WorldWideScience

Sample records for stable gas-phase species

  1. Gas phase thermal diffusion of stable isotopes

    International Nuclear Information System (INIS)

    Eck, C.F.

    1979-01-01

    The separation of stable isotopes at Mound Facility is reviewed from a historical perspective. The historical development of thermal diffusion from a laboratory process to a separation facility that handles all the noble gases is described. In addition, elementary thermal diffusion theory and elementary cascade theory are presented along with a brief review of the uses of stable isotopes

  2. Uptake of Organic Gas Phase Species by 1-Methylnaphthalene

    Science.gov (United States)

    Zhang, H.; Xia, J.; Davidovits, P.; Jayne, J. T.; Kolb, C. E.; Worsnop, D. R.

    2002-12-01

    Using a droplet train apparatus, the mass accommodation coefficients (α) on 1-methylnapthalene of gas phase m-xylene, ethylbenzene, butylbenzene, α-pinene, γ-terpinene, and 2-methyl-2-hexanol were measured as a function of temperature (265 K to 296 K). 1-methylnapthalene was selected as a surrogate for hydrophobic and aromatic hydrocarbons found in tropospheric aerosols. The mass accommodation coefficients (α) of all the molecules obtained from these measurements exhibit negative temperature dependence. The upper and lower values of α at 265 K and 296 K respectively are: for m-xylene 0.44 and 0.26; for ethylbenzene 0.37 and 0.22; for butylbenzene 0.47 and 0.31; for α-pinene 0.47 and 0.096; for γ-terpinene 0.39 and 0.12; for 2-methyl-2-hexanol 0.44 and 0.26. The uptake measurements also yielded values for the product HDl1/2 for most of the molecules studied (H = Henry's law constant, Dl = liquid phase diffusion coefficient). Using calculated values of Dl the Henry's law constant is obtained, and expressed in the form ln H (M/atm) = -A + B/T. The A and B values for the molecules studied are listed in Table 1. Table 1: A and B values for the Henry's law constant H expressed as ln H (M/atm) = -A + B/T \\ m-xylene: A=7.20, B=4060\\ethylbenzene: A=5.81, B=3660\\butylbenzene: A=16.95, B=7330α-pinene: A=15.69, B=6360\\2-methyl-2-hexanol: A=9.95, B=4760

  3. Dynamics of gas-phase transient species studied by dissociative photodetachment of molecular anions

    OpenAIRE

    Lu, Zhou

    2007-01-01

    Gas-phase transient species, such as the CH₃CO₂ and HOCO free radicals, play important roles in combustion and environment chemistry. In this thesis work, the dynamics of these two radicals were studied by dissociative photodetachment (DPD) of the negative ions, CH₃CO₂-С and HOCO⁻, respectively. The experiments were carried out with a fast-ion-beam photoelectron-photofragment coincidence (PPC) spectrometer. Mass-selected molecular anions in a fast ion beam were intercepted by a linearly polar...

  4. Single-step gas phase synthesis of stable iron aluminide nanoparticles with soft magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Vernieres, Jerome, E-mail: Jerome.vernieres@oist.jp; Benelmekki, Maria; Kim, Jeong-Hwan; Grammatikopoulos, Panagiotis; Diaz, Rosa E. [Nanoparticles by Design Unit, Okinawa Institute of Science and Technology (OIST) Graduate University, 1919-1 Tancha, Onna Son, Okinawa 904-0495 (Japan); Bobo, Jean-François [Centre d’Elaboration de Materiaux et d’Etudes Structurales (CEMES), 29 rue Jeanne Marvig, 31055 Toulouse Cedex 4 (France); Sowwan, Mukhles, E-mail: Mukhles@oist.jp [Nanoparticles by Design Unit, Okinawa Institute of Science and Technology (OIST) Graduate University, 1919-1 Tancha, Onna Son, Okinawa 904-0495 (Japan); Nanotechnology Research Laboratory, Al-Quds University, P.O. Box 51000, East Jerusalem, Palestine (Country Unknown)

    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.

  5. Identification of stable cytotoxic factors in the gas phase extract of cigarette smoke and pharmacological characterization of their cytotoxicity.

    Science.gov (United States)

    Noya, Yoichi; Seki, Koh-Ichi; Asano, Hiroshi; Mai, Yosuke; Horinouchi, Takahiro; Higashi, Tsunehito; Terada, Koji; Hatate, Chizuru; Hoshi, Akimasa; Nepal, Prabha; Horiguchi, Mika; Kuge, Yuji; Miwa, Soichi

    2013-12-06

    Smoking is a major risk factor for atherosclerotic vascular diseases, but the mechanism for its genesis is unknown. We have recently shown that the gas phase of cigarette smoke (nicotine- and tar-free cigarette smoke extract; CSE) likely to reach the systemic circulation contains stable substances which cause cytotoxicity like plasma membrane damage and cell death in cultured cells, and also that the plasma membrane damage is caused through sequential activation of protein kinase C (PKC) and NADPH oxidase (NOX) and the resulting generation of reactive oxygen species (PKC/NOX-dependent mechanism), whereas cell death is caused through PKC/NOX-dependent and -independent mechanisms. To identify these stable substances, the CSE was prepared by passing the main-stream smoke of 10 cigarettes through a Cambridge glass fiber filter, trapping of the smoke in a vessel cooled at -80°C, and subsequent dissolution in 10ml of water. The CSE was fractionated into nine fractions using reversed-phase HPLC, and each fraction was screened for cytotoxicity in cultured cells, using propidium iodide uptake assay for cell membrane damage and MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] reduction assay for cell viability. The cytotoxicity was positive in two of the nine fractions (Fr2 and Fr5). After extraction of the active fractions into dichloromethane, GC/MS analysis identified 2-cyclopenten-1-one (CPO) in Fr5 but none in Fr2. After derivatization of the active fractions with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride, GC/MS analysis identified acrolein, acetone and propionaldehyde in Fr2, and methyl vinyl ketone (MVK) in Fr5. After 4-h incubation, authentic acrolein and MVK induced concentration-dependent cytotoxicity with EC50 values of 75.9±8.2 and 47.0±8.0μM (mean±SEM; n=3), respectively, whereas acetone, propionaldehyde and CPO were without effect. However, after 24-h incubation, CPO induced concentration

  6. Effects of non-unity Lewis number of gas-phase species in turbulent nonpremixed sooting flames

    KAUST Repository

    Attili, Antonio; Bisetti, Fabrizio; Mueller, Michael E.; Pitsch, Heinz

    2016-01-01

    Turbulence statistics from two three-dimensional direct numerical simulations of planar n-heptane/air turbulent jets are compared to assess the effect of the gas-phase species diffusion model on flame dynamics and soot formation. The Reynolds number based on the initial jet width and velocity is around 15, 000, corresponding to a Taylor scale Reynolds number in the range 100 ≤ Reλ ≤ 150. In one simulation, multicomponent transport based on a mixture-averaged approach is employed, while in the other the gas-phase species Lewis numbers are set equal to unity. The statistics of temperature and major species obtained with the mixture-averaged formulation are very similar to those in the unity Lewis number case. In both cases, the statistics of temperature are captured with remarkable accuracy by a laminar flamelet model with unity Lewis numbers. On the contrary, a flamelet with a mixture-averaged diffusion model, which corresponds to the model used in the multi-component diffusion three-dimensional DNS, produces significant differences with respect to the DNS results. The total mass of soot precursors decreases by 20-30% with the unity Lewis number approximation, and their distribution is more homogeneous in space and time. Due to the non-linearity of the soot growth rate with respect to the precursors' concentration, the soot mass yield decreases by a factor of two. Being strongly affected by coagulation, soot number density is not altered significantly if the unity Lewis number model is used rather than the mixture-averaged diffusion. The dominant role of turbulent transport over differential diffusion effects is expected to become more pronounced for higher Reynolds numbers. © 2016 The Combustion Institute.

  7. Effects of non-unity Lewis number of gas-phase species in turbulent nonpremixed sooting flames

    KAUST Repository

    Attili, Antonio

    2016-02-13

    Turbulence statistics from two three-dimensional direct numerical simulations of planar n-heptane/air turbulent jets are compared to assess the effect of the gas-phase species diffusion model on flame dynamics and soot formation. The Reynolds number based on the initial jet width and velocity is around 15, 000, corresponding to a Taylor scale Reynolds number in the range 100 ≤ Reλ ≤ 150. In one simulation, multicomponent transport based on a mixture-averaged approach is employed, while in the other the gas-phase species Lewis numbers are set equal to unity. The statistics of temperature and major species obtained with the mixture-averaged formulation are very similar to those in the unity Lewis number case. In both cases, the statistics of temperature are captured with remarkable accuracy by a laminar flamelet model with unity Lewis numbers. On the contrary, a flamelet with a mixture-averaged diffusion model, which corresponds to the model used in the multi-component diffusion three-dimensional DNS, produces significant differences with respect to the DNS results. The total mass of soot precursors decreases by 20-30% with the unity Lewis number approximation, and their distribution is more homogeneous in space and time. Due to the non-linearity of the soot growth rate with respect to the precursors\\' concentration, the soot mass yield decreases by a factor of two. Being strongly affected by coagulation, soot number density is not altered significantly if the unity Lewis number model is used rather than the mixture-averaged diffusion. The dominant role of turbulent transport over differential diffusion effects is expected to become more pronounced for higher Reynolds numbers. © 2016 The Combustion Institute.

  8. Gas phase ion chemistry

    CERN Document Server

    Bowers, Michael T

    1979-01-01

    Gas Phase Ion Chemistry, Volume 2 covers the advances in gas phase ion chemistry. The book discusses the stabilities of positive ions from equilibrium gas-phase basicity measurements; the experimental methods used to determine molecular electron affinities, specifically photoelectron spectroscopy, photodetachment spectroscopy, charge transfer, and collisional ionization; and the gas-phase acidity scale. The text also describes the basis of the technique of chemical ionization mass spectrometry; the energetics and mechanisms of unimolecular reactions of positive ions; and the photodissociation

  9. Reactive species output of a plasma jet with a shielding gas device—combination of FTIR absorption spectroscopy and gas phase modelling

    International Nuclear Information System (INIS)

    Schmidt-Bleker, A; Winter, J; Iseni, S; Dünnbier, M; Reuter, S; Weltmann, K-D

    2014-01-01

    In this work, a simple modelling approach combined with absorption spectroscopy of long living species generated by a cold atmospheric plasma jet yields insight into relevant gas phase chemistry. The reactive species output of the plasma jet is controlled using a shielding gas device. The shielding gas is varied using mixtures of oxygen and nitrogen at various humidity levels. Through the combination of Fourier transform infrared (FTIR) spectroscopy, computational fluid dynamics (CFD) simulations and zero dimensional kinetic modelling of the gas phase chemistry, insight into the underlying reaction mechanisms is gained. While the FTIR measurements yield absolute densities of ozone and nitrogen dioxide in the far field of the jet, the kinetic simulations give additional information on reaction pathways. The simulation is fitted to the experimentally obtained data, using the CFD simulations of the experimental setup to estimate the correct evaluation time for the kinetic simulation. It is shown that the ozone production of the plasma jet continuously rises with the oxygen content in the shielding gas, while it significantly drops as humidity is increased. The production of nitrogen dioxide reaches its maximum at about 30% oxygen content in the shielding gas. The underlying mechanisms are discussed based on the simulation results. (paper)

  10. Gas-phase synthesis and structure of monomeric ZnOH: a model species for metalloenzymes and catalytic surfaces.

    Science.gov (United States)

    Zack, Lindsay N; Sun, Ming; Bucchino, Matthew P; Clouthier, Dennis J; Ziurys, Lucy M

    2012-02-16

    Monomeric ZnOH has been studied for the first time using millimeter and microwave gas-phase spectroscopy. ZnOH is important in surface processes and at the active site of the enzyme carbonic anhydrase. In the millimeter-wave direct-absorption experiments, ZnOH was synthesized by reacting zinc vapor, produced in a Broida-type oven, with water. In the Fourier-transform microwave measurements, ZnOH was produced in a supersonic jet expansion of CH(3)OH and zinc vapor, created by laser ablation. Multiple rotational transitions of six ZnOH isotopologues in their X(2)A' ground states were measured over the frequency range of 22-482 GHz, and splittings due to fine and hyperfine structure were resolved. An asymmetric top pattern was observed in the spectra, showing that ZnOH is bent, indicative of covalent bonding. From these data, spectroscopic constants and an accurate structure were determined. The Zn-O bond length was found to be similar to that in carbonic anhydrase and other model enzyme systems.

  11. Gas Phase Nanoparticle Synthesis

    Science.gov (United States)

    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.

  12. Gas phase ion chemistry

    CERN Document Server

    Bowers, Michael T

    1979-01-01

    Gas Phase Ion Chemistry, Volume 1 covers papers on the advances of gas phase ion chemistry. The book discusses the advances in flow tubes and the measurement of ion-molecule rate coefficients and product distributions; the ion chemistry of the earth's atmosphere; and the classical ion-molecule collision theory. The text also describes statistical methods in reaction dynamics; the state selection by photoion-photoelectron coincidence; and the effects of temperature and pressure in the kinetics of ion-molecule reactions. The energy distribution in the unimolecular decomposition of ions, as well

  13. Gas phase pulse radiolysis

    International Nuclear Information System (INIS)

    Jonah, C.D.; Andong Liu; Mulac, W.A.

    1987-01-01

    Gas phase pulse radiolysis, a technique which can be used to study many different phenomena in chemistry and physics, is discussed. As a source of small radicals, pulse radiolysis is important to the field of chemistry, particularly to combustion and atmospheric kinetics. The reactions of 1,3-butadiene, allene, ethylene and acetylene with OH are presented. 52 refs., 1 fig., 1 tab

  14. Gas-Phase Thermolyses

    DEFF Research Database (Denmark)

    Carlsen, Lars; Egsgaard, Helge

    1982-01-01

    The unimolecular gas-phase thermolyses of 1,2,3-oxadithiolan 2-oxide and thiiran 1-oxide have been studied by the flash vacuum thermolysis–field ionization mass spectrometry (f.v.t.–f.i.m.s.) technique in the temperature range from 1 043 to 1 404 K. The reactions are rationalized in terms of sulp...

  15. Gas-Phase Thermolyses

    DEFF Research Database (Denmark)

    Carlsen, Lars; Egsgaard, Helge

    1982-01-01

    The unimolecular gas-phase thermolyses of the four methyl and ethyl monothioacetates (5)–(8) have been studied by the flash vacuum thermolysis–field ionization mass spectrometry technique in the temperature range 883–1 404 K. The types of reactions verified were keten formation, thiono–thiolo rea...

  16. Gas-Phase Thermolysis

    DEFF Research Database (Denmark)

    Carlsen, Lars; Egsgaard, Helge; Schaumann, Ernst

    1980-01-01

    The unimolecular gas-phase thermolytic decomposition of three silylated thionocarboxylic acid derivatives (2b), (3), and (8) have been studied by the flash vacuum thermolysis–field ionization mass spectrometry technique in the temperature range from 783 to 1 404 K in order to elucidate its possible...... applicability as a route to thioketens. Only very minor amounts of the expected thioketens were found, whereas the corresponding ketens were obtained as the major products. A possible mechanism for keten formation is discussed....

  17. Trophic position of coexisting krill species: a stable isotope approach

    DEFF Research Database (Denmark)

    Agersted, Mette Dalgaard; Bode, Antonio; Nielsen, Torkel Gissel

    2014-01-01

    Four krill species with overlapping functional biology coexist in Greenland waters. Here, we used stable isotopes to investigate and discuss their trophic role and mode of coexistence. Bulk carbon (δ13C) and nitrogen (δ15N) stable isotope analyses of Thysanoessa longicaudata, T. inermis, T. raschii...

  18. Gas Phase Molecular Dynamics

    International Nuclear Information System (INIS)

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

    1999-01-01

    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 wave packet calculations that provide insights into energy flow between the vibrational modes of the molecule

  19. Laser spectroscopy and gas-phase chemistry in CVD

    International Nuclear Information System (INIS)

    Ho, P.; Breiland, W.G.; Coltrin, M.E.

    1986-01-01

    The experimental work involves the use of laser spectroscopic techniques for in situ measurements on the gas phase in a chemical vapor deposition reactor. The theoretical part of the program consists of a computer model of the coupled fluid mechanics and gas-phase chemical kinetics of silane decomposition and subsequent reactions of intermediate species. The laser measurements provide extensive data for thoroughly testing the predictive capabilities of the model

  20. Gas phase reactive collisions, experimental approach

    Directory of Open Access Journals (Sweden)

    Canosa A.

    2012-01-01

    Full Text Available Since 1937 when the first molecule in space has been identified, more than 150 molecules have been detected. Understanding the fate of these molecules requires having a perfect view of their photochemistry and reactivity with other partners. It is then crucial to identify the main processes that will produce and destroy them. In this chapter, a general view of experimental techniques able to deliver gas phase chemical kinetics data at low and very low temperatures will be presented. These techniques apply to the study of reactions between neutral reactants on the one hand and reactions involving charge species on the other hand.

  1. Reactive intermediates in the gas phase generation and monitoring

    CERN Document Server

    Setser, D W

    2013-01-01

    Reactive Intermediates in the Gas Phase: Generation and Monitoring covers methods for reactive intermediates in the gas phase. The book discusses the generation and measurement of atom and radical concentrations in flow systems; the high temperature flow tubes, generation and measurement of refractory species; and the electronically excited long-lived states of atoms and diatomic molecules in flow systems. The text also describes the production and detection of reactive species with lasers in static systems; the production of small positive ions in a mass spectrometer; and the discharge-excite

  2. Gas-phase mechanisms in the growth of ZrCyN1-y thin films by pulsed reactive crossed-beam laser ablation

    International Nuclear Information System (INIS)

    Spillmann, H.; Clerc, C.; Doebeli, M.; Willmott, P.R.

    2002-01-01

    Superhard zirconium carbonitride films have been grown via pulsed reactive crossed-beam laser ablation (PRCLA) using zirconium metal and a nitrogen- and carbon-containing gas pulse mixture. The control of stoichiometry was much simplified by using the thermally stable gas-phase species N 2 and CH 4 . The gas-phase processes are investigated using quadrupole mass spectroscopy and optical emission spectroscopy. The excitation of the ablation plume depends intimately on the collision partner of the gas pulse, in particular on its density of states and the probability of energy transfer to internal degrees of freedom

  3. Gas Phase Sulfur, Chlorine and Potassium Chemistry in Biomass Combustion

    DEFF Research Database (Denmark)

    Løj, Lusi Hindiyarti

    2007-01-01

    Gas Phase Sulfur, Chlorine and Alkali Metal Chemistry in Biomass Combustion Concern about aerosols formation, deposits, corrosion, and gaseous emissions during biomass combustion, especially straw, continues to be a driving force for investigation on S, Cl, K-containing species under combustions...... conditions. These trace species contained in the biomass structure will be released to the gas phase during combustion and contribute to the problems generated during the process. The investigation during this PhD project is done to stepwise improve the understanding in the chemistry and reduce...... the uncertainties. In the present work, the detailed kinetic model for gas phase sulfur, chlorine, alkali metal, and their interaction has been updated. The K/O/H/Cl chemistry, S chemistry, and their interaction can reasonably predict a range of experimental data. In general, understanding of the interaction...

  4. SVOC partitioning between the gas phase and settled dust indoors

    Science.gov (United States)

    Weschler, Charles J.; Nazaroff, William W.

    2010-09-01

    Semivolatile organic compounds (SVOCs) are a major class of indoor pollutants. Understanding SVOC partitioning between the gas phase and settled dust is important for characterizing the fate of these species indoors and the pathways by which humans are exposed to them. Such knowledge also helps in crafting measurement programs for epidemiological studies designed to probe potential associations between exposure to these compounds and adverse health effects. In this paper, we analyze published data from nineteen studies that cumulatively report measurements of dustborne and airborne SVOCs in more than a thousand buildings, mostly residences, in seven countries. In aggregate, measured median data are reported in these studies for 66 different SVOCs whose octanol-air partition coefficients ( Koa) span more than five orders of magnitude. We use these data to test a simple equilibrium model for estimating the partitioning of an SVOC between the gas phase and settled dust indoors. The results demonstrate, in central tendency, that a compound's octanol-air partition coefficient is a strong predictor of its abundance in settled dust relative to its gas phase concentration. Using median measured results for each SVOC in each study, dustborne mass fractions predicted using Koa and gas-phase concentrations correlate reasonably well with measured dustborne mass fractions ( R2 = 0.76). Combined with theoretical understanding of SVOC partitioning kinetics, the empirical evidence also suggests that for SVOCs with high Koa values, the mass fraction in settled dust may not have sufficient time to equilibrate with the gas phase concentration.

  5. SVOC partitioning between the gas phase and settled dust indoors

    DEFF Research Database (Denmark)

    Weschler, Charles J.; Nazaroff, W. W.

    2010-01-01

    Semivolatile organic compounds (SVOCs) are a major class of indoor pollutants. Understanding SVOC partitioning between the gas phase and settled dust is important for characterizing the fate of these species indoors and the pathways by which humans are exposed to them. Such knowledge also helps...

  6. Iodine removal from a gas phase

    International Nuclear Information System (INIS)

    Vikis, A. Ch.

    1982-01-01

    Iodine, e.g. radioactive iodine, present as one or more organic iodides, optionally with elemental iodine, in a gas phase (e.g. air) are removed by photochemically decomposing the organic iodides to elemental iodine, reacting the iodine produced, and any initially present with excess ozone, preferably photochemically produced in situ in the gas phase to produce solid iodine oxides, and removing the solid oxides from the gas phase. (author)

  7. Iodine removal from a gas phase

    International Nuclear Information System (INIS)

    Vikis, A.C.

    1984-01-01

    Iodine, e.g. radioactive iodine, present as one or more organic iodides, optionally with elemental iodine, in a gas phase (e.g. air) are removed by photochemically decomposing the organic iodides to elemental iodine, reacting the iodine produced, and any initially present with excess ozone, preferably photochemically produced in situ in the gas phase to produce solid iodine oxides, and removing the solid oxides from the gas phase

  8. An Introduction to the Gas Phase

    Science.gov (United States)

    Vallance, Claire

    2017-11-01

    'An Introduction to the Gas Phase' is adapted from a set of lecture notes for a core first year lecture course in physical chemistry taught at the University of Oxford. The book is intended to give a relatively concise introduction to the gas phase at a level suitable for any undergraduate scientist. After defining the gas phase, properties of gases such as temperature, pressure, and volume are discussed. The relationships between these properties are explained at a molecular level, and simple models are introduced that allow the various gas laws to be derived from first principles. Finally, the collisional behaviour of gases is used to explain a number of gas-phase phenomena, such as effusion, diffusion, and thermal conductivity.

  9. Gas phase chemistry and removal of CH3I during a severe accident

    International Nuclear Information System (INIS)

    Karhu, A.

    2001-01-01

    The purpose of this literature review was to gather valuable information on the behavior of methyl iodide on the gas phase during a severe accident. The potential of transition metals, especially silver and copper, to remove organic iodides from the gas streams was also studied. Transition metals are one of the most interesting groups in the context of iodine mitigation. For example silver is known to react intensively with iodine compounds. Silver is also relatively inert material and it is thermally stable. Copper is known to react with some radioiodine species. However, it is not reactive toward methyl iodide. In addition, it is oxidized to copper oxide under atmospheric conditions. This may limit the industrial use of copper.(au)

  10. Gas phase chemistry and removal of CH{sub 3}I during a severe accident

    Energy Technology Data Exchange (ETDEWEB)

    Karhu, A. [VTT. Energy, Esbo (Finland)

    2001-01-01

    The purpose of this literature review was to gather valuable information on the behavior of methyl iodide on the gas phase during a severe accident. The potential of transition metals, especially silver and copper, to remove organic iodides from the gas streams was also studied. Transition metals are one of the most interesting groups in the context of iodine mitigation. For example silver is known to react intensively with iodine compounds. Silver is also relatively inert material and it is thermally stable. Copper is known to react with some radioiodine species. However, it is not reactive toward methyl iodide. In addition, it is oxidized to copper oxide under atmospheric conditions. This may limit the industrial use of copper.(au)

  11. Infrared spectroscopy of gas-phase clusters using a free-electron laser

    International Nuclear Information System (INIS)

    Heijnsbergen, D. van; Helden, G. von; Meijer, G.

    2002-01-01

    Most clusters produced in the gas phase, especially those containing metals, remain largely uncharaterized, among these are transition metal - carbide, -oxide and -nitride clusters. A method for recording IR spectra of strongly bound gas-phase clusters is presented. It is based on a free-electron laser called Felix, characterized by wide wavelength tuning range, covering almost the full 'molecular finger print' region, high power and fluence which make it suited to excite gas-phase species i.e. gas -phase clusters. Neutral clusters were generated by laser vaporization technique, ions that were created after the interaction with the free-electron laser were analyzed in a flight mass spectrometer. Experiments were run with titanium carbide clusters and their IR spectra given. It was shown that this method is suited to strongly bound clusters with low ionization energies, a condition met for many pure metal clusters and metal compound clusters. (nevyjel)

  12. Heat stable peroxidases from Vigna species (V) | Mbassi | African ...

    African Journals Online (AJOL)

    Shoots of three landraces of a Vigna species from two climatic areas of Cameroon were evaluated for their content of heat-resistant peroxidases. The peroxidase activity in the three landraces was detected with a greater catalytic efficiency for oxidation of O-dianisidine relative to ABTS (2, 2'-azino-bis-(3- ...

  13. Gas-Phase Reactivity of Microsolvated Anions

    DEFF Research Database (Denmark)

    Thomsen, Ditte Linde

    the gas-phase α-effect. The experimental studies are performed by means of the flowing after glow selected ion flow tube technique, and these are supplemented by electronic structure calculations. The α-nucleophile employed is the microsolvated hydrogen peroxide anion whose reactivity is compared......Gas-phase studies of ion-molecule reactions shed light on the intrinsic factors that govern reactivity; and even solvent effects can be examined in the gasphase environment by employing microsolvated ions. An area that has received considerable attention with regard to the interplay between...... to that of a series of microsolvated oxygen centered anions. The association of the nucleophiles with a single water or methanol molecule allows the α-effect to be observed in the SN2 reaction with methyl chloride; this effect was not apparent in the reactions of the unsolvated anions. The results suggest...

  14. A retrospective analysis of pollen host plant use by stable and declining bumble bee species.

    Science.gov (United States)

    Kleijn, David; Raemakers, Ivo

    2008-07-01

    Understanding population declines has been the objective of a wide range of ecological studies. When species have become rare such studies are complicated because particular behavior or life history traits may be the cause but also the result of the decline of a species. We approached this problem by studying species' characteristics on specimens that were collected before the onset of their decline and preserved in natural history museums. In northwestern Europe, some bumble bee species declined dramatically during the 20th century whereas other, ecologically similar, species maintained stable populations. A long-standing debate focuses on whether this is caused by declining species having stricter host plant preferences. We compared the composition of pollen loads of five bumble bee species with stable populations and five with declining populations using museum specimens collected before 1950 in Belgium, England, and The Netherlands. Prior to 1950, the number of plant taxa in pollen loads of declining species was almost one-third lower than that in stable species even though individuals of stable and declining species generally originated from the same areas. There were no systematic differences in the composition of pollen loads between stable and declining species, but the plant taxa preferred by declining species before 1950 had experienced a stronger decline in the 20th century than those preferred by stable species. In 2004 and 2005, we surveyed the areas where bumble bees had been caught in the past and compared the composition of past and present pollen loads of the stable, but not of the by now locally extinct declining species. The number of collected pollen taxa was similar, but the composition differed significantly between the two periods. Differences in composition reflected the major changes in land use in northwestern Europe but also the spread of the invasive plant species Impatiens glandulifera. The main question now is why declining species

  15. Studies of matrix diffusion in gas phase

    International Nuclear Information System (INIS)

    Hartikainen, K.; Timonen, J.; Vaeaetaeinen, K.; Pietarila, H.

    1994-03-01

    The diffusion of solutes from fractures into rock matrix is an important factor in the safety analysis of disposal of radioactive waste. Laboratory measurements are needed to complement field investigations for a reliable determination of the necessary transport parameters. Measurements of diffusion coefficients in tight rock samples are usually time consuming because the diffusion processes are slow. On the other hand it is well known that diffusion coefficients in the gas phase are roughly four orders of magnitude larger than those in the liquid phase. Therefore, for samples whose structures do not change much upon drying, it is possible to estimate the diffusion properties of the liquid phase when the properties of the gas phase are known. Advantages of the gas method are quick and easy measurements. In the measurements nitrogen was used as the carrier gas and helium as the tracer gas, and standard techniques have been used for helium detection. Techniques have been developed for both channel flow and through-diffusion measurements. The breakthrough curves have been measured in every experiment and all measurements have been modelled by using appropriate analytical models. As a result matrix porosities and effective diffusion coefficients in the gas phase have been determined. (12 refs., 21 figs., 6 tabs.)

  16. Experimental station for gas phase fluorescence spectroscopy

    International Nuclear Information System (INIS)

    Stankiewicz, M.; Garcia, E. Melero; Ruiz, J. Alvarez; Erman, P.; Hatherly, P.A.; Kivimaeki, A.; Rachlew, E.; Rius i Riu, J.

    2004-01-01

    The details of an experimental setup for gas phase atomic and molecular fluorescence measurements using synchrotron radiation are described in this article. The most significant part of the apparatus is an optical arrangement, which allows for simultaneous measurements of dispersed as well as total fluorescence intensity using an effusive gas jet and an inbuilt gas cell assembled in a convenient plug and measure configuration. The first measurements concerning fluorescence of the N 2 molecule around the N 1s edge obtained with this setup are presented

  17. SILP catalysis in gas-phase hydroformylation and carbonylation

    Energy Technology Data Exchange (ETDEWEB)

    Riisager, A.; Fehrmann, R. [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Chemistry; Haumann, M.; Wasserscheid, P. [Univ. Erlangen-Nuernberg (Germany). Lehrstuhl fuer Chemische Reaktionstechnik

    2006-07-01

    Supported ionic liquid phase (SILP) catalysts are new materials consisting of an ionic liquid-metal catalyst solution highly dispersed on a porous support. The use of a non-volatile, ionic liquid catalyst phase in SILP catalysts results in a stable heterogeneous-type material with selectivity and efficiency like homogeneous catalysts. The silica-supported SILP Rh-bisphosphine hydroformylation catalyst exhibited good activities and excellent selectivities in gas phase hydroformylation with stability exceeding 700 hours time-on-stream. Spectroscopic and kinetic data confirmed the homogeneous nature of the catalyst. In the Rh- SILP catalysed carbonylation of methanol the formation of undesired by-products could be suppressed by variation of residence time and gas pressure. (orig.)

  18. Closed-cage tungsten oxide clusters in the gas phase.

    Science.gov (United States)

    Singh, D M David Jeba; Pradeep, T; Thirumoorthy, Krishnan; Balasubramanian, Krishnan

    2010-05-06

    During the course of a study on the clustering of W-Se and W-S mixtures in the gas phase using laser desorption ionization (LDI) mass spectrometry, we observed several anionic W-O clusters. Three distinct species, W(6)O(19)(-), W(13)O(29)(-), and W(14)O(32)(-), stand out as intense peaks in the regular mass spectral pattern of tungsten oxide clusters suggesting unusual stabilities for them. Moreover, these clusters do not fragment in the postsource decay analysis. While trying to understand the precursor material, which produced these clusters, we found the presence of nanoscale forms of tungsten oxide. The structure and thermodynamic parameters of tungsten clusters have been explored using relativistic quantum chemical methods. Our computed results of atomization energy are consistent with the observed LDI mass spectra. The computational results suggest that the clusters observed have closed-cage structure. These distinct W(13) and W(14) clusters were observed for the first time in the gas phase.

  19. Oxidative potential of gas phase combustion emissions - An underestimated and potentially harmful component of air pollution from combustion processes

    Science.gov (United States)

    Stevanovic, S.; Vaughan, A.; Hedayat, F.; Salimi, F.; Rahman, M. M.; Zare, A.; Brown, R. A.; Brown, R. J.; Wang, H.; Zhang, Z.; Wang, X.; Bottle, S. E.; Yang, I. A.; Ristovski, Z. D.

    2017-06-01

    The oxidative potential (OP) of the gas phase is an important and neglected aspect of environmental toxicity. Whilst prolonged exposure to particulate matter (PM) associated reactive oxygen species (ROS) have been shown to lead to negative health effects, the potential for compounds in gas phase to cause similar effects is yet to be understood. In this study we describe: the significance of the gas phase OP generated through vehicle emissions; discuss the origin and evolution of species contributing to measured OP; and report on the impact of gas phase OP on human lung cells. The model aerosol for this study was exhaust emitted from a Euro III Common-rail diesel engine fuelled with different blends of diesel and biodiesel. The gas phase of these emissions was found to be potentially as hazardous as the particle phase. Fuel oxygen content was found to negatively correlate with the gas phase OP, and positively correlate with particle phase OP. This signifies a complex interaction between reactive species present in gas and particle phase. Furthermore, this interaction has an overarching effect on the OP of both particle and gas phase, and therefore the toxicity of combustion emissions.

  20. High-resolution Measurements of Gas-Phase Hydrogen Chloride (HCl) in the Atmosphere by Cavity Ring Down Spectroscopy

    Science.gov (United States)

    Hoffnagle, John; Chen, Hongbing; Lee, Jim; Rella, Chris; Kim-Hak, David; Winkler, Renato; Markovic, Milos; Veres, Patrick

    2017-04-01

    Halogen radical species, such as chlorine and bromine atoms and their oxides, can greatly affect the chemical composition of the troposphere. Hydrogen chloride is the dominant (gas-phase) contributor to the tropospheric chlorine inventory. Real time in situ observations of HCl can provide an important window into the complex photochemical reaction pathways for chlorine in the atmosphere, including heterogeneous reactions on aerosol surfaces. In this work, we report a novel, commercially-available HCl gas-phase analyzer (G2108, Picarro Inc. Santa Clara, CA, USA) based upon Cavity Ring Down Spectroscopy (CRDS) in the near-infrared, and discuss its performance. With a measurement interval of approximately 2 seconds, a precision of better than 40 parts-per-trillion (1 sigma, 30 seconds), and a response time of approximately 1-2 minutes (10 - 90% rise time or 90 - 10% fall time), this analyzer is well-suited for measurements of atmospherically-relevant concentrations of HCl, in both laboratory and field. CRDS provides very stable measurements and low drift, requiring infrequent calibration of the instrument, and can therefore be operated remotely for extended periods of time. In this work we also present results from a laboratory intercomparison of the Picarro G2108 analyzer and an iodide ion time-of-flight Chemical Ionization Mass Spectrometer (CIMS), and the results of the analyzer time response tests.

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

    Science.gov (United States)

    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.

  2. Optical processes in the performance and recovery of gas-phase switches

    International Nuclear Information System (INIS)

    Gundersen, M.

    1982-01-01

    In this paper several optical processes that may be used to affect gas-phase switch performance and operation are discussed, and approaches using a laser to increase recovery rates of switches are presented. In the latter the laser is used during the recovery phase rather than the conductive or closure phase. This papper suggests that it should be possible to use a low-power laser (e.g., one that is technologically feasible to use as part of a switch) to assist in opening the switch by quenching excited atomic and/or molecular species. The application of laser-induced energy extraction to gas-phase switches is also discussed

  3. The gas phase structure of α -pinene, a main biogenic volatile organic compound

    Science.gov (United States)

    Neeman, Elias M.; Avilés Moreno, Juan Ramón; Huet, Thérèse R.

    2017-12-01

    The gas phase structure of the bicyclic atmospheric aerosol precursor α-pinene was investigated employing a combination of quantum chemical calculation and Fourier transform microwave spectroscopy coupled to a supersonic jet expansion. The very weak rotational spectra of the parent species and all singly substituted 13C in natural abundance have been identified, from 2 to 20 GHz, and fitted to Watson's Hamiltonian model. The rotational constants were used together with geometrical parameters from density functional theory and ab initio calculations to determine the rs, r0, and rm(1 ) structures of the skeleton, without any structural assumption in the fit concerning the heavy atoms. The double C=C bond was found to belong to a quasiplanar skeleton structure containing 6 carbon atoms. Comparison with solid phase structure is reported. The significant differences of α-pinene in gas phase and other gas phase bicyclic monoterpene structures (β-pinene, nopinone, myrtenal, and bicyclo[3.1.1]heptane) are discussed.

  4. Moisture effects on greenhouse gases generation in nitrifying gas-phase compost biofilters.

    Science.gov (United States)

    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

  5. Transferring pharmaceuticals into the gas phase

    Science.gov (United States)

    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.

  6. Resolving Gas-Phase Metallicity In Galaxies

    Science.gov (United States)

    Carton, David

    2017-06-01

    Chapter 2: As part of the Bluedisk survey we analyse the radial gas-phase metallicity profiles of 50 late-type galaxies. We compare the metallicity profiles of a sample of HI-rich galaxies against a control sample of HI-'normal' galaxies. We find the metallicity gradient of a galaxy to be strongly correlated with its HI mass fraction {M}{HI}) / {M}_{\\ast}). We note that some galaxies exhibit a steeper metallicity profile in the outer disc than in the inner disc. These galaxies are found in both the HI-rich and control samples. This contradicts a previous indication that these outer drops are exclusive to HI-rich galaxies. These effects are not driven by bars, although we do find some indication that barred galaxies have flatter metallicity profiles. By applying a simple analytical model we are able to account for the variety of metallicity profiles that the two samples present. The success of this model implies that the metallicity in these isolated galaxies may be in a local equilibrium, regulated by star formation. This insight could provide an explanation of the observed local mass-metallicity relation. Chapter 3 We present a method to recover the gas-phase metallicity gradients from integral field spectroscopic (IFS) observations of barely resolved galaxies. We take a forward modelling approach and compare our models to the observed spatial distribution of emission line fluxes, accounting for the degrading effects of seeing and spatial binning. The method is flexible and is not limited to particular emission lines or instruments. We test the model through comparison to synthetic observations and use downgraded observations of nearby galaxies to validate this work. As a proof of concept we also apply the model to real IFS observations of high-redshift galaxies. From our testing we show that the inferred metallicity gradients and central metallicities are fairly insensitive to the assumptions made in the model and that they are reliably recovered for galaxies

  7. Comparison of catalytic ethylene polymerization in slurry and gas phase

    NARCIS (Netherlands)

    Daftaribesheli, Majid

    2009-01-01

    Polyethylene (PE) with the annual consumption of 70 million tones in 2007 is mostly produced in slurry, gas-phase or combination of both processes. This work focuses on a comparison between the slurry and gas phase processes. Why does PE produced in theses two processes can show extremely different

  8. Study of Iodine Behavior in the Gas Phase during a Severe Accident

    International Nuclear Information System (INIS)

    Kim, Hanchul; Cho, Yeonghun; Ryu, Myunghyun

    2014-01-01

    Among the iodine species, the organic iodides produced from the reaction between iodine and organics such as paint, are not easily trapped by the filters during the containment venting following a severe accident. Korea Institute of Nuclear Safety (KINS) has been studying this issue, joining international research programs such as ISTP-EPICUR, OECDBIP and OECD-STEM. In the course of this study, a simple iodine model, RAIM (Radio-Active Iodine chemistry Model) has been developed (Oh et al., 2011), based on the IMOD methodology, and other previous studies. This paper deals with our recent activities on this study, including the development of the model for the iodine reactions in gas phase. Iodine reactions in gas phase were modeled and added to the RAIM code, taking into account several relevant reactions such as formation of ARP, iodine oxide, and organic iodides in gas phase. RAIM was then applied to analyze the S2-6-5-2 test for which iodine-loaded coupons were tested in gas phase. The analysis results show a reasonable estimation of volatile iodine concentration with the desorption rate constant of about 10 -6 s -1 , while those of the other iodine species overestimated for the whole period of the test. It reveals the need to determine appropriate values for the rate constants for formation of iodine oxides and organic iodides

  9. Diffusion Monte Carlo simulations of gas phase and adsorbed D2-(H2)n clusters

    Science.gov (United States)

    Curotto, E.; Mella, M.

    2018-03-01

    We have computed ground state energies and analyzed radial distributions for several gas phase and adsorbed D2(H2)n and HD(H2)n clusters. An external model potential designed to mimic ionic adsorption sites inside porous materials is used [M. Mella and E. Curotto, J. Phys. Chem. A 121, 5005 (2017)]. The isotopic substitution lowers the ground state energies by the expected amount based on the mass differences when these are compared with the energies of the pure clusters in the gas phase. A similar impact is found for adsorbed aggregates. The dissociation energy of D2 from the adsorbed clusters is always much higher than that of H2 from both pure and doped aggregates. Radial distributions of D2 and H2 are compared for both the gas phase and adsorbed species. For the gas phase clusters, two types of hydrogen-hydrogen interactions are considered: one based on the assumption that rotations and translations are adiabatically decoupled and the other based on nonisotropic four-dimensional potential. In the gas phase clusters of sufficiently large size, we find the heavier isotopomer more likely to be near the center of mass. However, there is a considerable overlap among the radial distributions of the two species. For the adsorbed clusters, we invariably find the heavy isotope located closer to the attractive interaction source than H2, and at the periphery of the aggregate, H2 molecules being substantially excluded from the interaction with the source. This finding rationalizes the dissociation energy results. For D2-(H2)n clusters with n ≥12 , such preference leads to the desorption of D2 from the aggregate, a phenomenon driven by the minimization of the total energy that can be obtained by reducing the confinement of (H2)12. The same happens for (H2)13, indicating that such an effect may be quite general and impact on the absorption of quantum species inside porous materials.

  10. The Genealogical Tree of Ethanol: Gas-phase Formation of Glycolaldehyde, Acetic Acid, and Formic Acid

    Science.gov (United States)

    Skouteris, Dimitrios; Balucani, Nadia; Ceccarelli, Cecilia; Vazart, Fanny; Puzzarini, Cristina; Barone, Vincenzo; Codella, Claudio; Lefloch, Bertrand

    2018-02-01

    Despite the harsh conditions of the interstellar medium, chemistry thrives in it, especially in star-forming regions where several interstellar complex organic molecules (iCOMs) have been detected. Yet, how these species are synthesized is a mystery. The majority of current models claim that this happens on interstellar grain surfaces. Nevertheless, evidence is mounting that neutral gas-phase chemistry plays an important role. In this paper, we propose a new scheme for the gas-phase synthesis of glycolaldehyde, a species with a prebiotic potential and for which no gas-phase formation route was previously known. In the proposed scheme, the ancestor is ethanol and the glycolaldehyde sister species are acetic acid (another iCOM with unknown gas-phase formation routes) and formic acid. For the reactions of the new scheme with no available data, we have performed electronic structure and kinetics calculations deriving rate coefficients and branching ratios. Furthermore, after a careful review of the chemistry literature, we revised the available chemical networks, adding and correcting several reactions related to glycolaldehyde, acetic acid, and formic acid. The new chemical network has been used in an astrochemical model to predict the abundance of glycolaldehyde, acetic acid, and formic acid. The predicted abundance of glycolaldehyde depends on the ethanol abundance in the gas phase and is in excellent agreement with the measured one in hot corinos and shock sites. Our new model overpredicts the abundance of acetic acid and formic acid by about a factor of 10, which might imply a yet incomplete reaction network.

  11. Stable Water Use Efficiency under Climate Change of Three Sympatric Conifer Species at the Alpine Treeline.

    Science.gov (United States)

    Wieser, Gerhard; Oberhuber, Walter; Gruber, Andreas; Leo, Marco; Matyssek, Rainer; Grams, Thorsten Erhard Edgar

    2016-01-01

    The ability of treeline associated conifers in the Central Alps to cope with recent climate warming and increasing CO2 concentration is still poorly understood. We determined tree ring stable carbon and oxygen isotope ratios of Pinus cembra, Picea abies, and Larix decidua trees from 1975 to 2010. Stable isotope ratios were compared with leaf level gas exchange measurements carried out in situ between 1979 and 2007. Results indicate that tree ring derived intrinsic water-use efficiency (iWUE) of P. cembra, P. abies and L. decidua remained constant during the last 36 years despite climate warming and rising atmospheric CO2. Temporal patterns in Δ(13)C and Δ(18)O mirrored leaf level gas exchange assessments, suggesting parallel increases of CO2-fixation and stomatal conductance of treeline conifer species. As at the study site soil water availability was not a limiting factor iWUE remained largely stable throughout the study period. The stability in iWUE was accompanied by an increase in basal area increment (BAI) suggesting that treeline trees benefit from both recent climate warming and CO2 fertilization. Finally, our results suggest that iWUE may not change species composition at treeline in the Austrian Alps due to similar ecophysiological responses to climatic changes of the three sympatric study species.

  12. Stable water use efficiency under climate change of three sympatric conifer species at the Alpine treeline

    Directory of Open Access Journals (Sweden)

    Gerhard eWieser

    2016-06-01

    Full Text Available The ability of treeline associated conifers in the Central Alps to cope with recent climate warming and increasing CO2 concentration is still poorly understood. We determined tree ring stable carbon and oxygen isotope ratios of Pinus cembra, Picea abies and Larix decidua trees from 1975-2010. Stable isotope ratios were compared with leaf level gas exchange measurements carried out in situ between 1979 and 2007. Results indicate that tree ring derived intrinsic water-use efficiency (iWUE of P. cembra, P. abies and L. decidua remained constant during the last 36 years despite climate warming and rising atmospheric CO2. Temporal patterns in Δ13C and Δ18O mirrored leaf level gas exchange assessments, suggesting parallel increases of CO2-fixation and stomatal conductance of treeline conifer species. As at the study site soil water availability was not a limiting factor iWUE remained largely stable throughout the study period. The stability in iWUE was accompanied by an increase in basal area increment (BAI suggesting that treeline trees benefit from both recent climate warming and CO2 fertilization. Finally, our results suggest that iWUE may not change species composition at treeline in the Austrian Alps due to similar ecophysiological responses to climatic changes of the three sympatric study species.

  13. Tobacco Smoke: Involvement of Reactive Oxygen Species and Stable Free Radicals in Mechanisms of Oxidative Damage, Carcinogenesis and Synergistic Effects with Other Respirable Particles

    Directory of Open Access Journals (Sweden)

    Konstantinos Fiotakis

    2009-02-01

    Full Text Available Tobacco smoke contains many toxic, carcinogenic and mutagenic chemicals, as well as stable and unstable free radicals and reactive oxygen species (ROS in the particulate and the gas phase with the potential for biological oxidative damage. Epidemiological evidence established that smoking is one of the most important extrinsic factor of premature morbidity and mortality. The objective of this study was to investigate oxidative and carcinogenic mechanisms of tobacco and synergistic action with other respirable particles in the respiratory system of smokers. Electron Paramagnetic Resonance (EPR and spin- trapping techniques were used to study stable free radicals in the cigarette tar, and unstable superoxide anion (O2·- and hydroxyl (HO· radicals in the smoke Results showed that the semiquinone radical system has the potential for redox recycling and oxidative action. Further, results proved that aqueous cigarette tar (ACT solutions can generate adducts with DNA nucleobases, particularly the mutagenic 8-hydroxy-2’-deoxyguanosine (a biomarker for carcinogenesis.Also, we observed synergistic effects in the generation of HO·, through the Fenton reaction, with environmental respirable particles (asbestos fibres, coal dust, etc. and ambient particulate matter (PM, such as PM10, PM2.5 and diesel exhaust particles (DEP. The highest synergistic effects was observed with the asbestos fibres (freshly grounded, PM2.5 and DEP. Finally, we discuss results from our previous study of conventional cellulose acetate filters and “bio-filters” with hemoglobin impregnated activated carbon, which showed that these filters do not substantially alter the free radical content of smoke in the particulate and in the gaseous phase.

  14. Tobacco Smoke: Involvement of Reactive Oxygen Species and Stable Free Radicals in Mechanisms of Oxidative Damage, Carcinogenesis and Synergistic Effects with Other Respirable Particles

    Science.gov (United States)

    Valavanidis, Athanasios; Vlachogianni, Thomais; Fiotakis, Konstantinos

    2009-01-01

    Tobacco smoke contains many toxic, carcinogenic and mutagenic chemicals, as well as stable and unstable free radicals and reactive oxygen species (ROS) in the particulate and the gas phase with the potential for biological oxidative damage. Epidemiological evidence established that smoking is one of the most important extrinsic factor of premature morbidity and mortality. The objective of this study was to investigate oxidative and carcinogenic mechanisms of tobacco and synergistic action with other respirable particles in the respiratory system of smokers. Electron Paramagnetic Resonance (EPR) and spin-trapping techniques were used to study stable free radicals in the cigarette tar, and unstable superoxide anion (O2•−) and hydroxyl (HO•) radicals in the smoke Results showed that the semiquinone radical system has the potential for redox recycling and oxidative action. Further, results proved that aqueous cigarette tar (ACT) solutions can generate adducts with DNA nucleobases, particularly the mutagenic 8-hydroxy-2’-deoxyguanosine (a biomarker for carcinogenesis). Also, we observed synergistic effects in the generation of HO•, through the Fenton reaction, with environmental respirable particles (asbestos fibres, coal dust, etc.) and ambient particulate matter (PM), such as PM10, PM2.5 and diesel exhaust particles (DEP). The highest synergistic effects was observed with the asbestos fibres (freshly grounded), PM2.5 and DEP. Finally, we discuss results from our previous study of conventional cellulose acetate filters and “bio-filters” with hemoglobin impregnated activated carbon, which showed that these filters do not substantially alter the free radical content of smoke in the particulate and in the gaseous phase. PMID:19440393

  15. Species A rotavirus NSP3 acquires its translation inhibitory function prior to stable dimer formation.

    Directory of Open Access Journals (Sweden)

    Hugo I Contreras-Treviño

    Full Text Available Species A rotavirus non-structural protein 3 (NSP3 is a translational regulator that inhibits or, under some conditions, enhances host cell translation. NSP3 binds to the translation initiation factor eIF4G1 and evicts poly-(A binding protein (PABP from eIF4G1, thus inhibiting translation of polyadenylated mRNAs, presumably by disrupting the effect of PABP bound to their 3'-ends. NSP3 has a long coiled-coil region involved in dimerization that includes a chaperone Hsp90-binding domain (HS90BD. We aimed to study the role in NSP3 dimerization of a segment of the coiled-coil region adjoining the HS90BD. We used a vaccinia virus system to express NSP3 with point mutations in conserved amino acids in the coiled-coil region and determined the effects of these mutations on translation by metabolic labeling of proteins as well as on accumulation of stable NSP3 dimers by non-dissociating Western blot, a method that separates stable NSP3 dimers from the monomer/dimerization intermediate forms of the protein. Four of five mutations reduced the total yield of NSP3 and the formation of stable dimers (W170A, K171E, R173E and R187E:K191E, whereas one mutation had the opposite effects (Y192A. Treatment with the proteasome inhibitor MG132 revealed that stable NSP3 dimers and monomers/dimerization intermediates are susceptible to proteasome degradation. Surprisingly, mutants severely impaired in the formation of stable dimers were still able to inhibit host cell translation, suggesting that NSP3 dimerization intermediates are functional. Our results demonstrate that rotavirus NSP3 acquires its function prior to stable dimer formation and remain as a proteasome target throughout dimerization.

  16. All-gas-phase synthesis of UiO-66 through modulated atomic layer deposition

    Science.gov (United States)

    Lausund, Kristian Blindheim; Nilsen, Ola

    2016-11-01

    Thin films of stable metal-organic frameworks (MOFs) such as UiO-66 have enormous application potential, for instance in microelectronics. However, all-gas-phase deposition techniques are currently not available for such MOFs. We here report on thin-film deposition of the thermally and chemically stable UiO-66 in an all-gas-phase process by the aid of atomic layer deposition (ALD). Sequential reactions of ZrCl4 and 1,4-benzenedicarboxylic acid produce amorphous organic-inorganic hybrid films that are subsequently crystallized to the UiO-66 structure by treatment in acetic acid vapour. We also introduce a new approach to control the stoichiometry between metal clusters and organic linkers by modulation of the ALD growth with additional acetic acid pulses. An all-gas-phase synthesis technique for UiO-66 could enable implementations in microelectronics that are not compatible with solvothermal synthesis. Since this technique is ALD-based, it could also give enhanced thickness control and the possibility to coat irregular substrates with high aspect ratios.

  17. The Ultrafast Wolff Rearrangement in the Gas Phase

    Science.gov (United States)

    Steinbacher, Andreas; Roeding, Sebastian; Brixner, Tobias; Nuernberger, Patrick

    The Wolff rearrangement of gas-phase 5-diazo Meldrum's acid is disclosed with femtosecond ion spectroscopy. Distinct differences are found for 267 nm and 200 nm excitation, the latter leading to even two ultrafast rearrangement reactions.

  18. Reticulated Vitreous Carbon Electrodes for Gas Phase Pulsed Corona Reactors

    National Research Council Canada - National Science Library

    Locke, B

    1998-01-01

    A new design for gas phase pulsed corona reactors incorporating reticulated vitreous carbon electrodes is demonstrated to be effective for the removal of nitrogen oxides from synthetic air mixtures...

  19. GAS PHASE ION CHEMISTRY OF COUMARINS: AB INITIO ...

    African Journals Online (AJOL)

    B. S. Chandravanshi

    The gas phase ion chemistry of coumarins using electron ionization (EI), positive chemical ionization (PCI) and ... Figure 1. Generic chemical structures of the coumarins in this study. ..... Part of this work was conducted using the resources of ...

  20. Reticulated Vitreous Carbon Electrodes for Gas Phase Pulsed Corona Reactors

    National Research Council Canada - National Science Library

    LOCKE, B

    1999-01-01

    A new design for gas phase pulsed corona reactors incorporating reticulated vitreous carbon electrodes is demonstrated to be effective for the removal of nitrogen oxides from synthetic air mixtures...

  1. Diode Laser Raman Scattering Prototype Gas-Phase Environmental Monitoring

    National Research Council Canada - National Science Library

    Benner, Robert

    1999-01-01

    We proposed developing a diode-laser-based, full spectrum Raman scattering instrument incorporating a multipass, external cavity enhancement cell for full spectrum, gas phase analysis of environmental pollutants...

  2. Ab initio treatment of gas phase GeO{sup 2+} doubly charged ion

    Energy Technology Data Exchange (ETDEWEB)

    Mogren Al Mogren, M. [Chemistry Department, Faculty of Science, King Saud University, PO Box 2455, Riyadh 11451 (Saudi Arabia); Ben Abdallah, D. [Laboratoire de Spectroscopie Atomique, Moléculaire et Applications – LSAMA, Université de Tunis, Tunis (Tunisia); Department of General Studies, Riyadh Corporation of Technology, Technical and Vocational Training Corporation, PO Box 42826, Riyadh 11551 (Saudi Arabia); Hochlaf, M., E-mail: hochlaf@univ-mlv.fr [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée (France)

    2015-01-13

    Highlights: • Theoretical investigation of the novel gas-phase molecular species GeO{sup 2+}. • Spectroscopic parameters of this dication in its electronic ground and exited states. • Theoretical double ionization spectrum of GeO. - Abstract: Using multi reference configuration interaction methodology in connection with a large basis set, we show that GeO{sup 2+} is a metastable species either in the ground or in the electronically excited states. This confirms the observation of this dication in gas phase by mass spectrometry. In addition, we derived a set of accurate spectroscopic terms for GeO{sup 2+} bound states. At the MRCI/aug-cc-pV5Z level of theory, the adiabatic double ionization energy of GeO is computed to be ∼28.93 eV.

  3. Comparison of catalytic ethylene polymerization in slurry and gas phase

    OpenAIRE

    Daftaribesheli, Majid

    2009-01-01

    Polyethylene (PE) with the annual consumption of 70 million tones in 2007 is mostly produced in slurry, gas-phase or combination of both processes. This work focuses on a comparison between the slurry and gas phase processes. Why does PE produced in theses two processes can show extremely different properties and extremely different reaction behaviour even if the same Ziegler-Natta (ZN) catalyst is used? Generally, it is known that the reason can be found in the differences of local condition...

  4. GAS-PHASE CHEMISTRY OF THE CYANATE ION, OCN−

    International Nuclear Information System (INIS)

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

    2015-01-01

    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. Determination of the Geographical Origin of All Commercial Hake Species by Stable Isotope Ratio (SIR) Analysis.

    Science.gov (United States)

    Carrera, Mónica; Gallardo, José M

    2017-02-08

    The determination of the geographical origin of food products is relevant to comply with the legal regulations of traceability, to avoid food fraud, and to guarantee food quality and safety to the consumers. For these reasons, stable isotope ratio (SIR) analysis using an isotope ratio mass spectrometry (IRMS) instrument is one of the most useful techniques for evaluating food traceability and authenticity. The present study was aimed to determine, for the first time, the geographical origin for all commercial fish species belonging to the Merlucciidae family using SIR analysis of carbon (δ 13 C) and nitrogen (δ 15 N). The specific results enabled their clear classification according to the FAO (Food and Agriculture Organization of the United Nations) fishing areas, latitude, and geographical origin in the following six different clusters: European, North African, South African, North American, South American, and Australian hake species.

  6. CHAOS. III. GAS-PHASE ABUNDANCES IN NGC 5457

    Energy Technology Data Exchange (ETDEWEB)

    Croxall, Kevin V.; Pogge, Richard W. [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Berg, Danielle A. [Center for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin Milwaukee, 1900 East Kenwood Boulevard, Milwaukee, WI 53211 (United States); Skillman, Evan D. [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States); Moustakas, John [Department of Physics and Astronomy, Siena College, 515 Loudon Road, Loudonville, NY 12211 (United States)

    2016-10-10

    We present Large Binocular Telescope observations of 109 H ii regions in NGC 5457 (M101) obtained with the Multi-Object Double Spectrograph. We have robust measurements of one or more temperature-sensitive auroral emission lines for 74 H ii regions, permitting the measurement of “direct” gas-phase abundances. Comparing the temperatures derived from the different ionic species, we find: (1) strong correlations of T [N ii] with T [S iii] and T [O iii], consistent with little or no intrinsic scatter; (2) a correlation of T [S iii] with T [O iii], but with significant intrinsic dispersion; (3) overall agreement between T [N ii], T [S ii], and T [O ii], as expected, but with significant outliers; (4) the correlations of T [N ii] with T [S iii] and T [O iii] match the predictions of photoionization modeling while the correlation of T [S iii] with T [O iii] is offset from the prediction of photoionization modeling. Based on these observations, which include significantly more observations of lower excitation H ii regions, missing in many analyses, we inspect the commonly used ionization correction factors (ICFs) for unobserved ionic species and propose new empirical ICFs for S and Ar. We have discovered an unexpected population of H ii regions with a significant offset to low values in Ne/O, which defies explanation. We derive radial gradients in O/H and N/O which agree with previous studies. Our large observational database allows us to examine the dispersion in abundances, and we find intrinsic dispersions of 0.074 ± 0.009 in O/H and 0.095 ± 0.009 in N/O (at a given radius). We stress that this measurement of the intrinsic dispersion comes exclusively from direct abundance measurements of H ii regions in NGC 5457.

  7. Kinetics of the gas-phase tritium oxidation reaction

    International Nuclear Information System (INIS)

    Failor, R.A.

    1989-01-01

    Homogeneous gas-phase kinetics of tritium oxidation (2T 2 + O 2 →2T 2 O) have been studied with a model that accounts explicitly for radiolysis of the major species and the kinetics of the subsequent reactions of ionic, excited-state, and neutral species. Results from model calculations are given for 10 -4 -1.0 mol% T 2 in O 2 (298 K, 1 atm). As the reaction evolves three different mechanisms control T 2 O production, each with a different overall rate expression and a different order with respect to the T 2 concentration. The effects of self-radiolysis of pure T 2 on the tritium oxidation reaction were calculated. Tritium atoms, the primary product of T 2 self-radiolysis, altered the oxidation mechanism only during the first few seconds following the initiation of the T 2 -O 2 reaction. Ozone, an important intermediate in T 2 oxidation, was monitored in-situ by U.V. absorption spectroscopy for 0.01-1.0 mol% T 2 an 1 atm O 2 . The shape of the experimental ozone time profile agreed with the model predictions. As predicted, the measured initial rate of ozone production varied linearly with initial T 2 concentration ([T 2 ] 0.6 o ), but at an initial rate one-third the predicted value. The steady-state ozone concentration ([O 3 ]ss) was predicted to be dependent on [T 2 ] 0.3 o , but the measured value was [T 2 ] 0.6 o , resulting in four times higher [O 3 ]ss than predicted for a 1.0% T 2 -O 2 mixture. Adding H 2 to the T 2 -O 2 mixture, to provide insight into the differences between the radiolytic and chemical behavior of the tritium, produced a greater decrease in [O 3 ]ss than predicted. Adjusting the reaction cell surface-to-volume ratio showed implications of minor surface removal of ozone

  8. Stable isotope-guided analysis of biomagnification profiles of arsenic species in a tropical mangrove ecosystem

    International Nuclear Information System (INIS)

    Tu, Nguyen Phuc Cam; Agusa, Tetsuro; Ha, Nguyen Ngoc; Tuyen, Bui Cach; Tanabe, Shinsuke; Takeuchi, Ichiro

    2011-01-01

    We performed stable carbon and nitrogen-guided analyses of biomagnification profiles of arsenic (As) species, including total As, lipid-soluble As, eight water-soluble As compounds (arsenobetaine (AB), arsenocholine (AC), tetramethylarsonium ion (TETRA), trimethylarsine oxide (TMAO), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenate (As[V]), and arsenite (As[III])), and non-extracted As in a tropical mangrove ecosystem in the Ba Ria Vung Tau, South Vietnam. Arsenobetaine was the predominant As species (65-96% of water-soluble As). Simple linear regression slopes of log-transformed concentrations of total As, As fractions or individual As compounds on stable nitrogen isotopic ratio (δ 15 N) values are regarded as indices of biomagnification. In this ecosystem, lipid-soluble As (slope, 0.130) and AB (slope, 0.108) were significantly biomagnified through the food web; total As and other water-soluble As compounds were not. To our knowledge, this is one of the first reports on biomagnification profiles of As compounds from a tropical mangrove ecosystem.

  9. Freedom: a transient fission-product release model for radioactive and stable species

    International Nuclear Information System (INIS)

    Macdonald, L.D.; Lewis, B.J.; Iglesias, F.C.

    1989-05-01

    A microstructure-dependent fission-gas release and swelling model (FREEDOM) has been developed for UO 2 fuel. The model describes the transient release behaviour for both the radioactive and stable fission-product species. The model can be applied over the full range of operating conditions, as well as for accident conditions that result in high fuel temperatures. The model accounts for lattice diffusion and grain-boundary sweeping of fusion products to the grain boundaries, where the fission gases accumulate in grain-face bubbles as a result of vacancy diffusion. Release of fission-gas to the free void of the fuel element occurs through the interlinkage of bubbles and cracks on the grain boundaries. This treatment also accounts for radioactive chain decay and neutron-induced transmutation effects. These phenomena are described by mass balance equations which are numerically solved using a moving-boundary, finite-element method with mesh refinement. The effects of grain-face bubbles on fuel swelling and fuel thermal conductivity are included in the ELESIM fuel performance code. FREEDOM has an accuracy of better than 1% when assessed against an analytic solution for diffusional release. The code is being evaluated against a fuel performance database for stable gas release, and against sweep-gas and in-cell fission-product release experiments at Chalk River for active species

  10. Gas phase reactivity of thermal metal clusters

    International Nuclear Information System (INIS)

    Castleman, A.W. Jr.; Harms, A.C.; Leuchtner, R.E.

    1991-01-01

    Reaction kinetics of metal cluster ions under well defined thermal conditions were studied using a flow tube reactor in combination with laser vaporization. Aluminum anions and cations were reacted with oxygen, and several species which are predicted jellium shell closings, were found to have special stability. Metal alloy cluster anions comprised of Al, V and Nb were also seen to react with oxygen. Alloy clusters with an even number of electrons reacted more slowly than odd electron species, and certain clusters appeared to be exceptionally unreactive. Copper cation clusters were observed to associate with carbon monoxide with reactivities that approach bulk behavior at surprisingly small cluster size. These reactions demonstrate how the rate of reaction changes with cluster size. (orig.)

  11. Gas phase reactivity of thermal metal clusters

    Science.gov (United States)

    Castleman, A. W., Jr.; Harms, A. C.; Leuchtner, R. E.

    1991-03-01

    Reaction kinetics of metal cluster ions under well defined thermal conditions were studied using a flow tube reactor in combination with laser vaporization. Aluminum anions and cations were reacted with oxygen, and several species which are predicted jellium shell closings, were found to have special stability. Metal alloy cluster anions comprised of Al, V and Nb were also seen to react with oxygen. Alloy clusters with an even number of electrons reacted more slowly than odd electron species, and certain clusters appeared to be exceptionally unreactive. Copper cation clusters were observed to associate with carbon monoxide with reactivities that approach bulk behavior at surprisingly small cluster size. These reactions demonstrate how the rate of reaction changes with cluster size.

  12. Reliable Refuge: Two Sky Island Scorpion Species Select Larger, Thermally Stable Retreat Sites.

    Science.gov (United States)

    Becker, Jamie E; Brown, Christopher A

    2016-01-01

    Sky island scorpions shelter under rocks and other surface debris, but, as with other scorpions, it is unclear whether these species select retreat sites randomly. Furthermore, little is known about the thermal preferences of scorpions, and no research has been done to identify whether reproductive condition might influence retreat site selection. The objectives were to (1) identify physical or thermal characteristics for retreat sites occupied by two sky island scorpions (Vaejovis cashi Graham 2007 and V. electrum Hughes 2011) and those not occupied; (2) determine whether retreat site selection differs between the two study species; and (3) identify whether thermal selection differs between species and between gravid and non-gravid females of the same species. Within each scorpion's habitat, maximum dimensions of rocks along a transect line were measured and compared to occupied rocks to determine whether retreat site selection occurred randomly. Temperature loggers were placed under a subset of occupied and unoccupied rocks for 48 hours to compare the thermal characteristics of these rocks. Thermal gradient trials were conducted before parturition and after dispersal of young in order to identify whether gravidity influences thermal preference. Vaejovis cashi and V. electrum both selected larger retreat sites that had more stable thermal profiles. Neither species appeared to have thermal preferences influenced by reproductive condition. However, while thermal selection did not differ among non-gravid individuals, gravid V. electrum selected warmer temperatures than its gravid congener. Sky island scorpions appear to select large retreat sites to maintain thermal stability, although biotic factors (e.g., competition) could also be involved in this choice. Future studies should focus on identifying the various biotic or abiotic factors that could influence retreat site selection in scorpions, as well as determining whether reproductive condition affects thermal

  13. Atomic and molecular gas phase spectrometry

    Science.gov (United States)

    Winefordner, J. D.

    1985-10-01

    The major goals of this research have been to develop diagnostical spectroscopic methods for measuring spatial/temporal temperatures and species of combustion flames and plasmas and to develop sensitive, selective, precise, reliable, rapid spectrometric methods of trace analysis of elements present in jet engine lubricating oils, metallurgical samples, and engine exhausts. The diagnostical approaches have been based upon the measurement of metal probes introduced into the flame or plasmas and the measurement of OH in flames. The measurement approaches have involved the use of laser-excited fluorescence, saturated absorption, polarization, and linear absorption. The spatial resolution in most studies is less than 1 cu mm and the temporal resolution is less than 10 ns with the use of pulsed lasers. Single pulse temperature and species measurements have also been carried out. Other diagnostical studies have involved the measurement of collisional redistribution of radiatively excited levels of Na and Tl in acetylene/02/Ar flames and the measurement of lifetimes and quantum efficiencies of atoms and ions in the inductively coupled plasmas, ICP. The latter studies indicate that the high electron number densities in ICPs are not efficient quenchers of excited atoms/ions. Temperatures of microwave atmospheric plasmas produced capacitatively and cool metastable N2 discharge produced by a dielectric discharge have also been measured.

  14. The properties of gas-phase multiply charged ions

    International Nuclear Information System (INIS)

    Newson, K.A.

    1999-01-01

    This thesis presents the results of a series of experiments investigating the reactivity of gas-phase molecular dications with various neutral collision partners, at collision energies between 3 and 13 eV in the laboratory frame, using a crossed-beam apparatus. The experiment involves the measurement of product ion intensities, which are determined by means of time-of-flight mass spectrometry. The experimental apparatus and methodology, together with the areas of theory important to ion chemistry, are described in the thesis. The product ions of greatest interest are those ions formed by bond-forming (chemical) reactivity. The relative intensities of such product ions, and those ions formed as a result of electron-transfer reactions, are, when recorded as a function of the collision energy, a powerful probe of the reaction mechanism. Additionally, where appropriate, the reactions are examined for isotope effects by using the isotopic analogue of the neutral collision partner. The results of the experiments indicate that no intermolecular isotope effects are present in the reactions of CF 2 2+ and CF 3 2+ with H 2 and D 2 neutral targets. In addition, the observed collision energy dependence is symptomatic of the absence of a barrier to reaction. These observations suggest that the reactions proceed via an impulsive direct reaction mechanism. Such a conclusion casts doubt on the applicability of the Landau-Zener model of H - /D - transfer reactivity. Other results presented in this thesis include the first reported observation of a bond-forming reaction between a molecular dication (CF2 2+ ) and a polyatomic neutral species (NH 3 ). Finally, the branching ratio of the products of bond-forming reactions between CF 2 2+ with HD indicates the operation of a strong intramolecular isotope effect, favouring the formation of the deuterated product. This observation points to a reaction mechanism in which the bond-formation is preceded by electron-transfer. (author)

  15. Dissociative attachment reactions of electrons with gas phase superacids

    International Nuclear Information System (INIS)

    Liu, X.

    1992-01-01

    Using the flowing afterglow Langmuir probe (FALP) technique, dissociative attachment coefficients β 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 ( max ) with free electrons in a thermal plasma, and the values of β obtained this far do not show a correlation between acidity and β. 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 3 ) 4 was found to be independent of temperature even though the β[HCo(PF 3 ) 4 ] increases with temperature. This proposes 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 β 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

  16. C and N Stable Isotope Variability in Soft Tissue of Invasive Species Ficopomatus Enigmaticus (Annelida, Polychaeta)

    Energy Technology Data Exchange (ETDEWEB)

    Cukrov, N. [Rudjer Boskovic Institute, Zagreb (Croatia); Cukrov, M. [Croatian Biospeleological Society, Zagreb (Croatia); Lojen, S. [Jozef Stefan Institute, Ljubliana (Slovenia)

    2013-07-15

    Ficopomatus enigmaticus (Fauvel, 1923) is a sedentary polychaete. An invasive species, F. enigmaticus has been found worldwide, inhabiting coastal brackish waters, lagoons and estuaries of both hemispheres. This tubeworm (Serpulidae) builds calcareous tubes on any hard substrate, with distinctive collar-like rings at irregular intervals, and is relatively easy to identify. It is an efficient suspension feeder, very tolerant and physiologically well adapted to temperature and salinity variations, eutrophic conditions and low dissolved oxygen content. It was introduced to the eastern Adriatic coast recently. Here we report the first record of C and N stable isotope variability in the soft tissue of F. enigmaticus from the Krka River Estuary and the Nertva River Delta. (author)

  17. Gas-phase photocatalysis in μ-reactors

    DEFF Research Database (Denmark)

    Vesborg, Peter Christian Kjærgaard; Olsen, Jakob Lind; Henriksen, Toke Riishøj

    2010-01-01

    Gas-phase photocatalysis experiments may benefit from the high sensitivity and good time response in product detection offered by μ-reactors. We demonstrate this by carrying out CO oxidation and methanol oxidation over commercial TiO2 photocatalysts in our recently developed high-sensitivity reac......Gas-phase photocatalysis experiments may benefit from the high sensitivity and good time response in product detection offered by μ-reactors. We demonstrate this by carrying out CO oxidation and methanol oxidation over commercial TiO2 photocatalysts in our recently developed high...

  18. Post-flame gas-phase sulfation of potassium chloride

    DEFF Research Database (Denmark)

    Li, Bo; Sun, Zhiwei; Li, Zhongshan

    2013-01-01

    The sulfation of KCl during biomass combustion has implications for operation and emissions: it reduces the rates of deposition and corrosion, it increases the formation of aerosols, and it leads to higher concentrations of HCl and lower concentrations of SO2 in the gas phase. Rigorously homogene......The sulfation of KCl during biomass combustion has implications for operation and emissions: it reduces the rates of deposition and corrosion, it increases the formation of aerosols, and it leads to higher concentrations of HCl and lower concentrations of SO2 in the gas phase. Rigorously...

  19. Device to remove hydrogen isotopes from a gas phase

    International Nuclear Information System (INIS)

    Morlock, G.; Wiesemes, J.; Bachner, D.

    1977-01-01

    The device described here guarantees the selective removal of hydrogen isotopes from gas phases in order to prevent the occurence of explosive H 2 gas mixtures, or to separate off radioactive tritium in nuclear plants from the gas phase. It consists of a closed container whose walls are selectively penetrable by hydrogen isotopes. It is simultaneously filled compactly and presssure-resistant with a metal bulk (e.g. powder, sponges or the like of titanium or other hydrogen isotope binding metal). Walling and bulk are maintained at suitable working temperatures by means of a system according to the Peltier effect. The whole thing is safeguarded by protective walling. (RB) [de

  20. Probing the Gas-Phase Dynamics of Graphene Chemical Vapour Deposition using in-situ UV Absorption Spectroscopy

    DEFF Research Database (Denmark)

    Shivayogimath, Abhay; Mackenzie, David; Luo, Birong

    2017-01-01

    The processes governing multilayer nucleation in the chemical vapour deposition (CVD) of graphene are important for obtaining high-quality monolayer sheets, but remain poorly understood. Here we show that higher-order carbon species in the gas-phase play a major role in multilayer nucleation...

  1. An Overview of Mode of Action and Analytical Methods for Evaluation of Gas Phase Activities of Flame Retardants

    Directory of Open Access Journals (Sweden)

    Khalifah A. Salmeia

    2015-03-01

    Full Text Available The latest techniques used to prove, describe and analyze the gas phase activity of a fire retardant used in polymeric materials are briefly reviewed. Classical techniques, such as thermogravimetric analysis or microscale combustion calorimetry, as well as complex and advanced analytical techniques, such as modified microscale combustion calorimeter (MCC, molecular beam mass spectroscopy and vacuum ultra violet (VUV photoionization spectroscopy coupled with time of flight MS (TOF-MS, are described in this review. The recent advances in analytical techniques help not only in determining the gas phase activity of the flame-retardants but also identify possible reactive species responsible for gas phase flame inhibition. The complete understanding of the decomposition pathways and the flame retardant activity of a flame retardant system is essential for the development of new eco-friendly-tailored flame retardant molecules with high flame retardant efficiency.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-02-01

    In this chapter we review the spectroscopic data for actinide molecules and the reaction dynamics for atomic and molecular actinides that have been examined in the gas phase or in inert cryogenic matrices. The motivation for this type of investigation is that physical properties and reactions can be studied in the absence of external perturbations (gas phase) or under minimally perturbing conditions (cryogenic matrices). This information can be compared directly with the results from high-level theoretical models. The interplay between experiment and theory is critically important for advancing our understanding of actinide chemistry. For example, elucidation of the role of the 5f electrons in bonding and reactivity can only be achieved through the application of experimentally verified theoretical models. Theoretical calculations for the actinides are challenging due the large numbers of electrons that must be treated explicitly and the presence of strong relativistic effects. This topic has been reviewed in depth in Chapter 17 of this series. One of the goals of the experimental work described in this chapter has been to provide benchmark data that can be used to evaluate both empirical and ab initio theoretical models. While gas-phase data are the most suitable for comparison with theoretical calculations, there are technical difficulties entailed in generating workable densities of gas-phase actinide molecules that have limited the range of species that have been characterized. Many of the compounds of interest are refractory, and problems associated with the use of high temperature vapors have complicated measurements of spectra, ionization energies, and reactions. One approach that has proved to be especially valuable in overcoming this difficulty has been the use of pulsed laser ablation to generate plumes of vapor from refractory actinide-containing materials. The vapor is entrained in an inert gas, which can be used to cool the actinide species to room

  3. Electron-beam synthesis of fuel in the gas phase

    International Nuclear Information System (INIS)

    Ponomarev, A.V.; Holodkova, E.M.; Ershov, B.G.

    2011-01-01

    Complete text of publication follows. Tendencies of world development focus attention on a vegetative biomass as on the major raw resource for future chemistry and a fuel industry. The significant potential for perfection of biomass conversion processes is concentrated in the field of radiation-chemical methods. Both the mode of post-radiation distillation and mode of electron-beam distillation of biomass have been investigated as well as the mode of gas-phase synthesis of liquid engine fuel from of biomass distillation products. Synergistic action of radiation and temperature has been analyzed at use of the accelerated electron beams allowing to combine radiolysis with effective radiation heating of a material without use of additional heaters. At dose rate above 1 kGy/s the electron-beam irradiation results in intensive decomposition of a biomass and evaporation of formed fragments with obtaining of a liquid condensate (∼ 60 wt%), CO 2 and Co gases (13-18 wt%) and charcoal in the residue. Biomass distillation at radiation heating allows to increase almost three times an organic liquid yield in comparison with pyrolysis. The majority of liquid products from cellulose is represented by the furan derivatives considered among the very perspective components for alternative engine fuels. Distilled-off gases and vapors are diluted with gaseous C 1 -C 5 alkanes and again are exposed to an irradiation to produce liquid fuel from a biomass. This transformation is based on a method of electron-beam circulation conversion of gaseous C 1 -C 5 alkanes (Ponomarev, A.V., Radiat. Phys. Chem., 78, 48, 2009) which consists in formation and removal of liquid products with high degree of carbon skeleton branching. The isomers ratio in a liquid may be controlled by means of change of an irradiation condition and initial gas composition. The irradiation of gaseous alkanes together with vaporous products of biomass destruction allows to synthesize the fuel enriched by conventional

  4. Gas-Phase IR Spectroscopy of Deprotonated Amino Acids

    NARCIS (Netherlands)

    Oomens, J.; Steill, J. D.; Redlich, B.

    2009-01-01

    Gas-phase infrared multiple photon dissociation (IRMPD) spectra have been recorded for the conjugate bases of a series of amino acids (Asp, Cys, Glu, Phe, Set, Trp, Tyr). The spectra are dominated by strong symmetric and antisymmetric carboxylate stretching modes around 1300 and 1600 cm(-1),

  5. Gas phase toluene isopropylation over high silica mordenite

    Indian Academy of Sciences (India)

    Mordenite (HM) catalysts with three different Si/Al ratios were compared for their activity and selectivities in gas phase toluene isopropylation with isopropanol. Catalyst with Si/Al ratio 44.9 offered better cumene selectivity, hence, it was chosen for detailed kinetic investigations. The influence of various process parameters ...

  6. Synthetical Analysis for Morphology, biological Species, and stable Isotopes (SAMSI) of single-cell planktonic foraminifer

    Science.gov (United States)

    Ujiie, Y.; Kimoto, K.; Ishimura, T.

    2017-12-01

    Planktonic foraminifers are widely used in the studies of paleontology and paleoceanography, because the morphology of their calcareous shells is enough highly variable to identify the morphospecies and the chemical composition of the shells reflect ambient seawater condition. Although the morphospecies were believed to represent environments associating with latitudinal temperature range of the world ocean, molecular phylogeographic studies have unveiled the presence of multiple biological species in a single morphospecies and their species-specific distributions. This implicates the actual complexity of planktonic foraminiferal ecology. Conversely, these biological species have a high potential for providing novel ecological and environmental information to us. In order to reassess the morphological and geochemical characters of biological species, the DNA extraction method with the guanidium isothiocyanate buffer was developed to preserve the calcareous shells. The present study carefully tested the physical and chemical damages of the DNA extraction process to the shells, by our novel approaches with geochemical analysis of the shells after non-destructive analysis for morphometrics on a same specimen. First, we checked the changes of the shell densities between pre- and post-DNA extraction by using the micro-focus X-ray CT (MXCT) scanning. Based on the simultaneous measurement of a sample and the standard material, we confirmed no significant changes to the shell densities through the DNA extraction process. As a next step, we compared stable oxygen and carbon isotopes among individuals of three sample sets: (1) no chemical and incubation as control, (2) incubation in the DNA extraction buffer at 65-70°C for 40 minutes as standard way, and (3) incubation in the DNA extraction buffer at 65-70°C for 120 minutes, by using the microscale isotopic analytical system (MICAL3c). Consequently, there were no significant differences among the three sample sets. These

  7. A comparison of stable caesium uptake by six grass species of contrasting growth strategy

    International Nuclear Information System (INIS)

    Willey, N.J.; Martin, M.H.

    1997-01-01

    Six plants in the family Gramineae were used to investigate the relationship between Cs uptake, nutrient regime and plant growth strategy sensu Grime (1979: Plant Growth Strategies and Vegetation Processes, John Wiley). The roots of 66 day old Elymus repens (L.) Gould., Bromus sterilis L., Agrostis stolonifera L., Anthoxanthum odoratum L., Festuca ovina L. and Nardus stricta L. plants grown in acid-washed sand at high and low nutrient levels were exposed to a 96 h pulse of stable Cs at 0.05 mM, 0.15 mM, 0.3 mM, 1.0 mM and 3.0 mM concentrations. Different nutrient regimes induced large differences in dry wt in E. repens, B. sterilis and A. stolonifera plants but only small differences in N. stricta and F. ovina plants. At high nutrient concentrations, A. stolonifera, A. odoratum, F. ovina and N. stricta shoots showed significantly greater increases in internal Cs concentration with rising external Cs concentrations than did E. repens and B. sterilis shoots. The relationship between increases in shoot and external Cs concentrations was statistically indistinguishable between species in plants grown at the low nutrient concentration. These patterns of Cs uptake ensured that with long-term high K concentrations the more competitive plants (E. repens and B. sterilis) accumulated higher concentrations of Cs from low external concentrations than did non-competitive plants or competitive plants grown at low nutrient levels. It is suggested that the relationship between plant growth strategy sensu Grime (1979) and Cs accumulation patterns may help to explain the different concentrations to which species accumulate radiocaesium from the soil. (author)

  8. Formation of gas-phase π-allyl radicals from propylene over bismuth oxide and γ-bismuth molybdate catalysts

    International Nuclear Information System (INIS)

    Martir, W.; Lunsford, J.H.

    1981-01-01

    Gas-phase π-allyl radicals were produced when propylene reacted over Bi 2 O 3 and γ-bismuth molybdate catalysts at 723 K. The pressure in the catalyst zone was varied between 5 x 10 -3 and 1 torr. The radicals were detected by EPR spectroscopy together with a matrix isolation technique in which argon was used as the diluent. The matrix was formed on a sapphire rod at 12 K which was located 33-cm downstream from the catalyst. Bismuth oxide was more effective in the production of gas-phase allyl radicals than γ-bismuth molybdate. By contrast α-bismuth molybdate was ineffective in forming allyl radicals and MoO 3 acted as a sink for radicals which were produced elsewhere in the system. Comparison of the π-allyl radical and the stable product concentrations over Bi 2 O 3 revealed that gas-phase radical recombination reactions served as a major pathway for the formation of 1,5-hexadiene. Addition of small amounts of gas-phase oxygen increased the concentration of allyl radicals, and at greater oxygen levels allyl peroxy radicals were detected. Because of the effect of temperature on the equilibrium between allyl and allyl peroxy radicals, the latter product must be formed in the cooler part of the system

  9. Non-labile silver species in biosolids remain stable throughout 50 years of weathering and ageing

    International Nuclear Information System (INIS)

    Donner, E.; Scheckel, K.; Sekine, R.; Popelka-Filcoff, R.S.; Bennett, J.W.; Brunetti, G.; Naidu, R.; McGrath, S.P.; Lombi, E.

    2015-01-01

    Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that biosolids Ag concentrations have decreased significantly over recent decades. XANES revealed the importance of reduced-sulfur binding environments for Ag speciation in materials ranging from freshly produced sludge to biosolids weathered under ambient environmental conditions for more than 50 years. Isotopic dilution with 110m Ag showed that Ag was predominantly non-labile in both fresh and aged biosolids (13.7% mean lability), with E-values ranging from 0.3 to 60 mg/kg and 5 mM CaNO 3 extractable Ag from 1.2 to 609 μg/kg (0.002–3.4% of the total Ag). This study indicates that at the time of soil application, biosolids Ag will be predominantly Ag-sulfides and characterised by low isotopic lability. - Highlights: • Biosolids silver (Ag) concentrations appear to have decreased in recent decades. • Ag 2 S dominates Ag speciation in freshly produced sludge. • Ag 2 S is also the dominant species in aged biosolids. • Upon land application biosolids will mainly contain Ag-sulfides and have low isotopic lability. - Analysis of historic and contemporary biosolids from three continents indicated decreasing wastewater silver releases, and non-labile, extremely stable silver speciation

  10. Gas-Phase Molecular Dynamics: Theoretical Studies In Spectroscopy and Chemical Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Yu H. G.; Muckerman, J.T.

    2012-05-29

    The main goal of this program is the development and application of computational methods for studying chemical reaction dynamics and molecular spectroscopy in the gas phase. We are interested in developing rigorous quantum dynamics algorithms for small polyatomic systems and in implementing approximate approaches for complex ones. Particular focus is on the dynamics and kinetics of chemical reactions and on the rovibrational spectra of species involved in combustion processes. This research also explores the potential energy surfaces of these systems of interest using state-of-the-art quantum chemistry methods, and extends them to understand some important properties of materials in condensed phases and interstellar medium as well as in combustion environments.

  11. Gas-Phase Molecular Dynamics: Theoretical Studies in Spectroscopy and Chemical Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Yu, H.G.; Muckerman, J.T.

    2010-06-01

    The goal of this program is the development and application of computational methods for studying chemical reaction dynamics and molecular spectroscopy in the gas phase. We are interested in developing rigorous quantum dynamics algorithms for small polyatomic systems and in implementing approximate approaches for complex ones. Particular focus is on the dynamics and kinetics of chemical reactions and on the rovibrational spectra of species involved in combustion processes. This research also explores the potential energy surfaces of these systems of interest using state-of-the-art quantum chemistry methods.

  12. Headspace analysis gas-phase infrared spectroscopy: a study of xanthate decomposition on mineral surfaces

    Science.gov (United States)

    Vreugdenhil, Andrew J.; Brienne, Stephane H. R.; Markwell, Ross D.; Butler, Ian S.; Finch, James A.

    1997-03-01

    The O-ethyldithiocarbonate (ethyl xanthate, CH 3CH 2OCS -2) anion is a widely used reagent in mineral processing for the separation of sulphide minerals by froth flotation. Ethyl xanthate interacts with mineral powders to produce a hydrophobic layer on the mineral surface. A novel infrared technique, headspace analysis gas-phase infrared spectroscopy (HAGIS) has been used to study the in situ thermal decomposition products of ethyl xanthate on mineral surfaces. These products include CS 2, COS, CO 2, CH 4, SO 2, and higher molecular weight alkyl-containing species. Decomposition pathways have been proposed with some information determined from 2H- and 13C-isotope labelling experiments.

  13. Conformational reduction of DOPA in the gas phase studied by laser desorption supersonic jet laser spectroscopy.

    Science.gov (United States)

    Ishiuchi, Shun-ichi; Mitsuda, Haruhiko; Asakawa, Toshiro; Miyazaki, Mitsuhiko; Fujii, Masaaki

    2011-05-07

    The conformational reduction in catecholamine neurotransmitters was studied by resonance enhanced multi photon ionization (REMPI), ultraviolet-ultraviolet (UV-UV) hole burning and infrared (IR) dip spectroscopy with applying a laser desorption supersonic jet technique to DOPA, which is one of the catecholamine neurotransmitters and has one more phenolic OH group than tyrosine. It is concluded that DOPA has a single observable conformer in the gas phase at low temperature. Quantum chemical calculations at several levels with or without the dispersion correction were also carried out to study stable conformations. From the comparison between the computational IR spectra and the experimental ones, the most stable structure was determined. It is strongly suggested that the conformational reduction is caused by electrostatic interactions, such as a dipole-dipole interaction, between the chain and OH groups. This journal is © the Owner Societies 2011

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

    Science.gov (United States)

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

    2011-09-07

    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.

  15. Long-lived gas-phase radicals from combustion

    Energy Technology Data Exchange (ETDEWEB)

    Kaneko, Takashi; Furusawa, Koji; Amano, Toshiji; Okubo, Yoichi; Tsuchiya, Jun' ichi; Yoshizawa, Fujiroku; Akutsu, Yoshiaki; Tamura, Masamitsu; Yoshida, Tadao (Univ. of Tokyo (Japan))

    1989-04-20

    On indoor air pollution or fire, it is feared that the gas-phase radicals from the combustion of inflammables or fuel seriously exert an influence on the organisms as harmful matter. The gas-phase radicals were studied using the electron spin resonance (ESR) spin-trapping technique. For the spin trap solution, 0.1 mol solution of {alpha}-phenyl-N-t-butylnitron in benzene was used. As a result, apparently long-lived and highly reactive oxygen-centered radicals were detected in the smoke from polyethylene, polypropylene, polystyrene, polymethylmethacrylate, cellulose, kerosene, benzene, acetone, methanol and butylalcohol. It is suggested that the production mechanism for the radicals should be different from olefin-NOx-air system reaction, which is considered for the radicals from cigarette smoke. 11 refs., 6 figs., 2 tabs.

  16. Reactions of newly formed fission products in the gas phase

    International Nuclear Information System (INIS)

    Strickert, R.G.

    1976-01-01

    A dynamic gas-flow system was constructed which stopped fission products in the gas phase and rapidly separated (in less than 2 sec) volatile compounds from non-volatile ones. The filter assembly designed and used was shown to stop essentially all non-volatile fission products. Between 5 percent and 20 percent of tellurium fission-product isotopes reacted with several hydrocarbon gases to form volatile compounds, which passed through the filter. With carbon monoxide gas, volatile tellurium compound(s) (probably TeCO) were also formed with similar efficiencies. The upper limits for the yields of volatile compounds formed between CO and tin and antimony fission products were shown to be less than 0.3 percent, so tellurium nuclides, not their precursors, reacted with CO. It was found that CO reacted preferentially with independently produced tellurium atoms; the reaction efficiency of beta-produced atoms was only 27 +- 3 percent of that of the independently formed atoms. The selectivity, which was independent of the over-all reaction efficiency, was shown to be due to reaction of independently formed atoms in the gas phase. The gas phase reactions are believed to occur mainly at thermal energies because of the independence of the yield upon argon moderator mole-fraction (up to 80 percent). It was shown in some experiments that about one-half of the TeCO decomposed in passing through a filter and that an appreciable fraction (approximately 20 percent) of the tellurium atoms deposited on the filter reacted agin with CO. Other tellurium atoms on the filter surface (those formed by beta decay and those formed independently but not reacting in the gas phase) also reacted with CO, but probably somewhat less efficiently than atoms formed by TeCO decomposition. No evidence was found for formation of TeCO as a direct result of beta-decay

  17. Gas phase fractionation method using porous ceramic membrane

    Science.gov (United States)

    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.

  18. Gas Phase Hydrogenation of Levulinic Acid to gamma-Valerolactone

    NARCIS (Netherlands)

    Bonrath, Werner; Castelijns, Anna Maria Cornelia Francisca; de Vries, Johannes Gerardus; Guit, Rudolf Philippus Maria; Schuetz, Jan; Sereinig, Natascha; Vaessen, Henricus Wilhelmus Leonardus Marie

    The gas phase hydrogenation of levulinic acid to gamma-valerolactone over copper and ruthenium based catalysts in a continuous fixed-bed reactor system was investigated. Among the catalysts a copper oxide based one [50-75 % CuO, 20-25 % SiO2, 1-5 % graphite, 0.1-1 % CuCO3/Cu(OH)(2)] gave

  19. Understanding Gas-Phase Ammonia Chemistry in Protoplanetary Disks

    Science.gov (United States)

    Chambers, Lauren; Oberg, Karin I.; Cleeves, Lauren Ilsedore

    2017-01-01

    Protoplanetary disks are dynamic regions of gas and dust around young stars, the remnants of star formation, that evolve and coagulate over millions of years in order to ultimately form planets. The chemical composition of protoplanetary disks is affected by both the chemical and physical conditions in which they develop, including the initial molecular abundances in the birth cloud, the spectrum and intensity of radiation from the host star and nearby systems, and mixing and turbulence within the disk. A more complete understanding of the chemical evolution of disks enables a more complete understanding of the chemical composition of planets that may form within them, and of their capability to support life. One element known to be essential for life on Earth is nitrogen, which often is present in the form of ammonia (NH3). Recent observations by Salinas et al. (2016) reveal a theoretical discrepancy in the gas-phase and ice-phase ammonia abundances in protoplanetary disks; while observations of comets and protostars estimate the ice-phase NH3/H2O ratio in disks to be 5%, Salinas reports a gas-phase NH3/H2O ratio of ~7-84% in the disk surrounding TW Hydra, a young nearby star. Through computational chemical modeling of the TW Hydra disk using a reaction network of over 5000 chemical reactions, I am investigating the possible sources of excess gas-phase NH3 by determining the primary reaction pathways of NH3 production; the downstream chemical effects of ionization by ultraviolet photons, X-rays, and cosmic rays; and the effects of altering the initial abundances of key molecules such as N and N2. Beyond providing a theoretical explanation for the NH3 ice/gas discrepancy, this new model may lead to fuller understanding of the gas-phase formation processes of all nitrogen hydrides (NHx), and thus fuller understanding of the nitrogen-bearing molecules that are fundamental for life as we know it.

  20. Gas phase decontamination of gaseous diffusion process equipment

    International Nuclear Information System (INIS)

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

    1994-01-01

    D ampersand D of the process facilities at the gaseous diffusion plants (GDPs) will be an enormous task. The EBASCO estimate places the cost of D ampersand 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

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

    Science.gov (United States)

    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...

  2. Exceptionally High Proton and Lithium Cation Gas-Phase Basicity of the Anti-Diabetic Drug Metformin.

    Science.gov (United States)

    Raczyńska, Ewa D; Gal, Jean-François; Maria, Pierre-Charles; Michalec, Piotr; Zalewski, Marcin

    2017-11-16

    Substituted biguanides are known for their biological effect, and a few of them are used as drugs, the most prominent example being metformin (1,1-dimethylbiguanide, IUPAC name: N,N-dimethylimidodicarbonimidic diamide). Because of the presence of hydrogen atoms at the amino groups, biguanides exhibit a multiple tautomerism. This aspect of their structures was examined in detail for unsubstituted biguanide and metformin in the gas phase. At the density functional theory (DFT) level {essentially B3LYP/6-311+G(d,p)}, the most stable structures correspond to the conjugated, push-pull, system (NR 2 )(NH 2 )C═N-C(═NH)NH 2 (R = H, CH 3 ), further stabilized by an internal hydrogen bond. The structural and energetic aspects of protonation and lithium cation adduct formation of biguanide and metformin was examined at the same level of theory. The gas-phase protonation energetics reveal that the more stable tautomer is protonated at the terminal imino C═NH site, still with an internal hydrogen bond maintaining the structure of the neutral system. The calculated proton affinity and gas-phase basicity of the two molecules reach the domain of superbasicity. By contrast, the lithium cation prefers to bind the less stable, not fully conjugated, tautomer (NR 2 )C(═NH)-NH-C(═NH)NH 2 of biguanides, in which the two C═NH groups are separated by NH. This less stable form of biguanides binds Li + as a bidentate ligand, in agreement with what was reported in the literature for other metal cations in the solid phase. The quantitative assessment of resonance in biguanide, in metformin and in their protonated forms, using the HOMED and HOMA indices, reveals an increase in electron delocalization upon protonation. On the contrary, the most stable lithium cation adducts are less conjugated than the stable neutral biguanides, because the metal cation is better coordinated by the not-fully conjugated bidentate tautomer.

  3. Gas phase precursors to anthropogenic secondary organic aerosol: detailed observations of 1,3,5-trimethylbenzene photooxidation

    Directory of Open Access Journals (Sweden)

    K. P. Wyche

    2009-01-01

    Full Text Available A series of photooxidation experiments were conducted in an atmospheric simulation chamber in order to investigate the oxidation mechanism and secondary organic aerosol (SOA formation potential of the model anthropogenic gas phase precursor, 1,3,5-trimethylbenzene. Alongside specific aerosol measurements, comprehensive gas phase measurements, primarily by Chemical Ionisation Reaction Time-of-Flight Mass Spectrometry (CIR-TOF-MS, were carried out to provide detailed insight into the composition and behaviour of the organic components of the gas phase matrix during SOA formation. An array of gas phase organic compounds was measured during the oxidation process, including several previously unmeasured primary bicyclic compounds possessing various functional groups. Analysis of results obtained during this study implies that these peroxide bicyclic species along with a series of ring opening products and organic acids contribute to SOA growth. The effect of varying the VOC/NOx ratio on SOA formation was explored, as was the effect of acid seeding. It was found that low NOx conditions favour more rapid aerosol formation and a higher aerosol yield, a result that implies a role for organic peroxides in the nucleation process and SOA growth.

  4. Fundamental thermochemical properties of amino acids: gas-phase and aqueous acidities and gas-phase heats of formation.

    Science.gov (United States)

    Stover, Michele L; Jackson, Virgil E; Matus, Myrna H; Adams, Margaret A; Cassady, Carolyn J; Dixon, David A

    2012-03-08

    The gas-phase acidities of the 20 L-amino acids have been predicted at the composite G3(MP2) level. A broad range of structures of the neutral and anion were studied to determine the lowest energy conformer. Excellent agreement is found with the available experimental gas-phase deprotonation enthalpies, and the calculated values are within experimental error. We predict that tyrosine is deprotonated at the CO(2)H site. Cysteine is predicted to be deprotonated at the SH but the proton on the CO(2)H is shared with the S(-) site. Self-consistent reaction field (SCRF) calculations with the COSMO parametrization were used to predict the pK(a)'s of the non-zwitterion form in aqueous solution. The differences in the non-zwitterion pK(a) values were used to estimate the free energy difference between the zwitterion and nonzwitterion forms in solution. The heats of formation of the neutral compounds were calculated from atomization energies and isodesmic reactions to provide the first reliable set of these values in the gas phase. Further calculations were performed on five rare amino acids to predict their heats of formation, acidities, and pK(a) values.

  5. Aromatic substitution in the gas phase. Alkylation of arenes by gaseous C4H9+ cations

    International Nuclear Information System (INIS)

    Cacace, F.; Ciranni, G.; Giacomello, P.

    1981-01-01

    Butyl cations, obtained in the dilute gas state from the radiolysis of butane in the pressure range from 70 to 750 torr, have been allowed to react with benzene, toluene, and their mixtures or with trace amounts of o-xylene in the gaseous system. The gas-phase butylation yields invariably sec-butylarenes, remarkably free of isomeric byproducts, namely n- and tert-butylarenes. Other alkylation experiments, where gaseous butyl cations from the reaction of butane with radiolytically formed H 3 + ions were used as reagent, confirmed the exclusive formation of sec-butylarenes. The butylation process displays the positional and substrate selectivity and the dependence of orientation on the pressure of the system, typical of other gas-phase ionic substitutions. At high pressures, orth-para orientation predominates in the sec-butylation of toluene, with a ortho:meta:para ratio of 43:30:27 at 715 torr. As the pressure is reduced, a gradual shift in favor of the thermodynamically most stable meta-substituted arenium ion is observed, leading to a ortho:meta:para ratio of 31:48:21 at 70 torr

  6. Mapping the conformational free energy of aspartic acid in the gas phase and in aqueous solution.

    Science.gov (United States)

    Comitani, Federico; Rossi, Kevin; Ceriotti, Michele; Sanz, M Eugenia; Molteni, Carla

    2017-04-14

    The conformational free energy landscape of aspartic acid, a proteogenic amino acid involved in a wide variety of biological functions, was investigated as an example of the complexity that multiple rotatable bonds produce even in relatively simple molecules. To efficiently explore such a landscape, this molecule was studied in the neutral and zwitterionic forms, in the gas phase and in water solution, by means of molecular dynamics and the enhanced sampling method metadynamics with classical force-fields. Multi-dimensional free energy landscapes were reduced to bi-dimensional maps through the non-linear dimensionality reduction algorithm sketch-map to identify the energetically stable conformers and their interconnection paths. Quantum chemical calculations were then performed on the minimum free energy structures. Our procedure returned the low energy conformations observed experimentally in the gas phase with rotational spectroscopy [M. E. Sanz et al., Phys. Chem. Chem. Phys. 12, 3573 (2010)]. Moreover, it provided information on higher energy conformers not accessible to experiments and on the conformers in water. The comparison between different force-fields and quantum chemical data highlighted the importance of the underlying potential energy surface to accurately capture energy rankings. The combination of force-field based metadynamics, sketch-map analysis, and quantum chemical calculations was able to produce an exhaustive conformational exploration in a range of significant free energies that complements the experimental data. Similar protocols can be applied to larger peptides with complex conformational landscapes and would greatly benefit from the next generation of accurate force-fields.

  7. Probing Vitamine C, Aspirin and Paracetamol in the Gas Phase: High Resolution Rotational Studies

    Science.gov (United States)

    Mata, S.; Cabezas, C.; Varela, M.; Pena, I.; Nino, A.; López, J. C.; Alonso, J. L.; Grabow, J.-U.

    2011-06-01

    A solid sample of Vitamin C (m.p. 190°C) vaporized by laser ablation has been investigated in gas phase and characterized through their rotational spectra. Two spectroscopy techniques has been used to obtain the spectra: a new design of broadband chirped pulse Fourier transform microwave spectroscopy with in-phase/quadrature-phase-modulation passage-acquired-coherence technique (IMPACT) and conventional laser ablation molecular beam Fourier transform microwave spectroscopy (LA-MB-FTMW). Up to now, two low-energy conformer have been observed and their rotational constants determined. Ab initio calculations at the MP2/6-311++G (d,p) level of theory predicted rotational constants which helped us to identify these conformers unequivocally. Among the molecules to benefit from the LA-MB-FTMW technique there are common important drugs never observed in the gas phase through rotational spectroscopy. We present here the results on acetyl salicylic acid and acetaminophen (m.p. 136°C), commonly known as aspirin and paracetamol respectively. We have observed two stable conformers of aspirin and two for paracetamol. The internal rotation barrier of the methyl group in aspirin has been determined for both conformers from the analysis of the A-E splittings due to the coupling of internal and overall rotation. J. L. Alonso, C. Pérez, M. E. Sanz, J. C. López, S. Blanco, Phys. Chem. Chem. Phys. 11,617-627 (2009)and references therein

  8. Mapping the conformational free energy of aspartic acid in the gas phase and in aqueous solution

    Science.gov (United States)

    Comitani, Federico; Rossi, Kevin; Ceriotti, Michele; Sanz, M. Eugenia; Molteni, Carla

    2017-04-01

    The conformational free energy landscape of aspartic acid, a proteogenic amino acid involved in a wide variety of biological functions, was investigated as an example of the complexity that multiple rotatable bonds produce even in relatively simple molecules. To efficiently explore such a landscape, this molecule was studied in the neutral and zwitterionic forms, in the gas phase and in water solution, by means of molecular dynamics and the enhanced sampling method metadynamics with classical force-fields. Multi-dimensional free energy landscapes were reduced to bi-dimensional maps through the non-linear dimensionality reduction algorithm sketch-map to identify the energetically stable conformers and their interconnection paths. Quantum chemical calculations were then performed on the minimum free energy structures. Our procedure returned the low energy conformations observed experimentally in the gas phase with rotational spectroscopy [M. E. Sanz et al., Phys. Chem. Chem. Phys. 12, 3573 (2010)]. Moreover, it provided information on higher energy conformers not accessible to experiments and on the conformers in water. The comparison between different force-fields and quantum chemical data highlighted the importance of the underlying potential energy surface to accurately capture energy rankings. The combination of force-field based metadynamics, sketch-map analysis, and quantum chemical calculations was able to produce an exhaustive conformational exploration in a range of significant free energies that complements the experimental data. Similar protocols can be applied to larger peptides with complex conformational landscapes and would greatly benefit from the next generation of accurate force-fields.

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

    Energy Technology Data Exchange (ETDEWEB)

    Qazi, H. I. A.; Li, He-Ping, E-mail: liheping@tsinghua.edu.cn; Zhang, Xiao-Fei; Bao, Cheng-Yu [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Nie, Qiu-Yue [School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin, Heilongjiang Province 150001 (China)

    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.

  10. Continuous-wave terahertz by photomixing: applications to gas phase pollutant detection and quantification

    Science.gov (United States)

    Hindle, Francis; Cuisset, Arnaud; Bocquet, Robin; Mouret, Gaël

    2008-03-01

    Recent advances in the development of monochromatic continuous-wave terahertz sources suitable for high resolution gas phase spectroscopy and pollution monitoring are reviewed. Details of a source using an ultra fast opto-electronic photomixing element are presented. The construction of a terahertz spectrometer using this source has allowed spectroscopic characterisation and application studies to be completed. Analysis of H 2S and OCS under laboratory conditions are used to demonstrate the spectrometer performance, and the determination of the transition line strengths and pressure self broadening coefficients for pure rotational transitions of OCS. The spectral purity 5 MHz, tunability 0.3 to 3 THz, and long wavelength ≈200 μm of this source have been exploited to identify and quantify numerous chemical species in cigarette smoke. The key advantages of this frequency domain are its high species selectivity and the possibility to make reliable measurements of gas phase samples heavily contaminated by aerosols and particles. To cite this article: F. Hindle et al., C. R. Physique 9 (2008).

  11. Noncovalent Halogen Bonding as a Mechanism for Gas-Phase Clustering

    DEFF Research Database (Denmark)

    Wegeberg, Christina; Donald, William A.; McKenzie, Christine

    2017-01-01

    in the crystalline phases of PhIO2 and its derivatives serve as models for the structures of larger gas-phase clusters, and calculations on simple model gas-phase dimer and trimer clusters result in similar motifs. This is the first account of halogen bonding playing an extensive role in gas-phase associations....

  12. Intrinsic folding of small peptide chains: spectroscopic evidence for the formation of beta-turns in the gas phase.

    Science.gov (United States)

    Chin, Wutharath; Dognon, Jean-Pierre; Piuzzi, François; Tardivel, Benjamin; Dimicoli, Iliana; Mons, Michel

    2005-01-19

    Laser desorption of model peptides coupled to laser spectroscopic techniques enables the gas-phase observation of genuine secondary structures of biology. Spectroscopic evidence for the formation of beta-turns in gas-phase peptide chains containing glycine and phenylalanine residues establishes the intrinsic stability of these forms and their ability to compete with other stable structures. The precise characterization of local minima on the potential energy surface from IR spectroscopy constitutes an acute assessment for the state-of-the-art quantum mechanical calculations also presented. The observation of different types of beta-turns depending upon the residue order within the sequence is found to be consistent with the residue propensities in beta-turns of proteins, which suggests that the prevalence of glycine in type II and II' turns stems essentially from an energetic origin, already at play under isolated conditions.

  13. Heterogeneous reactivity of sea spray particles during the CalNex field campaign: Insight from single particle measurements and correlations with gas phase measurements

    Science.gov (United States)

    Gaston, C. J.; Riedel, T. P.; Thornton, J. A.; Wagner, N.; Brown, S. S.; Quinn, P.; Bates, T. S.; Prather, K. A.

    2011-12-01

    Sea spray particles are ubiquitous in marine environments. Heterogeneous reactions between sea spray particles and gas phase pollutants, such as HNO3(g), and N2O5(g), alter particle composition by displacing particulate phase halogens in sea spray and releasing these halogen species into the gas phase; these halogen-containing gas phase species play a significant role in tropospheric ozone production. Measurements of both gas phase and particle phase species on board the R/V Atlantis during the CalNEX 2010 field campaign provided an opportunity to examine the impact of heterogeneous reactivity of marine aerosols along the California coast. During the cruise, coastal measurements were made near the Santa Monica and Port of Los Angeles regions to monitor the chemical processing of marine aerosols. Sea spray particles were analyzed since these particles were the major chloride-containing particles detected. Real-time single particle measurements made using an aerosol time-of-flight mass spectrometer (ATOFMS) revealed the nocturnal processing of sea spray particles through the loss of particulate chloride and a simultaneous gain in particulate nitrate. Gas phase measurements are consistent with the particle phase observations: As N2O5(g) levels rose overnight, the production of ClNO2(g) coincided with the decrease in particulate chloride. These observations provide unique insight into heterogeneous reactivity from both a gas and particle phase perspective. Results from these measurements can be used to better constrain the rate of heterogeneous reactions on sea spray particles.

  14. Methanol ice co-desorption as a mechanism to explain cold methanol in the gas-phase

    Science.gov (United States)

    Ligterink, N. F. W.; Walsh, C.; Bhuin, R. G.; Vissapragada, S.; van Scheltinga, J. Terwisscha; Linnartz, H.

    2018-05-01

    Context. Methanol is formed via surface reactions on icy dust grains. Methanol is also detected in the gas-phase at temperatures below its thermal desorption temperature and at levels higher than can be explained by pure gas-phase chemistry. The process that controls the transition from solid state to gas-phase methanol in cold environments is not understood. Aims: The goal of this work is to investigate whether thermal CO desorption provides an indirect pathway for methanol to co-desorb at low temperatures. Methods: Mixed CH3OH:CO/CH4 ices were heated under ultra-high vacuum conditions and ice contents are traced using RAIRS (reflection absorption IR spectroscopy), while desorbing species were detected mass spectrometrically. An updated gas-grain chemical network was used to test the impact of the results of these experiments. The physical model used is applicable for TW Hya, a protoplanetary disk in which cold gas-phase methanol has recently been detected. Results: Methanol release together with thermal CO desorption is found to be an ineffective process in the experiments, resulting in an upper limit of ≤ 7.3 × 10-7 CH3OH molecules per CO molecule over all ice mixtures considered. Chemical modelling based on the upper limits shows that co-desorption rates as low as 10-6 CH3OH molecules per CO molecule are high enough to release substantial amounts of methanol to the gas-phase at and around the location of the CO thermal desorption front in a protoplanetary disk. The impact of thermal co-desorption of CH3OH with CO as a grain-gas bridge mechanism is compared with that of UV induced photodesorption and chemisorption.

  15. Gas phase spectroscopic study of unstable molecules using FTIR technique

    International Nuclear Information System (INIS)

    Allaf, A.W.; Alibrahim, M.; Kassem, M.

    1998-01-01

    A new route has been developed, leading to the production of phosphorus (III) oxycyanide, OPCN and phosphorus (III) oxycyanate, OPOCN by an on-line process using phosphoryl chloride, POCL 3 as a starting material passed over heated silver at 870 Centigrade and then reacted with AgCN and KOCN heated at 270 Centigrade and 590 Centigrade to produce OPCN and OPOCN respectively. The gas phase fourier transform infrared spectra reported for the first time show the two characterized bonds of OPCN and OPOCN at 2165 cm -1 and 2130 cm -1 , assigned to the C≡N stretching fundamentals of OPCN and OPOCN respectively. (Author)

  16. Gas-phase spectroscopy of ferric heme-NO complexes

    DEFF Research Database (Denmark)

    Wyer, J.A.; Jørgensen, Anders; Pedersen, Bjarke

    2013-01-01

    and significantly blue-shifted compared to ferric heme nitrosyl proteins (maxima between 408 and 422 nm). This is in stark contrast to the Q-band absorption where the protein microenvironment is nearly innocent in perturbing the electronic structure of the porphyrin macrocycle. Photodissociation is primarily...... maxima of heme and its complexes with amino acids and NO. Not so innocent: Weakly bound complexes between ferric heme and NO were synthesised in the gas phase, and their absorption measured from photodissociation yields. Opposite absorption trends in the Soret-band are seen upon NO addition to heme ions...

  17. The nuclear liquid gas phase transition and phase coexistence

    International Nuclear Information System (INIS)

    Chomaz, Ph.

    2001-01-01

    In this talk we will review the different signals of liquid gas phase transition in nuclei. From the theoretical side we will first discuss the foundations of the concept of equilibrium, phase transition and critical behaviors in infinite and finite systems. From the experimental point of view we will first recall the evidences for some strong modification of the behavior of hot nuclei. Then we will review quantitative detailed analysis aiming to evidence phase transition, to define its order and phase diagram. Finally, we will present a critical discussion of the present status of phase transitions in nuclei and we will draw some lines for future development of this field. (author)

  18. The nuclear liquid gas phase transition and phase coexistence

    Energy Technology Data Exchange (ETDEWEB)

    Chomaz, Ph

    2001-07-01

    In this talk we will review the different signals of liquid gas phase transition in nuclei. From the theoretical side we will first discuss the foundations of the concept of equilibrium, phase transition and critical behaviors in infinite and finite systems. From the experimental point of view we will first recall the evidences for some strong modification of the behavior of hot nuclei. Then we will review quantitative detailed analysis aiming to evidence phase transition, to define its order and phase diagram. Finally, we will present a critical discussion of the present status of phase transitions in nuclei and we will draw some lines for future development of this field. (author)

  19. Angular intensity of a gas-phase field ionization source

    International Nuclear Information System (INIS)

    Orloff, J.; Swanson, L.W.

    1979-01-01

    Angular intensities of 1 μA sr -1 have been measured for a gas-phase field ionization source in an optical column under practical operating conditions. The source, which was differentially pumped and cooled to 77 K, utilized a -oriented iridium emitter and precooled hydrogen gas at 10 -2 Torr. The ion beam was collimated with an electrostatic lens and detected below an aperture subtending 0.164 msr. A transmitted current of approx.10 -10 A was measured at voltages corresponding to a field of approx. =2.2 V/A at the emitter

  20. Trace element and stable isotope analysis of fourteen species of marine invertebrates from the Bay of Fundy, Canada.

    Science.gov (United States)

    English, Matthew D; Robertson, Gregory J; Mallory, Mark L

    2015-12-15

    The Bay of Fundy, Canada, is a macrotidal bay with a highly productive intertidal zone, hosting a large abundance and diversity of marine invertebrates. We analysed trace element concentrations and stable isotopic values of δ(15)N and δ(13)C in 14 species of benthic marine invertebrates from the Bay of Fundy's intertidal zone to investigate bioaccumulation or biodilution of trace elements in the lower level of this marine food web. Barnacles (Balanus balanus) consistently had significantly greater concentrations of trace elements compared to the other species studied, but otherwise we found low concentrations of non-essential trace elements. In the range of trophic levels that we studied, we found limited evidence of bioaccumulation or biodilution of trace elements across species, likely due to the species examined occupying similar trophic levels in different food chains. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Niche segregation amongst sympatric species at exposed sandy shores with contrasting wrack availabilities illustrated by stable isotopic analysis

    OpenAIRE

    Bessa, Filipa; Baeta, Alexandra; Marques, João Carlos

    2014-01-01

    Wrack supplies (macroalgae, seagrasses and carrion) are a common feature of sandy beaches worldwide. These allochthonous inputs are a potential high-quality food subsidy for beach fauna, but little is known about the feeding ecology and niche segregation strategies of these species in beaches with limited wrack availabilities. We used stable isotopic ratios of nitrogen and carbon to examine the diets and niche segregation among three sympatric crustaceans, the amphipods Talitrus s...

  2. Gas-phase ion-molecule reactions and high-pressure mass spectrometer, 1

    International Nuclear Information System (INIS)

    Hiraoka, Kenzo

    1977-01-01

    The reasons for the fact that the research in gas-phase ion-molecule reactions, to which wide interest is shown, have greatly contributed to the physical and chemical fields are that, first it is essential in understanding general phenomena concerning ions, second, it can furnish many unique informations in the dynamics of chemical reactions, and third, usefulness of '' chemical ionization'' methods has been established as its application to chemical analysis. In this review, the history and trend of studies and equipments in gas-phase ion-molecule reactions are surveyed. The survey includes the chemical ionization mass spectrometer for simultaneously measuring the positive and negative ions utilizing a quadrupole mass spectrometer presented by Hunt and others, flowing afterglow method derived from the flowing method which traces neutral chemical species mainly optically, ion cyclotron resonance mass spectrometer, trapped ion mass spectrometer and others. Number of reports referred to ion-molecule reactions issued during the last one year well exceeds the total number of reports concerning mass spectrometers presented before 1955. This truly shows how active the research and development are in this field. (Wakatsuki, Y.)

  3. Gas phase absorption studies of photoactive yellow protein chromophore derivatives.

    Science.gov (United States)

    Rocha-Rinza, Toms; Christiansen, Ove; Rajput, Jyoti; Gopalan, Aravind; Rahbek, Dennis B; Andersen, Lars H; Bochenkova, Anastasia V; Granovsky, Alexander A; Bravaya, Ksenia B; Nemukhin, Alexander V; Christiansen, Kasper Lincke; Nielsen, Mogens Brøndsted

    2009-08-27

    Photoabsorption spectra of deprotonated trans p-coumaric acid and two of its methyl substituted derivatives have been studied in gas phase both experimentally and theoretically. We have focused on the spectroscopic effect of the location of the two possible deprotonation sites on the trans p-coumaric acid which originate to either a phenoxide or a carboxylate. Surprisingly, the three chromophores were found to have the same absorption maximum at 430 nm, in spite of having different deprotonation positions. However, the absorption of the chromophore in polar solution is substantially different for the distinct deprotonation locations. We also report on the time scales and pathways of relaxation after photoexcitation for the three photoactive yellow protein chromophore derivatives. As a result of these experiments, we could detect the phenoxide isomer within the deprotonated trans p-coumaric acid in gas phase; however, the occurrence of the carboxylate is uncertain. Several computational methods were used simultaneously to provide insights and assistance in the interpretation of our experimental results. The calculated excitation energies S(0)-S(1) are in good agreement with experiment for those systems having a negative charge on a phenoxide moiety. Although our augmented multiconfigurational quasidegenerate perturbation theory calculations agree with experiment in the description of the absorption spectrum of anions with a carboxylate functional group, there are some puzzling disagreements between experiment and some calculational methods in the description of these systems.

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

    International Nuclear Information System (INIS)

    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 6 , which is generated from the reaction of ClF 3 with the uranium deposits, by use of NaF traps

  5. A retrospective analysis of pollen host plant use by stable and declining bumble bee species

    NARCIS (Netherlands)

    Kleijn, D.; Raemakers, I.P.

    2008-01-01

    Understanding population declines has been the objective of a wide range of ecological studies. When species have become rare such studies are complicated because particular behavior or life history traits may be the cause but also the result of the decline of a species. We approached this problem

  6. Sex allocation promotes the stable co-occurrence of competitive species

    Science.gov (United States)

    Kobayashi, Kazuya

    2017-03-01

    Biodiversity has long been a source of wonder and scientific curiosity. Theoretically, the co-occurrence of competitive species requires niche differentiation, and such differences are well known; however, the neutral theory, which assumes the equivalence of all individuals regardless of the species in a biological community, has successfully recreated observed patterns of biodiversity. In this research, the evolution of sex allocation is demonstrated to be the key to resolving why the neutral theory works well, despite the observed species differences. The sex allocation theory predicts that female-biased allocation evolves in species in declining density and that this allocation improves population growth, which should lead to an increase in density. In contrast, when the density increases, a less biased allocation evolves, which reduces the population growth rate and leads to decreased density. Thus, sex allocation provides a buffer against species differences in population growth. A model incorporating this mechanism demonstrates that hundreds of species can co-occur over 10,000 generations, even in homogeneous environments, and reproduces the observed patterns of biodiversity. This study reveals the importance of evolutionary processes within species for the sustainability of biodiversity. Integrating the entire biological process, from genes to community, will open a new era of ecology.

  7. Raman study of vibrational dynamics of aminopropylsilanetriol in gas phase

    Science.gov (United States)

    Volovšek, V.; Dananić, V.; Bistričić, L.; Movre Šapić, I.; Furić, K.

    2014-01-01

    Raman spectrum of aminopropylsilanetriol (APST) in gas phase has been recorded at room temperature in macro chamber utilizing two-mirror technique over the sample tube. Unlike predominantly trans molecular conformation in condensed phase, the spectra of vapor show that the molecules are solely in gauche conformation with intramolecular hydrogen bond N⋯Hsbnd O which reduces the molecular energy in respect to trans conformation by 0.152 eV. The assignment of the molecular spectra based on the DFT calculation is presented. The strong vibrational bands at 354 cm-1, 588 cm-1 and 3022 cm-1 are proposed for verifying the existence of the ring like, hydrogen bonded structure. Special attention was devoted to the high frequency region, where hydrogen bond vibrations are coupled to stretchings of amino and silanol groups.

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

    Energy Technology Data Exchange (ETDEWEB)

    Classen, Nathan Robert [Iowa State Univ., Ames, IA (United States)

    2002-01-01

    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 β C-H insertion mechanism.

  9. Zpif's law in the liquid gas phase transition of nuclei

    International Nuclear Information System (INIS)

    Ma, Y.G.

    1999-01-01

    Zpif's law in the field of linguistics is tested in the nuclear disassembly within the framework of isospin dependent lattice gas model. It is found that the average cluster charge (or mass) of rank n in the charge (or mass) list shows exactly inversely to its rank, i.e., there exists Zpif's law, at the phase transition temperature. This novel criterion shall be helpful to search the nuclear liquid gas phase transition experimentally and theoretically. In addition, the finite size scaling of the effective phase transition temperature at which the Zpif's law appears is studied for several systems with different mass and the critical exponents of ν and β are tentatively extracted. (orig.)

  10. FLUIDDYNAMIC ASPECTS OF GAS-PHASE ETHYLENE POLYMERIZATION REACTOR DESIGN

    Directory of Open Access Journals (Sweden)

    Guardani R.

    1998-01-01

    Full Text Available The relative importance of design variables affecting the fluiddynamic behavior of a fluidized bed reactor for the gas-phase ethylene polymerization is discussed, based on mathematical modeling. The three-phase bubbling fluidized bed model is based on axially distributed properties for the bubble, cloud and emulsion phases, combined with correlations for population balance and entrainment. Under the operating conditions adopted in most industrial processes, the reactor performance is affected mainly by the reaction rate and solids entrainment. Simulation results indicate that an adequate design of the freeboard and particle collecting equipment is of primary importance in order to produce polymeric particles with the desired size distribution, as well as to keep entrainment and catalyst feed rates at adequate levels.

  11. Conformational Study of Taurine in the Gas Phase

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    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.; Barth, H.; Gober, M.K.; Kratz, J.V.; Bruechle, W.; Schaedel, M.; Schimpf, E.; Gober, M.K.; Kratz, J.V.; Zimmermann, H.P.

    1991-04-01

    On-line isothermal gas phase chromatography was used to study halides of 261 104 (T 1/2 = 65 s) and 262,263 105 (T 1/2 = 34 s and 27 s) produced an atom-at-a time via the reactions 248 Cm( 18 O, 5n) and 249 Bk( 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

  13. Technical Procedures Management in Gas-Phase Detoxification Laboratory

    International Nuclear Information System (INIS)

    Cardona Garcia, A. I.; Sanchez Cabrero, B.

    2000-01-01

    The natural cycle of Volatile Organic Compounds (VOCs) has been disturbed by the industrial and socioeconomic activities of human beings. This imbalance in the environment has affected the ecosystems and the human health. Initiatives have been planned to mitigate these adverse effects. In order to minimize the hazardous effects, initiatives have been proposed for the treatment of gaseous emissions. The solar photo catalysis appears as a clear and renewable technology in front of the conventional ones.In CIEMAT this line is being investigated as the base of a future implementation at a pre industrial scale.Technical procedures are written in this document for testing Gas-Phase detoxification at lab scale in the Renewable Energy Department (DER) CIEMAT- Madrid to eliminate the VOCs by using the solar photo catalysis technology. (Author) 34 refs

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

    Science.gov (United States)

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

    2014-12-01

    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.

  15. Gas-Phase Thermolysis of a Thioketen-S-Oxide

    DEFF Research Database (Denmark)

    Carlsen, Lars; Egsgaard, Helge; Schaumann, Ernst

    1980-01-01

    The unimolecular gas-phase thermolytic decomposition of 1,1,3,3-tetramethyl-2-thiocarbonylcyclohexane S-oxide (3) has been studied as a function of temperature by a flash vacuum thermolysis (f.v.t.) technique. The products detected are the carbenes (4) and (5), the ketone (6), the keten (7......), the thioketone (8), and the thioketen (9). The product ratio is highly dependent on the thermolysis temperature. The thermolysis of (3) is mechanistically rationalized by assuming the existence of only two concurrent primary processes, which are (a) extrusion of atomic oxygen, leading to the thioketen (9...... and CSO leading to the carbenes (5) and (4), respectively, are observed. Owing to an apparently very short half-life of the oxathiiran (10), only the decomposition products of the three-membered ring compound have been detected. These are the thioketone (8), formed by rearrangement of (10) into the α...

  16. Statistical Physics of Nanoparticles in the Gas Phase

    CERN Document Server

    Hansen, Klavs

    2013-01-01

    Thermal processes are ubiquitous and an understanding of thermal phenomena is essential for a complete description of the physics of nanoparticles, both for the purpose of modeling the dynamics of the particles and for the correct interpretation of experimental data. This book has the twofold aim to present coherently the relevant results coming from the recent scientific literature and to guide the readers through the process of deriving results, enabling them to explore the limits of the mathematical approximations and test the power of the method. The book is focused on the fundamental properties of nanosystems in the gas phase. For this reason there is a strong emphasis on microcanonical physics. Each chapter is enriched with exercises and 3 Appendices provide additional useful materials.

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

    Science.gov (United States)

    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.

  18. Laser diagnostics of a diamond depositing chemical vapour deposition gas-phase environment

    Energy Technology Data Exchange (ETDEWEB)

    Smith, James Anthony

    2002-07-01

    Studies have been carried out to understand the gas-phase chemistry underpinning diamond deposition in hot filament and DC-arcjet chemical vapour deposition (CVD) systems. Resonance enhanced Multiphoton lonisation (REMPI) techniques were used to measure the relative H atom and CH{sub 3} radical number densities and local gas temperatures prevalent in a hot filament reactor, operating on Ch{sub 4}/H{sub 2} and C{sub 2}H{sub 2}/H{sub 2} gas mixtures. These results were compared to a 3D-computer simulation, and hence provided an insight into the nature of the gas-phase chemistry with particular reference to C{sub 2}{yields}C{sub 1} species conversion. Similar experimental and theoretical studies were also carried out to explain the chemistry involved in NH{sub 3}/CH{sub 4}/H{sub 2} and N{sub 2}/CH{sub 4}/H{sub 2} gas mixtures. It was demonstrated that the reactive nature of the filament surface was dependent on the addition of NH{sub 3}, influencing atomic hydrogen production, and thus the H/C/N gas-phase chemistry. Studies of the DC-arcjet diamond CVD reactor consisted of optical emission spectroscopic studies of the plume during deposition from an Ar/H{sub 2}/CH{sub 4}/N{sub 2} gas mixture. Spatially resolved species emission intensity maps were obtained for C{sub 2}(d{yields}a), CN(B{yields}X) and H{sub {beta}} from Abel-inverted datasets. The C{sub 2}(d{yields}a) and CN(B{yields}X) emission intensity maps both show local maxima near the substrate surface. SEM and Laser Raman analyses indicate that N{sub 2} additions lead to a reduction in film quality and growth rate. Photoluminescence and SIMS analyses of the grown films provide conclusive evidence of nitrogen incorporation (as chemically bonded CN). Absolute column densities of C{sub 2}(a) in a DC-arcjet reactor operating on an Ar/H{sub 2}/CH{sub 4} gas mixture, were measured using Cavity ring down spectroscopy. Simulations of the measured C{sub 2}(v=0) transition revealed a rotational temperature of {approx

  19. Laser diagnostics of a diamond depositing chemical vapour deposition gas-phase environment

    International Nuclear Information System (INIS)

    Smith, James Anthony

    2002-01-01

    Studies have been carried out to understand the gas-phase chemistry underpinning diamond deposition in hot filament and DC-arcjet chemical vapour deposition (CVD) systems. Resonance enhanced Multiphoton lonisation (REMPI) techniques were used to measure the relative H atom and CH 3 radical number densities and local gas temperatures prevalent in a hot filament reactor, operating on Ch 4 /H 2 and C 2 H 2 /H 2 gas mixtures. These results were compared to a 3D-computer simulation, and hence provided an insight into the nature of the gas-phase chemistry with particular reference to C 2 →C 1 species conversion. Similar experimental and theoretical studies were also carried out to explain the chemistry involved in NH 3 /CH 4 /H 2 and N 2 /CH 4 /H 2 gas mixtures. It was demonstrated that the reactive nature of the filament surface was dependent on the addition of NH 3 , influencing atomic hydrogen production, and thus the H/C/N gas-phase chemistry. Studies of the DC-arcjet diamond CVD reactor consisted of optical emission spectroscopic studies of the plume during deposition from an Ar/H 2 /CH 4 /N 2 gas mixture. Spatially resolved species emission intensity maps were obtained for C 2 (d→a), CN(B→X) and H β from Abel-inverted datasets. The C 2 (d→a) and CN(B→X) emission intensity maps both show local maxima near the substrate surface. SEM and Laser Raman analyses indicate that N 2 additions lead to a reduction in film quality and growth rate. Photoluminescence and SIMS analyses of the grown films provide conclusive evidence of nitrogen incorporation (as chemically bonded CN). Absolute column densities of C 2 (a) in a DC-arcjet reactor operating on an Ar/H 2 /CH 4 gas mixture, were measured using Cavity ring down spectroscopy. Simulations of the measured C 2 (v=0) transition revealed a rotational temperature of ∼3300 K. This gas temperature is similar to that deduced from optical emission spectroscopy studies of the C 2 (d→a) transition. (author)

  20. The Northwest Infrared (NWIR) gas-phase spectral database of industrial and environmental chemicals: Recent updates

    Energy Technology Data Exchange (ETDEWEB)

    Brauer, Carolyn S.; Johnson, Timothy J.; Blake, Thomas A.; Sharpe, Steven W.; Sams, Robert L.; Tonkyn, Russell G.

    2014-05-22

    With continuing improvements in both standoff- and point-sensing techniques, there is an ongoing need for high-quality infrared spectral databases. The Northwest Infrared Database (NWIR) contains quantitative, gas-phase infrared spectra of nearly 500 pure chemical species that can be used for a variety of applications such as atmospheric monitoring, biomass burning studies, etc. The data, recorded at 0.1 cm-1 resolution, are pressure broadened to one atmosphere (N2) in order to mimic atmospheric conditions. Each spectrum is a composite composed of multiple individual measurements. Recent updates to the database include over 60 molecules that are known or suspected biomass-burning effluents. Examples from this set of measurements will be presented and experimental details will be discussed in the context of the utility of NWIR for environmental applications.

  1. Structure and dynamics of gas phase ions: Interplay between experiments and computations in IRMPD spectroscopy

    Science.gov (United States)

    Coletti, Cecilia; Corinti, Davide; Paciotti, Roberto; Re, Nazzareno; Crestoni, Maria Elisa; Fornarini, Simonetta

    2017-11-01

    The investigation of the molecular structure and dynamics of ions in gas phase is an item of increasing interest, due the role such species play in many areas of chemistry and physics, not to mention that they often represent elusive intermediates in more complex reaction mechanisms. Infrared Multiple Photon Dissociation spectroscopy is today one of the most advanced technique to this purpose, because of its high sensitivity to even small structure changes. The interpretation of IRMPD spectra strongly relies on high level quantum mechanical computations, so that a close interplay is needed for a detailed understanding of structure and kinetics properties which can be gathered from the many applications of this powerful technique. Recent advances in experiment and theory in this field are here illustrated, with emphasis on recent progresses for the elucidation of the mechanism of action of cisplatin, one of the most widely used anticancer drugs.

  2. Using species-specific enriched stable isotopes to study the effect of fresh mercury inputs in soil-earthworm systems.

    Science.gov (United States)

    Álvarez, C Rodríguez; Jiménez-Moreno, M; Bernardo, F J Guzmán; Martín-Doimeadios, R C Rodríguez; Nevado, J J Berzas

    2018-01-01

    The fate of mercury (Hg) in the soil-earthworm system is still far from being fully understood, especially regarding recurrent and challenging questions about the importance of the reactivity of exogenous Hg species. Thus, to predict the potential effect of Hg inputs in terrestrial ecosystems, it is necessary to evaluate separately the reactivity of the endogenous and exogenous Hg species and, for this purpose, the use of enriched stable isotope tracers is a promising tool. In the present work, earthworms (Lumbricus terrestris) were exposed to historically Hg contaminated soils from the Almadén mining district, Spain. The soils were either non-spiked, which contain only endogenous or native Hg naturally occurring in the soil, or spiked with isotopically enriched inorganic Hg ( 199 IHg), representing exogenous or spiked Hg apart from the native one. The differential reactivity of endogenous and exogenous Hg in the soil conditioned the processes of methylation, mobilization, and assimilation of inorganic Hg by earthworms. Both endogenous and exogenous Hg species also behave distinctly regarding their bioaccumulation in earthworms, as suggested by the bioaccumulation factors, being the endogenous methylmercury (MeHg) the species more readily bioaccumulated by earthworms and in a higher extent. To the best of our knowledge, this work demonstrates for the first time the potential of enriched stable isotopes to study the effects of fresh Hg inputs in soil-earthworm systems. The findings of this work can be taken as a case study on the dynamics of Hg species in complex terrestrial systems and open a new door for future experiments. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Conformational preferences of γ-aminobutyric acid in the gas phase and in water

    Science.gov (United States)

    Song, Il Keun; Kang, Young Kee

    2012-09-01

    The conformational study of γ-aminobutyric acid (GABA) has been carried out at the M06-2X/cc-pVTZ level of theory in the gas phase and the SMD M06-2X/cc-pVTZ level of theory in water. In the gas phase, the folded conformation gG1 with gauche- and gauche+ conformations for the Cβsbnd Cα and Cγsbnd Cβ bonds, respectively, is found to be lowest in energy and enthalpy, which can be ascribed to the favored hyperconjugative n → π* interaction between the lone electron pair of the amine nitrogen atom and the Cdbnd O bond of the carboxylic group and the favored antiparallel dipole-dipole interaction between the Nsbnd H bond and the Cdbnd O bond. In addition, the intramolecular hydrogen bonds between the carboxylic group and the amine Nsbnd H group have contributed to stabilize some low-energy conformers. However, the most preferred conformation is found to be tG1 and more stable by 0.4 kcal/mol in ΔG than the conformer gG1, in which the favored entropic term due to the conformational flexibility and the other favored n → σ*, σ → σ*, and π → σ* interactions seem to play a role. The conformational preferences of the neutral GABA calculated by ΔG's are reasonably consistent with the populations deduced from FT microwave spectroscopy in supersonic jets combined with laser ablation. In water, the two folded conformers Gg and gG of the zwitterionic GABA are dominantly populated, each of which has the population of 47%, and the hydrogen bond between the ammonium Nsbnd H group and the lone electron pair of the Csbnd O- group seems to be crucial in stabilizing these conformers. Our calculated result that the folded conformers preferentially exist in water is consistent with the 1H NMR experiments in D2O.

  4. Stable isotopes reveal the effect of trawl fisheries on the diet of commercially exploited species.

    Science.gov (United States)

    Hinz, Hilmar; Moranta, Joan; Balestrini, Stephen; Sciberras, Marija; Pantin, Julia R; Monnington, James; Zalewski, Alex; Kaiser, Michel J; Sköld, Mattias; Jonsson, Patrik; Bastardie, Francois; Hiddink, Jan Geert

    2017-07-24

    Bottom trawling can change food availability for benthivorous demersal species by (i) changing benthic prey composition through physical seabed impacts and (ii) by removing overall benthic consumer biomass increasing the net availability of benthic prey for remaining individuals. Thus trawling may both negatively and positively influence the quantity and quality of food available. Using δ 13 C and δ 15 N we investigated potential diet changes of three commercially exploited species across trawling gradients in the Kattegat (plaice, dab and Norway lobster (Nephrops)) and the Irish Sea (Nephrops). In the Kattegat, trawling affected primarily the biomass of benthic consumers, lowering competition. Nephrops showed significant positive relationships for δ 13 C and a domed relationship for δ 15 N with trawling. In the Irish Sea, intense trawling had a negative effect on benthic prey. δ 13 C and δ 15 N thus showed the inverse relationships to those observed in the Kattegat. Plaice from the Kattegat, showed a significant relationship with trawling intensity for δ 13 C, but not for δ 15 N. No relationship was found for dab. Changes of δ 13 C and δ 15 N correlated with changes in condition of species. The results show that the removal of demersal competitors and benthos by trawling can change the diets of commercial species, ultimately affecting their body condition.

  5. Stable isotopes reveal the effect of trawl fisheries on the diet of commercially exploited species

    DEFF Research Database (Denmark)

    Hinz, Hilmar; Moranta, Joan; Balestrini, Stephen

    2017-01-01

    both negatively and positively influence the quantity and quality of food available. Using δ 13C and δ 15N we investigated potential diet changes of three commercially exploited species across trawling gradients in the Kattegat (plaice, dab and Norway lobster (Nephrops)) and the Irish Sea (Nephrops...

  6. Liquid and Gas Phase Chemistry of Hypergolic Reactions between MMH and NTO or RFNA

    Science.gov (United States)

    Black, Ariel

    -step liquid phase chemical reaction model. These defining constants have never before been experimentally determined for MMH-NTO and can be employed to improve the accuracy of CFD combustion simulations. Induction delay times for MMH-RFNA ranged from 30 to 100 microseconds, agreeing with previously reported data, while MMH-NTO delays varied from 10 to 100 microseconds. Advanced ultraviolet and visible (UV-Vis) spectroscopic techniques were applied to conventional drop test analysis in order to study the emitting species in MMH-NTO and MMH-RFNA combustion reactions. A streak camera coupled with a spectrometer provided temporally resolved spectra for species emitting wavelengths from 250 to 950 nm within a one millimeter diameter point of interest above the reaction. The spectra were compared to known MMH-RFNA gas-phase reaction mechanisms and spectroscopic data reported in literature in an attempt to partially validate the proposed full and reduced MMH-RFNA reaction mechanisms and derive a connection to elementary reactions of MMH-NTO. MMH-NTO consistently produced brighter flames than MMH-RFNA and as such generally generated higher intensity signals for a given spectrometer setting. Both propellant combinations revealed conclusive evidence of OH and NH radicals and probable evidence of CN and/or CH radicals. In most tests OH* yielded the highest intensity signals with both RFNA and NTO. MMH-NTO revealed greater NH* intensity than MMH-RFNA. Additionally, species appeared later but peaked sooner relative to ignition for MMH-RFNA than for MMH-NTO. Efforts to draw correlations between these experimental results and existing reaction mechanisms proved to be challenging and are ongoing. A dominant, high intensity signal characteristic of sodium was an unexpected, but apparently not uncommon, observation, with varying opinions as to its origin.

  7. Cation disorder and gas phase equilibrium in an YBa 2Cu 3O 7- x superconducting thin film

    Science.gov (United States)

    Shin, Dong Chan; Ki Park, Yong; Park, Jong-Chul; Kang, Suk-Joong L.; Yong Yoon, Duk

    1997-02-01

    YBa 2Cu 3O 7- x superconducting thin films have been grown by in situ off-axis rf sputtering with varying oxygen pressure, Ba/Y ratio in a target, and deposition temperature. With decreasing oxygen pressure, increasing Ba/Y ratio, increasing deposition temperature, the critical temperature of the thin films decreased and the c-axis length increased. The property change of films with the variation of deposition variables has been explained by a gas phase equilibrium of the oxidation reaction of Ba and Y. Applying Le Chatelier's principle to the oxidation reaction, we were able to predict the relation of deposition variables and the resultant properties of thin films; the prediction was in good agreement with the experimental results. From the relation between the three deposition variables and gas phase equilibrium, a 3-dimensional processing diagram was introduced. This diagram has shown that the optimum deposition condition of YBa 2Cu 3O 7- x thin films is not a fixed point but can be varied. The gas phase equilibrium can also be applied to the explanation of previous results that good quality films were obtained at low deposition temperature using active species, such as O, O 3, and O 2+.

  8. C and N Stable Isotope Variability in Soft Tissue of Invasive Species Ficopomatus enigmaticus (Annelida, Polychaeta)

    International Nuclear Information System (INIS)

    Cukrov, Neven; Cukrov, Marijana; Lojen, Sonja

    2011-01-01

    Serpulidae Rafinesque, 1815 is a family of polychaete annelids with calcareous tubes found in worldwide from littoral to abyssal depths. Of more than 350 described species of serpulid polychaetes, Marifugia cavatica Absolon and Hrabe 1930 is the only known cave-dwelling stygobiotic and freshwater serpulid, five other serpulid species comprising the genus Ficopomatus are found in brackish water, otherwise serpulids are all marine organisms. Ficopomatus enigmaticus (Fauvel, 1923), previously known as Mercierella enigmatica, is a truly cosmopolitan with disjunct distribution. It has been found worldwide inhabiting coastal brackish waters, lagoons and estuaries of warm temperate areas of both hemispheres. This tubeworm builds calcareous tubes on any hard substrate. With distinctive collar-like rings at irregular intervals it is relatively easy to identify. It is an efficient suspension-feeder, very tolerant and physiologically well adapted to temperature and salinity variations, eutrophic conditions and low dissolved oxygen content. The fact that populations of F. enigmaticus appear near the ports suggests that the probable mechanism of introduction was ship fouling or ballast water. Generally, F. enigmaticus is considered as a fouling nuisance species which negatively affects ships, buoys and harbour structures.

  9. Gas-phase synthesis of semiconductor nanocrystals and its applications

    Science.gov (United States)

    Mandal, Rajib

    Luminescent nanomaterials is a newly emerging field that provides challenges not only to fundamental research but also to innovative technology in several areas such as electronics, photonics, nanotechnology, display, lighting, biomedical engineering and environmental control. These nanomaterials come in various forms, shapes and comprises of semiconductors, metals, oxides, and inorganic and organic polymers. Most importantly, these luminescent nanomaterials can have different properties owing to their size as compared to their bulk counterparts. Here we describe the use of plasmas in synthesis, modification, and deposition of semiconductor nanomaterials for luminescence applications. Nanocrystalline silicon is widely known as an efficient and tunable optical emitter and is attracting great interest for applications in several areas. To date, however, luminescent silicon nanocrystals (NCs) have been used exclusively in traditional rigid devices. For the field to advance towards new and versatile applications for nanocrystal-based devices, there is a need to investigate whether these NCs can be used in flexible and stretchable devices. We show how the optical and structural/morphological properties of plasma-synthesized silicon nanocrystals (Si NCs) change when they are deposited on stretchable substrates made of polydimethylsiloxane (PDMS). Synthesis of these NCs was performed in a nonthermal, low-pressure gas phase plasma reactor. To our knowledge, this is the first demonstration of direct deposition of NCs onto stretchable substrates. Additionally, in order to prevent oxidation and enhance the luminescence properties, a silicon nitride shell was grown around Si NCs. We have demonstrated surface nitridation of Si NCs in a single step process using non?thermal plasma in several schemes including a novel dual-plasma synthesis/shell growth process. These coated NCs exhibit SiNx shells with composition depending on process parameters. While measurements including

  10. A global model for SF6 plasmas coupling reaction kinetics in the gas phase and on the surface of the reactor walls

    International Nuclear Information System (INIS)

    Kokkoris, George; Panagiotopoulos, Apostolos; Gogolides, Evangelos; Goodyear, Andy; Cooke, Mike

    2009-01-01

    Gas phase and reactor wall-surface kinetics are coupled in a global model for SF 6 plasmas. A complete set of gas phase and surface reactions is formulated. The rate coefficients of the electron impact reactions are based on pertinent cross section data from the literature, which are integrated over a Druyvesteyn electron energy distribution function. The rate coefficients of the surface reactions are adjustable parameters and are calculated by fitting the model to experimental data from an inductively coupled plasma reactor, i.e. F atom density and pressure change after the ignition of the discharge. The model predicts that SF 6 , F, F 2 and SF 4 are the dominant neutral species while SF 5 + and F - are the dominant ions. The fit sheds light on the interaction between the gas phase and the reactor walls. A loss mechanism for SF x radicals by deposition of a fluoro-sulfur film on the reactor walls is needed to predict the experimental data. It is found that there is a net production of SF 5 , F 2 and SF 6 , and a net consumption of F, SF 3 and SF 4 on the reactor walls. Surface reactions as well as reactions between neutral species in the gas phase are found to be important sources and sinks of the neutral species.

  11. Diesel-related hydrocarbons can dominate gas phase reactive carbon in megacities

    Directory of Open Access Journals (Sweden)

    R. E. Dunmore

    2015-09-01

    Full Text Available Hydrocarbons are key precursors to two priority air pollutants, ozone and particulate matter. Those with two to seven carbons have historically been straightforward to observe and have been successfully reduced in many developed cities through air quality policy interventions. Longer chain hydrocarbons released from diesel vehicles are not considered explicitly as part of air quality strategies and there are few direct measurements of their gaseous abundance in the atmosphere. This study describes the chemically comprehensive and continuous measurements of organic compounds in a developed megacity (London, which demonstrate that on a seasonal median basis, diesel-related hydrocarbons represent only 20–30 % of the total hydrocarbon mixing ratio but comprise more than 50 % of the atmospheric hydrocarbon mass and are a dominant local source of secondary organic aerosols. This study shows for the first time that 60 % of the winter primary hydrocarbon hydroxyl radical reactivity is from diesel-related hydrocarbons and using the maximum incremental reactivity scale, we predict that they contribute up to 50 % of the ozone production potential in London. Comparing real-world urban composition with regulatory emissions inventories in the UK and US highlights a previously unaccounted for, but very significant, under-reporting of diesel-related hydrocarbons; an underestimation of a factor ~4 for C9 species rising to a factor of over 70 for C12 during winter. These observations show that hydrocarbons from diesel vehicles can dominate gas phase reactive carbon in cities with high diesel fleet fractions. Future control of urban particulate matter and ozone in such locations requires a shift in policy focus onto gas phase hydrocarbons released from diesels as this vehicle type continues to displace gasoline world-wide.

  12. Gas Phase Thz Spectroscopy of Organosulfide and Organophosphorous Compounds Using a Synchrotron Source

    Science.gov (United States)

    Cuisset, Arnaud; Smirnova, Irina; Bocquet, Robin; Hindle, Francis; Mouret, Gael; Sadovskii, Dmitrii A.; Pirali, Olivier; Roy, Pascale

    2011-06-01

    This study concerns the gas phase rovibrational spectroscopy of organosulfide and organophosphorous which are considered as non toxic model compounds in the analysis of chemical weapon materials, high pathogenic and mutagenic agents, and other environmentally interesting air-borne species. The coupling of the synchrotron radiation with multipass cells and the FTIR spectrometer allowed to obtain very conclusive results in term of sensitivity and resolution and improved the previous results obtained with classical sources. For DMSO, using an optical path of 150 m the spectra have been recorded at the ultimate resolution of 0.001 Cm-1 allowing to fully resolve the rotational structure of the lowest vibrational modes observed in the THz region. In the 290 - 420 Cm-1 region, the rovibrational spectrum of the "perpendicular" and "parallel" vibrational bands associated with, respectively, the asymmetric ν23 and symmetric ν11 bending modes of DMSO have been recorded with a resolution of 1.5× 10-3 Cm-1. The gas phase vibrational spectra of organophosphorous compounds were measured by FTIR spectroscopy using the vapor pressure of the compounds. Except for TBP, the room temperature vapor pressure was sufficient to detect all active vibrational modes from THz to NIR domain. Contrary to DMSO, the rotational patterns of alkyl phosphates and alkyl phosphonates could not be resolved; only a vibrational analysis may be performed. Nevertheless, the spectral fingerprints observed in the THz region allowed a clear discrimination between the molecules and between the different molecular conformations. A. Cuisset, G. Mouret, O. Pirali, P. Roy, F. Cazier, H. Nouali, J. Demaison, J. Phys. Chem. B, 2008, 112:, 12516-12525 A. Cuisset, L. Nanobashvili, I. Smirnova, R. Bocquet, F. Hindle, G. Mouret, O. Pirali, P. Roy and D. A. Sadovskií, Chem. Phys. Lett., 2010, 492: 30-34 I. Smirnova, A. Cuisset, R. Bocquet, F. Hindle, G. Mouret, O. Pirali, P. Roy, J. Phys. Chem. B, 2010, 114: 16936-16947.

  13. The Influence of Mixing in High Temperature Gas Phase Reactions

    DEFF Research Database (Denmark)

    Østberg, Martin

    1996-01-01

    by injection of NH3 with carrier gas into the flue gas. NH3 can react with NO and form N2, but a competing reaction path is the oxidation of NH3 to NO.The SNR process is briefly described and it is shown by chemical kinetic modelling that OH radicals under the present conditions will initiate the reaction......The objective of this thesis is to describe the mixing in high temperature gas phase reactions.The Selective Non-Catalytic Reduction of NOx (referred as the SNR process) using NH3 as reductant was chosen as reaction system. This in-furnace denitrification process is made at around 1200 - 1300 K...... diffusion. The SNR process is simulated using the mixing model and an empirical kinetic model based on laboratory experiments.A bench scale reactor set-up has been built using a natural gas burner to provide the main reaction gas. The set-up has been used to perform an experimental investigation...

  14. Gas phase reactions of nitrogen oxides with olefins

    Energy Technology Data Exchange (ETDEWEB)

    Altshuller, A P; Cohen, I

    1961-01-01

    The nature of the condensation products formed in the gas phase reactions of nitrogen dioxide and nitric oxide with pentene-1, 2-methylbutene-2, and 2-methylbutadiene-1,3 was investigated. The reactants were combined at partial pressures in the range of 0.1 to 2.5 mm with the total pressure at one atmosphere. The products were determined by infrared and ultraviolet spectroscopy and colorimetry. The condensates included primary and secondary nitro compounds and alkyl nitrates. Strong hydroxyl and single bond carbon to oxygen stretching vibrations indicate the presence of either nitroalcohols or simple aliphatic alcohols formed through oxidation reactions. Carbonyl stretching frequencies observable in some of the reactions support the conclusion that a portion of the reactants disappear by oxidation rather than by nitration processes. The available results do not indicate the presence of appreciable amounts of tert.-nitro compounds, conjugated nitro-olefins, or gem-dinitro-alkanes. The reactivities of the olefins with the nitrogen oxides are in the decreasing order: 2-methyl-butadiene-1,3, 2-methylbutene-2, pentene-1. 20 references.

  15. Frequency metrology of a photomixing source for gas phase spectroscopy

    Science.gov (United States)

    Hindle, Francis; Mouret, Gael; Yang, Chun; Cuisset, Arnaud; Bocquet, Robin; Lours, Michel; Rovera, Daniele

    2010-08-01

    The availability of frequency combs has opened new possibilities for the measurement of optical frequencies. Photomixing is an attractive solution for high resolution THz spectroscopy of gases due to the narrow spectral resolution and ability to access the 100 GHz to 3.5 THz range. One limitation of present photomixing spectrometers is the accuracy with which the THz frequency is established. Measurement of the centre frequency gas phase molecular transitions requires an accuracy better than 100 kHz in order to allow spectroscopic constants to be determined. Standard optical techniques like those employed in wavelength meters can only provide accuracies in the order of 50 MHz. We have used a turnkey fibre based frequency comb and a standard photomixing configuration to realize a THz synthesizer with an accuracy of around 50kHz. Two ECDLs used to pump the photomixer are phase locked onto the frequency comb and provide a tuning range of 10 MHz. In order to extend the tuning range an additional phase locked ECLD has been added to obtain a range in excess of 100 MHz. The absorption profiles of many Doppler limited transitions of carbonyl sulphide and formaldehyde have been measured to validate this instrument.

  16. Precursor-Less Coating of Nanoparticles in the Gas Phase

    Directory of Open Access Journals (Sweden)

    Tobias V. Pfeiffer

    2015-03-01

    Full Text Available This article introduces a continuous, gas-phase method for depositing thin metallic coatings onto (nanoparticles using a type of physical vapor deposition (PVD at ambient pressure and temperature. An aerosol of core particles is mixed with a metal vapor cloud formed by spark ablation by passing the aerosol through the spark zone using a hollow electrode configuration. The mixing process rapidly quenches the vapor, which condenses onto the core particles at a timescale of several tens of milliseconds in a manner that can be modeled as bimodal coagulation. Gold was deposited onto core nanoparticles consisting of silver or polystyrene latex, and silver was deposited onto gold nanoparticles. The coating morphology depends on the relative surface energies of the core and coating materials, similar to the growth mechanisms known for thin films: a coating made of a substance having a high surface energy typically results in a patchy coverage, while a coating material with a low surface energy will normally “wet” the surface of a core particle. The coated particles remain gas-borne, allowing further processing.

  17. Nucleation and dissociation of nano-particles in gas phase

    International Nuclear Information System (INIS)

    Feiden, P.

    2007-09-01

    This work deals with the study of nano-particles formation in gas phase and their dissociation pathways after an optical excitation. The clusters formation decomposes in two steps: a seed is formed (nucleation phase) and sticks atoms during its propagation in a sodium atomic vapor (growth phase). Those two steps have been observed separately for homogeneous Na n and heterogeneous Na n X particles (X = (NaOH) 2 or (Na 2 O) 2 ). The growth mechanism is well interpreted by a Monte Carlo simulation taking into account an accretion mechanism with hard-sphere cross section. The homogeneous nucleation mechanism has been highlighted by a direct comparison with the Classical Nucleation Theory predictions. The clusters fragmentation of ionic Na + (NaOH) p et Na + (NaF) p particles is studied in the second part. The way clusters fragment with size when they are excited optically is compared with theoretical previsions: this highlights the existence of an energetic barrier for special size of clusters. Finally, the fragmentation of doubly charged Na + Na + (NaOH) p clusters shows a competition between the fission into two single charged fragments and the unimolecular evaporation of a neutral fragment. (author)

  18. Atomic and molecular physics in the gas phase

    International Nuclear Information System (INIS)

    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

  19. Gas-phase nitrosation of ethylene and related events in the C2H4NO+ landscape.

    Science.gov (United States)

    Gerbaux, Pascal; Dechamps, Noemie; Flammang, Robert; Nam, Pham Cam; Nguyen, Minh Tho; Djazi, Fayçal; Berruyer, Florence; Bouchoux, Guy

    2008-06-19

    The C2H4NO(+) system has been examined by means of quantum chemical calculations using the G2 and G3B3 approaches and tandem mass spectrometry experiments. Theoretical investigation of the C2H4NO(+) potential-energy surface includes 19 stable C2H4NO(+) structures and a large set of their possible interconnections. These computations provide insights for the understanding of the (i) addition of the nitrosonium cation NO(+) to the ethylene molecule, (ii) skeletal rearrangements evidenced in previous experimental studies on comparable systems, and (iii) experimental identification of new C2H4NO(+) structures. It is predicted from computation that gas-phase nitrosation of ethylene may produce C2H4(*)NO(+) adducts, the most stable structure of which is a pi-complex, 1, stabilized by ca. 65 kJ/mol with respect to its separated components. This complex was produced in the gas phase by a transnitrosation process involving as reactant a complex between water and NO(+) (H2O.NO(+)) and the ethylene molecule and fully characterized by collisional experiments. Among the other C 2H 4NO (+) structures predicted by theory to be protected against dissociation or isomerization by significant energy barriers, five were also experimentally identified. These finding include structures CH3CHNO(+) (5), CH 3CNOH (+) ( 8), CH3NHCO(+) (18), CH3NCOH(+) (19), and an ion/neutral complex CH2O...HCNH(+) (12).

  20. Homolytic iodination and nitration of some benzene derivatives in the gas phase

    International Nuclear Information System (INIS)

    Vonk, W.F.M.

    1980-01-01

    Two gas phase reactions, involving the iodination and nitration of benzene derivatives, are described. The experimental techniques of the apparatus and the methods used are outlined. The kinetic H/D isotope effect in the gas phase nitration of benzene with NO 2 is determined. (C.F.)

  1. Are rapid transitions between invasive and native species caused by alternative stable states, and does it matter?

    Science.gov (United States)

    Hansen, Gretchen J A; Ives, Anthony R; Vander Zanden, M Jake; Carpenter, Stephen R

    2013-10-01

    Rapid transitions in ecosystem structure, or regime shifts, are a hallmark of alternative stable states (ASS). However, regime shifts can occur even when feedbacks are not strong enough to cause ASS. We investigated the potential for ASS to explain transitions between dominance of an invasive species, rusty crayfish (Orconectes rusticus), and native sunfishes (Lepomis spp.) in northern Wisconsin (USA) lakes. A rapid transition from Lepomis to rusty crayfish dominance occurred as rusty crayfish invaded Trout Lake, and the reverse transition resulted from an eight-year experimental removal of rusty crayfish from Sparkling Lake. We fit a stage-structured population model of species interactions to 31 years of time-series data from each lake. The model identified water level as an important driver, with drought conditions reducing rusty crayfish recruitment and allowing Lepomis dominance. The maximum-likelihood parameter estimates of the negative interaction between rusty crayfish and Lepomis led to ASS in the model, where each species was capable of excluding the other within a narrow range of environmental conditions. However, uncertainty in parameter estimates made it impossible to exclude the potential that rapid transitions were caused by a simpler threshold response lacking alternative equilibria. Simulated forward and backward transitions between species dominance occurred at different environmental conditions (i.e., hysteresis), even when the parameters used for simulation did not predict ASS as a result of slow species responses to environmental drivers. Thus, ASS are possible, but by no means certain, explanations for rapid transitions in this system, and our results highlight the difficulties associated with distinguishing ASS from other types of threshold responses. However, whether regime shifts are caused by ASS may be relatively unimportant in this system, as the range of conditions over which transitions occur is narrow, and under most conditions, the

  2. Monoterpene oxidation in an oxidative flow reactor: SOA yields and the relationship between bulk gas-phase properties and organic aerosol growth

    Science.gov (United States)

    Friedman, B.; Link, M.; Farmer, D.

    2016-12-01

    We use an oxidative flow reactor (OFR) to determine the secondary organic aerosol (SOA) yields of five monoterpenes (alpha-pinene, beta-pinene, limonene, sabinene, and terpinolene) at a range of OH exposures. These OH exposures correspond to aging timescales of a few hours to seven days. We further determine how SOA yields of beta-pinene and alpha-pinene vary as a function of seed particle type (organic vs. inorganic) and seed particle mass concentration. We hypothesize that the monoterpene structure largely accounts for the observed variance in SOA yields for the different monoterpenes. We also use high-resolution time-of-flight chemical ionization mass spectrometry to calculate the bulk gas-phase properties (O:C and H:C) of the monoterpene oxidation systems as a function of oxidant concentrations. Bulk gas-phase properties can be compared to the SOA yields to assess the capability of the precursor gas-phase species to inform the SOA yields of each monoterpene oxidation system. We find that the extent of oxygenated precursor gas-phase species corresponds to SOA yield.

  3. Determining Role of the Chain Mechanism in the Temperature Dependence of the Gas-Phase Rate of Combustion Reactions

    Science.gov (United States)

    Azatyan, V. V.; Bolod'yan, I. A.; Kopylov, N. P.; Kopylov, S. N.; Prokopenko, V. M.; Shebeko, Yu. N.

    2018-05-01

    It is shown that the strong dependence of the rate of gas-phase combustion reactions on temperature is determined by the high values of the reaction rate constants of free atoms and radicals. It is established that with a branched chain mechanism, a special role in the reaction rate temperature dependence is played by positive feedback between the concentrations of active intermediate species and the rate of their change. The role of the chemical mechanism in the temperature dependence of the process rate with and without inhibitors is considered.

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

    Energy Technology Data Exchange (ETDEWEB)

    Dawley, M. Michele [Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Tanzer, Katrin; Denifl, Stephan, E-mail: Stephan.Denifl@uibk.ac.at, E-mail: Sylwia.Ptasinska.1@nd.edu [Institut für Ionenphysik und Angewandte Physik, and Center for Molecular Biosciences Innsbruck (CMBI), Leopold-Franzens Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria); Carmichael, Ian [Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Ptasińska, Sylwia, E-mail: Stephan.Denifl@uibk.ac.at, E-mail: Sylwia.Ptasinska.1@nd.edu [Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

    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.

  5. Gas-Phase Combustion Synthesis of Aluminum Nitride Powder

    Science.gov (United States)

    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.

  6. Photodetachment of free hexahalogenometallate doubly charged anions in the gas phase: [ML6]2-, (M=Re, Os, Ir, Pt; L=Cl and Br)

    International Nuclear Information System (INIS)

    Wang, X.; Wang, L.

    1999-01-01

    We report the first observation and photodetachment photoelectron spectroscopic study of a series of hexahalogenometallates dianions MCl 6 2- (M=Re, Os, Ir, and Pt) and MBr 6 2- (M=Re, Ir, and Pt) in the gas phase. All of these species were found to be stable as free gaseous doubly charged anions. Photoelectron spectra of all the dianions were obtained at several detachment photon energies. The photon-energy-dependent spectra clearly revealed the dianion nature of these species and allowed the repulsive Coulomb barriers to be estimated. The binding energies of the second excess electron in MCl 6 2- (M=Re, Os, Ir, Pt) were determined to be 0.46 (5), 0.46 (5), 0.82 (5), and 1.58 (5) eV, respectively, and those in MBr 6 2- (M=Re, Ir, Pt) to be 0.76 (6), 0.96 (6), and 1.52 (6) eV, respectively. A wealth of electronic structure information about these metal complexes were obtained and low-lying and highly-excited electronic states of the corresponding singly charged anions were observed. Detachment from metal d orbitals or ligand orbitals were observed and could be clearly distinguished; detachments from the metal d-orbitals all occur at low binding energies whereas those from the ligand-dominated orbitals all take place at rather high binding energies. We also found a remarkable correlation between electron affinities measured in vacuo and the redox potentials obtained in the solution phase of these species. copyright 1999 American Institute of Physics

  7. An optical spectrum of a large isolated gas-phase PAH cation: C78H26+

    Science.gov (United States)

    Zhen, Junfeng; Mulas, Giacomo; Bonnamy, Anthony; Joblin, Christine

    2016-01-01

    A gas-phase optical spectrum of a large polycyclic aromatic hydrocarbon (PAH) cation - C78H26+- in the 410-610 nm range is presented. This large all-benzenoid PAH should be large enough to be stable with respect to photodissociation in the harsh conditions prevailing in the interstellar medium (ISM). The spectrum is obtained via multi-photon dissociation (MPD) spectroscopy of cationic C78H26 stored in the Fourier Transform Ion Cyclotron Resonance (FT-ICR) cell using the radiation from a mid-band optical parametric oscillator (OPO) laser. The experimental spectrum shows two main absorption peaks at 431 nm and 516 nm, in good agreement with a theoretical spectrum computed via time-dependent density functional theory (TD-DFT). DFT calculations indicate that the equilibrium geometry, with the absolute minimum energy, is of lowered, nonplanar C2 symmetry instead of the more symmetric planar D2h symmetry that is usually the minimum for similar PAHs of smaller size. This kind of slightly broken symmetry could produce some of the fine structure observed in some diffuse interstellar bands (DIBs). It can also favor the folding of C78H26+ fragments and ultimately the formation of fullerenes. This study opens up the possibility to identify the most promising candidates for DIBs amongst large cationic PAHs. PMID:26942230

  8. Fundamental limits on gas-phase chemical reduction of NOx in a plasma

    Energy Technology Data Exchange (ETDEWEB)

    Penetrante, B.M.; Hsiao, M.C.; Merritt, B.T.; Vogtlin, G.E. [Lawrence Livermore National Lab., CA (United States)

    1997-12-31

    In the plasma, the electrons do not react directly with the NOx molecules. The electrons collide mainly with the background gas molecules like N{sub 2}, O{sub 2} and H{sub 2}O. Electron impact on these molecules result partly in dissociation reactions that produce reactive species like N, O and OH. The NOx in the engine exhaust gas initially consist mostly of NO. The ground state nitrogen atom, N, is the only species that could lead to the chemical reduction of NO to N{sub 2}. The O radical oxidizes NO to NO{sub 2} leaving the same amount of NOx. The OH radical converts NO{sub 2} to nitric acid. Acid products in the plasma can easily get adsorbed on surfaces in the plasma reactor and in the pipes. When undetected, the absence of these oxidation products can often be mistaken for chemical reduction of NOx. In this paper the authors will examine the gas-phase chemical reduction of NOx. They will show that under the best conditions, the plasma can chemically reduce 1.6 grams of NOx per brake-horsepower-hour [g(NOx)/bhp-hr] when 5% of the engine output energy is delivered to the plasma.

  9. Detection methods for atoms and radicals in the gas phase

    Science.gov (United States)

    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.

  10. Importance of the gas phase role to the prediction of energetic material behavior: An experimental study

    International Nuclear Information System (INIS)

    Ali, A.N.; Son, S.F.; Asay, B.W.; Sander, R.K.

    2005-01-01

    Various thermal (radiative, conductive, and convective) initiation experiments are performed to demonstrate the importance of the gas phase role in combustion modeling of energetic materials (EM). A previously published condensed phase model that includes a predicted critical irradiance above which ignition is not possible is compared to experimental laser ignition results for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 2,4,6-trinitrotoluene (TNT). Experimental results conflict with the predicted critical irradiance concept. The failure of the model is believed to result from a misconception about the role of the gas phase in the ignition process of energetic materials. The model assumes that ignition occurs at the surface and that evolution of gases inhibits ignition. High speed video of laser ignition, oven cook-off and hot wire ignition experiments captures the ignition of HMX and TNT in the gas phase. A laser ignition gap test is performed to further evaluate the effect of gas phase laser absorption and gas phase disruption on the ignition process. Results indicate that gas phase absorption of the laser energy is probably not the primary factor governing the gas phase ignition observations. It is discovered that a critical gap between an HMX pellet and a salt window of 6 mm±0.4 mm exists below which ignition by CO 2 laser is not possible at the tested irradiances of 29 W/cm 2 and 38 W/cm 2 for HMX ignition. These observations demonstrate that a significant disruption of the gas phase, in certain scenarios, will inhibit ignition, independent of any condensed phase processes. These results underscore the importance of gas phase processes and illustrate that conditions can exist where simple condensed phase models are inadequate to accurately predict the behavior of energetic materials

  11. Importance of the gas phase role to the prediction of energetic material behavior: An experimental study

    Science.gov (United States)

    Ali, A. N.; Son, S. F.; Asay, B. W.; Sander, R. K.

    2005-03-01

    Various thermal (radiative, conductive, and convective) initiation experiments are performed to demonstrate the importance of the gas phase role in combustion modeling of energetic materials (EM). A previously published condensed phase model that includes a predicted critical irradiance above which ignition is not possible is compared to experimental laser ignition results for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 2,4,6-trinitrotoluene (TNT). Experimental results conflict with the predicted critical irradiance concept. The failure of the model is believed to result from a misconception about the role of the gas phase in the ignition process of energetic materials. The model assumes that ignition occurs at the surface and that evolution of gases inhibits ignition. High speed video of laser ignition, oven cook-off and hot wire ignition experiments captures the ignition of HMX and TNT in the gas phase. A laser ignition gap test is performed to further evaluate the effect of gas phase laser absorption and gas phase disruption on the ignition process. Results indicate that gas phase absorption of the laser energy is probably not the primary factor governing the gas phase ignition observations. It is discovered that a critical gap between an HMX pellet and a salt window of 6mm±0.4mm exists below which ignition by CO2 laser is not possible at the tested irradiances of 29W /cm2 and 38W/cm2 for HMX ignition. These observations demonstrate that a significant disruption of the gas phase, in certain scenarios, will inhibit ignition, independent of any condensed phase processes. These results underscore the importance of gas phase processes and illustrate that conditions can exist where simple condensed phase models are inadequate to accurately predict the behavior of energetic materials.

  12. Connecting long term species changes and their water competitions in temperate forest Mt. Baegun, Rep. of Korea using hydrogen and oxygen stable isotope analysis

    Science.gov (United States)

    Jeon, J.; Lee, H.; Lee, M.; Song, W.; Byeon, S.; Lee, B.; Cho, S.; Park, J.; Kim, H. S.

    2017-12-01

    Many dynamic vegetation model simulations have predicted dramatic changes in species composition of temperate forests due to climate changes and successional reasons. Especially, conifer species are expected to lose their habitats and to be replaced by broadleaf species. Similarly, our more than 15-years-long 880 permenant plots tree survey data in Mt. Baegun, Rep. of Korea, showed substantial decrease of conifer species and their productivities and increase of broadleaved species. One of main reasons for these changes in species could be attributed to the water competition among tree species in the same stand. Therefore, we investigated the differences in water uptake scheme between conifer and broadleaf species from the temperate forests of Korea using stable isotopes. Six study plots showing high competition (conifers vs. broadleaf species) based on previous vegetation survey were chosen and the species-specific water uptake depth was estimated by measuring hydrogen(δ2H) and oxygen(δ18O) ratio from the xylem sap and leaves of individual species and by comparing them with those of soil water from 5 depths, (10, 30, 50, 100 and 120 cm), which extracted by lysimeter. The collection was conducted from April 2016 to Nov 2017. The conifer species included Pinus densiflora and Chamaecyparis obtusa vs. broadleaved species included Carpinus laxiflora, Prunus sargentii, Styrax obassia, Lindera erythrocarpa and Quercus species such as Q. mongolica, Q. serrata, Q. accuticima. Preliminary results showed the stable isotope signatures of soil water was increased from 10 cm to 30 cm, and then decreased gradually until 120 cm. In addition, current dominant canopy species, Chamaecyparis obtusa absorbed majority of their water from 10 to 30 cm depth. In comparison, current mid canopy but one of upcoming dominant species, Styrax obassia's major water source was 30 cm and deeper of soil. Our results could be essential for the prediction of species composition under climate change

  13. Protein and Peptide Gas-phase Structure Investigation Using Collision Cross Section Measurements and Hydrogen Deuterium Exchange

    Science.gov (United States)

    Khakinejad, Mahdiar

    Protein and peptide gas-phase structure analysis provides the opportunity to study these species outside of their explicit environment where the interaction network with surrounding molecules makes the analysis difficult [1]. Although gas-phase structure analysis offers a unique opportunity to study the intrinsic behavior of these biomolecules [2-4], proteins and peptides exhibit very low vapor pressures [2]. Peptide and protein ions can be rendered in the gas-phase using electrospray ionization (ESI) [5]. There is a growing body of literature that shows proteins and peptides can maintain solution structures during the process of ESI and these structures can persist for a few hundred milliseconds [6-9]. Techniques for monitoring gas-phase protein and peptide ion structures are categorized as physical probes and chemical probes. Collision cross section (CCS) measurement, being a physical probe, is a powerful method to investigate gas-phase structure size [3, 7, 10-15]; however, CCS values alone do not establish a one to one relation with structure(i.e., the CCS value is an orientationally averaged value [15-18]. Here we propose the utility of gas-phase hydrogen deuterium exchange (HDX) as a second criterion of structure elucidation. The proposed approach incudes extensive MD simulations to sample biomolecular ion conformation space with the production of numerous, random in-silico structures. Subsequently a CCS can be calculated for these structures and theoretical CCS values are compared with experimental values to produce a pool of candidate structures. Utilizing a chemical reaction model based on the gas-phase HDX mechanism, the HDX kinetics behavior of these candidate structures are predicted and compared to experimental results to nominate the best in-silico structures which match (chemically and physically) with experimental observations. For the predictive approach to succeed, an extensive technique and method development is essential. To combine CCS

  14. Intermolecular interactions of trifluorohalomethanes with Lewis bases in the gas phase: an ab initio study.

    Science.gov (United States)

    Wang, Yi-Siang; Yin, Chih-Chien; Chao, Sheng D

    2014-10-07

    We perform an ab initio computational study of molecular complexes with the general formula CF3X-B that involve one trifluorohalomethane CF3X (X = Cl or Br) and one of a series of Lewis bases B in the gas phase. The Lewis bases are so chosen that they provide a range of electron-donating abilities for comparison. Based on the characteristics of their electron pairs, we consider the Lewis bases with a single n-pair (NH3 and PH3), two n-pairs (H2O and H2S), two n-pairs with an unsaturated bond (H2CO and H2CS), and a single π-pair (C2H4) and two π-pairs (C2H2). The aim is to systematically investigate the influence of the electron pair characteristics and the central atom substitution effects on the geometries and energetics of the formed complexes. The counterpoise-corrected supermolecule MP2 and coupled-cluster single double with perturbative triple [CCSD(T)] levels of theory have been employed, together with a series of basis sets up to aug-cc-pVTZ. The angular and radial configurations, the binding energies, and the electrostatic potentials of the stable complexes have been compared and discussed as the Lewis base varies. For those complexes where halogen bonding plays a significant role, the calculated geometries and energetics are consistent with the σ-hole model. Upon formation of stable complexes, the C-X bond lengths shorten, while the C-X vibrational frequencies increase, thus rendering blueshifting halogen bonds. The central atom substitution usually enlarges the intermolecular bond distances while it reduces the net charge transfers, thus weakening the bond strengths. The analysis based on the σ-hole model is grossly reliable but requires suitable modifications incorporating the central atom substitution effects, in particular, when interaction components other than electrostatic contributions are involved.

  15. Gas-phase thermal dissociation of uranium hexafluoride: Investigation by the technique of laser-powered homogeneous pyrolysis

    International Nuclear Information System (INIS)

    Bostick, W.D.; McCulla, W.H.; Trowbridge, L.D.

    1987-04-01

    In the gas-phase, uranium hexafluoride decomposes thermally in a quasi-unimolecular reaction to yield uranium pentafluoride and atomic fluorine. We have investigated this reaction using the relatively new technique of laser-powered homogeneous pyrolysis, in which a megawatt infrared laser is used to generate short pulses of high gas temperatures under strictly homogeneous conditions. In our investigation, SiF 4 is used as the sensitizer to absorb energy from a pulsed CO 2 laser and to transfer this energy by collisions with the reactant gas. Ethyl chloride is used as an external standard ''thermometer'' gas to permit estimation of the unimolecular reaction rate constants by a relative rate approach. When UF 6 is the reactant, CF 3 Cl is used as reagent to trap atomic fluorine reaction product, forming CF 4 as a stable indicator which is easily detected by infrared spectroscopy. Using these techniques, we estimate the UF 6 unimolecular reaction rate constant near the high-pressure limit. In the Appendix, we describe a computer program, written for the IBM PC, which predicts unimolecular rate constants based on the Rice-Ramsperger-Kassel theory. Parameterization of the theoretical model is discussed, and recommendations are made for ''appropriate'' input parameters for use in predicting the gas-phase unimolecular reaction rate for UF 6 as a function of temperature and gas composition and total pressure. 85 refs., 17 figs., 14 tabs

  16. Gas-phase water-mediated equilibrium between methylglyoxal and its geminal diol

    Science.gov (United States)

    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

  17. Collision induced dissociation of protonated N-nitrosodimethylamine by ion trap mass spectrometry: Ultimate carcinogens in gas phase

    Science.gov (United States)

    Kulikova, Natalia; Baker, Michael; Gabryelski, Wojciech

    2009-12-01

    Collision induced dissociation of protonated N-nitrosodimethylamine (NDMA) and isotopically labeled N-nitrosodimethyl-d6-amine (NDMA-d6) was investigated by sequential ion trap mass spectrometry to establish mechanisms of gas phase reactions leading to intriguing products of this potent carcinogen. The fragmentation of (NDMA + H+) occurs via two dissociation pathways. In the alkylation pathway, homolytic cleavage of the N-O bond of N-dimethyl, N'-hydroxydiazenium ion generates N-dimethyldiazenium distonic ion which reacts further by a CH3 radical loss to form methanediazonium ion. Both methanediazonium ion and its precursor are involved in ion/molecule reactions. Methanediazonium ion showed to be capable of methylating water and methanol molecules in the gas phase of the ion trap and N-dimethyldiazenium distonic ion showed to abstract a hydrogen atom from a solvent molecule. In the denitrosation pathway, a tautomerization of N-dimethyl, N'-hydroxydiazenium ion to N-nitrosodimethylammonium intermediate ion results in radical cleavage of the N-N bond of the intermediate ion to form N-dimethylaminium radical cation which reacts further through [alpha]-cleavage to generate N-methylmethylenimmonium ion. Although the reactions of NDMA in the gas phase are different to those for enzymatic conversion of NDMA in biological systems, each activation method generates the same products. We will show that collision induced dissociation of N-nitrosodiethylamine (NDEA) and N-nitrosodipropylamine (NDPA) is also a feasible approach to gain information on formation, stability, and reactivity of alkylating agents originating from NDEA and NDPA. Investigating such biologically relevant, but highly reactive intermediates in the condensed phase is hampered by the short life-times of these transient species.

  18. Gas-phase evolution of Ar/H2O and Ar/CH4 dielectric barrier discharge plasmas

    Science.gov (United States)

    Barni, Ruggero; Riccardi, Claudia

    2018-04-01

    We present some experimental results of an investigation aimed to hydrogen production with atmospheric pressure plasmas, based on the use of dielectric barrier discharges, fed with a high-voltage alternating signal at frequency 30-50 kHz, in mixtures of methane or water vapor diluted in argon. The plasma gas-phase of the discharge was investigated by means of optical and electrical diagnostics. The emission spectra of the discharges was measured with a wide band spectrometer and a photosensor module, based on a photomultiplier tube. A Rogowski coil allowed to measure the electric current flowing into the circuit and a high voltage probe was employed for evaluating the voltage at the electrodes. The analysis of the signals of voltage and current shows the presence of microdischarges between the electrodes in two alternating phases during the period of oscillation of the applied voltage. The hydrogen concentration in the gaseous mixture was measured too. Besides this experimental campaign, we present also results from a numerical modeling of chemical kinetics in the gas-phase of Ar/H2O and Ar/CH4 plasmas. The simulations were conducted under conditions of single discharge to study the evolution of the system and of fixed frequency repeated discharging. In particular in Ar/H2O mixtures we could study the evolution from early atomic dissociation in the discharge, to longer time scales, when chemical reactions take place producing an increase of the density of species such as OH, H2O2 and subsequently of H and H2. The results of numerical simulations provide some insights into the evolution happening in the plasma gas-phase during the hydrogen reforming process.

  19. Gas-phase Absorptions of {{\\rm{C}}}_{42}{{\\rm{H}}}_{18}^{+} near 8300 Å below 10 K: Astronomical Implications

    Science.gov (United States)

    Campbell, E. K.; Maier, J. P.

    2017-11-01

    The gas-phase electronic spectrum of {{{C}}}42{{{H}}}18+ ({{HBC}}+) with an origin band at 8281 \\mathringA has been measured below 10 {{K}} by photofragmentation of helium complexes ({{{C}}}42{{{H}}}18+{--}{{He}}n) in a radiofrequency trap. {{HBC}}+ is a medium-sized polycyclic aromatic hydrocarbon (PAH) cation, and using an ion trapping technique it has been possible to record a high-quality gas-phase spectrum to directly compare with astronomical observations. No diffuse interstellar bands (DIBs) have been reported at the wavelengths of the strongest absorption bands in the {{{C}}}42{{{H}}}18+ spectrum. Measurement of absolute absorption cross sections in the ion trap allows upper limits to the column density of this ion to be {10}12 {{cm}}-2, indicating that even PAH cations of this size, which are believed to be stable in the interstellar medium, should be excluded as candidates for at least the strong DIBs.

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

    Science.gov (United States)

    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

  1. Gas phase ion/molecule reactions as studied by Fourier Transform Ion Cyclotron Resonance mass spectrometry

    International Nuclear Information System (INIS)

    Joergensen, S.I.

    1985-01-01

    The subject of this thesis is gas phase ion/molecule reactions as studied by Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry (chapter 2 contains a short description of this method). Three chapters are mainly concerned with mechanistic aspects of gas phase ion/molecule reactions. An equally important aspect of the thesis is the stability and reactivity of α-thio carbanions, dipole stabilized carbanions and homoenolate anions, dealt with in the other four chapters. (Auth.)

  2. An atmospheric pressure flow reactor: Gas phase kinetics and mechanism in tropospheric conditions without wall effects

    Science.gov (United States)

    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.

  3. Defect formation in fluoropolymer films at their condensation from a gas phase

    Science.gov (United States)

    Luchnikov, P. A.

    2018-01-01

    The questions of radiation defects, factors of influence of electronic high-frequency discharge plasma components on the molecular structure and properties of the fluoropolymer vacuum films synthesized on a substrate from a gas phase are considered. It is established that at sedimentation of fluoropolymer coverings from a gas phase in high-frequency discharge plasma in films there are radiation defects in molecular and supramolecular structure because of the influence of active plasma components which significantly influence their main properties.

  4. Ultrafast electronic relaxation of excited state vitamin B12 in the gas phase

    International Nuclear Information System (INIS)

    Shafizadeh, Niloufar; Poisson, Lionel; Soep, Benoit

    2008-01-01

    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

  5. Wigner Distribution Functions as a Tool for Studying Gas Phase Alkali Metal Plus Noble Gas Collisions

    Science.gov (United States)

    2014-03-27

    WIGNER DISTRIBUTION FUNCTIONS AS A TOOL FOR STUDYING GAS PHASE ALKALI METAL PLUS NOBLE GAS COLLISIONS THESIS Keith A. Wyman, Second Lieutenant, USAF...the U.S. Government and is not subject to copyright protection in the United States. AFIT-ENP-14-M-39 WIGNER DISTRIBUTION FUNCTIONS AS A TOOL FOR...APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED AFIT-ENP-14-M-39 WIGNER DISTRIBUTION FUNCTIONS AS A TOOL FOR STUDYING GAS PHASE ALKALI METAL PLUS

  6. A new method for determining gas phase heat of formation of aromatic energetic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Keshavarz, Mohammad H. [Department of Chemistry, Malek-ashtar University of Technology, Shahin-shahr P. O. Box 83145/115 (Iran); Tehrani, Masoud K. [Department of Physics, Malek-ashtar University of Technology, Shahin-shahr P. O. Box 83145/115 (Iran)

    2007-04-15

    A new correlation is introduced for desk calculation of gas phase heat of formation of aromatic energetic compounds that contain the elements of carbon, hydrogen, nitrogen and oxygen. Predicted gas phase heats of formation for 26 energetic compounds have a root mean square of deviation from experiment of 20.67 kJ/mol, which is in good agreement with respect to measured values of oxygen-lean and oxygen-rich aromatic energetic compounds. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  7. Molecular structure determination of cyclootane by ab initio and electron diffraction methods in the gas phase

    OpenAIRE

    De Almeida, Wagner B.

    2000-01-01

    The determination of the molecular structure of molecules is of fundamental importance in chemistry. X-rays and electron diffraction methods constitute in important tools for the elucidation of the molecular structure of systems in the solid state and gas phase, respectively. The use of quantum mechanical molecular orbital ab initio methods offer an alternative for conformational analysis studies. Comparison between theoretical results and those obtained experimentally in the gas phase can ma...

  8. Time-resolved EPR study of singlet oxygen in the gas phase.

    Science.gov (United States)

    Ruzzi, Marco; Sartori, Elena; Moscatelli, Alberto; Khudyakov, Igor V; Turro, Nicholas J

    2013-06-27

    X-band EPR spectra of singlet O2((1)Δg) and triplet O2((3)Σg(-)) were observed in the gas phase under low molecular-oxygen pressures PO2 = 0.175-0.625 Torr, T = 293-323 K. O2((1)Δg) was produced by quenching of photogenerated triplet sensitizers naphthalene C8H10, perdeuterated naphthalene, and perfluoronaphthalene in the gas phase. The EPR spectrum of O2((1)Δg) was also observed under microwave discharge. Integrated intensities and line widths of individual components of the EPR spectrum of O2((3)Σg(-)) were used as internal standards for estimating the concentration of O2 species and PO2 in the EPR cavity. Time-resolved (TR) EPR experiments of C8H10 were the main focus of this Article. Pulsed irradiation of C8H10 in the presence of O2((3)Σg(-)) allowed us to determine the kinetics of formation and decay for each of the four components of the O2((1)Δg) EPR signal, which lasted for only a few seconds. We found that the kinetics of EPR-component decay fit nicely to a biexponential kinetics law. The TR EPR 2D spectrum of the third component of the O2((1)Δg) EPR spectrum was examined in experiments using C8H10. This spectrum vividly presents the time evolution of an EPR component. The largest EPR signal and the longest lifetime of O2((1)Δg), τ = 0.4 s, were observed at medium pressure PO2 = 0.4 Torr, T = 293 K. The mechanism of O2((1)Δg) decay in the presence of photosensitizers is discussed. EPR spectra of O2((1)Δg) evidence that the spin-rotational states of O2((1)Δg) are populated according to Boltzmann distribution in the studied time range of 10-100 ms. We believe that this is the first report dealing with the dependence of O2((1)Δg) EPR line width on PO2 and T.

  9. Advanced Laser-Based Techniques for Gas-Phase Diagnostics in Combustion and Aerospace Engineering.

    Science.gov (United States)

    Ehn, Andreas; Zhu, Jiajian; Li, Xuesong; Kiefer, Johannes

    2017-03-01

    Gaining information of species, temperature, and velocity distributions in turbulent combustion and high-speed reactive flows is challenging, particularly for conducting measurements without influencing the experimental object itself. The use of optical and spectroscopic techniques, and in particular laser-based diagnostics, has shown outstanding abilities for performing non-intrusive in situ diagnostics. The development of instrumentation, such as robust lasers with high pulse energy, ultra-short pulse duration, and high repetition rate along with digitized cameras exhibiting high sensitivity, large dynamic range, and frame rates on the order of MHz, has opened up for temporally and spatially resolved volumetric measurements of extreme dynamics and complexities. The aim of this article is to present selected important laser-based techniques for gas-phase diagnostics focusing on their applications in combustion and aerospace engineering. Applicable laser-based techniques for investigations of turbulent flows and combustion such as planar laser-induced fluorescence, Raman and Rayleigh scattering, coherent anti-Stokes Raman scattering, laser-induced grating scattering, particle image velocimetry, laser Doppler anemometry, and tomographic imaging are reviewed and described with some background physics. In addition, demands on instrumentation are further discussed to give insight in the possibilities that are offered by laser flow diagnostics.

  10. Gas-phase Dehydration of Glycerol over Supported Silicotungstic Acids Catalysts

    International Nuclear Information System (INIS)

    Kim, Yong Tae; Park, Eun Duck; Jung, Kwang Deog

    2010-01-01

    The gas-phase dehydration of glycerol to acrolein was carried out over 10 wt % HSiW catalysts supported on different supports, viz. γ-Al 2 O 3 , SiO 2 -Al 2 O 3 , TiO 2 , ZrO 2 , SiO 2 , AC, CeO 2 and MgO. The same reaction was also conducted over each support without HSiW for comparison. Several characterization techniques, N 2 -physisorption, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), the temperature-programmed desorption of ammonia (NH 3 - TPD), temperature-programmed oxidation (TPO) with mass spectroscopy and CHNS analysis were employed to characterize the catalysts. The glycerol conversion generally increased with increasing amount of acid sites. Ceria showed the highest 1-hydroxyacetone selectivity at 315 .deg. C among the various metal oxides. The supported HSiW catalyst showed superior catalytic activity to that of the corresponding support. Among the supported HSiW catalysts, HSiW/ZrO 2 and HSiW/SiO 2 -Al 2 O 3 showed the highest acrolein selectivity. In the case of HSiW/ZrO 2 , the initial catalytic activity was recovered after the removal of the accumulated carbon species at 550 .deg. C in the presence of oxygen

  11. GAS-PHASE CHEMISTRY OF THE CYANATE ION, OCN{sup −}

    Energy Technology Data Exchange (ETDEWEB)

    Cole, Callie A.; Wang, Zhe-Chen; Bierbaum, Veronica M. [Department of Chemistry and Biochemistry, 215 UCB, University of Colorado, Boulder, CO 80309 (United States); Snow, Theodore P. [Center for Astrophysics and Space Astronomy, 389 UCB, University of Colorado, Boulder, CO 80309 (United States)

    2015-10-10

    Cyanate (OCN{sup −}) 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{sup −} 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{sup −} 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{sup −}. 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{sup −} as a biomolecule precursor.

  12. Application of near ambient pressure gas-phase X-ray photoelectron spectroscopy to the investigation of catalytic properties of copper in methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Prosvirin, Igor P., E-mail: prosvirin@catalysis.ru [Boreskov Institute of Catalysis, Lavrentieva ave. 5, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk (Russian Federation); Bukhtiyarov, Andrey V., E-mail: avb@catalysis.ru [Boreskov Institute of Catalysis, Lavrentieva ave. 5, 630090 Novosibirsk (Russian Federation); Research and Educational Center for Energy Efficient Catalysis, Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk (Russian Federation); Bluhm, Hendrik, E-mail: hbluhm@lbl.gov [Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Bukhtiyarov, Valerii I., E-mail: vib@catalysis.ru [Boreskov Institute of Catalysis, Lavrentieva ave. 5, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk (Russian Federation); Research and Educational Center for Energy Efficient Catalysis, Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk (Russian Federation)

    2016-02-15

    Graphical abstract: - Highlights: • Selective oxidation of CH{sub 3}OH to CH{sub 2}O over a Cu foil has been studied by in situ gas phase XPS. • C1s and O1s spectra were used for identification of reagents and reaction products in a gas phase. • Catalytic data (conversions and reaction products yields) calculated from XPS spectra are in a good agreement with QMS results. • The possible reasons of the observed variations in reaction mechanism have been discussed. - Abstract: Application of near ambient pressure (NAP) X-ray photoelectron spectroscopy for characterization of catalytic properties of a heterogeneous catalyst through measurement and analysis of the core-level spectra from gas phase constituents, which become measurable in submillibar pressure range, has been demonstrated for the reaction of methanol oxidation over polycrystalline copper foil. To improve the accuracy of quantitative analysis of the gas phase signals for the routine XPS spectrometer with double Al/Mg anode used in these experiments, the sample was removed from XPS analysis zone, but it was still located in high-pressure gas cell. As consequence, only gas phase peaks from reagents and reaction products have been observed in XPS spectra. Quantitative analysis of the spectra has allowed us to calculate conversions of the reagents and yields of the reaction products, or, other words, to characterize the catalytic properties of the catalyst and to track their changes with temperature. Further comparison of the catalytic properties with concentration of the surface species measured by in situ XPS in separate experiments, but under the same conditions, gives a possibility to discuss the reaction mechanisms.

  13. CW EPR and 9 GHz EPR imaging investigation of stable paramagnetic species and their antioxidant activities in dry shiitake mushroom (Lentinus edodes).

    Science.gov (United States)

    Nakagawa, Kouichi; Hara, Hideyuki

    2016-01-01

    We investigated the antioxidant activities and locations of stable paramagnetic species in dry (or drying) shiitake mushroom (Lentinus edodes) using continuous wave (CW) electron paramagnetic resonance (EPR) and 9 GHz EPR imaging. CW 9 GHz EPR detected paramagnetic species (peak-to-peak linewidth (ΔHpp) = 0.57 mT) in the mushroom. Two-dimensional imaging of the sharp line using a 9 GHz EPR imager showed that the species were located in the cap and shortened stem portions of the mushroom. No other location of the species was found in the mushroom. However, radical locations and concentrations varied along the cap of the mushroom. The 9 GHz EPR imaging determined the exact location of stable paramagnetic species in the shiitake mushroom. Distilled water extracts of the pigmented cap surface and the inner cap of the mushroom showed similar antioxidant activities that reduced an aqueous solution of 0.1 mM 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl. The present results suggest that the antioxidant activities of the edible mushroom extracts are much weaker than those of ascorbic acid. Thus, CW EPR and EPR imaging revealed the location and distribution of stable paramagnetic species and the antioxidant activities in the shiitake mushroom for the first time.

  14. Activation of methane by zinc: gas-phase synthesis, structure, and bonding of HZnCH3.

    Science.gov (United States)

    Flory, Michael A; Apponi, Aldo J; Zack, Lindsay N; Ziurys, Lucy M

    2010-12-08

    The methylzinc hydride molecule, HZnCH3, has been observed in the gas phase for the first time in the monomeric form using high-resolution spectroscopic techniques. The molecule was synthesized by two methods: the reaction of dimethylzinc with hydrogen gas and methane in an AC discharge and the reaction of zinc vapor produced in a Broida-type oven with methane in a DC discharge. HZnCH3 was identified on the basis of its pure rotational spectrum, which was recorded using millimeter/submillimeter direct-absorption and Fourier transform microwave techniques over the frequency ranges 332-516 GHz and 18-41 GHz, respectively. Multiple rotational transitions were measured for this molecule in seven isotopic variants. K-ladder structure was clearly present in all of the spectra, indicating a molecule with C3v symmetry and a (1)A1 ground electronic state. Extensive quadrupole hyperfine structure arising from the (67)Zn nucleus was observed for the H(67)ZnCH3 species, suggesting covalent bonding to the zinc atom. From the multiple isotopic substitutions, a precise structure for HZnCH3 has been determined. The influence of the axial hydrogen atom slightly distorts the methyl group but stabilizes the Zn-C bond. This study suggests that HZnCH3 can be formed through the oxidative addition of zinc to methane in the gas phase under certain conditions. HZnCH3 is the first metal-methane insertion complex to be structurally characterized.

  15. Ion Mobility Spectrometry-Mass Spectrometry Coupled with Gas-Phase Hydrogen/Deuterium Exchange for Metabolomics Analyses

    Science.gov (United States)

    Maleki, Hossein; Karanji, Ahmad K.; Majuta, Sandra; Maurer, Megan M.; Valentine, Stephen J.

    2018-02-01

    Ion mobility spectrometry-mass spectrometry (IMS-MS) in combination with gas-phase hydrogen/deuterium exchange (HDX) and collision-induced dissociation (CID) is evaluated as an analytical method for small-molecule standard and mixture characterization. Experiments show that compound ions exhibit unique HDX reactivities that can be used to distinguish different species. Additionally, it is shown that gas-phase HDX kinetics can be exploited to provide even further distinguishing capabilities by using different partial pressures of reagent gas. The relative HDX reactivity of a wide variety of molecules is discussed in light of the various molecular structures. Additionally, hydrogen accessibility scoring (HAS) and HDX kinetics modeling of candidate ( in silico) ion structures is utilized to estimate the relative ion conformer populations giving rise to specific HDX behavior. These data interpretation methods are discussed with a focus on developing predictive tools for HDX behavior. Finally, an example is provided in which ion mobility information is supplemented with HDX reactivity data to aid identification efforts of compounds in a metabolite extract.

  16. Use of gas-phase ethanol to mitigate extreme UV/water oxidation of extreme UV optics

    Science.gov (United States)

    Klebanoff, L. E.; Malinowski, M. E.; Clift, W. M.; Steinhaus, C.; Grunow, P.

    2004-03-01

    A technique is described that uses a gas-phase species to mitigate the oxidation of a Mo/Si multilayer optic caused by either extreme UV (EUV) or electron-induced dissociation of adsorbed water vapor. It is found that introduction of ethanol (EtOH) into a water-rich gas-phase environment inhibits oxidation of the outermost Si layer of the Mo/Si EUV reflective coating. Auger electron spectroscopy, sputter Auger depth profiling, EUV reflectivity, and photocurrent measurements are presented that reveal the EUV/water- and electron/water-derived optic oxidation can be suppressed at the water partial pressures used in the tests (~2×10-7-2×10-5 Torr). The ethanol appears to function differently in two time regimes. At early times, ethanol decomposes on the optic surface, providing reactive carbon atoms that scavenge reactive oxygen atoms before they can oxidize the outermost Si layer. At later times, the reactive carbon atoms form a thin (~5 Å), possibly self-limited, graphitic layer that inhibits water adsorption on the optic surface. .

  17. Theoretical investigation of the long-lived metastable AlO{sup 2+} dication in gas phase

    Energy Technology Data Exchange (ETDEWEB)

    Sghaier, Onsi [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée (France); Abdallah, Hassan H. [Computational Nanotechnology Research Lab. CNRL, Salahaddin University, 44001 Erbil (Iraq); Department of Chemistry, College of Education, Salahaddin University, 44001 Erbil (Iraq); Abdullah, Hewa Y. [Computational Nanotechnology Research Lab. CNRL, Salahaddin University, 44001 Erbil (Iraq); Department of Physics, College of Education, Salahaddin University, 44001 Erbil (Iraq); Jaidane, Nejm Eddine [Laboratoire de Spectroscopie Atomique, Moléculaire et Applications – LSAMA, Université de Tunis, Tunis (Tunisia); Al Mogren, Muneerah Mogren [Chemistry Department, Faculty of Science, King Saud University, PO Box 2455, Riyadh 11451 (Saudi Arabia); Hochlaf, Majdi, E-mail: hochlaf@univ-mlv.fr [Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallée (France)

    2016-09-30

    Highlights: • Theoretical investigation of gas-phase molecular species AlO{sup 2+}. • Spectroscopic parameters of this dication in its electronic ground and exited states. • Theoretical double ionization spectrum of AlO. - Abstract: We report the results of a detailed theoretical study of the electronic ground and excited states of the gas-phase doubly charged ion AlO{sup 2+} using high-level ab initio computer calculations. Both standard and explicitly correlated methods were used to calculate their potential energy curves and spectroscopic parameters. These computations show that the ground state of AlO{sup 2+} is X{sup 2}Π. The internuclear equilibrium distance of AlO{sup 2+}(X{sup 2}Π) is computed 1.725 Å. We also deduced the adiabatic double ionization and charge stripping energies of AlO to be about 27.45 eV and 17.80 eV, respectively.

  18. Comprehensive Peptide Ion Structure Studies Using Ion Mobility Techniques: Part 3. Relating Solution-Phase to Gas-Phase Structures.

    Science.gov (United States)

    Kondalaji, Samaneh Ghassabi; Khakinejad, Mahdiar; Valentine, Stephen J

    2018-06-01

    Molecular dynamics (MD) simulations have been utilized to study peptide ion conformer establishment during the electrospray process. An explicit water model is used for nanodroplets containing a model peptide and hydronium ions. Simulations are conducted at 300 K for two different peptide ion charge configurations and for droplets containing varying numbers of hydronium ions. For all conditions, modeling has been performed until production of the gas-phase ions and the resultant conformers have been compared to proposed gas-phase structures. The latter species were obtained from previous studies in which in silico candidate structures were filtered according to ion mobility and hydrogen-deuterium exchange (HDX) reactivity matches. Results from the present study present three key findings namely (1) the evidence from ion production modeling supports previous structure refinement studies based on mobility and HDX reactivity matching, (2) the modeling of the electrospray process is significantly improved by utilizing initial droplets existing below but close to the calculated Rayleigh limit, and (3) peptide ions in the nanodroplets sample significantly different conformers than those in the bulk solution due to altered physicochemical properties of the solvent. Graphical Abstract ᅟ.

  19. The trophic ecology of key megafaunal species at the Pakistan Margin: Evidence from stable isotopes and lipid biomarkers

    Science.gov (United States)

    Jeffreys, Rachel M.; Wolff, George A.; Murty, Sarah J.

    2009-10-01

    The Arabian Sea is subject to intense seasonality resulting from biannual monsoons, which lead to associated large particulate fluxes and an abundance of organic carbon, a potential food source at the seafloor for benthic detritivores. We used the stable isotopes of carbon and nitrogen alongside lipid analyses to examine potential food sources (particulate and sedimentary organic matter, POM and SOM respectively) in order to determine trophic linkages for the twelve most abundant megafaunal species ( Pontocaris sp., Solenocera sp., Munidopsis aff. scobina, Actinoscyphia sp., Actinauge sp., Echinoptilum sp., Pennatula aff. grandis, Astropecten sp. Amphiura sp. Ophiura euryplax, Phormosoma placenta and Hyalinoecia sp.) at the Pakistan Margin between 140 and 1400 m water depth. This transect spans a steep gradient in oxygen concentrations and POM flux. Ranges of δ 13C and δ 15N values were narrow in POM and SOM (˜4‰ and ˜2‰ for δ 13C and δ 15N, respectively) with little evidence of temporal variability. Labile lipid compounds in SOM originating from phytoplankton did exhibit seasonal change in their concentrations at the shallowest sites, 140 and 300 m. Benthic megafauna had broad ranges in δ 13C and δ 15N (>10‰ and >8‰ for δ 13C and δ 15N, respectively) suggesting they occupy several trophic levels and utilize a variety of food sources. There is evidence for feeding niche separation between and within trophic groups. Lipid biomarkers in animal tissues indicate a mixture of food sources originating from both phytoplankton (C 20:5(n-3) and C 22:6(n-3)) and invertebrate prey (C 20:1 and C 22:1). Biomarkers originating from phytodetritus are conserved through trophic transfer to the predator/scavengers. Six species ( Pontocaris sp., Solenocera sp., Actinoscyphia sp., Echinoptilum sp., Amphiura sp. and Hyalinoecia sp.) showed a significant biochemical response to the seasonal supply of food and probably adapt their trophic strategy to low food

  20. DFT Study of dimers of dimethyl sulfoxide in gas phase

    Directory of Open Access Journals (Sweden)

    Reza Fazaeli

    2014-10-01

    Full Text Available Density functional (DFT calculations at M05-2x/aug-cc-pVDZ level were used to analyze the interactions between dimethyl sulfoxide (DMSO dimers. The structures obtained have been ana-lyzed with the Atoms in Molecules (AIMs and Natural Bond Orbital (NBO methodologies. Four minima were located on the potential energy surface of the dimers. Three types of interac-tions are observed, CH•••O, CH•••S hydrogen bonds and orthogonal interaction between the lone pair of the oxygen with the electron-deficient region of the sulfur atom. Stabilization energies of dimers including BSSE and ZPE are in the range 27–40 kJmol-1. The most stable conformers of dimers at DFT level is cyclic structure with antiparallel orientation of S=O groups pairing with three C–H∙∙∙O and a S∙∙∙O interactions.

  1. Spectroscopic studies of molecular iodine emitted into the gas phase by seaweed

    Directory of Open Access Journals (Sweden)

    S. M. Ball

    2010-07-01

    Full Text Available Time profiles of molecular iodine emissions from seven species of seaweed have been measured at high time resolution (7.5 s by direct spectroscopic quantification of the gas phase I2 using broadband cavity enhanced absorption spectroscopy. Substantial differences were found between species, both in the amounts of I2 emitted when the plants were exposed to air and in the shapes of their emission time profiles. Two species of kelp, Laminaria digitata and Laminaria hyperborea, were found to be the most potent emitters, producing an intense burst of I2 when first exposed to air. I2 was also observed from Saccharina latissima and Ascophyllum nodosum but in lower amounts and with broader time profiles. I2 mixing ratios from two Fucus species and Dictyopteris membranacea were at or below the detection limit of the present instrument (25 pptv. A further set of experiments investigated the time dependence of I2 emissions and aerosol particle formation when fragments of L. digitata were exposed to desiccation in air, to ozone and to oligoguluronate stress factors. Particle formation occurred in all L. digitata stress experiments where ozone and light were present, subject to the I2 mixing ratios being above certain threshold amounts. Moreover, the particle number concentrations closely tracked variations in the I2 mixing ratios, confirming the results of previous studies that the condensable particle-forming gases derive from the photochemical oxidation of the plant's I2 emissions. This work also supports the theory that particle nucleation in the coastal atmosphere occurs in "hot-spot" regions of locally elevated concentrations of condensable gases: the greatest atmospheric concentrations of I2 and hence of condensable iodine oxides are likely to be above plants of the most efficiently

  2. Stable isotope investigation of insect and plant use in the diets of two Puerto Rican bat species

    Science.gov (United States)

    We used stable isotope (δ13C, δ15N) analysis to estimate the importance of plants and insects to the diet of two nectar-feeding bats on Puerto Rico, the brown flower bat (Erophylla bombifrons) and the Greater Antillean long-tongued bat (Monophyllus redmani). Stable carbon and nit...

  3. Liquid-gas phase transition and isospin fractionation in intermediate energy heavy ion collisions

    International Nuclear Information System (INIS)

    Xing Yongzhong; Liu Jianye; Guo Wenjun

    2004-01-01

    The liquid-gas phase transition in the heavy ion collisions and nuclear matter has been an important topic and got achievements, such as, based on the studies by H.Q. Song et al the critical temperature of liquid-gas phase transition enhances with increasing the mass of system and reduces as the increase of the neutron proton ratio of system. As authors know that both the liquid-gas phase transition and the isospin fractionation occur in the spinodal instability region at the nuclear density below the normal nuclear density. In particular, these two dynamical processes lead to the separation of nuclear matter into the liquid phase and gas phase. In this case to compare their dynamical behaviors is interested. The authors investigate the dependence of isospin fractionation degree on the mass and neutron proton ratio of system by using the isospin dependent quantum molecular dynamics model. The authors found that the degree of isospin fractionation (N/Z) n /(N/Z) imf decreases with increasing the mass of the system. This is just similar to the enhance of the critical temperature of liquid-gas phase transition T c as the increase of system mass. Because the enhance of T c is not favorable for the liquid-gas transition taking place, which reduces the isospin fractionation process and leads to decrease of (N/Z) n /(N/Z) imf . However the degree of isospin fractionation enhances with increasing the neutron proton ratio of the system. It is just corresponding to the reduce of T c of the liquid-gas phase transition as the increase of the isospin fractionation of the system. Because the reduce of T c enhances the liquid-gas phase transition process and also prompts the isospin fractionation process leading the increase of the isospin fractionation degree. To sum up, there are very similar dynamical behaviors for the degree of isospin fractionation and the critical temperature of the liquid-gas phase transition. So dynamical properties of the liquid-gas phase transition can

  4. Thermoneutral isotope exchange reactions of cations in the gas phase

    International Nuclear Information System (INIS)

    Ausloos, P.; Lias, S.G.

    1981-01-01

    Rate constants have been measured for reactions of the type AD 2 + + MH → MD + ADH + , where AD 2 + is CD 3 CND + , CD 3 CDOD + , (CD 3 COCD 3 )D + , or (C 2 D 5 ) 2 OD + and the MH molecules are alcohols, acids, mercaptans, H 2 S, AsH 3 , PH 3 , or aromatic molecules. Rate constants are also presented for the reactions Ar/sub H/D + + D 2 O → Ar/sub d/D + + HDO, where Ar/sub H/D + is a deuteronated aromatic molecule and Ar/sub D/D + is the same species with a D atom incorporated on the ring. In all but two cases, the competing deuteron transfer is sufficiently endothermic that it cannot be observed under the conditions of the ICR experiments at 320 to 420 K. The efficiencies of the isotope exchange reactions are interpreted in terms of estimated potential surface cross sections for the reactions AD 2 + + MH → [AD 2 + MH] → [ADMHD + ] → [ADH + MD] → ADH + + MD. When the formation of the [ADMHD + ] complex is estimated to be thermoneutral or slightly endothermic, the isotope exchange process is inefficient (probability of a reactive collision 2 + MH] → [ADMHD + ] is exothermic. For most of the systems, trends in reaction efficiency appear to be related to factors such as dipole moments of reactant species (or for aromatic compounds, the electron-donating or -withdrawing properties of ring substituents) which influence the relative orientation of the two reactant species in the complex

  5. Gas-phase Crystallization of Titanium Dioxide Nanoparticles

    International Nuclear Information System (INIS)

    Ahonen, P.P.; Moisala, A.; Tapper, U.; Brown, D.P.; Jokiniemi, J.K.; Kauppinen, E.I.

    2002-01-01

    We have investigated the development of crystal morphology and phase in ultrafine titanium dioxide particles. The particles were produced by a droplet-to-particle method starting from propanolic titanium tetraisopropoxide solution, and calcined in a vertical aerosol reactor in air. Mobility size classified 40-nm diameter particles were conveyed to the aerosol reactor to investigate particle size changes at 20-1200 deg. C with 5-1-s residence time. In addition, polydisperse particles were used to study morphology and phase formation by electron microscopy. According to differential mobility analysis, the particle diameter was reduced to 21-23-nm at 600 deg. C and above. Precursor decomposition occurred between 20 deg. C and 500 deg. C. The increased mobility particle size at 700 deg. C and above was observed to coincide with irregular particles at 700 deg. C and 800 deg. C and faceted particles between 900 deg. C and 1200 deg. C, according to transmission electron microscopy. The faceted anatase particles were observed to approach a minimized surface energy by forming {101} and {001} crystallographic surfaces. Anatase phase was observed at 500-1200 deg. C and above 600 deg. C the particles were single crystals. Indications of minor rutile formation were observed at 1200 deg. C. The relatively stable anatase phase vs. temperature is attributed to the defect free structure of the observed particles and a lack of crystal-crystal attachment points

  6. Ion-Molecule Reaction of Gas-Phase Chromium Oxyanions: CrxOyHz- + H2O

    International Nuclear Information System (INIS)

    Gianotto, Anita Kay; Hodges, Brittany DM; Benson, Michael Timothy; Harrington, Peter Boves; Appelhans, Anthony David; Olson, John Eric; Groenewold, Gary Steven

    2003-01-01

    Chromium oxyanions having the general formula CrxOyHz- play a key role in many industrial, environmental, and analytical processes, which motivated investigations of their intrinsic reactivity. Reactions with water are perhaps the most significant, and were studied by generating CrxOyHz- in the gas phase using a quadrupole ion trap secondary ion mass spectrometer. Of the ions in the Cr1OyHz envelope (y = 2, 3, 4; z = 0, 1), only CrO2- was observed to react with H2O, producing the hydrated CrO3H2- at a slow rate (∼0.07% of the ion-molecule collision constant at 310 K). CrO3-, CrO4-, and CrO4H- were unreactive. In contrast, Cr2O4-, Cr2O5-, and Cr2O5H2- displayed a considerable tendency to react with H2O. Cr2O4- underwent sequential reactions with H2O, initially producing Cr2O5H2- at a rate that was ∼7% efficient. Cr2O5H2- then reacted with a second H2O by addition to form Cr2O6H4- (1.8% efficient) and by OH abstraction to form Cr2O6H3- (0.6% efficient). The reactions of Cr2O5- were similar to those of Cr2O5H2-: Cr2O5- underwent addition to form Cr2O6H2- (3% efficient) and OH abstraction to form Cr2O6H- (<1% efficient). By comparison, Cr2O6- was unreactive with H2O, and in fact, no further H2O addition could be observed for any of the Cr2O6Hz- anions. Hartree-Fock ab initio calculations showed that reactive CrxOyHz- species underwent nucleophilic attack by the incoming H2O molecules, which produced an initially formed adduct in which the water O was bound to a Cr center. The experimental and computational studies suggested that Cr2OyHz- species that have bi- or tricoordinated Cr centers are susceptible to attack by H2O; however, when the metal becomes tetracoordinate, reactivity stops. For the Cr2OyHz- anions the lowest energy structures all contained rhombic Cr2O2 rings with pendant O atoms and/or OH groups. The initially formed [Cr2Oy- + H2O] adducts underwent H rearrangement to a gem O atom to produce stable dihydroxy structures. The calculations indicated that

  7. Gas phase reactions of organic iodine in containment conditions

    International Nuclear Information System (INIS)

    Kaerkalae, T.; Holm, J.; Auvinen, A.; Zilliacus, R.; Kajolinna, T.; Tapper, U.; Gaenneskog, H.; Ekberg, C.

    2010-01-01

    In case of a hypothetical severe accident it is very likely that iodine at least partly deposits on painted walls of a reactor containment building. Iodine may react with painted surfaces to form organic iodine species. These organic species are a possible source of volatile iodine, which may increase the fraction of releasable iodine. Therefore, it is important to study the transport of organic iodine in containment conditions. Another question is, in which form are the organic iodides transported as gaseous molecules or as aerosol particles resulting from organic iodides reacting with radiolysis products. To answer this last question methyl iodide was fed into the EXSI facility in an air mixture. In some experiments the flow contained also humidity. The reactions took place in a quartz tube heated either to 50 deg. C, 90 deg. C or 120 deg. C. UV-light was used as a source of radiation to produce ozone from oxygen. A separate generator was also applied to reach higher ozone concentrations. Nucleated aerosol particles were collected on plane filters and gaseous iodine species were trapped in trapping bottles. Aerosol mass flow rate and size distribution as well as speciation of gaseous reaction products were measured with several on-line instruments. Collected aerosol particles were analysed with SEM. It was found that the formation of aerosol particles was very fast when ozone and methyl iodide were present in the facility. Even a very low concentration of ozone produced high number concentration of particles. The measured aerosol mass concentration increased with increasing temperature and ozone concentration. Because the particle diameter was quite small (<180 nm), their settling velocity is low. Therefore, iodine containing aerosols may exist in containment atmosphere for a long period of time. Part of methyl iodide was always transported through the facility regardless of experimental conditions. All ozone was consumed in the reactions when only UV-light was

  8. Experimental and numerical investigation of gas phase freeboard combustion

    DEFF Research Database (Denmark)

    Andersen, J.; Jensen, Peter Arendt; Meyer, K.E.

    2009-01-01

    Experimental data for velocity field, temperatures, and gas composition have been obtained from a 50 kW axisymmetric non-swirling natural gas fired combustion setup under two different settings. The reactor was constructed to simulate the conditions in the freeboard of a grate-fired boiler...... but under well-defined conditions. The experimental results are compared to computational fluid dynamics (CFD) modeling predictions, using the eddy dissipation model (EDM) its well as the eddy dissipation concept (EDC). The use of EDC allows for implementation of more advanced combustion schemes; we have...... tested the four-step global mechanism by Jones and Lindstedt (Combust. Flame 1988, 73, 233-249), and the 16 species and 41 reaction skeletal mechanism by Yang and Pope (Combust. Flame 1998, 112 16-32). The CFD model captured the main features of the combustion process and flow patterns. The application...

  9. Experimental and numerical investigation of gas phase freeboard combustion

    DEFF Research Database (Denmark)

    Andersen, Jimmy; Jensen, Peter Arendt; Hvid, S.L.

    2009-01-01

    In part 1 of the present work (10.1021/ef900752a), experimental data and computational fluid dynamics (CFD) modeling predictions for velocity field, temperatures, and major species were compared fora 50 kW axisymmetric, non-swirling natural gas Fired combustion setup, constructed to simulate...... the conditions in the freeboard of it grate-fired boiler. Here, in part 2, the ability of CFD to predict volatile N oxidation to NO and N(2) is evaluated. Trace amounts of ammonia were added to the natural gas, and local measurements of NH(3) and NO in the reactor were compared to modeling predictions. Different...... modeling approaches, including global schemes and analytically reduced mechanisms, were tested in the CFD calculations. In addition, the simplified schemes were compared to reference calculations with a detailed mechanism under isothermal plug flow reactor conditions. While none of the global ammonia...

  10. Photoresponse of the protonated Schiff-base retinal chromophore in the gas phase

    DEFF Research Database (Denmark)

    Toker, Jonathan; Rahbek, Dennis Bo; Kiefer, H V

    2013-01-01

    The fragmentation, initiated by photoexcitation as well as collisionally-induced excitation, of several retinal chromophores was studied in the gas phase. The chromophore in the protonated Schiff-base form (RPSB), essential for mammalian vision, shows a remarkably selective photoresponse. The sel......The fragmentation, initiated by photoexcitation as well as collisionally-induced excitation, of several retinal chromophores was studied in the gas phase. The chromophore in the protonated Schiff-base form (RPSB), essential for mammalian vision, shows a remarkably selective photoresponse...... modifications of the chromophore. We propose that isomerizations play an important role in the photoresponse of gas-phase retinal chromophores and guide internal conversion through conical intersections. The role of protein interactions is then to control the specificity of the photoisomerization in the primary...

  11. Radical Reactions in the Gas Phase: Recent Development and Application in Biomolecules

    Directory of Open Access Journals (Sweden)

    Yang Gao

    2014-01-01

    Full Text Available This review summarizes recent literature describing the use of gas phase radical reactions for structural characterization of complex biomolecules other than peptides. Specifically, chemical derivatization, in-source chemical reaction, and gas phase ion/ion reactions have been demonstrated as effective ways to generate radical precursor ions that yield structural informative fragments complementary to those from conventional collision-induced dissociation (CID. Radical driven dissociation has been applied to a variety of biomolecules including peptides, nucleic acids, carbohydrates, and phospholipids. The majority of the molecules discussed in this review see limited fragmentation from conventional CID, and the gas phase radical reactions open up completely new dissociation channels for these molecules and therefore yield high fidelity confirmation of the structures of the target molecules. Due to the extensively studied peptide fragmentation, this review focuses only on nonpeptide biomolecules such as nucleic acids, carbohydrates, and phospholipids.

  12. Molecular structure determination of cyclooctane by Ab Initio and electron diffraction methods in the gas phase

    International Nuclear Information System (INIS)

    Almeida, Wagner B. de

    2000-01-01

    The determination of the molecular structure of molecules is of fundamental importance in chemistry. X-rays and electron diffraction methods constitute in important tools for the elucidation of the molecular structure of systems in the solid state and gas phase, respectively. The use of quantum mechanical molecular orbital ab initio methods offer an alternative for conformational analysis studies. Comparison between theoretical results and those obtained experimentally in the gas phase can make a significant contribution for an unambiguous determination of the geometrical parameters. In this article the determination for an unambiguous determination of the geometrical parameters. In this article the determination of the molecular structure of the cyclooctane molecule by electron diffraction in the gas phase an initio calculations will be addressed, providing an example of a comparative analysis of theoretical and experimental predictions. (author)

  13. Hydrocarbon fuels from gas phase decarboxylation of hydrolyzed free fatty acid

    KAUST Repository

    Wang, Weicheng

    2012-01-01

    Gas phase decarboxylation of hydrolyzed free fatty acid (FFA) from canola oil has beeninvestigated in two fix-bed reactors by changing reaction parameters such as temperatures,FFA feed rates, and H 2-to-FFA molar ratios. FFA, which contains mostly C 18 aswell as a few C 16, C 20, C 22, and C 24 FFA, was fed into the boiling zone, evaporated, carriedby hydrogen flow at the rate of 0.5-20 ml/min, and reacted with the 5% Pd/C catalystin the reactor. Reactions were conducted atmospherically at 380-450 °C and the products,qualified and quantified through gas chromatography-flame ionization detector(GC-FID), showed mostly n-heptadecane and a few portion of n-C 15, n-C 19, n-C 21, n-C 23 as well as some cracking species. Results showed that FFA conversion increased withincreasing reaction temperatures but decreased with increasing FFA feed rates and H 2-to-FFA molar ratios. The reaction rates were found to decrease with higher temperatureand increase with higher H 2 flow rates. Highly selective heptadecane was achieved byapplying higher temperatures and higher H 2-to-FFA molar ratios. From the results, ascatalyst loading and FFA feed rate were fixed, an optimal reaction temperature of 415 °C as well as H 2-to-FFA molar ratio of 4.16 were presented. These results provided goodbasis for studying the kinetics of decarboxylation process. © 2012 American Society of Mechanical Engineers.

  14. Quantum chaos in ultracold collisions of gas-phase erbium atoms.

    Science.gov (United States)

    Frisch, Albert; Mark, Michael; Aikawa, Kiyotaka; Ferlaino, Francesca; Bohn, John L; Makrides, Constantinos; Petrov, Alexander; Kotochigova, Svetlana

    2014-03-27

    Atomic and molecular samples reduced to temperatures below one microkelvin, yet still in the gas phase, afford unprecedented energy resolution in probing and manipulating the interactions between their constituent particles. As a result of this resolution, atoms can be made to scatter resonantly on demand, through the precise control of a magnetic field. For simple atoms, such as alkalis, scattering resonances are extremely well characterized. However, ultracold physics is now poised to enter a new regime, where much more complex species can be cooled and studied, including magnetic lanthanide atoms and even molecules. For molecules, it has been speculated that a dense set of resonances in ultracold collision cross-sections will probably exhibit essentially random fluctuations, much as the observed energy spectra of nuclear scattering do. According to the Bohigas-Giannoni-Schmit conjecture, such fluctuations would imply chaotic dynamics of the underlying classical motion driving the collision. This would necessitate new ways of looking at the fundamental interactions in ultracold atomic and molecular systems, as well as perhaps new chaos-driven states of ultracold matter. Here we describe the experimental demonstration that random spectra are indeed found at ultralow temperatures. In the experiment, an ultracold gas of erbium atoms is shown to exhibit many Fano-Feshbach resonances, of the order of three per gauss for bosons. Analysis of their statistics verifies that their distribution of nearest-neighbour spacings is what one would expect from random matrix theory. The density and statistics of these resonances are explained by fully quantum mechanical scattering calculations that locate their origin in the anisotropy of the atoms' potential energy surface. Our results therefore reveal chaotic behaviour in the native interaction between ultracold atoms.

  15. A gas-phase reactor powered by solar energy and ethanol for H2 production

    International Nuclear Information System (INIS)

    Ampelli, Claudio; Genovese, Chiara; Passalacqua, Rosalba; Perathoner, Siglinda; Centi, Gabriele

    2014-01-01

    In the view of H 2 as the future energy vector, we presented here the development of a homemade photo-reactor working in gas phase and easily interfacing with fuel cell devices, for H 2 production by ethanol dehydrogenation. The process generates acetaldehyde as the main co-product, which is more economically advantageous with respect to the low valuable CO 2 produced in the alternative pathway of ethanol photoreforming. The materials adopted as photocatalysts are based on TiO 2 substrates but properly modified with noble (Au) and not-noble (Cu) metals to enhance light harvesting in the visible region. The samples were characterized by BET surface area analysis, Transmission Electron Microscopy (TEM) and UV–visible Diffusive Reflectance Spectroscopy, and finally tested in our homemade photo-reactor by simulated solar irradiation. We discussed about the benefits of operating in gas phase with respect to a conventional slurry photo-reactor (minimization of scattering phenomena, no metal leaching, easy product recovery, etc.). Results showed that high H 2 productivity can be obtained in gas phase conditions, also irradiating titania photocatalysts doped with not-noble metals. - Highlights: • A gas-phase photoreactor for H 2 production by ethanol dehydrogenation was developed. • The photocatalytic behaviours of Au and Cu metal-doped TiO 2 thin layers are compared. • Benefits of operating in gas phase with respect to a slurry reactor are presented. • Gas phase conditions and use of not-noble metals are the best economic solution

  16. Gain and loss mechanisms for neutral species in low pressure fluorocarbon plasmas by infrared spectroscopy

    International Nuclear Information System (INIS)

    Nelson, Caleb T.; Overzet, Lawrence J.; Goeckner, Matthew J.

    2012-01-01

    This article examines the chemical reaction pathways of stable neutral species in fluorocarbon plasmas. Octafluorocyclobutane (c-C 4 F 8 ) inductively coupled plasma discharges were found to primarily produce stable and metastable products downstream from the discharge, including c-C 4 F 8 , C 2 F 4 , C 2 F 6 , CF 4 , C 3 F 8 , C 4 F 10 , C 3 F 6 , and CF 2 . A novel analysis technique allows the estimation of gain and loss rates for neutral species in the steady state as functions of residence time, pressure, and discharge power. The gain and loss rates show that CF 4 , C 2 F 6 , C 3 F 8 , and C 4 F 10 share related gain mechanisms, speculated to occur at the surface. Further analysis confirms that CF 2 is predominantly produced at the chamber walls through electron impact dissociation of C 2 F 4 and lost through gas-phase addition reactions to form C 2 F 4 . Additionally, time-resolved FTIR spectra provide a second-order rate coefficient of 1.8 × 10 −14 cm 3 /s for the gas-phase addition of CF 2 to form C 2 F 4 . Finally, C 2 F 4, which is much more abundant than CF 2 in the discharge, is shown to be dominantly produced through electron impact dissociation of c-C 4 F 8 and lost through either surface or gas-phase addition reactions.

  17. Research in Korea on Gas Phase Synthesis and Control of Nanoparticles

    International Nuclear Information System (INIS)

    Choi, Mansoo

    2001-01-01

    Research activity into the gas phase synthesis of nanoparticles has witnessed rapid growth on a worldwide basis, which is also reflected by Korean research efforts. Nanoparticle research is inherently a multi-disciplinary activity involving both science and engineering. In this paper, the recent studies undertaken in Korea on the gas phase synthesis and control of nanoparticles are reviewed. Studies on the synthesis of various kinds of nanoparticles are first discussed with a focus on the different types of reactors used. Recent experimental and theoretical studies and newly developed methods of measuring and modeling nanoparticle growth are also reviewed

  18. FORTRAN program for calculating liquid-phase and gas-phase thermal diffusion column coefficients

    International Nuclear Information System (INIS)

    Rutherford, W.M.

    1980-01-01

    A computer program (COLCO) was developed for calculating thermal diffusion column coefficients from theory. The program, which is written in FORTRAN IV, can be used for both liquid-phase and gas-phase thermal diffusion columns. Column coefficients for the gas phase can be based on gas properties calculated from kinetic theory using tables of omega integrals or on tables of compiled physical properties as functions of temperature. Column coefficients for the liquid phase can be based on compiled physical property tables. Program listings, test data, sample output, and users manual are supplied for appendices

  19. Direct gas-phase epoxidation of propylene to propylene oxide through radical reactions: A theoretical study

    Science.gov (United States)

    Kizilkaya, Ali Can; Fellah, Mehmet Ferdi; Onal, Isik

    2010-03-01

    The gas-phase radical chain reactions which utilize O 2 as the oxidant to produce propylene oxide (PO) are investigated through theoretical calculations. The transition states and energy profiles were obtained for each path. The rate constants were also calculated. The energetics for the competing pathways indicate that PO can be formed selectively due to its relatively low activation barrier (9.3 kcal/mol) which is in a good agreement with the experimental value (11 kcal/mol) of gas-phase propylene epoxidation. The formation of the acrolein and combustion products have relatively high activation barriers and are not favored. These results also support the recent experimental findings.

  20. Acrolein Production by Gas-Phase Glycerol Dehydration Using PO₄/Nb₂O5 Catalysts.

    Science.gov (United States)

    Lee, Kyu Am; Ryoo, HeeKyoung; Ma, Byung Chol; Kim, Youngchul

    2018-02-01

    In this study, modified niobium oxide were prepared to study the addictive effects on the catalytic performance for gas-phase glycerol dehydration. The catalysts were characterized by N2 adsorption/desorption, XRD, NH3-TPD, FT-IR. The amount of phosphoric acid was up to 50 wt% in niobium. As a result, the highest glycerol conversion was achieved over 20 wt% PO4/Nb2O5. It indicates that the optimal amount of phosphoric acid leads the catalyst to have appropriate acidity which is an important factor for gas-phase glycerol dehydration.

  1. Laser spectroscopy of a halocarbocation in the gas phase: CH2I+.

    Science.gov (United States)

    Tao, Chong; Mukarakate, Calvin; Reid, Scott A

    2006-07-26

    We report the first gas-phase observation of the electronic spectrum of a simple halocarbocation, CH2I+. The ion was generated rotationally cold (Trot approximately 20 K) using pulsed discharge methods and was detected via laser spectroscopy. The identity of the spectral carrier was confirmed by modeling the rotational contour observed in the excitation spectra and by comparison of ground state vibrational frequencies determined by single vibronic level emission spectroscopy with Density Functional Theory (DFT) predictions. The transition was assigned as 3A1 gas phase should open new avenues for study of the structure and reactivity of these important ions.

  2. Gas phase THz spectroscopy of toxic agent simulant compounds using the AILES synchrotron beamline

    Science.gov (United States)

    Cuisset, A.; Smirnova, I.; Bocquet, R.; Hindle, F.; Mouret, G.; Yang, C.; Pirali, O.; Roy, P.

    2010-02-01

    A new study is currently underway aiming at recording and assigning the gas phase rovibrational spectra of several organophosphorus and organosulphur compounds in the THz frequency domain. Thanks to the exceptional properties of flux, brilliance and spectral range of the AILES beamline coupled to the FTIR spectrometer, the gas phase vibrational spectra of low volatility organophosphorous compounds have been recorded across the entire THz frequency range. High resolution FTIR spectroscopy was used to record the pure rotational and the low-frequency rovibrational spectrum of DMSO. A comparison between the spectra measured with the AILES beamline and the spectra obtained with optoelectronic THz sources is possible.

  3. Studies of gas phase ion/molecule reactions by Fourier transform ion cyclotron resonance mass spectrometry

    International Nuclear Information System (INIS)

    Kleingeld, J.C.

    1984-01-01

    An important field in which Fourier-transform ion cyclotron resonance has useful applications is that of gas phase ion chemistry, the subject of this thesis. First, the general picture of ion-molecule reactions in the gas phase is discussed. Next, some positive ion-molecule reactions are described, whereas the remaining chapters deal with negative ion-molecule reactions. Most of these studies have been performed using the FT-ICR method. Reactions involving H 3 O - and NH 4 - ions are described whereas the other chapters deal with larger organic complexes. (Auth.)

  4. Fischer Indole Synthesis in the Gas Phase, the Solution Phase, and at the Electrospray Droplet Interface.

    Science.gov (United States)

    Bain, Ryan M; Ayrton, Stephen T; Cooks, R Graham

    2017-07-01

    Previous reports have shown that reactions occurring in the microdroplets formed during electrospray ionization can, under the right conditions, exhibit significantly greater rates than the corresponding bulk solution-phase reactions. The observed acceleration under electrospray ionization could result from a solution-phase, a gas-phase, or an interfacial reaction. This study shows that a gas-phase ion/molecule (or ion/ion) reaction is not responsible for the observed rate enhancement in the particular case of the Fischer indole synthesis. The results show that the accelerated reaction proceeds in the microdroplets, and evidence is provided that an interfacial process is involved. Graphical Abstract GRAPHICAL ABSTRACT TEXT HERE] -->.

  5. The electron spectrum of UF6 recorded in the gas phase

    Science.gov (United States)

    Mârtensson, N.; Malmquist, P.-Å.; Svensson, S.; Johansson, B.

    1984-06-01

    Gas phase core and valence electron spectra from UF6, excited by AlKα monochromatized x rays, in the binding energy range 0-1000 eV are presented. It is shown that the AlKα excited valence electron spectrum can be used to reassign the highest occupied molecular orbital (HOMO) in UF6. Many-body effects on the core levels are discussed and core level lifetimes are determined. The shift between solid phase and gas phase electron binding energies for core lines is used to discuss the U5 f population in UF6.

  6. Is 30 years enough time to niche segregation between a non-native and a native congeneric fish species? Evidences from stable isotopes

    Directory of Open Access Journals (Sweden)

    Gustavo Henrique Zaia Alves

    2015-12-01

    Full Text Available The invasion of non-native species that are phylogenetically similar to native species was observed in the Upper Paraná River following the construction of the Itaipu hydroelectric plant and subsequent removal of a natural geographic barrier (Sete Quedas Falls. Endemic fish species from the Lower Paraná River, such as the piranha Serrasalmus marginatus, successfully colonized the new environment. A few years later, S. marginatus had become the dominant species, while the prevalence of the congeneric species, Serrasalmus maculatus, had declined. Considering that the two piranha species naturally coexist in the Pantanal and that S. marginatus is a non-native species in the Upper Paraná River floodplain, we hypothesized that trophic niche overlap between Serrasalmus species only occurred in the Upper Paraná River floodplain due to short-term co-existence. The study area in which the isotopic niche overlap between S. maculatus and S. marginatus was evaluated consisted of two ponds located in different floodplains, the Pantanal and the Upper Paraná River. We used carbon and nitrogen stable isotope analysis to elucidate the differences in the energy intake by the native and non-native species. We used mixing models and calculated the isotopic niche area and niche overlap to infer the nature of the trophic interactions between the species in both habitats. According to the mixing model, the predominant source of carbon for both species was terrestrial. Nevertheless, in Upper Paraná River, the δ13C signature of the two species differed significantly and the non-native species had a greater niche width than the native species. In the Pantanal, there were no differences in δ13C, but the species differed with respect to δ 15N, and the niche widths were narrow for both species.Based on these results, it can be inferred that the species depend on different food sources. Piranhas obtain energy from distinct prey species, which probably consume

  7. Gas-phase Precursors to Anthropogenic SOA: Using the MCM to Probe Detailed Observations of Aromatic Photo-oxidation

    Science.gov (United States)

    Rickard, A. R.; Wyche, K. P.; Metzger, A.; Monks, P. S.; Ellis, A. M.; Baltensperger, U.; Pilling, M. J.; Jenkin, M. E.

    2008-12-01

    The formation of photochemical ozone and particulate matter are major priorities in the determination of European air quality policies. Predictions of the future state of the atmosphere and the development of appropriate mitigation strategies rely on models, which necessarily incorporate chemistry. The Master Chemical Mechanism (MCM, http://mcm.leeds.ac.uk/MCM) is a near-explicit chemical mechanism originally conceived to model ozone formation in Europe but now also employed as a benchmark mechanism in a wide variety of applications where chemical detail is required. The MCM currently describes the detailed gas- phase tropospheric degradation of a 135 primary emitted volatile organic compounds (VOCs) leading to a mechanism containing ca. 5900 species and 13500 reactions. In order that the MCM continues to be a state-of-the-art resource for the atmospheric science community it resides under a constant regime of evaluation, development and improvement. Individual VOC photochemical mechanisms are evaluated using data obtained, under a variety of atmospheric conditions, from highly instrumented smog chambers. Smog chamber experiments are crucial, not only for mechanism evaluation, but also for mechanism development. Findings obtained from combined model and chamber studies can additionally provide key insight for guiding the directions of future laboratory experiments. Recently, the MCM was updated to MCMv3.1 in order to take into account recent advancements in the understanding of aromatic photo-oxidation, an important class of anthropogenic VOCs. As well as constituting precursors to secondary organic aerosol (SOA), aromatics generally have high photochemical ozone creation potentials (POCPs) and hence contribute significantly towards tropospheric ozone formation. In the work presented, a detailed gas-phase photochemical chamber box model, incorporating the MCMv3.1 degradation mechanism for 1,3,5-trimethylbenzene (TMB), has been used to simulate data measured during

  8. Micro-scale intermixing: a requisite for stable and synergistic co-establishment in a four-species biofilm.

    Science.gov (United States)

    Liu, Wenzheng; Russel, Jakob; Burmølle, Mette; Sørensen, Søren J; Madsen, Jonas S

    2018-04-18

    Microorganisms frequently coexist in complex multispecies communities, where they distribute non-randomly, reflective of the social interactions that occur. It is therefore important to understand how social interactions and local spatial organization influences multispecies biofilm succession. Here the localization of species pairs was analyzed in three dimensions in a reproducible four-species biofilm model, to study the impact of spatial positioning of individual species on the temporal development of the community. We found, that as the biofilms developed, species pairs exhibited distinct intermixing patterns unique to the four-member biofilms. Higher biomass and more intermixing were found in four-species biofilms compared to biofilms with fewer species. Intriguingly, in local regions within the four member biofilms where Microbacterium oxydans was scant, both biomass and intermixing of all species were lowered, compared to regions where M. oxydans was present at typical densities. Our data suggest that Xanthomonas retroflexus and M. oxydans, both low abundant biofilm-members, intermixed continuously during the development of the four-species biofilm, hereby facilitating their own establishment. In turn, this seems to have promoted distinct spatial organization of Stenotrophomonas rhizophila and Paenibacillus amylolyticus enabling enhanced growth of all four species. Here local intermixing of bacteria advanced the temporal development of a multi-species biofilm.

  9. N3 and O2 Protonated Conformers of the Cytosine Mononucleotides Coexist in the Gas Phase

    Science.gov (United States)

    Wu, R. R.; Hamlow, L. A.; He, C. C.; Nei, Y.-w.; Berden, G.; Oomens, J.; Rodgers, M. T.

    2017-08-01

    The gas-phase conformations of the protonated forms of the DNA and RNA cytosine mononucleotides, [pdCyd+H]+ and [pCyd+H]+, are examined by infrared multiple photon dissociation (IRMPD) action spectroscopy over the IR fingerprint and hydrogen-stretching regions complemented by electronic structure calculations. The low-energy conformations of [pdCyd+H]+ and [pCyd+H]+ and their relative stabilities are computed at the B3LYP/6-311+G(2d,2p)//B3LYP/6-311+G(d,p) and MP2(full)/6-311+G(2d,2p)//B3LYP/6-311+G(d,p) levels of theory. Comparisons of the measured IRMPD action spectra and B3LYP/6-311+G(d,p) linear IR spectra computed for the low-energy conformers allow the conformers present in the experiments to be determined. Similar to that found in previous IRMPD action spectroscopy studies of the protonated forms of the cytosine nucleosides, [dCyd+H]+ and [Cyd+H]+, both N3 and O2 protonated cytosine mononucleotides exhibiting an anti orientation of cytosine are found to coexist in the experimental population. The 2'-hydroxyl substituent does not significantly influence the most stable conformations of [pCyd+H]+ versus those of [pdCyd+H]+, as the IRMPD spectral profiles of [pdCyd+H]+ and [pCyd+H]+ are similar. However, the presence of the 2'-hydroxyl substituent does influence the relative intensities of the measured IRMPD bands. Comparisons to IRMPD spectroscopy studies of the deprotonated forms of the cytosine mononucleotides, [pdCyd-H]- and [pCyd-H]-, provide insight into the effects of protonation versus deprotonation on the conformational features of the nucleobase and sugar moieties. Likewise, comparisons to results of IRMPD spectroscopy studies of the protonated cytosine nucleosides provide insight into the influence of the phosphate moiety on structure. Comparison with previous ion mobility results shows the superiority of IRMPD spectroscopy for distinguishing various protonation sites.

  10. Electron attachment to DNA single strands: gas phase and aqueous solution.

    Science.gov (United States)

    Gu, Jiande; Xie, Yaoming; Schaefer, Henry F

    2007-01-01

    The 2'-deoxyguanosine-3',5'-diphosphate, 2'-deoxyadenosine-3',5'-diphosphate, 2'-deoxycytidine-3',5'-diphosphate and 2'-deoxythymidine-3',5'-diphosphate systems are the smallest units of a DNA single strand. Exploring these comprehensive subunits with reliable density functional methods enables one to approach reasonable predictions of the properties of DNA single strands. With these models, DNA single strands are found to have a strong tendency to capture low-energy electrons. The vertical attachment energies (VEAs) predicted for 3',5'-dTDP (0.17 eV) and 3',5'-dGDP (0.14 eV) indicate that both the thymine-rich and the guanine-rich DNA single strands have the ability to capture electrons. The adiabatic electron affinities (AEAs) of the nucleotides considered here range from 0.22 to 0.52 eV and follow the order 3',5'-dTDP > 3',5'-dCDP > 3',5'-dGDP > 3',5'-dADP. A substantial increase in the AEA is observed compared to that of the corresponding nucleic acid bases and the corresponding nucleosides. Furthermore, aqueous solution simulations dramatically increase the electron attracting properties of the DNA single strands. The present investigation illustrates that in the gas phase, the excess electron is situated both on the nucleobase and on the phosphate moiety for DNA single strands. However, the distribution of the extra negative charge is uneven. The attached electron favors the base moiety for the pyrimidine, while it prefers the 3'-phosphate subunit for the purine DNA single strands. In contrast, the attached electron is tightly bound to the base fragment for the cytidine, thymidine and adenosine nucleotides, while it almost exclusively resides in the vicinity of the 3'-phosphate group for the guanosine nucleotides due to the solvent effects. The comparatively low vertical detachment energies (VDEs) predicted for 3',5'-dADP(-) (0.26 eV) and 3',5'-dGDP(-) (0.32 eV) indicate that electron detachment might compete with reactions having high activation barriers

  11. Do medium heavy fragments give evidence for a liquid-gas phase transition

    International Nuclear Information System (INIS)

    Trockel, R.; Hildenbrand, K.D.; Lynen, U.; Mueller, W.F.J.; Rabe, H.J.; Sann, H.; Stelzer, H.; Wada, R.; Brummund, N.; Glasow, R.; Kampert, K.H.; Santo, R.; Pelte, D.; Pochodzalla, J.; Eckert, E.

    1985-09-01

    Light and medium heavy fragments have been measured in light ion induced reactions at intermediate energies. The energy spectra have been parametrized with moving source fits. The resulting temperatures and yields do not confirm the expectations of a liquid-gas phase transition. (orig.)

  12. Electron Attachment to the Gas Phase DNA Bases Cytosine and Thymine

    Czech Academy of Sciences Publication Activity Database

    Denifl, S.; Ptasiňska, S.; Probst, M.; Hrušák, Jan; Scheier, P.; Märk, T. D.

    2004-01-01

    Roč. 108, č. 31 (2004), s. 6562-6569 ISSN 1089-5639 R&D Projects: GA ČR GA203/02/0737 Institutional research plan: CEZ:AV0Z4040901 Keywords : gas-phase * cytosine * thymine Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.639, year: 2004

  13. How Pt nanoparticles affect TiO2-induced gas-phase photocatalytic oxidation reactions

    NARCIS (Netherlands)

    Fraters, B.D.; Amrollahi Buky, Rezvaneh; Mul, Guido

    2015-01-01

    The effect of Pt nanoparticles on the gas-phase photocatalytic oxidation activity of TiO2 is shown to be largely dependent on the molecular functionality of the substrate. We demonstrate that Pt nanoparticles decrease rates in photocatalytic oxidation of propane, whereas a strong beneficial effect

  14. A gas phase work station for the Brazilian National Synchrotron Laboratory

    International Nuclear Information System (INIS)

    Souza, G.G.B. de

    1988-01-01

    A gas phase work station which has been proposed to the Brazilian National Synchrotron Laboratory is described with emphasis on the broad spectrum of physical and chemical processes which can be studied with the incorporated instrumentation. (A.C.A.S.) [pt

  15. Gas-phase polynuclear aromatic hydrocarbons (PAH) in vehicle exhaust: A method for collection and analysis

    International Nuclear Information System (INIS)

    Seigl, W.O.; Chladek, E.

    1990-01-01

    Gas-phase polynuclear aromatic hydrocarbons (PAH) are emitted at low levels in vehicle exhaust compared to other hydrocarbon emissions. A method has been developed involving the trapping of gas phase emissions on Tenax, a macrorecticular porous polymer, followed by thermal desorption onto a capillary gas chromatography column. Gas chromatography/mass spectrometry (GC/MS) was used for the chemical analysis. A detection limit of 0.05 ng was achieved for several gas-phase PAH. This high sensitivity enables the speciation and quantitation of gas-phase PAH collected from a dilution tube during standard driving (test) cycles. The method was demonstrated for the analysis of 9 PAH in the exhaust from a 1987 vehicle (with and without catalyst) during the hot start transient phase of the EPA urban dynamometer driving schedule. The PAH measured include naphthalene, 2-methyl- and 1-methylnaphthalene, biphenyl, fluorene, phenanthrene, anthracene, fluoranthene and pyrene. The four most abundant PAH observed are naphthalene, 2-methyl and 1-methylnaphthalene, and biphenyl, in that order

  16. C-terminal peptide extension via gas-phase ion/ion reactions

    Science.gov (United States)

    Peng, Zhou; McLuckey, Scott A.

    2015-01-01

    The formation of peptide bonds is of great importance from both a biological standpoint and in routine organic synthesis. Recent work from our group demonstrated the synthesis of peptides in the gas-phase via ion/ion reactions with sulfo-NHS reagents, which resulted in conjugation of individual amino acids or small peptides to the N-terminus of an existing ‘anchor’ peptide. Here, we demonstrate a complementary approach resulting in the C-terminal extension of peptides. Individual amino acids or short peptides can be prepared as reagents by incorporating gas phase-labile protecting groups to the reactive C-terminus and then converting the N-terminal amino groups to the active ketenimine reagent. Gas-phase ion/ion reactions between the anionic reagents and doubly protonated “anchor” peptide cations results in extension of the “anchor” peptide with new amide bond formation at the C-terminus. We have demonstrated that ion/ion reactions can be used as a fast, controlled, and efficient means for C-terminal peptide extension in the gas phase. PMID:26640400

  17. ECO LOGIC INTERNATIONAL GAS-PHASE CHEMICAL REDUCTION PROCESS - THE THERMAL DESORPTION UNIT - APPLICATIONS ANALYSIS REPORT

    Science.gov (United States)

    ELI ECO Logic International, Inc.'s Thermal Desorption Unit (TDU) is specifically designed for use with Eco Logic's Gas Phase Chemical Reduction Process. The technology uses an externally heated bath of molten tin in a hydrogen atmosphere to desorb hazardous organic compounds fro...

  18. DEMONSTRATION BULLETIN: GAS-PHASE CHEMICAL REDUCTION - ECO LOGIC INTERNATIONAL, INC.

    Science.gov (United States)

    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 ...

  19. Structure Elucidation of Dimethylformamide-Solvated Alkylzinc Cations in the Gas Phase

    NARCIS (Netherlands)

    Dreiocker, F.; Oomens, J.; Meijer, Ajhm; Pickup, B. T.; Jackson, R. F. W.; Schafer, M.

    2010-01-01

    Organozinc iodides, useful for the synthesis of nonproteinogenic amino acids, are investigated in the gas phase by a combination of electrospray (ESI)-MS/MS, accurate ion mass measurements, and infrared multiphoton dissociation (IRMPD) spectroscopy employing a free electron laser. ESI allowed the

  20. Gas-phase infrared spectrum of the anionic GFP-chromophore

    NARCIS (Netherlands)

    Almasian, M.; Grzetic, J.; G. Berden,; Bakker, B.; Buma, W. J.; Oomens, J.

    2012-01-01

    The gas-phase IR spectrum of the anionic chromophore of the green fluorescent protein (p-hydroxy-benzylidene-2,3-dimethylimidazolidinone, HBDI) is recorded in the 800–1800 cm−1 frequency range using the free electron laser FELIX in combination with an electrospray ionization (ESI) Fourier

  1. Structure elucidation of dimethylformamide-solvated alkylzinc cations in the gas phase

    NARCIS (Netherlands)

    Dreiocker, F.; Oomens, J.; Meijer, A.J.H.M.; Pickup, B.T.; Jackson, R.F.W.; Schäfer, M.

    2010-01-01

    Organozinc iodides, useful for the synthesis of nonproteinogenic amino acids, are investigated in the gas phase by a combination of electrospray (ESI)-MS/MS, accurate ion mass measurements, and infrared multiphoton dissociation (IRMPD) spectroscopy employing a free electron laser. ESI allowed the

  2. Gas phase hydrogen peroxide production in atmospheric pressure glow discharges operating in He - H2O

    NARCIS (Netherlands)

    Vasko, C.A.; Veldhuizen, van E.M.; Bruggeman, P.J.

    2013-01-01

    The gas phase production of hydrogen peroxide (H2O2) in a RF atmospheric pressure glow discharge with helium and water vapour has been investigated as a function of the gas flow. It is shown that the production of H2O2 is through the recombination of two OH radicals in a three body collision and the

  3. Highly Selective Continuous Gas-Phase Methoxycarbonylation of Ethylene with Supported Ionic Liquid Phase (SILP) Catalysts

    DEFF Research Database (Denmark)

    Khokarale, Santosh Govind; Garcia Suárez, Eduardo José; Fehrmann, Rasmus

    2017-01-01

    Supported ionic liquid phase (SILP) technology was applied for the first time to the Pd-catalyzed continuous, gas-phase methoxycarbonylation of ethylene to selectively produce methyl propanoate (MP) in high yields. The influence of catalyst and reaction parameters such as, for example, ionic liquid...

  4. Gas-phase salt bridge interactions between glutamic acid and arginine

    NARCIS (Netherlands)

    Jaeqx, S.; Oomens, J.; Rijs, A.M.

    2013-01-01

    The gas-phase side chain-side chain (SC-SC) interaction and possible proton transfer between glutamic acid (Glu) and arginine (Arg) residues are studied under low-temperature conditions in an overall neutral peptide. Conformation-specific IR spectra, obtained with the free electron laser FELIX, in

  5. Humidity independent mass spectrometry for gas phase chemical analysis via ambient proton transfer reaction.

    Science.gov (United States)

    Zhu, Hongying; Huang, Guangming

    2015-03-31

    In this work, a humidity independent mass spectrometric method was developed for rapid analysis of gas phase chemicals. This method is based upon ambient proton transfer reaction between gas phase chemicals and charged water droplets, in a reaction chamber with nearly saturate humidity under atmospheric pressure. The humidity independent nature enables direct and rapid analysis of raw gas phase samples, avoiding time- and sample-consuming sample pretreatments in conventional mass spectrometry methods to control sample humidity. Acetone, benzene, toluene, ethylbenzene and meta-xylene were used to evaluate the analytical performance of present method. The limits of detection for benzene, toluene, ethylbenzene and meta-xylene are in the range of ∼0.1 to ∼0.3 ppbV; that of benzene is well below the present European Union permissible exposure limit for benzene vapor (5 μg m(-3), ∼1.44 ppbV), with linear ranges of approximately two orders of magnitude. The majority of the homemade device contains a stainless steel tube as reaction chamber and an ultrasonic humidifier as the source of charged water droplets, which makes this cheap device easy to assemble and facile to operate. In addition, potential application of this method was illustrated by the real time identification of raw gas phase chemicals released from plants at different physiological stages. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Ab initio study of gas phase and water-assisted tautomerization of ...

    Indian Academy of Sciences (India)

    WINTEC

    Water-assisted tautomerization in maleimide and formamide showed that difference in energy barrier reduces to 2⋅83 kcal/mol from 10⋅41 kcal/mol (in gas phase) at B3LYP level, which resulted that maleimide readily undergoes tautomerization in water molecule. Keywords. Ab Initio calculations; maleimide; formamide; ...

  7. Continuous gas-phase hydroformylation of 1-butene using supported ionic liquid phase (SILP) catalysts

    DEFF Research Database (Denmark)

    Haumann, Marco; Dentler, Katharina; Joni, Joni

    2007-01-01

    The concept of supported ionic liquid phase (SILP) catalysis has been extended to 1-butene hydroformylation. A rhodium-sulfoxantphos complex was dissolved in [BMIM][n-C8H17OSO3] and this solution was highly dispersed on silica. Continuous gas-phase experiments in a fixed-bed reactor revealed...

  8. Gas-phase UF6 enrichment monitor for enrichment plant safeguards

    International Nuclear Information System (INIS)

    Strittmatter, R.B.; Tape, J.W.

    1980-03-01

    An in-line enrichment monitor is being developed to provide real-time enrichment data for the gas-phase UF 6 feed stream of an enrichment plant. The nondestructive gamma-ray assay method can be used to determine the enrichment of natural UF 6 with a relative precision of better than 1% for a wide range of pressures

  9. Mid-IR spectra of different conformers of phenylalanine in the gas phase

    NARCIS (Netherlands)

    von Helden, G.; Compagnon, I.; Blom, M. N.; Frankowski, M.; Erlekam, U.; Oomens, J.; Brauer, B.; Gerber, R. B.; Meijer, G.

    2008-01-01

    The experimental mid- and far-IR spectra of six conformers of phenylalanine in the gas phase are presented. The experimental spectra are compared to spectra calculated at the B3LYP and at the MP2 level. The differences between B3LYP and MP2 IR spectra are found to be small. The agreement between

  10. Operando Spectroscopy of the Gas-Phase Aldol Condensation of Propanal over Solid Base Catalysts

    NARCIS (Netherlands)

    Hernández-giménez, Ana M.; Ruiz-martínez, Javier; Puértolas, Begoña; Pérez-ramírez, Javier; Bruijnincx, Pieter C. A.; Weckhuysen, Bert M.

    2017-01-01

    The gas-phase aldol condensation of propanal, taken as model for the aldehyde components in bio-oils, has been studied with a combined operando set-up allowing to perform FT-IR & UV–Vis diffuse reflectance spectroscopy (DRS) with on-line mass spectrometry (MS). The selected solid base catalysts, a

  11. Gas-Phase Oxidation of Aqueous Ethanol by Nanoparticle Vanadia/Anatase Catalysts

    DEFF Research Database (Denmark)

    Jørgensen, Betina; Kristensen, Steffen Buus; Kunov-Kruse, Andreas Jonas

    2009-01-01

    The gas-phase oxidation of aqueous ethanol with dioxygen has been examined with a new nanoparticle V2O5/TiO2 catalyst. Product selectivity could to a large extent be controlled by small alterations of reaction parameters, allowing production of acetaldehyde at a selectivity higher than 90%, near...

  12. Biofilm structure and mass transfer in a gas phase trickle-bed biofilter.

    Science.gov (United States)

    Zhu, X; Suidan, M T; Alonso, C; Yu, T; Kim, B J; Kim, B R

    2001-01-01

    Mass transport phenomena occurring in the biofilms of gas phase trickle-bed biofilters are investigated in this study. The effect of biofilm structure on mass transfer mechanisms is examined using experimental observation from the operating of biofilters, microelectrode techniques and microscopic examination. Since the biofilms of biofilters used for waste gas treatment are not completely saturated with water, there is not a distinguishable liquid layer outside the biofilm. Results suggest that due to this characteristic, gas phase substrates (such as oxygen or volatile organic compounds) may not be limited by the aqueous phase because transport of the compound into the biofilm can occur directly through non-wetted areas. On the other hand, for substrates that are present only in the liquid phase, such as nitrate, the mass transfer limitation is more serious because of the limited liquid supply. Microscopic observations show that a layered structure with void spaces exists within the biofilm. Oxygen concentration distributions along the depth of the biofilms are examined using an oxygen microelectrode. Results indicate that there are some high dissolved oxygen zones inside the biofilm, which suggests the existence of passages for oxygen transfer into the deeper sections of the biofilm in a gas phase trickle-bed biofilter. Both the low gas-liquid mass transfer resistance and the resulting internal structure contribute to the high oxygen penetration within the biofilms in gas phase trickle-bed biofilters.

  13. Multiple Multidentate Halogen Bonding in Solution, in the Solid State, and in the (Calculated) Gas Phase.

    Science.gov (United States)

    Jungbauer, Stefan H; Schindler, Severin; Herdtweck, Eberhardt; Keller, Sandro; Huber, Stefan M

    2015-09-21

    The binding properties of neutral halogen-bond donors (XB donors) bearing two multidentate Lewis acidic motifs toward halides were investigated. Employing polyfluorinated and polyiodinated terphenyl and quaterphenyl derivatives as anion receptors, we obtained X-ray crystallographic data of the adducts of three structurally related XB donors with tetraalkylammonium chloride, bromide, and iodide. The stability of these XB complexes in solution was determined by isothermal titration calorimetry (ITC), and the results were compared to X-ray analyses as well as to calculated binding patterns in the gas phase. Density functional theory (DFT) calculations on the gas-phase complexes indicated that the experimentally observed distortion of the XB donors during multiple multidentate binding can be reproduced in 1:1 complexes with halides, whereas adducts with two halides show a symmetric binding pattern in the gas phase that is markedly different from the solid state structures. Overall, this study demonstrates the limitations in the transferability of binding data between solid state, solution, and gas phase in the study of complex multidentate XB donors. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Gas-phase synthesis of magnesium nanoparticles : A high-resolution transmission electron microscopy study

    NARCIS (Netherlands)

    Kooi, B.J.; Palasantzas, G.; de Hosson, J.T.M.

    2006-01-01

    Magnesium nanoparticles with size above 10 nm, prepared by gas-phase syntheses, were investigated by high-resolution transmission electron microscopy. The dominant particle shape is a hexagonal prism terminated by Mg(0002) and Mg{1010} facets. Oxidation of Mg yields a MgO shell (similar to 3 nm

  15. Supported Rh-phosphine complex catalysts for continuous gas-phase decarbonylation of aldehydes

    DEFF Research Database (Denmark)

    Malcho, Phillip; Garcia-Suarez, Eduardo J.; Mentzel, Uffe Vie

    2014-01-01

    Heterogeneous silica supported rhodium-phosphine complex catalysts are employed for the first time in the catalytic decarbonylation of aldehydes in continuous gas-phase. The reaction protocol is exemplified for the decarbonylation of p-tolualdehyde to toluene and further extended to other aromatic...

  16. Hydrocarbon fuels from gas phase decarboxylation of hydrolyzed free fatty acid

    KAUST Repository

    Wang, Weicheng; Roberts, William L.; Stikeleather, Larry F.

    2012-01-01

    Gas phase decarboxylation of hydrolyzed free fatty acid (FFA) from canola oil has beeninvestigated in two fix-bed reactors by changing reaction parameters such as temperatures,FFA feed rates, and H 2-to-FFA molar ratios. FFA, which contains mostly C

  17. Gas phase polymerization of propylene. Reaction kinetics and molecular weight distribution

    NARCIS (Netherlands)

    Meier, G.B.; Weickert, G.; van Swaaij, Willibrordus Petrus Maria

    2001-01-01

    Gas-phase polymerizations have been executed at different temperatures, pressures, and hydrogen concentrations using Me2Si[Ind]2ZrCl2 / methylaluminoxane / SiO2(Pennsylvania Quarts) as a catalyst. The reaction rate curves have been described by a kinetic model, which takes into account the initially

  18. Why do disk galaxies present a common gas-phase metallicity gradient?

    Science.gov (United States)

    Chang, R.; Zhang, Shuhui; Shen, Shiyin; Yin, Jun; Hou, Jinliang

    2017-03-01

    CALIFA data show that isolated disk galaxies present a common gas-phase metallicity gradient, with a characteristic slope of -0.1dex/re between 0.3 and 2 disk effective radius re (Sanchez et al. 2014). Here we construct a simple model to investigate which processes regulate the formation and evolution.

  19. Gas-phase photoemission with soft x-rays: cross sections and angular distributions

    International Nuclear Information System (INIS)

    Shirley, D.A.; Kobrin, P.H.; Truesdale, C.M.; Lindle, D.W.; Ferrett, T.A.; Heimann, P.A.; Becker, U.; Kerkhoff, H.G.; Southworth, S.H.

    1983-09-01

    A summary is presented of typical gas-phase photoemission studies based on synchrotron radiation in the 50-5000 eV range, using beam lines at the Stanford Synchrotron Radiation Laboratory. Three topics are addressed: atomic inner-shell photoelectron cross sections and asymmetries, correlation peaks in rare gases, and core-level shape resonances in molecules

  20. Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules

    DEFF Research Database (Denmark)

    Boll, Rebecca; Rouzee, Arnaud; Adolph, Marcus

    2014-01-01

    This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray Free-Electron Laser. We present results of two experiments aimed at measuring photoelectron angular...

  1. The Stability of CI02 as a Product of Gas Phase Decontamination Treatments

    International Nuclear Information System (INIS)

    Simmons, D. W.

    1994-01-01

    The gas phase decontamination project is investigating the use of chlorine trifluoride (ClF 3 ) to fluorinate nonvolatile uranium deposits to produce uranium hexafluoride (UF 6 ) gas. The potential existence of chlorine dioxide (ClO 2 ) during gas phase decontamination with ClF 3 has been the subject of recent safety discussions. Some of the laboratory data collected during feasibility studies of the gas phase process has been evaluated for the presence of ClO 2 in the product gas stream. The preliminary evidence to date can be summarized as follows: (1) ClO 2 was not detected in the flow loop in the absence of ClF 3 ; (2) ClO 2 was not detected in the static reactors in the absence of both ClF 3 and ClF; and (3) ClO 2 was detected in a static reactor in the absence of all fluorinating gases. The experimental evidence suggests that ClO 2 will not exist in the presence of ClF 3 , ClF, or UF 6 . The data analyzed to date is insufficient to determine the stability of ClO 2 in the presence of ClO 2 F. Thermodynamic calculations of the ClF 3 + H 2 O system support the experimental evidence, and suggest that ClO 2 will not exist in the presence of ClO 2 F. Additional experimental efforts are needed to provide a better understanding of the gas phase ClF 3 treatments and the product gases. However, preliminary evidence to date suggests that ClO 2 should not be present as a product during the normal operations of the gas phase decontamination project

  2. The Stability of CI02 as a Product of Gas Phase Decontamination Treatments

    Energy Technology Data Exchange (ETDEWEB)

    D. W. Simmons

    1994-09-01

    The gas phase decontamination project is investigating the use of chlorine trifluoride (ClF{sub 3}) to fluorinate nonvolatile uranium deposits to produce uranium hexafluoride (UF{sub 6}) gas. The potential existence of chlorine dioxide (ClO{sub 2}) during gas phase decontamination with ClF{sub 3} has been the subject of recent safety discussions. Some of the laboratory data collected during feasibility studies of the gas phase process has been evaluated for the presence of ClO{sub 2} in the product gas stream. The preliminary evidence to date can be summarized as follows: (1) ClO{sub 2} was not detected in the flow loop in the absence of ClF{sub 3}; (2) ClO{sub 2} was not detected in the static reactors in the absence of both ClF{sub 3} and ClF; and (3) ClO{sub 2} was detected in a static reactor in the absence of all fluorinating gases. The experimental evidence suggests that ClO{sub 2} will not exist in the presence of ClF{sub 3}, ClF, or UF{sub 6}. The data analyzed to date is insufficient to determine the stability of ClO{sub 2} in the presence of ClO{sub 2}F. Thermodynamic calculations of the ClF{sub 3} + H{sub 2}O system support the experimental evidence, and suggest that ClO{sub 2} will not exist in the presence of ClO{sub 2}F. Additional experimental efforts are needed to provide a better understanding of the gas phase ClF{sub 3} treatments and the product gases. However, preliminary evidence to date suggests that ClO{sub 2} should not be present as a product during the normal operations of the gas phase decontamination project.

  3. Gas-phase fragmentation of coordination compounds: loss of CO(2) from inorganic carbonato complexes to give metal oxide ions

    Science.gov (United States)

    Dalgaard; McKenzie

    1999-10-01

    Using electrospray ionization mass spectrometry, novel transition metal oxide coordination complex ions are proposed as the products of the collision-induced dissociation (CID) of some carbonato complex ions through the loss of a mass equivalent to CO(2). CID spectra of [(tpa)CoCO(3)](+) (tpa = tris(2-pyridylmethyl)methylamine), [(bispicMe(2)en)Fe(&mgr;-O)(&mgr;-CO(3))Fe(bispicMe(2)en)]2+ (bispicMe(2)en = N,N'-dimethyl-N,N'-bis(2-pyridylmethy)eth- ane-1, 2-diamine) and [(bpbp)Cu(2)CO(3)](+) (bpbp(-) = bis[(bis-(2-pyridylmethyl)amino)methyl]-4-tertbutylpheno-lato(1-)), show peaks assigned to the mono- and dinuclear oxide cations, [(tpa)CoO](+), [(bispicMe(2)en)(2)Fe(2)(O)(2)]2+ and [(bpbp)Cu(2)O](+), as the dominant species. These results can be likened to the reverse of typical synthetic reactions in which metal hydroxide compounds react with CO(2) to give metal carbonato compounds. Because of the lack of available protons in the gas phase, novel oxide species rather than the more common hydroxide ions are generated. These oxide ions are relevant to the highly oxidizing species proposed in oxygenation reactions catalysed by metal oxides and metalloenzymes. Copyright 1999 John Wiley & Sons, Ltd.

  4. Gas-phase chemical characteristics of Asian emission plumes observed during ITCT 2K2 over the eastern North Pacific Ocean

    Science.gov (United States)

    Nowak, J. B.; Parrish, D. D.; Neuman, J. A.; Holloway, J. S.; Cooper, O. R.; Ryerson, T. B.; Nicks, D. K.; Flocke, F.; Roberts, J. M.; Atlas, E.; de Gouw, J. A.; Donnelly, S.; Dunlea, E.; Hübler, G.; Huey, L. G.; Schauffler, S.; Tanner, D. J.; Warneke, C.; Fehsenfeld, F. C.

    2004-12-01

    The gas-phase chemical characteristics of emission plumes transported from Asia across the Pacific Ocean observed during the Intercontinental Transport and Chemical Transformation experiment in 2002 (ITCT 2K2) are described. Plumes measured in the troposphere from an aircraft were separated from the background air in data analysis using 1-s measurements of carbon monoxide (CO), total reactive nitrogen (NOy), and other gas-phase species along with back trajectory analysis. On the basis of these measurements, Asian transport plumes with CO mixing ratios greater than 150 ppbv were observed on seven flights. Correlations between 1-s observations of CO, ozone (O3), and NOy are used to characterize the plumes. The NOy/CO ratios were similar in each plume and significantly lower than those derived from estimated Asian emission ratios, indicating substantial removal of soluble NOy species during transport. Observations of nitric oxide (NO), nitrogen dioxide (NO2), nitric acid (HNO3), peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), and alkyl nitrates are used with the NOy measurements to further distinguish the transport plumes by their NOy partitioning. NOy was primarily in the form of PAN in plumes that were transported in cold high-latitude and high-altitude regions, whereas in plumes transported in warmer, lower latitude and altitude regions, NOy was mainly HNO3. Additional gas-phase species enhanced in these plumes include sulfuric acid, methanol, acetone, propane, and ethane. The O3/CO ratio varied among the plumes and was affected by the mixing of anthropogenic and stratospheric influences. The complexity of this mixing prevents the determination of the relative contribution of anthropogenic and stratospheric influences to the observed O3 levels.

  5. Probing the Binding Interfaces of Protein Complexes Using Gas-Phase H/D Exchange Mass Spectrometry

    DEFF Research Database (Denmark)

    Mistarz, Ulrik H; Brown, Jeffery M; Haselmann, Kim F

    2016-01-01

    Fast gas-phase hydrogen/deuterium exchange mediated by ND3 gas and measured by mass spectrometry (gas-phase HDX-MS) is a largely unharnessed, fast, and sensitive method for probing primary- and higher-order polypeptide structure. Labeling of heteroatom-bound non-amide hydrogens in a sub-milliseco......Fast gas-phase hydrogen/deuterium exchange mediated by ND3 gas and measured by mass spectrometry (gas-phase HDX-MS) is a largely unharnessed, fast, and sensitive method for probing primary- and higher-order polypeptide structure. Labeling of heteroatom-bound non-amide hydrogens in a sub......-millisecond time span after electrospray ionization by ND3 gas can provide structural insights into protein conformers present in solution. Here, we have explored the use of gas-phase HDX-MS for probing the higher-order structure and binding interfaces of protein complexes originating from native solution...

  6. Determination of gas phase protein ion densities via ion mobility analysis with charge reduction.

    Science.gov (United States)

    Maisser, Anne; Premnath, Vinay; Ghosh, Abhimanyu; Nguyen, Tuan Anh; Attoui, Michel; Hogan, Christopher J

    2011-12-28

    We use a charge reduction electrospray (ESI) source and subsequent ion mobility analysis with a differential mobility analyzer (DMA, with detection via both a Faraday cage electrometer and a condensation particle counter) to infer the densities of single and multiprotein ions of cytochrome C, lysozyme, myoglobin, ovalbumin, and bovine serum albumin produced from non-denaturing (20 mM aqueous ammonium acetate) and denaturing (1 : 49.5 : 49.5, formic acid : methanol : water) ESI. Charge reduction is achieved through use of a Po-210 radioactive source, which generates roughly equal concentrations of positive and negative ions. Ions produced by the source collide with and reduce the charge on ESI generated drops, preventing Coulombic fissions, and unlike typical protein ESI, leading to gas-phase protein ions with +1 to +3 excess charges. Therefore, charge reduction serves to effectively mitigate any role that Coulombic stretching may play on the structure of the gas phase ions. Density inference is made via determination of the mobility diameter, and correspondingly the spherical equivalent protein volume. Through this approach it is found that for both non-denaturing and denaturing ESI-generated ions, gas-phase protein ions are relatively compact, with average densities of 0.97 g cm(-3) and 0.86 g cm(-3), respectively. Ions from non-denaturing ESI are found to be slightly more compact than predicted from the protein crystal structures, suggesting that low charge state protein ions in the gas phase are slightly denser than their solution conformations. While a slight difference is detected between the ions produced with non-denaturing and denaturing ESI, the denatured ions are found to be much more dense than those examined previously by drift tube mobility analysis, in which charge reduction was not employed. This indicates that Coulombic stretching is typically what leads to non-compact ions in the gas-phase, and suggests that for gas phase

  7. Using Gas-Phase Guest-Host Chemistry to Probe the Structures of b Ions of Peptides

    Science.gov (United States)

    Somogyi, Árpád; Harrison, Alex G.; Paizs, Béla

    2012-12-01

    Middle-sized b n ( n ≥ 5) fragments of protonated peptides undergo selective complex formation with ammonia under experimental conditions typically used to probe hydrogen-deuterium exchange in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Other usual peptide fragments like y, a, a*, etc., and small b n ( n ≤ 4) fragments do not form stable ammonia adducts. We propose that complex formation of b n ions with ammonia is characteristic to macrocyclic isomers of these fragments. Experiments on a protonated cyclic peptide and N-terminal acetylated peptides fully support this hypothesis; the protonated cyclic peptide does form ammonia adducts while linear b n ions of acetylated peptides do not undergo complexation. Density functional theory (DFT) calculations on the proton-bound dimers of all-Ala b 4 , b 5 , and b 7 ions and ammonia indicate that the ionizing proton initially located on the peptide fragment transfers to ammonia upon adduct formation. The ammonium ion is then solvated by N+-H…O H-bonds; this stabilization is much stronger for macrocyclic b n isomers due to the stable cage-like structure formed and entropy effects. The present study demonstrates that gas-phase guest-host chemistry can be used to selectively probe structural features (i.e., macrocyclic or linear) of fragments of protonated peptides. Stable ammonia adducts of b 9 , b 9 -A, and b 9 -2A of A8YA, and b 13 of A20YVFL are observed indicating that even these large b-type ions form macrocyclic structures.

  8. Growth and stable isotope signals associated with drought-related mortality in saplings of two coexisting pine species.

    Science.gov (United States)

    Herrero, Asier; Castro, Jorge; Zamora, Regino; Delgado-Huertas, Antonio; Querejeta, José I

    2013-12-01

    Drought-induced events of massive tree mortality appear to be increasing worldwide. Species-specific vulnerability to drought mortality may alter patterns of species diversity and affect future forest composition. We have explored the consequences of the extreme drought of 2005, which caused high sapling mortality (approx. 50 %) among 10-year-old saplings of two coexisting pine species in the Mediterranean mountains of Sierra Nevada (Spain): boreo-alpine Pinus sylvestris and Mediterranean P. nigra. Sapling height growth, leaf δ(13)C and δ(18)O, and foliar nitrogen concentration in the four most recent leaf cohorts were measured in dead and surviving saplings. The foliar isotopic composition of dead saplings (which reflects time-integrated leaf gas-exchange until mortality) displayed sharp increases in both δ(13)C and δ(18)O during the extreme drought of 2005, suggesting an important role of stomatal conductance (g(s)) reduction and diffusional limitations to photosynthesis in mortality. While P. nigra showed decreased growth in 2005 compared to the previous wetter year, P. sylvestris maintained similar growth levels in both years. Decreased growth, coupled with a sharper increase in foliar δ(18)O during extreme drought in dead saplings, indicate a more conservative water use strategy for P. nigra. The different physiological behavior of the two pine species in response to drought (further supported by data from surviving saplings) may have influenced 2005 mortality rates, which contributed to 2.4-fold greater survival for P. nigra over the lifespan of the saplings. This species-specific vulnerability to extreme drought could lead to changes in dominance and distribution of pine species in Mediterranean mountain forests.

  9. Foliar stable carbon and nitrogen isotopes in woody Mediterranean species with different life form and post-fire regeneration.

    Science.gov (United States)

    Saura-Mas, S; Lloret, F

    2010-01-01

    Wildfire is an important ecological disturbance factor in most Mediterranean ecosystems. In the Mediterranean Basin, most shrub species can regenerate after fire by resprouting or seeding. Here, we hypothesize that post-fire regenerative syndromes may potentially co-vary with traits directly related to functional properties involved in resource use. Thus, seeders with a shorter life span and smaller size would have lower water-use efficiency (WUE) than re-sprouting species and would take up nutrients such as nitrogen from more superficial parts of the soil. To test this hypothesis, we compared leaf (13)C and (15)N signatures from 29 co-existing species with different post-fire regeneration strategies. We also considered life form as an additional explanatory variable of the differences between post-fire regenerative groups. Our data support the hypothesis that seeder species (which mostly evolved in the Quaternary under a Mediterranean climate) have lower WUE and less stomatal control than non-seeders (many of which evolved under different climatic conditions in the Tertiary) and consequently greater consumption of water per unit biomass. This would be related to their smaller life forms, which tend to have lower WUE and shorter life and leaf lifespan. Differences in (15)N also support the hypothesis that resprouters have deeper root systems than non-resprouters. The study supports the hypothesis of an overlap between plant functional traits and plant attributes describing post-disturbance resilience.

  10. ICR studies of some anionic gas phase reactions and FTICR software design

    International Nuclear Information System (INIS)

    Noest, A.J.

    1983-01-01

    This thesis consists of two parts. Part one (Chs. 1-5) reports experimental results from mostly drift-cell ICR studies of negative ion-molecule reactions; part two (Chs. 6-11) concerns the design of software for an FTICR instrument. The author discusses successively: 1. ion cyclotron resonance spectrometry; 2. the gas phase allyl anion; 3. the (M-H) and (M-H2) anions from acetone; 4. negative ion-molecule reactions of aliphatic nitrites studied by cyclotron resonance; 5. homoconjugation versus charge-dipole interaction effects in the stabilization of carbanions in the gas phase; 6. the Fourier Transform ICR method; 7. the FTICR-software; 8. an efficient adaptive matcher filter for fast transient signals; 9. reduction of spectral peak height errors by time-domain weighing; 10. Chirp excitation; 11. Compact data storage. The book concludes with a Dutch and English summary (G.J.P.)

  11. Experimental redetermination of the gas-phase enthalpy of formation of ethyl 2-thiophenecarboxylate

    International Nuclear Information System (INIS)

    Santos, Ana Filipa L.O.M.; Ribeiro da Silva, Manuel A.V.

    2013-01-01

    The condensed phase standard (p° = 0.1 MPa) molar enthalpy of formation of ethyl-2-thiophenecarboxylate was derived from the remeasured standard molar energy of combustion, in oxygen, at T = 298.15 K, by rotating bomb combustion calorimetry and the standard molar enthalpy of vaporization, at T = 298.15 K, remeasured by Calvet microcalorimetry. Combining these two values, the following enthalpy of formation in the gas phase, at T = 298.15 K, was then derived for ethyl-2-thiophenecarboxylate: −(277.7 ± 2.9) kJ · mol −1 . The calculated gas-phase enthalpy of formation of the title compound, through the G3(MP2)//B3LYP approach was found to be 278.9 kJ · mol −1 , in excellent agreement with the experimental measured value

  12. Gas-phase infrared spectrum of phosphorus (III) oxycyanide, OPCN: experimental and theoretical investigations

    Science.gov (United States)

    Allaf, Abdul. W.; Kassem, M.; Alibrahim, M.; Boustani, Ihsan

    1999-03-01

    An attempt was made to observe the gas-phase infrared spectrum of Phosphorus (III) oxycyanide, OPCN for the first time. This molecule was produced by an on-line process using phosphorus (III) oxychloride, OPCl as precursor passed over heated AgCN. The products were characterised by the infrared spectra of their vapours. The low resolution gas-phase Fourier transform infrared spectrum shows two bands centered at 2165 and 1385 cm -1. These bands are assigned to, ν1 (CN stretch) and ν2 (OP stretch), respectively. Ab initio self-consistent-field (SCF) molecular orbital (MO) and Møller-Plesset second order perturbation theory (MP2) calculations were performed to determine the geometry, total energy and vibrational frequencies of OPCN.

  13. Gas-phase infrared spectrum of phosphorus (III) oxycyanide, OPCN: Experimental and theoretical and theoretical investigations

    International Nuclear Information System (INIS)

    Allaf, A.W.; Kassem, M.; Alibrahim, M.

    1999-01-01

    An attempt was made to observe the gas-phase infrared spectrum of phosphorus (III) oxycyanide, OPCN for the first time. This molecule was produced by on-line process using phosphorus (III) oxychloride, OPCI as precursor passed over heated Ag CN. The products were characterised by the infrared spectra of their vapours. The low resolution gas-phase Fourier transform infrared spectrum shows two bands at 2165 and 1385 cm -1 . These bands are assigned to ν 1 (C≡N stretch) and ν 2 (O=P stretch), respectively. Ab initio self-consistent-field (SCF) molecular orbital (MO) and Moeller - Plesset second order perturbation theory (MP2) calculations were performed to determine the geometry, total energy and vibrational frequencies of OPCN. (authors)

  14. Effect of duty-cycles on the air plasma gas-phase of dielectric barrier discharges

    Science.gov (United States)

    Barni, R.; Biganzoli, I.; Dell'Orto, E. C.; Riccardi, C.

    2015-10-01

    An experimental investigation concerning the effects of a duty-cycle in the supply of a dielectric barrier discharge in atmospheric pressure air has been performed. Electrical characteristics of the discharge have been measured, focusing mainly on the statistical properties of the current filaments and on dielectric surface charging, both affected by the frequent repetition of breakdown imposed by the duty-cycle. Information on the gas-phase composition was gathered too. In particular, a strong enhancement in the ozone formation rate is observed when suitable long pauses separate the active discharge phases. A simulation of the chemical kinetics in the gas-phase, based on a simplified discharge modeling, is briefly described in order to shed light on the observed increase in ozone production. The effect of a duty-cycle on surface modification of polymeric films in order to increase their wettability has been investigated too.

  15. Exploring the Photoreduction of Au(III) Complexes in the Gas-Phase

    Science.gov (United States)

    Marcum, Jesse C.; Kaufman, Sydney H.; Weber, J. Mathias

    2010-06-01

    We have used photodissociation spectroscopy to probe the electronic structure and photoreduction of Au(III) in gas-phase complexes containing Cl- and OH-. The gas-phase electronic spectrum of [AuCl_4]- closely resembles the aqueous solution spectrum, showing a lack of strong solvatochromic shifts. Substitution of Cl- ligands with OH- results in a strong blue shift, in agreement with ligand-field theory. Upon excitation, [AuCl_4]- can dissociate by loss of either one or two neutral Cl atoms, resulting in the reduction of gold from Au(III) to Au(II) and Au(I) respectively. The hydroxide substituted complex, [AuCl_2(OH)_2]-, demonstrates similar behavior but the only observable fragment channel is the loss of two neutral OH ligands, leading only to Au(I).

  16. Treatment of reduced sulphur compounds and SO2 by Gas Phase Advanced Oxidation

    DEFF Research Database (Denmark)

    Meusinger, Carl; Bluhme, Anders Brostrøm; Ingemar, Jonas L.

    2017-01-01

    Reduced sulphur compounds (RSCs) emitted from pig farms are a major problem for agriculture, due to their health and environmental impacts and foul odour. This study investigates the removal of RSCs, including H2S, and their oxidation product SO2 using Gas Phase Advanced Oxidation (GPAO). GPAO...... is a novel air cleaning technique which utilises accelerated atmospheric chemistry to oxidise pollutants before removing their oxidation products as particles. Removal efficiencies of 24.5% and 3.9% were found for 461 ppb of H2S and 714 ppb of SO2 in a laboratory system (volumetric flow Q = 75 m3/h......). A numerical model of the reactor system was developed to explore the basic features of the system; its output was in fair agreement with the experiment. The model verified the role of OH radicals in initiating the oxidation chemistry. All sulphur removed from the gas phase was detected as particulate matter...

  17. Photoelectron spectroscopy an introduction to ultraviolet photoelectron spectroscopy in the gas phase

    CERN Document Server

    Eland, J H D

    2013-01-01

    Photoelectron Spectroscopy: An Introduction to Ultraviolet Photoelectronspectroscopy in the Gas Phase, Second Edition Photoelectron Spectroscopy: An Introduction to Ultraviolet PhotoelectronSpectroscopy in the Gas Phase, Second Edition aims to give practical approach on the subject of photoelectron spectroscopy, as well as provide knowledge on the interpretation of the photoelectron spectrum. The book covers topics such as the principles and literature of photoelectron microscopy; the main features and analysis of photoelectron spectra; ionization techniques; and energies from the photoelectron spectra. Also covered in the book are topics suc as photoelectron band structure and the applications of photoelectron spectroscopy in chemistry. The text is recommended for students and practitioners of chemistry who would like to be familiarized with the concepts of photoelectron spectroscopy and its importance in the field.

  18. The nuclear liquid-gas phase transition: Present status and future perspectives

    International Nuclear Information System (INIS)

    Pochodzalla, J.; Imme, G.; Maddalena, V.

    1996-07-01

    More than two decades ago, the van der Waals behavior of the nucleon -nucleon force inspired the idea of a liquid-gas phase transition in nuclear matter. Heavy-ion reactions at relativistic energies offer the unique possibility for studying this phase transition in a finite, hadronic system. A general overview of this subject is given emphasizing the most recent results on nuclear calorimetry. (orig.)

  19. Conformational Study of DNA Sugars: from the Gas Phase to Solution

    Science.gov (United States)

    Uriarte, Iciar; Vallejo-López, Montserrat; Cocinero, Emilio J.; Corzana, Francisco; Davis, Benjamin G.

    2017-06-01

    Sugars are versatile molecules that play a variety of roles in the organism. For example, they are important in energy storage processes or as structural scaffolds. Here, we focus on the monosaccharide present in DNA by addressing the conformational and puckering properties in the gas phase of α- and β-methyl-2-deoxy-ribofuranoside and α- and β-methyl-2-deoxy-ribopiranoside. Other sugars have been previously studied in the gas phase The work presented here stems from a combination of chemical synthesis, ultrafast vaporization methods, supersonic expansions, microwave spectroscopy (both chirped-pulsed and Balle-Flygare cavity-based spectrometers) and NMR spectroscopy. Previous studies in the gas phase had been performed on 2-deoxyribose, but only piranose forms were detected. However, thanks to the combination of these techniques, we have isolated and characterized for the first time the conformational landscape of the sugar present in DNA in its biologically relevant furanose form. Our gas phase study serves as a probe of the conformational preferences of these biomolecules under isolation conditions. Thanks to the NMR experiments, we can characterize the favored conformations in solution and extract the role of the solvent in the structure and puckering of the monosaccharides. E. J. Cocinero, A. Lesarri, P. Écija, F. J. Basterretxea, J.-U. Grabow, J. A. Fernández, F. Castaño, Angew. Chem. Int. Edit. 2012, 51, 3119. P. Écija, I. Uriarte, L. Spada, B. G. Davis, W. Caminati, F. J. Basterretxea, A. Lesarri, E. J. Cocinero, Chem. Commun. 2016, 52, 6241. I. Peña, E. J. Cocinero, C. Cabezas, A. Lesarri, S. Mata, P. Écija, A. M. Daly, Á. Cimas, C. Bermúdez, F. J. Basterretxea, S. Blanco, J. A. Fernández, J. C. López, F. Castaño, J. L. Alonso, Angew. Chem. Int. Edit. 2013, 52, 11840.

  20. Gas Phase Transport, Adsorption and Surface Diffusion in Porous Glass Membrane

    Czech Academy of Sciences Publication Activity Database

    Yang, J.; Čermáková, Jiřina; Uchytil, Petr; Hamel, Ch.; Seidel-Morgenstern, A.

    2005-01-01

    Roč. 104, 2-4 (2005), s. 344-351 ISSN 0920-5861. [International Conference on Catalysis in Membrane Reactors /6./. Lahnstein, 06.07.2004-09.07.2004] R&D Projects: GA AV ČR(CZ) IAA4072402 Institutional research plan: CEZ:AV0Z40720504 Keywords : gas phase transport * vycor glass * adsorption Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.365, year: 2005

  1. Investigation of gas-phase decontamination of internally radioactively contaminated gaseous diffusion process equipment and piping

    International Nuclear Information System (INIS)

    Bundy, R.D.; Munday, E.B.

    1991-01-01

    Construction of the gaseous diffusion plants (GDPs) was begun during World War 2 to produce enriched uranium for defense purposes. These plants, which utilized UF 6 gas, were used primarily for this purpose through 1964. From 1959 through 1968, production shifted primarily to uranium enrichment to supply the nuclear power industry. Additional UF 6 -handling facilities were built in feed and fuel-processing plants associated with the uranium enrichment process. Two of the five process buildings at Oak ridge were shut down in 1964. Uranium enrichment activities at Oak Ridge were discontinued altogether in 1985. In 1987, the Department of Energy (DOE) decided to proceed with a permanent shutdown of the Oak Ridge Gaseous Diffusion Plant (ORGDP). DOE intends to begin decommissioning and decontamination (D ampersand D) of ORGDP early in the next century. The remaining two GDPs are expected to be shut down during the next 10 to 40 years and will also require D ampersand D, as will the other UF 6 -handling facilities. This paper presents an investigation of gas- phase decontamination of internally radioactively contaminated gaseous diffusion process equipment and piping using powerful fluorinating reagents that convert nonvolatile uranium compounds to volatile UF 6 . These reagents include ClF 3 , F 2 , and other compounds. The scope of D ampersand D at the GDPs, previous work of gas-phase decontamination, four concepts for using gas-phase decontamination, plans for further study of gas-phase decontamination, and the current status of this work are discussed. 13 refs., 15 figs

  2. Mechanisms of gas phase decomposition of C-nitro compounds from quantum chemical data

    International Nuclear Information System (INIS)

    Khrapkovskii, Grigorii M; Shamov, Alexander G; Nikolaeva, E V; Chachkov, D V

    2009-01-01

    Data on the mechanisms of gas-phase monomolecular decomposition of nitroalkanes, nitroalkenes and nitroarenes obtained using modern quantum chemical methods are described systematically. The attention is focused on the discussion of multistage decomposition of nitro compounds to elementary experimentally observed products. Characteristic features of competition of different mechanisms and the effect of molecular structure on the change in the Arrhenius parameters of the primary reaction step are considered.

  3. Origin of Asymmetric Charge Partitioning in the Dissociation of Gas-Phase Protein Homodimers

    OpenAIRE

    Jurchen, John C.; Williams, Evan R.

    2003-01-01

    The origin of asymmetric charge and mass partitioning observed for gas-phase dissociation of multiply charged macromolecular complexes has been hotly debated. These experiments hold the potential to provide detailed information about the interactions between the macromolecules within the complex. Here, this unusual phenomenon of asymmetric charge partitioning is investigated for several protein homodimers. Asymmetric charge partitioning in these ions depends on a number of factors, including ...

  4. Isospin and momentum dependence of liquid-gas phase transition in hot asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Xu, Jun; Ma, Hongru; Chen, Liewen; Li, Baoan

    2008-01-01

    The liquid-gas phase transition in hot neutron-rich nuclear matter is investigated within a self-consistent thermal model using different interactions with or without isospin and/or momentum dependence. The boundary of the phase-coexistence region is shown to be sensitive to the density dependence of the nuclear symmetry energy as well as the isospin and momentum dependence of the nuclear interaction. (author)

  5. LIAD-fs: A novel method for studies of ultrafast processes in gas phase neutral biomolecules

    International Nuclear Information System (INIS)

    Calvert, C R; Kelly, O; Duffy, M J; Belshaw, L; King, R B; Williams, I D; Greenwood, J B

    2012-01-01

    A new experimental technique for femtosecond (fs) pulse studies of gas phase biomolecules is reported. Using Laser-Induced Acoustic Desorption (LIAD) to produce a plume of neutral molecules, a time-delayed fs pulse is employed for ionisation/fragmentation, with subsequent products extracted and mass analysed electrostatically. By varying critical laser pulse parameters, this technique can be used to implement control over molecular fragmentation for a range of small biomolecules, with specific studies of amino acids demonstrated.

  6. Method and apparatus for selective capture of gas phase analytes using metal .beta.-diketonate polymers

    Science.gov (United States)

    Harvey, Scott D [Kennewick, WA

    2011-06-21

    A process and sensor device are disclosed that employ metal .beta.-diketonate polymers to selectively capture gas-phase explosives and weaponized chemical agents in a sampling area or volume. The metal .beta.-diketonate polymers can be applied to surfaces in various analytical formats for detection of: improvised explosive devices, unexploded ordinance, munitions hidden in cargo holds, explosives, and chemical weapons in public areas.

  7. Mechanisms of gas phase decomposition of C-nitro compounds from quantum chemical data

    Energy Technology Data Exchange (ETDEWEB)

    Khrapkovskii, Grigorii M; Shamov, Alexander G; Nikolaeva, E V; Chachkov, D V [Kazan State Technological University, Kazan (Russian Federation)

    2009-10-31

    Data on the mechanisms of gas-phase monomolecular decomposition of nitroalkanes, nitroalkenes and nitroarenes obtained using modern quantum chemical methods are described systematically. The attention is focused on the discussion of multistage decomposition of nitro compounds to elementary experimentally observed products. Characteristic features of competition of different mechanisms and the effect of molecular structure on the change in the Arrhenius parameters of the primary reaction step are considered.

  8. Thermodynamic Functions of Yttrium Trifluoride and Its Dimer in the Gas Phase

    Science.gov (United States)

    Osina, E. L.; Kovtun, D. M.

    2018-05-01

    New calculations of the functions for YF3 and Y2F6 in the gas phase using quantum-chemical calculations by MP2 and CCSD(T) methods are performed in connection with the ongoing work on obtaining reliable thermodynamic data of yttrium halides. The obtained values are entered in the database of the IVTANTERMO software complex. Equations approximating the temperature dependence of the reduced Gibbs energy in the T = 298.15-6000 K range of temperatures are presented.

  9. Spectroscopic evidence for gas-phase formation of successive beta-turns in a three-residue peptide chain.

    Science.gov (United States)

    Chin, Wutharath; Compagnon, Isabelle; Dognon, Jean-Pierre; Canuel, Clélia; Piuzzi, François; Dimicoli, Iliana; von Helden, Gert; Meijer, Gerard; Mons, Michel

    2005-02-09

    We report the first gas-phase spectroscopic study of a three-residue model of a peptide chain, Ac-Phe-Gly-Gly-NH2 (Ac = acetyl), using the IR/UV double resonance technique. The existence of at least five different conformers under supersonic expansion conditions is established, most of them exhibiting rather strong intramolecular H-bonds. One of the most populated conformers, however, exhibits a different H-bonding network characterized by two weak H-bonds. Comparison of the amide A and I/II experimental data with density functional theory calculations carried out on a series of selected conformations enables us to assign this conformer to two successive beta-turns along the peptide chain, the two H-bonds being of C10 type, i.e., each of them closing a 10-atom ring in the molecule. The corresponding form is found to be more stable than the 310 helix secondary structure (not observed), presumably because of specific effects due to the glycine residues.

  10. Gas-phase noncovalent functionalization of carbon nanotubes with a Ni(II) tetraaza[14]annulene complex

    Science.gov (United States)

    Basiuk, Vladimir A.; Henao-Holguín, Laura Verónica; Álvarez-Zauco, Edgar; Bassiouk, María; Basiuk, Elena V.

    2013-04-01

    The noncovalent functionalization of carbon nanotubes (CNTs) with aromatic polyazamacrocyclic compounds, based on π-π-interactions, keeps the intrinsic electronic structure of CNTs totally intact and allows for combining unique properties of the two interacting components. In addition to porphyrins and phthalocyanines, there are other, simpler compounds exhibiting similar properties, potentially useful for photovoltaic, catalytic and electrochemical applications: for example, tetraaza[14]annulenes. Many of them are highly thermally stable, which makes it possible to employ physical vapor deposition for the preparation of macrocycle-nanotube hybrids. One of such compounds is Ni(II) complex of 5,7,12,14-tetramethyldibenzo-1,4,8,11-tetraazacyclotetradeca-3,5,7,10,12,14-hexaene (also called Ni(II)-tetramethyldibenzotetraaza[14]annulene, or NiTMTAA for simplicity). In the present work, we attempted the noncovalent functionalization of both single-walled and multi-walled CNTs with NiTMTAA in the gas phase at two selected temperatures of 220 and 270 °C, which does not require the use of organic solvents and therefore can be considered as ecologically friendly. The nanohybrids obtained were characterized by means of scanning and transmission electron microscopy, energy dispersive X-ray, Fourier-transform infrared and Raman spectroscopy, as well as thermogravimetric analysis. An additional insight into the structure of adsorption complexes of NiTMTAA on CNTs was provided from density functional theory and molecular mechanics calculations.

  11. Gas-phase noncovalent functionalization of carbon nanotubes with a Ni(II) tetraaza[14]annulene complex

    Energy Technology Data Exchange (ETDEWEB)

    Basiuk, Vladimir A., E-mail: basiuk@nucleares.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510, México D.F. (Mexico); Henao-Holguín, Laura Verónica [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510, México D.F. (Mexico); Álvarez-Zauco, Edgar [Facultad de Ciencias, Universidad Nacional Autónoma de México, Circuito Exterior C.U., 04510, México D.F. (Mexico); Bassiouk, María [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510, México D.F. (Mexico); Basiuk, Elena V. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510, México D.F. (Mexico)

    2013-04-01

    The noncovalent functionalization of carbon nanotubes (CNTs) with aromatic polyazamacrocyclic compounds, based on π–π-interactions, keeps the intrinsic electronic structure of CNTs totally intact and allows for combining unique properties of the two interacting components. In addition to porphyrins and phthalocyanines, there are other, simpler compounds exhibiting similar properties, potentially useful for photovoltaic, catalytic and electrochemical applications: for example, tetraaza[14]annulenes. Many of them are highly thermally stable, which makes it possible to employ physical vapor deposition for the preparation of macrocycle–nanotube hybrids. One of such compounds is Ni(II) complex of 5,7,12,14-tetramethyldibenzo-1,4,8,11-tetraazacyclotetradeca-3,5,7,10,12, 14-hexaene (also called Ni(II)-tetramethyldibenzotetraaza[14]annulene, or NiTMTAA for simplicity). In the present work, we attempted the noncovalent functionalization of both single-walled and multi-walled CNTs with NiTMTAA in the gas phase at two selected temperatures of 220 and 270 °C, which does not require the use of organic solvents and therefore can be considered as ecologically friendly. The nanohybrids obtained were characterized by means of scanning and transmission electron microscopy, energy dispersive X-ray, Fourier-transform infrared and Raman spectroscopy, as well as thermogravimetric analysis. An additional insight into the structure of adsorption complexes of NiTMTAA on CNTs was provided from density functional theory and molecular mechanics calculations.

  12. Gas-phase noncovalent functionalization of carbon nanotubes with a Ni(II) tetraaza[14]annulene complex

    International Nuclear Information System (INIS)

    Basiuk, Vladimir A.; Henao-Holguín, Laura Verónica; Álvarez-Zauco, Edgar; Bassiouk, María; Basiuk, Elena V.

    2013-01-01

    The noncovalent functionalization of carbon nanotubes (CNTs) with aromatic polyazamacrocyclic compounds, based on π–π-interactions, keeps the intrinsic electronic structure of CNTs totally intact and allows for combining unique properties of the two interacting components. In addition to porphyrins and phthalocyanines, there are other, simpler compounds exhibiting similar properties, potentially useful for photovoltaic, catalytic and electrochemical applications: for example, tetraaza[14]annulenes. Many of them are highly thermally stable, which makes it possible to employ physical vapor deposition for the preparation of macrocycle–nanotube hybrids. One of such compounds is Ni(II) complex of 5,7,12,14-tetramethyldibenzo-1,4,8,11-tetraazacyclotetradeca-3,5,7,10,12, 14-hexaene (also called Ni(II)-tetramethyldibenzotetraaza[14]annulene, or NiTMTAA for simplicity). In the present work, we attempted the noncovalent functionalization of both single-walled and multi-walled CNTs with NiTMTAA in the gas phase at two selected temperatures of 220 and 270 °C, which does not require the use of organic solvents and therefore can be considered as ecologically friendly. The nanohybrids obtained were characterized by means of scanning and transmission electron microscopy, energy dispersive X-ray, Fourier-transform infrared and Raman spectroscopy, as well as thermogravimetric analysis. An additional insight into the structure of adsorption complexes of NiTMTAA on CNTs was provided from density functional theory and molecular mechanics calculations.

  13. Low-energy electron-induced dissociation in gas-phase nicotine, pyridine, and methyl-pyrrolidine

    Science.gov (United States)

    Ryszka, Michal; Alizadeh, Elahe; Li, Zhou; Ptasińska, Sylwia

    2017-09-01

    Dissociative electron attachment to nicotine, pyridine, and N-methyl-pyrrolidine was studied in the gas phase in order to assess their stability with respect to low-energy electron interactions. Anion yield curves for different products at electron energies ranging from zero to 15 eV were measured, and the molecular fragmentation pathways were proposed. Nicotine does not form a stable parent anion or a dehydrogenated anion, contrary to other biological systems. However, we have observed complex dissociation pathways involving fragmentation at the pyrrolidine side accompanied by isomerization mechanisms. Combining structure optimization and enthalpy calculations, performed with the Gaussian09 package, with the comparison with a deuterium-labeled N-methyl-d3-pyrrolidine allowed for the determination of the fragmentation pathways. In contrast to nicotine and N-methylpyrrolidine, the dominant pathway in dissociative electron attachment to pyridine is the loss of hydrogen, leading to the formation of an [M—H]- anion. The presented results provide important new information about the stability of nicotine and its constituent parts and contribute to a better understanding of the fragmentation mechanisms and their effects on the biological environment.

  14. Exponential-fitted methods for integrating stiff systems of ordinary differential equations: Applications to homogeneous gas-phase chemical kinetics

    Science.gov (United States)

    Pratt, D. T.

    1984-01-01

    Conventional algorithms for the numerical integration of ordinary differential equations (ODEs) are based on the use of polynomial functions as interpolants. However, the exact solutions of stiff ODEs behave like decaying exponential functions, which are poorly approximated by polynomials. An obvious choice of interpolant are the exponential functions themselves, or their low-order diagonal Pade (rational function) approximants. A number of explicit, A-stable, integration algorithms were derived from the use of a three-parameter exponential function as interpolant, and their relationship to low-order, polynomial-based and rational-function-based implicit and explicit methods were shown by examining their low-order diagonal Pade approximants. A robust implicit formula was derived by exponential fitting the trapezoidal rule. Application of these algorithms to integration of the ODEs governing homogenous, gas-phase chemical kinetics was demonstrated in a developmental code CREK1D, which compares favorably with the Gear-Hindmarsh code LSODE in spite of the use of a primitive stepsize control strategy.

  15. Shear viscosity of neutron-rich nucleonic matter near its liquid–gas phase transition

    International Nuclear Information System (INIS)

    Xu, Jun; Chen, Lie-Wen; Ko, Che Ming; Li, Bao-An; Ma, Yu Gang

    2013-01-01

    Within a relaxation time approach using free nucleon–nucleon cross sections modified by the in-medium nucleon masses that are determined from an isospin- and momentum-dependent effective nucleon–nucleon interaction, we investigate the specific shear viscosity (η/s) of neutron-rich nucleonic matter near its liquid–gas phase transition. It is found that as the nucleonic matter is heated at fixed pressure or compressed at fixed temperature, its specific shear viscosity shows a valley shape in the temperature or density dependence, with the minimum located at the boundary of the phase transition. Moreover, the value of η/s drops suddenly at the first-order liquid–gas phase transition temperature, reaching as low as 4–5 times the KSS bound of ℏ/4π. However, it varies smoothly for the second-order liquid–gas phase transition. Effects of the isospin degree of freedom and the nuclear symmetry energy on the value of η/s are also discussed

  16. Thermodynamic analysis of fuels in gas phase: ethanol, gasoline and ethanol - gasoline predicted by DFT method.

    Science.gov (United States)

    Neto, A F G; Lopes, F S; Carvalho, E V; Huda, M N; Neto, A M J C; Machado, N T

    2015-10-01

    This paper presents a theoretical study using density functional theory to calculate thermodynamics properties of major molecules compounds at gas phase of fuels like gasoline, ethanol, and gasoline-ethanol mixture in thermal equilibrium on temperature range up to 1500 K. We simulated a composition of gasoline mixture with ethanol for a thorough study of thermal energy, enthalpy, Gibbs free energy, entropy, heat capacity at constant pressure with respect to temperature in order to study the influence caused by ethanol as an additive to gasoline. We used semi-empirical computational methods as well in order to know the efficiency of other methods to simulate fuels through this methodology. In addition, the ethanol influence through the changes in percentage fractions of chemical energy released in combustion reaction and the variations on thermal properties for autoignition temperatures of fuels was analyzed. We verified how ethanol reduces the chemical energy released by gasoline combustion and how at low temperatures the gas phase fuels in thermal equilibrium have similar thermodynamic behavior. Theoretical results were compared with experimental data, when available, and showed agreement. Graphical Abstract Thermodynamic analysis of fuels in gas phase.

  17. Heavy haze in winter Beijing driven by fast gas phase oxidation

    Science.gov (United States)

    Lu, K.; Tan, Z.; Wang, H.; Li, X.; Wu, Z.; Chen, Q.; Wu, Y.; Ma, X.; Liu, Y.; Chen, X.; Shang, D.; Dong, H.; Zeng, L.; Shao, M.; Hu, M.; Fuchs, H.; Novelli, A.; Broch, S.; Hofzumahaus, A.; Holland, F.; Rohrer, F.; Bohn, B.; Georgios, G.; Schmitt, S. H.; Schlag, P.; Kiendler-Scharr, A.; Wahner, A.; Zhang, Y.

    2017-12-01

    Heavy haze conditions were frequently presented in the airsheds of Beijing and surrounding areas, especially during winter time. To explore the trace gas oxidation and the subsequent formation of aerosols, a comprehensive field campaign was performed at a regional site (in the campus of University of Chinese Academy of Science, UCAS) in Beijing winter 2016. Serious haze pollution processes were often observed with the fast increase of inorganic salt (especially nitrate) and these pollutions were always associated with enhanced humidity and the concentrations of PAN (PeroxyAcyl Nitrates) which is normally a marker of gas phase oxidations from NOx and VOCs. Moreover, based on the measurements of OH, HO2, RO2, total OH reactivity, N2O5, NO, NO2, SO2, particle concentrations/distributions/chemical compositions, and meteorological parameters, the gas phase oxidation rates that leads to the formation of sulfate, nitrate and secondary organic aerosols were estimated. These determined formation rates were clearly enhanced by several folds during pollution episodes compared to that of the clean air masses. Preliminary analysis result showed that the gas phase formation potential of nitrate and secondary organic aerosols were larger than the observed concentrations of nitrate and SOA of which the excess production may be explained by deposition and dilution.

  18. Improved machine learning method for analysis of gas phase chemistry of peptides

    Directory of Open Access Journals (Sweden)

    Ahn Natalie

    2008-12-01

    Full Text Available Abstract Background Accurate peptide identification is important to high-throughput proteomics analyses that use mass spectrometry. Search programs compare fragmentation spectra (MS/MS of peptides from complex digests with theoretically derived spectra from a database of protein sequences. Improved discrimination is achieved with theoretical spectra that are based on simulating gas phase chemistry of the peptides, but the limited understanding of those processes affects the accuracy of predictions from theoretical spectra. Results We employed a robust data mining strategy using new feature annotation functions of MAE software, which revealed under-prediction of the frequency of occurrence in fragmentation of the second peptide bond. We applied methods of exploratory data analysis to pre-process the information in the MS/MS spectra, including data normalization and attribute selection, to reduce the attributes to a smaller, less correlated set for machine learning studies. We then compared our rule building machine learning program, DataSqueezer, with commonly used association rules and decision tree algorithms. All used machine learning algorithms produced similar results that were consistent with expected properties for a second gas phase mechanism at the second peptide bond. Conclusion The results provide compelling evidence that we have identified underlying chemical properties in the data that suggest the existence of an additional gas phase mechanism for the second peptide bond. Thus, the methods described in this study provide a valuable approach for analyses of this kind in the future.

  19. The Gas-Phase Formation of Methyl Formate in Hot Molecular Cores

    Science.gov (United States)

    Horn, Anne; Møllendal, Harald; Sekiguchi, Osamu; Uggerud, Einar; Roberts, Helen; Herbst, Eric; Viggiano, A. A.; Fridgen, Travis D.

    2004-08-01

    Methyl formate, HCOOCH3, is a well-known interstellar molecule prominent in the spectra of hot molecular cores. The current view of its formation is that it occurs in the gas phase from precursor methanol, which is synthesized on the surfaces of grain mantles during a previous colder era and evaporates while temperatures increase during the process of high-mass star formation. The specific reaction sequence thought to form methyl formate, the ion-molecule reaction between protonated methanol and formaldehyde followed by dissociative recombination of the protonated ion [HCO(H)OCH3]+, has not been studied in detail in the laboratory. We present here the results of both a quantum chemical study of the ion-molecule reaction between [CH3OH2]+ and H2CO as well as new experimental work on the system. In addition, we report theoretical and experimental studies for a variety of other possible gas-phase reactions leading to ion precursors of methyl formate. The studied chemical processes leading to methyl formate are included in a chemical model of hot cores. Our results show that none of these gas-phase processes produces enough methyl formate to explain its observed abundance.

  20. Conformational Preferences of Glycerol in the Gas Phase and in Water

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Keun Hong [Korea Military Academy, Seoul (Korea, Republic of); Byun, Byung Jin; Kang, Young Kee [Chungbuk National University, Cheongju (Korea, Republic of)

    2012-03-15

    The conformational study of glycerol has been carried out using the M06-2X/cc-pVTZ level of theory in the gas phase and the SMD M06-2X/cc-pVTZ level of theory in water in order to understand its conformational preferences and solvation effects. Most of the preferred conformers of glycerol have two C{sub 5} hydrogen bonds in the gas phase, as found by the analysis of calorimetric data. It has been known that the solvation drove the hydrogen bonds of glycerol to be weaker and its potential surface to be fatter and that glycerol exists as an ensemble of many feasible local minima in water. The calculated populations of glycerol in the gas phase and in water are consistent with the observed values, which are better than the previously calculated ones at the G2(MP2), CBS-QB3, and SM5.42 HF/6-31G(d) levels of theory

  1. Statistical parameter characteristics of gas-phase fluctuations for gas-liquid intermittent flow

    Energy Technology Data Exchange (ETDEWEB)

    Matsui, G.; Monji, H.; Takaguchi, M. [Univ. of Tsukuba (Japan)

    1995-09-01

    This study deals with theoretical analysis on the general behaviour of statistical parameters of gas-phase fluctuations and comparison of statistical parameter characteristics for the real void fraction fluctuations measured with those for the wave form modified the real fluctuations. In order to investigate the details of the relation between the behavior of the statistical parameters in real intermittent flow and analytical results obtained from information on the real flow, the distributions of statistical parameters for general fundamental wave form of gas-phase fluctuations are discussed in detail. By modifying the real gas-phase fluctuations to a trapezoidaly wave, the experimental results can be directly compared with the analytical results. The analytical results for intermittent flow show that the wave form parameter, and the total amplitude of void fraction fluctuations, affects strongly on the statistical parameter characteristics. The comparison with experiment using nitrogen gas-water intermittent flow suggests that the parameters of skewness and excess may be better as indicators of flow pattern. That is, the macroscopic nature of intermittent flow can be grasped by the skewness and the excess, and the detailed flow structure may be described by the mean and the standard deviation.

  2. Systematic Search for Chemical Reactions in Gas Phase Contributing to Methanol Formation in Interstellar Space.

    Science.gov (United States)

    Gamez-Garcia, Victoria G; Galano, Annia

    2017-10-05

    A massive search for chemical routes leading to methanol formation in gas phase has been conducted using computational chemistry, at the CBS-QB3 level of theory. The calculations were performed at five different temperatures (100, 80, 50, 20, and 10 K) and at three pressures (0.1, 0.01, and 0.001 atm) for each temperature. The search was focused on identifying reactions with the necessary features to be viable in the interstellar medium (ISM). A searching strategy was applied to that purpose, which allowed to reduce an initial set of 678 possible reactions to a subset of 11 chemical routes that are recommended, for the first time, as potential candidates for contributing to methanol formation in the gas phase of the ISM. They are all barrier-less, and thus they are expected to take place at collision rates. Hopefully, including these reactions in the currently available models, for the gas-phase methanol formation in the ISM, would help improving the predicted fractional abundance of this molecule in dark clouds. Further investigations, especially those dealing with grain chemistry and electronic excited states, would be crucial to get a complete picture of the methanol formation in the ISM.

  3. Statistical parameter characteristics of gas-phase fluctuations for gas-liquid intermittent flow

    International Nuclear Information System (INIS)

    Matsui, G.; Monji, H.; Takaguchi, M.

    1995-01-01

    This study deals with theoretical analysis on the general behaviour of statistical parameters of gas-phase fluctuations and comparison of statistical parameter characteristics for the real void fraction fluctuations measured with those for the wave form modified the real fluctuations. In order to investigate the details of the relation between the behavior of the statistical parameters in real intermittent flow and analytical results obtained from information on the real flow, the distributions of statistical parameters for general fundamental wave form of gas-phase fluctuations are discussed in detail. By modifying the real gas-phase fluctuations to a trapezoidaly wave, the experimental results can be directly compared with the analytical results. The analytical results for intermittent flow show that the wave form parameter, and the total amplitude of void fraction fluctuations, affects strongly on the statistical parameter characteristics. The comparison with experiment using nitrogen gas-water intermittent flow suggests that the parameters of skewness and excess may be better as indicators of flow pattern. That is, the macroscopic nature of intermittent flow can be grasped by the skewness and the excess, and the detailed flow structure may be described by the mean and the standard deviation

  4. Gas-phase advanced oxidation as an integrated air pollution control technique

    Directory of Open Access Journals (Sweden)

    Getachew A. Adnew

    2016-03-01

    Full Text Available Gas-phase advanced oxidation (GPAO is an emerging air cleaning technology based on the natural self-cleaning processes that occur in the Earth’s atmosphere. The technology uses ozone, UV-C lamps and water vapor to generate gas-phase hydroxyl radicals that initiate oxidation of a wide range of pollutants. In this study four types of GPAO systems are presented: a laboratory scale prototype, a shipping container prototype, a modular prototype, and commercial scale GPAO installations. The GPAO systems treat volatile organic compounds, reduced sulfur compounds, amines, ozone, nitrogen oxides, particles and odor. While the method covers a wide range of pollutants, effective treatment becomes difficult when temperature is outside the range of 0 to 80 °C, for anoxic gas streams and for pollution loads exceeding ca. 1000 ppm. Air residence time in the system and the rate of reaction of a given pollutant with hydroxyl radicals determine the removal efficiency of GPAO. For gas phase compounds and odors including VOCs (e.g. C6H6 and C3H8 and reduced sulfur compounds (e.g. H2S and CH3SH, removal efficiencies exceed 80%. The method is energy efficient relative to many established technologies and is applicable to pollutants emitted from diverse sources including food processing, foundries, water treatment, biofuel generation, and petrochemical industries.

  5. Excited-state dynamics of a ruthenium(II) catalyst studied by transient photofragmentation in gas phase and transient absorption in solution

    Energy Technology Data Exchange (ETDEWEB)

    Imanbaew, D.; Nosenko, Y. [Fachbereich Chemie, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 52–54, 67663 Kaiserslautern (Germany); Forschungszentrum OPTIMAS, Erwin-Schrödinger-Str. 46, 67663 Kaiserslautern (Germany); Kerner, C. [Fachbereich Chemie, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 52–54, 67663 Kaiserslautern (Germany); Chevalier, K.; Rupp, F. [Fachbereich Physik, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 46, 67663 Kaiserslautern (Germany); Riehn, C., E-mail: riehn@chemie.uni-kl.de [Fachbereich Chemie, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 52–54, 67663 Kaiserslautern (Germany); Forschungszentrum OPTIMAS, Erwin-Schrödinger-Str. 46, 67663 Kaiserslautern (Germany); Thiel, W.R. [Fachbereich Chemie, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 52–54, 67663 Kaiserslautern (Germany); Diller, R. [Fachbereich Physik, Technische Universität Kaiserslautern, Erwin-Schrödinger-Str. 46, 67663 Kaiserslautern (Germany)

    2014-10-17

    Graphical abstract: - Highlights: • Ultrafast dynamics of new Ru(II) catalysts investigated in gas phase and solution. • Catalyst activation (HCl loss) achieved in ion trap by UV photoexcitation. • Electronic relaxation proceeds by IVR and IC followed by ground state dissociation. • No triplet formation in contrast to other Ru-polypyridine complexes. • Solvent prohibits catalyst activation in solution by fast vibrational cooling. - Abstract: We report studies on the excited state dynamics of new ruthenium(II) complexes [(η{sup 6}-cymene)RuCl(apypm)]PF{sub 6} (apypm=2-NR{sub 2}-4-(pyridine-2-yl)-pyrimidine, R=CH{sub 3} (1)/H (2)) which, in their active form [1{sup +}-HCl] and [2{sup +}-HCl], catalyze the transfer hydrogenation of arylalkyl ketones in the absence of a base. The investigations encompass femtosecond pump–probe transient mass spectrometry under isolated conditions and transient absorption spectroscopy in acetonitrile solution, both on the cations [(η{sup 6}-cymene)RuCl(apypm)]{sup +} (1{sup +}, 2{sup +}). Gas phase studies on mass selected ions were performed in an ESI ion trap mass spectrometer by transient photofragmentation, unambiguously proving the formation of the activated catalyst species [1{sup +}-HCl] or [2{sup +}-HCl] after photoexcitation being the only fragmentation channel. The primary excited state dynamics in the gas phase could be fitted to a biexponential decay, yielding time constants of <100 fs and 1–3 ps. Transient absorption spectroscopy performed in acetonitrile solution using femtosecond UV/Vis and IR probe laser pulses revealed additional deactivation processes on longer time scales (∼7–12 ps). However, the formation of the active catalyst species after photoexcitation could not be observed in solution. The results from both studies are compared to former CID investigations and DFT calculations concerning the activation mechanism.

  6. The stable microbiome of inter and sub-tidal anemone species under increasing pCO2.

    Science.gov (United States)

    Muller, Erinn M; Fine, Maoz; Ritchie, Kim B

    2016-11-23

    Increasing levels of pCO 2 within the oceans will select for resistant organisms such as anemones, which may thrive under ocean acidification conditions. However, increasing pCO 2 may alter the bacterial community of marine organisms, significantly affecting the health status of the host. A pH gradient associated with a natural volcanic vent system within Levante Bay, Vulcano Island, Italy, was used to test the effects of ocean acidification on the bacterial community of two anemone species in situ, Anemonia viridis and Actinia equina using 16 S rDNA pyrosequencing. Results showed the bacterial community of the two anemone species differed significantly from each other primarily because of differences in the Gammaproteobacteria and Epsilonproteobacteria abundances. The bacterial communities did not differ within species among sites with decreasing pH except for A. viridis at the vent site (pH = 6.05). In addition to low pH, the vent site contains trace metals and sulfide that may have influenced the bacteria community of A. viridis. The stability of the bacterial community from pH 8.1 to pH 7.4, coupled with previous experiments showing the lack of, or beneficial changes within anemones living under low pH conditions indicates that A. viridis and A. equina will be winners under future ocean acidification scenarios.

  7. An atmospheric pressure high-temperature laminar flow reactor for investigation of combustion and related gas phase reaction systems

    Energy Technology Data Exchange (ETDEWEB)

    Oßwald, Patrick; Köhler, Markus [Institute of Combustion Technology, German Aerospace Center (DLR), Pfaffenwaldring 38-40, D-70569 Stuttgart (Germany)

    2015-10-15

    A new high-temperature flow reactor experiment utilizing the powerful molecular beam mass spectrometry (MBMS) technique for detailed observation of gas phase kinetics in reacting flows is presented. The reactor design provides a consequent extension of the experimental portfolio of validation experiments for combustion reaction kinetics. Temperatures up to 1800 K are applicable by three individually controlled temperature zones with this atmospheric pressure flow reactor. Detailed speciation data are obtained using the sensitive MBMS technique, providing in situ access to almost all chemical species involved in the combustion process, including highly reactive species such as radicals. Strategies for quantifying the experimental data are presented alongside a careful analysis of the characterization of the experimental boundary conditions to enable precise numeric reproduction of the experimental results. The general capabilities of this new analytical tool for the investigation of reacting flows are demonstrated for a selected range of conditions, fuels, and applications. A detailed dataset for the well-known gaseous fuels, methane and ethylene, is provided and used to verify the experimental approach. Furthermore, application for liquid fuels and fuel components important for technical combustors like gas turbines and engines is demonstrated. Besides the detailed investigation of novel fuels and fuel components, the wide range of operation conditions gives access to extended combustion topics, such as super rich conditions at high temperature important for gasification processes, or the peroxy chemistry governing the low temperature oxidation regime. These demonstrations are accompanied by a first kinetic modeling approach, examining the opportunities for model validation purposes.

  8. An atmospheric pressure high-temperature laminar flow reactor for investigation of combustion and related gas phase reaction systems.

    Science.gov (United States)

    Oßwald, Patrick; Köhler, Markus

    2015-10-01

    A new high-temperature flow reactor experiment utilizing the powerful molecular beam mass spectrometry (MBMS) technique for detailed observation of gas phase kinetics in reacting flows is presented. The reactor design provides a consequent extension of the experimental portfolio of validation experiments for combustion reaction kinetics. Temperatures up to 1800 K are applicable by three individually controlled temperature zones with this atmospheric pressure flow reactor. Detailed speciation data are obtained using the sensitive MBMS technique, providing in situ access to almost all chemical species involved in the combustion process, including highly reactive species such as radicals. Strategies for quantifying the experimental data are presented alongside a careful analysis of the characterization of the experimental boundary conditions to enable precise numeric reproduction of the experimental results. The general capabilities of this new analytical tool for the investigation of reacting flows are demonstrated for a selected range of conditions, fuels, and applications. A detailed dataset for the well-known gaseous fuels, methane and ethylene, is provided and used to verify the experimental approach. Furthermore, application for liquid fuels and fuel components important for technical combustors like gas turbines and engines is demonstrated. Besides the detailed investigation of novel fuels and fuel components, the wide range of operation conditions gives access to extended combustion topics, such as super rich conditions at high temperature important for gasification processes, or the peroxy chemistry governing the low temperature oxidation regime. These demonstrations are accompanied by a first kinetic modeling approach, examining the opportunities for model validation purposes.

  9. Effect of Al content on the gas-phase dehydration of glycerol over silica-alumina-supported silicotungstic acid catalysts

    International Nuclear Information System (INIS)

    Kim, Yong Tae; You, Su Jin; Park, Eun Duck; Jung, Kwangdeog

    2012-01-01

    The gas-phase dehydration of glycerol to acrolein was carried out over silicotungstic acid (H 4 SiW 12 O 40 ·xH 2 O, HSiW) catalysts supported on SiO 2 , η-Al 2 O 3 , and silica-alumina with different Al contents. The HSiW catalysts supported on silica-alumina showed higher glycerol conversions and acrolein yields during the initial 2 h at 315.deg.C than did SiO 2 - and η-Al 2 O 3 -supported HSiW catalysts. Among the tested catalysts, HSiW/Si 0.9 Al 0.1Ox exhibited the highest space-time yield during the initial 2 h. The loaded HSiW species can change the acid types and suppress the formation of carbonaceous species on Al-rich silica-alumina. The deactivated HSiW supported on silica-alumina can be fully regenerated after calcination in air at 500.deg.C. As long as the molar ratio between water and glycerol was in the range of 2-11, the acrolein selectivity increased significantly with increasing water content in the feed, while the surface carbon content decreased owing to the suppression of heavy compounds

  10. Distribution of trace elements in organs of six species of cetaceans from the Ligurian Sea (Mediterranean), and the relationship with stable carbon and nitrogen ratios

    Energy Technology Data Exchange (ETDEWEB)

    Capelli, R. [Dipartimento di Chimica e Tecnologie Farmaceutiche ed Alimentari - Universita degli Studi di Genova - Via Brigata Salerno, 13 I-16147 Genova (Italy); Das, K. [MARE center, Laboratory for Oceanology, University of Liege, B6 Sart-Tilman, B-4000 Liege (Belgium); Pellegrini, R. De; Drava, G. [Dipartimento di Chimica e Tecnologie Farmaceutiche ed Alimentari - Universita degli Studi di Genova - Via Brigata Salerno, 13 I-16147 Genova (Italy); Lepoint, G. [MARE center, Laboratory for Oceanology, University of Liege, B6 Sart-Tilman, B-4000 Liege (Belgium); Miglio, C. [Dipartimento di Chimica e Tecnologie Farmaceutiche ed Alimentari - Universita degli Studi di Genova - Via Brigata Salerno, 13 I-16147 Genova (Italy); Minganti, V. [Dipartimento di Chimica e Tecnologie Farmaceutiche ed Alimentari - Universita degli Studi di Genova - Via Brigata Salerno, 13 I-16147 Genova (Italy)], E-mail: minganti@dictfa.unige.it; Poggi, R. [Museo Civico di Storia Naturale ' Giacomo Doria' - Via Brigata Liguria, 9 I-16121 Genova (Italy)

    2008-02-15

    Mercury (total and organic), cadmium, lead, copper, iron, manganese, selenium and zinc concentrations were measured in different organs of 6 different cetacean species stranded in an area of extraordinary ecological interest (Cetaceans' Sanctuary of the Mediterranean Sea) along the coast of the Ligurian Sea (North-West Mediterranean). Stable-isotopes ratios of carbon ({sup 13}C/{sup 12}C) and nitrogen ({sup 15}N/{sup 14}N) were also measured in the muscle. A significant relationship exists between {sup 15}N/{sup 14}N, mercury concentration and the trophic level. The distribution of essential and non-essential trace elements was studied on several organs, and a significant relationship between selenium and mercury, with a molar ratio close to 1, was found in the cetaceans' kidney, liver and spleen, regardless of their species. High selenium concentrations are generally associated with a low organic to total mercury ratio. While narrow ranges of concentrations were observed for essential elements in most organs, mercury and selenium concentrations are characterised by a wide range of variation. Bio-accumulation and bio-amplification processes in cetaceans can be better understood by comparing trace element concentrations with the stable-isotopes data.

  11. Wide band gap Ga2O3 as efficient UV-C photocatalyst for gas-phase degradation applications.

    Science.gov (United States)

    Jędrzejczyk, Marcin; Zbudniewek, Klaudia; Rynkowski, Jacek; Keller, Valérie; Grams, Jacek; Ruppert, Agnieszka M; Keller, Nicolas

    2017-12-01

    α, β, γ, and δ polymorphs of 4.6-4.8 eV wide band gap Ga 2 O 3 photocatalysts were prepared via a soft chemistry route. Their photocatalytic activity under 254 nm UV-C light in the degradation of gaseous toluene was strongly depending on the polymorph phase. α- and β-Ga 2 O 3 photocatalysts enabled achieving high and stable conversions of toluene with selectivities to CO 2 within the 50-90% range, by contrast to conventional TiO 2 photocatalysts that fully deactivate very rapidly on stream in similar operating conditions with rather no CO 2 production, no matter whether UV-A or UV-C light was used. The highest performances were achieved on the high specific surface area β-Ga 2 O 3 photocatalyst synthesized by adding polyethylene glycol (PEG) as porogen before precipitation, with stable toluene conversion and mineralization rate into CO 2 strongly overcoming those obtained on commercial β-Ga 2 O 3 . They were attributed to favorable physicochemical properties in terms of high specific surface area, small mean crystallite size, good crystallinity, high pore volume with large size mesopore distribution and appropriate surface acidity, and to the possible existence of a double local internal field within Ga 3+ units. In the degradation of hydrogen sulfide, PEG-derived β-Ga 2 O 3 takes advantage from its high specific surface area for storing sulfate, and thus for increasing its resistance to deactivation and the duration at total sulfur removal when compared to other β-Ga 2 O 3 photocatalysts. So, we illustrated the interest of using high surface area β-Ga 2 O 3 in environmental photocatalysis for gas-phase depollution applications.

  12. Global minimum profile error (GMPE) - a least-squares-based approach for extracting macroscopic rate coefficients for complex gas-phase chemical reactions.

    Science.gov (United States)

    Duong, Minh V; Nguyen, Hieu T; Mai, Tam V-T; Huynh, Lam K

    2018-01-03

    Master equation/Rice-Ramsperger-Kassel-Marcus (ME/RRKM) has shown to be a powerful framework for modeling kinetic and dynamic behaviors of a complex gas-phase chemical system on a complicated multiple-species and multiple-channel potential energy surface (PES) for a wide range of temperatures and pressures. Derived from the ME time-resolved species profiles, the macroscopic or phenomenological rate coefficients are essential for many reaction engineering applications including those in combustion and atmospheric chemistry. Therefore, in this study, a least-squares-based approach named Global Minimum Profile Error (GMPE) was proposed and implemented in the MultiSpecies-MultiChannel (MSMC) code (Int. J. Chem. Kinet., 2015, 47, 564) to extract macroscopic rate coefficients for such a complicated system. The capability and limitations of the new approach were discussed in several well-defined test cases.

  13. Modeling of gas-phase chemistry in the chemical vapor deposition of polysilicon in a cold wall system

    Energy Technology Data Exchange (ETDEWEB)

    Toprac, A.J.; Edgar, T.F.; Trachtenberg, I. (Univ. of Texas, Austin, TX (United States). Dept. of Chemical Engineering)

    1993-06-01

    The relative contribution of gas-phase chemistry to deposition processes is an important issue both from the standpoint of operation and modeling of these processes. In polysilicon deposition from thermally activated silane in a cold wall rapid thermal chemical vapor deposition (RTCVD) system, the relative contribution of gas-phase chemistry to the overall deposition rate was examined by a mass-balance model. Evaluating the process at conditions examined experimentally, the model indicated that gas-phase reactions may be neglected to good accuracy in predicting polysilicon deposition rate. The model also provided estimates of the level of gas-phase generated SiH[sub 2] associated with deposition on the cold-process chamber walls.

  14. Heterogeneity-enhanced gas phase formation in shallow aquifers during leakage of CO2-saturated water from geologic sequestration sites

    DEFF Research Database (Denmark)

    Plampin, Michael R.; Lassen, Rune Nørbæk; Sakaki, Toshihiro

    2014-01-01

    sands. Soil moisture sensors were utilized to observe the formation of gas phase near the porous media interfaces. Results indicate that the conditions under which heterogeneity controls gas phase evolution can be successfully predicted through analysis of simple parameters, including the dissolved CO2......, it is important to understand the physical processes that CO2 will undergo as it moves through naturally heterogeneous porous media formations. Previous studies have shown that heterogeneity can enhance the evolution of gas phase CO2 in some cases, but the conditions under which this occurs have not yet been...... quantitatively defined, nor tested through laboratory experiments. This study quantitatively investigates the effects of geologic heterogeneity on the process of gas phase CO2 evolution in shallow aquifers through an extensive set of experiments conducted in a column that was packed with layers of various test...

  15. Laboratory Studies on the Formation of Carbon-Bearing Molecules in Extraterrestrial Environments: From the Gas Phase to the Solid State

    Science.gov (United States)

    Jamieson, C. S.; Guo, Y.; Gu, X.; Zhang, F.; Bennett, C. J.; Kaiser, R. I.

    2006-01-01

    A detailed knowledge of the formation of carbon-bearing molecules in interstellar ices and in the gas phase of the interstellar medium is of paramount interest to understand the astrochemical evolution of extraterrestrial environments (1). This research also holds strong implications to comprehend the chemical processing of Solar System environments such as icy planets and their moons together with the atmospheres of planets and their satellites (2). Since the present composition of each interstellar and Solar System environment reflects the matter from which it was formed and the processes which have changed the chemical nature since the origin (solar wind, planetary magnetospheres, cosmic ray exposure, photolysis, chemical reactions), a detailed investigation of the physicochemical mechanisms altering the pristine environment is of paramount importance to grasp the contemporary composition. Once these underlying processes have been unraveled, we can identify those molecules, which belonged to the nascent setting, distinguish molecular species synthesized in a later stage, and predict the imminent chemical evolution of, for instance, molecular clouds. Laboratory experiments under controlled physicochemical conditions (temperature, pressure, chemical composition, high energy components) present ideal tools for simulating the chemical evolution of interstellar and Solar System environments. Here, laboratory experiments can predict where and how (reaction mechanisms; chemicals necessary) in extraterrestrial environments and in the interstellar medium complex, carbon bearing molecules can be formed on interstellar grains and in the gas phase. This paper overviews the experimental setups utilized in our laboratory to mimic the chemical processing of gas phase and solid state (ices) environments. These are a crossed molecular beams machine (3) and a surface scattering setup (4). We also present typical results of each setup (formation of amino acids, aldehydes, epoxides

  16. Why are tropical mountain passes "low" for some species? Genetic and stable-isotope tests for differentiation, migration and expansion in elevational generalist songbirds.

    Science.gov (United States)

    Gadek, Chauncey R; Newsome, Seth D; Beckman, Elizabeth J; Chavez, Andrea N; Galen, Spencer C; Bautista, Emil; Witt, Christopher C

    2018-05-01

    gradient, potentially concurrent with Holocene anthropogenic habitat conversion for agriculture. In different ways, each species defies the tendency for tropical birds to have long-term stable distributions and sedentary habits. We conclude that tropical elevational generalism is rare due to evolutionary instability. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

  17. Organotin persistence in contaminated marine sediments and porewaters: In situ degradation study using species-specific stable isotopic tracers

    Energy Technology Data Exchange (ETDEWEB)

    Furdek, Martina; Mikac, Nevenka [Division for Marine and Environmental Research, Rudjer Boskovic Institute, Bijenicka 54, Zagreb (Croatia); Bueno, Maite; Tessier, Emmanuel; Cavalheiro, Joana [Laboratoire de Chimie Analytique Bio-inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l’Environnement et les Matériaux, CNRS UMR 5254, Université de Pau et des Pays de l’Adour, Hélioparc Pau Pyrénées, 2, Av. P. Angot, 64053 Pau Cedex 9 (France); Monperrus, Mathilde, E-mail: mathilde.monperrus@univ-pau.fr [Laboratoire de Chimie Analytique Bio-inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l’Environnement et les Matériaux, CNRS UMR 5254, Université de Pau et des Pays de l’Adour, Hélioparc Pau Pyrénées, 2, Av. P. Angot, 64053 Pau Cedex 9 (France)

    2016-04-15

    Highlights: • Limiting step in OTC degradation in sediments is their desorption into porewater. • TBT persistence in contaminated sediments increases in sediments rich in organic matter. • DBT does not accumulate in sediments as degradation product of TBT. • TBT and DBT degradation in porewaters occurs with half-lives from 2.9 to 9.2 days. • PhTs degradation is slower than BuTs degradation in oxic porewaters. - Abstract: This paper provides a comprehensive study of the persistence of butyltins and phenyltins in contaminated marine sediments and presents the first data on their degradation potentials in porewaters. The study’s aim was to explain the different degradation efficiencies of organotin compounds (OTC) in contaminated sediments. The transformation processes of OTC in sediments and porewaters were investigated in a field experiment using species-specific, isotopically enriched organotin tracers. Sediment characteristics (organic carbon content and grain size) were determined to elucidate their influence on the degradation processes. The results of this study strongly suggest that a limiting step in OTC degradation in marine sediments is their desorption into porewaters because their degradation in porewaters occurs notably fast with half-lives of 9.2 days for tributyltin (TBT) in oxic porewaters and 2.9 ± 0.1 and 9.1 ± 0.9 days for dibutyltin (DBT) in oxic and anoxic porewaters, respectively. By controlling the desorption process, organic matter influences the TBT degradation efficiency and consequently defines its persistence in contaminated sediments, which thus increases in sediments rich in organic matter.

  18. Organotin persistence in contaminated marine sediments and porewaters: In situ degradation study using species-specific stable isotopic tracers

    International Nuclear Information System (INIS)

    Furdek, Martina; Mikac, Nevenka; Bueno, Maite; Tessier, Emmanuel; Cavalheiro, Joana; Monperrus, Mathilde

    2016-01-01

    Highlights: • Limiting step in OTC degradation in sediments is their desorption into porewater. • TBT persistence in contaminated sediments increases in sediments rich in organic matter. • DBT does not accumulate in sediments as degradation product of TBT. • TBT and DBT degradation in porewaters occurs with half-lives from 2.9 to 9.2 days. • PhTs degradation is slower than BuTs degradation in oxic porewaters. - Abstract: This paper provides a comprehensive study of the persistence of butyltins and phenyltins in contaminated marine sediments and presents the first data on their degradation potentials in porewaters. The study’s aim was to explain the different degradation efficiencies of organotin compounds (OTC) in contaminated sediments. The transformation processes of OTC in sediments and porewaters were investigated in a field experiment using species-specific, isotopically enriched organotin tracers. Sediment characteristics (organic carbon content and grain size) were determined to elucidate their influence on the degradation processes. The results of this study strongly suggest that a limiting step in OTC degradation in marine sediments is their desorption into porewaters because their degradation in porewaters occurs notably fast with half-lives of 9.2 days for tributyltin (TBT) in oxic porewaters and 2.9 ± 0.1 and 9.1 ± 0.9 days for dibutyltin (DBT) in oxic and anoxic porewaters, respectively. By controlling the desorption process, organic matter influences the TBT degradation efficiency and consequently defines its persistence in contaminated sediments, which thus increases in sediments rich in organic matter.

  19. Gas-Phase Reactions of Doubly Charged Lanthanide Cations with Alkanes and Alkenes. Trends in Metal(2+) Reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Gibson, John K.; Marcalo, Joaquim; Santos, Marta; Pires de Matos, Antonio; Haire, Richard G.

    2008-12-08

    The gas-phase reactivity of doubly-charged lanthanide cations, Ln2+ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), with alkanes (methane, ethane, propane, n-butane) and alkenes (ethene, propene, 1-butene) was studied by Fourier transform ion cyclotron resonance mass spectrometry. The reaction products consisted of different combinations of doubly-charged organometallic ions?adducts or species formed via metal-ion-induced hydrogen, dihydrogen, alkyl, or alkane eliminations from the hydrocarbons?and singly-charged ions that resulted from electron, hydride, or methide transfers from the hydrocarbons to the metal ions. The only lanthanide cations capable of activating the hydrocarbons to form doubly-charged organometallic ions were La2+, Ce2+, Gd2+, and Tb2+, which have ground-state or low-lying d1 electronic configurations. Lu2+, with an accessible d1 electronic configuration but a rather high electron affinity, reacted only through transfer channels. The remaining Ln2+ reacted via transfer channels or adduct formation. The different accessibilities of d1 electronic configurations and the range of electron affinities of the Ln2+ cations allowed for a detailed analysis of the trends for metal(2+) reactivity and the conditions for occurrence of bond activation, adduct formation, and electron, hydride, and methide transfers.

  20. A VUV photoionization measurement and ab-initio calculation of the ionization energy of gas phase SiO2

    Energy Technology Data Exchange (ETDEWEB)

    Kostko, Oleg; Ahmed, Musahid; Metz, Ricardo B.

    2008-12-05

    In this work we report on the detection and vacuum-ultraviolet (VUV) photoionization of gas phase SiO2 generated in situ via laser ablation of silicon in a CO2 molecular beam. The resulting species are investigated by single photon ionization with tunable VUV synchrotron radiation and mass analyzed using reflectron mass spectrometry. Photoionization efficiency (PIE) curves are recorded for SiO and SiO2 and ionization energy estimates are revealed from such measurements. A state-to-state ionizationenergy of 12.60 (+-0.05) eV is recorded by fitting two prominent peaks in the PIE curve for the following process: 1SUM O-Si-O --> 2PRODg [O-Si-O]+. Electronic structure calculations aid in the interpretation of the photoionization process and allow for identification of the symmetric stretch of 2PRODg [O-Si-O]+ which is observed in the PIE spectrum to be 0.11 eV (890 cm-1) above the ground state of the cation and agrees with the 892 cm-1 symmetric stretch frequency calculated at the CCSD(T)/aug-cc-pVTZ level.

  1. Hydroperoxide Measurements During Low-Temperature Gas-Phase Oxidation of n-Heptane and n-Decane

    KAUST Repository

    Rodriguez, Anne

    2017-02-13

    A wide range of hydroperoxides (C-C alkyl hydroperoxides, C-C alkenyl hydroperoxides, C ketohydroperoxides, and hydrogen peroxide (HO)), as well as ketene and diones, have been quantified during the gas-phase oxidation of n-heptane. Some of these species, as well as C alkenyl hydroperoxides and ketohydroperoxides, were also measured during the oxidation of n-decane. These experiments were performed using an atmospheric-pressure jet-stirred reactor at temperatures from 500 to 1100 K and one of three analytical methods, time-of-flight mass spectrometry combined with tunable synchrotron photoionization with a molecular beam sampling: time-of-flight mass spectrometry combined with laser photoionization with a capillary tube sampling, continuous wave cavity ring-down spectroscopy with sonic probe sampling. The experimental temperature at which the maximum mole fraction is observed increases significantly for alkyl hydroperoxides, alkenyl hydroperoxides, and then more so again for hydrogen peroxide, compared to ketohydroperoxides. The influence of the equivalence ratio from 0.25 to 4 on the formation of these peroxides has been studied during n-heptane oxidation. The up-to-date detailed kinetic oxidation models for n-heptane and for n-decane found in the literature have been used to discuss the possible pathways by which these peroxides, ketene, and diones are formed. In general, the model predicts well the reactivity of the two fuels, as well as the formation of major intermediates. (Figure Presented).

  2. Hydroperoxide Measurements During Low-Temperature Gas-Phase Oxidation of n-Heptane and n-Decane

    KAUST Repository

    Rodriguez, Anne; Herbinet, Olivier; Meng, Xiangzan; Fittschen, Christa; Wang, Zhandong; Xing, Lili; Zhang, Lidong; Battin-Leclerc, Fré dé rique

    2017-01-01

    A wide range of hydroperoxides (C-C alkyl hydroperoxides, C-C alkenyl hydroperoxides, C ketohydroperoxides, and hydrogen peroxide (HO)), as well as ketene and diones, have been quantified during the gas-phase oxidation of n-heptane. Some of these species, as well as C alkenyl hydroperoxides and ketohydroperoxides, were also measured during the oxidation of n-decane. These experiments were performed using an atmospheric-pressure jet-stirred reactor at temperatures from 500 to 1100 K and one of three analytical methods, time-of-flight mass spectrometry combined with tunable synchrotron photoionization with a molecular beam sampling: time-of-flight mass spectrometry combined with laser photoionization with a capillary tube sampling, continuous wave cavity ring-down spectroscopy with sonic probe sampling. The experimental temperature at which the maximum mole fraction is observed increases significantly for alkyl hydroperoxides, alkenyl hydroperoxides, and then more so again for hydrogen peroxide, compared to ketohydroperoxides. The influence of the equivalence ratio from 0.25 to 4 on the formation of these peroxides has been studied during n-heptane oxidation. The up-to-date detailed kinetic oxidation models for n-heptane and for n-decane found in the literature have been used to discuss the possible pathways by which these peroxides, ketene, and diones are formed. In general, the model predicts well the reactivity of the two fuels, as well as the formation of major intermediates. (Figure Presented).

  3. Delivering Transmembrane Peptide Complexes to the Gas Phase Using Nanodiscs and Electrospray Ionization

    Science.gov (United States)

    Li, Jun; Richards, Michele R.; Kitova, Elena N.; Klassen, John S.

    2017-10-01

    The gas-phase conformations of dimers of the channel-forming membrane peptide gramicidin A (GA), produced from isobutanol or aqueous solutions of GA-containing nanodiscs (NDs), are investigated using electrospray ionization-ion mobility separation-mass spectrometry (ESI-IMS-MS) and molecular dynamics (MD) simulations. The IMS arrival times measured for (2GA + 2Na)2+ ions from isobutanol reveal three different conformations, with collision cross-sections (Ω) of 683 Å2 (conformation 1, C1), 708 Å2 (C2), and 737 Å2 (C3). The addition of NH4CH3CO2 produced (2GA + 2Na)2+ and (2GA + H + Na)2+ ions, with Ω similar to those of C1, C2, and C3, as well as (2GA + 2H)2+, (2GA + 2NH4)2+, and (2GA + H + NH4)2+ ions, which adopt a single conformation with a Ω similar to that of C2. These results suggest that the nature of the charging agents, imparted by the ESI process, can influence dimer conformation in the gas phase. Notably, the POPC NDs produced exclusively (2GA + 2NH4)2+ dimer ions; the DMPC NDs produced both (2GA + 2H)2+ and (2GA + 2NH4)2+ dimer ions. While the Ω of (2GA + 2H)2+ is similar to that of C2, the (2GA + 2NH4)2+ ions from NDs adopt a more compact structure, with a Ω of 656 Å2. It is proposed that this compact structure corresponds to the ion conducting single stranded head-to-head helical GA dimer. These findings highlight the potential of NDs, combined with ESI, for transferring transmembrane peptide complexes directly from lipid bilayers to the gas phase. [Figure not available: see fulltext.

  4. Position for determining gas-phase volatile organic compound concentrations in transuranic waste containers. Revision 2

    Energy Technology Data Exchange (ETDEWEB)

    Connolly, M.J.; Liekhus, K.J. [Lockheed Martin Idaho Technologies Co., Idaho Falls, ID (United States). Idaho National Engineering and Environmental Lab.; Djordjevic, S.M.; Loehr, C.A.; Spangler, L.R. [Benchmark Environmental Corp. (United States)

    1998-06-01

    In the conditional no-migration determination (NMD) for the test phase of the Waste Isolation Pilot Plant (WIPP), the US Environmental Protection Agency (EPA) imposed certain conditions on the US Department of Energy (DOE) regarding gas phase volatile organic compound (VOC) concentrations in the void space of transuranic (TRU) waste containers. Specifically, the EPA required the DOE to ensure that each waste container has no layer of confinement that contains flammable mixtures of gases or mixtures of gases that could become flammable when mixed with air. The EPA also required that sampling of the headspace of waste containers outside inner layers of confinement be representative of the entire void space of the container. The EPA stated that all layers of confinement in a container would have to be sampled until DOE can demonstrate to the EPA that sampling of all layers is either unnecessary or can be safely reduced. A test program was conducted at the Idaho National Engineering and Environmental Laboratory (INEEL) to demonstrate that the gas phase VOC concentration in the void space of each layer of confinement in vented drums can be estimated from measured drum headspace using a theoretical transport model and that sampling of each layer of confinement is unnecessary. This report summarizes the studies performed in the INEEL test program and extends them for the purpose of developing a methodology for determining gas phase VOC concentrations in both vented and unvented TRU waste containers. The methodology specifies conditions under which waste drum headspace gases can be said to be representative of drum gases as a whole and describes a method for predicting drum concentrations in situations where the headspace concentration is not representative. The methodology addresses the approach for determining the drum VOC gas content for two purposes: operational period drum handling and operational period no-migration calculations.

  5. Position for determining gas phase volatile organic compound concentrations in transuranic waste containers. Revision 1

    International Nuclear Information System (INIS)

    Connolly, M.J.; Liekhus, K.J.; Djordjevic, S.M.; Loehr, C.A.; Spangler, L.R.

    1995-08-01

    In the conditional no-migration determination (NMD) for the test phase of the Waste Isolation Pilot Plant (WIPP), the US Environmental Protection Agency (EPA) imposed certain conditions on the US Department of Energy (DOE) regarding gas phase volatile organic compound (VOC) concentrations in the void space of transuranic (TRU) waste containers. Specifically, the EPA required the DOE to ensure that each waste container has no layer of confinement that contains flammable mixtures of gases or mixtures of gases that could become flammable when mixed with air. The EPA also required that sampling of the headspace of waste containers outside inner layers of confinement be representative of the entire void space of the container. The EPA stated that all layers of confinement in a container would have to be sampled until DOE can demonstrate to the EPA that sampling of all layers is either unnecessary or can be safely reduced. A test program was conducted at the Idaho National Engineering Laboratory (INEL) to demonstrate that the gas phase VOC concentration in the void space of each layer of confinement in vented drums can be estimated from measured drum headspace using a theoretical transport model and that sampling of each layer of confinement is unnecessary. This report summarizes the studies performed in the INEL test program and extends them for the purpose of developing a methodology for determining gas phase VOC concentrations in both vented and unvented TRU waste containers. The methodology specifies conditions under which waste drum headspace gases can be said to be representative of drum gases as a whole and describes a method for predicting drum concentrations in situations where the headspace concentration is not representative. The methodology addresses the approach for determining the drum VOC gas content for two purposes: operational period drum handling and operational period no-migration calculations

  6. Photoisomerization action spectroscopy of the carbocyanine dye DTC+ in the gas phase.

    Science.gov (United States)

    Adamson, Brian D; Coughlan, Neville J A; da Silva, Gabriel; Bieske, Evan J

    2013-12-19

    Molecular photoisomerization plays a crucial role in diverse biological and technological contexts. Here, we combine ion mobility spectrometry and laser spectroscopy to characterize the photoisomerization of molecular cations in the gas phase. The target molecular ions, polymethine dye cations 3,3'-diethylthiacarbocyanine (DTC(+)), are propelled through helium buffer gas by an electric field and are photoisomerized by light from a tunable laser. Photoexcitation over the 450-570 nm range converts trans-DTC(+) to cis-DTC(+), noticeably modifying the ions' arrival time distribution. The photoisomerization action spectrum, which has a maximum at 535 nm, resembles the absorption spectrum of DTC(+) in solution but is shifted 25 nm to shorter wavelength. Comparisons between measured and calculated mobilities suggest that the photoisomer involves a twist about the second C-C bond in the methine chain (8,9-cis isomer) rather than a twist about the first methine C-C bond (2,8-cis isomer). It is postulated that the excited gas-phase ions internally convert from the S1 Franck-Condon region to the S0 manifold and explore the conformational landscape as they cool through He buffer gas collisions. Master equation simulations of the relaxation process in the S0 manifold suggest that the 8,9-cis isomer is preferred over the 2,8-cis isomer because it lies lower in energy and because it is separated from the trans isomer by a substantially higher barrier. The study demonstrates that the photoisomerization of molecular ions can be probed selectively in the gas phase, providing insights into photoisomerization mechanisms and information on the solvent-free absorption spectrum.

  7. Gas-Phase Thermal Tautomerization of Imidazole-Acetic Acid: Theoretical and Computational Investigations

    Directory of Open Access Journals (Sweden)

    Saadullah G. Aziz

    2015-11-01

    Full Text Available The gas-phase thermal tautomerization reaction between imidazole-4-acetic (I and imidazole-5-acetic (II acids was monitored using the traditional hybrid functional (B3LYP and the long-range corrected functionals (CAM-B3LYP and ωB97XD with 6-311++G** and aug-cc-pvdz basis sets. The roles of the long-range and dispersion corrections on their geometrical parameters, thermodynamic functions, kinetics, dipole moments, Highest Occupied Molecular Orbital–Lowest Unoccupied Molecular Orbital (HOMO–LUMO energy gaps and total hyperpolarizability were investigated. All tested levels of theory predicted the preference of I over II by 0.750–0.877 kcal/mol. The origin of predilection of I is assigned to the H-bonding interaction (nN8→σ*O14–H15. This interaction stabilized I by 15.07 kcal/mol. The gas-phase interconversion between the two tautomers assumed a 1,2-proton shift mechanism, with two transition states (TS, TS1 and TS2, having energy barriers of 47.67–49.92 and 49.55–52.69 kcal/mol, respectively, and an sp3-type intermediate. A water-assisted 1,3-proton shift route brought the barrier height down to less than 20 kcal/mol in gas-phase and less than 12 kcal/mol in solution. The relatively high values of total hyperpolarizability of I compared to II were interpreted and discussed.

  8. The Gas-Phase Photophysics of Eosin Y and its Maleimide Conjugate.

    Science.gov (United States)

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

    2016-05-26

    The use of the xanthene family of dyes as fluorescent probes in a wide range of applications has provided impetus for the studying of their photophysical properties. In particular, recent advances in gas-phase techniques such as FRET that utilize such chromophores have placed a greater importance on the characterization of these properties in the gas phase. Additionally, the use of synthetic linker chains to graft the chromophores in a site-specific manner to their target system is ubiquitous. There is, however, often limited information on how the addition of such a linker chain may affect the photophysical properties of the chromophores, which is of fundamental importance for interpretation of experimental data reliant on grafted chromophores. Here, we present data on the optical spectroscopy of different protonation states of Eosin Y, a fluorescein derivative. We compare the photophysics of Eosin Y to its maleimide conjugate, and to the thioether product of the reaction of this conjugate with cysteamine. Comparison of the mass spectra following laser irradiation shows that very different relaxation takes place upon addition of the maleimide moiety but that the photophysics of the bare chromophore are restored upon addition of cysteamine. This radical change in the photophysics is interpreted in terms of charge-transfer states, whose energy relative to the S1 ← S0 transition of the chromophore is dependent on the conjugation of the maleimide moiety. We also show that the shape of the absorption band is unchanged in the gas-phase as compared to the solution-phase, showing a maximum with a shoulder toward the blue, and examination of isotope distributions of the isolated ions show that this shoulder cannot be due to the presence of dimers. Consideration of the fluorescence emission spectrum allows a tentative assignment of the shoulder to be due to a vibrational progression with a high Franck-Condon factor.

  9. Aqueous nitrite ion determination by selective reduction and gas phase nitric oxide chemiluminescence

    Science.gov (United States)

    Dunham, A. J.; Barkley, R. M.; Sievers, R. E.; Clarkson, T. W. (Principal Investigator)

    1995-01-01

    An improved method of flow injection analysis for aqueous nitrite ion exploits the sensitivity and selectivity of the nitric oxide (NO) chemilluminescence detector. Trace analysis of nitrite ion in a small sample (5-160 microL) is accomplished by conversion of nitrite ion to NO by aqueous iodide in acid. The resulting NO is transported to the gas phase through a semipermeable membrane and subsequently detected by monitoring the photoemission of the reaction between NO and ozone (O3). Chemiluminescence detection is selective for measurement of NO, and, since the detection occurs in the gas-phase, neither sample coloration nor turbidity interfere. The detection limit for a 100-microL sample is 0.04 ppb of nitrite ion. The precision at the 10 ppb level is 2% relative standard deviation, and 60-180 samples can be analyzed per hour. Samples of human saliva and food extracts were analyzed; the results from a standard colorimetric measurement are compared with those from the new chemiluminescence method in order to further validate the latter method. A high degree of selectivity is obtained due to the three discriminating steps in the process: (1) the nitrite ion to NO conversion conditions are virtually specific for nitrite ion, (2) only volatile products of the conversion will be swept to the gas phase (avoiding turbidity or color in spectrophotometric methods), and (3) the NO chemiluminescence detector selectively detects the emission from the NO + O3 reaction. The method is free of interferences, offers detection limits of low parts per billion of nitrite ion, and allows the analysis of up to 180 microL-sized samples per hour, with little sample preparation and no chromatographic separation. Much smaller samples can be analyzed by this method than in previously reported batch analysis methods, which typically require 5 mL or more of sample and often need chromatographic separations as well.

  10. Position for determining gas-phase volatile organic compound concentrations in transuranic waste containers. Revision 2

    International Nuclear Information System (INIS)

    Connolly, M.J.; Liekhus, K.J.

    1998-06-01

    In the conditional no-migration determination (NMD) for the test phase of the Waste Isolation Pilot Plant (WIPP), the US Environmental Protection Agency (EPA) imposed certain conditions on the US Department of Energy (DOE) regarding gas phase volatile organic compound (VOC) concentrations in the void space of transuranic (TRU) waste containers. Specifically, the EPA required the DOE to ensure that each waste container has no layer of confinement that contains flammable mixtures of gases or mixtures of gases that could become flammable when mixed with air. The EPA also required that sampling of the headspace of waste containers outside inner layers of confinement be representative of the entire void space of the container. The EPA stated that all layers of confinement in a container would have to be sampled until DOE can demonstrate to the EPA that sampling of all layers is either unnecessary or can be safely reduced. A test program was conducted at the Idaho National Engineering and Environmental Laboratory (INEEL) to demonstrate that the gas phase VOC concentration in the void space of each layer of confinement in vented drums can be estimated from measured drum headspace using a theoretical transport model and that sampling of each layer of confinement is unnecessary. This report summarizes the studies performed in the INEEL test program and extends them for the purpose of developing a methodology for determining gas phase VOC concentrations in both vented and unvented TRU waste containers. The methodology specifies conditions under which waste drum headspace gases can be said to be representative of drum gases as a whole and describes a method for predicting drum concentrations in situations where the headspace concentration is not representative. The methodology addresses the approach for determining the drum VOC gas content for two purposes: operational period drum handling and operational period no-migration calculations

  11. Deliberate and Accidental Gas-Phase Alkali Doping of Chalcogenide Semiconductors: Cu(In,Ga)Se2.

    Science.gov (United States)

    Colombara, Diego; Berner, Ulrich; Ciccioli, Andrea; Malaquias, João C; Bertram, Tobias; Crossay, Alexandre; Schöneich, Michael; Meadows, Helene J; Regesch, David; Delsante, Simona; Gigli, Guido; Valle, Nathalie; Guillot, Jérome; El Adib, Brahime; Grysan, Patrick; Dale, Phillip J

    2017-02-24

    Alkali metal doping is essential to achieve highly efficient energy conversion in Cu(In,Ga)Se 2 (CIGSe) solar cells. Doping is normally achieved through solid state reactions, but recent observations of gas-phase alkali transport in the kesterite sulfide (Cu 2 ZnSnS 4 ) system (re)open the way to a novel gas-phase doping strategy. However, the current understanding of gas-phase alkali transport is very limited. This work (i) shows that CIGSe device efficiency can be improved from 2% to 8% by gas-phase sodium incorporation alone, (ii) identifies the most likely routes for gas-phase alkali transport based on mass spectrometric studies, (iii) provides thermochemical computations to rationalize the observations and (iv) critically discusses the subject literature with the aim to better understand the chemical basis of the phenomenon. These results suggest that accidental alkali metal doping occurs all the time, that a controlled vapor pressure of alkali metal could be applied during growth to dope the semiconductor, and that it may have to be accounted for during the currently used solid state doping routes. It is concluded that alkali gas-phase transport occurs through a plurality of routes and cannot be attributed to one single source.

  12. Gas-Phase Photocatalytic Oxidation of Dimethylamine: The Reaction Pathway and Kinetics

    Directory of Open Access Journals (Sweden)

    Anna Kachina

    2007-01-01

    Full Text Available Gas-phase photocatalytic oxidation (PCO and thermal catalytic oxidation (TCO of dimethylamine (DMA on titanium dioxide was studied in a continuous flow simple tubular reactor. Volatile PCO products of DMA included ammonia, formamide, carbon dioxide, and water. Ammonia was further oxidized in minor amounts to nitrous oxide and nitrogen dioxide. Effective at 573 K, TCO resulted in the formation of ammonia, hydrogen cyanide, carbon monoxide, carbon dioxide, and water. The PCO kinetic data fit well to the monomolecular Langmuir-Hinshelwood model, whereas TCO kinetic behaviour matched the first-order process. No deactivation of the photocatalyst during the multiple long-run experiments was observed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Sylwester, Eric Robert [Univ. of California, Berkeley, CA (United States)

    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 ZrBr4, HfBr4, RfBr4, NbBr5, TaOBr3, HaCl5, WBr6, FrBr, and BiBr3. 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 (ΔHa) 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 ΔHa was observed: RfBr4 > ZrBr4 > HfBr4. The ΔHa 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 261Rf was performed. 261Rf was produced via the 248Cm(18O, 5n) reaction and observed with a half-life of 74-6+7 seconds, in excellent agreement with the previous measurement of 78-6+11 seconds. We recommend a new half-life of 75±7 seconds for 261Rf based on these two measurements. Preliminary studies in transforming HEVI from an isothermal (constant

  14. Enantioselective supramolecular devices in the gas phase. Resorcin[4]arene as a model system

    Directory of Open Access Journals (Sweden)

    Caterina Fraschetti

    2012-04-01

    Full Text Available This review describes the state-of-art in the field of the gas-phase reactivity of diastereomeric complexes formed between a chiral artificial receptor and a biologically active molecule. The presented experimental approach is a ligand-displacement reaction carried out in a nano ESI-FT-ICR instrument, supported by a thermodynamic MS-study and molecular-mechanics and molecular-dynamics (MM/MD computational techniques. The noncovalent ion–molecule complexes are ideal for the study of chiral recognition in the absence of complicating solvent and counterion effects.

  15. Zwitterionic states in gas-phase polypeptide ions revealed by 157-nm ultra-violet photodissociation

    DEFF Research Database (Denmark)

    Kjeldsen, Frank; Silivra, Oleg A; Zubarev, Roman A

    2006-01-01

    carboxylic groups relative to competing COOH losses (45 Da) from neutral carboxylic groups. Loss of CO2 is a strong indication of the presence of a zwitterionic [(+)...(-)...(+)] salt bridge in the gas-phase polypeptide cation. This method provides a tool for studying, for example, the nature of binding...... of the fragment formation should be taken into account. Cations of Trp-cage proteins exist preferentially as zwitterions, with the deprotonation position divided between the Asp9 residue and the C terminus in the ratio 3:2. The majority of dications of the same molecule are not zwitterions. Furthermore, 157-nm...

  16. Liquid-gas phase transition in asymmetric nuclear matter at finite temperature

    International Nuclear Information System (INIS)

    Maruyama, Toshiki; Tatsumi, Toshitaka; Chiba, Satoshi

    2010-01-01

    Liquid-gas phase transition is discussed in warm asymmetric nuclear matter. Some peculiar features are figured out from the viewpoint of the basic thermodynamics about the phase equilibrium. We treat the mixed phase of the binary system based on the Gibbs conditions. When the Coulomb interaction is included, the mixed phase is no more uniform and the sequence of the pasta structures appears. Comparing the results with those given by the simple bulk calculation without the Coulomb interaction, we extract specific features of the pasta structures at finite temperature.

  17. Wettability in the liquid Cu-Ag alloy – fireproof material – gas phase system

    Directory of Open Access Journals (Sweden)

    G. Siwiec

    2013-07-01

    Full Text Available In the present paper, results of wettability studies on the liquid metal – fireproof material – gas phase system using copper and Cu-Ag alloys as well as typical fireproof materials, i.e. aluminium oxide, magnesium oxide and graphite, are presented. Contact angle measurements were conducted at 1 373–1 573 K by means of a high-temperature microscope coupled with a camera and a computer equipped with a program for recording and analysing images. For the measurements, the sessile drop method was used.

  18. Solvation of ions in the gas-phase: a molecular dynamics simulation

    Science.gov (United States)

    Cabarcos, Orlando M.; Lisy, James M.

    1996-07-01

    Molecular dynamics simulations have been performed on the collision between a cesium ion and a cluster of twenty methanol molecules. This process, generating a solvated ion, was studied over a range (1 to 25 eV) of eight collision energies. Preliminary analysis of this gas phase solvation has included the distribution of final ion cluster sizes, fragmentation patterns, solvation timescales and energetics. Two distinct patterns have emerged: a ballistic penetration of the neutral cluster at the higher collision energies and an evaporative evolution of the cluster ion at lower collision energies.

  19. Fluorometric method for the determination of gas-phase hydrogen peroxide

    Science.gov (United States)

    Kok, Gregory L.; Lazrus, Allan L.

    1986-01-01

    The fluorometric gas-phase hydrogen peroxide procedure is based on the technique used by Lazrus et. al. for the determination of H2O2 in the liquid phase. The analytical method utilizes the reaction of H2O2 with horseradish peroxidase and p-hydroxphenylacetic acid (POPHA) to form the fluorescent dimer of POPHA. The analytical reaction responds stoichiometrically to both H2O2 and some organic hydroperoxides. To discriminate H2O2 from organic hydroperoxides, catalase is used to preferentially destroy H2O2. Using a dual-channel flow system the H2O2 concentration is determined by difference.

  20. A tetrapositive metal ion in the gas phase: Thorium(IV) coordinated by neutral tridentate ligands

    International Nuclear Information System (INIS)

    Gong, Yu; Tian, Guoxin; Rao, Linfeng; Gibson, John K.; Hu, Han-Shi; Li, Jun

    2013-01-01

    Sheltering thorium ions: A Th 4+ ion supported by three neutral tetramethyl-3-oxaglutaramide ligands (L=TMOGA) is produced in the gas phase by electrospray ionization. The thorium in chiral Th(L) 3 4+ is coordinated by nine oxygen atoms. Quantum chemical studies revealed a decrease in Th-O binding energies and bond orders and an increase in bond lengths, as the number of coordinating ligands increases. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. A tetrapositive metal ion in the gas phase: Thorium(IV) coordinated by neutral tridentate ligands

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Yu; Tian, Guoxin; Rao, Linfeng; Gibson, John K. [Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Hu, Han-Shi [Department of Chemistry and Laboratory of Organic Optoelectronics and Molecular Engineering of the Ministry of Education, Tsinghua University (China); Li, Jun [Department of Chemistry and Laboratory of Organic Optoelectronics and Molecular Engineering of the Ministry of Education, Tsinghua University (China); William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory (United States)

    2013-07-01

    Sheltering thorium ions: A Th{sup 4+} ion supported by three neutral tetramethyl-3-oxaglutaramide ligands (L=TMOGA) is produced in the gas phase by electrospray ionization. The thorium in chiral Th(L){sub 3}{sup 4+} is coordinated by nine oxygen atoms. Quantum chemical studies revealed a decrease in Th-O binding energies and bond orders and an increase in bond lengths, as the number of coordinating ligands increases. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Detection of OH on photolysis of styrene oxide at 193 nm in gas phase

    Science.gov (United States)

    Kumar, Awadhesh; SenGupta, Sumana; Pushpa, K. K.; Naik, P. D.; Bajaj, P. N.

    2006-10-01

    Photodissociation of styrene oxide at 193 nm in gas phase generates OH, as detected by laser-induced fluorescence technique. Under similar conditions, OH was not observed from ethylene and propylene oxides, primarily because of their low absorption cross-sections at 193 nm. Mechanism of OH formation involves first opening of the three-membered ring from the ground electronic state via cleavage of either of two C sbnd O bonds, followed by isomerization to enolic forms of phenylacetaldehyde and acetophenone, and finally scission of the C sbnd OH bond of enols. Ab initio molecular orbital calculations support the proposed mechanism.

  3. CASCADER: An m-chain gas-phase radionuclide transport and fate model

    International Nuclear Information System (INIS)

    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

  4. CASCADER: An M-chain gas-phase radionuclide transport and fate model

    International Nuclear Information System (INIS)

    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

  5. Liquid-gas phase transition in asymmetric nuclear matter at finite temperature

    Science.gov (United States)

    Maruyama, Toshiki; Tatsumi, Toshitaka; Chiba, Satoshi

    2010-03-01

    Liquid-gas phase transition is discussed in warm asymmetric nuclear matter. Some peculiar features are figured out from the viewpoint of the basic thermodynamics about the phase equilibrium. We treat the mixed phase of the binary system based on the Gibbs conditions. When the Coulomb interaction is included, the mixed phase is no more uniform and the sequence of the pasta structures appears. Comparing the results with those given by the simple bulk calculation without the Coulomb interaction, we extract specific features of the pasta structures at finite temperature.

  6. Gas Phase Vibrational Spectroscopy of Weakly Volatil Safe Taggants Using a Synchrotron Source

    Science.gov (United States)

    Cuisset, Arnaud; Hindle, Francis; Mouret, Gael; Gruet, Sebastien; Pirali, Olivier; Roy, Pascale

    2013-06-01

    The high performances of the AILES beamline of SOLEIL allow to study at medium resolution (0.5 cm^{-1}) the gas phase THz vibrational spectra of weakly volatil compounds. Between 2008 and 2010 we recorded and analyzed the THz/Far-IR spectra of phosphorous based nerve agents thanks to sufficient vapour pressures from liquid samples at room temperature. Recently, we extended these experiments towards the vibrational spectroscopy of vapour pressures from solid samples. This project is quite challenging since we target lower volatile compounds, and so requires very high sensitive spectrometers. Moreover a specially designed heated multipass-cell have been developped for the gas phase study of very weak vapor pressures. Thanks to skills acquired during initial studies and recent experiments performed on AILES with solid PAHs, we have recorded and assigned the gas phase vibrational fingerprints from the THz to the NIR spectral domain (10-4000 cm-1) of a set of targeted nitro-derivatives. The study was focused onto the para, ortho-mononitrotoluene (p-NT, o-NT), the 1,4 Dinitrobenzene (1,4 DNB), the 2,3-dimethyl-2,3-dinitrobutane (DMNB), and 2,4 and 2,6-dinitrotoluene (2,4-2,6 DNT), which are safe taggants widely used for the detection of commercial explosives. These taggants are usually added to plastic explosives in order to facilitate their vapour detection. Therefore, there is a continuous interest for their detection and identification in realistic conditions via optical methods. A first step consists in the recording of their gas phase vibrational spectra. These expected spectra focused onto molecules involved into defence and security domains are not yet available to date and will be very useful for the scientific community. This work is supported by the contract ANR-11-ASTR-035-01. A. Cuisset, G. Mouret, O. Pirali, P. Roy, F. Cazier, H. Nouali, J. Demaison, J. Phys. Chem. B, 2008, 112:, 12516-12525 I. Smirnova, A. Cuisset, R. Bocquet, F. Hindle, G. Mouret, O

  7. Gas-phase isotope fractionation factor for the proton-bound dimer of the ethoxide

    International Nuclear Information System (INIS)

    Ellenberger, M.R.; Farneth, W.E.; Dixon, D.A.

    1981-01-01

    The gas-phase isotope fractionation factor, phi/sub gp/, for A 2 L - where A = EtO and L = H or D has been measured by using ion cyclotron resonance spectroscopy. Two approaches to the formation of the A 2 L - dimers are presented. The value for phi/sub gp/ is 0.46 +- 0.1. This low value for phi/sub gp/ is consistent with motion of a proton in a potential with a small central maximum or no maximum

  8. A combined heating cooling stage for cluster thermalization in the gas phase

    International Nuclear Information System (INIS)

    Ievlev, D.N.; Kuester, A.; Enders, A.; Malinowski, N.; Schaber, H.; Kern, K.

    2003-01-01

    We report on the design and performance of a combined heating/cooling stage for the thermalization of clusters in a gas phase time-of-flight mass spectrometer. With this setup the cluster temperature can sensitively be adjusted within the range from 100 up to 800 K and higher. The unique combination of a heating stage with a subsequent cooling stage allows us to perform thermodynamic investigations on clusters at very high temperatures without quality losses in the spectra due to delayed fragmentation in the drift tube of the mass spectrometer. The performance of the setup is demonstrated by the example of (C 60 ) n clusters

  9. Gas-phase synthesis of magnesium nanoparticles: A high-resolution transmission electron microscopy study

    International Nuclear Information System (INIS)

    Kooi, B. J.; Palasantzas, G.; De Hosson, J. Th. M.

    2006-01-01

    Magnesium nanoparticles with size above 10 nm, prepared by gas-phase syntheses, were investigated by high-resolution transmission electron microscopy. The dominant particle shape is a hexagonal prism terminated by Mg(0002) and Mg(1010) facets. Oxidation of Mg yields a MgO shell (∼3 nm thick), which has an orientation relation with the Mg. Inhomogeneous facet oxidation influences their growth kinetics resulting in a relatively broad size and shape distribution. Faceted voids between Mg and MgO shells indicate a fast outward diffusion of Mg and vacancy rearrangement into voids. The faceting of polar (220) planes is assisted by electron irradiation

  10. Gas-phase hydrosilylation of cyclohexene in an experimental radiation-chemical accelerator apparatus

    International Nuclear Information System (INIS)

    Pecherkin, A.S.; Sidorov, V.I.; Chernyshev, E.A.

    1992-01-01

    A process for the synthesis of methylcyclohexyldichlorosilane (a basic monomer for the production of organosilicon photoresists) has been investigated and perfected on an experimental apparatus with an ELV-2 electron accelerator; this synthesis involves gas-phase radiation-induced hydrosilylation of cyclohexene by methyldichlorosilane. Basic characteristics of the yield of the desired product under static conditions were determined. With the help of experiments on the synthesis of methylcyclohexyldichlorosilane in a flow- through mode, the technical features of the process of radiation-chemical hydrosilylation of cyclohexene on an accelerator apparatus were determined and studied, the optimal conditions for the synthesis were determined, and an experimental batch of the desired product was produced

  11. Probing Protein Structure and Folding in the Gas Phase by Electron Capture Dissociation

    Science.gov (United States)

    Schennach, Moritz; Breuker, Kathrin

    2015-07-01

    The established methods for the study of atom-detailed protein structure in the condensed phases, X-ray crystallography and nuclear magnetic resonance spectroscopy, have recently been complemented by new techniques by which nearly or fully desolvated protein structures are probed in gas-phase experiments. Electron capture dissociation (ECD) is unique among these as it provides residue-specific, although indirect, structural information. In this Critical Insight article, we discuss the development of ECD for the structural probing of gaseous protein ions, its potential, and limitations.

  12. Theoretical predictions of properties and gas-phase chromatography behaviour of bromides of group-5 elements Nb, Ta, and element 105, Db.

    Science.gov (United States)

    Pershina, V; Anton, J

    2012-01-21

    Fully relativistic, four-component density functional theory electronic structure calculations were performed for MBr(5), MOBr(3), MBr(6)(-), KMBr(6), and MBr(5)Cl(-) of group-5 elements Nb, Ta, and element 105, Db, with the aim to predict adsorption behaviour of the bromides in gas-phase chromatography experiments. It was shown that in the atmosphere of HBr/BBr(3), the pentabromides are rather stable, and their stability should increase in the row Nb Ta > Db. This sequence is in agreement with the one observed in the "one-atom-at-a-time" chromatography experiments. Some other scenarios, such as surface oxide formation were also considered but found to be irrelevant. © 2012 American Institute of Physics

  13. Identification of isomers in the gas phase and as adsorbates by near-edge X-ray absorption fine structure spectroscopy: Cis- and trans-stilbene

    International Nuclear Information System (INIS)

    Püttner, Ralph; Schmidt-Weber, Philipp; Kampen, Thorsten; Kolczewski, Christine; Hermann, Klaus; Horn, Karsten

    2017-01-01

    Highlights: • NEXAFS spectra of the cis- and trans-isomer of stilbene reveal distinct differences by which the isomers can be distinguished. • DFT calculations using the transition potential approach assign specific transitions that are different in the two isomers. • On Si(100), these differences in NEXAFS are also observed, suggesting that their conformations survive in the bonding situation. • NEXAFS is thus shown to be a sensitive tool to distinguish isomers in adsorbed species. - Abstract: Near-edge x-ray absorption fine structure spectra of the cis- and trans-isomers of stilbene in the gas phase reveal clear differences, which are analyzed by results from density-functional theory calculations using the transition potential approach. The differences between the two species also occur in stilbene adsorbed on Si(100), opening the way towards studying structural changes in molecules in different surface environments, and configurational switching in organic molecules on surfaces in particular.

  14. Identification of isomers in the gas phase and as adsorbates by near-edge X-ray absorption fine structure spectroscopy: Cis- and trans-stilbene

    Energy Technology Data Exchange (ETDEWEB)

    Püttner, Ralph [Department of Physics, Freie Universität Berlin, 14195 Berlin (Germany); Schmidt-Weber, Philipp [Fritz Haber Institute of the Max Planck Society, 14195 Berlin (Germany); Kampen, Thorsten [SPECS Surface Nano Analysis GmbH, 13355 Berlin (Germany); Kolczewski, Christine [Deutsches Museum München, 80538 Munich (Germany); Hermann, Klaus [Fritz Haber Institute of the Max Planck Society, 14195 Berlin (Germany); Horn, Karsten, E-mail: horn@fhi-berlin.mpg.de [Fritz Haber Institute of the Max Planck Society, 14195 Berlin (Germany)

    2017-02-15

    Highlights: • NEXAFS spectra of the cis- and trans-isomer of stilbene reveal distinct differences by which the isomers can be distinguished. • DFT calculations using the transition potential approach assign specific transitions that are different in the two isomers. • On Si(100), these differences in NEXAFS are also observed, suggesting that their conformations survive in the bonding situation. • NEXAFS is thus shown to be a sensitive tool to distinguish isomers in adsorbed species. - Abstract: Near-edge x-ray absorption fine structure spectra of the cis- and trans-isomers of stilbene in the gas phase reveal clear differences, which are analyzed by results from density-functional theory calculations using the transition potential approach. The differences between the two species also occur in stilbene adsorbed on Si(100), opening the way towards studying structural changes in molecules in different surface environments, and configurational switching in organic molecules on surfaces in particular.

  15. A NEW NETWORK FOR HIGHER-TEMPERATURE GAS-PHASE CHEMISTRY. I. A PRELIMINARY STUDY OF ACCRETION DISKS IN ACTIVE GALACTIC NUCLEI

    International Nuclear Information System (INIS)

    Harada, Nanase; Herbst, Eric; Wakelam, Valentine

    2010-01-01

    We present a new interstellar chemical gas-phase reaction network for time-dependent kinetics that can be used for modeling high-temperature sources up to ∼800 K. This network contains an extended set of reactions based on the Ohio State University (OSU) gas-phase chemical network. The additional reactions include processes with significant activation energies, reverse reactions, proton exchange reactions, charge exchange reactions, and collisional dissociation. Rate coefficients already in the OSU network are modified for H 2 formation on grains, ion-neutral dipole reactions, and some radiative association reactions. The abundance of H 2 O is enhanced at high temperature by hydrogenation of atomic O. Much of the elemental oxygen is in the form of water at T ≥ 300 K, leading to effective carbon-rich conditions, which can efficiently produce carbon-chain species such as C 2 H 2 . At higher temperatures, HCN and NH 3 are also produced much more efficiently. We have applied the extended network to a simplified model of the accretion disk of an active galactic nucleus.

  16. Biofiltration of mixtures of gas-phase styrene and acetone with the fungus Sporothrix variecibatus

    Energy Technology Data Exchange (ETDEWEB)

    Rene, Eldon R.; Spackova, Radka; Veiga, Maria C. [University of La Coruna, Dpt. of Chemical Engineering, Campus da Zapateira, Rua da Fraga, 10, 15008 La Coruna (Spain); Kennes, Christian, E-mail: kennes@udc.es [University of La Coruna, Dpt. of Chemical Engineering, Campus da Zapateira, Rua da Fraga, 10, 15008 La Coruna (Spain)

    2010-12-15

    The biodegradation performance of a biofilter, inoculated with the fungus Sporothrix variecibatus, to treat gas-phase styrene and acetone mixtures under steady-state and transient conditions was evaluated. Experiments were carried out by varying the gas-flow rates (0.05-0.4 m{sup 3} h{sup -1}), leading to empty bed residence times as low as 17.1 s, and by changing the concentrations of gas-phase styrene (0.01-6.3 g m{sup -3}) and acetone (0.01-8.9 g m{sup -3}). The total elimination capacities were as high as 360 g m{sup -3} h{sup -1}, with nearly 97.5% removal of styrene and 75.6% for acetone. The biodegradation of acetone was inhibited by the presence of styrene, while styrene removal was affected only slightly by the presence of acetone. During transient-state experiments, increasing the overall pollutant load by almost 3-fold, i.e., from 220 to 600 g m{sup -3} h{sup -1}, resulted in a sudden drop of removal efficiency (>90-70%), but still high elimination capacities were maintained. Periodic microscopic observations revealed that the originally inoculated Sporothrix sp. remained present in the reactor and actively dominant in the biofilm.

  17. Oxo-exchange of gas-phase uranyl, neptunyl, and plutonyl with water and methanol.

    Science.gov (United States)

    Lucena, Ana F; Odoh, Samuel O; Zhao, Jing; Marçalo, Joaquim; Schreckenbach, Georg; Gibson, John K

    2014-02-17

    A challenge in actinide chemistry is activation of the strong bonds in the actinyl ions, AnO2(+) and AnO2(2+), where An = U, Np, or Pu. Actinyl activation in oxo-exchange with water in solution is well established, but the exchange mechanisms are unknown. Gas-phase actinyl oxo-exchange is a means to probe these processes in detail for simple systems, which are amenable to computational modeling. Gas-phase exchange reactions of UO2(+), NpO2(+), PuO2(+), and UO2(2+) with water and methanol were studied by experiment and density functional theory (DFT); reported for the first time are experimental results for UO2(2+) and for methanol exchange, as well as exchange rate constants. Key findings are faster exchange of UO2(2+) versus UO2(+) and faster exchange with methanol versus water; faster exchange of UO2(+) versus PuO2(+) was quantified. Computed potential energy profiles (PEPs) are in accord with the observed kinetics, validating the utility of DFT to model these exchange processes. The seemingly enigmatic result of faster exchange for uranyl, which has the strongest oxo-bonds, may reflect reduced covalency in uranyl as compared with plutonyl.

  18. Functionalized silica aerogels for gas-phase purification, sensing, and catalysis: A review

    Energy Technology Data Exchange (ETDEWEB)

    Amonette, James E.; Matyáš, Josef

    2017-09-01

    Silica aerogels have a rich history and a unique, fascinating gas-phase chemistry that has lent them to many diverse applications. This review starts with a brief discussion of the fundamental issues driving the movement of gases in silica aerogels and then proceeds to provide an overview of the work that has been done with respect to the purification of gases, sensing of individual gases, and uses of silica aerogels as catalysts for gas-phase reactions. Salient features of the research behind these different applications are presented, and, where appropriate, critical aspects that affect the practical use of the aerogels are noted. Specific sections under the gas-purification category focus on the removal of airborne nanoparticles, carbon dioxide, volatile organic compounds, sulfur gases and radioactive iodine from gas streams. The use of silica aerogels as sensors for humidity, oxygen, hydrocarbons, volatile acids and bases, various non-ammoniacal nitrogen gases, and viral particles is discussed. With respect to catalysis, the demonstrated use of silica aerogels as supports for oxidation, Fischer-Tropsch, alkane isomerization, and hydrogenation reactions is reviewed, along with a section on untested catalytic formulations involving silica aerogels. A short section focuses on recent developments in thermomolecular Knudsen compressor pumps using silica aerogel membranes. The review continues with an overview of the production methods, locations of manufacturing facilities globally, and a brief discussion of the economics before concluding with a few remarks about the present and future trends revealed by the work presented.

  19. Synchrotron and small bio-molecules in gas phase and liquid environment: new opportunities in Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Naves de Brito, A. [State University of Campinas (UNICAMP), SP (Brazil). Dept. of Applied Physics

    2011-07-01

    Full text: Two techniques are critically related to the photoelectric law, namely: photoelectron spectroscopy and photoelectron-photoion coincidence spectroscopy. Both are strongly used now a day within synchrotron laboratories. Our group is employing both to investigate fragmentation of bio-molecules in gas phase such as amino acids and DNA basis using V UV and soft x-ray photons. In the near future lager scale instruments developed in Brazil will allow unique opportunities to apply these two spectroscopic methods to molecules immersed in liquids such as water. We will present details from this advanced x-ray source and experimental stations with capabilities not present in other places in the world. Experiments connected to the molecular origin of live will be shown. Among them an experiment where we mimic the atmosphere at Titan moon producing bio- molecules will discussed. Another experiment will be presented where we test the Panspermia viability using special bacteria. We will also present experiments where frozen simple molecules connected to pre-biotic mate- rial are bombardment by UV photons and energetic particles showing interesting trends. Spectroscopic studies of gas phase photo-fragmentation of bio-molecules may be critical to understand in the future these molecules immersed in liquids. We plan to spend some time showing our recent results in this area. (author)

  20. Properties of clusters in the gas phase: V. Complexes of neutral molecules onto negative ions

    International Nuclear Information System (INIS)

    Keesee, R.G.; Lee, N.; Castleman, A.W. Jr.

    1980-01-01

    Ion--molecules association reactions of the form A - (B)/sub n1/-+B=A - (B)/sub n/ were studied over a range of temperatures in the gas phase using high pressure mass spectrometry. Enthalpy and entropy changes were determined for the stepwise clustering reactions of (1) sulfur dioxide onto Cl - , I - , and NO 2 - with n ranging from one to three or four, and onto SO 2 - and SO 3 - with n equal to one; and (2) carbon dioxide onto Cl - , I - , NO 2 - , CO 3 - , and SO 3 - with n equal to one. From these data and earlier hydration results, the order of the magnitude of the enthalpy changes on the association of the first neutral for a series of negative ions was found to parallel the gas-phase basicity of those anions. For any given ion, the relative order of the addition enthalpies among the neutrals was found to be dependent on the polarizabilities of the neutrals and on the covalency in the ion-neutral bond. Dispersion of charge via covalent bonding was found to affect significantly the succeeding clustering steps

  1. Gas phase collision dynamics by means of pulse-radiolysis methods

    International Nuclear Information System (INIS)

    Hatano, Yoshihiko

    1989-01-01

    After a brief survey of recent advances in gas-phase collision dynamics studies using pulse radiolysis methods, the following two topics in our research programs are presented with emphasis on the superior advantages of the pulse radiolysis methods over the various methods of gas-phase collision dynamics, such as beam methods, swarm methods and flow methods. One of the topics is electron attachment to van der Waals molecules. The attachment rates of thermal electrons to O 2 and other molecules in dense gases have been measured in wide ranges of both gas temperatures and pressures, from which experimental evidence has been obtained for electron attachment to van der Waals molecules. The results have been compared with theories and discussed in terms of the effect of van der Waals interaction on the electron attachment resonance. The obtained conclusions have been related with investigations of electron attachment, solvation and localization in the condensed phase. The other is Penning ionization and its related processes. The rate constants for the de-excitation of He(2 1 P), He(2 3 S), Ne( 3 P 0 ), Ne( 3 P 1 ), Ne( 3 P 2 ), Ar( 1 P 1 ), Ar( 3 P 1 ), by atoms and molecules have been measured in the temperature range from 100 to 300 K, thus obtaining the collisional energy dependence of the de-excitation cross sections. The results are compared in detail with theories classified according to the excited rare gas atoms in the metastable and resonance states. (author)

  2. Femtosecond time-resolved studies of coherent vibrational Raman scattering in large gas-phase molecules

    International Nuclear Information System (INIS)

    Hayden, C.C.; Chandler, D.W.

    1995-01-01

    Results are presented from femtosecond time-resolved coherent Raman experiments in which we excite and monitor vibrational coherence in gas-phase samples of benzene and 1,3,5-hexatriene. Different physical mechanisms for coherence decay are seen in these two molecules. In benzene, where the Raman polarizability is largely isotropic, the Q branch of the vibrational Raman spectrum is the primary feature excited. Molecules in different rotational states have different Q-branch transition frequencies due to vibration--rotation interaction. Thus, the macroscopic polarization that is observed in these experiments decays because it has many frequency components from molecules in different rotational states, and these frequency components go out of phase with each other. In 1,3,5-hexatriene, the Raman excitation produces molecules in a coherent superposition of rotational states, through (O, P, R, and S branch) transitions that are strong due to the large anisotropy of the Raman polarizability. The coherent superposition of rotational states corresponds to initially spatially oriented, vibrationally excited, molecules that are freely rotating. The rotation of molecules away from the initial orientation is primarily responsible for the coherence decay in this case. These experiments produce large (∼10% efficiency) Raman shifted signals with modest excitation pulse energies (10 μJ) demonstrating the feasibility of this approach for a variety of gas phase studies. copyright 1995 American Institute of Physics

  3. CASCADER: An M-chain gas-phase radionuclide transport and fate model

    International Nuclear Information System (INIS)

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

    1993-02-01

    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 diffusion. Furthermore, parent and daughter radionuclides may decay as they are transported in the soil. CASCADER is a gas-phase, one-space dimensional transport and fate model for M-chain radionuclides in very dry homogeneous or heterogeneous soil. This model contains barometric pressure-induced advection and diffusion together with linear irreversible and linear reversible sorption for each radionuclide. The advection velocity is derived from an embedded air-pumping submodel. The air-pumping submodel is based on an assumption of isothermal conditions, which is driven by barometric pressure. CASCADER allows the concentration of source radionuclides to decay via the classical Bateman chain of simple, first-order kinetic processes. The transported radionuclides also decay via first-order processes while in the soil. A mass conserving, flux-type inlet and exit set of boundary conditions are used. The user must supply the initial distribution for the parent radionuclide in the soil. The initial daughter distribution is found using equilibrium rules. The model is user friendly as it uses a prompt-driven, free-form input. The code is ANSI standard Fortran 77

  4. CASCADER: An m-chain gas-phase radionuclide transport and fate model

    International Nuclear Information System (INIS)

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

    1992-06-01

    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 as they are advected and/or dispersed. Furthermore, parent and daughter radionuclides may decay as they are transported in the soil. CASCADER is a gas-phase, one space dimensional transport and fate model for an m-chain of radionuclides in very dry soil. This model contains barometric pressure-induced advection and diffusion together with linear irreversible and linear reversible sorption for each radionuclide. The advocation velocity is derived from an embedded air-pumping submodel. The airpumping submodel is based on an assumption of isothermal conditions and is barometric pressure driven. CASCADER allows the concentration of source radionuclides to decay via the classical Bateman chain of simple, first-order kinetic processes. The transported radionuclides also decay via first-order processes while in the soil. A mass conserving, flux-type inlet and exit set of boundary conditions is used. The user must supply the initial distribution for the parent radionuclide in the soil. The initial daughter distribution is found using equilibrium rules. The model is user friendly as it uses a prompt-driven, free-form input. The code is ANSI standard Fortran 77

  5. Optical Absorptions of Oxygenated Carbon Chain Cations in the Gas Phase

    Science.gov (United States)

    Hardy, F.-X.; Rice, C. A.; Chakraborty, A.; Fulara, J.; Maier, J. P.

    2016-06-01

    The gas-phase electronic spectra of linear OC4O+ and a planar C6H2O+ isomer were obtained at a rotational temperature of ≈10 K. Absorption measurements in a 6 K neon matrix were followed by gas-phase observations in a cryogenic radiofrequency ion trap. The origin bands of the 1{}2{{{\\Pi }}}u ≤ftarrow X{}2{{{\\Pi }}}g transition of OC4O+ and the 1{}2A{}2 ≤ftarrow X{}2B1 of HCCC(CO)CCH+ lie at 417.31 ± 0.01 nm and 523.49 ± 0.01 nm, respectively. These constitute the first electronic spectra of oxygenated carbon chain cations studied under conditions that are relevant to the diffuse interstellar bands (DIBs), as both have a visible transition. The recent analysis of the 579.5 nm DIB indicates that small carriers, five to seven heavy atoms, continue to be possible candidates (Huang & Oka 2015). Astronomical implications are discussed regarding this kind of oxygenated molecules.

  6. Effect of dimethylamine on the gas phase sulfuric acid concentration measured by Chemical Ionization Mass Spectrometry

    CERN Document Server

    Rondo, L.; Kürten, A.; Adamov, A.; Bianchi, F.; Breitenlechner, M.; Duplissy, J.; Franchin, A.; Dommen, J.; Donahue, N. M.; Dunne, E. M.; Flagan, R. C.; Hakala, J.; Hansel, A.; Keskinen, H.; Kim, J.; Jokinen, T.; Lehtipalo, K.; Leiminger, M.; Praplan, A.; Riccobono, F.; Rissanen, M. P.; Sarnela, N.; Schobesberger, S.; Simon, M.; Sipilä, M.; Smith, J. N.; Tomé, A.; Tröstl, J.; Tsagkogeorgas, G.; Vaattovaara, P.; Winkler, P. M.; Williamson, C.; Wimmer, D.; Baltensperger, U.; Kirkby, J.; Kulmala, M.; Petäjä, T.; Worsnop, D. R.; Curtius, J.

    2016-01-01

    Sulfuric acid is widely recognized as a very important substance driving atmospheric aerosolnucleation. Based on quantum chemical calculations it has been suggested that the quantitative detectionof gas phase sulfuric acid (H2SO4) by use of Chemical Ionization Mass Spectrometry (CIMS) could be biased inthe presence of gas phase amines such as dimethylamine (DMA). An experiment (CLOUD7 campaign) was setup at the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber to investigate the quantitative detection ofH2SO4in the presence of dimethylamine by CIMS at atmospherically relevant concentrations. For the first time inthe CLOUD experiment, the monomer sulfuric acid concentration was measured by a CIMS and by two CI-APi-TOF(Chemical Ionization-Atmospheric Pressure interface-Time Of Flight) mass spectrometers. In addition, neutralsulfuric acid clusters were measured with the CI-APi-TOFs. The CLOUD7 measurements show that in the presenceof dimethylamine (<5 to 70 pptv) the sulfuric acid monomer measured by the CIMS...

  7. Biofiltration of mixtures of gas-phase styrene and acetone with the fungus Sporothrix variecibatus

    International Nuclear Information System (INIS)

    Rene, Eldon R.; Spackova, Radka; Veiga, Maria C.; Kennes, Christian

    2010-01-01

    The biodegradation performance of a biofilter, inoculated with the fungus Sporothrix variecibatus, to treat gas-phase styrene and acetone mixtures under steady-state and transient conditions was evaluated. Experiments were carried out by varying the gas-flow rates (0.05-0.4 m 3 h -1 ), leading to empty bed residence times as low as 17.1 s, and by changing the concentrations of gas-phase styrene (0.01-6.3 g m -3 ) and acetone (0.01-8.9 g m -3 ). The total elimination capacities were as high as 360 g m -3 h -1 , with nearly 97.5% removal of styrene and 75.6% for acetone. The biodegradation of acetone was inhibited by the presence of styrene, while styrene removal was affected only slightly by the presence of acetone. During transient-state experiments, increasing the overall pollutant load by almost 3-fold, i.e., from 220 to 600 g m -3 h -1 , resulted in a sudden drop of removal efficiency (>90-70%), but still high elimination capacities were maintained. Periodic microscopic observations revealed that the originally inoculated Sporothrix sp. remained present in the reactor and actively dominant in the biofilm.

  8. Photochemical reactions of triplet benzophenone and anthraquinone molecules with amines in the gas phase

    International Nuclear Information System (INIS)

    Zalesskaya, G.A.; Sambor, E.G.; Belyi, N.N.

    2004-01-01

    The intermolecular photoinduced reactions between triplet ketone molecules and aliphatic amines and pyridine are studied by the quenching of delayed fluorescence of anthraquinone and benzophenone vapors by diethylamine, dibutylamine, cyclohexylamine, triethylamine, and pyridine. In the temperature range 423-573 K, the delayed fluorescence quenching rate constants k q are estimated from changes in the decay rate constant and the intensity of delayed fluorescence upon increasing pressure of bath gases. It is ascertained that, in the gas phase, the mixtures under study exhibit both a negative and a positive dependence of k q on temperature, which indicates that some photoinduced reactions do not have activation barriers. The rate constant k q is shown to increase with decreasing ionization potential of the electron donors. This points to the importance of interactions with charge transfer in the photoreaction of triplet ketone molecules with aliphatic amines and pyridine in the gas phase. The relationship between k q and the change in the free energy ΔG upon the photoinduced intermolecular electron transfer, which is the primary stage of the photochemical reaction, is studied. It is shown that the dependence k q (ΔG) for the donor-acceptor pairs under study is described well by the Marcus equation, in which the average vibrational energies of the donor and acceptor are taken into account for the estimate of ΔG

  9. Effect of isotopic substitution upon the gas phase and solution electron affinities of nitrobenzene

    International Nuclear Information System (INIS)

    Stevenson, G.R.; Reiter, R.C.; Espe, M.E.; Bartmess, J.E.

    1987-01-01

    Ion cyclotron resonance and electron spin resonance have been utilized to determine the equilibrium constant for the electron transfer from the nitrobenzene anion radical to 15 N labeled nitrobenzene (Ph 14 NO 2 - + Ph 15 NO 2 ↔ Ph 14 NO 2 + Ph 15 NO 2 9 . It was found that the equilibrium constant is within experimental error of unity at 305 K. Molecular orbital calculations indicate that this might be accounted for by the shortening of the C-N bond and a counterbalancing lengthening of the N-O bonds upon electron attachment to nitrobenzene. An equilibrium constant that is much larger than unity can be observed in liquid ammonia at 208 K when K + serves as the gegenion (K/sub eq/ = 2.1). However, when Na + serves as the gegenion, the solution electron affinity of Ph 14 NO 2 is greater than that of Ph 15 NO 2 (K/sub eq/ = 0.4). These results are explained in terms of ion association. When the hydrogen atoms are replaced with deuteriums, the gas phase electron affinity is decreased. A similar decrease is observed in liquid ammonia. In the gas phase this is attributed to the slight lengthening of all the C-H bonds upon electron attachment

  10. Gas-phase pesticide measurement using iodide ionization time-of-flight mass spectrometry

    Directory of Open Access Journals (Sweden)

    T. Murschell

    2017-06-01

    Full Text Available Volatilization and subsequent processing in the atmosphere are an important environmental pathway for the transport and chemical fate of pesticides. However, these processes remain a particularly poorly understood component of pesticide lifecycles due to analytical challenges in measuring pesticides in the atmosphere. Most pesticide measurements require long (hours to days sampling times coupled with offline analysis, inhibiting observation of meteorologically driven events or investigation of rapid oxidation chemistry. Here, we present chemical ionization time-of-flight mass spectrometry with iodide reagent ions as a fast and sensitive measurement of four current-use pesticides. These semi-volatile pesticides were calibrated with injections of solutions onto a filter and subsequently volatilized to generate gas-phase analytes. Trifluralin and atrazine are detected as iodide–molecule adducts, while permethrin and metolachlor are detected as adducts between iodide and fragments of the parent analyte molecule. Limits of detection (1 s are 0.37, 0.67, 0.56, and 1.1 µg m−3 for gas-phase trifluralin, metolachlor, atrazine, and permethrin, respectively. The sensitivities of trifluralin and metolachlor depend on relative humidity, changing as much as 70 and 59, respectively, as relative humidity of the sample air varies from 0 to 80 %. This measurement approach is thus appropriate for laboratory experiments and potentially near-source field measurements.

  11. Chlorination of some eliphatic organic compounds in liquid and gas phase

    International Nuclear Information System (INIS)

    Hassan, A.A.

    1990-01-01

    The photochlorination of different organic compounds and the relative slectivities of different positions have been investigated in both gaseous and liquid phases at different temperatures. The results have shown that the relative selectivity generally decreased with increasing temperature and in the gas phase has a higher value. Polar solvents increase the selectivity relative to the chlorination of pure liquid phases. The differences in activation energy between two positions were much higher in the gas phases chlorination, relative to that in the liquid phase. It was also found that the functional groups have great influence on the rate of chlorine free radical attack on different positions, for example the electron withdrawing groups decreasing the selectivity on the first position, but the electron donating groups increase the selectivity on the first position, but the electron donating groups increase the selectivity on the first position. Furthermore it was found that the polar solvents, which stabilize the resonance between oxygen and carbon atoms, increases the selectivity on that position. 23 tabs.; 16 figs.; 50 refs

  12. GEM-AQ, an on-line global multiscale chemical weather modelling system: model description and evaluation of gas phase chemistry processes

    Directory of Open Access Journals (Sweden)

    J. W. Kaminski

    2008-06-01

    Full Text Available Tropospheric chemistry and air quality processes were implemented on-line in the Global Environmental Multiscale weather prediction model. The integrated model, GEM-AQ, was developed as a platform to investigate chemical weather at scales from global to urban. The current chemical mechanism is comprised of 50 gas-phase species, 116 chemical and 19 photolysis reactions, and is complemented by a sectional aerosol module with 5 aerosols types. All tracers are advected using the semi-Lagrangian scheme native to GEM. The vertical transport includes parameterized subgrid-scale turbulence and large scale deep convection. Dry deposition is included as a flux boundary condition in the vertical diffusion equation. Wet deposition of gas-phase species is treated in a simplified way, and only below-cloud scavenging is considered. The emissions used include yearly-averaged anthropogenic, and monthly-averaged biogenic, ocean, soil, and biomass burning emission fluxes, as well as NOx from lightning. In order to evaluate the ability to simulate seasonal variations and regional distributions of trace gases such as ozone, nitrogen dioxide and carbon monoxide, the model was run for a period of five years (2001–2005 on a global uniform 1.5°×1.5° horizontal resolution domain and 28 hybrid levels extending up to 10 hPa. Model results were compared with observations from satellites, aircraft measurement campaigns and balloon sondes. We find that GEM-AQ is able to capture the spatial details of the chemical fields in the middle and lower troposphere. The modelled ozone consistently shows good agreement with observations, except over tropical oceans. The comparison of carbon monoxide and nitrogen dioxide with satellite measurements emphasizes the need for more accurate, year-specific emissions fluxes for biomass burning and anthropogenic sources. Other species also compare well with available observations.

  13. Matrix Assisted and/or Laser Desorption Ionization Quadrupole Ion Trap Time-of-Flight Mass Spectrometry of WO3 Clusters Formation in Gas Phase. Nanodiamonds, Fullerene, and Graphene Oxide Matrices

    Science.gov (United States)

    Ausekar, Mayuri Vilas; Mawale, Ravi Madhukar; Pazdera, Pavel; Havel, Josef

    2018-03-01

    The formation of W x O y +●/-● clusters in the gas phase was studied by laser desorption ionization (LDI) and matrix assisted laser desorption ionization (MALDI) of solid WO3. LDI produced (WO3) n + ●/- ● ( n = 1-7) clusters. In MALDI, when using nano-diamonds (NDs), graphene oxide (GO), or fullerene (C60) matrices, higher mass clusters were generated. In addition to (WO3) n -● clusters, oxygen-rich or -deficient species were found in both LDI and MALDI (with the total number of clusters exceeding one hundred ≈ 137). This is the first time that such matrices have been used for the generation of(WO3) n + ●/-● clusters in the gas phase, while new high mass clusters (WO3) n -● ( n = 12-19) were also detected. [Figure not available: see fulltext.

  14. Multiphase flow and transport caused by spontaneous gas phase growth in the presence of dense non-aqueous phase liquid.

    Science.gov (United States)

    Roy, James W; Smith, James E

    2007-01-30

    Disconnected bubbles or ganglia of trapped gas may occur below the top of the capillary fringe through a number of mechanisms. In the presence of dense non-aqueous phase liquid (DNAPL), the disconnected gas phase experiences mass transfer of dissolved gases, including volatile components from the DNAPL. The properties of the gas phase interface can also change. This work shows for the first time that when seed gas bubbles exist spontaneous gas phase growth can be expected to occur and can significantly affect water-gas-DNAPL distributions, fluid flow, and mass transfer. Source zone behaviour was observed in three different experiments performed in a 2-dimensional flow cell. In each case, a DNAPL pool was created in a zone of larger glass beads over smaller glass beads, which served as a capillary barrier. In one experiment effluent water samples were analyzed to determine the vertical concentration profile of the plume above the pool. The experiments effectively demonstrated a) a cycle of spontaneous gas phase expansion and vertical advective mobilization of gas bubbles and ganglia above the DNAPL source zone, b) DNAPL redistribution caused by gas phase growth and mobilization, and c) that these processes can significantly affect mass transport from a NAPL source zone.

  15. The coupling effect of gas-phase chemistry and surface reactions on oxygen permeation and fuel conversion in ITM reactors

    KAUST Repository

    Hong, Jongsup

    2015-08-01

    © 2015 Elsevier B.V. The effect of the coupling between heterogeneous catalytic reactions supported by an ion transport membrane (ITM) and gas-phase chemistry on fuel conversion and oxygen permeation in ITM reactors is examined. In ITM reactors, thermochemical reactions take place in the gas-phase and on the membrane surface, both of which interact with oxygen permeation. However, this coupling between gas-phase and surface chemistry has not been examined in detail. In this study, a parametric analysis using numerical simulations is conducted to investigate this coupling and its impact on fuel conversion and oxygen permeation rates. A thermochemical model that incorporates heterogeneous chemistry on the membrane surface and detailed chemical kinetics in the gas-phase is used. Results show that fuel conversion and oxygen permeation are strongly influenced by the simultaneous action of both chemistries. It is shown that the coupling somewhat suppresses the gas-phase kinetics and reduces fuel conversion, both attributed to extensive thermal energy transfer towards the membrane which conducts it to the air side and radiates to the reactor walls. The reaction pathway and products, in the form of syngas and C2 hydrocarbons, are also affected. In addition, the operating regimes of ITM reactors in which heterogeneous- or/and homogeneous-phase reactions predominantly contribute to fuel conversion and oxygen permeation are elucidated.

  16. Heterogeneity-enhanced gas phase formation in shallow aquifers during leakage of CO2-saturated water from geologic sequestration sites

    Science.gov (United States)

    Plampin, Michael R.; Lassen, Rune N.; Sakaki, Toshihiro; Porter, Mark L.; Pawar, Rajesh J.; Jensen, Karsten H.; Illangasekare, Tissa H.

    2014-12-01

    A primary concern for geologic carbon storage is the potential for leakage of stored carbon dioxide (CO2) into the shallow subsurface where it could degrade the quality of groundwater and surface water. In order to predict and mitigate the potentially negative impacts of CO2 leakage, it is important to understand the physical processes that CO2 will undergo as it moves through naturally heterogeneous porous media formations. Previous studies have shown that heterogeneity can enhance the evolution of gas phase CO2 in some cases, but the conditions under which this occurs have not yet been quantitatively defined, nor tested through laboratory experiments. This study quantitatively investigates the effects of geologic heterogeneity on the process of gas phase CO2 evolution in shallow aquifers through an extensive set of experiments conducted in a column that was packed with layers of various test sands. Soil moisture sensors were utilized to observe the formation of gas phase near the porous media interfaces. Results indicate that the conditions under which heterogeneity controls gas phase evolution can be successfully predicted through analysis of simple parameters, including the dissolved CO2 concentration in the flowing water, the distance between the heterogeneity and the leakage location, and some fundamental properties of the porous media. Results also show that interfaces where a less permeable material overlies a more permeable material affect gas phase evolution more significantly than interfaces with the opposite layering.

  17. The stable carbon isotope biogeochemistry of acetate and other dissolved carbon species in deep subseafloor sediments at the northern Cascadia Margin

    Science.gov (United States)

    Heuer, Verena B.; Pohlman, John W.; Torres, Marta E.; Elvert, Marcus; Hinrichs, Kai-Uwe

    2009-01-01

    Ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor, but to date little is known about their metabolic activities. To better understand the biogeochemical processes in the deep biosphere, we investigate the stable carbon isotope chemistry of acetate and other carbon-bearing metabolites in sediment pore-waters. Acetate is a key metabolite in the cycling of carbon in anoxic sediments. Its stable carbon isotopic composition provides information on the metabolic processes dominating acetate turnover in situ. This study reports our findings for a methane-rich site at the northern Cascadia Margin (NE Pacific) where Expedition 311 of the Integrated Ocean Drilling Program (IODP) sampled the upper 190 m of sediment. At Site U1329, δ13C values of acetate span a wide range from −46.0‰ to −11.0‰ vs. VPDB and change systematically with sediment depth. In contrast, δ13C values of both the bulk dissolved organic carbon (DOC) (−21.6 ± 1.3‰ vs. VPDB) and the low-molecular-weight compound lactate (−20.9 ± 1.8‰ vs. VPDB) show little variability. These species are interpreted to represent the carbon isotopic composition of fermentation products. Relative to DOC, acetate is up to 23.1‰ depleted and up to 9.1‰ enriched in 13C. Broadly, 13C-depletions of acetate relative to DOC indicate flux of carbon from acetogenesis into the acetate pool while 13C-enrichments of pore-water acetate relative to DOC suggest consumption of acetate by acetoclastic methanogenesis. Isotopic relationships between acetate and lactate or DOC provide new information on the carbon flow and the presence and activity of specific functional microbial communities in distinct biogeochemical horizons of the sediment. In particular, they suggest that acetogenic CO2-reduction can coexist with methanogenic CO2-reduction, a notion contrary to the hypothesis that hydrogen levels are controlled by the thermodynamically most favorable electron

  18. Seasonal variation in water uptake patterns of three plant species based on stable isotopes in the semi-arid Loess Plateau.

    Science.gov (United States)

    Wang, Jian; Fu, Bojie; Lu, Nan; Zhang, Li

    2017-12-31

    Water is a limiting factor and significant driving force for ecosystem processes in arid and semi-arid areas. Knowledge of plant water uptake pattern is indispensable for understanding soil-plant interactions and species coexistence. The 'Grain for Green' project that started in 1999 in the Loess Plateau of China has led to large scale vegetation change. However, little is known about the water uptake patterns of the main plant species that inhabit in this region. In this study, the seasonal variations in water uptake patterns of three representative plant species, Stipa bungeana, Artemisia gmelinii and Vitex negundo, that are widely distributed in the semi-arid area of the Loess Plateau, were identified by using dual stable isotopes of δ 2 H and δ 18 O in plant and soil water coupled with a Bayesian mixing model MixSIAR. The soil water at the 0-120cm depth contributed 79.54±6.05% and 79.94±8.81% of the total water uptake of S. bungeana and A. gmelinii, respectively, in the growing season. The 0-40cm soil contributed the most water in July (74.20±15.20%), and the largest proportion of water (33.10±15.20%) was derived from 120-300cm soils in August for A. gmelinii. However, V. negundo obtained water predominantly from surface soil horizons (0-40cm) and then switched to deep soil layers (120-300cm) as the season progressed. This suggested that V. negundo has a greater degree of ecological plasticity as it could explore water sources from deeper soils as the water stress increased. This capacity can mainly be attributed to its functionally dimorphic root system. V. negundo may have a competitive advantage when encountering short-term drought. The ecological plasticity of plant water use needs to be considered in plant species selection and ecological management and restoration of the arid and semi-arid ecosystems in the Loess Plateau. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Uranium fluoride chemistry. Part 1. The gas phase reaction of uranium hexafluoride with alcohols

    International Nuclear Information System (INIS)

    Schnautz, N.G.; Venter, P.J.

    1992-01-01

    The reaction between uranium hexafluoride (UF 6 ) and simple alcohols in the gas phase was observed to proceed by way of three possible reaction pathways involving dehydration, deoxygenative fluorination, and ether formation. These reactions can best be explained by assuming that alcohols first react with UF 6 to afford the alkoxy uranium pentafluoride intermediate ROUF 5 , which reacts further to give the dehydration, deoxygenative fluorination, and ether products. In each of the above three reaction pathways, UF 6 is transformed to UOF 4 , which being as reactive toward alcohols as UF 6 , reacts further with the alcohol in question to finally afford the unreactive uranyl fluoride (UO 2 F 2 ). 6 refs., 2 tabs

  20. Optical investigation of gas-phase KCl/KOH sulfation in post flame conditions

    DEFF Research Database (Denmark)

    Weng, Wubin; chen, Shuang; Wu, Hao

    2018-01-01

    A counter-flow reactor setup was designed to investigate the gas-phase sulfation and homogeneous nucleation of potassium salts. Gaseous KOH and KCl were introduced into the post-flame zone of a laminar flat flame. The hot flame products mixed in the counter-flow with cold N2, with or without....... Depending on the potassium speciation in the inlet and the presence of SO2, they consisted of K2SO4, KCl, or K2CO3, respectively. The experiments showed that KOH was sulphated more readily than KCl, resulting in larger quantities of aerosols. The sulfation process in the counter-flow setup was simulated...... using a chemical kinetic model including a detailed subset for the Cl/S/K chemistry. Similar to the experimental results, much more potassium sulfate was predicted when seeding KOH compared to seeding KCl. For both KOH and KCl, sulfation was predicted to occur primarily through the reactions among...

  1. Direct method gas-phase oxygen abundances of four Lyman break analogs

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Jonathan S.; Croxall, Kevin V.; Pogge, Richard W. [Department of Astronomy, The Ohio State University, Columbus, OH 43201 (United States)

    2014-09-10

    We measure the gas-phase oxygen abundances in four Lyman break analogs using auroral emission lines to derive direct abundances. The direct method oxygen abundances of these objects are generally consistent with the empirically derived strong-line method values, confirming that these objects are low oxygen abundance outliers from the mass-metallicity (MZ) relation defined by star forming Sloan Digital Sky Survey galaxies. We find slightly anomalous excitation conditions (Wolf-Rayet features) that could potentially bias the empirical estimates toward high values if caution is not exercised in the selection of the strong-line calibration. The high rate of star formation and low oxygen abundance of these objects is consistent with the predictions of the fundamental metallicity relation, in which the infall of relatively unenriched gas simultaneously triggers an episode of star formation and dilutes the interstellar medium of the host galaxy.

  2. Zpif's law in the liquid gas phase transition of nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y.G. [China Center of Advanced Science and Technology (CCAST), Beijing, BJ (China). World Lab.; Shanghai Institute of Nuclear Research, Chinese Academy of Sciences, P.O. Box 800-204, Shanghai 201800 (China)

    1999-12-01

    Zpif's law in the field of linguistics is tested in the nuclear disassembly within the framework of isospin dependent lattice gas model. It is found that the average cluster charge (or mass) of rank n in the charge (or mass) list shows exactly inversely to its rank, i.e., there exists Zpif's law, at the phase transition temperature. This novel criterion shall be helpful to search the nuclear liquid gas phase transition experimentally and theoretically. In addition, the finite size scaling of the effective phase transition temperature at which the Zpif's law appears is studied for several systems with different mass and the critical exponents of {nu} and {beta} are tentatively extracted. (orig.)

  3. Atmospheric-pressure dielectric barrier discharge with capillary injection for gas-phase nanoparticle synthesis

    International Nuclear Information System (INIS)

    Ghosh, Souvik; Liu, Tianqi; Bilici, Mihai; Cole, Jonathan; Huang, I-Min; Sankaran, R Mohan; Staack, David; Mariotti, Davide

    2015-01-01

    We present an atmospheric-pressure dielectric barrier discharge (DBD) reactor for gas-phase nanoparticle synthesis. Nickel nanoparticles are synthesized by homogenous nucleation from nickelocene vapor and characterized online by aerosol mobility measurements. The effects of residence time and precursor concentration on particle growth are studied. We find that narrower distributions of smaller particles are produced by decreasing the precursor concentration, in agreement with vapor nucleation theory, but larger particles and aggregates form at higher gas flow rates where the mean residence time should be reduced, suggesting a cooling effect that leads to enhanced particle nucleation. In comparison, incorporating a capillary gas injector to alter the velocity profile is found to significantly reduce particle size and agglomeration. These results suggest that capillary gas injection is a better approach to decreasing the mean residence time and narrowing the residence time distribution for nanoparticle growth by producing a sharp and narrow velocity profile. (paper)

  4. Simulating the control of molecular reactions via modulated light fields: from gas phase to solution

    Science.gov (United States)

    Thallmair, Sebastian; Keefer, Daniel; Rott, Florian; de Vivie-Riedle, Regina

    2017-04-01

    Over the past few years quantum control has proven to be very successful in steering molecular processes. By combining theory with experiment, even highly complex control aims were realized in the gas phase. In this topical review, we illustrate the past achievements on several examples in the molecular context. The next step for the quantum control of chemical processes is to translate the fruitful interplay between theory and experiment to the condensed phase and thus to the regime where chemical synthesis can be supported. On the theory side, increased efforts to include solvent effects in quantum control simulations were made recently. We discuss two major concepts, namely an implicit description of the environment via the density matrix algorithm and an explicit inclusion of solvent molecules. By application to chemical reactions, both concepts conclude that despite environmental perturbations leading to more complex control tasks, efficient quantum control in the condensed phase is still feasible.

  5. UPS and DFT investigation of the electronic structure of gas-phase trimesic acid

    Energy Technology Data Exchange (ETDEWEB)

    Reisberg, L., E-mail: rebban@ut.ee [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); Pärna, R. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); MAX IV Laboratory, Lund University, Fotongatan 2, 225 94 Lund (Sweden); Kikas, A.; Kuusik, I.; Kisand, V. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia); Hirsimäki, M.; Valden, M. [Surface Science Laboratory, Optoelectronics Research Centre, Tampere University of Technology, FIN-33101 Tampere (Finland); Nõmmiste, E. [Institute of Physics, University of Tartu, W. Oswaldi 1, EE-50411 Tartu (Estonia)

    2016-11-15

    Highlights: • In the current study outer valence band electronic structure of benzene-1,3,5-tricarboxylic acid was interpreted. • Experimental and calculated trimesic acid (TMA) spectrum were compared to ones of benzene and benzoic acid. • It is shown that similarities between MO energies and shapes for benzene and TMA exists. • Addition of carboxyl groups to the benzene ring clearly correlates with increasing binding energy of HOMO. - Abstract: Benzene-1,3,5-tricarboxylic acid (trimesic acid, TMA) molecules in gas-phase have been investigated by using valence band photoemission. The photoelectron spectrum in the binding energy region from 9 to 22 eV is interpreted by using density functional theory calculations. The electronic structure of TMA is compared with benzene and benzoic acid in order to demonstrate changes in molecular orbital energies induced by addition of carboxyl groups to benzene ring.

  6. Relaxation rates of low-field gas-phase ^129Xe storage cells

    Science.gov (United States)

    Limes, Mark; Saam, Brian

    2010-10-01

    A study of longitudinal nuclear relaxation rates T1 of ^129Xe and Xe-N2 mixtures in a magnetic field of 3.8 mT is presented. In this regime, intrinsic spin relaxation is dominated by the intramolecular spin-rotation interaction due to persistent xenon dimers, a mechanism that can be quelled by introducing large amounts of N2 into the storage cell. Extrinsic spin relaxation is dominated by the wall-relaxation rate, which is the primary quantity of interest for the various low-field storage cells and coatings that we have tested. Previous group work has shown that extremely long gas-phase relaxation times T1 can be obtained, but only at large magnetic fields and low xenon densities. The current work is motivated by the practical benefits of retaining hyperpolarized ^129Xe for extended periods of time in a small magnetic field.

  7. Some insights into formamide formation through gas-phase reactions in the interstellar medium

    International Nuclear Information System (INIS)

    Redondo, Pilar; Barrientos, Carmen; Largo, Antonio

    2014-01-01

    We study the viability of different gas-phase ion-molecule reactions that could produce precursors of formamide in the interstellar medium. We analyze different reactions between cations containing a nitrogen atom (NH 3 + , NH 4 + , NH 3 OH + , and NH 2 OH + ) and neutral molecules having one carbonyl group (H 2 CO and HCOOH). First, we report a theoretical estimation of the reaction enthalpies for the proposed processes. Second, for more favorable reactions, from a thermodynamic point of view, we perform a theoretical study of the potential energy surface. In particular, the more exothermic processes correspond to the reactions of ionized and protonated hydroxylamine with formaldehyde. In addition, a neutral-neutral reaction has also been considered. The analysis of the potential energy surfaces corresponding to these reactions shows that these processes present a net activation barrier and that they cannot be considered as a source of formamide in space.

  8. Some Insights into Formamide Formation through Gas-phase Reactions in the Interstellar Medium

    Science.gov (United States)

    Redondo, Pilar; Barrientos, Carmen; Largo, Antonio

    2014-01-01

    We study the viability of different gas-phase ion-molecule reactions that could produce precursors of formamide in the interstellar medium. We analyze different reactions between cations containing a nitrogen atom (NH_{3}^{+}, NH_{4}^{+}, NH3OH+, and NH2OH+) and neutral molecules having one carbonyl group (H2CO and HCOOH). First, we report a theoretical estimation of the reaction enthalpies for the proposed processes. Second, for more favorable reactions, from a thermodynamic point of view, we perform a theoretical study of the potential energy surface. In particular, the more exothermic processes correspond to the reactions of ionized and protonated hydroxylamine with formaldehyde. In addition, a neutral-neutral reaction has also been considered. The analysis of the potential energy surfaces corresponding to these reactions shows that these processes present a net activation barrier and that they cannot be considered as a source of formamide in space.

  9. Predicting dermal absorption of gas-phase chemicals: transient model development, evaluation, and application

    DEFF Research Database (Denmark)

    Gong, M.; Zhang, Y.; Weschler, Charles J.

    2014-01-01

    A transient model is developed to predict dermal absorption of gas-phase chemicals via direct air-to-skin-to-blood transport under non-steady-state conditions. It differs from published models in that it considers convective mass-transfer resistance in the boundary layer of air adjacent to the skin....... Results calculated with this transient model are in good agreement with the limited experimental results that are available for comparison. The sensitivity of the modeled estimates to key parameters is examined. The model is then used to estimate air-to-skin-to-blood absorption of six phthalate esters...... and less absorbed into blood than would a steady-state model. In the 7-day scenario, results calculated by the transient and steady-state models converge over a time period that varies between 3 and 4days for all but the largest phthalate (DEHP). Dermal intake is comparable to or larger than inhalation...

  10. Gas-phase Hydrogenation of Crotonaldehyde Over Nickel-on-Kieselguhr Catalyst Pellets

    International Nuclear Information System (INIS)

    Uraz, C.; Atalay, F.; Atalay, S.

    2001-01-01

    Gas phase catalytic hydrogenation of crotonaldehyde to η-butanol was investigated. A nickel based commercial catalyst produced by Harshaw was used at constant temperatures ranging from 160 to 210deg; at pressures of 1.5, 2 , and 2.5 atm and at different crotonaldehyde to hydrogen feed ratios changing from 0.134 to 0.226. The conversion of crotonaldehyde at different operating conditions were determined and the reaction rates were calculated . The experimental results were fitted to ten langmuir-Hinshelwood/ Eley Rideal type models in addition to a homogeneous kinetics modal and the best modal was identified. The effects of external and internal mass transfer resistances were found to be negligible .(authors) refs 28., 2 figs , 4 tabs

  11. Effects of the liquid-gas phase transition and cluster formation on the symmetry energy

    International Nuclear Information System (INIS)

    Typel, S.; Wolter, H.H.; Roepke, G.; Blaschke, D.

    2014-01-01

    Various definitions of the symmetry energy are introduced for nuclei, dilute nuclear matter below saturation density and stellar matter, which is found in compact stars or core-collapse supernovae. The resulting differences are exemplified by calculations in a theoretical approach based on a generalized relativistic density functional for dense matter. It contains nucleonic clusters as explicit degrees of freedom with medium-dependent properties that are derived for light clusters from a quantum statistical approach. With such a model the dissolution of clusters at high densities can be described. The effects of the liquid-gas phase transition in nuclear matter and of cluster formation in stellar matter on the density dependence of the symmetry energy are studied for different temperatures. It is observed that correlations and the formation of inhomogeneous matter at low densities and temperatures causes an increase of the symmetry energy as compared to calculations assuming a uniform uncorrelated spatial distribution of constituent baryons and leptons. (orig.)

  12. Nanocrystalline AL2 O2 powders produced by laser induced gas phase reactions

    International Nuclear Information System (INIS)

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

    1993-01-01

    Nanocrystalline Al 2 O 3 powders were successfully synthesized by a CO 2 laser-driven gas-phase reaction involving trimethylaluminium (Al(CH 3 ) 3 ) and nitrous-oxide (N 2 O). Ethylene (C 2 H 4 ) was added as gas sensitizer. The as-synthesized powder particles showed a considerable carbon contamination and an amorphous-like structure. After thermal treatment at 1200-1400 degrees C, the powder was transformed to hexagonal a-Al 2 O 3 with very low carbon contamination as confirmed by X-ray diffraction, X-ray photo-electron spectroscopy and chemical analysis. The calcinated powders resulted to be spherical single crystal nanoparticles with a mean size of 15-20 nm, as determined by X-ray diffraction, electron microscopy and B.E.T. specific surface measurements. The laser synthesized Al 2 O 3 particles are well suited dispersoids for intermetallic alloy technology

  13. Liquid- and Gas-Phase Diffusion of Ferrocene in Thin Films of Metal-Organic Frameworks

    Directory of Open Access Journals (Sweden)

    Wencai Zhou

    2015-06-01

    Full Text Available The mass transfer of the guest molecules in nanoporous host materials, in particular in metal-organic frameworks (MOFs, is among the crucial features of their applications. By using thin surface-mounted MOF films in combination with a quartz crystal microbalance (QCM, the diffusion of ferrocene vapor and of ethanolic and hexanic ferrocene solution in HKUST-1 was investigated. For the first time, liquid- and gas-phase diffusion in MOFs was compared directly in the identical sample. The diffusion coefficients are in the same order of magnitude (~10−16 m2·s−1, whereas the diffusion coefficient of ferrocene in the empty framework is roughly 3-times smaller than in the MOF which is filled with ethanol or n-hexane.

  14. Liquid- and Gas-Phase Diffusion of Ferrocene in Thin Films of Metal-Organic Frameworks

    Science.gov (United States)

    Zhou, Wencai; Wöll, Christof; Heinke, Lars

    2015-01-01

    The mass transfer of the guest molecules in nanoporous host materials, in particular in metal-organic frameworks (MOFs), is among the crucial features of their applications. By using thin surface-mounted MOF films in combination with a quartz crystal microbalance (QCM), the diffusion of ferrocene vapor and of ethanolic and hexanic ferrocene solution in HKUST-1 was investigated. For the first time, liquid- and gas-phase diffusion in MOFs was compared directly in the identical sample. The diffusion coefficients are in the same order of magnitude (~10−16 m2·s−1), whereas the diffusion coefficient of ferrocene in the empty framework is roughly 3-times smaller than in the MOF which is filled with ethanol or n-hexane.

  15. Catalytic Gas-Phase Production of Lactide from Renewable Alkyl Lactates.

    Science.gov (United States)

    De Clercq, Rik; Dusselier, Michiel; Makshina, Ekaterina; Sels, Bert F

    2018-03-12

    A new route to lactide, which is a key building block of the bioplastic polylactic acid, is proposed involving a continuous catalytic gas-phase transesterification of renewable alkyl lactates in a scalable fixed-bed setup. Supported TiO 2 /SiO 2 catalysts are highly selective to lactide, with only minimal lactide racemization. The solvent-free process allows for easy product separation and recycling of unconverted alkyl lactates and recyclable lactyl intermediates. The catalytic activity of TiO 2 /SiO 2 catalysts was strongly correlated to their optical properties by DR UV/Vis spectroscopy. Catalysts with high band-gap energy of the supported TiO 2 phase, indicative of a high surface spreading of isolated Ti centers, show the highest turnover frequency per Ti site. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Melt-gas phase equilibria and state diagrams of the selenium-tellurium system

    Science.gov (United States)

    Volodin, V. N.; Trebukhov, S. A.; Burabaeva, N. M.; Nitsenko, A. V.

    2017-05-01

    The partial pressures of saturated vapor of the components in the Se-Te system are determined and presented in the form of temperature-concentration dependences from which the boundaries of the melt-gas phase transition are calculated at atmospheric pressure and vacuums of 2000 and 100 Pa. The existence of azeotropic mixtures is revealed. It is found that the points of inseparably boiling melts correspond to 7.5 at % of Se and 995°C at 101325 Pa, 10.9 at % at 673°C and 19.5 at % at 522°C in vacuums of 2000 and 100 Pa, respectively. A complete state diagram is constructed, including the fields of gas-liquid equilibria at atmospheric and low pressures, the boundaries of which allow us to assess the behavior of selenium and tellurium upon distillation fractionation.

  17. Gas-Phase Reactions of Dimethyl Disulfide with Aliphatic Carbanions - A Mass Spectrometry and Computational Study

    Science.gov (United States)

    Franczuk, Barbara; Danikiewicz, Witold

    2018-03-01

    Ion-molecule reactions of Me2S2 with a wide range of aliphatic carbanions differing by structure and proton affinity values have been studied in the gas phase using mass spectrometry techniques and DFT calculations. The analysis of the spectra shows a variety of product ions formed via different reaction mechanisms, depending on the structure and proton affinity of the carbanion. Product ions of thiophilic reaction ( m/z 47), SN2 ( m/z 79), and E2 elimination - addition sequence of reactions ( m/z 93) can be observed. Primary products of thiophilic reaction can undergo subsequent SN2 and proton transfer reactions. Gibbs free energy profiles calculated for experimentally observed reactions using PBE0/6-311+G(2d,p) method show good agreement with experimental results. [Figure not available: see fulltext.

  18. An improved stochastic algorithm for temperature-dependent homogeneous gas phase reactions

    CERN Document Server

    Kraft, M

    2003-01-01

    We propose an improved stochastic algorithm for temperature-dependent homogeneous gas phase reactions. By combining forward and reverse reaction rates, a significant gain in computational efficiency is achieved. Two modifications of modelling the temperature dependence (with and without conservation of enthalpy) are introduced and studied quantitatively. The algorithm is tested for the combustion of n-heptane, which is a reference fuel component for internal combustion engines. The convergence of the algorithm is studied by a series of numerical experiments and the computational cost of the stochastic algorithm is compared with the DAE code DASSL. If less accuracy is needed the stochastic algorithm is faster on short simulation time intervals. The new stochastic algorithm is significantly faster than the original direct simulation algorithm in all cases considered.

  19. Detailed investigation of proposed gas-phase syntheses of ammonia in dense interstellar clouds

    International Nuclear Information System (INIS)

    Herbst, E.; Defrees, D.J.; Mclean, A.D.; Molecular Research Institute, Palo Alto, CA; IBM Almaden Research Center, San Jose, CA)

    1987-01-01

    The initial reactions of the Herbst and Klemperer (1973) and the Dalgarno (1974) schemes (I and II, respectively) for the gas-phase synthesis of ammonia in dense interstellar clouds were investigated. The rate of the slightly endothermic reaction between N(+) and H2 to yield NH(+) and H (scheme I) under interstellar conditions was reinvestigated under thermal and nonthermal conditions based on laboratory data. It was found that the relative importance of this reaction in synthesizing ammonia is determined by how the laboratory data at low temperature are interpreted. On the other hand, the exothermic reaction between N and H3(+) to form NH2(+) + H (scheme II) was calculated to possess significant activation energy and, therefore, to have a negligible rate coefficient under interstellar conditions. Consequently, this reaction cannot take place appreciably in interstellar clouds. 41 references

  20. Gas-phase advanced oxidation for effective, efficient in situ control of pollution

    DEFF Research Database (Denmark)

    Johnson, Matthew Stanley; Nilsson, Elna Johanna Kristina; Svensson, Erik Anders

    2014-01-01

    In this article, gas-phase advanced oxidation, a new method for pollution control building on the photo-oxidation and particle formation chemistry occurring in the atmosphere, is introduced and characterized. The process uses ozone and UV-C light to produce in situ radicals to oxidize pollution......, generating particles that are removed by a filter; ozone is removed using a MnO2 honeycomb catalyst. This combination of in situ processes removes a wide range of pollutants with a comparatively low specific energy input. Two proof-of-concept devices were built to test and optimize the process...... particulate mass. Secondary pollution including formaldehyde and ultrafine particles might be generated, depending on the composition of the primary pollution....

  1. Gas-phase thermolysis reaction of formaldehyde diperoxide. Kinetic study and theoretical mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Jorge, Nelly Lidia [Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Av. Las Palmeras 4, 18100 Armilla, Granada (Spain); Area de Quimica Fisica Facultad de Ciencias Exactas y Naturales y Agrimensura, UNNE, Avda. Libertad 5460, 3400 Corrientes (Argentina); Romero, Jorge Marcelo [Area de Quimica Fisica Facultad de Ciencias Exactas y Naturales y Agrimensura, UNNE, Avda. Libertad 5460, 3400 Corrientes (Argentina); Grand, Andre [INAC, SCIB, Laboratoire ' Lesions des Acides Nucleiques' , UMR CEA-UJF E3, CEA-Grenoble, 17 Rue des Martyrs, 38054 Grenoble cedex 9 (France); Hernandez-Laguna, Alfonso, E-mail: ahlaguna@ugr.es [Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Av. Las Palmeras 4, 18100 Armilla, Granada (Spain)

    2012-01-17

    Highlights: Black-Right-Pointing-Pointer Kinetic and mechanism of the gas-phase thermolysis of tetroxane were determined. Black-Right-Pointing-Pointer Gas chromatography and computational potential energy surfaces were performed. Black-Right-Pointing-Pointer A mechanism in steps looked like the most probable mechanism. Black-Right-Pointing-Pointer A spin-orbit coupling appeared at the singlet and triple diradical open structures. Black-Right-Pointing-Pointer A non-adiabatic crossing from the singlet to the triplet state occurred. - Abstract: Gas-phase thermolysis reaction of formaldehyde diperoxide (1,2,4,5-tetroxane) was performed in an injection chamber of a gas chromatograph at a range of 463-503 K. The average Arrhenius activation energy and pre-exponential factor were 29.3 {+-} 0.8 kcal/mol and 5.2 Multiplication-Sign 10{sup 13} s{sup -1}, respectively. Critical points and reaction paths of the ground singlet and first triplet potential energy surfaces (PES) were calculated, using DFT method at BHANDHLYP/6-311+G{sup Asterisk-Operator Asterisk-Operator} level of the theory. Also, G3 calculations were performed on the reactant and products. Reaction by the ground-singlet and first-triplet states turned out to be endothermic and exothermic, respectively. The mechanism in three steps seemed to be the most probable one. An electronically non-adiabatic process appeared, in which a crossing, at an open diradical structure, from the singlet to the triplet state PES occurred, due to a spin-orbit coupling, yielding an exothermic reaction. Theoretical kinetic constant coming from the non- adiabatic transition from the singlet to the triplet state agrees with the experimental values.

  2. Reaction pathways for catalytic gas-phase oxidation of glycerol over mixed metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Suprun, W.; Glaeser, R.; Papp, H. [Leipzig Univ. (Germany). Inst. of Chemical Technology

    2011-07-01

    Glycerol as a main by-product from bio-diesel manufacture is a cheap raw material with large potential for chemical or biochemical transformations to value-added C3-chemicals. One possible way of glycerol utilization involves its catalytic oxidation to acrylic acid as an alternative to petrochemical routes. However, this catalytic conversion exhibits various problems such as harsh reaction conditions, severe catalyst coking and large amounts of undesired by-products. In this study, the reaction pathways for gas-phase conversion of glycerol over transition metal oxides (Mo, V und W) supported on TiO{sub 2} and SiO{sub 2} were investigated by two methods: (i) steady state experiments of glycerol oxidation and possible reactions intermediates, i.e., acrolein, 3-hydroxy propionaldehyde and acetaldehyde, and (ii) temperature-programmed surface reaction (TPSR) studies of glycerol conversion in the presence and in the absence of gas-phase oxygen. It is shown that the supported W-, V and Mo-oxides possess an ability to catalyze the oxidation of glycerol to acrylic acid. These investigations allowed us to gain a deeper insight into the reaction mechanism. Thus, based on the obtained results, three possible reactions pathways for the selective oxidation of glycerol to acrylic acid on the transition metal-containing catalysts are proposed. The major pathways in presence of molecular oxygen are a fast successive destructive oxidation of glycerol to CO{sub x} and the dehydration of glycerol to acrolein which is a rate-limiting step. (orig.)

  3. Gas-phase thermolysis reaction of formaldehyde diperoxide. Kinetic study and theoretical mechanisms

    International Nuclear Information System (INIS)

    Jorge, Nelly Lidia; Romero, Jorge Marcelo; Grand, André; Hernández-Laguna, Alfonso

    2012-01-01

    Highlights: ► Kinetic and mechanism of the gas-phase thermolysis of tetroxane were determined. ► Gas chromatography and computational potential energy surfaces were performed. ► A mechanism in steps looked like the most probable mechanism. ► A spin–orbit coupling appeared at the singlet and triple diradical open structures. ► A non-adiabatic crossing from the singlet to the triplet state occurred. - Abstract: Gas-phase thermolysis reaction of formaldehyde diperoxide (1,2,4,5-tetroxane) was performed in an injection chamber of a gas chromatograph at a range of 463–503 K. The average Arrhenius activation energy and pre-exponential factor were 29.3 ± 0.8 kcal/mol and 5.2 × 10 13 s −1 , respectively. Critical points and reaction paths of the ground singlet and first triplet potential energy surfaces (PES) were calculated, using DFT method at BHANDHLYP/6-311+G ∗∗ level of the theory. Also, G3 calculations were performed on the reactant and products. Reaction by the ground-singlet and first-triplet states turned out to be endothermic and exothermic, respectively. The mechanism in three steps seemed to be the most probable one. An electronically non-adiabatic process appeared, in which a crossing, at an open diradical structure, from the singlet to the triplet state PES occurred, due to a spin–orbit coupling, yielding an exothermic reaction. Theoretical kinetic constant coming from the non- adiabatic transition from the singlet to the triplet state agrees with the experimental values.

  4. The influence of gas phase velocity fluctuations on primary atomization and droplet deformation

    Science.gov (United States)

    Kourmatzis, A.; Masri, A. R.

    2014-02-01

    The effects of grid-generated velocity fluctuations on the primary atomization and subsequent droplet deformation of a range of laminar liquid jets are examined using microscopic high-speed backlit imaging of the break-up zone and laser Doppler anemometry of the gas phase separately. This is done for fixed gas mean flow conditions in a miniature wind tunnel experiment utilizing a selection of fuels, turbulence-generating grids and two syringe sizes. The constant mean flow allows for an isolated study of velocity fluctuation effects on primary atomization in a close approximation to homogeneous decaying turbulence. The qualitative morphology of the primary break-up region is examined over a range of turbulence intensities, and spectral analysis is performed in order to ascertain the break-up frequency which, for a case of no grid, compares well with the existing literature. The addition of velocity fluctuations tends to randomize the break-up process. Slightly downstream of the break-up region, image processing is conducted in order to extract a number of metrics, which do not depend on droplet sphericity, and these include droplet aspect ratio and orientation, the latter quantity being somewhat unconventional in spray characterization. A turbulent Weber number which takes into account gas phase fluctuations is utilized to characterize the resulting droplet shapes, in addition to a mean Weber number . Above a a clear positive relationship exists between the mean aspect ratio of droplets and the turbulent Weber number where is varied by altering all relevant variables including the velocity root mean square, the initial droplet diameter, the surface tension and the density.

  5. Molecular simulation of excess isotherm and excess enthalpy change in gas-phase adsorption.

    Science.gov (United States)

    Do, D D; Do, H D; Nicholson, D

    2009-01-29

    We present a new approach to calculating excess isotherm and differential enthalpy of adsorption on surfaces or in confined spaces by the Monte Carlo molecular simulation method. The approach is very general and, most importantly, is unambiguous in its application to any configuration of solid structure (crystalline, graphite layer or disordered porous glass), to any type of fluid (simple or complex molecule), and to any operating conditions (subcritical or supercritical). The behavior of the adsorbed phase is studied using the partial molar energy of the simulation box. However, to characterize adsorption for comparison with experimental data, the isotherm is best described by the excess amount, and the enthalpy of adsorption is defined as the change in the total enthalpy of the simulation box with the change in the excess amount, keeping the total number (gas + adsorbed phases) constant. The excess quantities (capacity and energy) require a choice of a reference gaseous phase, which is defined as the adsorptive gas phase occupying the accessible volume and having a density equal to the bulk gas density. The accessible volume is defined as the mean volume space accessible to the center of mass of the adsorbate under consideration. With this choice, the excess isotherm passes through a maximum but always remains positive. This is in stark contrast to the literature where helium void volume is used (which is always greater than the accessible volume) and the resulting excess can be negative. Our definition of enthalpy change is equivalent to the difference between the partial molar enthalpy of the gas phase and the partial molar enthalpy of the adsorbed phase. There is no need to assume ideal gas or negligible molar volume of the adsorbed phase as is traditionally done in the literature. We illustrate this new approach with adsorption of argon, nitrogen, and carbon dioxide under subcritical and supercritical conditions.

  6. Gas phase enthalpies of formation of nitrobenzamides using combustion calorimetry and thermal analysis

    International Nuclear Information System (INIS)

    Ximello, Arturo; Flores, Henoc; Rojas, Aarón; Adriana Camarillo, E.; Patricia Amador, M.

    2014-01-01

    Graphical abstract: - Highlights: • Formation enthalpies of the nitrobenzamides were derived from combustion calorimetry. • Enthalpies of vaporisation and sublimation were calculated by thermogravimetry. • From gas phase enthalpies of formation the stability of the isomers is studied. • Stability of isomers is not driven by a steric hindrance between functional groups. - Abstract: The standard molar energies of combustion of 2-nitrobenzamide, 3-nitrobenzamide and 4-nitrobenzamide were determined with an isoperibolic, static-bomb, combustion calorimeter. From the combustion results, the standard molar enthalpies of combustion and formation for these compounds in the condensed phase at T = 298.15 K were derived. Subsequently, to determine the enthalpies of sublimation, the vapour pressure data as a function of the temperature for the compounds under investigation were estimated using thermogravimetry by applying Langmuir’s equation, and the enthalpies of vaporisation were derived. Standard enthalpies of fusion were measured by differential scanning calorimetry then added to those of vaporisation to obtain reliable results for the enthalpy of sublimation. From the combustion and sublimation data, the gas phase enthalpies of formation were determined to be (−138.9 ± 3.5) kJ · mol −1 , (−122.9 ± 2.9) kJ · mol −1 and (−108.5 ± 3.7) kJ · mol −1 for the ortho, meta and para isomers of nitrobenzamide, respectively. The meaning of these results with regard to the enthalpic stability of these molecular structures is discussed herein

  7. Transport of Gas Phase Radionuclides in a Fractured, Low-Permeability Reservoir

    Science.gov (United States)

    Cooper, C. A.; Chapman, J.

    2001-12-01

    The U.S. Atomic Energy Commission (predecessor to the Department of Energy, DOE) oversaw a joint program between industry and government in the 1960s and 1970s to develop technology to enhance production from low-permeability gas reservoirs using nuclear stimulation rather than conventional means (e.g., hydraulic and/or acid fracturing). Project Rio Blanco, located in the Piceance Basin, Colorado, was the third experiment under the program. Three 30-kiloton nuclear explosives were placed in a 2134 m deep well at 1780, 1899, and 2039 m below the land surface and detonated in May 1973. Although the reservoir was extensively fractured, complications such as radionuclide contamination of the gas prevented production and subsequent development of the technology. Two-dimensional numerical simulations were conducted to identify the main transport processes that have occurred and are currently occurring in relation to the detonations, and to estimate the extent of contamination in the reservoir. Minor modifications were made to TOUGH2, the multiphase, multicomponent reservoir simulator developed at Lawrence Berkeley National Laboratories. The simulator allows the explicit incorporation of fractures, as well as heat transport, phase change, and first order radionuclide decay. For a fractured two-phase (liquid and gas) reservoir, the largest velocities are of gases through the fractures. In the gas phase, tritium and one isotope of krypton are the principle radionuclides of concern. However, in addition to existing as a fast pathway, fractures also permit matrix diffusion as a retardation mechanism. Another retardation mechanism is radionuclide decay. Simulations show that incorporation of fractures can significantly alter transport rates, and that radionuclides in the gas phase can preferentially migrate upward due to the downward gravity drainage of liquid water in the pores. This project was funded by the National Nuclear Security Administration, Nevada Operations Office

  8. Gas-phase ion/ion reactions of peptides and proteins: acid/base, redox, and covalent chemistries.

    Science.gov (United States)

    Prentice, Boone M; McLuckey, Scott A

    2013-02-01

    Gas-phase ion/ion reactions are emerging as useful and flexible means for the manipulation and characterization of peptide and protein biopolymers. Acid/base-like chemical reactions (i.e., proton transfer reactions) and reduction/oxidation (redox) reactions (i.e., electron transfer reactions) represent relatively mature classes of gas-phase chemical reactions. Even so, especially in regards to redox chemistry, the widespread utility of these two types of chemistries is undergoing rapid growth and development. Additionally, a relatively new class of gas-phase ion/ion transformations is emerging which involves the selective formation of functional-group-specific covalent bonds. This feature details our current work and perspective on the developments and current capabilities of these three areas of ion/ion chemistry with an eye towards possible future directions of the field.

  9. Equilibrium of particle nitrite with gas phase HONO: Tropospheric measurements in the high Arctic during polar sunrise

    Science.gov (United States)

    Li, Shao-Meng

    1994-12-01

    Gas phase HONO(g) and nitrite in particles of formation rate from HONO(g) photolysis was greater than from the photolysis of both O3 and CH2O by more than one order of magnitude during the sunlit period and led to moderately high levels of OH, e.g., 3×105 molecules cm-3 OH at noontime on April 5. Particle nitrite measurements showed a gradual increase in concentrations with increasing solar insolation, but the concentrations were generally less than 10 ppt. The pH and the sulfate molar concentrations of the particles and the water vapor mixing ratio indicate that the particles were highly acidic being approximately 70% (W/W) H2SO4 solution. In such highly concentrated H2SO4 solution, most particle nitrite should exist as hydrated nitrosonium ion H2ONO+. Taking this into consideration, the particle nitrite was in an approximate equilibrium with the measured HONO(g). This equilibrium, with HONO(g) rapidly photolyzed, was a good indication that the particles were effective sources of HONO(g) and implied rapid production of particle N(+III) during this period. Two possible pathways leading to the formation of particle N(+III) species are suggested, i.e., reduction of HNO3(aq) by SO2(g) and reduction of NO3-; (aq) by Br- (aq). However, N2O5 reaction with NaBr cannot be ruled out as the alternative HONO(g) formation mechanism which bypasses the equilibrium.

  10. Gas phase synthesis of non-bundled, small diameter single-walled carbon nanotubes with near-armchair chiralities

    Energy Technology Data Exchange (ETDEWEB)

    Mustonen, K.; Laiho, P.; Kaskela, A.; Zhu, Z.; Reynaud, O.; Houbenov, N.; Tian, Y.; Jiang, H.; Kauppinen, E. I., E-mail: esko.kauppinen@aalto.fi [Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto (Finland); Susi, T. [Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria); Nasibulin, A. G. [Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto (Finland); Skolkovo Institute of Science and Technology, Nobel str. 3, 143026 (Russian Federation); Saint-Petersburg State Polytechnical University, 29 Polytechniheskaya st., St. Petersburg, 195251 (Russian Federation)

    2015-07-06

    We present a floating catalyst synthesis route for individual, i.e., non-bundled, small diameter single-walled carbon nanotubes (SWCNTs) with a narrow chiral angle distribution peaking at high chiralities near the armchair species. An ex situ spark discharge generator was used to form iron particles with geometric number mean diameters of 3–4 nm and fed into a laminar flow chemical vapour deposition reactor for the continuous synthesis of long and high-quality SWCNTs from ambient pressure carbon monoxide. The intensity ratio of G/D peaks in Raman spectra up to 48 and mean tube lengths up to 4 μm were observed. The chiral distributions, as directly determined by electron diffraction in the transmission electron microscope, clustered around the (n,m) indices (7,6), (8,6), (8,7), and (9,6), with up to 70% of tubes having chiral angles over 20°. The mean diameter of SWCNTs was reduced from 1.10 to 1.04 nm by decreasing the growth temperature from 880 to 750 °C, which simultaneously increased the fraction of semiconducting tubes from 67% to 80%. Limiting the nanotube gas phase number concentration to ∼10{sup 5 }cm{sup −3} prevented nanotube bundle formation that is due to collisions induced by Brownian diffusion. Up to 80% of 500 as-deposited tubes observed by atomic force and transmission electron microscopy were individual. Transparent conducting films deposited from these SWCNTs exhibited record low sheet resistances of 63 Ω/□ at 90% transparency for 550 nm light.

  11. Process for removing a mixture containing iodine and alkyl iodine compounds from a gas phase or aqueous solution with ion-exchange resins

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, H; Mizuuchi, A; Yokoyama, F

    1968-10-04

    Iodine and alkyl iodine compounds are removed from a gas phase or aqueous solution containing salts, iodine and iodine compounds, such as the ambient gas in a reactor, if an accident should occur. The process comprises contacting the phase or solution: (a) with a hydrogen type strongly acidic cationic exchange resin, (b) with an anionic exchange resin containing quarternary ammonium and (c) with an anionic exchange resin containing free basic type tertiary amine, in this order or by reversing the order of the two anionic exchange resins. Although no problems arise in the liquid phase reaction, the ion-exchange resins in the gas phase reaction are desired in the moist state in order to stable maintain the migration speed of the materials to be removed regardless of the relative humidity of the amibent gas. In example I, Amberlite IRA-900 of 200 mm thickness as the lowermost bed, Amberlite IRA93 of 200 mm thickness as the middle bed and Amberlite 200 of 200 mm thickness as the uppermost bed were filled respectively, in a methacrylate resin cylinder with an inner diameter of 25 mm. A solution containing 15.9 mg/1 of iodine, 41.2 mg/1 of methyl iodide and 550 mg/1 of sodium carbonate flows at a rate of 15 liter/hr downward through the beds. As a result of testing, no iodine, iodine ions, iodic acid ions and methyl iodine were detected. The amount of water the beds could treat was 60 times the total quantity of the filled resins.

  12. Synergistic effects of liquid and gas phase discharges using pulsed high voltage for dyes degradation in the presence of oxygen.

    Science.gov (United States)

    Yang, Bin; Zhou, Minghua; Lei, Lecheng

    2005-07-01

    The technology of combined liquid and gas phase discharges (LGD) using pulsed high voltage for dyes degradation was developed in this study. Apparent synergistic effects for Acid orange II (AO) degradation in the presence of oxygen were observed. The enhancement of AO degradation rate was around 302%. Furthermore, higher energy efficiency was obtained comparing with individual liquid phase discharge (LD) or gas phase discharge process (GD). The AO degradation in the presence of oxygen by LGD proceeded through the direct ozone oxidation and the ozone decomposition induced by LD. Important operating parameters such as electrode distance, applied voltage, pulse repetition rate, and types of dyes were further investigated.

  13. The structure and conformations of piracetam (2-oxo-1-pyrrolidineacetamide): Gas-phase electron diffraction and quantum chemical calculations

    Science.gov (United States)

    Ksenafontov, Denis N.; Moiseeva, Natalia F.; Khristenko, Lyudmila V.; Karasev, Nikolai M.; Shishkov, Igor F.; Vilkov, Lev V.

    2010-12-01

    The geometric structure of piracetam was studied by quantum chemical calculations (DFT and ab initio), gas electron diffraction (GED), and FTIR spectroscopy. Two stable mirror symmetric isomers of piracetam were found. The conformation of pyrrolidine ring is an envelope in which the C4 atom deviates from the ring plane, the angle between the planes (C3 sbnd C4 sbnd C5) and (C2 sbnd C3 sbnd C5) is 154.1°. The direction of the deviation is the same as that of the side acetamide group. The piracetam molecule is stabilized in the gas phase by an intramolecular hydrogen bond between the N9H 2 group and the oxygen O6, bonded to C2. The principal structural parameters ( re, Å and ∠e, degrees; uncertainties are 3 σLS values) were found to be: r(С3 sbnd С4) = 1.533(1), r(C4 sbnd C5) = 1.540(1), r(N1 sbnd C5) = 1.456(1), r(C2 sbnd C3) = 1.520(1), r(N1 sbnd C7) = 1.452(1), r(C7 sbnd C8) = 1.537(1), r(N1 sbnd C2) = 1.365(2), r(C8 sbnd N9) = 1.360(2), r(C2 dbnd O6) = 1.229(1), r(C8 dbnd O10) = 1.221(1), ∠C2 sbnd N1 sbnd C5 = 113.4(6), ∠N1 sbnd C2 sbnd C3 = 106.9(6), ∠N1 sbnd C7 sbnd C8 = 111.9(6), ∠C7 sbnd C8 sbnd N9 = 112.5(6), ∠N1 sbnd C2 sbnd O6 = 123.0(4), ∠C3 sbnd N1 sbnd C7 = 120.4(4), ∠C7 sbnd C8 sbnd O10 = 120.2(4), ∠C5 sbnd N1 sbnd C2 sbnd O6 = 170(6), ∠C3 sbnd C2 sbnd N1 sbnd C7 = 178(6), ∠C2 sbnd N1 sbnd C7 sbnd C8 = 84.2, ∠N1 sbnd C7 sbnd C8 sbnd O10 = 111.9.

  14. A sub-grid, mixture-fraction-based thermodynamic equilibrium model for gas phase combustion in FIRETEC: development and results

    Science.gov (United States)

    M. M. Clark; T. H. Fletcher; R. R. Linn

    2010-01-01

    The chemical processes of gas phase combustion in wildland fires are complex and occur at length-scales that are not resolved in computational fluid dynamics (CFD) models of landscape-scale wildland fire. A new approach for modelling fire chemistry in HIGRAD/FIRETEC (a landscape-scale CFD wildfire model) applies a mixture– fraction model relying on thermodynamic...

  15. SITE PROGRAM DEMONSTRATION ECO LOGIC INTERNATIONAL GAS-PHASE CHEMICAL REDUCTION PROCESS, BAY CITY, MICHIGAN TECHNOLOGY EVALUATION REPORT

    Science.gov (United States)

    The SITE Program funded a field demonstration to evaluate the Eco Logic Gas-Phase Chemical Reduction Process developed by ELI Eco Logic International Inc. (ELI), Ontario, Canada. The Demonstration took place at the Middleground Landfill in Bay City, Michigan using landfill wa...

  16. Studies of some elementary processes involving electrons in the gas phase by pulse-radiolysis microwave-cavity technique

    International Nuclear Information System (INIS)

    Sunagawa, Takeyoshi; Makita, Takeshi; Musasa, Hirofumi; Tatsumi, Yoshitsugu; Shimamori, Hiroshi

    1995-01-01

    The pulse radiolysis-microwave cavity technique has been employed for detection of free electrons in the gas phase. Presented are results of the observation of electron disappearance by attachment to molecules, the electron thermalization (energy loss) processes in the presence of an electron-attaching compound, and the formation of electrons by Penning ionization. (author)

  17. Continuous fixed-bed gas-phase hydroformylation using supported ionic liquid-phase (SILP) Rh catalysts

    DEFF Research Database (Denmark)

    Riisager, Anders; Wasserscheid, Peter; Van Hal, R.

    2003-01-01

    Continuous flow gas-phase hydroformylation of propene was performed using novel supported ionic liquid-phase (SILP) catalysts containing immobilized Rh complexes of the biphosphine ligand sulfoxantphos in the ionic liquids 1-n-butyl-3-methylimidazolium hexafluorophosphate and halogen-free 1-n-butyl...

  18. IRMPD Action Spectroscopy of Alkali Metal Cation-Cytosine Complexes: Effects of Alkali Metal Cation Size on Gas Phase Conformation

    NARCIS (Netherlands)

    Yang, B.; Wu, R.R.; Polfer, N.C.; Berden, G.; Oomens, J.; Rodgers, M.T.

    2013-01-01

    The gas-phase structures of alkali metal cation-cytosine complexes generated by electrospray ionization are probed via infrared multiple photon dissociation (IRMPD) action spectroscopy and theoretical calculations. IRMPD action spectra of five alkali metal cation-cytosine complexes exhibit both

  19. Development and validation of a portable gas phase standard generation and calibration system for volatile organic compounds

    Science.gov (United States)

    P. Veres; J. B. Gilman; J. M. Roberts; W. C. Kuster; C. Warneke; I. R. Burling; J. de Gouw

    2010-01-01

    We report on the development of an accurate, portable, dynamic calibration system for volatile organic compounds (VOCs). The Mobile Organic Carbon Calibration System (MOCCS) combines the production of gas-phase VOC standards using permeation or diffusion sources with quantitative total organic carbon (TOC) conversion on a palladium surface to CO2 in the presence of...

  20. Measuring Gas-Phase Basicities of Amino Acids Using an Ion Trap Mass Spectrometer: A Physical Chemistry Laboratory Experiment

    Science.gov (United States)

    Sunderlin, Lee S.; Ryzhov, Victor; Keller, Lanea M. M.; Gaillard, Elizabeth R.

    2005-01-01

    An experiment is performed to measure the relative gas-phase basicities of a series of five amino acids to compare the results to literature values. The experiments use the kinetic method for deriving ion thermochemistry and allow students to perform accurate measurements of thermodynamics in a relatively short time.

  1. The coupling effect of gas-phase chemistry and surface reactions on oxygen permeation and fuel conversion in ITM reactors

    KAUST Repository

    Hong, Jongsup; Kirchen, Patrick; Ghoniem, Ahmed F.

    2015-01-01

    © 2015 Elsevier B.V. The effect of the coupling between heterogeneous catalytic reactions supported by an ion transport membrane (ITM) and gas-phase chemistry on fuel conversion and oxygen permeation in ITM reactors is examined. In ITM reactors

  2. AN ANALYSIS OF CO PRODUCTION IN COMETARY COMAE: CONTRIBUTIONS FROM GAS-PHASE PHENOMENA

    International Nuclear Information System (INIS)

    Pierce, Donna M.; A'Hearn, Michael F.

    2010-01-01

    Understanding the sources of CO in cometary comae is important for understanding comet chemistry and the roles comets have played in the development of the solar system. Among comets sampled to date, the CO abundances vary widely and no direct correlation of CO abundance with other known comet properties has been identified. The picture is complicated further by the discovery of CO production in the comae of some comets, most notably comets Halley and Hale-Bopp. In this study, we investigate the conditions under which CO can be produced in the coma via gas-phase phenomena. We include photochemistry of several parent molecules, as well as two-body chemical reactions that involve the parents and their photodissociative daughter and granddaughter products. We also consider the level of excitation of 'hot' hydrogen (H*) and O( 1 D) in the network, because the level of excitation of these reactants strongly influences reaction rates. Our results suggest that the dominant gas-phase contributor to CO formation is the photodissociation of H 2 CO. Even though typical abundances of H 2 CO are at ∼1% relative to water in the coma, it produces more CO than other processes due to its relatively short photodissociation lifetime. Because other studies have shown H 2 CO to have a distributed source as well, it suggests that at least some CO formation in the coma is connected to the H 2 CO distributed source. We take the time to examine the CO 2 /CO ratio and note that while the CO 2 /CO ratio in comets Halley, Hale-Bopp, and Hyakutake are noticeably different when only native CO is considered, the CO 2 /CO ratios show greater similarity when total CO is considered. Although this sample is relatively small, should the relatively similar CO 2 /CO Total ratio of ∼0.25 indeed be constant for comets with distributed CO sources, it suggests that the extended CO source of these comets is tied directly to the overall C, H, O chemistry of comets, as is likely to happen if hydrogenation

  3. Measuring the hydrogen/deuterium exchange of proteins at high spatial resolution by mass spectrometry: overcoming gas-phase hydrogen/deuterium scrambling.

    Science.gov (United States)

    Rand, Kasper D; Zehl, Martin; Jørgensen, Thomas J D

    2014-10-21

    acidic conditions where the amide hydrogen exchange rate is slowed by many orders of magnitude). The ability to localize the individual deuterated residues (the spatial resolution) is determined by the size (typically ∼7-15 residues) and the number of peptic peptides. These peptides provide a relatively coarse-grained picture of the protein dynamics. A fundamental understanding of the relationship between protein function/dysfunction and conformational dynamics requires in many cases higher resolution and ultimately single-residue resolution. In this Account, we summarize our efforts to achieve single-residue deuterium levels in proteins by electron-based or laser-induced gas-phase fragmentation methods. A crucial analytical requirement for this approach is that the pattern of deuterium labeling from solution is retained in the gas-phase fragment ions. It is therefore essential to control and minimize any occurrence of gas-phase randomization of the solution deuterium label (H/D scrambling) during the MS experiment. For this purpose, we have developed model peptide probes to accurately measure the onset and extent of H/D scrambling. Our analytical procedures to control the occurrence of H/D scrambling are detailed along with the physical parameters that induce it during MS analysis. In light of the growing use of gas-phase dissociation experiments to measure the HDX of proteins in order to obtain a detailed characterization and understanding of the dynamic conformations and interactions of proteins at the molecular level, we discuss the perspectives and challenges of future high-resolution HDX-MS methodology.

  4. Stable isotopes

    International Nuclear Information System (INIS)

    Evans, D.K.

    1986-01-01

    Seventy-five percent of the world's stable isotope supply comes from one producer, Oak Ridge Nuclear Laboratory (ORNL) in the US. Canadian concern is that foreign needs will be met only after domestic needs, thus creating a shortage of stable isotopes in Canada. This article describes the present situation in Canada (availability and cost) of stable isotopes, the isotope enrichment techniques, and related research programs at Chalk River Nuclear Laboratories (CRNL)

  5. Source characterization and exposure modeling of gas-phase polycyclic aromatic hydrocarbon (PAH) concentrations in Southern California

    Science.gov (United States)

    Masri, Shahir; Li, Lianfa; Dang, Andy; Chung, Judith H.; Chen, Jiu-Chiuan; Fan, Zhi-Hua (Tina); Wu, Jun

    2018-03-01

    Airborne exposures to polycyclic aromatic hydrocarbons (PAHs) are associated with adverse health outcomes. Because personal air measurements of PAHs are labor intensive and costly, spatial PAH exposure models are useful for epidemiological studies. However, few studies provide adequate spatial coverage to reflect intra-urban variability of ambient PAHs. In this study, we collected 39-40 weekly gas-phase PAH samples in southern California twice in summer and twice in winter, 2009, in order to characterize PAH source contributions and develop spatial models that can estimate gas-phase PAH concentrations at a high resolution. A spatial mixed regression model was constructed, including such variables as roadway, traffic, land-use, vegetation index, commercial cooking facilities, meteorology, and population density. Cross validation of the model resulted in an R2 of 0.66 for summer and 0.77 for winter. Results showed higher total PAH concentrations in winter. Pyrogenic sources, such as fossil fuels and diesel exhaust, were the most dominant contributors to total PAHs. PAH sources varied by season, with a higher fossil fuel and wood burning contribution in winter. Spatial autocorrelation accounted for a substantial amount of the variance in total PAH concentrations for both winter (56%) and summer (19%). In summer, other key variables explaining the variance included meteorological factors (9%), population density (15%), and roadway length (21%). In winter, the variance was also explained by traffic density (16%). In this study, source characterization confirmed the dominance of traffic and other fossil fuel sources to total measured gas-phase PAH concentrations while a spatial exposure model identified key predictors of PAH concentrations. Gas-phase PAH source characterization and exposure estimation is of high utility to epidemiologist and policy makers interested in understanding the health impacts of gas-phase PAHs and strategies to reduce emissions.

  6. Alterations in prostacyclin and thromboxane formation by chronic cigarette smoke exposure: temporal relationships and whole smoke vs. gas phase

    Energy Technology Data Exchange (ETDEWEB)

    Lubawy, W.C.; Culpepper, B.T.; Valentovic, M.A.

    1986-04-01

    Chronic cigarette smoke exposure in vivo causes decreased conversion of (/sup 14/C)arachidonic acid (AA) to prostacyclin (PGI2) by isolated aortic tissue and increased conversion to thromboxane (TXA2) by isolated platelets from rats. Alterations in the PGI2/TXA2 balance may be part of the mechanism through which smoking increases the risk of cardiovascular disease. To study the influence of smoke exposure duration on this response, male rats were exposed daily to 10 puffs of freshly generated cigarette smoke. Animals were killed after 1, 4, 14, 28 and 57 days of smoke exposure and 3, 7, 14 and 28 days after cessation of the 57-day of smoke-exposure regimen. Elevated carboxyhemoglobin levels during the smoke-exposure sessions verified smoke (gas phase) inhalation. Statistically significant alterations in prostacyclin synthesis preceded those of thromboxane. A decrease of 20-25% (P less than 0.05) in PGI2 production from (/sup 14/C)AA in isolated aortic tissue was found beginning 28 days after smoke was initiated and quickly rebounded when smoke exposure was terminated. Increased production of TXA2 from (/sup 14/C)AA by isolated platelets became statistically significant (P less than 0.05) on the 57th day and returned to normal 7-14 days after cessation of smoke exposure. To determine the effect of gas phase constituents on the PGI2/TXA2 balance a second series of experiments divided male and female Sprague-Dawley rats into sham, whole smoke and gas phase groups. Gas phase was produced by passing whole smoke through a Cambridge filter to remove particulate matter. Per cent COHb averaged 1.4 for sham, 7.8 for whole smoke and 9.4 for gas phase groups.

  7. Analysis of reaction products formed in the gas phase reaction of E,E-2,4-hexadienal with atmospheric oxidants: Reaction mechanisms and atmospheric implications

    Science.gov (United States)

    Colmenar, I.; Martin, P.; Cabañas, B.; Salgado, S.; Martinez, E.

    2018-03-01

    An analysis of reaction products for the reaction of E,E-2,4-hexadienal with chlorine atoms (Cl) and OH and NO3 radicals has been carried out at the first time with the aim of obtaining a better understanding of the tropospheric reactivity of α,β-unsaturated carbonyl compounds. Fourier Transform Infrared (FTIR) spectroscopy and Gas Chromatography-Mass Spectrometry with a Time of Flight detector (GC-TOFMS) were used to carry out the qualitative and/or quantitative analyses. Reaction products in gas and particulate phase were observed from the reactions of E,E-2,4- hexadienal with all oxidants. E/Z-Butenedial and maleic anhydride were the main products identified in gas phase. E-butenedial calculated molar yield ranging from 4 to 10%. A significant amount of multifunctional compounds (chloro and hydroxy carbonyls) was identified. These compounds could be formed in particulate phase explaining the ∼90% of unaccounted carbon in gas phase. The reaction with Cl atoms in the presence of NOx with a long reaction time gave Peroxy Acetyl Nitrate (PAN) as an additional product, which is known for being an important specie in the generation of the photochemical smog. Nitrated compounds were the major organic products from the reaction with the NO3 radical. Based on the identified products, the reaction mechanisms have been proposed. In these mechanisms a double bond addition of the atmospheric oxidant at C4/C5 of E,E-2,4-hexadienal is the first step for tropospheric degradation.

  8. Synthesis of refractory organic matter in the ionized gas phase of the solar nebula.

    Science.gov (United States)

    Kuga, Maïa; Marty, Bernard; Marrocchi, Yves; Tissandier, Laurent

    2015-06-09

    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.

  9. Gas-phase spectroscopic studies of heavy elements compounds (group V) using FTIR technique

    International Nuclear Information System (INIS)

    Allaf, A. W.; Ajji, Z.

    1998-12-01

    Antimony oxide trihalide, OSbX3 where X=F, CI and Br, and antimony (III) oxychloride, OSbC1 molecules were produced by an on-line process for the first time using antimony chloride SbC13 passed over heated silver oxide then followed by passing the obtained products over heated NaF and heated KBr for SbOF3 and OSbBr3, respectively. The obtained OSbC13 reacts with heated silver to produce OSbC1. The products have been characterized by the infrared spectra of their vapors. The low resolution gas-phase Fourier transform infrared spectrum, reported for the first time, shows the most characteristic band of OSbX3 at 1272, 1217 and 1200 cm -1 and the bands are assigned to the O=Sb stretching fundamental of OSbX3 were X=F, Cl and Br, respectively. The band at 1200 cm -1 needs more experimental investigation. The band at 924 cm -1 is assigned to the O=Sb stretching fundamental of OSbCl molecule. This result is in consistent with expectation and shifted to lower frequency in comparison with arsenic analogous molecule which is investigated by matrix-isolation technique. The work will be continued in order to cover the bismuth and arsenic compounds of similar structures. (author)

  10. Characterization of condensed phase nitric acid particles formed in the gas phase

    Institute of Scientific and Technical Information of China (English)

    Long Jia; Yongfu Xu

    2011-01-01

    The formation of nitric acid hydrates has been observed in a chamber during the dark reaction of NO2 with O3 in the presence of air.The size of condensed phase nitric acid was measured to be 40-100 nm and 20-65 nm at relative humidity (RH) ≤ 5% and RH = 67% under our experimental conditions, respectively.The nitric acid particles were collected on the glass fiber membrane and their chemical compositions were analyzed by infrared spectrum.The main components of nitric acid hydrates in particles are HNO3·3H2O and NO3-·xH2O (x≥ 4) at low RH, whereas at high RH HNO3·H2O, HNO3·2H2O, HNO3·3H2O and NO3-·xH2O (x≥ 4) all exist in the condensed phase.At high RH HNO3·xH2O (x ≤ 3) collected on the glass fiber membrane is greatly increased, while NO3-·xH2O (x ≥4) decreased, compared with low RH.To the best of our knowledge, this is the first time to report that condensed phase nitric acid can be generated in the gas phase at room temperature.

  11. Isomers and conformational barriers of gas phase nicotine, nornicotine and their protonated forms

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Tomoki; Farone, William A.; Xantheas, Sotiris S.

    2014-07-17

    We report extensive conformational searches of the neutral nicotine, nornicotine and their protonated analogs that are based on ab-initio second order Møller-Plesset perturbation (MP2) electronic structure calculations. Initial searches were performed with the 6-31G(d,p) and the energetics of the most important structures were further refined from geometry optimizations with the aug-cc-pVTZ basis set. Based on the calculated free energies at T=298 K for the gas phase molecules, neutral nicotine has two dominant trans conformers, whereas neutral nornicotine is a mixture of several conformers. For nicotine, the protonation on both the pyridine and the pyrrolidine sites is energetically competitive, whereas nornicotine prefers protonation on the pyridine nitrogen. The protonated form of nicotine is mainly a mixture of two pyridine-protonated trans conformers and two pyrrolidine-protonated trans conformers, whereas the protonated form of nornicotine is a mixture of four pyridine-protonated trans conformers. Nornicotine is conformationally more flexible than nicotine, however it is less protonated at the biologically important pyrrolidine nitrogen site. The lowest energy isomers for each case were found to interconvert via low (< 6 kcal/mol) rotational barriers around the pyridine-pyrrolidine bond.

  12. Nanoparticles from the Gas Phase as Building Blocks for Electrical Devices

    International Nuclear Information System (INIS)

    Fissan, H.; Kennedy, M.K.; Krinke, T.J.; Kruis, F.E.

    2003-01-01

    Electrical device development is driven by miniaturization and possibilities to use new chemical and physical effects. Nanotechnology offers both aspects. The structural dimensions of materials and devices are small and because of that large exchange surfaces are provided but also effects like quantum effects may occur and be used to get new or at least improved properties of nanostructured materials and devices.Nanoparticles are of special interest because of their nanodimensions in all three directions, so that nanoeffects become most prominent. They can be synthesized in solid materials, in liquids and in gases. Gas synthesis has several advantages compared to the other phases, especially the high cleanliness which can be achieved. In case of electrical devices the particles have to be deposited onto substrates in a structured way.The substrate may consist out of microelectronic devices in which the deposited nanoparticles are introduced for the basic function. In case of a transistor this would be the gate function, in case of a sensor this would be the sensing layer, where the contact with the measurement object takes place. For two kinds of particles SnO 2 and PbS, synthesized in the gas phase, we demonstrate the way how to create devices with improved sensor properties

  13. A Kinetic Study of the Gas-Phase Reaction of OH with Br2

    Science.gov (United States)

    Bryukov, Mikhail G.; Dellinger, Barry; Knyazev, Vadim D.

    2011-01-01

    An experimental, temperature-dependent kinetic study of the gas-phase reaction of the hydroxyl radical with molecular bromine (reaction 1) has been performed using a pulsed laser photolysis/pulsed-laser-induced fluorescence technique over a wide temperature range of 297 – 766 K, and at pressures between 6.68 and 40.29 kPa of helium. The experimental rate coefficients for reaction 1 demonstrate no correlation with pressure and exhibit a negative temperature dependence with a slight negative curvature in the Arrhenius plot. A non-linear least-squares fit with two floating parameters of the temperature dependent k1(T) data set using an equation of the form k1(T) = ATn yields the recommended expression k1(T) = 1.85×10−9T − 0.66 cm3 molecule−1 s−1 for the temperature dependence of the reaction 1 rate coefficient. The potential energy surface (PES) of reaction 1 was investigated using quantum chemistry methods. The reaction proceeds through formation of a weakly bound OH···Br2 complex and a PES saddle point with an energy below that of the reactants. Temperature dependence of the reaction rate coefficient was modeled using the RRKM method on the basis of the calculated PES. PMID:16854030

  14. Some insights into formamide formation through gas-phase reactions in the interstellar medium

    Energy Technology Data Exchange (ETDEWEB)

    Redondo, Pilar; Barrientos, Carmen; Largo, Antonio, E-mail: predondo@qf.uva.es [Computational Chemistry Group, Departamento de Química Física, Facultad de Ciencias, Universidad de Valladolid, E-47011 Valladolid (Spain)

    2014-01-10

    We study the viability of different gas-phase ion-molecule reactions that could produce precursors of formamide in the interstellar medium. We analyze different reactions between cations containing a nitrogen atom (NH{sub 3}{sup +}, NH{sub 4}{sup +}, NH{sub 3}OH{sup +}, and NH{sub 2}OH{sup +}) and neutral molecules having one carbonyl group (H{sub 2}CO and HCOOH). First, we report a theoretical estimation of the reaction enthalpies for the proposed processes. Second, for more favorable reactions, from a thermodynamic point of view, we perform a theoretical study of the potential energy surface. In particular, the more exothermic processes correspond to the reactions of ionized and protonated hydroxylamine with formaldehyde. In addition, a neutral-neutral reaction has also been considered. The analysis of the potential energy surfaces corresponding to these reactions shows that these processes present a net activation barrier and that they cannot be considered as a source of formamide in space.

  15. Role of isospin in nuclear-matter liquid-gas phase transition

    International Nuclear Information System (INIS)

    Ducoin, C.

    2006-10-01

    Nuclear matter presents a phase transition of the liquid-gas type. This well-known feature is due to the nuclear interaction profile (mean-range attractive, short-range repulsive). Symmetric-nuclear-matter thermodynamics is thus analogous to that of a Van der Waals fluid. The study shows up to be more complex in the case of asymmetric matter, composed of neutrons and protons in an arbitrary proportion. Isospin, which distinguishes both constituents, gives a measure of this proportion. Studying asymmetric matter, isospin is an additional degree of freedom, which means one more dimension to consider in the space of observables. The nuclear liquid-gas transition is associated with the multi-fragmentation phenomenon observed in heavy-ion collisions, and to compact-star physics: the involved systems are neutron rich, so they are affected by the isospin degree of freedom. The present work is a theoretical study of isospin effects which appear in the asymmetric nuclear matter liquid-gas phase transition. A mean-field approach is used, with a Skyrme nuclear effective interaction. We demonstrate the presence of a first-order phase transition for asymmetric matter, and study the isospin distillation phenomenon associated with this transition. The case of phase separation at thermodynamic equilibrium is compared to spinodal decomposition. Finite size effects are addressed, as well as the influence of the electron gas which is present in the astrophysical context. (author)

  16. Methods, fluxes and sources of gas phase alkyl nitrates in the coastal air.

    Science.gov (United States)

    Dirtu, Alin C; Buczyńska, Anna J; Godoi, Ana F L; Favoreto, Rodrigo; Bencs, László; Potgieter-Vermaak, Sanja S; Godoi, Ricardo H M; Van Grieken, René; Van Vaeck, Luc

    2014-10-01

    The daily and seasonal atmospheric concentrations, deposition fluxes and emission sources of a few C3-C9 gaseous alkyl nitrates (ANs) at the Belgian coast (De Haan) on the Southern North Sea were determined. An adapted sampler design for low- and high-volume air-sampling, optimized sample extraction and clean-up, as well as identification and quantification of ANs in air samples by means of gas chromatography mass spectrometry, are reported. The total concentrations of ANs ranged from 0.03 to 85 pptv and consisted primarily of the nitro-butane and nitro-pentane isomers. Air mass backward trajectories were calculated by the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to determine the influence of main air masses on AN levels in the air. The shorter chain ANs have been the most abundant in the Atlantic/Channel/UK air masses, while longer chain ANs prevailed in continental air. The overall mean N fluxes of the ANs were slightly higher for summer than those for winter-spring, although their contributions to the total nitrogen flux were low. High correlations between AN and HNO₂ levels were observed during winter/spring. During summer, the shorter chain ANs correlated well with precipitation. Source apportionment by means of principal component analysis indicated that most of the gas phase ANs could be attributed to traffic/combustion, secondary photochemical formation and biomass burning, although marine sources may also have been present and a contributing factor.

  17. Removal of pyridine from liquid and gas phase by copper forms of natural and synthetic zeolites

    International Nuclear Information System (INIS)

    Rehakova, Maria; Fortunova, Lubica; Bastl, Zdenek; Nagyova, Stanislava; Dolinska, Silvia; Jorik, Vladimir; Jona, Eugen

    2011-01-01

    Zeoadsorbents on the basis of copper forms of synthetic zeolite ZSM5 and natural zeolite of the clinoptilolite type (CT) have been studied taking into account their environmental application in removing harmful pyridine (py) from liquid and gas phase. Sorption of pyridine by copper forms of zeolites (Cu-ZSM5 and Cu-CT) has been studied by CHN, X-ray photoelectron spectroscopy, X-ray powder diffractometry, FTIR spectroscopy, thermal analysis (TG, DTA and DTG) and analysis of the surface areas and the pore volumes by low-temperature adsorption of nitrogen. The results of thermal analyses of Cu-ZSM5, Cu-(py) x ZSM5, Cu-CT and Cu-(py) x CT zeolitic products with different composition (x depends on the experimental conditions of sorption of pyridine) clearly confirmed their different thermal properties as well as the sorption of pyridine. In the zeolitic pyridine containing samples the main part of the pyridine release process occurs at considerably higher temperatures than is the boiling point of pyridine, which proves strong bond and irreversibility of py-zeolite interaction. FTIR spectra of Cu-(py) x zeolite samples showed well resolved bands of pyridine. The results of thermal analysis and FTIR spectroscopy are in a good agreement with the results of other used methods.

  18. Non-stationary filtration mode during chemical reactions with the gas phase

    Science.gov (United States)

    Zavialov, Ivan; Konyukhov, Andrey; Negodyaev, Sergey

    2015-04-01

    An experimental and numerical study of filtration accompanied by chemical reactions between displacing fluid and solid skeleton is considered. Glass balls (400-500 μm in diameter) were placed in 1 cm gap between two glass sheets and were used as model porous medium. The baking soda was added to the glass balls. The 70% solution of acetic acid was used as the displacer. The modeling porous medium was saturated with a mineral oil, and then 70% solution of colored acetic acid was pumped through the medium. The glass balls and a mineral oil have a similar refractive index, so the model porous medium was optically transparent. During the filtration, the gas phase was generated by the chemical reactions between the baking soda and acetic acid, and time-dependent displacement of the chemical reaction front was observed. The front of the chemical reaction was associated with the most intensive gas separation. The front moved, stopped, and then moved again to the area where it had been already. We called this process a secondary oxidation wave. To describe this effect, we added to the balance equations a term associated with the formation and disappearance of phases due to chemical reactions. The equations were supplemented by Darcy's law for multiphase filtration. Nonstationarity front propagation of the chemical reaction in the numerical experiment was observed at Damköhler numbers greater than 100. The mathematical modelling was agreed well with the experimental results.

  19. Local anticorrelation between star formation rate and gas-phase metallicity in disc galaxies

    Science.gov (United States)

    Sánchez Almeida, J.; Caon, N.; Muñoz-Tuñón, C.; Filho, M.; Cerviño, M.

    2018-06-01

    Using a representative sample of 14 star-forming dwarf galaxies in the local Universe, we show the existence of a spaxel-to-spaxel anticorrelation between the index N2 ≡ log ([N II]λ 6583/H α ) and the H α flux. These two quantities are commonly employed as proxies for gas-phase metallicity and star formation rate (SFR), respectively. Thus, the observed N2 to H α relation may reflect the existence of an anticorrelation between the metallicity of the gas forming stars and the SFR it induces. Such an anticorrelation is to be expected if variable external metal-poor gas fuels the star-formation process. Alternatively, it can result from the contamination of the star-forming gas by stellar winds and SNe, provided that intense outflows drive most of the metals out of the star-forming regions. We also explore the possibility that the observed anticorrelation is due to variations in the physical conditions of the emitting gas, other than metallicity. Using alternative methods to compute metallicity, as well as previous observations of H II regions and photoionization models, we conclude that this possibility is unlikely. The radial gradient of metallicity characterizing disc galaxies does not produce the correlation either.

  20. Resonant x-ray emission from gas-phase TiCl{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Hague, C.F.; Tronc, M. [Universite Pierre et Marie Curie, Paris (France); De Groot, F. [Univ. of Groningen (Netherlands)] [and others

    1997-04-01

    Resonant x-ray emission spectroscopy (RXES) has proved to be a powerful tool for studying the electronic structure of condensed matter. Over the past few years it has been used mainly for studying the valence bands of solids and condensed molecules. Very recently the advent of high brightness photon beams provided by third generation synchrotron radiation source undulators, associated with efficient x-ray emission spectrometers has made it possible to perform experiments on free diatomic molecular systems. RXE spectra of free molecules are of prime importance to gain insight into their electronic structure and bonding as they reflect the symmetry of orbitals engaged in the two-electron, two-step process with the l = 0, {+-}2 parity-conserving selection rule, and are free from solid state effects which can introduce difficulties in the interpretation. They provide information (more so than XAS) on the core excited states, and, when performed at fixed incident photon energy as a function of the emitted photon energy, on the electronic excitation (charge transfer, multiplet states). Moreover the anisotropy of the angular distribution of resonant x-ray emission affects the relative intensity of the emission peaks and provides information concerning the symmetries of final states. This is a preliminary report on what are the first RXE spectra of a 3d transition metal complex in the gas phase. The experiment concerns the Ti 3d {yields}2p emission spectrum of TiCl{sub 4} over the 450 to 470 eV region.

  1. Resonant x-ray emission from gas-phase TiCl4

    International Nuclear Information System (INIS)

    Hague, C.F.; Tronc, M.; De Groot, F.

    1997-01-01

    Resonant x-ray emission spectroscopy (RXES) has proved to be a powerful tool for studying the electronic structure of condensed matter. Over the past few years it has been used mainly for studying the valence bands of solids and condensed molecules. Very recently the advent of high brightness photon beams provided by third generation synchrotron radiation source undulators, associated with efficient x-ray emission spectrometers has made it possible to perform experiments on free diatomic molecular systems. RXE spectra of free molecules are of prime importance to gain insight into their electronic structure and bonding as they reflect the symmetry of orbitals engaged in the two-electron, two-step process with the l = 0, ±2 parity-conserving selection rule, and are free from solid state effects which can introduce difficulties in the interpretation. They provide information (more so than XAS) on the core excited states, and, when performed at fixed incident photon energy as a function of the emitted photon energy, on the electronic excitation (charge transfer, multiplet states). Moreover the anisotropy of the angular distribution of resonant x-ray emission affects the relative intensity of the emission peaks and provides information concerning the symmetries of final states. This is a preliminary report on what are the first RXE spectra of a 3d transition metal complex in the gas phase. The experiment concerns the Ti 3d →2p emission spectrum of TiCl 4 over the 450 to 470 eV region

  2. Soft X-ray photoemission spectroscopy of selected neurotransmitters in the gas phase

    Energy Technology Data Exchange (ETDEWEB)

    Maris, Assimo; Melandri, Sonia; Evangelisti, Luca; Caminati, Walther [Dipartimento di Chimica ' G. Ciamician' dell' Universita, Via Selmi 2, I-40126 Bologna (Italy); Giuliano, Barbara M. [Departamento de Quimica da Universidade de Coimbra, 3004-535 Coimbra (Portugal); Plekan, Oksana [Sincrotrone Trieste, in Area Science Park, I-34149 Basovizza, Trieste (Italy); Feyer, Vitaliy [Sincrotrone Trieste, in Area Science Park, I-34149 Basovizza, Trieste (Italy); Electronic Properties (PGI-6), Peter Gruenberg Institute, Forschungszentrum Juelich GmbH, Leo-Brandt-Strasse, 52428 Juelich (Germany); Richter, Robert [Sincrotrone Trieste, in Area Science Park, I-34149 Basovizza, Trieste (Italy); Coreno, Marcello [CNR-IMIP, Montelibretti, I-00016 Rome (Italy); Prince, Kevin C., E-mail: kevin.prince@elettra.trieste.it [Sincrotrone Trieste, in Area Science Park, I-34149 Basovizza, Trieste (Italy); CNR-IOM, Laboratorio TASC, I-34149 Basovizza, Trieste (Italy)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Neurotransmitter molecules. Black-Right-Pointing-Pointer Photoelectron spectroscopy. Black-Right-Pointing-Pointer Electronic structure. Black-Right-Pointing-Pointer Weak hydrogen bonding. -- Abstract: The valence molecular orbitals and core levels of tyramine, tryptamine and tryptophol in the gas phase have been studied using X-ray photoelectron spectroscopy (XPS) and theoretical methods. The energies of the outer valence region spectrum are found to be in agreement with previously reported He I spectra, while new data on the inner valence molecular orbitals are reported. The structures in the carbon, nitrogen and oxygen core level spectra of these molecules have been identified and assigned. These compounds are characterised by conformers with hydrogen bonding in which the {pi} systems of the phenol and indole groups act as hydrogen acceptors, but a spectroscopic signature of this hydrogen bond was not observed. This is in contrast with our previous spectra of amino acids, where conformers with specific hydrogen bonding showed strong effects in core level spectra. We attribute the difference to the weaker strength of the {pi}-hydrogen bonding.

  3. Gas-phase spectroscopy of synephrine by laser desorption supersonic jet technique.

    Science.gov (United States)

    Ishiuchi, Shun-ichi; Asakawa, Toshiro; Mitsuda, Haruhiko; Miyazaki, Mitsuhiko; Chakraborty, Shamik; Fujii, Masaaki

    2011-09-22

    In our previous work, we found that synephrine has six conformers in the gas phase, while adrenaline, which is a catecholamine and has the same side chain as synephrine, has been reported to have only two conformers. To determine the conformational geometries of synephrine, we measured resonance enhanced multiphoton ionization, ultraviolet-ultraviolet hole burning, and infrared dip spectra by utilizing the laser desorption supersonic jet technique. By comparing the observed infrared spectra with theoretical ones, we assigned geometries except for the orientations of the phenolic OH group. Comparison between the determined structures of synephrine and those of 2-methylaminno-1-phenylethanol, which has the same side chain as synephrine but no phenol OH group, leads to the conclusion that the phenolic OH group in synephrine does not affect the conformational flexibility of the side chain. In the case of adrenaline, which is expected to have 12 conformers if there are no interactions between the catecholic OH groups and the side chain, some interactions possibly exist between them because only two conformations are observed. By estimation of the dipole-dipole interaction energy between partial dipole moments of the catecholic OH groups and the side chain, it was concluded that the dipole-dipole interaction stabilizes specific conformers which are actually observed. © 2011 American Chemical Society

  4. Conformal and highly luminescent monolayers of Alq3 prepared by gas-phase molecular layer deposition.

    Science.gov (United States)

    Räupke, André; Albrecht, Fabian; Maibach, Julia; Behrendt, Andreas; Polywka, Andreas; Heiderhoff, Ralf; Helzel, Jonatan; Rabe, Torsten; Johannes, Hans-Hermann; Kowalsky, Wolfgang; Mankel, Eric; Mayer, Thomas; Görrn, Patrick; Riedl, Thomas

    2014-01-22

    The gas-phase molecular layer deposition (MLD) of conformal and highly luminescent monolayers of tris(8-hydroxyquinolinato)aluminum (Alq3) is reported. The controlled formation of Alq3 monolayers is achieved for the first time by functionalization of the substrate with amino groups, which serve as initial docking sites for trimethyl aluminum (TMA) molecules binding datively to the amine. Thereby, upon exposure to 8-hydroxyquinoline (8-HQ), the self-limiting formation of highly luminescent Alq3 monolayers is afforded. The growth process and monolayer formation were studied and verified by in situ quartz crystal monitoring, optical emission and absorption spectroscopy, and X-ray photoelectron spectroscopy. The nature of the MLD process provides an avenue to coat arbitrarily shaped 3D surfaces and porous structures with high surface areas, as demonstrated in this work for silica aerogels. The concept presented here paves the way to highly sensitive luminescent sensors and dye-sensitized metal oxides for future applications (e.g., in photocatalysis and solar cells).

  5. Gas Phase Rovibrational Spectroscopy of Dmso, Part II: Towards the Terahertz Observation of 4-FOLD Clusters

    Science.gov (United States)

    Cuisset, Arnaud; Martin-Drumel, Marie-Aline; Hindle, Francis; Mouret, Gael; Sadovskii, Dmitrii A.

    2013-06-01

    Benefiting of the exceptional properties of the AILES synchrotron beamline, the gas phase Far-IR spectrum of DMSO has been recorded and resolved. The rovibrational analysis allowed to discover a new rotational behaviour for a polyatomic molecule: the gyroscopic destabilization. In order to explain this phenomenon, we looked for four-fold energy clusters in the high resolution ground state THz spectrum of DMSO recorded with a sub-THz spectrometer based on a frequency multiplication chain. Pure rotational lines in the 5 lowest vibrationnally excited levels have been recorded below 700 GHz. With near 1000 rotational transitions assigned, high quantum numbers have been reached allowing to discover sequence of four-fold clusters in the out of plane bending mode of DMSO and to study the vibrational dependence of an unusual rotational dynamics. J. B. Brubach et al., AIP Conf. Proc., 1214, (81), 2010. A. Cuisset, L. Nanobashvili, I. Smirnova, R. Bocquet, F. Hindle, G. Mouret, O. Pirali, P. Roy, D. Sadovskii,Chem. Phys. Lett., 492,(30),2010 A. Cuisset, O. Pirali, D. Sadovskii,Phys. Rev. Lett., 109,(094101), 2012. G. Mouret, M. Guinet, A. Cuisset, L. Croizet, S. Eliet, R. Bocquet, F. Hindle, IEEE Sensors Journal, 13, 1, 2013.

  6. Gas-phase laser synthesis of aggregation-free, size-controlled hydroxyapatite nanoparticles

    International Nuclear Information System (INIS)

    Bapat, Parimal V.; Kraft, Rebecca; Camata, Renato P.

    2012-01-01

    Nanophase hydroxyapatite (HA) is finding applications in many areas of biomedical research, including bone tissue engineering, drug delivery, and intracellular imaging. Details in chemical composition, crystal phase makeup, size, and shape of HA nanoparticles play important roles in achieving the favorable biological responses required in these applications. Most of the nanophase HA synthesis techniques involve solution-based methods that exhibit substantial aggregation of particles upon precipitation. Typically these methods also have limited control over the particle size and crystal phase composition. In this study, we describe the gas-phase synthesis of aggregation-free, size-controlled HA nanoparticles with mean size in the 20–70 nm range using laser ablation followed by aerosol electrical mobility classification. Nanoparticle deposits with adjustable number concentration were obtained on solid substrates. Particles were characterized by transmission electron microscopy, atomic force microscopy, and X-ray diffraction. Samples are well represented by log-normal size distributions with geometric standard deviation σ g ≈ 1.2. The most suitable conditions for HA nanoparticle formation at a laser fluence of 5 J/cm 2 were found to be a temperature of 800 °C and a partial pressure of water of 160 mbar.

  7. Gas phase hydrolysis of formaldehyde to form methanediol: impact of formic acid catalysis.

    Science.gov (United States)

    Hazra, Montu K; Francisco, Joseph S; Sinha, Amitabha

    2013-11-21

    We find that formic acid (FA) is very effective at facilitating diol formation through its ability to reduce the barrier for the formaldehyde (HCHO) hydrolysis reaction. The rate limiting step in the mechanism involves the isomerization of a prereactive collision complex formed through either the HCHO···H2O + FA and/or HCHO + FA···H2O pathways. The present study finds that the effective barrier height, defined as the difference between the zero-point vibrational energy (ZPE) corrected energy of the transition state (TS) and the HCHO···H2O + FA and HCHO + FA···H2O starting reagents, are respectively only ∼1 and ∼4 kcal/mol. These barriers are substantially lower than the ∼17 kcal/mol barrier associated with the corresponding step in the hydrolysis of HCHO catalyzed by a single water molecule (HCHO + H2O + H2O). The significantly lower barrier heights for the formic acid catalyzed pathway reveal a new important role that organic acids play in the gas phase hydrolysis of atmospheric carbonyl compounds.

  8. Tailoring gas-phase CO2 electroreduction selectivity to hydrocarbons at Cu nanoparticles

    Science.gov (United States)

    Merino-Garcia, I.; Albo, J.; Irabien, A.

    2018-01-01

    Copper-based surfaces appear as the most active catalysts for CO2 electroreduction to hydrocarbons, even though formation rates and efficiencies still need to be improved. The aim of the present work is to evaluate the continuous gas-phase CO2 electroreduction to hydrocarbons (i.e. ethylene and methane) at copper nanoparticulated-based surfaces, paying attention to particle size influence (ranging from 25-80 nm) on reaction productivity, selectivity, and Faraday efficiency (FE) for CO2 conversion. The effect of the current density and the presence of a microporous layer within the working electrode are then evaluated. Copper-based gas diffusion electrodes are prepared by airbrushing the catalytic ink onto carbon supports, which are then coupled to a cation exchange membrane (Nafion) in a membrane electrode assembly. The results show that the use of smaller copper nanoparticles (25 nm) leads to a higher ethylene production (1148 μmol m-2 s-1) with a remarkable high FE (92.8%), at the same time, diminishing the competitive hydrogen evolution reaction in terms of FE. This work demonstrates the importance of nanoparticle size on reaction selectivity, which may be of help to design enhanced electrocatalytic materials for CO2 valorization to hydrocarbons.

  9. Release to the gas phase of metals, S and Cl during combustion of dedicated waste fractions

    DEFF Research Database (Denmark)

    Pedersen, Anne Juul; van Lith, Simone Cornelia; Frandsen, Flemming

    2010-01-01

    The release to the gas phase of inorganic elements such as alkali metals. Cl, S, and heavy metals in Waste-to-Energy (WtE) boilers is a challenge. Besides the risk of harmful emissions to the environment, inorganic elements released from the grate may cause severe ash deposition and corrosion...... and the link to the formation of fly ash and aerosols in full-scale waste incinerators. The release of metals, S and Cl from four dedicated waste fractions was quantified as a function of temperature in a lab-scale fixed-bed reactor. The waste fractions comprised chromated copper arsenate (CCA) impregnated....... The lab-scale release results were then compared with results from a related, full-scale partitioning study, in which test runs with the addition of similar, dedicated waste fractions to a base-load waste had been performed in a grate-fired WtE boiler. In general, the elements Al, Ca, Cr, Cu, Fe, Mg, Si...

  10. CdSe Nanoparticles with Clean Surfaces: Gas Phase Synthesis and Optical Properties

    Directory of Open Access Journals (Sweden)

    Zhang Hongwei

    2015-01-01

    Full Text Available CdSe nanoparticles (NPs were generated in gas phase with a magnetron plasma gas aggregation cluster beam source. Coagulation-free CdSe nanocrystals with very clean particle surface and interface, as well as a fairly uniform spatial distribution were obtained. The deposited NPs have a good dispersity with a mean diameter of about 4.8nm. A strong photoluminescence band corresponding to the near- band-edge transition of the CdSe NPs was observed. The CdSe NP films show a significant photoconductance induced by laser irradiation. With an applied bias voltage of 10V, the photo- induced current can be as high as 0.4mA under 0.01mW/mm2 405nm laser illumination. Our approach offers an alternative method for CdSe NP synthesis, which has the advantages such as high purity, good process and product control, as well as mass production, as compared to the existing methods.

  11. Using Gas Phase Reactions of Hexamethylene Triperoxide Diamine (HMTD) to Improve Detection in Mass Spectrometry

    Science.gov (United States)

    Colizza, Kevin; Yevdokimov, Alexander; McLennan, Lindsay; Smith, James L.; Oxley, Jimmie C.

    2018-01-01

    Our efforts to lower the detection limits of hexamethylene triperoxide diamine (HMTD) have uncovered previously unreported gas-phase reactions of primary and secondary amines with one of the six methylene carbons. The reaction occurs primarily in the atmospheric pressure chemical ionization (APCI) source and is similar to the behavior of alcohols with HMTD [1]. However, unlike alcohols, the amine reaction conserves the hydrogen peroxide on the intact product. Furthermore, with or without amines, HMTD is oxidized to tetramethylene diperoxide diamine dialdehyde (TMDDD) in a temperature-dependent fashion in the APCI source. Synthesized TMDDD forms very strong adducts (not products) to ammonium and amine ions in the electrospray ionization (ESI) source. Attempts to improve HMTD detection by generating TMDDD in the APCI source with post-column addition of amines were not successful. Signal intensity of the solvent related HMTD product in methanol, [HMTD+MeOH2-H2O2]+ (m/z 207.0975), was understandably related to the amount of methanol in the HMTD environment as it elutes into the source. With conditions optimized for this product, the detection of 100 pg on column was accomplished with a robust analysis of 300 pg (1.44 pmol) routinely performed on the Orbitrap mass spectrometers. [Figure not available: see fulltext.

  12. Combined synthesis and in situ coating of nanoparticles in the gas phase

    International Nuclear Information System (INIS)

    Laehde, Anna; Raula, Janne; Kauppinen, Esko I.

    2008-01-01

    Combined gas phase synthesis and coating of sodium chloride (NaCl) and lactose nanoparticles has been developed using an aerosol flow reactor. Nano-sized core particles were produced by the droplet-to-particle method and coated in situ by the physical vapour deposition of L-leucine vapour. The saturation of L-leucine in the reactor determined the resulting particle size and size distribution. In general, particle size increased with the addition of L-leucine and notable narrowing of the core particle size distribution was observed. In addition, homogeneous nucleation of the vapour, i.e. formation of pure L-leucine particles, was observed depending on the saturation conditions of L-leucine as well as the core particle characteristics. The effects of core particle properties, i.e. size and solid-state characteristics, on the coating process were studied by comparing the results for coated NaCl and lactose particles. During deposition, L-leucine formed a uniform coating on the surface of the core particles. The coating stabilised the nanoparticles and prevented the sintering of particles during storage.

  13. Metal-Organic Frameworks for Sensing Applications in the Gas Phase

    Directory of Open Access Journals (Sweden)

    Sabine Achmann

    2009-03-01

    Full Text Available Several metal-organic framework (MOF materials were under investigated to test their applicability as sensor materials for impedimetric gas sensors. The materials were tested in a temperature range of 120 °C - 240 °C with varying concentrations of O2, CO2, C3H8, NO, H2, ethanol and methanol in the gas atmosphere and under different test gas humidity conditions. Different sensor configurations were studied in a frequency range of 1 Hz -1 MHz and time-continuous measurements were performed at 1 Hz. The materials did not show any impedance response to O2, CO2, C3H8, NO, or H2 in the gas atmospheres, although for some materials a significant impedance decrease was induced by a change of the ethanol or methanol concentration in the gas phase. Moreover, pronounced promising and reversible changes in the electric properties of a special MOF material were monitored under varying humidity, with a linear response curve at 120 °C. Further investigations were carried out with differently doped MOF materials of this class, to evaluate the influence of special dopants on the sensor effect.

  14. The structure optimization of gas-phase surface discharge and its application for dye degradation

    Science.gov (United States)

    Ying, CAO; Jie, LI; Nan, JIANG; Yan, WU; Kefeng, SHANG; Na, LU

    2018-05-01

    A gas-phase surface discharge (GSD) was employed to optimize the discharge reactor structure and investigate the dye degradation. A dye mixture of methylene blue, acid orange and methyl orange was used as a model pollutant. The results indicated that the reactor structure of the GSD system with the ratio of tube inner surface area and volume of 2.48, screw pitch between a high-voltage electrode of 9.7 mm, high-voltage electrode wire diameter of 0.8 mm, dielectric tube thickness of 2.0 mm and tube inner diameter of 16.13 mm presented a better ozone (O3) generation efficiency. Furthermore, a larger screw pitch and smaller wire diameter enhanced the O3 generation. After the dye mixture degradation by the optimized GSD system, 73.21% and 50.74% of the chemical oxygen demand (COD) and total organic carbon removal rate were achieved within 20 min, respectively, and the biochemical oxygen demand (BOD) and biodegradability (BOD/COD) improved.

  15. Gas Phase Pressure Effects on the Apparent Thermal Conductivity of JSC-1A Lunar Regolith Simulant

    Science.gov (United States)

    Yuan, Zeng-Guang; Kleinhenz, Julie E.

    2011-01-01

    Gas phase pressure effects on the apparent thermal conductivity of a JSC-1A/air mixture have been experimentally investigated under steady state thermal conditions from 10 kPa to 100 kPa. The result showed that apparent thermal conductivity of the JSC-1A/air mixture decreased when pressure was lowered to 80 kPa. At 10 kPa, the conductivity decreased to 0.145 W/m/degree C, which is significantly lower than 0.196 W/m/degree C at 100 kPa. This finding is consistent with the results of previous researchers. The reduction of the apparent thermal conductivity at low pressures is ascribed to the Knudsen effect. Since the characteristic length of the void space in bulk JSC-1A varies over a wide range, both the Knudsen regime and continuum regime can coexist in the pore space. The volume ratio of the two regimes varies with pressure. Thus, as gas pressure decreases, the gas volume controlled by Knudsen regime increases. Under Knudsen regime the resistance to the heat flow is higher than that in the continuum regime, resulting in the observed pressure dependency of the apparent thermal conductivity.

  16. Decomposition of gas-phase diphenylether at 473 K by electron beam generated plasma

    CERN Document Server

    Kim, H H; Kojima, T

    2003-01-01

    Decomposition of gas-phase diphenylether (DPE) in the order of several parts per million by volume (ppmv) was studied as a model compound of dioxin using a flow-type electron-beam reactor at an elevated temperature of 473 K. The ground state oxygen ( sup 3 P) atoms played an important role in the decomposition of DPE resulting in the formation of 1,4-hydroquinone (HQ) as a major ring retaining product. The high yield of hydroquinone indicated that the breakage of ether bond (C-O) is important in the initial step of DPE decomposition. Ring cleavage products were CO and CO sub 2 , and NO sub 2 was also produced from background N sub 2 -O sub 2. The sum of the yields of HQ, CO sub 2 and CO accounts for over 90% of the removed DPE. Hydroxyl radicals (OH) were less important in the dilute DPE decomposition at a high water content, and were mostly consumed by recombination reactions to form hydrogen peroxide. The smaller the initial DPE concentrations, the higher the decomposition efficiency and the lower the yield...

  17. Gas-phase hydrolysis of triplet SO2: A possible direct route to atmospheric acid formation

    Science.gov (United States)

    Donaldson, D. James; Kroll, Jay A.; Vaida, Veronica

    2016-07-01

    Sulfur chemistry is of great interest to the atmospheric chemistry of several planets. In the presence of water, oxidized sulfur can lead to new particle formation, influencing climate in significant ways. Observations of sulfur compounds in planetary atmospheres when compared with model results suggest that there are missing chemical mechanisms. Here we propose a novel mechanism for the formation of sulfurous acid, which may act as a seed for new particle formation. In this proposed mechanism, the lowest triplet state of SO2 (3B1), which may be accessed by near-UV solar excitation of SO2 to its excited 1B1 state followed by rapid intersystem crossing, reacts directly with water to form H2SO3 in the gas phase. For ground state SO2, this reaction is endothermic and has a very high activation barrier; our quantum chemical calculations point to a facile reaction being possible in the triplet state of SO2. This hygroscopic H2SO3 molecule may act as a condensation nucleus for water, giving rise to facile new particle formation (NPF).

  18. Possibilities of gas-phase radio-chromatography application to permanent-gas analysis

    International Nuclear Information System (INIS)

    Dupuis, M.C.; Charrier, G.; Alba, C.; Massimino, D.

    1970-01-01

    The gas-phase radio-chromatography technique has been applied to the rapid analysis of permanent gases (H 2 , O 2 , N 2 , A, Kr, Xe, CO, CH 4 ) labelled with radioactive indicators ( 3 H, 37 A, 85 Kr, 133 Xe). After calibration, the components of such a mixture can be identified and their concentrations measured in less than two hours, using a sample volume of from 0.1 to 10 cm 3 . The minimum detectable activity is of the order of 10 -4 μC for each radioactive isotope. The measurements are reproducible to about 2 to 3 per cent. This work has been mainly concerned with the influence of parameters affecting the response of the radioactivity detector (ionization chamber or gas flow proportional counter). The method has very numerous applications both theoretically, for the study of chromatographic phenomena under ideal conditions (infinitesimal concentrations made possible by the use of radioactive tracers), and practically, for rapid and accurate radiochemical analysis of radioactive gas mixtures. (authors) [fr

  19. Modeled occupational exposures to gas-phase medical laser-generated air contaminants.

    Science.gov (United States)

    Lippert, Julia F; Lacey, Steven E; Jones, Rachael M

    2014-01-01

    Exposure monitoring data indicate the potential for substantive exposure to laser-generated air contaminants (LGAC); however the diversity of medical lasers and their applications limit generalization from direct workplace monitoring. Emission rates of seven previously reported gas-phase constituents of medical laser-generated air contaminants (LGAC) were determined experimentally and used in a semi-empirical two-zone model to estimate a range of plausible occupational exposures to health care staff. Single-source emission rates were generated in an emission chamber as a one-compartment mass balance model at steady-state. Clinical facility parameters such as room size and ventilation rate were based on standard ventilation and environmental conditions required for a laser surgical facility in compliance with regulatory agencies. All input variables in the model including point source emission rates were varied over an appropriate distribution in a Monte Carlo simulation to generate a range of time-weighted average (TWA) concentrations in the near and far field zones of the room in a conservative approach inclusive of all contributing factors to inform future predictive models. The concentrations were assessed for risk and the highest values were shown to be at least three orders of magnitude lower than the relevant occupational exposure limits (OELs). Estimated values do not appear to present a significant exposure hazard within the conditions of our emission rate estimates.

  20. Evaluation of Gas Phase Dispersion in Flotation under Predetermined Hydrodynamic Conditions

    Science.gov (United States)

    Młynarczykowska, Anna; Oleksik, Konrad; Tupek-Murowany, Klaudia

    2018-03-01

    Results of various investigations shows the relationship between the flotation parameters and gas distribution in a flotation cell. The size of gas bubbles is a random variable with a specific distribution. The analysis of this distribution is useful to make mathematical description of the flotation process. The flotation process depends on many variable factors. These are mainly occurrences like collision of single particle with gas bubble, adhesion of particle to the surface of bubble and detachment process. These factors are characterized by randomness. Because of that it is only possible to talk about the probability of occurence of one of these events which directly affects the speed of the process, thus a constant speed of flotation process. Probability of the bubble-particle collision in the flotation chamber with mechanical pulp agitation depends on the surface tension of the solution, air consumption, degree of pul aeration, energy dissipation and average feed particle size. Appropriate identification and description of the parameters of the dispersion of gas bubbles helps to complete the analysis of the flotation process in a specific physicochemical conditions and hydrodynamic for any raw material. The article presents the results of measurements and analysis of the gas phase dispersion by the size distribution of air bubbles in a flotation chamber under fixed hydrodynamic conditions. The tests were carried out in the Laboratory of Instrumental Methods in Department of Environmental Engineering and Mineral Processing, Faculty of Mining and Geoengineerin, AGH Univeristy of Science and Technology in Krakow.

  1. Laboratory investigations of the alpha-pinene/ozone gas-phase reaction

    International Nuclear Information System (INIS)

    Benner, C.L.

    1985-01-01

    In order to provide more insight into terpene photooxidation or ozonolysis reaction mechanisms, a radiotracer technique was developed. This technique was applied to an investigation of the 14 C-alpha-pinene/ozone reaction. In the first phase of the research, the carbon distribution at the conclusion of the ozonolysis reaction was determined by separating carbon-14-labelled gaseous products from labelled aerosols, and counting each phase by liquid scintillation methods. The resulting carbon balance was 38% to 60% filtered aerosols, 6% to 20% gas phase compounds, and 11% to 29% products absorbed on the reaction chamber walls. Recoveries of the alpha-pinene carbon-14 ranging from 79% to 97% were achieved using this method. The alpha-pinene concentrations in these experiments were close to ambient (1 part per billion), yet the carbon balance was similar to that observed at much higher concentrations (>1 part per million). In the second phase of the alpha-pinene study, both gas and aerosol products of the ozonolysis reaction were collected on cartridges impregnated with 2,4-dinitrophenylhydrazine, then analyzed by HPLC. In the final experiments, alpha-pinene aerosol was reacted with a silylating agent to improve the detection of organic acids and alcohols. The gas chromatographic/mass spectrometric analysis of the silylated aerosol products showed evidence of dimer/polymer formation occurring in the ozonolysis reaction

  2. A computational and spectroscopic study of the gas-phase conformers of adrenaline

    Science.gov (United States)

    Çarçabal, P.; Snoek, L. C.; van Mourik, T.

    The conformational landscapes of the neurotransmitter l-adrenaline (l-epinephrine) and its diastereoisomer pseudo-adrenaline, isolated in the gas phase and un-protonated, have been investigated by using a combination of mass-selected ultraviolet and infrared holeburn spectroscopy, following laser desorption of the sample into a pulsed supersonic argon jet, and DFT and ab initio computation (at the B3LYP/6-31+G*, MP2/6-31+G* and MP2/aug-cc-pVDZ levels of theory). Both for adrenaline and its diastereoisomer, pseudo-adrenaline, one dominant molecular conformation, very similar to the one seen in noradrenaline, has been observed. It could be assigned to an extended side-chain structure (AG1a) stabilized by an OH → N intramolecular hydrogen bond. An intramolecular hydrogen bond is also formed between the neighbouring hydroxyl groups on the catechol ring. The presence of further conformers for both diastereoisomers could not be excluded, but overlapping electronic spectra and low ion signals prevented further assignments.

  3. Gas-phase structure and fragmentation pathways of singly protonated peptides with N-terminal arginine.

    Science.gov (United States)

    Bythell, Benjamin J; Csonka, István P; Suhai, Sándor; Barofsky, Douglas F; Paizs, Béla

    2010-11-25

    The gas-phase structures and fragmentation pathways of the singly protonated peptide arginylglycylaspartic acid (RGD) are investigated by means of collision-induced-dissociation (CID) and detailed molecular mechanics and density functional theory (DFT) calculations. It is demonstrated that despite the ionizing proton being strongly sequestered at the guanidine group, protonated RGD can easily be fragmented on charge directed fragmentation pathways. This is due to facile mobilization of the C-terminal or aspartic acid COOH protons thereby generating salt-bridge (SB) stabilized structures. These SB intermediates can directly fragment to generate b(2) ions or facilely rearrange to form anhydrides from which both b(2) and b(2)+H(2)O fragments can be formed. The salt-bridge stabilized and anhydride transition structures (TSs) necessary to form b(2) and b(2)+H(2)O are much lower in energy than their traditional charge solvated counterparts. These mechanisms provide compelling evidence of the role of SB and anhydride structures in protonated peptide fragmentation which complements and supports our recent findings for tryptic systems (Bythell, B. J.; Suhai, S.; Somogyi, A.; Paizs, B. J. Am. Chem. Soc. 2009, 131, 14057-14065.). In addition to these findings we also report on the mechanisms for the formation of the b(1) ion, neutral loss (H(2)O, NH(3), guanidine) fragment ions, and the d(3) ion.

  4. Decomposition reaction rate of BCl3-C3H6(propene)-H2 in the gas phase.

    Science.gov (United States)

    Xiao, Jun; Su, Kehe; Liu, Yan; Ren, Hongjiang; Zeng, Qingfeng; Cheng, Laifei; Zhang, Litong

    2012-07-05

    The decomposition reaction rate in the BCl(3)-C(3)H(6)-H(2) gas phase reaction system in preparing boron carbides was investigated based on the most favorable reaction pathways proposed by Jiang et al. [Theor. Chem. Accs. 2010, 127, 519] and Yang et al. [J. Theor. Comput. Chem. 2012, 11, 53]. The rate constants of all the elementary reactions were evaluated with the variational transition state theory. The vibrational frequencies for the stationary points as well as the selected points along the minimum energy paths (MEPs) were calculated with density functional theory at the B3PW91/6-311G(d,p) level and the energies were refined with the accurate model chemistry method G3(MP2). For the elementary reaction associated with a transition state, the MEP was obtained with the intrinsic reaction coordinates, while for the elementary reaction without transition state, the relaxed potential energy surface scan was employed to obtain the MEP. The rate constants were calculated for temperatures within 200-2000 K and fitted into three-parameter Arrhenius expressions. The reaction rates were investigated by using the COMSOL software to solve numerically the coupled differential rate equations. The results show that the reactions are, consistent with the experiments, appropriate at 1100-1500 K with the reaction time of 30 s for 1100 K, 1.5 s for 1200 K, 0.12 s for 1300 K, 0.011 s for 1400 K, or 0.001 s for 1500 K, for propene being almost completely consumed. The completely dissociated species, boron carbides C(3)B, C(2)B, and CB, have very low concentrations, and C(3)B is the main product at higher temperatures, while C(2)B is the main product at lower temperatures. For the reaction time 1 s, all these concentrations approach into a nearly constant. The maximum value (in mol/m(3)) is for the highest temperature 1500 K with the orders of -13, -17, and -23 for C(3)B, C(2)B, and CB, respectively. It was also found that the logarithm of the overall reaction rate and reciprocal

  5. The role of char and tar in determining the gas-phase partitioning of nitrogen during biomass gasification

    International Nuclear Information System (INIS)

    Broer, Karl M.; Brown, Robert C.

    2015-01-01

    Highlights: • Switchgrass was gasified at an equivalence ratio of zero and 650–850 °C. • Short residence times were employed to minimize secondary reactions. • Char- and tar-bound nitrogen, NH_3, HCN, and N_2 were all significant products. • Increasing temperature leads to increased release of gaseous nitrogen compounds. • Kinetic models of gasification should include nitrogen release from char and tar. - Abstract: Gasification is an attractive option for converting biomass into fuels and chemicals. Most biomass contains significant amounts of fuel-bound nitrogen (FBN), which partially converts into ammonia (NH_3) and hydrogen cyanide (HCN) during gasification. These nitrogen compounds are problematic as they can lead to NO_X emissions or catalyst poisoning in downstream applications of syngas. FBN can convert to other products as well, including diatomic nitrogen (N_2), char-bound nitrogen (char-N), and tar-bound nitrogen (tar-N). Efforts to predict concentrations of NH_3 and HCN have been hindered by a lack of accurate, comprehensive measurements of nitrogen partitioning among gasification products. The present study gasified switchgrass under allothermal, short residence time conditions and measured NH_3, HCN, char-N, and tar-N as a function of temperature in the range of 650–850 °C with diatomic nitrogen determined by difference. It was found that a major portion of FBN was retained in the char and tar products. As temperature was increased, char and tar were consumed, releasing nitrogen as gaseous NH_3 and HCN. This increase in undesirable nitrogen compounds is contrary to the predictions of most gasification models, which overlook the presence of significant nitrogen in char and tar even if they include tar cracking and char gasification reactions. The results of this study demonstrate that gas-phase reactions alone are not sufficient to predict the fate of nitrogen during gasification. In order for modeling efforts to obtain more accurate

  6. Generation, Detection and characterization of Gas-Phase Transition Metal containing Molecules

    Energy Technology Data Exchange (ETDEWEB)

    Steimle, Timothy [Arizona State Univ., Tempe, AZ (United States)

    2015-12-15

    The objective of this project was to generate, detect, and characterize small, gas-phase, metal containing molecules. In addition to being relevant to high temperature chemical environments (e.g. plasmas and combustion), gas-phase experiments on metal containing molecules serve as the most direct link to a molecular-level theoretical model for catalysis. Catalysis (i.e. the addition of a small about of recoverable material to control the rate and direction of a chemical reaction) is critical to the petroleum and pharmaceutical industries as well as environmental remediation. Currently, the majority of catalytic materials are based on very expensive metals such as platinum (Pt), palladium (Pd), iridium (Ir,) rhenium (Re), and rhodium (Rh). For example, the catalyst used for converting linear hydrocarbon molecules (e.g. hexane) to cyclic molecules (e.g. cyclohexane) is a mixture of Pt and Re suspended on alumina. It enables straight chain alkanes to be converted into branched-chain alkanes, cyclohexanes and aromatic hydrocarbons which are used, amongst other things, to enhance the octane number of petrol. A second example is the heterogeneous catalysis used in automobile exhaust systems to: a) decrease nitrogen oxide; b) reduce carbon monoxide; and c) oxidize unburned hydrocarbons. The exhaust is vented through a high-surface area chamber lined with Pt, Pd, and Rh. For example, the carbon monoxide is catalytically converted to carbon dioxide by reaction with oxygen. The research results from this work have been published in readily accessible journals1-28. The ground and excited electronic state properties of small metal containing molecules that we determine were: a) electronic state distributions and lifetimes, b) vibrational frequencies, c) bond lengths and angles, d) hyperfine interactions, e) permanent electric dipole moments, mel, and f) magnetic dipoles, μm. In general terms, μel, gives insight into the charge distribution and mm into

  7. Formation of secondary organic aerosols from gas-phase emissions of heated cooking oils

    Directory of Open Access Journals (Sweden)

    T. Liu

    2017-06-01

    Full Text Available Cooking emissions can potentially contribute to secondary organic aerosol (SOA but remain poorly understood. In this study, formation of SOA from gas-phase emissions of five heated vegetable oils (i.e., corn, canola, sunflower, peanut and olive oils was investigated in a potential aerosol mass (PAM chamber. Experiments were conducted at 19–20 °C and 65–70 % relative humidity (RH. The characterization instruments included a scanning mobility particle sizer (SMPS and a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS. The efficiency of SOA production, in ascending order, was peanut oil, olive oil, canola oil, corn oil and sunflower oil. The major SOA precursors from heated cooking oils were related to the content of monounsaturated fat and omega-6 fatty acids in cooking oils. The average production rate of SOA, after aging at an OH exposure of 1. 7 × 1011 molecules cm−3 s, was 1. 35 ± 0. 30 µg min−1, 3 orders of magnitude lower compared with emission rates of fine particulate matter (PM2. 5 from heated cooking oils in previous studies. The mass spectra of cooking SOA highly resemble field-derived COA (cooking-related organic aerosol in ambient air, with R2 ranging from 0.74 to 0.88. The average carbon oxidation state (OSc of SOA was −1.51 to −0.81, falling in the range between ambient hydrocarbon-like organic aerosol (HOA and semi-volatile oxygenated organic aerosol (SV-OOA, indicating that SOA in these experiments was lightly oxidized.

  8. Gas Phase Chemistry and Molecular Complexity: How Far Do They Go?

    Science.gov (United States)

    Balucani, Nadia

    2016-07-01

    The accumulation of organic molecules of increasing complexity is believed to be an important step toward the emergence of life. But how massive organic synthesis could occur in primitive Earth, i.e. a water-dominated environment, is a matter of debate. Two alternative theories have been suggested so far: endogenous and exogenous synthesis. In the first theory, the synthesis of simple organic molecules having a strong prebiotic potential (simple prebiotic molecules SPMs, such as H2CO, HCN, HC3N, NH2CHO) occurred directly on our planet starting from simple parent molecules of the atmosphere, liquid water and various energy sources. Miller's experiment was a milestone in this theory, but it was later recognized that the complexity of a planet cannot be reproduced in a single laboratory experiment. Some SPMs have been identified in the N2-dominated atmosphere of Titan (a massive moon of Saturn), which is believed to be reminiscent of the primitive terrestrial atmosphere. As such, the atmosphere of Titan represents a planetary scale laboratory for the comprehension of SPM formation in an environment close enough to primitive Earth and is the current frontier in the endogenous theory exploration. In the exogenous theory, SPMs came from space, the carriers being comets, asteroids and meteorites. The rationale behind this suggestion is that plenty of SPMs have been observed in interstellar clouds (ISCs), including star-forming regions, and in small bodies like comets, asteroids and meteorites. Therefore, the basic idea is that SPMs were formed in the solar nebula, preserved during the early phases of the Solar System formation in the body of comets/asteroids/meteorites and finally delivered to Earth by cometary and meteoritic falls. In this contribution, the status of our knowledge on how SPMs can be formed in the gas phase, either in the primitive terrestrial atmosphere or in the cold nebula from which the Solar System originated, will be presented. Particular attention

  9. Condensation and dissociation rates for gas phase metal clusters from molecular dynamics trajectory calculations

    Science.gov (United States)

    Yang, Huan; Goudeli, Eirini; Hogan, Christopher J.

    2018-04-01

    In gas phase synthesis systems, clusters form and grow via condensation, in which a monomer binds to an existing cluster. While a hard-sphere equation is frequently used to predict the condensation rate coefficient, this equation neglects the influences of potential interactions and cluster internal energy on the condensation process. Here, we present a collision rate theory-molecular dynamics simulation approach to calculate condensation probabilities and condensation rate coefficients. We use this approach to examine atomic condensation onto 6-56-atom Au and Mg clusters. The probability of condensation depends upon the initial relative velocity (v) between atom and cluster and the initial impact parameter (b). In all cases, there is a well-defined region of b-v space where condensation is highly probable, and outside of which the condensation probability drops to zero. For Au clusters with more than 10 atoms, we find that at gas temperatures in the 300-1200 K range, the condensation rate coefficient exceeds the hard-sphere rate coefficient by a factor of 1.5-2.0. Conversely, for Au clusters with 10 or fewer atoms and for 14- and 28-atom Mg clusters, as cluster equilibration temperature increases, the condensation rate coefficient drops to values below the hard-sphere rate coefficient. Calculations also yield the self-dissociation rate coefficient, which is found to vary considerably with gas temperature. Finally, calculations results reveal that grazing (high b) atom-cluster collisions at elevated velocity (>1000 m s-1) can result in the colliding atom rebounding (bounce) from the cluster surface or binding while another atom dissociates (replacement). The presented method can be applied in developing rate equations to predict material formation and growth rates in vapor phase systems.

  10. Gas-phase chemistry of Mo, Ru, W, and Os metal carbonyl complexes

    International Nuclear Information System (INIS)

    Wang, Y.; Qin, Z.; Fan, F.L.

    2014-01-01

    Metal carbonyl complexes were used for studying the gas-phase chemical behavior of Mo, Ru, W and Os isotopes with an on-line low temperature isothermal gas chromatography apparatus. Short-lived Mo and Ru isotopes were produced by a 252 Cf spontaneous fission source. Short-lived nuclides of W and Os were produced using the heavy ion reactions 19 F + 159 Tb and 165 Ho, respectively. Short-lived products were thermalized in a recoil chamber filled with a gas mixture of helium and carbon monoxide. The carbonyls formed were then transported through capillaries to an isothermal chromatography column for study of the adsorption behavior as a function of temperature. On-line isothermal chromatography (IC) experiments on Teflon (PTFE) and quartz surfaces showed that short-lived isotopes of the listed elements can form carbonyl complexes which are very volatile and interact most likely in physical sorption processes. Deduced adsorption enthalpies of Mo and Ru carbonyls were -38 ± 2 kJ/mol and -36 ± 2 kJ/mol, respectively. These values are in good agreement with literature data, partly obtained with different chromatographic techniques. A validation of the applied Monte Carlo model to deduce adsorption enthalpies with Mo isotopes of different half-lives proved the validity of the underlying adsorption model. The investigations using a gas-jet system coupled to a heavy ion accelerator without any preseparator clearly showed the limitations of the approach. The He and CO gas mixture, which was directly added into the chamber, will result in decomposition of CO gas and produce some aerosol particles. After the experiment of 173 W and 179 Os in the heavy ion experiments, the Teflon column was covered by a yellowish deposit; the adsorption enthalpy of W and Os carbonyls could therefore not be properly deduced using Monte Carlo simulations. (orig.)

  11. Estimating fuel octane numbers from homogeneous gas-phase ignition delay times

    KAUST Repository

    Naser, Nimal

    2017-11-05

    Fuel octane numbers are directly related to the autoignition properties of fuel/air mixtures in spark ignition (SI) engines. This work presents a methodology to estimate the research and the motor octane numbers (RON and MON) from homogeneous gas-phase ignition delay time (IDT) data calculated at various pressures and temperatures. The hypothesis under investigation is that at specific conditions of pressure and temperature (i.e., RON-like and MON-like conditions), fuels with IDT identical to that of a primary reference fuel (PRF) have the same octane rating. To test this hypothesis, IDTs with a detailed gasoline surrogate chemical kinetic model have been calculated at various temperatures and pressures. From this dataset, temperatures that best represent RON and MON have been correlated at a specified pressure. Correlations for pressures in the range of 10–50 bar were obtained. The proposed correlations were validated with toluene reference fuels (TRF), toluene primary reference fuels (TPRF), ethanol reference fuels (ERF), PRFs and TPRFs with ethanol, and multi-component gasoline surrogate mixtures. The predicted RON and MON showed satisfactory accuracy against measurements obtained by the standard ASTM methods and blending rules, demonstrating that the present methodology can be a viable tool for a first approximation. The correlations were also validated against an extensive set of experimental IDT data obtained from literature with a high degree of accuracy in RON/MON prediction. Conditions in homogeneous reactors such as shock tubes and rapid compression machines that are relevant to modern SI engines were also identified. Uncertainty analysis of the proposed correlations with linear error propagation theory is also presented.

  12. Order from the disorder: hierarchical nanostructures self-assembled from the gas phase (Conference Presentation)

    Science.gov (United States)

    Di Fonzo, Fabio

    2017-02-01

    The assembly of nanoscale building blocks in engineered mesostructures is one of the fundamental goals of nanotechnology. Among the various processes developed to date, self-assembly emerges as one of the most promising, since it relays solely on basic physico-chemical forces. Our research is focused on a new type of self-assembly strategy from the gas-phase: Scattered Ballistic Deposition (SBD). SBD arises from the interaction of a supersonic molecular beam with a static gas and enables the growth of quasi-1D hierarchical mesostructures. Overall, they resemble a forest composed of individual, high aspect-ratio, tree-like structures, assembled from amorphous or crystalline nanoparticles. SBD is a general occurring phenomenon and can be obtained with different vapour or cluster sources. In particular, SBD by Pulsed Laser Deposition is a convenient physical vapor technique that allows the generation of supersonic plasma jets from any inorganic material irrespective of melting temperature, preserving even the most complex stoichiometries. One of the advantages of PLD over other vapour deposition techniques is extremely wide operational pressure range, from UHV to ambient pressure. These characteristics allowed us to develop quasi-1D hierarchical nanostructures from different transition metal oxides, semiconductors and metals. The precise control offered by the SBD-PLD technique over material properties at the nanoscale allowed us to fabricate ultra-thin, high efficiency hierarchical porous photonic crystals with Bragg reflectivity up to 85%. In this communication we will discuss the application of these materials to solar energy harvesting and storage, stimuli responsive photonic crystals and smart surfaces with digital control of their wettability behaviour.

  13. Multiscale Computational Analysis of Nitrogen and Oxygen Gas-Phase Thermochemistry in Hypersonic Flows

    Science.gov (United States)

    Bender, Jason D.

    Understanding hypersonic aerodynamics is important for the design of next-generation aerospace vehicles for space exploration, national security, and other applications. Ground-level experimental studies of hypersonic flows are difficult and expensive; thus, computational science plays a crucial role in this field. Computational fluid dynamics (CFD) simulations of extremely high-speed flows require models of chemical and thermal nonequilibrium processes, such as dissociation of diatomic molecules and vibrational energy relaxation. Current models are outdated and inadequate for advanced applications. We describe a multiscale computational study of gas-phase thermochemical processes in hypersonic flows, starting at the atomic scale and building systematically up to the continuum scale. The project was part of a larger effort centered on collaborations between aerospace scientists and computational chemists. We discuss the construction of potential energy surfaces for the N4, N2O2, and O4 systems, focusing especially on the multi-dimensional fitting problem. A new local fitting method named L-IMLS-G2 is presented and compared with a global fitting method. Then, we describe the theory of the quasiclassical trajectory (QCT) approach for modeling molecular collisions. We explain how we implemented the approach in a new parallel code for high-performance computing platforms. Results from billions of QCT simulations of high-energy N2 + N2, N2 + N, and N2 + O2 collisions are reported and analyzed. Reaction rate constants are calculated and sets of reactive trajectories are characterized at both thermal equilibrium and nonequilibrium conditions. The data shed light on fundamental mechanisms of dissociation and exchange reactions -- and their coupling to internal energy transfer processes -- in thermal environments typical of hypersonic flows. We discuss how the outcomes of this investigation and other related studies lay a rigorous foundation for new macroscopic models for

  14. Next Generation Offline Approaches to Trace Gas-Phase Organic Compound Speciation: Sample Collection and Analysis

    Science.gov (United States)

    Sheu, R.; Marcotte, A.; Khare, P.; Ditto, J.; Charan, S.; Gentner, D. R.

    2017-12-01

    Intermediate-volatility and semi-volatile organic compounds (I/SVOCs) are major precursors to secondary organic aerosol, and contribute to tropospheric ozone formation. Their wide volatility range, chemical complexity, behavior in analytical systems, and trace concentrations present numerous hurdles to characterization. We present an integrated sampling-to-analysis system for the collection and offline analysis of trace gas-phase organic compounds with the goal of preserving and recovering analytes throughout sample collection, transport, storage, and thermal desorption for accurate analysis. Custom multi-bed adsorbent tubes are used to collect samples for offline analysis by advanced analytical detectors. The analytical instrumentation comprises an automated thermal desorption system that introduces analytes from the adsorbent tubes into a gas chromatograph, which is coupled with an electron ionization mass spectrometer (GC-EIMS) and other detectors. In order to optimize the collection and recovery for a wide range of analyte volatility and functionalization, we evaluated a variety of commercially-available materials, including Res-Sil beads, quartz wool, glass beads, Tenax TA, and silica gel. Key properties for optimization include inertness, versatile chemical capture, minimal affinity for water, and minimal artifacts or degradation byproducts; these properties were assessed with a diverse mix of traditionally-measured and functionalized analytes. Along with a focus on material selection, we provide recommendations spanning the entire sampling-and-analysis process to improve the accuracy of future comprehensive I/SVOC measurements, including oxygenated and other functionalized I/SVOCs. We demonstrate the performance of our system by providing results on speciated VOCs-SVOCs from indoor, outdoor, and chamber studies that establish the utility of our protocols and pave the way for precise laboratory characterization via a mix of detection methods.

  15. EXPLORING SYSTEMATIC EFFECTS IN THE RELATION BETWEEN STELLAR MASS, GAS PHASE METALLICITY, AND STAR FORMATION RATE

    International Nuclear Information System (INIS)

    Telford, O. Grace; Dalcanton, Julianne J.; Skillman, Evan D.; Conroy, Charlie

    2016-01-01

    There is evidence that the well-established mass–metallicity relation in galaxies is correlated with a third parameter: star formation rate (SFR). The strength of this correlation may be used to disentangle the relative importance of different physical processes (e.g., infall of pristine gas, metal-enriched outflows) in governing chemical evolution. However, all three parameters are susceptible to biases that might affect the observed strength of the relation between them. We analyze possible sources of systematic error, including sample bias, application of signal-to-noise ratio cuts on emission lines, choice of metallicity calibration, uncertainty in stellar mass determination, aperture effects, and dust. We present the first analysis of the relation between stellar mass, gas phase metallicity, and SFR using strong line abundance diagnostics from Dopita et al. for ∼130,000 star-forming galaxies in the Sloan Digital Sky Survey and provide a detailed comparison of these diagnostics in an appendix. Using these new abundance diagnostics yields a 30%–55% weaker anti-correlation between metallicity and SFR at fixed stellar mass than that reported by Mannucci et al. We find that, for all abundance diagnostics, the anti-correlation with SFR is stronger for the relatively few galaxies whose current SFRs are elevated above their past average SFRs. This is also true for the new abundance diagnostic of Dopita et al., which gives anti-correlation between Z and SFR only in the high specific star formation rate (sSFR) regime, in contrast to the recent results of Kashino et al. The poorly constrained strength of the relation between stellar mass, metallicity, and SFR must be carefully accounted for in theoretical studies of chemical evolution.

  16. Estimating fuel octane numbers from homogeneous gas-phase ignition delay times

    KAUST Repository

    Naser, Nimal; Sarathy, Mani; Chung, Suk-Ho

    2017-01-01

    Fuel octane numbers are directly related to the autoignition properties of fuel/air mixtures in spark ignition (SI) engines. This work presents a methodology to estimate the research and the motor octane numbers (RON and MON) from homogeneous gas-phase ignition delay time (IDT) data calculated at various pressures and temperatures. The hypothesis under investigation is that at specific conditions of pressure and temperature (i.e., RON-like and MON-like conditions), fuels with IDT identical to that of a primary reference fuel (PRF) have the same octane rating. To test this hypothesis, IDTs with a detailed gasoline surrogate chemical kinetic model have been calculated at various temperatures and pressures. From this dataset, temperatures that best represent RON and MON have been correlated at a specified pressure. Correlations for pressures in the range of 10–50 bar were obtained. The proposed correlations were validated with toluene reference fuels (TRF), toluene primary reference fuels (TPRF), ethanol reference fuels (ERF), PRFs and TPRFs with ethanol, and multi-component gasoline surrogate mixtures. The predicted RON and MON showed satisfactory accuracy against measurements obtained by the standard ASTM methods and blending rules, demonstrating that the present methodology can be a viable tool for a first approximation. The correlations were also validated against an extensive set of experimental IDT data obtained from literature with a high degree of accuracy in RON/MON prediction. Conditions in homogeneous reactors such as shock tubes and rapid compression machines that are relevant to modern SI engines were also identified. Uncertainty analysis of the proposed correlations with linear error propagation theory is also presented.

  17. Electron Scattering Studies of Gas Phase Molecular Structure at High Temperature

    Science.gov (United States)

    Mawhorter, Richard J., Jr.

    A high precision counting electron diffraction study of the structure of gaseous sulfur dioxide as a function of temperature from 300(DEGREES) to 1000(DEGREES)K is presented. The results agree well with current theory, and yield insight into the effects of anharmonicity on molecular structure. Another aspect of molecular structure is the molecular charge density distribution. The difference (DELTA)(sigma) is between the electron scattering cross sections for the actual molecule and independent atom model (IAM) are a sensitive measure of the change in this distribution due to bond formation. These difference cross sections have been calculated using ab initio methods, and the results for a wide range of simple polyatomic molecules are presented. Such calculations are routinely done for a single, fixed molecular geometry, an approach which neglects the effects of the vibrational motion of real molecules. The effect of vibrational averaging is studied in detail for the three normal vibrational modes of H(,2)O in the ground state. The effects are small, lending credence to the practice of comparing cross sections calculated at a fixed geometry with inherently averaged experimental data. The efficacy of the standard formula used to account for vibrational averaging in the IAM is also examined. Finally, the nature of the ionic bond is probed with an experimental study of the structure of alkali chlorides, NaCl, KCl, RbCl, and CsCl, in the gas phase. Temperatures from 840-960(DEGREES)K were required to achieve the necessary vapor pressures of approximately 0.01 torr. A planar rhombic structure for the dimer molecule is confirmed, with a fairly uniform decrease of the chlorine-alkali-chlorine angle as the alkalis increase in size. The experiment also yields information on the amount of dimer present in the vapor, and these results are compared with thermodynamic values.

  18. Reactive and Energy Transfer Processes of the Neutral Radical Species HgBr in Gas Phase Collisions.

    Science.gov (United States)

    1981-11-05

    subsecuent spontaneousTV7. EW=Gt TRANSM PR Rq(63,0) TO 12) emision producing RqSrfX2r1/.- . Atomic excitation :i59Cr tR r1,2) 123 i •lf tercury is...3Pe (4.7 mr1 otate. 3 3 Bornstein, in a cross molecular bees chesilmitnoseene study, has placed the reective cross roction of 3P, Mg with st2 at...influenc, of molecular rotation on electronic motion arm considered by using the coupling aOhwaiO of lnd’l case (w). 2 In this came the spin S

  19. Analysis of local-scale background concentrations of methane and other gas-phase species in the Marcellus Shale

    Directory of Open Access Journals (Sweden)

    J. Douglas Goetz

    2017-02-01

    Full Text Available The Marcellus Shale is a rapidly developing unconventional natural gas resource found in part of the Appalachian region. Air quality and climate concerns have been raised regarding development of unconventional natural gas resources. Two ground-based mobile measurement campaigns were conducted to assess the impact of Marcellus Shale natural gas development on local scale atmospheric background concentrations of air pollution and climate relevant pollutants in Pennsylvania. The first campaign took place in Northeastern and Southwestern PA in the summer of 2012. Compounds monitored included methane (CH4, ethane, carbon monoxide (CO, nitrogen dioxide, and Proton Transfer Reaction Mass Spectrometer (PTR-MS measured volatile organic compounds (VOC including oxygenated and aromatic VOC. The second campaign took place in Northeastern PA in the summer of 2015. The mobile monitoring data were analyzed using interval percentile smoothing to remove bias from local unmixed emissions to isolate local-scale background concentrations. Comparisons were made to other ambient monitoring in the Marcellus region including a NOAA SENEX flight in 2013. Local background CH4 mole fractions were 140 ppbv greater in Southwestern PA compared to Northeastern PA in 2012 and background CH4 increased 100 ppbv from 2012 to 2015. CH4 local background mole fractions were not found to have a detectable relationship between well density or production rates in either region. In Northeastern PA, CO was observed to decrease 75 ppbv over the three year period. Toluene to benzene ratios in both study regions were found to be most similar to aged rural air masses indicating that the emission of aromatic VOC from Marcellus Shale activity may not be significantly impacting local background concentrations. In addition to understanding local background concentrations the ground-based mobile measurements were useful for investigating the composition of natural gas emissions in the region.

  20. Sensitivity study of experimental measures for the nuclear liquid-gas phase transition in the statistical multifragmentation model

    Science.gov (United States)

    Lin, W.; Ren, P.; Zheng, H.; Liu, X.; Huang, M.; Wada, R.; Qu, G.

    2018-05-01

    The experimental measures of the multiplicity derivatives—the moment parameters, the bimodal parameter, the fluctuation of maximum fragment charge number (normalized variance of Zmax, or NVZ), the Fisher exponent (τ ), and the Zipf law parameter (ξ )—are examined to search for the liquid-gas phase transition in nuclear multifragmention processes within the framework of the statistical multifragmentation model (SMM). The sensitivities of these measures are studied. All these measures predict a critical signature at or near to the critical point both for the primary and secondary fragments. Among these measures, the total multiplicity derivative and the NVZ provide accurate measures for the critical point from the final cold fragments as well as the primary fragments. The present study will provide a guide for future experiments and analyses in the study of the nuclear liquid-gas phase transition.

  1. Determination of the rate of crystal growth from the gas phase under conditions of turbulent free convection

    Science.gov (United States)

    Alad'Ev, S. I.

    1987-04-01

    Crystal growth in vertical and horizontal cylindrical vials, with the substrate and the source serving as the vial ends, is investigated analytically, assuming that the medium consists of a binary mixture of an active and an inert gas. The active gas is made up of the gaseous products of reactions taking place at the substrate and at the source. It is shown that turbulent free convection leads to an increase in crystal growth rate. All other conditions being equal, crystal growth in vertical vials is greater than that in horizontal ones; in both cases crystal growth rate increases with the vial radius, temperature gradient in the gas phase, and gas phase density. The results are compared with experimental data on the growth of Ge crystals in the Ge-GeI4 system.

  2. Comparisons between a gas-phase model of silane chemical vapor deposition and laser-diagnostic measurements

    International Nuclear Information System (INIS)

    Breiland, W.G.; Coltrin, M.E.; Ho, P.

    1986-01-01

    Theoretical modeling and experimental measurements have been used to study gas-phase chemistry in the chemical vapor deposition (CVD) of silicon from silane. Pulsed laser Raman spectroscopy was used to obtain temperature profiles and to obtain absolute density profiles of silane during deposition at atmospheric and 6-Torr total pressures for temperatures ranging from 500 to 800 0 C. Laser-excited fluorescence was used to obtain relative density profiles of Si 2 during deposition at 740 0 C in helium with 0-12 Torr added hydrogen. These measurements are compared to predictions from the theoretical model of Coltrin, Kee, and Miller. The predictions agree qualitatively with experiment. These studies indicate that fluid mechanics and gas-phase chemical kinetics are important considerations in understanding the chemical vapor deposition process

  3. Enhancing gas-phase reaction in a plasma using high intensity and high power ultrasonic acoustic waves

    DEFF Research Database (Denmark)

    2010-01-01

    is absorbed into said plasma (104), and where a sound pressure level of said generated ultrasonic high intensity and high power acoustic waves (102) is at least substantially 140 dB and where an acoustic power of said generated ultrasonic high intensity and high power acoustic waves (102); is at least...... substantially 100 W. In this way, a high sound intensity and power are obtained that efficiently enhances a gas-phase reaction in the plasma, which enhances the plasma process, e.g. enabling more efficient ozone or hydrogen generation using plasma in relation to reaction speed and/or obtained concentration......This invention relates to enhancing a gas-phase reaction in a plasma comprising: creating plasma (104) by at least one plasma source (106), and wherein that the method further comprises: generating ultrasonic high intensity and high power acoustic waves (102) having a predetermined amount...

  4. Two dimensional laser induced fluorescence in the gas phase: a spectroscopic tool for studying molecular spectroscopy and dynamics

    Science.gov (United States)

    Gascooke, Jason R.; Lawrance, Warren D.

    2017-11-01

    Two dimensional laser induced fluorescence (2D-LIF) extends the usual laser induced fluorescence technique by adding a second dimension, the wavelength at which excited states emit, thereby significantly enhancing the information that can be extracted. It allows overlapping absorption features, whether they arise from within the same molecule or from different molecules in a mixture, to be associated with their appropriate "parent" state and/or molecule. While the first gas phase version of the technique was published a decade ago, the technique is in its infancy, having been exploited by only a few groups to date. However, its potential in gas phase spectroscopy and dynamics is significant. In this article we provide an overview of the technique and illustrate its potential with examples, with a focus on those utilising high resolution in the dispersed fluorescence dimension.

  5. Simultaneous measurements of formaldehyde and nitrous acid in dews and gas phase in the atmosphere of Santiago, Chile

    Science.gov (United States)

    Rubio, María A.; Lissi, Eduardo; Villena, Guillermo; Elshorbany, Y. F.; Kleffmann, Jörg; Kurtenbach, Ralf; Wiesen, Peter

    2009-12-01

    The amounts of formaldehyde and nitrous acid (HONO) in gas phase and dews of Santiago de Chile were simultaneously measured. Formaldehyde concentrations values in the liquid phase (dews) correlate fairly well with those in the gaseous phase and are even higher than those expected from gas-dew equilibrium. On the other hand, nitrite concentrations in dews were considerably smaller (ca. 15 times) than those expected from the gas-phase concentrations. This under-saturation is attributed to diffusion limitations due to the relatively large HONO solubility. In agreement with this, under-saturation increases with the rate of dew formation and the pH of the collected waters, factors that should increase the rate of gas to liquid HONO transfer required to reach equilibrium.

  6. Identification of Guest-Host Inclusion Complexes in the Gas Phase by Electrospray Ionization-Mass Spectrometry

    Science.gov (United States)

    Mendes, De´bora C.; Ramamurthy, Vaidhyanathan; Da Silva, Jose´ P.

    2015-01-01

    In this laboratory experiment, students follow a step-by-step procedure to prepare and study guest-host complexes in the gas phase using electrospray ionization-mass spectrometry (ESI-MS). Model systems are the complexes of hosts cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) with the guest 4-styrylpyridine (SP). Aqueous solutions of CB7 or CB8…

  7. Gas-phase fragmentation of peptides to increase the spatial resolution of the Hydrogen Exchange Mass Spectrometry experiment

    DEFF Research Database (Denmark)

    Jensen, Pernille Foged; Rand, Kasper Dyrberg

    2016-01-01

    are produced after precursor ion selection and thus do not add complexity to the LC-MS analysis. The key to obtaining optimal spatial resolution in a hydrogen exchange mass spectrometry (HX-MS) experiment is the fragmentation efficiency. This chapter discusses common fragmentation techniques like collision....../D scrambling, thus making them suitable for HX applications. By combining the classic bottom-up HX-MS workflow with gas-phase fragmentation by ETD, detailed information on protein HX can be obtained....

  8. Gas Phase Emission Ratios From In-Use Diesel and CNG Curbside Passenger Buses in New York City

    Science.gov (United States)

    Herndon, S. C.; Shorter, J.; Canagaratna, M.; Jayne, J.; Nelson, D. D.; Wormhoudt, J. C.; Williams, P.; Silva, P. J.; Shi, Q.; Ghertner, A.; Zahniser, M.; Worsnop, D.; Kolb, C.; Lanni, T.; Drewnick, F.; Demerjian, K. L.

    2002-12-01

    The Aerodyne Mobile Laboratory simultaneously measured gas phase and particulate emissions from in use vehicles during two campaigns in New York City. The campaigns took place during two weeks in October, 2000 and four weeks in July-August, 2001. Passenger curbside buses were the primary focus of the study, but school buses and several other heavy duty diesel vehicles were also characterized. This paper describes the methodologies used to measure individual in use vehicles and presents the results of the gas phase measurements. Emission ratios for NO, NO2, SO2, N2O, CO, CH4 and H2CO relative to CO2 have been determined across several classes of buses. The gas phase concentrations were measured each second, using Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS). Some of the categories of buses into which the data has been sorted are; diesel (both 6V92 and Series 50) with and without the Continuous Regenerative Technology (CRT) retrofit, compressed natural gas powered(CNG) and hybrid diesel-electric buses. The New York Metropolitan Transit Authority (MTA) cooperated with this work, providing details about each of their buses followed. In addition to MTA buses, other New York City passenger bus operators were also measured. In September 2000, MTA began to switch to 30 ppm sulfur diesel fuel while it is believed the non MTA operators did not. The measured emission ratios show that low sulfur fuel greatly reduces the amount of SO2 per CO2. Roughly one third of the MTA fleet of diesel buses have been equipped with the CRT retrofit. The gas phase results of interest in this category show increased direct emission of NO2 and companion work (also submitted to the 12th CRC) show the impact the CRT refit has on particulate emissions. CNG buses show increased H2CO and CH4 emission ratios relative to diesel powered motors.

  9. Conceptual design for the field test and evaluation of the gas-phase UF6 enrichment meter

    International Nuclear Information System (INIS)

    Strittmatter, R.B.; Leavitt, J.N.; Slice, R.W.

    1980-12-01

    An in-line enrichment monitor is being developed to provide real-time enrichment data for the gas-phase UF 6 feed stream of an enrichment plant. Data from proof-of-principle measurements using a laboratory prototype system are presented. A conceptual design for an enrichment monitor to be field tested and evaluated at the Oak Ridge Gaseous Diffusion Plant is reported

  10. Valorization of Calcium Carbonate-Based Solid Wastes for the Treatment of Hydrogen Sulfide from the Gas Phase

    OpenAIRE

    Pham Xuan , Huynh; Pham Minh , Doan; Galera Martinez , Marta; Nzihou , Ange; Sharrock , Patrick

    2015-01-01

    International audience; This paper focuses on the valorization of calcium carbonate-based solid wastes for theremoval of hydrogen sulfide from gas phase. Two solid wastes taken from industrial sites for theproduction of sodium carbonate and sodium bicarbonate by the Solvay process® were analyzedby different physico-chemical methods. Calcium carbonate was found as the main component ofboth the solid wastes. Trace amounts of other elements such as Mg, Al, Fe, Si, Cl, Na etc. werealso present in...

  11. Gas-Phase Energetics of Actinide Oxides: An Assessment of Neutral and Cationic Monoxides and Dioxides from Thorium to Curium

    Science.gov (United States)

    Marçalo, Joaquim; Gibson, John K.

    2009-09-01

    An assessment of the gas-phase energetics of neutral and singly and doubly charged cationic actinide monoxides and dioxides of thorium, protactinium, uranium, neptunium, plutonium, americium, and curium is presented. A consistent set of metal-oxygen bond dissociation enthalpies, ionization energies, and enthalpies of formation, including new or revised values, is proposed, mainly based on recent experimental data and on correlations with the electronic energetics of the atoms or cations and with condensed-phase thermochemistry.

  12. Possibility of determining the concentration of the gas phase in a two-phase stream by an acoustical method

    Energy Technology Data Exchange (ETDEWEB)

    Butenko, A N; Potapenko, A E; Chistyakov, E S

    1976-01-01

    The method is based on the recording of the amplitude-frequency characteristics of a circular piezoelectric resonator (sensor) during movement of a stream of a two-phase medium. It is shown that the electrical voltage drop across the transducer and the natural oscillating frequency of the transducer depend on the concentration of the gas phase in the two-phase mixture, allowing an instrument to be developed for measurement of this concentration.

  13. FastChem: A computer program for efficient complex chemical equilibrium calculations in the neutral/ionized gas phase with applications to stellar and planetary atmospheres

    Science.gov (United States)

    Stock, Joachim W.; Kitzmann, Daniel; Patzer, A. Beate C.; Sedlmayr, Erwin

    2018-06-01

    For the calculation of complex neutral/ionized gas phase chemical equilibria, we present a semi-analytical versatile and efficient computer program, called FastChem. The applied method is based on the solution of a system of coupled nonlinear (and linear) algebraic equations, namely the law of mass action and the element conservation equations including charge balance, in many variables. Specifically, the system of equations is decomposed into a set of coupled nonlinear equations in one variable each, which are solved analytically whenever feasible to reduce computation time. Notably, the electron density is determined by using the method of Nelder and Mead at low temperatures. The program is written in object-oriented C++ which makes it easy to couple the code with other programs, although a stand-alone version is provided. FastChem can be used in parallel or sequentially and is available under the GNU General Public License version 3 at https://github.com/exoclime/FastChem together with several sample applications. The code has been successfully validated against previous studies and its convergence behavior has been tested even for extreme physical parameter ranges down to 100 K and up to 1000 bar. FastChem converges stable and robust in even most demanding chemical situations, which posed sometimes extreme challenges for previous algorithms.

  14. Rate of Isotope Exchange Reaction Between Tritiated Water in a Gas Phase and Water on the Surface of Piping Materials

    International Nuclear Information System (INIS)

    Nakashio, Nobuyuki; Yamaguchi, Junya; Kobayashi, Ryusuke; Nishikawa, Masabumi

    2001-01-01

    The system effect of tritium arises from the interaction of tritium in the gas phase with water on the surface of piping materials. It has been reported that the system effect can be quantified by applying the serial reactor model to the piping system and that adsorption and isotope exchange reactions play the main roles in the trapping of tritium. The isotope exchange reaction that occurs when the chemical form of tritium in the gas phase is in the molecular form, i.e., HT or T 2 , has been named isotope exchange reaction 1, and that which occurs when tritium in the gas phase is in water form, i.e., HTO or T 2 O, has been named isotope exchange reaction 2.The rate of isotope exchange reaction 2 is experimentally quantified, and the rate is observed to be about one-third of the rate of adsorption. The trapping and release behavior of tritium from the piping surface due to isotope exchange reaction 2 is also discussed. It is certified that swamping of water vapor to process gas is effective to release tritium from the surface contaminated with tritium

  15. Theoretical Study On The Interaction Between Xenon And Positive Silver Clusters In Gas Phase And On The (001) Chabazite Surface

    International Nuclear Information System (INIS)

    Hunter, D.

    2009-01-01

    A systematic study on the adsorption of xenon on silver clusters in the gas phase and on the (001) surface of silver-exchanged chabazite is reported. Density functional theory at the B3LYP level with the cluster model was employed. The results indicate that the dominant part of the binding is the σ donation, which is the charge transfer from the 5p orbital of Xe to the 5s orbital of Ag and is not the previously suggested d π -d π back-donation. A correlation between the binding energy and the degree of σ donation is found. Xenon was found to bind strongly to silver cluster cations and not to neutral ones. The binding strength decreases as the cluster size increases for both cases, clusters in the gas-phase and on the chabazite surface. The Ag + cation is the strongest binding site for xenon both in gas phase and on the chabazite surface with the binding energies of 73.9 and 14.5 kJ/mol, respectively. The results also suggest that the smaller silver clusters contribute to the negative chemical shifts observed in the 129 Xe NMR spectra in experiments.

  16. Gas-phase photoemission with soft x-rays: Cross sections and angular distributions

    International Nuclear Information System (INIS)

    Shirley, D.A.; Kobrin, P.H.; Truesdale, C.M.; Lindle, D.W.; Ferrett, T.A.; Heimann, P.A.; Becker, U.; Kerkhoff, H.G.; Southworth, S.H.

    1983-01-01

    A summary is presented of typical gas-phase photoemission studies based on synchrotron radiation in the 50-5000 eV range, using beam lines at the Stanford Synchrotron Radiation Laboratory. Three topics are addressed: atomic inner-shell photoelectron cross sections and asymmetries, correlation peaks in rare gases, and core-level shape resonances in molecules. Photoelectron cross-section σ(n iota) and asymmetry-parameter β(n iota) studies in mercury vapor at photon energies up to 270 eV (up to 600 eV for β/sub 4f/) extend coverage of these parameters to n≤5 and iota≤3. Comparison with Dirac-Slater and relativistic random-phase approximation calculations reveals systematic discrepancies. For example, distinct Cooper minima in σ(n iota) are observed but not predicted, while predicted β(n iota) values are typically too high. Correlation satellites have been studied for the K shells of helium (hν = 68-90 eV), neon (hν = 870-960 eV) and argon (hν = 3200-3320 eV). In helium the n=2 satellite peak was shown to have mainly 2p character at threshold, and its asymmetry was measured through the autoionizing resonance region. Tentative evidence was obtained that the neon satellites are less intense near threshold than in the high-energy limit, and that their intensities stay constant or decrease with increasing energy near threshold. A new satellite was observed in argon at 24.6 eV which appears to increase in intensity with energy. Molecular core-level shape resonances were observed for the first time by photoemission, yielding σ(hν) and β(hν) for core levels from 180 eV binding energy (S 2p in SF/sub 6/ and OCS) through C 1s in CO, CO/sub 2/ and CF/sub 4/, N 1s in N/sub 2/ and NO, and O 1s in CO and CO/sub 2/ to 2490 eV (S 1s in SF/sub 6/). Several conclusions can be drawn about the photoelectron and Auger cross sections and asymmetry parameters

  17. Gas Phase Sensing of Alcohols by Metal Organic Framework–Polymer Composite Materials

    Science.gov (United States)

    2017-01-01

    Affinity layers play a crucial role in chemical sensors for the selective and sensitive detection of analytes. Here, we report the use of composite affinity layers containing Metal Organic Frameworks (MOFs) in a polymeric matrix for sensing purposes. Nanoparticles of NH2-MIL-53(Al) were dispersed in a Matrimid polymer matrix with different weight ratios (0–100 wt %) and drop-casted on planar capacitive transducer devices. These coated devices were electrically analyzed using impedance spectroscopy and investigated for their sensing properties toward the detection of a series of alcohols and water in the gas phase. The measurements indicated a reversible and reproducible response in all devices. Sensor devices containing 40 wt % NH2-MIL-53(Al) in Matrimid showed a maximum response for methanol and water. The sensor response time slowed down with increasing MOF concentration until 40 wt %. The half time of saturation response (τ0.5) increased by ∼1.75 times for the 40 wt % composition compared to devices coated with Matrimid only. This is attributed to polymer rigidification near the MOF/polymer interface. Higher MOF loadings (≥50 wt %) resulted in brittle coatings with a response similar to the 100 wt % MOF coating. Cross-sensitivity studies showed the ability to kinetically distinguish between the different alcohols with a faster response for methanol and water compared to ethanol and 2-propanol. The observed higher affinity of the pure Matrimid polymer toward methanol compared to water allows also for a higher uptake of methanol in the composite matrices. Also, as indicated by the sensing studies with a mixture of water and methanol, the methanol uptake is independent of the presence of water up to 6000 ppm of water. The NH2-MIL-53(Al) MOFs dispersed in the Matrimid matrix show a sensitive and reversible capacitive response, even in the presence of water. By tuning the precise compositions, the affinity kinetics and overall affinity can be tuned, showing

  18. Accurate Gas Phase Formation Enthalpies of Alloys and Refractories Decomposition Products

    KAUST Repository

    Minenkov, Yury

    2017-01-17

    Accurate gas phase formation enthalpies, ΔHf, of metal oxides and halides are critical for the prediction of the stability of high temperature materials used in the aerospace and nuclear industries. Unfortunately, the experimental ΔHf values of these compounds in the most used databases, such as the NIST-JANAF database, are often reported with large inaccuracy, while some other ΔHf values clearly differ from the value predicted by CCSD(T) methods. To address this point, in this work we systematically predicted the ΔHf values of a series of these compounds having a group 4, 6, or 14 metal. The ΔHf values in question were derived within a composite Feller-Dixon-Peterson (FDP) scheme based protocol that combines the DLPNO-CCSD(T) enthalpy of ad hoc designed reactions and the experimental ΔHf values of few reference complexes. In agreement with other theoretical studies, we predict the ΔHf values for TiOCl2, TiOF2, GeF2, and SnF4 to be significantly different from the values tabulated in NIST-JANAF and other sources, which suggests that the tabulated experimental values are inaccurate. Similarly, the predicted ΔHf values for HfCl2, HfBr2, HfI2, MoOF4, MoCl6, WOF4, WOCl4, GeO2, SnO2, PbBr4, PbI4, and PbO2 also clearly differ from the tabulated experimental values, again suggesting large inaccuracy in the experimental values. In the case when largely different experimental values are available, we point to the value that is in better agreement with our results. We expect the ΔHf values reported in this work to be quite accurate, and thus, they might be used in thermodynamic calculations, because the effects from core correlation, relativistic effects, and basis set incompleteness were included in the DLPNO-CCSD(T) calculations. T1 and T2 values were thoroughly monitored as indicators of the quality of the reference Hartree-Fock orbitals (T1) and potential multireference character of the systems (T2).

  19. Finite size effects in liquid-gas phase transition of asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Pawlowski, P.

    2001-01-01

    Full text: Since the nuclear equation of state has been studied in astrophysical context as an element of neutron star or super-nova theories - a call for an evidence was produced in experimental nuclear physics. Heavy-ion collisions became a tool of study on thermodynamic properties of nuclear matter. A particular interest has been inspired here by critical behavior of nuclear systems, as a phase transition of liquid-gas type. A lot of efforts was put to obtain an experimental evidence of such a phenomenon in heavy-ion collisions. With the use of radioactive beams and high performance identification systems in a near future it will be possible to extend experimental investigation to asymmetric nuclear systems, where neutron-to-proton ratio is far from the stability line. This experimental development needs a corresponding extension of theoretical studies. To obtain a complete theory of the liquid-gas phase transition in small nuclear systems, produced in violent heavy-ion collisions, one should take into account two facts. First, that the nuclear matter forming nuclei is composed of protons and neutrons; this complicates the formalism of phase transitions because one has to deal with two separate, proton and neutron, densities and chemical potentials. The second and more important is that the surface effects are very strong in a system composed of a few hundreds of nucleons. This point is especially difficult to hold, because surface becomes an additional, independent state parameter, depending strongly on the geometrical configuration of the system, and introducing a non-local term in the equation of state. In this presentation we follow the recent calculation by Lee and Mekjian on the finite-size effects in small (A = 10 2 -10 3 ) asymmetric nuclear systems. A zero-range isospin-dependent Skyrme force is used to obtain a density and isospin dependent potential. The potential is then completed by additional terms giving contributions from surface and Coulomb

  20. Vibrational Spectra of Discrete UO22+ Halide Complexes in the Gas Phase

    International Nuclear Information System (INIS)

    Groenewold, G.S.; Van Stipdonk, Michael J.; Oomens, Jos; De Jong, Wibe A.; Gresham, Garold L.; Mcilwain, Michael

    2010-01-01

    The intrinsic binding of halide ions to the metal center in the uranyl molecule is a topic of ongoing research interest in both the actinide separations and theoretical communities. Investigations of structure in the condensed phases is frequently obfuscated by solvent interactions that can alter ligand binding and spectroscopic properties. The approach taken in this study is to move the uranyl halide complexes into the gas phase where they are free from solvent interactions, and then interrogate their vibrational spectroscopy using infrared multiple photon dissociation (IRMPD). The spectra of cationic coordination complexes having the composition (UO 2 (X)(ACO) 3 ) + (where X = F, Cl, Br and I; ACO = acetone) were acquired using electrospray for ion formation, and monitoring the ion signal from the photoelimination of ACO ligands. The studies showed that the asymmetric ν 3 UO 2 frequency was insensitive to halide identity as X was varied from Cl to I, suggesting that in these pseudo-octahedral complexes, changing the nucleophilicity of the halide did not appreciably alter its binding in the complex. The ν 3 peak in the spectrum of the F-containing complex was 9 cm -1 lower indicating stronger coordination in this complex. Similarly the ACO carbonyl stretches showed that the C=O frequency was relatively insensitive to the identity of the halide, although a modest shift to higher wavenumber was seen for the complexes with the more nucleophilic anions, consistent with the idea that they loosen solvent binding. Surprisingly, the ν 1 stretch was activated when the softer anions Cl, Br and I were present in the complexes. IR studies of the anionic complexes (UO 2 X 3 ) - (where X = Cl - , Br - and I - ) compared the ν 3 UO 2 modes versus halide, and showed that the ν 3 values decreased with increasing anion nucleophilicity. This observation was consistent with DFT calculations that indicated that (UO 2 X 2 ) - -X, and (UO 2 X 2 )·-X - dissociation energies