Science.gov

Sample records for pressure-dependent electron attachment

  1. Dissociative Electron Attachment

    NASA Astrophysics Data System (ADS)

    Arreola, Esmeralda; Esmeralda Arreola Collaboration; Leigh Hargreaves Collaboration

    Since the pioneering work of Boudiaffa et al., it has been understood that electrons, even with energies near or below the ionization threshold, are capable of initiating strand-breaks in human DNA. This discovery raised important questions for cancer treatments, since sub-ionizing electrons are known to be the most copiously produced secondary product of radiation therapy. But even to date these factors are largely excluded from dosimetry calculations. This lack of inclusion is, at least in part, certainly due to the dearth of fundamental data describing low-energy electron interactions with nucleotide molecules that form the basis of DNA. Understanding of how such slow electrons are able to damage DNA remains incomplete, but the strongly peaked nature of Boudiaffa et al.'s data gives strong hints at resonantly driven collision processes. DNA damage is therefore most likely driven by ``dissociative electron attachment'' (DEA). DEA is a rather complicated process to model due to the coupling of electronic and nuclear degrees of freedom in the molecule. At the California State University Fullerton, we are currently commissioning a new spectrometer to study dissociation channels, reaction rates and orientation effects in DEA collisions between slow electrons and nucleotide molecules. At the meeting we will present design parameters and commissioning data for this new apparatus.

  2. Pressure dependence of Hexanitrostilbene Raman/ electronic absorption spectra to validate DFT EOS

    NASA Astrophysics Data System (ADS)

    Farrow, Darcie; Alam, Kathleen; Martin, Laura; Fan, Hongyou; Kay, Jeffrey; Wixom, Ryan

    2015-06-01

    Due to its thermal stability and low vapor pressure, Hexanitrostilbene (HNS) is often used in high-temperature or vacuum applications as a detonator explosive or in mild detonating fuse. Toward improving the accuracy of the equation of state used in hydrodynamic simulations of the performance of HNS, we have measured the Raman and electronic absorption spectra of this material under static pressure in a diamond anvil cell. Density functional theory calculations were used to simulate the pressure dependence of the Raman/Electronic spectra along the Hugoniot and 300K isotherm for comparison and to aid in interpreting the data. We will discuss changes in the electronic structure of HNS under pressure, validation of a DFT predicted equation of state (EOS), and using this data as a basis for understanding future pulsed Raman measurements on dynamically compressed HNS samples.

  3. Pressure dependence of the structure and electronic properties of Sr3Ir2O7

    NASA Astrophysics Data System (ADS)

    Donnerer, C.; Feng, Z.; Vale, J. G.; Andreev, S. N.; Solovyev, I. V.; Hunter, E. C.; Hanfland, M.; Perry, R. S.; Rønnow, H. M.; McMahon, M. I.; Mazurenko, V. V.; McMorrow, D. F.

    2016-05-01

    We study the structural evolution of Sr3Ir2O7 as a function of pressure using x-ray diffraction. At a pressure of 54 GPa at room temperature, we observe a first-order structural phase transition, associated with a change from tetragonal to monoclinic symmetry and accompanied by a 4% volume collapse. Rietveld refinement of the high-pressure phase reveals a novel modification of the Ruddlesden-Popper structure, which adopts an altered stacking sequence of the perovskite bilayers. As the positions of the oxygen atoms could not be reliably refined from the data, we use density functional theory (local-density approximation+U +spin orbit) to optimize the crystal structure and to elucidate the electronic and magnetic properties of Sr3Ir2O7 at high pressure. In the low-pressure tetragonal phase, we find that the in-plane rotation of the IrO6 octahedra increases with pressure. The calculations further indicate that a bandwidth-driven insulator-metal transition occurs at ˜20 GPa, along with a quenching of the magnetic moment. In the high-pressure monoclinic phase, structural optimization resulted in complex tilting and rotation of the oxygen octahedra and strongly overlapping t2 g and eg bands. The t2 g bandwidth renders both the spin-orbit coupling and electronic correlations ineffectual in opening an electronic gap, resulting in a robust metallic state for the high-pressure phase of Sr3Ir2O7 .

  4. Pressure dependence of electronic properties of BaI{sub 2}

    SciTech Connect

    Kumar, Pradeep; Vedeshwar, Agnikumar G.

    2015-08-28

    We present Density Functional Theoretical (DFT) calculations of the electronic properties of scintillator material BaI{sub 2} under pressure which were carried out using Perdew-Burke-Ernzerhof genralized gradient approximation. We found that BaI{sub 2} is a direct band gap material with band gap calculated as 3.35 eV. The pressure effect on BaI{sub 2} indicates a linear monotonously decreasing band gap and increasing valence band width with pressure. We have observed the shifting of band extrema from the Γ point with pressure. The pressure coefficient of band gap is found to be −0.047 eV/GPa. The interatomic ionicity factor of BaI{sub 2} is found to be 0.51. Trends in bonding and ionicity under pressure are also discussed.

  5. Miniature Reversal Electron-Attachment Detector

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara

    1994-01-01

    Miniature reversal electron-attachment detector (miniREAD) enables direct injection of air or vapor at atmospheric pressure from monitored area into mass-spectrometric instrument to detect explosives, narcotics, or other substances, vapors of which suspected of being present in low concentrations. In comparison with older reversal electron-attachment detector, miniREAD simpler in design; more rugged; and easier to build, repair, and maintain. In addition, probably more sensitive.

  6. Electron Attachment to Molecules at Low Electron Energies

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Garscadden, A.; Wadehra, J. M.

    1994-01-01

    One of the most efficient ways of producing negative ions is by the process of dissociative electron attachment to molecules. Here, a diatomic or polyatomic molecule dissociates, by the impact of a low energy electron, into component atoms (or smaller molecular species) while the incident electron attaches itself to one of the dissociating fragments.

  7. Vibrationally Resolved Electron Attachment to Oxygen Clusters

    SciTech Connect

    Matejcik, S.; Kiendler, A.; Stampfli, P.; Stamatovic, A.; Maerk, T.D.

    1996-10-01

    Highly monochromiatized electrons (with 30meV FWHM) are used in a crossed beam experiment to investigate electron attachment to oxygen clusters (O{sub 2}){sub {ital n}} at electron energies from approximately 0 to 2eV.At energies close to zero, the attachment cross section for the reaction (O{sub 2}){sub {ital n}}+{ital e}{r_arrow}O{sub 2}{sup {minus}} rises strongly with decreasing electron energy compatible with {ital s}-wave electron capture to (O{sub 2}){sub {ital n}}. Peaks in the attachment cross section present at higher energies can be ascribed to vibrational levels of the oxygen anion. The vibrational spacings observed can be quantitatively accounted for by model calculations. {copyright} {ital 1996 The American Physical Society.}

  8. Note: Theoretical study on the gas pressure dependence of x-ray yield in TE{sub 111} cavity based electron cyclotron resonance x-ray source

    SciTech Connect

    Selvakumaran, T. S. Sen, Soubhadra; Baskaran, R.

    2014-11-15

    Adopting Langevin methodology, a pressure dependent frictional force term which represents the collisional effect is added to the Lorentz equation. The electrons are assumed to be starting from the uniformly distributed co-ordinates on the central plane. The trajectory of each electron is numerically simulated by solving the modified Lorentz equation for a given pressure. The Bremsstrahlung x-ray energy spectrum for each electron crossing the cavity wall boundary is obtained using the Duane-Hunt law. The total x-ray yield is estimated by adding the spectral contribution of each electron. The calculated yields are compared with the experimental results and a good agreement is found.

  9. Electron attachment rate constant measurement by photoemission electron attachment ion mobility spectrometry (PE-EA-IMS)

    NASA Astrophysics Data System (ADS)

    Su, Desheng; Niu, Wenqi; Liu, Sheng; Shen, Chengyin; Huang, Chaoqun; Wang, Hongmei; Jiang, Haihe; Chu, Yannan

    2012-12-01

    Photoemission electron attachment ion mobility spectrometry (PE-EA-IMS), with a source of photoelectrons induced by vacuum ultraviolet radiation on a metal surface, has been developed to study electron attachment reaction at atmospheric pressure using nitrogen as the buffer gas. Based on the negative ion mobility spectra, the rate constants for electron attachment to tetrachloromethane and chloroform were measured at ambient temperature as a function of the average electron energy in the range from 0.29 to 0.96 eV. The experimental results are in good agreement with the data reported in the literature.

  10. Dissociative electron attachment studies on acetone

    SciTech Connect

    Prabhudesai, Vaibhav S. Tadsare, Vishvesh; Ghosh, Sanat; Gope, Krishnendu; Davis, Daly; Krishnakumar, E.

    2014-10-28

    Dissociative electron attachment (DEA) to acetone is studied in terms of the absolute cross section for various fragment channels in the electron energy range of 0–20 eV. H{sup −} is found to be the most dominant fragment followed by O{sup −} and OH{sup −} with only one resonance peak between 8 and 9 eV. The DEA dynamics is studied by measuring the angular distribution and kinetic energy distribution of fragment anions using Velocity Slice Imaging technique. The kinetic energy and angular distribution of H{sup −} and O{sup −} fragments suggest a many body break-up for the lone resonance observed. The ab initio calculations show that electron is captured in the multi-centered anti-bonding molecular orbital which would lead to a many body break-up of the resonance.

  11. Pressure dependence of the configurational bistability and deep electronic levels of the MFe center in InP

    NASA Astrophysics Data System (ADS)

    Samara, G. A.; Barnes, C. E.

    2006-04-01

    The influence of hydrostatic pressure on the structural bistability and electronic properties of the processing-induced MFe center in Fe-doped n -type InP was investigated. Earlier work has shown that, when occupied by electrons, the center can be reversibly placed in either of two configurations, termed A and B , by the proper choice of electric biasing conditions and temperature. Pressure strongly modifies the energetics and kinetics of the various electronic transitions and of the transformations associated with the center. The activation volumes (ΔV*) for these processes were determined. In the absence of barriers to electron capture, or for small barriers, ΔV* can be interpreted as the breathing mode relaxation associated with electron emission or capture. At pressures ⩾8kbar , the center exists only in the A configuration regardless of bias conditions, because at these pressures the energetics and kinetics of the various processes have changed so much as to always favor the A configuration. It is also shown that, whereas the A⇄B transformations are charge state controlled at 1bar , this is not the case at high pressure where the transformations can be brought about without electron emission or hole capture. Earlier tentative atomic models for the center are discussed, and it is shown that some features of one of the models including the signs of the breathing mode relaxations associated with the various electron emissions are consistent with the experimental results, but issues remain. The results are also found to be generally consistent with first-principles calculations on defects in InP, but it is emphasized that whereas these calculations are for simple defects, the defects associated with the MFe center are more complex.

  12. High resolution electron attachment to CO₂ clusters.

    PubMed

    Denifl, Stephan; Vizcaino, Violaine; Märk, Tilmann D; Illenberger, Eugen; Scheier, Paul

    2010-01-01

    Electron attachment to CO₂ clusters performed at high energy resolution (0.1 eV) is studied for the first time in the extended electron energy range from threshold (0 eV) to about 10 eV. Dissociative electron attachment (DEA) to single molecules yields O(-) as the only fragment ion arising from the well known (2)Π(u) shape resonance (ion yield centered at 4.4 eV) and a core excited resonance (at 8.2 eV). On proceeding to CO₂ clusters, non-dissociated complexes of the form (CO₂)(n)(-) including the monomer CO₂(-) are generated as well as solvated fragment ions of the form (CO₂)(n)O(-). The non-decomposed complexes appear already within a resonant feature near threshold (0 eV) and also within a broad contribution between 1 and 4 eV which is composed of two resonances observed for example for (CO₂)(4)(-) at 2.2 eV and 3.1 eV (peak maxima). While the complexes observed around 3.1 eV are generated via the (2)Π(u) resonance as precursor with subsequent intracluster relaxation, the contribution around 2.2 eV can be associated with a resonant scattering feature, recently discovered in single CO₂ in the selective excitation of the higher energy member of the well known Fermi dyad [M. Allan, Phys. Rev. Lett., 2001, 87, 0332012]. Formation of (CO₂)(n)(-) in the threshold region involves vibrational Feshbach resonances (VFRs) as previously discovered via an ultrahigh resolution (1 meV) laser photoelectron attachment method [E. Leber, S. Barsotti, I. I. Fabrikant, J. M. Weber, M.-W. Ruf and H. Hotop, Eur. Phys. J. D, 2000, 12, 125]. The complexes (CO₂)(n)O(-) clearly arise from DEA at an individual molecule within the cluster involving both the (2)Π(u) and the core excited resonance. PMID:21491691

  13. Electron attachment to indole and related molecules

    SciTech Connect

    Modelli, Alberto; Jones, Derek; Pshenichnyuk, Stanislav A.

    2013-11-14

    Gas-phase formation of temporary negative ion states via resonance attachment of low-energy (0–6 eV) electrons into vacant molecular orbitals of indoline (I), indene (II), indole (III), 2-methylen-1,3,3-trimethylindoline (IV), and 2,3,3-trimethyl-indolenine (V) was investigated for the first time by electron transmission spectroscopy (ETS). The description of their empty-level structures was supported by density functional theory and Hartree-Fock calculations, using empirically calibrated linear equations to scale the calculated virtual orbital energies. Dissociative electron attachment spectroscopy (DEAS) was used to measure the fragment anion yields generated through dissociative decay channels of the parent molecular anions of compounds I-V, detected with a mass filter as a function of the incident electron energy in the 0–14 eV energy range. The vertical and adiabatic electron affinities were evaluated at the B3LYP/6-31+G(d) level as the anion/neutral total energy difference. The same theoretical method is also used for evaluation of the thermodynamic energy thresholds for production of the negative fragments observed in the DEA spectra. The loss of a hydrogen atom from the parent molecular anion ([M-H]{sup −}) provides the most intense signal in compounds I-IV. The gas-phase DEAS data can provide support for biochemical reaction mechanisms in vivo involving initial hydrogen abstraction from the nitrogen atom of the indole moiety, present in a variety of biologically important molecules.

  14. Pressure dependence of electronic structure and superconductivity of the MnX (X = N, P, As, Sb)

    PubMed Central

    Chong, XiaoYu; Jiang, YeHua; Zhou, Rong; Feng, Jing

    2016-01-01

    A recently experimental discovered (Cheng et al., Phys. Rev. Lett. 114, 117001 (2015)) of superconductivity on the border of long-range magnetic order in the itinerant-electron helimagnet MnP via the application of high pressure makes MnP the first Mn-based superconductor. In this paper, we carry out first-principles calculations on MnX (X = N, P, As, Sb) and find superconducting critical temperature TC of MnP sharply increases near the critical pressure PC ≈ 8 GPa, which is in good agreement with the experiments. Electron-phonon coupling constant λ and electronic density of states at the Fermi level N (EF) are found to increase with pressure for MnP, which lead to the increase of TC of MnP. Moreover, we also find that the TC of MnAs and MnSb are higher than MnP, implying that the MnAs and MnSb may be the more potential Mn-based superconducting materials. PMID:26902857

  15. Dynamics of Dissociative Electron Attachment to Methane

    NASA Astrophysics Data System (ADS)

    Rescigno, T. N.; Douguet, N.; Fonseca, S.; Orel, A. E.; Slaughter, D. S.; Belkacem, A.

    2015-05-01

    We present the results of a theoretical ad experimental study of dissociative electron attachment (DEA) to CH4. The total DEA cross section is dominated by a single broad peak centered near 10 eV, leading predominantly to H-/CH4 and CH2-/CH4dissociation channels. We will present evidence that both of these ion channels result from excitation of a triply degenerate Feshbach resonance (doubly excited negative ion state) of 2T2 symmetry whose parent is the lowest excited triplet state of the neutral molecule. We will present calculated angular distributions based on analysis of the entrance amplitudes obtained from the results of complex Kohn scattering calculations along with experimentally measured angular distributions obtained using the COLTRIMS method. Work performed under the auspices of the US DOE by the LBNL and supported by the U.S. DOE Office of Basic Energy Sciences, Division of Chemical Sciences.

  16. Investigations Of Electron Attachment To Nitro-Compounds Towards Explosives

    SciTech Connect

    Mauracher, A.; Denifl, S.; Probst, M.; Maerk, T. D.; Scheier, P.

    2009-05-02

    Electron attachment to gas phase nitrobenzene, all three isomers of mononitrotoluene and 2,4,6-trinitrotoluene is studied by means of two crossed electron-molecular beam experiments. We point out the formation of long-lived metastable parent anions and the most abundant anions produced via dissociative electron attachment (DEA). The experimental results are supported by quantum-chemical calculations, to determine the electronic configuration of selected molecular orbitals or the electrostatic potential mapped on an isosurface of the total electron density to find preferential sites of electron attachment.

  17. Date attachable offline electronic cash scheme.

    PubMed

    Fan, Chun-I; Sun, Wei-Zhe; Hau, Hoi-Tung

    2014-01-01

    Electronic cash (e-cash) is definitely one of the most popular research topics in the e-commerce field. It is very important that e-cash be able to hold the anonymity and accuracy in order to preserve the privacy and rights of customers. There are two types of e-cash in general, which are online e-cash and offline e-cash. Both systems have their own pros and cons and they can be used to construct various applications. In this paper, we pioneer to propose a provably secure and efficient offline e-cash scheme with date attachability based on the blind signature technique, where expiration date and deposit date can be embedded in an e-cash simultaneously. With the help of expiration date, the bank can manage the huge database much more easily against unlimited growth, and the deposit date cannot be forged so that users are able to calculate the amount of interests they can receive in the future correctly. Furthermore, we offer security analysis and formal proofs for all essential properties of offline e-cash, which are anonymity control, unforgeability, conditional-traceability, and no-swindling.

  18. Date attachable offline electronic cash scheme.

    PubMed

    Fan, Chun-I; Sun, Wei-Zhe; Hau, Hoi-Tung

    2014-01-01

    Electronic cash (e-cash) is definitely one of the most popular research topics in the e-commerce field. It is very important that e-cash be able to hold the anonymity and accuracy in order to preserve the privacy and rights of customers. There are two types of e-cash in general, which are online e-cash and offline e-cash. Both systems have their own pros and cons and they can be used to construct various applications. In this paper, we pioneer to propose a provably secure and efficient offline e-cash scheme with date attachability based on the blind signature technique, where expiration date and deposit date can be embedded in an e-cash simultaneously. With the help of expiration date, the bank can manage the huge database much more easily against unlimited growth, and the deposit date cannot be forged so that users are able to calculate the amount of interests they can receive in the future correctly. Furthermore, we offer security analysis and formal proofs for all essential properties of offline e-cash, which are anonymity control, unforgeability, conditional-traceability, and no-swindling. PMID:24982931

  19. Date Attachable Offline Electronic Cash Scheme

    PubMed Central

    Sun, Wei-Zhe; Hau, Hoi-Tung

    2014-01-01

    Electronic cash (e-cash) is definitely one of the most popular research topics in the e-commerce field. It is very important that e-cash be able to hold the anonymity and accuracy in order to preserve the privacy and rights of customers. There are two types of e-cash in general, which are online e-cash and offline e-cash. Both systems have their own pros and cons and they can be used to construct various applications. In this paper, we pioneer to propose a provably secure and efficient offline e-cash scheme with date attachability based on the blind signature technique, where expiration date and deposit date can be embedded in an e-cash simultaneously. With the help of expiration date, the bank can manage the huge database much more easily against unlimited growth, and the deposit date cannot be forged so that users are able to calculate the amount of interests they can receive in the future correctly. Furthermore, we offer security analysis and formal proofs for all essential properties of offline e-cash, which are anonymity control, unforgeability, conditional-traceability, and no-swindling. PMID:24982931

  20. Upper critical field, pressure-dependent superconductivity and electronic anisotropy of Sm4Fe2As2Te(1-x)O(4-y)F(y).

    PubMed

    Pisoni, A; Katrych, S; Szirmai, P; Náfrádi, B; Gaál, R; Karpinski, J; Forró, L

    2016-03-23

    We present a detailed study of the electrical transport properties of a recently discovered iron-based superconductor: Sm4Fe2As2Te0.72O2.8F1.2. We followed the temperature dependence of the upper critical field by resistivity measurement of single crystals in magnetic fields up to 16 T, oriented along the two main crystallographic directions. This material exhibits a zero-temperature upper critical field of 90 T and 65 T parallel and perpendicular to the Fe2As2 planes, respectively. An unprecedented superconducting magnetic anisotropy γH=H(c2)(ab)/H(c2)(c) ~ 14 is observed near Tc, and it decreases at lower temperatures as expected in multiband superconductors. Direct measurement of the electronic anisotropy was performed on microfabricated samples, showing a value of ρ(c)/ρ(ab)(300K) ~ 5 that rises up to 19 near Tc . Finally, we have studied the pressure and temperature dependence of the in-plane resistivity. The critical temperature decreases linearly upon application of hydrostatic pressure (up to 2 GPa) similarly to overdoped cuprate superconductors. The resistivity shows saturation at high temperatures, suggesting that the material approaches the Mott-Ioffe-Regel limit for metallic conduction. Indeed, we have successfully modelled the resistivity in the normal state with a parallel resistor model that is widely accepted for this state. All the measured quantities suggest strong pressure dependence of the density of states. PMID:26895190

  1. Applying a Trochoidal Electron Monochromator in Dissociative Electron Attachment Scattering

    NASA Astrophysics Data System (ADS)

    Arreola, Esmeralda

    2016-03-01

    Since the pioneering work of Boudiaffa et al., it has been understood that electrons, even with energies near or below the ionization threshold, are capable of initiating strand-breaks in human DNA. This discovery raised important questions for cancer treatments, since sub-ionizing electrons are known to be the most copiously produced secondary product of radiation therapy. But even to date these factors are largely excluded from dosimetry calculations. This lack of inclusion is, at least in part, certainly due to the dearth of fundamental data describing low-energy electron interactions with nucleotide molecules that form the basis of DNA. Understanding of how such slow electrons are able to damage DNA remains incomplete, but the strongly peaked nature of Boudiaffa et al.'s data gives strong hints at resonantly driven collision processes. DNA damage is therefore most likely driven by ``dissociative electron attachment'' (DEA). DEA is a rather complicated process to model due to the coupling of electronic and nuclear degrees of freedom in the molecule. At the California State University Fullerton, we are currently commissioning a new spectrometer to study dissociation channels, reaction rates and orientation effects in DEA collisions between slow electrons and nucleotide molecules. At the meeting we will present design parameters and commissioning data for this new apparatus.

  2. Imaging the molecular dynamics of dissociative electron attachment to water

    SciTech Connect

    Adaniya, Hidihito; Rudek, B.; Osipov, Timur; Haxton, Dan; Weber, Thorsten; Rescigno, Thomas N.; McCurdy, C.W.; Belkacem, Ali

    2009-10-19

    Momentum imaging experiments on dissociative electron attachment to the water molecule are combined with ab initio theoretical calculations of the angular dependence of the quantum mechanical amplitude for electron attachment to provide a detailed picture of the molecular dynamics of dissociation attachment via the two lowest energy Feshbach resonances. The combination of momentum imaging experiments and theory can reveal dissociation dynamics for which the axial recoil approximation breaks down and thus provides a powerful reaction microscope for DEA to polyatomics.

  3. BEHAVIOR OF EXCESS ELECTRONS IN SUPERCRITICAL FLUIDS - ELECTRON ATTACHMENT

    SciTech Connect

    NISHIKAWA,M.; HOLROYD,R.A.; ITOH,K.

    1999-07-01

    The behavior of excess electrons in supercritical ethane was investigated by measuring mobility and reaction rates. Mobilities were measured by means of a time-of-flight method at 306--320K as a function of pressure. Mobility values decreased at all temperatures with increasing pressure, but showed a small minimum or a shoulder at the pressure where the compressibility {chi}{sub T} has a peak. Electron attachment to CO{sub 2}, NO, pyrimidine and C{sub 2}F{sub 4} over the same temperature range was studied as a function of pressure. Both attachment rate constants k{sub a} for NO and C{sub 2}F{sub 4}, and equilibrium constants K({double_bond}k{sub a}/k{sub d}) for CO{sub 2} and pyrimidine increased sharply at pressures of {chi}{sub T} peaks. Activation volumes V{sub a}* and reaction volumes {Delta}V{sub r} are very large and negative in the critical region. The volume change is mainly due to electrostriction around ions formed. The results are compared to volume changes predicted by, a compressible continuum model.

  4. Measuring Traces Of Oxygen By Resonant Electron Attachment

    NASA Technical Reports Server (NTRS)

    Man, Kin Fung; Boumsellek, Said; Chutjian, Ara

    1995-01-01

    Method of detecting trace amounts of oxygen based on dissociative attachment of electrons to oxygen molecules followed by measurement of resulting flux of negative oxygen ions in mass spectrometer. High sensitivity achieved in method by exploiting resonance in dissociative attachment of electrons to oxygen molecules: electron-attachment cross section rises to high peak at incident electron kinetic energy of 6.2 eV. Relative concentrations below 1 ppb detected. Devised to increase sensitivity of detection of oxygen in processing chambers in which oxygen regarded as contaminant; for example, chambers used in making semiconductor devices and in growing high-purity crystals.

  5. Electron attachment to propargyl chloride, 305-540 K

    SciTech Connect

    Bopp, Joseph C.; Miller, Thomas M.; Friedman, Jeffrey F.; Shuman, Nicholas S.; Viggiano, A. A.

    2010-10-21

    Electron attachment to propargyl chloride (HC{identical_to}C-CH{sub 2}Cl) was studied in a flowing-afterglow Langmuir-probe apparatus from 305 to 540 K. The sole ion product in this temperature range is Cl{sup -}. Electron attachment is very inefficient, requiring correction for a competing process of electron recombination with molecular cations produced in reaction between Ar{sup +} and propargyl chloride and subsequent ion-molecule reactions. The electron attachment rate coefficient was measured to be 1.6x10{sup -10} cm{sup 3} s{sup -1} at 305 K and increased to 1.1x10{sup -9} cm{sup 3} s{sup -1} at 540 K.

  6. Atomic selectivity in dissociative electron attachment to dihalobenzenes.

    PubMed

    Kim, Namdoo; Sohn, Taeil; Lee, Sang Hak; Nandi, Dhananjay; Kim, Seong Keun

    2013-10-21

    We investigated electron attachment to three dihalobenzene molecules, bromochlorobenzene (BCB), bromoiodobenzene (BIB) and chloroiodobenzene (CIB), by molecular beam photoelectron spectroscopy. The most prominent product of electron attachment in the anion mass spectra was the atomic fragment of the less electronegative halogen of the two, i.e., Br(-) for BCB and I(-) for BIB and CIB. Photoelectron spectroscopy and ab initio calculations suggested that the approaching electron prefers to attack the less electronegative atom, a seemingly counterintuitive finding but consistent with the mass spectrometric result. For the iodine-containing species BIB and CIB, the photoelectron spectrum consists of bands from both the molecular anion and atomic I(-), the latter of which is produced by photodissociation of the former. Molecular orbital analysis revealed that a large degree of orbital energy reordering takes place upon electron attachment. These phenomena were shown to be readily explained by simple molecular orbital theory and the electronegativity of the halogen atoms.

  7. Electron attachment to the phthalide molecule

    SciTech Connect

    Asfandiarov, N. L.; Pshenichnyuk, S. A.; Vorob’ev, A. S.; Nafikova, E. P.; Lachinov, A. N.; Kraikin, V. A.; Modelli, A.

    2015-05-07

    Phthalide, the simplest chain of conductive polymer thin film, was investigated by means of Electron Transmission Spectroscopy, Negative Ion Mass Spectrometry, and density functional theory quantum chemistry. It has been found that formation of gas-phase long-lived molecular anions of phthalide around 0.7 eV takes place through cleavage of a C–O bond of the pentacyclic ring of the parent molecular anion to give a vibrationally excited (electronically more stable) open-ring molecular anion. The energy of the transition state for ring opening of the parent negative ion is calculated to be 0.65 eV above the neutral ground state of the molecule. The energy (2.64 eV) evaluated for the corresponding transition state in the neutral molecule is much higher, so that the process of electron detachment from the anion must lead to a neutral molecule with its initial pentacyclic structure. The average lifetime of the molecular negative ions formed at an electron energy of 0.75 eV and 80 °C is measured to be about 100 μs. The known switching effect of thin phthalide films could stem from the presence of a similar open/closed transition state also in the polymer.

  8. Electron attachment to chlorine azide at 298 and 400 K

    SciTech Connect

    Freel, Keith; Friedman, Jeffrey F.; Miller, Thomas M.; Viggiano, A. A.; Heaven, Michael C.

    2010-04-07

    Electron attachment to chlorine azide (ClN{sub 3}) was studied using a flowing-afterglow Langmuir-probe apparatus. Electron attachment rates were measured to be 3.5x10{sup -8} and 4.5x10{sup -8} cm{sup 3} s{sup -1} at 298 and 400 K, respectively, with an estimated 35% absolute accuracy. Cl{sup -} was the sole ion product of the attachment reaction; weak ion signals were observed for other anions and attributed to impurities and secondary ion-molecule reactions. Assuming a relative uncertainty of {+-}10% for these data, an activation energy for the attachment reaction may be given as 24{+-}10 meV.

  9. Reversal electron attachment ionizer for detection of trace species

    NASA Technical Reports Server (NTRS)

    Bernius, Mark T. (Inventor); Chutjian, Ara (Inventor)

    1989-01-01

    An in-line reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region and executing a reversal of the electrons, such that the electrons possess zero kinetic energy at the point of reversal, may be used to produce both negative and positive ions. A sample gas is introduced at the point of electron reversal for low energy electron-(sample gas) molecule attachment with high efficiency. The attachment process produces negative ions from the sample gas, which includes species present in trace (minute) amounts. These ions are extracted efficiently and directed to a mass analyzer where they may be detected and identified. The generation and detection of positive ions is accomplished in a similar fashion with minimal adjustment to potentials applied to the apparatus.

  10. Reversal electron attachment ionizer for detection of trace species

    NASA Technical Reports Server (NTRS)

    Bernius, Mark T. (Inventor); Chutjian, Ara (Inventor)

    1990-01-01

    An in-line reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region and executing a reversal of said electrons, such that the electrons possess zero kinetic energy at the point of reversal, may be used to produce both negative and positive ions. A sample gas is introduced at the point of electron reversal for low energy electron-(sample gas) molecule attachment with high efficiency. The attachment process produces negative ions from the sample gas, which includes species present in trace (minute) amounts. These ions are extracted efficiently and directed to a mass analyzer where they may be detected and identified. The generation and detection of positive ions is accomplished in a similar fashion with minimal adjustment to potentials applied to the apparatus.

  11. The Dynamics of Dissociative Electron Attachment to Small Polyatomic Molecules

    NASA Astrophysics Data System (ADS)

    Rescigno, Thomas

    2013-09-01

    Dissociative electron attachment (DEA) is a resonant process in which an electron attaches to a molecule to form an unstable anion which subsequently fragments into stable products. DEA to small polyatomic molecules is often governed by complex electronic and nuclear dynamics that is intrinsically multi-dimensional. One-dimensional treatments of the dissociation dynamics based on resonance scattering theory, while often successful in modeling the energy dependence of total cross sections, can mask the complexity of post-attachment dynamics which is revealed by the observed angular dependence of the reaction products. The dissociation evolves on transient anion potential energy surfaces and often involves conical intersections which can result in a complete breakdown of the axial recoil approximation. I will use the examples of DEA to water, carbon dioxide and methanol to illustrate the discussion. Work performed under auspices of USDOE by LBNL under contract DE-AC02-05CH11231 and supported by OBES, Division of Chemical Sciences.

  12. Electron attachment and ion mobility in hydrocarbons and related systems

    SciTech Connect

    Bakale, G.

    1988-01-01

    During the last two decades, a firm base for the emerging field of liquid state electronics (LSE) has developed through studies of the transport and reaction properties of excess electrons in a variety of liquid-phase systems. Pulse-conductivity techniques were used in many of these studies to measure the mobilities of electrons and ions in pure liquids as well as the rate constants of electron attachment to a wide variety of electron-accepting solutes. Results obtained through such studies have interdisciplinary implications that are described in the discussion that follows which includes examples of the contributions of LSE to physics, chemistry and biology. 42 refs.

  13. Electron attachment to the SF{sub 6} molecule

    SciTech Connect

    Smirnov, B. M. Kosarim, A. V.

    2015-09-15

    Various models for transition between electron and nuclear subsystems are compared in the case of electron attachment to the SF{sub 6} molecule. Experimental data, including the cross section of electron attachment to this molecule as a function of the electron energy and vibrational temperature, the rate constants of this process in swarm experiments, and the rates of the chemionization process involving Rydberg atoms and the SF{sub 6} molecule, are collected and treated. Based on the data and on the resonant character of electron capture into an autodetachment ion state in accordance with the Breit–Wigner formula, we find that intersection of the molecule and negative ion electron terms proceeds above the potential well bottom of the molecule with the barrier height 0.05–0.1 eV, and the transition between these electron terms has both the tunnel and abovebarrier character. The limit of small electron energies e for the electron attachment cross section at room vibrational temperature takes place at ε ≪ 2 meV, while in the range 2 meV ≪ ε ≪ 80 meV, the cross section is inversely proportional to ε. In considering the attachment process as a result of the interaction between the electron and vibrational degrees of freedom, we find the coupling factor f between them to be f = aT at low vibrational temperatures T with a ≈ 3 × 10{sup −4} K{sup −1}. The coupling factor is independent of the temperature at T > 400 K.

  14. Electron Attachment to CO2 Embedded in Superfluid He Droplets

    PubMed Central

    2014-01-01

    Electron attachment to CO2 embedded in superfluid He droplets leads to ionic complexes of the form (CO2)n– and (CO2)nO– and, at much lower intensities, He containing ions of the form Hem(CO2)nO–. At low energies (<5 eV), predominantly the non-decomposed complexes (CO2)n– are formed via two resonance contributions, similar to electron attachment to pristine CO2 clusters. The significantly different shapes and relative resonance positions, however, indicate particular quenching and mediation processes in CO2@He. A series of further resonances in the energy range up to 67 eV can be assigned to electronic excitation of He and capture of the inelastically scattered electron generating (CO2)n– and two additional processes where an intermediately formed He* leads to the nonstoichiometric anions (CO2)nO–. PMID:24818738

  15. Dynamics of Dissociative Electron Attachment to Uracil and Furane

    NASA Astrophysics Data System (ADS)

    Fonseca Dos Santos, Samantha; Douguet, Nicolas; Orel, Ann; Rescigno, Thomas

    2016-05-01

    We present the results of a theoretical study of dissociative electron attachment (DEA) to Uracil and Furan. In both cases we will present calculated angular distributions based on analysis of the entrance amplitudes obtained from the results of complex Kohn scattering calculations. For uracil, we will compare our results with available experimentally measured angular distributions obtained using the COLTRIMS method.

  16. High Resolution Studies of Electron Attachment to Molecules

    SciTech Connect

    Braun, M.; Ruf, M.-W.; Hotop, H.; Fabrikant, I. I.

    2009-05-02

    In this paper, we survey recent progress in studies of anion formation via (dissociative) electron attachment (DEA) to simple molecules, as measured with the laser photoelectron attachment (LPA) method at high resolution. The limiting (E{yields}0) threshold behavior of the cross sections is elucidated for s-wave and p-wave attachment. Cusps at onsets for vibrational excitation (VE), due to interaction of the DEA channnel with the VE channel, are clearly detected, and vibrational Feshbach resonances just below vibrational onsets are observed for molecules with sufficiently strong long-range attraction between the electron and the molecule. From the LPA anion yields, absolute DEA cross sections (energy range typically E = 0.001-2 eV) are determined with reference to rate coefficients for thermal electron attachment at the appropriate gas temperature (normally T{sub G} = 300 K). The experimental data are compared with theoretical cross sections, calculated within the framework of an R-matrix or an Effective Range theory approach.

  17. Ultralow Energy Electron Attachment at Sub-Millielectron Volt Resolution

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Kortyna, A.; Darrach, M. R.; Howe, P. -T.

    1999-01-01

    The technique of rare-gas photoionization has been extended by use of direct laser ionization to electron energies epsilon in the range 0-100 meV, with a resolution Delta(epsilon) of 0.4-0.5 meV (FWHM). Tunable UV light at (Lambda)276 nm is produced using a pulsed Nd:YAG laser and nonlinear mixing techniques. The beam is frequency tripled in a pulsed jet of xenon. The VUV radiation, tunable at (Lambda)92 nm, is then used to photoionize Xe at its 2P(sub 1/2) threshold (single-photon ionization). The photoelectrons produced interact with admixed target gas to generate negative ions through the s-wave capture process. Recent results in electron attachment to SF(sub 6) will be reported which show resonance structure at the opening of the ground-state vibrational channels. This structure corresponds to the process of vibrational excitation + attachment, which is superimposed on the underlying s-wave (direct) capture process. It should be a general phenomenon, present in a wide variety of zero-energy electron attaching molecules.

  18. Dissociative electron attachment to HBr: A temperature effect

    SciTech Connect

    Fedor, J.; Cingel, M.; Skalny, J. D.; Scheier, P.; Maerk, T. D.; Cizek, M.; Kolorenc, P.; Horacek, J.

    2007-02-15

    The effects of rovibrational temperature on dissociative electron attachment to hydrogen bromide has been investigated from the experimental and theoretical point of view. Theoretical calculations based on the nonlocal resonance model predict a strong temperature effect on the Br{sup -} fragment ion yield due to population of higher vibrational and rotational states. A crossed beam experimental setup consisting of a temperature controlled effusive molecular beam and a trochoidal electron monochromator has been used to confirm this prediction. The high degree of agreement between experiment and theory indicates the validity of the theoretical model and its underlying physical picture.

  19. Electron attachment to antipyretics: possible implications of their metabolic pathways.

    PubMed

    Pshenichnyuk, Stanislav A; Modelli, Alberto

    2012-06-21

    The empty-level structures and formation of negative ion states via resonance attachment of low-energy (0-15 eV) electrons into vacant molecular orbitals in a series of non-steroidal anti-inflammatory drugs (NSAIDs), namely aspirin, paracetamol, phenacetin, and ibuprofen, were investigated in vacuo by electron transmission and dissociative electron attachment (DEA) spectroscopies, with the aim to model the behavior of these antipyretic agents under reductive conditions in vivo. The experimental findings are interpreted with the support of density functional theory calculations. The negative and neutral fragments formed by DEA in the gas phase display similarities with the main metabolites of these commonly used NSAIDs generated in vivo by the action of cytochrome P450 enzymes, as well as with several known active agents. It is concluded that xenobiotic molecules which possess pronounced electron-accepting properties could in principle follow metabolic pathways which parallel the gas-phase dissociative decay channels observed in the DEA spectra at incident electron energies below 1 eV. Unwanted side effects as, e.g., hepatoxicity or carcinogenicity produced by the NSAIDs under study in human organism are discussed within the "free radical model" framework, reported earlier to describe the toxic action of the well-known model toxicant carbon tetrachloride. PMID:22779593

  20. Electron attachment to antipyretics: possible implications of their metabolic pathways.

    PubMed

    Pshenichnyuk, Stanislav A; Modelli, Alberto

    2012-06-21

    The empty-level structures and formation of negative ion states via resonance attachment of low-energy (0-15 eV) electrons into vacant molecular orbitals in a series of non-steroidal anti-inflammatory drugs (NSAIDs), namely aspirin, paracetamol, phenacetin, and ibuprofen, were investigated in vacuo by electron transmission and dissociative electron attachment (DEA) spectroscopies, with the aim to model the behavior of these antipyretic agents under reductive conditions in vivo. The experimental findings are interpreted with the support of density functional theory calculations. The negative and neutral fragments formed by DEA in the gas phase display similarities with the main metabolites of these commonly used NSAIDs generated in vivo by the action of cytochrome P450 enzymes, as well as with several known active agents. It is concluded that xenobiotic molecules which possess pronounced electron-accepting properties could in principle follow metabolic pathways which parallel the gas-phase dissociative decay channels observed in the DEA spectra at incident electron energies below 1 eV. Unwanted side effects as, e.g., hepatoxicity or carcinogenicity produced by the NSAIDs under study in human organism are discussed within the "free radical model" framework, reported earlier to describe the toxic action of the well-known model toxicant carbon tetrachloride.

  1. Electron attachment to antipyretics: Possible implications of their metabolic pathways

    NASA Astrophysics Data System (ADS)

    Pshenichnyuk, Stanislav A.; Modelli, Alberto

    2012-06-01

    The empty-level structures and formation of negative ion states via resonance attachment of low-energy (0-15 eV) electrons into vacant molecular orbitals in a series of non-steroidal anti-inflammatory drugs (NSAIDs), namely aspirin, paracetamol, phenacetin, and ibuprofen, were investigated in vacuo by electron transmission and dissociative electron attachment (DEA) spectroscopies, with the aim to model the behavior of these antipyretic agents under reductive conditions in vivo. The experimental findings are interpreted with the support of density functional theory calculations. The negative and neutral fragments formed by DEA in the gas phase display similarities with the main metabolites of these commonly used NSAIDs generated in vivo by the action of cytochrome P450 enzymes, as well as with several known active agents. It is concluded that xenobiotic molecules which possess pronounced electron-accepting properties could in principle follow metabolic pathways which parallel the gas-phase dissociative decay channels observed in the DEA spectra at incident electron energies below 1 eV. Unwanted side effects as, e.g., hepatoxicity or carcinogenicity produced by the NSAIDs under study in human organism are discussed within the "free radical model" framework, reported earlier to describe the toxic action of the well-known model toxicant carbon tetrachloride.

  2. Dissociative Electron Attachment to Hydrocarbons. A Laboratory Study

    NASA Astrophysics Data System (ADS)

    Szymanska, E.; Mason, N. J.

    2011-05-01

    Laboratory studies of PAHs continue to be essential if we are to interpret the wealth and variety of processes contributing to star formation. In the realm of gas-phase kinetics reactions involving negative ions are being studied to help modellers understand the role of these species in interstellar chemistry. Observations have shown that PAHs molecules are abundant and ubiquitous in the interstellar medium of galaxies, play an important role in its physical and chemical characteristics and form a key link between small hydrocarbon species and large carbonaceous grains. There is therefore considerable interest in the mechanisms by which these molecules and their anions may form. One method is electron induced chemistry within the icy mantles on the surface of dust grains. In particular it has been recently shown that functional group dependence exists in electron attachment processes giving rise to site selective fragmentation of molecules at the C-H, O-H and N-H bonds at energies well beyond the threshold for the breaking of any of these bonds allowing novel forms of chemistry that have little or no activation barriers, such as are necessary in the ISM. In this poster we present the results of recent studies on dissociative electron attachment (DEA) to PAHs using an improved version of a Velocity Map Imaging (VMI) spectrometer comprised of a magnetically collimated and low energy pulsed electron gun, a Faraday cup, an effusive molecular beam, a pulsed field ion extraction, a time of flight analyzer and a two-dimensional position sensitive detector consisting of microchannel plate and a phosphor screen. The VMI spectrometer measures the kinetic energy and angular distribution of the fragment anions produced in the dissociative electron attachment process. Kinetic energy measurements provide information on the internal energies of the fragment anions and determine the dissociation limits of the parent negative ion resonant states responsible for the dissociative

  3. Electron attachment and positive ion chemistry of monohydrogenated fluorocarbon radicals

    SciTech Connect

    Wiens, Justin P.; Shuman, Nicholas S.; Miller, Thomas M.; Viggiano, Albert A.

    2015-08-21

    Rate coefficients and product branching fractions for electron attachment and for reaction with Ar{sup +} are measured over the temperature range 300–585 K for three monohydrogenated fluorocarbon (HFC) radicals (CF{sub 3}CHF, CHF{sub 2}CF{sub 2}, and CF{sub 3}CHFCF{sub 2}), as well as their five closed-shell precursors (1-HC{sub 2}F{sub 4}I, 2-HC{sub 2}F{sub 4}I, 2-HC{sub 2}F{sub 4}Br, 1-HC{sub 3}F{sub 6}I, 2-HC{sub 3}F{sub 6}Br). Attachment to the HFC radicals is always fairly inefficient (between 0.1% and 10% of the Vogt–Wannier capture rate), but generally faster than attachment to analogous perfluorinated carbon radicals. The primary products in all cases are HF-loss to yield C{sub n}F{sub m−1}{sup −} anions, with only a minor branching to F{sup −} product. In all cases the temperature dependences are weak. Attachment to the precursor halocarbons is near the capture rate with a slight negative temperature dependence in all cases except for 2-HC{sub 2}F{sub 4}Br, which is ∼10% efficient at 300 K and becomes more efficient, approaching the capture rate at higher temperatures. All attachment kinetics are successfully reproduced using a kinetic modeling approach. Reaction of the HFC radicals with Ar{sup +} proceeds at or near the calculated collisional rate coefficient in all cases, yielding a wide variety of product ions.

  4. Dissociation dynamics in the dissociative electron attachment to carbon dioxide

    NASA Astrophysics Data System (ADS)

    Nag, Pamir; Nandi, Dhananjay

    2015-05-01

    Dissociative electron attachment (DEA) to gas phase CO2 has been probed using a velocity slice imaging technique. DEA to CO2 produces only an O- ionic fragment and shows two major resonances located at 4.4 and 8.2 eV, respectively. The kinetic energy and angular distribution of the O- ions are measured around the second resonance with higher efficiency and sensitivity that provide details of the DEA dynamics. The kinetic energy distributions are in good agreement with the previous reports. However, the distinct angular distributions show substantial difference from the two recent studies within the limited electron energies. Our angular distribution results show two negative ion resonant states are involved in the underlying DEA process at the entire electron energies over the second resonance. We discussed the recent conflicting findings in the angular distribution results. The forward-backward asymmetry observed in the angular distributions is explained due to the interference effect of different partial waves associated with the attaching electron.

  5. ERIC, A New Electron Attachment Spectrometer For Radicals

    NASA Astrophysics Data System (ADS)

    Field, Thomas; Slattery, Andrew; Adams, Daryl; Morrison, David

    2004-09-01

    A new spectrometer, ERIC (electron radical interaction chamber), has been developed to study dissociative electron attachment to unstable molecules such as free radicals. It includes a trochoidal electron monochromator and a time-of-flight mass spectrometer. Radicals are generated with a microwave discharge at 2.45 GHz. Preliminary data are presented for SO, S_2O and S_2O2 radicals formed when a mixture of helium and sulphur dioxide was passed through the microwave discharge. Several new resonacnes are observed with the discharge on, which are assigned to the radicals. Absolute cross sections for these processes have been estimated. Website ; http://www.qub.ac.uk/mp/ampr/radical.html

  6. Dissociative electron attachment and vibrational excitation of the chlorine molecule

    NASA Astrophysics Data System (ADS)

    Kolorenč, Přemysl; Horáček, Jiří

    2006-12-01

    This paper is aimed at the theoretical investigation of the inelastic processes taking place in resonant collisions of low-energy electrons with the chlorine molecule. Dissociative electron attachment and vibrational excitation of Cl2 by electron impact is investigated in the energy range 0-1.5eV , where the Σu+2 resonance plays the central role. The calculations were carried out within the framework of the nonlocal resonance model. This approach makes it possible to calculate the integrated cross sections of the above-mentioned processes for a variety of initial and final rovibrational states of the target molecule. The present model is constructed on the basis of ab initio fixed-nuclei R -matrix calculations using the so-called Feshbach-Fano R -matrix method. The Schwinger-Lanczos algorithm was utilized to solve the Lippmann-Schwinger equation describing the motion of the nuclei.

  7. Low-energy dissociative electron attachment to CF2

    NASA Astrophysics Data System (ADS)

    Chourou, S. T.; Larson, Ã.; Orel, A. E.

    2015-08-01

    We present the results of a theoretical study of dissociative electron attachment (DEA) of low-energy electrons to CF2. We carried out electron scattering calculations using the complex Kohn variational method at the static-exchange and relaxed self-consistent field (SCF) level at the equilibrium geometry and compare our differential cross sections to other results. We then repeated these calculations as a function of the three internal degrees of freedom to obtain the resonance energy surfaces and autoionization widths. We use this data as input to form the Hamiltonian relevant to the nuclear dynamics. The multidimensional wave equation is solved using the multiconfiguration time-dependent Hartree (MCTDH) approach within the local approximation.

  8. High resolution dissociative electron attachment to gas phase adenine

    SciTech Connect

    Huber, D.; Beikircher, M.; Denifl, S.; Zappa, F.; Matejcik, S.; Bacher, A.; Grill, V.; Maerk, T. D.; Scheier, P.

    2006-08-28

    The dissociative electron attachment to the gas phase nucleobase adenine is studied using two different experiments. A double focusing sector field mass spectrometer is utilized for measurements requiring high mass resolution, high sensitivity, and relative ion yields for all the fragment anions and a hemispherical electron monochromator instrument for high electron energy resolution. The negative ion mass spectra are discussed at two different electron energies of 2 and 6 eV. In contrast to previous gas phase studies a number of new negative ions are discovered in the mass spectra. The ion efficiency curves for the negative ions of adenine are measured for the electron energy range from about 0 to 15 eV with an electron energy resolution of about 100 meV. The total anion yield derived via the summation of all measured fragment anions is compared with the total cross section for negative ion formation measured recently without mass spectrometry. For adenine the shape of the two cross section curves agrees well, taking into account the different electron energy resolutions; however, for thymine some peculiar differences are observed.

  9. Dissociative attachment reactions of electrons with strong acid molecules

    SciTech Connect

    Adams, N.G.; Smith, D.; Viggiano, A.A.; Paulson, J.F.; Henchman, M.J.

    1986-06-15

    Using the flowing afterglow/Langmuir probe (FALP) technique, we have determined (at variously 300 and 570 K) the dissociative attachment coefficients ..beta.. for the reactions of electrons with the common acids HNO/sub 3/ (producing NO/sup -//sub 2/) and H/sub 2/SO/sub 4/ (HSO/sup -//sub 4/), the superacids FSO/sub 3/H (FSO/sup -//sub 3/), CF/sub 3/SO/sub 3/H (CF/sub 3/SO/sup -//sub 3/), ClSO/sub 3/H (ClSO/sup -//sub 3/,Cl/sup -/), the acid anhydride (CF/sub 3/SO/sub 2/)/sub 2/O (CF/sub 3/SO/sup -//sub 3/), and the halogen halides HBr (Br/sup -/) and HI (I/sup -/). The anions formed in the reactions are those given in the parentheses. The reactions with HF and HCl were investigated, but did not occur at a measurable rate since they are very endothermic. Dissociative attachment is rapid for the common acids, the superacids, and the anhydride, the measured ..beta.. being appreciable fractions of the theoretical maximum ..beta.. for such reactions, ..beta../sub max/. The HI reaction is very fast ( ..beta..approx...beta../sub max/) but the HBr reaction occurs much more slowly because it is significantly endothermic. The data indicate that the extreme acidity of the (Bronsted-type) superacids has its equivalence in the very efficient gas-phase dissociative attachment which these species undergo when reacting with free electrons. The anions of the superacids generated in these reactions, notably FSO/sup -//sub 3/ and CF/sub 3/SO/sup -//sub 3/, are very stable (unreactive) implying exceptionally large electron affinities for the FSO/sub 3/ and CF/sub 3/SO/sub 3/ radicals.

  10. Pressure dependence of the conduction-electron-spin-resonance linewidth of the α and β phases of di-bis(ethylene- diothiolo)tetrathiafulvalene triiodide

    NASA Astrophysics Data System (ADS)

    Forró, L.; Sekretarczyk, G.; Krupski, M.; Schweitzer, D.; Keller, H.

    1987-02-01

    We report conduction-electron-spin-resonance linewidth (ΔH) measurements of the α and β phases of the organic conductor di-bis(ethylenediothiolo)tetrathiafulvalene triiodide [(BEDT-TTF)2I3] in the 80-300 K temperature range under applied pressures of up to 5 kbar. ΔH increases under pressure in contrast to the predictions of the Elliot formula for the spin relaxation in metals. The pressure derivative d(lnΔH)/dP is -5.5+/-1%/kbar and 9.8+/-1%/kbar for the α and β phases of (BEDT-TTF)2I3 respectively.

  11. Revealing Dissociative Electron Attachment Dynamics in Polyatomic Molecules Using Momentum Imaging Experiments and Electron Scattering Calculations

    NASA Astrophysics Data System (ADS)

    Belkacem, Ali; Slaughter, Daniel

    2015-05-01

    Understanding electron-driven chemical reactions is important for improving a variety of technological applications such as materials processing and the important role they play in the radiation damage in bulk matter. Furthermore, dissociative electron attachment often exhibits site-selective bond cleavage, which holds promise for prediction and precise control of electron-driven chemical reactions. Recent dynamical studies of these reactions have demonstrated that an understanding of anion dissociation dynamics beyond simple one-dimensional models is crucial in interpreting the measured fragment angular distributions. We combine ion fragment momentum imaging experiments with electron attachment entrance amplitude calculations to interrogate the non-Born-Oppenheimer dynamics of dissociative electron attachment in polyatomic molecules. We will report recent experimental developments in molecules of technological interest including methanol, methane and uracil. Work supported by Chemical Sciences, Geosciences and Biosciences division of BES/DOE.

  12. Electron attachment to carbon dioxide clusters at very low electron energies

    SciTech Connect

    Stamatovic, A.; Leiter, K.; Ritter, W.; Stephan, K.; Maerk, T.D.

    1985-09-15

    Electron attachment to CO/sub 2/ clusters formed by nozzle expansion was investigated in a crossed molecular-beam--electron-impact--mass spectrometer system. In addition to cluster ions previously observed at 3--4 eV electron energy we observe presently cluster ions produced at around zero electron energy. Some of these ions are likely produced by a less dissociative production mechanism allowing the probing of cluster beams with better reliability than previously.

  13. Detection of New Dissociative Electron Attachment Channels in NO

    NASA Technical Reports Server (NTRS)

    Orient, O. J.; Chutjian, A.

    1995-01-01

    Three dissociative electron attachment channels have been detected and identified in NO via measurement of the O minus (exp 2)P fragment energy. In addition to the known N((exp 2 D(exp 0)) + O minus (exp 2)P channel, two new channels N((exp 1 S(exp 0)) + 0 (2 P) and N(exp 2)P(exp 0) + O(exp 2)P were detected. Cross sections for each of the channels are reported by normalizing the scattering intensities to previously measured total cross sections. The experimental approach uses solenoidal magnetic confinement of the electrons and ions, and trochoidal energy analysis of the low-energy ions.

  14. Removal of aromatic compounds in gas by electron attachment

    SciTech Connect

    Tamon, Hajime; Imanaka, Hiroyuki; Sano, Noriaki; Okazaki, Morio; Tanthapanichakoon, W.

    1998-07-01

    Ultrahigh gas purification has been of interest in various fields: (1) removal of indoor air pollutants, (2) complete removal of dioxins from incineration plants, (3) complete removal of radioactive iodine compounds, (4) simultaneous removal of NO{sub x} and SO{sub x} in exhaust gases from cogeneration plants, (5) removal and decomposition of chlorofluorocarbons (CFCs) and volatile organic compounds (VOCs), (6) ultrahigh purification of gas used for semiconductor industries, etc. A corona-discharge reactor was applied to remove benzene and p-dichlorobenzene from nitrogen and a nitrogen-oxygen mixture. Although benzene was not effectively removed from nitrogen by electron attachment, the removal efficiency was improved greatly by mixing oxygen. On the other hand, the high removal efficiencies of p-dichlorobenzene were obtained in nitrogen or a nitrogen-oxygen mixture. The removal mechanism was studied based on the contribution of the ozone reaction and the analysis of the deposit on the anode of the reactor. As a result, the ozone reaction does not contribute to the removals. An FT-IR measurement and thermogravimetry suggest that benzene or p-dichlorobenzene is decomposed by dissociative electron attachment and deposits as polycyclic aromatic compounds of a high boiling point on the anode surface.

  15. Electron attachment to 2-nitro-m-xylene

    NASA Astrophysics Data System (ADS)

    Alizadeh, E.; Graupner, K.; Mauracher, A.; Haughey, S.; Edtbauer, A.; Probst, M.; Märk, T. D.; Field, T. A.; Scheier, P.

    2010-01-01

    Electron attachment to nitroaromatic compound 2-nitro-m-xylene in gas phase has been performed utilizing a double focusing two sector mass spectrometer with high mass resolution (m/[Delta]m [approximate] 2500). At low energy (below 20 eV), electron interactions with the neutral 2-nitro-m-xylene molecule reveal a very rich fragmentation pattern. A total of 60 fragment anions have been detected and the ion yield for all observed negative ions has been recorded as a function of the incident electron energy, among them a long lived (metastable) non-dissociated parent anion which is formed at energies near zero eV, and some ions observed at the mass numbers 26, 42 and 121. Comparison of calculated isotopic patterns with measured ion yields for these fragment anions and their successors in the mass spectrum, allows the assignment of the chemical composition of these fragments as CN- (26 Da), CNO- (42 Da) and C8H9O- (121 Da). Electron attachment to 2-nitro-m-xylene leads to anion formation at four energy ranges. Between 0 eV and 2 eV only few product ions are formed. Between 4.6 eV and 6.1 eV all fragment anions are formed and for most of them the anion yield reaches its maximum value in this range. NO2- which is the most abundant product [M-H]- and O- are the only fragments that exhibit a feature at 7.4 eV, 8.1 eV and 7.9 eV, respectively. About half of the fragment anions exhibit a broad, mostly low-intensity resonance between 9 eV and 10 eV.

  16. Dissociative electron attachment to the gas-phase nucleobase hypoxanthine

    NASA Astrophysics Data System (ADS)

    Dawley, M. Michele; Tanzer, Katrin; Carmichael, Ian; Denifl, Stephan; Ptasińska, Sylwia

    2015-06-01

    We present high-resolution measurements of the dissociative electron attachment (DEA) to isolated gas-phase hypoxanthine (C5H4N4O, Hyp), a tRNA purine base. The anion mass spectra and individual ion efficiency curves from Hyp were measured as a function of electron energy below 9 eV. The mass spectra at 1 and 6 eV exhibit the highest anion yields, indicating possible common precursor ions that decay into the detectable anionic fragments. The (Hyp - H) anion (C5H3N4O-) exhibits a sharp resonant peak at 1 eV, which we tentatively assign to a dipole-bound state of the keto-N1H,N9H tautomer in which dehydrogenation occurs at either the N1 or N9 position based upon our quantum chemical computations (B3LYP/6-311+G(d,p) and U(MP2-aug-cc-pVDZ+)) and prior studies with adenine. This closed-shell dehydrogenated anion is the dominant fragment formed upon electron attachment, as with other nucleobases. Seven other anions were also observed including (Hyp - NH)-, C4H3N4-/C4HN3O-, C4H2N3-, C3NO-/HC(HCN)CN-, OCN-, CN-, and O-. Most of these anions exhibit broad but weak resonances between 4 and 8 eV similar to many analogous anions from adenine. The DEA to Hyp involves significant fragmentation, which is relevant to understanding radiation damage of biomolecules.

  17. Dissociative electron attachment to the gas-phase nucleobase hypoxanthine

    SciTech Connect

    Dawley, M. Michele; Tanzer, Katrin; Denifl, Stephan E-mail: Sylwia.Ptasinska.1@nd.edu; Carmichael, Ian; Ptasińska, Sylwia E-mail: Sylwia.Ptasinska.1@nd.edu

    2015-06-07

    We present high-resolution measurements of the dissociative electron attachment (DEA) to isolated gas-phase hypoxanthine (C{sub 5}H{sub 4}N{sub 4}O, Hyp), a tRNA purine base. The anion mass spectra and individual ion efficiency curves from Hyp were measured as a function of electron energy below 9 eV. The mass spectra at 1 and 6 eV exhibit the highest anion yields, indicating possible common precursor ions that decay into the detectable anionic fragments. The (Hyp − H) anion (C{sub 5}H{sub 3}N{sub 4}O{sup −}) exhibits a sharp resonant peak at 1 eV, which we tentatively assign to a dipole-bound state of the keto-N1H,N9H tautomer in which dehydrogenation occurs at either the N1 or N9 position based upon our quantum chemical computations (B3LYP/6-311+G(d,p) and U(MP2-aug-cc-pVDZ+)) and prior studies with adenine. This closed-shell dehydrogenated anion is the dominant fragment formed upon electron attachment, as with other nucleobases. Seven other anions were also observed including (Hyp − NH){sup −}, C{sub 4}H{sub 3}N{sub 4}{sup −}/C{sub 4}HN{sub 3}O{sup −}, C{sub 4}H{sub 2}N{sub 3}{sup −}, C{sub 3}NO{sup −}/HC(HCN)CN{sup −}, OCN{sup −}, CN{sup −}, and O{sup −}. Most of these anions exhibit broad but weak resonances between 4 and 8 eV similar to many analogous anions from adenine. The DEA to Hyp involves significant fragmentation, which is relevant to understanding radiation damage of biomolecules.

  18. A dissociative electron attachment cross-section estimator

    NASA Astrophysics Data System (ADS)

    Munro, James J.; Harrison, Stephen; Fujimoto, Milton M.; Tennyson, Jonathan

    2012-11-01

    Dissociative electron attachment (DEA) is the major process where molecules are destroyed in low-energy plasmas. DEA cross sections are therefore important for a whole variety of applications but are both hard to measure or compute accurately. A method for estimating DEA cross sections based a simple resonance plus survival model is presented. Test results are presented for DEA of molecular oxygen and molecular chlorine, for which experimental measurements are available for comparison, and SiBr and SiBr2, for which no previous data is available. The estimator has been implemented as part of Quantemol-N expert system which uses the R-matrix method to predict resonance positions and widths.

  19. Isotope effect in dissociative electron attachment to HCN

    SciTech Connect

    Chourou, S. T.; Orel, A. E.

    2011-03-15

    We performed nuclear dynamics calculations on HCN and DCN to study the isotope effect in dissociative electron attachment. Our previous calculations at 333 K led to a ratio {sigma}{sup (CN-/HCN)}/{sigma}{sup (CN-/DCN)} of about 13, which is significantly higher than recent experimental findings. This discrepancy is attributed to the neglect of correlation and polarization effects in the scattering calculation performed. We carried out a relaxed-self-consistent field calculation to determine the variation of the resonance parameters under these effects. We observe a shift in the positions of the shape resonance as well as a narrowing of the autoionization widths resulting in an isotope ratio of 3.2 at T=333 K; in closer agreement with the measured value.

  20. Precursor anion states in dissociative electron attachment to chlorophenol isomers

    NASA Astrophysics Data System (ADS)

    Kossoski, F.; Varella, M. T. do N.

    2016-07-01

    We report a theoretical study on low-energy (<10 eV) elastic electron scattering from chlorophenol isomers, namely, para-chlorophenol (pCP), meta-chlorophenol (mCP), and ortho-chlorophenol (oCP). The calculations were performed with the Schwinger multichannel method with pseudopotentials, and analysis of the computed integral cross sections and virtual orbitals revealed one σCCl ∗ , one σOH ∗ , and three π∗ shape resonances. We show that electron capture into the two lower lying π∗ orbitals initiates dissociative processes that lead to the elimination of the chloride ion, accounting for the two overlapping peaks where this fragment was observed. Despite the relatively small differences on the energetics of the π∗ resonances, a major isomeric effect was found on their corresponding autodetachment lifetimes, which accounts for the observed increasing cross sections in the progression pCP < mCP < oCP. In particular, dissociation from the π1 ∗ anion of pCP is largely suppressed because of the unfavorable mixing with the σCCl ∗ state. We found the intramolecular hydrogen bond present in oCP to have the opposite effects of stabilizing the σCCl ∗ resonance and destabilizing the σOH ∗ resonance. We also suggest that the hydrogen abstraction observed in chlorophenols and phenol actually takes place by a mechanism in which the incoming electron is directly attached to the dissociative σOH ∗ orbital.

  1. Chiral Sensitivity in the Dissociative Electron Attachment of Halocamphor Molecules

    NASA Astrophysics Data System (ADS)

    Dreiling, Joan

    2016-05-01

    We have demonstrated chirally-dependent molecular destruction when incident longitudinally-spin-polarized (chiral) electrons break bonds in chiral molecules. This chiral sensitivity was observed through an asymmetry in the dissociative electron attachment (DEA) reaction rate with chiral 3-bromocamphor (C10 H15 BrO). Such an observation provides an unambiguous demonstration of the idea underlying the Vester-Ulbricht hypothesis, which attempts to explain the origins of the homochirality that is observed in many biological systems. While the lack of inversion symmetry in these reactions allows the effects we observe to occur, their dynamic causes are poorly understood. We have further studied the asymmetries in the DEA rates for two additional halocamphor molecules, 3-iodocamphor (C10 H15 IO) and 10-iodocamphor, in a systematic effort to illuminate the mechanisms responsible for the chiral sensitivity. The DEA signal depends on the sign of the incident electron helicity for a given target handedness in all molecules, and it varies with both the atomic number and the location of the heaviest atom in the molecule. Surprisingly, the DEA asymmetries for 10-iodocamphor, in which the heaviest atom is farther from a chiral center than for the other molecules, produced the largest asymmetries. This work was performed at the University of Nebraska-Lincoln. This project was funded by NSF Grant PHY-1206067.

  2. Ion Momentum Imaging of Dissociative Electron Attachment to Small Molecules

    NASA Astrophysics Data System (ADS)

    Fogle, Michael

    2015-09-01

    In recent years, low energy dissociative electron attachment (DEA) interactions have been of interest to varying biological and technological applications. To study the dynamics resulting from DEA, we used an ion-momentum imaging apparatus based on the Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) technique in which a molecular beam is crossed by a pulsed electron beam. The beam interaction takes place in a 4 π pulsed electrostatic spectrometer that collects the anion fragments resulting from DEA. The molecular beam is formed by a supersonic expansion which results in a well-localized and cold target. Using this apparatus we have investigated the DEA dynamics for several small molecules: CO2 at the 4 eV shape resonance and the 8 eV Feshbach resonance; N2O at the 2.3 eV shape resonance; HCCH at the 3 eV shape resonance; and CF4 near the 7 eV resonance. An overview of these experimental ion-momentum results will be compared to ab initio electronic structure and fixed-nuclei scattering calculations to gauge the resulting dynamics driven by DEA. In many cases, conical intersections play a pivotal role in driving the dynamics. Some of these systems exhibit non-axial recoil conditions indicative of a bending dynamics in the transitory negative ion state while others exhibit a direct axial recoil dissociation without any bending. This work is supported by the National Science Foundation under Contract NSF-PHYS1404366.

  3. Evaporative attachment of slow electrons to free sodium clusters

    NASA Astrophysics Data System (ADS)

    Rabinovich, Roman Mikhailovich

    We have carried out a measurement of the mass spectra of sodium cluster anions formed in the collisions of free neutral sodium clusters with beam of low energy (0.1 eV) electrons. Anions covering the size ranges from Na-7 to Na-92 and from Na-132 to Na-144 were observed. The anion mass spectra were recorded simultaneously with those of the precursor cluster beam, which allowed us to monitor the effect of electron capture on the relative abundances of various cluster sizes. The anion mass spectra demonstrated significant restructuring with respect to the precursor beam: a downshift of the shell-closing magic numbers, a change in the shape of the overall intensity envelope, and, significantly, an alteration in the relative intensities of the open-shell peaks located between the magic numbers. This alteration did not represent a simple pattern shift by one electron number, and required an accurate analysis. The restructuring of the mass spectra was treated theoretically by means of an evaporative attachment model, consisting of three steps: (a) electron capture by the strong polarization potential of the cluster, (b) rapid dissipation of the electron energy into the internal vibrational energy of the cluster (cluster heating), and a statistical evaporative cooling process (monomer and dimer evaporations). The analysis yielded results in good agreement with the experimental data and explained the fine structure of the observed abundance restructuring patterns. Based on an accurate statistical description of dimer evaporation we derived an adjustment to the previous literature values of sodium cluster dimer evaporation energies, which had been obtained from cluster photodissociation experiments. The exponential sensitivity of the evaporation process to the cluster evaporation energies allowed us to verify the validity of this adjustment. The corrected evaporation energies for dimers were found to be approximately 20% higher than the original values. The results

  4. Dissociative electron attachment to CO2 produces molecular oxygen

    NASA Astrophysics Data System (ADS)

    Wang, Xu-Dong; Gao, Xiao-Fei; Xuan, Chuan-Jin; Tian, Shan Xi

    2016-03-01

    Until recently, it was widely regarded that only one reaction pathway led to the production of molecular oxygen in Earth's prebiotic primitive atmosphere: a three-body recombination reaction of two oxygen atoms and a third body that removes excess energy. However, an additional pathway has recently been observed that involves the photodissociation of CO2 on exposure to ultraviolet light. Here we demonstrate a further pathway to O2 production, again from CO2, but via dissociative electron attachment (DEA). Using anion-velocity image mapping, we provide experimental evidence for a channel of DEA to CO2 that produces O2(X3Σ-g) + C-. This observed channel coexists in the same energy range as the competitive three-body dissociation of CO2 to give O + O + C-. The abundance of low-energy electrons in interstellar space and the upper atmosphere of Earth suggests that the contributions of these pathways are significant and should be incorporated into atmospheric chemistry models.

  5. Precursor anion states in dissociative electron attachment to chlorophenol isomers.

    PubMed

    Kossoski, F; Varella, M T do N

    2016-07-28

    We report a theoretical study on low-energy (<10 eV) elastic electron scattering from chlorophenol isomers, namely, para-chlorophenol (pCP), meta-chlorophenol (mCP), and ortho-chlorophenol (oCP). The calculations were performed with the Schwinger multichannel method with pseudopotentials, and analysis of the computed integral cross sections and virtual orbitals revealed one σCCl (∗), one σOH (∗), and three π(∗) shape resonances. We show that electron capture into the two lower lying π(∗) orbitals initiates dissociative processes that lead to the elimination of the chloride ion, accounting for the two overlapping peaks where this fragment was observed. Despite the relatively small differences on the energetics of the π(∗) resonances, a major isomeric effect was found on their corresponding autodetachment lifetimes, which accounts for the observed increasing cross sections in the progression pCP < mCP < oCP. In particular, dissociation from the π1 (∗) anion of pCP is largely suppressed because of the unfavorable mixing with the σCCl (∗) state. We found the intramolecular hydrogen bond present in oCP to have the opposite effects of stabilizing the σCCl (∗) resonance and destabilizing the σOH (∗) resonance. We also suggest that the hydrogen abstraction observed in chlorophenols and phenol actually takes place by a mechanism in which the incoming electron is directly attached to the dissociative σOH (∗) orbital. PMID:27475364

  6. Detection of explosives, nerve agents, and illicit substances by zero-energy electron attachment

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Darrach, M. R.

    2000-01-01

    The Reversal Electron Attachment Detection (READ) method, developed at JPL/Caltech, has been used to detect a variety of substances which have electron-attachment resonances at low and intermediate electron energies. In the case of zero-energy resonances, the cross section (hence attachment probability and instrument sensitivity) is mediated by the so-called s-wave phenomenon, in which the cross sections vary as the inverse of the electron velocity. Hence this is, in the limit of zero electron energy or velocity, one of the rare cases in atomic and molecular physics where one carries out detection via infinite cross sections.

  7. Predictive a priori pressure-dependent kinetics.

    PubMed

    Jasper, Ahren W; Pelzer, Kenley M; Miller, James A; Kamarchik, Eugene; Harding, Lawrence B; Klippenstein, Stephen J

    2014-12-01

    The ability to predict the pressure dependence of chemical reaction rates would be a great boon to kinetic modeling of processes such as combustion and atmospheric chemistry. This pressure dependence is intimately related to the rate of collision-induced transitions in energy E and angular momentum J. We present a scheme for predicting this pressure dependence based on coupling trajectory-based determinations of moments of the E,J-resolved collisional transfer rates with the two-dimensional master equation. This completely a priori procedure provides a means for proceeding beyond the empiricism of prior work. The requisite microcanonical dissociation rates are obtained from ab initio transition state theory. Predictions for the CH4 = CH3 + H and C2H3 = C2H2 + H reaction systems are in excellent agreement with experiment. PMID:25477457

  8. Predictive a priori pressure-dependent kinetics.

    PubMed

    Jasper, Ahren W; Pelzer, Kenley M; Miller, James A; Kamarchik, Eugene; Harding, Lawrence B; Klippenstein, Stephen J

    2014-12-01

    The ability to predict the pressure dependence of chemical reaction rates would be a great boon to kinetic modeling of processes such as combustion and atmospheric chemistry. This pressure dependence is intimately related to the rate of collision-induced transitions in energy E and angular momentum J. We present a scheme for predicting this pressure dependence based on coupling trajectory-based determinations of moments of the E,J-resolved collisional transfer rates with the two-dimensional master equation. This completely a priori procedure provides a means for proceeding beyond the empiricism of prior work. The requisite microcanonical dissociation rates are obtained from ab initio transition state theory. Predictions for the CH4 = CH3 + H and C2H3 = C2H2 + H reaction systems are in excellent agreement with experiment.

  9. Small-scale plasma irregularities produced during electron attachment chemical releases

    NASA Technical Reports Server (NTRS)

    Scales, W. A.; Bernhardt, P. A.; Ganguli, G.; Siefring, C. L.; Rodriguez, P.

    1994-01-01

    In situ measurements of small-scale plasma density irregularities made during sounding rocket experiments that released electron attachment materials into the ionosphere are presented. A 2D electrostatic simulation model that includes attachment chemistry is used to study the source and evolution of these irregularities. The simulation shows (1) that large electron flow velocity shears develop on the boundary of the electron depletion and (2) these shears drive a plasma instability that is the likely source of the irregularities.

  10. Electron affinity of trans-2-C4F8 from electron attachment-detachment kinetics.

    PubMed

    Van Doren, Jane M; Condon, Laura R; DeSouza-Goding, Antonet; Miller, Thomas M; Bopp, Joseph C; Viggiano, A A

    2010-01-28

    Electron attachment and detachment kinetics of 2-C(4)F(8) were studied over the temperature range 298-487 K with a flowing-afterglow Langmuir-probe apparatus. Only parent anions were formed in the attachment process throughout this temperature range. At the highest temperatures, thermal electron detachment of the parent anions is important. Analysis of the 2-C(4)F(8) gas showed an 82/18 mixture of trans/cis isomers. The kinetic data at the higher temperatures were used to determine the electron affinity EA(trans-2-C(4)F(8)) = 0.79 +/- 0.06 eV after making some reasonable assumptions. The same quantity was calculated using the G3(MP2) compound method, yielding 0.74 eV. The kinetic data were not sufficient to establish a reliable value for EA(cis-2-C(4)F(8)), but G3(MP2) calculations give a value 0.017 eV greater than that for trans-2-C(4)F(8). MP2 and density functional theory were used to study the structural properties of the neutral and anion isomers.

  11. Substrate dependence of electron-stimulated O - yields from dissociative electron attachment to physisorbed O2

    NASA Astrophysics Data System (ADS)

    Huels, M. A.; Parenteau, L.; Sanche, L.

    1994-03-01

    We present measurements of O- electron stimulated desorption yields obtained under identical experimental conditions from 0.15 monolayers (ML) of O2 deposited onto disordered substrates consisting of 4 ML of either Kr, Xe, C2H6, C2H4, N2O, CH3Cl, or H2O, all condensed on Pt (polycrystalline). The resulting O- yield functions, for incident electron energies below 20 eV, are compared to that obtained from the O2/Kr solid; this allows us to assess the order of magnitude effects of the local substrate environment on dissociative electron attachment (DEA) via the 2Πu and gas phase forbidden 2Σ+g,u resonances of O-2. We note that, in addition to electron energy losses in the substrate prior to DEA to O2 and post-dissociation interactions of the O- with the substrate molecules, charge or energy transfer from the O-2 transient anion to a substrate molecule, and capture of the incident electron into a dissociative anion resonance of the substrate molecule may contribute to a reduced O- yield from the physisorbed O2. In the case of O2 deposited on amorphous ice, we find that the O- signal from DEA to O2 is completely absent for electron energies below 14 eV; we attribute this to a complete quenching of the dissociative O-2(2Πu, 2Σ+) resonances by the adjacent water molecules.

  12. Irreversible electron attachment--a key to DNA damage by solvated electrons in aqueous solution.

    PubMed

    Westphal, K; Wiczk, J; Miloch, J; Kciuk, G; Bobrowski, K; Rak, J

    2015-11-01

    The TYT and TXT trimeric oligonucleotides, where X stands for a native nucleobase, T (thymine), C (cytosine), A (adenine), or G (guanine), and Y indicates a brominated analogue of the former, were irradiated with ionizing radiation generated by a (60)Co source in aqueous solutions containing Tris as a hydroxyl radical scavenger. In the past, these oligomers were bombarded with low energy electrons under an ultra-high vacuum and significant damage to TXT trimers was observed. However, in aqueous solution, hydrated electrons do not produce serious damage to TXT trimers although the employed radiation dose exceeded many times the doses used in radiotherapy. Thus, our studies demonstrate unequivocally that hydrated electrons, which are the major form of electrons generated during radiotherapy, are a negligible factor in damage to native DNA. It was also demonstrated that all the studied brominated nucleobases have a potential to sensitize DNA under hypoxic conditions. Strand breaks, abasic sites and the products of hydroxyl radical attachment to nucleobases have been identified by HPLC and LC-MS methods. Although all the bromonucleobases lead to DNA damage under the experimental conditions of the present work, bromopyrimidines seem to be the radiosensitizers of choice since they lead to more strand breaks than bromopurines.

  13. Electron attachment properties of c-C4F8O in different environments

    NASA Astrophysics Data System (ADS)

    Chachereau, A.; Fedor, J.; Janečková, R.; Kočišek, J.; Rabie, M.; Franck, C. M.

    2016-09-01

    The electron attachment properties of octafluorotetrahydrofuran (c-C4F8O) are investigated using two complementary experimental setups. The attachment and ionization cross sections of c-C4F8O are measured using an electron beam experiment. The effective ionization rate coefficient, electron drift velocity and electron diffusion coefficient in c-C4F8O diluted to concentrations lower than 0.6% in the buffer gases N2, CO2 and Ar, are measured using a pulsed Townsend experiment. A kinetic model is proposed, which combines the results of the two experiments.

  14. Effect of Near-Threshold Ionization on Electron Attachment in Gaseous Dielectrics

    NASA Astrophysics Data System (ADS)

    Sugawara, Hirotake; Ishigaki, Takuya; Hirochi, Yuuki; Sakai, Yosuke

    2004-11-01

    It has been predicted that near-threshold ionization (NTI) in a gaseous dielectric inhibits the development of electron avalanche when the gaseous dielectric has a sufficient capability for low-energy electron attachment. The NTI leaves little energy for the primary and secondary electrons involved in the ionization; thus, both electrons can be captured by dielectric gas molecules without further ionization. A computational estimation indicates that this process can occur in SF6.

  15. 46 CFR 67.218 - Optional filing of instruments in portable document format as attachments to electronic mail.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... format as attachments to electronic mail. 67.218 Section 67.218 Shipping COAST GUARD, DEPARTMENT OF... format as attachments to electronic mail. (a) Any instrument identified as eligible for filing and recording under § 67.200 may be submitted in portable document format (.pdf) as an attachment to...

  16. Note: Coherent resonances observed in the dissociative electron attachment to carbon monoxide

    SciTech Connect

    Wang, Xu-Dong; Xuan, Chuan-Jin; Tian, Shan Xi; Luo, Yi

    2015-08-14

    Succeeding our previous finding about coherent interference of the resonant states of CO{sup −} formed by the low-energy electron attachment [Tian et al. Phys. Rev. A 88, 012708 (2013)], here we provide further evidence of the coherent interference. The completely backward distributions of the O{sup −} fragment of the temporary CO{sup −} are observed with anion velocity map imaging technique in an electron energy range of 11.3–12.6 eV and explained as the results of the coherent interferences of three resonant states. Furthermore, the state configuration of the interference is changed with the increase of electron attachment energy.

  17. Note: Coherent resonances observed in the dissociative electron attachment to carbon monoxide.

    PubMed

    Wang, Xu-Dong; Xuan, Chuan-Jin; Luo, Yi; Tian, Shan Xi

    2015-08-14

    Succeeding our previous finding about coherent interference of the resonant states of CO(-) formed by the low-energy electron attachment [Tian et al. Phys. Rev. A 88, 012708 (2013)], here we provide further evidence of the coherent interference. The completely backward distributions of the O(-) fragment of the temporary CO(-) are observed with anion velocity map imaging technique in an electron energy range of 11.3-12.6 eV and explained as the results of the coherent interferences of three resonant states. Furthermore, the state configuration of the interference is changed with the increase of electron attachment energy.

  18. Electron impact ionization and attachment cross sections for H2S. [in comet and planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Rao, M. V. V. S.; Srivastava, S. K.

    1993-01-01

    Experiments were performed to measure, by electron impact, appearance potentials and the cross sections for ionization, dissociative ionization, and electron attachment for H2S. Results are presented, and discussed individually, for both positive and negative ions. A schematic diagram of the experimental setup is included.

  19. Electron attachment to the interhalogens ClF, ICl, and IBr

    NASA Astrophysics Data System (ADS)

    Miller, T. M.; Wiens, J. P.; Sawyer, J. C.; Shuman, N. S.; Viggiano, A. A.; Khamesian, M.; Kokoouline, V.; Fabrikant, I. I.

    2016-05-01

    Electron attachment rate coefficients have been measured for the interhalogens ClF, ICl, and IBr over the range 300-900 K using a flowing-afterglow Langmuir-probe apparatus. The ClF case was also studied theoretically. ClF was found to attach electrons somewhat inefficiently with a rate coefficient of 7.5x 10-9 cm3/s at 300 K, doubling by 700 K. Even so, attachment to ClF is more efficient than seen earlier for F2 and Cl2, which brings up the interesting distinction that attachment to F2 and Cl2 is known to have p-wave threshold behavior, while in ClF the inversion symmetry is broken, allowing an s-wave component. The increase in the rate coefficient for attachment to ClF with temperature was found to be less pronounced than with F2 and Cl2. Ab initio potential energy curves were calculated for ClF and ClF-, and R-matrix theory was used to obtain the resonance widths and energies for the ground state curve crossing, which takes place near the equilibrium internuclear separation in ClF. A local complex potential model was used to calculate attachment cross sections and thermal rate coefficients. There is reasonable agreement between theory and experiment within the estimated 25% uncertainties in the data. Cl- is the only product ion from thermal electron attachment to ClF. Attachment to ICl is even less efficient by almost an order of magnitude than to ClF, namely, 9.5x 10-10 cm3/s at 300 K. Attachment to IBr is small enough that we place an upper limit of < 10-10 cm3/s at 300 K. Supported by AFOSR, DOE, and NSF.

  20. Probing dissociative electron attachment through heavy-Rydberg ion-pair production in Rydberg atom collisions

    NASA Astrophysics Data System (ADS)

    Buathong, S.; Kelley, M.; Dunning, F. B.

    2016-10-01

    Electron transfer in collisions between low-n, n = 12, Rydberg atoms and targets that attach low-energy electrons can lead to the formation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair that orbit each other at large separations. Measurements of the velocity and angular distribution of ion-pair states produced in collisions with 1,1,1-C2Cl3F3, CBrCl3, BrCN, and Fe(CO)5 are used to show that electron transfer reactions furnish a new technique with which to examine the lifetime and decay energetics of the excited intermediates formed during dissociative electron capture. The results are analyzed with the aid of Monte Carlo simulations based on the free electron model of Rydberg atom collisions. The data further highlight the capabilities of Rydberg atoms as a microscale laboratory in which to probe the dynamics of electron attachment reactions.

  1. Dissociative electron attachment to dinitrogen pentoxide, N{sub 2}O{sub 5}

    SciTech Connect

    Cicman, P.; Buchanan, G.A.; Marston, G.; Gulejova, B.; Skalny, J.D.; Mason, N.J.; Scheier, P.; Maerk, T.D.

    2004-11-22

    Electron attachment was studied in gaseous dinitrogen pentoxide, N{sub 2}O{sub 5}, for incident electron energies between a few meV and 10 eV. No stable parent anion N{sub 2}O{sub 5}{sup -} was observed but several anionic fragments (NO{sub 3}{sup -}, NO{sub 2}{sup -}, NO{sup -}, O{sup -}, and O{sub 2}{sup -}) were detected using quadrupole mass spectrometry. Many of these dissociative pathways were found to be coupled and provide detailed information on the dynamics of N{sub 2}O{sub 5} fragmentation. Estimates of the cross sections for production of each of the anionic fragments were made and suggest that electron attachment to N{sub 2}O{sub 5} is amongst the most efficient attachment reactions recorded for nonhalogenated polyatomic systems.

  2. Dissociative electron attachments to ethanol and acetaldehyde: A combined experimental and simulation study

    NASA Astrophysics Data System (ADS)

    Wang, Xu-Dong; Xuan, Chuan-Jin; Feng, Wen-Ling; Tian, Shan Xi

    2015-02-01

    Dissociation dynamics of the temporary negative ions of ethanol and acetaldehyde formed by the low-energy electron attachments is investigated by using the anion velocity map imaging technique and ab initio molecular dynamics simulations. The momentum images of the dominant fragments O-/OH- and CH3- are recorded, indicating the low kinetic energies of O-/OH- for ethanol while the low and high kinetic energy distributions of O- ions for acetaldehyde. The CH3- image for acetaldehyde also shows the low kinetic energy. With help of the dynamics simulations, the fragmentation processes are qualitatively clarified. A new cascade dissociation pathway to produce the slow O- ion via the dehydrogenated intermediate, CH3CHO- (acetaldehyde anion), is proposed for the dissociative electron attachment to ethanol. After the electron attachment to acetaldehyde molecule, the slow CH3- is produced quickly in the two-body dissociation with the internal energy redistributions in different aspects before bond cleavages.

  3. Effect of cluster environment on the electron attachment to 2-nitrophenol*

    NASA Astrophysics Data System (ADS)

    Kočišek, Jaroslav; Grygoryeva, Kateryna; Lengyel, Jozef; Fárník, Michal; Fedor, Juraj

    2016-04-01

    Effect of cluster environment on the electron attachment to 2-nitrophenol (2NP) is studied in homogeneous 2NP clusters and heterogeneous clusters of 2NP, argon and water. The cluster environment significantly reduces fragmentation of 2NP after electron attachment. Parent cluster anions 2NPn- are primary reaction products in both, homogeneous and heterogeneous clusters. Non-dissociative electron attachment to homogeneous clusters proceeds at low energies <2 eV, presumably via dipole-supported states. In heterogeneous clusters, the interaction with low energy (<2 eV) electrons is shielded by the solvent. Surprisingly, the energetic threshold for the electron attachment rises with the number (n) of 2NP molecules in the cluster (2NP)n-. This rise can be either due to a strong change of the 2NP conformation induced by the cluster environment or due to the the competition with electron autodetachment after proton transfer that has been first observed by Allan in the formic acid dimer [M. Allan, Phys. Rev. Lett. 98, 123201 (2007)]. We observe the same threshold rise for complex Arm·(2NP)n- and H2O·(2NP)n- anions. This indicates that the electron attachment to 2-nitrophenol in cluster environment is more influenced by the solute - solute interaction compared to the solute - solvent interaction. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2016-70074-0

  4. Dissociative attachment of electrons to vibronically excited SO{sub 2}

    SciTech Connect

    Kumar, S.V.K.; Ashoka, V.S.; Krishnakumar, E.

    2004-11-01

    Dissociative electron attachment (DEA) to vibronically excited SO{sub 2} in the Clements' band in the 288 to 298 nm region has been studied. The O{sup -} ion yield, to a first approximation, follows the photo absorption spectrum in this range indicating the DEA process to be independent of the vibrational levels in this band. This is in contrast to what is generally observed for vibrational level dependence from the electronic ground state. The current measurements also do not show any qualitative change in the dissociative attachment process due to change of symmetry as one moves from the peaks to the valleys of the Clements band.

  5. Dissociative electron attachment to C{sub 2}F{sub 5} radicals

    SciTech Connect

    Haughey, Sean A.; Field, Thomas A.; Langer, Judith; Shuman, Nicholas S.; Miller, Thomas M.; Friedman, Jeffrey F.; Viggiano, A. A.

    2012-08-07

    Dissociative electron attachment to the reactive C{sub 2}F{sub 5} molecular radical has been investigated with two complimentary experimental methods; a single collision beam experiment and a new flowing afterglow Langmuir probe technique. The beam results show that F{sup -} is formed close to zero electron energy in dissociative electron attachment to C{sub 2}F{sub 5}. The afterglow measurements also show that F{sup -} is formed in collisions between electrons and C{sub 2}F{sub 5} molecules with rate constants of 3.7 Multiplication-Sign 10{sup -9} cm{sup 3} s{sup -1} to 4.7 Multiplication-Sign 10{sup -9} cm{sup 3} s{sup -1} at temperatures of 300-600 K. The rate constant increases slowly with increasing temperature, but the rise observed is smaller than the experimental uncertainty of 35%.

  6. Imaging of the dissociation dynamics of polyatomic molecules following low-energy electron resonant attachment

    NASA Astrophysics Data System (ADS)

    Belkacem, Ali

    2014-05-01

    There is a very large body of experimental work on dissociative electron attachment to molecules but the majority of that work is focused on the measurement of absolute total cross sections or energetic positions of the resonances. There is scarce information on the dynamics of electron attachment and the subsequent dissociation that often involves highly non-Born-Oppenheimer dynamics, funneling through conical intersections or intricate nuclear motion during the dissociation process. Through COLTRIMS detection techniques we investigate the electron attachment in a fixed-in-frame manner that yields direct information on the symmetries of the neutral and negatively charged resonant states. We will present a study that combines experimental data along with theoretical analysis of dissociative electron attachment to carbon dioxide, methanol and uracil. In these studies we demonstrated that an understanding of anion dissociation dynamics beyond simple one-dimensional models is crucial in interpreting the measured angular distributions. This work is supported by the Chemical Sciences Biosciences and Geosciences Division, Basic Energy Sciences, DOE.

  7. Dissociative Electron Attachment to Carbon Dioxide via the 8.2 eV Feshbach resonance

    SciTech Connect

    Slaughter, Dan; Adaniya, Hidihito; Rescigno, Tom; Haxton, Dan; Orel, Ann; McCurdy, Bill; Belkacem, Ali

    2011-08-17

    Momentum imaging experiments on dissociative electron attachment (DEA) to CO{sub 2} are combined with the results of ab initio calculations to provide a detailed and consistent picture of the dissociation dynamics through the 8.2 eV resonance, which is the major channel for DEA in CO{sub 2}. The present study resolves several puzzling misconceptions about this system.

  8. Electronic Communications Technologies and the Transition to College: Links to Parent-Child Attachment and Adjustment

    ERIC Educational Resources Information Center

    Sarigiani, Pamela A.; Trumbell, Jill M.; Camarena, Phame M.

    2013-01-01

    Electronic communications technologies (ECTs) help college students and parents remain in contact. Because recent reports have emphasized a link between ECTs, helicopter parenting, and autonomy issues, this study focused on the significance of contact patterns for attachment and student adjustment. First-semester college students (199 female, 81…

  9. Early time evolution of negative ion clouds and electron density depletions produced during electron attachment chemical release experiments

    NASA Technical Reports Server (NTRS)

    Scales, W. A.; Bernhardt, P. A.; Ganguli, G.

    1994-01-01

    Two-dimensional electrostatic particle-in-cell simulations are used to study the early time evolution of electron depletions and negative ion clouds produced during electron attachment chemical releases in the ionosphere. The simulation model considers the evolution in the plane perpendicular to the magnetic field and a three-species plasma that contains electrons, positive ions, and also heavy negative ions that result as a by-product of the electron attachment reaction. The early time evolution (less than the negative ion cyclotron period) of the system shows that a negative charge surplus initially develops outside of the depletion boundary as the heavy negative ions move across the boundary. The electrons are initially restricted from moving into the depletion due to the magnetic field. An inhomogenous electric field develops across the boundary layer due to this charge separation. A highly sheared electron flow velocity develops in the depletion boundary due to E x B and Delta-N x B drifts that result from electron density gradients and this inhomogenous electric field. Structure eventually develops in the depletion boundary layer due to low-frequency electrostatic waves that have growth times shorter than the negative ion cyclotron period. It is proposed that these waves are most likely produced by the electron-ion hybrid instability that results from sufficiently large shears in the electron flow velocity.

  10. Momentum Imaging of the Dynamics of Dissociative Electron Attachment to Uracil

    NASA Astrophysics Data System (ADS)

    Slaughter, Dan; Kawarai, Yu; Weber, Thorsten; Azuma, Yoshiro; Winstead, Carl; McKoy, Vince; Belkacem, Ali

    2013-05-01

    Observation of the dynamics of dissociative electron attachment (DEA) in biomolecules has recently become possible by momentum imaging of the fragments resulting from the dissociating transient anion resonance. A momentum spectrometer featuring a 4 π solid angle of detection is combined with a pulsed electron beam and effusive molecular beam in a crossed geometry to measure the full 3D momentum distribution of dissociating negative ions. Guided by electronic structure calculations that indicate the most likely orientation of the molecule at the time of attachment, we present key aspects of the dynamics of ring-breaking dissociation of the transient anion formed upon DEA to the nucleobase uracil. Performed under the auspices of the US DOE by LBNL under Contract DE-AC02-05CH11231.

  11. Dissociative Electron Attachment Dynamics in the Nucleobase Uracil and Related Molecules

    NASA Astrophysics Data System (ADS)

    Slaughter, Daniel; Kuriyama, Yosuke; Kawarai, Yu; Azuma, Yoshiro; Winstead, Carl; McKoy, Vincent; Weber, Thorsten; Belkacem, Ali

    2015-05-01

    We report the dynamics of dissociative electron attachment (DEA) in the biologically-relevant molecule uracil and the diazines pyrazine and pyrimidine. Our DEA reaction microscope consists of a 3D momentum-imaging spectrometer, a pulsed low-energy electron gun and an effusive gas target. The experimental approach allows the measurement of kinetic energy and angular distributions of ionic fragments produced by DEA, in some cases elucidating the total kinetic energy release following two-body breakup. By comparison of calculations of the electron attachment probability in the molecular frame with measured ion angular distributions, we determine that one of the uracil anion resonances could be a Feshbach resonance and we compare the dynamics of the dissociation of the uracil anion with the diazines. Work supported by Chemical Sciences, Geosciences and Biosciences division of BES/DOE

  12. Dissociative Electron Attachment to Phosphoric Acid Esters: The Direct Mechanism for Single Strand Breaks in DNA

    SciTech Connect

    Koenig, Constanze; Kopyra, Janina; Bald, Ilko; Illenberger, Eugen

    2006-07-07

    We use dibutyl phosphate to simulate the behavior of the phosphate group in DNA towards the attack of low energy electrons. We find that the compound undergoes effective dissociative electron attachment within a low energy resonant feature at 1 eV and a further resonance peaking at 8 eV. The dissociative electron attachment (DEA) reactions are associated with the direct cleavage of the C-O and the P-O bond but also the excision of the PO{sup -}, PO{sub 3}{sup -}, H{sub 2}PO{sub 3}{sup -} units. For the phosphate group coupled in the DNA network these reactions represent single strand breaks. We hence propose that the most direct mechanism of single strand breaks occurring in DNA at subexcitation energies (<4 eV) is due to DEA directly to the phosphate group.

  13. Analysis by kinetic modeling of the temperature dependence of thermal electron attachment to CF3Br.

    PubMed

    Troe, Jürgen; Miller, Thomas M; Shuman, Nicholas S; Viggiano, Albert A

    2012-07-14

    Experimental data from the literature for cross sections and rate constants for dissociative electron attachment to CF(3)Br, with separately varied electron and gas temperatures, are analyzed by a kinetic modeling approach. The analysis suggests that electronic and nuclear contributions to the rate constants can be roughly separated, the former leading to a negative temperature coefficient, the latter to a positive temperature coefficient. The nuclear factor in the rate constant is found to be of Arrhenius form with an activation energy which is close to the energy of crossing of the CF(3)Br and CF(3)Br(-) potential curves along the CBr bond. PMID:22803532

  14. Anomalously Large Chiral Sensitivity in the Dissociative Electron Attachment of 10-Iodocamphor

    NASA Astrophysics Data System (ADS)

    Dreiling, J. M.; Lewis, F. W.; Mills, J. D.; Gay, T. J.

    2016-03-01

    We have studied dissociative electron attachment (DEA) between low energy (≤0.6 eV ) longitudinally polarized electrons and gas-phase chiral targets of 3-bromocamphor (C10 H15 BrO ), 3-iodocamphor (C10 H15 IO ), and 10-iodocamphor. The DEA rate depends on the sign of the incident electron helicity for a given target handedness, and it varies with both the atomic number (Z ) and location of the heaviest atom in the molecule. While simple dynamic mechanisms can account for the asymmetry dependence on Z , they fail to explain the large asymmetry variation with the heavy atom location.

  15. Three-body breakup in dissociative electron attachment to the water molecule

    SciTech Connect

    Haxton, Daniel J.; Rescigno, Thomas N.; McCurdy, C. William

    2008-08-28

    We report the results of {\\em ab initio} calculations on dissociative electron attachment (DEA) to water that demonstrate the importance of including three-body breakup in the dissociation dynamics. While three-body breakup is ubiquitous in the analogous process of dissociative recombination, its importance in low-energy dissociative electron attachment to a polyatomic target has not previously been quantified. Our calculations, along with our earlier studies of DEA into two-body channels, indicate that three-body breakup is a major component of the observed O- cross section. The local complex potential model provides a generally accurate picture of the experimentallyobserved features in this system, reproducing some quantitatively, others qualitatively, and one not at all.

  16. Resonance electron attachment to plant hormones and its likely connection with biochemical processes

    SciTech Connect

    Pshenichnyuk, Stanislav A.; Modelli, Alberto

    2014-01-21

    Gas-phase formation of temporary negative ion states via resonance attachment of low-energy (0–6 eV) electrons into vacant molecular orbitals of salicylic acid (I) and its derivatives 3-hydroxy- (II) and 4-hydroxybenzoic acid (III), 5-cloro salicylic acid (IV) and methyl salicylate (V) was investigated for the first time by electron transmission spectroscopy. The description of their empty-level structures was supported by density functional theory and Hartree-Fock calculations, using empirically calibrated linear equations to scale the calculated virtual orbital energies. Dissociative electron attachment spectroscopy (DEAS) was used to measure the fragment anion yields generated through dissociative decay channels of the parent molecular anions of compounds I–V, detected with a mass filter as a function of the incident electron energy in the 0–14 eV energy range. The most intense negative fragment produced by DEA to isomers I–III is the dehydrogenated molecular anion [M–H]{sup −}, mainly formed at incident electron energies around 1 eV. The vertical and adiabatic electron affinities were evaluated at the B3LYP/6-31+G(d) level as the anion/neutral total energy difference. The same theoretical method was also used for evaluation of the thermodynamic energy thresholds for production of the negative fragments observed in the DEA spectra. The gas-phase DEAS data can provide support for biochemical reaction mechanisms in vivo.

  17. Resonance electron attachment to plant hormones and its likely connection with biochemical processes.

    PubMed

    Pshenichnyuk, Stanislav A; Modelli, Alberto

    2014-01-21

    Gas-phase formation of temporary negative ion states via resonance attachment of low-energy (0-6 eV) electrons into vacant molecular orbitals of salicylic acid (I) and its derivatives 3-hydroxy- (II) and 4-hydroxybenzoic acid (III), 5-cloro salicylic acid (IV) and methyl salicylate (V) was investigated for the first time by electron transmission spectroscopy. The description of their empty-level structures was supported by density functional theory and Hartree-Fock calculations, using empirically calibrated linear equations to scale the calculated virtual orbital energies. Dissociative electron attachment spectroscopy (DEAS) was used to measure the fragment anion yields generated through dissociative decay channels of the parent molecular anions of compounds I-V, detected with a mass filter as a function of the incident electron energy in the 0-14 eV energy range. The most intense negative fragment produced by DEA to isomers I-III is the dehydrogenated molecular anion [M-H](-), mainly formed at incident electron energies around 1 eV. The vertical and adiabatic electron affinities were evaluated at the B3LYP/6-31+G(d) level as the anion/neutral total energy difference. The same theoretical method was also used for evaluation of the thermodynamic energy thresholds for production of the negative fragments observed in the DEA spectra. The gas-phase DEAS data can provide support for biochemical reaction mechanisms in vivo. PMID:25669385

  18. Resonance electron attachment to plant hormones and its likely connection with biochemical processes.

    PubMed

    Pshenichnyuk, Stanislav A; Modelli, Alberto

    2014-01-21

    Gas-phase formation of temporary negative ion states via resonance attachment of low-energy (0-6 eV) electrons into vacant molecular orbitals of salicylic acid (I) and its derivatives 3-hydroxy- (II) and 4-hydroxybenzoic acid (III), 5-cloro salicylic acid (IV) and methyl salicylate (V) was investigated for the first time by electron transmission spectroscopy. The description of their empty-level structures was supported by density functional theory and Hartree-Fock calculations, using empirically calibrated linear equations to scale the calculated virtual orbital energies. Dissociative electron attachment spectroscopy (DEAS) was used to measure the fragment anion yields generated through dissociative decay channels of the parent molecular anions of compounds I-V, detected with a mass filter as a function of the incident electron energy in the 0-14 eV energy range. The most intense negative fragment produced by DEA to isomers I-III is the dehydrogenated molecular anion [M-H](-), mainly formed at incident electron energies around 1 eV. The vertical and adiabatic electron affinities were evaluated at the B3LYP/6-31+G(d) level as the anion/neutral total energy difference. The same theoretical method was also used for evaluation of the thermodynamic energy thresholds for production of the negative fragments observed in the DEA spectra. The gas-phase DEAS data can provide support for biochemical reaction mechanisms in vivo.

  19. Resonance electron attachment to plant hormones and its likely connection with biochemical processes

    NASA Astrophysics Data System (ADS)

    Pshenichnyuk, Stanislav A.; Modelli, Alberto

    2014-01-01

    Gas-phase formation of temporary negative ion states via resonance attachment of low-energy (0-6 eV) electrons into vacant molecular orbitals of salicylic acid (I) and its derivatives 3-hydroxy- (II) and 4-hydroxybenzoic acid (III), 5-cloro salicylic acid (IV) and methyl salicylate (V) was investigated for the first time by electron transmission spectroscopy. The description of their empty-level structures was supported by density functional theory and Hartree-Fock calculations, using empirically calibrated linear equations to scale the calculated virtual orbital energies. Dissociative electron attachment spectroscopy (DEAS) was used to measure the fragment anion yields generated through dissociative decay channels of the parent molecular anions of compounds I-V, detected with a mass filter as a function of the incident electron energy in the 0-14 eV energy range. The most intense negative fragment produced by DEA to isomers I-III is the dehydrogenated molecular anion [M-H]-, mainly formed at incident electron energies around 1 eV. The vertical and adiabatic electron affinities were evaluated at the B3LYP/6-31+G(d) level as the anion/neutral total energy difference. The same theoretical method was also used for evaluation of the thermodynamic energy thresholds for production of the negative fragments observed in the DEA spectra. The gas-phase DEAS data can provide support for biochemical reaction mechanisms in vivo.

  20. Dissociative electron attachments to ethanol and acetaldehyde: A combined experimental and simulation study

    SciTech Connect

    Wang, Xu-Dong; Xuan, Chuan-Jin; Feng, Wen-Ling; Tian, Shan Xi

    2015-02-14

    Dissociation dynamics of the temporary negative ions of ethanol and acetaldehyde formed by the low-energy electron attachments is investigated by using the anion velocity map imaging technique and ab initio molecular dynamics simulations. The momentum images of the dominant fragments O{sup −}/OH{sup −} and CH{sub 3}{sup −} are recorded, indicating the low kinetic energies of O{sup −}/OH{sup −} for ethanol while the low and high kinetic energy distributions of O{sup −} ions for acetaldehyde. The CH{sub 3}{sup −} image for acetaldehyde also shows the low kinetic energy. With help of the dynamics simulations, the fragmentation processes are qualitatively clarified. A new cascade dissociation pathway to produce the slow O{sup −} ion via the dehydrogenated intermediate, CH{sub 3}CHO{sup −} (acetaldehyde anion), is proposed for the dissociative electron attachment to ethanol. After the electron attachment to acetaldehyde molecule, the slow CH{sub 3}{sup −} is produced quickly in the two-body dissociation with the internal energy redistributions in different aspects before bond cleavages.

  1. Electron attachment and detachment, and the electron affinities of C5F5N and C5HF4N.

    PubMed

    Van Doren, Jane M; Kerr, Donna M; Miller, Thomas M; Viggiano, A A

    2005-09-15

    Rate constants have been measured for electron attachment to C5F5N (297-433 K) and to 2, 3, 5, 6-C5HF4N (303 K) using a flowing-afterglow Langmuir-probe apparatus (at a He gas pressure of 133 Pa). In both cases only the parent anion was formed in the attachment process. The attachment rate constants measured at room temperature are 1.8 +/- 0.5 X 10(-7) and 7 +/- 3 X 10(-10) cm(-3) s(-1), respectively. Rate constants were also measured for thermal electron detachment from the parent anions of these molecules. For C5F5N- detachment is negligible at room temperature, but increases to 2530 +/- 890 s(-1) at 433 K. For 2, 3, 5, 6-C5HF4N-, the detachment rate at 303 K was 520 +/- 180 s(-1). The attachment/detachment equilibrium yielded experimental electron affinities EA(C5F5N)=0.70 +/- 0.05 eV and EA(2, 3, 5, 6-C5HF4N)=0.40 +/- 0.08 eV. Electronic structure calculations were carried out for these molecules and related C5HxF5-xN using density-functional theory and the G3(MP2)//B3LYP compound method. The EAs are found to decrease by 0.25 eV, on average, with each F substitution by H. The calculated EAs are in good agreement with the present experimental results.

  2. Carbon monoxide dissociative attachment and resonant dissociation by electron-impact

    NASA Astrophysics Data System (ADS)

    Laporta, V.; Tennyson, J.; Celiberto, R.

    2016-02-01

    Low-energy dissociative electron attachment and resonant electron impact dissociation of CO molecule are considered. Ro-vibrationally resolved cross sections and rate coefficients for both the processes are calculated using an ab-initio model based on the low-lying \\text{X}{{}2}\\Pi resonance of CO-. Final results show that the cross sections increases very rapidly as a function of the ro-vibrational level; these cross sections should be useful for understanding kinetic dissociation of CO in strongly non-equilibrium plasmas.

  3. A first-principles study of electron attachment to the fully hydrated bromonucleobases

    NASA Astrophysics Data System (ADS)

    Wieczór, Miłosz; Wityk, Paweł; Czub, Jacek; Chomicz, Lidia; Rak, Janusz

    2014-03-01

    Degradation mechanism of four brominated nucleobases (BrX), potential DNA radiosensitizers, is studied in explicit water solution, using ab initio molecular dynamics. Several fs long dynamics is needed to localize an electron on the nucleobase. Produced by electron attachment BrX anion radical degrades through the bromide anion abstraction, barrier-free (purines) or with low barrier (pyrimidines), to a reactive nucleobase radical. Such differences in dissociative behavior of purines and pyrimidines suggest that brominated purine anions should dissociate more effectively than their pyrimidine counterparts.

  4. Monte Carlo calculations on the influence of attachment on the thermalization of secondary electrons in an electron-beam-sustained discharge

    SciTech Connect

    Schaefer, G.; Reinking, G.F.; Schoenbach, K.H.

    1987-01-01

    Monte Carlo calculations have been performed on the relaxation of initial secondary electrons in electron-beam-sustained discharges at low values of the reduced electric field strength, E/N. In pure nitrogen, thermalizing electrons contribute to a secondary maximum of the distribution function in the energy range between 3.5 and 8 eV where the cross section for inelastic collisions in nitrogen has a minimum. This maximum is not found if the secondary electrons are produced at low energies. Admixtures of attachers with an attachment cross section in this energy range cause significant attachment of the initial secondary electrons. The calculations also demonstrate that even in molecular buffer gases, the inelastic cross sections of the attacher admixture have to be considered to gain correct distribution functions and attachment rates.

  5. Studying dissociative electron attachment through formation of heavy-Rydberg ion-pair states

    NASA Astrophysics Data System (ADS)

    Kelley, Michael; Buathong, Sitti; Dunning, F. Barry

    2016-05-01

    Following dissociative electron transfer in collisions between Rydberg atoms and electron-attaching targets, it is possible for the resulting pair of ions to remain electrostatically bound, forming heavy-Rydberg ion-pair states. Precise measurement of the velocity distributions of such ion-pair states provides information concerning the dissociation dynamics of the excited intermediates initially created by electron transfer. Here, electric-field-induced dissociation is used to detect the product ion pairs and observe their velocity distributions. These distributions are analyzed with the aid of a Monte Carlo collision code that models the electron transfer. Measurements with a number of different target species show that through this analysis, dissociation energetics, the branching ratios into different dissociation products, and the lifetimes of the excited intermediates can be examined. Research supported by the Robert A. Welch Foundation.

  6. Simulation of high-speed (orbital) releases of electron attachment materials in the ionosphere

    NASA Technical Reports Server (NTRS)

    Scales, W. A.; Bernhardt, P. A.

    1991-01-01

    The dynamics of ionospheric plasma irregularities produced by the release of electron attachment materials at orbital velocities across the geomagnetic field is studied. A two-dimensional electrostatic fluid model which includes electron attachment and mutual neutralization chemistry, self-consistent electric fields, and three-species transport is developed. Numerical simulations are performed to study the behavior at early and at late times after the release. At early times, of the order of or less than the attachment material neutral collision time, the negative ion cloud produced by the release may structure owing to the shear in the E x B velocity within the cloud. At high altitudes the cloud may bifurcate and form vortices on the back. At lower altitudes where ion-neutral collisional effects dominate, this structuring is suppressed. At late times, after a plasma depletion has formed due to neutralization chemistry, the cloud structures by the E x B interchange instability. Depending on the release altitude, the depletion structures by the collisional or inertial limit of this instability.

  7. Insensitivity of the pressure dependences of characteristic energy scales in Ce1–xRxCoIn₅ (R=Yb,Y,Gd) to the electronic configuration of the rare-earth ion

    SciTech Connect

    White, B. D.; Hamlin, J. J.; Huang, K.; Shu, L.; Lum, I. K.; Baumbach, R. E.; Janoschek, M.; Maple, M. B.

    2012-09-11

    Cooperative Ce and Yb valence fluctuations have recently been proposed as the mechanism responsible for stabilizing correlated electron phenomena in Ce₁₋xYbxCoIn₅ over an unexpectedly large range of concentrations. In order to better understand the origins and character of this stability, we have measured the effect of applied pressure on relevant energy scales such as the superconducting critical (Tc) and Kondo-lattice coherence (T*) temperatures of Ce₁₋xRxCoIn₅ with R=Yb, Y, and Gd. Electrical resistivity measurements were performed under applied pressure on samples doped with intermediate-valent Yb and stable-valent Gd and Y, and the responses of Tc and T* to increased pressure in these systems are compared. The character of Tc(P) and T*(P) in Ce₁₋xRxCoIn₅ depends only on their respective ambient-pressure values Tc(0) and T*(0), independent of the electronic configuration of R or concentration x. The consequences of this result are discussed within the context of possible cooperative valence fluctuations in Ce₁₋xYbxCoIn₅.

  8. Insensitivity of the pressure dependences of characteristic energy scales in Ce1–xRxCoIn₅ (R=Yb,Y,Gd) to the electronic configuration of the rare-earth ion

    DOE PAGES

    White, B. D.; Hamlin, J. J.; Huang, K.; Shu, L.; Lum, I. K.; Baumbach, R. E.; Janoschek, M.; Maple, M. B.

    2012-09-11

    Cooperative Ce and Yb valence fluctuations have recently been proposed as the mechanism responsible for stabilizing correlated electron phenomena in Ce₁₋xYbxCoIn₅ over an unexpectedly large range of concentrations. In order to better understand the origins and character of this stability, we have measured the effect of applied pressure on relevant energy scales such as the superconducting critical (Tc) and Kondo-lattice coherence (T*) temperatures of Ce₁₋xRxCoIn₅ with R=Yb, Y, and Gd. Electrical resistivity measurements were performed under applied pressure on samples doped with intermediate-valent Yb and stable-valent Gd and Y, and the responses of Tc and T* to increased pressure inmore » these systems are compared. The character of Tc(P) and T*(P) in Ce₁₋xRxCoIn₅ depends only on their respective ambient-pressure values Tc(0) and T*(0), independent of the electronic configuration of R or concentration x. The consequences of this result are discussed within the context of possible cooperative valence fluctuations in Ce₁₋xYbxCoIn₅.« less

  9. Low energy electron attachment to cyanamide (NH{sub 2}CN)

    SciTech Connect

    Tanzer, Katrin; Denifl, Stephan E-mail: Stephan.Denifl@uibk.ac.at; Pelc, Andrzej E-mail: Stephan.Denifl@uibk.ac.at; Huber, Stefan E.; Czupyt, Z.

    2015-01-21

    Cyanamide (NH{sub 2}CN) is a molecule relevant for interstellar chemistry and the chemical evolution of life. In the present investigation, dissociative electron attachment to NH{sub 2}CN has been studied in a crossed electron–molecular beams experiment in the electron energy range from about 0 eV to 14 eV. The following anionic species were detected: NHCN{sup −}, NCN{sup −}, CN{sup −}, NH{sub 2}{sup −}, NH{sup −}, and CH{sub 2}{sup −}. The anion formation proceeds within two broad electron energy regions, one between about 0.5 and 4.5 eV and a second between 4.5 and 12 eV. A discussion of possible reaction channels for all measured negative ions is provided. The experimental results are compared with calculations of the thermochemical thresholds of the anions observed. For the dehydrogenated parent anion, we explain the deviation between the experimental appearance energy of the anion with the calculated corresponding reaction threshold by electron attachment to the isomeric form of NH{sub 2}CN—carbodiimide.

  10. Observation of the dynamics leading to a conical intersection in dissociative electron attachment to water

    SciTech Connect

    Haxton, Dan; Adaniya, Hidihito; Slaughter, Dan; Rudek, B.; Osipov, Timur; Weber, Thorsten; Rescigno, Tom; McCurdy, Bill; Belkacem, Ali

    2011-06-08

    Following prior work on the lower-energy resonances, we apply techniques of momentum imaging and ab initio scattering calculations to the process of dissociative electron attachment to water via the highest-energy {sup 2}B{sub 2} resonance. We focus on the H{sup -} anion fragment, which is produced via dynamics passing through and avoiding the conical intersection with the lower A{sub 1} state, leading to OH ((sup 2}{Pi} ) and OH ({sup 2}{Sigma} ), respectively. The momentum imaging technique, when combined with theoretical calculations on the attachment amplitude and dissociation dynamics, demonstrates that the angular distributions provide a signature of the location of the conical intersection in the space of nuclear con gurations.

  11. Observation of the dynamics leading to a conical intersection in dissociative electron attachment to water

    SciTech Connect

    Haxton, D.; Adaniya, H.; Slaughter, D. S.; Rudek, B.; Osipov, T.; Weber, T.; Rescigno, T. N.; McCurdy, C. W.; Belkacem, A.

    2011-08-11

    Following prior work on the lower-energy resonances, we apply techniques of momentum imaging and ab initio scattering calculations to the process of dissociative electron attachment to water via the highest-energy {sup 2}B{sub 2} resonance. We focus on the H{sup -} anion fragment, which is produced via dynamics passing through and avoiding the conical intersection with the lower A{sub 1} state, leading to OH ({sup 2}{Pi} ) and OH ({sup 2}{Sigma} ), respectively. The momentum imaging technique, when combined with theoretical calculations on the attachment amplitude and dissociation dynamics, demonstrates that the angular distributions provide a signature of the location of the conical intersection in the space of nuclear configurations.

  12. Effects of two vibrational modes in the dissociative electron attachment to CF{sub 3}Cl

    SciTech Connect

    Tarana, Michal; Wielgus, Pawel; Roszak, Szczepan; Fabrikant, Ilya I.

    2009-05-15

    We present a study of multimode effects in dissociative electron attachment to CF{sub 3}Cl molecules using a time-independent version of the local complex potential theory. Symmetric stretch C-Cl vibrations {nu}{sub 3} and symmetric deformation (or so-called umbrella) vibrations {nu}{sub 2} are included. The neutral and anion potential energy surfaces are calculated using the second-order Moeller-Plesset perturbation theory with an empirical adjustment of the vertical attachment energy. The final-state vibrational distribution in the CF{sub 3}({nu}{sub 2}) fragment is dominated by the {nu}{sub 2}=2 state. We also find an increase in the total cross section as compared with the one-dimensional calculations. This is explained by an increase in the anion survival probability.

  13. Low-energy electron attachment to SF6. III. From thermal detachment to the electron affinity of SF6.

    PubMed

    Viggiano, Albert A; Miller, Thomas M; Friedman, Jeffrey F; Troe, Jürgen

    2007-12-28

    The thermal attachment of electrons to SF(6) is measured in a flowing-afterglow Langmuir-probe apparatus monitoring electron concentrations versus axial position in the flow tube. Temperatures between 300 and 670 K and pressures of the bath gas He in the range of 0.3-9 Torr are employed. Monitoring the concentrations of SF(6)(-) and SF(5)(-), the latter of which does not detach electrons under the applied conditions, an onset of thermal detachment and dissociation of SF(6) at temperatures above about 530 K is observed. Analysis of the mechanism allows one to deduce thermal detachment rate coefficients. Thermal dissociation rate coefficients for the reaction SF(6)(-)-->SF(5)(-)+F can only be estimated by unimolecular rate theory based on the results from Part I and II of this series. Under the applied conditions they are found to be smaller than detachment rate coefficients. Combining thermal attachment and detachment rates in a third-law analysis, employing calculated vibrational frequencies of SF(6) and SF(6)(-), leads to the electron affinity (EA) of SF(6)(-). The new value of EA=1.20(+/-0.05) eV is significantly higher than previous recommendations which were based on less direct methods.

  14. Electron attachment to Ni(PF{sub 3}){sub 4} and Pt(PF{sub 3}){sub 4}

    SciTech Connect

    Friedman, Jeffrey F.; Miller, Thomas M.; Friedman-Schaffer, Jessica K.; Rekha, G. K.; Stevens, Amy E.; Viggiano, A. A

    2008-03-14

    An experimental study has been made of thermal electron attachment to the transition-metal trifluorophosphine complexes Ni(PF{sub 3}){sub 4} and Pt(PF{sub 3}){sub 4} using a flowing-afterglow Langmuir-probe apparatus. Both complexes are efficient at electron attachment, although the rate constants are somewhat less than collisional. The rate constant for electron attachment to Ni(PF{sub 3}){sub 4} is 1.9x10{sup -7} cm{sup 3} s{sup -1} at room temperature, about a factor of 2 less than collisional. The activation energy is 39{+-}5 meV for the attachment reaction. The rate constant for electron attachment to Pt(PF{sub 3}){sub 4} is 5.4x10{sup -8} cm{sup 3} s{sup -1} at room temperature, and the activation energy is 84{+-}8 meV. For both complexes, a PF{sub 3} ligand is lost on electron attachment, and only the M(PF{sub 3}){sub 3}{sup -} ion is observed in the negative-ion mass spectrum. Density functional calculations were carried out on Ni(PF{sub 3}){sub 4} and various fragments in order to describe the thermochemistry of the attachment reaction.

  15. Electron attachment in ice-HCl clusters: an ab initio study.

    PubMed

    Li, Xifeng; Sanche, Léon; Rauk, Arvi; Armstrong, David

    2005-05-26

    Experimental work has shown that small amounts of HCl strongly enhance electron capture in ice films. The purpose of the present study was to investigate the effect of adsorbed HCl on the interaction of electrons with small clusters of water. Studies were made with clusters of 6 and 12 water molecules with various geometries both with and without one HCl attached. A number of distinct HCl coordination motifs were examined. All of the neutral structures with HCl exhibited zero thresholds for electron attachment and formed dipole bound anionic states (DBS). The relaxation processes for these "initial DBS" depended on the number of H(2)O (n) and on the number and type of H-bonds to the HCl (x). The initial DBS of systems with only O-H...Cl H-binding underwent dissociative electron attachment (DEA), forming H atoms. Relaxation for systems with ClH...OH(2) bonds was more complex. For the two layer n = 12 systems with x = 2 or 3 the HCl proton moved to the nearest oxygen to form H(3)O(+). Then rearrangement of the proton network occurred, and the Cl(-) became solvated by three HO-H...Cl(-) bonds. The presence of Cl(-) and H(3)O(+) increases the dipole moment and the electron binding energy (EBE) of the network. Further stabilization is achieved by decay into deeper DBS electron traps and/or by reaction of the excess electron with H(3)O(+) to form H(*) atoms. The HCl(H(2)O)(6) clusters with a single Cl-H...OH(2) bond behaved differently. They increased their stability by becoming more linear. This raised the dipole moment and the EBE therefore increased, reducing the total energy. None of these species showed any signs of increasing the number of H-bonds to Cl. The implication of these observations for the interpretation of the results of the experiments with 0.2 monolayer of HCl on 5 monolayer of H(2)O at 20 K, and on the possible role of cosmic ray-induced ionization in polar stratospheric clouds in ozone depletion is discussed.

  16. Electron attachment to amino acid clusters in helium nanodroplets: Glycine, alanine, and serine

    NASA Astrophysics Data System (ADS)

    Ferreira da Silva, F.; Denifl, S.; Märk, T. D.; Ellis, A. M.; Scheier, P.

    2010-06-01

    The first detailed study of electron attachment to amino acid clusters is reported. The amino acids chosen for investigation were glycine, alanine, and serine. Clusters of these amino acids were formed inside helium nanodroplets, which provide a convenient low temperature (0.37 K) environment for growing noncovalent clusters. When subjected to low energy (2 eV) electron impact the chemistry for glycine and alanine clusters was found to be similar. In both cases, parent cluster anions were the major products, which contrasts with the corresponding monomers in the gas phase, where the dehydrogenated products ([AAn-H]-, where AA=amino acid monomer) dominate. Serine clusters are different, with the major product being the parent anion minus an OH group, an outcome presumably conferred by the facile loss of an OH group from the β carbon of serine. In addition to the bare parent anions and various fragment anions, helium atoms are also observed attached to both the parent anion clusters and the dehydrogenated parent anion clusters. Finally, we present the first anion yield spectra of amino acid clusters from doped helium nanodroplets as a function of incident electron energy.

  17. Absolute cross sections for dissociative electron attachment to HCN and DCN

    SciTech Connect

    May, O.; Kubala, D.; Allan, M.

    2010-07-15

    Absolute partial cross sections for the formation of CN{sup -} in dissociative electron attachment to HCN and DCN have been measured using a time-of-flight ion spectrometer combined with a trochoidal electron monochromator to be 940pm{sup 2} for CN{sup -}/HCN and 340pm{sup 2} for CN{sup -}/DCN at peaks of the bands due to the {sup 2{Pi}}-shape resonance. The dissociative electron attachment bands were then recorded under higher resolution, 60 meV, with a trochoidal monochromator plus quadrupole mass filter combination and found to have a nearly vertical onset at the threshold energy and to peak at 1.85 eV. Broad structure was observed on the bands, assigned to formation of vibrationally excited CN{sup -}, from which the branching ratios could be determined to be 1,0.49, and 0.22 for the formation of CN{sup -} in the v=0,1, and 2 states, respectively. The results are compared to the recent multidimensional ab initio calculations of Chourou and Orel [Phys. Rev. A 80, 032709 (2009)].

  18. Fragmentation dynamics in dissociative electron attachment to CO probed by velocity slice imaging.

    PubMed

    Nag, Pamir; Nandi, Dhananjay

    2015-03-21

    Complete dissociation dynamics in electron attachment to carbon monoxide (CO) have been studied using the newly developed velocity slice imaging (VSI) technique. Both kinetic energy and angular distributions of O(-) ions formed by dissociative electron attachment (DEA) to CO molecules have been measured for 9, 9.5, 10, 10.5, 11, and 11.5 eV incident electron energies around the resonance. Detailed observations conclusively show that two separate DEA reactions lead to the formation of O(-) ions in the ground (2)P state along with the neutral C atoms in the ground (3)P state and the first excited (1)D state, respectively. Within the axial recoil approximation and involving four partial waves, our angular distribution results clearly indicate that the two reactions leading to O(-) formation proceed through the specific resonant state(s). For the first process, more than one intermediate state is involved. On the other hand, for the second process, only one state is involved. The observed forward-backward asymmetry is explained in terms of the interference between the different partial waves that are involved in the processes.

  19. Comment on "Coherent interference in the resonant dissociative electron attachment to carbon monoxide"

    NASA Astrophysics Data System (ADS)

    Nag, Pamir; Nandi, Dhananjay

    2015-05-01

    In a recent article [Phys. Rev. A 88, 012708 (2013), 10.1103/PhysRevA.88.012708], Tian et al. claimed coherent interference among the various negative ion resonant states involved in the dissociative electron attachment (DEA) to carbon monoxide (CO) by investigating O- angular distribution using the anion velocity time-sliced map imaging technique. However, our recent detailed study [Phys. Chem. Chem. Phys. 17, 7130 (2015), 10.1039/C4CP05678G] on DEA to CO using the identical technique shows that the above claim can be questioned.

  20. Negative-ion formation in the explosives RDX, PETN, and TNT by using the reversal electron attachment detection technique

    NASA Technical Reports Server (NTRS)

    Boumsellek, S.; Alajajian, S. H.; Chutjian, A.

    1992-01-01

    First results of a beam-beam, single-collision study of negative-ion mass spectra produced by attachment of zero-energy electrons to the molecules of the explosives RDX, PETN, and TNT are presented. The technique used is reversal electron attachment detection (READ) wherein the zero-energy electrons are produced by focusing an intense electron beam into a shaped electrostatic field which reverses the trajectory of electrons. The target beam is introduced at the reversal point, and attachment occurs because the electrons have essentially zero longitudinal and radial velocity. The READ technique is used to obtain the 'signature' of molecular ion formation and/or fragmentation for each explosive. Present data are compared with results from atmospheric-pressure ionization and negative-ion chemical ionization methods.

  1. Direct experimental observation of weakly-bound character of the attached electron in europium anion.

    PubMed

    Cheng, Shi-Bo; Castleman, A W

    2015-01-01

    Direct experimental determination of precise electron affinities (EAs) of lanthanides is a longstanding challenge to experimentalists. Considerable debate exists in previous experiment and theory, hindering the complete understanding about the properties of the atomic anions. Herein, we report the first precise photoelectron imaging spectroscopy of europium (Eu), with the aim of eliminating prior contradictions. The measured EA (0.116 ± 0.013 eV) of Eu is in excellent agreement with recently reported theoretical predictions, providing direct spectroscopic evidence that the additional electron is weakly attached. Additionally, a new experimental strategy is proposed that can significantly increase the yield of the lanthanide anions, opening up the best opportunity to complete the periodic table of the atomic anions. The present findings not only serve to resolve previous discrepancy but also will help in improving the depth and accuracy of our understanding about the fundamental properties of the atomic anions. PMID:26198741

  2. Direct experimental observation of weakly-bound character of the attached electron in europium anion

    PubMed Central

    Cheng, Shi-Bo; Castleman, A. W.

    2015-01-01

    Direct experimental determination of precise electron affinities (EAs) of lanthanides is a longstanding challenge to experimentalists. Considerable debate exists in previous experiment and theory, hindering the complete understanding about the properties of the atomic anions. Herein, we report the first precise photoelectron imaging spectroscopy of europium (Eu), with the aim of eliminating prior contradictions. The measured EA (0.116 ± 0.013 eV) of Eu is in excellent agreement with recently reported theoretical predictions, providing direct spectroscopic evidence that the additional electron is weakly attached. Additionally, a new experimental strategy is proposed that can significantly increase the yield of the lanthanide anions, opening up the best opportunity to complete the periodic table of the atomic anions. The present findings not only serve to resolve previous discrepancy but also will help in improving the depth and accuracy of our understanding about the fundamental properties of the atomic anions. PMID:26198741

  3. Structure and energetics in dissociative electron attachment to HFeCo3(CO)12

    NASA Astrophysics Data System (ADS)

    T P, Ragesh Kumar; Barth, Sven; Bjornsson, Ragnar; Ingólfsson, Oddur

    2016-08-01

    Here we report structural parameters on the heteronuclear transition metal complex HFeCo3(CO)12 and its anion formed upon electron attachment, as well as the thermochemical thresholds for sequential CO loss and the loss of the apical group (as Fe(CO)- 3 and Fe(CO)- 4). Geometrical parameters from single crystal X-ray diffraction are compared with calculated values from density functional theory calculations, for the neutral and anionic ground state of this transition metal cluster. Further, experimental appearance energies for sequential CO loss and the formation of Fe(CO)- 3 and Fe(CO)- 4 are compared to the respective calculated threshold values. Geometry optimizations were performed at the BP86/def2-TZVP level of theory while the threshold energies were calculated at the PBE0/ma-def2-TZVP level of theory. The SOMO of the anion is found to have a clear Fe-Co anti-bonding character resulting in elongation of the Fe-Co bonds and the transformation of one of the terminal Co-CO groups to a bridging Co-CO-Fe group upon electron attachment. The thermochemical threshold PBE0 calculations are concordant with the observed appearance energies and structural parameters from single crystal X-ray diffraction for the neutral molecule are well reproduced at the BP86/def2-TZVP level of theory.

  4. Covalent attachment of FeFe hydrogenases to carbon electrodes for direct electron transfer.

    PubMed

    Baffert, Carole; Sybirna, Kateryna; Ezanno, Pierre; Lautier, Thomas; Hajj, Viviane; Meynial-Salles, Isabelle; Soucaille, Philippe; Bottin, Hervé; Léger, Christophe

    2012-09-18

    Direct electron transfer between enzymes and electrodes is now commonly achieved, but obtaining protein films that are very stable may be challenging. This is particularly crucial in the case of hydrogenases, the enzymes that catalyze the biological conversion between dihydrogen and protons, because the instability of the hydrogenase films may prevent the use of these enzymes as electrocatalysts of H(2) oxidation and production in biofuel cells and photoelectrochemical cells. Here we show that two different FeFe hydrogenases (from Chamydomonas reinhardtii and Clostridium acetobutylicum) can be covalently attached to functionalized pyrolytic graphite electrodes using peptidic coupling. In both cases, a surface patch of lysine residues makes it possible to favor an orientation that is efficient for fast, direct electron transfer. High hydrogen-oxidation current densities are maintained for up to one week, the only limitation being the intrinsic stability of the enzyme. We also show that covalent attachment has no effect on the catalytic properties of the enzyme, which means that this strategy can also used be for electrochemical studies of the catalytic mechanism. PMID:22891965

  5. Structure and energetics in dissociative electron attachment to HFeCo3(CO)12*

    NASA Astrophysics Data System (ADS)

    P, Ragesh Kumar T.; Barth, Sven; Bjornsson, Ragnar; Ingólfsson, Oddur

    2016-08-01

    Here we report structural parameters on the heteronuclear transition metal complex HFeCo3(CO)12 and its anion formed upon electron attachment, as well as the thermochemical thresholds for sequential CO loss and the loss of the apical group (as Fe(CO)-3 and Fe(CO)-4). Geometrical parameters from single crystal X-ray diffraction are compared with calculated values from density functional theory calculations, for the neutral and anionic ground state of this transition metal cluster. Further, experimental appearance energies for sequential CO loss and the formation of Fe(CO)-3 and Fe(CO)-4 are compared to the respective calculated threshold values. Geometry optimizations were performed at the BP86/def2-TZVP level of theory while the threshold energies were calculated at the PBE0/ma-def2-TZVP level of theory. The SOMO of the anion is found to have a clear Fe-Co anti-bonding character resulting in elongation of the Fe-Co bonds and the transformation of one of the terminal Co-CO groups to a bridging Co-CO-Fe group upon electron attachment. The thermochemical threshold PBE0 calculations are concordant with the observed appearance energies and structural parameters from single crystal X-ray diffraction for the neutral molecule are well reproduced at the BP86/def2-TZVP level of theory. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2016-70164-y

  6. Mass Spectrometric Investigation of Anions Formed upon Free Electron Attachment to Nucleobase Molecules and Clusters Embedded in Superfluid Helium Droplets

    SciTech Connect

    Denifl, Stephan; Zappa, Fabio; Maehr, Ingo; Lecointre, Julien; Probst, Michael; Maerk, Tilmann D.; Scheier, Paul

    2006-07-28

    Here we report the first mass spectrometric study of negative ions formed via free electron attachment (EA) to nucleobases (NBs) embedded in helium clusters. Pure and mixed clusters of adenine and thymine have been formed by pickup of isolated NB molecules by cold helium droplets. In contrast to EA of isolated molecules in the gas phase we observe a long-lived parent anion NB{sup -} and, in addition, parent cluster ions NB{sub n}{sup -} up to size n=6. Moreover, we show that a low energy electron penetrating into a doped helium droplet causes efficient damage of the embedded nucleobases via resonant, site selective, dissociative electron attachment.

  7. Rate-based screening of pressure-dependent reaction networks

    NASA Astrophysics Data System (ADS)

    Matheu, David M.; Lada, Thomas A.; Green, William H.; Dean, Anthony M.; Grenda, Jeffrey M.

    2001-08-01

    Computer tools to automatically generate large gas-phase kinetic models find increasing use in industry. Until recently, mechanism generation algorithms have been restricted to generating kinetic models in the high-pressure limit, unless special adjustments are made for particular cases. A new approach, recently presented, allows the automated generation of pressure-dependent reaction networks for chemically and thermally activated reactions (Grenda et al., 2000; Grenda and Dean, in preparation; Grenda et al., 1998; see Refs. [1-3]). These pressure-dependent reaction networks can be quite large and can contain a large number of unimportant pathways. We thus present an algorithm for the automated screening of pressure-dependent reaction networks. It allows a computer to discover and incorporate pressure-dependent reactions in a manner consistent with the existing rate-based model generation method. The new algorithm works by using a partially-explored (or "screened") pressure-dependent reaction network to predict rate constants, and updating predictions as more parts of the network are discovered. It requires only partial knowledge of the network connectivity, and allows the user to explore only the important channels at a given temperature and pressure. Applications to vinyl + O 2, 1-naphthyl + acetylene and phenylvinyl radical dissociation are presented. We show that the error involved in using a truncated pressure-dependent network to predict a rate constant is insignificant, for all channels whose yields are significantly greater than a user-specified tolerance. A bound for the truncation error is given. This work demonstrates the feasibility of using screened networks to predict pressure-dependent rate constants k(T,P).

  8. Negative ion resonances in carbon monoxide. Probing dissociative electron attachment in CO by velocity slice imaging

    NASA Astrophysics Data System (ADS)

    Gope, Krishnendu; Tadsare, Vishvesh; Prabhudesai, Vaibhav S.; Mason, Nigel J.; Krishnakumar, E.

    2016-06-01

    Dissociative electron attachment to CO leading to the formation of O- is studied using the velocity slice imaging technique. The angular distributions we obtained for the C(3P) and the C(1D) limits are found to be considerably different from a recent set of measurements [Tian et al., Phys. Rev. A 88, 012708 (2013); Wang et al., J. Chem. Phys. 143, 066101 (2015)] using a similar technique. The analysis of our results indicate incoherent contributions from states of Σ and Π symmetries to both these dissociation channels and rules out the need to invoke coherent excitation of several resonances, in contrast to what has been done in the above publications. We try to correlate these resonances to those observed in inelastic scattering and transmission experiments. We also confirm the presence of a third dissociation channel leading to C(1S) limit.

  9. Reply to ``Comment on `Coherent interference in the resonant dissociative electron attachment to carbon monoxide' ''

    NASA Astrophysics Data System (ADS)

    Tian, Shan Xi; Luo, Yi

    2015-05-01

    We respond to Nag and Nandi's Comment on our paper [Phys. Rev. A 88, 012708 (2013), 10.1103/PhysRevA.88.012708], in which the arguments arise from the data analyses of the angular distributions of O¯ produced in the dissociative electron attachments to CO at 10.5 or 10.6 eV although the same technique, anion-velocity time-sliced map imaging, was used. The forward distribution in the O¯ image observed by Nag and Nandi arises from the low momentum resolution and distortion in their ion velocity imaging measurements. These artifacts are due to their arbitrary elongation of the ion flight tube and the uncertainty in the size control of the reaction volume.

  10. Equation-of-motion coupled cluster method for high spin double electron attachment calculations

    SciTech Connect

    Musiał, Monika Lupa, Łukasz; Kucharski, Stanisław A.

    2014-03-21

    The new formulation of the equation-of-motion (EOM) coupled cluster (CC) approach applicable to the calculations of the double electron attachment (DEA) states for the high spin components is proposed. The new EOM equations are derived for the high spin triplet and quintet states. In both cases the new equations are easier to solve but the substantial simplification is observed in the case of quintets. Out of 21 diagrammatic terms contributing to the standard DEA-EOM-CCSDT equations for the R{sub 2} and R{sub 3} amplitudes only four terms survive contributing to the R{sub 3} part. The implemented method has been applied to the calculations of the excited states (singlets, triplets, and quintets) energies of the carbon and silicon atoms and potential energy curves for selected states of the Na{sub 2} (triplets) and B{sub 2} (quintets) molecules.

  11. Temperature dependence of the cross section for the fragmentation of thymine via dissociative electron attachment

    NASA Astrophysics Data System (ADS)

    Kopyra, Janina; Abdoul-Carime, Hassan

    2015-05-01

    Providing experimental values for absolute Dissociative Electron Attachment (DEA) cross sections for nucleobases at realistic biological conditions is a considerable challenge. In this work, we provide the temperature dependence of the cross section, σ, of the dehydrogenated thymine anion (T - H)- produced via DEA. Within the 393-443 K temperature range, it is observed that σ varies by one order of magnitude. By extrapolating to a temperature of 313 K, the relative DEA cross section for the production of the dehydrogenated thymine anion at an incident energy of 1 eV decreases by 2 orders of magnitude and the absolute value reaches approximately 6 × 10-19 cm2. These quantitative measurements provide a benchmark for theoretical prediction and also a contribution to a more accurate description of the effects of ionizing radiation on molecular medium.

  12. Temperature dependence of the cross section for the fragmentation of thymine via dissociative electron attachment

    SciTech Connect

    Kopyra, Janina; Abdoul-Carime, Hassan

    2015-05-07

    Providing experimental values for absolute Dissociative Electron Attachment (DEA) cross sections for nucleobases at realistic biological conditions is a considerable challenge. In this work, we provide the temperature dependence of the cross section, σ, of the dehydrogenated thymine anion (T − H){sup −} produced via DEA. Within the 393-443 K temperature range, it is observed that σ varies by one order of magnitude. By extrapolating to a temperature of 313 K, the relative DEA cross section for the production of the dehydrogenated thymine anion at an incident energy of 1 eV decreases by 2 orders of magnitude and the absolute value reaches approximately 6 × 10{sup −19} cm{sup 2}. These quantitative measurements provide a benchmark for theoretical prediction and also a contribution to a more accurate description of the effects of ionizing radiation on molecular medium.

  13. Identification of overlapping resonances in dissociative electron attachment to chlorine molecules

    NASA Astrophysics Data System (ADS)

    Nag, Pamir; Nandi, Dhananjay

    2016-01-01

    A combined highly differential momentum imaging experiment and ab initio potential-energy curve calculation using density-functional theory (DFT) have been performed to understand the broad resonant peak around 5.7 eV due to dissociative electron attachment (DEA) to the chlorine molecule. Both the kinetic energy and angular distribution over the entire 2 π angle of the fragment negative ions have been measured. Two heavily overlapping resonances are identified for the observed broad resonant peak that could settle the long-standing debate. The symmetry of the involved two temporary negative ion (TNI) states are determined from the angular distribution data. Experimental observations are strongly supported with the computed potential-energy curve using DFT.

  14. Novel Analytical Techniques Based on a Enhanced Electron Attachment Process - Final Report - 09/15/1996 - 06/15/2001

    SciTech Connect

    Pinnaduwage, Lal A.; Buchanan, Michelle V.

    2001-06-15

    Present analytical methodologies for the detection of chlorinated compounds important to DOE's environmental restoration program, such as DNAPLs [dense non-aqueous phase liquids - such as carbon tetrachloride, trichloroethylene (TCE), perchloroethylene (PCE)], polychlorinated biphenyls (PCB), and others, involve detection by negative-ion-based analytical techniques. These techniques exploit electron attachment to analyte molecules in their ground electronic states, and are limited to particular compounds with appropriate electron capture cross sections. For example, PCB contamination is detected by analysis of mixtures of chlorinated homologues of these biphenyls. Homologues with lower numbers of chlorines do not efficiently attach thermal electrons and thus are not detected by either electron capture chromatographic detectors or by negative ion chemical ionization mass spectrometry. We proposed three novel analytical techniques based on enhanced negative-ion formation via electron attachment to highly-excited electronic states of molecules. In one of the proposed techniques, the excited states of the (analyte) molecules are populated via laser excitation; the resulting negative ions are mass analyzed for identification. The other two proposed techniques utilize a specialized gas discharge for the formation of excited species (and low-energy electrons for attachment), and thus will provide a cost-effective method if successful. In one version, the negative ions will be mass analyzed -as in the laser-based technique- and in the other, the decrease in electron density due to excited state attachment will be monitored (electron capture detector mode). A plasma mixing scheme will be employed to excite the analyte molecules so that the excited states of the analyte molecules will not be destroyed by the discharge.

  15. Metastable anions of dinitrobenzene: Resonances for electron attachment and kinetic energy release

    SciTech Connect

    Mauracher, A.; Denifl, S.; Edtbauer, A.; Hager, M.; Probst, M.; Scheier, P.; Echt, O.; Maerk, T. D.; Field, T. A.; Graupner, K.

    2010-12-28

    Attachment of free, low-energy electrons to dinitrobenzene (DNB) in the gas phase leads to DNB{sup -} as well as several fragment anions. DNB{sup -}, (DNB-H){sup -}, (DNB-NO){sup -}, (DNB-2NO){sup -}, and (DNB-NO{sub 2}){sup -} are found to undergo metastable (unimolecular) dissociation. A rich pattern of resonances in the yield of these metastable reactions versus electron energy is observed; some resonances are highly isomer-specific. Most metastable reactions are accompanied by large average kinetic energy releases (KER) that range from 0.5 to 1.32 eV, typical of complex rearrangement reactions, but (1,3-DNB-H){sup -} features a resonance with a KER of only 0.06 eV for loss of NO. (1,3-DNB-NO){sup -} offers a rare example of a sequential metastable reaction, namely, loss of NO followed by loss of CO to yield C{sub 5}H{sub 4}O{sup -} with a large KER of 1.32 eV. The G4(MP2) method is applied to compute adiabatic electron affinities and reaction energies for several of the observed metastable channels.

  16. Dissociative electron attachment in nanoscale ice films: Temperature and morphology effects

    SciTech Connect

    Simpson, W.C.; Sieger, M.T.; Orlando, T.M.

    1997-11-01

    The electron-stimulated desorption (ESD) of D{sup {minus}} ions from condensed D{sub 2}O films is investigated. Three low-energy peaks are observed which are identified as arising from excitation of {sup 2}B{sub 1}, {sup 2}A{sub 1}, and {sup 2}B{sub 2} dissociative electron attachment (DEA) resonances. A fourth, higher energy feature is also seen in the D{sup {minus}} yield which is likely due to the formation of a transient anion state that dissociates and/or decays into a dissociative excited state. The energies and ion yields of the resonances vary with the temperature and morphology of the D{sub 2}O film. Below 60 K, the work function of the ice films changes with temperature and the DEA resonances shift in energy. The D{sup {minus}} ESD yield generally increases with temperature, but it deviates from this trend at temperatures corresponding to structural phase transitions in ice. The ({sup 2}B{sub 1}) D{sup {minus}} temperature dependence is remarkably similar to that observed for the ESD of low-energy D{sup +} ions from D{sub 2}O ice, even though the two originate from different electronic excitations. These results are attributed to thermally induced changes in the hydrogen bonding network, which changes the lifetimes of the predissociative states that lead to ESD and which also allows for the reorientation of surface molecules. {copyright} {ital 1997 American Institute of Physics.}

  17. Dissociative electron attachment in nanoscale ice films: Thickness and charge trapping effects

    SciTech Connect

    Simpson, W.C.; Orlando, T.M.

    1998-03-01

    The yield and kinetic energy (KE) distributions of D{sup {minus}} ions produced via dissociative electron attachment (DEA) resonances in nanoscale D{sub 2}O ice films are collected as a function of film thickness. The {sup 2}B{sub 1}, {sup 2}A{sub 1}, and {sup 2}B{sub 2} DEA resonances shift to higher energies and their D{sup {minus}} ion yields first increase and then decrease as the D{sub 2}O films thicken. The D{sup {minus}} KE distributions also shift to higher energy with increasing film thickness. We interpret the changes in the DEA yield and the D{sup {minus}} KE distributions in terms of modifications in the electronic and geometric structure of the surface of the film as it thickens. A small amount of charge build-up occurs following prolonged electron beam exposure at certain energies, which primarily affects the D{sup {minus}} KE distributions. Charge trapping measurements indicate that an enhancement in the trapping cross section occurs at energies near zero and between 6 and 10 eV. {copyright} {ital 1998 American Institute of Physics.}

  18. Experimental and modeling study of thermal rate coefficients and cross sections for electron attachment to C(60).

    PubMed

    Viggiano, Albert A; Friedman, Jeffrey F; Shuman, Nicholas S; Miller, Thomas M; Schaffer, Linda C; Troe, Jürgen

    2010-05-21

    Thermal electron attachment to C(60) has been studied by relative rate measurements in a flowing afterglow Langmuir probe apparatus. The rate coefficients of the attachment k(1) are shown to be close to 10(-6) cm(3) s(-1) with a small negative temperature coefficient. These results supersede measurements from the 1990s which led to much smaller values of k(1) with a large positive temperature coefficient suggesting an activation barrier. Theoretical modeling of k(1) in terms of generalized Vogt-Wannier capture theory shows that k(1) now looks more consistent with measurements of absolute attachment cross sections sigma(at) than before. The comparison of capture theory and experimental rate or cross section data leads to empirical correction factors, accounting for "intramolecular vibrational relaxation" or "electron-phonon coupling," which reduce k(1) below the capture results and which, on a partial wave-selected level, decrease with increasing electron energy.

  19. Experimental and modeling study of thermal rate coefficients and cross sections for electron attachment to C(60).

    PubMed

    Viggiano, Albert A; Friedman, Jeffrey F; Shuman, Nicholas S; Miller, Thomas M; Schaffer, Linda C; Troe, Jürgen

    2010-05-21

    Thermal electron attachment to C(60) has been studied by relative rate measurements in a flowing afterglow Langmuir probe apparatus. The rate coefficients of the attachment k(1) are shown to be close to 10(-6) cm(3) s(-1) with a small negative temperature coefficient. These results supersede measurements from the 1990s which led to much smaller values of k(1) with a large positive temperature coefficient suggesting an activation barrier. Theoretical modeling of k(1) in terms of generalized Vogt-Wannier capture theory shows that k(1) now looks more consistent with measurements of absolute attachment cross sections sigma(at) than before. The comparison of capture theory and experimental rate or cross section data leads to empirical correction factors, accounting for "intramolecular vibrational relaxation" or "electron-phonon coupling," which reduce k(1) below the capture results and which, on a partial wave-selected level, decrease with increasing electron energy. PMID:20499963

  20. Experimental and modeling study of thermal rate coefficients and cross sections for electron attachment to C60

    NASA Astrophysics Data System (ADS)

    Viggiano, Albert A.; Friedman, Jeffrey F.; Shuman, Nicholas S.; Miller, Thomas M.; Schaffer, Linda C.; Troe, Jürgen

    2010-05-01

    Thermal electron attachment to C60 has been studied by relative rate measurements in a flowing afterglow Langmuir probe apparatus. The rate coefficients of the attachment k1 are shown to be close to 10-6 cm3 s-1 with a small negative temperature coefficient. These results supersede measurements from the 1990s which led to much smaller values of k1 with a large positive temperature coefficient suggesting an activation barrier. Theoretical modeling of k1 in terms of generalized Vogt-Wannier capture theory shows that k1 now looks more consistent with measurements of absolute attachment cross sections σat than before. The comparison of capture theory and experimental rate or cross section data leads to empirical correction factors, accounting for "intramolecular vibrational relaxation" or "electron-phonon coupling," which reduce k1 below the capture results and which, on a partial wave-selected level, decrease with increasing electron energy.

  1. Cross sections for 14-eV e-H{sub 2} resonant collisions: Dissociative electron attachment

    SciTech Connect

    Celiberto, R.; Janev, R. K.; Wadehra, J. M.; Laricchiuta, A.

    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.

  2. Rare reaction channels in real-time time-dependent density functional theory: the test case of electron attachment

    NASA Astrophysics Data System (ADS)

    Lacombe, Lionel; Dinh, P. Huong Mai; Reinhard, Paul-Gerhard; Suraud, Eric; Sanche, Leon

    2015-08-01

    We present an extension of standard time-dependent density functional theory (TDDFT) to include the evaluation of rare reaction channels, taking as an example of application the theoretical modelling of electron attachment to molecules. The latter process is of great importance in radiation-induced damage of biological tissue for which dissociative electron attachment plays a decisive role. As the attachment probability is very low, it cannot be extracted from the TDDFT propagation whose mean field provides an average over various reaction channels. To extract rare events, we augment TDDFT by a perturbative treatment to account for the occasional jumps, namely electron capture in our test case. We apply the modelling to electron attachment to H2O, H3O+, and (H2O)2. Dynamical calculations have been done at low energy (3-16 eV). We explore, in particular, how core-excited states of the targets show up as resonances in the attachment probability. Contribution to the Topical Issue "COST Action Nano-IBCT: Nano-scale Processes Behind Ion-Beam Cancer Therapy", edited by Andrey Solov'yov, Nigel Mason, Gustavo García, Eugene Surdutovich.

  3. A DFT study of the ionization and electron attachment of 2-azido pyridine

    NASA Astrophysics Data System (ADS)

    Elshakre, Mohamed

    2015-03-01

    A DFT study using B3LYP/6-31G(d,p) level of theory is pursued to investigate the energy and geometry changes of 2-azido pyridine isomers in the S0, D0+, and D0-. In S0, cis-2 azidopyridine is the most stable, followed by cyclic tetrazole and trans isomer is the least stable. In D0+, the cis isomer is the most stable, followed by trans isomer, and tetrazole isomer is the least stable. In the D0- state, the trans form is the most stable, followed by the cis and the tetrazolo form is the least stable. Single point vertical excitation energy calculations of the cis form gave four excited states at 266.4, 239.4, 199.4, and 196.1 nm, all having π-π∗ character. For trans isomer, five excited states at, 256.7, 250.3, 229.7, 199.0, 197.0 nm all resulting from π-π∗ transitions. For the tetrazole isomer, seven excited states at 269.3, 242.7, 198.0, 187.2, 183.9, 182.1, 178.7 nm all resulting from π-π∗ transitions. The geometries of the 3 isomers show noticeable changes in bond lengths, bond angles and dihedral angles, upon ionization and electron attachment. The ionization results in a remarkable variation of the NBO atomic charges as a result of ionization and electron attachment. where electron density of HOMO of the D0+ state is found to be much lower than that of the HOMO of the S0 in the case of ionization. The dipole moment calculations show that tetrazole isomer has the largest polarization in the S0 state, followed by cis isomer and trans isomer is the least polarized. The same pattern is found in the D0+ state. In the D0- state, trans isomer is the highest polarized, followed by the cis, and tetrazole isomer is the least polarized. The rotational constants calculations of cis- isomer show that the cation is elongated along the long in-plane axis and compressed along the two short out-of-plane axes while the anion is compressed along the long in-plane axis, and elongated along the two short out-of plane axes. The cation and anion of trans isomer show

  4. Kinetics of low energy electron attachment to some fluorinated alcohols in the gas phase

    NASA Astrophysics Data System (ADS)

    Wnorowski, K.; Wnorowska, J.; Kopyra, J.; Michalczuk, B.; Szamrej, I.; Barszczewska, W.

    2014-01-01

    Thermal electron attachment processes in the mixtures of CH3CH2OH, CF3CH2OH, CF3CF2CH2OH, (CF3)2CHOH and CH3CH(OH)CF3 with carbon dioxide have been investigated using an electron Pulsed Townsend technique. Measurements were carried out in the temperature range (298-413) K. The obtained rate coefficients depended on temperature in accordance to Arrhenius equation. From the fit to the experimental data points with function ln(k) = ln(A)-Ea/kBT the activation energies (Ea's) were determined. The rate coefficients at 298 K are equal to 3.2 × 10-13 cm3 s-1, 5.1 × 10-11 cm3 s-1, 1.1 × 10-10 cm3 s-1, 3.0 × 10-10 cm3 s-1 and 2.6 × 10-11 cm3 s-1 and activation energies are: 0.37 eV, 0.25 eV, 0.28 eV, 0.20 eV and 0.23 eV, respectively for CH3CH2OH, CF3CH2OH, CF3CF2CH2OH, (CF3)2CHOH and CH3CH(OH)CF3.

  5. Oxidant enhancement in martian dust devils and storms: storm electric fields and electron dissociative attachment.

    PubMed

    Delory, Gregory T; Farrell, William M; Atreya, Sushil K; Renno, Nilton O; Wong, Ah-San; Cummer, Steven A; Sentman, Davis D; Marshall, John R; Rafkin, Scot C R; Catling, David C

    2006-06-01

    Laboratory studies, numerical simulations, and desert field tests indicate that aeolian dust transport can generate atmospheric electricity via contact electrification or "triboelectricity." In convective structures such as dust devils and dust storms, grain stratification leads to macroscopic charge separations and gives rise to an overall electric dipole moment in the aeolian feature, similar in nature to the dipolar electric field generated in terrestrial thunderstorms. Previous numerical simulations indicate that these storm electric fields on Mars can approach the ambient breakdown field strength of approximately 25 kV/m. In terrestrial dust phenomena, potentials ranging from approximately 20 to 160 kV/m have been directly measured. The large electrostatic fields predicted in martian dust devils and storms can energize electrons in the low pressure martian atmosphere to values exceeding the electron dissociative attachment energy of both CO2 and H2O, which results in the formation of the new chemical products CO/O- and OH/H-, respectively. Using a collisional plasma physics model, we present calculations of the CO/O- and OH/H- reaction and production rates. We demonstrate that these rates vary geometrically with the ambient electric field, with substantial production of dissociative products when fields approach the breakdown value of approximately 25 kV/m. The dissociation of H2O into OH/H- provides a key ingredient for the generation of oxidants; thus electrically charged dust may significantly impact the habitability of Mars. PMID:16805701

  6. Pressure Dependence of the EFG in Semimetallic Arsenic and Antimony

    NASA Astrophysics Data System (ADS)

    Hill, G. J.; Keartland, J. M.; Hoch, M. J. R.

    1998-07-01

    The pressure variation of the axial EFG at the ion sites in semimetallic arsenic and antimony, at am-bient temperature, has been investigated using pulsed NQR. A weakly nonlinear decrease of the EFG is observed in both systems. The data are analyzed in terms of the lattice contribution to the EFG, which involves a lattice of point monopoles immersed in a uniform, compensating, background charge. The pressure dependence of the EFG obtained from the present measurements is far weaker than the pres-sure dependence of the calculated lattice contribution. Our results support previous suggestions that va-lence effects are important in determining the EFG in these semimetals.

  7. Density functional and theoretical study of the temperature and pressure dependency of the plasmon energy of solids

    SciTech Connect

    Attarian Shandiz, M. Gauvin, R.

    2014-10-28

    The temperature and pressure dependency of the volume plasmon energy of solids was investigated by density functional theory calculations. The volume change of crystal is the major factor responsible for the variation of valence electron density and plasmon energy in the free electron model. Hence, to introduce the effect of temperature and pressure for the density functional theory calculations of plasmon energy, the temperature and pressure dependency of lattice parameter was used. Also, by combination of the free electron model and the equation of state based on the pseudo-spinodal approach, the temperature and pressure dependency of the plasmon energy was modeled. The suggested model is in good agreement with the results of density functional theory calculations and available experimental data for elements with the free electron behavior.

  8. Dissociative electron attachment to the H2O molecule II: nucleardynamics on coupled electronic surfaces within the local complexpotential model

    SciTech Connect

    Haxton, Daniel J.; Rescigno, Thomas N.; McCurdy, C. William

    2006-12-21

    We report the results of a first-principles study of dissociative electron attachment (DEA) to H{sub 2}O. The cross sections were obtained from nuclear dynamics calculations carried out in full dimensionality within the local complex potential model by using the multi-configuration time-dependent Hartree method. The calculations employ our previously obtained global, complex-valued, potential energy surfaces for the three ({sup 2}B{sub 1}, {sup 2}A{sub 1}, and {sup 2}B{sub 2}) electronic Feshbach resonances involved in this process. These three metastable states of H{sub 2}O{sup -} undergo several degeneracies, and we incorporate both the Renner-Teller coupling between the {sup 2}B{sub 1} and {sup 2}A{sub 1} states, as well as the conical intersection between the {sup 2}A{sub 1} and {sup 2}B{sub 2} states, into our treatment. The nuclear dynamics are inherently multi-dimensional and involve branching between different final product arrangements as well as extensive excitation of the diatomic fragment. Our results successfully mirror the qualitative features of the major fragment channels observed, but are less successful in reproducing the available results for some of the minor channels. We comment on the applicability of the local complex potential model to such a complicated resonant system.

  9. Probing royal demolition explosive (1,3,5-trinitro-1,3,5-triazocyclohexane) by low-energy electrons: Strong dissociative electron attachment near 0 eV.

    PubMed

    Sulzer, P; Mauracher, A; Ferreira da Silva, F; Denifl, S; Märk, T D; Probst, M; Limão-Vieira, P; Scheier, P

    2009-10-14

    Low energy electron attachment to gas phase royal demolition explosive (RDX) (and RDX-A3) has been performed by means of a crossed electron-molecular beam experiment in an electron energy range from 0 to 14 eV with an energy resolution of approximately 70 meV. The most intense signals are observed at 102 and 46 amu and assigned to C(2)H(4)N(3)O(2) (-) and NO(2) (-), respectively. Anion efficiency curves of 16 anions have been measured. Product ions are observed mainly in the low energy region, near 0 eV arising from surprisingly complex reactions associated with multiple bond cleavages and structural and electronic rearrangement. The remarkable instability of RDX to electron attachment with virtually thermal electrons reflects the highly explosive nature of this compound. The present results are compared to other explosive aromatic nitrocompounds studied in our laboratory recently.

  10. Possibility of formation of rare-earth negative ions by attachment of [ital f] electrons to the atomic ground state

    SciTech Connect

    Datta, D.; Beck, D.R. )

    1993-06-01

    Some recent experiments indicate that certain rare-earth negative ions exist. Some local-density calculations indicate that attachment of [ital f] electrons is most favorable for Tm and Md. Here we investigate by means of relativistic configuration-interaction methods whether Tm[sup [minus

  11. Direct measurement of the characteristic three-body electron attachment time in the atmospheric air in direct current electric field

    SciTech Connect

    Shutov, A. V.; Smetanin, I. V.; Ionin, A. A.; Levchenko, A. O.; Seleznev, L. V.; Sinitsyn, D. V.; Ustinovskii, N. N.; Zvorykin, V. D.

    2013-07-15

    We report the results of theoretical and experimental study of the characteristic time for three-body attachment of electrons produced by 100 fs UV laser pulse in the atmosphere air in the external DC electric field ranged from 0.2 to 10 kV/cm.

  12. Electron-drift velocity and ionization and attachment coefficients in gases/mixtures for diffuse-discharge opening switches

    NASA Astrophysics Data System (ADS)

    Carter, J. G.; Hunter, S. R.; Christophorou, L. G.; Lakdawala, V. K.

    The data presented show that it is possible to find gases and gas mixtures which have the desirable drift velocity, electron attachment, and breakdown strength characteristics required for diffuse-discharge opening switch applications. Several such gases and gas mixtures were identified and their approximate operating conditions were indicated.

  13. Queued History based Mediator Identification for an Incentive Attached peer to peer Electronic Coupon System

    NASA Astrophysics Data System (ADS)

    Shojima, Taiki; Ikkai, Yoshitomo; Komoda, Norihisa

    An incentive attached peer to peer (P2P) electronic coupon system is proposed in which users forward e-coupons to potential users by providing incentives to those mediators. A service provider needs to acquire distribution history for incentive payment by recording UserIDs (UIDs) in the e-coupons, since this system is intended for pure P2P environment. This causes problems of dishonestly altering distribution history. In order to solve such problems, distribution history is realized in a couple of queues structure. They are the UID queue, and the public key queue. Each element of the UID queue at the initial state consists of index, a secret key, and a digital signature. In recording one's UID, the encrypted UID is enqueued to the UID queue with a new digital signature created by a secret key of the dequeued element, so that each UID cannot be altered. The public key queue provides the functionality of validating digital signatures on mobile devices. This method makes it possible both each UID and sequence of them to be certificated. The availability of the method is evaluated by quantifying risk reduction using Fault Tree Analysis (FTA). And it's recognized that the method is better than common encryption methods.

  14. Formation of carbon chain molecular anions by radiative electron attachment and their destruction by photodetachment

    NASA Astrophysics Data System (ADS)

    Khamesian, Marjan; Douguet, Nicolas; Raoult, Maurice; Dulieu, Olivier; Kokoouline, Viatcheslav

    2016-05-01

    Several negative ions Cn H- (n = 4 , 6 , 8), Cn N- (n = 1 , 3 , 5) have been recently observed in the interstellar medium (ISM). A possible mechanism of formation is radiative electron attachment (REA). In this study we develop a first principle theoretical approach to study the REA and apply the approach to the formation of the negative molecular ions CN-, C2 H-, C3 N-, C4 H-, C5 N-, C6 H-, and C8 H-. The theoretical approach is based on the UK R-matrix calculations. Cross sections and rate coefficients for formation of these ions by REA to the corresponding neutral radicals are calculated. There is no experimental data on REA of these ions. However, using a similar approach we have also calculated cross sections for photodetachment of the negative ions and compared the obtained results with available experimental data. The good agreement with photodetachment experimental data provides a confirmation that the REA cross sections obtained in this study is also reliable. NSF Grant PHYS-1506391.

  15. Gas Phase Dissociative Electron Attachment to Formamide Derivatives NMF and DMF

    NASA Astrophysics Data System (ADS)

    Li, Zhou; Dawley, M. Michele; Ptasinska, Sylwia

    2015-09-01

    Fragmentation of biomolecules, such as nucleobases, induced by low energy electrons can lead to the break of DNA strands. Dissociative electron attachment (DEA), which can occur due to low energy interactions, is initiated with the formation of transient negative ions which exhibit characteristic resonant profiles in the product ion yield. The consequent fragmentation process can either be as simple as a single bond cleavage or a relatively complex process involving multiple bond rearrangements. Measurements of resonant peaks in ion yields and identification of ion products provide information of the resonant energies of the parent molecules as well as the fragmentation pathways. N-methylformamide (NMF) and dimethylformamide (DMF) are both derivatives of formamide which is the simplest structure containing the peptide bond linkage. In this work we identified anion fragments and measured resonance profiles of produced anions due to DEA to NMF and DMF. The anionic species produced from the two molecules were compared as well as the resonant positions and ion yields. Based on this comparison, the DEA process to the two molecules bears similarities such as leading to breaking of peptide bonds (C-N), as well as discrepancies such as absence of OCN- in DEA to DMF. The selective property of H atom loss, which is reported in the DEA to formamide, is also justified in our experiment since no dehydrogenated DMF anion was detected. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences under Award Number DE-FC02-04ER15533.

  16. Negative-ion formation in the explosives RDX, PETN, and TNT using the Reversal Electron Attachment Detection (READ) technique

    NASA Technical Reports Server (NTRS)

    Chutijian, Ara; Boumsellek, S.; Alajajian, S. H.

    1992-01-01

    In the search for high sensitivity and direct atmospheric sampling of trace species, techniques have been developed such as atmospheric-sampling, glow-discharge ionization (ASGDI), corona discharge, atmospheric pressure ionization (API), electron-capture detection (ECD), and negative-ion chemical ionization (NICI) that are capable of detecting parts-per-billion to parts-per-trillion concentrations of trace species. These techniques are based on positive- or negative-ion formation via charge-transfer to the target, or electron capture under multiple-collision conditions in a Maxwellian distribution of electron energies at the source temperature. One drawback of the high-pressure, corona- or glow-discharge devices is that they are susceptible to interferences either through indistinguishable product masses, or through undesired ion-molecule reactions. The ASGDI technique is relatively immune from such interferences, since at target concentrations of less than 1 ppm the majority of negative ions arises via electron capture rather than through ion-molecule chemistry. A drawback of the conventional ECD, and possibly of the ASGDI, is that they exhibit vanishingly small densities of electrons with energies in the range 0-10 millielectron volts (meV), as can be seen from a typical Maxwellian electron energy distribution function at T = 300 K. Slowing the electrons to these subthermal (less than 10 meV) energies is crucial, since the cross section for attachment of several large classes of molecules is known to increase to values larger than 10(exp -12) sq cm at near-zero electron energies. In the limit of zero energy these cross sections are predicted to diverge as epsilon(exp -1/2), where epsilon is the electron energy. In order to provide a better 'match' between the electron energy distribution function and attachment cross section, a new concept of attachment in an electrostatic mirror was developed. In this scheme, electrons are brought to a momentary halt by

  17. Theoretical study of pressure dependence of transition temperature of In and Pb

    SciTech Connect

    Kumar, Priyank; Bhatt, N. K.; Vyas, P. R.; Gohel, V. B.

    2015-08-28

    Recently proposed structured local pseudopotential (PP) by Fiolhais et al. has been successfully used to compute superconducting state parameters (SSP): electron-phonon coupling strength (λ), Coulomb pseudopotential (μ*), critical temperature (T{sub c}), effective interaction strength (N{sub 0}V), isotopic effect parameter (α) and their pressure dependence of non-transition metals In and Pb as a test case. Pressure dependence of the Debye temperature has been computed by Gruneisen model. Present results are in good agreement with experimental and other theoretical results. Present study has been further extended to estimate volume (critical volume) at which λ=μ*, where Tc and N{sub 0}V becomes zero. The presently used model is found to be transferable at the extreme environment without any adjustment of parameters further alongwith its simplicity and predictivity.

  18. Cross sections for 14-eV e-H{sub 2} resonant collisions: Isotope effect in dissociative electron attachment

    SciTech Connect

    Celiberto, R.; Janev, R. K.; Wadehra, J. M.; Laricchiuta, A.

    2011-07-15

    The process of dissociative attachment of electrons to molecular hydrogen and its isotopes in the energy range at approximately 14 eV is investigated. The dissociative electron attachment cross sections for all six hydrogen isotopes are calculated over an extended range of electron energies using the local complex potential model with the excited Rydberg {sup 2}{Sigma}{sub g}{sup +} electronic state of H{sub 2}{sup -} acting as the intermediate resonant state. A significant isotope effect in theoretical electron attachment cross sections is observed, in agreement with previous predictions and experimental observations. A two-parameter analytic expression for the cross section is derived from the theory that fits accurately the numerically calculated cross sections for all isotopes. Similarly, an analytic mass-scaling relation is derived from the theory that accurately reproduces the numerically calculated rate coefficients for all isotopes in the 0.1-1000 eV temperature range by using the rate coefficient for the H{sub 2} isotope only. The latter is represented by an analytic fit expression with two parameters only.

  19. Mechanistic investigation on pressure dependency of Heckel parameter.

    PubMed

    Patel, Sarsvatkumar; Kaushal, Aditya Mohan; Bansal, Arvind Kumar

    2010-04-15

    This work proposed to study the influence of varying compaction pressure on the plastic energy, elasticity (Young's modulus), particle yield strength, strain hardening, and applied pressures on derived Heckel parameter using material with different densification and deformation mechanisms: ibuprofen (IBN), paracetamol (PCM) (elastic behavior), methyl cellulose (Me-Cel), microcrystalline cellulose (MCC), sodium chloride (NaCl) (plastic behavior), and dicalcium phosphate (DCP) (brittle fracture). Force-displacement data were captured during in-die compaction for all materials having different deformation behavior. The apparent mean yield pressure (Py), plastic energy, Young's moduli, strain hardening parameter and rate of increase in Py were calculated from force-displacement compaction profiles obtained across a pressure range of 65-260 MPa. Materials under confined compression loading showed pressure dependent biphasic behavior in Py upon increasing pressure from 65 MPa to 260 MPa. IBN and PCM showed pressure dependency due to simultaneous elasticity and strain hardening upon increasing applied pressure. Me-Cel, MCC, and NaCl showed lower pressure dependency while DCP showed higher change in Py upon increasing pressure as a result of higher yield strength of DCP particles. Apparent mean yield pressure from Heckel analysis was significantly affected by the applied pressure, viscoelastic behavior, particle yield strength, and strain hardening. The simultaneously occurring events of elastic deformation and strain hardening give a false increase in Py at higher applied pressures.

  20. Dissociative electron attachment to the nitroamine HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine).

    PubMed

    Postler, Johannes; Goulart, Marcelo M; Matias, Carolina; Mauracher, Andreas; Ferreira da Silva, Filipe; Scheier, Paul; Limão-Vieira, Paulo; Denifl, Stephan

    2013-05-01

    In the present study, dissociative electron attachment (DEA) measurements with gas phase HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, C4H8N8O8, have been performed by means of a crossed electron-molecular beam experiment. The most intense signals are observed at 46 and 176 u and assigned to NO2(-) and C3H6N5O4(-), respectively. Anion efficiency curves for 15 negatively charged fragments have been measured in the electron energy region from about 0-20 eV with an energy resolution of ~0.7 eV. Product anions are observed mainly in the low energy region, near 0 eV, arising from surprisingly complex reactions associated with multiple bond cleavages and structural and electronic rearrangement. The remarkable instability of HMX towards electron attachment with virtually zero kinetic energy reflects the highly explosive nature of this compound. Substantially different intensity ratios of resonances for common fragment anions allow distinguishing the nitroamines HMX and royal demolition explosive molecule (RDX) in negative ion mass spectrometry based on free electron capture.

  1. Low energy (0-4 eV) electron impact to N(2)O clusters: Dissociative electron attachment, ion-molecule reactions, and vibrational Feshbach resonances.

    PubMed

    Vizcaino, Violaine; Denifl, Stephan; Märk, Tilmann D; Illenberger, Eugen; Scheier, Paul

    2010-10-21

    Electron attachment to clusters of N(2)O in the energy range of 0-4 eV yields the ionic complexes [(N(2)O)(n)O](-), [(N(2)O)(n)NO](-), and (N(2)O)(n) (-) . The shape of the ion yields of the three homologous series differs substantially reflecting the different formation mechanisms. While the generation of [(N(2)O)(n)O](-) can be assigned to dissociative electron attachment (DEA) of an individual N(2)O molecule in the target cluster, the formation of [(N(2)O)(n)NO](-) is interpreted via a sequence of ion molecule reactions involving the formation of O(-) via DEA in the first step. The nondecomposed complexes (N(2)O)(n) (-) are preferentially formed at very low energies (below 0.5 eV) as a result of intramolecular stabilization of a diffuse molecular anion at low energy. The ion yields of [(N(2)O)(n)O](-) and (N(2)O)(n) (-) versus electron energy show sharp peaks at the threshold region, which can be assigned to vibrational Feshbach resonances mediated by the diffuse anion state as already observed in an ultrahigh resolution electron attachment study of N(2)O clusters [E. Leber, S. Barsotti, J. Bömmels, J. M. Weber, I. I. Fabrikant, M.-W. Ruf, and H. Hotop, Chem. Phys. Lett. 325, 345 (2000)]. PMID:20969408

  2. Comparative electron paramagnetic resonance investigation of reduced graphene oxide and carbon nanotubes with different chemical functionalities for quantum dot attachment

    NASA Astrophysics Data System (ADS)

    Pham, Chuyen V.; Krueger, Michael; Eck, Michael; Weber, Stefan; Erdem, Emre

    2014-03-01

    Electron paramagnetic resonance (EPR) spectroscopy has been applied to different chemically treated reduced graphene oxide (rGO) and multiwalled carbon nanotubes (CNTs). A narrow EPR signal is visible at g = 2.0029 in both GO and CNT-Oxide from carbon-related dangling bonds. EPR signals became broader and of lower intensity after oxygen-containing functionalities were reduced and partially transformed into thiol groups to obtain thiol-functionalized reduced GO (TrGO) and thiol-functionalized CNT (CNT-SH), respectively. Additionally, EPR investigation of CdSe quantum dot-TrGO hybrid material reveals complete quenching of the TrGO EPR signal due to direct chemical attachment and electronic coupling. Our work confirms that EPR is a suitable tool to detect spin density changes in different functionalized nanocarbon materials and can contribute to improved understanding of electronic coupling effects in nanocarbon-nanoparticle hybrid nano-composites promising for various electronic and optoelectronic applications.

  3. Pressure Dependence of the Charge-Density-Wave Gap in Rare-Earth Tri-Tellurides

    SciTech Connect

    Sacchetti, A.; Arcangeletti, E.; Perucchi, A.; Baldassarre, L.; Postorino, P.; Lupi, S.; Ru, N.; Fisher, I.R.; Degiorgi, L.; /Zurich, ETH

    2009-12-14

    We investigate the pressure dependence of the optical properties of CeTe{sub 3}, which exhibits an incommensurate charge-density-wave (CDW) state already at 300 K. Our data are collected in the mid-infrared spectral range at room temperature and at pressures between 0 and 9 GPa. The energy for the single particle excitation across the CDW gap decreases upon increasing the applied pressure, similarly to the chemical pressure by rare-earth substitution. The broadening of the bands upon lattice compression removes the perfect nesting condition of the Fermi surface and therefore diminishes the impact of the CDW transition on the electronic properties of RTe{sub 3}.

  4. Pressure dependence of the photocycle kinetics of bacteriorhodopsin.

    PubMed Central

    Klink, B U; Winter, R; Engelhard, M; Chizhov, I

    2002-01-01

    The pressure dependence of the photocycle kinetics of bacteriorhodopsin from Halobacterium salinarium was investigated at pressures up to 4 kbar at 25 degrees C and 40 degrees C. The kinetics can be adequately modeled by nine apparent rate constants, which are assigned to irreversible transitions of a single relaxation chain of nine kinetically distinguishable states P(1) to P(9). All states except P(1) and P(9) consist of two or more spectral components. The kinetic states P(2) to P(6) comprise only the two fast equilibrating spectral states L and M. From the pressure dependence, the volume differences DeltaV(o)(LM) between these two spectral states could be determined that range from DeltaV(o)(LM) = -11.4 +/- 0.7 ml/mol (P(2)) to DeltaV(o)(LM) = 14.6 +/- 2.8 mL/mol (P(6)). A model is developed that explains the dependence of DeltaV(o)(LM) on the kinetic state by the electrostriction effect of charges, which are formed and neutralized during the L/M transition. PMID:12496115

  5. Electron transport through a diazonium-based initiator layer to covalently attached polymer brushes of ferrocenylmethyl methacrylate.

    PubMed

    Lillethorup, Mie; Torbensen, Kristian; Ceccato, Marcel; Pedersen, Steen Uttrup; Daasbjerg, Kim

    2013-11-01

    A versatile method based on electrografting of aryldiazonium salts was used to introduce covalently attached initiators for atom transfer radical polymerization (ATRP) on glassy carbon surfaces. Polymer brushes of ferrocenylmethyl methacrylate were prepared from the surface-attached initiators, and these films were thoroughly analyzed using various techniques, including X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRRAS), ellipsometry, and electrochemistry. Of particular interest was the electrochemical characterization of the electron transfer through the diazonium-based initiator layer to the redox centers in the polymer brush films. It was found that the apparent rate constant of electron transfer decreases exponentially with the dry-state thickness of this layer. To investigate the electron transfer in the brushes themselves, scanning electrochemical microscopy (SECM) was applied, thereby allowing the effect from the initiator layer to be excluded. The unusual transition feature of the approach curves recorded suggests that an initial fast charge transfer to the outermost-situated ferrocenyl groups is followed by a slower electron transport involving the neighboring redox units. PMID:24144237

  6. CARBON-RICH MOLECULAR CHAINS IN PROTOPLANETARY AND PLANETARY ATMOSPHERES: QUANTUM MECHANISMS AND ELECTRON ATTACHMENT RATES FOR ANION FORMATION

    SciTech Connect

    Carelli, F.; Grassi, T.; Gianturco, F. A.; Satta, M.

    2013-09-10

    The elementary mechanisms through which molecular polyynes could form stable negative ions after interacting with free electrons in planetary atmospheres (e.g., Titan's) are analyzed using quantum scattering calculations and quantum structure methods. The case of radical species and of nonpolar partners are analyzed via specific examples for both the C{sub n}H and HC{sub n}H series, with n values from 4 to 12. We show that attachment processes to polar radicals are dominating the anionic production and that the mediating role of dipolar scattering states is crucial to their formation. The corresponding attachment rates are presented as calculated upper limits to their likely values and are obtained down to the low temperatures of interest. The effects of the computed rates, when used in simple evolutionary models, are also investigated and presented in detail.

  7. Low-energy electron attachment to C 6F 5X (X=F, Cl, Br and I)

    NASA Astrophysics Data System (ADS)

    Shimamori, Hiroshi; Sunagawa, Takeyoshi; Ogawa, Yuji; Tatsumi, Yoshitsugu

    1994-09-01

    Rate constants have been measured for electron attachment to C 6F 5X (X=F, Cl, Br and I) in Xe buffer gas at room temperature at the mean electron energy between 0.04 and 2 eV using the pulse-radiolysis microwave-cavity method combined with microwave heating. The cross sections as a function of electron energy have been derived by unfolding the obtained rate constants. The rate constants at thermal energy are all the same, around 2 × 10 -7 cm 3 molecule -1 s -1, for C 6F 5X, and decrease monotonically with increasing mean energy. The cross sections have a peak at ≈0 eV for each compound. Only C 6F 6 shows another cross-section maximum at ≈0.75 eV. The discrepancy in the rate constants at thermal energy with those in previous reports is discussed.

  8. Pressure-dependent isotopic composition of iron alloys.

    PubMed

    Shahar, A; Schauble, E A; Caracas, R; Gleason, A E; Reagan, M M; Xiao, Y; Shu, J; Mao, W

    2016-04-29

    Our current understanding of Earth's core formation is limited by the fact that this profound event is far removed from us physically and temporally. The composition of the iron metal in the core was a result of the conditions of its formation, which has important implications for our planet's geochemical evolution and physical history. We present experimental and theoretical evidence for the effect of pressure on iron isotopic composition, which we found to vary according to the alloy tested (FeO, FeH(x), or Fe3C versus pure Fe). These results suggest that hydrogen or carbon is not the major light-element component in the core. The pressure dependence of iron isotopic composition provides an independent constraint on Earth's core composition. PMID:27126042

  9. Pressure-dependent isotopic composition of iron alloys.

    PubMed

    Shahar, A; Schauble, E A; Caracas, R; Gleason, A E; Reagan, M M; Xiao, Y; Shu, J; Mao, W

    2016-04-29

    Our current understanding of Earth's core formation is limited by the fact that this profound event is far removed from us physically and temporally. The composition of the iron metal in the core was a result of the conditions of its formation, which has important implications for our planet's geochemical evolution and physical history. We present experimental and theoretical evidence for the effect of pressure on iron isotopic composition, which we found to vary according to the alloy tested (FeO, FeH(x), or Fe3C versus pure Fe). These results suggest that hydrogen or carbon is not the major light-element component in the core. The pressure dependence of iron isotopic composition provides an independent constraint on Earth's core composition.

  10. Pressure-dependent isotopic composition of iron alloys

    NASA Astrophysics Data System (ADS)

    Shahar, A.; Schauble, E. A.; Caracas, R.; Gleason, A. E.; Reagan, M. M.; Xiao, Y.; Shu, J.; Mao, W.

    2016-04-01

    Our current understanding of Earth’s core formation is limited by the fact that this profound event is far removed from us physically and temporally. The composition of the iron metal in the core was a result of the conditions of its formation, which has important implications for our planet’s geochemical evolution and physical history. We present experimental and theoretical evidence for the effect of pressure on iron isotopic composition, which we found to vary according to the alloy tested (FeO, FeHx, or Fe3C versus pure Fe). These results suggest that hydrogen or carbon is not the major light-element component in the core. The pressure dependence of iron isotopic composition provides an independent constraint on Earth’s core composition.

  11. Theoretical study of radiative electron attachment to CN, C{sub 2}H, and C{sub 4}H radicals

    SciTech Connect

    Douguet, Nicolas; Fonseca dos Santos, S.; Orel, Ann E.; Raoult, Maurice; Dulieu, Olivier

    2015-06-21

    A first-principle theoretical approach to study the process of radiative electron attachment is developed and applied to the negative molecular ions CN{sup −}, C{sub 4}H{sup −}, and C{sub 2}H{sup −}. Among these anions, the first two have already been observed in the interstellar space. Cross sections and rate coefficients for formation of these ions by direct radiative electron attachment to the corresponding neutral radicals are calculated. For the CN molecule, we also considered the indirect pathway, in which the electron is initially captured through non-Born-Oppenheimer coupling into a vibrationally resonant excited state of the anion, which then stabilizes by radiative decay. We have shown that the contribution of the indirect pathway to the formation of CN{sup −} is negligible in comparison to the direct mechanism. The obtained rate coefficients for the direct mechanism at 30 K are 7 × 10{sup −16} cm{sup 3}/s for CN{sup −}, 7 × 10{sup −17} cm{sup 3}/s for C{sub 2}H{sup −}, and 2 × 10{sup −16} cm{sup 3}/s for C{sub 4}H{sup −}. These rates weakly depend on temperature between 10 K and 100 K. The validity of our calculations is verified by comparing the present theoretical results with data from recent photodetachment experiments.

  12. Equation of motion coupled cluster methods for electron attachment and ionization potential in fullerenes C60 and C70

    SciTech Connect

    Bhaskaran-Nair, Kiran; Kowalski, Karol; Moreno, Juana; Jarrell, Mark; Shelton, William A.

    2014-08-21

    Discovery of fullerenes has opened a entirely new chapter in chemistry due to their wide range of properties which holds exciting applications in numerous disciplines of science. The Nobel Prize in Chemistry 1996 was awarded jointly to Robert F. Curl Jr., Sir Harold W. Kroto and Richard E. Smalley in recoginition for their discovery of this new carbon allotrope. In this letter we are reporting ionization potential and electron attachment studies on fullerenes (C60 and C70) obtained with novel parallel implementation of the EA-EOM-CCSD and IP-EOM-CCSD methods in NWChem program package.

  13. Low energy (0-4 eV) electron impact to N{sub 2}O clusters: Dissociative electron attachment, ion-molecule reactions, and vibrational Feshbach resonances

    SciTech Connect

    Vizcaino, Violaine; Denifl, Stephan; Maerk, Tilmann D.; Scheier, Paul; Illenberger, Eugen

    2010-10-21

    Electron attachment to clusters of N{sub 2}O in the energy range of 0-4 eV yields the ionic complexes [(N{sub 2}O){sub n}O]{sup -}, [(N{sub 2}O){sub n}NO]{sup -}, and (N{sub 2}O){sub n}{sup -} . The shape of the ion yields of the three homologous series differs substantially reflecting the different formation mechanisms. While the generation of [(N{sub 2}O){sub n}O]{sup -} can be assigned to dissociative electron attachment (DEA) of an individual N{sub 2}O molecule in the target cluster, the formation of [(N{sub 2}O){sub n}NO]{sup -} is interpreted via a sequence of ion molecule reactions involving the formation of O{sup -} via DEA in the first step. The nondecomposed complexes (N{sub 2}O){sub n}{sup -} are preferentially formed at very low energies (below 0.5 eV) as a result of intramolecular stabilization of a diffuse molecular anion at low energy. The ion yields of [(N{sub 2}O){sub n}O]{sup -} and (N{sub 2}O){sub n}{sup -} versus electron energy show sharp peaks at the threshold region, which can be assigned to vibrational Feshbach resonances mediated by the diffuse anion state as already observed in an ultrahigh resolution electron attachment study of N{sub 2}O clusters [E. Leber, S. Barsotti, J. Boemmels, J. M. Weber, I. I. Fabrikant, M.-W. Ruf, and H. Hotop, Chem. Phys. Lett. 325, 345 (2000)].

  14. Radicals Formed in N-Acetyl-Proline by Electron Attachment: ESR Spectroscopy and Computational Studies

    PubMed Central

    Kheir, Jeanette F.; Chomicz, Lidia; Rak, Janusz; Bowen, Kit H.; Sevilla, Michael D.

    2011-01-01

    In this study, the reactions of electrons with N-acetyl-proline are investigated by electron spin resonance (ESR) spectroscopy and DFT theory. Electrons are produced by gamma irradiation or by photo-ionization of K4Fe(CN)6 in a neutral 7.5 M LiCl-D2O aqueous glasses at low temperatures with identical results. Electrons are found to add to both the peptide bond and the carboxyl group of the acetyl-proline moiety at 77K. On annealing both the electron adducts undergo fragmentation of the peptide bond between the nitrogen and the alpha carbon of the peptide structure. However the peptide bond electron adduct radical reacts much more rapidly than the carboxyl group electron adduct radical. The DFT calculations predict that the carboxyl adduct is substantially more stable than the peptide bond adduct, with the activation barrier to N-Cα cleavage 3.7 kcal/mol for the amide electron adducts and 23 kcal/mol for the carboxyl adducts in agreement with the relative reactivity found by experiment. PMID:22044351

  15. Modulation instability and dissipative rogue waves in ion-beam plasma: Roles of ionization, recombination, and electron attachment

    SciTech Connect

    Guo, Shimin Mei, Liquan

    2014-11-15

    The amplitude modulation of ion-acoustic waves is investigated in an unmagnetized plasma containing positive ions, negative ions, and electrons obeying a kappa-type distribution that is penetrated by a positive ion beam. By considering dissipative mechanisms, including ionization, negative-positive ion recombination, and electron attachment, we introduce a comprehensive model for the plasma with the effects of sources and sinks. Via reductive perturbation theory, the modified nonlinear Schrödinger equation with a dissipative term is derived to govern the dynamics of the modulated waves. The effect of the plasma parameters on the modulation instability criterion for the modified nonlinear Schrödinger equation is numerically investigated in detail. Within the unstable region, first- and second-order dissipative ion-acoustic rogue waves are present. The effect of the plasma parameters on the characteristics of the dissipative rogue waves is also discussed.

  16. Periodicity in Attachment Organelle Revealed by Electron Cryotomography Suggests Conformational Changes in Gliding Mechanism of Mycoplasma pneumoniae

    PubMed Central

    Kawamoto, Akihiro; Matsuo, Lisa; Kato, Takayuki; Yamamoto, Hiroki

    2016-01-01

    ABSTRACT Mycoplasma pneumoniae, a pathogenic bacterium, glides on host surfaces using a unique mechanism. It forms an attachment organelle at a cell pole as a protrusion comprised of knoblike surface structures and an internal core. Here, we analyzed the three-dimensional structure of the organelle in detail by electron cryotomography. On the surface, knoblike particles formed a two-dimensional array, albeit with limited regularity. Analyses using a nonbinding mutant and an antibody showed that the knoblike particles correspond to a naplike structure that has been observed by negative-staining electron microscopy and is likely to be formed as a complex of P1 adhesin, the key protein for binding and gliding. The paired thin and thick plates feature a rigid hexagonal lattice and striations with highly variable repeat distances, respectively. The combination of variable and invariant structures in the internal core and the P1 adhesin array on the surface suggest a model in which axial extension and compression of the thick plate along a rigid thin plate is coupled with attachment to and detachment from the substrate during gliding. PMID:27073090

  17. Enhancements in dissociative electron attachment to CF4, chlorofluorocarbons and hydrochlorofluorocarbons adsorbed on H2O ice

    NASA Astrophysics Data System (ADS)

    Lu, Q.-B.; Sanche, L.

    2004-02-01

    We report that the absolute cross sections for dissociative attachment of ˜0 eV electrons to chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are strongly enhanced by the presence of H2O ice. The absolute cross sections for CFCl3, CHF2Cl, and CH3CF2Cl on water ice are measured to be ˜8.9×10-14, ˜5.1×10-15, and ˜4.9×10-15 cm2 at ˜0 eV, respectively. The former value is about 1 order of magnitude higher than that in the gas phase, while the latter two are 3-4 orders higher. In contrast, the resonances at electron energies ⩾2.0 eV are strongly suppressed either for CFCs and HCFCs or for CF4 adsorbed on H2O ice. The cross-section enhancement is interpreted to be due to electron transfer from precursor states of the solvated electron in ice to an unfilled molecular orbital of CFCs or HCFCs followed by its dissociation. This study indicates that electron-induced dissociation is a significant process leading to CFC and HCFC fragmentation on ice surfaces.

  18. Enhancements in dissociative electron attachment to CF4, chlorofluorocarbons and hydrochlorofluorocarbons adsorbed on H2O ice.

    PubMed

    Lu, Q-B; Sanche, L

    2004-02-01

    We report that the absolute cross sections for dissociative attachment of approximately 0 eV electrons to chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are strongly enhanced by the presence of H2O ice. The absolute cross sections for CFCl3, CHF2Cl, and CH3CF2Cl on water ice are measured to be approximately 8.9 x 10(-14), approximately 5.1 x 10(-15), and approximately 4.9 x 10(-15) cm2 at approximately 0 eV, respectively. The former value is about 1 order of magnitude higher than that in the gas phase, while the latter two are 3-4 orders higher. In contrast, the resonances at electron energies > or = 2.0 eV are strongly suppressed either for CFCs and HCFCs or for CF4 adsorbed on H2O ice. The cross-section enhancement is interpreted to be due to electron transfer from precursor states of the solvated electron in ice to an unfilled molecular orbital of CFCs or HCFCs followed by its dissociation. This study indicates that electron-induced dissociation is a significant process leading to CFC and HCFC fragmentation on ice surfaces. PMID:15268383

  19. Pressure dependence of prototype structures of metastable niobium oxides

    NASA Astrophysics Data System (ADS)

    Obara, Kozo

    1993-03-01

    Faculty of Engineering, Kagoshima University, Korimoto, 1-21-40, Kagoshima 890, Japan Pressure dependences of prototypes of nonstoichiometric metastable niobium oxides formed by a magnetron sputtering system were investigated. The morphology of derived crystals depended strongly on the argon pressure. At argon pressure PAr< 0.2 Torr, thin microcrystals with five types of superlattice structures were derived. Observed lattice constants were transformed into one another by simple lattice deformations within 1% error. All types of superlattice structures were related to the cubic lattice a0 = 3.22 Å. At PAr > 0.3 Torr, metastable niobium oxide super-fine particles with a cubic lattice constant a = 3.44 Å were obtained. Unique relationships between lattice constants were found on the oxidized niobium super-fine particles, NbO and NbO2 formed above 0.3 Torr within 0.5% error. In this case, the lattice structure with a = 3.44 ,Å (BCC) is related to all structures. These lattices a0 = 3.22 ,Å and a = 3.44 Å seem to be the prototypes at PAr ≤ 0.2 Torr and PAr ≥ 0.3 Tort, respectively. These structural changes due to pressure difference depend on the density and the enthalpy of vacancies in as-grown crystals. The density of vacancies is related to the condensation rate of the crystals.

  20. Comparative electron paramagnetic resonance investigation of reduced graphene oxide and carbon nanotubes with different chemical functionalities for quantum dot attachment

    SciTech Connect

    Pham, Chuyen V.; Krueger, Michael E-mail: emre.erdem@physchem.uni-freiburg.de; Eck, Michael; Weber, Stefan; Erdem, Emre E-mail: emre.erdem@physchem.uni-freiburg.de

    2014-03-31

    Electron paramagnetic resonance (EPR) spectroscopy has been applied to different chemically treated reduced graphene oxide (rGO) and multiwalled carbon nanotubes (CNTs). A narrow EPR signal is visible at g = 2.0029 in both GO and CNT-Oxide from carbon-related dangling bonds. EPR signals became broader and of lower intensity after oxygen-containing functionalities were reduced and partially transformed into thiol groups to obtain thiol-functionalized reduced GO (TrGO) and thiol-functionalized CNT (CNT-SH), respectively. Additionally, EPR investigation of CdSe quantum dot-TrGO hybrid material reveals complete quenching of the TrGO EPR signal due to direct chemical attachment and electronic coupling. Our work confirms that EPR is a suitable tool to detect spin density changes in different functionalized nanocarbon materials and can contribute to improved understanding of electronic coupling effects in nanocarbon-nanoparticle hybrid nano-composites promising for various electronic and optoelectronic applications.

  1. Observation of dihalide elimination upon electron attachment to oxalyl chloride and oxalyl bromide, 300-550 K

    SciTech Connect

    Van Doren, Jane M.; Hogan, Kathleen B.; Miller, Thomas M.; Viggiano, A.A.

    2006-05-14

    Rate coefficients have been measured for electron attachment to oxalyl chloride [ClC(O)C(O)Cl] and oxalyl bromide [BrC(O)C(O)Br] in He gas at 133 Pa pressure over the temperature range of 300-550 K. With oxalyl chloride, the major ion product of attachment is Cl{sub 2}{sup -} at all temperatures (66% at 300 K); its importance increases slightly as temperature increases. Two other product ions formed are Cl{sup -} (18% at 300 K) and the phosgene anion CCl{sub 2}O{sup -} (16% at 300 K) and appear to arise from a common mechanism. With oxalyl bromide, the Br{sub 2}{sup -} channel represents almost half of the ion product of attachment, independent of temperature. Br{sup -} accounts for the remainder. For oxalyl chloride, the attachment rate coefficient is small [(1.8{+-}0.5)x10{sup -8} cm{sup 3} s{sup -1} at 300 K], and increases with temperature. The attachment rate coefficient for oxalyl bromide [(1.3{+-}0.4)x10{sup -7} cm{sup 3} s{sup -1} at 300 K] is nearly collisional and increases only slightly with temperature. Stable parent anions C{sub 2}Cl{sub 2}O{sub 2}{sup -} and C{sub 2}Br{sub 2}O{sub 2}{sup -} and adduct anions Cl{sup -}(C{sub 2}Cl{sub 2}O{sub 2}) and Br{sup -}(C{sub 2}Br{sub 3}O{sub 2}) were observed but are not primary attachment products. G2 and G3 theories were applied to determine geometries of products and energetics of the electron attachment and ion-molecule reactions studied. Electron attachment to both oxalyl halide molecules leads to a shorter C-C bond and longer C-Cl bond in the anions formed. Trans and gauche conformers of the neutral and anionic oxalyl halide species have similar energies and are more stable than the cis conformer, which lies 100-200 meV higher in energy. For C{sub 2}Cl{sub 2}O{sub 2}, C{sub 2}Cl{sub 2}O{sub 2}{sup -}, and C{sub 2}Br{sub 2}O{sub 2}{sup -}, the trans conformer is the most stable conformation. The calculations are ambiguous as to the oxalyl bromide geometry (trans or gauche), the result depending on the

  2. Plane wave density functional theory studies of the structural and the electronic properties of amino acids attached to graphene oxide via peptide bonding

    NASA Astrophysics Data System (ADS)

    Min, Byeong June; Jeong, Hae Kyung; Lee, ChangWoo

    2015-08-01

    We studied via plane wave pseudopotential total-energy calculations within the local spin density approximation (LSDA) the electronic and the structural properties of amino acids (alanine, glycine, and histidine) attached to graphene oxide (GO) by peptide bonding. The HOMO-LUMO gap, the Hirshfeld charges, and the equilibrium geometrical structures exhibit distinctive variations that depend on the species of the attached amino acid. The GO-amino acid system appears to be a good candidate for a biosensor.

  3. Resonant electron attachment to polar aromatic molecules: consequences for their chemistry in the interstellar medium

    NASA Astrophysics Data System (ADS)

    Carelli, Fabio; Satta, Mauro; Gianturco, Franco A.

    2013-11-01

    In this paper we present and discuss the results obtained from ab-initio quantum scattering calculations of the response from neutral aromatic species like C6H5 (phenyl) and C6H4 (benzyne, ortho isomer) to low-energy electron collisions. Our main purpose is to investigate the possible mechanisms that can lead to the final formation of their stable negative ions under astrophysical conditions, by linking low-lying metastable anionic states to bound anionic states. Quantum chemical calculations were also employed to confirm the features of the metastable resonant states found by the scattering calculations, while the role of the permanent dipole moments of both systems on the scattering behaviour for near-threshold electrons is also analysed in some detail. The possible energy redistribution paths for stabilizing both anionic species under ISM conditions are discussed in the conclusions.

  4. Equation of motion coupled cluster methods for electron attachment and ionization potential in polyacenes

    SciTech Connect

    Bhaskaran-Nair, Kiran; Kowalski, Karol; Jarrell, Mark; Moreno, Juana; Shelton, William A.

    2015-11-05

    Polyacenes have attracted considerable attention due to their use in organic based optoelectronic materials. Polyacenes are polycyclic aromatic hydrocarbons composed of fused benzene rings. Key to understanding and design of new functional materials is an understanding of their excited state properties starting with their electron affinity (EA) and ionization potential (IP). We have developed a highly accurate and com- putationally e*fficient EA/IP equation of motion coupled cluster singles and doubles (EA/IP-EOMCCSD) method that is capable of treating large systems and large basis set. In this study we employ the EA/IP-EOMCCSD method to calculate the electron affinity and ionization potential of naphthalene, anthracene, tetracene, pentacene, hex- acene and heptacene. We have compared our results with other previous theoretical studies and experimental data. Our EA/IP results are in very good agreement with experiment and when compared with the other theoretical investigations our results represent the most accurate calculations as compared to experiment.

  5. Computational study of dissociative electron attachment to π-allyl ruthenium (II) tricarbonyl bromide

    NASA Astrophysics Data System (ADS)

    Thorman, Rachel M.; Bjornsson, Ragnar; Ingólfsson, Oddur

    2016-08-01

    Motivated by the current interest in low energy electron induced fragmentation of organometallic complexes in focused electron beam induced deposition (FEBID) we have evaluated different theoretical protocols for the calculation of thermochemical threshold energies for DEA to the organometallic complex π-allyl ruthenium (II) tricarbonyl bromide. Several different computational methods including density functional theory (DFT), hybrid-DFT and coupled cluster were evaluated for their ability to predict these threshold energies and compared with the respective experimental values. Density functional theory and hybrid DFT methods were surprisingly found to have poor reliability in the modelling of several DEA reactions; however, the coupled cluster method LPNO-pCCSD/2a was found to produce much more accurate results. Using the local correlation pair natural orbital (LPNO) methodology, high level coupled cluster calculations for open-shell systems of this size are now affordable, paving the way for reliable theoretical DEA predictions of such compounds.

  6. An All-Elastomeric Transparent and Stretchable Temperature Sensor for Body-Attachable Wearable Electronics.

    PubMed

    Trung, Tran Quang; Ramasundaram, Subramaniyan; Hwang, Byeong-Ung; Lee, Nae-Eung

    2016-01-20

    A transparent stretchable (TS) gated sensor array with high optical transparency, conformality, and high stretchability of up to 70% is demonstrated. The TS-gated sensor array has high responsivity to temperature changes in objects and human skin. This unprecedented TS-gated sensor array, as well as the integrated platform of the TS-gated sensor with a transparent and stretchable strain sensor, show great potential for application to wearable skin electronics for recognition of human activity.

  7. Computational study of dissociative electron attachment to π-allyl ruthenium (II) tricarbonyl bromide

    NASA Astrophysics Data System (ADS)

    Thorman, Rachel M.; Bjornsson, Ragnar; Ingólfsson, Oddur

    2016-08-01

    Motivated by the current interest in low energy electron induced fragmentation of organometallic complexes in focused electron beam induced deposition (FEBID) we have evaluated different theoretical protocols for the calculation of thermochemical threshold energies for DEA to the organometallic complex π-allyl ruthenium (II) tricarbonyl bromide. Several different computational methods including density functional theory (DFT), hybrid-DFT and coupled cluster were evaluated for their ability to predict these threshold energies and compared with the respective experimental values. Density functional theory and hybrid DFT methods were surprisingly found to have poor reliability in the modelling of several DEA reactions; however, the coupled cluster method LPNO-pCCSD/2a was found to produce much more accurate results. Using the local correlation pair natural orbital (LPNO) methodology, high level coupled cluster calculations for open-shell systems of this size are now affordable, paving the way for reliable theoretical DEA predictions of such compounds. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  8. Theoretical treatment of excited electronic states of adsorbates on metals: Electron attachment to CO 2 adsorbed on K-modified Pt(1 1 1)

    NASA Astrophysics Data System (ADS)

    Sremaniak, Laura S.; Whitten, Jerry L.

    Theoretical studies of photoinduced processes involving electron attachment to CO 2 adsorbed on Pt(1 1 1) in the presence of a coadsorbed K atom are reported. First principles theoretical methods suitable for describing electronic states embedded in a near continuum of metal to metal excitations are described. Wave functions are constructed by ab initio configuration interaction methods which allow a rigorous resolution of states and differentiation between competing pathways of molecular desorption and dissociation. An embedding theory is used to achieve high accuracy in the adsorbate-surface region. Compared to CO 2 adsorbed on Pt(1 1 1), the K promoter lowers the work function of the system from 5.6 to 5.2 eV and decreases the energy required to form the electron attached excited electronic state from 6.8 to 5.6 eV. However, stabilization of CO 2 depends strongly on orientation and proximity to the K adatom. The most favorable pathway leading to dissociation requires that CO 2 be adsorbed at a site that does not share Pt atoms with the K adsorption site, i.e., at next-nearest neighbor sites. As was found for Pt(1 1 1) without a K adatom, the dissociation pathway involves bending of CO 2 in the excited state followed by possible dissociation on the excited state surface where the barrier height is reduced from its value of 1.0 eV on the Pt surface to 0.34 eV. As is the case for the unmodified surface, dissociation could also occur after return to the ground state potential energy surface via vibrational processes.

  9. Pressure dependence of critical temperature of bulk FeSe from spin fluctuation theory

    NASA Astrophysics Data System (ADS)

    Hirschfeld, Peter; Kreisel, Andreas; Wang, Yan; Tomic, Milan; Jeschke, Harald; Jacko, Anthony; Valenti, Roser; Maier, Thomas; Scalapino, Douglas

    2013-03-01

    The critical temperature of the 8K superconductor FeSe is extremely sensitive to pressure, rising to a maximum of 40K at about 10GPa. We test the ability of the current generation of fluctuation exchange pairing theories to account for this effect, by downfolding the density functional theory electronic structure for each pressure to a tight binding model. The Fermi surface found in such a procedure is then used with fixed Hubbard parameters to determine the pairing strength using the random phase approximation for the spin singlet pairing vertex. We find that the evolution of the Fermi surface captured by such an approach is alone not sufficient to explain the observed pressure dependence, and discuss alternative approaches. PJH, YW, AK were supported by DOE DE-FG02-05ER46236, the financial support of MT, HJ, and RV from the DFG Schwerpunktprogramm 1458 is kindly acknowledged.

  10. Electron angular distributions and attachment rates in o-Benzyne and Phenyl aromatic molecules: the effect of the permanent dipoles

    NASA Astrophysics Data System (ADS)

    Carelli, Fabio; Gianturco, Franco A.

    2013-12-01

    Free, gas-phase polycyclic aromatic hydrocarbons (PAHs) and related species are currently considered to play an important role in the interstellar/circumstellar medium as they are thought to significantly contribute to both Diffuse and Unidentified infrared interstellar bands. They are also considered fundamental blocks of the interstellar dust and several formation mechanisms were proposed with regard to their interstellar/circumstellar synthesis. In this paper we therefore present and discuss the results obtained from ab initio quantum scattering calculations of the response from neutral polar aromatic single-ring species to low-energies electron collisions. Our main purpose is here to provide new values for the rate constants for electron attachment to orthobenzyne and to phenyl molecules by discussing in detail the effects of the long-range dipole interaction in the framework of the Born perturbative approximation at the first order. We shall further discuss the specific behavior of the electrons' diffusion by such molecules, especially in the low-energy range of the scattered particles' energies as guided by their permanent dipole moments. We shall also provide accurate numerical fittings for both rates and give explicitly the fitting parameters for their possible use in evolutionary models.

  11. Barrier-Free Intermolecular Proton Transfer Induced by Excess Electron Attachment to the Complex of Alanine with Uracil

    SciTech Connect

    Dabkowska, Iwona; Rak, Janusz; Gutowski, Maciej S.; Nilles, J.M.; Stokes, Sarah; Bowen, Kit H.

    2004-04-01

    The photoelectron spectrum of the uracil-alanine anionic complex (UA)- has been recorded with 2.540 eV photons. This spectrum reveals a broad feature with a maximum between 1.6-2.1 eV. The vertical electron detachment energy is too large to be attributed to an (UA)- anionic complex in which an intact uracil anion is solvated by alanine, or vice versa. The neutral and anionic complexes of uracil and alanine were studied at the B3LYP and second order Moeller-Plesset level of theory with 6-31++G** basis sets. The neutral complexes form cyclic hydrogen bonds and the three most stable neutral complexes are bound by 0.72, 0.61 and 0.57 eV. The electron hole in complexes of uracil with alaninie is localized on uracil, but the formation of a complex with alanine strongly modulates the vertical ionization energy of uracil. The theoretical results indicate that the excess electron in (UA)- occupies a p* orbital localized on uracil. The excess electron attachment to the complex can induce a barrier-free proton transfer (BFPT) from the carboxylic group of alanine to the O8 atom of uracil. As a result, the four most stable structures of the uracil-alanine anionic complex can be characterized as the neutral radical of hydrogenated uracil solvated by the anion of deprotonated alanine. Our current results for the anionic complex of uracil with alanine are similar to our previous results for the anion of uracil with glycine [Eur. Phys. J. D 20, 431 (2002)], and together they indicate that the BFPT process is not very sensitive to the nature of the amino acid's hydrophobic residual group. The BFPT to the O8 atom of uracil may be relevant to the damage suffered by nucleic acid bases due to exposure to low energy electrons.

  12. Equation of motion coupled cluster methods for electron attachment and ionization potential in polyacenes

    NASA Astrophysics Data System (ADS)

    Bhaskaran-Nair, Kiran; Kowalski, Karol; Jarrell, Mark; Moreno, Juana; Shelton, William A.

    2015-11-01

    Polyacenes have attracted considerable attention due to their various applications in organic optoelectronic materials. This study focuses on linear polyacenes and their electron affinity (EA) and ionization potential (IP) properties. We have employed our recent implementation of EA/IP equation of motion coupled cluster singles and doubles (EA/IP-EOMCCSD) methods which are accurate, computationally efficient and are capable of treating large systems employing reasonable basis sets size. The EA/IP results obtained for naphthalene, anthracene, tetracene, pentacene, hexacene and heptacene are in a good agreement with experiment. Comparison between quality of excitation energies obtained from IP-EOMCCSD and EE-EOMCCSD formalisms were also studied.

  13. Formation of aminyl radicals on electron attachment to AZT: Abstraction from the sugar phosphate backbone vs. one-electron oxidation of Guanine

    PubMed Central

    Adhikary, Amitava; Khanduri, Deepti; Pottiboyina, Venkata; Rice, Cory T.; Sevilla, Michael D.

    2010-01-01

    Employing electron spin resonance (ESR) spectroscopy, we have characterized the radicals formed in 3′-Azido-3′-deoxythymidine (3′-AZT) and in its 5′-analog 5′-azido-5′-deoxythymidine (5′-AZT) after electron attachment in γ-irradiated aqueous (H2O or D2O) glassy (7.5 M LiCl) systems. ESR spectral studies and theoretical calculations show that the predominant site of electron capture in 3′-AZT and in 5′-AZT is at the azide group and not at the thymine moiety. The azide group in AZT is therefore more electron affinic than the most electron affinic DNA base, thymine. Electron attachment to 3′-AZT and 5′-AZT results in an unstable azide anion radical intermediate (RN3•−) that is too short lived to be observed in our work even at 77 K. At 77 K we observe the neutral aminyl radical (RNH•) after loss of N2 from RN3•− followed by protonation of nitrene anion radical (RN•−) to give RNH•. The expected RN•− intermediate is not observed as protonation from water is complete at 77 K even in under highly basic conditions. Formation of RND• in D2O solutions confirms water as the source of the NH proton in the RNH•. Our assignments to these radicals are aided by DFT calculations for hyperfine coupling constants which closely match the experimental values. On annealing to higher temperatures (ca. 160–170 K), RNH• undergoes bimolecular hydrogen abstraction reactions from the thymine methyl group and the sugar moiety resulting in the formation of the thymine allyl radical (UCH2•) and two sugar radicals - C3′•, C5′•. RNH• also results in one-electron oxidation of the guanine base in 3′-AZG. This work provides a potential mechanism for the reported radiosensitization effects of AZT. PMID:20575557

  14. Development of a Pressure-Dependent Constitutive Model with Combined Multilinear Kinematic and Isotropic Hardening

    NASA Technical Reports Server (NTRS)

    Allen Phillip A.; Wilson, Christopher D.

    2003-01-01

    The development of a pressure-dependent constitutive model with combined multilinear kinematic and isotropic hardening is presented. The constitutive model is developed using the ABAQUS user material subroutine (UMAT). First the pressure-dependent plasticity model is derived. Following this, the combined bilinear and combined multilinear hardening equations are developed for von Mises plasticity theory. The hardening rule equations are then modified to include pressure dependency. The method for implementing the new constitutive model into ABAQUS is given.

  15. Electron attachment to CF3 and CF3Br at temperatures up to 890 K: experimental test of the kinetic modeling approach.

    PubMed

    Shuman, Nicholas S; Miller, Thomas M; Viggiano, Albert A; Troe, Jürgen

    2013-05-28

    Thermal rate constants and product branching fractions for electron attachment to CF3Br and the CF3 radical have been measured over the temperature range 300-890 K, the upper limit being restricted by thermal decomposition of CF3Br. Both measurements were made in Flowing Afterglow Langmuir Probe apparatuses; the CF3Br measurement was made using standard techniques, and the CF3 measurement using the Variable Electron and Neutral Density Attachment Mass Spectrometry technique. Attachment to CF3Br proceeds exclusively by the dissociative channel yielding Br(-), with a rate constant increasing from 1.1 × 10(-8) cm(3) s(-1) at 300 K to 5.3 × 10(-8) cm(3) s(-1) at 890 K, somewhat lower than previous data at temperatures up to 777 K. CF3 attachment proceeds through competition between associative attachment yielding CF3 (-) and dissociative attachment yielding F(-). Prior data up to 600 K showed the rate constant monotonically increasing, with the partial rate constant of the dissociative channel following Arrhenius behavior; however, extrapolation of the data using a recently proposed kinetic modeling approach predicted the rate constant to turn over at higher temperatures, despite being only ~5% of the collision rate. The current data agree well with the previous kinetic modeling extrapolation, providing a demonstration of the predictive capabilities of the approach. PMID:23742484

  16. Time-resolved radiation chemistry: Dynamics of electron attachment to uracil following UV excitation of iodide-uracil complexes

    SciTech Connect

    King, Sarah B.; Yandell, Margaret A.; Stephansen, Anne B.; Neumark, Daniel M.

    2014-12-14

    Electron attachment to uracil was investigated by applying time-resolved photoelectron imaging to iodide-uracil (I{sup –}U) complexes. In these studies, an ultraviolet pump pulse initiated charge transfer from the iodide to the uracil, and the resulting dynamics of the uracil temporary negative ion were probed. Five different excitation energies were used, 4.00 eV, 4.07 eV, 4.14 eV, 4.21 eV, and 4.66 eV. At the four lowest excitation energies, which lie near the vertical detachment energy of the I{sup –}U complex (4.11 eV), signatures of both the dipole bound (DB) as well as the valence bound (VB) anion of uracil were observed. In contrast, only the VB anion was observed at 4.66 eV, in agreement with previous experiments in this higher energy range. The early-time dynamics of both states were highly excitation energy dependent. The rise time of the DB anion signal was ∼250 fs at 4.00 eV and 4.07 eV, ∼120 fs at 4.14 eV and cross-correlation limited at 4.21 eV. The VB anion rise time also changed with excitation energy, ranging from 200 to 300 fs for excitation energies 4.00–4.21 eV, to a cross-correlation limited time at 4.66 eV. The results suggest that the DB state acts as a “doorway” state to the VB anion at 4.00–4.21 eV, while direct attachment to the VB anion occurs at 4.66 eV.

  17. The branching ratio of anions in thermal electron attachment to halogenated fluorocompounds

    NASA Astrophysics Data System (ADS)

    Nakagawa, Seiko

    2002-08-01

    The temperature dependence of the formation of negative ions from C6F5X, C6F4X2 ( X= Cl, Br, I) , XC6F4Br ( X= Cl, CF3, BrC6F4, CN) , and NC 5F 4Br was studied using negative chemical ionization mass spectrometry. Cl - and the parent negative ion for chlorofluorobenzene, Br-, ( M- Br) - (M=parent molecule), and the parent negative ion for bromofluorocarbon, and I - and (M-I) - for iodofluorobenzene were observed. The intensity of (M-X) - and the parent negative ion relative to that of halide ion changes with temperature. The relative intensity, C6F4X-/ X- ( X= Br, I) of 1,2-C 6F 4X 2 is smaller than that of 1,4-C 6F 4X 2. It seems that the heat of formation of (M-X) -+X relative to that of (M-X)+X - in 1,2-C 6F 4X 2 would be higher than in 1,4-C 6F 4X 2 and C 6F 5X. The temperature dependence of the relative ratio, (M-Br) -/Br -, can lead the relative trend of the electron affinity of M-Br, as C 6F 4CN>CF 3C 6F 4>C 6F 4C 6F 4Br>C 5F 4N>C 6F 4Cl>C 6F 4Br>C 6F 5. This is correlated with the atomic charge distribution of (M-Br) - calculated using the Hartree-Fock method.

  18. Electron Attachment in Low-Energy Electron Elastic Collisions with Au and Pt Atoms: Identification of Excited Anions

    NASA Astrophysics Data System (ADS)

    Msezane, A. Z.; Eure, A.; Felfli, Z.; Sokolovski, D.

    2009-11-01

    The recent Regge-pole methodology has been benchmarked [1] on the accurately measured binding energies of the excited Ge= and Sn= anions [2] through the binding energies (BEs) extracted from the Regge-pole calculated elastic total cross sections (TCSs). Here the methodology is applied together with a Thomas-Fermi type potential that incorporates the vital core polarization interaction to investigate the possibility of forming excited Au= and Pt= anions in low-energy electron elastic collisions with Au and Pt atoms. From the positions of the characteristic extremely narrow resonances in the total cross sections, we extract the binding energies of the excited Au= and Pt= anions formed as Regge resonances during the collisions. The angular life of the complexes thus formed is used to differentiate the stable excited bound states of the anions from the shape resonances [3]. The BEs for the excited Au= and Pt= anions are found to be 0.475eVand 0.543eV, respectively, challenging both theory and experiment to verify. [1] A. Msezane et al, Phys. Rev. A, Submitted (2009) [2] M. Scheer et al, Phys. Rev. A 58, 2844 (1998) [3] Z. Felfli et al, Phys. Rev. A 79, 012714 (2009)

  19. Kinetics of electron attachment to OH and HNO3 and mutual neutralization of Ar+ with NO2- and NO3- at 300 and 500 K

    NASA Astrophysics Data System (ADS)

    Shuman, Nicholas S.; Miller, Thomas M.; Viggiano, A. A.

    2012-03-01

    The electron attachment rate constant to nitric acid (HNO3) has been measured in a flowing afterglow-Langmuir probe (FALP) apparatus at 300 and 500 K using three independent methods: the traditional FALP technique of monitoring electron depletion, "one-gas" VENDAMS (variable electron and neutral density attachment mass spectrometry), and "two-gas" VENDAMS. The three measurements are in agreement with a 300 K weighted average of 1.4 ± 0.3 × 10-7 cm3 s-1, 2 to 10 times higher than previously reported values. Attachment is primarily dissociative yielding NO2- as previously reported, but for the first time a small endothermic channel to produce OH- was also observed at 500 K. From the one-gas VENDAMS data, associative attachment to the OH produced in the primary attachment was found to occur with an effective two body rate constant of 1.2 ± _{0.7}^3 × 10-11 cm3 s-1 at 300 K, the first reported rate constant for this radical species. Finally, ion-ion neutralization rate constants of NO2- and NO3- with Ar+ were determined to be 5.2 ± _{2.5}^{1.5} × 10-8 and 4.5 ± 2.5 × 10-8 cm3 s-1 at 300 K, respectively.

  20. The wavelength dependence of photoinduced hot electron dissociative attachment to methyl bromide adsorbed on gallium arsenide (110)

    SciTech Connect

    Camillone, N. III; Khan, K.A.; Lasky, P.J.; Wu, L.; Moryl, J.E.; Osgood, R.M. Jr.

    1998-11-01

    The wavelength dependence of photoinduced dissociation of CH{sub 3}Br via dissociative electron attachment (DEA) of {open_quotes}hot{close_quotes} electrons for one monolayer CH{sub 3}Br adsorbed on GaAs(110) has been measured. The cross section for dissociation is found to decrease monotonically by two orders of magnitude as the incident wavelength is varied from 308 to 550 nm. There is an apparent threshold near 490 nm (2.5 eV), well below the gas phase photodissociation threshold near 250 nm (5.0 eV), but in good agreement with a simple estimate based on expected values for the decrease in the photoemission threshold and the lowering of the molecular affinity level upon adsorption of CH{sub 3}Br on a semiconductor surface. The observed threshold is found to move to higher energy as dissociation of the monolayer proceeds. Based on the work of Hasselbrink and co-workers [F. Weik, A. de Meijere, and E. Hasselbrink, J. Chem. Phys. {bold 99}, 682 (1993)], a simple theoretical model is developed which considers the tunneling of hot electrons through the interfacial barrier between the physisorbed CH{sub 3}Br and the GaAs. The results of our theoretical model in conjunction with those of earlier {ital ab initio} calculations [S. Black, R. Friesner, P. H. Lu, and R. M. Osgood, Jr., Surf. Sci. {bold 382}, 154 (1997)] suggest that the adsorbate affinity level is centered at {approximately}0.6 eV above the (adsorbate- modified) vacuum level of the substrate. This value corresponds to a {approximately}1.8 eV stabilization of the negative ion resonance upon adsorption. {copyright} {ital 1998 American Institute of Physics.}

  1. Pressure dependence of donor excitation spectra in AlSb

    SciTech Connect

    Hsu, L.; McCluskey, M.D.; Haller, E.E.

    2002-01-16

    We have investigated the behavior of ground to bound excited-state electronic transitions of Se and Te donors in AlSb as a function of hydrostatic pressure. Using broadband far-infrared Fourier transform spectroscopy, we observe qualitatively different behaviors of the electronic transition energies of the two donors. While the pressure derivative of the Te transition energy is small and constant, as might be expected for a shallow donor, the pressure derivatives of the Se transition energies are quadratic and large at low pressures, indicating that Se is actually a deep donor. In addition, at pressures between 30 and 50 kbar, we observe evidence of an anti-crossing between one of the selenium electronic transitions and a two-phonon mode.

  2. Pressure dependent resistivity and magnetic measurements on superconducting KFe2As2

    NASA Astrophysics Data System (ADS)

    Kaluarachchi, Udhara; Taufour, Valentin; Tanatar, Makariy A.; Kim, Stella K.; Liu, Yong; Lograsso, Thomas A.; Bud'Ko, Sergey L.; Canfield, Paul C.; Foroozani, Neda; Lim, Jinhyuk; Schilling, James S.

    2014-03-01

    Ba1-xKxFe2As2 shows superconductivity at Tc ~ 38 K at the optimal doping (x ~ 0 . 4). However, superconductivity is still observed up to the extreme hole doping (x = 1) in KFe2As2 with a reduced Tc ~ 3 . 4 K. At this extreme limit, there is no observed electron pocket in this compound. The superconducting state is believed to be of a different symmetry than in the other 122 iron based superconductors. By means of resistivity, magnetization and AC susceptibility under pressure, we investigate the properties of this material. The pressure dependence of Tc has a change of slope around 2 GPa possibly consistent with a transition to a superconducting state of a different symmetry [F. F. Tafti, et al., Nature Physics 9, 349 (2013)]. We will compare measurements performed in different pressure media and discuss the evolution of the electronic correlations with applied pressure. Work at Ames Laboratory supported by AFOSR-MURI grant FA9550-09-1-0603 and by US DOE under the Contract No. DE-AC02-07CH11358. Work at Washington University supported by NSF Grant No. DMR-1104742 and by the Carnegie/DOE Alliance Center through NNSA/DOE Grant No. DE-FC52-08NA28554.

  3. Pressure-dependent Raman scattering study of CoV2O4

    NASA Astrophysics Data System (ADS)

    Byrum, Taylor; Gleason, Samuel; Zhou, Haidong; Cooper, S. Lance

    2015-03-01

    The AV2O4 (A = Cd, Mn, Mg, Zn, Co) spinel family provides a fertile ground to explore the crossover between electron localization and itinerancy, which can be tuned with chemical (A-site substitution) and/or physical pressure. CoV2O4 resides closest to the predicted itinerant electron limit for the vanadium spinel family. Recent experiments have shown the existence of a critical V-V separation by inducing a metallic transition in CoV2O4 with a pressure of ~6 GPa. While the structure of CoV2O4 has been theoretically suggested to remain cubic through the metallic transition, no structural measurements under pressure have been performed. Raman spectroscopy is well suited to address this issue, as it is sensitive to even subtle structural changes. In this presentation, I present a pressure-dependent Raman scattering study of CoV2O4 to elucidate the role the structure plays in the metallic transition. Research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Award DE-FG02-07ER46453. T. Byrum was partially supported by the NSF Graduate Research Fellowship Program under Grant Number DGE-1144245.

  4. Electron attachment to CF{sub 3} and CF{sub 3}Br at temperatures up to 890 K: Experimental test of the kinetic modeling approach

    SciTech Connect

    Shuman, Nicholas S.; Miller, Thomas M.; Viggiano, Albert A.; Troe, Juergen

    2013-05-28

    Thermal rate constants and product branching fractions for electron attachment to CF{sub 3}Br and the CF{sub 3} radical have been measured over the temperature range 300-890 K, the upper limit being restricted by thermal decomposition of CF{sub 3}Br. Both measurements were made in Flowing Afterglow Langmuir Probe apparatuses; the CF{sub 3}Br measurement was made using standard techniques, and the CF{sub 3} measurement using the Variable Electron and Neutral Density Attachment Mass Spectrometry technique. Attachment to CF{sub 3}Br proceeds exclusively by the dissociative channel yielding Br{sup -}, with a rate constant increasing from 1.1 Multiplication-Sign 10{sup -8} cm{sup 3} s{sup -1} at 300 K to 5.3 Multiplication-Sign 10{sup -8} cm{sup 3} s{sup -1} at 890 K, somewhat lower than previous data at temperatures up to 777 K. CF{sub 3} attachment proceeds through competition between associative attachment yielding CF{sub 3}{sup -} and dissociative attachment yielding F{sup -}. Prior data up to 600 K showed the rate constant monotonically increasing, with the partial rate constant of the dissociative channel following Arrhenius behavior; however, extrapolation of the data using a recently proposed kinetic modeling approach predicted the rate constant to turn over at higher temperatures, despite being only {approx}5% of the collision rate. The current data agree well with the previous kinetic modeling extrapolation, providing a demonstration of the predictive capabilities of the approach.

  5. On the relation between the activation energy for electron attachment reactions and the size of their thermal rate coefficients.

    PubMed

    Hotop, H; Ruf, M-W; Kopyra, J; Miller, T M; Fabrikant, I I

    2011-02-14

    Rate coefficients k(T) for dissociative electron attachment (DEA) to molecules in many cases exhibit a more or less strong rise with increasing temperature T (the electron temperature T(e) and the molecular temperature T(G) are assumed to be in thermal equilibrium, i.e., T = T(e) = T(G)). This rise is frequently modeled by the Arrhenius equation k(T) = k(A) exp[-E(a)∕(k(B)T)], and an activation energy E(a) is deduced from fits to the experimental data k(T). This behavior reflects the presence of an energy barrier for the anion on its path to the dissociated products. In a recent paper [J. Kopyra, J. Wnorowska, M. Foryś, and I. Szamrej, Int. J. Mass Spectrom. 268, 60 (2007)] it was suggested that the size of the rate coefficients for DEA reactions at room temperature exhibits an exponential dependence on the activation energy, i.e., k(E(a); T ≈ 300 K) = k(1) exp[-E(a)∕E(0)]. More recent experimental data for molecules with high barriers [T. M. Miller, J. F. Friedman, L. C. Schaffer, and A. A. Viggiano, J. Chem. Phys. 131, 084302 (2009)] are compatible with such a correlation. We investigate the validity and the possible origin of this dependence by analyzing the results of R-matrix calculations for temperature-dependent rate coefficients of exothermic DEA processes with intermediate barrier toward dissociation. These include results for model systems with systematically varied barrier height as well as results of molecule-specific calculations for CH(3)Cl, CH(3)Br, CF(3)Cl, and CH(2)Cl(2) (activation energies above 0.2 eV) involving appropriate molecular parameters. A comparison of the experimental and theoretical results for the considered class of molecules (halogenated alkanes) supports the idea that the exponential dependence of k(T = 300 K) on the activation energy reflects a general phenomenon associated with Franck-Condon factors for getting from the initial neutral vibrational levels to the dissociating final anion state in a direct DEA process

  6. SURFACE FINISHES ON STAINLESS STEEL REDUCE BACTERIAL ATTACHMENT AND EARLY BIOFILM FORMATION: SCANNING ELECTRON AND ATOMIC FORCE MICROSCOPY STUDY

    EPA Science Inventory

    Three common finishing treatments of stainless steel that are used for equipment during poultry processing were tested for resistance to bacterial contamination. Methods were developed to measure attached bacteria and to identify factors that make surface finishes susceptible or ...

  7. Interesting pressure dependence of power factor in BiTeI

    NASA Astrophysics Data System (ADS)

    Guo, San-Dong; Wang, Jian-Li

    2016-06-01

    We investigate pressure dependence of electronic structures and thermoelectric properties in BiTeI by using a modified Becke and Johnson exchange potential. Spin–orbit coupling (SOC) effects are also included due to giant Rashba splitting. Thermoelectric properties are illuminated through solving Boltzmann transport equations within the constant scattering time approximation. The calculated energy band gap of 0.36 eV agrees well with the experimental value of 0.38 eV. As the pressure increases, the energy band gap first decreases, and then increases. The Rashba energy has the opposite trend with the energy band gap. SOC has obvious detrimental influence on the power factor in both n-type and p-type doping. For low doping concentration, the power factor has the same trend with the energy band gap with increasing pressure, but shows a monotonic changing trend in high doping. It is found that the pressure can induce a significantly enhanced power factor in high n-type doping, which can be understood as pressure leading to two-dimensional-like density of states in the conduction bands. These results suggest that BiTeI may be a potential candidate for efficient thermoelectricity in n-type doping by pressure, turning an ordinary insulator into a topological insulator.

  8. Effect of interband interactions on the pressure dependence on transition temperature of MgB2

    NASA Astrophysics Data System (ADS)

    Ogbuu, Okechukwu A.; Abah, Obinna

    2015-12-01

    A two-band BCS model with interactions, both phonon and non-phonon induced interactions, were employed to investigate the pressure dependence on superconducting transition temperature of two-band superconductor. We derived the transition temperature and its pressure dependence within Bogoliubov--Valatin formalism for magnesium diboride superconductor. We examined the influence of interband interactions on transition temperature at varying pressure and analyzed the relevance of this calculation in magnesium diboride, MgB2.

  9. A simple way to model the pressure dependency of rock velocity

    NASA Astrophysics Data System (ADS)

    Han, Tongcheng

    2016-04-01

    Modeling the pressure dependency of rock velocity is important for interpreting and comparing the seismic and earthquake data from different depths. This study develops a multicomponent differential effective medium model for the elastic properties of porous rocks with two types of pores in the grain background without mixing order. The developed model is applied to modeling the pressure dependent elastic velocity of porous rocks by incorporating the variation of stiff and compliant porosity as a function of pressure. The pressure dependent stiff and compliant porosity were inverted from the measured total porosity under pressure using a dual porosity model, and the unknown constant stiff and compliant pore aspect ratios were inverted by best fitting the modeled velocity to the measured data. Application of the approach to a low porosity granite and a medium porosity sandstone sample showed that the pressure dependency of rock velocity can be satisfactorily modeled by the developed model using the pressure dependent stiff and compliant porosity and carefully estimated stiff and compliant pore aspect ratio values.

  10. Attachment Disorganization.

    ERIC Educational Resources Information Center

    Solomon, Judith, Ed.; George, Carol, Ed.

    Disorganized attachment relationships were first formally identified on the basis of the anomalous behavior of some infants during laboratory separations and reunions with the parent. This book presents new research and theory on the topic of attachment disorganization, an area of investigation that is of increasing importance in the study of…

  11. Study of Thermodynamic Properties of Zinc-Blende Semiconductors:. Temperature and Pressure Dependences

    NASA Astrophysics Data System (ADS)

    Hieu, Ho Khac; Hung, Vu Van

    Using the statistical moment method (SMM), the temperature and pressure dependences of thermodynamic quantities of zinc-blende-type semiconductors have been investigated. The analytical expressions of the nearest-neighbor distances, the change of volumes and the mean-square atomic displacements (MSDs) have been derived. Numerical calculations have been performed for a series of zinc-blende-type semiconductors: GaAs, GaP, GaSb, InAs, InP and InSb. The agreement between our calculations and both earlier other theoretical results and experimental data is a support for our new theory in investigating the temperature and pressure dependences of thermodynamic quantities of semiconductors.

  12. Dissociative electron attachment to DNA-diamine thin films: Impact of the DNA close environment on the OH- and O- decay channels

    NASA Astrophysics Data System (ADS)

    Boulanouar, Omar; Fromm, Michel; Mavon, Christophe; Cloutier, Pierre; Sanche, Léon

    2013-08-01

    We measure the desorption of anions stimulated by the impact of 0-20 eV electrons on highly uniform thin films of plasmid DNA-diaminopropane. The results are accurately correlated with film thickness and composition by AFM and XPS measurements, respectively. Resonant structures in the H-, O-, and OH- yield functions are attributed to the decay of transient anions into the dissociative electron attachment (DEA) channel. The diamine induces ammonium-phosphate bridges along the DNA backbone, which suppresses the DEA O- channel and in counter-part increases considerably the desorption of OH-. The close environment of the phosphate groups may therefore play an important role in modulating the rate and type of DNA damages induced by low energy electrons.

  13. Dissociative electron attachment to DNA-diamine thin films: Impact of the DNA close environment on the OH− and O− decay channels

    PubMed Central

    Boulanouar, Omar; Fromm, Michel; Mavon, Christophe; Cloutier, Pierre; Sanche, Léon

    2013-01-01

    We measure the desorption of anions stimulated by the impact of 0–20 eV electrons on highly uniform thin films of plasmid DNA-diaminopropane. The results are accurately correlated with film thickness and composition by AFM and XPS measurements, respectively. Resonant structures in the H−, O−, and OH− yield functions are attributed to the decay of transient anions into the dissociative electron attachment (DEA) channel. The diamine induces ammonium-phosphate bridges along the DNA backbone, which suppresses the DEA O− channel and in counter-part increases considerably the desorption of OH−. The close environment of the phosphate groups may therefore play an important role in modulating the rate and type of DNA damages induced by low energy electrons. PMID:23927286

  14. Dissociative electron attachment to DNA-diamine thin films: Impact of the DNA close environment on the OH{sup −} and O{sup −} decay channels

    SciTech Connect

    Boulanouar, Omar; Fromm, Michel; Mavon, Christophe; Cloutier, Pierre; Sanche, Léon

    2013-08-07

    We measure the desorption of anions stimulated by the impact of 0–20 eV electrons on highly uniform thin films of plasmid DNA-diaminopropane. The results are accurately correlated with film thickness and composition by AFM and XPS measurements, respectively. Resonant structures in the H{sup −}, O{sup −}, and OH{sup −} yield functions are attributed to the decay of transient anions into the dissociative electron attachment (DEA) channel. The diamine induces ammonium-phosphate bridges along the DNA backbone, which suppresses the DEA O{sup −} channel and in counter-part increases considerably the desorption of OH{sup −}. The close environment of the phosphate groups may therefore play an important role in modulating the rate and type of DNA damages induced by low energy electrons.

  15. Demonstration of the branching ratio inversion for the electron attachment to phosphoryl chloride POCl3 in the gas phase between 300 and 200 K

    NASA Astrophysics Data System (ADS)

    Carles, Sophie; Saidani, Ghassen; Le Garrec, Jean-Luc; Guen, Ngary; Mitchell, James B. A.; Viggiano, Albert A.; Shuman, Nicholas S.

    2016-04-01

    Electron attachment to phosphoryl chloride (phosphorus oxychloride) POCl3 has been studied in the gas phase by mass spectrometry at several low temperatures (47.7, 74.5, 169.7 and 199.5 K) with the CRESU method. By measuring over this temperature range and data from [8], we have demonstrated the inversion of the branching ratio between the exothermic non-dissociative exit channel POCl3- and the thermo-neutral dissociative exit channel POCl2- + Cl. A kinetic model in terms of statistical theory is used to fit the experimental data.

  16. First-principles characterisation of the pressure-dependent elastic anisotropy of SnO2 polymorphs

    NASA Astrophysics Data System (ADS)

    Das, Pratik Kumar; Chowdhury, Anjan; Mandal, Nibir; Arya, A.

    2016-06-01

    Using DFT calculations, this study investigates the pressure-dependent variations of elastic anisotropy in the following SnO2 phases: rutile-type (tetragonal; P42/mnm), CaCl2-type (orthorhombic; Pnnm)-, α-PbO2-type (orthorhombic; Pbcn)- and fluorite-type (cubic; Fm-3m). Experimentally, these polymorphs undergo sequential structural transitions from rutile-type → CaCl2-type → α-PbO2-type → fluorite-type with increasing pressure at 11.35, 14.69 and 58.22 GPa, respectively. We estimate the shear anisotropy (A1 and A3) on {1 0 0} and {0 0 1} crystallographic planes of the tetragonal phase and (A1, A2 and A3) on {1 0 0}, {0 1 0} and {0 0 1} crystallographic planes of the orthorhombic phases. The rutile-type phase shows strongest shear anisotropy on the {0 0 1} planes (A2 > 4.8), and the degree of anisotropy increases nonlinearly with pressure. In contrast, the anisotropy is almost absent on the {1 0 0} planes (ie A1 1) irrespective of the pressure. The CaCl2-type phase exhibits similar shear anisotropy behaviour preferentially on {0 0 1} (A3 > 5), while A1 and A2 remain close to 1. The α-PbO2-type phase shows strikingly different elastic anisotropy characterised by a reversal in anisotropy (A3 > 1 to < 1) with increasing pressure at a threshold value of 38 GPa. We provide electronic density of states and atomic configuration to account for this pressure-dependent reversal in shear anisotropy. Our study also analyses the directional Young's moduli for the tetragonal and orthorhombic phases as a function of pressure. Finally, we estimate the band gaps of these four SnO2 phases as a function of pressure which are in agreement with the previous results.

  17. THE INFLUENCE OF PRESSURE-DEPENDENT VISCOSITY ON THE THERMAL EVOLUTION OF SUPER-EARTHS

    SciTech Connect

    Stamenkovic, Vlada; Noack, Lena; Spohn, Tilman; Breuer, Doris E-mail: Lena.Noack@dlr.de E-mail: Tilman.Spohn@dlr.de

    2012-03-20

    We study the thermal evolution of super-Earths with a one-dimensional (1D) parameterized convection model that has been adopted to account for a strong pressure dependence of the viscosity. A comparison with a 2D spherical convection model shows that the derived parameterization satisfactorily represents the main characteristics of the thermal evolution of massive rocky planets. We find that the pressure dependence of the viscosity strongly influences the thermal evolution of super-Earths-resulting in a highly sluggish convection regime in the lower mantles of those planets. Depending on the effective activation volume and for cooler initial conditions, we observe with growing planetary mass even the formation of a conductive lid above the core-mantle boundary (CMB), a so-called CMB-lid. For initially molten planets our results suggest no CMB-lids but instead a hot lower mantle and core as well as sluggish lower mantle convection. This implies that the initial interior temperatures, especially in the lower mantle, become crucial for the thermal evolution-the thermostat effect suggested to regulate the interior temperatures in terrestrial planets does not work for massive planets if the viscosity is strongly pressure dependent. The sluggish convection and the potential formation of the CMB-lid reduce the convective vigor throughout the mantle, thereby affecting convective stresses, lithospheric thicknesses, and heat fluxes. The pressure dependence of the viscosity may therefore also strongly affect the propensity of plate tectonics, volcanic activity, and the generation of a magnetic field of super-Earths.

  18. Pressure dependence of the melting temperature of solids - Rare-gas solids

    NASA Technical Reports Server (NTRS)

    Schlosser, Herbert; Ferrante, John

    1991-01-01

    A method presented by Schlosser et al. (1989) for analyzing the pressure dependence of experimental melting-temperature data is applied to rare-gas solids. The plots of the logarithm of the reduced melting temperature vs that of the reduced pressure are straight lines in the absence of phase transitions. The plots of the reduced melting temperatures for Ar, Kr, and Xe are shown to be approximately straight lines.

  19. Electron attachment line shapes, cross sections, and rate constants at ultralow energies in CF3SO3H, (CF3SO2)2O, and CF3I

    NASA Technical Reports Server (NTRS)

    Alajajian, S. H.; Man, K.-F.; Chutjian, A.

    1991-01-01

    Electron attachment cross sections are reported in the energy range 0-160 meV, and at resolutions of 6.0-6.5 meV (FWHM) for the molecules CF3SO3H (triflic acid), (CF3SO2)2O (triflic anhydride), and CF3I (methyl iodide). Use is made of the Kr photoionization method. Attachment line shapes are deconvoluted from the spectral slit (electron energy) function, and are converted to cross sections by normalization to thermal attachment rate constants at 300 K. Rate constants as a function of mean electron energy are calculated from the cross sections using a Maxwellian electron energy distribution function. Present data are compared with flowing-afterglow, Langmuir-probe results in triflic acid and anhydride, and with high-Rydberg ionization results in CF3I.

  20. Pressure dependence of metal-insulator transition in perovskites RNiO3 ( R=Eu , Y, Lu)

    NASA Astrophysics Data System (ADS)

    Cheng, J.-G.; Zhou, J.-S.; Goodenough, J. B.; Alonso, J. A.; Martinez-Lope, M. J.

    2010-08-01

    High-pressure experiments on the RNiO3 perovskites with smaller rare-earth R3+ ions complete our study of the crossover from itinerant to localized e -electron behavior associated with the low-spin Ni(III):t6e1 ion. By measuring second-sintered samples in a multianvil module, we have observed a clear anomaly of ρ(T) at TIM and obtained the pressure dependence of TIM for the RNiO3 ( R=Eu , Y, Lu) that are different from the published data supporting a charge-ordering model. Instead, they are comparable to that for the orbital-ordering insulator LaMnO3 . Our distinct results show clearly that where the crossover is approached from the localized-electron side by increasing the orbital overlap integral, a cooperative Jahn-Teller distortion prevents charge transfer from molecular e orbitals on strongly bonded NiO6/2 clusters to more weakly bonded Ni(III) centers. However, where the crossover is approached from the itinerant-electron side as in the perovskite CaFeO3 , a disproportionation charge transfer may occur. In a separate experiment in which the powder samples were pressed in a Bridgman anvil device without a pressure medium, we have shown after releasing pressure that the samples were reduced. This irreversible effect should be distinguished from the hydrostatic-pressure effect on the physical properties of the RNiO3 perovskites.

  1. Dissociative electron attachment to methyl chloride: A quasi-diatomic potential curve for the fragmentation of the metastable CH3Cl- anion

    NASA Astrophysics Data System (ADS)

    Mach, P.; Urban, J.; Staemmler, V.

    2009-02-01

    Potential energy curves have been calculated for the dissociation of the neutral CH3Cl molecule and its negative ion into CH3 + Cl and CH3 +Cl- , respectively. The neutral molecule and the anion could be treated by means of standard wave function based quantum chemical ab initio methods for C-Cl distances larger than about 2.4 Å, where CH3Cl- is a stable anion. In the present calculation MP3 and CCSD(T) were employed. At shorter C-Cl distances the CH3Cl- anion is only metastable and cannot be treated by such methods. We have applied a stabilization scheme, first proposed by Nestmann and Peyerimhoff, to stabilize the metastable anion by adding extra positive charges to the molecule. By this trick it was possible to generate the resonance energy Eres and width Γ as functions of the C-Cl distance in the resonance regime between 1.5 and 2.5 Å. The calculated values for the threshold energy Ethresh and the exothermicity ΔE0 of the DEA (dissociative electron attachment) process are in very good agreement with experiment; the vertical attachment energy (VAE) is smaller than its experimental counterpart.

  2. Equation of motion coupled cluster methods for electron attachment and ionization potential in fullerenes C60 and C70.

    PubMed

    Bhaskaran-Nair, Kiran; Kowalski, Karol; Moreno, Juana; Jarrell, Mark; Shelton, William A

    2014-08-21

    In both molecular and periodic solid-state systems there is a need for the accurate determination of the ionization potential and the electron affinity for systems ranging from light harvesting polymers and photocatalytic compounds to semiconductors. The development of a Green's function approach based on the coupled cluster (CC) formalism would be a valuable tool for addressing many properties involving many-body interactions along with their associated correlation functions. As a first step in this direction, we have developed an accurate and parallel efficient approach based on the equation of motion-CC technique. To demonstrate the high degree of accuracy and numerical efficiency of our approach we calculate the ionization potential and electron affinity for C60 and C70. Accurate predictions for these molecules are well beyond traditional molecular scale studies. We compare our results with experiments and both quantum Monte Carlo and GW calculations. PMID:25149783

  3. Effects of temperature and isotopic substitution on electron attachment dynamics of guanine-cytosine base pair: Ring-polymer and classical molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Minoshima, Yusuke; Seki, Yusuke; Takayanagi, Toshiyuki; Shiga, Motoyuki

    2016-06-01

    The dynamical process of electron attachment to a guanine-cytosine pair in the normal (h-GC) and deuterated (d-GC) forms has been studied theoretically by semiclassical ring-polymer molecular dynamics (RPMD) simulations using the empirical valence bond model. The initially formed dipole-bound anion is converted rapidly to the valence-bound anion within about 0.1 ps in both h-GC and d-GC. However, the subsequent proton transfer in h-GC occurs with a rate five times greater than the deuteron transfer in d-GC. The change of rates with isotopic substitution and temperature variation in the RPMD simulations are quantitatively and qualitatively different from those in the classical molecular dynamics (MD) simulations, demonstrating the importance of nuclear quantum effects on the dynamics of this system.

  4. Angular dependence of dissociative electron attachment topolyatomic molecules: application to the 2B1 metastable state of the H2Oand H2S anions

    SciTech Connect

    Haxton, Daniel J.; McCurdy, C. William; Rescigno, Thomas N.

    2006-01-12

    The angular dependence of dissociative electron attachment (DEA) to polyatomic targets is formulated in the local complex potential model, under the assumption that the axial recoil approximation describes the dissociation dynamics. An additional approximation, which is found to be valid in the case of H2O but not in the case of H2S, makes it possible to describe the angular dependence of DEA solely from an analysis of the fixed-nuclei entrance amplitude, without carrying out nuclear dynamics calculations. For H2S, the final-vibrational-state-specific angular dependence of DEA is obtained by incorporating the variation of the angular dependence of the entrance amplitude with nuclear geometry into the nuclear dynamics. Scattering calculations using the complex Kohn method and, for H2S, full quantum calculations of the nuclear dynamics using the Multi-Configuration Time-Dependent Hartree method, are performed.

  5. Electronic grade and flexible semiconductor film employing oriented attachment of colloidal ligand-free PbS and PbSe nanocrystals at room temperature

    NASA Astrophysics Data System (ADS)

    Shanker, G. Shiva; Swarnkar, Abhishek; Chatterjee, Arindom; Chakraborty, S.; Phukan, Manabjyoti; Parveen, Naziya; Biswas, Kanishka; Nag, Angshuman

    2015-05-01

    Electronic grade semiconductor films have been obtained via the sintering of solution processed PbS and PbSe nanocrystals at room temperature. Prior attempts to achieve similar films required the sintering of nanocrystals at higher temperatures (>350 °C), which inhibits the processing of such films on a flexible polymer substrate, and it is also expensive. We reduced the sintering temperature by employing two important strategies: (i) use of ligand-free nanocrystals and (ii) oriented attachment of nanocrystals. Colloidal ligand-free PbS and PbSe nanocrystals were synthesized at 70 °C with high yield (~70%). However, these nanocrystals start to agglomerate with time in formamide, and upon the removal of the solvation energy, nanocrystals undergo oriented attachment, forming larger elongated crystals. PbS and PbSe nanocrystal films made on both glass and flexible substrates at room temperature exhibit Ohmic behavior with optimum DC conductivities of 0.03 S m-1 and 0.08 S m-1, respectively. Mild annealing of the films at 150 °C increases the conductivity values to 1.1 S m-1 and 137 S m-1 for PbS and PbSe nanocrystal films, respectively. AC impedance was measured to distinguish the contributions from grain and grain boundaries to the charge transport mechanism. Charge transport properties remain similar after the repeated bending of the film on a flexible polymer substrate. Reasonably high thermoelectric Seebeck coefficients of 600 μV K-1 and 335 μV K-1 for PbS and PbSe nanocrystal pellets, respectively, were obtained at room temperature.Electronic grade semiconductor films have been obtained via the sintering of solution processed PbS and PbSe nanocrystals at room temperature. Prior attempts to achieve similar films required the sintering of nanocrystals at higher temperatures (>350 °C), which inhibits the processing of such films on a flexible polymer substrate, and it is also expensive. We reduced the sintering temperature by employing two important strategies

  6. Specific anion effects on the pressure dependence of the protein-protein interaction potential.

    PubMed

    Möller, Johannes; Grobelny, Sebastian; Schulze, Julian; Steffen, Andre; Bieder, Steffen; Paulus, Michael; Tolan, Metin; Winter, Roland

    2014-04-28

    We present a study on ion specific effects on the intermolecular interaction potential V(r) of dense protein solutions under high hydrostatic pressure conditions. Small-angle X-ray scattering in combination with a liquid-state theoretical approach was used to determine the effect of structure breaking/making salt anions (Cl(-), SO4(2-), PO4(3-)) on the intermolecular interaction of lysozyme molecules. It was found that besides the Debye-Hückel charge screening effect, reducing the repulsiveness of the interaction potential V(r) at low salt concentrations, a specific ion effect is observed at high salt concentrations for the multivalent kosmotropic anions, which modulates also the pressure dependence of the protein-protein interaction potential. Whereas sulfate and phosphate strongly influence the pressure dependence of V(r), chloride anions do not. The strong structure-making effect of the multivalent anions, dominating for the triply charged PO4(3-), renders the solution structure less bulk-water-like at high salt concentrations, which leads to an altered behavior of the pressure dependence of V(r). Hence, the particular structural properties of the salt solutions are able to influence the spatial organization and the intermolecular interactions of the proteins, in particular upon compression. These results are of interest for exploring the combined effects of ionic strength, temperature and pressure on the phase behavior of protein solutions, but may also be of relevance for understanding pressure effects on the hydration behavior of biological matter under extreme environmental conditions.

  7. Specific anion effects on the pressure dependence of the protein-protein interaction potential.

    PubMed

    Möller, Johannes; Grobelny, Sebastian; Schulze, Julian; Steffen, Andre; Bieder, Steffen; Paulus, Michael; Tolan, Metin; Winter, Roland

    2014-04-28

    We present a study on ion specific effects on the intermolecular interaction potential V(r) of dense protein solutions under high hydrostatic pressure conditions. Small-angle X-ray scattering in combination with a liquid-state theoretical approach was used to determine the effect of structure breaking/making salt anions (Cl(-), SO4(2-), PO4(3-)) on the intermolecular interaction of lysozyme molecules. It was found that besides the Debye-Hückel charge screening effect, reducing the repulsiveness of the interaction potential V(r) at low salt concentrations, a specific ion effect is observed at high salt concentrations for the multivalent kosmotropic anions, which modulates also the pressure dependence of the protein-protein interaction potential. Whereas sulfate and phosphate strongly influence the pressure dependence of V(r), chloride anions do not. The strong structure-making effect of the multivalent anions, dominating for the triply charged PO4(3-), renders the solution structure less bulk-water-like at high salt concentrations, which leads to an altered behavior of the pressure dependence of V(r). Hence, the particular structural properties of the salt solutions are able to influence the spatial organization and the intermolecular interactions of the proteins, in particular upon compression. These results are of interest for exploring the combined effects of ionic strength, temperature and pressure on the phase behavior of protein solutions, but may also be of relevance for understanding pressure effects on the hydration behavior of biological matter under extreme environmental conditions. PMID:24626853

  8. Pressure dependence of structural and dynamical properties in melt sulfur: Evidence for two successive chain breakages

    NASA Astrophysics Data System (ADS)

    Zhao, G.; Mu, H. F.

    2014-11-01

    Using ab initio molecular dynamics simulations, the pressure dependence of structural and dynamical properties in melt sulfur along 1085 K isotherm was studied with pressure range from 4.18 to 15.8 GPa. It was found that the atomic chains in melt sulfur abruptly break twice with increasing pressure. The electric density of state near EF and the diffusion coefficient both show abrupt increase along with these two times of breakages. These changes would strongly influence the physical properties such as conductivity and viscosity. However, the density discontinuity along the isotherm, indication of a first-order phase transition, was not found.

  9. Pressure dependence of wall relaxation in polarized {sup 3}He gaseous cells

    SciTech Connect

    Zheng, W.; Gao, H.; Ye, Q.; Zhang, Y.

    2011-06-15

    We have observed a linear pressure dependence of longitudinal relaxation time T{sub 1} at 4.2 and 295 K in gaseous {sup 3}He cells made of either bare Pyrex glass or Cs- or Rb-coated Pyrex due to paramagnetic sites in the cell wall. The paramagnetic wall relaxation is previously thought to be independent of {sup 3}He pressure. We develop a model to interpret the observed wall relaxation by taking into account the diffusion process, and our model gives a good description of the data.

  10. Pressure dependence of quality factors of graphene nano-mechanical resonators

    NASA Astrophysics Data System (ADS)

    Khaksaran, M. Hadi; Yanik, Cenk; Karakan, M. Cagatay; Ari, Atakan Bekir; Hanay, M. Selim; Kaya, Ismet I.

    In recent few years, low mass density and high stiffness of graphene has drawn attention for developing high frequency mechanical resonators with high quality factor at the same time. As a single-atom thick material, graphene has many desirable properties for high-frequency sensor applications compared to top-down nano-mechanical resonators . In this work we address the energy dissipation in graphene resonators due to viscous damping. We experimentally measure the pressure dependence of the quality factor of a graphene nano-mechanical resonator to understand its interaction with fluids at high frequencies. This work is supprted by TUBITAK under Grant Number 112T990.

  11. Electronic transport in oligo-para-phenylene junctions attached to carbon nanotube electrodes: Transition-voltage spectroscopy and chirality

    SciTech Connect

    Brito Silva, C. A. Jr.; Silva, S. J. S. da; Leal, J. F. P.; Pinheiro, F. A.; Del Nero, J.

    2011-06-15

    We have investigated, by means of a nonequilibrium Green's function method coupled to density functional theory, the electronic transport properties of molecular junctions composed of oligo-para-phenylene (with two, three, four, and five phenyl rings) covalently bridging the gap between metallic carbon nanotubes electrodes. We have found that the current is strongly correlated to a purely geometrical chiral parameter, both on-resonance and off-resonance. The Fowler-Nordheim plot exhibits minima, V{sub min}, that occur whenever the tail of a resonant transmission peak enters in the bias window. This result corroborates the scenario in which the coherent transport model gives the correct interpretation to transition voltage spectroscopy (TVS). We have shown that V{sub min} corresponds to voltages where a negative differential resistance (NDR) occurs. The finding that V{sub min} corresponds to voltages that exhibit NDR, which can be explained only in single-molecule junctions within the coherent transport model, further confirms the applicability of such models to adequately interpret TVS. The fact that the electrodes are organic is at the origin of differences in the behavior of V{sub min} if compared to the case of molecular junctions with nonorganic contacts treated so far.

  12. Kinetics following addition of sulfur fluorides to a weakly ionized plasma from 300 to 500 K: Rate constants and product determinations for ion-ion mutual neutralization and thermal electron attachment to SF5, SF3, and SF2

    NASA Astrophysics Data System (ADS)

    Shuman, Nicholas S.; Miller, Thomas M.; Hazari, Nilay; Luzik, Eddie D.; Viggiano, A. A.

    2010-12-01

    Rate constants for several processes including electron attachment to SF2, SF3, and SF5 and individual product channels of ion-ion mutual neutralization between SF6-, SF5-, and SF4- with Ar+ were determined by variable electron and neutral density attachment mass spectrometry. The experiments were conducted with a series of related neutral precursors (SF6, SF4, SF5Cl, SF5C6H5, and SF3C6F5) over a temperature range of 300-500 K. Mutual neutralization rate constants for SF6-, SF5-, and SF4- with Ar+ are reported with uncertainties of 10-25% and show temperature dependencies in agreement with the theoretical value of T-0.5. Product branching in the mutual neutralizations is temperature independent and dependent on the electron binding energy of the anion. A larger fraction of product neutrals from the SF6- mutual neutralization (0.9 ±0.1) are dissociated than in the SF5- mutual neutralization (0.65 ± 0.2), with the SF4- (0.7 ± 0.3) likely lying in between. Electron attachment to SF5 (k = 2.0 × 10-8 ±21 cm3 s-1 at 300 K) and SF3 (4 ± 3 × 10-9 cm3 s-1 at 300 K) show little temperature dependence. Rate constants of electron attachment to closed-shell SFn species decrease as the complexity of the neutral decreases.

  13. Pressure-dependent OH yields in alkene + HO2 reactions: a theoretical study.

    PubMed

    Zádor, Judit; Klippenstein, Stephen J; Miller, James A

    2011-09-15

    The major bimolecular product of alkyl + O(2) reactions is alkene + hydroperoxyl radical (HO(2)), but in the reverse direction, the reactants are reformed to a very limited extent only. The most important products of the alkene + HO(2) reactions are alkylperoxy radical (ROO(•)), hydroxyl radical (OH) + cyclic ether, and the corresponding hydroperoxyalkyl ((•)QOOH) species. Moreover, abstraction of allylic hydrogens can compete with the addition, further complicating the possible outcome of this reaction type and its effect on low-temperature combustion chemistry. In this paper, six alkene + HO(2) reactions and the reaction between an unsaturated oxygenate and HO(2) are studied based on previously established potential energy surfaces. The studied unsaturated compounds are ethene, propene, 1-butene, trans-2-butene, isobutene, cyclohexene, and vinyl alcohol. Using multiwell master equations, temperature- (300-1200 K) and pressure-dependent rate coefficients and branching fractions are calculated for these reactions. The importance of this reaction type for the combustion of unsaturated compounds is also assessed, and we show that, to get reliable results, it is important to include the pressure-dependence of the rate coefficients in the calculations. PMID:21819062

  14. Brillouin-scattering determination of the acoustic properties and their pressure dependence for three polymeric elastomers.

    PubMed

    Stevens, Lewis L; Orler, E Bruce; Dattelbaum, Dana M; Ahart, Muhtar; Hemley, Russell J

    2007-09-14

    The acoustic properties of three polymer elastomers, a cross-linked poly(dimethylsiloxane) (Sylgard 184), a cross-linked terpolymer poly(ethylene-vinyl acetate-vinyl alcohol), and a segmented thermoplastic poly(ester urethane) copolymer (Estane 5703), have been measured from ambient pressure to approximately 12 GPa by using Brillouin scattering in high-pressure diamond anvil cells. The Brillouin-scattering technique is a powerful tool for aiding in the determination of equations of state for a variety of materials, but to date has not been applied to polymers at pressures exceeding a few kilobars. For the three elastomers, both transverse and longitudinal acoustic modes were observed, though the transverse modes were observed only at elevated pressures (>0.7 GPa) in all cases. From the Brillouin frequency shifts, longitudinal and transverse sound speeds were calculated, as were the C(11) and C(12) elastic constants, bulk, shear, and Young's moduli, and Poisson's ratios, and their respective pressure dependencies. P-V isotherms were then constructed, and fit to several empirical/semiempirical equations of state to extract the isothermal bulk modulus and its pressure derivative for each material. Finally, the lack of shear waves observed for any polymer at ambient pressure, and the pressure dependency of their appearance is discussed with regard to instrumental and material considerations.

  15. Brillouin-scattering determination of the acoustic properties and their pressure dependence for three polymeric elastomers

    NASA Astrophysics Data System (ADS)

    Stevens, Lewis L.; Orler, E. Bruce; Dattelbaum, Dana M.; Ahart, Muhtar; Hemley, Russell J.

    2007-09-01

    The acoustic properties of three polymer elastomers, a cross-linked poly(dimethylsiloxane) (Sylgard® 184), a cross-linked terpolymer poly(ethylene-vinyl acetate-vinyl alcohol), and a segmented thermoplastic poly(ester urethane) copolymer (Estane® 5703), have been measured from ambient pressure to approximately 12GPa by using Brillouin scattering in high-pressure diamond anvil cells. The Brillouin-scattering technique is a powerful tool for aiding in the determination of equations of state for a variety of materials, but to date has not been applied to polymers at pressures exceeding a few kilobars. For the three elastomers, both transverse and longitudinal acoustic modes were observed, though the transverse modes were observed only at elevated pressures (>0.7GPa) in all cases. From the Brillouin frequency shifts, longitudinal and transverse sound speeds were calculated, as were the C11 and C12 elastic constants, bulk, shear, and Young's moduli, and Poisson's ratios, and their respective pressure dependencies. P-V isotherms were then constructed, and fit to several empirical/semiempirical equations of state to extract the isothermal bulk modulus and its pressure derivative for each material. Finally, the lack of shear waves observed for any polymer at ambient pressure, and the pressure dependency of their appearance is discussed with regard to instrumental and material considerations.

  16. Attachment Apparatus

    SciTech Connect

    Morrison, Edward F.

    1998-08-18

    The present invention includes an attachment apparatus comprising a rotation limiting member adapted to be threaded onto a threaded member; and a preload nut adapted to be threaded onto the threaded member. The rotation limiting member comprises a plurality of pins; and the preload nut comprises plurality of slots, preferably wherein the plurality of pins and the plurality of slots are the same in number, which is preferably three. The plurality of pins of the rotation limiting member are filled into a corresponding plurality of slots of the preload nut to form a rotatable unit adapted to be threaded onto the threaded member. In use, the rotatable unit is threaded onto the threaded member. The present invention thus provides a unitized removable device for holes, including holes other than circular in shape, which have an established depth before an end of, or before an enlargement of the hole. The configuration of some exposed part of the device, or the head, is shaped and formed for its intended purpose, such as clamping, anchor points, eye bolts, stud anchor, and the like. The device allows for the installation, preloading and removal of all components of the device, as a unit, without damage to the member for which attachment is required by simple rotations of some exposed part of the device.

  17. Pressure dependence of resistivity and magnetoresistivity in layered manganates (La,Sr){sub 3}Mn{sub 2}O{sub 7}

    SciTech Connect

    Mahesh, R.; Wang, R.; Itoh, M.

    1998-01-01

    Preliminary results on the pressure dependence of resistivity and magnetoresistivity in layered manganates La{sub 2{minus}2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} (x=0.3, 0.4, 0.5) are reported. Layered manganates show remarkable differences in their electron transport behavior under pressure due to the inherent structural as well as electronic and magnetic anisotropy compared to the isotropic perovskite counterparts. The pressure-induced effects and coupled magnetic field and pressure effects bring forth subtle features which enable us to distinguish the nature of electronic transitions in these layered manganates. {copyright} {ital 1998} {ital The American Physical Society}

  18. Mesospheric removal of very long-lived greenhouse gases SF6 and CFC-115 by metal reactions, Lyman-α photolysis, and electron attachment.

    PubMed

    Totterdill, Anna; Kovács, Tamás; Gómez Martín, Juan Carlos; Feng, Wuhu; Plane, John M C

    2015-03-12

    The fluorinated gases SF6 and C2F5Cl (CFC-115) are chemically inert with atmospheric lifetimes of many centuries which, combined with their strong absorption of IR radiation, results in unusually high global warming potentials. Very long lifetimes imply that mesospheric sinks could make important contributions to their atmospheric removal. In order to investigate this, the photolysis cross sections at the prominent solar Lyman-α emission line (121.6 nm), and the reaction kinetics of SF6 and CFC-115 with the neutral meteoric metal atoms Na, K, Mg, and Fe over large temperature ranges, were measured experimentally. The Na and K reactions exhibit significant non-Arrhenius behavior; quantum chemistry calculations of the potential energy surfaces for the SF6 reactions indicate that the Na and K reactions with SF6 are probably activated by vibrational excitation of the F-SF5 (v3) stretching mode. A limited set of kinetic measurements on Na + SF5CF3 are also presented. The atmospheric removal of these long-lived gases by a variety of processes is then evaluated. For SF6, the removal processes in decreasing order of importance are electron attachment, VUV photolysis, and reaction with K, Na, and H. For CFC-115, the removal processes in decreasing order of importance are reaction with O((1)D), VUV photolysis, and reaction with Na, K, and H.

  19. Pressure dependence of the critical temperature of microemulsions near a critical end point

    NASA Astrophysics Data System (ADS)

    Goyette, J.; Bose, T. K.; Thoen, J.; Lalanne, J. R.

    1989-10-01

    Experimental data for the pressure dependence of the critical temperature (dTc/dP) are reported for several microemulsions of n-dodecane, water, n-pentanol, and sodium dodecylsulfate, with critical points along a critical line ending at a critical end point (CEP). Negative dTc/dP values, substantially decreasing near the CEP, are obtained for all the microemulsions investigated. Using two-scale-factor universality and combining dTc/dP with correlation-length critical-amplitude ξ0 values, we also find that a density anomaly is very likely unobservable experimentally. From the negative sign of dTc/dP it can also be concluded that if there is any critical contribution of the density anomaly to the refractive index n, it must be opposite to the anomaly recently reported for n by Rebbouh and Lalanne [J. Chem. Phys. 90, 1175 (1989)].

  20. Temperature and pressure dependence of viscosity of quantum liquid 4He according to significant structure theory

    PubMed Central

    Ryoo, Ryong; John, Mu Shik; Eyring, Henry

    1980-01-01

    Both solid-like and gas-like flow structures are considered in the calculation of viscosity of liquid 4He using the significant structure theory of liquids. The predominance of quantum mechanical zero-point motion over that arising from thermal excitation is taken into account for the solid-like motion of molecules. The viscosity of liquid 4He under its own vapor pressure calculated over its whole temperature range is in reasonably good agreement with experimental data. The pressure dependence of viscosity also was obtained. The calculation does not yield good results at high densities where the free jumping of molecules into the nearest neighboring vacancies through the kinetic zero-point motion is no longer plausible. PMID:16592856

  1. Pressure dependence on the reaction propagation rate of PETN at high pressure

    SciTech Connect

    Foltz, M.F.

    1993-04-01

    The reaction propagation rate (RPR) of the sensitive high explosive pentaerythritol tetranitrate (PETN) was measured in a diamond anvil cell (DAC) over the pressure range of 2--20 GPa. The experimental technique used is the same as that previously reported. The RPR data shows that it burns one to two orders of magnitude faster in the DAC than 1,3,5,-triamino-2,4,6-trinitrobenzene (TATB) and nitromethane (CH{sub 3}NO{sub 2}) respectively. The PETN RPR curve did not show sample pressure-dependent behavior like that of nitromethane, but instead varied abruptly like the RPR curve of TATB. In order to interpret these changes, static-pressure DAC mid-IR FTIR spectra were taken of micro-pellets of PETN embedded in KBr. The relationship between changes in the spectra, the RPR curve, and published single crystal PETN wedge test data are discussed.

  2. Pressure dependence of various phase transitions for the miscible block copolymer blends

    NASA Astrophysics Data System (ADS)

    Ryu, Du Yeol; Lee, Yonghoon; Lee, Hoyeon; Kim, Yeongsik; Yonsei University Team

    2015-03-01

    The phase behaviors of block copolymer (BCP) blends composed of the weakly interacting (with no specific interaction) polystyrene-b-poly(n-butyl methacrylate) (PS-b-PnBMA) and deuterated polystyrene-b-poly-(n-hexyl methacrylate) (dPS-b-PnHMA) were investigated by Small-Angle Neutron Scattering (SANS) and Depolarized Light Scattering (DPLS) measurements. The various composition-dependent phase behaviors were generated due to a miscible phase between the PnBMA and PnHMA blocks in the BCP blends. To elucidate the origin and difference in baroplasticity of weakly interacting BCP blends, the pressure dependence of transition temperatures was evaluated using enthalpic and volumetric changes at phase transitions. We also demonstrate that the entropic compressibility for the miscible BCP blends is a baroplastic indicator, which was characterized by the negative volume change on mixing (Vmix) at transitions.

  3. Comparison of radiative-convective models with constant and pressure-dependent lapse rates

    NASA Technical Reports Server (NTRS)

    Hummel, J. R.; Kuhn, W. R.

    1981-01-01

    One of the most commonly used models for studying climatic processes is the convective adjustment radiation model. In current radiation models, stable temperature profiles are maintained with a convective adjustment in which the temperature lapse rate is set equal to a critical lapse rate whenever the computed lapse rates exceed the critical value. First introduced by Manabe and Strickler (1964), a variety of convective adjustment models are now in use. It is pointed out that on a global scale, moist adiabatic processes, and thus moist adiabatic lapse rates, approximate the atmospheric temperature profile. Comparisons of profiles from a one-dimensional-radiative-convective model have been made using the conventional 6.5 K/km as the critical lapse rate and the pressure-dependent moist adiabatic lapse rates. For a clear sky and a single effective cloud the surface temperatures are 1 to 3 K higher with the constant 6.5 K/km critical lapse rate.

  4. Pressure dependent elastic constants of alpha and gamma cyclotrimethylene trinitramine: A quantum mechanical study

    SciTech Connect

    Taylor, DeCarlos E.

    2014-08-07

    The elastic constants of the α and γ polymorphs of cyclotrimethylene trinitramine (RDX) have been computed using dispersion corrected density functional theory (DFT). The DFT results validate the values obtained in several experiments using ultrasonic and impulsive stimulated thermal scattering techniques and disagree with those obtained using Brillouin scattering which, in general, exceed the other experimental and theoretical results. Compressibility diagrams at zero pressure are presented for the ab, ac, and bc crystallographic planes, and the anisotropic linear compressibility within the ac plane of α-RDX at 0 GPa, observed using ultrasonic and impulsive stimulated thermal scattering measurements, is verified using DFT. The pressure dependence of the elastic constants of α-RDX (0–4 GPa) and γ-RDX (4–8 GPa) is also presented.

  5. Critical Exponents and Pressure Dependence of Tc of La(Ca)MnO3

    NASA Astrophysics Data System (ADS)

    Souza, Jose A.; White, B. D.; Neumeier, J. J.; Yu, Y.-K.; Dos Santos, C. A. M.

    2007-03-01

    Measurements of heat capacity and thermal expansion for La1- xCaxMnO3 with x = 0, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, and 1 are reported. Using a model proposed previously (Souza et al. Phys. Rev. Lett. 94, 207209 (2005)), which utilizes both heat capacity (CP) and thermal expansion coefficient (μ) data, the pressure dependencies of Tc, dTc/dP, are obtained for all samples. dTc/dP decreases as the Ca doping increases. Critical behavior using both CP and μ is evaluated for the samples. The critical exponent α increases from 0.13, for LaMnO3 to 0.97 for x = 0.30. As Ca content is increased further, α drops reaching 0.11, for CaMnO3.

  6. Pressure Dependence of Superconductivity in FeSe studied by DC Magnetic Measurements

    NASA Astrophysics Data System (ADS)

    Miyoshi, Kiyotaka; Mutou, Eriko; Morishita, Koh; Fujiwara, Kenji; Takeuchi, Jun

    2012-12-01

    Pressure dependence of superconductivity in FeSe has been investigated by DC magnetic measurements under high pressure up to 5 GPa using miniature diamond anvil cell combined with commercial SQUID magnetometer. The specimens with nominal composition FeSex (x = 0.80-1.00) were prepared from iron pieces and selenium shot firing at 1075 °C. The specimens containing no impurity phase of hexagonal FeSe were obtained for 0.80<=x<=0.96. For all of the specimens, it has been found that Tc increases in two steps by the application of pressure P, showing a local maximum of Tc~12 K at P~1 GPa, and Tc is nearly pressure independent above ~3 GPa. The maximum value Tcmax above 3 GPa is 15-20 K for 0.80<=x<=0.98 but ~25 K for x>=0.99.

  7. Goddard rattler-jamming mechanism for quantifying pressure dependence of elastic moduli of grain packs

    SciTech Connect

    Pride, Steven R.; Berryman, James G.

    2009-01-05

    An analysis is presented to show how it is possible for unconsolidated granular packings to obey overall non-Hertzian pressure dependence due to the imperfect and random spatial arrangements of the grains in these packs. With imperfect arrangement, some gaps that remain between grains can be closed by strains applied to the grain packing. As these gaps are closed, former rattler grains become jammed and new stress-bearing contacts are created that increase the elastic stiffness of the packing. By allowing for such a mechanism, detailed analytical expressions are obtained for increases in bulk modulus of a random packing of grains with increasing stress and strain. Only isotropic stress and strain are considered in this analysis. The model is shown to give a favorable fit to laboratory data on variations in bulk modulus due to variations in applied pressure for bead packs.

  8. Pressure-dependent kinetics of initial reactions in iso-octane pyrolysis.

    PubMed

    Ning, HongBo; Gong, ChunMing; Li, ZeRong; Li, XiangYuan

    2015-05-01

    This study focuses on the studies of the main pressure-dependent reaction types of iso-octane (iso-C8H18) pyrolysis, including initial C-C bond fission of iso-octane, isomerization, and β-scission reactions of the alkyl radicals produced by the C-C bond fission of iso-octane. For the C-C bond fission of iso-octane, the minimum energy potentials are calculated at the CASPT2(2e,2o)/6-31+G(d,p)//CAS(2e,2o)/6-31+G(d,p) level of theory. For the isomerization and the β-scission reactions of the alkyl radicals, the optimization of the geometries and the vibrational frequencies of the reactants, transition states, and products are performed at the B3LYP/CBSB7 level, and their single point energies are calculated by using the composite CBS-QB3 method. Variable reaction coordinate transition state theory (VRC-TST) is used for the high-pressure limit rate constant calculation and Rice-Ramsperger-Kassel-Marcus/master equation (RRKM/ME) is used to calculate the pressure-dependent rate constants of these channels with pressure varying from 0.01-100 atm. The rate constants obtained in this work are in good agreement with those available from literatures. We have updated the rate constants and thermodynamic parameters for species involved in these reactions into a current chemical kinetic mechanism and also have improved the concentration profiles of main products such as C3H6 and C4H6 in the shock tube pyrolysis of iso-octane. The results of this study provide insight into the pyrolysis of iso-octane and will be helpful in the future development of branched paraffin kinetic mechanisms.

  9. Attachment and proliferation of human oral fibroblasts to titanium surfaces blasted with TiO2 particles. A scanning electron microscopic and histomorphometric analysis.

    PubMed

    Mustafa, K; Silva Lopez, B; Hultenby, K; Wennerberg, A; Arvidson, K

    1998-06-01

    The purpose of this study was to determine the effect of c.p. titanium surfaces blasted with TiO2 particles on the biological responses of human gingival fibroblasts (HGF). Fibroblast morphology and attachment were investigated on turned (control) titanium surfaces and those blasted with 45 microns (standard), 45-63 microns, and 63-90 microns TiO2 particles. The specimens were analyzed using a confocal laser scanner and SEM. The cell profile areas were measured using a semiautomatic interactive image analyser. The figures were expressed as percent of attachment. The turned samples had the smoothest surfaces and the roughest were those blasted with 63-90 microns. All TiO2 blasted specimens had homogeneous surfaces. Cells appeared to flatten, spread and form cellular bridges with the adjacent cells. Fibroblasts on the turned titanium surfaces appeared to follow the direction of the fine irregularities on the surface but tended to spread haphazardly on the blasted surfaces. The attachment assays showed no significant difference in the percentage of fibroblast cell attachment on the standard surfaces compared to the turned surfaces. Both surfaces blasted with 45-63 microns or 63-90 microns had significantly (P < 0.05) lower percentages of cell attachment than the control. The surfaces blasted with 63-90 microns particles had the lowest rate of cell attachment. A significant correlation (P < 0.01) was found between the degree of particle size and attachment of fibroblasts after 1-72 h. It is concluded that surface micro-texture influences the attachment and growth of HGF: surfaces blasted with 45 microns TiO2 do not inhibit fibroblast attachment and smooth or finely grooved surfaces could be conducive to cellular attachment. PMID:10530134

  10. Pressure dependence of optical transitions in In{sub 0.15}Ga{sub 0.85}N/GaN multiple quantum wells

    SciTech Connect

    Shan, W.; Ager, J.W. III, and; Walukiewicz, W.; Haller, E.E. |; McCluskey, M.D.; Johnson, N.M.; Bour, D.P.

    1998-10-01

    The effects of hydrostatic pressure on optical transitions in In{sub 0.15}Ga{sub 0.85}N/GaN multiple quantum wells (MQW{close_quote}s) have been studied. The optical transition associated with confined electron and hole states in the MQW{close_quote}s was found to shift linearly to higher energy with pressure but exhibit a significantly weaker pressure dependence compared to bulklike thick epitaxial-layer samples. Similar pressure coefficients obtained by both photomodulation and photoluminescence measurements rule out the possibility of the transition involving localized states deep in the band gap. We found that the difference in the compressibility of In{sub x}Ga{sub 1{minus}x}N and GaN induces a tensile strain in the compressively strained In{sub x}Ga{sub 1{minus}x}N well layers, partially compensating the externally applied hydrostatic pressure. This mechanical effect is primarily responsible for the smaller pressure dependence of the optical transitions in the In{sub x}Ga{sub 1{minus}x}N/GaN MQW{close_quote}s. In addition, the pressure-dependent measurements allow us to identify a spectral feature observed at an energy below the GaN band gap. We conclude that this feature is due to transitions from ionized Mg acceptor states to the conduction band in the {ital p}-type GaN cladding layer rather than a confined transition in the MQW{close_quote}s. {copyright} {ital 1998} {ital The American Physical Society}

  11. Temperature and pressure dependences of kimberlite melts viscosity (experimental-theoretical study)

    NASA Astrophysics Data System (ADS)

    Persikov, Eduard; Bykhtiyarov, Pavel; Cokol, Alexsander

    2016-04-01

    Experimental data on temperature and pressure dependences of viscosity of model kimberlite melts (silicate 82 + carbonate 18, wt. %, 100NBO/T = 313) have been obtained for the first time at 100 MPa of CO2 pressure and at the lithostatic pressures up to 7.5 GPa in the temperature range 1350 oC - 1950 oC using radiation high gas pressure apparatus and press free split-sphere multi - anvil apparatus (BARS). Experimental data obtained on temperature and pressure dependences of viscosity of model kimberlite melts at moderate and high pressures is compared with predicted data on these dependences of viscosity of basaltic melts (100NBO/T = 58) in the same T, P - range. Dependences of the viscosity of model kimberlite and basaltic melts on temperature are consistent to the exponential Arrenian equation in the T, P - range of experimental study. The correct values of activation energies of viscous flow of kimberlite melts have been obtained for the first time. The activation energies of viscous flow of model kimberlite melts exponentially increase with increasing pressure and are equal: E = 130 ± 1.3 kJ/mole at moderate pressure (P = 100 MPa) and E = 160 ± 1.6 kJ/mole at high pressure (P = 5.5 GPa). It has been established too that the viscosity of model kimberlite melts exponentially increases on about half order of magnitude with increasing pressures from 100 MPa to 7.5 GPa at the isothermal condition (1800 oC). It has been established that viscosity of model kimberlite melts at the moderate pressure (100 MPa) is lover on about one order of magnitude to compare with the viscosity of basaltic melts, but at high pressure range (5.5 - 7.5 GPa), on the contrary, is higher on about half order of magnitude at the same values of the temperatures. Here we use both a new experimental data on viscosity of kimberlite melts and our structural chemical model for calculation and prediction the viscosity of magmatic melts [1] to determine the fundamental features of viscosity of

  12. Lower mantle dynamics and the role of pressure-dependent thermodynamic and transport properties

    NASA Astrophysics Data System (ADS)

    Tosi, N.; Yuen, D. A.; Cadek, O.

    2010-12-01

    We have carried out numerical simulations of large aspect-ratio 2-D mantle convection that feature pressure-dependent thermal expansivity and conductivity along with the major mantle phase transitions, including the deep phase change from perovskite (pv) to post-perovskite (ppv). The rheological law is Newtonian and has both temperature- and pressure-dependences, while the extended Boussinesq approximation is assumed for the energetics. We have analyzed the combined effects of a strongly decreasing thermal expansivity, according to the diffraction experiments on pv by Katsura et al. (2009), and steeply increasing lattice thermal conductivity based on different models obtained from experiments (Ohta, 2010) and first principles (de Koker, 2010; Tang and Dong, 2010). Since ppv is expected to have a relatively weak rheology with respect to pv (Hunt et al., 2009; Ammann et al., 2010) and a large thermal conductivity (Ohta, 2010), we have also assumed that the transition from pv to ppv is accompanied by both a reduction in viscosity by 1 order of magnitude and by a 50% increase in conductivity. As long as the thermal expansivity and conductivity are constant, ppv exerts small but noticeable effects: it destabilizes the D" layer, causes focusing of the heat flux peaks and a slight increase of the average mantle temperature and of the temporal and spatial frequency of upwellings. The destabilizing character of ppv is strong enough to affect the stability of mantle plumes even in the presence of a large decrease of the thermal expansivity which otherwise, without ppv, delivers remarkably stable large upwellings. However we have found that if a sufficiently large thermal conductivity near the core-mantle is also accounted for, lower mantle plumes are stabilized for a geologically long time-span in excess of billion of years, even in the presence of the disturbances induced by the pv-ppv transition. Preliminary results confirm the validity of these findings even for thermo

  13. Platform to investigate aqueous outflow system structure and pressure-dependent motion using high-resolution spectral domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Hariri, Sepideh; Johnstone, Murray; Jiang, Yi; Padilla, Steven; Zhou, Zhehai; Reif, Roberto; Wang, Ruikang K.

    2014-10-01

    The aqueous outflow system (AOS) is responsible for maintaining normal intraocular pressure (IOP) in the eye. Structures of the AOS have an active role in regulating IOP in healthy eyes and these structures become abnormal in the eyes with glaucoma. We describe a newly developed system platform to obtain high-resolution images of the AOS structures. By incorporating spectral domain optical coherence tomography (SD-OCT), the platform allows us to systematically control, image, and quantitate the responses of AOS tissue to pressure with a millisecond resolution of pulsed flow. We use SD-OCT to image radial limbal segments from the surface of the trabecular meshwork (TM) with a spatial resolution of ˜5 μm in ex vivo nonhuman primate eyes. We carefully insert a cannula into Schlemm's canal (SC) to control both pressures and flow rates. The experimental results demonstrate the capability of the platform to visualize the unprecedented details of AOS tissue components comparable to that delivered by scanning electron microscopy, as well as to delineate the complex pressure-dependent relationships among the TM, structures within the SC, and collector channel ostia. The described technique provides a new means to characterize the anatomic and pressure-dependent relationships of SC structures, particularly the active motion of collagenous elements at collector channel ostia; such relationships have not previously been amenable to study. Experimental findings suggest that continuing improvements in the OCT imaging of the AOS may provide both insights into the glaucoma enigma and improvements in its management.

  14. A model describing the pressure dependence of the band gap energy for the group III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Zhao, Chuan-Zhen; Wei, Tong; Sun, Xiao-Dong; Wang, Sha-Sha; Lu, Ke-Qing

    2016-08-01

    A model describing the pressure dependence of the band gap energy for the group III-V semiconductors has been developed. It is found that the model describes the pressure dependence of the band gap energy very well. It is also found that, although the pressure dependence of the band gap energy for both the conventional III-V semiconductors and the dilute nitride alloys can be described well by the model in this work, the physical mechanisms for them are different. In addition, the influence of the nonlinear compression of the lattice on the band gap energy is smaller than that of the coupling interaction between the N level and the conduction band minimum of the host material.

  15. Focal cartilage defect compromises fluid-pressure dependent load support in the knee joint.

    PubMed

    Dabiri, Yaghoub; Li, LePing

    2015-06-01

    A focal cartilage defect involves tissue loss or rupture. Altered mechanics in the affected joint may play an essential role in the onset and progression of osteoarthritis. The objective of the present study was to determine the compromised load support in the human knee joint during defect progression from the cartilage surface to the cartilage-bone interface. Ten normal and defect cases were simulated with a previously tested 3D finite element model of the knee. The focal defects were considered in both condyles within high load-bearing regions. Fluid pressurization, anisotropic fibril-reinforcement, and depth-dependent mechanical properties were considered for the articular cartilages and menisci. The results showed that a small cartilage defect could cause 25% reduction in the load support of the knee joint due to a reduced capacity of fluid pressurization in the defect cartilage. A partial-thickness defect could cause a fluid pressure decrease or increase in the remaining underlying cartilage depending on the defect depth. A cartilage defect also increased the shear strain at the cartilage-bone interface, which was more significant with a full-thickness defect. The effect of cartilage defect on the fluid pressurization also depended on the defect sites and contact conditions. In conclusion, a focal cartilage defect causes a fluid-pressure dependent load reallocation and a compromised load support in the joint, which depend on the defect depth, site, and contact condition.

  16. Pressure dependent tailored attributes of silicon nanoneedles grown by VHF plasma technique

    NASA Astrophysics Data System (ADS)

    Mohammed, Yasir Hussein; Sakrani, Samsudi Bin; Rohani, Md Supar

    2016-06-01

    Gold (Au) catalysts assisted well-aligned silicon nanoneedles (SiNNs) are synthesized using very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) method. The tailored morphology and the optical reflectance of such NNs are inspected as a function of varying reactor pressure (200-800 mTorr). FESEM images revealed the growth of high density SiNNs with diameter ranging from 45 to 600 nm and length as much as 5.66 ± 0.2 μm. Overall morphology of these NNs are found to be highly sensitive to the pressure variation, where appreciably aligned thinner NNs are achieved at 600 mTorr pressure. The presence of globule at the NNs tip authenticated their VLS mechanism mediated growth. The reactor pressure sensitivity of the aspect ratio, lattice parameters, Raman modes, and reflectance are demonstrated. XRD patterns manifested SiNNs cubic crystalline phase with preferred orientation along <111> direction. The occurrence of NNs high crystallinity is further supported by the Raman and HRTEM data. The reflectance of SiNNs grown at 600 mTorr exhibited remarkable reduction (˜6.3%) than those obtained at other pressures. This reactor pressure dependent significant modification in the physical properties of synthesized SiNNs may be prospective for the development of optoelectronics.

  17. Pressure Dependence of Anharmonic Effective Pair Potentials in Rock Salt Type AgI

    SciTech Connect

    Yoshiasa, Akira; Sugahara, Masahiko; Fukui, Hiroshi; Arima, Hiroshi; Ohtaka, Osamu; Okube, Maki; Katayama, Yoshinori; Murai, Kei-ichiro

    2007-02-02

    Pressure dependence of anharmonic effective pair potentials V(u)=au2/2+bu3/3{exclamation_point} for the I-Ag bond in rock salt type AgI has been investigated by EXAFS Debye-Waller factors. EXAFS measurements near the I K-edge were performed under pressure up to 6.0 GPa using a multi-anvil high-pressure device and synchrotron radiation from SPring-8, Hyogo. The potential parameter a for rock-salt type is 1.66(5) eV/A2 at 1.0 GPa and increases to 1.88(6) eV/A2 at 6.0 GPa. The phonon energies in rock salt type AgI under pressure have been estimated using the potential parameter a by calculating the dynamical matrix. The anharmonic effective pair potential for each phase is influenced by pressure and becomes steeper with increasing pressure while the extent of anharmonicity decreases with pressure.

  18. Fluidic origami with embedded pressure dependent multi-stability: a plant inspired innovation.

    PubMed

    Li, Suyi; Wang, K W

    2015-10-01

    Inspired by the impulsive movements in plants, this research investigates the physics of a novel fluidic origami concept for its pressure-dependent multi-stability. In this innovation, fluid-filled tubular cells are synthesized by integrating different Miura-Ori sheets into a three-dimensional topological system, where the internal pressures are strategically controlled similar to the motor cells in plants. Fluidic origami incorporates two crucial physiological features observed in nature: one is distributed, pressurized cellular organization, and the other is embedded multi-stability. For a single fluidic origami cell, two stable folding configurations can coexist due to the nonlinear relationships among folding, crease material deformation and internal volume change. When multiple origami cells are integrated, additional multi-stability characteristics could occur via the interactions between pressurized cells. Changes in the fluid pressure can tailor the existence and shapes of these stable folding configurations. As a result, fluidic origami can switch between being mono-stable, bistable and multi-stable with pressure control, and provide a rapid 'snap-through' type of shape change based on the similar principles as in plants. The outcomes of this research could lead to the development of new adaptive materials or structures, and provide insights for future plant physiology studies at the cellular level. PMID:26400197

  19. Pressure-dependent upper critical field of FeSe superconductor

    NASA Astrophysics Data System (ADS)

    Kaluarachchi, Udhara; Taufour, Valentin; Böhmer, Anna; Tanatar, Makariy; Bud'Ko, Sergey; Kogan, Vladimir; Prozorov, Ruslan; Canfield, Paul

    In FeSe, the superconducting transition temperature Tc (~ 9 K at ambient pressure) has a complicated pressure dependence with a local maximum near p1 ~ 0.8 GPa and a local minimum at p2 ~ 1.2GPa. In this work, we study the upper critical field, Hc 2 , c (T) , of FeSe using c-axis resistivity measurements under hydrostatic pressure up to 1.56 GPa with the magnetic field H ∥c. Application of both current and magnetic field along the same axis reduces the flux flow motion and give sharper transition in applied fields. We observe a non-monotonic evolution of the slope of Hc 2 , c (T) |Tc with pressure, with changes around p1 and p2. We employ two-band orbital Hc 2 , c calculation to show that the data can be explained using the Fermi velocities extracted from the recent quantum oscillations study [ 1 ] over the whole pressure range. [ 1 ] Terashima et al. arXiv:1510.01840v1 [cond-mat.supr-con] (2015) This work is supported by the US DOE, Basic Energy Sciences under Contract No. DE-AC02-07CH11358.

  20. Fluidic origami with embedded pressure dependent multi-stability: a plant inspired innovation

    PubMed Central

    Li, Suyi; Wang, K. W.

    2015-01-01

    Inspired by the impulsive movements in plants, this research investigates the physics of a novel fluidic origami concept for its pressure-dependent multi-stability. In this innovation, fluid-filled tubular cells are synthesized by integrating different Miura-Ori sheets into a three-dimensional topological system, where the internal pressures are strategically controlled similar to the motor cells in plants. Fluidic origami incorporates two crucial physiological features observed in nature: one is distributed, pressurized cellular organization, and the other is embedded multi-stability. For a single fluidic origami cell, two stable folding configurations can coexist due to the nonlinear relationships among folding, crease material deformation and internal volume change. When multiple origami cells are integrated, additional multi-stability characteristics could occur via the interactions between pressurized cells. Changes in the fluid pressure can tailor the existence and shapes of these stable folding configurations. As a result, fluidic origami can switch between being mono-stable, bistable and multi-stable with pressure control, and provide a rapid ‘snap-through’ type of shape change based on the similar principles as in plants. The outcomes of this research could lead to the development of new adaptive materials or structures, and provide insights for future plant physiology studies at the cellular level. PMID:26400197

  1. A 3-D constitutive model for pressure-dependent phase transformation of porous shape memory alloys.

    PubMed

    Ashrafi, M J; Arghavani, J; Naghdabadi, R; Sohrabpour, S

    2015-02-01

    Porous shape memory alloys (SMAs) exhibit the interesting characteristics of porous metals together with shape memory effect and pseudo-elasticity of SMAs that make them appropriate for biomedical applications. In this paper, a 3-D phenomenological constitutive model for the pseudo-elastic behavior and shape memory effect of porous SMAs is developed within the framework of irreversible thermodynamics. Comparing to micromechanical and computational models, the proposed model is computationally cost effective and predicts the behavior of porous SMAs under proportional and non-proportional multiaxial loadings. Considering the pressure dependency of phase transformation in porous SMAs, proper internal variables, free energy and limit functions are introduced. With the aim of numerical implementation, time discretization and solution algorithm for the proposed model are also presented. Due to lack of enough experimental data on multiaxial loadings of porous SMAs, we employ a computational simulation method (CSM) together with available experimental data to validate the proposed constitutive model. The method is based on a 3-D finite element model of a representative volume element (RVE) with random pores pattern. Good agreement between the numerical predictions of the model and CSM results is observed for elastic and phase transformation behaviors in various thermomechanical loadings.

  2. Pressure dependent tailored attributes of silicon nanoneedles grown by VHF plasma technique

    NASA Astrophysics Data System (ADS)

    Mohammed, Yasir Hussein; Sakrani, Samsudi Bin; Rohani, Md Supar

    2016-06-01

    Gold (Au) catalysts assisted well-aligned silicon nanoneedles (SiNNs) are synthesized using very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) method. The tailored morphology and the optical reflectance of such NNs are inspected as a function of varying reactor pressure (200-800 mTorr). FESEM images revealed the growth of high density SiNNs with diameter ranging from 45 to 600 nm and length as much as 5.66 ± 0.2 μm. Overall morphology of these NNs are found to be highly sensitive to the pressure variation, where appreciably aligned thinner NNs are achieved at 600 mTorr pressure. The presence of globule at the NNs tip authenticated their VLS mechanism mediated growth. The reactor pressure sensitivity of the aspect ratio, lattice parameters, Raman modes, and reflectance are demonstrated. XRD patterns manifested SiNNs cubic crystalline phase with preferred orientation along <111> direction. The occurrence of NNs high crystallinity is further supported by the Raman and HRTEM data. The reflectance of SiNNs grown at 600 mTorr exhibited remarkable reduction (∼6.3%) than those obtained at other pressures. This reactor pressure dependent significant modification in the physical properties of synthesized SiNNs may be prospective for the development of optoelectronics.

  3. Focal cartilage defect compromises fluid-pressure dependent load support in the knee joint.

    PubMed

    Dabiri, Yaghoub; Li, LePing

    2015-06-01

    A focal cartilage defect involves tissue loss or rupture. Altered mechanics in the affected joint may play an essential role in the onset and progression of osteoarthritis. The objective of the present study was to determine the compromised load support in the human knee joint during defect progression from the cartilage surface to the cartilage-bone interface. Ten normal and defect cases were simulated with a previously tested 3D finite element model of the knee. The focal defects were considered in both condyles within high load-bearing regions. Fluid pressurization, anisotropic fibril-reinforcement, and depth-dependent mechanical properties were considered for the articular cartilages and menisci. The results showed that a small cartilage defect could cause 25% reduction in the load support of the knee joint due to a reduced capacity of fluid pressurization in the defect cartilage. A partial-thickness defect could cause a fluid pressure decrease or increase in the remaining underlying cartilage depending on the defect depth. A cartilage defect also increased the shear strain at the cartilage-bone interface, which was more significant with a full-thickness defect. The effect of cartilage defect on the fluid pressurization also depended on the defect sites and contact conditions. In conclusion, a focal cartilage defect causes a fluid-pressure dependent load reallocation and a compromised load support in the joint, which depend on the defect depth, site, and contact condition. PMID:25727068

  4. An experimental study on the pressure dependence of viscosity in silicate melts

    NASA Astrophysics Data System (ADS)

    Del Gaudio, Piero; Behrens, Harald

    2009-07-01

    The effect of pressure on melt viscosity was investigated for five compositions along the join An(CaAl2Si2O8)-Di(CaMgSi2O6) and four alkali silicates containing lithium, sodium, and potassium in constant ratio of ˜1:1:1, but alkali-silica ratios are varying. The experiments were performed in an internally heated gas pressure vessel at pressures from 50 to 400 MPa in the viscosity range from 108 to 1011.5 Paṡs using parallel plate viscometry. The polymerized An composition shows a negative pressure dependence of viscosity while the other, more depolymerized compositions of the join An-Di have neutral to positive pressure coefficients. The alkali silicates display neutral to slightly positive pressure coefficients for melt viscosity. These findings in the high viscosity range of 108-1011 Paṡs, where pressure appears to be more efficient than in low viscous melts at high temperature, are consistent with previous results on the viscosity of polymerized to depolymerized melts in the system NaAlSi3O8-CaMgSi2O6 by Behrens and Schulze [H. Behrens and F. Schulze, Am. Mineral. 88, 1351 (2003)]. Thus we confirm that the sign of the pressure coefficient for viscosity is mainly related to the degree of melt polymerization in silicate and aluminosilicate melts.

  5. Fluidic origami with embedded pressure dependent multi-stability: a plant inspired innovation.

    PubMed

    Li, Suyi; Wang, K W

    2015-10-01

    Inspired by the impulsive movements in plants, this research investigates the physics of a novel fluidic origami concept for its pressure-dependent multi-stability. In this innovation, fluid-filled tubular cells are synthesized by integrating different Miura-Ori sheets into a three-dimensional topological system, where the internal pressures are strategically controlled similar to the motor cells in plants. Fluidic origami incorporates two crucial physiological features observed in nature: one is distributed, pressurized cellular organization, and the other is embedded multi-stability. For a single fluidic origami cell, two stable folding configurations can coexist due to the nonlinear relationships among folding, crease material deformation and internal volume change. When multiple origami cells are integrated, additional multi-stability characteristics could occur via the interactions between pressurized cells. Changes in the fluid pressure can tailor the existence and shapes of these stable folding configurations. As a result, fluidic origami can switch between being mono-stable, bistable and multi-stable with pressure control, and provide a rapid 'snap-through' type of shape change based on the similar principles as in plants. The outcomes of this research could lead to the development of new adaptive materials or structures, and provide insights for future plant physiology studies at the cellular level.

  6. An experimental study on the pressure dependence of viscosity in silicate melts.

    PubMed

    Del Gaudio, Piero; Behrens, Harald

    2009-07-28

    The effect of pressure on melt viscosity was investigated for five compositions along the join An(CaAl(2)Si(2)O(8))-Di(CaMgSi(2)O(6)) and four alkali silicates containing lithium, sodium, and potassium in constant ratio of approximately 1:1:1, but alkali-silica ratios are varying. The experiments were performed in an internally heated gas pressure vessel at pressures from 50 to 400 MPa in the viscosity range from 10(8) to 10(11.5) Pas using parallel plate viscometry. The polymerized An composition shows a negative pressure dependence of viscosity while the other, more depolymerized compositions of the join An-Di have neutral to positive pressure coefficients. The alkali silicates display neutral to slightly positive pressure coefficients for melt viscosity. These findings in the high viscosity range of 10(8)-10(11) Pas, where pressure appears to be more efficient than in low viscous melts at high temperature, are consistent with previous results on the viscosity of polymerized to depolymerized melts in the system NaAlSi(3)O(8)-CaMgSi(2)O(6) by Behrens and Schulze [H. Behrens and F. Schulze, Am. Mineral. 88, 1351 (2003)]. Thus we confirm that the sign of the pressure coefficient for viscosity is mainly related to the degree of melt polymerization in silicate and aluminosilicate melts.

  7. Paternal Attachment, Parenting Beliefs and Children's Attachment

    ERIC Educational Resources Information Center

    Howard, Kimberly S.

    2010-01-01

    Relationships between fathers' romantic attachment style, parenting beliefs and father-child attachment security and dependence were examined in a diverse sample of 72 fathers of young children. Paternal romantic attachment style was coded based on fathers' endorsement of a particular style represented in the Hazan and Shaver Three-Category…

  8. Attachment: Implications for Counselors.

    ERIC Educational Resources Information Center

    Pistole, M. Carole

    1989-01-01

    Discusses how attachment theory can be useful strategy for producing therapeutic change and more productive client functioning. Addresses basic attachment theory concepts and parallels between counseling and attachment. Provides case example to focus, integrate, and elaborate elements presented. (Author)

  9. SPH calculations of asteroid disruptions: The role of pressure dependent failure models

    NASA Astrophysics Data System (ADS)

    Jutzi, Martin

    2015-03-01

    We present recent improvements of the modeling of the disruption of strength dominated bodies using the Smooth Particle Hydrodynamics (SPH) technique. The improvements include an updated strength model and a friction model, which are successfully tested by a comparison with laboratory experiments. In the modeling of catastrophic disruptions of asteroids, a comparison between old and new strength models shows no significant deviation in the case of targets which are initially non-porous, fully intact and have a homogeneous structure (such as the targets used in the study by Benz and Asphaug, 1999). However, for many cases (e.g. initially partly or fully damaged targets and rubble-pile structures) we find that it is crucial that friction is taken into account and the material has a pressure dependent shear strength. Our investigations of the catastrophic disruption threshold Q D * as a function of target properties and target sizes up to a few 100 km show that a fully damaged target modeled without friction has a Q D * which is significantly (5-10 times) smaller than in the case where friction is included. When the effect of the energy dissipation due to compaction (pore crushing) is taken into account as well, the targets become even stronger ( Q D * is increased by a factor of 2-3). On the other hand, cohesion is found to have an negligible effect at large scales and is only important at scales ≲ 1 km. Our results show the relative effects of strength, friction and porosity on the outcome of collisions among small (≲ 1000 km) bodies. These results will be used in a future study to improve existing scaling laws for the outcome of collisions (e.g. Leinhardt and Stewart, 2012).

  10. Pressure dependence of Kapitza resistance at gold/water and silicon/water interfaces

    SciTech Connect

    Pham, An; Kim, BoHung; Barisik, Murat

    2013-12-28

    We conducted non-equilibrium molecular dynamics simulations to investigate Kapitza length at solid/liquid interfaces under the effects of bulk liquid pressures. Gold and silicon were utilized as hydrophilic and hydrophobic solid walls with different wetting surface behaviors, while the number of confined liquid water molecules was adjusted to obtain different pressures inside the channels. The interactions of solid/liquid couples were reparameterized accurately by measuring the water contact angle of solid substrates. In this paper, we present a thorough analysis of the structure, normal stress, and temperature distribution of liquid water to elucidate thermal energy transport across interfaces. Our results demonstrate excellent agreement between the pressures of liquid water in nano-channels and published thermodynamics data. The pressures measured as normal stress components were characterized using a long cut-off distance reinforced by a long-range van der Waals tail correction term. To clarify the effects of bulk liquid pressures on water structure at hydrophilic and hydrophobic solid surfaces, we defined solid/liquid interface spacing as the distance between the surface and the peak value of the first water density layer. Near the gold surface, we found that interface spacing and peak value of first water density layer were constant and did not depend on bulk liquid pressure; near the silicon surface, those values depended directly upon bulk liquid. Our results reveal that the pressure dependence of Kapitza length strongly depends on the wettability of the solid surface. In the case of the hydrophilic gold surface, Kapitza length was stable despite increasing bulk liquid pressure, while it varied significantly at the hydrophobic silicon surface.

  11. Temperature- and pressure-dependent phase behavior of monoacylglycerides monoolein and monoelaidin.

    PubMed Central

    Czeslik, C; Winter, R; Rapp, G; Bartels, K

    1995-01-01

    We used x-ray and neutron diffraction to study the temperature- and pressure-dependent structure and phase behavior of the monoacylglycerides 1-monoelaidin (ME) and 1-monoolein (MO) in excess water. The monoacylglycerides were chosen for investigation of their phase behavior because they exhibit mesomorphic phases with one-, two-, and three-dimensional periodicity, such as lamellar, an inverted hexagonal and bicontinuous cubic phases, in a rather easily accessible temperature and pressure range. We studied the structure, stability, and transformations of the different phases over a wide temperature and pressure range, explored the epitaxial relations that exist between different phases, and established a relationship between the chemical structure of the lipid molecules and their phase behavior. For both systems, a temperature-pressure phase diagram has been determined in the temperature range from 0 to 100 degrees C at pressures from ambient up to 1400 bar, and drastic differences in phase behavior are found for the two systems. In MO-water dispersions, the cubic phase Pn3m extends over a large phase field in the T,p-plane. At temperatures above 95 degrees C, the inverted hexagonal phase is found. In the lower temperature region, a crystalline lamellar phase is induced at higher pressures. The phases found in ME-water include the lamellar crystalline Lc phase, the L beta gel phase, the L alpha liquid-crystalline phase, and two cubic phases belonging to the crystallographic space groups Im3m and Pn3m. In addition, the existence of metastable phases has been exploited. Between coexisting metastable cubic structures, a metric relationship has been found that is predicted theoretically on the basis of the curvature elastic energy approximation only. Images FIGURE 1 PMID:7787028

  12. Pressure dependence of the emission in CaF2 : Yb2+

    NASA Astrophysics Data System (ADS)

    Mahlik, S.; Lazarowska, A.; Grinberg, M.; Wells, J.-P. R.; Reid, M. F.

    2015-08-01

    We present a detailed spectroscopic investigation of CaF2 doped with Yb2+ performed at high hydrostatic pressure which is applied in a diamond anvil cell. At ambient pressure and at temperatures lower than 175 K, the luminescence consists of a single broad band peaked at 18 500 cm-1, attributed to the recombination of impurity-trapped excitons. Increasing pressure causes the luminescence to be observable at higher temperature. At a pressure of 72 kbar luminescence can be observed up to 275 K. The emission lineshape does not strongly depend on pressure below 85 kbar. However, at 85 kbar it is blue shifted to 21 630 cm-1. This is attributed to the known phase transition of the CaF2 crystal from cubic to the orthorhombic phase. The absolute energy of the ground and 4f135d states of Yb2+ as well as the energy of the impurity-trapped exciton with respect to valence and conduction bands have been estimated. The results, are discussed in comparison with the pressure dependences observed for the luminescence of BaF2 : Eu2+ and CaF2 : Eu2+. The difference between the spectral properties of Eu2+ and Yb2+ is attributable to the fact that the ground and 4f65d states of Eu2+ are placed deeper in the CaF2 bandgap than the ground and excited 4f135d states of Yb2+, whereas the energies of the impurity-trapped exciton states for Yb2+ and Eu2+ with respect to the conduction band are approximately the same.

  13. Pressure-Dependent Yields and Product Branching Ratios in the Broadband Photolysis of Chlorine Nitrate

    NASA Technical Reports Server (NTRS)

    Nickolaisen, Scott L.; Sander, Stanley P.; Friedl, Randall R.

    1996-01-01

    The photolysis of chlorine nitrate was studied using broadband flash photolysis coupled with long-path ultraviolet-visible absorption spectroscopy. Branching ratios for the Cl + NO3 and ClO + NO2 product channels were determined from time-dependent measurements of ClO and NO3 concentrations. Yields of the ClO and NO3 products displayed a dependence on the bath gas density and the spectral distribution of the photolysis pulse. Product yields decreased with increasing bath gas density regardless of the spectral distribution of the photolysis pulse; however, the decrease in product yield was much more pronounced when photolysis was limited to longer wavelengths. For photolysis in a quartz cell (lambda > 200 nm) the yield decreased by a factor of 2 over the pressure 10-100 Torr. In a Pyrex cell (lambda > 300 nm), the yield decreased by a factor of 50 over the same pressure range. When photolysis was limited to lambda > 350 nm, the yield decreased by a factor of 250. Branching ratios for the photolysis channels [ClONO2 + h.nu yields ClO + NO2 (1a) and ClONO2 + h.nu yields Cl + NO3 (lb)] were determined from the relative ClO and NO3 product yields at various pressures. Although the absolute product yield displayed a pressure dependence, the branching between the two channels was independent of pressure. The relative branching ratios (assuming negligible contributions from other channels) are 0.61 +/- 0.20 for channel 1a and 0.39 +/- 0.20 for channel lb for photolysis with lambda > 200 nm and 0.44 +/- 0.08 for channel 1a and 0.56 +/- 0.08 for channel 1b for photolysis with lambda > 300 nm. The implications of these results for the chemistry of the lower stratosphere are discussed.

  14. Modelling the role of electron attachment rates on column density ratios for C n H‑/C n H (n=4,6,8) in dense molecular clouds

    NASA Astrophysics Data System (ADS)

    Gianturco, F. A.; Grassi, T.; Wester, R.

    2016-10-01

    The fairly recent detection of a variety of anions in the interstellar molecular clouds have underlined the importance of realistically modelling the processes governing their abundance. To pursue this task, our earlier calculations for the radiative electron attachment (REA) rates for C4H‑, C6H‑, and C8H‑ are employed in the present work, within a broad network of other concurrent reactions, to generate the corresponding column density ratios of anion/neutral (A/N) relative abundances. The latter are then compared with those obtained in recent years from observational measurements. The calculations involved the time-dependent solutions of a large network of chemical processes over an extended time interval and included a series of runs in which the values of REA rates were repeatedly scaled over several orders of magnitude. Macroscopic parameters for the Clouds’ modelling were also varied to cover a broad range of physical environments. It was found that, within the range and quality of the processes included in the present network,and selected from state-of-the-art astrophysical databases, the REA values required to match the observed A/N ratios needed to be reduced by orders of magnitude for C4H‑ case, while the same rates for C6H‑ and C8H‑ only needed to be scaled by much smaller factors. The results suggest that the generally proposed formation of interstellar anions by REA mechanism is overestimated by current models for the C4H‑ case, for which is likely to be an inefficient path to formation. This path is thus providing a rather marginal contribution to the observed abundances of C4H‑, the latter being more likely to originate from other chemical processes in the network, as we discuss in some detail in the present work. Possible physical reasons for the much smaller differences against observations found instead for the values of the (A/N) ratios in two other, longer members of the series are put forward and analysed within the

  15. A Pressure-dependent Model for the Regulation of Lipoprotein Lipase by Apolipoprotein C-II*

    PubMed Central

    Meyers, Nathan L.; Larsson, Mikael; Olivecrona, Gunilla; Small, Donald M.

    2015-01-01

    Apolipoprotein C-II (apoC-II) is the co-factor for lipoprotein lipase (LPL) at the surface of triacylglycerol-rich lipoproteins. LPL hydrolyzes triacylglycerol, which increases local surface pressure as surface area decreases and amphipathic products transiently accumulate at the lipoprotein surface. To understand how apoC-II adapts to these pressure changes, we characterized the behavior of apoC-II at multiple lipid/water interfaces. ApoC-II adsorption to a triacylglycerol/water interface resulted in large increases in surface pressure. ApoC-II was exchangeable at this interface and desorbed on interfacial compressions. These compressions increase surface pressure and mimic the action of LPL. Analysis of gradual compressions showed that apoC-II undergoes a two-step desorption, which indicates that lipid-bound apoC-II can exhibit at least two conformations. We characterized apoC-II at phospholipid/triacylglycerol/water interfaces, which more closely mimic lipoprotein surfaces. ApoC-II had a large exclusion pressure, similar to that of apoC-I and apoC-III. However, apoC-II desorbed at retention pressures higher than those seen with the other apoCs. This suggests that it is unlikely that apoC-I and apoC-III inhibit LPL via displacement of apoC-II from the lipoprotein surface. Upon rapid compressions and re-expansions, re-adsorption of apoC-II increased pressure by lower amounts than its initial adsorption. This indicates that apoC-II removed phospholipid from the interface upon desorption. These results suggest that apoC-II regulates the activity of LPL in a pressure-dependent manner. ApoC-II is provided as a component of triacylglycerol-rich lipoproteins and is the co-factor for LPL as pressure increases. Above its retention pressure, apoC-II desorbs and removes phospholipid. This triggers release of LPL from lipoproteins. PMID:26026161

  16. Thermal convection in a 3D spherical shell with strongly temperature and pressure dependent viscosity

    NASA Astrophysics Data System (ADS)

    Stemmer, K.; Harder, H.; Hansen, U.

    2004-12-01

    temperature dependent viscosity (Δ η =104-10^5) typically a few upwelling plume structures develop. The large scale structure of the plume stays intact over a long time while the plume geometry varies on a smaller scale. The downflows are generally organized in two-dimensional sheetlike flows. Additional pressure dependence strongly influences the dynamics even if the magnitude of pressure variation is relatively small. For an appropriate combination of pressure- and temperature-dependence we observe a well developed high-viscosity zone in the lower mantle.

  17. 2,3-Dimethyl-2-butene (TME) ozonolysis: pressure dependence of stabilized Criegee intermediates and evidence of stabilized vinyl hydroperoxides.

    PubMed

    Drozd, Greg T; Kroll, Jesse; Donahue, Neil M

    2011-01-20

    We present measurements of the pressure dependence of stabilized Criegee intermediate (SCI) formation utilizing a hexafluoroacetone scavenger. SCI yields in the ozonolysis of 2,3-dimethyl-2-butene (TME) were measured in a high pressure flow reactor within a range of 50-710 Torr. Within this pressure range, SCI yields increase linearly with pressure. A zero pressure intercept of about 15% indicates that a significant fraction of CI are formed below the barrier to isomerization. By comparison of our results of the pressure dependence of SCI formation and both prompt and long-time OH yields, our results indicate that OH formation from ozonolysis proceeds via at least two intermediates, the SCI and presumably a vinylhydroperoxide (VHP).

  18. Temperature and high-pressure dependent x-ray absorption of SmNiO3 at the Ni K and Sm L3 edges

    NASA Astrophysics Data System (ADS)

    Massa, Néstor E.; Ramos, Aline Y.; Tolentino, Helio C. N.; Sousa-Neto, Narcizo M.; Fonseca, Jairo, Jr.; Alonso, José Antonio

    2015-12-01

    We report on x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) measurements of SmNiO3 from 20 K to 600 K and up to 38 GPa at the Ni K and Sm L3 edges. A multiple component pre-Ni K edge tail is understood, originating from 1 s transitions to 3d-4p states while a post-edge shoulder increases distinctively smoothly, at about the insulator to metal phase transition (TIM), due to the reduction of electron-phonon interactions as the Ni 3d and O 2p band overlap triggers the metallic phase. This effect is concomitant with pressure-induced Ni-O-Ni angle increments toward more symmetric Ni3+ octahedra of the rhombohedral R¯3c space group. Room temperature pressure-dependent Ni white line peak energies have an abrupt ˜3.10 ± 0.04 GPa valence discontinuity from non-equivalent Ni3+δ + Ni3-δ charge disproportionate net unresolved absorber turning at ˜TIM into Ni3+ of the orthorhombic Pbnm metal oxide phase. At 20 K the overall white line response, still distinctive at TIM ˜8.1 ± 0.6 GPa is much smoother due to localization. Octahedral bond contraction up to 38 GPa and at 300 K and 20 K show breaks in its monotonic increase at the different structural changes. The Sm L3 edge does not show distinctive behaviors either at 300 K or 20 K up to about 35 GPa but the perovskite Sm cage, coordinated to eight oxygen atoms, undergoes strong uneven bond contractions at intermediate pressures where we found the coexistence of octahedral and rhombohedral superexchange angle distortions. We found that the white line pressure-dependent anomaly may be used as an accurate alternative for delineating pressure-temperature phase diagrams.

  19. Platform to investigate aqueous outflow system structure and pressure-dependent motion using high-resolution spectral domain optical coherence tomography

    PubMed Central

    Hariri, Sepideh; Johnstone, Murray; Jiang, Yi; Padilla, Steven; Zhou, Zhehai; Reif, Roberto; Wang, Ruikang K.

    2014-01-01

    Abstract. The aqueous outflow system (AOS) is responsible for maintaining normal intraocular pressure (IOP) in the eye. Structures of the AOS have an active role in regulating IOP in healthy eyes and these structures become abnormal in the eyes with glaucoma. We describe a newly developed system platform to obtain high-resolution images of the AOS structures. By incorporating spectral domain optical coherence tomography (SD-OCT), the platform allows us to systematically control, image, and quantitate the responses of AOS tissue to pressure with a millisecond resolution of pulsed flow. We use SD-OCT to image radial limbal segments from the surface of the trabecular meshwork (TM) with a spatial resolution of ∼5  μm in ex vivo nonhuman primate eyes. We carefully insert a cannula into Schlemm’s canal (SC) to control both pressures and flow rates. The experimental results demonstrate the capability of the platform to visualize the unprecedented details of AOS tissue components comparable to that delivered by scanning electron microscopy, as well as to delineate the complex pressure-dependent relationships among the TM, structures within the SC, and collector channel ostia. The described technique provides a new means to characterize the anatomic and pressure-dependent relationships of SC structures, particularly the active motion of collagenous elements at collector channel ostia; such relationships have not previously been amenable to study. Experimental findings suggest that continuing improvements in the OCT imaging of the AOS may provide both insights into the glaucoma enigma and improvements in its management. PMID:25349094

  20. Competing mechanism driving diverse pressure dependence of thermal conductivity of X Te (X =Hg ,Cd , and Zn)

    NASA Astrophysics Data System (ADS)

    Ouyang, Tao; Hu, Ming

    2015-12-01

    Effectively engineering the lattice thermal conductivity of materials is a key interest of the current thermal science community. Pressure or compressive strain is one of the most worthwhile processes to modify the thermal transport property of materials, due to its robust tunability and flexibility of realization. While it is well documented in the literature that the application of hydrostatic pressure normally increases the thermal conductivity of bulk materials, little work has been performed on abnormal pressure-dependent thermal conductivity and the governing mechanism has not been fully understood yet. In this paper, taking bulk telluride systems X Te (X =Hg ,Cd ,Zn ) as examples, we show, by combining first-principle calculation and the phonon Boltzmann transport equation, that the thermal conductivity presents diverse pressure dependence although they belong to the same group. The thermal conductivity of ZnTe is independent of pressure, while abnormal negative pressure dependence of thermal conductivity is observed in HgTe. As for CdTe, the trend falls in between HgTe and ZnTe and relies largely on the temperature. By comparing the key contributors of the lattice thermal conductivity, we find that the diverse pressure dependence of the lattice thermal conductivity is governed by the competition between the enhancement of group velocity of longitudinal acoustic and optic modes and the reduction of phonon relaxation time of transverse acoustic modes, with both effects being fully quantified by our calculation. Comparison with traditional bulk systems such as silicon further underpins the governing mechanism. The correlation between the diverse thermal transport phenomena and the nature of the atomic bonding is also qualitatively established. These findings are expected to deepen our understanding of manipulating phonon transport of bulk materials via simple compressive strain and are also helpful for related applications, such as optimizing thermoelectric

  1. Measurement of Pressure Dependent Fluorescence Yield of Air: Calibration Factor for UHECR Detectors

    SciTech Connect

    Belz, J.W.; Burt, G.W.; Cao, Z.; Chang, F.Y.; Chen, C.C.; Chen, C.W.; Chen, P.; Field, C.; Findlay, J.; Huntemeyer, Petra; Huang, M.A.; Hwang, W.-Y.P.; Iverson, R.; Jones, B.F.; Jui, C.C.H.; Kirn, M.; Lin, G.-L.; Loh, E.C.; Maestas, M.M.; Manago, N.; Martens, K.; /Montana U. /Utah U. /Taiwan, Natl. Taiwan U. /SLAC /Rutgers U., Piscataway

    2005-07-06

    In a test experiment at the Final Focus Test Beam of the Stanford Linear Accelerator Center, the fluorescence yield of 28.5 GeV electrons in air and nitrogen was measured. The measured photon yields between 300 and 400 nm at 1 atm and 29 C are Y(760 Torr){sup air} = 4.42 {+-} 0.73 and Y(760 Torr){sup N{sub 2}} = 29.2 {+-} 4.8 photons per electron per meter. Assuming that the fluorescence yield is proportional to the energy deposition of a charged particle traveling through air, good agreement with measurements at lower particle energies is observed.

  2. A multilayer grating with a novel layer structure for a flat-field spectrograph attached to transmission electron microscopes in energy region of 2-4 keV

    SciTech Connect

    Imazono, T.; Koike, M.; Koeda, M.; Nagano, T.; Sasai, H.; Oue, Y.; Yonezawa, Z.; Kuramoto, S.; Terauchi, M.; Takahashi, H.; Handa, N.; Murano, T.

    2012-05-17

    A multilayer mirror with a novel layer structure to uniformly enhance the reflectivity in a few keV energy range at a fixed angle of incidence is invented and applied to a multilayer grating for use in a flat-field spectrograph attached to a conventional electron microscope. The diffraction efficiency of the fabricated multilayer grating having the new layer structure is evaluated at the angle of incidence of 88.65 deg. in the energy region of 2.1-4.0 keV. It is shown that the multilayer grating is effective to uniformly enhance the diffraction efficiency and able to be practically used in this energy region.

  3. Belt attachment and system

    DOEpatents

    Schneider, Abraham D.; Davidson, Erick M.

    2016-02-02

    Disclosed herein is a belt assembly including a flexible belt with an improved belt attachment. The belt attachment includes two crossbars spaced along the length of the belt. The crossbars retain bearings that allow predetermined movement in six degrees of freedom. The crossbars are connected by a rigid body that attaches to the bearings. Implements that are attached to the rigid body are simply supported but restrained in pitching rotation.

  4. Adolescent Attachment and Psychopathology.

    ERIC Educational Resources Information Center

    Rosenstein, Diana S.; Horowitz, Harvey A.

    1996-01-01

    In relationships among attachment classification, psychopathology, and personality, traits were examined in a group of 60 psychiatrically hospitalized adolescents. Attachment was examined in 27 adolescent-mother pairs. Both adolescent and maternal attachment status were overwhelmingly insecure and were highly concordant. Results support a model of…

  5. Pressure dependence of the refractive index in wurtzite and rocksalt indium nitride

    SciTech Connect

    Oliva, R.; Yamaguchi, T.; Nanishi, Y.

    2014-12-08

    We have performed high-pressure Fourier transform infrared reflectance measurements on a freestanding InN thin film to determine the refractive index of wurtzite InN and its high-pressure rocksalt phase as a function of hydrostatic pressure. From a fit to the experimental refractive-index curves including the effect of the high-energy optical gaps, phonons, free carriers, and the direct (fundamental) band-gap in the case of wurtzite InN, we obtain pressure coefficients for the low-frequency (electronic) dielectric constant ε{sub ∞}. Negative pressure coefficients of −8.8 × 10{sup −2 }GPa{sup −1} and −14.8 × 10{sup −2 }GPa{sup −1} are obtained for the wurtzite and rocksalt phases, respectively. The results are discussed in terms of the electronic band structure and the compressibility of both phases.

  6. Constraining Data Mining with Physical Models: Voltage- and Oxygen Pressure-Dependent Transport in Multiferroic Nanostructures

    SciTech Connect

    Strelcov, Evgheni; Belianinov, Alexei; Hsieh, Ying-Hui; Chu, Ying-Hao; Kalinin, Sergei V.

    2015-08-27

    Development of new generation electronic devices requires understanding and controlling the electronic transport in ferroic, magnetic, and optical materials, which is hampered by two factors. First, the complications of working at the nanoscale, where interfaces, grain boundaries, defects, and so forth, dictate the macroscopic characteristics. Second, the convolution of the response signals stemming from the fact that several physical processes may be activated simultaneously. Here, we present a method of solving these challenges via a combination of atomic force microscopy and data mining analysis techniques. Rational selection of the latter allows application of physical constraints and enables direct interpretation of the statistically significant behaviors in the framework of the chosen physical model, thus distilling physical meaning out of raw data. We demonstrate our approach with an example of deconvolution of complex transport behavior in a bismuth ferrite–cobalt ferrite nanocomposite in ambient and ultrahigh vacuum environments. Measured signal is apportioned into four electronic transport patterns, showing different dependence on partial oxygen and water vapor pressure. These patterns are described in terms of Ohmic conductance and Schottky emission models in the light of surface electrochemistry. Finally and furthermore, deep data analysis allows extraction of local dopant concentrations and barrier heights empowering our understanding of the underlying dynamic mechanisms of resistive switching.

  7. Constraining Data Mining with Physical Models: Voltage- and Oxygen Pressure-Dependent Transport in Multiferroic Nanostructures

    DOE PAGES

    Strelcov, Evgheni; Belianinov, Alexei; Hsieh, Ying-Hui; Chu, Ying-Hao; Kalinin, Sergei V.

    2015-08-27

    Development of new generation electronic devices requires understanding and controlling the electronic transport in ferroic, magnetic, and optical materials, which is hampered by two factors. First, the complications of working at the nanoscale, where interfaces, grain boundaries, defects, and so forth, dictate the macroscopic characteristics. Second, the convolution of the response signals stemming from the fact that several physical processes may be activated simultaneously. Here, we present a method of solving these challenges via a combination of atomic force microscopy and data mining analysis techniques. Rational selection of the latter allows application of physical constraints and enables direct interpretation ofmore » the statistically significant behaviors in the framework of the chosen physical model, thus distilling physical meaning out of raw data. We demonstrate our approach with an example of deconvolution of complex transport behavior in a bismuth ferrite–cobalt ferrite nanocomposite in ambient and ultrahigh vacuum environments. Measured signal is apportioned into four electronic transport patterns, showing different dependence on partial oxygen and water vapor pressure. These patterns are described in terms of Ohmic conductance and Schottky emission models in the light of surface electrochemistry. Finally and furthermore, deep data analysis allows extraction of local dopant concentrations and barrier heights empowering our understanding of the underlying dynamic mechanisms of resistive switching.« less

  8. Constraining Data Mining with Physical Models: Voltage- and Oxygen Pressure-Dependent Transport in Multiferroic Nanostructures.

    PubMed

    Strelcov, Evgheni; Belianinov, Alexei; Hsieh, Ying-Hui; Chu, Ying-Hao; Kalinin, Sergei V

    2015-10-14

    Development of new generation electronic devices necessitates understanding and controlling the electronic transport in ferroic, magnetic, and optical materials, which is hampered by two factors. First, the complications of working at the nanoscale, where interfaces, grain boundaries, defects, and so forth, dictate the macroscopic characteristics. Second, the convolution of the response signals stemming from the fact that several physical processes may be activated simultaneously. Here, we present a method of solving these challenges via a combination of atomic force microscopy and data mining analysis techniques. Rational selection of the latter allows application of physical constraints and enables direct interpretation of the statistically significant behaviors in the framework of the chosen physical model, thus distilling physical meaning out of raw data. We demonstrate our approach with an example of deconvolution of complex transport behavior in a bismuth ferrite-cobalt ferrite nanocomposite in ambient and ultrahigh vacuum environments. Measured signal is apportioned into four electronic transport patterns, showing different dependence on partial oxygen and water vapor pressure. These patterns are described in terms of Ohmic conductance and Schottky emission models in the light of surface electrochemistry. Furthermore, deep data analysis allows extraction of local dopant concentrations and barrier heights empowering our understanding of the underlying dynamic mechanisms of resistive switching. PMID:26312554

  9. Pressure dependence of space charge deposition in piezoelectric polymer foams: simulations and experimental verification

    NASA Astrophysics Data System (ADS)

    Harris, Scott; Mellinger, Axel

    2012-06-01

    The piezoelectric activity of PQ-50 cellular polypropylene (PP) foam (an example of a so-called ferroelectret) is measured after repeated charging in a nitrogen atmosphere at a range of pressures between 61 and 381 kPa. The results are compared against simulations using a multilayer electromechanical model based on Townsend's model of Paschen breakdown and a realistic distribution of void heights determined from scanning electron micrographs. The modeled piezoelectric coefficients versus pressure are in good agreement with experimental data when adjusted Paschen coefficients are used, indicating that the Paschen curve for electric breakdown in gases needs to be modified for dielectric barrier discharges in microcavities. The highest d 33 coefficients were achieved for pressures above 251 kPa. For previously uncharged PP foam, the model predicts an optimal charging pressure of 186 kPa.

  10. Temperature and pressure dependent Mott potentials and their influence on self-limiting oxide film growth

    NASA Astrophysics Data System (ADS)

    Cai, Na; Zhou, Guangwen; Müller, Kathrin; Starr, David E.

    2012-10-01

    Classic Cabrera-Mott theory stipulates that the limited oxide-film growth results from electron tunneling from the metal through the oxide film to adsorbed oxygen. This leads to an electric field across the oxide film that assists ion migration for low-temperature oxide-film growth. Here, we show that the field-driven oxide-film growth can be manipulated via the temperature and pressure of oxidation. The magnitude of the self-generated electric field depends on the oxygen surface coverage that exhibits a Langmuir isotherm behavior with changes in temperature and oxygen pressure. These observations demonstrate the ability to tune an interfacial reaction via self-adaptation to its environment.

  11. Vapour pressure dependence and thermodynamics of cylindrical metal-organic framework mesoparticles: an ESEM study.

    PubMed

    Sievers, Torsten K; Genre, Caroline; Bonnefond, Florent; Demars, Thomas; Ravaux, Johann; Meyer, Daniel; Podor, Renaud

    2013-10-14

    Self-assembly of neodymium nitrate and 2,5-dihydroxyl-1,4-benzoquinone (DHBQ) leads to the formation of a metal organic framework (MOF) of formula [Nd2(DHBQ)3(H2O)6]·18H2O. X-ray diffraction studies show that its crystalline structure is that of a two-dimensional coordination polymer packed in parallel sheets, with organised clusters of water molecules lying between the sheets and bridging them via a dense H-bond network. However, instead of forming faceted crystals, this MOF assembles into unusually shaped cylindrical particles of micrometre size. Scanning electron microscopy revealed that the particles are indeed mesoparticles from aggregated MOF crystalline nano-grains. The mesoparticles are stimuli-responsive and shrink in size upon exposure to reduced water vapour pressure. The shrinkage is isotropic and depends on temperature, which allows measuring the coexistence curve of water inside the particles and in the gas phase. Owing to an elaborated environmental scanning-electron microscopy (ESEM) study, it was possible to determine the association energy of water in the mesoparticles. We found a value of 16 ± 6.5 kJ mol(-1). Since the only water present in the particles is the lattice water in the nano-grains, this association energy is the lattice energy of water in the nano-sized MOF crystals. This value allowed us to draw a model for the building process of these originally shaped cylindrical mesoparticles. This is the first example of determination of a thermodynamic value by ESEM.

  12. Blade attachment assembly

    DOEpatents

    Garcia-Crespo, Andres Jose; Delvaux, John McConnell; Miller, Diane Patricia

    2016-05-03

    An assembly and method for affixing a turbomachine rotor blade to a rotor wheel are disclosed. In an embodiment, an adaptor member is provided disposed between the blade and the rotor wheel, the adaptor member including an adaptor attachment slot that is complementary to the blade attachment member, and an adaptor attachment member that is complementary to the rotor wheel attachment slot. A coverplate is provided, having a coverplate attachment member that is complementary to the rotor wheel attachment slot, and a hook for engaging the adaptor member. When assembled, the coverplate member matingly engages with the adaptor member, and retains the blade in the adaptor member, and the assembly in the rotor wheel.

  13. Redox signaling via oxidative inactivation of PTEN modulates pressure-dependent myogenic tone in rat middle cerebral arteries.

    PubMed

    Gebremedhin, Debebe; Terashvili, Maia; Wickramasekera, Nadi; Zhang, David X; Rau, Nicole; Miura, Hiroto; Harder, David R

    2013-01-01

    The present study examined the level of generation of reactive oxygen species (ROS) and roles of inactivation of the phosphatase PTEN and the PI3K/Akt signaling pathway in response to an increase in intramural pressure-induced myogenic cerebral arterial constriction. Step increases in intraluminal pressure of cannulated cerebral arteries induced myogenic constriction and concomitant formation of superoxide (O2 (.-)) and its dismutation product hydrogen peroxide (H2O2) as determined by fluorescent HPLC analysis, microscopic analysis of intensity of dihydroethidium fluorescence and attenuation of pressure-induced myogenic constriction by pretreatment with the ROS scavenger 4,hydroxyl-2,2,6,6-tetramethylpiperidine1-oxyl (tempol) or Mito-tempol or MitoQ in the presence or absence of PEG-catalase. An increase in intraluminal pressure induced oxidation of PTEN and activation of Akt. Pharmacological inhibition of endogenous PTEN activity potentiated pressure-dependent myogenic constriction and caused a reduction in NPo of a 238 pS arterial KCa channel current and an increase in [Ca(2+)]i level in freshly isolated cerebral arterial muscle cells (CAMCs), responses that were attenuated by Inhibition of the PI3K/Akt pathway. These findings demonstrate an increase in intraluminal pressure induced increase in ROS production triggered redox-sensitive signaling mechanism emanating from the cross-talk between oxidative inactivation of PTEN and activation of the PI3K/Akt signaling pathway that involves in the regulation of pressure-dependent myogenic cerebral arterial constriction.

  14. Linking the pressure dependency of elastic and electrical properties of porous rocks by a dual porosity model

    NASA Astrophysics Data System (ADS)

    Han, Tongcheng; Gurevich, Boris; Pervukhina, Marina; Clennell, Michael Ben; Zhang, Junfang

    2016-04-01

    Knowledge about the pressure dependency of elastic and electrical properties is important for a variety of geophysical applications. We present a technique to invert for the stiff and compliant porosity from velocity measurements made as a function of differential pressure on saturated sandstones. A dual porosity concept is used for dry rock compressibility and a squirt model is employed for the pressure and frequency dependent elastic properties of the rocks when saturated. The total porosity obtained from inversion shows satisfactory agreement with experimental results. The electrical cementation factor was determined using the inverted porosity in combination with measured electrical conductivity. It was found that cementation factor increased exponentially with increasing differential pressure during isostatic loading. Elastic compressibility, electrical cementation factor and electrical conductivity of the saturated rocks correlate linearly with compliant porosity, and electrical cementation factor and electrical conductivity exhibit linear correlations with elastic compressibility of the saturated rocks under loading. The results show that the dual porosity concept is sufficient to explain the pressure dependency of elastic, electrical and joint elastic-electrical properties of saturated porous sandstones.

  15. Attachment Without Fear

    PubMed Central

    Bell, David C.

    2012-01-01

    John Bowlby hypothesized an attachment system that interacts with caregiving, exploration, and fear systems in the brain, with a particular emphasis on fear. Neurobiological research confirms many of his hypotheses and also raises some new questions. A psychological model based on this neurobiological research is presented here. The model extends conventional attachment theory by describing additional attachment processes independent of fear. In this model, the attachment elements of trust, openness, and dependence interact with the caregiving elements of caring, empathy, and responsibility. PMID:22879835

  16. Structural phase diagram for ultra-thin epitaxial Fe 3 O 4  / MgO(0 0 1) films: thickness and oxygen pressure dependence

    DOE PAGES

    Alraddadi, S.; Hines, W.; Yilmaz, T.; Gu, G. D.; Sinkovic, B.

    2016-02-19

    A systematic investigation of the thickness and oxygen pressure dependence for the structural properties of ultra-thin epitaxial magnetite (Fe3O4) films has been carried out; for such films, the structural properties generally differ from those for the bulk when the thickness ≤10 nm. Iron oxide ultra-thin films with thicknesses varying from 3 nm to 20 nm were grown on MgO (001) substrates using molecular beam epitaxy under different oxygen pressures ranging from 1 × 10-7 torr to 1 × 10-5 torr. The crystallographic and electronic structures of the films were characterized using low energy electron diffraction (LEED) and x-ray photoemission spectroscopymore » (XPS), respectively. Moreover, the quality of the epitaxial Fe3O4 ultra-thin films was judged by magnetic measurements of the Verwey transition, along with complementary XPS spectra. We observed that under the same growth conditions the stoichiometry of ultra-thin films under 10 nm transforms from the Fe3O4 phase to the FeO phase. In this work, a phase diagram based on thickness and oxygen pressure has been constructed to explain the structural phase transformation. It was found that high-quality magnetite films with thicknesses ≤20 nm formed within a narrow range of oxygen pressure. An optimal and controlled growth process is a crucial requirement for the accurate study of the magnetic and electronic properties for ultra-thin Fe3O4 films. Furthermore, these results are significant because they may indicate a general trend in the growth of other oxide films, which has not been previously observed or considered.« less

  17. Time, temperature and water pressure dependent reheating of volcanic plugs, conduits and domes

    NASA Astrophysics Data System (ADS)

    Kennedy, B. M.; Jellinek, M.; Russell, K.

    2009-12-01

    Active lava domes show periodic magma supply and are frequently re-intruded and reheated. We propose that the timescale, temperature, and water pressure of reheating control whether crack and bubble networks open or close, and whether or not gas can escape. Interpretations of historic eruptions indicate open, permeable magmatic systems favour degassing and non-explosive eruptions, whereas, closed impermeable systems favour pressure build up and explosive eruptions. Despite the observations and interpretations mentioned above, the evolution of open and closed systems during reheating remains poorly understood. We reheated rhyolite dome and pumice samples under open (atmospheric pressure and dry) and closed (pressurized and wet) conditions. Open and closed porosity was measured before and after experiments by helium pycnometry, textures were examined with the Scanning Electron Microscope (SEM), and bulk water contents were measured by infrared spectroscopy during loss on ignition. Open (atmospheric pressure, 200-1100°C) experiments show that (1) short timescales and low temperatures allow degassing without deformation, (2) intermediate timescales and temperatures favour bubble and crack growth, and (3) longer timescales and higher temperatures produce bubble collapse and crack healing. Closed experiments at (450C-750°C and 2-10 MPa) show that, (1) low temperatures and high pressures promote rehydration (regassing) without deformation, and (2) high temperatures at all pressures allow degassing with bubble collapse. Our results indicate that during reheating of an open silicic volcanic plug residual water will degas with little deformation, unless mafic magma temperatures and longer timescales occur. Bubble collapse in remelted enclaves of rhyolite supports that the explosivity of the 1886 basaltic eruption of Mt. Tarawera, New Zealand, may have been enhanced by extreme reheating and sealing of the rhyolite plug by reheating from hot basaltic magma. In contrast, our

  18. Anisotropic Hc2 , thermodynamic and transport measurements, and pressure dependence of Tc in K2Cr3As3 single crystals

    DOE PAGES

    Kong, Tai; Bud'ko, Sergey L.; Canfield, Paul C.

    2015-01-30

    We present a detailed study of single crystalline K2Cr3As3 and analyze its thermodynamic and transport properties, anisotropic Hc2(T), and initial pressure dependence of Tc. In zero field, the temperature-dependent resistivity is metallic. Deviation from a linear temperature dependence is evident below 100 K and a T3 dependence is roughly followed from just above Tc (~10K) to ~40K. Anisotropic Hc2(T) data were measured up to 140 kOe with field applied along and perpendicular to the rodlike crystals. For the applied field perpendicular to the rod, Hc2(T) is linear with a slope ~–70 kOe/K. For field applied along the rod, the slopemore » is about –120 kOe/K below 70 kOe. Above 70 kOe, the magnitude of the slope decreases to ~–70 kOe/K. The electronic specific heat coefficient γ, just above Tc, is 73 mJ/mol K2; the Debye temperature ΘD is 220 K. As a result, the specific heat jump at the superconducting transition ΔC~2.2γTc. Finally, for hydrostatic pressures up to ~7 kbar, Tc decreases under pressure linearly at a rate of –0.034K/kbar.« less

  19. Equation of motion coupled cluster methods for electron attachment and ionization potential in fullerenes C{sub 60} and C{sub 70}

    SciTech Connect

    Bhaskaran-Nair, Kiran; Kowalski, Karol; Moreno, Juana; Jarrell, Mark; Shelton, William A.

    2014-08-21

    In both molecular and periodic solid-state systems there is a need for the accurate determination of the ionization potential and the electron affinity for systems ranging from light harvesting polymers and photocatalytic compounds to semiconductors. The development of a Green's function approach based on the coupled cluster (CC) formalism would be a valuable tool for addressing many properties involving many-body interactions along with their associated correlation functions. As a first step in this direction, we have developed an accurate and parallel efficient approach based on the equation of motion-CC technique. To demonstrate the high degree of accuracy and numerical efficiency of our approach we calculate the ionization potential and electron affinity for C{sub 60} and C{sub 70}. Accurate predictions for these molecules are well beyond traditional molecular scale studies. We compare our results with experiments and both quantum Monte Carlo and GW calculations.

  20. Infant Feeding and Attachment.

    ERIC Educational Resources Information Center

    Ainsworth, Mary D. Salter; Tracy, Russel L.

    This paper has two major purposes: first, to consider how infant feeding behavior may fit into attachment theory; and second, to cite some evidence to show how an infant's early interaction with his mother in the feeding situation is related to subsequent development. It was found that sucking and rooting are precursor attachment behaviors that…

  1. Temperament and Attachment Disorders

    ERIC Educational Resources Information Center

    Zeanah, Charles H.; Fox, Nathan A.

    2004-01-01

    Reviewed in this article is research on children with reactive attachment disorder (RAD) who exhibit specific patterns of socially aberrant behavior resulting from being maltreated or having limited opportunities to form selective attachments. There are no data explaining why 2 different patterns of the disorder, an emotionally withdrawn-inhibited…

  2. Attachment Line Blockage Models

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Photographs shows the attachment-line experiment model with fairing and fence for supersonic attachment-line experiments. The fairing is intended to eliminate the wing/fuselage juncture shock and align the flow for the streamlined fence. The streamlined fence traps the turbulent fuselage boundary layer to prevent turbulent contamination of the leading edge flow.

  3. Separation and Attachment

    ERIC Educational Resources Information Center

    Honig, Alice Sterling

    2005-01-01

    Developing secure attachments with babies gives them a very special gift--the foundation for good infant mental health! In this article, the author discusses how to develop secure attachments with babies. Babies who are in the care of others during the day often suffer from separations from their special adults. Thirteen "tips" to ensure that…

  4. Attachment and Cognition.

    ERIC Educational Resources Information Center

    De Riuter, Corine, Ed.; Van IJzendoorn, Marinus H., Ed.

    1993-01-01

    The five chapters and epilogue of this special issue present theoretical and empirical contributions on the relevance of attachment theory to cognitive development and education. A literature review is followed by explorations of attachment theory and emotions, cognitive development, literacy, and the communication effectiveness of the mother.…

  5. Angular dependence of dissociative electron attachment to polyatomic molecules: Application to the {sup 2}B{sub 1} metastable state of the H{sub 2}O and H{sub 2}S anions

    SciTech Connect

    Haxton, Daniel J.; McCurdy, C. William; Rescigno, Thomas N.

    2006-06-15

    The angular dependence of dissociative electron attachment (DEA) to polyatomic targets is formulated in the local complex potential model, under the assumption that the axial recoil approximation describes the dissociation dynamics. An additional approximation, which is found to be valid in the case of H{sub 2}O but not in the case of H{sub 2}S, makes it possible to describe the angular dependence of DEA solely from an analysis of the fixed-nuclei entrance amplitude, without carrying out nuclear dynamics calculations. For H{sub 2}S, the final-vibrational-state-specific angular dependence of DEA is obtained by incorporating the variation of the angular dependence of the entrance amplitude with nuclear geometry into the nuclear dynamics. Scattering calculations using the complex Kohn method and, for H{sub 2}S, full quantum calculations of the nuclear dynamics using the multiconfiguration time-dependent Hartree method, are performed.

  6. Adolescent attachment and psychopathology.

    PubMed

    Rosenstein, D S; Horowitz, H A

    1996-04-01

    The relationships among attachment classification, psychopathology, and personality traits were examined in a group of 60 psychiatrically hospitalized adolescents. The concordance of attachment classification was examined in 27 adolescent-mother pairs. Both adolescent and maternal attachment status were overwhelmingly insecure and were highly concordant. Adolescents showing a dismissing attachment organization were more likely to have a conduct or substance abuse disorder, narcissistic or antisocial personality disorder, and self-reported narcissistic, antisocial, and paranoid personality traits. Adolescents showing a preoccupied attachment organization were more likely to have an affective disorder, obsessive-compulsive, histrionic, borderline or schizotypal personality disorder, and self-reported avoidant, anxious, and dysthymic personality traits. The results support a model of development of psychopathology based partially on relational experiences with parents.

  7. Pressure dependence of the absolute rate constant for the reaction OH + C2H2 from 228 to 413 K

    NASA Technical Reports Server (NTRS)

    Michael, J. V.; Nava, D. F.; Payne, W. A.; Stief, L. J.; Borkowski, R. P.

    1980-01-01

    The pressure dependence of the absolute rate constant for the reaction of the hydroxyl radical with acetylene, important in both atmospheric and combustion chemistry, is determined for temperatures between 228 and 413 K. The flash photolysis-resonance fluorescence technique was employed at five temperatures over wide ranges of pressure and acetylene concentrations, with the OH produced by water photolysis and hydroxyl resonance fluorescent photons measured by multiscaling techniques. Results indicate that, except at the lowest temperature, the bimolecular rate constant for the reaction depends strongly on total pressure, with the pressure effect becoming more pronounced with increasing temperature. At limiting high pressures, the rate constant is found to be equal to 6.83 + or - 1.19 x 10 to the -12th exp (-646 + or - 47/T) cu cm/molecule per sec, where T is the temperature. Results thus demonstrate the importance of environmental conditions in theoretical studies of atmospheric and combustion product compositions

  8. Theoretical study of band gap in CuAlO2: Pressure dependence and self-interaction correction

    NASA Astrophysics Data System (ADS)

    Nakanishi, Akitaka; Katayama-Yoshida, Hiroshi

    2012-08-01

    By using first-principles calculations, we studied the energy gaps of delafossite CuAlO2: (1) pressure dependence and (2) self-interaction correction (SIC). Our simulation shows that CuAlO2 transforms from a delafossite structure to a leaning delafossite structure at 60 GPa. The energy gap of CuAlO2 increases through the structural transition due to the enhanced covalency of Cu 3d and O 2p states. We implemented a self-interaction correction (SIC) into first-principles calculation code to go beyond local density approximation and applied it to CuAlO2. The energy gap calculated within the SIC is close to experimental data while one calculated without the SIC is about 1 eV smaller than the experimental data.

  9. Pressure dependencies of magnetostrictive strain and d coefficient in Terfenol-D after thermal or magnetic annealing

    NASA Astrophysics Data System (ADS)

    Galloway, N.; Greenough, R. D.; Jenner, A. G. I.; Schulze, M. P.

    1994-11-01

    The pressure dependence of the magnetostrictive strain coefficient, d(sub 33), and maximum strains in applied fields of 120 kA/m have been measured in samples of Terfenol-D before and after thermal or magnetic annealing. Application of an annealing field, H(sub a), parallel to the (111) axes which are normal to grains oriented along the (11-2) axis, leads to an increase in d(sub 33) of as much as 81%, with applied uniaxial prestresses as low as 3 MPa. The variation of optimum d(sub 33) values as a function of stress applied along the (11-2) axis shows anomalous oscillations after magnetic annealing. The thermal and magnetic effects of the annealing are discussed and a mechanism to explain magnetic annealing is proposed.

  10. Pressure-dependent structures of amorphous red phosphorus and the origin of the first sharp diffraction peaks.

    PubMed

    Zaug, Joseph M; Soper, Alan K; Clark, Simon M

    2008-11-01

    Characterizing the nature of medium-range order (MRO) in liquids and disordered solids is important for understanding their structure and transport properties. However, accurately portraying MRO, as manifested by the first sharp diffraction peak (FSDP) in neutron and X-ray scattering measurements, has remained elusive for more than 80 years. Here, using X-ray diffraction of amorphous red phosphorus compressed to 6.30 GPa, supplemented with micro-Raman scattering studies, we build three-dimensional structural models consistent with the diffraction data. We discover that the pressure dependence of the FSDP intensity and line position can be quantitatively accounted for by a characteristic void distribution function, defined in terms of average void size, void spacing and void density. This work provides a template to unambiguously interpret atomic and void-space MRO across a broad range of technologically promising network-forming materials. PMID:18849976

  11. Electron-beam lithography and molecular liftoff for directed attachment of DNA nanostructures on silicon: top-down meets bottom-up.

    PubMed

    Pillers, Michelle; Goss, Valerie; Lieberman, Marya

    2014-06-17

    CONSPECTUS: Our work on lithographic patterning of DNA nanostructures was inspired by a collaboration on molecular electronic devices known as quantum-dot cellular automata or QCA. QCA is a paradigm for computation in which information is transmitted and processed through the interaction of coupled electrical charges or magnetic dipoles. We began to explore the idea of molecular scale QCA and found that ab initio methods, a thermodynamic Ising model, and larger scale circuit design work suggested that circuits that did computationally interesting things could function at room temperature if made from molecular QCA cells of chemically reasonable design. But how could the QCA cells be patterned to form the complex arrays needed for computationally interesting circuitry, and how could those arrays of molecular circuitry be integrated with conventional electronic inputs and outputs? Top-down methods lacked the spatial resolution and high level of parallelism needed to make molecular circuits. Bottom-up chemical synthesis lacked the ability to fabricate arbitrary and heterogeneous structures tens to hundreds of nanometers in size. Chemical self-assembly at the time could produce structures in the right size scale, but was limited to homogeneous arrays. A potential solution to this conundrum was just being demonstrated in the late 1990s and early 2000s: DNA nanostructures self-assembled from oligonucleotides, whose high information density could handle the creation of arbitrary structures and chemical inhomogeneity. Our group became interested in whether DNA nanostructures could function as self-assembling circuit boards for electrical or magnetic QCA systems. This Account focuses on what we learned about the interactions of DNA nanostructures with silicon substrates and, particularly, on how electron-beam lithography could be used to direct the binding of DNA nanostructures on a variety of functional substrates.

  12. Electron microscopic imaging revealed the flexible filamentous structure of the cell attachment protein P2 of Rice dwarf virus located around the icosahedral 5-fold axes.

    PubMed

    Miyazaki, Naoyuki; Higashiura, Akifumi; Higashiura, Tomoko; Akita, Fusamichi; Hibino, Hiroyuki; Omura, Toshihiro; Nakagawa, Atsushi; Iwasaki, Kenji

    2016-02-01

    The minor outer capsid protein P2 of Rice dwarf virus (RDV), a member of the genus Phytoreovirus in the family Reoviridae, is essential for viral cell entry. Here, we clarified the structure of P2 and the interactions to host insect cells. Negative stain electron microscopy (EM) showed that P2 proteins are monomeric and flexible L-shaped filamentous structures of ∼20 nm in length. Cryo-EM structure revealed the spatial arrangement of P2 in the capsid, which was prescribed by the characteristic virion structure. The P2 proteins were visualized as partial rod-shaped structures of ∼10 nm in length in the cryo-EM map and accommodated in crevasses on the viral surface around icosahedral 5-fold axes with hydrophobic interactions. The remaining disordered region of P2 assumed to be extended to the radial direction towards exterior. Electron tomography clearly showed that RDV particles were away from the cellular membrane at a uniform distance and several spike-like densities, probably corresponding to P2, connecting a viral particle to the host cellular membrane during cell entry. By combining the in vitro and in vivo structural information, we could gain new insights into the detailed mechanism of the cell entry of RDV.

  13. Attachment-related psychodynamics.

    PubMed

    Shaver, Phillip R; Mikulincer, Mario

    2002-09-01

    Because there has been relatively little communication and cross-fertilization between the two major lines of research on adult attachment, one based on coded narrative assessments of defensive processes, the other on simple self-reports of 'attachment style' in close relationships, we here explain and review recent work based on a combination of self-report and other kinds of method, including behavioral observations and unconscious priming techniques. The review indicates that considerable progress has been made in testing central hypotheses derived from attachment theory and in exploring unconscious, psychodynamic processes related to affect-regulation and attachment-system activation. The combination of self-report assessment of attachment style and experimental manipulation of other theoretically pertinent variables allows researchers to test causal hypotheses. We present a model of normative and individual-difference processes related to attachment and identify areas in which further research is needed and likely to be successful. One long-range goal is to create a more complete theory of personality built on attachment theory and other object relations theories.

  14. Electron

    NASA Astrophysics Data System (ADS)

    Springford, Michael

    1997-03-01

    1. J. J. Thomson and the discovery of the electron A. B. P. Pippard; 2. The isolated electron W. N. Cottingham; 3. The relativistic electron D. I. Olive; 4. The electron glue B. L. Gyorffy; 5. The electron fluid P. Coleman; 6. The magnetic electron G. G. Lonzarich; 7. The paired electron A. J. Leggett; 8. The heavy electron M. Springford; 9. The coherent electron Y. Imry and M. Peskin; 10. The composite electron R. Nicholas; 11. The electron in the cosmos M. S. Longair.

  15. Electron

    NASA Astrophysics Data System (ADS)

    Springford, Michael

    2008-12-01

    1. J. J. Thomson and the discovery of the electron A. B. P. Pippard; 2. The isolated electron W. N. Cottingham; 3. The relativistic electron D. I. Olive; 4. The electron glue B. L. Gyorffy; 5. The electron fluid P. Coleman; 6. The magnetic electron G. G. Lonzarich; 7. The paired electron A. J. Leggett; 8. The heavy electron M. Springford; 9. The coherent electron Y. Imry and M. Peskin; 10. The composite electron R. Nicholas; 11. The electron in the cosmos M. S. Longair.

  16. Electron reactions in model liquids and biological systems

    SciTech Connect

    Bakale, G.; Gregg, E.C.

    1982-01-01

    Progress is reported in the following studies: (1) Field-dependent electron attachment; (2) Dependence of electron attachment rate on electron-acceptor dipole moment; (3) Electron attachment in i-octane/TMS mixtures; (4) Electron attachment/detachment equilibria; (5) Electron attachment to reversed micelles; (6) Electron attachment to chemical carcinogens; (7) Radiation-induced bacterial mutagenesis; and (8) Bacterial mutagenicity of nitrobenzene derivatives. 14 references. (ACR)

  17. The neurobiology of attachment.

    PubMed

    Insel, T R; Young, L J

    2001-02-01

    It is difficult to think of any behavioural process that is more intrinsically important to us than attachment. Feeding, sleeping and locomotion are all necessary for survival, but humans are, as Baruch Spinoza famously noted, "a social animal" and it is our social attachments that we live for. Over the past decade, studies in a range of vertebrates, including humans, have begun to address the neural basis of attachment at a molecular, cellular and systems level. This review describes some of the important insights from this work.

  18. Mirror Attachment For Borescope

    NASA Technical Reports Server (NTRS)

    Gearhart, John F.; Peloquin, James E.

    1994-01-01

    Attachment for articulated borescope provides views into small, normally inaccessible spaces. Simple small round mirror on extension arm welded to borescope head. Tilted at angle to axis of borescope head, mirror provides views sideways to borescope head. Disassembly of turbopump blades not necessary to enable fluorescent-penetrant-dye inspection. Attachment used to inspect difficult-to-reach internal parts of other assemblies. Also used for inspection with ordinary white light.

  19. Micromechanical die attachment surcharge

    DOEpatents

    Filter, William F.; Hohimer, John P.

    2002-01-01

    An attachment structure is disclosed for attaching a die to a supporting substrate without the use of adhesives or solder. The attachment structure, which can be formed by micromachining, functions purely mechanically in utilizing a plurality of shaped pillars (e.g. round, square or polygonal and solid, hollow or slotted) that are formed on one of the die or supporting substrate and which can be urged into contact with various types of mating structures including other pillars, a deformable layer or a plurality of receptacles that are formed on the other of the die or supporting substrate, thereby forming a friction bond that holds the die to the supporting substrate. The attachment structure can further include an alignment structure for precise positioning of the die and supporting substrate to facilitate mounting the die to the supporting substrate. The attachment structure has applications for mounting semiconductor die containing a microelectromechanical (MEM) device, a microsensor or an integrated circuit (IC), and can be used to form a multichip module. The attachment structure is particularly useful for mounting die containing released MEM devices since these devices are fragile and can otherwise be damaged or degraded by adhesive or solder mounting.

  20. Surface strain engineering through Tb doping to study the pressure dependence of exciton-phonon coupling in ZnO nanoparticles

    SciTech Connect

    Sharma, A.; Dhar, S. Singh, B. P.; Nayak, C.; Bhattacharyya, D.; Jha, S. N.

    2013-12-07

    A compressive hydrostatic strain has been found to develop in the ZnO lattice as a result of accumulation of Tb ions on the surface of the nanoparticles for Tb mole-fraction less than 0.04. This hydrostatic strain can be controlled up to ≈14 GPa by varying the Tb mole-fraction. Here, we have utilized this novel technique of surface strain engineering through Tb doping for introducing hydrostatic compressive strain in the lattice to study the pressure dependent electronic and vibrational properties of ZnO nanoparticles. Our study reveals that when subjected to pressure, nanoparticles of ZnO behave quite differently than bulk in many aspects. Unlike bulk ZnO, which is reported to go through a wurtzite to rock-salt structural phase transition at ≈8 GPa, ZnO nanoparticles do not show such transition and remain in wurtzite phase even at 14 GPa of pressure. Furthermore, the Grüneisen parameters for the optical phonon modes are found to be order of magnitude smaller in ZnO nanoparticles as compared to bulk. Our study also suggests an increase of the dielectric constant with pressure, which is opposite to what has been reported for bulk ZnO. Interestingly, it has also been found that the exciton-phonon interaction depends strongly upon pressure in this system. The exciton-phonon coupling has been found to decrease as pressure increases. A variational technique has been adopted to theoretically calculate the exciton-LO phonon coupling coefficient in ZnO nanoparticles as a function of pressure, which shows a good agreement with the experimental results. These findings imply that surface engineering of ZnO nanoparticles with Tb could indeed be an efficient tool to enhance and control the optical performance of this material.

  1. A new apparatus for study of pressure-dependent laminar premixed flames with vacuum ultraviolet photoionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Zhou, Z. Y.; Wang, Y.; Tang, X. F.; Wu, W. H.; Qi, F.

    2013-01-01

    We report a home-made combustion apparatus for study of pressure-dependent laminar premixed flames with tunable vacuum ultraviolet photoionization mass spectrometry. The instrument consists of a flame chamber, a photoionization chamber with a single-stage sampling system, an ion transfer/storage system, and an orthogonal-acceleration reflectron time-of-flight mass spectrometer. Preliminary results of fuel-rich C2H4/O2/Ar flames at pressures of 30, 150, and 760 Torr have been obtained with this instrument. Compared to previous instruments [T. A. Cool, A. McIlroy, F. Qi, P. R. Westmoreland, L. Poisson, D. S. Peterka, and M. Ahmed, Rev. Sci. Instrum. 76, 094102 (2005), 10.1063/1.2010307; F. Qi, R. Yang, B. Yang, C. Q. Huang, L. X. Wei, J. Wang, L. S. Sheng, and Y. W. Zhang, Rev. Sci. Instrum. 77, 084101 (2006)], 10.1063/1.2234855, performances of the new apparatus have higher mass resolution (˜3500 at m/z = 40), better detection limit (<1 ppm), and broader dynamic range (better than 5 order of magnitude).

  2. Effects of high pressure-dependent leakoff and high process-zone stress in coal-stimulation treatments

    SciTech Connect

    Ramurthy, M.; Lyons, B.; Hendrickson, R.B.; Barree, R.D.; Magill, D.R.

    2009-08-15

    Hydraulic fracturing in coals has been studied extensively over the last two decades; however, there are factors that were often ignored or incorrectly diagnosed, resulting in screenouts. Assuming that a majority of the perforations are open and there are no problems with the stimulation fluids, screenouts during coal hydraulic-fracture treatments can be attributed to either high pressure-dependent leakoff (PDL), high process-zone stress (PZS) or in some cases both. The objective of this work is to discuss, help identify, and present solutions to address these reservoir-related issues such that screenouts can be avoided in optimized refracture treatments and new well stimulations. The tools for identifying these reservoir-related parameters include a diagnostic fracture-injection test (DFIT) and a grid-oriented fully functional 3D fracture simulator with shear decoupling. An example for each respective case is presented in this paper. In the first example, in which high PZS was considered to be the dominant reason for screenout or pressure out, the well was restimulated successfully by implementing the solutions presented in this paper. In the second example, in which high PDL was considered to be the main reason for screenout, there were several wells in the same project area that exhibited the same behavior resulting in screenouts. After implementing the solutions presented in this paper to address high PDL, all new wells were stimulated successfully without any issues.

  3. Pressure dependence of backbone chemical shifts in the model peptides Ac-Gly-Gly-Xxx-Ala-NH2.

    PubMed

    Erlach, Markus Beck; Koehler, Joerg; Crusca, Edson; Kremer, Werner; Munte, Claudia E; Kalbitzer, Hans Robert

    2016-06-01

    For a better understanding of nuclear magnetic resonance (NMR) detected pressure responses of folded as well as unstructured proteins the availability of data from well-defined model systems are indispensable. In this work we report the pressure dependence of chemical shifts of the backbone atoms (1)H(α), (13)C(α) and (13)C' in the protected tetrapeptides Ac-Gly-Gly-Xxx-Ala-NH2 (Xxx one of the 20 canonical amino acids). Contrary to expectation the chemical shifts of these nuclei have a nonlinear dependence on pressure in the range from 0.1 to 200 MPa. The polynomial pressure coefficients B 1 and B 2 are dependent on the type of amino acid studied. The coefficients of a given nucleus show significant linear correlations suggesting that the NMR observable pressure effects in the different amino acids have at least partly the same physical cause. In line with this observation the magnitude of the second order coefficients of nuclei being direct neighbors in the chemical structure are also weakly correlated. PMID:27335085

  4. Pressure dependence of the absolute rate constant for the reaction OH + C2H2 from 228 to 413K

    NASA Technical Reports Server (NTRS)

    Michael, J. V.; Nava, D. F.; Borokowski, R. P.; Payne, W. A.; Stief, L. J.

    1980-01-01

    The pressure dependence of absolute rate constants for the reaction of OH + C2H2 yields products has been examined at five temperatures ranging from 228 to 413 K. The experimental techniques which was used is flash photolysis-resonance fluoresence. OH was produced by water photolysis and hydroxyl resonance fluorescent photons were measured by multiscaling techniques. The results indicate that the low pressure bimolecular rate constant is 4 x 10 the the minus 13th power cu cm molecule (-1) s(-1) over the temperature range studied. A substantial increase in the bimolecular rate constant with an increase in pressure was observed at all temperatures except 228 K. This indicates the importance of initial adduct formation and subsequent stablization. The high pressure results are well represented by the Arrhenius expression (k sub bi) sub infinity = (6.83 + or - 1.19) x 10 to the minus 12th power exp(-646 + or - 47/T)cu cm molecule (-1) s(-1). The results are compared to previous investigated and are theoretically discussed. The implications of these results on modeling of terrestrial and planetary atmospheres and also in combustion chemistry are discussed.

  5. Pressure dependence of the absolute rate constant for the reaction Cl + C2H2 from 210-361 K

    NASA Technical Reports Server (NTRS)

    Brunning, J.; Stief, L. J.

    1985-01-01

    In recent years, considerable attention has been given to the role of chlorine compounds in the catalytic destruction of stratospheric ozone. However, while some reactions have been studied extensively, the kinetic data for the reaction of Cl with C2H2 is sparse with only three known determinations of the rate constant k3. The reactions involved are Cl + C2H2 yields reversibly ClC2H2(asterisk) (3a) and ClC2H2(asterisk) + M yields ClC2H2 + M (3b). In the present study, flash photolysis coupled with chlorine atomic resonance fluorescence have been employed to determine the pressure and temperature dependence of k3 with the third body M = Ar. Room temperature values are also reported for M = N2. The pressure dependence observed in the experiments confirms the expectation that the reaction involves addition of Cl to the unsaturated C2H2 molecule followed by collisional stabilization of the resulting adduct radical.

  6. Perils of Neglecting Lattice Relaxation in the Pressure Dependence of Deep Luminescence Bands in Wide Gap Semiconductors

    NASA Astrophysics Data System (ADS)

    Iota, V.; Weinstein, B. A.

    1998-03-01

    Deep defect states are often assumed to be insensitive to pressure because of their localized atomic-like character. In apparent conflict with this, experiments on widegap II-VI materials find that the pressure shifts of many 'midgap' photoluminescence (PL) bands associated with large-lattice-relaxation defects are more rapid than the shift of the bandgap(B. Weinstein, T. Ritter, et. al., Phys. Stat. Sol. (b) 198), 167 (1996). To study this, we measured the effects of pressure on the PL and PL-excitation (PLE) bands arising from the Zn-vacancy (V_Zn) and the P_Se deep acceptor centers in ZnSe. Using the observed pressure variation of the Stokes shifts and the established 1 atm. configuration coordinate (CC) models( D.Y. Jeon, H.P Gislason, G.D. Watkins, Phys. Rev. B 48), 7872 (1993), we were able to infer quantitative CC-diagrams at any pressure. Our results show that the pressure dependence of the lattice relaxation contributes a substantial fraction (several meV/kbar) to the overall shift of the PL-bands, and, hence, must be included. For the case of the V_Zn, simple calculations of the Jahn-Teller splitting using dangling-bond orbitals support this conclusion. figures

  7. Pressure dependent low temperature kinetics for CN + CH3CN: competition between chemical reaction and van der Waals complex formation.

    PubMed

    Sleiman, Chantal; González, Sergio; Klippenstein, Stephen J; Talbi, Dahbia; El Dib, Gisèle; Canosa, André

    2016-06-01

    The gas phase reaction between the CN radical and acetonitrile CH3CN was investigated experimentally, at low temperatures, with the CRESU apparatus and a slow flow reactor to explore the temperature dependence of its rate coefficient from 354 K down to 23 K. Whereas a standard Arrhenius behavior was found at T > 200 K, indicating the presence of an activation barrier, a dramatic increase in the rate coefficient by a factor of 130 was observed when the temperature was decreased from 168 to 123 K. The reaction was found to be pressure independent at 297 K unlike the experiments carried out at 52 and 132 K. The work was complemented by ab initio transition state theory based master equation calculations using reaction pathways investigated with highly accurate thermochemical protocols. The role of collisional stabilization of a CNCH3CN van der Waals complex and of tunneling induced H atom abstractions were also considered. The experimental pressure dependence at 52 and 132 K is well reproduced by the theoretical calculations provided that an anharmonic state density is considered for the van der Waals complex CH3CNCN and its Lennard-Jones radius is adjusted. Furthermore, these calculations indicate that the experimental observations correspond to the fall-off regime and that tunneling remains small in the low-pressure regime. Hence, the studied reaction is essentially an association process at very low temperature. Implications for the chemistry of interstellar clouds and Titan are discussed.

  8. Pressure dependence of backbone chemical shifts in the model peptides Ac-Gly-Gly-Xxx-Ala-NH2.

    PubMed

    Erlach, Markus Beck; Koehler, Joerg; Crusca, Edson; Kremer, Werner; Munte, Claudia E; Kalbitzer, Hans Robert

    2016-06-01

    For a better understanding of nuclear magnetic resonance (NMR) detected pressure responses of folded as well as unstructured proteins the availability of data from well-defined model systems are indispensable. In this work we report the pressure dependence of chemical shifts of the backbone atoms (1)H(α), (13)C(α) and (13)C' in the protected tetrapeptides Ac-Gly-Gly-Xxx-Ala-NH2 (Xxx one of the 20 canonical amino acids). Contrary to expectation the chemical shifts of these nuclei have a nonlinear dependence on pressure in the range from 0.1 to 200 MPa. The polynomial pressure coefficients B 1 and B 2 are dependent on the type of amino acid studied. The coefficients of a given nucleus show significant linear correlations suggesting that the NMR observable pressure effects in the different amino acids have at least partly the same physical cause. In line with this observation the magnitude of the second order coefficients of nuclei being direct neighbors in the chemical structure are also weakly correlated.

  9. Pressure dependent mechanical and thermodynamical properties of Hg0.91Mn0.09Te semiconductor

    NASA Astrophysics Data System (ADS)

    Varshney, D.; Sapkale, R.; Dagaonkar, G. J.; Varshney, M.

    2011-02-01

    The mechanical, thermodynamical and elastic properties of Hg0.91Mn0.09Te compound are calculated by formulating an effective interionic interaction potential. This potential consists of the long-range Coulomb, three body force parameter, the Hafemeister and Flygare type short-range overlap repulsion extended upto the second neighbor ions and the van der Waals (vdW) interaction. The estimated values of phase transition pressure have revealed reasonably good agreement with the available experimental data on the phase transition pressure P t = 11.5 GPa and the vast volume discontinuity in pressure-volume (PV) phase diagram indicate the structural phase transition from zincblende (B3) to rock salt (B1) structure. Later on, the Poisson's ratio ν, the ratio R S/B of S (Voigt averaged shear modulus) over B (bulk modulus), elastic anisotropy parameter, elastic wave velocity, average wave velocity and Debye temperature as functions of pressure is calculated. From Poisson's ratio and the ratio R S/B it is inferred that Hg0.91Mn0.09Te is brittle in nature in both B3 phase and B1 phase. To our knowledge this is the first quantitative theoretical prediction of the pressure dependence of ductile (brittle) nature of Hg0.91Mn0.09Te compounds and still awaits experimental confirmations.

  10. Pressure dependent low temperature kinetics for CN + CH3CN: competition between chemical reaction and van der Waals complex formation.

    PubMed

    Sleiman, Chantal; González, Sergio; Klippenstein, Stephen J; Talbi, Dahbia; El Dib, Gisèle; Canosa, André

    2016-06-01

    The gas phase reaction between the CN radical and acetonitrile CH3CN was investigated experimentally, at low temperatures, with the CRESU apparatus and a slow flow reactor to explore the temperature dependence of its rate coefficient from 354 K down to 23 K. Whereas a standard Arrhenius behavior was found at T > 200 K, indicating the presence of an activation barrier, a dramatic increase in the rate coefficient by a factor of 130 was observed when the temperature was decreased from 168 to 123 K. The reaction was found to be pressure independent at 297 K unlike the experiments carried out at 52 and 132 K. The work was complemented by ab initio transition state theory based master equation calculations using reaction pathways investigated with highly accurate thermochemical protocols. The role of collisional stabilization of a CNCH3CN van der Waals complex and of tunneling induced H atom abstractions were also considered. The experimental pressure dependence at 52 and 132 K is well reproduced by the theoretical calculations provided that an anharmonic state density is considered for the van der Waals complex CH3CNCN and its Lennard-Jones radius is adjusted. Furthermore, these calculations indicate that the experimental observations correspond to the fall-off regime and that tunneling remains small in the low-pressure regime. Hence, the studied reaction is essentially an association process at very low temperature. Implications for the chemistry of interstellar clouds and Titan are discussed. PMID:27199083

  11. Attachment and coercive sexual behavior.

    PubMed

    Smallbone, S W; Dadds, M R

    2000-01-01

    This study examined the relationships between childhood attachment and coercive sexual behavior. One hundred sixty-two male undergraduate students completed self-report measures of childhood maternal attachment, childhood paternal attachment, adult attachment, antisociality, aggression, and coercive sexual behavior. As predicted, insecure childhood attachment, especially insecure paternal attachment, was associated with antisociality, aggression, and coercive sexual behavior. Moreover, childhood attachment independently predicted coercive sexual behavior after antisociality and aggression were statistically controlled. The hypothesis that paternal avoidant attachment would predict coercive sexual behavior independently of its relationship with aggression and antisociality was also supported. Posthoc analysis indicated that maternal anxious attachment was associated with antisociality and that paternal avoidant attachment was associated with both antisociality and coercive sexual behavior. These results are consistent with criminological and psychological research linking adverse early family experiences with offending and lend support to an attachment-theoretical framework for understanding offending behavior in general and sexual offending behavior in particular.

  12. Autism and Attachment: The Attachment Q-Sort

    ERIC Educational Resources Information Center

    Rutgers, Anna H.; Van Ijzendoorn, Marinus H.; Bakermans-Kranenburg, Marian J.; Swinkels, Sophie H. N.

    2007-01-01

    Children with autism are able to show secure attachment behaviours to their parents/caregivers. Most studies on attachment in children with autism used a (modified) Strange Situation Procedure (SSP) to examine attachment security. An advantage of the Attachment Q-Sort (AQS) over the SSP is that it can be attuned to the secure-base behaviour of…

  13. Ceramic blade attachment system

    DOEpatents

    Boyd, G.L.

    1994-12-13

    A turbine blade having a preestablished rate of thermal expansion is attached to a turbine wheel having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine blade. The turbine blade has a root portion having a pair of recessed portions thereon. The turbine wheel includes a plurality of openings in which the turbine blade is positioned. Each of the openings have a pair of grooves therein in which are positioned a pair of pins having a generally rectangular cross-section and a reaction surface thereon. A pair of cylindrical rollers interposed respective ones of the pair of reaction surfaces and the pair of recessed portions. The attachment system or turbine assembly provides an economical, reliable and effective attachment of a component having a preestablished rate of thermal expansion to a component having a greater preestablished rate of thermal expansion. 3 figures.

  14. Ceramic blade attachment system

    DOEpatents

    Boyd, Gary L.

    1994-01-01

    A turbine blade having a preestablished rate of thermal expansion is attached to a turbine wheel having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine blade. The turbine blade has a root portion having a pair of recessed portions thereon. The turbine wheel includes a plurality of openings in which the turbine blade is positioned. Each of the openings have a pair of grooves therein in which are positioned a pair of pins having a generally rectangular cross-section and a reaction surface thereon. A pair of cylindrical rollers interposed respective ones of the pair of reaction surfaces and the pair of recessed portions. The attachment system or turbine assembly provides an economical, reliable and effective attachment of a component having a preestablished rate of thermal expansion to a component having a greater preestablished rate of thermal expansion.

  15. Magnetically attached sputter targets

    DOEpatents

    Makowiecki, D.M.; McKernan, M.A.

    1994-02-15

    An improved method and assembly for attaching sputtering targets to cathode assemblies of sputtering systems which includes a magnetically permeable material is described. The magnetically permeable material is imbedded in a target base that is brazed, welded, or soldered to the sputter target, or is mechanically retained in the target material. Target attachment to the cathode is achieved by virtue of the permanent magnets and/or the pole pieces in the cathode assembly that create magnetic flux lines adjacent to the backing plate, which strongly attract the magnetically permeable material in the target assembly. 11 figures.

  16. Magnetically attached sputter targets

    DOEpatents

    Makowiecki, Daniel M.; McKernan, Mark A.

    1994-01-01

    An improved method and assembly for attaching sputtering targets to cathode assemblies of sputtering systems which includes a magnetically permeable material. The magnetically permeable material is imbedded in a target base that is brazed, welded, or soldered to the sputter target, or is mechanically retained in the target material. Target attachment to the cathode is achieved by virtue of the permanent magnets and/or the pole pieces in the cathode assembly that create magnetic flux lines adjacent to the backing plate, which strongly attract the magnetically permeable material in the target assembly.

  17. Internal pipe attachment mechanism

    DOEpatents

    Bast, R.M.; Chesnut, D.A.; Henning, C.D.; Lennon, J.P.; Pastrnak, J.W.; Smith, J.A.

    1994-12-13

    An attachment mechanism is described for repairing or extending fluid carrying pipes, casings, conduits, etc. utilizing one-way motion of spring tempered fingers to provide a mechanical connection between the attachment mechanism and the pipe. The spring tempered fingers flex to permit insertion into a pipe to a desired insertion depth. The mechanical connection is accomplished by reversing the insertion motion and the mechanical leverage in the fingers forces them outwardly against the inner wall of the pipe. A seal is generated by crushing a sealing assembly by the action of setting the mechanical connection. 6 figures.

  18. Internal pipe attachment mechanism

    DOEpatents

    Bast, Richard M.; Chesnut, Dwayne A.; Henning, Carl D.; Lennon, Joseph P.; Pastrnak, John W.; Smith, Joseph A.

    1994-01-01

    An attachment mechanism for repairing or extending fluid carrying pipes, casings, conduits, etc. utilizing one-way motion of spring tempered fingers to provide a mechanical connection between the attachment mechanism and the pipe. The spring tempered fingers flex to permit insertion into a pipe to a desired insertion depth. The mechanical connection is accomplished by reversing the insertion motion and the mechanical leverage in the fingers forces them outwardly against the inner wall of the pipe. A seal is generated by crushing a sealing assembly by the action of setting the mechanical connection.

  19. Ladder attachment platform

    DOEpatents

    Swygert,; Richard, W [Springfield, SC

    2012-08-28

    A ladder attachment platform is provided that includes a base for attachment to a ladder that has first and second side rails and a plurality of rungs that extend between in a lateral direction. Also included is a user platform for having a user stand thereon that is carried by the base. The user platform may be positioned with respect to the ladder so that it is not located between a first plane that extends through the first side rail and is perpendicular to the lateral direction and a second plane that extends through the second side rail and is perpendicular to the lateral direction.

  20. Pressure-dependent seismic reflection amplitude changes in crystalline crust: lessons learned at the Continental Deep Drilling Site (KTB)

    NASA Astrophysics Data System (ADS)

    Beilecke, T.; Bram, K.; Buske, S.

    2010-01-01

    We conducted an active seismic experiment aimed at measuring changes in seismic reflection amplitudes as a consequence of fresh water injection and corresponding pressure changes at the German Continental Deep Drilling site (KTB). The injection took place at the bottom of the 4-km-deep pilot borehole in the SE2 fault zone in crystalline rock units between the springs of 2004 and 2005. Prior to the experiment, theoretical calculations indicated a possible increase in the compressional wave reflection coefficient as a result of an injection-induced reduction of the seismic velocities within the fault zone. Despite good repeatability of the emitted source signals, the experiment suffered from missing the clear reflection signals expected from the fault zone with regard to seismic data from past experiments. Applying various data-processing steps did not enhance the signals enough to obtain clear reflections or even pressure-dependent reflection amplitude changes. The signal-to-noise ratio remains smaller than the effects under observation. Provided that reflections are present in the data, the error bar of the recorded signals is of the order of 100 per cent. Therefore, we conclude that the experiment was not successful in seismically measuring pressure variations. However, important lessons for land seismic time-lapse measurements in crystalline environments have been learned: (i) The source should be capable of emitting frequencies below 30 Hz. (ii) The detector array setup proved to be partly questionable because in a scattering environment like the crystalline rocks at the KTB site, the incidence of a plane wave precondition might be violated for high-frequency signals. (iii) Near-surface variations of elastic properties likely influence seismic monitoring. (iv) Using a step function, that is a first-order pressure discontinuity, to model the subsurface pressure build-up, is very likely too simple an approach.

  1. Neurobiology of social attachments.

    PubMed

    Coria-Avila, Genaro A; Manzo, Jorge; Garcia, Luis I; Carrillo, Porfirio; Miquel, Marta; Pfaus, James G

    2014-06-01

    Many types of social attachments can be observed in nature. We discuss the neurobiology of two types (1) intraspecific (with a partner) and (2) parental (with the offspring). Stimuli related to copulation facilitate the first, whereas pregnancy, parturition and lactation facilitate the second. Both types develop as consequence of cohabitation. These events seem to stimulate similar neural pathways that increase (1) social recognition, (2) motivation, reward; and (3) decrease fear/anxiety. Subregions of the amygdala and cortex facilitate social recognition and also disinhibition to decrease rejection responses. The interrelationship between MeA, BNST, LS may mediate the activation of NAcc via the mPOA to increase motivation and reward. Cortical areas such as the ACC discriminate between stimuli. The interaction between OT and D2-type receptors in NAcc shell facilitates intraspecific attachment, but D1-type appears to facilitate parental attachment. This difference may be important for maternal females to direct their attention, motivation and expression of attachment toward the appropriate target. PMID:24769402

  2. Quick-attach clamp

    NASA Technical Reports Server (NTRS)

    Vano, A. E.

    1968-01-01

    Clamp of the slideable jaw type can be applied to moving lines such as cables or ropes. The clamp has a trigger-operated jaw that can be attached to a redrop parachute on a moving tow cable. The trigger mechanism maintains the jaws retracted in the housing until they are released for clamping.

  3. Attachment and Personality Disorders

    ERIC Educational Resources Information Center

    Sinha, Preeti; Sharan, Pratap

    2007-01-01

    Personality disorders (PDs) arise from core psychopathology of interpersonal relationships and understanding of self and others. The distorted representations of self and others, as well as unhealthy relationships that characterize persons with various PDs, indicate the possibility that persons with PDs have insecure attachment. Insecure…

  4. Pressure-dependent helix inversion of poly(quinoxaline-2,3-diyl)s containing chiral side chains in non-aqueous solvents.

    PubMed

    Nagata, Yuuya; Takeda, Ryohei; Suginome, Michinori

    2015-06-30

    Poly(quinoxaline-2,3-diyl)s with chiral (S)-2-butoxymethyl side chains dissolved in 1,2-dichloroethane experience a reversible pressure-dependent helix inversion from P- to M-helical structures between 0.1 MPa and 200 MPa.

  5. God attachment, mother attachment, and father attachment in early and middle adolescence.

    PubMed

    Sim, Tick Ngee; Yow, Amanda Shixian

    2011-06-01

    The present study examined the interplay of attachment to God, attachment to mother, and attachment to father with respect to adjustment (hope, self-esteem, depression) for 130 early and 106 middle adolescents in Singapore. Results showed that the parental attachments were generally linked (in expected directions) to adjustment. God attachment, however, had unique results. At the bivariate level, God attachment was only linked to early adolescents' self-esteem. When considered together with parental attachments (including interactions), God attachment did not emerge as the key moderator in attachment interactions and yielded some unexpected results (e.g., being positively linked to depression). These results are discussed viz-a-viz the secure base and safe haven functions that God and parental attachments may play during adolescence.

  6. Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV).

    PubMed

    Francés-Monerris, Antonio; Segarra-Martí, Javier; Merchán, Manuela; Roca-Sanjuán, Daniel

    2015-12-01

    Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N-H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N-H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π1 (-) and π2 (-) states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases.

  7. Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV)

    NASA Astrophysics Data System (ADS)

    Francés-Monerris, Antonio; Segarra-Martí, Javier; Merchán, Manuela; Roca-Sanjuán, Daniel

    2015-12-01

    Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N-H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N-H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π1- and π2- states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases.

  8. Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV)

    SciTech Connect

    Francés-Monerris, Antonio; Segarra-Martí, Javier; Merchán, Manuela; Roca-Sanjuán, Daniel

    2015-12-07

    Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N–H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N–H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π{sub 1}{sup −} and π{sub 2}{sup −} states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases.

  9. Turbine nozzle attachment system

    DOEpatents

    Norton, P.F.; Shaffer, J.E.

    1995-10-24

    A nozzle guide vane assembly having a preestablished rate of thermal expansion is positioned in a gas turbine engine and is attached to conventional metallic components. The nozzle guide vane assembly includes a pair of legs extending radially outwardly from an outer shroud and a pair of mounting legs extending radially inwardly from an inner shroud. Each of the pair of legs and mounting legs have a pair of holes therein. A plurality of members attached to the gas turbine engine have a plurality of bores therein which axially align with corresponding ones of the pair of holes in the legs. A plurality of pins are positioned within the corresponding holes and bores radially positioning the nozzle guide vane assembly about a central axis of the gas turbine engine. 3 figs.

  10. Turbine nozzle attachment system

    DOEpatents

    Norton, Paul F.; Shaffer, James E.

    1995-01-01

    A nozzle guide vane assembly having a preestablished rate of thermal expansion is positioned in a gas turbine engine and being attached to conventional metallic components. The nozzle guide vane assembly includes a pair of legs extending radially outwardly from an outer shroud and a pair of mounting legs extending radially inwardly from an inner shroud. Each of the pair of legs and mounting legs have a pair of holes therein. A plurality of members attached to the gas turbine engine have a plurality of bores therein which axially align with corresponding ones of the pair of holes in the legs. A plurality of pins are positioned within the corresponding holes and bores radially positioning the nozzle guide vane assembly about a central axis of the gas turbine engine.

  11. Leadership and attachment theory.

    PubMed

    Bresnahan, Christopher G; Mitroff, Ian I

    2007-09-01

    Comments on the six articles contained in the special issue of the American Psychologist (January 2007) devoted to leadership, written by W. Bennis; S. J. Zaccaro; V. H. Vroom and A. G. Yago; B. J. Avolio; R. J. Sternberg; and R. J. Hackman and R. Wageman. The current authors opine that the inclusion of attachment theory in the study of leadership could strengthen leadership theories as a whole.

  12. Computational and ESR studies of electron attachment to decafluorocyclopentane, octafluorocyclobutane, and hexafluorocyclopropane: electron affinities of the molecules and the structures of their stable negative ions as determined from 13C and 19F hyperfine coupling constants.

    PubMed

    ElSohly, Adel M; Tschumper, Gregory S; Crocombe, Richard A; Wang, Jih Tzong; Williams, Ffrancon

    2005-08-01

    High-resolution ESR spectra of the ground-state negative ions of hexafluorocyclopropane (c-C3F6*-), octafluorocyclobutane (c-C4F8*-), and decafluorocyclopentane (c-C5F10*-) are reported and their isotropic 19F hyperfine coupling constants (hfcc) of 198.6 +/- 0.4 G, 147.6 +/- 0.4 G, and 117.9 +/- 0.4 G, respectively, are in inverse ratio to the total number of fluorine atoms per anion. Together with the small value of 5.2 +/- 0.4 G determined for the isotropic 13C hfcc of c-C4F8*-, these results indicate that in each case the singly occupied molecular orbital (SOMO) is delocalized over the equivalent fluorines and possesses a nodal plane through the carbon atoms of a time-averaged D(nh) structure. A series of quantum chemical computations were carried out to further characterize these anions and their neutral counterparts. Both the B3LYP density functional and second-order Møller-Plesset perturbation theory (MP2) indicate that c-C3F6*- adopts a D(3h) geometry and a (2)A2'' ground electronic state, that c-C4F8*- adopts a D(4h) geometry and a (2)A2u ground electronic state, and that c-C5F10*- adopts a C(s) structure and a (2)A' electronic state. Moreover, the 19F hyperfine coupling constants computed with the MP2 method and a high quality triple-zeta basis set are within 1% of the experimental values. Also, the values computed for the 13C hfcc of c-C4F8*- are consistent with the experimental value of 5.2 G. Therefore, in keeping with the ESR results, these negative ions derived from first-row elements can be characterized as pi* species. In addition, the hypervalency of these perfluorocycloalkane radical anions has been clarified.

  13. Magnetic attachment mechanism

    NASA Technical Reports Server (NTRS)

    Wu, Mitchell B. (Inventor); Harwell, William D. (Inventor)

    1988-01-01

    A magnetic attachment mechanism adapted for interfacing with the manipulator arm of a remote manipulator system and comprising a pair of permanent magnets of rare earth material are arranged in a stator-rotor relationship. The rotor magnet is journalled for rotation about its longitudinal axis between pole plates of the stator magnet, each of which includes an adhering surface. In a first rotary position corresponding to the ON condition, each of the poles of the rotor magnet is closely adjacent to a stator magnet pole plate of like polarity whereby the respective magnet fields are additive for producing a strong magnetic field emanating from the adhering surfaces for attracting a ferrous magnetic plate, or the like, affixed to the payload. When the rotor magnet is rotated to a second position corresponding to the OFF condition, each of the poles of the rotor magnet is disposed closely adjacent to a pole plate of unlike polarity whereby the magnetic fields of the magnets are in cancelling relationship at the adhering surfaces, which permits the release of a payload. An actuator for selectively rotating the rotor magnet between the ON and OFF positions is provided for interfacing and connecting the magnetic attachment mechanism with a manipulator arm. For affecting an optimal rigidized attachment the payload is provided with guide means cooperable with guide means on the housing of the mechanism for directing adhering surfaces of the polar plates to the ferrous plate.

  14. Left-eigenstate completely renormalized equation-of-motion coupled-cluster methods: Review of key concepts, extension to excited states of open-shell systems, and comparison with electron-attached and ionized approaches

    NASA Astrophysics Data System (ADS)

    Piecuch, Piotr; Gour, Jeffrey R.; Włoch, Marta

    The recently proposed left-eigenstate completely renormalized (CR) coupled-cluster (CC) method with singles, doubles, and noniterative triples, termed CR-CC(2,3) Piecuch and Włoch, J Chem Phys, 2005, 123, 224105; Piecuch et al. Chem Phys Lett, 2006, 418, 467 and the companion CR-EOMCC(2,3) methodology, which has been previously applied to singlet excited states of closed-shell molecular systems Włoch et al. Mol Phys, 2006, 104, 2149 and in which relatively inexpensive noniterative corrections due to triple excitations derived from the biorthogonal method of moments of CC equations (MMCC) are added to the CC singles and doubles (CCSD) or equation-of-motion (EOM) CCSD energies, have been extended to excited states of open-shell species. The resulting highly efficient computer codes for the open-shell CR-EOMCC(2,3) approach exploiting the recursively generated intermediates and fast matrix multiplication routines have been developed and interfaced with the GAMESS package, enabling CR-EOMCC(2,3) calculations for singlet as well as nonsinglet ground and excited states of closed- and open-shell systems using the restricted Hartree-Fock or restricted open-shell Hartree-Fock references. A number of important mathematical and algorithmic details related to formal aspects and computer implementation of the CR-EOMCC(2,3) method have been discussed, in addition to overviewing the key concepts behind the CR-EOMCC(2,3) and biorthogonal MMCC methodologies for ground and excited states, and the numerical results involving low-lying states of the CH, CNC, C2N, N3, and NCO species, including states dominated by two-electron transitions, have been presented. The results of the CR-EOMCC(2,3) calculations have been compared with other CC/EOMCC approaches, including the EOMCCSD and EOMCC singles, doubles, and triples methods, and their full and active-space valence counterparts based on the electron-attached and ionized EOMCC methodologies, and the predecessor of CR-EOMCC(2,3) termed

  15. Kinetics following addition of sulfur fluorides to a weakly ionized plasma from 300 to 500 K: Rate constants and product determinations for ion-ion mutual neutralization and thermal electron attachment to SF{sub 5}, SF{sub 3}, and SF{sub 2}

    SciTech Connect

    Shuman, Nicholas S.; Miller, Thomas M.; Viggiano, A. A.; Hazari, Nilay; Luzik, Eddie D. Jr.

    2010-12-21

    Rate constants for several processes including electron attachment to SF{sub 2}, SF{sub 3}, and SF{sub 5} and individual product channels of ion-ion mutual neutralization between SF{sub 6}{sup -}, SF{sub 5}{sup -}, and SF{sub 4}{sup -} with Ar{sup +} were determined by variable electron and neutral density attachment mass spectrometry. The experiments were conducted with a series of related neutral precursors (SF{sub 6}, SF{sub 4}, SF{sub 5}Cl, SF{sub 5}C{sub 6}H{sub 5}, and SF{sub 3}C{sub 6}F{sub 5}) over a temperature range of 300-500 K. Mutual neutralization rate constants for SF{sub 6}{sup -}, SF{sub 5}{sup -}, and SF{sub 4}{sup -} with Ar{sup +} are reported with uncertainties of 10-25% and show temperature dependencies in agreement with the theoretical value of T{sup -0.5}. Product branching in the mutual neutralizations is temperature independent and dependent on the electron binding energy of the anion. A larger fraction of product neutrals from the SF{sub 6}{sup -} mutual neutralization (0.9 {+-}0.1) are dissociated than in the SF{sub 5}{sup -} mutual neutralization (0.65 {+-} 0.2), with the SF{sub 4}{sup -} (0.7 {+-} 0.3) likely lying in between. Electron attachment to SF{sub 5} (k= 2.0 x 10{sup -8} {+-}{sub 1}{sup 2} cm{sup 3} s{sup -1} at 300 K) and SF{sub 3} (4 {+-} 3 x 10{sup -9} cm{sup 3} s{sup -1} at 300 K) show little temperature dependence. Rate constants of electron attachment to closed-shell SF{sub n} species decrease as the complexity of the neutral decreases.

  16. Adopting Children with Attachment Problems.

    ERIC Educational Resources Information Center

    Hughes, Daniel A.

    1999-01-01

    Notes that attachment behavior in infants is a facet of normal child development, and that children with attachment problems require special attention during and after the adoption process. Presents actions needed to increase the probability that such children can be successfully adopted, detailed attachment patterns, and parenting strategies and…

  17. Understanding Attachment: Beliefs about Conflict.

    ERIC Educational Resources Information Center

    Pistole, M. Carole; Arricale, Frank

    2003-01-01

    Examines attachment prototype, attachment-related feelings about conflict, style of expressing conflict, and conflict tactics using self-report questionnaires from 188 volunteer college students. Analysis indicated that persons who endorsed secure attachment reported feeling less threat from arguing; persons endorsing dismissing attachment…

  18. Attachment and Relationships: Beyond Parenting.

    ERIC Educational Resources Information Center

    Honig, Alice Sterling

    Using a question-answer format, this paper examines the concept of attachment and its importance for parents and caregivers of young children. Twenty topics are addressed through an examination of relevant theory, research findings, and clinical evidence: (1) a "who's who" list of researchers on attachment; (2) definition of attachment; (3)…

  19. Attachment: Theoretical Development and Critique

    ERIC Educational Resources Information Center

    Slater, Ruth

    2007-01-01

    Zeanah argues that ethological attachment theory, as outlined by John Bowlby, has provided one of the most important frameworks for understanding crucial risk and protective factors in social and emotional development. However, although attachment theory and the notion of attachment disorders have influenced such initiatives, many psychologists,…

  20. Attachment Theory: Retrospect and Prospect.

    ERIC Educational Resources Information Center

    Bretherton, Inge

    1985-01-01

    Provides overview of attachment theory as parented by John Bowlby in "Attachment and Loss". Uses two major concepts from this work to interpret refinements and elaborations of attachment theory attibuted to Mary Ainsworth. Considers how recent insights into development of socioemotional understanding and development of event representation can be…

  1. Electron attachment to MoF{sub 6}, ReF{sub 6}, and WF{sub 6}; reaction of MoF{sub 6}{sup -} with ReF{sub 6} and reaction of Ar{sup +} with MoF{sub 6}

    SciTech Connect

    Friedman, Jeffrey F.; Stevens, Amy E.; Miller, Thomas M.; Viggiano, A.A.

    2006-06-14

    Rate constants were measured for electron attachment to MoF{sub 6}, ReF{sub 6}, and WF{sub 6} in 133 Pa of helium gas using a flowing-afterglow Langmuir-probe apparatus. The experiment is a thorny one because the molecules tend to form oxide impurities on feedline surfaces and because of thermal decomposition of MoF{sub 6} on surfaces as the gas temperature is increased. The electron attachment rate constant for MoF{sub 6} is (2.3{+-}0.8)x10{sup -9} cm{sup 3} s{sup -1} at 297 K; only MoF{sub 6}{sup -} is formed in the temperature range of 297-385 K. The rate constant increases with temperature up to the point where decomposition becomes apparent. Electron attachment to ReF{sub 6} occurs with a rate constant of (2.4{+-}0.8)x10{sup -9} cm{sup 3} s{sup -1} at 297 K; only ReF{sub 6}{sup -} is produced. MoF{sub 6}{sup -} reacts with ReF{sub 6} to form ReF{sub 6}{sup -} on essentially every collision, showing definitively that the electron affinity of ReF{sub 6} is greater than that of MoF{sub 6}. A rate constant of (5.0{+-}1.3)x10{sup -10} cm{sup 3} s{sup -1} was measured for this ion-molecule reaction at 304 K. The reverse reaction is not observed. The reaction of Ar{sup +} with MoF{sub 6} was found to produce MoF{sub 5}{sup +}+F, with a rate constant of (1.8{+-}0.5)x10{sup -9} cm{sup 3} s{sup -1}. WF{sub 6} attaches electrons so slowly at room temperature that the attachment rate was below detection level ({<=}10{sup -12} cm{sup 3} s{sup -1}). By 552 K, the attachment rate constant reaches a value of (2{+-}1)x10{sup -10} cm{sup 3} s{sup -1}.

  2. Unusual properties of high-compliance porosity extracted from measurements of pressure-dependent wave velocities in rocks

    NASA Astrophysics Data System (ADS)

    Zaitsev, Vladimir Y.; Radostin, Andrey V.; Pasternak, Elena; Dyskin, Arcady

    2016-04-01

    Conventionally the interpretation of wave velocities and their variations under load is conducted assuming that closable cracks have simple planar shapes, like the popular model of penny-shape cracks. For such cracks, the proportion between complementary variations in different elastic parameters of rocks (such as S- and P-wave velocities) is strictly pre-determined, in particular, it is independent of the crack aspect ratio and rather weakly dependent on the Poisson's ratio of the intact rock. Real rocks, however, contain multitude of cracks of different geometry. Faces of such cracks can exhibit complex modes of interaction when closed by external load, which may result in very different ratios between normal- and shear compliances of such defects. In order to describe the reduction of different elastic moduli, we propose a model in which the compliances of crack-like defects are explicitly decoupled and are not predetermined, so that the ratio q between total normal- and shear- compliances imparted to the rock mass (as well as individual values of these compliances) can be estimated from experimental data on reduction of different elastic moduli (e.g., pressure dependences of P- and S-wave velocities). Physically, the so-extracted ratio q can be interpreted as intrinsic property of individual crack-like defects similar to each other, or as a characteristic of proportion between concentrations of pure normal cracks with very large q and pure shear cracks with q→0. The latter case can correspond, e.g., to saturated cracks in which weakly-compressible liquid prevents crack closing under normal loading. It can be shown that for conventional dry planar cracks, the compliance ratio is q ˜2. The developed model applied to the data on wave-velocity variations with external pressure indicates that elastic properties of the real crack-like defects in rocks can differ considerably from the usually assumed ones. Comparison with experimental data on variations P- and S

  3. Magnetic attachment mechanism

    NASA Technical Reports Server (NTRS)

    Harwell, William D. (Inventor); Wu, Mitchell B. (Inventor)

    1990-01-01

    A magnetic attachment mechanism adapted for interfacing with the manipulator arm (11) of a remote manipulator system and comprising a pair of permanent magnets (31,32) of rare earth material which are arranged in a stator-rotor relationship. The rotor magnet (32), is journalled for rotation about its longitudinal axis between pole plates (35,36) of the stator magnet (31), each of which includes an adhering surface (35a,36a). In a first rotary position corresponding to the ON condition, each of the poles of the rotor magnet (32) is closely adjacent a stator magnet pole plate of like polarity whereby the respective magnet fields are additive for producing a strong magnetic field emanating from the adhering surfaces (35a,36a) for attracting a ferrous magnetic plate 20, or the like, affixed to the payload (20 or 50). When the rotor magnet (32) is rotated to a second position corresponding to the OFF condition, each of the poles of the rotor magnet (31) is disposed closely adjacent a pole plate of unlike polarity whereby the magnetic fields of the magnets are in cancelling relationship at the adhering surfaces (35a,36a) which permits the release of a payload. An actuator (51 or 70) for selectively rotating the rotor magnet (32) between the ON and OFF positions is provided for interfacing and connecting the magnetic attachment mechanism with a manipulator arm. For effecting an optimal rigidized attachment the payload is provided with guides (91,92) cooperable with guides (96,16,17) on the housing of the mechanism for directing adhering surfaces (35a,36a) of the polar plates to the ferrous plate (20).

  4. Space Station attached payloads

    NASA Technical Reports Server (NTRS)

    Clark, Lenwood G.

    1990-01-01

    The Space Station Freedom is being designed and developed with user requirements being used to shape the configuration. Plans include accommodation provisions for a wide variety of attached payloads including the Earth sciences research activities which are the focus of this conference. The station program is even beginning some preliminary payload manifesting which involves planning for accommodation of payload during the station's assembly flights. Potential payload organizations should be aware of the station's plans for payload accommodations so as to guide their own payload activities for future space station use.

  5. Flared tube attachment fitting

    NASA Technical Reports Server (NTRS)

    Alkire, I. D.; King, J. P., Jr.

    1980-01-01

    Tubes can be flared first, then attached to valves and other flow line components, with new fitting that can be disassembled and reused. Installed fitting can be disassembled so parts can be inspected. It can be salvaged and reused without damaging flared tube; tube can be coated, tempered, or otherwise treated after it has been flared, rather than before, as was previously required. Fitting consists of threaded male portion with conical seating surface, hexagonal nut with hole larger than other diameter of flared end of tube, and split ferrule.

  6. Anomalous pressure dependence of magnetic ordering temperature in Tb revealed by resistivity measurements to 141 GPa. Comparison with Gd and Dy

    SciTech Connect

    Lim, J.; Fabbris, G.; Haskel, D.; Schilling, J. S.

    2015-05-26

    In previous studies the pressure dependence of the magnetic ordering temperature To of Dy was found to exhibit a sharp increase above its volume collapse pressure of 73 GPa, appearing to reach temperatures well above ambient at 157 GPa. In a search for a second such lanthanide, electrical resistivity measurements were carried out on neighboring Tb to 141 GPa over the temperature range 3.8 - 295 K. Below Tb’s volume collapse pressure of 53 GPa, the pressure dependence To(P) mirrors that of both Dy and Gd. However, at higher pressures To(P) for Tb becomes highly anomalous. This result, together with the very strong suppression of superconductivity by dilute Tb ions in Y, suggests that extreme pressure transports Tb into an unconventional magnetic state with an anomalously high magnetic ordering temperature.

  7. Anomalous pressure dependence of magnetic ordering temperature in Tb revealed by resistivity measurements to 141 GPa. Comparison with Gd and Dy

    DOE PAGES

    Lim, J.; Fabbris, G.; Haskel, D.; Schilling, J. S.

    2015-05-26

    In previous studies the pressure dependence of the magnetic ordering temperature To of Dy was found to exhibit a sharp increase above its volume collapse pressure of 73 GPa, appearing to reach temperatures well above ambient at 157 GPa. In a search for a second such lanthanide, electrical resistivity measurements were carried out on neighboring Tb to 141 GPa over the temperature range 3.8 - 295 K. Below Tb’s volume collapse pressure of 53 GPa, the pressure dependence To(P) mirrors that of both Dy and Gd. However, at higher pressures To(P) for Tb becomes highly anomalous. This result, together withmore » the very strong suppression of superconductivity by dilute Tb ions in Y, suggests that extreme pressure transports Tb into an unconventional magnetic state with an anomalously high magnetic ordering temperature.« less

  8. Ceramic blade attachment system

    DOEpatents

    Frey, G.A.; Jimenez, O.D.

    1996-12-03

    A turbine blade having a preestablished rate of thermal expansion is attached to a turbine flange having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine blade. The turbine flange includes a first upstanding flange and a second upstanding flange having a groove formed between them. The turbine flange further includes a recess. Each of the first and second upstanding flanges have a plurality of bores therein. A turbine blade has a first member and a second member positioned in one of the groove and the recess. Each of the first member and the second member have a plurality of bores therein. A pin is positioned in respective ones of the plurality of bores in the first and second upstanding members and the first and second members and attach the blade to the turbine flange. The pin has a preestablished rate of thermal expansion being substantially equal to the rate of thermal expansion of the blade. 4 figs.

  9. Ceramic blade attachment system

    DOEpatents

    Frey, deceased, Gary A.; Jimenez, Oscar D.

    1996-01-01

    A turbine blade having a preestablished rate of thermal expansion is attached to a turbine flange having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine blade. The turbine flange includes a first upstanding flange and a second upstanding flange having a groove formed therebetween. The turbine flange further includes a recess. Each of the first and second upstanding flanges have a plurality of bores therein. A turbine blade has a first member and a second member positioned in one of the groove and the recess. Each of the first member and the second member have a plurality of bores therein. And, a pin is positioned in respective ones of the plurality of bores in the first and second upstanding members and the first and second members and attach the blade to the turbine flange. The pin has a preestablished rate of thermal expansion being substantially equal to the rate of thermal expansion of the blade.

  10. Attachment of Thiobacillus thiooxidans to sulfur crystals.

    PubMed

    SCHAEFFER, W I; HOLBERT, P E; UMBREIT, W W

    1963-01-01

    Schaeffer, W. I. (Rutgers, The State University, New Brunswick, N.J.), P. E. Holbert, and W. W. Umbreit. Attachment of Thiobacillus thiooxidans to sulfur crystals. J. Bacteriol. 85:137-140. 1963.-Electron micrographs of replicas of sulfur crystals before and after attack by Thiobacillus thiooxidans show that the microorganisms erode the crystal in the area immediately adjacent to the cell. When there are many cells, the entire crystal surface appears eroded.

  11. Ceramic blade attachment system

    DOEpatents

    Shaffer, J.E.

    1995-07-11

    A turbine blade having a preestablished rate of thermal expansion is attached to a turbine disc having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine blade and forms a turbine assembly. The turbine blade has a root portion defining a pair of sides having a pair of grooves therein. The turbine assembly includes a pair of flanges between which the turbine blades are positioned. Each of the pair of flanges has a plurality of grooves defined therein. The grooves within the pair of flanges are aligned with the grooves in the blades and have a space formed therebetween. A plurality of spherical balls are positioned within the space. The plurality of spherical balls has a preestablished rate of thermal expansion being equal to the preestablished rate of thermal expansion of the turbine blade. 4 figs.

  12. Ceramic blade attachment system

    DOEpatents

    Shaffer, James E.

    1995-01-01

    A turbine blade having a preestablished rate of thermal expansion is attached to a turbine disc having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine blade and forms a turbine assembly. The turbine blade has a root portion defining a pair of sides having a pair of grooves therein. The turbine assembly includes a pair of flanges between which the turbine blades are positioned. Each of the pair of flanges has a plurality of grooves defined therein. The grooves within the pair of flanges are aligned with the grooves in the blades and have a space formed therebetween. A plurality of spherical balls are positioned within the space. The plurality of spherical balls has a preestablished rate of thermal expansion being equal to the preestablished rate of thermal expansion of the turbine blade.

  13. Ceramic blade attachment system

    DOEpatents

    Shaffer, James E.

    1995-01-01

    A turbine blade having a preestablished rate of thermal expansion is attached to a turbine wheel having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine blade. The turbine blade has a root portion having a first groove and a second groove therein. The turbine wheel includes a plurality of openings in which the turbine blade is positioned. Each of the openings has a first groove and a second groove therein. The space or void formed between the first grooves and the second grooves has a plurality of spherical balls positioned therein. The plurality of spherical balls has a preestablished rate of thermal expansion being equal to the preestablished rate of thermal expansion of the turbine blade.

  14. Ceramic blade attachment system

    DOEpatents

    Shaffer, J.E.

    1995-01-10

    A turbine blade having a preestablished rate of thermal expansion is attached to a turbine wheel having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine blade. The turbine blade has a root portion having a first groove and a second groove therein. The turbine wheel includes a plurality of openings in which the turbine blade is positioned. Each of the openings has a first groove and a second groove therein. The space or void formed between the first grooves and the second grooves has a plurality of spherical balls positioned therein. The plurality of spherical balls has a preestablished rate of thermal expansion being equal to the preestablished rate of thermal expansion of the turbine blade. 4 figures.

  15. An attachment perspective on psychopathology

    PubMed Central

    MIKULINCER, MARIO; SHAVER, PHILIP R.

    2012-01-01

    In recent years, attachment theory, which was originally formulated to describe and explain infant-parent emotional bonding, has been applied to the study of adolescent and adult romantic relationships and then to the study of psychological processes, such as interpersonal functioning, emotion regulation, coping with stress, and mental health. In this paper, we offer a brief overview of the attachment perspective on psychopathology. Following a brief account of attachment theory, we go on to explain how the study of individual differences in adult attachment intersects with the study of psychopathology. Specifically, we review research findings showing that attachment insecurity is a major contributor to mental disorders, and that the enhancement of attachment security can facilitate amelioration of psychopathology. PMID:22294997

  16. Borderline disorder and attachment pathology.

    PubMed

    West, M; Keller, A; Links, P; Patrick, J

    1993-02-01

    In this paper, the authors investigate the theoretical and empirical association between dysfunctions of the attachment system and borderline personality disorder. Attachment theory focuses on the maintenance of a sense of safety and security through a close personal relationship with a particular person. Based on a biological behavioural system, functional attachment relationships in adulthood rely on experiences and expectations of security within the relationship. These issues are also important to the definition and dynamics of borderline personality disorder. The dimensions and patterns of reciprocal attachment were compared with other scales measuring components of psychopathology and interpersonal relationships. In a sample of 85 female outpatients, only four of the attachment scales--feared loss, secure base, compulsive care-seeking and angry withdrawal--identified patients with high scores on a measure of borderline disorder. Of these four scales, feared loss had the predominant effect. These empirical results support the hypothesized relationship between dysfunctions of the attachment system and borderline disorder.

  17. Pressure-dependent studies of the DX centre in Si- and Sn-doped n +GaAs

    NASA Astrophysics Data System (ADS)

    Portal, J. C.; Maude, D. K.; Foster, T. J.; Eaves, L.; Dmowski, L.; Nathan, M.; Heiblum, M.; Harris, J. J.; Beall, R. B.; Simmonds, P. E.

    Shubnikov-de Haas and persistent photoconductivity measurements are used to study the effect of hydrostatic pressure on the free electron concentration, mobility, and the occupancy of the DX centre in MBE grown n +GaAs heavily doped with either Si or Sn. The results show that the DX centre produces a resonant donor level between the Γ- and L- conduction band minima at a concentration comparable with the doping level. The position and occupancy of the DX centre are calculated using Fermi-Dirac statistics. For the Si-doped samples comparison with local vibrational mode measurements indicate that the DX level can be identified with Si Ga.

  18. Electromagnetic attachment mechanism

    NASA Technical Reports Server (NTRS)

    Monford, Leo G., Jr. (Inventor)

    1992-01-01

    An electromagnetic attachment mechanism is disclosed for use as an end effector of a remote manipulator system. A pair of electromagnets, each with a U-shaped magnetic core with a pull-in coil and two holding coils, are mounted by a spring suspension system on a base plate of the mechanism housing with end pole pieces adapted to move through openings in the base plate when the attractive force of the electromagnets is exerted on a strike plate of a grapple fixture affixed to a target object. The pole pieces are spaced by an air gap from the strike plate when the mechanism first contacts the grapple fixture. An individual control circuit and power source is provided for the pull-in coil and one holding coil of each electromagnet. A back-up control circuit connected to the two power sources and a third power source is provided for the remaining holding coils. When energized, the pull-in coils overcome the suspension system and air gap and are automatically de-energized when the pole pieces move to grapple and impose a preload force across the grapple interface. A battery backup is a redundant power source for each electromagnet in each individual control circuit and is automatically connected upon failure of the primary source. A centerline mounted camera and video monitor are used in cooperation with a target pattern on the reflective surface of the strike plate to effect targeting and alignment.

  19. α-β Transition in Quartz: Temperature and Pressure Dependence of the Thermodynamic Quantities for β-Quartz and β-Cristobalite as Piezoelectric Materials

    NASA Astrophysics Data System (ADS)

    Lider, M. C.; Yurtseven, H.

    2014-12-01

    Temperature and pressure dependencies of the thermal expansivity (αp), isothermal compressibility (κT) and the specific heat (Cp - Cv) are studied for piezoelectric materials, in particular, for β-quartz. By analyzing the temperature (at 1 atm) and pressure (at 848 K) dependence of the observed volume V from the literature, the thermodynamic functions (αp, κT and Cp - Cv) are obtained and the Pippard relations (Cp - Cv vs. Vαp and αp vs. κT) close to the transition from the β-quartz to the β-cristobalite are examined.

  20. Pressure dependence of the irreversibility line in Bi2Sr2CaCu2O(8+delta): role of anisotropy in flux-line formation

    PubMed

    Raphael; Reeves; Skelton; Kendziora

    2000-02-14

    One of the important problems of high-temperature superconductivity is to understand and ultimately to control fluxoid motion. Here we present data on the pressure dependence of the irreversibility line measured up to 2.5 GPa. We observe that the application of pressure changes the interplanar coupling by decreasing the c-axis length, without significantly disturbing the intraplanar superconductivity. Our results directly show the relationship between lattice spacing and the irreversibility line in Bi(2)Sr(2)CaCu(2)O(8+delta), and demonstrate the potential for a dramatic reduction in the flux motion.

  1. Diode laser detection of greenhouse gases in the near-infrared region by wavelength modulation spectroscopy: pressure dependence of the detection sensitivity.

    PubMed

    Asakawa, Takashi; Kanno, Nozomu; Tonokura, Kenichi

    2010-01-01

    We have investigated the pressure dependence of the detection sensitivity of CO(2), N(2)O and CH(4) using wavelength modulation spectroscopy (WMS) with distributed feed-back diode lasers in the near infrared region. The spectral line shapes and the background noise of the second harmonics (2f) detection of the WMS were analyzed theoretically. We determined the optimum pressure conditions in the detection of CO(2), N(2)O and CH(4), by taking into consideration the background noise in the WMS. At the optimum total pressure for the detection of CO(2), N(2)O and CH(4), the limits of detection in the present system were determined.

  2. Pressure dependence of harmonic and an harmonic lattice dynamics in MgO: A first-principles calculation and implications for lattice thermal conductivity

    SciTech Connect

    Tang, Xiaoli; Dong, Jianjun

    2009-06-01

    We report a recent first-principles calculation of harmonic and anharmonic lattice dynamics of MgO. The 2nd order harmonic and 3rd order anharmonic interatomic interaction terms are computed explicitly, and their pressure dependences are discussed. The phonon mode Grueneisen parameters derived based on our calculated 3rd order lattice anharmonicity are in good agreement with those estimated using the finite difference method. The implications for lattice thermal conductivity at high pressure are discussed based on a simple kinetic transport theory.

  3. Attachment and adolescent psychosocial functioning.

    PubMed

    Allen, J P; Moore, C; Kuperminc, G; Bell, K

    1998-10-01

    To explore the meaning and function of attachment organization during adolescence, its relation to multiple domains of psychosocial functioning was examined in a sample of 131 moderately at-risk adolescents. Attachment organization was assessed using the Adult Attachment Interview; multiple measures of functioning were obtained from parents, adolescents, and their peers. Security displayed in adolescents' organization of discourse about attachment experiences was related to competence with peers (as reported by peers), lower levels of internalizing behaviors (as reported by adolescents), and lower levels of deviant behavior (as reported by peers and by mothers). Preoccupation with attachment experiences, seen in angry or diffuse and unfocused discussion of attachment experiences, was linked to higher levels of both internalizing and deviant behaviors. These relations generally remained even when other attachment-related constructs that had been previously related to adolescent functioning were covaried in analysis. Results are interpreted as suggesting an important role for attachment organization in a wide array of aspects of adolescent psychosocial development. PMID:9839424

  4. The Legacy of Early Attachments.

    ERIC Educational Resources Information Center

    Thompson, Ross A.

    2000-01-01

    Evaluates what has been learned regarding the impact of early close relationships on psychological development, by examining the origins of continuity and change in attachment security and its prediction of later behavior. Evaluates research on impact of changing family circumstances and quality of care on attachment security. Offers new…

  5. The legacy of early attachments.

    PubMed

    Thompson, R A

    2000-01-01

    The impact of early close relationships on psychological development is one of the enduring questions of developmental psychology that is addressed by attachment theory and research. This essay evaluates what has been learned, and offers ideas for future research, by examining the origins of continuity and change in the security of attachment early in life, and its prediction of later behavior. The discussion evaluates research on the impact of changing family circumstances and quality of care on changes in attachment security, and offers new hypotheses for future study. Considering the representations (or internal working models) associated with attachment security as developing representations, the discussion proposes that (1) attachment security may be developmentally most influential when the working models with which it is associated have sufficiently matured to influence other emerging features of psychosocial functioning; (2) changes in attachment security are more likely during periods of representational advance; and (3) parent-child discourse and other relational influences shape these developing representations after infancy. Finally, other features of early parent-child relationships that develop concurrently with attachment security, including negotiating conflict and establishing cooperation, also must be considered in understanding the legacy of early attachments.

  6. Ultra-sensitive pressure dependence of bandgap of rutile-GeO{sub 2} revealed by many body perturbation theory

    SciTech Connect

    Samanta, Atanu; Singh, Abhishek K.; Jain, Manish

    2015-08-14

    The reported values of bandgap of rutile GeO{sub 2} calculated by the standard density functional theory within local-density approximation (LDA)/generalized gradient approximation (GGA) show a wide variation (∼2 eV), whose origin remains unresolved. Here, we investigate the reasons for this variation by studying the electronic structure of rutile-GeO{sub 2} using many-body perturbation theory within the GW framework. The bandgap as well as valence bandwidth at Γ-point of rutile phase shows a strong dependence on volume change, which is independent of bandgap underestimation problem of LDA/GGA. This strong dependence originates from a change in hybridization among O-p and Ge-(s and p) orbitals. Furthermore, the parabolic nature of first conduction band along X-Γ-M direction changes towards a linear dispersion with volume expansion.

  7. Attachment behaviors in autistic children.

    PubMed

    Sigman, M; Ungerer, J A

    1984-09-01

    The social behaviors of 14 autistic children and 14 normal children of equivalent mental age were observed during a free-play situation as well as during separation from and reunion with their mothers and a stranger. As a group, the autistic children showed evidence of attachment to their mothers, directing more social behaviors and more physical contact to their caregivers than to the stranger during the reunion episodes. Within the autistic group, the children who showed an increase in attachment behaviors in response to separation and reunion demonstrated more advanced symbolic play skills than those autistic children who showed no change in attachment behaviors. One possible explanation may be that autistic children require more advanced levels of symbolic ability to form attachments to others than is necessary for the development of attachments in normal children.

  8. On the exploitation of Armstrong-Frederik type nonlinear kinematic hardening in the numerical integration and finite-element implementation of pressure dependent plasticity models

    NASA Astrophysics Data System (ADS)

    Metzger, Mario; Seifert, Thomas

    2013-09-01

    In this paper, an unconditionally stable algorithm for the numerical integration and finite-element implementation of a class of pressure dependent plasticity models with nonlinear isotropic and kinematic hardening is presented. Existing algorithms are improved in the sense that the number of equations to be solved iteratively is significantly reduced. This is achieved by exploitation of the structure of Armstrong-Frederik-type kinematic hardening laws. The consistent material tangent is derived analytically and compared to the numerically computed tangent in order to validate the implementation. The performance of the new algorithm is compared to an existing one that does not consider the possibility of reducing the number of unknowns to be iterated. The algorithm is used to implement a time and temperature dependent cast iron plasticity model, which is based on the pressure dependent Gurson model, in the finite-element program ABAQUS. The implementation is applied to compute stresses and strains in a large-scale finite-element model of a three cylinder engine block. This computation proofs the applicability of the algorithm in industrial practice that is of interest in applied sciences.

  9. Pressure dependency of localization degree in heavy fermion CeIn3: A density functional theory analysis

    PubMed Central

    Yazdani-Kachoei, M.; Jalali-Asadabadi, S.; Ahmad, Iftikhar; Zarringhalam, Kourosh

    2016-01-01

    Two dramatic discrepancies between previous reliable experimental and ab initio DFT results are identified to occur at two different pressures in CeIn3, as discussed through the paper. We physically discuss sources of the phenomena and indicate how to select an appropriate functional for a given pressure. We show that these discrepancies are due to the inaccuracy of the DFT + U scheme with arbitrary Ueff and that hybrid functionals can provide better agreement with experimental data at zero pressure. The hybrid B3PW91 approach provides much better agreement with experimental data than the GGA + U. The DFT + U scheme proves to be rather unreliable since it yields completely unpredictable oscillations for the bulk modulus with increasing values of Ueff. Our B3PW91 results show that the best lattice parameter (bulk modulus) is obtained using a larger value of α parameter, 0.4 (0.3 or 0.2), than that of usually considered for the AFM phase. We find that for hybrid functionals, the amount of non-local exchange must first be calibrated before conclusions are drawn. Therefore, we first systematically optimize the α parameter and using it investigate the magnetic and electronic properties of the system. We present a theoretical interpretation of the experimental results and reproduce them satisfactorily. PMID:27553428

  10. Osmotic pressure-dependent release profiles of payloads from nanocontainers by co-encapsulation of simple salts

    NASA Astrophysics Data System (ADS)

    Behzadi, Shahed; Rosenauer, Christine; Kappl, Michael; Mohr, Kristin; Landfester, Katharina; Crespy, Daniel

    2016-06-01

    The encapsulation of payloads in micro- to nano-scale capsules allows protection of the payload from the surrounding environment and control of its release profile. Herein, we program the release of hydrophilic payloads from nanocontainers by co-encapsulating simple inorganic salts for adjusting the osmotic pressure. The latter either leads to a burst release at high concentrations of co-encapsulated salts or a sustained release at lower concentrations. Osmotic pressure causes swelling of the nanocapsule's shell and therefore sustained release profiles can be adjusted by crosslinking it. The approach presented allows for programing the release of payloads by co-encapsulating inexpensive salts inside nanocontainers without the help of stimuli-responsive materials.The encapsulation of payloads in micro- to nano-scale capsules allows protection of the payload from the surrounding environment and control of its release profile. Herein, we program the release of hydrophilic payloads from nanocontainers by co-encapsulating simple inorganic salts for adjusting the osmotic pressure. The latter either leads to a burst release at high concentrations of co-encapsulated salts or a sustained release at lower concentrations. Osmotic pressure causes swelling of the nanocapsule's shell and therefore sustained release profiles can be adjusted by crosslinking it. The approach presented allows for programing the release of payloads by co-encapsulating inexpensive salts inside nanocontainers without the help of stimuli-responsive materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01882c

  11. Charge Transfer in FeOCl Intercalation Compounds and its Pressure Dependence: An X-ray Spectroscopic Study

    SciTech Connect

    I Jarrige; Y Cai; S Shieh; H Ishii; N Hiraoka; S Karna; W Li

    2011-12-31

    We present a study of charge transfer in Na-intercalated FeOCl and polyaniline-intercalated FeOCl using high-resolution x-ray absorption spectroscopy and resonant x-ray emission spectroscopy at the Fe-K edge. By comparing the experimental data with ab initio simulations, we are able to unambiguously distinguish the spectral changes which appear due to intercalation into those of electronic origin and those of structural origin. For both systems, we find that about 25% of the Fe sites are reduced to Fe{sup 2+} via charge transfer between FeOCl and the intercalate. This is about twice as large as the Fe{sup 2+} fraction reported in studies using Moessbauer spectroscopy. This discrepancy is ascribed to the fact that the charge transfer occurs on the same time scale as the Moessbauer effect itself. Our result suggests that every intercalated atom or molecule is involved in the charge-transfer process, thus making this process a prerequisite for intercalation. The Fe{sup 2+} fraction is found to increase with pressure for polyaniline-FeOCl, hinting at an enhancement of the conductivity in the FeOCl intercalation compounds under pressure.

  12. Charge transfer in FeOCl intercalation compounds and its pressure dependence: An x-ray spectroscopic study

    SciTech Connect

    Jarrige, I.; Cai, Y. Q.; Shieh, S. R.; Ishii, H.; Hiraoka, N.; Karna, S.; Li, W.-H.

    2010-10-15

    We present a study of charge transfer in Na-intercalated FeOCl and polyaniline-intercalated FeOCl using high-resolution x-ray absorption spectroscopy and resonant x-ray emission spectroscopy at the Fe K edge. By comparing the experimental data with ab initio simulations, we are able to unambiguously distinguish the spectral changes which appear due to intercalation into those of electronic origin and those of structural origin. For both systems, we find that about 25% of the Fe sites are reduced to Fe{sup 2+} via charge transfer between FeOCl and the intercalate. This is about twice as large as the Fe{sup 2+} fraction reported in studies using Moessbauer spectroscopy. This discrepancy is ascribed to the fact that the charge transfer occurs on the same time scale as the Moessbauer effect itself. Our result suggests that every intercalated atom or molecule is involved in the charge-transfer process, thus making this process a prerequisite for intercalation. The Fe{sup 2+} fraction is found to increase with pressure for polyaniline-FeOCl, hinting at an enhancement of the conductivity in the FeOCl intercalation compounds under pressure.

  13. Asynchronous Distance Learning: E-mail Attachments Used as the Medium for Assigned Coursework.

    ERIC Educational Resources Information Center

    Worrells, D. Scott

    2002-01-01

    Postsecondary students were sent case studies to analyze and submit via electronic mail attachments. Results of an evaluation indicate that the benefits of using electronic mail for course work far outweigh the disadvantages. (Contains 10 references.) (JOW)

  14. Attachment Theory: Contributions to Group Work.

    ERIC Educational Resources Information Center

    Pistole, M. Carole

    1997-01-01

    Describes attachment theory, explores its application to group counseling, and elaborates points of interest to group workers. Focuses on attachment styles, attachment and caregiving, the group leader's goals, the group as an attachment experience, interventions based on attachment theory, its use in psychoeducational groups, and complexities in…

  15. Everything You Want To Know about Attachment.

    ERIC Educational Resources Information Center

    Honig, Alice Sterling

    This paper discusses infant attachment, which it defines as a long-lasting emotional bond revealed when a child under stress seeks out and tries to stay close to a specific figure. The paper addresses: (1) What is attachment? Who are the pioneers in attachment theory?; (2) How do we notice attachment in action?; (3) Is attachment the only…

  16. Phenotypes of Non-Attached Pseudomonas aeruginosa Aggregates Resemble Surface Attached Biofilm

    PubMed Central

    Alhede, Morten; Kragh, Kasper Nørskov; Qvortrup, Klaus; Allesen-Holm, Marie; van Gennip, Maria; Christensen, Louise D.; Jensen, Peter Østrup; Nielsen, Anne K.; Parsek, Matt; Wozniak, Dan; Molin, Søren; Tolker-Nielsen, Tim; Høiby, Niels; Givskov, Michael; Bjarnsholt, Thomas

    2011-01-01

    For a chronic infection to be established, bacteria must be able to cope with hostile conditions such as low iron levels, oxidative stress, and clearance by the host defense, as well as antibiotic treatment. It is generally accepted that biofilm formation facilitates tolerance to these adverse conditions. However, microscopic investigations of samples isolated from sites of chronic infections seem to suggest that some bacteria do not need to be attached to surfaces in order to establish chronic infections. In this study we employed scanning electron microscopy, confocal laser scanning microscopy, RT-PCR as well as traditional culturing techniques to study the properties of Pseudomonas aeruginosa aggregates. We found that non-attached aggregates from stationary-phase cultures have comparable growth rates to surface attached biofilms. The growth rate estimations indicated that, independently of age, both aggregates and flow-cell biofilm had the same slow growth rate as a stationary phase shaking cultures. Internal structures of the aggregates matrix components and their capacity to survive otherwise lethal treatments with antibiotics (referred to as tolerance) and resistance to phagocytes were also found to be strikingly similar to flow-cell biofilms. Our data indicate that the tolerance of both biofilms and non-attached aggregates towards antibiotics is reversible by physical disruption. We provide evidence that the antibiotic tolerance is likely to be dependent on both the physiological states of the aggregates and particular matrix components. Bacterial surface-attachment and subsequent biofilm formation are considered hallmarks of the capacity of microbes to cause persistent infections. We have observed non-attached aggregates in the lungs of cystic fibrosis patients; otitis media; soft tissue fillers and non-healing wounds, and we propose that aggregated cells exhibit enhanced survival in the hostile host environment, compared with non-aggregated bacterial

  17. Modulation of Candida albicans attachment to human epithelial cells by bacteria and carbohydrates.

    PubMed Central

    Centeno, A; Davis, C P; Cohen, M S; Warren, M M

    1983-01-01

    The effects of carbohydrates (mannose and dextrose). Escherichia coli 07KL. and Klebsiella pneumoniae on Candida albicans attachment to epithelial cells was studied. Dextrose had no effect on yeast attachment to epithelial cells. Conversely, mannose significantly decreased both yeast and piliated bacterial attachment (E. coli 07KL, heavily piliated K. pneumoniae) whereas having no effect on nonpiliated K. pneumoniae attachment to epithelial cells. The number of yeasts attaching to epithelial cells was enhanced by preincubation of epithelial cells with piliated strains of bacteria, whereas preincubation with nonpiliated strains of bacteria had no effect on yeast attachment. Scanning electron microscopy showed that piliated bacteria and yeasts were juxtaposed on the epithelial cell surface. These data suggest that certain piliated strains of bacteria can enhance C. albicans attachment to epithelial cells and that type 1 pili of bacteria can be a factor in the enhanced attachment of C. albicans to epithelial cells. Images PMID:6132878

  18. Attachment: A Concept That Counts.

    ERIC Educational Resources Information Center

    Giblin, Paul

    1994-01-01

    Explores the concept of "attachment" from the perspectives of love and work; marriage, parenting, and child development; triangles and the family emotional field; and evaluation instruments. (Author/JBJ)

  19. Attachment at work and performance.

    PubMed

    Neustadt, Elizabeth A; Chamorro-Premuzic, Tomas; Furnham, Adrian

    2011-09-01

    This paper examines the relations between self-reported attachment orientation at work and personality, self-esteem, trait emotional intelligence (aka emotional self-efficacy), and independently assessed career potential and job performance. Self-report data were collected from 211 managers in an international business in the hospitality industry; independent assessments of these managers' job performance and career potential were separately obtained from the organization. A self-report measure of romantic attachment was adapted for application in the work context; a two-factor solution was found for this measure. Secure/autonomous attachment orientation at work was positively related to self-esteem, trait emotional intelligence, extraversion, agreeableness, and conscientiousness, and also to job performance. Not only was secure/autonomous attachment orientation at work statistically predictive of job performance, but the new measure also made a distinct contribution, beyond conscientiousness, to this prediction. PMID:21838647

  20. Social attachments and traumatic stress

    PubMed Central

    Bryant, Richard A.

    2016-01-01

    The extent to which we engage with our social world has been central to our survival as a species and, accordingly, is relevant to how we cope with trauma and adversity. This review summarises current knowledge about the importance of social connections from an evolutionary perspective, as well as integrating this with a discussion of prevailing attachment theories. Experimental research supporting the potential benefit of attachments for managing adversity are presented, along with a review of how these benefits are moderated by individual differences in attachment style. The potential impact of trauma on attachment systems, and the manner in which this can compound trauma stress is discussed. Finally, a broader overview of social network analysis is introduced and it is proposed that a more sociocentric framework of trauma response would promote a fuller understanding of how social processes moderate trauma response. PMID:26996531

  1. A new method to simulate convection with strongly temperature- and pressure-dependent viscosity in a spherical shell: Applications to the Earth's mantle

    NASA Astrophysics Data System (ADS)

    Stemmer, K.; Harder, H.; Hansen, U.

    2006-08-01

    We present a new finite volume code for modeling three-dimensional thermal convection in a spherical shell with strong temperature- and pressure-dependent viscosity. A new discretization formulation of the viscous term, tailored to the finite volume method on a colocated grid, enables laterally variable viscosity. A smoothed cubed-sphere grid is used to avoid pole problems which occur in latitude-longitude grids with spherical coordinates. The spherical shell is topologically divided into six cubes. The equations are formulated in primitive variables, and are treated in the Cartesian cubes. In order to ensure mass conservation a SIMPLER pressure correction procedure is applied and to handle strong viscosity variations of Δ η = 10 7 and high Rayleigh numbers of Ra = 10 8 the pressure correction algorithm is combined with a pressure weighted interpolation method to satisfy the incompressibility condition and to avoid oscillatory pressure solutions. The model is validated by a comparison of diagnostical parameters of steady-state cubic and tetrahedral convection with other published spherical models and a detailed convergence test on successively refined grids. Lateral variable fluid properties have a significant influence on the convection pattern and heat flow dynamics. The influence of temperature- and pressure-dependent viscosity on the flow is systematically analyzed for basal and mixed-mode heated thermal convection in the spherical shell. A new method to classify the simulations to the mobile, transitional or stagnant-lid regime is given by means of a comparison of selected diagnostical parameters, a significantly improved classification as compared to the common surface layer mobility criterion. A scaling law for the interior temperature and viscosity in the stagnant-lid regime is given. Purely basal heating and strongly temperature-dependent rheology stabilize plume positions and yield with a weak time dependence of the convecting system, while the amount

  2. Rietveld refinement study of the pressure dependence of the internal structural parameter u in the wurtzite phase of ZnO

    SciTech Connect

    Liu, H.; Ding, Y.; Somayazulu, M.; Qian, J.; Shu, J.; Hausermann, D.; Mao, H.-k.

    2010-07-19

    The pressure dependence of the internal structural parameter u of the wurtzite phase of ZnO was studied using high resolution angular dispersive x-ray diffraction up to 12 GPa in a helium pressure medium. The u parameter increases with pressure up to about 0.430 at about 5.6 GPa, and then rapidly decrease to about 0.380 during the phase transition. Two models of the phase transition path were proposed recently by first-principles calculations [A. M. Saitta and F. Decremps, Phys. Rev. B 70, 035214 (2004); S. Limpijumnong and S. Jungthawan, Phys. Rev. B 70, 054104 (2004)]. These possible mechanisms responsible for the wurtzite-to-rocksalt phase transition under high pressure are experimentally evaluated based on our results. The bulk moduli of the wurtzite and rocksalt phase at zero pressure were estimated as 135.3 {+-} 1.8 and 177.4 {+-} 4.6 GPa, respectively.

  3. Measurement of the pressure dependence of the direct band gap of In0.53Ga0.47As using stimulated emission

    NASA Astrophysics Data System (ADS)

    People, R.; Jayaraman, A.; Wecht, K. W.; Sivco, D. L.; Cho, A. Y.

    1988-06-01

    Stimulated emission, obtainable at high optical pumping levels, has been used to follow the pressure dependence of the Γ-band gap of molecular beam epitaxial In0.53Ga0.47As on (001)InP. Hydrostatic pressure was generated using a diamond anvil cell, and all measurements were made at room temperature. The gap varies sublinearly with pressure for P≳10 kbar, having an initial slope of 12.44 meV/kbar. The deviation from a linear behavior is largely due to nonlinearities in the equation of state at higher pressures. The deformation potential (Ξd+ (1)/(3) Ξu-a) =-(7.79±0.4)eV, for the Γ-band gap.

  4. Photoluminescence study of LiNbO3:Cr3+; W4+ at high pressure. Pressure dependence of spectroscopic parameters and local structure of Cr3+

    NASA Astrophysics Data System (ADS)

    Sánchez-Alejo, M. A.; Rodríguez, F.; Barreda-Argüeso, J. A.; Camarillo, I.; Flores J., C.; Murrieta S., H.; Hernández A., J. M.; Jaque, F.; Camarillo, E.

    2016-10-01

    In this study, the photoluminescence properties of congruent codoped LiNbO3:Cr3+; W4+, crystals have been systematically investigated by performing photoluminescence studies at room temperature in the 0-280 kbar pressure range. In particular, we focus on the influence that hydrostatic pressure has on the 2E→ 4A2 (R-lines) transitions of Cr3+. It has been observed that the pressure dependence of the spectral position of the R-lines associated with both Cr3+ centres β and γ shows a bilinear behaviour with an abrupt slope change near 210 kbar. This change is related to the existence of a pressure-induced structural phase transition in the LiNbO3 host. The analysis of experimental results provides the Racah parameters B and C and the crystal field parameter 10Dq and their pressure and volume, through the crystal field theory and equation of state, dependences.

  5. Direction-Specific Interactions Control Crystal Growth by Oriented Attachment

    NASA Astrophysics Data System (ADS)

    Li, Dongsheng; Nielsen, Michael H.; Lee, Jonathan R. I.; Frandsen, Cathrine; Banfield, Jillian F.; De Yoreo, James J.

    2012-05-01

    The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials, yet the alignment process and attachment mechanism have not been established. We performed high-resolution transmission electron microscopy using a fluid cell to directly observe oriented attachment of iron oxyhydroxide nanoparticles. The particles undergo continuous rotation and interaction until they find a perfect lattice match. A sudden jump to contact then occurs over less than 1 nanometer, followed by lateral atom-by-atom addition initiated at the contact point. Interface elimination proceeds at a rate consistent with the curvature dependence of the Gibbs free energy. Measured translational and rotational accelerations show that strong, highly direction-specific interactions drive crystal growth via oriented attachment.

  6. Activating Attachments Reduces Memories of Traumatic Images.

    PubMed

    Bryant, Richard A; Foord, Rachael

    2016-01-01

    Emotional memories, and especially intrusive memories, are a common feature of many psychological disorders, and are overconsolidated by stress. Attachment theory posits that activation of mental representations of attachment figures can reduce stress and boost coping. This study tested the proposition that attachment activation would reduce consolidation of emotional and intrusive memories. Sixty-seven undergraduate students viewed subliminal presentations of traumatic and neutral images, which were preceded by subliminal presentations of either attachment-related images or non-attachment-related images; free recall and intrusive memories were assessed two days later. Participants with low avoidant attachment tendencies who received the attachment primes recalled fewer memories and reported fewer intrusions than those who received the non-attachment primes. Unexpectedly, those with high anxious attachment tendencies reported fewer memories. These findings generally accord with attachment theory, and suggest that consolidation of emotional memories can be moderated by activation of attachment representations. PMID:27631498

  7. Activating Attachments Reduces Memories of Traumatic Images.

    PubMed

    Bryant, Richard A; Foord, Rachael

    2016-01-01

    Emotional memories, and especially intrusive memories, are a common feature of many psychological disorders, and are overconsolidated by stress. Attachment theory posits that activation of mental representations of attachment figures can reduce stress and boost coping. This study tested the proposition that attachment activation would reduce consolidation of emotional and intrusive memories. Sixty-seven undergraduate students viewed subliminal presentations of traumatic and neutral images, which were preceded by subliminal presentations of either attachment-related images or non-attachment-related images; free recall and intrusive memories were assessed two days later. Participants with low avoidant attachment tendencies who received the attachment primes recalled fewer memories and reported fewer intrusions than those who received the non-attachment primes. Unexpectedly, those with high anxious attachment tendencies reported fewer memories. These findings generally accord with attachment theory, and suggest that consolidation of emotional memories can be moderated by activation of attachment representations.

  8. Activating Attachments Reduces Memories of Traumatic Images

    PubMed Central

    Foord, Rachael

    2016-01-01

    Emotional memories, and especially intrusive memories, are a common feature of many psychological disorders, and are overconsolidated by stress. Attachment theory posits that activation of mental representations of attachment figures can reduce stress and boost coping. This study tested the proposition that attachment activation would reduce consolidation of emotional and intrusive memories. Sixty-seven undergraduate students viewed subliminal presentations of traumatic and neutral images, which were preceded by subliminal presentations of either attachment-related images or non-attachment-related images; free recall and intrusive memories were assessed two days later. Participants with low avoidant attachment tendencies who received the attachment primes recalled fewer memories and reported fewer intrusions than those who received the non-attachment primes. Unexpectedly, those with high anxious attachment tendencies reported fewer memories. These findings generally accord with attachment theory, and suggest that consolidation of emotional memories can be moderated by activation of attachment representations. PMID:27631498

  9. Partner attachment and interpersonal characteristics.

    PubMed

    Kilmann, Peter R; Finch, Holmes; Parnell, Michele M; Downer, Jason T

    2013-01-01

    This study investigated partner attachment and interpersonal characteristics in 134 nonclinical couples in long-term marriages. Irrespective of gender, spouses with greater anxiety over abandonment or discomfort with closeness endorsed dysfunctional relationship beliefs to a greater extent. On the anxiety over abandonment dimension, husbands with higher scores were rated less aggressive, less controlling, and more rebellious, whereas wives with higher scores were rated more dependent, more self-critical, and less competitive. Husbands higher on discomfort with closeness were rated less cooperative and responsible and were rated more aggressive and rebellious. Matched secure couples reported lower marital dissatisfaction than matched insecure or mismatched couples. Future research should contrast samples of nonclinical and clinical couples by marital duration to identify specific partner behaviors that are likely to foster marital dissatisfaction within particular attachment pairings. The authors' findings suggest the importance of marital therapists being attuned to the attachment-related beliefs and interpersonal styles uniquely operating within each couple.

  10. Three-Dimensional Computed Tomography as a Method for Finding Die Attach Voids in Diodes

    NASA Technical Reports Server (NTRS)

    Brahm, E. N.; Rolin, T. D.

    2010-01-01

    NASA analyzes electrical, electronic, and electromechanical (EEE) parts used in space vehicles to understand failure modes of these components. The diode is an EEE part critical to NASA missions that can fail due to excessive voiding in the die attach. Metallography, one established method for studying the die attach, is a time-intensive, destructive, and equivocal process whereby mechanical grinding of the diodes is performed to reveal voiding in the die attach. Problems such as die attach pull-out tend to complicate results and can lead to erroneous conclusions. The objective of this study is to determine if three-dimensional computed tomography (3DCT), a nondestructive technique, is a viable alternative to metallography for detecting die attach voiding. The die attach voiding in two- dimensional planes created from 3DCT scans was compared to several physical cross sections of the same diode to determine if the 3DCT scan accurately recreates die attach volumetric variability

  11. 10 CFR 75.15 - Facility attachments.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 2 2010-01-01 2010-01-01 false Facility attachments. 75.15 Section 75.15 Energy NUCLEAR... Accounting and Control for Facilities § 75.15 Facility attachments. (a) The Facility Attachment or Transitional Facility Attachment will document the determinations referred to in § 75.10 and will contain...

  12. Attachment Theory, Counseling Process, and Supervision.

    ERIC Educational Resources Information Center

    Pistole, M. Carole; Watkins, C. Edward, Jr.

    1995-01-01

    Focuses on attachment theory's relationship to counseling process and supervision so as to heighten appreciation of attachment theory's complexity. Illustrates attachment constructs in action and discusses counseling process, concentrating on the ways attachment theory can contribute to understanding the client-counselor relationship and change…

  13. Young Children's Emotional Attachment to Stories.

    ERIC Educational Resources Information Center

    Alexander, Kristin J.; Miller, Peggy J.; Hengst, Julie A.

    2001-01-01

    Interviewed 32 families concerning their narrative practices, basic information about the children's story attachments, and the mothers' beliefs and practices concerning their children's attachments. Found that story attachments were social in two ways: Children created relationships with story characters, and formed story attachments with…

  14. Parent characteristics linked with daughters' attachment styles.

    PubMed

    Kilmann, Peter R; Vendemia, Jennifer M C; Parnell, Michele M; Urbaniak, Geoffrey C

    2009-01-01

    This study investigated links between parent characteristics and daughters' attachment styles for 90 female undergraduates and their married biological parents. Parents with a secure attachment pattern were rated as more accepting, less controlling, more competent, and more consistent in showing love and affection to their daughter in contrast to parents with an insecure attachment pattern. Significant positive associations were found between mothers' fearful attachment scores and the fearful, preoccupied, and dismissive attachment scores of daughters. Daughters of matched secure parents were more likely to report a secure attachment style, while daughters of matched insecure parents were more likely to report an insecure attachment style.

  15. Pressure Dependent OH and HO2 Calibration of the Fluorescence Assay by Gas Expansion (FAGE) Instrument Using the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC)

    NASA Astrophysics Data System (ADS)

    Winiberg, F.; Smith, S. C.; Seakins, P.

    2012-12-01

    The hydroxyl (OH) and hydroperoxy (HO2) radical are very important tropospheric radical species. The balance between OH and HO2 (the HOx cycle) can give understanding of localised atmospheric composition. OH and HO2 is measured in both ground and aircraft based campaigns using FAGE. Calibration of this non-absolute fluorescence technique is traditionally achieved by H2O photolysis. Operation of FAGE at varying pressure can affect the instrument sensitivity to HOx due to internal fluorescence cell pressure changes. These are traditionally accounted by varying the inlet pinhole size of the instrument, however this may alter the gas expansion and hence the instrument sensitivity to OH and HO2 (COH and CHO2 respectively). Presented here are the initial results from independent OH and HO2 pressure dependent calibration methods using the stainless steel HIRAC chamber, which can operate at various pressures (0.1 - 1 bar). The OH calibration method uses the loss rate of a well characterised hydrocarbon upon reaction with OH to infer the OH concentration measured by FAGE in the HIRAC chamber. A photolytic OH source ((CH3)3COOH) was used and all reactants were measured using calibrated GC-FID and FTIR. For HO2 calibrations, formaldehyde, HCHO, is photolysed (λ < 300 nm) in the presence of O2 to form 2HO2 to steady state, and the post-photolysis HO2 decay is monitored using FAGE. The decay is a function of the second order HO2 self-reaction, for which the rate is well known. As [HO2] = SHO2 x CHO2 (where SHO2 is the FAGE HO2 signal), the second order rate equation can be rearranged and a plot of 1/SHO2 vs. time yields CHO2. Preliminary experiments for the OH calibration method show discrepancies between traditional and hydrocarbon decay techniques. This is thought to be due to as yet unknown OH loss processes and conditioning of the HIRAC chamber. For the HO2 pressure dependent calibrations were in good agreement with traditional methods validating the widely used

  16. Bar overdentures utilizing the Locator attachment.

    PubMed

    Schneider, A L; Kurtzman, G M

    2001-01-01

    Implant-retained overdentures are a restorative option for both the fully and partially edentulous arches. A new attachment, the Locator, which features a reduced interarch requirement and the advantage of built-in guide planes providing precise insertion, is described. The Locator is an advancement in attachment technology, with an improved design combined from the best features of a ball attachment, an ERA attachment, and a cap attachment.

  17. On the propagation of a quasi-static disturbance in a heterogeneous, deformable, and porous medium with pressure-dependent properties

    SciTech Connect

    Vasco, D.W.

    2011-10-01

    Using an asymptotic technique, valid when the medium properties are smoothly-varying, I derive a semi-analytic expression for the propagation velocity of a quasi-static disturbance traveling within a nonlinear-elastic porous medium. The phase, a function related to the propagation time, depends upon the properties of the medium, including the pressure-sensitivities of the medium parameters, and on pressure and displacement amplitude changes. Thus, the propagation velocity of a disturbance depends upon its amplitude, as might be expected for a nonlinear process. As a check, the expression for the phase function is evaluated for a poroelastic medium, when the material properties do not depend upon the fluid pressure. In that case, the travel time estimates agree with conventional analytic estimates, and with values calculated using a numerical simulator. For a medium with pressure-dependent permeability I find general agreement between the semi-analytic estimates and estimates from a numerical simulation. In this case the pressure amplitude changes are obtained from the numerical simulator.

  18. Silane-initiated nucleation in chemically active plasmas: validation of density functionals, mechanisms, and pressure-dependent variational transition state calculations.

    PubMed

    Bao, Junwei Lucas; Truhlar, Donald G

    2016-04-21

    The growth of anionic silicon hydride clusters is a critically important process in nanodusty plasmas. In the current study, we focus on the formation of homologs of silylene (Sin+1H2n+2(-), n = 3, 4) and silyl (SinH2n+1(-), n = 4, 5) anions via anion-neutral reaction pathways. Species like silyl or silylene anions and their related elementary reactions, which are involved in the formation of silicon hydride clusters, were not used in developing exchange-correlation (xc) density functionals (i.e., they were not included in the training set of semiempirical density functionals); therefore, we explored the accuracy of various widely used xc density functionals based on reaction energies and barrier heights. Among the 21 density functionals we tested, M06-2X has the best performance for a hybrid functional, and MN15-L has the best performance for a local functional. Thermal rate constants of the elementary reactions involved in the reaction mechanism are calculated using M06-2X and multistructural canonical variational transition state theory with the small-curvature tunneling approximation (MS-CVT/SCT). The pressure dependence of unimolecular isomerization reactions is treated with system-specific quantum RRK theory (SS-QRRK) and the Lindemann-Hinshelwood mechanism.

  19. Closeup view of an External Tank (ET) Attach Ring undergoing ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Close-up view of an External Tank (ET) Attach Ring undergoing preparations in the Processing Building of the Rotation Processing and Surge Facility at Kennedy Space Center. After preparations are complete the ET Attach Ring will be mated to the top of the Aft Motor Segment. The most prominent features in this view are the ET/Solid Rocket Booster Struts in the center and left in the view and the Aft Integrated Electronics Assembly located on the right side if the ring in this view. - Space Transportation System, Solid Rocket Boosters, Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

  20. Thinking of attachments reduces noradrenergic stress response.

    PubMed

    Bryant, Richard A; Chan, Lilian

    2015-10-01

    Although there is much evidence that activating mental representations of attachments figure is beneficial for psychological health and can reduce stress response, no research has directly investigated whether attachment activation can ameliorate hormonal stress response. This study investigated whether activating an attachment figure or a non-attachment figure following administration of a socially evaluated cold pressor test to elicit stress impacted on glucocorticoid and noradrenergic response. Participants (N = 61) provided baseline salivary samples, underwent a cold pressor test, then imagined an attachment or non-attachment figure, and finally provided subsequent saliva samples. Participants who imagined a non-attachment figure had greater noradrenergic response following the stressor than those who imagined an attachment figure. These findings highlight that activating attachment representations can ameliorate the immediate noradrenergic stress response.

  1. Engineered microtopographies and surface chemistries direct cell attachment and function

    NASA Astrophysics Data System (ADS)

    Magin, Chelsea Marie

    Harrison, in 1914, first recognized that cells respond to physicochemical cues such as substratum topography when he observed that fibroblasts elongated while cultured on spider silk. Recently, techniques developed in the micro-electronics industry have been used to create molds for producing microscaled topographies with various shapes and spatial arrangements. Although these patterning techniques are well-established, very little is known about the mechanisms underlying cell sensing and response to microtopographies. In this work cellular micro-environments with varying surface topographies and chemistries were evaluated with marine organisms and mammalian cells to investigate cellular sensing and response. Biofouling---the accumulation of micro-organisms, plants, and animals on submerged surfaces---is an environmental and economic concern. Engineered topographies, replicated in polydimethylsiloxane elastomer (PDMSe) and functionalized poly(ethylene glycol)-dimethacrylate (PEGDMA) hydrogels, were evaluated for inhibition of marine fouling organism attachment. Microtopographies replicated in PDMSe inhibited attachment of the marine bacterium, Cobetia marina up to 99% versus smooth. The average normalized attachment densities of cells of C. marina and zoospores of the green algae Ulva on PDMSe topographies scaled inversely with the Engineered Roughness Index (ERIII), a representation of surface energy. Attachment densities of Ulva from four assays and C. marina from two growth phases to PDMSe surfaces scaled inversely with one equation: ERI II multiplied by the Reynolds number of the organism (Re) (R 2 = 0.77). The same microtopographies created in PDMSe reduced the initial attachment density and attachment strength of cells of the diatoms Navicula incerta and Seminavis robusta compared to smooth PDMSe. The average normalized attachment density of Navicula after exposure to shear stress (48 Pa) was correlated with the contact area between the diatom and a

  2. Split ring containment attachment device

    SciTech Connect

    Sammel, A.G.

    1995-12-31

    A containment attachment device is described for operatively connecting a glovebag to plastic sheeting covering hazardous material. The device includes an inner split ring member connected on one end to a middle ring member wherein the free end of the split ring member is inserted through a slit in the plastic sheeting to captively engage a generally circular portion of the plastic sheeting. A collar portion having an outer ring portion is provided with fastening means for securing the device together wherein the glovebag is operatively connected to the collar portion. Hazardous material such as radioactive waste may be sealed in plastic bags for small items or wrapped in plastic sheeting for large items. Occasionally the need arises to access the hazardous material in a controlled manner, that is, while maintaining total containment. Small items could be placed entirely inside a containment glovebag. However, it may not be possible or practical to place large items inside a containment; instead, one or more glovebags could be attached to the plastic sheeting covering the hazardous material. It is this latter application for which the split ring containment attachment device is intended.

  3. Pressure Dependent Mass Fraction in Noble Gas Mass Spectrometers: A Possible Explanation for the Excessive Dispersion in the EARTHTIME Fish Canyon/Alder Creek Inter-Calibration Experiment

    NASA Astrophysics Data System (ADS)

    Turrin, B. D.; Swisher, C. C.; Mana, S.

    2011-12-01

    Mass spectrometer fractionation bias (mass discrimination) is a ubiquitous phenomenon in noble gas mass spectroscopy and must be corrected for in order to obtain accurate-high precision isotopic ratios that are used in isotopic age calculations. Temporal variations in mass fractionation are well known phenomena and have been reported in several studies (eg. Turrin et al., 2010 and references therein). Here we report on the pressure dependency on mass spectrometer fractionation bias. In our experiment, we varied by a factor of five the signal size of aliquots of atmospheric argon delivered from an automated air pipette system. The measured mass discrimination difference (MD) as determined by the 40Ar/36Ar ratio between the 1-fold and 5-fold air pipette shots is ~5%. The air 40Ar/36Ar aliquots were measured using a MAP 215-50 operating in pulse counting mode. The air measurements were interspersed with measurements of Alder Creek (AC) sanidine and Fish Canyon (FC) sanidine that were co-irradiated for 0.75 hours. The grain sizes for the two mineral standards were chosen such that the AC sample yielded 40Ar signals of about 50 kcps, similar to that delivered by a single aliquot delivered by the air pipette. The FC grains were about 5-10 times greater (150-600 kcps) than the single air aliquot. Following the analyses, we applied the MD correction to both the FC and AC analyses. When the MD as determined from the single pipette data (which matches 40Ar beam intensity of the AC sample) is applied to both the AC and FC data a "J" of 1.579±0.001x10-4 is obtained from the FC data and an age of 1183 ±4 ka for AC. However, when the MD as determined from the multiple aliquot pipette data (with an 40Ar beam similar to that of the FC analyses) is applied to the FC data a "J" of 1.588±0.001x10-4 is obtained and an AC age of 1189 ±4 ka the same age at the 95% confidence level, the reported age for AC. We conclude that variation in MD over signal sizes typically analyzed in 40Ar

  4. Influence of the critical Fe atomic volume on the magnetism of Fe-rich metallic glasses evidenced by pressure-dependent measurements

    NASA Astrophysics Data System (ADS)

    Kiss, L. F.; Kemény, T.; Bednarčík, J.; Gamcová, J.; Liermann, H.-P.

    2016-06-01

    Despite the intensive studies for decades, it is still not well understood how qualitatively different magnetic behaviors can occur in a narrow composition range for the Fe-rich Fe-transition metal (TM) amorphous alloys. In this study of amorphous F e100 -xZ rx (x =7 , 9, 12) metallic glasses, normal ferromagnetism (FM) is found at 12 % Zr where only the FM-paramagnetic (PM) transition is observed at the Curie temperature, TC. In contrast, spin-glass (SG)-PM transition at a temperature, Tg, called SG temperature, is only observed at 7 % Zr, while in the transient re-entrant composition range (x =8 -11 ) , an SG-FM transition at a temperature, Tf, called spin-freezing temperature, is also observed at low temperature besides the normal FM-PM transition at TC. In order to understand this unusual behavior, a detailed characterization of pressure (atomic volume), composition, and temperature dependence of the magnetic properties is coupled with high pressure synchrotron x-ray diffraction determination of the pressure dependence of the atomic volume. The results on F e100 -xZ rx (x =7 , 9, 12) are compared to those obtained for the FM C o91Z r9 metallic glass not showing any kind of anomalous magnetic properties. It is confirmed that the unusual behavior is caused by a granularlike magnetic structure where weakly coupled magnetic clusters are embedded into a FM bulk matrix. Since the mechanism of the magnetization reversal was found to be of the curling type rather than homogeneous rotation, the energy barrier determining the blocking temperature of the clusters is calculated as AR, where A is the exchange constant and R is the cluster size, in contrast to the usual characterization of the energy barrier by KV where K is the anisotropy energy and V is the cluster volume. The volume fraction of the FM part is a fast changing function of the bulk composition: Almost 100% FM fraction is found at 12 % of Zr while no trace of real FM is observed at 7 at % Zr. The driving

  5. Adult attachment processes: individual and couple perspectives.

    PubMed

    Bartholomew, K

    1997-09-01

    This paper overviews a new approach to understanding the range of difficulties experienced in close attachment relationships in adulthood. Drawing on the work of Bowlby, four prototypic adult attachment patterns are defined in terms of the intersection of two underlying dimensions, the positivity of the person's self-image and the positivity of the person's image of others (Bartholomew, 1990; Bartholomew & Horowitz, 1991). The distinct interpersonal difficulties associated with each attachment pattern are described. Findings are presented indicating that individual differences in attachment have implications for the quality of adults' romantic relationships, and that attachment theory may be helpful in understanding violent spousal relationships. Five current issues in the study of adult attachment are addressed: the stability of attachment patterns, the associations between attachment and general personality factors, the relative merits of categorical and prototype assessments of attachment, the identification of multiple attachments in adulthood, and the specificity of adult attachment patterns. It is suggested that the four-category model of adult attachment is especially sensitive to the range and complexity of attachment-related difficulties experienced in adulthood.

  6. Pressure Dependence of Electrical Transport in the Triangular Antiferromagnetic Insulators FeGa2S4 and Fe2Ga2S5

    NASA Astrophysics Data System (ADS)

    Tomita, Takahiro; Nambu, Yusuke; Nakatsuji, Satoru; Koeda, Shinji; Hedo, Masato; Uwatoko, Yoshiya

    2009-09-01

    NiGa2S4, FeGa2S4, and Fe2Ga2S5 are layered triangular lattice antiferromagnets. Although the single-layer systems NiGa2S4 with S=1 and FeGa2S4 with S=2 are both insulators and have two-dimensional (2D) spin-disordered states, the bilayer system Fe2Ga2S5, which has an effective buckled honeycomb lattice of S=2, is a semiconductor and exhibits an antiferromagnetic long-range order at 110 K. Here, we present our results of the resistivity measurements of single crystals of FeGa2S4 and Fe2Ga2S5 under pressures of up to 8 GPa. We have observed a kink in the temperature dependence of the resistivity ρ(T) of FeGa2S4 under a pressure of 8 GPa, which is attributable to a transition from a 2D frozen spin-disordered state to a three-dimensional (3D) spin-ordered state. In either FeGa2S4 or Fe2Ga2S5, we have observed no transition into a metallic state within pressure range of up to 8 GPa, despite the fact that the resistivities of both FeGa2S4 and Fe2Ga2S5 show decreases with an increase in pressure at room temperature. The energy gap of FeGa2S4 estimated from the temperature dependences of the resistivities show negative pressure dependences.

  7. Pressure Dependence of the Acid/Base Equilibria of Methyl Orange in Aqueous Solutions to 1000 bars at 20°C

    SciTech Connect

    Suleimenov, Oleg M; Boily, Jean F

    2006-07-31

    The pressure dependence on the acid/base equilibria of methyl orange in aqueous solution was measured at 20°C in the 1-1000 bar range with a newly designed flow-through spectrophotometric cell. Combined chemometric and thermodynamic analyses of uv-vis spectrophotometric data were used to extract the dissociation constants as well as the changes in molar volume and isothermal compressibility of methyl orange as a function of pressure. The results show increasing pressure promotes the deprotonation of the methyl orange, with pK values ranging from 3.505 at 1 bar to 3.445 (0.002) at 1000 bars. Increasing pressure also yields small values of negative changes in the molar volume ranging from –6.9 cm3∙mol-1 at 1 bar to –1.7 cm3∙mol-1 at 1000 bars. The isothermal compressibility of methyl orange in this pressure range was estimated using the 2nd derivative of 2nd and 3rd order polynomial fits to the constants and gave rise to a constant value of –48.4x 10-4 cm3∙mol-1∙bar-1 in the former case, and increasing values from -107×10-4 cm3∙mol-1∙bar-1 at 1 bar to 3.43×10-4 cm3∙mol-1∙bar-1 at 1000 bars in the latter case. Molar absorption coefficients for the protonated and deprotonated species were also shown to be only slightly affected by pressure changes and can be used to accurately predict the absorption spectra of methyl orange as a function of pressure.

  8. Probing the stability of the M2(Benzene)3 M = Fe, Co, and Ni structures upon electron attachment (deletion) and solvated iron clusters by benzene molecules: Fe2(Benzene)4

    NASA Astrophysics Data System (ADS)

    Flores, Raul; Cortes, Hector F.; Castro, Miguel

    2016-01-01

    Rice-ball (RB) and multiple decker sandwich (MDS) structures of clusters containing transition metal atoms and benzene (Bz) molecules, [M2Bz3]±1 M = Fe, Co, and Ni were studied by means of density functional theory all-electron calculations including dispersion correction as in the BPW91-D2 method. A RB geometry was identified for the ground state (GS) of neutral Fe2Bz3. However, consistent with reported experimental results, RB and MDS structures may occur for the Fe2Bz3- ion. The RB and MDS isomers of Co2Bz3 are degenerate; they have comparable ionization energies; this finding is in agreement with the experimental results, where two isomers were identified also. Experiment and theory suggest that the Co2Bz3- ion has similar geometry, MDS, as the neutral parent. RB and MDS motifs are degenerate for both Ni2Bz3 and Ni2Bz3+ . A RB form is predicted for Ni2Bz3- . In the GS of Fe2Bz4 one benzene molecule was found in the outer region of the RB Fe2Bz3 subcluster; it presents a binding energy (D0) of 4.6 kcal/mol, being originated from weak van der Waals forces. Thus, bridging the internal ligands, the fourth molecule has solvent behavior in the singlet Fe2Bz4 GS. Likewise, 3 + 1 MDS isomers of Fe2Bz4 were found at higher energies, ≈ 13.1 kcal/mol, from the GS. In Fe2Bz4-, the RB motif yields the GS with a D0 of 6.7 kcal/mol for the solvent unit. Having a D0 of 9.0 kcal/mol for such moiety the MDS Fe2Bz4- ion is near in energy (3.6 kcal/mol) to the Fe2Bz4- GS. The GS has an electron affinity (EA) of 0.40 eV. Notably, the MDS isomer has a larger EA (0.83 eV). The outer molecule in the 3 + 1 RB GS is stabilized by a network of dipole Cδ--Hδ+-Cδ- interactions, formed between the external (internal) hydrogen atoms and the π-electrons of the internal (external) benzene rings. Dipole C-Hintδ+-Cextδ- interactions predominate in the 3 + 1 MDS isomers.

  9. Cyber aggression within adolescents' romantic relationships: linkages to parental and partner attachment.

    PubMed

    Wright, Michelle F

    2015-01-01

    Extensive research has examined face-to-face aggression within adolescents' romantic relationships, but little attention has been given to the role of electronic technologies in adolescents' perpetuation of these behaviors. Thus, this study examined the relationship of anxious and avoidant partner attachments to partner-directed cyber aggression, assessed 1 year later among 600 adolescents (54% female). After accounting for gender and previous behaviors, anxious partner attachment was related to later partner-directed cyber aggression. In addition, insecure parental attachment from adolescents' mothers was related positively to insecure partner attachment and had an indirect effect on their partner-directed cyber aggression through the mediation of anxious partner attachment. This study provides insight into the impact of electronic technologies on adolescents' romantic relationships.

  10. Attachment in Middle Childhood: Progress and Prospects

    ERIC Educational Resources Information Center

    Bosmans, Guy; Kerns, Kathryn A.

    2015-01-01

    Contrary to the substantial amount of research on infant, preschool, adolescent, and adult attachment, middle childhood has long been neglected by the international attachment research community. In the past two decades, however, there has been a steep increase in research focusing on middle childhood attachment. This article provides an overview…

  11. 14 CFR 33.25 - Accessory attachments.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Accessory attachments. 33.25 Section 33.25... STANDARDS: AIRCRAFT ENGINES Design and Construction; General § 33.25 Accessory attachments. The engine must operate properly with the accessory drive and mounting attachments loaded. Each engine accessory drive...

  12. 21 CFR 872.3165 - Precision attachment.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Precision attachment. 872.3165 Section 872.3165...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3165 Precision attachment. (a) Identification. A precision attachment or preformed bar is a device made of austenitic alloys or alloys containing 75...

  13. After Love: Attachment Styles and Grief Themes.

    ERIC Educational Resources Information Center

    Pistole, M. Carole

    1996-01-01

    Examines the association of attachment organization and recalled grief responses following the dissolution of a romantic relationship. Data based on college students' (N=118) responses resulted in four interpretable grief themes. Preoccupied attachment predicted self-reproach, fearful attachment predicted partner blame, whereas both fearful and…

  14. Attachment Relationships: Self-Disclosure and Trust.

    ERIC Educational Resources Information Center

    Pistole, M. Carole

    1993-01-01

    Examined differences in trust and self-disclosure associated with secure, anxious/ambivalent, and avoidant attachment. Findings from 98 undergraduate students revealed that, in general, subjects who reported themselves as securely attached also reported, in comparison with avoidant attachment, higher levels of trust in partner, amount of…

  15. Genetic and Environmental Influence on Attachment Disorganization

    ERIC Educational Resources Information Center

    Spangler, Gottfried; Johann, Monika; Ronai, Zsolt; Zimmermann, Peter

    2009-01-01

    Background: Empirical studies demonstrate that maternal sensitivity is associated with attachment security in infancy, while maternal frightening/frightened behavior is related to attachment disorganization. However, attachment disorganization is also predicted by individual dispositions in infancy. Indeed, recent studies indicate a link between…

  16. Attachment: Building Secure Relationships in Early Childhood.

    ERIC Educational Resources Information Center

    Harrison, Linda

    2003-01-01

    Attachment describes the unique human ability to form lasting relationships with others, and to maintain these relationships over time and distance. Research into attachment has shown that children have the potential to form many attachment relationships, and that each relationship can contribute to the child's growing sense of self. This booklet…

  17. Preferred Attachment in Affiliation Networks

    NASA Astrophysics Data System (ADS)

    Bloznelis, Mindaugas; Götze, Friedrich

    2014-08-01

    Vertices of an affiliation network are linked to attributes and two vertices are declared adjacent whenever they share a common attribute. For example, two customers of an internet shop (or video-sharing website) are called adjacent if they have purchased (or downloaded) the same or similar items. Assuming that each newly arrived customer is linked preferentially to already popular items we obtain a preferred attachment affiliation network that evolves in time. We show that the fraction of customers having neighbours scales as for large . Here is the ratio between the two intensities: intensity of the flow of customers and that of the newly arriving items.

  18. Split ring containment attachment device

    DOEpatents

    Sammel, Alfred G.

    1996-01-01

    A containment attachment device 10 for operatively connecting a glovebag 200 to plastic sheeting 100 covering hazardous material. The device 10 includes an inner split ring member 20 connected on one end 22 to a middle ring member 30 wherein the free end 21 of the split ring member 20 is inserted through a slit 101 in the plastic sheeting 100 to captively engage a generally circular portion of the plastic sheeting 100. A collar potion 41 having an outer ring portion 42 is provided with fastening means 51 for securing the device 10 together wherein the glovebag 200 is operatively connected to the collar portion 41.

  19. DNA attachment to support structures

    DOEpatents

    Balhorn, Rodney L.; Barry, Christopher H.

    2002-01-01

    Microscopic beads or other structures are attached to nucleic acids (DNA) using a terminal transferase. The transferase adds labeled dideoxy nucleotide bases to the ends of linear strands of DNA. The labels, such as the antigens digoxigenin and biotin, bind to the antibody compounds or other appropriate complementary ligands, which are bound to the microscopic beads or other support structures. The method does not require the synthesis of a synthetic oligonucleotide probe. The method can be used to tag or label DNA even when the DNA has an unknown sequence, has blunt ends, or is a very large fragment (e.g., >500 kilobase pairs).

  20. Examining Relations among Attachment, Religiosity, and New Age Spirituality Using the Adult Attachment Interview

    ERIC Educational Resources Information Center

    Granqvist, Pehr; Ivarsson, Tord; Broberg, Anders G.; Hagekull, Berit

    2007-01-01

    This study was the first to examine relations between attachment and religion-spirituality in adults using a developmentally validated attachment assessment, the Adult Attachment Interview. Security of attachment was expected to be linked to a religiosity-spirituality that is socially based on the parental relationships and reflects extrapolation…

  1. Methane production by attached film

    DOEpatents

    Jewell, William J.

    1981-01-01

    A method for purifying wastewater of biodegradable organics by converting the organics to methane and carbon dioxide gases is disclosed, characterized by the use of an anaerobic attached film expanded bed reactor for the reaction process. Dilute organic waste material is initially seeded with a heterogeneous anaerobic bacteria population including a methane-producing bacteria. The seeded organic waste material is introduced into the bottom of the expanded bed reactor which includes a particulate support media coated with a polysaccharide film. A low-velocity upward flow of the organic waste material is established through the bed during which the attached bacterial film reacts with the organic material to produce methane and carbon dioxide gases, purified water, and a small amount of residual effluent material. The residual effluent material is filtered by the film as it flows upwardly through the reactor bed. In a preferred embodiment, partially treated effluent material is recycled from the top of the bed to the bottom of the bed for further treatment. The methane and carbon dioxide gases are then separated from the residual effluent material and purified water.

  2. Attachment relationship experiences and childhood psychopathology.

    PubMed

    Zeanah, Charles H; Keyes, Angela; Settles, Lisa

    2003-12-01

    Human infants form attachments to their caregivers gradually over the course of the first year of life. Qualitatively different types of attachments, which can be identified by the end of the first year, are broadly predictive of subsequent adaptive outcomes for young children. "Disorganized" patterns of attachment have the strongest links to concurrent and subsequent psychopathology, and considerable research has demonstrated both within-the-child and environmental correlates of disorganized attachment. Clinical disorders of attachment have been demonstrated to arise under conditions of social deprivation, such as institutionalization and maltreatment. An emotionally withdrawn/inhibited pattern and an indiscriminate/disinhibited pattern both have been described. Although these clinical types arise under similar conditions of environmental adversity, they tend to have different courses over time. We describe recent findings and highlight areas of emerging consensus and areas of continuing controversy regarding both disorganized patterns of attachment and clinical disorders of attachment in young children. PMID:14998869

  3. Attachment style and adjustment to divorce.

    PubMed

    Yárnoz-Yaben, Sagrario

    2010-05-01

    Divorce is becoming increasingly widespread in Europe. In this study, I present an analysis of the role played by attachment style (secure, dismissing, preoccupied and fearful, plus the dimensions of anxiety and avoidance) in the adaptation to divorce. Participants comprised divorced parents (N = 40) from a medium-sized city in the Basque Country. The results reveal a lower proportion of people with secure attachment in the sample group of divorcees. Attachment style and dependence (emotional and instrumental) are closely related. I have also found associations between measures that showed a poor adjustment to divorce and the preoccupied and fearful attachment styles. Adjustment is related to a dismissing attachment style and to the avoidance dimension. Multiple regression analysis confirmed that secure attachment and the avoidance dimension predict adjustment to divorce and positive affectivity while preoccupied attachment and the anxiety dimension predicted negative affectivity. Implications for research and interventions with divorcees are discussed.

  4. Modular Apparatus and Method for Attaching Multiple Devices

    NASA Technical Reports Server (NTRS)

    Okojie, Robert S (Inventor)

    2015-01-01

    A modular apparatus for attaching sensors and electronics is disclosed. The modular apparatus includes a square recess including a plurality of cavities and a reference cavity such that a pressure sensor can be connected to the modular apparatus. The modular apparatus also includes at least one voltage input hole and at least one voltage output hole operably connected to each of the plurality of cavities such that voltage can be applied to the pressure sensor and received from the pressure sensor.

  5. Wear simulation effects on overdenture stud attachments.

    PubMed

    Rutkunas, Vygandas; Mizutani, Hiroshi; Takahashi, Hidekazu; Iwasaki, Naohiko

    2011-01-01

    The aim of this study was to evaluate wear effects on overdenture resilient attachments. Six commercially available attachments were investigated: ERA orange and white (EO and EW), Locator pink, white and blue (LRP, LRW and LRB) and OP anchor (OP). Five specimens were used for wear simulation while other two specimens served as controls. Fifteen thousands insertion-removal cycles were simulated. Dimensional changes and surface characteristics were evaluated using light microscopy and SEM, respectively. Sudden decrease of retentive force was characteristic for EO and EW attachments. Retentive force of Locator attachments fluctuated throughout the wear simulation period. Dimensional changes and surface wear was more expressed on plastic cores than on plastic rings of attachment males. Based on SEM analysis, some of the specimens obtained smoother surface after wear simulation. Mechanism of retention loss of resilient overdenture attachments can be only partially explained by dimensional changes and surface alterations.

  6. Mechanics of membrane-cytoskeleton attachment in Paramecium

    NASA Astrophysics Data System (ADS)

    Campillo, C.; Jerber, J.; Fisch, C.; Simoes-Betbeder, M.; Dupuis-Williams, P.; Nassoy, P.; Sykes, C.

    2012-12-01

    In this paper we assess the role of the protein MKS1 (Meckel syndrome type 1) in the cortical membrane mechanics of the ciliated protist Paramecium. This protein is known to be crucial in the process of cilium formation, and we investigate its putative role in membrane-cytoskeleton attachment. Therefore, we compare cells where the gene coding for MKS1 is silenced to wild-type cells. We found that scanning electron microscopy observation of the cell surface reveals a cup-like structure in wild-type cells that is lost in silenced cells. Since this structure is based on the underlying cytoskeleton, one hypothesis to explain this observation is a disruption of membrane attachment to the cytoskeleton in the absence of MKS1 that should affect plasma membrane mechanics. We test this by probing the mechanics of wild-type and silenced cells by micropipette aspiration. Strikingly, we observe that, at the same aspiration pressure, the membrane of silenced cells is easily aspirated by the micropipette whereas that of wild-type cells enters only at a moderate velocity, an effect that suggests a detachment of the membrane from the underlying cytoskeleton in silenced cells. We quantify this detachment by measuring the deformation of the cell cortex and the rate of cell membrane entry in the micropipette. This study offers a new perspective for the characterization of membrane-cytoskeleton attachment in protists and paves the way for a better understanding of the role of membrane-cortex attachment in cilium formation.

  7. Posttranslational modification of Klebsiella pneumoniae flavodoxin by covalent attachment of coenzyme A, shown by sup 31 P NMR and electrospray mass spectrometry, prevents electron transfer from the nifJ protein to nitrogenase. A possible new regulatory mechanism for biological nitrogen fixation

    SciTech Connect

    Thorneley, R.N.F.; Ashby, G.A.; Drummond, M.H.; Eady, R.R.; Huff, S.; Macdonald, C.J. ); Abell, C.; Schneier, A. )

    1992-02-04

    A strain of Escherichia coli (71-18) that produces ca. 15% of its soluble cytoplasmic protein as a flavodoxin, the Klebsiella pneumoniae nifF gene product, has been constructed. The flavodoxin was purified using FPLC and resolved into two forms, designated KpFldI and KpFldII, which were shown to have identical N-terminal amino acid sequences (30 residues) in agreement with that predicted by the K. pneumoniae nifF DNA sequence. {sup 31}P NMR, electrospray mass spectrometry, UV-visible spectra, and thiol group estimations showed that the single cysteine residue (position 68) of KpFldI is posttranslationally modified in KpFldII by the covalent, mixed disulfide, attachment of coenzyme A. KpFldII was inactive as an electron carrier between the K. pneumoniae nifJ product (a pyruvate-flavodoxin oxidoreductase) and K. pneumoniae nifH product (the Fe-protein of nitrogenase). This novel posttranslational modification of a flavodoxin is discussed in terms of the regulation of nitrogenase activity in vivo in response to the level of dissolved O{sub 2} and the carbon status of diazotrophic cultures.

  8. Overdenture locator attachments for atrophic mandible

    PubMed Central

    Mahajan, Neerja; Thakkur, Rahul K

    2013-01-01

    Implant-supported overdentures provide a good opportunity for dentists to improve oral health and quality-of-life of patients. Atrophic mandible poses a significant challenge to successful oral rehabilitation with dental implants. In this article, the fabrication of lower overdenture by two narrow platform implants is described with dual retentive, resilient, self-locating locator attachment system. The locator attachment system has the lowest profile in comparison with the ball and bar attachments and is versatile up to 40° of divergence between two implants. By using locators as attachments, we can meet functional, economic and social expectation of patients with ease and satisfaction. PMID:24403798

  9. Overdenture locator attachments for atrophic mandible.

    PubMed

    Mahajan, Neerja; Thakkur, Rahul K

    2013-10-01

    Implant-supported overdentures provide a good opportunity for dentists to improve oral health and quality-of-life of patients. Atrophic mandible poses a significant challenge to successful oral rehabilitation with dental implants. In this article, the fabrication of lower overdenture by two narrow platform implants is described with dual retentive, resilient, self-locating locator attachment system. The locator attachment system has the lowest profile in comparison with the ball and bar attachments and is versatile up to 40° of divergence between two implants. By using locators as attachments, we can meet functional, economic and social expectation of patients with ease and satisfaction.

  10. Pressure dependence of half metallic behavior of Co{sub 2}VZ (Z=Si, Ge)-An ab initio Study

    SciTech Connect

    Seema, K. Kumar, Ranjan

    2014-04-24

    The structural, electronic and magnetic properties of Co-based Heusler compounds Co{sub 2}VZ (Z=Si, Ge) under pressure are studied using first-principles density functional theory. The total magnetic moment decreases on compression. Under application of external pressure, the valence band and conduction band are shifted downward which leads to modification of electronic structure. True half metallic to nearly half metallic transition is observed at 30 GPa, 50 GPa for Co{sub 2}VSi and Co{sub 2}VGe respectively. Around 100 GPa, Co{sub 2}VGe shows complete metallic behavior. The half metal to metal transition is accompanied by quenching of magnetic moment.

  11. Biliprotein maturation: the chromophore attachment.

    PubMed

    Scheer, H; Zhao, K-H

    2008-04-01

    Biliproteins are a widespread group of brilliantly coloured photoreceptors characterized by linear tetrapyrrolic chromophores, bilins, which are covalently bound to the apoproteins via relatively stable thioether bonds. Covalent binding stabilizes the chromoproteins and is mandatory for phycobilisome assembly; and, it is also important in biliprotein applications such as fluorescence labelling. Covalent binding has, on the other hand, also considerably hindered biliprotein research because autocatalytic chromophore additions are rare, and information on enzymatic addition by lyases was limited to a single example, an EF-type lyase attaching phycocyanobilin to cysteine-alpha84 of C-phycocyanin. The discovery of new activities for the latter lyases, and of new types of lyases, have reinvigorated research activities in the subject. So far, work has mainly concentrated on cyanobacterial phycobiliproteins. Methodological advances in the process, however, as well as the finding of often large numbers of homologues, opens new possibilities for research on the subsequent assembly/disassembly of the phycobilisome in cyanobacteria and red algae, on the assembly and organization of the cryptophyte light-harvesting system, on applications in basic research such as protein folding, and on the use of phycobiliproteins for labelling.

  12. Smartphone attachment for stethoscope recording.

    PubMed

    Thompson, Jeff

    2015-01-01

    With the ubiquity of smartphones and the rising technology of 3D printing, novel devices can be developed that leverage the "computer in your pocket" and rapid prototyping technologies toward scientific, medical, engineering, and creative purposes. This paper describes such a device: a simple 3D-printed extension for Apple's iPhone that allows the sound from an off-the-shelf acoustic stethoscope to be recorded using the phone's built-in microphone. The attachment's digital 3D files can be easily shared, modified for similar phones and devices capable of recording audio, and in combination with 3D printing technology allow for fabrication of a durable device without need for an entire factory of expensive and specialized machining tools. It is hoped that by releasing this device as an open source set of printable files that can be downloaded and reproduced cheaply, others can make use of these developments where access to cost-prohibitive, specialized medical instruments are not available. Coupled with specialized smartphone software ("apps"), more sophisticated and automated diagnostics may also be possible on-site. PMID:25626549

  13. 47 CFR 1.10007 - What applications can I file electronically?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... list of applications or notifications that must be filed electronically, see the IBFS Web site at http..., you must attach documentation to your electronic application before filing. We accept attachments...

  14. Process for attaching molecular wires and devices to carbon nanotubes and compositions thereof

    NASA Technical Reports Server (NTRS)

    Tour, James M. (Inventor); Bahr, Jeffrey L. (Inventor); Yang, Jiping (Inventor)

    2008-01-01

    The present invention is directed towards processes for covalently attaching molecular wires and molecular electronic devices to carbon nanotubes and compositions thereof. Such processes utilize diazonium chemistry to bring about this marriage of wire-like nanotubes with molecular wires and molecular electronic devices.

  15. Sintered Ag die attach as a solution to improve thermal performance of high power modules

    NASA Astrophysics Data System (ADS)

    Mansi, Mohammed S.

    The move to smaller electronics packages with higher numbers of I/Os has significantly increased power densities. The increase of power density puts more emphasis on finding solutions to improve the thermal performance of electronics packages. In wire bonded chips, the die attach layer plays a significant role in thermal performance as it establishes the main heat dissipation path from the chip. The use of sintered Ag as a die attach material to improve thermal performance is investigated in this research. A thermal simulation tool (FloTHERM) was used to study the thermal performance of five different sintered Ag die attach materials and compare their performance to the performance of silver filled epoxy die attach. Thermal simulation results showed low thermal improvement in the Theta-JA (thetaJA) value while higher thermal improvement in the Theta-JC (thetaJC) value was observed. Also, this research correlates the thermal simulation results with real-world measurements.

  16. Electron stimulated oxidation of silicon surfaces

    SciTech Connect

    Munoz, M.C.; Sacedon, J.L.

    1981-04-15

    Experimental evidence of electron stimulated oxidation (ESO) has been given for Si(111) 7 x 7 surface. In a first stage, the oxide thickness as a function of time shows a linear relationship; in a second stage, the growth rate quickly decreases and a pressure dependent saturation oxide thickness is reached. During the oxidation process an electrical potential does exist across the oxide, as is required in the Cabrera--Mott theory. The linear kinetics and the electrical potential are shown to be explicable in terms of a modified coupled-current approach based on the Cabrera--Mott theory, provided a semiphenomenological pressure dependent parameter is included. This represents a contribution of the surface reaction to the transport equation. The saturation has been explained as due to the decrease of the negative surface charge (donor levels) which produces a decrease of the electron current.

  17. [Effects of Gravity on Attachment of Tendon to Bone

    NASA Technical Reports Server (NTRS)

    Johnson, Roger B.

    1997-01-01

    We have received and processed all samples for either light or scanning electron microscopic analysis and have completed the histomorphometric analysis. We have characterized the changes caused by spaceflight to tendon attachments to the calcaneus, tibia, fibula and femur and compared them to hindlimbs and forelimbs from NIH.RZ. Soleus muscle histomorphometry has also been completed. Our results suggest severe osteoporosis in the femur, fibula and tibia of animals coincident to spaceflight, which had not resolved after 4-5 days following return to earth. This was evident at all sites, including sites of tendon attachments. This atrophy was not evident in the calcaneus. No muscle atrophy was evident. Comparison of scanning photomicrographs of flight animals with other lactating animals demonstrated structural similarities and suggested that it might be worthwhile to assess whether lactation is a factor in development of the osteoporosis in the spaceflight animals. In addition, evaluation of total calcium utilization by spaceflight animals would be beneficial.

  18. Loss and Disorganization from an Attachment Perspective

    ERIC Educational Resources Information Center

    Thomson, Paula

    2010-01-01

    In this article, it is hypothesized that disorganizing, disorienting, and unresolved states of mind about loss experiences, as classified by the Adult Attachment Interview (AAI) coding system, may offer insight into the bereaved mind and may guide clinical treatment approaches. This article discusses pre-loss attachment organizations and the…

  19. Dental magnetic attachment: toward third generation devices.

    PubMed

    Tegawa, Yoshinori; Kinouchi, Yohsuke

    2008-03-01

    Toward realizing the performance of functional and versatile dental magnetic attachments in the third generation required for individual prosthesis, it is important to control retentive characteristics of the attachments. For this purpose, three new types of magnetic attachment, i.e., split-pole type with a slant magnetization, modified split-pole type, and cylinder type, have been developed and evaluated in terms of the restoring force as well as the retentive force. The new attachments are designed to have high corrosion resistance, combining magnetic and nonmagnetic stainless steels and microlaser welding similar to the usual cup-yoke and sandwich-yoke types. It has been found that the two split-pole types have stronger restoring force and the cylinder type has weaker restoring force in comparison with the usual magnetic attachments. The attachments can be used properly and selectively according to individual requirement on abutment state and denture retention. As a result, the newly developed attachments may provide flexible retention performance useful for more effective and extensive applications of a magnetic attachment.

  20. Attachment Disorder, Basic Trust and Educational Psychology

    ERIC Educational Resources Information Center

    King, Michael G.; Newnham, Karyn

    2008-01-01

    The label Attachment Disorder (AD) is used as either a description of a child's presentation, or as a diagnostic category. It is unclear whether this label is intended to be identical with the DSM-IV Reactive Attachment Disorder (RAD) diagnostic category, or if it is a separate diagnosis based on Randolph's Questionnaire and the premises…

  1. Attachment Parenting: A Style That Works.

    ERIC Educational Resources Information Center

    Sears, William

    1995-01-01

    Discusses the benefits of attachment parenting, which emphasizes parental commitment, a low-stress pregnancy, childbirth preparation, breast-feeding with child-led weaning, prompt response to the baby's crying, flexible sleeping arrangements, close-knit father-mother-baby functioning, and the avoidance of detachment parenting. Attachment parenting…

  2. Attachment Representations and Time Perspective in Adolescence

    ERIC Educational Resources Information Center

    Laghi, Fiorenzo; D'Alessio, Maria; Pallini, Susanna; Baiocco, Roberto

    2009-01-01

    This study examines the relationship between attachment to parents and peers, time perspective and psychological adjustment in adolescence. 2,665 adolescents (M age = 17.03 years, SD = 1.48) completed self-report measures about parent and peer attachment, time perspective, sympathy and self-determination. Subjects were divided into four groups…

  3. An Attachment Perspective on Anger among Adolescents

    ERIC Educational Resources Information Center

    Konishi, Chiaki; Hymel, Shelley

    2014-01-01

    Extending John Bowlby's hypothesis that dysfunctional anger is a predictable outcome of insecure attachments to parents, this study investigated the relationship between current parent-adolescent attachment and both the experience and expression of anger. Participants included 776 students (379 boys and 397 girls) in grades 8-12. As predicted…

  4. Attachment and Socioemotional Problems in Middle Childhood

    ERIC Educational Resources Information Center

    Moss, Ellen; Lecompte, Vanessa

    2015-01-01

    In this article, we will evaluate the evidence concerning links between attachment and behavior problems in the middle childhood period. We will first provide a general introduction to the question of attachment and maladaptation in the middle childhood period, and then examine the recent empirical evidence with respect to both externalizing and…

  5. Genetic and Environmental Influences on Adolescent Attachment

    ERIC Educational Resources Information Center

    Fearon, Pasco; Shmueli-Goetz, Yael; Viding, Essi; Fonagy, Peter; Plomin, Robert

    2014-01-01

    Background: Twin studies consistently point to limited genetic influence on attachment security in the infancy period, but no study has examined whether this remains the case in later development. This study presents the findings from a twin study examining the relative importance of genetic and environmental influences on attachment in…

  6. An Attachment Model of University Connectedness

    ERIC Educational Resources Information Center

    Wilson, Steffen; Gore, Jonathan

    2013-01-01

    Students with high levels of connectedness to the university have been found to be more likely to complete their college degree than are students with low levels of university connectedness. This study examined the role of parental and peer attachment as distal predictors of school connectedness. As predicted, it was found that attachment style to…

  7. 78 FR 52868 - Pole Attachment Complaint Procedures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-27

    ... regulations concerning pole attachments outlined in the DATES section. DATES: Effective August 27, 2013, the amendments to Sec. Sec. 1.1403(e) and 1.1404 published at 63 FR 12025, March 12, 1998,have been approved by... COMMISSION 47 CFR Part 1 Pole Attachment Complaint Procedures AGENCY: Federal Communications...

  8. Parent-Child Attachment and Emotion Regulation

    ERIC Educational Resources Information Center

    Brumariu, Laura E.

    2015-01-01

    Given the centrality of both parent-child attachment and emotion regulation in children's development and adjustment, it is important to evaluate the relations between these constructs. This article discusses conceptual and empirical links between attachment and emotion regulation in middle childhood, highlights progress and challenges in the…

  9. Adolescent Self-Esteem, Attachment and Loneliness

    ERIC Educational Resources Information Center

    Dhal, Anubha; Bhatia, Sangeeta; Sharma, Vidhi; Gupta, Priyanka

    2007-01-01

    Objectives: To assess self-esteem, loneliness and attachment styles among adolescents and examine their association with each other and with age and gender. Method: Adolescents (55 males and 55 females) from a public school in Delhi, aged 10-13 years were administered Coopersmith Self-Esteem Inventory (School Form), Attachment Scale and UCLA…

  10. Psychophysical Scaling of Attachment and Loss.

    ERIC Educational Resources Information Center

    Tarnai, John

    Few studies have attempted to measure the strength of attachment in personal relationships or the stress associated with the loss of those relationships. To measure the perceived strength of attachment and stress of loss of 20 typical relationships (e.g.,wife or husband, father, son, daughter, brother, sister, friend, lover, grandparents, and…

  11. Adult Attachment as a Risk Factor for Intimate Partner Violence : The "Mispairing" of Partners' Attachment Styles

    ERIC Educational Resources Information Center

    Doumas, Diana M.; Pearson, Christine L.; Elgin, Jenna E.; McKinley, Lisa L.

    2008-01-01

    This study examined the relationship between intimate partner violence and adult attachment in a sample of 70 couples. The attachment style of each partner and the interaction of the partners' attachment styles were examined as predictors of intimate partner violence. Additional analyses were conducted to examine violence reciprocity and to…

  12. Correlates of Attachment at Age 3: Construct Validity of the Preschool Attachment Classification System

    ERIC Educational Resources Information Center

    Moss, Ellen; Bureau, Jean-Francois; Cyr, Chantal; Mongeau, Chantal; St-Laurent, Diane

    2004-01-01

    This study examined correlates of attachment at age 3 to further validate preschool separation-reunion measures. Three-year-olds (N = 150) and their mothers participated in a separation-reunion protocol, the Preschool Attachment Classification System (PACS: J. Cassidy & R. S. Marvin with the MacArthur Working Group on Attachment, 1992), and a…

  13. Adult Attachment, Culturally Adjusted Attachment, and Interpersonal Difficulties of Taiwanese Adults

    ERIC Educational Resources Information Center

    Wang, Chia-Chih DC; Scalise, Dominick A.

    2010-01-01

    This study examines the applicability of Western adult attachment perspectives to interpersonal difficulties experienced by individuals with indigenous Chinese cultural backgrounds. A total of 275 Taiwanese university students completed self-report surveys of adult attachment, ideal attachment, and interpersonal problems. Culturally adjusted…

  14. Attachment Patterns in the Psychotherapy Relationship: Development of the Client Attachment to Therapist Scale.

    ERIC Educational Resources Information Center

    Mallinckrodt, Brent; And Others

    1995-01-01

    Describes development of an instrument, the Client Attachment to Therapist Scale (CATS). CATS factors correlated in expected directions with survey measures of object relations, client-rated working alliance, social self-efficacy, and adult attachment. Cluster analysis revealed four types of client attachment. Discusses implications of attachment…

  15. Attachment and Autism: Parental Attachment Representations and Relational Behaviors in the Parent-Child Dyad

    ERIC Educational Resources Information Center

    Seskin, Lynn; Feliciano, Eileen; Tippy, Gil; Yedloutschnig, Ruby; Sossin, K. Mark; Yasik, Anastasia

    2010-01-01

    While attachment research has demonstrated that parents' internal working models of attachment relationships tend to be transmitted to their children, affecting children's developmental trajectories, this study specifically examines associations between adult attachment status and observable parent, child, and dyadic behaviors among children with…

  16. Comparison of poultry processing equipment surfaces for susceptibility to bacterial attachment and biofilm formation.

    PubMed

    Arnold, J W; Silvers, S

    2000-08-01

    During processing of poultry meat products, broiler carcasses come in contact with many solid surfaces. Bacteria from the carcasses can attach to wet equipment surfaces, form biofilms, and provide a source of cross-contamination for subsequent carcasses. In this study an array of common equipment surface materials was compared for susceptibility to bacterial attachment and biofilms. To model mixed microbial populations relevant to poultry processing, samples were taken directly from the processing line and exposed to the surface materials. Whole carcasses were rinsed with phosphate-buffered saline (100 mL), and the rinse was diluted in nutrient broth. Absorbance values (412 nm) of the suspensions at varying dilutions containing test surfaces were compared hourly with controls without test surfaces. The kinetics of bacterial attachment and biofilm formation on test surfaces were determined under the influence of pH, time, and bacterial cell density, and the elemental composition of the surface materials was determined by energy-dispersive X-ray analysis. Our results showed that surfaces vary in affinity for bacterial attachment and biofilm formation. Analysis by spectrophotometry and scanning electron microscopy confirmed that attachment to stainless steel, polyethylene, and belting was not significantly different from controls. Attachment to picker-finger rubber was significantly less than attachment to stainless steel and the other surfaces. In fact, picker-finger rubber inhibits bacterial contamination. An increased understanding of bacterial attachment and biofilm formation will assist in the development of interventions to counteract these processes and, thereby, enhance plant sanitation and pathogen control.

  17. Electron-excited molecule interactions

    SciTech Connect

    Christophorou, L.G. Tennessee Univ., Knoxville, TN . Dept. of Physics)

    1991-01-01

    In this paper the limited but significant knowledge to date on electron scattering from vibrationally/rotationally excited molecules and electron scattering from and electron impact ionization of electronically excited molecules is briefly summarized and discussed. The profound effects of the internal energy content of a molecule on its electron attachment properties are highlighted focusing in particular on electron attachment to vibrationally/rotationally and to electronically excited molecules. The limited knowledge to date on electron-excited molecule interactions clearly shows that the cross sections for certain electron-molecule collision processes can be very different from those involving ground state molecules. For example, optically enhanced electron attachment studies have shown that electron attachment to electronically excited molecules can occur with cross sections 10{sup 6} to 10{sup 7} times larger compared to ground state molecules. The study of electron-excited molecule interactions offers many experimental and theoretical challenges and opportunities and is both of fundamental and technological significance. 54 refs., 15 figs.

  18. Therapeutic limits from an attachment perspective.

    PubMed

    O'Sullivan, Lisha; Ryan, Virginia

    2009-04-01

    This article applies attachment theory and relevant research to therapeutic limit setting and focuses particularly on child-centred, non-directive play therapy (NDPT) practice. We review the role of limits in therapeutic change and examine whether therapeutic limit setting exhibits properties similar to those evident in typical adult-child relationships, a topic not previously considered in the literature. The first section identifies properties considered inherent in optimal attachment relationships from a limit setting perspective, drawing particularly on Heard and Lake's (1997) extension of Bowlby's attachment theory. The next section discusses therapists' use of limit setting from an attachment standpoint, distinguishing features of therapeutic limit setting which reflect properties evident in sensitive adult-child attachments. Finally, implications for further research and practice in child therapy are explored.

  19. Sleep and Attachment in Preterm Infants

    PubMed Central

    Schwichtenberg, A.J.; Shah, Prachi E.; Poehlmann, Julie

    2012-01-01

    Infants born preterm are at elevated risk for social emotional difficulties. However, factors contributing to this risk are largely understudied. Within the present study, we explored infant sleep as a biosocial factor that may play a role in infant social emotional development. Within a prospective longitudinal design, we examined parent-reported sleep patterns and observed parenting quality as predictors of infant-mother attachment in 171 infants born preterm. Using structural equation modeling, we examined main effect and moderator models linking infant sleep patterns and parenting with attachment security. Sleep patterns characterized by more daytime sleep and positive/responsive parenting predicted infant attachment security. Parent-reported nighttime sleep patterns were unrelated to attachment in this sample of infants born preterm. These results indicate that daytime sleep and parenting quality may be important for emerging attachment relationships in infants born preterm. PMID:23482430

  20. The Antimicrobial Activity of Porphyrin Attached Polymers

    NASA Astrophysics Data System (ADS)

    Thompson, Lesley

    2008-03-01

    We are interested in testing the antimicrobial activity of a porphyrin that is attached to a polymer. The porphyrin (5-(4-carboxyphenyl)-10,15,20-tris-(4-pryridyl)) was synthesized from methyl 4-formyl benzoate, 4-pyridinecarboxaldehyde, and pyrrole and attached to a copolymer of polystyrene/poly(vinyl benzyl chloride), which was synthesized by free radical polymerization. The antimicrobial activity of the polymer-attached porphyrin was then determined for gram-negative E. Coli grown to 0.80 OD. In this procedure, glass slides were coated with polymer-attached porphyrin via dip-coating, and the E. Coli bacteria were plated in Luria Broth media. The plates were subsequently exposed to light overnight before they were incubated as porphyrins act as photo-sensitizers when irradiated with light. The polymer-attached porphyrin did exhibit antimicrobial activity and parameters that affect its efficiency will be discussed.

  1. Attachment and capitalizing on positive events.

    PubMed

    Gosnell, Courtney L; Gable, Shelly L

    2013-01-01

    Although previous work has examined how individual differences in attachment security affect support processes for negative events, little work has looked at how attachment security affects support for positive events (capitalization). In a 10-day diary study of romantic couples, we examined the association between individual differences in attachment security and perceptions of capitalization support. We also examined how attachment security moderated the relationship between capitalization support and daily emotions, relationship satisfaction, and life satisfaction. The results showed that stronger avoidance orientations were associated with reduced perceptions of partner responsiveness. Anxiety moderated the association between responsive support and daily outcomes; for those high (versus low) on anxiety, daily relationship and life satisfaction were more strongly tied to partners' capitalization responses, and more negative emotions were experienced regarding those responses. Overall, insecure attachment was associated with mixed reactions to receiving responsive capitalization support. PMID:23582025

  2. Attachment to groups: theory and measurement.

    PubMed

    Smith, E R; Murphy, J; Coats, S

    1999-07-01

    Aspects of people's identification with groups may be understood by borrowing theoretical ideas and measurement strategies from research on attachment in close relationships. People have mental models of the self as a group member and of groups as sources of identity and esteem. These models affect thoughts, emotions, and behaviors related to group membership. Three studies show that two dimensions of attachment to groups, attachment anxiety and avoidance, can be assessed with good reliability, validity, and over-time stability. These factors are distinct from relationship attachment and from other measures of group identification. Group attachment predicts several important outcomes, including emotions concerning the group, time and activities shared with a group, social support, collective self-esteem, and ways of resolving conflict. This conceptualization provides new insights into the nature of people's psychological ties to groups.

  3. Security of attachment and preschool friendships.

    PubMed

    Park, K A; Waters, E

    1989-10-01

    Attachment theory proposes that the quality of the mother-child tie predicts the quality of a child's other close relationships. The purpose of this study was to test whether security of attachment to mother is related to the quality of a preschooler's best friendships. 33 4-year-old and their best friends participated (mean age = 46 months). Attachment Q-set data were collected to score security of mother-child attachment. Security data were used to classify the friend pairs as secure-secure or secure-insecure. Best friend dyads were observed for a 1-hour free-play session. Each pair's behavior was described with the Dyadic Relationships Q-set, a measure designed to describe the behavior of a pair of children. Secure-secure pairs were more harmonious, less controlling, more responsive, and happier than secure-insecure pairs. The results are related to previous work on attachment and social competence.

  4. Attachment of Agrobacterium to plant surfaces

    PubMed Central

    Matthysse, Ann G.

    2014-01-01

    Agrobacterium tumefaciens binds to the surfaces of inanimate objects, plants, and fungi. These bacteria are excellent colonizers of root surfaces. In addition, they also bind to soil particles and to the surface of artificial or man-made substances, such as polyesters and plastics. The mechanisms of attachment to these different surfaces have not been completely elucidated. At least two types of binding have been described unipolarpolysaccharide-dependent polar attachment and unipolar polysaccharide-independent attachment (both polar and lateral). The genes encoding the enzymes for the production of the former are located on the circular chromosome, while the genes involved in the latter have not been identified. The expression of both of these types of attachment is regulated in response to environmental signals. However, the signals to which they respond differ so that the two types of attachment are not necessarily expressed coordinately. PMID:24926300

  5. Continuous monitoring of bacterial attachment

    NASA Technical Reports Server (NTRS)

    Koeing, D. W.; Mishra, S. K.; Pierson, D. L.

    1994-01-01

    A major concern with the Space Station Freedom (SSF) water supply system is the control of longterm microbial contamination and biofilm development in the water storage and distribution systems. These biofilms have the potential for harboring pathogens as well as microbial strains containing resistance factors that could negatively influence crew health. The proposed means for disinfecting the water system on SSF (iodine) may encourage the selection of resistant strains. In fact, biofilm bacteria were observed in water lines from the Space Shuttle Columbia (OV-102); therefore, an alternative remediation method is required to disinfect spacecraft water lines. A thorough understanding of colonization events and the physiological parameters that will influence bacteria adhesion is required. The limiting factor for development of this technology is the ability to continuously monitor adhesion events and the effects of biocides on sessile bacteria. Methods were developed to allow bacterial adhesion and subsequent biocidal treatment to be monitored continuously. This technique couples automated image analysis with a continuous flow of a bacterial suspension through an optical flow cell. A strain of Pseudomonas cepacia isolated from the water supply of the Space Shuttle Discovery (OV-103) during STS-39 was grown in a nitrogen-limited continuous culture. This culture was challenged continuously with iodine during growth, and the adhesion characteristics of this strain was measure with regard to flow rate. Various biocides (ozone, hypochlorite, and iodine) were added to the flow stream to evaluate how well each chemical removed the bacteria. After biocide treatment, a fresh bacterial suspension was introduced into the flow cell, and the attachment rate was evaluated on the previously treated surface. This secondary fouling was again treated with biocide to determine the efficacy of multiple batch chemical treatments in removing biofilm.

  6. Pressure-dependent relaxation in the photoexcited mott insulator ET-F2TCNQ: influence of hopping and correlations on quasiparticle recombination rates.

    PubMed

    Mitrano, M; Cotugno, G; Clark, S R; Singla, R; Kaiser, S; Stähler, J; Beyer, R; Dressel, M; Baldassarre, L; Nicoletti, D; Perucchi, A; Hasegawa, T; Okamoto, H; Jaksch, D; Cavalleri, A

    2014-03-21

    We measure the ultrafast recombination of photoexcited quasiparticles (holon-doublon pairs) in the one dimensional Mott insulator ET-F(2)TCNQ as a function of external pressure, which is used to tune the electronic structure. At each pressure value, we first fit the static optical properties and extract the electronic bandwidth t and the intersite correlation energy V. We then measure the recombination times as a function of pressure, and we correlate them with the corresponding microscopic parameters. We find that the recombination times scale differently than for metals and semiconductors. A fit to our data based on the time-dependent extended Hubbard Hamiltonian suggests that the competition between local recombination and delocalization of the Mott-Hubbard exciton dictates the efficiency of the recombination.

  7. Pressure-dependent measurements on n+ GaAs (Si, Sn): the effect of deep donor (DX) states on the electrical properties and persistent photoconductivity

    NASA Astrophysics Data System (ADS)

    Foster, T. J.; Maude, D. K.; Eaves, L.; Portal, J. C.; Dmowski, L.; Nathan, M.; Heiblum, M.; Harris, J. J.; Beall, R. B.

    1988-10-01

    Shubnikov-de Haas and persistent photoconductivity measurements are used to study the mobility, free electron density (n) and the occupancy of the DX centre in heavily doped n-GaAs as a function of doping level and hydrostatic pressure. The results show that the DX centre produces a resonant donor level between the Γ - and L-conduction band minima at a concentration comparable with the doping level. For the Si-doped samples, comparison with local vibration mode measurements indicates that the DX level can be identified with SiGa. The level acts to pin the Fermi energy at electron concentrations around 1.8 × 1019 cm-3. Analysis of the results indicates that macroscopic charge separation is not responsible for persistent photoconductivity in these samples.

  8. Longitudinal association between adolescent attachment, adult romantic attachment, and emotion regulation strategies.

    PubMed

    Pascuzzo, Katherine; Cyr, Chantal; Moss, Ellen

    2013-01-01

    Attachment security towards parents and peers in adolescence, and romantic attachment styles and emotion regulation strategies in young adulthood, were evaluated using an eight-year longitudinal design. Fifty-six young adults completed the Inventory of Parent and Peer Attachment (IPPA) at age 14, and then, at age 22, the Experience in Close Relationships (ECR) and the Coping Inventory for Stressful Situations (CISS), an emotion regulation questionnaire concerning coping strategies, including task-oriented versus emotion-oriented foci. Results indicated that greater insecurity to parents and peers in adolescence predicted a more anxious romantic attachment style and greater use of emotion-oriented strategies in adulthood. Concurrently, anxious adult attachment style was related to more emotion-oriented strategies, whereas an avoidant attachment style was related to less support-seeking. Analyses also identified emotion-oriented coping strategies as a partial mediator of the link between adolescent attachment insecurity to parents and adult anxious attachment, and a complete mediator of the association between adolescent attachment insecurity to peers and adult anxious attachment. These findings support the core assumption of continuity in attachment theory, where relationships to parents influence close romantic relationships in adulthood.

  9. Preschool teacher attachment and attention skills.

    PubMed

    Commodari, Elena

    2013-01-01

    Attention underlies and energizes all cognitive and behavioral activities. Many studies showed that the quality of child attachment (both to parental and non parental figures) influences cognitive functions and attention. This study aimed to investigate the relationships among attachment to preschool teachers and attention in a sample of preschoolers. In particular, the study analyzed whether child attachment security to preschool teachers influences the different aspects of their attention skills. In addition, gender- and age-related differences in attention and teacher attachment were explored. Research was conducted using two standardized instruments: the Attention and Concentration Battery, and the Attachment Q Sort. Participants were 279 children (147 male, 132 female) who attended two preschools in a town in Southern Italy. Descriptive analyses, t-tests analyses, and correlation and regression analyses were carried out. Findings highlighted several interesting points concerning the relationships that occur among attachment to preschool teachers and attention. Children with secure attachments presented higher reaction time and better auditory, visual, and visual spatial selectivity and maintenance.

  10. Environmental and genetic influences on early attachment

    PubMed Central

    Gervai, Judit

    2009-01-01

    Attachment theory predicts and subsequent empirical research has amply demonstrated that individual variations in patterns of early attachment behaviour are primarily influenced by differences in sensitive responsiveness of caregivers. However, meta-analyses have shown that parenting behaviour accounts for about one third of the variance in attachment security or disorganisation. The exclusively environmental explanation has been challenged by results demonstrating some, albeit inconclusive, evidence of the effect of infant temperament. In this paper, after reviewing briefly the well-demonstrated familial and wider environmental influences, the evidence is reviewed for genetic and gene-environment interaction effects on developing early attachment relationships. Studies investigating the interaction of genes of monoamine neurotransmission with parenting environment in the course of early relationship development suggest that children's differential susceptibility to the rearing environment depends partly on genetic differences. In addition to the overview of environmental and genetic contributions to infant attachment, and especially to disorganised attachment relevant to mental health issues, the few existing studies of gene-attachment interaction effects on development of childhood behavioural problems are also reviewed. A short account of the most important methodological problems to be overcome in molecular genetic studies of psychological and psychiatric phenotypes is also given. Finally, animal research focusing on brain-structural aspects related to early care and the new, conceptually important direction of studying environmental programming of early development through epigenetic modification of gene functioning is examined in brief. PMID:19732441

  11. An attachment research perspective on ADHD.

    PubMed

    Kissgen, Ruediger; Franke, Sebastian

    2016-06-01

    Since the beginning of clinical attachment research in the mid-1980s the number of research projects in this area has been continuously increasing. The research questions so far can be allocated to numerous medical disciplines such as psychosomatic medicine, adult psychiatry or child and adolescent psychiatry. Recently, children with ADHD and their families have also become subjects of this branch of research. Their specific behavioral characteristics from early childhood on constitute unique challenges on the parent-child interaction. If these interactions develop in a suboptimal way, children may develop an insecure or even a disorganized attachment quality. The latter represents a risk factor for a clinically significant psychopathological development.This article initially presents basic principles of attachment theory and discusses the relevance of the cardinal symptoms of ADHD for clinical attachment research. Subsequently, it outlines and discusses the main results of existing research regarding attachment and ADHD. It concludes with a perspective on research questions that need to be addressed in the future with regard to a transgenerational model that highlights the importance of parental attachment representations to the development of children's attachment quality.

  12. Nuclear reactor fuel rod attachment system

    DOEpatents

    Not Available

    1980-09-17

    A reusable system is described for removably attaching a nuclear reactor fuel rod to a support member. A locking cap is secured to the fuel rod and a locking strip is fastened to the support member. The locking cap has two opposing fingers shaped to form a socket having a body portion. The locking strip has an extension shaped to rigidly attach to the socket's body portion. The locking cap's fingers are resiliently deflectable. For attachment, the locking cap is longitudinally pushed onto the locking strip causing the extension to temporarily deflect open the fingers to engage the socket's body portion. For removal, the process is reversed.

  13. Attachment and Socioemotional Problems in Middle Childhood.

    PubMed

    Moss, Ellen; Lecompte, Vanessa

    2015-01-01

    In this article, we will evaluate the evidence concerning links between attachment and behavior problems in the middle childhood period. We will first provide a general introduction to the question of attachment and maladaptation in the middle childhood period, and then examine the recent empirical evidence with respect to both externalizing and internalizing profiles. We will conclude with a discussion of new directions in research on this issue including the search for possible mediators and moderators of attachment/behavior problem associations. PMID:26086128

  14. Measuring preferential attachment in evolving networks

    NASA Astrophysics Data System (ADS)

    Jeong, H.; Néda, Z.; Barabási, A. L.

    2003-02-01

    A key ingredient of many current models proposed to capture the topological evolution of complex networks is the hypothesis that highly connected nodes increase their connectivity faster than their less connected peers, a phenomenon called preferential attachment. Measurements on four networks, namely the science citation network, Internet, actor collaboration and science coauthorship network indicate that the rate at which nodes acquire links depends on the node's degree, offering direct quantitative support for the presence of preferential attachment. We find that for the first two systems the attachment rate depends linearly on the node degree, while for the last two the dependence follows a sublinear power law.

  15. Praziquantel inhibits Schistosoma mansoni attachment in vitro.

    PubMed

    da-Silva, S P; Noel, F

    1990-01-01

    Male adult Schistosoma mansoni worms were placed in a glass dish containing Tyrode solution and observed for 15 min after addition of praziquantel (0.01 to 1 microM). Praziquantel promoted a concentration- and time-dependent inhibition of sucker-mediated attachment of the worm. Attachment inhibition was correlated with shortening of the parasite. We propose that the rapid and total inhibition of worm attachment observed in vitro with 1 microM praziquantel indicates that therapeutic concentrations of this drug should promote a rapid hepatic shift, in vivo, which may facilitate host tissue reaction. PMID:2101049

  16. Give Them Roots, Then Let Them Fly: Understanding Attachment Therapy.

    ERIC Educational Resources Information Center

    McKelvey, Carole A., Ed.

    This book describes attachment theory, presents the attachment therapy program in place at the Evergreen Attachment Center at Evergreen, Colorado, and examines the implications of attachment therapy. The chapters are: (1) "An Overview" (Carole A. McKelvey, John Alston); (2) "Attachment Theory and Assessment" (Michael Orlans, Terry Levy); (3)…

  17. 30 CFR 77.1437 - End attachment retermination.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false End attachment retermination. 77.1437 Section... MINES Personnel Hoisting Wire Ropes § 77.1437 End attachment retermination. Damaged or deteriorated wire... at an attachment; (b) Improper installation of an attachment; (c) Slippage at an attachment; or...

  18. 30 CFR 77.1436 - Drum end attachment.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Drum end attachment. 77.1436 Section 77.1436... Hoisting Wire Ropes § 77.1436 Drum end attachment. (a) For drum end attachment, wire rope shall be attached... anchor bolts, clamps, or wedges, provided that the attachment is a design feature of the hoist...

  19. Attachment and Children: Citations From Selected Data Bases.

    ERIC Educational Resources Information Center

    Baskin, Linda B., Comp.

    This bibliography compiles citations from seven selected data bases on the topic of attachment and children. The citations are grouped into eight categories: (1) Attachment -- General; (2) Institutions -- Hospitals, Prisons; (3) Day Care and Attachment; (4) Handicapped Children and Attachment; (5) Separation; (6) Child Abuse and Attachment; (7)…

  20. A Review of the Psychometric Properties of Selected Attachment Instruments.

    ERIC Educational Resources Information Center

    Garbarino, Jennifer J.

    Attachment theory asserts that human beings are innately programmed to seek and form attachments with others. The assumption that the quality of early attachment relationships will be functionally related to subsequent attachment styles and competencies provides the theoretical basis for extending the theory of attachment to the study of adult…