Sample records for molecular collision processes

  1. Semiclassical theory of electronically nonadiabatic transitions in molecular collision processes

    NASA Technical Reports Server (NTRS)

    Lam, K. S.; George, T. F.

    1979-01-01

    An introductory account of the semiclassical theory of the S-matrix for molecular collision processes is presented, with special emphasis on electronically nonadiabatic transitions. This theory is based on the incorporation of classical mechanics with quantum superposition, and in practice makes use of the analytic continuation of classical mechanics into the complex space of time domain. The relevant concepts of molecular scattering theory and related dynamical models are described and the formalism is developed and illustrated with simple examples - collinear collision of the A+BC type. The theory is then extended to include the effects of laser-induced nonadiabatic transitions. Two bound continuum processes collisional ionization and collision-induced emission also amenable to the same general semiclassical treatment are discussed.

  2. Dissociative processes in electron-molecular ion collisions

    NASA Astrophysics Data System (ADS)

    Djuric, Nada; Dunn, Gordon H.

    1998-10-01

    There is renewed interest in dissociation of molecular ions, primarily due to needs for modeling plasma generators for etching and deposition and for modeling edge plasmas for fusion reactors. At the same time, there are improvements in experimental techniques; e.g. use of heavy-ion storage rings has opened possibilities in dissociation studies of vibrationally relaxed molecular ions. At electron energies below the dissociation energy (D_e) of a molecular ion, the most importanat process is dissociative recombination (DR). Once the energy is above D_e, dissociative excitation (DE) is allowed, and at even higher energies dissociative ionization (DI) is energetically possible. In JILA we set up an apparatus wherein light fragment ions from DE of heteronuclear molecular ions are detected. In the heavy-ion storage ring at Stockholm (CRYRING) detection of neutral fragments was used for DE and DR studies. We will discuss the techniques and give examples of DE and DI obtainet at JILA and CRYRING [1,2,3]. Work supported in part by the Office of Fusion Energy of the U. S. DOE under Contract No. DE-A105-86ER53237 with NIST and in part by the Swedish Natural Science Research Council. 1. N. Djuric et al., Phys. Rev. A 56, 2887 (1997). 2. J. Semaniak et al., Ap. J. 498, 886 (1998). 3. J. R. Peterson et al., J. Chem. Phys. 108, 1978 (1998)

  3. Formation of cold molecular ions by radiative processes in cold ion-atom collisions

    SciTech Connect

    Rakshit, Arpita [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Deb, Bimalendu [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Raman Center for Atomic, Molecular and Optical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

    2011-02-15

    We discuss theoretically ion-atom collisions at low energy and predict the possibility of the formation of a cold molecular ion by photoassociation. We present results from radiative homo- and heteronuclear atom-ion cold collisions that reveal threshold behavior of atom-ion systems.

  4. Real-time monitoring of molecular-beam epitaxy processes with coaxial impact-collision ion scattering spectroscopy (CAICISS)

    Microsoft Academic Search

    M. Katayama; E. Nomura; H. Soejima; S. Hayashi; M. Aono

    1990-01-01

    Coaxial impact-collision ion scattering spectroscopy (CAICISS) is a novel form of low-energy ion scattering spectroscopy (ISS), in which a pulsed-beam low-energy ion source and a time-of-flight ion energy analyzer are placed coaxially so as to cover the experimental scattering angle at 180°. It is demonstrated that CAICISS is useful for monitoring molecular-beam epitaxy (MBE) processes in real time by taking

  5. Modeling of molecular nitrogen collisions and dissociation processes for direct simulation Monte Carlo

    NASA Astrophysics Data System (ADS)

    Parsons, Neal; Levin, Deborah A.; van Duin, Adri C. T.; Zhu, Tong

    2014-12-01

    The Direct Simulation Monte Carlo (DSMC) method typically used for simulating hypersonic Earth re-entry flows requires accurate total collision cross sections and reaction probabilities. However, total cross sections are often determined from extrapolations of relatively low-temperature viscosity data, so their reliability is unknown for the high temperatures observed in hypersonic flows. Existing DSMC reaction models accurately reproduce experimental equilibrium reaction rates, but the applicability of these rates to the strong thermal nonequilibrium observed in hypersonic shocks is unknown. For hypersonic flows, these modeling issues are particularly relevant for nitrogen, the dominant species of air. To rectify this deficiency, the Molecular Dynamics/Quasi-Classical Trajectories (MD/QCT) method is used to accurately compute collision and reaction cross sections for the N2(^1? _g+)-N2(^1? _g+) collision pair for conditions expected in hypersonic shocks using a new potential energy surface developed using a ReaxFF fit to recent advanced ab initio calculations. The MD/QCT-computed reaction probabilities were found to exhibit better physical behavior and predict less dissociation than the baseline total collision energy reaction model for strong nonequilibrium conditions expected in a shock. The MD/QCT reaction model compared well with computed equilibrium reaction rates and shock-tube data. In addition, the MD/QCT-computed total cross sections were found to agree well with established variable hard sphere total cross sections.

  6. Modeling of molecular nitrogen collisions and dissociation processes for direct simulation Monte Carlo.

    PubMed

    Parsons, Neal; Levin, Deborah A; van Duin, Adri C T; Zhu, Tong

    2014-12-21

    The Direct Simulation Monte Carlo (DSMC) method typically used for simulating hypersonic Earth re-entry flows requires accurate total collision cross sections and reaction probabilities. However, total cross sections are often determined from extrapolations of relatively low-temperature viscosity data, so their reliability is unknown for the high temperatures observed in hypersonic flows. Existing DSMC reaction models accurately reproduce experimental equilibrium reaction rates, but the applicability of these rates to the strong thermal nonequilibrium observed in hypersonic shocks is unknown. For hypersonic flows, these modeling issues are particularly relevant for nitrogen, the dominant species of air. To rectify this deficiency, the Molecular Dynamics/Quasi-Classical Trajectories (MD/QCT) method is used to accurately compute collision and reaction cross sections for the N2(?g+1)-N2(?g+1) collision pair for conditions expected in hypersonic shocks using a new potential energy surface developed using a ReaxFF fit to recent advanced ab initio calculations. The MD/QCT-computed reaction probabilities were found to exhibit better physical behavior and predict less dissociation than the baseline total collision energy reaction model for strong nonequilibrium conditions expected in a shock. The MD/QCT reaction model compared well with computed equilibrium reaction rates and shock-tube data. In addition, the MD/QCT-computed total cross sections were found to agree well with established variable hard sphere total cross sections. PMID:25527935

  7. Molecular collisions coming into focus.

    PubMed

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

    2014-08-14

    The Stark deceleration method exploits the concepts of charged particle accelerator physics to produce beams of neutral polar molecules with an almost perfect quantum state purity, a tunable velocity and a narrow velocity distribution. These monochromatic molecular beams offer interesting perspectives for precise studies of molecular scattering processes, in particular when used in conjunction with state-of-the-art laser-based detection techniques such as velocity map imaging. Here, we describe crossed beam scattering experiments in which the Stark deceleration method is combined with the velocity map imaging technique. The narrow velocity spread of Stark-decelerated molecular beams results in scattering images with unprecedented velocity and angular resolution. We demonstrate this by resolving quantum diffraction oscillations in state-to-state inelastic differential scattering cross sections for collisions between NO radicals and rare gas atoms. We describe the future prospects of this "best-of-two-worlds" combination, ranging from scattering studies at low collision energies to bimolecular scattering using two decelerators, and discuss the challenges that lie ahead to achieve these goals. PMID:24967721

  8. Tight-binding molecular-dynamics simulation of buckyball collisions

    SciTech Connect

    Zhang, B.L.; Wang, C.Z.; Chan, C.T.; Ho, K.M. (Iowa State Univ., Ames (United States))

    1993-04-01

    The collisions between C[sub 60] molecules are studied by tight-binding molecular-dynamics simulations. We observe three different regimes of behavior as the collisions become more and more energetic: bouncing, fusion, and fragmentation. The critical energies for fusion and fragmentation as well as details of the energy transfer during the collision process for the bouncing regime are investigated. The collisions at several specific energies and orientations produce interesting novel molecules, such as small baby cages, caps, and even a Russian-Doll molecule in which a small cage is trapped in a bigger one. 28 refs., 5 figs., 2 tabs.

  9. The 2011 Dynamics of Molecular Collisions Conference

    SciTech Connect

    Nesbitt, David J. [JILA, NIST

    2011-07-11

    The Dynamics of Molecular Collisions Conference focuses on all aspects of molecular collisions--experimental & theoretical studies of elastic, inelastic, & reactive encounters involving atoms, molecules, ions, clusters, & surfaces--as well as half collisions--photodissociation, photo-induced reaction, & photodesorption. The scientific program for the meeting in 2011 included exciting advances in both the core & multidisciplinary forefronts of the study of molecular collision processes. Following the format of the 2009 meeting, we also invited sessions in special topics that involve interfacial dynamics, novel emerging spectroscopies, chemical dynamics in atmospheric, combustion & interstellar environments, as well as a session devoted to theoretical & experimental advances in ultracold molecular samples. Researchers working inside & outside the traditional core topics of the meeting are encouraged to join the conference. We invite contributions of work that seeks understanding of how inter & intra-molecular forces determine the dynamics of the phenomena under study. In addition to invited oral sessions & contributed poster sessions, the scientific program included a formal session consisting of five contributed talks selected from the submitted poster abstracts. The DMC has distinguished itself by having the Herschbach Medal Symposium as part of the meeting format. This tradition of the Herschbach Medal was first started in the 2007 meeting chaired by David Chandler, based on a generous donation of funds & artwork design by Professor Dudley Herschbach himself. There are two such awards made, one for experimental & one for theoretical contributions to the field of Molecular Collision Dynamics, broadly defined. The symposium is always held on the last night of the meeting & has the awardees are asked to deliver an invited lecture on their work. The 2011 Herschbach Medal was dedicated to the contributions of two long standing leaders in Chemical Physics, Professor Yuan T. Lee & Professor George Schatz. Professor Lee’s research has been based on the development & use of advanced chemical kinetics & molecular beams to investigate & manipulate the behavior of fundamental chemical reactions. Lee’s work has been recognized by many awards, including the Nobel Prize for Chemistry in 1986, as well as Sloan Fellow, Dreyfus Scholar, Fellowship in the American Academy of Arts & Sciences, Fellowship in the American Physical Society, Guggenheim Fellow, Member National Academy of Sciences, Member Academia Sinica, E.O. Lawrence Award, Miller Professor, Berkeley, Fairchild Distinguished Scholar, Harrison Howe Award, Peter Debye Award, & the National Medal of Science. Lee also has served as the President of the Academia Sinica in Taiwan (ROC). Professor Schatz’s research group is interested in using theory & computation to describe physical phenomena in a broad range of applications relevant to chemistry, physics, biology & engineering. Among the types of applications that we interested are: optical properties of nanoparticles & nanoparticle assemblies; using theory to model polymer properties; DNA structure, thermodynamics & dynamics; modeling self assembly & nanopatterning; & gas phase reaction dynamics. Among his many awards & distinctions have been appointment as an Alfred P. Sloan Research Fellow, Camille & Henry Dreyfus Teacher-Scholar, the Fresenius Award, Fellow of the American Physical Society, the Max Planck Research Award, Fellowship in the American Association for the Advancement of Science, & election to the International Academy of Quantum Molecular Sciences & the American Academy of Arts & Sciences. Dr Schatz is also lauded for his highly successful work as Editor for the Journal of Physical Chemistry. We requested $10,000 from DOE in support of this meeting. The money was distributed widely among the student & post doctoral fellows & some used to attract the very best scientists in the field. The organizers were committed to encouraging women & minorities as well as encourage the field of Chemical Physics in scientific

  10. Aligned molecular collisions and a stereodynamical mechanism for selective chirality

    Microsoft Academic Search

    Vincenzo Aquilanti; Gaia Grossi; Andrea Lombardi; Glauciete S. Maciel; Federico Palazzetti

    2011-01-01

    Investigations of the stereodynamics of elementary processes provide the background for perspective demonstration of the manifestation\\u000a of chiral effects in molecular collisions. Advances in experimental vacuum technology allow the generation of molecular beams\\u000a containing oriented molecules. Here, we focus on collisional alignment, a molecular polarization phenomenon occurring in supersonic\\u000a expansions of gaseous mixtures. The underlying physical mechanisms, relevant gas-phase experiments

  11. A Molecular Dynamics Simulation of C60-C60 Collision

    NASA Astrophysics Data System (ADS)

    Liu, Lei; Chen, Kaitai; Li, Yufen

    1993-12-01

    The formation process of C120-complex in C60-C60 collision has been clearly demonstrated by a molecular dynamics simulation. The complex, with a peanut-shell-like structure, is in a quite stable dynamical state. The results are consistent with recent observations.

  12. Formation of negative hydrogen ions in 7-keV OH+ + Ar and OH+ + acetone collisions: a general process for H-bearing molecular species

    E-print Network

    Juhász, Zoltán; Rangama, Jimmy; Bene, Erika; Sorgunlu-Frankland, Burcu; Frémont, François; Chesnel, Jean-Yves

    2015-01-01

    We demonstrate that the formation of negative hydrogen ions (H-) occurs in a wide class of atomic and molecular collisions. In our experiments, H- emission from hydroxyl cations and acetone molecules was observed in keV-energy collisions. We show that hydride (H-) anions are formed via direct collisional fragmentation of molecules, followed by electron grabbing by fast hydrogen fragments. Such general mechanism in hydrogen-containing molecules may significantly influence reaction networks in planetary atmospheres and astrophysical media and new reaction pathways may have to be added in radiolysis studies.

  13. Division XII / Commission 14 / Working Group Collision Processes

    NASA Astrophysics Data System (ADS)

    Peach, Gillian; Dimitrijevic, Milan S.

    2012-04-01

    Research in atomic and molecular collision processes and spectral line broadening has been very active since our last report, Peach, Dimitrijevi? & Stancil 2009. Given the large volume of the published literature and the limited space available, we have attempted to identify work most relevant to astrophysics. Since our report can not be comprehensive, additional publications can be found in the databases at the web addresses listed in the final section. Elastic and inelastic collisions among electrons, atoms, ions, and molecules are included and charge transfer can be very important in collisions between heavy particles.

  14. Molecular collision cross sections and vibrational relaxation in carbon dioxide

    Microsoft Academic Search

    R. Marriott

    1964-01-01

    A numerical method, previously developed for the calculation of partial cross sections for the collisional excitation of molecular vibrational states, has been extended to make proper allowance for the effect of the repulsive centrifugal potential term on the matrix transition elements. This treatment of molecular collisions has been applied to a study of vibrational relaxation in carbon dioxide. Cross sections

  15. Gaussian Process Model for Collision Dynamics of Complex Molecules

    E-print Network

    Cui, Jie

    2015-01-01

    We show that a Gaussian Process model can be combined with a small number of scattering calculations to provide an accurate multi-dimensional dependence of scattering observables on the experimentally controllable parameters (such as the collision energy, temperature or external fields) as well as the potential energy surface parameters. This can be used for solving the inverse scattering problem, the prediction of collision properties of a specific molecular system based on the information for another molecule, the efficient calculation of thermally averaged observables and for reducing the error of the molecular dynamics calculations by averaging over the potential energy surface variations. We show that, trained by a combination of classical and quantum dynamics calculations, the model provides an accurate description of the scattering cross sections, even near scattering resonances. In this case, the classical calculations stabilize the model against uncertainties arising from wildly varying correlations ...

  16. Self-similarity in random collision processes

    NASA Astrophysics Data System (ADS)

    Ben-Avraham, Daniel; Ben-Naim, Eli; Lindenberg, Katja; Rosas, Alexandre

    2003-11-01

    Kinetics of collision processes with linear mixing rules are investigated analytically. The velocity distribution becomes self-similar in the long-time limit and the similarity functions have algebraic or stretched exponential tails. The characteristic exponents are roots of transcendental equations and vary continuously with the mixing parameters. In the presence of conservation laws, the velocity distributions become universal.

  17. The "Collisions Cube" Molecular Dynamics Simulator.

    ERIC Educational Resources Information Center

    Nash, John J.; Smith, Paul E.

    1995-01-01

    Describes a molecular dynamics simulator that employs ping-pong balls as the atoms or molecules and is suitable for either large lecture halls or small classrooms. Discusses its use in illustrating many of the fundamental concepts related to molecular motion and dynamics and providing a three-dimensional perspective of molecular motion. (JRH)

  18. TOPICAL REVIEW: Collisions near threshold in atomic and molecular physics

    Microsoft Academic Search

    H. R. Sadeghpour; J. L. Bohn; M. J. Cavagnero; B. D. Esry; I. I. Fabrikant; J. H. Macek; A. R. P. Rau

    2000-01-01

    We review topics of current interest in the physics of electronic, atomic and molecular scattering in the vicinity of thresholds. Starting from phase space arguments, we discuss the modifications of the Wigner law that are required to deal with scattering by Coulomb, dipolar and dispersion potentials, as well as aspects of threshold behaviour observed in ultracold atomic collisions. We employ

  19. Quantum molecular dynamics and particle production in heavy ion collisions

    Microsoft Academic Search

    S. W. Huang; A. Faessler; G. Q. Li; D. T. Khoa; E. Lehmann; M. A. Matin; N. Ohtsuka; R. K. Puri

    1993-01-01

    The production of photons, kaons, antikaons and antiprotons in heavy-ion collisions is calculated in the framework of ``quantum'' molecular dynamics (QMD). The Skyrme potentials, with parameters chosen to generate the soft and hard nuclear equations of state(EOS), are used in the propagation of nucleons within QMD. The sensitivity of the production of each type of particle to the EOS is

  20. Laser-enhanced dynamics in molecular rate processes

    NASA Technical Reports Server (NTRS)

    George, T. F.; Zimmerman, I. H.; Devries, P. L.; Yuan, J.-M.; Lam, K.-S.; Bellum, J. C.; Lee, H.-W.; Slutsky, M. S.

    1978-01-01

    The present discussion deals with some theoretical aspects associated with the description of molecular rate processes in the presence of intense laser radiation, where the radiation actually interacts with the molecular dynamics. Whereas for weak and even moderately intense radiation, the absorption and stimulated emission of photons by a molecular system can be described by perturbative methods, for intense radiation, perturbation theory is usually not adequate. Limiting the analysis to the gas phase, an attempt is made to describe nonperturbative approaches applicable to the description of such processes (in the presence of intense laser radiation) as electronic energy transfer in molecular (in particular atom-atom) collisions; collision-induced ionization and emission; and unimolecular dissociation.

  1. Molecular dynamics simulation of generation process of SWNTs

    Microsoft Academic Search

    Yasushi Shibuta; Shigeo Maruyama

    2002-01-01

    The formation mechanism of single-walled carbon nanotubes (SWNTs) was studied with the molecular dynamics simulation. Starting from randomly distributed carbon and Ni atoms, random cage structures of carbon atoms with a few Ni atoms were obtained after 6ns simulation. In the next process the cell size was artificially shrunk for realization of proceeding collisions of precursor clusters within the computational

  2. PAMOP: Petascale Atomic, Molecular and Optical Collision Calculations

    E-print Network

    McLaughlin, Brendan M; Pindzola, Michael S; Müller, Alfred

    2015-01-01

    Petaflop architectures are currently being utilized efficiently to perform large scale computations in Atomic, Molecular and Optical Collisions. We solve the Schr\\"odinger or Dirac equation for the appropriate collision problem using the R-matrix or R-matrix with pseudo-states approach. We briefly outline the parallel methodology used and implemented for the current suite of Breit-Pauli and DARC codes. In this report, various examples are shown from our theoretical results compared with experimental results obtained from Synchrotron Radiation facilities where the Cray architecture at HLRS is playing an integral part in our computational projects.

  3. Studies of fluctuation processes in nuclear collisions

    SciTech Connect

    Ayik, S.

    1990-04-01

    This report summarizes the progress on grant No. FG05--89ER40530 during the period August 15, 1989 to April 15, 1990. Most of the activity during this period was foucsed on providing a detailed description of a one-body transport model (stochastic BUU), and developing a method for obtaining approximate numerical solutions of the equation of motion. The stochastic BUU model goes beyond the standard BUU by incorporating dynamical fluctuations into the equation of motion. Therefore, it opens up a possibility for a dynamical description of multifragmentation processes in nuclear collisions at intermediate energies. Results of the first numerical calculations for head-on collisions of {sup 12}C + {sup 12}C and {sup 40}Ca + {sup 40}Ca systems at various energies are included in this report. The preliminary calculations have already revealed the substantial effects of fluctuations on the production mechanism of the intermediate mass fragments, and on the rare particle production mechanism in nuclear collisions. Work has also continued on establishing the connection between the one-body transport model and the collective transport models familiar from previous studies.

  4. Elastic Cross Sections for Electron Collisions with Molecules Relevant to Plasma Processing

    Microsoft Academic Search

    J.-S. Yoon; M.-Y. Song; H. Kato; M. Hoshino; H. Tanaka; M. J. Brunger; S. J. Buckman; H. Cho

    2010-01-01

    Absolute electron-impact cross sections for molecular targets, including their radicals, are important in developing plasma reactors and testing various plasma processing gases. Low-energy electron collision data for these gases are sparse and only the limited cross section data are available. In this report, elastic cross sections for electron-polyatomic molecule collisions are compiled and reviewed for 17 molecules relevant to plasma

  5. Young-type interference in ionizing collisions between helium and hydrogen molecular ions

    NASA Astrophysics Data System (ADS)

    Zhang, S. F.; Ma, X.; Fischer, D.; Moshammer, R.; Voitkiv, A.; Suske, J.; Kühnel, K. U.; Hagmann, S.; Krauss, A.; Zhang, R. T.; Guo, D. L.; Ullrich, J.

    2012-11-01

    Young-type interference in the ionization of helium in collisions with hydrogen molecular ions is investigated using a reaction microscope. Fringes are observed in the transverse momentum exchange between the collision partners.

  6. Accuracy of molecular data in the understanding of ultracold collisions

    SciTech Connect

    Dulieu, O. (Laboratoire des Collisions Atomiques et Moleculaires, Batiment 351, Universite Paris-Sud, 91405 Orsay Cedex (France)); Julienne, P. (Molecular Physics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)); Weiner, J. (Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742 (United States))

    1994-01-01

    We show through close-coupled quantum-scattering calculations that the cross section for fine-structure-changing collisions between excited [sup 2][ital P][sub 3/2] and ground [sup 2][ital S][sub 1/2] [ital A] atoms of the same species, where [ital A]=Rb or Cs, is very sensitive to the molecular potentials and spin-orbit matrix elements of the alkali-metal-dimer species. Spectroscopic studies of these species are needed to extract accurate parameters. New high-resolution photoassociation spectroscopy of trapped atoms could be used for this purpose.

  7. Improved molecular collision models for nonequilibrium rarefied gases

    NASA Astrophysics Data System (ADS)

    Parsons, Neal

    The Direct Simulation Monte Carlo (DSMC) method typically used to model thermochemical nonequilibrium rarefied gases requires accurate total collision cross sections, reaction probabilities, and molecular internal energy exchange models. However, the baseline total cross sections are often determined from extrapolations of relatively low-temperature viscosity data, reaction probabilities are defined such that experimentally determined equilibrium reaction rates are replicated, and internal energy relaxation models are phenomenological in nature. Therefore, these models have questionable validity in modeling strongly nonequilibrium gases with temperatures greater than those possible in experimental test facilities. To rectify this deficiency, the Molecular Dynamics/Quasi-Classical Trajectories (MD/QCT) method can be used to accurately compute total collision cross sections, reaction probabilities, and internal energy exchange models based on first principles for hypervelocity collision conditions. In this thesis, MD/QCT-based models were used to improve simulations of two unique nonequilibrium rarefied gas systems: the Ionian atmosphere and hypersonic shocks in Earth's atmosphere. The Jovian plasma torus flows over Io at ? 57 km/s, inducing high-speed collisions between atmospheric SO2 and the hypervelocity plasma's O atoms and ions. The DSMC method is well-suited to model the rarefied atmosphere, so MD/QCT studies are therefore conducted to improve DSMC collision models of the critical SO2-O collision pair. The MD/QCT trajectory simulations employed a new potential energy surface that was developed using a ReaxFF fit to a set of ab initio calculations. Compared to the MD/QCT results, the baseline DSMC models are found to significantly under-predict total cross sections, use reaction probabilities that are unrealistically high, and give unphysical internal energies above the dissociation energy for non-reacting inelastic collisions and under-predicts post-dissociation SO internal energy. Implemented into DSMC, the MD/QCT-based models had a significant effect on simulations of simple, thermal nonequilibrium heat bath and 2D counterflow cases approximating the upper atmospheric conditions of Io. In high-fidelity 1D simulations of the atmosphere of Io, the MD/QCT models predicted approximately half the SO2 atmospheric dissociation due to O and O+ bombardment and a temperature rise due to plasma heating further from the Ionian surface than the existing baseline methodologies. Hypersonic spacecraftre-entering Earth's atmosphere experience significant heating from the post-shock gas. The DSMC method is used to model hypersonic shocks during the early stages of re-entry because of the rarefied nature of the atmosphere at high altitudes. Improved modeling of the N-N 2 and N2-N 2 collision pairs are thus generated with MD/QCT. For the N-N2 pair, a potential energy surface developed at NASA Ames is used and, for the N2-N2 pair, a new potential energy surface is developed using a ReaxFF fit to recent advanced ab initio computations. The MD/QCT-computed total cross sections agreed well with the baseline models, but the MD/QCT reaction probabilities exhibited better physical behavior, a stronger dependence on initial molecular internal energy, and were generally lower than the baseline DSMC chemistry models for strong nonequilibrium conditions, but higher for equilibrium conditions. Furthermore, the MD/QCT results predicted faster rotational-translational energy relaxation for the N-N2 pair and faster vibrational-translational energy relaxation for the N2-N2 pair. The MD/QCT models were tested in DSMC simulations of 2D axisymmetric hypersonic flow over a blunt body and thermal nonequilibrium heat bath cases. The MD/QCT models led to increased post-shock N2 dissociation and faster rates of internal energy relaxation, each of which led to corresponding decreases in translational temperature.

  8. The rate coefficients of the chemi-ionization processes in slow Li*(n) + Na collisions

    NASA Astrophysics Data System (ADS)

    Ignjatovi?, Lj M.; Mihajlov, A. A.; Klyucharev, A. N.

    2008-01-01

    The semi-classical method for determining the rate coefficients of the chemi-ionization processes in slow non-symmetric atom-Rydberg atom collisions is applied to the Li*(n) + Na case. Calculated rate coefficients are compared with the existing experimental data from the literature. Obtained results have confirmed that resonant mechanism of non-elastic processes in atom-Rydberg atom collisions are fully applicable to non-symmetric chemi-ionization processes. The rate coefficients of such processes in Li*(n) + Na collisions are determined in the regions of principal quantum number and temperature 4 <= n <= 20 and 700 K <= T <= 1100 K which can be of interest for possible further experiments. Also, the potential curves of several lowest ? states of the molecular ion LiNa+, as well as the values of the square of dipole matrix element for the transition between X2?+- and A2?+-states, are presented in this paper.

  9. Calculation of total cross sections for charge exchange in molecular collisions

    NASA Technical Reports Server (NTRS)

    Ioup, J.

    1979-01-01

    Areas of investigation summarized include nitrogen ion-nitrogen molecule collisions; molecular collisions with surfaces; molecular identification from analysis of cracking patterns of selected gases; computer modelling of a quadrupole mass spectrometer; study of space charge in a quadrupole; transmission of the 127 deg cylindrical electrostatic analyzer; and mass spectrometer data deconvolution.

  10. Studies of fluctuation processes in nuclear collisions

    Microsoft Academic Search

    S. Ayik

    1992-01-01

    This report discusses the following topics: Relativistic Boltzmann-Langevin model for heavy-ion collision; K+ production far below free neucleon-nucleon threshold; and damping of collective vibrations in a memory-dependent transport model.

  11. Studies of fluctuation processes in nuclear collisions

    SciTech Connect

    Ayik, S.

    1992-02-01

    This report discusses the following topics: Relativistic Boltzmann-Langevin model for heavy-ion collision; K+ production far below free neucleon-nucleon threshold and damping of collective vibrations in a memory-dependent transport model.

  12. Collision processes of e + H2+ and its isotopes

    NASA Astrophysics Data System (ADS)

    Takagi, Hidekazu

    2012-11-01

    Theoretical study using multi-channel quantum defect theory is reported on the collisions between some isotopes of hydrogen molecular ion and an electron. The dissociative recombination, dissociative excitation, and vibrational transition are investigated for H2+, D2+, T2+, HD+, DT+.

  13. Molecular dynamics based chemistry models of hypervelocity collisions of O(3P) + SO2(X, 1A1) in DSMC

    NASA Astrophysics Data System (ADS)

    Parsons, Neal; Levin, Deborah A.; van Duin, Adri C. T.

    2013-01-01

    A significant process in the formation of the unique atmosphere of Io, a Jovian moon, is collision-induced dissociation of sulfur dioxide. The direct simulation Monte Carlo method (DSMC) is used to model the rarefied gas dynamics of the Ionian atmosphere. However, there is a lack of reliable reaction and collision cross sections needed for hypervelocity conditions. In this work, collisions between SO2 and O were studied using molecular dynamics/quasi-classical trajectories methods with the potential of Murrell and a force field for reactive systems (ReaxFF). Dissociation to SO was found to be the significant reacting process, but at higher collision energies, complete atomization of SO2 was found to frequently occur. In contrast, dissociation to O2 was found to be mostly negligible and formation of SO3 occurred only at low impact velocities. The chemistry and collision models developed from the Murrell and ReaxFF methods were implemented in DSMC simulations and compared to the baseline DSMC collision and reaction models. It was found that the selection of both the dissociation reaction cross section and the non-reactive collision model has a significant effect on the counterflow, shock gas dynamic structure.

  14. Excitation processes in H--Kr collisions

    NASA Astrophysics Data System (ADS)

    Esaulov, V. A.; Grouard, J. P.; Hall, R. I.; Montmagnon, J. L.

    1987-03-01

    An electron spectroscopy study of H--Kr collisions in the 20-500-eV collision energy range revealed the excitation of (2s2) 1S, (2p2) 1D, and (2s2p) 1P states of H- and of the (5s2) 2P3/2,1/2 Kr- state. The angular distribution of electrons produced from the decay of these states is reported. An anisotropic distribution for the (2s2) 1S state is observed at these energies as was previously reported for H- collisions with He, Ar, and H2 by Risley and co-workers [Phys. Rev. A 9, 1115 (1974) and IEEE Trans. Nuc. Sci. NS26, 1027 (1979)]. Relative cross sections for the excitation of these states are deduced from the angular distributions.

  15. Multielectron processes in ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Zamkov, Mikhail Anatolyevich

    Multielectron interactions in fast ion-atom collisions were investigated using high-resolution projectile Auger electron spectroscopy. Experimental studies were performed by measuring state-resolved projectile Auger cross sections utilizing a novel high-efficiency hemispherical detector-analyzer. Experimental data were used both to test the predictions of recent theoretical calculations and to provide a basis for the development of new atomic models. A novel experimental technique for the determination of the metastable 1s2s 3S ion fraction has been developed and subsequently used to measure the metastable fraction in fast He-like beams. The dominant contribution to the formation of the metastable 1s2s 3 S state in collisions of He-like ions with atomic targets was identified. A model for the calculation of the metastable ion fraction has been developed and successfully applied for predictions of absolute values and energy dependence of the metastable content. Having the accurate knowledge of the metastable 1s2s 3S state fraction enabled a novel approach for the investigation of the triply excited 2s2p2 2D resonance produced in collisions of metastable B3+ ions with H2 targets by resonant transfer excitation. The results were compared to existing theoretical calculations within the 1/Z expansion method. A new experimental technique for studying multielectron capture in ion-atom collisions has been introduced by measuring state-selective differential cross sections of intermediate multiexcited states. Measurements of the Auger electron emission in the direction of the ion beam were used to determine the absolute single differential cross sections for the triple electron capture to all autoionizing KLL states. The results were compared to cross sections calculated within the independent particle model. The study of triple electron capture stimulated a new experimental technique that relies on a strong projectile-Coulomb interaction to populate triply excited states in Li-like ions. The production of these states is realized in energetic ion atom collisions by triple electron capture. The method is demonstrated by studying triply excited 2s2p 2 2Se, 2,4 Pe, 2De, and 2p3 2Po, 2Do states of fluorine formed in fast collisions of bare F9+ ions with Ar and Kr targets; both experimentally, using zero-degree Auger projectile electron spectroscopy and theoretically, using the hyperspherical close coupling method.

  16. Studies of fluctuation processes in nuclear collisions

    Microsoft Academic Search

    S. Ayik

    1993-01-01

    Investigations of various aspects of heavy-ion collisions were carried out in the framework of the Boltzmann-Langevin Model (BLM). In a previous work, by projection of the BLM onto a collective space, a memory-dependent collective transport model was reduced. This model was applied to thermal fission to investigate the influence of the memory effects on the fission dynamics. Some results of

  17. Studies of fluctuation processes in nuclear collisions

    Microsoft Academic Search

    Ayik

    1993-01-01

    Investigations of various aspects of heavy-ion collisions were carried out in the framework of the Boltzmann-Langevin Model (BLM). In a previous work, by projection the BLM onto a collective space, a memory-dependent collective transport model was reduced. This model was applied to thermal fission to investigate the influence of the memory effects on the fission dynamics. Some results of the

  18. A one-body transport model of fluctuation processes in nuclear collisions

    SciTech Connect

    Ayik, S. (Tennessee Technological Univ., Cookeville, TN (USA)); Gregoire, C.; Suraud, E.; Stryjewski, J.; Belkacem, M. (Grand Accelerateur National d'Ions Lourds (GANIL), 14 - Caen (France))

    1990-01-01

    Many aspects of a many-body system can be described in terms of one- body transport models in which the system at any time is characterized by its single-particle density rather than by the full many-body information. In these one-body models evaluation of the single-particle density is determined by a transport equation which contains the self-consistent mean-field potential and a collision term due to binary two-body collisions. Recently, this approach in a semi-classical limit with a Boltzmann-Uehling-Uhlenbeck (BUU) form of a collision term has been applied to nuclear collisions at intermediate energies. Common to all one-body models, only the average effects of two-body collisions are retained in the equation of motion and higher order correlations are entirely neglected. This approximation corresponds to an ensemble averaging which is evident, for example, from the molecular chaos assumption'' introduced in derivation of Boltzmann equation. As a result, these one-body models determine the ensemble averaged single-particle density and cannot provide a description for the fluctuation processes in nuclear collisions. On the other hand, at low and intermediate energies dynamical fluctuations are substantial due to large available phase space for decay into many final states. Therefore, it is of great interest to improve one-body transport models by incorporating dynamical fluctuations due to high order correlations into the equation of motion. 5 refs., 3 figs.

  19. Cold atomic and molecular collisions: approaching the universal loss regime

    NASA Astrophysics Data System (ADS)

    Frye, Matthew D.; Julienne, Paul S.; Hutson, Jeremy M.

    2015-04-01

    We investigate the behaviour of single-channel theoretical models of cold and ultracold collisions that take account of inelastic and reactive processes using a single parameter to represent short-range loss. We present plots of the resulting energy-dependence of elastic and inelastic or reactive cross-sections over the full parameter space of loss parameters and short-range phase shifts. We then test the single-channel model by comparing it with the results of coupled-channel calculations of rotationally inelastic collisions between LiH molecules and Li atoms. We find that the range of cross-sections predicted by the single-channel model becomes increasingly accurate as the initial LiH rotational quantum number increases, with a corresponding increase in the number of open loss channels. The results suggest that coupled-channel calculations at very low energy (in the s-wave regime) could in some cases be used to estimate a loss parameter and then to predict the range of possible loss rates at higher energy, without the need for explicit coupled-channel calculations for higher partial waves.

  20. Molecular processes in a high temperature shock layer

    NASA Technical Reports Server (NTRS)

    Guberman, S. L.

    1984-01-01

    Models of the shock layer encountered by an Aeroassisted Orbital Transfer Vehicle require as input accurate cross sections and rate constants for the atomic and molecular processes that characterize the shock radiation. From the estimated atomic and molecular densities in the shock layer and the expected residence time of 1 m/s, it can be expected that electron-ion collision processes will be important in the shock model. Electron capture by molecular ions followed by dissociation, e.g., O2(+) + e(-) yields 0 + 0, can be expected to be of major importance since these processes are known to have high rates (e.g., 10 to the -7th power cu/cm/sec) at room temperature. However, there have been no experimental measurements of dissociative recombination (DR) at temperatures ( 12000K) that are expected to characterize the shock layer. Indeed, even at room temperature, it is often difficult to perform experiments that determine the dependence of the translational energy and quantum yields of the product atoms on the electronic and vibrational state of the reactant molecular ions. Presented are ab initio quantum chemical studies of DR for molecular ions that are likely to be important in the atmospheric shock layer.

  1. Applications of cross sections for electron-molecule collision processes

    SciTech Connect

    Cartwright, D.C.

    1985-01-01

    The role of electron-molecule collision cross sections is discussed for the study of the ionospheric and auroral processes in planetary atmospheres and of discharge-pumped lasers. These two areas emphasize the importance of further theoretical and experimental studies concerning electron-impact processes. 13 refs., 3 figs., 2 tabs. (WRF)

  2. ALPGEN, a generator for hard multiparton processes in hadronic collisions

    Microsoft Academic Search

    Michelangelo L. Mangano; Fulvio Piccinini; Antonio D. Polosa; Mauro Moretti; Roberto Pittau

    2003-01-01

    This paper presents a new event generator, ALPGEN, dedicated to the study of multiparton hard processes in hadronic collisions. The code performs, at the leading order in QCD and EW interactions, the calculation of the exact matrix elements for a large set of parton-level processes of interest in the study of the Tevatron and LHC data. The current version of

  3. Introductory paper 1. The role of atomic and molecular processes in fusion research

    Microsoft Academic Search

    M. F. A. Harrison

    1978-01-01

    This paper considers the relevance of atomic and molecular processes to researh into controlled nuclear fusion and in particular their effects upon the magnetically confined plasma in Tokamak experiments and conceptual Tokamak reactors. The relative significance of collective phenomena and of single particle collisions to both plasma heating and loss processes are discussed and the pertinent principles of plasma refuelling

  4. Effect of molecular weight on polymer processability

    SciTech Connect

    Karg, R.F.

    1983-01-01

    Differences in rheological behavior due to the polymer molecular weight and molecular weight distribution have been shown with the MPT. SBR polymers having high molecular weight fractions develop higher stress relaxation time values due to the higher degree of polymer entanglements. Tests conducted at increasing temperatures show the diminishing influence of the polymer entanglements upon stress relaxation time. EPDM polymers show stress relaxation time and head pressure behavior which correlates with mill processability. As anticipated, compounded stock of EPDM have broad molecular weight distribution has higher stress relaxation time values than EPDM compounds with narrow molecular weight distribution.

  5. Collision dynamics of the associative ionization process arising from collisions between two excited sodium 3p atoms

    Microsoft Academic Search

    1986-01-01

    Associative ionization (AI) in collisions between Na(3p) atoms, Na(3p) + Na(3p) ..-->.. Naâ\\/sup +\\/ + e⁻ was studied in detail in a crossed-atomic-beam apparatus. The primary object of the work is to determine the mechanisms by which the AI reactive collision process takes place. First studied was the collision energy dependence of the AI cross section. The accessed collision energy

  6. Studies of fluctuation processes in nuclear collisions

    NASA Astrophysics Data System (ADS)

    Ayik, S.

    1993-02-01

    Investigations of various aspects of heavy-ion collisions were carried out in the framework of the Boltzmann-Langevin Model (BLM). In a previous work, by projection of the BLM onto a collective space, a memory-dependent collective transport model was reduced. This model was applied to thermal fission to investigate the influence of the memory effects on the fission dynamics. Some results of the calculations are presented. In addition, a reduction of the relativistic BLM to a two-fluid model was carried out, and transport coefficients associated with fluid dynamical variables were derived. Then this model was applied to investigate equilibration and fluctuation properties in a counter-streaming nuclear fluid.

  7. Ab initio quantum chemistry in the molecular model of atomic collisions

    Microsoft Academic Search

    A. Macías; A. Riera

    1982-01-01

    We present an introduction to the application of ab initio methods of Quantum Chemistry to the molecular model of atomic collisions. This includes the choice and calculation of molecular wavefunctions using the well known Self Consistent Field and Configuration Interaction methods; the calculation of dynamical couplings and a detailed study of diabatic states. To make the article self contained, we

  8. FORMATION OF MASSIVE MOLECULAR CLOUD CORES BY CLOUD-CLOUD COLLISION

    SciTech Connect

    Inoue, Tsuyoshi [Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa 252-5258 (Japan); Fukui, Yasuo, E-mail: inouety@phys.aoyama.ac.jp [Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan)

    2013-09-10

    Recent observations of molecular clouds around rich massive star clusters including NGC 3603, Westerlund 2, and M20 revealed that the formation of massive stars could be triggered by a cloud-cloud collision. By using three-dimensional, isothermal, magnetohydrodynamics simulations with the effect of self-gravity, we demonstrate that massive, gravitationally unstable, molecular cloud cores are formed behind the strong shock waves induced by cloud-cloud collision. We find that the massive molecular cloud cores have large effective Jeans mass owing to the enhancement of the magnetic field strength by shock compression and turbulence in the compressed layer. Our results predict that massive molecular cloud cores formed by the cloud-cloud collision are filamentary and threaded by magnetic fields perpendicular to the filament.

  9. Molecular dynamics simulation of energy exchanges during hydrogen collision with graphite sheets

    SciTech Connect

    Sun Jizhong; Li Shouyang; Wang Dezhen [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology and College of Advanced Science and Technology, Dalian University of Technology, Dalian 116024 (China); Stirner, Thomas [University of Applied Sciences Deggendorf, Edlmairstr. 6-8, D-94469 Deggendorf (Germany); Chen Junlin [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2010-06-15

    Experiments show that the energy of particles incident on divertor plates in fusion devices seldom exceeds 100 eV. Trim code and its variants are not suitable to predict the sputtering yield of carbon-based divertor plates for this energy range and, therefore, a dynamic model, taking into account the C-H bond formation and breaking, and the structure of carbon, is needed. In this paper, the molecular dynamics method is employed to investigate collision processes between incident hydrogen atoms and a graphene sheet. The simulation results demonstrate that the collision processes cannot be adequately described by a simple binary approximation. The energy transfer from the projectile to the graphite sheet exhibits a very complicated behavior when the kinetic energy of the incident hydrogen atom is below 30 eV, strongly depending on the impact position. When its kinetic energy is lower than 0.35 eV, the incident hydrogen is always reflected back from the single, perfect graphite sheet; when its kinetic energy is higher than 0.35 eV, then whether the incident particle penetrates the graphite sheet, is reflected back or is adsorbed depends on the impact position. In certain areas of the graphite sheet, either adsorption or reflection of an incident hydrogen atom can occur in two different energy ranges.

  10. Free molecular collision cross section calculation methods for nanoparticles and complex ions with energy accommodation

    SciTech Connect

    Larriba, Carlos, E-mail: clarriba@umn.edu; Hogan, Christopher J.

    2013-10-15

    The structures of nanoparticles, macromolecules, and molecular clusters in gas phase environments are often studied via measurement of collision cross sections. To directly compare structure models to measurements, it is hence necessary to have computational techniques available to calculate the collision cross sections of structural models under conditions matching measurements. However, presently available collision cross section methods contain the underlying assumption that collision between gas molecules and structures are completely elastic (gas molecule translational energy conserving) and specular, while experimental evidence suggests that in the most commonly used background gases for measurements, air and molecular nitrogen, gas molecule reemission is largely inelastic (with exchange of energy between vibrational, rotational, and translational modes) and should be treated as diffuse in computations with fixed structural models. In this work, we describe computational techniques to predict the free molecular collision cross sections for fixed structural models of gas phase entities where inelastic and non-specular gas molecule reemission rules can be invoked, and the long range ion-induced dipole (polarization) potential between gas molecules and a charged entity can be considered. Specifically, two calculation procedures are described detail: a diffuse hard sphere scattering (DHSS) method, in which structures are modeled as hard spheres and collision cross sections are calculated for rectilinear trajectories of gas molecules, and a diffuse trajectory method (DTM), in which the assumption of rectilinear trajectories is relaxed and the ion-induced dipole potential is considered. Collision cross section calculations using the DHSS and DTM methods are performed on spheres, models of quasifractal aggregates of varying fractal dimension, and fullerene like structures. Techniques to accelerate DTM calculations by assessing the contribution of grazing gas molecule collisions (gas molecules with altered trajectories by the potential interaction) without tracking grazing trajectories are further discussed. The presented calculation techniques should enable more accurate collision cross section predictions under experimentally relevant conditions than pre-existing approaches, and should enhance the ability of collision cross section measurement schemes to discern the structures of gas phase entities.

  11. Dynamics of electron correlation processes in atoms and atomic collisions

    NASA Astrophysics Data System (ADS)

    Stolterfoht, N.

    1990-08-01

    The dynamics of electron correlation processes are discussed for atoms and ion-atom collision systems. These processes are introduced in analogy with stationary electron correlation phenomena which are well known from atomic structure theory. The role of the Hartree-Fock method in finding a solution within the independent-particle model is pointed out. The concept of configuration interaction is discussed in order to clarify the verification of electron correlation processes. Configuration mixing is treated in stationary states involving bound and continuum electrons. It is pointed out that a specific electron correlation effect in a stationary state corresponds to an analogous effect in a state which evolves in time. In separated atoms emphasis is given to the Auger effect. In ion-atom collisions double ionization and double excitation are analyzed as examples for processes involving dynamic electron correlation.

  12. Collision dynamics of methyl radicals and highly vibrationally excited molecules using crossed molecular beams

    SciTech Connect

    Chu, P.M.Y.

    1991-10-01

    The vibrational to translational (V{yields}T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V{yields}T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH{sub 3} production from the thermal decomposition of azomethane. Elastic scattering of methyl radical and neon was used to differentiate between the methyl radicals and the residual azomethane in the molecular beam.

  13. 1982 bibliography of atomic and molecular processes

    SciTech Connect

    Barnett, C.F.; Crandall, D.H.; Gilbody, H.B.; Gregory, D.C.; Kirkpatrick, M.I.; McDaniel, E.W.; McKnight, R.H.; Meyer, F.W.; Morgan, T.J.; Phaneuf, R.A. (comps.)

    1984-05-01

    This annotated bibliography includes papers on atomic and molecular processes published during 1982. Sources include scientific journals, conference proceedings, and books. Each entry is designated by one or more of the 114 categories of atomic and molecular processes used by the Controlled Fusion Atomic Data Center, Oak Ridge National Laboratory to classify data. Also indicated is whether the work was experimental or theoretical, what energy range was covered, what reactants were investigated, and the country of origin of the first author. Following the bibliographical listing, the entries are indexed according to the categories and according to reactants within each subcategory.

  14. Bibliography of atomic and molecular processes, 1983

    SciTech Connect

    Barnett, C.F.; Crandall, D.H.; Gilbody, H.B.; Gregory, D.C.; Kirkpatrick, M.I.; McDaniel, E.W.; McKnight, R.H.; Meyer, F.W.; Morgan, T.J.; Phaneuf, R.A. (comps.)

    1984-10-01

    This annotated bibliography includes papers on atomic and molecular processes published during 1983. Sources include scientific journals, conference proceedings, and books. Each entry is designated by one or more of the 114 categories of atomic and molecular processes used by the Controlled Fusion Atomic Data Center, Oak Ridge National Laboratory to classify data. Also indicated is whether the work was experimental or theoretical, what energy range was covered, what reactants were investigated, and the country of origin of the first author. Following the bibliographical listing, the entries are indexed according to the categories and according to reactants within each subcategory.

  15. 1985 bibliography of atomic and molecular processes

    SciTech Connect

    Barnett, C.F.; Gilbody, H.B.; Gregory, D.C.; Griffin, P.M.; Havener, C.C.; Howald, A.M.; Kirkpatrick, M.I.; McDaniel, E.W.; Meyer, F.W.; Morgan, T.J. (comps.)

    1986-06-01

    This annotated bibliography includes papers on atomic and molecular processes published during 1985. Sources include scientific journals, conference proceedings, and books. Each entry is designated by one or more of the 114 categories of atomic and molecular processes used by the Controlled Fusion Atomic Data Center, Oak Ridge National Laboratory to classify data. Also indicated is whether the work was experimental or theoretical, what energy range was covered, what reactants were investigated, and the country of origin of the first author. Following the bibliographical listing, the entries are indexed according to the categories and according to reactants within each subcategory.

  16. Accelerator-based atomic and molecular collision physics

    SciTech Connect

    Datz, S. [Oak Ridge National Laboratory, TN (United States)

    1993-05-01

    Accelerators have been shown to have great utility in addressing a broad range of problems in experimental atomic physics. There are, of course, phenomena such as inner-shell MO promotion which can occur only at high collision energies. At much higher energies, large transient Coulomb fields can be generated which lead to copious production electron-positron pairs and to capture of electrons from the negative continuum. But in addition, many advantages can be gained by carrying out low-energy (center-of-mass) collisions at high laboratory energies, specifically in a single pass mode or in multi-pass modes in ion storage rings in which, e.g., collision in the milli-electron volt region can be achieved for electron-molecule reactions. Certain advantages also accrue using {open_quotes}reverse kinematics{close_quotes} in which high velocity ions collide with almost {open_quotes}stationary{close_quotes} electrons as in resonant transfer and excitation (RTE) and collisions of energetic ions in the dense {open_quotes}electron gas{close_quotes} found in crystal channels.

  17. Neighbor list collision-driven molecular dynamics simulation for nonspherical hard particles. I. Algorithmic details

    Microsoft Academic Search

    Aleksandar Donev; Salvatore Torquato; Frank H. Stillinger

    2005-01-01

    In this first part of a series of two papers, we present in considerable detail a collision-driven molecular dynamics algorithm for a system of non-spherical particles, within a parallelepiped simulation domain, under both periodic or hard-wall boundary conditions. The algorithm extends previous event-driven molecular dynamics algorithms for spheres, and is most efficient when applied to systems of particles with relatively

  18. Resource Paper: Molecular Excited State Relaxation Processes.

    ERIC Educational Resources Information Center

    Rhodes, William

    1979-01-01

    Develops the concept of oscillatory v dissipative limits as it applies to electronic excited state processes in molecular systems. Main emphasis is placed on the radiative and nonradiative dynamics of the excited state of a molecule prepared by interaction with light or some other excitation source. (BT)

  19. Molecular sieving silica membrane fabrication process

    DOEpatents

    Raman, Narayan K. (400 Maple St. SE., Apartment 112, Albuquerque, NM 87106); Brinker, Charles Jeffrey (14 Eagle Nest Dr., NE., Albuquerque, NM 87122)

    1998-01-01

    A process for producing a molecular sieve silica membrane comprising depositing a hybrid organic-inorganic polymer comprising at least one organic constituent and at least one inorganic constituent on a porous substrate material and removing at least a portion of the at least one organic constituent of the hybrid organic-inorganic polymer, forming a porous film.

  20. Molecular sieving silica membrane fabrication process

    DOEpatents

    Raman, Narayan K. (Monroeville, PA); Brinker, Charles Jeffrey (Albuquerque, NM)

    1999-01-01

    A process for producing a molecular sieve silica membrane comprising depositing a hybrid organic-inorganic polymer comprising at least one organic constituent and at least one inorganic constituent on a porous substrate material and removing at least a portion of the at least one organic constituent of the hybrid organic-inorganic polymer, forming a porous film.

  1. Molecular sieving silica membrane fabrication process

    DOEpatents

    Raman, N.K.; Brinker, C.J.

    1999-08-10

    A process is described for producing a molecular sieve silica membrane comprising depositing a hybrid organic-inorganic polymer comprising at least one organic constituent and at least one inorganic constituent on a porous substrate material and removing at least a portion of the at least one organic constituent of the hybrid organic-inorganic polymer, forming a porous film. 11 figs.

  2. The relationship between continental collision process and metamorphic pattern in the Himalayan collision belts

    NASA Astrophysics Data System (ADS)

    Oh, Chang-Whan

    2015-04-01

    Both UHP and HP eclogites are reported from the Kaghan Valley and Tso Morari Massif in the western part of the Himalayan collision belt (Ghazanfar and Chaudhry, 1987; Thakur, 1983). UHP eclogites in the Kaghan record peak metamorphic conditions of 770 °C and 30 kbar (O'Brien et al., 2001) and was retrograded into the epidote-amphibolite or blueschist (580-610 °C, 10-13 kbar; Lombardo and Rolfo, 2000). Sensitive high-resolution ion microprobe dating of zircon reveals that the UHP eclogite formed at ca. 46 Ma (Kaneko et al., 2003; Parrish et al., 2006). The Tso Morari UHP eclogite had formed at 750 °C, > 39 kbar (Mukheerjee et al., 2003; Bundy, 1980) and underwent amphibolite facies retro-grade metamorphism (580 °C, 11 kbar) during uplift (Guillot et al., 2008). Peak metamorphism of the Tso Morari Massif was dated at ca. 53-55 Ma (Leech et al., 2005). Only HP eclogites have been reported from the mid-eastern part of the Himalayan collision belt (Lombardo and Rolfo, 2000; Corrie et al., 2010). The HP eclogite in the mid-eastern part may have formed at ca. > 780 °C and 20 kbar and was overprinted by high-pressure granulite facies metamorphism (780-750°C, 12-10 kbar) at ca. 30 Ma (Groppo et al. 2007; Corrie et al., 2010). HP granulite (890 °C, 17-18 kbar) is reported from the NBS, at the eastern terminus of the Himalayan collision belt; the granulite was subjected to retrograde metamorphism to produce lower-pressure granulite (875-850°C, 10-5 kbar), representing near-isothermal decompression (Liu and Zhong, 1997). The HP granulite metamorphism may have occurred at ca. 22-25 Ma. Along the Himalayan collision belt, peak metamorphism changes eastward from UHP eclogite facies through HP eclogite facies to high-pressure granulite facies, indicating a progressive eastwards decrease in the depth of subduction of continental crust and an eastwards increase in the geothermal gradient. The peak metamorphic ages also decrease from 53-46 Ma in the west to 22-25 Ma in the east indicating propagation of collision towards east. The following collision model of the Himalayan collision belt is proposed based on data published in previous studies. Collision between the Indian and Asian blocks started in the west before ca. 55 Ma. In the western part, the amount of oceanic slab subducted prior to continent collision was enough to pull the continental crust down to the depths of UHP metamorphism, as a wide ocean existed between the Asian and Indian blocks prior to collision. Following UHP metamorphism, oceanic slab break-off started at ca. 55~46 Ma in the west due to the very strong buoyancy of the deeply subducted continental block. In contrast, the subduction of continental crust continued at this time in the middle and eastern parts of the belt. The zone of break-off migrated eastward, initiating a change from steep- to low-angle subduction. Final break-off may have occurred in the easternmost part of the belt at ca. 22-25 Ma. The depth of slab break-off decreased toward the east due to the westward decrease of the amount of subducted oceanic crust along the Himalayan collision belt, resulting eastwards decrease of an uplifting rate due to a decrease in buoyancy of the continental slab. The slower uplift resulted in a longer period of thermal relaxation and a higher geothermal gradient. In the west, the high rate of uplift resulted the epidote amphibolite facies (580-610°C) retrograde metamorphic overprint on the UHP eclogites, whereas the relatively slow uplift in the mid-eastern part caused high-grade granulites (850°C) retrograde metamorphic overprint on the HP eclogites. The study indicates that the metamorphic pattern along the collision belt is strongly related to the amount of subducted oceanic crust between continents before collision and the depth of slab break-off. Therefore metamorphic pattern can be used to interpret both the disappeared and ongoing tectonic process during continental collision.

  3. Non-equilibrium fission processes in intermediate energy nuclear collisions

    SciTech Connect

    Loveland, W.; Casey, C.; Xu, Z.; Seaborg, G.T.; Aleklett, K.; Sihver, L.

    1989-04-01

    We have measured the target fragment yields, angular and energy distributions for the interaction of 12-16 MeV/A/sup 32/S with /sup 165/Ho and /sup 197/Au and for the interaction of 32 and 44 MeV/A /sup 40/Ar with /sup 197/Au. The Au fission fragments associated with the peripheral collision peak in the folding angle distribution originate in a normal, ''slow'' fission process in which statistical equilibrium has been established. At the two lowest projectile energies, the Au fission fragments associated with the central collision peak in the folding angle distribution originate in part from ''fast'' (/tau//approximately//sup /minus/23/s), non-equilibrium processes. Most of the Ho fission fragments originate in non- equilibrium processes. The fast, non-equilibrium process giving rise to these fragments has many of the characteristics of ''fast fission'', but the cross sections associated with these fragments are larger than one would expect from current theories of ''fast fission. '' 14 refs., 8 figs.

  4. Vibrational relaxation in H/sub 2/ molecules by wall collisions: applications to negative ion source processes

    SciTech Connect

    Karo, A.M.; Hiskes, J.R.; Hardy, R.J.

    1984-10-01

    In the volume of a hydrogen discharge, H/sub 2/ molecules, excited to high vibrational levels (v'' > 6), are formed either by fast-electron collisions or from H/sub 2//sup +/ ions that are accelerated across the discharge-wall potential that undergo Auger neutralization prior to impact with the discharge chamber wall. We have used computer molecular dynamics to study the de-excitation and re-excitation of vibrationally-excited H/sub 2/ molecules undergoing repeated wall collisions. The initial translational energies range from thermal to 100 eV and the initial vibrational states range from v'' = 2 to v'' = 12. The average loss or gain of vibrational, rotational, translational, and total molecular energies and the survival rates of the molecules have been evaluated. At thermal energies vibrational de-excitation is the predominant process, and a consistent picture emerges of rapid energy redistribution into all the molecular degrees of freedom and a slower rate of loss of total molecular energy to the wall. At higher translational energies (1 to 100 eV) a substantial fraction of the molecules survive with large (v'' > 6) vibrational energy. This vibrational population provides a contribution to the total excited vibrational population comparable to that from the fast-electron collision process.

  5. Double pendulum model for tennis stroke including a collision process

    E-print Network

    Youn, Sun-Hyun

    2015-01-01

    By means of adding a collision process between the ball and racket in double pendulum model, we analyzed the tennis stroke. It is possible that the speed of the rebound ball does not simply depend on the angular velocity of the racket, and higher angular velocity sometimes gives lower ball speed. We numerically showed that the proper time lagged racket rotation increases the speed of the rebound ball by 20%. We also showed that the elbow should move in order to add the angular velocity of the racket.

  6. Transfer excitation processes in ion-atom collisions at high energies

    SciTech Connect

    Hahn, Y. (Department of Physics, University of Connecticut, Storrs, Connecticut 06268 (US))

    1989-09-15

    A theory of ion-atom and ion-molecular collisions at high energies is formulated in which the projectile ions undergo simultaneous electron transfer and excitation (TE). A unified description of both resonant and nonresonant processes is presented. The resonant mode (RTE) is mediated by one of the target electrons, which excites the projectile and at the same time is captured by the projectile ion, thus forming a doubly excited intermediate state of the projectile ion. In the impulse approximation, this is related to the dielectronic recombination process in electron-ion collisions. The same doubly excited states can also be formed by one of the target electrons and the target core, interacting with the projectile ion in which the target core does the exciting and the electron is simply transferred. This is a nonresonant process (NTE), although the projectile is again left in a doubly excited state. We propose here still another mechanism for the formation of doubly excited states, UTE. The new process involves two target electrons in a nonresonant way, just as in the NTE, such that the electron that excites the projectile is left in the continuum, as viewed in the projectile rest frame. Some of the experimental evidence for these reactions is discussed.

  7. Cold state-selected molecular collisions and reactions.

    PubMed

    Stuhl, Benjamin K; Hummon, Matthew T; Ye, Jun

    2014-01-01

    Over the past decade, and particularly the past five years, a quiet revolution has been building at the border between atomic physics and experimental quantum chemistry. The rapid development of techniques for producing cold and even ultracold molecules without a perturbing rare-gas cluster shell is now enabling the study of chemical reactions and scattering at the quantum scattering limit with only a few partial waves contributing to the incident channel. Moreover, the ability to perform these experiments with nonthermal distributions comprising one or a few specific states enables the observation and even full control of state-to-state collision rates in this computation-friendly regime: This is perhaps the most elementary study possible of scattering and reaction dynamics. PMID:24423374

  8. Excitation processes in proton collisions with Li atoms

    NASA Astrophysics Data System (ADS)

    Lee, Teck-Ghee; Pindzola, M. S.

    2011-05-01

    Excitation processes in proton collisions with Li are studied by direct solution of the time-dependent Schrödinger equation in cylindrical coordinates. Within a straight-line trajectory approximation, a time-dependent close-coupling method based on an expansion of a one-electron 3D wavefunction in rotational functions is used to calculate excitation cross sections at incident energies ranging from 10 keV to 200 keV. A peudopotential method is used to treat the 1s2 core. The time-evolved wavefunction which includes all the inelastic processes, including charge transfer, excitation and ionization, is projected onto the lattice states to obtain excitation cross sections for the Li(2s) to Li(2p,3l,4l) transitions. Results are compared with the existing data. This work was supported in part by grants from US DOE. Computational work was carried out at NERSC in Oakland, California.

  9. Near-threshold inelastic collisions using molecular beams with a tunable velocity.

    PubMed

    Gilijamse, Joop J; Hoekstra, Steven; van de Meerakker, Sebastiaan Y T; Groenenboom, Gerrit C; Meijer, Gerard

    2006-09-15

    Molecular scattering behavior has generally proven difficult to study at low collision energies. We formed a molecular beam of OH radicals with a narrow velocity distribution and a tunable absolute velocity by passing the beam through a Stark decelerator. The transition probabilities for inelastic scattering of the OH radicals with Xe atoms were measured as a function of the collision energy in the range of 50 to 400 wavenumbers, with an overall energy resolution of about 13 wavenumbers. The behavior of the cross-sections for inelastic scattering near the energetic thresholds was accurately measured, and excellent agreement was obtained with cross-sections derived from coupled-channel calculations on ab initio computed potential energy surfaces. PMID:16973875

  10. Near-Threshold Inelastic Collisions Using Molecular Beams with a Tunable Velocity

    NASA Astrophysics Data System (ADS)

    Gilijamse, Joop J.; Hoekstra, Steven; van de Meerakker, Sebastiaan Y. T.; Groenenboom, Gerrit C.; Meijer, Gerard

    2006-09-01

    Molecular scattering behavior has generally proven difficult to study at low collision energies. We formed a molecular beam of OH radicals with a narrow velocity distribution and a tunable absolute velocity by passing the beam through a Stark decelerator. The transition probabilities for inelastic scattering of the OH radicals with Xe atoms were measured as a function of the collision energy in the range of 50 to 400 wavenumbers, with an overall energy resolution of about 13 wavenumbers. The behavior of the cross-sections for inelastic scattering near the energetic thresholds was accurately measured, and excellent agreement was obtained with cross-sections derived from coupled-channel calculations on ab initio computed potential energy surfaces.

  11. A molecular dynamics study of defect production due to low-energy collisions

    NASA Astrophysics Data System (ADS)

    Finder, J. M.; Richards, D. F.; Adams, J. B.

    1999-07-01

    Molecular dynamics (MD) simulations of collision cascades were studied in order to understand the effect of energy, temperature and direction of the primary knock-on atom (PKA) on the defect production in single crystal silicon for low-energy collision events. MD simulations were performed with ion energies ranging from 100 eV to 1 keV where the PKA was directed along the three major crystallographic directions at 0, 300 and 600 K. Collision cascades resulting from PKA energies above 100 eV appeared to undergo a solid- to liquid-like transformation at the height of the cascade event. Upon cooling, the liquid-like regions collapse resulting in the formation of numerous isolated defects and clusters of defects. We found that bulk and near-surface collision events followed the modified Kinchin-Pease model for defect production in silicon for the energies studied. Minimal temperature dependence was found for collision events that occurred in the bulk of the silicon crystal within the first 10 ps of the simulation.

  12. Towards the simulation of molecular collisions with a superconducting quantum computer

    NASA Astrophysics Data System (ADS)

    Geller, Michael

    2013-05-01

    I will discuss the prospects for the use of large-scale, error-corrected quantum computers to simulate complex quantum dynamics such as molecular collisions. This will likely require millions qubits. I will also discuss an alternative approach [M. R. Geller et al., arXiv:1210.5260] that is ideally suited for today's superconducting circuits, which uses the single-excitation subspace (SES) of a system of n tunably coupled qubits. The SES method allows many operations in the unitary group SU(n) to be implemented in a single step, bypassing the need for elementary gates, thereby making large computations possible without error correction. The method enables universal quantum simulation, including simulation of the time-dependent Schrodinger equation, and we argue that a 1000-qubit SES processor should be capable of achieving quantum speedup relative to a petaflop supercomputer. We speculate on the utility and practicality of such a simulator for atomic and molecular collision physics. I will discuss the prospects for the use of large-scale, error-corrected quantum computers to simulate complex quantum dynamics such as molecular collisions. This will likely require millions qubits. I will also discuss an alternative approach [M. R. Geller et al., arXiv:1210.5260] that is ideally suited for today's superconducting circuits, which uses the single-excitation subspace (SES) of a system of n tunably coupled qubits. The SES method allows many operations in the unitary group SU(n) to be implemented in a single step, bypassing the need for elementary gates, thereby making large computations possible without error correction. The method enables universal quantum simulation, including simulation of the time-dependent Schrodinger equation, and we argue that a 1000-qubit SES processor should be capable of achieving quantum speedup relative to a petaflop supercomputer. We speculate on the utility and practicality of such a simulator for atomic and molecular collision physics. Work supported by the US National Science Foundation CDI program.

  13. The n-p bremsstrahlung in heavy ion collision processes

    NASA Astrophysics Data System (ADS)

    Blann, M.

    1990-01-01

    The goal is to summarize the current status of the interpretation of energetic gamma-rays in heavy ion collisions via the n-p-bremsstrahlung mechanism. An essential element of the topic is a transport equation to approximate the fast non-equilibrium nucleon-nucleon cascade/emission stage of the heavy ion reactions. It is during this stage that it was expected that the n-p-bremsstrahlung processes produced energetic photons. The Boltzmann master equation (BME) model which will be used as the transport code is briefly described, deferring to earlier works for a more complete description, and present but a single representative comparison with an experimental neutron emission spectrum. The status of the elementary n-p-gamma cross section needed to extend the transport code to photon emission in heavy ion reactions, and the status of these comparisons with data are summarized.

  14. Multielectron removal processes in He{sup 2+}+Na collisions

    SciTech Connect

    Knoop, S.; Hasan, V. G.; Morgenstern, R.; Hoekstra, R. [KVI, Atomic Physics, Rijksuniversiteit Groningen, Zernikelaan 25, NL-9747 AA, Groningen (Netherlands)

    2006-06-15

    Multielectron processes have been studied by measuring the Na{sup 2+} and Na{sup 3+} recoil momenta resulting from 10 keV/amu He{sup 2+}+Na(3s) collisions. The Na{sup 2+} Q-value spectrum shows that transfer ionization dominates two-electron removal. Double capture populates mostly singly excited He(1snl) states. A smaller fraction of double capture leads to doubly excited He. Na{sup 3+} recoil ions are created by double capture into the He ground state and the emission of a third electron into the continuum. The Na{sup 3+} recoil ion is not left in its triplet ground state but in one of the low-lying excited singlet terms due to spin conservation.

  15. Dynamical processes of low-energy carbon ion collision with the graphene supported by diamond

    NASA Astrophysics Data System (ADS)

    Dai, Jinxia; Zhang, Chao; Mao, Fei; Cheng, Wei; Zhang, Feng-Shou

    2014-09-01

    The dynamical processes of a low-energy carbon ion collision with the graphene sheet supported by diamond at three impact positions are studied by using empirical potential molecular dynamics simulations. The energy transformation and the structural evolution have been studied. Five types of processes are observed: adsorption, hybridization, defects formation in diamond, atom emission and transmission. We find that the irradiation damage is closely related to the incident energy and impact position. In our simulations, as the projectile collides at a graphene atom, it transfers most of its energy to the primary knock-on atom, and defects are created in graphene. When the projectile moves perpendicular towards the center of a C-C bond in the graphene sheet, the energy transferred from the projectile to the atoms associated with the bond increases firstly and then decreases with the increasing incident energy, and the graphene sheet remains two-dimensional crystal structure after collision when the incident energy is larger than 360 eV. While the impact location is the center of a hexagonal ring on the graphene sheet, the energy transferred from the projectile to the atoms of the target ring is very small regardless of how large is the incident energy, and the graphene sheet is able to keep perfect crystal structure when the incident energy is larger than 34 eV.

  16. Molecular-state study of He2+-H(1s) and H+-He+(1s) collisions

    NASA Astrophysics Data System (ADS)

    Kimura, M.; Thorson, W. R.

    1981-12-01

    We have computed direct and charge-exchange excitation cross sections for (a) He2+-H(1s) collisions at projectile energies 1 - 20 keV, and for (b) H+-He+(1s) collisions at c.m. energies 1.6 to 8 keV, using the close-coupling method with HeH2+ molecular states as basis and electron translation-factor corrections based on molecular-state switching functions. Basis sets with up to 10 and 12 molecular states have been used, and good convergence of results as a function of basis size is found. The results are compared with recent theoretical calculations of Winter, Lane, and Hatton and with experimental values. For process (a) total charge-transfer cross sections are in generally good agreement with those found by Winter et al. using Bates-McCarroll translation factors and, less quantitatively, so are individual state cross sections for He+(2s,2p0,2p±1). For process (b) significant differences with the results of Winter et al. are found; these appear to be traceable to the different treatments of the electron translational factors used. Charge-transfer cross sections of Winter, Hatton, and Lane

    [Phys. Rev. A 22, 930 (1980)]
    are 14 - 32% higher than those found here using comparable basis sets, and individual state cross sections for direct excitation to He+(2s,2p0,2p±1) are also systematically larger than ours (by as much as a factor of 2 in some cases), although values for individual states are only poorly converged in both calculations. Very good agreement is found in all cases with recent experimental measurements.

  17. Two Electron Processes in Proton-Helium Collisions

    Microsoft Academic Search

    Samuel Wright Bross

    1993-01-01

    Cross sections differential in projectile scattering angle for formation of hydrogen atoms have been measured utilizing recoil ion coincidence techniques in 50 to 175 keV proton-helium collisions. The experimental method allowed separation of the post collision charge states of the target atoms. With a knowledge of the amount of each helium recoil ion charge state produced at each scattering angle,

  18. The Atomic and Molecular Universe: Collisions in Hot Plasmas to the Building Blocks of Life

    NASA Astrophysics Data System (ADS)

    Chutjian, Ara

    2010-03-01

    Basic atomic and molecular collision phenomena are operative at the core of an enormous range of astrophysical plasmas, including the interstellar medium (ISM), protostellar regions, stars, our Sun, and planetary atmospheres, ionospheres, & magnetospheres. Laboratory measurements of cross sections and lifetimes are needed to establish plasma charge-state distributions. A required database includes absolute electron- impact excitation, ionization, and recombination cross sections in highly-charged ions (HCIs); photoionization cross sections; and absolute single- and multiple charge-exchange cross sections between a neutral target and an HCI, as when a solar/stellar wind meets a circumstellar cloud or passing comet to generate X- rays via charge exchange. Since satellites and spacecraft often detect photons from the astronomical object, the infrared-to-X- ray emissions are governed by a balance between collisional excitation and radiative decay, so that accurate lifetimes, branching fractions, and Einstein A and B coefficients are also needed. On yet another level, observations in the infrared-to- millimeter wave region from, for example, the Green Bank Telescope, Spitzer, Sofia, Herschel, and the James Webb Telescope provide information on molecular formation in the ISM and protostellar regions. Over 144 atomic, molecular, and ionic species have been identified to date. Recent laboratory results will be given on formation of some of these polyatomic molecules in superthermal, ground-state H- and O-atom collisions with simple, grain-adsorbed species, and results compared to the impressive array of space spectroscopic data.

  19. Molecular Dynamics Simulation of Defect Production in Collision Cascades in Zircon

    SciTech Connect

    Devanathan, Ram; Corrales, Louis R.; Weber, William J.; Chartier, Alain; Meis, Constantin

    2005-01-01

    Defect production in collision cascades in zircon has been examined by molecular dynamics simulations using a partial charge model combined with the Ziegler-Biersack-Littmark potential. U, Zr, Si and O recoils with energies ranging from 250 eV to 5 keV were simulated in the NVE ensemble. To obtain good statistics, 5-10 cascades in randomly chosen directions were simulated for each ion and energy. The damage consists of mainly Si and O Frenkel pairs, a smaller number of Zr Frenkel pairs, and Zr on Si antisite defects. Defect production, interstitial clustering, ion beam mixing and Si-O-Si polymerization increase with PKA mass and energy.

  20. ATOMIC AND MOLECULAR PHYSICS: Lie Algebraic Approach to Energy Transfer for Collinear Collision of Two Anharmonic Diatomic Molecules

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Yan; Wang, Peng-Cheng; Qiu, Jian-Feng; Wang, Jin-Xi; Hou, Li-Xia; Xie, Jin-Dong Ding, Shi-Liang

    2010-02-01

    An anharmonic oscillator algebra model is used to study the collinear collisions of two diatomic molecules. The transition probability for vibration-vibration energy transfer is presented. For an application of the method, we talk about the collision of N2+CO, N2+O2, and N2+N2. Through long time averaging, the transition probability changes to the function of total energy of the system. Comparing the results with the quantum results, we can see that the dynamical Lie algebraic method is useful for describing the anharmonic diatomic molecular collision.

  1. Overview on collision processes of highly charged ions with atoms present status and problems

    SciTech Connect

    Janev, R.K.

    1983-05-01

    This paper provides a brief discussion on the present status of the collision physics of highly charged ions with atoms. The emphasis is on the main achievements in understanding and describing the most important collision processes, and as charge transfer, ionization and Auger-type processes, and even more on those open problems which, due either to their scientific or practical importance, represent challenges to current research in this field. The paper concentrates on general ideas and problems whose development and solutions have advanced or will advance our basic understanding of the collision dynamics of multiply charged ions with atoms.

  2. Molecular Processing of Polymers with Cyclodextrins

    NASA Astrophysics Data System (ADS)

    Tonelli, Alan E.

    We summarize our recent studies employing the cyclic starch derivatives called cyclodextrins (CDs) to both nanostructure and functionalize polymers. Two important structural characteristics of CDs are taken advantage of to achieve these goals. First the ability of CDs to form noncovalent inclusion complexes (ICs) with a variety of guest molecules, including many polymers, by threading and inclusion into their relatively hydrophobic interior cavities, which are roughly cylindrical with diameters of ˜ 0.5 - 1.0 nm. ?-, ?-, and ?-CD contain six, seven, and eight ?-1,4-linked glucose units, respectively. Warm water washing of polymer-CD-ICs containing polymer guests insoluble in water or treatment with amylase enzymes serves to remove the host CDs and results in the coalescence of the guest polymers into solid samples. When guest polymers are coalesced from the CD-ICs by removing their host CDs, they are observed to solidify with structures, morphologies, and even conformations that are distinct from bulk samples made from their solutions and melts. Molecularly mixed, intimate blends of two or more polymers that are normally immiscible can be obtained from their common CD-ICs, and the phase segregation of incompatible blocks can be controlled (suppressed or increased) in CD-IC coalesced block copolymers. In addition, additives may be more effectively delivered to polymers in the form of their crystalline CD-ICs or soluble CD-rotaxanes. Secondly, the many hydroxyl groups attached to the exterior rims of CDs, in addition to conferring water solubility, provide an opportunity to covalently bond them to polymers either during their syntheses or via postpolymerization reactions. Polymers containing CDs in their backbones or attached to their side chains are observed to more readily accept and retain additives, such as dyes and fragrances. Processing with CDs can serve to both nanostructure and functionalize polymers, leading to greater understanding of their behaviors and to new properties and applications.

  3. Excitation processes in H/sup -/-Kr collisions

    SciTech Connect

    Esaulov, V.A.; Grouard, J.P.; Hall, R.I.; Montmagnon, J.L.

    1987-03-15

    An electron spectroscopy study of H/sup -/-Kr collisions in the 20--500-eV collision energy range revealed the excitation of (2s/sup 2/) /sup 1/S, (2p/sup 2/) /sup 1/D, and (2s2p) /sup 1/P states of H/sup -/ and of the (5s/sup 2/) /sup 2/P/sub 3/2,1/2/ Kr/sup -/ state. The angular distribution of electrons produced from the decay of these states is reported. An anisotropic distribution for the (2s/sup 2/) /sup 1/S state is observed at these energies as was previously reported for H/sup -/ collisions with He, Ar, and H/sub 2/ by Risley and co-workers (Phys. Rev. A 9, 1115 (1974) and IEEE Trans. Nuc. Sci. NS26, 1027 (1979)). Relative cross sections for the excitation of these states are deduced from the angular distributions.

  4. Collision Warning and Sensor Data Processing in Urban Areas

    Microsoft Academic Search

    Christoph Mertz; David Duggins; Jay Gowdy; John Kozar; Robert MacLachlan; Aaron Steinfeld; Arne Suppé; Charles Thorpe; Chieh-Chih Wang

    Providing drivers with comprehensive assistance systems has long been a goal for the automotive industry. The challenge is on many fronts, from building sensors, analyzing sensor data, automated understanding of traffic situations and appropriate interaction with the driver. These issues are discussed with the example of a collision warning system for transit buses.

  5. Plasma and collision processes of hypervelocity meteorite impact in the prehistory of life

    NASA Astrophysics Data System (ADS)

    Managadze, G.

    2010-07-01

    A new concept is proposed, according to which the plasma and collision processes accompanying hypervelocity impacts of meteorites can contribute to the arising of the conditions on early Earth, which are necessary for the appearance of primary forms of living matter. It was shown that the processes necessary for the emergence of living matter could have started in a plasma torch of meteorite impact and have continued in an impact crater in the case of the arising of the simplest life form. It is generally accepted that planets are the optimal place for the origin and evolution of life. In the process of forming the planetary systems the meteorites, space bodies feeding planet growth, appear around stars. In the process of Earth's formation, meteorite sizes ranged from hundreds and thousands of kilometres. These space bodies consisted mostly of the planetesimals and comet nucleus. During acceleration in Earth's gravitational field they reached hypervelocity and, hitting the surface of planet, generated powerful blowouts of hot plasma in the form of a torch. They also created giant-size craters and dense dust clouds. These bodies were composed of all elements needed for the synthesis of organic compounds, with the content of carbon being up to 5%-15%. A new idea of possible synthesis of the complex organic compounds in the hypervelocity impact-generated plasma torch was proposed and experimentally confirmed. A previously unknown and experimentally corroborated feature of the impact-generated plasma torch allowed a new concept of the prehistory of life to be developed. According to this concept the intensive synthesis of complex organic compounds arose during meteoritic bombardment in the first 0.5 billion years at the stage of the planet's formation. This most powerful and destructive action in Earth's history could have played a key role and prepared conditions for the origin of life. In the interstellar gas-dust clouds, the synthesis of simple organic matter could have been explained by an identical process occurring in the plasma torch of hypervelocity collisions between submicron size dust particles. It is assumed that the processes occurred in the highly unbalanced hot plasma simultaneously with the synthesis of simple and complicated organic compounds, thereby ensuring their ordering and assembly. Bona fide experimental evidence presented below indicates that the physical fields generated in the plasma environment in the process of the formation and expansion of the torch meet the main requirements toward “true” local chiral fields. These fields were very likely to be capable to trigger the initial, weak breaking of enantiomer symmetry and determine the “sign” of the asymmetry of the bioorganic world. These fields could have worked as “trapping” fields influencing spontaneous processes occurring in highly overheated and nonequilibrium plasma in the state that is far from the thermodynamical branch of equilibrium and may have contributed to the formation of an environment needed for the synthesis of homochiral molecular structures, which, in turn, were needed for the emergence of the primary forms of living matter. It has been shown experimentally that the plasma-chemical processes in the torch have high catalytic properties and assure the rise of the chemical reaction rates by 10-100 million times. In the process of the plasma flyaway this in turn can assure the fast formation of simple and complicated organic compounds, including hyper-branched polymers. It is possible to assume that predominantly inorganic substances from meteorites were used for the synthesis of complicated organic compounds on early Earth. A laboratory experiment with hypervelocity impact plasma torch modelling by a laser with a Q-switch mode has shown the possibility of high-molecular organic compound synthesis, with mass of approximately 5000 a.m.u. by meteorite impact with an effective diameter of 100 mkm. The target contained only H, C, N and O elements in inorganic forms. The approximation of the curve received in these experimen

  6. Gas-Phase Molecular Dynamics: High Resolution Spectroscopy and Collision Dynamics of Transient Species

    SciTech Connect

    Hall, G.E.

    2011-05-31

    This research is carried out as part of the Gas-Phase Molecular Dynamics program in the Chemistry Department at Brookhaven National Laboratory. Chemical intermediates in the elementary gas-phase reactions involved in combustion chemistry are investigated by high resolution spectroscopic tools. Production, reaction, and energy transfer processes are investigated by transient, double resonance, polarization and saturation spectroscopies, with an emphasis on technique development and connection with theory, as well as specific molecular properties.

  7. Formation of giant molecular clouds in global spiral structures: The role of orbital dynamics and cloud-cloud collisions

    NASA Technical Reports Server (NTRS)

    Roberts, W. W., Jr.; Stewart, G. R.

    1987-01-01

    The different roles played by orbital dynamics and dissipative cloud-cloud collisions in the formation of giant molecular clouds (GMCs) in a global spiral structure are investigated. The interstellar medium (ISM) is simulated by a system of particles, representing clouds, which orbit in a spiral-perturbed, galactic gravitational field. The overall magnitude and width of the global cloud density distribution in spiral arms is very similar in the collisional and collisionless simulations. The results suggest that the assumed number density and size distribution of clouds and the details of individual cloud-cloud collisions have relatively little effect on these features. Dissipative cloud-cloud collisions play an important steadying role for the cloud system's global spiral structure. Dissipative cloud-cloud collisions also damp the relative velocity dispersion of clouds in massive associations and thereby aid in the effective assembling of GMC-like complexes.

  8. Waldmann-Snider collision integrals and nonspherical molecular interaction. II - DWBA-scattering amplitude and cross sections for linear molecules

    Microsoft Academic Search

    W. E. Koehler

    1975-01-01

    The binary scattering amplitude matrix is derived from the general interaction potential between linear molecules. The first-order distorted wave Born approximation (DWBA) is used which is applicable for small nonsphericity of the interaction. The molecular cross sections determining the most important Waldmann-Snider collision integrals are calculated. In particular, the scattering cross section, the orientation cross sections for vector- and tensor

  9. Half-Collision Dynamics of Excited Metal Atom Quenching Processes

    NASA Astrophysics Data System (ADS)

    Wallace, Ingvar Axel, II

    Half-collision studies of the quenching of excited states of Zn by Xe and Cd by H_2, CH_4 and i-C_4H _{10} have been undertaken and have provided information concerning the role of alignment of the excited metal atom p-orbital as well as other dynamical information and details about the potential energy surfaces (curves) involved in the quenching process. Van der Waals complexes of a single metal atom with a rare gas atom or quencher molecule are prepared using a supersonic expansion of the metal vapor, carrier gas and quencher gas. To provide a more detailed understanding of van der Waals bonding involving closed shell metal atoms, spectroscopic investigations of the MgcdotNe, Zncdot Ar and ZncdotKr C ^1Pi_1 and X^1 Sigma_0^+ states as well as the ZncdotXe D^1Sigma _0^+ and X^1Sigma _0^+ states via laser induced fluorescence have also been performed. No fluorescence is observed from the Zn cdotXe C^1Pi_1 state which predissociates to Zn(4s4p^3 P_{rm J}) + Xe, permitting the C state to be characterized via a Zn(4s4p^3P_2) "action spectrum." Modeling of the deeply bound C state and the shallow D state using Morse potentials suggests that the long range tail of the C state curve crosses the inner wall of the D state curve. For the CdcdotCH _4 and CdcdotC _4H_{10} complexes, fluorescence is not observed from either the C or D states. However, Cd(5s5p^3P _{rm J}) action spectra are obtained for C and D state excitation. A Cd(5s5p ^3P_0) action spectrum is observed as a result of CdcdotCH _4 A and B state excitation. Rotational structure is observed in the vibrational bands and has permitted characterization of the Cdcdot CH_4 X and A states within a pseudodiatomic approximation and provided evidence for hindered rotation of the methane molecule. When CdcdotH_2 or CdcdotD_2 is excited to the red of the Cd(5s5p^1 P_1 >=ts 5s5s^1S_0) atomic transition, fluorescence is again absent while Cd(5s5p ^3P_{rm J}) action spectra are observed. The observation in the spectra of vibrational structure, which is superimposed on a continuum, suggests that two processes lead to predissociation. The vibrational structure observed is not consistent with an excited state bound solely by van der Waals forces. It is proposed that the vibrational motion in this state results from the coupling of symmetric stretch and bending vibrations in a C_{rm 2v} geometry.

  10. Anomalous four-fermion processes in electron-positron collisions

    Microsoft Academic Search

    F. A. Berends; A. I. van Sighem

    1995-01-01

    This paper studies the electroweak production of all possible four-fermion collisions with non-standard triple gauge boson couplings. All CP conserving couplings are considered. It is an extension of the methods and strategy, which were recently used for the Standard Model electroweak production of four-fermion final states. Since the fermions are taken to be massless the matrix elements can be evaluated

  11. Anomalous four-fermion processes in electron-positron collisions

    Microsoft Academic Search

    F. A. Berends; A. I. van Sighem

    1995-01-01

    This paper studies the electroweak production of all possible four-fermion states in $e^+e^-$ collisions with non-standard triple gauge boson couplings. All $CP$ conserving couplings are considered. It is an extension of the methods and strategy, which were recently used for the Standard Model electroweak production of four-fermion final states. Since the fermions are taken to be massless the matrix elements

  12. First evidence of hard scattering processes in single tagged ?? collisions

    Microsoft Academic Search

    P. Abreu; W. Adam; T. Adye; E. Agasi; I. Ajinenko; R. Aleksan; G. D. Alekseev; P. P. Allport; S. Almehed; F. M. L. Almeida; S. J. Alvsvaag; U. Amaldi; A. Andreazza; M. L. Andrieux; P. Antilogus; W. D. Apel; Y. Arnoud; B. Åsman; J. E. Augustin; A. Augustinus; P. Baillon; P. Bambade; F. Barao; R. Barate; G. Barbiellini; D. Y. Bardin; G. J. Barker; A. Baroncelli; O. Barring; J. A. Barrio; W. Bartl; M. J. Bates; M. Battaglia; M. Baubillier; J. Baudot; K. H. Becks; M. Begalli; P. Beilliere; P. Beltran; A. C. Benvenuti; M. Berggren; D. Bertrand; F. Bianchi; M. Bigi; M. S. Bilenky; P. Billoir; J. Bjarne; D. Bloch; S. Blyth; V. Bocci; P. N. Bogolubov; T. Bolognese; M. Bonesini; W. Bonivento; P. S. L. Booth; G. Borisov; C. Bosio; B. Bostjancic; S. Bosworth; O. Botner; B. Bouquet; C. Bourdarios; T. J. V. Bowcock; M. Bozzo; S. Braibant; P. Branchini; K. D. Brand; R. A. Brenner; H. Briand; C. Bricman; L. Brillault; R. C. A. Brown; J. M. Brunet; L. Bugge; T. Buran; A. Buys; M. Caccia; M. Calvi; A. J. Camacho Rozas; T. Camporesi; V. Canale; M. Canepa; K. Cankocak; F. Cao; F. Carena; P. Carrilho; L. Carroll; C. Caso; V. Cassio; M. V. Castillo Gimenez; A. Cattai; F. R. Cavallo; L. Cerrito; V. Chabaud; A. Chan; Ph. Charpentier; L. Chaussard; J. Chauveau; P. Checchia; G. A. Chelkov; P. Chliapnikov; V. Chorowicz; J. T. M. Chrin; V. Cindro; P. Collins; J. L. Contreras; R. Contri; E. Cortina; G. Cosme; F. Couchot; H. B. Crawley; D. Crennell; G. Crosetti; J. Cuevas Maestro; S. Czellar; E. Dahl-Jensen; J. Dahm; B. Dalmagne; M. Dam; G. Damgaard; E. Daubie; A. Daum; P. D. Dauncey; M. Davenport; W. Da Silva; C. Defoix; P. Delpierre; N. Demaria; A. De Angelis; H. De Boeck; W. De Boer; S. De Brabandere; C. De Clercq; M. D. M. De Fez Laso; C. De La Vaissiere; B. De Lotto; A. De Min; L. De Paula; C. De Saint-Jean; H. Dijkstra; L. Di Ciaccio; F. Djama; J. Dolbeau; M. Donszelmann; K. Doroba; M. Dracos; J. Drees; M. Dris; Y. Dufour; F. Dupont; D. Edsall; R. Ehret; T. Ekelof; G. Ekspong; M. Elsing; J. P. Engel; N. Ershaidat; M. Espirito Santo; D. Fassouliotis; M. Feindt; A. Ferrer; T. A. Filippas; A. Firestone; H. Foeth; E. Fokitis; F. Fontanelli; F. Formenti; J. L. Fousset; B. Franek; P. Frenkiel; D. C. Fries; A. G. Frodesen; R. Fruhwirth; F. Fulda-Quenzer; H. Furstenau; J. Fuster; D. Gamba; M. Gandelman; C. Garcia; J. Garcia; C. Gaspar; U. Gasparini; Ph. Gavillet; E. N. Gazis; D. Gele; J. P. Gerber; D. Gillespie; R. Gokieli; B. Golob; V. M. Golovatyuk; J. J. Gomez Y Cadenas; G. Gopal; L. Gorn; M. Gorski; V. Gracco; F. Grard; E. Graziani; G. Grosdidier; P. Gunnarsson; J. Guy; U. Haedinger; F. Hahn; M. Hahn; S. Hahn; S. Haider; Z. Hajduk; A. Hakansson; A. Hallgren; K. Hamacher; W. Hao; F. J. Harris; V. Hedberg; R. Henriques; J. J. Hernandez; J. A. Hernando; P. Herquet; H. Herr; T. L. Hessing; E. Higon; H. J. Hilke; T. S. Hill; S. O. Holmgren; P. J. Holt; D. Holthuizen; P. F. Honore; M. Houlden; J. Hrubec; K. Huet; K. Hultqvist; P. Ioannou; P. S. Iversen; J. N. Jackson; R. Jacobsson; P. Jalocha; G. Jarlskog; P. Jarry; B. Jean-Marie; E. K. Johansson; L. Jonsson; P. Juillot; M. Kaiser; G. Kalmus; F. Kapusta; M. Karlsson; E. Karvelas; A. Katargin; S. Katsanevas; E. C. Katsoufis; R. Keranen; B. A. Khomenko; N. N. Khovanski; B. King; N. J. Kjaer; H. Klein; A. Klovning; P. Kluit; A. Koch-Mehrin; J. H. Koehne; B. Koene; P. Kokkinias; M. Koratzinos; K. Korcyl; A. V. Korytov; V. Kostioukhine; C. Kourkoumelis; O. Kouznetsov; P.-H. Kramer; C. Kreuter; J. Krolikowski; I. Kronkvist; W. Krupinski; K. Kulka; K. Kurvinen; C. Lacasta; I. Laktineh; C. Lambropoulos; J. W. Lamsa; L. Lanceri; P. Langefeld; V. Lapin; I. Last; J. P. Laugier; R. Lauhakangas; G. Leder; F. Ledroit; R. Leitner; Y. Lemoigne; J. Lemonne; G. Lenzen; V. Lepeltier; T. Lesiak; J. M. Levy; E. Lieb; D. Liko; R. Lindner; A. Lipniacka; I. Lippi; B. Loerstad; M. Lokajicek; J. G. Loken; A. Lopez-Fernandez; M. A. Lopez Aguera; M. Los; D. Loukas; J. J. Lozano; P. Lutz; L. Lyons; G. Maehlum; J. Maillard; A. Maio; A. Maltezos; F. Mandl; J. Marco; B. Marechal; M. Margoni; J. C. Marin; C. Mariotti; A. Markou; T. Maron; S. Marti; C. Martinez-Rivero; F. Martinez-Vidal; F. Matorras; C. Matteuzzi; G. Matthiae; M. Mazzucato; M. Mc Cubbin; R. Mc Kay; R. Mc Nulty; J. Medbo; C. Meroni; W. T. Meyer; A. Miagkov; M. Michelotto; E. Migliore; I. Mikulec; L. Mirabito; W. A. Mitaroff; G. V. Mitselmakher; U. Mjoernmark; T. Moa; R. Moeller; K. Moenig; M. R. Monge; P. Morettini; H. Mueller; W. J. Murray; B. Muryn; G. Myatt; F. Naraghi; F. L. Navarria; S. Navas; P. Negri; S. Nemecek; W. Neumann; N. Neumeister; R. Nicolaidou; B. S. Nielsen; V. Nikolaenko; P. Niss; A. Nomerotski; A. Normand; V. Obraztsov; A. G. Olshevski; R. Orava; K. Osterberg; A. Ouraou; P. Paganini; M. Paganoni; R. Pain; H. Palka; Th. D. Papadopoulou; L. Pape; F. Parodi; A. Passeri; M. Pegoraro

    1995-01-01

    For the first time, multihadronic production from single tagged ?? collisions has been studied, where one of the scattered leptons was tagged at very low virtual photon absolute mass squared (?Q2? = 0.06 (GeV\\/c2)2). Data collected during 1991 and 1992 in the DELPHI experiment at LEP are shown to agree well with predictions which included the non-perturbative vector meson dominance

  13. Low energy inelastic atomic and molecular collisions. Final report, 11 June 1979-15 January 1981

    SciTech Connect

    Pollack, E.; Smith, W.W.

    1981-04-15

    Ar(++) + Ar collisions are studied with particular emphasis on the single electron capture channels. The dominant process is found to result in Ar(+)(2P) + Ar(+)(3s23p4nl). A weaker process, attributed to the presence of a highly excited Ar(++) state is also seen in the angular range investigated. Our Work on D(+) + H2 showed that rotational excitation of the H2 electronic ground state is the important quasi-elastic process in the E theta 2<1.5 keV deg sq region investigated. Electronic excitation of H2 is seen to occur over a small E theta range. In addition ion-molecule work resulted in a model which could explain previous He(+) + H2 charge-exchange results. Reliable grazing-incidence soft x-ray spectra were taken for the first time showing multiplet and charge-state structure in the 60-100A range from collisions of intense 80-150 keV P(+) and S(+) ion beams with an Ar gas target.

  14. Plasma and collision processes of hypervelocity meteorite impact in the prehistory of life

    Microsoft Academic Search

    G. Managadze

    2010-01-01

    A new concept is proposed, according to which the plasma and collision processes accompanying hypervelocity impacts of meteorites can contribute to the arising of the conditions on early Earth, which are necessary for the appearance of primary forms of living matter. It was shown that the processes necessary for the emergence of living matter could have started in a plasma

  15. All electroweak four fermion processes in electron-positron collisions

    E-print Network

    F. A. Berends; R. Kleiss; R. Pittau

    1994-04-21

    This paper studies the electroweak production of all possible four fermion states in e+ e- collisions. Since the methods employed to evaluate the complete matrix elements and phase space are very general, all four fermion final states in which the charged particles are detected can be considered. Also all kinds of experimental cuts can be imposed. With the help of the constructed event generator a large number of illustrative results is obtained, which show the relevance of backgrounds to a number of signals. For LEP 200 the W-pair signal and its background are discussed, for higher energies also Z-pair and single W and Z signals and backgrounds are presented.

  16. Processes of excitation transfer in collisions of metastable atoms with ions: Matrix elements of exchange interaction

    SciTech Connect

    Belyaev, A.K. [Russian State Pedagogical Univ., St. Petersburg (Russian Federation); Stankova, K.S. [Inst. of Solid-State Physics, Sofia (Bulgaria)

    1995-10-01

    The processes of excitation transfer in collisions of metastable singlet and triplet helium atoms and metastable triplet neon atoms with the ground-state krypton, argon, and xenon ions are theoretically studied. Expressions for the many-electron matrix elements of exchange interaction are derived and investigated. The partial cross sections and the rate constants are calculated for the proposed multichannel model. The excited states of heavy inert gas ions are shown to be nonuniformly populated. It is predicted that the processes of collisions with the singlet metastable helium atoms are characterized by considerably smaller parameters than the processes of collisions with the triplet metastable helium atoms. The theory is compared with the available experimental data. 16 refs.

  17. Cross sections for ionization of rare gas excimers by electron impact and atomic and molecular processes in excimer lasers. Final report 1 Apr 78-30 Sep 79

    SciTech Connect

    Flannery, M.R.; McCann, K.J.

    1980-03-01

    Theoretical cross sections for ionization of metastable excimers - helium, neon, argon, krypton and xenon - and of metastable mercury are presented. Systematic trends in inelastic form factors and Born cross sections for collisional transitions between excited neighboring levels of atoms are discovered and discussed. Key cycles of atomic and molecular collision processes in excimer lasers are delineated and discussed.

  18. Cross sections for ionization of rare gas excimers by electron impact and atomic and molecular processes in excimer lasers. Final report 1 Apr 78-30 Sep 79

    Microsoft Academic Search

    M. R. Flannery; K. J. McCann

    1980-01-01

    Theoretical cross sections for ionization of metastable excimers - helium, neon, argon, krypton and xenon - and of metastable mercury are presented. Systematic trends in inelastic form factors and Born cross sections for collisional transitions between excited neighboring levels of atoms are discovered and discussed. Key cycles of atomic and molecular collision processes in excimer lasers are delineated and discussed.

  19. Cold collisions of polyatomic molecular radicals with S-state atoms in a magnetic field: an ab initio study of He + CH2(X) collisions.

    PubMed

    Tscherbul, T V; Grinev, T A; Yu, H-G; Dalgarno, A; K?os, Jacek; Ma, Lifang; Alexander, Millard H

    2012-09-14

    We develop a rigorous quantum mechanical theory for collisions of polyatomic molecular radicals with S-state atoms in the presence of an external magnetic field. The theory is based on a fully uncoupled space-fixed basis set representation of the multichannel scattering wave function. Explicit expressions are presented for the matrix elements of the scattering Hamiltonian for spin-1/2 and spin-1 polyatomic molecular radicals interacting with structureless targets. The theory is applied to calculate the cross sections and thermal rate constants for spin relaxation in low-temperature collisions of the prototypical organic molecule methylene [CH(2)(X(3)B(1))] with He atoms. To this end, two accurate three-dimensional potential energy surfaces (PESs) of the He-CH(2)(X(3)B(1)) complex are developed using the state-of-the-art coupled-cluster method including single and double excitations along with a perturbative correction for triple excitations and large basis sets. Both PESs exhibit shallow minima and are weakly anisotropic. Our calculations show that spin relaxation in collisions of CH(2), CHD, and CD(2) molecules with He atoms occurs at a much slower rate than elastic scattering over a large range of temperatures (1 ?K-1 K) and magnetic fields (0.01-1 T), suggesting excellent prospects for cryogenic helium buffer-gas cooling of ground-state ortho-CH(2)(X(3)B(1)) molecules in a magnetic trap. Furthermore, we find that ortho-CH(2) undergoes collision-induced spin relaxation much more slowly than para-CH(2), which indicates that magnetic trapping can be used to separate nuclear spin isomers of open-shell polyatomic molecules. PMID:22979854

  20. Multiple electron transfer processes in collisions of N6+ and O7+ with methane

    NASA Astrophysics Data System (ADS)

    Guevara, N. L.; Teixeira, E.; Hall, B.; Deumens, E.; Öhrn, Y.; Sabin, J. R.

    2009-12-01

    Recent experiments on collision processes of O7+ and N6+ ions colliding with methane at the same velocity show unexpected differences in the fragmentation cross sections of the methane. Despite the expected similarity of these two processes, as both projectiles are hydrogenic, the mechanisms of electron transfer are different and lead to different fragmentation cross sections. In the present work, the collisions between N6+ and O7+ ions and methane are investigated theoretically at equal velocities corresponding to projectile energies of 30 and 35 keV, respectively. Electron-nuclear dynamics is used to study multiple electron transfer processes occurring in these collisions. Several multiple charge transfer probabilities are calculated and results, averaged over various orientations of the methane molecule, are reported. The collisions proceed in two stages: a fast stage of electron transfer from methane to the ion, and a much slower stage of breakup of the methane. We find and explain the intuitively unexpected result that the total charge transfer cross section for N6+ is slightly larger, but that the O7+ leaves the methane in a higher charged state with higher probability, leading to more fragmentation in the collisions with O7+ .

  1. Anomalous four-fermion processes in electron-positron collisions

    E-print Network

    F. A. Berends; A. I. van Sighem

    1995-06-22

    This paper studies the electroweak production of all possible four-fermion states in $e^+e^-$ collisions with non-standard triple gauge boson couplings. All $CP$ conserving couplings are considered. It is an extension of the methods and strategy, which were recently used for the Standard Model electroweak production of four-fermion final states. Since the fermions are taken to be massless the matrix elements can be evaluated efficiently, but certain phase space cuts have to be imposed to avoid singularities. Experimental cuts are of a similar nature. With the help of the constructed event generator a number of illustrative results is obtained for $W$-pair production. These show on one hand the distortions of the Standard Model angular distributions caused by either off-shell effects or initial state radiation. On the other hand, also the modifications of distributions due to anomalous couplings are presented, considering either signal diagrams or all diagrams.

  2. From molecular activities and processes to biological function.

    PubMed

    van Helden, J; Naim, A; Lemer, C; Mancuso, R; Eldridge, M; Wodak, S J

    2001-03-01

    This paper describes how biological function can be represented in terms of molecular activities and processes. It presents several key features of a data model that is based on a conceptual description of the network of interactions between molecular entities within the cell and between cells. This model is implemented in the aMAZE database that presently deals with information on metabolic pathways, gene regulation, sub- or supracellular locations, and transport. It is shown that this model constitutes a useful generalisation of data representations currently implemented in metabolic pathway databases, and that it can furthermore include multiple schemes for categorising and classifying molecular entities, activities, processes and localisations. In particular, we highlight the flexibility offered by our system in representing multiple molecular activities and their control, in viewing biological function at different levels of resolution and in updating this view as our knowledge evolves. PMID:11465065

  3. Exchange of microtubule molecular motors during melanosome transport in Xenopus laevis melanophores is triggered by collisions with intracellular obstacles.

    PubMed

    Bruno, Luciana; Echarte, Maria Mercedes; Levi, Valeria

    2008-01-01

    The observation that several cargoes move bidirectionally along microtubules in vivo raised the question regarding how molecular motors with opposed polarity coordinate during transport. In this work, we analyzed the switch of microtubule motors during the transport of melanosomes in Xenopus melanophores by registering trajectories of these organelles moving along microtubules using a fast and precise tracking method. We analyzed in detail the intervals of trajectories showing reversions in the original direction of transport and processive motion in the opposite direction for at least 250 nm. In most of the cases, the speed of the melanosome before the reversion slowly decreases with time approaching zero then, the organelle returns over the same path moving initially at a very high speed and slowing down with time. These results could be explained according to a model in which reversions are triggered by an elastic collision of the cargo with obstacles in the cytosol. This interaction generates a force opposed to the movement of the motor-driven organelle increasing the probability of detaching the active motors from the track. The model can explain reversions in melanosome trajectories as well as other characteristics of in vivo transport along microtubules observed by other authors. Our results suggest that the crowded cytoplasm plays a key role in regulating the coordination of microtubules-dependent motors. PMID:19002657

  4. Photochemotherapy: Molecular And Cellular Processes Involved

    NASA Astrophysics Data System (ADS)

    Spikes, John D.

    1989-03-01

    In photochemotherapy, as exemplified by the photodynamic therapy of tumors, a photosensitizing drug is administered to the patient; then, after a period of time to permit the most effective anatomical distribution of the drug, the diseased area is illuminated using an appropriate source of light of wavelengths absorbed by the sensitizer. In the tumor case, this results in the photochemical alteration of critical kinds of biornolecules in the diseased tissue, which interferes with the normal activities of certain cell organelles. This, in turn, leads to the injury or death of diseased cells in the treated area. This paper briefly reviews the reactive chemical species that can be formed in biological systems by illuminated sensitizers (triplet states of sensitizer molecules, free radicals of sensitizers and cellular components, singlet oxygen, superoxide, hydrogen peroxide, hydroxyl radical) and the kinds of biochemical changes they produce in essential cellular molecules (nucleic acids, proteins, unsaturated lipids, etc.). Also reviewed are the effects of these molecular changes on the structure and function of mammalian cell organelles (membranes, mitochondria, nuclear components, etc.) and the mechanisms of the resulting injury or killing of the cells.

  5. Reduction of the reflected pressure wave in the molecular-dynamics simulation of energetic particle-solid collisions

    NASA Astrophysics Data System (ADS)

    Moseler, Michael; Nordiek, Johannes; Haberland, Hellmut

    1997-12-01

    The collision of an energetic, heavy particle with a solid generates a pressure wave. This leads to a difficulty in modeling the collision by molecular dynamics, as the wave is reflected at the boundary of the necessarily finite simulation zone, making any long-term prediction unreliable. A method has been developed that can drastically reduce the amplitude of the reflected wave. The impact region is described by a realistic potential that is embedded into a much larger harmonic system having the same elastic properties. The high-frequency response is corrected by an additional damping. Using this scheme the impact of an energetic copper cluster onto a copper surface was simulated. The final shape of the surface differed significantly from the outcome of the simulation using conventional Langevin molecular dynamics.

  6. Crossed molecular beam studies of rotational energy transfer in nitric oxide collisions with carbon monoxide and diatomic oxygen

    Microsoft Academic Search

    Joel Andrew Bacon

    1997-01-01

    Crossed molecular beam measurements of state-resolved differential cross sections for NO + O2 and NO + CO inelastic collisions at a relative kinetic energy of 442 cm-1 are reported. The initial states (NO 2Pi1\\/2, \\/nu = 0, j <= 2.5, CO 1Sigma+,\\/ \\/nu = 0, O2\\/ 3Sigma g\\/sp-,\\/ \\/nu = 0) were prepared by pulsed supersonic expansions of pure NO,

  7. Dielectronic processes and electron correlation in energetic ion-atom collisions

    NASA Astrophysics Data System (ADS)

    Stolterfoht, N.

    1991-04-01

    Concepts of electron correlation in energetic ion-atom collisions are discussed in terms of dielectronic processes which are due to two-electron transitions produced by the electron-electron interaction. These dynamic processes are associated with configuration interaction occurring during the collision in the four-body ion-atom system or after the collision in the atomic three-body system. As in previous work, formal aspects of electron correlation in ion-atom collision are introduced in analogy with the treatment in atomic-structure theory. The full electron-electron interaction is partitioned into a mean potential of the passive electrons postulated within the framework of the independent particle model and the residual mutual interaction between two active electrons. Various cases of the interaction of electrons located initially at different nuclear centers are treated. As an example for a dielectronic process, the Bates-Griffing scattering mechanism is discussed concerning the interactions of two electrons centered at the projectile and the target. Furthermore, interferences between the nucleus-electron and electron-electron interaction are analyzed for the process of double excitation.

  8. An Intestinal Surgery Simulator: Real-Time Collision Processing and Visualization

    E-print Network

    Paris-Sud XI, Université de

    An Intestinal Surgery Simulator: Real-Time Collision Processing and Visualization Laks Raghupathi, we present a method for animating the small intestine and the mesentery (the tissue that connects of the intestine. An efficient curvature detection method, along with an adaptive sampling algorithm, is presented

  9. Growth rates of atmospheric molecular clusters determined from cluster appearance times and collision-evaporation fluxes

    NASA Astrophysics Data System (ADS)

    Kontkanen, Jenni; Olenius, Tinja; Lehtipalo, Katrianne; Vehkamäki, Hanna; Kulmala, Markku

    2015-04-01

    The probability of freshly formed particles to survive to climatically relevant sizes is determined by the competition between the coagulation loss rate and the particle growth rate. Therefore, various methods have been developed to deduce the growth rates from measured particle size distributions. Recently, the growth rates of sub-3nm clusters have been determined based on the appearance times of different cluster sizes. However, it is not clear to what extent these growth rates are consistent with the growth rates corresponding to molecular fluxes between clusters. In this work, we simulated the time evolution of a population of sub-3 nm molecular clusters and compared the growth rates determined (1) from the cluster appearance times and (2) from the collision-evaporation fluxes between different cluster sizes. We performed a number of simulations by varying the ambient conditions and the properties of the model substance. In the first simulation set, the Gibbs free energy of the formation of the clusters was assumed to have a single maximum and no minima, corresponding to a monotonically increasing stability as a function of cluster size. The saturation vapor pressure was selected so that the growth proceeded solely via monomer additions. The growth rates were determined separately for each cluster. However, to see the effect of finite size resolution, we also performed simulations where the clusters were grouped into size bins, for which we determined the growth rates. In the second simulation set, the saturation vapor pressure was lowered so that the collisions of small clusters significantly contributed to the growth. As the growth rate of a single cluster is ambiguous in this case, the growth rates were determined only for different size bins. We performed simulations using a similar free energy profile as in other simulations but we also used a free energy profile containing a local minimum, corresponding to small stable clusters. Our simulations show that there may be significant differences between the growth rates determined with the two approaches. The growth rates determined from the appearance times of clusters were generally higher than the flux-equivalent growth rates. The difference between the growth rates was largest for the smallest clusters but its magnitude varied depending on the properties of the model substance and on the ambient conditions, such as the external sink. The use of size bins increased the difference, especially if the width of the size bins was large. In the simulations where non-monomer collisions significantly contributed to the growth, the difference between the two growth rates was smallest in the conditions with high cluster concentrations. Furthermore, when the free energy profile had a minimum, the difference was generally smaller than in the simulations with no minima. While this work assesses the qualitative behavior of the size-dependent growth rates, and calls for caution in the interpretation of growth rates deduced from experiments, quantitative comparisons require information on the specific substance and conditions of interest.

  10. Molecular dynamics simulations for CO2 spectra. II. The far infrared collision-induced absorption band

    NASA Astrophysics Data System (ADS)

    Hartmann, J.-M.; Boulet, C.; Jacquemart, D.

    2011-03-01

    Classical molecular dynamics simulations have been carried out for gaseous CO2 starting from various anisotropic intermolecular potential energy surfaces. Through calculations for a large number of molecules treated as rigid rotors, the time evolution of the interaction-induced electric dipole vector is obtained and the Laplace transform of its autocorrelation function gives the collision-induced absorption rototranslational spectrum. The results are successfully compared with those of previous similar calculations before studies of the influences of the intermolecular potential and induced-dipole components are made. The calculated spectra show a significant sensitivity to anisotropic forces consistently with previous analyses limited to the spectral moments. The present results also demonstrate the importance of vibrational and back-induction contributions to the induced dipole. Comparisons between measured far infrared (0-250 cm-1) spectra at different temperatures and results calculated without the use of any adjustable parameter are made. When the best and more complete input data are used, the quality of our predictions is similar to that obtained by Gruszka et al. [Mol. Phys. 93, 1007 (1998)] after the introduction of ad hoc short-range overlap contributions. Our results thus largely obviate the need for such contributions the magnitudes of which remain questioned. Nevertheless, problems remain since, whereas good agreements with measurements are obtained above 50 cm-1, the calculations significantly underestimate the absorption below, a problem which is discussed in terms of various possible error sources.

  11. Could the Collision of CMEs in the Heliosphere be Super-Elastic? (ii) Influence of the Initial Speed of CMEs on Their Collision Process

    NASA Astrophysics Data System (ADS)

    Shen, F.; Wang, Y.; Shen, C.; Feng, X. S.

    2014-12-01

    In this presentation, we analyze and quantitatively study the influence of the initial speed of the two coronal mass ejections (CMEs) on the CMEs collision process in the heliosphere using a three-dimensional (3-D) numerical magnetohydrodynamics (MHD) simulation. Our recent study [Shen et al., 2013, hereinafter referred to as paper 1] validated numerically that the collision of CMEs in two CMEs interaction event in 2008 November could be super-elastic. To study how the initial speed of the CMEs influences the CMEs collision process, five cases with different initial speed and speed difference are selected. Results show that whether the collision of CMEs could be super-elastic or not is mostly rely on the initial speed difference of the two CMEs rather than the initial speed itself. In the super-elastic cases, the additional magnetic and thermal energies are converted into kinetic energy.

  12. 1979 bibliography of atomic and molecular processes. [Bibliography

    SciTech Connect

    None

    1980-08-01

    This annotated bibliography lists 2146 works on atomic and molecular processes reported in publications dated 1979. Sources include scientific journals, conference proceedings, and books. Each entry is designated by one or more of the 114 categories of atomic and molecular processes used by the Controlled Fusion Atomic Data Center, Oak Ridge National Laboratory, to classify data. Also indicated is whether the work was experimental or theoretical, what energy range was covered, what reactants were investigated, and the country of origin of the first author. Following the bibliographical listing are indexes of reactants and authors.

  13. 1978 bibliography of atomic and molecular processes. [Bibliography

    SciTech Connect

    Not Available

    1980-03-01

    This annotated bibliography lists 2557 works on atomic and molecular processes reported in publications dated 1978. Sources include scientific journals, conference proceedings, and books. Each entry is designated by one or more of the 114 categories of atomic and molecular processes used by the Controlled Fusion Atomic Data Center to classify data. Also indicated is whether the work was experimental or theoretical, what energy range was covered, what reactants were investigated, and the country of origin of the first author. Following the bibliographical listing are indexes of reactants and authors.

  14. Textual collisions: the writing process and the Modernist experiment 

    E-print Network

    Hollis, Erin Michelle

    2005-08-29

    This dissertation explores textual junctures such as this in the compositional processes of James Joyce, Djuna Barnes, Mina Loy and Ezra Pound that illuminate how these modernists negotiated the fraught position of being an author in the early...

  15. Molecular Cell SMADs Stimulate miRNA Processing

    E-print Network

    Bedwell, David M.

    Molecular Cell Previews SMADs Stimulate miRNA Processing Thomas Treiber1 and Gunter Meister1,2,* 1 mechanistic insights into how SMAD proteins regu- lated the biogenesis of a specific subset of human mi, activation of SMAD proteins (SMADs), the transducers of TGFb signaling, have been shown to positively

  16. A Simple Method for Modeling Collision Processes in Plasmas with a Kappa Energy Distribution

    E-print Network

    Hahn, Michael

    2015-01-01

    We demonstrate that a nonthermal distribution of particles described by a kappa distribution can be accurately approximated by a weighted sum of Maxwell-Boltzmann distributions. We apply this method to modeling collision processes in kappa-distribution plasmas, with a particular focus on atomic processes important for solar physics. The relevant collision process rate coefficients are generated by summing appropriately weighted Maxwellian rate coefficients. This method reproduces the rate coefficients for a kappa distribution to an estimated accuracy of better than 5%. This is equal to or better than the accuracy of rate coefficients generated using "reverse engineering" methods, which attempt to extract the needed cross sections from the published Maxwellian rate coefficient data and then reconvolve the extracted cross sections with the desired kappa distribution. Our approach of summing Maxwellian rate coefficients is easy to implement using existing spectral analysis software. Moreover, the weights in the ...

  17. Important Atomic, Molecular and Radiative Processes in Low Pressure Discharge Lamps

    NASA Astrophysics Data System (ADS)

    Lister, Graeme G.

    2007-08-01

    Low pressure discharges are used in a number of light sources, of which the most important application for general lighting is the fluorescent lamp (FL). In conventional FL, electrical energy is converted to UV radiation through excitation of mercury atoms; the UV is then converted to visible radiation using a phosphor. Other atomic radiators, such as sodium and rare gases, are used for applications but are unsuitable for general lighting. In recent years, there has been strong interest in finding alternative atomic and molecular radiators and research is continuing. The efficiency of producing light in a low pressure discharge depends on the balance between ionization processes, which sustain the plasma, and the excitation of atoms or molecules into radiating states through electron impact excitation and collisions between atoms in excited states. Since radiation emitted at one point in the discharge may be absorbed and re-emitted several times before it finally reaches the wall, radiation transport also plays a significant role in determining the fraction of electrical energy which is converted to radiation. Numerical models can help guide the development of more efficient light sources, but there is currently a lack of data for a number of important fundamental processes. This paper will describe the important physical processes in low pressure discharge light sources, and discuss the requirements for new and improved atomic and molecular data.

  18. Visual displays that directly interface and provide read-outs of molecular states via molecular graphics processing units.

    PubMed

    Poje, Julia E; Kastratovic, Tamara; Macdonald, Andrew R; Guillermo, Ana C; Troetti, Steven E; Jabado, Omar J; Fanning, M Leigh; Stefanovic, Darko; Macdonald, Joanne

    2014-08-25

    The monitoring of molecular systems usually requires sophisticated technologies to interpret nanoscale events into electronic-decipherable signals. We demonstrate a new method for obtaining read-outs of molecular states that uses graphics processing units made from molecular circuits. Because they are made from molecules, the units are able to directly interact with molecular systems. We developed deoxyribozyme-based graphics processing units able to monitor nucleic acids and output alphanumerical read-outs via a fluorescent display. Using this design we created a molecular 7-segment display, a molecular calculator able to add and multiply small numbers, and a molecular automaton able to diagnose Ebola and Marburg virus sequences. These molecular graphics processing units provide insight for the construction of autonomous biosensing devices, and are essential components for the development of molecular computing platforms devoid of electronics. PMID:25044570

  19. Electron Transfer Processes to Continuum in Near-Relativistic Ion-Atom Collisions

    SciTech Connect

    Hagmann, S. [Institut fuer Kernphysik, Univ. Frankfurt (Germany); GSI, Darmstadt (Germany); Stoehlker, Th.; Fritzsche, S. [GSI, Darmstadt (Germany); Physik Institut, Univ. Heidelberg (Germany); Surzhykov, A. [Max Planck Institut fuer Kernphysik, Heidelberg (Germany); Physik Institut, Univ. Heidelberg (Germany); Jakubassa-Amundsen, D. [Mathemat. Inst., LMU-Muenchen (Germany); Najjari, B.; Voitkiv, A.; Ullrich, J.; Moshammer, R. [Max Planck Institut fuer Kernphysik, Heidelberg (Germany); Kozhuharov, C.; Gumberidze, A.; Spillmann, U.; Reuschl, R.; Hess, S.; Trotsenko, S.; Bosch, F.; Liesen, D. [GSI, Darmstadt (Germany); Nofal, M. [GSI, Darmstadt (Germany); Max Planck Institut fuer Kernphysik, Heidelberg (Germany); Doerner, R. [Institut fuer Kernphysik, Univ. Frankfurt (Germany); Rothard, H. [CIRIL-Ganil, Caen (France)] (and others)

    2009-03-10

    Theories for electron transfer to the continuum have encountered considerable difficulties to take into account the intrinsic many-electron processes in the capture channel. This may partially be attributed to large momentum transfers involved and thus collision systems are mostly not in the realm of first order perturbation theories. For this reason we have studied collision systems where simultaneously distinct competing electron transfer processes are found to be active, like radiative (RECC) and non-radiative electron capture to continuum (ECC) in the relativistic domain where one or two even active electrons are involved; here another, though distinct, transfer process, the projectile electron loss to continuum (ELC), permits additionally to study the dynamics of ionization very close to threshold. We have studied these electron transfer processes simultaneously in forward electron emission in two systems of different projectile Compton profile, U{sup 88+}+N{sub 2} and Sn{sup 47+}+N{sub 2} collisions using the forward electron spectrometer at the supersonic jet-target of the ESR storage ring. We report first results and compare with theory.

  20. The kinetic one-dimensional equation with frequency of collisions, affine depending on the module molecular velocity

    E-print Network

    A. L. Bugrimov; A. V. Latyshev; A. A. Yushkanov

    2014-03-09

    The one-dimensional kinetic equation with integral of collisions type BGK (Bhatnagar, Gross and Krook) and frequency of collisions affine depending on the module of molecular velocity is constructed. Laws of preservation of number of particles, momentum and energy at construction equation are used. Separation of variables leads to the characteristic equation. The system of the dispersion equations is entered. Its determinant is called as dispersion function. It is investigated continuous and discrete spectra of the characteristic equation. The set of zero of the dispersion equation makes the discrete spectrum of the characteristic equation. The eigen solutions of the kinetic equation corresponding to discrete spectrum are found. The solution of the characteristic equation in space of the generalized functions leads to eigen functions corresponding to the continuous spectrum. Results of the spent analysis in the form of the theorem about structure of the general solution of the entered kinetic equation are formulated.

  1. K-shell processes in heavy-ion collisions in solids and the local plasma approximation

    SciTech Connect

    Kadhane, Umesh; Tribedi, Lokesh C. [Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005 (India); Montanari, C.C. [Instituto de Astronomia y Fisca del Espacio, CONICET-UBA, Buenos Aires (Argentina)

    2003-03-01

    We have investigated K-shell vacancy production due to ionization and electron transfer processes, in collisions of highly charged oxygen ions with various solid targets such as Cl, K, Ti, Fe, and Cu at energies between 1.5 and 6.0 MeV/u. The K-shell ionization cross sections were derived from the measured K x-ray cross sections. An ab initio theoretical model based on the local plasma approximation (LPA), which is an extension of the dielectric formalism to consider core electrons, provides an explanation of the measured data only qualitatively. In case of asymmetric collisions (Z{sub p}/Z{sub t}<0.35, Z{sub p}, Z{sub t} being the atomic numbers of the projectile and target, respectively) and at higher energies, the LPA model explains the data to some extent but deviates for more symmetric collision systems. On the other hand, a perturbed-stationary-state (PSS) calculation (ECPSSR), including the corrective terms due to energy (E) loss, Coulomb (C) deflection, and relativistic (R) wave functions designed for ion-atom collisions agree quite well with the data for different combinations of target and projectile elements. In addition, we have also measured the K(target)-K(projectile) electron transfer cross sections and compared them with a model based on perturbed-stationary-state approximation.

  2. Short Range Radar Signal Processing for Lateral Collision Warning in Road Traffic Scenarios

    Microsoft Academic Search

    Dirk Bank

    2007-01-01

    This paper introduces signal processing algorithms of single-sensor-multi-target-tracking, sensor data fusion, and multi-sensor-multi-target-tracking developed for designing a novel lateral collision warning function. In order to improve the perception of road vehicles, an experimental vehicle has been equipped with arrays of three short range radar sensors on both sides. With the aid of such sensor arrangements, lateral objects (e.g. cars, trucks,

  3. Molecular and dust scattering processes in astrophysical environments

    NASA Astrophysics Data System (ADS)

    Lupu, Roxana-Elena

    2009-06-01

    Understanding the formation and evolution of structure in the universe requires knowledge of the stellar energy output and its processing by gas and dust, evaluating the abundances of atomic and molecular species, and constraining thermodynamic parameters. Molecules, with molecular hydrogen and carbon monoxide being the most abundant, are a major component of the interstellar medium, and play an essential role in structure formation, by participating in gas cooling. Molecular fluorescence studies aim to provide a better interpretation of far-ultraviolet observations, constraining the molecular abundances and their interaction with the radiation field. The fluorescent emission lines offer a set of diagnostics for molecules complementary to absorption line spectroscopy and to observations at infrared and radio wavelengths, but are often poorly reproduced by models. In this work, I have developed and expanded fluorescence models for molecular hydrogen and carbon monoxide, and employed them in determining the spatial distribution of CO in cometary comae, in characterizing the effects of partial frequency redistribution for emission line scattering in planetary atmospheres and reflection nebulae, and in abundance determinations from Bowen fluorescence lines of H 2 in planetary nebulae. Follow-up optical and infrared observations were used in addition to UV data to diagnose molecular excitation, temperature, and spatial distribution in planetary nebula M27. Knowledge of the spectral energy distribution of the exciting stars in the far- ultraviolet is essential in constraining both the fluorescence models and understanding the scattering properties of nebular gas and dust. Sounding rocket observations of the Trifid and Orion nebulae, performed as part of this work, provided the necessary dynamic range and spatial resolution to measure simultaneously the nebular scattered light and the spectral energy distribution of the illuminating stars. These low extinction sight lines offered a unique view of the intrinsic stellar output below 1200 Å, and an excellent proving ground for the instrument performance. The analysis of these observations using fluorescence and dust scattering models is underway.

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    Based on the time-dependent density functional theory, a method is developed to study ion-atom collision dynamics, which self-consistently couples the quantum mechanical description of electron dynamics with the classical treatment of the ion motion. Employing real-time and real-space method, the coordinate space translation technique is introduced to allow one to focus on the region of target or projectile depending on the actual concerned process. The benchmark calculations are performed for the collisions of He2+ + Ne, and the time evolution of electron density distribution is monitored, which provides interesting details of the interaction dynamics between the electrons and ion cores. The cross sections of single and many electron capture and loss have been calculated in the energy range of 1-1000 keV/amu, and the results show a good agreement with the available experiments over a wide range of impact energies.

  5. Interstellar Processes Leading to Molecular Deuterium Enrichment and Their Detection

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.; Kliss, Mark (Technical Monitor)

    2001-01-01

    Large deuterium (D) enrichments in meteoritic materials indicate that interstellar organic materials survived incorporation into parent bodies within the forming Solar System. These enrichments are likelier due to one or more of four distinct astrochemical processes. These are (1) low temperature gas phase ion-molecule reactions; (2) low temperature gas-grain reactions; (3) gas phase unimolecular photodissociation, and (4) ultraviolet photolysis in D-enriched ice mantles. Each of these processes should be associated with molecular carriers having, distinct regiochemical signatures (D placement on the product molecules, correlation with specific chemical functionalities, etc.). These processes are reviewed and specific spectroscopic signatures for the detection of these processes in space are identified and described.

  6. Molecular dynamics simulations for CO2 spectra. III. Permanent and collision-induced tensors contributions to light absorption and scattering

    NASA Astrophysics Data System (ADS)

    Hartmann, J.-M.; Boulet, C.

    2011-05-01

    Classical molecular dynamics simulations have been performed for gaseous CO2 starting from an accurate anisotropic intermolecular potential. Through calculations of the evolutions of the positions and orientations of a large number of molecules, the time evolutions of the permanent and collision-induced electric dipole vector and polarizability tensor are obtained. These are computed from knowledge of static molecular parameters taking only the leading induction terms into account. The Laplace transforms of the auto-correlation functions of these tensors then directly yield the light absorption and scattering spectra. These predictions are, to our knowledge, the first in which the contributions of permanent and collision-induced tensors are simultaneously taken into account for gaseous CO2, without any adjusted parameter. Comparisons between computations and measurements are made for absorption in the region of the ?3 infrared band and for depolarized Rayleigh scattering in the roto-translational band. They demonstrate the quality of the model over spectral ranges from the band center to the far wings where the spectrum varies by several orders of magnitude. The contributions of the permanent and interaction-induced (dipole and polarizability) tensors are analyzed for the first time, through the purely permanent (allowed), purely induced, and cross permanent/induced components of the spectra. It is shown that, while the purely induced contribution is negligible when compared to the collision-broadened allowed component, the cross term due to interferences between permanent and induced tensors significantly participates to the wings of the bands. This successfully clarifies the long lasting, confusing situation for the mechanisms governing the wings of the CO2 spectra considered in this work

  7. Application of real-time low-energy ion scattering spectroscopy to heterointerface formation processes of molecular beam epitaxially grown III-V compound semiconductors

    Microsoft Academic Search

    M. Tamura; T. Saitoh; N. Sugiyama; A. Hashimoto; S. Ohkouchi; N. Ikoma; Y. Morishita

    1994-01-01

    Coaxial impact-collision ion scattering spectroscopy (CAICISS) has been applied for the in situ analysis of heterointerface formation processes and related phenomena of III-V compound semiconductors in a CAICISS\\/molecular beam epitaxy (MBE) system where CAICISS was directly combined with an MBE chamber. We first demonstrate that CAICISS is useful for studying surface step structures by taking vicinal GaAs (100) surfaces as

  8. Ion-Neutral Collisions in the Interstellar Medium: Wave Damping and Elimination of Collisionless Processes

    NASA Astrophysics Data System (ADS)

    Spangler, Steven R.; Savage, Allison H.; Redfield, Seth

    2011-09-01

    Most phases of the interstellar medium contain neutral atoms in addition to ions and electrons. This introduces differences in plasma physics processes in those media relative to the solar corona and the solar wind at a heliocentric distance of 1 astronomical unit. In this paper, we consider two well-diagnosed, partially-ionized interstellar plasmas. The first is the Warm Ionized Medium (WIM) which is probably the most extensive phase in terms of volume. The second is the gas of the Local Clouds of the Very Local Interstellar Medium (VLISM). Ion-neutral interactions seem to be important in both media. In the WIM, ion-neutral collisions are relatively rare, but sufficiently frequent to damp magnetohydrodynamic (MHD) waves (as well as propagating MHD eddies) within less than a parsec of the site of generation. This result raises interesting questions about the sources of turbulence in the WIM. In the case of the VLISM, the ion-neutral collision frequency is higher than that in the WIM, because the hydrogen is partially neutral rather than fully ionized. We present results showing that prominent features of coronal and solar wind turbulence seem to be absent in VLISM turbulence. For example, ion temperature does not depend on ion mass. This difference may be due to ion-neutral collisions, which distribute power from more effectively heated massive ions such as iron to other ion species and neutral atoms.

  9. Inelastic clump collision model for non-Gaussian velocity distribution in molecular clouds

    E-print Network

    Shigeru Ida; Y-h. Taguchi

    1995-09-11

    Non-Gaussian velocity distribution in star forming region is reproduced by inelastic clump collision model. We numerically calculated the evolution of inelastic hard spheres in sheared flow, which corresponds to cloud clumps in differential galactic rotation. This system fluctuates largely around equilibrium state, creating clusters with inelastic collisions and destroying them with shear motion. The fluctuation makes spheres have non-Gaussian velocity distribution with nearly exponential tail. How far from Gaussian distribution depends upon coefficient of restitution, which can produce the variety of degree of deviation from Gaussian among regions.

  10. Time ordering of two-step processes in energetic ion-atom collisions: Basic formalism

    NASA Astrophysics Data System (ADS)

    Stolterfoht, N.

    1993-10-01

    The semiclassical approximation is applied in second order to describe time ordering of two-step processes in energetic ion-atom collisions. Emphasis is given to the conditions for interferences between first- and second-order terms. In systems with two active electrons, time ordering gives rise to a pair of associated paths involving a second-order process and its time-inverted process. Combining these paths within the independent-particle frozen orbital model, time ordering is lost. It is shown that the loss of time ordering modifies the second-order amplitude so that its ability to interfere with the first-order amplitude is essentially reduced. Time ordering and the capability for interference is regained, as one path is blocked by means of the Pauli exclusion principle. The time-ordering formalism is prepared for papers dealing with collision experiments of single excitation [Stolterfoht et al., following paper, Phys. Rev. A 48, 2986 (1993)] and double excitation [Stolterfoht et al. (unpublished)].

  11. Finding Novel Molecular Connections between Developmental Processes and Disease

    PubMed Central

    Park, Jisoo; Wick, Heather C.; Kee, Daniel E.; Noto, Keith; Maron, Jill L.; Slonim, Donna K.

    2014-01-01

    Identifying molecular connections between developmental processes and disease can lead to new hypotheses about health risks at all stages of life. Here we introduce a new approach to identifying significant connections between gene sets and disease genes, and apply it to several gene sets related to human development. To overcome the limits of incomplete and imperfect information linking genes to disease, we pool genes within disease subtrees in the MeSH taxonomy, and we demonstrate that such pooling improves the power and accuracy of our approach. Significance is assessed through permutation. We created a web-based visualization tool to facilitate multi-scale exploration of this large collection of significant connections (http://gda.cs.tufts.edu/development). High-level analysis of the results reveals expected connections between tissue-specific developmental processes and diseases linked to those tissues, and widespread connections to developmental disorders and cancers. Yet interesting new hypotheses may be derived from examining the unexpected connections. We highlight and discuss the implications of three such connections, linking dementia with bone development, polycystic ovary syndrome with cardiovascular development, and retinopathy of prematurity with lung development. Our results provide additional evidence that plays a key role in the early pathogenesis of polycystic ovary syndrome. Our evidence also suggests that the VEGF pathway and downstream NFKB signaling may explain the complex relationship between bronchopulmonary dysplasia and retinopathy of prematurity, and may form a bridge between two currently-competing hypotheses about the molecular origins of bronchopulmonary dysplasia. Further data exploration and similar queries about other gene sets may generate a variety of new information about the molecular relationships between additional diseases. PMID:24874013

  12. The Chemi-Ionization Processes in Slow Collisions of Rydberg Atoms with Ground State Atoms: Mechanism and Applications

    E-print Network

    Mihajlov, A A; Ignjatovic, Lj M; Klyucharev, A N; 10.1007/s10876-011-0438-7

    2012-01-01

    In this article the history and the current state of research of the chemiionization processes in atom-Rydberg atom collisions is presented. The principal assumptions of the model of such processes based on the dipole resonance mechanism, as well as the problems of stochastic ionization in atom-Rydberg atom collisions, are exposed. The properties of the collision kinetics in atom beams of various types used in contemporary experimentations are briefly described. Results of the calculation of the chemi-ionization rate coefficients are given and discussed for the range of the principal quantum number values 5 chemi-ionization processes in astrophysical and laboratory low-temperature plasmas, and the contemporary methods of their investigation are described. Also the directions of further research of chemi-ionization processes are discussed in this article.

  13. High-Resolution Imaging of Velocity-Controlled Molecular Collisions Using Counterpropagating Beams

    NASA Astrophysics Data System (ADS)

    Vogels, Sjoerd N.; Onvlee, Jolijn; von Zastrow, Alexander; Groenenboom, Gerrit C.; van der Avoird, Ad; van de Meerakker, Sebastiaan Y. T.

    2014-12-01

    We present ultrahigh-resolution measurements of state-to-state inelastic differential cross sections for NO-Ne and NO-Ar collisions, obtained by combining the Stark deceleration and velocity map imaging techniques. We show that for counterpropagating crossed beam geometries, the effect of the velocity spreads of the reagent beams on the angular resolution of the images is minimized. Furthermore, the counterpropagating geometry results in images that are symmetric with respect to the relative velocity vector. This allows for the use of inverse Abel transformation methods that enhance the resolution further. State-resolved diffraction oscillations in the differential cross sections are measured with an angular resolution approaching 0.3°. Distinct structures observed in the cross sections gauge the quality of recent ab initio potential energy surfaces for NO-rare-gas atom collisions with unprecedented precision.

  14. ATOMIC AND MOLECULAR PHYSICS: Collision-Induced Coherence Effect on Coherent Population Transfer

    NASA Astrophysics Data System (ADS)

    Yang, Xi-Hua; Zhang, Jun; Zhang, Hui-Fang; Yan, Xiao-Na

    2009-07-01

    We investigate the effect of collision-induced coherence on coherent population transfer with the stimulated Raman adiabatic passage technique in a double A-type four-level system with a widely separated excited doublet. It is shown that when the two pulsed lasers with Rabi frequencies nearly comparable to the energy separation of the doublet are tuned to the particular frequency where the condition for quantum interference is satisfied, the very low transfer efficiency due to the nonadiabatic coupling between the two degenerate adiabatic states could be enhanced significantly with the increase of the collisional decay rates in a moderate range. The enhanced transfer efficiency results from the weakening of the nonadiabatic coupling between the two degenerate adiabatic states realized through collision-induced destructive quantum interference.

  15. Helium Molecular Energy States as Detected by Collisions of the Second Kind in Helium

    Microsoft Academic Search

    Roland Meyerott

    1946-01-01

    From a survey of the literature on spectra enhanced by collisions of the second kind, which take place in helium, evidence is presented for the existence in measurable concentrations of both the helium molecule-ion and the helium metastable molecule. From the intensity distribution of the enhanced spectra, the repulsive energy between two helium atoms at separations of 1.052A and 1.090A

  16. The molecular signalling processes underlying olfactory learning and memory formation in honeybees

    E-print Network

    The molecular signalling processes underlying olfactory learning and memory formation in honeybees December 2011 Abstract ­ The honeybee Apis mellifera provides the opportunity to study molecular signalling, indi- vidual honeybees Apis mellifera perform hier- archic behaviour during brood care, social

  17. Genomic Signal Processing: Predicting Basic Molecular Biological Principles

    NASA Astrophysics Data System (ADS)

    Alter, Orly

    2005-03-01

    Advances in high-throughput technologies enable acquisition of different types of molecular biological data, monitoring the flow of biological information as DNA is transcribed to RNA, and RNA is translated to proteins, on a genomic scale. Future discovery in biology and medicine will come from the mathematical modeling of these data, which hold the key to fundamental understanding of life on the molecular level, as well as answers to questions regarding diagnosis, treatment and drug development. Recently we described data-driven models for genome-scale molecular biological data, which use singular value decomposition (SVD) and the comparative generalized SVD (GSVD). Now we describe an integrative data-driven model, which uses pseudoinverse projection (1). We also demonstrate the predictive power of these matrix algebra models (2). The integrative pseudoinverse projection model formulates any number of genome-scale molecular biological data sets in terms of one chosen set of data samples, or of profiles extracted mathematically from data samples, designated the ``basis'' set. The mathematical variables of this integrative model, the pseudoinverse correlation patterns that are uncovered in the data, represent independent processes and corresponding cellular states (such as observed genome-wide effects of known regulators or transcription factors, the biological components of the cellular machinery that generate the genomic signals, and measured samples in which these regulators or transcription factors are over- or underactive). Reconstruction of the data in the basis simulates experimental observation of only the cellular states manifest in the data that correspond to those of the basis. Classification of the data samples according to their reconstruction in the basis, rather than their overall measured profiles, maps the cellular states of the data onto those of the basis, and gives a global picture of the correlations and possibly also causal coordination of these two sets of states. Mapping genome-scale protein binding data using pseudoinverse projection onto patterns of RNA expression data that had been extracted by SVD and GSVD, a novel correlation between DNA replication initiation and RNA transcription during the cell cycle in yeast, that might be due to a previously unknown mechanism of regulation, is predicted. (1) Alter & Golub, Proc. Natl. Acad. Sci. USA 101, 16577 (2004). (2) Alter, Golub, Brown & Botstein, Miami Nat. Biotechnol. Winter Symp. 2004 (www.med.miami.edu/mnbws/alter-.pdf)

  18. Graphics processing units accelerated semiclassical initial value representation molecular dynamics

    SciTech Connect

    Tamascelli, Dario; Dambrosio, Francesco Saverio [Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy)] [Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy); Conte, Riccardo [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States)] [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States); Ceotto, Michele, E-mail: michele.ceotto@unimi.it [Dipartimento di Chimica, Università degli Studi di Milano, via Golgi 19, 20133 Milano (Italy)] [Dipartimento di Chimica, Università degli Studi di Milano, via Golgi 19, 20133 Milano (Italy)

    2014-05-07

    This paper presents a Graphics Processing Units (GPUs) implementation of the Semiclassical Initial Value Representation (SC-IVR) propagator for vibrational molecular spectroscopy calculations. The time-averaging formulation of the SC-IVR for power spectrum calculations is employed. Details about the GPU implementation of the semiclassical code are provided. Four molecules with an increasing number of atoms are considered and the GPU-calculated vibrational frequencies perfectly match the benchmark values. The computational time scaling of two GPUs (NVIDIA Tesla C2075 and Kepler K20), respectively, versus two CPUs (Intel Core i5 and Intel Xeon E5-2687W) and the critical issues related to the GPU implementation are discussed. The resulting reduction in computational time and power consumption is significant and semiclassical GPU calculations are shown to be environment friendly.

  19. Solution processed molecular floating gate for flexible flash memories

    PubMed Central

    Zhou, Ye; Han, Su-Ting; Yan, Yan; Huang, Long-Biao; Zhou, Li; Huang, Jing; Roy, V. A. L.

    2013-01-01

    Solution processed fullerene (C60) molecular floating gate layer has been employed in low voltage nonvolatile memory device on flexible substrates. We systematically studied the charge trapping mechanism of the fullerene floating gate for both p-type pentacene and n-type copper hexadecafluorophthalocyanine (F16CuPc) semiconductor in a transistor based flash memory architecture. The devices based on pentacene as semiconductor exhibited both hole and electron trapping ability, whereas devices with F16CuPc trapped electrons alone due to abundant electron density. All the devices exhibited large memory window, long charge retention time, good endurance property and excellent flexibility. The obtained results have great potential for application in large area flexible electronic devices. PMID:24172758

  20. A molecular dynamics simulation of the destruction of explosive molecules at high-velocity collisions

    Microsoft Academic Search

    A. A. Selezenev; A. Yu. Aleinikov; I. V. Briginas

    2008-01-01

    The infrared spectra and the energies of dissociation of R-NO2 bonds (R?C, N, and O) were calculated for explosive molecules (trinitrotoluene, hexogen, octogen, pentaerythrityl tetranitrate,\\u000a triaminotrinitrobenzene, and nitromethane). The time of kinetic energy redistribution over intramolecular vibrational modes\\u000a for these molecules (the V-V relaxation time) was calculated by the molecular dynamics simulation method. Molecular dynamics simulations were also used\\u000a to

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

    PubMed

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

    2001-02-01

    Radiative electron capture, the time-reversed photoionization process occurring in ion-atom collisions, provides presently the only access to photoionization studies for very highly charged ions. By applying the deceleration mode of the ESR storage ring, we studied this process in low-energy collisions of bare uranium ions with low- Z target atoms. This technique allows us to extend the current information about photoionization to much lower energies than those accessible for neutral heavy elements in the direct reaction channel. The results prove that for high- Z systems, higher-order multipole contributions and magnetic corrections persist even at energies close to the threshold. PMID:11177990

  2. Molecular solution processing of metal chalcogenide thin film solar cells

    NASA Astrophysics Data System (ADS)

    Yang, Wenbing

    The barrier to utilize solar generated electricity mainly comes from their higher cost relative to fossil fuels. However, innovations with new materials and processing techniques can potentially make cost effective photovoltaics. One such strategy is to develop solution processed photovoltaics which avoid the expensive vacuum processing required by traditional solar cells. The dissertation is mainly focused on two absorber material system for thin film solar cells: chalcopyrite CuIn(S,Se)2 (CISS) and kesterite Cu2ZnSn(S,Se) 4 organized in chronological order. Chalcopyrite CISS is a very promising material. It has been demonstrated to achieve the highest efficiency among thin film solar cells. Scaled-up industry production at present has reached the giga-watt per year level. The process however mainly relies on vacuum systems which account for a significant percentage of the manufacturing cost. In the first section of this dissertation, hydrazine based solution processed CISS has been explored. The focus of the research involves the procedures to fabricate devices from solution. The topics covered in Chapter 2 include: precursor solution synthesis with a focus on understanding the solution chemistry, CISS absorber formation from precursor, properties modification toward favorable device performance, and device structure innovation toward tandem device. For photovoltaics to have a significant impact toward meeting energy demands, the annual production capability needs to be on TW-level. On such a level, raw materials supply of rare elements (indium for CIS or tellurium for CdTe) will be the bottleneck limiting the scalability. Replacing indium with zinc and tin, earth abundant kesterite CZTS exhibits great potential to reach the goal of TW-level with no limitations on raw material availability. Chapter 3 shows pioneering work towards solution processing of CZTS film at low temperature. The solution processed devices show performances which rival vacuum-based techniques and is partially attributed to the ease in controlling composition and CZTS phase through this technique. Based on this platform, comprehensive characterization on CZTS devices is carried out including solar cells and transistors. Especially defects properties are exploited in Chapter 4 targeting to identify the limiting factors for further improvement on CZTS solar cells efficiency. Finally, molecular structures and precursor solution stability have been explored, potentially to provide a universal approach to process multinary compounds.

  3. Validity of central field approximations in molecular scattering - Low energy CO-He collisions

    NASA Technical Reports Server (NTRS)

    Monchick, L.; Green, S.

    1975-01-01

    Close-coupled calculations have been carried out on collisions of helium and carbon monoxide interacting via a theoretical interaction potential which is believed to reproduce accurately the true interaction of this system. These are compared with an equivalent set of calculations for the spherical average of this potential. It is concluded that the latter approximation holds reasonably well for transport-property calculations but not for differential and total scattering cross sections. As a consequence, conservation of scattering-cross-section theorems that are based on this interaction potential do not hold well.

  4. Inelastic collisions in molecular oxygen at low temperature (4 <= T <= 34 K). Close-coupling calculations versus experiment

    NASA Astrophysics Data System (ADS)

    Pérez-Ríos, J.; Tejeda, G.; Fernández, J. M.; Hernández, M. I.; Montero, S.

    2011-05-01

    Close-coupling calculations and experiment are combined in this work, which is aimed at establishing a set of state-to-state rate coefficients for elementary processes ij ? ?m in O2:O2 collisions at low temperature involving the rotational states i, j, ?, m of the vibrational ground state of 16O2(^3? _g^-). First, a set of cross sections for inelastic collisions is calculated as a function of the collision energy at the converged close-coupled level via the MOLSCAT code, using a recent ab-initio potential energy surface for O2-O2 [M. Bartolomei et al., J. Chem. Phys. 133, 124311 (2010), 10.1063/1.3479395]. Then, the corresponding rates for the temperature range 4 ? T ? 34 K are derived from the cross sections. The link between theory and experiment is a Master Equation which accounts for the time evolution of rotational populations in a reference volume of gas in terms of the collision rates. This Master Equation provides a linear function of the rates for each rotational state and temperature. In the experiment, the evolution of rotational populations is measured by Raman spectroscopy in a tiny reference volume (?2 × 10-4 mm3) of O2 travelling along the axis of a supersonic jet at a velocity of ?700 m/s. The accuracy of the calculated rates is assessed experimentally for 10 ? T ? 34 K by means of the Master Equation. The rates, jointly with their confidence interval estimated by Monte Carlo simulation, account to within the experimental uncertainty for the evolution of the populations of the N = 1, 3, 5, 7 rotational triads along the supersonic jet. Confidence intervals range from ?6% for the dominant rates at 34 K, up to ?17% at 10 K. These results provide an experimental validation of state-to-state rates for O2:O2 inelastic collisions calculated in the close-coupling approach and, indirectly, of the anisotropy of the O2-O2 intermolecular potential employed in the calculation for energies up to 300 cm-1.

  5. From molecular shuttles to directed procession of nanorings

    Microsoft Academic Search

    Dan Li; Dagong Fan; Wenwei Zheng; Yongkang Le; Zhisong Wang

    2008-01-01

    Synthetic molecular shuttles prove that controllable nanoscale translation is possible in the curious shape of molecular rings encircling a linear track. However, a shuttle ring’s movement is limited between a pair of binding sites. Ring-locking may provide a molecular mechanism for implementing a major requirement for inchworm nanowalkers. Here we propose a nanowalker in the form of track-encircling molecular rings

  6. Crustal processes cause adakitic chemical signatures in syn-collision magmatism from SE Iran

    NASA Astrophysics Data System (ADS)

    Allen, Mark; Kheirkhah, Monireh; Neill, Iain

    2015-04-01

    We report new elemental and Nd-Sr isotopic analyses for Late Cenozoic intrusive and extrusive rocks emplaced in SE Iran as part of the wider syn-collision magmatic province within the Turkish-Iranian Plateau. The sample sites are near the town of Dehaj in Kerman Province. Most of the rocks are from stocks and batholiths, interpreted as the roots of central volcanoes. Age controls are not precise, but the rocks are likely to be Late Miocene-Quaternary in age. Basaltic to andesitic lavas crop out nearby; their relationships to the intrusive rocks are uncertain. Geochemically, the entire range of rocks from basalt lavas through to rhyolitic intrusives ranges from 51-71 wt.% silica and isotopic signatures are similar to Bulk Earth, without any clear evidence for large-scale crustal contamination. The basaltic to andesitic lavas appear to have variable and often high La/Yb and Sr/Y such that they range from calc-alkaline arc-like rocks to adakitic compositions depending on the degree of fractionation. The intrusive rocks seem to form a separate suite, with clear indications of increasing Sr/Y and Dy/Yb with fractionation. Previous interpretations relate adakitic magmatism to Tethyan oceanic slab break-off and slab melting beneath the collision zone. However, as the 'adakitic signature' is increasingly apparent in more evolved magmas, at least in the intrusives, adakite generation is more likely to have occurred during melt evolution from an initial low Sr/Y and low La/Yb parent. This parental melt may have been similar in starting composition to proposed non-adakitic basaltic melts from elsewhere in the collision zone. The high Sr/Yb and La/Yb signatures are best explained by the suppression of plagioclase fractionation by high magmatic water contents, promoting incompatible behaviour of Sr. Conversely, Y and Yb are compatible during amphibole and garnet fractionation at crustal or uppermost mantle levels. Rather than a localised slab break-off or melting effect, the Dehaj magmatism may have developed its geochemical signature during deep fractionation as the ascent of the magmas was impeded by thick orogenic crust. The rocks may be seen as just another part of the widespread syn-collision magmatism that has affected widespread areas of Turkey, Iran, Armenia and neighbouring countries in the last ~10-15 Ma, and need not be used as markers for debateable geodynamic events such as break-off. Adakites are also present in NE Iran without any obvious association with subduction processes. We argue that magmatism across much of the plateau is linked at least in part to mantle upwelling following Miocene slab break-off, but also to small-scale convection beneath the collision zone, as predicted by numerical modelling. Particular compositions such as those at Dehaj are influenced by local sources and differentiation processes, but there is no need for independent triggers for initial melting across disparate locations.

  7. Collision tectonics

    SciTech Connect

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

    1985-01-01

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

  8. Molecular epidemiology biomarkers-Sample collection and processing considerations

    SciTech Connect

    Holland, Nina T. [Environmental Health Sciences, School of Public Health, University of California, 317 Warren Hall, Berkeley 94720-7360 (United States)]. E-mail: ninah@berkeley.edu; Pfleger, Laura [Environmental Health Sciences, School of Public Health, University of California, 317 Warren Hall, Berkeley 94720-7360 (United States); Berger, Eileen [Input Automation Inc., Sonoma Mountain Road, Glen Ellen, CA 95442 (United States); Ho, Alan [Environmental Health Sciences, School of Public Health, University of California, 317 Warren Hall, Berkeley 94720-7360 (United States); Bastaki, Maria [Environmental Health Sciences, School of Public Health, University of California, 317 Warren Hall, Berkeley 94720-7360 (United States)

    2005-08-07

    Biomarker studies require processing and storage of numerous biological samples with the goals of obtaining a large amount of information and minimizing future research costs. An efficient study design includes provisions for processing of the original samples, such as cryopreservation, DNA isolation, and preparation of specimens for exposure assessment. Use of standard, two-dimensional and nanobarcodes and customized electronic databases assure efficient management of large sample collections and tracking results of data analyses. Standard operating procedures and quality control plans help to protect sample quality and to assure validity of the biomarker data. Specific state, federal and international regulations are in place regarding research with human samples, governing areas including custody, safety of handling, and transport of human samples. Appropriate informed consent must be obtained from the study subjects prior to sample collection and confidentiality of results maintained. Finally, examples of three biorepositories of different scale (European Cancer Study, National Cancer Institute and School of Public Health Biorepository, University of California, Berkeley) are used to illustrate challenges faced by investigators and the ways to overcome them. New software and biorepository technologies are being developed by many companies that will help to bring biological banking to a new level required by molecular epidemiology of the 21st century.

  9. Atomic and molecular surface and volume processes in the analysis of negative hydrogen discharges

    SciTech Connect

    Hiskes, J.R.; Karo, A.M.

    1989-07-03

    The principal source of negative ion generation in hydrogen discharges is now recognized to be low-energy electron attachment to H/sub 2/(/nu//prime//prime/) molecules excited to the middle portion of the vibrational spectrum. Electron excitation processes are generally taken to be the principal source of H/sub 2/(/nu//prime//prime/) generation, with high-energy excitations through the singlet spectrum being the principal excitation process populating the active portion of the vibrational spectrum. A description of the collisional re-excitation from level /nu//prime//prime/, to level /nu//prime//prime/, requires 15 /times/ 15 matrix of cross sections linking all initial and final levels. These cross sections have been evaluated and incorporated into the modelling code. An additional source of vibrational excitation may be derived from recombination of H/sub 2//sup +/ and H/sub 3//sup +/ ions on the surfaces of the discharge. In this case the molecular ions will impinge with kinetic energies given by the plasma potential, 1--10 eV. In this paper we report the evaluation of H/sub 2/(/nu//prime//prime/) resulting from the surface recombination process. The use of low-work-function materials for the discharge surfaces makes possible two additional source of negative ions: the direct formation of negative ions by hydrogen atoms rebounding from the surface, and the dissociation of H/sub 2//sup /minus// ions formed in the surface selvage. A recent paper has demonstrated the efficacy of Ba surfaces as an active medium for H/sup /minus// formation. Here we shall extend our discussion to H/sub 2//sup +/, H/sub 3//sup +/ collisions on Ba surfaces and inventory the generation of H, H/sub 2/(/nu//prime//prime/), and H/sup /minus// rebounding from these surfaces. 16 refs., 4 figs.

  10. Molecular-dynamics-based study of the collisions of hyperthermal atomic oxygen with graphene using the ReaxFF reactive force field.

    PubMed

    Srinivasan, Sriram Goverapet; van Duin, Adri C T

    2011-11-24

    In this work, we have investigated the hyperthermal collisions of atomic oxygens with graphene through molecular dynamics simulations using the ReaxFF reactive force field. First, following Paci et al. (J. Phys. Chem. A 2009, 113, 4677 - 4685), 5-eV energetic collisions of atomic oxygen with a 24-atom pristine graphene sheet and a sheet with a single vacancy defect, both functionalized with oxygen atoms in the form of epoxides, were studied. We found that the removal of an O(2) molecule from the surface of the graphene sheet occurs predominantly through an Eley-Rideal-type reaction mechanism. Our results, in terms of the number of occurrences of various reactive events, compared well with those reported by Paci et al. Subsequently, energetic collisions of atomic oxygen with a 25-times-expanded pristine sheet were investigated. The steady-state oxygen coverage was found to be more than one atom per three surface carbon atoms. Under an oxygen impact, the graphene sheet was always found to buckle along its diagonal. In addition, the larger sheet exhibited trampoline-like behavior, as a result of which we observed a much larger number of inelastic scattering events than those reported by Paci et al. for the smaller system. Removal of O(2) from the larger sheet occurred strictly through an Eley-Rideal-type reaction. Investigation of the events leading to the breakup of a pristine unfunctionalized graphene sheet and the effects of the presence of a second layer beneath the graphene sheet in an AB arrangement was done through successive impacts with energetic oxygen atoms on the structures. Breakup of a graphene sheet was found to occur in two stages: epoxide formation, followed by the creation and growth of defects. Events leading to the breakup of a two-layer graphene stack included epoxide formation, transformation from an AB to an AA arrangement as a result of interlayer bonding, defect formation and expansion in the top layer, and finally erosion of the bottom layer. We observed that the breakup of the two-layer stack occurred through a sequential, layer-by-layer, erosion process. PMID:21942282

  11. Molecular Dynamics Model of Ultraviolet Matrix-Assisted Laser Desorption/Ionization Including Ionization Processes

    E-print Network

    Zhigilei, Leonid V.

    Molecular Dynamics Model of Ultraviolet Matrix-Assisted Laser Desorption/Ionization Including A molecular dynamics model of UV-MALDI including ionization processes is presented. In addition and Dreisewerd has considered the MALDI case in detail.3 Molecular dynamics simulations of MALD (without

  12. Molecular Dynamics Simulations of growth Process of SWNTs in CCVD Method from alcohol

    E-print Network

    Maruyama, Shigeo

    Molecular Dynamics Simulations of growth Process of SWNTs in CCVD Method from alcohol Yasushi with the classical molecular dynamics simulations. Starting from randomly distributed carbon atoms and a Ni cluster to the catalytic metal particle after around 100 ns molecular dynamics simulation, we picked up the metal particle

  13. Validity of approximate methods in molecular scattering - Thermal HCl-He collisions

    NASA Technical Reports Server (NTRS)

    Green, S.; Monchick, L.

    1975-01-01

    Accurate close coupling scattering calculations are presented for thermal energy HCl-He collisions. The interaction potential is obtained from the Gordon-Kim electron gas model, adjusted to have the correct long-range multipole form. A variety of phenomenological cross sections are computed from the close coupling S matrix, and these are compared with results from several commonly employed approximate methods. In particular, it is found that the total integral, total differential, and gas kinetic cross sections are accurately predicted by the central field approximation which retains just the spherical average of the interaction. Integral inelastic cross sections are represented quite accurately by the coupled states approximation of McGuire and Kouri, but only qualitatively by the effective potential method of Rabitz.

  14. Continuous-scan time-resolved FTIR spectroscopy measurements of high energy molecular collisions

    NASA Astrophysics Data System (ADS)

    Sloan, J. J.; Neil, W. S.; Roscoe, J.; Kong, F.-A.

    1998-06-01

    We have studied the dynamics of gas phase collisions between high energy radicals and several small molecules under low pressure conditions, which enable us to resolve single collision events. The experiments are carried out in a fast-flow, low pressure chemiluminescence emission apparatus. Using nanosecond laser photofragmentation, we create pulses of high energy radicals in a flowing stream of a reagent molecule, then record a series of broad-band IR spectra of the emission from the products of the resulting reaction, using time-resolved FTIR spectroscopy (TRFTS). Our TRFTS instrument uses a continuous scan Michelson interferometer to which we have added a data acquisition system of our own design. The latter is based on VME architecture, and permits time resolutions between 1 ?s and 3 ms at the full spectral bandwidth and maximum spectral resolution of the interferometer. Slower time resolutions, down to a few tens of milliseconds, can be obtained at reduced spectral bandwidths. The work to be reported uses a time resolution of a few tens of nanoseconds for the first spectrum, then from 1-3 ?s for the second and subsequent spectra; typically, we record in excess of 20 spectra. The principal observable is the infrared emission from the vibrationally and rotationally excited products of the reaction. This is a very low-background experiment; the sensitivity is on the order of 10-15 moles/litre/quantum state. Where more than one reaction is possible, the relative intensities of the various spectra give the branching ratios for the different channels, while the time dependence of the emission gives the reaction kinetics.

  15. Molecular beam epitaxy for advanced gate stack materials and processes

    NASA Astrophysics Data System (ADS)

    Locquet, Jean-Pierre

    2005-03-01

    The material requirements for future CMOS generations - as given by the ITRS roadmap - are very challenging. This includes a high K dielectric without a low K interfacial layer, a high mobility channel and the appropriate metal gate. With the help of two projects INVEST and ET4US, we are building up a molecular beam epitaxy (MBE) infrastructure to grow this material set on large area wafers that can be further processed into small scale devices. In the INVEST project, we have developed an MBE system for the growth of complex oxides on semiconductors. The system follows the overall design of a production tool and is equipped with an RF atomic oxygen source, effusion cells, e-beam evaporators and a differential pumping stage. The oxide growth process starts with desorbing the initial surface oxide on the Si wafers in ultra-high vacuum and high temperature to create a clean reconstructed 2x1 surface. Using the atomic oxygen it is possible to oxidize the surface in a well controlled manner at low temperature and to grow very thin and dense SiOx layers, followed by the growth of 2-6 nm amorphous high K dielectrics. The process parameters permit to tune the interface layer from a SiOx rich to a silicide rich interface with a significant impact on the capacitance and the leakage. Initial focus is on developing an optimized growth recipe for high quality amorphous HfO2 and LaHfO3.5 films. This recipe was subsequently used to make wafers for a transistor batch that gave us the first N short channel MBE MOSFET's (100 nm) using an etched gate process flow. Some highlights of the first batch for 3nm HfO2 MOSFET are a high mobility (> 270 cm^2/Vs) with a corresponding low leakage current of 2 mA/cm^2). While there were some process issues for LaHfO3.5, the 3 nm MOSFET showed very low leakage currents below 10-6 A/cm^2. Interestingly all the LaHFO3.5 MOSFETs showed very low threshold voltage instabilities. In collaboration with C. Marchiori, M. Sousa, A.Guiller, H. Siegwart, D. Caimi, J. Fompeyrine, D. J Webb, C. Rossel, R. Germann of IBM Research GmbH Zurich Switzerland; L. Pantisano, M. Claes, T. Conard, M. Demand, W. Deweerd, S. DeGendt, M. Heyns, M. Houssa, M. Aoulaiche, G. Lujan, L. Ragnarsson, E. Rohr, T. Schram of IMEC Leuven Belgium; J. Hooker, Z.M Rittersma, Y. Furukawa of Philips Research Leuven Belgium and J. W. Seo of EPFL Lausanne Switzerland.

  16. Excimer Formation and Photodissociation Processes in Aromatic Molecular Clusters.

    NASA Astrophysics Data System (ADS)

    Sun, Sheng

    Excimer formation and photodissociation processes in the aromatic molecular clusters have been investigated in supersonic free jets using various spectroscopic methods. Taking naphthalene clusters as a model system, we have observed size and excess energy dependence on the excimer formation process. The energy threshold for excimer formation in naphthalene trimer occurs at ~870 cm^{-1} with a formation time of ~32 ns. Naphthalene dimer and tetramer have much lower energy barriers and thus exhibit relatively faster excimer formation rates. The structural differences between the clusters are invoked to account for the different excimer formation behaviors. Naphthalene/durene mixed complexes manifest the solvent effect on the excimer formation process by elevating the threshold excess energy and retarding the rate of the excimer formation. This impedance of the excimer formation by the solvent adduct is explained as due to the geometrical restriction and may be used to control the excimer formation process. We have also discovered another important photoprocess in the excimer species--the excimer photodissociation on a repulsive potential. An aromatic cluster in its lowest excimer state can absorb another photon to reach an upper excimer state. Because of the repulsive nature of this upper excimer state, the excimer core dissociates into monomer fragments, one of which is electronically excited. The strong absorption of the excimer state corresponds to an intervalence transition between the two states which are split by the configuration interaction of exciton resonance (ER) and charge resonance (CR) terms. Measurements of the photodepletion of the excimer fluorescence as a function of the photodissociation laser wavelength yields the absorption spectrum of the excimer. The spectrum so obtained has an intensity maximum at about 720 nm for naphthalene and 850 nm for fluorene. These transition energies are in reasonable agreement with the results of the previous theoretical calculations. Detailed analysis of the spectra shows that the lowest excimer state of naphthalene clusters correlates with the S_2 (second excited singlet) state of the monomer, while the corresponding state of the fluorene dimer correlates with the S_1 state of the monomer.

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

    SciTech Connect

    Lu Zhenzhong; Chen Deying; Fan Rongwei; Xia Yuanqin

    2012-01-02

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

  18. A non-adiabatic wavepacket dynamical study of the low energy charge transfer process in the S3+ + H collision

    NASA Astrophysics Data System (ADS)

    ?abuda, Marta; González-Vázquez, Jesús; Martín, Fernando; González, Leticia

    2012-05-01

    The collisional system S3+ + H ? S2+ + H+ has been studied using a time-dependent wavepacket methodology in two-dimensions. Using available potential energy surfaces and coupling matrix elements obtained from multireference ab initio calculations, five non-adiabatically coupled electronic states of 1? symmetry have been included in the dynamical simulations. The collision has been studied in the low energy regime of 1-10 eV. The wavepacket treatment accounts for the description of the collision including all possible impact parameters simultaneously in all spatial directions of the considered plane. The molecular movie of the scattered products arising from charge transfer yields the angular distribution and the total charge transfer probability vs. initial kinetic energy of the projectile. A detailed analysis of the forward, sideways, and backward scattering mechanisms showing different patterns is presented.

  19. Interplay of soft and hard processes and hadron p{sub T} spectra in pA and AA collisions

    SciTech Connect

    Wang, Enke; Wang, Xin-Nian

    2001-09-01

    Motivated by a schematic model of multiple parton scattering within the Glauber formalism, the transverse momentum spectra in pA and AA collisions are analyzed in terms of a nuclear modification factor with respect to pp collisions. The existing data at the CERN Super Proton Synchrotron energies are shown to be consistent with the picture of Glauber multiple scattering in which the interplay between soft and hard processes and the effect of absorptive processes lead to nontrivial nuclear modification of the particle spectra. Relative to the additive model of incoherent hard scattering, the spectra are enhanced at large p{sub T} (hard) by multiple scattering while suppressed at low p{sub T} (soft) by absorptive correction with the transition occurring at around a scale p{sub 0}{approx}1-2 GeV/c that separates soft and hard processes. Around the same scale, the p{sub T} spectra in pp collisions also change from an exponential form at low p{sub T} to a power-law behavior at high p{sub T}. At very large p{sub T}>>p{sub 0}, the nuclear enhancement is shown to decrease as 1/p{sub T}{sup 2}. Implications of these nuclear effects on the study of jet quenching, parton thermalization, and collective radial flow in high-energy AA collisions are discussed.

  20. Characterization of Polarity of Plasma-Assisted Molecular Beam Epitaxial GaN{0001} Film Using Coaxial Impact Collision Ion Scattering Spectroscopy

    Microsoft Academic Search

    Saki Sonoda; Saburo Shimizu; Yasumasa Suzuki; Krishnan Balakrishnan; Jun-ichi Shirakashi; Hajime Okumura

    2000-01-01

    Effects of the initial nitridation of a sapphire(0001) substrate and the thickness of a low-temperature GaN buffer layer on the polarity of GaN{0001} films grown by rf plasma-assisted molecular beam epitaxy (MBE) have been investigated by coaxial impact collision ion scattering spectroscopy (CAICISS). The volume ratios of each domain in grown GaN{0001} films, that is, (0001) and (000\\\\bar{1}), were evaluated

  1. Terminating Structure of Plasma-Assisted Molecular Beam Epitaxial GaN{0001} Film Surface Identified by Coaxial Impact Collision Ion Scattering Spectroscopy

    Microsoft Academic Search

    Saburo Shimizu; Yasumasa Suzuki; Takaharu Nishihara; Shigeki Hayashi; Makoto Shinohara

    1998-01-01

    Terminating structures of the GaN{0001} films grown on nitrided sapphire(0001) substrates by plasma-assisted molecular beam epitaxy (MBE) have been investigated by coaxial impact collision ion scattering spectroscopy (CAICISS). The analyses of incidence angle dependences of time of flight (TOF) spectra have shown that the surfaces of GaN films grown under both N-rich and Ga-rich conditions are (000\\\\=1) N-planes terminated with

  2. Atomic collision effects during PLD processes: nonstoichiometry control in transparent superconductors

    NASA Astrophysics Data System (ADS)

    Hitosugi, Taro; Packwood, D.; Shiraki, S.

    2014-03-01

    The pulsed laser deposition (PLD) growth processes of spinel lithium titanates, Li4Ti5O12 and LiTi2O4, on MgAl2O4 (111) substrates are investigated. Although a Li4Ti5O12 target was used for the depositions, the Li/Ti atomic ratio of the species arriving at the substrate during deposition was only ~0.5, enabling high quality LiTi2O4 films to be prepared with a rocking curve full-width at half-maximum of ~0.05°. The LiTi2O4 epitaxial thin films exhibited high conductivity at room temperature (~3.0 × 103 ?-1cm-1) and a superconducting transition temperature of ~13.3 K. These values are the highest recorded for epitaxial thin films. Moreover, the effect of collisions between the atoms in a plume were studied quantitatively. These results demonstrate the importance of the target composition, providing further insight into Licontaining metal-oxide deposition processes using PLD.

  3. Spin-Alignment and Quasi-Molecular Resonances in Heavy-Ion Collision

    E-print Network

    R. Nouicer; C. Beck; S. J. Sanders; A. Szanto de Toledo; Sl. Cavallaro; E. Uegaki; Y. Abe

    1998-03-10

    Fragment-fragment-$\\gamma$ triple coincidence measurements of the $^{28}$Si~$+$~$^{28}$Si reaction at E$_{\\rm c.m.}$~=~55.8 MeV, carefully chosen to populate a well known quasi-molecular resonance in $^{56}$Ni, have been performed at the VIVITRON tandem facility by using the Eurogam Phase~II $\\gamma$-ray spectrometer. In the $^{28}$Si~$+$~$^{28}$Si reaction, the resonant behavior of the $^{28}$Si $+$ $^{28}$Si exit-channel is clearly observed by the present fragment-fragment coincidence data. The more unexpected result is the spin disalignment of the $^{28}$Si $+$ $^{28}$Si resonance. This has been demonstrated first by the measured angular distributions of the elastic 0$^{+}$, inelastic 2$^{+}$ and mutual excitation channels 2$^{+}-2^{+}$, which are dominated by a unique and pure partial wave with L = 38 ${\\rm \\hbar}$, and has been confirmed by measuring their particle-$\\gamma$ angular correlations with Eurogam Phase II. The spin disalignment supports new molecular model predictions, in which the observed resonance would correspond to the ''Butterfly mode''. A discussion concerning the {\\it spin alignment and spin disalignment} for different systems : $^{12}$C~$+$~$^{12}$C, $^{24}$Mg~$+$~$^{24}$Mg and $^{28}$Si~$+$~$^{28}$Si will be given.}

  4. Stopping powers and cross sections due to two-photon processes in relativistic nucleus-nucleus collision

    NASA Technical Reports Server (NTRS)

    Cheung, Wang K.; Norbury, John W.

    1992-01-01

    The radiation dose received from high energy galactic cosmic rays (GCR) is a limiting factor in the design of long duration space flights and the building of lunar and martian habitats. It is of vital importance to have an accurate understanding of the interactions of GCR in order to assess the radiation environment that the astronauts will be exposed to. Although previous studies have concentrated on the strong interaction process in GCR, there are also very large effects due to electromagnetic (EM) interactions. In this report we describe our first efforts at understanding these EM production processes due to two-photon collisions. More specifically, we shall consider particle production processes in relativistic heavy ion collisions (RHICs) through two-photon exchange.

  5. Molecular dynamics simulation of Li surface erosion and bubble formation

    E-print Network

    Harilal, S. S.

    Molecular dynamics simulation of Li surface erosion and bubble formation Z. Insepov *, A. Hassanein Structure and dynamical properties of liquid Li containing He atoms were studied by the Molecular Dynamics devices. Molecular dynamics (MD) method is capable of studying important collision processes and providing

  6. Direct and charge-exchange excitation processes in H+-H(1s) collisions at 1 to 7 keV

    NASA Astrophysics Data System (ADS)

    Kimura, M.; Thorson, W. R.

    1981-10-01

    We have computed direct and charge-exchange cross sections for H++H(1s)-->H++H(nl) collisions, for projectile energies 1-7 keV, using the close-coupling method with H2+ molecular states modified by electron translation factors (ETF's); switching functions recently derived analytically for exact H2+ states were used to construct ETF corrections. Basis sets with up to 10 molecular states were used in systematic calculations, and good convergence is found for all atomic cross sections with n<=2. Results have been compared with other theoretical calculations [especially that of Crothers and Hughes (1978-1979)] and with recent experiments. Where differences between our results and those of Crothers and Hughes are found, our results agree more closely with experiment. The most notable case is the H(2s) charge-exchange (and direct) cross sections, where our results show no minimum whatever near E=2-4 keV, in agreement with experiments of Morgan et al. (1980) and Hill et al. (1979), but in strong disagreement with the calculations of Crothers and Hughes and 1969 experiments of Bayfield. In one case discrepancies between our results and those of Crothers and Hughes can be shown to arise from their treatment of ETF effects (using a different switching function for the 2p?u state)-i.e., they obtain a much larger population of the 4f?u state than is found here. We have also carried out selected studies with larger basis sets (up to 16u states) to examine the behavior of cross sections for excitation to atomic levels with n>=3. These studies strongly suggest that a "ladder-climbing" sequence of excitations via upper levels is the dominant process by which ionization occurs in H+-H(1s) collisions at these energies.

  7. Collision-induced dissociation of Nb x O{/y +} ( x = 1, 2, y = 2-12) clusters: crossed molecular beams and collision cell studies

    NASA Astrophysics Data System (ADS)

    Mihesan, Claudia; Glodi?, Pavle; Velegrakis, Michalis

    2015-03-01

    Oxygen-rich niobium oxide clusters are formed by mixing laser-produced Nb plasma with pure oxygen, and their stability is investigated by mass spectrometry and collision-induced dissociation. We use an experimental configuration recently developed by our group, where the cluster ions beam is crossed with a secondary beam of noble gas atoms, and the fragments are rejected by a retarding field energy analyzer. In this way, the relative collision cross sections of Nb x O{/y +} ( x = 1, 2, y = 2-12) clusters have been measured and information about their fragmentation channels has been obtained.

  8. Cenozoic Mountain Building Process in the Greater Caucasus, from Subduction to Collision

    NASA Astrophysics Data System (ADS)

    Wang, S. J.; Lee, Y. H.; Chung, S. L.; Okrostsvaridze, A.

    2014-12-01

    The Arabia-Eurasia collision propagates from south to north which results in the south Caspian Sea northward subducting and rapid exhumation in the Greater Caucasus. In this study we conduct the apatite fission track dating combing with previous thermochronolgy data to reveal the comprehensive exhumation history of the Greater Caucasus. The Greater Caucasus shows the bivegent-wedge shape and the highest metamorphic grade shows in the central axis area and decreases to northward and southward. The apatite shows in the central axis area (ca. 2-5 Ma) with highest elevation indicates the highest uplift and exhumation rate area that indicates the all the Caucasus start to rapid exhumation since the Pliocene. The apatite ages increases the ages to the east and west which indicates decreasing the exhumation. Variation the exhumation along the strike of mountain infers different convergence process. To the eastern side the transition or oceanic North Anatolia crust subduct to the Eurasia plate and North Anatolia continent crust subduct and collide with Eurasia plate that result in high exhumation rate in the central Greater Caucasus.

  9. a Quasiclassical Trajectory Study of Impulsive Collisions Between Hydroxyl (= 1-9, K = 1,2,5,10) and Molecular Oxygen in the Upper Mesophere

    NASA Astrophysics Data System (ADS)

    Gilbert, Kathleen L.

    Observations of the hydroxyl airglow are widely used as a remote sensing tool in the study of middle atmosphere dynamics. To assess the validity of this technique, a comprehensive understanding of the excitation and emission processes is required. The effect of collisional quenching of vibrationally excited OH by O_2 remains an outstanding problem in interpreting OH airglow intensity variations. Impulsive collisions between OH^*(nu = 1-9, K = 1,2,5,10) and O_2 are modelled using quasiclassical trajectories to investigate the distribution of product OH^ * states. The mode of vibrational deactivation depends on whether the O or H atom is hit: V-T transfer results in the first case, V-R in the second case. The modelled quenching rates are inconsistent with measured rates of total removal from the vibrational levels via collisions with O_2, indicating that the interaction is not well approximated by impulsive collisions for all vibrational levels. The similarity between the present results and highly excited rotational levels in the lower vibrational levels observed in the airglow support the possibility that impulsive collisions are occurring with another collision partner. In that case, the same mechanism that produces highly excited K^{''} states from collisions with the H atom on OH may also produce significant single quantum quenching (Delta K ~ 0) of the higher vibrational levels due to collisions with the O atom. The internal energy loss associated with these transitions is much greater than kT in the upper mesosphere. Therefore, there is some heating associated with this process.

  10. Coulomb-influenced collisions in aerosols and dusty plasmas

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, Ranganathan; Hogan, Christopher J., Jr.

    2012-02-01

    In aerosol and dusty plasma systems, the behavior of suspended particles (grains) is often strongly influenced by collisions occurring between ions and particles, as well as between particles themselves. In determining the collision kernel or collision rate coefficient for such charged entities, complications arise in that the collision process can be completely described neither by continuum transport mechanics nor by free molecular (ballistic) mechanics; that is, collisions are transition regime processes. Further, both the thermal energy and the potential energy between colliding entities can strongly influence the collision rate and must be considered. Flux-matching theory, originally developed by Fuchs, is frequently applied for calculation of collision rate coefficients under these circumstances. However, recent work suggests that crucial assumptions in flux-matching theory are not appropriate to describe transition regime collisions in the presence of potential interactions. Here, we combine dimensional analysis and mean first passage time calculations to infer the collision kernel between dilute charged entities suspended in a light background gas at thermal equilibrium. The motion of colliding entities is described by a Langevin equation, and Coulombic interactions are considered. It is found that the dimensionless collision kernel for these conditions, H, is a function of the diffusive Knudsen number, KnD (in contrast to the traditional Knudsen number), and the potential energy to thermal energy ratio, ?E. For small and large KnD, it is found that the dimensionless collision kernels inferred from mean first passage time calculations collapse to the appropriate continuum and free molecular limiting forms, respectively. Further, for repulsive collisions (?E negative) or attractive collisions with ?E<0.5, calculated results are in excellent agreement with flux-matching theory predictions, and the dimensionless collision kernel can be determined conveniently via use of the H(KnD) relationship found for hard-sphere collisions with modified definitions of H and KnD to account for potential energy. However, for ?E>0.5, it is found that flux-matching theory predictions substantially underestimate the collision kernel. We find that the collision process in this regime is governed by the minimum of KnD and Kn? (Kn?=3KnD/2?E), and based on calculations, propose a function H(KnD, Kn?) for collision kernel evaluation. The situations for which ?E>0.5 apply to singly charged nanoparticles and multiply charged submicrometer and supermicrometer particles, and are thus prevalent in both aerosol and dusty plasma environments.

  11. Studies of fluctuation processes in nuclear collisions. Progress report, February 15, 1991February 29, 1992

    Microsoft Academic Search

    Ayik

    1992-01-01

    This report discusses the following topics: Relativistic Boltzmann-Langevin model for heavy-ion collision; K+ production far below free neucleon-nucleon threshold and damping of collective vibrations in a memory-dependent transport model.

  12. Studies of fluctuation processes in nuclear collisions. Progress report, February 15, 1991--February 29, 1992

    SciTech Connect

    Ayik, S.

    1992-02-01

    This report discusses the following topics: Relativistic Boltzmann-Langevin model for heavy-ion collision; K+ production far below free neucleon-nucleon threshold and damping of collective vibrations in a memory-dependent transport model.

  13. Free-electron laser induced processes in thin molecular ice.

    PubMed

    Siemer, Björn; Roling, Sebastian; Frigge, Robert; Hoger, Tim; Mitzner, Rolf; Zacharias, Helmut

    2014-01-01

    Intermolecular reactions in and on icy films on silicate and carbonaceous grains constitute a major route for the formation of new molecular constituents in interstellar molecular clouds. In more diffuse regions and in protoplanetary discs, energetic radiation can trigger reaction routes far from thermal equilibrium. As an analog of interstellar ice-covered dust grains, highly-oriented pyrolytic graphite (HOPG) covered with D2O, NO, and H atoms is irradiated by ultrashort XUV pulses and the desorbing ionic and neutral products are analysed. The yields of several products show a nonlinear intensity dependence and thus enable the elucidation of reaction dynamics by two-pulse correlated desorption. PMID:25302398

  14. Stopping powers and cross sections due to two-photon processes in relativistic nucleus-nucleus collisions

    NASA Technical Reports Server (NTRS)

    Cheung, Wang K.; Norbury, John W.

    1994-01-01

    The effects of electromagnetic-production processes due to two-photon exchange in nucleus-nucleus collisions are discussed. Feynman diagrams for two-photon exchange are evaluated using quantum electrodynamics. The total cross section and stopping power for projectile and target nuclei of identical charge are found to be significant for heavy nuclei above a few GeV per nucleon-incident energy.

  15. Parton Energy Loss and Modified Beam Quark Distribution Functions in Drell-Yan Process in p+A Collisions

    Microsoft Academic Search

    Hongxi Xing; Yun Guo; Enke Wang; Xin-Nian Wang

    2011-01-01

    Within the framework of generalized collinear factorization in perturbative QCD (pQCD), we study the effect of initial multiple parton scattering and induced parton energy loss in Drell-Yan (DY) process in proton-nucleus collisions. We express the contribution from multiple parton scattering and induced gluon radiation to the DY dilepton spectra in terms of nuclear modified effective beam quark distribution functions. The

  16. Absolute Doubly Differential Cross Sections for Ejection of Electrons in - and Five-Body Collisions of 20 TO 114-KEV Protons on Atomic and Molecular Hydrogen.

    NASA Astrophysics Data System (ADS)

    Kerby, George W., III

    A crossed-beam experiment was performed to detect ejected electrons from ground-state atomic and molecular hydrogen after collisions with 20- to 114-keV protons. Because a pure atomic hydrogen target is not readily attainable, a method has been devised which yields atomic to molecular hydrogen doubly differential cross section (DDCS) ratios. Since the molecular hydrogen DDCS's were independently measured, the atomic cross sections could be directly calculated. Absolute cross sections differential in electron energy and angle were measured for electron energies ranging from 1.5 to 400 eV and scattering angles from 15^circ to 165^circ with respect to the fast beam. Electrons and ions were energy analyzed by an electrostatic hemispherical analyzer, which has an energy resolution of 5% and is rotatable in the scattering plane about the collision center. Atomic hydrogen is produced by a radio-frequency discharge of the type devised by J. Slevin. Hydrogen gas effuses from a 1 mm diameter nozzle in a nearly cos theta distribution. The projectile beam intersects the thermal gas targets 4 mm below the tip of the nozzle. Dissociation fractions of 74% and atomic hydrogen densities of 7 times 10 ^{11} cm^ {-3} were typical. The fraction of dissociated hydrogen was measured by detecting the reduced 9-eV ion signal from the molecular target when the RF is on. This characteristic ion signal originates from the coulomb breakup of the molecule and dissociative channels of excited H _sp{2}{+}. An auxiliary experiment was performed to determine the target densities with the aid of a low-resolution magnetic mass spectrometer after the slow recoil ions were extracted from the collision volume by a weak electric field. Comparisons of the atomic cross sections are made with theories such as the classical-trajectory Monte Carlo (CTMC) method, the plane-wave Born approximation (PWBA) and the continuum-distorted-wave eikonal-initial-state (CDW-EIS) approximation.

  17. Evolutionary processes and evolutionary noise at the molecular level

    Microsoft Academic Search

    Emile Zuckerkandl

    1976-01-01

    Summary The distinction between molecular sites that mainly carry out general functions and sites committed to specific functions is analyzed, notably in terms of different evolutionary variabilities. Functional density is defined as the proportion of sites involved in specific functions. Weighted functional density, by representing the relative variability at specific-function sites is to some extent a measure of the specificity

  18. A Hybrid approach to molecular continuum processes combiningGaussian basis functions and the discrete variable representation

    SciTech Connect

    Rescigno, Thomas N.; Horner, Daniel A.; Yip, Frank L.; McCurdy,C. William

    2005-08-29

    Gaussian basis functions, routinely employed in molecular electronic structure calculations, can be combined with numerical grid-based functions in a discrete variable representation to provide an efficient method for computing molecular continuum wave functions. This approach, combined with exterior complex scaling, obviates the need for slowly convergent single-center expansions, and allows one to study a variety of electron-molecule collision problems. The method is illustrated by computation of various bound and continuum properties of H2+.

  19. Rotational inelastic cross sections for OCS-Ar, OCS-He, OCS-H2 collisions - A comparison between theory and experiment. [applicable to interstellar processes

    NASA Technical Reports Server (NTRS)

    Broquier, M.; Picard-Bersellini, A.; Whitaker, B. J.; Green, S.

    1986-01-01

    The experimental determination of absorption line profiles for OCS nu3 vibrational transitions broadened by collisions with Ar, He, and H3 buffer gases is reported. The experimental method using diode laser spectroscopy in the five micron region is described. The data are compared with theoretical values obtained using intermolecular potentials previously suggested for these systems and infinite order sudden approximation molecular scattering calculations.

  20. Thermodynamics of irreversible processes and derivation of a system of differential equations for molecular transfer

    Microsoft Academic Search

    P. V. Tsoi

    1965-01-01

    On the basis of the linear laws of the thermodynamics of irreversible processes and the law of conservation of matter, a system of differential equations is derived for molecular transfer in the presence of n interrelated flows of generalized charges.

  1. Cloud–Cloud Collision as a Trigger of the High-mass Star Formation: a Molecular Line Study in RCW120

    NASA Astrophysics Data System (ADS)

    Torii, K.; Hasegawa, K.; Hattori, Y.; Sano, H.; Ohama, A.; Yamamoto, H.; Tachihara, K.; Soga, S.; Shimizu, S.; Okuda, T.; Mizuno, N.; Onishi, T.; Mizuno, A.; Fukui, Y.

    2015-06-01

    RCW 120 is a Galactic H ii region that has a beautiful ring shape that is bright in the infrared. Our new CO J = 1–0 and J = 3–2 observations performed with the NANTEN2, Mopra, and ASTE telescopes have revealed that two molecular clouds with a velocity separation of 20 km s?1 are both physically associated with RCW 120. The cloud at ?8 km s?1 apparently traces the infrared ring, while the other cloud at ?28 km s?1 is distributed just outside the opening of the infrared ring, interacting with the H ii region as suggested by the high kinetic temperature of the molecular gas and by the complementary distribution with the ionized gas. A spherically expanding shell driven by the H ii region is usually considered to be the origin of the observed ring structure in RCW 120. Our observations, however, indicate no evidence of the expanding motion in the velocity space, which is inconsistent with the expanding shell model. We postulate an alternative that, by applying the model introduced by Habe & Ohta, the exciting O star in RCW 120 was formed by a collision between the present two clouds at a collision velocity of ?30 km s?1. In the model, the observed infrared ring can be interpreted as the cavity created in the larger cloud by the collision, whose inner surface is illuminated by the strong ultraviolet radiation after the birth of the O star. We discuss that the present cloud–cloud collision scenario explains the observed signatures of RCW 120, i.e., its ring morphology, coexistence of the two clouds and their large velocity separation, and absence of the expanding motion.

  2. A molecular dynamics simulation of the fullerene formation process

    Microsoft Academic Search

    Yasutaka Yamaguchi; Shigeo Maruyama

    1998-01-01

    A molecular dynamics simulation starting from 500 isolated carbon atoms resulted in several closed caged structures under suitable temperature control. A caged C70 cluster that appeared in the simulation was traced back to study the dynamics and structure of Cn precursors: simple chain and ring for n<20, tangled poly-cyclic structure for 2030. Furthermore, it

  3. MOLECULAR CLOUDS IN THE TRIFID NEBULA M20: POSSIBLE EVIDENCE FOR A CLOUD-CLOUD COLLISION IN TRIGGERING THE FORMATION OF THE FIRST GENERATION STARS

    SciTech Connect

    Torii, K.; Enokiya, R.; Sano, H.; Yoshiike, S.; Hanaoka, N.; Ohama, A.; Furukawa, N.; Dawson, J. R.; Moribe, N.; Oishi, K.; Nakashima, Y.; Okuda, T.; Yamamoto, H.; Kawamura, A.; Mizuno, N.; Onishi, T.; Fukui, Y. [Department of Physics and Astrophysics, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Maezawa, H. [Department of Astrophysics, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); Mizuno, A., E-mail: torii@a.phys.nagoya-u.ac.jp [Solar-Terrestrial Environment Laboratory, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan)

    2011-09-01

    A large-scale study of the molecular clouds toward the Trifid Nebula, M20, has been made in the J = 2-1 and J = 1-0 transitions of {sup 12}CO and {sup 13}CO. M20 is ionized predominantly by an O7.5 star HD164492. The study has revealed that there are two molecular components at separate velocities peaked toward the center of M20 and that their temperatures-30-50 K as derived by a large velocity gradient analysis-are significantly higher than the 10 K of their surroundings. We identify the two clouds as the parent clouds of the first generation stars in M20. The mass of each cloud is estimated to be {approx}10{sup 3} M{sub sun} and their separation velocity is {approx}8 km s{sup -1} over {approx}1-2 pc. We find that the total mass of stars and molecular gas in M20 is less than {approx}3.2 x 10{sup 3} M{sub sun}, which is too small by an order of magnitude to gravitationally bind the system. We argue that the formation of the first generation stars, including the main ionizing O7.5 star, was triggered by the collision between the two clouds in a short timescale of {approx}1 Myr, a second example alongside Westerlund 2, where a super-star cluster may have been formed due to cloud-cloud collision triggering.

  4. Simultaneous process and molecular design/selection through property integration 

    E-print Network

    Qin, Xiaoyun

    2007-04-25

    The overall purpose of this work is to develop systematic methodology for the simultaneous design and selection of processes and molecules (materials). A propertybased approach is used to develop an interface between process ...

  5. Effects of adsorption and roughness upon the collision processes at the convertor surface of a plasma sputter negative ion source

    SciTech Connect

    Kenmotsu, T.; Wada, M. [Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto 610-0394 (Japan)

    2012-02-15

    Atomic collision processes associated with surface production of negative hydrogen ions (H{sup -}) by particle reflection at molybdenum surface immersed in hydrogen plasma have been investigated. To calculate sputtering yields of Cs, as well as energy spectra and angular distributions of reflected hydrogen atoms from molybdenum surface by H{sup +} ion and Cs{sup +} ion bombardments, a Monte Carlo simulation code ACAT (Atomic Collision in Amorphous Target) was run with the corresponding surface conditions. A fractal surface model has been developed and adopted to ACAT for evaluating the effect due to roughness of target material. The results obtained with ACAT have indicated that the retention of hydrogen atoms leads to the reduction in sputtering yields of Cs, and the surface roughness does largely affect the sputtering yields of Cs.

  6. A theoretical study of charge transfer and ionization processes in He+-H2O collisions

    NASA Astrophysics Data System (ADS)

    Murakami, Mitsuko; Kirchner, Tom; Horbatsch, Marko; Lüdde, Hans Jürgen

    2011-05-01

    A recently introduced method for the description of ion-molecule collisions is extended to deal with a situation, in which not only target but also projectile electrons undergo transitions. All initially populated orbitals are propagated simultaneously in the same effective mean-field potential to ensure their orthogonality at all times. The asymptotic solutions are combined to many-electron transition probabilities by using the inclusive probabilities formalism which respects the Pauli principle. It will be shown that this analysis has interesting consequences for the charge transfer channels in intermediate energy He+-H2O collisions. This work has been supported by NSERC Canada and SHARCNET.

  7. Interfacial process of nucleation and molecular nucleation templator

    NASA Astrophysics Data System (ADS)

    Liu, X. Y.

    2001-07-01

    Interfacial effects of nucleation inhibition and promotion were identified from the nucleation of paracetamol. Unlike the classic interfacial effects, which are caused by the change in nucleation barrier, the nonepitaxial interfacial effects are only associated with kink integration kinetics. Methylparaben inhibits nucleation by increasing the desolvation free energy barrier, which is revealed as the nonepitaxial interfacial effect of nucleation inhibition. Polysaccharide revealed its nonepitaxial interfacial effects of nucleation promotion by lowering the conformation entropic barrier via liquid molecule preordering. Polysaccharide can be regarded as an example of molecular nucleation promoter based on the nonepitaxial interfacial effects.

  8. VUV diagnostic of electron impact processes in low temperature molecular hydrogen plasma

    E-print Network

    Komppula, J

    2015-01-01

    Novel methods for diagnostics of molecular hydrogen plasma processes, such as ionization, production of high vibrational levels, dissociation of molecules via excitation to singlet and triplet states and production of metastable states, are presented for molecular hydrogen plasmas in corona equilibrium. The methods are based on comparison of rate coefficients of plasma processes and optical emission spectroscopy of lowest singlet and triplet transitions, i.e. Lyman-band ($B^1\\Sigma^+_u \\rightarrow X^1\\Sigma^+_g$) and molecular continuum ($a^3\\Sigma^+_g \\rightarrow b^3\\Sigma^+_u$), of the hydrogen molecule in VUV wavelength range. Comparison of rate coefficients of spin-allowed and/or spin-forbidden excitations reduces the uncertainty caused by the non-equilibrium distributions of electron energy and molecular vibrational level, which are typically known poorly in plasma sources. The described methods are applied to estimate the rates of various plasma processes in a filament arc discharge.

  9. Systematic Investigation of Negative Cooper-Frye Contributions in Heavy Ion Collisions Using Coarse-grained Molecular Dynamics

    E-print Network

    Oliinychenko, D; Petersen, H

    2014-01-01

    In most heavy ion collision simulations involving relativistic hydrodynamics, the Cooper-Frye formula is applied to transform the hydrodynamical fields to particles. In this article the so-called negative contributions in the Cooper-Frye formula are studied using a coarse-grained transport approach. The magnitude of negative contributions is investigated as a function of hadron mass, collision energy in the range of $E_{\\rm lab} = 5$--$160A$ GeV, collision centrality and the energy density transition criterion defining the hypersurface. The microscopic results are compared to negative contributions expected from hydrodynamical treatment assuming local thermal equilibrium. The main conclusion is that the number of actual microscopic particles flying inward is smaller than the negative contribution one would expect in an equilibrated scenario. The largest impact of negative contributions is found to be on the pion rapidity distribution at midrapidity in central collisions. For this case negative contributions i...

  10. Protein Molecular Structures, Protein SubFractions, and Protein Availability Affected by Heat Processing: A Review

    SciTech Connect

    Yu,P.

    2007-01-01

    The utilization and availability of protein depended on the types of protein and their specific susceptibility to enzymatic hydrolysis (inhibitory activities) in the gastrointestine and was highly associated with protein molecular structures. Studying internal protein structure and protein subfraction profiles leaded to an understanding of the components that make up a whole protein. An understanding of the molecular structure of the whole protein was often vital to understanding its digestive behavior and nutritive value in animals. In this review, recently obtained information on protein molecular structural effects of heat processing was reviewed, in relation to protein characteristics affecting digestive behavior and nutrient utilization and availability. The emphasis of this review was on (1) using the newly advanced synchrotron technology (S-FTIR) as a novel approach to reveal protein molecular chemistry affected by heat processing within intact plant tissues; (2) revealing the effects of heat processing on the profile changes of protein subfractions associated with digestive behaviors and kinetics manipulated by heat processing; (3) prediction of the changes of protein availability and supply after heat processing, using the advanced DVE/OEB and NRC-2001 models, and (4) obtaining information on optimal processing conditions of protein as intestinal protein source to achieve target values for potential high net absorbable protein in the small intestine. The information described in this article may give better insight in the mechanisms involved and the intrinsic protein molecular structural changes occurring upon processing.

  11. Applying CLIPS to control of molecular beam epitaxy processing

    NASA Technical Reports Server (NTRS)

    Rabeau, Arthur A.; Bensaoula, Abdelhak; Jamison, Keith D.; Horton, Charles; Ignatiev, Alex; Glover, John R.

    1990-01-01

    A key element of U.S. industrial competitiveness in the 1990's will be the exploitation of advanced technologies which involve low-volume, high-profit manufacturing. The demands of such manufacture limit participation to a few major entities in the U.S. and elsewhere, and offset the lower manufacturing costs of other countries which have, for example, captured much of the consumer electronics market. One such technology is thin-film epitaxy, a technology which encompasses several techniques such as Molecular Beam Epitaxy (MBE), Chemical Beam Epitaxy (CBE), and Vapor-Phase Epitaxy (VPE). Molecular Beam Epitaxy (MBE) is a technology for creating a variety of electronic and electro-optical materials. Compared to standard microelectronic production techniques (including gaseous diffusion, ion implantation, and chemical vapor deposition), MBE is much more exact, though much slower. Although newer than the standard technologies, MBE is the technology of choice for fabrication of ultraprecise materials for cutting-edge microelectronic devices and for research into the properties of new materials.

  12. Systematic Investigation of Negative Cooper-Frye Contributions in Heavy Ion Collisions Using Coarse-grained Molecular Dynamics

    E-print Network

    D. Oliinychenko; P. Huovinen; H. Petersen

    2015-03-18

    In most heavy ion collision simulations involving relativistic hydrodynamics, the Cooper-Frye formula is applied to transform the hydrodynamical fields to particles. In this article the so-called negative contributions in the Cooper-Frye formula are studied using a coarse-grained transport approach. The magnitude of negative contributions is investigated as a function of hadron mass, collision energy in the range of $E_{\\rm lab} = 5$--$160A$ GeV, collision centrality and the energy density transition criterion defining the hypersurface. The microscopic results are compared to negative contributions expected from hydrodynamical treatment assuming local thermal equilibrium. The main conclusion is that the number of actual microscopic particles flying inward is smaller than the negative contribution one would expect in an equilibrated scenario. The largest impact of negative contributions is found to be on the pion rapidity distribution at midrapidity in central collisions. For this case negative contributions in equilibrium constitute 8--13\\% of positive contributions depending on collision energy, but only 0.5--4\\% in cascade calculation. The dependence on the collision energy itself is found to be non-monotonous with a maximum at 10-20$A$ GeV.

  13. Systematic investigation of negative Cooper-Frye contributions in heavy ion collisions using coarse-grained molecular dynamics

    NASA Astrophysics Data System (ADS)

    Oliinychenko, D.; Huovinen, P.; Petersen, H.

    2015-02-01

    In most heavy ion collision simulations involving relativistic hydrodynamics, the Cooper-Frye formula is applied to transform the hydrodynamical fields to particles. In this article the so-called negative contributions in the Cooper-Frye formula are studied using a coarse-grained transport approach. The magnitude of negative contributions is investigated as a function of hadron mass, collision energy in the range of Elab=5 -160 A GeV, collision centrality, and the energy density transition criterion defining the hypersurface. The microscopic results are compared to negative contributions expected from hydrodynamical treatment assuming local thermal equilibrium. The main conclusion is that the number of actual microscopic particles flying inward is smaller than the negative contribution one would expect in an equilibrated scenario. The largest impact of negative contributions is found to be on the pion rapidity distribution at midrapidity in central collisions. For this case negative contributions in equilibrium constitute 8-13% of positive contributions, depending on collision energy, but only 0.5-4% in cascade calculation. The dependence on the collision energy itself is found to be nonmonotonous with a maximum at 10 - 20 A GeV.

  14. Exclusive processes in electron-ion collisions in the dipole formalism

    SciTech Connect

    Cazaroto, E. R.; Navarra, F. S. [Instituto de Fisica, Universidade de Sao Paulo, C.P. 66318, 05314-970 Sao Paulo, SP (Brazil); Carvalho, F. [Departamento de Ciencias Exatas e da Terra, Universidade Federal de Sao Paulo, Campus Diadema, Rua Prof. Artur Riedel, 275, Jd. Eldorado, 09972-270 Diadema, SP (Brazil); Goncalves, V. P. [Instituto de Fisica e Matematica, Universidade Federal de Pelotas, Caixa Postal 354, 96010-900 Pelotas, RS (Brazil)

    2013-03-25

    We compare the predictions of two saturation models for production of vector mesons and of photons in electron-ion collisions. The models considered are the b-CGC and the rcBK. The calculations were made in the kinematical range of the LHeC and of the future eRHIC.

  15. Measurement of the weak mixing angle with the Drell-Yan process in proton-proton collisions at the LHC

    SciTech Connect

    Chatrchyan, S. [Yerevan Physics Institute (Armenia); et al.,

    2011-12-01

    A multivariate likelihood method to measure electroweak couplings with the Drell-Yan process at the LHC is presented. The process is described by the dilepton rapidity, invariant mass, and decay angle distributions. The decay angle ambiguity due to the unknown assignment of the scattered constituent quark and antiquark to the two protons in a collision is resolved statistically using correlations between the observables. The method is applied to a sample of dimuon events from proton-proton collisions at sqrt(s) = 7 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 1.1 inverse femtobarns. From the dominant u-ubar, d-dbar to gamma*/Z to opposite sign dimuons process, the effective weak mixing angle parameter is measured to be sin^2(theta[eff]) = 0.2287 +/- 0.0020 (stat.) +/- 0.0025 (syst.). This result is consistent with measurements from other processes, as expected within the standard model.

  16. Deformation processes in polycrystalline Zr by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Lu, Zizhe; Noordhoek, Mark J.; Chernatynskiy, Aleksandr; Sinnott, Susan B.; Phillpot, Simon R.

    2015-07-01

    Molecular dynamics simulation is used to characterize the deformation behavior of polycrystalline Zr. The predictions of two different potentials, an embedded atom method potential and a charge optimized many body potential are compared. The experimentally observed prismatic dislocations, pyramidal dislocations and twinning behaviors are produced in the simulations of [ 1 1 2 bar 0 ] and [0 0 0 1] textured structures and in fully 3D structure simulations. The relationship between the generalized stacking fault energy and the mechanical properties is discussed. In particular we find that the different shapes of the generalized stacking-fault energy curve for the two different interatomic descriptions of Zr have a significant effect on the deformation mechanisms. The deformation behavior of Zr is compared with analogous simulations of deformation of polycrystalline Mg.

  17. Atmospheric processes on ice nanoparticles in molecular beams

    PubMed Central

    Fárník, Michal; Poterya, Viktoriya

    2014-01-01

    This review summarizes some recent experiments with ice nanoparticles (large water clusters) in molecular beams and outlines their atmospheric relevance: (1) Investigation of mixed water–nitric acid particles by means of the electron ionization and sodium doping combined with photoionization revealed the prominent role of HNO3 molecule as the condensation nuclei. (2) The uptake of atmospheric molecules by water ice nanoparticles has been studied, and the pickup cross sections for some molecules exceed significantly the geometrical sizes of the ice nanoparticles. (3) Photodissociation of hydrogen halides on water ice particles has been shown to proceed via excitation of acidically dissociated ion pair and subsequent biradical generation and H3O dissociation. The photodissociation of CF2Cl2 molecules in clusters is also mentioned. Possible atmospheric consequences of all these results are briefly discussed. PMID:24790973

  18. Molecular Modeling of Environmentally Important Processes: Reduction Potentials

    ERIC Educational Resources Information Center

    Lewis, Anne; Bumpus, John A.; Truhlar, Donald G.; Cramer, Christopher J.

    2004-01-01

    The increasing use of computational quantum chemistry in the modeling of environmentally important processes is described. The employment of computational quantum mechanics for the prediction of oxidation-reduction potential for solutes in an aqueous medium is discussed.

  19. An overview of atomic and molecular processes in critical velocity ionization

    Microsoft Academic Search

    S. T. Lai; E. Murad; W. J. McNeil

    1989-01-01

    The authors present an overview of the time development of some atomic and molecular processes in critical ionization velocity (CIV). In the preonset stage, metastable states play an important role: they provide an energy pooling mechanism allowing low-energy electrons to participate in the ionization process; they may explain the low energy threshold was well as the fast time scale in

  20. "Modeling Heterogeneous Catalytic Reactions: From the Molecular Process to the Technical System"

    E-print Network

    "Modeling Heterogeneous Catalytic Reactions: From the Molecular Process to the Technical System" O for Heterogeneous Catalysis: Concepts, Status and Frontiers Karsten Reuter Fritz-Haber-Institut der Max processing, envisioned to ulti- mately enable a rational design of novel catalysts and im- proved production

  1. Threshold-Resummed Cross Section for the Drell-Yan Process in Pion-Nucleon Collisions at COMPASS

    E-print Network

    Matthias Aicher; Andreas Schäfer; Werner Vogelsang

    2011-04-18

    We present a study of the Drell-Yan process in pion-proton collisions including next-to-leading-logarithmic threshold-resummed contributions. We analyze rapidity-integrated as well as rapidity-differential cross sections in the kinematic regime relevant for the COMPASS fixed target experiment. We find that resummation leads to a significant enhancement of the cross section compared to fixed-order calculations in this regime. Particularly large corrections arise at large forward and backward rapidities of the lepton pair. We also study the scale dependence of the cross section and find it to be substantially reduced by threshold resummation.

  2. Chemical conversion processes utilizing catalyst containing crystalline gallosilicate molecular sieves having the erionite-type structure

    SciTech Connect

    Occelli, M.J.

    1990-08-07

    This patent describes a process for the acid catalyzed chemical conversion of a feedstock containing organic compounds into reaction products. It comprises: contacting the feedstock under acid catalyzed conversion conditions with a catalyst comprising a catalytically active, crystalline, galliosilicate molecular sieve, wherein the molecular sieve comprises silicon, gallium as oxygen, has an x-ray powder diffraction pattern characteristic of the erionite structure and contains less than about 0.10 weight percent alumina.

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  4. Molecular processes in a high temperature shock layer

    NASA Technical Reports Server (NTRS)

    Guberman, S. L.

    1985-01-01

    The development of techniques for the calculation of electron capture widths, electronic wave functions, cross sections and rates needed for the description of the dissociative recombination (DR) of molecular ions with electrons were described. The cross sections and rates were calculated by using harmonic oscillator wave functions for the ion and a delta function approximation for the continuum vibrational wave function in the repulsive dissociative channel. In order to obtain DR cross sections of quantitative accuracy, a computer program which solves the one dimensional nuclear motion wave equation was revised to calculate the cross sections and rates. The program and the new results are described. Included is a discussion of large windows found in the dissociative recombination cross sections from excited ion vibrational levels. These windows have not been previously reported in the literature. The magnitude of the DR cross sections for several dissociative routes are sensitive to the location of the crossing of the neutral and ion potential curves. Studies of the effects of basis set and CI wave function size on vertical excitation energies are described. Preliminary studies on N2 and O2 using large scale wave functions are also reported.

  5. All electroweak four-fermion processes in electron-positron collisions

    Microsoft Academic Search

    F. A. Berends; R. Pittau; R. Kleiss

    1994-01-01

    This paper studies the electroweak production of all possible four-fermion states in e+e- collisions. Since the methods employed to evaluate the complete matrix elements and phase space are very general, all four-fermion final states in which the charged particles are detected can be considered. Also all kinds of experimental cuts can be imposed. With the help of the constructed event

  6. Studies of fluctuation processes in nuclear collisions. Progress report, March 1, 1992February 28, 1993

    Microsoft Academic Search

    Ayik

    1993-01-01

    Investigations of various aspects of heavy-ion collisions were carried out in the framework of the Boltzmann-Langevin Model (BLM). In a previous work, by projection the BLM onto a collective space, a memory-dependent collective transport model was reduced. This model was applied to thermal fission to investigate the influence of the memory effects on the fission dynamics. Some results of the

  7. Strike-slip faults offshore southern Taiwan: implications for the oblique arc-continent collision processes

    Microsoft Academic Search

    Shi-Chie Fuh; Char-Shine Liu; Neil Lundberg; Donald L. Reed

    1997-01-01

    Taiwan is the site of present-day oblique arc-continent collision between the Luzon arc of the Philippine Sea plate and the Chinese continental margin. The major structural pattern revealed from marine geophysical studies in the area offshore southern Taiwan is that of a doubly-vergent orogenic belt, bounded by significant zones of thrusting on the west and east of the submarine accretionary

  8. First evidence of hard scattering processes in single tagged gammagamma collisions

    Microsoft Academic Search

    P. Abreu; W. Adam; T. Adye; E. Agasi; I. Ajinenko; R. Aleksan; G. D. Alekseev; P. P. Allport; S. Almehed; F. M. L. Almeida; S. J. Alvsvaag; U. Amaldi; A. Andreazza; M. L. Andrieux; P. Antilogus; W.-D. Apel; Y. Arnoud; B. Åsman; J.-E. Augustin; A. Augustinus; P. Baillon; P. Bambade; F. Barao; R. Barate; G. Barbiellini; D. Y. Bardin; G. J. Barker; A. Baroncelli; O. Barring; J. A. Barrio; W. Bartl; M. J. Bates; M. Battaglia; M. Baubillier; J. Baudot; K.-H. Becks; M. Begalli; P. Beilliere; P. Beltran; A. C. Benvenuti; M. Berggren; D. Bertrand; F. Bianchi; M. Bigi; M. S. Bilenky; P. Billoir; J. Bjarne; D. Bloch; S. Blyth; V. Bocci; P. N. Bogolubov; T. Bolognese; M. Bonesini; W. Bonivento; P. S. L. Booth; G. Borisov; C. Bosio; B. Bostjancic; S. Bosworth; O. Botner; B. Bouquet; C. Bourdarios; T. J. V. Bowcock; M. Bozzo; S. Braibant; P. Branchini; K. D. Brand; R. A. Brenner; H. Briand; C. Bricman; L. Brillault; R. C. A. Brown; J.-M. Brunet; L. Bugge; T. Buran; A. Buys; M. Caccia; M. Calvi; A. J. Camacho Rozas; T. Camporesi; V. Canale; M. Canepa; K. Cankocak; F. Cao; F. Carena; P. Carrilho; L. Carroll; C. Caso; V. Cassio; M. V. Castillo Gimenez; A. Cattai; F. R. Cavallo; L. Cerrito; V. Chabaud; A. Chan; Ph. Charpentier; L. Chaussard; J. Chauveau; P. Checchia; G. A. Chelkov; P. Chliapnikov; V. Chorowicz; J. T. M. Chrin; V. Cindro; P. Collins; J. L. Contreras; R. Contri; E. Cortina; G. Cosme; F. Couchot; H. B. Crawley; D. Crennell; G. Crosetti; J. Cuevas Maestro; S. Czellar; E. Dahl-Jensen; J. Dahm; B. Dalmagne; M. Dam; G. Damgaard; E. Daubie; A. Daum; P. D. Dauncey; M. Davenport; W. da Silva; C. Defoix; P. Delpierre; N. Demaria; A. de Angelis; H. de Boeck; W. de Boer; S. de Brabandere; C. de Clercq; M. D. M. de Fez Laso; C. de La Vaissiere; B. de Lotto; A. de Min; L. de Paula; C. de Saint-Jean; H. Dijkstra; L. di Ciaccio; F. Djama; J. Dolbeau; M. Donszelmann; K. Doroba; M. Dracos; J. Drees; M. Dris; Y. Dufour; F. Dupont; D. Edsall; R. Ehret; T. Ekelof; G. Ekspong; M. Elsing; J.-P. Engel; N. Ershaidat; M. Espirito Santo; D. Fassouliotis; M. Feindt; A. Ferrer; T. A. Filippas; A. Firestone; H. Foeth; E. Fokitis; F. Fontanelli; F. Formenti; J.-L. Fousset; B. Franek; P. Frenkiel; D. C. Fries; A. G. Frodesen; R. Fruhwirth; F. Fulda-Quenzer; H. Furstenau; J. Fuster; D. Gamba; M. Gandelman; C. Garcia; J. Garcia; C. Gaspar; U. Gasparini; Ph. Gavillet; E. N. Gazis; D. Gele; J.-P. Gerber; D. Gillespie; R. Gokieli; B. Golob; V. M. Golovatyuk; J. J. Gomez Y Cadenas; G. Gopal; L. Gorn; M. Gorski; V. Gracco; F. Grard; E. Graziani; G. Grosdidier; P. Gunnarsson; J. Guy; U. Haedinger; F. Hahn; M. Hahn; S. Hahn; S. Haider; Z. Hajduk; A. Hakansson; A. Hallgren; K. Hamacher; W. Hao; F. J. Harris; V. Hedberg; R. Henriques; J. J. Hernandez; J. A. Hernando; P. Herquet; H. Herr; T. L. Hessing; E. Higon; H. J. Hilke; T. S. Hill; S.-O. Holmgren; P. J. Holt; D. Holthuizen; P. F. Honore; M. Houlden; J. Hrubec; K. Huet; K. Hultqvist; P. Ioannou; P.-S. Iversen; J. N. Jackson; R. Jacobsson; P. Jalocha; G. Jarlskog; P. Jarry; B. Jean-Marie; E. K. Johansson; L. Jonsson; P. Juillot; M. Kaiser; G. Kalmus; F. Kapusta; M. Karlsson; E. Karvelas; A. Katargin; S. Katsanevas; E. C. Katsoufis; R. Keranen; B. A. Khomenko; N. N. Khovanski; B. King; N. J. Kjaer; H. Klein; A. Klovning; P. Kluit; A. Koch-Mehrin; J. H. Koehne; B. Koene; P. Kokkinias; M. Koratzinos; K. Korcyl; A. V. Korytov; V. Kostioukhine; C. Kourkoumelis; O. Kouznetsov; P.-H. Kramer; C. Kreuter; J. Krolikowski; I. Kronkvist; W. Krupinski; K. Kulka; K. Kurvinen; C. Lacasta; I. Laktineh; C. Lambropoulos; J. W. Lamsa; L. Lanceri; P. Langefeld; V. Lapin; I. Last; J.-P. Laugier; R. Lauhakangas; G. Leder; F. Ledroit; R. Leitner; Y. Lemoigne; J. Lemonne; G. Lenzen; V. Lepeltier; T. Lesiak; J. M. Levy; E. Lieb; D. Liko; R. Lindner; A. Lipniacka; I. Lippi; B. Loerstad; M. Lokajicek; J. G. Loken; A. Lopez-Fernandez; M. A. Lopez Aguera; M. Los; D. Loukas; J. J. Lozano; P. Lutz; L. Lyons; G. Maehlum; J. Maillard; A. Maio; A. Maltezos; F. Mandl; J. Marco; B. Marechal; M. Margoni; J.-C. Marin; C. Mariotti; A. Markou; T. Maron; S. Marti; C. Martinez-Rivero; F. Martinez-Vidal; F. Matorras; C. Matteuzzi; G. Matthiae; M. Mazzucato; M. Mc Cubbin; R. Mc Kay; R. Mc Nulty; J. Medbo; C. Meroni; W. T. Meyer; A. Miagkov; M. Michelotto; E. Migliore; I. Mikulec; L. Mirabito; W. A. Mitaroff; G. V. Mitselmakher; U. Mjoernmark; T. Moa; R. Moeller; K. Moenig; M. R. Monge; P. Morettini; H. Mueller; W. J. Murray; B. Muryn; G. Myatt; F. Naraghi; F. L. Navarria; S. Navas; P. Negri; S. Nemecek; W. Neumann; N. Neumeister; R. Nicolaidou; B. S. Nielsen; V. Nikolaenko; P. Niss; A. Nomerotski; A. Normand; V. Obraztsov; A. G. Olshevski; R. Orava; K. Osterberg; A. Ouraou; P. Paganini; M. Paganoni; R. Pain; H. Palka; Th. D. Papadopoulou; L. Pape; F. Parodi; A. Passeri; M. Pegoraro

    1995-01-01

    For the first time, multihadronic production from single tagged gammagamma collisions has been studied, where one of the scattered leptons was tagged at very low virtual photon absolute mass squared ( = 0.06GeV\\/(c2))2 ). Data collected during 1991 and 1992 in the DELPHI experiment at LEP are shown to agree well with predictions which included the non-perturbative vector meson dominance

  9. Final Report, "Molecular Design of Hydrocarbon Oxidation Catalytic Processes"

    SciTech Connect

    Professor Francisco Zaera

    2007-08-09

    The main goal of this project had been to use model systems to correlate selectivities in partial oxidation catalysis with the presence of specific sites on the surface of the catalyst. Extensive work was performed this year on characterizing oxygen-treated nickel surfaces by chemical means. Specifically, the surface chemistry of ammonia coadsorbed with atomic oxygen on Ni(110) single-crystal surfaces was studied by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). It was determined that at intermediate oxygen coverages direct ammonia adsorption on nickel sites is suppressed, but a new high-temperature reaction regime is generated at 400 K where NHx surface fragments are rehydrogenated concurrently with the production of water and molecular hydrogen. The extensive isotope scrambling and hydrogen transfer seen from nitrogen- to oxygen-containing surface intermediates, and the optimum yields seen for this 400 K state at intermediate oxygen coverages, strongly suggest the direct interaction of the adsorbed ammonia with oxygen atoms at the end of the –Ni–O- rows that form upon reconstruction of the surface. Hydrogen transfer between ammonia and oxygen appears to take place directly via hydrogen bonding, and to be reversible but biased towards water formation. An equilibrium is reached between the produced water and the reacting surface oxygen and hydrogen. The strong influence of the OH surface groups on the thermal chemistry of the adsorbed ammonia was interpreted in terms of the adsorbing geometry of the OH groups on the surface, and of hydrogen bonding between adsorbed OH and NH3 species. In terms of alcohol reactivity, the adsorption of 2-iodoethanol, a precursor for the preparation of 2-hydroxyethyl and oxametallacycle surface species, was found to lead to two configurations involving either just the iodine atom or both iodine and hydroxyl ends of the molecule. A complex chemical behavior starts around 140 K with the production of small amounts of ethylene and water, most likely via the concerted decomposition or disproportionation of the adsorbed molecular species. The bulk of the 2-iodoethanol decomposes at about 150 K via an initial carbon-iodine scission to form –O(H)CH2CH2– (~80%) and 2-hydroxyethyl (~20%) intermediates. Two competing reactions are involved with the subsequent conversion of the 2-hydroxyethyl species around 160 K, a reductive elimination with surface hydrogen to yield ethanol, and a ?-H elimination to surface vinyl alcohol. The –O(H)CH2CH2–, on the other hand, dehydrogenates to a –OCH2CH2– oxametallacycle species about the same temperature. Both 2-hydroxyethyl and oxametallacycle species tautomerize to acetaldehyde, around 210 K and above 250 K, respectively, and some of that acetaldehyde desorbs while the rest decomposes to hydrogen and carbon monoxide. We contend that a better understanding of the surface chemistry of oxygen-containing surfaces can lead to better selectivities in catalysis. This is arguably the most important issue in the field of catalysis in the near future, and one that impacts several technologies of interest to DOE such as the manufacturing of speciality chemicals and the control and removal of pollutants. Additional work was performed on the characterization of the chemistry of methyl and methylene adsorbed species on oxygen-treated nickel surfaces. Complex chemistry was observed involving not only hydrogenation and dehydrogenation steps, but also C-C couplings and methylene insertions to produce heavier hydrocarbons, and oxygen insertion reactions that yield oxygenates. Finally, a dual titration technique employing xenon and a chemically sensitive probe was developed to identify minority catalytic sites on oxide surfaces. In the case of oxygen-treated Ni(110) single crystals, it was found that both hydrogen transfer with adsorbed water or ammonia and certain hydrocarbon hydrogenation reactions take place at the end of the –Ni–O rows that form in this system. Carbon and nitrogen oxides, on the other hand, display no pre

  10. Coffee husk composting: An investigation of the process using molecular and non-molecular tools

    PubMed Central

    Shemekite, Fekadu; Gómez-Brandón, María; Franke-Whittle, Ingrid H.; Praehauser, Barbara; Insam, Heribert; Assefa, Fassil

    2014-01-01

    Various parameters were measured during a 90-day composting process of coffee husk with cow dung (Pile 1), with fruit/vegetable wastes (Pile 2) and coffee husk alone (Pile 3). Samples were collected on days 0, 32 and 90 for chemical and microbiological analyses. C/N ratios of Piles 1 and 2 decreased significantly over the 90 days. The highest bacterial counts at the start of the process and highest actinobacterial counts at the end of the process (Piles 1 and 2) indicated microbial succession with concomitant production of compost relevant enzymes. Denaturing gradient gel electrophoresis of rDNA and COMPOCHIP microarray analysis indicated distinctive community shifts during the composting process, with day 0 samples clustering separately from the 32 and 90-day samples. This study, using a multi-parameter approach, has revealed differences in quality and species diversity of the three composts. PMID:24369846

  11. Impact of molecular clustering inside nanopores on desorption processes.

    PubMed

    Tsotsalas, Manuel; Hejcik, Pavel; Sumida, Kenji; Kalay, Ziya; Furukawa, Shuhei; Kitagawa, Susumu

    2013-03-27

    Understanding the sorption kinetics of nanoporous systems is crucial for the development and design of novel porous materials for practical applications. Here, using a porous coordination polymer/quartz crystal microbalance (PCP/QCM) hybrid device, we investigate the desorption of various vapor molecules featuring different degrees of intermolecular (hydrogen bonding) or molecule-framework interactions. Our findings reveal that strong intermolecular interactions lead to the desorption process proceeding via an unprecedented metastable state, wherein the guest molecules are clustered within the pores, causing the desorption rate to be temporarily slowed. The results demonstrate the considerable impact of the chemical nature of an adsorbate on the kinetics of desorption, which is also expected to influence the efficiency of certain processes, such as desorption by gas purge. PMID:23470206

  12. Molecular Analysis of Phr Peptide Processing in Bacillus subtilis

    Microsoft Academic Search

    Sophie Stephenson; Christian Mueller; Min Jiang; Marta Perego

    2003-01-01

    In Bacillus subtilis, an export-import pathway regulates production of the Phr pentapeptide inhibitors of Rap proteins. Processing of the Phr precursor proteins into the active pentapeptide form is a key event in the initiation of sporulation and competence development. The PhrA (ARNQT) and PhrE (SRNVT) peptides inhibit the RapA and RapE phosphatases, respectively, whose activity is directed toward the Spo0FP

  13. Collision Cascade and Sputtering Process in a Polymer A. Delcorte* and P. Bertrand

    E-print Network

    , molecular overlayers, biological molecules and tissues, are involved in a large number of technologically already been used to model the sputtering of solid benzene samples.13 Another implementation of the long

  14. Deviation from a Maxwellian velocity distribution in regions of interstellar molecular hydrogen

    NASA Technical Reports Server (NTRS)

    Gould, R. J.; Levy, M.

    1976-01-01

    The deviation from a Maxwellian velocity distribution caused by excitation of the J = 2 rotational level of parahydrogen (followed by radiative decay) in a molecular hydrogen gas is investigated. It is noted that inelastic collisions deplete the high-velocity tail of the distribution, while elastic collisions tend to refill it; the resulting steady-state distribution has a small depletion in the tail which slightly reduces the cooling rate of the gas. The elastic-collision transport is approximated by a continuous process, a simplified expression is obtained for the inelastic-collision operator, and the Boltzmann equation is then solved analytically. A correction to the inelastic-collision rate is evaluated, and it is found that the relative magnitude of the effect of tail depletion on the inelastic-collision rate is strongly temperature-dependent. The critical molecular density above which the J = 2 level deexcites by superelastic collisions is shown to be a weak function of temperature.

  15. Inelastic vibrational processes in charge transfers between H/D and molecular ions

    NASA Astrophysics Data System (ADS)

    Heczko, Sarah L.; Bacani, Kieffer G.; Strom, Richard A.; Andrianarijaona, Vola M.; Seely, David G.; Havener, Charles C.

    2014-03-01

    Charge transfer on molecule proceeds through dynamically coupled electronic, vibrational, and rotational degrees of freedom. The inelastic vibrational processes, which go along with the reaction, can be experimentally investigated by using H/D systems, which do not allow multi-electron capture. Using the upgraded ion-atom merged-beams apparatus at Oak Ridge National Laboratory, absolute direct charge transfer cross sections for H2+, D2+, CO+, O2+, and H3+ are measured from keV/u collision energies where the collision is considered ``ro-vibrationally frozen'' to few eV/u energies where collision times are long enough to sample vibrational modes. The measurements presented here benchmark high energy theory and vibrationally specific adiabatic theory (V. M. Andrianarijaona et al., Phys. Rev. A 84, 062716, 2011). Research supported by the NASA Solar & Heliospheric Physics Program NNH07ZDA001N, the Office of Fusion Energy Sciences and Division of Chemical Sciences, Geosciences, and Biosciences, the Office of Basic Energy Sciences of the US Department of Energy. VA et al. is supported by the National Science Foundation through Grant No. PHY-106887.

  16. Quantum correlation dynamics in photosynthetic processes assisted by molecular vibrations

    E-print Network

    G. L. Giorgi; M. Roncaglia; F. A. Raffa; M. Genovese

    2015-01-30

    During the long course of evolution, nature has learnt how to exploit quantum effects. In fact, recent experiments reveal the existence of quantum processes whose coherence extends over unexpectedly long time and space ranges. In particular, photosynthetic processes in light-harvesting complexes display a typical oscillatory dynamics ascribed to quantum coherence. Here, we consider the simple model where a dimer made of two chromophores is strongly coupled with a quasi-resonant vibrational mode. We observe the occurrence of wide oscillations of genuine quantum correlations, between electronic excitations and the environment, represented by vibrational bosonic modes. Such a quantum dynamics has been unveiled through the calculation of the negativity of entanglement and the discord, indicators widely used in quantum information for quantifying the resources needed to realize quantum technologies. We also discuss the possibility of approximating additional weakly-coupled off-resonant vibrational modes, simulating the disturbances induced by the rest of the environment, by a single vibrational mode. Within this approximation, one can show that the off-resonant bath behaves like a classical source of noise.

  17. Spatially Resolved Atomic and Molecular Spectroscopy in Microelectronics Processing Plasmas

    SciTech Connect

    Hebner, G.A.

    1998-10-14

    Plasma processing of microelectronic materials is strongly dependent on the generation and control of neutral radial and ion species generated in a plasma. For example, process uniformity across a #er is drken by a combination of plasma charged particle and neutral uniformity. Due to extensive rexarch and engineering the current generation of commercial plasma reactors can generate very radially uniform ion distributions, usually better than ~ 2 perwnt as determined by ion saturation measurements. Due in part to the difficulty associated with determining the neutral radial distributions, control of the neutral radical uniformity is less well developed. This abstract will review our recent measurements of the spatial distribution of severaI important atomic and molecukw species in inductively coupled plasmas through C12 / BCIJ / Ar containing gas mixtures. Measured species include the ground state Cl and BC1 densities as well as the metastable argon density. The fbeus of this review will be on the experimental techniques and results. In addition to assisting in the development of a fbndarnental understanding of the important pkunna physics, these measurements have been used to benchmark multi dimensional plasma discharge codes.

  18. Bibliography of atomic and molecular processes. Volume 1, 1978-1981

    SciTech Connect

    Barnett, C.F.; Crandall, D.H.; Farmer, B.J. (comps.)

    1982-10-01

    This annotated bibliography lists 10,676 works on atomic and molecular processes reported in publications dated 1978-1981. Sources include scientific journals, conference proceedings, and books. Each entry is designated by one or more of the 114 categories of atomic and molecular processes used by the Controlled Fusion Atomic Data Center, Oak Ridge National Laboratory to classify data. Also indicated is whether the work was experimental or theoretical, what energy range was covered, what reactants were investigated, and the county of origin of the first author. Following the bibliographical listing, the entries are indexed according to the categories and according to reactants within each subcategory.

  19. Neighbor list collision-driven molecular dynamics simulation for nonspherical hard particles.II. Applications to ellipses and ellipsoids

    Microsoft Academic Search

    Aleksandar Donev; Salvatore Torquato; Frank H. Stillinger

    2005-01-01

    We apply the algorithm presented in the first part of this series of papers to systems of hard ellipses and ellipsoids. The theoretical machinery needed to treat such particles, including the overlap potentials, is developed in full detail. We describe an algorithm for predicting the time of collision for two moving ellipses or ellipsoids. We present performance results for our

  20. Photonic, Electronic and Atomic Collisions

    NASA Astrophysics Data System (ADS)

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

    2006-11-01

    Plenary. Electron collisions - past, present and future / J. W. McConkey. Collisions of slow highly charged ions with surfaces / J. Burgdörfer ... [et al.]. Atomic collisions studied with "reaction-microscopes" / R. Moshammer ... [et al.]. Rydberg atoms: a microscale laboratory for studying electron-molecule tnteractions / F. B. Dunning -- Collisions involvintg photons. Quantum control of photochemical reaction dynamics and molecular functions / M. Yamaki ... [et al.]. Manipulating and viewing Rydberg wavepackets / R. R. Jones. Angle-resolved photoelectrons as a probe of strong-field interactions / M. Vrakking. Ultracold Rydberg atoms in a structured environment / I. C. H. Liu and J. M. Rost. Synchrotron-radiation-based recoil ion momentum spectroscopy of laser cooled and trapped cesium atoms / L. H. Coutinho. Reconstruction of attosecond pulse trains / Y. Mairesse ... [et al.]. Selective excitation of metastable atomic states by Femto- and attosecond laser pulses / A. D. Kondorskiy. Accurate calculations of triple differential cross sections for double photoionization of the hygrogen molecule / W. Vanroose ... [et al.]. Double and triple photoionization of Li and Be / J. Colgan, M. S. Pindzola and F. Robicheaux. Few/many body dynamics in strong laser fields / J. Zanghellini and T. Brabec. Rescattering-induced effects in electron-atom scattering in the presence of a circularly polarized laser field / A. V. Flegel ... [et al.]. Multidimensional photoelectron spectroscopy / P. Lablanquie ... [et al.]. Few photon and strongly driven transitions in the XUV and beyond / P. Lambropoulos, L. A. A. Nikolopoulos and S. I. Themelis. Ionization dynamics of atomic clusters in intense laser pulses / U. Saalmann and J. M. Rost. On the second order autocorrelation of an XUV attosecond pulse train / E. P. Benis ... [et al.]. Evidence for rescattering in molecular dissociation / I. D. Williams ... [et al.]. Photoionizing ions using synchrotron radiation / R. Phaneuf. Photo double ionization of fixed in space deuterium molecules / T. Weber ... [et al.]. Coherence and intramolecular scattering in molecular photoionization / U. Becker. Experimental observation of interatomic coulombic decay in neon dimers / T. Jahnke ... [et al.]. Ionization by short UV laser pulses: secondary ATI peaks of the electron spectrum / V. D. Rodríguez, E. Cormier and R. Gayet. Molecular frame photoemission in photoionization of H[symbol] and D[symbol]: the role of dissociation on autoionization of the Q[symbol] and Q[symbol] doubly excited states / D. Dowek, M. Lebech and J. C. Houver. 3p photoemission of 3d transition metals - atoms, molecules and clusters / M. Martins -- Collisions involving electrons. Spin-resolved collisions of electrons with atoms and molecules / G. F. Hanne. Calculation of ionization and excitation processes using the convergent close-coupling method / D. V. Fursa, I. Bray and A. T. Stelbovics. The B-spline R-matrix method for electron and photon collisions with atoms and ions / O. Zatsarinny and K. Bartschat. Absolute angle-differential cross sections for excitation of neon atoms electrons of energy 16.6-19.2 eV / M. Allan ... [et al.]. Studies of QED and nuclear size effects with highly charged ions in an EBIT / J. R. Crespo López-Urrutia ... [et al.]. Recombination of astrophysically relevant ions: Be-like C, N, and O / M. Fogle ... [et al.]. Dissociation and excitation of molecules and molecular ions by electron impact / A. E. Orel and J. Royal state-selective X-ray study of the radiative recombination of U[symbol] ions with cooling electrons / M. Pajek ... [et al.]. Electron collisions with trapped, metastable helium / L. J. Uhlmann ... [et al.]. Non-dipole effects in electron and photon impact ionization / N. L. S. Martin. Electron driven processes in atmospheric behaviour / L. Campbell, M. J. Brunger and P. J. 0. Teubner. Calculation of excitation and ionization for electron-molecule collisions at intermediate energies / J. D. Gorfinkiel. Absolute total cross sections for electron-CH[symbol] scattering at intermediate en

  1. Collision-induced dissociation of aminophospholipids (PE, MMPE, DMPE, PS): an apparently known fragmentation process revisited.

    PubMed

    Pittenauer, Ernst; Rehulka, Pavel; Winkler, Wolfgang; Allmaier, Günter

    2015-07-01

    A new type of low-mass substituted 4-oxazolin product ions of [M + H](+) precursor ions of aminophospholipids (glycerophosphatidylethanolamine, glycerophosphatidyl-N-methylethanolamine, glycerophosphatidyl-N,N-dimethylethanolamine, glycerophosphatidylserine) resulting from high-energy collision-induced dissociation (matrix-assisted laser desorption/ionization time-of-flight/reflectron time-of-flight mass spectrometry) and low-energy collision-induced dissociation (e.g., electrospray ionization quadrupole reflectron time-of-flight mass spectrometry) with accurate mass determination is described; these were previously misidentified as CHO-containing radical cationic product ions. The mechanism for the formation of these ions is proposed to be via rapid loss of water followed by cyclization to an 11-membered-ring transition state for the sn-1 fatty acid substituent and to a ten-membered-ring transition state for the sn-2 fatty acid substituent, and via final loss of monoacylglycerol phosphate, leading to substituted 4-oxazolin product ions. The minimum structural requirement for this interesting skeletal rearrangement fragmentation is an amino group linked to at least one hydrogen atom (i.e., ethanolamine, N-methylethanolamine, serine). Therefore, N,N-dimethylethanolamine derivates do not exhibit this type of fragmentation. The analytical value of these product ions is given by the fact that by post source decay and particularly high-energy collision-induced dissociation achieved via matrix-assisted laser desorption/ionization time-of-flight/reflectron time-of-flight mass spectrometry, the sn-2-related substituted 4-oxazolin product ion is always significantly more abundant than the sn-1-related one, which is quite helpful for detailed structural analysis of complex lipids. All other important product ions found are described in detail (following our previously published glycerophospholipid product ion nomenclature; Pittenauer and Allmaier, Int. J. Mass. Spectrom. 301:90-1012, 2011). PMID:25633216

  2. Atomic Realization of the Young Single Electron Interference Process in Individual Autoionization Collisions

    NASA Astrophysics Data System (ADS)

    Barrachina, R. O.; Žitnik, M.

    2006-11-01

    Young's double-slit demonstration, applied to the interference of single electrons, is considered to be one of the most beautiful experiments in Physics. This "gedanken" experiment proposed by R. Feynman in 1963, was achieved quite recently. Of course, the diffraction of electrons by atomic arrays had already been studied many decades before, but the novelty in these experiments was that one electron at a time collides with a single two-slit arrangement. Here we propose a novel atomic realization of a Young interference experiment, where a single electron source and a two-center scatterer are prepared in each collision event.

  3. Collision-induced dissociation studies on Fe(O2)n(+) (n = 1-6) clusters: application of a new technique based on crossed molecular beams.

    PubMed

    Velegrakis, Michalis; Mihesan, Claudia; Jadraque, Maria

    2013-04-11

    Gas-phase oxygen-rich iron oxide clusters Fe(O2)n(+) (n = 1-6), are produced in a molecular beam apparatus. Their stability and structure are investigated by measuring the fragmentation cross-sections from collision-induced-dissociation experiments. For this purpose, two different techniques have been employed. The first one relies on the measurement of the fragments resulting after collisional activation and subsequent dissociation of mass selected cluster ions in a molecular beam passing through a cell filled with noble gas atoms. The second one is a new approach that we introduce and is based on crossed molecular beams to measure the fragmentation cross-sections, in a more efficient manner without mass selection of the individual clusters. The cross-sections obtained with the different techniques are compared with each other as well as with theoretical ones resulting from the application of a simple geometrical projection model. Finally, the general trends observed are compared with results for other Fe-molecule clusters available in the literature. PMID:23480732

  4. A Molecular Dynamics Simulation of Interaction between Catalytic Metals and Carbon Atoms on Formation Process of an SWNT

    E-print Network

    Maruyama, Shigeo

    A Molecular Dynamics Simulation of Interaction between Catalytic Metals and Carbon Atoms) are calculated by molecular dynamics method. The simulation technique and initial condition are same as our of the Co and Fe clusters after 100 ns molecular dynamics simulation of the clustering process. #12;

  5. In-Line Detection and Measurement of Molecular Contamination in Semiconductor Process Solutions

    NASA Astrophysics Data System (ADS)

    Wang, Jason; West, Michael; Han, Ye; McDonald, Robert C.; Yang, Wenjing; Ormond, Bob; Saini, Harmesh

    2005-09-01

    This paper discusses a fully automated metrology tool for detection and quantitative measurement of contamination, including cationic, anionic, metallic, organic, and molecular species present in semiconductor process solutions. The instrument is based on an electrospray ionization time-of-flight mass spectrometer (ESI-TOF/MS) platform. The tool can be used in diagnostic or analytical modes to understand process problems in addition to enabling routine metrology functions. Metrology functions include in-line contamination measurement with near real-time trend analysis. This paper discusses representative organic and molecular contamination measurement results in production process problem solving efforts. The examples include the analysis and identification of organic compounds in SC-1 pre-gate clean solution; urea, NMP (N-Methyl-2-pyrrolidone) and phosphoric acid contamination in UPW; and plasticizer and an organic sulfur-containing compound found in isopropyl alcohol (IPA). It is expected that these unique analytical and metrology capabilities will improve the understanding of the effect of organic and molecular contamination on device performance and yield. This will permit the development of quantitative correlations between contamination levels and process degradation. It is also expected that the ability to perform routine process chemistry metrology will lead to corresponding improvements in manufacturing process control and yield, the ability to avoid excursions and will improve the overall cost effectiveness of the semiconductor manufacturing process.

  6. Angular distribution of [delta] electrons emitted in collisions of 1. 0-MeV/u F[sup [ital q]+] ([ital q]=4,6,8,9) with molecular hydrogen

    SciTech Connect

    Liao, C.; Richard, P.; Grabbe, S.R.; Bhalla, C.P.; Zouros, T.J.M.; Hagmann, S. (J.R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506-2604 (United States))

    1994-08-01

    The angular distribution, as well as the energy distribution of [delta] electrons produced in collisions of 1.0-MeV/u F[sup [ital q]+] ([ital q]=4,6,8,9) ions with molecular hydrogen, have been studied for laboratory observation angles ([theta][sub [ital L

  7. Belowground Carbon Cycling Processes at the Molecular Scale: An EMSL Science Theme Advisory Panel Workshop

    SciTech Connect

    Hess, Nancy J.; Brown, Gordon E.; Plata, Charity

    2014-02-21

    As part of the Belowground Carbon Cycling Processes at the Molecular Scale workshop, an EMSL Science Theme Advisory Panel meeting held in February 2013, attendees discussed critical biogeochemical processes that regulate carbon cycling in soil. The meeting attendees determined that as a national scientific user facility, EMSL can provide the tools and expertise needed to elucidate the molecular foundation that underlies mechanistic descriptions of biogeochemical processes that control carbon allocation and fluxes at the terrestrial/atmospheric interface in landscape and regional climate models. Consequently, the workshop's goal was to identify the science gaps that hinder either development of mechanistic description of critical processes or their accurate representation in climate models. In part, this report offers recommendations for future EMSL activities in this research area. The workshop was co-chaired by Dr. Nancy Hess (EMSL) and Dr. Gordon Brown (Stanford University).

  8. Permeation Process of Small Molecules across Lipid Membranes Studied by Molecular Dynamics Simulations

    Microsoft Academic Search

    Herman J. C. Berendsen; Siewert J. Marrink

    1996-01-01

    The transport of small molecules across a phospholipid membrane is studied by molecular dynamics simulations. The effects of size, hydrophobicity, and asphericity of the penetrants on the permeation process are investigated. For this purpose, permeability coefficients of oxygen and ammonia are computed using an inhomogeneous solubility-diffusion model and compared to the previously computed results of the permeation of water. Furthermore,

  9. MOLECULAR-LEVEL PROCESS GOVERNING THE INTERACTION OF CONTAMINANTS WITH IRON AND MANGANESE OXIDES

    EPA Science Inventory

    Many of the inorganic and organic contaminants present in sediments at DOE sites can be altered or destroyed by reduction and oxidation (redox) reactions occurring at mineral surfaces. A fundamental understanding of such redox processes provided by molecular-level studies on stru...

  10. Folic Acid: Nutritional Biochemistry, Molecular Biology, and Role in Disease Processes

    Microsoft Academic Search

    Mark Lucock

    2000-01-01

    This paper reviews the chemistry, metabolism, and molecular biology of folic acid, with a particular emphasis on how it is, or may be, involved in many disease processes. Folic acid prevents neural tube defects like spina bifida, while its ability to lower homocysteine suggests it might have a positive influence on cardiovascular disease. A role for this B vitamin in

  11. MZmine 2: Modular framework for processing, visualizing, and analyzing mass spectrometry-based molecular profile data

    Microsoft Academic Search

    Tomas Pluskal; Sandra Castillo; Alejandro Villar-Briones; Matej Oresic

    2010-01-01

    Background: Mass spectrometry (MS) coupled with online separation methods is commonly applied for differential and quantitative profiling of biological samples in metabolomic as well as proteomic research. Such approaches are used for systems biology, functional genomics, and biomarker discovery, among others. An ongoing challenge of these molecular profiling approaches, however, is the development of better data processing methods. Here we

  12. C@SZR v *2 Molecular Dynamics of the Formation Process of Fullerene

    E-print Network

    Maruyama, Shigeo

    ·N--²*1 ·C·@SÛZR ­Î·v *2 Molecular Dynamics of the Formation Process of Fullerene (1st Report, Carbon, Cluster 1.·@,Í,¶,ß,É ·@1985 "N,ÉKroto ,ç (1) ,Í·C··"ZZ--¿,ðOE·[U·[,Å·ö"-,³ ,¹·C"¯Zz,É'´¹`¬­c'£,É,æ,Á,Ä--âC C60 ,Ì

  13. ATOMIC AND MOLECULAR PHYSICS: Influence of Isotope Substitution Helium Atom on Partial Cross Sections in He-HF Collisions

    NASA Astrophysics Data System (ADS)

    Yu, Chun-Ri; Zhang, Jie; Chen, Li; Jiang, Gui-Sheng; Huang, Guo-Dong

    2009-11-01

    Close-coupling equation and anisotropic potential developed in our previous research are applied to HF-3He (4He, 6He, 8He, 10He) collision system, and partial cross sections (PCSs) at the incident energy of 40 meV are calculated. By analyzing the differences of these PCSs, change rules of PCSs with the increase of partial wave number, and with the change of the mass of isotope substitution helium atom are obtained. The results show that excitation PCSs converge faster than elastic PCSs for collision energy and each of systems considered here. Also excitation PCSs converge more rapidly for high-excited states. Tail effect is present only in elastic scattering and low-excited states but not in high-excited states. With the increase of the mass of isotope substitution helium atom, converging speed of elastic, total inelastic, and state-to-state excitation PCS slows down, and the maxima of these PCSs undergoes a regular change.

  14. An overview of atomic and molecular processes in critical velocity ionization

    Microsoft Academic Search

    Shu T. Lai; Edmond Murad; William J. McNeil

    1989-01-01

    An overview of the time development of some atomic and molecular processes in critical ionization velocity (CIV) is presented. In the preonset stage, metastable states play an important role: they provide an energy-pooling mechanism allowing low-energy electrons to participate in the ionization process they may explain the low-energy threshold was well as the fast time scale in the onset of

  15. Using neural networks to construct models of the molecular beam epitaxy process

    Microsoft Academic Search

    Kyeong K. Lee; Terence Brown; Georgianna Dagnall; Robert Bicknell-Tassius; April Brown; Gary S. May

    2000-01-01

    This paper presents the systematic characterization of the molecular beam epitaxy (MBE) process to quantitatively model the effects of process conditions on film qualities. A five-layer, undoped AlGaAs and InGaAs single quantum well structure grown on a GaAs substrate is designed and fabricated. Six input factors (time and temperature for oxide removal, substrate temperatures for AlGaAs and InGaAs layer growth,

  16. Molecular Diversity and Characterization of Tetracycline-Resistant Staphylococcus aureus Isolates from a Poultry Processing Plant†

    PubMed Central

    Huys, Geert; D'Haene, Klaas; Van Eldere, Johan; von Holy, Alexander; Swings, Jean

    2005-01-01

    DNA fingerprinting and molecular characterization showed that the tetracycline-resistant Staphylococcus aureus population of a South African poultry processing plant comprised one or possibly several tet(K)-containing endemic clones that contaminated chicken and machinery surfaces at all sampled processing stages. The tet(K) gene was transferable by filter mating to S. aureus recipient 80CR5 and was located on a pT181-like plasmid. PMID:15640240

  17. Studies of fluctuation processes in nuclear collisions. [Dept. of Physics, Tennessee Technological Univ. , Cookeville, Tennessee

    SciTech Connect

    Ayik, S.

    1993-02-01

    Investigations of various aspects of heavy-ion collisions were carried out in the framework of the Boltzmann-Langevin Model (BLM). In a previous work, by projection the BLM onto a collective space, a memory-dependent collective transport model was reduced. This model was applied to thermal fission to investigate the influence of the memory effects on the fission dynamics. Some results of the calculations are presented. In addition a reduction of the relativistic BLM to a two-fluid model was carried out, and transport coefficients associated with fluid dynamical variables was carried out. Then this model was applied to investigate equilabration and fluctuation properties in a counter-streaming nuclear fluid.

  18. Studies of fluctuation processes in nuclear collisions. Progress report, March 1, 1992--February 28, 1993

    SciTech Connect

    Ayik, S.

    1993-02-01

    Investigations of various aspects of heavy-ion collisions were carried out in the framework of the Boltzmann-Langevin Model (BLM). In a previous work, by projection the BLM onto a collective space, a memory-dependent collective transport model was reduced. This model was applied to thermal fission to investigate the influence of the memory effects on the fission dynamics. Some results of the calculations are presented. In addition a reduction of the relativistic BLM to a two-fluid model was carried out, and transport coefficients associated with fluid dynamical variables was carried out. Then this model was applied to investigate equilabration and fluctuation properties in a counter-streaming nuclear fluid.

  19. Turbulent thermalization process in heavy-ion collisions at ultrarelativistic energies

    NASA Astrophysics Data System (ADS)

    Berges, J.; Boguslavski, K.; Schlichting, S.; Venugopalan, R.

    2014-04-01

    The nonequilibrium evolution of heavy-ion collisions is studied in the limit of weak coupling at very high energy employing lattice simulations of the classical Yang-Mills equations. Performing the largest classical-statistical simulations to date, we find that the dynamics of the longitudinally expanding plasma becomes independent of the details of the initial conditions. After a transient regime dominated by plasma instabilities and free streaming, the subsequent space-time evolution is governed by a nonthermal fixed point, where the system exhibits the self-similar dynamics characteristic of wave turbulence. This allows us to distinguish between different kinetic scenarios in the classical regime. Within the accuracy of our simulations, the scaling behavior found is consistent with the "bottom-up" thermalization scenario [R. Baier, A. H. Mueller, D. Schiff, and D. T. Son, Phys. Lett. B 502, 51 (2001)].

  20. ?(1475) and f 1(1420) resonances in the decay processes J/? ? ?(??, ??0, ??) and in ??* collisions

    NASA Astrophysics Data System (ADS)

    Achasov, N. N.; Shestakov, G. N.

    2011-09-01

    A scenario that removes the contradiction between the suppression of the ?(1475) ? ?? decay width and the strong coupling of ?(1475) to the ??, ??, and ??0 channels and which leads to a nontrivial prediction for the manifestation of ?(1475) in ??*( Q 2) collisions is considered. Data on the dependence of the cross section for the reaction ??*( Q 2) ? Kbar K? on the photon virtuality in the energy range 1.35-1.55 GeV are explained here by the production of an ?(1475) resonance in contrast to their standard interpretation in terms of the f 1(1420) resonance. Experimental verification of the present explanation requires determining the spin-parity of resonance contributions, R, in the reactions ??*( Q 2) R ? R ? Kbar K? and J/? ? ? R ? ?(??0, ??).

  1. Electron Collision Processes with Carbon Dioxide: Resolving Long-Standing Paradoxes

    NASA Astrophysics Data System (ADS)

    Rescigno, T. N.; Haxton, D. J.; McCurdy, C. W.

    2012-10-01

    The principal features of low-energy electron-CO2 collisions have been known and studied for over forty years. The scattering is characterized by a rapid rise in the total cross section below 1 eV, anomalous threshold behavior for excitation of symmetric stretch and bending vibrational modes, resonant vibrational excitation near 4 eV with weak ``boomerang'' structure in the excitation cross sections and dissociative electron attachment cross sections leading to CO + O^- which peak near 4 eV and 8 eV and have angular distributions which show large deviations from axial recoil. The nuclear dynamics associated with all these features is intrinsically polyatomic in nature and cannot be described with one-dimensional models. The present study provides a consistent description of all these phenomena and resolves a number long-standing paradoxes and misconceptions found in the extant literature.

  2. Improvement of thermoelectric efficiency of the polyaniline molecular junction by the doping process.

    PubMed

    Golsanamlou, Zahra; Tagani, Meysam Bagheri; Soleimani, Hamid Rahimpour

    2015-05-13

    Thermoelectric properties of a polyaniline molecular junction with face centered cubic electrodes are investigated using the Green function formalism in a linear response regime in the presence of the doping process. Doping causes the increase of thermopower and the figure of merit (ZT) and the decrease of electrical conductance as found experimentally in the work of Li et al., (Synthetic. Metals, 2010, 160, 1153-1158). We also find that the ZT increases with the molecular length in short polyanilines. [Golsanamlou et al., Phys. Chem. Chem. Phys., 2000, 35, 3523]. PMID:25929682

  3. In-silico design of computational nucleic acids for molecular information processing

    PubMed Central

    2013-01-01

    Within recent years nucleic acids have become a focus of interest for prototype implementations of molecular computing concepts. During the same period the importance of ribonucleic acids as components of the regulatory networks within living cells has increasingly been revealed. Molecular computers are attractive due to their ability to function within a biological system; an application area extraneous to the present information technology paradigm. The existence of natural information processing architectures (predominately exemplified by protein) demonstrates that computing based on physical substrates that are radically different from silicon is feasible. Two key principles underlie molecular level information processing in organisms: conformational dynamics of macromolecules and self-assembly of macromolecules. Nucleic acids support both principles, and moreover computational design of these molecules is practicable. This study demonstrates the simplicity with which one can construct a set of nucleic acid computing units using a new computational protocol. With the new protocol, diverse classes of nucleic acids imitating the complete set of boolean logical operators were constructed. These nucleic acid classes display favourable thermodynamic properties and are significantly similar to the approximation of successful candidates implemented in the laboratory. This new protocol would enable the construction of a network of interconnecting nucleic acids (as a circuit) for molecular information processing. PMID:23647621

  4. Vortex-Surface Collisions^

    NASA Astrophysics Data System (ADS)

    Conlisk, A. T.

    1998-11-01

    The interaction of vortices with solid surfaces occurs in many different situations including, but not limited to tornadoes, propeller wakes, flows over swept wings and missile forebodies, turbomachinery flows, blade-vortex interactions and tip vortex-surface interactions on helicopters. Often, parts of a system must operate within such flows and thus encounter these vortices. In the present paper we discuss the nature of a particular subset of interactions called ``collisions''. A ``collision'' is characterized by the fact that the core of the vortex is permanently altered; usually the core is locally destroyed. The focus is on fully three-dimensional collisions although two-dimensional collisions are discussed as well. Examples of collisions in helicopter aerodynamics and turbomachinery flows are discussed and the dynamics of the vortex core during a collision process are illustrated for a 90^o collision. ^Supported by the US Army Research Office

  5. Tectonic significance of the Eratosthenes Seamount: a continental fragment in the process of collision with a subduction zone in the eastern Mediterranean (Ocean Drilling Program Leg 160)

    Microsoft Academic Search

    Alastair H. F Robertson

    1998-01-01

    One of the objectives of ODP Leg 160 in the eastern Mediterranean Sea (April–May, 1995) was concerned with the study of processes of genesis and incipient collision of an inferred crustal fragment, the Eratosthenes Seamount, with the active margin of the Eurasian plate to the north, represented by southern Cyprus. The upper part of the Eratosthenes Seamount (i.e. upper several

  6. Molecular clouds toward the super star cluster NGC 3603; possible evidence for a cloud-cloud collision in triggering the cluster formation

    SciTech Connect

    Fukui, Y.; Ohama, A.; Hanaoka, N.; Furukawa, N.; Torii, K.; Hasegawa, K.; Fukuda, T.; Soga, S.; Moribe, N.; Kuroda, Y.; Hayakawa, T.; Kuwahara, T.; Yamamoto, H.; Okuda, T. [Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya 464-8602 (Japan); Dawson, J. R. [School of Mathematics and Physics, University of Tasmania, Sandy Bay Campus, Churchill Avenue, Sandy Bay, TAS 7005 (Australia); Mizuno, N.; Kawamura, A. [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Onishi, T.; Maezawa, H. [Department of Astrophysics, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531 (Japan); Mizuno, A., E-mail: fukui@a.phys.nagoya-u.ac.jp [Solar-terrestrial Environment Laboratory, Nagoya University, Chikusa-ku, Nagoya 464-8601 (Japan)

    2014-01-01

    We present new large field observations of molecular clouds with NANTEN2 toward the super star cluster NGC 3603 in the transitions {sup 12}CO(J = 2-1, J = 1-0) and {sup 13}CO(J = 2-1, J = 1-0). We suggest that two molecular clouds at 13 km s{sup –1} and 28 km s{sup –1} are associated with NGC 3603 as evidenced by higher temperatures toward the H II region, as well as morphological correspondence. The mass of the clouds is too small to gravitationally bind them, given their relative motion of ?20 km s{sup –1}. We suggest that the two clouds collided with each other 1 Myr ago to trigger the formation of the super star cluster. This scenario is able to explain the origin of the highest mass stellar population in the cluster, which is as young as 1 Myr and is segregated within the central sub-pc of the cluster. This is the second super star cluster along with Westerlund 2 where formation may have been triggered by a cloud-cloud collision.

  7. Process evaluation of an open architecture real-time molecular laboratory platform.

    PubMed

    Felder, Robin A; Jackson, Keith D; Walter, Adam M

    2014-10-01

    The needs of molecular diagnostic laboratories that perform both Food and Drug Administration-cleared as well as laboratory-developed tests are usually not met on a single analytical platform. Furthermore, little information is available about the direct impact of molecular automation on labor costs and efficiency in clinical laboratories. We performed a process impact analysis from time and motion studies of a novel molecular diagnostic robotic system designed to automate sample preparation, extraction, and analysis. All 27 preanalytical tasks were quantified for the amount of time spent preparing 24 specimens for analysis. These steps were completed in 899 s (14 min, 59 s) followed by 7887 s (131 min, 27 s) of instrument operation independent of operator control (walk-away time). Postanalytical results evaluation required 1 min per specimen. The instrument automatically extracted the nucleic acid from the specimen, added the eluted DNA to the amplification reagents, and performed the analysis. Only 12% of the total instrument operations required relatively unskilled human labor. Thus, the availability of automated molecular diagnostic instruments will facilitate the expansion of molecular testing in the clinical laboratory because they reduce operator costs with respect to time and complexity of the tasks they are asked to perform. PMID:24811476

  8. Molecular control of electron and hole transfer processes: Theory and applications

    SciTech Connect

    Newton, M.D. [Brookhaven National Lab., Upton, NY (United States). Dept. of Chemistry; Cave, R.J. [Harvey Mudd Coll., Claremont, CA (United States). Dept. of Chemistry

    1996-02-01

    Recent decades have seen remarkable advances in microscopic understanding of electron transfer (ET) processes in widely ranging contexts, including solid-state, liquid solution, and complex biological assemblies. The primary goal of this chapter is to report recent advances in the modeling, calculation, and analysis of electronic coupling in complex molecular aggregates, thereby allowing an assessment of current progress toward the goal of molecular-level control and design. The control of electron transfer kinetics (i.e., enhancing desired processes, while inhibiting others) involves, of course, system energetics (especially activation and reorganization energies) as well as electronic coupling, which is most directly relevant only after the system has reached the appropriate point (or region) along the reaction coordinate. Nevertheless, to focus the discussion in this chapter, the authors will consider such energetics, and the associated molecular and solvent coordinates which control then, only to the extent that they bear on the analysis of the electronic coupling. In the following sections they first discuss the formulation of basic ET models, including the definition of initial and final states, the role of orbitals and 1-particle models in a many-electron context, the utility of various effective Hamiltonians, and the role of vibronic as well as purely electronic effects. With these theoretical tools in hand, they then examine very recent applications to complex molecular systems using the techniques of computational quantum chemistry, followed by detailed analysis of the numerical results. They then conclude with some comments regarding the current ``state of the art`` and remaining challenges.

  9. Molecular Basis of a Million-Fold Affinity Maturation Process in a Protein-Protein Interaction

    SciTech Connect

    D Bonsor; S Postel; B Pierce; N Wang; P Zhu; R Buonpane; Z Weng; D Kranz; E Sundberg

    2011-12-31

    Protein engineering is becoming increasingly important for pharmaceutical applications where controlling the specificity and affinity of engineered proteins is required to create targeted protein therapeutics. Affinity increases of several thousand-fold are now routine for a variety of protein engineering approaches, and the structural and energetic bases of affinity maturation have been investigated in a number of such cases. Previously, a 3-million-fold affinity maturation process was achieved in a protein-protein interaction composed of a variant T-cell receptor fragment and a bacterial superantigen. Here, we present the molecular basis of this affinity increase. Using X-ray crystallography, shotgun reversion/replacement scanning mutagenesis, and computational analysis, we describe, in molecular detail, a process by which extrainterfacial regions of a protein complex can be rationally manipulated to significantly improve protein engineering outcomes.

  10. Effect of vacuum processing on outgassing within an orbiting molecular shield

    NASA Technical Reports Server (NTRS)

    Outlaw, R. A.

    1982-01-01

    The limiting hydrogen number density in an orbiting molecular shield is highly dependent on the outgassing rates from the materials of construction for the shield, experimental apparatus, and other hardware contained within the shield. Ordinary degassing temperatures used for ultrahigh vacuum studies (less than 450 C) are not sufficient to process metals so that the contribution to the number density within the shield due to outgassing is less than the theoretically attainable level (approximately 200 per cu. cm). Pure aluminum and type 347 stainless steel were studied as candidate shield materials. Measurements of their hydrogen concentration and diffusion coefficients were made, and the effects of high temperature vacuum processing (greater than 600 C) on their resulting outgassing rates was determined. The densities in a molecular shield due to the outgassing from either metal were substantially less ( 0.003) than the density due to the ambient atomic hydrogen flux at an orbital altitude of 500 km.

  11. Molecular weight distribution for NOM in different drinking water treatment processes

    Microsoft Academic Search

    Dong An; Jia-xiu Song; Wei Gao; Guo-guang Chen; Nai-yun Gao

    2009-01-01

    The purpose of this paper was to analyze molecular weight (MW) distribution in different drinking water treatment processes, and to find out the relationship between dissolved organic carbon (DOC) and disinfection by-products formation potential (DBPFP) in treated water. The results showed that in conventional water treatment, compared with similar methods, namely chlorination (Cl2) and potassium permanganate (KMnO4), pre-ozonation can reduce

  12. Molecular dynamics study of scratching velocity dependency in AFM-based nanometric scratching process

    Microsoft Academic Search

    Junjie Zhang; Tao Sun; Yongda Yan; Yingchun Liang

    2009-01-01

    Three-dimensional molecular dynamics simulations are performed to investigate the AFM-based nanometric scratching process of monocrystalline copper. The effects of scratching velocities (1, 10, and 100m\\/s) on the chip pattern, scratching resistance, dislocation movement, and workpiece deformation are studied. The results show that the scratching resistance increases with the increase in scratching velocity. The higher scratching velocity results in larger chip

  13. Processing of microporous VPI-5 molecular sieve by using supercritical CO 2: stability and adsorption properties

    Microsoft Academic Search

    J Garc??a-Carmona; M. A Fanovich; J Llibre; R Rodr??guez-Clemente; C Domingo

    2002-01-01

    The stability and adsorption behavior of the microporous molecular sieve VPI-5, an AlPO4 hydrate phase, processed using supercritical carbon dioxide (SCCO2) as a solvent, were explored. Different thermal treatments up to 373 K were carried out on samples of VPI-5 previously treated with methanol, ethanol or 2-propanol. The thermally treated samples were characterized by X-ray diffraction and low-temperature N2 adsorption.

  14. The PhyLoTA Browser: Processing GenBank for Molecular Phylogenetics Research

    Microsoft Academic Search

    MICHAEL J. SANDERSON; Darren Boss; Duhong Chen; KAREN A. CRANSTON; Andre Wehe

    2008-01-01

    As an archive of sequence data for over 165,000 species, GenBank is an indispensable resource for phy- logenetic inference. Here we describe an informatics processing pipeline and online database, the PhyLoTA Browser (http:\\/\\/loco.biosci.arizona.edu\\/pb), which offers a view of GenBank tailored for molecular phylogenetics. The first re- lease of the Browser is computed from 2.6 million sequences representing the taxonomically enriched

  15. Dislocation processes in the deformation of nanocrystalline aluminium by molecular-dynamics simulation

    Microsoft Academic Search

    Vesselin Yamakov; Dieter Wolf; Simon R. Phillpot; Amiya K. Mukherjee; Herbert Gleiter; Forschungszentrum Karlsruhe

    2002-01-01

    The mechanical behaviour of nanocrystalline materials (that is, polycrystals with a grain size of less than 100 nm) remains controversial. Although it is commonly accepted that the intrinsic deformation behaviour of these materials arises from the interplay between dislocation and grain-boundary processes, little is known about the specific deformation mechanisms. Here we use large-scale molecular-dynamics simulations to elucidate this intricate

  16. PTtD evolution of continental crust during subduction-collision processes : example of the Briançonnais domain (Western Alps, France).

    NASA Astrophysics Data System (ADS)

    Strzerzynski, P.; Guillot, S.; Leloup, P. H.; Arnaud, N.; Vidal, O.; Ledru, P.; Courrioux, G.; Darmendrail, X.

    2009-04-01

    Understanding exhumation processes of high to ultra-high pressure (HP to UHP) terrains during plate convergence is a major challenge for the comprehension of plate convergence processes and mountain building. Contemporaneous contraction and extension coupled with erosion are frequently proposed to drive the exhumation process. In the internal alpine belt, HP and UHP metamorphism are recorded both in the Piemont oceanic unit and in the continental units such as the Internal Crystalline Massifs and the Briançonnais zone. In the western Alps, the consensus is to relate the top to NW then W directed D1 thrusting phase to nappe stacking and exhumation of the HP to UHP units within a subduction channel. Although there is an agreement on the occurrence of a top to the east D2 tectonic phase, its significance in terms of shortening or extensional deformation is controversial. On one hand, top to the east D2 shear zones and associated folds are interpreted as backthrusts or backfolds active during the Oligocene syn-collisional shortening phase, post-dating the exhumation of the HP units. On the other hand, D2 structures are interpreted as top the east normal faults that are active during the exhumation of the HP unit within a subduction channel. To decipher between these two different interpretations, we conducted a combined structural, petrological and geochronological study of the Modane-Aussois area in order to build a PTtD path of the Briançonnais zone. The current construction of a high velocity railway tunnel between the Maurienne and Susa valleys provides the opportunity to gather a large amount of geological data in the internal Western Alps and to extend surface observation at depth. We provide a structural analysis on ductile and brittle domains. New PT estimates are obtained using pseudosection and multiequilibra methods. Ar/Ar step heating on phengite provide time constraint on tectonic phases. Then, in light of our data and available literature, we focus on the significance of the D2 structures in the internal Western Alps. Results indicate that polyphased tectonic occurs during exhumation. The first deformation phase (D1) is characterized by nappe stacking in a context of top to the NW shearing, between 37 and 35 Ma deformation occurs between 1.0 and 0.5 GPa and 360-350°C. Top to the East deformation phase (D2) is associated with decompression up to 0.1 GPa and cooling down to 280°C. D2 deformations end at 31Ma. Following these phases of ductile deformation, two successive brittle deformation phases are evidenced: the first one is characterized by a N-S direction of extension and produce the overall tilting toward the south of the studied zone. The second one is characterized by E-W direction of extension. In the Internal Alps, the transition between Oceanic-continental subduction and continental collision occurred at 32Ma. In this context, D1 deformations that are dated between 37 and 35 Ma are clearly related to continental subduction. In the same way, brittle deformation phases are the expression of continental collision. The D2 tectonic phase took place at the transition between subduction and collision. Its attribution to one of these two processes remains ambiguous and will be discussed at the light of these new results.

  17. Molecular-Level Processes Governing the Interaction of Contaminants with Iron and Manganese Oxides - Final Report

    SciTech Connect

    Brown Jr., G. E.; Chambers, S. A.

    1999-10-31

    Many of the inorganic and organic contaminants present in sediments at DOE sites can be altered or destroyed by reduction and oxidation (redox) reactions occurring at mineral surfaces. A fundamental understanding of such redox processes provided by molecular-level studies on structurally and compositionally well-defined mineral surfaces will lead to: (i) improved models of contaminant fate and transport in geochemical systems, and (ii) optimized manipulation of these processes for remediation purposes. To contribute to this understanding, we will study, both experimentally and theoretically, redox processes involving three important contaminants - chromate ion, carbon tetrachloride, and trichloroethene TCE, on the following iron and manganese oxides - hematite, magnetite, maghemite, and pyrolusite. These oxides and their hydroxylated analogs commonly occur as coatings on minerals or as interfaces in the subsurface environment. Single-crystal surfaces of these oxides will be synthesized in carefully controlled fashion by molecular beam epitaxy. These surfaces, as well as high surface are powdered samples of these oxides, will be used in spectroscopic and kinetic experiments in both aqueous and gas phases. Our goal is to identify products and to determine the kinetics and mechanisms of surface-catalyzed redox reaction of Cr(VI) and CR(III), and the reductive dechlorination of carbon tetrachloride and TCE. The combination of theory and experiment will provide the base information needed to scale from the molecular level to the microscopic grain level minerals.

  18. All-dry processible and PAG-attached molecular glasses for improved lithographic performance

    NASA Astrophysics Data System (ADS)

    Krysak, Marie; Kolb, Tristan; Neuber, Christian; Schmidt, Hans-Werner; Ober, Christopher K.

    2010-04-01

    As the semiconductor industry moves forward, resolution limits are being pushed to the sub-30 nm regime. In order to meet these demands, radical new resist design and processes must be explored. We have developed a molecular glass system for all-dry processing conditions. Physical vapor deposition (PVD) has been used for film formation onto silicon wafers. PVD deposits a uniform film of controlled thickness free from impurities that are often introduced by casting solvents used in traditional spin coating methods. Thermal development is used as an alternative to processing in solvents in order to prevent resist swelling and pattern collapse by capillary forces. The deposited molecule is designed to crosslink upon E-beam irradiation without additives, and therefore form a homogeneous, single component film. PAG-attached molecular glasses have been synthesized in order to promote film homogeneity as well. By tethering PAG directly to the molecular glass core, issues such as PAG aggregation can be remedied. Acid migration, which increases blur and LER, can also be hindered.

  19. Utilization of efficient gradient and Hessian computations in the force field optimization process of molecular simulations

    NASA Astrophysics Data System (ADS)

    Hülsmann, Marco; Kopp, Sonja; Huber, Markus; Reith, Dirk

    2013-01-01

    Computer simulations of chemical systems, especially systems of condensed matter, are highly important for both scientific and industrial applications. Thereby, molecular interactions are modeled on a microscopic level in order to study their impact on macroscopic phenomena. To be capable of predicting physical properties quantitatively, accurate molecular models are indispensable. Molecular interactions are described mathematically by force fields, which have to be parameterized. Recently, an automated gradient-based optimization procedure was published by the authors based on the minimization of a loss function between simulated and experimental physical properties. The applicability of gradient-based procedures is not trivial at all because of two reasons: firstly, simulation data are affected by statistical noise, and secondly, the molecular simulations required for the loss function evaluations are extremely time-consuming. Within the optimization process, gradients and Hessians were approximated by finite differences so that additional simulations for the respective modified parameter sets were required. Hence, a more efficient approach to computing gradients and Hessians is presented in this work. The method developed here is based on directional instead of partial derivatives. It is compared with the classical computations with respect to computation time. Firstly, molecular simulations are replaced by fit functions that define a functional dependence between specific physical observables and force field parameters. The goal of these simulated simulations is to assess the new methodology without much computational effort. Secondly, it is applied to real molecular simulations of the three chemical substances phosgene, methanol and ethylene oxide. It is shown that up to 75% of the simulations can be avoided using the new algorithm.

  20. ATOMIC AND MOLECULAR PHYSICS: Relativistic Distorted-Wave Collision Strengths of Ni-, Cu- and Zn-like Au Ions

    NASA Astrophysics Data System (ADS)

    Yang, Ning-Xuan; Dong, Chen-Zhong; Jiang, Jun

    2009-05-01

    Excitation energies and electron impact excitation strengths from the ground states of Ni-, Cu- and Zn-like Au ions are calculated. The collision strengths are computed by a 213-levels expansion for the Ni-like Au ion, 405-levels expansion for the Cu-like Au ion and 229-levels expansion for the Zn-like Au ion. Configuration interactions are taken into account for all levels included. The target state wavefunctions are calculated by using the Grasp92 code. The continuum orbits are computed in the distorted-wave approximation, in which the direct and exchange potentials among all the electrons are included. Excellent agreement is found when the results are compared with previous calculations and recent measurements.

  1. Heavy particle atomic collisions in astrophysics: Beyond H and He targets

    SciTech Connect

    Stancil, P.C.; Krstic, P.S.; Schultz, D.R.

    1998-06-01

    The physical conditions relating to the emission of x-rays from Jovian and cometary atmospheres and to supernova ejecta are briefly described. Emphasis is placed on elucidating the relevance and importance of atomic collision processes, the availability of data, and the outstanding data needs for modeling these environments. Some preliminary theoretical studies of electron capture for important collisions systems, involving molecular and atomic metal targets, are presented.

  2. Evaluation of the Influence of Amino Acid Composition on the Propensity for Collision-Induced Dissociation of Model Peptides Using Molecular Dynamics Simulations

    SciTech Connect

    Cannon, William R.; Taasevigen, Danny J.; Baxter, Douglas J.; Laskin, Julia

    2007-09-01

    The dynamical behavior of model peptides was evaluated with respect to their ability to form internal proton donor-acceptor pairs using molecular dynamics simulations. The proton donor-acceptor pairs are postulated to be prerequisites for peptide bond cleavage resulting in formation of b and y ions during low energy collision-induced dissociation in tandem mass spectrometry (MS/MS). The simulations for the polyalanine pentamer Ala5H+ were compared to experimental data from collision energy-resolved surface induced dissociation (SID) studies. The results of the simulation are insightful into the events that likely lead up to the fragmentation of peptides. 9-mer polyalanine-based model peptides were used to examine the dynamical effect of each of the 20 common amino acids on the probability to form donor-acceptor pairs at labile peptide bonds. A continuous range of probabilities was observed as a function of the substituted amino acid. However, the location of the peptide bond involved in the donor-acceptor pair plays a critical role in the dynamical behavior. This influence of position on the probability of forming a donor-acceptor pair would be hard to predict from statistical analyses on experimental spectra of aggregate, diverse peptides. In addition, the inclusion of basic side chains in the model peptides alters the probability of forming donor-acceptor pairs across the entire backbone. In this case there are still more ionizing protons than basic residues, but the side chains of the basic amino acids form stable hydrogen bond networks with the peptide carbonyl oxygens and thus act to prevent free access of “mobile protons” to labile peptide bonds. It is clear from the work that the identification of peptides from low-energy CID using automated computational methods should consider the location of the fragmenting bond as well as the amino acid composition.

  3. Comparison of nonequilibrium processes in p+Ni and p+Au collisions at GeV energies

    E-print Network

    Budzanowski, A; Filges, D; Goldenbaum, F; Hodde, H; Jarczyk, L; Kamys, B; Kistryn, M; Kistryn, St; Kliczewski, St; Kowalczyk, A; Kozik, E; Kulessa, P; Machner, H; Magiera, A; Piskor-Ignatowicz, B; Pysz, K; Rudy, Z; Siudak, R; Wojciechowski, M

    2009-01-01

    The energy and angular dependence of double differential cross sections d2sigma/dOmega dE were measured for p, d, t, 3,4,6He, 6,7,8Li, 7,9,10Be, 10,11B, and C produced in collisions of 1.2, 1.9, and 2.5 GeV protons with a Ni target. The shape of the spectra and angular distributions does almost not change whereas the absolute value of the cross sections increases by a factor about 1.7 for all ejectiles in this beam energy range. It was found that energy and angular dependencies of the cross sections cannot be reproduced by the microscopic model of intranuclear cascade with coalescence of nucleons and the statistical model for evaporation of particles from excited, equilibrated residual nuclei. The inclusion of nonequilibrium processes, described by a phenomenological model of the emission from fast and hot moving sources, resulting from break-up of the target nucleus by impinging proton, leads to very good reproduction of data. Cross sections of these processes are quite large, exhausting approximately half o...

  4. Molecular Clock of Neutral Mutations in a Fitness-Increasing Evolutionary Process

    PubMed Central

    Iijima, Leo; Suzuki, Shingo; Hashimoto, Tomomi; Oyake, Ayana; Kobayashi, Hisaka; Someya, Yuki; Narisawa, Dai; Yomo, Tetsuya

    2015-01-01

    The molecular clock of neutral mutations, which represents linear mutation fixation over generations, is theoretically explained by genetic drift in fitness-steady evolution or hitchhiking in adaptive evolution. The present study is the first experimental demonstration for the molecular clock of neutral mutations in a fitness-increasing evolutionary process. The dynamics of genome mutation fixation in the thermal adaptive evolution of Escherichia coli were evaluated in a prolonged evolution experiment in duplicated lineages. The cells from the continuously fitness-increasing evolutionary process were subjected to genome sequencing and analyzed at both the population and single-colony levels. Although the dynamics of genome mutation fixation were complicated by the combination of the stochastic appearance of adaptive mutations and clonal interference, the mutation fixation in the population was simply linear over generations. Each genome in the population accumulated 1.6 synonymous and 3.1 non-synonymous neutral mutations, on average, by the spontaneous mutation accumulation rate, while only a single genome in the population occasionally acquired an adaptive mutation. The neutral mutations that preexisted on the single genome hitchhiked on the domination of the adaptive mutation. The successive fixation processes of the 128 mutations demonstrated that hitchhiking and not genetic drift were responsible for the coincidence of the spontaneous mutation accumulation rate in the genome with the fixation rate of neutral mutations in the population. The molecular clock of neutral mutations to the fitness-increasing evolution suggests that the numerous neutral mutations observed in molecular phylogenetic trees may not always have been fixed in fitness-steady evolution but in adaptive evolution. PMID:26177190

  5. Onland signatures of the Palawan microcontinental block and Philippine mobile belt collision and crustal growth process: A review

    Microsoft Academic Search

    Graciano P. Yumul; Carla B. Dimalanta; Edanjarlo J. Marquez; Karlo L. Queaño

    2009-01-01

    The collision of the Palawan microcontinental block with the Philippine mobile belt had significantly influenced the geological evolution of the Philippines. Multiple collisions involving several fragments, through space and time, resulted into the collage of terranes of varying origin exposed in this part of central Philippines. Cusping of the overriding plate, volcanic arc gap, ophiolite emplacement, incipient back-arc rifting, island

  6. Modeling droplet collision and coalescence in an icing wind tunnel and the influence of these processes on droplet

    E-print Network

    Frey, Pascal

    Modeling droplet collision and coalescence in an icing wind tunnel and the influence in an icing wind tunnel is presented here. The mutual interactions taking place within the dispersed phase content (LWC) in the bottom half of the wind tunnel. Droplet collision tends to influence the size

  7. Dipolar degrees of freedom and isospin equilibration processes in heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Papa, M.; Berceanu, I.; Acosta, L.; Amorini, F.; Agodi, C.; Anzalone, A.; Auditore, L.; Cardella, G.; Cavallaro, S.; Chatterjee, M. B.; De Filippo, E.; Francalanza, L.; Geraci, E.; Grassi, L.; Gnoffo, B.; Han, J.; La Guidara, E.; Lanzalone, G.; Lombardo, I.; Maiolino, C.; Minniti, T.; Pagano, A.; Pagano, E. V.; Pirrone, S.; Politi, G.; Porto, F.; Quattrocchi, L.; Rizzo, F.; Rosato, E.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

    2015-04-01

    The dipolar degrees of freedom on the 48Ca+27Al system at 40 MeV/nucleon have been investigated for the first time with the 4 ? multidetector CHIMERA. The global variable was measured for well-reconstructed events in binary dissipative processes. Both the close link with isospin equilibration processes and its insensitivity to later statistical hot source decays have been discussed. This latter feature provides the opportunity to investigate globally and exclusively the dynamics of the equilibration processes. At this first level of investigation the experimental evidence, supported by the study of the reference system 27Al+40Ca and the auxiliary one 27Ca+48Ca , substantially agree with the CoMD-III calculations by describing the isovectorial forces through stiffness parameter values ? ?0.8 -1.2 .

  8. Deformation Mechanism and Punch Taper Effects on Nanoimprint Process by Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Hsu, Quang-Cherng; Wu, Chen-Da; Fang, Te-Hua

    2004-11-01

    A molecular dynamics analysis model is proposed to study the effects of parameters on the nanoimprint process, for example, taper angle, imprint depth and spring back. The nanoimprint process comprises one punch and one specimen at an isothermal state of 400 K, while the deformed material is a copper fcc single crystal and the punch material is a nickel fcc single crystal. There were a total of 10,080 atoms in copper measuring 12.02 nm and 5.72 nm in length and height, respectively. There were a total of 4,200 atoms in nickel with a typical length and depth in a punch tooth of 6.24 nm and 3.52 nm, respectively. Computer simulation codes based on Hamiltonian dynamics, periodical boundary conditions and the Morse potential function were used to simulate the nanoimprint process. By varying the punch taper angle and the imprint depth, useful information about the nanoimprint process was obtained.

  9. Studies on Deformation Mechanism and Punch Taper Effects on Nanoimprint Processes by Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Hsu, Quang-Cherng; Wu, Chen-Da; Fang, Te-Hua

    2004-06-01

    A molecular dynamics analysis model is proposed to study the effects of parameters on nanoimprint process, for example: taper angle, imprint depth and spring back. The nanoimprint process comprises one punch and one specimen at an isothermal state of 400K, while the deformed material is a copper FCC single crystal and the punch material is a nickel FCC single crystal. There were a total of 10,080 atoms in copper measuring 12.02 nm × 5.72 nm in length and height, respectively. There were a total of 4,200 atoms in nickel where the typical length and depth in punch tooth are 6.24 nm × 3.52 nm, respectively. Computer simulation codes based on Hamiltonian dynamics, periodical boundary conditions and Morse potential function were used to simulate the nanoimprint processes. By varying the punch taper angle and the imprinting depth, useful information for nanoimprint process has been obtained.

  10. New Insights Into the Fission Process by the Study of Relativistic Nuclear Collisions

    SciTech Connect

    Kelic, Aleksandra; Schmidt, Karl-Heinz [GSI, Planckstr. 1, Darmstadt, D-64291 (Germany)

    2007-05-22

    An experimental and theoretical campaign dedicated to a better understanding of the fission process has been started at GSI several years ago. The waste amount of data measured at GSI gave new information on different aspects of the nuclear-fission process, such as nuclear viscosity at small deformation, transient effects, influence of shell effects on mass- and charge-division in fission, pairing correlations. All this lead to a development of a model, which proved successful in describing fragment formation in spallation and fragmentation reactions.

  11. The role of orbital dynamics and cloud-cloud collisions in the formation of giant molecular clouds in global spiral structures

    NASA Technical Reports Server (NTRS)

    Roberts, William W., Jr.; Stewart, Glen R.

    1987-01-01

    The role of orbit crowding and cloud-cloud collisions in the formation of GMCs and their organization in global spiral structure is investigated. Both N-body simulations of the cloud system and a detailed analysis of individual particle orbits are used to develop a conceptual understanding of how individual clouds participate in the collective density response. Detailed comparisons are made between a representative cloud-particle simulation in which the cloud particles collide inelastically with one another and give birth to and subsequently interact with young star associations and stripped down simulations in which the cloud particles are allowed to follow ballistic orbits in the absence of cloud-cloud collisions or any star formation processes. Orbit crowding is then related to the behavior of individual particle trajectories in the galactic potential field. The conceptual picture of how GMCs are formed in the clumpy ISMs of spiral galaxies is formulated, and the results are compared in detail with those published by other authors.

  12. Reducing Si population in the ISM by charge exchange collisions with He+: a quantum modelling of the process

    NASA Astrophysics Data System (ADS)

    Satta, M.; Grassi, T.; Gianturco, F. A.; Yakovleva, S. A.; Belyaev, A. K.

    2013-12-01

    The possible losses of silicon atom population during star-forming evolution and in the (photon-dominated region) PDR environments of the interstellar medium (ISM) can have different origins, one being the charge exchange (CE) encounter with the helium cations (Si + He+) one of the most abundant species in those environments. This work investigates the different features of the likely interaction potentials leading to asymptotic partners like Si, Si+, Si++ and He or He+, in order to determine the influence of more accurate cross-sections on the chemical evolution of the ISM. We analyse the behaviour of interacting Si and He atoms by using ab initio quantum molecular methods. To obtain the corresponding transition probabilities, we employ a simple sequential grouping of single-crossing Landau-Zener events, and the time-dependent rate coefficients for the CE processes involved are obtained over a broad range of the gas temperatures. The results are seen to differ substantially from an earlier Langevin-type modelling of such process and further suggest a much more complex variety of possible molecular evolution mechanisms. We find, in fact, the unexpected presence of electron shake-off effects leading to Si++ generation yielding to emission of an electron, which has never been considered before and that, although with markedly smaller cross-sections, can indeed contribute to Si losses after the primary CE event. The consequences of these novel findings are tested on evolutionary model calculations and the results discussed in detail.

  13. Use of Molecular Typing Methods To Trace the Dissemination ofListeria monocytogenesin a Shrimp Processing Plant

    Microsoft Academic Search

    M. T. DESTRO; M. F. F. LEITAO; M. FARBER

    1996-01-01

    Molecular typing of bacteria has been widely used in epidemiological studies but not as extensively for tracing the transmission of pathogenic bacteria in food plants. This study was conducted to examine the potential use of two molecular typing methods, random amplified polymorphic DNA (RAPD) analysis and pulsed-field gel electrophoresis (PFGE), to traceListeria monocytogenescontamination in a shrimp processing plant. Ribotyping and

  14. Laser-induced fluorescence studies of a supersonic molecular beam of bromine : Vibrational and rotational relaxation of bromine and collision-free lifetimes for Br2(B3 Pi))

    Microsoft Academic Search

    S. J. Bullman; J. W. Farthing; J. C. Whitehead

    1981-01-01

    Laser-induced fluorescence has been employed to measure collision-free lifetimes of various vibrational levels of Br2(B3 Pi(0u+)) using a supersonic molecular beam of bromine. The lifetimes lie in the range 3·2-5·8 mus and are in accord with previous studies. Using time-of-flight and laser-induced fluorescence methods, the efficiencies of rotational and vibrational relaxation of ground state Br2 have been studied by measuring

  15. Experiments on the Dynamics of Molecular Processes: a Chronicle of Fifty Years

    NASA Astrophysics Data System (ADS)

    Boato, Giovanni; Volpi, Gian Gualberto

    1999-10-01

    This paper reviews the way in which, in the Italy of the years immediately after World War II, interest in the dynamics of molecular processes was awakened. The narrative begins with the work of a small number of chemists and physicists who, in the initial stage, interacted closely. In the course of the years, their interests diverged and younger people joined the newly formed groups. Even now, after half a century, a common approach can still to be seen regarding how to attack problems and perform experiments. Experimental work is discussed, bringing out the common viewpoint of fields as diverse as mass spectrometry, isotope effects, chemical kinetics, molecular beams, molecule-molecule interactions, molecule-ion interactions, molecule-surface interactions, and plasma chemistry.

  16. In Situ Microscopic Observation of the Crystallization Process of Molecular Microparticles by Fluorescence Switching.

    PubMed

    Ye, Xin; Liu, Yang; Lv, Yun; Liu, Guangfeng; Zheng, Xiaoxin; Han, Quanxiang; Jackson, Kenneth A; Tao, Xutang

    2015-06-26

    To clearly understand the solid-state amorphous-to-crystalline transformation is a long-standing challenge because such crystallization occuring in confined environments is difficult to observe directly. We developed an in situ and real-time imaging procedure to record the interface evolution in a solid-state crystallization of molecular amorphous particles. The method, by employing a tetra-substituted ethene with novel morphology-dependent fluorescence, which can distinguish the interfaces between the crystalline and amorphous phase by fluorescence color, is a simple and practical method to probe the inner process of a molecular microparticle. The crystallization of amorphous microparticles in different cases was clearly recorded, where the perfect microparticles and those with defects demonstrate diverse destinies. The details disclosed in this observation will deepen the understanding for a series of solid-state crystallization that we know little about before. PMID:25974083

  17. Entropy and chemical change. 1: Characterization of product (and reactant) energy distributions in reactive molecular collisions: Information and enthropy deficiency

    NASA Technical Reports Server (NTRS)

    Bernstein, R. B.; Levine, R. D.

    1972-01-01

    Optimal means of characterizing the distribution of product energy states resulting from reactive collisions of molecules with restricted distributions of initial states are considered, along with those for characterizing the particular reactant state distribution which yields a given set of product states at a specified total energy. It is suggested to represent the energy-dependence of global-type results in the form of square-faced bar plots, and of data for specific-type experiments as triangular-faced prismatic plots. The essential parameters defining the internal state distribution are isolated, and the information content of such a distribution is put on a quantitative basis. The relationship between the information content, the surprisal, and the entropy of the continuous distribution is established. The concept of an entropy deficiency, which characterizes the specificity of product state formation, is suggested as a useful measure of the deviance from statistical behavior. The degradation of information by experimental averaging is considered, leading to bounds on the entropy deficiency.

  18. Molecular Studies on the Ecology of Listeria monocytogenes in the Smoked Fish Processing Industry

    PubMed Central

    Norton, Dawn M.; McCamey, Meghan A.; Gall, Kenneth L.; Scarlett, Janet M.; Boor, Kathryn J.; Wiedmann, Martin

    2001-01-01

    We have applied molecular approaches, including PCR-based detection strategies and DNA fingerprinting methods, to study the ecology of Listeria monocytogenes in food processing environments. A total of 531 samples, including raw fish, fish during the cold-smoking process, finished product, and environmental samples, were collected from three smoked fish processing facilities during five visits to each facility. A total of 95 (17.9%) of the samples tested positive for L. monocytogenes using a commercial PCR system (BAX for Screening/Listeria monocytogenes), including 57 (27.7%) environmental samples (n = 206), 8 (7.8%) raw material samples (n = 102), 23 (18.1%) samples from fish in various stages of processing(n = 127), and 7 (7.3%) finished product samples (n = 96). L. monocytogenes was isolated from 85 samples (16.0%) using culture methods. Used in conjunction with a 48-h enrichment in Listeria Enrichment Broth, the PCR system had a sensitivity of 91.8% and a specificity of 96.2%. To track the origin and spread of L. monocytogenes, isolates were fingerprinted by automated ribotyping. Fifteen different ribotypes were identified among 85 isolates tested. Ribotyping data established possible contamination patterns, implicating raw materials and the processing environment as potential sources of finished product contamination. Analysis of the distribution of ribotypes revealed that each processing facility had a unique contamination pattern and that specific ribotypes persisted in the environments of two facilities over time (P ? 0.0006). We conclude that application of molecular approaches can provide critical information on the ecology of different L. monocytogenes strains in food processing environments. This information can be used to develop practical recommendations for improved control of this important food-borne pathogen in the food industry. PMID:11133446

  19. Molecular formula analysis of fragment ions by isotope-selective collision-induced dissociation tandem mass spectrometry of pharmacologically active compounds.

    PubMed

    Bianco, Giuliana; Buchicchio, Alessandro; Lelario, Filomena; Cataldi, Tommaso R I

    2014-12-01

    The purpose of this work is to explore the mass fragment characterization of commonly used drugs through a novel approach, which involves isotope-selective tandem mass spectrometry (MS/MS). Collision-induced dissociation (CID) was performed with a low-resolution linear ion trap mass spectrometer in positive electrospray ionization. Three pharmacologically active ingredients, i.e. omeprazole, meloxicam and brinzolamide, selected as model compounds in their own formulation, were investigated as a sodiated adduct [C17 H19 N3 O3 S?+?Na](+) (omeprazole) and as protonated adducts, [C14 H13 N3 O4 S2 ?+?H](+) and [C12 H21 N3 O5 S3 ?+?H](+) , meloxicam and brinzolamide, respectively. Selecting a narrow window of ±0.5 m/z units, precursor ion fragmentation by CID-MS/MS of isotopologues A?+?0, A?+?1 and A?+?2 was found very useful to confirm the chemical formula of product ions, thus aiding the establishment of characteristic fragmentation pathways of all three examined compounds. The correctness of putative molecular formula of product ions was easily demonstrated by exploiting the isotope peak abundance ratios (i.e. IF+0 /IF+1 and IF+0 /IF+2 ) as simple constraints in low-resolution MS instrumentations. PMID:25476951

  20. Actualities on molecular pathogenesis and repairing processes of cerebral damage in perinatal hypoxic-ischemic encephalopathy

    PubMed Central

    2010-01-01

    Hypoxic-ischemic encephalopathy (HIE) is the most important cause of cerebral damage and long-term neurological sequelae in the perinatal period both in term and preterm infant. Hypoxic-ischemic (H-I) injuries develop in two phases: the ischemic phase, dominated by necrotic processes, and the reperfusion phase, dominated by apoptotic processes extending beyond ischemic areas. Due to selective ischemic vulnerability, cerebral damage affects gray matter in term newborns and white matter in preterm newborns with the typical neuropathological aspects of laminar cortical necrosis in the former and periventricular leukomalacia in the latter. This article summarises the principal physiopathological and biochemical processes leading to necrosis and/or apoptosis of neuronal and glial cells and reports recent insights into some endogenous and exogenous cellular and molecular mechanisms aimed at repairing H-I cerebral damage. PMID:20846380

  1. Evolution and stability of shock waves in dissipative gases characterized by activated inelastic collisions

    E-print Network

    Sirmas, Nick

    2015-01-01

    Previous experiments have revealed that shock waves driven through dissipative gases may become unstable, for example, in granular gases, and in molecular gases undergoing strong relaxation effects. The mechanisms controlling these instabilities are not well understood. We successfully isolated and investigated this instability in the canonical problem of piston driven shock waves propagating into a medium characterized by inelastic collision processes. We treat the standard model of granular gases, where particle collisions are taken as inelastic with constant coefficient of restitution. The inelasticity is activated for sufficiently strong collisions. Molecular dynamic simulations were performed for 30,000 particles. We find that all shock waves investigated become unstable, with density non-uniformities forming in the relaxation region. The wavelength of these fingers is found comparable to the characteristic relaxation thickness. Shock Hugoniot curves for both elastic and inelastic collisions were obtaine...

  2. Reorganization energy of electron transfer processes in ionic fluids: A molecular Debye-Hueckel approach

    SciTech Connect

    Xiao Tiejun; Song Xueyu [Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)

    2013-03-21

    The reorganization energy of electron transfer processes in ionic fluids is studied under the linear response approximation using a molecule Debye-Hueckel theory. Reorganization energies of some model reactants of electron transfer reactions in molten salts are obtained from molecular simulations and a molecule Debye-Hueckel approach. Good agreements between simulation results and the results from our theoretical calculations using the same model Hamiltonian are found. Applications of our theory to electron transfer reactions in room temperature ionic liquids further demonstrate that our theoretical approach presents a reliable and accurate methodology for the estimation of reorganization energies of electron transfer reactions in ionic fluids.

  3. Bond formation in C+59 - C60 collisions

    NASA Astrophysics Data System (ADS)

    Zettergren, H.; Rousseau, P.; Wang, Y.; Seitz, F.; Chen, T.; Gatchell, M.; Alexander, J. D.; Stockett, M. H.; Rangama, J.; Chesnel, J. Y.; Capron, M.; Poully, J. C.; Domaracka, A.; Méry, A.; Maclot, S.; Vizcaino, V.; Schmidt, H. T.; Adoui, L.; Alcamí, M.; Tielens, A. G. G. M.; Martín, F.; Huber, B. A.; Cederquist, H.

    2014-04-01

    In this work, we show that keV-ions are able to remove single carbon atoms from individual fullerenes in clusters of C60 molecules. This very efficiently leads to the formation of exotic C+119 dumbbell molecules through secondary C+59 + C60 collisions within the fragmenting cluster. Such molecular fusion processes are inherently different from those induced by photons where only products with even numbers of carbon atoms are observed. Thus, ion collisions ignite unique and hitherto overlooked secondary reactions in small aggregates of matter. This relates to the question on how complex molecules may form in e.g. space.

  4. Characterization of skin penetration processes of organic molecules using molecular similarity and QSAR analysis.

    PubMed

    Santos-Filho, Osvaldo A; Hopfinger, A J; Zheng, Tao

    2004-01-01

    Molecular similarity and QSAR analyses have been used to develop compact, robust, and definitive models for skin penetration by organic compounds. The QSAR models have been sought to provide an interpretation and characterization of plausible molecular mechanisms of skin penetration. A training set of 40 structurally diverse compounds were selected to be representative of a parent set of 152 compounds in terms of both structural diversity and range in measured skin penetration. The subset of 40 compounds was used in a series of QSAR analyses in the search for the most significant, compact, and straightforward skin penetration QSAR models. Molecular dynamics simulations were employed to determine a set of MI (membrane-interaction) descriptors for each test compound (solute) interacting with a model DMPC monolayer membrane model. The MI-QSAR models may capture features of cellular membrane lateral transverse transport involved in the overall skin penetration process by organic compounds. An additional set of intramolecular solute descriptors, the non-MI-QSAR descriptors, were computed and added to the trial pool of descriptors for building QSAR models. All QSAR models were constructed using multidimensional linear regression fitting and a genetic algorithm optimization function. QSAR models were constructed using only non-MI-QSAR descriptors and using a combination of both these descriptor sets. It was found that a combination of non-MI-QSAR and MI-QSAR descriptors yielded the optimum models, not only with respect to the statistical measures of fit but also regarding model predictivity. PMID:16028358

  5. Onland signatures of the Palawan microcontinental block and Philippine mobile belt collision and crustal growth process: A review

    NASA Astrophysics Data System (ADS)

    Yumul, Graciano P., Jr.; Dimalanta, Carla B.; Marquez, Edanjarlo J.; Queaño, Karlo L.

    2009-05-01

    The collision of the Palawan microcontinental block with the Philippine mobile belt had significantly influenced the geological evolution of the Philippines. Multiple collisions involving several fragments, through space and time, resulted into the collage of terranes of varying origin exposed in this part of central Philippines. Cusping of the overriding plate, volcanic arc gap, ophiolite emplacement, incipient back-arc rifting, island rotation and tilting, raised coastal terraces, metamorphism, intrusion of igneous rocks and steepened subducted slab as seen in focal mechanism solutions are some of the manifestations of this collision. A late Early Miocene to early Middle Miocene age (20-16 Ma) is proposed for the major collision between the Palawan indenter and the Philippine mobile belt. The collision boundary is located from the northern part of Mindoro through the central mountain range swinging east of Sibuyan Island in the Romblon Island Group and finally threading along the Buruanga Peninsula and eastern side of the Antique Ophiolite Complex before exiting and connecting with the Negros Trench. The collision, through accretion and crustal thickening, has contributed to the crustal growth of the Philippine archipelago.

  6. Laser wavelength effect on charge transfer and excitation processes in laser-assisted collisions of Li+ + H

    NASA Astrophysics Data System (ADS)

    Domínguez-Gutiérrez, F. Javier; Cabrera-Trujillo, R.

    2014-05-01

    Total, n = 2 , and 3 charge transfer and n = 2 target excitation probabilities for collision of Li+ with ground state atomic hydrogen are calculated numerically, in the impact energy collision range 0.25-5 keV. The total wave function at the end of the dynamics of the collision is obtained by solving the time-dependent Schrödinger equation by means the finite-difference method. We use a pseudo-potential method to model the electronic structure of the Li+ ion. The n = 2 , and 3 charge transfer and n = 2 target excitation probabilities are obtained by projecting the stationary states of Lithium and Hydrogen neutral atoms to the total wave function of the collision, respectively; the stationary states of Li and H are obtained numerically. To assess the validity of our method, our numerical results have been compared with those obtained experimentally and by other theoretical methods found in the literature. We study the laser-assited collision by using a short (3 fs at FWHM) and intense (3.15 ×12 W/cm2) Gaussian laser pulse. We consider a wavelength range between 400 - 1000 nm in steps of 100 nm. Finally, we analyze the laser assisted collision by a qualitatively way with a two level approach. We acknowledge support from grant PAPIIT IN 110-714 and CONACyT (Ph.D. scholarship).

  7. Thermal- and urea-induced unfolding processes of glutathione S-transferase by molecular dynamics simulation.

    PubMed

    Li, Jiahuang; Chen, Yuan; Yang, Jie; Hua, Zichun

    2015-05-01

    The Schistosoma juponicum 26 kDa glutathione S-transferase (sj26GST) consists of the N-terminal domain (N-domain), containing three alpha-helices (named H1-H3) and four anti-parallel beta-strands (S1-S4), and the C-terminal domain (C-domain), comprising five alpha-helices (named H4-H8). In present work, molecular dynamics simulations and fluorescence spectroscopic were used to gain insights into the unfolding process of sj26GST. The molecular dynamics simulations on sj26GST subunit both in water and in 8 M urea were carried out at 300 K, 400 K and 500 K, respectively. Spectroscopic measurements were employed to monitor structural changes. Molecular dynamics simulations of sj26GST subunit induced by urea and temperature showed that the initial unfolding step of sj26GST both in water and urea occurred on N-domain, involving the disruption of helices H2, H3 and strands S3 and S4, whereas H6 was the last region exposed to solution and was the last helix to unfold. Moreover, simulations analyses combining with fluorescence and circular dichroism spectra indicated that N-domain could not fold independent, suggesting that correct folding of N-domain depended on its interactions with C-domain. We further proposed that the folding of GSTs could begin with the hydrophobic collapse of C-domain whose H4, H5, H6 and H7 could move close to each other and form a hydrophobic core, especially H6 wrapped in the hydrophobic center and beginning spontaneous formation of the helix. S3, S4, H3, and H2 could form in the wake of the interaction between C-domain and N-domain. The paper can offer insights into the molecular mechanism of GSTs unfolding. © 2014 Wiley Periodicals, Inc. Biopolymers 103: 247-259, 2015. PMID:25403814

  8. Cold collisions between boson or fermion molecules

    SciTech Connect

    Kajita, Masatoshi [Communications Research Laboratory, 4-2-1, Nukui-Kitamachi, Koganei, Tokyo 184-8795 (Japan)

    2004-01-01

    We theoretically investigate collisions between electrostatically trapped cold polar molecules and compare boson and fermion isotopes. Evaporative cooling seems possible for fermion molecules as the ratio of the collision loss cross section to the elastic collision cross section (R) gets smaller as the molecular temperature T lowers. With boson molecules, R gets larger as T lowers, which makes evaporative cooling difficult. The elastic collision cross section between fermion molecules can be larger than that for boson molecules with certain conditions.

  9. Processing of hydroxyapatite reinforced ultrahigh molecular weight polyethylene for biomedical applications.

    PubMed

    Fang, Liming; Leng, Yang; Gao, Ping

    2005-06-01

    A new method for processing hydroxyapatite/ultrahigh molecular weight polyethylene (HA/UHMWPE) composite has been developed by combining wet ball milling and swelling. Sintered HA particles were ground in ethanol to approximately 50 nm in diameter. The nano-sized HA particles were mechanically mixed with UHMWPE in the ball mill and then compression molded into solid slabs. The slabs were then swollen in a pharmaceutical grade paraffin oil to enhance the UHMWPE chain mobility and HA/UHMWPE interface adhesion before final hot press. The resultant composite exhibits a two-zone network structure formed by a homogeneous HA-rich phase and a UHMWPE-rich phase. This process resulted in a 90% increase in Young's modulus and a 50% increase in the yield strength of HA/UHMWPE composite, comparing with those of unfilled UHMWPE. PMID:15621236

  10. Observation of the amorphous zinc oxide recrystalline process by molecular dynamics simulation

    PubMed Central

    Lin, Ken-Huang; Sun, Shih-Jye; Ju, Shin-Pon; Tsai, Jen-Yu; Chen, Hsin-Tsung; Hsieh, Jin-Yuan

    2013-01-01

    The detailed structural variations of amorphous zinc oxide (ZnO) as well as wurtzite (B4) and zinc blende (B3) crystal structures during the temperature elevation process were observed by molecular dynamics simulation. The amorphous ZnO structure was first predicted through the simulated-annealing basin-hopping algorithm with the criterion to search for the least stable structure. The density and X-ray diffraction profiles of amorphous ZnO of the structure were in agreement with previous reports. The local structural transformation among different local structures and the recrystalline process of amorphous ZnO at higher temperatures are observed and can explain the structural transformation and recrystalline mechanism in a corresponding experiment [Bruncko et al., Thin Solid Films 520, 866-870 (2011)]. PMID:23509413

  11. Direct observation of single Ostwald ripening processes by molecular dynamics simulation.

    PubMed

    Kraska, Thomas

    2008-10-01

    Ostwald ripening is an important growth process in many scientific disciplines ranging from material science, geology, biophysics, and product formulation. Here ripening of argon clusters in a vapor phase is observed directly in constant energy molecular dynamics simulations serving as a model system for large-time scale ripening processes. Starting from an initial metastable equilibrium between the vapor phase and two clusters Ostwald ripening is initiated by the addition of kinetic energy. This mimics local thermal fluctuations in a larger system. It appears that there is not necessarily a close encounter of two clusters before ripening sets in. Also no static density bridge between two ripening clusters is observed. The onset of ripening is rather related to the different evaporation dynamics of clusters of different size. It can start at the moment energy is added or with some delay, depending on the difference in cluster size and dynamics. PMID:18783194

  12. Wavelet analysis of molecular dynamics: Efficient extraction of time-frequency information in ultrafast optical processes

    SciTech Connect

    Prior, Javier; Castro, Enrique [Departamento de Física Aplicada, Universidad Politécnica de Cartagena, Cartagena 30202 (Spain)] [Departamento de Física Aplicada, Universidad Politécnica de Cartagena, Cartagena 30202 (Spain); Chin, Alex W. [Theory of Condensed Matter Group, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE (United Kingdom)] [Theory of Condensed Matter Group, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Almeida, Javier; Huelga, Susana F.; Plenio, Martin B. [Institut für Theoretische Physik, Albert-Einstein-Allee 11, Universität Ulm, D-89069 Ulm (Germany)] [Institut für Theoretische Physik, Albert-Einstein-Allee 11, Universität Ulm, D-89069 Ulm (Germany)

    2013-12-14

    New experimental techniques based on nonlinear ultrafast spectroscopies have been developed over the last few years, and have been demonstrated to provide powerful probes of quantum dynamics in different types of molecular aggregates, including both natural and artificial light harvesting complexes. Fourier transform-based spectroscopies have been particularly successful, yet “complete” spectral information normally necessitates the loss of all information on the temporal sequence of events in a signal. This information though is particularly important in transient or multi-stage processes, in which the spectral decomposition of the data evolves in time. By going through several examples of ultrafast quantum dynamics, we demonstrate that the use of wavelets provide an efficient and accurate way to simultaneously acquire both temporal and frequency information about a signal, and argue that this greatly aids the elucidation and interpretation of physical process responsible for non-stationary spectroscopic features, such as those encountered in coherent excitonic energy transport.

  13. Acceleration of early-photon fluorescence molecular tomography with graphics processing units.

    PubMed

    Wang, Xin; Zhang, Bin; Cao, Xu; Liu, Fei; Luo, Jianwen; Bai, Jing

    2013-01-01

    Fluorescence molecular tomography (FMT) with early-photons can improve the spatial resolution and fidelity of the reconstructed results. However, its computing scale is always large which limits its applications. In this paper, we introduced an acceleration strategy for the early-photon FMT with graphics processing units (GPUs). According to the procedure, the whole solution of FMT was divided into several modules and the time consumption for each module is studied. In this strategy, two most time consuming modules (Gd and W modules) were accelerated with GPU, respectively, while the other modules remained coded in the Matlab. Several simulation studies with a heterogeneous digital mouse atlas were performed to confirm the performance of the acceleration strategy. The results confirmed the feasibility of the strategy and showed that the processing speed was improved significantly. PMID:23606899

  14. X-Ray Emission from Stellar Jets by Collision against High-density Molecular Clouds: an Application to HH 248

    NASA Astrophysics Data System (ADS)

    López-Santiago, J.; Bonito, R.; Orellana, M.; Miceli, M.; Orlando, S.; Ustamujic, S.; Albacete-Colombo, J. F.; de Castro, E.; Gómez de Castro, A. I.

    2015-06-01

    We investigate the plausibility of detecting X-ray emission from a stellar jet that impacts a dense molecular cloud, a scenario that may be typical for classical T Tauri stars with jets in dense star-forming complexes. We first model the impact of a jet against a dense cloud using two-dimensional axisymmetric hydrodynamic simulations, exploring different configurations of the ambient environment. Then, we compare our results with XMM-Newton observations of the Herbig–Haro object HH 248, where extended X-ray emission aligned with the optical knots is detected at the edge of the nearby IC 434 cloud. Our simulations show that a jet can produce plasma with temperatures up to 107 K, consistent with production of X-ray emission, after impacting a dense cloud. We find that jets denser than the ambient medium but less dense than the cloud produce detectable X-ray emission only at impact with the cloud. From an exploration of the model parameter space, we constrain the physical conditions (jet density and velocity and cloud density) that reproduce the intrinsic luminosity and emission measure of the X-ray source possibly associated with HH 248 well. Thus, we suggest that the extended X-ray source close to HH 248 corresponds to a jet impacting a dense cloud.

  15. Applications of quantum field theory to atomic collisions and chemical reactions. Renewal proposal summary 1 July 83-30 June 84

    SciTech Connect

    Girardeau, M.D.

    1983-04-01

    Methods of quantum field theory will be applied to prediction of atomic and molecular collision and reaction phenomena. Emphasis will be on (a) reactive collisions such as D+H2yieldD+H+, D+H2yieldD+H+2, and A+BCyieldAB+C; (b) theory of resonance and transition states and their influence on such reactive processes and on scattering processes such as e+Hyielde+h; (c) electromagnetic absorption due to such transition states.

  16. 390 IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING, VOL. 2, NO. 3, JUNE 2008 Optimal Design of a Molecular Recognizer

    E-print Network

    Tlusty, Tsvi

    390 IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING, VOL. 2, NO. 3, JUNE 2008 Optimal Design of a Molecular Recognizer: Molecular Recognition as a Bayesian Signal Detection Problem Yonatan Savir and Tsvi framework of signal detection theory, we treat the molecular recognition process as a signal detection

  17. GR@PPA 2.8: Initial-state jet matching for weak-boson production processes at hadron collisions

    NASA Astrophysics Data System (ADS)

    Odaka, Shigeru; Kurihara, Yoshimasa

    2012-04-01

    The initial-state jet matching method introduced in our previous studies has been applied to the event generation of single W and Z production processes and diboson (WW, WZ and ZZ) production processes at hadron collisions in the framework of the GR@PPA event generator. The generated events reproduce the transverse momentum spectra of weak bosons continuously in the entire kinematical region. The matrix elements (ME) for hard interactions are still at the tree level. As in previous versions, the decays of weak bosons are included in the matrix elements. Therefore, spin correlations and phase-space effects in the decay of weak bosons are exact at the tree level. The program package includes custom-made parton shower programs as well as ME-based hard interaction generators in order to achieve self-consistent jet matching. The generated events can be passed to general-purpose event generators to make the simulation proceed down to the hadron level. Catalogue identifier: ADRH_v3_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADRH_v3_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 112 146 No. of bytes in distributed program, including test data, etc.: 596 667 Distribution format: tar.gz Programming language: Fortran; with some included libraries coded in C and C++ Computer: All Operating system: Any UNIX-like system RAM: 1.6 Mega bytes at minimum Classification: 11.2 Catalogue identifier of previous version: ADRH_v2_0 Journal reference of previous version: Comput. Phys. Comm. 175 (2006) 665 External routines: Bash and Perl for the setup, and CERNLIB, ROOT, LHAPDF, PYTHIA according to the user's choice. Does the new version supersede the previous version?: No, this version supports only a part of the processes included in the previous versions. Nature of problem: We need to combine those processes including 0 jet and 1 jet in the matrix elements using an appropriate matching method, in order to simulate weak-boson production processes in the entire kinematical region. Solution method: The leading logarithmic components to be included in parton distribution functions and parton showers are subtracted from 1-jet matrix elements. Custom-made parton shower programs are provided to ensure satisfactory performance of the matching method. Reasons for new version: An initial-state jet matching method has been implemented. Summary of revisions: Weak-boson production processes associated with 0 jet and 1 jet can be consistently merged using the matching method. Restrictions: The built-in parton showers are not compatible with the PYTHIA new PS and the HERWIG PS. Unusual features: A large number of particles may be produced by the parton showers and passed to general-purpose event generators. Running time: About 10 min for initialization plus 25 s for every 1k-event generation for W production in the LHC condition, on a 3.0-GHz Intel Xeon processor with the default setting.

  18. Close-coupling calculations of low-energy inelastic and elastic processes in $^4$He collisions with H$_2$: A comparative study of two potential energy surfaces

    E-print Network

    T. G. Lee; C. Rochow; R. Martin; T. K. Clark; R. C. Forrey; N. Balakrishnan; P. C. Stancil; D. R. Schultz; A. Dalgarno; G. J. Ferland

    2004-12-09

    The two most recently published potential energy surfaces (PESs) for the HeH$_2$ complex, the so-called MR (Muchnick and Russek) and BMP (Boothroyd, Martin, and Peterson) surfaces, are quantitatively evaluated and compared through the investigation of atom-diatom collision processes. The BMP surface is expected to be an improvement, approaching chemical accuracy, over all conformations of the PES compared to that of the MR surface. We found significant differences in inelastic rovibrational cross sections computed on the two surfaces for processes dominated by large changes in target rotational angular momentum. In particular, the H$_2$($\

  19. Collinear Collision Chemistry: 1. A Simple Model for Inelastic and Reactive Collision Dynamics

    ERIC Educational Resources Information Center

    Mahan, Bruce H.

    1974-01-01

    Discusses a model for the collinear collision of an atom with a diatomic molecule on a simple potential surface. Indicates that the model can provide a framework for thinking about molecular collisions and reveal many factors which affect the dynamics of reactive and inelastic collisions. (CC)

  20. Molecular reordering processes on ice (0001) surfaces from long timescale simulations

    NASA Astrophysics Data System (ADS)

    Pedersen, Andreas; Wikfeldt, Kjartan T.; Karssemeijer, Leendertjan; Cuppen, Herma; Jónsson, Hannes

    2014-12-01

    We report results of long timescale adaptive kinetic Monte Carlo simulations aimed at identifying possible molecular reordering processes on both proton-disordered and ordered (Fletcher) basal plane (0001) surfaces of hexagonal ice. The simulations are based on a force field for flexible molecules and span a time interval of up to 50 ?s at a temperature of 100 K, which represents a lower bound to the temperature range of earth's atmosphere. Additional calculations using both density functional theory and an ab initio based polarizable potential function are performed to test and refine the force field predictions. Several distinct processes are found to occur readily even at this low temperature, including concerted reorientation (flipping) of neighboring surface molecules, which changes the pattern of dangling H-atoms, and the formation of interstitial defects by the downwards motion of upper-bilayer molecules. On the proton-disordered surface, one major surface roughening process is observed that significantly disrupts the crystalline structure. Despite much longer simulation time, such roughening processes are not observed on the highly ordered Fletcher surface which is energetically more stable because of smaller repulsive interaction between neighboring dangling H-atoms. However, a more localized process takes place on the Fletcher surface involving a surface molecule transiently leaving its lattice site. The flipping process provides a facile pathway of increasing proton-order and stabilizing the surface, supporting a predominantly Fletcher-like ordering of low-temperature ice surfaces. Our simulations also show that eventual proton-disordered patches on the surface may induce significant local reconstructions. Further, a subset of the molecules on the Fletcher surface are susceptible to forming interstitial defects which might provide active sites for various chemical reactions in the atmosphere.

  1. Formulation and numerical analysis of diatomic molecular dissociation using Boltzmann kinetic equation

    NASA Astrophysics Data System (ADS)

    Yano, Ryosuke; Suzuki, Kojiro; Kuroda, Hisayasu

    2007-01-01

    The direct description of chemical reactions by the Boltzmann equation still involves some difficulties in the kinetic theory. In this paper, we describe diatomic molecular dissociation due to transitions of vibrational quantum states resulting from inelastic collisions. These can be described by the Wang Chang-Uhlenbeck (WCU) equation. To avoid direct evaluation of the strong nonlinear collision kernel of the WCU equation, we used a kinetic equation. For accurate description of the dissociation process, we describe improvements we made to the conventional inelastic collision model (the so-called Morse model). Combining this inelastic collision model with the gas mixture model by Oguchi, we formulated a model for representing diatomic molecular dissociations. We validated this model by simulating a hypersonic shock layer with diatomic molecular dissociation.

  2. Processing of meteoritic organic materials as a possible analog of early molecular evolution in planetary environments.

    PubMed

    Pizzarello, Sandra; Davidowski, Stephen K; Holland, Gregory P; Williams, Lynda B

    2013-09-24

    The composition of the Sutter's Mill meteorite insoluble organic material was studied both in toto by solid-state NMR spectroscopy of the powders and by gas chromatography-mass spectrometry analyses of compounds released upon their hydrothermal treatment. Results were compared with those obtained for other meteorites of diverse classifications (Murray, GRA 95229, Murchison, Orgueil, and Tagish Lake) and found to be so far unique in regard to the molecular species released. These include, in addition to O-containing aromatic compounds, complex polyether- and ester-containing alkyl molecules of prebiotic appeal and never detected in meteorites before. The Sutter's Mill fragments we analyzed had likely been altered by heat, and the hydrothermal conditions of the experiments realistically mimic early Earth settings, such as near volcanic activity or impact craters. On this basis, the data suggest a far larger availability of meteoritic organic materials for planetary environments than previously assumed and that molecular evolution on the early Earth could have benefited from accretion of carbonaceous meteorites both directly with soluble compounds and, for a more protracted time, through alteration, processing, and release from their insoluble organic materials. PMID:24019471

  3. Dissolving process of a cellulose bunch in ionic liquids: a molecular dynamics study.

    PubMed

    Li, Yao; Liu, Xiaomin; Zhang, Suojiang; Yao, Yingying; Yao, Xiaoqian; Xu, Junli; Lu, Xingmei

    2015-07-21

    In recent years, a variety of ionic liquids (ILs) were found to be capable of dissolving cellulose and mechanistic studies were also reported. However, there is still a lack of detailed information at the molecular level. Here, long time molecular dynamics simulations of cellulose bunch in 1-ethyl-3-methylimidazolium acetate (EmimAc), 1-ethyl-3-methylimidazolium chloride (EmimCl), 1-butyl-3-methylimidazolium chloride (BmimCl) and water were performed to analyze the inherent interaction and dissolving mechanism. Complete dissolution of the cellulose bunch was observed in EmimAc, while little change took place in EmimCl and BmimCl, and nothing significant happened in water. The deconstruction of the hydrogen bond (H-bond) network in cellulose was found and analyzed quantitatively. The synergistic effect of cations and anions was revealed by analyzing the whole dissolving process. Initially, cations bind to the side face of the cellulose bunch and anions insert into the cellulose strands to form H-bonds with hydroxyl groups. Then cations start to intercalate into cellulose chains due to their strong electrostatic interaction with the entered anions. The H-bonds formed by Cl(-) cannot effectively separate the cellulose chain and that is the reason why EmimCl and BmimCl dissolve cellulose more slowly. These findings deepen people's understanding on how ILs dissolve cellulose and would be helpful for designing new efficient ILs to dissolve cellulose. PMID:26095890

  4. Accelerated Molecular Dynamics Simulations with the AMOEBA Polarizable Force Field on Graphics Processing Units.

    PubMed

    Lindert, Steffen; Bucher, Denis; Eastman, Peter; Pande, Vijay; McCammon, J Andrew

    2013-11-12

    The accelerated molecular dynamics (aMD) method has recently been shown to enhance the sampling of biomolecules in molecular dynamics (MD) simulations, often by several orders of magnitude. Here, we describe an implementation of the aMD method for the OpenMM application layer that takes full advantage of graphics processing units (GPUs) computing. The aMD method is shown to work in combination with the AMOEBA polarizable force field (AMOEBA-aMD), allowing the simulation of long time-scale events with a polarizable force field. Benchmarks are provided to show that the AMOEBA-aMD method is efficiently implemented and produces accurate results in its standard parametrization. For the BPTI protein, we demonstrate that the protein structure described with AMOEBA remains stable even on the extended time scales accessed at high levels of accelerations. For the DNA repair metalloenzyme endonuclease IV, we show that the use of the AMOEBA force field is a significant improvement over fixed charged models for describing the enzyme active-site. The new AMOEBA-aMD method is publicly available (http://wiki.simtk.org/openmm/VirtualRepository) and promises to be interesting for studying complex systems that can benefit from both the use of a polarizable force field and enhanced sampling. PMID:24634618

  5. Processing of meteoritic organic materials as a possible analog of early molecular evolution in planetary environments

    PubMed Central

    Pizzarello, Sandra; Davidowski, Stephen K.; Holland, Gregory P.; Williams, Lynda B.

    2013-01-01

    The composition of the Sutter’s Mill meteorite insoluble organic material was studied both in toto by solid-state NMR spectroscopy of the powders and by gas chromatography–mass spectrometry analyses of compounds released upon their hydrothermal treatment. Results were compared with those obtained for other meteorites of diverse classifications (Murray, GRA 95229, Murchison, Orgueil, and Tagish Lake) and found to be so far unique in regard to the molecular species released. These include, in addition to O-containing aromatic compounds, complex polyether- and ester-containing alkyl molecules of prebiotic appeal and never detected in meteorites before. The Sutter’s Mill fragments we analyzed had likely been altered by heat, and the hydrothermal conditions of the experiments realistically mimic early Earth settings, such as near volcanic activity or impact craters. On this basis, the data suggest a far larger availability of meteoritic organic materials for planetary environments than previously assumed and that molecular evolution on the early Earth could have benefited from accretion of carbonaceous meteorites both directly with soluble compounds and, for a more protracted time, through alteration, processing, and release from their insoluble organic materials. PMID:24019471

  6. Ultra-cold Atom CollisionsUltra-cold Atom Collisions and Quantum Dynamics atand Quantum Dynamics at

    E-print Network

    Band, Yehuda B.

    Ultra-cold Atom CollisionsUltra-cold Atom Collisions and Quantum Dynamics atand Quantum Dynamics are available at Ben-Gurion University to carry out research in ultra-cold atomic and molecular physics

  7. A domain decomposition parallel processing algorithm for molecular dynamics simulations of polymers

    NASA Astrophysics Data System (ADS)

    Brown, David; Clarke, Julian H. R.; Okuda, Motoi; Yamazaki, Takao

    1994-10-01

    We describe in this paper a domain decomposition molecular dynamics algorithm for use on distributed memory parallel computers which is capable of handling systems containing rigid bond constraints and three- and four-body potentials as well as non-bonded potentials. The algorithm has been successfully implemented on the Fujitsu 1024 processor element AP1000 machine. The performance has been compared with and benchmarked against the alternative cloning method of parallel processing [D. Brown, J.H.R. Clarke, M. Okuda and T. Yamazaki, J. Chem. Phys., 100 (1994) 1684] and results obtained using other scalar and vector machines. Two parallel versions of the SHAKE algorithm, which solves the bond length constraints problem, have been compared with regard to optimising the performance of this procedure.

  8. Low temperature conversion of molecular species via a hybrid plasma discharge -- catalytic process

    NASA Astrophysics Data System (ADS)

    Barnat, Ed

    2008-10-01

    Various avenues are being perused towards developing more sustainable energy sources to meet current and future energy requirements. Central to these energy surety related concerns is the efficiency of a given processes (chemical reaction) employed for synthesis of these fuels or energy sources. We present results from our preliminary studies on using low-temperature non-equilibrium discharges, coupled to active surfaces as a means of efficiently dissociating key molecular species that may be used towards fuel synthesis. Specifically, we focus on dissociating carbon dioxide to form carbon monoxide which is used in conjunction with hydrogen to generate syngas and higher hydrocarbons. While studies have been performed using various plasma sources, we primarily use a ``hybrid'' plasmas with tuned E/N that has been demonstrated to efficiently dissociate carbon dioxide[1]. [1] S. N. Andreev et. al, Spectrochimica Acta A 60, 3361 (2004).

  9. Many-body processes in atomic and molecular physics. Progress report

    SciTech Connect

    Chu, S.I.

    1981-01-01

    A proposal is presented for theoretical efforts towards the following projects: (1) carry out rotational predissociation lifetime calculations of several van der Waals molecules for which accurate potential energy surfaces were obtained recently by van der Waals molecular spectroscopic methods; (2) development and extension of the complex coordinate - coupled channel formalism to vibrational predissociation studies; (3) Floquet theory study of the quantum dynamics of multiphoton excitation of vibrational-rotational states of small molecules by laser light; (4) development and extension of the method of complex quasi-vibrational energy formalism to the study of intense field multiphoton dissociation of diatomic molecules and to photodissociation process in the presence of shape resonances; (5) investigation of the external field effects in multiphoton excitation and dissociation of small molecules. Depending on time and resources, several other projects may also be pursued. A detailed discussion covering these proposed projects is presented.

  10. The dynamics of cargo driven by molecular motors in the context of asymmetric simple exclusion processes

    E-print Network

    Carla Goldman; Elisa T. Sena

    2008-10-07

    We consider the dynamics of cargo driven by a collection of interacting molecular motors in the context of an asymmetric simple exclusion processes (ASEP). The model is formulated to account for i) excluded volume interactions, ii) the observed asymmetry of the stochastic movement of individual motors and iii) interactions between motors and cargo. Items (i) and (ii) form the basis of ASEP models and have already been considered in the literature to study the behavior of motor density profile [Parmeggiani 03]. Item (iii) is new. It is introduced here as an attempt to describe explicitly the dependence of cargo movement on the dynamics of motors. The steady-state solutions of the model indicate that the system undergoes a phase transition of condensation type as the motor density varies. We study the consequences of this transition to the properties of cargo velocity.

  11. Molecular Dynamics Simulations of the Roller Nanoimprint Process: Adhesion and Other Mechanical Characteristics

    PubMed Central

    2009-01-01

    Molecular dynamics simulations using tight-binding many body potential are carried out to study the roller imprint process of a gold single crystal. The effect of the roller tooth’s taper angle, imprint depth, imprint temperature, and imprint direction on the imprint force, adhesion, stress distribution, and strain are investigated. A two-stage roller imprint process was obtained from an imprint force curve. The two-stage imprint process included the imprint forming with a rapid increase of imprint force and the unloading stage combined with the adhesion stage. The results show that the imprint force and adhesion rapidly increase with decreasing taper angle and increasing imprint depth. The magnitude of the maximum imprint force and the time at which this maximum occurs are proportional to the imprint depth, but independent of the taper angle. In a comparison of the imprint mechanisms with a vertical imprint case, while high stress and strain regions are concentrated below the mold for vertical imprint, they also occur around the mold in the case of roller imprint. The regions were only concentrated on the substrate atoms underneath the mold in vertical imprint. Plastic flow increased with increasing imprint temperature. PMID:20596431

  12. Identification of molecular processes needed for vascular formation through transcriptome analysis of different vascular systems

    PubMed Central

    2013-01-01

    Background Vascular system formation has been studied through molecular and genetic approaches in Arabidopsis, a herbaceous dicot that is used as a model system. Different vascular systems have developed in other plants such as crops and trees. Uncovering shared mechanisms underlying vascular development by transcriptome analysis of different vascular systems may help to transfer knowledge acquired from Arabidopsis to other economically important species. Results Conserved vascular genes and biological processes fundamental to vascular development were explored across various plants. Through comparative transcriptome analysis, 226 genes from Arabidopsis, 217 genes from poplar and 281 genes from rice were identified as constituting 107 conserved vascular gene groups. These gene groups are expressed mainly in vascular tissues and form a complex coexpression network with multiple functional connections. To date, only half of the groups have been experimentally investigated. The conserved vascular gene groups were classified into 9 essential processes for vascular development. 18 groups (17%) lack of annotations were classified as having unknown functions. Conclusion The study provides a map of fundamental biological processes conserved across different vascular systems. It identifies gaps in the experimental investigation of pathways active in vascular formation, which if explored, could lead to a more complete understanding of vascular development. PMID:23548001

  13. INELASTIC PROCESSES IN 0.11000 keV/u COLLISIONS OF Ne q+ (q=710) IONS WITH ATOMIC HYDROGEN

    E-print Network

    for such a divertor would have potentially subjected the divertor plates to a very large amount of energy (e.g. 20 to 40 MW/m 2 or more [1]). In contrast, current designs call for the reduction of this tremendous heat transfer, hydrogen and impurity radiation, ionization, and elastic collisions between the recycling gas

  14. Multistatic FMCW radar for collision avoidance applications, optimization of the antenna configuration and improvement of the data processing

    Microsoft Academic Search

    H. T. Steenstra; F. L. Muller; P. J. F. Swart

    1999-01-01

    A multistatic FMCW RADAR system with 2 transmit and 2 receive antennas is to be used to avoid collisions of autonomous guided vehicles used in the Rotterdam harbour. It turns out that in this application data interrogation is `cheaper' than data association.

  15. Reactive multiparticle collision dynamics

    NASA Astrophysics Data System (ADS)

    Rohlf, Katrin; Fraser, Simon; Kapral, Raymond

    2008-07-01

    A mesoscopic dynamics method for the simulation of spatially distributed chemically reacting systems under equilibrium and nonequilibrium conditions is described. Non-reactive collisions are modeled by multiparticle collision dynamics that conserves mass, momentum and energy. Reactive collisions are described by birth-death stochastic processes. The dynamics is governed by a Markov chain in the full phase space of the system, which reduces to mass action rate laws in the mean field limit. Simulations on the Selkov model are carried out to illustrate the simulation method.

  16. Peripheral processes 2 {yields} 3 and 2 {yields} 4 in QED and QCD in p-p-bar high-energy collisions

    SciTech Connect

    Ahmadov, A. I., E-mail: ahmadov@theor.jinr.ru; Bystritskiy, Yu. M., E-mail: bystr@theor.jinr.ru; Kuraev, E. A., E-mail: kuraev@theor.jinr.ru [Joint Institute for Nuclear Research (Russian Federation)

    2011-10-15

    Differential cross sections of processes with high-energy p(-p)p collisions-creation of a scalar, a pseudoscalar and a lepton pair-are considered in the Weizsacker-Williams approximation in QED in the QCD framework, processes with conversion of the initial proton (antiproton) to fermionic jets accompanied with one gluon jet and the state of two gluons and a quark-antiquark pair (without a rapidity gap) are considered in the framework of the effective Regge action of Lipatov's theory. The process of creation of a Higgs boson accompanied with two fermionic jets is considered. The azimuthal correlation in the process of two gluon jets separated by a rapidity gap is investigated. The gluon Reggeization effects are taken into account. Some distributions are illustrated by numerical calculations.

  17. The impact of environmental stress on male reproductive development in plants: biological processes and molecular mechanisms

    PubMed Central

    de Storme, Nico; Geelen, Danny

    2014-01-01

    In plants, male reproductive development is extremely sensitive to adverse climatic environments and (a)biotic stress. Upon exposure to stress, male gametophytic organs often show morphological, structural and metabolic alterations that typically lead to meiotic defects or premature spore abortion and male reproductive sterility. Depending on the type of stress involved (e.g. heat, cold, drought) and the duration of stress exposure, the underlying cellular defect is highly variable and either involves cytoskeletal alterations, tapetal irregularities, altered sugar utilization, aberrations in auxin metabolism, accumulation of reactive oxygen species (ROS; oxidative stress) or the ectopic induction of programmed cell death (PCD). In this review, we present the critically stress-sensitive stages of male sporogenesis (meiosis) and male gametogenesis (microspore development), and discuss the corresponding biological processes involved and the resulting alterations in male reproduction. In addition, this review also provides insights into the molecular and/or hormonal regulation of the environmental stress sensitivity of male reproduction and outlines putative interaction(s) between the different processes involved. PMID:23731015

  18. The crystallization process of liquid vanadium studied by ab initio molecular dynamics.

    PubMed

    Debela, T T; Wang, X D; Cao, Q P; Zhang, D X; Jiang, J Z

    2014-04-16

    We present a study of the crystallization process in liquid vanadium over a temperature range from 3000?K down to 1500?K using ab initio molecular dynamics simulations. Short-range order evolution during solidification is studied using various structural analysis methods. We show that the icosahedral-like short-range order is detected in the stable liquid phase and grows upon supercooling. The system undergoes a first-order phase transition (from a liquid to a solid state) at a temperature of about 1600?K. The crystal nucleation process is further studied using the time-temperature transformation mechanism by annealing the system at 1650?K. The nucleation is examined using bond-orientational order and density fluctuation analysis. Our finding is that various precursors appear in the region of high bond-orientational order with the majority having body-centered cubic (bcc)-like symmetry. This bcc-like region grows on annealing via thermal fluctuations. Our results reveal that the bond-orientational order precedes the density fluctuation, and is the main driving factor for nucleation. PMID:24675173

  19. Fast Analysis of Molecular Dynamics Trajectories with Graphics Processing Units—Radial Distribution Function Histogramming

    PubMed Central

    Stone, John E.; Kohlmeyer, Axel

    2011-01-01

    The calculation of radial distribution functions (RDFs) from molecular dynamics trajectory data is a common and computationally expensive analysis task. The rate limiting step in the calculation of the RDF is building a histogram of the distance between atom pairs in each trajectory frame. Here we present an implementation of this histogramming scheme for multiple graphics processing units (GPUs). The algorithm features a tiling scheme to maximize the reuse of data at the fastest levels of the GPU’s memory hierarchy and dynamic load balancing to allow high performance on heterogeneous configurations of GPUs. Several versions of the RDF algorithm are presented, utilizing the specific hardware features found on different generations of GPUs. We take advantage of larger shared memory and atomic memory operations available on state-of-the-art GPUs to accelerate the code significantly. The use of atomic memory operations allows the fast, limited-capacity on-chip memory to be used much more efficiently, resulting in a fivefold increase in performance compared to the version of the algorithm without atomic operations. The ultimate version of the algorithm running in parallel on four NVIDIA GeForce GTX 480 (Fermi) GPUs was found to be 92 times faster than a multithreaded implementation running on an Intel Xeon 5550 CPU. On this multi-GPU hardware, the RDF between two selections of 1,000,000 atoms each can be calculated in 26.9 seconds per frame. The multi-GPU RDF algorithms described here are implemented in VMD, a widely used and freely available software package for molecular dynamics visualization and analysis. PMID:21547007

  20. Fast analysis of molecular dynamics trajectories with graphics processing units-Radial distribution function histogramming

    SciTech Connect

    Levine, Benjamin G., E-mail: ben.levine@temple.ed [Institute for Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, PA (United States); Stone, John E., E-mail: johns@ks.uiuc.ed [Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Kohlmeyer, Axel, E-mail: akohlmey@temple.ed [Institute for Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, PA (United States)

    2011-05-01

    The calculation of radial distribution functions (RDFs) from molecular dynamics trajectory data is a common and computationally expensive analysis task. The rate limiting step in the calculation of the RDF is building a histogram of the distance between atom pairs in each trajectory frame. Here we present an implementation of this histogramming scheme for multiple graphics processing units (GPUs). The algorithm features a tiling scheme to maximize the reuse of data at the fastest levels of the GPU's memory hierarchy and dynamic load balancing to allow high performance on heterogeneous configurations of GPUs. Several versions of the RDF algorithm are presented, utilizing the specific hardware features found on different generations of GPUs. We take advantage of larger shared memory and atomic memory operations available on state-of-the-art GPUs to accelerate the code significantly. The use of atomic memory operations allows the fast, limited-capacity on-chip memory to be used much more efficiently, resulting in a fivefold increase in performance compared to the version of the algorithm without atomic operations. The ultimate version of the algorithm running in parallel on four NVIDIA GeForce GTX 480 (Fermi) GPUs was found to be 92 times faster than a multithreaded implementation running on an Intel Xeon 5550 CPU. On this multi-GPU hardware, the RDF between two selections of 1,000,000 atoms each can be calculated in 26.9 s per frame. The multi-GPU RDF algorithms described here are implemented in VMD, a widely used and freely available software package for molecular dynamics visualization and analysis.

  1. A molecular dynamics study of metal coating on SWNT Abstract Metal coating process on single-walled carbon nanotube (SWNTs) was investigated

    E-print Network

    Maruyama, Shigeo

    SWNT A molecular dynamics study of metal coating on SWNT 1) , 1) , 1) ( 1) ) Abstract Metal coating process on single-walled carbon nanotube (SWNTs) was investigated using molecular dynamics simulations size and temperature highlight the roles of molecular dynamics on the resulting metal morphologies. [1

  2. Chronic alcohol exposure negatively impacts the physiological and molecular parameters of the renal biotin reabsorption process.

    PubMed

    Subramanian, Veedamali S; Subramanya, Sandeep B; Said, Hamid M

    2011-03-01

    Normal body homeostasis of biotin is critically dependent on its renal recovery by kidney proximal tubular epithelial cells, a process that is mediated by the sodium-dependent multivitamin transporter (SMVT; a product of the SLC5A6 gene). Chronic ethanol consumption interferes with the renal reabsorption process of a variety of nutrients, including water-soluble vitamins. To date, however, there is nothing known about the effect of chronic alcohol feeding on physiological and molecular parameters of the renal biotin reabsorption process. We addressed these issues using rats and transgenic mice carrying the human SLC5A6 (P1P2) 5'-regulatory region as an in vivo model systems of alcohol exposure, and cultured human renal proximal tubular epithelial HK-2 cells chronically exposed to alcohol as an in vitro model of alcohol exposure. The [(3)H]biotin uptake results showed that chronic ethanol feeding in rats leads to a significant inhibition in carrier-mediated biotin transport across both renal brush border and basolateral membrane domains. This inhibition was associated with a marked reduction in the level of expression of SMVT protein, mRNA, and heterogenous nuclear RNA (hnRNA). Furthermore, studies with transgenic mice carrying the SLC5A6 5'-regulatory region showed that chronic alcohol feeding leads to a significant decrease in promoter activity. Studies with HK-2 cells chronically exposed to alcohol again showed a marked reduction in carrier-mediated biotin uptake, which was associated with a significant reduction in promoter activity of the human SLC5A6 5'-regulatory region. These findings demonstrate for the first time that chronic ethanol feeding inhibits renal biotin transport and that this effect is, at least in part, being exerted at the transcriptional level. PMID:21209005

  3. Inelastic processes in 11000 keV/u collisions of Be q+ (q=24) ions with atomic and molecular

    E-print Network

    ­Z materials such as C, boronated carbon fibers, or beryllium. Thus, the interest in beryllium (Z=4) since, in its one­ active­electron, many­active­electron, or model­potential formulations serves as a very

  4. On determining continuum quantities of non-equilibrium processes via molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Fu, Yao

    In this dissertation, a high-fidelity atomistic-to-continuum link for highly non-equilibrium processes has been established by making several modifications to Hardy's theory. Although Hardy's thermomechanical quantities were derived analytically to conserve mass, momentum and energy, they have not been rigorously tested and validated numerically in the past. Hence the first task was to investigate the effectiveness of ensemble averaging in removing thermal fluctuations and compare with conventional time averaging for fcc crystals simulated using both equilibrium and non-equilibrium molecular dynamics (MD) simulations, where the non-equilibrium process was introduced by a shock impact. It has been found that the ensemble averaging has better convergence than time averaging due to the statistical independence of the thermomechanical quantities computed using ensemble averaging. The second task was to test the validity of Hardy's theory by checking if it is able to conserve mass, momentum and energy numerically. A few highly non-equilibrium processes were simulated using MD, including Gaussian wave and shock impact propagation in 1D and 3D fcc crystals. Based on the test results, a new normalization rule has been proposed so that the computed thermomechanical quantities can conserve the fundamental properties more accurately. To a large extent, Hardy's theory has been found to be valid regardless of the width of the localization function, the interatomic potential and crystal structure, and with and without ensemble averaging. To further test the validity of Hardy's theory for more complex non-equilibrium processes, where plastic deformation is accomplished through dislocation glide and slip band emission, a crack propagation problem in iron crystal with a pre-created center crack is simulated using MD. The computed Hardy's thermomechanical quantities can generally conserve mass, momentum and energy. Exceptions have been found around the crack region, where the computed quantities cannot obey the balance of energy but still conserve mass and momentum. The results from this dissertation will help 1) inspire confidence in employing Hardy's theory with the proposed modifications to analyze MD simulation results, especially for non-equilibrium thermomechanical processes and 2) pave the way for concurrent atomistic/continuum coupled simulations.

  5. Applications of neural networks to real-time data processing at the Environmental and Molecular Sciences Laboratory (EMSL)

    Microsoft Academic Search

    Paul E. Keller; Richard T. Kouzes; Lars J. Kangas

    1993-01-01

    Detailed design of the Environmental and Molecular Sciences Laboratory (EMSL) at the Pacific Northwest Laboratory (PNL) is nearing completion and construction is scheduled to begin later this year. This facility will assist in the environmental restoration and waste management mission at the Hanford Site. This paper identifies several real-time data processing applications within the EMSL where neural networks can potentially

  6. Magnitude of long-term non-lithostatic pressure variations in lithospheric processes: insight from thermo-mechanical subduction/collision models

    NASA Astrophysics Data System (ADS)

    Gerya, Taras

    2014-05-01

    On the one hand, the principle of lithostatic pressure is habitually used in metamorphic geology to calculate paleo-depths of metamorphism from mineralogical pressure estimates given by geobarometry. On the other hand, it is obvious that this lithostatic (hydrostatic) pressure principle should only be valid for an ideal case of negligible deviatoric stresses during the long-term development of the entire tectono-metamorphic system - the situation, which newer comes to existence in natural lithospheric processes. The question is therefore not "Do non-lithostatic pressure variations exist?" but " What is the magnitude of long-term non-lithostatic pressure variations in various lithospheric processes, which can be recorded by mineral equilibria of respective metamorphic rocks?". The later question is, in particular, relevant for various types of high-pressure (HP) and ultrahigh-pressure (UHP) rocks, which are often produced in convergent plate boundary settings (e.g., Hacker and Gerya, 2013). This question, can, in particular, be answered with the use of thermo-mechanical models of subduction/collision processes employing realistic P-T-stress-dependent visco-elasto-brittle/plastic rheology of rocks. These models suggest that magnitudes of pressure deviations from lithostatic values can range >50% underpressure to >100% overpressure, mainly in the regions of bending of rheologically strong mantle lithosphere (Burg and Gerya, 2005; Li et al., 2010). In particular, strong undepresures along normal faults forming within outer rise regions of subducting plates can be responsible for downward water suction and deep hydration of oceanic slabs (Faccenda et al., 2009). Weaker HP and UHP rocks of subduction/collision channels are typically subjected to lesser non-lithostatic pressure variations with characteristic magnitudes ranging within 10-20% from the lithostatic values (Burg and Gerya, 2005; Li et al., 2010). The strength of subducted crustal rocks and the degree of confinement of the subduction/collision channel are the key factors controlling this magnitude (Burg and Gerya, 2005; Li et al., 2010). High-temperature (>700 C) UHP rocks formed by continental crust subduction typically demonstrate negligible non-lithostatic pressure variations at peak metamorphic conditions, although these variations can be larger at the prograde stage (Gerya et al., 2008; Li et al., 2010). However, the variability of tectonic mechanisms by which UHP rocks can form (e.g., Sizova et al., 2012; Hacker and Gerya, 2013) precludes generalization of this result for all types of UHP-complexes. References Burg, J.-P., Gerya, T.V. (2005) Viscous heating and thermal doming in orogenic metamorphism: numerical modeling and geological implications. J. Metamorph. Geol., 23, 75-95. Faccenda, M., Gerya, T.V., Burlini, L. (2009) Deep slab hydration induced by bending related variations in tectonic pressure. Nature Geoscience, 2, 790-793. Gerya T.V., Perchuk, L.L., Burg J.-P. (2008) Transient hot channels: perpetrating and regurgitating ultrahigh-pressure, high temperature crust-mantle associations in collision belts. Lithos, 103, 236-256. Hacker, B., Gerya, T.V. (2013) Paradigms, new and old, for ultrahigh-pressure tectonism. Tectonophysics, 603, 79-88. Li, Z., Gerya, T.V., Burg, J.P. (2010) Influence of tectonic overpressure on P-T paths of HP-UHP rocks in continental collision zones: Thermomechanical modelling. J. Metamorphic Geol., 28, 227-247. Sizova, E., Gerya, T., Brown M. (2012) Exhumation mechanisms of melt-bearing ultrahigh pressure crustal rocks during collision of spontaneously moving plates. Journal of Metamorphic Geology, 30, 927-955.

  7. Nonthermal surface chemistry: collision-induced reactions of NH3 on Pt{111}

    NASA Astrophysics Data System (ADS)

    Szulczewski, Greg J.; Levis, Robert J.

    1994-07-01

    We report the collision-induced desorption and dissociation of two molecular forms of ammonia bound to a Pt{111} single crystal by a beam of translationaly energetic, neutral noble gas atoms. In this experiment the probability for desorption at low coverage is measured as a function of the collision energy between an Ar atom and chemisorbed ammonia molecule and is found to be independent of the Ar beam angle of incidence. At higher initial ammonia coverages the probability of collision-induced desorption is greater since the NH3/Pt{111} binding energy is much weaker. In addition we observe formation of surface NHx products generated in a process known as collision-induced dissociation.

  8. Quantum-state resolved bimolecular collisions of velocity-controlled OH with NO radicals

    E-print Network

    Kirste, Moritz; Schewe, H Christian; Meijer, Gerard; Liu, Kopin; van der Avoird, Ad; Janssen, Liesbeth M C; Gubbels, Koos B; Groenenboom, Gerrit C; van de Meerakker, Sebastiaan Y T

    2012-01-01

    Whereas atom-molecule collisions have been studied with complete quantum state resolution, interactions between two state-selected molecules have proven much harder to probe. Here, we report the measurement of state-resolved inelastic scattering cross sections for collisions between two open-shell molecules that are both prepared in a single quantum state. Stark-decelerated OH radicals were scattered with hexapole-focused NO radicals in a crossed beam configuration. Rotationally and spin-orbit inelastic scattering cross sections were measured on an absolute scale for collision energies between 70 and 300 cm$^{-1}$. These cross sections show fair agreement with quantum coupled-channels calculations using a set of coupled model potential energy surfaces based on ab initio calculations for the long-range non-adiabatic interactions and a simplistic short-range interaction. This comparison reveals the crucial role of electrostatic forces in complex molecular collision processes.

  9. Quantum-state resolved bimolecular collisions of velocity-controlled OH with NO radicals.

    PubMed

    Kirste, Moritz; Wang, Xingan; Schewe, H Christian; Meijer, Gerard; Liu, Kopin; van der Avoird, Ad; Janssen, Liesbeth M C; Gubbels, Koos B; Groenenboom, Gerrit C; van de Meerakker, Sebastiaan Y T

    2012-11-23

    Whereas atom-molecule collisions have been studied with complete quantum-state resolution, interactions between two state-selected molecules have proven much harder to probe. Here, we report the measurement of state-resolved inelastic scattering cross sections for collisions between two open-shell molecules that are both prepared in a single quantum state. Stark-decelerated hydroxyl (OH) radicals were scattered with hexapole-focused nitric oxide (NO) radicals in a crossed-beam configuration. Rotationally and spin-orbit inelastic scattering cross sections were measured on an absolute scale for collision energies between 70 and 300 cm(-1). These cross sections show fair agreement with quantum coupled-channels calculations using a set of coupled model potential energy surfaces based on ab initio calculations for the long-range nonadiabatic interactions and a simplistic short-range interaction. This comparison reveals the crucial role of electrostatic forces in complex molecular collision processes. PMID:23180857

  10. Rotational state-changing cold collisions of hydroxyl ions with helium

    E-print Network

    Hauser, Daniel; Carelli, Fabio; Spieler, Steffen; Lakhmanskaya, Olga; Endres, Eric S; Kumar, Sunil S; Gianturco, Franco; Wester, Roland

    2015-01-01

    Cold molecules are important for many applications, from fundamental precision measurements, quantum information processing, quantum-controlled chemistry, to understanding the cold interstellar medium. Molecular ions are known to be cooled efficiently in sympathetic collisions with cold atoms or ions. However, little knowledge is available on the elementary cooling steps, because the determination of quantum state-to-state collision rates at low temperature is prohibitively challenging for both experiment and theory. Here we present a method to manipulate molecular quantum states by non-resonant photodetachment. Based on this we provide absolute quantum scattering rate coefficients under full quantum state control for the rotationally inelastic collision of hydroxyl anions with helium. Experiment and quantum scattering theory show excellent agreement without adjustable parameters. Very similar rate coefficients are obtained for two different isotopes, which is linked to several quantum scattering resonances a...

  11. Real-time study of the adiabatic energy loss in an atomic collision with a metal cluster

    E-print Network

    Baer, Roi

    Real-time study of the adiabatic energy loss in an atomic collision with a metal cluster Roi Baer approach by comparing to a real-time Ehrenfest molecular dynamics simulation of such a process. The electrons are treated realistically using standard approximations to time-dependent density functional

  12. Molecular characterization of dissolved organic matter through a desalination process by high resolution mass spectrometry.

    PubMed

    Cortés-Francisco, Nuria; Caixach, Josep

    2013-09-01

    The effect of different water treatments such as ultrafiltration (UF) and reverse osmosis (RO) on dissolved organic matter (DOM) is still unknown. Electrospray ionization Fourier transform orbitrap mass spectrometry has been used to provide valuable information of marine DOM evolution through a desalination process on a molecular scale. In the present manuscript, the characterization of four real composite water samples from a desalination pilot plant installed in the coast of Barcelona (Spain) has been carried out. The sampling was performed on each point of the pilot plant: raw seawater (RSW), UF effluent, brine RO and permeate RO. The mass spectra of the different samples show several thousand peaks, however for the present screening study, only the mass range m/z 200-500 and the main signals in this mass range (relative intensities ?1%) have been considered. The analysis of RSW and UF samples reveal that there is little effect on DOM by the UF pilot. However, when the water is treated on the RO an important change on DOM has been observed. The recurring periodical patterns found in RSW and UF are lost in Permeate RO sample. Compounds with more aliphatic character, with higher H/C ratio (H/Cav 1.72) are present in the Permeate and some of them have been tentatively identified as fatty acids. PMID:23879562

  13. Molecular Insights into Plant-Microbial Processes and Carbon Storage in Mangrove Ecosystems

    NASA Astrophysics Data System (ADS)

    Romero, I. C.; Ziegler, S. E.; Fogel, M.; Jacobson, M.; Fuhrman, J. A.; Capone, D. G.

    2009-12-01

    Mangrove forests, in tropical and subtropical coastal zones, are among the most productive ecosystems, representing a significant global carbon sink. We report new molecular insights into the functional relationship among microorganisms, mangrove trees and sediment geochemistry. The interactions among these elements were studied in peat-based mangrove sediments (Twin Cays, Belize) subjected to a long-term fertilization experiment with N and P, providing an analog for eutrophication. The composition and ?13C of bacterial PLFA showed that bacteria and mangrove trees had similar nutrient limitation patterns (N in the fringe mangrove zone, P in the interior zone), and that fertilization with N or P can affect bacterial metabolic processes and bacterial carbon uptake (from diverse mangrove sources including leaf litter, live and dead roots). PCR amplified nifH genes showed a high diversity (26% nifH novel clones) and a remarkable spatial and temporal variability in N-fixing microbial populations in the rhizosphere, varying primarily with the abundance of dead roots, PO4-3 and H2S concentrations in natural and fertilized environments. Our results indicate that eutrophication of mangrove ecosystems has the potential to alter microbial organic matter remineralization and carbon release with important implications for the coastal carbon budget. In addition, we will present preliminary data from a new study exploring the modern calibration of carbon and hydrogen isotopes of plant leaf waxes as a proxy recorder of past environmental change in mangrove ecosystems.

  14. Molecular mechanism of the inhibition effect of Lipoxin A4 on corneal dissolving pathology process

    PubMed Central

    Zhou, Hong-Yan; Hao, Ji-Long; Bi, Miao-Miao; Wang, Shuang; Zhang, Hong; Zhang, Wen-Song

    2013-01-01

    AIM Excessive dissolve of corneal tissue induced by MMPs which were activated by cytokins and chemokines will lead to corneal ulcer. The molecular mechanism of Lipoxin A4 (LXA4) on corneal collagen degradation in three dimensions was investigated. METHODS Rabbit corneal fibroblasts were harvested and suspended in serum-free MEM. Type I collagen, DMEM, collagen reconstitution buffer and corneal fibroblast suspension were mixed on ice. The resultant mixture solidified in an incubator, after which test reagents and plasminogen was overlaid and the cultures were returned to the incubator. The supernatants from collagen gel incubations were collected and the amount of hydroxyproline in the hydrolysate was measured. Immunoblot analysis of MMP-1, -3 and TMMP-1,-2 was performed. MMP-2,-9 was detected by the method of Gelatin zymography. Cytotoxicity assay was measured. RESULTS LXA4 inhibited corneal collagen degradation in a dose and time manner. LXA4 inhibited the IL-1? induced increases in the pro-MMP-1, -2, -3, -9 and active MMP-1, -2, -3, -9 in a concentration dependent manner. LXA4 could also inhibit the IL-1? induced increases in TIMP-1, -2. CONCLUSION As a potent anti-inflammation reagent, LXA4 can inhibit corneal collagen degradation induced by IL-1? in corneal fibroblasts thus inhibiting corneal dissolving pathology process. PMID:23550231

  15. Molecular Mechanisms Mediating the Adaptive Regulation of Intestinal Riboflavin Uptake Process

    PubMed Central

    Subramanian, Veedamali S.; Ghosal, Abhisek; Kapadia, Rubina; Nabokina, Svetlana M.; Said, Hamid M.

    2015-01-01

    The intestinal absorption process of vitamin B2 (riboflavin, RF) is carrier-mediated, and all three known human RF transporters, i.e., hRFVT-1, -2, and -3 (products of the SLC52A1, 2 & 3 genes, respectively) are expressed in the gut. We have previously shown that the intestinal RF uptake process is adaptively regulated by substrate level, but little is known about the molecular mechanism(s) involved. Using human intestinal epithelial NCM460 cells maintained under RF deficient and over-supplemented (OS) conditions, we now show that the induction in RF uptake in RF deficiency is associated with an increase in expression of the hRFVT-2 & -3 (but not hRFVT-1) at the protein and mRNA levels. Focusing on hRFVT-3, the predominant transporter in the intestine, we also observed an increase in the level of expression of its hnRNA and activity of its promoter in the RF deficiency state. An increase in the level of expression of the nuclear factor Sp1 (which is important for activity of the SLC52A3 promoter) was observed in RF deficiency, while mutating the Sp1/GC site in the SLC52A3 promoter drastically decreased the level of induction in SLC52A3 promoter activity in RF deficiency. We also observed specific epigenetic changes in the SLC52A3 promoter in RF deficiency. Finally, an increase in hRFVT-3 protein expression at the cell surface was observed in RF deficiency. Results of these investigations show, for the first time, that transcriptional and post-transcriptional mechanisms are involved in the adaptive regulation of intestinal RF uptake by the prevailing substrate level. PMID:26121134

  16. Stochastic dynamics of small ensembles of non-processive molecular motors: The parallel cluster model

    NASA Astrophysics Data System (ADS)

    Erdmann, Thorsten; Albert, Philipp J.; Schwarz, Ulrich S.

    2013-11-01

    Non-processive molecular motors have to work together in ensembles in order to generate appreciable levels of force or movement. In skeletal muscle, for example, hundreds of myosin II molecules cooperate in thick filaments. In non-muscle cells, by contrast, small groups with few tens of non-muscle myosin II motors contribute to essential cellular processes such as transport, shape changes, or mechanosensing. Here we introduce a detailed and analytically tractable model for this important situation. Using a three-state crossbridge model for the myosin II motor cycle and exploiting the assumptions of fast power stroke kinetics and equal load sharing between motors in equivalent states, we reduce the stochastic reaction network to a one-step master equation for the binding and unbinding dynamics (parallel cluster model) and derive the rules for ensemble movement. We find that for constant external load, ensemble dynamics is strongly shaped by the catch bond character of myosin II, which leads to an increase of the fraction of bound motors under load and thus to firm attachment even for small ensembles. This adaptation to load results in a concave force-velocity relation described by a Hill relation. For external load provided by a linear spring, myosin II ensembles dynamically adjust themselves towards an isometric state with constant average position and load. The dynamics of the ensembles is now determined mainly by the distribution of motors over the different kinds of bound states. For increasing stiffness of the external spring, there is a sharp transition beyond which myosin II can no longer perform the power stroke. Slow unbinding from the pre-power-stroke state protects the ensembles against detachment.

  17. Stochastic dynamics of small ensembles of non-processive molecular motors: The parallel cluster model

    SciTech Connect

    Erdmann, Thorsten; Albert, Philipp J.; Schwarz, Ulrich S. [BioQuant, Heidelberg University, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany and Institute for Theoretical Physics, Heidelberg University, Philosophenweg 19, 69120 Heidelberg (Germany)

    2013-11-07

    Non-processive molecular motors have to work together in ensembles in order to generate appreciable levels of force or movement. In skeletal muscle, for example, hundreds of myosin II molecules cooperate in thick filaments. In non-muscle cells, by contrast, small groups with few tens of non-muscle myosin II motors contribute to essential cellular processes such as transport, shape changes, or mechanosensing. Here we introduce a detailed and analytically tractable model for this important situation. Using a three-state crossbridge model for the myosin II motor cycle and exploiting the assumptions of fast power stroke kinetics and equal load sharing between motors in equivalent states, we reduce the stochastic reaction network to a one-step master equation for the binding and unbinding dynamics (parallel cluster model) and derive the rules for ensemble movement. We find that for constant external load, ensemble dynamics is strongly shaped by the catch bond character of myosin II, which leads to an increase of the fraction of bound motors under load and thus to firm attachment even for small ensembles. This adaptation to load results in a concave force-velocity relation described by a Hill relation. For external load provided by a linear spring, myosin II ensembles dynamically adjust themselves towards an isometric state with constant average position and load. The dynamics of the ensembles is now determined mainly by the distribution of motors over the different kinds of bound states. For increasing stiffness of the external spring, there is a sharp transition beyond which myosin II can no longer perform the power stroke. Slow unbinding from the pre-power-stroke state protects the ensembles against detachment.

  18. Reactive molecular dynamics simulations of switching processes of azobenzene-based monolayer on surface

    NASA Astrophysics Data System (ADS)

    Tian, Ziqi; Wen, Jin; Ma, Jing

    2013-07-01

    It is a challenge to simulate the switching process of functional self-assembled monolayers (SAMs) on metal surfaces, since the systems consist of thousands of atoms and the switching is triggered by quantum-mechanical events. Herein a molecular dynamics simulation with a reactive rotation potential of N=N bond is implemented to investigate the dynamic conformational changes and packing effects on the stimuli-responsive isomerization of the terminally thiol functionalized azobiphenyls (AZOs), which are bound on the Au(111) surface. To, respectively, distinguish the time evolutions that start from cis and trans initial configurations, two different functions are established to model the potential energy curves for cis-to-trans and trans-to-cis transitions, instead of the only one cosine function used in the conventional non-reactive force fields. In order to simulate the conformation transitions of the AZO film on surface, a random switching function, depending on the N=N twisting angle, is constructed to consider both forward and backward cis/trans isomerization events and to trigger the reaction by changing the N atom types automatically. The factors that will influence the isomerization process, including the choice of ensembles and thermostat algorithms, the time intervals separating each switching, and the forms of the switching function, are systematically tested. Most AZO molecules switch from the cis to trans configuration with a coverage of 5.76 × 10-6 mol/m2 on a picosecond time scale, and a low coverage might make the switching irreversible, which is in agreement with the experiments.

  19. Comparison of nonequilibrium processes in p+Ni and p+Au collisions at GeV energies

    Microsoft Academic Search

    A. Budzanowski; M. Fidelus; D. Filges; F. Goldenbaum; H. Hodde; L. Jarczyk; B. Kamys; M. Kistryn; A. Kowalczyk; E. Kozik; P. Kulessa; H. Machner; A. Magiera; B. Piskor-Ignatowicz; K. Pysz; Z. Rudy; R. Siudak; M. Wojciechowski

    2009-01-01

    The energy and angular dependence of double differential cross sections\\u000ad2sigma\\/dOmega dE were measured for p, d, t, 3,4,6He, 6,7,8Li, 7,9,10Be,\\u000a10,11B, and C produced in collisions of 1.2, 1.9, and 2.5 GeV protons with a Ni\\u000atarget. The shape of the spectra and angular distributions does almost not\\u000achange whereas the absolute value of the cross sections increases by

  20. Comparison of nonequilibrium processes in p+Ni and p+Au collisions at GeV energies

    Microsoft Academic Search

    A. Budzanowski; M. Fidelus; D. Filges; F. Goldenbaum; H. Hodde; L. Jarczyk; B. Kamys; M. Kistryn; A. Kowalczyk; E. Kozik; P. Kulessa; H. Machner; A. Magiera; B. Piskor-Ignatowicz; K. Pysz; Z. Rudy; R. Siudak; M. Wojciechowski

    2010-01-01

    The energy and angular dependence of double differential cross sections d2sigma\\/dOmegadE were measured for p,d,t, He3,4,6, Li6,7,8, Be7,9,10, B10,11, and C produced in collisions of 1.2, 1.9, and 2.5 GeV protons with a Ni target. The shape of the spectra and angular distributions almost does not change whereas the absolute value of the cross sections increases by a factor ~1.7

  1. Comparison of nonequilibrium processes in p+Ni and p+Au collisions at GeV energies

    Microsoft Academic Search

    A. Budzanowski; M. Kistryn; E. Kozik; M. Fidelus; L. Jarczyk; B. Kamys; A. Kowalczyk; A. Magiera; Z. Rudy; M. Wojciechowski; D. Filges; F. Goldenbaum; H. Machner; H. Hodde; P. Kulessa; K. Pysz; R. Siudak; B. Piskor-Ignatowicz

    2010-01-01

    The energy and angular dependence of double differential cross sections d{sup 2}\\/ddE were measured for p,d,t, {sup 3,4,6}He, {sup 6,7,8}Li, {sup 7,9,10}Be, {sup 10,11}B, and C produced in collisions of 1.2, 1.9, and 2.5 GeV protons with a Ni target. The shape of the spectra and angular distributions almost does not change whereas the absolute value of the cross sections

  2. High Energy Collision of Particles in the Vicinity of Extremal Black Holes in Higher Dimensions: Banados-Silk-West Process as Linear Instability of Extremal Black Holes

    E-print Network

    Naoki Tsukamoto; Masashi Kimura; Tomohiro Harada

    2014-01-06

    We study high energy particle collisions around the higher dimensional black holes. It is shown that the center of mass energy can be arbitrarily large in the vicinity of the event horizon like the Banados, Silk and West (BSW) process in four dimensions if the following two conditions are satisfied: (i) the horizon is extremal and (ii) the parameters of either of the two colliding particles are fine-tuned, which is called a critical particle condition. We also show that a test particle which satisfies the critical particle condition can reach the event horizon from a distant region for a simple case. Finally, we discuss the relation between the BSW process and the linear instability of test fields around the extremal black holes, the latter of which has been recently found by Aretakis.

  3. High Energy Collision of Particles in the Vicinity of Extremal Black Holes in Higher Dimensions: Banados-Silk-West Process as Linear Instability of Extremal Black Holes

    E-print Network

    Tsukamoto, Naoki; Harada, Tomohiro

    2014-01-01

    We study high energy particle collisions around the higher dimensional black holes. It is shown that the center of mass energy can be arbitrarily large in the vicinity of the event horizon like the Banados, Silk and West (BSW) process in four dimensions if the following two conditions are satisfied: (i) the horizon is extremal and (ii) the parameters of either of the two colliding particles are fine-tuned, which is called a critical particle condition. We also show that a test particle which satisfies the critical particle condition can reach the event horizon from a distant region for a simple case. Finally, we discuss the relation between the BSW process and the linear instability of test fields around the extremal black holes, the latter of which has been recently found by Aretakis.

  4. Molecular processes studied at a single-molecule level using DNA origami nanostructures and atomic force microscopy.

    PubMed

    Bald, Ilko; Keller, Adrian

    2014-01-01

    DNA origami nanostructures allow for the arrangement of different functionalities such as proteins, specific DNA structures, nanoparticles, and various chemical modifications with unprecedented precision. The arranged functional entities can be visualized by atomic force microscopy (AFM) which enables the study of molecular processes at a single-molecular level. Examples comprise the investigation of chemical reactions, electron-induced bond breaking, enzymatic binding and cleavage events, and conformational transitions in DNA. In this paper, we provide an overview of the advances achieved in the field of single-molecule investigations by applying atomic force microscopy to functionalized DNA origami substrates. PMID:25191873

  5. Teaching the Process of Molecular Phylogeny and Systematics: A Multi-Part Inquiry-Based Exercise

    ERIC Educational Resources Information Center

    Lents, Nathan H.; Cifuentes, Oscar E.; Carpi, Anthony

    2010-01-01

    Three approaches to molecular phylogenetics are demonstrated to biology students as they explore molecular data from "Homo sapiens" and four related primates. By analyzing DNA sequences, protein sequences, and chromosomal maps, students are repeatedly challenged to develop hypotheses regarding the ancestry of the five species. Although these…

  6. Decision Processes During Development of Molecular Biomarkers for Gonadal Phenotypic Sex

    EPA Science Inventory

    Molecular biomarkers for determination of gonadal phenotypic sex in the Japanese medaka (Oryzias latipes), will serve as a case study. The medaka has unique features that aid in the development of appropriate molecular biomarkers of gonad phenotype, a) genetic sex can be determin...

  7. Thermal decomposition process in algaenan of Botryococcus braunii race L. Part 2: Molecular dynamics simulations using the ReaxFF reactive force field

    E-print Network

    Goddard III, William A.

    Thermal decomposition process in algaenan of Botryococcus braunii race L. Part 2: Molecular simulation results on pyrolysis of a molecular model of the algaenan Botryococcus braunii race L biopolymer cracking process within algaenan race L biopolymers. The simulations indicate that the thermal

  8. A study of quark energy loss via Drell-Yan process in p+A collisions at Fermilab

    NASA Astrophysics Data System (ADS)

    Liu, Kun; E906/SeaQuest Collaboration

    2013-10-01

    E906/SeaQuest is a new fixed-target experiment being operated at Fermi National Accelerator Laboratory. Using the 120 GeV proton beam from the main injector, E906/SeaQuest measures the Drell-Yan productions in the dimuon mass range 4-8 GeV in p+p and p+A collisions over a wide xF range, with A = D, C, Fe, W. These new measurements will help us to clarify the nature of parton energy loss mechanisms in nuclear medium. Parton energy loss in QGP is considered the dominant contributor to the observed jet quenching phenomena at RHIC and LHC. Since the center of mass energy of p+A collisions at E906/SeaQuest is low and out of the nuclear shadowing region, the measurements will provide the clean determination of parton energy loss effect in cold nuclear medium. E906/SeaQuest conducted a short commissioning run in 2012 and will resume data taking in September 2013. I will present the current status and the prospect of the parton energy loss measurements with the E906/SeaQuest experiment at Fermilab.

  9. Tandem oxidative processes catalyzed by polymer-incarcerated multimetallic nanoclusters with molecular oxygen.

    PubMed

    Miyamura, Hiroyuki; Kobayashi, Sh?

    2014-04-15

    Heterogeneous catalysis and one-pot tandem reactions are key for efficient and practical organic syntheses and for green and sustainable chemistry. Heterogeneous catalysts can be recovered and reused. These catalysts can be applied to efficient systems, such as continuous-flow systems. Tandem reactions often proceed via highly reactive but unstable intermediates. Tandem reactions do not require workup or much purification of the intermediate. This Account summarizes recent developments that we have made in the field of multifunctional heterogeneous metal nanocluster catalysts for use in tandem reactions based on aerobic oxidation reactions as key processes. We constructed our heterogeneous metal nanoclusters via two important procedures--microencapsulation and cross-linking--using polystyrene-based copolymers with cross-linking moieties. These frameworks can efficiently stabilize small metal nanoclusters to maintain high catalytic activity without aggregation and leaching of nanoclusters. Aggregation and leaching are prevented by weak but multiple interactions between metal nanocluster surfaces and benzene rings in the copolymer as well as by the physical envelopment of cross-linked polymer backbones. Small nanoclusters, including multimetallic alloy clusters (nanoalloys), can be "imprisoned" into these cross-linked polymer composites. The term we use for these processes is polymer incarceration. Direct oxidative esterifications were achieved with polymer-incarcerated (PI) Au nanocluster catalysts. Amides were synthesized from alcohols and amines under aerobic oxidative conditions with PI bimetallic nanocluster catalysts composed of Au and Fe-group metals that formed separated nanoclusters rather than alloys. Oxidative lactam formation from amino alcohols was also achieved. On the other hand, imines could be prepared selectively from alcohols and amines with PI Au-Pd bimetallic nanoclusters. We also achieved the integration of the aerobic oxidation of allylic alcohols and the following Michael reaction catalyzed by trimetallic PI catalysts containing Au-Pd alloy nanoclusters and tetraalkoxyborates as cross-linkers. All of these heterogeneous catalysts could be recovered by simple operations and reused without significant loss of activity or any leaching of metals. We have demonstrated that the polymer incarceration method enables the simultaneous immobilization of several metals, with which we can achieve one-pot tandem oxidative processes using molecular oxygen as an oxidant within the multifunctional heterogeneous catalysts. Suitable choices of metals and bimetallic structures are crucial for the reactivity and the selection of reaction pathways. PMID:24661043

  10. Ion Collision, Theory

    SciTech Connect

    Shukla, Anil K.

    2013-09-11

    The outcome of a collision between an ion and neutral species depends on the chemical and physical properties of the two reactants, their relative velocities, and the impact parameter of their trajectories. These include elastic and inelastic scattering of the colliding particles, charge transfer (including dissociative charge transfer), atom abstraction, complex formation and dissociation of the colliding ion. Each of these reactions may be characterized in terms of their energy-dependent rate coefficients, cross sections and reaction kinetics. A theoretical framework that emphasizes simple models and classical mechanics is presented for these processes. Collision processes are addressed in two categories of low-energy and high-energy collisions. Experiments under thermal or quasi-thermal conditions–swarms, drift tubes, chemical ionization and ion cyclotron resonance are strongly influenced by long-range forces and often involve collisions in which atom exchange and extensive energy exchange are common characteristics. High-energy collisions are typically impulsive, involve short-range intermolecular forces and are direct, fast processes.

  11. Tuning ultracold collisions of excited rotational dipolar molecules

    NASA Astrophysics Data System (ADS)

    Wang, Gaoren; Quéméner, Goulven

    2015-03-01

    We investigate the ultracold collisions of rotationally excited dipolar molecules in free-space, taking the hetero-nuclear bi-alkali molecule of KRb as an example. We show that we can sharply tune the elastic, inelastic and reactive rate coefficients of lossy molecular collisions when a second rotationally excited colliding channel crosses the threshold of the initial colliding channel, with the help of an applied electric field, as found by Avdeenkov et al for non-lossy molecules (Phys. Rev. A 73 022707). We can increase or decrease the inelastic and reactive processes whether the second channel is above or below the initial channel. This is seen for both bosonic and fermionic molecules. Additionally, we include the electric quadrupole and octopole moment to the dipole moment in the expression of the long-range multipole–multipole interaction. We found that for processes mediated by the incident channel, such as elastic and reactive collisions, the inclusion of quadrupole and octopole moments is not important at ultralow energies. The moments are important for processes mediated by state-to-state transitions like inelastic collisions.

  12. Molecular-dynamics simulation of clustering processes in sea-ice floes

    E-print Network

    Herman, Agnieszka

    2011-01-01

    In seasonally ice-covered seas and along the margins of perennial ice pack, i.e. in regions with medium ice concentrations, the ice cover typically consists of separate floes interacting with each other by inelastic collisions. In this paper, hitherto unexplored analogies between this type of ice cover and two-dimensional granular gases are used to formulate a model of ice dynamics at the floe level. The model consists of: (i) momentum equations for floe motion between collisions, formulated in the form of a Stokes-flow problem, with floe-size dependent time constant and equilibrium velocity, and (ii) hard-disk collision model. The numerical algorithm developed is suitable for simulating particle-laden flow of $N$ disk-shaped floes with arbitrary size distribution. The model is applied to study clustering phenomena in sea ice with power-law floe-size distribution. In particular, the influence of the average ice concentration $\\bar{A}$ on the formation and characteristics of clusters is analyzed in detail. The...

  13. Collision Animations

    NSDL National Science Digital Library

    University of Leeds School of Earth and Environment

    This series of interactive Flash animation explores all aspects of the India-Eurasian continental collision. Animations show the motion of the two continents, the growth of the Himalayas, earthquakes resulting from their collision, and the incredible rate of erosion of the newly formed mountains.

  14. Theoretical calculations of the collision cross sections and rate coefficients for the hyperfine transitions of interstellar molecular ortho-NH3 colliding with He

    Microsoft Academic Search

    Ji Chen; Ya-Hui Zhang; Tian-Chun Zhou

    1997-01-01

    In this paper, the collision cross sections and the rate coefficients for the hyperfine transitions of interstellar molecules of ortho-NH3 colliding with He are calculated by solving the coupled equations in the CS (Coupled State) approximation with the R-matrix propagation method. The results provide useful fundamental data for the investigation of astronomical information.

  15. Use of molecular typing methods to trace the dissemination of Listeria monocytogenes in a shrimp processing plant.

    PubMed Central

    Destro, M T; Leitão, M F; Farber, J M

    1996-01-01

    Molecular typing of bacteria has been widely used in epidemiological studies but not as extensively for tracing the transmission of pathogenic bacteria in food plants. This study was conducted to examine the potential use of two molecular typing methods, random amplified polymorphic DNA (RAPD) analysis and pulsed-field gel electrophoresis (PFGE), to trace Listeria monocytogenes contamination in a shrimp processing plant. Ribotyping and phase typing were also performed on a select number of strains. One hundred fifteen strains of L. monocytogenes collected in different areas of a shrimp processing plant were first serotyped and then subtyped by molecular typing. RAPD and PFGE showed great promise for typing L. monocytogenes isolates since distinguishable and reproducible DNA polymorphisms were obtained. When the composite profile from both (RAPD and PFGE) methods was generated, there was an increase in the discriminatory power to discern differences between strains of L. monocytogenes. The results indicated that environmental strains all fell into composite profile groupings unique to the environment, while strains from both water and utensils shared another composite profile group. L. monocytogenes fresh shrimp isolates belonging to one profile group were found in different areas of the processing line. This same profile group was also present in food handlers from the processing and packaging areas of the plant. PMID:8593073

  16. Event characterization in (very) asymmetric collisions

    NASA Astrophysics Data System (ADS)

    David, Gabor

    2015-03-01

    Event-by-event reconstruction of the collision geometry using some incarnation of the Glauber-model is a widely accepted method in studying heavy ion collisions. While there is no known problem with the procedure when applied to the collision of two large ions, we will argue that in very asymmetric collisions, like p(d)+A with at least one hard scattering process occuring the event geometry deduced with the simple Glauber-model may be biased.

  17. Angular distribution of Auger electrons emitted through the resonant transfer and excitation process following O sup 5+ +He collisions

    SciTech Connect

    Benhenni, M.; Shafroth, S.M.; Swenson, J.K.; Schulz, M.; Giese, J.P.; Schoene, H.; Vane, C.R.; Dittner, P.F.; Datz, S. (Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC (USA) Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN (USA))

    1990-10-08

    This Letter reports the first measurements of the angular distribution of Auger electrons emitted from the decay of the (1{ital s}2{ital s}2{ital p}{sup 2}){sup 3}{ital D} O{sup 4+**} doubly excited state formed predominantly through resonant transfer and excitation (RTE) in collisions of 13-MeV O{sup 5+} projectiles with He. The (1{ital s}2{ital s}2{ital p}{sup 2}){sup 3}{ital D} angular distribution is strongly peaked along the beam direction, in agreement with recent calculations of the RTE angle-dependent impulse approximation. Furthermore, interference effects between the RTE and the elastic target direct-ionization channels are observed.

  18. Supersonic cloud collision. I.

    NASA Astrophysics Data System (ADS)

    Anathpindika, S.

    2009-09-01

    Context: It has long been suggested that shocks might play an important role in altering the form of the interstellar medium (ISM). Shocks enhance gas density and sufficiently dense regions may become self gravitating. Potential star-forming clouds within larger molecular clouds, move randomly at supersonic speeds and a collision between them, is highly inelastic. Aims: Depending on the precollision velocity, colliding molecular clouds produce a slab that is either shock-compressed or pressure-confined. In a sequel of two Papers (I and II), we simulate molecular cloud collision and investigate the dynamical evolution of such slabs. Shocked slabs appear susceptible to hydrodynamic instabilities and, in the present Paper (I), we study the effect of strong shear between slab layers on the dynamic evolution of a shock compressed gas slab. Head-on and off-centre cloud collisions have been examined in this work. Self gravity is included in all our simulations. Methods: Simulations presented were performed using the smoothed particle hydrodynamics (SPH) numerical scheme. Individual, precollision clouds are modelled as pressure-confined Bonnor-Ebert spheres. However, for simplicity the thermodynamic details of the problem are simplified and the gas temperature is evolved simply by a barytropic equation of state. Obviously, the gas suffers to some extent from thermal inertial effects. However, we note that the dynamical timescale is much smaller than the local sound crossing time so that any such effects should have minimum influence. Results: Strong shocks are highly radiative. Thus a highly supersonic cloud collision produces a cold, roughly isothermal shock compressed gas slab. We find that the shocked slab is susceptible to dynamical instabilities like the gravitational instability, Kelvin-Helmholtz (KH) instability and the non linear thin shell instability (NTSI). Rapid growth of instabilities within the slab produces structure in it. The NTSI competes with the gravitational instability and the fate of the shocked slab apparently depends on the relative dominance of either of the two instabilities. Dominance of the NTSI causes turbulent mixing between slab layers and dissipates internal energy. Eventually the slab collapses to form a thin elongated body, aligned with the collision axis, and star formation may commence in it. Our hydrodynamical models discussed here suggest that, high-velocity cloud collisions may be a viable mechanism for the formation of observed filamentary structure in the ISM.

  19. Vibrational energy transfer in shocked molecular crystals.

    PubMed

    Hooper, Joe

    2010-01-01

    We consider the process of establishing thermal equilibrium behind an ideal shock front in molecular crystals and its possible role in initiating chemical reaction at high shock pressures. A new theory of equilibration via multiphonon energy transfer is developed to treat the scattering of shock-induced phonons into internal molecular vibrations. Simple analytic forms are derived for the change in this energy transfer at different Hugoniot end states following shock compression. The total time required for thermal equilibration is found to be an order of magnitude or faster than proposed in previous work; in materials representative of explosive molecular crystals, equilibration is predicted to occur within a few picoseconds following the passage of an ideal shock wave. Recent molecular dynamics calculations are consistent with these time scales. The possibility of defect-induced temperature localization due purely to nonequilibrium phonon processes is studied by means of a simple model of the strain field around an inhomogeneity. The specific case of immobile straight dislocations is studied, and a region of enhanced energy transfer on the order of 5 nm is found. Due to the rapid establishment of thermal equilibrium, these regions are unrelated to the shock sensitivity of a material but may allow temperature localization at high shock pressures. Results also suggest that if any decomposition due to molecular collisions is occurring within the shock front itself, these collisions are not enhanced by any nonequilibrium thermal state. PMID:20078172

  20. Experimental study of mu -atomic and mu -molecular processes in pure helium and deuterium-helium mixtures

    Microsoft Academic Search

    V. M. Bystritsky; V. F. Boreiko; W. Czaplinski; M. Filipowicz; V. V. Gerasimov; O. Huot; P. E. Knowles; F. Mulhauser; V. N. Pavlov; N. P. Popov; L. A. Schaller; H. Schneuwly; V. G. Sandukovsky; V. A. Stolupin; V. P. Volnykh; J. Wozniak

    2005-01-01

    We present experimental results of mu -atomic and mu -molecular processes induced by negative muons in pure helium and helium-deuterium mixtures. The experiment was performed at the Paul Scherrer Institute (Switzerland). We measured relative intensities of muonic x-ray K series transitions in (muHe3,4)* atoms in pure helium as well as in helium-deuterium mixtures. The dmuHe3 radiative decay probabilities for two

  1. Experimental study of $\\\\mu$atomic and $\\\\mu$molecular processes in pure helium and deuterium--helium mixtures

    Microsoft Academic Search

    V. M. Bystritsky; V. F. Boreiko; M. Filipowicz; V. V. Gerasimov; O. Huot; P. E. Knowles; F. Mulhauser; V. N. Pavlov; N. P. Popov; L. A. Schaller; H. Schneuwly; V. G. Sandukovsky; V. A. Stolupin; V. P. Volnykh; J. Wozniak

    2003-01-01

    We present experimental results of $\\\\mu$--atomic and $\\\\mu$--molecular processes induced by negative muons in pure helium and helium--deuterium mixtures. The experiment was performed at the Paul Scherrer Institute (Switzerland). We measured muonic x--ray $K$ series transitions relative intensities in $(\\\\mu{}^{3,4}\\\\mathrm{He})^*$ atoms in pure helium as well as in helium--deuterium mixture. The muon stopping powers ratio between helium and deuterium atoms

  2. Double-Spin Asymmetry A{sub LT} for Polarized Drell-Yan Process in pp-bar Collisions: Wandzura-Wilczek Contribution

    SciTech Connect

    Koike, Yuji; Yoshida, Shinsuke [Department of Physics, Niigata University, Ikarashi, Niigata 950-2181 (Japan); Tanaka, Kazuhiro [Department of Physics, Juntendo University, Inba, Chiba 270-1695 (Japan)

    2009-08-04

    The longitudinal-transverse spin asymmetry A{sub LT} in the polarized Drell-Yan process depends on twist-3 quark distributions of nucleon. In addition to the contributions associated with the twist-3 operators, these distributions contain the 'Wandzura-Wilczek (WW)' part, which is determined by a certain integral of twist-2 distributions. The recently obtained empirical information on the transversity allows a realistic estimate of the WW contribution to A{sub LT} for the polarized pp-bar collisions. Our results indicate that rather large A{sub LT}({approx}10%) can be observed in the proposed spin experiments at GSI, with novel pattern as a function of dilepton mass compared with A{sub TT} and A{sub LL}.

  3. Reversible Simulations of Elastic Collisions

    SciTech Connect

    Perumalla, Kalyan S [ORNL; Protopopescu, Vladimir A [ORNL

    2013-01-01

    Consider a system of N identical hard spherical particles moving in a d-dimensional box and undergoing elastic, possibly multi-particle, collisions. We develop a new algorithm that recovers the pre-collision state from the post-collision state of the system, across a series of consecutive collisions, \\textit{with essentially no memory overhead}. The challenge in achieving reversibility for an n-particle collision (where, in general, n<< N) arises from the presence of nd-d-1 degrees of freedom (arbitrary angles) during each collision, as well as from the complex geometrical constraints placed on the colliding particles. To reverse the collisions in a traditional simulation setting, all of the particular realizations of these degrees of freedom (angles) during the forward simulation must be tracked. This requires memory proportional to the number of collisions, which grows very fast with N and d, thereby severely limiting the \\textit{de facto} applicability of the scheme. This limitation is addressed here by first performing a pseudo-randomization of angles, which ensures determinism in the reverse path for any values of n and d. To address the more difficult problem of geometrical and dynamic constraints, a new approach is developed which correctly samples the constrained phase space. Upon combining the pseudo-randomization with correct phase space sampling, perfect reversibility of collisions is achieved, as illustrated for n<=3, d=2, and n=2, d=3. This result enables, for the first time, reversible simulations of elastic collisions with essentially zero memory accumulation. In principle, the approach presented here could be generalized to larger values of n, which would be of definite interest for molecular dynamics simulations at high densities.

  4. Efficient inverted polymer solar cells with thermal-evaporated and solution-processed small molecular electron extraction layer

    NASA Astrophysics Data System (ADS)

    Sun, Fu-Zhou; Shi, Ai-Li; Xu, Zai-Quan; Wei, Huai-Xin; Li, Yan-Qing; Lee, Shuit-Tong; Tang, Jian-Xin

    2013-04-01

    Efficient inverted polymer solar cell is reported upon by integrating with a small molecular 1,3,5-tri(phenyl-2-benzimi-dazolyl)-benzene (TPBi) electron extraction layer (EEL) at low processing temperature with thermal-evaporation and solution-process, resulting in the power conversion efficiencies of 3.70% and 3.47%, respectively. The potential of TPBi as an efficient EEL is associated with its suitable electronic energy level for electron extraction and hole blocking from the active layer to the indium tin oxide cathode.

  5. Applications of neural networks to real-time data processing at the Environmental and Molecular Sciences Laboratory (EMSL)

    SciTech Connect

    Keller, P.E.; Kouzes, R.T.; Kangas, L.J.

    1993-06-01

    Detailed design of the Environmental and Molecular Sciences Laboratory (EMSL) at the Pacific Northwest Laboratory (PNL) is nearing completion and construction is scheduled to begin later this year. This facility will assist in the environmental restoration and waste management mission at the Hanford Site. This paper identifies several real-time data processing applications within the EMSL where neural networks can potentially be beneficial. These applications include real-time sensor data acquisition and analysis, spectral analysis, process control, theoretical modeling, and data compression.

  6. Energetics of particle collisions near dirty rotating extremal black holes: Banados-Silk-West effect versus Penrose process

    E-print Network

    O. B. Zaslavskii

    2012-10-07

    If two particles collide near the horizon of a rotating extremal black hole, under certain conditions the energy E_{c.m.} in the center-of-mass frame can grow without limit (the so-called Banados-Silk-West effect). We consider collisions that produce two other particles. We show that for a generic dirty (surrounded by matter) black hole, there exist upper bounds on the energy and mass of product particles which can be detected at infinity. As a result, the positive energy gain is possible but is quite modest. It mainly depends on two numbers in which near-horizon behavior of the metric is encoded. The obtained results suggest astrophysical limits on the possibility of observation of the products of the collisional Banados-Silk-West effect. These results are consistent with recent calculations for the Kerr metric, extending them to generic dirty black holes. It is shown that for dirty black holes there are types of scenarios of energy extraction impossible in the Kerr case.

  7. Competition of coalescence and "fireball" processes in nonequilibrium emission of light charged particles from p+Au collisions

    E-print Network

    Budzanowski, A; Filges, D; Goldenbaum, F; Hodde, H; Jarczyk, L; Kamys, B; Kistryn, M; Kistryn, St; Kliczewski, St; Kowalczyk, A; Kozik, E; Kulessa, P; Machner, H; Magiera, A; Piskor-Ignatowicz, B; Pysz, K; Rudy, Z; Siudak, R; Wojciechowski, M

    2008-01-01

    The energy and angular dependence of double differential cross sections was measured for p,d,t,He,Li,Be, and B isotopes produced in collisions of 1.2 and 1.9 GeV protons with Au target. The shape of the spectra and angular distributions almost does not change in the beam energy range from 1.2 to 2.5 GeV, however, the absolute value of the cross sections increases for all ejectiles. A phenomenological model of two emitting, moving sources reproduces very well spectra and angular distributions of intermediate mass fragments. Double differential cross sections for light charged particles (LCP) were analyzed in the frame of the microscopic model of intranuclear cascade (INC) with coalescence of nucleons and statistical model for evaporation of particles from excited residual nuclei. Energy and angular dependencies of data agree satisfactorily neither with predictions of microscopic intranuclear cascade calculations for protons, nor with coalescence calculations for other LCP. Phenomenological inclusion of another...

  8. Cosmic Collisions

    NSDL National Science Digital Library

    This Web site, created to complement the Museum's Cosmic Collisions space show, takes a look at the hypersonic impacts that drive the dynamic and continuing evolution of the universe. The site includes a one-minute QuickTime preview of the space show, a collection of 26 scientific simulations and visualizations, a look at the fusion of cutting-edge astrophysics research and state-of-the-art science visualization expertise that went into creating Cosmic Collisions and other information.

  9. Will spin-relaxation times in molecular magnets permit quantum information processing?

    PubMed

    Ardavan, Arzhang; Rival, Olivier; Morton, John J L; Blundell, Stephen J; Tyryshkin, Alexei M; Timco, Grigore A; Winpenny, Richard E P

    2007-02-01

    Using X-band pulsed electron-spin resonance, we report the intrinsic spin-lattice (T1) and phase-coherence (T2) relaxation times in molecular nanomagnets for the first time. In Cr7M heterometallic wheels, with M=Ni and Mn, phase-coherence relaxation is dominated by the coupling of the electron spin to protons within the molecule. In deuterated samples T2 reaches 3 micros at low temperatures, which is several orders of magnitude longer than the duration of spin manipulations, satisfying a prerequisite for the deployment of molecular nanomagnets in quantum information applications. PMID:17358891

  10. Modeling enzymatic processes: A molecular simulation analysis of the origins of regioselectivity

    NASA Astrophysics Data System (ADS)

    Pieraccini, Stefano; Sironi, Maurizio; Colombo, Giorgio

    2006-02-01

    Enzymes hold a great synthetic importance as catalysts for the selective transformation of compounds. We have investigated the origins of the regioselectivity difference in the subtilisin mediated acylation of D- and L-benzylglucopiranoside compounds. Using molecular dynamics and QM/MM calculations we have investigated the molecular recognition of the substrates by the enzyme active site and the differences in energy of the tetrahedral intermediates (TI) mimicking the acylation transition states leading to different selectivities. QM/MM analysis of the energy-structure correlations of the TIs shows a clustering towards lower energy of the conformations corresponding to the major experimental products for each enantiomer.

  11. 2008 Atomic and Molecular Interactions GRC-July 6-11, 2008

    Microsoft Academic Search

    Arthur Suits; Nancy Ryan Gray

    2009-01-01

    The Atomic and Molecular Interactions Gordon Conferences is justifiably recognized for its broad scope, touching on areas ranging from fundamental gas phase and gas-condensed matter collision dynamics, to laser-molecule interactions, photophysics, and unimolecular decay processes. The meeting has traditionally involved scientists engaged in fundamental research in gas and condensed phases and those who apply these concepts to systems of practical

  12. Merging Galaxies, Cosmic Collisions

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Exciting Hubble Space Telescope images of more than a dozen very distant colliding galaxies indicate that, at least in some cases, big massive galaxies form through collisions between smaller ones, in a generation after generation never-ending story. The Hubble image shows the paired galaxies very close together with streams of stars being pulled out of the galaxies. The colliding 'parent' galaxies lose their shape and smoother galaxies are formed. The whole merging process can take less than a billion years. The Hubble Space Telescope imaged 81 galaxies in the galaxy cluster 8 billion light-years away. Astronomers say the collisions have never been observed before at this frequency. Many of the collisions involve very massive galaxies, and the end result will be even more massive galaxies.

  13. Molecular Chaperones of Leishmania: Central Players in Many Stress-Related and -Unrelated Physiological Processes

    PubMed Central

    Requena, Jose M.; Montalvo, Ana M.; Fraga, Jorge

    2015-01-01

    Molecular chaperones are key components in the maintenance of cellular homeostasis and survival, not only during stress but also under optimal growth conditions. Folding of nascent polypeptides is supported by molecular chaperones, which avoid the formation of aggregates by preventing nonspecific interactions and aid, when necessary, the translocation of proteins to their correct intracellular localization. Furthermore, when proteins are damaged, molecular chaperones may also facilitate their refolding or, in the case of irreparable proteins, their removal by the protein degradation machinery of the cell. During their digenetic lifestyle, Leishmania parasites encounter and adapt to harsh environmental conditions, such as nutrient deficiency, hypoxia, oxidative stress, changing pH, and shifts in temperature; all these factors are potential triggers of cellular stress. We summarize here our current knowledge on the main types of molecular chaperones in Leishmania and their functions. Among them, heat shock proteins play important roles in adaptation and survival of this parasite against temperature changes associated with its passage from the poikilothermic insect vector to the warm-blooded vertebrate host. The study of structural features and the function of chaperones in Leishmania biology is providing opportunities (and challenges) for drug discovery and improving of current treatments against leishmaniasis. PMID:26167482

  14. Molecular Chaperones of Leishmania: Central Players in Many Stress-Related and -Unrelated Physiological Processes.

    PubMed

    Requena, Jose M; Montalvo, Ana M; Fraga, Jorge

    2015-01-01

    Molecular chaperones are key components in the maintenance of cellular homeostasis and survival, not only during stress but also under optimal growth conditions. Folding of nascent polypeptides is supported by molecular chaperones, which avoid the formation of aggregates by preventing nonspecific interactions and aid, when necessary, the translocation of proteins to their correct intracellular localization. Furthermore, when proteins are damaged, molecular chaperones may also facilitate their refolding or, in the case of irreparable proteins, their removal by the protein degradation machinery of the cell. During their digenetic lifestyle, Leishmania parasites encounter and adapt to harsh environmental conditions, such as nutrient deficiency, hypoxia, oxidative stress, changing pH, and shifts in temperature; all these factors are potential triggers of cellular stress. We summarize here our current knowledge on the main types of molecular chaperones in Leishmania and their functions. Among them, heat shock proteins play important roles in adaptation and survival of this parasite against temperature changes associated with its passage from the poikilothermic insect vector to the warm-blooded vertebrate host. The study of structural features and the function of chaperones in Leishmania biology is providing opportunities (and challenges) for drug discovery and improving of current treatments against leishmaniasis. PMID:26167482

  15. A MOLECULAR-DYNAMICS STUDY: NUCLEATION PROCESSES AND STRUCTURAL TRANSFORMATION OF

    E-print Network

    Entel, P.

    experiments have been made on ultra-thin iron films on copper sub- strates, because it is possible to grow;2 Method 2.1 Model The method of molecular-dynamics (MD) simulations which we used in this work, is based atoms i and j. The function Fi is the embedding energy of atom i depending on the electron density

  16. Time-dependent many-electron approach to slow ion-atom collisions for systems with several active electrons

    NASA Astrophysics Data System (ADS)

    Runge, Keith; Micha, David A.

    2000-08-01

    We develop a first-principles molecular dynamics for slow ion-atom collisions, where a many-electron system is described over time allowing for its self-consistent coupling to evolving nuclear motions. Our treatment combines an eikonal description of nuclear motions and time-dependent Hartree-Fock states and introduces molecular orbitals written as linear combinations of traveling atomic functions to derive general matrix equations for state-to-state cross sections and to calculate properties. A ``relax-and-drive'' procedure is employed to propagate solutions to the coupled equations with different time scales for electronic transitions and nuclear displacements. Reduced differential cross sections have been calculated for elastic, electron transfer, and excitation processes in He++D collisions, and they compare very well to experimental values and other calculations. In addition, we present results for the evolution of atomic populations during collisions.

  17. The fabrication of rare earth covalent luminescent hybrid materials with potential molecular bridge by in situ sol-gel process

    SciTech Connect

    Zhao Limin [Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092 (China); Yan Bing [Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092 (China)]. E-mail: byan@tongji.edu.cn

    2006-01-05

    1,2,4-Benzenetricar boxylic acid (abbreviated as TMA) was modified to achieve a functional molecular bridge (TMA-APMES) with double reactivity by the reaction with a cross-linking molecule (3-aminopropyl-methyl-diethoxylsiliane, APMES). The modified functional ligand further behaves as a bridge both coordinates to Ln{sup 3+} through oxygen atom and occurs in situ sol-gel process with matrix precursor (tetraethoxysilane, TEOS) through co-hydrolysis and co-polycondensation reaction. Then a novel molecular hybrid material (named as hybrid Ln{sup 3+}) with double chemical bond (Tb-O coordination bond and Si-O covalent bond) resulted. Ultraviolet absorption, phosphorescence, and fluorescence spectra were applied to characterize the photophysical properties of the obtained hybrid material. The strong luminescence of Tb{sup 3+} substantiates optimum energy couple and effective intramolecular energy transfer between the triplet state energy of modified ligand bridge and emissive energy level of Tb{sup 3+}.

  18. Analytic first derivatives of floating occupation molecular orbital-complete active space configuration interaction on graphical processing units.

    PubMed

    Hohenstein, Edward G; Bouduban, Marine E F; Song, Chenchen; Luehr, Nathan; Ufimtsev, Ivan S; Martínez, Todd J

    2015-07-01

    The floating occupation molecular orbital-complete active space configuration interaction (FOMO-CASCI) method is a promising alternative to the state-averaged complete active space self-consistent field (SA-CASSCF) method. We have formulated the analytic first derivative of FOMO-CASCI in a manner that is well-suited for a highly efficient implementation using graphical processing units (GPUs). Using this implementation, we demonstrate that FOMO-CASCI gradients are of similar computational expense to configuration interaction singles (CIS) or time-dependent density functional theory (TDDFT). In contrast to CIS and TDDFT, FOMO-CASCI can describe multireference character of the electronic wavefunction. We show that FOMO-CASCI compares very favorably to SA-CASSCF in its ability to describe molecular geometries and potential energy surfaces around minimum energy conical intersections. Finally, we apply FOMO-CASCI to the excited state hydrogen transfer reaction in methyl salicylate. PMID:26156469

  19. Optimal molecular profiling of tissue and tissue components: defining the best processing and microdissection methods for biomedical applications.

    PubMed

    Bova, G Steven; Eltoum, Isam A; Kiernan, John A; Siegal, Gene P; Frost, Andra R; Best, Carolyn J M; Gillespie, John W; Su, Gloria H; Emmert-Buck, Michael R

    2005-02-01

    Isolation of well-preserved pure cell populations is a prerequisite for sound studies of the molecular basis of any tissue-based biological phenomenon. This article reviews current methods for obtaining anatomically specific signals from molecules isolated from tissues, a basic requirement for productive linking of phenotype and genotype. The quality of samples isolated from tissue and used for molecular analysis is often glossed over or omitted from publications, making interpretation and replication of data difficult or impossible. Fortunately, recently developed techniques allow life scientists to better document and control the quality of samples used for a given assay, creating a foundation for improvement in this area. Tissue processing for molecular studies usually involves some or all of the following steps: tissue collection, gross dissection/identification, fixation, processing/embedding, storage/archiving, sectioning, staining, microdissection/annotation, and pure analyte labeling/identification and quantification. We provide a detailed comparison of some current tissue microdissection technologies, and provide detailed example protocols for tissue component handling upstream and downstream from microdissection. We also discuss some of the physical and chemical issues related to optimal tissue processing, and include methods specific to cytology specimens. We encourage each laboratory to use these as a starting point for optimization of their overall process of moving from collected tissue to high quality, appropriately anatomically tagged scientific results. In optimized protocols is a source of inefficiency in current life science research. Improvement in this area will significantly increase life science quality and productivity. The article is divided into introduction, materials, protocols, and notes sections. Because many protocols are covered in each of these sections, information relating to a single protocol is not contiguous. To get the greatest benefit from this article, readers are advised to read through the entire article first, identify protocols appropriate to their laboratory for each step in their workflow, and then reread entries in each section pertaining to each of these single protocols. PMID:15699569

  20. Molecular-level processes governing the interaction of contaminants with iron and manganese oxides. 1997 annual progress report

    SciTech Connect

    Chambers, S.A. [Pacific Northwest National Lab., Richland, WA (US); Brown, G. [Stanford Univ., CA (US). Dept. of Geological and Environmental Sciences

    1997-06-01

    'The central tenet of this proposal is that a fundamental understanding of specific mineral surface-site reactivities will substantially improve reactive transport models of contaminants in geologic systems, and will allow more effective remediation schemes to be devised. Most large-scale, macroscopic models employ global chemical reaction kinetics and thermochemistry. However, such models do not incorporate molecular-level input critical to the detailed prediction of how contaminants interact with minerals in the subsurface. A first step leading to the incorporation of molecular-level processes in large-scale macroscopic models is the ability to understand which molecular-level processes will dominate the chemistry at the microscopic grain level of minerals. To this end, the research focuses on the fundamental mechanisms of redox chemistry at mineral surfaces. As much of this chemistry in sediments involves the Fe(III)/Fe(II) and Mn(IV)/Mn(II) couples, the authors focus on mineral phases containing these species. Of particular interest is the effect of the local coordination environment of Fe and Mn atoms on their reactivity toward contaminant species. Studies of the impact of local atomic structure on reactivity in combination with knowledge about the types and amounts of various surfaces on natural grain- size minerals provide the data for statistical models. These models in turn form the basis of the larger-scale macroscopic descriptions of reactivity that are needed for reactive transport models. A molecular-level understanding of these mechanisms will enhance the ability to design much greater performance efficiency, cost effectiveness, and remediation strategies that have minimal negative impact on the local environment. For instance, a comprehensive understanding of how minerals that contain Fe(II) reduce oxyanions and chlorinated organics should enable the design of other Fe(II)-containing remediation materials in a way that is synergistic with existing minerals in the subsurface environment.'

  1. Measurement of the differential cross section of the photoinitiated reactive collision of O(1D)+D2 using only one molecular beam: A study by three dimensional velocity mapping

    NASA Astrophysics Data System (ADS)

    Kauczok, S.; Maul, C.; Chichinin, A. I.; Gericke, K.-H.

    2010-06-01

    In order to measure the state selective double differential cross section of a reactive collision, the preparation of the reactants with defined initial velocities and quantum states in number densities high enough to achieve an acceptable count rate is most important. At the same time, secondary collisions have to be prevented in order to ensure that the nascent products are not thermalized. Usually, the best way to control the initial conditions is to use crossed molecular beams, but the number density decreases quadratically with the distance from the nozzle orifice which can be a problem, especially if a molecular product with a large number of populated states is to be analyzed state specifically by REMPI spectroscopy. In this contribution we would like to present a method for measuring the quantum state selective differential cross section of a photoinitiated reaction that combines the advantages of the PHOTOLOC technique (high reactant densities) and the parallel beams technique used by the groups of Kitsopoulos, Orr-Ewing, and Suits (defined relative velocity of the reactants). Moreover, an algorithm based on a Bayesian backward reconstruction developed by W. H. Richardson [J. Opt. Soc. Am. 62, 55 (1972)] has been derived. Both, one reactant and the precursor of the other reactant, are present in the same molecular beam and the center of mass velocity is selected by shifting the dissociation and the detection laser in time and space. Like in comparable methods, this produces a bias in the measured velocity distribution due to the fact that the reaction takes place in the whole volume surrounding the laser beams. This has been also reported by Toomes et al. in the case of the parallel beams technique and presents a general problem of probing reaction products by REMPI spectroscopy. To account for this, we develop a general approach that can be easily adapted to other conditions. The bias is removed in addition to deconvolution from the spread in reactant velocities. Using the benchmark system O(D1)+D2 with N2O as the precursor, we demonstrate that the technique is also applicable in a very general sense (i.e., also with a large spread in reactant velocities, products much faster than reactants) and therefore can be used also if such unfortunate conditions cannot be avoided. Since the resulting distribution of velocities in the laboratory frame is not cylindrically symmetric, three dimensional velocity mapping is the method of choice for the detection of the ionized products. For the reconstruction, the distance between the two laser beams is an important parameter. We have measured this distance using the photodissociation of HBr at 193 nm, detecting the H atoms near 243 nm. The collision energy resulting from the 193 nm photodissociation of N2O is 5.2±1.9 kcal/mol. Our results show a preference for backward scattered D atoms with the OH partner fragment in the high vibrational states (v =4-6), in accord with previously published results claiming the growing importance of a linear abstraction mechanism for collision energies higher than 2.4 kcal/mol.

  2. Molecular fountain.

    SciTech Connect

    Strecker, Kevin E.; Chandler, David W.

    2009-09-01

    A molecular fountain directs slowly moving molecules against gravity to further slow them to translational energies that they can be trapped and studied. If the molecules are initially slow enough they will return some time later to the position from which they were launched. Because this round trip time can be on the order of a second a single molecule can be observed for times sufficient to perform Hz level spectroscopy. The goal of this LDRD proposal was to construct a novel Molecular Fountain apparatus capable of producing dilute samples of molecules at near zero temperatures in well-defined user-selectable, quantum states. The slowly moving molecules used in this research are produced by the previously developed Kinematic Cooling technique, which uses a crossed atomic and molecular beam apparatus to generate single rotational level molecular samples moving slowly in the laboratory reference frame. The Kinematic Cooling technique produces cold molecules from a supersonic molecular beam via single collisions with a supersonic atomic beam. A single collision of an atom with a molecule occurring at the correct energy and relative velocity can cause a small fraction of the molecules to move very slowly vertically against gravity in the laboratory. These slowly moving molecules are captured by an electrostatic hexapole guiding field that both orients and focuses the molecules. The molecules are focused into the ionization region of a time-of-flight mass spectrometer and are ionized by laser radiation. The new molecular fountain apparatus was built utilizing a new design for molecular beam apparatus that has allowed us to miniaturize the apparatus. This new design minimizes the volumes and surface area of the machine allowing smaller pumps to maintain the necessary background pressures needed for these experiments.

  3. Investigation of material removal mechanism of silicon wafer in the chemical mechanical polishing process using molecular dynamics simulation method

    NASA Astrophysics Data System (ADS)

    Han, Xuesong; Hu, Yuanzhong; Yu, Siyuan

    2009-06-01

    Chemical mechanical polishing (CMP) technology, being the mainstream technique of acquiring global planarization and nanometer level surface, has already become an attractive research item. In the case of CMP process, the indentation depth lies in the range of nanometer or sub-nanometer, huge hydrostatic pressure induced in the local deformation area which makes the material removal and surface generation process different from traditional manufacturing process. In order to investigate the physical essence of CMP technique, the authors carry out molecular dynamics (MD) analysis of chemical mechanical polishing of a silicon wafer. The simulation result shows that huge hydrostatic pressure is induced in the local area and leads to the silicon atom transform from the classical diamond structure ( ? silicon) to metal structure ( ? silicon). This important factor results in the ductile fracture of silicon and then in the acquisition of a super-smooth surface.

  4. Study of applied magnetic field magnetoplasmadynamic thrusters with particle-in-cell code with Monte Carlo collision. I. Computation methods and physical processes

    SciTech Connect

    Tang Haibin; Cheng Jiao; Liu Chang [School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); York, Thomas M. [Ohio State University, Columbus, Ohio 43235 (United States)

    2012-07-15

    A two-dimensional axisymmetric electromagnetic particle-in-cell code with Monte Carlo collision conditions has been developed for an applied-field magnetoplasmadynamic thruster simulation. This theoretical approach establishes a particle acceleration model to investigate the microscopic and macroscopic characteristics of particles. This new simulation code was used to study the physical processes associated with applied magnetic fields. In this paper (I), detail of the computation procedure and results of predictions of local plasma and field properties are presented. The numerical model was applied to the configuration of a NASA Lewis Research Center 100-kW magnetoplasmadynamic thruster which has well documented experimental results. The applied magnetic field strength was varied from 0 to 0.12 T, and the effects on thrust were calculated as a basis for verification of the theoretical approach. With this confirmation, the changes in the distributions of ion density, velocity, and temperature throughout the acceleration region related to the applied magnetic fields were investigated. Using these results, the effects of applied field on physical processes in the thruster discharge region could be represented in detail, and those results are reported.

  5. From Molecular Structure to Global Processes : NMR Spectroscopy in Analytical/Environmental Chemistry

    NASA Astrophysics Data System (ADS)

    Simpson, A.

    2009-04-01

    NMR Spectroscopy is arguably the most powerful tool to elucidate structure and probe molecular interactions. A range of NMR approaches will be introduced with emphasis on addressing and understanding structure and reactivity of soil organic matter at the molecular level. The presentation will be split into three main sections. The first section will look at evidence from advanced NMR based approaches that when considered synergistically describes the major structural components in soil organic matter. Multidimensional NMR spectroscopy (1-3D NMR), automated pattern matching, spectral simulations, diffusion NMR and hybrid-diffusion NMR will be introduced in context of molecular structure. Finally the structural components in soil will be contrasted to those found in aquatic dissolved organic matter. Secondly molecular interactions of natural organic matter will be considered. Advanced structural studies have provided detailed spectral assignments which in turn permit the reactivity of various soil components to be elucidated. Aggregation and self-association of soil and dissolved organic matter will be discussed along with the structural components likely responsible for aggregation/colloid formation. Interactions of soil organic matter with anthropogenic chemicals will also be considered and NMR techniques based on "Saturation Transfer Difference" introduced. These techniques are extremely powerful and can be used to both; describe mechanistically how anthropogenic chemicals sorb to whole soils and identify the structural components (lignin, protein, cellulose, etc..) that are responsible for the binding/sorption in soil. In the last section, the "big questions" and challenges facing the field will be considered along with some novel experimental NMR based approaches that should, in future, assist in providing answers to these questions.

  6. Formations of Dumbbell C118 and C119 inside Clusters of C60 Molecules by Collision with ? Particles

    NASA Astrophysics Data System (ADS)

    Zettergren, H.; Rousseau, P.; Wang, Y.; Seitz, F.; Chen, T.; Gatchell, M.; Alexander, J. D.; Stockett, M. H.; Rangama, J.; Chesnel, J. Y.; Capron, M.; Poully, J. C.; Domaracka, A.; Méry, A.; Maclot, S.; Schmidt, H. T.; Adoui, L.; Alcamí, M.; Tielens, A. G. G. M.; Martín, F.; Huber, B. A.; Cederquist, H.

    2013-05-01

    We report highly selective covalent bond modifications in collisions between keV alpha particles and van der Waals clusters of C60 fullerenes. Surprisingly, C119+ and C118+ are the dominant molecular fusion products. We use molecular dynamics simulations to show that C59+ and C58+ ions—effectively produced in prompt knockout processes with He2+—react rapidly with C60 to form dumbbell C119+ and C118+. Ion impact on molecular clusters in general is expected to lead to efficient secondary reactions of interest for astrophysics. These reactions are different from those induced by photons.

  7. Isolating signatures of major cloud-cloud collisions using position-velocity diagrams

    NASA Astrophysics Data System (ADS)

    Haworth, T. J.; Tasker, E. J.; Fukui, Y.; Torii, K.; Dale, J. E.; Shima, K.; Takahira, K.; Habe, A.; Hasegawa, K.

    2015-06-01

    Collisions between giant molecular clouds are a potential mechanism for triggering the formation of massive stars, or even super star clusters. The trouble is identifying this process observationally and distinguishing it from other mechanisms. We produce synthetic position-velocity diagrams from models of cloud-cloud collisions, non-interacting clouds along the line of sight, clouds with internal radiative feedback and a more complex cloud evolving in a galactic disc, to try and identify unique signatures of collision. We find that a broad bridge feature connecting two intensity peaks, spatially correlated but separated in velocity, is a signature of a high-velocity cloud-cloud collision. We show that the broad bridge feature is resilient to the effects of radiative feedback, at least to around 2.5 Myr after the formation of the first massive (ionizing) star. However for a head-on 10 km s-1 collision, we find that this will only be observable from 20 to 30 per cent of viewing angles. Such broad-bridge features have been identified towards M20, a very young region of massive star formation that was concluded to be a site of cloud-cloud collision by Torii et al., and also towards star formation in the outer Milky Way by Izumi et al.

  8. Beyond the Floquet theorem: generalized Floquet formalisms and quasienergy methods for atomic and molecular multiphoton processes in intense laser fields

    NASA Astrophysics Data System (ADS)

    Chu, Shih-I.; Telnov, Dmitry A.

    2004-02-01

    The advancement of high-power and short-pulse laser technology in the past two decades has generated considerable interest in the study of multiphoton and very high-order nonlinear optical processes of atomic and molecular systems in intense and superintense laser fields, leading to the discovery of a host of novel strong-field phenomena which cannot be understood by the conventional perturbation theory. The Floquet theorem and the time-independent Floquet Hamiltonian method are powerful theoretical framework for the study of bound-bound multiphoton transitions driven by periodically time-dependent fields. However, there are a number of significant strong-field processes cannot be directly treated by the conventional Floquet methods. In this review article, we discuss several recent developments of generalized Floquet theorems, formalisms, and quasienergy methods, beyond the conventional Floquet theorem, for accurate nonperturbative treatment of a broad range of strong-field atomic and molecular processes and phenomena of current interests. Topics covered include (a) artificial intelligence (AI)-most-probable-path approach (MPPA) for effective treatment of ultralarge Floquet matrix problem; (b) non-Hermitian Floquet formalisms and complex quasienergy methods for nonperturbative treatment of bound-free and free-free processes such as multiphoton ionization (MPI) and above-threshold ionization (ATI) of atoms and molecules, multiphoton dissociation (MPD) and above-threshold dissociation (ATD) of molecules, chemical bond softening and hardening, charge-resonance enhanced ionization (CREI) of molecular ions, and multiple high-order harmonic generation (HHG), etc.; (c) many-mode Floquet theorem (MMFT) for exact treatment of multiphoton processes in multi-color laser fields with nonperiodic time-dependent Hamiltonian; (d) Floquet-Liouville supermatrix (FLSM) formalism for exact nonperturbative treatment of time-dependent Liouville equation (allowing for relaxations and dephasing mechanisms) and high-order nonlinear optical processes (such as intensity-dependent nonlinear optical susceptibilities and multiphoton resonance fluorescence, etc.); (e) generalized Floquet approaches for the treatment of nonadiabatic and complex geometric phases involving multiphoton transitions; (f) generalized Floquet techniques for the treatment of multiphoton processes in intense laser pulse fields with nonperiodic time-dependent Hamiltonians; (g) Floquet formulations of time-dependent density functional theory (DFT) and time-dependent current DFT for nonperturbative treatment of multiphoton processes of many-electron quantum systems in periodic or polychromatic ( quasiperiodic) laser fields. For each generalized Floquet approach, we present also the corresponding development of new computational techniques for facilitating the study of strong-field processes and phenomena. The advancement of these generalized Floquet formalisms and quasienergy methods provides powerful new theoretical frameworks and accurate computational methods for nonperturbative and ab initio treatment of a wide range of interesting and challenging laser-induced chemical and physical processes and insightful exploration of strong-field atomic and molecular physics.

  9. Time-dependent density-functional theory for molecular processes in strong fields: Study of multiphoton processes and dynamical response of individual valence electrons of N2 in intense laser fields

    E-print Network

    Chu, Xi; Chu, Shih-I

    2001-11-14

    We present a time-dependent density-functional theory (TDDFT) with proper asymptotic long-range potential for nonperturbative treatment of multiphoton processes of many-electron molecular systems in intense laser fields. ...

  10. Nuclear Instruments and Methods in Physics Research B 297 (2013) 2328 Comparison of molecular dynamics and binary collision approximation simulations for

    E-print Network

    Nordlund, Kai

    2013-01-01

    Nuclear Instruments and Methods in Physics Research B 297 (2013) 23­28 Comparison of molecular, Southern Methodist University, Dallas, Texas 75205, USA cHarvard School of Engineering and Applied Sciences bombardment [1, 2]. Ion irradiation at keV energies causes surface and near-surface radiation damage due

  11. Ab inito molecular-dynamics study of EC decomposition process on Li2O2 surfaces

    NASA Astrophysics Data System (ADS)

    Ando, Yasunobu; Ikeshoji, Tamio; Otani, Minoru

    2015-03-01

    We have simulated electrochemical reactions of the EC molecule decomposition on Li2O2 substrate by ab initio molecular dynamics combined with the effective screening medium method. EC molecules adsorb onto the peroxide spontaneously. We find through the analysis of density of states that the adsorption state is stabilized by hybridization of the sp2 orbital and the surface states of the Li2O2. After adsorption, EC ring opens, which leads to the decomposition of the peroxide and the formation of a carboxy group. This kind of alkyl carbonates formed on the Li2O2 substrate was found in experiments actually Nanosystem Research Institute, AIST; ESICB, Kyoto University

  12. Close-coupling calculations of low-energy inelastic and elastic processes in 4He collisions with H2: A comparative study of two potential energy surfaces.

    PubMed

    Lee, Teck-Ghee; Rochow, C; Martin, R; Clark, T K; Forrey, R C; Balakrishnan, N; Stancil, P C; Schultz, D R; Dalgarno, A; Ferland, Gary J

    2005-01-01

    The two most recently published potential energy surfaces (PESs) for the HeH2 complex, the so-called MR (Muchnick and Russek) and BMP (Boothroyd, Martin, and Peterson) surfaces, are quantitatively evaluated and compared through the investigation of atom-diatom collision processes. The BMP surface is expected to be an improvement, approaching chemical accuracy, over all conformations of the PES compared to that of the MR surface. We found significant differences in inelastic rovibrational cross sections computed on the two surfaces for processes dominated by large changes in target rotational angular momentum. In particular, the H2(nu=1,j=0) total quenching cross section computed using the BMP potential was found to be a factor of 1000 larger than that obtained with the MR surface. A lesser discrepancy persists over a large range of energies from the ultracold to thermal and occurs for other low-lying initial rovibrational levels. The MR surface was used in previous calculations of the H2(nu=1,j=0) quenching rate coefficient and gave results in close agreement with the experimental data of Audibert et al. which were obtained for temperatures between 50 and 300 K. Examination of the rovibronic coupling matrix elements, which are obtained following a Legendre expansion of the PES, suggests that the magnitude of the anisotropy of the BMP potential is too large in the interaction region. However, cross sections for elastic and pure rotational processes obtained from the two PESs differ typically by less than a factor of 2. The small differences may be ascribed to the long-range and anharmonic components of the PESs. Exceptions occur for (nu=10,j=0) and (nu=11,j=1) where significant enhancements have been found for the low-energy quenching and elastic cross sections due to zero-energy resonances in the BMP PES which are not present in the MR potential. PMID:15638586

  13. ATOMIC AND MOLECULAR PHYSICS: Interference Angle on Quantum Rotational Energy Transfer in Na + Na2 (A1 ?+u, v = 8 ~ b3?0u, v = 14) Molecular Collision System

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Li; Miao, Gang; Li, Jian; Ma, Feng-Cai

    2009-12-01

    In order to study the collisional quantum interference (CQI) on rotational energy transfer in atom-diatom system, we have studied the relation of the integral interference angle and differential interference angle in Na + Na2 (A1 ?+u, v = 8 ~ b3?0u, v = 14) collision system. In this paper, based on the first-Born approximation of time-dependent perturbation theory and taking into accounts the anisotropic effect of Lennard-Jones interaction potentials, we present a theoretical model of collisional quantum interference in intramolecular rotational energy transfer, and a relationship between differential and integral interference angles.

  14. Computational study of alkali-metal-noble gas collisions in the presence of nonresonant lasers - Na + Xe + h/2/pi/omega sub 1 + h/2/pi/omega sub 2 system

    NASA Technical Reports Server (NTRS)

    Devries, P. L.; Chang, C.; George, T. F.; Laskowski, B.; Stallcop, J. R.

    1980-01-01

    The collision of Na with Xe in the presence of both the rhodamine-110 dye laser and the Nd-glass laser is investigated within a quantum-mechanical close-coupled formalism, utilizing ab initio potential curves and transition dipole matrix elements. Both one- and two-photon processes are investigated; the Na + Xe system is not asymptotically resonant with the radiation fields, so that these processes can only occur in the molecular collision region. The one-photon processes are found to have measurable cross sections at relatively low intensities; even the two-photon process has a significant section for field intensities as low as 10 MW/sq cm.

  15. Theoretical study of charge transfer dynamics in collisions of C6+ carbon ions with pyrimidine nucleobases

    NASA Astrophysics Data System (ADS)

    Bacchus-Montabonel, M. C.

    2012-07-01

    A theoretical approach of the charge transfer dynamics induced by collision of C6+ ions with biological targets has been performed in a wide collision energy range by means of ab-initio quantum chemistry molecular methods. The process has been investigated for the target series thymine, uracil and 5-halouracil corresponding to similar molecules with different substituent on carbon C5. Such a study may be related to hadrontherapy treatments by C6+carbon ions and may provide, in particular, information on the radio-sensitivity of the different bases with regard to ion-induced radiation damage. The results have been compared to a previous analysis concerning the collision of C4+ carbon ions with the same biomolecular targets and significant charge effects have been pointed out.

  16. Resonant charge transfer process in ion-metal surface collisions: effect of the presence of vacancies on the surface

    NASA Astrophysics Data System (ADS)

    Silva, J. A. M. C.; Wolfgang, J.; Borisov, A. G.; Gauyacq, J. P.; Nordlander, P.; Teillet-Billy, D.

    In this paper an investigation of how the presence of a vacancy on a metal surface influences the energy shift and broadening of negative ion states near the surface is presented. Results for H - and F - ions in the vicinity of a surface vacancy defect on an Al(1 1 1) surface are included. The vacancy-induced electron potential is calculated using a density functional method and the Coupled Angular Mode (CAM) method is used to determine the shift and broadening of H - and F - levels. The results show that the vacancy induces a repulsive potential, shifting the negative ion levels up, while narrowing the width. These two effects have opposite influences on the resonant charge transfer process. Their approximate cancellation makes the RCT process in these systems relatively insensitive to vacancies in the surface layer.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  18. Molecular dynamics study on the mechanism of AFM-based nanoscratching process with water-layer lubrication

    NASA Astrophysics Data System (ADS)

    Ren, Jiaqi; Zhao, Jinsheng; Dong, Zeguang; Liu, Pinkuan

    2015-08-01

    The atomic force microscopy (AFM) based direct nanoscratching has been thoroughly studied but the mechanism of nanoscratching with water-layer lubrication is yet to be well understood. In current study, three-dimensional molecular dynamics (MD) simulations are conducted to evaluate the effects of the water-layer lubrication on the AFM-based nanoscratching process on monocrystalline copper. Comparisons of workpiece deformation, scratching forces, and friction coefficients are made between the water-lubricated and dry scratching under various thickness of water layer, scratching depth and scratching velocity. Simulation results reveal that the water layer has positive impact on the surface quality and significant influence on the scratching forces (normal forces and tangential forces). The friction coefficients of the tip in water-lubricated nanoscratching are significantly bigger than those in the dry process. Our simulation results shed lights on a promising AFM-based nanofabrication method, which can assist to get nanoscale surface morphologies with higher quality than traditional approaches.

  19. Changes in Molecular Characteristics of Cereal Carbohydrates after Processing and Digestion

    PubMed Central

    Kasprzak, Miros?aw Marek; Lærke, Helle Nygaard; Knudsen, Knud Erik Bach

    2012-01-01

    Different extraction, purification and digestion methods were used to investigate the molecular properties of carbohydrates in arabinoxylan and ?-glucan concentrates, dietary fiber (DF) rich breads and ileum content of bread fed pigs. The breads studied were: a low DF wheat bread (WF), whole meal rye bread (GR), rye bread with kernels (RK), wheat bread supplemented with wheat arabinoxylan concentrate (AX) and wheat bread supplemented with oat ?-glucan concentrate (BG). The weight average molecular weight (Mw) of extractable carbohydrates in ?-glucan concentrate decreased eight-fold after inclusion in the BG bread when exposed to in vitro digestion, while the Mw of purified extractable carbohydrates in AX bread was reduced two-fold, and remained almost unaffected until reaching the terminal ileum of pigs. Similarly, the Mw of purified extractable carbohydrates in GR and RK bread was not significantly changed in the ileum. The AX bread resulted in the highest concentration of dissolved arabinoxylan in the ileum among all the breads that caused a substantial increased in ileal AX viscosity. Nevertheless, for none of the breads, the Mw of extractable carbohydrates was related neither to the bread extract nor ileal viscosity. PMID:23222731

  20. Conformational processing of oncogenic v-Src kinase by the molecular chaperone Hsp90

    PubMed Central

    Boczek, Edgar E.; Reefschläger, Lasse G.; Dehling, Marco; Struller, Tobias J.; Häusler, Elisabeth; Seidl, Andreas; Kaila, Ville R. I.; Buchner, Johannes

    2015-01-01

    Hsp90 is a molecular chaperone involved in the activation of numerous client proteins, including many kinases. The most stringent kinase client is the oncogenic kinase v-Src. To elucidate how Hsp90 chaperones kinases, we reconstituted v-Src kinase chaperoning in vitro and show that its activation is ATP-dependent, with the cochaperone Cdc37 increasing the efficiency. Consistent with in vivo results, we find that Hsp90 does not influence the almost identical c-Src kinase. To explain these findings, we designed Src kinase chimeras that gradually transform c-Src into v-Src and show that their Hsp90 dependence correlates with compactness and folding cooperativity. Molecular dynamics simulations and hydrogen/deuterium exchange of Hsp90-dependent Src kinase variants further reveal increased transitions between inactive and active states and exposure of specific kinase regions. Thus, Hsp90 shifts an ensemble of conformations of v-Src toward high activity states that would otherwise be metastable and poorly populated. PMID:26056257

  1. MOLSCAT: MOLecular SCATtering

    NASA Astrophysics Data System (ADS)

    Hutson, Jeremy M.; Green, Sheldon

    2012-06-01

    MOLSCAT is a FORTRAN code for quantum mechanical (coupled channel) solution of the nonreactive molecular scattering problem and was developed to obtain collision rates for molecules in the interstellar gas which are needed to understand microwave and infrared astronomical observations. The code is implemented for various types of collision partners. In addition to the essentially exact close coupling method several approximate methods, including the Coupled States and Infinite Order Sudden approximations, are provided.

  2. Mass transfer of SCWO processes: Molecular diffusion and mass transfer coefficients of inorganic nitrate species in sub- and supercritical water

    SciTech Connect

    Goemans, M.G.E.; Gloyna, E.F. [Univ. of Texas, Austin, TX (United States). Dept. of Civil Engineering; Buelow, S.J. [Los Alamos National Lab., NM (United States)

    1996-04-01

    Molecular diffusion coefficients of lithium-, sodium-, potassium-, cesium-, calcium-, and strontium nitrate in subcritical water were determined by analysis of Taylor dispersion profiles. Pressures ranged from 300 to 500 bar at temperatures ranging from 25{degrees}C to 300{degrees}C. The reported diffusion values were determined at infinite dilution. Molecular diffusion coefficients were 10 to 20 times faster in near-critical subcritical water than in water at ambient temperature and pressure (ATP). These findings implied that the diffusion rates were more liquid like than they were gas like, hence experimental results were correlated with diffusion models for liquids. The subcritical diffusion data presented in this work, and supercritical diffusion results published elsewhere were correlated with hydrodynamic diffusion equations. Both the Wilke-Chang correlation and the Stokes-Einstein equation yielded predictions within 10% of the experimental results if the structure of the diffusing species could be estimated. The effect of the increased diffusion rates on mass transfer rates in supercritical water oxidation applications was quantified, with emphasis on heterogeneous oxidation processes. This study and results published elsewhere showed that diffusion limited conditions are much more likely to be encountered in SCWO processes than commonly acknowledged.

  3. Calculations of diffusion and diffusion-limited processes in Ni3Al using accelerated molecular dynamics

    E-print Network

    Daw, Murray S.

    . This agrees well with experiment, except that the experiments show this structure setting in a temperatures of deformation mech- anisms in intermetallic alloys have revealed several interest- ing diffusion process controlling deformation of intermetallics [1]. However, several unusual processes have been

  4. Stochastic simulations of cargo transport by processive molecular motors Christian B. Korn,1

    E-print Network

    Schwarz, Ulrich

    kinesin-like processive motors. Our newly developed adhesive motor dynamics algorithm combines in sufficiently large numbers. Processive motors such as kinesins remain attached to their tracks for a relatively cytoskeletal motors predominantly act as transport engines for cargo particles, including vesicles, small

  5. Invisible Collisions

    NSDL National Science Digital Library

    Keri Hallau

    2009-01-01

    This activity relates an elastic collision to the change in a satellite’s or spacecraft’s speed and direction resulting from a planetary fly-by, often called a “gravity assist” maneuver. Both hands-on and online interactive methods are used to explore these topics.

  6. Study of Higgs boson production and its b-bbar decay in gamma-gamma processes in proton-nucleus collisions at the LHC

    E-print Network

    David d'Enterria; Jean-Philippe Lansberg

    2010-01-11

    We explore for the first time the possibilities to measure an intermediate-mass (mH = 115-140 GeV/c^2) Standard-Model Higgs boson in electromagnetic proton-lead (pPb) interactions at the CERN Large Hadron Collider (LHC) via its b-bbar decay. Using equivalent Weizsaecker-Williams photon fluxes and Higgs effective field theory for the coupling gamma-gamma --> H, we obtain a leading-order cross section of the order of 0.3 pb for exclusive Higgs production in elastic (pPb --> gamma-gamma --> p H Pb) and semielastic (pPb --> gamma-gamma --> Pb H X) processes at sqrt(s) = 8.8 TeV. After applying various kinematics cuts to remove the main backgrounds (gamma-gamma --> b-bbar and misidentified gamma-gamma-->q-qbar events), we find that a Higgs boson with mH = 120 GeV/c^2 could be observed in the b-bbar channel with a 3sigma-significance integrating 300 pb^-1 with an upgraded pA luminosity of 10^31 cm^-2s^-1. We also provide for the first time semielastic Higgs cross sections, along with elastic t-tbar cross sections, for electromagnetic pp, pA and AA collisions at the LHC.

  7. Particle-in-cell/Monte Carlo collision simulation of the ionization process of surface-wave plasma discharges resonantly excited by surface plasmon polaritons

    SciTech Connect

    Chen Zhaoquan [College of Electrical and Information Engineering, Anhui University of Science and Technology, Huainan, Anhui 232001 (China); State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian, Liaoning 116024 (China); State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Ye Qiubo [College of Electrical and Information Engineering, Anhui University of Science and Technology, Huainan, Anhui 232001 (China); Communications Research Centre, 3701 Carling Ave., Ottawa K2H 8S2 (Canada); Xia Guangqing [State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian, Liaoning 116024 (China); Hong Lingli; Hu Yelin; Zheng Xiaoliang; Li Ping [College of Electrical and Information Engineering, Anhui University of Science and Technology, Huainan, Anhui 232001 (China); Zhou Qiyan [College of Electrical and Information Engineering, Anhui University of Science and Technology, Huainan, Anhui 232001 (China); State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Hu Xiwei; Liu Minghai [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

    2013-03-15

    Although surface-wave plasma (SWP) sources have many industrial applications, the ionization process for SWP discharges is not yet well understood. The resonant excitation of surface plasmon polaritons (SPPs) has recently been proposed to produce SWP efficiently, and this work presents a numerical study of the mechanism to produce SWP sources. Specifically, SWP resonantly excited by SPPs at low pressure (0.25 Torr) are modeled using a two-dimensional in the working space and three-dimensional in the velocity space particle-in-cell with the Monte Carlo collision method. Simulation results are sampled at different time steps, in which the detailed information about the distribution of electrons and electromagnetic fields is obtained. Results show that the mode conversion between surface waves of SPPs and electron plasma waves (EPWs) occurs efficiently at the location where the plasma density is higher than 3.57 Multiplication-Sign 10{sup 17} m{sup -3}. Due to the effect of the locally enhanced electric field of SPPs, the mode conversion between the surface waves of SPPs and EPWs is very strong, which plays a significant role in efficiently heating SWP to the overdense state.

  8. First-principles molecular dynamics simulations of (sulfuric acid)1(dimethylamine)1 cluster formation

    NASA Astrophysics Data System (ADS)

    Loukonen, Ville; Bork, Nicolai; Vehkamäki, Hanna

    2013-05-01

    The clustering process (sulfuric acid) + (base)?(sulfuric acid)1(base)1 is of fundamental importance in the atmospheric new-particle formation. Especially interesting are the collisions where a proton transfer reaction can happen, as the reaction often leads to relatively strongly bound clusters. Here, we studied the clustering process of (sulfuric acid) + (dimethylamine) ? (sulfuric acid)1(dimethylamine)1 using first-principles molecular dynamics simulations. The collision of the two molecules was simulated starting with various spatial orientations and the evolution of the cluster was followed in the NVE ensemble. The simulations suggest that the proton transfer reaction takes place regardless of the intial collision orientation. However, due to the energy released in the process, the newly-formed cluster is not able to reach the minimun energy configuration, which might affect the following growth processes.

  9. Molecular configurations in the droplet detachment process of a complex liquid

    NASA Astrophysics Data System (ADS)

    Sattler, R.; Kityk, A.; Wagner, C.

    2007-05-01

    We studied the microscopic polymer conformations in the droplet detachment process of an elastic semidilute polyelectrolytic xanthan solution by measuring the instantaneous birefringence. As in earlier studies, we observe the suppression of the finite time singularity of the pinch-off process and the occurrence of an elastic filament. Our microscopic measurements reveal that the relatively stiff xanthan molecules are already significantly prestretched to about 90% of their final extension at the moment the filament appears. At later stages of the detachment process, we find evidence of a concentration enhancement due to the elongational flow.

  10. Molecular configurations in a droplet detachment process of a complex liquid

    E-print Network

    Sattler, R; Wagner, C

    2006-01-01

    We studied the microscopic polymer conformations in the droplet detachment process of an elastic semi-dilute polyelectrolytic Xanthan solution by measuring the instantaneous birefringence. As in earlier studies, we observe the suppression of the finite time singularity of the pinch-off process and the occurrence of an elastic filament. Our microscopic measurements reveal that the relatively stiff Xanthan molecules are already significantly pre-stretched to about 90 % of their final extension at the moment the filament appears. At later stages of the detachment process, we find evidence of a concentration enhancement due to the elongational flow.

  11. Operational Collision Avoidance

    NASA Technical Reports Server (NTRS)

    Guit, Bill

    2015-01-01

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

  12. Chemical models of interstellar gas-grain processes. III - Molecular depletion in NGC 2024

    NASA Astrophysics Data System (ADS)

    Charnley, S. B.

    1997-11-01

    The chemistry arising from the exchange of molecules between dust and gas in ultradense cool cores is described. Under certain assumptions concerning molecule-grain binding energies and dust temperature, slight warming of cold dust grains can induce selective desorption of mantle volatiles. It is theoretically possible for ultradense cores to become depleted in CO but to remain abundant in N2 and so be relatively rich in nitrogen-bearing molecules. This effect may explain the apparent depletion of CO and the presence of ammonia in several cores within the NGC 2024 cloud. The theory implies that heavy metal atoms should be almost entirely absent from the gas phase of high-density cores, and that a mantle of CO, O2, N2 and other weakly bound molecules should cover water ice mantles, forming a 'volatile crust'. Molecular observations are suggested which will allow a test of this model.

  13. SKA studies of nearby galaxies: star-formation, accretion processes and molecular gas across all environments

    NASA Astrophysics Data System (ADS)

    Beswick, R.; Brinks, E.; Perez-Torres, M.; Richards, A. M. S.; Aalto, S.; Alberdi, A.; Argo, M. K.; van Bemmel, I.; Conway, J. E.; Dickinson, C.; Fenech, D.; Gray, M. D.; Kloeckner, H. R.; Murphy, E.; Muxlow, T. W. B.; Peel, M. W.; Rushton, A.; Schinnerer, E.

    The SKA will be a transformational instrument in the study of our local Universe. In particular, by virtue of its high sensitivity (both to point sources and diffuse low surface brightness emission), angular resolution and the frequency ranges covered, the SKA will undertake a very wide range of astrophysical research in the field of nearby galaxies. By surveying vast numbers of nearby galaxies of all types with $\\mu$Jy sensitivity and sub-arcsecond angular resolutions at radio wavelengths, the SKA will provide the cornerstone of our understanding of star-formation and accretion activity in the local Universe. In this chapter we outline the key continuum and molecular line science areas where the SKA, both during phase-1 and when it becomes the full SKA, will have a significant scientific impact.

  14. Investigations of the structures and molecular processes in polar Langmuir-Blodgett superlattices

    SciTech Connect

    Walsh, S.P.

    1992-01-01

    The principle focus of this research was to prepare polar ultrathin films using an alternating monolayer adaptation of the traditional Langmuir-Blodgett (LB) technique, and to investigate the role that structure (physical and chemical) plays upon the outward manifestation of this internal polarization: pyroelectricity. A specially designed film trough was prepared such that two separate monolayers could be independently manipulated. Alternating bilayer assemblies were be prepared by translating the deposition substrate above and below the surface of the floating monolayers as needed without disruption of the stability of the Langmuir films. Long chain diacetylenic acid and amine amphiphiles were prepared. The diacetylenic amine compound was thoroughly investigated at the gas-water interface. Common conditions of monolayer stability for the acid/amine amphiphile pairs and the concept of isoelectric deposition were developed. Homogeneous and heterogeneous LB assemblies were prepared. Chemical and structural investigations were performed using a combination of x-ray diffraction and FTIR spectroscopic techniques. The melting temperatures of the unpolymerized structures were dependent on organization and ionization of the individual molecules. Solid state polymerization of the diacetylenic multilayers was found to somewhat disrupt the organization of the assemblies, but to suppress monolayer melting. The pyroelectric response in such structures was molecular, not chemical, in nature with the polarization changing as a result of molecular librations. Electrical characterizations of the assemblies showed the thin films to behave as good dielectrics. Pyroelectric responses of the ionized assemblies containing free counter ions were unexpectedly low. It was felt that the low values were due to either a damping of the librational moments by the presence of the counter ions, or that the mobility of these ions offset the librational dipoles of these polar groups.

  15. Competition of coalescence and 'fireball' processes in nonequilibrium emission of light charged particles from p+Au collisions

    SciTech Connect

    Budzanowski, A.; Kistryn, M.; Kliczewski, St.; Kozik, E. [H. Niewodniczanski Institute of Nuclear Physics PAN, Radzikowskiego 152, PL-31342 Krakow (Poland); Fidelus, M.; Jarczyk, L.; Kamys, B.; Kistryn, St.; Kowalczyk, A.; Magiera, A.; Rudy, Z.; Wojciechowski, M. [M. Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, PL-30059 Krakow (Poland); Filges, D.; Goldenbaum, F.; Machner, H. [Institut fuer Kernphysik, Forschungszentrum Juelich, D-52425 Juelich (Germany); Hodde, H. [Institut fuer Strahlen- und Kernphysik, Bonn University, D-53121 Bonn (Germany); Kulessa, P.; Pysz, K.; Siudak, R. [H. Niewodniczanski Institute of Nuclear Physics PAN, Radzikowskiego 152, PL-31342 Krakow (Poland); Institut fuer Kernphysik, Forschungszentrum Juelich, D-52425 Juelich (Germany); Piskor-Ignatowicz, B. [M. Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, PL-30059 Krakow (Poland); Institut fuer Kernphysik, Forschungszentrum Juelich, D-52425 Juelich (Germany)

    2008-08-15

    The energy and angular dependence of the double differential cross sections d{sup 2}{sigma}/d{omega}dE were measured for p,d,t,{sup 3,4,6}He, {sup 6,7,8,9}Li, {sup 7,9,10}Be, and {sup 10,11,12}B isotopes produced in reactions of 1.2- and 1.9-GeV protons on a Au target. The beam energy dependence of the data, supplemented by the cross sections from a previous experiment at 2.5 GeV, is very smooth. The shape of the spectra and angular distributions do not change significantly in the beam energy range from 1.2 to 2.5 GeV. However, the absolute value of the cross sections increases for all ejectiles. The intermediate mass fragment spectra and their angular distributions are very well reproduced by a phenomenological model of two emitting, moving sources, with parameters smoothly varying with energy. The double differential cross sections for light charged particles were analyzed in the framework of the microscopic model calculations of intranuclear cascade, including the coalescence of nucleons and a statistical model for evaporation of particles from excited residual nuclei. However, the energy and angular dependencies of the data agree with neither predictions of the microscopic intranuclear cascade calculations for protons nor the coalescence calculations for other light charged particles. A very good description of the data is achieved by the phenomenological inclusion of the emission of light charged particles from a 'fireball' (i.e., a fast and hot moving source). It was found that the nonequilibrium processes are very important for the production of light charged particles. They exhaust 40%-80% of the total cross section--depending on the emitted particles. Coalescence and fireball emission yield comparable contributions to the cross sections with the exception of the {sup 3}He data where coalescence clearly dominates. For all light charged particles, the ratio of nonequilibrium processes to processes proceeding through a phase of statistical equilibrium does not change significantly between the beam energies of 1.2 and 2.5 GeV.

  16. Molecular Architecture of the Human Pre-mRNA 3? Processing Complex

    Microsoft Academic Search

    Yongsheng Shi; Dafne Campigli Di Giammartino; Derek Taylor; Ali Sarkeshik; William J. Rice; John R. Yates III; Joachim Frank; James L. Manley

    2009-01-01

    SUMMARY Pre-mRNA 30 end formation is an essential step in eukaryotic gene expression. Over half of human genes produce alternatively polyadenylated mRNAs, suggesting that regulated polyadenylation is an important mechanism for posttranscriptional gene control. Although a number of mammalian mRNA 30 processing factors have been identified, the full protein composition of the 30 processing machinery has not been determined, and

  17. Molecular characterization of the immune system: emergence of proteins, processes, and domains

    Microsoft Academic Search

    Csaba Ortutay; Markku Siermala; Mauno Vihinen

    2007-01-01

    Many genes and proteins are required to carry out the processes of innate and adaptive immunity. For many studies, including\\u000a systems biology, it is necessary to have a clear and comprehensive definition of the immune system, including the genes and\\u000a proteins that take part in immunological processes. We have identified and cataloged a large portion of the human immunology-related\\u000a genes,

  18. Field-based evidence of sedimentary and tectonic processes related to continental collision: the Early Cenozoic basins of Central Eastern Turkey 

    E-print Network

    Booth, Matthew Graham

    2013-07-01

    Turkey is widely accepted to have formed from a collage of microcontinents that rifted from the northern margin of Gondwana and assembled from the Mesozoic to Mid Cenozoic in response to the closure, collision and suturing ...

  19. Molecular dynamics study of dynamic and structural properties of supercooled liquid and glassy iron in the rapid-cooling processes

    NASA Astrophysics Data System (ADS)

    Cao, Qi-Long; Huang, Duo-Hui; Yang, Jun-Sheng; Wan, Min-Jie; Wang, Fan-Hou

    2014-10-01

    Molecular dynamics simulations were applied to study the dynamic and structural properties of supercooled liquid and glassy iron in the rapid-cooling processes. The mean-square displacement and the non-Gaussian parameter were used to describe the dynamic properties. The evolution of structural properties was investigated using the pair distribution functions and bond-angle distribution functions. Results for dynamic and structural relaxations indicate that the dynamic features are consistently correlated with the structure evolution, and there are three temperature regions as the temperature decreases: (1) at higher temperatures (1500 K, 1300 K, and 1100 K), the system remains in the liquid characteristics during the overall relaxation process. (2) At medial temperatures (1050 K, 900 K, and 700 K), a fast ?-relaxation is followed by a much slower ?-relaxation. There is a little change in the structural properties in the ?-relaxation region, while major configuration rearrangements occurred in the ?-relaxation range and the crystallization process was completed at the end of ?-relaxation region. (3) At lower temperature (500 K), the system shows glassy characteristics during the overall relaxation process. In addition, the melting temperature, glass transition temperature and diffusion coefficients of supercooled liquid iron are also computed.

  20. Inelastic vector soliton collisions: a lattice-based quantum representation: One contribution of 21 to a Theme 'Connecting scales: micro, meso and macro processes'

    Microsoft Academic Search

    George Vahala; Linda Vahala; Jeffrey Yepez

    2004-01-01

    Lattice-based quantum algorithms are developed for vector soliton collisions in the completely integrable Manakov equations, a system of coupled nonlinear Schrödinger (coupled-NLS) equations that describe the propagation of pulses in a birefringent fibre of unity cross-phase modulation factor. Under appropriate conditions the exact 2-soliton vector solutions yield inelastic soliton collisions, in agreement with the theoretical predictions of Radhakrishnan et al.

  1. Molecular dynamic simulations of the elastic and inelastic surface scattering of nanoparticles.

    PubMed

    Stace, Anthony J

    2014-02-21

    Molecular dynamics calculations have been undertaken to simulate the collision of a solid, rotating nanoparticle with a planar, two-dimensional surface at thermal velocities (linear and rotational) equivalent to 500 K. During the course of a collision, mechanisms have been introduced into the simulation process that allows for the dissipation of kinetic energy and for components of linear and angular velocity to couple. Although previous studies of particle-particle collisions have used a similar energy dissipation procedure, in these first calculations on particle-surface collisions, it is found that the mechanism actually facilitates the movement of particles across a surface. It is also shown that the direction of travel of particles on a surface is strongly influenced by their rotational motion. PMID:24399047

  2. Probing GPDs in ultraperipheral collisions

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  3. Functional genomics approach for identification of molecular processes underlying neurodegenerative disorders in prion diseases.

    PubMed

    Basu, Urmila; Guan, Le Luo; Moore, Stephen S

    2012-08-01

    Prion diseases or transmissible spongiform encephalopathies (TSEs) are infectious neurodegenerative disorders leading to death. These include Cresutzfeldt-Jakob disease (CJD), familial, sporadic and variant CJD and kuru in humans; and animal TSEs include scrapie in sheep, bovine spongiform encephalopathy (BSE) in cattle, chronic wasting disease (CWD) of mule deer and elk, and transmissible mink encephalopathy. All these TSEs share common pathological features such as accumulation of mis-folded prion proteins in the central nervous system leading to cellular dysfunction and cell death. It is important to characterize the molecular pathways and events leading to prion induced neurodegeneration. Here we discuss the impact of the functional genomics approaches including microarrays, subtractive hybridization and microRNA profiling in elucidating transcriptional cascades at different stages of disease. Many of these transcriptional changes have been observed in multiple neurodegenerative diseases which may aid in identification of biomarkers for disease. A comprehensive characterization of expression profiles implicated in neurodegenerative disorders will undoubtedly advance our understanding on neuropathology and dysfunction during prion disease and other neurodegenerative disorders. We also present an outlook on the future work which may focus on analysis of structural genetic variation, genome and transcriptome sequencing using next generation sequencing with an integrated approach on animal and human TSE related studies. PMID:23372423

  4. Molecular Dynamics of Generation Process of Double-Walled Carbon Nanotubes from Peapods

    E-print Network

    Maruyama, Shigeo

    extensively investigated [6] due to its potential for more large-scale production of SWNTs. We have developed a high-purity production technique for SWNTs using a low-temperature alcohol CCVD method [7-11]. Smith et selective synthesis of DWNTs. For a better understanding of formation mechanism of DWNTs in these processes

  5. Molecular characterization of Ara h 1 before and after thermal processing.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heating and other processing techniques can alter food allergens depending upon the method and matrix involved. The increased allergenicity of Ara h 1 protein isolated from roasted peanuts is thought to be caused, at least in part, by chemical modifications. To identify what specific modifications a...

  6. Quantum photonic base states: concept and molecular modeling. Managing chemical process descriptions beyond semi-classic schemes.

    PubMed

    Tapia, O

    2014-02-01

    Four fundamental aspects bearing on molecular simulations are considered: (1) A different perception of quantum states; mappings from abstract Hilbert space down to laboratory levels; (2) Introduction of photon number Fock space; photonic bases tie together matter-to-photon quantum states: coherent photon-matter states. (3) Chemical tenets framed via photonic-base-states incorporating and defining multi-partite basis sets. (4) Entanglement provides a quantum-physical view connectable to a chemical bond concept. Amplitude modulations of physical quantum states realize (express) chemical change; Feshbach resonance states as a royal path to handle an equivalent to bond breaking/forming by coupling continuum-to-discrete base states. We observe that, for driving chemical processes within photonic framework, microwaves enter not only as heating sources but can act naturally in a quantum physical manner as causes for catalytic activity. PMID:24526381

  7. Mathematical model and calculation algorithm of micro and meso levels of separation process of gaseous mixtures in molecular sieves

    NASA Astrophysics Data System (ADS)

    Umarova, Zhanat; Botayeva, Saule; Yegenova, Aliya; Usenova, Aisaule

    2015-05-01

    In the given article, the main thermodynamic aspects of the issue of modeling diffusion transfer in molecular sieves have been formulated. Dissipation function is used as a basic notion. The differential equation, connecting volume flow with the change of the concentration of catchable component has been derived. As a result, the expression for changing the concentration of the catchable component and the coefficient of membrane detecting has been received. As well, the system approach to describing the process of gases separation in ultra porous membranes has been realized and micro and meso-levels of mathematical modeling have been distinguished. The non-ideality of the shared system is primarily taken into consideration at the micro-level and the departure from the diffusion law of Fick has been taken into account. The calculation method of selectivity considering fractal structure of membranes has been developed at the meso level. The calculation algorithm and its software implementation have been suggested.

  8. SCC-DFTB Energy Barriers for Single and Double Proton Transfer Processes in the Model Molecular Systems Malonaldehyde and Porphycene

    SciTech Connect

    Walewski, L. [Warsaw University; Krachtus, D [University of Heidelberg; Fischer, S. [University of Heidelberg; Smith, Jeremy C [ORNL; Bala, P. [Institute of Physics, Nicolaus Copernicus University, Toru?, Poland; Lesyng, B. [Warsaw University

    2005-09-01

    Self-consistent charge-density functional tight-binding SCC-DFTB is a computationally efficient method applicable to large (bio)molecular systems in which (bio)chemical reactions may occur. Among these reactions are proton transfer processes. This method, along with more advanced ab initio techniques, is applied in this study to compute intramolecular barriers for single and double proton transfer processes in the model systems, malonaldehyde and porphycene, respectively. SCC-DFTB is compared with experimental data and higher-level ab initio calculations. For malonaldehyde, the SCC-DFTB barrier height is 3.1 kcal/mol in vacuo and 4.2 kcal/mol in water solution. In the case of porphycene, the minimum energy pathways for double intramolecular proton transfer were determined using the conjugate peak refinement (CPR) method. Six isomers of porphycene were ordered according to energy. The only energetically allowed pathway was found to connect two symmetrical trans states via an unstable cis-A isomer. The SCC-DFTB barrier heights are 11.1 kcal/mol for the trans-cis-A process, and 7.4 kcal/mol for the reverse cis-A-trans one with the energy difference of 3.7 kcal/mol between the trans- and cis-A states. The method provides satisfactory energy results when compared with reference ab initio and experimental data.

  9. Selectivity Principle of the Ligand Escape Process from a Two-Gate Tunnel in Myoglobin: Molecular Dynamics Simulation

    NASA Astrophysics Data System (ADS)

    Sheu, Sheh-Yi

    2008-02-01

    We proposed a selectivity principle for the ligand escape process from two fluctuating bottlenecks in a cavity with a multi-gate inside a myoglobin pocket. Our analytical theory proposed a fluctuating bottleneck model for a Brownian particle passing through two gates on a cavity surface of an enzyme protein and has determined the escape rate in terms of the time-dependent gate function and the competition effect. It illustrated that with two (or more than two) gates on a cavity surface the gate modulation, which is controlled by protein fluctuation, dominates the ligand escape pathway. We have performed a molecular dynamics simulation to investigate the selectivity principle of the ligand escape process from two-gate tunnel in myoglobin. The simulation results confirm our theoretical conjecture. It indicates that the escape process is actually entropy driven and the ligand escape pathway is chosen via the gate modulation. This suggests an interesting intrinsic property, which is that the oxy-myoglobin tertiary structure is favorable to the departure of the ligand from one direction rather than through a biased random walk.

  10. Molecular recognition: comparative study of a tunable host-guest system by using a fluorescent model system and collision-induced dissociation mass spectrometry on dendrimers.

    PubMed

    Pittelkow, Michael; Nielsen, Christian B; Broeren, Maarten A C; van Dongen, Joost L J; van Genderen, Marcel H P; Meijer, E W; Christensen, Jørn B

    2005-08-19

    Host-guest interactions between the periphery of adamantylurea-functionalized dendrimers (host) and ureido acetic acid derivatives (guest) were shown to be specific, strong and spatially well-defined. The binding becomes stronger when using phosphonic or sulfonic acid derivatives. In the present work we have quantified the binding constants for the host-guest interactions between two different host motifs and six different guest molecules. The host molecules, which resemble the periphery of a poly(propylene imine) dendrimer, have been fitted with an anthracene-based fluorescent probe. The two host motifs differ in terms of the length of the spacer between a tertiary amine and two ureido functionalities. The guest molecules all contain an acidic moiety (either a carboxylic acid, a phosphonic acid, or a sulfonic acid) and three of them also contain an ureido moiety capable of forming multiple hydrogen bonds to the hosts. The binding constants for all 12 host-guest complexes have been determined by using fluorescence titrations by monitoring the increase in fluorescence of the host upon protonation by the addition of the guest. The binding constants could be tuned by changing the design of the acidic part of the guest. The formation of hydrogen bonds gives, in all cases, higher association constants, demonstrating that the host is more than a proton sensor. The host with the longer spacer (propyl) shows higher association constants than the host with the shorter spacer (ethyl). The gain in association constants are higher when the urea function is added to the guests for the host with the longer spacer, indicating a better fit. Collision-induced dissociation mass spectrometry (CID-MS) is used to study the stability of the six motifs using the corresponding third generation dendrimer. A similar trend is found when the six different guests are compared. PMID:15991204

  11. Molecular dynamics simulation of cytochrome c3: studying the reduction processes using free energy calculations.

    PubMed Central

    Soares, C M; Martel, P J; Mendes, J; Carrondo, M A

    1998-01-01

    The tetraheme cytochrome c3 from Desulfovibrio vulgaris Hildenborough is studied using molecular dynamics simulation studies in explicit solvent. The high heme content of the protein, which has its core almost entirely made up of c-type heme, presents specific problems in the simulation. Instability in the structure is observed in long simulations above 1 ns, something that does not occur in a monoheme cytochrome, suggesting problems in heme parametrization. Given these stability problems, a partially restrained model, which avoids destruction of the structure, was created with the objective of performing free energy calculations of heme reduction, studies that require long simulations. With this model, the free energy of reduction of each individual heme was calculated. A correction in the long-range electrostatic interactions of charge groups belonging to the redox centers had to be made in order to make the system physically meaningful. Correlation is obtained between the calculated free energies and the experimental data for three of four hemes. However, the relative scale of the calculated energies is different from the scale of the experimental free energies. Reasons for this are discussed. In addition to the free energy calculations, this model allows the study of conformational changes upon reduction. Even if the precise details of the structural changes that take place in this system upon individual heme reduction are probably out of the reach of this study, it appears that these structural changes are small, similarly to what is observed for other redox proteins. This does not mean that their effect is minor, and one example is the conformational change observed in propionate D from heme I when heme II becomes reduced. A motion of this kind could be the basis of the experimentally observed cooperativity effects between heme reduction, namely positive cooperativity. PMID:9545034

  12. Controlling charge carrier injection in solution processed pentacene transistors by molecular engineering of the electrodes

    Microsoft Academic Search

    Sangameshwar Rao Saudari; Cherie Kagan

    2009-01-01

    We present the device performance of pentacene transistors fabricated from a solution deposited precursor. The bottom-contact pentacene transistors are fabricated by spin-coating N-sulfinylacetamidopentacene precursor followed by thermal conversion of the precursor into pentacene. Hole mobilities >0.1 cm^2\\/Vs and Ion\\/Ioff>10^5 are repeatedly achieved by this process. The metal-semiconductor interface in organic transistors plays a very important role in charge carrier injection

  13. The changes of membrane performance with polyamide molecular structure in the reverse osmosis process

    Microsoft Academic Search

    C. K Kim; J. H Kim; I. J Roh; J. J Kim

    2000-01-01

    In order to develop high performance membranes for the reverse osmosis process, thin film composite membranes were prepared by the interfacial polymerization with various acyl chloride solutions and amine solutions containing poly(m-aminostyrene), (PmAS). PmAS was prepared by reducing poly(m-nitrostyrene) that was obtained by the free radical polymerization of 3-nitrostyrene. The results related to changes in the membrane performance with interfacial

  14. ARTICLE Molecular Dynamic Simulation on the Absorbing Process of Isolating and Coating of ?-olefin Drag Reducing Polymer

    NASA Astrophysics Data System (ADS)

    Li, Bing; Sheng, Xiang; Xing, Wen-guo; Dong, Gui-lin; Liu, Yong-jun; Zhang, Chang-qiao; Chen, Xiang-jun; Zhou, Ning-ning; Qin, Zhan-bo

    2010-12-01

    The absorbing process in isolating and coating process of ?-olefin drag reducing polymer was studied by molecular dynamic simulation method, on basis of coating theory of ?-olefin drag reducing polymer particles with polyurethane as coating material. The distributions of sodium laurate, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate on the surface of ?-olefin drag reducing polymer particles were almost the same, but the bending degrees of them were obviously different. The bending degree of SLA molecules was greater than those of the other two surfactant molecules. Simulation results of absorbing and accumulating structure showed that, though hydrophobic properties of surfactant molecules were almost the same, water density around long chain sulfonate sodium was bigger than that around alkyl sulfate sodium. This property goes against useful absorbing and accumulating on the surface of ?-olefin drag reducing polymer particles; simulation results of interactions of different surfactant and multiple hydroxyl compounds on surface of particles showed that, interactions of different surfactant and one kind of multiple hydroxyl compound were similar to those of one kind of surfactant and different multiple hydroxyl compounds. These two contrast types of interactions also exhibited the differences of absorbing distribution and closing degrees to surface of particles. The sequence of closing degrees was derived from simulation; control step of addition polymerization interaction in coating process was absorbing mass transfer process, so the more closed to surface of particle the multiple hydroxyl compounds were, the easier interactions with isocyanate were. Simulation results represented the compatibility relationship between surfactant and multiple hydroxyl compounds. The isolating and coating processes of ?-olefin drag reducing polymer were further understood on molecule and atom level through above simulation research, and based on the simulation, a referenced theoretical basis was provided for practical optimal selection and experimental preparation of ?-olefin drag reducing polymer particles suspension isolation agent.

  15. Combined papillary and mucoepidermoid carcinoma of the thyroid gland: a possible collision tumor diagnosed on fine-needle cytology. Report of a case with immunocytochemical and molecular correlations.

    PubMed

    Fulciniti, Franco; Vuttariello, Emilia; Calise, Celeste; Monaco, Mario; Pezzullo, Luciano; Chiofalo, Maria Grazia; Di Gennaro, Francesca; Malzone, Maria Gabriella; Campanile, Anna Cipolletta; Losito, Nunzia Simona; Botti, Gerardo; Chiappetta, Gennaro

    2015-05-01

    Fine-needle cytology (FNC) is frequently used to diagnose thyroid nodules discovered by palpation or imaging studies. Molecular tests on FNC material may increase its diagnostic accuracy. We report a case of a classic papillary thyroid carcinoma combined with a mucoepidermoid carcinoma correctly identified on FNC. The papillary component had a classic immunophenotype (CK19+, TTF1+), while the mucoepidermoid one was only focally CK19+. Point mutations (BRAF and RAS) and rearrangements (RET/PTC) of the papillary component have been also investigated on FNC samples, with resulting concurrent rearrangements of RET/PTC1 and RET/PTC3, but no point mutations. The histogenesis of combined papillary and mucoepidermoid carcinoma of the thyroid still remains partly unsettled, and further genomic studies are needed to shed some more light on this peculiar neoplasm. PMID:25771987

  16. Integrated Collision Avoidance System for Air Vehicle

    NASA Technical Reports Server (NTRS)

    Lin, Ching-Fang (Inventor)

    2013-01-01

    Collision with ground/water/terrain and midair obstacles is one of the common causes of severe aircraft accidents. The various data from the coremicro AHRS/INS/GPS Integration Unit, terrain data base, and object detection sensors are processed to produce collision warning audio/visual messages and collision detection and avoidance of terrain and obstacles through generation of guidance commands in a closed-loop system. The vision sensors provide more information for the Integrated System, such as, terrain recognition and ranging of terrain and obstacles, which plays an important role to the improvement of the Integrated Collision Avoidance System.

  17. Ensemble velocity of non-processive molecular motors with multiple chemical states

    E-print Network

    Andrej Vilfan

    2014-09-27

    We study the ensemble velocity of non-processive motor proteins, described with multiple chemical states. In particular, we discuss the velocity as a function of ATP concentration. Even a simple model which neglects the strain-dependence of transition rates, reverse transition rates and nonlinearities in the elasticity can show interesting functional dependencies, which deviate significantly from the frequently assumed Michaelis-Menten form. We discuss how the oder of events in the duty cycle can be inferred from the measured dependence. The model also predicts the possibility of velocity reversal at a certain ATP concentration if the duty cycle contains several conformational changes of opposite directionalities.

  18. Synchronization of elastically coupled processive molecular motors and regulation of cargo transport.

    PubMed

    Kohler, Felix; Rohrbach, Alexander

    2015-01-01

    The collective work of motor proteins plays an important role in cellular transport processes. Since measuring intermotor coupling and hence a comparison to theoretical predictions is difficult, we introduce the synchronization as an alternative observable for motor cooperativity. This synchronization can be determined from the ratio of the mean times of motor resting and stepping. Results from a multistate Markov chain model and Brownian dynamics simulations, describing the elastically coupled motors, coincide well. Our model can explain the experimentally observed effect of strongly increased transport velocities and powers by the synchronization and coupling of myosin V and kinesin I. PMID:25679637

  19. Analysis of discharge characteristics of the inertial electrostatic confinement fusion using a particle code with Monte Carlo collision scheme

    Microsoft Academic Search

    Takuya Sakai; Kazuyuki Noborio; Y. Yamamoto

    2002-01-01

    In this paper, we study the mechanism of a self-maintaining discharge in the Inertial Electrostatic Confinement Fusion (IECF) with D2 gas. We developed a 1-D particle code with Monte Carlo collision scheme including atomic and molecular processes of ion, energetic neutral, and electron impact based on the PDS-1 code. Also we developed the energy dependent transparency model of the cathode,

  20. Cross sections for 14-eV e-H{sub 2} resonant collisions: Dissociative electron attachment

    SciTech Connect

    Celiberto, R. [Department of Water Engineering and Chemistry, Polytechnic of Bari, 70125 Bari (Italy); Janev, R. K. [Macedonian Academy of Sciences and Arts, 1000 Skopje (Macedonia, The Former Yugoslav Republic of); Wadehra, J. M. [Department of Physics, Wayne State University, Detroit, Michigan 48202 (United States); Laricchiuta, A. [Institute of Inorganic Methodologies and Plasmas, CNR, 70125 Bari (Italy)

    2009-07-15

    The dissociative electron attachment (DEA) process in electron-H{sub 2} molecule collisions, involving the {sup 2}{sigma}{sub g}{sup +} excited electronic Rydberg state of molecular hydrogen ion H{sub 2}{sup -}, is investigated theoretically. The DEA cross section has been calculated within the local complex potential approximation. The convoluted cross section, which presents a peak located at the incident energy of about 14 eV, compares favorably with available experimental data.

  1. Differential scattering cross sections for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2. [for atmospheric processes modeling

    NASA Technical Reports Server (NTRS)

    Newman, J. H.; Smith, K. A.; Stebbings, R. F.; Chen, Y. S.

    1985-01-01

    This paper reports the first results of an experimental program established to provide cross section data for use in modeling various atmospheric processes. Absolute cross sections, differential in the scattering angle, have been measured for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2 at laboratory scattering angles between 0.1 deg and 5 deg. The results are the sums of cross sections for elastic and inelastic scattering of helium atoms; charged collision products are not detected. Integration of the differential cross section data yields integral cross sections consistent with measurements by other workers. The apparatus employs a position-sensitive detector for both primary and scattered particles and uses a short target cell with a large exit aperture to ensure a simple and well-defined apparatus geometry.

  2. Molecular recognition and substrate mimicry drive the electron-transfer process between MIA40 and ALR

    PubMed Central

    Banci, Lucia; Bertini, Ivano; Calderone, Vito; Cefaro, Chiara; Ciofi-Baffoni, Simone; Gallo, Angelo; Kallergi, Emmanouela; Lionaki, Eirini; Pozidis, Charalambos; Tokatlidis, Kostas

    2011-01-01

    Oxidative protein folding in the mitochondrial intermembrane space requires the transfer of a disulfide bond from MIA40 to the substrate. During this process MIA40 is reduced and regenerated to a functional state through the interaction with the flavin-dependent sulfhydryl oxidase ALR. Here we present the mechanistic basis of ALR–MIA40 interaction at atomic resolution by biochemical and structural analyses of the mitochondrial ALR isoform and its covalent mixed disulfide intermediate with MIA40. This ALR isoform contains a folded FAD-binding domain at the C-terminus and an unstructured, flexible N-terminal domain, weakly and transiently interacting one with the other. A specific region of the N-terminal domain guides the interaction with the MIA40 substrate binding cleft (mimicking the interaction of the substrate itself), without being involved in the import of ALR. The hydrophobicity-driven binding of this region ensures precise protein–protein recognition needed for an efficient electron transfer process. PMID:21383138

  3. New Insight into the Colonization Processes of Common Voles: Inferences from Molecular and Fossil Evidence

    PubMed Central

    Tougard, Christelle; Renvoisé, Elodie; Petitjean, Amélie; Quéré, Jean-Pierre

    2008-01-01

    Elucidating the colonization processes associated with Quaternary climatic cycles is important in order to understand the distribution of biodiversity and the evolutionary potential of temperate plant and animal species. In Europe, general evolutionary scenarios have been defined from genetic evidence. Recently, these scenarios have been challenged with genetic as well as fossil data. The origins of the modern distributions of most temperate plant and animal species could predate the Last Glacial Maximum. The glacial survival of such populations may have occurred in either southern (Mediterranean regions) and/or northern (Carpathians) refugia. Here, a phylogeographic analysis of a widespread European small mammal (Microtus arvalis) is conducted with a multidisciplinary approach. Genetic, fossil and ecological traits are used to assess the evolutionary history of this vole. Regardless of whether the European distribution of the five previously identified evolutionary lineages is corroborated, this combined analysis brings to light several colonization processes of M. arvalis. The species' dispersal was relatively gradual with glacial survival in small favourable habitats in Western Europe (from Germany to Spain) while in the rest of Europe, because of periglacial conditions, dispersal was less regular with bottleneck events followed by postglacial expansions. Our study demonstrates that the evolutionary history of European temperate small mammals is indeed much more complex than previously suggested. Species can experience heterogeneous evolutionary histories over their geographic range. Multidisciplinary approaches should therefore be preferentially chosen in prospective studies, the better to understand the impact of climatic change on past and present biodiversity. PMID:18958287

  4. Potential for spin-based information processing in a thin-film molecular semiconductor

    NASA Astrophysics Data System (ADS)

    Warner, Marc; Din, Salahud; Tupitsyn, Igor S.; Morley, Gavin W.; Stoneham, A. Marshall; Gardener, Jules A.; Wu, Zhenlin; Fisher, Andrew J.; Heutz, Sandrine; Kay, Christopher W. M.; Aeppli, Gabriel

    2013-11-01

    Organic semiconductors are studied intensively for applications in electronics and optics, and even spin-based information technology, or spintronics. Fundamental quantities in spintronics are the population relaxation time (T1) and the phase memory time (T2): T1 measures the lifetime of a classical bit, in this case embodied by a spin oriented either parallel or antiparallel to an external magnetic field, and T2 measures the corresponding lifetime of a quantum bit, encoded in the phase of the quantum state. Here we establish that these times are surprisingly long for a common, low-cost and chemically modifiable organic semiconductor, the blue pigment copper phthalocyanine, in easily processed thin-film form of the type used for device fabrication. At 5K, a temperature reachable using inexpensive closed-cycle refrigerators, T1 and T2 are respectively 59ms and 2.6?s, and at 80K, which is just above the boiling point of liquid nitrogen, they are respectively 10?s and 1?s, demonstrating that the performance of thin-film copper phthalocyanine is superior to that of single-molecule magnets over the same temperature range. T2 is more than two orders of magnitude greater than the duration of the spin manipulation pulses, which suggests that copper phthalocyanine holds promise for quantum information processing, and the long T1 indicates possibilities for medium-term storage of classical bits in all-organic devices on plastic substrates.

  5. A model for energy transfer in collisions of atoms with highly excited molecules.

    PubMed

    Houston, Paul L; Conte, Riccardo; Bowman, Joel M

    2015-05-21

    A model for energy transfer in the collision between an atom and a highly excited target molecule has been developed on the basis of classical mechanics and turning point analysis. The predictions of the model have been tested against the results of trajectory calculations for collisions of five different target molecules with argon or helium under a variety of temperatures, collision energies, and initial rotational levels. The model predicts selected moments of the joint probability distribution, P(Jf,?E) with an R(2) ? 0.90. The calculation is efficient, in most cases taking less than one CPU-hour. The model provides several insights into the energy transfer process. The joint probability distribution is strongly dependent on rotational energy transfer and conservation laws and less dependent on vibrational energy transfer. There are two mechanisms for rotational excitation, one due to motion normal to the intermolecular potential and one due to motion tangential to it and perpendicular to the line of centers. Energy transfer is found to depend strongly on the intermolecular potential and only weakly on the intramolecular potential. Highly efficient collisions are a natural consequence of the energy transfer and arise due to collisions at "sweet spots" in the space of impact parameter and molecular orientation. PMID:25907301

  6. Horizontal molecular orientation in solution-processed organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Komino, T.; Inoue, M.; Kim, J.-H.; Ribierre, J. C.; Adachi, C.

    2015-02-01

    Horizontal orientation of the emission transition dipole moments achieved in glassy vapor-deposited organic thin films leads to an enhancement of the light out-coupling efficiency in organic light-emitting diodes (OLEDs). Here, our combined study of variable angle spectroscopic ellipsometry and angle dependent photoluminescence demonstrates that such a horizontal orientation can be achieved in glassy spin-coated organic films based on a composite blend of a heptafluorene derivative as a dopant and a 4,4'-bis(N-carbazolyl)-1,1'-biphenyl as a host. Solution-processed fluorescent OLEDs with horizontally oriented heptafluorene emitters were then fabricated and emitted deep blue electroluminescence with an external quantum efficiency as high as 5.3%.

  7. Quantitative molecular-mixing measurements using digital processing of absorption images

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Schneider, S. P.; Collicott, S. H.

    1995-09-01

    Absorption imaging was used to measure the chemical product formed in a nonpremixed reacting turbulent water-jet. A collimated light-beam was absorbed by red phenolphthalein formed through a chemical reaction between neutral (pH 7) jet fluid and alkaline tank fluid. The integrated absorption was imaged on a CCD camera. Standard single-point absorption technique was thus extended to allow simultaneous measurement of absorption over a two-dimensional field. Digital image processing techniques were applied to obtain the time-average of the integrated chemical product. Product-concentration profiles in the natural jet were obtained using Abel inversion. The chemical product present six diameters downstream of the jet exit was increased 35 percent by the addition of two tabs.

  8. Molecular relaxation processes of 2-bromopropane in solutions from IR ?(C-Br) band shape analysis

    NASA Astrophysics Data System (ADS)

    Bratu, I.; Grecu, R.; Constantinescu, R.; Iliescu, T.

    1998-03-01

    The infrared (C-Br) stretching band profile of 2-bromopropane in pure liquid and in solution was studied. The frequency shifts, described by the Buckingham equation, account for the influence of the polarity and polarizability of the solvents. To evaluate the importance of the last term in the Buckingham equation, which describes the mutual influence of these two effects, a linear multidimensional regression analysis was done. The correlation factor increased when the cross term was considered. The concentration dependence of the FWHH (full width at half height) can be related to the vibrational relaxation processes, among them vibrational dephasing being the most important. More information about mechanisms responsible for the vibrational bandshape can be obtained from the correlation function ?( t). As a result of modelling the experimental CF with Kubo-Rothschild's model, the modulation of the vibrational frequencies is found to be of intermediate type.

  9. Molecular dynamical simulation of the behavior of early precipitated stage in aging process in dilute Cu-Cr alloy

    SciTech Connect

    Feng, J.; Liu, L.; Chen, J.; Du, Y.; Zhou, R. [Key Laboratory of Advanced Materials of Precious-Nonferrous Metals, Education Ministry of China, and Key Lab of Advanced Materials of Yunnan Province, Kunming University of Science and Technology, Kunming 650093 (China); Xiao, B. [Department of Physics, School of Science and Engineering, Tulane University, New Orleans 70118 (United States)

    2010-06-15

    The aging behaviors of Cu-Cr alloys in the early stage at different temperatures are investigated by molecular dynamics simulations. First principles potentials are used for the interactions between Cu and Cr atoms. The initial behavior of precipitation is characterized by transmission electron microscope and electron energy disperse spectroscopy. The results showed that Cu-Cr supersaturated solid solution is thermodynamically unstable. The mean-square displacements of the atoms are used to describe the diffusivity. At room temperature, the atoms only show harmonic vibrations near the equilibrium positions. The mutual diffusion at 873 K is different from the unidirectional diffusion in low temperatures. The calculation shows that aging process is accelerated with increasing temperature, which is not only due to the lower diffusion activation energy of Cr at higher temperature, but also because Cu atoms are also participated in the aging process. When ''aging'' at 1073 K, the precipitation of Cr element is dissolved again into Cu matrix, which is an ''over-aging'' state of Cu-Cr alloy at high temperature.

  10. n-type doping through tethered functionality: a new paradigm for molecular design of solution-processed organic thermoelectrics

    NASA Astrophysics Data System (ADS)

    Russ, Boris; Robb, Maxwell J.; Popere, Bhooshan C.; Perry, Erin E.; Urban, Jeffrey J.; Chabinyc, Michael L.; Hawker, Craig J.; Segalman, Rachel A.

    2015-03-01

    A scarcity of stable n-type doping mechanisms compatible with facile processing has been a major impediment to the advancement of n-type (electron transporting) organic thermoelectric materials. We recently demonstrated that trimethylammonium functionalization with hydroxide counterions, tethered to a perylene diimide core by alkyl spacers, facilitated solution-processing and resulted in extremely high carrier concentrations (1020carriers/cm3) and best-in-class thermoelectric performance in thin films. In this presentation, we report our recent findings on the underlying mechanism enabling charge carrier generation in these self-doping materials and its influence on material thermoelectric behavior. To draw these conclusions, we complement thermoelectric characterization with insights into chemical, electronic, and structural properties from XPS, optical spectroscopy, EPR, and GIWAXS experiments. Furthermore, we show that doping through tethered functionality can be extended to other n-type small molecule systems of interest, including naphthalene diimides and diketopyrrolopyrroles. Our findings help shape promising molecular design strategies for future enhancements in n-type thermoelectric performance.

  11. Direct transfer-adsorption: The new molecular dynamics transition mechanism of nano-diamond preparation by laser shock processing

    NASA Astrophysics Data System (ADS)

    Ren, X. D.; Tang, S. X.; Zheng, L. M.; Yuan, S. Q.; Ren, N. F.; Yang, H. M.; Wang, Y.; Zhou, W. F.; Xu, S. D.

    2015-07-01

    Laser shock processing induced structural transformation in graphite cluster of about 3 nm diameter is simulated through molecular dynamics simulations. The Brenner potential is utilized to characterize short-range order while Lennard-Jones potential for long-range order. The effect of high-energy laser shock on graphite was simulated with corresponding temperature and pressure load applied to the graphite cluster. The graphite cluster was found to transform into nano-diamond, crystal structures and amorphous carbon after heating-pressing and annealing-decompression by analyzing pair distribution function g(r) and atomic snapshots process. An interesting mechanism 'direct transfer-adsorption' for promoting peripheral carbon atoms of the graphite cluster into the inner layer and transforming bonds from sp2-type to sp3-type within the inner carbon atoms is investigated. The 'direct transfer-adsorption' mechanism, which prevails under the conditions of a temperature higher than 4300 K and a pressure higher than 15 GPa, is at fast cooling rates and high densities. And the 'direct transfer-adsorption' mechanism plays a key role in the conversion from graphite to diamond.

  12. The role of angular momentum in collision-induced vibration-rotation relaxation in polyatomics.

    PubMed

    McCaffery, Anthony J; Osborne, Mark A; Marsh, Richard J; Lawrance, Warren D; Waclawik, Eric R

    2004-07-01

    Vibrational relaxation of the 6(1) level of S(1)((1)B(2u)) benzene is analyzed using the angular momentum model of inelastic processes. Momentum-(rotational) angular momentum diagrams illustrate energetic and angular momentum constraints on the disposal of released energy and the effect of collision partner on resultant benzene rotational excitation. A kinematic "equivalent rotor" model is introduced that allows quantitative prediction of rotational distributions from inelastic collisions in polyatomic molecules. The method was tested by predicting K-state distributions in glyoxal-Ne as well as J-state distributions in rotationally inelastic acetylene-He collisions before being used to predict J and K distributions from vibrational relaxation of 6(1) benzene by H(2), D(2), and CH(4). Diagrammatic methods and calculations illustrate changes resulting from simultaneous collision partner excitation, a particularly effective mechanism in p-H(2) where some 70% of the available 6(1)-->0(0) energy may be disposed into 0-->2 rotation. These results support the explanation for branching ratios in 6(1)-->0(0) relaxation given by Waclawik and Lawrance and the absence of this pathway for monatomic partners. Collision-induced vibrational relaxation in molecules represents competition between the magnitude of the energy gap of a potential transition and the ability of the colliding species to generate the angular momentum (rotational and orbital) needed for the transition to proceed. Transition probability falls rapidly as DeltaJ increases and for a given molecule-collision partner pair will provide a limit to the gap that may be bridged. Energy constraints increase as collision partner mass increases, an effect that is amplified when J(i)>0. Large energy gaps are most effectively bridged using light collision partners. For efficient vibrational relaxation in polyatomics an additional requirement is that the molecular motion of the mode must be capable of generating molecular rotation on contact with the collision partner in order to meet the angular momentum requirements. We postulate that this may account for some of the striking propensities that characterize polyatomic energy transfer. PMID:15260535

  13. Inelastic rate processes in molecular junctions: Current-induced nuclear excitation and bath-induced vibrational decoherence

    NASA Astrophysics Data System (ADS)

    Jorn, Ryan Paul

    The technological potential for constructing electronic devices comprised of active elements on the nano- and subnanoscale has inspired a surge of interest in the conductance of individual molecules. Several demonstrations now exist which show that the tunneling current through a molecular device can interact with the vibrational degrees of freedom to initiate chemical dynamics and mechanical manipulation. Targeting single molecules provides ample motivations for both new fundamental studies in surface chemistry as well as the construction of individually driven molecular machines. The thrust of the research presented here is to understand these large amplitude motions and develop theoretical tools capable of describing nuclear dynamics initiated in a molecular junction. The focus in the subsequent chapters is on inelastic resonance transport which has been well studied in the contexts of gas phase scattering and surface electron spectroscopies. The rate for current-induced excitation is introduced as the observable for the nuclear dynamics and is formulated within a time independent scattering theory. Application is made to both bound-bound and bound-free transitions in the nuclear subspace and the effect of the coordinate dependence of the electronic coupling on the dynamics is discussed extensively. Having established the rigorous formulation for the excitation process, the qualitative Menzel-Gomer-Redhead theory is used along with established electronic structure methods to investigate the nature of the resonance state and its impact on the inelasticity of the charge transport. Application is made to a candidate molecular machine, a lithium rattle, and a hybrid silicon-organic system previously probed with scanning tunneling microscopy. The former study elucidates the role of charge localization in determining the extent of nuclear dynamics initiated by the current. Focusing on the dynamics induced for cyclopentene on the silicon surface demonstrates the importance of charge localization on the silicon dimer to produce inelastic events leading to desorption and possible failure of an electronic device. The role of the environment to dissipate energy away from the reaction coordinate is examined within density matrix theory incorporating the role of electrode phonons and generation of electron-hole pairs. Vibrational relaxation is implemented using the well-known Redfield theory and adapted to the Bloch model to describe the relaxation rates to these external degrees of freedom. The model system of CO adsorbed to various transition metals is examined to validate the methods used and qualitative agreement with experiment is shown. Finally, a scattering theory of density matrices is constructed to unite the description of the current-induced excitation with energy relaxation to the dissipative environment. The competition between these rate processes is explored for a variety of bias voltages and temperatures. It is shown that the use of master equations within the secular approximation neglects important components of the quantum dynamics.

  14. Dried Blood Spots - Preparing and Processing for Use in Immunoassays and in Molecular Techniques

    PubMed Central

    Grüner, Nico; Stambouli, Oumaima; Ross, R. Stefan

    2015-01-01

    The idea of collecting blood on a paper card and subsequently using the dried blood spots (DBS) for diagnostic purposes originated a century ago. Since then, DBS testing for decades has remained predominantly focused on the diagnosis of infectious diseases especially in resource-limited settings or the systematic screening of newborns for inherited metabolic disorders and only recently have a variety of new and innovative DBS applications begun to emerge. For many years, pre-analytical variables were only inappropriately considered in the field of DBS testing and even today, with the exception of newborn screening, the entire pre-analytical phase, which comprises the preparation and processing of DBS for their final analysis has not been standardized. Given this background, a comprehensive step-by-step protocol, which covers al the essential phases, is proposed, i.e., collection of blood; preparation of blood spots; drying of blood spots; storage and transportation of DBS; elution of DBS, and finally analyses of DBS eluates. The effectiveness of this protocol was first evaluated with 1,762 coupled serum/DBS pairs for detecting markers of hepatitis B virus, hepatitis C virus, and human immunodeficiency virus infections on an automated analytical platform. In a second step, the protocol was utilized during a pilot study, which was conducted on active drug users in the German cities of Berlin and Essen. PMID:25867233

  15. Potential for spin-based information processing in a thin-film molecular semiconductor

    NASA Astrophysics Data System (ADS)

    Warner, Marc; Din, Salahud; Tupitsyn, Igor; Morley, Gavin; Stoneham, Marshall; Gardener, Jules; Wu, Zhenlin; Fisher, Andrew; Heutz, Sandrine; Kay, Christopher; Aeppli, Gabriel

    2014-03-01

    Organic semiconductors are studied intensively for applications in electronics and optics, and even spin-based information technology, or spintronics. Fundamental quantities in spintronics are the population relaxation time (T1) and the phase memory time (T2) : T1 measures the lifetime of a classical bit, in this case embodied by a spin oriented either parallel or antiparallel to an external magnetic field, and T2 measures the corresponding lifetime of a quantum bit, encoded in the phase of the quantum state. Here we establish that these times are surprisingly long for a common, low-cost and chemically modifiable organic semiconductor, the blue pigment copper phthalocyanine, in easily processed thin-film form of the type used for device fabrication. At 5 K, a temperature reachable using inexpensive closed-cycle refrigerators, T1 and T2 are respectively 59 ms and 2.6 ms, and at 80 K, which is just above the boiling point of liquid nitrogen, they are respectively 10 ms and 1 ms, demonstrating that the performance of thin-film copper phthalocyanine is superior to that of single-molecule magnets over the same temperature range.

  16. Gravitropism of cut shoots is mediated by oxidative processes: A physiological and molecular study

    NASA Astrophysics Data System (ADS)

    Philosoph-Hadas, Sonia; Friedman, Haya; Meir, Shimon

    2012-07-01

    The signal transduction events occurring during shoot gravitropism are mediated through amyloplasts sedimentation, reorientation of actin filaments in the endodermis, and differential changes in level and action of auxin, associated with differential growth leading to shoot curvature. Since increase in reactive oxygen species (ROS) was shown to be associated with growth, we examined the possible use of antioxidants in controlling the gravitropic response, via their interaction with events preceding shoot bending. Reoriented snapdragon (Antirrhinum majus L.) spikes and tomato (Solanum lycopersicum cv. MicroTom) shoots showed a visual upward bending after a lag period of 3 or 5 h, respectively, which was inhibited by the antioxidants N-acetyl-cysteine (NAC) and reduced glutathione (GSH). This suggests the involvement of oxidative reactions in the process. The two antioxidants prevented the sedimentation of amyloplasts to the bottom of the endodermis cells following 0.5-5 h of snapdragon shoot reorientation, suggesting that oxidative reactions are involved already at a very early signal perception stage prior to the visual bending. In addition, a differential distribution in favor of the lower shoot side of various oxidative elements, including H2O2 concentrations and activity of the NADPH-oxidase enzyme, was observed during reorientation of snapdragon spikes. Application of the two antioxidants reduced the levels of these elements and abolished their differential distribution across the shoot. On the other hand, the activity of the antioxidative enzyme, superoxide dismutase (SOD), which was not differentially distributed across the shoot, increased significantly following application of the two antioxidants. The auxin redistribution in reoriented shoots was analyzed using transgenic tomato plants expressing the GUS reporter gene under the Aux/IAA4 promoter (a generous gift of M. Bouzayen, France). GUS response, detected in control shoots 4 h after their reorientation in favor of the lower shoot side was completely eliminated in the NAC-treated shoots, in which the bending response was inhibited. These results suggest that the gravitropic-induced asymmetric auxin redistribution precedes shoot bending, and NAC inhibits this response by abolishing the auxin gradient across the shoot. Our microarray analysis of tomato shoots, using the Affymetrix Tomato GeneChip, revealed differential changes in expression of 266 genes, occurring during the initial 0.5-5 h of shoot reorientation prior to bending. The differential changes in expression of auxin-related genes in favor of the lower shoot side occurred already following 0.5 h of reorientation, while those of cell wall-related genes, associated with shoot bending, occurred only 3 h following shoot reorientation. Among the identified genes, 11 genes were related to auxin, and 36 genes were associated with oxidative processes, demonstrating the involvement of ROS in early events of shoot gravitropism. Taken together, our results suggest that ROS mediate the early gravity-induced amyloplast sedimentation required for signal perception, as well as the lateral auxin movement across the shoot, which is necessary for the auxin asymmetric distribution leading to shoot upward bending.

  17. Molecular Dynamics simulations of the electrospray process: formation of NaCl clusters via the charged residue mechanism.

    PubMed

    Konermann, Lars; McAllister, Robert G; Metwally, Haidy

    2014-10-16

    Electrospray ionization (ESI) produces desolvated ions from solution phase analytes for mass spectrometric detection. The final steps of gas phase ion formation from nanometer-sized solvent droplets remain a matter of debate. According to the ion evaporation model (IEM), analytes are ejected from the droplet surface via field emission, whereas the charged residue model (CRM) envisions that ions are released upon droplet evaporation to dryness. Exposure of salt solutions to ESI conditions produces a range of cluster ions. Despite the rich literature on these systems, it is still unclear if these salt clusters form via the CRM or the IEM. The current study explores the formation of Na(n)Cl(m)((n-m)+) clusters from aqueous sodium chloride solution under positive and negative polarity conditions. Molecular dynamics (MD) methods are used for simulating the temporal evolution of charged NaCl-containing water droplets. A trajectory stitching approach is developed for continuously removing evaporated moieties from the simulation, thereby dramatically reducing computational cost. In addition, this procedure ensures adequate temperature control and eliminates evaporative cooling that would otherwise slow down the process. Continuous water evaporation leads to progressive droplet shrinkage, while the emission of solvated single ions ensures that the system remains at ca. 90% of the Rayleigh limit. Early during the process all ions in the droplet behave as freely dissolved species, but after a few nanoseconds at 370 K the systems gradually morph into amorphous wet salt aggregates. Ultimately, free Na(n)Cl(m)((n-m)+) clusters form as the last solvent molecules evaporate. Our data therefore provide direct evidence that sodium chloride cluster formation during ESI proceeds via the CRM. The IEM nonetheless plays an ancillary role, as it allows the system to shed charge (mostly in the form of hydrated Na(+) or Cl(-)) during droplet shrinkage. It appears that this study marks the first successful MD simulation of complete CRM processes. PMID:25242574

  18. Collision avoidance at sea

    Microsoft Academic Search

    Thomas L. Vincent

    The problem of collision avoidance between surface ships may be examined from the perspective of either macro or micro collision avoidance. In macro collision avoidance the pilot of a ship would try for maintaining a given mileage separation between his own ship and others. Micro collision avoidance would be concerned with manoeuvres between ships of less than a given separation

  19. Molecular dynamics of an epoxy resin modified with an epoxidized poly(styrene–butadiene) linear block copolymer during cure and microphase separation processes

    Microsoft Academic Search

    E. Serrano; G. Kortaberria; P. Arruti; A. Tercjak; I. Mondragon

    2009-01-01

    Molecular dynamics of diglycidyl ether of bisphenol A (DGEBA) epoxy resin modified with an epoxidized poly(styrene-b-butadiene) (SepB) linear block copolymer has been monitored during cure and microphase separation process by dielectric relaxation spectroscopy (DRS) for wide frequency and temperature ranges. Different primary and secondary relaxation processes have been analyzed for neat components and ternary mixture. Relaxational behaviour has been modelled

  20. Experimental and ab initio studies of the reactive processes in gas phase i-C{sub 3}H{sub 7}Br and i-C{sub 3}H{sub 7}OH collisions with potassium ions

    SciTech Connect

    López, E.; Lucas, J. M.; Andrés, J. de; Albertí, M.; Aguilar, A., E-mail: a.aguilar@ub.edu [Departament de Química Física, Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès, 1, 08028 Barcelona (Spain); Bofill, J. M. [Departament de Química Orgànica, Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès, 1, 08028 Barcelona (Spain); Bassi, D. [Dipartimento di Fisica, Università degli Studi di Trento, 38123 Povo-Trento (Italy)

    2014-10-28

    Collisions between potassium ions and neutral i-C{sub 3}H{sub 7}Br and i-C{sub 3}H{sub 7}OH, all in their electronic ground state, have been studied in the 0.10–10.00 eV center of mass (CM) collision energy range, using the radiofrequency-guided ion beam technique. In K{sup +} + i-C{sub 3}H{sub 7}Br collisions KHBr{sup +} formation was observed and quantified, while the analogous KH{sub 2}O{sup +} formation in K{sup +} + i-C{sub 3}H{sub 7}OH was hardly detected. Moreover, formation of the ion-molecule adducts and their decomposition leading to C{sub 3}H{sub 7}{sup +} and either KBr or KOH, respectively, have been observed. For all these processes, absolute cross-sections were measured as a function of the CM collision energy. Ab initio structure calculations at the MP2 level have given information about the potential energy surfaces (PESs) involved. In these, different stationary points have been characterized using the reaction coordinate method, their connectivity being ensured by using the intrinsic-reaction-coordinate method. From the measured excitation function for KHBr{sup +} formation the corresponding thermal rate constant at 303 K has been calculated. The topology of the calculated PESs allows an interpretation of the main features of the reaction dynamics of both systems, and in particular evidence the important role played by the potential energy wells in controlling the reactivity for the different reaction channels.

  1. COMPLEMENTARY MOLECULAR AND ELEMENTAL DETECTION OF SPECIATED THIOARSENICALS USING ESI-MS IN COMBINATION WITH A XENON-BASED COLLISION-CELL ICP-MS WITH APPLICATION TO FORTIFIED NIST FREEZE-DRIED URINE

    EPA Science Inventory

    The simultaneous detection of arsenic and sulfur in thio-arsenicals was achieved using xenonbased collision cell ICP-MS in combination with HPLC. In an attempt to minimize the 16O16O+ interference at m/z 32, both sample introduction and collision cell experimental parameters were...

  2. Collision avoidance for general aviation

    Microsoft Academic Search

    Thomas Billingsley; Mykel Kochenderfer; James Chryssanthacopoulos

    2011-01-01

    • Approach based on Markov decision process used to optimize collision avoidance logic for GA • Compared current TCAS and Descend\\/Climb responsive coordination with GA optimized logic — Optimized logic safer than TCAS and D\\/C against non-GA and GA intruder aircraft — Performance against GA intruders also resulted in lower Pr(NMAC) • Probability of alert and reversal with optimized logic

  3. Rotational state-changing cold collisions of hydroxyl ions with helium

    NASA Astrophysics Data System (ADS)

    Hauser, Daniel; Lee, Seunghyun; Carelli, Fabio; Spieler, Steffen; Lakhmanskaya, Olga; Endres, Eric S.; Kumar, Sunil S.; Gianturco, Franco; Wester, Roland

    2015-06-01

    Cold molecules are important for many applications, from fundamental precision measurements, quantum information processing, quantum-controlled chemistry, to understanding the cold interstellar medium. Molecular ions are known to be cooled efficiently in sympathetic collisions with cold atoms or ions. However, little knowledge is available on the elementary cooling steps, because the determination of quantum state-to-state collision rates at low temperature is very challenging for both experiment and theory. Here we present a method to manipulate molecular quantum states by non-resonant photodetachment. Based on this we provide absolute quantum scattering rate coefficients under full quantum state control for the rotationally inelastic collision of hydroxyl anions with helium. Experiment and quantum scattering theory show excellent agreement without adjustable parameters. Very similar rate coefficients are obtained for two different isotopes, which is linked to several quantum scattering resonances appearing at different energies. The presented method is also applicable to polyatomic systems and will help elucidate non-radiative processes in polyaromatic hydrocarbons and protein chromophores.

  4. Coupled Molecular Switching Processes in Ordered Mono- and Multilayers of Stimulus-Responsive Rotaxanes on Gold Surfaces

    PubMed Central

    2015-01-01

    Interfaces provide the structural basis for function as, for example, encountered in nature in the membrane-embedded photosystem or in technology in solar cells. Synthetic functional multilayers of molecules cooperating in a coupled manner can be fabricated on surfaces through layer-by-layer self-assembly. Ordered arrays of stimulus-responsive rotaxanes undergoing well-controlled axle shuttling are excellent candidates for coupled mechanical motion. Such stimulus-responsive surfaces may help integrate synthetic molecular machines in larger systems exhibiting even macroscopic effects or generating mechanical work from chemical energy through cooperative action. The present work demonstrates the successful deposition of ordered mono- and multilayers of chemically switchable rotaxanes on gold surfaces. Rotaxane mono- and multilayers are shown to reversibly switch in a coupled manner between two ordered states as revealed by linear dichroism effects in angle-resolved NEXAFS spectra. Such a concerted switching process is observed only when the surfaces are well packed, while less densely packed surfaces lacking lateral order do not exhibit such effects. PMID:25782057

  5. Effect of twin boundary on nanoimprint process of bicrystal Al thin film studied by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Xie, Yue-Hong; Xu, Jian-Gang; Song, Hai-Yang; Zhang, Yun-Guang

    2015-02-01

    The effects of a twin boundary (TB) on the mechanical properties of two types of bicrystal Al thin films during the nanoimprint process are investigated by using molecular dynamics simulations. The results indicate that for the TB direction parallel to the imprinting direction, the yield stress reaches the maximum for the initial dislocation nucleation when the mould directly imprints to the TB, and the yield stress first decreases with the increase of the marker interval and then increases. However, for the TB direction perpendicular to the imprinting direction, the effect of the TB location to the imprinting forces is very small, and the yield stress is greater than that with the TB direction parallel to the imprinting direction. The results also demonstrate that the direction of the slip dislocations and the deformation of the thin film caused by spring-back are different due to various positions and directions of the TB. Project supported by the National Natural Science Foundation of China (Grant No. 10902083), the Program for New Century Excellent Talent in University of Ministry of Education of China (Grant No. NCET-12-1046), the Program for New Scientific and Technological Star of Shaanxi Province, China (Grant No. 2012KJXX-39), and the Program for Natural Science Basic Research Plan in Shaanxi Province, China (Grant No. 2014JQ1036).

  6. Metamorphism and Continental Collision

    NSDL National Science Digital Library

    Kenneth Howard

    Physical Geology students are required to understand the processes involved in plate tectonics. They are expected to know the geologic differences between continents and ocean basins and should be able to recall and use simple geologic terms to describe geologic processes and events. This activity is designed to improve student comprehension of the varied Earth materials and complex processes involved in plate collisions. The activity synthesizes material covered during the first eight weeks of Physical Geology on plate tectonics, rock types, volcanoes, and Earth's composition. The instructor introduces the exercise to the students as a component of the college's Critical Thinking Initiative. The "hook" for the students is that the exercise represents a chance for self-appraisal of course content and understanding prior to the next semester test. The grading rubric for the lab is discussed with the students in terms of the Bloom Pyramid so that they can assess their level of progress in the course.

  7. A LOW-COST PROCESS FOR THE SYNTHESIS OF NANOSIZE YTTRIA-STABILIZED ZIRCONIA (YSZ) BY MOLECULAR DECOMPOSITION

    SciTech Connect

    Anil V. Virkar

    2004-05-06

    This report summarizes the results of work done during the performance period on this project, between October 1, 2002 and December 31, 2003, with a three month no-cost extension. The principal objective of this work was to develop a low-cost process for the synthesis of sinterable, fine powder of YSZ. The process is based on molecular decomposition (MD) wherein very fine particles of YSZ are formed by: (1) Mixing raw materials in a powder form, (2) Synthesizing compound containing YSZ and a fugitive constituent by a conventional process, and (3) Selectively leaching (decomposing) the fugitive constituent, thus leaving behind insoluble YSZ of a very fine particle size. While there are many possible compounds, which can be used as precursors, the one selected for the present work was Y-doped Na{sub 2}ZrO{sub 3}, where the fugitive constituent is Na{sub 2}O. It can be readily demonstrated that the potential cost of the MD process for the synthesis of very fine (or nanosize) YSZ is considerably lower than the commonly used processes, namely chemical co-precipitation and combustion synthesis. Based on the materials cost alone, for a 100 kg batch, the cost of YSZ made by chemical co-precipitation is >$50/kg, while that of the MD process should be <$10/kg. Significant progress was made during the performance period on this project. The highlights of the progress are given here in a bullet form. (1) From the two selected precursors listed in Phase I proposal, namely Y-doped BaZrO{sub 3} and Y-doped Na{sub 2}ZrO{sub 3}, selection of Y-doped Na{sub 2}ZrO{sub 3} was made for the synthesis of nanosize (or fine) YSZ. This was based on the potential cost of the precursor, the need to use only water for leaching, and the short time required for the process. (2) For the synthesis of calcia-stabilized zirconia (CSZ), which has the potential for use in place of YSZ in the anode of SOFC, Ca-doped Na{sub 2}ZrO{sub 3} was demonstrated as a suitable precursor. (3) Synthesis of Y-doped Na{sub 2}ZrO{sub 3} and Ca-doped Na{sub 2}ZrO{sub 3} was achieved using a conventional calcination process. The corresponding surface area was {approx}1 to 2 m{sup 2}/g. (4) By leaching with water, nanosize (very fine) YSZ and CSZ powders were synthesized. The corresponding surface area was {approx}65 m{sup 2}/g. This demonstrates the MD concept, namely macroscopic precursor {yields} leaching {yields} very fine (nanosize) product. (5) Crystallite size was determined by TEM ({approx}5 nm). (6) Anode-supported cells, with YSZ and CSZ made by the MD process, were successfully made by a conventional pressing and sintering process. (7) Single cells were made with as-synthesized YSZ and CSZ as a constituent in anode support. (8) A single cell (LSM + YSZ cathode) was tested at 800 C with H{sub 2}/air, with maximum power density of {approx}1.2 W/cm{sup 2}. (9) Dense samples of both YSZ and CSZ made by the MD process were fabricated. (10) Preliminary cost analysis, based on materials cost only, showed that the cost of YSZ powder made by the MD process should be considerably lower than that made by either chemical co-precipitation or combustion synthesis. For an anode-supported cell design, for an assumed power density of 0.5 W/cm{sup 2}, the cost of YSZ made by the MD process is estimated to be {approx}$5/kW. By contrast, the cost per kW for chemical co-precipitation or combustion synthesis is {approx}$70/kW and {approx}$23/kW, respectively. Efforts are currently underway to fabricate 5 cm x 5 cm active anode-supported cells with YSZ made by the MD process.

  8. Molecular processes in comets

    NASA Technical Reports Server (NTRS)

    Dalgarno, A.

    1993-01-01

    A major effort was expended in developing procedures for calculating by quantum-mechanical methods the cross sections for the photodissociation of the hydroxyl radical OH. The molecule OH is the primary dissociation product of water and observations of OH when combined with a determination of the lifetime of OH in the solar radiation field can be used to calculate the rate of release of water from comets. There are many possible photodissociation channels whose efficiency depends upon the details of the spectrum of the radiation. We have calculated the potential energy curves of all the states of OH that can be reached by electric dipole absorption from the ground X(exp 2)(Pi) state by photons with energies up to about 12 eV.

  9. Intramembranous bone healing process subsequent to tooth extraction in mice: micro-computed tomography, histomorphometric and molecular characterization.

    PubMed

    Vieira, Andreia Espindola; Repeke, Carlos Eduardo; Ferreira Junior, Samuel de Barros; Colavite, Priscila Maria; Biguetti, Claudia Cristina; Oliveira, Rodrigo Cardoso; Assis, Gerson Francisco; Taga, Rumio; Trombone, Ana Paula Favaro; Garlet, Gustavo Pompermaier

    2015-01-01

    Bone tissue has a significant potential for healing, which involves a significant the interplay between bone and immune cells. While fracture healing represents a useful model to investigate endochondral bone healing, intramembranous bone healing models are yet to be developed and characterized. In this study, a micro-computed tomography, histomorphometric and molecular (RealTimePCRarray) characterization of post tooth-extraction alveolar bone healing was performed on C57Bl/6 WT mice. After the initial clot dominance (0h), the development of a provisional immature granulation tissue is evident (7d), characterized by marked cell proliferation, angiogenesis and inflammatory cells infiltration; associated with peaks of growth factors (BMP-2-4-7,TGF?1,VEGFa), cytokines (TNF?, IL-10), chemokines & receptors (CXCL12, CCL25, CCR5, CXCR4), matrix (Col1a1-2, ITGA4, VTN, MMP1a) and MSCs (CD105, CD106, OCT4, NANOG, CD34, CD146) markers expression. Granulation tissue is sequentially replaced by more mature connective tissue (14d), characterized by inflammatory infiltrate reduction along the increased bone formation, marked expression of matrix remodeling enzymes (MMP-2-9), bone formation/maturation (RUNX2, ALP, DMP1, PHEX, SOST) markers, and chemokines & receptors associated with healing (CCL2, CCL17, CCR2). No evidences of cartilage cells or tissue were observed, strengthening the intramembranous nature of bone healing. Bone microarchitecture analysis supports the evolving healing, with total tissue and bone volumes as trabecular number and thickness showing a progressive increase over time. The extraction socket healing process is considered complete (21d) when the dental socket is filled by trabeculae bone with well-defined medullary canals; it being the expression of mature bone markers prevalent at this period. Our data confirms the intramembranous bone healing nature of the model used, revealing parallels between the gene expression profile and the histomorphometric events and the potential participation of MCSs and immune cells in the healing process, supporting the forthcoming application of the model for the better understanding of the bone healing process. PMID:26023920

  10. Intramembranous Bone Healing Process Subsequent to Tooth Extraction in Mice: Micro-Computed Tomography, Histomorphometric and Molecular Characterization

    PubMed Central

    Vieira, Andreia Espindola; Repeke, Carlos Eduardo; Ferreira Junior, Samuel de Barros; Colavite, Priscila Maria; Biguetti, Claudia Cristina; Oliveira, Rodrigo Cardoso; Assis, Gerson Francisco; Taga, Rumio; Trombone, Ana Paula Favaro; Garlet, Gustavo Pompermaier

    2015-01-01

    Bone tissue has a significant potential for healing, which involves a significant the interplay between bone and immune cells. While fracture healing represents a useful model to investigate endochondral bone healing, intramembranous bone healing models are yet to be developed and characterized. In this study, a micro-computed tomography, histomorphometric and molecular (RealTimePCRarray) characterization of post tooth-extraction alveolar bone healing was performed on C57Bl/6 WT mice. After the initial clot dominance (0h), the development of a provisional immature granulation tissue is evident (7d), characterized by marked cell proliferation, angiogenesis and inflammatory cells infiltration; associated with peaks of growth factors (BMP-2-4-7,TGF?1,VEGFa), cytokines (TNF?, IL-10), chemokines & receptors (CXCL12, CCL25, CCR5, CXCR4), matrix (Col1a1-2, ITGA4, VTN, MMP1a) and MSCs (CD105, CD106, OCT4, NANOG, CD34, CD146) markers expression. Granulation tissue is sequentially replaced by more mature connective tissue (14d), characterized by inflammatory infiltrate reduction along the increased bone formation, marked expression of matrix remodeling enzymes (MMP-2-9), bone formation/maturation (RUNX2, ALP, DMP1, PHEX, SOST) markers, and chemokines & receptors associated with healing (CCL2, CCL17, CCR2). No evidences of cartilage cells or tissue were observed, strengthening the intramembranous nature of bone healing. Bone microarchitecture analysis supports the evolving healing, with total tissue and bone volumes as trabecular number and thickness showing a progressive increase over time. The extraction socket healing process is considered complete (21d) when the dental socket is filled by trabeculae bone with well-defined medullary canals; it being the expression of mature bone markers prevalent at this period. Our data confirms the intramembranous bone healing nature of the model used, revealing parallels between the gene expression profile and the histomorphometric events and the potential participation of MCSs and immune cells in the healing process, supporting the forthcoming application of the model for the better understanding of the bone healing process. PMID:26023920

  11. Chloroplast mRNA 3'-end processing by a high molecular weight protein complex is regulated by nuclear encoded RNA binding proteins.

    PubMed Central

    Hayes, R; Kudla, J; Schuster, G; Gabay, L; Maliga, P; Gruissem, W

    1996-01-01

    In the absence of efficient transcription termination correct 3'-end processing is an essential step in the synthesis of stable chloroplast mRNAs in higher plants. We show here that 3'-end processing in vitro involves endonucleolytic cleavage downstream from the mature terminus, followed by exonucleolytic processing to a stem-loop within the 3'-untranslated region. These processing steps require a high molecular weight complex that contains both endoribonucleases and an exoribonuclease. In the presence of ancillary RNA binding proteins the complex correctly processes the 3'-end of precursor RNA. In the absence of these ancillary proteins 3'-end maturation is prevented and plastid mRNAs are degraded. Based on these results we propose a novel mechanism for the regulation of mRNA 3'-end processing and stability in chloroplasts. Images PMID:8605883

  12. Effects of conditioning temperature and time during the pelleting process on feed molecular structure, pellet durability index, and metabolic features of co-products from bio-oil processing in dairy cows.

    PubMed

    Huang, Xuewei; Christensen, Colleen; Yu, Peiqiang

    2015-07-01

    The objectives of this study were to systematically determine effects of conditioning temperature (70, 80, and 90°C), time (50 and 75 s), and interaction (temperature × time) during the pelleting process on co-products from bio-oil processing (canola meal) in terms of processing-induced changes on (1) protein molecular structure, (2) pellet durability index, (3) detailed chemical profile, (4) metabolic features and fractions of protein and carbohydrate, (5) total digestible nutrients and energy values, and (6) rumen degradable and undegradable content. Pellet durability was increased with increasing conditioning time. Chemical and carbohydrate profiles of co-products were not altered by pelleting process under different conditioning temperatures and times. With regard to protein fraction profiles, pellets conditioned for 50 s had higher soluble crude protein (SCP) and lower neutral detergent insoluble crude protein (NDICP) contents than those conditioned for 75 s (21.7 vs. 20.1% SCP, 16.0 vs. 16.5% NDICP, respectively). Total digestible nutrients and energy values were not altered by processing. Samples conditioned for 50 s had a higher content of rapidly degradable protein fraction (PA2) than those conditioned for 75 s (21.7 vs. 21.1% crude protein). In addition, the slowly degradable true protein fraction (PB2) was affected by the interaction of conditioning temperature and time. However, carbohydrate fractions did not differ with different conditioning temperatures and time. Different temperatures and time of conditioning during pelleting process greatly affect protein profiles without altering carbohydrate profiles. Molecular structure analyses also showed that pelleting altered inherent protein molecular structures of the co-products from bio-oil processing. Future study is needed to detect how molecular structure changes affect nutrient availability in dairy cattle. PMID:25958276

  13. Molecular spectroscopic investigation on fractionation-induced changes on biomacromolecule of co-products from bioethanol processing to explore protein metabolism in ruminants

    NASA Astrophysics Data System (ADS)

    Zhang, Xuewei; Yan, Xiaogang; Beltranena, Eduardo; Yu, Peiqiang

    2014-03-01

    Fractionation processing is an efficient technology which is capable to redesign/redevelop a new food or feed product with a specified chemical and nutrient profile. This processing technique was able to produce four different fractions (called "A", "B", "C", "D" fractions/treatments) with different nutrient profile form a co-product of bioethanol processing [wheat dried distillers grains with soluble (DDGS)]. To date, there is no study on the effect of fractionation processing on inherent molecular structure of different fractions and how the processing-induced structural change affect the metabolic characteristics of protein and nutrient availability. The objectives of this experiment were to: (1) investigate the effect of fractionation processing on changes of protein functional groups (amide I, amide II, and their ratio) and molecular structure (modeled ?-helix, ?-sheet, and their ratio), and (2) study the relationship between the fractionation processing-induced changes of protein molecular structure and nutrients availability as well as the metabolic characteristics of protein. The hypothesis of this study was that the fractionation processing changes the molecular structure and such changes affect the metabolic characteristics of protein. The protein molecular structure spectral profile of the fractions A, B, C and D were identified by Fourier-transform infrared attenuated total reflection spectroscopy (FT/IR-ATR). The results showed that the fractionation processing significantly affected the protein molecular spectral profiles. The differences in amide I to amide II peak area and height ratios were strongly significant (P < 0.01) among the treatment fractions, ranging from 4.98 to 6.33 and 3.28 to 4.00, respectively. The difference in the modeled protein ?-helix to ?-sheet ratio was also strongly significant (P < 0.01) among the treatment fractions. Multivariate molecular spectral analysis with cluster (CLA) and principal component analyses (PCA) showed that there are no clear distinguished clusters and ellipses among the fractions (A, B, C and D) in the protein amide I and II region ca. 1726-1485 cm-1. The correlation study showed that the modeled ?-helix to ?-sheet ratio tended to have a negative correlation with truly absorbed rumen undegraded protein (ARUPDVE: r = -0.944, P = 0.056 < 0.10) and total truly absorbed protein in the small intestine (DVE: r = -0.946, P = 0.054 < 0.10), but there was no correlation between the ?-helix to ?-sheet ratio and the degraded protein balance (DPBOEB: P = 0.267 < 0.10). In conclusion, the fractionation processing changed the molecular structural spectral profiles in terms of amide I to II ratio and ?-helix to ?-sheet ratio. These changes negatively affected the metabolic characteristics of protein and true protein supply. These results indicated that spectral features of different fractions could be used as a potential tool to predict true protein nutritive value.

  14. Effect of thermal processing on estimated metabolizable protein supply to dairy cattle from camelina seeds: relationship with protein molecular structural changes.

    PubMed

    Peng, Quanhui; Khan, Nazir A; Wang, Zhisheng; Zhang, Xuewei; Yu, Peiqiang

    2014-08-20

    This study evaluated the effect of thermal processing on the estimated metabolizable protein (MP) supply to dairy cattle from camelina seeds (Camelina sativa L. Crantz) and determined the relationship between heat-induced changes in protein molecular structural characteristics and the MP supply. Seeds from two camelina varieties were sampled in two consecutive years and were either kept raw or were heated in an autoclave (moist heating) or in an air-draft oven (dry heating) at 120 °C for 1 h. The MP supply to dairy cattle was modeled by three commonly used protein evaluation systems. The protein molecular structures were analyzed by Fourier transform/infrared-attenuated total reflectance molecular spectroscopy. The results showed that both the dry and moist heating increased the contents of truly absorbable rumen-undegraded protein (ARUP) and total MP and decreased the degraded protein balance (DPB). However, the moist-heated camelina seeds had a significantly higher (P < 0.05) content of ARUP and total MP and a significantly lower (P < 0.05) content of DPB than did the dry-heated camelina seeds. The regression equations showed that intensities of the protein molecular structural bands can be used to estimate the contents of ARUP, MP, and DPB with high accuracy (R(2) > 0.70). These results show that protein molecular structural characteristics can be used to rapidly assess the MP supply to dairy cattle from raw and heat-treated camelina seeds. PMID:25046194

  15. Intermediate states in the binding process of folic acid to folate receptor ?: insights by molecular dynamics and metadynamics.

    PubMed

    Della-Longa, Stefano; Arcovito, Alessandro

    2015-01-01

    Folate receptor ? (FR?) is a cell surface, glycophosphatidylinositol-anchored protein which has focussed attention as a therapeutic target and as a marker for the diagnosis of cancer. It has a high affinity for the dietary supplemented folic acid (FOL), carrying out endocytic transport across the cell membrane and delivering the folate at the acidic pH of the endosome. Starting from the recently reported X-ray structure at pH 7, 100 ns classical molecular dynamics simulations have been carried out on the FR?-FOL complex; moreover, the ligand dissociation process has been studied by metadynamics, a recently reported method for the analysis of free-energy surfaces (FES), providing clues on the intermediate states and their energy terms. Multiple dissociation runs were considered to enhance the configurational sampling; a final clustering of conformations within the averaged FES provides the representative structures of several intermediate states, within an overall barrier for ligand escape of about 75 kJ/mol. Escaping of FOL to solvent occurs while only minor changes affect the FR? conformation of the binding pocket. During dissociation, the FOL molecule translates and rotates around a turning point located in proximity of the receptor surface. FOL at this transition state assumes an "L" shaped conformation, with the pteridin ring oriented to optimize stacking within W102 and W140 residues, and the negatively charged glutamate tail, outside the receptor, interacting with the positively charged R103 and R106 residues, that contrary to the bound state, are solvent exposed. We show that metadynamics method can provide useful insights at the atomistic level on the effects of point-mutations affecting functionality, thus being a very promising tool for any study related to folate-targeted drug delivery or cancer therapies involving folate uptake. PMID:25323390

  16. Molecular dynamics investigation of the active site dynamics of mycobacterial cyclopropane synthase during various stages of the cyclopropanation process.

    PubMed

    Choudhury, Chinmayee; Deva Priyakumar, U; Sastry, G Narahari

    2014-07-01

    Mycobacterial cyclopropane synthase 1 (CmaA1) is one of the most important drug targets in anti tuberculosis drug discovery as it is responsible for cis-cyclopropanation at the distal position of unsaturated mycolates, which is an essential step for the pathogenicity, persistence and drug resistance. Five representative models of CmaA1 which correspond to different stages in the cyclopropanation process have been studied using molecular dynamics (MD) simulations. The MD simulations and structural analyses provide a detailed account of the structural changes in the active sites of CmaA1. CmaA1 has two distinct binding sites, i.e., cofactor binding site (CBS) and acyl substrate binding site (ASBS). The apo state of CmaA1 corresponds to a closed conformation where the CBS is inaccessible due to the existence of H-bond between Pro202 of loop10 (L10) and Asn11 of N-terminal ?1 helix. However, cofactor binding leads to the breaking of this H-bond and thus the H-bond is absent in the holo form. The hydrophobic side chains orient towards the inner side of the ASBS upon cofactor binding to create a hydrophobic environment for the substrate. The cofactor and substrate tend to come close to each other facilitated by opening of L10 to exchange the methyl group from the cofactor to the substrate. The MD study also revealed that the system tends to regain the apo conformation within 40ns after releasing the product. PMID:24780591

  17. Mixing processes during the evolution of red giants with moderate metal deficiencies: the role of molecular-weight barriers

    NASA Astrophysics Data System (ADS)

    Charbonnel, Corinne; Brown, Jeffery A.; Wallerstein, George

    1998-04-01

    We have assembled accurate abundance data for Li, C, and N as well as the (12}C/({13)) C ratio for five field giants with [Fe/H] =~ - 0.6 including Arcturus and two stars in the globular cluster 47 Tuc. Using their very precise Mbol values obtained from HIPPARCOS parallaxes, we can place them into an evolutionary sequence. The sequence shows that the (12}C/({13)) C ratios drops from ~ 20 to near 7 between Mbol =3D +1 and +0.5, while Li disappears. At the same time the (12}C/({14)) N ratio diminishes by 0.2 to 0.4 dex. The two stars in 47 Tuc with Mbol near -2.0 show even lower (12}C/({14)) N ratios by 0.4 dex indicating further mixing as they evolved to the top of the red giant branch. These observations confirm the existence of an extra-mixing process that becomes efficient on the red giant branch only when the low-mass stars reach the so-called luminosity function bump. We use the values of the carbon isotopic ratio observed in our sample to get constraints on the mu -barriers that may shield the central regions of a star from extra-mixing. We show that the same value of the critical gradient of molecular weight leads to (12}C/({13)) C ratios observed at different metallicities. This ``observational critical mu -gradient'' is in very good agreement with the one which is expected to stabilize meridional circulation. This result provides strong clues on the nature of the extra-mixing which occurs on the RGB, and indicates that it is related to rotation. Based partially on observations obtained at the Dominion Astrophysical Observatory, National Research Council, Canada

  18. Sputter deposition of nanocrystalline beta-SiC films and molecular dynamics simulations of the sputter process.

    PubMed

    Ziebert, Carlos; Ye, Jian; Ulrich, Sven; Prskalo, Alen-Pilip; Schmauder, Siegfried

    2010-02-01

    Thin nanocrystalline films of silicon carbide (SiC) have been deposited on Si substrates by rf magnetron sputtering in pure Ar atmosphere. Simultaneously classical molecular dynamics (MD) simulations of sputtering of beta-SiC by Ar atoms were performed using IMD and Materials Explorer software with a combination of the Tersoff and the Ziegler-Biersack-Littmark (ZBL) potential in order to get more insight into the sputter process. In experiments the bias voltage (0 to -40 V) has been varied at constant substrate temperature of 900 degrees C to investigate the influence on the composition, the constitution and the mechanical properties of crystalline beta-SiC films. At second the substrate temperature has been varied between 900 degrees C and 100 degrees C to find the minimum substrate temperature that is needed to get nanocrystalline beta-SiC under the applied sputter conditions (ceramic SiC target, 300 W rf power, 18 cm target-substrate distance, 50 sccm Ar gas flow, 0.26 Pa total gas pressure). The films have been characterized by electron probe micro-analysis (EPMA), X-ray diffraction (XRD), Raman spectroscopy and atomic force microscopy (AFM). Hardness and residual stress have been investigated by nanoindentation and wafer bending. In the MD simulations the sputter yield was determined as a function of the energy of the incident Ar atoms (in the interesting range for sputter deposition, i.e., 50-1000 eV). To our knowledge this is the first time that the sputter yield of a SiC target was determined as a function of the energy of the incident Ar atoms in the low energy range by using MD simulations and compared with experimental results. PMID:20352766

  19. Fusion of two C 60 molecules and fragmentation of the fusion product caused by C 60?C 60 collisions

    NASA Astrophysics Data System (ADS)

    Xia, Yueyuan; Xing, Yuelin; Tan, Chunyu; Mei, Liangmo; Yang, Hong

    1996-04-01

    Molecular fusion of two C 60 molecules in C 60?C 60 collisions and the stability of the reaction products are studied using molecular dynamics simulations. It shows that the shape of the fusion product depends on the collision energy and the classical impact parameter between the mass centres of the two colliding partners. At impact parameter b = 0, two C 60 molecules, colliding at energy E0 = 50 eV in the laboratory frame, coalesce to form a very stable dumbbell-shaped C 120 cluster, which never fragments. When the incident energy increases to 400 eV, the two C 60 molecules fuse to form a common larger C 120 cluster, completely losing the geometry of the original C 60 cages. However, the C 120 formed in this case is highly deformed and the intrinsic 'heat' energy stored in it is increasing gradually until the 'temperature' of the cluster goes high enough to result in a fragmentation process, which starts with a sequential evaporation of C-dimers, C-trimers, individually C atoms and other small C clusters. Collisions of C 60 molecules at larger impact parameters cause rotating motion of the coalescence products. All these coalescence reactions induced by the collisions of C 60 molecules are shown to have deep inelastic behaviour.

  20. Collision risk management in geosynchronous orbit

    NASA Astrophysics Data System (ADS)

    Jenkin, A. B.; Peterson, G. E.

    2004-01-01

    A systematic method has been developed for managing long-term collision risk posed to operational satellites in geosynchronous orbit. Long-term collision risk reduction is achieved by proper selection of local collision probability thresholds that trigger actions to reduce risk. Such actions can be requests for more accurate orbital data, special sensor tasking, or collision avoidance maneuvers. The cost of collision risk reduction is measured by the frequency of actions taken to reduce the collision risk. This action frequency is dependent on the accuracy of the orbital data and the frequency of close approaches. A case study was performed for a set of satellites. The analysis used position error models for two-line element sets. A conjunction simulation was used to process approximately three years of archived orbital data, including publicly available two-line element sets, in order to generate conjunction statistics. From these results, a graphical representation called a ?-plot was generated. This plot permits the selection of thresholds as a function of total risk reduction and tolerable action frequency. Results of the study indicate that collision risk management in geosynchronous orbit can be very costly using data of insufficiently high accuracy, because data errors induce high action frequency for even modest amounts of collision risk reduction.

  1. Direct determination of collision rates beyond the Lennard-Jones model through state-resolved measurements of strong and weak collisions.

    PubMed

    Havey, Daniel K; Liu, Qingnan; Li, Ziman; Elioff, Michael; Fang, Maosen; Neudel, Joshua; Mullin, Amy S

    2007-04-01

    We describe a new approach for measuring absolute rates for molecular collisions including contributions of both strong and weak collisions. Elastic and inelastic collisions are monitored using high-resolution transient IR spectroscopy by measuring increases in the velocity distributions of individual rotational states of scattered molecules. Weak collisional energy transfer is detected by measuring velocity increases for the low-energy rotational states. This technique is illustrated for the collisional relaxation of highly vibrationally excited pyrazine (108 kcal/mol) with HOD. The observed collision rate is nearly twice the Lennard-Jones collision rate. PMID:17388341

  2. Predicting the Knudsen paradox in long capillaries by decomposing the flow into ballistic and collision parts

    NASA Astrophysics Data System (ADS)

    Tatsios, Giorgos; Stefanov, Stefan K.; Valougeorgis, Dimitris

    2015-06-01

    The well-known Knudsen paradox observed in pressure driven rarefied gas flows through long capillaries is quantitatively explored by decomposing the particle distribution function into its ballistic and collision parts. The classical channel, tube, and duct Poiseuille flows are considered. The solution is obtained by a typical direct simulation Monte Carlo algorithm supplemented by a suitable particle decomposition indexation process. It is computationally confirmed that in the free-molecular and early transition regimes the reduction rate of the ballistic flow is larger than the increase rate of the collision flow deducing the Knudsen minimum of the overall flow. This description interprets in a precise, quantitative manner the appearance of the Knudsen minimum and verifies previously reported qualitative physical arguments.

  3. Transport processes and structural properties of the Cu 3Au and Ni 3Al(1 1 1) surface by molecular dynamics simulations

    Microsoft Academic Search

    Ch. E Lekka; D. G Papageorgiou; G. A Evangelakis

    2003-01-01

    Using an effective potential model in analogy to the tight-binding scheme in the second-moment approximation, we investigated the transport processes and the structural properties of the Cu3Au and Ni3Al(111) surfaces by molecular dynamics simulations. We found that in the case of the Cu3Au(111) surface both Cu and Au adatoms are unstable and penetrating into the bulk (already at room temperature)

  4. A Theoretical Study on Initial Processes of Li-Ion Transport at the Electrolyte\\/Cathode Interface: A Quantum Chemical Molecular Dynamics Approach

    Microsoft Academic Search

    Tomaru Ogawa; Masayuki Miyano; Yasuhiro Suzuki; Ai Suzuki; Hideyuki Tsuboi; Nozomu Hatakeyama; Akira Endou; Hiromitsu Takaba; Momoji Kubo; Akira Miyamoto

    2010-01-01

    Initial processes of Li-ion transport at the electrolyte\\/cathode interface of a Li-ion battery were investigated using an ultra-accelerated quantum chemical molecular dynamics (UA-QCMD) simulator. This simulator was based on our in-house tight-binding quantum chemical (TB-QC) simulator and MD simulator. The parameterization for LiCoO2 crystal and ethylene carbonate (EC) molecule in UA-QCMD was first carried out to show the fine agreement

  5. Ab initio potential energy surfaces and nonadiabatic collision dynamics in H(+)+O(2) system.

    PubMed

    Amaran, Saieswari; Kumar, Sanjay

    2008-04-21

    The adiabatic potential energy surfaces for the lowest five electronic states of (3)A" symmetry for the H(+)+O(2) collision system have been obtained at the multireference configuration interaction level of accuracy using Dunning's correlation consistent polarized valence triple zeta basis set. The radial nonadiabatic coupling terms and the mixing angle between the lowest two electronic states (1 (3)A" and 2 (3)A"), which adiabatically correlate in the asymptotic limit to H((2)S)+O(2) (+)(X (2)Pi(g)) and H(+)+O(2)(X (3)Sigma(g)(-)), respectively, have been computed using ab initio procedures at the same level of accuracy to yield the corresponding quasidiabatic potential energy matrix. The computed strengths of the vibrational coupling matrix elements reflect the trend observed for inelastic vibrational excitations of O(2) in the experiments at collision energy of 9.5 eV. The quantum dynamics has been preformed on the newly obtained coupled quasidiabatic potential energy surfaces under the vibrational close-coupling rotational infinite-order sudden framework at the experimental collision energy of 9.5 eV. The present theoretical results for vibrational elastic/inelastic excitations of O(2) are in overall good agreement with the available experimental data obtained from the proton energy-loss spectra in molecular beam experiments [F. A. Gianturco et al., J. Phys. B 14, 667 (1981)]. The results for the complementary charge transfer processes are also presented at this collision energy. PMID:18433227

  6. Electronic excitation of ground state atoms by collision with heavy gas particles

    NASA Technical Reports Server (NTRS)

    Hansen, C. Frederick

    1993-01-01

    Most of the important chemical reactions which occur in the very high temperature air produced around space vehicles as they enter the atmosphere were investigated both experimentally and theoretically, to some extent at least. One remaining reaction about which little is known, and which could be quite important at the extremely high temperatures that will be produced by the class of space vehicles now contemplated - such as the AOTV - is the excitation of bound electron states due to collisions between heavy gas particles. Rates of electronic excitation due to free electron collisions are known to be very rapid, but because these collisions quickly equilibrate the free and bound electron energy, the approach to full equilibrium with the heavy particle kinetic energy will depend primarily on the much slower process of bound electron excitation in heavy particle collisions and the subsequent rapid transfer to free electron energy. This may be the dominant mechanism leading to full equilibrium in the gas once the dissociation process has depleted the molecular states so the transfer between molecular vibrational energy and free electron energy is no longer available as a channel for equilibration of free electron and heavy particle kinetic energies. Two mechanisms seem probable in electronic excitation by heavy particle impact. One of these is the collision excitation and deexcitation of higher electronic states which are Rydberg like. A report, entitled 'Semi-Classical Theory of Electronic Excitation Rates', was submitted previously. This presented analytic expressions for the transition probabilities, assuming that the interaction potential is an exponential repulsion with a perturbation ripple due to the dipole-induced dipole effect in the case of neutral-neutral collisions, and to the ion-dipole interaction in the case of ion-neutral collisions. However the above may be, there is little doubt that excitation of ground state species by collision occurs at the point where the initial and final potentials cross, or at least come very close. Therefore, this mechanism would be applicable to the case where a gas is initially at very low temperature suddenly subjected to high energy heavy particle bombardment. This situation would model the measurement of excitation cross section by molecular beam techniques, for example. The purpose is to report values of cross sections and rate coefficients for collision excitation of ground state atoms estimated with the Landau-Zener transition theory and to compare results with measurement of excitation cross sections for a beam of Hydrogen atoms impacting Argon atom targets. Some very dubious approximations are used, and the comparison with measurement is found less than ideal, but results are at least consistent within order of magnitude. The same model is then applied to the case of N-N atom collisions, even though the approximations then become even more doubtful. Still the rate coefficients obtained are at least plausible in both magnitude and functional form, and as far as I am aware these are the only estimates available for such rate coefficients.

  7. RAINBOW SCATTERING IN INELASTIC MOLECULAR COLLISIONS

    E-print Network

    Thomas, Lowell D.

    2013-01-01

    angular momentum are similarly defined initial kinetic energy rotational energy (constant j), five uniquely define a trajectory.angular revealed researchers have, however, arrived at different and sometimes case. has trajectory

  8. How are completely desolvated ions produced in electrospray ionization: insights from molecular dynamics simulations.

    PubMed

    Daub, Christopher D; Cann, Natalie M

    2011-11-15

    We apply molecular dynamics (MD) simulations to study the final phase of electrospray ionization (ESI), where an ion loses all of its associated solvent molecules. By applying an electric field to a cluster of H(2)O molecules solvating an ion and including a surrounding gas of varying pressure, we demonstrate that collisions with the gas play a major role in removing this final layer of solvent. We make quantitative predictions of the critical velocity required for the cluster to start losing molecules via collisions with gas and propose that this should be important in real ESI experiments. Such collisions have heretofore not been explicitly considered in discussions of the ESI process. PMID:22017403

  9. A collision avoidance system for workpiece protection

    SciTech Connect

    Schmitt, D.J.; Weber, T.M.; Novak, J.L. [Sandia National Labs., Albuquerque, NM (United States); Maslakowski, J.E. [Rockwell International Corp., Canoga Park, CA (United States). Rocketdyne Div.

    1995-04-01

    This paper describes an application of Sandia`s non-contact capacitive sensing technology for collision avoidance during the manufacturing of rocket engine thrust chambers. The collision avoidance system consists of an octagon shaped collar with a capacitive proximity sensor mounted on each face. The sensors produced electric fields which extend several inches from the face of the collar and detect potential collisions between the robot and the workpiece. A signal conditioning system processes the sensor output and provides varying voltage signals to the robot controller for stopping the robot.

  10. Cold heteronuclear atom-ion collisions.

    PubMed

    Zipkes, Christoph; Palzer, Stefan; Ratschbacher, Lothar; Sias, Carlo; Köhl, Michael

    2010-09-24

    We study cold heteronuclear atom-ion collisions by immersing a trapped single ion into an ultracold atomic cloud. Using ultracold atoms as reaction targets, our measurement is sensitive to elastic collisions with extremely small energy transfer. The observed energy-dependent elastic atom-ion scattering rate deviates significantly from the prediction of Langevin but is in full agreement with the quantum mechanical cross section. Additionally, we characterize inelastic collisions leading to chemical reactions at the single particle level and measure the energy-dependent reaction rate constants. The reaction products are identified by in-trap mass spectrometry, revealing the branching ratio between radiative and nonradiative charge exchange processes. PMID:21230769

  11. Electron-energy spectra of H- doubly excited states resulting from collisions of H- with He

    NASA Astrophysics Data System (ADS)

    Kimura, M.; Sato, H.; Hino, K.; Matsuzawa, M.

    1994-09-01

    Electron-energy spectra for H- doubly excited states resulting from collisions of H- with He are rigorously calculated within a semiclassical molecular representation by including couplings between doubly excited states and continuum states and their interference with direct-detachment processes. An energy sampling procedure, based on the Gauss quadratures, is used to discretize continuum states. The present theoretical result clarifies mechanisms of excitation to doubly excited states, quantitatively reproduces the experimental spectra first observed by Risley and Geballe in 1974, separates the contributions from each of three doubly excited states, and identifies the cause of the interference between channels arising from double-electron excitation and direct detachment with simultaneous excitation.

  12. Globular Cluster Formation From Giant Molecular Clouds in Colliding Galaxies

    NASA Astrophysics Data System (ADS)

    Ozernoy, L.

    1997-05-01

    Galaxy collisions whenever they occur face-on should be accompanied by collisions between giant molecular clouds (GMCs) located in the central few kpc of the galaxies. The cloud-cloud collisions trigger, during the time when the central parts of galaxies cross each other, gravitational instability in the bulk of the GMCs. This process, as I show, can result in the formation of many so called `super star clusters' (SSCs). The proposed model explains the basic observational features of SSCs: (i) appearance in irregular and spiral galaxies of all types; (ii) independence of the formation process on metallicity of gas; (iii) a more or less simultaneous formation of ~ 10(5-10^6) stars in each GMC before the gas as a building material is blown out. An unambiguous signature of this model is that the ages of globular clusters in a given galaxy would reveal a distribution in the form of discrete peaks (each related to the respected collision of the parent galaxy) rather than be distributed continuously. The majority of galaxy collisions are grazing and therefore they do not involve the bulk of then-available GMCs. Although the ram pressure of the intercloud gas is strong enough to induce some star formation in the GMCs of grazingly colliding galaxies, this process differs substantially from the head-on collision case. It is also worth noting the difference with a collisionally-induced star formation in the central part of the Milky Way Galaxy(1) , which results from the difference in velocities of the colliding GMCs. Finally, I discuss a conjecture that the GMC collision mechanism could also be responsible for globular cluster (then CSS) formation prior to, or in parallel with, the galaxy formation by collisions of protogalactic clouds(2) . (1) Ozernoy, L.M., 1997, ``Starbursts in Our Home Galaxy", in Star Formation, Near and Far (Eds. S.S. Holt & L.G. Mundy). AIP Conf. Proc. (in press) (2) Ozernoy, L.M., 1989, ``Primeval and `Rejuvenated' Galaxies", in Ann. New York Acad. Sci. 571, 219

  13. Cross Sections for Electron Collisions with Carbon Monoxide

    NASA Astrophysics Data System (ADS)

    Itikawa, Yukikazu

    2015-03-01

    Cross section data are collected and reviewed for electron collisions with carbon monoxide. Collision processes included are total scattering, elastic scattering, momentum transfer, excitations of rotational, vibrational and electronic states, ionization, and dissociation. For each process, recommended values of the cross sections are presented, when possible. The literature has been surveyed through to the end of 2013.

  14. Processing, Characterization and Fretting Wear of Zinc Oxide and Silver Nanoparticles Reinforced Ultra High Molecular Weight Polyethylene Biopolymer Nanocomposite

    NASA Astrophysics Data System (ADS)

    Alam, Fahad; Kumar, Anil; Patel, Anup Kumar; Sharma, Rajeev K.; Balani, Kantesh

    2015-04-01

    Ultra-high molecular weight polyethylene (UHMWPE) is the most widely used biopolymer for articulating surfaces, such as an acetabular cup liner interfacing with a metal/ceramic femoral head. However, the formation of wear debris leads to the aseptic loosening of implants. Thus, in order to improve the life span via enhancing the fretting wear resistance, UHMWPE is reinforced with ZnO/Ag nanoparticles. It is envisaged that the ZnO/Ag addition will also exhibit antibacterial properties. In the current study, the synergetic effect of the reinforcement of ZnO/Ag nanoparticles (0-3 wt.% combinations) on the fretting wear behavior of a UHMWPE matrix is assessed. The phase characterization of compression- molded UHMWPE-Ag-ZnO biopolymer nanocomposites has elicited the retention of starting phases. All samples were processed at >98% density using compression molding. Silver and ZnO reinforcement showed enhanced hardness ~20.4% for U3A and 42.0% for U3Z. Fretting wear performance was evaluated at varying loads (5-15 N), keeping in mind the weight at different joints, with constant frequency (5 Hz) as well as amplitude of oscillation (100 µm). Laser surface profilometry showed change of wear volume from 8.6 × 10-5 mm3 for neat polymer to 5.8 × 10-5 mm3 with 1 wt.% Ag + 1 wt.% ZnO reinforcement (at 15 N load). Consequently, the mechanics of resistance offered by Ag and ZnO is delineated in the UHMWPE matrix. Further, S. aureus viability reduction is ~28.7% in cases with 1 wt.% Ag addition, ~42.5% with 1 wt.% ZnO addition, but synergistically increase to ~58.6% and 47.1% when each of Ag and ZnO is added with 1 wt.% and 3 wt.%, respectively (when compared to that of the UHMWPE control sample). Increased wear resistance and superior bioactivity and enhanced anti-bacterial properties of 1 wt.% Ag + 1 wt.% ZnO and 3 wt.% Ag + 3 wt.% ZnO shows the potential use of ZnO-Ag-UHMWPE biopolymer composites as an articulating surface.

  15. Computational study of alkali-metal--noble-gas collisions in the presence of nonresonant lasers: Na+Xe+h. omega. /sub 1/+h. omega. /sub 2/ system

    SciTech Connect

    DeVries, P.L.; Chang, C.; George, T.F.; Laskowski, B.; Stallcop, J.R.

    1980-08-01

    The collision of Na with Xe in the presence of both the rhodamine-110 dye laser and the Nd:glass laser is investigated within a quantum-mechanical close-coupled formalism, utilizing ab initio potential curves and transition dipole matrix elements. Both one- and two-photon processes are investigated; the Na+Xe system is not asymptotically resonant with the radiation fields, so that these processes can only occur in the molecular collision region. The one-photon processes are found to have measurable cross sections at relatively low intensities; even the two-photon process has a significant cross section for field intensities as low as 10 MW/cm/sup 2/.

  16. Ultracold ionizing collisions in metastable xenon

    Microsoft Academic Search

    Chad Ryan Orzel

    1999-01-01

    This work presents the results of a series of experiments investigating Penning and associative ionization collisions in laser-cooled samples of metastable xenon. An absolute measurement of the collisional rate coefficient for the ionizing collision process is made for an unpolarized sample of 132 Xe, and the rate coefficients for unpolarized samples of three bosonic (132Xe, 134Xe, and 136Xe) and two

  17. Concentrating materials covered by molecular imprinted nanofiltration layer with reconfigurability prepared by a surface sol-gel process for gas-selective detection.

    PubMed

    Imahashi, Masahiro; Hayashi, Kenshi

    2013-09-15

    Sensors that recognize molecules are acquired for the comprehensive detection of great many kinds of gases. Adsorbents with high molecular recognition and condensation ability were developed for selective gas sensing with a molecular imprinting technique. Developed adsorbents have multilayer structures consisted of a chemically modified polymer layer on the surface of a substrate covered by a TiO2 gel monolayer by the surface sol-gel process. Ellipsometry measurements showed that the 6-nm-thick layers deposited on the substrate. Cavities of molecular templates were imprinted on these layers, and thus, the film acts as a molecular gas filter without concentrating ability, which could form specific binding sites for various molecules that confirmed using solid-phase microextraction and gas chromatography-mass spectrometry. Gases were selectively absorbed into an accumulating adsorption layer and other gas molecules were blocked by the nanofiltration. These developed adsorbents enabled effective concentration ability and the filtration of gases or odors. In addition, these filters possess the flexibility to be easily configured with specific surface properties to interact with volatile molecules under appropriate conditions. A successful multiplex filter, imprinted simultaneously on an adsorbent with different sites, was demonstrated. PMID:23800374

  18. Cloud droplet collisions under different turbulent intensities

    NASA Astrophysics Data System (ADS)

    Chen, Sisi; Zwijzen, Kevin; Vaillancourt, Paul; Bartello, Peter; Yau, Man-kong

    2015-04-01

    Turbulence has long been postulated to have a large contribution in accelerating cloud droplet growth through the collision-coalescence process. Previous studies have shown that turbulence can enhance the collision kernel and may speed up the warm rain processes and even increase the precipitation. We use the Direct Numerical Simulation (DNS) model from Franklin et al. (2005) to simulate the motion of cloud droplets and their collisions under the effects of turbulence. In order to expand the range of investigated Reynolds number, we parallelize the code using MPI technique, so that larger and more energetic scales in the flow can be resolved. Previous DNS studies either span a narrow range of Reynolds number or just a few dissipation rates. This work will be based on a wide range of Reynolds number (R? is from 63 to 589) and eddy dissipation rates (from 50 to 1500 cm2 s-3). The purpose is to quantify the influence of Reynolds number (box size) and turbulence intensity (i.e. eddy dissipation rate) on the collision statistics (for example, the relative radial velocity, the radial distribution function, and the collision kernel) to shed light on future microphysics parameterizations for collision statistics under different turbulent conditions. The droplet radii range from 5 to 25 ?m because these sizes are crucial to the formation of larger droplets important for effective gravitational collisional growth. The collision statistics between pairs of those sizes are studied. The results show no dependency of collision statics on Reynolds number, in contrast to the conclusions of some previous studies. On the other hand the collision kernel increases monotonically with dissipation rate in a close-to-linear manner.

  19. Magnetismo Molecular (Molecular Magentism)

    SciTech Connect

    Reis, Mario S [Universidade Federal Fluminense, Brasil; Moreira Dos Santos, Antonio F [ORNL

    2010-07-01

    The new synthesis processes in chemistry open a new world of research, new and surprising materials never before found in nature can now be synthesized and, as a wonderful result, observed a series of physical phenomena never before imagined. Among these are many new materials the molecular magnets, the subject of this book and magnetic properties that are often reflections of the quantum behavior of these materials. Aside from the wonderful experience of exploring something new, the theoretical models that describe the behavior these magnetic materials are, in most cases, soluble analytically, which allows us to know in detail the physical mechanisms governing these materials. Still, the academic interest in parallel this subject, these materials have a number of properties that are promising to be used in technological devices, such as in computers quantum magnetic recording, magnetocaloric effect, spintronics and many other devices. This volume will journey through the world of molecular magnets, from the structural description of these materials to state of the art research.

  20. Dynamical Studies of Resonant Electron-Molecule Collisions

    NASA Astrophysics Data System (ADS)

    Slaughter, Daniel

    2014-10-01

    A unique capability of low-energy electrons is to break molecular bonds through low-energy resonant processes. We report a combined experimental and theoretical study on the dynamics following dissociative electron attachment (DEA) at low collision energies that induce ring-breaking in uracil. The experiments employ a DEA reaction microscope, consisting of a 3D momentum-imaging negative ion spectrometer, a pulsed low-energy electron gun and an effusive gas target. Building further upon a recently-established technique [2--5], fragment ion kinetic energy and angular distributions resulting from DEA are measured and compared with ab initio scattering calculations to reveal key aspects of the dynamics of the transient anion system. Recent experiments on other related systems will also be presented. Supported by Chemical Sciences, Geosciences and Biosciences division of BES/DOE.