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Sample records for gas phase structure

  1. Amphipols Outperform Dodecylmaltoside Micelles in Stabilizing Membrane Protein Structure in the Gas Phase

    PubMed Central

    2014-01-01

    Noncovalent mass spectrometry (MS) is emerging as an invaluable technique to probe the structure, interactions, and dynamics of membrane proteins (MPs). However, maintaining native-like MP conformations in the gas phase using detergent solubilized proteins is often challenging and may limit structural analysis. Amphipols, such as the well characterized A8-35, are alternative reagents able to maintain the solubility of MPs in detergent-free solution. In this work, the ability of A8-35 to retain the structural integrity of MPs for interrogation by electrospray ionization-ion mobility spectrometry-mass spectrometry (ESI-IMS-MS) is compared systematically with the commonly used detergent dodecylmaltoside. MPs from the two major structural classes were selected for analysis, including two β-barrel outer MPs, PagP and OmpT (20.2 and 33.5 kDa, respectively), and two α-helical proteins, Mhp1 and GalP (54.6 and 51.7 kDa, respectively). Evaluation of the rotationally averaged collision cross sections of the observed ions revealed that the native structures of detergent solubilized MPs were not always retained in the gas phase, with both collapsed and unfolded species being detected. In contrast, ESI-IMS-MS analysis of the amphipol solubilized MPs studied resulted in charge state distributions consistent with less gas phase induced unfolding, and the presence of lowly charged ions which exhibit collision cross sections comparable with those calculated from high resolution structural data. The data demonstrate that A8-35 can be more effective than dodecylmaltoside at maintaining native MP structure and interactions in the gas phase, permitting noncovalent ESI-IMS-MS analysis of MPs from the two major structural classes, while gas phase dissociation from dodecylmaltoside micelles leads to significant gas phase unfolding, especially for the α-helical MPs studied. PMID:25495802

  2. Gas-Phase Structures of Ketene and Acetic Acid from Acetic Anhydride Using Very-High-Temperature Gas Electron Diffraction.

    PubMed

    Atkinson, Sandra J; Noble-Eddy, Robert; Masters, Sarah L

    2016-03-31

    The gas-phase molecular structure of ketene has been determined using samples generated by the pyrolysis of acetic anhydride (giving acetic acid and ketene), using one permutation of the very-high-temperature (VHT) inlet nozzle system designed and constructed for the gas electron diffraction (GED) apparatus based at the University of Canterbury. The gas-phase structures of acetic anhydride, acetic acid, and ketene are presented and compared to previous electron diffraction and microwave spectroscopy data to show improvements in data extraction and manipulation with current methods. Acetic anhydride was modeled with two conformers, rather than a complex dynamic model as in the previous study, to allow for inclusion of multiple pyrolysis products. The redetermined gas-phase structure of acetic anhydride (obtained using the structure analysis restrained by ab initio calculations for electron diffraction method) was compared to that from the original study, providing an improvement on the description of the low vibrational torsions compared to the dynamic model. Parameters for ketene and acetic acid (both generated by the pyrolysis of acetic anhydride) were also refined with higher accuracy than previously reported in GED studies, with structural parameter comparisons being made to prior experimental and theoretical studies. PMID:26916368

  3. Gas Phase Structure of Amino Acids: La-Mb Studies

    NASA Astrophysics Data System (ADS)

    Mata, I. Pena S.; Sanz, M. E.; Vaquero, V.; Cabezas, C.; Perez, C.; Blanco, S.; López, J. C.; Alonso, J. L.

    2009-06-01

    Recent improvements in our laser ablation molecular beam Fourier transform microwave (LA-MB-FTMW) spectrometer such as using Laval-type nozzles and picoseconds Nd:YAG lasers (30 to 150 ps) have allowed a major step forward in the capabilities of this experimental technique as demonstrated by the last results in serine cysteine and threonine^a for which seven, six and seven conformers have been respectively identified. Taking advantage of these improvements we have investigated the natural amino acids metionine, aspartic and glutamic acids and the γ-aminobutyric acid (GABA) with the aim of identify and characterize their lower energy conformers. Searches in the rotational spectra have lead to the identification of seven conformers of metionine, six and five of aspartic and glutamic acids, respectively, and seven for the γ-aminobutyric. These conformers have been unambiguously identified by their spectroscopic constants. In particular the ^{14}N nuclear quadrupole coupling constants, that depend heavily on the orientation of the amino group with respect to the principal inertial axes of the molecule, prove to be a unique tool to distinguish unambigously between conformations with similar rotational constants. For the γ-aminobutyric acid two of the seven observed structures are stablized by an intramolecular interaction n-π*. Two new conformers of proline have been identified together with the two previously observed. J. L. Alonso, C. Pérez, M. E. Sanz, J. C. López, S. Blanco, Phys.Chem.Chem.Phys., 2009, 11, 617. D. B. Atkinson, M. A. Smith, Rev. Sci. Instrum. 1995, 66, 4434 S. Blanco, M. E. Sanz, J. C. López, J. L. Alonso, Proc. Natl. Acad. Sci. USA2007, 104, 20183. M. E. Sanz, S. Blanco, J. C. López, J. L. Alonso, Angew. Chem. Int. Ed.,2008, 120, 6312. A. Lesarri, S. Mata, E. J. Cocinero, S. Blanco, J.C. López, J. L. Alonso, Angew. Chem. Int. Ed. , 2002, 41, 4673

  4. Reinvestigation of the gas-phase structure of tris(trifluoromethyl)arsine

    NASA Astrophysics Data System (ADS)

    Berger, Raphael J. F.; Mitzel, Norbert W.

    2010-08-01

    The gas-phase structure of tris(trifluoromethyl)arsine (As(CF)3) at ambient temperature has been re-investigated by means of electron diffraction. Substantial higher accuracy in structural parameters compared to the previous investigation has been achieved. In contrast to the previously reported C3v structure we found C3 symmetry. Selected r structure parameters are: As-C = 2.007(2) Å; C-As-C = 95.5(3)°. The experimental structure parameters are compared to parameters obtained in HF/TZVPP and MP2/TZVPP calculations, the latter being in excellent agreement with the experimental structure.

  5. Cryogenic Ion Mobility-Mass Spectrometry: Tracking Ion Structure from Solution to the Gas Phase.

    PubMed

    Servage, Kelly A; Silveira, Joshua A; Fort, Kyle L; Russell, David H

    2016-07-19

    Electrospray ionization (ESI) combined with ion mobility-mass spectrometry (IM-MS) is adding new dimensions, that is, structure and dynamics, to the field of biological mass spectrometry. There is increasing evidence that gas-phase ions produced by ESI can closely resemble their solution-phase structures, but correlating these structures can be complicated owing to the number of competing effects contributing to structural preferences, including both inter- and intramolecular interactions. Ions encounter unique hydration environments during the transition from solution to the gas phase that will likely affect their structure(s), but many of these structural changes will go undetected because ESI-IM-MS analysis is typically performed on solvent-free ions. Cryogenic ion mobility-mass spectrometry (cryo-IM-MS) takes advantage of the freeze-drying capabilities of ESI and a cryogenically cooled IM drift cell (80 K) to preserve extensively solvated ions of the type [M + xH](x+)(H2O)n, where n can vary from zero to several hundred. This affords an experimental approach for tracking the structural evolution of hydrated biomolecules en route to forming solvent-free gas-phase ions. The studies highlighted in this Account illustrate the varying extent to which dehydration can alter ion structure and the overall impact of cryo-IM-MS on structural studies of hydrated biomolecules. Studies of small ions, including protonated water clusters and alkyl diammonium cations, reveal structural transitions associated with the development of the H-bond network of water molecules surrounding the charge carrier(s). For peptide ions, results show that water networks are highly dependent on the charge-carrying species within the cluster. Specifically, hydrated peptide ions containing lysine display specific hydration behavior around the ammonium ion, that is, magic number clusters with enhanced stability, whereas peptides containing arginine do not display specific hydration around the

  6. The effect of molecular dynamics sampling on the calculated observable gas-phase structures.

    PubMed

    Tikhonov, Denis S; Otlyotov, Arseniy A; Rybkin, Vladimir V

    2016-07-21

    In this study, we compare the performance of various ab initio molecular dynamics (MD) sampling methods for the calculation of the observable vibrationally-averaged gas-phase structures of benzene, naphthalene and anthracene molecules. Nose-Hoover (NH), canonical and quantum generalized-Langevin-equation (GLE) thermostats as well as the a posteriori quantum correction to the classical trajectories have been tested and compared to the accurate path-integral molecular dynamics (PIMD), static anharmonic vibrational calculations as well as to the experimental gas electron diffraction data. Classical sampling methods neglecting quantum effects (NH and canonical GLE thermostats) dramatically underestimate vibrational amplitudes for the bonded atom pairs, both C-H and C-C, the resulting radial distribution functions exhibit nonphysically narrow peaks. This deficiency is almost completely removed by taking the quantum effects on the nuclei into account. The quantum GLE thermostat and a posteriori correction to the canonical GLE and NH thermostatted trajectories capture most vibrational quantum effects and closely reproduce computationally expensive PIMD and experimental radial distribution functions. These methods are both computationally feasible and accurate and are therefore recommended for calculations of the observable gas-phase structures. A good performance of the quantum GLE thermostat for the gas-phase calculations is encouraging since its parameters have been originally fitted for the condensed-phase calculations. Very accurate molecular structures can be predicted by combining the equilibrium geometry obtained at a high level of electronic structure theory with vibrational amplitudes and corrections calculated using MD driven by a lower level of electronic structure theory. PMID:27331660

  7. The structure of chloromethyl thiocyanate, CH2ClSCN, in gas and crystalline phases.

    PubMed

    Berrueta Martínez, Y; Rodríguez Pirani, L S; Erben, M F; Reuter, C G; Vishnevskiy, Y V; Stammler, H G; Mitzel, N W; Della Védova, C O

    2015-06-28

    The structural and conformational properties of chloromethyl thiocyanate, CH2ClSCN, were studied in the solid phase and in the gas phase using in situ low-temperature single-crystal X-ray diffraction experiments (XRD) and gas electron diffraction (GED), respectively. Depending on the mutual orientation of the Cl-C bond and the -SCN group, two conformations, gauche and anti, were found to coexist in the gas phase. The gauche conformer, with a dihedral angle φ(ClC-SC) = 71.8(4)°, is the most stable form, with an abundance of 89(3)% at ambient temperature. High level quantum-chemical calculations at the CCSD(T)/cc-pVTZ level of approximation reproduce these experimental results. In the solid state only gauche conformers were found to be present. The crystal structure shows specific intermolecular interactions including chalcogen-type interactions. The experimental electron density distribution was determined by high-angle X-ray diffraction. The atoms in molecules (AIM) theory was applied to analyze the charge density topology for a better characterization of intermolecular interactions present in the crystal. PMID:26017187

  8. Gas-phase acidities of tetrahedral oxyacids from ab initio electronic structure theory

    SciTech Connect

    Rustad, J.R.; Dixon, D.A.; Kubicki, J.D.; Felmy, A.R.

    2000-05-04

    Density functional calculations have been performed on several protonation states of the oxyacids of Si, P, V, As, Cr, and S. Structures and vibrational frequencies are in good agreement with experimental values where these are available. A reasonably well-defined correlation between the calculated gas-phase acidities and the measured pK{sub a} in aqueous solution has been found. The pK{sub a}/gas-phase acidity slopes are consistent with those derived from previous molecular mechanics calculations on ferric hydrolysis and the first two acidity constants for orthosilicic acid. The successive deprotonation of other H{sub n}TO{sub 4} species, for a given tetrahedral anion T are roughly consistent with this slope, but not to the extent that there is a universal correlation among all species.

  9. Structural Isomerization of the Gas Phase 2-NORBORNYL Cation Revealed with Infrared Spectroscopy and Computational Chemistry

    NASA Astrophysics Data System (ADS)

    Mauney, Daniel; Mosley, Jonathan; Duncan, Michael A.

    2014-06-01

    The non-classical structure of the 2-norborny cation (C_7H11+) which was at the center of "the most heated chemical controversy of our time" has been observed in the condensed phase and recently using X-ray crystallography. However, no gas phase vibrational spectrum has been collected. The C_7H11+ cation is produced via H_3+ protonation of norbornene by pulsed discharge in a supersonic expansion of H_2/Ar. Ions are mass-selected and probed using infrared photodissociation spectroscopy. Due to high exothermicity, protonation via H_3+ leads to a structural isomerization to the global minimum structure 1,3-dimethylcyclopentenyl (DMCP+). Experiments are currently being conducted to find softer protonation techniques that could lead to the authentic 2-norbornyl cation. Schleyer,P.v.R. et. al.; Stable Carbocation Chemistry, John Wiley & Sons,Inc.; New York, 1997, Chapter 2

  10. Nonstatistical UV Fragmentation of Gas-Phase Peptides Reveals Conformers and Their Structural Features.

    PubMed

    Kopysov, Vladimir; Makarov, Alexander; Boyarkin, Oleg V

    2016-03-17

    Solving the 3D structure of a biomolecule requires recognition of its conformers and measurements of their individual structural identities, which can be compared with calculations. We employ the phenomenon of nonstatistical photofragmentation, detected by a combination of UV cold ion spectroscopy and high-resolution mass spectrometry, to identify the main conformers of gas-phase peptides and to recover individual UV absorption and mass spectra of all of these conformers in a single laser scan. We first validate this approach with a benchmark dipeptide, Tyr-Ala, and then apply it to a decapeptide, gramicidin S. The revealed characteristic structural difference between the conformers of the latter identifies some of the previously calculated structures of gramicidin S as the most likely geometries of its remaining unsolved conformer. PMID:26950179

  11. UV/Vis Action Spectroscopy and Structures of Tyrosine Peptide Cation Radicals in the Gas Phase.

    PubMed

    Viglino, Emilie; Shaffer, Christopher J; Tureček, František

    2016-06-20

    We report the first application of UV/Vis photodissociation action spectroscopy for the structure elucidation of tyrosine peptide cation radicals produced by oxidative intramolecular electron transfer in gas-phase metal complexes. Oxidation of Tyr-Ala-Ala-Ala-Arg (YAAAR) produces Tyr-O radicals by combined electron and proton transfer involving the phenol and carboxyl groups. Oxidation of Ala-Ala-Ala-Tyr-Arg (AAAYR) produces a mixture of cation radicals involving electron abstraction from the Tyr phenol ring and N-terminal amino group in combination with hydrogen-atom transfer from the Cα positions of the peptide backbone. PMID:27159034

  12. Liquid-Gas Relative Permeabilities in Fractures: Effects of Flow Structures, Phase Transformation and Surface Roughness

    SciTech Connect

    Chih-Ying Chen

    2005-06-30

    and between smooth-walled and rough-walled fractures. We then used these experimental data to verify and calibrate a field-scale method for inferring steam-water relative permeabilities from production data. After that, actual production data from active geothermal fields at The Geysers and Salton Sea in California were used to calculate the relative permeabilities of steam and water. These theoretical, experimental, and in-situ results provide better understanding of the likely behavior of geothermal, gascondensate, and steam injection reservoirs. From this work, the main conclusions are: (1) the liquid-gas relative permeabilities in fractures can be modeled by characterizing the flow structures which reflect the interactions among fluids and the rough fracture surface; (2) the steam-water flow behavior in fractures is different from air-water flow in the aspects of relative permeability, flow structure and residual/immobile phase saturations.

  13. Electronic Structure and Gas-Phase Behaviour of the Heaviest Elements

    SciTech Connect

    Pershina, V.; Anton, J.; Jacob, T.; Borschevsky, A.

    2010-04-30

    Electronic structures and gas-phase adsorption behaviour of the heaviest elements 112, 113 and 114 and of their lighter homologs Hg, Tl and Pb is studied on the basis of ab initio Dirac-Coulomb atomic and four-component Density Functional Theory molecular and cluster calculations. The heaviest elements were shown to have low adsorption enthalpies on Teflon and should, therefore, be well transported through Teflon capillaries from the target chamber to the chemistry set up. Adsorption enthalpies of these elements on the Au(111) surface are predicted as -44.5 kJ/mol, -158.6 kJ/mol and -68.5 kJ/mol, respectively, giving the following sequence in the adsorption temperatures 113>114>112.

  14. Gas Phase Nanoparticle Synthesis

    NASA Astrophysics Data System (ADS)

    Granqvist, Claes; Kish, Laszlo; Marlow, William

    This book deals with gas-phase nanoparticle synthesis and is intended for researchers and research students in nanomaterials science and engineering, condensed matter physics and chemistry, and aerosol science. Gas-phase nanoparticle synthesis is instrumental to nanotechnology - a field in current focus that raises hopes for environmentally benign, resource-lean manufacturing. Nanoparticles can be produced by many physical, chemical, and even biological routes. Gas-phase synthesis is particularly interesting since one can achieve accurate manufacturing control and hence industrial viability.

  15. Native electrospray ionization and electron-capture dissociation for comparison of protein structure in solution and the gas phase

    PubMed Central

    Zhang, Hao; Cui, Weidong

    2013-01-01

    The importance of protein and protein-complex structure motivates improvements in speed and sensitivity of structure determination in the gas phase and comparison with that in solution or solid state. An opportunity for the gas phase measurement is mass spectrometry (MS) combined with native electrospray ionization (ESI), which delivers large proteins and protein complexes in their near-native states to the gas phase. In this communication, we describe the combination of native ESI, electron-capture dissociation (ECD), and top-down MS for exploring the structures of ubiquitin and cytochrome c in the gas phase and their relation to those in the solid-state and solution. We probe structure by comparing the protein's flexible regions, as predicted by the B-factor in X-ray crystallography, with the ECD fragments. The underlying hypothesis is that maintenance of structure gives fragments that can be predicted from B-factors. This strategy may be applicable in general when X-ray structures are available and extendable to the study of intrinsically disordered proteins. PMID:24363606

  16. Structure and reactivity of benzoylnitrene radical anion in the gas phase.

    PubMed

    Wijeratne, Neloni R; Wenthold, Paul G

    2007-12-01

    The open-shell benzoylnitrene radical anion, readily generated by electron ionization of benzoylazide, undergoes unique chemical reactivity with radical reagents and Lewis acids in the gas phase. Reaction with nitric oxide, NO, proceeds by loss of N2 and formation of benzoate ion. This novel reaction is also observed to occur with phenylnitrene anion, forming phenoxide. Similar reactivity was observed in the reaction between benzoylnitrene radical anion and NO2, forming benzoate ion and nitrous oxide. Electronic structure calculations indicate that the reaction has a high-energy barrier that is overcome by the energy released by bond formation. Benzoylnitrene radical anion also transfers oxygen anion to NO and NO2 as well as to CS2 and SO2. In contrast, phenylnitrene anion reacts with carbon disulfide by C+ or CS+ abstraction, forming S- or S2-. Electronic structure calculations indicate that benzoylnitrene in the ground state resembles a slightly polarized benzoate anion, but with a free radical localized on the nitrogen. PMID:18001090

  17. Hydrogen-bonded glycine-HCN complexes in gas phase: structure, energetics, electric properties and cooperativity

    NASA Astrophysics Data System (ADS)

    Machado da Silva, Arnaldo; Chakrabarty, Sumana; Chaudhuri, Puspitapallab

    2015-03-01

    Twelve hydrogen-bonded complexes of glycine and hydrogen cyanide have been studied using high-level quantum-chemical calculations in gas phase. In particular, six 1:1 glycine-HCN dimers and six 1:2 glycine-HCN trimers have been considered. Besides the characteristics of the hydrogen bonds and their effect on molecular structure and energetics, several molecular electric properties have been calculated utilising two different models: MP2/6-31++G(d,p) and DFT-B3LYP/6-31++G(d,p). Although the structural parameters calculated by the two models are similar, equilibrium electronic energies of the clusters show model dependence. The lowest energy dimer is same in both the models which is ca. 3.0 kcal/mol more stable than the highest energy dimer. However, the lowest energy trimer is different in two methods. The energetic difference of stability between the highest and lowest trimer is 4.2 kcal/mol (4.4 kcal/mol) at an MP2 (B3LYP) level of calculation. The bond angles of glycine, in particular, are quite sensitive to the hydrogen-bond formation. Four out of six trimers are found to be strongly cooperative in both the models. Significant changes of dipole moments and polarisabilities of isolated glycine and hydrogen cyanide are observed due to the formation of hydrogen bonding. The Rayleigh scattering intensities of all clusters are much larger than those of their constituent monomers.

  18. Gas Phase Spectra and Structural Determination of Glucose 6 Phosphate Using Cryogenic Ion Vibrational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kregel, Steven J.; Voss, Jonathan; Marsh, Brett; Garand, Etienne

    2014-06-01

    Glucose-6-Phosphate (G6P) is one member of a class of simple phosphorylated sugars that are relevant in biological processes. We have acquired a gas phase infrared spectrum of G6P- using cryogenic ion vibrational spectroscopy (CIVS) in a home-built spectrometer. The experimental spectrum was compared with calculated vibrational spectra from a systematic conformer search. For both of the α and β anomers, results show that only the lowest energy conformers are present in the gas phase. If spectral signatures for similar sugars could be cataloged, it would allow for conformer-specific determination of mixture composition, for example, for glycolyzation processes.

  19. An enormous vibrational motion: the gas-phase structure of dimethyl-bis(methoxyethynyl) germanium.

    PubMed

    Borisenko, Konstantin B; Yezhov, Roman N; Gruener, Sergej V; Robertson, Heather E; Rankin, David W H

    2004-11-21

    The structure of dimethyl-bis(methoxyethynyl) germanium has been determined in the gas phase by electron diffraction utilising flexible restraints from quantum chemical calculations. Theoretical methods (B3LYP/6-311+G* and MP2/6-311+G*) predict a low barrier to rotation of the methoxy groups in the molecule in addition to low-frequency vibrations of the long ethynyl chains. In the equilibrium structure the Ge-C[triple bond]C angles of the two methoxyethynyl fragments in the molecule are computed to deviate by up to 4 degrees from the linear arrangement. As a consequence of low-frequency large-amplitude vibrational motion the experimental structure of these fragments without applying vibrational corrections deviates considerably from linearity, while the structure corrected for vibrational effects using the harmonic approximation and taking into account a non-linear transformation between internal and Cartesian coordinates (r(h1)) shows closer agreement with theory. The main experimental structural parameters of dimethyl-bis(methoxyethynyl) germanium (r(h1)) are: r(Ge-C)(mean), 192.5(1) pm; DeltaGeC =r(Ge-C(methyl))-r(Ge-C(ethynyl)), 4.5(5) pm, r(C[triple bond]C)(mean), 122.8(2) pm; r(C-O)(mean), 138.9(3) pm; DeltaCO =r(C(methyl)-O)-r(C(ethynyl)-O), 14.5(2) pm, r(C-H)(mean), 109.1(4) pm; [angle](X-C-H)(mean)(X = Ge,O), 109(1) degree; [angle]C(ethynyl)-Ge-C(ethynyl), 108.1(4) degree; [angle]C(methyl)-Ge-C(methyl), 113.4(5) degree; [angle]Ge-C[triple bond]C, 163(1) degree; [angle]C[triple bond]C-O, 176(2) degree; [angle]C-O-C, 115.2(6) degree; methoxy group torsion, tau, 36(9) degree from the position in which the C-O bond eclipses the further Ge-C(ethynyl) bond. PMID:15540132

  20. Molecular structures of vinylarsine, vinyldichloroarsine and arsine studied by gas-phase electron diffraction and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Noble-Eddy, Robert; Masters, Sarah L.; Rankin, David W. H.; Robertson, Heather E.; Guillemin, Jean-Claude

    2010-08-01

    The molecular structures of vinylarsine (CH 2dbnd CHAsH 2), vinyldichloroarsine (CH 2dbnd CHAsCl 2) and arsine (AsH 3) have been determined from gas-phase electron diffraction data and, in the case of vinylarsine, rotation constants, employing the SARACEN method. The structure of vinylarsine represents the first complete gas-phase structure of a primary arsine. The experimental geometric parameters generally show good agreement with those obtained using ab initio calculations. Key structural parameters ( rh1) for vinylarsine are rAs-H = 150.5(4) pm, rAs-C = 195.1(1) pm and ∠C-C-As = 119.4(2)°. The bonding and conformational trends in both vinylarsine and vinyldichloroarsine are compared to those found in the analogous amines and phosphines.

  1. Gas-Phase Neutral Binary Oxide Clusters: Distribution, Structure, and Reactivity toward CO.

    PubMed

    Wang, Zhe-Chen; Yin, Shi; Bernstein, Elliot R

    2012-09-01

    Neutral binary (vanadium-cobalt) oxide clusters are generated and detected in the gas phase for the first time. Their reactivities toward carbon monoxide (CO) are studied both experimentally and theoretically. Experimental results suggest that neutral VCoO4 can react with CO to generate VCoO3 and CO2. Density functional theory studies show parallel results as well as provide detailed reaction mechanisms. PMID:26292125

  2. Going clean: structure and dynamics of peptides in the gas phase and paths to solvation.

    PubMed

    Baldauf, Carsten; Rossi, Mariana

    2015-12-16

    The gas phase is an artificial environment for biomolecules that has gained much attention both experimentally and theoretically due to its unique characteristic of providing a clean room environment for the comparison between theory and experiment. In this review we give an overview mainly on first-principles simulations of isolated peptides and the initial steps of their interactions with ions and solvent molecules: a bottom up approach to the complexity of biological environments. We focus on the accuracy of different methods to explore the conformational space, the connections between theory and experiment regarding collision cross section evaluations and (anharmonic) vibrational spectra, and the challenges faced in this field. PMID:26598600

  3. Going clean: structure and dynamics of peptides in the gas phase and paths to solvation

    NASA Astrophysics Data System (ADS)

    Baldauf, Carsten; Rossi, Mariana

    2015-12-01

    The gas phase is an artificial environment for biomolecules that has gained much attention both experimentally and theoretically due to its unique characteristic of providing a clean room environment for the comparison between theory and experiment. In this review we give an overview mainly on first-principles simulations of isolated peptides and the initial steps of their interactions with ions and solvent molecules: a bottom up approach to the complexity of biological environments. We focus on the accuracy of different methods to explore the conformational space, the connections between theory and experiment regarding collision cross section evaluations and (anharmonic) vibrational spectra, and the challenges faced in this field.

  4. Structure of olefin-imidacloprid and gas-phase fragmentation chemistry of its protonated form.

    PubMed

    Fusetto, Roberto; White, Jonathan M; Hutton, Craig A; O'Hair, Richard A J

    2016-02-01

    One of the major insect metabolites of the widely used neonicotinoid insecticide imidacloprid, 1 (1-[(6-chloro-3-pyridinyl)methyl]-N-nitro-1H-imidazol-2-amine), is the olefin 2. To better understand how the structure of olefin 2 relates to the gas-phase fragmentation of its protonated form, 2H(+), X-ray crystallography, tandem mass spectrometry experiments and DFT calculations were carried out. Olefin 2 was found to be in a tautomeric form where the proton is on the N(1) position of the imidazole ring and forms a hydrogen bond to one of the oxygen atoms of the coplanar nitroamine group. Under conditions of low-energy collision-induced dissociation (CID) in a linear ion trap, 2H(+), formed via electrospray ionization (ESI), fragments via a major loss of water, together with minor competing losses of HNO2 and NO2•.This contrasts with 1H+, which mainly undergoes bond homolysis via NO2• loss. Thus, installation of the double bond in 2 plays a key role in facilitating the loss of water. DFT calculations, carried out using the B3LYP/6-311G++(d,p) level of theory, revealed that loss of water was energetically more favourable compared to HNO2 and NO2• loss. Three multistep, energetically accessible mechanisms were identified for loss of water from 2H(+), and these have the following barriers: (I) direct proton transfer from N(5) of the pyridine to O(1) on the NO2 group (119 kJ mol(-1)); (II) rotation of the N(2)-N(4) bond (117 kJ mol(-1)); (III) 1,3-intramolecular proton transfer between the two oxygen atoms of the NO2 group (145 kJ mol(-1)). Given that the lowest barrier for the losses of HNO2 and NO2• is 156 kJ mol(-1), it is likely that all three water loss mechanisms occur concurrently. PMID:26726997

  5. Gas-phase structure and reactivity of the keto tautomer of the deoxyguanosine radical cation.

    PubMed

    Feketeová, Linda; Chan, Bun; Khairallah, George N; Steinmetz, Vincent; Maître, Philippe; Radom, Leo; O'Hair, Richard A J

    2015-10-21

    Guanine radical cations are formed upon oxidation of DNA. Deoxyguanosine (dG) is used as a model, and the gas-phase infrared (IR) spectroscopic signature and gas-phase unimolecular and bimolecular chemistry of its radical cation, dG˙(+), A, which is formed via direct electrospray ionisation (ESI/MS) of a methanolic solution of Cu(NO3)2 and dG, are examined. Quantum chemistry calculations have been carried out on 28 isomers and comparisons between their calculated IR spectra and the experimentally-measured spectra suggest that A exists as the ground-state keto tautomer. Collision-induced dissociation (CID) of A proceeds via cleavage of the glycosidic bond, while its ion–molecule reactions with amine bases occur via a number of pathways including hydrogen-atom abstraction, proton transfer and adduct formation. A hidden channel, involving isomerisation of the radical cation via adduct formation, is revealed through the use of two stages of CID, with the final stage of CID showing the loss of CH2O as a major fragmentation pathway from the reformed radical cation, dG˙(+). Quantum chemistry calculations on the unimolecular and bimolecular reactivity are also consistent with A being present as a ground-state keto tautomer. PMID:25942055

  6. Structural Analysis of Perfluoropropanoyl Fluoride in the Gas, Liquid, and Solid Phases.

    PubMed

    Berrueta Martínez, Yanina; Reuter, Christian G; Vishnevskiy, Yury V; Bava, Yanina B; Picone, A Lorena; Romano, Rosana M; Stammler, Hans-Georg; Neumann, Beate; Mitzel, Norbert W; Della Védova, Carlos O

    2016-04-21

    The coexistence of two conformers in perfluoropropanoyl fluoride, CF3CF2C(O)F, differing in the CC-CF dihedral angle (gauche 85(10)% and anti 15(10)%), has been determined by means of gas-phase electron diffraction (GED). Quantum-chemical calculations performed at the MP2 and B3LYP approximations and cc-pVTZ basis sets reproduce the experimental values with confidence. By contrast, FTIR spectra give no clear evidence for the anti-conformer in the gas phase. Information on this less abundant but stable rotamer is obtained from matrix-isolation/FTIR spectroscopy and liquid Raman spectroscopy. In situ crystallization and single-crystal X-ray diffraction (XRD) data reveal the presence of solely the gauche-conformation in the solid state. A set of intermolecular interactions including C═O···C═O, C-F···F-C, and F···C═O is detected. The nature of bonding and the relative stabilities of gauche- and anti-conformers are explored using natural bond orbitals. PMID:27023801

  7. Gas-liquid two-phase flow structure in the multi-scale weighted complexity entropy causality plane

    NASA Astrophysics Data System (ADS)

    Tang, Yi; Zhao, An; Ren, Ying-yu; Dou, Fu-Xiang; Jin, Ning-De

    2016-05-01

    The multi-scale weighted complexity entropy causality plane (MS-WCECP) is proposed for characterizing the physical structure of complex system. Firstly we use the method to investigate typical nonlinear time series. Compared with the multi-scale complexity entropy causality plane (MS-CECP), the MS-WCECP can not only uncover the dynamic information loss of complex system with the increase of scale, but also can characterize the complexity of nonlinear dynamic system. In particular, the algorithm of MS-WCECP performs strong anti-noise ability. Then we calculate the MS-WCECP for the conductance fluctuating signals measured from vertical upward gas-liquid two-phase flow experiments in a small diameter pipe, the results demonstrate that the MS-WCECP is a useful approach for exploring the stability and complexity in gas-liquid two-phase flows.

  8. Exploring Salt Bridge Structures of Gas-Phase Protein Ions using Multiple Stages of Electron Transfer and Collision Induced Dissociation

    NASA Astrophysics Data System (ADS)

    Zhang, Zhe; Browne, Shaynah J.; Vachet, Richard W.

    2014-04-01

    The gas-phase structures of protein ions have been studied by electron transfer dissociation (ETD) and collision-induced dissociation (CID) after electrospraying these proteins from native-like solutions into a quadrupole ion trap mass spectrometer. Because ETD can break covalent bonds while minimally disrupting noncovalent interactions, we have investigated the ability of this dissociation technique together with CID to probe the sites of electrostatic interactions in gas-phase protein ions. By comparing spectra from ETD with spectra from ETD followed by CID, we find that several proteins, including ubiquitin, CRABP I, azurin, and β-2-microglobulin, appear to maintain many of the salt bridge contacts known to exist in solution. To support this conclusion, we also performed calculations to consider all possible salt bridge patterns for each protein, and we find that the native salt bridge pattern explains the experimental ETD data better than nearly all other possible salt bridge patterns. Overall, our data suggest that ETD and ETD/CID of native protein ions can provide some insight into approximate location of salt bridges in the gas phase.

  9. Exploring Salt Bridge Structures of Gas-Phase Protein Ions using Multiple Stages of Electron Transfer and Collision Induced Dissociation

    PubMed Central

    Zhang, Zhe; Browne, Shaynah J.; Vachet, Richard W.

    2014-01-01

    The gas-phase structures of protein ions have been studied by electron transfer dissociation (ETD) and collision-induced dissociation (CID) after electrospraying these proteins from native-like solutions into a quadrupole ion trap mass spectrometer. Because ETD can break covalent bonds while minimally disrupting non-covalent interactions, we have investigated the ability of this dissociation technique together with CID to probe the sites of electrostatic interactions in gas phase protein ions. By comparing spectra from ETD with spectra from ETD followed by CID, we find that several proteins, including ubiquitin, CRABP I, azurin, and β-2-microglobulin, appear to maintain many of the salt bridge contacts known to exist in solution. To support this conclusion, we also performed calculations to consider all possible salt bridge patterns for each protein, and we find that the native salt bridge pattern explains the experimental ETD data better than nearly all other possible salt bridge patterns. Overall, our data suggest that ETD and ETD/CID of native protein ions can provide some insight into approximate location of salt bridges in the gas phase. PMID:24496600

  10. Microwave spectra and gas phase structural parameters for N-hydroxypyridine-2(1H)-thione.

    PubMed

    Daly, Adam M; Mitchell, Erik G; Sanchez, Daniel A; Block, Eric; Kukolich, Stephen G

    2011-12-22

    The microwave spectrum for N-hydroxypyridine-2(1H)-thione (pyrithione) was measured in the frequency range 6-18 GHz, providing accurate rotational constants and nitrogen quadrupole coupling strengths for three isotopologues, C(5)H(4)(32)S(14)NOH, C(5)H(4)(32)S(14)NOD, and C(5)H(4)(34)S(14)NOH. Pyrithione was found to be in a higher concentration in the gas phase than the other tautomer, 2-mercaptopyridine-N-oxide (MPO). Microwave spectroscopy is best suited to determine which structure predominates in the gas phase. The measured rotational constants were used to accurately determine the coordinates of the substituted atoms and provided sufficient data to determine some of the important structural parameters for pyrithione, the only tautomer observed in the present work. The spectra were obtained using a pulsed-beam Fourier transform microwave spectrometer, with sufficient resolution to allow accurate measurements of the (14)N nuclear quadrupole hyperfine interactions. Ab initio calculations provided structural parameters and quadrupole coupling strengths that are in very good agreement with measured values. The experimental rotational constants for the parent compound are A = 3212.10(1), B = 1609.328(7), and C = 1072.208(6) MHz, yielding the inertial defect Δ(0) = -0.023 amu·Å(2) for the C(5)H(4)(32)S(14)NOH isotopologue. The observed near zero inertial defect clearly indicates a planar structure. The least-squares fit structural analysis yielded the experimental bond lengths R(O-H) = 0.93(2) Å, R(C-S) = 1.66(2) Å, and angle (N-O-H) = 105(4)° for the ground state structure. PMID:22070758

  11. An Experimental and Computational Investigation into the Gas-Phase Acidities of Tyrosine and Phenylalanine: Three Structures for Deprotonated Tyrosine

    SciTech Connect

    Bokatzian, Samantha S.; Stover, Michele L.; Plummer, Chelsea E.; Dixon, David A.; Cassady, Carolyn J.

    2014-11-06

    Using mass spectrometry and correlated molecular orbital theory, three deprotonated structures were revealed for the amino acid tyrosine. The structures were distinguished experimentally by ion/molecule reactions involving proton transfer and trimethylsilyl azide. Gas-phase acidities from proton transfer reactions and from G3(MP2) calculations generally agree well. The lowest energy structure, which was only observed experimentally using electrospray ionization from aprotic solvents, is deprotonated at the carboxylic acid group and is predicted to be highly folded. A second unfolded carboxylate structure is several kcal/mol higher in energy and primarily forms from protic solvents. Protic solvents also yield a structure deprotonated at the phenolic side chain, which experiments find to be intermediate in energy to the two carboxylate forms. G3(MP2) calculations indicate that the three structures differ in energy by only 2.5 kcal/mol, yet they are readily distinguished experimentally. Structural abundance ratios are dependent upon experimental conditions, including the solvent and accumulation time of ions in a hexapole. Under some conditions, carboxylate ions may convert to phenolate ions. For phenylalanine, which lacks a phenolic group, only one deprotonated structure was observed experimentally when electrosprayed from protic solvent. This agrees with G3(MP2) calculations that find the folded and unfolded carboxylate forms to differ by 0.3 kcal/mol.

  12. An experimental and computational investigation into the gas-phase acidities of tyrosine and phenylalanine: three structures for deprotonated tyrosine.

    PubMed

    Bokatzian, Samantha S; Stover, Michele L; Plummer, Chelsea E; Dixon, David A; Cassady, Carolyn J

    2014-11-01

    Using mass spectrometry and correlated molecular orbital theory, three deprotonated structures were revealed for the amino acid tyrosine. The structures were distinguished experimentally by ion/molecule reactions involving proton transfer and trimethylsilyl azide. Gas-phase acidities from proton transfer reactions and from G3(MP2) calculations generally agree well. The lowest energy structure, which was only observed experimentally using electrospray ionization from aprotic solvents, is deprotonated at the carboxylic acid group and is predicted to be highly folded. A second unfolded carboxylate structure is several kcal/mol higher in energy and primarily forms from protic solvents. Protic solvents also yield a structure deprotonated at the phenolic side chain, which experiments find to be intermediate in energy to the two carboxylate forms. G3(MP2) calculations indicate that the three structures differ in energy by only 2.5 kcal/mol, yet they are readily distinguished experimentally. Structural abundance ratios are dependent upon experimental conditions, including the solvent and accumulation time of ions in a hexapole. Under some conditions, carboxylate ions may convert to phenolate ions. For phenylalanine, which lacks a phenolic group, only one deprotonated structure was observed experimentally when electrosprayed from protic solvent. This agrees with G3(MP2) calculations that find the folded and unfolded carboxylate forms to differ by 0.3 kcal/mol. PMID:25299802

  13. Terpenes in the gas phase: The structural conformation of S-(-)-perillaldehyde investigated by microwave spectroscopy and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Avilés Moreno, Juan Ramón; Partal Ureña, Francisco; López González, Juan Jesús; Huet, Thérèse R.

    2009-04-01

    S-(-)-perillaldehyde (C 10H 14O) has been characterized in the gas phase using a Fourier transform microwave spectroscopy experiment in a supersonic molecular beam. Two conformers - with the isopropenyl group in the equatorial position - have been detected and described by a set of molecular parameters including the principal rotational constants and the quartic centrifugal distortion parameters. Quantum chemical calculations indicate that a third conformer might not be observed due to relaxation processes in the jet. The gas phase results are compared with the liquid phase IR-Raman-VCD spectra. Our study shows that gas phase spectroscopy is a powerful tool for characterizing monoterpenes.

  14. Structural variability in transition metal oxide clusters: gas phase vibrational spectroscopy of V3O(6-8)+.

    PubMed

    Asmis, Knut R; Wende, Torsten; Brümmer, Mathias; Gause, Oliver; Santambrogio, Gabriele; Stanca-Kaposta, E Cristina; Döbler, Jens; Niedziela, Andrzej; Sauer, Joachim

    2012-07-14

    We present gas phase vibrational spectra of the trinuclear vanadium oxide cations V(3)O(6)(+)·He(1-4), V(3)O(7)(+)·Ar(0,1), and V(3)O(8)(+)·Ar(0,2) between 350 and 1200 cm(-1). Cluster structures are assigned based on a comparison of the experimental and simulated IR spectra. The latter are derived from B3LYP/TZVP calculations on energetically low-lying isomers identified in a rigorous search of the respective configurational space, using higher level calculations when necessary. V(3)O(7)(+) has a cage-like structure of C(3v) symmetry. Removal or addition of an O-atom results in a substantial increase in the number of energetically low-lying structural isomers. V(3)O(8)(+) also exhibits the cage motif, but with an O(2) unit replacing one of the vanadyl oxygen atoms. A chain isomer is found to be most stable for V(3)O(6)(+). The binding of the rare gas atoms to V(3)O(6-8)(+) clusters is found to be strong, up to 55 kJ/mol for Ar, and markedly isomer-dependent, resulting in two interesting effects. First, for V(3)O(7)(+)·Ar and V(3)O(8)(+)·Ar an energetic reordering of the isomers compared to the bare ion is observed, making the ring motif the most stable one. Second, different isomers bind different number of rare gas atoms. We demonstrate how both effects can be exploited to isolate and assign the contributions from multiple isomers to the vibrational spectrum. The present results exemplify the structural variability of vanadium oxide clusters, in particular, the sensitivity of their structure on small perturbations in their environment. PMID:22499393

  15. Experimental observation of the transition between gas-phase and aqueous solution structures for acetylcholine, nicotine, and muscarine ions.

    PubMed

    Seydou, Mahamadou; Grégoire, Gilles; Liquier, Jean; Lemaire, J; Schermann, Jean Pierre; Desfrançois, Charles

    2008-03-26

    Structural information on acetylcholine and its two agonists, nicotine, and muscarine has been obtained from the interpretation of infrared spectra recorded in the gas-phase or in low pH aqueous solutions. Simulated IR spectra have been obtained using explicit water molecules or a polarization continuum model. The conformational space of the very flexible acetylcholine ions is modified by the presence of the solvent. Distances between its pharmacophoric groups cover a lower range in hydrated species than in isolated species. A clear signature of the shift of protonation site in nicotine ions is provided by the striking change of their infrared spectrum induced by hydration. On the contrary, structures of muscarine ions are only slightly influenced by the presence of water. PMID:18311975

  16. Higher-order structure of nucleic acids in the gas phase: top-down analysis of base-pairing interactions

    PubMed Central

    Fabris, D.; Kellersberger, K.A.; Wilhide, J.A.

    2012-01-01

    Non-ergodic as well as ergodic activation methods are capable of maintaining the integrity of base pairs during the top-down analysis of nucleic acids. Here, we investigate the significance of this characteristic in the investigation of higher-order structures of increasing complexity. We show that cognate fragments produced by typical backbone cleavages may not be always detected as separate sequence ions, but rather as individual products that remain associated through mutual pairing contacts. This effect translates into unintended masking of cleavage events that take place in double-stranded regions, thus leading to the preferential detection of fragments originating from unpaired regions. Such effect is determined by the stability of the weak non-covalent association between complementary stretches, which is affected by base composition, length of the double-stranded structure, and charge of the precursor ion selected for analysis. Although such effect may prevent the achievement of full sequence coverage for primary structure determination, it may provide the key to correctly differentiate double- versus single-stranded regions, in what could be defined as gas-phase footprinting experiments. In light of the critical role played by base pairs in defining the higher-order structure of nucleic acids, these approaches will be expected to support an increased utilization of mass spectrometry for the investigation of nucleic acid structure and dynamics. PMID:24027423

  17. PIV Measurement of Transient 3-D (Liquid and Gas Phases) Flow Structures Created by a Spreading Flame over 1-Propanol

    NASA Technical Reports Server (NTRS)

    Hassan, M. I.; Kuwana, K.; Saito, K.

    2001-01-01

    In the past, we measured three-D flow structure in the liquid and gas phases that were created by a spreading flame over liquid fuels. In that effort, we employed several different techniques including our original laser sheet particle tracking (LSPT) technique, which is capable of measuring transient 2-D flow structures. Recently we obtained a state-of-the-art integrated particle image velocimetry (IPIV), whose function is similar to LSPT, but it has an integrated data recording and processing system. To evaluate the accuracy of our IPIV system, we conducted a series of flame spread tests using the same experimental apparatus that we used in our previous flame spread studies and obtained a series of 2-D flow profiles corresponding to our previous LSPT measurements. We confirmed that both LSPT and IPIV techniques produced similar data, but IPIV data contains more detailed flow structures than LSPT data. Here we present some of newly obtained IPIV flow structure data, and discuss the role of gravity in the flame-induced flow structures. Note that the application of IPIV to our flame spread problems is not straightforward, and it required several preliminary tests for its accuracy including this IPIV comparison to LSPT.

  18. Probing the structures of gas-phase rhodium cluster cations by far-infrared spectroscopy

    SciTech Connect

    Harding, D. J.; Gruene, P.; Haertelt, M.; Meijer, G.; Fielicke, A.; Hamilton, S. M.; Hopkins, W. S.; Mackenzie, S. R.; Neville, S. P.; Walsh, T. R.

    2010-12-07

    The geometric structures of small cationic rhodium clusters Rh{sub n}{sup +} (n = 6-12) are investigated by comparison of experimental far-infrared multiple photon dissociation spectra with spectra calculated using density functional theory. The clusters are found to favor structures based on octahedral and tetrahedral motifs for most of the sizes considered, in contrast to previous theoretical predictions that rhodium clusters should favor cubic motifs. Our findings highlight the need for further development of theoretical and computational methods to treat these high-spin transition metal clusters.

  19. Gas-Phase Structures of Linalool and Coumarin Studied by Microwave Spectroscopy

    NASA Astrophysics Data System (ADS)

    Nguyen, H. V. L.; Stahl, W.; Grabow, J.-U.

    2013-06-01

    The microwave spectra of two natural substances, linalool and coumarin, were recorded in the microwave range from 9 to 16 GHz and 8.5 to 10.5 GHz, respectively.Linalool is an acyclic monoterpene and the main component of lavender oil. It has a structure with many possible conformations. The geometry of the lowest energy conformer has been determined by a combination of microwave spectroscopy and quantum chemical calculations. Surprisingly, a globular rather than a prolate shape was found. This structure is probably stabilized by a π interaction between two double bonds which are arranged in two stacked layers of atoms within the molecule. A-E splittings due to the internal rotation of one methyl group could be resolved and the barrier to internal rotation was determined to be 400.20(64) cm^{-1}. The standard deviation of the fit was close to experimental accuracy. For an identification of the observed conformer not only the rotational constants but also the internal rotation parameters of one of the methyl groups were needed. Coumarin is a widely used flavor in perfumery as sweet woodruff scent. The aromatic structure allows solely for one planar conformer, which was found under molecular beam conditions and compared to other molecules with similar structures. Here, the rotational spectrum could be described by a set of parameters including the rotational constants and the centrifugal distortion constants using a semi-rigid molecule Hamiltonian. Furthermore, the rotational transitions of all nine ^{13}C isotopologues were measured in natural abundance. As a consequence, the microwave structure of coumarin could be almost completely determined.

  20. Gas-phase chemical dynamics

    SciTech Connect

    Weston, R.E. Jr.; Sears, T.J.; Preses, J.M.

    1993-12-01

    Research in this program is directed towards the spectroscopy of small free radicals and reactive molecules and the state-to-state dynamics of gas phase collision, energy transfer, and photodissociation phenomena. Work on several systems is summarized here.

  1. The gas-phase structure of azetidine: Microwave spectroscopy, and electron diffraction and normal coordinate analysis

    NASA Astrophysics Data System (ADS)

    Günther, Horst; Schrem, Gisela; Oberhammer, Heinz

    1984-03-01

    The geometric structure of azetidine has been determined by a combined analysis of electron diffraction and microwave data, implementing the results of a normal coordinate analysis. The following geometric parameters ( rz values) for the ring skeleton have been obtained: C sbnd N = 1.473 (3), C sbnd C = 1.563 (3)Å, CNC = 91.2 (0.4)° and puckering angle θ = 29.7 (1.4)°. The microwave spectra were analyzed for the ground state of the parent and N-deuterated species and for the υ = 1 and υ = 2 states of the puckering vibration of the parent species. Dipole moments and nitrogen quadrupole coupling constants were determined. The structural parameters are compared to previous experimental and theoretical results for azetidine and are discussed in context with the isoelectronic cyclobutane and oxetane.

  2. Investigation of the gas-phase structure and rotational barrier of trimethylsilyl trifluoromethanesulfonate and comparison with covalent sulfonates

    NASA Astrophysics Data System (ADS)

    Defonsi Lestard, María E.; Tuttolomondo, María E.; Varetti, Eduardo L.; Wann, Derek A.; Robertson, Heather E.; Rankin, David W. H.; Altabef, Aida Ben

    2010-12-01

    The molecular structure of trimethylsilyl trifluoromethanesulfonate, CF 3SO 2OSi(CH 3) 3, has been determined in the gas phase from electron-diffraction data supplemented by ab initio (MP2) and DFT calculations using 6-31G(d), 6-311++G(d,p) and 6-311G++(3df,3pd) basis sets. Both experimental and theoretical data indicate that only one gauche conformer is possible by rotating about the O-S bond. The anomeric effect is a fundamental stereoelectronic interaction and presents a profound influence on the electronic geometry. We have investigated the origin of the anomeric effect by means of NBO and AIM analysis. A natural bond orbital analysis showed that the lpπ[O bonded to Si)] → σ *[C-S] hyperconjugative interaction favors the gauche conformation. In addition, comparison of the structural and stereoelectronic properties of the title molecule with those of silyl trifluoromethanesulfonate and methyl trifluoromethanesulfonate has been carried out.

  3. Singularity of influence of stochastic and order phase structures on optical quality of gas-dynamic laser active medium flow

    NASA Astrophysics Data System (ADS)

    Kovalevsky, Valery O.; Lobachev, Vitaly V.

    2002-02-01

    Detail analysis of active medium flow structure is presented. Schlieren method photography of flow is processed to reconstruct parameters both stochastic and order phase components. Properties of random part including correlation function, spectrum of spatial frequency, scale of turbulence, are determined by digital filtering. It was possible to compare influence of random and regular phase distortions on radiation divergence structure.

  4. Rotational spectra and gas phase structure of the maleimide - Formic acid doubly hydrogen bonded dimer

    NASA Astrophysics Data System (ADS)

    Pejlovas, Aaron M.; Kukolich, Stephen G.

    2016-03-01

    Rotational transitions were measured for the maleimide - formic acid doubly hydrogen bonded dimer using a Flygare-Balle type pulsed-beam Fourier transform microwave spectrometer. No splittings caused by possible concerted double proton tunneling motion were observed. Experimental rotational constants (MHz), quadrupole coupling constants (MHz), and centrifugal distortion constants (kHz) were determined for the parent and three deuterium substituted isotopologues. The values for the parent are A = 2415.0297(10), B = 784.37494(38), C = 592.44190(33), DJ = 0.0616(64), DJK = -0.118(35), DK = -1.38(15), 1.5χaa = 2.083(14), and 0.25(χbb-χcc) = 1.1565(29). The hydrogen bond lengths were determined using a nonlinear least squares structure fitting program. Rotational constants for this complex are consistent with a planar structure, with an inertial defect of Δ = -0.528 amu Å2. The B3LYP calculation yielded rotational constants within 0.1% of the experimental values.

  5. Conformational Transformation of Five-Membered Rings: the Gas Phase Structure of 2-METHYLTETRAHYDROFURAN

    NASA Astrophysics Data System (ADS)

    Van, Vinh; Nguyen, Ha Vinh Lam; Stahl, Wolfgang

    2015-06-01

    2-Methyltetrahydrofuran (2-MeTHF) is a promising environmentally friendly solvent and biofuel component which is derived from renewable resources. Following the principles of Green Chemistry, 2-MeTHF has been evaluated in various fields like organometallics, metathesis, and biosynthesis on the way to more eco-friendly syntheses. Cyclopentane as the prototype of five-membered rings is well-known to exist as twist or envelope structures. However, the conformational analysis of its heterocyclic derivative 2-methyl-tetrahydrothiophene (MTTP) yielded two stable twist conformers and two envelope transition states. Here, we report on the heavy atom r_s structure of the oxygen-analog of MTTP, 2-MeTHF, studied by a combination of molecular beam Fourier transform microwave spectroscopy and quantum chemistry. One conformer of 2-MeTHF was observed and highly accurate molecular parameters were determined using the XIAM program. In addition, all 13C-isotopologues were assigned in natural abundance of 1%. A structural determination based on the r_s positions of all carbon atoms was achieved via Kraitchman's equations. The methyl group in 2-MeTHF undergoes internal rotation and causes A-E splittings of the rotational lines. The barrier was calculated to be 1142 wn at the MP2/6-311++G(d,p) level of theory, which is rather high. Accordingly, narrow A-E splittings could be observed for only a few transitions. However, the barrier height could be fitted while the angles between the internal rotor axis and the principal axes of inertia were taken from the experimental geometry. V. Pace, P. Hoyos, L. Castoldi, P. Domínguez de María, A. R. Alcántara, ChemSusChem 5 (2012), 1369-1379. a) D. F. Aycock, Org. Process Res. Dev. 11 (2007),156-159. b) M. Smoleń, M. Kȩdziorek, K. Grela, Catal. Commun. 44 (2014), 80-84. V. Van, C. Dindic, H.V.L. Nguyen, W. Stahl, ChemPhysChem 16 (2015), 291-294. H. Hartwig, H. Dreizler, Z. Naturforsch. A 51 (1996), 923-932. J. Kraitchman, Am. J. Phys. 21

  6. A benchmark study of molecular structure by experimental and theoretical methods: Equilibrium structure of uracil from gas-phase electron diffraction data and coupled-cluster calculations

    NASA Astrophysics Data System (ADS)

    Vogt, Natalja; Khaikin, Leonid S.; Grikina, Olga E.; Rykov, Anatolii N.

    2013-10-01

    The equilibrium structure of uracil, one of the nucleobases, which build nucleic acids, has been determined for the first time by the gas-phase electron diffraction (GED) method. The necessary rovibrational corrections to the experimental internuclear distances have been calculated with quadratic and cubic force constants in the MP2(all)/cc-pVTZ approximation. For the first time, the equilibrium structure has been optimized by the very time-consuming coupled-cluster method with single and double excitations and perturbative treatment of connected triples using the correlation-consistent polarized weighted core-valence triple-zeta basis set with all electrons being correlated (CCSD(T)(all)/cc-pwCVTZ). The optimized structural parameters have been corrected for the diffuse-function effects and extrapolated to the higher basis set (cc-pwCVQZ) using results of MP2 computations (named as best ab initio structure). The GED equilibrium structure remarkably agrees with the best ab initio one as well as with that one derived from microwave (MW) rotational constants by Puzzarini and Barone. Thus, it has been revealed that the precise experiment and coupled-cluster calculations yield the same results when accurate vibrational corrections (including anharmonic ones) are considered in the experimental structural analysis. Moreover, it has been shown that the equilibrium structure derived from the GED data, being in general of one order less accurate than that determined from the MW rotational constants, is still reliable and accurate.

  7. Structural effect of the in situ generated titania on its ability to oxidize and capture the gas-phase elemental mercury.

    PubMed

    Lee, Tai Gyu; Hyun, Jung Eun

    2006-01-01

    Structural effect of the in situ generated TiO(2) sorbent particle was examined for its ability to capture elemental mercury under UV irradiation in a simulated combustion flue gas. Titania particles were prepared by thermal gas-phase oxidation of Titanium (IV) isopropoxide (TTIP) using a high temperature electric furnace reactor. The structural characteristics of the in situ generated TiO(2) at various synthesis temperatures were investigated; size distribution and the geometric mean diameter were measured using a scanning mobility particle sizer, while fractal dimension and radius of gyration were evaluated from the transmission electron microscopy images. Results from the Hg(0) capture experiment show that with increasing titania synthesis temperature, the overall aggregate size increases and the morphology becomes more open-structured to gas-phase Hg(0) and UV light, resulting in the improved mercury removal capability. PMID:15949836

  8. Molecular structures of benzoic acid and 2-hydroxybenzoic acid, obtained by gas-phase electron diffraction and theoretical calculations.

    PubMed

    Aarset, Kirsten; Page, Elizabeth M; Rice, David A

    2006-07-20

    The structures of benzoic acid (C6H5COOH) and 2-hydroxybenzoic acid (C6H4OHCOOH) have been determined in the gas phase by electron diffraction using results from quantum chemical calculations to inform restraints used on the structural parameters. Theoretical methods (HF and MP2/6-311+G(d,p)) predict two conformers for benzoic acid, one which is 25.0 kJ mol(-1) (MP2) lower in energy than the other. In the low-energy form, the carboxyl group is coplanar with the phenyl ring and the O-H group eclipses the C=O bond. Theoretical calculations (HF and MP2/6-311+G(d,p)) carried out for 2-hydroxybenzoic acid gave evidence for seven stable conformers but one low-energy form (11.7 kJ mol(-1) lower in energy (MP2)) which again has the carboxyl group coplanar with the phenyl ring, the O-H of the carboxyl group eclipsing the C=O bond and the C=O of the carboxyl group oriented toward the O-H group of the phenyl ring. The effects of internal hydrogen bonding in 2-hydroxybenzoic acid can be clearly observed by comparison of pertinent structural parameters between the two compounds. These differences for 2-hydroxybenzoic acid include a shorter exocyclic C-C bond, a lengthening of the ring C-C bond between the substituents, and a shortening of the carboxylic single C-O bond. PMID:16836466

  9. Equilibrium structure and relative stability of glyceraldehyde conformers: Gas-phase electron diffraction (GED) and quantum-chemical studies

    NASA Astrophysics Data System (ADS)

    Vogt, Natalja; Atavin, Evgenii G.; Rykov, Anatolii N.; Popov, Evgenii V.; Vilkov, Lev V.

    2009-11-01

    For the first time, the five dimensional (5-D) analysis of potential energy surface (PES) from quantum-chemical calculations was carried out to predict reliably the various glyceraldehyde (GLA) conformers. 36 conformers with relative stabilities up to 38 kJ/mol were found in the B3LYP approximation. According to results of MP2/cc-pVQZ calculations, the molecule exists at the experimental temperature of 388 K as a mixture of five conformers in the ratio I:II:III:IV:V = 63:18:4:10:5. Contrary to the theoretical conclusion of Lovas et al., the conformer IV is predicted to be more stable than the conformer III. Our result can explain why the conformer IV could be detected in the microwave (MW) spectroscopic experiment by Lovas et al., whereas the conformer III could not. For the first time, thermal-average and equilibrium structural parameters of GLA (main conformer) have been determined from gas-phase electron diffraction (GED) data. Vibrational corrections to the experimental bond lengths were determined using quadratic and cubic force constants from high-level ab initio calculations (MP2/cc-pVTZ). It was shown that the experimental intensities are sensitive to the contribution of the second conformer (27(15)%). Rotational constants calculated from MP2/cc-pVQZ geometries were found to be in excellent agreement with the experimental rotational constants corrected for anharmonic effects.

  10. Structures of protonated thymine and uracil and their monohydrated gas-phase ions from ultraviolet action spectroscopy and theory.

    PubMed

    Pedersen, Sara Øvad; Byskov, Camilla Skinnerup; Turecek, Frantisek; Brøndsted Nielsen, Steen

    2014-06-19

    The strong UV chromophores thymine (Thy) and uracil (Ura) have identical heteroaromatic rings that only differ by one methyl substituent. While their photophysics has been elucidated in detail, the effect on the excited states of base protonation and single water molecules is less explored. Here we report gas-phase absorption spectra of ThyH(+) and UraH(+) and monohydrated ions and demonstrate that the substituent is not only responsible for spectral shifts but also influences the tautomer distribution, being different for bare and monohydrated ions. Spectra interpretation is aided by calculations of geometrical structures and transition energies. The lowest free-energy tautomer (denoted 178, enol-enol form) accounts for 230-280 nm (ThyH(+)) and 225-270 nm (UraH(+)) bands. ThyH(+) hardly absorbs above 300 nm, whereas a discernible band is measured for UraH(+) (275-320 nm), ascribed to the second lowest free-energy tautomer (138, enol-keto form) comprising a few percent of the UraH(+) population at room temperature. Band widths are similar to those measured of cold ions in support of very short excited-state lifetimes. Attachment of a single water increases the abundance of 138 relative to 178, 138 now clearly present for ThyH(+). 138 resembles more the tautomer present in aqueous solution than 178 does, and 138 may indeed be a relevant transition structure. The band of ThyH(+)(178) is unchanged, that of UraH(+)(178) is nearly unchanged, and that of UraH(+)(138) blue-shifts by about 10 nm. In stark contrast to protonated adenine, more than one solvating water molecule is required to re-establish the absorption of ThyH(+) and UraH(+) in aqueous solution. PMID:24874819

  11. Gas phase structures and charge localization in small aluminum oxide anions: Infrared photodissociation spectroscopy and electronic structure calculations.

    PubMed

    Song, Xiaowei; Fagiani, Matias R; Gewinner, Sandy; Schöllkopf, Wieland; Asmis, Knut R; Bischoff, Florian A; Berger, Fabian; Sauer, Joachim

    2016-06-28

    We use cryogenic ion trap vibrational spectroscopy in combination with quantum chemical calculations to study the structure of mono- and dialuminum oxide anions. The infrared photodissociation spectra of D2-tagged AlO1-4 (-) and Al2O3-6 (-) are measured in the region from 400 to 1200 cm(-1). Structures are assigned based on a comparison to simulated harmonic and anharmonic IR spectra derived from electronic structure calculations. The monoaluminum anions contain an even number of electrons and exhibit an electronic closed-shell ground state. The Al2O3-6 (-) anions are oxygen-centered radicals. As a result of a delicate balance between localization and delocalization of the unpaired electron, only the BHLYP functional is able to qualitatively describe the observed IR spectra of all species with the exception of AlO3 (-). Terminal Al-O stretching modes are found between 1140 and 960 cm(-1). Superoxo and peroxo stretching modes are found at higher (1120-1010 cm(-1)) and lower energies (850-570 cm(-1)), respectively. Four modes in-between 910 and 530 cm(-1) represent the IR fingerprint of the common structural motif of dialuminum oxide anions, an asymmetric four-member Al-(O)2-Al ring. PMID:27369513

  12. Gas phase structures and charge localization in small aluminum oxide anions: Infrared photodissociation spectroscopy and electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Song, Xiaowei; Fagiani, Matias R.; Gewinner, Sandy; Schöllkopf, Wieland; Asmis, Knut R.; Bischoff, Florian A.; Berger, Fabian; Sauer, Joachim

    2016-06-01

    We use cryogenic ion trap vibrational spectroscopy in combination with quantum chemical calculations to study the structure of mono- and dialuminum oxide anions. The infrared photodissociation spectra of D2-tagged AlO1-4- and Al2O3-6- are measured in the region from 400 to 1200 cm-1. Structures are assigned based on a comparison to simulated harmonic and anharmonic IR spectra derived from electronic structure calculations. The monoaluminum anions contain an even number of electrons and exhibit an electronic closed-shell ground state. The Al2O3-6- anions are oxygen-centered radicals. As a result of a delicate balance between localization and delocalization of the unpaired electron, only the BHLYP functional is able to qualitatively describe the observed IR spectra of all species with the exception of AlO3-. Terminal Al-O stretching modes are found between 1140 and 960 cm-1. Superoxo and peroxo stretching modes are found at higher (1120-1010 cm-1) and lower energies (850-570 cm-1), respectively. Four modes in-between 910 and 530 cm-1 represent the IR fingerprint of the common structural motif of dialuminum oxide anions, an asymmetric four-member Al-(O)2-Al ring.

  13. Gas Phase Molecular Dynamics

    SciTech Connect

    Hall, G.E.; Prrese, J.M.; Sears, T.J.; Weston, R.E.

    1999-05-21

    The goal of this research is the understanding of elementary chemical and physical processes important in the combustion of fossil fuels. Interest centers on reactions involving short-lived chemical intermediates and their properties. High-resolution high-sensitivity laser absorption methods are augmented by high temperature flow-tube reaction kinetics studies with mass spectrometric sampling. These experiments provide information on the energy levels, structures and reactivity of molecular flee radical species and, in turn, provide new tools for the study of energy flow and chemical bond cleavage in the radicals in chemical systems. The experimental work is supported by theoretical and computational work using time-dependent quantum wavepacket calculations that provide insights into energy flow between the vibrational modes of the molecule.

  14. Molecular structure and conformational composition of 1,1-dichlorobutane: a gas-phase electron diffraction and ab initio investigation

    NASA Astrophysics Data System (ADS)

    Aarset, Kirsten; Hagen, Kolbjørn; Stølevik, Reidar

    1997-09-01

    Gas-phase electron diffraction data obtained at 23°C, together with results from ab initio molecular orbital calculations ( {HF}/{6-31 G(d)}). were used to determine the structure and conformational composition of 1,1-dichlorobutane. Of the five distinguishable conformers (AA, G + A, AG +, G + G + and G + G -), the G + A conformer was found to be the low-energy form, and the investigation also indicated that certain amounts of the AA and G + G - conformers might be present. The symbols describing the conformers refer to torsion about the C 1C 2 and C 2C 3 bonds, anti (A) with H 5C 1C 2C 3 and C 1C 2C 3C 4 torsion angles of 180° and gauche (G + or G -) with torsion angles of + 60° or 300° (-60°) respectively. The results for the principal distances ( rg) and angles (∠ α) from the combined electron diffraction/ab initio study for the G + A conformer, with estimated 2σ uncertainties, were as follows: r( C1 C2) = 1.521(4) Å, r( C2 C3) = 1.539(4) Å, r( C3 C4) = 1.546(4) Å, r( C Cl6) = 1.782(3) Å, r( CCl7) = 1.782(3) Å, = 1.106(6) Å, ∠C 1C 2C 3 = 114.4(13)°, ∠C 2C 3C 4 = 112.5(13)°, ∠CCCl 6 = 110.4(7)°, ∠CCCl 7 = 111.9(7)°, <∠CCH> = 108.9(47)°. Only average values for r(CC), r(CCl), r(CH), ∠CCC, ∠CCX and ∠CCH were determined in the least-square refinements; the differences between the values for these parameters in the same conformer and between the different conformers were kept constant at the values obtained from the ab initio molecular orbital calculations.

  15. Simulation of phase structures

    SciTech Connect

    Lawson, J.

    1995-04-20

    This memo outlines a procedure developed by the author to extract information from phase measurements and produce a simulated phase structure for use in modeling optical systems, including characteristic optics for the Beamlet and NIF laser systems. The report includes an IDL program listing.

  16. Toward a Rational Design of Highly Folded Peptide Cation Conformations. 3D Gas-Phase Ion Structures and Ion Mobility Characterization

    NASA Astrophysics Data System (ADS)

    Pepin, Robert; Laszlo, Kenneth J.; Marek, Aleš; Peng, Bo; Bush, Matthew F.; Lavanant, Helène; Afonso, Carlos; Tureček, František

    2016-07-01

    Heptapeptide ions containing combinations of polar Lys, Arg, and Asp residues with non-polar Leu, Pro, Ala, and Gly residues were designed to study polar effects on gas-phase ion conformations. Doubly and triply charged ions were studied by ion mobility mass spectrometry and electron structure theory using correlated ab initio and density functional theory methods and found to exhibit tightly folded 3D structures in the gas phase. Manipulation of the basic residue positions in LKGPADR, LRGPADK, KLGPADR, and RLGPADK resulted in only minor changes in the ion collision cross sections in helium. Replacement of the Pro residue with Leu resulted in only marginally larger collision cross sections for the doubly and triply charged ions. Disruption of zwitterionic interactions in doubly charged ions was performed by converting the C-terminal and Asp carboxyl groups to methyl esters. This resulted in very minor changes in the collision cross sections of doubly charged ions and even slightly diminished collision cross sections in most triply charged ions. The experimental collision cross sections were related to those calculated for structures of lowest free energy ion conformers that were obtained by extensive search of the conformational space and fully optimized by density functional theory calculations. The predominant factors that affected ion structures and collision cross sections were due to attractive hydrogen bonding interactions and internal solvation of the charged groups that overcompensated their Coulomb repulsion. Structure features typically assigned to the Pro residue and zwitterionic COO-charged group interactions were only secondary in affecting the structures and collision cross sections of these gas-phase peptide ions.

  17. An Unexpected Gas-Phase Binding Motif for Metal Dication Complexation with Peptides: Irmpd Spectroscopic Structure Determination

    NASA Astrophysics Data System (ADS)

    Dunbar, Robert C.; Steill, Jeffrey; Polfer, Nicolas; Berden, Giel; Oomens, Jos

    2011-06-01

    The favorable orientation of the amide linkage and the aromatic side chain of N-terminal Phe or Trp leads to several favorable motifs for metal ion binding to dipeptides, having distinct characteristics in the IR spectrum. Infrared multiple photon photodissociation spectroscopy using the FELIX free electron laser has enabled clear resolution of these isomeric forms. The spectral patterns of complexes of small dications (Mg2+, Ni2+ and Co2+) reveal an unexpected new isomeric form, in which the metal ion displaces the amide hydrogen, forming a metal-nitrogen bond with covalent character which is unprecedented in such gas-phase complexes. Spectra of the ions were acquired by irradiating the cell of the Fourier-transform ion cyclotron resonance mass spectrometer with infrared light from the FELIX laser at wavelengths in the approximate range 500 to 1900 Cm-1.

  18. Structural exploration and Förster theory modeling for the interpretation of gas-phase FRET measurements: Chromophore-grafted amyloid-β peptides

    NASA Astrophysics Data System (ADS)

    Kulesza, Alexander; Daly, Steven; MacAleese, Luke; Antoine, Rodolphe; Dugourd, Philippe

    2015-07-01

    The distance-dependence of excitation energy transfer, e.g., being described by Förster theory (Förster resonance energy transfer (FRET)), allows the use of optical techniques for the direct observation of structural properties. Recently, this technique has been successfully applied in the gas phase. The detailed interpretation of the experimental FRET results, however, relies on the comparison with structural modeling. We therefore present a complete first-principles modeling approach that explores the gas-phase structure of chromophore-grafted peptides and achieves accurate predictions of FRET efficiencies. We apply the approach to amyloid-β 12-28 fragments, known to be involved in amyloid plaque formation connected to Alzheimer's disease. We sample structures of the peptides that are grafted with 5-carboxyrhodamine 575 (Rh575) and QSY-7 chromophores by means of replica-exchange molecular dynamics simulations upon an Amber-type forcefield parametrization as a function of the charge state. The generated ensembles provide chromophore-distance and -orientation distributions which are used with the spectral parameters of the Rh575/QSY-7 chromophores to model FRET-efficiencies for the systems. The theoretical values agree with the experimental average "action"-FRET efficiencies and motivate to use the herein reported parametrization, sampling, and FRET-modeling technique in future studies on the structural properties and aggregation-behavior of related systems.

  19. Structural exploration and Förster theory modeling for the interpretation of gas-phase FRET measurements: Chromophore-grafted amyloid-β peptides.

    PubMed

    Kulesza, Alexander; Daly, Steven; MacAleese, Luke; Antoine, Rodolphe; Dugourd, Philippe

    2015-07-14

    The distance-dependence of excitation energy transfer, e.g., being described by Förster theory (Förster resonance energy transfer (FRET)), allows the use of optical techniques for the direct observation of structural properties. Recently, this technique has been successfully applied in the gas phase. The detailed interpretation of the experimental FRET results, however, relies on the comparison with structural modeling. We therefore present a complete first-principles modeling approach that explores the gas-phase structure of chromophore-grafted peptides and achieves accurate predictions of FRET efficiencies. We apply the approach to amyloid-β 12-28 fragments, known to be involved in amyloid plaque formation connected to Alzheimer's disease. We sample structures of the peptides that are grafted with 5-carboxyrhodamine 575 (Rh575) and QSY-7 chromophores by means of replica-exchange molecular dynamics simulations upon an Amber-type forcefield parametrization as a function of the charge state. The generated ensembles provide chromophore-distance and -orientation distributions which are used with the spectral parameters of the Rh575/QSY-7 chromophores to model FRET-efficiencies for the systems. The theoretical values agree with the experimental average "action"-FRET efficiencies and motivate to use the herein reported parametrization, sampling, and FRET-modeling technique in future studies on the structural properties and aggregation-behavior of related systems. PMID:26178129

  20. The effect of the granulometric composition of a hydroxyapatite powder on the structure and phase composition of coatings deposited by the detonation gas spraying technique

    NASA Astrophysics Data System (ADS)

    Popova, A. A.; Yakovlev, V. I.; Legostaeva, E. V.; Sitnikov, A. A.; Sharkeev, Yu. P.

    2013-04-01

    The granulometric composition of a hydroxyapatite powder has been investigated. The initial powder has been classified into particle size ranges (0.1-10, 10-20, 20-30, and 50-300 μm). Coatings prepared from a hydroxyapatite powder of different size have been deposited by the detonation gas spraying technique. The structure and phase composition of the coatings have been studied. Changing the initial granulometric composition of the powder mixture is shown to provide control over the sprayed surface roughness.

  1. Rate processes in gas phase

    NASA Technical Reports Server (NTRS)

    Hansen, C. F.

    1983-01-01

    Reaction-rate theory and experiment are given a critical review from the engineers' point of view. Rates of heavy-particle, collision-induced reaction in gas phase are formulated in terms of the cross sections and activation energies for reaction. The effect of cross section function shape and of excited state contributions to reaction both cause the slope of Arrhenius plots to differ from the true activation energy, except at low temperature. The master equations for chemically reacting gases are introduced, and dissociation and ionization reactions are shown to proceed primarily from excited states about kT from the dissociation or ionization limit. Collision-induced vibration, vibration-rotation, and pure rotation transitions are treated, including three-dimensional effects and conservation of energy, which have usually been ignored. The quantum theory of transitions at potential surface crossing is derived, and results are found to be in fair agreement with experiment in spite of some questionable approximations involved.

  2. Cryogenic neon matrix-isolation FTIR spectroscopy of evaporated ionic liquids: geometrical structure of cation-anion 1:1 pair in the gas phase.

    PubMed

    Akai, Nobuyuki; Parazs, David; Kawai, Akio; Shibuya, Kazuhiko

    2009-04-01

    Low-temperature infrared spectra of thermally evaporated ionic liquids, 1-ethyl- and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and bis(trifluoromethanesulfonyl)amide have been measured in a cryogenic Ne matrix. The experimental IR spectrum of bis(trifluoromethanesulfonyl)amide can be reproduced theoretically by not B3LYP/6-31G* but MP2/6-31G* calculation, which suggests that the vibrational analysis for ionic liquids composed of bis(trifluoromethanesulfonyl)imide anion would be more successfully performed using the MP2 calculation. By comparison of the matrix-isolation spectra of the ionic liquids with the MP2 calculation, their geometrical structures in the gas phase are determined to be of C(2-position)-H(+)...N(-) interaction structure, which corresponds to the geometry of the energetically second-lowest ion-pair structure. The present study may provide a valuable clue to understand a vaporization mechanism of ionic liquid. PMID:19281187

  3. Shell structure and phase relations in electronic properties of metal nanowires from an electron-gas model

    NASA Astrophysics Data System (ADS)

    Han, Yong; Liu, Da-Jiang

    2010-09-01

    The electronic and dynamic properties of metal nanowires are analyzed by using a minimal electron-gas model (EGM), in which the nanowire is treated as a close system with variable Fermi energy as a function of nanowire radius. We show that the planar surface energy and the curvature energy from the EGM are reasonably consistent with those from previous stabilized-jellium-model calculations, especially for metals with low electron densities. The EGM shell structure due to the fillings of quantum-well subbands is similar to that from the stabilized jellium model. The crossings between subbands and Fermi energy level for the metal nanowire correspond to cusps on the chemical-potential curve versus nanowire radius, but inflection points on the surface-free-energy curve versus the radius, as in the case of metal nanofilms. We also find an oscillatory variation in electron density versus radius at the nanowire center with a global oscillation period which approximately equals half Fermi wavelength. Wire string tension, average binding energy, and thermodynamic stability from the EGM are in good agreement with the data from previous first-principles density-functional theory calculations. We also compare our model with those from previous reported free-electron models, in which the nanowire is treated as an open system with a constant Fermi energy. We demonstrate that the fundamental thermodynamic properties depend sensitively on the way that the potential wall is constructed in the models.

  4. Probing the electronic structure and metal-metal bond of Re{sub 2}Cl{sub 8}{sup 2{minus}} in the gas phase

    SciTech Connect

    Wang, X.B.; Wang, L.S.

    2000-03-08

    Re{sub 2}Cl{sub 8}{sup 2{minus}}, the classical metal complex with a metal-metal multiple bond, was observed in the gas phase for the first time using electrospray. Photodetachment photoelectron spectroscopy (PES) was used to probe its electronic structure, metal-metal bonding, and gas-phase molecular properties. The PES spectra provide a unique and direct picture about the occupied molecular orbitals (Mos) of Re{sub 2}Cl{sub 8}{sup 2{minus}}. Detachments from the metal-metal and metal-ligand bonding Mos were clearly observed and distinguished. The authors found that the metal-metal bonding Mos from the d orbitals ({delta}, {pi}, and {sigma}) have low electron binding energies and yielded three well-resolved detachment bands. The metal-ligand or pure ligand Mos all have higher binding energies and give congested PES features. The ground state of Re{sub 2}Cl{sub 8}{sup 2{minus}} with a configuration of {hor{underscore}ellipsis}{sigma}{sup 2}{pi}{sup 4}{delta}{sup 2} and a formal quadruple Re-Re bond is unequivocally confirmed. The PES spectra yielded a 1.00 eV adiabatic binding energy for the second excess electron in the doubly charged anion. The magnitude of the intramolecular Coulomb repulsion was estimated to be {approximately}2.3 eV using photo-energy-dependent PES spectra. Despite its electronic stability, Re{sub 2}Cl{sub 8}{sup 2{minus}} was found to be metastable against the loss of a Cl{sup {minus}} in the gas phase, suggesting that the Re-Cl bond strength is less than 2.3 eV.

  5. Surface-Induced Dissociation Mass Spectra as a Tool for Distinguishing Different Structural Forms of Gas-Phase Multimeric Protein Complexes.

    PubMed

    Quintyn, Royston S; Zhou, Mowei; Yan, Jing; Wysocki, Vicki H

    2015-12-01

    One attractive feature of ion mobility mass spectrometry (IM-MS) lies in its ability to provide experimental collision cross section (CCS) measurements, which can be used to distinguish different conformations that a protein complex may adopt during its gas-phase unfolding. However, CCS values alone give no detailed information on subunit structure within the complex. Consequently, structural characterization typically requires molecular modeling, which can have uncertainties without experimental support. One method of obtaining direct experimental evidence on the structures of these intermediates is utilizing gas-phase activation techniques that can effectively dissociate the complexes into substructures while preserving the native topological information. The most commonly used activation method, collision-induced dissociation (CID) with low-mass target gases, typically leads to unfolding of monomers of a protein complex. Here, we describe a method that couples IM-MS and surface-induced dissociation (SID) to dissociate the source-activated precursors of three model protein complexes: C-reactive protein (CRP), transthyretin (TTR), and concanavalin A (Con A). The results of this study confirm that CID involves the unfolding of the protein complex via several intermediates. More importantly, our experiments also indicate that retention of similar CCS between different intermediates does not guarantee retention of structure. Although CID spectra (at a given collision energy) of source-activated, mass-selected precursors do not distinguish between native-like, collapsed, and expanded forms of a protein complex, dissociation patterns and/or average charge states of monomer products in SID of each of these forms are unique. PMID:26499904

  6. Simple setup for gas-phase H/D exchange mass spectrometry coupled to electron transfer dissociation and ion mobility for analysis of polypeptide structure on a liquid chromatographic time scale.

    PubMed

    Mistarz, Ulrik H; Brown, Jeffery M; Haselmann, Kim F; Rand, Kasper D

    2014-12-01

    Gas-phase hydrogen/deuterium exchange (HDX) is a fast and sensitive, yet unharnessed analytical approach for providing information on the structural properties of biomolecules, in a complementary manner to mass analysis. Here, we describe a simple setup for ND3-mediated millisecond gas-phase HDX inside a mass spectrometer immediately after ESI (gas-phase HDX-MS) and show utility for studying the primary and higher-order structure of peptides and proteins. HDX was achieved by passing N2-gas through a container filled with aqueous deuterated ammonia reagent (ND3/D2O) and admitting the saturated gas immediately upstream or downstream of the primary skimmer cone. The approach was implemented on three commercially available mass spectrometers and required no or minor fully reversible reconfiguration of gas-inlets of the ion source. Results from gas-phase HDX-MS of peptides using the aqueous ND3/D2O as HDX reagent indicate that labeling is facilitated exclusively through gaseous ND3, yielding similar results to the infusion of purified ND3-gas, while circumventing the complications associated with the use of hazardous purified gases. Comparison of the solution-phase- and gas-phase deuterium uptake of Leu-Enkephalin and Glu-Fibrinopeptide B, confirmed that this gas-phase HDX-MS approach allows for labeling of sites (heteroatom-bound non-amide hydrogens located on side-chains, N-terminus and C-terminus) not accessed by classical solution-phase HDX-MS. The simple setup is compatible with liquid chromatography and a chip-based automated nanoESI interface, allowing for online gas-phase HDX-MS analysis of peptides and proteins separated on a liquid chromatographic time scale at increased throughput. Furthermore, online gas-phase HDX-MS could be performed in tandem with ion mobility separation or electron transfer dissociation, thus enabling multiple orthogonal analyses of the structural properties of peptides and proteins in a single automated LC-MS workflow. PMID:25375223

  7. A carbon foam with a bimodal micro–mesoporous structure prepared from larch sawdust for the gas-phase toluene adsorption

    SciTech Connect

    Liu, Shouxin; Huang, Zhanhua; Wang, Rui

    2013-07-15

    Highlights: ► Network carbon foam containing a bimodal pore distribution was prepared from Larch. ► Liquefaction route was used for the preparation of morphology controllable carbon. ► Pore structure of carbon foam was controlled through KOH activation. - Abstract: A carbon foam with a bimodal micro–mesopore distribution, was prepared by submitting larch sawdust to liquefaction, resinification, foaming, carbonization and KOH activation. The morphology, pore texture and crystal microstructure was characterized by scanning and transmission electron microscopy, nitrogen adsorption analysis and X-ray powder diffraction. A honeycomb structure with adjacent cells was observed for the precursor of carbon foam. After KOH activation, the cell wall of precursor shrunk and broke. This lead to the formation of a well-connected 3D network and developed ligament pore structure (surface area of 554–1918 m{sup 2}/g) containing bimodal pores, 2.1 and 3.9 nm in diameter. The porous carbon foam prepared at 700 °C exhibited a much higher gas-phase toluene removal than commercial activated carbon fiber owing to the 3D network and bimodal pore structure.

  8. Structural characterization of gas-phase cysteine and cysteine methyl ester complexes with zinc and cadmium dications by infrared multiple photon dissociation spectroscopy.

    PubMed

    Coates, Rebecca A; McNary, Christopher P; Boles, Georgia C; Berden, Giel; Oomens, Jos; Armentrout, P B

    2015-10-21

    Structural characterization of gas-phase ions of cysteine (Cys) and cysteine methyl ester (CysOMe) complexed to zinc and cadmium is investigated by infrared multiple photon dissociation (IRMPD) action spectroscopy using a free electron laser in combination with density functional theory calculations. IRMPD spectra are measured for [Zn(Cys-H)](+), [Cd(Cys-H)](+), [Zn(CysOMe-H)](+), [Cd(CysOMe-H)](+) and CdCl(+)(CysOMe) and are accompanied by quantum mechanical calculations of the predicted linear absorption spectra at the B3LYP/6-311+G(d,p) (Zn(2+) complexes) and B3LYP/def2TZVP levels (Cd(2+) complexes). On the basis of these experiments and calculations, the conformation that best reproduces the IRMPD spectra for the complexes of the deprotonated amino acids, [M(Cys-H)](+) and [M(CysOMe-H)](+), is a charge-solvated (CS) tridentate structure where the metal dication binds to the amine and carbonyl groups of the amino acid backbone and the deprotonated sulfur atom of the side chain, [N,CO,S(-)]. The intact amino acid complex, CdCl(+)(CysOMe) binds in the equivalent motif [N,CO,S]. These binding motifs are in agreement with the predicted ground structures of these complexes at the B3LYP, B3LYP-GD3BJ (with empirical dispersion corrections), B3P86, and MP2(full) levels. PMID:25880327

  9. He I photoelectron spectra and gas-phase electronic structures of end-functionalized [3]- and [5]-ladderanes.

    PubMed

    Friscić, Tomislav; Klasinc, Leo; Kovac, Branka; Macgillivray, Leonard R

    2008-02-21

    [3]- and [5]-ladderanes obtained by way of template-controlled syntheses conducted in the organic solid state have been characterized via He I photoelectron (PE) spectroscopy. The results provide a first correlation with X-ray crystallographic structure data and establish the reliability of quantum chemical DFT (B3LYP/6-31G*) and ab initio HF calculations in predicting geometrical and electronic structures of molecular ladder frameworks. PMID:18225866

  10. Gas-Phase Structure of Amyloid-β (12 - 28) Peptide Investigated by Infrared Spectroscopy, Electron Capture Dissociation and Ion Mobility Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Le, Thi Nga; Poully, Jean Christophe; Lecomte, Frédéric; Nieuwjaer, Nicolas; Manil, Bruno; Desfrançois, Charles; Chirot, Fabien; Lemoine, Jerome; Dugourd, Philippe; van der Rest, Guillaume; Grégoire, Gilles

    2013-12-01

    The gas-phase structures of doubly and triply protonated Amyloid-β12-28 peptides have been investigated through the combination of ion mobility (IM), electron capture dissociation (ECD) mass spectrometry, and infrared multi-photon dissociation (IRMPD) spectroscopy together with theoretical modeling. Replica-exchange molecular dynamics simulations were conducted to explore the conformational space of these protonated peptides, from which several classes of structures were found. Among the low-lying conformers, those with predicted diffusion cross-sections consistent with the ion mobility experiment were further selected and their IR spectra simulated using a hybrid quantum mechanical/semiempirical method at the ONIOM DFT/B3LYP/6-31 g(d)/AM1 level. In ECD mass spectrometry, the c/z product ion abundance (PIA) has been analyzed for the two charge states and revealed drastic differences. For the doubly protonated species, N - Cα bond cleavage occurs only on the N and C terminal parts, while a periodic distribution of PIA is clearly observed for the triply charged peptides. These PIA distributions have been rationalized by comparison with the inverse of the distances from the protonated sites to the carbonyl oxygens for the conformations suggested from IR and IM experiments. Structural assignment for the amyloid peptide is then made possible by the combination of these three experimental techniques that provide complementary information on the possible secondary structure adopted by peptides. Although globular conformations are favored for the doubly protonated peptide, incrementing the charge state leads to a conformational transition towards extended structures with 310- and α-helix motifs.

  11. Base pair analogs in the gas phase.

    PubMed

    Roscioli, Joseph R; Pratt, David W

    2003-11-25

    A rotationally resolved electronic spectrum of the gas-phase dimer 2-aminopyridine.2-pyridone, an analog of the adenine.thymine base pair, has been observed and assigned, leading to precise measurements of its moments of inertia and preliminary determinations of its structure. A Watson-Crick configuration results, with N...H-N and N-H...O hydrogen bond lengths of 2.898 and 2.810 A, respectively. The two bases are found not to be coplanar; a dihedral angle of 6.1 degrees between the base planes is also estimated from the measured moments of inertia. Possible chemical and biological implications of these results are discussed. PMID:14612563

  12. Structured Pd-Au/Cu-fiber catalyst for gas-phase hydrogenolysis of dimethyl oxalate to ethylene glycol.

    PubMed

    Zhang, Li; Han, Lupeng; Zhao, Guofeng; Chai, Ruijuan; Zhang, Qiaofei; Liu, Ye; Lu, Yong

    2015-07-01

    Galvanic co-deposition of 0.5 wt% Au and 0.1 wt% Pd on a microfibrous-structure using 8 μm Cu-fibers delivers a Pd-Au/Cu-fiber catalyst, which is highly active, selective and stable for the hydrogenolysis of dimethyl oxalate to ethylene glycol. Au and Pd synergistically promote the hydrogenolysis activity of Cu(+) sites, while Au also critically stabilizes Cu(+) sites to prevent deep reductive deactivation. PMID:26040855

  13. Energetics and structural characterization of isomers using ion mobility and gas-phase H/D exchange: Learning from lasso peptides.

    PubMed

    Hanozin, Emeline; Morsa, Denis; De Pauw, Edwin

    2015-08-01

    State-of-the-art characterization of proteins using MS namely relies on fragmentation methods that allow exploring featured dissociative reaction pathways. These pathways are often initiated by a series of potentially informative mass-constant conformational changes that are nonetheless frequently overlooked by lack of adequate investigation techniques. In the present study, we propose a methodology to readily address both structural and energetic aspects of stereoisomerization reactions using ion mobility coupled with MS. To this end, a commercial spectrometer was used as a reactor comprising an energy resolved collisional activation step intended at promoting controlled conformational changes and a structural assignment step dedicated to the identification of the generated isomers. This identification relies on ion mobility and other on-line coupled techniques, namely an originally designed gas-phase H/D exchange experiment. We here apply this methodology to characterize the isomerization kinetics of capistruin, a 19-residue long lasso-folded peptide. We expect this approach to bring insights into the physical origin of global dissociation thresholds monitored in MS/MS experiments and to set a promising basis for quantitative investigations of the stability of different molecular folds. PMID:25821205

  14. Prioritizing testing of organic compounds detected as gas phase air pollutants: structure-activity study for human contact allergens.

    PubMed Central

    Johnson, R; Macina, O T; Graham, C; Rosenkranz, H S; Cass, G R; Karol, M H

    1997-01-01

    Organic compounds that are used or generated anthropogenically in large quantities in cities can be identified through their presence in the urban atmosphere and in air pollutant source emissions. Compounds identified by this method were screened to evaluate their potential to act as contact allergens. The CASE and MULTICASE computer programs, which are based on the detection of structure-activity relationships (SAR), were used to evaluate this potential. These relationships first are determined by comparing chemical structures to biological activity within a learning set comprised of 458 compounds, each of which had been tested experimentally in human trials for its sensitization potential. Using the information contained in this learning set, CASE and MULTICASE predicted the activity of 238 compounds found in the atmosphere for their ability to act as contact allergens. The analysis finds that 21 of 238 compounds are predicted to be active contact allergens (probability >0.5), with potencies ranging from mild to very strong. The compounds come from chemical classes that include chlorinated aromatics and chlorinated hydrocarbons, N-containing compounds, phenols, alkenes, and an S-containing compound. Using the measured airborne concentrations or emission rates of these compounds as an indication of the extent of their use, together with their predicted potencies, provides an efficient method to prioritize the experimental assessment of contact sensitization of untested organic compounds that can be detected as air pollutants. Images Figure 1. PMID:9300925

  15. Capturing Polyradical Protein Cations after an Electron Capture Event: Evidence for their Stable Distonic Structures in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Baba, Takashi; Campbell, J. Larry

    2015-08-01

    We report on the formation and "capture" of polyradical protein cations after an electron capture event. Performed in a unique electron-capture dissociation (ECD) instrument, these experiments can generate reduced forms of multiply protonated proteins by sequential charge reduction using electrons with ~1 eV. The true structures of these possible polyradicals is considered: Do the introduced unpaired electrons recombine quickly to form a new two-electron bond, or do these unpaired electrons exist as radical sites with appropriate chemical reactivity? Using an established chemical probe—radical quenching with molecular oxygen—we demonstrate that these charge-reduced protein cations are indeed polyradicals that form adducts with up to three molecules of oxygen (i.e., tri-radical protein cations) that are stable for at least 100 ms.

  16. GAS PHASE EXPOSURE HISTORY DERIVED FROM MATERIAL PHASE CONCENTRATION PROFILES USING SOLID PHASE MICRO-EXTRACTION

    EPA Science Inventory

    EPA Identifier: F8P31059
    Title: Gas Phase Exposure History Derived from Material Phase Concentration Profiles Using Solid Phase Micro-Extraction
    Fellow (Principal Investigator): Jonathan Lewis McKinney
    Institution: University of Missouri - ...

  17. The gas-phase bis-uranyl nitrate complex [(UO2)(2)(NO3)(5)](-): infrared spectrum and structure

    SciTech Connect

    Gary S. Groenewold; Michael J. van Stipdonk; Jos Oomens; Wibe de Jong; Michael E. McIlwain

    2011-12-01

    The infrared spectrum of the bis-uranyl nitrate complex [(UO{sub 2}){sub 2}(NO{sub 3}){sub 5}]{sup -} was measured in the gas phase using multiple photon dissociation (IRMPD). Intense absorptions corresponding to the nitrate symmetric and asymmetric vibrations, and the uranyl asymmetric vibration were observed. The nitrate nu3 vibrations indicate the presence of nitrate in a bridging configuration bound to both uranyl cations, and probably two distinct pendant nitrates in the complex. The coordination environment of the nitrate ligands and the uranyl cations were compared to those in the mono-uranyl complex. Overall, the uranyl cation is more loosely coordinated in the bis-uranyl complex [(UO{sub 2}){sub 2}(NO{sub 3}){sub 5}]{sup -} compared to the mono-complex [UO{sub 2}(NO{sub 3}){sub 3}]{sup -}, as indicated by a higher O-U-O asymmetric stretching (nu3) frequency. However, the pendant nitrate ligands are more strongly bound in the bis-complex than they are in the mono-uranyl complex, as indicated by the {nu}{sub 3} frequencies of the pendant nitrate, which are split into nitrosyl and O-N-O vibrations as a result of bidentate coordination. These phenomena are consistent with lower electron density donation per uranyl by the nitrate bridging two uranyl centers compared to that of a pendant nitrate in the mono-uranyl complex. The structure was calculated using density functional theory (B3LYP functional), which produced a structure in which the two uranyl molecules bridged by a single nitrate coordinated in a bis-bidentate fashion. Each uranyl molecule was coordinated by two pendant nitrate ligands. The corresponding vibrational spectrum was in excellent agreement with the IRMPD measurement, confirming the structural assignment.

  18. Thermal phases of interstellar and quasar gas

    NASA Technical Reports Server (NTRS)

    Lepp, S.; Mccray, R.; Shull, J. M.; Woods, D. T.; Kallman, T.

    1985-01-01

    Interstellar gas may be in a variety of thermal phases, depending on how it is heated and ionized; here a unified picture of the equation of state of interstellar and quasar gas is presented for a variety of such mechanisms over a broad range of temperatures, densities, and column densities of absorbing matter. It is found that for select ranges of gas pressure, photoionizing flux, and heating, three thermally stable phases are allowed: coronal gas (T above 100,000 K); warm gas (T about 10,000 K); and cold gas (T less than 100 K). With attenuation of ultraviolet and X-ray radiation, the cold phase may undergo a transition to molecules. In quasar broad-line clouds, this transition occurs at column density N(H) = about 10 to the 23rd/sq cm and could result in warm molecular cores and observable emission from H2 and OH. The underlying atomic physics behind each of these phase transitions and their relevance to interstellar matter and quasars are discussed.

  19. Structural verification for GAS experiments

    NASA Technical Reports Server (NTRS)

    Peden, Mark Daniel

    1992-01-01

    The purpose of this paper is to assist the Get Away Special (GAS) experimenter in conducting a thorough structural verification of its experiment structural configuration, thus expediting the structural review/approval process and the safety process in general. Material selection for structural subsystems will be covered with an emphasis on fasteners (GSFC fastener integrity requirements) and primary support structures (Stress Corrosion Cracking requirements and National Space Transportation System (NSTS) requirements). Different approaches to structural verifications (tests and analyses) will be outlined especially those stemming from lessons learned on load and fundamental frequency verification. In addition, fracture control will be covered for those payloads that utilize a door assembly or modify the containment provided by the standard GAS Experiment Mounting Plate (EMP). Structural hazard assessment and the preparation of structural hazard reports will be reviewed to form a summation of structural safety issues for inclusion in the safety data package.

  20. Microwave Spectrum for a Second Higher Energy Conformer of Cyclopropanecarboxylic Acid and Determination of the Gas Phase Structure of the Ground State.

    PubMed

    Pejlovas, Aaron M; Lin, Wei; Kukolich, Stephen G

    2015-10-01

    Microwave spectra for a higher-energy conformer of cyclopropanecarboxylic acid (CPCA) were measured using a Flygare-Balle-type pulsed-beam Fourier transform microwave spectrometer. The rotational constants (in megahertz) and centrifugal distortion constants (in kilohertz) for this higher-energy conformer are A = 7452.3132(57), B = 2789.8602(43), C = 2415.0725(40), DJ = 0.29(53), and DJK = 2.5(12). Differences between rotational constants for this excited-state conformation and the ground state are primarily due to the acidic OH bond moving from a position cis relative to the cyclopropyl group about the C1-C9 bond to the more stable trans conformation. Calculations indicate that the relative abundance of the higher-energy state should be 15% to 17% at room temperature, but the observed relative abundance for the supersonic expansion conditions is about 1%. The measurements of rotational transitions for the trans form of CPCA were extended to include all of the unique (13)C singly substituted positions. These measurements, along with previously measured transitions of the parent and -OD isotopologues, were used to determine a best-fit gas-phase structure. PMID:26359681

  1. Electrothermal vaporization, part 1: gas phase chemistry

    NASA Astrophysics Data System (ADS)

    Majidi, Vahid; Xu, Ning; Smith, Robert G.

    2000-01-01

    This manuscript is the first of a two-part publication on evaluation of vaporization and atomization processes in electrothermal vaporizers (ETV). Part 1 is specifically focused on gas phase (and heterogeneous) chemistry in ETVs. Molecular absorption spectroscopy and thermogravimetric analysis (in conjunction with gas-phase mass spectrometry) are used to investigate the vaporization of Mg, Ca, Sr, Ba, Co and Ni (chloride and nitrate salts). Graphite, Pt, and Ta were used as substrate material for vaporizers to elucidate some observations of gas-phase chemistry. The experiments in Part I and II of this series are intentionally performed using wall vaporization to closely mimic the conditions used when ETV is employed as a sample introduction device.

  2. The gas-phase bis-uranyl nitrate complex [(UO2)2(NO3)5]-: infrared spectrum and structure

    SciTech Connect

    Groenewold, G. S.; van Stipdonk, Michael J.; Oomens, Jos; De Jong, Wibe A.; McIIwain, Michael E.

    2011-12-01

    The infrared spectrum of the bis-uranyl nitrate complex [(UO2)2(NO3)5]- was measured in the gas phase using multiple photon dissociation (IRMPD). Intense absorptions corresponding to the nitrate symmetric and asymmetric vibrations, and the uranyl asymmetric vibration were observed. The nitrate v3 vibrations indicate the presence of nitrate in a bridging configuration bound to both uranyl cations, and probably two distinct pendant nitrates in the complex. The coordination environment of the nitrate ligands and the uranyl cations were compared to those in the mono-uranyl complex. Overall, the uranyl cation is more loosely coordinated in the bis-uranyl complex [(UO2)2(NO3)5]- compared to the mono-complex [UO2(NO3)3]-, as indicated by a higher O-U-O asymmetric stretching (v3) frequency. However, the pendant nitrate ligands are more strongly bound in the bis-complex than they are in the mono-uranyl complex, as indicated by the v3 frequencies of the pendant nitrate, which are split into nitrosyl and O-N-O vibrations as a result of bidentate coordination. These phenomena are consistent with lower electron density donation per uranyl by the nitrate bridging two uranyl centers compared to that of a pendant nitrate in the mono-uranyl complex. The lowest energy structure predicted by density functional theory (B3LYP functional) calculations was one in which the two uranyl molecules bridged by a single nitrate coordinated in a bis-bidentate fashion. Each uranyl molecule was coordinated by two pendant nitrate ligands. The corresponding vibrational spectrum was in excellent agreement with the IRMPD measurement, confirming the structural assignment.

  3. Mass Spectrometry Study of Multiply Negatively Charged, Gas-Phase NaAOT Micelles: How Does Charge State Affect Micellar Structure and Encapsulation?

    NASA Astrophysics Data System (ADS)

    Fang, Yigang; Liu, Fangwei; Liu, Jianbo

    2013-01-01

    We report the formation and characterization of multiply negatively charged sodium bis(2-ethylhexyl) sulfosuccinate (NaAOT) aggregates in the gas phase, by electrospray ionization of methanol/water solution of NaAOT followed by detection using a guided-ion-beam tandem mass spectrometer. Singly and doubly charged aggregates dominate the mass spectra with the compositions of [Nan-zAOTn]z- ( n = 1-18 and z = 1-2). Solvation by water was detected only for small aggregates [Nan-1AOTnH2O]- of n = 3-9. Incorporation of glycine and tryptophan into [Nan-zAOTn]z- aggregates was achieved, aimed at identifying effects of guest molecule hydrophobicity on micellar solubilization. Only one glycine molecule could be incorporated into each [Nan-zAOTn]z- of n ≥ 7, and at most two glycine molecules could be hosted in that of n ≥ 13. In contrast to glycine, up to four tryptophan molecules could be accommodated within single aggregates of n ≥ 6. However, deprotonation of tryptophan significantly decrease its affinity towards aggregates. Collision-induced dissociation (CID) was carried out for mass-selected aggregate ions, including measurements of product ion mass spectra for both empty and amino acid-containing aggregates. CID results provide a probe for aggregate structures, surfactant-solute interactions, and incorporation sites of amino acids. The present data was compared with mass spectrometry results of positively charged [Nan+zAOTn]z+ aggregates. Contrary to their positive analogues, which form reverse micelles, negatively charged aggregates may adopt a direct micelle-like structure with AOT polar heads exposed and amino acids being adsorbed near the micellar outer surface.

  4. Mass spectrometry study of multiply negatively charged, gas-phase NaAOT micelles: how does charge state affect micellar structure and encapsulation?

    PubMed

    Fang, Yigang; Liu, Fangwei; Liu, Jianbo

    2013-01-01

    We report the formation and characterization of multiply negatively charged sodium bis(2-ethylhexyl) sulfosuccinate (NaAOT) aggregates in the gas phase, by electrospray ionization of methanol/water solution of NaAOT followed by detection using a guided-ion-beam tandem mass spectrometer. Singly and doubly charged aggregates dominate the mass spectra with the compositions of [Na(n-z)AOT(n)](z-) (n = 1-18 and z = 1-2). Solvation by water was detected only for small aggregates [Na(n-1)AOT(n)H(2)O](-) of n = 3-9. Incorporation of glycine and tryptophan into [Na(n-z)AOT(n)](z-) aggregates was achieved, aimed at identifying effects of guest molecule hydrophobicity on micellar solubilization. Only one glycine molecule could be incorporated into each [Na(n-z)AOT(n)](z-) of n ≥ 7, and at most two glycine molecules could be hosted in that of n ≥ 13. In contrast to glycine, up to four tryptophan molecules could be accommodated within single aggregates of n ≥ 6. However, deprotonation of tryptophan significantly decrease its affinity towards aggregates. Collision-induced dissociation (CID) was carried out for mass-selected aggregate ions, including measurements of product ion mass spectra for both empty and amino acid-containing aggregates. CID results provide a probe for aggregate structures, surfactant-solute interactions, and incorporation sites of amino acids. The present data was compared with mass spectrometry results of positively charged [Na(n+z)AOT(n)](z+) aggregates. Contrary to their positive analogues, which form reverse micelles, negatively charged aggregates may adopt a direct micelle-like structure with AOT polar heads exposed and amino acids being adsorbed near the micellar outer surface. PMID:23247969

  5. Phase Transition of Methane Gas Hydrate and Response of Marine Gas Hydrate Systems to Environmental Changes

    NASA Astrophysics Data System (ADS)

    Xu, W.

    2003-12-01

    Gas hydrates, which contain mostly methane as the gas component in marine sediment, are stable under relatively high pressure and low temperature conditions such as those found along continental margins and permafrost regions. Its stability is mostly controlled by in-situ pressure, temperature and salinity of pore fluid. Environmentally introduced changes in pressure and temperature can affect the stability of gas hydrate in marine sediment. While certain changes may enhance the process of gas hydrate formation, we are much more interested in the resultant dissociation processes, which may contribute to sub-marine slope instability, seafloor sediment failure, formation of mud volcanoes and pock marks, potential vulnerability of engineering structures, and the risk to drilling and production. We have been developing models to quantify phase transition processes of marine gas hydrates and to investigate the response of marine gas hydrate systems to environmental changes. Methane gas hydrate system is considered as a three-component (water, methane, salt) four-phase (liquid, gas, hydrate, halite) system. Pressure, temperature and salinity of pore fluid constrain the stability of gas hydrate and affect phase transition processes via their effects on methane solubility and fluid density and enthalpy. Compared to the great quantity of studies on its stability in the literature, in-depth research on phase transition of gas hydrate is surprisingly much less. A method, which employs pressure, enthalpy, salinity and methane content as independent variables, is developed to calculate phase transition processes of the three-component four-phase system. Temperature, an intensive thermodynamic parameter, is found not sufficient in describing phase transition of gas hydrate. The extensive thermodynamic parameter enthalpy, on the other hand, is found to be sufficient both in calculation of the phase transition processes and in modeling marine gas hydrate systems. Processes

  6. Continuous-Flow Gas-Phase Bioreactors

    NASA Technical Reports Server (NTRS)

    Wise, Donald L.; Trantolo, Debra J.

    1994-01-01

    Continuous-flow gas-phase bioreactors proposed for biochemical, food-processing, and related industries. Reactor contains one or more selected enzymes dehydrated or otherwise immobilized on solid carrier. Selected reactant gases fed into reactor, wherein chemical reactions catalyzed by enzyme(s) yield product biochemicals. Concept based on discovery that enzymes not necessarily placed in traditional aqueous environments to function as biocatalysts.

  7. Gas-Phase Infrared; JCAMP Format

    National Institute of Standards and Technology Data Gateway

    SRD 35 NIST/EPA Gas-Phase Infrared; JCAMP Format (PC database for purchase)   This data collection contains 5,228 infrared spectra in the JCAMP-DX (Joint Committee for Atomic and Molecular Physical Data "Data Exchange") format.

  8. EPA GAS PHASE CHEMISTRY CHAMBER STUDIES

    EPA Science Inventory

    Gas-phase smog chamber experiments are being performed at EPA in order to evaluate a number of current chemical mechanisms for inclusion in EPA regulatory and research models. The smog chambers are 9000 L in volume and constructed of 2-mil teflon film. One of the chambers is co...

  9. Gas phase chemistry of the transactinides

    NASA Astrophysics Data System (ADS)

    Türler, A.

    1999-01-01

    In the past few years the gas phase chemistry of the first three transactinide elements rutherfordium (element 104), dubnium (element 105) and seaborgium (element 106) has been studied experimentally using OLGA, the On-line Gas chemistry Apparatus, developed at Paul Scherrer Institute. In each experiment, the investigated transactinide element was identified by measuring the characteristic decay properties of its isotopes. In the chemistry of rutherfordium and dubnium evidence for relativistic effects were found, as predicted previously in theoretical calculations. For the first time, the volatility of Sg oxychlorides in comparison to its lighter homologues W and Mo was measured. Also, the half-lives and SF-branches of the nuclides 265Sg and 266Sg were determined. Finally, prospects for a chemical separation of bohrium (element 107) and hassium (element 108) using gas phase chemistry will be discussed.

  10. The C 1s and N 1s near edge x-ray absorption fine structure spectra of five azabenzenes in the gas phase.

    PubMed

    Vall-llosera, G; Gao, B; Kivimäki, A; Coreno, M; Alvarez Ruiz, J; de Simone, M; Agren, H; Rachlew, E

    2008-01-28

    Near edge x-ray absorption fine structure spectra have been measured and interpreted by means of density functional theory for five different azabenzenes (pyridine, pyridazine, pyrimidine, pyrazine, and s-triazine) in the gas phase. The experimental and theoretical spectra at the N 1s and C 1s edges show a strong resonance assigned to the transition of the 1s electron in the respective N or C atoms to the lowest unoccupied molecular orbital with pi(*) symmetry. As opposed to the N 1s edge, at the C 1s edge this resonance is split due to the different environments of the core hole atom in the molecule. The shift in atomic core-level energy due to a specific chemical environment is explained with the higher electronegativity of the N atom compared to the C atom. The remaining resonances below the ionization potential (IP) are assigned to sigma or pi [corrected] orbitals with mixed valence/Rydberg [corrected] character. Upon N addition, a reduction of intensity is observed in the Rydberg region at both edges as compared to the intensity in the continuum. Above the IP one or more resonances are seen and ascribed here to transitions to sigma(*) orbitals. Calculating the experimental and theoretical Delta(pi) term values at both edges, we observe that they are almost the same within +/-1 eV as expected for isoelectronic bonded pairs. The term values of the pi(*) and sigma(*) resonances are discussed in terms of the total Z number of the atoms participating in the bond. PMID:18247958

  11. Charged supramolecular assemblies of surfactant molecules in gas phase.

    PubMed

    Bongiorno, David; Ceraulo, Leopoldo; Indelicato, Sergio; Turco Liveri, Vincenzo; Indelicato, Serena

    2016-01-01

    The aim of this review is to critically analyze recent literature on charged supramolecular assemblies formed by surfactant molecules in gas phase. Apart our specific interest on this research area, the stimuli to undertake the task arise from the widespread theoretical and applicative benefits emerging from a comprehensive view of this topic. In fact, the study of the formation, stability, and physicochemical peculiarities of non-covalent assemblies of surfactant molecules in gas phase allows to unveil interesting aspects such as the role of attractive, repulsive, and steric intermolecular interactions as driving force of supramolecular organization in absence of interactions with surrounding medium and the size and charge state dependence of aggregate structural and dynamical properties. Other interesting aspects worth to be investigated are joined to the ability of these assemblies to incorporate selected solubilizates molecules as well as to give rise to chemical reactions within a single organized structure. In particular, the incorporation of large molecules such as proteins has been of recent interest with the objective to protect their structure and functionality during the transition from solution to gas phase. Exciting fall-out of the study of gas phase surfactant aggregates includes mass and energy transport in the atmosphere, origin of life and simulation of supramolecular aggregation in the interstellar space. Moreover, supramolecular assemblies of amphiphilic molecules in gas phase could find remarkable applications as atmospheric cleaning agents, nanosolvents and nanoreactors for specialized chemical processes in confined space. Mass spectrometry techniques have proven to be particularly suitable to generate these assemblies and to furnish useful information on their size, size polydispersity, stability, and structural organization. On the other hand molecular dynamics simulations have been very useful to rationalize many experimental findings and to

  12. Gas phase atomic and molecular processes

    NASA Astrophysics Data System (ADS)

    Zhu, Cheng

    We perform fully quantum mechanical calculations of the lithium 2 p -2 s and sodium 3 p -3 s resonance lines pressure broadened by collisions with helium atoms. Using carefully constructed potential energy surfaces and transition dipole moments, we have obtained the emission and absorption coefficients at temperatures from 200 to 3000 K at wavelengths between 500 and 1000 nm for lithium and at temperatures from 158 to 3000 K at wavelengths between 500 and 760 nm for sodium. Contributions from quasi-bound levels are included. Our results are in good agreement with experiment. These broadened line profiles are important in developing effective diagnostics on the temperatures, densities, albedos and composition of the atmospheres of brown dwarfs and extrasolar giant planets. We compute the diffusion coefficients of ground and excited-state lithium and sodium atoms in a helium gas. They are valuable in predicting the sign and magnitude of the light-induced drift for the gas mixture. We calculate the dispersion coefficients of the long range interactions of alkali-metal atoms with molecular hydrogen and helium atoms. The uncertainties in our results are less than 2%. We study the relaxation of the v = 1 vibrational level of carbon monoxide induced by collisions with helium three atoms in ultracold temperatures. We confirm the Wigner's threshold law which states that in the zero temperature limit the inelastic quenching cross sections are inversely proportional to the velocity of the incident atom. Our calculations agree well with experiment and we find enhanced rate coefficients as compared to those for 4 He-CO. We study the chemistry of hydrogen fluoride in the interstellar medium. We consider fine-structure collisions and find that most fluorine atoms reside in the ground 2 P 3/ 2 state. We calculate the rate coefficients for the reaction of F( 2 P 3/2 ) atoms in collisions with H 2 . Our results agree well with experiment. We confirm the conclusions of Neufeld et al

  13. Comparison of electrical and optical characteristics in gas-phase and gas-liquid phase discharges

    NASA Astrophysics Data System (ADS)

    Qazi, H. I. A.; Nie, Qiu-Yue; Li, He-Ping; Zhang, Xiao-Fei; Bao, Cheng-Yu

    2015-12-01

    This paper presents an AC-excited argon discharge generated using a gas-liquid (two-phase) hybrid plasma reactor, which mainly consists of a powered needle electrode enclosed in a conical quartz tube and grounded deionized water electrode. The discharges in the gas-phase, as well as in the two-phase, exhibit two discharge modes, i.e., the low current glow-like diffuse mode and the high current streamer-like constrict mode, with a mode transition, which exhibits a negative resistance of the discharges. The optical emission spectral analysis shows that the stronger diffusion of the water vapor into the discharge region in the two-phase discharges boosts up the generation of OH (A-X) radicals, and consequently, leads to a higher rotational temperature in the water-phase plasma plume than that of the gas-phase discharges. Both the increase of the power input and the decrease of the argon flow rate result in the increase of the rotational temperature in the plasma plume of the water-phase discharge. The stable two-phase discharges with a long plasma plume in the water-phase under a low power input and gas flow rate may show a promising prospect for the degradation of organic pollutants, e.g., printing and dyeing wastewater, in the field of environmental protection.

  14. Comparison of electrical and optical characteristics in gas-phase and gas-liquid phase discharges

    SciTech Connect

    Qazi, H. I. A.; Li, He-Ping Zhang, Xiao-Fei; Bao, Cheng-Yu; Nie, Qiu-Yue

    2015-12-15

    This paper presents an AC-excited argon discharge generated using a gas-liquid (two-phase) hybrid plasma reactor, which mainly consists of a powered needle electrode enclosed in a conical quartz tube and grounded deionized water electrode. The discharges in the gas-phase, as well as in the two-phase, exhibit two discharge modes, i.e., the low current glow-like diffuse mode and the high current streamer-like constrict mode, with a mode transition, which exhibits a negative resistance of the discharges. The optical emission spectral analysis shows that the stronger diffusion of the water vapor into the discharge region in the two-phase discharges boosts up the generation of OH (A–X) radicals, and consequently, leads to a higher rotational temperature in the water-phase plasma plume than that of the gas-phase discharges. Both the increase of the power input and the decrease of the argon flow rate result in the increase of the rotational temperature in the plasma plume of the water-phase discharge. The stable two-phase discharges with a long plasma plume in the water-phase under a low power input and gas flow rate may show a promising prospect for the degradation of organic pollutants, e.g., printing and dyeing wastewater, in the field of environmental protection.

  15. Centrifugal Liquid/Gas Separator With Phase Detectors

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.

    1994-01-01

    Centrifugal liquid/gas separator that includes phase (liquid or gas) detectors helps ensure exclusiveness of each phase at its assigned outlet. Acoustic sensors in centrifugal liquid/gas separator measure speeds of sound in nominally pure liquid and nominally pure gas at liquid and gas outlets respectively. When speed of sound is that of pure liquid or gas, valve opens to let liquid or gas flow out.

  16. Receptors useful for gas phase chemical sensing

    DOEpatents

    Jaworski, Justyn W; Lee, Seung-Wuk; Majumdar, Arunava; Raorane, Digvijay A

    2015-02-17

    The invention provides for a receptor, capable of binding to a target molecule, linked to a hygroscopic polymer or hydrogel; and the use of this receptor in a device for detecting the target molecule in a gaseous and/or liquid phase. The invention also provides for a method for detecting the presence of a target molecule in the gas phase using the device. In particular, the receptor can be a peptide capable of binding a 2,4,6-trinitrotoluene (TNT) or 2,4,-dinitrotoluene (DNT).

  17. Gas phase chemistry of chlorine nitrate

    SciTech Connect

    Okumura, M.; Moore, T.A.; Crellin, K.C.

    1995-12-31

    Chlorine nitrate (ClONO{sub 2}) is a reservoir of both ClO{sub x} and NO{sub x} radicals in Earth`s stratosphere, and its decomposition is important in determining the abundance of stratospheric ozone. We present experimental and theoretical studies that explore the mechanisms and dynamics of processes leading to ClONO{sub 2} destruction in the stratosphere. Molecular beam photodissociation experiments have been performed to determine the decomposition pathways of ClONO{sub 2} upon excitation at 308 nm and to explore the possibility of a long-lived excited state. We have also investigated the reaction of chlorine nitrate with chloride ions Cl{sup -} in the gas phase. The gas phase ionic reaction may elucidate ionic mechanisms of heterogeneous reactions occurring on the surfaces of Polar Stratospheric Cloud particles and also raise doubts about proposed schemes to mitigate ozone depletion by electrifying the stratosphere.

  18. The gas-phase acidity of nitrocyclopropane

    NASA Astrophysics Data System (ADS)

    Bartmess, John E.; Wilson, Burton; Sorensen, Daniel N.; Bloor, John E.

    1992-09-01

    Nitrocyclopropane is 10.5 kcal mol-1 weaker as an acid in the gas phase than its open-chain analog, 2-nitropropane. This is attributed to the conflicting hybridization requirements for carbanion stabilization by the cyclopropyl ring and by the nitro group. Based on reactivities, the deprotonated form does not ring-open to either the 2-nitroallyl anion or the 1-nitroallyl anion.

  19. Negative ion gas-phase chemistry of arenes.

    PubMed

    Danikiewicz, Witold; Zimnicka, Magdalena

    2016-01-01

    Reactions of aromatic and heteroaromatic compounds involving anions are of great importance in organic synthesis. Some of these reactions have been studied in the gas phase and are occasionally mentioned in reviews devoted to gas-phase negative ion chemistry, but no reviews exist that collect all existing information about these reactions. This work is intended to fill this gap. In the first part of this review, methods for generating arene anions in the gas phase and studying their physicochemical properties and fragmentation reactions are presented. The main topics in this part are as follows: processes in which gas-phase arene anions are formed, measurements and calculations of the proton affinities of arene anions, proton exchange reactions, and fragmentation processes of substituted arene anions, especially phenide ions. The second part is devoted to gas-phase reactions of arene anions. The most important of these are reactions with electrophiles such as carbonyl compounds and α,β-unsaturated carbonyl and related compounds (Michael acceptors). Other reactions including oxidation of arene anions and halogenophilic reactions are also presented. In the last part of the review, reactions of electrophilic arenes with nucleophiles are discussed. The best known of these is the aromatic nucleophilic substitution (SN Ar) reaction; however, other processes that lead to the substitution of a hydrogen atom in the aromatic ring are also very important. Aromatic substrates in these reactions are usually but not always nitroarenes bearing other substituents in the ring. The first step in these reactions is the formation of an anionic σ-adduct, which, depending on the substituents in the aromatic ring and the structure of the attacking nucleophile, is either an intermediate or a transition state in the reaction path. In the present review, we attempted to collect the results of both experimental and computational studies of the aforementioned reactions conducted since the

  20. Analysis of the gas phase reactivity of chlorosilanes.

    PubMed

    Ravasio, Stefano; Masi, Maurizio; Cavallotti, Carlo

    2013-06-27

    Trichlorosilane is the most used precursor to deposit silicon for photovoltaic applications. Despite of this, its gas phase and surface kinetics have not yet been completely understood. In the present work, it is reported a systematic investigation aimed at determining what is the dominant gas phase chemistry active during the chemical vapor deposition of Si from trichlorosilane. The gas phase mechanism was developed calculating the rate constant of each reaction using conventional transition state theory in the rigid rotor-harmonic oscillator approximation. Torsional vibrations were described using a hindered rotor model. Structures and vibrational frequencies of reactants and transition states were determined at the B3LYP/6-31+G(d,p) level, while potential energy surfaces and activation energies were computed at the CCSD(T) level using aug-cc-pVDZ and aug-cc-pVTZ basis sets extrapolating to the complete basis set limit. As gas phase and surface reactivities are mutually interlinked, simulations were performed using a microkinetic surface mechanism. It was found that the gas phase reactivity follows two different routes. The disilane mechanism, in which the formation of disilanes as reaction intermediates favors the conversion between the most stable monosilane species, and the radical pathway, initiated by the decomposition of Si2HCl5 and followed by a series of fast propagation reactions. Though both mechanisms are active during deposition, the simulations revealed that above a certain temperature and conversion threshold the radical mechanism provides a faster route for the conversion of SiHCl3 into SiCl4, a reaction that favors the overall Si deposition process as it is associated with the consumption of HCl, a fast etchant of Si. Also, this study shows that the formation of disilanes as reactant intermediates promotes significantly the gas phase reactivity, as they contribute both to the initiation of radical chain mechanisms and provide a catalytic route for

  1. Structure, Mechanical Properties, and Fracture Behavior of a Fe-Cr-V Alloy Doped with Nitrogen by High-Temperature Gas-Phase Nitriding

    NASA Astrophysics Data System (ADS)

    Nikulin, Sergey A.; Khatkevich, Vladimir M.; Rogachev, Stanislav O.; Denisenko, Kristina S.

    2015-12-01

    The microstructure, phase composition, and room-temperature mechanical properties of the corrosion-resistant Fe-20pctCr-5pctV alloy doped with nitrogen by high-temperature gas-phase nitriding under different conditions have been investigated. The nitriding of the Fe-20pctCr-5pctV alloy at T = 1223 K to 1373 K (950 °C to 1100 °C) and subsequent annealing at T = 973 K (700 °C) lead to the precipitation of large vanadium nitride and disperse chromium nitride particles in the ferrite matrix. Such a treatment increases the strength of the Fe-20pctCr-5pctV alloy at room temperature by 1.6 times, while maintaining the adequate relative elongation. The alloy in the initial state and after nitriding is highly resistant to corrosion.

  2. Gas-Phase Photoionization Of A Protein

    NASA Astrophysics Data System (ADS)

    Milosavljevic, A. R.; Giuliani, A.; Nicolas, C.; Gil, J.-F.; Lemaire, J.; Refregiers, M.; Nahon, L.

    2010-07-01

    We present preliminary results on gas phase photoionization of electrosprayproduced multiply protonated cytochrome c protein (104 amino acids; ˜12.4 kDa), which has been achieved with a newly developed experimental system for spectroscopy of electrosprayed ions in a linear quadrupole ion trap using a monochromatized vacuum ultraviolet (VUV) synchrotron radiation and tandem mass spectrometry method. The investigation of proteins in the gas phase, where they are free of the influence of counterions and solvent molecules, offer a possibility to understand their intrinsic molecular properties. However, due to limited both ion densities and available number of photons, the use of synchrotron radiation for the trapped ions spectroscopy is a rather challenging task. The feasibility of coupling a Fourier transform ion cyclotron resonance ion trap with soft x-ray synchrotron beamline and the first successful use of synchrotron radiation for spectroscopy of electrosprayed negative ions stored in a three-dimensional quadrupole ion trap have been demonstrated only recently (R. Thissen et al., 2008, Phys. Rev. Lett., 100, 223001; A. Giulliani et al., Proc. 57th ASMS Conf., Philadelphia, 2009). The present results are the first reported on photoionization of kDa species in the gas phase and are valuable regarding both a fundamental interest of accessing physical properties of large biological ions isolated in vacuo and potential development of a new technique for proteomics.

  3. Inductive and steric effects on the gas-phase structure of tert-butyl acetate. Electron diffraction and ab initio MO investigations

    SciTech Connect

    Takeuchi, Hiroshi; Enmi, Jun-ichiro; Onozaki, Manabu; Egawa, Toru; Konaka, Shigehiro

    1994-09-01

    Gas electron diffusion and HF/4-21 G calculations on geometric parameters and harmonic force constants are used to study the molecular structure of tert-butyl acetate. This determined that C{sub 1} = O{sub 2} is (cis) to O{sub 4}-C{sub 5} and the tert-butyl group is staggered to the C{sub 1}-O{sub 4} bond. The structural parameters are also determined. C{sub 1}-O{sub 4} bond length shortening is rationalized in terms of the resonance effect and the electron-releasing inductive effect of substituents. 29 refs., 4 figs., 4 tabs.

  4. Development of a new Structure-Activity Relationship (SAR) for gas-phase reactions of NO3 radicals with organic compounds

    NASA Astrophysics Data System (ADS)

    Kerdouci, J.; Picquet-Varrault, B.; Doussin, J.

    2010-12-01

    kinetic database on NO3-oxidation rate constants. This allowed us to develop a new SAR for the gas-phase reactions of NO3 with organic compounds which is based exclusively on correlations between the molecular structures and the rate constants. This new SAR is based on experimental rate constants of 150 molecules and has been developed for alkanes, alkenes (simple and cyclic alkenes, dienes and terpenes) and saturated and unsaturated oxygenated species (alcohols, carbonyls, ethers and esters). Results and performances of this SAR will be discussed here. References [1] Geyer, A., et al., J. Geophys. Res., 108 (2003), 4368. [2] Grosjean, D. and E.L. Williams, Atmospheric Environment. Part A. General Topics, 26 (1992), 1395-1405. [3] Pfrang, C., et al., Atmospheric Environment, 40 (2006), 1180-1186. [4] Kwok, E.S.C. and R. Atkinson, Atmospheric Environment, 29 (1995), 1685-1695. [5] Jenkin, M.E., S.M. Saunders, and M.J. Pilling, Atmospheric Environment, 31(1997), 81-104. [6] Aumont, B., S. Szopa, and S. Madronich, Atmospheric Chemistry and Physics, 5 (2005), 2497-2517.

  5. Gas-phase structures of sterically crowded disilanes studied by electron diffraction and quantum chemical methods: 1,1,2,2-tetrakis(trimethylsilyl)disilane and 1,1,2,2-tetrakis(trimethylsilyl)dimethyldisilane.

    PubMed

    Schwabedissen, Jan; Lane, Paul D; Masters, Sarah L; Hassler, Karl; Wann, Derek A

    2014-07-14

    The gas-phase structures of the disilanes 1,1,2,2-tetrakis(trimethylsilyl)disilane [(Me3Si)2HSiSiH(SiMe3)2] (1) and 1,1,2,2-tetrakis(trimethylsilyl)dimethyldisilane [(Me3Si)2MeSiSiMe(SiMe3)2] (2) have been determined by density functional theoretical calculations and by gas electron diffraction (GED) employing the SARACEN method. For each of 1 and 2 DFT calculations revealed four C2-symmetric conformers occupying minima on the respective potential-energy surfaces; three conformers were estimated to be present in sufficient quantities to be taken into account when fitting the GED data. For (Me3Si)2RSiSiR(SiMe3)2 [R = H (1), CH3 (2)] the lowest energy conformers were found by GED to have RSiSiR dihedral angles of 87.7(17)° for 1 and -47.0(6)° for 2. For each of 1 and 2 the presence of bulky and flexible trimethylsilyl groups dictates many aspects of the geometric structures in the gas phase, with the molecules often adopting structures that reduce steric strain. PMID:24873858

  6. Gas phase thermochemistry of organogermanium compounds

    SciTech Connect

    Engel, J.P.

    1993-12-07

    A variety of silyl- and alkyl-germylene precursors have been synthesized and subsequently pyrolyzed in the gas phase. Arrhenius parameters were obtained employing a pulsed-stirred flow reactor for these unimolecular decompositions. These precursors are divided into two major categories by mechanism of germylene extrusion: {alpha}-elimination precursors and germylacetylenes. The extrusion of germylenes from germylacetylene precursors is of primary interest. A mechanism is proposed employing a germacyclopropene intermediate. Evidence supporting this mechanism is presented. In the process of exploring germylacetylenes as germylene precursors, an apparent dyatropic rearrangement between germanium and silicon was observed. This rearrangement was subsequently explored.

  7. Vaccum Gas Tungsten Arc Welding, phase 1

    NASA Technical Reports Server (NTRS)

    Weeks, J. L.; Krotz, P. D.; Todd, D. T.; Liaw, Y. K.

    1995-01-01

    This two year program will investigate Vacuum Gas Tungsten Arc Welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. VGTAW appears to offer a significant improvement in weldability because of the clean environment and lower heat input needed. The overall objective of the program is to develop the VGTAW technology and implement it into a manufacturing environment that will result in lower cost, better quality and higher reliability aerospace components for the space shuttle and other NASA space systems. Phase 1 of this program was aimed at demonstrating the process's ability to weld normally difficult-to-weld materials. Phase 2 will focus on further evaluation, a hardware demonstration and a plan to implement VGTAW technology into a manufacturing environment. During Phase 1, the following tasks were performed: (1) Task 11000 Facility Modification - an existing vacuum chamber was modified and adapted to a GTAW power supply; (2) Task 12000 Materials Selection - four difficult-to-weld materials typically used in the construction of aerospace hardware were chosen for study; (3) Task 13000 VGTAW Experiments - welding experiments were conducted under vacuum using the hollow tungsten electrode and evaluation. As a result of this effort, two materials, NARloy Z and Incoloy 903, were downselected for further characterization in Phase 2; and (4) Task 13100 Aluminum-Lithium Weld Studies - this task was added to the original work statement to investigate the effects of vacuum welding and weld pool vibration on aluminum-lithium alloys.

  8. Giddings Austin chalk enters deep lean-gas phase

    SciTech Connect

    Moritis, G.

    1995-12-25

    Deep lean gas is the latest phase in the growth of the Giddings field Austin chalk play. The first phase involved drilling vertical oil and gas wells. Next came the horizontal well boom in the shallower Austin chalk area, which is still continuing. And now this third phase places horizontal laterals in the Austen chalk at about 14,000--15,000 ft to produce lean gas. The article describes the producing wells and gas gathering.

  9. Gas-Phase Acidities of Phosphorylated Amino Acids.

    PubMed

    Stover, Michele L; Plummer, Chelsea E; Miller, Sean R; Cassady, Carolyn J; Dixon, David A

    2015-11-19

    Gas-phase acidities and heats of formation have been predicted at the G3(MP2)/SCRF-COSMO level of theory for 10 phosphorylated amino acids and their corresponding amides, including phospho-serine (pSer), -threonine (pThr), and -tyrosine (pTyr), providing the first reliable set of these values. The gas-phase acidities (GAs) of the three named phosphorylated amino acids and their amides have been determined using proton transfer reactions in a Fourier transform ion cyclotron mass spectrometer. Excellent agreement was found between the experimental and predicted GAs. The phosphate group is the deprotonation site for pSer and pThr and deprotonation from the carboxylic acid generated the lowest energy anion for pTyr. The infrared spectra were calculated for six low energy anions of pSer, pThr, and pTyr. For deprotonated pSer and pThr, good agreement is found between the experimental IRMPD spectra and the calculated spectra for our lowest energy anion structure. For pTyr, the IR spectra for a higher energy phosphate deprotonated structure is in good agreement with experiment. Additional experiments tested electrospray ionization (ESI) conditions for pTyr and determined that variations in solvent, temperature, and voltage can result in a different experimental GA value, indicating that ESI conditions affect the conformation of the pTyr anion. PMID:26492552

  10. Substituent effects on the gas-phase acidity of silane

    SciTech Connect

    Gordon, M.S.; Volk, D.E. ); Gano, D.R. )

    1989-12-20

    In a previous paper, the gas-phase acidities of XH{sub n} compounds (X = C, N, O, F, Si, P, S, Cl) were predicted with ab initio wave functions. At the MP4{sup 2} level of theory with extended basis sets acidities for these species were determined to be within 2 kcal/mol of experimental value. In the present work, with 6-31G(d) geometries and full MP4/MC-311++G{sup 6}(3df,2pd) energies, the effects of CH{sub 3}, NH{sub 2}, OH, F, SiH{sub 3}, PH{sub 2}, SH, and Cl on the gas-phase acidity of silane are examined. Only a few related calculations have been carried out. All calculations were performed with Gaussian86, and all structures were verified as minima by diagonalizing the analytically determined hessians. Only the valence electrons were correlated in the perturbation theory calculations.

  11. Computational phase diagrams of noble gas hydrates under pressure.

    PubMed

    Teeratchanan, Pattanasak; Hermann, Andreas

    2015-10-21

    We present results from a first-principles study on the stability of noble gas-water compounds in the pressure range 0-100 kbar. Filled-ice structures based on the host water networks ice-Ih, ice-Ic, ice-II, and C0 interacting with guest species He, Ne, and Ar are investigated, using density functional theory (DFT) with four different exchange-correlation functionals that include dispersion effects to various degrees: the non-local density-based optPBE-van der Waals (vdW) and rPW86-vdW2 functionals, the semi-empirical D2 atom pair correction, and the semi-local PBE functional. In the He-water system, the sequence of stable phases closely matches that seen in the hydrogen hydrates, a guest species of comparable size. In the Ne-water system, we predict a novel hydrate structure based on the C0 water network to be stable or at least competitive at relatively low pressure. In the Ar-water system, as expected, no filled-ice phases are stable; however, a partially occupied Ar-C0 hydrate structure is metastable with respect to the constituents. The ability of the different DFT functionals to describe the weak host-guest interactions is analysed and compared to coupled cluster results on gas phase systems. PMID:26493915

  12. Computational phase diagrams of noble gas hydrates under pressure

    NASA Astrophysics Data System (ADS)

    Teeratchanan, Pattanasak; Hermann, Andreas

    2015-10-01

    We present results from a first-principles study on the stability of noble gas-water compounds in the pressure range 0-100 kbar. Filled-ice structures based on the host water networks ice-Ih, ice-Ic, ice-II, and C0 interacting with guest species He, Ne, and Ar are investigated, using density functional theory (DFT) with four different exchange-correlation functionals that include dispersion effects to various degrees: the non-local density-based optPBE-van der Waals (vdW) and rPW86-vdW2 functionals, the semi-empirical D2 atom pair correction, and the semi-local PBE functional. In the He-water system, the sequence of stable phases closely matches that seen in the hydrogen hydrates, a guest species of comparable size. In the Ne-water system, we predict a novel hydrate structure based on the C0 water network to be stable or at least competitive at relatively low pressure. In the Ar-water system, as expected, no filled-ice phases are stable; however, a partially occupied Ar-C0 hydrate structure is metastable with respect to the constituents. The ability of the different DFT functionals to describe the weak host-guest interactions is analysed and compared to coupled cluster results on gas phase systems.

  13. Computational phase diagrams of noble gas hydrates under pressure

    SciTech Connect

    Teeratchanan, Pattanasak Hermann, Andreas

    2015-10-21

    We present results from a first-principles study on the stability of noble gas-water compounds in the pressure range 0-100 kbar. Filled-ice structures based on the host water networks ice-I{sub h}, ice-I{sub c}, ice-II, and C{sub 0} interacting with guest species He, Ne, and Ar are investigated, using density functional theory (DFT) with four different exchange-correlation functionals that include dispersion effects to various degrees: the non-local density-based optPBE-van der Waals (vdW) and rPW86-vdW2 functionals, the semi-empirical D2 atom pair correction, and the semi-local PBE functional. In the He-water system, the sequence of stable phases closely matches that seen in the hydrogen hydrates, a guest species of comparable size. In the Ne-water system, we predict a novel hydrate structure based on the C{sub 0} water network to be stable or at least competitive at relatively low pressure. In the Ar-water system, as expected, no filled-ice phases are stable; however, a partially occupied Ar-C{sub 0} hydrate structure is metastable with respect to the constituents. The ability of the different DFT functionals to describe the weak host-guest interactions is analysed and compared to coupled cluster results on gas phase systems.

  14. Gas-phase photocatalytic oxidation of acrylonitrile.

    PubMed

    Krichevskaya, Marina; Jõks, Svetlana; Kachina, Anna; Preis, Sergei

    2009-05-01

    Photocatalytic oxidation (PCO) of acrylonitrile (AN) on titanium dioxide in the gaseous phase was studied. AN readily undergoes photocatalytic degradation in a gas-solid system by using TiO(2) Degussa P25. The AN PCO volatile products, visible in the infrared spectra, included nitrogen dioxide, nitrous oxide, carbon dioxide, water, hydrogen cyanide and carbon monoxide. Longer contact time resulted in deeper oxidation of AN with decreasing hydrogen cyanide and increasing nitrogen dioxide content. The effect of temperature increasing from 60 to 130 degrees C was observed to be slightly negative in terms of AN degradation rate. However, the effect of increased temperature was noticeable in terms of the character and yields of the PCO products: HCN peaks diminished with growing peaks of NO(2). PMID:19424531

  15. Phase ordering kinetics of the Bose gas

    SciTech Connect

    Damle, K.; Majumdar, S.N.; Sachdev, S.

    1996-12-01

    We study the approach to equilibrium of a Bose gas to a superfluid state. We point out that dynamic scaling, characteristic of far from equilibrium phase-ordering systems, should hold. We stress the importance of a nondissipative Josephson precession term in driving the system to a new universality class. A model of coarsening in dimension {ital d}=2, involving a quench between two temperatures below the equilibrium superfluid transition temperature ({ital T}{sub {ital c}}), is exactly solved and demonstrates the relevance of the Josephson term. Numerical results on quenches from above {ital T}{sub {ital c}} in {ital d}=2,3 provide evidence for the scaling picture postulated. {copyright} {ital 1996 The American Physical Society.}

  16. Phase transitions in a gas of anyons

    NASA Astrophysics Data System (ADS)

    MacKenzie, R.; Nebia-Rahal, F.; Paranjape, M. B.; Richer, J.

    2010-10-01

    We continue our numerical Monte Carlo simulation of a gas of closed loops on a 3 dimensional lattice, however, now in the presence of a topological term added to the action which corresponds to the total linking number between the loops. We compute the linking number using a novel approach employing certain notions from knot theory. Adding the topological term converts the particles into anyons. Interpreting the model as an effective theory that describes the 2+1-dimensional Abelian Higgs model in the asymptotic strong-coupling regime, the topological linking number simply corresponds to the addition to the action of the Chern-Simons term. The system continues to exhibit a phase transition as a function of the vortex mass as it becomes small. We find the following new results. The Chern-Simons term has no effect on the Wilson loop. On the other hand, it does effect the ’t Hooft loop of a given configuration, adding the linking number of the ’t Hooft loop with all of the dynamical vortex loops. We find the unexpected result that both the Wilson loop and the ’t Hooft loop exhibit a perimeter law even though there are no massless particles in the theory, in both phases of the theory. It should be noted that our method suffers from numerical instabilities if the coefficient of the Chern-Simons term is too large; thus, we have restricted our results to small values of this parameter. Furthermore, interpreting the lattice loop gas as an effective theory describing the Abelian Higgs model is only known to be true in the infinite coupling limit; for strong but finite coupling this correspondence is only a conjecture, the validity of which is beyond the scope of this article.

  17. Phase transitions in a gas of anyons

    SciTech Connect

    MacKenzie, R.; Nebia-Rahal, F.; Paranjape, M. B.; Richer, J.

    2010-10-01

    We continue our numerical Monte Carlo simulation of a gas of closed loops on a 3 dimensional lattice, however, now in the presence of a topological term added to the action which corresponds to the total linking number between the loops. We compute the linking number using a novel approach employing certain notions from knot theory. Adding the topological term converts the particles into anyons. Interpreting the model as an effective theory that describes the 2+1-dimensional Abelian Higgs model in the asymptotic strong-coupling regime, the topological linking number simply corresponds to the addition to the action of the Chern-Simons term. The system continues to exhibit a phase transition as a function of the vortex mass as it becomes small. We find the following new results. The Chern-Simons term has no effect on the Wilson loop. On the other hand, it does effect the 't Hooft loop of a given configuration, adding the linking number of the 't Hooft loop with all of the dynamical vortex loops. We find the unexpected result that both the Wilson loop and the 't Hooft loop exhibit a perimeter law even though there are no massless particles in the theory, in both phases of the theory. It should be noted that our method suffers from numerical instabilities if the coefficient of the Chern-Simons term is too large; thus, we have restricted our results to small values of this parameter. Furthermore, interpreting the lattice loop gas as an effective theory describing the Abelian Higgs model is only known to be true in the infinite coupling limit; for strong but finite coupling this correspondence is only a conjecture, the validity of which is beyond the scope of this article.

  18. Gas-phase protonation thermochemistry of adenosine.

    PubMed

    Touboul, David; Bouchoux, Guy; Zenobi, Renato

    2008-09-18

    The goal of this work was to obtain a detailed insight on the gas-phase protonation energetic of adenosine using both mass spectrometric experiments and quantum chemical calculations. The experimental approach used the extended kinetic method with nanoelectrospray ionization and collision-induced dissociation tandem mass spectrometry. This method provides experimental values for proton affinity, PA(adenosine) = 979 +/- 1 kJ.mol (-1), and for the "protonation entropy", Delta p S degrees (adenosine) = S degrees (adenosineH +) - S degrees (adenosine) = -5 +/- 5 J.mol (-1).K (-1). The corresponding gas-phase basicity is consequently equal to: GB(adenosine) = 945 +/- 2 kJ.mol (-1) at 298K. Theoretical calculations conducted at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31+G(d,p) level, including 298 K enthalpy correction, predict a proton affinity value of 974 kJ.mol (-1) after consideration of isodesmic proton transfer reactions with pyridine as the reference base. Moreover, computations clearly showed that N3 is the most favorable protonation site for adenosine, due to a strong internal hydrogen bond involving the hydroxyl group at the 2' position of the ribose sugar moiety, unlike observations for adenine and 2'-deoxyadenosine, where protonation occurs on N1. The existence of negligible protonation entropy is confirmed by calculations (theoretical Delta p S degrees (adenosine) approximately -2/-3 J.mol (-1).K (-1)) including conformational analysis and entropy of hindered rotations. Thus, the calculated protonation thermochemical properties are in good agreement with our experimental measurements. It may be noted that the new PA value is approximately 10 kJ.mol (-1) lower than the one reported in the National Institute of Standards and Technology (NIST) database, thus pointing to a correction of the tabulated protonation thermochemistry of adenosine. PMID:18720985

  19. Transferring pharmaceuticals into the gas phase

    NASA Astrophysics Data System (ADS)

    Christen, Wolfgang; Krause, Tim; Rademann, Klaus

    2008-11-01

    The dissolution of molecules of biological interest in supercritical carbon dioxide is investigated using pulsed molecular beam mass spectrometry. Due to the mild processing temperatures of most supercritical fluids, their adiabatic expansion into vacuum permits to transfer even thermally very sensitive substances into the gas phase, which is particularly attractive for pharmaceutical and biomedical applications. In addition, supercritical CO2constitutes a chemically inert solvent that is compatible with hydrocarbon-free ultrahigh vacuum conditions. Here, we report on the dissolution and pulsed supersonic jet expansion of caffeine (C8H10N4O2), the provitamin menadione (C11H8O2), and the amino acid derivative l-phenylalanine tert-butyl ester hydrochloride (C6H5CH2CH(NH2)COOC(CH3)3[dot operator]HCl), into vacuum. An on-axis residual gas analyzer is used to monitor the relative amounts of solute and solvent in the molecular beam as a function of solvent densityE The excellent selectivity and sensitivity provided by mass spectrometry permits to probe even trace amounts of solutes. The strong density variation of CO2 close to the critical point results in a pronounced pressure dependence of the relative ion currents of solute and solvent molecules, reflecting a substantial change in solubility.

  20. Gas: A Neglected Phase in Remediation of Metals and Radionuclides

    SciTech Connect

    Denham, Miles E.; Looney, Brian B

    2005-09-28

    The gas phase is generally ignored in remediation of metals and radionuclides because it is assumed that there is no efficient way to exploit it. In the literal sense, all remediations involve the gas phase because this phase is linked to the liquid and solid phases by vapor pressure and thermodynamic relationships. Remediation methods that specifically use the gas phase as a central feature have primarily targeted volatile organic contaminants, not metals and radionuclides. Unlike many organic contaminants, the vapor pressure and Henry's Law constants of metals and radionuclides are not generally conducive to direct air stripping of dissolved contaminants. Nevertheless, the gas phase can play an important role in remediation of inorganic contaminants and provide opportunities for efficient, cost effective remediation. The objective here is to explore ways in which manipulation of the gas phase can be used to facilitate remediation of metals and radionuclides.

  1. Gas-phase interaction of protonated lysine with water

    NASA Astrophysics Data System (ADS)

    Rozman, Marko; Srzic, Dunja; Klasinc, Leo

    2006-07-01

    Gas-phase interaction of LysH+ with D2O has been investigated in order to elucidate the H/D exchange reaction mechanism and possibility of water assisted ion-zwitterion structure formation. The proceed of the interaction is modeled by DFT calculations. Potential energy profiles for: the perturbation from ion-molecule to ion-zwitterion structure, the "flip-flop" and the "bridging" mechanism are presented. Analysis of H/D exchange kinetics results for LysH+ with D2O and CD3OD measured in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer agree with ion-molecule structure of LysH+. Both experimental and theoretical findings suggest that during interaction of LysH+ with D2O isotopic exchange is favored over the water assisted conformational change from ion-molecule into ion-zwitterion structure.

  2. Quantum Control of Femtochemistry in the Gas Phase, Liquid Phase and on Surfaces

    NASA Astrophysics Data System (ADS)

    Gerber, Gustav

    2008-03-01

    By using coherent control techniques we control the behavior of quantum systems on their natural fs-time scale by applying ultrashort coherent light fields in the wavelength range from the IR to the UV. These laser pulses can be variably shaped in space and time using a laser pulse shaper consisting of a liquid-crystal display [1]. Laser-optimized femtochemistry in the gas phase and liquid phase is one field in which this new technique is successfully employed. Automated optimization of branching ratios and total product yields of gas phase photodissociation reactions as well as chemically selective molecular excitation in the liquid phase is performed [2][3]. Structural changes of a molecule in the liquid phase have been controlled by laser-optimized photoisomerization of a cyanine dye molecule [4] and of retinal in bacteriorhodopsin [5]. So far, optimal control techniques have been restricted to gas phase and condensed phase optimization experiments. Recently we have demonstrated femtosecond laser-assisted catalytic reactions on a Pd(100) single crystal surface. By applying a closed-loop optimal control scheme, we manipulate these reactions and selectively optimize the ratio of different bond-forming reaction channels, in contrast to previous quantum control experiments aiming at bond-cleavage. The results represent a first step towards selective photocatalysis of molecules. [1] T. Baumert et al, Appl. Phys. B 65, 779 (1997) [2] A. Assion et al, Science 282, 919(1998); T. Brixner et al, J. Mod. Opt. 50, 539 (2003) [3] T. Brixner et al, Nature, Vol. 414, 57 (2001) and J. Chem. Phys. 118, 3692 (2003) [4] G. Krampert et al, Phys. Rev. Lett. 94, 068305 (2005) [5] G. Vogt et al, Chem. Phys. Lett. 433, 211 (2006) P. Nuernberger et al, Phys. Chem. Chem. Phys. 9, 2470 (2007)

  3. The molecular structures, conformations and force fields of bis(chloroimino)butanedinitrile as studied by gas-phase electron diffraction and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Thomassen, H.; Gundersen, S.; Samdal, S.

    2009-06-01

    Quantum chemical calculations using levels up to MP2(Full)/aug-cc-pVTZ have been applied. B3LYP calculations using the 6-31G* basis set reveal that there are four conformations of bis(chloroimino)butanedinitrile. The planar anti-ZZ conformer with C2h symmetry is the most stable conformer. The non-planar EE conformer with C2 symmetry, the non-planar EZ conformer with C1 symmetry and the non-planar ZZ conformer with C2 symmetry are 16.8, 22.7, 27.2 kJ/mol, respectively, less stable than the planar anti-ZZ conformer according toB3LYP/6-31G* calculations. Calculated frequencies for the planar anti-ZZ conformer have been compared with observed frequencies, and some reassignments have been proposed. Several models have been used in the gas-phase electron diffraction analysis. The most reliable results are expected to be obtained using a dynamic model where the large amplitude motion is simulated by a harmonic angular motion using a Gaussian distribution about the central C sbnd C bond. Only the planar anti-ZZ conformer was used in the final refinements due to the high energy difference to the other conformers. The most important bond distances ( ra, Ångstrom) and bond angles (∠ α, degrees) are [GED/MP2(Full)/aug-cc-pVTZ]: rC 1sbnd C 2 = [1.509(15), 1.460], rC 2 = N 3 = [1.295(6), 1.292], rN 3sbnd Cl 5 = [1.706(5), 1.696], rC 2sbnd C 7 = [1.434(11), 1.421], rC 7tbnd N 9 = [1.165(4), 1.170], ∠C 1sbnd C 2dbnd N 3 = [114.5(11), 115.6], ∠C 2dbnd N 3sbnd Cl 5 = [115.0(4), 115.0], ∠C 1sbnd C 2sbnd C 7 = [118.8(8), 118.5], ∠C 2sbnd C 7tbnd N 9 = [178.2(15), 177.4]. The dihedral angle N 3C 2C 7N 9 is 0°, i.e. the cyano groups are bended towards the Cl atom. Error estimates from electron diffraction are given as: σr = 2.5[σ lsq2 + (0.001r) 2] ½ for bond distances and σ∠ = 2.5σ lsq for bond angles.

  4. Gas-phase basicity of 2-furaldehyde.

    PubMed

    Ricci, Andreina; Piccolella, Simona; Pepi, Federico; Patsilinakos, Alexandros; Ragno, Rino; Garzoli, Stefania; Giacomello, Pierluigi

    2012-11-01

    2-Furaldehyde (2-FA), also known as furfural or 2-furancarboxaldehyde, is an heterocyclic aldehyde that can be obtained from the thermal dehydration of pentose monosaccharides. This molecule can be considered as an important sustainable intermediate for the preparation of a great variety of chemicals, pharmaceuticals and furan-based polymers. Despite the great importance of this molecule, its gas-phase basicity (GB) has never been measured. In this work, the GB of 2-FA was determined by the extended Cooks's kinetic method from electrospray ionization triple quadrupole tandem mass spectrometric experiments along with theoretical calculations. As expected, computational results identify the aldehydic oxygen atom of 2-FA as the preferred protonation site. The geometries of O-O-cis and O-O-trans 2-FA and of their six different protomers were calculated at the B3LYP/aug-TZV(d,p) level of theory; proton affinity (PA) values were also calculated at the G3(MP2, CCSD(T)) level of theory. The experimental PA was estimated to be 847.9 ± 3.8 kJ mol(-1), the protonation entropy 115.1 ± 5.03 J mol(-1) K(-1) and the GB 813.6 ± 4.08 kJ mol(-1) at 298 K. From the PA value, a ΔH°(f) of 533.0 ± 12.4 kJ mol(-1) for protonated 2-FA was derived. PMID:23147827

  5. Hydrocarbon radical thermochemistry: Gas-phase ion chemistry techniques

    SciTech Connect

    Ervin, Kent M.

    2014-03-21

    Final Scientific/Technical Report for the project "Hydrocarbon Radical Thermochemistry: Gas-Phase Ion Chemistry Techniques." The objective of this project is to exploit gas-phase ion chemistry techniques for determination of thermochemical values for neutral hydrocarbon radicals of importance in combustion kinetics.

  6. Pressure Dependence of Gas-Phase Reaction Rates

    ERIC Educational Resources Information Center

    De Persis, Stephanie; Dollet, Alain; Teyssandier, Francis

    2004-01-01

    It is presented that only simple concepts, mainly taken from activated-complex or transition-state theory, are required to explain and analytically describe the influence of pressure on gas-phase reaction kinetics. The simplest kind of elementary gas-phase reaction is a unimolecular decomposition reaction.

  7. Gas-Phase Fragmentation Analysis of Nitro-Fatty Acids

    NASA Astrophysics Data System (ADS)

    Bonacci, Gustavo; Asciutto, Eliana K.; Woodcock, Steven R.; Salvatore, Sonia R.; Freeman, Bruce A.; Schopfer, Francisco J.

    2011-09-01

    Nitro-fatty acids are electrophilic signaling mediators formed in increased amounts during inflammation by nitric oxide and nitrite-dependent redox reactions. A more rigorous characterization of endogenously-generated species requires additional understanding of their gas-phase induced fragmentation. Thus, collision induced dissociation (CID) of nitroalkane and nitroalkene groups in fatty acids were studied in the negative ion mode to provide mass spectrometric tools for their structural characterization. Fragmentation of nitroalkanes occurred mainly through loss of the NO{2/-} anion or neutral loss of HNO2. The CID of nitroalkenes proceeds via a more complex cyclization, followed by fragmentation to nitrile and aldehyde products. Gas-phase fragmentation of nitroalkene functional groups with additional γ or δ unsaturation occurred through a multiple step cyclization reaction process, leading to 5 and 6 member ring heterocyclic products and carbon chain fragmentation. Cyclization products were not obtained during nitroalkane fragmentation, highlighting the role of double bond π electrons during NO{2/-} rearrangements, stabilization and heterocycle formation. The proposed structures, mechanisms and products of fragmentation are supported by analysis of 13C and 15N labeled parent molecules, 6 different nitroalkene positional isomers, 6 nitroalkane positional isomers, accurate mass determinations at high resolution and quantum mechanics calculations. Multiple key diagnostic ion fragments were obtained through this analysis, allowing for the precise placement of double bonds and sites of fatty acid nitration, thus supporting an ability to predict nitro positions in biological samples.

  8. Gas-phase protonation thermochemistry of arginine.

    PubMed

    Bouchoux, Guy; Desaphy, Sylvain; Bourcier, Sophie; Malosse, Christian; Bimbong, Rosa Ngo Biboum

    2008-03-20

    The gas-phase basicity (GB), proton affinity (PA), and protonation entropy (DeltapS degrees (M)=S degrees (MH+)-S degrees (M)) of arginine (Arg) have been experimentally determined by the extended kinetic method using an electrospray ionization quadrupole time-of-flight (ESI-Q-TOF) mass spectrometer. This method provides GB(Arg)=1004.3+/-2.2 (4.9) kJ.mol(-1) (indicated errors are standard deviations, and in parentheses, 95% confidence limits are given). Consideration of previous experimental data using a fast atom bombardment ionization tandem sector mass spectrometer slightly modifies these estimates since GB(Arg)=1005.9+/-3.1 (6.6) kJ.mol(-1). Lower limits of the proton affinity, PA(Arg)=1046+/-4 (7) kJ.mol(-1), and of the "protonation entropy", DeltapS degrees (Arg)=S degrees (ArgH+)-S degrees (Arg)=-27+/-7 (15) J.mol(-1).K(-1), are also provided by the experiments. Theoretical calculations conducted at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31+G(d,p) level, including 298 K enthalpy correction, predict a proton affinity value of ca. 1053 kJ.mol-1 after consideration of isodesmic proton-transfer reactions with guanidine as the reference base. Computations including explicit treatment of hindered rotations and mixing of conformers confirm that a noticeable entropy loss does occur upon protonation, which leads to a theoretical DeltapS degrees (Arg) term of ca. -45 J.mol(-1).K(-1). The following evaluated thermochemical parameter values are proposed: GB(Arg)=1005+/-3 kJ.mol(-1); PA(Arg)=1051+/-5 kJ.mol(-1), and DeltapS degrees (Arg)=-45+/-12 J.mol(-1).K(-1). PMID:18288831

  9. Infrared photodissociation spectroscopy of protonated neurotransmitters in the gas phase

    NASA Astrophysics Data System (ADS)

    MacLeod, N. A.; Simons, J. P.

    2007-03-01

    Protonated neurotransmitters have been produced in the gas phase via a novel photochemical scheme: complexes of the species of interest, 1-phenylethylamine, 2-amino-1-phenylethanol and the diastereo-isomers, ephedrine and pseudoephedrine, with a suitable proton donor, phenol (or indole), are produced in a supersonic expansion and ionized by resonant two photon ionization of the donor. Efficient proton transfer generates the protonated neurotransmitters, complexed to a phenoxy radical. Absorption of infrared radiation, and subsequent evaporation of the phenoxy tag, coupled with time of flight mass spectrometry, provides vibrational spectra of the protonated (and also hydrated) complexes for comparison with the results of quantum chemical computation. Comparison with the conformational structures of the neutral neurotransmitters (established previously) reveals the effect of protonation on their structure. The photochemical proton transfer strategy allows spectra to be recorded from individual laser shots and their quality compares favourably with that obtained using electro-spray or matrix assisted laser desorption ion sources.

  10. Gas holdup in three-phase immobilized cell bioreactors

    SciTech Connect

    Bajpai, R.; Thompson, J.E.; Davison, B.

    1989-01-01

    A number of studies in the published literature deal with gas holdup in three-phase reactors. However, very few address the cases in which the solid density approaches that of the liquid phases and where low gas velocities are involved. These conditions are commonly encountered in immobilized-cell bubble columns and in fluidized-bed bioreactors. This paper reports the effect of gas and liquid velocity upon gas holdup and bed expansion in fluidized-bed bioreactors. For liquid-fluidization of low-density alginate beads in the absence of gas, the terminal sedimentation velocity (v/sub T/), of the particles is a constant and expansion of the bed follows Richardson and Zaki's correlation. In the presence of gas, however, the apparent terminal sedimentation velocity value is affected by the velocity of the gas and liquid phases. For gas velocities above a minimum value, the calculated value of v/sub T/ depends upon liquid velocity only and a constant bed expansion was observed for a range of gas and liquid flow rates. For the gas-liquid interactions, a modified drift-flux model was found to be valid. For superficial gas velocities between 5 and 17 cm/min, the modified drift-flux velocity was observed to be a function of gas velocity suggesting the prevalence of a coalescence regime. 21 refs., 4 figs., 1 tab.

  11. Comparison of liquid-phase and gas-phase pure thermal cracking on n-hexadecane

    SciTech Connect

    Wu, G.; Katsumura, Yosuke; Matsuura, Chihiro; Ishigure, Kenkichi; Kubo, Junichi

    1996-12-01

    Thermal cracking of n-hexadecane in the mild temperature (330--375 C) range has been investigated in liquid and gas phases. The kinetic data of liquid-phase cracking are shown to be very similar to those of gas-phase cracking. However, the pattern and distribution of the products are greatly phase dependent. In liquid-phase cracking, there is an equimolar distribution of n-alkane and 1-alkene products in the C{sub 3}--C{sub 13} range at low conversion; when the conversion is increased, more alkanes than alkenes are produced. To the contrary, more alkenes than alkanes are always determined in products from gas-phase cracking. Liquid-phase cracking gives a low selectivity of gas products and a high selectivity of addition compounds (C{sub 18}--C{sub 30}), whereas gas-phase cracking produces a large amount of gas products and no addition compounds. The phase dependence of products can be interpreted in terms of a low concentration of hexadecane, under which {beta}-scission occurs more preferentially than in liquid phase. Reaction mechanisms are suggested based on the product analysis to account for cracking behaviors of liquid-phase and gas-phase cracking.

  12. Spectroscopic studies of kinetically trapped conformations in the gas phase: the case of triply protonated bradykinin.

    PubMed

    Voronina, Liudmila; Rizzo, Thomas R

    2015-10-21

    Understanding the relation between the gas-phase structure of biological molecules and their solution-phase structure is important when attempting to use gas-phase techniques to address biologically relevant questions. Directly after electrospray ionization, molecules can be kinetically trapped in a state that retains some "memory" of its conformation in solution and is separated from the lowest-energy gas-phase structure by barriers on the potential energy surface. In order to identify and characterize kinetically trapped structures, we have explored the conformational space of triply protonated bradykinin in the gas phase by combining field-asymmetric ion mobility spectrometry (FAIMS) with cold ion spectroscopy. We isolate three distinct conformational families and characterize them by recording their UV-photofragment spectra and vibrational spectra. Annealing of the initial conformational distribution produced by electrospray reveals that one of the conformational families is kinetically trapped, while two others are stable, gas-phase structures. We compare our results to previously published results obtained using drift-tube ion mobility spectrometry (IMS) and propose a correspondence between the conformational families separated by FAIMS and those by IMS. PMID:25940085

  13. Gas-Liquid Flows and Phase Separation

    NASA Technical Reports Server (NTRS)

    McQuillen, John

    2004-01-01

    Common issues for space system designers include:Ability to Verify Performance in Normal Gravity prior to Deployment; System Stability; Phase Accumulation & Shedding; Phase Separation; Flow Distribution through Tees & Manifolds Boiling Crisis; Heat Transfer Coefficient; and Pressure Drop.The report concludes:Guidance similar to "A design that operates in a single phase is less complex than a design that has two-phase flow" is not always true considering the amount of effort spent on pressurizing, subcooling and phase separators to ensure single phase operation. While there is still much to learn about two-phase flow in reduced gravity, we have a good start. Focus now needs to be directed more towards system level problems .

  14. Phase structure of soliton molecules

    SciTech Connect

    Hause, A.; Hartwig, H.; Seifert, B.; Stolz, H.; Boehm, M.; Mitschke, F.

    2007-06-15

    Temporal optical soliton molecules were recently demonstrated; they potentially allow further increase of data rates in optical telecommunication. Their binding mechanism relies on the internal phases, but these have not been experimentally accessible so far. Conventional frequency-resolved optical gating techniques are not suited for measurement of their phase profile: Their algorithms fail to converge due to zeros both in their temporal and their spectral profile. We show that the VAMPIRE (very advanced method of phase and intensity retrieval of E-fields) method performs reliably. With VAMPIRE the phase profile of soliton molecules has been measured, and further insight into the mechanism is obtained.

  15. Phase structure of soliton molecules

    NASA Astrophysics Data System (ADS)

    Hause, A.; Hartwig, H.; Seifert, B.; Stolz, H.; Böhm, M.; Mitschke, F.

    2007-06-01

    Temporal optical soliton molecules were recently demonstrated; they potentially allow further increase of data rates in optical telecommunication. Their binding mechanism relies on the internal phases, but these have not been experimentally accessible so far. Conventional frequency-resolved optical gating techniques are not suited for measurement of their phase profile: Their algorithms fail to converge due to zeros both in their temporal and their spectral profile. We show that the VAMPIRE (very advanced method of phase and intensity retrieval of E -fields) method performs reliably. With VAMPIRE the phase profile of soliton molecules has been measured, and further insight into the mechanism is obtained.

  16. Incommensurate Structure of Phosphorus Phase IV

    SciTech Connect

    Fujihisa, Hiroshi; Gotoh, Yoshito; Yamawaki, Hiroshi; Sakashita, Mami; Takeya, Satoshi; Honda, Kazumasa; Akahama, Yuichi; Kawamura, Haruki; Ohishi, Yasuo

    2007-04-27

    There are six known phases for phosphorus at room temperature under high pressure. Only the structure of phase IV, which exists from 107 GPa to 137 GPa, remains unsolved. We performed a powder x-ray diffraction experiment and a Rietveld analysis and successfully determined its structure to be an incommensurately modulated structure by only 1 site of atomic position. High-pressure phases of halogens and chalcogens have previously been shown to have a similar modulated structure; however, phosphorus phase IV is different from them and was shown to be the third case.

  17. Atomic and molecular physics in the gas phase

    SciTech Connect

    Toburen, L.H.

    1990-09-01

    The spatial and temporal distributions of energy deposition by high-linear-energy-transfer radiation play an important role in the subsequent chemical and biological processes leading to radiation damage. Because the spatial structures of energy deposition events are of the same dimensions as molecular structures in the mammalian cell, direct measurements of energy deposition distributions appropriate to radiation biology are infeasible. This has led to the development of models of energy transport based on a knowledge of atomic and molecular interactions process that enable one to simulate energy transfer on an atomic scale. Such models require a detailed understanding of the interactions of ions and electrons with biologically relevant material. During the past 20 years there has been a great deal of progress in our understanding of these interactions; much of it coming from studies in the gas phase. These studies provide information on the systematics of interaction cross sections leading to a knowledge of the regions of energy deposition where molecular and phase effects are important and that guide developments in appropriate theory. In this report studies of the doubly differential cross sections, crucial to the development of stochastic energy deposition calculations and track structure simulation, will be reviewed. Areas of understanding are discussed and directions for future work addressed. Particular attention is given to experimental and theoretical findings that have changed the traditional view of secondary electron production for charged particle interactions with atomic and molecular targets.

  18. Mixed Stationary Liquid Phases for Gas-Liquid Chromatography.

    ERIC Educational Resources Information Center

    Koury, Albert M.; Parcher, Jon F.

    1979-01-01

    Describes a laboratory technique for use in an undergraduate instrumental analysis course that, using the interpretation of window diagrams, prepares a mixed liquid phase column for gas-liquid chromatography. A detailed procedure is provided. (BT)

  19. STRUCTURED MOLECULAR GAS REVEALS GALACTIC SPIRAL ARMS

    SciTech Connect

    Sawada, Tsuyoshi; Hasegawa, Tetsuo; Koda, Jin

    2012-11-01

    We explore the development of structures in molecular gas in the Milky Way by applying the analysis of the brightness distribution function and the brightness distribution index (BDI) in the archival data from the Boston University-Five College Radio Astronomy Observatory {sup 13}CO J = 1-0 Galactic Ring Survey. The BDI measures the fractional contribution of spatially confined bright molecular emission over faint emission extended over large areas. This relative quantity is largely independent of the amount of molecular gas and of any conventional, pre-conceived structures, such as cores, clumps, or giant molecular clouds. The structured molecular gas traced by higher BDI is located continuously along the spiral arms in the Milky Way in the longitude-velocity diagram. This clearly indicates that molecular gas changes its structure as it flows through the spiral arms. Although the high-BDI gas generally coincides with H II regions, there is also some high-BDI gas with no/little signature of ongoing star formation. These results support a possible evolutionary sequence in which unstructured, diffuse gas transforms itself into a structured state on encountering the spiral arms, followed by star formation and an eventual return to the unstructured state after the spiral arm passage.

  20. High resolution ion mobility measurements for gas phase proteins: correlation between solution phase and gas phase conformations

    NASA Astrophysics Data System (ADS)

    Hudgins, Robert R.; Woenckhaus, Jürgen; Jarrold, Martin F.

    1997-11-01

    Our high resolution ion mobility apparatus has been modified by attaching an electrospray source to perform measurements for biological molecules. While the greater resolving power permits the resolution of more conformations for BPTI and cytochrome c, the resolved features are generally much broader than expected for a single rigid conformation. A major advantage of the new experimental configuration is the much gentler introduction of ions into the drift tube, so that the observed gas phase conformations appear to more closely reflect those present in solution. For example, it is possible to distinguish between the native state of cytochrome c and the methanol-denatured form on the basis of the ion mobility measurements; the mass spectra alone are not sensitive enough to detect this change. Thus this approach may provide a quick and sensitive tool for probing the solution phase conformations of biological molecules.

  1. Electron spectrometer for gas-phase spectroscopy

    SciTech Connect

    Bozek, J.D.; Schlachter, A.S.

    1997-04-01

    An electron spectrometer for high-resolution spectroscopy of gaseous samples using synchrotron radiation has been designed and constructed. The spectrometer consists of a gas cell, cylindrical electrostatic lens, spherical-sector electron energy analyzer, position-sensitive detector and associated power supplies, electronics and vacuum pumps. Details of the spectrometer design are presented together with some representative spectra.

  2. Phase-field Modeling of Gas Bubbles and Thermal Conductivity Evolution in Nuclear Fuels

    SciTech Connect

    Hu, Shenyang Y.; Henager, Charles H.; Heinisch, Howard L.; Stan, Marius; Baskes, Michael I.; Valone, Steven

    2009-07-15

    The major factors that influence the thermal conductivity of the ceramics and metals are temperature, stoichiometry, microstructure, porosity, and point defects. Nuclear fuels and structure materials are subject to a severe radiation environment and their properties, including thermal conductivity change significantly with time and irradiation level. In particular, the accumulation of fission products and the formation of He bubbles can decrease the heat transfer, leading to overheating of the fuel element. In this work, we use the phase-field method to study the effect of microstructural changes on thermal conductivity. We developed a phase-field model to simulate the He bubble formation and growth in a single/polycrystalline material with defects. The model takes into account the generation of gas atoms and defects, gas atom diffusivity inhomogeneity, gas atom segregation, and gas bubble nucleation. With the model, we simulated the gas bubble and temperature evolution, and calculated the effect of gas bubble volume fraction on effective thermal conductivity.

  3. Characterizing the correlations between local phase fractions of gas-liquid two-phase flow with wire-mesh sensor.

    PubMed

    Tan, C; Liu, W L; Dong, F

    2016-06-28

    Understanding of flow patterns and their transitions is significant to uncover the flow mechanics of two-phase flow. The local phase distribution and its fluctuations contain rich information regarding the flow structures. A wire-mesh sensor (WMS) was used to study the local phase fluctuations of horizontal gas-liquid two-phase flow, which was verified through comparing the reconstructed three-dimensional flow structure with photographs taken during the experiments. Each crossing point of the WMS is treated as a node, so the measurement on each node is the phase fraction in this local area. An undirected and unweighted flow pattern network was established based on connections that are formed by cross-correlating the time series of each node under different flow patterns. The structure of the flow pattern network reveals the relationship of the phase fluctuations at each node during flow pattern transition, which is then quantified by introducing the topological index of the complex network. The proposed analysis method using the WMS not only provides three-dimensional visualizations of the gas-liquid two-phase flow, but is also a thorough analysis for the structure of flow patterns and the characteristics of flow pattern transition. This article is part of the themed issue 'Supersensing through industrial process tomography'. PMID:27185959

  4. Intramolecular structure and dynamics of mequinol and guaiacol in the gas phase: Rotationally resolved electronic spectra of their S{sub 1} states

    SciTech Connect

    Ruiz-Santoyo, José Arturo; Rodríguez-Matus, Marcela; Álvarez-Valtierra, Leonardo E-mail: gmerino@mda.cinvestav.mx; Cabellos, José Luis; Merino, Gabriel E-mail: gmerino@mda.cinvestav.mx; Yi, John T.; Pratt, David W.; Schmitt, Michael

    2015-09-07

    The molecular structures of guaiacol (2-methoxyphenol) and mequinol (4-methoxyphenol) have been studied using high resolution electronic spectroscopy in a molecular beam and contrasted with ab initio computations. Mequinol exhibits two low frequency bands that have been assigned to electronic origins of two possible conformers of the molecule, trans and cis. Guaiacol also shows low frequency bands, but in this case, the bands have been assigned to the electronic origin and vibrational modes of a single conformer of the isolated molecule. A detailed study of these bands indicates that guaiacol has a vibrationally averaged planar structure in the ground state, but it is distorted along both in-plane and out-of-plane coordinates in the first electronically excited state. An intramolecular hydrogen bond involving the adjacent   –OH and   –OCH{sub 3} groups plays a major role in these dynamics.

  5. STAEBL: Structural tailoring of engine blades, phase 2

    NASA Technical Reports Server (NTRS)

    Hirschbein, M. S.; Brown, K. W.

    1984-01-01

    The Structural Tailoring of Engine Blades (STAEBL) program was initiated at NASA Lewis Research Center in 1980 to introduce optimal structural tailoring into the design process for aircraft gas turbine engine blades. The standard procedure for blade design is highly iterative with the engineer directly providing most of the decisions that control the design process. The goal of the STAEBL program has been to develop an automated approach to generate structurally optimal blade designs. The program has evolved as a three-phase effort with the developmental work being performed contractually by Pratt & Whitney Aircraft. Phase 1 was intended as a proof of concept in which two fan blades were structurally tailored to meet a full set of structural design constraints while minimizing DOC+I (direct operating cost plus interest) for a representative aircraft. This phase was successfully completed and was reported in reference 1 and 2. Phase 2 has recently been completed and is the basis for this discussion. During this phase, three tasks were accomplished: (1) a nonproprietary structural tailoring computer code was developed; (2) a dedicated approximate finite-element analysis was developed; and (3) an approximate large-deflection analysis was developed to assess local foreign object damage. Phase 3 is just beginning and is designed to incorporated aerodynamic analyses directly into the structural tailoring system in order to relax current geometric constraints.

  6. Measuring Complementary Electronic Structure Properties of both Deposited and Gas Phase Clusters using STM, UPS, and PES: Size-Selected Clusters on Surfaces

    SciTech Connect

    Bowen, Kit H.

    2014-03-05

    In this project, we studied size-selected cluster interactions with surfaces, with other clusters on surfaces, and with external stimuli. These studies focused on mobility as a function of cluster size, surface morphologies as a function of composition and coverage, ion-induced modification and reactivity of clusters as a function of composition, the structural evolution of cluster cuboids culminating in the characterization of theoretically-predicted “baby crystal” clusters, and unusual fractal pattern formation due to deposition.

  7. Phase structure in a chiral model of nuclear matter

    SciTech Connect

    Phat, Tran Huu; Anh, Nguyen Tuan; Tam, Dinh Thanh

    2011-08-15

    The phase structure of symmetric nuclear matter in the extended Nambu-Jona-Lasinio (ENJL) model is studied by means of the effective potential in the one-loop approximation. It is found that chiral symmetry gets restored at high nuclear density and a typical first-order phase transition of the liquid-gas transition occurs at zero temperature, T=0, which weakens as T grows and eventually ends up with a second-order critical point at T=20 MeV. This phase transition scenario is confirmed by investigating the evolution of the effective potential versus the effective nucleon mass and the equation of state.

  8. The gas-phase structure and some reactions of the bulky primary silane (Me(3)Si)(3)CSiH(3) and the solid-state structure of the bulky dialkyl disilane [(Me(3)Si)(3)CSiH(2)](2).

    PubMed

    Masters, Sarah L; Rankin, David W H; Cordes, David B; Bätz, Karin; Lickiss, Paul D; Boag, Neil M; Redhouse, Alan D; Whittaker, Stephen M

    2010-10-21

    The molecular structure of the bulky primary silane, (Me(3)Si)(3)CSiH(3), in the gas phase has been determined by electron diffraction. Photolysis of (Me(3)Si)(3)CSiH(3) affords a convenient route to the bulky dialkyl disilane, [(Me(3)Si)(3)CSiH(2)](2), which is the first 1,2-dialkyldisilane to be structurally characterised by single-crystal X-ray diffraction. The disilane has an unusually large Si-Si-C angle of 120.05(9)°. PMID:20697646

  9. Structures of [M(Ura-H)(H2 O)n ](+) (M = Mg, Ca, Sr, Ba; n = 1-3) complexes in the gas phase by IRMPD spectroscopy and theoretical studies.

    PubMed

    Power, Barry; Haldys, Violette; Salpin, Jean-Yves; Fridgen, Travis D

    2016-03-01

    The structures of singly and doubly (and for Mg, triply) hydrated group 2 metal dications bound to deprotonated uracil were explored in the gas phase using infrared multiple photon dissociation spectroscopy in the mid-infrared region (1000-1900 cm(-1) ) and the O-H/N-H stretching region (2700-3800 cm(-1) ) in a Fourier transform ion cyclotron resonance mass spectrometer. The infrared multiple photon dissociation spectra were then compared with the computed IR spectra for various isomers. Calculations were performed using B3LYP with the 6-31 + G(d,p) basis set for all atoms except Ba(2+) and Sr(2+) , for which the LANL2DZ or the def2-TZVPP basis sets with relativistic core potentials were used. Atoms-in-molecules analysis was conducted for all lowest energy structures. The lowest energy isomers in all cases are those in which the one uracil is deprotonated at the N3 position, and the metal is coordinated to the N3 and O4 of uracil. Regardless of the degree of solvation, all water molecules are bound to the metal ion and participate in a hydrogen bond with a carbonyl of the uracil moiety. PMID:26956390

  10. The hydrothermal evolution of the phase and shape of ZnS nanostructures and their gas-sensing properties.

    PubMed

    Hu, Pengfei; Gong, Guodong; Zhan, Fangyi; Zhang, Yuan; Li, Rong; Cao, Yali

    2016-02-14

    This work presents the evolution of the phase and shape of ZnS along the hydrothermal holding time or the dosage of the surfactant. The ZnS sensor obviously showed phase-/defect-dependent gas-sensing performances indicating that the wurtzite-type structure, as well the defect will improve its gas-sensing activities. PMID:26781594

  11. Photoionization of cold gas phase coronene and its clusters: Autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation

    NASA Astrophysics Data System (ADS)

    Bréchignac, Philippe; Garcia, Gustavo A.; Falvo, Cyril; Joblin, Christine; Kokkin, Damian; Bonnamy, Anthony; Parneix, Pascal; Pino, Thomas; Pirali, Olivier; Mulas, Giacomo; Nahon, Laurent

    2014-10-01

    Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail. Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory.

  12. Ab initio structural and spectroscopic study of HPS{sup x} and HSP{sup x} (x = 0,+1,−1) in the gas phase

    SciTech Connect

    Yaghlane, Saida Ben; Cotton, C. Eric; Francisco, Joseph S. E-mail: hochlaf@univ-mlv.fr; Linguerri, Roberto; Hochlaf, Majdi E-mail: hochlaf@univ-mlv.fr

    2013-11-07

    Accurate ab initio computations of structural and spectroscopic parameters for the HPS/HSP molecules and corresponding cations and anions have been performed. For the electronic structure computations, standard and explicitly correlated coupled cluster techniques in conjunction with large basis sets have been adopted. In particular, we present equilibrium geometries, rotational constants, harmonic vibrational frequencies, adiabatic ionization energies, electron affinities, and, for the neutral species, singlet-triplet relative energies. Besides, the full-dimensional potential energy surfaces (PESs) for HPS{sup x} and HSP{sup x} (x = −1,0,1) systems have been generated at the standard coupled cluster level with a basis set of augmented quintuple-zeta quality. By applying perturbation theory to the calculated PESs, an extended set of spectroscopic constants, including τ, first-order centrifugal distortion and anharmonic vibrational constants has been obtained. In addition, the potentials have been used in a variational approach to deduce the whole pattern of vibrational levels up to 4000 cm{sup −1} above the minima of the corresponding PESs.

  13. OH radical formation from the gas-phase reaction of ozone with terminal alkenes and the relationship between structure and mechanism

    SciTech Connect

    Paulson, S.E.; Chung, M.Y.; Hasson, A.S.

    1999-10-14

    The reactions of ozone with alkenes have been shown recently to lead to the direct production of OH radicals in quantities that vary from 7 to 100% depending on the structure of the alkene. OH radicals are the most important oxidizing species in the lower atmosphere, and the OH-alkene reaction is a large source of new OH radicals, important in urban and rural air during both day and night. Evidence for OH formation comes both from low-pressure direct measurements and from tracer experiments at high pressure. With the goal of measuring OH formation yields with good precision, a small-ratio relative rate technique was developed. This method uses small amounts of fast-reacting aromatics and aliphatic ethers to trace OH formation yields. Here, the authors report OH formation yields for a series of terminal alkenes reacting with ozone. Measured OH yields were 0.29 {+-} 0.05, 0.24 {+-} 0.05, 0.18 {+-} 0.04, and 0.10 {+-} 0.03 for 1-butene, 1-pentene, 1-hexene, and 1-octene, respectively. For the methyl-substituted terminal alkenes methyl propene and 2-methyl-1-butene, OH yields were 0.72 {+-} 0.12 and 0.67 {+-} 0.12, respectively. The results are discussed both in terms of their atmospheric implications and the relationship between structure and OH formation.

  14. Photoionization of cold gas phase coronene and its clusters: Autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation

    SciTech Connect

    Bréchignac, Philippe Falvo, Cyril; Parneix, Pascal; Pino, Thomas; Pirali, Olivier; Garcia, Gustavo A.; Nahon, Laurent; Joblin, Christine; Kokkin, Damian; Bonnamy, Anthony; Mulas, Giacomo

    2014-10-28

    Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail. Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory.

  15. Photoionization of cold gas phase coronene and its clusters: autoionization resonances in monomer, dimer, and trimer and electronic structure of monomer cation.

    PubMed

    Bréchignac, Philippe; Garcia, Gustavo A; Falvo, Cyril; Joblin, Christine; Kokkin, Damian; Bonnamy, Anthony; Parneix, Pascal; Pino, Thomas; Pirali, Olivier; Mulas, Giacomo; Nahon, Laurent

    2014-10-28

    Polycyclic aromatic hydrocarbons (PAHs) are key species encountered in a large variety of environments such as the Interstellar Medium (ISM) and in combustion media. Their UV spectroscopy and photodynamics in neutral and cationic forms are important to investigate in order to learn about their structure, formation mechanisms, and reactivity. Here, we report an experimental photoelectron-photoion coincidence study of a prototypical PAH molecule, coronene, and its small clusters, in a molecular beam using the vacuum ultraviolet (VUV) photons provided by the SOLEIL synchrotron facility. Mass-selected high resolution threshold photoelectron (TPES) and total ion yield spectra were obtained and analyzed in detail. Intense series of autoionizing resonances have been characterized as originating from the monomer, dimer, and trimer neutral species, which may be used as spectral fingerprints for their detection in the ISM by VUV absorption spectroscopy. Finally, a full description of the electronic structure of the monomer cation was made and discussed in detail in relation to previous spectroscopic optical absorption data. Tentative vibrational assignments in the near-threshold TPES spectrum of the monomer have been made with the support of a theoretical approach based on density functional theory. PMID:25362317

  16. Gas phase acetaldehyde production in a continuous bioreactor

    SciTech Connect

    Hwang, Soon Ook . Dept. of Chemical Engineering); Trantolo, D.J. . Center for Biotechnology Engineering); Wise, D.L. . Dept. of Chemical Engineering Northeastern Univ., Boston, MA . Center for Biotechnology Engineering)

    1993-08-20

    The gas phase continuous production of acetaldehyde was studied with particular emphasis on the development of biocatalyst (alcohol oxidase on solid phase support materials) for a fixed bed reactor. Based on the experimental results in a batch bioreactor, the biocatalysts were prepared by immobilization of alcohol oxidase on Amberlite IRA-400, packed into a column, and the continuous acetaldehyde production in the gas phase by alcohol oxidase was performed. The effects of the reaction temperature, flow rates of gaseous stream, and ethanol vapor concentration on the performance of the continuous bioreactor were investigated.

  17. Gas-phase diffusion in porous media: Comparison of models

    SciTech Connect

    Webb, S.W.

    1998-09-01

    Two models are commonly used to analyze gas-phase diffusion in porous media in the presence of advection, the Advective-Dispersive Model (ADM) and the Dusty-gas Model (DGM). The ADM, which is used in TOUGH2, is based on a simple linear addition of advection calculated by Darcy`s law and ordinary diffusion using Fick`s law with a porosity-tortuosity-gas saturation multiplier to account for the porous medium. Another approach for gas-phase transport in porous media is the Dusty-Gas Model. This model applies the kinetic theory of gases to the gaseous components and the porous media (or dust) to combine transport due to diffusion and advection that includes porous medium effects. The two approaches are compared in this paper.

  18. Para-Hydrogen-Enhanced Gas-Phase Magnetic Resonance Imaging

    SciTech Connect

    Bouchard, Louis-S.; Kovtunov, Kirill V.; Burt, Scott R.; Anwar,M. Sabieh; Koptyug, Igor V.; Sagdeev, Renad Z.; Pines, Alexander

    2007-02-23

    Herein, we demonstrate magnetic resonance imaging (MRI) inthe gas phase using para-hydrogen (p-H2)-induced polarization. A reactantmixture of H2 enriched in the paraspin state and propylene gas is flowedthrough a reactor cell containing a heterogenized catalyst, Wilkinson'scatalyst immobilized on modified silica gel. The hydrogenation product,propane gas, is transferred to the NMR magnet and is spin-polarized as aresult of the ALTADENA (adiabatic longitudinal transport and dissociationengenders net alignment) effect. A polarization enhancement factor of 300relative to thermally polarized gas was observed in 1D1H NMR spectra.Enhancement was also evident in the magnetic resonance images. This isthe first demonstration of imaging a hyperpolarized gaseous productformed in a hydrogenation reaction catalyzed by a supported catalyst.This result may lead to several important applications, includingflow-through porous materials, gas-phase reaction kinetics and adsorptionstudies, and MRI in low fields, all using catalyst-free polarizedfluids.

  19. Constant volume gas cell optical phase-shifter

    DOEpatents

    Phillion, Donald W.

    2002-01-01

    A constant volume gas cell optical phase-shifter, particularly applicable for phase-shifting interferometry, contains a sealed volume of atmospheric gas at a pressure somewhat different than atmospheric. An optical window is present at each end of the cell, and as the length of the cell is changed, the optical path length of a laser beam traversing the cell changes. The cell comprises movable coaxial tubes with seals and a volume equalizing opening. Because the cell is constant volume, the pressure, temperature, and density of the contained gas do not change as the cell changes length. This produces an exactly linear relationship between the change in the length of the gas cell and the change in optical phase of the laser beam traversing it. Because the refractive index difference between the gas inside and the atmosphere outside is very much the same, a large motion must be made to change the optical phase by the small fraction of a wavelength that is required by phase-shifting interferometry for its phase step. This motion can be made to great fractional accuracy.

  20. Theoretical study of the gas-phase structure, thermochemistry, and decomposition mechanisms of NH{sub 4}NO{sub 2} and NH{sub 4}N(NO{sub 2}){sub 2}

    SciTech Connect

    Mebel, A.M.; Lin, M.C.; Morokuma, K.; Melius, C.F.

    1995-05-04

    The structures, energetics, and decomposition mechanisms of gaseous ammonium nitrite (NH{sub 4}NO{sub 2}) and ammonium dinitramide [ADN, NH{sub 4}N(NO{sub 2}){sub 2}] have been studied theoretically by different ab initio molecular orbital approaches. In the gas phase, both species have the structures of molecular complexes, [NH{sub 3}]-[HX]. The ionic geometries, [NH{sub 4}{sup +}][X{sup -}], are not local minima on the potential energy surface and would not be stable after vaporization. For NH{sub 4}NO{sub 2}, [NH{sub 3}]-[trans-HONO] is the most stable isomer, and [NH{sub 3}]-[cis-HONO] and [NH{sub 3}]-[HNO{sub 2}] structures lie higher by 1.4 and 8.4 kcal/mol at the G1 level of theory. For the gaseous ADN, [NH{sub 3}]-HN(NO{sub 2}){sub 2} is the most stable structure, while the [NH{sub 3}]-[ON(O)NNO{sub 2}] isomer is 2.3 kcal/mol less favorable. The calculated dissociation energies of the [NH{sub 3}]-[HX] complex to NH{sub 3} and HX are 8-9 and 12-14 kcal/mol for NH{sub 4}NO{sub 2} and ADN, respectively. The energies for elimination of the NO{sub 2} group from HN(NO{sub 2}){sub 2} and HON(O)NNO{sub 2} are found to be 38-40 kcal/mol, while the barrier for HON(O)NNO{sub 2} dissociation is about 42 kcal/mol. 27 refs., 5 figs., 5 tabs.

  1. Broadband Microwave Spectroscopy as a Tool to Study the Structures of Odorant Molecules and Weakly Bound Complexes in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Zinn, Sabrina; Betz, Thomas; Medcraft, Chris; Schnell, Melanie

    2015-06-01

    The rotational spectrum of trans-cinnamaldehyde ((2E)-3-phenylprop-2-enal) has been obtained with chirped-pulse microwave spectroscopy in the frequency range of 2 - 8.5 GHz. The odorant molecule is the essential component in cinnamon oil and causes the characteristic smell. In the measured high-resolution spectrum, we were able to assign the rotational spectra of two conformers of trans-cinnamaldehyde as well as all singly 13C-substituted species of the lowest-energy conformer in natural abundance. Two different methods were used to determine the structure from the rotational constants, which will be compared within this contribution. In addition, the current progress of studying ether-alcohol complexes, aiming at an improved understanding of the interplay between hydrogen bonding and dispersion interaction, will be reported. Here, a special focus is placed on the complexes of diphenylether with small aliphatic alcohols.

  2. Oscillatory burning of solid propellants including gas phase time lag.

    NASA Technical Reports Server (NTRS)

    T'Ien, J. S.

    1972-01-01

    An analysis has been performed for oscillatory burning of solid propellants including gas phase time lag. The gaseous flame is assumed to be premixed and laminar with a one-step overall chemical reaction. The propellant is assumed to decompose according to the Arrenhius Law, with no condensed phase reaction. With this model, strong gas phase resonance has been found in certain cases at the characteristic gas-phase frequencies, but the peaking of the acoustic admittance is in the direction favoring the damping of pressure waves. At still higher frequencies, moderate wave-amplifying ability was found. The limit of low frequency response obtained previously by Denison and Baum was recovered, and the limitations of the quasi-steady theory were investigated.

  3. Analysis of volatile phase transport in soils using natural radon gas as a tracer

    SciTech Connect

    Chen, C.; Thomas, D.M.

    1992-01-01

    We have conducted a field study of soil gas transport processes using radon gas as a naturally occurring tracer. The .experiment monitored soil gas radon activity, soil moisture, and soil temperature at three depths in the shallow soil column; barometric pressure, rainfall and wind speed were monitored at the soil surface. Linear and multiple regression analysis of the data sets has shown that the gas phase radon activities under natural environmental conditions are influenced by soil moisture content, barometric pressure variations, soil temperature and soil structure. The effect of wind speed on subsurface radon activities under our field conditions has not been demonstrated.

  4. Analysis of volatile phase transport in soils using natural radon gas as a tracer

    SciTech Connect

    Chen, C.; Thomas, D.M.

    1992-12-31

    We have conducted a field study of soil gas transport processes using radon gas as a naturally occurring tracer. The .experiment monitored soil gas radon activity, soil moisture, and soil temperature at three depths in the shallow soil column; barometric pressure, rainfall and wind speed were monitored at the soil surface. Linear and multiple regression analysis of the data sets has shown that the gas phase radon activities under natural environmental conditions are influenced by soil moisture content, barometric pressure variations, soil temperature and soil structure. The effect of wind speed on subsurface radon activities under our field conditions has not been demonstrated.

  5. Relating gas phase to solution conformations: Lessons from disordered proteins

    PubMed Central

    Beveridge, Rebecca; Phillips, Ashley S.; Denbigh, Laetitia; Saleem, Hassan M.; MacPhee, Cait E.

    2015-01-01

    In recent years both mass spectrometry (MS) and ion mobility mass spectrometry (IM‐MS) have been developed as techniques with which to study proteins that lack a fixed tertiary structure but may contain regions that form secondary structure elements transiently, namely intrinsically disordered proteins (IDPs). IM‐MS is a suitable method for the study of IDPs which provides an insight to conformations that are present in solution, potentially enabling the analysis of lowly populated structural forms. Here, we describe the IM‐MS data of two IDPs; α‐Synuclein (α‐Syn) which is implicated in Parkinson's disease, and Apolipoprotein C‐II (ApoC‐II) which is involved in cardiovascular diseases. We report an apparent discrepancy in the way that ApoC‐II behaves in the gas phase. While most IDPs, including α‐Syn, present in many charge states and a wide range of rotationally averaged collision cross sections (CCSs), ApoC‐II presents in just four charge states and a very narrow range of CCSs, independent of solution conditions. Here, we compare MS and IM‐MS data of both proteins, and rationalise the differences between the proteins in terms of different ionisation processes which they may adhere to. PMID:25920945

  6. Relating gas phase to solution conformations: Lessons from disordered proteins.

    PubMed

    Beveridge, Rebecca; Phillips, Ashley S; Denbigh, Laetitia; Saleem, Hassan M; MacPhee, Cait E; Barran, Perdita E

    2015-08-01

    In recent years both mass spectrometry (MS) and ion mobility mass spectrometry (IM-MS) have been developed as techniques with which to study proteins that lack a fixed tertiary structure but may contain regions that form secondary structure elements transiently, namely intrinsically disordered proteins (IDPs). IM-MS is a suitable method for the study of IDPs which provides an insight to conformations that are present in solution, potentially enabling the analysis of lowly populated structural forms. Here, we describe the IM-MS data of two IDPs; α-Synuclein (α-Syn) which is implicated in Parkinson's disease, and Apolipoprotein C-II (ApoC-II) which is involved in cardiovascular diseases. We report an apparent discrepancy in the way that ApoC-II behaves in the gas phase. While most IDPs, including α-Syn, present in many charge states and a wide range of rotationally averaged collision cross sections (CCSs), ApoC-II presents in just four charge states and a very narrow range of CCSs, independent of solution conditions. Here, we compare MS and IM-MS data of both proteins, and rationalise the differences between the proteins in terms of different ionisation processes which they may adhere to. PMID:25920945

  7. Synthesis, structure and gas-phase reactivity of the mixed silver hydride borohydride nanocluster [Ag3(μ3-H)(μ3-BH4)LPh3]BF4 (LPh = bis(diphenylphosphino)methane)

    NASA Astrophysics Data System (ADS)

    Zavras, Athanasios; Ariafard, Alireza; Khairallah, George N.; White, Jonathan M.; Mulder, Roger J.; Canty, Allan J.; O'Hair, Richard A. J.

    2015-10-01

    Borohydrides react with silver salts to give products that span multiple scales ranging from discrete mononuclear compounds through to silver nanoparticles and colloids. The cluster cations [Ag3(H)(BH4)L3]+ are observed upon electrospray ionization mass spectrometry of solutions containing sodium borohydride, silver(i) tetrafluoroborate and bis(dimethylphosphino)methane (LMe) or bis(diphenylphosphino)methane (LPh). By adding NaBH4 to an acetonitrile solution of AgBF4 and LPh, cooled to ca. -10 °C, we have been able to isolate the first mixed silver hydride borohydride nanocluster, [Ag3(μ3-H)(μ3-BH4)LPh3]BF4, and structurally characterise it via X-ray crystallography. Combined gas-phase experiments (LMe and LPh) and DFT calculations (LMe) reveal how loss of a ligand from the cationic complexes [Ag3(H)(BH4)L3]+ provides a change in geometry that facilitates subsequent loss of BH3 to produce the dihydride clusters, [Ag3(H)2Ln]+ (n = 1 and 2). Together with the results of previous studies (Girod et al., Chem. - Eur. J., 2014, 20, 16626), this provides a direct link between mixed silver hydride/borohydride nanoclusters, silver hydride nanoclusters, and silver nanoclusters.Borohydrides react with silver salts to give products that span multiple scales ranging from discrete mononuclear compounds through to silver nanoparticles and colloids. The cluster cations [Ag3(H)(BH4)L3]+ are observed upon electrospray ionization mass spectrometry of solutions containing sodium borohydride, silver(i) tetrafluoroborate and bis(dimethylphosphino)methane (LMe) or bis(diphenylphosphino)methane (LPh). By adding NaBH4 to an acetonitrile solution of AgBF4 and LPh, cooled to ca. -10 °C, we have been able to isolate the first mixed silver hydride borohydride nanocluster, [Ag3(μ3-H)(μ3-BH4)LPh3]BF4, and structurally characterise it via X-ray crystallography. Combined gas-phase experiments (LMe and LPh) and DFT calculations (LMe) reveal how loss of a ligand from the cationic complexes [Ag

  8. X-Ray structural and gas phase studies of silver(i) perfluorinated carboxylate complexes with 2,2'-bipyridyl as potential precursors for chemical vapour deposition (CVD).

    PubMed

    Szłyk, Edward; Szczesny, Robert; Wojtczak, Andrzej

    2010-02-21

    [Ag(CF(3)COO)(bpy)] (), [Ag(2)(C(2)F(5)COO)(2)(bpy)] () and [Ag(2)(C(3)F(7)COO)(2)(bpy)] () were prepared and characterized by MS-EI, (1)H, (13)C NMR, variable-temperature IR (VT-IR) spectroscopy (solid sample and evolved volatile species) and thermal analysis. Single-crystal X-ray diffraction data revealed the polymeric structure for [Ag(2)(C(2)F(5)COO)(2)(bpy)] and [Ag(6)(C(3)F(7)COO)(6)(bpy)(4)], with bridging bpy ligand, whereas for [Ag(CF(3)COO)(bpy)] the dimeric system with monodentately linked carboxylate was noted. Mass spectra analysis of () over 30-300 degrees C indicates the presence of binuclear ions [(RCOO)Ag(2)](+) as a main volatile particles, which can be transported in CVD process. VT-IR studies of gases evolved during the thermal decomposition process, demonstrate the presence of fluorocarbon species and CO(2) as the most abundant molecules. Thermal analysis of () revealed a multi-stage decomposition mechanism resulting in Ag(0) formation below 290 degrees C. Compounds were tested for silver metal spray pyrolysis and obtained layers were characterized by scanning electron microscopy (SEM-EDX) and XRD. PMID:20449428

  9. Substrate-free gas-phase synthesis of graphene

    NASA Astrophysics Data System (ADS)

    Dato, Albert Manglallan

    Graphene is a single atomic layer of sp2-bonded carbon atoms tightly packed in a two-dimensional honeycomb lattice. The material possesses remarkable properties and has been envisioned for use in numerous applications. Contemporary graphene production techniques require substrates or graphite crystals to create graphene. Furthermore, these approaches involve multiple steps, and sometimes non-ambient conditions, to produce atomically-thin sheets. This dissertation presents the first substrate-free gas-phase graphene synthesis method. The technique can synthesize graphene in a single step at atmospheric pressure, without the use of graphite or substrates. The novel synthesis method was discovered through experiments that tested the hypothesis that graphene could be synthesized through the delivery of alcohols into argon plasmas. The experiments presented in this dissertation were conducted in an atmospheric-pressure microwave plasma reactor. Solid carbon materials were produced by delivering liquid ethanol droplets directly into argon plasmas. Numerous characterization techniques were used to unambiguously prove that the synthesized materials were clean and highly ordered graphene sheets. Additional studies investigated the effects of variable experimental parameters on the graphene synthesis process. The applied microwave power did not significantly affect the types of structures produced in the reactor. Lowering the volumetric flow rate of the plasma gas resulted in the synthesis of graphitic particles. The composition of the precursors delivered into the reactor also affected graphene synthesis. Graphene was not produced through the delivery of methanol or isopropyl alcohol droplets. However, graphene was obtained through dimethyl ether, which is an organic compound with the same atomic composition as ethanol. Thus, the flow rate and precursor composition significantly affected the nucleation, growth, and residence time of the materials created during experiments

  10. Porous Silicon Structures as Optical Gas Sensors

    PubMed Central

    Levitsky, Igor A.

    2015-01-01

    We present a short review of recent progress in the field of optical gas sensors based on porous silicon (PSi) and PSi composites, which are separate from PSi optochemical and biological sensors for a liquid medium. Different periodical and nonperiodical PSi photonic structures (bares, modified by functional groups or infiltrated with sensory polymers) are described for gas sensing with an emphasis on the device specificity, sensitivity and stability to the environment. Special attention is paid to multiparametric sensing and sensor array platforms as effective trends for the improvement of analyte classification and quantification. Mechanisms of gas physical and chemical sorption inside PSi mesopores and pores of PSi functional composites are discussed. PMID:26287199

  11. A novel phase shifting structured illumination microscopy

    NASA Astrophysics Data System (ADS)

    Singh, Veena; Dubey, Vishesh; Ahmad, Azeem; Singh, Gyanendra; Mehta, D. S.

    2016-03-01

    This paper describes a new and novel phase shifting technique for qualitative as well as quantitative measurement in microscopy. We have developed a phase shifting device which is robust, inexpensive and involves no mechanical movement. In this method, phase shifting is implemented using LED array, beam splitters and defocused projection of Ronchi grating. The light from the LEDs are made incident on the beam splitters at spatially different locations. Due to variation in the geometrical distances of LEDs from the Ronchi grating and by sequentially illuminating the grating by switching on one LED at a time the phase shifted grating patterns are generated. The phase shifted structured patterns are projected onto the sample using microscopic objective lens. The phase shifted deformed patterns are recorded by a CCD camera. The initial alignment of the setup involves a simple procedure for the calibration for equal fringe width and intensity such that the phase shifted fringes are at equal phase difference. Three frame phase shifting algorithm is employed for the reconstruction of the phase map. The method described here is fully automated so that the phase shifted images are recorded just by switching of LEDs and has been used for the shape measurement of microscopic industrial objects. The analysis of the phase shifted images provides qualitative as well as quantitative information about the sample. Thus, the method is simple, robust and low cost compared to PZT devices commonly employed for phase shifting.

  12. Gas phase synthesis of two ensembles of silicon nanoparticles

    NASA Astrophysics Data System (ADS)

    Mohan, A.; de Jong, M. M.; Poulios, I.; Schropp, R. E. I.; Rath, J. K.

    2015-09-01

    Dusty plasmas provide a very favorable environment for the growth of silicon nanocrystals. For application of silicon nanocrystals in a solar cell, the fabrication of monodisperse silicon quantum dots has been challenging. We report a single step method to synthesize silicon (Si) nanoparticles in a custom designed dedicated plasma reactor. The nanoparticles produced in the gas phase belong to two different phases exhibiting different structural and optical properties. Particles made in the bulk of the plasma are aggregates of crystalline particles with a mean size of 100 nm. Particles made in locally enhanced plasma regions produced at holes present in the grounded electrode contain free-standing quantum sized particles with crystallites (with mean size of 2.95 nm) embedded within an amorphous matrix. We provide insight on different plasma processes leading to the formation of aggregates and free-standing particles. We hypothesize that the free standing particles are formed due to the excess energetic electrons present in locally enhanced discharges.

  13. Structures of diamond-like phases

    SciTech Connect

    Greshnyakov, V. A.; Belenkov, E. A.

    2011-07-15

    The diamond-like phases containing carbon atoms with the same degree of hybridization, which is close to sp{sup 3}, are classified. It is found that twenty such phases can exist, and ten of them are described for the first time. Molecular mechanics and semi-empirical quantum-mechanical methods are used to calculate the geometrically optimized structures of diamond-like phase clusters and to determine their structural parameters and properties, such as the density, the bulk modulus, and the sublimation energy. The difference between the properties of the diamond-like phases and those of diamond is found to be determined by the difference between the structures of these phases and diamond.

  14. Collision-induced gas phase dissociation rates

    NASA Technical Reports Server (NTRS)

    Hansen, C. Frederick

    1990-01-01

    The Landau-Zener theory of reactive cross sections was applied to diatomic molecules dissociating from a ladder of vibrational states. The result predicts a dissociation rate that is quite well duplicated by an Arrhenius function having a preexponential temperature dependence of about T(sub -1/2), at least for inert collision partners. This relation fits experimental data reasonably well. The theory is then used to calculate the effect of vibrational nonequilibrium on dissociation rate. For Morse oscillators, the results are about the same as given by Hammerling, Kivel, and Teare in their analytic approximation for harmonic oscillators, though at very high temperature a correction for the partition function limit is included. The empirical correction for vibration nonequilibrium proposed by Park, which is a convenient algorithm for CFD calculations, is modified to prevent a drastic underestimation of dissociation rates that occurs with this method when vibrational temperature is much smaller than the kinetic temperature of the gas.

  15. Nuclear Structure of the Noble Gas

    NASA Astrophysics Data System (ADS)

    Seong, Nakyeong

    Modern physics usually pictures the nuclear structure as about sphere and treats various detailed situation as perturbative, which may be obscured. In addition, the explanation why 235U undergoes nuclear fission and 238U does not is too difficult and unclear for the people to understand. However, in this paper, we introduce a new approach on the nuclear structure of the noble gas, which simultaneously can explain several phenomena that is obscurely elucidated by modern physics. We consider a 1:1 ratio between protons and neutrons and need the concept of the symmetry of the nuclear structure, because the electron's shell of the noble gas is fully occupied. From these, we can predict the number of neutrons of each noble gas exactly

  16. On the interplay between geometrical structure and magnetic anisotropy: a relativistic density-functional study of mixed Pt-Co and Pt-Fe trimers and tetramers in the gas-phase and supported on graphene.

    PubMed

    Błoński, Piotr; Hafner, Jürgen

    2015-02-01

    The structural and magnetic properties of mixed Pt-Co and Pt-Fe trimers and tetramers in the gas-phase and supported on a free-standing graphene layer have been calculated using density-functional theory. The influence of the strong magnetic moments of the 3d atoms on the Pt atoms and the influence of the strong spin-orbit coupling contributed by the Pt atoms on the 3d atoms have been studied in detail. All mixed trimers form isocele triangles in the gas-phase. On a graphene layer the structure is influenced by the strong binding of the 3d atoms, leading to an asymmetric configuration for Pt-rich and more symmetric structures for 3d-rich clusters. The magnetic anisotropy energy defined as the energy difference for easy and hard magnetization directions varies between 5 and 13 meV/atom for the free trimers, but is strongly reduced to values between 0.7 and 6.6 meV/atom for the graphene-supported clusters. The saddle-point energy representing the barrier against magnetization reversal is on average 3 meV/atom for free trimers, it is reduced to 2 meV/atom for the more symmetric PtCo(Fe)(2) clusters, and to only about 0.3 meV/atom for the asymmetric Pt(2)Co(Fe) cluster on graphene. For the mixed tetramers the strong magnetism stabilizes a flat geometric structure, except for Pt(3)Co which forms a distorted trigonal pyramid. The geometry of the graphene-supported tetramers is very different due to the requirement of a good match to the substrate. Large magnetic anisotropy energies are found for free Pt(3)Co where the change of the magnetization direction also induces a transition from a high- to a low-moment magnetic isomer. For all other free tetramers the magnetic anisotropy energy ranges between 3 to 5 meV/atom only, it is further reduced to 0.4 to 3.8 meV/atom for the graphene-supported tetramers. The reduction is strongest for Pt(3)Fe/graphene because of the asymmetric structure of the adsorption complex. The barriers against magnetization reversal range between

  17. Capillary gas chromatography with two new moderately high temperature phases.

    NASA Technical Reports Server (NTRS)

    Pollock, G. E.

    1972-01-01

    Gas chromatography test results are presented for two new moderately high-temperature phases of Dexsil 400-GC with free hydroxyl end groups (uncapped) and with end groups covered by trimethyl silyl groups (capped). The two Dexsil 400-GC phases were tested for their ability to resolve N-TFA-DL-(+)-2-butyl esters and n-butyl esters, as well as fatty acid methyl esters and hydrocarbon standards. Generally the more polar uncapped phase was superior to the capped phase in all separation comparisons, except for the hydrocarbons.

  18. Freeze drying for gas chromatography stationary phase deposition

    DOEpatents

    Sylwester, Alan P.

    2007-01-02

    The present disclosure relates to methods for deposition of gas chromatography (GC) stationary phases into chromatography columns, for example gas chromatography columns. A chromatographic medium is dissolved or suspended in a solvent to form a composition. The composition may be inserted into a chromatographic column. Alternatively, portions of the chromatographic column may be exposed or filled with the composition. The composition is permitted to solidify, and at least a portion of the solvent is removed by vacuum sublimation.

  19. Gas purification in the dense phase at the CATS terminal

    SciTech Connect

    Openshaw, P.J.; Carnell, P.J.H.; Rhodes, E.F.

    1999-07-01

    The purification and transportation of natural gas at very high pressures can help to minimize the capital cost of pipelines and processing equipment. However, complex mixtures of hydrocarbons undergo unusual phase changes, such as retrograde condensation, as the temperature and pressure are altered. The Central Area Transmission System (CATS) is a joint venture of Amoci, BG, Amerada Hess, Phillips, Agip and Fina operated by Amoco on behalf of the owners. The design of the CATS terminal has provided an interesting processing challenge. The terminal receives a total of 1.6 Bscf/d of rich gas from a number of offshore fields. All are relatively sweet but the small amounts of H{sub 2}S and Hg are removed. Fixed bed technology was selected as the most economic purification process, while minimizing hydrocarbon loss and operator involvement. Conventionally, the raw gas would be split into the different hydrocarbon fractions and each would be processed separately. This would require the installation of a large number of reactors. A more elegant solution is to treat the gas on arrival at the terminal in the dense phase. This option raised questions around whether a fixed bed would be prone to fouling, could the pressure drop be kept low enough to avoid phase separation and would inadvertent wetting by condensation cause problems. Details are given of the test work carried out to prove the viability of using fixed bed technology for dense phase gas processing, the eventual design adopted and the performance over the first year of service.

  20. Gas phase radiative effects in diffusion flames

    NASA Astrophysics Data System (ADS)

    Bedir, Hasan

    Several radiation models are evaluated for a stagnation point diffusion flame of a solid fuel in terms of accuracy and computational time. Narrowband, wideband, spectral line weighted sum of gray gases (SLWSGG), and gray gas models are included in the comparison. Radiative heat flux predictions by the nongray narrowband, wideband, and SLWSGG models are found to be in good agreement with each other, whereas the gray gas models are found to be inaccurate. The narrowband model, the most complex among the models evaluated, is then applied first to a solid fuel and second to a pure gaseous diffusion flame. A polymethylmethacrylate (PMMA) diffusion flame in a stagnation point geometry is solved with the narrowband model with COsb2, Hsb2O, and MMA vapor included in participating species. A detailed account of the emission and absorption from these species as well as the radiative heat fluxes are given as a function of the stretch rate. It is found that at low stretch rate the importance of radiation is increased due to an increase in the optical thickness, and a decrease in the conductive heat flux. Results show that COsb2 is the biggest emitter and absorber in the flame, MMA vapor is the second and Hsb2O is the least important. A pure gaseous flame in an opposed jet configuration is solved with the narrowband radiation model with CO as the fuel, and Osb2 as the oxidizer. Detailed. chemical kinetics and transport are incorporated into the combustion model with the use of the CHEMKIN and TRANSPORT software packages. The governing equations are solved with a modified version of the OPPDIF code. Dry and wet CO flames as well as COsb2 dilution are studied. Comparison of the results with and without the consideration of radiation reveals that the radiation is important for the whole flammable range of dry CO flames and for the low stretch rates of wet flames. Without the consideration of radiation the temperature and the species mole fractions (especially of minor species

  1. Calculation of two-phase flow in gas turbine combustors

    SciTech Connect

    Tolpadi, A.K.

    1995-10-01

    A method is presented for computing steady two-phase turbulent combusting flow in a gas turbine combustor. The gas phase equations are solved in an Eulerian frame of reference. The two-phase calculations are performed by using a liquid droplet spray combustion a model and treating the motion of the evaporating fuel droplets in a Lagrangian frame of reference. The numerical algorithm employs nonorthogonal curvilinear coordinates, a multigrid iterative solution procedure, the standard k-{epsilon} turbulence model, and a combustion model comprising an assumed shape probability density function and the conserved scalar formulation. The trajectory computation of the fuel provides the source terms for all the gas phase equations. This two-phase model was applied to a real piece of combustion hardware in the form of a modern GE/SNECMA single annular CFM56 turbofan engine combustor. For the purposes of comparison, calculations were also performed by treating the fuel as a single gaseous phase. The effect on the solution of two extreme situations of the fuel as a gas and initially as a liquid was examined. The distribution of the velocity field and the conserved scalar within the combustor, as well as the distribution of the temperature field in the reaction zone and in the exhaust, were all predicted with the combustor operating both at high-power and low-power (ground idle) conditions. The calculated exit gas temperature was compared with test rig measurements. Under both low and high-power conditions, the temperature appeared to show an improved agreement with the measured data when the calculations were performed with the spray model as compared to a single-phase calculation.

  2. The Gas-Phase Deuterium Fractionation of Formaldehyde

    NASA Astrophysics Data System (ADS)

    Osamura, Yoshihiro; Roberts, Helen; Herbst, Eric

    2005-03-01

    The dominant mechanism for the deuteration of formaldehyde in the gas phase of low-temperature interstellar cloud cores occurs via reaction with the deuterating ions H2D+, HD+2, and D+3. Until now, it has been assumed that deuteration leads to an ion that, on recombination with electrons, can produce a deuterated neutral species with a statistical branching fraction. Quantum chemical calculations reported here, however, show an entirely different picture, in which the deuteration of formaldehyde leads to the molecular ion H2COD+, where the deuterium binds only on the oxygen side of the molecule. The structure is quite stable, while an alternative structure, H2DCO+, cannot be produced in a straightforward manner. Dissociative recombination of H2COD+ to reproduce a formaldehyde structure then removes the deuteration if the dissociation is direct, i.e., it occurs without change of structure. There are several possible indirect mechanisms by which dissociative recombination can lead to HDCO, however. For example, if the direct products are HCOD+H, it is possible that subsequent isomerization to HDCO can occur, although this involved process is unlikely. Another possibility is isomerization during the actual dissociation of the H2COD intermediate. Models of deuterium fractionation in which dissociative recombination is predominantly direct are presented, and it is found that the deuterium fractionation of formaldehyde to form both HDCO and D2CO can still occur via other mechanisms, although with less efficiency than previously obtained. If the dissociative recombination is half indirect, however, then we can recover the previously calculated efficiency.

  3. Selective transport of amino acids into the gas phase: driving forces for amino acid solubilization in gas-phase reverse micelles.

    PubMed

    Fang, Yigang; Bennett, Andrew; Liu, Jianbo

    2011-01-28

    We report a study on encapsulation of various amino acids into gas-phase sodium bis(2-ethylhexyl) sulfosuccinate (NaAOT) reverse micelles, using electrospray ionization guided-ion-beam tandem mass spectrometry. Collision-induced dissociation of mass-selected reverse micellar ions with Xe was performed to probe structures of gas-phase micellar assemblies, identify solute-surfactant interactions, and determine preferential incorporation sites of amino acids. Integration into gas-phase reverse micelles depends upon amino acid hydrophobicity and charge state. For examples, glycine and protonated amino acids (such as protonated tryptophan) are encapsulated within the micellar core via electrostatic interactions; while neutral tryptophan is adsorbed in the surfactant layer. As verified using model polar hydrophobic compounds, the hydrophobic effect and solute-interface hydrogen-bonding do not provide sufficient driving force needed for interfacial solubilization of neutral tryptophan. Neutral tryptophan, with a zwitterionic structure, is intercalated at the micellar interface between surfactant molecules through complementary effects of electrostatic interactions between tryptophan backbone and AOT polar heads, and hydrophobic interactions between tryptophan side chain and AOT alkyl tails. Protonation of tryptophan could significantly improve its incorporation capacity into gas-phase reverse micelles, and displace its incorporation site from the micellar interfacial zone to the core; protonation of glycine, on the other hand, has little effect on its encapsulation capacity. Another interesting observation is that amino acids of different isoelectric points could be selectively encapsulated into, and transported by, reverse micelles from solution to the gas phase, based upon their competition for protonation and subsequent encapsulation within the micellar core. PMID:21140022

  4. Polymerization in the gas phase, in clusters, and on nanoparticle surfaces.

    PubMed

    El-Shall, M Samy

    2008-07-01

    Gas phase and cluster experiments provide unique opportunities to quantitatively study the effects of initiators, solvents, chain transfer agents, and inhibitors on the mechanisms of polymerization. Furthermore, a number of important phenomena, unique structures, and novel properties may exist during gas-phase and cluster polymerization. In this regime, the structure of the growing polymer may change dramatically and the rate coefficient may vary significantly upon the addition of a single molecule of the monomer. These changes would be reflected in the properties of the oligomers deposited from the gas phase. At low pressures, cationic and radical cationic polymerizations may proceed in the gas phase through elimination reactions. In the same systems at high pressure, however, the ionic intermediates may be stabilized, and addition without elimination may occur. In isolated van der Waals clusters of monomer molecules, sequential polymerization with several condensation steps can occur on a time scale of a few microseconds following the ionization of the gas-phase cluster. The cluster reactions, which bridge gas-phase and condensed-phase chemistry, allow examination of the effects of controlled states of aggregation. This Account describes several examples of gas-phase and cluster polymerization studies where the most significant results can be summarized as follows: (1) The carbocation polymerization of isobutene shows slower rates with increasing polymerization steps resulting from entropy barriers, which could explain the need for low temperatures for the efficient propagation of high molecular weight polymers. (2) Radical cation polymerization of propene can be initiated by partial charge transfer from an ionized aromatic molecule such as benzene coupled with covalent condensation of the associated propene molecules. This novel mechanism leads exclusively to the formation of propene oligomer ions and avoids other competitive products. (3) Structural information

  5. Bond-Specific Dissociation Following Excitation Energy Transfer for Distance Constraint Determination in the Gas Phase

    PubMed Central

    2015-01-01

    Herein, we report chemistry that enables excitation energy transfer (EET) to be accurately measured via action spectroscopy on gaseous ions in an ion trap. It is demonstrated that EET between tryptophan or tyrosine and a disulfide bond leads to excited state, homolytic fragmentation of the disulfide bond. This phenomenon exhibits a tight distance dependence, which is consistent with Dexter exchange transfer. The extent of fragmentation of the disulfide bond can be used to determine the distance between the chromophore and disulfide bond. The chemistry is well suited for the examination of protein structure in the gas phase because native amino acids can serve as the donor/acceptor moieties. Furthermore, both tyrosine and tryptophan exhibit unique action spectra, meaning that the identity of the donating chromophore can be easily determined in addition to the distance between donor/acceptor. Application of the method to the Trpcage miniprotein reveals distance constraints that are consistent with a native-like fold for the +2 charge state in the gas phase. This structure is stabilized by several salt bridges, which have also been observed to be important previously in proteins that retain native-like structures in the gas phase. The ability of this method to measure specific distance constraints, potentially at numerous positions if combined with site-directed mutagenesis, significantly enhances our ability to examine protein structure in the gas phase. PMID:25174489

  6. Bond-specific dissociation following excitation energy transfer for distance constraint determination in the gas phase.

    PubMed

    Hendricks, Nathan G; Lareau, Nichole M; Stow, Sarah M; McLean, John A; Julian, Ryan R

    2014-09-24

    Herein, we report chemistry that enables excitation energy transfer (EET) to be accurately measured via action spectroscopy on gaseous ions in an ion trap. It is demonstrated that EET between tryptophan or tyrosine and a disulfide bond leads to excited state, homolytic fragmentation of the disulfide bond. This phenomenon exhibits a tight distance dependence, which is consistent with Dexter exchange transfer. The extent of fragmentation of the disulfide bond can be used to determine the distance between the chromophore and disulfide bond. The chemistry is well suited for the examination of protein structure in the gas phase because native amino acids can serve as the donor/acceptor moieties. Furthermore, both tyrosine and tryptophan exhibit unique action spectra, meaning that the identity of the donating chromophore can be easily determined in addition to the distance between donor/acceptor. Application of the method to the Trpcage miniprotein reveals distance constraints that are consistent with a native-like fold for the +2 charge state in the gas phase. This structure is stabilized by several salt bridges, which have also been observed to be important previously in proteins that retain native-like structures in the gas phase. The ability of this method to measure specific distance constraints, potentially at numerous positions if combined with site-directed mutagenesis, significantly enhances our ability to examine protein structure in the gas phase. PMID:25174489

  7. Structural phase transitions in monolayer molybdenum dichalcogenides

    NASA Astrophysics Data System (ADS)

    Choe, Duk-Hyun; Sung, Ha June; Chang, Kee Joo

    2015-03-01

    The recent discovery of two-dimensional materials such as graphene and transition metal dichalcogenides (TMDs) has provided opportunities to develop ultimate thin channel devices. In contrast to graphene, the existence of moderate band gap and strong spin-orbit coupling gives rise to exotic electronic properties which vary with layer thickness, lattice structure, and symmetry. TMDs commonly appear in two structures with distinct symmetries, trigonal prismatic 2H and octahedral 1T phases which are semiconducting and metallic, respectively. In this work, we investigate the structural and electronic properties of monolayer molybdenum dichalcogenides (MoX2, where X = S, Se, Te) through first-principles density functional calculations. We find a tendency that the semiconducting 2H phase is more stable than the metallic 1T phase. We show that a spontaneous symmetry breaking of 1T phase leads to various distorted octahedral (1T') phases, thus inducing a metal-to-semiconductor transition. We discuss the effects of carrier doping on the structural stability and the modification of the electronic structure. This work was supported by the National Research Foundation of Korea (NRF) under Grant No. NRF-2005-0093845 and Samsung Science and Technology Foundation under Grant No. SSTFBA1401-08.

  8. LOW COST IMAGER FOR POLLUTANT GAS LEAK DETECTION - PHASE II

    EPA Science Inventory

    An inexpensive imaging Instrument to quickly locate leaks of methane and other greenhouse and VOC gases would reduce the cost and effort expended by industry to comply with EPA regulations. In Phase I, of this WBIR program, a new gas leak visualization camera was demonstrated...

  9. Statistical and Microscopic Approach to Gas Phase Chemical Kinetics.

    ERIC Educational Resources Information Center

    Perez, J. M.; Quereda, R.

    1983-01-01

    Describes advanced undergraduate laboratory exercise examining the dependence of the rate constants and the instantaneous concentrations with the nature and energy content in a gas-phase complex reaction. Computer program (with instructions and computation flow charts) used with the exercise is available from the author. (Author/JN)

  10. Apparatus for the premixed gas phase combustion of liquid fuels

    SciTech Connect

    Roffe, G.A.; Trucco, H.A.

    1981-04-21

    This invention relates to improvements in the art of liquid fuel combustion and, more particularly, concerns a method and apparatus for the controlled gasification of liquid fuels, the thorough premixing of the then gasified fuel with air and the subsequent gas-phase combustion of the mixture to produce a flame substantially free of soot, carbon monoxide, nitric oxide and unburned fuel.

  11. INVESTIGATION OF GAS-PHASE OZONE AS A POTENTIAL BIOCIDE

    EPA Science Inventory

    The paper presents data on the effect of ozone on both vegetative and spore-forming fungi as well as on spore-forming bacteria. (NOTE: Despite the wide use of ozone generators in indoor air cleaning, there is little research data on ozone's biocidal activity in the gas phase.) Dr...

  12. Can the ordinary chondrites have condensed from a gas phase

    NASA Technical Reports Server (NTRS)

    Herndon, J. M.; Suess, H. E.

    1977-01-01

    The conditions under which ordinary chondrites containing iron in three different chemical states can form in thermodynamic equilibrium with a gas phase are calculated. Hydrogen depletion factors of 100-1000 are obtained and the formation of liquid condensates from residual gases occurs at pressures (prior to hydrogen depletion) of roughly equal to or greater than 1 atm.

  13. Ion-Molecule Reactions in Gas Phase Radiation Chemistry.

    ERIC Educational Resources Information Center

    Willis, Clive

    1981-01-01

    Discusses some aspects of the radiation chemistry of gases, focusing on the ion-molecule and charge neutralization reactions which set study of the gas phase apart. Uses three examples that illustrate radiolysis, describing the radiolysis of (1) oxygen, (2) carbon dioxide, and (3) acetylene. (CS)

  14. Jahn-Teller solitons, structural phase transitions, and phase separation.

    PubMed

    Clougherty, Dennis P

    2006-02-01

    It is demonstrated that under common conditions a molecular solid subject to Jahn-Teller interactions supports stable Q-ball-like nontopological solitons. Such solitons represent a localized lump of excess electric charge in periodic motion accompanied by a time-dependent shape distortion of a set of adjacent molecules. The motion of the distortion can correspond to a true rotation or to a pseudorotation about the symmetric shape configuration. These solitons are stable for Jahn-Teller coupling strengths below a critical value; however, as the Jahn-Teller coupling approaches this critical value, the size of the soliton diverges signaling an incipient structural phase transition. The soliton phase mimics features commonly attributed to phase separation in complex solids. PMID:16486846

  15. Jahn-Teller Solitons, Structural Phase Transitions, and Phase Separation

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.

    2006-02-01

    It is demonstrated that under common conditions a molecular solid subject to Jahn-Teller interactions supports stable Q-ball-like nontopological solitons. Such solitons represent a localized lump of excess electric charge in periodic motion accompanied by a time-dependent shape distortion of a set of adjacent molecules. The motion of the distortion can correspond to a true rotation or to a pseudorotation about the symmetric shape configuration. These solitons are stable for Jahn-Teller coupling strengths below a critical value; however, as the Jahn-Teller coupling approaches this critical value, the size of the soliton diverges signaling an incipient structural phase transition. The soliton phase mimics features commonly attributed to phase separation in complex solids.

  16. Novel stationary phases based on asphaltenes for gas chromatography.

    PubMed

    Boczkaj, Grzegorz; Momotko, Malwina; Chruszczyk, Dorota; Przyjazny, Andrzej; Kamiński, Marian

    2016-07-01

    We present the results of investigations on the possibility of the application of the asphaltene fraction isolated from the oxidized residue from vacuum distillation of crude oil as a stationary phase for gas chromatography. The results of the investigation revealed that the asphaltene stationary phases can find use for the separation of a wide range of volatile organic compounds. The experimental values of Rohrschneider/McReynolds constants characterize the asphaltenes as stationary phases of medium polarity and selectivity similar to commercially available phases based on alkyl phthalates. Isolation of asphaltenes from the material obtained under controlled process conditions allows the production of a stationary phase having reproducible sorption properties and chromatographic columns having the same selectivity. Unique selectivity and high thermal stability make asphaltenes attractive as a material for stationary phases for gas chromatography. A low production cost from a readily available raw material (oxidized petroleum bitumens) is an important economic factor in case of application of the asphaltene stationary phases for preparative and process separations. PMID:27144876

  17. Gas-phase electronic spectrum of the indole radical cation

    NASA Astrophysics Data System (ADS)

    Chalyavi, N.; Catani, K. J.; Sanelli, J. A.; Dryza, V.; Bieske, E. J.

    2015-08-01

    The visible and near-UV electronic spectrum of the indole radical cation is measured in the gas phase by photodissociation of indole+-Ar and indole+-He complexes in a tandem mass spectrometer. A series of resolved vibronic transitions extending from 610 to 460 nm are assigned to the D2 ← D0 band system, while weak transitions between 390 and 360 nm are assigned to the D3 ← D0 system, and a stronger, broad, unresolved absorption between 350 and 300 nm is attributed to the D4 ← D0 system. Time-dependent density functional theory calculations are used to assign vibronic structure of the D2 ← D0 band system, and show that the main active vibrational modes correspond to in-plane ring deformations. The strongest D2 ← D0 vibronic transitions of indole+-He do not correspond with any catalogued diffuse interstellar bands, even considering band displacements of up to 50 cm-1possibly caused by the attached He atom.

  18. Exploring structural phase transitions of ion crystals

    PubMed Central

    Yan, L. L.; Wan, W.; Chen, L.; Zhou, F.; Gong, S. J.; Tong, X.; Feng, M.

    2016-01-01

    Phase transitions have been a research focus in many-body physics over past decades. Cold ions, under strong Coulomb repulsion, provide a repealing paradigm of exploring phase transitions in stable confinement by electromagnetic field. We demonstrate various conformations of up to sixteen laser-cooled 40Ca+ ion crystals in a home-built surface-electrode trap, where besides the usually mentioned structural phase transition from the linear to the zigzag, two additional phase transitions to more complicated two-dimensional configurations are identified. The experimental observation agrees well with the numerical simulation. Heating due to micromotion of the ions is analysed by comparison of the numerical simulation with the experimental observation. Our investigation implies very rich and complicated many-body behaviour in the trapped-ion systems and provides effective mechanism for further exploring quantum phase transitions and quantum information processing with ultracold trapped ions. PMID:26865229

  19. Neutral line chaos and phase space structure

    NASA Technical Reports Server (NTRS)

    Burkhart, Grant R.; Speiser, Theodore W.; Martin, Richard F., Jr.; Dusenbery, Paul B.

    1991-01-01

    Phase space structure and chaos near a neutral line are studied with numerical surface-of-section (SOS) techniques and analytic methods. Results are presented for a linear neutral line model with zero crosstail electric field. It was found that particle motion can be divided into three regimes dependening on the value of the conserved canonical momentum, Py, and the conserved Hamiltonian, h. The phase space structure, using Poincare SOS plots, is highly sensitive to bn = Bn/B0 variations, but not to h variations. It is verified that the slow motion preserves the action, Jz, as evaluated by Sonnerup (1971), when the period of the fast motion is smaller than the time scale of the slow motion. Results show that the phase space structure and particle chaos depend sensitively upon Py and bn, but are independent of h.

  20. Gas Phase Reactivity of Carboxylates with N-Hydroxysuccinimide Esters

    NASA Astrophysics Data System (ADS)

    Peng, Zhou; McGee, William M.; Bu, Jiexun; Barefoot, Nathan Z.; McLuckey, Scott A.

    2015-01-01

    N-hydroxysuccinimide (NHS) esters have been used for gas-phase conjugation reactions with peptides at nucleophilic sites, such as primary amines (N-terminus, ɛ-amine of lysine) or guanidines, by forming amide bonds through a nucleophilic attack on the carbonyl carbon. The carboxylate has recently been found to also be a reactive nucleophile capable of initiating a similar nucleophilic attack to form a labile anhydride bond. The fragile bond is easily cleaved, resulting in an oxygen transfer from the carboxylate-containing species to the reagent, nominally observed as a water transfer. This reactivity is shown for both peptides and non-peptidic species. Reagents isotopically labeled with O18 were used to confirm reactivity. This constitutes an example of distinct differences in reactivity of carboxylates between the gas phase, where they are shown to be reactive, and the solution phase, where they are not regarded as reactive with NHS esters.

  1. Liquid-gas phase transition in nuclear matter including strangeness

    SciTech Connect

    Wang, P.; Leinweber, D.B.; Williams, A.G.; Thomas, A.W.

    2004-11-01

    We apply the chiral SU(3) quark mean field model to study the properties of strange hadronic matter at finite temperature. The liquid-gas phase transition is studied as a function of the strangeness fraction. The pressure of the system cannot remain constant during the phase transition, since there are two independent conserved charges (baryon and strangeness number). In a range of temperatures around 15 MeV (precise values depending on the model used) the equation of state exhibits multiple bifurcates. The difference in the strangeness fraction f{sub s} between the liquid and gas phases is small when they coexist. The critical temperature of strange matter turns out to be a nontrivial function of the strangeness fraction.

  2. Evolution of structure during phase transitions

    SciTech Connect

    Martin, J.E.; Wilcoxon, J.P.; Anderson, R.A.

    1996-03-01

    Nanostructured materials can be synthesized by utilizing the domain growth that accompanies first-order phase separation. Structural control can be achieved by appropriately selecting the quench depth and the quench time, but in order to do this in a mindful fashion one must understand the kinetics of domain growth. The authors have completed detailed light scattering studies of the evolution of structure in both temperature- and field-quenched phase transitions in two and three dimensional systems. They have studied these systems in the quiescent state and in shear and have developed theoretical models that account for the experimental results.

  3. Gas-phase exposure history derived from material-phase concentration profiles

    NASA Astrophysics Data System (ADS)

    Morrison, G. C.; Little, J. C.; Xu, Y.; Rao, M.; Enke, D.

    Non-reactive gas-phase pollutants such as benzene diffuse into indoor furnishings and leave behind a unique material-phase concentration profile that serves as a record of the past gas-phase indoor concentrations. The inverse problem to be solved is the diffusion equation in a slab such as vinyl flooring. Using knowledge of the present material-phase concentration profile in the slab, we seek to determine the historical material-phase concentration at the surface exposed to indoor air, and hence the historical gas-phase concentration, which can be used directly to determine exposure. The problem as posed has a unique solution that may be solved using a variety of approaches. We use a trained artificial neural network (ANN) to derive solutions for hypothetical exposure scenarios. The ANN results show that it is possible to estimate the intensity and timing of past exposures from the material-phase concentration profile in a building material. The overall method is limited by (1) the resolution of techniques for measuring spatial material-phase concentration profiles, (2) how far back in time we seek to determine exposure and (3) the representational power of the ANN solution. For example, we estimate that this technique can estimate exposure to phenol up to 0.5 y in the past from analyses of vinyl flooring.

  4. Structural support bracket for gas flow path

    DOEpatents

    None

    2016-08-02

    A structural support system is provided in a can annular gas turbine engine having an arrangement including a plurality of integrated exit pieces (IEPs) forming an annular chamber for delivering gases from a plurality of combustors to a first row of turbine blades. A bracket structure is connected between an IEP and an inner support structure on the engine. The bracket structure includes an axial bracket member attached to an IEP and extending axially in a forward direction. A transverse bracket member has an end attached to the inner support structure and extends circumferentially to a connection with a forward end of the axial bracket member. The transverse bracket member provides a fixed radial position for the forward end of the axial bracket member and is flexible in the axial direction to permit axial movement of the axial bracket member.

  5. Cold flame on Biofilm - Transport of Plasma Chemistry from Gas to Liquid Phase

    NASA Astrophysics Data System (ADS)

    Kong, Michael

    2014-10-01

    One of the most active and fastest growing fields in low-temperature plasma science today is biological effects of gas plasmas and their translation in many challenges of societal importance such as healthcare, environment, agriculture, and nanoscale fabrication and synthesis. Using medicine as an example, there are already three FDA-approved plasma-based surgical procedures for tissue ablation and blood coagulation and at least five phase-II clinical trials on plasma-assisted wound healing therapies. A key driver for realizing the immense application potential of near room-temperature ambient pressure gas plasmas, commonly known as cold atmospheric plasmas or CAP, is to build a sizeable interdisciplinary knowledge base with which to unravel, optimize, and indeed design how reactive plasma species interact with cells and their key components such as protein and DNA. Whilst a logical objective, it is a formidable challenge not least since existing knowledge of gas discharges is largely in the gas-phase and therefore not directly applicable to cell-containing matters that are covered by or embedded in liquid (e.g. biofluid). Here, we study plasma inactivation of biofilms, a jelly-like structure that bacteria use to protect themselves and a major source of antimicrobial resistance. As 60--90% of biofilm is made of water, we develop a holistic model incorporating physics and chemistry in the upstream CAP-generating region, a plasma-exit region as a buffer for as-phase transport, and a downstream liquid region bordering the gas buffer region. A special model is developed to account for rapid chemical reactions accompanied the transport of gas-phase plasma species through the gas-liquid interface and for liquid-phase chemical reactions. Numerical simulation is used to illustrate how key reactive oxygen species (ROS) are transported into the liquid, and this is supported with experimental data of both biofilm inactivation using plasmas and electron spin spectroscopy (ESR

  6. Gas phase decontamination of gaseous diffusion process equipment

    SciTech Connect

    Bundy, R.D.; Munday, E.B.; Simmons, D.W.; Neiswander, D.W.

    1994-03-01

    D&D of the process facilities at the gaseous diffusion plants (GDPs) will be an enormous task. The EBASCO estimate places the cost of D&D of the GDP at the K-25 Site at approximately $7.5 billion. Of this sum, nearly $4 billion is associated with the construction and operation of decontamination facilities and the dismantlement and transport of contaminated process equipment to these facilities. In situ long-term low-temperature (LTLT) gas phase decontamination is being developed and demonstrated at the K-25 site as a technology that has the potential to substantially lower these costs while reducing criticality and safeguards concerns and worker exposure to hazardous and radioactive materials. The objective of gas phase decontamination is to employ a gaseous reagent to fluorinate nonvolatile uranium deposits to form volatile LJF6, which can be recovered by chemical trapping or freezing. The LTLT process permits the decontamination of the inside of gas-tight GDP process equipment at room temperature by substituting a long exposure to subatmospheric C1F for higher reaction rates at higher temperatures. This paper outlines the concept for applying LTLT gas phase decontamination, reports encouraging laboratory experiments, and presents the status of the design of a prototype mobile system. Plans for demonstrating the LTLT process on full-size gaseous diffusion equipment are also outlined briefly.

  7. Preconceptual design of the gas-phase decontamination demonstration cart

    SciTech Connect

    Munday, E.B.

    1993-12-01

    Removal of uranium deposits from the interior surfaces of gaseous diffusion equipment will be a major portion of the overall multibillion dollar effort to decontaminate and decommission the gaseous diffusion plants. Long-term low-temperature (LTLT) gas-phase decontamination is being developed at the K-25 Site as an in situ decontamination process that is expected to significantly lower the decontamination costs, reduce worker exposure to radioactive materials, and reduce safeguard concerns. This report documents the preconceptual design of the process equipment that is necessary to conduct a full-scale demonstration of the LTLT method in accordance with the process steps listed above. The process equipment and method proposed in this report are not intended to represent a full-scale production campaign design and operation, since the gas evacuation, gas charging, and off-gas handling systems that would be cost effective in a production campaign are not cost effective for a first-time demonstration. However, the design presented here is expected to be applicable to special decontamination projects beyond the demonstration, which could include the Deposit Recovery Program. The equipment will therefore be sized to a 200 ft size 1 converter (plus a substantial conservative design margin), which is the largest item of interest for gas phase decontamination in the Deposit Recovery Program. The decontamination equipment will allow recovery of the UF{sub 6}, which is generated from the reaction of ClF{sub 3} with the uranium deposits, by use of NaF traps.

  8. Lattice-gas models of phase separation: interfaces, phase transitions, and multiphase flow

    SciTech Connect

    Rothman, D.H. ); Zaleski, S. )

    1994-10-01

    Momentum-conserving lattice gases are simple, discrete, microscopic models of fluids. This review describes their hydrodynamics, with particular attention given to the derivation of macroscopic constitutive equations from microscopic dynamics. Lattice-gas models of phase separation receive special emphasis. The current understanding of phase transitions in these momentum-conserving models is reviewed; included in this discussion is a summary of the dynamical properties of interfaces. Because the phase-separation models are microscopically time irreversible, interesting questions are raised about their relationship to real fluid mixtures. Simulation of certain complex-fluid problems, such as multiphase flow through porous media and the interaction of phase transitions with hydrodynamics, is illustrated.

  9. Experimental on two sensors combination used in horizontal pipe gas-water two-phase flow

    NASA Astrophysics Data System (ADS)

    Wu, Hao; Dong, Feng

    2014-04-01

    Gas-water two phase flow phenomenon widely exists in production and living and the measurement of it is meaningful. A new type of long-waist cone flow sensor has been designed to measure two-phase mass flow rate. Six rings structure of conductance probe is used to measure volume fraction and axial velocity. The calibration of them have been made. Two sensors have been combined in horizontal pipeline experiment to measure two-phase flow mass flow rate. Several model of gas-water two-phase flow has been discussed. The calculation errors of total mass flow rate measurement is less than 5% based on the revised homogeneous flow model.

  10. Experimental on two sensors combination used in horizontal pipe gas-water two-phase flow

    SciTech Connect

    Wu, Hao; Dong, Feng

    2014-04-11

    Gas-water two phase flow phenomenon widely exists in production and living and the measurement of it is meaningful. A new type of long-waist cone flow sensor has been designed to measure two-phase mass flow rate. Six rings structure of conductance probe is used to measure volume fraction and axial velocity. The calibration of them have been made. Two sensors have been combined in horizontal pipeline experiment to measure two-phase flow mass flow rate. Several model of gas-water two-phase flow has been discussed. The calculation errors of total mass flow rate measurement is less than 5% based on the revised homogeneous flow model.

  11. Gas Phase Chemical Detection with an Integrated Chemical Analysis System

    SciTech Connect

    Baca, Albert G.; Casalnuovo, Stephen A.; Frye-Mason, Gregory C.; Heller, Edwin J.; Hietala, Susan L.; Hietala, Vincent M.; Kottenstette, Richard J.; Lewis, Patrick R.; Manginell, Ronald P.; Matzke, Carloyn M.; Reno, John L.; Sasaki, Darryl Y.; Schubert, W. Kent

    1999-07-08

    Microfabrication technology has been applied to the development of a miniature, multi-channel gas phase chemical laboratory that provides fast response, small size, and enhanced versatility and chemical discrimination. Each analysis channel includes a sample concentrator followed by a gas chromatographic separator and a chemically selective surface acoustic wave detector array to achieve high sensitivity and selectivity. The performance of the components, individually and collectively, is described. The design and performance of novel micromachined acoustic wave devices, with the potential for improved chemical sensitivity, are also described.

  12. Collaborative Advanced Gas Turbine Program: Phase 1. Final report

    SciTech Connect

    Hollenbacher, R.; Kesser, K.; Beishon, D.

    1994-12-01

    The Collaborative Advanced Gas Turbine (CAGT) Program is an advanced gas turbine research and development program whose goal is to accelerate the commercial availability, to within the turn of the century, of high efficiency aeroderivative gas turbines for electric power generating applications. In the first project phase, research was conducted to prove or disprove the research hypothesis that advanced aeroderivative gas turbine systems can provide a promising technology alternative, offering high efficiency and good environmental performance characteristics in modular sizes, for utility applications. This $5 million, Phase 1 research effort reflects the collaborative efforts of a broad and international coalition of industries and organizations, both public and private, that have pooled their resources to assist in this research. Included in this coalition are: electric and gas utilities, the Electric Power Research Institute, the Gas Research Institute and the principal aircraft engine manufacturers. Additionally, the US Department of Energy (DOE) and the California Energy Commission have interacted with the CAGT on both technical and executive levels as observers and sources of funding. The three aircraft engine manufacturer-led research teams participating in this research include: Rolls-Royce, Inc., and Bechtel; the Turbo Power and Marine Division of United Technologies and Fluor Daniel; and General Electric Power Generation, Stewart and Stevenson, and Bechtel. Each team has investigated advanced electric power generating systems based on their high-thrust (60,000 to 100,000 pounds) aircraft engines. The ultimate goal of the CAGT program is that the community of stakeholders in the growing market for natural-gas-fueled, electric power generation can collectively provide the right combination of market-pull and technology-push to substantially accelerate the commercialization of advanced, high efficiency aeroderivative technologies.

  13. Structural phase transition in evolving networks.

    PubMed

    Kim, Sang-Woo; Noh, Jae Dong

    2009-08-01

    A network as a substrate for dynamic processes may have its own dynamics. We propose a model for networks which evolve together with diffusing particles through a coupled dynamics and investigate emerging structural property. The model consists of an undirected weighted network of fixed mean degree and randomly diffusing particles of fixed density. The weight w of an edge increases by the amount of traffics through its connecting nodes or decreases by a constant factor. Edges are removed with the probability P(rew)=1/(1+w) and replaced by new ones having w=0 at random locations. We find that the model exhibits a structural phase transition between the homogeneous phase characterized by an exponentially decaying degree distribution and the heterogeneous phase characterized by the presence of hubs. The hubs emerge as a consequence of a positive feedback between the particle and the edge dynamics. PMID:19792212

  14. Lightweight solar concentrator structures, phase 2

    NASA Technical Reports Server (NTRS)

    Williams, Brian E.; Kaplan, Richard B.

    1993-01-01

    This report summarizes the results of the program conducted by Ultramet under SBIR Phase 2 Contract NAS3-25418. The objective of this program was to develop lightweight materials and processes for advanced high accuracy Space Solar Concentrators using rigidized foam for the substrate structure with an integral optical surface.

  15. Chemistry inside molecular containers in the gas phase

    NASA Astrophysics Data System (ADS)

    Lee, Tung-Chun; Kalenius, Elina; Lazar, Alexandra I.; Assaf, Khaleel I.; Kuhnert, Nikolai; Grün, Christian H.; Jänis, Janne; Scherman, Oren A.; Nau, Werner M.

    2013-05-01

    Inner-phase chemical reactions of guest molecules encapsulated in a macromolecular cavity give fundamental insight into the relative stabilization of transition states by the surrounding walls of the host, thereby modelling the situation of substrates in enzymatic binding pockets. Although in solution several examples of inner-phase reactions are known, the use of cucurbiturils as macrocyclic hosts and bicyclic azoalkanes as guests has now enabled a systematic mass spectrometric investigation of inner-phase reactions in the gas phase, where typically the supply of thermal energy results in dissociation of the supramolecular host-guest assembly. The results reveal a sensitive interplay in which attractive and repulsive van der Waals interactions between the differently sized hosts and guests need to be balanced with a constrictive binding to allow thermally activated chemical reactions to compete with dissociation. The results are important for the understanding of supramolecular reactivity and have implications for catalysis.

  16. Acoustic Instabilities Driven by Slip Between a Condensed Phase and the Gas Phase in Combustion Systems

    NASA Technical Reports Server (NTRS)

    DiCicco, M.; Buckmaster, J.

    1994-01-01

    In the context of gas turbine combustion chambers, this study describes how slip affects the response time of fuel sprays to pressure fluctuations in a gaseous flow field. Slip between the condensed and gas phases is shown to cause fuel vapor mass fraction fluctuations upstream of the reaction zone. A resulting oscillating heat release can drive the pressure fluctuations, depending on the phase difference between them. This generates an acoustic instability. With relevance to previous experimental results, differences are explored in the evaporation characteristics among three different fuel sprays (JP-4, JP-5, and D-2) in relation to their effect on the magnitude of the fuel vapor mass fraction perturbations.

  17. Structural assembly demonstration experiment, phase 1

    NASA Technical Reports Server (NTRS)

    Akin, David L.; Bowden, Mary L.; Miller, Rene H.

    1983-01-01

    The goal of this phase of the structural assembly and demonstration experiment (SADE) program was to begin to define a shuttle flight experiment that would yield data to compare on-orbit assembly operations of large space structures with neutral buoyancy simulations. In addition, the experiment would be an early demonstration of structural hardware and human capabilities in extravehicular activity (EVA). The objectives of the MIT study, as listed in the statement of work, were: to provide support in establishing a baseline neutral buoyancy testing data base, to develop a correlation technique between neutral buoyancy test results and on-orbit operations, and to prepare the SADE experiment plan (MSFC-PLAN-913).

  18. Gas-phase reactivity of ruthenium carbonyl cluster anions.

    PubMed

    Henderson, Matthew A; Kwok, Samantha; McIndoe, J Scott

    2009-04-01

    Partially-ligated anionic ruthenium carbonyl clusters react with alkenes, arenes, and alkanes in the gas phase; the products undergo extensive C-H activation and lose dihydrogen and carbon monoxide under collision-induced dissociation conditions. Triethylsilane and phenylsilane are also reactive towards the unsaturated clusters, and oxygen was shown to rapidly break down the cluster core by oxidative cleavage of the metal-metal bonds. These qualitative gas-phase reactivity studies were conducted using an easily-installed and inexpensive modification of a commercial electrospray ionization mass spectrometer. Interpretation of the large amounts of data generated in these studies is made relatively straightforward by employing energy-dependent electrospray ionization mass spectrometry (EDESI-MS). PMID:19185511

  19. Kinetics of gas phase tetramethyldioxetane decomposition and chemiluminescence

    SciTech Connect

    Cannon, B.D.; Crim, F.F.

    1981-11-04

    Pulsed-laser excitation of overtone vibrations or a weak electronic transition in gas-phase tetramethyldioxetane in combination with temporally and spectrally resolved detection of decomposition product luminescence reveals the presence, along with electronically excited acetone, of an additional emitting species which is not observed in solution studies. The emission is at shorter wavelengths than the acetone phosphorescence, and the emitting species has a zero-pressure decay rate of 0.019 +- 0.014 ..mu..s/sup -1/. The rapid collisional quenching which occurs on roughly every other encounter (k/sub q/ = 5.6 ..mu..s/sup -1/ torr/sup -1/) explains the inability of solution measurements to detect this feature of the tetramethyldioxetane decomposition kinetics. This newly observed component is likely to extend the interpretation of gas-phase decomposition experiments using infrared multiphoton absorption or collisions with fast Xe atoms to excite tetramethyldioxetane.

  20. Ionization of vitamin C in gas phase: Theoretical study.

    PubMed

    Abyar, Fatemeh; Farrokhpour, Hossein

    2016-07-01

    In this work, the gas phase ionization energies and photoelectron spectra of four important conformers of vitamin C were calculated. Symmetry adapted cluster/configuration interaction methodology employing the single and double excitation operators (SAC-CI SD-R) along with D95++(d,p) basis set were used for the calculations. Thermochemistry calculations were also performed on all possible conformers of vitamin C to find the relative stability of conformers in the gas phase. The calculated ionization bands of each conformer were assigned by calculating the contribution of natural bonding orbital (NBO) in the calculated canonical molecular orbitals involved in the ionization. SAC-CI calculations showed that the first ionization band of vitamin C is related to the π electrons of CC bond of the ring of molecule although, there is the lone electron pairs of oxygen atoms and π electrons of CO bond in the molecule. PMID:27092998

  1. Structure of nanoscale gas bubbles in metals

    SciTech Connect

    Caro, A. Schwen, D.; Martinez, E.

    2013-11-18

    A usual way to estimate the amount of gas in a bubble inside a metal is to assume thermodynamic equilibrium, i.e., the gas pressure P equals the capillarity force 2γ/R, with γ the surface energy of the host material and R the bubble radius; under this condition there is no driving force for vacancies to be emitted or absorbed by the bubble. In contrast to the common assumption that pressure inside a gas or fluid bubble is constant, we show that at the nanoscale this picture is no longer valid. P and density can no longer be defined as global quantities determined by an equation of state (EOS), but they become functions of position because the bubble develops a core-shell structure. We focus on He in Fe and solve the problem using both continuum mechanics and empirical potentials to find a quantitative measure of this effect. We point to the need of redefining an EOS for nanoscale gas bubbles in metals, which can be obtained via an average pressure inside the bubble. The resulting EOS, which is now size dependent, gives pressures that differ by a factor of two or more from the original EOS for bubble diameters of 1 nm and below.

  2. Gas phase fractionation method using porous ceramic membrane

    DOEpatents

    Peterson, Reid A.; Hill, Jr., Charles G.; Anderson, Marc A.

    1996-01-01

    Flaw-free porous ceramic membranes fabricated from metal sols and coated onto a porous support are advantageously used in gas phase fractionation methods. Mean pore diameters of less than 40 .ANG., preferably 5-20 .ANG. and most preferably about 15 .ANG., are permeable at lower pressures than existing membranes. Condensation of gases in small pores and non-Knudsen membrane transport mechanisms are employed to facilitate and increase membrane permeability and permselectivity.

  3. A varying polytropic gas universe and phase space analysis

    NASA Astrophysics Data System (ADS)

    Khurshudyan, M.

    2016-05-01

    In this paper, we will consider a phenomenological model of a dark fluid that is able to explain an accelerated expansion of our low redshift universe and the phase transition to this accelerated expanding universe. Recent developments in modern cosmology towards understanding of the accelerated expansion of the large scale universe involve various scenarios and approaches. Among these approaches, one of well-known and accepted practice is modeling of the content of our universe via dark fluid. There are various models of dark energy fluid actively studied in recent literature and polytropic gas is among them. In this work, we will consider a varying polytropic gas which is a phenomenological modification of polytropic gas. Our model of varying polytropic dark fluid has been constructed to analogue to a varying Chaplygin gas actively discussed in the literature. We will consider interacting models, where dark matter is a pressureless fluid, to have a comprehensive picture. Phase space analysis is an elegant mathematical tool to earn general understanding of large scale universe and easily see an existence of a solution to cosmological coincidence problem. Imposing some constraints on parameters of the models, we found late time attractors for each case analytically. Cosmological consequences for the obtained late time attractors are discussed.

  4. Two-phase, gas-liquid flows in static mixers

    SciTech Connect

    Shah, N.F.; Kale, D.D. )

    1992-02-01

    This paper reports that static mixers are used for many gas-liquid two-phase operations. some of the typical applications are processing of natural gas to remove hydrogen sulfide or carbon dioxide, waste water treatment, dissolution of gases, hydrogenation, chlorination, and so on. They have experimentally studied the pressure drop for oxygen-water system in a bubble column packed with Sulzer-Koch-type mixing elements. They observed that the ratio of pressure drop through the packed bubble column to that through the unpacked one was slightly greater than one. The suitability of static mixers to mix fluids of very widely different viscosities has been demonstrated. Two-phase operations in polymer industry involve very viscous fluids. Due to the high viscosity of these fluids, the flow will be predominantly in laminar region for both fluids. There are no data on gas-liquid two-phase systems incorporating viscous Newtonian and non-Newtonian fluids where flows are predominantly in laminar region.

  5. Parenchymal mechanics, gas mixing, and the slope of phase III.

    PubMed

    Wilson, Theodore A

    2013-07-01

    A model of parenchymal mechanics is revisited with the objective of investigating the differences in parenchymal microstructure that underlie the differences in regional compliance that are inferred from gas-mixing studies. The stiffness of the elastic line elements that lie along the free edges of alveoli and form the boundary of the lumen of the alveolar duct is the dominant determinant of parenchymal compliance. Differences in alveolar size cause parallel shifts of the pressure-volume curve, but have little effect on compliance. However, alveolar size also affects the relation between surface tension and pressure during the breathing cycle. Thus regional differences in alveolar size generate regional differences in surface tension, and these drive Marangoni surface flows that equilibrate surface tension between neighboring acini. Surface tension relaxation introduces phase differences in regional volume oscillations and a dependence of expired gas concentration on expired volume. A particular example of different parenchymal properties in two neighboring acini is described, and gas exchange in this model is calculated. The efficiency of mixing and slope of phase III for the model agree well with published data. This model constitutes a new hypothesis concerning the origin of phase III. PMID:23599394

  6. Gas Phase Model of Surface Reactions for N{2} Afterglows

    NASA Astrophysics Data System (ADS)

    Marković, V. Lj.; Petrović, Z. Lj.; Pejović, M. M.

    1996-07-01

    The adequacy of the homogeneous gas phase model as a representation of the surface losses of diffusing active particles in gas phase is studied. As an example the recent data obtained for the surface recombination coefficients are reanalyzed. The data were obtained by the application of the breakdown delay times which consists of the measurements of the breakdown delay times t_d as a function of the afterglow period tau. It was found that for the conditions of our experiment, the diffusion should not be neglected as the final results are significantly different when obtained by approximate gas phase representation and by exact numerical solution to the diffusion equation. While application of the gas phase effective coefficients to represent surface losses gives an error in the value of the recombination coefficient, it reproduces correctly other characteristics such as order of the process which can be obtained from simple fits to the experimental data. Dans cet article, nous étudions la validité du modèle approximatif représentant les pertes superficielles des particules actives qui diffusent de la phase gazeuse comme pertes dans la phase homogène du gaz. Les données actuelles du coefficient de recombination en surface sont utilisées par cette vérification . Les données experimentales sont obtenues en utilisant la technique qui consiste en la mesure du temps de retard du début de la décharge en fonction de la période de relaxation. Nous avons trouvé que, pour nos conditions expérimentales, la diffusion ne peut être négligée. Aussi, les résultats finals sont considérablement différents quand ils sont obtenus en utilisant le modèle approximatif par comparaison aves les résultats obtenus par la solution numérique exacte de l'équation de la diffusion. L'application des coefficients effectifs dans la phase gaseuse pour la présentation des pertes superficielles donne, pour les coefficients de la recombinaison, des valeurs qui diffèrent en

  7. Carbon Dioxide Separation from Flue Gas by Phase Enhanced Absorption

    SciTech Connect

    Tim Fout

    2007-06-30

    A new process, phase enhanced absorption, was invented. The method is carried out in an absorber, where a liquid carrier (aqueous solution), an organic mixture (or organic compound), and a gas mixture containing a gas to be absorbed are introduced from an inlet. Since the organic mixture is immiscible or at least partially immiscible with the liquid carrier, the organic mixture forms a layer or small parcels between the liquid carrier and the gas mixture. The organic mixture in the absorber improves mass transfer efficiency of the system and increases the absorption rate of the gas. The organic mixture serves as a transportation media. The gas is finally accumulated in the liquid carrier as in a conventional gas-liquid absorption system. The presence of the organic layer does not hinder the regeneration of the liquid carrier or recovery of the gas because the organic layer is removed by a settler after the absorption process is completed. In another aspect, the system exhibited increased gas-liquid separation efficiency, thereby reducing the costs of operation and maintenance. Our study focused on the search of the organic layer or transportation layer to enhance the absorption rate of carbon dioxide. The following systems were studied, (1) CO{sub 2}-water system and CO{sub 2}-water-organic layer system; (2) CO{sub 2}-Potassium Carbonate aqueous solution system and CO{sub 2}-Potassium Carbonate aqueous solution-organic layer system. CO{sub 2}-water and CO{sub 2}-Potassium Carbonate systems are the traditional gas-liquid absorption processes. The CO{sub 2}-water-organic layer and CO{sub 2}-Potassium Carbonate-organic layer systems are the novel absorption processes, phase enhanced absorption. As we mentioned early, organic layer is used for the increase of absorption rate, and plays the role of transportation of CO{sub 2}. Our study showed that the absorption rate can be increased by adding the organic layer. However, the enhanced factor is highly depended on the

  8. Dynamic and Structural Gas Turbine Engine Modeling

    NASA Technical Reports Server (NTRS)

    Turso, James A.

    2003-01-01

    Model the interactions between the structural dynamics and the performance dynamics of a gas turbine engine. Generally these two aspects are considered separate, unrelated phenomena and are studied independently. For diagnostic purposes, it is desirable to bring together as much information as possible, and that involves understanding how performance is affected by structural dynamics (if it is) and vice versa. This can involve the relationship between thrust response and the excitation of structural modes, for instance. The job will involve investigating and characterizing these dynamical relationships, generating a model that incorporates them, and suggesting and/or developing diagnostic and prognostic techniques that can be incorporated in a data fusion system. If no coupling is found, at the least a vibration model should be generated that can be used for diagnostics and prognostics related to blade loss, for instance.

  9. Investigation of condensed and early stage gas phase hypergolic reactions

    NASA Astrophysics Data System (ADS)

    Dennis, Jacob Daniel

    Traditional hypergolic propellant combinations, such as those used on the space shuttle orbital maneuvering system first flown in 1981, feature hydrazine based fuels and nitrogen tetroxide (NTO) based oxidizers. Despite the long history of hypergolic propellant implementation, the processes that govern hypergolic ignition are not well understood. In order to achieve ignition, condensed phase fuel and oxidizer must undergo simultaneous physical mixing and chemical reaction. This process generates heat, intermediate condensed phase species, and gas phase species, which then may continue to react and generate more heat until ignition is achieved. The process is not well understood because condensed and gas phase reactions occur rapidly, typically in less than 200 μs, on much faster timescales than traditional diagnostic methods can observe. A detailed understanding of even the gas phase chemistry is lacking, but is critical for model development. Initial research has provided confidence that a study of condensed phase hypergolic reactions is useful and possible. Results obtained using an impinging jet apparatus have shown a critical residence time of 0.3 ms is required for the reaction between monomethylhydrazine (MMH) and red fuming nitric acid (RFNA, ~85% HNO3 + 15% N2O4) to achieve conditions favorable for ignition. This critical residence time spans the time required for liquid phase reactions to occur at the fuel/oxidizer interface and can give some insight into the reaction rates for this propellant combination. Experiments performed in a forced mixing constant volume reactor have demonstrated that the chamber pressurization rate for MMH/RFNA can be significantly reduced by diluting the MMH with deionized water. This result indicates that propellant dilution can slow the chemical reaction rates to occur over observable time scales. The research described in this document consists of two efforts that contribute knowledge to the propulsion community regarding the

  10. Theoretical Study of the Pyrolysis of Methyltrichlorosilane in the Gas Phase. 1.Thermodynamics

    SciTech Connect

    Ge, Yingbin; Gordon, Mark S.; Battaglia, Francine; Fox, Rodney O.

    2007-03-01

    Structures and energies of the gas-phase species produced during and after the various unimolecular decomposition reactions of methyltrichlorosilane (MTS) with the presence of H2 carrier gas were determined using second-order perturbation theory (MP2). Single point energies were obtained using singles + doubles coupled cluster theory, augmented by perturbative triples, CCSD(T). Partition functions were obtained using the harmonic oscillator-rigid rotor approximation. A 114-reaction mechanism is proposed to account for the gas-phase chemistry of MTS decompositions. Reaction enthalpies, entropies, and Gibbs free energies for these reactions were obtained at 11 temperatures ranging from 0 to 2000 K including room temperature and typical chemical vapor deposition (CVD) temperatures. Calculated and experimental thermodynamic properties such as heat capacities and entropies of various species and reaction enthalpies are compared, and theory is found to provide good agreement with experiment.

  11. Synthesis, structural characterization, and gas-phase unimolecular reactivity of the silver hydride nanocluster [Ag3((PPh2)2CH2)3(μ3-H)](BF4)2.

    PubMed

    Zavras, Athanasios; Khairallah, George N; Connell, Timothy U; White, Jonathan M; Edwards, Alison J; Mulder, Roger J; Donnelly, Paul S; O'Hair, Richard A J

    2014-07-21

    A bis(diphenylphosphino)methane-ligated trinuclear silver hydride nanocluster, [Ag3((Ph2P)2CH2)3(μ3-H)](BF4)2, featuring three silver(I) ions coordinated to a μ3-hydride, and its deuteride analogue, [Ag3((Ph2P)2CH2)3(μ3-D)](BF4)2, have been isolated and structurally characterized using electrospray ionization mass spectrometry (ESI-MS), X-ray crystallography, NMR and IR spectroscopy. The position of the deuteride in [Ag3((Ph2P)2CH2)3(μ3-D)](BF4)2 was determined by neutron diffraction. ESI-MS of [Ag3L3(μ3-H/D)](BF4)2 [L = ((Ph2P)2CH2)2] produces [Ag3L3(μ3-H/D)](2+) and [Ag3L3(μ3-H/D)(BF4)](+). A rich gas-phase ion chemistry of [Ag3L3(μ3-H/D)](2+) is observed under conditions of collision-induced dissociation (CID) and electron-capture dissociation (ECD). CID gives rise to the following complementary ion pairs: [Ag3L2](+) and [L+(H/D)](+); [Ag2(H/D)L2](+) and [AgL](+); [Ag2(H/D)L](+) and [AgL2](+). ECD gives rise to a number of dissociation channels including loss of the bis(phosphine) ligand, fragmentation of a coordinated bis(phosphine) ligand via C-P bond activation, and loss of a hydrogen (deuterium) atom with concomitant formation of [Ag3L3](+). Under CID conditions, [Ag3L3(μ3-H/D)(BF4)](+) fragments via ligand loss, the combined loss of a ligand and [H,B,F4], and cluster fragmentation to give [Ag2(BF4)L2](+) and [Ag2(L-H)L](+) [where (L-H) = (Ph2P)2CH(-)]. PMID:24991699

  12. Theory of Gas Injection: Interaction of Phase Behavior and Flow

    NASA Astrophysics Data System (ADS)

    Dindoruk, B.

    2015-12-01

    The theory of gas injection processes is a central element required to understand how components move and partition in the reservoir as one fluid is displacing another (i.e., gas is displacing oil). There is significant amount of work done in the area of interaction of phase-behavior and flow in multiphase flow conditions. We would like to present how the theory of gas injection is used in the industry to understand/design reservoir processes in various ways. The tools that are developed for the theory of gas injection originates from the fractional flow theory, as the first solution proposed by Buckley-Leveret in 1940's, for water displacing oil in porous media. After 1960's more and more complex/coupled equations were solved using the initial concept(s) developed by Buckley-Leverett, and then Welge et al. and others. However, the systematic use of the fractional flow theory for coupled set of equations that involves phase relationships (EOS) and phase appearance and disappearance was mainly due to the theory developed by Helfferich in early 80's (in petroleum literature) using method of characteristics primarily for gas injection process and later on by the systematic work done by Orr and his co-researchers during the last two decades. In this talk, we will present various cases that use and extend the theory developed by Helfferich and others (Orr et al., Lake et al. etc.). The review of various injection systems reveals that displacement in porous media has commonalities that can be represented with a unified theory for a class of problems originating from the theory of gas injection (which is in a way generalized Buckley-Leverett problem). The outcome of these solutions can be used for (and are not limited to): 1) Benchmark solutions for reservoir simulators (to quantify numerical dispersion, test numerical algorithms) 2) Streamline simulators 3) Design of laboratory experiments and their use (to invert the results) 4) Conceptual learning and to investigate

  13. Gas phase oxidation downstream of a catalytic combustor

    NASA Technical Reports Server (NTRS)

    Tien, J. S.; Anderson, D. N.

    1979-01-01

    Effect of the length available for gas-phase reactions downstream of the catalytic reactor on the emission of CO and unburned hydrocarbons was investigated. A premixed, prevaporized propane/air feed to a 12/cm/diameter catalytic/reactor test section was used. The catalytic reactor was made of four 2.5 cm long monolithic catalyst elements. Four water cooled gas sampling probes were located at positions between 0 and 22 cm downstream of the catalytic reactor. Measurements of unburned hydrocarbon, CO, and CO2 were made. Tests were performed with an inlet air temperature of 800 K, a reference velocity of 10 m/s, pressures of 3 and 600,000 Pa, and fuel air equivalence ratios of 0.14 to 0.24. For very lean mixtures, hydrocarbon emissions were high and CO continued to be formed downstream of the catalytic reactor. At the highest equivalence ratios tested, hydrocarbon levels were much lower and CO was oxidized to CO2 in the gas phase downstream. To achieve acceptable emissions, a downstream region several times longer than the catalytic reactor could be required.

  14. Gas phase contributions to topochemical hydride reduction reactions

    SciTech Connect

    Kobayashi, Yoji; Li, Zhaofei; Hirai, Kei; Tassel, Cédric; Loyer, François; Ichikawa, Noriya; Abe, Naoyuki; Yamamoto, Takafumi; Shimakawa, Yuichi; and others

    2013-11-15

    Alkali and alkali earth hydrides have been used as solid state reductants recently to yield many interesting new oxygen-deficient transition metal oxides. These reactions have tacitly been assumed to be a solid phase reaction between the reductant and parent oxide. We have conducted a number of experiments with physical separation between the reductant and oxides, and find that in some cases reduction proceeds even when the reagents are physically separated, implying reactions with in-situ generated H{sub 2} and, to a lesser extent, getter mechanisms. Our findings change our understanding of these topochemical reactions, and should enhance the synthesis of additional new oxides and nanostructures. - Graphical abstract: Topochemical reductions with hydrides: Solid state or gas phase reaction? Display Omitted - Highlights: • SrFeO{sub 2} and LaNiO{sub 2} were prepared by topochemical reduction of oxides. • Separating the reducing agent (CaH{sub 2}, Mg metal) from the oxide still results in reduction. • Such topochemical reactions can occur in the gas phase.

  15. a Nucleoside Under Observation in the Gas Phase: a Rotational Study of Uridine

    NASA Astrophysics Data System (ADS)

    Peña, Isabel; Alonso, José L.

    2014-06-01

    The nucleoside of uridine has been placed in the gas phase by laser ablation and the most stable C2{'}-anti conformation characterized by broadband chirped pulse (CP-FTMW) and narrowband molecular beam Fourier transform microwave (LA-MB-FTMW) spectroscopies. The quadrupole hyperfine structure, originated by two 14N nuclei, has been completely resolved. Intramolecular hydrogen bonds involving uracil and ribose moieties have been found to play an important role in the stabilization of the nucleoside.

  16. Structural and relative energy assessments of DFT functionals and the MP2 method to describe the gas phase methylation of nitronates: [R(1)R(2)CNO2](-) + CH3I.

    PubMed

    Mahmood, Ayyaz; Longo, Ricardo L

    2016-06-22

    The performances of 26 combinations of density-functional theory (DFT) functionals or second-order Møller-Plesset (MP2) methods and basis sets were evaluated for the calculation of the activation energy (Δ(‡)E), the energy available (ΔRCE) to the reactant complex, the energy of reaction (ΔrE), and rotational constants of the main structures involved in the methylation reactions of nitronates, [R(1)R(2)CNO2](-) + CH3I, in the gas phase, where R(1) = R(2) = H, R(1) = H and R(2) = CH3, R(1) = R(2) = CH3, and R(1) + R(2) = c-(CH2)2. The separated reactants and products, the reactant and product complexes, and the transition states were considered, leading to 43 data points for the statistical analysis for each method under assessment. Five statistical quantifiers: the mean signed error (MSE), the mean unsigned error (MUE), the percent mean relative error (% MRE), best and worse (BW), and the confidence interval (CI) were used to assess the performance of methods relative to the CCSD(T)/CBS//MP2/aug-cc-pVTZ reference method. The DFT functionals included the widely applied B3LYP and M06-2X global-hybrids and the recently available DSD-PBEP86, DSD-PBEP86-D3BJ and PWPB95 double-hybrids. The basis sets involved an effective core potential (ECP) for describing the inner electrons of iodine such as LANL2DZdp and aug-cc-pVXZ-PP (X = D, T, and Q), and all-electron basis sets for the remaining atoms. The energy available to the reactant complex is described quite well by all methods, however, only the MP2/aug-cc-pVTZ-PP method provided values within 2 kcal mol(-1) (8.4 kJ mol(-1)) from the reference method for Δ(‡)E and ΔrE. Amongst the DFT methods, the global-hybrid M06-2X functional produced the best overall results including BW and CI. Notice that all methods yielded the smallest Δ(‡)E for the C-methylation pathway. The rotational constants of the reactant complexes and the transition state structures were compared, for which the MP2 method and the M06-2X

  17. Phase-locked measurements of gas-liquid horizontal flows

    NASA Astrophysics Data System (ADS)

    Zadrazil, Ivan; Matar, Omar; Markides, Christos

    2014-11-01

    A flow of gas and liquid in a horizontal pipe can be described in terms of various flow regimes, e.g. wavy stratified, annular or slug flow. These flow regimes appear at characteristic gas and liquid Reynolds numbers and feature unique wave phenomena. Wavy stratified flow is populated by low amplitude waves whereas annular flow contains high amplitude and long lived waves, so called disturbance waves, that play a key role in a liquid entrainment into the gas phase (droplets). In a slug flow regime, liquid-continuous regions travel at high speeds through a pipe separated by regions of stratified flow. We use a refractive index matched dynamic shadowgraphy technique using a high-speed camera mounted on a moving robotic linear rail to track the formation and development of features characteristic for the aforementioned flow regimes. We show that the wave dynamics become progressively more complex with increasing liquid and gas Reynolds numbers. Based on the shadowgraphy measurements we present, over a range of conditions: (i) phenomenological observations of the formation, and (ii) statistical data on the downstream velocity distribution of different classes of waves. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

  18. Semiphenomenological model for gas-liquid phase transitions.

    PubMed

    Benilov, E S; Benilov, M S

    2016-03-01

    We examine a rarefied gas with inter-molecular attraction. It is argued that the attraction force amplifies random density fluctuations by pulling molecules from lower-density regions into high-density regions and thus may give rise to an instability. To describe this effect, we use a kinetic equation where the attraction force is taken into account in a way similar to how electromagnetic forces in plasma are treated in the Vlasov model. It is demonstrated that the instability occurs when the temperature T is lower than a certain threshold value T(s) depending on the gas density. It is further shown that, even if T is only marginally lower than T(s), the instability generates clusters with density much higher than that of the gas. These results suggest that the instability should be interpreted as a gas-liquid phase transition, with T(s) being the temperature of saturated vapor and the high-density clusters representing liquid droplets. PMID:27078333

  19. Product energy deposition of CN + alkane H abstraction reactions in gas and solution phases

    NASA Astrophysics Data System (ADS)

    Glowacki, David R.; Orr-Ewing, Andrew J.; Harvey, Jeremy N.

    2011-06-01

    In this work, we report the first theoretical studies of post-transition state dynamics for reaction of CN with polyatomic organic species. Using electronic structure theory, a newly developed analytic reactive PES, a recently implemented rare-event acceleration algorithm, and a normal mode projection scheme, we carried out and analyzed quasi-classical and classical non-equilibrium molecular dynamics simulations of the reactions CN + propane (R1) and CN + cyclohexane (R2). For (R2), we carried out simulations in both the gas phase and in a CH2Cl2 solvent. Analysis of the results suggests that the solvent perturbations to the (R2) reactive free energy surface are small, leading to product energy partitioning in the solvent that is similar to the gas phase. The distribution of molecular geometries at the respective gas and solution phase variational association transition states is very similar, leading to nascent HCN which is vibrationally excited in both its CH stretching and HCN bending coordinates. This study highlights the fact that significant non-equilibrium energy distributions may follow in the wake of solution phase bimolecular reactions, and may persist for hundreds of picoseconds despite frictional damping. Consideration of non-thermal distributions is often neglected in descriptions of condensed-phase reactivity; the extent to which the present intriguing observations are widespread remains an interesting question.

  20. Phasing macromolecular structures via structure-invariant algebra.

    PubMed

    Hauptman, H; Han, F

    1993-01-01

    Owing to the breakdown of Friedel's law when anomalous scatterers are present, unique values of the three-phase structure invariants in the whole range from 0 to 2pi are determined by measured values of diffraction intensities alone. Two methods are described for going from presumed known values of these invariants to the values of the individual phases. The first, dependent on a scheme for resolving the 2pi ambiguity in the estimate omega(HK) of the triplet phi(H) + phi(K) + phi(-H-K), solves by least squares the resulting redundant system of linear equations phi(H) + phi(K) + phi(-H-K) = omega(HK). The second attempts to minimize the weighted sum of squares of differences between the true values of the cosine and sine invariants and their estimates. The latter method is closely related to one based on the 'minimal principle' which determines the values of a large set of phases as the constrained global minimum of a function of all the phases in the set. Both methods work in the sense that they yield values of the individual phases substantially better than the values of the initial estimates of the triplets. However, the second method proves to be superior to the first but requires, in addition to estimates of the triplets, initial estimates of the values of the individual phases. PMID:15299539

  1. Fluorescence Spectroscopy of Gas-phase Polycyclic Aromatic Hydrocarbons

    NASA Technical Reports Server (NTRS)

    Thomas, J. D.; Witt, A. N.

    2006-01-01

    The purpose of this investigation was to produce fluorescence spectra of polycyclic aromatic hydrocarbon (PAH) molecules in the gas-phase for comparison with blue luminescence (BL) emission observed in astrophysical sources Vijh et al. (2004, 2005a,b). The BL occurs roughly from 350 to 450 nm, with a sharp peak near 380 nm. PAHs with three to four rings, e.g. anthracene and pyrene, were found to produce luminescence in the appropriate spectral region, based on existing studies. Relatively few studies of the gas-phase fluorescence of PAHs exist; those that do exist have dealt primarily with the same samples commonly available for purchase such as pyrene and anthracene. In an attempt to understand the chemistry of the nebular environment we also obtained several nitrogen substituted PAHs from our colleagues at NASA Ames. In order to simulate the astrophysical environment we also took spectra by heating the PAHs in a flame. The flame environment counteracts the formation of eximers and permits the spectroscopy of free-flying neutral molecules. Experiments with coal tar demonstrate that fluorescence spectroscopy reveals primarily the presence of the smallest molecules, which are most abundant and which possess the highest fluorescence efficiencies. One gas-phase PAH that seems to fit the BL spectrum most closely is phenanthridine. In view of the results from the spectroscopy of coal tar, a compound containing a mixture of PAHs ranging from small to very large PAH molecules, we can not preclude the presence of larger PAHs in interstellar sources exhibiting BL.

  2. Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates.

    PubMed

    Miskowiec, Andrew; Kirkegaard, Marie C; Huq, Ashfia; Mamontov, Eugene; Herwig, Kenneth W; Trowbridge, Lee; Rondinone, Adam; Anderson, Brian

    2015-12-10

    We report a novel production method for uranium oxyfluoride [(UO2)7F14(H2O)7]·4H2O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl fluoride, UO2F2, through the gas phase at ambient temperatures followed by desiccation by equilibration with a dry environment. We follow the structure of [(UO2)7F14(H2O)7]·4H2O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous structure), and a water molecule binds as an equatorial ligand to the uranyl ion. Quasielastic neutron scattering results compare well with previous measurements of mineral hydrates. The two groups of structurally distinct water molecules in D perform restricted motion on a length scale commensurate with the O-H bond (r = 0.92 Å). The more tightly bound equatorial ligand waters rotate slower (Dr = 2.2 ps(-1)) than their hydrogen-bonded partners (Dr = 28.7 ps(-1)). PMID:26575434

  3. Multiscale Aspects of Modeling Gas-Phase Nanoparticle Synthesis

    PubMed Central

    Buesser, B.; Gröhn, A.J.

    2013-01-01

    Aerosol reactors are utilized to manufacture nanoparticles in industrially relevant quantities. The development, understanding and scale-up of aerosol reactors can be facilitated with models and computer simulations. This review aims to provide an overview of recent developments of models and simulations and discuss their interconnection in a multiscale approach. A short introduction of the various aerosol reactor types and gas-phase particle dynamics is presented as a background for the later discussion of the models and simulations. Models are presented with decreasing time and length scales in sections on continuum, mesoscale, molecular dynamics and quantum mechanics models. PMID:23729992

  4. Gas-phase chemiluminescent reactions of ozone with monoterpenes

    NASA Astrophysics Data System (ADS)

    Arora, P. K.; Chatha, J. P. S.; Vohra, K. G.

    1983-08-01

    Chemiluminescent reactions of ozone with monoterpenes such as linallol, geraniol, d-limonene and α-pinene have been studied in the gas phase at low pressures. Methylglyoxal phosphorescence has been observed in the first two reactions. Emissions from HCHO( 1A 2) and glyoxal ( 3A u) are observed in the reaction of ozone with d-limonene and formation of excited glyoxal is found to be first order in ozone. The reaction of ozone with β-pinene gives rise to emission from a α-dicarbonyl compound and this is found to be first order in ozone. The mechanisms for the formation of excited species are proposed.

  5. The solar system/interstellar medium connection - Gas phase abundances

    NASA Technical Reports Server (NTRS)

    Lutz, Barry L.

    1987-01-01

    Gas-phase abundances in the outer solar system are presented as diagnostics of the interstellar medium at the time of the solar system formation, some 4.55 billion years ago. Possible influences of the thermal and chemical histories of the primitive solar nebula and of the processes which led to the formation and evolution of the outer planets and comets on the elemental and molecular composition of the primordial matter are outlined. The major components of the atmospheres of the outer planets and of the comae of comets are identified, and the cosmogonical and cosmological implications are discussed.

  6. Neurotransmitters in the Gas Phase: La-Mb Studies

    NASA Astrophysics Data System (ADS)

    Cabezas, C.; Mata, S.; López, J. C.; Alonso, J. L.

    2011-06-01

    LA-MB-FTMW spectroscopy combines laser ablation with Fourier transform microwave spectroscopy in supersonic jets overcoming the problems of thermal decomposition associated with conventional heating methods. We present here the results on LA-MB-FTMW studies of some neurotransmitters. Six conformers of dopamine, four of adrenaline, five of noradrenaline and three conformers of serotonin have been characterized in the gas phase. The rotational and nuclear quadrupole coupling constants extracted from the analysis of the rotational spectrum are directly compared with those predicted by ab initio methods to achieve the conclusive identification of different conformers and the experimental characterization of the intramolecular forces at play which control conformational preferences.

  7. Electronic structure engineering of various structural phases of phosphorene.

    PubMed

    Kaur, Sumandeep; Kumar, Ashok; Srivastava, Sunita; Tankeshwar, K

    2016-07-21

    We report the tailoring of the electronic structures of various structural phases of phosphorene (α-P, β-P, γ-P and δ-P) based homo- and hetero-bilayers through in-plane mechanical strains, vertical pressure and transverse electric field by employing density functional theory. In-plane biaxial strains have considerably modified the electronic bandgap of both homo- and hetero-bilayers while vertical pressure induces metallization in the considered structures. The γ-P homo-bilayer structure showed the highest ultimate tensile strength (UTS ∼ 6.21 GPa) upon in-plane stretching. Upon application of a transverse electric field, the variation in the bandgap of hetero-bilayers was found to be strongly dependent on the polarity of the applied field which is attributed to the counterbalance between the external electric field and the internal field induced by different structural phases and heterogeneity in the arrangements of atoms of each surface of the hetero-bilayer system. Our results demonstrate that the electronic structures of the considered hetero- and homo-bilayers of phosphorene could be modified by biaxial strain, pressure and electric field to achieve the desired properties for future nano-electronic devices. PMID:27334095

  8. Stabilizing the hexagonal close packed structure of hard spheres with polymers: Phase diagram, structure, and dynamics.

    PubMed

    Edison, John R; Dasgupta, Tonnishtha; Dijkstra, Marjolein

    2016-08-01

    We study the phase behaviour of a binary mixture of colloidal hard spheres and freely jointed chains of beads using Monte Carlo simulations. Recently Panagiotopoulos and co-workers predicted [Nat. Commun. 5, 4472 (2014)] that the hexagonal close packed (HCP) structure of hard spheres can be stabilized in such a mixture due to the interplay between polymer and the void structure in the crystal phase. Their predictions were based on estimates of the free-energy penalty for adding a single hard polymer chain in the HCP and the competing face centered cubic (FCC) phase. Here we calculate the phase diagram using free-energy calculations of the full binary mixture and find a broad fluid-solid coexistence region and a metastable gas-liquid coexistence region. For the colloid-monomer size ratio considered in this work, we find that the HCP phase is only stable in a small window at relatively high polymer reservoir packing fractions, where the coexisting HCP phase is nearly close packed. Additionally we investigate the structure and dynamic behaviour of these mixtures. PMID:27497577

  9. Stabilizing the hexagonal close packed structure of hard spheres with polymers: Phase diagram, structure, and dynamics

    NASA Astrophysics Data System (ADS)

    Edison, John R.; Dasgupta, Tonnishtha; Dijkstra, Marjolein

    2016-08-01

    We study the phase behaviour of a binary mixture of colloidal hard spheres and freely jointed chains of beads using Monte Carlo simulations. Recently Panagiotopoulos and co-workers predicted [Nat. Commun. 5, 4472 (2014)] that the hexagonal close packed (HCP) structure of hard spheres can be stabilized in such a mixture due to the interplay between polymer and the void structure in the crystal phase. Their predictions were based on estimates of the free-energy penalty for adding a single hard polymer chain in the HCP and the competing face centered cubic (FCC) phase. Here we calculate the phase diagram using free-energy calculations of the full binary mixture and find a broad fluid-solid coexistence region and a metastable gas-liquid coexistence region. For the colloid-monomer size ratio considered in this work, we find that the HCP phase is only stable in a small window at relatively high polymer reservoir packing fractions, where the coexisting HCP phase is nearly close packed. Additionally we investigate the structure and dynamic behaviour of these mixtures.

  10. Phase diagram of van der Waals-like phase separation in a driven granular gas.

    PubMed

    Khain, Evgeniy; Meerson, Baruch; Sasorov, Pavel V

    2004-11-01

    Equations of granular hydrostatics are used to compute the phase diagram of the recently discovered van der Waals-like phase separation in a driven granular gas. The model two-dimensional system consists of smooth hard disks in a rectangular box, colliding inelastically with each other and driven by a "thermal" wall at zero gravity. The spinodal line and the critical point of the phase separation are determined. Close to the critical point, the spinodal and binodal (coexistence) lines are determined analytically. Effects of the finite size of the confining box in the direction parallel to the thermal wall are investigated. These include suppression of the phase separation by heat conduction in the lateral direction and a change from supercritical to subcritical bifurcation. PMID:15600606

  11. Site-selective patterning of organic luminescent molecules via gas phase deposition.

    PubMed

    Hao, Juanyuan; Lu, Nan; Wu, Qiong; Hu, Wei; Chen, Xiaodong; Zhang, Hongyu; Wu, Ying; Wang, Yue; Chi, Lifeng

    2008-05-20

    In this paper, we present a bottom-up approach to pattern organic luminescent molecules with a feature size down to sub-100 nm over wafer-sized areas. This method is based on the selective gas deposition of organic molecules on self-organized patterned structures, which consist of an organic monolayer with two different phases rather than different materials. The site selectivity is controllable by deposition rate and the pattern features. The reason for the site selectivity may be due to the nucleation and diffusion behaviors of the deposited organic molecules on different monolayer phases. PMID:18370416

  12. Printing nanoparticles from the liquid and gas phases using nanoxerography

    NASA Astrophysics Data System (ADS)

    Barry, Chad R.; Steward, Michael G.; Lwin, Nyein Z.; Jacobs, Heiko O.

    2003-10-01

    This paper reports on the directed self-assembly of nanoparticles onto charged surface areas with a resolution of 200 nm from the liquid phase and 100 nm from the gas phase. The charged areas required for this type of nanoxerographic printing were fabricated using a parallel method that employs a flexible, electrically conductive, electrode to charge a thin-film electret. As electrodes, we used metal-coated polymeric stamps and 10 µm thick doped silicon wafers carrying a pattern in topography. Each electrode was brought in contact with a thin-film electret on an n-doped silicon substrate. The charge pattern was transferred into the thin-film electret by applying a voltage pulse between the conductive electrode and the silicon substrate. Areas as large as 1 cm2 were patterned with charge with 100 nm scale resolution in 10 s. These charge patterns attract nanoparticles. A liquid-phase assembly process where electrostatic forces compete with disordering forces due to ultrasonication has been developed to assemble nanoparticles onto charged based receptors in 10 s from a liquid suspension. A gas-phase assembly process was developed that uses a transparent particle assembly module to direct particles towards the charged surface while monitoring the total charge of assembled particles. Nanoparticles were generated using a tube furnace by evaporation and condensation at the outlet. The electrostatically directed assembly of 10-100 nm sized metal (gold, silver) and 30 nm sized carbon particles was accomplished with a resolution 500-1000 times greater than the resolution of existing xerographic printers.

  13. The partitioning of ketones between the gas and aqueous phases

    NASA Astrophysics Data System (ADS)

    Betterton, Eric A.

    Most ketones are not significantly hydrated; they therefore retain their chromophore and they could be photolytically degraded in solution yielding a variety of products including carboxylic acids, aldehydes and radicals. It is difficult to accurately model the partitioning of ketones between the gas phase and aqueous phase because of the lack suitable estimates of the Henry's Law constants; consequently the fate and environmental effects of ketones cannot be confidently predicted. Here we report the experimental determination of the Henry's Law constants of a series of ketones that has yielded a simple straight line equation to predict the Henry's Law constants of simple aliphatic ketones: log H ∗ =0.23Σσ ∗ + 1.51; where H ∗ is the effective Henry's Law constant (M atm -1, and Σσ ∗ is the Taft polar substituents constants. The results for 25°C are (M atm -1) CH 3COCH 3, 32; C 6H 5COCH 3, 110; CH 2ClCOCH 3, 59; CH 3COCOCH 3, 74; CF 3COCH 3, 138. Acetophenone appears to have an abnormally high H ∗. Most low molecular weight aliphatic ketones are predicted to characterized by H ∗⩾30 M atm -1 and therefore they are expected to be found in the aqueous phase at concentrations of ⩾5 - 0.5 μM (given a typical gas-phase concentration range of 1-10 ppbv). The expected rate of decomposition of ketones due to photolysis in hydrometers is briefly discussed.

  14. MOLECULAR SPECTROSCPY AND REACTIONS OF ACTINIDES IN THE GAS PHASE AND CRYOGENIC MATRICES

    SciTech Connect

    Heaven, Michael C.; Gibson, John K.; Marcalo, Joaquim

    2009-02-01

    temperature or below. For many spectroscopic measurements, low temperatures have been achieved by co-condensing the actinide vapor in rare gas or inert molecule host matrices. Spectra recorded in matrices are usually considered to be minimally perturbed. Trapping the products from gas-phase reactions that occur when trace quantities of reactants are added to the inert host gas has resulted in the discovery of many new actinide species. Selected aspects of the matrix isolation data were discussed in chapter 17. In the present chapter we review the spectroscopic matrix data in terms of its relationship to gas-phase measurements, and update the description of the new reaction products found in matrices to reflect the developments that have occurred during the past two years. Spectra recorded in matrix environments are usually considered to be minimally perturbed, and this expectation is borne out for many closed shell actinide molecules. However, there is growing evidence that significant perturbations can occur for open shell molecules, resulting in geometric distortions and/or electronic state reordering. Studies of actinide reactions in the gas phase provide an opportunity to probe the relationship between electronic structure and reactivity. Much of this work has focused on the reactions of ionic species, as these may be selected and controlled using various forms of mass spectrometry. As an example of the type of insight derived from reaction studies, it has been established that the reaction barriers for An+ ions are determined by the promotion energies required to achieve the 5fn6d7s configuration. Gas-phase reaction studies also provide fundamental thermodynamic properties such as bond dissociation and ionization energies. In recent years, an increased number of gas-phase ion chemistry studies of bare (atomic) and ligated (molecular) actinide ions have appeared, in which relevant contributions to fundamental actinide chemistry have been made. These studies were initiated

  15. Dusty Plasma Structures in Gas Mixtures

    SciTech Connect

    Popova, D. V.; Antipov, S. N.; Petrov, O. F.; Fortov, V. E.

    2008-09-07

    The possibility of attainment of large Mach numbers is analyzed for the case of heavy ions drifting in a light gas. Under conditions of typical experiments with dust structures in plasmas, the use of the mixture of light and heavy gases is shown to make it possible to suppress the ion heating in the electric field and to form supersonic flows characterized by large Mach numbers. The drift of krypton ions in helium is considered as an example. Experiments with dc glow discharge at 1-10% of Kr show that the transition to the discharge in mixture leads to increase of interaction anisotropy and reinforcement of coupling of dust particles in the direction of ion drift. On the other hand, under certain conditions the phenomenon of abnormal 'heating' of dust particles was observed when the particles can obtain high kinetic energy which is several orders of magnitude higher than typical.

  16. Gas-phase reactions of cyclopropenylidene with protonated alkyl amines.

    PubMed

    Lin, Ziqing; Tan, Lei; Yang, Yang; Dai, Mingji; Tureček, František; Ouyang, Zheng; Xia, Yu

    2016-04-21

    Vinylidene carbenes (C3H2) are of high interest to interstellar, combustion, and organic chemistry. Due to their high instability, the direct experimental investigation of their chemical reactivity has rarely been achieved. Herein, we report a first study on the reactions of cyclopropenylidene (c-C3H2) with protonated alkyl amines in the gas phase using a home-built ion trap mass spectrometer. The high gas-phase basicity (GB) of ((1)A1) c-C3H2 (calculated as 920 kJ mol(-1)) facilitates the formation of a proton-bound dimer with protonated amines as the first step in the reaction. The dimer can stay as it is or rearrange to a covalent product. The formation of the covalent complex is highly exothermic and its yield is affected by the GB of alkyl amines. The highest yield (82%) was achieved when the GB of the amine was slightly lower but comparable to that of c-C3H2. Our results demonstrate a new reaction pathway of c-C3H2, which has long been considered as a "dead end" in interstellar carbon chemistry. PMID:26978226

  17. Gas-phase reactivity of novel Ziegler-Natta catalysts

    SciTech Connect

    Alameddin, N.G.; Eyler, J.R.; Richardson, D.E.

    1994-12-31

    The discovery of soluble group 4 metallocene-based catalysts for the Ziegler-Natta polymerization of olefins has generated considerable interest in the field. In particular, the versatility of the Cp (cyclopentadienyl) ligand has made practical the development of a host of novel catalysts which can produce extremely regiospecific and stereospecific polymers. With further improvements in activity and stability, these catalysts are expected to make a major impact on the polymerization industry. Presently, catalyst design is driven by using the steric and electronic properties of the ligands to guide the monomer addition. However, since these ligands have considerable steric bulk, the choice of solvent will significantly affect their catalytic properties. Therefore, an understanding of the intrinsic reactivity of these catalysts independent of a solvent is one of the first steps to building a better catalyst. The work in progress is a study of the reactivity of zircononene-based catalysts in the gas phase. The authors are in the process of studying the rates of reaction of a series of these compounds with H{sub 2} as well as with a number of olefins. In the gas phase, the intrinsic reactivity of these catalysts is revealed and their chemistry can be studied in detail.

  18. Fatigue Reliability of Gas Turbine Engine Structures

    NASA Technical Reports Server (NTRS)

    Cruse, Thomas A.; Mahadevan, Sankaran; Tryon, Robert G.

    1997-01-01

    The results of an investigation are described for fatigue reliability in engine structures. The description consists of two parts. Part 1 is for method development. Part 2 is a specific case study. In Part 1, the essential concepts and practical approaches to damage tolerance design in the gas turbine industry are summarized. These have evolved over the years in response to flight safety certification requirements. The effect of Non-Destructive Evaluation (NDE) methods on these methods is also reviewed. Assessment methods based on probabilistic fracture mechanics, with regard to both crack initiation and crack growth, are outlined. Limit state modeling techniques from structural reliability theory are shown to be appropriate for application to this problem, for both individual failure mode and system-level assessment. In Part 2, the results of a case study for the high pressure turbine of a turboprop engine are described. The response surface approach is used to construct a fatigue performance function. This performance function is used with the First Order Reliability Method (FORM) to determine the probability of failure and the sensitivity of the fatigue life to the engine parameters for the first stage disk rim of the two stage turbine. A hybrid combination of regression and Monte Carlo simulation is to use incorporate time dependent random variables. System reliability is used to determine the system probability of failure, and the sensitivity of the system fatigue life to the engine parameters of the high pressure turbine. 'ne variation in the primary hot gas and secondary cooling air, the uncertainty of the complex mission loading, and the scatter in the material data are considered.

  19. Insights into the structures of the gas-phase hydrated cations M⁺(H₂O)(n)Ar (M = Li, Na, K, Rb, and Cs; n = 3-5) using infrared photodissociation spectroscopy and thermodynamic analysis.

    PubMed

    Ke, Haochen; van der Linde, Christian; Lisy, James M

    2015-03-12

    The hydration of alkali cations yields a variety of structural conformers with varying numbers of water molecules in the first solvation shell. How these ions move from the aqueous phase into biological systems, such as at the entrance of an ion channel, depends on the interplay between competing intermolecular forces, which first must involve ion-water and water-water interactions. New infrared action spectra, using argon as a messenger or "spy", for Li(+), Na(+), and K(+), with up to five water molecules are reported, and new structural conformers determined from ab initio calculations, combined with previous results on Rb(+) and Cs(+), have identified structural transitions at each hydration level. These transitions are a result of the delicate balance between competing noncovalent interactions and represent a quantitative microscopic view of the macroscopic enthalpy-entropy competition between energy and structural variety. Smaller cations (Li(+) and Na(+)), with higher charge density, yield structural configurations with extended linear networks of hydrogen bonds. Larger cations (Rb(+) and Cs(+)), with lower charge density, generate configurations with cyclic hydrogen-bonded water subunits. It appears that K(+) is somewhat unique, with very simple (and predominantly) single structural conformers. This has led to the suggestion that K(+) can "move" easily in or through biological systems, concealing its identity as an ion, under the "appearance" or disguise of a water molecule. PMID:25651135

  20. Engine exhaust particulate and gas phase contributions to vascular toxicity.

    PubMed

    Campen, Matthew; Robertson, Sarah; Lund, Amie; Lucero, Joann; McDonald, Jacob

    2014-05-01

    Cardiovascular health effects of near-roadway pollution appear more substantial than other sources of air pollution. The underlying cause of this phenomenon may simply be concentration-related, but the possibility remains that gases and particulate matter (PM) may physically interact and further enhance systemic vascular toxicity. To test this, we utilized a common hypercholesterolemic mouse model (Apolipoprotein E-null) exposed to mixed vehicle emission (MVE; combined gasoline and diesel exhausts) for 6 h/d × 50 d, with additional permutations of removing PM by filtration and also removing gaseous species from PM by denudation. Several vascular bioassays, including matrix metalloproteinase-9 protein, 3-nitrotyrosine and plasma-induced vasodilatory impairments, highlighted that the whole emissions, containing both particulate and gaseous components, was collectively more potent than MVE-derived PM or gas mixtures, alone. Thus, we conclude that inhalation of fresh whole emissions induce greater systemic vascular toxicity than either the particulate or gas phase alone. These findings lend credence to the hypothesis that the near-roadway environment may have a more focused public health impact due to gas-particle interactions. PMID:24730681

  1. ENGINE EXHAUST PARTICULATE AND GAS PHASE CONTRIBUTIONS TO VASCULAR TOXICITY

    PubMed Central

    Campen, Matthew; Robertson, Sarah; Lund, Amie; Lucero, Joann; McDonald, Jacob

    2014-01-01

    Cardiovascular health effects of near-roadway pollution appear more substantial than other sources of air pollution. The underlying cause of this phenomenon may simply be concentration-related, but the possibility remains that gases and particulate matter (PM) may physically interact and further enhance systemic vascular toxicity. To test this, we utilized a common hypercholesterolemic mouse model (Apolipoprotein E-null) exposed to mixed vehicular emissions (MVE; combined gasoline and diesel exhausts) for 6 h/d × 50 days, with additional permutations of removing PM by filtration and also removing gaseous species from PM by denudation. Several vascular bioassays, including matrix metalloproteinase 9 (MMP9) protein, 3-nitrotyrosine, and plasma-induced vasodilatory impairments, highlighted that the whole emissions, containing both particulate and gaseous components, was collectively more potent than MVE-derived PM or gas mixtures, alone. Thus, we conclude that inhalation of fresh whole emissions induce greater systemic vascular toxicity than either the particulate or gas phase alone. These findings lend credence to the hypothesis that the near-roadway environment may have a more focused public health impact due to gas-particle interactions. PMID:24730681

  2. Project ARGO: Gas phase formation in simulated microgravity

    NASA Technical Reports Server (NTRS)

    Powell, Michael R.; Waligora, James M.; Norfleet, William T.; Kumar, K. Vasantha

    1993-01-01

    The ARGO study investigated the reduced incidence of joint pain decompression sickness (DCS) encountered in microgravity as compared with an expected incidence of joint pain DCS experienced by test subjects in Earth-based laboratories (unit gravity) with similar protocols. Individuals who are decompressed from saturated conditions usually acquire joint pain DCS in the lower extremities. Our hypothesis is that the incidence of joint pain DCS can be limited by a significant reduction in the tissue gas micronuclei formed by stress-assisted nucleation. Reductions in dynamic and kinetic stresses in vivo are linked to hypokinetic and adynamic conditions of individuals in zero g. We employed the Doppler ultrasound bubble detection technique in simulated microgravity studies to determine quantitatively the degree of gas phase formation in the upper and lower extremities of test subjects during decompression. We found no evidence of right-to-left shunting through pulmonary vasculature. The volume of gas bubble following decompression was examined and compared with the number following saline contrast injection. From this, we predict a reduced incidence of DCS on orbit, although the incidence of predicted mild DCS still remains larger than that encountered on orbit.

  3. Synthesis of Cu nanopowders by condensation from the gas phase

    NASA Astrophysics Data System (ADS)

    Chepkasov, IV; Gafner, Yu Ya; Zobov, K. V.; Batoroev, S. B.; Bardakhanov, S. P.

    2016-02-01

    In order to determine the most efficient regimes of copper nanoparticles synthesis, a series of experiments were conducted by evaporation and subsequent condensation of the raw material in an argon atmosphere. During the tests it was found that an increase of evaporation rate increases significantly the average size of the synthesized particles. However, the study of the dependence of dimensional parameters of the produced clusters on the intensity of the buffer gas flow rate has encountered significant difficulties associated because the results significantly divergent from the previously conducted experiments on the synthesis of transition metal oxides. In order to solve this contradiction the computer simulation was held of copper atoms condensation from the gas phase for the three different cooling rates and for the two final temperatures T = 373 K and T = 77 K. It was found after analysis that the rate of cooling of the gas mixture and the final temperature directly influences the number and the size of particles produced. For instance, with the 10 times of cooling rate decreases the average size of the particles obtained had increased by 2.7 times at a final temperature of 77 K and by 3.1 times at Tf = 373 K.

  4. Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates

    DOE PAGESBeta

    Miskowiec, Andrew J.; Kirkegaard, Marie C.; Huq, Ashfia; Mamontov, Eugene; Herwig, Kenneth W.; Trowbridge, Lee D.; Rondinone, Adam Justin; Anderson, Brian B.

    2015-11-17

    We report a novel production method for uranium oxy uoride [(UO2)7F14(H2O)7] 4H2O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl uoride, UO2F2, through the gas phase at ambient temperatures fol- lowed by desiccation by equilibration with a dry environment. We follow the structure of [(UO2)7F14(H2O)7] 4H2O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous struc- ture), and a water molecule binds as an equatorial ligand to the uranyl ion. Quasielas- tic neutron scattering results compare well with previousmore » measurements of mineral hydrates. The two groups of structurally distinct water molecules in D perform re- stricted motion on a length scale commensurate with the O{H bond (r = 0.92 A). The more tightly bound equatorial ligand waters rotate slower (Dr = 2.2 ps-1) than their hydrogen-bonded partners (Dr = 28.7 ps-1).« less

  5. Structural Phase Transitions and Water Dynamics in Uranyl Fluoride Hydrates

    SciTech Connect

    Miskowiec, Andrew J.; Kirkegaard, Marie C.; Huq, Ashfia; Mamontov, Eugene; Herwig, Kenneth W.; Trowbridge, Lee D.; Rondinone, Adam Justin; Anderson, Brian B.

    2015-11-17

    We report a novel production method for uranium oxy uoride [(UO2)7F14(H2O)7] 4H2O, referred to as structure D. Structure D is produced as a product of hydrating anhydrous uranyl uoride, UO2F2, through the gas phase at ambient temperatures fol- lowed by desiccation by equilibration with a dry environment. We follow the structure of [(UO2)7F14(H2O)7] 4H2O through an intermediate, liquid-like phase, wherein the coordination number of the uranyl ion is reduced to 5 (from 6 in the anhydrous struc- ture), and a water molecule binds as an equatorial ligand to the uranyl ion. Quasielas- tic neutron scattering results compare well with previous measurements of mineral hydrates. The two groups of structurally distinct water molecules in D perform re- stricted motion on a length scale commensurate with the O{H bond (r = 0.92 A). The more tightly bound equatorial ligand waters rotate slower (Dr = 2.2 ps-1) than their hydrogen-bonded partners (Dr = 28.7 ps-1).

  6. Surfactants from the gas phase may promote cloud droplet formation.

    PubMed

    Sareen, Neha; Schwier, Allison N; Lathem, Terry L; Nenes, Athanasios; McNeill, V Faye

    2013-02-19

    Clouds, a key component of the climate system, form when water vapor condenses upon atmospheric particulates termed cloud condensation nuclei (CCN). Variations in CCN concentrations can profoundly impact cloud properties, with important effects on local and global climate. Organic matter constitutes a significant fraction of tropospheric aerosol mass, and can influence CCN activity by depressing surface tension, contributing solute, and influencing droplet activation kinetics by forming a barrier to water uptake. We present direct evidence that two ubiquitous atmospheric trace gases, methylglyoxal (MG) and acetaldehyde, known to be surface-active, can enhance aerosol CCN activity upon uptake. This effect is demonstrated by exposing acidified ammonium sulfate particles to 250 parts per billion (ppb) or 8 ppb gas-phase MG and/or acetaldehyde in an aerosol reaction chamber for up to 5 h. For the more atmospherically relevant experiments, i.e., the 8-ppb organic precursor concentrations, significant enhancements in CCN activity, up to 7.5% reduction in critical dry diameter for activation, are observed over a timescale of hours, without any detectable limitation in activation kinetics. This reduction in critical diameter enhances the apparent particle hygroscopicity up to 26%, which for ambient aerosol would lead to cloud droplet number concentration increases of 8-10% on average. The observed enhancements exceed what would be expected based on Köhler theory and bulk properties. Therefore, the effect may be attributed to the adsorption of MG and acetaldehyde to the gas-aerosol interface, leading to surface tension depression of the aerosol. We conclude that gas-phase surfactants may enhance CCN activity in the atmosphere. PMID:23382211

  7. Feasibility of gas-phase decontamination of gaseous diffusion equipment

    SciTech Connect

    Munday, E.B.; Simmons, D.W.

    1993-02-01

    The five buildings at the K-25 Site formerly involved in the gaseous diffusion process contain 5000 gaseous diffusion stages as well as support facilities that are internally contaminated with uranium deposits. The gaseous diffusion facilities located at the Portsmouth Gaseous Diffusion Plant and the Paducah Gaseous Diffusion Plant also contain similar equipment and will eventually close. The decontamination of these facilities will require the most cost-effective technology consistent with the criticality, health physics, industrial hygiene, and environmental concerns; the technology must keep exposures to hazardous substances to levels as low as reasonably achievable (ALARA). This report documents recent laboratory experiments that were conducted to determine the feasibility of gas-phase decontamination of the internal surfaces of the gaseous diffusion equipment that is contaminated with uranium deposits. A gaseous fluorinating agent is used to fluorinate the solid uranium deposits to gaseous uranium hexafluoride (UF{sub 6}), which can be recovered by chemical trapping or freezing. The lab results regarding the feasibility of the gas-phase process are encouraging. These results especially showed promise for a novel decontamination approach called the long-term, low-temperature (LTLT) process. In the LTLT process: The equipment is rendered leak tight, evacuated, leak tested, and pretreated, charged with chlorine trifluoride (ClF{sub 3}) to subatmospheric pressure, left for an extended period, possibly > 4 months, while processing other items. Then the UF{sub 6} and other gases are evacuated. The UF{sub 6} is recovered by chemical trapping. The lab results demonstrated that ClF{sub 3} gas at subatmospheric pressure and at {approx} 75{degree}F is capable of volatilizing heavy deposits of uranyl fluoride from copper metal surfaces sufficiently that the remaining radioactive emissions are below limits.

  8. CASCADER: An M-chain gas-phase radionuclide transport and fate model. Volume 4 -- Users guide to CASCADR9

    SciTech Connect

    Cawlfield, D.E.; Emer, D.F.; Lindstrom, F.T.; Shott, G.J.

    1993-09-01

    Chemicals and radionuclides move either in the gas-phase, liquid-phase, or both phases in soils. They may be acted upon by either biological or abiotic processes through advection and/or dispersion. Additionally during the transport of parent and daughter radionuclides in soil, radionuclide decay may occur. This version of CASCADER called CASCADR9 starts with the concepts presented in volumes one and three of this series. For a proper understanding of how the model works, the reader should read volume one first. Also presented in this volume is a set of realistic scenarios for buried sources of radon gas, and the input and output file structure for CASCADER9.

  9. Phase transitions in a 3 dimensional lattice loop gas

    NASA Astrophysics Data System (ADS)

    MacKenzie, Richard; Nebia-Rahal, F.; Paranjape, M. B.

    2010-06-01

    We investigate, via Monte Carlo simulations, the phase structure of a system of closed, nonintersecting but otherwise noninteracting, loops in 3 Euclidean dimensions. The loops correspond to closed trajectories of massive particles and we find a phase transition as a function of their mass. We identify the order parameter as the average length of the loops at equilibrium. This order parameter exhibits a sharp increase as the mass is decreased through a critical value, the behavior seems to be a crossover transition. We believe that the model represents an effective description of the broken-symmetry sector of the 2+1 dimensional Abelian Higgs model, in the extreme strong coupling limit. The massive gauge bosons and the neutral scalars are decoupled, and the relevant low-lying excitations correspond to vortices and antivortices. The functional integral can be approximated by a sum over simple, closed vortex loop configurations. We present a novel fashion to generate nonintersecting closed loops, starting from a tetrahedral tessellation of three space. The two phases that we find admit the following interpretation: the usual Higgs phase and a novel phase which is heralded by the appearance of effectively infinitely long loops. We compute the expectation value of the Wilson loop operator and that of the Polyakov loop operator. The Wilson loop exhibits perimeter law behavior in both phases implying that the transition corresponds neither to the restoration of symmetry nor to confinement. The effective interaction between external charges is screened in both phases, however there is a dramatic increase in the polarization cloud in the novel phase as shown by the energy shift introduced by the Wilson loop.

  10. Gas-phase Ion Isomer Analysis Reveals the Mechanism of Peptide Sequence Scrambling

    PubMed Central

    Jia, Chenxi; Wu, Zhe; Lietz, Christopher B.; Liang, Zhidan; Cui, Qiang; Li, Lingjun

    2014-01-01

    Peptide sequence scrambling during mass spectrometry-based gas-phase fragmentation analysis causes misidentification of peptides and proteins. Thus, there is a need to develop an efficient approach to probing the gas-phase fragment ion isomers related to sequence scrambling and the underlying fragmentation mechanism, which will facilitate the development of bioinformatics algorithm for proteomics research. Herein, we report on the first use of electron transfer dissociation (ETD)-produced diagnostic fragment ions to probe the components of gas-phase peptide fragment ion isomers. In combination with ion mobility spectrometry (IMS) and formaldehyde labeling, this novel strategy enables qualitative and quantitative analysis of b-type fragment ion isomers. ETD fragmentation produced diagnostic fragment ions indicative of the precursor ion isomer components, and subsequent IMS analysis of b ion isomers provided their quantitative and structural information. The isomer components of three representative b ions (b9, b10, and b33 from three different peptides) were accurately profiled by this method. IMS analysis of the b9 ion isomers exhibited dynamic conversion among these structures. Furthermore, molecular dynamics simulation predicted theoretical drift time values which were in good agreement with experimentally measured values. Our results strongly support the mechanism of peptide sequence scrambling via b ion cyclization, and provide the first experimental evidence to support that the conversion from molecular precursor ion to cyclic b ion (M→cb) pathway is less energetically (or kinetically) favored. PMID:24313304

  11. The use of gas-phase substrates to study enzyme catalysis at low hydration.

    PubMed Central

    Dunn, Rachel V; Daniel, Roy M

    2004-01-01

    Although there are varying estimates as to the degree of enzyme hydration required for activity, a threshold value of ca. 0.2 g of water per gram of protein has been widely accepted. The evidence upon which this is based is reviewed here. In particular, results from the use of gas-phase substrates are discussed. Results using solid-phase enzyme-substrate mixtures are not altogether in accord with those obtained using gas-phase substrates. The use of gaseous substrates and products provides an experimental system in which the hydration of the enzyme can be easily controlled, but which is not limited by diffusion. All the results show that increasing hydration enhances activity. The results using gas-phase substrates do not support the existence of a critical hydration value below which enzymatic activity is absent, and suggest that enzyme activity is possible at much lower hydrations than previously thought; they do not support the notion that significant hydration of the surface polar groups is required for activity. However, the marked improvement of activity as hydration is increased suggests that water does play a role, perhaps in optimizing the structure or facilitating the flexibility required for maximal activity. PMID:15306385

  12. Elusive Sulfurous Acid: Gas-Phase Basicity and IR Signature of the Protonated Species.

    PubMed

    Sinha, Rajeev K; Scuderi, Debora; Maitre, Philippe; Chiavarino, Barbara; Crestoni, Maria Elisa; Fornarini, Simonetta

    2015-05-01

    The ion corresponding to protonated sulfurous acid, H3SO3(+), has been successfully delivered into the gas phase by electrospray ionization of the solution of a suitable precursor and an in-source fragmentation process. The neutral acid is a highly elusive molecule. However, its gas-phase basicity has been ascertained by means of a kinetic study of proton-transfer reactivity. The structure of the H3SO3(+) sampled ion has been probed by IRMPD spectroscopy in two complementary IR frequency ranges in conjunction with density functional theory calculations and found to conform to a trihydroxosulfonium ion. The characteristic IR signatures may aid in deciphering the presence of this species in extraterrestrial atmospheres. PMID:26263321

  13. Transport simulations of the pre-thermal-quench phase in ASDEX Upgrade massive gas injection experiments

    NASA Astrophysics Data System (ADS)

    Fable, E.; Pautasso, G.; Lehnen, M.; Dux, R.; Bernert, M.; Mlynek, A.; the ASDEX Upgrade Team

    2016-02-01

    The pre-thermal-quench (PTQ) phase of the massive gas injection (MGI) scenario to terminate the tokamak plasma discharge is studied by means of one-dimensional (1D) transport simulations. This phase is characterized by the cold-front penetration in the hot plasma after the gas has been released from the valves, and before the actual thermal quench takes place, with consequent plasma disruption at lower stored energy. The comparison between the simulations and the ASDEX Upgrade (AUG) experiments allows to gain insight in the observed dependencies and time scales. Despite the genuine three-dimensional structure of the problem, it is shown that the 1D simulations are already giving experimentally relevant answers, the reason for which will be discussed in detail. Influence of unknown parameters and simplifying assumptions are also discussed.

  14. DYNAMIC MODELING STRATEGY FOR FLOW REGIME TRANSITION IN GAS-LIQUID TWO-PHASE FLOWS

    SciTech Connect

    X. Wang; X. Sun; H. Zhao

    2011-09-01

    In modeling gas-liquid two-phase flows, the concept of flow regime has been used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are often flow regime dependent. Currently, the determination of the flow regimes is primarily based on flow regime maps or transition criteria, which are developed for steady-state, fully-developed flows and widely applied in nuclear reactor system safety analysis codes, such as RELAP5. As two-phase flows are observed to be dynamic in nature (fully-developed two-phase flows generally do not exist in real applications), it is of importance to model the flow regime transition dynamically for more accurate predictions of two-phase flows. The present work aims to develop a dynamic modeling strategy for determining flow regimes in gas-liquid two-phase flows through the introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation and destruction of the interfacial area, such as the fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation; and fluid particle coalescence and condensation, respectively. For the flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shape (which are correlated), namely small bubbles and large bubbles. A preliminary approach to dynamically identifying the flow regimes is provided, in which discriminators are based on the predicted information, such as the void fraction and interfacial area concentration of small bubble and large bubble groups. This method is expected to be applied to computer codes to improve their predictive capabilities of gas-liquid two-phase flows, in particular for the applications in

  15. Carbon and Noble Gas Isotope Banks in Two-Phase Flow: Changes in Gas Composition During Migration

    NASA Astrophysics Data System (ADS)

    Sathaye, K.; Larson, T.; Hesse, M. A.

    2015-12-01

    In conjunction with the rise of unconventional oil and gas production, there has been a recent rise in interest in noble gas and carbon isotope changes that can occur during the migration of natural gas. Natural gas geochemistry studies use bulk hydrocarbon composition, carbon isotopes, and noble gas isotopes to determine the migration history of gases from source to reservoir, and to trace fugitive gas leaks from reservoirs to shallow groundwater. We present theoretical and experimental work, which helps to explain trends observed in gas composition in various migration scenarios. Noble gases are used as tracers for subsurface fluid flow due to distinct initial compositions in air-saturated water and natural gases. Numerous field studies have observed enrichments and depletions of noble gases after gas-water interaction. A theoretical two-phase gas displacement model shows that differences in noble gas solubility will cause volatile gas components will become enriched at the front of gas plumes, leaving the surrounding residual water stripped of dissolved gases. Changes in hydrocarbon gas composition are controlled by gas solubility in both formation water and residual oil. In addition to model results, we present results from a series of two-phase flow experiments. These results demonstrate the formation of a noble gas isotope banks ahead of a main CO2 gas plume. Additionally, we show that migrating hydrocarbon gas plumes can sweep biogenic methane from groundwater, significantly altering the isotope ratio of the gas itself. Results from multicomponent, two-phase flow experiments qualitatively agree with the theoretical model, and previous field studies. These experimentally verified models for gas composition changes can be used to aid source identification of subsurface gases.

  16. Detection of unknown gas-phase chemical plumes in hyperspectral imagery

    NASA Astrophysics Data System (ADS)

    Theiler, James; Wohlberg, Brendt

    2013-05-01

    Gas-phase chemical plumes exhibit, particularly in the infrared, distinctive emission signatures as a function of wavelength. Hyperspectral imagery can exploit this distinctiveness to detect specific chemicals, even at low concentrations, using matched filters that are tailored both the the specific structure of the chemical signature and to the statistics of the background clutter. But what if the chemical species is unknown? One can apply matched filters to a long list of candidate chemicals (or chemical mixtures), or one can treat the problem as one of anomaly detection. In this case, however, the anomalous signals of interest are not completely unknown. Gas spectra are generically sparse (absorbing or emitting at only a few wavelengths), and this property can be exploited to enhance the sensitivity of anomaly detection algorithms. This paper investigates the utility of sparse signal anomaly detection for the problem of finding plumes of gas with unknown chemistry in hyperspectral imagery.

  17. Structure analysis of turbulent liquid phase by POD and LSE techniques

    SciTech Connect

    Munir, S. Muthuvalu, M. S.; Siddiqui, M. I.; Heikal, M. R. Aziz, A. Rashid A.

    2014-10-24

    In this paper, vortical structures and turbulence characteristics of liquid phase in both single liquid phase and two-phase slug flow in pipes were studied. Two dimensional velocity vector fields of liquid phase were obtained by Particle image velocimetry (PIV). Two cases were considered one single phase liquid flow at 80 l/m and second slug flow by introducing gas at 60 l/m while keeping liquid flow rate same. Proper orthogonal decomposition (POD) and Linear stochastic estimation techniques were used for the extraction of coherent structures and analysis of turbulence in liquid phase for both cases. POD has successfully revealed large energy containing structures. The time dependent POD spatial mode coefficients oscillate with high frequency for high mode numbers. The energy distribution of spatial modes was also achieved. LSE has pointed out the coherent structured for both cases and the reconstructed velocity fields are in well agreement with the instantaneous velocity fields.

  18. Specific, trace gas induced phase transition in copper(II)oxide for highly selective gas sensing

    NASA Astrophysics Data System (ADS)

    Kneer, J.; Wöllenstein, J.; Palzer, S.

    2014-08-01

    Here, we present results on the investigation of the percolation phase transition in copper(II)oxide (CuO) and show how it may be used to determine trace gas concentrations. This approach provides a highly selective sensing mechanism for the detection of hydrogen sulfide even in oxygen depleted atmospheres. In real-world applications, this scenario is encountered in biogas plants and natural gas facilities, where reliable H2S sensing and filtering are important because of the destructive effects H2S has on machinery. As opposed to gas detection via standard metal-oxide reaction routes, the percolation dynamics are demonstrated to be independent of the surface morphology in accordance with the universality of phase transitions. The sensing behavior of ink-jet printed CuO layers was tested for a large set of parameters including layer temperature, hydrogen sulfide (H2S) and oxygen concentration, as well as the sensitivity towards other gas species. The electrical percolation of the sensing layer is heralded by a dramatic drop in the overall resistivity of the CuO layer for temperatures below 200 °C. The observed percolation phenomena in this temperature regime are unique to H2S even in comparison with related volatile thio-compounds making the sensing mechanism highly selective. At elevated temperatures above 300 °C, the phase transition does not occur. This enables two distinct operational modes which are tunable via the sensor temperature and also allows for resetting the sensing layer after an electrical breakthrough.

  19. Macromolecular structure phasing by neutron anomalous diffraction

    PubMed Central

    Cuypers, Maxime G.; Mason, Sax A.; Mossou, Estelle; Haertlein, Michael; Forsyth, V. Trevor; Mitchell, Edward P.

    2016-01-01

    In this report we show for the first time that neutron anomalous dispersion can be used in a practical manner to determine experimental phases of a protein crystal structure, providing a new tool for structural biologists. The approach is demonstrated through the use of a state-of-the-art monochromatic neutron diffractometer at the Institut Laue-Langevin (ILL) in combination with crystals of perdeuterated protein that minimise the level of hydrogen incoherent scattering and enhance the visibility of the anomalous signal. The protein used was rubredoxin in which cadmium replaced the iron at the iron-sulphur site. While this study was carried out using a steady-state neutron beam source, the results will be of major interest for capabilities at existing and emerging spallation neutron sources where time-of-flight instruments provide inherent energy discrimination. In particular this capability may be expected to offer unique opportunities to a rapidly developing structural biology community where there is increasing interest in the identification of protonation states, protein/water interactions and protein-ligand interactions – all of which are of central importance to a wide range of fundamental and applied areas in the biosciences. PMID:27511806

  20. Macromolecular structure phasing by neutron anomalous diffraction.

    PubMed

    Cuypers, Maxime G; Mason, Sax A; Mossou, Estelle; Haertlein, Michael; Forsyth, V Trevor; Mitchell, Edward P

    2016-01-01

    In this report we show for the first time that neutron anomalous dispersion can be used in a practical manner to determine experimental phases of a protein crystal structure, providing a new tool for structural biologists. The approach is demonstrated through the use of a state-of-the-art monochromatic neutron diffractometer at the Institut Laue-Langevin (ILL) in combination with crystals of perdeuterated protein that minimise the level of hydrogen incoherent scattering and enhance the visibility of the anomalous signal. The protein used was rubredoxin in which cadmium replaced the iron at the iron-sulphur site. While this study was carried out using a steady-state neutron beam source, the results will be of major interest for capabilities at existing and emerging spallation neutron sources where time-of-flight instruments provide inherent energy discrimination. In particular this capability may be expected to offer unique opportunities to a rapidly developing structural biology community where there is increasing interest in the identification of protonation states, protein/water interactions and protein-ligand interactions - all of which are of central importance to a wide range of fundamental and applied areas in the biosciences. PMID:27511806

  1. Application of Phase-field Method in Predicting Gas Bubble Microstructure Evolution in Nuclear Fuels

    SciTech Connect

    Hu, Shenyang Y.; Li, Yulan; Sun, Xin; Gao, Fei; Devanathan, Ramaswami; Henager, Charles H.; Khaleel, Mohammad A.

    2010-04-30

    Fission product accumulation and gas bubble microstructure evolution in nuclear fuels strongly affect thermo-mechanical properties such as thermal conductivity, gas release, volumetric swelling and cracking, and hence the fuel performance. In this paper, a general phase-field model is developed to predict gas bubble formation and evolution. Important materials processes and thermodynamic properties including the generation of gas atoms and vacancies, sinks for vacancies and gas atoms, the elastic interaction among defects, gas re-solution, and inhomogeneity of elasticity and diffusivity are accounted for in the model. The simulations demonstrate the potential application of the phase-field method in investigating 1) heterogeneous nucleation of gas bubbles at defects; 2) effect of elastic interaction, inhomogeneity of material properties, and gas re-solution on gas bubble microstructures; and 3) effective properties from the output of phase-field simulations such as distribution of defects, gas bubbles, and stress fields.

  2. Native like helices in a specially designed β peptide in the gas phase.

    PubMed

    Schubert, Franziska; Pagel, Kevin; Rossi, Mariana; Warnke, Stephan; Salwiczek, Mario; Koksch, Beate; von Helden, Gert; Blum, Volker; Baldauf, Carsten; Scheffler, Matthias

    2015-02-21

    In the natural peptides, helices are stabilized by hydrogen bonds that point backward along the sequence direction. Until now, there is only little evidence for the existence of analogous structures in oligomers of conformationally unrestricted β amino acids. We specifically designed the β peptide Ac-(β(2)hAla)6-LysH(+) to form native like helical structures in the gas phase. The design follows the known properties of the peptide Ac-Ala6-LysH(+) that forms a α helix in isolation. We perform ion-mobility mass-spectrometry and vibrational spectroscopy in the gas phase, combined with state-of-the-art density-functional theory simulations of these molecular systems in order to characterize their structure. We can show that the straightforward exchange of alanine residues for the homologous β amino acids generates a system that is generally capable of adopting native like helices with backward oriented H-bonds. By pushing the limits of theory and experiments, we show that one cannot assign a single preferred structure type due to the densely populated energy landscape and present an interpretation of the data that suggests an equilibrium of three helical structures. PMID:25611682

  3. Conformational Study of Taurine in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Cortijo, Vanessa; Sanz, M. Eugenia; López, Juan C.; Alonso, José L.

    2009-08-01

    The conformational preferences of the amino sulfonic acid taurine (NH2-CH2-CH2-SO3H) have been investigated in the gas phase by laser ablation molecular beam Fourier transform microwave spectroscopy (LA-MB-FTMW) in the 6-14 GHz frequency range. One conformer has been observed, and its rotational, centrifugal distortion, and hyperfine quadrupole coupling constants have been determined from the analysis of its rotational spectrum. Comparison of the experimental constants with those calculated theoretically identifies the detected conformer unambiguously. The observed conformer of taurine is stabilized by an intramolecular hydrogen bond O-H···N between the hydrogen of the sulfonic acid group and the nitrogen atom of the amino group.

  4. Gas-phase synthesis of magnetic metal/polymer nanocomposites.

    PubMed

    Starsich, Fabian H L; Hirt, Ann M; Stark, Wendelin J; Grass, Robert N

    2014-12-19

    Highly magnetic metal Co nanoparticles were produced via reducing flame spray pyrolysis, and directly coated with an epoxy polymer in flight. The polymer content in the samples varied between 14 and 56 wt% of nominal content. A homogenous dispersion of Co nanoparticles in the resulting nanocomposites was visualized by electron microscopy. The size and crystallinity of the metallic fillers was not affected by the polymer, as shown by XRD and magnetic hysteresis measurements. The good control of the polymer content in the product nanocomposite was shown by elemental analysis. Further, the successful polymerization in the gas phase was demonstrated by electron microscopy and size measurements. The presented effective, dry and scalable one-step synthesis method for highly magnetic metal nanoparticle/polymer composites presented here may drastically decrease production costs and increase industrial yields. PMID:25422410

  5. Reduced-background gas-phase absorption spectroscopy.

    PubMed

    Sweetser, J N; Trebino, R

    1998-08-15

    We propose and demonstrate a new method for single-shot multiplex absorption spectroscopy that permits enhanced sensitivity in the simultaneous measurement of multiple spectral lines in rapidly changing gas-phase media, such as turbulent flames. It uses an ultrashort laser pulse that propagates through the absorbing medium, for which the relevant absorption information resides in the free-induction decay that is trailing behind the transmitted pulse. Time gating out most of the transmitted pulse, but not the free-induction decay, enhances the relative fraction of light that contains absorption information when the spectrum is measured. This procedure reduces the background associated with the input light, thus enhancing detection sensitivity. PMID:18087501

  6. Dissociative attachment reactions of electrons with gas phase superacids

    SciTech Connect

    Liu, X.

    1992-01-01

    Using the flowing afterglow Langmuir probe (FALP) technique, dissociative attachment coefficients [beta] for reactions of electrons with gas phase superacids HCo(PF[sub 3])[sub 4], HRh(PF[sub 3])[sub 4] and carbonyl hydride complexes HMn(CO)[sub 5], HRe(CO)[sub 5] have been determined under thermal conditions over the approximate temperature range 300[approximately]550 K. The superacids react relatively slowly (<1/20 of [beta][sub max]) with free electrons in a thermal plasma, and the values of [beta] obtained this far do not show a correlation between acidity and [beta]. The pioneer researchers in this field had speculated that any superacid would be a rapid attacher of electrons; it was found that this speculation is not true in general. The product distribution of electron attachment reaction to HCo(PF[sub 3])[sub 4] was found to be independent of temperature even though the [beta][HCo(PF[sub 3])[sub 4

  7. Silicon Nanowire-Based Devices for Gas-Phase Sensing

    PubMed Central

    Cao, Anping; Sudhölter, Ernst J.R.; de Smet, Louis C.P.M.

    2014-01-01

    Since their introduction in 2001, SiNW-based sensor devices have attracted considerable interest as a general platform for ultra-sensitive, electrical detection of biological and chemical species. Most studies focus on detecting, sensing and monitoring analytes in aqueous solution, but the number of studies on sensing gases and vapors using SiNW-based devices is increasing. This review gives an overview of selected research papers related to the application of electrical SiNW-based devices in the gas phase that have been reported over the past 10 years. Special attention is given to surface modification strategies and the sensing principles involved. In addition, future steps and technological challenges in this field are addressed. PMID:24368699

  8. Regenerable Air Purification System for Gas-Phase Contaminant Control

    NASA Technical Reports Server (NTRS)

    Constantinescu, Ileana C.; Qi, Nan; LeVan, M. Douglas; Finn, Cory K.; Finn, John E.; Luna, Bernadette (Technical Monitor)

    2000-01-01

    A regenerable air purification system (RAPS) that uses water vapor to displace adsorbed contaminants from an. adsorbent column into a closed oxidation loop is under development through cooperative R&D between Vanderbilt University and NASA Ames Research Center. A unit based on this design can be used for removing trace gas-phase contaminants from spacecraft cabin air or from polluted process streams including incinerator exhaust. Recent work has focused on fabrication and operation of a RAPS breadboard at NASA Ames, and on measurement of adsorption isotherm data for several important organic compounds at Vanderbilt. These activities support the use and validation of RAPS modeling software also under development at Vanderbilt, which will in turn be used to construct a prototype system later in the project.

  9. Regenerable Air Purification System for Gas-Phase Contaminant Control

    NASA Technical Reports Server (NTRS)

    Constantinescu, Ileana C.; Finn, John E.; LeVan, M. Douglas; Lung, Bernadette (Technical Monitor)

    2000-01-01

    Tests of a pre-prototype regenerable air purification system (RAPS) that uses water vapor to displace adsorbed contaminants from an adsorbent column have been performed at NASA Ames Research Center. A unit based on this design can be used for removing trace gas-phase contaminants from spacecraft cabin air or from polluted process streams including incinerator exhaust. During the normal operation mode, contaminants are removed from the air on the column. Regeneration of the column is performed on-line. During regeneration, contaminants are displaced and destroyed inside the closed oxidation loop. In this presentation we discuss initial experimental results for the performance of RAPS in the removal and treatment of several important spacecraft contaminant species from air.

  10. Synthesis and Gas Phase Thermochemistry of Germanium-Containing Compounds

    SciTech Connect

    Nathan Robert Classen

    2002-12-31

    The driving force behind much of the work in this dissertation was to gain further understanding of the unique olefin to carbene isomerization observed in the thermolysis of 1,1-dimethyl-2-methylenesilacyclobutane by finding new examples of it in other silicon and germanium compounds. This lead to the examination of a novel phenylmethylenesilacyclobut-2-ene, which did not undergo olefin to carbene rearrangement. A synthetic route to methylenegermacyclobutanes was developed, but the methylenegermacyclobutane system exhibited kinetic instability, making the study of the system difficult. In any case the germanium system decomposed through a complex mechanism which may not include olefin to carbene isomerization. However, this work lead to the study of the gas phase thermochemistry of a series of dialkylgermylene precursors in order to better understand the mechanism of the thermal decomposition of dialkylgermylenes. The resulting dialkylgermylenes were found to undergo a reversible intramolecular {beta} C-H insertion mechanism.

  11. Surfactants from the gas phase may promote cloud droplet formation

    PubMed Central

    Sareen, Neha; Schwier, Allison N.; Lathem, Terry L.; Nenes, Athanasios; McNeill, V. Faye

    2013-01-01

    Clouds, a key component of the climate system, form when water vapor condenses upon atmospheric particulates termed cloud condensation nuclei (CCN). Variations in CCN concentrations can profoundly impact cloud properties, with important effects on local and global climate. Organic matter constitutes a significant fraction of tropospheric aerosol mass, and can influence CCN activity by depressing surface tension, contributing solute, and influencing droplet activation kinetics by forming a barrier to water uptake. We present direct evidence that two ubiquitous atmospheric trace gases, methylglyoxal (MG) and acetaldehyde, known to be surface-active, can enhance aerosol CCN activity upon uptake. This effect is demonstrated by exposing acidified ammonium sulfate particles to 250 parts per billion (ppb) or 8 ppb gas-phase MG and/or acetaldehyde in an aerosol reaction chamber for up to 5 h. For the more atmospherically relevant experiments, i.e., the 8-ppb organic precursor concentrations, significant enhancements in CCN activity, up to 7.5% reduction in critical dry diameter for activation, are observed over a timescale of hours, without any detectable limitation in activation kinetics. This reduction in critical diameter enhances the apparent particle hygroscopicity up to 26%, which for ambient aerosol would lead to cloud droplet number concentration increases of 8–10% on average. The observed enhancements exceed what would be expected based on Köhler theory and bulk properties. Therefore, the effect may be attributed to the adsorption of MG and acetaldehyde to the gas–aerosol interface, leading to surface tension depression of the aerosol. We conclude that gas-phase surfactants may enhance CCN activity in the atmosphere. PMID:23382211

  12. Thermodynamics for a hadronic gas of fireballs with internal color structures and chiral fields

    SciTech Connect

    Zakout, Ismail; Greiner, Carsten

    2008-09-15

    The thermodynamic partition function for a gas of color-singlet bags consisting of fundamental and adjoint particles in both U(N{sub c}) and SU(N{sub c}) group representations is reviewed in detail. The constituent particle species are assumed to satisfy various thermodynamic statistics. The gas of bags is probed to study the phase transition for nuclear matter in extreme conditions. These bags are interpreted as the Hagedorn states, and they are the highly excited hadronic states produced below the phase transition point to the quark-gluon plasma (QGP). The hadronic density of states has the Gross-Witten critical point and exhibits a third-order phase transition from a hadronic phase dominated by the discrete low-lying hadronic mass spectrum particles to another hadronic phase dominated by the continuous Hagedorn states. The Hagedorn threshold production is found just above the highest known experimental discrete low-lying hadronic mass spectrum. The subsequent Hagedorn phase undergoes a first-order deconfinement phase transition to an explosive QGP. The role of the chiral phase transition in the phases of the discrete low-lying mass spectrum and the continuous Hagedorn mass spectrum is also considered. It is found to be crucial in the phase transition diagram. Alternative scenarios are briefly discussed for the Hagedorn gas undergoing a higher order phase transition through multiple processes of internal color-flavor structure modification.

  13. Hydration of potassiated amino acids in the gas phase.

    PubMed

    Wincel, Henryk

    2007-12-01

    The thermochemistry of stepwise hydration of several potassiated amino acids was studied by measuring the gas-phase equilibria, AAK(+)(H(2)O)(n-1) + H(2)O = AAK(+)(H(2)O)(n) (AA = Gly, AL, Val, Met, Pro, and Phe), using a high-pressure mass spectrometer. The AAK(+) ions were obtained by electrospray and the equilibrium constants K(n-1,n) were measured in a pulsed reaction chamber at 10 mbar bath gas, N(2), containing a known partial pressure of water vapor. Determination of the equilibrium constants at different temperatures was used to obtain the DeltaH(n)(o), DeltaS(n)(o), and DeltaG(n)(o) values. The results indicate that the water binding energy in AAK(+)(H(2)O) decreases as the K(+) affinity to AA increases. This trend in binding energies is explained in terms of changes in the side-chain substituent, which delocalize the positive charge from K(+) to AA in AAK(+) complexes, varying the AAK(+)-H(2)O electrostatic interaction. PMID:17928233

  14. Gas phase chromatography of halides of elements 104 and 105

    SciTech Connect

    Tuerler, A.; Gregorich, K.E.; Czerwinski, K.R.; Hannink, N.J.; Henderson, R.A.; Hoffman, D.C.; Kacher, C.D.; Kadkhodayan, B.; Kreek, S.A.; Lee, D.M.; Leyba, J.D.; Nurmia, M.J. ); Gaeggeler, H.W.; Jost, D.T.; Kovacs, J.; Scherer, U.W.; Vermeulen, D.; Weber, A. , Villigen ); Barth, H.; Gober, M.K.; Kratz, J.V. (Philipps-Univ., Marburg

    1991-04-01

    On-line isothermal gas phase chromatography was used to study halides of {sup 261}104 (T{sub {1/2}} = 65 s) and {sup 262,263}105 (T{sub {1/2}} = 34 s and 27 s) produced an atom-at-a time via the reactions {sup 248}Cm({sup 18}O, 5n) and {sup 249}Bk({sup 18}O, 5n, 4n), respectively. Using HBr and HCl gas as halogenating agents, we were able to produce volatile bromides and chlorides of the above mentioned elements and study their behavior compared to their lighter homologs in Groups 4 or 5 of the periodic table. Element 104 formed more volatile bromides than its homolog Hf. In contrast, element 105 bromides were found to be less volatile than the bromides of the group 5 elements Nb and Ta. Both 104 and Hf chlorides were observed to be more volatile than their respective bromides. 31 refs., 8 figs.

  15. Gas phase plasma impact on phenolic compounds in pomegranate juice.

    PubMed

    Herceg, Zoran; Kovačević, Danijela Bursać; Kljusurić, Jasenka Gajdoš; Jambrak, Anet Režek; Zorić, Zoran; Dragović-Uzelac, Verica

    2016-01-01

    The aim of the study was to evaluate the effect of gas phase plasma on phenolic compounds in pomegranate juice. The potential of near infrared reflectance spectroscopy combined with partial least squares for monitoring the stability of phenolic compounds during plasma treatment was explored, too. Experiments are designed to investigate the effect of plasma operating conditions (treatment time 3, 5, 7 min; sample volume 3, 4, 5 cm(3); gas flow 0.75, 1, 1.25 dm(3) min(-1)) on phenolic compounds and compared to pasteurized and untreated pomegranate juice. Pasteurization and plasma treatment resulted in total phenolic content increasing by 29.55% and 33.03%, respectively. Principal component analysis and sensitivity analysis outputted the optimal treatment design with plasma that could match the pasteurized sample concerning the phenolic stability (5 min/4 cm(3)/0.75 dm(3) min(-1)). Obtained results demonstrate the potential of near infrared reflectance spectroscopy that can be successfully used to evaluate the quality of pomegranate juice upon plasma treatment considering the phenolic compounds. PMID:26213024

  16. Gas phase hydrogen permeation in alpha titanium and carbon steels

    NASA Technical Reports Server (NTRS)

    Johnson, D. L.; Shah, K. K.; Reeves, B. H.; Gadgeel, V. L.

    1980-01-01

    Commercially pure titanium and heats of Armco ingot iron and steels containing from 0.008-1.23 w/oC were annealed or normalized and machined into hollow cylinders. Coefficients of diffusion for alpha-Ti and alpha-Fe were determined by the lag-time technique. Steady state permeation experiments yield first power pressure dependence for alpha-Ti and Sievert's law square root dependence for Armco iron and carbon steels. As in the case of diffusion, permeation data confirm that alpha-titanium is subject to at least partial phase boundary reaction control while the steels are purely diffusion controlled. The permeation rate in steels also decreases as the carbon content increases. As a consequence of Sievert's law, the computed hydrogen solubility decreases as the carbon content increases. This decreases in explained in terms of hydrogen trapping at carbide interfaces. Oxidizing and nitriding the surfaces of alpha-titanium membranes result in a decrease in the permeation rate for such treatment on the gas inlet surfaces but resulted in a slight increase in the rate for such treatment on the gas outlet surfaces. This is explained in terms of a discontinuous TiH2 layer.

  17. Tracking Gas Phase Composition in Oil evaporation and Oxidation Experiments

    NASA Astrophysics Data System (ADS)

    Amador-Muñoz, O.; Zhang, H.; Misztal, P. K.; Worton, D.; Drozd, G.; Goldstein, A. H.

    2015-12-01

    Primary Organic Aerosol (POA) is emitted directly by anthropogenic or natural sources, whereas Secondary Organic Aerosol (SOA) is formed in the atmosphere through chemical reactions that result from conversion of more volatile species into lower volatility oxidized products and their subsequent condensation to the particulate phase. We studied SOA formation from evaporation of Macondo crude oil (MC 252) using a wind tunnel coupled to a flow tube oxidation reactor. Ozone, UV lights, and water vapor were used to make OH radicals. Organic compounds in the gas phase, both those evaporated from the wind tunnel and those formed in the flow tube oxidation experiments, were monitored using proton-transfer-reaction mass spectrometry (PTR-qMS and PTR-TOF-MS). We observed approximately 400 different species. Compounds with less than C10 were mostly evaporated in the first 5 hours when maximum SOA formation was also obtained. Hydrocarbons with carbon number (11-14) were still present in the oil after 12 h of continuous evaporation at wind speed of 2 m s-1. We will show the implications of these results for the production of SOA related to the range of evaporated chemical size and reactivity.

  18. Full field gas phase velocity measurements in microgravity

    NASA Technical Reports Server (NTRS)

    Griffin, Devon W.; Yanis, William

    1995-01-01

    Measurement of full-field velocities via Particle Imaging Velocimetry (PIV) is common in research efforts involving fluid motion. While such measurements have been successfully performed in the liquid phase in a microgravity environment, gas-phase measurements have been beset by difficulties with seeding and laser strength. A synthesis of techniques developed at NASA LeRC exhibits promise in overcoming these difficulties. Typical implementation of PIV involves forming the light from a pulsed laser into a sheet that is some fraction of a millimeter thick and 50 or more millimeters wide. When a particle enters this sheet during a pulse, light scattered from the particle is recorded by a detector, which may be a film plane or a CCD array. Assuming that the particle remains within the boundaries of the sheet for the second pulse and can be distinguished from neighboring particles, comparison of the two images produces an average velocity vector for the time between the pulses. If the concentration of particles in the sampling volume is sufficiently large but the particles remain discrete, a full field map may be generated.

  19. The Decomposition of Hydrazine in the Gas Phase and over an Iridium Catalyst

    SciTech Connect

    Schmidt, Michael W.; Gordon, Mark S.

    2013-09-30

    Hydrazine is an important rocket fuel, used as both a monopropellant and a bipropellant. This paper presents theoretical results to complement the extensive experimental studies of the gas phase and Ir catalyzed decompositions involved in the monopropellant applications of hydrazine. Gas phase electronic structure theory calculations that include electron correlation predict that numerous molecular and free radical reactions occur within the same energy range as the basic free radical pathways: NN bond breaking around 65 kcal/mol and NH bond breaking around 81 kcal/mol. The data suggest that a revision to existing kinetics modeling is desirable, based on the energetics and the new elementary steps reported herein. A supported Ir-6 octahedron model for the Shell 405 Iridium catalyst used in thrusters was developed. Self-Consistent Field and electron correlation calculations (with core potentials and associated basis sets) find a rich chemistry for hydrazine on this catalyst model. The model catalyst provides dramatically lower NN and NH bond cleavage energies and an even smaller barrier to breaking the NH bond by NH2 abstractions. Thus, the low temperature decomposition over the catalyst is interpreted in terms of consecutive NH2 abstractions to produce ammonia and nitrogen. The higher temperature channel, which has hydrogen and nitrogen products, may be due to a mixture of two mechanisms. These two mechanisms are successive NH cleavages with surface H + H recombinations, and the same type of assisted H-2 eliminations found to occur in the gas phase part of this study.

  20. Kinetics of gas phase oxygen control system (OCS) for stagnant and flowing Pb-Bi Systems

    NASA Astrophysics Data System (ADS)

    Lefhalm, C. H.; Knebel, J. U.; Mack, K. J.

    2001-07-01

    Pb and Pb-Bi are known to be very corrosive to structural materials at elevated temperatures. In recent studies, the necessity of measurement and control of the oxygen concentration in the liquid metal in order to safely operate a liquid Pb or Pb-Bi loop has been shown. The dynamic behaviour of the gas phase oxygen control system (OCS), which was developed at Forschungszentrum Karlsruhe (FZK), is investigated with respect to diffusion as the limiting process of oxygen exchange between the gas phase and the liquid metal. In this paper the development of a physical model for this diffusion process is described and compared to experimental results of a stagnant liquid Pb-Bi system. The experimental findings are in very good agreement with the theoretical equations describing the thermodynamic and kinetic behaviour of such a system. Recent investigations in a Pb-Bi loop at the Karlsruhe Lead Laboratory (KALLA) indicate that this gas phase OCS is a promising candidate system for an accelerator-driven subcritical system (ADS).

  1. Gas-Phase Photoluminescence Characterization of Stoichiometrically Pure Nonanuclear Lanthanoid Hydroxo Complexes Comprising Europium or Gadolinium.

    PubMed

    Greisch, Jean-François; Chmela, Jiří; Harding, Michael E; Klopper, Wim; Kappes, Manfred M; Schooss, Detlef

    2016-04-01

    Gas-phase photoluminescence measurements involving mass-spectrometric techniques enable determination of the properties of selected molecular systems with knowledge of their exact composition and unaffected by matrix effects such as solvent interactions or crystal packing. The resulting reduced complexity facilitates a comparison with theory. Herein, we provide a detailed report of the intrinsic luminescence properties of nonanuclear europium(III) and gadolinium(III) 9-hydroxyphenalen-1-one (HPLN) hydroxo complexes. Luminescence spectra of [Eu9(PLN)16(OH)10](+) ions reveal an europium-centered emission dominated by a 4-fold split Eu(III) hypersensitive transition, while photoluminescence lifetime measurements for both complexes support an efficient europium sensitization via a PLN-centered triplet-state manifold. The combination of gas-phase measurements with density functional theory computations and ligand-field theory is used to discuss the antiprismatic core structure of the complexes and to shed light on the energy-transfer mechanism. This methodology is also employed to fit a new set of parameters, which improves the accuracy of ligand-field computations of Eu(III) electronic transitions for gas-phase species. PMID:26974169

  2. Gas Phase Chromatography of some Group 4, 5, and 6 Halides

    SciTech Connect

    Sylwester, Eric Robert

    1998-10-01

    Gas phase chromatography using The Heavy Element Volatility Instrument (HEVI) and the On Line Gas Apparatus (OLGA III) was used to determine volatilities of ZrBr{sub 4}, HfBr{sub 4}, RfBr{sub 4}, NbBr{sub 5}, TaOBr{sub 3}, HaCl{sub 5}, WBr{sub 6}, FrBr, and BiBr{sub 3}. Short-lived isotopes of Zr, Hf, Rf, Nb, Ta, Ha, W, and Bi were produced via compound nucleus reactions at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory and transported to the experimental apparatus using a He gas transport system. The isotopes were halogenated, separated from the other reaction products, and their volatilities determined by isothermal gas phase chromatography. Adsorption Enthalpy ({Delta}H{sub a}) values for these compounds were calculated using a Monte Carlo simulation program modeling the gas phase chromatography column. All bromides showed lower volatility than molecules of similar molecular structures formed as chlorides, but followed similar trends by central element. Tantalum was observed to form the oxybromide, analogous to the formation of the oxychloride under the same conditions. For the group 4 elements, the following order in volatility and {Delta}H{sub a} was observed: RfBr{sub 4} > ZrBr{sub 4} > HfBr{sub 4}. The {Delta}H{sub a} values determined for the group 4, 5, and 6 halides are in general agreement with other experimental data and theoretical predictions. Preliminary experiments were performed on Me-bromides. A new measurement of the half-life of {sup 261}Rf was performed. {sup 261}Rf was produced via the {sup 248}Cm({sup 18}O, 5n) reaction and observed with a half-life of 74{sub -6}{sup +7} seconds, in excellent agreement with the previous measurement of 78{sub -6}{sup +11} seconds. We recommend a new half-life of 75{+-}7 seconds for {sup 261}Rf based on these two measurements. Preliminary studies in transforming HEVI from an isothermal (constant temperature) gas phase chromatography instrument to a thermochromatographic (variable temperature

  3. Thermodynamics of the sorption of organic compounds on polyethylene glycol 400-permethylated β-cyclodextrin stationary phase and its enantioselectivity in gas chromatography

    NASA Astrophysics Data System (ADS)

    Kuraeva, Yu. G.; Onuchak, L. A.; Evdokimova, M. A.

    2016-08-01

    The thermodynamic characteristics of sorption of 24 organic compounds of various classes from the gas phase on the binary stationary phase based on polyethylene glycol 400 and permethylated β-cyclodextrin were determined. The influence of geometrical structure and optical activity of organic compounds on the possibility of forming sorbate-macrocycle complexes was examined. It was found that the studied stationary phase shows the enantioselectivity towards low-polar terpenes under the conditions of gas chromatography.

  4. Determining the properties of gas-phase clusters

    NASA Astrophysics Data System (ADS)

    Hopkins, W. Scott

    2015-11-01

    As our understanding of clusters has improved, we have found that rather than being models for surface and condensed phase phenomena, clusters often display chemical and physical properties that are quite distinct from those of their atomic constituents or associated bulk materials. Indeed, identifying and utilising the unique properties of dimensionally confined species is a major theme in nanotechnology. Consequently, numerous experimental and computational methods have been employed to investigate the structures and properties of cluster systems. In this article, the techniques of infrared multiple photon dissociation and differential mobility spectrometry are discussed using the examples of [Ag.B12F12]- and tetraalkylammonium/solvent ionic clusters, respectively.

  5. Phase transition dynamics of liquid phase precipitation from a supersaturated gas mixture.

    PubMed

    Pines, V; Zlatkowski, M; Chait, A

    2004-11-01

    This work presents a self-consistent description of phase transition dynamics of disperse liquid phase precipitating from a supersaturated gas mixture. The unified approach integrates the macroscale transport phenomena of cloud dynamics with the essential microphysical kinetic processes of droplet condensation, evaporation, and droplet collisions simultaneously taking place in stochastic population of liquid droplets. A complete set of governing equations with well-defined dissipative fluxes and kinetic rates is derived for phase transition dynamics from nucleation to postnucleation to coarsening stages. The local thermodynamics of precipitating system, which is considered as ternary mixture of disperse liquid phase and water vapor with dry air, is redefined to explicitly include on equal basis both the vapor content and liquid content into the fundamental thermodynamic relations and equation of state. The molecular kinetic flux regularization method for growth of submicron droplets is reexamined to include, among others, significant contribution of vapor molecular energy flux into total heat flux, resulting in new expressions for the droplet temperature, growth rate, and effective diffusion coefficients. The local kinetic rates are determined on the basis of microscale kinetic equation for the droplet distribution function. This is in contrast to commonly used semiempirical parametrization schemes for kinetic rates with adjustable parameters, wherein the probabilistic aspects of microphysical processes are not rigorously addressed. Stochastic diffusion interactions among droplets competing for the available water vapor and modifications in the kinetic equation for droplets growing in stochastic population with direct long-range diffusion interactions amongst them are discussed and formulated as well. PMID:15527359

  6. Online Measurements of Highly Oxidized Organics in the Gas and Particle phase during SOAS and SENEX

    NASA Astrophysics Data System (ADS)

    Lopez-Hilfiker, F.; Lee, B. H.; Mohr, C.; Ehn, M.; Rubach, F.; Mentel, T. F.; Kleist, E.; Thornton, J. A.

    2014-12-01

    We present measurements of a large suite of gas and particle phase organic compounds made with a Filter Inlet for Gas and AEROsol (FIGAERO) coupled to a high resolution time of flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington and with airborne HR-ToF-CIMS measurements. The FIGAERO instrument was deployed on the Jülich Plant Atmosphere Chamber to study α-pinene oxidation, and subsequently at the SMEAR II forest station in Hyytiälä, Finland and the SOAS ground site, in Brent Alabama. During the Southern Atmosphere Study, a gas-phase only version of the HR-ToF-CIMS was deployed on the NOAA WP-3 aircraft as part of SENEX. We focus here on highly oxygenated organic compounds derived from monoterpene oxidation detected both aloft during SENEX and at the ground-based site during SOAS. In both chamber and the atmosphere, many highly oxidized, low volatility compounds were observed in the gas and particles and many of the same compositions detected in the gas-phase were detected in the particles upon temperature programmed thermal desorption. The fraction of a given compound measured in the particle phase follows expected trends with elemental composition such as O/C ratios, but many compounds would not be well described by an absorptive partitioning model assuming unity activity coefficients. The detailed structure in the thermograms reveals a significant contribution from large molecular weight organics and/or oligomers in both chamber and ambient aerosol samples. Approximately 50% of the measured organics in the particle phase are associated with compounds having effective vapour pressures 4 or more orders of magnitude lower than commonly measured monoterpene oxidation products. We discuss the implications of these findings for measurements of gas-particle partitioning and for evaluating the contribution of monoterpene oxidation to organic aerosol formation and growth. We also use the aircraft measurements and a

  7. Evidence for α-helices in the gas phase: a case study using Melittin from honey bee venom.

    PubMed

    Florance, Hannah V; Stopford, Andrew P; Kalapothakis, Jason M; McCullough, Bryan J; Bretherick, Andrew; Barran, Perdita E

    2011-09-01

    Gas phase methodologies are increasingly used to study the structure of proteins and peptides. A challenge to the mass spectrometrist is to preserve the structure of the system of interest intact and unaltered from solution into the gas phase. Small peptides are very flexible and can present a number of conformations in solution. In this work we examine Melittin a 26 amino acid peptide that forms the active component of honey bee venom. Melittin is haemolytic and has been shown to form an α-helical tetrameric structure by X-ray crystallography [M. Gribskov et al., The RCSB Protein Data Bank, 1990] and to be helical in high concentrations of methanol. Here we use ion mobility mass spectrometry, molecular dynamics and gas-phase HDX to probe its structure in the gas phase and specifically interrogate whether the helical form can be preserved. All low energy calculated structures possess some helicity. In our experiments we examine the peptide following nano-ESI from solutions with varying methanol content. Ion mobility gives collision cross sections (CCS) that compare well with values found from molecular modelling and from other reported structures, but with inconclusive results regarding the effect of solvent. There is only a slight increase in CCS with charge, showing minimal coloumbically driven unfolding. HDX supports preservation of some helical content into the gas phase and again shows little difference in the exchange rates of species sprayed from different solvents. The [M + 3H](3+) species has two exchanging populations both of which exhibit faster exchange rates than observed for the [M + 2H](2+) species. One interpretation for these results is that the time spent being analysed is sufficient for this peptide to form a helix in the 'ultimate' hydrophobic environment of a vacuum. PMID:21701716

  8. Separation of dialkyl sulfides by metallo-mesogenic stationary phases for complexation gas chromatography.

    PubMed

    Chen, Jian-Lian; Liu, Chuen-Ying

    2007-08-17

    A copper mesogenic side-chain polymer (P-C(15)CuC(18)) was cross-linked onto the capillary wall as a stationary film for gas chromatography (GC) separation of alkyl sulfides. These organic sulfides are of interest for their large health impact because of their wide range of volatiles and high reactivities toward metals. Different GC parameters for optimal separation efficiency are discussed for use with a mesogenic polymer column along with flame photometric detection (FPD). Both the carrier gas flow-rate and column temperature were studied to determine the relationship of plate height to the chemical structure of the solutes, as well as to determine the morphology of the mesogenic polymer. Van 't Hoff plots show phase transitions of the stationary mesophase as the column temperature was varied. The results reveal that the separation mechanism might be based on ligand exchange and polarity interaction between the analytes and the stationary phase, with the vapor pressure of the analytes also being important. The former interaction dominates in the lamellar crystalline phase and the latter interaction dominates in the hexagonal columnar-discotic phase. With high reproducibility for retention time (RSD< or =0.37%) and for peak area (RSD< or =5.16%), the GC-FPD system produced linear calibration graphs (r> or =0.9918) for the determination of 13 sulfides with a detection limit below 2.5 ng. PMID:17568598

  9. Heat Transfer Characteristics of Liquid-Gas Taylor Flows incorporating Microencapsulated Phase Change Materials

    NASA Astrophysics Data System (ADS)

    Howard, J. A.; Walsh, P. A.

    2014-07-01

    This paper presents an investigation on the heat transfer characteristics associated with liquid-gas Taylor flows in mini channels incorporating microencapsulated phase change materials (MPCM). Taylor flows have been shown to result in heat transfer enhancements due to the fluid recirculation experienced within liquid slugs which is attributable to the alternating liquid slug and gas bubble flow structure. Microencapsulated phase change materials (MPCM) also offer significant potential with increased thermal capacity due to the latent heat required to cause phase change. The primary aim of this work was to examine the overall heat transfer potential associated with combining these two novel liquid cooling technologies. By investigating the local heat transfer characteristics, the augmentation/degradation over single phase liquid cooling was quantified while examining the effects of dimensionless variables, including Reynolds number, liquid slug length and gas void fraction. An experimental test facility was developed which had a heated test section and allowed MPCM-air Taylor flows to be subjected to a constant heat flux boundary condition. Infrared thermography was used to record high resolution experimental wall temperature measurements and determine local heat transfer coefficients from the thermal entrance point. 30.2% mass particle concentration of the MPCM suspension fluid was examined as it provided the maximum latent heat for absorption. Results demonstrate a significant reduction in experimental wall temperatures associated with MPCM-air Taylor flows when compared with the Graetz solution for conventional single phase coolants. Total enhancement in the thermally developed region is observed to be a combination of the individual contributions due to recirculation within the liquid slugs and also absorption of latent heat. Overall, the study highlights the potential heat transfer enhancements that are attainable within heat exchange devices employing MPCM

  10. Measurement of Gas-phase Acids in Diesel Exhaust

    NASA Astrophysics Data System (ADS)

    Wentzell, J. J.; Liggio, J.; Li, S.; Vlasenko, A. L.; Staebler, R. M.; Brook, J.; Lu, G.; Poitras, M.; Chan, T.

    2012-12-01

    Gas-phase acids were measured using chemical ionization mass spectrometry (CIMS) as part of the Diesel Engine Emission Research Experiment (DEERE). The CIMS technique, utilizing acetate ion (CH3COO-) as a reagent ion, proved to be a rapid (measurements on the order of seconds) and sensitive (several counts/pptv) method of quantifying the acid emissions. Diluted diesel exhaust measurements were made from a Constant Volume Sampling dilution tunnel using a light duty (1.9L turbocharged Volkswagen Jetta TDI) diesel engine equipped with an OEM diesel oxidation catalyst and exhaust gas recirculation, mounted on an engine dynamometer. Acids measured included isocyanic, nitrous, nitric, propionic and sum of lactic and oxalic, as well as other unidentified compounds. Complimentary measurements of CO, CO2, Total Hydrocarbon (THC), and NOx, were also performed. Several engine modes (different engine rpm and torque outputs) at steady state were examined to determine their effect on acid emissions. Emission rates with respect to NOx and fuel based emission factors were determined. Measurements of HONO fuel emission factors agree well with real-world measurements within a traffic tunnel.1 The first estimate of isocyanic acid emission factors from a diesel engine is reported, and suggests that the emission of this highly toxic compound in diesel exhaust should not be ignored. 1. Kurtenbach, R., Becker, K. H., Gomes, J. A. G., Kleffmann, J.,Lorzer, J. C., Spittler, M., Wiesen, P., Ackermann, R., Geyer, A.,and Platt, U.: Investigations of emissions and heterogeneous formation of HONO in a road traffic tunnel, Atmos. Environ., 35, 3385-3394, doi:10.1016/S1352-2310(01)00138-8, 2001.

  11. SSME structural dynamic model development, phase 2

    NASA Technical Reports Server (NTRS)

    Foley, M. J.; Wilson, V. L.

    1985-01-01

    A set of test correlated mathematical models of the SSME High Pressure Oxygen Turbopump (HPOTP) housing and rotor assembly was produced. New analysis methods within the EISI/EAL and SPAR systems were investigated and runstreams for future use were developed. The LOX pump models have undergone extensive modification since the first phase of this effort was completed. The rotor assembly from the original model was abandoned and a new, more detailed model constructed. A description of the new rotor math model is presented. Also, the pump housing model was continually modified as additional test data have become available. This model is documented along with measured test results. Many of the more advanced features of the EAL/SPAR finite element analysis system were exercised. These included the cyclic symmetry option, the macro-element procedures, and the fluid analysis capability. In addition, a new tool was developed that allows an automated analysis of a disjoint structure in terms of its component modes. A complete description of the implementation of the Craig-Bampton method is given along with two worked examples.

  12. Studies of cluster-assembled materials: From gas phase to condensed phase

    NASA Astrophysics Data System (ADS)

    Gao, Lin

    . After being mass gated in a reflectron equipped time-of-flight mass spectrometer (TOF-MS) and deposited onto TEM grids, the resultant specimens can be loaded onto high-resolution TEM investigation via electron diffraction. In conclusion, soft-landing of mass selected clusters has been shown to be a successful approach to obtain structural information on Zr-Met-Car cluster-assembled materials collected from the gas phase. TEM images indicate the richness of the morphologies associated with these cluster crystals. However, passivation methods are expected to be examined further to overcome the limited stabilities of these novel clusters. From this initial study, it's shown the promising opportunity to study other Met-Cars species and more cluster-based materials. Experimental results of reactions run with a solvothermal synthesis method obtained while searching for new Zr-C cluster assembled materials, are reported. One unexpected product in single crystal form was isolated and tentatively identified by X-ray diffraction to be [Zr6i O(OH)O12·2(Bu)4], with space group P2 1/n and lattice parameters of a = 12.44 A, b = 22.06 A, c = 18.40 A, alpha = 90°, beta = 105°, gamma = 90°, V = 4875 A3 and R 1 = 3.15% for the total observed data (I ≥ 2 sigma I) and oR2 = 2.82%. This novel hexanuclear Zr(IV)-oxo-hydroxide cluster anion may be the first member in polyoxometalates class with metal atoms from the IVB group and having Oh symmetry. Alternatively, it may be the first member in {[(Zr6Z)X 12]X6}m- class with halides replaced by oxo- and hydroxyl groups and with an increased oxidation state of Zr. It is predicted to bear application potentials directed by both families. This work could suggest a direction in which the preparation of Zr-C cluster-assembled materials in a liquid environment may be eventually fulfilled. 1,3-Bis(diethylphosphino)propane (depp) protected small gold clusters are studied via multiple techniques, including Electrospray Ionization Mass Spectrometry

  13. 1-Phenyl-1,2-dicarba-closo-dodecaborane, 1-Ph-1,2-closo-C(2)B(10)H(11). Synthesis, Characterization, and Structure As Determined in the Gas Phase by Electron Diffraction, in the Crystalline Phase at 199 K by X-ray Diffraction, and by ab Initio Computations.

    PubMed

    Brain, Paul T.; Cowie, Jill; Donohoe, David J.; Hnyk, Drahomír; Rankin, David W. H.; Reed, David; Reid, Bruce D.; Robertson, Heather E.; Welch, Alan J.; Hofmann, Matthias; Schleyer, Paul von Ragué

    1996-03-13

    The compound 1-phenyl-1,2-dicarba-closo-dodecaborane(12), 1-C(6)H(5)-1,2-closo-C(2)B(10)H(11) (1), has been synthesized and characterized by a complete assignment of its (11)B NMR spectrum via (11)B{(1)H}/(11)B{(1)H} (COSY), (1)H{(11)B(selective)} and (1)H{(11)B}/(1)H{(11)B} (COSY) spectroscopy. An electron- and X-ray diffraction investigation of 1, complemented by ab initio calculations, has been undertaken. The gas-phase electron-diffraction (GED) data can be fitted by several models describing conformations which differ in the position of the phenyl ring with respect to the carborane cage. Local symmetries ofC(2)(v)() and D(6)(h)() for the 1,2-C(2)B(10) and C(6) moieties, respectively, were adopted in the GED model in order to simplify the problem. In addition, constraints among the close-lying C-C and B-B bonds were employed. However, even though such simplifications led to satisfactory refinements (R(G) = 0.069-0.071), a unique, definitive solution could not be gained. The (C-C)(mean), (C-B)(mean) and (B-B)(mean) bond lengths,r(a), are ca. 1.44, 1.72, and 1.78 Å, respectively. The C(6) hexagon, with r(a)(C-C) = ca. 1.394 Å, either eclipses the C(1)-C(2) vector (overall C(s)() symmetry) or more or less eclipses the C(1)-B(4) cluster bond (overall C(1) symmetry). In contrast, in the solid at 199 K, the ring lies at a position intermediate between the two GED positions, as determined by X-ray crystallography [C(8)H(16)B(10), monoclinic P2(1)/a: a = 12.047(3) Å, b = 18.627(4) Å, c = 12.332(5) Å, beta = 110.09(4) degrees, Z = 8]. The C-B distances span the range 1.681(6)-1.743(5) Å, and B-B lengths lie between 1.756(6) and 1.795(6) Å. A similar conformation was found for the theoretical (RHF/6-31G level) structure which was fully optimized in C(1) symmetry. The r(e) distances are consistent with the dimensions derived in the experimental studies. IGLO calculations of the (11)B chemical shifts, in addition to SCF single-point energies of the GED structures

  14. Electrical impedance imaging in two-phase, gas-liquid flows: 1. Initial investigation

    NASA Technical Reports Server (NTRS)

    Lin, J. T.; Ovacik, L.; Jones, O. C.

    1991-01-01

    The determination of interfacial area density in two-phase, gas-liquid flows is one of the major elements impeding significant development of predictive tools based on the two-fluid model. Currently, these models require coupling of liquid and vapor at interfaces using constitutive equations which do not exist in any but the most rudimentary form. Work described herein represents the first step towards the development of Electrical Impedance Computed Tomography (EICT) for nonintrusive determination of interfacial structure and evolution in such flows.

  15. Measuring Uptake Coefficients and Henry's Law Constants of Gas-Phase Species with Models for Secondary Organic Aerosol

    NASA Astrophysics Data System (ADS)

    Fairhurst, M. C.; Waring-Kidd, C.; Ezell, M. J.; Finlayson-Pitts, B. J.

    2014-12-01

    Volatile organic compounds (VOC) are oxidized in the atmosphere and their products contribute to secondary organic aerosol (SOA) formation. These particles have been shown to have effects on visibility, climate, and human health. Current models typically under-predict SOA concentrations from field measurements. Underestimation of these concentrations could be a result of how models treat particle growth. It is often assumed that particles grow via instantaneous thermal equilibrium partitioning between liquid particles and gas-phase species. Recent work has shown that growth may be better represented by irreversible, kinetically limited uptake of gas-phase species onto more viscous, tar-like SOA. However, uptake coefficients for these processes are not known. The goal of this project is to measure uptake coefficients and solubilities for different gases onto models serving as proxies for SOA and determine how they vary based on the chemical composition of the gas and the condensed phase. Experiments were conducted using two approaches: attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and a flow system coupled to a mass spectrometer. The ATR crystal was coated with the SOA proxy and the gas-phase species introduced via a custom flow system. Uptake of the gas-phase species was characterized by measuring the intensity of characteristic IR bands as a function of time, from which a Henry's law constant and initial estimate of uptake coefficients could be obtained. Uptake coefficients were also measured in a flow system where the walls of the flow tube were coated with the SOA proxy and gas-phase species introduced via a moveable inlet. Uptake coefficients were derived from the decay in gas-phase species measured by mass spectrometry. The results of this work will establish a structure-interaction relationship for uptake of gases into SOA that can be implemented into regional and global models.

  16. TRANSITION STATE FOR THE GAS-PHASE REACTION OF URANIUM HEXAFLUORIDE WITH WATER

    SciTech Connect

    Garrison, S; James Becnel, J

    2008-03-18

    Density Functional Theory and small-core, relativistic pseudopotentials were used to look for symmetric and asymmetric transitions states of the gas-phase hydrolysis reaction of uranium hexafluoride, UF{sub 6}, with water. At the B3LYP/6-31G(d,p)/SDD level, an asymmetric transition state leading to the formation of a uranium hydroxyl fluoride, U(OH)F{sub 5}, and hydrogen fluoride was found with an energy barrier of +77.3 kJ/mol and an enthalpy of reaction of +63.0 kJ/mol (both including zero-point energy corrections). Addition of diffuse functions to all atoms except uranium led to only minor changes in the structure and relative energies of the reacting complex and transition state. However, a significant change in the product complex structure was found, significantly reducing the enthalpy of reaction to +31.9 kJ/mol. Similar structures and values were found for PBE0 and MP2 calculations with this larger basis set, supporting the B3LYP results. No symmetric transition state leading to the direct formation of uranium oxide tetrafluoride, UOF{sub 4}, was found, indicating that the reaction under ambient conditions likely includes several more steps than the mechanisms commonly mentioned. The transition state presented here appears to be the first published transition state for the important gas-phase reaction of UF{sub 6} with water.

  17. Transition state for the gas-phase reaction of uranium hexafluoride with water.

    PubMed

    Garrison, Stephen L; Becnel, James M

    2008-06-19

    Density functional theory and small-core, relativistic pseudopotentials were used to look for symmetric and asymmetric transition states of the gas-phase hydrolysis reaction of uranium hexafluoride, UF 6, with water. At the B3LYP/6-31G(d,p)/SDD level, an asymmetric transition state leading to the formation of a uranium hydroxyl fluoride, U(OH)F 5, and hydrogen fluoride was found with an energy barrier of +77.3 kJ/mol and an enthalpy of reaction of +63.0 kJ/mol (both including zero-point energy corrections). Addition of diffuse functions to all atoms except uranium led to only minor changes in the structures and relative energies of the reacting complex and transition state. However, a significant change in the structure of the product complex was found, significantly reducing the enthalpy of reaction to +31.9 kJ/mol. Similar structures and values were found for PBE0 and MP2 calculations with this larger basis set, supporting the B3LYP results. No symmetric transition state leading to the direct formation of uranium oxide tetrafluoride, UOF 4, was found, indicating that the reaction under ambient conditions likely includes several more steps than the mechanisms commonly mentioned. The transition state presented here appears to be the first published transition state for the important gas-phase reaction of UF 6 with water. PMID:18500792

  18. Ab initio molecular crystal structures, spectra, and phase diagrams.

    PubMed

    Hirata, So; Gilliard, Kandis; He, Xiao; Li, Jinjin; Sode, Olaseni

    2014-09-16

    Conspectus Molecular crystals are chemists' solids in the sense that their structures and properties can be understood in terms of those of the constituent molecules merely perturbed by a crystalline environment. They form a large and important class of solids including ices of atmospheric species, drugs, explosives, and even some organic optoelectronic materials and supramolecular assemblies. Recently, surprisingly simple yet extremely efficient, versatile, easily implemented, and systematically accurate electronic structure methods for molecular crystals have been developed. The methods, collectively referred to as the embedded-fragment scheme, divide a crystal into monomers and overlapping dimers and apply modern molecular electronic structure methods and software to these fragments of the crystal that are embedded in a self-consistently determined crystalline electrostatic field. They enable facile applications of accurate but otherwise prohibitively expensive ab initio molecular orbital theories such as Møller-Plesset perturbation and coupled-cluster theories to a broad range of properties of solids such as internal energies, enthalpies, structures, equation of state, phonon dispersion curves and density of states, infrared and Raman spectra (including band intensities and sometimes anharmonic effects), inelastic neutron scattering spectra, heat capacities, Gibbs energies, and phase diagrams, while accounting for many-body electrostatic (namely, induction or polarization) effects as well as two-body exchange and dispersion interactions from first principles. They can fundamentally alter the role of computing in the studies of molecular crystals in the same way ab initio molecular orbital theories have transformed research practices in gas-phase physical chemistry and synthetic chemistry in the last half century. In this Account, after a brief summary of formalisms and algorithms, we discuss applications of these methods performed in our group as compelling

  19. Phototransformation of polychlorinated aromatics in gas phase and on aerosol

    NASA Astrophysics Data System (ADS)

    Zhang, Xinzhong

    1999-12-01

    A number of polychlorinated aromatics have been shown to pose health risks even at very low concentration levels. However, routes of introduction of these toxic congeners into the environment remain unclear. It is speculated that some of the toxic congeners may evolve, in part, from transformation of other less toxic congeners. The most likely route for these transformations is photolysis during atmospheric transport. An investigation of this phenomenon was undertaken in this study, and phototransformation of selected polychlorinated aromatics, representing the compound of environmental concern, such as PCDDs, PCDFs and PCBs, in gas phase were examined. The study involved monitoring the effect of various atmospheres on phototransformation mechanism and kinetics. The experimental setup consisted of the photoreactor coupled to a vapor generator, a particle generator, an electrostatic classifier, and a particle counter. This arrangement permitted introduction of contaminants at known concentrations in vapor or aerosol form. The contaminants were irradiated for varied periods and the disappearance kinetics was studied as a function of irradiation time. The correlation between congeners and the photodegradation pathway was also investigated. The first order kinetic constants and the quantum yields were measured. The experimental results showed that the vapor phase phototransformation rates are affected by the atmospheric parameters, e.g., phototransformation rates are significantly enhanced in the presence of oxygen. In general, less chlorinated compounds decomposed faster than higher chlorinated ones. The reductive dechlorination was evidenced through the formation of products with less chlorine substitution. The presence of hydrogen donors significantly increased the yield of the reductive dechlorination products. The oxygen dominated the phototransformation rates by the mechanisms other than reductive dechlorination. The phototransformation rates of the PCDDs

  20. Characterization of Horizontal Gas-Liquid Two-Phase Flow Using Markov Model-Based Complex Network

    NASA Astrophysics Data System (ADS)

    Hu, Li-Dan; Jin, Ning-De; Gao, Zhong-Ke

    2013-05-01

    Horizontal gas-liquid two-phase flow widely exists in many physical systems and chemical engineering processes. Compared with vertical upward gas-liquid two-phase flow, investigations on dynamic behavior underlying horizontal gas-liquid flows are quite limited. Complex network provides a powerful framework for time series analysis of complex dynamical systems. We use a network generation method based on Markov transition probability to infer directed weighted complex networks from signals measured from horizontal gas-liquid two-phase flow experiment and find that the networks corresponding to different flow patterns exhibit different network structure. To investigate the dynamic characteristics of horizontal gas-liquid flows, we construct a number of complex networks under different flow conditions, and explore the network indices for each constructed network. In addition, we investigate the sample entropy of different flow patterns. Our results suggest that the network statistic can well represent the complexity in the transition among different flow patterns and further allows characterizing the interface fluctuation behavior in horizontal gas-liquid two-phase flow.

  1. Laser-driven synthesis of nanocrystalline alumina powders from gas-phase precursors

    NASA Astrophysics Data System (ADS)

    Borsella, E.; Botti, S.; Giorgi, R.; Martelli, S.; Turtù, S.; Zappa, G.

    1993-09-01

    Carbon dioxide laser synthesis from gaseous precursors has been successfully applied to produce nanosized Al2O3 particles. Trimethylaluminum [Al(CH3)3] and nitrous-oxide (N2O) were used as gas phase reactants. Ethylene (C2H4) was added as sensitizer gas. The as-synthesized powder particles showed considerable carbon contamination and an amorphouslike structure. After thermal treatment at 1200-1400 °C, the powder transformed to hexagonal α-Al2O3 with very low carbon contamination, confirmed by x-ray diffraction, x-ray photoelectron spectroscopy, and chemical analysis. The thermally treated powder was composed of spherical single-crystal nanoparticles with a mean size of 15-20 nm, as determined by x-ray diffraction, electron microscopy, and Brunauer-Emmett-Teller specific surface measurements. The laser synthesized Al2O3 particles are suitable dispersoids for intermetallic alloy technology.

  2. Visible and ultraviolet spectroscopy of gas phase rhodamine 575 cations.

    PubMed

    Daly, Steven; Kulesza, Alexander; Knight, Geoffrey; MacAleese, Luke; Antoine, Rodolphe; Dugourd, Philippe

    2015-06-01

    The visible and ultraviolet spectroscopy of gas phase rhodamine 575 cations has been studied experimentally by action-spectroscopy in a modified linear ion trap between 220 and 590 nm and by time-dependent density functional theory (TDDFT) calculations. Three bands are observed that can be assigned to the electronic transitions S0 → S1, S0 → S3, and S0 → (S8,S9) according to the theoretical prediction. While the agreement between theory and experiment is excellent for the S3 and S8/S9 transitions, a large shift in the value of the calculated S1 transition energy is observed. A theoretical analysis of thermochromism, potential vibronic effects, and-qualitatively-electron correlation revealed it is mainly the latter that is responsible for the failure of TDDFT to accurately reproduce the S1 transition energy, and that a significant thermochromic shift is also present. Finally, we investigated the nature of the excited states by analyzing the excitations and discussed their different fragmentation behavior. We hypothesize that different contributions of local versus charge transfer excitations are responsible for 1-photon versus 2-photon fragmentation observed experimentally. PMID:25961329

  3. Surface plasmon sensing of gas phase contaminants using optical fiber.

    SciTech Connect

    Thornberg, Steven Michael; White, Michael I.; Rumpf, Arthur Norman; Pfeifer, Kent Bryant

    2009-10-01

    Fiber-optic gas phase surface plasmon resonance (SPR) detection of several contaminant gases of interest to state-of-health monitoring in high-consequence sealed systems has been demonstrated. These contaminant gases include H{sub 2}, H{sub 2}S, and moisture using a single-ended optical fiber mode. Data demonstrate that results can be obtained and sensitivity is adequate in a dosimetric mode that allows periodic monitoring of system atmospheres. Modeling studies were performed to direct the design of the sensor probe for optimized dimensions and to allow simultaneous monitoring of several constituents with a single sensor fiber. Testing of the system demonstrates the ability to detect 70mTorr partial pressures of H{sub 2} using this technique and <280 {micro}Torr partial pressures of H{sub 2}S. In addition, a multiple sensor fiber has been demonstrated that allows a single fiber to measure H{sub 2}, H{sub 2}S, and H{sub 2}O without changing the fiber or the analytical system.

  4. Gas-phase Chemistry of the Cyanate Ion, OCN-

    NASA Astrophysics Data System (ADS)

    Cole, Callie A.; Wang, Zhe-Chen; Snow, Theodore P.; Bierbaum, Veronica M.

    2015-10-01

    Cyanate (OCN-) is the only ion to date whose presence has been confirmed in the icy mantles that coat interstellar dust grains. Understanding the chemical behavior of cyanate at a fundamental level is therefore integral to the advancement of astrochemistry. We seek to unravel the chemistry of this intriguing anion through a combination of gas-phase experiments and theoretical explorations. Our approach is twofold: first, employing a flowing afterglow-selected ion flow tube apparatus, the reactions between OCN- and three of the most abundant atomic species in the interstellar medium, hydrogen, nitrogen, and oxygen, are examined. Hydrogen atoms readily react by associative detachment, but the remarkable stability of OCN- does not give rise to an observable reaction with either nitrogen or oxygen atoms. To explain these results, the potential energy surfaces of several reactions are investigated at the B3LYP/6-311++G(d,p) level of theory. Second, collision induced dissociation experiments involving deprotonated uracil, thymine, and cytosine in an ion trap mass spectrometer reveal an interesting connection between these pyrimidine nucleobase anions and OCN-. Theoretical calculations at the B3LYP/6-311++G(d,p) level of theory are performed to delineate the mechanisms of dissociation and explore the possible role of OCN- as a biomolecule precursor.

  5. Infrared and Ultraviolet Spectroscopy of Gas-Phase Imidazolium and Pyridinium Ionic Liquids.

    NASA Astrophysics Data System (ADS)

    Young, Justin W.; Booth, Ryan S.; Annesley, Christopher; Stearns, Jaime A.

    2015-06-01

    Ionic liquids (ILs) are a highly variable and potentially game-changing class of molecules for a number of Air Force applications such as satellite propulsion, but the complex nature of IL structure and intermolecular interactions makes it difficult to adequately predict structure-property relationships in order to make new IL-based technology a reality. For example, methylation of imidazolium ionic liquids leads to a substantial increase in viscosity but the underlying physical mechanism is not understood. In addition, the role of hydrogen bonding in ILs, and especially its relationship to macroscopic properties, is a matter of ongoing research. Here we describe the gas-phase spectroscopy of a series of imidazolium- and pyridinium-based ILs, using a combination of infrared spectroscopy and density functional theory to establish the intermolecular interactions present in various ILs, to assess how well they are described by theory, and to relate microscopic structure to macroscopic properties.

  6. Gas-phase electronic transitions of C₁₇H₁₂N⁺ at 15 K.

    PubMed

    Hardy, F-X; Rice, C A; Gause, O; Maier, J P

    2015-03-01

    The electronic spectrum of C17H12N(+), phenanthrene with a side chain, was measured in the gas phase at a vibrational and rotational temperature of ∼15 K in an ion trap using a resonant multiphoton dissociation technique. The C17H12N(+) structure was produced in a chemical ionization source and identified by a comparison with theoretical calculations of stable structures and excitation energies. The (3), (2), (1) (1)A ← X (1)A electronic transitions of this nitrogen-containing aromatic species with 30 atoms have origin band maxima at 23,586 ± 1 cm(-1), 16,120 ± 50 cm(-1), and 14,519 ± 30 cm(-1). Distinct vibrational structure in the (3) (1)A state is observed, and assignments are made. Astronomical aspects are considered. PMID:25264926

  7. Phase transitions and domain structures in multiferroics

    NASA Astrophysics Data System (ADS)

    Vlahos, Eftihia

    2011-12-01

    Thin film ferroelectrics and multiferroics are two important classes of materials interesting both from a scientific and a technological prospective. The volatility of lead and bismuth as well as environmental issues regarding the toxicity of lead are two disadvantages of the most commonly used ferroelectric random access memory (FeRAM) materials such as Pb(Zr,Ti)O3 and SrBi2Ta2O9. Therefore lead-free thin film ferroelectrics are promising substitutes as long as (a) they can be grown on technologically important substrates such as silicon, and (b) their T c and Pr become comparable to that of well established ferroelectrics. On the other hand, the development of functional room temperature ferroelectric ferromagnetic multiferroics could lead to very interesting phenomena such as control of magnetism with electric fields and control of electrical polarization with magnetic fields. This thesis focuses on the understanding of material structure-property relations using nonlinear optical spectroscopy. Nonlinear spectroscopy is an excellent tool for probing the onset of ferroelectricity, and domain dynamics in strained ferroelectrics and multiferroics. Second harmonic generation was used to detect ferroelectricity and the antiferrodistortive phase transition in thin film SrTiO3. Incipient ferroelectric CaTiO3 has been shown to become ferroelectric when strained with a combination of SHG and dielectric measurements. The tensorial nature of the induced nonlinear polarization allows for probing of the BaTiO3 and SrTiO3 polarization contributions in nanoscale BaTiO3/SrTiO3 superlattices. In addition, nonlinear optics was used to demonstrate ferroelectricity in multiferroic EuTiO3. Finally, confocal SHG and Raman microscopy were utilized to visualize polar domains in incipient ferroelectric and ferroelastic CaTiO3.

  8. Concurrence of aqueous and gas phase contamination of groundwater in the Wattenberg oil and gas field of northern Colorado.

    PubMed

    Li, Huishu; Son, Ji-Hee; Carlson, Kenneth H

    2016-01-01

    The potential impact of rapid development of unconventional oil and natural gas resources using hydraulic fracturing and horizontal drilling on regional groundwater quality has received significant attention. Major concerns are methane or oil/gas related hydrocarbon (such as TPHs, BTEX including benzene, toluene, ethybenzene and xylene) leaks into the aquifer due to the failure of casing and/or stray gas migration. Previously, we investigated the relationship between oil and gas activity and dissolved methane concentration in a drinking water aquifer with the major finding being the presence of thermogenic methane contamination, but did not find detectable concentrations of TPHs or BTEX. To understand if aqueous and gas phases from the producing formation were transported concurrently to drinking water aquifers without the presence of oil/gas related hydrocarbons, the ionic composition of three water groups was studied: (1) uncontaminated deep confined aquifer, (2) suspected contaminated groundwater - deep confined aquifer containing thermogenic methane, and (3) produced water from nearby oil and gas wells that would represent aqueous phase contaminants. On the basis of quantitative and spatial analysis, we identified that the "thermogenic methane contaminated" groundwater did not have similarities to produced water in terms of ionic character (e.g. Cl/TDS ratio), but rather to the "uncontaminated" groundwater. The analysis indicates that aquifer wells with demonstrated gas phase contamination have not been contacted by an aqueous phase from oil and gas operations according to the methodology we use in this study and the current groundwater quality data from COGCC. However, the research does not prove conclusively that this the case. The results may provide insight on contamination mechanisms since improperly sealed well casing may result in stray gas but not aqueous phase transport. PMID:26519629

  9. DEMONSTRATION OF FUEL CELLS TO RECOVER ENERGY FROM LANDFILL GAS: PHASE II. PRETREATMENT SYSTEM PERFORMANCE MEASUREMENT

    EPA Science Inventory

    The report describes-Phase II of a demonstration of the utilization of commercial phosphoric acid fuel cells to recover energy from landfill gas. his phase consisted primarily of the construction and testing of a Gas Pretreatment Unit (GPU) whose function is to remove those impur...

  10. Magnetic field dependence of the product yields of cycloheptanone photolysis in the dilute gas phase

    NASA Astrophysics Data System (ADS)

    Stich, E. M.; Baumeister, W. F.; Huber, J. Robert

    1984-07-01

    The product yields of the gas-phase photolysis of cycloheptanone were measured in magnetic fields up to 10 kG. The magnetic-field effect is explained in terms of the radical pair model. A reaction mechanism is proposed that explains the magnetic field dependence, pressure dependence, and excitation enegy dependence of the gas-phase photochemistry of cycloheptanone.

  11. DEMONSTRATION OF FUEL CELLS TO RECOVER ENERGY FROM LANDFILL GAS: PHASE II. PRETREATMENT SYSTEM PERFORMANCE MEASUREMENT

    EPA Science Inventory

    The report describes Phase II of a demonstration of the utilization of commercial phosphoric acid fuel cells to recover energy from landfill gas. This phase consisted primarily of the construction and testing of a Gas Pretreatment Unit (GPU) whose function is to remove those impu...

  12. GAS PHASE SELECTIVE PHOTOXIDATION OF ALCOHOLS USING LIGHT-ACTIVATED TITANIUM DIOXIDE AND MOLECULAR OXYGEN

    EPA Science Inventory

    Gas Phase Selective Oxidation of Alcohols Using Light-Activated Titanium Dioxide and Molecular Oxygen

    Gas phase selective oxidations of various primary and secondary alcohols are studied in an indigenously built stainless steel up-flow photochemical reactor using ultravi...

  13. Density fluctuations of a hard-core Bose gas in a one-dimensional lattice near the Mott insulating phase

    SciTech Connect

    Ates, C.; Moseley, Ch.; Ziegler, K.

    2005-06-15

    The characteristic oscillations of the density-density correlation function and the resulting structure factor are studied for a hard-core Bose gas in a one-dimensional lattice. Their wavelength diverges as the system undergoes a continuous transition from an incommensurate to a Mott insulating phase. The transition is associated with a unit static structure factor and a vanishing sound velocity. The qualitative picture is unchanged when a weak confining potential is applied to the system.

  14. Discontinuous phase transition in a dimer lattice gas

    NASA Astrophysics Data System (ADS)

    Dickman, Ronald

    2012-05-01

    I study a dimer model on the square lattice with nearest neighbor exclusion as the only interaction. Detailed simulations using tomographic entropic sampling show that as the chemical potential is varied, there is a strongly discontinuous phase transition, at which the particle density jumps by about 18% of its maximum value, 1/4. The transition is accompanied by the onset of orientational order, to an arrangement corresponding to the {1/2, 0, 1/2} structure identified by Phares et al. [Physica B 409, 1096 (2011)] in a dimer model with finite repulsion at fixed density. Using finite-size scaling and Binder's cumulant, the expected scaling behavior at a discontinuous transition is verified in detail. The discontinuous transition can be understood qualitatively given that the model possesses eight equivalent maximum-density configurations, so that its coarse-grained description corresponds to that of the q = 8 Potts model.

  15. Heat flow anomalies in oil- and gas-bearing structures

    SciTech Connect

    Sergiyenko, S.I.

    1988-02-01

    The main features of the distribution of heat flow values in oil, gas and gas-condensate fields on the continents have been discussed by Makarenko and Sergiyenko. The method of analysis used made it possible to establish that the presence of hydrocarbons in formations leads to high heat-flow, regardless of the age of folding of the potentially oil- and gas-bearing zones. Only in regions adjacent to marginal Cenozoic folded mountain structures and in zones of Cenozoic volcanism is the world average higher, by 2.5 to 10%, than in the oil- and gas-bearing structures in those regions. The earlier analysis of the distribution of heat flow values in oil and gas structures was based on 403 measurements. The author now has nearly doubled the sample population, enabling him substantially to revise the ideas on the distribution of heat flow values and the development of the thermal regime of local oil and gas structures. He notes that the method previously used, comparing heat flow values on young continental platforms with values in local oil and gas structures, makes it possible to estimate the thermal effect of the presence of oil and gas. This conclusion stems from the fact that the overwhelming majority of heat flow measurements were made on various kinds of positive structural forms, and distortions of the thermal field caused by thermal anisotropy phenomena are equally characteristic of both productive and nonproductive structures. As a result, for the first time a continuous time series of heat flow measurements over oil and gas structures in various tectonic regions, with ages of consolidation ranging from the Precambrian to the Cenozoic, was established. 26 references.

  16. Quasi-two-dimensional diamond crystals: Deposition from a gaseous phase and structural-morphological properties

    NASA Astrophysics Data System (ADS)

    Alexeev, A. M.; Ismagilov, R. R.; Ashkinazi, E. E.; Orekhov, A. S.; Malykhin, S. A.; Obraztsov, A. N.

    2016-07-01

    Diamond films predominantly consisting of plane micrometer-size crystallites with a thickness of several dozen nanometers have been deposited from a methane-hydrogen gas mixture activated by a dc gas discharge. The crystallite structure has been studied by scanning and transmission electron microscopy and diffraction. A possible mechanism of formation of plane crystallites during deposition of diamond from the gas phase has been discussed. It has been shown that the results agree with the theoretical concepts of formation of crystals with a face-centered cubic lattice.

  17. Liquid phase reaction-bonding of structural ceramics and composites

    SciTech Connect

    Chiang, Y.M. . Dept. of Materials Science and Engineering)

    1988-01-01

    Synthesis of ceramics via the reaction of a solid precursor with either a gas or liquid phase has a number of advantages compared to conventional sintering technology. These advantages are known for gas-phase processes. The authors have explored the potential for synthesizing high performance ceramics in the model system reaction-bonded silicon carbide, in which liquid silicon is used to infiltrate carbonaceous preforms. In this paper results are presented that illustrate the use of alloyed-melts to obtain dense silicon carbide composites with residual refractory silicide phases, such as MoSi/sub 2/, rather than the residual silicon phase which has heretofore limited high temperature properties. Infiltration processing considerations, such as the ultimate infiltration dimensions possible in the presence of simultaneous reaction, are discussed. Microstructure and mechanical properties characterization in the SIC-MoSi/sub 2/ system are presented. Other refractory ceramics systems to which liquid-phase reaction-bonding may be applied are discussed.

  18. Quantifying the stabilizing effects of protein–ligand interactions in the gas phase

    PubMed Central

    Allison, Timothy M.; Reading, Eamonn; Liko, Idlir; Baldwin, Andrew J.; Laganowsky, Arthur; Robinson, Carol V.

    2015-01-01

    The effects of protein–ligand interactions on protein stability are typically monitored by a number of established solution-phase assays. Few translate readily to membrane proteins. We have developed an ion-mobility mass spectrometry approach, which discerns ligand binding to both soluble and membrane proteins directly via both changes in mass and ion mobility, and assesses the effects of these interactions on protein stability through measuring resistance to unfolding. Protein unfolding is induced through collisional activation, which causes changes in protein structure and consequently gas-phase mobility. This enables detailed characterization of the ligand-binding effects on the protein with unprecedented sensitivity. Here we describe the method and software required to extract from ion mobility data the parameters that enable a quantitative analysis of individual binding events. This methodology holds great promise for investigating biologically significant interactions between membrane proteins and both drugs and lipids that are recalcitrant to characterization by other means. PMID:26440106

  19. Gas-Phase Amidation of Carboxylic Acids with Woodward's Reagent K Ions

    NASA Astrophysics Data System (ADS)

    Peng, Zhou; Pilo, Alice L.; Luongo, Carl A.; McLuckey, Scott A.

    2015-06-01

    Gas-phase amidation of carboxylic acids in multiply-charged peptides is demonstrated via ion/ion reactions with Woodward's reagent K (wrk) in both positive and negative mode. Woodward's reagent K, N-ethyl-3-phenylisoxazolium-3'-sulfonate, is a commonly used reagent that activates carboxylates to form amide bonds with amines in solution. Here, we demonstrate that the analogous gas-phase chemistry occurs upon reaction of the wrk ions and doubly protonated (or doubly deprotonated) peptide ions containing the carboxylic acid functionality. The reaction involves the formation of the enol ester intermediate in the electrostatic complex. Upon collisional activation, the ethyl amine on the reagent is transferred to the activated carbonyl carbon on the peptide, resulting in the formation of an ethyl amide (addition of 27 Da to the peptide) with loss of a neutral ketene derivative. Further collision-induced dissociation (CID) of the products and comparison with solution-phase amidation product confirms the structure of the ethyl amide.

  20. Ultrafast electron diffraction from laser-aligned molecules in the gas phase

    NASA Astrophysics Data System (ADS)

    Yang, Jie

    Ultrafast electron diffraction has emerged since the end of last century, and has become an increasingly important tool for revealing great details of molecular dynamics. In comparison to spectroscopic techniques, ultrafast electron diffraction directly probes time-resolved structure of target molecules, and therefore can potentially provide "molecular movies" of the reactions being studied. These molecular movies are critical for understanding and ultimately controlling the energy conversion pathways and efficiencies of photochemical processes. In this dissertation, I have focused on ultrafast electron diffraction from gas-phase molecules, and have investigated several long-standing challenges that have been preventing researchers from being able to achieve 3-D molecular movies of photochemical reactions. The first challenge is to resolve the full 3-D structure for molecules in the gas phase. The random orientation of molecules in the gas phase smears out the diffraction signal, which results in only 1-D structural information being accessible. The second challenge lies in temporal resolution. In order to resolve coherent nuclear motions on their natural time scale, a temporal resolution of ˜200 femtosecond or better is required. However, due to experimental limitations the shortest temporal resolution that had been achieved was only a few picoseconds in early 2000, by Zewail group from Caltech. The first challenge is tackled by laser-alignment. In the first half of the dissertation, I approach this method both theoretically and experimentally, and demonstrate that by using a short laser pulse to transiently align target molecules in space, 3-D molecular structure can be reconstructed ab-initio from diffraction patterns. The second half of the dissertation presents two experiments, both of which are important steps toward imaging coherent nuclear motions in real time during photochemical reactions. The first experiment simultaneously resolves molecular alignment

  1. Calix[4]pyrroles: highly selective stationary phases for gas chromatographic separations.

    PubMed

    Fan, Jing; Wang, Zhenzhong; Li, Qian; Qi, Meiling; Shao, Shijun; Fu, Ruonong

    2014-10-01

    Calix[4]pyrroles offer a great potential as stationary phases for gas chromatography (GC) due to their unique structures and physicochemical properties. Herein we present the first report of using two calix[4]pyrroles, namely meso-tetra-cyclohexylcalix[4]pyrrole (THCP) and meso-octamethylcalix[4]pyrrole (OMCP). These stationary phases were statically coated onto capillary columns and investigated in terms of column efficiency, polarity, separation performance, thermal stability and repeatability. The columns achieved column efficiencies of 2200-3000plates/m and exhibited nonpolar nature with an average polarity of 67 for THCP and 64 for OMCP, respectively. THCP stationary phase shows high selectivity for analytes of different polarity and exhibits nice peak shapes, especially for aldehydes, alcohols and anilines that are prone to severe peak tailing in GC analysis. Interestingly, THCP stationary phase possesses superior resolving ability for aniline and benzenediol positional isomers while OMCP shows preferential selectivity for nonpolar analytes such as hexane isomers. Moreover, calix[4]pyrrole columns also have good thermal stability up to 260°C and repeatability with a relative standard deviation (RSD%) of less than 0.10% for run-to-run and less than 5.2% for column-to-column. This work demonstrates the unique separation performance of calix[4]pyrroles and their promising future as a new class of GC stationary phases. PMID:25173993

  2. Study of solid/gas phase photocatalytic reactions by electron ionization mass spectrometry.

    PubMed

    Nuño, Manuel; Ball, Richard J; Bowen, Chris R

    2014-08-01

    This paper describes a novel methodology for the real-time study of solid-gas phase photocatalytic reactions in situ. A novel reaction chamber has been designed and developed to facilitate the investigation of photoactive materials under different gas compositions. UV irradiation in the wavelength of ranges 376-387 and 381-392 nm was provided using specially designed high efficiency light emitting diode arrays. The experiments used air containing 190 ppm NO2 in a moist environment with a relative humidity of 0.1%. Photocatalytic samples consisting of pressed pellets of rutile and anatase crystalline forms of TiO2 were monitored over a period of 150 min. An ultra-high vacuum right angled bleed valve allowed a controlled flow of gas from the main reaction chamber at atmospheric pressure to a residual gas analyser operating at a vacuum of 10(-5)  mbar. The apparatus and methodology have been demonstrated to provide high sensitivity (ppb). The rate of degradation of NO2 attributed to reaction at the TiO2 surface was sensitive to both crystal structures (anatase or rutile) and wavelength of irradiation. PMID:25044899

  3. Phase structures of holographic screen thermodynamics

    NASA Astrophysics Data System (ADS)

    Jiang, Wei-Jian; Chen, Yi-Xin; Li, Jian-Long

    2014-07-01

    Holographic screens are the generalization of the event horizon of a black hole in entropic force scheme, which are defined by setting Newton potential ϕ constant, i.e. e2ϕ = c = const. We demonstrate that the integrated first law of thermodynamics is equivalent to the (r-r) component of Einstein equations, so that we strengthen the correspondence between thermodynamics and gravity. We show that there are not only the first law of thermodynamics, but also kinds of phase transitions of holographic screens. These phase transitions are characterized by the discontinuity of their heat capacities. In (n+1)-dimensional Reissner-Nordström-anti-de Sitter (RN-AdS) spacetime, we analyze three kinds of phase transitions, which are of the holographic screens with Q = 0 (charge), constant Φ (electrostatic potential) and nonzero constant Q. In the Q = 0 case, only the holographic screens with 0≤c<1 can undergo phase transition. In the constant Φ case, the constraints become as 0<= c+16˜ {Γ }2Φ 2<1, where ˜ {Γ } is a dimensional-dependent parameter. By verifying the Ehrenfest equations, we show that the phase transitions in this case are all second order phase transitions. In the constant Q case, there might be two, or one, or no phase transitions of holographic screens, depending on the values of Q and c.

  4. Structural basis for Gas6–Axl signalling

    PubMed Central

    Sasaki, Takako; Knyazev, Pjotr G; Clout, Naomi J; Cheburkin, Yuri; Göhring, Walter; Ullrich, Axel; Timpl, Rupert; Hohenester, Erhard

    2006-01-01

    Receptor tyrosine kinases of the Axl family are activated by the vitamin K-dependent protein Gas6. Axl signalling plays important roles in cancer, spermatogenesis, immunity, and platelet function. The crystal structure at 3.3 Å resolution of a minimal human Gas6/Axl complex reveals an assembly of 2:2 stoichiometry, in which the two immunoglobulin-like domains of the Axl ectodomain are crosslinked by the first laminin G-like domain of Gas6, with no direct Axl/Axl or Gas6/Gas6 contacts. There are two distinct Gas6/Axl contacts of very different size, both featuring interactions between edge β-strands. Structure-based mutagenesis, protein binding assays and receptor activation experiments demonstrate that both the major and minor Gas6 binding sites are required for productive transmembrane signalling. Gas6-mediated Axl dimerisation is likely to occur in two steps, with a high-affinity 1:1 Gas6/Axl complex forming first. Only the minor Gas6 binding site is highly conserved in the other Axl family receptors, Sky/Tyro3 and Mer. Specificity at the major contact is suggested to result from the segregation of charged and apolar residues to opposite faces of the newly formed β-sheet. PMID:16362042

  5. The structure of hydrophobic gas diffusion electrodes.

    NASA Technical Reports Server (NTRS)

    Giner, J.

    1972-01-01

    The 'flooded agglomerate' model of the Teflon-bonded gas diffusion electrode is discussed. A mathematical treatment of the 'flooded agglomerate' model is given; it can be used to predict the performance of the electrode as a function of measurable physical parameters.

  6. The Conformation of Pentanoates in the Solid and in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Merkens, Carina; Stadtmüller, Tom; Englert, Ulli; Mouhib, Halima; Stahl, Wolfgang

    2014-07-01

    Suitable derivatives of the four isomeric pentanoates have been structurally characterized in the solid and the gas phase. For the latter, the volatile ethyl esters of valeric, isovaleric, methylbutyric, and pivalic acid were investigated by a combination of molecular beam Fourier transform microwave (MB-FTMW) spectroscopy and theoretical calculations. Crystalline salts rather than esters were formed by reaction between the carboxylic acids and trans-1,2-diaminocyclohexane. For both gaseous and crystalline methylbutyrates, an essentially perpendicular arrangement of carboxylate and methyl group was observed; earlier structure determinations documented in the data base agree with this result. Two competing conformers of favourable energy were relevant for the corresponding isovalerates: They were associated with torsion angles around 20° and 50° between the carboxylate and the alkyl chain. Good agreements in conformation have also been achieved for our experimentally observed unbranched valerate derivatives and fully branched pivalates in solid and gas phase. Despite the apparent simplicity of the pentanoates, the identification of their lowest energy conformers represents a challenge for different methods and levels of theory.

  7. Synthesis of alloys with controlled phase structure

    DOEpatents

    Guthrie, S.E.; Thomas, G.J.; Bauer, W.; Yang, N.Y.C.

    1999-04-20

    A method is described for preparing controlled phase alloys useful for engineering and hydrogen storage applications. This novel method avoids melting the constituents by employing vapor transport, in a hydrogen atmosphere, of an active metal constituent, having a high vapor pressure at temperatures {approx_equal}300 C and its subsequent condensation on and reaction with the other constituent (substrate) of an alloy thereby forming a controlled phase alloy and preferably a single phase alloy. It is preferred that the substrate material be a metal powder such that diffusion of the active metal constituent, preferably magnesium, and reaction therewith can be completed within a reasonable time and at temperatures {approx_equal}300 C thereby avoiding undesirable effects such as sintering, local compositional inhomogeneities, segregation, and formation of unwanted second phases such as intermetallic compounds. 4 figs.

  8. Synthesis of alloys with controlled phase structure

    DOEpatents

    Guthrie, Stephen Everett; Thomas, George John; Bauer, Walter; Yang, Nancy Yuan Chi

    1999-04-20

    A method for preparing controlled phase alloys useful for engineering and hydrogen storage applications. This novel method avoids melting the constituents by employing vapor transport, in a hydrogen atmosphere, of an active metal constituent, having a high vapor pressure at temperatures .apprxeq.300 C. and its subsequent condensation on and reaction with the other constituent (substrate) of an alloy thereby forming a controlled phase alloy and preferably a single phase alloy. It is preferred that the substrate material be a metal powder such that diffusion of the active metal constituent, preferably magnesium, and reaction therewith can be completed within a reasonable time and at temperatures .apprxeq.300 C. thereby avoiding undesirable effects such as sintering, local compositional inhomogeneities, segregation, and formation of unwanted second phases such as intermetallic compounds.

  9. Gas-Phase Combustion Synthesis of Aluminum Nitride Powder

    NASA Technical Reports Server (NTRS)

    Axelbaum, R. L.; Lottes, C. R.; Huertas, J. I.; Rosen, L. J.

    1996-01-01

    Due to its combined properties of high electrical resistivity and high thermal conductivity aluminum nitride (AlN) is a highly desirable material for electronics applications. Methods are being sought for synthesis of unagglomerated, nanometer-sized powders of this material, prepared in such a way that they can be consolidated into solid compacts having minimal oxygen content. A procedure for synthesizing these powders through gas-phase combustion is described. This novel approach involves reacting AlCl3, NH3, and Na vapors. Equilibrium thermodynamic calculations show that 100% yields can be obtained for these reactants with the products being AlN, NaCl, and H2. The NaCl by-product is used to coat the AlN particles in situ. The coating allows for control of AlN agglomeration and protects the powders from hydrolysis during post-flame handling. On the basis of thermodynamic and kinetic considerations, two different approaches were employed to produce the powder, in co-flow diffusion flame configurations. In the first approach, the three reactants were supplied in separate streams. In the second, the AlCl3 and NH3 were premixed with HCl and then reacted with Na vapor. X-ray diffraction (XRD) spectra of as-produced powders show only NaCl for the first case and NaCl and AlN for the second. After annealing at 775 C tinder dynamic vacuum, the salt was removed and XRD spectra of powders from both approaches show only AlN. Aluminum metal was also produced in the co-flow flame by reacting AlCl3 with Na. XRD spectra of as-produced powders show the products to be only NaCl and elemental aluminum.

  10. Gas phase selective hydrogenation over oxide supported Ni-Au.

    PubMed

    Cárdenas-Lizana, Fernando; Keane, Mark A

    2015-11-14

    The chemoselective continuous gas phase (T = 573 K; P = 1 atm) hydrogenation of nitroarenes (p-chloronitrobenzene (p-CNB) and m-dinitrobenzene (m-DNB)) has been investigated over a series of oxide (Al2O3 and TiO2) supported Au and Ni-Au (1 : 10 mol ratio; 0.1-1 mol% Au) catalysts. Monometallic supported Au with mean particle size 3-9 nm promoted exclusive formation of p-chloroaniline (p-CAN) and m-nitroaniline (m-NAN). Selective hydrogenation rate was higher over smaller Au particles and can be attributed to increased surface hydrogen (from TPD measurements) at higher metal dispersion. (S)TEM analysis has confirmed an equivalent metal particle size for the supported bimetallics at the same Au loading where TPR indicates Ni-Au interaction and EDX surface mapping established Ni in close proximity to Au on isolated nanoparticles with a composition (Au/Ni) close to the bulk value (= 10). Increased spillover hydrogen due to the incorporation of Ni in the bimetallics resulted in elevated -NO2 group reduction rate. Full selectivity to p-CAN was maintained over all the bimetallic catalysts. Conversion of m-DNB over the lower loaded Ni-Au/Al2O3 generated m-NAN as sole product. An increase in Ni content (0.01 → 0.1 mol%) or a switch from Al2O3 to TiO2 as support resulted in full -NO2 reduction (to m-phenylenediamine). Our results demonstrate the viability of Ni-promotion of Au in the continuous production of functionalised anilines. PMID:25752655

  11. Dissociative Attachment Reactions of Electrons with Gas Phase Superacids

    NASA Astrophysics Data System (ADS)

    Liu, Xifan

    Using the flowing afterglow Langmuir probe (FALP) technique, dissociative attachment coefficients beta for reactions of electrons with gas phase superacids HCo(PF_3)_4, HRh(PF _3)_4 and carbonyl hydride complexes HMn(CO)_5, HRe(CO) _5 have been determined under thermal conditions over the approximate temperature range 300~ 550 K. The superacids react relatively slowly (< 1/20 of beta_{rm max}) with free electrons in a thermal plasma, and the values of beta obtained this far do not show a correlation between acidity and beta. The pioneer researchers in this field had speculated that any superacid would be a rapid attacher of electrons; we found that this speculation is not true in general. The product distribution of electron attachment reaction to HCo(PF_3)_4 was found to be independent of temperature even though the beta (HCo(PF_3)_4 ) increases with temperature. This leads us to propose that the electron attachment process occurs well before the excited complex dissociates. In addition, the activation energy of HCo(PF_3)_4 for electron attachment has been derived from the Arrhenius plots. The carbonyl hydride complexes, HMn(CO) _5 and HRe(CO)_5, react relatively rapidly (>1/4 of beta_{rm max}) with free electrons in thermal plasma. This indicates that these reactions cannot be significantly endothermic. Observation of rapid attachment for these non-superacids shows that the Mn-CO and Re-CO bonds are weaker than the Mn-H and Re-H bonds, respectively. Comparisons between the carbonyl and trifluorophosphine cases implies that fast electron capture is related more to the CO ligand than to the transition -metal species.

  12. IV-VI semiconductor lasers for gas phase biomarker detection

    NASA Astrophysics Data System (ADS)

    McCann, Patrick; Namjou, Khosrow; Roller, Chad; McMillen, Gina; Kamat, Pratyuma

    2007-09-01

    A promising absorption spectroscopy application for mid-IR lasers is exhaled breath analysis where sensitive, selective, and speedy measurement of small gas phase biomarker molecules can be used to diagnose disease and monitor therapies. Many molecules such as nitric oxide, ethane, formaldehyde, acetaldehyde, acetone, carbonyl sulfide, and carbon disulfide have been connected to diseases or conditions such as asthma, oxidative stress, breast cancer, lung cancer, diabetes, organ transplant rejection, and schizophrenia. Measuring these and other, yet to be discovered, biomarker molecules in exhaled breath with mid-IR lasers offers great potential for improving health care since such tests are non-invasive, real-time, and do not require expensive consumables or chemical reagents. Motivated by these potential benefits, mid-IR laser spectrometers equipped with presently available cryogenically-cooled IV-VI lasers mounted in compact Stirling coolers have been developed for clinical research applications. This paper will begin with a description of the development of mid-IR laser instruments and their use in the largest known exhaled breath clinical study ever performed. It will then shift to a description of recent work on the development of new IV-VI semiconductor quantum well materials and laser fabrication methods that offer the promise of low power consumption (i.e. efficient) continuous wave emission at room temperature. Taken together, the demonstration of compelling clinical applications with large market opportunities and the clear identification of a viable pathway to develop low cost mid-IR laser instrumentation can create a renewed focus for future research and development efforts within the mid-IR materials and devices area.

  13. Gas-Phase Combustion Synthesis of Nonoxide Nanoparticles in Microgravity

    NASA Technical Reports Server (NTRS)

    Axelbaum, R. L.; Kumfer, B. M.; Sun, Z.; Chao, B. H.

    2001-01-01

    Gas-phase combustion synthesis is a promising process for creating nanoparticles for the growing nanostructure materials industry. The challenges that must be addressed are controlling particle size, preventing hard agglomerates, maintaining purity, and, if nonoxides are synthesized, protecting the particles from oxidation and/or hydrolysis during post-processing. Sodium-halide Flame Encapsulation (SFE) is a unique methodology for producing nonoxide nanoparticles that addresses these challenges. This flame synthesis process incorporates sodium and metal-halide chemistry, resulting in nanoparticles that are encapsulated in salt during the early stages of their growth in the flame. Salt encapsulation has been shown to allow control of particle size and morphology, while serving as an effective protective coating for preserving the purity of the core particles. Metals and compounds that have been produced using this technology include Al, W, Ti, TiB2, AlN, and composites of W-Ti and Al-AlN. Oxygen content in SFE synthesized nano- AlN has been measured by neutron activation analysis to be as low as 0.54wt.%, as compared to over 5wt.% for unprotected AlN of comparable size. The overall objective of this work is to study the SFE process and nano-encapsulation so that they can be used to produce novel and superior materials. SFE experiments in microgravity allow the study of flame and particle dynamics without the influence of buoyancy forces. Spherical sodium-halide flames are produced in microgravity by ejecting the halide from a spherical porous burner into a quiescent atmosphere of sodium vapor and argon. Experiments are performed in the 2.2 sec Drop Tower at the NASA-Glenn Research Center. Numerical models of the flame and particle dynamics were developed and are compared with the experimental results.

  14. 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.

  15. Microphase formation at a 2D solid-gas phase transition.

    PubMed

    Schuman, Adam W; Bsaibes, Thomas S; Schlossman, Mark L

    2014-10-01

    Density modulated micro-separated phases (microphases) occur at 2D liquid interfaces in the form of alternating regions of high and low density domains. Brewster angle microscopy (BAM) images demonstrate the existence of microphases in cluster, stripe, and mosaic morphologies at the buried interface between hexane and water with fluoro-alkanol surfactant dissolved in the bulk hexane. At high temperature, the surfactant assembles at the interface in a 2D gaseous state. As the system is cooled additional surfactants condense onto the interface, which undergoes a 2D gas-solid phase transition. Microphase structure is observed within a few degrees of this transition in the form of clusters and labyrinthine stripes. Microphases have been observed previously in a number of other systems; nevertheless, we demonstrate that adsorption transitions at the liquid-liquid interface provide a convenient way to observe a full sequence of temperature-dependent 2D phases, from gas to cluster to stripe to mosaic to inverted stripe phases, as well as coexistence between some of these microphases. Cracking and fracture of the clusters reveal that they are a solid microphase. Theories of microphases often predict a single length scale for cluster and stripe phases as a result of the competition between an attractive and a repulsive interaction. Our observation that two characteristic length scales are required to describe clusters whose diameter is much larger than the stripe period, combined with the solid nature of the clusters, suggests that a long-range elastic interaction is relevant. These results complement earlier X-ray measurements on the same system. PMID:25088351

  16. Laboratory Investigations of Titan Haze Formation: Characterization of Gas Phase and Particle Phase Nitrogen

    NASA Astrophysics Data System (ADS)

    Horst, Sarah; Yoon, Heidi; Li, Rui; deGouw, Joost; Tolbert, Margaret

    2014-11-01

    Prior to the arrival of the Cassini-Huygens spacecraft, aerosol production in Titan’s atmosphere was believed to begin in the stratosphere where chemical processes are predominantly initiated by far ultraviolet (FUV) radiation. However, the discovery of very heavy ions, coupled with Cassini Ultraviolet Imaging Spectrograph (UVIS) occultation measurements that show haze absorption up to 1000 km altitude (Liang et al., 2007), indicates that haze formation initiates in the thermosphere. The energy environment of the thermosphere is significantly different from the stratosphere; in particular there is a greater flux of extreme ultraviolet (EUV) photons and energetic particles available to initiate chemical reactions, including the destruction of N2, in the upper atmosphere. The discovery of previously unpredicted nitrogen species in measurements of Titan’s atmosphere by the Cassini Ion and Neutral Mass Spectrometer (INMS) indicates that nitrogen participates in the chemistry to a much greater extent than was appreciated before Cassini (Vuitton et al., 2007). Additionally, measurements obtained by the Aerosol Collector Pyrolyzer (ACP) carried by Huygens to Titan’s surface may indicate that Titan’s aerosols contain significant amounts of nitrogen (Israël et al., 2005, 2006). The degree of nitrogen incorporation in the haze particles is important for understanding the diversity of molecules that may be present in Titan’s atmosphere and on its surface. We have conducted a series of Titan atmosphere simulation experiments using either spark discharge (tesla coil) or FUV photons (deuterium lamp) to initiate chemistry in CH4/N2 gas mixtures ranging from 0.01% CH4/99.99% N2 to 10% CH4/90% N2. We obtained in situ measurements using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) to measure the particle composition as a function of particle size and a proton-transfer ion-trap mass spectrometer (PIT-MS) to measure the composition of gas phase

  17. The effects of bubbles on the structure of upward gas-liquid flow

    NASA Astrophysics Data System (ADS)

    Gubaidulin, D. A.; Snigerev, B. A.

    2016-01-01

    The paper presents the results of study of the local structure of turbulent gas-liquid flow in vertical pipe. A mathematical model based on the use of Eulerian description for both phases taking into account the action of different forces of interfacial interaction. Special attention is paid to the development of approaches for the simulation of polydispersed bubbly flows taking into account processes of coagulation and fragmentation. Comparison of simulation results with experimental data showed that the developed approach allows to obtain detailed information about the structures of turbulent gas-liquid flows, the distribution of bubbles by size.

  18. Capillary effects on gas hydrate three-phase stability in marine sediments

    NASA Astrophysics Data System (ADS)

    Liu, X.; Flemings, P. B.

    2013-12-01

    We study the three-phase (Liquid + Gas + Hydrate) stability of the methane hydrate system in marine sediments by considering the capillary effects on both hydrate and free gas phases. The aqueous CH4 solubilities required for forming hydrate (L+H) and free gas (L+G) in different pore sizes can be met in a three-phase zone. The top of the three-phase zone shifts upward in sediments as the water depth increases and the mean pore size decreases. The thickness of the three-phase zone increases as the pore size distribution widens. The top of the three-phase zone can either overlie the three-phase stability depth at deepwater Blake Ridge or underlie the three-phase stability depth at Hydrate Ridge in shallow water. Our model prediction is compatible with worldwide observations that the bottom-simulating reflector is systematically shifted upward relative to the bulk equilibrium depth as water depth (pressure) is increased. The gas hydrate and free gas saturations of the three-phase zone at Blake Ridge Comparison of the globally compiled BSR temperatures with the three-phase equilibrium curves for the systems of pure CH4 + 3.5 wt.% seawater (solid line) and pure CH4 + 2.0 wt.% seawater (dotted line). The discrepancies between the observed BSR temperature and the calculated three-phase temperature are systematically larger in deep water than in shallow water.

  19. The Relative Importance of Aqueous-Phase and Gas-Phase Phenol Oxidation as Sources of SOA (Invited)

    NASA Astrophysics Data System (ADS)

    Anastasio, C.; Smith, J.

    2010-12-01

    The oxidation of phenols is a source of secondary organic aerosol (SOA) in the gas phase as well as in aqueous phases (e.g., cloud and fog drops and water-containing aerosol particles). The relative importance of the gas- and aqueous-phase pathways depends largely on three factors: (1) the partitioning of phenols between the gaseous and condensed phases, (2) the rates of reaction in each phase, and (3) the yields of SOA in each phase. Our goal in this work is to determine the relative importance of these two pathways as sources of SOA. Using previously published rate constants, as well as newly determined kinetics and SOA yield data in the aqueous phase, we find that in a cloudy atmosphere both aqueous- and gas-phase sinks are significant for phenols with high vapor pressures (e.g., phenol itself), but that aqueous-phase sinks can dominate for phenols with lower vapor pressures (e.g., phenols with multiple hydroxy or methoxy substituents). In regions with wood combustion (a major source of phenols), our calculations indicate that destruction of phenols within wood smoke particles is very important and that reaction with particulate triplet excited states is a major sink.

  20. Using a plenoptic sensor to reconstruct vortex phase structures.

    PubMed

    Wu, Chensheng; Ko, Jonathan; Davis, Christopher C

    2016-07-15

    A branch point problem and its solution commonly involve recognizing and reconstructing a vortex phase structure around a singular point. In laser beam propagation through random media, the destructive phase contributions from various parts of a vortex phase structure will cause a dark area in the center of the beam's intensity profile. This null of intensity can, in turn, prevent the vortex phase structure from being recognized. In this Letter, we show how to use a plenoptic sensor to transform the light field of a vortex beam so that a simple and direct reconstruction algorithm can be applied to reveal the vortex phase structure. As a result, we show that the plenoptic sensor is effective in detecting branch points and can be used to reconstruct phase distortion in a beam in a wide sense. PMID:27420487

  1. CO2 Capture from Flue Gas by Phase Transitional Absorption

    SciTech Connect

    Liang Hu

    2009-06-30

    A novel absorption process called Phase Transitional Absorption was invented. What is the Phase Transitional Absorption? Phase Transitional Absorption is a two or multi phase absorption system, CO{sub 2} rich phase and CO{sub 2} lean phase. During Absorption, CO{sub 2} is accumulated in CO{sub 2} rich phase. After separating the two phases, CO{sub 2} rich phase is forward to regeneration. After regeneration, the regenerated CO{sub 2} rich phase combines CO{sub 2} lean phase to form absorbent again to complete the cycle. The advantage for Phase Transitional Absorption is obvious, significantly saving on regeneration energy. Because CO{sub 2} lean phase was separated before regeneration, only CO{sub 2} rich phase was forward to regeneration. The absorption system we developed has the features of high absorption rate, high loading and working capacity, low corrosion, low regeneration heat, no toxic to environment, etc. The process evaluation shows that our process is able to save 80% energy cost by comparing with MEA process.

  2. All metal valve structure for gas systems

    DOEpatents

    Baker, Ray W.; Pawlak, Donald A.; Ramey, Alford J.

    1984-11-13

    A valve assembly with a resilient metal seat member is disclosed for providing a gas-tight seal in a gas handling system. The valve assembly also includes a valve element for sealing against the valve seat member; and an actuating means for operating the valve element. The valve seat member is a one-piece stainless steel ring having a central valve port and peripheral mounting flange, and an annular corrugation in between. A groove between the first and second ridges serves as a flexure zone during operation of the valve member and thus provides the seating pressure between the inner ridge or valve seat and the valve element. The outer annular ridge has a diameter less than said valve element to limit the seating motion of the valve element, preventing non-elastic deformation of the seat member.

  3. Condensed-phase versus gas-phase ozonolysis of catechol: A combined experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Barnum, Timothy J.; Medeiros, Nicholas; Hinrichs, Ryan Z.

    2012-08-01

    Anthropogenic emissions of volatile aromatic compounds contribute to the formation of secondary organic aerosols (SOA), especially in urban environments. Aromatic SOA precursors typically require oxidation by hydroxyl radicals, although recent work suggests that ozonolysis of 1,2-benzenediols produces SOA in high yields. We employed attenuated total reflectance and transmission infrared spectroscopy to investigate the heterogeneous ozonolysis of catechol thin films. Formation of the dominant condensed-phase product muconic acid was highly dependent on relative humidity (RH) with few products detected below 40% RH and a maximum reactive uptake coefficient of γ = (5.6 ± 0.5) × 10-5 measured at 81.2% RH. We also performed quantum chemical calculations mapping out several reaction pathways for the homogeneous ozonolysis of gaseous catechol. 1,3-cycloaddition transition states were rate limiting with the most favorable activation energies at 45.4 and 47.1 kJ mol-1 [CCSD(T)/6-311++G(d,p)] corresponding to addition across and adjacent to the diol Cdbnd C, respectively. Gas-phase rate constants, calculated using transition state theory, were six orders of magnitude slower than experimental values. In contrast, a calculated activation energy was lower for the ozonolysis of a catechol•H2O complex, which serves as a first-approximation for modeling the ozonolysis of condensed-phase catechol. These combined results suggests that homogeneous ozonolysis of catechol may not be important for the formation of secondary organic aerosols but that ozonolysis of surface-adsorbed catechol may contribute to SOA growth.

  4. Phase structure of a single urban intersection: a simulation study

    NASA Astrophysics Data System (ADS)

    Ebrahim Foulaadvand, M.; Fukui, M.; Belbasi, S.

    2010-07-01

    We study the phase structure of a cellular automata model proposed by Belbasi and Foulaadvand to describe the vehicular traffic flow at the intersection of two perpendicular streets. A set of traffic lights operating in a fixed-time scheme controls the traffic flow. A closed boundary condition is applied to the streets, each of which conducts a unidirectional flow. Streets are single-lane and cars cannot turn upon reaching the intersection. Via extensive Monte Carlo simulations it is shown that the model phase diagram consists of ten phases. The flow characteristics in each phase are investigated and the types of phase transitions between phases are specified.

  5. Dual-phase Cr-Ta alloys for structural applications

    DOEpatents

    Liu, Chain T.; Brady, Michael P.; Zhu, Jiahong; Tortorelli, Peter F.

    2001-01-01

    Dual phase alloys of chromium containing 2 to 11 atomic percent tantalum with minor amounts of Mo, Cr, Ti, Y, La, Cr, Si and Ge are disclosed. These alloys contain two phases including Laves phase and Cr-rich solid solution in either eutectic structures or dispersed Laves phase particles in the Cr-rich solid solution matrix. The alloys have superior mechanical properties at high temperature and good oxidation resistance when heated to above 1000.degree. C. in air.

  6. Small-animal microangiography using phase-contrast X-ray imaging and gas as contrast agent

    NASA Astrophysics Data System (ADS)

    Lundström, Ulf; Larsson, Daniel H.; Westermark, Ulrica K.; Burvall, Anna; Hertz, Hans M.

    2014-03-01

    We use propagation-based phase-contrast X-ray imaging with gas as contrast agent to visualize the microvasculature in small animals like mice and rats. The radiation dose required for absorption X-ray imaging is proportional to the minus fourth power of the structure size to be detected. This makes small vessels impossible to image at reasonable radiation doses using the absorption of conventional iodinated contrast agents. Propagation-based phase contrast gives enhanced contrast for high spatial frequencies by moving the detector away from the sample to let phase variations in the transmitted X-rays develop into intensity variations at the detector. Blood vessels are normally difficult to observe in phase contrast even with iodinated contrast agents as the density difference between blood and most tissues is relatively small. By injecting gas into the blood stream this density difference can be greatly enhanced giving strong phase contrast. One possible gas to use is carbon dioxide, which is a clinically accepted X-ray contrast agent. The gas is injected into the blood stream of patients to temporarily displace the blood in a region and thereby reduce the X-ray absorption in the blood vessels. We have shown that this method can be used to image blood vessels down to 8 μm in diameter in mouse ears. The low dose requirements of this method indicate a potential for live small-animal imaging and longitudinal studies of angiogenesis.

  7. Three-phase measurements of oil and gas trapping in sand packs

    NASA Astrophysics Data System (ADS)

    Al Mansoori, Saleh K.; Iglauer, Stefan; Pentland, Christopher H.; Blunt, Martin J.

    2009-10-01

    We measure the trapped saturations of oil and gas as a function of initial saturation in water-wet sand packs. We start with a water-saturated column and inject octane (oil), while water and oil are produced from the bottom. Once water production has ceased, air (gas) then enters from the top, allowing oil and gas to drain under gravity for different times. Finally water is then injected from the bottom to trap both oil and gas. The columns are sliced and the fluids analyzed using gas chromatography. We find that for high initial gas saturations more gas can be trapped in the presence of oil than in a two-phase (gas/water) system. The residual gas saturation can be over 20% compared to 14% in two-phase flow [Al Mansoori SK, Iglauer S, Pentland CH, Bijeljic B, Blunt MJ. Measurements of non-wetting phase trapping applied to carbon dioxide storage. Energy Procedia 2009;1(1):3173-80]. This is unlike previous measurements on consolidated media, where the trapped gas saturation is either similar or lower to that reached in an equivalent two-phase experiment. For lower initial gas saturation, the amount of trapping follows the initial-residual trend seen in two-phase experiments. The amount of oil trapped is insensitive to initial gas saturation or the amount of gas that is trapped, again in contrast to measurements on consolidated media. More oil is trapped than would be predicted from an equivalent two-phase (oil/water) system, although the trapped saturation is never larger than the maximum reached in two-phase flow (around 11%) [Pentland CH, Al Mansoori SK, Iglauer S, Bijeljic B, Blunt MJ. Measurement of non-wetting phase trapping in sand packs. In: SPE 115697, proceedings of the SPE annual technical conference and exhibition, Denver, Colorado, USA; 21-24 September 2008]. These initially surprising results are explained in the context of oil layer stability and the competition between snap-off and piston-like advance. In two-phase systems, displacement is principally

  8. FLUE GAS DESULFURIZATION PILOT STUDY. PHASE II. APPLICABILITY STUDY

    EPA Science Inventory

    The North Atlantic Treaty Organization Committee on the Challenges of Modern Society (NATO-CCMS) Flue Gas Desulfurization (FGD) Study Group prepared status reports on 12 FGD processes. Results of this work are summarized in NATO Report No. 95 titled 'Flue Gas Desulfurization Pilo...

  9. Dissolved gas transport in the presence of a trapped gas phase: Experimental evaluation of a two-dimensional kinetic model

    SciTech Connect

    Donaldson, J.H.; Istok, J.D.; O`Reilly, K.T.

    1998-01-01

    Quantitative information on dissolved gas transport in ground water aquifers is needed for a variety of site characterization and remedial design applications. The objective of this study was to gain further understanding of dissolved gas transport in the presence of trapped gas in the pore space of an otherwise water saturated porous medium, using a combination of laboratory experiments and numerical modeling. Transport experiments were conducted in a large-scale laboratory physical aquifer model containing a homogeneous sandpack. Tracer (Br{sup {minus}}) and dissolved gas (O{sub 2} or H{sub 2}) plumes were created using a two-well injection/extraction scheme and then were allowed to drift in a uniform flow field. Plume locations and shapes were monitored by measuring tracer and dissolved gas concentrations as a function of position within the sandpack and time. In all experiments, partitioning of the dissolved gases between the mobile ground water and stationary trapped gas phases resulted in substantial retardation and tailing of the dissolved O{sub 2} and H{sub 2} plumes relative to the Br{sup {minus}} plumes. Most observed plume features could be reproduced in simulations performed with a numerical model that combined the advection-dispersion equation with diffusion controlled mass transfer of dissolved gas between the mobile aqueous and stationary trapped gas phases. Fitted values of the volumetric trapped gas content and mass transfer coefficient ranged from 0.04 to 0.08 and from 10{sup {minus}6} to 10{sup {minus}5} sec{sup {minus}1}, respectively. Sensitivity analyses were used to examine how systematic variations in these parameters would be expected to affect dissolved gas transport under a range of potential field conditions. The experimental and modeling results indicate that diffusion controlled mass transfer should be considered when predicting dissolved gas transport in ground water aquifers in the presence of trapped gas.

  10. [Characteristics of water-gas two-phase CO2 transport in unsaturated zone].

    PubMed

    Yu, Yanxin; Chen, Jiajun; Wang, Jinsheng; Yun, Ying; Li, Shushen; Wang, Zhiming

    2003-07-01

    The migration of CO2 in soil was simulated through use of soil column, especially the transformation of CO2 between water and gas phases at wetting front was studied. The soil column in the test was 1 m long and the concentration of CO2 solution was 748 mg/L. Through analysis, it was shown that CO2 migration in water phase was governed by advection, dispersion, reaction and mass transfer between water and gas phases, that in gas phase by advection, dispersion, mass transfer between two phases. Sampling method under dynamic condition of two phase flow in soil column was approached and mass transfer coefficient from water phase to gas phase was determined as 0.00061. This showed that there was certain mass transformation of CO2 from water phase to gas phase and yet it was not so significant. This study can provide the quantitative scientific bases for safety assessment of geological disposal of low and intermediate level radioactive waste and environmental impact assessment of solid waste disposal by landfilling. PMID:14551970

  11. A new method for measurement of gas-phase ammonia and amines in air

    NASA Astrophysics Data System (ADS)

    Dawson, M. L.; Gomez, A.; Arquero, K. D.; Perraud, V. M.; Finlayson-Pitts, B. J.

    2013-12-01

    Accurately predicting particle formation and growth from gas phase precursors is an essential component of modeling the impact of particulate matter on human health, visibility and climate. While the reactions of ammonia with nitric and sulfuric acids to form particulate nitrate and sulfate particles is well known, it has been recently recognized that gas-phase amines, even at low ppb levels, significantly enhance particle formation from common atmospheric acids. As a result, accurate data on the sources, sinks and typical background concentrations of gas-phase amines, are crucial to predicting new particle formation in the atmosphere. However, gas-phase amines are notoriously difficult to measure, as they have a tendency to stick to surfaces, including sampling lines and inlets. In addition, background amine concentrations in the atmosphere are typically a few ppb or lower, requiring low detection limits for ambient sampling techniques. Here we report the development of a simple, reliable method for detection of gas-phase amines at atmospherically relevant concentrations using collection on a cation exchange sorbent followed by in-line extraction and ion chromatography. Gas-phase standards of several amines and ammonia are used to characterize the technique and results from ambient samples in an agricultural area are presented. The application of this technique to field measurements as well as to laboratory measurements of new particle formation from gas-phase ammonia and amines are discussed.

  12. Phase structure of fuzzy black holes

    NASA Astrophysics Data System (ADS)

    Digal, S.; Govindarajan, T. R.; Gupta, Kumar S.; Martin, X.

    2012-01-01

    Noncommutative deformations of the BTZ black holes are described by non- commutative cylinders. We study the scalar fields in this background. The spectrum is studied analytically and through numerical simulations we establish the existence of novel `stripe phases'. These are different from stripes on Moyal spaces and stable due to topo- logical obstruction.

  13. Phase structure of QCD for heavy quarks

    NASA Astrophysics Data System (ADS)

    Fischer, Christian S.; Luecker, Jan; Pawlowski, Jan M.

    2015-01-01

    We investigate the nature of the deconfinement and Roberge-Weiss transition in the heavy quark regime for finite real and imaginary chemical potential within the functional approach to continuum QCD. We extract the critical phase boundary between the first-order and crossover regions and also explore tricritical scaling. Our results confirm previous ones from finite volume lattice studies.

  14. Laser Additive Manufacturing of Gas Permeable Structures

    NASA Astrophysics Data System (ADS)

    Klahn, C.; Bechmann, F.; Hofmann, S.; Dinkel, M.; Emmelmann, C.

    Laser additive manufacturing offers a variety of new design possibilities. In mold making laser additive manufactured inserts with conformal cooling channels are already state of the art. Pneumatic ejectors for injection molds are a new application for laser additive manufacturing. The pneumatic ejectors require a durable gas permeable material. This material is produced by placing the scan vectors for the laser additive manufacturing process in a defined pattern. Trials with different plastics proofed the function and reliability of the pneumatic ejector concept in the injection molding cycle.

  15. Photoinduced intermolecular cross-linking of gas phase triacylglycerol lipid ions.

    PubMed

    Nie, Shuai; Pham, Huong T; Blanksby, Stephen J; Reid, Gavin E

    2015-01-01

    Complex mixtures of plant derived triglycerol (TG) lipids are commonly used as feedstock components for the production of industrial polymers. However, there remains a need for the development of analytical strategies to investigate the intrinsic intermolecular cross-linking reactivity of individual TG molecules within these mixtures as a function of their structures and physicochemical properties, and for the characterization of the resultant products. Here, to address this need, we describe a novel multistage tandem mass spectrometry based method for intermolecular cross-linking and subsequent structural characterization of TG lipid ions in the gas phase. Cross-linking reactions were initiated using 266 nm ultraviolet photodissociation tandem mass spectrometry (UVPD-MS/MS) of saturated or unsaturated TG dimers introduced via electrospray ionization into a linear ion trap mass spectrometer as noncovalent complexes with protonated 3,4-, 2,4- or 3,5- diiodoaniline (diIA). UVPD resulted in the initial formation of an anilinyl biradical via the sequential loss of two iodine radicals, which underwent further reaction to yield multiple cross-linked TG products along with competing noncross-linking processes. These chemistries are proposed to occur via sequential combinations of hydrogen abstraction (H-abstraction), radical addition and radical recombination. Multistage collision induced dissociation tandem mass spectrometry (CID-MS(n)) was used to obtain evidence for the structures and mechanisms of formation for these products, as a function of both the TG lipid and diIA ion structures. The efficiency of the UVPD reaction was shown to be dependent on the number of unsaturation sites present within the TG lipids. However, when unsaturation sites were present, formation of the cross-linked and noncross-linked product ions via H-abstraction and radical addition mechanisms was found to be competitive. Finally, the identity of the anilinyl biradical (e.g., 3,4- versus 2

  16. Gas-phase lithium cation affinity of glycine.

    PubMed

    Bourcier, Sophie; Chiaa, Ru Xuan; Mimbong, Rosa Ngo Biboum; Bouchoux, Guy

    2015-01-01

    The gas-phase lithium cation binding thermochemistry of glycine has been determined theoretically by quantum chemical calculations at the G4 level and experimentally by the extended kinetic method using electrospray ionization quadrupole time-of-flight tandem mass spectrometry. The lithium cation affinity of glycine, ∆(Li)H°(298)(GLY), i.e. the∆(Li)H°(298) of the reaction GlyLi(+)→ Gly + Li(+)) given by the G4 method is equal to 241.4 kJ.mol(-1) if only the most stable conformer of glycine is considered or to 242.3 kJ.mol(-1) if the 298K equilibrium mixture of neutral conformers is included in the calculation. The ∆(Li)H°(298)(GLY) deduced from the extended kinetic method is obviously dependent on the choice of the Li(+) affinity scale, thus∆(Li)H°(298)(GLY) is equal to 228.7±0.9(2.0) kJ.mol(- 1) if anchored to the recently re-evaluated lithium cation affinity scale but shifted to 235.4±1.0 kJ.mol(-1) if G4 computed lithium cation affinities of the reference molecules is used. This difference of 6.3 kJ.mol(-1) may originate from a compression of the experimental lithium affinity scale in the high ∆(Li)H°(298) region. The entropy change associated with the reaction GlyLi(+)→Gly + Li(+) reveals a gain of approximately 15 J.mol(-) 1.K(-1) with respect to monodentate Li(+) acceptors. The origin of this excess entropy is attributed to the bidentate interaction between the Li(+) cation and both the carbonyl oxygen and the nitrogen atoms of glycine. The computed G4 Gibbs free energy,∆(Li)G°(298)(GLY) is equal to 205.3 kJ.mol(-1), a similar result, 201.0±3.4 kJ.mol(-1), is obtained from the experiment if the∆(Li)G°(298) of the reference molecules is anchored on the G4 results. PMID:26307695

  17. Detection methods for atoms and radicals in the gas phase

    NASA Astrophysics Data System (ADS)

    Hack, W.

    This report lists atoms and free radicals in the gas phase which are of interest for environmental and flame chemistry and have been detected directly. The detection methods which have been used are discussed with respect to their range of application, specificity and sensitivity. In table 1, detection methods for the five atoms of group IV (C, Si, Ge, Sn, Pb) and about 60 radicals containing at least one atom of group IV are summarized (CH, Cd, Cf, CC1, CBr, Cn, Cs, CSe, CH2, CD2, Chf, Cdf, CHC1, CHBr, CF2, CC12, CBr2, CFC1, CFBr, CH3, CD3, CF3, CH2F, CH2C1, CH2Br, CHF2, CHC12, CHBr2, Hco, Fco, CH30, CD30, CH2OH, CH3S, Nco, CH4N, CH302, CF302; C2, C2N, C2H, C20, C2HO, C2H3, C2F3, C2H5, C2HsO, C2H4OH, CH3CO, CD3CO, C2H3O, C2H502, CH3COO2, C2H4N, C2H6N, C3; Si, SiF, SiF2, SiO, SiC, Si2; Ge, GeC, GeO, GeF, GeF2, GeCl2, Sn, SnF, SnO, SnF2, Pb, PbF, PbF2, PbO, PbS). In table 2 detection methods for about 25 other atoms and 60 radicals are listed: (H, D, O, O2, Oh, Od, HO2, DO2, F, Ci, Br, I, Fo, Cio, BrO, Io, FO2, C1O2, Li, Na, K, Rb, Cs, N, N3, Nh, Nd, Nf, Nci, NBr, NH2, ND2, Nhd, Nhf, NF2, NC12, N2H3, No, NO2, NO3, Hno, Dno, P, Ph, Pd, Pf, Pci, PH2, PD2, PF2, Po, As, AsO, AsS, Sb, Bi, S, S2, Sh, Sd, Sf, SF2, So, Hso, Dso, Sn, Se, Te, Se2, SeH, SeD, SeF, SeO, SeS, SeN, TeH, TeO, Bh, BH2, Bo, Bn, B02, Cd, Hg, UF5). The tables also cite some recent kinetic applications of the various methods.

  18. The Noble Gas Record of Gas-Water Phase Interaction in the Tight-Gas-Sand Reservoirs of the Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Ballentine, C. J.; Zhou, Z.; Harris, N. B.

    2015-12-01

    The mass of hydrocarbons that have migrated through tight-gas-sandstone systems before the permeability reduces to trap the hydrocarbon gases provides critical information in the hydrocarbon potential analysis of a basin. The noble gas content (Ne, Ar, Kr, Xe) of the groundwater has a unique isotopic and elemental composition. As gas migrates through the water column, the groundwater-derived noble gases partition into the hydrocarbon phase. Determination of the noble gases in the produced hydrocarbon phase then provides a record of the type of interaction (simple phase equilibrium or open system Rayleigh fractionation). The tight-gas-sand reservoirs of the Rocky Mountains represent one of the most significant gas resources in the United States. The producing reservoirs are generally developed in low permeability (averaging <0.1mD) Upper Cretaceous fluvial to marginal marine sandstones and commonly form isolated overpressured reservoir bodies encased in even lower permeability muddy sediments. We present noble gas data from producing fields in the Greater Green River Basin, Wyoming; the the Piceance Basin, Colorado; and in the Uinta Basin, Utah. The data is consistent from all three basins. We show how in each basin the noble gases record open system gas migration through a water column at maximum basin burial. The data within an open system model indicates that the gas now in-place represents the last ~10% of hydrocarbon gas to have passed through the water column, most likely prior to permeability closedown.

  19. Enhancement of gas-phase diffusion in the presence of liquid

    NASA Astrophysics Data System (ADS)

    Webb, S.; Angert, A.

    2003-04-01

    Gas diffusion in porous media occurs in both the gas and liquid phases. In many instances, gas diffusion in the liquid phase is ignored. However, under many conditions, gas diffusion in the liquid phase may be more important than gas diffusion in the gas phase. Two different cases will be examined in this work. The first case is a continuous liquid path between the gas concentrations of interest modeled after Jury et al. (1984). The second case is the situation at low liquid saturation where liquid islands exist. For the first case, Jury's model can be rewritten as a ratio of the total gas diffusion in the gas and liquid phases to that just in the gas phase. The liquid diffusion coefficient is approximately 10-4 times the gas diffusion coefficient consistent with Jury et al. (1984). The ratio of total diffusion to gas-phase diffusion is then only a function of Henry's constant and the liquid saturation. For higher values of Henry's constant, such as for CO2 and O2, the effect of diffusion in the liquid phase is small except at high liquid saturations. For small values of Henry's constant, such as for some VOCs and explosive compounds, diffusion in the liquid phase dominates for low and moderate liquid saturation values. The second case is the enhancement of diffusion caused by liquid islands at low liquid saturation. Enhanced vapor diffusion across liquid islands has been observed and modeled by Webb and Ho (1999), where condensation and evaporation occur on opposite ends of the liquid island. Vapor diffusion enhancement of up to a factor of 10 has been observed. Similarly, gas can diffuse through the liquid island. For high values of Henry's constant, gas diffusion through liquid islands is negligible and can be ignored. For small values of Henry's constant, diffusion through liquid islands may be much greater than diffusion through gas, so the rate is enhanced. The work was sponsored by the Geneva International Center for Humanitarian Demining (GICHD) under the

  20. Atomic Structure and Phase Transformations in Pu Alloys

    SciTech Connect

    Schwartz, A J; Cynn, H; Blobaum, K M; Wall, M A; Moore, K T; Evans, W J; Farber, D L; Jeffries, J R; Massalski, T B

    2008-04-28

    Plutonium and plutonium-based alloys containing Al or Ga exhibit numerous phases with crystal structures ranging from simple monoclinic to face-centered cubic. Only recently, however, has there been increased convergence in the actinides community on the details of the equilibrium form of the phase diagrams. Practically speaking, while the phase diagrams that represent the stability of the fcc {delta}-phase field at room temperature are generally applicable, it is also recognized that Pu and its alloys are never truly in thermodynamic equilibrium because of self-irradiation effects, primarily from the alpha decay of Pu isotopes. This article covers past and current research on several properties of Pu and Pu-(Al or Ga) alloys and their connections to the crystal structure and the microstructure. We review the consequences of radioactive decay, the recent advances in understanding the electronic structure, the current research on phase transformations and their relations to phase diagrams and phase stability, the nature of the isothermal martensitic {delta} {yields} {alpha}{prime} transformation, and the pressure-induced transformations in the {delta}-phase alloys. New data are also presented on the structures and phase transformations observed in these materials following the application of pressure, including the formation of transition phases.

  1. Dynamic Modeling Strategy for Flow Regime Transition in Gas-Liquid Two-Phase Flows

    SciTech Connect

    Xia Wang; Xiaodong Sun; Benjamin Doup; Haihua Zhao

    2012-12-01

    In modeling gas-liquid two-phase flows, the concept of flow regimes has been widely used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are flow regime dependent. Current nuclear reactor safety analysis codes, such as RELAP5, classify flow regimes using flow regime maps or transition criteria that were developed for steady-state, fully-developed flows. As twophase flows are dynamic in nature, it is important to model the flow regime transitions dynamically to more accurately predict the two-phase flows. The present work aims to develop a dynamic modeling strategy to determine flow regimes in gas-liquid two-phase flows through introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation of the interfacial area, fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation, and the destruction of the interfacial area, fluid particle coalescence and condensation. For flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shapes, namely group-1 and group-2 bubbles. A preliminary approach to dynamically identify the flow regimes is discussed, in which discriminator s are based on the predicted information, such as the void fraction and interfacial area concentration. The flow regime predicted with this method shows good agreement with the experimental observations.

  2. The gas-phase thermal chemistry of tetralin and related model systems

    SciTech Connect

    Malandra, J.

    1993-05-01

    The thesis is divided into 5 papers: gas-phase thermal decomposition of tetralin; flash vacuum pyrolysis of 3-benzocycloheptenone and 1,3, 4,5-tetrahydro-2-benzothiepin-2,2-dioxide (model systems for gas-phase pyrolysis of tetralin); high-temperature gas-phase reactions of o-allylbenzyl radicals generated by flash vacuum pyrolysis of is(o-allylbenzyl) oxalate; flash vacuum pyrolysis of 1,4-diphenylbutane; and flash vacuum pyrolysis of o-allyltoluene, o-(3-butenyl)toluene and o-(pentenyl)toluene were also used.

  3. 2D ice from first principles: structures and phase transitions

    NASA Astrophysics Data System (ADS)

    Chen, Ji; Schusteritsch, Georg; Pickard, Chris J.; Salzmann, Christoph G.; Michaelides, Angelos

    Despite relevance to disparate areas such as cloud microphysics and tribology, major gaps in the understanding of the structures and phase transitions of low-dimensional water ice remain. Here we report a first principles study of confined 2D ice as a function of pressure. We find that at ambient pressure hexagonal and pentagonal monolayer structures are the two lowest enthalpy phases identified. Upon mild compression the pentagonal structure becomes the most stable and persists up to ca. 2 GPa at which point square and rhombic phases are stable. The square phase agrees with recent experimental observations of square ice confined within graphene sheets. We also find a double layer AA stacked square ice phase, which clarifies the difference between experimental observations and earlier force field simulations. This work provides a fresh perspective on 2D confined ice, highlighting the sensitivity of the structures observed to both the confining pressure and width.

  4. Detection of the Elusive Triazane Molecule (N3 H5 ) in the Gas Phase.

    PubMed

    Förstel, Marko; Maksyutenko, Pavlo; Jones, Brant M; Sun, Bing-Jian; Chen, Shih-Hua; Chang, Agnes H-H; Kaiser, Ralf I

    2015-10-26

    We report the detection of triazane (N3 H5 ) in the gas phase. Triazane is a higher order nitrogen hydride of ammonia (NH3 ) and hydrazine (N2 H4 ) of fundamental importance for the understanding of the stability of single-bonded chains of nitrogen atoms and a potential key intermediate in hydrogen-nitrogen chemistry. The experimental results along with electronic-structure calculations reveal that triazane presents a stable molecule with a nitrogen-nitrogen bond length that is a few picometers shorter than that of hydrazine and has a lifetime exceeding 6±2 μs at a sublimation temperature of 170 K. Triazane was synthesized through irradiation of ammonia ice with energetic electrons and was detected in the gas phase upon sublimation of the ice through soft vacuum ultraviolet (VUV) photoionization coupled with a reflectron-time-of-flight mass spectrometer. Isotopic substitution experiments exploiting [D3 ]-ammonia ice confirmed the identification through the detection of its fully deuterated counterpart [D5 ]-triazane (N3 D5 ). PMID:26331382

  5. Single-step gas phase synthesis of stable iron aluminide nanoparticles with soft magnetic properties

    SciTech Connect

    Vernieres, Jerome Benelmekki, Maria; Kim, Jeong-Hwan; Grammatikopoulos, Panagiotis; Diaz, Rosa E.; Bobo, Jean-François; Sowwan, Mukhles

    2014-11-01

    Soft magnetic alloys at the nanoscale level have long generated a vivid interest as candidate materials for technological and biomedical purposes. Consequently, controlling the structure of bimetallic nanoparticles in order to optimize their magnetic properties, such as high magnetization and low coercivity, can significantly boost their potential for related applications. However, traditional synthesis methods stumble upon the long standing challenge of developing true nanoalloys with effective control over morphology and stability against oxidation. Herein, we report on a single-step approach to the gas phase synthesis of soft magnetic bimetallic iron aluminide nanoparticles, using a versatile co-sputter inert gas condensation technique. This method allowed for precise morphological control of the particles; they consisted of an alloy iron aluminide crystalline core (DO{sub 3} phase) and an alumina shell, which reduced inter-particle interactions and also prevented further oxidation and segregation of the bimetallic core. Remarkably, the as-deposited alloy nanoparticles show interesting soft magnetic properties, in that they combine a high saturation magnetization (170 emu/g) and low coercivity (less than 20 Oe) at room temperature. Additional functionality is tenable by modifying the surface of the particles with a polymer, to ensure their good colloidal dispersion in aqueous environments.

  6. Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry.

    PubMed

    Campbell, J Larry; Yang, Amy Meng-Ci; Melo, Luke R; Hopkins, W Scott

    2016-07-01

    In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogen-deuterium exchange (HDX)-a probe of ion structure in mass spectrometry-actually altered analyte ion structure by tautomerization. For the N- and O-protonated tautomers of 4-aminobenzoic acid, when separated using DMS and subjected to subsequent HDX with trace levels of D2O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D2O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the O-protonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-aminobenzoic acid upon solvation with eight CH3OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS. Graphical Abstract ᅟ. PMID:27094827

  7. Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry

    NASA Astrophysics Data System (ADS)

    Campbell, J. Larry; Yang, Amy Meng-Ci; Melo, Luke R.; Hopkins, W. Scott

    2016-04-01

    In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogen-deuterium exchange (HDX)—a probe of ion structure in mass spectrometry—actually altered analyte ion structure by tautomerization. For the N- and O-protonated tautomers of 4-aminobenzoic acid, when separated using DMS and subjected to subsequent HDX with trace levels of D2O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D2O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the O-protonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-aminobenzoic acid upon solvation with eight CH3OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS.

  8. Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry

    NASA Astrophysics Data System (ADS)

    Campbell, J. Larry; Yang, Amy Meng-Ci; Melo, Luke R.; Hopkins, W. Scott

    2016-07-01

    In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogen-deuterium exchange (HDX)—a probe of ion structure in mass spectrometry—actually altered analyte ion structure by tautomerization. For the N- and O-protonated tautomers of 4-aminobenzoic acid, when separated using DMS and subjected to subsequent HDX with trace levels of D2O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D2O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the O-protonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-aminobenzoic acid upon solvation with eight CH3OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS.

  9. Distillation tray structural parameter study: Phase 1

    NASA Technical Reports Server (NTRS)

    Winter, J. Ronald

    1991-01-01

    The purpose here is to identify the structural parameters (plate thickness, liquid level, beam size, number of beams, tray diameter, etc.) that affect the structural integrity of distillation trays in distillation columns. Once the sensitivity of the trays' dynamic response to these parameters has been established, the designer will be able to use this information to prepare more accurate specifications for the construction of new trays. Information is given on both static and dynamic analysis, modal response, and tray failure details.

  10. Gas-Phase Dopant-Induced Conformational Changes Monitored with Transversal Modulation Ion Mobility Spectrometry.

    PubMed

    Meyer, Nicole Andrea; Root, Katharina; Zenobi, Renato; Vidal-de-Miguel, Guillermo

    2016-02-16

    The potential of a Transversal Modulation Ion Mobility Spectrometry (TMIMS) instrument for protein analysis applications has been evaluated. The Collision Cross Section (CCS) of cytochrome c measured with the TMIMS is in agreement with values reported in the literature. Additionally, it enables tandem IMS-IMS prefiltration in dry gas and in vapor doped gas. The chemical specificity of the different dopants enables interesting studies on the structure of proteins as CCS changed strongly depending on the specific dopant. Hexane produced an unexpectedly high CCS shift, which can be utilized to evaluate the exposure of hydrophobic parts of the protein. Alcohols produced higher shifts with a dual behavior: an increase in CCS due to vapor uptake at specific absorption sites, followed by a linear shift typical for unspecific and unstable vapor uptake. The molten globule +8 shows a very specific transition. Initially, its CCS follows the trend of the compact folded states, and then it rapidly increases to the levels of the unfolded states. This strong variation suggests that the +8 charge state undergoes a dopant-induced conformational change. Interestingly, more sterically demanding alcohols seem to unfold the protein more effectively also in the gas phase. This study shows the capabilities of the TMIMS device for protein analysis and how tandem IMS-IMS with dopants could provide better understanding of the conformational changes of proteins. PMID:26845079

  11. Two-stage coal liquefaction without gas-phase hydrogen

    DOEpatents

    Stephens, H.P.

    1986-06-05

    A process is provided for the production of a hydrogen-donor solvent useful in the liquefaction of coal, wherein the water-gas shift reaction is used to produce hydrogen while simultaneously hydrogenating a donor solvent. A process for the liquefaction of coal using said solvent is also provided. The process enables avoiding the use of a separate water-gas shift reactor as well as high pressure equipment for liquefaction. 3 tabs.

  12. The gas-phase metallicity of central and satellite galaxies in the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Pasquali, Anna; Gallazzi, Anna; van den Bosch, Frank C.

    2012-09-01

    We exploit the galaxy groups catalogue of Yang et al. and the galaxy properties measured in the Sloan Digital Sky Survey Data Releases 4 and 7 to study how the gas-phase metallicities of star-forming galaxies depend on environment. We find that satellite and central galaxies follow a qualitatively similar stellar mass (M★)-gas-phase metallicity relation, whereby their gas-phase metallicity increases with M★. Satellites, though, have higher gas-phase metallicities than equally massive centrals, and this difference increases with decreasing stellar mass. We find a maximum offset of 0.06 dex at log(M★/h-2 M⊙) ≃ 8.25. At fixed halo mass, centrals are more metal rich than satellites by ˜0.5 dex on average. This is simply due to the fact that, by definition, centrals are the most massive galaxies in their groups, and the fact that gas-phase metallicity increases with stellar mass. More interestingly, we also find that the gas-phase metallicity of satellites increases with halo mass (Mh) at fixed stellar mass. This increment is more pronounced for less massive galaxies, and, at M★ ≃ 109 h-2 M⊙, corresponds to ˜0.15 dex across the range 11 < log (Mh/h-1 M⊙) < 14. We also show that low-mass satellite galaxies have higher gas-phase metallicities than central galaxies of the same stellar metallicity. This difference becomes negligible for more massive galaxies of roughly solar metallicity. We demonstrate that the observed differences in gas-phase metallicity between centrals and satellites at fixed M★ are not a consequence of stellar mass stripping (advocated by Pasquali et al. in order to explain similar differences but in stellar metallicity), nor to the past star formation history of these galaxies as quantified by their surface mass density or gas mass fraction. Rather, we argue that these trends probably originate from a combination of three environmental effects: (i) strangulation, which prevents satellite galaxies from accreting new, low

  13. An investigation into the flow behavior of a single phase gas system and a two phase gas/liquid system in normal gravity with nonuniform heating from above

    NASA Technical Reports Server (NTRS)

    Disimile, Peter J.; Heist, Timothy J.

    1990-01-01

    The fluid behavior in normal gravity of a single phase gas system and a two phase gas/liquid system in an enclosed circular cylinder heated suddenly and nonuniformly from above was investigated. Flow visualization was used to obtain qualitative data on both systems. The use of thermochromatic liquid crystal particles as liquid phase flow tracers was evaluated as a possible means of simultaneously gathering both flow pattern and temperature gradient data for the two phase system. The results of the flow visualization experiments performed on both systems can be used to gain a better understanding of the behavior of such systems in a reduced gravity environment and aid in the verification of a numerical model of the system.

  14. Gas-phase lithium cation basicity of histamine and its agonist 2-([beta]-aminoethyl)-pyridine

    NASA Astrophysics Data System (ADS)

    Hallmann, M.; Raczynska, E. D.; Gal, J. F.; Maria, P. C.

    2007-11-01

    The gas-phase lithium cation basicities (LCBs) were obtained for histamine (HA) and its agonist 2-([beta]-aminoethyl)-pyridine (AEP) from collision-induced dissociation of lithium adducts using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). For measurements, MeO(CH2)2OMe, Et3PO and (Me2N)3PO (HMPA) were used as the reference compounds. The experimental LCB of AEP was located between those of Et3PO and (Me2N)3PO. The experimental LCB of HA was found to be higher than those of AEP and HMPA by more than 2 kcal mol-1 clearly indicating that the LCB of HA is higher than any LCB for a neutral base yet measured (crown-ethers excepted). The experimental LCBs of the parent bases (pyridine and imidazole) are lower by more than 10 kcal mol-1. In parallel, DFT calculations {B3LYP/6-31G*//B3LYP/6-31G* and B3LYP/6-311+G**//B3LYP/6-31G*} were performed for HA, AEP and their lithium adducts. Among the 22 reasonable conformations of the HA-Li+ adduct, only one appears to be significantly more stable than the others. This is also the case for one structure among seven conformations of the AEP-Li+ adduct. These two stable structures have the [`]scorpion' conformation, in which the Li+ cation is almost equally chelated by two basic nitrogen atoms, the ring N-aza and the chain N-amino. Other HA-Li+ and AEP-Li+ conformations have noticeably higher energies than the [`]scorpion' structures. The difference between the DFT calculated LCBs of HA and AEP (about 4 kcal mol-1) is in agreement with that experimentally obtained (>2 kcal mol-1). The high experimental and theoretical values of LCB for HA and AEP militate in favor of a strong chelation of Li+ by both ligands in the gas-phase. This chelation effect was also evidenced previously for the proton gas-phase basicity.

  15. Strain induced incommensurate structures in vicinity of reconstructive phase transitions

    NASA Astrophysics Data System (ADS)

    Korzhenevskii, A. L.; Dmitriev, V.

    2015-09-01

    General conditions controlling the formation of incommensurate phases in crystals undergoing reconstructive phase transitions are analyzed in the framework of a model-free phenomenological approach. A universal trend to stabilizing such intermediate phases in the vicinity of reconstructive phase transitions stems from the fact that certain high-order improper Lifshitz invariants reduce at such transformations to ones bi-linearly coupling critical displacement gradients and strains or even to the proper Lifshitz invariant. The approach developed here introduces a universal mechanism for the formation both of premartensite incommensurate phases and complex structures with giant unit cells, as found in some elemental crystals at high pressure.

  16. Phase decorrelation of coherent structures in a free shear layer

    NASA Technical Reports Server (NTRS)

    Ho, Chih-Ming; Zohar, Yitshak; Foss, Judith K.; Buell, Jeffrey C.

    1991-01-01

    The vortices near the origin of an initially laminar mixing layer have a single frequency with a well-defined phase; i.e., there is little phase jitter. Further downstream, however, the phase jitter increases suddenly. Even when the flow is forced, this same transition is observed. The forcing partially loses its influence because of the decorrelation of the phase between the forcing signal and the passing coherent structures. In the present investigation, this phenomenon is documented and the physical mechanism responsible for the phase decorrelation is identified.

  17. Structural comparison of nickel electrodes and precursor phases

    NASA Technical Reports Server (NTRS)

    Cornilsen, Bahne C.; Shan, Xiaoyin; Loyselle, Patricia

    1989-01-01

    Researchers summarize previous Raman spectroscopic results and discuss important structural differences in the various phases of active mass and active mass precursors. Raman spectra provide unique signatures for these phases, and allow one to distinguish each phase, even when the compound is amorphous to x rays (i.e., does not scatter x rays because of a lack of order and/or small particle size). The structural changes incurred during formation, charge and discharge, cobalt addition, and aging are discussed. The oxidation states and dopant contents are explained in terms of the nonstoichiometric structures.

  18. Phase-field simulation of gas bubble growth and flow in a Hele-Shaw cell

    NASA Astrophysics Data System (ADS)

    Sun, Ying

    2005-11-01

    A diffuse interface model has been developed for gas bubble growth and dynamics in a supersaturated liquid. The liquid becomes supersaturated in the gas species because of a drop in the pressure or temperature. The bubbles grow by gas diffusion in the liquid towards the bubble interfaces. During bubble growth, flows are induced by the large density contrast between the phases. The bubbles coarsen due to surface tension effects. The process widely exists in biological systems, materials processing, oil recovery, and other applications. The flows in the gas and liquid phases are solved using a diffuse interface model for two-phase flows with surface tension, phase change, and density and viscosity differences between the phases. This diffuse-interface model for flow is coupled with a phase-field equation for calculating the interface motion, and a species conservation equation for the gas transport. The model is validated for a single bubble growing inside a semi-infinite liquid, and convergence of the results with respect to the interface width is demonstrated. Large-scale numerical simulations for multiple bubbles inside a Hele-Shaw cell reveal the presence of complex interface dynamics and flows. The bubble dynamics, including coarsening and coalescence, are investigated as a function of the initial gas concentration, surface tension, and the density and viscosity contrasts between the phases.

  19. Gas-phase mercury reduction to measure total mercury in the flue gas of a coal-fired boiler.

    PubMed

    Meischen, Sandra J; Van Pelt, Vincent J; Zarate, Eugene A; Stephens, Edward A

    2004-01-01

    Gaseous elemental and total (elemental + oxidized) mercury (Hg) in the flue gas from a coal-fired boiler was measured by a modified ultraviolet (UV) spectrometer. Challenges to Hg measurement were the spectral interferences from other flue gas components and that UV measures only elemental Hg. To eliminate interference from flue gas components, a cartridge filled with gold-coated sand removed elemental Hg from a flue gas sample. The Hg-free flue gas was the reference gas, eliminating the spectral interferences. To measure total Hg by UV, oxidized Hg underwent a gas-phase, thermal-reduction in a quartz cell heated to 750 degrees C. Simultaneously, hydrogen was added to flash react with the oxygen present forming water vapor and preventing Hg re-oxidation as it exits the cell. Hg concentration results are in parts per billion by volume Hg at the flue gas oxygen concentration. The modified Hg analyzer and the Ontario Hydro method concurrently measured Hg at a field test site. Measurements were made at a 700-MW steam turbine plant with scrubber units and selective catalytic reduction. The flue gas sampled downstream of the selective catalytic reduction contained 2100 ppm SO2 and 75 ppm NOx. Total Hg measured by the Hg analyzer was within 20% of the Ontario Hydro results. PMID:14871013

  20. CIUSuite: A Quantitative Analysis Package for Collision Induced Unfolding Measurements of Gas-Phase Protein Ions.

    PubMed

    Eschweiler, Joseph D; Rabuck-Gibbons, Jessica N; Tian, Yuwei; Ruotolo, Brandon T

    2015-11-17

    Ion mobility-mass spectrometry (IM-MS) is a technology of growing importance for structural biology, providing complementary 3D structure information for biomolecules within samples that are difficult to analyze using conventional analytical tools through the near-simultaneous acquisition of ion collision cross sections (CCSs) and masses. Despite recent advances in IM-MS instrumentation, the resolution of closely related protein conformations remains challenging. Collision induced unfolding (CIU) has been demonstrated as a useful tool for resolving isocrossectional protein ions, as they often follow distinct unfolding pathways when subjected to collisional heating in the gas phase. CIU has been used for a variety of applications, from differentiating binding modes of activation state-selective kinase inhibitors to characterizing the domain structure of multidomain proteins. With the growing utilization of CIU as a tool for structural biology, significant challenges have emerged in data analysis and interpretation, specifically the normalization and comparison of CIU data sets. Here, we present CIUSuite, a suite of software modules designed for the rapid processing, analysis, comparison, and classification of CIU data. We demonstrate these tools as part of a series of workflows for applications in comparative structural biology, biotherapeutic analysis, and high throughput screening of kinase inhibitors. These examples illustrate both the potential for CIU in general protein analysis as well as a demonstration of best practices in the interpretation of CIU data. PMID:26489593

  1. Metal-ligand redox reactions in gas-phase quaternary peptide-metal complexes by electrospray ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Vaisar, T.; Gatlin, C. L.; Turecek, F.

    1997-03-01

    The dipeptides Phe-Leu, Leu-Phe, Leu-Ala, and Ala-Leu form quaternary complexes of the type [Cu(II)(peptide - 2H+M)bpy]+ in the gas phase when electrosprayed in the presence of Cu(II) salts, 2.2'-bipyridyl (bpy), and an alkali hydroxide (MOH). The gas-phase complexes decarboxylate on collisional activation at low ion kinetic energies. The resulting ions undergo unusual eliminations of neutral Na, K, and Rb, which depend on the peptide structure. The ionization energy of the decarboxylated Phe-Leu-Cu-bpy complex was bracketed at 4.2 eV. Other collision-induced dissociations also depend on the alkali metal ion and the peptide structure. Ab initio calculations on a model system are reported and used to discuss the electronic properties of the peptide complexes.

  2. IRMPD Spectroscopy: Evidence of Hydrogen Bonding in the Gas Phase Conformations of Lasso Peptides and their Branched-Cyclic Topoisomers.

    PubMed

    Jeanne Dit Fouque, Kevin; Lavanant, Hélène; Zirah, Séverine; Steinmetz, Vincent; Rebuffat, Sylvie; Maître, Philippe; Afonso, Carlos

    2016-06-01

    Lasso peptides are natural products characterized by a mechanically interlocked topology. The conformation of lasso peptides has been probed in the gas phase using ion mobility-mass spectrometry (IM-MS) which showed differences in the lasso and their unthreaded branched-cyclic topoisomers depending on the ion charge states. To further characterize the evolution of gas phase conformations as a function of the charge state and to assess associated changes in the hydrogen bond network, infrared multiple photon dissociation (IRMPD) action spectroscopy was carried out on two representative lasso peptides, microcin J25 (MccJ25) and capistruin, and their branched-cyclic topoisomers. For the branched-cyclic topoisomers, spectroscopic evidence of a disruption of neutral hydrogen bonds were found when comparing the 3+ and 4+ charge states. In contrast, for the lasso peptides, the IRMPD spectra were found to be similar for the two charge states, suggesting very little difference in gas phase conformations upon addition of a proton. The IRMPD data were thus found consistent and complementary to IM-MS, confirming the stable and compact structure of lasso peptides in the gas phase. PMID:27171649

  3. A Phase-Field Approach to Modeling Hydrate Formation on Methane Gas Bubbles in a Water Column

    NASA Astrophysics Data System (ADS)

    Fu, X.; Cueto-Felgueroso, L.; Waite, W. F.; Ruppel, C. D.; Juanes, R.

    2014-12-01

    Methane hydrates are water-based crystalline solids, where gas molecules are trapped inside the lattice structure formed by water. Most commonly found in deep ocean floors where low temperature and high pressure are primal conditions for hydrate to form, gas hydrates contain most of the world's mobile carbon and yet it remains an important and open question how methane leakage from gas hydrate impacts ocean and the atmosphere. While current work focus on the breakdown of gas hydrate in marine environment and the the release of methane from seafloor, few studies explore the fate of a single or a plume of methane bubbles when entering the water column after the release. We propose to study the fate of an individual and a series of methane bubbles through mathematical modeling, specifically using a phase-field approach. Phase-field modeling is a mathematical framework that describes systems that are out of thermodynamic equilibrium. First introduced in the context of solidification process and phase transitions, it has since been adopted in the field of multiphase flow. In this work, we present a new phase-field formulation for multiphase/multicomponent flows that allows us to model the fate of methane bubbles in the water system as a nonequilibrium process.

  4. Development of Numerical Simulation Method for Compressible Gas-Liquid Two-Phase Flows

    NASA Astrophysics Data System (ADS)

    Tamura, Y.

    2015-12-01

    A numerical simulation method of compressible gas-liquid two-phase flow is developed for analyses of a cavitation bubble. Thermodynamic state of both phases is described with stiffened gas equation of state. Interface of two phases is captured by Level-Set method. As internal energy jump between two phases is critical for the stability of computation, total energy equation is modified so that inviscid flux of energy is smoothly connected across the interface. Detail of governing equations as well as their discretization is described followed by the result of one-dimensional simple example computation.

  5. Gas-phase water-mediated equilibrium between methylglyoxal and its geminal diol

    PubMed Central

    Axson, Jessica L.; Takahashi, Kaito; De Haan, David O.; Vaida, Veronica

    2010-01-01

    In aqueous solution, aldehydes, and to a lesser extent ketones, hydrate to form geminal diols. We investigate the hydration of methylglyoxal (MG) in the gas phase, a process not previously considered to occur in water-restricted environments. In this study, we spectroscopically identified methylglyoxal diol (MGD) and obtained the gas-phase partial pressures of MG and MGD. These results, in conjunction with the relative humidity, were used to obtain the equilibrium constant, KP, for the water-mediated hydration of MG in the gas phase. The Gibbs free energy for this process, ΔG°, obtained as a result, suggests a larger than expected gas-phase diol concentration. This may have significant implications for understanding the role of organics in atmospheric chemistry. PMID:20142510

  6. DETERMINATION OF CHLOROETHENES IN ENVIRONMENTAL BIOLOGICAL SAMPLES USING GAS CHROMATOGRAPHY COUPLED WITH SOLID PHASE MICRO EXTRACTION

    EPA Science Inventory

    An analytical method has been developed to determine the chloroethene series, tetrachloroethene (PCE), trichloroethene (TCE),cisdichloroethene (cis-DCE) andtransdichloroethene (trans-DCE) in environmental biotreatment studies using gas chromatography coupled with a solid phase mi...

  7. Phase Separation and Pair Condensation in a Spin-Imbalanced 2D Fermi Gas.

    PubMed

    Mitra, Debayan; Brown, Peter T; Schauß, Peter; Kondov, Stanimir S; Bakr, Waseem S

    2016-08-26

    We study a two-component quasi-two-dimensional Fermi gas with imbalanced spin populations. We probe the gas at different interaction strengths and polarizations by measuring the density of each spin component in the trap and the pair momentum distribution after time of flight. For a wide range of experimental parameters, we observe in-trap phase separation characterized by the appearance of a spin-balanced core surrounded by a polarized gas. Our momentum space measurements indicate pair condensation in the imbalanced gas even for large polarizations where phase separation vanishes, pointing to the presence of a polarized pair condensate. Our observation of zero momentum pair condensates in 2D spin-imbalanced gases opens the way to explorations of more exotic superfluid phases that occupy a large part of the phase diagram in lower dimensions. PMID:27610853

  8. FACTORS INFLUENCING THE DEPOSITION OF A COMPOUND THAT PARTITIONS BETWEEN GAS AND PARTICULATE PHASES

    EPA Science Inventory

    How will atmospheric deposition behave for a compound when it reversibly sorbs between gas and atmospheric particulate phases? Two factors influence the answer. What physical mechanisms occur in the sorption process? What are the concentration and composition of atmospheric par...

  9. Phase structure rewrite systems in information retrieval

    NASA Technical Reports Server (NTRS)

    Klingbiel, P. H.

    1985-01-01

    Operational level automatic indexing requires an efficient means of normalizing natural language phrases. Subject switching requires an efficient means of translating one set of authorized terms to another. A phrase structure rewrite system called a Lexical Dictionary is explained that performs these functions. Background, operational use, other applications and ongoing research are explained.

  10. Different structures of monoclinic martensitic phases in titanium nickelide

    NASA Astrophysics Data System (ADS)

    Voronin, V. I.; Naish, V. E.; Novoselova, T. V.; Pushin, V. G.; Sagaradze, I. V.

    2000-03-01

    The detailed theoretical and experimental analysis has been undertaken to bring to light the true structure of the monoclinic phase in titanium nickelide (NiTi). Theoretical models for such a phase have been proposed to describe the experimental data. In addition to the well-known B19‧ phase two more structures - new monoclinic M phase with Cm space group and triclinic phase with P1 space group - have been produced and analyzed in detail. Diffraction patterns have been obtained from different NiTi samples by using the neutron diffractometer IVV2 at different temperatures. From the refinement by DBWS-9411 program all these neutron patterns have been decoded successfully. The proposed new structures and stereotype B19‧ one agree with correspondent experimental data and the agreement is quite good.

  11. Gas-phase Mechanisms of Sulfur Isotope Mass-independent Fractionation

    NASA Astrophysics Data System (ADS)

    Lyons, J. R.

    2006-12-01

    Mass-independent fractionation (MIF) in sulfur isotopes in ancient sulfur-bearing rocks (Farquhar et al. 2000a) is interpreted as evidence for gas-phase MIF processes in the early Earth atmosphere. This interpretation is made by analogy with oxygen isotope MIF in the modern atmosphere (produced during ozone formation), and by laboratory photolysis experiments on SO2 (Farquhar et al. 2001; Wing et al. 2004) that yield both elemental sulfur and sulfate with S MIF signatures at wavelengths above and below the SO2 dissociation limit. What is lacking is a quantitative understanding of the mechanisms of gas-phase S MIF. Quantification is essential in order to extract the full implications of sulfur MIF throughout Earth history, including for bacterial sulfate reduction processes which largely conserve D33S and D36S. Several sulfur MIF mechanisms are possible. The most obvious is the gas-phase thiozone reaction, which is isovalent to the ozone formation reaction. Ozone formation produces a well-known MIF signature in oxygen isotopes (Thiemens and Heidenreich 1983), and a symmetry-dependent non-RRKM mechanism has been proposed as the origin of O MIF (Gao and Marcus 2001). It is possible and perhaps likely that S3 formation also proceeds by a non-RRKM process. Data are lacking on isotopic (an even non-isotopic) rates of S3 formation, so it is not possible to make definitive statements about MIF in S3 at this time. However modeling results suggest that the vapor pressure of S2 is too low for gas-phase S3 formation to be significant. Two additional species that may exhibit a non-RRKM MIF signature are S2O2 and S4. Again, there is a lack of isotopomer-specific kinetic data for these reactions, and gas-phase formation of S4 is likely inconsequential. Perhaps the most obvious mechanism is simply the primary act of SO2 photolysis. The SO2 absorption spectrum is highly structured, with strong vibronic bands above and below the dissociation limit. In contrast H2S, with its mostly

  12. Gas Phase UTE MRI of Propane and Propene

    PubMed Central

    Kovtunov, Kirill V.; Romanov, Alexey S.; Salnikov, Oleg G.; Barskiy, Danila A.; Chekmenev, Eduard Y.; Koptyug, Igor V.

    2016-01-01

    1H MRI of gases can potentially enable functional lung imaging to probe gas ventilation and other functions. In this work, 1H MR images of hyperpolarized and thermally polarized propane gas were obtained using UTE (ultrashort echo time) pulse sequence. A 2D image of thermally polarized propane gas with ~0.9×0.9 mm2 spatial resolution was obtained in less than 2 seconds, demonstrating that even non-hyperpolarized hydrocarbon gases can be successfully utilized for conventional proton MRI. The experiments were also performed with hyperpolarized propane gas and demonstrated acquisition of high-resolution multi-slice FLASH 2D images in ca. 510 s and non slice-selective 2D UTE MRI images in ca. 2 s. The UTE approach adopted in this study can be potentially used for medical lung imaging. Furthermore, the possibility to combine UTE with selective suppression of 1H signals from one of the two gases in a mixture is demonstrated in this MRI study. The latter can be useful for visualizing industrially important processes where several gases may be present, e.g., gas-solid catalytic reactions. PMID:27478870

  13. A DMPA Langmuir monolayer study: from gas to solid phase. An atomistic description by molecular dynamics Simulation.

    PubMed

    Giner-Casares, J J; Camacho, L; Martín-Romero, M T; Cascales, J J López

    2008-03-01

    In this work, a DMPA Langmuir monolayer at the air/water interface was studied by molecular dynamics simulations. Thus, an atomistic picture of a Langmuir monolayer was drawn from its expanded gas phase to its final solid condensed one. In this sense, some properties of monolayers that were traditionally poorly or even not reproduced in computer simulations, such as lipid domain formation or pressure-area per lipid isotherm, were properly reproduced in this work. Thus, the physical laws that control the lipid domain formation in the gas phase and the structure of lipid monolayers from the gas to solid condensed phase were studied. Thanks to the atomistic information provided by the molecular dynamics simulations, we were able to add valuable information to the experimental description of these processes and to access experimental data related to the lipid monolayers in their expanded phase, which is difficult or inaccessible to study by experimental techniques. In this sense, properties such as lipids head hydration and lipid structure were studied. PMID:18225932

  14. Structured illumination quantitative phase microscopy for enhanced resolution amplitude and phase imaging

    PubMed Central

    Chowdhury, Shwetadwip; Izatt, Joseph

    2013-01-01

    Structured illumination microscopy (SIM) is an established microscopy technique typically used to image samples at resolutions beyond the diffraction limit. Until now, however, achieving sub-diffraction resolution has predominantly been limited to intensity-based imaging modalities. Here, we introduce an analogue to conventional SIM that allows sub-diffraction resolution, quantitative phase-contrast imaging of optically transparent objects. We demonstrate sub-diffraction resolution amplitude and quantitative-phase imaging of phantom targets and enhanced resolution quantitative-phase imaging of cells. We report a phase accuracy to within 5% and phase noise of 0.06 rad. PMID:24156044

  15. An atmospheric pressure flow reactor: Gas phase kinetics and mechanism in tropospheric conditions without wall effects

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L.; Davis, Dennis D.; Hansen, Merrill

    1988-01-01

    A new type of gas phase flow reactor, designed to permit the study of gas phase reactions near 1 atm of pressure, is described. A general solution to the flow/diffusion/reaction equations describing reactor performance under pseudo-first-order kinetic conditions is presented along with a discussion of critical reactor parameters and reactor limitations. The results of numerical simulations of the reactions of ozone with monomethylhydrazine and hydrazine are discussed, and performance data from a prototype flow reactor are presented.

  16. Sulfur hexafluoride: Optimal use as a gas-phase, infrared sensitizer

    SciTech Connect

    Stanley, A.E.; Ludwick, L.M.; White, D.; Andrews, D.E.; Godbey, S.E. )

    1992-12-01

    Investigations into the use of sulfur hexafluoride, SF[sub 6], as a gas-phase, infrared photochemical sensitizer have revealed several interesting phenomena. The expedient use of SF[sub 6] can produce an optimal quantity of nitrated product in the gas-phase, laser-induced nitration of cyclopentane. The optimal utilization of sulfur hexafluoride required critical optimization of both frequency and quantity. The results are described herein. 12 refs., 3 figs., 1 tab.

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

    SciTech Connect

    Hall G. E.; Goncharov, V.

    2012-05-29

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

  18. Ultrafast electronic relaxation of excited state vitamin B 12 in the gas phase

    NASA Astrophysics Data System (ADS)

    Shafizadeh, Niloufar; Poisson, Lionel; Soep, Benoıˆt

    2008-06-01

    The time evolution of electronically excited vitamin B 12 (cyanocobalamin) has been observed for the first time in the gas phase. It reveals an ultrafast decay to a state corresponding to metal excitation. This decay is interpreted as resulting from a ring to metal electron transfer. This opens the observation of the excited state of other complex biomimetic systems in the gas phase, the key to the characterisation of their complex evolution through excited electronic states.

  19. Conformational preferences of flavone and isoflavone in the gas phase, aqueous solution and organic solution

    NASA Astrophysics Data System (ADS)

    Ishiki, Hamilton Mitsugu; Alemán, Carlos; Galembeck, Sérgio Emanuel

    1998-05-01

    Flavone and isoflavone are an important class of secondary metabolites that are widely distributed in nature. In this Letter we have determined the conformational preferences of each compound in the gas phase, aqueous solution and organic solution. Gas-phase calculations were performed using AM1, MNDO, HF/3-21G, HF/6-31G(d) and B3-LYP/6-31G(d) calculations. Besides solution calculations were performed using the MST solvation model.

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

    SciTech Connect

    Hall, G.E.

    2011-05-31

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

  1. Folding of Protein Ions in the Gas Phase after Cation-to-Anion Proton-Transfer Reactions.

    PubMed

    Laszlo, Kenneth J; Munger, Eleanor B; Bush, Matthew F

    2016-08-01

    The structure and folding of a protein in solution depends on noncovalent interactions within the protein and those with surrounding ions and molecules. Decoupling these interactions in solution is challenging, which has hindered the development of accurate physics-based models for structure prediction. Investigations of proteins in the gas phase can be used to selectively decouple factors affecting the structures of proteins. Here, we use cation-to-anion proton-transfer reactions (CAPTR) to reduce the charge states of denatured ubiquitin ions in the gas phase, and ion mobility to probe their structures. In CAPTR, a precursor charge state is selected (P) and reacted with monoanions to generate charge-reduced product ions (C). Following each CAPTR event, denatured ubiquitin ions (13+ to 6+) yield products that rapidly isomerize to structures that have smaller collision cross sections (Ω). The Ω values of CAPTR product ions depend strongly on C and very weakly on P. Pre- and post-CAPTR activation was then used to probe the potential-energy surfaces of the precursor and product ions, respectively. Post-CAPTR activation showed that ions of different P fold differently and populate different regions of the potential-energy surface of that ion. Finally, pre-CAPTR activation showed that the structures of protein ions can be indirectly investigated using ion mobility of their CAPTR product ions, even for subtle structural differences that are not apparent from ion mobility characterization of the activated precursor ions. More generally, these results show that CAPTR strongly complements existing techniques for characterizing the structures and dynamics of biological molecules in the gas phase. PMID:27399988

  2. Optical pyrometer based on the gas phase photoacoustic effect.

    PubMed

    Meng, Xiangling; Diebold, Gerald J

    2016-05-15

    A photoacoustic cell containing an infrared active gas and equipped with a pair of infrared transmitting windows that alternately views two bodies at different temperatures through a pair of chopping wheels acts as a differential detector of the radiation emitted by the two bodies. A theory for the photoacoustic signal shows that the device acts to monitor the difference in the incidances between the two bodies integrated over the absorptions of the gas in the cell. Experiments are reported showing that the response of the pyrometer depends on the relative temperatures of heated bodies, the absorption coefficient of the gas in the cell, and the modulation frequency of the chopping wheels. The instrument is shown to be a sensitive detector of a null in the integrated incidance of the two bodies. PMID:27176967

  3. Two Dimensional Ice from First Principles: Structures and Phase Transitions.

    PubMed

    Chen, Ji; Schusteritsch, Georg; Pickard, Chris J; Salzmann, Christoph G; Michaelides, Angelos

    2016-01-15

    Despite relevance to disparate areas such as cloud microphysics and tribology, major gaps in the understanding of the structures and phase transitions of low-dimensional water ice remain. Here, we report a first principles study of confined 2D ice as a function of pressure. We find that at ambient pressure hexagonal and pentagonal monolayer structures are the two lowest enthalpy phases identified. Upon mild compression, the pentagonal structure becomes the most stable and persists up to ∼2  GPa, at which point the square and rhombic phases are stable. The square phase agrees with recent experimental observations of square ice confined within graphene sheets. This work provides a fresh perspective on 2D confined ice, highlighting the sensitivity of the structures observed to both the confining pressure and the width. PMID:26824547

  4. Two Dimensional Ice from First Principles: Structures and Phase Transitions

    NASA Astrophysics Data System (ADS)

    Chen, Ji; Schusteritsch, Georg; Pickard, Chris J.; Salzmann, Christoph G.; Michaelides, Angelos

    2016-01-01

    Despite relevance to disparate areas such as cloud microphysics and tribology, major gaps in the understanding of the structures and phase transitions of low-dimensional water ice remain. Here, we report a first principles study of confined 2D ice as a function of pressure. We find that at ambient pressure hexagonal and pentagonal monolayer structures are the two lowest enthalpy phases identified. Upon mild compression, the pentagonal structure becomes the most stable and persists up to ˜2 GPa , at which point the square and rhombic phases are stable. The square phase agrees with recent experimental observations of square ice confined within graphene sheets. This work provides a fresh perspective on 2D confined ice, highlighting the sensitivity of the structures observed to both the confining pressure and the width.

  5. Formation of complex organic molecules in cold objects: the role of gas-phase reactions

    NASA Astrophysics Data System (ADS)

    Balucani, Nadia; Ceccarelli, Cecilia; Taquet, Vianney

    2015-04-01

    While astrochemical models are successful in reproducing many of the observed interstellar species, they have been struggling to explain the observed abundances of complex organic molecules. Current models tend to privilege grain surface over gas-phase chemistry in their formation. One key assumption of those models is that radicals trapped in the grain mantles gain mobility and react on lukewarm ( ≳ 30 K) dust grains. Thus, the recent detections of methyl formate (MF) and dimethyl ether (DME) in cold objects represent a challenge and may clarify the respective role of grain-surface and gas-phase chemistry. We propose here a new model to form DME and MF with gas-phase reactions in cold environments, where DME is the precursor of MF via an efficient reaction overlooked by previous models. Furthermore, methoxy, a precursor of DME, is also synthesized in the gas phase from methanol, which is desorbed by a non-thermal process from the ices. Our new model reproduces fairly well the observations towards L1544. It also explains, in a natural way, the observed correlation between DME and MF. We conclude that gas-phase reactions are major actors in the formation of MF, DME and methoxy in cold gas. This challenges the exclusive role of grain-surface chemistry and favours a combined grain-gas chemistry.

  6. APPLICATIONS ANALYSIS REPORT: ECO LOGIC INTERNATIONAL GAS-PHASE CHEMICAL REDUCTION PROCESS - THE REACTOR SYSTEM

    EPA Science Inventory

    This report details the Superfund Innovative Technology Evaluation of Eco Logic International's gas-phase chemical reduction process, with an emphasis on their Reactor System. he Eco Logic process employees a high temperature reactor filled with hydrogen gas as the means to destr...

  7. DEMONSTRATION BULLETIN: GAS-PHASE CHEMICAL REDUCTION - ECO LOGIC INTERNATIONAL, INC.

    EPA Science Inventory

    The patented Eco Logic Process employs a gas-phase reduction reaction of hydrogen with organic and chlorinated organic compounds at elevated temperatures to convert aqueous and oily hazardous contaminants into a hydrocarbon-rich gas product. After passing through a scrubber, the ...

  8. Reactions of metal cluster anions with inorganic and organic molecules in the gas phase.

    PubMed

    Zhao, Yan-Xia; Liu, Qing-Yu; Zhang, Mei-Qi; He, Sheng-Gui

    2016-07-28

    The study of gas phase ion-molecule reactions by state-of-the-art mass spectrometric experiments in conjunction with quantum chemistry calculations offers an opportunity to clarify the elementary steps and mechanistic details of bond activation and conversion processes. In the past few decades, a considerable number of publications have been devoted to the ion-molecule reactions of metal clusters, the experimentally and theoretically tractable models for the active phase of condensed phase systems. The focus of this perspective concerns progress on activation and transformation of important inorganic and organic molecules by negatively charged metal clusters. The metal cluster anions cover bare metal clusters as well as ligated systems with oxygen, carbon, and nitrogen, among others. The following important issues have been summarized and discussed: (i) dependence of chemical reactivity and selectivity on cluster structures and sizes, metals and metal oxidation states, odd-even electron numbers, etc. and (ii) effects of doping, ligation, and pre-adsorption on the reactivity of metal clusters toward rather inert molecules. PMID:27346242

  9. Numerical simulation of gas-solid two-phase flow in U-beam separator

    NASA Astrophysics Data System (ADS)

    Zhou, X. Y.; Zhang, H. Z.; Chen, X. P.; Ruan, J. M.; Dou, H. S.

    2015-01-01

    Numerical simulation is carried out for gas-solid two-phase flow in a U-beam separator. In this study, the U-beam is altered with the inlet fins in order to improve the performance of the separator. The inlet fin angle of the separator are 30°, 35°, 40°, 45°, 50°, 55 ° and 60°. The governing equations are the Reynolds-Averaged Navier-Stokes equation with the standard k-epsilon model and the discrete phase model (DPM) describing the discrete two - phase flow as well as stochastic tracking model. Results show that the pressure drop deviation with fins is within 3% from those without fins. It is found that there is a maximum separation efficiency at the fin angle of 35°. Fin induces generation of a stagnation region which could collect particles and lead to change of vortical structures. The fin induced flow also causes the turbulent intensity inside the baffle to decrease to facilitate separation.

  10. Graphitic carbon nitride as high-resolution stationary phase for gas chromatographic separations.

    PubMed

    Zheng, Yunzhong; Qi, Meiling; Fu, Ruonong

    2016-07-01

    This work presents the first example of utilization of graphitic carbon nitride (g-C3N4) as stationary phase for capillary gas chromatographic (GC) separations. The statically coated g-C3N4 column showed the column efficiencies of 3760 plates/m and weak polarity. Its resolving capability and retention behaviours were investigated by using the Grob test mixture, and mixtures of diverse types of analytes, and structural and positional isomers. The results showed superior separation performance of the g-C3N4 stationary phase for some critical analytes and preferential retention for aromatic analytes. Specifically, it exhibited high-resolution capability for aromatic and aliphatic isomers such as methylnaphthalenes and dimethylnaphthalenes, phenanthrene and anthracene and alkane isomers. In addition, g-C3N4 column showed excellent thermal stability up to 280°C and good repeatability with relative standard deviation (RSD) values less than 0.09% for intra-day, below 0.23% for inter-day and in the range of 1.9-8.4% for between-column, respectively. The advantageous separation performance shows the potential of g-C3N4 and related materials as stationary phase in GC and other separation technologies. PMID:27266332

  11. Thermodynamic and kinetic stability of zwitterionic histidine: Effects of gas phase hydration

    NASA Astrophysics Data System (ADS)

    Lee, Sung-Sik; Kim, Ju-Young; Han, Yuna; Shim, Hyun-Jin; Lee, Sungyul

    2015-09-01

    We present calculations for histidine-(H2O)n (n = 0-6) to examine the effects of micro-hydrating water molecules on the relative stability of the zwitterionic vs. canonical forms of histidine. We calculate the structures and Gibbs free energies of the conformers at wB97XD/6-311++G(d,p) level of theory. We find that six water molecules are required to produce the thermodynamically stable histidine zwitterion. By calculating the barriers of canonical ↔ zwitterionic transformation, we predict that both the most stable canonical and zwitterionic forms of histidine-(H2O)6 may be observed in low temperature gas phase environment.

  12. Process Conditions and Microstructures of Ceramic Coatings by Gas Phase Deposition Based on Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Mauer, G.; Hospach, A.; Zotov, N.; Vaßen, R.

    2013-03-01

    Plasma spraying at very low pressure (50-200 Pa) is significantly different from atmospheric plasma conditions (APS). By applying powder feedstock, it is possible to fragment the particles into very small clusters or even to evaporate the material. As a consequence, the deposition mechanisms and the resulting coating microstructures could be quite different compared to conventional APS liquid splat deposition. Thin and dense ceramic coatings as well as columnar-structured strain-tolerant coatings with low thermal conductivity can be achieved offering new possibilities for application in energy systems. To exploit the potential of such a gas phase deposition from plasma spray-based processes, the deposition mechanisms and their dependency on process conditions must be better understood. Thus, plasma conditions were investigated by optical emission spectroscopy. Coating experiments were performed, partially at extreme conditions. Based on the observed microstructures, a phenomenological model is developed to identify basic growth mechanisms.

  13. MOGADOC (Molecular Gas Phase Documentation) — An interactive computerised search/retrieval system

    NASA Astrophysics Data System (ADS)

    Lohr, A.; Mez-Starck, B.; Schirdewahn, H.-G.; Watson, D. G.

    1983-02-01

    For 22 years the Section for Structure Documentation (SSD), University of Ulm, has provided a documentation service covering the literature of molecules studied in the gas phase by electron diffraction, microwave spectroscopy and other techniques. Much of the information which has been accumulated over these years has now been keyboarded to constitute a computerised database. An interactive search/retrieval system, MOGADOC, has been written using the SIMULA language implemented on the UNIVAC 1100/82 computer at the University of Freiburg. MOGADOC enables the user to search the database on the basis of bibliographic, chemical and physical search terms. SIMULA is claimed to be the only general purpose high level programming language which is reasonable wide spread and allows direct implementation of abstract data types.

  14. Gas-phase pyrolysis mechanisms of 3-anilino-1-propanol: Density functional theory study

    NASA Astrophysics Data System (ADS)

    Zhao, Jing; Tang, Ming-Sheng; Wei, Dong-Hui; Zhao, Chu-Feng; Zhang, Wen-Jing; Wang, Hong-Ming

    The gas-phase pyrolytic decomposition mechanisms of 3-anilino-1-propanol with the products of aniline, ethylene, and formaldehyde or N-methyl aniline and aldehyde were studied by density functional theory. The geometries of the reactant, transition states, and intermediates were optimized at the B3LYP/6-31G (d, p) level. Vibration analysis was carried out to confirm the transition state structures, and the intrinsic reaction coordinate method was performed to search the minimum energy path. Four possible reaction channels are shown, including two concerted reactions of direct pyrolytic decomposition and two indirect channels in which the reactant first becomes a ring-like intermediate, followed by concerted pyrogenation. One of the concerted reactions in the direct pyrolytic decomposition has the lowest activation barrier among all the four channels, and so, it occurs more often than others. The results appear to be consistent with the experimental outcomes.

  15. A numerical study of two-phase flow in gas turbine combustors

    NASA Astrophysics Data System (ADS)

    Tolpadi, A. K.

    1992-07-01

    A method is presented for computing steady two-phase turbulent combusting flow in a gas turbine combustor. The gas phase equations are solved in an Eulerian frame of reference. The two-phase calculations are performed by using a liquid droplet spray combustion model and treating the motion of the evaporating fuel droplets in a Lagrangian frame of reference. The numerical algorithm employs nonorthogonal curvilinear coordinates, a multigrid iterative solution procedure, the standard k-epsilon turbulence model, and a combustion model made up of an assumed shape probability density function and the conserved scalar formulation. The trajectory computation of the fuel provides the source terms for all the gas phase equations. Results of the application of the two-phase model to a modern GE/SNECMA single annular CFM56 turbofan engine combustor are reported.

  16. Comparison of Gas and Adsorbed Phase X-ray Photoemission Spectra of Oxidized Organics on Ice

    NASA Astrophysics Data System (ADS)

    Newberg, J. T.; Bluhm, H.

    2011-12-01

    Most uptake studies of small chain organics on ice surfaces at near ambient conditions have been performed using flow tube and other methods which monitor the disappearance of the gas phase. We will present results using synchrotron based, ambient pressure X-ray photoemission spectroscopy which allows for the probing of the ice surface directly at near ambient conditions. C 1s XPS and C K-edge NEXAFS gas phase and adsorbed phase spectra will be compared for 2-propanol, acetone, and 1-propanal on ice at -45 C. Uptake experiments give rise to first order Langmuirian isotherms. Acetone and 2-propanol show little difference in the photoemission spectra between the gas phase and adsorbed phase, suggesting that adsorption occurs molecularly. However, adsorption of 1-propanal shows evidence of chemical transformation (oxidation) at the interface of ice. Further studies are underway to better understand this adsorption behavior.

  17. Moisture effects on greenhouse gases generation in nitrifying gas-phase compost biofilters.

    PubMed

    Maia, Guilherme D N; Day, George B; Gates, Richard S; Taraba, Joseph L; Coyne, Mark S

    2012-06-01

    Gas-phase compost biofilters are extensively used in concentrated animal feeding operations to remove odors and, in some cases, ammonia from air sources. The expected biochemical pathway for these predominantly aerobic systems is nitrification. However, non-uniform media with low oxygen levels can shift biofilter microbial pathways to denitrification, a source of greenhouse gases. Several factors contribute to the formation of anoxic/anaerobic zones: media aging, media and particle structure, air velocity distribution, compaction, biofilm thickness, and moisture content (MC) distribution. The present work studies the effects of media moisture conditions on ammonia (NH(3)) removal and greenhouse gas generation (nitrous oxide, N(2)O and methane, CH(4)) for gas-phase compost biofilters subject to a 100-day controlled drying process. Continuous recordings were made for the three gases and water vapor (2.21-h sampling cycle, each cycle consisted of three gas species, and water vapor, for a total of 10,050 data points). Media moisture conditions were classified into three corresponding media drying rate (DR) stages: Constant DR (wetter media), falling DR, and stable-dry system. The first-half of the constant DR period (0-750 h; MC=65-52%, w.b.) facilitated high NH(3) removal rates, but higher N(2)O generation and no CH(4) generation. At the drier stages of the constant DR (750-950 h; MC=52-48%, w.b.) NH(3) removal remained high but N(2)O net generation decreased to near zero. In the falling DR stage (1200-1480 h; MC=44-13%) N(2)O generation decreased, CH(4) increased, and NH(3) was no longer removed. No ammonia removal or greenhouse gas generation was observed in the stable-dry system (1500-2500 h; MC=13%). These results indicate that media should remain toward the drier region of the constant DR (in close proximity to the falling DR stage; MC=50%, approx.), to maintain high levels of NH(3) removal, reduced levels of N(2)O generation, and nullify levels of CH(4

  18. High pressure structural phase transitions of PbPo

    NASA Astrophysics Data System (ADS)

    Bencherif, Y.; Boukra, A.; Zaoui, A.; Ferhat, M.

    2012-09-01

    First-principles calculations have been performed to investigate the high pressure phase transitions and dynamical properties of the less known lead polonium compound. The calculated ground state parameters for the NaCl phase show good agreement with the experimental data. The obtained results show that the intermediate phase transition for this compound is the orthorhombic Pnma phase. The PbPo undergoes from the rocksalt to Pnma phase at 4.20 GPa. Further structural phase transition from intermediate to CsCl phase has been found at 8.5 GPa. In addition, phonon dispersion spectra were derived from linear-response to density functional theory. In particular, we show that the dynamical properties of PbPo exhibit some peculiar features compared to other III-V compounds. Finally, thermodynamics properties have been also addressed from quasiharmonic approximation.

  19. Comparing the gas-phase fragmentation reactions of protonated and radical cations of the tripeptides GXR

    NASA Astrophysics Data System (ADS)

    Wee, Sheena; O'Hair, Richard A. J.; McFadyen, W. David

    2004-05-01

    Electrospray ionization (ESI) mass spectrometry of methanolic solutions of mixtures of the copper salt (2,2':6',2''-terpyridine)copper(II) nitrate monohydrate ([Cu(II)(tpy)(NO3)2].H2O) and a tripeptide GXR (where X = 1 of the 20 naturally occurring amino acids) yielded [Cu(II)(tpy)(GXR)][radical sign]2+ ions, which were then subjected to collision induced dissociation (CID). In all but one case (GRR), these [Cu(II)(tpy)(GXR)][radical sign]2+ ions fragment to form odd electron GXR[radical sign]+ radical cations with sufficient abundance to examine their gas-phase fragmentation reactions. The GXR[radical sign]+ radical cations undergo a diverse range of fragmentation reactions which depend on the nature of the side chain of X. Many of these reactions can be rationalized as arising from the intermediacy of isomeric distonic ions in which the charge (i.e. proton) is sequestered by the highly basic arginine side chain and the radical site is located at various positions on the tripeptide including the peptide back bone and side chains. The radical sites in these distonic ions often direct the fragmentation reactions via the expulsion of small radicals (to yield even electron ions) or small neutrals (to form radical cations). Both classes of reaction can yield useful structural information, allowing for example, distinction between leucine and isoleucine residues. The gas-phase fragmentation reactions of the GXR[radical sign]+ radical cations are also compared to their even electron [GXR+H]+ and [GXR+2H]2+ counterparts. The [GXR+H]+ ions give fewer sequence ions and more small molecule losses while the [GXR+2H]2+ ions yield more sequence information, consistent with the [`]mobile proton model' described in previous studies. In general, all three classes of ions give complementary structural information, but the GXR[radical sign]+ radical cations exhibit a more diverse loss of small species (radicals and neutrals). Finally, links between these gas-phase results and key

  20. Formation of Structured Water and Gas Hydrate by the Use of Xenon Gas in Vegetable Tissue

    NASA Astrophysics Data System (ADS)

    Ando, Hiroko; Suzuki, Toru; Kawagoe, Yoshinori; Makino, Yoshio; Oshita, Seiichi

    Freezing is a valuable technique for food preservation. However, vegetables are known to be softening remarkably after freezing and thawing process. It is expected to find alternative technique instead of freezing. Recently, the application of structured water and/or gas hydrate had been attempted to prolong the preservation of vegetable. In this study, the formation process of structure water and/or gas hydrate in pure water and carrot tissue was investigated by using NMR relaxation times, T1 and T2, of which applying condition was up to 0.4MPa and 0.8MPa at 5oC. Under the pressure of 0.4MPa, no gas hydrate was appeared, however, at 0.8MPa, formation of gas hydrate was recognized in both water and carrot tissue. Once the gas hydrate formation process in carrot tissue started, T1 and T2 increased remarkably. After that, as the gas hydrate developed, then T1 and T2 turned to decrease. Since this phenomenon was not observed in pure water, it is suggested that behavior of NMR relaxation time just after the formation of gas hydrate in carrot tissue may be peculiar to compartment system such as inter and intracellular spaces.

  1. Core Level Spectroscopy and Tautomerism of Key Biomolecules in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Feyer, V.; Plekan, O.; Richter, R.; Prince, K. C.; Coreno, M.; Giuliano, B. M.; Evangelisti, L.; Melandri, S.; Caminati, W.; Trofimov, A. B.; Zaytseva, I. L.; Moskovskaya, T. E.; Gromov, E. V.; Schirmer, J.

    2010-06-01

    The nucleobases cytosine, thymine and uracil are pyrimidine derivatives. They pair with their complementary purines, guanine and adenine, through hydrogen bonding to form DNA and RNA chains. The tautomeric forms of DNA bases are capable of unusual base pairing like thymine-guanine and cytosine-adenine and create mutations, which are the precursors of some molecular-based diseases. Low energy spectroscopies such as microwave, laser and infrared techniques are commonly used as methods to investigate the conformatonal and tautomeric equilibria of biomolecules, while the high energy technique of x-ray photoemission spectroscopy (XPS) has yielded a smaller amount of significant structural information about biomolecules in the gas phase. In the present studies we successfully apply XPS to the study of five nucleic acid base tautomers, as well as the prototypical system 2-hydroxypyridimine and the related molecules S-methyl-2-thiouracil and 2-thiouracil in the vapor phase. XPS is a quantitative technique, allowing the experimental determination of the populations of keto and enol tautomers at known equilibrium temperatures: it is difficult to obtain this information otherwise. The effect of different substituents on stability of tautomers has been revealed. Quantum chemistry calculations have been carried out in order to obtain information about the structure, relative stability and difference in populations of the tautomers and conformers under study.

  2. Quantitative structure retention relationship studies for predicting relative retention times of chlorinated phenols on gas chromatography.

    PubMed

    Li, Shi-Yin; Sun, Cheng; Wang, Yu; Xu, Shi-Fen; Yao, Shu-Chun; Wang, Lian-Sheng

    2002-07-01

    A new method of quantitative structure-retention relationship (QSRR) studies was reported for predicting gas chromatography (GC) relative retention times (RRTs) of chlorinated phenols (CPs) using a DB-5 column. Chemical descriptors were calculated from the molecular structure of CPs and related to their gas chromatographic RRTs by using multiple linear regression analysis. The proposed model had a multiple square correlation coefficient R2 = 0.970, standard error SE = 0.0472, and significant level P = 0.0000. The QSRR model also reveals that the gas chromatographic relative retention times of CPs are associated with physicochemical property interactions with the stationary phase, and influenced by the number of chlorine and oxygen in the CP mOlecules. PMID:12211996

  3. Industrial fuel gas plant project. Phase II. Memphis industrial fuel gas plant. Final report. [U-GAS process

    SciTech Connect

    Not Available

    1983-01-01

    The Industrial Fuel Gas Plant produces a nominal 50 billion Btu/day of product gas. The entire IFG production will be sold to MLGW. Under normal conditions, 20% of the output of the plant will be sold by MLGW to the local MAPCO refinery and exchanged for pipeline quality refinery gas. The MAPCO refinery gas will be inserted into the Memphis Natural Gas Distribution System. A portion (normally 10%) of the IFG output of the plant will be diverted to a Credit Generation Unit, owned by MLGW, where the IFG will be upgraded to pipeline quality (950 Btu/SCF). This gas will be inserted into MLGW's Natural Gas Distribution System. The remaining output of the IFG plant (gas with a gross heating value of 300 Btu/SCF) will be sold by MLGW as Industrial Fuel Gas. During periods when the IFG plant is partially or totally off-stream, natural gas from the Memphis Natural Gas Distribution System will be sent to an air mixing unit where the gas will be diluted to a medium Btu content and distributed to the IFG customers. Drawing 2200-1-50-00104 is the plant block flow diagram showing the process sequence and process related support facilities of this industrial plant. Each process unit as well as each process-related support facility is described briefly.

  4. Ceramic stationary gas turbine development. Final report, Phase 1

    SciTech Connect

    1994-09-01

    This report summarizes work performed by Solar Turbines Inc. and its subcontractors during the period September 25, 1992 through April 30, 1993. The objective of the work is to improve the performance of stationary gas turbines in cogeneration through implementation of selected ceramic components.

  5. Gas phase dispersion in a small rotary kiln

    SciTech Connect

    Spencer, B.B.

    1981-07-01

    A study was made of nonideal flow of gas in a rotary kiln reactor. A rotating tube 0.165 m in diameter by 2.17 m long, with internal lifting flights, was operated at room temperature. Rotational speeds from 2.0 to 7.0 rpm, air flow rates from 0.351 to 4.178 m/sup 3//h, and solid contents of 0.0, 5.1, and 15.3% of tube volume were studied. Residence time distribution of the gas was measured by means of the pulse injection technique using a helium tracer. A model was developed based on dispersive flow that exchanges with a deadwater region. Two parameters, a dispersion number describing bulk gas flow and an interchange factor describing exchange between the flow region and the gas trapped in the solids bed, were sufficient to correlate the data, but these parameters are sensitive to experimental error. The model is applicable to analysis of other flow systems, such as packed beds.

  6. AN ADVANCED FLUE GAS MONITOR FOR SO2 - PHASE I

    EPA Science Inventory

    The development of an instrument for continuously monitoring SO2 levels in flue gas is proposed. The SO2 will be detected by means of an electrochemical sensor cell, which operates in a three-electrode potentiostatic mode. The proposed innovation is develop-ment of an advan...

  7. NANOMATERIAL SOLUTIONS FOR HOT COAL GAS CLEANUP - PHASE I

    EPA Science Inventory

    Integrated gasification combined cycle (IGCC) is a new coal gasification technique that efficiently uses the hot (900-1500°C) generated syngas to power both steam and gas turbines. Due to regulations, this syngas must be free of sulfur and purification is normally carried ...

  8. Processes forming Gas, Tar, and Coke in Cellulose Gasification from Gas-Phase Reactions of Levoglucosan as Intermediate.

    PubMed

    Fukutome, Asuka; Kawamoto, Haruo; Saka, Shiro

    2015-07-01

    The gas-phase pyrolysis of levoglucosan (LG), the major intermediate species during cellulose gasification, was studied experimentally over the temperature range of 400-900 °C. Gaseous LG did not produce any dehydration products, which include coke, furans, and aromatic substances, although these are characteristic products of the pyrolysis of molten LG. Alternatively, at >500 °C, gaseous LG produced only fragmentation products, such as noncondensable gases and condensable C1 -C3 fragments, as intermediates during noncondensable gas formation. Therefore, it was determined that secondary reactions of gaseous LG can result in the clean (tar- and coke-free) gasification of cellulose. Cooling of the remaining LG in the gas phase caused coke formation by the transition of the LG to the molten state. The molecular mechanisms that govern the gas- and molten-phase reactions of LG are discussed in terms of the acid catalyst effect of intermolecular hydrogen bonding to promote the molten-phase dehydration reactions. PMID:26099988

  9. Simplified procedure for encapsulating cytochrome c in silica aerogel nanoarchitectures while retaining gas-phase bioactivity.

    PubMed

    Harper-Leatherman, Amanda S; Iftikhar, Mariam; Ndoi, Adela; Scappaticci, Steven J; Lisi, George P; Buzard, Kaitlyn L; Garvey, Elizabeth M

    2012-10-16

    Cytochrome c (cyt. c) has been encapsulated in silica sol-gels and processed to form bioaerogels with gas-phase activity for nitric oxide through a simplified synthetic procedure. Previous reports demonstrated a need to adsorb cyt. c to metal nanoparticles prior to silica sol-gel encapsulation and processing to form aerogels. We report that cyt. c can be encapsulated in aerogels without added nanoparticles and retain structural stability and gas-phase activity for nitric oxide. While the UV-visible Soret absorbance and nitric oxide response indicate that cyt. c encapsulated with nanoparticles in aerogels remains slightly more stable and functional than cyt. c encapsulated alone, these properties are not very different in the two types of aerogels. From UV-visible and Soret circular dichroism results, we infer that cyt. c encapsulated alone self-organizes to reduce contact with the silica gel in a way that may bear at least some resemblance to the way cyt. c self-organizes into superstructures of protein within aerogels when nanoparticles are present. Both the buffer concentration and the cyt. c concentration of solutions used to synthesize the bioaerogels affect the structural integrity of the protein encapsulated alone within the dried aerogels. Optimized bioaerogels are formed when cyt. c is encapsulated from 40 mM phosphate buffered solutions, and when the loaded cyt. c concentration in the aerogel is in the range of 5 to 15 μM. Increased viability of cyt. c in aerogels is also observed when supercritical fluid used to produce aerogels is vented over relatively long times. PMID:22924640

  10. Cloud draft structure and trace gas transport

    NASA Technical Reports Server (NTRS)

    Scala, John R.; Tao, Wei-Kuo; Thompson, Anne M.; Simpson, Joanne; Garstang, Michael; Pickering, Kenneth E.; Browell, Edward V.; Sachse, Glen W.; Gregory, Gerald L.; Torres, Arnold L.

    1990-01-01

    During the second Amazon Boundary Layer Experiment (ABLE 2B), meteorological observations, chemical measurements, and model simulations are utilized in order to interpret convective cloud draft structure and to analyze its role in transport and vertical distribution of trace gases. One-dimensional photochemical model results suggest that the observed poststorm changes in ozone concentration can be attributed to convective transports rather than photochemical production and the results of a two-dimensional time-dependent cloud model simulation are presented for the May 6, 1987 squall system. The mesoscale convective system exhibited evidence of significant midlevel detrainment in addition to transports to anvil heights. Chemical measurements of O3 and CO obtained in the convective environment are used to predict photochemical production within the troposphere and to corroborate the cloud model results.

  11. Gas phase condensation of superparamagnetic iron oxide-silica nanoparticles - control of the intraparticle phase distribution

    NASA Astrophysics Data System (ADS)

    Stötzel, C.; Kurland, H.-D.; Grabow, J.; Müller, F. A.

    2015-04-01

    Spherical, softly agglomerated and superparamagnetic nanoparticles (NPs) consisting of maghemite (γ-Fe2O3) and amorphous silica (SiO2) were prepared by CO2 laser co-vaporization (CoLAVA) of hematite powder (α-Fe2O3) and quartz sand (SiO2). The α-Fe2O3 portion of the homogeneous starting mixtures was gradually increased (15 mass%-95 mass%). It was found that (i) with increasing iron oxide content the NPs' morphology changes from a nanoscale SiO2 matrix with multiple γ-Fe2O3 inclusions to Janus NPs consisting of a γ-Fe2O3 and a SiO2 hemisphere to γ-Fe2O3 NPs each carrying one small SiO2 lens on its surface, (ii) the multiple γ-Fe2O3 inclusions accumulate at the NPs' inner surfaces, and (iii) all composite NPs are covered by a thin layer of amorphous SiO2. These morphological characteristics are attributed to (i) the phase segregation of iron oxide and silica within the condensed Fe2O3-SiO2 droplets, (ii) the temperature gradient within these droplets which arises during rapid cooling in the CoLAVA process, and (iii) the significantly lower surface energy of silica when compared to iron oxide. The proposed growth mechanism of these Fe2O3-SiO2 composite NPs during gas phase condensation can be transferred to other systems comprising a glass-network former and another component that is insoluble in the regarding glass. Thus, our model will facilitate the development of novel functional composite NPs for applications in biomedicine, optics, electronics, or catalysis.Spherical, softly agglomerated and superparamagnetic nanoparticles (NPs) consisting of maghemite (γ-Fe2O3) and amorphous silica (SiO2) were prepared by CO2 laser co-vaporization (CoLAVA) of hematite powder (α-Fe2O3) and quartz sand (SiO2). The α-Fe2O3 portion of the homogeneous starting mixtures was gradually increased (15 mass%-95 mass%). It was found that (i) with increasing iron oxide content the NPs' morphology changes from a nanoscale SiO2 matrix with multiple γ-Fe2O3 inclusions to Janus NPs

  12. Gas phase investigations of sulfonium salts by electrospray ft-icr/ms

    NASA Astrophysics Data System (ADS)

    Katritzky, Alan R.; Shipkova, Petia A.; Watson, Clifford H.; Eyler, John R.; Kevill, Dennis N.

    1997-11-01

    Twelve sulfonium salts were studied by electrospray Fourier transform ion cyclotron resonance mass spectrometry. Collisionally activated dissociation, CAD, reactions, using neutral argon as the collision gas, were performed to investigate dissociation pathways in the gas phase and to study the stabilizing/destabilizing effects of electron donating/withdrawing substituents on the sulfonium ions. Ion-molecule reactions were attempted to identify SN2 reaction mechanisms, but to date we have detected exclusively SN1-type reactions in the gas phase. Literature reports on the mass spectrometry of sulfonium cations are reviewed.

  13. Control of gas phase nanoparticle shape and its effect on MRI relaxivity

    NASA Astrophysics Data System (ADS)

    Aktaş, Sıtkı; Thornton, Stuart C.; Binns, Chris; Lari, Leonardo; Pratt, Andrew; Kröger, Roland; Horsfield, Mark A.

    2015-03-01

    We have used a sputtering gas aggregation source to produce Fe@FeO nanoparticles with different shapes, by annealing them at different temperatures in the gas phase. Without annealing, the most common shape found for the nanoparticles is cubic but annealing the nanoparticles at 1129 °C transforms the cubes into cuboctahedra. Measurements of the MRI relaxivity show that the cubic nanoparticles have a higher performance by a factor of two, which is attributed to a higher saturation magnetization for this shape. This indicates that the shape-control enabled by gas-phase synthesis is important for obtaining optimal performance in applications.

  14. A pressure cell for nonresonant inelastic x-ray scattering studies of gas phases

    SciTech Connect

    Minzer, M.; Bradley, J. A.; Musgrave, R.; Seidler, G. T.; Skilton, A.

    2008-08-15

    We report the design and performance of a gas-phase sample cell for measurements of momentum transfer (q) dependent nonresonant inelastic x-ray scattering (NRIXS). NRIXS measurements from He gas at 2 MPa (20 bars) readily demonstrate dipole-allowed and dipole-forbidden final states for two-electron excitations. Direct comparison of gas-phase NRIXS measurements with the corresponding nonresonant electron energy loss spectroscopy results (EELS) will be a valuable method for characterizing systematic errors in either technique for studies that require absolute normalization of the double differential cross section.

  15. ANALYSIS OF A GAS-PHASE PARTITIONING TRACER TEST CONDUCTED THROUGH FRACTURED MEDIA

    EPA Science Inventory

    The gas-phase partitioning tracer method was used to estimate non-aqueous phase liquid (NAPL), water, and air saturations in the vadose zone at a chlorinated-solvent contaminated field site in Tucson, AZ. The tracer test was conducted in a fractured clay system that is the confin...

  16. Two parametric flow measurement in gas-liquid two-phase flow

    NASA Astrophysics Data System (ADS)

    Chen, Z.; Chen, C.; Xu, Y.; Zhao, Z.

    The importance and current development of two parametric measurement during two-phase flow are briefly reviewed in this paper. Gas-liquid two-phase two parametric metering experiments were conducted by using an oval gear meter and a sharp edged orifice mounted in series in a horizontal pipe. Compressed air and water were used as gas and liquid phases respectively. The correlations, which can be used to predict the total flow rate and volumetric quality of two-phase flow or volumetric flow rate of each phase, have also been proposed in this paper. Comparison of the calculated values of flow rate of each phase from the correlations with the test data showed that the root mean square fractional deviation for gas flow rate is 2.9 percent and for liquid flow rate 4.4 percent. The method proposed in this paper can be used to measure the gas and liquid flow rate in two-phase flow region without having to separate the phases.

  17. Phases of a polar spin-1 Bose gas in a magnetic field

    NASA Astrophysics Data System (ADS)

    Kis-Szabó, Krisztián; Szépfalusy, Péter; Szirmai, Gergely

    2007-05-01

    The two Bose Einstein condensed phases of a polar spin-1 gas at nonzero magnetizations and temperatures are investigated. The Hugenholtz Pines theorem is generalized to this system. Crossover to a quantum phase transition is also studied. Results are discussed in a mean field approximation.

  18. Separation of gas from liquid in a two-phase flow system

    NASA Technical Reports Server (NTRS)

    Hayes, L. G.; Elliott, D. G.

    1973-01-01

    Separation system causes jets which leave two-phase nozzles to impinge on each other, so that liquid from jets tends to coalesce in center of combined jet streams while gas phase is forced to outer periphery. Thus, because liquid coalescence is achieved without resort to separation with solid surfaces, cycle efficiency is improved.

  19. Gas hydrate inhibition by perturbation of liquid water structure

    NASA Astrophysics Data System (ADS)

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong

    2015-06-01

    Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates.

  20. Gas hydrate inhibition by perturbation of liquid water structure.

    PubMed

    Sa, Jeong-Hoon; Kwak, Gye-Hoon; Han, Kunwoo; Ahn, Docheon; Lee, Kun-Hong

    2015-01-01

    Natural gas hydrates are icy crystalline materials that contain hydrocarbons, which are the primary energy source for this civilization. The abundance of naturally occurring gas hydrates leads to a growing interest in exploitation. Despite their potential as energy resources and in industrial applications, there is insufficient understanding of hydrate kinetics, which hinders the utilization of these invaluable resources. Perturbation of liquid water structure by solutes has been proposed to be a key process in hydrate inhibition, but this hypothesis remains unproven. Here, we report the direct observation of the perturbation of the liquid water structure induced by amino acids using polarized Raman spectroscopy, and its influence on gas hydrate nucleation and growth kinetics. Amino acids with hydrophilic and/or electrically charged side chains disrupted the water structure and thus provided effective hydrate inhibition. The strong correlation between the extent of perturbation by amino acids and their inhibition performance constitutes convincing evidence for the perturbation inhibition mechanism. The present findings bring the practical applications of gas hydrates significantly closer, and provide a new perspective on the freezing and melting phenomena of naturally occurring gas hydrates. PMID:26082291

  1. Calculations on fission gas behaviour in the high burnup structure

    NASA Astrophysics Data System (ADS)

    Blair, P.; Romano, A.; Hellwig, Ch.; Chawla, R.

    2006-05-01

    The behaviour of fission gas in high burnup fuel during steady-state and transient conditions is of special interest for safety reasons. Despite this, mechanistic models that reflect the fission gas transport processes and reliably predict the evolution of the remaining fission gas in the high burnup structure (HBS) are largely missing today. We start to address this problem by developing a one-dimensional, mass balance model and apply it to LWR UO 2 fuel at the moderate temperatures found in the rim region. We examine the quantity of gas remaining in the HBS fuel matrix at steady state and compare it with experimental values. We find that the current model reproduces the 0.2 wt% observed xenon concentration under certain conditions, viz. fast grain boundary diffusion and an effective volume diffusion coefficient. A sensitivity analysis is also conducted for the model parameters, the relative importance for which is not well established a priori.

  2. Gas distribution equipment in hydrogen service - Phase II

    NASA Technical Reports Server (NTRS)

    Jasionowski, W. J.; Huang, H. D.

    1980-01-01

    The hydrogen permeability of three different types of commercially available natural gas polyethylene pipes was determined. Ring tensile tests were conducted on permeability-exposed and as-received samples. Hydrogen-methane leakage experiments were also performed. The results show no selective leakage of hydrogen via Poiseuille, turbulent, or orifice flow (through leaks) on the distribution of blends of hydrogen and methane. The data collected show that the polyethylene pipe is 4 to 6 times more permeable to hydrogen than to methane.

  3. Structural and dynamical transformations between neighboring dense microemulsion phases

    SciTech Connect

    Kotlarchyk, M. ); Sheu, E.Y. ); Capel, M. )

    1992-07-15

    A small-angle x-ray scattering (SAXS) study of dense AOT-water-decane microemulsions (AOT denotes sodium bis(2-ethylhexyl) sulfosuccinate) was undertaken in order to delineate clearly the phase behavior and corresponding structural transitions for AOT-plus-water volume fractions ranging from {phi}=0.60 to 0.95. Spectra were collected for temperatures between {ital T}=3 and 65 {degree}C. The resulting {ital T}-vs-{phi} phase diagram indicates three distinct structural domains when the water-to-AOT molar ratio is fixed at {ital W}=40.8, namely, the previously investigated {ital L}{sub 2} droplet phase, a high-temperature {ital L}{sub {alpha}} lamellar phase, and a low-temperature {ital L}{sub 3} phase consisting of randomly connected lamellar sheets. A significantly wide coexistence region accompanies the droplet-to-lamellar phase transition, which is demonstrated to be first order. For {ital W} between 15 and 40, an analysis of the lamellar structure using a one-dimensional paracrystal model produces a Hosemann {ital g} factor indicative of an approximately constant variation in the lamellar spacing of about 8%. The SAXS study was supplemented by dielectric-relaxation, shear-viscosity, and quasielastic light-scattering measurements in order to substantiate the observed phase transitions and further our understanding of the structural and dynamical properties of the {ital L}{sub 3} phase. It was found that the {ital L}{sub 3} phase exhibits Newtonian behavior up to a shear rate of 790 s{sup {minus}1}, in contradiction to previous theoretical considerations. The phase exhibits two distinct relaxation modes. A relaxation time of {similar to}1 ms characterizes the Brownian motion of a single lamellar sheet, while the motion of the entire interconnected sheet assembly has a relaxation time on the order of 1 s.

  4. Structural Measurements from Images of Noble Gas Diffusion

    NASA Astrophysics Data System (ADS)

    Cadman, Robert V.; Kadlecek, Stephen J.; Emami, Kiarash; MacDuffie Woodburn, John; Vahdat, Vahid; Ishii, Masaru; Rizi, Rahim R.

    2009-03-01

    Magnetic resonance imaging of externally polarized noble gases such as ^3He has been used for pulmonary imaging for more than a decade. Because gas diffusion is impeded by the alveoli, the diffusion coefficient of gas in the lung, measured on a time scale of milliseconds, is reduced compared to that of the same gas mixture in the absence of restrictions. When the alveolar walls decay, as in emphysema, diffusivity in the lung increases. In this paper, the relationship between diffusion measurements and the size of the restricting structures will be discussed. The simple case of diffusion in an impermeable cylinder, a structure similar to the upper respiratory airways in mammals, has been studied. A procedure will be presented by which airways of order 2 mm in diameter may be accurately measured; demonstration experiments with plastic tubes will also be presented. The additional developments needed before this technique becomes practical will be briefly discussed.

  5. Shock-wave structure in a partially ionized gas

    NASA Technical Reports Server (NTRS)

    Lu, C. S.; Huang, A. B.

    1974-01-01

    The structure of a steady plane shock in a partially ionized gas has been investigated using the Boltzmann equation with a kinetic model as the governing equation and the discrete ordinate method as a tool. The effects of the electric field induced by the charge separation on the shock structure have also been studied. Although the three species of an ionized gas travel with approximately the same macroscopic velocity, the individual distribution functions are found to be very different. In a strong shock the atom distribution function may have double peaks, while the ion distribution function has only one peak. Electrons are heated up much earlier than ions and atoms in a partially ionized gas. Because the interactions of electrons with atoms and with ions are different, the ion temperature can be different from the atom temperature.

  6. Spray characterization and gas phase interaction downstream of a simplified atomizer

    NASA Astrophysics Data System (ADS)

    Hebrard, P.; Trichet, P.; Millan, P.

    1992-07-01

    A detailed study of the flowfield produced by a simplified airblast atomizer was performed. This atomizer consists of an annular liquid sheet introduced into coflowing nonswirling and swirling air flow fields. Droplet size and velocity were measured in the resultant spray using a two components Phase/Doppler Particle Analyzer. A complete set of measurements was obtained at axial locations from 8 mm to 150 mm downstream from the nozzle. Laser velocimetry was also employed to measure the gas phase properties. The effect of swirl on droplet transport process is examined for this type of airblast atomizer and the results demonstrate the strong influence the spray has on the gas phase.

  7. Evolution of natural gas composition: Predictive multi-phase reaction-transport modeling

    SciTech Connect

    Ortoleva, P.J.; Chang, K.A.; Maxwell, J.M.

    1995-12-31

    A computational modeling approach is used to investigate reaction and transport processes affecting natural gas composition over geological time. Three basic stages are integrated -- gas generation from organic solids or liquids, interactions during source rock expulsion to the reservoir and reactions within the reservoir. Multi-phase dynamics is handled by solving the fully coupled problem of phase-to-phase transfer, intra-phase organic and inorganic reactions and redox and other reactions between fluid phase molecules and minerals. Effects of capillarity and relative permeability are accounted for. Correlations will be determined between gas composition, temperature history, the mineralogy of rocks with which the gas was in contact and the composition of source organic phases. Questions of H{sub 2}S scavenging by oxidizing minerals and the production or removal of CO{sub 2} are focused upon. Our three spatial dimensional, reaction-transport simulation approach has great promise for testing general concepts and as a practical tool for the exploration and production of natural gas.

  8. Gas-rich and gas-poor structures through the stream velocity effect

    NASA Astrophysics Data System (ADS)

    Popa, Cristina; Naoz, Smadar; Marinacci, Federico; Vogelsberger, Mark

    2016-08-01

    Using adiabatic high-resolution numerical simulations, we quantify the effect of the streaming motion of baryons with respect to dark matter at the time of recombination on structure formation and evolution. Formally a second-order effect, the baryonic stream velocity has proven to have significant impact on dark matter halo abundance, as well as on the gas content and morphology of small galaxy clusters. In this work, we study the impact of stream velocity on the formation and gas content of haloes with masses up to 109 M⊙, an order of magnitude larger than previous studies. We find that the non-zero stream velocity has a sizable impact on the number density of haloes with masses ≲ few × 107 M⊙ up to z = 10, the final redshift of our simulations. Furthermore, the gas stream velocity induces a suppression of the gas fraction in haloes, which at z = 10 is ˜10 per cent for objects with M ˜ 107 M⊙, as well as a flattening of the gas density profiles in the inner regions of haloes. We further identify and study the formation, in the context of a non-zero stream velocity, of moderately long lived gas-dominated structures at intermediate redshifts 10 < z < 20, which Naoz and Narayan have recently proposed as potential progenitors of globular clusters.

  9. Gas-rich and gas poor structures through the stream velocity effect

    NASA Astrophysics Data System (ADS)

    Popa, Cristina; Naoz, Smadar; Marinacci, Federico; Vogelsberger, Mark

    2016-05-01

    Using adiabatic high-resolution numerical simulations we quantify the effect of the streaming motion of baryons with respect to dark matter at the time of recombination on structure formation and evolution. Formally a second order effect, the baryonic stream velocity has proven to have significant impact on dark matter halo abundance, as well as on the gas content and morphology of small galaxy clusters. In this work, we study the impact of stream velocity on the formation and gas content of haloes with masses up to 109M⊙, an order of magnitude larger than previous studies. We find that the non-zero stream velocity has a sizable impact on the number density of haloes with masses ≲ few× 107M⊙ up to z = 10, the final redshift of our simulations. Furthermore, the gas stream velocity induces a suppression of the gas fraction in haloes, which at z=10 is ˜10% for objects with M ˜ 107M⊙, as well as a flattening of the gas density profiles in the inner regions of haloes. We further identify and study the formation, in the context of a non-zero stream velocity, of moderately long lived gas dominated structures at intermediate redshifts 10 < z < 20, which Naoz and Narayan have recently proposed as potential progenitors of globular clusters.

  10. Gas phase heterogeneous catalytic oxidation of alkanes to aliphatic ketones and/or other oxygenates

    SciTech Connect

    Lin, Manhua; Wang, Xiang; Yeom, Younghoon

    2015-03-17

    A catalyst, its method of preparation and its use for producing aliphatic ketones by subjecting alkanes C.sub.3 to C.sub.9 to a gas phase catalytic oxidation in the presence of air or oxygen, and, optionally, steam and/or one or more diluting gases. The catalyst comprises a catalytically active mixed metal oxide phase and a suitable support material onto and/or into which the active catalytic phase id dispersed.

  11. Gas phase heterogeneous catalytic oxidation of alkanes to aliphatic ketones and/or other oxygenates

    SciTech Connect

    Lin, Manhua; Wang, Xiang; Yeom, Younghoon

    2015-09-29

    A catalyst, its method of preparation and its use for producing aliphatic ketones by subjecting alkanes C.sub.3 to C.sub.9 to a gas phase catalytic oxidation in the presence of air or oxygen, and, optionally, steam and/or one or more diluting gases. The catalyst comprises a catalytically active mixed metal oxide phase and a suitable support material onto and/or into which the active catalytic phase is dispersed.

  12. Lung Structure and the Intrinsic Challenges of Gas Exchange.

    PubMed

    Hsia, Connie C W; Hyde, Dallas M; Weibel, Ewald R

    2016-04-01

    Structural and functional complexities of the mammalian lung evolved to meet a unique set of challenges, namely, the provision of efficient delivery of inspired air to all lung units within a confined thoracic space, to build a large gas exchange surface associated with minimal barrier thickness and a microvascular network to accommodate the entire right ventricular cardiac output while withstanding cyclic mechanical stresses that increase several folds from rest to exercise. Intricate regulatory mechanisms at every level ensure that the dynamic capacities of ventilation, perfusion, diffusion, and chemical binding to hemoglobin are commensurate with usual metabolic demands and periodic extreme needs for activity and survival. This article reviews the structural design of mammalian and human lung, its functional challenges, limitations, and potential for adaptation. We discuss (i) the evolutionary origin of alveolar lungs and its advantages and compromises, (ii) structural determinants of alveolar gas exchange, including architecture of conducting bronchovascular trees that converge in gas exchange units, (iii) the challenges of matching ventilation, perfusion, and diffusion and tissue-erythrocyte and thoracopulmonary interactions. The notion of erythrocytes as an integral component of the gas exchanger is emphasized. We further discuss the signals, sources, and limits of structural plasticity of the lung in alveolar hypoxia and following a loss of lung units, and the promise and caveats of interventions aimed at augmenting endogenous adaptive responses. Our objective is to understand how individual components are matched at multiple levels to optimize organ function in the face of physiological demands or pathological constraints. PMID:27065169

  13. CASCADER: An m-chain gas-phase radionuclide transport and fate model. Volume 2, User`s manual for CASCADR8

    SciTech Connect

    Cawlfield, D.E.; Been, K.B.; Emer, D.F.; Lindstrom, F.T.; Shott, G.J.

    1993-06-01

    Chemicals and radionuclides move either in the gas-phase, liquid-phase, or both phases in soils. They may be acted upon by either biological or abiotic processes through advection and/or diffusion. Furthermore, parent and daughter radionuclides may decay as they are transported in the soil. This is volume two to the CASCADER series, titled CASCADR8. It embodies the concepts presented in volume one of this series. To properly understand how the CASCADR8 model works, the reader should read volume one first. This volume presents the input and output file structure for CASCADR8, and a set of realistic scenarios for buried sources of radon gas.

  14. Two-phase turbine engines. [using gas-liquid mixture accelerated in nozzles

    NASA Technical Reports Server (NTRS)

    Elliott, D. G.; Hays, L. G.

    1976-01-01

    A description is given of a two-phase turbine which utilizes a uniform mixture of gas and liquid accelerated in nozzles of the types reported by Elliott and Weinberg (1968). The mixture acts directly on an axial flow or tangential impulse turbine or is separated into gas and liquid streams which operate separately on a gas turbine and a hydraulic turbine. The basic two-phase cycles are examined, taking into account working fluids, aspects of nozzle expansion, details of turbine cycle operation, and the effect of mixture ratio variation. Attention is also given to two-phase nozzle efficiency, two-phase turbine operating characteristics and efficiencies, separator turbines, and impulse turbine experiments.

  15. Phase-correction algorithm of deformed grating images in the depth measurement of weld pool surface in gas tungsten arc welding

    NASA Astrophysics Data System (ADS)

    Wei, Yiqing; Liu, Nansheng; Hu, Xian; Ai, Xiaopu

    2011-05-01

    The principle and system structure of the depth measurement of weld pool surface in tungsten insert gas (TIG) welding are first introduced in the paper, then the problem of the common phase lines is studied. We analyze the causes and characteristics of the phase lines, and propose a phase correction method based on line ratio. The paper presents the principle and detail processing steps of this phase correction algorithm, and then the effectiveness and processing characteristics of the algorithm are verified by simulation. Finally, the algorithm is applied to phase processing in the depth measurement of the TIG weld pool surface and obtains satisfying results.

  16. The influence of porosity and structural parameters on different kinds of gas hydrate dissociation

    PubMed Central

    Misyura, S. Y.

    2016-01-01

    Methane hydrate dissociation at negative temperatures was studied experimentally for different artificial and natural samples, differing by macro- and micro-structural parameters. Four characteristic dissociation types are discussed in the paper. The internal kinetics of artificial granule gas hydrates and clathrate hydrates in coal is dependent on the porosity, defectiveness and gas filtration rate. The density of pores distribution in the crust of formed ice decreases by the several orders of magnitude and this change significantly the rate of decay. Existing models for describing dissociation at negative temperatures do not take into account the structural parameters of samples. The dissociation is regulated by internal physical processes that must be considered in the simulation. Non-isothermal dissociation with constant external heat flux was simulated numerically. The dissociation is simulated with consideration of heat and mass transfer, kinetics of phase transformation and gas filtering through a porous medium of granules for the negative temperatures. It is shown that the gas hydrate dissociation in the presence of mainly microporous structures is fundamentally different from the disintegration of gas hydrates containing meso and macropores. PMID:27445113

  17. The influence of porosity and structural parameters on different kinds of gas hydrate dissociation

    NASA Astrophysics Data System (ADS)

    Misyura, S. Y.

    2016-07-01

    Methane hydrate dissociation at negative temperatures was studied experimentally for different artificial and natural samples, differing by macro- and micro-structural parameters. Four characteristic dissociation types are discussed in the paper. The internal kinetics of artificial granule gas hydrates and clathrate hydrates in coal is dependent on the porosity, defectiveness and gas filtration rate. The density of pores distribution in the crust of formed ice decreases by the several orders of magnitude and this change significantly the rate of decay. Existing models for describing dissociation at negative temperatures do not take into account the structural parameters of samples. The dissociation is regulated by internal physical processes that must be considered in the simulation. Non-isothermal dissociation with constant external heat flux was simulated numerically. The dissociation is simulated with consideration of heat and mass transfer, kinetics of phase transformation and gas filtering through a porous medium of granules for the negative temperatures. It is shown that the gas hydrate dissociation in the presence of mainly microporous structures is fundamentally different from the disintegration of gas hydrates containing meso and macropores.

  18. The influence of porosity and structural parameters on different kinds of gas hydrate dissociation.

    PubMed

    Misyura, S Y

    2016-01-01

    Methane hydrate dissociation at negative temperatures was studied experimentally for different artificial and natural samples, differing by macro- and micro-structural parameters. Four characteristic dissociation types are discussed in the paper. The internal kinetics of artificial granule gas hydrates and clathrate hydrates in coal is dependent on the porosity, defectiveness and gas filtration rate. The density of pores distribution in the crust of formed ice decreases by the several orders of magnitude and this change significantly the rate of decay. Existing models for describing dissociation at negative temperatures do not take into account the structural parameters of samples. The dissociation is regulated by internal physical processes that must be considered in the simulation. Non-isothermal dissociation with constant external heat flux was simulated numerically. The dissociation is simulated with consideration of heat and mass transfer, kinetics of phase transformation and gas filtering through a porous medium of granules for the negative temperatures. It is shown that the gas hydrate dissociation in the presence of mainly microporous structures is fundamentally different from the disintegration of gas hydrates containing meso and macropores. PMID:27445113

  19. Molecular Dynamics Simulation for the Dynamics and Kinetics of Folding Peptides in the Gas Phase.

    PubMed

    Litinas, Iraklis; Koutselos, Andreas D

    2015-12-31

    The conformations of flexible molecular species, such as oligomers and oligopeptides, and their interconversion in the gas phase have been probed by ion mobility spectrometry measurements. The ion motion is interpreted through the calculation of effective cross sections in the case of stable conformations of the macromolecules. However, when the molecular structures transform to each other as the ions collide with gas atoms during their flight through the drift tube, the introduction of an average cross section is required. To provide a direct way for the reproduction of the ion motion, we employ a nonequilibrium molecular dynamics simulation method and consider a molecular model that consists of two connected stiff cylindrical bodies interacting through an intramolecular model potential. With this procedure we have calculated the ion mobility as a function of temperature for a prototype peptide that converts between a helical and an extended globular form. The results are in good agreement with ion mobility spectrometry data confirming that an angular vibration coordinate can be used for the interpretation of the shifting of the drift-time distributions at high temperatures. The approach produces mean kinetic energies as well as various combined distributions of the ion degrees of freedom. It is easily applied to flexible macromolecular ions and can be extended to include additional degrees of freedom. PMID:26641107

  20. Hydration energies of sodiated amino acids from gas-phase equilibria determinations.

    PubMed

    Wincel, Henryk

    2007-07-01

    The sequential hydration of a number of sodiated amino acids is investigated using a high-pressure mass spectrometer. Ions produced continuously by electrospray are injected into the reaction chamber in the pulsed mode where the hydration equilibria, AANa+(H2O)n-1+H2O=AANa+(H2O)n (AA=Val, Pro, Met, Phe, and Gln), and the temperature dependence of the equilibrium constants are measured in the gas phase at 10 mbar (N2 bath gas and known pressure of H2O). The thermochemical properties, DeltaH degrees n, DeltaS degrees n, and DeltaG degrees n, for the hydrated systems are determined and discussed in conjunction with the structural forms. The results show that the binding energies of water to the AANa+ complexes decrease with the increasing number of water molecules. The present results from equilibrium measurements are compared to those from earlier studies obtained by other techniques. A correlation between the free energy changes for the addition of the first and second water molecules to AANa+, and the corresponding sodium ion affinities, is observed. Generally, the hydration free energy becomes weaker as the AA-Na+ bond strength increases. PMID:17559201

  1. Synthesis of refractory organic matter in the ionized gas phase of the solar nebula

    PubMed Central

    Kuga, Maïa; Marty, Bernard; Marrocchi, Yves; Tissandier, Laurent

    2015-01-01

    In the nascent solar system, primitive organic matter was a major contributor of volatile elements to planetary bodies, and could have played a key role in the development of the biosphere. However, the origin of primitive organics is poorly understood. Most scenarios advocate cold synthesis in the interstellar medium or in the outer solar system. Here, we report the synthesis of solid organics under ionizing conditions in a plasma setup from gas mixtures (H2(O)−CO−N2−noble gases) reminiscent of the protosolar nebula composition. Ionization of the gas phase was achieved at temperatures up to 1,000 K. Synthesized solid compounds share chemical and structural features with chondritic organics, and noble gases trapped during the experiments reproduce the elemental and isotopic fractionations observed in primitive organics. These results strongly suggest that both the formation of chondritic refractory organics and the trapping of noble gases took place simultaneously in the ionized areas of the protoplanetary disk, via photon- and/or electron-driven reactions and processing. Thus, synthesis of primitive organics might not have required a cold environment and could have occurred anywhere the disk is ionized, including in its warm regions. This scenario also supports N2 photodissociation as the cause of the large nitrogen isotopic range in the solar system. PMID:26039983

  2. Synthesis of refractory organic matter in the ionized gas phase of the solar nebula.

    PubMed

    Kuga, Maïa; Marty, Bernard; Marrocchi, Yves; Tissandier, Laurent

    2015-06-01

    In the nascent solar system, primitive organic matter was a major contributor of volatile elements to planetary bodies, and could have played a key role in the development of the biosphere. However, the origin of primitive organics is poorly understood. Most scenarios advocate cold synthesis in the interstellar medium or in the outer solar system. Here, we report the synthesis of solid organics under ionizing conditions in a plasma setup from gas mixtures (H2(O)-CO-N2-noble gases) reminiscent of the protosolar nebula composition. Ionization of the gas phase was achieved at temperatures up to 1,000 K. Synthesized solid compounds share chemical and structural features with chondritic organics, and noble gases trapped during the experiments reproduce the elemental and isotopic fractionations observed in primitive organics. These results strongly suggest that both the formation of chondritic refractory organics and the trapping of noble gases took place simultaneously in the ionized areas of the protoplanetary disk, via photon- and/or electron-driven reactions and processing. Thus, synthesis of primitive organics might not have required a cold environment and could have occurred anywhere the disk is ionized, including in its warm regions. This scenario also supports N2 photodissociation as the cause of the large nitrogen isotopic range in the solar system. PMID:26039983

  3. Photoisomerization action spectrum of retinal protonated Schiff base in the gas phase

    SciTech Connect

    Coughlan, N. J. A.; Catani, K. J.; Adamson, B. D.; Wille, U.; Bieske, E. J.

    2014-04-28

    The photophysical behaviour of the isolated retinal protonated n-butylamine Schiff base (RPSB) is investigated in the gas phase using a combination of ion mobility spectrometry and laser spectroscopy. The RPSB cations are introduced by electrospray ionisation into an ion mobility mass spectrometer where they are exposed to tunable laser radiation in the region of the S{sub 1} ← S{sub 0} transition (420–680 nm range). Four peaks are observed in the arrival time distribution of the RPSB ions. On the basis of predicted collision cross sections with nitrogen gas, the dominant peak is assigned to the all-trans isomer, whereas the subsidiary peaks are assigned to various single, double and triple cis geometric isomers. RPSB ions that absorb laser radiation undergo photoisomerization, leading to a detectable change in their drift speed. By monitoring the photoisomer signal as a function of laser wavelength an action spectrum, extending from 480 to 660 nm with a clear peak at 615 ± 5 nm, is obtained. The photoisomerization action spectrum is related to the absorption spectrum of isolated retinal RPSB molecules and should help benchmark future electronic structure calculations.

  4. Research on the two-phase flow and separation mechanism in the oil-gas cyclone separator

    NASA Astrophysics Data System (ADS)

    Wang, L. Z.; Gao, X.; Feng, J. M.; Peng, X. Y.

    2015-08-01

    The cyclone separator has attracted increasing attention due to its small size, rapid construction and high separation efficiency. This study investigated its gas-liquid two-phase flow and separation characteristics experimentally and numerically. A numerical model of two- phase flow in the cyclone separator was proposed using the Euler-Lagrange method. The distribution of pressure, tangential and axial velocity in the gas-phase flow field was obtained, and the oil droplet movement was traced. Separation efficiency was also studied experimentally, and the diameter distributions of oil droplets at the inlet and the outlet of the separator were measured by a Malvern laser particle size analyser to verify the simulation model. Based on high-speed photography technology, the oil film distribution and flow pattern on the wall of the cyclone separator were visualised. The variation of oil-gas two-phase flow in the cyclone separator was compared under various inlet flow rates. Based on the results, an improved structure was proposed, and the performance of the improved separator was investigated experimentally.

  5. Self-Assembled Multimetallic/Peptide Complexes: Structures and Unimolecular Reactions of [Mn (GlyGly-H)2n-1 ](+) and Mn+1 (GlyGly-H2n ](2+) Clusters in the Gas Phase.

    PubMed

    Moghaddam, Maryam B; Jami-Alahmadi, Yasaman; Fridgen, Travis D

    2015-10-26

    The unimolecular chemistry and structures of self-assembled complexes containing multiple alkaline-earth-metal dications and deprotonated GlyGly ligands are investigated. Singly and doubly charged ions [Mn (GlyGly-H)n-1 ](+) (n=2-4), [Mn+1 (GlyGly-H)2n ](2+) (n=2,4,6), and [M(GlyGly-H)GlyGly](+) were observed. The losses of 132 Da (GlyGly) and 57 Da (determined to be aminoketene) were the major dissociation pathways for singly charged ions. Doubly charged Mg(2+) clusters mainly lost GlyGly, whereas those containing Ca(2+) or Sr(2+) also underwent charge separation. Except for charge separation, no loss of metal cations was observed. Infrared multiple photon dissociation spectra were the most consistent with the computed IR spectra for the lowest energy structures, in which deprotonation occurs at the carboxyl acid groups and all amide and carboxylate oxygen atoms are complexed to the metal cations. The N-H stretch band, observed at 3350 cm(-1) , is indicative of hydrogen bonding between the amine nitrogen atoms and the amide hydrogen atom. This study represents the first into large self-assembled multimetallic complexes bound by peptide ligands. PMID:26279054

  6. Ligand field spectroscopy of Cu(II) and Ag(II) complexes in the gas phase: theory and experiment.

    PubMed

    Puskar, Ljiljana; Cox, Hazel; Goren, Alan; Aitken, Georgina D C; Stace, Anthony J

    2003-01-01

    Ligand field spectra have been recorded in the gas phase for the two series of complexes containing either Cu(II) or Ag(II) in association with pyridine. Where comparisons are possible, the gas phase spectra match those recorded in the condensed phase; however, for Ag(II) systems the results differ in interpretation. The Ag(II) data are attributed to a ligand-to-metal charge transfer process, and the Cu(II) data (spectral region and extinction coefficient) match the characteristics of a d-d transition. A detailed theoretical analysis of two complexes. [Cu(py)4]2+ and [Ag(py)4]2+ provides evidence of a minimum energy, D4h structure and two less stable D2h and D2d structures within approximately 60 kJ mol(-1). From these structures it is possible to identify a range of optically and vibronically allowed transitions that could contribute to spectra observed in the gas phase. In the case of calculations on [Ag(py)4]2+ there is strong evidence of an electronic transition that would account for the observation of charge transfer in the experiments. Less detailed calculations on [Cu(py)6]2+ and [Ag(py)6]2+ show structural evidence of extensive Jahn Teller distortion. Taken together with incremental binding energies calculated for complexes containing between two and six pyridine molecules, these results show that the level of theory adopted is capable of providing a semi-quantitative understanding of the experimental data. PMID:14527220

  7. Hydration of gas-phase ytterbium ion complexes studied by experiment and theory

    SciTech Connect

    Rutkowski, Philip X; Michelini, Maria C.; Bray, Travis H.; Russo, Nino; Marcalo, Joaquim; Gibson, John K.

    2011-02-11

    Hydration of ytterbium (III) halide/hydroxide ions produced by electrospray ionization was studied in a quadrupole ion trap mass spectrometer and by density functional theory (DFT). Gas-phase YbX{sub 2}{sup +} and YbX(OH){sup +} (X = OH, Cl, Br, or I) were found to coordinate from one to four water molecules, depending on the ion residence time in the trap. From the time dependence of the hydration steps, relative reaction rates were obtained. It was determined that the second hydration was faster than both the first and third hydrations, and the fourth hydration was the slowest; this ordering reflects a combination of insufficient degrees of freedom for cooling the hot monohydrate ion and decreasing binding energies with increasing hydration number. Hydration energetics and hydrate structures were computed using two approaches of DFT. The relativistic scalar ZORA approach was used with the PBE functional and all-electron TZ2P basis sets; the B3LYP functional was used with the Stuttgart relativistic small-core ANO/ECP basis sets. The parallel experimental and computational results illuminate fundamental aspects of hydration of f-element ion complexes. The experimental observations - kinetics and extent of hydration - are discussed in relationship to the computed structures and energetics of the hydrates. The absence of pentahydrates is in accord with the DFT results, which indicate that the lowest energy structures have the fifth water molecule in the second shell.

  8. A Phase-Field Method for Simulating Fluid-Structure Interactions in Multi-Phase Flow

    NASA Astrophysics Data System (ADS)

    Zheng, Xiaoning; Karniadakis, George

    2015-11-01

    We investigate two-phase flow instabilities by numerical simulations of fluid structure interactions in two-phase flow. The first case is a flexible pipe conveying two fluids, which exhibits self-sustained oscillations at high Reynolds number and tension related parameter. Well-defined two-phase flow patterns, i.e., slug flow and bubbly flow, are observed. The second case is external two-phase cross flow past a circular cylinder, which induces a Kelvin-Helmholtz instability due to density stratification. We solve the Navier-Stokes equation coupled with the Cahn-Hilliard equation and the structure equation in an arbitrary Lagrangian Eulerian (ALE) framework. For the fluid solver, a spectral/hp element method is employed for spatial discretization and backward differentiation for time discretization. For the structure solver, a Galerkin method is used in Lagrangian coordinates for spatial discretization and the Newmark- β scheme for time discretization.

  9. Antiplasmodial Drugs in the Gas Phase: A CID and DFT Study of Quinolon-4( 1H)-Imine Derivatives

    NASA Astrophysics Data System (ADS)

    Amorim Madeira, Paulo J.; Sitoe, Ana Raquel Fernandes; Gonçalves, Daniel; Rodrigues, Tiago; Guedes, Rita C.; Lopes, Francisca; Moreira, Rui; Bronze, M. Rosário

    2014-09-01

    The gas-phase behavior of 12 quinolon-4( 1H)-imine derivatives with antiplasmodial activity was investigated using electrospray ionization tandem mass spectrometry together with collision induced dissociation and density functional theory (DFT) calculations. The most probable protonation site was predicted by calculating the proton affinity (PA) values for each possible protonation site and it was found to be the imine nitrogen for all compounds under study. Fragmentation pathways of the protonated molecules were proposed and the assignment of product ion structures was performed taking into account theoretical calculations. The nature of the quinoline substituent was found to influence the gas-phase behavior of the compounds under study. The data acquired allowed to bracket the proton affinity of the quinolin-4-imine scaffold, which can be a useful starting point to choose appropriate references for determining PA values of this scaffold.

  10. Generation and Characterization of a Distonic Biradical Anion Formed from an Enediynone Prodrug in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Yang, Linan; Bekele, Tefsit; Lipton, Mark A.; Kenttämaa, Hilkka I.

    2013-04-01

    A negatively charged biradical intermediate was successfully generated in the gas phase via cyclization of the deprotonated bicyclo[8.3.0]trideca-12-ene-2,7-diyn-1-one precursor. The inherent negative charge of this biradical allows its characterization via collision-activated dissociation and reactions with a variety of neutral substrates in an FT-ICR mass spectrometer. Although the biradical is unreactive toward reagents that usually react rapidly with positively charged biradicals, such as dimethyl disulfide, it reacts with the halogen-containing substrates carbon tetrachloride, carbon tetrabromide, and bromotrichloromethane via bromine or chlorine atom abstraction, which supports its biradical structure. The results presented in this study indicate that cyclizations commonly used in solution to form biradical intermediates from enediyne compounds may also occur in the gas phase. [Figure not available: see fulltext.

  11. Generation and Characterization of a Distonic Biradical Anion Formed from an Enediynone Prodrug in the Gas Phase

    PubMed Central

    Yang, Linan; Bekele, Tefsit; Lipton, Mark A.

    2013-01-01

    A negatively charged biradical intermediate was successfully generated in the gas phase via cyclization of the deprotonated bicyclo[8.3.0]trideca-12-ene-2,7-diyn-1-one precursor. The inherent negative charge of this biradical allows its characterization via collision-activated dissociation and reactions with a variety of neutral substrates in an FT-ICR mass spectrometer. Although the biradical is unreactive toward reagents that usually react rapidly with positively charged biradicals, such as dimethyl disulfide, it reacts with the halogen-containing substrates carbon tetrachloride, carbon tetrabromide and bromotrichloromethane via bromine or chlorine atom abstraction, which supports its biradical structure. The results presented in this study indicate that cyclizations commonly used in solution to form biradical intermediates from enediyne compounds may also occur in the gas phase. PMID:23512422

  12. Electron-beam synthesis of fuel in the gas phase

    NASA Astrophysics Data System (ADS)

    Ponomarev, A. V.; Holodkova, E. M.; Ershov, B. G.

    2012-09-01

    Electron-beam synthesis of liquid fuel from gaseous alkanes was upgraded for formation of conventional and alternative fuel from biomass or pyrolysis oil. Bio-feedstock conversion algorithm includes two consecutive stages: (1) initial macromolecules' transformation to low-molecular-weight intermediates; (2) transformation of these intermediates to stable fuel in gaseous alkanes' atmosphere. Radicals originated from alkanes participate in alkylation/hydrogenation of biomass intermediates. Chemical fixation of gaseous alkanes is amplified in the presence of biomass derivatives due to suppression of gas regeneration reactions, higher molar mass of reagents and lower volatility of radiolytic intermediates.

  13. Germanium-silicon alloy and core-shell nanocrystals by gas phase synthesis

    NASA Astrophysics Data System (ADS)

    Mehringer, Christian; Kloner, Christian; Butz, Benjamin; Winter, Benjamin; Spiecker, Erdmann; Peukert, Wolfgang

    2015-03-01

    In this work we present a novel route to synthesize well defined germanium-silicon alloy (GexSi1-x) and core-shell nanocrystals (NCs) employing monosilane (SiH4) and monogermane (GeH4) as precursors in a continuously operated two-stage hot-wall aerosol reactor setup. The first hot-wall reactor stage (HWR I) is used to produce silicon (Si) seed particles from SiH4 pyrolysis in Argon (Ar). The resulting seeding aerosol is fed into the second reactor stage (HWR II) and a mixture of SiH4 and GeH4 is added. The ratio of the precursors in the feed, their partial pressures, the synthesis temperature in HWR II and the overall pressure are varied depending on the desired morphology and composition. Alloy particle production is achieved in the heterogeneous surface reaction regime, meaning that germanium (Ge) and Si are deposited on the seed surface simultaneously. The NCs can be synthesized with any desired composition, whilst maintaining a mean diameter around 30 nm with a geometric standard deviation (GSD) around 1.25. The absorption behavior and the related fundamental optical band gap energy in dependence on the alloy composition are exemplarily presented. They prove the possibility to tailor NC properties for electronical and opto-electronical applications. In the homogeneous gas phase reaction regime facetted Ge-Si core-shell structures are accessible. The Ge deposition on the seeds precedes the Si deposition due to different gas phase reaction kinetics of the precursors. The Si layer grows epitaxially on the Ge core and is around 5 nm thick.In this work we present a novel route to synthesize well defined germanium-silicon alloy (GexSi1-x) and core-shell nanocrystals (NCs) employing monosilane (SiH4) and monogermane (GeH4) as precursors in a continuously operated two-stage hot-wall aerosol reactor setup. The first hot-wall reactor stage (HWR I) is used to produce silicon (Si) seed particles from SiH4 pyrolysis in Argon (Ar). The resulting seeding aerosol is fed into

  14. Detecting the temporal structure of intermittent phase locking

    PubMed Central

    Ahn, Sungwoo; Park, Choongseok; Rubchinsky, Leonid L.

    2011-01-01

    This study explores a method to characterize temporal structure of intermittent phase locking in oscillatory systems. When an oscillatory system is in a weakly synchronized regime away from a synchronization threshold, it spends most of the time in parts of its phase space away from synchronization state. Therefore characteristics of dynamics near this state (such as its stability properties/Lyapunov exponents or distributions of the durations of synchronized episodes) do not describe system’s dynamics for most of the time. We consider an approach to characterize the system dynamics in this case, by exploring the relationship between the phases on each cycle of oscillations. If some overall level of phase locking is present, one can quantify when and for how long phase locking is lost, and how the system returns back to the phase-locked state. We consider several examples to illustrate this approach: coupled skewed tent maps, which stability can be evaluated analytically, coupled Rössler and Lorenz oscillators, undergoing through different intermittencies on the way to phase synchronization, and a more complex example of coupled neurons. We show that the obtained measures can describe the differences in the dynamics and temporal structure of synchronization/desynchronization events for the systems with similar overall level of phase locking and similar stability of synchronized state. PMID:21867267

  15. Detecting the temporal structure of intermittent phase locking.

    PubMed

    Ahn, Sungwoo; Park, Choongseok; Rubchinsky, Leonid L

    2011-07-01

    This study explores a method to characterize the temporal structure of intermittent phase locking in oscillatory systems. When an oscillatory system is in a weakly synchronized regime away from a synchronization threshold, it spends most of the time in parts of its phase space away from the synchronization state. Therefore characteristics of dynamics near this state (such as its stability properties and Lyapunov exponents or distributions of the durations of synchronized episodes) do not describe the system's dynamics for most of the time. We consider an approach to characterize the system dynamics in this case by exploring the relationship between the phases on each cycle of oscillations. If some overall level of phase locking is present, one can quantify when and for how long phase locking is lost, and how the system returns back to the phase-locked state. We consider several examples to illustrate this approach: coupled skewed tent maps, the stability of which can be evaluated analytically; coupled Rössler and Lorenz oscillators, undergoing through different intermittency types on the way to phase synchronization; and a more complex example of coupled neurons. We show that the obtained measures can describe the differences in the dynamics and temporal structure of synchronization and desynchronization events for the systems with a similar overall level of phase locking and similar stability of the synchronized state. PMID:21867267

  16. Detecting the temporal structure of intermittent phase locking

    NASA Astrophysics Data System (ADS)

    Ahn, Sungwoo; Park, Choongseok; Rubchinsky, Leonid L.

    2011-07-01

    This study explores a method to characterize the temporal structure of intermittent phase locking in oscillatory systems. When an oscillatory system is in a weakly synchronized regime away from a synchronization threshold, it spends most of the time in parts of its phase space away from the synchronization state. Therefore characteristics of dynamics near this state (such as its stability properties and Lyapunov exponents or distributions of the durations of synchronized episodes) do not describe the system’s dynamics for most of the time. We consider an approach to characterize the system dynamics in this case by exploring the relationship between the phases on each cycle of oscillations. If some overall level of phase locking is present, one can quantify when and for how long phase locking is lost, and how the system returns back to the phase-locked state. We consider several examples to illustrate this approach: coupled skewed tent maps, the stability of which can be evaluated analytically; coupled Rössler and Lorenz oscillators, undergoing through different intermittency types on the way to phase synchronization; and a more complex example of coupled neurons. We show that the obtained measures can describe the differences in the dynamics and temporal structure of synchronization and desynchronization events for the systems with a similar overall level of phase locking and similar stability of the synchronized state.

  17. Analysis of Developing Gas/liquid Two-Phase Flows

    SciTech Connect

    Elena A. Tselishcheva; Michael Z. Podowski; Steven P. Antal; Donna Post Guillen; Matthias Beyer; Dirk Lucas

    2010-06-01

    The goal of this work is to develop a mechanistically based CFD model that can be used to simulate process equipment operating in the churn-turbulent regime. The simulations were performed using a state-of-the-art computational multiphase fluid dynamics code, NPHASE–CMFD [Antal et al,2000]. A complete four-field model, including the continuous liquid field and three dispersed gas fields representing bubbles of different sizes, was first carefully tested for numerical convergence and accuracy, and then used to reproduce the experimental results from the TOPFLOW test facility at Forschungszentrum Dresden-Rossendorf e.V. Institute of Safety Research [Prasser et al,2007]. Good progress has been made in simulating the churn-turbulent flows and comparison the NPHASE-CMFD simulations with TOPFLOW experimental data. The main objective of the paper is to demonstrate capability to predict the evolution of adiabatic churn-turbulent gas/liquid flows. The proposed modelling concept uses transport equations for the continuous liquid field and for dispersed bubble fields [Tselishcheva et al, 2009]. Along with closure laws based on interaction between bubbles and continuous liquid, the effect of height on air density has been included in the model. The figure below presents the developing flow results of the study, namely total void fraction at different axial locations along the TOPFLOW facility test section. The complete model description, as well as results of simulations and validation will be presented in the full paper.

  18. Development of a gas phase source for perfluoroalkyl acids to examine atmospheric sampling methods.

    PubMed

    MacInnis, John J; VandenBoer, Trevor C; Young, Cora J

    2016-06-21

    An inability to produce environmentally relevant gaseous mixing ratios of perfluoroalkyl acids (PFAAs), ubiquitous global contaminants, limits the analytical reliability of atmospheric chemists to make accurate gas and particulate measurements that are demonstrably free of interferences due to sampling artefacts. A gas phase source for PFAAs based on the acid displacement mechanism using perfluoropropionate (PFPrA), perfluorobutanoate (PFBA), perfluorohexanoate (PFHxA), and perfluorooctanoate (PFOA) has been constructed. The displacement efficiency of gas phase perfluorocarboxylic acids (PFCAs) is inversely related to chain length. Decreasing displacement efficiencies for PFPrA, PFBA, PFHxA, and PFOA were 90% ± 20%, 40% ± 10%, 40% ± 10%, 9% ± 4%, respectively. Generating detectable amounts of gas phase perfluorosulfonic acids (PFSAs) was not possible. It is likely that lower vapour pressure and much higher acidity play a role in this lack of emission. PFCA emission rates were not elevated by increasing relative humidity (25%-75%), nor flow rate of carrier gas from 33-111 sccm. Overall, reproducible gaseous production of PFCAs was within the error of the production of hydrochloric acid (HCl) as a displacing acid (±20%) and was accomplished using a dry nitrogen flow of 33 ± 2 sccm. A reproducible mass emission rate of 0.97 ± 0.10 ng min(-1) (n = 8) was observed for PFBA. This is equivalent to an atmospheric mixing ratio of 12 ppmv, which is easily diluted to environmentally relevant mixing ratios of PFBA. Conversely, generating gas phase perfluorononanoic acid (PFNA) by sublimating the solid acid under the same conditions produced a mass emission rate of 2800 ng min(-1), which is equivalent to a mixing ratio of 18 ppthv and over a million times higher than suspected atmospheric levels. Thus, for analytical certification of atmospheric sampling methods, generating gas phase standards for PFCAs is best accomplished using acid displacement under dry conditions

  19. Gas-phase products and secondary aerosol yields from the photooxidation of 16 different terpenes

    NASA Astrophysics Data System (ADS)

    Lee, Anita; Goldstein, Allen H.; Kroll, Jesse H.; Ng, Nga L.; Varutbangkul, Varuntida; Flagan, Richard C.; Seinfeld, John H.

    2006-09-01

    The photooxidation of isoprene, eight monoterpenes, three oxygenated monoterpenes, and four sesquiterpenes were conducted individually at the Caltech Indoor Chamber Facility under atmospherically relevant HC:NOx ratios to monitor the time evolution and yields of SOA and gas-phase oxidation products using PTR-MS. Several oxidation products were calibrated in the PTR-MS, including formaldehyde, acetaldehyde, formic acid, acetone, acetic acid, nopinone, methacrolein + methyl vinyl ketone; other oxidation products were inferred from known fragmentation patterns, such as pinonaldehyde; and other products were identified according to their mass to charge (m/z) ratio. Numerous unidentified products were formed, and the evolution of first- and second-generation products was clearly observed. SOA yields from the different terpenes ranged from 1 to 68%, and the total gas- plus particle-phase products accounted for ˜50-100% of the reacted carbon. The carbon mass balance was poorest for the sesquiterpenes, suggesting that the observed products were underestimated or that additional products were formed but not detected by PTR-MS. Several second-generation products from isoprene photooxidation, including m/z 113, and ions corresponding to glycolaldehyde, hydroxyacetone, methylglyoxal, and hydroxycarbonyls, were detected. The detailed time series and relative yields of identified and unidentified products aid in elucidating reaction pathways and structures for the unidentified products. Many of the unidentified products from these experiments were also observed within and above the canopy of a Ponderosa pine plantation, confirming that many products of terpene oxidation can be detected in ambient air using PTR-MS, and are indicative of concurrent SOA formation.

  20. Gas-phase uranyl, neptunyl, and plutonyl: hydration and oxidation studied by experiment and theory.

    PubMed

    Rios, Daniel; Michelini, Maria C; Lucena, Ana F; Marçalo, Joaquim; Bray, Travis H; Gibson, John K

    2012-06-18

    The following monopositive actinyl ions were produced by electrospray ionization of aqueous solutions of An(VI)O(2)(ClO(4))(2) (An = U, Np, Pu): U(V)O(2)(+), Np(V)O(2)(+), Pu(V)O(2)(+), U(VI)O(2)(OH)(+), and Pu(VI)O(2)(OH)(+); abundances of the actinyl ions reflect the relative stabilities of the An(VI) and An(V) oxidation states. Gas-phase reactions with water in an ion trap revealed that water addition terminates at AnO(2)(+)·(H(2)O)(4) (An = U, Np, Pu) and AnO(2)(OH)(+)·(H(2)O)(3) (An = U, Pu), each with four equatorial ligands. These terminal hydrates evidently correspond to the maximum inner-sphere water coordination in the gas phase, as substantiated by density functional theory (DFT) computations of the hydrate structures and energetics. Measured hydration rates for the AnO(2)(OH)(+) were substantially faster than for the AnO(2)(+), reflecting additional vibrational degrees of freedom in the hydroxide ions for stabilization of hot adducts. Dioxygen addition resulted in UO(2)(+)(O(2))(H(2)O)(n) (n = 2, 3), whereas O(2) addition was not observed for NpO(2)(+) or PuO(2)(+) hydrates. DFT suggests that two-electron three-centered bonds form between UO(2)(+) and O(2), but not between NpO(2)(+) and O(2). As formation of the UO(2)(+)-O(2) bonds formally corresponds to the oxidation of U(V) to U(VI), the absence of this bonding with NpO(2)(+) can be considered a manifestation of the lower relative stability of Np(VI). PMID:22656318