper we investigate the coupling of single gold nanoparticles to a graphene sheet, and multiple gold nanoparticles with a graphene sheet using COMSOL Multiphysics. By using these simulations we are able to determine the electric field strength and associated hot-spots for various gold nanoparticle-graphene systems. The Au nanoparticles were modelled as 8 nm diameter spheres on 1.5 nm thick (5 layers) graphene, with properties of graphene obtained from the refractive index data of Weber 2 and the Au refractive index data from Palik 3. The field was incident along the plane of the sheet with polarisation tested for both s and p. The study showed strong localised interaction between the Au and graphene with limited spread; however the double particle case where the graphene sheet separated two Au nanoparticles showed distinct interaction between the particles and graphene. An offset was introduced (up to 4 nm) resulting in much reduced coupling between the opposed particles as the distance apart increased. Findings currently suggest that the graphene layer has limited interaction with incident fields with a single particle present whilst reducing the coupling region to a very fine area when opposing particles are involved. It is hoped that the results of this research will provide insight into graphene-plasmon interactions and spur the development of the next generation of sensing devices.

  3. 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

  4. 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

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

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongzhen; Prosperetti, Andrea

    2002-11-01

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

  6. Reducing Collisional Breakup Of A System Of Charged Particles To Practical Computation: Electron-Impact Ionization Of Hydrogen

    SciTech Connect

    McCurdy, C.W.; Baertschy, M.; Isaacs, W.A.; Rescigno, T.N.

    2001-08-24

    It has been a goal of researchers in the area of atomic collisions for nearly half a century to reduce to practical computation the simplest problem in collisional ionization: the electron-impact ionization of atomic hydrogen. The principal barrier to solving this problem has been the difficult boundary conditions that apply to the complete breakup of a system charged particles. We describe how this goal has been accomplished in the last five years by the application of the mathematical transformation of ''exterior complex scaling'' together with an appropriate formalism for computing the breakup amplitudes from a numerical representation of the complete solution of the Schrodinger equation. Some successes of other recent approaches to this problem are also described.

  7. 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.

  8. 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.

  9. Probabilistic approach to nonlinear wave-particle resonant interaction

    NASA Astrophysics Data System (ADS)

    Artemyev, A. V.; Neishtadt, A. I.; Vasiliev, A. A.; Mourenas, D.

    2017-02-01

    In this paper we provide a theoretical model describing the evolution of the charged-particle distribution function in a system with nonlinear wave-particle interactions. Considering a system with strong electrostatic waves propagating in an inhomogeneous magnetic field, we demonstrate that individual particle motion can be characterized by the probability of trapping into the resonance with the wave and by the efficiency of scattering at resonance. These characteristics, being derived for a particular plasma system, can be used to construct a kinetic equation (or generalized Fokker-Planck equation) modeling the long-term evolution of the particle distribution. In this equation, effects of charged-particle trapping and transport in phase space are simulated with a nonlocal operator. We demonstrate that solutions of the derived kinetic equations agree with results of test-particle tracing. The applicability of the proposed approach for the description of space and laboratory plasma systems is also discussed.

  10. Coulomb-tail effect of electron-electron interaction on nonsequential double ionization

    NASA Astrophysics Data System (ADS)

    Zhou, Yueming; Huang, Cheng; Lu, Peixiang

    2011-08-01

    With the classical ensemble model, we investigate the manifestations of the Coulomb tail of electron-electron interaction in nonsequential double ionization by comparing the results from the short-range electron-electron interaction with those from the Coulombic electron-electron interaction. At the intensity below the recollision threshold, the two-electron momentum distributions in the direction parallel to the laser polarization show an anticorrelated behavior for the Coulombic electron-electron interaction while a correlated behavior for the short-range interaction, which indicates the responsibility of the Coulomb tail of the electron-electron interaction for the experimentally observed anticorrelated emission [Y. Liu, S. Tschuch, A. Rudenko, M. Durr, M. Siegel, U. Morgner, R. Moshammer, and J. Ullrich, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.101.053001 101, 053001 (2008)]. In the transverse direction, for the Coulombic electron-electron interaction, the two electrons exhibit no effect of repulsion at an intensity below the recollision threshold while a strong repulsion effect at an intensity above the threshold, which becomes weaker as the laser intensity further increases. Back analysis shows that the role of the Coulomb tail of electron-electron interaction leads asymmetric energy sharing (AES) to be prevalent at recollision. This AES results in the two electrons leaving the ion at different times or with different initial momenta, which is responsible for the anticorrelated behavior in the parallel direction and the intensity-dependent repulsion effect in the transverse direction.

  11. Coulomb-tail effect of electron-electron interaction on nonsequential double ionization

    SciTech Connect

    Zhou Yueming; Huang Cheng; Lu Peixiang

    2011-08-15

    With the classical ensemble model, we investigate the manifestations of the Coulomb tail of electron-electron interaction in nonsequential double ionization by comparing the results from the short-range electron-electron interaction with those from the Coulombic electron-electron interaction. At the intensity below the recollision threshold, the two-electron momentum distributions in the direction parallel to the laser polarization show an anticorrelated behavior for the Coulombic electron-electron interaction while a correlated behavior for the short-range interaction, which indicates the responsibility of the Coulomb tail of the electron-electron interaction for the experimentally observed anticorrelated emission [Y. Liu, S. Tschuch, A. Rudenko, M. Durr, M. Siegel, U. Morgner, R. Moshammer, and J. Ullrich, Phys. Rev. Lett. 101, 053001 (2008)]. In the transverse direction, for the Coulombic electron-electron interaction, the two electrons exhibit no effect of repulsion at an intensity below the recollision threshold while a strong repulsion effect at an intensity above the threshold, which becomes weaker as the laser intensity further increases. Back analysis shows that the role of the Coulomb tail of electron-electron interaction leads asymmetric energy sharing (AES) to be prevalent at recollision. This AES results in the two electrons leaving the ion at different times or with different initial momenta, which is responsible for the anticorrelated behavior in the parallel direction and the intensity-dependent repulsion effect in the transverse direction.

  12. 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.

  13. Interacting Brownian dynamics in a nonequilibrium particle bath.

    PubMed

    Steffenoni, Stefano; Kroy, Klaus; Falasco, Gianmaria

    2016-12-01

    We set up a mesoscopic theory for interacting Brownian particles embedded in a nonequilibrium environment, starting from the microscopic interacting many-body theory. Using nonequilibrium linear-response theory, we characterize the effective dynamical interactions on the mesoscopic scale and the statistics of the nonequilibrium environmental noise, arising upon integrating out the fast degrees of freedom. As hallmarks of nonequilibrium, the breakdown of the fluctuation-dissipation and action-reaction relations for Brownian degrees of freedom is exemplified with two prototypical models for the environment, namely active Brownian particles and stirred colloids.

  14. Plasma lipid analysis by hydrophilic interaction liquid chromatography coupled with electrospray ionization tandem mass spectrometry.

    PubMed

    Sonomura, Kazuhiro; Kudoh, Shinobu; Sato, Taka-Aki; Matsuda, Fumihiko

    2015-06-01

    A novel method for the analysis of endogenous lipids and related compounds was developed employing hydrophilic interaction liquid chromatography with electrospray ionization tandem mass spectrometry. A hydrophilic interaction liquid chromatography with carbamoyl stationary phase achieved clear separation of phosphatidylcholine, lysophosphatidylcholine, sphingomyelin, ceramide, and mono-hexsosyl ceramide groups with good peak area repeatability (RSD% < 10) and linearity (R(2) > 0.99). The established method was applied to human plasma assays and a total of 117 endogenous lipids were successfully detected and reproducibly identified. In addition, we investigated the simultaneous detection of small polar metabolites such as amino and organic acids co-existing in the same biological samples processed in a single analytical run with lipids. Our results show that hydrophilic interaction liquid chromatography is a useful tool for human plasma lipidome analysis and offers more comprehensive metabolome coverage.

  15. 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. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. 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.

  17. Persistent entanglement in arrays of interacting particles.

    PubMed

    Briegel, H J; Raussendorf, R

    2001-01-29

    We study the entanglement properties of a class of N-qubit quantum states that are generated in arrays of qubits with an Ising-type interaction. These states contain a large amount of entanglement as given by their Schmidt measure. They also have a high persistency of entanglement which means that approximately N/2 qubits have to be measured to disentangle the state. These states can be regarded as an entanglement resource since one can generate a family of other multiparticle entangled states such as the generalized Greenberger-Horne-Zeilinger states of

  18. 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.

  19. 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.

  20. Effects of magnetic interactions in antiferromagnetic ferrihydrite particles

    NASA Astrophysics Data System (ADS)

    Berquó, Thelma S.; Erbs, Jasmine J.; Lindquist, Anna; Penn, R. Lee; Banerjee, Subir K.

    2009-04-01

    The effects of magnetic interactions in the magnetic properties of six-line ferrihydrite particles were investigated by studying the behavior of aggregated versus coated particles. Four different coating agents (sugar, alginate, lactate and ascorbate) were employed in order to obtain dispersed particles and prevent particle agglomeration; one sub-sample was allowed to dry with no coating agent. The five sets of ferrihydrite particles were from the same batch and the size was estimated as 3.6 ± 0.4 nm in length. Low temperature magnetization, ac susceptibility and Mössbauer spectroscopy data showed contrasting blocking temperatures for uncoated and coated samples with a decrease of TP from about 50 K to 12 K, respectively. The contributions from magnetic interactions were recognized in magnetic measurements and the effective anisotropy constant for non-interacting ferrihydrite was estimated as (100 ± 10) × 103 J m-3. Overall, employing sugar and alginate as coating agents was more successful in preventing particle aggregation and magnetic interactions. In contrast, ascorbate and lactate were unsuitable due to the chemical reaction between the coating agent and ferrihydrite surface.

  1. Design of bio-mimetic particles with enhanced vascular interaction.

    PubMed

    Lee, Sei-Young; Ferrari, Mauro; Decuzzi, Paolo

    2009-08-25

    The majority of particle-based delivery systems for the 'smart' administration of therapeutic and imaging agents have a spherical shape, are made by polymeric or lipid materials, have a size in the order of few hundreds of nanometers and a negligibly small relative density to aqueous solutions. In the microcirculation and deep airways of the lungs, where the creeping flow assumption holds, such small spheres move by following the flow stream lines and are not affected by external volume force fields. A delivery system should be designed to drift across the stream lines and interact repeatedly with the vessel walls, so that vascular interaction could be enhanced. The numerical approach presented in [Gavze, E., Shapiro, M., 1997. Particles in a shear flow near a solid wall: effect of nonsphericity on forces and velocities. International Journal of Multiphase Flow 23, 155-182.] is, here, proposed as a tool to analyze the dynamics of arbitrarily shaped particles in a creeping flow, and has been extended to include the contribution of external force fields. As an example, ellipsoidal particles with aspect ratio 0.5 are considered. In the absence of external volume forces, a net lateral drift (margination) of the particles has been observed for Stokes number larger than unity (St>1); whereas, for smaller St, the particles oscillate with no net lateral motion. Under these conditions, margination is governed solely by particle inertia (geometry and particle-to-fluid density ratio). In the presence of volume forces, even for fairly small St, margination is observed but in a direction dictated by the external force field. It is concluded that a fine balance between size, shape and density can lead to EVI particles (particles with enhanced vascular interaction) that are able to sense endothelial cells for biological and biophysical abnormalities, mimicking circulating platelets and leukocytes.

  2. Simulations of Shock Wave Interaction with a Particle Cloud

    NASA Astrophysics Data System (ADS)

    Koneru, Rahul; Rollin, Bertrand; Ouellet, Frederick; Annamalai, Subramanian; Balachandar, S.'Bala'

    2016-11-01

    Simulations of a shock wave interacting with a cloud of particles are performed in an attempt to understand similar phenomena observed in dispersal of solid particles under such extreme environment as an explosion. We conduct numerical experiments in which a particle curtain fills only 87% of the shock tube from bottom to top. As such, the particle curtain upon interaction with the shock wave is expected to experience Kelvin-Helmholtz (KH) and Richtmyer-Meshkov (RM) instabilities. In this study, the initial volume fraction profile matches with that of Sandia Multiphase Shock Tube experiments, and the shock Mach number is limited to M =1.66. In these simulations we use a Eulerian-Lagrangian approach along with state-of-the-art point-particle force and heat transfer models. Measurements of particle dispersion are made at different initial volume fractions of the particle cloud. A detailed analysis of the evolution of the particle curtain with respect to the initial conditions is presented. This work was supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, Contract No. DE-NA0002378.

  3. Effects of Hydrodynamic Interaction in Aerosol Particle Settling: Mesoscopic Particle-level Full Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Li, Shuiqing; Yang, Mengmeng; Marshall, Jeffrey

    2014-11-01

    A new mesoscopic particle-level approach is developed for the full dynamics simulation (FDS) of the settling of systems of aerosol micro-particles. The approach efficiently combines an adhesive discrete-element method for particle motions and an Oseen dynamics method for hydrodynamic interactions. Compared to conventional Stokeslet and Oseenlet simulations, the FDS not only accounts for the cloud-scale fluid inertia effect and the particle inertia effect, but also overcomes the singularity problem using a soft-sphere model of adhesive contact. The effect of hydrodynamic interactions is investigated based on FDS results. The particle inertia is found to reduce the mobility of particle clouds and to elongate the cloud on vertical direction. Meanwhile, the fluid inertia decreases the settling velocity by weakening the hydrodynamic interaction and tends to flatten the cloud, leading to breakup. Expressions for the settling velocity of particle cloud are proposed with consideration of fluid inertia effect and the cloud shape. Finally, the transformation in settling behavior from a finite particle cloud to an unbounded uniform suspension is explained. This work has been funded by the National Natural Science Funds of China (No. 50976058), and by the National Key Basic Research and Development Program (2013CB228506).

  4. Particle and energy dependence of the statistical fluctuations of an ionization chamber current

    NASA Astrophysics Data System (ADS)

    Purghel, Lidia; Vaˆlcov, Nicolae

    For the purpose of getting more detailed information concerning the processes leading to statistical fluctuations of an ionization chamber current, measurements with various radioactive sources have been done. By using the experimental arrangement described elsewhere [A. Necula et al. Nucl. Instr. and Meth. A 332 (1993) 501] the mean value and the standard deviation of the ionization current for 3H (water vapours), 60Co (sealed source), 85Kr (gas), 204Tl (8 mm diameter disk) and 239Pu (10 mm diameter disk), beta, gamma and alpha sources have been measured. A statistical model explaining the experimental data is proposed.

  5. 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.

  6. 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.

  7. Interaction mechanisms of Ionizable Organic Pollutants with Aromatized Biochar: Adsorption Experiments and DFT Calculations

    NASA Astrophysics Data System (ADS)

    Zhang, Kun; Chen, Baoliang

    2017-04-01

    The molecular interaction between biochars and ionizable organic pollutants (IOPs) are of great concern in natural environments, however the underlying mechanisms and their quantification under different pH range are not vivid. The adsorption of IOPs onto high temperature biochars derived from bamboo wood biomass (BW700) was conducted to quantify the various interactions between sorbent surface and IOPs under different pH conditions. The aromatized surface of BW700 were characterized by Fourier Transformed Infrared spectroscopy (FT-IR), Brunauer-Emmet-Teller (BET) specific surface area with N2 and CHN elemental compositions. Seven IOPs were selected as model sorbates, and batch sorption experiments were conducted to quantify the ratio of π-π interactions and hydrogen bonding interactions. The pH-dependent adsorption curves and the adsorption isotherms not only indicated that the adsorption capacity was related with species of IOPs, but also showed the presence of adsorbing peak owing some of the other mechanisms when taking the ice-like adlayer into consideration. Finally, density functional theory (DFT) calculations provided a possible structure of the complex combined with ice-like adlayer with aromatic substrate of BW700, and indicated that the formation of extra adsorption sites originated from the X-H ... O-H ... π interactions. The contribution of π-π interactions, hydrogen bonding interactions and X-H ... O-H ... π interactions were distinguished by the pKa value of IOPs owing to their species. Our findings provide new insight for distinction and quantification of various interactions under different pH conditions, and it is the first time to put forward the X-H ... O-H ... π interactions for the interaction mechanism of IOPs with biochar.

  8. Analytical solutions of minimum ionization particle induced current shapes of silicon detectors and simulation of charge collection properties

    SciTech Connect

    Eremin, V.; Chen, W.; Li, Z.

    1993-11-01

    A new analytical, one dimensional method to obtain the induced current shapes and simulation of chasrge shapes for p{sup +} {minus}n{minus}n{sup +} silicon detectors in the case of minimum ionization particle has been developed here. jExact solutions have been found for both electron and hole current shapes. Simulations of induced charge shapes of detectors have also been given. The results of this work are consistent with the earlier work where a semi-analytical method had been used.

  9. 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.

  10. 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.

  11. 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

  12. 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).

  13. 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.

  14. Soft wall effects on interacting particles in billiards.

    PubMed

    Oliveira, H A; Manchein, C; Beims, M W

    2008-10-01

    The effect of physically realizable wall potentials (soft walls) on the dynamics of two interacting particles in a one-dimensional (1D) billiard is examined numerically. The 1D walls are modeled by the error function and the transition from hard to soft walls can be analyzed continuously by varying the softness parameter sigma . For sigma-->0 the 1D hard wall limit is obtained and the corresponding wall force on the particles is the delta function. In this limit the interacting particle dynamics agrees with previous results obtained for the 1D hard walls. We show that the two interacting particles in the 1D soft walls model is equivalent to one particle inside a soft right triangular billiard. Very small values of sigma substantiously change the dynamics inside the billiard and the mean finite-time Lyapunov exponent decreases significantly as the consequence of regular islands which appear due to the low-energy double collisions (simultaneous particle-particle-1D wall collisions). The rise of regular islands and sticky trajectories induced by the 1D wall softness is quantified by the number of occurrences of the most probable finite-time Lyapunov exponent. On the other hand, chaotic motion in the system appears due to the high-energy double collisions. In general we observe that the mean finite-time Lyapunov exponent decreases when sigma increases, but the number of occurrences of the most probable finite-time Lyapunov exponent increases, meaning that the phase-space dynamics tends to be more ergodiclike. Our results suggest that the transport efficiency of interacting particles and heat conduction in periodic structures modeled by billiards will strongly be affected by the smoothness of physically realizable walls.

  15. 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.

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

    DOE PAGES

    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

  17. 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

  18. A transition-state interaction shifts nucleobase ionization toward neutrality to facilitate small ribozyme catalysis.

    PubMed

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

    2012-10-17

    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 pK(a) values for the Ade38 N1 imino group of a hairpin ribozyme in distinct conformational states. A transition-state analogue gave a pK(a) 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 pK(a), we determined crystal structures of hairpin ribozyme variants containing single-atom substitutions at the active site and measured their respective Ade38 N1 pK(a) values. This approach led to the identification of a single interaction in the transition-state conformation that elevates the base pK(a) > 0.8 log unit relative to the precatalytic state. The agreement of the microscopic and macroscopic pK(a) values and the accompanying structural analysis supports 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.

  19. Interactions of casein micelles with calcium phosphate particles.

    PubMed

    Tercinier, Lucile; Ye, Aiqian; Anema, Skelte G; Singh, Anne; Singh, Harjinder

    2014-06-25

    Insoluble calcium phosphate particles, such as hydroxyapatite (HA), are often used in calcium-fortified milks as they are considered to be chemically unreactive. However, this study showed that there was an interaction between the casein micelles in milk and HA particles. The caseins in milk were shown to bind to the HA particles, with the relative proportions of bound β-casein, αS-casein, and κ-casein different from the proportions of the individual caseins present in milk. Transmission electron microscopy showed no evidence of intact casein micelles on the surface of the HA particles, which suggested that the casein micelles dissociated either before or during binding. The HA particles behaved as ion chelators, with the ability to bind the ions contained in the milk serum phase. Consequently, the depletion of the serum minerals disrupted the milk mineral equilibrium, resulting in dissociation of the casein micelles in milk.

  20. Effect of ion streaming on particle-particle interactions in a dusty plasma

    SciTech Connect

    Vyas, Vivek; Kushner, Mark J.

    2005-02-15

    Dust particles in low-temperature, low-pressure plasmas form Coulomb crystals and display collective behavior under select conditions. The trajectories of ions can be perturbed as they pass by negatively charged dust particles and, in some cases, will converge beyond the particle. This process, called ion streaming, produces a positive potential in the wakefield of the particle that can be large enough to perturb interparticle dynamics. In this paper, we discuss results from a three-dimensional model for dust particle transport in plasma processing reactors with which we investigated the effects of ion streaming on particle-particle interactions. When including the wakefield potential produced by ion streaming, dust particles can form vertically correlated pairs when trapped in electrical potential wells. The ion-streaming force was found to be significant only over a select range of pressures and for given combinations of particle sizes and mass densities. The formation of vertically correlated pairs critically depends on the shape of the potential well. Wakefield forces can also affect the order of multilayer lattices by producing vertical correlations between particles in adjacent layers.

  1. Evaluation of DNA/Ligand Interactions by Electrospray Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Brodbelt, Jennifer S.

    2010-07-01

    Electrospray ionization mass spectrometry (ESI-MS) has enabled the detection and characterization of DNA/ligand complexes, including evaluation of both relative binding affinities and selectivities of DNA-interactive ligands. The noncovalent complexes that are transferred from the solution to the gas phase retain the signature of the native species, thus allowing the use of MS to screen DNA/ligand complexes, reveal the stoichiometries of the complexes, and provide insight into the nature of the interactions. Ligands that bind to DNA via metal-mediated modes and those that bind to unusual DNA structures, such as quadruplexes, are amenable to ESI. Chemical probe methods applied to DNA/ligand complexes with ESI-MS detection afford information about ligand-binding sites and conformational changes of DNA that occur upon ligand binding.

  2. Asymmetric exclusion process in a system of interacting Brownian particles.

    PubMed

    Eduardo de Oliveira Rodrigues, José; Dickman, Ronald

    2010-06-01

    We study a continuous-space version of the totally asymmetric simple exclusion process (TASEP), consisting of interacting Brownian particles subject to a driving force in a periodic array of potential wells. Particles are inserted into the leftmost well at rate α, hop to the right at unit rate, and are removed at the rightmost well at rate β. Our study is motivated by recent experiments on colloidal particles in a periodic potential generated by an optical tweezers array. Particles spend most of the time near potential minima, approximating the situation on the lattice; a short-range repulsive interaction prevents two particles from occupying the same potential well. A constant driving force, representing Stokes drag on particles suspended in a moving fluid, leads to biased motion. Our results for the density profile and current, obtained via numerical integration of the Langevin equation and dynamic Monte Carlo simulations, indicate that the continuous-space model exhibits phase transitions analogous to those observed in the lattice TASEP. The correspondence is not exact, however, due to the lack of particle-hole symmetry in our model.

  3. Experimental verification of interactions between randomly distributed fine magnetic particles

    NASA Astrophysics Data System (ADS)

    Taketomi, Susamu; Shull, Robert D.

    2003-10-01

    We experimentally examined whether or not a magnetic fluid (MF) is really superparamagnetic by comparing the initial magnetic susceptibilities of the mother MFs with those of their highly diluted solutions (more than 1000 times diluted) in which the dipole-dipole interaction between the particles was negligible. We used three mother MFs, SA 1, SB 1, and SC 1, and their highly diluted solutions, SA 2, SB 2, and SC 2, respectively. The particles' dispersability was best in SA 1 and poorest in SC 1. From the static field experiment, it was found that the mutual interaction between the particles in SB 1, and SC 1 made clusters of particles with magnetically closed flux circuits even at zero field while no interaction was detected in SA 1. The initial complex magnetic susceptibility, χ˜, as a function of temperature, T, under an AC field experiment revealed that the complex susceptibility of both the samples SA 1 and SA 2 showed peaks as a function of T. However, their χ˜ vs. T curves were not similar, leading to the conclusion that the sample SA 1 was not superparamagnetic. Instead, SA 1 was a magnetic spin-glass induced by the weak interaction between the particle spins. The existence of the spin-glass state was also confirmed by the Volgel-Fulcher law dependence of the AC-susceptibility peak temperature, Tp, or the frequency of the AC field.

  4. Effects of Wave-Particle Interactions on Radiation Belt Development

    NASA Astrophysics Data System (ADS)

    Zheng, Y.; Fok, M.; Khazanov, G. V.; Ober, D. M.; Gallagher, D. L.

    2002-12-01

    In this presentation, the effects of wave-particle interactions on radiation belt development will be investigated. The tool of this investigation is the kinetic Radiation Belt model that solves the convection-diffusion equation of plasma distributions in the 10keV to MeV range, with the addition of a plasmasphere model and a diffusion coefficient model. The boundary condtions of the Radiation Belt model are driven by solar wind and IMF. The purpose of the plasmasphere model is to provide the density profile of the cold core plasma, which is used in the diffusion coefficient model for calculating the diffusion coefficients of different types of wave-particle interactions. Therefore the effects of wave-particle interactions on the development of the Radiation Belt can be incorporated and modeled in a more realistic fashion. We will present the model logic and the model validation by comparing measured particle fluxes with the model calculations for several magnetic storms. We hope, through this modeling effort, that the comparison study will shed light on the evolution of the Radiation Belt and on the contribution of different physical processes involved, particularly wave-particle interactions.

  5. 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.

  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. Search for highly ionizing particles in e/sup +/e/sup -/ collisions at. sqrt. s = 29 GeV

    SciTech Connect

    Fryberger, D.; Coan, T.E.; Kinoshita, K.; Price, P.B.

    1984-04-01

    The results of the analysis of data taken in the continuation of a previously reported search for highly ionizing particles at PEP are presented. Assemblies consisting of Lexan and CR-39 plastic track detectors were exposed in two runs to integrated luminosities of 30 x 10/sup 36/ cm/sup -2/ and 150 x 10/sup 36/ cm/sup -2/. The search was sensitive to particles with magnetic charge 20e< or =g< or =200e or electric charge 3< or =Z< or =180. A combined (95% C.L.) upper limit on the production cross section of sigma<3.2 x 10/sup -38/ cm/sup 2/ is obtained, improving our previous limits by more than an order of magnitude.

  8. Ionizer assisted air filtration for collection of submicron and ultrafine particles-evaluation of long-term performance and influencing factors.

    PubMed

    Shi, Bingbing; Ekberg, Lars

    2015-06-02

    Previous research has demonstrated that unipolar ionization can enhance the filter performance to collect airborne particles, aeroallergens, and airborne microorganisms, without affecting the filter pressure drop. However, there is a lack of research on the long-term system performance as well as the influence of environmental and operational parameters. In this paper, both field and laboratory tests were carried out to evaluate the long-term particle collection efficiency of a synthetic filter of class M6 with and without ionization. The effect of air velocity, temperature, relative humidity, and particle concentration were further investigated in laboratory tests. Results showed that ionization enhanced the filtration efficiency by 40%-units during most of the operation time. When the ionization system was managed by periodically switching the ionizer polarity, the filtration efficiency against PM0.3-0.5 was maintained above 50% during half a year. Furthermore, the pressure drop of the ionizer-assisted M6 filter was 25-30% lower than that of a filter of class F7. The evaluation of various influencing factors demonstrated that (1) air moisture reduced the increase of filtration efficiency; (2) higher upstream particle concentration and air velocity decreased the filtration efficiency; and (3) the air temperature had very limited effect on the filtration efficiency.

  9. Three-Dimensional Electromagnetic Monte Carlo Particle-in-Cell Simulations of Critical Ionization Velocity Experiments in Space

    NASA Technical Reports Server (NTRS)

    Wang, J.; Biasca, R.; Liewer, P. C.

    1996-01-01

    Although the existence of the critical ionization velocity (CIV) is known from laboratory experiments, no agreement has been reached as to whether CIV exists in the natural space environment. In this paper we move towards more realistic models of CIV and present the first fully three-dimensional, electromagnetic particle-in-cell Monte-Carlo collision (PIC-MCC) simulations of typical space-based CIV experiments. In our model, the released neutral gas is taken to be a spherical cloud traveling across a magnetized ambient plasma. Simulations are performed for neutral clouds with various sizes and densities. The effects of the cloud parameters on ionization yield, wave energy growth, electron heating, momentum coupling, and the three-dimensional structure of the newly ionized plasma are discussed. The simulations suggest that the quantitative characteristics of momentum transfers among the ion beam, neutral cloud, and plasma waves is the key indicator of whether CIV can occur in space. The missing factors in space-based CIV experiments may be the conditions necessary for a continuous enhancement of the beam ion momentum. For a typical shaped charge release experiment, favorable CIV conditions may exist only in a very narrow, intermediate spatial region some distance from the release point due to the effects of the cloud density and size. When CIV does occur, the newly ionized plasma from the cloud forms a very complex structure due to the combined forces from the geomagnetic field, the motion induced emf, and the polarization. Hence the detection of CIV also critically depends on the sensor location.

  10. Multi-particle interaction in a model of the hydrophobic interaction

    NASA Astrophysics Data System (ADS)

    Bedeaux, D.; Koper, G. J. M.; Ispolatov, S.; Widom, B.

    2001-03-01

    The multi-particle potential of mean force between interstitial solute molecules in Ben-Naim's one-dimensional, many-state lattice model is calculated. The solution is a direct extension of an earlier calculation of the two-particle interaction by Kolomeisky and Widom (Faraday Dis. 112 (1999) 81). It is found that the many-particle interaction potential is a sum of pair potentials between neighboring particles only. An exact equation of state, expressing the activity in the temperature and the pressure, is derived. The resulting solubility of a gaseous hydrophobe, which is defined osmotically, is calculated and found to increase considerably with the gas density.

  11. Irreversible aggregation of interacting particles in one dimension.

    PubMed

    Sidi Ammi, Hachem; Chame, Anna; Touzani, M'hammed; Benyoussef, Abdelilah; Pierre-Louis, Olivier; Misbah, Chaouqi

    2005-04-01

    We present a study of the aggregation of interacting particles in one dimension. This situation, for example, applies to atoms trapped along linear defects at the surface of a crystal. Simulations are performed with two lattice models. In the first model, the borders of atoms and islands interact in a vectorial manner via force monopoles. In the second model, each atom carries a dipole. These two models lead to qualitatively similar but quantitatively different behaviors. In both cases, the final average island size S(f) does not depend on the interactions in the limits of very low and very high coverages. For intermediate coverages, S(f) exhibits an asymmetric behavior as a function of the interaction strength: while it saturates for attractive interactions, it decreases for repulsive interactions. A class of mean-field models is designed, which allows one to retrieve the interaction dependence on the coverage dependence of the average island size with a good accuracy.

  12. Interaction mechanisms between ceramic particles and atomized metallic droplets

    NASA Astrophysics Data System (ADS)

    Wu, Yue; Lavernia, Enrique J.

    1992-10-01

    The present study was undertaken to provide insight into the dynamic interactions that occur when ceramic particles are placed in intimate contact with a metallic matrix undergoing a phase change. To that effect, Al-4 wt pct Si/SiCp composite droplets were synthesized using a spray atomization and coinjection approach, and their solidification microstructures were studied both qualitatively and quantitatively. The present results show that SiC particles (SiCp) were incor- porated into the matrix and that the extent of incorporation depends on the solidification con- dition of the droplets at the moment of SiC particle injection. Two factors were found to affect the distribution and volume fraction of SiC particles in droplets: the penetration of particles into droplets and the entrapment and/or rejection of particles by the solidification front. First, during coinjection, particles collide with the atomized droplets with three possible results: they may penetrate the droplets, adhere to the droplet surface, or bounce back after impact. The extent of penetration of SiC particles into droplets was noted to depend on the kinetic energy of the particles and the magnitude of the surface energy change in the droplets that occurs upon impact. In liquid droplets, the extent of penetration of SiC particles was shown to depend on the changes in surface energy, ΔEs, experienced by the droplets. Accordingly, large SiC particles encoun- tered more resistance to penetration relative to small ones. In solid droplets, the penetration of SiC particles was correlated with the dynamic pressure exerted by the SiC particles on the droplets during impact and the depth of the ensuing crater. The results showed that no pene- tration was possible in such droplets. Second, once SiC particles have penetrated droplets, their final location in the microstructure is governed by their interactions with the solidification front. As a result of these interactions, both entrapment and rejection of

  13. Particle interactions of fluticasone propionate and salmeterol xinafoate detected with single particle aerosol mass spectrometry (SPAMS).

    PubMed

    Jetzer, Martin; Morrical, Bradley; Fergenson, David; Imanidis, Georgios

    2017-08-29

    Particle co-associations between the active pharmaceutical ingredients fluticasone propionate and salmeterol xinafoate were examined in dry powder inhaled (DPI) and metered dose inhaled (MDI) combination products. Single Particle Aerosol Mass Spectrometry was used to investigate the particle interactions in Advair Diskus(®) (500/50 mcg) and Seretide(®) (125/25 mcg). A simple rules tree was used to identify each compound, either alone or co-associated at the level of the individual particle, using unique marker peaks in the mass spectra for the identification of each drug. High levels of drug particle co-association (fluticasone-salmeterol) were observed in the aerosols emitted from Advair Diskus(®) and Seretide(®). The majority of the detected salmeterol particles were found to be in co-association with fluticasone in both tested devices. Another significant finding was that rather coarse fluticasone particles (in DPI) and fine salmeterol particles (both MDI and DPI) were forming the particle co-associations. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    PubMed

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

    2015-03-20

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

  15. Statistical mechanics of point particles with a gravitational interaction

    NASA Astrophysics Data System (ADS)

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

    2000-04-01

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

  16. Particle transport in 3 He-rich events: wave-particle interactions and particle anisotropy measurements

    NASA Astrophysics Data System (ADS)

    Tsurutani, B. T.; Zhang, L. D.; Mason, G. L.; Lakhina, G. S.; Hada, T.; Arballo, J. K.; Zwickl, R. D.

    2002-04-01

    Energetic particles and MHD waves are studied using simultaneous ISEE-3 data to investigate particle propagation and scattering between the source near the Sun and 1 AU. 3 He-rich events are of particular interest because they are typically low intensity "scatter-free" events. The largest solar proton events are of interest because they have been postulated to generate their own waves through beam instabilities. For 3 He-rich events, simultaneous interplanetary magnetic spectra are measured. The intensity of the interplanetary "fossil" turbulence through which the particles have traversed is found to be at the "quiet" to "intermediate" level of IMF activity. Pitch angle scattering rates and the corresponding particle mean free paths l

  17. Particle Swarm Optimization With Interswarm Interactive Learning Strategy.

    PubMed

    Qin, Quande; Cheng, Shi; Zhang, Qingyu; Li, Li; Shi, Yuhui

    2016-10-01

    The learning strategy in the canonical particle swarm optimization (PSO) algorithm is often blamed for being the primary reason for loss of diversity. Population diversity maintenance is crucial for preventing particles from being stuck into local optima. In this paper, we present an improved PSO algorithm with an interswarm interactive learning strategy (IILPSO) by overcoming the drawbacks of the canonical PSO algorithm's learning strategy. IILPSO is inspired by the phenomenon in human society that the interactive learning behavior takes place among different groups. Particles in IILPSO are divided into two swarms. The interswarm interactive learning (IIL) behavior is triggered when the best particle's fitness value of both the swarms does not improve for a certain number of iterations. According to the best particle's fitness value of each swarm, the softmax method and roulette method are used to determine the roles of the two swarms as the learning swarm and the learned swarm. In addition, the velocity mutation operator and global best vibration strategy are used to improve the algorithm's global search capability. The IIL strategy is applied to PSO with global star and local ring structures, which are termed as IILPSO-G and IILPSO-L algorithm, respectively. Numerical experiments are conducted to compare the proposed algorithms with eight popular PSO variants. From the experimental results, IILPSO demonstrates the good performance in terms of solution accuracy, convergence speed, and reliability. Finally, the variations of the population diversity in the entire search process provide an explanation why IILPSO performs effectively.

  18. 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.

  19. Acoustofluidics 15: streaming with sound waves interacting with solid particles.

    PubMed

    Sadhal, S S

    2012-08-07

    In Part 15 of the tutorial series "Acoustofluidics-exploiting ultrasonic standing waves forces and acoustic streaming in microfluidic systems for cell and particle manipulation," we examine the interaction of acoustic fields with solid particles. The main focus here is the interaction of standing waves with spherical particles leading to streaming, together with some discussion on one non-spherical case. We begin with the classical problem of a particle at the velocity antinode of a standing wave, and then treat the problem of a sphere at the velocity node, followed by the intermediate situation of a particle between nodes. Finally, we discuss the effect of deviation from sphericity which brings about interesting fluid mechanics. The entire Focus article is devoted to the analysis of the nonlinear fluid mechanics by singular perturbation methods, and the study of the streaming phenomenon that ensues from the nonlinear interaction. With the intention of being instructive material, this tutorial cannot by any means be considered 'complete and comprehensive' owing to the complexity of the class of problems being covered herein.

  20. Acceleration of Vaporization, Atomization, and Ionization Efficiencies in Inductively Coupled Plasma by Merging Laser-Ablated Particles with Hydrochloric Acid Gas.

    PubMed

    Nakazawa, Takashi; Izumo, Saori; Furuta, Naoki

    2016-01-01

    To accelerate the vaporization, atomization, and ionization efficiencies in laser ablation inductively coupled plasma mass spectrometry, we merged HCl gas with laser-ablated particles before introduction into the plasma, to convert their surface constituents from oxides to lower-melting chlorides. When particles were merged with HCl gas generated from a HCl solution at 200°C, the measured concentrations of elements in the particles were 135% higher on average than the concentrations in particles merged with ultrapure water vapor. Particle corrosion and surface roughness were observed by scanning electron microscopy, and oxide conversion to chlorides was confirmed by X-ray photoelectron spectroscopy. Under the optimum conditions, the recoveries of measured elements improved by 23% on average, and the recoveries of elements with high-melting oxides (Sr, Zr, and Th) improved by as much as 36%. These results indicate that vaporization, atomization, and ionization in the ICP improved when HCl gas was merged with the ablated particles.

  1. Measuring Protein-Ligand Interactions Using Liquid Sample Desorption Electrospray Ionization Mass Spectrometry

    PubMed Central

    Liu, Pengyuan; Zhang, Jiang; Ferguson, Carly N.; Chen, Hao; Loo, Joseph A.

    2014-01-01

    We have shown previously that liquid sample desorption electrospray ionization-mass spectrometry (DESI-MS) is able to measure large proteins and noncovalently-bound protein complexes (to 150 kDa) (Ferguson et al., Anal. Chem. 2011, 83, 6468-6473). In this study, we further investigate the application of liquid sample DESI-MS to probe protein-ligand interactions. Liquid sample DESI allows the direct formation of intact protein-ligand complex ions by spraying ligands toward separate protein sample solutions. This type of “reactive” DESI methodology can provide rapid information on binding stiochiometry, selectivity, and kinetics, as demonstrated by the binding of ribonuclease A (RNaseA, 13.7 kDa) with cytidine nucleotide ligands and the binding of lysozyme (14.3 kDa) with acetyl chitose ligands. A higher throughput method for ligand screening by liquid sample DESI was demonstrated, in which different ligands were sequentially injected as a segmented flow for DESI ionization. Furthermore, supercharging to enhance analyte charge can be integrated with liquid sample DESI-MS without interfering with the formation of protein-ligand complexes. PMID:24237005

  2. 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.

  3. Noisy quantum walks of two indistinguishable interacting particles

    NASA Astrophysics Data System (ADS)

    Siloi, Ilaria; Benedetti, Claudia; Piccinini, Enrico; Piilo, Jyrki; Maniscalco, Sabrina; Paris, Matteo G. A.; Bordone, Paolo

    2017-02-01

    We investigate the dynamics of continuous-time two-particle quantum walks on a one-dimensional noisy lattice. Depending on the initial condition, we show how the interplay between particle indistinguishability and interaction determines distinct propagation regimes. A realistic model for the environment is considered by introducing non-Gaussian noise as time-dependent fluctuations of the tunneling amplitudes between adjacent sites. We observe that the combined effect of particle interaction and fast noise (weak coupling with the environment) provides a faster propagation compared to the noiseless case. This effect can be understood in terms of the band structure of the Hubbard model, and a detailed analysis as a function of both noise and system parameters is presented.

  4. Water vapor interactions with FeOOH particle surfaces

    NASA Astrophysics Data System (ADS)

    Song, Xiaowei; Boily, Jean-François

    2013-02-01

    Interactions between iron (oxyhydr)oxide particle surfaces and water are of fundamental importance to natural and technological processes. In this Letter, we probe the interactions between submicron-sized lepidocrocite (γ-FeOOH) surfaces and gaseous water using Fourier transform infrared spectroscopy. Formation of hydrogen bonds between different lepidocrocite surface OH functional groups and water was specifically monitored in the O-H stretching region. Molecular dynamics simulations of the dominant crystallographic terminations of these particles provided insights into interfacial water structures and hydrogen bonding networks. Theoretical power spectra were moreover used to validate interpretations of experimental spectra. This Letter constrains our understanding of incipient water adsorption reactions leading to thermodynamically stable and reversible thin water films at FeOOH particle surfaces. It also suggests that these water layers are structurally analogous precursors to those occurring at a FeOOH surfaces contacted with liquid water.

  5. 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.

  6. Electrostatic interactions of colloidal particles at vanishing ionic strength.

    PubMed

    Sainis, Sunil K; Merrill, Jason W; Dufresne, Eric R

    2008-12-02

    Electrostatic interactions of colloidal particles are typically screened by mobile ions in the solvent. We measure the forces between isolated pairs of colloidal polymer microspheres as the density of bulk ions vanishes. The ionic strength is controlled by varying the concentration of surfactant (NaAOT) in a nonpolar solvent (hexadecane). While interactions are well-described by the familiar screened-Coulomb form at high surfactant concentrations, they are experimentally indistinguishable from bare Coulomb interactions at low surfactant concentration. Interactions are strongest just above the critical micelle concentration, where particles can obtain high surface potentials without significant screening, kappaa < 1. Exploiting the absence of significant charge renormalization, we are able to construct a simple thermodynamic model capturing the role of reverse micelles in charging the particle surface. These measurements provide novel access to electrostatic forces in the limit where the particle size is much less than the screening length, which is relevant not just to the nonpolar suspensions described here, but also to aqueous suspensions of nanoparticles.

  7. DLVO interaction energies between hollow spherical particles and collector surfaces

    USDA-ARS?s Scientific Manuscript database

    The surface element integration technique was used to systematically study Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies/forces between hollow spherical particles (HPs) and a planar surface or two intercepting half planes under different ionic strength conditions. The inner and outer ...

  8. 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.

  9. Valence ionized states of iron pentacarbonyl and eta5-cyclopentadienyl cobalt dicarbonyl studied by symmetry-adapted cluster-configuration interaction calculation and collision-energy resolved Penning ionization electron spectroscopy.

    PubMed

    Fukuda, Ryoichi; Ehara, Masahiro; Nakatsuji, Hiroshi; Kishimoto, Naoki; Ohno, Koichi

    2010-02-28

    Valence ionized states of iron pentacarbonyl Fe(CO)(5) and eta(5)-cyclopentadienyl cobalt dicarbonyl Co(eta(5)-C(5)H(5))(CO)(2) have been studied by ultraviolet photoelectron spectroscopy, two-dimensional Penning ionization electron spectroscopy (2D-PIES), and symmetry-adapted cluster-configuration interaction calculations. Theory provided reliable assignments for the complex ionization spectra of these molecules, which have metal-carbonyl bonds. Theoretical ionization energies agreed well with experimental observations and the calculated wave functions could explain the relative intensities of PIES spectra. The collision-energy dependence of partial ionization cross sections (CEDPICS) was obtained by 2D-PIES. To interpret these CEDPICS, the interaction potentials between the molecules and a Li atom were examined in several coordinates by calculations. The relation between the slope of the CEDPICS and the electronic structure of the ionized states, such as molecular symmetry and the spatial distribution of ionizing orbitals, was analyzed. In Fe(CO)(5), an attractive interaction was obtained for the equatorial CO, while the interaction for the axial CO direction was repulsive. For Co(eta(5)-C(5)H(5))(CO)(2), the interaction potential in the direction of both Co-C-O and Co-Cp ring was attractive. These anisotropic interactions and ionizing orbital distributions consistently explain the relative slopes of the CEDPICS.

  10. Valence ionization spectra of group six metal hexacarbonyls studied by the symmetry-adapted cluster-configuration interaction method.

    PubMed

    Fukuda, Ryoichi; Hayaki, Seigo; Nakatsuji, Hiroshi

    2009-11-07

    The valence ionization spectra up to 20 eV of group six metal carbonyls, chromium hexacarbonyl, molybdenum hexacarbonyl, and tungsten hexacarbonyl were studied by the symmetry-adapted cluster-configuration interaction (SAC-CI) method. The assignments of the spectra are given based on reliable SAC-CI calculations. The relativistic effects including the spin-orbit effects are important for the ionization spectrum of W(CO)(6). The relation between the metal-CO distance and ionization energies was examined. The lowest ionization energies of the three metal carbonyls are approximately the same because of the energy dependence of the metal-CO length and relativistic effects. In Cr(CO)(6), the Cr-CO interaction significantly increases the lowest ionization energy in comparison with Mo(CO)(6) and W(CO)(6) because of the relatively short metal-CO bond length. The relativistic effect reduces the lowest ionization energy of W(CO)(6) because the effective core potential of 5d electrons is more efficiently screened as a result of the relativistic contraction of the inner electrons.

  11. Strong-field ionization rates of linear polyenes simulated with time-dependent configuration interaction with an absorbing potential.

    PubMed

    Krause, Pascal; Schlegel, H Bernhard

    2014-11-07

    The strong field ionization rates for ethylene, trans 1,3-butadiene, and trans,trans 1,3,5-hexatriene have been calculated using time-dependent configuration interaction with single excitations and a complex absorbing potential (TDCIS-CAP). The calculations used the aug-cc-pVTZ basis set with a large set of diffuse functions (3 s, 2 p, 3 d, and 1 f) on each atom. The absorbing boundary was placed 3.5 times the van der Waals radius from each atom. The simulations employed a seven-cycle cosine squared pulse with a wavelength of 800 nm. Ionization rates were calculated for intensities ranging from 0.3 × 10(14) W/cm(2) to 3.5 × 10(14) W/cm(2). Ionization rates along the molecular axis increased markedly with increasing conjugation length. By contrast, ionization rates perpendicular to the molecular axis were almost independent of the conjugation length.

  12. Strong-field ionization rates of linear polyenes simulated with time-dependent configuration interaction with an absorbing potential

    NASA Astrophysics Data System (ADS)

    Krause, Pascal; Schlegel, H. Bernhard

    2014-11-01

    The strong field ionization rates for ethylene, trans 1,3-butadiene, and trans,trans 1,3,5-hexatriene have been calculated using time-dependent configuration interaction with single excitations and a complex absorbing potential (TDCIS-CAP). The calculations used the aug-cc-pVTZ basis set with a large set of diffuse functions (3 s, 2 p, 3 d, and 1 f) on each atom. The absorbing boundary was placed 3.5 times the van der Waals radius from each atom. The simulations employed a seven-cycle cosine squared pulse with a wavelength of 800 nm. Ionization rates were calculated for intensities ranging from 0.3 × 1014 W/cm2 to 3.5 × 1014 W/cm2. Ionization rates along the molecular axis increased markedly with increasing conjugation length. By contrast, ionization rates perpendicular to the molecular axis were almost independent of the conjugation length.

  13. Theoretical study of γ-aminobutyric acid conformers: Intramolecular interactions and ionization energies

    NASA Astrophysics Data System (ADS)

    Wang, Ke-Dong; Wang, Mei-Ting; Meng, Ju

    2014-10-01

    Allowing for all combinations of internal single-bond rotamers, 1,296 unique trial structures of γ-Aminobutyric acid (GABA) are obtained. All of these structures are optimized at the M06-2X level of theory and a total of 68 local minimal conformers are found. The nine low-lying conformers are used for further studies. According to the calculated relative Gibbs free energies at M06-2X level of theory, we find that the dispersion is important for the relative energy of GABA. The intramolecular hydrogen bonds and hyperconjugative interaction and their effects on the conformational stability are studied. The results show that both of them have great influence on the conformers. The vertical ionization energies (VIE) are calculated and match the experimental data well. The results show that the neutral GABA in the gas phase is a multi-conformer system and at least four conformations exist.

  14. 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.

  15. Light-particle single ionization of argon: Influence of the projectile charge sign

    SciTech Connect

    Otranto, S.; Olson, R. E.

    2009-07-15

    The ionization of the 3p orbital of argon by incident electrons and positrons is studied by means of the post version of the continuum distorted wave-eikonal initial-state model. Results are presented at both 200 and 500 eV impact energies for conditions amenable to present experiments. Differences in the fully differential cross sections (FDCSs) are analyzed and the influence of the projectile charge sign on the emission dynamics is discussed. The FDCSs are found to display the classic binary plus recoil peak structure at 500 eV, but transition to a more complicated four-lobed structure at the lower impact energy.

  16. Differential potential of anisotropic ionization of cosmic particles in the ionosphere

    NASA Astrophysics Data System (ADS)

    Velinov, P. I.

    A determination of the profiles of electron production rates during vertical and quasi-vertical penetrations of solar cosmic rays is presented. A possible quantitative interpretation of particle penetrations with complicated spatial distributions is also presented in the light of recent data acquisitions from the High Altitude Plasma Instrument of the Dynamics Explorer-1 satellite. Two types of particles are found to participate in the precipitation. The first is characterized by double-maximum Maxwell distributions: a high-energy isotropic component and a low-energy anisotropic component. The particles of the second type are parallel and antiparallel with respect to geomagnetic field lines.

  17. 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.

  18. 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

  19. 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.

  20. pH-responsive aqueous foams stabilized by ionizable latex particles.

    PubMed

    Binks, Bernard P; Murakami, Ryo; Armes, Steven P; Fujii, Syuji; Schmid, Andreas

    2007-08-14

    We have designed a type of colloidal particle whose surface characteristics are sensitive to the pH of the aqueous phase in which they are dispersed. Particles of polystyrene latex stabilized by poly(acrylic acid) can act as stabilizers of aqueous foams by adsorbing at the air-water surface. Foams can be prepared and stabilized only at pH values below the isoelectric point where particles are either uncharged and flocculated or acquire a positive charge. At high pH where particles are anionic, no foam forms. This influence of pH on foamability and stability applies to both pH-dependent and pH-responsive systems.

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

    DOE PAGES

    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

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. 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.

  5. High-rate axial-field ionization chamber for particle identification of Radioactive beams

    NASA Astrophysics Data System (ADS)

    Desouza, Romualdo; Vadas, Justin; Singh, Varinderjit; Visser, G.; Alexander, A.; Hudan, S.; Huston, J.; Wiggins, B.; Chbihi, A.; Famiano, M.; Bischak, M.

    2017-01-01

    The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. The detector is optimized for use with low-energy radioactive beams (<) 5 MeV/A. A fast charge sensitive amplifier (CSA) integrated into the detector design is also described. Coupling this fast CSA to the axial field ionization chamber produces an output pulse with a rise-time of 60 to 70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate while providing a time resolution of 6 to 8 ns. Tests with an α source establish the detector energy resolution as 8 % for an energy deposit of 3.5 MeV. Beam tests indicate that the detector is an effective tool for the characterization of low-energy radioactive beams at beam intensities up to 3 x 105 ions/s. Supported by the U.S. DOE under Award # DE-FG02-88ER-40404 and the NSF under Grant No. 1342962.

  6. Single and double ionization of helium by the impact of fast charged particles

    NASA Astrophysics Data System (ADS)

    Jones, S.; Madison, D. H.; Macek, Joseph H.

    2005-12-01

    A survey of the recent literature shows that paradoxes abound in electron- and ion-impact ionization of helium. For example, Schulz et al. [M. Schulz, R. Moshammer, D. Fischer, H. Kollmus, D.H. Madison, S. Jones, J. Ullrich, Nature 422 (2003) 48] found that first-Born and three-body distorted-wave (3DW) theories reproduced their data for single ionization of helium by very fast fully stripped carbon ions in the scattering plane, but not outside the scattering plane. For much slower impacting carbon ions, however, Madison et al. [D.H. Madison, D. Fischer, M. Foster, M. Schulz, R. Moshammer, S. Jones, J. Ullrich, Phys. Rev. Lett. 91 (2003) 253201] found good agreement between 3DW theory and experiment, even outside the scattering plane. This creates a dilemma, since distorted-wave perturbation theories are generally thought to improve with increasing, not decreasing, projectile speed! In this contribution, we will address these and other issues, and suggest possible ways of proceeding.

  7. High-rate axial-field ionization chamber for particle identification of radioactive beams

    NASA Astrophysics Data System (ADS)

    Vadas, J.; Singh, Varinderjit; Visser, G.; Alexander, A.; Hudan, S.; Huston, J.; Wiggins, B. B.; Chbihi, A.; Famiano, M.; Bischak, M. M.; deSouza, R. T.

    2016-11-01

    The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. Optimized for use with low-energy radioactive beams (< 5 MeV / A) the detector presents only three 0.5 μm/cm2 foils to the beam in addition to the detector gas. A fast charge sensitive amplifier (CSA) integrated into the detector design is also described. Coupling this fast CSA to the axial field ionization chamber produces an output pulse with a risetime of 60-70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate and providing a time resolution of 6-8 ns. Tests with an α source establish the detector energy resolution as ∼ 8 % for an energy deposit of ∼3.5 MeV. The energy resolution with beams of 2.5 and 4.0 MeV/A 39K ions and the dependence of the energy resolution on beam intensity is measured. At an instantaneous rate of 3×105 ions/s the energy resolution has degraded to 14% with a pileup of 12%. The good energy resolution of this detector at rates up to 3×105 ions/s makes it an effective tool in the characterization of low-energy radioactive beams.

  8. Electrokinetic particle-electrode interactions at high frequencies

    NASA Astrophysics Data System (ADS)

    Yariv, Ehud; Schnitzer, Ory

    2013-01-01

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

  9. 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.

  10. Does the ionization potential condition employed in QTP functionals mitigate the self-interaction error?

    NASA Astrophysics Data System (ADS)

    Ranasinghe, Duminda S.; Margraf, Johannes T.; Jin, Yifan; Bartlett, Rodney J.

    2017-01-01

    Though contrary to conventional wisdom, the interpretation of all occupied Kohn-Sham eigenvalues as vertical ionization potentials is justified by several formal and numerical arguments. Similarly, the performance of density functional approximations (DFAs) for fractionally charged systems has been extensively studied as a measure of one- and many-electron self-interaction errors (MSIEs). These complementary perspectives (initially recognized in ab initio dft) are shown to lead to the unifying concept that satisfying Bartlett's IP theorem in DFA's mitigates self-interaction errors. In this contribution, we show that the IP-optimized QTP functionals (reparameterization of CAM-B3LYP where all eigenvalues are approximately equal to vertical IPs) display reduced self-interaction errors in a variety of tests including the He2+ potential curve. Conversely, the MSIE-optimized rCAM-B3LYP functional also displays accurate orbital eigenvalues. It is shown that the CAM-QTP and rCAM-B3LYP functionals show improved dissociation limits, fundamental gaps and thermochemical accuracy compared to their parent functional CAM-B3LYP.

  11. 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.

  12. Interaction between biopolyelectrolytes and sparingly soluble mineral particles.

    PubMed

    Versluis, Peter; Popp, Alois K; Velikov, Krassimir P

    2011-01-04

    We investigate the complex physicochemical behavior of dispersions containing calcium carbonate (CaCO(3)) particles, a sparingly soluble mineral salt; and carrageenans, negatively charged biopolyelectrolytes containing sulfate groups. We reveal that the carrageenans suspend and stabilize CaCO(3) particles in neutral systems by absorbing on the particle surface which provides electrosteric stabilization. In addition, carrageenans provide a weak apparent yield stress which keeps the particles suspended for several months. The absorption measurements of carrageenan on the CaCO(3) particle indicate that more carrageenan is removed from the solution than expected from the case of a simple monolayer adsorption. Confocal laser scanning microscopy observations confirm that polyelectrolyte-containing precipitate is formed in both CaCO(3)-carrageenan and CaCl(2)-carrageenan mixtures. On the basis of these results, we confirm that in the presence of carrageenan some CaCO(3) dissolves and the Ca(2+) ions interact with the sulfate groups leading to aggregation and formation of particle-like structures. These new insights are important for fundamental understanding of other mineral-polyelectrolyte systems and have important implications for various industrial applications where calcium carbonate is used.

  13. Gas interaction effects on lunar bonded particles and their implications

    NASA Technical Reports Server (NTRS)

    Mukherjee, N. R.

    1976-01-01

    Results are reported for an experimental investigation of gas-interaction effects on different Apollo 11 and Apollo 12 lunar-soil samples containing bonded particles. In the experiments, lunar fines were exposed to pure O2, pure water vapor, HCl, NH3, N2, HCOOH, and CH3NH2, in order to observe whether bonded particles would separate. In addition, repeated gas adsorption/desorption measurements were performed to determine the nature and reactive properties of the particle surfaces, and surface areas were measured for comparison with analogous terrestrial samples to determine whether the surface areas of highly radiation-damaged particles were larger or smaller. It is found that N2 is apparently ineffective in separating bonded particles and that the ratio of Apollo 11 to Apollo 12 bonded particles separated by a particular gas exposure ranges from 2.5 to 3.0. Possible reasons for differences in material surface properties at the two Apollo sites are considered, and it is concluded that material from a certain depth at some other site was transported to the Apollo 12 site and mixed with the original material in recent years (considerably less than 2000 years ago).

  14. Quantum particle interacting with a metallic particle: Spectra from quantum Langevin theory

    NASA Astrophysics Data System (ADS)

    Loh, W. M. Edmund; Ooi, C. H. Raymond

    2017-01-01

    The effect of a nearby metallic particle on the quantum optical properties of a quantum particle in the four-level double Raman configuration is studied using the quantum Langevin approach. We obtain analytical expressions for the correlated quantum fields of Stokes and anti-Stokes photons emitted from the system and perform analysis on how the interparticle distance, the direction of observation or detection, the strengths of controllable laser fields, the presence of surface plasmon resonance, and the number density of the quantum particle affect the quantum spectra of the Stokes and anti-Stokes fields. We explore the physics behind the quantum-particle-metallic-nanoparticle interaction within the dipole approximation, that is, when the interparticle distance is much larger than the sizes of the particles. Our results show the dependence of the spectra on the interparticle distance in the form of oscillatory behavior with damping as the interparticle distance increases. At weaker laser fields the enhancement of quantum fields which manifests itself in the form of a Fano dip in the central peak of the spectra becomes significant. Also, the quantum-particle-metallic-nanoparticle coupling, which is affected by the size of the metallic nanoparticle and the number density of the quantum particle, changes the angular dependence of the spectra by breaking the angular rotational symmetry. In the presence of surface plasmon resonance the oscillatory dependence of the spectra on the interparticle distance and angles of observation becomes even stronger due to the plasmonic enhancement effect.

  15. Self-diffusion in a system of interacting Langevin particles.

    PubMed

    Dean, D S; Lefèvre, A

    2004-06-01

    The behavior of the self-diffusion constant of Langevin particles interacting via a pairwise interaction is considered. The diffusion constant is calculated approximately within a perturbation theory in the potential strength about the bare diffusion constant. It is shown how this expansion leads to a systematic double expansion in the inverse temperature beta and the particle density rho. The one-loop diagrams in this expansion can be summed exactly and we show that this result is exact in the limit of small beta and rhobeta constants. The one-loop result can also be resummed using a semiphenomenological renormalization group method which has proved useful in the study of diffusion in random media. In certain cases the renormalization group calculation predicts the existence of a diverging relaxation time signaled by the vanishing of the diffusion constant, possible forms of divergence coming from this approximation are discussed. Finally, at a more quantitative level, the results are compared with numerical simulations, in two dimensions, of particles interacting via a soft potential recently used to model the interaction between coiled polymers.

  16. Losses and nonlinear steady-state particle distribution functions for fully ionized tokamak-plasmas in the collisional transport regimes

    NASA Astrophysics Data System (ADS)

    Sonnino, G.

    2011-03-01

    Fully ionized L-mode tokamak plasmas in the fully collisional (Pfirsch-Schlüter) and in the low-collisional (banana) nonlinear transport regimes are analyzed. We derive the expressions for particles and heat losses together with the steady-state particle distribution functions in the several collisional transport regimes. The validity of the nonlinear closure equations, previously derived, has been indirectly tested by checking that the obtained particle distribution functions are indeed solutions of the nonlinear, steady-state, Vlasov-Landau gyro-kinetic equations. A quite encouraging result is the fact that, for L-mode tokamak plasmas a dissymmetry appears between the ion and electron transport coefficients: the latter submits to a nonlinear correction, which makes the radial electron coefficients much larger than the former. In particular we show that when the L-mode JET plasma is out of the linear region, the Pfirsch-Schlüter electron transport coefficients are corrected by an amplification factor, which may reach values of order 102. Such a correction is absent for ions. On the contrary, in the banana regime, the ion transport coefficients are increased by a factor 2 and the nonlinear corrections for electrons are negligible. These results are in line with experiments.

  17. Ionizing radiation induced catalysis on metal oxide particles. 1998 annual progress report

    SciTech Connect

    Fryberger, T.; Chambers, S.A.; Daschbach, J.L.; Henderson, M.A.; Peden, C.H.F.; Su, Y.; Wang, Y.

    1998-06-01

    'High-level radioactive waste storage tanks within DOE sites contain significant amounts of organic components (solid and liquid phases) in the form of solvents, extractants, complexing agents, process chemicals, cleaning agents and a variety of miscellaneous compounds. These organics pose several safety and pretreatment concerns, particularly for the Hanford tank waste. Remediation technologies are needed that significantly reduce the amounts of problem organics without resulting in toxic or flammable gas emissions, and without requiring thermal treatments. These restrictions pose serious technological barriers for current organic destruction methods which utilize oxidation achieved by thermal or chemical activation. This project focuses on using ionizing radiation (a,b,g) to catalytically destroy organics over oxide materials through reduction/oxidation (redox) chemistry resulting from electron-hole (e{sup -}/h{sup +}) pair generation. Conceptually this process is an extension of visible and near-UV photocatalytic processes known to occur at the interfaces of narrow bandgap semiconductors in both solution and gas phases. In these processes, an electron is excited across the energy gap between the filled and empty states in the semiconductor. The excited electron does reductive chemistry and the hole (where the electron was excited from) does oxidative chemistry. The energy separation between the hole and the excited electron reflects the redox capability of the e{sup -}/h{sup +} pair, and is dictated by the energy of the absorbed photon and the bandgap of the material. The use of ionizing radiation overcomes optical transparency limitations associated with visible and near-UV illumination (g-rays penetrate much farther into a solution than UV/Vis light), and permits the use of wider bandgap materials (such as ZrO{sub 2}) which possess potentially greater redox capabilities than those with narrow bandgap materials. Experiments have been aimed at understanding the

  18. Angular Dependence of Ionization by Circularly Polarized Light Calculated with Time-Dependent Configuration Interaction with an Absorbing Potential.

    PubMed

    Hoerner, Paul; Schlegel, H Bernhard

    2017-02-16

    The angular dependence of ionization by linear and circularly polarized light has been examined for N2, NH3, H2O, CO2, CH2O, pyrazine, methyloxirane, and vinyloxirane. Time-dependent configuration interaction with single excitations and a complex absorbing potential was used to simulate ionization by a seven cycle 800 nm cosine squared pulse with intensities ranging from 0.56 × 10(14) to 5.05 × 10(14) W cm(-2). The shapes of the ionization yield for linearly polarized light can be understood primarily in terms of the nodal structure of the highest occupied orbitals. Depending on the orbital energies, ionization from lower-lying orbitals may also make significant contributions to the shapes. The shapes of the ionization yield for circularly polarized light can be readily explained in terms of the shapes for linearly polarized light. Averaging the results for linear polarization over orientations perpendicular to the direction of propagation yields shapes that are in very good agreement with direct calculations of the ionization yield by circularly polarized light.

  19. Electrostatic interactions between diffuse soft multi-layered (bio)particles: beyond Debye-Hückel approximation and Deryagin formulation.

    PubMed

    Duval, Jérôme F L; Merlin, Jenny; Narayana, Puranam A L

    2011-01-21

    dramatically change depending on the interplay between characteristic Debye length, thickness of ion-permeable layers and their respective protolytic features (e.g. location, magnitude and sign of charge density). This formalism extends a recent model by Ohshima which is strictly limited to interaction between soft mono-shell particles within Deryagin and Debye-Hückel approximations under conditions where ionizable sites are completely dissociated.

  20. A study for the detection of ionizing particles with phototransistors on thick high-resistivity silicon substrates

    NASA Astrophysics Data System (ADS)

    Batignani, G.; Angelini, C.; Bisogni, M. G.; Boscardin, M.; Bettarini, S.; Bondioli, M.; Bosisio, L.; Bucci, F.; Calderini, G.; Carpinelli, M.; Ciacchi, M.; Dalla Betta, G. F.; Dittongo, S.; Forti, F.; Giorgi, M. A.; Gregori, P.; Han, D. J.; Manfredi, P. F.; Manghisoni, M.; Marchiori, G.; Neri, N.; Novelli, M.; Paoloni, E.; Piemonte, C.; Rachevskaia, I.; Rama, M.; Ratti, L.; Re, V.; Rizzo, G.; Ronchin, S.; Rosso, V.; Simi, G.; Speziali, V.; Stefanini, A.; Zorzi, N.

    2004-09-01

    We report on bipolar NPN phototransistors fabricated at ITC-IRST on thick high-resistivity silicon substrates. The phototransistor emitter is composed of a phosphorus n+ implant, the base is a diffused high-energy boron implant, and the collector is the 600-800 μm thick silicon bulk, contacted on the backplane. We have studied the current amplification for two different doping profiles of the emitter, obtaining values of β ranging from 60 to 3000. For various emitter and base configurations, we measured the static device characteristics and extracted the leakage currents and the base resistance, verifying the fundamental relationship between them and the total base capacitances. The use of such phototransistors to detect ionizing particles is exploited and discussed.

  1. Fitted empirical reference cross sections for K-shell ionization by alpha particles

    SciTech Connect

    Paul, H.; Bolik, O. )

    1993-05-01

    On the basis of the authors' collection of experimental x-ray and Auger production cross-section data for H and He ions, a table is presented of best-fitted cross sections for K-shell vacancy production (direct ionization plus electron capture) by [sup 4]He ions on all elements from [sub 6]C to [sub 92]U. Experimental values are first converted (if necessary) to vacancy production cross sections using fluorescence yields with an approximate correction for the effect of multiple ionization. These values are then normalized, i.e., divided, by an improved version (due to Benka et al.) of the ECPSSR theory by Brandt and Lapicki, to which a correction for electron capture by the projectile (following Lapicki and McDaniel) has been added. Since is has been found empirically that the normalized cross sections (which describe the deviation of theory from experiment), at a certain scaled projectile speed, depend only on the ratio of projectile and target atomic numbers, the data for both He and H ions can be used as input. The normalized values are averaged, fitted by a polynomial, and multiplied by theory to produce best reference cross sections. Discrepant data sets are rejected using a statistical criterion which compares the deviations found to the errors stated in the original publications. The error assigned to the cross section consists of a calculated random contribution and an estimated systematic contribution that describes the limitations of the method. A list of the experimental input data (for [sup 1]H, [sup 2]H, [sup 3]He, and [sup 4]He projectiles) and a table showing the consistency or inconsistency of these data are also given. 30 refs., 2 figs., 1 tab.

  2. Probing the Pathways and Interactions Controlling Crystallization by Particle Attachment

    NASA Astrophysics Data System (ADS)

    De Yoreo, J. J.; Li, D.; Chun, J.; Schenter, G.; Mundy, C.; Rosso, K. M.

    2016-12-01

    Crystallization by particle attachment appears to be a widespread mechanism of mineralization. Yet many long-standing questions surrounding nucleation and assembly of precursor particles remain unanswered, due in part to a lack of tools to probe mineralization dynamics with adequate spatial and temporal resolution. Here we report results of liquid phase TEM studies of nucleation and particle assembly in a number of mineral systems. We interpret the results within a framework that considers the impact of both the complexity of free energy landscapes and kinetic factors associated with high supersaturation or slow dynamics. In the calcium carbonate system, the need for high supersturations to overcome the high barrier to nucleation of calcite leads to simultaneous occurrence of multiple pathways, including direct formation of all the common ploymorphs, as well as two-step pathways through which initial precursors, particularly ACC, undergo a direct transformation to a more stable phase. Introduction of highly charged polymers that bind calcium inhibits nucleation, but directs the pathway to a metastable amorphous phase that no longer transforms to more stable polymorphs. Experiments in the iron oxide and oxyhydroxide systems show that, when high supersaturations lead to nucleation of many nanoprticles, further growth occurs through a combination of particle aggregation events and Ostwald ripening. In some cases, aggregation occurs only through oriented attachment on lattice matched faces, leading to single crystals with complex topologies and internal twin boundaries, while in others aggregation results initially in poor co-alignment, but over time the particles undergo atomic rearrangements to achieve a single crystal structure. AFM-based measurements of forces between phyllosilicate surfaces reveal the importance of long-range dispersion interactions in driving alignment, as well as the impact of electrolyte concentration and temperature on the competition of those

  3. Atypical energetic particle events observed prior energetic particle enhancements associated with corotating interaction regions

    NASA Astrophysics Data System (ADS)

    Khabarova, Olga; Malandraki, Olga; Zank, Gary; Jackson, Bernard; Bisi, Mario; Desai, Mihir; Li, Gang; le Roux, Jakobus; Yu, Hsiu-Shan

    2017-04-01

    Recent studies of mechanisms of particle acceleration in the heliosphere have revealed the importance of the comprehensive analysis of stream-stream interactions as well as the heliospheric current sheet (HCS) - stream interactions that often occur in the solar wind, producing huge magnetic cavities bounded by strong current sheets. Such cavities are usually filled with small-scale magnetic islands that trap and re-accelerate energetic particles (Zank et al. ApJ, 2014, 2015; le Roux et al. ApJ, 2015, 2016; Khabarova et al. ApJ, 2015, 2016). Crossings of these regions are associated with unusual variations in the energetic particle flux up to several MeV/nuc near the Earth's orbit. These energetic particle flux enhancements called "atypical energetic particle events" (AEPEs) are not associated with standard mechanisms of particle acceleration. The analysis of multi-spacecraft measurements of energetic particle flux, plasma and the interplanetary magnetic field shows that AEPEs have a local origin as they are observed by different spacecraft with a time delay corresponding to the solar wind propagation from one spacecraft to another, which is a signature of local particle acceleration in the region embedded in expanding and rotating background solar wind. AEPEs are often observed before the arrival of corotating interaction regions (CIRs) or stream interaction regions (SIRs) to the Earth's orbit. When fast solar wind streams catch up with slow solar wind, SIRs of compressed heated plasma or more regular CIRs are created at the leading edge of the high-speed stream. Since coronal holes are often long-lived structures, the same CIR re-appears often for several consecutive solar rotations. At low heliographic latitudes, such CIRs are typically bounded by forward and reverse waves on their leading and trailing edges, respectively, that steepen into shocks at heliocentric distances beyond 1 AU. Energetic ion increases have been frequently observed in association with CIR

  4. [Research in elementary particles and interactions]. Technical progress report

    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.

  5. Quantum breathing mode of interacting particles in harmonic traps

    NASA Astrophysics Data System (ADS)

    Bauch, Sebastian; Hochstuhl, David; Balzer, Karsten; Bonitz, Michael

    2010-04-01

    The breathing mode - the uniform radial expansion and contraction of a system of interacting particles - is analyzed. Extending our previous work [Bauch et al 2009 Phys. Rev. B. 80 054515] we present a systematic analysis of the breathing mode for fermions with an inverse power law interaction potential w(r) ~ r-dwith d = 1,2,3 in the whole range of coupling parameters. The results thus cover the range from the ideal "gas" to the Wigner crystal-like state. In addition to exact results for two particles obtained from a solution of the time-dependent Schrödinger equation we present results for N = 4,6 from multiconfiguration time-dependent Hartree-Fock simulations.

  6. 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.

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

    SciTech Connect

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

    2016-05-15

    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.

  8. Interfacial interactions between plastic particles in plastics flotation.

    PubMed

    Wang, Chong-qing; Wang, Hui; Gu, Guo-hua; Fu, Jian-gang; Lin, Qing-quan; Liu, You-nian

    2015-12-01

    Plastics flotation used for recycling of plastic wastes receives increasing attention for its industrial application. In order to study the mechanism of plastics flotation, the interfacial interactions between plastic particles in flotation system were investigated through calculation of Lifshitz-van der Waals (LW) function, Lewis acid-base (AB) Gibbs function, and the extended Derjaguin-Landau-Verwey-Overbeek potential energy profiles. The results showed that van der Waals force between plastic particles is attraction force in flotation system. The large hydrophobic attraction, caused by the AB Gibbs function, is the dominant interparticle force. Wetting agents present significant effects on the interfacial interactions between plastic particles. It is found that adsorption of wetting agents promotes dispersion of plastic particles and decreases the floatability. Pneumatic flotation may improve the recovery and purity of separated plastics through selective adsorption of wetting agents on plastic surface. The relationships between hydrophobic attraction and surface properties were also examined. It is revealed that there exists a three-order polynomial relationship between the AB Gibbs function and Lewis base component. Our finding provides some insights into mechanism of plastics flotation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Dynamics of a suspension of interacting yolk-shell particles

    NASA Astrophysics Data System (ADS)

    Sánchez Díaz, L. E.; Cortes-Morales, E. C.; Li, X.; Chen, Wei-Ren; Medina-Noyola, M.

    2014-12-01

    In this work we study the self-diffusion properties of a liquid of hollow spherical particles (shells) bearing a smaller solid sphere in their interior (yolks). We model this system using purely repulsive hard-body interactions between all (shell and yolk) particles, but assume the presence of a background ideal solvent such that all the particles execute free Brownian motion between collisions, characterized by short-time self-diffusion coefficients D^0s for the shells and D^0y for the yolks. Using a softened version of these interparticle potentials we perform Brownian dynamics simulations to determine the mean squared displacement and intermediate scattering function of the yolk-shell complex. These results can be understood in terms of a set of effective Langevin equations for the N interacting shell particles, pre-averaged over the yolks' degrees of freedom, from which an approximate self-consistent description of the simulated self-diffusion properties can be derived. Here we compare the theoretical and simulated results between them, and with the results for the same system in the absence of yolks. We find that the yolks, which have no effect on the shell-shell static structure, influence the dynamic properties in a predictable manner, fully captured by the theory.

  10. Alpha particle heating at comet-solar wind interaction regions

    NASA Technical Reports Server (NTRS)

    Sharma, A. S.; Papadopoulos, K.

    1995-01-01

    The satellite observations at comet Halley have shown strong heating of solar wind alpha particles over an extended region dominated by high-intensity, low-frequency turbulence. These waves are excited by the water group pickup ions and can energize the solar wind plasma by different heating processes. The alpha particle heating by the Landau damping of kinetic Alfven waves and the transit time damping of low-frequency hydromagnetic waves in this region of high plasma beta are studied in this paper. The Alfven wave heating was shown to be the dominant mechanism for the observed proton heating, but it is found to be insufficient to account for the observed alpha particle heating. The transit time damping due to the interaction of the ions with the electric fields associated with the magnetic field compressions of magnetohydrodynamic waves is found to heat the alpha particles preferentially over the protons. Comparison of the calculated heating times for the transit time damping with the observations from comet Halley shows good agreement. These processes contribute to the thermalization of the solar wind by the conversion of its directed energy into the thermal energy in the transition region at comet-solar wind interaction.

  11. Dynamics of a suspension of interacting yolk-shell particles

    SciTech Connect

    Sánchez Díaz, L. E.; Cortes-Morales, E. C.; Li, X.; Chen, Wei-Ren; Medina-Noyola, M.

    2014-12-01

    In this work we study the self-diusion properties of a liquid of hollow spherical particles (shells) bearing a smaller solid sphere in their interior (yolks). We model this system using purely repulsive hard-body interactions between all (shell and yolk) particles, but assume the presence of a background ideal solvent such that all the particles execute free Brownian motion between collisions, characterized by short-time self-diusion coecients D0 s for the shells and D0 y for the yolks. Using a softened version of these interparticle potentials we perform Brownian dynamics simulations to determine the mean squared displacement and intermediate scattering function of the yolk-shell complex. These results can be understood in terms of a set of eective Langevin equations for the N interacting shell particles, pre-averaged over the yolks' degrees of freedom, from which an approximate self-consistent description of the simulated self-diusion properties can be derived. Here we compare the theoretical and simulated results between them, and with the results for the same system in the absence of yolks. We nd that the yolks, which have no eect on the shell-shell static structure, in uence the dynamic properties in a predictable manner, fully captured by the theory.

  12. Dynamics of a suspension of interacting yolk-shell particles

    DOE PAGES

    Sánchez Díaz, L. E.; Cortes-Morales, E. C.; Li, X.; ...

    2014-12-01

    In this work we study the self-diusion properties of a liquid of hollow spherical particles (shells) bearing a smaller solid sphere in their interior (yolks). We model this system using purely repulsive hard-body interactions between all (shell and yolk) particles, but assume the presence of a background ideal solvent such that all the particles execute free Brownian motion between collisions, characterized by short-time self-diusion coecients D0 s for the shells and D0 y for the yolks. Using a softened version of these interparticle potentials we perform Brownian dynamics simulations to determine the mean squared displacement and intermediate scattering function ofmore » the yolk-shell complex. These results can be understood in terms of a set of eective Langevin equations for the N interacting shell particles, pre-averaged over the yolks' degrees of freedom, from which an approximate self-consistent description of the simulated self-diusion properties can be derived. Here we compare the theoretical and simulated results between them, and with the results for the same system in the absence of yolks. We nd that the yolks, which have no eect on the shell-shell static structure, in uence the dynamic properties in a predictable manner, fully captured by the theory.« less

  13. Sideband growth in nonlinear Landau wave-particle interaction.

    NASA Technical Reports Server (NTRS)

    Brinca, A. L.

    1972-01-01

    The distortion of the electron velocity distribution caused by a large amplitude Landau wave is determined analytically for the initial-value problem. The resulting stability of electrostatic perturbations impressed on the evolving plasma is studied. Narrow sidebands of the applied frequency experience consecutive growths of large magnitude during the early stages of the nonlinear wave-particle interaction. The significance of the derived results to both wave propagation experiments and triggered VLF emissions in the magnetosphere is discussed.

  14. Enhanced fluctuations of interacting particles confined in a box

    NASA Astrophysics Data System (ADS)

    Delfau, Jean-Baptiste; Coste, Christophe; Saint Jean, Michel

    2012-04-01

    We study the position fluctuations of interacting particles aligned in a finite cell that avoid any crossing in equilibrium with a thermal bath. The focus is put on the influence of the confining force directed along the cell length. We show that the system may be modeled as a 1D chain of particles with identical masses, linked with linear springs of varying spring constants. The confining force may be accounted for by linear springs linked to the walls. When the confining force range is increased toward the inside of the chain, a paradoxical behavior is exhibited. The outermost particles fluctuations are enhanced, whereas those of the inner particles are reduced. A minimum of fluctuations is observed at a distance of the cell extremities that scales linearly with the confining force range. Those features are in very good agreement with the model. Moreover, the simulations exhibit an asymmetry in their fluctuations which is an anharmonic effect. It is characterized by the measurement of the skewness, which is found to be strictly positive for the outer particles when the confining force is short ranged.

  15. Fluctuations of absorption of interacting diffusing particles by multiple absorbers

    NASA Astrophysics Data System (ADS)

    Agranov, Tal; Meerson, Baruch

    2017-06-01

    We study fluctuations of particle absorption by a three-dimensional domain with multiple absorbing patches. The domain is in contact with a gas of interacting diffusing particles. This problem is motivated by living cell sensing via multiple receptors distributed over the cell surface. Employing the macroscopic fluctuation theory, we calculate the covariance matrix of the particle absorption by different patches, extending previous works which addressed fluctuations of a single current. We find a condition when the sign of correlations between different patches is fully determined by the transport coefficients of the gas and is independent of the problem's geometry. We show that the fluctuating particle flux field typically develops vorticity. We establish a simple connection between the statistics of particle absorption by all the patches combined and the statistics of current in a nonequilibrium steady state in one dimension. We also discuss connections between the absorption statistics and (i) statistics of electric currents in multiterminal diffusive conductors and (ii) statistics of wave transmission through disordered media with multiple absorbers.

  16. Turbulence-particle interactions under surface gravity waves

    NASA Astrophysics Data System (ADS)

    Paskyabi, Mostafa Bakhoday

    2016-11-01

    The dispersion and transport of single inertial particles through an oscillatory turbulent aquatic environment are examined numerically by a Lagrangian particle tracking model using a series of idealised test cases. The turbulent mixing is incorporated into the Lagrangian model by the means of a stochastic scheme in which the inhomogeneous turbulent quantities are governed by a one-dimensional k- ɛ turbulence closure scheme. This vertical mixing model is further modified to include the effects of surface gravity waves including Coriolis-Stokes forcing, wave breaking, and Langmuir circulations. To simplify the complex interactions between the deterministic and the stochastic phases of flow, we assume a time-invariant turbulent flow field and exclude the hydrodynamic biases due to the effects of ambient mean current. The numerical results show that the inertial particles acquire perturbed oscillations traced out as time-varying sinking/rising orbits in the vicinity of the sea surface under linear and cnoidal waves and acquire a non-looping single arc superimposed with the high-frequency fluctuations beneath the nonlinear solitary waves. Furthermore, we briefly summarise some recipes through the course of this paper on the implementation of the stochastic particle tracking models to realistically describe the drift and suspension of inertial particles throughout the water column.

  17. Tensor interaction contributions to single-particle energies

    SciTech Connect

    Brown, B. A.; Duguet, T.; Otsuka, T.; Abe, D.; Suzuki, T.

    2006-12-15

    We calculate the contribution of the nucleon-nucleon tensor interaction to single-particle energies with finite-range G-matrix potentials and with zero-range Skyrme potentials. The Skx Skyrme parameters including the zero-range tensor terms with strengths calibrated to the finite-range results are refitted to nuclear properties. The fit allows the zero-range proton-neutron tensor interaction as calibrated to the finite-range potential results which gives the observed change in the single-particle gap {epsilon}(h{sub 11/2})-{epsilon}(g{sub 7/2}) going from {sup 114}Sn to {sup 132}Sn. However, the experimental l dependence of the spin-orbit splittings in {sup 132}Sn and {sup 208}Pb is not well described when the tensor is added, owing to a change in the radial dependence of the total spin-orbit potential. The gap shift and a good fit to the l dependence can be recovered when the like-particle tensor interaction is opposite in sign to that required for the G matrix.

  18. Cell (A549)-particle (Jasada Bhasma) interactions using Raman spectroscopy.

    PubMed

    Pyrgiotakis, G; Bhowmick, T K; Finton, K; Suresh, A K; Kane, S G; Bellare, J R; Moudgil, B M

    2008-06-01

    Current methods for the evaluation of cell interactions with particles are nonspecific, slow, and invasive to the cells. Raman spectroscopy is a noninvasive technique, and is used in the present study to investigate particle-cell interactions. The main focus of the present study is to employ Raman spectroscopy for investigating the interaction of human lung adenocarcinoma cell line (A549) with the particulate system Jasada Bhasma, a traditional Indian medicine. Jasada Bhasma is a unique preparation of zinc and is traditionally used for the treatment of various diseases like diabetes, age-related eye diseases, and as a health promotional tonic. The Raman spectral analysis is executed by identifying the difference in intracellular DNA/RNA, and proteins and lipids concentration between particles--treated and untreated cells. Comparison between Bhasma-treated and -untreated cells indicates that vibrational peaks corresponding to the DNA/RNA molecule show a significant increase in cells treated with the Jasada Bhasma. Apart from the DNA molecule, several other vibrational peaks related to the protein molecules also show a significant increase in A549 cells after treatment with Bhasma. These results indicate that Bhasma treatment of A549 possibly delays DNA degradation and enables retention of higher amount of protein molecules in the cells.

  19. Surface charge features of kaolinite particles and their interactions

    NASA Astrophysics Data System (ADS)

    Gupta, Vishal

    Kaolinite is both a blessing and a curse. As an important industrial mineral commodity, kaolinite clays are extensively used in the paper, ceramic, paint, plastic and rubber industries. In all these applications the wettability, aggregation, dispersion, flotation and thickening of kaolinite particles are affected by its crystal structure and surface properties. It is therefore the objective of this research to investigate selected physical and surface chemical properties of kaolinite, specifically the surface charge of kaolinite particles. A pool of advanced analytical techniques such as XRD, XRF, SEM, AFM, FTIR and ISS were utilized to investigate the morphological and surface chemistry features of kaolinite. Surface force measurements revealed that the silica tetrahedral face of kaolinite is negatively charged at pH>4, whereas the alumina octahedral face of kaolinite is positively charged at pH<6, and negatively charged at pH>8. Based on electrophoresis measurements, the apparent iso-electric point for kaolinite particles was determined to be less than pH 3. In contrast, the point of zero charge was determined to be pH 4.5 by titration techniques, which corresponds to the iso-electric point of between pH 4 and 5 as determined by surface force measurements. Results from kaolinite particle interactions indicate that the silica face--alumina face interaction is dominant for kaolinite particle aggregation at low and intermediate pH values, which explains the maximum shear yield stress at pH 5-5.5. Lattice resolution images reveal the hexagonal lattice structure of these two face surfaces of kaolinite. Analysis of the silica face of kaolinite showed that the center of the hexagonal ring of oxygen atoms is vacant, whereas the alumina face showed that the hexagonal surface lattice ring of hydroxyls surround another hydroxyl in the center of the ring. High resolution transmission electron microscopy investigation of kaolinite has indicated that kaolinite is indeed

  20. Efficient implementation of restricted active space configuration interaction with the hole and particle approximation.

    PubMed

    Casanova, David

    2013-04-05

    The restricted active space configuration interaction (RASCI) formalism with the hole and particle truncation of the wavefunction, that is, RASCI(h,p), holds very nice properties such as balanced treatment of ground and low-lying excited states, spin-completeness, large flexibility of the wavefunction, and moderate computational cost. In this article, I present a new implementation of the RASCI(h,p) method using a general algorithm based on the integral-driven approach. The new implementation allows to choose any electronic configuration as the single reference in combination with an excitation operator with any number of ionization, electron attachment, or spin-flip (SF) excitations. The applicability and good performance of the new computational code is tested in the ground state calculation of water molecule with increasingly large active spaces and up to the full-CI limit, the calculation of all-trans linear polyenes with variable number of SF excitations, and the low-lying states of fluorine molecule with a double-ionization potential operator. Copyright © 2012 Wiley Periodicals, Inc.

  1. Colloidal Particles and Liquid Interfaces: A Spectrum of Interactions

    NASA Astrophysics Data System (ADS)

    Kaz, David Martin

    Young's law predicts that a colloidal sphere in equilibrium with a liquid interface will straddle the two fluids, its height above the interface defined by an equilibrium contact angle. This equilibrium analysis has been used to explain why colloids often bind to liquid interfaces, an effect first observed a century ago by Ramsden and Pickering and later exploited in a wide range of material processes, including emulsification, water purification, mineral recovery, encapsulation, and the making of nanostructured materials. But little is known about the dynamics of binding, or any aspect of the interaction between a particle and an interface outside of equilibrium. This thesis explores the spectrum of particle-interface interactions, from non-binding to non-adsorptive binding and finally adsorptive binding and the relaxation toward equilibrium that ensues. Chapter 2 reviews the importance of interfacial particles in materials science, and serves as a partial motivation for the work presented here. Chapter 3 describes the apparatus and experimental procedures employed in the acquisition of our data, with a short review of experiments that led to the current set. Special attention is paid to the optical apparatus and the custom sample cells we designed. Chapter 4 deals with non-adsorptive interactions between colloidal particles and liquid interfaces. A theoretical discussion founded on (but not wedded to) classical DLVO theory is presented before the results of our experiments are analyzed. It is shown that particle-interface interactions may be purely repulsive or contain an attractive component that results in binding to the interface that is not associated with breach. In chapter 5 the adsorption of polystyrene microspheres to a water-oil interface is shown to be characterized by a sudden breach and an unexpectedly slow relaxation. Particles do not reach equilibrium even after 100 seconds, and the relaxation appears logarithmic in time, suggesting that complete

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

    NASA Astrophysics Data System (ADS)

    Moser, Thomas; Seiringer, Robert

    2016-11-01

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

  3. Design and calibration of a rocket-borne electron spectrometer for investigation of particle ionization in the nighttime midlatitude E region

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    An explanation was developed for the formation, near midnight at midlatitudes, of a broad electron density layer extending approximately from 120 to 180 km and usually referred to as the intermediate E layer. The responsible mechanism is believed to be the converging vertical ion drifts resulting from winds of the solar semidiurnal tide. Numerical solutions of the continuity equation appropriate to the intermediate layer is described for particular models of ion drift, diffusion coefficents, and ionization production. Analysis of rocket observations of the layer show that the ionization rate is highly correlated with the planetary geomagnetic index, K sub p. Particle flux measurements support the idea that energetic electrons are the principal source of this ionization. A semiconductor spectrometer experiment for investigation of the particle flux, spectrum, and angular properties was designed and successfully flown on a Nike Apache rocket. A detailed description of the theory, design, and calibration of the experiment and some preliminary results presented.

  4. Enhanced ionization of the Martian nightside ionosphere during solar energetic particle events

    NASA Astrophysics Data System (ADS)

    Nemec, F.; Morgan, D. D.; Dieval, C.; Gurnett, D. A.; Futaana, Y.

    2013-12-01

    The nightside ionosphere of Mars is highly variable and very irregular, controlled to a great extent by the configuration of the crustal magnetic fields. The ionospheric reflections observed by the MARSIS radar sounder on board the Mars Express spacecraft in this region are typically oblique (reflection by a distant feature), so that they cannot be used to determine the peak altitude precisely. Nevertheless, the peak electron density can be in principle readily determined. However, in more than 90% of measurements the peak electron densities are too low to be detected. We focus on the time intervals of solar energetic particle (SEP) events. One may expect high energy particle precipitation into the nightside ionosphere to increase the electron density there. Thus, comparison of characteristics between SEP/no-SEP time intervals is important to understand the formation mechanism of the nightside ionosphere. The time intervals of SEP events are determined using the increase in the background counts recorded by the ion sensor (IMA) of the ASPERA-3 particle instrument on board Mars Express. Then we use MARSIS measurements to determine how much the nightside ionosphere is enhanced during these time intervals. We show that the peak electron densities during these periods are large enough to be detected in more than 30% of measurements, while the reflections from the ground almost entirely disappear, indicating that the nightside electron densities are tremendously increased as compared to the normal nightside conditions. The influence of various parameters on the formation of the nightside ionosphere is thoroughly discussed.

  5. Particle interactions in kaolinite suspensions and corresponding aggregate structures.

    PubMed

    Gupta, Vishal; Hampton, Marc A; Stokes, Jason R; Nguyen, Anh V; Miller, Jan D

    2011-07-01

    The surface charge densities of the silica face surface and the alumina face surface of kaolinite particles, recently determined from surface force measurements using atomic force microscopy, show a distinct dependence on the pH of the system. The silica face was found to be negatively charged at pH>4, whereas the alumina face surface was found to be positively charged at pH<6, and negatively charged at pH>8. The surface charge densities of the silica face and the alumina face were utilized in this study to determine the interaction energies between different surfaces of kaolinite particles. Results indicate that the silica face-alumina face interaction is dominant for kaolinite particle aggregation at low pH. This face-face association increases the stacking of kaolinite layers, and thereby promotes the edge-face (edge-silica face and edge-alumina face) and face-face (silica face-alumina face) associations with increasing pH, and hence the maximum shear-yield stress at pH 5-5.5. With further increase in pH, the face-face and edge-face association decreases due to increasing surface charge density on the silica face and the edge surfaces, and decreasing surface charge density on the alumina face. At high pH, all kaolinite surfaces become negatively charged, kaolinite particles are dispersed, and the suspension is stabilized. The face-face association at low pH has been confirmed from cryo-SEM images of kaolinite aggregates taken from suspension which show that the particles are mostly organized in a face-face and edge-face manner. At higher pH conditions, the cryo-SEM images of the kaolinite aggregates reveal a lower degree of consolidation and the edge-edge association is evident.

  6. Wave particle interactions in Jupiter's magnetosphere: Implications for auroral and magnetospheric particle distributions

    NASA Astrophysics Data System (ADS)

    Saur, Joachim; Schreiner, Anne; Barry, Mauk; Clark, George; Kollman, Peter

    2017-04-01

    We investigate the occurrence and the role of wave particle interaction processes, i.e., Landau and cyclotron damping, in Jupiter's magnetosphere. Therefore we calculate kinetic length and temporal scales, which we cross-compare at various regions within Jupiter's magnetosphere. Based on these scales, we investigate the roles of possible wave particle mechanisms in each region, e.g., Jupiter's plasma sheet, the auroral acceleration region and the polar ionosphere. We thereby consider that the magnetospheric regions are coupled through convective transport, Alfven and other wave modes. We particularly focus on the role of kinetic Alfven waves in contributing to Jupiter's aurora. Our results will aid the interpretation of particle distribution functions measured by the JEDI instrument onboard the JUNO spacecraft.

  7. Observations of the UARS Particle Environment Monitor and computation of ionization rates in the middle and upper atmosphere during a geomagnetic storm

    NASA Technical Reports Server (NTRS)

    Sharber, J. R.; Frahm, R. A.; Winningham, J. D.; Biard, J. C.; Lummerzheim, D.; Rees, M. H.; Chenette, D. L.; Gaines, E. E.; Nightingale, R. W.; Imhof, W. L.

    1993-01-01

    In this paper we present observations made by the Particle Environment Monitor (PEM) instruments during the geomagnetic storm of 8-9 November, 1991. Ionization and energy deposition rates as functions of altitude in the middle and upper atmosphere by incident electrons and positive ions in the storm interval are computed. The suite of PEM instruments provides a systematic measurement of energetic particles and their associated X-rays over an energy range not fully covered by previous satellite missions.

  8. Observations of the UARS Particle Environment Monitor and computation of ionization rates in the middle and upper atmosphere during a geomagnetic storm

    NASA Technical Reports Server (NTRS)

    Sharber, J. R.; Frahm, R. A.; Winningham, J. D.; Biard, J. C.; Lummerzheim, D.; Rees, M. H.; Chenette, D. L.; Gaines, E. E.; Nightingale, R. W.; Imhof, W. L.

    1993-01-01

    In this paper we present observations made by the Particle Environment Monitor (PEM) instruments during the geomagnetic storm of 8-9 November, 1991. Ionization and energy deposition rates as functions of altitude in the middle and upper atmosphere by incident electrons and positive ions in the storm interval are computed. The suite of PEM instruments provides a systematic measurement of energetic particles and their associated X-rays over an energy range not fully covered by previous satellite missions.

  9. Noncanonical interactions between serum transferrin and transferrin receptor evaluated with electrospray ionization mass spectrometry

    PubMed Central

    Leverence, Rachael; Mason, Anne B.; Kaltashov, Igor A.

    2010-01-01

    The primary route of iron acquisition in vertebrates is the transferrin receptor (TfR) mediated endocytotic pathway, which provides cellular entry to the metal transporter serum transferrin (Tf). Despite extensive research efforts, complete understanding of Tf-TfR interaction mechanism is still lacking owing to the complexity of this system. Electrospray ionization mass spectrometry (ESI MS) is used in this study to monitor the protein/receptor interaction and demonstrate the ability of metal-free Tf to associate with TfR at neutral pH. A set of Tf variants is used in a series of competition and displacement experiments to bracket TfR affinity of apo-Tf at neutral pH (0.2–0.6 μM). Consistent with current models of endosomal iron release from Tf, acidification of the protein solution results in a dramatic change of binding preferences, with apo-Tf becoming a preferred receptor binder. Contrary to the current models implying that the apo-Tf/TfR complex dissociates almost immediately upon exposure to the neutral environment at the cell surface, our data indicate that this complex remains intact. Iron-loaded Tf displaces apo-Tf from TfR, making it available for the next cycle of iron binding, transport and delivery to tissues. However, apo-Tf may still interfere with the cellular uptake of engineered Tf molecules whose TfR affinity is affected by various modifications (e.g., conjugation to cytotoxic molecules). This work also highlights the great potential of ESI MS as a tool capable of providing precise details of complex protein-receptor interactions under conditions that closely mimic the environment in which these encounters occur in physiological systems. PMID:20404192

  10. Apoptotic activity of 5-fluorouracil in breast cancer cells transformed by low doses of ionizing α-particle radiation.

    PubMed

    Ponce-Cusi, Richard; Calaf, Gloria M

    2016-02-01

    Globally, breast cancer in women is the leading cause of cancer death. This fact has generated an interest to obtain insight into breast tumorigenesis and also to develop drugs to control the disease. Ras is a proto-oncogene that is activated as a response to extracellular signals. As a member of the Ras GTPase superfamily, Rho-A is an oncogenic and a critical component of signaling pathways leading to downstream gene regulation. In chemotherapy, apoptosis is the predominant mechanism by which cancer cells die. However, even when the apoptotic machinery remains intact, survival signaling may antagonize the cell death by signals. The aim of this study was to evaluate 5-fluorouracil (5-FU) in cells transformed by low doses of ionizing α-particle radiation, in breast cancer cell lines on these genes, as well as apoptotic activity. We used two cell lines from an in vitro experimental breast cancer model. The MCF-10F and Tumor2 cell lines. MCF-10F was exposed to low doses of high linear energy transfer (LET) α-particles radiation (150 keV/µm). Tumor2, is a malignant and tumorigenic cell line obtained from Alpha5 (60cGy+E/60cGy+E) injected into the nude mice. Results indicated that 5-FU decreased H-ras, Rho-A, p53, Stat1 and increased Bax gene expression in Tumor2 and decreased Rac1, Rho-A, NF-κB and increased Bax and caspase-3 protein expression in Tumor2. 5-FU decreased H-ras, Bcl-xL and NF-κB and increased Bax gene expression. 5-FU decreased Rac1, Rho-A protein expression and increased Bax and caspase-3 protein expression in MDA-MB-231. Flow cytometry indicated 21.5% of cell death in the control MCF-10F and 80% in Tumor2 cell lines. It can be concluded that 5-FU may exert apoptotic activity in breast cancer cells transformed by low doses of ionizing α-particles in vitro regulating genes of Ras family and related to apoptosis such as Bax, Bcl-xL and NF-κB expression.

  11. Application of single-particle laser desorption/ionization time-of-flight mass spectrometry for detection of polycyclic aromatic hydrocarbons from soot particles originating from an industrial combustion process.

    PubMed

    Zimmermann, R; Ferge, T; Gälli, M; Karlsson, R

    2003-01-01

    Combustion-related soot particles were sampled in situ from the stoker system of a 0.5 MW incineration pilot plant (feeding material was wood) at two different heights over the feed bed in the third air supply zone. The collected particles were re-aerosolized by a powder-dispersing unit and analyzed by a single-particle laser desorption/ionization (LDI) time-of-flight mass spectrometer (aerosol-time-of-flight mass spectrometry, ATOFMS). The ATOFMS instrument characterizes particles according to their aerodynamic size (laser velocimetry) and chemical composition (LDI mass spectrometry). Chemical species from the particles are laser desorbed/ionized by 266 nm Nd:YAG laser pulses. ATOFMS results on individual 'real world' particles in general give information on the bulk inorganic composition. Organic compounds, which are of much lower concentrations, commonly are not detectable. However, recent off-line laser microprobe mass spectrometric (LMMS) experiments on bulk soot aerosol samples have emphasized that organic compounds can be desorbed and ionized without fragmentation in LDI experiments from black carbonaceous matrices. This paper reports the successful transfer of the off-line results to on-line analysis of airborne soot particles by ATOFMS. The detection of polycyclic aromatic hydrocarbons from soot particles is addressed in detail. The results are interpreted in the context of the recent LMMS results. Furthermore, their relevance with respect to possible applications in on-line monitoring of combustion processes is discussed. Copyright 2003 John Wiley & Sons, Ltd.

  12. Specific interaction between negative atmospheric ions and organic compounds in atmospheric pressure corona discharge ionization mass spectrometry.

    PubMed

    Sekimoto, Kanako; Sakai, Mami; Takayama, Mitsuo

    2012-06-01

    The interaction between negative atmospheric ions and various types of organic compounds were investigated using atmospheric pressure corona discharge ionization (APCDI) mass spectrometry. Atmospheric negative ions such as O(2)(-), HCO(3)(-), COO(-)(COOH), NO(2)(-), NO(3)(-), and NO(3)(-)(HNO(3)) having different proton affinities served as the reactant ions for analyte ionization in APCDI in negative-ion mode. The individual atmospheric ions specifically ionized aliphatic and aromatic compounds with various functional groups as atmospheric ion adducts and deprotonated analytes. The formation of the atmospheric ion adducts under certain discharge conditions is most likely attributable to the affinity between the analyte and atmospheric ion and the concentration of the atmospheric ion produced under these conditions. The deprotonated analytes, in contrast, were generated from the adducts of the atmospheric ions with higher proton affinity attributable to efficient proton abstraction from the analyte by the atmospheric ion.

  13. Interactive computational models of particle dynamics using virtual reality

    SciTech Connect

    Canfield, T.; Diachin, D.; Freitag, L.; Heath, D.; Herzog, J.; Michels, W.

    1996-12-31

    An increasing number of industrial applications rely on computational models to reduce costs in product design, development, and testing cycles. Here, the authors discuss an interactive environment for the visualization, analysis, and modification of computational models used in industrial settings. In particular, they focus on interactively placing massless, massed, and evaporating particulate matter in computational fluid dynamics applications.they discuss the numerical model used to compute the particle pathlines in the fluid flow for display and analysis. They briefly describe the toolkits developed for vector and scalar field visualization, interactive particulate source placement, and a three-dimensional GUI interface. This system is currently used in two industrial applications, and they present the tools in the context of these applications. They summarize the current state of the project and offer directions for future research.

  14. Model-independent analyses of dark-matter particle interactions

    SciTech Connect

    Anand, Nikhil; Fitzpatrick, A. Liam; Haxton, W. C.

    2015-03-24

    A model-independent treatment of dark-matter particle elastic scattering has been developed, yielding the most general interaction for WIMP-nucleon low-energy scattering, and the resulting amplitude has been embedded into the nucleus, taking into account the selection rules imposed by parity and time-reversal. One finds that, in contrast to the usual spin-independent/spin-dependent (SI/SD) formulation, the resulting cross section contains six independent nuclear response functions, three of which are associated with possible velocity-dependent interactions. We find that current experiments are four orders of magnitude more sensitive to derivative couplings than is apparent in the standard SI/SD treatment, which necessarily associated such interactions with cross sections proportional to v2T ~ 10⁻⁶, where vT is the WIMP velocity relative to the center of mass of the nuclear target.

  15. Model-independent analyses of dark-matter particle interactions

    DOE PAGES

    Anand, Nikhil; Fitzpatrick, A. Liam; Haxton, W. C.

    2015-03-24

    A model-independent treatment of dark-matter particle elastic scattering has been developed, yielding the most general interaction for WIMP-nucleon low-energy scattering, and the resulting amplitude has been embedded into the nucleus, taking into account the selection rules imposed by parity and time-reversal. One finds that, in contrast to the usual spin-independent/spin-dependent (SI/SD) formulation, the resulting cross section contains six independent nuclear response functions, three of which are associated with possible velocity-dependent interactions. We find that current experiments are four orders of magnitude more sensitive to derivative couplings than is apparent in the standard SI/SD treatment, which necessarily associated such interactions withmore » cross sections proportional to v2T ~ 10⁻⁶, where vT is the WIMP velocity relative to the center of mass of the nuclear target.« less

  16. Understanding particle size and distance driven competition of interparticle interactions and effective single-particle anisotropy

    NASA Astrophysics Data System (ADS)

    Pacakova, B.; Mantlikova, A.; Niznansky, D.; Kubickova, S.; Vejpravova, J.

    2016-05-01

    Magnetic response of single-domain nanoparticles (NPs) in concentrated systems is strongly affected by mutual interparticle interactions. However, particle proximity significantly influences single-particle effective anisotropy. To solve which of these two phenomena plays a dominant role in the magnetic response of real NP systems, systematic study on samples with well-defined parameters is required. In our work, we prepared a series of nanocomposites constituted of highly-crystalline and well-isolated CoFe2O4 NPs embedded in an amorphous SiO2 matrix using a single-molecule precursor method. This preparation method enabled us to reach a wide interval of particle size and concentration. We observed that the characteristic parameters of the single-domain state (coercivity, blocking temperature) and dipole-dipole interaction energy ({{E}\\text{d-\\text{d}}} ) scaled with each other and increased with increasing {{≤ft({{d}\\text{XRD}}/r\\right)}3} , where d XRD was the NP diameter and r was the interparticle distance. Our results are in excellent agreement with Monte-Carlo simulations of the particle growth. Moreover, we demonstrated that the contribution of {{E}\\text{d-\\text{d}}} acting as an additional energetic barrier to the superspin reversal or as an average static field did not sufficiently explain how the concentrated NP systems responded to an external magnetic field. Alternations in the blocking temperature and coercivity of our NP systems accounted for reformed relaxations of the NP superspins and modified effective anisotropy energy of the interacting NPs. Therefore, the concept of modified NP effective anisotropy explains the magnetic response of our concentrated NP systems better than the concept of the energy barrier influenced by interparticle interactions.

  17. Bond rupture between colloidal particles with a depletion interaction

    SciTech Connect

    Whitaker, Kathryn A.; Furst, Eric M.

    2016-05-15

    The force required to break the bonds of a depletion gel is measured by dynamically loading pairs of colloidal particles suspended in a solution of a nonadsorbing polymer. Sterically stabilized poly(methyl methacrylate) colloids that are 2.7 μm diameter are brought into contact in a solvent mixture of cyclohexane-cyclohexyl bromide and polystyrene polymer depletant. The particle pairs are subject to a tensile load at a constant loading rate over many approach-retraction cycles. The stochastic nature of the thermal rupture events results in a distribution of bond rupture forces with an average magnitude and variance that increases with increasing depletant concentration. The measured force distribution is described by the flux of particle pairs sampling the energy barrier of the bond interaction potential based on the Asakura–Oosawa depletion model. A transition state model demonstrates the significance of lubrication hydrodynamic interactions and the effect of the applied loading rate on the rupture force of bonds in a depletion gel.

  18. A battery model that fully couples mechanics and electrochemistry at both particle and electrode levels by incorporation of particle interaction

    NASA Astrophysics Data System (ADS)

    Wu, Bin; Lu, Wei

    2017-08-01

    This paper develops a multi-scale mechanical-electrochemical model which enables fully coupled mechanics and electrochemistry at both particle and electrode levels. At the particle level, solid diffusion is modeled using a generalized chemical potential to capture the effects of mechanical stress and phase transformation. At the electrode level, the stress arising from particle interaction is incorporated in a continuum model. This particle interaction stress is in addition to the traditional concept of intercalation stress inside isolated particles. The particle and continuum electrode levels are linked by the particle interaction stress as loads on the particle surface, and by consideration of stress on the electrochemical reaction rate on the particle surface. The effect of mechanical stress on electrochemical reaction results in a stress-dependent over-potential between particle and electrolyte. Stress gradient in an electrode leads to inhomogeneous intercalation/deintercalation currents for particles depending on their interaction stress with neighbors, resulting in stress gradient induced inhomogeneous state of charge. Conversely, non-uniform intercalation/deintercalation currents in an electrode lead to stress between particles. With this model we have an important finding: an electrochemically inactive region in an electrode causes stress built-up. This model provides a powerful tool to address various problems such as fracture in-between particles.

  19. Water interaction with laboratory-simulated fossil fuel combustion particles.

    PubMed

    Popovicheva, O B; Kireeva, E D; Shonija, N K; Khokhlova, T D

    2009-10-01

    To clarify the impact of fossil fuel combustion particles' composition on their capacity to take up water, we apply a laboratory approach in which the method of deposition of compounds, identified in the particulate coverage of diesel and aircraft engine soot particles, is developed. It is found that near-monolayer organic/inorganic coverage of the soot particles may be represented by three groups of fossil fuel combustion-derived particulate matter with respect to their Hansh's coefficients related to hydrophilic properties. Water adsorption measurements show that nonpolar organics (aliphatic and aromatic hydrocarbons) lead to hydrophobization of the soot surface. Acidic properties of organic compounds such as those of oxidized PAHs, ethers, ketones, aromatic, and aliphatic acids are related to higher water uptake, whereas inorganic acids and ionic compounds such as salts of organic acids are shown to be responsible for soot hydrophilization. This finding allows us to quantify the role of the chemical identity of soot surface compounds in water uptake and the water interaction with fossil fuel combustion particles in the humid atmosphere.

  20. Event-chain Monte Carlo algorithms for three- and many-particle interactions

    NASA Astrophysics Data System (ADS)

    Harland, J.; Michel, M.; Kampmann, T. A.; Kierfeld, J.

    2017-02-01

    We generalize the rejection-free event-chain Monte Carlo algorithm from many-particle systems with pairwise interactions to systems with arbitrary three- or many-particle interactions. We introduce generalized lifting probabilities between particles and obtain a general set of equations for lifting probabilities, the solution of which guarantees maximal global balance. We validate the resulting three-particle event-chain Monte Carlo algorithms on three different systems by comparison with conventional local Monte Carlo simulations: i) a test system of three particles with a three-particle interaction that depends on the enclosed triangle area; ii) a hard-needle system in two dimensions, where needle interactions constitute three-particle interactions of the needle end points; iii) a semiflexible polymer chain with a bending energy, which constitutes a three-particle interaction of neighboring chain beads. The examples demonstrate that the generalization to many-particle interactions broadens the applicability of event-chain algorithms considerably.

  1. Desorption electrospray ionization-based imaging of interaction between vascular graft and human body.

    PubMed

    Bodzon-Kulakowska, Anna; Drabik, Anna; Mystkowska, Joanna; Chlabicz, Michal; Gacko, Marek; Dabrowski, Jan R; Mielczarek, Przemyslaw; Silberring, Jerzy; Suder, Piotr

    2016-01-01

    The desorption electrospray ionization-mass spectrometry imaging (DESI-MSI) is known as a fast and convenient MS-based method for lipid imaging in various biological materials. Here, we applied this technique to visualize lipid distribution in a vascular graft removed from a patient's body. This is a good example of the DESI system capabilities toward imaging of interaction between artificial material and living tissues. Detailed analysis allowed for visualization of the spatial distribution of selected lipids in this implanted, artificial material. Not only DESI-MSI allowed visualization of lipid distribution in the investigated material but also enabled identification of the detected molecular species using MS/MS. Here, this technique was successfully used to evaluate the saturation and spatial distribution of endogenous lipids in the artificial vascular graft. Unambiguous identification of the lipids was done with the aid of fragmentation procedure. We also showed that various lipids localize preferably in graft material or internal plaque existing inside the graft. © 2015 Wiley Periodicals, Inc.

  2. The eye (and brain) as ionizing particle detector? First results from the ALTEA - space experiment

    NASA Astrophysics Data System (ADS)

    Narici, Livio

    The first part of ALTEA-Space experiments have been performed on the ISS (USLab) between August 2006 and July 2007. The ALTEA hardware features 6 particle telescopes each with 6 striped 8 x 16 cm2 silicon planes arranged alternately in the x and y direction. These detectors are hold by helmet shaped holder. ALTEA features also a light tight visual stimulation unit, a 32 channel EEG cap and electronics, a 3-buttons pushbutton. Two different experiment modalities were run: DOSI and CNSM. The former is the study of the radiation environment of the USLab, and results from these measurements are mostly covered by other papers in this conference; the latter is the study of the electrophysiological activity in coincidence with particle traveling through the eye/brain of the astronaut, with specific reference to the observed light flashes. In this paper we will present first results from these measurements and discuss, within this panorama, the amount of the measured radiation in the brain/eye. Seven CNSM sessions have been performed (on three astronauts), with a total of 20 light flashes perceived. Comparisons with previous measurements in Low Earth Orbit and during the flights to the Moon will be also shown

  3. Nano to micro particle size distribution measurement in the fluid by interactive force apparatus for fine particle processing.

    PubMed

    Fujita, Toyohisa; Dodbiba, Gjergj; Okaya, Katsunori; Matsuo, Seiji; Wang, Li Pang; Onda, Kana; Otsuki, Akira

    2013-12-01

    The direct measurement of fine particles size distribution of dispersions or coagulations in liquid is important for water purification, fine particles separation for recycling and mineral processing, as well as the new material production. The nano to micro particle size is usually measured by light scattering method; however, it is difficult to measure at high concentration of suspension. Here, a novel dynamical method by using the interactive force measurement between particles in liquid under electric field is used for measuring distribution of fine particle. Three types of nano to submicron particles, that is well-dispersed nano particles, coagulated nano particles and settled submicron particles, have been measured by interactive force measurement method. The particle size distributions are compered with the size distributions of dried particles measured by TEM or SEM. The well-dispersed nano particle size distribution by interactive force measurement is influenced by the nano size surfactant micelles. The size distribution of coagulated nano particles in water is larger than the result by TEM. On the other hand, the submicron nickel particle size distribution is similar with the one analyzed by SEM.

  4. Water interaction with hydrophobic and hydrophilic soot particles.

    PubMed

    Popovicheva, Olga; Persiantseva, Natalia M; Shonija, Natalia K; DeMott, Paul; Koehler, Kirsten; Petters, Markus; Kreidenweis, Sonia; Tishkova, Victoria; Demirdjian, Benjamin; Suzanne, Jean

    2008-05-07

    The interaction of water with laboratory soots possessing a range of properties relevant for atmospheric studies is examined by two complementary methods: gravimetrical measurement of water uptake coupled with chemical composition and porosity analysis and HTDMA (humidified tandem differential mobility analyzer) inference of water uptake accompanied by separate TEM (transmission electron microscopy) analysis of single particles. The first method clarifies the mechanism of water uptake for bulk soot and allows the classification of soot with respect to its hygroscopicity. The second method highlights the dependence of the soot aerosol growth factor on relative humidity (RH) for quasi-monodisperse particles. Hydrophobic and hydrophilic soot are qualitatively defined by their water uptake and surface polarity: laboratory soot particles are thus classified from very hydrophobic to very hydrophilic. Thermal soot particles produced from natural gas combustion are classified as hydrophobic with a surface of low polarity since water is found to cover only half of the surface. Graphitized thermal soot particles are proposed for comparison as extremely hydrophobic and of very low surface polarity. Soot particles produced from laboratory flame of TC1 aviation kerosene are less hydrophobic, with their entire surface being available for statistical monolayer water coverage at RH approximately 10%. Porosity measurements suggest that, initially, much of this surface water resides within micropores. Consequently, the growth factor increase of these particles to 1.07 at RH > 80% is attributed to irreversible swelling that accompanies water uptake. Hysteresis of adsorption/desorption cycles strongly supports this conclusion. In contrast, aircraft engine soot, produced from burning TC1 kerosene in a gas turbine engine combustor, has an extremely hydrophilic surface of high polarity. Due to the presence of water soluble organic and inorganic material it can be covered by many water

  5. Erosion processes due to energetic particle-surface interaction

    SciTech Connect

    Schmid, K.; Roth, J.

    2010-05-20

    The interaction of the fast particles from the hot plasma of a magnetic confinement fusion experiment with the first wall is one of the most challenging problems toward the realization of a fusion power plant. The erosion of the first wall by the fast particles leads to life time limitations and the radiative cooling of the plasma by the eroded impurity species lowers the energy confinement. Apart from these obvious consequences also the trapping of large quantities of the fuelling species (deuterium and tritium) in re-deposited layers of the eroded species poses a problem due to accumulation of large radiative inventories and plasma fuelling inefficiency. The source of all these challenges is the erosion of first wall components due to physical sputtering, chemical erosion and radiation enhanced sublimation. This paper will give an overview about the physical principles behind these erosion channels.

  6. Resonant wave-particle interactions modified by intrinsic Alfvenic turbulence

    SciTech Connect

    Wu, C. S.; Lee, K. H.; Wang, C. B.; Wu, D. J.

    2012-08-15

    The concept of wave-particle interactions via resonance is well discussed in plasma physics. This paper shows that intrinsic Alfven waves can qualitatively modify the physics discussed in conventional linear plasma kinetic theories. It turns out that preexisting Alfven waves can affect particle motion along the ambient magnetic field and, moreover, the ensuing force field is periodic in time. As a result, the meaning of the usual Landau and cyclotron resonance conditions becomes questionable. It turns out that this effect leads us to find a new electromagnetic instability. In such a process intrinsic Alfven waves not only modify the unperturbed distribution function but also result in a different type of cyclotron resonance which is affected by the level of turbulence. This instability might enable us to better our understanding of the observed radio emission processes in the solar atmosphere.

  7. Wave-particle Interactions in Space and Laboratory Plasmas

    NASA Astrophysics Data System (ADS)

    An, Xin

    This dissertation presents a study of wave-particle interactions in space and in the laboratory. To be concrete, the excitation of whistler-mode chorus waves in space and in the laboratory is studied in the first part. The relaxation of whistler anisotropy instability relevant to whistler-mode chorus waves in space is examined. Using a linear growth rate analysis and kinetic particle-in-cell simulations, the electron distributions are demonstrated to be well-constrained by the whistler anisotropy instability to a marginal-stability state, consistent with measurements by Van Allen Probes. The electron parallel beta beta ∥e separates the excited whistler waves into two groups: (i) quasi-parallel whistler waves for beta∥e > 0.02 and (ii) oblique whistler waves close to the resonance cone for beta∥e < 0.02. The saturated magnetic field energy of whistler waves roughly scales with the square of the electron beta beta∥e. 2, as shown in bothsatellite observations and particle-in-cell simulations. Motivated by the puzzles of chorus waves in space and by their recognized importance, the excitation of whistler-mode chorus waves is studied in the Large Plasma Device by the injection of a helical electron beam into a cold plasma. Incoherent broadband whistler waves similar to magnetospheric hiss are observed in the laboratory plasma. Their mode structures are identified by the phase-correlation technique. It is demonstrated that the waves are excited through a combination of Landau resonance, cyclotron resonance and anomalous cyclotron resonance. To account for the finite size effect of the electron beam, linear unstable eigenmodes of whistler waves are calculated by matching the eigenmode solution at the boundary. It is shown that the perpendicular wave number inside the beam is quantized due to the constraint imposed by the boundary condition. Darwin particle-in-cell simulations are carried out to study the simultaneous excitation of Langmuir and whistler waves in a

  8. Wave-particle interactions in the magnetosphere of Uranus

    SciTech Connect

    Kurth, W.S.; Gurnett, D.A.; Scarf, F.L.; Coroniti, F.V.

    1988-07-01

    The Voyager 2 encounter of Uranus has provided observations of plasma waves in and near the magnetosphere. These data, while the first from Uranus, will also be the only direct information on wave-particle interactions at this planet for many years to come. The observations include electrostatic waves upstream of the bow shock, turbulence in the shock, Bernstein emissions and whistler mode waves in the magnetosphere, broadband electrostatic noise in the magnetotail, and a number of the other types of plasma waves which have yet to be clearly identified. Each of these types of waves exist in a plasma environment which both supports the growth of the waves and is modified by interactions with the waves. Wave-particle interactions provide the channels through which the waves can accelerate, scatter, or thermalize the plasmas. The most spectacular example in the case of Uranus is the extremely intense whistler mode activity in the inner magnetosphere which is the source of strong pitch angle diffusion. The resulting electron precipitation is sufficient to produce the auroral emissions observed by Voyager. The strong diffusion, however, presents the problem of supplying electrons in the range of 5 to 40 keV in order to support the losses to the atmosphere.

  9. Wave-particle interactions in the magnetosphere of Uranus

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.; Gurnett, D. A.; Coroniti, F. V.; Scarf, F. L.

    1991-01-01

    The Voyager 2 encounter of Uranus has provided observations of plasma waves in and near the magnetosphere. These data, while the first from Uranus, will also be the only direct information on wave-particle interactions at this planet for many years to come. The observations include electrostatic waves upstream of the bow shock, turbulence in the shock Bernstein emissions and whistler mode waves in the magnetosphere, broadband electrostatic noise in the magnetotail, and a number of the other types of plasma waves which have yet to be clearly identified. Each of these types of waves exist in a plasma environment which both supports the growth of the waves and is modified by interactions with the waves. Wave-particle interactions provide the channels through which the waves can accelerate, scatter, or thermalize the plasmas. The most spectacular example in the case of Uranus is the extremely intense whistler mode activity in the inner magnetosphere which is the source of strong pitch angle diffusion. The resulting electron precipitation is sufficient to produce the auroral emissions observed by Voyager. The strong diffusion, however, presents the problem of supplying electrons in the range of 5 to 40 keV in order to support the losses to the atmosphere.

  10. Wave-particle interactions in the magnetosphere of Uranus

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.; Coroniti, F. V.

    1988-01-01

    The Voyager 2 encounter of Uranus has provided observations of plasma waves in and near the magnetosphere. These data, while the first from Uranus, will also be the only direct information on wave-particle interactions at this planet for many years to come. The observations include electrostatic waves upstream of the bow shock, turbulence in the shock, Bernstein emissions and whistler mode waves in the magnetosphere, broadband electrostatic noise in the magnetotail, and a number of the other types of plasma waves which have yet to be clearly identified. Each of these types of waves exist in a plasma environment which both supports the growth of the waves and is modified by interactions with the waves. Wave-particle interactions provide the channels through which the waves can accelerate, scatter, or thermalize the plasmas. The most spectacular example in the case of Uranus is the extremely intense whistler mode activity in the inner magnetosphere which is the source of strong pitch angle diffusion. The resulting electron precipitation is sufficient to produce the auroral emissions observed by Voyager. The strong diffusion, however, presents the problem of supplying electrons in the range of 5 to 40 keV in order to support the losses to the atmosphere.

  11. Interaction of tallow and hay particle size on ruminal parameters.

    PubMed

    Lewis, W D; Bertrand, J A; Jenkins, T C

    1999-07-01

    Four nonlactating ruminally cannulated Holstein cows were used in a 4 x 4 Latin square experiment with 4 21-d periods to determine if the effects of dietary fat would be affected by hay particle length. Treatments consisted of two levels of tallow (0 and 5%) and two hay particle lengths (short-cut and long-cut) in a 2 x 2 factorial. Diets contained alfalfa hay, corn silage, and concentrate [1:1:2, dry matter (DM) basis] fed as a total mixed ration (TMR) once per day. Samples of the 0 and 5% tallow TMR were ground and incubated in situ in polyester bags for 24 and 48 h. Ruminal samples were taken on day 21 at 0800 h and at 2-h intervals until 1600 h. The total tract digestibilities of acid detergent fiber (ADF) and neutral detergent fiber (NDF) were not affected by tallow or by hay by tallow interactions. There was a trend for tallow to improve total tract digestibility of crude protein (CP) (70.2 vs. 74.7%). After 48 h of ruminal incubation, tallow significantly decreased the digestibilities of DM, ADF, and NDF. No hay length by tallow interactions for DM, NDF, ADF or CP digestibilities occurred after 24 or 48 h. Tallow increased concentrations of propionate and decreased concentrations of acetate and valerate and the acetate-to-propionate ratio. Total volatile fatty acids increased when tallow was added to diets with short-cut hay, which suggests that when unprotected fat is added to diets with a high level of hay, a short-cut hay length may be advantageous. This result may be due to shorter rumen retention time of feed particles, which reduces the time for fatty acids to exert antimicrobial effects. Or, it may because the increased surface area of the hay particle provides more area for microbial attachment and increased fermentation.

  12. Particle size and particle-particle interactions on tensile properties and reinforcement of corn flour particles in natural rubber

    USDA-ARS?s Scientific Manuscript database

    Renewable corn flour has a significant reinforcement effect in natural rubber. The corn flour was hydrolyzed and microfluidized to reduce its particle size. Greater than 90% of the hydrolyzed corn flour had an average size of ~300 nm, a reduction of 33 times compared to unhydrolyzed corn flour. Comp...

  13. Measurement of Charged Particle Interactions in Spacecraft and Planetary Habitat Shielding Materials

    NASA Technical Reports Server (NTRS)

    Zeitlin, Cary J.; Heilbronn, Lawrence H.; Miller, Jack; Wilson, John W.; Singleterry, Robert C., Jr.

    2003-01-01

    Accurate models of health risks to astronauts on long-duration missions outside the geomagnetosphere will require a full understanding of the radiation environment inside a spacecraft or planetary habitat. This in turn requires detailed knowledge of the flux of incident particles and their propagation through matter, including the nuclear interactions of heavy ions that are a part of the Galactic Cosmic Radiation (GCR). The most important ions are likely to be iron, silicon, oxygen, and carbon. Transport of heavy ions through complex shielding materials including self-shielding of tissue modifies the radiation field at points of interest (e.g., at the blood-forming organs). The incident flux is changed by two types of interactions: (1) ionization energy loss, which results in reduced particle velocity and higher LET (Linear Energy Transfer); and (2) nuclear interactions that fragment the incident nuclei into less massive ions. Ionization energy loss is well understood, nuclear interactions less so. Thus studies of nuclear fragmentation at GCR-like energies are needed to fill the large gaps that currently exist in the database. These can be done at only a few accelerator facilities where appropriate beams are available. Here we report results from experiments performed at the Brookhaven National Laboratory s Alternating Gradient Synchrotron (AGS) and the Heavy Ion Medical Accelerator in Chiba, Japan (HIMAC). Recent efforts have focused on extracting charge-changing and fragment production cross sections from silicon beams at 400, 600, and 1200 MeV/nucleon. Some energy dependence is observed in the fragment production cross sections, and as in other data sets the production of fragments with even charge numbers is enhanced relative to those with odd charge numbers. These data are compared to the NASA-LaRC model NUCFRG2. The charge-changing cross section data are compared to recent calculations using an improved model due to Tripathi, which accurately predicts the

  14. Study of dust particle charging in weakly ionized inert gases taking into account the nonlocality of the electron energy distribution function

    SciTech Connect

    Filippov, A. V. Dyatko, N. A.; Kostenko, A. S.

    2014-11-15

    The charging of dust particles in weakly ionized inert gases at atmospheric pressure has been investigated. The conditions under which the gas is ionized by an external source, a beam of fast electrons, are considered. The electron energy distribution function in argon, krypton, and xenon has been calculated for three rates of gas ionization by fast electrons: 10{sup 13}, 10{sup 14}, and 10{sup 15} cm{sup −1}. A model of dust particle charging with allowance for the nonlocal formation of the electron energy distribution function in the region of strong plasma quasi-neutrality violation around the dust particle is described. The nonlocality is taken into account in an approximation where the distribution function is a function of only the total electron energy. Comparative calculations of the dust particle charge with and without allowance for the nonlocality of the electron energy distribution function have been performed. Allowance for the nonlocality is shown to lead to a noticeable increase in the dust particle charge due to the influence of the group of hot electrons from the tail of the distribution function. It has been established that the screening constant virtually coincides with the smallest screening constant determined according to the asymptotic theory of screening with the electron transport and recombination coefficients in an unperturbed plasma.

  15. Interactive data exploration and particle tracking for general circulation models

    NASA Technical Reports Server (NTRS)

    Rosenbaum, R. I.; Peskin, R. L.; Walther, S. S.; Zinn, H. P.

    1995-01-01

    The SCENE environment for interactive visualization of complex data sets is discussed. This environment is used to create tools for graphical exploration of atmospheric flow models. These tools may be extended by the user in a seamless manner, so that no programming is required. A module for accurately tracing field lines and particle trajectories in SCENE is presented. This is used to examine the flowfield qualitatively with streamlines and pathlines and to identify critical points in the velocity field. The paper also describes a visualization tool for general circulation models on which the primary features of the environment are demonstrated.

  16. Reduced Quasilinear Models for Energetic Particles Interaction with Alfvenic Eigenmodes

    SciTech Connect

    Ghantous, Katy

    2013-11-01

    The Line Broadened Quasilinear (LBQ) and the 1.5D reduced models are able to predict the effect of Alfvenic eigenmodes' interaction with energetic particles in burning plasmas. This interaction can result in energetic-particle losses that can damage the first wall, deteriorate the plasma performance, and even prevent ignition. The 1.5D model assumes a broad spectrum of overlapping modes and, based on analytic expressions for the growth and damping rates, calculates the pressure profiles that the energetic particles relax to upon interacting with the modes. 1.5D is validated with DIII-D experiments and predicted neutron losses consistent with observation. The model is employed to predict alpha-particle fusion-product losses in a large-scale operational parameter-space for burning plasmas. \\par The LBQ model captures the interaction both in the regime of isolated modes as well as in the conventional regime of overlapping modes. Rules were established that allow quasilinear equations to replicate the expected steady-state saturation levels of isolated modes. The fitting formula is improved and the model is benchmarked with a Vlasov code, BOT. The saturation levels are accurately predicted and the mode evolution is well-replicated in the case of steady-state evolution where the collisions are high enough that coherent structures do not form. When the collisionality is low, oscillatory behavior can occur. LBQ can also exhibit non-steady behavior, but the onset of oscillations occurs for much higher collisional rates in BOT than in LBQ. For certain parameters of low collisionality, hole-clump creation and frequency chirping can occur which are not captured by the LBQ model. Also, there are cases of non-steady evolution without chirping which is possible for LBQ to study. However the results are inconclusive since the periods and amplitudes of the oscillations in the mode evolution are not well-replicated. If multiple modes exist, they can grow to the point of overlap

  17. Field theories and exact stochastic equations for interacting particle systems

    SciTech Connect

    Andreanov, Alexei; Lefevre, Alexandre; Biroli, Giulio; Bouchaud, Jean-Philippe

    2006-09-15

    We consider the dynamics of interacting particles with reaction and diffusion. Starting from the underlying discrete stochastic jump process we derive a general field theory describing the dynamics of the density field, which we relate to an exact stochastic equation on the density field. We show how our field theory maps onto the original Doi-Peliti formalism, allowing us to clarify further the issue of the 'imaginary' Langevin noise that appears in the context of reaction-diffusion processes. Our procedure applies to a wide class of problems and is related to large deviation functional techniques developed recently to describe fluctuations of nonequilibrium systems in the hydrodynamic limit.

  18. Reduced quasilinear models for energetic particles interaction with Alfvenic eigenmodes

    NASA Astrophysics Data System (ADS)

    Ghantous, Katy

    The Line Broadened Quasilinear (LBQ) and the 1.5D reduced models are able to predict the effect of Alfvenic eigenmodes' interaction with energetic particles in burning plasmas. This interaction can result in energetic-particle losses that can damage the first wall, deteriorate the plasma performance, and even prevent ignition. The 1.5D model assumes a broad spectrum of overlapping modes and, based on analytic expressions for the growth and damping rates, calculates the pressure profiles that the energetic particles relax to upon interacting with the modes. 1.5D is validated with DIII-D experiments and predicted neutron losses consistent with observation. The model is employed to predict alpha-particle fusion-product losses in a large-scale operational parameter-space for burning plasmas. The LBQ model captures the interaction both in the regime of isolated modes as well as in the conventional regime of overlapping modes. Rules were established that allow quasilinear equations to replicate the expected steady-state saturation levels of isolated modes. The fitting formula is improved and the model is benchmarked with a Vlasov code, BOT. The saturation levels are accurately predicted and the mode evolution is well-replicated in the case of steady-state evolution where the collisions are high enough that coherent structures do not form. When the collisionality is low, oscillatory behavior can occur. LBQ can also exhibit non-steady behavior, but the onset of oscillations occurs for much higher collisional rates in BOT than in LBQ. For certain parameters of low collisionality, hole-clump creation and frequency chirping can occur which are not captured by the LBQ model. Also, there are cases of non-steady evolution without chirping which is possible for LBQ to study. However the results are inconclusive since the periods and amplitudes of the oscillations in the mode evolution are not well-replicated. If multiple modes exist, they can grow to the point of overlap which

  19. Time fluctuations in isolated quantum systems of interacting particles.

    PubMed

    Zangara, Pablo R; Dente, Axel D; Torres-Herrera, E J; Pastawski, Horacio M; Iucci, Aníbal; Santos, Lea F

    2013-09-01

    Numerically, we study the time fluctuations of few-body observables after relaxation in isolated dynamical quantum systems of interacting particles. Our results suggest that they decay exponentially with system size in both regimes, integrable and chaotic. The integrable systems considered are solvable with the Bethe ansatz and have a highly nondegenerate spectrum. This is in contrast with integrable Hamiltonians mappable to noninteracting ones. We show that the coefficient of the exponential decay depends on the level of delocalization of the initial state with respect to the energy shell.

  20. SERENA: a Novel Instrument Package on board BepiColombo-MPO to study Neutral and Ionized Particles in the Hermean Environment

    NASA Astrophysics Data System (ADS)

    Orsini, S.; Livi, S.; Torkar, K.; Barabash, S.; Milillo, A.; Wurz, P.; di Lellis, A. M.; Kallio, E.

    2009-06-01

    SERENA (`Search for Exospheric Refilling and Emitted Natural Abundances') is an instrument package that will fly on board the BepiColombo Mercury Planetary Orbiter (MPO) it will investigate the Mercury's complex particle environment that surrounds the planet. Such an environment is composed by thermal and directional neutral atoms (exosphere) originating via surface release and charge-exchange processes, and by ionized particles originated through photo-ionization and again by surface release processes. In order to accomplish the scientific goals, in-situ analysis of the environmental elements is necessary, and for such a purpose the SERENA instrument shall include four units: two Neutral Particle Analyzers (ELENA and STROFIO) and two Ion Spectrometers (MIPA and PICAM). The scientific merit of SERENA is presented, and the basic characteristics of the four units are described, with a focus on novel technological aspects.

  1. Photofragmentation, state interaction, and energetics of Rydberg and ion-pair states: Resonance enhanced multiphoton ionization of HI

    SciTech Connect

    Hróðmarsson, Helgi Rafn; Wang, Huasheng; Kvaran, Ágúst

    2014-06-28

    Mass resolved resonance enhanced multiphoton ionization data for hydrogen iodide (HI), for two-photon resonance excitation to Rydberg and ion-pair states in the 69 600–72 400 cm{sup −1} region were recorded and analyzed. Spectral perturbations due to homogeneous and heterogeneous interactions between Rydberg and ion-pair states, showing as deformations in line-positions, line-intensities, and line-widths, were focused on. Parameters relevant to photodissociation processes, state interaction strengths and spectroscopic parameters for deperturbed states were derived. Overall interaction and dynamical schemes to describe the observations are proposed.

  2. Development of 1D Particle-in-Cell Code and Simulation of Plasma-Wall Interactions

    NASA Astrophysics Data System (ADS)

    Rose, Laura P.

    This thesis discusses the development of a 1D particle-in-cell (PIC) code and the analysis of plasma-wall interactions. The 1D code (Plasma and Wall Simulation -- PAWS) is a kinetic simulation of plasma done by treating both electrons and ions as particles. The goal of this thesis is to study near wall plasma interaction to better understand the mechanism that occurs in this region. The main focus of this investigation is the effects that secondary electrons have on the sheath profile. The 1D code is modeled using the PIC method. Treating both the electrons and ions as macroparticles the field is solved on each node and weighted to each macro particle. A pre-ionized plasma was loaded into the domain and the velocities of particles were sampled from the Maxwellian distribution. An important part of this code is the boundary conditions at the wall. If a particle hits the wall a secondary electron may be produced based on the incident energy. To study the sheath profile the simulations were run for various cases. Varying background neutral gas densities were run with the 2D code and compared to experimental values. Different wall materials were simulated to show their effects of SEE. In addition different SEE yields were run, including one study with very high SEE yields to show the presence of a space charge limited sheath. Wall roughness was also studied with the 1D code using random angles of incidence. In addition to the 1D code, an external 2D code was also used to investigate wall roughness without secondary electrons. The roughness profiles where created upon investigation of wall roughness inside Hall Thrusters based off of studies done on lifetime erosion of the inner and outer walls of these devices. The 2D code, Starfish[33], is a general 2D axisymmetric/Cartesian code for modeling a wide a range of plasma and rarefied gas problems. These results show that higher SEE yield produces a smaller sheath profile and that wall roughness produces a lower SEE yield

  3. Fast scalable visualization techniques for interactive billion-particle walkthrough

    NASA Astrophysics Data System (ADS)

    Liu, Xinlian

    This research develops a comprehensive framework for interactive walkthrough involving one billion particles in an immersive virtual environment to enable interrogative visualization of large atomistic simulation data. As a mixture of scientific and engineering approaches, the framework is based on four key techniques: adaptive data compression based on space-filling curves, octree-based visibility and occlusion culling, predictive caching based on machine learning, and scalable data reduction based on parallel and distributed processing. In terms of parallel rendering, this system combines functional parallelism, data parallelism, and temporal parallelism to improve interactivity. The visualization framework will be applicable not only to material simulation, but also to computational biology, applied mathematics, mechanical engineering, and nanotechnology, etc.

  4. Sedimentation of concentrated monodisperse colloidal suspensions: role of collective particle interaction forces.

    PubMed

    Vesaratchanon, Jan S; Nikolov, Alex; Wasan, Darsh T

    2008-06-01

    The sedimentation velocities and concentration profiles of low-charge, monodisperse hydroxylate latex particle suspensions were investigated experimentally as a function of the particle concentration to study the effects of the collective particle interactions on suspension stability. We used the Kossel diffraction technique to measure the particle concentration profile and sedimentation rate. We conducted the sedimentation experiments using three different particle sizes. Collective hydrodynamic interactions dominate the particle-particle interactions at particle concentrations up to 6.5 vol%. However, at higher particle concentrations, additional collective particle-particle interactions resulting from the self-depletion attraction cause particle aggregation inside the suspension. The collective particle-particle interaction forces play a much more important role when relatively small particles (500 nm in diameter or less) are used. We developed a theoretical model based on the statistical particle dynamics simulation method to examine the role of the collective particle interactions in concentrated suspensions in the colloidal microstructure formation and sedimentation rates. The theoretical results agree with the experimentally-measured values of the settling velocities and concentration profiles.

  5. Interaction forces between particles containing grafted or adsorbed polymer layers.

    PubMed

    Tadros, Tharwat

    2003-07-01

    The interaction forces between particles containing grafted or adsorbed polymer layers have been investigated using rheological and surface force measurements. Polystyrene latex dispersions with grafted poly(ethylene oxide) (PEO) chains (M=2000) were used for the rheological measurements. Results were also obtained for latex dispersions stabilised with adsorbed graft copolymers of poly(methyl methacrylate-methacrylic acid) with methoxy capped PEO chains (M=750). The relative viscosity eta(r)-volume fraction phi curves for the latex dispersions with grafted PEO chains were established for three particle radii of 77.5, 306 and 502 nm. For comparison the eta(r)-phi curve was calculated using the Dougherty-Krieger equation. This allows one to obtain the adsorbed layer thickness delta as a function of phi. The results showed a decrease of delta with increase of phi, which was attributed to the interpenetration and/or compression of the PEO chains on increasing phi. Viscoelastic measurements as a function of phi showed a change from predominantly viscous to predominantly elastic response at a critical volume fraction, which indicated the onset of the strong steric repulsion when the polymer layers begin to overlap. A similar trend was obtained with the latex particles containing adsorbed graft copolymer layers. A scaling law was used to fit the elastic part of the logG'-log phi curve (where G' is the elastic modulus). This fit could be used to estimate the compressibility of the PEO chains. The correlation of the rheology of concentrated sterically stabilised dispersions with interparticle interactions was investigated by measuring the energy-distance curves for the graft copolymer that was adsorbed on smooth mica sheets. Using de Gennes scaling theory, it was possible to calculate the energy of interaction between the polymer layers. The high frequency modulus of the latex dispersions was obtained as a function of the volume fraction and the results were compared with

  6. On the interaction between radon progeny and particles generated by electronic and traditional cigarettes

    NASA Astrophysics Data System (ADS)

    Vargas Trassierra, C.; Cardellini, F.; Buonanno, G.; De Felice, P.

    2015-04-01

    During their entire lives, people are exposed to the pollutants present in indoor air. Recently, Electronic Nicotine Delivery Systems, mainly known as electronic cigarettes, have been widely commercialized: they deliver particles into the lungs of the users but a "second-hand smoke" has yet to be associated to this indoor source. On the other hand, the naturally-occurring radioactive gas, i.e. radon, represents a significant risk for lung cancer, and the cumulative action of these two agents could be worse than the agents separately would. In order to deepen the interaction between radon progeny and second-hand aerosol from different types of cigarettes, a designed experimental study was carried out by generating aerosol from e-cigarette vaping as well as from second-hand traditional smoke inside a walk-in radon chamber at the National Institute of Ionizing Radiation Metrology (INMRI) of Italy. In this chamber, the radon present in air comes naturally from the floor and ambient conditions are controlled. To characterize the sidestream smoke emitted by cigarettes, condensation particle counters and scanning mobility particle sizer were used. Radon concentration in the air was measured through an Alphaguard ionization chamber, whereas the measurement of radon decay product in the air was performed with the Tracelab BWLM Plus-2S Radon daughter Monitor. It was found an increase of the Potential Alpha-Energy Concentration (PAEC) due to the radon decay products attached to aerosol for higher particle number concentrations. This varied from 7.47 ± 0.34 MeV L-1 to 12.6 ± 0.26 MeV L-1 (69%) for the e-cigarette. In the case of traditional cigarette and at the same radon concentration, the increase was from 14.1 ± 0.43 MeV L-1 to 18.6 ± 0.19 MeV L-1 (31%). The equilibrium factor increases, varying from 23.4% ± 1.11% to 29.5% ± 0.26% and from 30.9% ± 1.0% to 38.1 ± 0.88 for the e-cigarette and traditional cigarette, respectively. These growths still continue for long

  7. Quantifying Protein-Fatty Acid Interactions Using Electrospray Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Liu, Lan; Kitova, Elena N.; Klassen, John S.

    2011-02-01

    The application of the direct electrospray ionization mass spectrometry (ESI-MS) assay to quantify interactions between bovine β-lactoglobulin (Lg) and a series of fatty acids (FA), CH3(CH2)xCOOH, where x = 6 (caprylic acid, CpA), 8 (capric acid, CA), 10 (lauric acid, LA), 12 (myristic acid, MA), 14 (palmitic acid, PA) and 16 (stearic acid, SA), is described. Control ESI-MS binding measurements performed on the Lg-PA interaction revealed that both the protonated and deprotonated gas phase ions of the (Lg + PA) complex are prone to dissociate in the ion source, which leads to artificially small association constants ( K a ). The addition of imidazole, a stabilizing solution additive, at high concentration (10 mM) increased the relative abundance of (Lg + PA) complex measured by ESI-MS in both positive and negative ion modes. The K a value measured in negative ion mode and using sampling conditions that minimize in-source dissociation is in good agreement with a value determined using a competitive fluorescence assay. The K a values measured by ESI-MS for the Lg interactions with MA and SA are also consistent with values expected based on the fluorescence measurements. However, the K a values measured using optimal sampling conditions in positive ion mode are significantly lower than those measured in negative ion mode for all of the FAs investigated. It is concluded that the protonated gaseous ions of the (Lg + FA) complexes are kinetically less stable than the deprotonated ions. In-source dissociation was significant for the complexes of Lg with the shorter FAs (CpA, CA, and LA) in both modes and, in the case of CpA, no binding could be detected by ESI-MS. The affinities of Lg for CpA, CA, and LA determined using the reference ligand ESI-MS assay, a method for quantifying labile protein-ligand complexes that are prone to in-source dissociation, were found to be in good agreement with reported values.

  8. Double-resonant fast particle-wave interaction

    NASA Astrophysics Data System (ADS)

    Schneller, M.; Lauber, Ph.; Brüdgam, M.; Pinches, S. D.; Günter, S.

    2012-10-01

    In future fusion devices fast particles must be well confined in order to transfer their energy to the background plasma. Magnetohydrodynamic instabilities like toroidal Alfvén eigenmodes or core-localized modes such as beta-induced Alfvén eigenmodes and reversed shear Alfvén eigenmodes, both driven by fast particles, can lead to significant losses. This is observed in many ASDEX Upgrade discharges. This study applies the drift-kinetic HAGIS code with the aim of understanding the underlying resonance mechanisms, especially in the presence of multiple modes with different frequencies. Of particular interest is the resonant interaction of particles simultaneously with two different modes, referred to as ‘double-resonance’. Various mode overlapping scenarios with different q profiles are considered. It is found that, depending on the radial mode distance, double-resonance is able to enhance growth rates as well as mode amplitudes significantly. Surprisingly, no radial mode overlap is necessary for this effect. Quite the contrary is found: small radial mode distances can lead to strong nonlinear mode stabilization of a linearly dominant mode.

  9. Specific influence of univalent cations on the ionization of alumina-coated TiO2 particles and on the adsorption of poly(acrylic)acid.

    PubMed

    Malgat, Alexandre; Boisvert, Jean-Philippe; Daneault, Claude

    2004-01-15

    A surface counterion titration method was used to monitor the interaction of monovalents cations (Li(+), Na(+), TMA(+)) with the surface of alumina-coated TiO(2) particles in concentrated media at different pH and electrolyte concentrations. This method allows measuring separately the negative and positive contribution to the surface charge. It showed that Cl(-) and TMA(+) are indifferent ions, but Li(+) and Na(+) specifically adsorb on the non-ionized alumina surface sites. The binding sequence of cations is Li(+)>Na(+)>TMA(+) at all ionic strengths investigated and is consistent with the structure-making and structure-breaking model developed a few decades ago. Polyacrylic acid (PAA) previously neutralized with the corresponding hydroxide (LiOH, NaOH, TMAOH) has been adsorbed on the alumina surface at different pH. The polymer counterion has a significant influence on the polymer adsorption. The sequence of the surface coverage as a function of the polymer counterion follows the order Li-PAA > Na-PAA > TMA-PAA. The much higher surface coverage with Li-PAA and Na-PAA compared to TMA-PAA is explained by the specific adsorption of Li-PAA and Na-PAA on the nonionized alumina surface sites, the same way LiCl and NaCl do.

  10. Aspects of wave-particle interactions at mid-latitudes

    NASA Astrophysics Data System (ADS)

    Smith, A. J.

    Arguably the most significant source of particle precipitation into the ionosphere at mid-latitudes (L ~ 2-3), at least for electrons in the tens to hundreds of keV energy range, is that which arises from the interaction between trapped particles and whistler-mode waves in the magnetosphere. Quasi-steady plasmaspheric hiss has long been postulated as a major class of waves contributing to the loss of radiation belt particles but recent studies have suggested that under some conditions, impulsive precipitation caused by interactions with lightning-generated whistlers may be equally important as a loss process. Such lightning-induced electron precipitation (LEP) and its ionospheric signature is the subject of this paper. Although LEP may be detected and studied by a variety of ground-based, balloon-borne and satellite-borne sensors, through optical emissions, X-ray production, enhanced conductivity, or the direct measurement of the precipitating particles themselves, a technique using ground-based narrow-band VLF receivers to measure the Trimpi effect (the transient perturbations in amplitude and/or phase of received narrow-band VLF transmissions) caused by LEP-associated ionisation enhancements has become increasingly popular due to its simple instrumentation and wide field of view. Most work has concentrated on the 2 < L < 3 region where typical whistler spectra, trapped electron energy distributions and magnetospheric plasma densities and magnetic field strengths are most favourable for the Trimpi effect. In order to use the technique to study in detail the characteristics and distribution of LEP (and its importance as a trapped-particle loss mechanism), using a network of intersecting transmitter-receiver great-circle paths (TRGCPs), a consensus on how to interpret the observational data is crucial, though this has recently been the subject of controversy. Whilst most studies suggest that only LEP within ~200 km of the TRGCP gives rise to an observable Trimpi

  11. Probing Competitive Noncovalent Interactions: Resonance Enhanced Two-Photon Ionization (R2PI) Spectroscopy of Haloaromatic Clusters

    NASA Astrophysics Data System (ADS)

    Nyambo, Silver; Muzangwa, Lloyd; Uhler, Brandon; Reid, Scott A.

    2013-06-01

    Non-covalent interactions in bromobenzene have been studied here using resonance two-photon ionization (R2PI) spectroscopy combined with a linear TOF-mass spectrometer. Bromobenzene clusters were created in a supersonic expansion with helium as a carrier gas. The molecules were excited and ionized from the ground state in a two stage process. The general trend observed in the R2PI spectra of all the clusters is the broadness and a red-shift relative to the monomer absorption. Optimized dimer and trimer structures were calculated at the M06-2x/aug-cc-pVDZ level, which show that π-stacked and C-H/π interactions are most important in these clusters. TD-DFT calculations of the different cluster conformers have been carried out to assess the geometry changes active upon electronic excitation. The theoretical studies are helpful in explaining trends observed in the R2PI spectra.

  12. Strong interactive massive particles from a strong coupled theory

    SciTech Connect

    Khlopov, Maxim Yu.; Kouvaris, Chris

    2008-03-15

    Minimal walking technicolor models can provide a nontrivial solution for cosmological dark matter, if the lightest technibaryon is doubly charged. Technibaryon asymmetry generated in the early Universe is related to baryon asymmetry, and it is possible to create an excess of techniparticles with charge (-2). These excessive techniparticles are all captured by {sup 4}He, creating techni-O-helium tOHe atoms, as soon as {sup 4}He is formed in big bang nucleosynthesis. The interaction of techni-O-helium with nuclei opens new paths to the creation of heavy nuclei in big bang nucleosynthesis. Because of the large mass of technibaryons, the tOHe ''atomic'' gas decouples from the baryonic matter and plays the role of dark matter in large scale structure formation, while structures in small scales are suppressed. Nuclear interactions with matter slow down cosmic techni-O-helium in the Earth below the threshold of underground dark matter detectors, thus escaping severe cryogenic dark matter search constraints. On the other hand, these nuclear interactions are not sufficiently strong to exclude this form of strongly interactive massive particles by constraints from the XQC experiment. Experimental tests of this hypothesis are possible in the search for tOHe in balloon-borne experiments (or on the ground) and for its charged techniparticle constituents in cosmic rays and accelerators. The tOHe atoms can cause cold nuclear transformations in matter and might form anomalous isotopes, offering possible ways to exclude (or prove?) their existence.

  13. Interaction of dilute colloidal particles in a mixed solvent

    SciTech Connect

    Kurnaz, M.L.; Maher, J.V.

    1995-06-01

    We have measured the second virial coefficient {ital B}{sub 2} of very dilute colloidal dispersions of charge-stabilized polystyrene latex spheres in the one-phase region of the mixed solvent 2,6-lutidine plus water. These measurements were made as a function of temperature for two solvent compositions, both of which are richer in 2,6-lutidine than the binary liquid mixture`s critical composition. The temperature ranges started deep in the one-phase region and approached the coexistence curve but did not penetrate the region of reversible aggregation near the coexistence curve. Very large, positive (repulsive-interaction) virial coefficients are observed at temperatures far from the aggregation zone and for calibration samples whose solvent is pure water. These large values of {ital B}{sub 2} are impossible to model without invoking long-range repulsive interactions whose origin is difficult to explain. As the temperature is brought nearer to the aggregation zone, the virial coefficient plunges through zero to large negative (attractive-interaction) values. Crude modeling suggests that the observed changes in the interactions are not inconsistent with a temperature-dependent attraction arising from adsorption layer energetics operating at distances of a few solvent-fluctuation correlation lengths from the particle surfaces.

  14. Quantum chaos and thermalization in isolated systems of interacting particles

    NASA Astrophysics Data System (ADS)

    Borgonovi, F.; Izrailev, F. M.; Santos, L. F.; Zelevinsky, V. G.

    2016-04-01

    This review is devoted to the problem of thermalization in a small isolated conglomerate of interacting constituents. A variety of physically important systems of intensive current interest belong to this category: complex atoms, molecules (including biological molecules), nuclei, small devices of condensed matter and quantum optics on nano- and micro-scale, cold atoms in optical lattices, ion traps. Physical implementations of quantum computers, where there are many interacting qubits, also fall into this group. Statistical regularities come into play through inter-particle interactions, which have two fundamental components: mean field, that along with external conditions, forms the regular component of the dynamics, and residual interactions responsible for the complex structure of the actual stationary states. At sufficiently high level density, the stationary states become exceedingly complicated superpositions of simple quasiparticle excitations. At this stage, regularities typical of quantum chaos emerge and bring in signatures of thermalization. We describe all the stages and the results of the processes leading to thermalization, using analytical and massive numerical examples for realistic atomic, nuclear, and spin systems, as well as for models with random parameters. The structure of stationary states, strength functions of simple configurations, and concepts of entropy and temperature in application to isolated mesoscopic systems are discussed in detail. We conclude with a schematic discussion of the time evolution of such systems to equilibrium.

  15. Copper-silver ionization at a US hospital: interaction of treated ...

    EPA Pesticide Factsheets

    Tap water sampling and surface analysis of copper pipe/bathroom porcelain were performed to explore the fate of copper and silver during the first nine months of copper-silver ionization (CSI) applied to cold and hot water at a hospital in Cincinnati, Ohio. Ions dosed by CSI into the water at its point of entry to the hospital were inadvertently removed from hot water by a cation-exchange softener in one building (average removal of 72% copper and 51% silver). Copper at the tap was replenished from corrosion of the building’s copper pipes but was typically unable to reach 200 µg/L in first-draw and flushed hot and cold water samples. Unlike copper, silver solubility was not restricted by the incoming water’s high pH of 8.5. Cold water lines had >20 µg/L silver at most of the taps that were sampled, which further increased after flushing. However, silver plating onto copper pipe surfaces (particularly in the hot water line) prevented reaching 20 µg/L silver in hot water of many taps. Aesthetically displeasing purple/grey stains in bathroom porcelain were attributed to chlorargyrite [AgCl(s)], an insoluble precipitate that formed when CSI-dosed Ag+ ions combined with Cl- ions that were present in the incoming water. Overall, CSI aims to control Legionella bacteria in drinking water, but plumbing material interactions, aesthetics and other implications also deserve consideration to holistically evaluate in-building drinking water disinfection. To inform the

  16. Attosecond pulse formation via switching of resonant interaction by tunnel ionization

    NASA Astrophysics Data System (ADS)

    Antonov, V. A.; Akhmedzhanov, T. R.; Radeonychev, Y. V.; Kocharovskaya, Olga

    2015-02-01

    We derive an analytical solution uncovering the origin of few-cycle attosecond pulse formation from vacuum-ultraviolet (VUV) radiation in an atomic gas simultaneously irradiated by a moderately strong infrared (IR) laser field, which does not perturb atoms in the ground state, but induces rapid quasistatic ionization from the excited states [Polovinkin et al., Opt. Lett. 36, 2296 (2011), 10.1364/OL.36.002296]. The derived solution shows that the pulses are produced due to periodic switching of the resonant interaction between the incident VUV radiation and the atoms: turning it off near the crests of the IR-field strength and switching it back on near the IR-field zero crossings. We extend the method originally proposed by Polovinkin et al. [Opt. Lett. 36, 2296 (2011), 10.1364/OL.36.002296] to non-hydrogen-like media and show that the pulses can be produced from resonant VUV radiation in a variety of atomic gases. The pulses are nearly bandwidth limited without external adjustment of phases of the generated sidebands. Proximity of the carrier frequency of the produced pulses to intra-atomic resonances may allow their efficient utilization for nondestructive steering of ultrafast dynamics of the bound electrons. The experimental possibilities for attosecond pulse formation from 58.4 nm VUV radiation in helium and from 73.6 nm VUV radiation in neon dressed by the 3.9 μm laser field, as well as from 122 nm VUV radiation in atomic hydrogen dressed by C O2 -laser field are discussed.

  17. Determination of Isoflavone Content in SRM 3238 Using Liquid Chromatography-Particle Beam/Electron Ionization Mass Spectrometry

    PubMed Central

    Zhang, Lynn X.; Burdette, Carolyn Q.; Phillips, Melissa M.; Rimmer, Catherine A.; Marcus, R. Kenneth

    2016-01-01

    The characterization of marker components in botanical materials is a challenging task and the increased consumption of botanicals and dietary supplements demands a greater understanding of the associated health benefits and risks. In order to successfully acquire and compare clinical results and correlate health trends, accurate, precise, and validated methods of analysis must be developed. Presented here is the development of a quantitative method for the determination of soy isoflavones (daidzin, glycitin, genistin, daidzein, and genistein) using liquid chromatography-particle beam/electron ionization mass spectrometry (LC-PB/EIMS). An internal standard (IS) approach for quantitation using 7-hydroxy-4-chromone as the IS compound was employed, with response factors for each individual isoflavone obtained from calibrant solutions. The results from this method were compared with the certified and reference values for NIST SRM 3238 Soy-Containing Solid Oral Dosage Form to demonstrate that the method was in control. Results obtained using LC-PB/EIMS were consistent with the NIST certified or reference values and their uncertainties for all five isoflavones, demonstrating that the LC-PB/EIMS approach is both accurate and precise when used for the determination of the target isoflavones in soy-containing dietary supplement finished products, while simultaneously providing structural information. PMID:26651559

  18. Spin-dependent effects in high-order above-threshold ionization: spin-orbit interaction and exchange effects

    NASA Astrophysics Data System (ADS)

    Milošević, D. B.

    2017-08-01

    Spin-dependent effects in atomic processes can be caused by the spin-orbit interaction or/and by the requirement that the wave function of identical electrons is antisymmetric. Such effects are usually neglected in strong-field physics. We show two examples, supported by theoretical results and numerical calculations, in which these effects are important. The first one is based on strong-field ionization of Xe atoms by a bicircular field. The corresponding momentum distribution of spin-polarized electrons emitted in the above-threshold ionization process exhibits wavelength-dependent fast oscillations. For longer wavelengths and small electron emission angle there is a wide photoelectron kinetic energy region in which the spin asymmetry parameter changes continuously from large positive to large negative values. In addition, the emission time of such electrons in high-order above-threshold ionization is determined on the attosecond time scale. The second process considered is high-order above-threshold ionization of excited Li+ ions. We have found that in this case, even in the absence of spin-orbit coupling, the photoelectron momentum distribution strongly depends on the initial spin state. In the singlet state we have characteristic minima, which are caused by the destructive interference of the direct and exchange rescattering amplitudes. Such minima are absent in the triplet state.

  19. Strong-field ionization rates of linear polyenes simulated with time-dependent configuration interaction with an absorbing potential

    SciTech Connect

    Krause, Pascal; Schlegel, H. Bernhard

    2014-11-07

    The strong field ionization rates for ethylene, trans 1,3-butadiene, and trans,trans 1,3,5-hexatriene have been calculated using time-dependent configuration interaction with single excitations and a complex absorbing potential (TDCIS-CAP). The calculations used the aug-cc-pVTZ basis set with a large set of diffuse functions (3 s, 2 p, 3 d, and 1 f) on each atom. The absorbing boundary was placed 3.5 times the van der Waals radius from each atom. The simulations employed a seven-cycle cosine squared pulse with a wavelength of 800 nm. Ionization rates were calculated for intensities ranging from 0.3 × 10{sup 14} W/cm{sup 2} to 3.5 × 10{sup 14} W/cm{sup 2}. Ionization rates along the molecular axis increased markedly with increasing conjugation length. By contrast, ionization rates perpendicular to the molecular axis were almost independent of the conjugation length.

  20. Weakly interacting massive particle-nucleus elastic scattering response

    NASA Astrophysics Data System (ADS)

    Anand, Nikhil; Fitzpatrick, A. Liam; Haxton, W. C.

    2014-06-01

    Background: A model-independent formulation of weakly interacting massive particle (WIMP)-nucleon scattering was recently developed in Galilean-invariant effective field theory. Purpose: Here we complete the embedding of this effective interaction in the nucleus, constructing the most general elastic nuclear cross section as a factorized product of WIMP and nuclear response functions. This form explicitly defines what can and cannot be learned about the low-energy constants of the effective theory—and consequently about candidate ultraviolet theories of dark matter—from elastic scattering experiments. Results: We identify those interactions that cannot be reliably treated in a spin-independent/spin-dependent (SI/SD) formulation: For derivative- or velocity-dependent couplings, the SI/SD formulation generally mischaracterizes the relevant nuclear operator and its multipolarity (e.g., scalar or vector) and greatly underestimates experimental sensitivities. This can lead to apparent conflicts between experiments when, in fact, none may exist. The new nuclear responses appearing in the factorized cross section are related to familiar electroweak nuclear operators such as angular momentum l⃗(i) and the spin-orbit coupling σ⃗(i).l⃗(i). Conclusions: To unambiguously interpret experiments and to extract all of the available information on the particle physics of dark matter, experimentalists will need to (1) do a sufficient number of experiments with nuclear targets having the requisite sensitivities to the various operators and (2) analyze the results in a formalism that does not arbitrarily limit the candidate operators. In an appendix we describe a code that is available to help interested readers implement such an analysis.

  1. Raman scattering investigation of VOCs in interaction with ice particles

    NASA Astrophysics Data System (ADS)

    Facq, Sébastien; Oancea, Adriana; Focsa, Cristian; Chazallon, Bertrand

    2010-05-01

    Cirrus clouds that form in the Earth's upper troposphere (UT) are known to play a significant role in the radiation budget and climate [1]. These clouds that cover about 35% of the Earth's surface [2] are mainly composed of small ice particles that can provide surfaces for trace gas interactions [3]. Volatile Organic Compounds (VOCs) are present in relative high abundance in the UT [4][5]. They promote substantial sources of free OH radicals that are responsible for driving photochemical cycles in the atmosphere. Their presence can both influence the oxidizing capacity and the ozone budget of the atmosphere. VOCs can interact with ice particles via different trapping processes (adsorption, diffusion, freezing, and co-deposition, i.e., incorporation of trace gases during growing ice conditions) which can result in the perturbation of the chemistry and photochemistry of the UT. Knowledge of the incorporation processes of VOCs in ice particles is important in order to understand and predict their impact on the ice particles structure and reactivity and more generally on the cirrus cloud formation. This proceeds via the in-situ characterization of the ice condensed phase in a pressure and temperature range of the UT. An important mechanism of UT cirrus cloud formation is the heterogeneous ice freezing process. In this study, we examine and characterize the interaction of a VOC, i.e., ethanol (EtOH) with ice particles during freezing. Vibrational spectra of water O-H and EtOH C-H spectral regions are analysed using confocal micro-Raman spectroscopy. Information at the molecular level on the surface structure can be derived from accompanying changes observed in band shapes and vibrational mode frequencies. Depending of the EtOH content, different crystalline phases have been identified and compared to hydrates previously reported for the EtOH-water system. Particular attention is paid on the effect of EtOH aqueous solutions cooling rate and droplet sizes on the phases

  2. The calculation of ionization energies by perturbation, configuration interaction and approximate coupled pair techniques and comparisons with green's function methods for Ne, H 2O and N 2

    NASA Astrophysics Data System (ADS)

    Bacskay, George B.

    1980-05-01

    The vertical valence ionization potentials of Ne, H 2O and N 2 have been calculated by Rayleigh-Schrödinger perturbation and configuration interaction methods. The calculations were carried out in the space of a single determinant reference state and its single and double excitations, using both the N and N - 1 electron Hartree-Fock orbitals as hole/particle bases. The perturbation series for the ion state were generally found to converge fairly slowly in the N electron Hartree-Fock (frozen) orbital basis, but considerably faster in the appropriate N - 1 electron RHF (relaxed) orbital basis. In certain cases, however, due to near-degeneracy effects, partial, and even complete, breakdown of the (non-degenerate) perturbation treatment was observed. The effects of higher excitations on the ionization potentials were estimated by the approximate coupled pair techniques CPA' and CPA″ as well as by a Davidson type correction formula. The final, fully converged CPA″ results are generally in good agreement with those from PNO-CEPA and Green's function calculations as well as experiment.

  3. Magnetic interaction of Janus magnetic particles suspended in a viscous fluid.

    PubMed

    Seong, Yujin; Kang, Tae Gon; Hulsen, Martien A; den Toonder, Jaap M J; Anderson, Patrick D

    2016-02-01

    We studied the magnetic interaction between circular Janus magnetic particles suspended in a Newtonian fluid under the influence of an externally applied uniform magnetic field. The particles are equally compartmentalized into paramagnetic and nonmagnetic sides. A direct numerical scheme is employed to solve the magnetic particulate flow in the Stokes flow regime. Upon applying the magnetic field, contrary to isotropic paramagnetic particles, a single Janus particle can rotate due to the magnetic torque created by the magnetic anisotropy of the particle. In a two-particle problem, the orientation of each particle is found to be an additional factor that affects the critical angle separating the nature of magnetic interaction. Using multiparticle problems, we show that the orientation of the particles has a significant influence on the dynamics of the particles, the fluid flow induced by the actuated particles, and the final conformation of the particles. Straight and staggered chain structures observed experimentally can be reproduced numerically in a multiple particle problem.

  4. A new mechanism for relativistic particle acceleration via wave-particle interaction

    NASA Astrophysics Data System (ADS)

    Lapenta, Giovanni; Markidis, Stefano; Marocchino, Alberto

    2006-10-01

    Often in laboratory, space and astrophysical plasma, high energy populations are observed. Two puzzling factors still defy our understanding. First, such populations of high energy particles produce power law distributions that are not only ubiquitous but also persistent in time. Such persistence is in direct contradiction to the H theorem that states the ineluctable transition of physical systems towards thermodynamic equilibrium, and ergo Maxwellian distributions. Second, such high energy populations are efficiently produced, much more efficiently than processes that we know can produce. A classic example of such a situation is cosmic rays where power alws extend up to tremendolus energy ranges. In the present work, we identify a new mechanism for particle acceleration via wave-particle interaction. The mechanism is peculiar to special relativity and has no classical equivalent. That explains why it is not observed in most simulation studies of plasma processes, based on classical physics. The mechanism is likely to be active in systems undergoing streaming instabilities and in particular shocked systems. The new mechanism can produce energy increases vastly superior to previously known mechanisms (such as Fermi acceleration) and can hold the promise of explaining at least some of the observed power laws.

  5. The effect of particle-particle interaction forces on the flow properties of silica slurries

    SciTech Connect

    Harbottle, David; Fairweather, Michael; Biggs, Simon; Rhodes, Dominic

    2007-07-01

    Preliminary work has been completed to investigate the effect of particle-particle interaction forces on the flow properties of silica slurries. Classically hydro-transport studies have focused on the flow of coarse granular material in Newtonian fluids. However, with current economical and environmental pressures, the need to increase solid loadings in pipe flow has lead to studies that examine non-Newtonian fluid dynamics. The flow characteristics of non-Newtonian slurries can be greatly influenced through controlling the solution chemistry. Here we present data on an 'ideal' slurry where the particle size and shape is controlled together with the solution chemistry. We have investigated the effect of adsorbed cations on the stability of a suspension, the packing nature of a sediment and the frictional forces to be overcome during re-slurrying. A significant change in the criteria assessed was observed as the electrolyte concentration was increased from 0.1 mM to 1 M. In relation to industrial processes, such delicate control of the slurry chemistry can greatly influence the optimum operating conditions of non-Newtonian pipe flows. (authors)

  6. Threshold separation distance for attractive interaction between dust particles

    SciTech Connect

    Jabdaraghi, R. Najafi; Sobhanian, S.

    2008-09-07

    Interaction between dust grains in a dusty plasma could be both repulsive and attractive. The Coulomb interaction between two negatively charged dust particulates and the electrostatic force between them are repulsive, while the shadowing force affecting them is attractive. We show in this paper that in some experimental conditions, there is some grain separation zone for which the attractive shadowing force is larger than the repulsive forces between them. In experimental conditions, for the grains separation distance r = 0.4 cm the shadowing force is almost equal to the electrostatic force between them and for r>0.4 cm the shadowing force exceeds the electrostatic force. So the resultant interaction force will be attractive. The possibility of dust crystal formation in this zone and also the motion of dust particles in the resultant potential of the form V = -(a/r)+(b/r{sup 2}) will be discussed. This form of potential comes from the combination electrostatic (F{sub es} (c/r{sup 3})) and shadowing (F{sub shadow} = -(d/r{sup 2})) forces.

  7. Foamy Virus Protein—Nucleic Acid Interactions during Particle Morphogenesis

    PubMed Central

    Hamann, Martin V.; Lindemann, Dirk

    2016-01-01

    Compared with orthoretroviruses, our understanding of the molecular and cellular replication mechanism of foamy viruses (FVs), a subfamily of retroviruses, is less advanced. The FV replication cycle differs in several key aspects from orthoretroviruses, which leaves established retroviral models debatable for FVs. Here, we review the general aspect of the FV protein-nucleic acid interactions during virus morphogenesis. We provide a summary of the current knowledge of the FV genome structure and essential sequence motifs required for RNA encapsidation as well as Gag and Pol binding in combination with details about the Gag and Pol biosynthesis. This leads us to address open questions in FV RNA engagement, binding and packaging. Based on recent findings, we propose to shift the point of view from individual glycine-arginine-rich motifs having functions in RNA interactions towards envisioning the FV Gag C-terminus as a general RNA binding protein module. We encourage further investigating a potential new retroviral RNA packaging mechanism, which seems more complex in terms of the components that need to be gathered to form an infectious particle. Additional molecular insights into retroviral protein-nucleic acid interactions help us to develop safer, more specific and more efficient vectors in an era of booming genome engineering and gene therapy approaches. PMID:27589786

  8. Particle-in-Cell Simulations of Electron-Impact and Tunneling Ionization Effects for Beam-Plasma and Laser-Plasma Applications

    NASA Astrophysics Data System (ADS)

    Bruhwiler, David

    2002-11-01

    Laser-driven (LWFA) and beam-driven (PWFA) plasma accelerators can sustain electron plasma waves with longitudinal electric fields on the order of the nonrelativistic wave breaking field, which is routinely of order 100 GV/m in table-top LWFA experiments. The laser pulse can create its own plasma from a gas jet via field-induced tunneling ionization of the neutral atoms, which leads to blue-shifting at the leading edge of the pulse, as well as steepening due to pump depletion and other effects. Tunneling ionization is also a critical issue for some proposed PWFA experiments, with gradients exceeding 5 GV/m. In addition, electron impact ionization can lead to important effects like particle trapping in PWFA concepts. We will present simulation results from the particle-in-cell code OOPIC [D.L. Bruhwiler et al., Phys. Rev. S.T. A, Issue 10 (2001); www.techxhome.com/products/oopic/], which demonstrate the physical effects of these ionization processes in a few interesting cases, including detailed comparison with experiments from the l'OASIS lab at LBNL [W.P. Leemans et al., Phys. Plasmas 8, 2510 (2001)] and a brief discussion of the algorithms.

  9. Particle acceleration at corotating interaction regions in the heliosphere

    SciTech Connect

    Tsubouchi, K.

    2014-11-01

    Hybrid simulations are performed to investigate the dynamics of both solar wind protons and interplanetary pickup ions (PUIs) around the corotating interaction region (CIR). The one-dimensional system is applied in order to focus on processes in the direction of CIR propagation. The CIR is bounded by forward and reverse shocks, which are responsible for particle acceleration. The effective acceleration of solar wind protons takes place when the reverse shock (fast wind side) favors a quasi-parallel regime. The diffusive process accounts for this acceleration, and particles can gain energy in a suprathermal range (on the order of 10 keV). In contrast, the PUI acceleration around the shock differs from the conventional model in which the motional electric field along the shock surface accelerates particles. Owing to their large gyroradius, PUIs can gyrate between the upstream and downstream, several proton inertial lengths away from the shock. This 'cross-shock' gyration results in a net velocity increase in the field-aligned component, indicating that the magnetic mirror force is responsible for acceleration. The PUIs that remain in the vicinity of the shock for a long duration (tens of gyroperiods) gain much energy and are reflected back toward the upstream. These reflected energetic PUIs move back and forth along the magnetic field between a pair of CIRs that are magnetically connected. The PUIs are repeatedly accelerated in each reflection, leading to a maximum energy gain close to 100 keV. This mechanism can be evaluated in terms of 'preacceleration' for the generation of anomalous cosmic rays.

  10. Coupled electrostatic and material surface stresses yield anomalous particle interactions and deformation

    SciTech Connect

    Kemp, B. A. Nikolayev, I.; Sheppard, C. J.

    2016-04-14

    Like-charges repel, and opposite charges attract. This fundamental tenet is a result of Coulomb's law. However, the electrostatic interactions between dielectric particles remain topical due to observations of like-charged particle attraction and the self-assembly of colloidal systems. Here, we show, using both an approximate description and an exact solution of Maxwell's equations, that nonlinear charged particle forces result even for linear material systems and can be responsible for anomalous electrostatic interactions such as like-charged particle attraction and oppositely charged particle repulsion. Furthermore, these electrostatic interactions and the deformation of such particles have fundamental implications for our understanding of macroscopic electrodynamics.

  11. Soft particle production in very high energy hadron interactions

    NASA Astrophysics Data System (ADS)

    Ebr, Jan; Nečesal, Petr; Ridky, Jan

    2017-04-01

    Indications of a discrepancy between simulations and data on the number of muons in cosmic ray (CR) showers exist over a large span of energies. We focus in particular on the excess of multi-muon bundles observed by the DELPHI detector at LEP and on the excess in the muon number in general reported by the Pierre Auger Observatory. Even though the primary CR energies relevant for these experiments differ by orders of magnitude, we can find a single mechanism which can simultaneously increase predicted muon counts for both, while not violating constraints from accelerators or from the longitudinal shower development as observed by the Pierre Auger Observatory. We present a brief motivation and describe a practical implementation of such a model, based on the addition of soft particles to interactions above a chosen energy threshold. Results of an extensive set of simulations show the behavior of this model in various parts of a simplified parameter space.

  12. Atoms and Ions Interacting with Particles and Fields: Final Report

    SciTech Connect

    Robicheaux, Francis

    2014-09-18

    This grant supported research in basic atomic, molecular and optical physics related to the interactions of atoms with particles and fields. The duration of the grant was the 10 year period from 8/2003 to 8/2013. All of the support from the grant was used to pay salaries of the PI, postdocs, graduate students, and undergraduates and travel to conferences and meetings. The results were in the form of publications in peer reviewed journals. There were 65 peer reviewed publications over these 10 years with 8 of the publications in Physical Review Letters; all of the other articles were in respected peer reviewed journals (Physical Review A, New Journal of Physics, Journal of Physics B, ...). I will disuss the results for the periods of time relevant for each grant period.

  13. Aerosol mass spectrometry: particle-vaporizer interactions and their consequences for the measurements

    NASA Astrophysics Data System (ADS)

    Drewnick, F.; Diesch, J.-M.; Faber, P.; Borrmann, S.

    2015-04-01

    The Aerodyne Aerosol Mass Spectrometer (AMS) is a frequently used instrument for on-line measurement of the ambient sub-micron aerosol composition. With the help of calibrations and a number of assumptions on the flash vaporization and electron impact ionization processes this instrument provides robust quantitative information on various ambient aerosol components. However, when measuring close to certain anthropogenic sources or in marine environments, several of these assumptions may not be met and measurement results might easily be misinterpreted. Here we discuss various aspects of the interaction of aerosol particles with the AMS tungsten vaporizer and the consequences for the measurement results: semi-refractory components, i.e. components that vaporize but do not flash vaporize at the vaporizer and ionizer temperatures, like metal halides (e.g. chlorides, bromides or iodides of Al, Ba, Cd, Cu, Fe, Hg, K, Na, Pb, Sr, Zn) can be measured semi-quantitatively despite their relatively slow vaporization from the vaporizer. Even though non-refractory components (e.g. NH4NO3 or (NH4)2SO4) vaporize quickly, their differences in vaporization kinetics can result in undesired biases in ion collection efficiency in the measurements. Chemical reactions with water vapor and oxygen from the aerosol flow can have an influence on the mass spectra for certain components (e.g. NH4NO3, (NH4)2SO4, organic species). Finally, chemical reactions of the aerosol with the vaporizer surface can result in additional signals in the mass spectra (e.g. WO2C2-related signals from particulate Cl) and in conditioning or contamination of the vaporizer with potential memory effects influencing the mass spectra of subsequent measurements. Laboratory experiments that investigate these particle-vaporizer interactions are presented and are discussed together with field results showing that measurements of typical continental or urban aerosols are not significantly affected while laboratory

  14. Aerosol mass spectrometry: particle-vaporizer interactions and their consequences for the measurements

    NASA Astrophysics Data System (ADS)

    Drewnick, F.; Diesch, J.-M.; Faber, P.; Borrmann, S.

    2015-09-01

    The Aerodyne aerosol mass spectrometer (AMS) is a frequently used instrument for on-line measurement of the ambient sub-micron aerosol composition. With the help of calibrations and a number of assumptions on the flash vaporization and electron impact ionization processes, this instrument provides robust quantitative information on various non-refractory ambient aerosol components. However, when measuring close to certain anthropogenic or marine sources of semi-refractory aerosols, several of these assumptions may not be met and measurement results might easily be incorrectly interpreted if not carefully analyzed for unique ions, isotope patterns, and potential slow vaporization associated with semi-refractory species. Here we discuss various aspects of the interaction of aerosol particles with the AMS tungsten vaporizer and the consequences for the measurement results: semi-refractory components - i.e., components that vaporize but do not flash-vaporize at the vaporizer and ionizer temperatures, like metal halides (e.g., chlorides, bromides or iodides of Al, Ba, Cd, Cu, Fe, Hg, K, Na, Pb, Sr, Zn) - can be measured semi-quantitatively despite their relatively slow vaporization from the vaporizer. Even though non-refractory components (e.g., NH4NO3 or (NH4)2SO4) vaporize quickly, under certain conditions their differences in vaporization kinetics can result in undesired biases in ion collection efficiency in thresholded measurements. Chemical reactions with oxygen from the aerosol flow can have an influence on the mass spectra for certain components (e.g., organic species). Finally, chemical reactions of the aerosol with the vaporizer surface can result in additional signals in the mass spectra (e.g., WO2Cl2-related signals from particulate Cl) and in conditioning or contamination of the vaporizer, with potential memory effects influencing the mass spectra of subsequent measurements. Laboratory experiments that investigate these particle-vaporizer interactions are

  15. Dynamics of particle--turbulence interaction at the dissipative scales

    NASA Astrophysics Data System (ADS)

    Bocanegra Evans, Humberto; Dam, Nico; van de Water, Willem; JM Burgerscentrum Collaboration; COST Action, Particles in Turbulence Collaboration

    2013-11-01

    We present results of a novel phosphorescent tagging technique that is particularly suited to study particle-laden flows. Using phosphorescent droplets we probe the dynamics of particle-turbulence interaction at the dissipative length scales. We create a cloud of droplets within a chamber capable of generating homogeneous, isotropic turbulence with zero-mean flow. The droplets have Stokes number St ~ 1 , and the flow is intensely turbulent, with Reynolds number Reλ ~ 500 . Using a frequency-tripled Nd:YAG laser, we can tag a variety of volumes, such as thin slabs or thin, pencil-like cylinders. The droplets in these volumes glow during a few Kolmogorov times. By tracking the fate of pencil-shaped clouds using a fast (5 kHz) camera, we come to the surprising conclusion that they disperse faster than fluid elements, with a spreading rate reaching a maximum at St ~ 2 . Sheets of tagged droplets display preferential concentration at work; we discuss statistical quantities that can capture these events. This project is funded by Fundamenteel Onderzoek der Materie (FOM).

  16. Microscopic theory of polymer-mediated interactions between spherical particles

    SciTech Connect

    Chatterjee, A.P.; Schweizer, K.S.

    1998-12-01

    We develop an analytic integral equation theory for treating polymer-induced effects on the structure and thermodynamics of dilute suspensions of hard spheres. Results are presented for the potential of mean force, free energy of insertion per particle into a polymer solution, and the second virial coefficient between spheres. The theory makes predictions for all size ratios between the spheres and the polymer coil dimension. Based on the Percus{endash}Yevick (PY) closure, the attractive polymer-induced depletion interaction is predicted to be too weak under athermal conditions to induce a negative value for the second virial coefficient, B{sub 2}{sup cc}, between spheres in the colloidal limit when the spheres are much larger than the coil size. A nonmonotonic dependence of the second virial coefficient on polymer concentration occurs for small enough particles, with the largest polymer-mediated attractions and most negative B{sub 2}{sup cc} occurring near the dilute{endash}semidilute crossover concentration. Predictions for the polymer-mediated force between spheres are compared to the results of computer simulations and scaling theory. {copyright} {ital 1998 American Institute of Physics.}

  17. Interaction of Escherichia coli and Soil Particles in Runoff

    PubMed Central

    Muirhead, Richard William; Collins, Robert Peter; Bremer, Philip James

    2006-01-01

    A laboratory-scale model system was developed to investigate the transport mechanisms involved in the horizontal movement of bacteria in overland flow across saturated soils. A suspension of Escherichia coli and bromide tracer was added to the model system, and the bromide concentration and number of attached and unattached E. coli cells in the overland flow were measured over time. Analysis of the breakthrough curves indicated that the E. coli and bromide were transported together, presumably by the same mechanism. This implied that the E. coli was transported by advection with the flowing water. Overland-flow transport of E. coli could be significantly reduced if the cells were preattached to large soil particles (>45 μm). However, when unattached cells were inoculated into the system, the E. coli appeared to attach predominantly to small particles (<2 μm) and hence remained unattenuated during transport. These results imply that in runoff generated by saturation-excess conditions, bacteria are rapidly transported across the surface and have little opportunity to interact with the soil matrix. PMID:16672484

  18. A Massively Parallel Particle Code for Rarefied Ionized and Neutral Gas Flows in Earth and Planetary Atmospheres, Ionospheres and Magnetospheres

    NASA Technical Reports Server (NTRS)

    Combi, Michael R.

    2004-01-01

    In order to understand the global structure, dynamics, and physical and chemical processes occurring in the upper atmospheres, exospheres, and ionospheres of the Earth, the other planets, comets and planetary satellites and their interactions with their outer particles and fields environs, it is often necessary to address the fundamentally non-equilibrium aspects of the physical environment. These are regions where complex chemistry, energetics, and electromagnetic field influences are important. Traditional approaches are based largely on hydrodynamic or magnetohydrodynamic MHD) formulations and are very important and highly useful. However, these methods often have limitations in rarefied physical regimes where the molecular collision rates and ion gyrofrequencies are small and where interactions with ionospheres and upper neutral atmospheres are important.

  19. Highly asymmetric interactions between globin chains during hemoglobin assembly revealed by electrospray ionization mass spectrometry.

    PubMed

    Griffith, Wendell P; Kaltashov, Igor A

    2003-08-26

    Dynamics of bovine hemoglobin assembly was investigated by monitoring monomers/oligomers equilibria in solution with electrospray ionization mass spectrometry and circular dichroism spectroscopy. Intensities of ionic signals corresponding to various protein species (tetramers, dimers, heme-deficient dimers, as well as apo- and holo-monomers) were used to estimate relative fractions of these species in solution as a function of pH. The fraction of folded protein for each observed species was estimated based on charge-state distributions of corresponding ionic species in the mass spectra. The cumulative numbers (averaged across the entire protein population) were in good agreement with circular dichroism data at the Soret band and in the far-UV region, respectively. The mass spectral data confirm that hemoglobin dissociation involves a step where heme is first lost from the beta-chain of the alpha beta-dimer to form a heme-deficient dimeric species. This dimer dissociates further to produce a holo-alpha-chain and an apo-beta-chain. The former is tightly folded into a comparatively compact structure at neutral pH, while the latter always exhibits significant backbone disorder. Acidification of the protein solution to pH 4 leads to partial heme dissociation and significant increase of the backbone flexibility in the alpha-chains as well. Complete dissociation of the heme from the alpha-chains at a pH below 4 coincides with the total disappearance of the dimeric and tetrameric hemoglobin species from the mass spectra. The experimental data provide strong evidence that binding of a partially unstructured apo-beta-chain to a tightly folded holo-alpha-chain to form a heme-deficient dimer is the initial step of hemoglobin assembly. Such binding locks the beta-chain in a highly ordered conformation, which allows for an efficient heme acquisition, followed by docking of two hemoglobin dimers to form a tetrameric form of the protein. The asymmetry of the roles of the two

  20. Theoretical and experimental examination of particle-particle interaction effects on induced dipole moments and dielectrophoretic responses of multiple particle chains.

    PubMed

    Moncada-Hernandez, Hector; Nagler, Eliot; Minerick, Adrienne R

    2014-07-01

    Dielectrophoresis (DEP), an electrokinetic phenomenon based on particle polarizations in nonuniform electric fields, is increasingly employed for particle and cell characterizations and manipulations in microdevices. However, particle number densities are rarely varied and particle-particle interactions are largely overlooked, but both affect particle's effective polarizations by changing the local electric field, which directly impacts particle assembly into chains. This work examines theoretical and experimental particle-particle interactions and dielectrophoretic responses in nonuniform electric fields, then presents individual and chain velocities of spherical polystyrene microparticles and red blood cells (RBCs) under DEP forces in a modified quadruple electrode microdevice. Velocities are independently compared between 1, 2, 3, and 4 polystyrene beads and RBCs assembled into chains aligned with the electric field. Simulations compared induced dipole moments for particles experiencing the same (single point) and changing (multiple points) electric fields. Experiments and simulations are compared by plotting DEP velocities versus applied signal frequency from 1 kHz to 80 MHz. Simulations indicate differences in the DEP force exerted on each particle according to chain position. Simulations and experiments show excellent qualitative agreement; chains with more particles experienced a decrease in the DEP response for both polystyrene beads and RBCs. These results advance understanding of the extent that induced dipole polarizations with multiple particle chains affect observed behaviors in electrokinetic cellular diagnostic systems.

  1. Search for highly ionizing particles in e/sup +/e/sup -/ collisions at. sqrt. s-bar = 29 GeV

    SciTech Connect

    Kinoshita, K.; Price, P.B.; Fryberger, D.

    1982-01-11

    In a search for highly ionizing particles at PEP, Lexan and CR-39 plastic track detectors were exposed to an integrated luminosity of approx.10/sup 37/ cm/sup -2/ at an energy of 29 GeV in the center of mass. The search was sensitive to particles with magnetic charge 20e< or approx. =g< or approx. =200e or electric charge 3< or approx. =Z< or approx. =180. An upper limit on the production cross section of sigma<0.9 x 10/sup -36/ cm/sup 2/ (95% C.L.) is obtained.

  2. High-Resolution Electrospray Ionization Mass Spectrometry Analysis of Water- Soluble Organic Aerosols Collected with a Particle into Liquid Sampler

    SciTech Connect

    Bateman, Adam P.; Nizkorodov, Serguei; Laskin, Julia; Laskin, Alexander

    2010-10-01

    This work demonstrates the utility of a particle-into-liquid sampler (PILS) a technique traditionally used for identification of inorganic ions present in ambient or laboratory aerosols for the analysis of water soluble organic aerosol (OA) using high resolution electrospray ionization mass spectrometry (HR ESI-MS). Secondary organic aerosol (SOA) was produced from 0.5 ppm mixing ratios of limonene and ozone in a 5 m3 Teflon chamber. SOA was collected simultaneously using a traditional filter sampler and a PILS. The filter samples were later extracted with either water or acetonitrile, while the aqueous PILS samples were analyzed directly. In terms of peak intensities, types of detectable compounds, average O:C ratios, and organic mass to organic carbon ratios, the resulting high resolution mass spectra were essentially identical for the PILS and filter based samples. SOA compounds extracted from both filter/acetonitrile extraction and PILS/water extraction accounted for >95% of the total ion current in ESI mass spectra. This similarity was attributed to high solubility of limonene SOA in water. In contrast, significant differences in detected ions and peak abundances were observed for pine needle biomass burning organic aerosol (BBOA) collected with PILS and filter sampling. The water soluble fraction of BBOA is considerably smaller than for SOA, and a number of unique peaks were detectable only by the filter/acetonitrile method. The combination of PILS collection with HR-ESI-MS analysis offers a new approach for molecular analysis of the water-soluble organic fraction in biogenic SOA, aged photochemical smog, and BBOA.

  3. Acoustically mediated long-range interaction among multiple spherical particles exposed to a plane standing wave

    NASA Astrophysics Data System (ADS)

    Zhang, Shenwei; Qiu, Chunyin; Wang, Mudi; Ke, Manzhu; Liu, Zhengyou

    2016-11-01

    In this work, we study the acoustically mediated interaction forces among multiple well-separated spherical particles trapped in the same node or antinode plane of a standing wave. An analytical expression of the acoustic interaction force is derived, which is accurate even for the particles beyond the Rayleigh limit. Interestingly, the multi-particle system can be decomposed into a series of independent two-particle systems described by pairwise interactions. Each pairwise interaction is a long-range interaction, as characterized by a soft oscillatory attenuation (at the power exponent of n = -1 or -2). The vector additivity of the acoustic interaction force, which is not well expected considering the nonlinear nature of the acoustic radiation force, is greatly useful for exploring a system consisting of a large number of particles. The capability of self-organizing a big particle cluster can be anticipated through such acoustically controllable long-range interaction.

  4. Calculating the Annihilation Rate of Weakly Interacting Massive Particles

    NASA Astrophysics Data System (ADS)

    Baumgart, Matthew; Rothstein, Ira Z.; Vaidya, Varun

    2015-05-01

    We develop a formalism that allows one to systematically calculate the weakly interacting massive particle (WIMP) annihilation rate into gamma rays whose energy far exceeds the weak scale. A factorization theorem is presented which separates the radiative corrections stemming from initial-state potential interactions from loops involving the final state. This separation allows us to go beyond the fixed order calculation, which is polluted by large infrared logarithms. For the case of Majorana WIMPs transforming in the adjoint representation of SU(2), we present the result for the resummed rate at leading double-log accuracy in terms of two initial-state partial-wave matrix elements and one hard matching coefficient. For a given model, one may calculate the cross section by finding the tree level matching coefficient and determining the value of a local four-fermion operator. The effects of resummation can be as large as 100% for a 20 TeV WIMP. However, for lighter WIMP masses relevant for the thermal relic scenario, leading-log resummation modifies the Sudakov factors only at the 10% level. Furthermore, given comparably sized Sommerfeld factors, the total effect of radiative corrections on the semi-inclusive photon annihilation rate is found to be percent level. The generalization of the formalism to other types of WIMPs is discussed.

  5. Feebly interacting dark matter particle as the inflaton

    NASA Astrophysics Data System (ADS)

    Tenkanen, Tommi

    2016-09-01

    We present a scenario where a Z 2-symmetric scalar field ϕ first drives cosmic inflation, then reheats the Universe but remains out-of-equilibrium itself, and finally comprises the observed dark matter abundance, produced by particle decays à la freeze-in mechanism. We work model-independently without specifying the interactions of the scalar field besides its self-interaction coupling, λϕ 4, non-minimal coupling to gravity, ξϕ 2 R, and coupling to another scalar field, gϕ 2 σ 2. We find the scalar field ϕ serves both as the inflaton and a dark matter candidate if 10-9 ≲ λ ≲ g ≲ 10-7 and 3 keV ≲ m ϕ ≲ 85 MeV for ξ ={O}(1) . Such a small value of the non-minimal coupling is also found to be of the right magnitude to produce the observed curvature perturbation amplitude within the scenario. We also discuss how the model may be distinguished from other inflationary models of the same type by the next generation CMB satellites.

  6. Direct isotope ratio analysis of individual uranium-plutonium mixed particles with various U/Pu ratios by thermal ionization mass spectrometry.

    PubMed

    Suzuki, Daisuke; Esaka, Fumitaka; Miyamoto, Yutaka; Magara, Masaaki

    2015-02-01

    Uranium and plutonium isotope ratios in individual uranium-plutonium (U-Pu) mixed particles with various U/Pu atomic ratios were analyzed without prior chemical separation by thermal ionization mass spectrometry (TIMS). Prior to measurement, micron-sized particles with U/Pu ratios of 1, 5, 10, 18, and 70 were produced from uranium and plutonium certified reference materials. In the TIMS analysis, the peaks of americium, plutonium, and uranium ion signals were successfully separated by continuously increasing the evaporation filament current. Consequently, the uranium and plutonium isotope ratios, except the (238)Pu/(239)Pu ratio, were successfully determined for the particles at all U/Pu ratios. This indicates that TIMS direct analysis allows for the measurement of individual U-Pu mixed particles without prior chemical separation.

  7. Real-time gas and particle-phase organic acids measurement at a forest site using chemical ionization high-resolution time-of-flight mass spectrometry during BEACHON-RoMBAS

    NASA Astrophysics Data System (ADS)

    Yatavelli, L. R.; Stark, H.; Kimmel, J.; Cubison, M.; Day, D. A.; Jayne, J.; Thornton, J. A.; Worsnop, D. R.; Jimenez, J. L.

    2011-12-01

    We present measurement of organic acids in gas and aerosol particles conducted in a ponderosa pine forest during July and August 2011 as part of the Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen - Rocky Mountain Biogenic Aerosol Study (BEACHON-RoMBAS; http://tinyurl.com/BEACHON-RoMBAS). The measurement technique is based on chemical ionization, high-resolution time-of-flight mass spectrometry and utilizes a Micro-Orifice Volatilization Impactor [MOVI-CI-HR-ToFMS; Yatavelli et al., AS&T, 2010] to collect sub-micron aerosol particles while simultaneously measuring the gas-phase composition. The collected particles are subsequently analyzed by temperature-programmed thermal desorption. The reagent ion chosen for this campaign is the acetate anion (CH3C(O)O-, m/z 59), which reacts selectively via proton transfer with compounds that are stronger gas-phase acids than acetic acid [Veres et al., IJMS, 2008]. Preliminary results show substantial particle-phase concentrations of biogenic oxidation products such as hydroxy-glutaric acid, pinic acid, pinonic acid, and hydroxy-pinonic acid along with numerous lower and higher molecular weight organic acids. Correlations of the organic acid concentrations with meteorological, gas and aerosol parameters measured by other instrumentation are investigated in order to understand the formation, transformation, and partitioning of gas and particle-phase organic acids in a forested environment dominated by terpenes.

  8. Dynamically Tuning Particle Interactions and Assemblies at Soft Interfaces: Reversible Order-Disorder Transitions in 2D Particle Monolayers.

    PubMed

    Park, Bum Jun; Lee, Daeyeon

    2015-09-16

    Particles trapped at fluid interfaces experience long-range interactions that determine their assembly behavior. Because particle interactions at fluid interfaces tend to be unusually strong, once particles organize themselves into a 2D assembly, it is challenging to induce changes in their microstructure. In this report, a new approach is presented to induce reversible order-disorder transitions (ODTs) in the 2D monolayer of colloidal particles trapped at a soft gel-fluid interface. Particles at the soft interface, consisting of a nonpolar superphase and a weakly gelled subphase, initially form a monolayer with a highly ordered structure. The structure of this monolayer can be dynamically varied by the addition or removal of the oil phase. Upon removing the oil via evaporation, the initially ordered particle monolayer undergoes ODT, driven by capillary attractions. The ordered monolayer can be recovered through disorder-to-order transition by simply adding oil atop the particle-laden soft interface. The possibility to dynamically tune the interparticle interactions using soft interfaces can potentially enable control of the transport and mechanical properties of particle-laden interfaces and provide model systems to study particle-laden soft interfaces that are relevant to biological tissues or organs.

  9. Effect of confining walls on the interaction between particles in a nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Fukuda, Jun-ichi; Lev, Bohdan I.; Yokoyama, Hiroshi

    2003-06-01

    We investigate theoretically how the confining walls of a nematic cell affect the interaction of particles mediated by the elastic deformation of a nematic liquid crystal. We consider the case where strong homeotropic or planar anchoring is imposed on the flat parallel walls so that the director on the wall surfaces is fixed and uniform alignment is achieved in the bulk. This set-up is more realistic experimentally than any other previous theoretical studies concerning the elastic-deformation-mediated interactions that assume an infinite medium. When the anchoring on the particle surfaces is weak, an exact expression of the interaction between two particles can be obtained. The two-body interaction can be regarded as the interaction between one particle and an infinite array of 'mirror images' of the other particle. We also obtain the 'self-energy' of one particle, the interaction of a particle with confining walls, which is interpreted along the same way as the interaction of one particle with its mirror images. We show that the walls play a different role in homeotropic and planar cells, which is attributed to the difference in the symmetry of the cells. We also present the landscapes of the interaction energy when one particle is fixed and demonstrate that the interaction is sensitively dependent on the fixed particle as well as the interparticle distance.

  10. Lubrication analysis of interacting rigid cylindrical particles in confined shear flow

    SciTech Connect

    Cardinaels, R.; Stone, H. A.

    2015-07-15

    Lubrication analysis is used to determine analytical expressions for the elements of the resistance matrix describing the interaction of two rigid cylindrical particles in two-dimensional shear flow in a symmetrically confined channel geometry. The developed model is valid for non-Brownian particles in a low-Reynolds-number flow between two sliding plates with thin gaps between the two particles and also between the particles and the walls. Using this analytical model, a comprehensive overview of the dynamics of interacting cylindrical particles in shear flow is presented. With only hydrodynamic interactions, rigid particles undergo a reversible interaction with no cross-streamline migration, irrespective of the confinement value. However, the interaction time of the particle pair substantially increases with confinement, and at the same time, the minimum distance between the particle surfaces during the interaction substantially decreases with confinement. By combining our purely hydrodynamic model with a simple on/off non-hydrodynamic attractive particle interaction force, the effects of confinement on particle aggregation are qualitatively mapped out in an aggregation diagram. The latter shows that the range of initial relative particle positions for which aggregation occurs is increased substantially due to geometrical confinement. The interacting particle pair exhibits tangential and normal lubrication forces on the sliding plates, which will contribute to the rheology of confined suspensions in shear flow. Due to the combined effects of the confining walls and the particle interaction, the particle velocities and resulting forces both tangential and perpendicular to the walls exhibit a non-monotonic evolution as a function of the orientation angle of the particle pair. However, by incorporating appropriate scalings of the forces, velocities, and doublet orientation angle with the minimum free fraction of the gap height and the plate speed, master curves for

  11. The interaction of solid particles with laser beams

    NASA Astrophysics Data System (ADS)

    Misconi, Nebil Y.; Rusk, Edwin T.; Oliver, John P.

    1989-04-01

    Light scattering curves of intensity vs. scattering angle were made of layers of transparent silica particles, single silica particles isolated by optical levitation; using an Argon ion laser light source and a goniometer mounted silicon photodiode detector. Scattering measurements of spherical particles demonstrated an excellent agreement with Mie theory. Spheroids and irregular particles were also measured. Dynamics of particles in a space environment were studied both theoretically, and experimentally inside a 10 to the -7th power Torr vacuum chamber. Research in this area will be continued to determine the effective moment arm of optically induced particle rotation.

  12. Experimental Studies of Elementary Particle Interactions at High Energies

    SciTech Connect

    Goulianos, Konstantin

    2013-07-31

    This is the final report of a program of research on ``Experimental Studies of Elementary Particle Interactions at High Energies'' of the High Energy Physics (HEP) group of The Rockefeller University. The research was carried out using the Collider Detector at Fermilab (CDF) and the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC) at CERN. Three faculty members, two research associates, and two postdoctoral associates participated in this project. At CDF, we studied proton-antiproton collisions at an energy of 1.96 TeV. We focused on diffractive interactions, in which the colliding antiproton loses a small fraction of its momentum, typically less than 1%, while the proton is excited into a high mass state retaining its quantum numbers. The study of such collisions provides insight into the nature of the diffractive exchange, conventionally referred to as Pomeron exchange. In studies of W and Z production, we found results that point to a QCD-based interpretation of the diffractive exchange, as predicted in a data-driven phenomenology developed within the Rockefeller HEP group. At CMS, we worked on diffraction, supersymmetry (SUSY), dark matter, large extra dimensions, and statistical applications to data analysis projects. In diffraction, we extended our CDF studies to higher energies working on two fronts: measurement of the single/double diffraction and of the rapidity gap cross sections at 7 TeV, and development of a simulation of diffractive processes along the lines of our successful model used at CDF. Working with the PYTHIA8 Monte Carlo simulation authors, we implemented our model as a PYTHIA8-MBR option in PYTHIA8 and used it in our data analysis. Preliminary results indicate good agreement. We searched for SUSY by measuring parameters in the Constrained Minimal Supersymmetric extension of the Standard Model (CMSSM) and found results which, combined with other experimental constraints and theoretical considerations, indicate that the

  13. Effect of the deformability of guest particles on the tensile strength of tablets from interactive mixtures.

    PubMed

    Mangal, Sharad; Lakio, Satu; Gengenbach, Thomas; Larson, Ian; Morton, David A V

    2016-12-05

    In this study, we investigated the influence of deformability of specifically-engineered guest particles on the tensile strength of tablets of interactive mixtures. The binder polyvinylpyrrolidone (PVP) of different molecular weights were spray dried with l-leucine to create guest particle formulations. The guest particle formulations were characterized by their particle size, surface l-leucine concentration and glass transition temperature (Tg). These spray-dried particles were then blended with paracetamol to form interactive mixtures, which were compacted into tablets and tablet tensile strength and elastic recovery were determined. The guest particles had particle diameters in the range of 1-10μm, and surfaces that were l-leucine enriched. The Tg of guest particle formulations increased with increasing molecular weight of the PVP. All the guest particle formulations formed an observed homogeneous interactive mixture with paracetamol. The tensile strength of the tablets of interactive mixtures increased with decreasing Tg of the guest particles. In these interactive mixtures, higher tensile strength was also associated with lower tablet elastic recovery. The elastic recovery of the tablets showed a correlation with the elastic recovery of the tablets of guest particles. Thus, our results indicated that the deformability of guest particles dictates the tensile strength of the tablets of these interactive mixtures.

  14. Ionization Energies of Lanthanides

    ERIC Educational Resources Information Center

    Lang, Peter F.; Smith, Barry C.

    2010-01-01

    This article describes how data are used to analyze the pattern of ionization energies of the lanthanide elements. Different observed pathways of ionization between different ground states are discussed, and the effects of pairing, exchange, and orbital interactions on ionization energies of the lanthanides are evaluated. When all the above…

  15. Ionization Energies of Lanthanides

    ERIC Educational Resources Information Center

    Lang, Peter F.; Smith, Barry C.

    2010-01-01

    This article describes how data are used to analyze the pattern of ionization energies of the lanthanide elements. Different observed pathways of ionization between different ground states are discussed, and the effects of pairing, exchange, and orbital interactions on ionization energies of the lanthanides are evaluated. When all the above…

  16. Effects of hydrodynamic interactions on rectified transport of self-propelled particles

    NASA Astrophysics Data System (ADS)

    Ai, Bao-quan; He, Ya-feng; Zhong, Wei-rong

    2017-01-01

    Directed transport of self-propelled particles is numerically investigated in a three-dimensional asymmetric potential. Beside the steric repulsive forces, hydrodynamic interactions between particles have been taken into account in an approximate way. From numerical simulations, we find that hydrodynamic interactions can strongly affect the rectified transport of self-propelled particles. Hydrodynamic interactions enhance the performance of the rectified transport when particles can easily pass across the barrier of the potential, and reduce the rectified transport when particles are mainly trapped in the potential well.

  17. Numerical investigation of shock interaction with one-dimensional transverse array of particles in air

    SciTech Connect

    Mehta, Y.; Jackson, T. L. Balachandar, S.; Zhang, J.

    2016-03-14

    In this paper, we present numerical simulations of shock propagation in air over a one-dimensional transverse array of particles. Simulations are carried out by varying the particle spacing and shock Mach number. We compute the unsteady inviscid drag coefficient as a function of time and make relevant comparisons to that for a single particle. We find that deviations in the drag coefficient in time from that of a single particle can be correlated to the acoustic-particle interaction time. Finally, we investigate and classify the interaction of the bow shocks in front of the transverse array of particles.

  18. Effect of the Mo/ller interaction on electron-impact ionization of high-Z hydrogenlike ions

    NASA Astrophysics Data System (ADS)

    Moores, D. L.; Reed, K. J.

    1995-01-01

    We have investigated the effects of the Mo/ller interaction in relativistic distorted-wave calculations of cross sections for electron-impact ionization of high-Z hydrogenlike ions. We found that the Mo/ller interaction significantly increases the cross section for hydrogenlike uranium, and brings our calculated results into very good agreement with experimental results reported by Marrs, Elliott, and Knapp [Phys. Rev. Lett. 72, 4082 (1994)]. We found similar increases in the cross sections for other hydrogenlike ions. Our results also show that these effects become important at much lower collision energy than previously reported [D. L. Moores and M. S. Pindzola, Phys. Rev. A 41, 3603 (1990)]. With the Mo/ller interaction included, our cross sections for these ions are in good agreement with preliminary results obtained in recent experiments on the electron-beam ion trap (EBIT).

  19. The Isolation of DNA by Polycharged Magnetic Particles: An Analysis of the Interaction by Zeta Potential and Particle Size.

    PubMed

    Haddad, Yazan; Xhaxhiu, Kledi; Kopel, Pavel; Hynek, David; Zitka, Ondrej; Adam, Vojtech

    2016-04-20

    Magnetic isolation of biological targets is in major demand in the biotechnology industry today. This study considers the interaction of four surface-modified magnetic micro- and nanoparticles with selected DNA fragments. Different surface modifications of nanomaghemite precursors were investigated: MAN37 (silica-coated), MAN127 (polyvinylpyrrolidone-coated), MAN158 (phosphate-coated), and MAN164 (tripolyphosphate-coated). All particles were positive polycharged agglomerated monodispersed systems. Mean particle sizes were 0.48, 2.97, 2.93, and 3.67 μm for MAN37, MAN127, MAN164, and MAN158, respectively. DNA fragments exhibited negative zeta potential of -0.22 mV under binding conditions (high ionic strength, low pH, and dehydration). A decrease in zeta potential of particles upon exposure to DNA was observed with exception of MAN158 particles. The measured particle size of MAN164 particles increased by nearly twofold upon exposure to DNA. Quantitative PCR isolation of DNA with a high retrieval rate was observed by magnetic particles MAN127 and MAN164. Interaction between polycharged magnetic particles and DNA is mediated by various binding mechanisms such as hydrophobic and electrostatic interactions. Future development of DNA isolation technology requires an understanding of the physical and biochemical conditions of this process.

  20. The Isolation of DNA by Polycharged Magnetic Particles: An Analysis of the Interaction by Zeta Potential and Particle Size

    PubMed Central

    Haddad, Yazan; Xhaxhiu, Kledi; Kopel, Pavel; Hynek, David; Zitka, Ondrej; Adam, Vojtech

    2016-01-01

    Magnetic isolation of biological targets is in major demand in the biotechnology industry today. This study considers the interaction of four surface-modified magnetic micro- and nanoparticles with selected DNA fragments. Different surface modifications of nanomaghemite precursors were investigated: MAN37 (silica-coated), MAN127 (polyvinylpyrrolidone-coated), MAN158 (phosphate-coated), and MAN164 (tripolyphosphate-coated). All particles were positive polycharged agglomerated monodispersed systems. Mean particle sizes were 0.48, 2.97, 2.93, and 3.67 μm for MAN37, MAN127, MAN164, and MAN158, respectively. DNA fragments exhibited negative zeta potential of −0.22 mV under binding conditions (high ionic strength, low pH, and dehydration). A decrease in zeta potential of particles upon exposure to DNA was observed with exception of MAN158 particles. The measured particle size of MAN164 particles increased by nearly twofold upon exposure to DNA. Quantitative PCR isolation of DNA with a high retrieval rate was observed by magnetic particles MAN127 and MAN164. Interaction between polycharged magnetic particles and DNA is mediated by various binding mechanisms such as hydrophobic and electrostatic interactions. Future development of DNA isolation technology requires an understanding of the physical and biochemical conditions of this process. PMID:27104527

  1. Study of collective effect in ionization cooling

    SciTech Connect

    Huang, D.; Ng, K.Y.; Roberts, T.J.; /MUONS Inc., Batavia

    2009-09-01

    As a charged particle passes through a non-gaseous medium, it polarizes the medium and induces wake fields behind it. Same thing happens in ionization cooling. The interaction with wake fields perturbs the stopping power of beam particles. The perturbation strongly depends on the densities of both the incident beam and the medium. To understand this collective effect, detailed studies have been carried out. Both analytic and simulation results are obtained and compared.

  2. Random particle methods applied to broadband fan interaction noise

    NASA Astrophysics Data System (ADS)

    Dieste, M.; Gabard, G.

    2012-10-01

    Predicting broadband fan noise is key to reduce noise emissions from aircraft and wind turbines. Complete CFD simulations of broadband fan noise generation remain too expensive to be used routinely for engineering design. A more efficient approach consists in synthesizing a turbulent velocity field that captures the main features of the exact solution. This synthetic turbulence is then used in a noise source model. This paper concentrates on predicting broadband fan noise interaction (also called leading edge noise) and demonstrates that a random particle mesh method (RPM) is well suited for simulating this source mechanism. The linearized Euler equations are used to describe sound generation and propagation. In this work, the definition of the filter kernel is generalized to include non-Gaussian filters that can directly follow more realistic energy spectra such as the ones developed by Liepmann and von Kármán. The velocity correlation and energy spectrum of the turbulence are found to be well captured by the RPM. The acoustic predictions are successfully validated against Amiet's analytical solution for a flat plate in a turbulent stream. A standard Langevin equation is used to model temporal decorrelation, but the presence of numerical issues leads to the introduction and validation of a second-order Langevin model.

  3. Consistent thermodynamic framework for interacting particles by neglecting thermal noise.

    PubMed

    Nobre, Fernando D; Curado, Evaldo M F; Souza, Andre M C; Andrade, Roberto F S

    2015-02-01

    An effective temperature θ, conjugated to a generalized entropy s(q), was introduced recently for a system of interacting particles. Since θ presents values much higher than those of typical room temperatures T≪θ, the thermal noise can be neglected (T/θ≃0) in these systems. Moreover, the consistency of this definition, as well as of a form analogous to the first law of thermodynamics, du=θds(q)+δW, were verified lately by means of a Carnot cycle, whose efficiency was shown to present the usual form, η=1-(θ(2)/θ(1)). Herein we explore further the heat contribution δQ=θds(q) by proposing a way for a heat exchange between two such systems, as well as its associated thermal equilibrium. As a consequence, the zeroth principle is also established. Moreover, we consolidate the first-law proposal by following the usual procedure for obtaining different potentials, i.e., applying Legendre transformations for distinct pairs of independent variables. From these potentials we derive the equation of state, Maxwell relations, and define response functions. All results presented are shown to be consistent with those of standard thermodynamics for T>0.

  4. Consistent thermodynamic framework for interacting particles by neglecting thermal noise

    NASA Astrophysics Data System (ADS)

    Nobre, Fernando D.; Curado, Evaldo M. F.; Souza, Andre M. C.; Andrade, Roberto F. S.

    2015-02-01

    An effective temperature θ , conjugated to a generalized entropy sq, was introduced recently for a system of interacting particles. Since θ presents values much higher than those of typical room temperatures T ≪θ , the thermal noise can be neglected (T /θ ≃0 ) in these systems. Moreover, the consistency of this definition, as well as of a form analogous to the first law of thermodynamics, d u =θ d sq+δ W , were verified lately by means of a Carnot cycle, whose efficiency was shown to present the usual form, η =1 -(θ2/θ1) . Herein we explore further the heat contribution δ Q =θ d sq by proposing a way for a heat exchange between two such systems, as well as its associated thermal equilibrium. As a consequence, the zeroth principle is also established. Moreover, we consolidate the first-law proposal by following the usual procedure for obtaining different potentials, i.e., applying Legendre transformations for distinct pairs of independent variables. From these potentials we derive the equation of state, Maxwell relations, and define response functions. All results presented are shown to be consistent with those of standard thermodynamics for T >0 .

  5. Van Allen Probes Observations of Direct Wave Particle Interactions

    NASA Astrophysics Data System (ADS)

    Fennell, J. F.; Roeder, J. L.; Kurth, W. S.; Henderson, M. G.; Larsen, B.; Hospodarsky, G. B.; Blake, J. B.; Claudepierre, S. G.; Clemmons, J. H.; Spence, H.; Funsten, H. O.; Reeves, G. D.; Kletzing, C.; Wygant, J. R.

    2013-12-01

    We present observations of wave-particle interactions observed on the Van Allen Probes during an interval of sporadic increases or bursts of 20-30 keV electron fluxes observed in conjunction with bursts of chorus activity. The electron flux and chorus burst occurred on a nearly one for one basis during an hour interval on January 13, 2013. The electron angular distributions changed during the burst events such that flux increases evolved from Sinn(α) type angular distributions to form maxima in the electron angular distributions at 75-80° local pitch angle with the fluxes at 90° and <60° remaining the same as in the pre and post burst distributions. These events occurred well outside the plasmasphere following a minor plasma injection. They were observed on both Van Allen Probes spacecraft, which were relatively close together. The plasma density, electron gyro-frequency and pitch angle of peak flux in a burst was used to estimate the resonant electron energy. The result of ~25 keV is consistent with the energies of the electrons showing the flux enhancements observed by the ECT/MagEIS and ECT/HOPE spectrometers. These results will be described in detail and questions concerning the source of such events will be discussed.

  6. Interactions of energetic particles and clusters with solids

    SciTech Connect

    Averback, R.S.; Hsieh, Horngming . Dept. of Materials Science and Engineering); Diaz de la Rubia, T. ); Benedek, R. )

    1990-12-01

    Ion beams are being applied for surface modifications of materials in a variety of different ways: ion implantation, ion beam mixing, sputtering, and particle or cluster beam-assisted deposition. Fundamental to all of these processes is the deposition of a large amount of energy, generally some keV's, in a localized area. This can lead to the production of defects, atomic mixing, disordering and in some cases, amorphization. Recent results of molecular dynamics computer simulations of energetic displacement cascades in Cu and Ni with energies up to 5 keV suggest that thermal spikes play an important role in these processes. Specifically, it will be shown that many aspects of defect production, atomic mixing and cascade collapse'' can be understood as a consequence of local melting of the cascade core. Included in this discussion will be the possible role of electron-phonon coupling in thermal spike dynamics. The interaction of energetic clusters of atoms with solid surfaces has also been studied by molecular dynamics simulations. this process is of interest because a large amount of energy can be deposited in a small region and possibly without creating point defects in the substrate or implanting cluster atoms. The simulations reveal that the dynamics of the collision process are strongly dependent on cluster size and energy. Different regimes where defect production, local melting and plastic flow dominate will be discussed. 43 refs., 7 figs.

  7. Effects of corotating interaction regions on Ulysses high energy particles

    SciTech Connect

    Droege, W.; Kunow, H.; Heber, B.; Mueller-Mellin, R.; Sierks, H.; Wibberenz, G.; Raviart, A.; Ducros, R.; Ferrando, P.; Rastoin, C.; Paizis, C.; Gosling, J. T.

    1996-07-20

    We investigate the intensity variation of low energy ({approx}6-23 MeV/N) heliospheric ions and of galactic protons (250-2200 MeV) observed by the Kiel Electron Telescope onboard the Ulysses spacecraft associated with Corotating Interaction Regions (CIR) from mid-1992 to end of June 1995. This period covers Ulysses' transit to high southern latitudes, the south polar pass, return to the solar equator and ascent to the north pole up to 70 deg. We find that the flux of high energy protons exhibits a periodicity of about 26 days with a relative intensity variation of 10%. At latitudes below {approx}50 deg. the recurrent variations of galactic protons are in coincidence with the passage of CIRs and enhancements of low energies protons and alpha particles which are accelerated at the shocks of the CIRs. The modulation of galactic protons is observed up to high southern latitudes, where the signatures of a CIR are no longer visible in plasma or magnetic field data. The periodicity does not depend on latitude and its phase apparently remains constant during Ulysses' pass over the south pole as well as through the solar equator.

  8. Effects of corotating interaction regions on Ulysses high energy particles

    SciTech Connect

    Droege, W.; Kunow, H.; Heber, B.; Mueller-Mellin, R.; Sierks, H.; Wibberenz, G.; Raviart, A.; Ducros, R.; Ferrando, P.; Rastoin, C.; Gosling, J.T.

    1996-07-01

    We investigate the intensity variation of low energy ({approximately}6{endash}23MeV/N) heliospheric ions and of galactic protons (250{endash}2200 MeV) observed by the Kiel Electron Telescope onboard the Ulysses spacecraft associated with Corotating Interaction Regions (CIR) from mid-1992 to end of June 1995. This period covers Ulysses{close_quote} transit to high southern latitudes, the south polar pass, return to the solar equator and ascent to the north pole up to 70{degree}. We find that the flux of high energy protons exhibits a periodicity of about 26 days with a relative intensity variation of 10{percent}. At latitudes below {approximately}50{degree} the recurrent variations of galactic protons are in coincidence with the passage of CIRs and enhancements of low energies protons and alpha particles which are accelerated at the shocks of the CIRs. The modulation of galactic protons is observed up to high southern latitudes, where the signatures of a CIR are no longer visible in plasma or magnetic field data. The periodicity does not depend on latitude and its phase apparently remains constant during Ulysses{close_quote} pass over the south pole as well as through the solar equator. {copyright} {ital 1996 American Institute of Physics.}

  9. Low energy charged particles interacting with amorphous solid water layers

    SciTech Connect

    Horowitz, Yonatan; Asscher, Micha

    2012-04-07

    The interaction of charged particles with condensed water films has been studied extensively in recent years due to its importance in biological systems, ecology as well as interstellar processes. We have studied low energy electrons (3-25 eV) and positive argon ions (55 eV) charging effects on amorphous solid water (ASW) and ice films, 120-1080 ML thick, deposited on ruthenium single crystal under ultrahigh vacuum conditions. Charging the ASW films by both electrons and positive argon ions has been measured using a Kelvin probe for contact potential difference (CPD) detection and found to obey plate capacitor physics. The incoming electrons kinetic energy has defined the maximum measurable CPD values by retarding further impinging electrons. L-defects (shallow traps) are suggested to be populated by the penetrating electrons and stabilize them. Low energy electron transmission measurements (currents of 0.4-1.5 {mu}A) have shown that the maximal and stable CPD values were obtained only after a relatively slow change has been completed within the ASW structure. Once the film has been stabilized, the spontaneous discharge was measured over a period of several hours at 103 {+-} 2 K. Finally, UV laser photo-emission study of the charged films has suggested that the negative charges tend to reside primarily at the ASW-vacuum interface, in good agreement with the known behavior of charged water clusters.

  10. Microscale simulations of shock interaction with large assembly of particles for developing point-particle models

    NASA Astrophysics Data System (ADS)

    Thakur, Siddharth; Neal, Chris; Mehta, Yash; Sridharan, Prasanth; Jackson, Thomas; Balachandar, S.

    2017-01-01

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

  11. Significance of particle size and charge capacity in TiO2 nanoparticle-lipid interactions.

    PubMed

    Vakurov, Alex; Drummond-Brydson, Rik; Ugwumsinachi, Oji; Nelson, Andrew

    2016-07-01

    The activity of submicron sized titanium oxide (TiO2) particles towards biomembrane models is coupled to their charge carrying capacity and their primary particle size. Electrochemical methods using a phospholipid layer on mercury (Hg) membrane model have been used to determine the phospholipid monolayer activity of TiO2 as an indicator of biomembrane activity. The particles were characterised for size, by dynamic light scattering (DLS) and scanning electron microscopy (SEM), and for charge, by acid-base titration. TiO2 nanoparticles aggregate in 0.1moldm(-3) solutions of KCl. The charge capacity of TiO2 nanoparticles depends on their primary particle size and is unaffected by aggregation. TiO2 particles of ∼40nm primary particle size interact significantly with phospholipid layers. Aggregation of these particles initially has a small effect on this interaction but long term aggregation influences the interaction whereby the aggregates penetrate the lipid layer rather than adsorbing on the surface. Fulvic acid does not inhibit the ∼40nm particle/phospholipid interaction. P25 TiO2 particles of larger particle size interact less strongly with phospholipid layers and the interaction is alleviated following particle aggregation. The semiconductor properties of TiO2 are evident in voltammograms showing electron transfer to TiO2 adsorbed on uncoated Hg. Copyright © 2016. Published by Elsevier Inc.

  12. A coarse grained stochastic particle interacting system for tropical convection

    NASA Astrophysics Data System (ADS)

    Khouider, B.

    2012-12-01

    Climate models (GCMs) fail to represent adequately the variability associated with organized convection in the tropics. This deficiency is believed to hinder medium and long range weather forecasts, over weeks to months. GCMs use very complex sub-grid models, known as cumulus parameterizations, to represent the effects of clouds and convection as well as other unresolved processes. Cumulus parameterizations are intrinsically deterministic and are typically based on the quasi-equilibrium theory, which assumes that convection instantaneously consumes the atmospheric instability produced by radiation. In this talk, I will discuss a stochastic model for organized tropical convection based on a particle interacting system defined on a microscopic lattice. An order parameter is assumed to take the values 0,1,2,3 at a any given lattice site according to whether it is a clear site or it is occupied by a cloud of a one of the three types: congestus, deep, or stratiform, following intuitive rules motivated by recent satellite observations and various field campaigns conducted over the Indian Ocean and Western Pacific. The microscopic Markov process is coarse-grained systematically to obtain a multidimensional birth-death process with immigration, following earlier work done by Katsoulakis, Majda, and Vlachos (JCP 2003) for the case of the Ising model where the order parameter takes the values 0 and 1. The coarse grained birth-death process is a stochastic model, intermediate between the microscopic lattice model and the deterministic mean field limit, that is used to represent the sub-grid scale variability of the underlying physical process (here the cloud cover) with a negligible computational overhead and yet permits both local interactions between lattice sites and two-way interactions between the cloud cover and the large-scale climate dynamics. The new systematic coarse-graining, developed here for the multivalued order parameter, provides a unifying framework

  13. Particle and nanoparticle interactions with fibrinogen: the importance of aggregation in nanotoxicology.

    PubMed

    Kendall, Michaela; Ding, Ping; Kendall, Kevin

    2011-03-01

    Ingested, inhaled or injected particles come into contact with biological fluids containing polymers, such as the protein fibrinogen. We studied interactions between well-characterized submicron particles or nanoparticles (NPs) and human fibrinogen. In vitro aggregation and zeta potential measurements of different sized and functionalized polystyrene, carbon black and silica NPs suspended in fibrinogen solutions were made. Particle size, surface charge and aggregation behaviour significantly changed in the presence of fibrinogen. Polymer (protein) bridging and bridge flocculation was observed. We concluded: (1) NP aggregation rate in a fibrinogen solution depended on particle surface type; (2) amine-functionalized particles aggregated more slowly in fibrinogen; and (3) particle morphology strongly influenced biologically available surface for protein attachment, but this did not correlate well with particle surface area for complex particles (calculated or measured). Interaction of particles and NPs with pro-coagulant polymers may therefore dictate the NP surface dose presentation to cells/organs and subsequent cellular effects, in and ex vivo.

  14. A validation of a simple model for the calculation of the ionization energies in X-ray laser-cluster interactions

    SciTech Connect

    White, Jeff; Ackad, Edward

    2015-02-15

    The outer-ionization of an electron from a cluster is an unambiguous quantity, while the inner-ionization threshold is not, resulting in different microscopic quantum-classical hybrid models used in laser-cluster interactions. A simple local ionization threshold model for the change in the ionization energy is proposed and examined, for atoms and ions, at distances in between the initial configuration of the cluster to well into the cluster's disintegration. This model is compared with a full Hartree-Fock energy calculation which accounts for the electron correlation effects using the coupled cluster method with single and double excitations with perturbative triples (CCSD(T)). Good agreement is found between the two lending a strong theoretical support to works which rely on such models for the final and transient properties of the laser-cluster interaction.

  15. Interaction of a shock wave with an array of particles and effect of particles on the shock wave weakening

    NASA Astrophysics Data System (ADS)

    Bulat, P. V.; Ilyina, T. E.; Volkov, K. N.; Silnikov, M. V.; Chernyshov, M. V.

    2017-06-01

    Two-phase systems that involve gas-particle or gas-droplet flows are widely used in aerospace and power engineering. The problems of weakening and suppression of detonation during saturation of a gas or liquid flow with the array of solid particles are considered. The tasks, associated with the formation of particles arrays, dust lifting behind a travelling shock wave, ignition of particles in high-speed and high-temperature gas flows are adjoined to safety of space flight. The mathematical models of shock wave interaction with the array of solid particles are discussed, and numerical methods are briefly described. The numerical simulations of interaction between sub- and supersonic flows and an array of particles being in motionless state at the initial time are performed. Calculations are carried out taking into account the influence that the particles cause on the flow of carrier gas. The results obtained show that inert particles significantly weaken the shock waves up to their suppression, which can be used to enhance the explosion safety of spacecrafts.

  16. Effects of particle-fluid density ratio on the interactions between the turbulent channel flow and finite-size particles

    NASA Astrophysics Data System (ADS)

    Yu, Zhaosheng; Lin, Zhaowu; Shao, Xueming; Wang, Lian-Ping

    2017-09-01

    ratios. For the neutrally buoyant case, the balance theory predicts a positive interphase force on the particles arising from the negative gradient of the particle inner stress, which cannot be predicted by the drag formula based on the phase-averaged slip velocity. In addition, our results show that both particle collision and particle-turbulence interaction play roles in the formation of the inhomogeneous distribution of the particles at the density ratio of the order of 10.

  17. Experimental investigation of particle surface interactions for turbomachinery application

    NASA Astrophysics Data System (ADS)

    Hamed, A.; Tabakoff, W.

    This paper describes an experimental investigation to determine the particle restitution characteristics after impacting solid targets in a particulate flow wind tunnel. The tests simulate the two phase flow conditions encountered in turbomachinery operating in particle laden flow environments. Both incoming and rebounding velocities are measured using a three color Argon Ion laser in backward scattered mode through a window in the tunnel section containing the impact target. The experimental results are presented for ash particles impinging on RENE 41 targets at different impact conditions. The presented results are applicable to particle dynamics simulations in gas turbine engines and to the prediction of the associated blade surface erosion.

  18. Size effects in aerosol particle interactions: the van der Waals potential and collision rates

    SciTech Connect

    Marlow, W H

    1980-01-01

    Three effects which are explicitly dependent on aerosol particle size are identified and discussed. They are focussed about the particle collision rate and how it relates to the properties of the gas, the particle, and the particle's interaction potential energy which play roles in particle-particle collision rates. By incorporating the conduction electronic free path effect for conductors into the frequency-dependent dielectric constants of silver and graphite, particle size effects in the Lifshitz-van der Waals potentials for identical pairs of 1 nm and 100 nm particles are evaluated. Water and tetradecane particle interaction potentials for the same size particles are also calculated to illustrate size effects due to the retardation of the interaction. These potentials are then used to calculate the enhancement of the particle collision rates above their values in the absence of any potential at various gas pressures. The roles of the interaction potential in collision among identical pairs of particles of differing compositions is also briefly discussed.

  19. Photoelectron resonance capture ionization-aerosol mass spectrometry of the ozonolysis products of oleic acid particles: Direct measure of higher molecular weight oxygenates

    NASA Astrophysics Data System (ADS)

    Zahardis, James; Lafranchi, Brian W.; Petrucci, Giuseppe A.

    2005-04-01

    The heterogeneous reaction of particle-phase 9-octadecenoic acid (oleic acid) and gas-phase ozone in a flow reactor was studied by photoelectron resonance capture ionization (PERCI) mass spectrometry. This soft ionization technique facilitated one of the first simultaneous, direct observations of all four of the major products predicted for this reaction: nonanal, nonanoic acid, 9-oxononanoic acid, and azelaic acid. In addition, a series of higher molecular weight oxygenated compounds were observed directly for the first time. The proposed structures are all cyclic oxygenates and contain the oxygen-oxygen moiety, including secondary ozonides and cyclic geminal diperoxides. Mechanisms for the formation of these products are proposed. The mechanisms are generally 1,3-dipolar cycloadditions that lead to five- and six-member oxygen-containing rings. The mechanisms are shown to involve short-lived Criegee intermediates reacting with aldehydes and other Criegee intermediates. Atmospheric implications of these higher molecular weight compounds are suggested and include enhancing the fatty acid medium's capacity to act as a source of radicals due to the prominence of the peroxide moiety. The low volatility coupled with the high polarity of these compounds may alter particle phase hygroscopicity that can enhance the cloud condensation nuclei properties of these particles.

  20. The interaction of melanin with ionizing and UVC radiations: Characterization of thymine damage

    SciTech Connect

    Huselton, C.A.

    1988-01-01

    These studies were undertaken to determine whether melanin could protect DNA against the harmful effects of ionizing or UVC radiations. A simple, in vitro, model system was developed to evaluate eumelanin (Sigma melanin) as a radioprotector of solutions of 0.1 mM thymine or thymidine exposed to 570Gy of ionizing radiation. Sigma melanin was compared to several amino acids, other biomolecules or to other forms of melanin. To investigate the role of melanin as a passive screen of UVC radiation, melanotic (I{sub 3}), amelanotic (AMEL) cells (both derived from a Cloudman S91 melanoma) and non-melanotic (EMT6) cells were labelled with radioactive dTHd and exposed to 0, 1, 5 or 10KJ/m{sup 2} of UVC. The DNA was extracted; the bases hydrolyzed with concentrated HCl. Thymine bases were separated by reverse phase HPLC. No difference in dimer content was observed between I{sub 3} and AMEL cells, but EMT6 cells had nearly twice the amount of dimer. Overall thymine degradation was more pronounced in I{sub 3} cells than in the other two cell lines, due to the production of non-dimer thymine damage. This damage was identified as thymine glycol by HPLC and mass spectrometry. Melanin, upon exposure to UVC, appears to enhance thymine damage by producing oxidative damage.

  1. Dynamic cross correlation studies of wave particle interactions in ULF phenomena

    NASA Technical Reports Server (NTRS)

    Mcpherron, R. L.

    1979-01-01

    Magnetic field observations made by satellites in the earth's magnetic field reveal a wide variety of ULF waves. These waves interact with the ambient particle populations in complex ways, causing modulation of the observed particle fluxes. This modulation is found to be a function of species, pitch angle, energy and time. The characteristics of this modulation provide information concerning the wave mode and interaction process. One important characteristic of wave-particle interactions is the phase of the particle flux modulation relative to the magnetic field variations. To display this phase as a function of time a dynamic cross spectrum program has been developed. The program produces contour maps in the frequency time plane of the cross correlation coefficient between any particle flux time series and the magnetic field vector. This program has been utilized in several studies of ULF wave-particle interactions at synchronous orbit.

  2. Chaotic delocalization of two interacting particles in the classical Harper model

    NASA Astrophysics Data System (ADS)

    Shepelyansky, Dima L.

    2016-06-01

    We study the problem of two interacting particles in the classical Harper model in the regime when one-particle motion is absolutely bounded inside one cell of periodic potential. The interaction between particles breaks integrability of classical motion leading to emergence of Hamiltonian dynamical chaos. At moderate interactions and certain energies above the mobility edge this chaos leads to a chaotic propulsion of two particles with their diffusive spreading over the whole space both in one and two dimensions. At the same time the distance between particles remains bounded by one or two periodic cells demonstrating appearance of new composite quasi-particles called chaons. The effect of chaotic delocalization of chaons is shown to be rather general being present for Coulomb and short range interactions. It is argued that such delocalized chaons can be observed in experiments with cold atoms and ions in optical lattices.

  3. Dynamic cross correlation studies of wave particle interactions in ULF phenomena

    NASA Technical Reports Server (NTRS)

    Mcpherron, R. L.

    1979-01-01

    Magnetic field observations made by satellites in the earth's magnetic field reveal a wide variety of ULF waves. These waves interact with the ambient particle populations in complex ways, causing modulation of the observed particle fluxes. This modulation is found to be a function of species, pitch angle, energy and time. The characteristics of this modulation provide information concerning the wave mode and interaction process. One important characteristic of wave-particle interactions is the phase of the particle flux modulation relative to the magnetic field variations. To display this phase as a function of time a dynamic cross spectrum program has been developed. The program produces contour maps in the frequency time plane of the cross correlation coefficient between any particle flux time series and the magnetic field vector. This program has been utilized in several studies of ULF wave-particle interactions at synchronous orbit.

  4. Atomic data for controlled fusion research. Volume III. Particle interactions with surfaces

    SciTech Connect

    Thomas, E.W.

    1985-02-01

    This report provides a handbook of data concerning particle solid interactions that are relevant to plasma-wall interactions in fusion devices. Published data have been collected, assessed, and represented by a single functional relationship which is presented in both tabular and graphical form. Mechanisms reviewed here include sputtering, secondary electron emission, particle reflection, and trapping.

  5. The model of the mechanical interaction of particles with the combustion products in a nozzle

    NASA Astrophysics Data System (ADS)

    Teterev, A. V.; Mandrik, P. A.; Misuchenko, N. I.; Rudak, L. V.

    2017-07-01

    This article describes the development of model of interaction of condensed particles with the gas flow in the Laval nozzle. Conducted parametric calculations have shown that the interaction of particles with the combustion products, even with a relatively small volume content may lead to a qualitative change in the internal flow in the Laval nozzle, and thereby influence the characteristics of the nozzle.

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

    SciTech Connect

    Frank, Rupert L.; Seiringer, Robert

    2012-09-15

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

  7. Cellular interactions of surface modified nanoporous silicon particles

    NASA Astrophysics Data System (ADS)

    Bimbo, Luis M.; Sarparanta, Mirkka; Mäkilä, Ermei; Laaksonen, Timo; Laaksonen, Päivi; Salonen, Jarno; Linder, Markus B.; Hirvonen, Jouni; Airaksinen, Anu J.; Santos, Hélder A.

    2012-05-01

    In this study, the self-assembly of hydrophobin class II (HFBII) on the surface of thermally hydrocarbonized porous silicon (THCPSi) nanoparticles was investigated. The HFBII-coating converted the hydrophobic particles into more hydrophilic ones, improved the particles' cell viability in both HT-29 and Caco-2 cell lines compared to uncoated particles, and enhanced the particles' cellular association. The amount of HFBII adsorbed onto the particles was also successfully quantified by both the BCA assay and a HPLC method. Importantly, the permeation of a poorly water-soluble drug, indomethacin, loaded into THCPSi particles across Caco-2 monolayers was not affected by the protein coating. In addition, 125I-radiolabelled HFBII did not extensively permeate the Caco-2 monolayer and was found to be stably adsorbed onto the THCPSi nanoparticles incubated in pH 7.4, which renders the particles the possibility for further track-imaging applications. The results highlight the potential of HFBII coating for improving wettability, increasing biocompatibility and possible intestinal association of PSi nanoparticulates for drug delivery applications.In this study, the self-assembly of hydrophobin class II (HFBII) on the surface of thermally hydrocarbonized porous silicon (THCPSi) nanoparticles was investigated. The HFBII-coating converted the hydrophobic particles into more hydrophilic ones, improved the particles' cell viability in both HT-29 and Caco-2 cell lines compared to uncoated particles, and enhanced the particles' cellular association. The amount of HFBII adsorbed onto the particles was also successfully quantified by both the BCA assay and a HPLC method. Importantly, the permeation of a poorly water-soluble drug, indomethacin, loaded into THCPSi particles across Caco-2 monolayers was not affected by the protein coating. In addition, 125I-radiolabelled HFBII did not extensively permeate the Caco-2 monolayer and was found to be stably adsorbed onto the THCPSi

  8. Simulation of Alfven wave-resonant particle interaction

    SciTech Connect

    Berk, H.L.; Breizman, B.N.; Pekker, M.

    1995-07-01

    New numerical simulations are presented on the self-consistent dynamics of energetic particles and a set of unstable discrete shear Alfven modes in a tokamak. Our code developed for these simulations has been previously tested in the simulations of the bump-on-tail instability model. The code has a Hamiltonian structure for the mode-particle coupling, with the superimposed wave damping, particle source and classical relaxation processes. In the alpha particle-Alfven wave problem, we observe a transition from a single mode saturation to the mode overlap and global quasilinear diffusion, which is qualitatively similar to that observed in the bump-on-tail model. We demonstrate a considerable enhancement in the wave energy due to the resonance overlap. We also demonstrate the effect of global diffusion on the energetic particle losses.

  9. Cell and Particle Interactions and Aggregation During Electrophoretic Motion

    NASA Technical Reports Server (NTRS)

    Davis, Robert H.

    2000-01-01

    The objectives of this research were (i) to perform experiments for observing and quantifying electrophoretic aggregation, (ii) to develop a theoretical description to appropriately analyze and compare with the experimental results, (iii) to study the combined effects of electrophoretic and gravitational aggregation of large particles, and the combined effects of electrophoretic and Brownian aggregation of small particles, and (iv) to perform a preliminary design of a potential future flight experiment involving electrophoretic aggregation. Electrophoresis refers to the motion of charged particles, droplets or molecules in response to an applied electric field. Electrophoresis is commonly used for analysis and separation of biological particles or molecules. When particles have different surface charge densities or potentials, they will migrate at different velocities in an electric field. This differential migration leads to the possibility that they will collide and aggregate, thereby preventing separation.

  10. Two-phase flow predictions of the turbulent flow in a combustion chamber including particle-particle interactions

    NASA Astrophysics Data System (ADS)

    Breuer, Michael; Alletto, Michael

    2011-12-01

    Relying on large-eddy simulation (LES) and an efficient algorithm to track a huge number of Lagrangian particles through turbulent flow fields in general complex 3D domains, the flow in a pipe and a model combustion chamber is tackled. The influence of particle-fluid (two-way coupling) as well as particle-particle interactions (four-way coupling) is investigated. The latter is modeled based on deterministic collision detection. First, the LES results of a particle-laden vertical pipe flow with a specular wall and a mass loading of 110% are evaluated based on DNS data from the literature. Second, the predicted LES data of a ring combustion chamber at two different mass loadings (22% and 110%) are analyzed and compared with experimental measurements.

  11. Relationship between the cohesion of guest particles on the flow behaviour of interactive mixtures.

    PubMed

    Mangal, Sharad; Gengenbach, Thomas; Millington-Smith, Doug; Armstrong, Brian; Morton, David A V; Larson, Ian

    2016-05-01

    In this study, we aimed to investigate the effects cohesion of small surface-engineered guest binder particles on the flow behaviour of interactive mixtures. Polyvinylpyrrolidone (PVP) - a model pharmaceutical binder - was spray-dried with varying l-leucine feed concentrations to create small surface-engineered binder particles with varying cohesion. These spray-dried formulations were characterised by their particle size distribution, morphology and cohesion. Interactive mixtures were produced by blending these spray-dried formulations with paracetamol. The resultant blends were visualised under scanning electron microscope to confirm formation of interactive mixtures. Surface coverage of paracetamol by guest particles as well as the flow behaviour of these mixtures were examined. The flow performance of interactive mixtures was evaluated using measurements of conditioned bulk density, basic flowability energy, aeration energy and compressibility. With higher feed l-leucine concentrations, the surface roughness of small binder particles increased, while their cohesion decreased. Visual inspection of the SEM images of the blends indicated that the guest particles adhered to the surface of paracetamol resulting in effective formation of interactive mixtures. These images also showed that the low-cohesion guest particles were better de-agglomerated that consequently formed a more homogeneous interactive mixture with paracetamol compared with high-cohesion formulations. The flow performance of interactive mixtures changed as a function of the cohesion of the guest particles. Interactive mixtures with low-cohesion guest binder particles showed notably improved bulk flow performance compared with those containing high-cohesion guest binder particles. Thus, our study suggests that the cohesion of guest particles dictates the flow performance of interactive mixtures.

  12. Interaction of Particles and Turbulence in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Dacles-Mariani, Jennifer S.; Dobrovolskis, A. R.; Cuzzi, J. N.; DeVincenzi, Donald L. (Technical Monitor)

    1996-01-01

    The most widely accepted theories for the formation of the Solar system claim that small solid particles continue to settle into a thin layer at the midplane of the Solar nebula until it becomes gravitationally unstable and collapses directly into km-sized planetesimals. This scenario has been challenged on at least two grounds: (1) due to turbulence, the particles may not settle into a thin layer, and (2) a thin layer may not be unstable. The Solar nebula contains at least three sources of turbulence: radial shear, vertical shear, and thermal convection. The first of these is small and probably negligible, while the last is poorly understood. However, the second contribution is likely to be substantial. The particle-rich layer rotates at nearly the Keplerian speed, but the surrounding gaseous nebula rotates slower because it is partly supported by pressure. The resulting shear generates a turbulent boundary layer which stirs the particles away from the midplane, and forestalls gravitational instability. Our previous work used a 'zero-equation' (Prandtl) model to predict the intensity of shear-generated turbulence, and enabled us to demonstrate numerically that settling of particles to the midplane is self-limiting. However, we neglected the possibility that mass loading by particles might damp the turbulence. To explore this, we have developed a more sophisticated 'one-equation' model which incorporates local generation, transport, and dissipation of turbulence, as well as explicit damping of turbulence by particles. We also include a background level of global turbulence to represent other sources. Our results indicate that damping flattens the distribution of particles somewhat, but that background turbulence thickens the particle layer.

  13. A quantum mechanical/molecular mechanical approach to the investigation of particle-molecule interactions

    NASA Astrophysics Data System (ADS)

    Sloth, Marianne; Bilde, Merete; Mikkelsen, Kurt V.

    2003-06-01

    A quantum mechanical/molecular mechanical aerosol model is developed to describe the interaction between gas phase molecules and atmospheric particles. The model enables the calculation of interaction energies and time-dependent properties. We use the model to investigate how a succinic acid molecule interacts with an aqueous particle. We show how the interaction energies and linear response properties (excitation energies, transition moments, and polarizabilities) depend on the distance between aerosol particle and molecule and on their relative orientation. The results are compared with those obtained previously using a dielectric continuum model [Sloth et al., J. Phys. Chem. (submitted)].

  14. Separable wave equation for three Coulomb interacting particles

    NASA Astrophysics Data System (ADS)

    Colavecchia, F. D.; Gasaneo, G.; Garibotti, C. R.

    1998-02-01

    We consider a separable approximation to the Schrödinger equation for the three-body Coulomb problem and found its exact solution above the ionization threshold. This wave function accounts for different possible asymptotic behaviors and reduces to the well-known product of three two-body Coulomb waves (C3) for scattering conditions. The momenta and position-dependent modifications recently proposed for the Sommerfeld parameters, as an improvement to the C3 model, are analyzed. We show how these changes can be included in our model as a suitable physically based variations in the separable approximation for the wave equation.

  15. Particle interaction in oscillatory Couette and Poiseuille flows

    NASA Astrophysics Data System (ADS)

    Fathi, Nima; Ingber, Marc; Vorobieff, Peter

    2013-11-01

    In oscillating Poiseuille flows of relatively dense suspensions, the direction of particle migration changes with the amplitude of oscillation. High amplitudes produce migration toward low shear rate regions of the flow, and vice versa, low oscillation amplitude results in particle migration toward the high shear rate region. We demonstrate that a similar behavior can be observed in a two-particle system, where it can be physically interpreted more easily, and discuss numerical modeling and experimental studies of oscillatory Poiseuille and Couette flows. This research is supported by the National Science Foundation and (in part) by a gift from the Procter & Gamble Company.

  16. Microbial interactions lead to rapid micro-scale successions on model marine particles.

    PubMed

    Datta, Manoshi S; Sliwerska, Elzbieta; Gore, Jeff; Polz, Martin F; Cordero, Otto X

    2016-06-17

    In the ocean, organic particles harbour diverse bacterial communities, which collectively digest and recycle essential nutrients. Traits like motility and exo-enzyme production allow individual taxa to colonize and exploit particle resources, but it remains unclear how community dynamics emerge from these individual traits. Here we track the taxon and trait dynamics of bacteria attached to model marine particles and demonstrate that particle-attached communities undergo rapid, reproducible successions driven by ecological interactions. Motile, particle-degrading taxa are selected for during early successional stages. However, this selective pressure is later relaxed when secondary consumers invade, which are unable to use the particle resource but, instead, rely on carbon from primary degraders. This creates a trophic chain that shifts community metabolism away from the particle substrate. These results suggest that primary successions may shape particle-attached bacterial communities in the ocean and that rapid community-wide metabolic shifts could limit rates of marine particle degradation.

  17. Microbial interactions lead to rapid micro-scale successions on model marine particles

    PubMed Central

    Datta, Manoshi S.; Sliwerska, Elzbieta; Gore, Jeff; Polz, Martin F.; Cordero, Otto X.

    2016-01-01

    In the ocean, organic particles harbour diverse bacterial communities, which collectively digest and recycle essential nutrients. Traits like motility and exo-enzyme production allow individual taxa to colonize and exploit particle resources, but it remains unclear how community dynamics emerge from these individual traits. Here we track the taxon and trait dynamics of bacteria attached to model marine particles and demonstrate that particle-attached communities undergo rapid, reproducible successions driven by ecological interactions. Motile, particle-degrading taxa are selected for during early successional stages. However, this selective pressure is later relaxed when secondary consumers invade, which are unable to use the particle resource but, instead, rely on carbon from primary degraders. This creates a trophic chain that shifts community metabolism away from the particle substrate. These results suggest that primary successions may shape particle-attached bacterial communities in the ocean and that rapid community-wide metabolic shifts could limit rates of marine particle degradation. PMID:27311813

  18. Effects of ionizing radiation on the immune system with special emphasis on the interaction of dendritic and T cells.

    PubMed

    Manda, Katrin; Glasow, Annegret; Paape, Daniel; Hildebrandt, Guido

    2012-01-01

    Dendritic cells (DCs), as professional antigen-presenting cells, are members of the innate immune system and function as key players during the induction phase of adaptive immune responses. Uptake, processing, and presentation of antigens direct the outcome toward either tolerance or immunity. The cells of the immune system are among the most highly radiosensitive cells in the body. For high doses of ionizing radiation (HD-IR) both immune-suppressive effects after whole body irradiation and possible immune activation during tumor therapy were observed. On the other hand, the effects of low doses of ionizing radiation (LD-IR) on the immune system are controversial and seem to show high variability among different individuals and species. There are reports revealing that protracted LD-IR can result in radioresistance. But immune-suppressive effects of chronic LD-IR are also reported, including the killing or sensitizing of certain cell types. This article shall review the current knowledge of radiation-induced effects on the immune system, paying special attention to the interaction of DCs and T cells.

  19. Effective Semi-empirical Interaction Potential for Dusty Particles

    SciTech Connect

    Ramazanov, T. S.; Dzhumagulova, K. N.; Omarbakiyeva, Y. A.; Dosbolayev, M. K.; Jumabekov, A. N.

    2008-09-07

    The Poisson equation was numerically solved on the basis of the experimental correlation functions of dusty particles. Calculations were performed with real parameters of dusty plasma. Reconstructed potential has oscillated character; the minimums coincide to maximums of correlation functions.

  20. Approach to the unification of elementary particle interactions

    SciTech Connect

    Gaillard, M.K.

    1981-09-01

    The assumption that the grand unified theory (GUT) emerges as an effective theory describing bound states of N = 8 supergravity preons should determine the GUT particle spectrum and constrain their couplings. Analysis of the spectrum has led to some possibly encouraging indications. At the least, the particle content in scalars, vectors and fermions needed to reproduce SU(5) phenomenology can be found among the states of the EGMZ multiplet.

  1. Interactive design environment transportation channel of relativistic charged particle beams

    NASA Astrophysics Data System (ADS)

    Osadchuk, I. O.; Averyanov, G. P.; Budkin, V. A.

    2017-01-01

    Considered a modern implementation of a computer environment for the design of channels of transportation of high-energy charged particle beams. The environment includes a software package for the simulation of the dynamics of charged particles in the channel, operating means for changing parameters of the channel, the elements channel optimization and processing of the output characteristics of the beam with the graphical output the main output parameters.

  2. Particle Pusher for the Investigation of Wave-Particle Interactions in the Magnetic Centrifugal Mass Filter (MCMF)

    NASA Astrophysics Data System (ADS)

    Kulp-McDowall, Taylor; Ochs, Ian; Fisch, Nathaniel

    2016-10-01

    A particle pusher was constructed in MATLAB using a fourth order Runge-Kutta algorithm to investigate the wave-particle interactions within theoretical models of the MCMF. The model simplified to a radial electric field and a magnetic field focused in the z direction. Studies on an average velocity calculation were conducted in order to test the program's behavior in the large radius limit. The results verified that the particle pusher was behaving correctly. Waves were then simulated on the rotating particles with a periodic divergenceless perturbation in the Bz component of the magnetic field. Preliminary runs indicate an agreement of the particle's motion with analytical predictions-ie. cyclic contractions of the doubly rotating particle's gyroradius.The next stage of the project involves the implementation of particle collisions and turbulence within the particle pusher in order to increase its accuracy and applicability. This will allow for a further investigation of the alpha channeling electrode replacement thesis first proposed by Abraham Fetterman in 2011. Made possible by Grants from the Princeton Environmental Institute (PEI) and the Program for Plasma Science and Technology (PPST).

  3. Angular Dependence of Strong Field Ionization of CH3X (X = F, Cl, Br, or I) Using Time-Dependent Configuration Interaction with an Absorbing Potential.

    PubMed

    Hoerner, Paul; Schlegel, H Bernhard

    2017-08-10

    Methyl halides have been used to test basis set effects on simulations of strong field ionization using time dependent configuration interaction with an absorbing potential. Standard atom centered basis sets need to be augmented by several sets of diffuse functions on each atom so that the wave function in the strong field can interact with the absorbing potential used to model ionization. An absorbing basis of 3 s functions, 2 p functions, 3 d functions, and 1 f function is sufficient for CH3F. Large absorbing basis sets with 4 s functions, 3 or 4 p functions, 4 or 5 d functions, and 2 f functions are recommended for the heavier halogens. The simulations used static fields in the 0.035-0.07 au range to explore the angular dependence of ionization of methyl halides. CH3F ionizes mainly from the methyl group; CH3Cl and CH3Br show ionization from both the methyl group and the halogen, and CH3I ionizes almost exclusively from the pπ orbitals of the iodine.

  4. Wave-particle interaction in the Faraday waves.

    PubMed

    Francois, N; Xia, H; Punzmann, H; Shats, M

    2015-10-01

    Wave motion in disordered Faraday waves is analysed in terms of oscillons or quasi-particles. The motion of these oscillons is measured using particle tracking tools and it is compared with the motion of fluid particles on the water surface. Both the real floating particles and the oscillons, representing the collective fluid motion, show Brownian-type dispersion exhibiting ballistic and diffusive mean squared displacement at short and long times, respectively. While the floating particles motion has been previously explained in the context of two-dimensional turbulence driven by Faraday waves, no theoretical description exists for the random walk type motion of oscillons. It is found that the r.m.s velocity ⟨μ̃(osc)⟩(rms) of oscillons is directly related to the turbulent r.m.s. velocity ⟨μ̃⟩(rms) of the fluid particles in a broad range of vertical accelerations. The measured ⟨μ̃(osc)⟩(rms) accurately explains the broadening of the frequency spectra of the surface elevation observed in disordered Faraday waves. These results suggest that 2D turbulence is the driving force behind both the randomization of the oscillons motion and the resulting broadening of the wave frequency spectra. The coupling between wave motion and hydrodynamic turbulence demonstrated here offers new perspectives for predicting complex fluid transport from the knowledge of wave field spectra and vice versa.

  5. Metal-Sulfur Valence Orbital Interaction Energies in Metal–Dithiolene Complexes: Determination of Charge and Overlap Interaction Energies by Comparison of Core and Valence Ionization Energy Shifts

    PubMed Central

    Wiebelhaus, Nicholas J.; Cranswick, Matthew A.; Klein, Eric L.; Lockett, L. Tori; Lichtenberger, Dennis L.; Enemark, John H.

    2011-01-01

    The electronic interactions between metals and dithiolenes are important in the biological processes of many metalloenzymes as well as in diverse chemical and material applications. Of special note is the ability of the dithiolene ligand to support metal centers in multiple coordination environments and oxidation states. To better understand the nature of metal-dithiolene electronic interactions, new capabilities in gas-phase core photoelectron spectroscopy for molecules with high sublimation temperatures have been developed and applied to a series of molecules of the type Cp2M(bdt) (Cp = η5-cyclopentadienyl, M = Ti, V, Mo, and bdt = benzenedithiolato). Comparison of the gas-phase core and valence ionization energy shifts provides a unique quantitative energy measure of valence orbital overlap interactions between the metal and sulfur orbitals that is separated from the effects of charge redistribution. The results explain the large amount of sulfur character in the redox-active orbitals and the ‘leveling’ of oxidation state energies in metal-dithiolene systems. The experimentally-determined orbital interaction energies reveal a previously unidentified overlap interaction of the predominantly sulfur HOMO of the bdt ligand with filled π orbitals of the Cp ligands, suggesting that direct dithiolene interactions with other ligands bound to the metal could be significant for other metal-dithiolene systems in chemistry and biology. PMID:21988484

  6. Altered Telomere Nuclear Matrix Interactions and Nucleosomal Periodicity in Ataxia Telangiectasia Cells before and after Ionizing Radiation Treatment

    PubMed Central

    Smilenov, Lubomir B.; Dhar, Sonu; Pandita, Tej K.

    1999-01-01

    Cells derived from ataxia telangiectasia (A-T) patients show a prominent defect at chromosome ends in the form of chromosome end-to-end associations, also known as telomeric associations, seen at G1, G2, and metaphase. Recently, we have shown that the ATM gene product, which is defective in the cancer-prone disorder A-T, influences chromosome end associations and telomere length. A possible hypothesis explaining these results is that the defective telomere metabolism in A-T cells are due to altered interactions between the telomeres and the nuclear matrix. We examined these interactions in nuclear matrix halos before and after radiation treatment. A difference was observed in the ratio of soluble versus matrix-associated telomeric DNA between cells derived from A-T and normal individuals. Ionizing radiation treatment affected the ratio of soluble versus matrix-associated telomeric DNA only in the A-T cells. To test the hypothesis that the ATM gene product is involved in interactions between telomeres and the nuclear matrix, we examined such interactions in human cells expressing either a dominant-negative effect or complementation of the ATM gene. The phenotype of RKO colorectal tumor cells expressing ATM fragments containing a leucine zipper motif mimics the altered interactions of telomere and nuclear matrix similar to that of A-T cells. A-T fibroblasts transfected with wild-type ATM gene had corrected telomere-nuclear matrix interactions. Further, we found that A-T cells had different micrococcal nuclease digestion patterns compared to normal cells before and after irradiation, indicating differences in nucleosomal periodicity in telomeres. These results suggest that the ATM gene influences the interactions between telomeres and the nuclear matrix, and alterations in telomere chromatin could be at least partly responsible for the pleiotropic phenotypes of the ATM gene. PMID:10490633

  7. Submicrometer particle removal indoors by a novel electrostatic precipitator with high clean air delivery rate, low ozone emissions, and carbon fiber ionizer.

    PubMed

    Kim, H-J; Han, B; Kim, Y-J; Oda, T; Won, H

    2013-10-01

    A novel positive-polarity electrostatic precipitator (ESP) was developed using an ionization stage (0.4 × 0.4 × 0.14 m(3) ) with 16 carbon fiber ionizers in each channel and a collection stage (0.4 × 0.4 × 0.21 m(3) ) with parallel metallic plates. The single-pass collection efficiency and clean air delivery rate (CADR) were measured by standard tests using KCl particles in 0.25-0.35 μm. Performance was determined using the Deutsch equation and established diffusion and field charging theories and also compared with the commercialized HEPA filter-type air cleaner. Experimental results showed that the single-pass collection efficiency of the ESP ranged from 50 to 95% and decreased with the flow rate (10-20 m(3) /min), but increased with the voltage applied to the ionizers (6 to 8 kV) and collection plates (-5 to -7 kV). The ESP with 18 m(3) /min achieved a CADR of 12.1 m(3) /min with a voltage of 8 kV applied to the ionization stage and with a voltage of -6 kV applied to the collection stage. The concentration of ozone in the test chamber (30.4 m(3) ), a maximum value of 5.4 ppb over 12 h of continuous operation, was much lower than the current indoor regulation (50 ppb). © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Plasma/particle interaction in subsonic argon/helium thermal plasma jets

    SciTech Connect

    Swank, W.D.; Fincke, J.R.; Haggard, D.C.

    1993-04-01

    Understanding the behavior of a particle and the interactions between a particle and the plasma surrounding it is important to the development and optimization of the plasma spray coating process. This is an experimental study of the interaction between a subsonic thermal plasma jet and injected nickel-aluminum particles. The velocity, temperature and composition of the gas flow field is mapped using an enthalpy probe/mass spectrometer system. The particle flow field is examined by simultaneously measuring the in-flight size, velocity, and temperature of individual particles. The complex interaction between the gas and particle flow fields is examined by combining the two sets of data. Particle and gas temperatures and velocities are compared in the vicinity of a nominal substrate standoff distance and axially along the median particle trajectory. The temperature and velocity difference is shown to vary substantially depending on the particle`s trajectory. By the time a particle on the median trajectory reaches the nominal substrate stand off of 63.5 mm it is transferring it`s heat and momentum to the plasma gas.

  9. Resonant wave-particle interaction in the radiation belts: quasi-linear scattering vs. nonlinear acceleration.

    NASA Astrophysics Data System (ADS)

    Artemyev, Anton; Agapitov, Oleksiy; Krasnoselskikh, Vladimir; Mourenas, Didier; Vasiliev, Alexei

    Wave-particle resonant interaction is the main mechanism responsible for electron acceleration and scattering in the radiation belts. There are two approaches describing this interaction - quasi-linear theory describes particle diffusion in momentum space, while nonlinear trapping of particles by high-amplitude waves can describe fast particle acceleration. The diffusion approach is more developed and widely used now. However, many modern observations in the radiation belts suggest the presence of significant population of large amplitude waves which can be responsible for nonlinear wave-particle interaction. We show that such nonlinear wave-particle resonant interaction corresponds to the fast transport of particles in phase space. We show that the general approach for the description of the evolution of the particle velocity distribution based on the Fokker-Plank equation can be modified to consider the process of nonlinear wave-particle interaction, including particle trapping. Such a modification consists in one additional operator describing fast particle jumps in phase space. The proposed approach is illustrated by considering the acceleration of relativistic electrons by strongly oblique whistler waves. We determine the typical variation of electron phase-density due to nonlinear wave-particle interaction and compare this variation with pitch-angle/energy diffusion due to quasi-linear electron scattering. We show that relation between nonlinear and quasi-linear effects is controlled by the distribution of wave-amplitudes. When this distribution has a heavy tail, nonlinear effects can become dominant in the formation of the electron energy distribution. We compare effectiveness of quasi-linear diffusion and nonlinear trapping for conditions typical for Earth radiation belts.

  10. Determination of isoflavone content in soy, red clover, and kudzu dietary supplement materials by liquid chromatography-particle beam/electron ionization mass spectrometry.

    PubMed

    Burdette, Carolyn Q; Marcus, R Kenneth

    2013-01-01

    Increased consumption of dietary supplements brings about important requirements of analytical methods to allow accurate and precise measurements of the chemical composition of these botanical materials. Presented here is the isoflavone content in proposed National Institute of Standards and Technology standard reference materials (SRMs) determined by LC-particle beam/electron ionization MS. Botanical materials (soy, red clover, and kudzu) are characterized for the content of a suite of five isoflavones (puerarin, daidzein, genistein, formononetin, and biochanin A). These compounds are of interest due to correlations with certain health benefits. An RP chromatographic separation was first optimized using UV-Vis spectrophotometric detection. The LC output was then introduced to an electron ionization source using a particle beam interface on an Extrel Benchmark MS system. The separation was carried out using a commercial C18 column and a linear gradient using water and methanol (both containing 0.1% trifluoroacetic acid as mobile phases A and B, at a flow rate of 1.0 mL/min over 40 min. LOD values for the isoflavones were determined to be at the ng level. Quantitation was performed using an internal standard (IS) approach with 7-hydroxy-4-chromone as the IS compound. The levels of isoflavones in the botanical products were determined for the proposed SRMs.

  11. Investigation of protein-protein noncovalent interactions in soybean agglutinin by electrospray ionization time-of-flight mass spectrometry.

    PubMed

    Tang, X J; Brewer, C F; Saha, S; Chernushevich, I; Ens, W; Standing, K G

    1994-09-01

    Noncovalent interactions in soybean agglutinin (SBA) were studied on an electrospray ionization (ESI) time-of-flight mass spectrometer constructed recently at the University of Manitoba. The high m/z range and high sensitivity of the instrument together with mild ESI interface conditions turned out to be ideal for detecting this noncovalently bonded tetrameric protein (MW approximately 116,000 Da) in low charge states (z = 23 to 27). By altering the acetonitrile content of the SBA solutions it was shown that the observed SBA tetramers are due to structurally specific noncovalent associations in solution. Octamers and dodecamers (MW approximately 350,000 Da) were also detected. Information on the quaternary structure of the tetramers was obtained by analyzing the fragment-ion spectrum resulting from the collision-induced dissociation of the tetramer ions.

  12. Laser desorption/ionization mass spectrometry of dye-sensitized solar cells: identification of the dye-electrolyte interaction.

    PubMed

    Ellis, Hanna; Leandri, Valentina; Hagfeldt, Anders; Boschloo, Gerrit; Bergquist, Jonas; Shevchenko, Denys

    2015-05-01

    Dye-sensitized solar cells (DSCs) have great potential to provide sustainable electricity from sunlight. The photoanode in DSCs consists of a dye-sensitized metal oxide film deposited on a conductive substrate. This configuration makes the photoanode a perfect sample for laser desorption/ionization mass spectrometry (LDI-MS). We applied LDI-MS for the study of molecular interactions between a dye and electrolyte on the surface of a TiO2 photoanode. We found that a dye containing polyoxyethylene groups forms complexes with alkali metal cations from the electrolyte, while a dye substituted with alkoxy groups does not. Guanidinium ion forms adducts with neither of the two dyes. Copyright © 2015 John Wiley & Sons, Ltd.

  13. Interaction Between Cytochrome c and the Hapten 2,4-Dinitro-fluorobenzene by Electrospray Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Wu, Bo; Chu, Yan-qiu; Dai, Zhao-yun; Ding, Chuan-fan

    2008-06-01

    Allergic contact dermatitis is a delayed hypersensitivity reaction, which results from skin exposure to low molecular weight chemicals such as haptens. To clarify the pathogenic mechanism, electrospray ionization mass spectrometry (ESI-MS) and hydrogen/deuterium (H/D) exchange, as well as UV spectroscopy, were applied to determine the interaction between the model protein cytochrome c (cyt c) and the hapten 2,4-dinitro-fluorobenzene (DNFB). The ESI-MS results demonstrate that the conformation of cyt c can change from native folded state into partially unfolded state with the increase of DNFB. The equilibrium state H/D exchange followed by ESI-MS further confirms the above results. UV spectroscopy indicates that the strong-field coordination between iron of heme (prosthetic group) and His18 or Met80 of cyt c is not obviously affected by the hapten.

  14. Inner-shell ionization of rotating linear molecules in the presence of spin-dependent interactions: Entanglement between a photoelectron and an auger electron

    NASA Astrophysics Data System (ADS)

    Ghosh, R.; Chandra, N.; Parida, S.

    2009-03-01

    This paper reports results of a theoretical study of angle- and spin-resolved photo-Auger electron coincident spectroscopy in the form of entanglement between these two particles emitted from a linear molecule. First, we develop an expression for a density matrix needed for studying spin-entanglement between a photoelectron and an Auger electron. In order to properly represent the molecular symmetries, nuclear rotation, and the spin-dependent interactions (SDIs), we have used symmetry adapted wavefunctions in Hund’s coupling scheme (a) for all the species participating in this two-step process. This expression shows that spin-entanglement in a photo-Auger electron pair in the presence of SDIs very strongly depends upon, among other things, polarization of the ionizing radia- tion, directions of motion and of spin polarization of two ejected electrons, and the dynamics of photoionization and of Auger decay. We have applied this expression, as an example, to a generic linear molecule in its J0, M0 = 0 state. This model calculation clearly brings out the salient features of the spin-entanglement of a photo-Auger electron pair in the presence of the SDIs.

  15. High-Density Microfluidic Particle-Cluster-Array Device for Parallel and Dynamic Study of Interaction between Engineered Particles.

    PubMed

    Kim, Hojin; Lee, Sanghyun; Lee, Wonhyung; Kim, Joonwon

    2017-08-01

    A high-density and high-performance microfluidic particle-cluster-array device utilizing a novel hydrodynamically tunable pneumatic valve (HTPV) is reported for parallel and dynamic monitoring of the interactions taking place in particle clusters. The key concept involves passive operation of the HTPV through elastic deformation of a thin membrane using only the hydrodynamic force inherent in microchannel flows. This unique feature allows the discrete and high-density (≈30 HTPVs mm(-2) ) arrangement of numerous HTPVs in a microfluidic channel without any pneumatic connection. In addition, the HTPV achieves high-performance clustering (≈92%) of three different particles in an array format through the optimization of key design and operating parameters. Finally, a contamination-free, parallel, and dynamic biochemical analysis strategy is proposed, which employs a simple one-inlet-one-outlet device operated by the effective combination of several techniques, including particle clustering, the interactions between engineered particles, two-phase partitioning and dehydration control of aqueous plugs, and shape/color-based particle identification. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Wave - fluid particle interaction in the Faraday waves

    NASA Astrophysics Data System (ADS)

    Francois, Nicolas; Xia, Hua; Punzmann, Horst; Shats, Michael

    2016-11-01

    Faraday waves are parametrically excited perturbations that appear on a liquid surface when the latter is vertically vibrated. Recently it has been discovered that: 1) such wave field can be described as a disordered lattice made of localised oscillating excitations, termed oscillons, 2) the horizontal motion of fluid particles on the water surface reproduces in detail the motion of fluid in two-dimensional turbulence. Here we report experimental measurements of the motion of both entities using Particle Image Velocimetry and Particle Tracking Velocimetry techniques. Those techniques allow to measure Lagrangian and Eulerian features of the oscillon motion and compare them with those of the fluid motion. A strong coupling is uncovered between the erratic motion of the waves and the turbulent agitation of the fluid particles. Both motions show Brownian-type dispersion and the r.m.s velocity of oscillons is directly related to the r.m.s. velocity of the fluid particles in a broad range of vertical accelerations. These results offer new perspectives for predicting surface fluid transport from the knowledge of the wave fields and vice versa. In particular, the broadening of the wave spectra at high wave amplitude can be predicted if the 2D turbulence energy is known. This work was supported by the Australian Research Council's Discovery Projects funding scheme (DP150103468 and DP160100863). NF acknowledges support by the Australian Research Council's DECRA Award (DE160100742).

  17. Detection of Ionizing Radiation using Solar Blind Air Fluorescence

    DTIC Science & Technology

    2013-06-01

    through the atmosphere some of the energy is transferred into the excitation of diatomic gasses, in particular N2. This effect is responsible for... energy cosmic rays that interact with the Earth’s atmosphere to generate large cascades of ionizing particles. This effect is also used for daytime...for the detection, on cloudless moonless nights, of ionization tracks from individual cosmic rays of sufficiently high energy (> 1018 eV). The yield

  18. An approach to mineral particle-air bubble interaction in turbulent flow of flotation cell

    SciTech Connect

    Lu, S.; Song, S.; Gou, J.; Pan, Y.

    1995-12-31

    The calculated potential energies of interaction between hydrophobic particle of three minerals (rhodochrosite, quartz and talc) and air bubble show that the energy of hydrophobic interaction is the dominant factor for their attachment. An attachment rate equation, integrating particle-bubble collision and adhesion by introducing a capture efficiency, has been put forward. It was found that the hydrophobic particle-