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1

Acidity of dealuminated ?-zeolites via coupled nh 3stepwise temperature programmed desorption (STPD) and FT-IR spectroscopy  

Microsoft Academic Search

Ammonia stepwise temperature programmed desorption (STPD) and FT-IR spectroscopy have been used to study the acidity of dealuminated ?-zeolites with Si\\/Al ratios in the range of 14.5 to 132. A carefully optimized temperature profile starting at 150 °C (in order to exclude physisorbed NH3) revealed five peaks at about 180 °C, 250 °C, 350 °C, 440 °C, and 540 °C.

Gary M. Robb; Wenmin Zhang; Panagiotis G. Smirniotis

1998-01-01

2

Characterization of the acidity of ultrastable Y, mordenite, and ZSM-12 via NH 3stepwise temperature programmed desorption and Fourier transform infrared spectroscopy  

Microsoft Academic Search

The acidity of ultrastable Y (USY), mordenite, and ZSM-12 of variable Si\\/Al ratios has been characterized by coupling NH3-stepwise temperature programmed desorption (STPD) and FT-IR. The former technique allows us to quantify accurately the ammonia chemisorbed on acid sites of different strengths. In contrast to other acidic oxide catalysts, it was found that protonated zeolites possess distinct limits of acid

Wenmin Zhang; Eric C. Burckle; Panagiotis G. Smirniotis

1999-01-01

3

Temperature Programmed Desorption Study of Graphene Oxide  

NASA Astrophysics Data System (ADS)

Graphene oxide is an electrical insulator that shows potential for use in nanoscale electronic devices. An understanding of the thermal stability of graphene oxide sheets is important since the electrical, chemical, and mechanical properties of graphene oxide will change as it is reduced at elevated temperatures. In this study, graphene oxide films were grown by deposition of an aqueous solution of graphene oxide onto oxygen plasma cleaned silicon nitride on silicon substrates. The thermal stability of these films was studied by temperature programmed desorption under ultra-high vacuum conditions up to 350 ^oC. The primary decomposition components of the films are H2O, CO2 and CO. Desorption of these components starts at ˜70 ^oC and is completed by ˜150^oC. Coverage dependent measurements indicate that the desorption kinetics are second order. An activation energy of 162 meV for CO2 desorption has been determined.

Clark, Nicholas; Field, Daniel; Rieman, Simona; Ventrice, Carl; Jung, Inhwa; Yang, Dongxing; Piner, Richard; Ruoff, Rodney

2009-03-01

4

A dynamic calibration technique for temperature programmed desorption spectroscopy  

NASA Astrophysics Data System (ADS)

A novel, rapid and accurate calibration procedure as a means for quantitative gas desorption measurement by temperature programmed desorption (TPD) spectroscopy is presented. Quantitative measurement beyond the linear regime of the instrument is achieved by associating an instantaneous calibrated molar flow rate of gas to the detector response. This technique is based on fundamental methods, and is independently verified by comparison to the hydrogen desorption capacity of a known standard metal hydride with known stoichiometry. The TPD calibration procedure described here may be used for any pure gas, and the accuracy is demonstrated for the specific case of hydrogen.

Hurst, K. E.; Heben, M. J.; Blackburn, J. L.; Gennett, T.; Dillon, A. C.; Parilla, P. A.

2013-02-01

5

Surface reaction mechanisms of hydrazine on Si(100)-2×1 surface: NH3 desorption pathways  

NASA Astrophysics Data System (ADS)

Multireference as well as single-reference wave functions were adopted to study the surface reaction mechanisms of hydrazine. The initial surface mechanisms resemble those of ammonia and its methyl derivatives. MRMP2 values indicate that the lifetime of initial molecularly adsorbed species should be longer than previously suggested. High energy path as well as low energy path of subsequent surface reactions were found. The theoretical initial surface product of low energy path is consistent with the experimentally suggested structure. Both paths eventually lead to very stable surface products, which are also consistent with the experimentally suggested structures. The reaction channels of the experimentally observed NH3 desorptions were also revealed. It was shown that the high reactivity of hydrazine as compared to ammonia and its methyl derivatives is due to the high nucleophilic ability of the additional nitrogen atom of hydrazine.

Lim, Chultack; Choi, Cheol Ho

2004-01-01

6

Reduction Kinetics of Graphene Oxide Determined by Temperature Programmed Desorption  

NASA Astrophysics Data System (ADS)

Graphene oxide, which is an electrical insulator, shows promise for use in several technological applications such as dielectric layers in nanoscale electronic devices or as the active region of chemical sensors. In principle, graphene oxide films could also be used as a precursor for the formation of large-scale graphene films by either thermal or chemical reduction of the graphene oxide. In order to determine the thermal stability and reduction kinetics of graphene oxide, temperature program desorption (TPD) measurements have been performed on multilayer films of graphene oxide deposited on SiO2/Si(100) substrates. The graphene oxide was exfoliated from the graphite oxide source material by slow-stirring in aqueous solution, which produces single-layer platelets with an average lateral size of ˜10 ?m. From the TPD measurements, it was determined that the decomposition process begins at ˜80 ^oC. The primary desorption products of the graphene oxide films for temperatures up to 300 ^oC are H2O, CO2, and CO, with only trace amounts of O2 being detected. An activation energy of 1.4 eV/molecule was determined by assuming an Arrhenius dependence for the decomposition process.

Ventrice, Carl; Clark, Nicholas; Field, Daniel; Geisler, Heike; Jung, Inhwa; Yang, Dongxing; Piner, Richard; Ruoff, Rodney

2009-10-01

7

The oxidized soot surface: Theoretical study of desorption mechanisms involving oxygenated functionalities and comparison with temperature programed desorption experiments  

Microsoft Academic Search

The desorption mechanism for oxygenated functionalities on soot is investigated by quantum mechanical calculations on functionalized polycyclic aromatic hydrocarbon (PAH) models and compared with recently published temperature programed desorption-mass spectrometry results. Substituents on PAHs of increasing size (up to 46 carbon atoms in the parent PAH) are chosen to reproduce the local features of an oxidized graphenic soot platelet. Initially,

Gianluca Barco; Andrea Maranzana; Giovanni Ghigo; Mauro Causà; Glauco Tonachini

2006-01-01

8

Design and construction of a semiautomatic temperature programmed desorption apparatus for ultrahigh vacuum  

Microsoft Academic Search

A computer-controlled system that allows acquisition of large volumes of temperature programmed desorption data under ultrahigh vacuum conditions has been designed and tested. The vacuum part of the system consists of a sample mounted on a rotation-translation manipulator, a shielded quadrupole mass spectrometer for the desorption flux measurement, and a collimated molecular beam doser for adsorbate delivery. The experiment involves

Petro Kondratyuk; John T. Yates

2005-01-01

9

Interactions of NH3, Coadsorbed with PF3, on Ru(001).  

National Technical Information Service (NTIS)

NH3, coadsorbed with PF3, on Ru(001) has been studied by temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS shows that the P-F stretching frequency decreases in the presence of NH3. This is explained by t...

Y. Zhou Z. M. Liu J. M. White

1990-01-01

10

Temperature-Programmed Desorption of Oxalate from the Goethite Surface  

SciTech Connect

The TPD-FTIR technique was used to investigate the relative thermal stabilities and decomposition reactions of different oxalate complexes adsorbed on the dry goethite surface. The measurements showed that important differences in coordination have a considerable impact on the thermal stability of the surface complexes. Three important stages of desorption were identified from both TPD (Figure 1) and FTIR data in the 300-900 K range. Stage I (300-440 K) corresponds to the desorption of weakly-bound oxalate molecules with decomposition pathways characteristic of oxalic acid. Stage II (440-520 K) corresponds to the dehydration of key surface OH2 groups responsible in stabilizing hydrogen-bonded surface complexes. These species can either decompose via typical oxalic acid decomposition pathways or convert to metal-bonded surface complexes. Finally, Stage III (520-660 K) corresponds to the thermal decomposition of all metal-bonded oxalate complexes, proceeding through a two-electron reduction pathway that converts oxalate to CO2. Experiments in the absence of oxalate were used to assess the contributions from dehydration, dehydroxylation and decarbonation reactions from the goethite bulk.

Boily, Jean F.

2007-08-31

11

Determining desorption pre-exponential factors from temperature-programmed desorption spectra when the surface is nonuniform  

SciTech Connect

To find desorption pre-exponential factors from temperature-programmed desorption (TPD) spectra, we develop procedures using both the TPD spectra and their derivatives. First, an approximate method is derived using peak temperatures. This method is formally identical with one used for determining pre-exponential factors and desorption activation energies when desorptions are energetically uniform. The method can be used when the pre-exponential factor is constant. We next develop an iterative process that also uses peak temperatures, and again is usable when the pre-exponential factor is constant. This iterative approach should give more exact values of pre-exponential factors than the approximate approach. Using the first derivatives of TPD spectra over the entire range of temperatures leads to a second iterative process. This last procedure allows determination of energy-dependent pre-exponential factors. 8 refs., 13 figs.

Brown, L.F.; Chemburkar, R.M.

1991-03-15

12

Interactions of phenylglycine with amorphous solid water studied by temperature-programmed desorption and photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

Temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) have been employed to study the interactions of phenylglycine (PheGly) with amorphous solid water (ASW) nanolayers (10–50 ML). First, the adsorption and growth of PheGly layers on an AlOx/NiAl(110) surface have been examined. After that, mixed PheGly–ASW layers have been grown on the alumina surface at 110 K. Alternatively, PheGly molecules (from submonolayer to multilayer coverages) have been deposited on top of the ASW surfaces. In mixed PheGly–ASW nanolayers the PheGly phase displays hydrophobic behavior and accumulates near the surfaces of the films, while top-deposited PheGly wets the ASW films forming closed overlayers at low coverages. H2O desorption from the PheGly–ASW films is strongly influenced by the PheGly molecules, i.e., the crystallization of ASW is partially inhibited in the vicinity of the amino acid and a lower desorption temperature of H2O molecules than from pure ASW layers was detected. Thicker PheGly overlayers on ASW provide a kinetic restriction to H2O desorption from the underlying ASW layers until the PheGly molecules become mobile and develop pathways for water desorption at higher temperatures. The results are discussed with respect to the previously obtained data for glycine–ASW layered systems. It has been demonstrated that the substitution of the hydrogen atom in glycine with a phenyl group does not lead to detectable changes in the pathways of ASW desorption. However, desorption of PheGly differs from the desorption of glycine from the similarly structured glycine–ASW nanolayers. The differences are interpreted in terms of adsorbate–adsorbate and adsorbate–substrate interactions.

Tzvetkov, George; Netzer, Falko P.

2013-07-01

13

Negative ion formation in electron-stimulated desorption of CF2Cl2 coadsorbed with polar NH3 on Ru(0001).  

PubMed

Photon-induced dissociation of CF2Cl2 (freon-12) in the stratosphere contributes substantially to atmospheric ozone depletion. We report recent results on dissociation and negative ion formation in electron-stimulated desorption (ESD) of CF2Cl2 on Ru(0001), when CF2Cl2 is coadsorbed with a polar molecule (NH3), for electron energies ranging from 50 to 300 eV. Two different time-of-flight methods are used in this investigation: (a) an ESD ion angular distribution detector with wide collection angle and (b) a quadrupole mass spectrometer with narrow collection angle and high mass resolution. Many negative ESD fragments are seen (F-, Cl-, FCl-, CF-, F2-, and Cl2-), whose intensities depend on the surface preparation. Using both detectors we observe a giant enhancement of Cl- and F- yields for ESD of CF2Cl2 coadsorbed with approximately 1 ML of NH3; this enhancement (>10(3) for Cl-) is specific to certain ions, and is attributed to an increased probability of dissociative electron attachment due to "trapped" low-energy secondary electrons, i.e., precursor states of the solvated electron in NH3. In further studies, the influence of polar NH3 spacer layers (1-10 ML) on ESD of top-layer CF2Cl2 is determined, and compared with thick films of condensed CF2Cl2. The magnitudes and energy dependences of the Cl- yields are different in these cases, due to several contributing factors. PMID:15267934

Solovev, S; Kusmierek, D O; Madey, T E

2004-01-01

14

Monte Carlo simulations of temperature-programmed and isothermal desorption from single-crystal surfaces  

SciTech Connect

The kinetics of temperature-programmed and isothermal desorption have been simulated with a Monte Carlo model. Included in the model are the elementary steps of adsorption, surface diffusion, and desorption. Interactions between adsorbates and the metal as well as interactions between the adsorbates are taken into account with the Bond-Order-Conservation-Morse-Potential method. The shape, number, and location of the TPD peaks predicted by the simulations is shown to be sensitive to the binding energy, coverage, and coordination of the adsorbates. In addition, the occurrence of lateral interactions between adsorbates is seen to strongly effect the distribution of adsorbates is seen to strongly effect the distribution of adsorbates on the surface. Temperature-programmed desorption spectra of a single type of adsorbate have been simulated for the following adsorbate-metal systems: CO on Pd(100); H{sub 2} on Mo(100); and H{sub 2} on Ni(111). The model predictions are in good agreement with experimental observation. TPD spectra have also been simulated for two species coadsorbed on a surface; the model predictions are in qualitative agreement with the experimental results for H{sub 2} coadsorbed with strongly bound atomic species on Mo(100) and Fe(100) surfaces as well as for CO and H{sub 2} coadsorbed on Ni(100) and Rh(100) surfaces. Finally, the desorption kinetics of CO from Pd(100) and Ni(100) in the presence of gas-phase CO have been examined. The effect of pressure is seen to lead to an increase in the rate of desorption relative to the rate observed in the absence of gas-phase CO. This increase arises as a consequence of higher coverages and therefore stronger lateral interactions between the adsorbed CO molecules.

Lombardo, S.J. (California Inst. of Tech., Pasadena, CA (USA). Dept. of Chemical Engineering Lawrence Berkeley Lab., CA (USA))

1990-08-01

15

Determination of Acid/Base Properties by Temperature Programmed Desorption (TPD) and Adsorption Calorimetry  

NASA Astrophysics Data System (ADS)

The characterization of the acidity of zeolites and related materials is of great importance for applications of these materials, particularly in the petrochemical industry and environmental sciences. This chapter provides a comparison of the two most widely used techniques for the study of acid/base properties of zeolites, namely temperature-programmed desorption and adsorption calorimetry. The information needed to perform and interpret these experiments as well as advantages and limitations of these methods are summarized. The curves and data obtained for the two most studied zeolites Y and ZSM-5 are discussed, which can be particularly useful for young researchers in this field.

Damjanovi?, Ljiljana; Auroux, Aline

16

TEMPERATURE-PROGRAMMED DESORPTION: PRINCIPLES, INSTRUMENT DESIGN, AND DEMONSTRATION WITH NAALH4  

SciTech Connect

This article is a brief introduction to temperature-programmed desorption (TPD), an analytical technique devised to analyze, in this case, materials for their potential as hydrogen storage materials. The principles and requirements of TPD are explained and the different components of a generic TPD apparatus are described. The construction of a modified TPD instrument from commercially available components is reported together with the control and acquisition technique used to create a TPD spectrum. The chemical and instrumental parameters to be considered in a typical TPD experiment and the analytical utility of the technique are demonstrated by the dehydrogenation of titanium-doped NaAlH{sub 4} by means of thermally programmed desorption.

Stowe, A; Ragaiy Zidan, R

2006-11-07

17

The oxidized soot surface: Theoretical study of desorption mechanisms involving oxygenated functionalities and comparison with temperature programed desorption experiments  

NASA Astrophysics Data System (ADS)

The desorption mechanism for oxygenated functionalities on soot is investigated by quantum mechanical calculations on functionalized polycyclic aromatic hydrocarbon (PAH) models and compared with recently published temperature programed desorption-mass spectrometry results. Substituents on PAHs of increasing size (up to 46 carbon atoms in the parent PAH) are chosen to reproduce the local features of an oxidized graphenic soot platelet. Initially, the study is carried out on unimolecular fragmentation (extrusion, in some cases) processes producing HO, CO, or CO2, in model ketones, carboxylic acids, lactones, anhydrides, in one aldehyde, one peroxyacid, one hydroperoxide, one secondary alcohol, and one phenol. Then, a bimolecular process is considered for one of the carboxylic acids. Furthermore, some cooperative effect which can take place by involving two vicinal carboxylic groups (derived from anhydride hydrolysis) is investigated for other four bifunctionalized models. The comparison between the computed fragmentation (desorption) barriers for the assessed mechanisms and the temperature at which maxima occur in TPD spectra (for HO, CO, or CO2 desorption) offers a suggestion for the assignment of these maxima to specific functional groups, i.e., a key to the description of the oxidized surface. Notably, the computations suggest that (1) the desorption mode from a portion of a graphenic platelet functionalized by a carboxylic or lactone groups is significantly dependent from the chemical and geometric local environment. Consequently, we propose that (2) not all carboxylic groups go lost at the relatively low temperatures generally stated, and (3) lactone groups can be identified as producing not only CO2 but also CO.

Barco, Gianluca; Maranzana, Andrea; Ghigo, Giovanni; Causà, Mauro; Tonachini, Glauco

2006-11-01

18

Effects of surface coordination on the temperature-programmed desorption of oxalate from goethite  

SciTech Connect

The temperature-programmed desorption (TPD) of weakly-bound, hydrogen-bonded and metal-bonded oxalate complexes at the goethite surface was investigated in the 300-900 K range with concerted Fourier Transform Infrared (FTIR) measurements (TPD-FTIR). These reactions took place with the concomitant dehydroxylation reaction of goethite to hematite and decarbonation of bulk-occluded carbonate. The measurements revealed three important stages of desorption. Stage I (300-440 K) corresponds to the desorption of weakly-and/or un-bound oxalate molecules in the goethite powder with a thermal decomposition reaction pathway characteristic of oxalic acid. Stage II (440-520 K) corresponds to a thermally-driven dehydration of hydrogen-bonded surface complexes, leading to a partial desorption via oxalic acid thermal decomposition pathways and to a partial conversion to metal-bonded surface complexes. This latter mechanism led to the increase in FTIR bands characteristic of these complexes. Finally, Stage III (520-660 K) corresponds to the thermal decomposition of the metal-bonded oxalate complex, proceeding through a 2 electron reduction pathway.

Boily, Jean F.; Szanyi, Janos; Felmy, Andrew R.

2007-11-15

19

Temperature programmed desorption characterization of oxidized uranium surfaces: Relation to some gas-uranium reactions  

SciTech Connect

The chemisorption characteristics and surface composition of oxidation overlayers developing on metals when exposed to oxidizing atmospheres are important in determining the protective ability of these layers against certain gas-phase reactions (e.g., corrosion and hydriding). In the present study, a special setup of supersonic molecular beam-temperature-programmed desorption was utilized to determine the different chemisorbed species present on oxidized uranium surfaces. The main identified species included water (in different binding forms) and hydrogen. The latter hydrogen originates from the water-uranium oxidation reaction, which produces uranium dioxide and two types of hydrogen: a near surface hydride and a surface-chemisorbed form that desorbs at a lower temperature than that of the hydride. Assignments of the different water desorption peaks to different binding sites were proposed. In general, four water desorption features were identified (labeled W{sub 0}, W{sub 1}, W{sub 2}, and W{sub 3}, respectively, in the order of increasing desorption temperatures). These features correspond to a reversibly chemisorbed molecular form (W{sub 0}), a more tightly bound water (chemisorbed on different type of oxide sites) or hydroxyl clusters (W{sub 1}), and strongly bounded (possibly isolated) hydroxyl groups (W{sub 2}). The highest temperature peak (W{sub 3}) is related to the formation of complex water-carbo-oxy compounds and is present only on oxidation overlayers, which contain proper chemisorbed carbo-oxy species. The relation of the water and hydrogen thermal release behavior to some problems addressed to certain effects observed in hydrogen-uranium and water-uranium reactions is discussed. For the latter, a microscopic mechanism is proposed.

Danon, A.; Koresh, J.E.; Mintz, M.H.

1999-08-31

20

Characterization of early-stage coal oxidation by temperature-programmed desorption  

SciTech Connect

To obtain representative temperature-programmed desorption (TPD) profiles of young oxidized chars up to 1650{degree}C with minimal reactor wall interferences, the chemistry and physics of four ceramic materials has been critically reviewed. A two-staged experimental apparatus is then uniquely designed to produce chars in an Al{sub 2}O{sub 3} flow reactor with 1-21% O{sub 2} followed by in situ TPD with a SiC tube. Comparison of TPD profiles of oxidized chars with those from pyrolyzed chars and ashes suggests early-stage char oxidation is profoundly influenced by oxygen from three sources: organic oxygen, mineral matters, and gas phase O{sub 2}. Young chars oxidized at 1000{degree}C with less than 0.3 s residence time shows CO desorption peaks during TPD at three distinct temperatures: 730, 1280, and 1560{degree}C. The peaks at 730{degree}C are mainly caused by incomplete devolatilization. The peaks at 1280{degree}C mainly represent desorption of stable surface oxides and incomplete devolatilization. Increasing the gas phase oxidants notably increases the amount of stable surface oxides. The broad peaks between 1400 and 1650{degree}C are attributed to the reactions of oxidants decomposed from minerals and carbon in the char or SiC tube. Gas-phase oxygen shifts these reactions to lower temperatures. Detailed oxygen balance based on the CO and CO{sub 2} yields and elemental compositions of both pyrolysis and oxidized chars reveals that oxygen uptakes are very high, +0.056 mg O per mg of carbon, in chars derived from bituminous coal, whereas lignite chars show negative oxygen uptake, -0.020 mg O per mg of carbon, in char. Indeed, lignite char seems to possess little amount of stable surface oxides other than those contributed by the minerals. The extensive emissions of CO from lignite chars during TPD seem to suggest that either O{sub 2} or minerals promotes the oxygen transfer on char surface and subsequent carbon oxidation. 85 refs., 5 figs., 4 tabs.

Wei-Yin Chen; Guang Shi; Shaolong Wan [University of Mississippi, University, MI (United States). Department of Chemical Engineering

2008-11-15

21

Comparing deuterium retention in tungsten films measured by temperature programmed desorption and nuclear reaction analysis  

NASA Astrophysics Data System (ADS)

Tungsten (W) films with thicknesses ranging between 1 and 12 ?m deposited by magnetron sputtering on silicon substrates were used as a model system for comparing the deuterium (D) retention measured by both temperature programmed desorption (TPD) and nuclear reaction analysis (NRA). Samples were loaded with deuterium ex-situ with an ECR plasma at 370 and 600 K with an energy of 38 eV per deuteron. To avoid diffusion of D into the silicon substrate and to increase adhesion a copper interlayer was applied. The results show that all implanted D atoms were retained exclusively in the W films. The distribution of D is homogenous throughout the W layer with an atomic fraction of 3 ± 0.4 × 10-3. With increasing W thickness the D profile extends to correspondingly larger depths with practically identical D concentration. For W films with a thickness lower than the NRA information depth of about 8 ?m the total retained D amount measured by TPD and NRA is in excellent agreement. As expected, for films thicker than the NRA information depth, TPD deviates from NRA.

Wang, P.; Jacob, W.; Gao, L.; Dürbeck, T.; Schwarz-Selinger, T.

2013-04-01

22

Sum-frequency generation and temperature-programed desorption studies of formic acid on MgO(001) surfaces  

Microsoft Academic Search

Adsorption and decomposition of formic acid on MgO(001) surfaces were studied by means of Sum-Frequency Generation (SFG), Temperature-Programed Desorption (TPD) and Atomic Force Microscopy (AFM). Formic acid was dissociatively adsorbed on MgO(001) surfaces at room temperature. From SFG and TPD measurements, the existence of several different types of formate species was deduced and all species mainly decomposed into CO and

K. Domen; H. Yamamoto; N. Watanabe; A. Wada; C. Hirose

1995-01-01

23

Desorption of H sub 2 O and H sub 2 from steel and LiAlO sub 2 by temperature programmed desorption  

SciTech Connect

Temperature programmed desorption (TPD) measurements with a steel sample tube and helium sweep gas in progress to provide data describing the kinetics of desorption of H{sub 2}O(g) and H{sub 2}(g) from ceramic tritium breeders. Preliminary blank experiments indicated that the steel can be a reactive participant with H{sub 2}O being consumed and H{sub 2} being evolved. There is also evidence of some dissolution of H{sub 2} in the steel. However, it is possible to stabilize the steel in the absence of added H{sub 2} so that useful desorption measurements with H{sub 2}O(g) can be made. Initial work was on the LiA1O{sub 2} {minus} H{sub 2}O(g) system. Fresh samples of LiA1O{sub 2} bear large amounts of absorbed H{sub 2}O. TPD spectra were measured for LiA1O{sub 2} that had been equilibrated in a helium stream with 200 ppm H{sub 2}O(g) at temperatures from 473 to 773 K. Several techniques of data analysis were applied. Questions of possible peak overlap still remain to be resolved. An activation energy for desorption of H{sub 2}O(g) of approximately 120 kJ/mol appears to be associated with the sample equilibrated at 673 K. This result agrees with the values reported in the literature for decomposition of LiOH, and suggests that some sites on LiA1O{sub 2} might resemble sites on Li{sub 2}O on their adsorptive properties. For a 773 K equilibration, the activation energy of desorption appears considerably higher. 6 refs., 4 figs.

Fischer, A.K.; Johnson, C.E.

1989-01-01

24

Tube effects and the kinetics of desorption of H sub 2 O/H sub 2 from LiAlO sub 2 by temperature programmed desorption measurements  

SciTech Connect

Temperature programmed desorption (TPD) measurements are in progress to provide data describing the kinetics of desorption of H{sub 2}O(g) and H{sub 2}(g) from ceramic tritium breeders. Preliminary blank experiments indicated that the steel can be a reactive participant with H{sub 2}O being consumed and H{sub 2} being evolved. There is also evidence of some dissolution of H{sub 2} in the steel. However, it is possible to stabilize the tube in the absence of added H{sub 2} so that useful measurements with H{sub 2}O(g) can be made. Initial work is on the LiAlO{sub 2}-H{sub 2}O(g) system. Fresh samples of LiAlO{sub 2} bear large amounts of adsorbed H{sub 2}O. TPD spectra were measured for LiAlO{sub 2} that had been equilibrated with 200 ppM H{sub 2}O(g) at temperatures from 473 to 773 K. Several techniques of data analysis were applied. There still remain questions of possible peak overlap to resolve for all cases. An activation energy of desorption of H{sub 2}O(g) of approximately 120 kJ/mol appears to be associated with the sample equilibrated at 673 K. When compared with the same value reported in the literature for decomposition of LiOH, this result suggests that some sites on LiAlO{sub 2} might resemble sites on Li{sub 2}O in their adsorptive properties. For the 773 K equilibration, the activation energy of desorption appears considerably higher. 6 refs., 4 figs.

Fischer, A.K.; Johnson, C.E.

1989-01-01

25

Interaction of acetone with single wall carbon nanotubes at cryogenic temperatures: a combined temperature programmed desorption and theoretical study.  

PubMed

The interaction of acetone with single wall carbon nanotubes (SWCNTs) at low temperatures was studied by a combination of temperature programmed desorption (TPD) and dispersion-augmented density-functional-based tight binding (DFTB-D) theoretical simulations. On the basis of the results of the TPD study and theoretical simulations, the desorption peaks of acetone can be assigned to the following adsorption sites: (i) sites with energy of approximately 75 kJ mol (-1) ( T des approximately 300 K)endohedral sites of small diameter nanotubes ( approximately 7.7 A); (ii) sites with energy 40-68 kJ mol (-1) ( T des approximately 240 K)acetone adsorption on accessible interstitial, groove sites, and endohedral sites of larger nanotubes ( approximately 14 A); (iii) sites with energy 25-42 kJ mol (-1) ( T des approximately 140 K)acetone adsorption on external walls of SWCNTs and multilayer adsorption. Oxidatively purified SWCNTs have limited access to endohedral sites due to the presence of oxygen functionalities. Oxygen functionalities can be removed by annealing to elevated temperature (900 K) opening access to endohedral sites of nanotubes. Nonpurified, as-received SWCNTs are characterized by limited access for acetone to endohedral sites even after annealing to elevated temperatures (900 K). Annealing of both purified and as-produced SWCNTs to high temperatures (1400 K) leads to reduction of access for acetone molecules to endohedral sites of small nanotubes, probably due to defect self-healing and cap formation at the ends of SWCNTs. No chemical interaction between acetone and SWCNTs was detected for low temperature adsorption experiments. Theoretical simulations of acetone adsorption on finite pristine SWCNTs of different diameters suggest a clear relationship of the adsorption energy with tube sidewall curvature. Adsorption of acetone is due to dispersion forces, with its C-O bond either parallel to the surface or O pointing away from it. No significant charge transfer or polarization was found. Carbon black was used to model amorphous carbonaceous impurities present in as-produced SWCNTs. Desorption of acetone from carbon black revealed two peaks at approximately 140 and approximately 180-230 K, similar to two acetone desorption peaks from SWCNTs. The characteristic feature of acetone desorption from SWCNTs was peak at approximately 300 K that was not observed for carbon black. Care should be taken when assigning TPD peaks for molecules desorbing from carbon nanotubes as amorphous carbon can interfere. PMID:18613702

Kazachkin, Dmitry; Nishimura, Yoshifumi; Irle, Stephan; Morokuma, Keiji; Vidic, Radisav D; Borguet, Eric

2008-07-10

26

Processes for desorption from LiAlO sub 2 treated with H sub 2 as studied by temperature programmed desorption  

SciTech Connect

The energetics and kinetics of the evolution of H{sub 2}O and H{sub 2} from LiAlO{sub 2} are being studied by the temperature programmed desorption technique. The concentrations of H{sub 2}, H{sub 2}O, N{sub 2}, and O{sub 2} in a helium stream during a temperature ramp are measured simultaneously with a mass spectrometer. Blank experiments with an empty sample tube showed that square wave spikes of H{sub 2} introduced into the helium gas stream were severely distorted by reaction with the tube walls. The tube could be stabilized, however, by sufficiently prolonged heat treatment with H{sub 2} so that H{sub 2} peaks would not be distorted up to approximately 923 K(650{degree}C). The amount of H{sub 2}adsorption/desorption is small compared to the amount of H{sub 2}O adsorption/desorption. After prolonged treatment with helium containing 990 ppm H{sub 2} at 400{degree}C, H{sub 2}O evolution into the He-H{sub 2} stream was observed during 473 to 1023 K (200 to 750{degree}C) ramps at rates of 2 or 5.6 K/min. The different peak shapes reflecting this process were deconvoluted to show that they are composites of only 2 or 3 reproducible processes. The activation energies and pre-exponential terms was evaluated. The different behavior originates in the differences among different surface sites for adsorption. The interpretation of higher temperature peaks (above 873 K (650{degree}C)) must still consider the possibility of contributions from interactions with steel walls. It was found that H{sub 2} enhances evolution of N{sub 2} from the steel. 1 tab., 6 figs., 11 refs.

Fischer, A.K.

1990-01-01

27

The effect of oxygen vacancies on the binding interactions of NH3 with rutile TiO2(110) -1×1  

SciTech Connect

A series of NH3 temperature-programmed desorption (TPD) spectra was taken after the NH3 dose at 70 K on rutile TiO2(110)-1×1 surfaces with the oxygen vacancy (VO) concentrations of ~0% (p-TiO2) and 5% (r-TiO2), respectively, to study the effect of VO’s on the desorption energy of NH3 as a function of the coverage, ?. Our results show that at zero coverage limit, the desorption energy of NH3 on r-TiO2 is 115 kJ/mol, which is 10 kJ/mol less than that on p-TiO2. The desorption energy from the Ti4+ sites decreases with increasing ? due to the repulsive NH3 - NH3 interactions and approaches ~ 55 kJ/mol upon the saturation of Ti4+ sites (? = 1 monolayer, ML) on both p- and r-TiO2. The absolute saturation coverage is determined to be about 10% smaller on r-TiO2 than that on p-TiO2. Further, the trailing edges of the NH3 TPD spectra on the hydroxylated TiO2(110) (h-TiO2) appear to be the same as that on r-TiO2 while those on oxidized TiO2(110) (o-TiO2) shift to higher temperatures. We present the detailed analysis of the results and reconcile the observed differences based on the repulsive adsorbate-adsorbate interactions between neighboring NH3 molecules and the surface charge associated with the presence of VO’s. Besides NH3, no other reaction products are observed in the TPD spectra.

Kim, Boseong; Li, Zhenjun; Kay, Bruce D.; Dohnalek, Zdenek; Kim, Yu Kwon

2012-11-21

28

Interaction between Water Molecules and Zinc Sulfide Nanoparticles Studied by Temperature-Programmed Desorption and Molecular Dynamics Simulations.  

SciTech Connect

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We have investigated the bonding of water molecules to the surfaces of ZnS nanoparticles (2-3 nm sphalerite) using temperature-programmed desorption (TPD). The activation energy for water desorption was derived as a function of the surface coverage through kinetic modeling of the experimental TPD curves. The binding energy of water equals the activation energy of desorption if it is assumed that the activation energy for adsorption is nearly zero. Molecular dynamics (MD) simulations of water adsorption on 3 and 5 nm sphalerite nanoparticles provided insights into the adsorption process and water binding at the atomic level. Water binds with the ZnS nanoparticle surface mainly via formation of Zn-O bonds. As compared with bulk ZnS crystals, ZnS nanoparticles can adsorb more water molecules per unit surface area due to the greatly increased curvature, which increases the distance between adjacent adsorbed molecules. Results from both TPD and MD show that the water binding energy increases with decreasing the water surface coverage. We attribute the increase in binding energy with decreasing surface water coverage to the increasing degree of surface under-coordination as removal of water molecules proceeds. MD also suggests that the water binding energy increases with decreasing particle size due to the further distance and hence lower interaction between adsorbed water molecules on highly curved smaller particle surfaces. Results also show that the binding energy, and thus the strength of interaction of water, is highest in isolated nanoparticles, lower in nanoparticle aggregates, and lowest in bulk crystals. Given that water binding is driven by surface energy reduction, we attribute the decreased binding energy for aggregated as compared to isolated particles to the decrease in surface energy that occurs as the result of inter-particle interactions.

Zhang, Hengzon; Rustad, James R.; Banfield, Jillian F.

2007-05-23

29

UV-Raman spectroscopy, X-ray photoelectron spectroscopy, and temperature programmed desorption studies of model and bulk heterogeneous catalysts  

SciTech Connect

X-ray photoelectron spectroscopy (XPS) and Temperature Programmed Desorption (TPD) have been used to investigate the surface structure of model heterogeneous catalysts in ultra-high vacuum (UHV). UV-Raman spectroscopy has been used to probe the structure of bulk model catalysts in ambient and reaction conditions. The structural information obtained through UV-Raman spectroscopy has been correlated with both the UHV surface analysis and reaction results. The present day propylene and ethylene polymerization catalysts (Ziegler-Natta catalysts) are prepared by deposition of TiCl{sub 4} and a Al(Et){sub 3} co-catalyst on a microporous Mg-ethoxide support that is prepared from MgCl{sub 2} and ethanol. A model thin film catalyst is prepared by depositing metallic Mg on a Au foil in a UHV chamber in a background of TiCl{sub 4} in the gas phase. XPS results indicate that the Mg is completely oxidized to MgCl{sub 2} by TiCl{sub 4} resulting in a thin film of MgCl{sub 2}/TiCl{sub x}, where x = 2, 3, and 4. To prepare an active catalyst, the thin film of MgCl{sub 2}/TiCl{sub x} on Au foil is enclosed in a high pressure cell contained within the UHV chamber and exposed to {approx}1 Torr of Al(Et){sub 3}.

Tewell, Craig R.

2002-08-19

30

Selectivity of dielectric heating: temperature-programmed desorption (TPD) experiments and initiation of thermo-chromatographic pulses.  

PubMed

The occurrence and extent of selective dielectric heating with microwaves (MW) and radio waves (RW) was studied with a variety of model systems using temperature-programmed desorption (TPD). Over a wide pressure and temperature range, selectivity effects were neither found for polar adsorbates (compared to non-polar compounds) nor expressed by an overheating of metal clusters supported on a nearly MW- and RW-transparent support. In contrast, significant temperature gradients between particles consisting of materials with various dielectric losses could be established under certain conditions. The utilization of adsorbates significantly modifying the dielectric properties of a material was investigated as a further approach to initiate selective dielectric heating. Applying water as a coupling medium, a combined heat and mass transport, which we call a thermo-chromatographic pulse, can be created in a packed-bed column consisting of various zeolites. In this case, selective heating of bed zones by more than 100 K was observed. The suitability of a material for the creation of thermo-chromatographic pulses depends on its dielectric properties as well as on its sorption properties with respect to water or other coupling media. The study provided further insight into not only the potential but also the limitations of selective dielectric heating of solid materials relevant to chemical engineering, environmental technology and sorption processing. PMID:19227066

Roland, Ulf; Buchenhorst, Daniel; Kraus, Markus; Kopinke, Frank-Dieter

2008-01-01

31

Characterization of Lewis acid sites on the (100) surface of ?-AlF3: Ab initio calculations of NH3 adsorption  

NASA Astrophysics Data System (ADS)

The current study employs hybrid-exchange density functional theory to show that the Lewis base, NH3, binds to the ?-AlF3 (100) surface with a binding energy (BE) of up to -1.96 eV per molecule. This is characteristic of a strong Lewis acid. The binding of NH3 to the surface is predominately due to electrostatic interactions. There is only a small charge transfer from the NH3 molecule to the surface. The BE as a function of coverage is computed and used to develop a lattice Monte Carlo model which is used to predict the temperature programed desorption (TPD) spectrum. Comparison with experimental TPD studies of NH3 from ?-AlF3 strongly suggests that these structural models and binding mechanisms are good approximations to those that occur on real AlF3 surfaces.

Bailey, C. L.; Wander, A.; Mukhopadhyay, S.; Searle, B. G.; Harrison, N. M.

2008-06-01

32

Characterization of Lewis acid sites on the (100) surface of beta-AlF3: Ab initio calculations of NH3 adsorption.  

PubMed

The current study employs hybrid-exchange density functional theory to show that the Lewis base, NH(3), binds to the beta-AlF(3) (100) surface with a binding energy (BE) of up to -1.96 eV per molecule. This is characteristic of a strong Lewis acid. The binding of NH(3) to the surface is predominately due to electrostatic interactions. There is only a small charge transfer from the NH(3) molecule to the surface. The BE as a function of coverage is computed and used to develop a lattice Monte Carlo model which is used to predict the temperature programed desorption (TPD) spectrum. Comparison with experimental TPD studies of NH(3) from beta-AlF(3) strongly suggests that these structural models and binding mechanisms are good approximations to those that occur on real AlF(3) surfaces. PMID:18554039

Bailey, C L; Wander, A; Mukhopadhyay, S; Searle, B G; Harrison, N M

2008-06-14

33

Low-temperature selective catalytic reduction of NO with NH3 over nanoflaky MnOx on carbon nanotubes in situ prepared via a chemical bath deposition route  

NASA Astrophysics Data System (ADS)

Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD). The SEM, TEM, XRD results and N2 adsorption-desorption analysis indicated that the CNTs were surrounded by nanoflaky MnOx and the obtained catalyst exhibited a large surface area as well. Compared with the MnOx/CNT and MnOx/TiO2 catalysts prepared by an impregnation method, the nf-MnOx@CNTs presented better NH3-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn4+ and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnOx@CNTs. The H2-TPR and NH3-TPD results demonstrated that the nf-MnOx@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnOx@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N2 with NH3. In addition, the nf-MnOx@CNT catalyst also presented favourable stability and H2O resistance.Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD). The SEM, TEM, XRD results and N2 adsorption-desorption analysis indicated that the CNTs were surrounded by nanoflaky MnOx and the obtained catalyst exhibited a large surface area as well. Compared with the MnOx/CNT and MnOx/TiO2 catalysts prepared by an impregnation method, the nf-MnOx@CNTs presented better NH3-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn4+ and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnOx@CNTs. The H2-TPR and NH3-TPD results demonstrated that the nf-MnOx@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnOx@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N2 with NH3. In addition, the nf-MnOx@CNT catalyst also presented favourable stability and H2O resistance. Electronic supplementary information (ESI) available: TEM images, XRD patterns, N2 adsorption-desorption isotherms, TG-DTA curves, in situ time-resolved XRD patterns, stability test and H2O resistance study of the catalysts. See DOI: 10.1039/c3nr02631k

Fang, Cheng; Zhang, Dengsong; Cai, Sixiang; Zhang, Lei; Huang, Lei; Li, Hongrui; Maitarad, Phornphimon; Shi, Liyi; Gao, Ruihua; Zhang, Jianping

2013-09-01

34

Thermal stability of water and hydroxyl on the surface of the Moon from temperature-programmed desorption measurements of lunar analog materials  

NASA Astrophysics Data System (ADS)

The adsorption of molecular water onto lunar analog materials was investigated under ultra-high vacuum with the goal to better understand the thermal stability and evolution of water on the lunar surface. Temperature-programmed desorption (TPD) experiments show that lunar-analog basaltic-composition glass is hydrophobic, with water-water interactions dominating over surface chemisorption. This suggests that lunar agglutinates will tend not to adsorb water at temperatures above where water clusters and multilayer ice forms. The basalt JSC-1A lunar mare analog, which is a complex mixture of minerals and glass, adsorbs water above 180 K with an adsorption profile that extends to 400 K, showing evidence for a continuum of water adsorption sites. Bancroft albite adsorbs more water, more strongly, than JSC-1A, with a well-defined desorption peak near 225 K. This suggests that mineral surfaces will adsorb more water than mare or mature (glassy, agglutinate rich) surfaces and may explain the association of water with fresh feldspathic craters at high latitudes. The activation energies for the thermal desorption of water from these materials were determined, and along with values from the literature, used to model the grain-to-grain migration of water within the lunar regolith. These models suggest that a combination of recombinative desorption of hydroxyl along with molecular desorption of water and its subsequent migration within and out of the regolith may explain observed diurnal variations in the distribution of water and hydroxyl on the illuminated Moon.

Hibbitts, C. A.; Grieves, G. A.; Poston, M. J.; Dyar, M. D.; Alexandrov, A. B.; Johnson, M. A.; Orlando, T. M.

2011-05-01

35

Low-temperature selective catalytic reduction of NO with NH3 over nanoflaky MnOx on carbon nanotubes in situ prepared via a chemical bath deposition route.  

PubMed

Nanoflaky MnOx on carbon nanotubes (nf-MnOx@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH3. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD). The SEM, TEM, XRD results and N2 adsorption-desorption analysis indicated that the CNTs were surrounded by nanoflaky MnOx and the obtained catalyst exhibited a large surface area as well. Compared with the MnOx/CNT and MnOx/TiO2 catalysts prepared by an impregnation method, the nf-MnOx@CNTs presented better NH3-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn(4+) and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnOx@CNTs. The H2-TPR and NH3-TPD results demonstrated that the nf-MnOx@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnOx@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N2 with NH3. In addition, the nf-MnOx@CNT catalyst also presented favourable stability and H2O resistance. PMID:23928911

Fang, Cheng; Zhang, Dengsong; Cai, Sixiang; Zhang, Lei; Huang, Lei; Li, Hongrui; Maitarad, Phornphimon; Shi, Liyi; Gao, Ruihua; Zhang, Jianping

2013-08-09

36

Measurement of the Reversible Hydrogen Storage Capacity of Milligram Ti-6A1-4V Alloy Samples with Temperature Programmed Desorption and Volumetric Techniques  

SciTech Connect

We report the results of a study using temperature programmed desorption (TPD) and a volumetric sorption technique to measure the hydrogen storage capacity of the Ti-6Al-4V alloy. Samples of various sizes and surface treatments were studied to obtain a statistically meaningful value for the maximum hydrogen storage capacity, as well as to understand the effect of sample size, sample oxidation, and hydrogen charging conditions on the measured capacity. We find a maximum reversible hydrogen storage capacity of {approx} 3.76 wt% with hydrogen exposures near ambient temperature and pressure. This value is higher than any reported in the literature previously, possibly due to the utilization of very small particles and rapid hydrogen exposures, which allow for equilibration times of approximately 1 h. Comparison of a variety of samples indicates that the measured hydrogen capacity is affected by surface oxidation. Samples generated in a strongly oxidizing environment exhibit decreased hydrogen uptake. The implications of these results are discussed with regards to previously reported capacity values in the literature.

Blackburn, J. L.; Parilla, P. A.; Gennett, T.; Hurst, K. E.; Dillon, A. C.; Heben, M. J.

2007-01-01

37

Temperature-programmed decomposition desorption of mercury species over activated carbon sorbents for mercury removal from coal-derived fuel gas  

SciTech Connect

The mercury (Hg{sup 0}) removal process for coal-derived fuel gas in the integrated gasification combined cycle (IGCC) process will be one of the important issues for the development of a clean and highly efficient coal power generation system. Recently, iron-based sorbents, such as iron oxide (Fe{sub 2}O{sub 3}), supported iron oxides on TiO{sub 2}, and iron sulfides, were proposed as active mercury sorbents. The H{sub 2}S is one of the main impurity compounds in coal-derived fuel gas; therefore, H{sub 2}S injection is not necessary in this system. HCl is also another impurity in coal-derived fuel gas. In this study, the contribution of HCl to the mercury removal from coal-derived fuel gas by a commercial activated carbon (AC) was studied using a temperature-programmed decomposition desorption (TPDD) technique. The TPDD technique was applied to understand the decomposition characteristics of the mercury species on the sorbents. The Hg{sup 0}-removal experiments were carried out in a laboratory-scale fixed-bed reactor at 80-300{sup o}C using simulated fuel gas and a commercial AC, and the TPDD experiments were carried out in a U-tube reactor in an inert carrier gas (He or N{sub 2}) after mercury removal. The following results were obtained from this study: (1) HCl contributed to the mercury removal from the coal-derived fuel gas by the AC. (2) The mercury species captured on the AC in the HCl{sup -} and H{sub 2}S-presence system was more stable than that of the H{sub 2}S-presence system. (3) The stability of the mercury surface species formed on the AC in the H{sub 2}S-absence and HCl-presence system was similar to that of mercury chloride (HgClx) species. 25 refs., 12 figs., 1 tab.

M. Azhar Uddin; Masaki Ozaki; Eiji Sasaoka; Shengji Wu [Okayama University, Okayama (Japan). Faculty of Environmental Science and Technology

2009-09-15

38

In situ supported MnOx-CeOx on carbon nanotubes for the low-temperature selective catalytic reduction of NO with NH3  

NASA Astrophysics Data System (ADS)

The MnOx and CeOx were in situ supported on carbon nanotubes (CNTs) by a poly(sodium 4-styrenesulfonate) assisted reflux route for the low-temperature selective catalytic reduction (SCR) of NO with NH3. X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD) have been used to elucidate the structure and surface properties of the obtained catalysts. It was found that the in situ prepared catalyst exhibited the highest activity and the most extensive operating-temperature window, compared to the catalysts prepared by impregnation or mechanically mixed methods. The XRD and TEM results indicated that the manganese oxide and cerium oxide species had a good dispersion on the CNT surface. The XPS results demonstrated that the higher atomic concentration of Mn existed on the surface of CNTs and the more chemisorbed oxygen species exist. The H2-TPR results suggested that there was a strong interaction between the manganese oxide and cerium oxide on the surface of CNTs. The NH3-TPD results demonstrated that the catalysts presented a larger acid amount and stronger acid strength. In addition, the obtained catalysts exhibited much higher SO2-tolerance and improved the water-resistance as compared to that prepared by impregnation or mechanically mixed methods.The MnOx and CeOx were in situ supported on carbon nanotubes (CNTs) by a poly(sodium 4-styrenesulfonate) assisted reflux route for the low-temperature selective catalytic reduction (SCR) of NO with NH3. X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD) have been used to elucidate the structure and surface properties of the obtained catalysts. It was found that the in situ prepared catalyst exhibited the highest activity and the most extensive operating-temperature window, compared to the catalysts prepared by impregnation or mechanically mixed methods. The XRD and TEM results indicated that the manganese oxide and cerium oxide species had a good dispersion on the CNT surface. The XPS results demonstrated that the higher atomic concentration of Mn existed on the surface of CNTs and the more chemisorbed oxygen species exist. The H2-TPR results suggested that there was a strong interaction between the manganese oxide and cerium oxide on the surface of CNTs. The NH3-TPD results demonstrated that the catalysts presented a larger acid amount and stronger acid strength. In addition, the obtained catalysts exhibited much higher SO2-tolerance and improved the water-resistance as compared to that prepared by impregnation or mechanically mixed methods. Electronic supplementary information (ESI) available: SEM images and EDS analysis, TEM images, and XPS spectrum of samples. See DOI: 10.1039/c2nr33006g

Zhang, Dengsong; Zhang, Lei; Shi, Liyi; Fang, Cheng; Li, Hongrui; Gao, Ruihua; Huang, Lei; Zhang, Jianping

2013-01-01

39

Secondary ion emission induced by fission fragment impact in CO-NH(3) and CO-NH(3)-H(2)O ices: modification in the CO-NH(3) ice structure.  

PubMed

CO-NH(3) and CO-NH(3)-H(2)O ices at 25-130 K were bombarded by (252)Cf fission fragments ( approximately 65 MeV at the target surface) and the emitted secondary ions were analyzed by time-of-flight mass spectrometry (TOF-SIMS). It is observed that the mass spectra obtained from both ices have similar patterns. The production of hybrid ions (formed from CO and NH(3) molecules) emitted from CO-NH(3) ice has already been reported by R. Martinez et al., Int. J. Mass. Spectrom. 262 (2006) 195; here, the secondary ion emission and the modifications of the CO--NH(3) ice structure during the temperature increase of the ice are addressed. These studies are expected to throw light on the sputtering from planetary and interstellar ices and the possible formation of new organic molecules in CO-NH(3)-H(2)O ice by megaelectronvolt ion bombardment. The presence of water in the CO-NH(3) ice mixture generates molecular ion series such as (NH(3))(p-q)(H(2)O)(q)CO(+) and replaces the cluster series (NH(3))(n)NH(4) (+) emission by the hybrid series (NH(3))(I-i)(H(2)O)(i=1, 2...I)H(+). The distribution of NH(3) and H(2)O molecules within the cluster groups indicates that ammonia and water mix homogeneously in the icy condensate at T = 25 K. The desorption yield distribution of the cluster series (NH(3))(n)NH(4) (+) is described by the sum of two exponential functions: one, slow-decreasing, attributed to the fragmentation of the solid target into clusters; and another, fast-decreasing, due to a local sublimation followed by recombination of ammonia molecules. The analysis of the time-temperature dependence of these two yield components gives information on the formation process of molecular ions, the transient composition of the ice target and structural changes of the ice. Data suggest that the amorphous and porous structure of the NH(3) ice, formed by the condensation of the CO--NH(3) gas at T = 25 K, survives CO sublimation until the occurrence of a phase transition around 80 K, which produces a more fragile ice structure. PMID:17902107

Martinez, R; Farenzena, L S; Iza, P; Ponciano, C R; Homem, M G P; de Brito, A Naves; Wien, K; da Silveira, E F

2007-10-01

40

Evaluation of solid lubricants: temperature programmed desorption of MOS/sub 2/ on molybdenum and of ion-implanted MOS/sub 2/ on molybdenum. Final report  

SciTech Connect

Thermal programmed desorption (TPD) is utilized in order to assess the lubricating properties of metal dichalcogenide films applied to a number of metal substrates. TPD spectra documenting desorption and decomposition products were analyzed for MoS/sub 2/ burnished on molybdenum metal with and without subsequent 86-kV nitrogen ion implantation. Desorption order, rate, energy, and the pre-exponential of evolved lubricant and nitrogen species from the molybdenum substrates were determined. The surface chemistry of heated lubricant-substrate system was investigated by means of x-ray photoelectron spectroscopy (XPS).

Burns, R.P.; Piece, D.E.; Dauplaise, H.M.; Gabriel, K.A.; Mizerka, L.J.

1988-11-01

41

Plasma-assisted CuO/CeO2/TiO2-?-Al2O3 catalysts for NO + CH4 reaction and NO temperature programmed desorption studies  

NASA Astrophysics Data System (ADS)

The removal of NO and CH4 has been studied with a hybrid system integrating plasma activation and four Cu-based catalysts. The best catalytic performance was observed for catalysts obtained from CuO/CeO2/TiO2/?-Al2O3.The efficiency of NO removal decreased with the order: 12%CuO/10%CeO2/15%TiO2/?-Al2O3 > 12%CuO/15%TiO2/?-Al2O3 > 12%CuO/?-Al2O3 > 12% CuO/TiO2. Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD) Temperature-programmed reduction (H2-TPR) and NO temperature-programmed desorption (NO-TPD) experiments were carried out to gain insight into the synergetic effects with the catalysts. The results revealed that copper species existed as bulk CuO crystalline for all the catalysts, H2-TPR suggested that the Cu2+ incorporated TiO2 or CeO2 lattice and crystalline CuO might be the most active component for NO removal, and NO-TPD studies indicated that 12%CuO/10%CeO2/15%TiO2/?-Al2O3 catalyst had lower NO desorption temperature and larger peak area, which seemed to be responsible for the better catalytic activity over NO + CH4 reactions than other catalysts.

Li, Huijuan; Jiang, Xiaoyuan; Zheng, Xiaoming

2013-09-01

42

Adsorption and decomposition of NH3 on Ir(111): A density functional theory study  

NASA Astrophysics Data System (ADS)

The adsorption and decomposition of NH3 on Ir(111) have been studied using the density functional theory calculations. The recombinative nitrogen desorption has also been investigated. The configurations and stability of NHx(x = 0–3) species have been performed using frequency analysis. The corresponding reaction energies, the activation energies and the structure of the transition states have been determined and analyzed in detail. Including the zero point energy correction, the calculated activation barrier energy for NHx(x = 1–3) dehydrogenation is between 0.94 eV and 1.05 eV, and that for the recombination desorption of N2 is 1.55 eV, which indicates that the N2 recombinative desorption is the rate-limiting step for the NH3 decomposition on Ir(111). The NH3 desorption energy (0.82 eV) is lower than the NH3 dehydrogenation barrier, which indicates that the ammonia rather desorbs than dissociates from a thermodynamic point of view, consistent with the experimental results. But the competition between desorption and dissociation can be controlled in practice via the applied pressure and temperature.

Huang, Wuying; Cheng, Chun; Feng, Eryin

2013-10-01

43

NH3 observations in outflows (Sepulveda+, 2011)  

NASA Astrophysics Data System (ADS)

We present the results of the observations of the (J,K)=(1,1) and the (J,K)=(2,2) inversion transitions of the NH3 molecule towards a large sample of 40 regions with molecular or optical outflows, using the 37m radio telescope of the Haystack Observatory. We detected NH3 emission in 27 of the observed regions and we mapped this emission in 25 of them. Additionally, we searched for the 616-523 H2O maser line towards six regions, detecting H2O maser emission in two of them. We estimate the physical parameters of the regions mapped in NH3 and, for each particular region, we analyze the distribution of high density gas and its relationship with the presence of young stellar objects We confirm with a larger sample of regions that the NH3 line emission is more intense towards molecular outflow sources than towards sources with optical outflow, suggesting a possible evolutionary scheme in which young stellar objects associated with molecular outflows lose progressively their neighboring high-density gas, weakening both the NH3 emission and the molecular outflow in the process, and making optical jets more easily detectable as the total amount of gas decreases. (6 data files).

Sepulveda, I.; Anglada, G.; Estalella, R.; Lopez, R.; Girart, J. M.; Yang, J.

2010-11-01

44

A study of the reactions of ethanol on CeO{sub 2} and Pd/CeO{sub 2} by steady state reactions, temperature programmed desorption, and in situ FT-IR  

SciTech Connect

The reaction of ethanol on unreduced and H{sub 2}-reduced CeO{sub 2} and 1 wt% Pd/CeO{sub 2} has been investigated by steady state reactions, temperature programmed desorption (TPD), and in situ Fourier transform infrared (FT-IR) spectroscopy. Steady state reactions have shown a zero reaction order dependency for diatomic oxygen at and above 20%, while the addition of Pd to CeO{sub 2} decreases the apparent activation energy of the reaction from 75 kJ/mol on CeO{sub 2} alone to 40 kJ/mol (Pd/CeO{sub 2}). TPD experiments following ethanol adsorption on both CeO{sub 2} and Pd/CeO{sub 2} have shown desorption profiles corresponding to unreacted ethanol and various reaction and decomposition products (acetaldehyde, acetone, CO, CO{sub 2}, and methane). Ethanol conversion to reaction products was increased by the addition of Pd, from 15 to 30% on CeO{sub 2} and H{sub 2}-reduced CeO{sub 2}, to 71 and 63% on Pd/CeO{sub 2} and H{sub 2}-reduced Pd/CeO{sub 2}, respectively.

Yee, A.; Morrison, S.J.; Idriss, H. [Univ. of Auckland (New Zealand)

1999-09-10

45

CO interaction with ultrathin MgO films on a Mo(100) surface studied by infrared reflection--absorption spectroscopy, temperature programmed desorption, and x-ray photoelectron spectroscopy  

SciTech Connect

The interaction of CO with MgO ultrathin films grown on a Mo(100) surface is studied using infrared reflection--absorption spectroscopy, temperature programmed thermal desorption (TPD), and x-ray photoelectron spectroscopy. CO adsorbed on 7 ML of MgO shows an infrared band at 2178 cm{sup {minus}1}. This blue-shift of the CO stretching frequency relative to that of CO in the gas phase (2143 cm{sup {minus}1}) is attributed to electron charge transfer from the CO 5{sigma} orbital to the MgO surface. It is further shown that CO adsorption induces a 0.4 eV shift in the Mg(2{ital p}) and O(1{ital s}) core levels of the MgO thin films to lower binding energy, consistent with the charge transfer from CO molecules to the MgO thin films. The TPD spectra indicate that CO molecules on the MgO thin films desorb in the 100--180 K sample temperature range. The CO adsorption heat on 7 ML of MgO is deduced to be 9.9 kcal/mol using an isothermal adsorption method.

He, J.; Corneille, J.S.; Estrada, C.A.; Wu, M.; Goodman, D.W. (Department of Chemistry, Texas A M University, College Station, Texas 77843-3255 (United States))

1992-07-01

46

Structural phase transitions in the perovskite-type layer compounds NH3(CH2)3NH3CdCl4, NH3(CH2)4NH3MnCl4, and NH3(CH2)5NH3CdCl4  

Microsoft Academic Search

The structural phase transitions in the perovskite-type layer-structure compounds [NH3(CH2)3NH3]CdCl4 (Tc=375 K), [NH3(CH2)4NH3]MnCl4 (Tc=382 K), and [NH3(CH2)5NH3]CdCl4 (Tc=338 K) have been studied by 35Cl and deuteron quadrupole resonance spectroscopy, birefringence, and dilatation measurements, optical-domain investigations and group-theoretical considerations. The results show that this transition, which is for all three compounds of second order, is basically a dynamic order-disorder transition of

R. Kind; S. Plesko; P. Günter; J. Roos; J. Fousek

1981-01-01

47

Temperature Programmed Desorption Study of Graphene Oxide  

Microsoft Academic Search

Graphene oxide is an electrical insulator that shows potential for use in nanoscale electronic devices. An understanding of the thermal stability of graphene oxide sheets is important since the electrical, chemical, and mechanical properties of graphene oxide will change as it is reduced at elevated temperatures. In this study, graphene oxide films were grown by deposition of an aqueous solution

Nicholas Clark; Daniel Field; Simona Rieman; Carl Ventrice; Inhwa Jung; Dongxing Yang; Richard Piner; Rodney Ruoff

2009-01-01

48

The decomposition and chemistry of Ru3(CO)12 on TiO2(1 1 0) studied with X-ray photoelectron spectroscopy and temperature programmed desorption  

NASA Astrophysics Data System (ADS)

The decomposition process of triruthenium dodecacarbonyl (Ru3(CO)12) on single crystal TiO2(1 1 0) has been investigated using synchrotron-based high resolution photoemission spectroscopy and temperature programmed desorption (TPD). Ruthenium carbonyl adsorbs molecularly on TiO2(1 1 0) at 100 K. When dosing at room temperature, the molecule dissociatively adsorbs forming a Ru3(CO)m (m ? 10) species on the surface. TPD spectra for ruthenium carbonyl dosed at 100 K and 300 K are quite different in peak numbers and shape, indicating that the ruthenium carbonyl decomposition is sensitive to the preparation procedure. Both TPD and photoemission demonstrate that around 700 K, the decarbonylation process is completed yielding almost pure Ru particles. A small amount of CO adsorbs on the obtained Ru particles after large CO exposures (60 100 L) at 300 K. The Ru particles can be oxidized to form RuO2 at 600 K with an O2 pressure of ˜1 × 10-6 Torr (>400 L exposure). In addition, the chemical activity of the Ru metal particles dispersed on TiO2(1 1 0) has also been examined with SO2 and compared to that of a Ru(0 0 1) single crystal. SO2 is easily decomposed by the Ru particles at room temperature, producing S and O adatoms. SO4 is the main product of the reaction of SO2 with the titania support, and the presence of the Ru particles favors a SO4,ads ? Sads + nOads + mO2,gas transformation at elevated temperature.

Zhao, Xueying; Hrbek, Jan; Rodriguez, José A.

2005-01-01

49

Theoretical and experimental analysis of ammonia ionic clusters produced by 252Cf fragment impact on an NH3 ice target.  

PubMed

Positive and negatively charged ammonia clusters produced by the impact of (252)Cf fission fragments (FF) on an NH(3) ice target have been examined theoretical and experimentally. The ammonia clusters generated by (252)Cf FF show an exponential dependence of the cluster population on its mass, and the desorption yields for the positive (NH(3))(n)NH(4)(+) clusters are 1 order of magnitude higher than those for the negative (NH(3))(n)NH(2)(-) clusters. The experimental population analysis of (NH(3))(n)NH(4)(+) (n = 0-18) and (NH(3))(n)NH(2)(-) (n = 0-8) cluster series show a special stability at n = 4 and 16 and n = 2, 4, and 6, respectively. DFT/B3LYP calculations of the (NH(3))(0)(-)(8)NH(4)(+) clusters show that the structures of the more stable conformers follow a clear pattern: each additional NH(3) group makes a new hydrogen bond with one of the hydrogen atoms of an NH(3) unit already bound to the NH(4)(+) core. For the (NH(3))(0)(-)(8)NH(2)(-) clusters, the DFT/B3LYP calculations show that, within the calculation error, the more stable conformers follow a clear pattern for n = 1-6: each additional NH(3) group makes a new hydrogen bond to the NH(2)(-) core. For n = 7 and 8, the additional NH(3) groups bind to other NH(3) groups, probably because of the saturation of the NH(2)(-) core. Similar results were obtained at the MP2 level of calculation. A stability analysis was performed using the commonly defined stability function E(n)(-)(1) + E(n)(+1) - 2E(n), where E is the total energy of the cluster, including the zero point correction energy (E = E(t) + ZPE). The trend on the relative stability of the clusters presents an excellent agreement with the distribution of experimental cluster abundances. Moreover, the stability analysis predicts that the (NH(3))(4)NH(4)(+) and the even negative clusters [(NH(3))(n)NH(2)(-), n = 2, 4, and 6] should be the most stable ones, in perfect agreement with the experimental results. PMID:16913675

Fernandez-Lima, F A; Ponciano, C R; Chaer Nascimento, M A; da Silveira, E F

2006-08-24

50

NH3 observations of southern cold cores  

NASA Astrophysics Data System (ADS)

We propose an NH3 spectral line study of southern massive star formation sources that have been mapped in millimetre continuum emission using the SIMBA bolometer on the SEST. Following a multiwavelength investigation into these cores, using followup and existing submillimetre continuum observations as well as archival infrared data, we have drawn spectral energy distribution (SED) diagrams for the cores. SED profiling reveals source specific parameters such as their temperature and luminosity. Analysis of our SED fits indicates a differentiation in temperature for cores devoid of methanol maser sources and/or UC HII regions compared to those associated with these objects. This has led us to propose that this temperature differentiation is indicative of an evolutionary sequence for the cores in our sample. We now need an independent determination of the temperature of the cores in order to test the robustness of our SED fits and hypotheses drawn from these fits. A systematic determination of the temperature of all the cores in the sample will allow determination of the temperature and subsequent analysis of cores without enough data to SED profile. Ammonia is an excellent molecular cloud thermometer and is perfectly suited to this work.

Hill, Tracey; Cunningham, Maria; Burton, Michael; Minier, Vincent

2008-04-01

51

Can aluminum nitride nanotubes detect the toxic NH3 molecules?  

NASA Astrophysics Data System (ADS)

The sensitivity of aluminum nitride nanotubes (AlNNTs) to NH3 molecules was investigated using DFT calculations. It was found that NH3 molecule cannot be detected by pristine AlNNTs, since it cannot change the HOMO-LUMO energy gap (Eg) of the tube upon adsorption process. Our results demonstrated that doping an oxygen atom in the vicinity of adsorption site makes the AlNNT electrical conductivity strongly sensitive to the NH3 molecule. It suggests that O-doped AlNNT would be a potential candidate for the NH3 molecule detection. The present results provide guidance to experimental scientists in developing nanotube-based chemical sensors.

Ahmadi Peyghan, Ali; Omidvar, Akbar; Hadipour, Nasser L.; Bagheri, Zhargham; Kamfiroozi, Mohammad

2012-04-01

52

NH3 Production In Comet C/2002 T7 LINEAR  

NASA Astrophysics Data System (ADS)

We observed Comet C/2002 T7 LINEAR (C/T7) from 3-9 May 2004 using CSHELL at the NASA/IRTF. High-resolution spectra of parent volatiles were acquired, emphasizing the oxygen, hydrocarbon, and nitrile chemistry. A major goal was to detect and measure the relative abundance of NH3. At infrared wavelengths, NH3 is difficult to detect since it requires a significant geocentric velocity to shift the strongest NH3 emissions out of the terrestrial atmospheric water absorption. The high Doppler shift (- 65 km/s) of C/T7 during early May made it an excellent target for searching NH3. Several lines of the Q-branch and R-branch of the ?1 band were detected. NH3 is the dominant (observable) nitrogen-containing volatile in comets, present at 1% relative to water. Previously at infrared wavelengths, a single line of the ?1 band near 3-?m was detected in comet C/1995 O1 Hale-Bopp, and a more secure infrared detection was achieved in 153P/Ikeya-Zhang. Our 153P NH3 spectra showed that the NH3 molecule was not rotationally relaxed as previously thought and that a different model was needed to predict line g-factors. Our goal for observing NH3 in C/T7 was to observe a range of rotational levels and transitions to test a newer rotationally equilibrated model for NH3. This paper presents results of that test based on spectra obtained for C/T7. We present production rates and relative abundances to water for C/T7 and we apply this model to our other NH3 detections from past comets. We also compare our results with NH3 production rates reported from radio observations by other groups. We gratefully acknowledge support from the NSF RUI Program to KM-S and the NASA PAST to MJM, MAD, and NDR.

Magee-Sauer, Karen P.; Feuss, J. W.; Dello Russo, N.; DiSanti, M. A.; Bonev, B. P.; Gibb, E. L.; Villanueva, G. L.; Anderson, W. M.; Mumma, M. J.

2006-09-01

53

Photoionization of Yb(NH3)n complexes.  

PubMed

The ionization energies of complexes between a rare-earth metal (Yb) and ammonia were measured for the first time. Using photoionization mass spectrometry under molecular-beam conditions, the adiabatic ionization energies of Yb(NH3)n were determined for n=1-10. Ab initio calculations were also carried out in support of this work and were found to be in excellent agreement with experiment. The combined findings from theory and experiment are consistent with formation of "interior" complexes in which the Yb atom is embedded within a shell of NH3 molecules, rather than sitting on the surface of an (NH3)n cluster. The calculations also suggest that Yb can accommodate up to eight NH3 molecules in its first solvation shell before steric repulsion makes occupancy of the second solvation shell more favourable energetically. The experimental ionization data are consistent with this prediction, as demonstrated by below-trend adiabatic ionization energies for the n=9 and 10 complexes. The ionization energies of Yb(NH3)n complexes closely follow those for complexes of alkali metal atoms with NH3, which suggests that a valence electron will eventually detach from the Yb atom to form a solvated electron in Yb(NH3)n when n is sufficiently large. PMID:23090714

Guttridge, Matthew J; Don, Sadna H; Ellis, Andrew M

2012-10-22

54

Herschel/HIFI deepens the circumstellar NH3 enigma  

NASA Astrophysics Data System (ADS)

Context. Circumstellar envelopes (CSEs) of a variety of evolved stars have been found to contain ammonia (NH3) in amounts that exceed predictions from conventional chemical models by many orders of magnitude. Aims: The observations reported here were performed in order to better constrain the NH3 abundance in the CSEs of four, quite diverse, oxygen-rich stars using the NH3 ortho JK = 10-00 ground-state line. Methods: We used the Heterodyne Instrument for the Far Infrared aboard Herschel to observe the NH3 JK = 10-00 transition near 572.5 GHz, simultaneously with the ortho-H2O JKa , Kc = 11,0 - 10,1 transition, toward VY CMa, OH 26.5+0.6, IRC+10420, and IK Tau. We conducted non-LTE radiative transfer modeling with the goal to derive the NH3 abundance in these objects' CSEs. For the last two stars, Very Large Array imaging of NH3 radio-wavelength inversion lines were used to provide further constraints, particularly on the spatial extent of the NH3-emitting regions. Results: We find remarkably strong NH3 emission in all of our objects with the NH3 line intensities rivaling those of the ground state H2O line. The NH3 abundances relative to H2 are very high and range from 2×10-7 to 3×10-6 for the objects we have studied. Conclusions: Our observations confirm and even deepen the circumstellar NH3 enigma. While our radiative transfer modeling does not yield satisfactory fits to the observed line profiles, it does lead to abundance estimates that confirm the very high values found in earlier studies. New ways to tackle this mystery will include further Herschel observations of more NH3 lines and imaging with the Expanded Very Large Array. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendix A (page 5) is only available in electronic form at http://www.aanda.org

Menten, K. M.; Wyrowski, F.; Alcolea, J.; De Beck, E.; Decin, L.; Marston, A. P.; Bujarrabal, V.; Cernicharo, J.; Dominik, C.; Justtanont, K.; de Koter, A.; Melnick, G.; Neufeld, D. A.; Olofsson, H.; Planesas, P.; Schmidt, M.; Schöier, F. L.; Szczerba, R.; Teyssier, D.; Waters, L. B. F. M.; Edwards, K.; Olberg, M.; Phillips, T. G.; Morris, P.; Salez, M.; Caux, E.

2010-10-01

55

Biodegradation of monohalogenated alkanes by soil NH 3 -oxidizing bacteria  

Microsoft Academic Search

.   Although cooxidative biodegradation of monohalogenated hydrocarbons has been well studied in the model NH3-oxidizing bacterium, Nitrosomonas europaea, virtually no information exists about cooxidation of these compounds by native populations of NH3-oxidizing bacteria. To address this subject, nitrifying activity was stimulated to 125–400 nmol NO3\\u000a – produced g–1 soil h–1 by first incubating a Ca(OH)2-amended, silt loam soil (pH 7.0±0.2) at field

K. N. Duddleston; D. J. Arp; P. J. Bottomley

2002-01-01

56

Physical Temperature Measurements of L1551 from NH3 Observations  

NASA Astrophysics Data System (ADS)

We present NH3 and HC7N images of dark cloud L1551 produced from archive observations of the Robert C. Byrd Green Bank Telescope (GBT). The observations were fully calibrated with the GBT pipeline, and the NH3 line strengths are used to compute the physical temperature and number density of NH3 in the region. The observations of dark cloud L1551 reveal regions of strong emission of NH3 (1,1) emission and much weaker emission of NH3 (2,2) and HC7N J=21-20 lines. We were able to determine a physical-temperature range of 11 to 19 Kelvin for this cloud, but feel that the methods used to obtain these data are applicable beyond this single object. Therefore, we further present our method for using the NH3 (1,1) line fits to constrain model fits of the density, velocity, and temperature distributions of the other transitions. These data were produced using the spectral-line data-reduction pipeline and are provided as examples of data available from the GBT archive.

Towner, Allison P.; Hosmer, L.; Langston, G.

2013-01-01

57

Synthesis, structures and hydrogen storage properties of two new H-enriched compounds: Mg(BH4)2(NH3BH3)2 and Mg(BH4)2·(NH3)2(NH3BH3).  

PubMed

The synthesis, crystal structure and dehydrogenation performances of two new H-enriched compounds, Mg(BH4)2(NH3BH3)2 and Mg(BH4)2·(NH3)2(NH3BH3), are reported. Due to the introduction of ammonia ligands, the Mg(BH4)2·(NH3)2(NH3BH3) exhibits dramatically improved dehydrogenation properties over its parent compound. PMID:24002106

Chen, Xiaowei; Yuan, Feng; Gu, Qinfen; Yu, Xuebin

2013-09-24

58

The thermal reactivity of HCN and NH3 in interstellar ice analogues  

NASA Astrophysics Data System (ADS)

HCN is a molecule central to interstellar chemistry, since it is the simplest molecule containing a carbon-nitrogen bond and its solid state chemistry is rich. The aim of this work was to study the NH3 + HCN ? NH+4CN- thermal reaction in interstellar ice analogues. Laboratory experiments based on Fourier transform infrared spectroscopy and mass spectrometry were performed to characterize the NH+4CN- reaction product and its formation kinetics. This reaction is purely thermal and can occur at low temperatures in interstellar ices without requiring non-thermal processing by photons, electrons or cosmic rays. The reaction rate constant has a temperature dependence of k(T) = 0.016+ 0.010- 0.006 s^{-1}exp (-2.7± 0.4 text{kJ mol}^{-1}/RT) when NH3 is much more abundant than HCN. When both reactants are diluted in water ice, the reaction is slowed down. We have estimated the CN- ion band strength to be A_{text{CN}^-} = 1.8 ± 1.5 × 10-17 cm molecule-1 at both 20 and 140 K. NH+4CN- exhibits zeroth-order multilayer desorption kinetics with a rate of k_{text{des}}(T) = 1028 molecule cm-2 s^{-1}exp (-38.0± 1.4text{ kJ mol}^{-1}/RT). The NH3 + HCN ? NH+4CN- thermal reaction is of primary importance because (i) it decreases the amount of HCN available to be hydrogenated into CH2NH, (ii) the NH+4 and CN- ions react with species such as H2CO and CH2NH to form complex molecules and (iii) NH+4CN- is a reservoir of NH3 and HCN, which can be made available to a high-temperature chemistry.

Noble, J. A.; Theule, P.; Borget, F.; Danger, G.; Chomat, M.; Duvernay, F.; Mispelaer, F.; Chiavassa, T.

2013-02-01

59

Circumstellar envelope of W3(OH) - NH3 observations  

SciTech Connect

Observations of absorption in the 1.3 cm (J,K) = (1,1) amd (2,2) lines of NH3 toward the ultracompact H II region W3(OH) made at subarcsecond resolution with the VLA are reported. Maps of optical depth, beam-filling factor, column density, and rotational temperature are presented. The NH3 absorption is similar to the OH maser emission in velocity, extent, and location, a result which suggests that both species are constituents of the same clumpy molecular envelope. The optical depths are nearly constant across the maps, while the beam-filling factors and the (2,2)-(1,1) rotational temperature decrease from west to east. The NH3 maps and the OH maser results indicate that the thermal and turbulent pressures in the ultracompact H II region are comparable to the magnetic and ram pressures from the surrounding neutral material that appears to be falling inward. 27 references.

Reid, M.J.; Myers, P.C.; Bieging, J.H.

1987-01-01

60

Urban NH3 levels and sources in a Mediterranean environment  

NASA Astrophysics Data System (ADS)

Urban NH3 concentrations were mapped in Barcelona (Spain) by means of passive samplers (dosimeters). Average NH3 levels were 9.5 ?g m-3 in summer and 4.4 ?g m-3 in winter, higher than those reported in other urban background sites in Europe, this being especially notable in summer. During this season, values were significantly higher at urban background than at traffic sites, probably indicating the impact of emissions from biological sources, such as humans, sewage systems and garbage containers. Thus, the volatilization of NH3 from the aerosol phase seems to be significant enough during summer to dominate over traffic emissions. Conversely, in winter levels were higher at traffic sites, suggesting a contribution from vehicle emissions. Indeed, NH3 levels decreased by 55% with increasing distance (50 m) to the direct emissions from traffic. A significant correlation between NH3 concentrations averaged for the different districts of the city and the number of waste containers per hm2 was also obtained, highlighting the necessity for controlling and reducing the emissions from garbage collection systems. The urban topography of the Barcelona historical city centre, characterised by narrow streets with a high population density, seemed to exert a strong influence on NH3 levels, with levels reaching up to 30 ?g m-3 as a consequence of limited dispersion and ventilation conditions. The impact of the sewage system emissions was also detected with an increase of levels when measuring immediately above the source, even though further studies are required to evaluate the relevance of these emissions.

Reche, Cristina; Viana, Mar; Pandolfi, Marco; Alastuey, Andrés; Moreno, Teresa; Amato, Fulvio; Ripoll, Anna; Querol, Xavier

2012-09-01

61

A Sensitive Survey of Ammonia (NH3) in Comets  

NASA Astrophysics Data System (ADS)

Being the fully reduced form of nitrogen, ammonia (NH3) is a key molecule for understanding the nitrogen chemistry in comets and to properly characterize the primordial conditions under which these icy bodies formed. Yet, its abundance has not been well characterized, even though NH3 is a major reservoir of volatile nitrogen in comets. To date the abundance has been directly measured in only 10 comets, all at radio and infrared wavelengths. This small sample is largely due to the difficulty in measuring emission from NH3 since its emission is normally weak, can be affected by terrestrial extinction, and (without sufficient spectral resolution) is not resolved from other volatile cometary emissions. In this paper, we present a search for NH3 in seven comets using archival data acquired by our Team using the NIRSPEC instrument at the Keck-2 telescope and the CSHELL instrument at the NASA Infrared Telescope Facility, both atop Mauna Kea, HI. Using an updated fluorescence model that is based on millions of ammonia spectral lines (Villanueva et al., in prep.), we present relative abundances of NH3 with respect to H2O. We find the relative abundance of NH3/H2O varies from 0.3% to 1.6% in these seven comets, and we compare this indicator with other properties measured for these comets (isotopic fractionation and mixing ratios of selected primary volatiles). We gratefully acknowledge support from NASA’s Postdoctoral Program (LP), the NASA Astrobiology Institute (PI MJM), NASA’s Planetary Astronomy (PI GLV; PI MJM; PI DiSanti) and Planetary Atmospheres (PI DiSanti, PI Villanueva) programs, and from NSF Planetary Astronomy program (PI BPB).

Magee-Sauer, Karen P.; Villanueva, G. L.; Bonev, B. P.; Paganini, L.; DiSanti, M. A.; Mumma, M. J.

2012-10-01

62

INVERSE MODEL ESTIMATION AND EVALUATION OF SEASONAL NH 3 EMISSIONS  

EPA Science Inventory

The presentation topic is inverse modeling for estimate and evaluation of emissions. The case study presented is the need for seasonal estimates of NH3 emissions for air quality modeling. The inverse modeling application approach is first described, and then the NH...

63

Crystal structure and thermal behavior of two new organic monosulfates NH3(CH2)5NH3SO4 1.5H2O and NH3(CH2)9NH3SO4 H2O  

NASA Astrophysics Data System (ADS)

The chemical preparation, the calorimetric studies and the crystal structure are given for two new organic sulfates NH3(CH2)5NH3SO4 1.5H2O (DAP-S) and NH3(CH2)9NH3SO4·H2O (DAN-S). DAP-S is monoclinic P21/n with unit cell dimensions: a=11.9330(2) Å; b=10.9290(2) Å; c=17.5260(2) Å; ?=101.873(1)°; V=2236.77(6) Å3; and Z=8. Its atomic arrangement is described as inorganic layers of SO42- units and water molecules separated by organic chains. DAN-S is monoclinic P21/c with unit cell parameters: a=5.768(2) Å; b=25.890(10) Å; c=11.177(5) Å; ?=115.70(4)°; V=1504.0(11) Å3 and Z=4. Its structure exhibits infinite chains, parallel to the [100] direction where the organic cations are interconnected. In both structures a network of strong and weak hydrogen bonds connects the different components in the building of the crystal.

Belhouchet, M.; Savariault, J. M.; Mhiri, T.

2005-07-01

64

Mechanisms for NH3 decomposition on Si(100)-(2 x 1) surface: a quantum chemical cluster model study.  

PubMed

In this paper, we present a detailed mechanism for the complete decomposition of NH3 to NHx(a) (x = 0-2). Our calculations show that the initial decomposition of NH3 to NH2(a) and H(a) is facile, with a transition-state energy 7.4 kcal mol-1 below the vacuum level. Further decomposition to N(a) or recombination-desorption to NH3(g) is hindered by a large barrier of approximately 46 kcal mol-1. There are two plausible NH2 decomposition pathways: 1) NH2(a) insertion into the surface Si-Si dimer bond, and 2) NH2(a) insertion into the Si-Si backbond. We find that pathway (1) leads to the formation of a surface Si = N unit, similar to a terminal Si = Nt pair in silicon nitride, Si3N4, while pathway (2) leads to the formation of a near-planar, subsurface Si3N unit, in analogy to a central nitrogen atom (Nc) bounded to three silicon atoms in the Si3N4 environment. Based on these results, a plausible microscopic mechanism for the nitridation of the Si(100)-(2 x 1) surface by NH3 is proposed. PMID:12561306

Xu, Xin; Kang, Song-Yun; Yamabe, Tokio

2002-12-01

65

The solvation of two electrons in the gaseous clusters of Na- (NH3)n and Li- (NH3)n.  

PubMed

Alkali metal ammonia clusters, in their cationic, neutral, and anionic form, are molecular models for the alkali-ammonia solutions, which have rich variation of phases with the solvated electrons playing an important role. With two s electrons, the Na(-)(NH(3))(n) and Li(-)(NH(3))(n) clusters are unique in that they capture the important aspect of the coupling between two solvated electrons. By first principles calculations, we demonstrate that the two electrons are detached from the metal by n = 10, which produces a cluster with a solvated electron pair in the vicinity of a solvated alkali cation. The coupling of the two electrons leads to either the singlet or triplet state, both of which are stable. They are also quite distinct from the hydrated anionic clusters Na(-)(H(2)O)(n) and Li(-)(H(2)O)(n), in that the solvated electrons are delocalized and widely distributed among the solvent ammonia molecules. The Na(-)(NH(3))(n) and Li(-)(NH(3))(n) series, therefore, provide another interesting type of molecular model for the investigation of solvated electron pairs. PMID:22462864

Zhang, Han; Liu, Zhi-Feng

2012-03-28

66

Advanced ammonia (NH3) monitoring system for industrial applications  

Microsoft Academic Search

The present paper describes an Electro-Optical Monitoring System developed for the real time in-situ monitoring of Ammonia (NH3) emissions, at very low concentrations in air, well below the hazardous levels. Ammonia is the starting chemical for almost all industrially produced nitrogen compounds and is therefore one of the most important inorganic raw materials. Due to its unique chemical and physical

Oded Spector; Esther Jacobson

1999-01-01

67

CO+NH3 plasma etching for magnetic thin films  

NASA Astrophysics Data System (ADS)

Etching of magnetic thin films has been studied using CO/NH3 plasma with an electron cyclotron resonance plasma source and DC sample bias. Etch rates were proportional to bias power density. The maximum etch rate was 127nm/min. Both the pressure dependence of Ni-Fe etch rate and the results of appearance mass spectroscopy suggested that the chemical reaction induced by energetic CO molecules enhanced the etch rate.

Kubota, Hitoshi; Ueda, Kousei; Ando, Yasuo; Miyazaki, Terunobu

2004-05-01

68

Communication: Overtone (2NH) spectroscopy of NH3-Ar  

NASA Astrophysics Data System (ADS)

The ? (11) <-- ? (00) 2NH (?1+?3) band of the NH3-Ar van der Waals complex formed in a supersonic jet expansion, with origin at 6628 cm-1 was recorded at high-resolution using cavity ring down spectroscopy. The analysis leads to upper state rotational constants and J-dependent predissociation lifetimes estimated from linewidth analysis, with a mean value about 0.6 ns.

Didriche, K.; Földes, T.; Vanfleteren, T.; Herman, M.

2013-05-01

69

Scattering resonances in slow NH3-He collisions.  

PubMed

We theoretically study slow collisions of NH(3) molecules with He atoms, where we focus in particular on the observation of scattering resonances. We calculate state-to-state integral and differential cross sections for collision energies ranging from 10(-4) cm(-1) to 130 cm(-1), using fully converged quantum close-coupling calculations. To describe the interaction between the NH(3) molecules and the He atoms, we present a four-dimensional potential energy surface, based on an accurate fit of 4180 ab initio points. Prior to collision, we consider the ammonia molecules to be in their antisymmetric umbrella state with angular momentum j = 1 and projection k = 1, which is a suitable state for Stark deceleration. We find pronounced shape and Feshbach resonances, especially for inelastic collisions into the symmetric umbrella state with j = k = 1. We analyze the observed resonant structures in detail by looking at scattering wavefunctions, phase shifts, and lifetimes. Finally, we discuss the prospects for observing the predicted scattering resonances in future crossed molecular beam experiments with a Stark-decelerated NH(3) beam. PMID:22360237

Gubbels, Koos B; van de Meerakker, Sebastiaan Y T; Groenenboom, Gerrit C; Meijer, Gerard; van der Avoird, Ad

2012-02-21

70

Observational constraints on solar nebula nitrogen chemistry - N2\\/NH3  

Microsoft Academic Search

Observations of N2(+) and NH2 in Comet Halley and N2H(+) and NH3 in nine Galactic star-forming regions are used to determine the average N2\\/NH3 abundance ratio in these objects. For Comet Halley, N2\\/NH3 of about 0.1 is found, and for the quiescent gas in a sample of star-forming regions, N2\\/NH3 of about 170 +\\/- 100. The cometary N2\\/NH3 ratio corrected

Maria Womack; Susan Wyckoff; L. M. Ziurys

1992-01-01

71

Structural phase transitions in the perovskite-type layer compounds NH3(CH2)3NH3CdCl4, NH3(CH2)4NH3MnCl4, and NH3(CH2)5NH3CdCl4  

NASA Astrophysics Data System (ADS)

The structural phase transitions in the perovskite-type layer-structure compounds [NH3(CH2)3NH3]CdCl4 (Tc=375 K), [NH3(CH2)4NH3]MnCl4 (Tc=382 K), and [NH3(CH2)5NH3]CdCl4 (Tc=338 K) have been studied by 35Cl and deuteron quadrupole resonance spectroscopy, birefringence, and dilatation measurements, optical-domain investigations and group-theoretical considerations. The results show that this transition, which is for all three compounds of second order, is basically a dynamic order-disorder transition of the alkylenediammonium chains, each of which can take on four different states (two all-trans states and two twisted states). The high-temperature phase is characterized by a dynamical disorder of the chains between the four possible states, the twisted states being less populated because of their higher potential energy. In the low-temperature phase, well below the phase transition, the chains are completely ordered in one of the two all-trans states. A strong even-odd effect, concerning the number of carbon atoms in the alkylene chains, has been observed in the temperature dependence of the static dielectric constant and in the critical exponent ? of the order parameter. This is connected with the symmetry of the chains in the all-trans state which is mm2 for "odd" chains and 2m for "even" chains. In contrast to the "even" chains the "odd" chains can thus carry a permanent electric dipole moment. As a consequence the phase transition in the two Cd compounds is of antiferrodistortive nature and leads from a paraelectric phase to an antiferroelectric phase, whereas the Mn compound undergoes a proper ferroelastic transition, although the microscopic mechanism is the same for both types. It is shown that the order-disorder transition in these compounds can be described adequately with a microscopic rigid-lattice model in the mean-field approximation.

Kind, R.; Plesko, S.; Günter, P.; Roos, J.; Fousek, J.

1981-05-01

72

First NH3 detection of the Orion Bar  

NASA Astrophysics Data System (ADS)

Odin has successfully observed three regions in the Orion A cloud, i.e. Ori KL, Ori S and the Orion Bar, in the 572.5 GHz rotational ground state line of ammonia, ortho-NH3 (J,K) = (1,0) -> (0,0), and the result for the Orion Bar represents the first detection in an ammonia line. Several velocity components are present in the data. Specifically, the observed line profile from the Orion Bar can be decomposed into two components, which are in agreement with observations in high-J CO lines by Wilson et al. (\\cite{wilson01}). Using the source model for the Orion Bar by these authors, our Odin observation implies a total ammonia abundance of NH3/H2 = 5x 10-9. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation has been the industrial prime contractor.

Larsson, B.; Liseau, R.; Bergman, P.; Bernath, P.; Black, J. H.; Booth, R. S.; Buat, V.; Curry, C. L.; Encrenaz, P.; Falgarone, E.; Feldman, P.; Fich, M.; Florén, H. G.; Frisk, U.; Gerin, M.; Gregersen, E. M.; Harju, J.; Hasegawa, T.; Johansson, L. E. B.; Kwok, S.; Lecacheux, A.; Liljeström, T.; Mattila, K.; Mitchell, G. F.; Nordh, L. H.; Olberg, M.; Olofsson, G.; Pagani, L.; Plume, R.; Ristorcelli, I.; Sandqvist, Aa.; Schéele, F. v.; Tothill, N. F. H.; Volk, K.; Wilson, C. D.; Hjalmarson, Å.

2003-05-01

73

The origin of 15 NH 3 produced from the reaction of 14 NH 3 and 15 NO over vanadia-based SCR catalysts  

Microsoft Academic Search

The effects of H2O and the vanadia content of the catalyst on the formation of15NH3 during the reaction of15NO and14NH3 in the absence of O2 over V2O5-based catalysts have been determined by mass spectrometry and Fourier transform infrared spectroscopy. At 450°C, the contribution of15NH3 to the total nitrogen-containing products remains constant at about 20% for water concentrations from 0 to

Bronwyn L. Duffy; H. Edward Curry-Hyde; Noel W. Cant; Peter F. Nelson

1994-01-01

74

Fast Reactions NO(+)(H2O)(n) + NH3 yields NH4(+)(H2O)(n-1) + HNO2, n equals 1-3, and NO(+)NH3 + NH3 yields NH4(+) + ONNH2.  

National Technical Information Service (NTIS)

An afterglow technique has been utilized to measure the reaction NO(+).H2O+NH3 yields NH4(+)+HNO2 quantitatively and to observe qualitatively similar reactions of the ions NO(+).(H2O)2 and NO(+).(H2O)3 with NH3. The experiment was straightforward, N2 gas ...

F. C. Fehsenfeld E. E. Ferguson

1970-01-01

75

Ab initio potential energy surfaces for NH((3)sigma(-))-NH((3)sigma(-)) with analytical long range.  

PubMed

We present four-dimensional ab initio potential energy surfaces for the three different spin states of the NH((3)Sigma(-))-NH((3)Sigma(-)) complex. The potentials are partially based on the work of Dhont et al. [J. Chem. Phys. 123, 184302 (2005)]. The surface for the quintet state is obtained at the RCCSD(T)/augmented correlation-consistent polarized valence triple-zeta (aug-cc-pVTZ) level of theory and the energy differences with the singlet and triplet states are calculated at the complete active space with nth-order perturbation theory/aug-cc-pVTZ (n=2,3) level of theory. The ab initio potentials are fitted to coupled spherical harmonics in the angular coordinates, and the long range is further expanded as a power series in 1/R. The RCCSD(T) potential is corrected for a size-consistency error of about 0.5x10(-6) E(h) prior to fitting. The long-range coefficients obtained from the fit are found to be in good agreement with first and second-order perturbation theory calculations. PMID:20001043

Janssen, Liesbeth M C; Groenenboom, Gerrit C; van der Avoird, Ad; Zuchowski, Piotr S; Podeszwa, Rafa?

2009-12-14

76

Ternary nucleation of HSO4, NH3, and in the atmosphere  

Microsoft Academic Search

Classical theory of binary homogeneous nucleation is extended to the ternary system H2SO4-NH3-H20. For NH3 mixing ratios exceeding about 1 ppt, the presence of NH3 enhances the binary H2SO4-H20 nucleation rate by several orders of magnitude. The Gibbs free energies of formation of the critical H2SO4-NH3-H20 cluster, as calculated by two independent approaches, are in substantial agreement. The finding that

P. Korhonen; M. Kulmala; A. Laaksonen; Y. Viisanen; R. McGraw; J. H. Seinfeld

1999-01-01

77

Photochemistry of NH3, CH4 and PH3. Possible applications to the Jovian planets  

Microsoft Academic Search

Photolysis of NH3 at 185 nm in the presence of a two-fold excess of CH4 results in the loss of about 0.25 mole of CH4 per mole of NH3 decomposed (DeltaCH4\\/DeltaNH3). The loss arises from the abstraction of hydrogen atoms from CH4 by photolytically generated hot hydrogen atoms, the presence of which is established by the constancy of DeltaCH4\\/DeltaNH3 between

J. P. Ferris; J. Y. Morimoto; Robert Benson; Alain Bossard

1982-01-01

78

Photochemistry of NH 3 , CH 4 and PH 3 . Possible applications to the Jovian planets  

Microsoft Academic Search

Photolysis of NH3 at 185 nm in the presence of a two-fold excess of CH4 results in the loss of about 0.25 mole of CH4 per mole of NH3 decomposed (?CH4\\/?NH3). The loss arises from the abstraction of hydrogen atoms from CH4 by photolytically generated hot hydrogen atoms, the presence of which is established by the constancy of ?CH4\\/?NH3 between

J. P. Ferris; J. Y. Morimoto; Robert Benson; Alain Bossard

1982-01-01

79

Enhanced removal of NH 3 during composting by a biotrickling filter inoculated with nitrifying bacteria  

Microsoft Academic Search

A biotrickling filter (BTF) was used to treat NH3 emitted from the exhaust gases of cattle manure compost. Results of the non-biofilm experiment suggested that NH3 could not be removed effectively only through biofilm adsorption. The absence of NH4+ bio-oxidation resulted in an increase in free ammonia, which had a negative effect on NH3 removal. After biofilm culture, NH3 removal

Niantao Xue; Qunhui Wang; Chuanfu Wu; Lanhe Zhang; Weimin Xie

2010-01-01

80

Low temperature pressure broadening of NH3 by D2  

NASA Astrophysics Data System (ADS)

We report experimentally measured cross sections for pressure broadening of ammonia inversion transitions by J=0, ortho-D2 at temperatures of 18-40 K. These measurements were made in a quasiequilibrium cell using the collisional cooling technique. Cross sections for broadening of the metastable (J,K)=(1, 1), (2, 2) and (3, 3) inversion transitions ranged from 67.5 Å2 for (1, 1) at 20.0 K to 100.1 Å2 for (3, 3) at 25.0 K. The J=0, ortho-D2 cross sections were found to be consistently larger than previously measured cross sections for low temperature broadening of NH3 by both He and H2.

Willey, Daniel R.; Timlin, Robert E.; Ruggiero, Charles D.; Sulai, Ibrahim A.

2004-01-01

81

Réduction catalytique sélective de NO par NH3 en présence d'oxygène sur zéolithes NaY échangées au cuivre  

NASA Astrophysics Data System (ADS)

A series of Cu-NaY, prepared by ion-exchange and impregnation, was characterized by temperature programmed reduction (TPR) and oxidation (TPO) and also tested for the selective catalytic reduction (SCR) of NO by NH3 in an oxygen rich atmosphere, and in the NH3 oxidation. From the TPR profiles, the amount of isolated Cu2+ species, [Cu-O-Cu]2+ dimer species and CuO aggregates were evaluated. The TPO of Cu^+-NaY issued from the reduction of Cu2+-NaY by NH3, shows that NO alone cannot perform the reoxidation of Cu+ to Cu2+ below 873 K, but this reaction is enhanced in the presence of NO/O2 with respect to O2 alone. The SCR of NO with NH3 in 3% O2 leads to three peaks in the NO conversion curve, when conducted in the temperature programmed reaction mode. The first peak is a transient effect due to the impossible regeneration of Cu+ to Cu2+. As soon as the reoxydation of Cu+ to Cu2+ become feasible by NO/O2, the reaction starts (second peak) and would be related to the presence of copper in supercages. The formation of N2O in this temperature range occurs in the presence of copper oxide aggregates. The final conversion, at high temperature leads to 100% conversion of NO and is due to a better oxidation of Cu+ by NO/O2 and O2 alone. In this latter temperature range, the formation of N2O comes mainly from the reaction between NO and NH3 in the sodalite cavities but also from the oxidation of NH3. Une série de catalyseurs Cu-NaY, préparés par échange et imprégnation, a été caractérisée par réduction (TPR) et oxsydation (TPO) en température programmée et a été testée en réduction catalytique sélective (SCR) de NO par NH3 et en oxydation de NH3. La TPR a permis d'évaluer les différentes espèces cuivre présentes (Cu2+, [Cu-O-Cu]2+, CuO) dans les solides préparés. La TPO de Cu^+-NaY, obtenu par réduction de Cu2+-NaY par NH3 montre que NO seul ne réoxyde pas Cu+ en Cu2+ en dessous de 873 K, et que cette réaction est favorisée en présence de NO/O2 par rapport à O2 seul. En SCR de NO par NH3 en présence de 3 % O2 trois pics de conversion de NO sont observés si la réaction est réalisée en température programmée. Le premier pic de conversion vers 420 K est un phénomène transitoire en raison de l'impossibilité de réoxyder Cu+ en Cu2+ dans ce domaine de température . La deuxième vague vers 500 K apparaît dès que la réoxydation par le mélange NO/O2 devient possible et serait due à la présence de Cu en supercages. La formation de N2O dans cette zone de température se produit en présence d'agrégats d'oxyde de cuivre dans le solide. Enfin dès que la réoxydation de l'ensemble des ions Cu+ est possible, la conversion en NO devient totale pour des températures supérieures à 610 K. La formation de N2O dans ce dernier domaine de température provient principalement de la réaction entre NO et NH3 dans les cages sodalites mais aussi de l'oxydation de NH3.

Delahay, G.; Kieger, S.; Neveua, B.; Coq, B.

1999-03-01

82

Dimers of heptapnictide anions: As14 4- and P14 4- in the crystal structures of [Rb(18-crown-6)]4As14.6NH3 and [Li(NH3)4]4P14.NH3.  

PubMed

Compounds [Rb(18-crown-6)]4As14.6NH3 (1) and [Li(NH3)4]4P14.NH3 (2) were prepared by the reaction of Rb4As6 with SbPh3 and 18-crown-6 and by the reduction of white phosphorus with elemental lithium in liquid ammonia, respectively. Both were characterized by low-temperature single-crystal X-ray structure analysis. They were found to contain the Ci symmetrical Pn14(4-) anion (Pn = P, As), which consists of two nortricyclane-like Pn7-cages connected by a single bond. Molecular complexes of [Rb(18-crown-6)(NH3)]2[Rb(18-crown-6)]2As14 are formed in 1, which are connected to fanfold sheets via N-H...O bonds. The anion is isolated in 2, and N-H...N bonds result in the formation of {[Li(NH3)4](mu-NH3)2[Li(NH3)4]}2+ cationic complexes. PMID:16903728

Hanauer, Tobias; Aschenbrenner, Jürgen C; Korber, Nikolaus

2006-08-21

83

Intervalence Transfer in the Dimer ((NH3)5RuII(4,4'-bpy)RuIII(NH3)5)(5+),  

National Technical Information Service (NTIS)

We have reinvestigated the solvent dependence of the intervalence absorption band energy in the mixed-valence dimer (NH3)5Ru(4,4'-bipyridine)Ru(NH3)5)5+. From the new results we conclude that: 1) There is a considerable contribution to the apparent band e...

J. T. Hupp T. J. Meyer

1987-01-01

84

(C4H3SCH2NH3)2(CH3NH3)Pb2I7: non-centrosymmetrical crystal structure of a bilayer hybrid perovskite.  

PubMed

The analysis of the crystal structure of (C4H3SCH2NH3)2(CH3NH3)Pb2I7, displaying a well-ordered acentric inorganic Pb2I7(3-) bilayer, is reported, and compared to the related monolayer hybrid perovskite. PMID:12357824

Zhu, Xu-Hui; Mercier, Nicolas; Riou, Amédée; Blanchard, Philippe; Frère, Pierre

2002-09-21

85

Optical Constants of NH3 and NH3:N2 Amorphous Ices in the Near-infrared and Mid-infrared Regions  

NASA Astrophysics Data System (ADS)

Ammonia ice has been detected on different astrophysical media ranging from interstellar medium (ISM) particles to the surface of various icy bodies of our solar system, where nitrogen is also present. We have carried out a detailed study of amorphous NH3 ice and NH3:N2 ice mixtures, based on infrared (IR) spectra in the mid-IR (MIR) and near-IR (NIR) regions, supported by theoretical quantum chemical calculations. Spectra of varying ice thicknesses were obtained and optical constants were calculated for amorphous NH3 at 15 K and 30 K and for a NH3:N2 mixture at 15 K over a 500-7000 cm–1 spectral range. These spectra have improved accuracy over previous data, where available. Moreover, we also obtained absolute values for the band strengths of the more prominent IR features in both spectral regions. Our results indicate that the estimated NH3 concentration in ISM ices should be scaled upward by ~30%.

Zanchet, Alexandre; Rodríguez-Lazcano, Yamilet; Gálvez, Óscar; Herrero, Víctor J.; Escribano, Rafael; Maté, Belén

2013-11-01

86

Hydrogen atom transfer in indole(NH_3)n clusters: formation dynamics of (NH_{3)_{n-1}NH4}, n = 1 6, fragments  

NASA Astrophysics Data System (ADS)

The H atom transfer reaction in electronically excited indole(NH3)n clusters is studied in pump-probe experiments with femtosecond laser pulses. By applying different probe photon energies we are able to detect the dissociation products (NH3)_{n-1}NH4 for n = 1 6. Furthermore we show that the analysis of the corresponding ion signals is not distorted by contributions from larger cluster ions due to evaporation of NH3 molecules. The formation times of the products are ca. 140 ps for n=2 4 and about 80 ps for n=5,6.

Lippert, H.; Stert, V.; Hesse, L.; Schulz, C. P.; Radloff, W.; Hertel, I. V.

2002-09-01

87

Reduction Kinetics of Graphene Oxide Determined by Temperature Programmed Desorption  

Microsoft Academic Search

Graphene oxide, which is an electrical insulator, shows promise for use in several technological applications such as dielectric layers in nanoscale electronic devices or as the active region of chemical sensors. In principle, graphene oxide films could also be used as a precursor for the formation of large-scale graphene films by either thermal or chemical reduction of the graphene oxide.

Carl Ventrice; Nicholas Clark; Daniel Field; Heike Geisler; Inhwa Jung; Dongxing Yang; Richard Piner; Rodney Ruoff

2009-01-01

88

Analyte separation utilizing temperature programmed desorption of a preconcentrator mesh  

DOEpatents

A method and system for controllably releasing contaminants from a contaminated porous metallic mesh by thermally desorbing and releasing a selected subset of contaminants from a contaminated mesh by rapidly raising the mesh to a pre-determined temperature step or plateau that has been chosen beforehand to preferentially desorb a particular chemical specie of interest, but not others. By providing a sufficiently long delay or dwell period in-between heating pulses, and by selecting the optimum plateau temperatures, then different contaminant species can be controllably released in well-defined batches at different times to a chemical detector in gaseous communication with the mesh. For some detectors, such as an Ion Mobility Spectrometer (IMS), separating different species in time before they enter the IMS allows the detector to have an enhanced selectivity.

Linker, Kevin L. (Albuquerque, NM); Bouchier, Frank A. (Albuquerque, NM); Theisen, Lisa (Albuquerque, NM); Arakaki, Lester H. (Edgewood, NM)

2007-11-27

89

Ultrasensitive gaseous NH3 sensor based on ionic liquid-mediated signal-on electrochemiluminescence.  

PubMed

This work reports that ammonia (NH(3)) can be used as an efficient co-reactant for tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL) in ionic liquids (ILs), on the basis of which a signal-on ECL sensor for directly detecting gaseous NH(3) has been developed. The NH(3) ECL sensor has a very high sensitivity, with a detection limit of 10 ppt NH(3) (at signal-to-noise ratio of 3) without any preconcentration. The high sensitivity is mainly due to the zero ECL background of Ru(bpy)(3)(2+) in the ILs, strong co-reactant ECL activity of NH(3), and high solubility of NH(3) in imidazolium-based ILs. Additionally, the ECL sensor shows an excellent selectivity against common interfering gases and a wide linear response range from 10 ppt to 10 ppm. PMID:22728516

Chen, Lichan; Huang, Danjun; Zhang, Yuanjin; Dong, Tongqing; Zhou, Chen; Ren, Shuyan; Chi, Yuwu; Chen, Guonan

2012-06-25

90

Laser-Induced Reactivity of NH_3 on GaAs Surface  

NASA Astrophysics Data System (ADS)

We have studied the reactivity of NH3 on GaAs (100) surface irradiated by 280 nm laser beam at low fluence (< 50 mJ cm^{-2} per pulse) in an experimental set-up which allows a very sensitive characterization of the surface state using mass spectrometry. Thanks to this analysis technique we could follow desorbed NHx (x = 2, 3) species during the laser treatment; this phase achieved, GaN^+ could be identified as an evidence of N fixation using laser desorption mass spectrometry of the treated surface. This characterization mode demonstrates the fluence and laser shot number dependencies on laser treatment efficiency. At 280 nm the N fixation is maximum for laser fluence of about 25 mJ cm^{-2} (per pulse). Still even in the best nitridation conditions, the process appears to be of little efficiency, since it leads to the formation of less than one monolayer of GaN. These results combined with a numerical model of GaAs laser heating give evidence for the laser-induced nitridation to be thermally assisted. Nous avons étudié la réactivité de NH3 sur la surface d'un échantillon de GaAs irradié par un faisceau laser UV (280 nm) de faible fluence (< 50 mJ cm^{-2}). Les expériences ont été menées dans un dispositif expérimental utilisant la spectrométrie de masse et permettant une caractérisation présise de l'état de la surface. Grâce à cette technique d'analyse nous avons pu suivre les espèces NHx^+ (x = 2, 3) désorbées pendant le traitement laser, cette étape terminée, nous avons détecté, par la spectrométrie de masse associée à la désorption laser, les ions GaN^+ émis depuis la surface traitée, ils indiquent que la nitruration de GaAs s'est bien produite pendant le traitement. Cette technique de caractérisation nous a permis d'étudier l'influence de la fluence et du nombre de tirs laser sur l'efficacité du traitement. À 280 nm l'efficacité de la nitruration assistée par laser du GaAs est maximum pour une fluence laser proche de 25 mJ cm^{-2} (par tir). Cependant même dans les conditions optimales de nitruration, le processus apparaît peu efficace puisqu'il conduit à la formation de moins d'une monocouche de GaN. Ces résultats expérimentaux couplés à un modèle numérique du chauffage laser de GaAs ont montré que le laser produit, pour les réactions de surface, des effets essentiellement thermiques proches de ceux obtenus par un chauffage conventionnel, lent, du substrat de GaAs.

Vivet, L.; Dubreuil, B.; Gibert-Legrand, T.; Barthe, M. F.; Perrin, C.

1997-01-01

91

Solvation effects on angular distributions in H- (NH3)n and NH2(-) (NH3)n photodetachment: role of solute electronic structure.  

PubMed

We report 355 and 532 nm photoelectron imaging results for H(-)(NH(3))(n) and NH(2)(-)(NH(3))(n), n = 0-5. The photoelectron spectra are consistent with the electrostatic picture of a charged solute (H(-) or NH(2)(-)) solvated by n ammonia molecules. For a given number of solvent molecules, the NH(2)(-) core anion is stabilized more strongly than H(-), yet the photoelectron angular distributions for solvated H(-) deviate more strongly from the unsolvated limit than those for solvated NH(2)(-). Hence, we conclude that solvation effects on photoelectron angular distributions are dependent on the electronic structure of the anion, i.e., the type of the initial orbital of the photodetached electron, rather than merely the strength of solvation interactions. We also find evidence of photofragmentation and autodetachment of NH(2)(-)(NH(3))(2-5), as well as autodetachment of H(-)(NH(3))(5), upon 532 nm excitation of these species. PMID:22047233

Grumbling, Emily R; Sanov, Andrei

2011-10-28

92

Chemisorption of NH 3 at the open ends of boron nitride nanotubes: a DFT study  

Microsoft Academic Search

Considering the thermodynamic aspects and reaction pathways of chemical adsorption of NH3 molecule at the open ends of boron nitride nanotubes (BNNTs), theoretically, it was found that the open-ended BNNTs are able\\u000a to cleave the N–H bond of NH3 via a one- or two-stepwise mechanism. The N-enriched and B-enriched open-ended BNNTs show a nucleophilic and electrophilic\\u000a behavior toward the NH3,

Ali Ahmadi; Javad Beheshtian; Nasser L. Hadipour

2011-01-01

93

Solid–gas equilibrium in chemical heat pumps: the NH 3–CoCl 2 system  

Microsoft Academic Search

The design of heat transfer equipment used in chemical heat pumps requires a knowledge of the temperature at which heat is produced during the synthesis reaction and the temperature at which it is used during the decomposition reaction. The existing equilibrium data in the literature for the reaction, CoCl2·2NH3+4NH3=CoCl2·6NH3 was obtained at pressures of 1 atm or less. Data at

Josée Trudel; Sophie Hosatte; Marten Ternan

1999-01-01

94

Exchange interaction as studied by EPR in a two-dimensional molecular composite [NH 3?(CH 2) 4?NH 3]MnCl 4  

Microsoft Academic Search

A single crystal of the two-dimensional structure [NH3(CH2)4NH3]MnCl4 is studied by Electron Paramagnetic Resonance (EPR) when rotated around a?, b and c axes, at X-band and room temperature. Magnetic susceptibility was also measured on a powder sample between 5 and 300 K. Intralayer exchange interaction Jk = (4.6 ± 0.4) K calculated from anisotropy of the EPR linewidth is in

Jean-Claude Bissey; Nathalie Filloleau; Nguyen-Ba Chanh; René Berger; Serge Flandrois

1998-01-01

95

Prospects for producing ultracold NH_{3} molecules by sympathetic cooling: A survey of interaction potentials  

Microsoft Academic Search

We investigate the possibility of producing ultracold NH3 molecules by\\u000asympathetic cooling in a bath of ultracold atoms. We consider the interactions\\u000aof NH3 with alkali-metal and alkaline-earth atoms, and with Xe, using ab initio\\u000acoupled-cluster calculations. For Rb-NH3 and Xe-NH3 we develop full potential\\u000aenergy surfaces, while for the other systems we characterize the stationary\\u000apoints (global and local

Jeremy M. Hutson

2008-01-01

96

Ternary nucleation of H2SO4, NH3, and H2O in the atmosphere  

Microsoft Academic Search

Classical theory of binary homogeneous nucleation is extended to the ternary system H2SO4-NH3-H2O. For NH3 mixing ratios exceeding about 1 ppt, the presence of NH3 enhances the binary H2SO4-H2O nucleation rate by several orders of magnitude. The Gibbs free energies of formation of the critical H2SO4-NH3-H2O cluster, as calculated by two independent approaches, are in substantial agreement. The finding that

P. Korhonen; M. Kulmala; A. Laaksonen; Y. Viisanen; R. McGraw; J. H. Seinfeld

1999-01-01

97

Thermodynamics of cluster ions containing NH3 and H2SO4  

NASA Astrophysics Data System (ADS)

The stability of cluster ions of the form NH4+(NH3)X(H2SO4)Y and HSO4-(NH3)x(H2SO4)y was studied with an ion-molecule flow reactor coupled to a quadrupole mass spectrometer. Equilibrium constants for the association of NH3 with these species were measured and Gibbs free energy changes were derived. The binding of NH3 appears to be enhanced by the presence H2SO4, and vice versa. These stable cluster ions may be important precursors for atmospheric aerosols. .

Froyd, Karl D.; Lovejoy, Edward R.

2000-08-01

98

Time Resolved Measurement of Ecosystem-Atmosphere NH3 Exchange Using the Eddy Covariance Technique  

NASA Astrophysics Data System (ADS)

Quantifying ammonia fluxes between the land surface and atmosphere is required for effective control of air quality, improving agricultural practices, and understanding natural ecosystem function. Ammonia (NH3) is emitted in large but uncertain amounts from animal agriculture, in lesser amounts from imperfect use of nitrogen fertilizers in crop agriculture, from catalytic converters used on automobiles and other energy related industrial processes, and exchanged between the ecosystem and atmosphere by natural ecosystem processes on vast spatial scales. To address the need for accurate, time-resolved NH3 flux measurements, we have developed an eddy covariance (EC) instrument for direct measurements of NH3 flux. EC flux measurements of NH3 were not previously possible because instruments were not sufficiently sensitive at high frequencies required to capture rapid variations in surface layer NH3 concentrations. To overcome this hurdle we combined a tunable-diode-laser (TDL) spectrometer with a fast-response NH3 sampling inlet and automated pulse-response calibration system. Laboratory tests of the inlet system demonstrate that the response to 10 ppb step in NH3 concentration is well described by a double exponential model with (1/e) times of 0.3 (85% response) and 1.5 (15% response) seconds. This response combined with a routinely measured instrument stability of ~ 0.1 ppb (on 30 minute timescales) indicates that the instrumental contribution to noise in NH3 flux measurements is ~ 0.2 umol NH3 m-2 hr-1, sufficient to stringently test models for NH3 exchange under most conditions. Recent results of field work to verify the instrument performance and observe examples of NH3 exchange will be presented.

Fischer, M. L.; Littlejohn, D.

2005-12-01

99

SEASONAL NH 3 EMISSIONS FOR ANNUAL 2001 CMAQ SIMULATION: INVERSE MODEL ESTIMATION AND EVALUATION  

EPA Science Inventory

The formation of ammonium nitrate aerosols is often limited by ammonia (NH3), and sulfate aerosols are predominantly in the form of ammonium sulfate. While NH3plays a central role in the prediction of nitrate and sulfate aerosols, inherent uncertainty exist...

100

Effects of atmospheric ammonia (NH 3) on terrestrial vegetation: a review  

Microsoft Academic Search

At the global scale, among all N (nitrogen) species in the atmosphere and their deposition on to terrestrial vegetation and other receptors, NH3 (ammonia) is considered to be the foremost. The major sources for atmospheric NH3 are agricultural activities and animal feedlot operations, followed by biomass burning (including forest fires) and to a lesser extent fossil fuel combustion. Close to

S. V Krupa

2003-01-01

101

Seasonal NH 3 emissions for the continental united states: Inverse model estimation and evaluation  

NASA Astrophysics Data System (ADS)

Significant uncertainty exists in the seasonal distribution of NH 3 emissions since the predominant sources are animal husbandry and fertilizer application. Previous studies that estimated bottom-up and top-down NH 3 emissions have provided the most comprehensive information available about the seasonality of NH 3 emissions. In this study, this bottom-up and top-down emission information is combined with the most recent 2001 USEPA National Emission Inventory (NEI) to construct a best prior estimate of seasonal NH 3 emissions. These emission estimates are then used in an annual 2001 USEPA Community Multiscale Air Quality (CMAQ) model simulation for the continental United States. A key objective of this study is to evaluate these prior NH 3 emission estimates and test the top-down inverse modeling method for a different year and a larger modeling domain than used previously. Based on the final posterior NH 3 emission estimates, the inverse modeling results suggest that the annual total NEI NH 3 emissions are reasonable and that a previous high bias in older USEPA emission inventories has been addressed in the updated inventory. Inverse modeling results suggest that the prior NH 3 emission estimates should be increased in the summer and decreased in the winter, while results for the spring and fall are questionable due to precipitation prediction biases. A final conclusion from this study is that total NH x (NH 3 and aerosol NH 4+) air concentration data are essential for quantitative top-down analyses of NH 3 emissions that can extend beyond what is possible using precipitation chemistry data.

Gilliland, Alice B.; Wyat Appel, K.; Pinder, Robert W.; Dennis, Robin L.

102

1,3-propanediammonium tetrachloromanganate(II) (NH3CH2CH2CH2NH3)MnCl4: A canted quasi-two-dimensional antiferromagnet  

Microsoft Academic Search

The magnetic susceptibilities of single crystals of 1,3-propanediammonium tetrachloromanganate(II),(NH3CH2CH2CH2NH3)MnCl4, have been measured from 4.2 to 220°K. High-field magnetization measurements below the transition temperature are reported. In moderate magnetic fields, the material undergoes a transition to an antiferromagnetic state at TN=43.6°K with the b axis being the preferred axis. Near-zero-field susceptibility measurements below TN reveal a more complex behavior suggestive of

D. Bruce Losee; Kenneth T. McGregor; William E. Estes; William E. Hatfield

1976-01-01

103

Matrix Isolation Spectroscopy and Nuclear Spin Conversion of NH3 and ND3 in Solid Parahydrogen  

NASA Astrophysics Data System (ADS)

We present matrix isolation infrared absorption spectra of NH3 and ND3 trapped in solid parahydrogen (pH2) at temperatures around 1.8 K. We used the relatively slow nuclear spin conversion (NSC) of NH3 and ND3 in freshly deposited pH2 samples as a tool to assign the sparse vibration-inversion-rotation (VIR) spectra of NH3 in the regions of the -2, -4, 2-4, -1, and -3 bands and ND3 in the regions of the -2, -4, -1, and -3 fundamentals. Partial assignments are also presented for various combination bands of NH3. Detailed analysis of the -2 bands of NH3 and ND3 indicates that both isotopomers are nearly free rotors; that the vibrational energy is blue-shifted by 1-2%; and that the rotational constants and inversion tunneling splitting are 91-94% and 67-75%, respectively, of the gas-phase values. The line shapes of the VIR absorptions are narrow (0.2-0.4 cm-1) for upper states that cannot rotationally relax and broad (>1 cm-1) for upper states that can rotationally relax. We report and assign a number of NH3-induced infrared absorption features of the pH2 host near 4150 cm-1, along with a cooperative transition that involves simultaneous vibrational excitation of a pH2 molecule and rotation-inversion excitation of NH3. The NSCs of NH3 and ND3 were found to follow first-order kinetics with rate constants at 1.8 K of k = 1.88(16) - 10-3 s-1 and k = 1.08(8) - 10-3 s-1, respectively. These measured rate constants are compared to previous measurements for NH3 in an Ar matrix and with the rate constants measured for other dopant molecules isolated in solid pH2.

Ruzi, Mahmut; Anderson, David T.

2013-10-01

104

Leaf-Atmosphere NH3 Exchange in Barley Mutants with Reduced Activities of Glutamine Synthetase.  

PubMed Central

Mutants of barley (Hordeum vulgare L. cv Maris Mink) with 47 or 66% of the glutamine synthetase (GS) activity of the wild type were used for studies of NH3 exchange with the atmosphere. Under normal light and temperature conditions, tissue NH4+ concentrations were higher in the two mutants compared with wild-type plants, and this was accompanied by higher NH3 emission from the leaves. The emission of NH3 increased with increasing leaf temperatures in both wild-type and mutant plants, but the increase was much more pronounced in the mutants. Similar results were found when the light intensity (photosynthetic photon flux density) was increased. Compensation points for NH3 were estimated by exposing intact shoots to 10 nmol NH3 mol-1 air under conditions with increasing temperatures until the plants started to emit NH3. Referenced to 25[deg]C, the compensation points were 5.0 nmol mol-1 for wild-type plants, 8.3 nmol mol-1 for 47% GS mutants, and 11.8 nmol mol-1 for 66% GS mutants. Compensation points for NH3 in single, nonsenescent leaves were estimated on the basis of apoplastic pH and NH4+ concentrations. These values were 0.75, 3.46, and 7.72 nmol mol-1 for wild type, 47% GS mutants, and 66% GS mutants, respectively. The 66% GS mutant always showed higher tissue NH4+ concentrations, NH3 emission rates, and NH3 compensation points compared with the 47% GS mutant, indicating that NH4+ release was curtailed by some kind of compensatory mechanism in plants with only 47% GS activity.

Mattsson, M.; Hausler, R. E.; Leegood, R. C.; Lea, P. J.; Schjoerring, J. K.

1997-01-01

105

Selective NH 3 oxidation to N 2 in a wet stream  

Microsoft Academic Search

Al2O3 and ZSM-5 supported Pd, Rh and Pt catalysts were studied for NH3 oxidation at 200–350°C in comparison with V2O5\\/TiO2 and Co-ZSM-5 catalysts at 250–400°C. The precious metal catalysts are very active for NH3 oxidation in this temperature range. With the addition of 5% H2O vapor, the NH3 conversion is not affected at high temperatures but decreases at 200–250°C. Generally,

Yuejin Li; John N. Armor

1997-01-01

106

Dominating influence of nh 3 on the oxidation of aqueous SO 2: The coupling of NH 3 and SO 2 in atmospheric water  

NASA Astrophysics Data System (ADS)

The oxidation of SO 2 in atmospheric water (cloud, rain, liquid aerosol and fog) is influenced by the presence of NH 3. The enhancing effect of NH 3 is especially pronounced if the oxidation occurs with an oxidant such as O 3 for which the reaction rate increases strongly with increasing pH, because NH 3 (i) codetermines the pH of the water and thus in turn the solubility of SO 2, and (ii) provides acid neutralizing capacity as well as buffer intensity to the heterogeneous atmosphere-water system in counteracting the acidity produced by the oxidation of SO 2. At low buffer intensity, the acidity production leads to the alleviation of further SO 2-oxidation. A computer model is used to assess the influence of SO 2, NH 3 and other potential acids and bases, of aerosols and of the liquid water content on the composition and its temporal variation of closed or open atmospheric systems as a consequence of SO 2 oxidation by O 3. An essential corollary to this model is a definition of atmospheric alkalinity (or acidity). Model results are compared with field data obtained in measuring the temporal variation in urban/rural fog composition.

Behra, Philippe; Sigg, Laura; Werner, Stumm

107

A study of a bubble absorber using a plate heat exchanger with NH 3–H 2O, NH 3–LiNO 3 and NH 3–NaSCN  

Microsoft Academic Search

There is a continuous research effort being carried out worldwide on the development of absorption cooling systems with the objective of increasing their performance, one important area is the search for more efficient heat exchangers and alternative working fluids that can improve the performance of NH3–H2O and H2O–LiBr that are commonly used in commercial absorption refrigeration machines. In this work

J. Cerezo; R. Best; R. J. Romero

2011-01-01

108

Radiation Damage and Recovery in Polarized 14NH3 Ammonia Targets at Jefferson Lab  

NASA Astrophysics Data System (ADS)

Dynamically nuclear polarized solid ammonia offers an attractive combination of high polarization, comparatively high dilution factor and high radiation damage resistance as a target material in electron scattering experiments. Polarized 14NH3, provided by the University of Virginia Polarized Target Group, was used as target material in two simultaneous experiments at Thomas Jefferson National Accelerator Facility in the spring of 2009. Target polarization performance for both experiments is discussed, as is previously unseen behavior in irradiated 14NH3.

Maxwell, J. D.

2011-01-01

109

Photochemical reactions in interstellar grains photolysis of co, NH 3 , and H 2 O  

Microsoft Academic Search

A simulation of the organic layer accreted onto interstellar dust particles was prepared by slow deposition of a CO:NH3:H2O gas mixture on an Al block at 10K, with concomitant irradiation with vacuum UV. The residues were analyzed by GC-MS, HPLC, and near IR; a reaction pathway leading from NH3 to complex alcohol, fatty acid, and amide products in 27 stages

V. K. Agarwal; W. Schutte; J. M. Greenberg; J. P. Ferris; R. Briggs; Steven Connor; C. P. E. M. Van de Bult; F. Baas

1985-01-01

110

Selective NH 3 gas sensor based on Langmuir-Blodgett polypyrrole film  

Microsoft Academic Search

Polypyrrole thin films have been deposited onto a glass substrate by the Langmuir-Blodgett technique to fabricate a selective ammonia (NH3) gas sensor. The d.c. electrical resistance of the sensing elements is found to exhibit a specific increase upon exposure to different gases such as NH3, CO, CH4, H2 in N2 and pure O2. The polypyrrole thin-film detector shows a considerable

M. Penza; E. Milella; M. B. Alba; A. Quirini; L. Vasanelli

1997-01-01

111

Contact-Hole Etching with NH3Added C5F8 Pulse-Modulated Plasma  

Microsoft Academic Search

For plasma etching, an alternative perfluorocarbon (PFC) gas is necessary in order to minimize the effect on global warming. Etching contact holes of sub-0.1-mum size in SiO2 is studied using an etching gas with a small greenhouse effect, cyclic (c-) C5F8 containing various other gases (O2, H2 and NH3). Adding NH3 to pulse-modulated plasma is quite effective for improving the

Masahiro Ooka; Shin Yokoyama

2005-01-01

112

Dry Cleaning Technology for Removal of Silicon Native Oxide Employing Hot NH3\\/NF3 Exposure  

Microsoft Academic Search

A new dry cleaning technology for removal of silicon (Si) native oxides from contact holes employing a hot ammonium (NH3)\\/nitrogen trifluoride (NF3) mixture has been studied. The NH3\\/NF3 mixture heated at a high temperature in a quartz tube enabled etching of the silicon dioxide (SiO2) film placed in the downstream region. The mechanism of the etching reaction which was investigated

Hiroki Ogawa; Tomoharu Arai; Michihiko Yanagisawa; Takanori Ichiki; Yasuhiro Horiike

2002-01-01

113

New Cation-Diffusing Phase of (CH3NH3)5Bi2Cl11  

NASA Astrophysics Data System (ADS)

A new phase transition of (CH3NH3)5Bi2Cl11 was found at 520 K by proton NMR and differential thermal analysis. By the phase transition, the activation energy of translational diffusion of CH3NH3+ cation was reduced from 83 kJ/mol to 29 kJ/mol. Rotational motion of the cation in the low-temperature phase is also discussed.

Nagatomo, Shigenori; Takeda, Sadamu; Yamaguchi, Kizashi; Iwata, Makoto; Ishibashi, Yoshihiro

1995-02-01

114

Superconductivity in (NH3)yCs0.4FeSe  

NASA Astrophysics Data System (ADS)

Alkali-metal-intercalated FeSe materials, (NH3)yM0.4FeSe (M: K, Rb, and Cs), have been synthesized using the liquid NH3 technique. (NH3)yCs0.4FeSe shows a superconducting transition temperature (Tc) as high as 31.2 K, which is higher by 3.8 K than the Tc of nonammoniated Cs0.4FeSe. The Tcs of (NH3)yK0.4FeSe and (NH3)yRb0.4FeSe are almost the same as those of nonammoniated K0.4FeSe and Rb0.4FeSe. The Tc of (NH3)yCs0.4FeSe shows a negative pressure dependence. A clear correlation between Tc and lattice constant c is found for ammoniated metal-intercalated FeSe materials, suggesting a correlation between Fermi-surface nesting and superconductivity.

Zheng, Lu; Izumi, Masanari; Sakai, Yusuke; Eguchi, Ritsuko; Goto, Hidenori; Takabayashi, Yasuhiro; Kambe, Takashi; Onji, Taiki; Araki, Shingo; Kobayashi, Tatsuo C.; Kim, Jungeun; Fujiwara, Akihiko; Kubozono, Yoshihiro

2013-09-01

115

Numerical analysis of a mixture of Ar/NH3 microwave plasma chemical vapor deposition reactor  

NASA Astrophysics Data System (ADS)

A two-dimensional fluid model has been used to investigate the properties of plasma in Ar/NH3 microwave electron cyclotron resonance discharge at low pressure. The electromagnetic field model solved by the three-dimensional Simpson method is coupled to a fluid plasma model. The finite difference method was employed to discrete the governing equations. 40 species (neutrals, radicals, ions, and electrons) are consisted in the model. In total, 75 electron-neutral, 43 electron-ion, 167 neutral-neutral, 129 ion-neutral, 28 ion-ion, and 90 3-body reactions are used in the model. According to the simulation, the distribution of the densities of the considered plasma species has been showed and the mechanisms of their variations have been discussed. It is found that the main neutrals (Ar*, Ar**, NH3*, NH, H2, NH2, H, and N2) are present at high densities in Ar/NH3 microwave electron cyclotron resonance discharge when the mixing ratio of Ar/NH3 is 1:1 at 20 Pa. The density of NH is more than that of NH2 atom. And NH3+ are the most important ammonia ions. But the uniformity of the space distribution of NH3+ is lower than the other ammonia ions.

Li, Zhi; Zhao, Zhen; Li, Xuehui

2012-06-01

116

Evaluation of a regional air-quality model with bidirectional NH3 exchange coupled to an agroecosystem modelecosystem model  

EPA Science Inventory

Atmospheric ammonia (NH3) is the primary atmospheric base and an important precursor for inorganic particulate matter and when deposited NH3 contributes to surface water eutrophication, soil acidification and decline in species biodiversity. Flux measurement...

117

Na3[B20H17NH3]: synthesis and liposomal delivery to murine tumors.  

PubMed Central

The polyhedral borane ion [n-B20H18]2- reacts with liquid ammonia in the presence of a suitable base to produce an apical-equatorial (ae) isomer of the [B20H17NH3]3- ion, [1-(2'-B10H9)-2-NH3B10H8]3-. The structure of this product has been confirmed by 11B NMR spectroscopy and x-ray crystallography. This species undergoes acid-catalyzed rearrangement to an apical-apical (a2) isomer, [1-(1'-B10H9)-2-NH3B10H8]3-, whose structure has been determined by 11B NMR spectroscopy. The sodium salts of both the ae and the a2 isomers of [B20H17NH3]3- have been encapsulated within small unilamellar liposomes, composed of distearoyl phosphatidylcholine/cholesterol (1:1), and investigated as boron-delivery agents for boron neutron capture therapy (BNCT) of cancer. The biodistribution of boron was determined after the injection of liposomal suspensions into BALB/c mice bearing EMT6 tumors. Both [B20H17NH3]3- isomers exhibited excellent tumor uptake and selectivity at very low injected doses, achieving peak tumor boron concentrations of 30-40 micrograms of B/g of tissue and tumor/blood boron ratios of approximately 5. The enhanced retention of the [B20H17NH3]3- isomers by EMT6 tumors may be attributed to their facile intracellular oxidation to an extremely reactive NH3-substituted [n-B20H18]2- ion, the electrophilic [B20H17NH3]- ion. Both isomers of [B20H17NH3]3- are at least 0.5 V more easily oxidized than other previously investigated species containing 20 boron atoms. In another experiment, [ae-B20H17NH3]3- was encapsulated in liposomes prepared with 5% PEG-2000-distearoyl phosphatidylethanolamine in the liposome membrane. As expected, these liposomes exhibited a longer circulation lifetime in the biodistribution experiment, resulting in the continued accumulation of boron in the tumor over the entire 48-hr experiment and reaching a maximum of 47 micrograms of B/g of tumor.

Feakes, D A; Shelly, K; Knobler, C B; Hawthorne, M F

1994-01-01

118

Influence of desorption on the indoor concentration of toxic gases  

Microsoft Academic Search

A theoretical model is developed which considers the influence of both deposition and desorption processes on the indoor concentration of toxic gases. The model is based on a simplification of the Langmuir theory. Model parameters for NH3, Cl2, the nerve agent sarin, and a simulant for the nerve agent VX are calculated from available experiments with common indoor materials. The

Edvard Karlsson; Ueli Huber

1996-01-01

119

Experimental researches on characteristics of vapor–liquid equilibrium of NH 3–H 2O–LiBr system  

Microsoft Academic Search

An improved system of NH3–H2O–LiBr was proposed for overcoming the drawback of NH3–H2O absorption refrigeration system. The LiBr was added to NH3–H2O system anticipating a decrease in the content of water in the NH3–H2O–LiBr system. An equilibrium cell was used to measure thermal property of the ternary NH3–H2O–LiBr mixtures. The pressure–temperature data for their vapor–liquid equilibrium (VLE) data were measured

Yuyuan Wu; Yan Chen; Tiehui Wu

2006-01-01

120

Effects of atmospheric ammonia (NH3) on terrestrial vegetation: a review.  

PubMed

At the global scale, among all N (nitrogen) species in the atmosphere and their deposition on to terrestrial vegetation and other receptors, NH3 (ammonia) is considered to be the foremost. The major sources for atmospheric NH3 are agricultural activities and animal feedlot operations, followed by biomass burning (including forest fires) and to a lesser extent fossil fuel combustion. Close to its sources, acute exposures to NH3 can result in visible foliar injury on vegetation. NH3 is deposited rapidly within the first 4-5 km from its source. However, NH3 is also converted in the atmosphere to fine particle NH4+ (ammonium) aerosols that are a regional scale problem. Much of our current knowledge of the effects of NH3 on higher plants is predominantly derived from studies conducted in Europe. Adverse effects on vegetation occur when the rate of foliar uptake of NH3 is greater than the rate and capacity for in vivo detoxification by the plants. Most to least sensitive plant species to NH3 are native vegetation > forests > agricultural crops. There are also a number of studies on N deposition and lichens, mosses and green algae. Direct cause and effect relationships in most of those cases (exceptions being those locations very close to point sources) are confounded by other environmental factors, particularly changes in the ambient SO2 (sulfur dioxide) concentrations. In addition to direct foliar injury, adverse effects of NH3 on higher plants include alterations in: growth and productivity, tissue content of nutrients and toxic elements, drought and frost tolerance, responses to insect pests and disease causing microorganisms (pathogens), development of beneficial root symbiotic or mycorrhizal associations and inter species competition or biodiversity. In all these cases, the joint effects of NH3 with other air pollutants such as all-pervasive O3 or increasing CO2 concentrations are poorly understood. While NH3 uptake in higher plants occurs through the shoots, NH4+ uptake occurs through the shoots, roots and through both pathways. However, NH4+ is immobile in the soil and is converted to NO3- (nitrate). In agricultural systems, additions of NO3- to the soil (initially as NH3 or NH4+) and the consequent increases in the emissions of N2O (nitrous oxide, a greenhouse gas) and leaching of NO3- into the ground and surface waters are of major environmental concern. At the ecosystem level NH3 deposition cannot be viewed alone, but in the context of total N deposition. There are a number of forest ecosystems in North America that have been subjected to N saturation and the consequent negative effects. There are also heathlands and other plant communities in Europe that have been subjected to N-induced alterations. Regulatory mitigative approaches to these problems include the use of N saturation data or the concept of critical loads. Current information suggests that a critical load of 5-10 kg ha(-1) year(-1) of total N deposition (both dry and wet deposition combined of all atmospheric N species) would protect the most vulnerable terrestrial ecosystems (heaths, bogs, cryptogams) and values of 10-20 kg ha(-1) year(-1) would protect forests, depending on soil conditions. However, to derive the best analysis, the critical load concept should be coupled to the results and consequences of N saturation. PMID:12713921

Krupa, S V

2003-01-01

121

Mesoscopic CH3NH3PbI3/TiO2 heterojunction solar cells.  

PubMed

We report for the first time on a hole conductor-free mesoscopic methylammonium lead iodide (CH(3)NH(3)PbI(3)) perovskite/TiO(2) heterojunction solar cell, produced by deposition of perovskite nanoparticles from a solution of CH(3)NH(3)I and PbI(2) in ?-butyrolactone on a 400 nm thick film of TiO(2) (anatase) nanosheets exposing (001) facets. A gold film was evaporated on top of the CH(3)NH(3)PbI(3) as a back contact. Importantly, the CH(3)NH(3)PbI(3) nanoparticles assume here simultaneously the roles of both light harvester and hole conductor, rendering superfluous the use of an additional hole transporting material. The simple mesoscopic CH(3)NH(3)PbI(3)/TiO(2) heterojunction solar cell shows impressive photovoltaic performance, with short-circuit photocurrent J(sc)= 16.1 mA/cm(2), open-circuit photovoltage V(oc) = 0.631 V, and a fill factor FF = 0.57, corresponding to a light to electric power conversion efficiency (PCE) of 5.5% under standard AM 1.5 solar light of 1000 W/m(2) intensity. At a lower light intensity of 100W/m(2), a PCE of 7.3% was measured. The advent of such simple solution-processed mesoscopic heterojunction solar cells paves the way to realize low-cost, high-efficiency solar cells. PMID:23043296

Etgar, Lioz; Gao, Peng; Xue, Zhaosheng; Peng, Qin; Chandiran, Aravind Kumar; Liu, Bin; Nazeeruddin, Md K; Grätzel, Michael

2012-10-11

122

DFT investigation of NH3 physisorption on CuSO4 impregnated SiO2.  

PubMed

In this quantum chemical investigation, NH(3) physisorption onto a model of copper sulfate impregnated silica is compared with pure silica and copper sulfate adsorbents. The physisorption process is modeled as direct binding of the NH(3) molecule to the adsorption site of the dry adsorbents and as displacement of a H(2)O molecule by NH(3) in the hydrated complexes. The surface of silica is represented by a hydroxyl group attached to a silsesquioxane cage, H(7)Si(8)O(12)(OH) and silica impregnated with CuSO(4) by the most stable configuration of the cluster containing a CuSO(4) ion pair placed adjacent to the silica cage. H(2)O is systematically added to the dehydrated adsorbents to investigate the role of water in NH(3) adsorption. Modeling hydrated environments of each type of adsorbent is focused on H(2)O molecules that directly coordinate with the active sites. The results indicate that the binding energy of adsorbing NH(3) onto the mixed adsorbent is greater than in pure silica. This enhanced binding in the mixed adsorbent is consistent with improved Brønsted acidity of the silanol in the presence of CuSO(4). PMID:22456452

Ambati, Jyothirmai; Saiyed, Hamzah; Rankin, Stephen E

2012-03-29

123

Nitrogen conversion in relation to NH3 and HCN during microwave pyrolysis of sewage sludge.  

PubMed

The nitrogen conversions in relation to NH3 and HCN were investigated during microwave pyrolysis of sewage sludge. The nitrogen distributions and evolution of nitrogen functionalities in the char, tar, and gas fractions were conducted. The results suggested that the thermal cracking of protein in sludge produced three important intermediate compounds, including the amine-N, heterocyclic-N, and nitrile-N compounds. The deamination of amine-N compounds resulted from labile proteins cracking led to the formation of NH3 (about 7.5% of SS-N) between 300 and 500 °C. The cracking of nitrile-N and heterocyclic-N compounds in the tars from the dehydrogenation and polymerization of amine-N generated HCN (6.6%) from 500 to 800 °C, respectively. Moreover, the ring-opening of heterocyclic-N in the char and tar contributed to the release of NH3 accounting for about 18.3% of SS-N with the temperature increasing from 500 to 800 °C. Specifically, the thermal cracking of amine-N, heterocyclic-N and nitrile-N compounds contributed to above 80% of the total (HCN+NH3) productions. Consequently, it might be able to reduce the HCN and NH3 emissions through controlling the three intermediates production at the temperature of 500-800 °C. PMID:23477529

Tian, Yu; Zhang, Jun; Zuo, Wei; Chen, Lin; Cui, Yanni; Tan, Tao

2013-03-20

124

Insertion Compounds of 2H-TaS2?NH3  

PubMed Central

A new method of intercalating metals into layer compounds has been developed using electrolytic generation from the salt solution in ammonia. The results suggest that metals that are soluble in ammonia will form a homogeneous metal-ammonia intercalate layer, NH3·Mx, when x is less than the limiting solubility of M in NH3. The superconducting transition temperature (Tc) was found to increase as the c-axis expansion [2? = c(TaS2·NH3·Mx) - c(2H-TaS2)] decreased when M = lithium, sodium, and potassium. Of all the alkali metals, potassium gave the most stable compounds and the highest Tc, 4.7°K. Images

Meyer, S. F.; Acrivos, J. V.; Geballe, T. H.

1975-01-01

125

Photoacoustic system for NH3 detection in a selective catalytic reactor  

NASA Astrophysics Data System (ADS)

A new instrument specifically developed for measuring NH3 concentrations at the inlet and outlet of an SCR reactor is described. It is based on the photoacoustic technique and can perform an online and in-situ n-point measurement grid. The major problem is the severe interference of CO2 combustion gas that absorbs at the same wavelength used for NH3, lowering the sensitivity of the technique. A 13CO2 tunable laser emitting at three wavelengths has been used in order to evaluate simultaneously the CO2 and NH3 concentration. The integrated measurements have been done by a simple differential absorption technique by using a pyroelectric detector; the spatially resolved measurements have been carried out through the analysis of the acoustic wave generated by the laser beam and collected by four microphones perpendicularly disposed. Experimental tests on a 35 MW industrial plant and comparison with traditional sampling methods are presented.

Pintus, Nice; Carrer, I.; Del Corno, A.; Fiorina, Lorenzo; Zanzottera, Eugenio

1995-09-01

126

Neutron quasielastic scattering by (CH3NH3)5Bi2Cl11  

NASA Astrophysics Data System (ADS)

(CH3NH3)+-cation rotation in crystalline (CH3NH3)5Bi2Cl11 was studied by the QNS. The following (no doubt simplified) models were considered: 1. All cations are equivalent and rotate as a whole around C-N axes 2. Majority of cations behave as in point (1) and the remaining ones do not move (for the neutron observation window). 3. All CH3 groups rotate, whereas all NH3 groups do not move. The QNS measurements exclude the possibilities (1) and (3). A transition at ca. 160-170 K was confirmed in the measurements, as connected with an increase of the quasielastic component intensity observed via a dip of the EISF.

Jakubas, R.; Janik, J. A.; Krawczyk, J.; Mayer, J.; Stanek, T.; Steinsvoll, O.

1998-04-01

127

Mixing of dust and NH3 observed globally over anthropogenic dust sources  

NASA Astrophysics Data System (ADS)

The global distribution of dust column burden derived from MODIS Deep Blue aerosol products is compared to NH3 column burden retrieved from IASI infrared spectra. We found similarities in their spatial distributions, in particular their hot spots are often collocated over croplands and to a lesser extent pastures. Globally, we found 22% of dust burden collocated with NH3. This confirms the importance of anthropogenic dust from agriculture. Regionally, the Indian subcontinent has the highest amount of dust mixed with NH3 (26%), mostly over cropland and during the pre-monsoon season. North Africa represents 50% of total dust burden but accounts for only 4% of mixed dust, which is found over croplands and pastures in Sahel and the coastal region of the Mediterranean. In order to evaluate the radiative effect of this mixing on dust optical properties, we derive the mass extinction efficiency for various mixtures of dust and NH3, using AERONET sunphotometers data. We found that for dusty days the coarse mode mass extinction efficiency decreases from 0.62 to 0.48 m2 g-1 as NH3 burden increases from 0 to 40 mg m-2. The fine mode extinction efficiency, ranging from 4 to 16 m2 g-1, does not appear to depend on NH3 concentration or relative humidity but rather on mineralogical composition and mixing with other aerosols. Our results imply that a significant amount of dust is already mixed with ammonium salt before its long range transport. This in turn will affect dust lifetime, and its interactions with radiation and cloud properties.

Ginoux, P.; Clarisse, L.; Clerbaux, C.; Coheur, P.-F.; Dubovik, O.; Hsu, N. C.; Van Damme, M.

2012-05-01

128

Mixing of dust and NH3 observed globally over anthropogenic dust sources  

NASA Astrophysics Data System (ADS)

The global distribution of dust column burden derived from MODIS Deep Blue aerosol products is compared to NH3 column burden retrieved from IASI infrared spectra. We found similarities in their spatial distributions, in particular their hot spots are often collocated over croplands and to a lesser extent pastures. Globally, we found 22% of dust burden collocated with NH3, with only 1% difference between land-use databases. This confirms the importance of anthropogenic dust from agriculture. Regionally, the Indian subcontinent has the highest amount of dust mixed with NH3 (26%), mostly over cropland and during the pre-monsoon season. North Africa represents 50% of total dust burden but accounts for only 4% of mixed dust, which is found over croplands and pastures in Sahel and the coastal region of the Mediterranean. In order to evaluate the radiative effect of this mixing on dust optical properties, we derive the mass extinction efficiency for various mixtures of dust and NH3, using AERONET sunphotometers data. We found that for dusty days the coarse mode mass extinction efficiency decreases from 0.62 to 0.48 m2 g-1 as NH3 burden increases from 0 to 40 mg m-2. The fine mode extinction efficiency, ranging from 4 to 16 m2 g-1, does not appear to depend on NH3 concentration or relative humidity but rather on mineralogical composition and mixing with other aerosols. Our results imply that a significant amount of dust is already mixed with ammonium salt before its long range transport. This in turn will affect dust lifetime, and its interactions with radiation and cloud properties.

Ginoux, P.; Clarisse, L.; Clerbaux, C.; Coheur, P.-F.; Dubovik, O.; Hsu, N. C.; Van Damme, M.

2012-08-01

129

Quantum IR line list of NH3 and isotopologues for ISM and dwarf studies  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) was the first polyatomic molecule observed in the ISM. Its importance in interstellar molecules is only second to CO because its rovibrational spectroscopic signature can be used very effectively at deducing the conditions of the interstellar environment such as temperature and density, and because it is found in so many different interstellar objects in a wide temperature range. However, experimental determination of NH3 IR spectra is extremely difficult due to the large-amplutide inversion vibration, and the existing HITRAN2008 database for NH3 is limited in temperature, coverage, completeness, and accuracy. With rapid progress in theoretical chemistry and computational resources, now we are able to generate a highly reliable/accurate IR line list of NH3 (and its isotopologues) for astronomical studies. Exact quantum rovibrational computations on an empirically refined potential energy surface (with nonadiabatic corrections included) have achieved accuracies of 0.02-0.05 cm-1 (for line position) and better than 85-95% (for line intensity) for both NH3 and 15NH3 spectra. The unique feature of our work is that our predictions are essentially as accurate as reproducing existing measurements, suitable for synthetic simulation of various astrophysical environments or objects. The reliabilty and accuracy of our predictions for missing bands and higher energies computed on HSL-2 (Fig. 1) have been proved by the most recent high-resolution experiments and extended up to 7000 cm-1. See Huang et al. 2008, Huang et al. 2011, & Sung et al. 2012 for more details.

Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.; Sung, Keeyoon; Brown, Linda R.

2013-03-01

130

Global distributions and trends of atmospheric ammonia (NH3) from IASI satellite observations  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) emissions in the atmosphere have strongly increased in the past decades, largely because of the intensive livestock production and use of fertilizers. As a short-lived species, NH3 is highly variable in the atmosphere and its concentration is generally small, except in and close to local source areas. While ground-based measurements are possible, they are challenging and sparse. Advanced infrared sounders in orbit have recently demonstrated their capability to measure NH3, offering a new tool to refine global and regional budgets. In this paper we describe an improved retrieval scheme of NH3 total columns from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI). It exploits the hyperspectral character of this instrument by using an extended spectral range (800-1200 cm-1) where NH3 is optically active. This scheme consists of the calculation of a dimensionless spectral index from the IASI level1C radiances, which is subsequently converted to a total NH3 column using look-up-tables built from forward radiative transfer model simulations. We show how to retrieve the NH3 total columns from IASI quasi-globally and twice daily, above both land and sea, without large computational resources and with an improved detection limit. The retrieval also provides error characterization on the retrieved columns. Five years of IASI measurements (1 November 2007 to 31 October 2012) have been processed to acquire the first global and multiple-year dataset of NH3 total columns, which are evaluated and compared to similar products from other retrieval methods. Spatial distributions from the five years dataset are provided and analyzed at global and regional scales. We show in particular the ability of this method to identify smaller emission sources than those reported previously, as well as transport patterns above sea. The five year time series is further examined in terms of seasonality and inter-annual variability (in particular as a function of fire activity) separately for the Northern and Southern Hemispheres.

Van Damme, M.; Clarisse, L.; Heald, C. L.; Hurtmans, D.; Ngadi, Y.; Clerbaux, C.; Dolman, A. J.; Erisman, J. W.; Coheur, P. F.

2013-09-01

131

Adsorption and desorption of hydrogen on graphene with dimer conversion  

NASA Astrophysics Data System (ADS)

We apply non-equilibrium thermodynamics to describe the adsorption and desorption of molecular hydrogen on graphene. Lateral interactions, precursor states in both adsorption and desorption, and limited dimer conversion are important to explain semi-quantitatively the main features of temperature-programmed desorption spectra. All energy and vibrational parameters are taken from density functional calculations. Deficiencies in previous attempts are discussed. We also point out the need for a multi-dimensional dynamic theory.

Xia, Yu; Wang, Weiliang; Li, Zhibing; Kreuzer, H. Juergen

2013-11-01

132

Molecular motions in perovskite type layered compounds (NH3(CH2)nNH3)MnCl4, with n = 3, 4, 5; An incoherent neutron scattering study  

Microsoft Academic Search

Dynamics of the alkylene chains and of the NH+3 polar heads in (NH3(CH2)nNH3)MnCl4 compounds (n =3, 4, 5) were studied by means of incoherent neutron scattering techniques. In the disordered phases, the propylene chains (n = 3) keep an ``all trans'' structure while a conformational equilibrium between ``trans'' and ``twisted'' states is evidenced for longer chain compounds; in addition, the

F. Guillaume; C. Sourisseau; A. J. Dianoux

1989-01-01

133

Kinetics of gas-liquid reaction between NO and Co(NH3)6(2+).  

PubMed

Wet ammonia desulphurization process can be retrofitted for combined removal of SO2 and NO from the flue gas by adding soluble cobalt(II) salts into the aqueous ammonia solutions. The Co(NH3)6(2+) formed by ammonia binding with Co2+ is the active constituent of scrubbing NO from the flue gas streams. A stirred vessel with a plane gas-liquid interface was used to measure the chemical absorption rates of nitric oxide into the Co(NH3)6(2+) solution under anaerobic and aerobic conditions separately. The experiments manifest that the nitric oxide absorption reaction can be regarded as instantaneous when nitric oxide concentration levels are parts per million ranges. The gas-liquid reaction becomes gas film controlling as Co(NH3)6(2+) concentration exceeds 0.02 mol/l. The NO absorption rate is proportional to the nitric oxide inlet concentration. Oxygen in the gas phase is favorable to the absorption of nitric oxide. But it is of little significance to increase the oxygen concentration above 5.2%. The NO absorption rate decreases with temperature. The kinetic equation of NO absorption into the Co(NH3)6(2+) solution under aerobic condition can be written as. PMID:15869841

Long, Xiang-li; Xiao, Wen-De; Yuan, Wei-kang

2005-08-31

134

Projections of SO2, NOx, NH3 and VOC Emissions in East Asia Up to 2030  

Microsoft Academic Search

Starting from an inventory of SO2, NOx, VOC and NH3 emissions for the years 1990 and 1995 in East Asia (Japan, South and North Korea, China, Mongolia and Taiwan), the temporal development of the emissions of the four air pollutants is projected to the year 2030 based on scenarios of economic development. The projections are prepared at a regional level

Z. Klimont; J. Cofala; W. Schöpp; M. Amann; D. G. Streets; Y. Ichikawa; S. Fujita

2001-01-01

135

Highly sensitive NH 3 sensor using Pt catalyzed silica coating over WO 3 thick films  

Microsoft Academic Search

Ammonia gas sensing properties of a single layer WO3 thick film and a double layer sensor structure having a supported catalyst on it have been investigated. The single layer sensor exhibited low response to NH3. An enhancement in gas response was achieved by doping WO3 with Pt, Pd or Au. Ammonia sensing properties of the WO3 thick film was improved

Vibha Srivastava; Kiran Jain

2008-01-01

136

Structures and vibrations of phenol(NH3)2-4 clusters  

NASA Astrophysics Data System (ADS)

Vibronic spectra of PhOH(NH3)n clusters with n=2-4 have been obtained by resonant two-photon ionization, recorded at the mass channels of the fragment ions (NH3)nH+. The PhOH(NH3)2-4 spectra show long progressions of at least one low frequency vibration pointing to different S0 and S1 geometries along this coordinate. In addition, the vibronic bands of the n=2 cluster are split into two components. A tunneling motion is discussed, which may be responsible for these splittings. To get more information about the structure of PhOH(NH3)2 in the electronic ground state, IR-UV double resonance spectroscopy has been applied. Possible geometries for the n=2-4 clusters are considered based on a comparison between the experimental data and theoretical results from ab initio calculations, performed at the Hartree-Fock and second-order Møller-Plesset perturbation theory level.

Schmitt, M.; Jacoby, Ch.; Gerhards, M.; Unterberg, C.; Roth, W.; Kleinermanns, K.

2000-08-01

137

Laboratory Tests of NH 3\\/CO2 Cascade System for Supermarket Refrigeration  

Microsoft Academic Search

The development of a laboratory test rig of an NH3\\/CO2 cascade system is presented in this paper along with a theoretical model that simulates the performance of the system. The system solution under investigation replicates a medium size supermarket in Sweden, it is designed to fulfil the general requirements of the supermarket and operate within its temperature boundaries. Several possibilities

SAMER SAWALHA; JÖRGEN ROGSTAM; PER-OLOF NILSSON

138

Monitoring of NH 3 gas by LB polypyrrole-based SAW sensor  

Microsoft Academic Search

Surface acoustic wave (SAW) devices have been fabricated and tested as sensors of NH3 in gaseous phase. Polypyrrole films, prepared by Langmuir-Blodgett (LB) technique, have been deposited onto the surface of SAW devices as gas absorbent layers. Simultaneous measurements of SAW phase velocity and attenuation have been carried out in order to investigate the sensing mechanisms. The sensor response shows

M. Penza; E. Milella; V. I. Anisimkin

1998-01-01

139

Superconductivity in YbxMyHfNCl (M=NH3 and THF)  

NASA Astrophysics Data System (ADS)

We report the observation of superconductivity in rare-earth metal cointercalated compounds Ybx(M)yHfNCl with M = NH3 and tetrahydrofuran (THF). The superconducting transition temperature is about 23 and 24.6 K for Yb0.2(NH3)yHfNCl and Yb0.3(NH3)yHfNCl, respectively. Replacing the NH3 with a larger molecule THF, the superconducting transition temperature increases to 25.2 K in Yb0.2(THF)yHfNCl, which is almost the same as the highest Tc reported in the alkali-metal intercalated HfNCl superconductors. The Tc of Yb0.2(THF)yHfNCl is apparently suppressed by pressure up to 0.5 GPa, while the pressure effect on Tc becomes very small above 0.5 GPa. Our results suggest that for the most part, the superconductivity in these layered intercalated superconductors does not rely on intercalated metal ions, even magnetic ions.

Ye, Guojun; Ying, Jianjun; Yan, Yajun; Luo, Xigang; Cheng, Peng; Xiang, Ziji; Wang, Aifeng; Chen, Xianhui

2012-10-01

140

Estimation of NH3 Bi-Directional Flux from Managed Agricultural Soils  

EPA Science Inventory

The Community Multi-Scale Air Quality model (CMAQ v4.7) contains a bi-directional ammonia (NH3) flux option that computes emission and deposition of ammonia derived from commercial fertilizer via a temperature dependent parameterization of canopy and soil compensation ...

141

Characterization of a high pressure, high temperature modification of ammonia borane (BH3NH3).  

PubMed

At elevated pressures (above 1.5 GPa) dihydrogen bonded ammonia borane, BH3NH3, undergoes a solid-solid phase transition with increasing temperature. The high pressure, high temperature (HPHT) phase precedes decomposition and evolves from the known high pressure, low temperature form with space group symmetry Cmc21 (Z = 4). Structural changes of BH3NH3 with temperature were studied at around 6 GPa in a diamond anvil cell by synchrotron powder diffraction. At this pressure the Cmc21 phase transforms into the HPHT phase at around 140?°C. The crystal system, unit cell, and B and N atom position parameters of the HPHT phase were extracted from diffraction data, and a hydrogen ordered model with space group symmetry Pnma (Z = 4) subsequently established from density functional calculations. However, there is strong experimental evidence that HPHT-BH3NH3 is a hydrogen disordered rotator phase. A reverse transition to the Cmc21 phase is not observed. When releasing pressure at room temperature to below 1.5 GPa the ambient pressure (hydrogen disordered) I4mm phase of BH3NH3 is obtained. PMID:23927270

Nylén, Johanna; Eriksson, Lars; Benson, Daryn; Häussermann, Ulrich

2013-08-01

142

Photochemistry of NH3, CH4 and PH3. Possible applications to the Jovian planets  

NASA Astrophysics Data System (ADS)

Photolysis of NH3 at 185 nm in the presence of a two-fold excess of CH4 results in the loss of about 0.25 mole of CH4 per mole of NH3 decomposed (?CH4/?NH3). The loss arises from the abstraction of hydrogen atoms from CH4 by photolytically generated hot hydrogen atoms, the presence of which is established by the constancy of ?CH4/?NH3 between 298 and 156 K and by the quenching of the abstraction reaction when either H2 or SF6 is added. From the latter result, it can be concluded that NH3 photolysis in the H2-abundant atmosphere of Jupiter is not responsible for the presence of the carbon compounds observed there such as ethane, acetylene, and hydrogen cyanide, but may have had a role in the early atmosphere of Titan. Photolysis of PH3 with a 206 nm light source gives P2H4, which in turn is converted to a red-brown solid (P4?). The course of the photolysis is not changed appreciably when the temperature is lowered to 157 K except that the concentration of P2H4 increases. The presence of H2 has no effect on the P2H4 yield. Photolysis of 9?1 NH3?PH3 gives a rate of decomposition of PH3 that is comparable with that observed by the direct photolysis of PH3. Comparable amounts of P2H4 and the red-brown solid are also observed. The mechanisms of these photochemical reactions together with their implications to the atmospheric chemistry of Jupiter are discussed. The structures of the compounds responsible for the wide array of colorse.g., brown, red and white, observed in the atmosphere of Jupiter have been the subject of extensive speculation. One theory suggests that these colors are due to organic materials formed by the action of either solar ultraviolet light or electric discharges on mixtures of CH4, NH3 and NH4HS in the Jovian atmosphere (Ponnamperuma, 1976; Khareet al., 1978). An alternative hypothesis is that the colors are due to inorganic compounds resulting from the photolysis of NH4HS and PH3 (Lewis and Prinn, 1970; Prinn and Lewis, 1975). In this paper we will summarize our experiments which were designed to test some of these hypotheses.

Ferris, J. P.; Morimoto, J. Y.; Benson, Robert; Bossard, Alain

1982-09-01

143

Molecular motions in perovskite type layered compounds (NH3(CH2)nNH3)MnCl4, with n = 3, 4, 5; An incoherent neutron scattering study  

NASA Astrophysics Data System (ADS)

Dynamics of the alkylene chains and of the NH+3 polar heads in (NH3(CH2)nNH3)MnCl4 compounds (n =3, 4, 5) were studied by means of incoherent neutron scattering techniques. In the disordered phases, the propylene chains (n = 3) keep an ``all trans'' structure while a conformational equilibrium between ``trans'' and ``twisted'' states is evidenced for longer chain compounds; in addition, the NH3 groups perform independent oscillations. The phase sequences in all these compounds are then discussed. I.L.L. 156 X, 38042 Grenoble, France.

Guillaume, F.; Sourisseau, C.; Dianoux, A. J.

1989-01-01

144

[H3N(CH2)7NH3]8(CH3NH3)2Sn(IV)Sn(II)12I46- a mixed-valent hybrid compound with a uniquely templated defect-perovskite structure.  

PubMed

The incorporation of H(3)N(CH(2))(7)NH(3) with CH(3)NH(3)SnI(3) resulted in the formation of a mixed-valent and semiconducting (Eg = 0.84 eV) organic-based perovskite, [H(3)N(CH(2))(7)NH(3)](8)(CH(3)NH(3))(2)Sn(iv)Sn(ii)(12)I(46), with a unique 3D defect-perovskite structure with ordered vacancies at the Sn and I sites. PMID:15614368

Guan, Jun; Tang, Zhongjia; Guloy, Arnold M

2004-11-19

145

A Water Maser and NH3 Survey of GLIMPSE Extended Green Objects  

NASA Astrophysics Data System (ADS)

We present the results of a Nobeyama 45 m H2O maser and NH3 survey of all 94 northern GLIMPSE extended green objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5 ?m emission. We observed the NH3(1,1), (2,2), and (3,3) inversion lines, and detected emission toward 97%, 63%, and 46% of our sample, respectively (median rms ~ 50 mK). The H2O maser detection rate is 68% (median rms ~ 0.11 Jy). The derived H2O maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on mid-infrared (MIR) properties or maser associations. H2O masers and warm dense gas, as indicated by emission in the higher-excitation NH3 transitions, are most frequently detected toward EGOs also associated with both Class I and II CH3OH masers. Ninety-five percent (81%) of such EGOs are detected in H2O (NH3(3,3)), compared to only 33% (7%) of EGOs without either CH3OH maser type. As populations, EGOs associated with Class I and/or II CH3OH masers have significantly higher NH3 line widths, column densities, and kinetic temperatures than EGOs undetected in CH3OH maser surveys. However, we find no evidence for statistically significant differences in H2O maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1 mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic H2O maser luminosity and clump number density. H2O maser luminosity is weakly correlated with clump (gas) temperature and clump mass.

Cyganowski, C. J.; Koda, J.; Rosolowsky, E.; Towers, S.; Donovan Meyer, J.; Egusa, F.; Momose, R.; Robitaille, T. P.

2013-02-01

146

Hydrogen Polyphosphides P3H2(3-) and P3H3(2-): synthesis and crystal structure of K3(P3H2).2.3NH3, Rb3(P3H2).NH3, [Rb(18-crown-6)]2(P3H3).7.5NH3, and [Cs(18-crown-6)]2(P3H3).7NH3.  

PubMed

The incongruous solvation of polyphosphides and phosphanes or the direct reduction of white phosphorus in liquid ammonia leads to the hydrogen polyphosphides catena-dihydrogen triphosphide, P(3)H(2)(3-), and catena-trihydrogen triphosphide, P(3)H(3)(2-), in the crystalline compounds K(3)(P(3)H(2)).2.3NH(3) (1), Rb(3)(P(3)H(2)).NH(3) (2), [Rb(18-crown-6)](2)(P(3)H(3)).7.5NH(3) (3), and [Cs(18-crown-6)](2)(P(3)H(3)).7NH(3) (4). PMID:19235955

Kraus, Florian; Aschenbrenner, Jürgen C; Klamroth, T; Korber, Nikolaus

2009-03-01

147

Spectroscopic line parameters of 14NH3 at 1.5 µm  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) is one of the major opacity sources in the atmosphere of outer planets, low mass brown dwarfs, and possibly extrasolar planets, particu- larly in the 1.5 µm region (the H-band). Spectroscopic information of NH3 in this region, however, is completely missing in the HITRAN database. In order to remedy de ciency of the spectroscopic data in the 1.5 µm region, we analyze the laboratory spectra recorded with the McMath-Pierce Fourier transform spectrometer (FTS) on Kitt Peak Observatory in Arizona. Preliminary results are discussed for a few lines, which includes their line positions, strengths, lower state energies, and quantum assignments. The full analysis is in progress.

Sung, K.; Brown, L. R.

2011-05-01

148

Electron beam induced chemical dry etching and imaging in gaseous NH3 environments  

NASA Astrophysics Data System (ADS)

We report the use of ammonia (NH3) vapor as a new precursor for nanoscale electron beam induced etching (EBIE) of carbon, and an efficient imaging medium for environmental scanning electron microscopy (ESEM). Etching is demonstrated using amorphous carbonaceous nanowires grown by electron beam induced deposition (EBID). It is ascribed to carbon volatilization by hydrogen radicals generated by electron dissociation of NH3 adsorbates. The volatilization process is also effective at preventing the buildup of residual hydrocarbon impurities that often compromise EBIE, EBID and electron imaging. We also show that ammonia is a more efficient electron imaging medium than H2O, which up to now has been the most commonly used ESEM imaging gas.

Lobo, Charlene J.; Martin, Aiden; Phillips, Matthew R.; Toth, Milos

2012-09-01

149

Submillimeter spectrum of NH3-H2O dimer in its equilibrium gas phase  

NASA Astrophysics Data System (ADS)

The first observation of the microwave spectrum of the NH3-H2O molecular complex in its equilibrium gas phase is reported. Earlier, the spectrum of NH3-H2O was observed only in nonequilibrium cold supersonic molecular beams. As in the previous paper [1] dealing with the observation of the equilibrium spectrum of HF-HF dimer, we use a submillimeter spectrometer with a BWT and acoustic detector and a cooled absoprtion cell. The submillimeter line frequencies continuing the series known from the beam investigations have been measured. New series, which obviously correspond to the higher states of the dimer, have been detected. The primary results of the analysis of the dimer spectrum together with the earlier data are presented.

Zobov, N. F.; Karyakin, E. N.; Krupnov, A. F.; Suenram, R. D.

1995-07-01

150

Thin film polypyrrole\\/SWCNTs nanocomposites-based NH 3 sensor operated at room temperature  

Microsoft Academic Search

A PPY\\/SWCNTs nanocomposite-based sensor with relatively high sensitivity and fast response–recovery was developed for detection of NH3 gas at room temperature. The gas-sensitive composite thin film was prepared using chemical polymerization and spin-coating techniques, and characterized by Fourier transformed infrared spectra and field-emission scanning electron microscopy. The results reveal that the conjugated structure of the PPY layer was formed and

Nguyen Van Hieu; Nguyen Quoc Dung; Phuong Dinh Tam; Tran Trung; Nguyen Duc Chien

2009-01-01

151

Leaching of roast-reduced manganese nodules in NH 3–(NH 4) 2CO 3 medium  

Microsoft Academic Search

Reduction roast–ammonia leach process developed at NML for extraction of valuable metals from manganese nodules yielded low cobalt recovery (56%), although copper and nickel recoveries were >90% (Jana et al., 1999b). With an aim to increase the cobalt recovery, a modified NH3–(NH4)2CO3 leaching flow-sheet have been developed for treatment of reduced manganese nodules. The major steps of this flow sheet

D. Mishra; R. R. Srivastava; K. K. Sahu; T. B. Singh; R. K. Jana

2011-01-01

152

Imaging studies of the photodissociation of NH3+ and ND3+ cations.  

PubMed

Velocity map ion imaging methods have been used to study the photofragmentation dynamics of state-selected NH3+ and ND3+ cations. The cations were prepared in selected nu2+ bending vibrational levels of the ground (x2A'') electronic state by two-photon resonant, three-photon ionization of NH3(ND3), via several different nu2' levels of the and ' Rydberg states. Subsequent excitation to the A2E state by absorption of a 207.6 nm photon resulted in N-H(D) bond fission and NH2+(ND2+) fragment ion formation. These fragments exhibit isotropic recoil velocity distributions, which peak at low kinetic energy but extend to the maximum allowed by energy conservation. Such findings accord with conclusions from earlier electron induced photoionization and photoelectron-photoion coincidence studies of NH3 at similar total energies (defined relative to the ground-state neutral) and, as previously, can be rationalized in terms of excitation to the Jahn-Teller distorted state, rapid radiationless transfer via one or more conical intersections linking the and state potential energy surfaces (PESs) and subsequent unimolecular decay on the latter PES. Weak NH2+ and NH+ fragment ion signals are also observed when exciting with the ionization laser only; imaging these fragment ions provides some insights into their likely formation mechanisms. PMID:19216561

Webb, Alexander D; Nahler, N Hendrik; Ashfold, Michael N R

2009-04-23

153

Nitrogen Hyperfine Splittings in the Electron Spin Resonance Spectrum of the Cr(NH3)5NO(2+) Ion.  

National Technical Information Service (NTIS)

A well-resolved esr spectrum of Cr(NH3)5NO2+ in DMF solution is reported which appears to be the first reported example of an NH3 ligand (14N) hyperfine splitting. The esr data, combined with MO calculations, provide considerable information concerning th...

P. T. Manoharan H. A. Kuska M. T. Rogers

1967-01-01

154

SIMPLE DESIGN FOR AUTOMATION OF TUNGSTEN(VI) OXIDE TECHNIQUE FOR MEASUREMENT OF NH3, AND HNO3  

EPA Science Inventory

The tungstic acid technique for collection and analysis of NH3 and HNO3 concentrations in the ambient air has been automated in a simple and cost-effective design. The design allows complete separation of HNO3 and NH3 during detection. Unattended operation in field trials has bee...

155

Dechlorination of PCBs, CAHs, herbicides and pesticides neat and in soils at 25 °C using Na\\/NH 3  

Microsoft Academic Search

Na\\/NH3 reductions have been used to dehalogenate polychlorinated biphenyls (PCBs), chlorinated aliphatic hydrocarbons (CAHs) and pesticides at diffusion controlled rates at room temperature in model compound studies in both dry NH3 and when water was added. The rate ratio of dechlorination (aliphatic and aromatic compounds) versus reaction of the solvated electron with water is very large, allowing wet soils or

Charles U. Pittman; Jinbao He

2002-01-01

156

Density functional study of adsorption properties of NO and NH3 over CuO/?-Al2O3 catalyst  

NASA Astrophysics Data System (ADS)

Currently, selective catalytic reduction (SCR) of NOx with NH3 has been widely applied to reduce the emission of nitrogen oxides from mobile and stationary sources. But the detailed SCR reaction mechanism is still controversial and lacks the related comparative study of molecule modeling. The SCR reaction belongs to the gas-solid multiphase reaction, in which the adsorption of NH3 and NO by the catalysts plays an important role. In the present study, the adsorption properties of NH3 and NO on both the dry and partially hydroxylated ?-Al2O3 (1 1 0) surfaces supported CuO were revealed using the density-function theory (DFT) calculations. The results showed that NH3 could be adsorbed strongly on the dry (1 1 0) surface in the form of coordinated NH3 and NH4+. Some of the coordinated NH3 could then undergo H-abstraction and form the -NH2 species. NO could be adsorbed weakly on the dry surface, and could also be adsorbed as bidentate nitrates or bridged nitrites. However, the adsorption activation of NH3 and NO on the partially hydroxylated surface was much weaker. The results of the DFT calculations are in good agreement with the experimental results and provided detailed clues to understand the adsorption mechanism of NH3 and NO on the CuO/?-Al2O3 catalysts.

Cao, Fan; Su, Sheng; Xiang, Jun; Sun, Lushi; Hu, Song; Zhao, Qingsen; Wang, Pengying; Lei, Siyuan

2012-11-01

157

Morphology and hydrogen desorption characteristic of Ni-TiN nanocomposite particle prepared by RF plasma  

Microsoft Academic Search

Ni-TiN nanocomposite particles are prepared by RF plasma. Dumbbell-like and dice-like morphologies are seen. Hydrogen sorption-desorption characteristics of the nanocomposite particles were examined by temperature-programmed desorption measurements. Hydrogen desorption at 500–700 K is observed, which implies that a new adsorption state of hydrogen exists. Hydrogen desorption characteristics are not so influenced by coadsorption of CO. The results are compared with

Y. Sakka; H. Okuyama; T. Uchikoshi; S. Ohno

1997-01-01

158

Rovibrational spectra of ammonia. II. Detailed analysis, comparison, and prediction of spectroscopic assignments for 14NH3, 15NH3, and 14ND3.  

PubMed

Several aspects of ammonia rovibrational spectra have been investigated using the new HSL-2 potential energy surface that includes an approximate correction for nonadiabatic effects. The unprecedented accuracy of rovibrational energy levels and transition energies computed using HSL-2 was demonstrated in Part I of this study. For (14)NH(3), new assignments for a few ?(3) + ?(4) band transitions and energy levels are suggested, and discrepancies between computed and HITRAN energy levels in the 2?(4) band are analyzed (2?(4) is the most difficult band below 5000 cm(-1)). New assignments are suggested for existing or missing 2?(4) levels. Several new vibrational bands are identified from existing, unassigned HITRAN data, including 2?(2) + ?(4), (?(3) + ?(4)) -A(')?A("), ?(1) + 2?(2), and 2?(2) + 2?(4). The strong mixing between the 2?(4) and 2?(2) + ?(4) bands is carefully examined and found to be the source of the difficulties in the experimental modeling of 2?(4). Discussion is presented for preliminary J = 10 results, where the overall root-mean-square error is estimated to be less than 0.039 cm(-1). The analysis of the 4?(2) band demonstrates both the reliability and the accuracy of predictions from HSL-2. The full list of computed J = 0 band origins (with assignments) and the inversion splittings up to 7000-8000 cm(-1) above the zero-point energy are presented. J = 0-2 levels are reported for those bands below 5100 cm(-1) that are missing from the HITRAN database. For (15)NH(3), excellent agreement is found for the available ?(2) and ?(3) + ?(4)(E) transition energies, but significant deficiencies are shown for HITRAN levels and several corrections are suggested. The (15)N isotopic effects are presented for the J = 0-6 levels of 13 HITRAN bands. For (14)ND(3), we reproduce the pure rotational inversion spectra line frequencies with an accuracy similar to that for (14)NH(3). However, it is not possible to reproduce simultaneously all four pairs of inversion-split vibrational fundamentals to better than 0.05 cm(-1) uncertainty. It is suggested that a reanalysis of some suspicious (14)ND(3) fundamental bands is required. The analyses presented here and in Part I show that rovibrational energy levels and transition frequencies computed with HSL-2 (with nonadiabatic corrections) remain highly accurate well beyond the experimental data used in the refinement procedure. Calculations using HSL-2 are capable of revealing many deficiencies in experimental analyses of ammonia spectra and provide reliable predictions with similar accuracy. It is expected that the results of this study will be useful in the future interpretation of high-resolution spectra from laboratory experiments or from astronomical observations. The present work represents a very significant advance in the state of our knowledge of the spectroscopy of ammonia and its isotopologues. PMID:21280739

Huang, Xinchuan; Schwenke, David W; Lee, Timothy J

2011-01-28

159

Magneto-optical effects of excitons in the layered perovskite-type material (C6H13NH3)2(CH3NH3)Pb2I7  

NASA Astrophysics Data System (ADS)

Magnetoabsorption spectra of (C6H13NH3)2(CH3NH3)Pb2I7, a layered perovskite-type material with ``bilayer'' [PbI6]-octahedra planes, measured under pulsed magnetic fields up to 41 T at 4.2 K show that its lowest-exciton Bohr radius is 6.9 Å. This is 35% longer than that of (C6H13NH3)2PbI4, a monolayer-well counterpart, and demonstrates the effect of the well-layer thickness.

Kataoka, Takeshi; Kondo, Takashi; Ito, Ryoichi; Sasaki, Satoshi; Uchida, Kazuhito; Miura, Noboru

1994-07-01

160

Application of Temperature Dependent Computerized Control of Desorption for Catalyst Surface Characterization.  

National Technical Information Service (NTIS)

The dissertation discusses the applications of temperature-programmed desorption and its limits in the characterisation of catalyst surfaces and in heterogeneous catalysis. Further, the quantitative information of the TPD spectra is critically reviewed. (...

E. Morales de Leguizamon

1984-01-01

161

High Temperature Interaction Between H2, CH4, NH3 and Ilmenite  

NASA Astrophysics Data System (ADS)

Three different reductive gaseous agents H2, CH4 and NH3 have been employed to investigate the high temperature reduction of ilmenite (FeTiO3). Thermogravimetry and mass spectrometry techniques have been utilized in the investigation of the reactions behavior. Considerations have been made on the parallel reactions due to the change of the components ratio ongoing the reduction process. In particular the catalytic effect of the metallic iron on the decomposition of methane in the second reaction and of ammonia in the last one is being discussed as well as the formation of important by-products.

de Maria, Giovanni; Brunetti, Bruno; Trionfetti, Giuseppe; Ferro, Daniela

2003-01-01

162

Phase Transition in (CH3NH3)3Bi2Br9 Single Crystal  

NASA Astrophysics Data System (ADS)

The successive phase transitions in (CH3NH3)3Bi2Br9 (MABB) single crystal have been investigated by measuring of dielectric and elastic dispersion and Brillouin and Raman scattering. Softening of the elastic constant c66 and critical slowing down of the order parameter, which belongs to the Eg representation, have been found in the phase I. No optical soft mode has been observed. The phase transition from the phase I to the phase II has been discussed by the Landau theory.

Iwata, Makoto; Eguchi, Masahito; Ishibashi, Yoshihiro; Sasaki, Shigeo; Shimizu, Hiroyasu; Kawai, Taketoshi; Shimanuki, Shigetaka

1993-09-01

163

Dispersal of dense protostellar material - NH3 hot cores and outflows in Sagittarius B2  

SciTech Connect

VLA observations of Sgr B2 in six ammonia transitions have uncovered two 200-K condensations with approximately 0.2 pc diameters associated with water maser sources which are similar to the Orion hot core but are more massive. Total NH3 mass of the northern source is 1000 times higher than in the Orion hot core. The hot core emission traces dense gas around newly formed massive stars, and is produced during a relatively brief stage after the star begins to heat the surrounding medium and before the dense gas is dispersed by outflow and the emergence of an expanding H II region. 36 references.

Vogel, S.N.; Genzel, R.; Palmer, P.

1987-05-01

164

Experimental and theoretical studies of reactions of neutral vanadium and tantalum oxide clusters with NO and NH3.  

PubMed

Reactions of neutral vanadium and tantalum oxide clusters with NO, NH(3), and an NO/NH(3) mixture in a fast flow reactor are investigated by time of flight mass spectrometry and density functional theory (DFT) calculations. Single photon ionization through a 46.9 nm (26.5 eV) extreme ultraviolet (EUV) laser is employed to detect both neutral cluster distributions and reaction products. Association products VO(3)NO and V(2)O(5)NO are detected for V(m)O(n) clusters reacting with pure NO, and reaction products, TaO(3,4)(NO)(1,2), Ta(2)O(5)NO, Ta(2)O(6)(NO)(1-3), and Ta(3)O(8)(NO)(1,2) are generated for Ta(m)O(n) clusters reacting with NO. In both instances, oxygen-rich clusters are the active metal oxide species for the reaction M(m)O(n)+NO?M(m)O(n)(NO)(x). Both V(m)O(n) and Ta(m)O(n) cluster systems are very active with NH(3). The main products of the reactions with NH(3) result from the adsorption of one or two NH(3) molecules on the respective clusters. A gas mixture of NO:NH(3) (9:1) is also added into the fast flow reactor: the V(m)O(n) cluster system forms stable, observable clusters with only NH(3) and no V(m)O(n)(NO)(x)(NH(3))(y) species are detected; the Ta(m)O(n) cluster system forms stable, observable mixed clusters, Ta(m)O(n)(NO)(x)(NH(3))(y), as well as Ta(m)O(n)(NO)(x) and Ta(m)O(n)(NH(3))(y) individual clusters, under similar conditions. The mechanisms for the reactions of neutral V(m)O(n) and Ta(m)O(n) clusters with NO/NH(3) are explored via DFT calculations. Ta(m)O(n) clusters form stable complexes based on the coadsorption of NO and NH(3). V(m)O(n) clusters form weakly bound complexes following the reaction pathway toward end products N(2)+H(2)O without barrier. The calculations give an interpretation of the experimental data that is consistent with the condensed phase reactivity of V(m)O(n) catalyst and suggest the formation of intermediates in the catalytic chemistry. PMID:21054039

Heinbuch, S; Dong, F; Rocca, J J; Bernstein, E R

2010-11-01

165

Optical absorption spectra in the quasi-two-dimensional antiferromagnets (NH3(CH2)nNH3)MnCl4 (n=2, 3, 4, 5). II. Theoretical  

Microsoft Academic Search

For pt.I see ibid., vol.21, p.4795 (1988). Optical absorption spectra under magnetic field and uniaxial stress in (NH3(CH2)nNH3)MnCl4 (n=2, 3, 4, 5) were analysed within the framework of a ligand-field approximation. All of the lines that appeared at low temperature are magnon-assisted transitions, and they make drastic shifts at the spin-flop transition. It was concluded that the spectral shifts at

N. Watanabe; N. Kojima; I. Tsujikawa

1988-01-01

166

UV induced Chemistry of Polycyclic Aromatic Hydrocarbons in NH_3-containing Interstellar Ice Analogues  

NASA Astrophysics Data System (ADS)

Polycyclic Aromatic Hydrocarbons are expected to be widely present in the interstellar medium. For the typical temperatures in space, they will freeze out on icy dust grains, like other species, such as water and ammonia. Optical spectra of PAHs in water ice have become available recently using a new setup at Leiden (OASIS - Optical Absorption Setup for Ice Spectroscopy). This setup allows to study the time resolved PAH and PAH photoproduct behavior upon hard UV photolysis, evidencing an active PAH chemistry in the ice for temperatures in the 15-150 K regime. The matrix surrounding turns out to be very important. As an extension of the previous PAH:H2O ices, here the first results are presented for UV irradiated PAH:NH3 and PAH:NH3/H2O ices. In this way PAH destruction and molecule formation can be monitored in situ and on line. It is found that whereas H2O ices particularly result in the formation of PAH-cations, ammonia seems to favor the formation of anions in the ice. After photolysis is stopped, the PAH anion signal vanishes. At this stage these results are interpreted by assuming that charged species form in interstellar ice by electron transfer from ammonia photoproducts, rather than acid-base proton transfer.

Cuylle, S. H.; Tenenbaum, E. D.; Bouwman, J.; Linnartz, H.

2011-05-01

167

Neutral tricoordinated beryllium(0) compounds--isostructural to BH(3) but isoelectronic to NH(3).  

PubMed

The electronic structure and reactivity of neutral tricoordinated Be(0) compounds BeL(3), L = CO (1), NHC (2) and PMe(3) (3) are explored by quantum mechanical calculations. These BeL(3) complexes are found to be planar or nearly planar like electron deficient BH3 but isoelectronic with NH3 and possess three L?Be donor-acceptor bonds. The Be atom can be considered as sp(2)-hybridized with a lone pair in the highly diffused 2p(z)-orbital in contrast to the sp(3) hybridization in isoelectronic NH(3). Even though the lone pair on Be is stabilized through ?-back donation or hyperconjugative interaction with the ligands, yet it is highly reactive towards Lewis acids such as H(+), BH(3) and W(CO)(5). The calculated gas phase protonation energies reveal that the NHC complex 2 and the trimethylphosphine complex 3 are 'super basic' in nature. Promising ligand property of BeL(3) has also been noted with BH(3) and transition metal fragment W(CO)(5). Besides, the reactivity of 2 and 3 is found to be more as compared to 1. PMID:23360926

De, Susmita; Parameswaran, Pattiyil

2013-04-01

168

Re-analysis of ammonia spectra: Updating the HITRAN 14NH3 database  

NASA Astrophysics Data System (ADS)

The data incorporated in the HITRAN database for 14NH3 are analyzed using a comprehensive and consistent set of quantum numbers, empirical lower energy levels and the BYTe variationally calculated line list as reference points. Labelings are checked to ensure that they obey both the usual selection rules and the HITRAN labeling formalisms; the problems identified are corrected where possible. Further assignments are brought into question by combination difference (CD) checking of implied upper energy levels. The CD analysis yields an 89% complete 14NH3 energy level list up to 6610 cm?1 and J=21, self-consistent to 0.1 cm?1. In combination with the 1723 previously unassigned and unlabeled lines in HITRAN a total of 2529 problem lines were identified for re-analysis. The compiled energy level list was used to label and assign the set of problem transitions, resulting in a total of 249 new assignments and a further 368 new labelings. Assignment by comparison with the reference line list resulted in 111 further new line assignments and 14 new labelings. Intensities are checked against recent measurements and BYTe. New intensities are proposed for the ?2 band with new intensities and line positions for the 2?2??2 and new line lists are created for the ?2??2, ?2??4 and ?4??4 bands. BYTe band intensities are analyzed to identify other regions of missing intensity.

Down, Michael J.; Hill, Christian; Yurchenko, Sergei N.; Tennyson, Jonathan; Brown, Linda R.; Kleiner, Isabelle

2013-11-01

169

Enhanced electroluminescence of silicon-rich silicon nitride light-emitting devices by NH3 plasma and annealing treatment  

NASA Astrophysics Data System (ADS)

Silicon-rich silicon nitride (SRSN) films were deposited on p-type silicon substrates using a conventional plasma-enhanced chemical vapor deposition (PECVD) system. Before deposition, silicon substrate was pre-treated by NH3 plasma in the PECVD system. And devices with metal-insulator-semiconductor (MIS) structure were fabricated using indium tin oxides (ITO) as anode and aluminum (Al) film as cathode. It was found that after 1100 °C annealing the electroluminescence (EL) intensity of NH3 plasma pre-treated MIS devices was increased greatly comparing with that of without NH3 plasma pre-treated devices. It is due to the passivation or reducing of interfacial states and nonradiative defects in SRSN films by the NH3 plasma pre-treatment and high-temperature annealing that enhanced the EL intensity of the SRSN MIS devices.

Li, Dongsheng; Huang, Jianhao; Yang, Deren

2009-05-01

170

NMR study of monomethylammonium cation in (CH3NH3)5Bi2Cl11 ferroelectric polycrystal.  

PubMed

Spin-lattice relaxation times T1 and T1p are determined for protons in three polycrystals (CH3NH3)5Bi2Cl11, (CD3NH3)5Bi2Cl11 and (CH3ND3)5Bi2Cl11. The temperature dependencies of the relaxation times obtained for (CH3NH3)5Bi2Cl11 and (CD3NH3)5Bi2Cl11 are interpreted as a result of correlated motions of the three-proton groups of the monomethylammonium cation. The minimum of the T1p relaxation time is explained as a result of the oscillations of the symmetry axis of the whole cation. PMID:10378430

Medycki, W

1999-05-01

171

Effects of NH 3 Plasma Treatment of the Substrate on Metal Organic Chemical Vapor Deposition of Copper Films  

NASA Astrophysics Data System (ADS)

Surface modification by NH3 plasma treatment enabled selective copper (Cu) chemical vapor deposition (CVD) andchanged the structure of the deposited Cu film. After NH3 plasma treatment of the substrate, Cu nucleation was suppressedon borophosphosilicate glass (BPSG), while Cu films were formed on TiN. NH3 plasma treatment was not as effective as N2 plasma treatment in inducing the selectivity. The lower efficiency of the NH3 plasma in inducing the selectivitycan be explained by the generation of NH++ or H species. A Cu film deposited on plasma-treated TiN showed larger grainsand enhanced (111) preferential orientation compared with that deposited on untreated TiN, which could be explained in termsof surface energy minimization.

Kim, Young; Jung, Donggeun; Kim, Dong; Min, Suk-Ki

1998-08-01

172

Immobilization of enzyme and antibody on ALD-HfO2-EIS structure by NH3 plasma treatment  

NASA Astrophysics Data System (ADS)

Thin hafnium oxide layers deposited by an atomic layer deposition system were investigated as the sensing membrane of the electrolyte-insulator-semiconductor structure. Moreover, a post-remote NH3 plasma treatment was proposed to replace the complicated silanization procedure for enzyme immobilization. Compared to conventional methods using chemical procedures, remote NH3 plasma treatment reduces the processing steps and time. The results exhibited that urea and antigen can be successfully detected, which indicated that the immobilization process is correct.

Wang, I.-Shun; Lin, Yi-Ting; Huang, Chi-Hsien; Lu, Tseng-Fu; Lue, Cheng-En; Yang, Polung; Pijanswska, Dorota G.; Yang, Chia-Ming; Wang, Jer-Chyi; Yu, Jau-Song; Chang, Yu-Sun; Chou, Chien; Lai, Chao-Sung

2012-03-01

173

Mechanism of the selective catalytic reduction of NO x with NH 3 over environmental-friendly iron titanate catalyst  

Microsoft Academic Search

The reaction mechanism of the selective catalytic reduction (SCR) of NOx with NH3 over environmental-friendly iron titanate catalyst (FeTiOx) was investigated in detail. Over the iron titanate crystallite with specific Fe–O–Ti structure, both Brønsted and Lewis acid sites were present and involved in the SCR reaction. NH3 mainly adsorbed on titanium sites in the form of ionic NH4+ and coordinated

Fudong Liu; Hong He; Changbin Zhang; Wenpo Shan; Xiaoyan Shi

2011-01-01

174

Characteristics of TiN thin films grown by ALD using TiCl 4 and NH 3  

Microsoft Academic Search

Titanium nitride thin film was deposited on a silicon wafer by the Atomic Layer Deposition (ALD) method using TiCl4 and NH3 as source chemicals. Nitrogen gas was used for carrying the TiCl4 and purging the reactants. The gases were introduced into the reaction chamber in the sequence of TiCl4?N2?NH3?N2 for the saturated surface reaction on the wafer. TiN film was

C. H. Ahn; S. G. Cho; H. J. Lee; K. H. Park; S. H. Jeong

2001-01-01

175

Cr–Sn oxide thin films: Electrical and spectroscopic characterisation with CO, NO 2, NH 3 and ethanol  

Microsoft Academic Search

We have studied the electrical responses of Cr–Sn oxide thin films towards CO, NO2, NH3 and ethanol vapours at different temperatures and for different concentrations. Moreover, we employed FT-IR absorbance and UV–vis–NIR diffuse reflectance spectroscopies to study the electronic transitions caused by reducing treatments with ethanol and CO. Conductance measurements, performed with CO, NO2, NH3 and ethanol, show low responses

S. Morandi; E. Comini; G. Faglia; G. Ghiotti

2006-01-01

176

Immobilization of enzyme and antibody on ALD-HfO2-EIS structure by NH3 plasma treatment.  

PubMed

Thin hafnium oxide layers deposited by an atomic layer deposition system were investigated as the sensing membrane of the electrolyte-insulator-semiconductor structure. Moreover, a post-remote NH3 plasma treatment was proposed to replace the complicated silanization procedure for enzyme immobilization. Compared to conventional methods using chemical procedures, remote NH3 plasma treatment reduces the processing steps and time. The results exhibited that urea and antigen can be successfully detected, which indicated that the immobilization process is correct. PMID:22401350

Wang, I-Shun; Lin, Yi-Ting; Huang, Chi-Hsien; Lu, Tseng-Fu; Lue, Cheng-En; Yang, Polung; Pijanswska, Dorota G; Yang, Chia-Ming; Wang, Jer-Chyi; Yu, Jau-Song; Chang, Yu-Sun; Chou, Chien; Lai, Chao-Sung

2012-03-08

177

Immobilization of enzyme and antibody on ALD-HfO2-EIS structure by NH3 plasma treatment  

PubMed Central

Thin hafnium oxide layers deposited by an atomic layer deposition system were investigated as the sensing membrane of the electrolyte-insulator-semiconductor structure. Moreover, a post-remote NH3 plasma treatment was proposed to replace the complicated silanization procedure for enzyme immobilization. Compared to conventional methods using chemical procedures, remote NH3 plasma treatment reduces the processing steps and time. The results exhibited that urea and antigen can be successfully detected, which indicated that the immobilization process is correct.

2012-01-01

178

Reliability of NH3 as the temperature probe of cold cloud cores  

NASA Astrophysics Data System (ADS)

Context. The temperature is a central parameter affecting the chemical and physical properties of dense cores of interstellar clouds and their potential evolution towards star formation. The chemistry and the dust properties are temperature dependent and, therefore, interpretation of any observation requires the knowledge of the temperature and its variations. Direct measurement of the gas kinetic temperature is possible with molecular line spectroscopy, the ammonia molecule, NH3, being the most commonly used tracer. Aims: We want to determine the accuracy of the temperature estimates derived from ammonia spectra. The normal interpretation of NH3 observations assumes that all the hyperfine line components are tracing the same volume of gas. However, in the case of strong temperature gradients they may be sensitive to different layers and this could cause errors in the optical depth and gas temperature estimates. Methods: We examine a series of spherically symmetric cloud models, 1.0 and 0.5 M? Bonnor-Ebert spheres, with different radial temperature profiles. We calculate synthetic NH3 spectra and compare the derived column densities and temperatures to the actual values in the models. Results: For high signal-to-noise observations, the estimated gas kinetic temperatures are within ~0.3 K of the real mass averaged temperature and the column densities are correct to within ~10%. When the S/N ratio of the (2, 2) spectrum decreases below 10, the temperature errors are of the order of 1 K but without a significant bias. Only when the density of the models is increased by a factor of a few, the results begin to show significant bias because of the saturation of the (1, 1) main group. Conclusions: The ammonia spectra are found to be a reliable tracer of the real mass averaged gas temperature. Because the radial temperature profiles of the cores are not well constrained, the central temperature could still be different from this value. If the cores are optically very thick, there are no longer guarantees of the accuracy of the estimates.

Juvela, M.; Harju, J.; Ysard, N.; Lunttila, T.

2012-02-01

179

Double core hole creation and subsequent Auger decay in NH3 and CH4 molecules.  

PubMed

Energies of the hollow molecules CH(4)(2+) and NH(3)(2+) with double vacancies in the 1s shells have been measured using an efficient coincidence technique combined with synchrotron radiation. The energies of these states have been determined accurately by high level electronic structure calculations and can be well understood on the basis of a simple theoretical model. Their major decay pathway, successive Auger emissions, leads first to a new form of triply charged ion with a core hole and two valence vacancies; experimental evidence for such a state is presented with its theoretical interpretation. Preedge 2-hole-1-particle (2h-1p) states at energies below the double core-hole states are located in the same experiments and their decay pathways are also identified. PMID:21231301

Eland, J H D; Tashiro, M; Linusson, P; Ehara, M; Ueda, K; Feifel, R

2010-11-19

180

Crack-Free Thick AlN Films Obtained by NH3 Nitridation of Sapphire Substrates  

NASA Astrophysics Data System (ADS)

We demonstrate that NH3 nitridation of sapphire substrates effectively suppresses cracks in AlN epilayers. The sapphire nitridation promoted three-dimensional (3D) growth at the initial stage, in contrast to the 2D growth mode on non-nitrided sapphire. The coalescence of 3D columnar grains in the process created voids, which act as strain absorber and thus crack-free thick epilayers were obtained. The control of nitridation period is also found important. The optimum nitridation period realized an atomically-smooth epilayer with superior structural quality. On the other hand, the least nitrided sapphire exhibited high twist mosaic of the grains which complicate the epilayer smoothing process, and the longer nitridation promoted slow recovery of a smooth epilayer.

Banal, Ryan G.; Akashi, Yosuke; Matsuda, Kazuhisa; Hayashi, Yuki; Funato, Mitsuru; Kawakami, Yoichi

2013-08-01

181

Temperature programmed decomposition of uranyl nitrate hexahydrate  

Microsoft Academic Search

Temperature programmed decomposition (TPD) of uranyl nitrate hexahydrate has been studied using evolved gas analysis mass spectrometry (EGA-MS) in the temperature range 300–1400 K. Thermogravimetric (TGA) investigations were performed in the temperature range 300–1100 K. An attempt has been made to resolve the complexity of decomposition behaviour through suitable comparison of TGA and EGA-MS data. Kinetic control regimes for various

S. Dash; M. Kamruddin; Santanu Bera; P. K. Ajikumar; A. K. Tyagi; S. V. Narasimhan; Baldev Raj

1999-01-01

182

Ce-Ti amorphous oxides for selective catalytic reduction of NO with NH3: confirmation of Ce-O-Ti active sites.  

PubMed

The amorphous Ce-Ti mixed oxides were reported to be catalysts for selective catalytic reduction of NO(x) with NH(3), in which Ce and not Ti acts as their solvent in spite of the fact that Ce is low in content. The amorphous catalysts were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) equipped with selective area electron diffraction (SAED). The Ce-Ti amorphous oxide shows higher activity than its crystalline counterpart at lower temperatures. Moreover, the presence of small CeO(2) crystallites as for the impregnated sample is deleterious to activity. The Ce-O-Ti short-range order species with the interaction between Ce and Ti in atomic scale was confirmed for the first time to be the active site using temperature programmed reduction with H(2) (H(2)-TPR), in situ FTIR spectra of NO adsorption, X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine-structure (XAFS). Lastly, the Ce-O-Ti structure was directly observed by field-emission TEM (FETEM). PMID:22888951

Li, Ping; Xin, Ying; Li, Qian; Wang, Zhongpeng; Zhang, Zhaoliang; Zheng, Lirong

2012-08-21

183

Chemical Thermal Desorption System.  

National Technical Information Service (NTIS)

A field portable chemical thermal desorption system. The system comprises a desorption tube, an injection needle operatively connected to the desorption tube, a needle valve operatively connected to the injection needle, a heater operatively connected to ...

A. Alcaraz C. Koester J. D. Eckels

2004-01-01

184

Dechlorination of PCBs, CAHs, herbicides and pesticides neat and in soils at 25 degrees C using Na/NH3.  

PubMed

Na/NH3 reductions have been used to dehalogenate polychlorinated biphenyls (PCBs), chlorinated aliphatic hydrocarbons (CAHs) and pesticides at diffusion controlled rates at room temperature in model compound studies in both dry NH3 and when water was added. The rate ratio of dechlorination (aliphatic and aromatic compounds) versus reaction of the solvated electron with water is very large, allowing wet soils or sludges to be remediated without an unreasonable consumption of sodium. Several soils, purposely contaminated with 1,1,1-trichloroethane, 1-chlorooctane and tetrachloroethylene, were remediated by slurring the soils in NH3 followed by addition of sodium. The consumption of sodium per mole of chlorine removed was examined as a function of both the hazardous substrate's concentration in the soil and the amount of water present. The Na consumption per Cl removed increases as the amount of water increases and as the substrate concentration in soil decreases. However, remediation was still readily accomplished from 5000 to 3000ppm to sub ppm levels of RCl in the presence of substantial amounts of water. PCB- and dioxin-contaminated oils were remediated with Na/NH3 as were PCB-contaminated soils and sludges from contaminated sites. Ca/NH3 treatments also successfully remediated PCB-contaminated clay, sandy and organic soils but laboratory studies demonstrated that Ca was less efficient than Na when substantial amounts of water were present. The advantages of solvated electron reductions using Na/NH3 include: (1) very rapid dehalogenation rates at ambient temperature, (2) soils (even clay soils) break down into particles and slurry nicely in NH3, (3) liquid ammonia handling technology is well known and (4) removal from soils, recovery and recycle of ammonia is easy due to its low boiling point. Finally, dechlorination is extremely fast even for the 'corner' chlorines in the substrate Mirex (structure in Eq. (5)). PMID:11975998

Pittman, Charles U; He, Jinbao

2002-05-01

185

Competition Between Co(NH3)63+ and Inner Sphere Mg2+ Ions in the HDV Ribozyme  

PubMed Central

Divalent cations play critical structural and functional roles in many RNAs. While the hepatitis delta virus (HDV) ribozyme can undergo self-cleavage in the presence of molar concentrations of monovalent cations, divalent cations such as Mg2+ are required for efficient catalysis under physiological conditions. Moreover, the cleavage reaction can be inhibited with Co(NH3)63+, an analog of Mg(H2O)62+. Here, the binding of Mg2+ and Co(NH3)63+ to the HDV ribozyme are studied by Raman microscopic analysis of crystals. Raman difference spectra acquired at different metal ion conditions reveal changes in the ribozyme. When Mg2+ alone is introduced to the ribozyme, inner sphere coordination of Mg(H2O)x2+ (x?5) to non-bridging PO2? oxygen, and changes in base stretches and phosphodiester group conformation are observed. In addition, binding of Mg2+ induces deprotonation of a cytosine assigned to the general acid C75, consistent with solution studies. When Co(NH3)63+ alone is introduced, deprotonation of C75 is again observed, as are distinctive changes in base vibrational ring modes and phosphodiester backbone conformation. In contrast to Mg2+ binding, Co(NH3)63+ binding does not perturb PO2? group vibrations, consistent with its ability to make only outer sphere contacts. Surprisingly, competitive binding studies reveal that Co(NH3)63+ ions displace some inner sphere-coordinated magnesium species, including ions coordinated to PO2? groups or the N7 of a guanine, likely G1 at the active site. These observations contrast with the tenet that Co(NH3)63+ ions displace only outer sphere magnesium ions. Overall, our data support two classes of inner sphere Mg2+-PO2? binding sites: sites that Co(NH3)63+ can displace, and others it cannot.

Gong, Bo; Chen, Jui-Hui; Bevilacqua, Philip C.; Golden, Barbara L.; Carey, Paul R.

2009-01-01

186

Phase polymorphism of novel [Ru(NH3)6](ClO4)3—Comparison with [Ru(NH3)6](BF4)3. Part II  

NASA Astrophysics Data System (ADS)

[Ru(NH3)6](ClO4)3 undergoes two phase transitions at: TC1=290.3 K and TC2=74.8 K , thus exhibits three crystalline phases in the temperature range of 5–310 K. For the detected phase transitions, thermal effects were determined. Fourier transform far- and middle-infrared spectra (FT-FIR and FT-MIR), recorded at 8–350 K, suggest that reorientational motions of the NH3 ligands are very fast (?R?10?12 s above TC1) and are significantly slowed down below TC2. X-ray single crystal diffraction (XRSCD) measurements revealed that in the high temperature phase (above TC1) the compound belongs to the cubic Fm3¯m (No. 225) space group, whereas in the intermediate phase the unit cell parameter doubles and the space group is Ia3¯(No. 206). 1H NMR studies revealed that the following reorientational motions are liberated during heating: three-fold reorientation of NH3 ligands, three-fold reorientation of the entire [Ru(NH3)6]3+ cation, and isotropic reorientation of this cation. In the high temperature phase I the cations perform isotropic reorientations with the estimated activation energy equal to ca. 30.1 kJ mol?1. Comparison with adequate results obtained earlier for [Ru(NH3)6](BF4)3 and for other similar compounds was made and general regularities were drawn.

Do??ga, Diana; Mikuli, Edward; Górska, Natalia; Inaba, Akira; Ho?derna-Natkaniec, Krystyna; Nitek, Wojciech

2013-08-01

187

Decrease of water vapor desorption by Si film coating on stainless steel  

Microsoft Academic Search

Surface modification of stainless steel by Si coating was attempted to reduce water desorption in an evacuation process. Outgassing properties of stainless steel plates with and without Si coating including dependence on deposition condition were compared by temperature programmed desorption and throughput method. The outgassing rate of a Si coated sample at optimized condition was reduced to about 1\\/10 of

S. S. Inayoshi; S. Tsukahara; A. Kinbara

1999-01-01

188

Global analytical potential energy surface for the electronic ground state of NH3 from high level ab initio calculations.  

PubMed

The analytical, full-dimensional, and global representation of the potential energy surface of NH(3) in the lowest adiabatic electronic state developed previously (Marquardt, R.; et al. J. Phys. Chem. B 2005, 109, 8439–8451) is improved by adjustment of parameters to an enlarged set of electronic energies from ab initio calculations using the coupled cluster method with single and double substitutions and a perturbative treatment of connected triple excitations (CCSD(T)) and the method of multireference configuration interaction (MRCI). CCSD(T) data were obtained from an extrapolation of aug-cc-pVXZ results to the basis set limit (CBS), as described in a previous work (Yurchenko, S.N.; et al. J. Chem. Phys 2005, 123, 134308); they cover the region around the NH3 equilibrium structures up to 20,000 hc cm(–1). MRCI energies were computed using the aug-cc-pVQZ basis to describe both low lying singlet dissociation channels. Adjustment was performed simultaneously to energies obtained from the different ab initio methods using a merging strategy that includes 10,000 geometries at the CCSD(T) level and 500 geometries at the MRCI level. Characteristic features of this improved representation are NH3 equilibrium geometry r(eq)(NH(3)) ? 101.28 pm, ?(eq)(NH(3)) ? 107.03°, the inversion barrier at r(inv)(NH(3)) ? 99.88 pm and 1774 hc cm(–1) above the NH(3) minimum, and dissociation channel energies 41,051 hc cm(–1) (for NH(3) ? ((2)B(2))NH(2) + ((2)S(1/2))H) and 38,450 hc cm(–1) (for NH(3) ? ((3)?(–))NH +((1)?(g)(+))H(2)); the average agreement between calculated and experimental vibrational line positions is 11 cm(–1) for (14)N(1)H(3) in the spectral region up to 5000 cm(–1). A survey of our current knowledge on the vibrational spectroscopy of ammonia and its isotopomers is also given. PMID:23688044

Marquardt, Roberto; Sagui, Kenneth; Zheng, Jingjing; Thiel, Walter; Luckhaus, David; Yurchenko, Sergey; Mariotti, Fabio; Quack, Martin

2013-08-01

189

Evaluation of a regional air-quality model with bidirectional NH3 exchange coupled to an agroecosystem model  

NASA Astrophysics Data System (ADS)

Atmospheric ammonia (NH3) is the primary atmospheric base and an important precursor for inorganic particulate matter and when deposited NH3 contributes to surface water eutrophication, soil acidification and decline in species biodiversity. Flux measurements indicate that the air-surface exchange of NH3 is bidirectional. However, the effects of bidirectional exchange, soil biogeochemistry and human activity are not parameterized in air quality models. The US Environmental Protection Agency's (EPA) Community Multiscale Air-Quality (CMAQ) model with bidirectional NH3 exchange has been coupled with the United States Department of Agriculture's (USDA) Environmental Policy Integrated Climate (EPIC) agroecosystem model. The coupled CMAQ-EPIC model relies on EPIC fertilization timing, rate and composition while CMAQ models the soil ammonium (NH4+) pool by conserving the ammonium mass due to fertilization, evasion, deposition, and nitrification processes. This mechanistically coupled modeling system reduced the biases and error in NHx (NH3 + NH4+) wet deposition and in ambient aerosol concentrations in an annual 2002 Continental US (CONUS) domain simulation when compared to a 2002 annual simulation of CMAQ without bidirectional exchange. Fertilizer emissions estimated in CMAQ 5.0 with bidirectional exchange exhibits markedly different seasonal dynamics than the US EPA's National Emissions Inventory (NEI), with lower emissions in the spring and fall and higher emissions in July.

Bash, J. O.; Cooter, E. J.; Dennis, R. L.; Walker, J. T.; Pleim, J. E.

2013-03-01

190

High Resolution Infrared and Microwave Spectra of NH3-HCCH and NH3-OCS Complexes: Studies of Weak C-H\\cdotsN Hydrogen Bond and Electric Multipole Interactions  

NASA Astrophysics Data System (ADS)

C-H\\cdotsN weak hydrogen bond is of much current interest. We report the first high resolution infrared spectroscopic study of a prototypical C-H\\cdotsN bonded system, i.e. NH3-HCCH, at the vicinity of the ?4 band of NH3. The spectrum has been recorded using an infrared spectrometer equipped with an astigmatic multipass cell aligned for 366 passes and a room temperature external cavity quantum cascade laser at the 6 ?m region. The perpendicular band spectrum of symmetric top rotor observed is consistent with the previous microwave and infrared studies at 3 ?m. We also extended the previous microwave measurement to higher J and K. For the related NH3-OCS complex, microwave spectrum of J up to 6 and infrared spectrum at the vicinity of the ?4 band of NH3 have been recorded and analyzed for the first time. Comparison has been made with the previously studied isoelectronic complexes such as NH3-N2O and NH3-CO2. The source of the difference will be discussed with the aid of ab initio calculations. G.T. Fraser, K.R. Leopold, and W. Klemperer, J. Chem. Phys. 80(4), 1423, (1984) G. Hilpert, G.T. Fraser, and A.S. Pine, J. Chem. Phys. 105(15), 6183, (1996) G.T. Fraser, D.D. Nelson, JR., G.J. Gerfen, and W. Klemperer, J. Chem. Phys. 83(11), 5442, (1985) G.T. Fraser, K.R. Leopold, and W. Klemperer, J. Chem. Phys. 81(6), 2577, (1984)

Liu, Xunchen; Xu, Yunjie

2011-06-01

191

Optical absorption spectra in the quasi-two-dimensional antiferromagnets (NH3(CH2)nNH3)MnCl4 (n=2, 3, 4, 5). I. Experimental  

Microsoft Academic Search

Optical absorption spectra in the quasi-two-dimensional antiferromagnet (NH3(CH2)nNH3)MnCl4 (n=2, 3, 4, 5) were investigated. In the transitions 6A1g(S) to 4A1g(G), 4Eg(G), 4T2g(D), 4Eg(D) and 4T1g(P), much fine structure caused by electric dipole transition appeared at low temperature. It was concluded that fine structure resulted from magnon-assisted transitions by taking into account the temperature dependence of the spectra. In these compounds,

N. Watanabe; N. Kojima; T. Ban; I. Tsujikawa

1988-01-01

192

Polymorphism of [Zn(NH 3) 4](ClO 4) 2 and [Zn(NH 3) 4](BF 4) 2 studied by differential scanning calorimetry and far infrared spectroscopy  

Microsoft Academic Search

The phase transitions in [Zn(NH3)4](ClO4)2 and [Zn(NH3)4](BF4)2 were determined by differential scanning calorimetry (DSC) and the discovered phases were identified by far infrared spectroscopy (FT-FIR). Four solid phases were found for both the compounds. The characteristic changes in the FT-FIR absorption spectra were observed in the particular phases of both the compounds at temperatures predicted by the DSC. Additionally, the

A. Migda?-Mikuli; E. Mikuli; ?. Hetma?czyk; E. ?ciesi?ska; J. ?ciesi?ski; S. Wróbel; N. Górska

2001-01-01

193

Herschel/HIFI observations of CO, H2O and NH3 in Monoceros R2  

NASA Astrophysics Data System (ADS)

Context. Mon R2, at a distance of 830 pc, is the only ultracompact H ii region (UCH ii) where the associated photon-dominated region (PDR) can be resolved with Herschel. Owing to its brightness and proximity, it is one of the best-suited sources for investigating the chemistry and physics of highly UV-irradiated PDRs. Aims: Our goal is to estimate the abundance of H2O and NH3 in this region and investigate their origin. Methods: We present new observations ([C ii], 12CO, 13CO, C18O, o-H2O, p-H2O, o-H_218O and o-NH3) obtained with the HIFI instrument onboard Herschel and the IRAM-30 m telescope. We investigated the physical conditions in which these lines arise by analyzing their velocity structure and spatial variations. Using a large velocity gradient approach, we modeled the line intensities and derived an average abundance of H2O and NH3 across the region. Finally, we modeled the line profiles with a non-local radiative transfer model and compared these results with the abundance predicted by the Meudon PDR code. Results: The variations of the line profiles and intensities indicate complex geometrical and kinematical patterns. In several tracers ([C ii], CO 9 ? 8 and H2O) the line profiles vary significantly with position and have broader line widths toward the H ii region. The H2O lines present strong self-absorption at the ambient velocity and emission in high-velocity wings toward the H ii region. The emission in the o-H_218O ground state line reaches its maximum value around the H ii region, has smaller linewidths and peaks at the velocity of the ambient cloud. Its spatial distribution shows that the o-H_218O emission arises in the PDR surrounding the H ii region. By modeling the o-H_218O emission and assuming the standard [16O] / [18O] = 500, we derive a mean abundance of o-H2O of ~10-8 relative to H2. The ortho-H2O abundance, however, is larger (~1 × 10-7) in the high-velocity wings detected toward the H ii region. Possible explanations for this larger abundance include an expanding hot PDR and/or an outflow. Ammonia seems to be present only in the envelope of the core with an average abundance of ~2 × 10-9 relative to H2. Conclusions: The Meudon PDR code, which includes only gas-phase chemical networks, can account for the measured water abundance in the high velocity gas as long as we assume that it originates from a ? 1 mag hot expanding layer of the PDR, i.e. that the outflow has only a minor contribution to this emission. To explain the water and ammonia abundances in the rest of the cloud, the molecular freeze out and grain surface chemistry would need to be included. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

Pilleri, P.; Fuente, A.; Cernicharo, J.; Ossenkopf, V.; Berné, O.; Gerin, M.; Pety, J.; Goicoechea, J. R.; Rizzo, J. R.; Montillaud, J.; González-García, M.; Joblin, C.; Le Bourlot, J.; Le Petit, F.; Kramer, C.

2012-08-01

194

Doping effect on the adsorption of NH3 molecule onto graphene quantum dot: From the physisorption to the chemisorption  

NASA Astrophysics Data System (ADS)

The adsorption of ammonia molecule onto a graphene hexagonal flake, aluminum (Al) and boron (B) doped graphene flakes (graphene quantum dots, GQDs) are investigated using density functional theory. We found that NH3 molecule is absorbed to the hollow site through the physisorption mechanism without altering the electronic properties of GQD. However, the adsorption energy of NH3 molecule onto the Al- and B-doped GQDs increases with respect GQD resulting chemisorption. The adsorption of NH3 onto the Al-doped and B-doped GQDs makes graphene locally buckled, i.e., B- doped and Al-doped GQDs are not planar. The adsorption mechanism onto a GQD is different than that of graphene. This study reveals important features of the edge passivation and doping effects of the adsorption mechanism of external molecules onto the graphene quantum dots.

Seyed-Talebi, Seyedeh Mozhgan; Beheshtian, J.; Neek-amal, M.

2013-09-01

195

Effect of bulking agent on the reduction of NH3 emissions during thermophilic composting of night-soil sludge.  

PubMed

Night-soil sludge contains a high percentage of nitrogen and releases large amounts of ammonia when it is composted. In this research, three types of bulking agents, sawdust, perlite, and activated carbon, were used, and the effects of these bulking agents on the reduction of NH3 emissions during thermophilic composting were evaluated. It was found that not only is sawdust the most effective agent in reducing NH3 emissions, but that it also effectively promotes organic matter decomposition. Increases in the mixing ratio of sawdust in the range adopted in the present research, from 70% to 92% on a dry-weight basis, appeared to cause no adverse effects on the decomposition of sludge itself. And the higher the mixing ratio of sawdust, the more effective the reduction in NH3 emissions, however this effect was not enough to completely suppress these emissions, even at the highest mixing ratio. PMID:11720264

Nakasaki, K; Ohtaki, A; Takano, H

2001-08-01

196

The tropospheric abundances of NH3 and PH3 in Jupiter's Great Red Spot, from Voyager IRIS observations  

NASA Astrophysics Data System (ADS)

The tropospheric abundances of NH3 and PH3 in Jupiter's Great Red Spot (GRS) are presently determined on the basis of a group of Voyager IRIS spectra, and compared with those of the surrounding South Tropical Zone (STZ) obtained from another two groups of IRIS spectra, in order to characterize the GRS's chemistry and dynamics. Although the GRS is believed to be a region of strong vertical transport, NH3 depletion is surprisingly found to occur below the tropopause within the GRS. Since one of the STZ's selections has a temperature-pressure profile similar to that of the GRS below the 300 mbar level, condensation cannot explain the low NH3 abundance in the GRS.

Griffith, Caitlin A.; Bezard, Bruno; Owen, Tobias; Gautier, Daniel

1992-07-01

197

Observation of DCl and upper limit to NH3 on Venus  

NASA Astrophysics Data System (ADS)

To search for DCl in the Venus atmosphere, a spectrum near the D35Cl (1-0) R4 line at 2141.54 cm-1 was observed using the CSHELL spectrograph at NASA IRTF. Least square fitting to the spectrum by a synthetic spectrum results in a DCl mixing ratio of 17.8 ± 6.8 ppb. Comparing to the HCl abundance of 400 ± 30 ppb (Krasnopolsky [2010a] Icarus, 208, 314-322), the DCl/HCl ratio is equal to 280 ± 110 times the terrestrial D/H = 1.56 × 10-4. This ratio is similar to that of HDO/H2O = 240 ± 25 times the terrestrial HDO/H2O from the VEX/SOIR occultations at 70-110 km. Photochemistry in the Venus mesosphere converts H from HCl to that in H2O with a rate of 1.9 × 109 cm-2 s-1 (Krasnopolsky [2012] Icarus, 218, 230-246). The conversion involves photolysis of HCl; therefore, the photochemistry tends to enrich D/H in HCl and deplete in H2O. Formation of the sulfuric acid clouds may affect HDO/H2O as well. The enriched HCl moves down by mixing to the lower atmosphere where thermodynamic equilibriums for H2 and HCl near the surface correspond to D/H = 0.71 and 0.74 times that in H2O, respectively. Time to establish these equilibriums is estimated at ˜3 years and comparable to the mixing time in the lower atmosphere. Therefore, the enriched HCl from the mesosphere gives D back to H2O near the surface. Comparison of chemical and mixing times favors a constant HDO/H2O up to ˜100 km and DCl/HCl equal to D/H in H2O times 0.74. Ammonia is an abundant form of nitrogen in the reducing environments. Thermodynamic equilibriums with N2 and NO near the surface of Venus give its mixing ratio of 10-14 and 6 × 10-7, respectively. A spectrum of Venus near the NH3 line at 4481.11 cm-1 was observed at NASA IRTF and resulted in a two-sigma upper limit of 6 ppb for NH3 above the Venus clouds. This is an improvement of the previous upper limit by a factor of 5. If ammonia exists at the ppb level or less in the lower atmosphere, it quickly dissociates in the mesosphere and weakly affects its photochemistry.

Krasnopolsky, Vladimir

2012-05-01

198

DRIFT study of manganese/ titania-based catalysts for low-temperature selective catalytic reduction of NO with NH3.  

PubMed

Manganese oxides and iron-manganese oxides supported on TiO2 were prepared by the sol-gel method and used for low-temperature selective catalytic reduction (SCR) of NO with NH3. Base on the previous study, Mn(0.4)/ TiO2 and Fe(0.1)-Mn(0.4)/TiO2 were then selected to carry out the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) investigation for revealing the reaction mechanism. The DRIFT spectroscopy for the adsorption of NH3 indicated the presence of coordinated NH3 and NH4+ on both of the two catalysts. When NO was introduced, the coordinated NH3 on the catalyst surface was consumed rapidly, indicating these species could react with NO effectively. When NH3 was introduced into the sample preadsorbed with NO + O2, SCR reaction would not proceed on Mn(0.4)/TiO2. However, for Fe(0.1)-Mn(0.4)/ TiO2 the bands due to coordinated NH3 on Fe2O3 were formed. Simultaneously, the bidentate nitrates were transformed to monodentate nitrates and NH4+ was detected. And NO2 from the oxidation of NO on catalyst could react with NH4+ leading to the reduction of NO. Therefore, it was suggested that the SCR reaction on Fe(0.1)-Mn(0.4)/TiO2 could also take place in a different way from the reactions on Mn(0.4)/TiO2 proposed by other researchers. Furthermore, the SCR reaction steps for these two kinds of catalysts were proposed. PMID:17874791

Wu, Zhongbiao; Jiang, Boqiong; Liu, Yue; Wang, Haiqiang; Jin, Ruiben

2007-08-15

199

Re-analysis of the ? of NH3 in C/2002 LINEAR T7 Using CSHELL at the NASA IRTF  

NASA Astrophysics Data System (ADS)

NH3 is the dominant (observable) nitrogen-containing volatile in comets, present at 1% relative to water. At infrared wavelengths, NH3 (?1 band) is difficult to detect since it requires a significant geocentric velocity to shift the strongest NH3 emissions (Q-branch) out of the terrestrial atmospheric water absorption. The P- and R- branches are less dependent on geocentric velocity, but since they are generally weaker lines, they are challenging to detect. The 3-micron region is rich in molecular emissions (HCN, OH, H2O, C2H2, NH2, and other minor species), so that for many lines of the P- and R- branches, the ability to resolve these faint emissions from nearby brighter emission lines requires careful spectral registration of images. Previously, we applied and tested our model of fluorescence efficiency factors for NH3 in C/2002 T7 (LINEAR). The high Doppler shift (- 66 km/s) of C/T7 during early May 2004 made it an excellent target for searching for NH3 through its strongest IR emission lines. While the Q-branch lines were detected with high signal to noise, the sQ33 line of NH3 was on the wing of a deep atmospheric absorption. Other lines were fainter and near brighter emissions or atmospheric absorptions. The ability to accurately use the sQ33 emission and P- and R-branch lines, we discovered that our atmospheric model and algorithms needed improvement. Upgrades to our algorithms include an improved spectral transmittance model and spectral registration routines (Villanueva et al. 2006). This work will present a re-analysis of the 3-micron region from the high quality data set of C/2002 LINEAR T7 using the improved atmospheric transmittance models and data analysis algorithms from Villanueva et al. KM-S would like to acknowledge support from the National Science Foundation RUI Program No. 0407052.

Magee-Sauer, Karen P.; Villanueva, G. L.; Mumma, M. J.; Bonev, B.; DiSanti, M. A.; Dello Russo, N.; Lippi, M.; Gibb, E. L.

2008-09-01

200

Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants  

PubMed Central

Background In plants, nitrate (NO3-) nutrition gives rise to a natural N isotopic signature (?15N), which correlates with the ?15N of the N source. However, little is known about the relationship between the ?15N of the N source and the 14N/15N fractionation in plants under ammonium (NH4+) nutrition. When NH4+ is the major N source, the two forms, NH4+ and NH3, are present in the nutrient solution. There is a 1.025 thermodynamic isotope effect between NH3 (g) and NH4+ (aq) which drives to a different ?15N. Nine plant species with different NH4+-sensitivities were cultured hydroponically with NO3- or NH4+ as the sole N sources, and plant growth and ?15N were determined. Short-term NH4+/NH3 uptake experiments at pH 6.0 and 9.0 (which favours NH3 form) were carried out in order to support and substantiate our hypothesis. N source fractionation throughout the whole plant was interpreted on the basis of the relative transport of NH4+ and NH3. Results Several NO3--fed plants were consistently enriched in 15N, whereas plants under NH4+ nutrition were depleted of 15N. It was shown that more sensitive plants to NH4+ toxicity were the most depleted in 15N. In parallel, N-deficient pea and spinach plants fed with 15NH4+ showed an increased level of NH3 uptake at alkaline pH that was related to the 15N depletion of the plant. Tolerant to NH4+ pea plants or sensitive spinach plants showed similar trend on 15N depletion while slight differences in the time kinetics were observed during the initial stages. The use of RbNO3 as control discarded that the differences observed arise from pH detrimental effects. Conclusions This article proposes that the negative values of ?15N in NH4+-fed plants are originated from NH3 uptake by plants. Moreover, this depletion of the heavier N isotope is proportional to the NH4+/NH3 toxicity in plants species. Therefore, we hypothesise that the low affinity transport system for NH4+ may have two components: one that transports N in the molecular form and is associated with fractionation and another that transports N in the ionic form and is not associated with fractionation.

2011-01-01

201

trans -(NH 3 ) 2 Pt II -modified deoxyoligonucleotides as potential antisense agents: cross-linking reactions between two 12-mers  

Microsoft Academic Search

An approach is presented which probes the possible use of trans-[(NH3)2PtCl]+-modified deoxyoligonucleotides in the antisense strategy. It consists of (1) the selective platination of an oligonucleotide\\u000a containing 11 pyrimidine (T, C) bases as well as a single guanine (G) as a Pt-anchoring group at the 5?-end to give trans-[(NH3)2Pt{5?-d(GN7T2C2T2C2T2C}Cl]10–\\u000a 1 (\\

Matthias B. L. Janik; Bernhard Lippert

1999-01-01

202

DFT based study of transition metal nano-clusters for electrochemical NH3 production.  

PubMed

Theoretical studies of the possibility of producing ammonia electrochemically at ambient temperature and pressure without direct N2 dissociation are presented. Density functional theory calculations were used in combination with the computational standard hydrogen electrode to calculate the free energy profile for the reduction of N2 admolecules and N adatoms on transition metal nanoclusters in contact with an acidic electrolyte. This work has established linear scaling relations for the dissociative reaction intermediates NH, NH2, and NH3. In addition, linear scaling relations for the associative reaction intermediates N2H, N2H2, and N2H3 have been determined. Furthermore, correlations between the adsorption energies of N, N2, and H have been established. These scaling relations and the free energy corrections are used to establish volcanoes describing the onset potential for electrochemical ammonia production and hence describe the potential determining steps for the electrochemical ammonia production. The competing hydrogen evolution reaction has also been analyzed for comparison. PMID:23598667

Howalt, J G; Bligaard, T; Rossmeisl, J; Vegge, T

2013-04-19

203

TOPICAL REVIEW: Competing interactions in molecular adsorption: NH3 on Si(001)  

NASA Astrophysics Data System (ADS)

Ammonia is a good model system for the study of co-adsorption interactions, including indirect effects such as charge and strain-induced local effects on adsorption sites, and direct interactions such as hydrogen bonding. On the Si(001) surface, it adsorbs molecularly, via a dative bond from the N atom to the down atom of a buckled dimer, and is therefore very sensitive to the local charge conditions. It will then dissociate into -H and -NH2 groups, adsorbed on the dangling bonds of the Si dimers. The NH2 groups do not diffuse, so any correlations deriving from interactions during adsorption are preserved, and can be derived by analysis of the arrangements of the NH2 groups. Hydrogen-bonding interactions are crucial in understanding the behaviour of this system, with significant co-adsorption interactions occurring both along and across rows, outweighing the electrostatic or buckling-related effects. In recent years, there have been several scanning tunnelling microscopy studies and extensive computational modelling of the NH3 on Si(001) system, attempting to determine a dominant mechanism governing co-adsorption effects. In this review, I will discuss both experimental and theoretical results, make a comparison with similar molecules such as phosphine (PH3), and review the different ways in which experimentalists and modellers have approached this complex system.

Owen, J. H. G.

2009-11-01

204

Association of Electroactive Counterions with Polyelectrolytes. 5. Electrostatic Binding of Ru(NH3)6(3+) and Co(NH3)6(3+) to Polyacrylates. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

The spontaneous association of M(NH3)6(3+) complexes (M = Ru, Co) with polyacrylate anions (PAAs) in aqueous solution was investigated by means of cyclic and rotating disk voltammetry at graphite electrodes. Equilibrium constants, Kb, for the association ...

R. Jiang F. C. Anson

1992-01-01

205

The electronic structure of organic-inorganic hybrid compounds: (NH4)2CuCl4, (CH3NH3)2CuCl4 and (C2H5NH3)2CuCl4  

NASA Astrophysics Data System (ADS)

Hybrid organic-inorganic compounds are an intriguing class of materials that have been experimentally studied over the past few years because of a potential broad range of applications. The electronic and magnetic properties of three organic-inorganic hybrid compounds with compositions (NH4)2CuCl4, (CH3NH3)2CuCl4 and (C2H5NH3)2CuCl4 are investigated for the first time with density functional theory plus on-site Coulomb interaction. A strong Coulomb interaction on the copper causes a relatively weak exchange coupling within the layers of the octahedral network, in good agreement with experiment. The character of the exchange interaction (responsible for magnetic behavior) is analyzed. The calculations reveal that (C2H5NH3)2CuCl4 has the strongest Jahn-Teller (JT) distortion in comparison with the two other compounds. The easy axis of magnetization is investigated, showing a weak anisotropic interaction between inter-layer Cu2+ ions in the (C2H5NH3)2CuCl4 structure. Orbital ordering is concluded from our partial density of states calculations: a cooperation of the JT distortion with an antiferro-distortive pattern.

Zolfaghari, P.; de Wijs, G. A.; de Groot, R. A.

2013-07-01

206

Reactions of H+(pyridine)m(H2O)n and H+(NH3)1(pyridine)m(H2O)n with NH3: experiments and kinetic modelling  

NASA Astrophysics Data System (ADS)

Reactions between pyridine containing water cluster ions, H+(pyridine)1(H2O)n, H+(pyridine)2(H2O)n and H+(NH3)1(pyridine)1(H2O)n (n up to 15) with NH3 have been studied experimentally using a quadrupole time-of-flight mass spectrometer. The product ions in the reaction between H+(pyridine)m(H2O)n (m = 1 to 2) and NH3 have been determined for the first time. It is found that the reaction mainly leads to cluster ions of the form H+(NH3)1(pyridine)m(H2O)n-x, with x = 1 or 2 depending on the initial size of the reacting cluster ion. For a given number of water molecules (from 5 to 15) in the cluster ion, rate coefficients are found to be slightly lower than those for protonated pure water clusters reacting with ammonia. The rate coefficients obtained from this study are used in a kinetic cluster ion model under tropospheric conditions. The disagreement between ambient ground level measurements and previous models are discussed in relation to the results from our model and future experimental directions are suggested.

Ryding, M. J.; Jonsson, Å. M.; Zatula, A. S.; Andersson, P. U.; Uggerud, E.

2012-03-01

207

Surface modification of polypropylene microporous membranes to improve their antifouling property in MBR: NH 3 plasma treatment  

Microsoft Academic Search

To improve the antifouling property of polypropylene hollow fiber microporous membranes (PPHFMMs) in a membrane bioreactor (MBR) for wastewater treatment, PPHFMMs were subjected to surface modification by NH3 plasma treatment. Structural and morphological changes of the membranes were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Water contact angle, which reflects the hydrophilicity of the membrane surface,

Hai-Yin Yu; Meng-Xin Hu; Zhi-Kang Xu; Jian-Li Wang; Shu-Yuan Wang

2005-01-01

208

Kinetic evaluation of H2S and NH3 biofiltration for two media used for wastewater lift station emissions.  

PubMed

In this study, biofiltration using a natural wood chip medium and a commercial biofiltration medium was evaluated for the removal of moderate concentrations of hydrogen sulfide (H2S) (up to 100 parts per million by volume [ppmv]) in the presence of significant concentrations of ammonia (NH3). These levels were chosen as representative of wastewater lift station emissions in the Brownsville, TX, area. NH3-removing portions of the biofilms may compete with H2S-removing portions and inhibit H2S removal. H2S process removal efficiencies for the commercial and natural media ranged from 90 to 96% depending on inlet loading and media type and bed height. Kinetic analysis of the H2S removal process followed apparent first-order reaction behavior. The average first-order reaction rates were 0.03 sec(-1) for the commercial medium and 0.09 sec(-1) for the natural medium. Pressure drops across the columns ranged from 0.41 in. H2O/ft for the commercial medium to 1.41 in. H2O/ft for the natural medium. NH3 gas levels of up to 80 ppmv did not affect the H2S removal process efficiency, and calculated kinetic rate constants for H2S removal remained almost the same. The NH3 gas also was removed simultaneously with the H2S up to 98% removal efficiency by the commercial medium. PMID:14871010

Jones, Kim D; Martinez, Al; Maroo, Ketankumar; Deshpande, Sonali; Boswell, James

2004-01-01

209

Measurement of prenucleation molecular clusters in the NH3, H2SO4, H2O system  

NASA Astrophysics Data System (ADS)

The molecular cluster ions HSO4-(H2SO4)n-1(NH3)m corresponding to the neutral species (H2SO4)n(NH3)m for n = 2 to 6 and m = 0 to n-1 have been observed at temperatures up to ~285 K. A transverse chemical ionization apparatus was located inside a cooled flow tube where water, sulfuric acid, and ammonia vapors mixed and formed clusters. The complexities of the experimental technique and the interpretation of the results are extensively discussed. Typical NH3 and H2SO4 concentrations were 2 × 109 cm-3, i.e, ~100 pptv at atmospheric pressure. For these conditions, cluster concentrations were estimated to be a few times 106 cm-3 and the critical, particle-forming cluster likely contained 2 H2SO4 molecules at 275 K. The results are consistent with the species (H2SO4)2NH3 playing an important role in the formation of new particles in the atmosphere.

Hanson, D. R.; Eisele, F. L.

2002-06-01

210

Antiferromagnetism in the quasi-two-dimensional (CH3NH3)2CuBr4 crystal  

NASA Astrophysics Data System (ADS)

In this paper we are reporting the results of the experimental investigations of magnetic properties of quasi-two-dimensional (CH3NH3)2CuBr4 crystal. The field and temperature dependencies are studied in different orientations of magnetic field with respect to the crystallographic axes. The possible reasons of peculiarities of magnetization behavior are discussed.

Patrin, G. S.; Volkov, N. V.; Prokhorova, I. V.

2003-03-01

211

Numerical model of an Ar/NH3 atmospheric pressure direct current discharge in parallel plate geometry  

NASA Astrophysics Data System (ADS)

A one dimensional fluid model is used to investigate the role of ammonia added to an argon DC discharge at atmospheric pressure. The equations solved are the particle balances, assuming a drift-diffusion approximation for the fluxes, and the electron energy balance equation. The self-consistent electric field is obtained from the simultaneous solution of Poisson's equation. The electron-neutral collision rates are expressed as a function of the average electron energy. The model is comprised of 40 species (neutrals, radicals, ions, and electrons). In total, 75 electron-neutral, 43 electron-ion, 167 neutral-neutral, 129 ion-neutral, 28 ion-ion, and 90 3-body reactions are used in the model. The effects of gas mixing ratio on the densities of plasma species are systematically investigated. The calculated densities of the main plasma species are presented. It is found that in an Ar/NH3 plasma, the main neutrals (Ar*, Ar**, NH3*, NH, H2, NH2, H, and N2) are present at high densities. The Ar2+ and Ar+ ions are the dominant ions in the plasma. Furthermore, the NH3+ ions have a relatively higher density than other ammonia ions, whereas the density of other ions is negligible. Finally, a comparison is made between a pure Ar discharge and dielectric barrier discharge in a mixture of Ar/NH3. It is demonstrated that gas mixing ratio has a significant effect on the densities of plasma species, besides ammonia radical molecules and ammonia ions, and it also affects their ratio. Once the mixing ratio of Ar/NH3 is close to 1:1 at atmospheric pressure, the densities of NH, NH2+ and NH4+ reach to the maximum. The maximum of the different positive ammonia ions corresponds to the different ammonia mixing ratio.

Li, Zhi; Zhao, Zhen; Li, Xuehui

2012-03-01

212

DFT study of coverage-depended adsorption of NH3 on TiO2-B (100) surface.  

PubMed

A previous study showed that TiO(2)-B (100) surface is very unique. It is characterised by high activity and a loose structure. In this study, we studied the adsorption of ammonia on TiO(2)-B (100) surface at coverages ranging from 1/6 ML to 1 ML using ab initio density functional calculations. We also investigated the adsorption of an isolated ammonia molecule on TiO(2)-B (001) surface to compare the different activities of TiO(2)-B (100) and (001) surfaces towards NH(3). The results showed that the TiO(2)-B (100) surface is more reactive towards NH(3) molecule than TiO(2)-B (001) surface, and the Lewis acid site on TiO(2)-B (100) surface is more acidic. The decrease rate of the average molecular adsorption energy of NH(3) with coverage on TiO(2)-B (100) surface is substantially lower than that on a rutile (011) surface above 1/2 ML coverage due to the open structure of TiO(2)-B (100) surface. The average molecular adsorption energy shows a linear dependence on the coverage of y = 111.0 - 36.3x on TiO(2)-B (100) surface. The possibility of NH(3) molecule onto the Ti(5c) site is nearly equal to forming a dimer with adsorbed NH(3) on TiO(2)-B (100) surface at 5/6 ML coverage. PMID:22955312

Guo, Xiao-Jing; Liu, Weijia; Fang, Wei; Cai, Lu; Zhu, Yudan; Lu, Linghong; Lu, Xiaohua

2012-09-06

213

EFEKTIVITAS SISTEM SARINGAN MULTIMEDIA DALAM MENURUNKAN TSS, BOD, NH3-N , PO4 DAN TOTAL COLIFORM PADA LIMBAH CAIR RUMAH TANGGA  

Microsoft Academic Search

This research aimed to determine (1) the concentration of TSS, BOD, NH3-N, PO4, and total coliform on domestic waste water before and after treatment, (2) percentage of concentration decreasing of TSS, BOD, NH3-N, PO4, and total coliform on domestic waste water after treatment, (3) Find out the most effective combination of medium in decreasing the concentration of TSS, BOD, NH3-N,

Andi Susilawaty; Muhammad Hasyim Djaffar; Anwar Daud

214

p-n junctions on Ga-face GaN grown by NH3 molecular beam epitaxy with low ideality factors and low reverse currents  

Microsoft Academic Search

A comprehensive analysis of forward and reverse current of Ga-face GaN p-n junctions grown by NH3 molecular beam epitaxy (NH3-MBE) on metal organic chemical vapor deposition (MOCVD) GaN:Fe on sapphire is presented. NH3-MBE has a great potential for growing low leakage vertical devices due to its nitrogen-rich growth. Diodes with the lowest n-doping of n~3.5×1017 cm-3 exhibit an extremely low

Christophe A. Hurni; Oliver Bierwagen; Jordan R. Lang; Brian M. McSkimming; Chad S. Gallinat; Erin C. Young; David A. Browne; Umesh K. Mishra; James S. Speck

2010-01-01

215

p-n junctions on Ga-face GaN grown by NH3 molecular beam epitaxy with low ideality factors and low reverse currents  

Microsoft Academic Search

A comprehensive analysis of forward and reverse current of Ga-face GaN p-n junctions grown by NH3 molecular beam epitaxy (NH3-MBE) on metal organic chemical vapor deposition (MOCVD) GaN:Fe on sapphire is presented. NH3-MBE has a great potential for growing low leakage vertical devices due to its nitrogen-rich growth. Diodes with the lowest n-doping of n?3.5×1017 cm?3 exhibit an extremely low

Christophe A. Hurni; Oliver Bierwagen; Jordan R. Lang; Brian M. McSkimming; Chad S. Gallinat; Erin C. Young; David A. Browne; Umesh K. Mishra; James S. Speck

2010-01-01

216

Crystal structure of the ionic liquid EtNH3NO3-insights into the thermal phase behavior of protic ionic liquids.  

PubMed

The crystal structure of the salt ethylammonium nitrate (EtNH(3)NO(3)) has been determined. EtNH(3)NO(3) is one of the most widely studied protic ionic liquids (PILs)-ILs formed by proton transfer from a Brønsted acid to a Brønsted base. The structural features from the crystal structure, in concert with a Raman spectroscopic analysis of the ions, provide direct insight as to why EtNH(3)NO(3) melts below ambient temperature, while other related salts (such as EtNH(3)Cl) do not. PMID:23099473

Henderson, Wesley A; Fylstra, Paul; De Long, Hugh C; Trulove, Paul C; Parsons, Simon

2012-12-14

217

NH3 formation and utilization in regenerationof Pt/Ba/Al2O3 NOx storage-reduction catalyst with H2  

SciTech Connect

The nature of H2 regeneration of a model Pt/Ba/Al2O3 LNT catalyst was investigated with specific focus on intra-catalyst formation and utilization of NH3 and its role in catalyst regeneration. In-situ measurements of the transient intra-catalyst species (H2, NH3, N2, NOx) distributions at different temperatures were used to detail the reaction evolution along the catalyst axis. Comparison of the species transients identifies unique individual natures for the reductant (H2), inert product (N2) and intermediate-reductant product (NH3) which readily explain the conventional effluent species sequence as an integral effect. The data demonstrates that NH3 is created on similar timescales as the N2 product inside the catalyst, but consumed as aggressively as H2 reductant along the catalyst. This spatiotemporal NH3 behavior experimentally confirms that Intermediate-NH3 regeneration pathway is active. Analysis at 200 and 325 C indicates equivalent local NOx storage, H2 consumption and regeneration effectiveness, but differing NH3/N2 ratio, suggesting a temperature-dependence of partitioning between Direct-H2 and Intermediate-NH3 regeneration pathways. Further experimental and numerical work is needed to more clearly understand the partitioning between the possible regeneration pathways. Nevertheless, the experimental data show that intermediate NH3 plays a significant role in LNT catalyst regeneration.

Partridge Jr, William P [ORNL; Choi, Jae-Soon [ORNL

2009-01-01

218

Effect of Hydrostatic Pressure on the Phase Transitions in Ferroelectric (CH3NH3)5Bi2Cl11 (MAPCB) and (CH3NH3)5Bi2Br11 (MAPBB)  

NASA Astrophysics Data System (ADS)

Effect of hydrostatic pressure on the phase transitions and dielectric anomalies has been studied for ferroelectric (CH3NH3)5Bi2Cl11 (MAPCB) and (CH3NH3)5Bi2Br11 (MAPBB) in a pressure range up to about 650 MPa. The Curie temperatures T c (311 K in MAPCB, 307 K in MAPBB at 0 MPa) increase with increasing pressure with initial pressure coefficients (dT c/dp)p=0 of 0.063 K/MPa and 0.060 K/MPa for MAPCB and MAPBB, respectively. In MAPCB, the temperature at which the dielectric constant shows a diffuse anomaly (around 160 K at 0 MPa) increases linearly with increasing pressure with a rate of 0.057 K/MPa. The dielectric anomaly becomes more and more diffusive as pressure increases.

Gesi, Kazuo; Iwata, Makoto; Ishibashi, Yoshihiro

1995-07-01

219

Phase transitions in the ferroelectric crystals [CH3NH3]5Bi2Cl11 and [CH3NH3]5Bi2Br11 studied by the nonlinear dielectric effect  

NASA Astrophysics Data System (ADS)

The real part of the complex electric permittivity at low frequencies and at several biasing fields (between 0 and 5×105V/m ) has been measured in ferroelectric crystals [CH3NH3]5Bi2Cl11 (MAPCB) and [CH3NH3]5Bi2Br11 (MAPBB) in the temperature range covering the temperature of the ferroelectric phase transitions. Comparative measurements for the known triglycine sulphate (NH2CH2COOH)3H2SO4 crystal have been used as a test of the validity and of possible errors in the determination of the ferroelectric equation of state by the method applied. The estimates of the critical parameters TC , ? , and ? then have been evaluated for MAPCB and MAPBB on the basis of the Widom-Griffiths scaling hypothesis. Complementary pyroelectric measurements of the spontaneous polarization providing the critical exponent ? are in accordance with the parameters obtained.

Szklarz, P.; Ga??zka, M.; Zieli?ski, P.; Bator, G.

2006-11-01

220

Star-forming regions of the Aquila rift cloud complex. I. NH3 tracers of dense molecular cores  

NASA Astrophysics Data System (ADS)

Aims: The physics of star formation is an important part of Galactic evolution. Most stars are formed in high-density environments (n > 104 cm-3) and emit lines of diverse molecular transitions. In the present part of our survey we search for ammonia emitters in the Aquila rift complex, which trace the densest regions of molecular clouds. Methods: From a CO survey carried out with the Delingha 14-m telescope we selected ~150 targets for observations in other molecular lines. Here we describe the mapping observations in the NH3(1, 1) and (2, 2) inversion lines of the first 49 sources performed with the Effelsberg 100-m telescope. Results: The NH3(1, 1) emission lines are detected in 12 and the (2, 2) in 7 sources. Among the newly discovered NH3 sources, our sample includes the following well-known clouds: the starless core L694-2, the Serpens cloud cluster B, the Serpens dark cloudL572, the filamentary dark cloud L673, the isolated protostellar source B335, and the complex star-forming region Serpens South. Angular sizes between 40'' and 80'' (~0.04-0.08 pc) are observed for compact starless cores but can be as large as 9' (~0.5 pc) for filamentary dark clouds. The measured kinetic temperatures of the clouds lie between 9 K and 18 K. From NH3 excitation temperatures of 3-8 K we determine H2 densities with typical values of ~ (0.4-4) × 104 cm-3. The masses of the mapped cores range between ~0.05 and ~ 0.5 M?. The relative ammonia abundance X = [NH3]/[H2] varies from 1 × 10-7 to 5 × 10-7 with the mean ? X ? = (2.7 ± 0.6) × 10-7 (estimated from spatially resolved cores assuming a filling factor of ? = 1). In two clouds, we observe kinematically split NH3 profiles separated by ~1 km s-1. The splitting is most likely due to bipolar molecular outflows, for one of which we determine an acceleration of V ? ? 0.03 km s-1 yr-1. A starless core with significant rotational energy is found to have a higher kinetic temperature than the other ones, which is probably caused by magnetic energy dissipation. Appendices and Table 2 are available in electronic form at http://www.aanda.org

Levshakov, S. A.; Henkel, C.; Reimers, D.; Wang, M.; Mao, R.; Wang, H.; Xu, Y.

2013-05-01

221

[NH3, N2O, CH4 and CO2 emissions from growing process of caged broilers].  

PubMed

To obtain Ammonia and greenhouse gas (GHG) emission factors of caged broilers, ammonia (NH3), methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions of broilers aged 0 d to 42 days were monitored in caged broilers production systems located in Shandong province. Gas concentrations of incoming and exhaust air streams were measured by using INNOVA 1312 multi-gas monitor with multi-channel samplers. Building ventilation rates were determined by on site FANS (Fan Assessment Numeration System) measurement systems. The NH3 emission factors showed a trend of increase at the beginning and then decreased with the broiler ages. The NH3 emission rates were 8.5 to 342.1 mg x (d x bird)(-1) and the average daily emission rate was 137.9 mg x (d x bird)(-1) [48.6 g x (d x AU)(-1)] over the 42-d period. The GHGs emission rates were 19.5-351.9 mg x (d x bird)(-1) with an average of 154.5 mg x (d x bird)(-1) [54.4 g x (d x AU)(-1)] for CH4, and 2.2- 152.9 g x (d x bird)(-10 with an average of 65.9 g x (d x bird)(-1) [23.2 kg x (d x AU)(-1)] for CO2. No emission of N2O was observed. The CH4 and CO2 emission rates increased with the increase of broilers ages. The total NH3 emission over the 42 d growing period averaged (5.65 +/- 1.02) g x (bird x life cycle)(-1). The NH3 emission contribution in different growth phase to the total emission were 33.6% in growth phase 1 (0-17 day, GP1), 36.4% in GP2 (18-27 days), and 29.9% in GP3 (28-42 days), respectively. The NH3 emission in GP2 was significantly higher than emission in GP1 and GP3. CH4 and CO2 cumulative emission rates were (6.30 +/- 0.16) g x (bird(-1) x life cycle)(-1) and (2.68 +/- 0.18) kg x (bird x life cycle)(-1), respectively. The cumulative emission rates of CH4 and CO2 in GP3 were significantly higher than emission rates in GP2 and in GP1, accounting for 50% of total emissions. The results of this study could provide the data support for mitigation of gas emission from broilers production. PMID:23947019

Zhou, Zhong-Kai; Zhu, Zhi-Ping; Dong, Hong-Min; Chen, Yong-Xing; Shang, Bin

2013-06-01

222

Effects of preadsorbed oxygen on the bonding and desorption kinetics of CO on Ni(110)  

SciTech Connect

The effects of oxygen preadsorption on CO adsorption and CO desorption kinetics have been studied by temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). It is found that preadsorbed oxygen decreased total CO uptake at 120 K by no more than 20% even though the adsorption and desorption energies are strongly affected. The presence of oxygen causes several new desorption states to appear in the TPD whose populations depend sensitively upon oxygen predose. Using published results for the structure of oxygen covered Ni(110) and the present HREELS measurements, the desorption states have been assigned to structurally distinct bonding sites. Using the variation in heating rates method, the first order desorption energies and preexponential factors are obtained as a function of CO coverage for various oxygen predoses. The relationship between the desorption energies and the bonding sites, especially with regard to the distance of CO from neighboring oxygen atoms, is discussed.

Feigerle, C.S. (Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996-1600 (USA)); Overbury, S.H.; Huntley, D.R. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6201 (USA))

1991-05-01

223

Structural, energetic and thermodynamic analyses of Ca(BH4)2·2NH3 from first principles calculations  

NASA Astrophysics Data System (ADS)

Ca(BH4)2·2NH3 is a relatively new compound with potential application in hydrogen storage. Here the fundamental properties of the compound, such as electronic structure, energetic and thermodynamic properties, were comprehensively studied using first-principles calculations. Results from electronic density of states (DOS) and electron localization function (ELF) indicate the covalent bond nature of the N-H bond and the B-H bond. Charge density analyses show weak ionic interactions between the Ca atom and the NH3 complexes or the (BH4)- complexes. The calculated vibration frequencies of B-H and N-H are in good agreement with other theoretical and experimental results. Furthermore, we calculated the reaction enthalpy and reaction Gibbs free energy at a range of temperature 0-700 K. Our results are in good agreement with experimental results in literature. Possible reaction mechanism of the decomposition reaction is proposed.

Yuan, Peng-Fei; Wang, Fei; Sun, Qiang; Jia, Yu; Guo, Zheng-Xiao

2012-01-01

224

Excellent activity and selectivity of Cu-SSZ-13 in the selective catalytic reduction of NOx with NH3  

SciTech Connect

Superior activity and selectivity of a Cu ion-exchanged SSZ-13 zeolite in the selective catalytic reduction (SCR) of NOx with NH3 were observed, in comparison to Cu-beta and Cu-ZSM-5 zeolites. Cu-SSZ-13 was not only more active in the NOx SCR reaction over the entire temperature range studied (up to 550 °C), but also more selective toward nitrogen formation, resulting in significantly lower amounts of NOx by-products (i.e., NO2 and N2O) than the other two zeolites. In addition, Cu-SSZ-13 demonstrated the highest activity and N2 formation selectivity in the oxidation of NH3. The results of this study strongly suggest that Cu-SSZ-13 is a promising candidate as a catalyst for NOx SCR with great potential in after-treatment systems for either mobile or stationary sources.

Kwak, Ja Hun; Tonkyn, Russell G.; Kim, Do Heui; Szanyi, Janos; Peden, Charles HF

2010-10-21

225

Effect of hydrogen generated by dielectric barrier discharge of NH3 on selective non-catalytic reduction process.  

PubMed

Plasma-assisted selective non-catalytic reduction (SNCR) has been investigated to clarify which species generated by the plasma play a crucial role in NO reduction. We find that the presence of O(2) is indispensable and only H(2) is observed to be a stable product by dielectric barrier discharge (DBD) of NH(3). As the extent of NH(3) decomposition by DBD increases, the commencement temperature of SNCR processes is lowered and the working temperature window is widened. This propensity may be attributed to the chemical reaction of H(2) with O(2) to generate OH and H radicals which make it possible to yield NH(2) radicals even at low temperature. PMID:19230950

Byun, Youngchul; Ko, Kyung Bo; Cho, Moohyun; Namkung, Won; Shin, Dong Nam; Koh, Dong Jun

2009-02-23

226

Electronic and magnetic properties of an organic multiferroic: (C2H5NH3)2CuCl4  

NASA Astrophysics Data System (ADS)

(C2H5NH3)2CuCl4 was proposed to be a ferroelectric material with dominant ferromagnetic interactions. Using first-principles calculations we find that the insulating state and in-plane ferromagnetism induced by d-d orbital order can be expressed well by generalized gradient approximation (GGA) at ambient pressure. While the Jahn Teller distortion (JTD) is suppressed under critical pressure of 4 GPa, as a result the new d orbital order leads to in-plane antiferromagnetism. Meanwhile the conventional GGA gives a wrong metal state. Our results suggest that (C2H5NH3)2CuCl4 is a strong correlated charge transfer insulator, while the depress of JTD by pressure changes it to a Mott Hubbard insulator.

Ding, Jun; Li, HaiSheng; Wen, LiWei; Kang, XiuBao; Li, HaiDong; Zhang, JianMin

2013-11-01

227

Effect of tube radius on the exohedral chemical functionalization of boron-nitride zigzag nanotubes with NH3  

NASA Astrophysics Data System (ADS)

The interaction between zigzag BNNTs with chirality index n=3-10 and ammonia has been studied at the level of B3LYP/6-31G*. Ammonia can be chemically adsorbed on (3,0) to (7,0) BNNTs and physically adsorbed on other studied BNNTs. From NBO analysis charge transfer occur from NH3 to BNNTs and change in the natural electron configuration of B atom of BNNTs at adsorption site for the (3,0) and (4,0) BNNTs cases is larger than others. The DOS result show that after functionalization of BNNTs with NH3 molecules electronic properties of tubes are largely preserved and can be viewed as some kind of harmless modification. Electronic analysis revealed that the interaction of zigzag BNNTs with ammonia is more electrostatic (ionic) in nature, rather than the sole covalent and electrostatic nature increased with increasing of tube diameter.

Zahedi, Ehsan

2012-09-01

228

Low-Temperature Phase Transition and Structural Relationships of (CH3NH3)3Bi2Cl9  

NASA Astrophysics Data System (ADS)

(CH3NH3)3Bi2Cl9 exhibits two phase transitions at Tc1=349 K and Tc2=247 K. The upper transition is probably isomorphous and reveals itself by the anomalous evolution of the lattice parameters. This behavior is explained to be due to increasing thermal motion of the methylammonium cations. The space group in both phases is Pnma. Single crystal X-ray work performed at 215 K indicates P212121 as probable space group for the low-temperature phase with a=20.43(1), b=7.644(3), c=13.225(4) Å, and Z=4. Symmetry analysis allows one to ascribe nearly tricritical character to the low-temperature phase transition. Structural relationships of (CH3NH3)3Bi2Cl9 are displayed in the form of a group-subgroup diagram.

Belkyal, I.; Mokhlisse, R.; Tanouti, B.; Hesse, K.-F.; Depmeier, W.

2000-12-01

229

Influence of sulfation on iron titanate catalyst for the selective catalytic reduction of NO x with NH 3  

Microsoft Academic Search

Iron titanate catalyst (FeTiOx) is a potential candidate for the substitution of conventional V2O5–WO3 (MoO3)\\/TiO2 and Fe\\/Cu-zeolite catalysts for the selective catalytic reduction (SCR) of NOx with NH3 because of its high SCR activity and N2 selectivity in the medium temperature range. Due to the presence of small amount of SO2 in typical diesel exhaust derived from combustion of sulfur-containing

Fudong Liu; Kiyotaka Asakura; Hong He; Wenpo Shan; Xiaoyan Shi; Changbin Zhang

2011-01-01

230

Rotation-vibration motion of pyramidal XY 3 molecules described in the Eckart frame: Theory and application to NH 3  

Microsoft Academic Search

We present a new model for the rotation-vibration motion of pyramidal XY3 molecules, based on the Hougen–Bunker–Johns approach. Inversion is treated as a large-amplitude motion, while the small-amplitude vibrations are described by linearized stretching and bending coordinates. The rotation–vibration Schrödinger equation is solved variationally. We report three applications of the model to NH3 using an analytic potential function derived from

Miguel Carvajal; Per Jensen; Jingjing Zheng; Walter Thiel

2005-01-01

231

Removal of SO 2 from O 2-containing flue gas by activated carbon fiber (ACF) impregnated with NH 3  

Microsoft Academic Search

Adsorption of SO2 from the O2-containing flue gas by granular activated carbons (GACs) and activated carbon fibers (ACFs) impregnated with NH3 was studied in this technical note. Experimental results showed that the ACFs were high-quality adsorbents due to their unique textural properties. In the presence of moisture, the desulphurization efficiency for the ACFs was improved significantly due to the formation

Lüsi Xu; Jia Guo; Feng Jin; Hancai Zeng

2006-01-01

232

CH3NH3PbI3 perovskite/fullerene planar-heterojunction hybrid solar cells.  

PubMed

All-solid-state donor/acceptor planar-heterojunction (PHJ) hybrid solar cells are constructed and their excellent performance measured. The deposition of a thin C60 fullerene or fullerene-derivative (acceptor) layer in vacuum on a CH3 NH3 PbI3 perovskite (donor) layer creates a hybrid PHJ that displays the photovoltaic effect. Such heterojunctions are shown to be suitable for the development of newly structured, hybrid, efficient solar cells. PMID:23775589

Jeng, Jun-Yuan; Chiang, Yi-Fang; Lee, Mu-Huan; Peng, Shin-Rung; Guo, Tzung-Fang; Chen, Peter; Wen, Ten-Chin

2013-06-18

233

ARTICLES: Dissociation of UF6 molecules involving excitation of combination modes by NH3-N2 laser radiation  

Microsoft Academic Search

The results are presented of a study of the dissociation of UF6 molecules as a result of simultaneous interaction of resonant (NH3-N2 laser) and quasiresonant (CO2 laser) infrared fields with upsilo3 + upsilo5 (821.827 cm-1) and upsilo1 + upsilo4 (852.8 cm-1) combination vibrations. The method used to record the dissociation process (observation of the HF* luminescence) made it possible to

V. G. Averin; M. Akhrarov; G. S. Baronov; B. I. Vasil'ev; Arkadii Z. Grasyuk; M. G. Morozov; E. P. Skvortsova; A. B. Yastrebkov

1983-01-01

234

Phase transitions in CH3NH3ClO4 and CH3ND3ClO4  

Microsoft Academic Search

Infrared and Raman spectra (10–5000 cm) of CH3NH3ClO4 and CH3ND3ClO4 were investigated in the temperature range 90–470 K. Single crystal Raman spectral studies were also carried out at 310 and 90 K. Assignments of the measured frequencies to the internal modes have been made. Based on a systematic temperature dependent study of widths and frequencies of prominent bands, the phase

T. K. K. Srinivasan; M. Mylrajan

1992-01-01

235

Conformation of organic chain in phase transition of hybrid (Cl 2 H 25 NH 3 ) 2 MnCl 4  

Microsoft Academic Search

The structural change in phase transition of hybrid (Cl2H25NH3)2MnCl4 was investigated. The temperature and the structures of the phase transition is investigated by thermal gravimetry (TG) and\\u000a differential scanning calorimetry (DSC), infrared spectrum (IR) and X-ray diffraction (XRD). The results suggest that the\\u000a phase transition is reversible and the structural change arises from the conformation change of the organic chain.

Liling Guo; Yubing Sun; Ao Mei; Yadong Dai; Hanxing Liu

2008-01-01

236

NH 3, N 2O and CH 4 emissions during passively aerated composting of straw-rich pig manure  

Microsoft Academic Search

Straw-rich manure from organic pig farming systems was composted in passively aerated static piles to estimate the effect of monthly turning on organic matter degradation and NH3, N2O and CH4 emissions. Turning enhanced the rate of drying and degradation. The four-month treatment degraded 57±3% of the initial organic matter in the turned piles, while only 40±5% in the static piles.

G. L. Szanto; H. V. M. Hamelers; W. H. Rulkens; A. H. M. Veeken

2007-01-01

237

Model-based control system design in a urea-SCR aftertreatment system based on NH 3 sensor feedback  

Microsoft Academic Search

This paper presents preliminary control system simulation results in a urea-selective catalytic reduction (SCR) aftertreatment\\u000a system based on NH3 sensor feedback. A four-state control-oriented lumped parameter model is used to analyze the controllability and observability\\u000a properties of the urea-SCR plant. A model-based estimator is designed via simulation and a control system is developed with\\u000a design based on a sliding mode

M. Devarakonda; G. Parker; J. H. Johnson; V. Strots

2009-01-01

238

Effects of NH3-plasma nitridation on the electrical characterizations of low-k hydrogen silsesquioxane with copper interconnects  

Microsoft Academic Search

The interaction between copper interconnects and low-k hydrogen silsesquioxane (HSQ) film was investigated using a Cu\\/HSQ\\/Si metal insulation semiconductor capacitor and NH3 plasma post-treatment. Owing to serious diffusion of copper atoms in HSQ film, degradations of the dielectric properties are significant with the increase of thermal stress. The leakage current behavior in high field conduction is well explained by the

Po-Tsun Liu; Ting-Chang Chan; Ya-Liang Yang; Yi-Fang Cheng; Simon M. Sze

2000-01-01

239

An attempt for NH3 detection based on quartz resonator with thin SnO2 film  

Microsoft Academic Search

The sensitivity of quartz resonators with a thin layer of tin oxide (SnO2) deposited on them is investigated for the registration of ammonia in air. The measurements are carried out at NH 3 concentrations from 10 ppm to 5000 ppm. A correlation is found between the relative change of the resonator's frequency (?f\\/f) and concentration in the investigated interval. The

V. Georgieva; L. Spassov; V. Georgiev

1999-01-01

240

Enhanced electroluminescence of silicon-rich silicon nitride light-emitting devices by NH 3 plasma and annealing treatment  

Microsoft Academic Search

Silicon-rich silicon nitride (SRSN) films were deposited on p-type silicon substrates using a conventional plasma-enhanced chemical vapor deposition (PECVD) system. Before deposition, silicon substrate was pre-treated by NH3 plasma in the PECVD system. And devices with metal–insulator–semiconductor (MIS) structure were fabricated using indium tin oxides (ITO) as anode and aluminum (Al) film as cathode. It was found that after 1100°C

Dongsheng Li; Jianhao Huang; Deren Yang

2009-01-01

241

Evidence that Fungal MEP Proteins Mediate Diffusion of the Uncharged Species NH3 across the Cytoplasmic Membrane  

PubMed Central

Methylammonium and ammonium (MEP) permeases of Saccharomyces cerevisiae belong to a ubiquitous family of cytoplasmic membrane proteins that transport only ammonium (NH4+ + NH3). Transport and accumulation of the ammonium analog [14C]methylammonium, a weak base, led to the proposal that members of this family were capable of energy-dependent concentration of the ammonium ion, NH4+. In bacteria, however, ATP-dependent conversion of methylammonium to ?-N-methylglutamine by glutamine synthetase precludes its use in assessing concentrative transport across the cytoplasmic membrane. We have confirmed that methylammonium is not metabolized in the yeast S. cerevisiae and have shown that it is little metabolized in the filamentous fungus Neurospora crassa. However, its accumulation depends on the energy-dependent acidification of vacuoles. A ?vph1 mutant of S. cerevisiae and a ?vma1 mutant, which lack vacuolar H+-ATPase activity, had large (fivefold or greater) defects in the accumulation of methylammonium, with little accompanying defect in the initial rate of transport. A vma-1 mutant of N. crassa largely metabolized methylammonium to methylglutamine. Thus, in fungi as in bacteria, subsequent energy-dependent utilization of methylammonium precludes its use in assessing active transport across the cytoplasmic membrane. The requirement for a proton gradient to sequester the charged species CH3NH3+ in acidic vacuoles provides evidence that the substrate for MEP proteins is the uncharged species CH3NH2. By inference, their natural substrate is NH3, a gas. We postulate that MEP proteins facilitate diffusion of NH3 across the cytoplasmic membrane and speculate that human Rhesus proteins, which lie in the same domain family as MEP proteins, facilitate diffusion of CO2.

Soupene, Eric; Ramirez, Robert M.; Kustu, Sydney

2001-01-01

242

HCN, C2H2, and NH3 abundances in comet C/LINEAR 2002 T7  

NASA Astrophysics Data System (ADS)

We present quantitative measurements of HCN, C2H2, and NH3 emissions near 3.0 ? m in comet C/LINEAR 2002 T7. The observations were obtained using the CSHELL instrument at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. CSHELL incorporates a 256x256 InSb array detector with a long slit, which provides high spectral resolution (R ˜ 2 x104) sufficient to resolve individual cometary emission lines, coupled with high spatial resolution for determining the distribution of species within the coma. The dates of observations were UT 2004 3May, 4 May, 6 May, 8 May and 9 May. The high Doppler shift ( ˜ - 65 km/s) of T7 during the early May time period made it an excellent target for detection of NH3. In other comets observed since Hyakutake, stronger lines of NH3 overlapped with atmospheric absorptions. Several lines of the Q-branch and R-branch of the ? 1 band were detected. The apparition of T7 was also favorable for detection of the ? 3 band of C2H2 and resulted in detection of (at least) 6 ro-vibrational lines of the molecule, the greatest number of C2H2 lines detected in any comet to date. We routinely observe a wide range of ro-vibrational lines of the ? 3 band of HCN in comets. In T7, at least 10 lines of the P- and R- branch were detected allowing an accurate determination of the rotational temperature and production rate. Numerous other emissions were detected within these spectra (H2O hot-band emission, OH prompt emission, and NH2). Several (relatively strong) unidentified emission lines were also observed. Spectra, production rates, rotational temperatures, and relative abundances of HCN, C2H2, and NH3 will be presented and discussed. KM-S would like to acknowledge support from the National Science Foundation RUI Program No. 0407052.

Magee-Sauer, K.; Dello Russo, N.; DiSanti, M. A.; Bonev, B.; Gibb, E. L.; Mumma, M. J.

2004-11-01

243

Computational exploration of the six-dimensional vibration–rotation–tunneling dynamics of (NH3)2  

Microsoft Academic Search

In order to address the well-known problem that the nearly cyclic structure of (NH3)2 deduced from microwave spectra differs greatly from the hydrogen-bonded equilibrium structure obtained from abinitio calculations, we have calculated the vibration–rotation–tunneling (VRT) states of this complex, and explicitly studied the effects of vibrational averaging. The potential used is a spherical expansion of a site–site potential which was

J. W. I. van Bladel; A. van der Avoird; P. E. S. Wormer; R. J. Saykally

1992-01-01

244

Duty ratio impact on SiN films deposited in SiH 4NH 3 plasma at room temperature  

Microsoft Academic Search

Silicon nitride (SiN) films were deposited by using pulsed plasma-enhanced chemical vapor deposition system. The experiments were conducted from SiH4 and NH3 plasma at room temperature. The duty ratio was varied in the range 40–90%. Duty ratio-induced ion energy diagnostics was conducted using a non-invasive ion energy analyzer. Ion energy variables collected include a high ion energy (Eh), a low

Daehyun Kim; Byungwhan Kim; Neung-Goo Yoon

245

Selective catalytic reduction of NO x by NH 3 on Fe\\/HBEA zeolite catalysts in oxygen-rich exhaust  

Microsoft Academic Search

This paper deals with the systematic study of Fe\\/HBEA zeolites for the selective catalytic reduction (SCR) of NOx by NH3 in diesel exhaust. The catalysts are prepared by incipient wetness impregnation of H-BEA zeolite (Si\\/Al=12.5). The SCR examinations performed under stationary conditions show that the pattern with a Fe load of 0.25wt.% (0.25Fe\\/HBEA) reveals pronounced performance. The turnover frequency at

Peter Balle; Bastian Geiger; Sven Kureti

2009-01-01

246

Free NH 3 quantum rotations in Hofmann clathrates: structure factors and line widths studied by inelastic neutron scattering  

NASA Astrophysics Data System (ADS)

Quantum rotations of NH 3 groups in Hofmann clathrates Ni-Ni-C 6H 6 and Ni-Ni-C 12H 10 have been studied using inelastic neutron scattering. Calculations of the dynamical structure factor for a free uniaxial quantum rotor reproduce the neutron scattering data with respect to their Q- and T-dependence as well as the relative intensities for the 0 ? 1, 0 ? 2 and 1 ? 2 transitions. Though the effective NH 3 rotation constant is different from the gas phase value, the effective radius of rotation (i.e., the average distance of protons from the rotation axis) is equal or very close to the geometrical value r = 0.94 Å for a NH 3 group. Comparing the experimental data with the calculated dynamical structure factor for the 0 ? 3 transition it could be shown, that the corresponding transition line, in contrast to transitions between j = 0,1,2 levels measured so far, has a finite width at T = 0 K.

Sobolev, O.; Vorderwisch, P.; Desmedt, A.

2005-01-01

247

Use of multilayer techniques for XPS identification of various nitrogen environments in the Si/NH3 system  

NASA Astrophysics Data System (ADS)

The experimental ability to reach rapidly, under UHV and on the same substrate holder, the high temperatures (1100 K) required for silicon surface reconstructions and the low temperatures (80 K) needed to condense ammonia molecularly or to adsorb this gas dissociatively on specific silicon surface states, allowed us to elaborate thin multilayers made up of various combinations of the nitrogen chemical environments involved in the Si/NH3 system. Included in a surface laye (< 50 Å) corresponding to the analysing electron escape depth of a X-ray photoelectron spectrometer, they lead one to obtain the binding energy signatures for molecular ammonia (NH3), amide (NH2) and imide (NH) fragments and nitrides (Si3N) by simultaneously and easily comparable N 1s core level recordings. The results confirm that beside the Ts dependence of the degree of dissociation of NH3, the silicon surface state configuration (Si(100)-2 × 1. Si(111)-7 × 7 a-Si) is another important parameter explaining the presence of differently adsorbed N, NH or NH2 groups.

Bischoff, J. L.; Lutz, F.; Bolmont, D.; Kubler, L.

1991-07-01

248

N2O and NH3 emissions from a bioreactor landfill operated under limited aerobic degradation conditions.  

PubMed

The combination of leachate recirculation and aeration to landfill may be an efficient way for in-situ nitrogen removal. However, nitrogenous substances contained in the landfill layer are concomitantly transformed into N2O and NH3, leading to increased emissions into the atmosphere. In the present study, the emissions of N2O and NH3 were measured under conditions of fresh or partially stabilized refuse with or without leachate recirculation or intermittent aeration. The results showed that the largest N2O emission (12.4 mg-N/L of the column) was observed in the aerated column loaded with partially stabilized refuse and recycled with the leachate of low C/N ratio; while less than 0.33 mg-N/L of the column was produced in the other columns. N2O production was positively correlated with the prolonged aerobic time and negatively related with the C/N ratio in the recycled leachate. NH3 volatilization increased with enhanced gas flow and concentration of free ammonia in the leachate, and the highest cumulative volatilization quantity was 1.7 mg-N/L of the column. PMID:22066225

He, Pinjing; Yang, Na; Gu, Huili; Zhang, Hua; Shao, Liming

2011-01-01

249

Detailed chemistry of NH3/N2O/Ar flames by mass spectrometry, laser-induced fluorescence, and modeling  

NASA Astrophysics Data System (ADS)

Experimental and chemical modeling studies of a 60-Torr Nh3/N2O/Ar::1.03/1.59/0.54 flame are performed in order to provide further testing and refinements of a detailed chemical mechanisms developed previously in our laboratory. This mechanism consists of 87 reactions and 20 species and is denoted VS. Flame temperatures are measured with a coated, thin-wire thermocouple and by OH and NH by laser- induced fluorescence (LIF). Species concentration profile of NH3, N2O, N2, NO, O2, NH and OH are recorded using molecular beam pass spectrometry and/or LIF. The experimental species mole fractions are then compared to PREMIX laminar flame code calculations, which use the measured temperature profile and one of two detailed N/O/H chemical mechanisms, VS or VS-modified, as input. The PREMIX calculations using the VS mechanism predict very well the shapes of the experimental NH3, N2O, N2 H2O, NO, OH and NH profiles throughout the flame. They overpredict, however, the O2/Ar mole fraction ratio at 16.25 mm by 61 percent. Sensitivity analyses suggest refinements to the VS mechanisms. These refinements, along with rate analyses of the PREMIX results, are presented and discussed.

Sausa, Ross C.; Venizelos, D. T.

1999-01-01

250

Improved characteristics for MOHOS memory with oxygen-rich GdO as charge storage layer annealed by NH3  

NASA Astrophysics Data System (ADS)

Characteristics of metal-oxide-high-k-oxide-silicon (MOHOS) memories with oxygen-rich or oxygen-deficient GdO as charge storage layer annealed by NH3 or N2 are investigated. Transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction are used to analyze the cross-sectional quality, composition and crystallinity, respectively, of the stacked gate dielectric with a structure of Al/Al2O3/GdO/SiO2/Si. The MOHOS capacitor with oxygen-rich GdO annealed in NH3 exhibits a good trade-off among its memory properties: large memory window (4.8 V at ±12 V, 1 s), high programming speed (2.6 V at ±12 V/100 ?s), good endurance and retention properties (window degradation of 5 % after 105 program/erase cycles and charge loss of 18.6 % at 85 °C after 10 years, respectively) due to passivation of oxygen vacancies, generation of deep-level traps in the grain boundaries of the GdO layer and suppression of the interlayer between GdO and SiO2 by the NH3 annealing.

Liu, Lu; Xu, J. P.; Chen, J. X.; Lai, P. T.

2013-10-01

251

Kinetics of selective catalytic reduction of NO by NH3 on Fe-Mo/ZSM-5 catalyst.  

PubMed

The catalyst of Fe-Mo/ZSM-5 has been found to be more active than Fe-ZSM-5 and Mo/ZSM-5 separately for selective catalytic reduction (SCR) of nitric oxide (NO) with NH3. The kinetics of the SCR reaction in the presence of O2 was studied in this work. The results showed that the observed reaction orders were 0.74-0.99, 0.01-0.13, and 0 for NO, O2 and NH3 at 350-450 degrees C, respectively. And the apparent activation energy of the SCR was 65 kJ/mol on the Fe-Mo/ZSM-5 catalyst. The SCR mechanism was also deduced. Adsorbed NO species can react directly with adsorbed ammonia species on the active sites to form N2 and H2O. Gaseous 02 might serve as a reoxidizing agent for the active sites that have undergone reduction in the SCR process. It is also important to note that a certain amount of NO was decomposed directly over the Fe-Mo/ZSM-5 catalyst in the absence of NH3. PMID:18277659

Li, Zhe; Shen, Lin-tao; Huang, Wei; Xie, Ke-chang

2007-01-01

252

Magnetoabsorption of the lowest exciton in perovskite-type compound (CH3NH3)PbI3  

NASA Astrophysics Data System (ADS)

Magnetoabsorption spectra of (CH3NH3)PbI3 are investigated in the Faraday configuration up to 40 T at 4.2 K. The compound consists of three-dimensional networks of corner-sharing octahedra [PbI6]4-. The Zeeman splitting and the diamagnetic shift are observed, and the effective g-factor and the diamagnetic coefficient are 1.2 +/- 0.1 and (2.7 +/- 0.1) × 10-6 eV/T2, respectively. From the diamagnetic shift, the Bohr radius, the binding energy and the reduced mass of the exciton are estimated to be 28 Å, 37 meV and 0.12m0, respectively. The exciton in (CH3NH3)PbI3 is one of typical Wannier-type excitons with large radius, which is in contrast with the exciton in (C10H21NH3)2PbI4, consisting of two-dimensional networks of [PbI6]4-.

Hirasawa, M.; Ishihara, T.; Goto, T.; Uchida, K.; Miura, N.

1994-07-01

253

Properties of LaAlO3 thin film on GaAs(1 0 0) treated by in situ NH3 plasma  

NASA Astrophysics Data System (ADS)

LaAlO3 film was grown on GaAs by PEALD.The LaAlO3 film remain amorphous after 500 °C annealing.The GaAs/LaAlO3 interface was optimized by in situ NH3 plasma nitridation.In situ NH3 plasma nitridation improved electric properties of MOS.

Jia, T. T.; Cheng, X. H.; Chao, D.; Xu, D. W.; Wang, Z. J.; Xia, C.; Zhang, Y. W.; Yu, Y. H.

2013-07-01

254

Effect of High NH3 Input Partial Pressure on Hydride Vapor Phase Epitaxy of InN Using Nitrided (0001) Sapphire Substrates  

NASA Astrophysics Data System (ADS)

The influence of the source gas supply sequence prior to growth and the NH3 input partial pressure (PoNH3) on the nucleation of InN islands during the initial stages of hydride vapor phase epitaxy on a nitrided (0001) sapphire substrate was investigated. The crystalline quality of the InN layer after subsequent lateral growth was also examined. When NH3 was flowed prior to growth, single-crystal hexagonal InN islands formed. When InN was grown with a higher PoNH3, the number of InN islands decreased remarkably while their diameter increased. The crystalline quality of InN grown on the hexagonal islands with a high PoNH3 significantly improved with increasing growth time. A strong PL spectrum was observed only from InN layers grown with a high PoNH3. It was thus revealed that an NH3 preflow and a high PoNH3 are effective for producing InN with high crystalline quality and good optical and electrical properties.

Togashi, Rie; Yamamoto, Sho; Karlsson, K. Fredrik; Murakami, Hisashi; Kumagai, Yoshinao; Holtz, Per-Olof; Koukitu, Akinori

2013-08-01

255

Ternary homogeneous nucleation of H2SO4, NH3, and H2O under conditions relevant to the lower troposphere  

NASA Astrophysics Data System (ADS)

Ternary homogeneous nucleation (THN) of H2SO4, NH3 and H2O has been used to explain new particle formation in various atmospheric regions, yet laboratory measurements of THN have failed to reproduce atmospheric observations. Here, we report first laboratory observations of THN made under conditions relevant to the lower troposphere ([H2SO4] of 106-107 cm-3, [NH3] of 0.08-20 ppbv, and a temperature of 288 K). Our observations show that NH3 can enhance atmospheric H2SO4 aerosol nucleation and the enhancement factor (EF) in nucleation rate (J) due to NH3 (the ratio of J measured with vs. without NH3) increases linearly with increasing [NH3] and increases with decreasing [H2SO4] and RH. Two chemical ionization mass spectrometers (CIMS) are used to measure [H2SO4] and [NH3], as well as possible impurities of amines in the nucleation system. Aerosol number concentrations are measured with a water condensation counter (CPC, TSI 3786). The slopes of Log J vs. Log [H2SO4], Log J vs. Log RH, and Log J vs. Log [NH3] are 3-5, 1-4, and 1, respectively. These slopes and the threshold of [H2SO4] required for the unity nucleation vary only fractionally in the presence and absence of NH3. These observations can be used to improve aerosol nucleation models to assess how man-made SO2 and NH3 affect aerosol formation and CCN production at the global scale.

Benson, D. R.; Yu, J. H.; Markovich, A.; Lee, S.-H.

2011-05-01

256

Classical and quantum-mechanical modeling of the stimulated desorption of ammonia from Cu(111)  

Microsoft Academic Search

Results from quasi-classical and quantum-mechanical calculations for the UV-laser induced photodesorption of NH3 and ND3 from Cu(111) are presented and compared. A two-dimensional, two-electronic state model is employed to describe the dynamics of this desorption system, in which the out-of-plane bending mode has been identified as playing an important role. Quantum-mechanical calculations employ the wave-packet method to solve the time-dependent

Eckart Hasselbrink; Martin Wolf; Stephen Holloway; Peter Saalfrank

1996-01-01

257

Evaluation of a regional air-quality model with bi-directional NH3 exchange coupled to an agro-ecosystem model  

NASA Astrophysics Data System (ADS)

Atmospheric ammonia (NH3) is the primary atmospheric base and an important precursor for inorganic particulate matter and when deposited NH3 contributes to surface water eutrophication, soil acidification and decline in species biodiversity. Flux measurements indicate that the air-surface exchange of NH3 is bi-directional. However, the effects of bi-directional exchange, soil biogeochemistry and human activity are not parameterized in air quality models. The US Environmental Protection Agency (EPA)'s Community Multiscale Air-Quality (CMAQ) model with bi-directional NH3 exchange has been coupled with the United States Department of Agriculture (USDA)'s Environmental Policy Integrated Climate (EPIC) agro-ecosystem model's nitrogen geochemistry algorithms. CMAQ with bi-directional NH3 exchange coupled to EPIC connects agricultural cropping management practices to emissions and atmospheric concentrations of reduced nitrogen and models the biogeochemical feedback on NH3 air-surface exchange. This coupled modeling system reduced the biases and error in NHx (NH3 + NH4+) wet deposition and in ambient aerosol concentrations in an annual 2002 Continental US (CONUS) domain simulation when compared to a 2002 annual simulation of CMAQ without bi-directional exchange. Fertilizer emissions estimated in CMAQ 5.0 with bi-directional exchange exhibits markedly different seasonal dynamics than the US EPA's National Emissions Inventory (NEI), with lower emissions in the spring and fall and higher emissions in July.

Bash, J. O.; Cooter, E. J.; Dennis, R. L.; Walker, J. T.; Pleim, J. E.

2012-08-01

258

Lattice potential energy and standard molar enthalpy in the formation of 1—dodecylamine hydrobromide (1-C12H25NH3·Br)(s)  

NASA Astrophysics Data System (ADS)

This paper reports that 1-dodecylamine hydrobromide (1-C12H25NH3·Br)(s) has been synthesized using the liquid phase reaction method. The lattice potential energy of the compound 1-C12H25NH3·Br and the ionic volume and radius of the 1-C12H25NH3+ cation are obtained from the crystallographic data and other auxiliary thermodynamic data. The constant-volume energy of combustion of 1-C12H25NH3·Br(s) is measured to be ?cUmo(1-C12H25NH3·Br, s) = -(7369.03±3.28) kJ·mol-1 by means of an RBC-II precision rotating-bomb combustion calorimeter at T = (298.15±0.001) K. The standard molar enthalpy of combustion of the compound is derived to be ?cHmo(1-C12H25NH3·Br, s) = -(7384.52±3.28) kJ·mol-1 from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound is calculated to be ?fHmo(1-C12H25NH3·Br, s)=-(1317.86±3.67) kJ·mol-1 from the standard molar enthalpy of combustion of the title compound and other auxiliary thermodynamic quantities through a thermochemical cycle.

Liu, Yu-Pu; Di, You-Ying; Dan, Wen-Yan; He, Dong-Hua; Kong, Yu-Xia; Yang, Wei-Wei

2011-02-01

259

The H2O Southern Galactic Plane Survey: NH3 (1,1) and (2,2) catalogues  

NASA Astrophysics Data System (ADS)

The H2O Southern Galactic Plane Survey (HOPS) has mapped a 100° strip of the Galactic plane (-70° > l > 30°, |b| < 0°.5) using the 22 m Mopra antenna at 12 mm wavelengths. Observations were conducted in on-the-fly mode using the Mopra spectrometer (MOPS), targeting water masers, thermal molecular emission and radio-recombination lines. Foremost among the thermal lines are the 23 GHz transitions of NH3 J,K = (1,1) and (2,2), which trace the densest parts of molecular clouds (n > 104 cm-3). In this paper, we present the NH3 (1,1) and (2,2) data, which have a resolution of 2 arcmin and cover a velocity range of ±200 km s-1. The median sensitivity of the NH3 data cubes is ?T mb =0.20±0.06 K. For the (1,1) transition, this sensitivity equates to a 3.2 kpc distance limit for detecting a 20 K, 400 M? cloud at the 5? level. Similar clouds of mass 5000 M? would be detected as far as the Galactic Centre, while 30 000 M? clouds would be seen across the Galaxy. We have developed an automatic emission finding procedure based on the Australian Telescope National Facility (ATNF) DUCHAMP software and have used it to create a new catalogue of 669 dense molecular clouds. The catalogue is 100 per cent complete at the 5? detection limit (Tmb = 1.0 K). A preliminary analysis of the ensemble cloud properties suggests that the near-kinematic distances are favoured. The cloud positions are consistent with current models of the Galaxy containing a long bar. Combined with other Galactic plane surveys this new molecular-line data set constitutes a key tool for examining Galactic structure and evolution. Data cubes, spectra and catalogues are available to the community via the HOPS website.

Purcell, C. R.; Longmore, S. N.; Walsh, A. J.; Whiting, M. T.; Breen, S. L.; Britton, T.; Brooks, K. J.; Burton, M. G.; Cunningham, M. R.; Green, J. A.; Harvey-Smith, L.; Hindson, L.; Hoare, M. G.; Indermuehle, B.; Jones, P. A.; Lo, N.; Lowe, V.; Phillips, C. J.; Thompson, M. A.; Urquhart, J. S.; Voronkov, M. A.; White, G. L.

2012-11-01

260

A new family of superconducting fullerides, Na(NH3)(x)C60(x = 2-8)  

NASA Astrophysics Data System (ADS)

A series of A3C60 fulleride superconductors (A is an alkali metal) with superconducting transition temperatures ((Tc)s) between 2.5 and 33 K has been reported. The (Tc)s of these materials are closely correlated to their f.c.c. lattice parameters, with the higher Tc materials having larger unit cell lengths. Recently, the Tc of the superconducting Na2CsC60 has been raised from 10.5 K to 29.6 K by ammonia intercalation. The resulting intercalated compound, NaC(Na(NH3)4)C60 has an expanded unit cell compared to the starting material, with a larger cation Na(NH3)(4+), occupying the octahedral site. The sodium-doped C60 with nominal composition Na3C60, however, does not show superconductivity and was reported to undergo a disproportionation reaction into two f.c.c. phases, Na2C60 and Na6C60 below 250 K. Here we report on the ammonia intercalation of Na3C60. Up to four superconducting phases with (Tc)s occurring near 6.7, 11.5, 13.5, and 16.5 K were observed in the compounds Na3(NH3)(x)C60 (x approximately = 2 = 8). All these phases gave significant superconducting shielding fractions (between 15 and 80% at 5 K). These compounds were characterized by use of AC susceptibility and SQUID measurements, TGA, and x-ray powder diffraction.

Schlueter, J. A.; Smart, J. L.; Wang, H. H.

261

Thermochemistry of Lewis adducts of BH3 and nucleophilic substitution of triethylamine on NH3BH3 in tetrahydrofuran.  

PubMed

The thermochemistry of the formation of Lewis base adducts of BH(3) in tetrahydrofuran (THF) solution and the gas phase and the kinetics of substitution on ammonia borane by triethylamine are reported. The dative bond energy of Lewis adducts were predicted using density functional theory at the B3LYP/DZVP2 and B3LYP/6-311+G** levels and correlated ab initio molecular orbital theories, including MP2, G3(MP2), and G3(MP2)B3LYP, and compared with available experimental data and accurate CCSD(T)/CBS theory results. The analysis showed that the G3 methods using either the MP2 or the B3LYP geometries reproduce the benchmark results usually to within ~1 kcal/mol. Energies calculated at the MP2/aug-cc-pVTZ level for geometries optimized at the B3LYP/DZVP2 or B3LYP/6-311+G** levels give dative bond energies 2-4 kcal/mol larger than benchmark values. The enthalpies for forming adducts in THF were determined by calorimetry and compared with the calculated energies for the gas phase reaction: THFBH(3) + L ? LBH(3) + THF. The formation of NH(3)BH(3) in THF was observed to yield significantly more heat than gas phase dative bond energies predict, consistent with strong solvation of NH(3)BH(3). Substitution of NEt(3) on NH(3)BH(3) is an equilibrium process in THF solution (K ? 0.2 at 25 °C). The reaction obeys a reversible bimolecular kinetic rate law with the Arrhenius parameters: log A = 14.7 ± 1.1 and E(a) = 28.1 ± 1.5 kcal/mol. Simulation of the mechanism using the SM8 continuum solvation model shows the reaction most likely proceeds primarily by a classical S(N)2 mechanism. PMID:20932027

Potter, Robert G; Camaioni, Donald M; Vasiliu, Monica; Dixon, David A

2010-10-08

262

Theoretical NH{_3} Spectra in 5800-7000 CM-1 Region and CO{_2} IR Intensity: Updates  

NASA Astrophysics Data System (ADS)

Recently we have successfully applied the "Best Theory + High-resolution Experimental Data" strategy to NH{_3} and CO{_2}. The essential strategy is to refine a high quality, purely ab initio potential energy surface (PES) with reliable high resolution experimental data, so the IR line lists computed on the refined PES and dipole moment surface (DMS) can go beyond simple data reproduction. The goal is to make reliable predictions for higher J/K/energy rovibrational transitions with similar accuracies, i.e. 0.01-0.03 cm-1. The reliability and accuracy of data included in the refinement largely determines the quality of predictions and the ultimate merit of our work. With recent 14NH{_3} experiments in 5800 - 7000 cm-1, the effective coverage (with 0.01-0.03 cm-1 accuracy) of our NH{_3} PES has extended to this complex spectral region. Excellent agreement between current experiment analysis and our primitive HSL-3 PES refinement will be presented, and source of discrepancies will be discussed. The synergy between the experiments and theory is of great value. For CO{_2}, we have updated the theoretical IR intensity of the 12C16O{_2} line list with a more reliable DMS, then carried out very detailed comparisons with both pure experimental data and HITRAN/CDSD models. Results suggest that our line lists should be useful for the astronomical or earth-based detection of CO{_2} isotopologues. X. Huang, D.W. Schwenke, and T.J. Lee, J. Chem. Phys. 129, 214304 (2008); J. Chem. Phys. 134, 044320/044321 (2011). X. Huang, D.W. Schwenke, S.A. Tashkun, and T.J. Lee J. Chem. Phys. 136, submitted (2012).

Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.; Sung, Keeyoon; Brown, Linda R.; Tashkun, Sergey A.

2012-06-01

263

Sub-ppm NH3 sensor for control of de-nitrification process using diode laser spectroscopy  

NASA Astrophysics Data System (ADS)

Diode laser absorption spectroscopy (DLAS) has become an important analytical technique for highly sensitive and specific gas concentration measurements as it is reliable, fast and accurate. In this work a diode laser sensor has been developed to monitor ammonia at sub-ppm in 1510-nm region. The system was designed to control the de-nitrification process with selective catalytic reduction (SCR) abatement system. To ensure that NOx is reacted completely and to avoid secondary pollution resulted from ammonia slip, it is essential to monitor emissions of ammonia for controlling the amount of NH3 injection. NH3 concentration is demanded not to exceed 5ppm, preferably 2-3ppm. In order to provide enough sensitivity, the sensor uses DLAS with wavelength modulation as AC detection of absorption line derivatives, at frequencies where the laser noise is reduced, coupled with coherent electronic detection techniques. Experiment results demonstrate that the sensor with the second-harmonic detection shows in-situ, continuous measurements with low detection limit (60 ppb), fast response (<1s) and long-term stability all of which is difficult to obtain with conventional techniques such as wet chemical analysis, non-dispersive infrared (NDIR). In addition, the influence of water vapor on ammonia measurements due to line broadening effects is investigated. A real-time spectrum analysis algorithm is developed. The systematic measurement error is corrected by means of the line width measurements based on fast pattern correlation analysis of second-harmonic line shape. This offers the advantage of accurate NH3 concentration measurement even though the moisture content is above 40%.

Gu, Haitao; Liu, Lipeng; Li, Ying; Chen, Ren; Wen, Luhong; Wang, Jian

2008-12-01

264

Interaction of vacuum ultraviolet light with a low-k organosilicate glass film in the presence of NH3  

NASA Astrophysics Data System (ADS)

In situ x-ray photoemission spectroscopy (XPS) and ex situ Fourier transform infrared spectroscopy (FTIR) were used to characterize effects on organosilicate films of 147 nm irradiation in the presence of 10-4 Torr NH3. XPS and FTIR data indicate Si-O and Si-C bond scission, with nitridation only at Si sites. Photoirradiation causes the surface layer to become enriched in sp2 carbon. FTIR spectra of silanol formation upon exposure to ambient indicate reactive sites in the bulk have lifetimes of up to six days. XPS data indicate lifetimes of ~minutes for surface states. Nitrogen uptake passivates with longer exposure times, indicating surface densification.

Behera, Swayambhu; Lee, Joe; Gaddam, Sneha; Pokharel, Sundari; Wilks, Justin; Pasquale, Frank; Graves, David; Kelber, Jeffry A.

2010-07-01

265

Quasi-one-dimensional antiferromagnetism in (CH3NH3)MnCl3 . 2H2O  

Microsoft Academic Search

(CH3NH3)MnCl3?2H2O, MMC, contains chains of cis-[MnCl4(H2O)2] octahedra corner-linked via single Cl atoms. These chains are very similar to those in CsMnCl3?2H2O, CMC, but more widely separated by the larger cations. We have measured the magnetic susceptibilities of MMC between ?1 and 100 K at 80 Hz and its heat capacity between ?1 and 20 K. Susceptibilities above ?10 K are

Satoru Simizu; Jiing-Yann Chen; S. A. Friedberg

1984-01-01

266

Electrocrystallization of palladium from Pd(NH 3 ) 4 Cl 2 bath on stainless steel 316L  

Microsoft Academic Search

Electrochemical deposition of palladium from 0.04 M Pd(NH3)4Cl2, NH4Cl, and NH4OH bath (pH?=?10) on stainless steel electrode was studied by voltammetry, chronopotentiometry, and chronoamperometry. Crossovers\\u000a in cyclic voltammograms demonstrate that the deposition of palladium proceed via a nucleation\\/growth mechanism. Chronopotentiograms\\u000a indicate that palladium reduction is not controlled by diffusion and Sand’s law is not obeyed. In the early stage of the

I. Danaee; F. Shoghi; M. Dehghani Mobarake; M. Kameli

2010-01-01

267

Anti and gauche conformers of an inorganic butane analogue, NH3BH2NH2BH3.  

PubMed

The crystal structures of an inorganic butane analogue, NH(3)BH(2)NH(2)BH(3) (DDAB), were determined using single crystal X-ray diffraction, revealing both anti and gauche conformations. The anti conformation is stabilized by intermolecular dihydrogen bonds in the crystal whereas two gauche conformations of DDAB observed in its 18-crown-6 adducts are stabilized by an intramolecular dihydrogen bond. The two gauche conformations show rotational isomerization but whether they are a pair of enantiomers is yet to be defined. PMID:22760200

Chen, Xuenian; Gallucci, Judith; Campana, Charles; Huang, Zhenguo; Lingam, Hima Kumar; Shore, Sheldon G; Zhao, Ji-Cheng

2012-07-04

268

Highly Sensitive NH3 Detection Based on Organic Field Effect Transistors with Tris(pentafluorophenyl)Borane as Receptor  

PubMed Central

We have increased organic field-effect transistor (OFET) NH3 response using tris-(pentafluorophenyl)borane (TPFB) as receptor. OFETs with this additive detect concentrations of 450 ppb v/v, with a limit of detection of 350 ppb, the highest sensitivity yet from semiconductor films; in comparison, when triphenylmethane (TPM) and triphenylborane (TFB) were used as an additive, no obvious improvement of sensitivity was observed. These OFETs also show considerable selectivity with respect to common organic vapors, and stability to storage. Furthermore, excellent memory of exposure was achieved by keeping the exposed devices in a sealed container stored at ?30°C, the first such capability demonstrated with OFETs.

Huang, Weiguo; Besar, Kalpana; LeCover, Rachel; Rule, Ana Maria; Breysse, Patrick N.; Katz, Howard E.

2012-01-01

269

Adiabatic reduction and hysteresis of the LFI model for NO + NH 3 on Pt{1 0 0}  

NASA Astrophysics Data System (ADS)

The Lombardo-Fink-Imbihl (LFI) model for the NO + NH 3 reaction on Pt{1 0 0} consists of seven coupled ordinary differential equations (ODEs). Here, we present a numerical analysis for relaxation oscillations in the LFI and show that it cannot be adiabatically reduced to two coupled ODEs. We argue that this is because of the explicit consideration of the trapping processes of NO from 1 × 1 to hex phases in the kinetic mechanism of the reaction. Our analysis shows that an adiabatic reduction to three coupled ODEs can be achieved. Moreover, we examine the hysteretic behavior in detail.

Uecker, H.; Imbihl, R.; Rafti, M.; Irurzun, I. M.; Vicente, J. L.; Mola, E. E.

2003-12-01

270

Effect of internal bias field on domain switching in (CH3NH3)5Bi2Br11 crystal  

NASA Astrophysics Data System (ADS)

In this report we investigate the microscopic features of 180° domain wall dynamics and relate its dynamics to the defect structure in unipolar methylammonium bromobismuthate, (CH3NH3)5Bi2Br11, single crystal. The switching and spontaneous backswitching processes have been studied by observation of domain structure by using nematic liquid crystal method and by switching current registration. We found a two-step relaxation decay of polarization induced by Eb; the fast one decays on the time scale of milliseconds, while the slow one lasts over seconds. In the late-time regime, the stretched-exponential function was used as an empirical fit of relaxation data.

Matyjasek, K.; Rogowski, R. Z.

2006-04-01

271

Intermediates in the reduction of N(2) to NH(3): synthesis of iron eta(2) hydrazido(1-) and diazene complexes.  

PubMed

Iron complexes containing hydrazido(1-) and diazene ligands were investigated as potential intermediates in the reduction of N(2) to NH(3). Generation of cis-[Fe(DMeOPrPE)(2)(eta(2)-N(2)H(3))](+) and cis-Fe(DMeOPrPE)(2)(eta(2)-N(2)H(2)) (DMeOPrPE = 1,2-bis(dimethoxypropylphosphino)ethane) was achieved by addition of base to cis-[Fe(DMeOPrPE)(2)(N(2)H(4))](2+). The hydrazine, hydrazido(1-), and diazene complexes can be interconverted by protonation/deprotonation reactions. PMID:19488434

Crossland, Justin L; Balesdent, Chantal G; Tyler, David R

2009-04-14

272

Rate constants and branching ratios for the reaction of CH radicals with NH3: a combined experimental and theoretical study.  

PubMed

The reaction between CH radicals and NH(3) molecules is known to be rapid down to at least 23 K {at which temperature k = (2.21 ± 0.17) × 10(-10) cm(3) molecule(-1) s(-1): Bocherel ; et al. J. Phys. Chem. 1996, 100, 3063}. However, there have been only limited theoretical investigations of this reaction and its products are not known. This paper reports (i) ab initio quantum chemical calculations on the energy paths that lead to various reaction products, (ii) calculations of the overall rate constant and branching ratios to different products using transition state and master equation methods, and (iii) an experimental determination of the H atom yield from the reaction. The ab initio calculations show that reaction occurs predominantly via the initial formation of a datively bound HC-NH(3) complex and reveal low energy pathways to three sets of reaction products: H(2)CNH + H, HCNH(2) + H, and CH(3) + NH. The transition state calculations indicate the roles of "outer" and "inner" transition states and yield rate constants between 20 and 320 K that are in moderate agreement with the experimental values. These calculations and those using the master equation approach show that the branching ratio for the most exothermic reaction, to H(2)CNH + H, is ca. 96% throughout the temperature range covered by the calculations, with those to HCNH(2) + H and CH(3) + NH being (4 ± 3)% and <0.3%, respectively. In the experiments, multiple photon dissociation of CHBr(3) was used to generate CH radicals and laser-induced fluorescence at 121.56 nm (VUV-LIF) was employed to observe H atoms. By comparing signals from CH + NH(3) with those from CH + CH(4), where the yield of H atoms is known to be unity, it is possible to estimate that the yield of H atoms from CH + NH(3) is equal to 0.89 ± 0.07 (2?), in satisfactory agreement with the theoretical estimate. PMID:22126589

Blitz, Mark A; Talbi, Dahbia; Seakins, Paul W; Smith, Ian W M

2011-12-23

273

Conformation, protein recognition and repair of DNA interstrand and intrastrand cross-links of Antitumor trans-(PtCl2(NH3)(thiazole))  

Microsoft Academic Search

Replacement of one ammine in clinically ineffective trans-(PtCl2(NH3)2) (transplatin) by a planar N- heterocycle, thiazole, results in significantly enhanced cytotoxicity. Unlike 'classical' cisplatin {cis-(PtCl2(NH3)2)} or transplatin, modification of DNA by this prototypical cytotoxic transplatinum complex trans-(PtCl2(NH3)(thiazole)) (trans-PtTz) leads to monofunctional and bifunctional intra or interstrand adducts in roughly equal proportions. DNA fragments containing site-specific bifunctional DNA adducts of trans-PtTz were

Victoria Marini; Petros Christofis; Olga Novakova; Jana Kasparkova; Nicholas Farrell; Viktor Brabec

274

The structure and catalytic activity of anatase and rutile titania supported manganese oxide catalysts for selective catalytic reduction of NO by NH3.  

PubMed

The structure and catalytic properties of anatase and rutile supported manganese oxide catalysts prepared by impregnation method have been studied by using X-ray diffraction (XRD), laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy (XPS), H(2) temperature-programmed reduction (H(2)-TPR) and BET surface area measurements combined with activity testing of selective catalytic reduction (SCR) of NO by NH(3). It has been shown that the manganese oxide loadings on the two TiO(2) supports exert great influences on the SCR activity. For the rutile supported manganese oxide catalysts, increasing manganese oxide loading leads to the increase of reducibility of dispersed manganese oxide species and the rate constant k, which reaches a maximum around 9.6 × 10(-6) mol g(Mn)(-1) s(-1) at 0.5 mmol Mn per 100 m(2) TiO(2). When the manganese oxide loading is beyond this value, the existence of amorphous MnO(x) multiple layers will certainly reduce the ratio of manganese oxide species exposed on the surface and the reducibility of dispersed manganese oxide species, resulting in the rapid decrease of rate constant k. The LRS and XPS results have revealed that for the anatase supported manganese oxide catalysts manganese oxide species exist in Mn(+4) as a major species with Mn(+3) species and partially undecomposed Mn-nitrate as the minor species. Under the SCR reaction conditions, Mn(+3) species on anatase are oxidized to Mn(+4) species, inserting in the surface of anatase and promoting the anatase-to-rutile transformation in the surface layers of the anatase support. Since these Mn(4+) cations are actually dispersed on the support with a rutile shell-anatase core structure and its concentration is very near to that of MnO(x)/TiO(2) (R) catalyst, the relation between the rate constant k and the MnO(x) loading on the anatase support is similar to that on the rutile support, and that the rate constant k values for anatase and rutile supported manganese oxide catalysts are very close at the same MnO(x) loading. PMID:21258687

Zhuang, Ke; Qiu, Jing; Tang, Fushun; Xu, Bolian; Fan, Yining

2011-01-24

275

[Catalytic performance of a novel ceramic-supported vanadium oxide catalyst for NO reduction with NH3].  

PubMed

A novel TiO2/Al2O3/ceramic cordierite honeycomb (CC)-supported V2O5-MoO3-WO3 monolithic catalyst was studied for the selective reduction of NO with NH3. The effects of reaction temperature, space velocity, NH3/NO ratio and oxygen content on selective catalytic reduction (SCR) activity were evaluated. Two other V2O5-MoO3-WO3 monolithic catalysts supported on Al2O3/CC or TiO2/CC support, two types of pellet catalysts supported on TiO2/Al2O3 or Al2O3, as well as three types of pellet catalysts V2O5-MoO3-WO3-Al2O3 and V2O5-MoO3-WO3-TiO2 were tested for comparison. The experiment results showed that this catalyst had a higher catalytic activity for SCR with comparison to others. The results of characterization showed, the preparation method of this catalyst can give rise to a higher Brunauer, Emmett, Teller (BET) surface area and pore volume, which was strongly related with the highly active performance of this catalyst. At the same time, the function of the combined carrier of TiO2/Al2O3 cannot be excluded. PMID:15330412

Tian, Liu-qing; Ye, Dai-qi

2004-01-01

276

Catalyst Temperature Dependence of NH3 Decomposition for InN Grown by Metal Organic Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

In this paper, we report an independent catalyst heating system on the Pt-catalyst metal organic vapor phase epitaxy (MOVPE) for Indium nitride (InN) growth, and the dependence of the NH3 decomposition rate on the Pt catalyst temperature (RT to 1000 °C) using a quadrupole mass spectrometer (Q-MS). When the catalyst temperature is increased above the growth temperature of InN, the NH3 decomposition rate is enhanced. The grain size of InN becomes larger and the full width at half maximum (FWHM) of the X-ray rocking curve (XRC) was drastically decreased. The increase of N atoms results in the incorporation of nitrogen into the InN layer and thus improves the crystal quality of InN. However, active H increases sharply when the catalyst heater temperature is over about 850 °C. Therefore, a great improvement in the crystal quality of InN film is expected by optimizing the growth condition including a catalyst temperature not exceeding 850 °C.

Sugita, Kenichi; Hironaga, Daizo; Mihara, Akihiro; Hashimoto, Akihiro; Yamamoto, Akio

2013-08-01

277

[Rb(18-crown-6)][Rb([2.2.2]-cryptand)]Rb2Sn9?5NH3  

PubMed Central

The crystal structure of the title compound, poly[[(4,7,13,16,21,24-hexa­oxa-1,10-diaza­bicyclo­[8.8.8]hexa­cosa­ne)rubidium] [[(1,4,7,10,13,16-hexa­oxacyclo­octa­deca­ne)rubidium]di-?-rubidium-?-nona­stannide] penta­ammonia], {[Rb(C18H36N2O6)][Rb3Sn9(C12H24O6)C12H24O6)]·5NH3}n represents the first ammoniate of a Zintl anion together with two different chelating substances, namely 18-crown-6 and [2.2.2]-cryptand. The involvement of these large mol­ecules in the crystal structure of [Rb(18-crown-6)][Rb([2.2.2]-cryptand)]Rb2Sn9·5NH3 leads to the formation of a new structural motif, namely one-dimensionally extended double strands running parallel to [100] and built by Sn9 4? cages and Rb+ cations. The double strands are shielded by 18-crown-6 and [2.2.2]-cryptand. The cations are additionally coordin­ated by ammonia mol­ecules. One of the four independent Rb+ cations is disordered over two sets of sites in a 0.74?(2):0.26?(2) ratio.

Gaertner, Stefanie; Korber, Nikolaus

2011-01-01

278

Triggering N2 Uptake via Redox Induced Expulsion of Coordinated NH3 and N2 Silylation at Trigonal Bipyramidal Iron  

PubMed Central

The biological reduction of nitrogen to ammonia may occur via one of two predominant pathways in which nitrogenous NxHy intermediates including hydrazine (N2H4), diazene (N2H2), nitride (N3-) and imide (NH2-) may be involved. To test the validity of hypotheses concerning iron’s direct role in the stepwise reduction of N2, iron model systems are needed. Such systems can test the chemical compatibility of iron with various proposed NxHy intermediates, and the reactivity patterns of such species. Here we describe a TBP (SiPR3)Fe-L scaffold (SiPR3 represents [Si(o-C6H4PR2)3]?; R = Ph and iPr) where the apical site is occupied by nitrogenous ligands such as N2, N2H4, NH3 and N2R. The system accommodates terminally bound N2 in the three formal oxidation states (iron(0), +1, and +2). N2 uptake is demonstrated via displacement of its reduction partners NH3 and N2H4, and N2 functionalizaton is illustrated via electrophilic silylation.

Lee, Yunho; Mankad, Neal P.

2010-01-01

279

A novel chemical detector using colorimetric sensor array and pattern recognition methods for the concentration analysis of NH3.  

PubMed

With a colorimetric sensor array comprising chemoresponsive dyes, a simple, rapid, and cost-effective integrated system for differentiating low-concentration gases was described. The system could be used to identify gases by detecting the color change information of the chemoresponsive dyes based on porphyrins before and after reaction with the target gas; the colorimetric sensor array images were collected by a charge coupled device and processed with image analysis to get the color changes of the dyes in the array. Temperature, humidity, and flux of the chamber could be detected and displayed on the personal computer screen. A low-concentration [30-210 ppb (parts per 10(9))] NH(3) was detected by the system. This prototype successfully differentiated four concentration levels of NH(3) in less than 1 min. Pattern recognition methods, such as the backpropagation neural network and the radial basis function neural network, validated the effect of the developed sensor system both with 100% classification with feature vectors at single time point as inputs. PMID:21034125

Luo, Xiao-gang; Liu, Ping; Hou, Chang-jun; Huo, Dan-qun; Dong, Jia-le; Fa, Huan-bao; Yang, Mei

2010-10-01

280

Subsolidus phase diagram of binary system in the perovskite type layer compounds ( n -C n H 2n+1 NH 3 ) 2 MnCl 4  

Microsoft Academic Search

The thermotropic phase transitions in the perovskite type layer compound (n-C10H21NH3)2MnCl4 and (n-C14H29NH3)2MnCl4 were synthesized and, at the same time, a series of their mixtures C10Mn-C14Mn were prepared. The experimental binary phase diagram of C10Mn-C14Mn was established by differential thermal analysis (DTA), IR and X-ray diffraction. In the phase diagram new material (n-C10H21NH3)(n-C14H29NH3)MnCl4 and two eutectoid invariants were observed, two

K. Wu; J. Zhang

2009-01-01

281

THERMAL DESORPTION TREATMENT  

EPA Science Inventory

Thermal desorption is an ex situ means to physically separate volatile and some semivolatile contaminants from soil, sediments, sludges, and filter cakes. or wastes containing up to 10% organics or less, thermal desorption can be used alone for site remediation. t also may find a...

282

Influence of NH 3 flow rate on pyridine-like N content and NO electrocatalytic oxidation of N-doped multiwalled carbon nanotubes  

Microsoft Academic Search

Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) have been prepared by pyrolysis of pyridine and iron phthalocyanine\\u000a over an iron catalyst at 850 °C at various ammonia gas (NH3) flow rates. X-ray photoelectron spectroscopy results reveal that the pyridine-like nitrogen (N) content can be controlled\\u000a by changing the flow rate of NH3, and that pyridine-like N plays an important role: it can increase

Wei-Xin LvRui; Rui Zhang; Ting-Liang Xia; Hong-Mei Bi; Ke-Ying Shi

2011-01-01

283

The abundances of CH4, CH3D, NH3, and PH3 in the troposphere of Jupiter derived from high-resolution 1100-1200\\/cm spectra  

Microsoft Academic Search

High-resolution spectra of the 1100-1200\\/cm region of the central part of Jupiter obtained in March 1980 and April 1981 are analyzed. The best fit NH3 distribution curve reveals a higher than solar mixing ratio, the abundance of NH3 to that of H2 being (3.3 + or - 1.7) x 10 to the -4th, below the 147 K layer (greater than

R. F. Knacke; S. J. Kim; S. T. Ridgway; A. T. Tokunaga

1982-01-01

284

Optimization and field application of a filter pack system for the simultaneous sampling of atmospheric HN0 3, NH 3 AND SO 2  

Microsoft Academic Search

Optimization and field application of a filter pack system for the simultaneous collection of atmospheric gas-phase HN03, NH3 and S02 have been studied. A Teflon prefilter was used to remove particulate matter. Nylon filter, oxalic-acid-treated Whatman 41 filter and sodium-carbonate-treated Whatman 41 filter were used for the collection of HN03, NH3 and S02, respectively. For the collection of gas-phase HN03,

Duran Karaka?; Semra G. Tuncel

1997-01-01

285

Density functional study on the adsorption and surface reactions on SiO 2 in TiN-CVD using TiCl 4 and NH 3  

Microsoft Academic Search

We have investigated the following surface reactions theoretically, in order to elucidate the mechanism of the initial step of TiN chemical vapor deposition (CVD) on amorphous SiO2 surfaces using TiCl4 and NH3 as material gases: (i) adsorption of TiCl4 and NH3 onto the SiO2 surface; (ii) surface reactions of the Langmuir–Hinshelwood mechanism and the Eley–Rideal mechanism between the adsorbates produced

Tatsuo Tanaka; Tohru Nakajima; Koichi Yamashita

2002-01-01

286

Experimental and Theoretical Investigation of Homogeneous Gaseous Reaction of CO(2)(g) + nH(2)O(g) + nNH(3)(g) ? Products (n = 1, 2).  

PubMed

Decreasing CO(2) emissions into the atmosphere is key for reducing global warming. To facilitate the CO(2) emission reduction efforts, our laboratory conducted experimental and theoretical investigations of the homogeneous gaseous reaction of CO(2)(g) + nH(2)O(g) + nNH(3)(g) ? (NH(4))HCO(3)(s)/(NH(4))(2)CO(3)(s) (n = 1 and 2) using Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy and ab initio molecular orbital theory. Our FTIR-ATR experimental results indicate that (NH(4))(2)CO(3)(s) and (NH(4))HCO(3)(s) are formed as aerosol particulate matter when carbon dioxide reacts with ammonia and water in the gaseous phase at room temperature. Ab initio study of this chemical system suggested that the reaction may proceed through formation of NH(3)·H(2)O(g), NH(3)·CO(2)(g), and CO(2)·H(2)O(g) complexes. Subsequent complexes, NH(3)·H(2)O·CO(2) and (NH(3))(2)·H(2)O·CO(2), can be formed by adding gaseous reactants to the NH(3)·H(2)O(g), NH(3)·CO(2)(g), and CO(2)·H(2)O(g) complexes, respectively. The NH(3)·H(2)O·CO(2) and (NH(3))(2)·H(2)O·CO(2) complexes can then be rearranged to produce (NH(4))HCO(3) and (NH(4))(2)CO(3) as final products via a transition state, and the NH(3) molecule acts as a medium accepting and donating hydrogen atoms in the rearrangement process. Our computational results also reveal that the presence of an additional water molecule can reduce the activation energy of the rearrangement process. The high activation energy predicted in the present work suggests that the reaction is kinetically not favored, and our experimental observation of (NH(4))HCO(3)(s) and (NH(4))(2)CO(3)(s) may be attributed to the high concentrations of reactants increasing the reaction rate of the title reactions in the reactor. PMID:22900762

Li, Zhuangjie; Zhang, Baoquan

2012-08-29

287

Theoretical investigations of spin-orbit coupling and kinetics in reaction W + NH3 ? N?WH3.  

PubMed

The hydrogen-transfer reaction of W + NH(3) incorporates four possible diabatic reaction pathways along with septet, quintet, triplet, and singlet states. The intersystem crossings thus play an important role in the reaction mechanisms. In this work, ab initio and DFT methods are used to determine all possible intermediates, transition states, products, and intersystem crossing points as well as the spin-orbit couplings. The mechanism of hydrogen elimination is further revealed by the natural bond orbital analysis. From the rate constants yielded by a nonadiabatic transition state theory, we find that two intersystem crossings significantly change the reaction pathways. Finally, we suggest a feasible reaction pathway with exothermicity 72.8 kcal/mol, which is consistent with the experimental measurements. PMID:22356227

Si, Yubing; Zhang, Weiwei; Zhao, Yi

2012-03-06

288

NH3-annealed atomic-layer-deposited silicon nitride as a high-k gate dielectric with high reliability  

NASA Astrophysics Data System (ADS)

Extremely thin (equivalent oxide thickness, Teq=1.2 nm) silicon-nitride high-k (?r=7.2) gate dielectrics have been formed at low temperatures (<=550 °C) by an atomic-layer-deposition (ALD) technique with subsequent NH3 annealing at 550 °C. A remarkable reduction in leakage current, especially in the low dielectric voltage region, which will be the operating voltage for future technologies, has made it a highly potential gate dielectric for future ultralarge-scale integrated devices. Suppressed soft breakdown events are observed in ramped voltage stressing. This suppression is thought to be due to a strengthened structure of Si-N bonds and the smoothness and uniformity at the poly-Si/ALD-silicon-nitride interface.

Nakajima, Anri; Khosru, Quazi D. M.; Yoshimoto, Takashi; Kidera, Toshirou; Yokoyama, Shin

2002-02-01

289

Isolates identification and characteristics of microorganisms in biotrickling filter and biofilter system treating H2S and NH3.  

PubMed

A combination system of biotrickling filter (BTF) and biofilter (BF), adopting surfactant-modified clinoptilolite and surfactant-modified wood chip as the media respectively, was applied to treat H2S and NH3 simultaneously. The identification and sole carbon sources utilization patterns of isolates in the combination system were studied by Biolog system. The isolates were identified as Bacillus sphaericus, Geobacillus themoglucosidasius (55 degrees C) and Micrococcus luteus (ATCC 9341) in BTF, and Aspergillus sydowii (Bainier & Sartory) Thorm & Church in BF. Among 95 substrate classes supplied by Biolog system, the carboxylic acids and methyl esters had the highest utilization extent for the four species, followed by the amino acids and peptides. The descending sequence of carbon sources utilization capability of isolates was A. sydowii (52.6%), M. luteus (39.5%), B. sphaericus (21.6%), and G. thermoglucosidasius (17.7%). PMID:17966875

Guang-Hui, Yu; Xiao-Jun, Xu; Pin-Jing, He

2007-01-01

290

Exploring Deep Icy World Oceans through New Experimental Equations of State for Aqueous MgSO4 and NH3  

NASA Astrophysics Data System (ADS)

Observational evidence supports the presence of very deep oceans in Europa, Ganymede, Callisto, Titan, and Enceladus. Thermal models for other bodies to be more thoroughly explored also suggest internal liquid layers in the present or past. Hydrostatic pressure at the bottom oceans in the three largest of the solar system's icy world oceans exceeds the formation pressures of high-pressure ice phases. Temperature- and pressure-dependent thermodynamic effects on fluid transport and phase stability may have profound geophysical and astrobiological implications, but experimental constraints on these properties are only now becoming available. In this context, we present equations of state for aqueous NH3 and MgSO4 derived from speeds of sound obtained by the method of impulsive stimulated scattering. Using these, we provide new constraints on the presence of liquids within ice layers at the tops and bottoms of icy world oceans.

Vance, S.; Brown, J.

2011-12-01

291

[Nano-MnO(x) catalyst for the selective catalytic reduction of NO by NH3 in low-temperature].  

PubMed

Nanometer particles composed of manganese oxides (Nano-MnO(x)), which prepared by rheological phase reaction method, show superior low-temperature SCR activity for NO with NH3 in the presence of excess O2. In experiments, the NO conversion is 98.25% at 80 degrees C, and nearly 100% NO could be converted in 100 - 150 degrees C. Due to the reason of competing adsorption, H2O has a slight impact on the activity and the deactivation of SO2 is reversible. The experiments implied that the superior low-temperature catalytic activity of Nano-MnO(x) was mainly due to its high BET specific areas and poor crystallinity. PMID:17489185

Tang, Xiao-Long; Hao, Ji-Ming; Xu, Wen-Guo; Li, Jun-Hua

2007-02-01

292

Effect of humidity on the a.c. impedance of CH3NH3SnCl3 hybrid films  

NASA Astrophysics Data System (ADS)

Impedance spectroscopy measurements show that complex conductivity of thermally ablated CH3NH3SnCl3 films is strongly enhanced when humidity increases. Coplanar two-electrode test devices are modeled through an equivalent circuit comprising one resistance and two constant phase elements. It is shown that the influence of ambient humidity is mainly resistive. The dynamic responses of the devices to humidification/dehumidification cycles point out that the a.c. current varies by more than three orders of magnitude when humidity is varied between dry air and 80% relative humidity. The rise times are few hundred seconds while fall times are as short as few tens of seconds. This observation suggests that impedance variations are determined by mechanisms involving loosely bound water molecules physisorbed at the surface of the hybrid film. The results obtained are discussed in terms of protonic conduction.

Mosca, R.; Ferro, P.; Besagni, T.; Calestani, D.; Chiarella, F.; Licci, F.

2011-09-01

293

Optical Absorption in Band-Edge Region of ( CH3NH3)3Bi2I9 Single Crystals  

NASA Astrophysics Data System (ADS)

Optical absorption spectra were measured around the band edge in ( CH3NH3)3Bi2I9 single crystals. In the very thin crystals, an intrinsic exciton band appears clearly at 2.51 eV at low temperatures, and the absorption peak remains even at room temperature reflecting a large binding energy of more than 300 meV. The exciton band does not show a discontinuous shift near the temperature where the methylammonium ions induce a structural phase transition. This fact indicates that the exciton states are independent of the methylammonium ions. The origin of the exciton band is examined on the basis of the annealing effect on the absorption bands in vacuum-evaporated films. The lower energy tail of the exciton band obeys the Urbach rule between 78 and 350 K. The detailed analysis by the Urbach rule reveals that the exciton-phonon interaction in the present system is relatively strong.

Kawai, Taketoshi; Ishii, Atsuko; Kitamura, Takako; Shimanuki, Shigetaka; Iwata, Makoto; Ishibashi, Yoshihiro

1996-05-01

294

Kinetics of ferroelectric switching in unipolar (CH3NH3)5Bi2Br11 crystal  

NASA Astrophysics Data System (ADS)

Ferroelectric switching in unipolar (CH3NH3)5Bi2Br11 crystal has been studied by optical observation of the domain structure in low electric fields and switching current registration in high fields. We discuss investigations on the temporal behaviour of the electric polarization in static electric fields as well as polarization decay after removal of the electric field. The backswitching process appears to have a correlation to a defect-induced internal field in the crystal. For the interpretation of experimental data we utilize the classical nucleation and growth model of phase transformation (e.g. Avrami-Kolmogorov theory). An analysis assuming a statistical distribution of the characteristic domain growth times is proposed to explain and to find the functional form of the experimental data.

Rogowski, R. Z.; Matyjasek, K.; Jakubas, R.

2005-12-01

295

Specific Heat and Phase Transition Phenomena in (CH3NH3)5Bi2Cl11  

NASA Astrophysics Data System (ADS)

Specific heat of (CH3NH3)5Bi2Cl11 was measured by adiabatic calorimetry between 13 K and 325 K. A typical second-order type of anomaly was observed at 307.4 K. The enthalpy and entropy of transition were determined as 3.06 kJ mol-1 and 10.6 J K-1 mol-1, respectively. A broad hump in the curve of specific heat was found around 160 K. Its contribution was estimated as the excess specific heat extending from about 100 K to 200 K over an assumed normal base line, which results in the values of enthalpy and entropy as 1.57 kJ mol-1 and 9.85 J K-1 mol-1, respectively. The phase transition in the crystal was discussed in connection with such specific heat anomalies.

Iwata, Makoto; Tojo, Takeo; Atake, Tooru; Ishibashi, Yoshihiro

1994-10-01

296

Molecular dynamics of the methylammonium cation in [CH3NH3]5Bi2Cl11.  

PubMed

The 1H relaxation times T1 of methylammonium in chlorobismuthate(III) were measured in the temperature range from 50 to 270 K with a SXP 4/100 Bruker pulse spectrometer at 55.2 MHz. It was found that the T1 temperature dependence has three minima. The individual relaxation rates of the three-proton groups can be described by the O'Reilly and Tsang formula. The results obtained from the fitting procedure, using the typical Woessner formula for complex compounds, allow to conclude that the low-temperature minimum is due to the relaxation of all CH3 groups and the other two minima are due to the relaxation of two and four NH3 groups, respectively. This assignment is based on the X-ray results showing that methylammonium cations are differently bonded in this crystal. PMID:7827971

Medycki, W; Pi?lewski, N; Jakubas, R

1993-09-01

297

Phase transitions in layer structured (C10H21NH3)2SnCl6  

NASA Astrophysics Data System (ADS)

Phase transitions in the quasi-two-dimensional layer structured (C10H21NH3)2SnCl6, an order-disorder transition and a conformational transition of the hydrocarbon chains, were studied by means of 1H NMR (nuclear magnetic resonance). A newly defined order parameter in the low-temperature phase, the dipolar splitting of the rigid hydrocarbon lineshape component, was shown to represent the order-disorder motion of the hydrocarbon chains, explicitly revealing its three-dimensionality. The conformational transition was marked by a discontinuity in the spin-lattice relaxation rate (1/T1). On the other hand, no obvious anomaly was observed in the spin-lattice relaxation rate at the order-disorder transition at 200 MHz, whereas a weak anomaly was observed at 45 MHz, indicating that the critical dynamics associated with the order-disorder transition is manifest in the low-frequency region of the spectral density.

Lee, K. W.; Park, M. W.; Rhee, C.; Lee, Cheol Eui; Kang, J. K.; Kim, K.-W.; Lee, K.-S.

1998-02-01

298

Intestinal lumen and mucosal microclimate H+ and NH3 concentrations as factors in the etiology of experimental amebiasis.  

PubMed

Axenically cultivated Entamoeba histolytica, trophozoites, strains HM-1:IMSS and HM-38, were suspended in solutions of NaCl, 330 mOsm, of varying pH and ammonium concentrations. Short-term viability was inversely proportional to the ammonia concentration of the medium and was independent of the ammonium concentration and pH. The NH3-induced ameba killing was associated with a cellular alkalosis and cell swelling. While short-term trophozoite viability was unaffected by changes in the medium pH over the range 5.5-8.0, long-term viability was reduced by high pH, and of three pH values tested (6.27, 7.27, and 8.27), trophozoite growth was greatest at the lower value. Chemotaxis was observed in media over the pH range 5.5-8.0, and attenuated chemotaxis was observed in trophozoites in media containing NH3 (0.1 mM). The cecal content total ammonia concentration and pH and the in vivo mucosal microclimate pH were measured in young adult male rats, hamsters, and gerbils. Ceca of the three rodent species were also inoculated with HM-38 trophozoites and 7 days later the cecal contents were studied for signs of amebic infection. Infections were absent in the rat, the species with highest luminal total ammonia concentration and mucosal microclimate pH. All gerbils were infected. This species had the lowest mucosal microclimate pH. The hamster, with the intermediate microclimate pH, had a low infection rate (1 of 5). It is proposed that when ammonium diffuses from the large intestinal lumen into a more basic mucosal microclimate, it is converted to ammonia, and the combination of this ammonia and the high microclimate pH threatens Entamoeba trophozoite viability and reduces the probability of a given ameba penetrating the mucus blanket and invading the mucosal epithelium. PMID:2908580

Leitch, G J

1988-05-01

299

Thermal desorption of C6H6 from surfaces of astrophysical relevance.  

PubMed

The thermal desorption of C(6)H(6) from two astrophysically relevant surfaces has been studied using temperature programmed desorption. Desorption from an amorphous SiO(2) substrate was used as a mimic for bare interstellar grains, while multilayer films of amorphous solid water (ASW) were used to study the adsorption of C(6)H(6) on grains surrounded by H(2)O dominated icy mantles. Kinetic parameters were obtained through a combination of kinetic modeling, leading edge analysis, and by considering a distribution of binding sites on the substrate. The latter is shown to have a significant impact on the desorption of small exposures of C(6)H(6) from the amorphous SiO(2) substrate. In the case of adsorption on ASW, dewetting behavior and fractional order desorption at low coverage strongly suggest the formation of islands of C(6)H(6) on the H(2)O surface. The astrophysical implications of these observations are briefly outlined. PMID:20059103

Thrower, J D; Collings, M P; Rutten, F J M; McCoustra, M R S

2009-12-28

300

Thermal desorption of C6H6 from surfaces of astrophysical relevance  

NASA Astrophysics Data System (ADS)

The thermal desorption of C6H6 from two astrophysically relevant surfaces has been studied using temperature programmed desorption. Desorption from an amorphous SiO2 substrate was used as a mimic for bare interstellar grains, while multilayer films of amorphous solid water (ASW) were used to study the adsorption of C6H6 on grains surrounded by H2O dominated icy mantles. Kinetic parameters were obtained through a combination of kinetic modeling, leading edge analysis, and by considering a distribution of binding sites on the substrate. The latter is shown to have a significant impact on the desorption of small exposures of C6H6 from the amorphous SiO2 substrate. In the case of adsorption on ASW, dewetting behavior and fractional order desorption at low coverage strongly suggest the formation of islands of C6H6 on the H2O surface. The astrophysical implications of these observations are briefly outlined.

Thrower, J. D.; Collings, M. P.; Rutten, F. J. M.; McCoustra, M. R. S.

2009-12-01

301

Geometric Structure and Desorption Kinetics of CO on Cr2O3(0001)/Cr(110)  

NASA Astrophysics Data System (ADS)

The Cr(110) surface is unique in that its native oxide grows epitaxially. Since understanding the adsorption and desorption kinetics of simple molecules on transition metal oxides is important for understanding catalytic phenomena, we have studied the adsorption geometry and desorption kinetics of CO on the epitaxial Cr2O3(0001) surface. The adsorption of CO was performed at 120 K and produced a weak (3 x 3) R 30^o reconstruction, as monitored by low energy electron diffraction (LEED). To determine the activation energy and desorption kinetics, temperature programmed desorption (TPD) measurements have been performed at heating rates of 5, 10, 25, and 50 ^oC/min. The results of the TPD measurements indicate that the desorption is approximately 1^st order and has an activation energy of 0.52 eV/molecule (50 kJ/mol).

Arellano, Gabriel; Redding, Sy; Walters, Jennifer; Clark, Nicholas; Rieman, Simona; Geisler, Heike; Ventrice, Carl

2009-10-01

302

Field desorption of lithium fluoride  

SciTech Connect

Layers of lithium fluoride (LiF), [similar to]10 nm thick, were field desorbed from iridium substrates at temperatures between 25 and 600 [degree]C. The electric field was increased until desorption of the salt layer occurred. Combined mass spectroscopy and field desorption microscopy characterized the desorption process. During desorption, ions of the form (LiF)[sub [ital n

Stintz, A.; Panitz, J.A. (Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131 (United States))

1995-03-01

303

Low Dislocation Densities of Nitride-Based Light-Emitting Diodes with a Preflow of NH3 Source before Growth of AlN Buffer Layer  

NASA Astrophysics Data System (ADS)

In this study, the AlN buffer layer grown on c-plane sapphire (Al2O3) substrates by metal--organic chemical vapor deposition (MOCVD) was controlled by a preflow of the NH3 source. With the treatment of NH3 preflow, the monolayer of AlN was formed on the surface of a sapphire substrate by the decomposition of the NH3 source and Al2O3 substrate. It was found that the density of threading dislocations significantly decreased owing to the abatement of lattice mismatch between a GaN layer and a sapphire substrate. At an injection current of 350 mA, the light output intensity of the light-emitting diode (LED) with NH3 preflow was increased by 14.1% compared with that of a conventional LED. On the other hand, LEDs with NH3 preflow treatment could endure electrostatic discharge (ESD) surges up to -3000 V and caused a low rate of light output degradation at a high ambient temperature.

Wang, Chun-Kai; Chiou, Yu-Zung; Sun, De-Jun; Chiang, Tsung-Hsun

2013-01-01

304

Theoretical study of the hydrogen release mechanism from a lithium derivative of ammonia borane, LiNH2BH3-NH3BH3  

NASA Astrophysics Data System (ADS)

Ammonia borane and lithium amidoborane proved to have potential as efficient hydrogen storage materials. Although a combination of both compounds, LiNH2BH3-NH3BH3 has been shown to have even better hydrogen release characteristics, the inherent process was not clear. We determined the reaction mechanism of H2 release from LiNH2BH3-NH3BH3 using computational quantum chemistry methods (MP2 and CCSD(T) methods and aug-cc-pVnZ basis sets). The energy barrier for H2 release becomes lower than in pure LiNH2BH3 or NH3BH3 in agreement with experiment. Relevant transition structures are analyzed in detail and the initial formation of a cyclic adduct is likely responsible for the strong reduction of energy barriers.

Swinnen, Saartje; Nguyen, Vinh Son; Nguyen, Minh Tho

2011-11-01

305

Synthesis of New Crystalline Pu(V) Compounds from Solutions: II. Double Pu(V) Oxalates with Co(NH 3 ) 6 3+ Ions in the Outer Sphere  

Microsoft Academic Search

Crystalline compounds of the general composition Co(NH3)6PuO2(C2O4)2nH2O (n = 2, 3, 5) were isolated from freshly prepared neutral oxalate solutions of Pu(V) by addition of Co(NH3)6\\u000a \\u0009\\u0009\\u0009\\u0009\\u0009\\u0009\\u0009\\u00093+ ions. These compounds are fairly stable in storage in air and poorly soluble in water. Previously unknown double Np(V) oxalates\\u000a Co(NH3)6NpO2(C2O4)nH2O (n = 2, 5) were also synthesized and studied. All the compounds

N. N. Krot; A. A. Bessonov; M. S. Grigor’ev; I. A. Charushnikova; V. I. Makarenkov

2005-01-01

306

Effects of loading different metal ions on an activated carbon on the desorption activation energy of dichloromethane\\/trichloromethane  

Microsoft Academic Search

The effects of loading Fe3+, Mg2+, Cu2+ or Ag+ on activated carbons (ACs) on interaction of the carbon surfaces with dichloromethane (DCM) and trichloromethane (TCM) were investigated. Temperature-programmed desorption (TPD) experiments were conducted to measure the desorption activation energy of DCM\\/TCM on the ACs separately doped with ions Fe3+, Mg2+, Cu2+ and Ag+. The absolute hardness and electronegativity of DCM

Qibin Xia; Zhong Li; Limin Xiao; Zhijuan Zhang; Hongxia Xi

2010-01-01

307

Kinetics of hydrogen adsorption and desorption on Si(100) surfaces  

NASA Astrophysics Data System (ADS)

The kinetics of molecular hydrogen reactions at the Si (100) surface has been studied by simulation to extract the physics underlying two unexpected experimental observations: apparently first-order desorption kinetics and an increase in sticking probability with hydrogen coverage. At a partially H-terminated Si(100) surface, each Si dimer assumes an unoccupied dimer (UOD), singly occupied dimer (SOD), or doubly occupied dimer (DOD) structure. In our hydrogen reaction model based on an inter-dimer mechanism, a site consisting of an adjacent pair of a DOD and a UOD (DOD/UOD) is a key component for the desorption and adsorption kinetics of hydrogen at the Si(100) surface. To simulate reaction kinetics of both reactions, DU (D: DOD, U: UOD) and SS (S: SOD) pathways are proposed: DU pathway claims that the adsorption as well as desorption of hydrogen takes place at common sites having a cis-configured SOD/SOD pair that is transformed transiently from a DOD/UOD pair by H(D) diffusion. Thus the adsorption obeys the so-called 4H mechanism, but the desorption obeys the 2H mechanism. SS pathway claims that the adsorption occurs at sites having a UOD/UOD pair, and the desorption occurs at sites having a cis-configured SOD/SOD pair that is generated by diffusion of isolated SODs. To simulate temperature-programmed-desorption spectra and sticking probability vs coverage curves, thermo-statistics for a lattice-gas system characterized with parameters for hydrogen pairing and dimer clustering is used to evaluate equilibrium populations of DOD/UOD pairs and isolated SODs. The model simulation based on the above reaction model successfully reproduces all of the complicated, coverage dependent adsorption and desorption reactions of hydrogen at Si(100) surfaces. Specifically, at high coverage above 0.1 ML majority of the adsorption and desorption proceed along the DU pathway. Hence, it is suggested that the adsorption and desorption in the high coverage regime are not microscopically reversible. On the other hand, at low coverages below 0.1 ML, the simulation shows up that the majority of adsorption proceeds along the SS pathway, and the desorption by the DU pathway. Since both reactions obey the 2H mechanism, it is suggested that the desorption and adsorption in the low coverage regime are microscopically reversible.

Narita, Yuzuru; Inanaga, Shoji; Namiki, Akira

2013-06-01

308

Improved Determination of the 10-00 Rotational Frequency of NH3D+ from the High-resolution Spectrum of the ?4 Infrared Band  

NASA Astrophysics Data System (ADS)

The high-resolution spectrum of the ?4 band of NH3D+ has been measured by difference frequency IR laser spectroscopy in a multipass hollow cathode discharge cell. From the set of molecular constants obtained from the analysis of the spectrum, a value of 262817 ± 6 MHz (±3?) has been derived for the frequency of the 10-00 rotational transition. This value supports the assignment to NH3D+ of lines at 262816.7 MHz recorded in radio astronomy observations in Orion-IRc2 and the cold prestellar core B1-bS.

Doménech, J. L.; Cueto, M.; Herrero, V. J.; Tanarro, I.; Tercero, B.; Fuente, A.; Cernicharo, J.

2013-07-01

309

Decomposition pathways for the photoactivated anticancer complex cis,trans,cis-[Pt(N3)2(OH)2(NH3)2]: insights from DFT calculations.  

PubMed

Density functional theory (DFT) and time-dependent DFT (TD-DFT) provide new insights into the photodegradation pathways of the cytotoxic complex cis,trans,cis-[Pt(N(3))(2)(OH)(2)(NH(3))(2)] allowing assignment of (1)LMCT transitions in the visible region of the UV-Vis spectrum; upon excitation to these low-energy (1)LMCT states, release of one N(3)(-) ligand is facilitated, and on triplet formation, the dissociation of both NH(3) and N(3)(-) groups trans to each other is promoted with no apparent reduction of the Pt(IV) centre. PMID:19890514

Salassa, Luca; Phillips, Hazel I A; Sadler, Peter J

2009-09-23

310

Metal solid solutions obtained by thermolysis of Pt and Re salts. Crystal structure of [Pt(NH 3 ) 4 ](ReO 4 ) 2  

Microsoft Academic Search

A complex salt of tetraammineplatinum(II) perrhenate [Pt(NH3)4](ReO4)2 has been synthesized. Crystal data: a = 5.1847(6) ?, b = 7.7397(8) ?, c = 7.9540(9) ?, ? = 69.531(3), ? = 79.656(3), ? = 77.649(3), V = 290,19(6) ?3, space group \\u000a $$P\\\\bar 1$$\\u000a , Z = 1, d\\u000a \\u000a x\\u000a = 4.370 g\\/cm3. The products of decomposition of [Pt(NH3)4](ReO4)2 in a hydrogen atmosphere

I. V. Korolkov; A. V. Zadesenets; S. A. Gromilov; K. V. Yusenko; I. A. Baidina; S. V. Korenev

2006-01-01

311

Preparation of UH3 by the reaction of U with NH3 or with a mixture of H2 and N2  

NASA Astrophysics Data System (ADS)

To examine how a high nitrogen activity and high hydrogen activity can be obtained by keeping the extent of dissociation of NH3 below its dissociation equilibrium, reactions of U with static NH3 were carried out at 250 C. The formation of N-rich U2N(3+x) and that of UH3 are discussed from a thermodynamic point of view. The experimental results suggest, however, that the formation of UH3 must be ascribed to a much lower activation energy for its formation.

Hirota, Masayuki; Katsura, Masahiro; Takahashi, Hiroyuki; Miyake, Masanobu

1994-10-01

312

Pyroelectric and Dilatometric Studies on the Low Temperature Ferroelectric Phase Transition of (CH3NH3)5Bi2Br11  

NASA Astrophysics Data System (ADS)

The results of the linear thermal expansion studies on (CH3NH3)5Bi2Br11 single crystals in the temperature range 60-340 K are presented. The thermal anomaly in the vicinity of 77 K is assigned to the phase transition classified as close to first order type. The pyroelectric measurements of (CH3NH3)5Bi2Br11 were carried out in the range of 45-320 K along the a- and c-axis. The step-like change in the spontaneous polarization along the a-axis at 77 K indicates a discontinuous character of ferroelectric transition.

Dziedzic, J.; Mróz, J.; Jakubas, R.

2006-09-01

313

The relationship between NH3 emissions from a poultry farm and soil NO and N2O fluxes from a downwind forest  

NASA Astrophysics Data System (ADS)

Intensive livestock farms emit large concentrations of NH3, most of which is deposited very close to the source. The presence of trees enhances the deposition. Rates to downwind forests can exceed 40 kg N ha-1 y-1. The steep gradient in large NH3 concentrations of 34.3±20.4, 47.6±24.9, 21.7±16.8 µg NH3 m3 at the edge of a forest 15, 30 and 45 m downwind of the farm to near background concentrations within 270 m downwind (1.15±0.7 µg NH3 m3) provides an ideal site to study the effect of different rates of atmospheric NH3 concentrations and inferred deposition on biological and chemical processes under similar environmental conditions. We have investigated the effect of different NH3 concentrations and implied deposition rates on the flux of NO and N2O from soil in a mixed woodland downwind of a large poultry farm (160 000 birds) in Scotland, which has been operating for about 40 years. Measurements were carried out for a 6 month period, with hourly NO flux measurements, daily N2O fluxes close to the farm and monthly at all sites, and monthly cumulative wet and dry N deposition. The increased NH3 and NH4+ deposition to the woodland increased emissions of NO and N2O and soil available NH4+ and NO3- concentrations. Average NO and N2O fluxes measured 15, 25 and 45 m downwind of the farm were 111.2±41.1, 123.3±40.7, 38.3±28.8 µg NO-N m-2 h-1 and 9.9±7.5, 34.3±33.3 and 21.2±6.1 µg N2O-N m-2 h-1, respectively. At the background site 270 m downwind the N2O flux was reduced to 1.75±2.1 µg N2O-N m-2 h-1. NO emissions were significantly influenced by seasonal and daily changes in soil temperature and followed a diurnal pattern with maximum emissions approximately 3 h after noon. For N2O no consistent diurnal pattern was observed. Changes in soil moisture content had a less clear effect on the NO and N2O flux. In spite of the large NO and N2O emissions accounting for >3% of the N deposited to the woodland downwind of the farm, extrapolation to the entire British poultry flock suggests that these NH3 emissions contribute to less than 0.5% and 0.02%, respectively of the total annual UK NOx and N2O emissions.

Skiba, U.; Dick, J.; Storeton-West, R.; Lopez-Fernandez, S.; Woods, C.; Tang, S.; Vandijk, N.

2006-08-01

314

NH3 Survey of the Vela-C and Vela-D Dust Cores Selected by BLAST  

NASA Astrophysics Data System (ADS)

The Balloon-borne Large Aperture Submillimeter Telescope (BLAST; Pascale et al. 2008) is the closest precursor of the Herschel Space Observatory. During its second Long Duration Ballon flight in 2006, BLAST mapped about 50 square degrees in the Vela Molecular Ridge (VMR) at a sensitivity of <~1 solar mass. The continuum observations were carried out simultaneously at 250, 350, and 500 micron, i.e., at the peak (or very near it) of the cold cores SED. Thus the VMR cores found by BLAST represent an excellent sample of dense cores in which to study the initial conditions for star formation and the earliest phases of core evolution. The combination of (sub)mm and molecular line observations is a powerful method to determine the dynamical state of starless cores detected at submm wavelengths. Therefore, we propose coordinated observations of NH3(1,1) and (2,2), with the Parkes telescope, and of various molecular tracers with the Mopra telescope, of this sample.

Olmi, Luca; Burton, Michael; Giannini, Teresa; Lorenzetti, Dario; Massi, Fabrizio; Elia, Davide; de Luca, Massimo

2009-04-01

315

Effect of hyperfine interactions on ultracold molecular collisions: NH(3?-) with Mg(1S) in magnetic fields  

NASA Astrophysics Data System (ADS)

We investigate the effect of hyperfine interactions on ultracold molecular collisions in magnetic fields, using 24Mg(1S)+14NH(3?-) as a prototype system. We explore the energy and magnetic-field dependence of the cross sections, comparing the results with previous calculations that neglected hyperfine interactions [A.O.G. Wallis and J. M. Hutson, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.183201 103, 183201 (2009)]. The main effect of hyperfine interactions for spin relaxation cross sections is that the kinetic energy release of the dominant outgoing channels does not reduce to zero at low fields. This results in reduced centrifugal suppression of the cross sections and increased inelastic cross sections at low energy and low field. We also analyze state-to-state cross sections, for various initial states, and show that hyperfine interactions introduce additional mechanisms for spin relaxation. In particular, there are hyperfine-mediated collisions to outgoing channels that are not centrifugally suppressed. However, for Mg+NH these unsuppressed channels make only small contributions to the total cross sections. We consider the implications of our results for sympathetic cooling of NH by Mg and conclude that the ratio of elastic to inelastic cross sections remains high enough for sympathetic cooling to proceed.

González-Martínez, Maykel L.; Hutson, Jeremy M.

2011-11-01

316

Organic chemistry of NH3 and HCN induced by an atmospheric abnormal glow discharge in N2-CH4 mixtures  

NASA Astrophysics Data System (ADS)

The formation of the chemical products produced in an atmospheric glow discharge fed by a N2-CH4 gas mixture has been studied using Fourier Transform InfraRed (FTIR) and Optical Emission Spectrometry (OES). The measurements were carried out in a flowing regime at ambient temperature and pressure with CH4 concentrations ranging from 0.5% to 2%. In the recorded emission spectra the lines of the second positive system CN system and the first negative system of N2 were found to be the most intensive but atomic H?, H?, and C (247 nm) lines were also observed. FTIR-measurements revealed HCN and NH3 to be the major products of the plasma with traces of C2H2. These same molecules have been detected in Titan's atmosphere and the present experiments may provide some novel insights into the chemical and physical mechanisms prevalent in Titan's atmosphere with these smaller species believed to be the precursors of heavier organic species in Titan's atmosphere and on its surface.

Horvath, G.; Krcma, F.; Polachova, L.; Klohnova, K.; Mason, N. J.; Zahoran, M.; Matejcik, S.

2011-01-01

317

Two mixed-NH3/amine platinum (II) anticancer complexes featuring a dichloroacetate moiety in the leaving group.  

PubMed

Two mixed-NH3/amine platinum (II) complexes of 3-dichoroacetoxylcyclobutane-1, 1-dicarboxylate have been prepared in the present study and characterized by elemental analysis and IR, HPLC-MS and (1)H, (13)C-NMR. The complexes exist in equilibrium between two position isomeric forms and undergo hydrolysis reaction in aqueous solution, releasing the platinum pharmacophores and dichloroacetate which is a small-molecular cell apoptosis inducer. Both complexes were evaluated for in vitro cytotoxic profile in A549, SGC-7901 and SK-OV-3 caner cells as well as in BEAS-2B normal cells. They exhibit markedly cytoxicity toward cancer cells by selectively inducing the apoptosis of cancer cells, whereas leaving normal cells less affected. They have also the ability to overcome the resistance of SK-OV-3 cancer cells to cisplatin. Our findings offer an alternative novel way to develop platinum drugs which can both overcome the drug resistance and selectively target tumor cells. PMID:23955304

Liu, Weiping; Su, Jia; Jiang, Jing; Li, Xingyao; Ye, Qingsong; Zhou, Hongyu; Chen, Jialin; Li, Yan

2013-08-19

318

Monte Carlo study of a compressible pseudospin model for (CH3NH3)5Bi2Cl11  

NASA Astrophysics Data System (ADS)

A two-sublattice peudospin model with distance-dependent interaction parameters is constructed for the ferroelectric phase transition at 307 K and for the isomorphous anomaly at 180 K in pentakis (methylammonium) undecachlorodibismuthate (III) (CH3NH3)5Bi2Cl11. A series of Monte Carlo simulations involving continuous degrees of freedom of deformation is performed for the model. The critical temperatures turn out about 23% lower than those resulting from the mean-field treatment for the three-dimensional fcc lattice in the absence of coupling with strain. An upward shift in the critical temperature then is found due to the coupling with the strain. The multiple histogram method is used to obtain the theoretical predictions for the temperature dependence of the spontaneous polarization, dielectric susceptibility, and specific heat. The existence of a narrow peak in the specific heat and the ratio of the Curie constants close to 4 are confirmed. Evidence is given of the usefulness of the Monte Carlo method with fairly small simulation boxes for the studies of isomorphous anomalies.

Kuchta, B.; Carpentier, P.; Jakubas, R.; ZajaÇ, W.; Zieli?ski, P.

2001-06-01

319

GaN materials growth by MOVPE in a new-design reactor using DMHy and NH3  

NASA Astrophysics Data System (ADS)

Thin films of GaN were grown on template substrates of 4-?m-thick GaN layers on sapphire substrates by low-pressure metal organic vapour-phase epitaxy (LP-MOVPE) in a new-design reactor with the shape T. Wide range of growth temperature from 520 to 1100 °C was explored. At low temperature growth between 550 and 690 °C, dimethylhydrazine (DMHy) was used as source of atomic nitrogen while ammonia (NH3) was used at high temperature growth (1000 1100 °C). At low temperature micro-Raman spectroscopy revealed a significant relaxation of the selection rules for the scattering by the optical phonons in the films grown at lower temperatures. Variation of the intensity ratio for E2H and E1 phonon modes has been attributed to changes in the structural quality of the films grown at different temperatures. At high temperature, the quality of GaN layers were comparable to that of the substrate before growth.

Gautier, S.; Sartel, C.; Ould-Saad, S.; Martin, J.; Sirenko, A.; Ougazzaden, A.

2007-01-01

320

Double proton transfers in complexes of formic acid with CH 4, NH 3, H 2O, HF and H 2  

NASA Astrophysics Data System (ADS)

Double proton migrations in complexes of formic acid with CH 4, NH 3, H 2O, HF and H 2 have been studied in the gas phase by ab initio (RHF/6-31G ?? and MP2/6-31G ??) calculations. The calculations show that the molecules HY, where H = CH 3, NH 2, OH, F and H, promote double proton migration in the complexes. The energy barriers calculated by the RHF/6-31G ?? (MP2/6-31G ??) method for these reactions are 74.0 (54.7), 19.9 (11.8), 26.4 (14.4), 20.2 (10.6) and 58.3 (46.0) kcal/mol, respectively. The height of the energy barrier of this reaction depends on the proximity of the two hydrogen bonds to the linear configuration and the bond configuration at Y to the corresponding 'elemental' S E2 transition state structure, as well as on the acidity (energy) of the Y?H bond and the basicity (proton affinity) of Y.

Minyaev, Ruslan M.

1996-11-01

321

Wagging motion of hydrogen-bonded wire in the excited-state multiple proton transfer process of 7-hydroxyquinoline·(NH3)3 cluster  

NASA Astrophysics Data System (ADS)

In this work, the dynamics of hydrogen bonds (as well as the hydrogen-bonded wire) in excited-state tautomerization of 7-hydroxyquinoline·(NH3)3 (7HQ?(NH3)3) cluster has been investigated by using time-dependent density functional theory (TDDFT). It shows that upon an excitation, the hydrogen bond between -OH group in 7-hydroxyquinoline (7HQ) and NH3 moiety would extremely strengthened in S1 state, which could effectively facilitate the releasing of the proton from the phenolic group of 7HQ moiety to the hydrogen-bonded wire and the forming an Eigen-like cationic wire (NH⋯NH4+⋯NH) in the cluster. To fulfill the different optimal angles of NH4+ in the wire, a wagging motion of hydrogen-bonded wire would occur in excited state. Moreover, the wagging motion of the hydrogen-bonded wire would effectively promote excited-state proton transfer reaction. As the results, an excited-state multiple proton transfer (ESMPT) mechanism containing two concerted and asymmetrical processes has been proposed for the proton transfer dynamics of 7HQ?(NH3)3 cluster.

Liu, Yu-Hui; Lan, Sheng-Cheng; Li, Chun-Ran

2013-08-01

322

Nitriding of Titanium and Its Alloys by N2, NH3 or Mixtures of N2 + H2 in a DC Arc Plasma at Low Pressures.  

National Technical Information Service (NTIS)

The dc glow discharges in different gas mixtures of Ar + N2, Ar + NH3 or Ar + N2 + H2 result in the surface nitriding of Ti metal and its alloy (Ti6Al4V). Various gas mixtures were used in order to establish the main active species governing the nitriding...

R. Avni

1984-01-01

323

Synthesis, structure, and photovoltaic property of a nanocrystalline 2H perovskite-type novel sensitizer (CH3CH2NH3)PbI3.  

PubMed

A new nanocrystalline sensitizer with the chemical formula (CH3CH2NH3)PbI3 is synthesized by reacting ethylammonium iodide with lead iodide, and its crystal structure and photovoltaic property are investigated. X-ray diffraction analysis confirms orthorhombic crystal phase with a?=?8.7419(2) Å, b?=?8.14745(10) Å, and c?=?30.3096(6) Å, which can be described as 2?H perovskite structure. Ultraviolet photoelectron spectroscopy and UV-visible spectroscopy determine the valence band position at 5.6?eV versus vacuum and the optical bandgap of ca. 2.2?eV. A spin coating of the CH3CH2NH3I and PbI2 mixed solution on a TiO2 film yields ca. 1.8-nm-diameter (CH3CH2NH3)PbI3 dots on the TiO2 surface. The (CH3CH2NH3)PbI3-sensitized solar cell with iodide-based redox electrolyte demonstrates the conversion efficiency of 2.4% under AM 1.5?G one sun (100?mW/cm2) illumination. PMID:22738298

Im, Jeong-Hyeok; Chung, Jaehoon; Kim, Seung-Joo; Park, Nam-Gyu

2012-06-28

324

SURFATM-NH3: a model combining the surface energy balance and bi-directional exchanges of ammonia applied at the field scale  

NASA Astrophysics Data System (ADS)

A new biophysical model SURFATM-NH3, simulating the ammonia (NH3) exchange between terrestrial ecosystems and the atmosphere is presented. SURFATM-NH3 consists of two coupled models: (i) an energy budget model and (ii) a pollutant exchange model, which distinguish the soil and plant exchange processes. The model describes the exchanges in terms of adsorption to leaf cuticles and bi-directional transport through leaf stomata and soil. The results of the model are compared with the flux measurements over grassland during the GRAMINAE Integrated Experiment at Braunschweig, Germany. The dataset of GRAMINAE allows the model to be tested in various climatic and agronomic conditions: prior to cutting, after cutting and then after the application of mineral fertilizer. The whole comparison shows close agreement between model and measurements for energy budget and ammonia fluxes. The major controls on the soil and plant emission potential are the physicochemical parameters for liquid-gas exchanges which are integrated in the compensation points for live leaves, litter and the soil surface. Modelled fluxes are highly sensitive to soil and plant surface temperatures, highlighting the importance of accurate estimates of these terms. The model suggests that the net flux depends not only on the foliar (stomatal) compensation point but also that of leaf litter. SURFATM-NH3 represents a comprehensive approach to studying pollutant exchanges and its link with plant and soil functioning. It also provides a simplified generalised approach (SVAT model) applicable for atmospheric transport models.

Personne, E.; Loubet, B.; Herrmann, B.; Mattsson, M.; Schjoerring, J. K.; Nemitz, E.; Sutton, M. A.; Cellier, P.

2009-01-01

325

SURFATM-NH3: a model combining the surface energy balance and bi-directional exchanges of ammonia applied at the field scale  

NASA Astrophysics Data System (ADS)

A new biophysical model SURFATM-NH3, simulating the ammonia (NH3) exchange between terrestrial ecosystems and the atmosphere is presented. SURFATM-NH3 consists of two coupled models: (i) an energy budget model and (ii) a pollutant exchange model, which distinguish the soil and plant exchange processes. The model describes the exchanges in terms of adsorption to leaf cuticles and bi-directional transport through leaf stomata and soil. The results of the model are compared with the flux measurements over grassland during the GRAMINAE Integrated Experiment at Braunschweig, Germany. The dataset of GRAMINAE allows the model to be tested in various meteorological and agronomic conditions: prior to cutting, after cutting and then after the application of mineral fertilizer. The whole comparison shows close agreement between model and measurements for energy budget and ammonia fluxes. The major controls on the ground and plant emission potential are the physicochemical parameters for liquid-gas exchanges which are integrated in the compensation points for live leaves, litter and the soil surface. Modelled fluxes are highly sensitive to soil and plant surface temperatures, highlighting the importance of accurate estimates of these terms. The model suggests that the net flux depends not only on the foliar (stomatal) compensation point but also that of leaf litter. SURFATM-NH3 represents a comprehensive approach to studying pollutant exchanges and its link with plant and soil functioning. It also provides a simplified generalised approach (SVAT model) applicable for atmospheric transport models.

Personne, E.; Loubet, B.; Herrmann, B.; Mattsson, M.; Schjoerring, J. K.; Nemitz, E.; Sutton, M. A.; Cellier, P.

2009-08-01

326

A study of the OMVPE growth mechanisms using internal reflectance spectroscopy to examine adsorption of TMGa and NH3 and surface reactions between them  

NASA Astrophysics Data System (ADS)

Internal reflection spectroscopy spectra show that NH3 and ND3 chemisorb onto (100) and (111)A GaAs surfaces. Adsorption occurs by the formation of Ga—N bonds via Lewis acid-base reactions which are identified by an absorption band between 1325 and 1100 cm-1 with peaks near 1285, 1220 and 1150 cm-1. No NH3 absorption bands are detected when the (111)B surface is exposed. TMGa also chemisorbs onto the (100) GaAs surface. The adsorption spectra of NH3 + TMGa is a function of the order in which the reactants are introduced. When NH3 is introduced first, the reactivity is much greater as is evidenced by the almost total elimination of absorption peaks associated with N—H and CH3 peaks which suggests that the reactions are surface catalyzed methane elimination reactions. Implications of the requirement that the hydride be adsorbed and the methyls react with the hydrogen atoms from the hydride to ALE and MOMBE growth are discussed. Also, consistent explanations are presented for why growth on the (111)B surface is difficult, the growth rate is independent of the hydride partial pressure under normal growth conditions, the incorporation of C into GaAs has an orientational dependence, and As is more preferentially incorporated into GaAsP at the lower growth temperatures.

Tripathi, A.; Mazzarese, D.; Conner, W. C.; Jones, K. A.

1989-01-01

327

Origin of the visible-light photoactivity of NH3-treated TiO2: Effect of nitrogen doping and oxygen vacancies  

NASA Astrophysics Data System (ADS)

N-doped and oxygen-deficient TiO2 photocatalysts were obtained by heating commercial TiO2 in NH3 atmosphere, followed by a postcalcination process. Catalysts were characterized by X-ray diffraction (XRD), N2-sorption BET surface area, X-ray photoelectron spectroscopy (XPS), Elemental analysis (EA), UV/vis diffuse reflectance spectroscopy (DRS), Electron spin resonance (ESR) and Photoluminescence (PL). It shows that the NH3-heat-treatment of TiO2 resulted in not only nitrogen doping but also creation of oxygen vacancies with optical absorption in visible-light region. The postcalcination achieved several beneficial effects including dramatic removal of surface amino species, a rapid decrease in surface Ti3+ species, and a low recombination rate of photogenerated carriers on the co-doped TiO2. The photocatalytic measurement was carried out by the degradation of gas-phase benzene under visible light irradiation. At steady state, the photocatalytic conversion rate of benzene over the postannealed catalyst was 35.8%, accompanied by the yield of 115 ppmv CO2, which was much higher than that on the NH3-treated TiO2 before postcalcination or the H2-treated TiO2 catalysts. Results show that the visible-light activity of the NH3-treated TiO2 is attributed to a synergistic effect of substitutional nitrogen species and oxygen vacancies in TiO2.

Chen, Yilin; Cao, Xiaoxin; Lin, Bizhou; Gao, Bifen

2013-01-01

328

Variable mass energy transformation and storage (VMETS) system using NH 3–H 2O as working fluid. Part 2: Modeling and simulation under partial storage strategy  

Microsoft Academic Search

This paper is the second part of our study on a new variable mass energy transformation and storage (VMETS) system using NH3–H2O as working fluid. In the previous study, the working principle and flow of the new system have been introduced, whilst the dynamic models of the new system have been developed and the simulation under the full storage strategy

S. M. Xu; L. Zhang; J. Liang; R. Du

2007-01-01

329

Collector Material Desorption Tests.  

National Technical Information Service (NTIS)

To obtain long cathode lifetimes, the surface of the spent beam collector for the photocathode rf power source (called the Lasertron) must have a low coefficient of desorption of gas molecules by electrons. We assembled a low voltage (less than or equal t...

J. J. Welch C. K. Sinclair

1986-01-01

330

High-performance temperature-programmed microfabricated gas chromatography columns  

Microsoft Academic Search

This paper reports the first development of high-performance, silicon-glass micro-gas chromatography (?GC) columns having integrated heaters and temperature sensors for temperature programming, and integrated pressure sensors for flow control. These 3-m long, 150-?m wide and 250-?m deep columns, integrated on a 3.3 cm square die, were fabricated using a silicon-on-glass dissolved wafer process. Demonstrating the contributions to heat dissipation from

Masoud Agah; Joseph A. Potkay; Gordon Lambertus; Richard Sacks; Kensall D. Wise

2005-01-01

331

CH4/NH3/H2O spark tholin: Chemical analysis and interaction with Jovian aqueous clouds  

NASA Astrophysics Data System (ADS)

The organic solid (tholin) produced by spark discharge in a CH4 + NH3 + H2O atmosphere is investigated, along with the separable components of its water-soluble fraction. The chemistry of this material serves as a provisional model for the interaction of Jovian organic heteropolymers with the deep aqueous clouds of Jupiter. Intact (unhydrolyzed) tholin is resolved into four chemically distinct fractions by high-pressure liquid chromatography (HPLC). Gel filtration chromatography reveals abundant components at molecular weights ?600-700 and 200-300 Da. Gas chromatography/mass spectrometry of derivatized hydrolysis products of unfractionated tholin shows about 10% by mass protein and nonprotein amino acids, chiefly glycine, alanine, aspartic acid, ?-alanine, and ?-aminobutyric acid, and 12% by mass other organic acids and hydroxy acids. The stereospecificity of alanine is investigated and shown to be racemic. The four principal HPLC fractions yield distinctly different proportions of amino acids. Chemical tests show that small peptides or organic molecules containing multiple amino acid precursors are a possibility in the intact tholins, but substantial quantities of large peptides are not indicated. Candidate 700-Da molecules have a central unsaturated, hydrocarbon- and nitrile-rich core, linked by acid-labile (ester or amide) bonds to amino acid and carboxylic acid side groups. The core is probably not HCN ``polymer.'' The concentration of amino acids from tholin hydrolysis in the lower aqueous clouds of Jupiter, about 0.1 ?M, is enough to maintain small populations of terrestrial microorganisms even if the amino acids must serve as the sole carbon source.

McDonald, Gene D.; Khare, Bishun N.; Reid Thompson, W.; Sagan, Carl

1991-12-01

332

Desorption of chlorine organic solvents  

Microsoft Academic Search

Adsorption methods are being used more and more widely to treat gaseous discharges containing chlorohydrocarbons. However, recovery of the chlorohydrocarbons has not been studied sufficiently, and the desorption of the solvents with steam is particularly understudied. We investigated desorption of a number of solvents from industrial active carbon AR-3. Desorption was done with live steam in the 105 to 150°C.

N. I. Petrova; K. M. Nikolaev

1982-01-01

333

Using stable isotopes of reactive N in dry and wet deposition to investigate the source, transport, and fate of NOx and NH3  

NASA Astrophysics Data System (ADS)

Reactive N emissions (NH3 and NOx) can reach the land surfaces via both wet (NH4+, NO3) and dry (NOx, HNO3, NH3, NH4+) depositional processes. Together, these reactive N compounds are important global contributors to air and water quality degradation. Although nitrate concentrations in wet deposition have decreased in the U.S. during the last two decades due to NOx emission regulations set forth by the Clean Air Act, ammonium concentrations in wet deposition have recently increased. In order to further decrease NOx emissions and decrease NH3 emissions, additional tools for reactive N source apportionment are essential. The stable isotopic composition of reactive N may be one such tool for characterizing source, transport, and fate of reactive N emissions. Here, we present results from a comprehensive inventory of the isotopic composition of reactive N emission sources, focusing mainly on agricultural and fossil fuel sources. We build on these inventory results by tracing reactive N emissions across multiple landscapes including: a dairy operation, a conventionally managed cornfield, a tallgrass prairie, and a concentrated animal feeding operation. We then use two examples to illustrate how reactive N isotopes can be used in a regional context. First, we illustrate how passive NH3 samplers deployed at nine U.S. monitoring sites reflect spatial variations in predominant NH3 sources. Secondly, we reconstruct the regional influence of agricultural NOx emissions to nitrate deposition recorded in an ice core from Summit, Greenland. These results reveal significant evidence that the trend in the N isotopic composition of 20th century nitrate deposition in Greenland was driven by increasing biogenic soil NOx emissions induced by fertilizer application in the US over the last century. Together, these studies demonstrate the isotopic composition of reactive N emissions can be an additional tool for investigators to source and trace reactive N emissions in both historical and modern contexts and across spatial scales.

Felix, J.; Elliott, E. M.

2011-12-01

334

Characteristics of SiO x N y films deposited by inductively coupled plasma enhanced chemical vapor deposition using HMDS\\/NH 3\\/O 2\\/Ar for water vapor diffusion barrier  

Microsoft Academic Search

SiOxNy thin films were deposited by inductively coupled plasma enhanced chemical vapor deposition (ICP-PECVD) using hexamethyldisilazane (HMDS, 99.9%)\\/NH3\\/O2\\/Ar at a low temperature, and examined for use as a water vapor diffusion barrier. The film characteristics were investigated as a function of the O2:NH3 ratio. An increase in the O2:NH3 ratio decreased the level of impurities such as –CHx, N–H in

J. H. Lee; C. H. Jeong; H. B. Kim; J. T. Lim; S. J. Kyung; G. Y. Yeom

2006-01-01

335

Influence of ceria modification on the properties of TiO2-ZrO2 supported V2O5 catalysts for selective catalytic reduction of NO by NH3.  

PubMed

TiO(2)-ZrO(2) (hereafter denoted as Ti-Zr) supported V(2)O(5) catalysts with different loadings of CeO(2) were synthesized, and their physicochemical properties were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), in situ Fourier transform infrared spectroscopy (in situ FT-IR) and temperature-programmed reduction (TPR). Their catalytic activities toward the NO(x) reduction reaction with NH(3) were tested. We found that with the addition of CeO(2), more NO was removed in a wide temperature range of 220-500 °C. As the CeO(2) content was increased from 10% to 20% (i.e., the molar ratio of Ce to Ti-Zr), NO conversion increased significantly; after that, increasing CeO(2) content, however, decreased NO conversion. In particular, the addition of CeO(2) to V(2)O(5)/Ti-Zr suppressed the coke deposition and rendered a stable and high catalytic activity. The characterization results indicated that: (1) the deposited vanadium and cerium oxides were highly dispersed over the Ti-Zr support, and in addition to ZrV(2)O(7), a common binary compound observed in V(2)O(5)/Ti-Zr, CeVO(4) and Ce(3)ZrO(8) was formed upon increasing CeO(2) content; (2) the introduction of CeO(2) to V(2)O(5)/Ti-Zr sample promoted the redox ability of the resulting catalysts; and (3) the Ce-containing catalysts possessed the greater amount of surface acidic and active intermediate. PMID:22464542

Zhang, Yaping; Zhu, Xiaoqiang; Shen, Kai; Xu, Haitao; Sun, Keqin; Zhou, Changcheng

2012-03-12

336

Thermal Desorption of Galliumchloride Adsorbed on GaAs (100)  

NASA Astrophysics Data System (ADS)

Adsorption and desorption of galliumchloride (GaCl) on GaAs surfaces are investigated to understand the self-limiting process in the chloride atomic layer epitaxy (ALE). Adsorption energy of GaCl on GaAs (100) surfaces is determined by temperature programmed desorption (TPD). As stabilized 2× 4 surfaces and Ga stabilized 4× 6 reconstructed surfaces are exposed to a GaCl molecular beam which is produced by a newly designed GaCl cell. GaCl desorption is observed on both 2× 4 and 4× 6 surfaces, while the desorption of GaClx (x=2, 3), AsClx (x=1˜ 3) and Cl2 are not detected. The adsorption energy of GaCl, Ead, is calculated to be 38 kcal/mol for the 2× 4 surface and 32 kcal/mol for the 4× 6 surface. The adsorbed species in chloride ALE process is also discussed with reference to the surface residence time of GaCl.

Sasaoka, Chiaki; Kato, Yoshitake; Usui, Akira

1991-10-01

337

An analytical potential energy function to model protonated peptide soft-landing experiments. The CH3NH3+/CH4 interactions.  

PubMed

To model soft-landing of peptide ions on surfaces, it is important to have accurate intermolecular potentials between these ions and surfaces. As part of this goal, ab initio calculations at the MP2/aug-cc-pVTZ level of theory, with basis set superposition error (BSSE) corrections, were performed to determine both the long-range attractive and short-range repulsive potentials for CH(4) interacting with the -NH(3)(+) group of CH(3)NH(3)(+). Potential energy curves for four different orientations between CH(4) and CH(3)NH(3)(+) were determined from the calculations to obtain accurate descriptions of the interactions between the atoms of CH(4) and those of -NH(3)(+). A universal analytic function was not found that could accurately represent both the long-range and short-range potentials for collision energies as high as those obtained in surface-induced-dissociation (SID) experiments. Instead, long-range and short-range analytic potentials were developed separately, by simultaneously fitting the four ab initio potential energy curves with a sum of two-body interactions between the atoms of CH(4) and -NH(3)(+), and then connecting these long-range and short-range two-body potentials with switching functions. Following a previous work [J. Am. Chem. Soc., 2002, 124, 1524], these two-body potentials may be used to describe the interactions of the N and H atoms of the -NH(3)(+) group of a protonated peptide ion with the H and C atoms of alkane-type surfaces such as alkyl thiol self-assembled monolayers and H-terminated diamond. Accurate short-range and long-range potentials are imperative to model protonated peptide ion soft-landing experiments. The former controls the collision energy transfer, whereas the latter describes the binding of the ion to the surface. A comparison of the ab initio potential energy curves for CH(3)NH(3)(+)/CH(4) with those for NH(4)(+)/CH(4) shows that they give nearly identical two-body interactions between the atoms of -NH(3)(+) and those of CH(4), showing that the smaller NH(4)(+)/CH(4) system may be used to obtain the two-body potentials. A comparison of the four ab initio potential energy curves reported here for CH(3)NH(3)(+)/CH(4), with those given by the AMBER and CHARMM molecular mechanical potentials, show that these latter potentials "roughly" approximate the long-range attractions, but are grossly in error for the short-range repulsions. The work reported here illustrates that high-level ab initio calculations of intermolecular potentials between small model molecules may be used to develop accurate analytical intermolecular potentials between peptide ions and surfaces. PMID:18665306

Deb, Bipasha; Hu, Wenfang; Song, Kihyung; Hase, William L

2008-06-16

338

Temperature-Programmed Reduction Studies of V-Ag Catalysts  

Microsoft Academic Search

In H2\\/N2atmosphere, the reduction behavior of V-Ag catalysts with V\\/Ag atomic ratios 1\\/0, 9\\/1, 3\\/1, 2.16\\/1, 1.5\\/1, 1\\/1, and 0\\/1 were studied by temperature-programmed reduction (TPR), X-ray diffraction (XRD), and ultraviolet diffuse reflectance spectra (UVDRS). The results showed that the reduction processes of Ag2V4O11, Ag2V4O10.84, and Ag1.2V3O8are all the same while the reduction temperature was raised; they were first reduced

Xin Ge; Hui-liang Zhang

1998-01-01

339

Thermal, dielectric properties and vibrational spectra of [n-C4H9NH3]2[BiBr5] crystal  

NASA Astrophysics Data System (ADS)

[n-C4H9NH3]2[BiBr5] exhibits five solid solid structural phase transitions; at 309 (1st order), 291 (1st), 240 (1st), 219 (close to 2nd) and at 166 K (1st). The phase transitions at 291 and 240 K are accompanied by distinct dielectric anomalies. The dielectric relaxation process was found to appear over the phases (III) and (I). The infrared spectra for [n-C4H9NH3]2[BiBr5] were measured in the region of the internal vibration of the n-butylammonium cation (4000 400 cm-1) between 12 and 320 K. The temperature changes of wavenumbers and of a width for many of the internal modes of the n-butylammonium clearly indicate the contribution of the organic sublattice to the phase transition mechanism.

Tarasiewicz, J.; Jakubas, R.; Baran, J.; Pietraszko, A.

2006-07-01

340

Nanostructured Pt(NH3)4Cl2/SiO2 for nanomedicine: catalytic degradation of DNA in cancer cells  

PubMed Central

In vivo suppression of glioblastoma multiforme (GBM) in Wistar rats using silica-shelled biocatalytic Pt(NH3)4Cl2 nanoparticles is reported. These nanoparticles were synthesized by a sol-gel technique and characterized by SEM and HRTEM imaging. We confirmed morphological uniformity (30 nm) and surface acidity of the nanoparticles, respectively, by TEM imaging and FTIR spectral analysis. Interestingly, treatment of Wistar rats intraperitoneally inoculated with C6 cells using the biocatalysts resulted in considerable tumor shrinkage. Efficiency of the biocatalyst to shrink a tumor is superior to that by the commercial cytotoxic agent cisplatin. The tumor suppression property of Pt(NH3)4Cl2 nanoparticles is attributed to catalytic damage of DNA in C6 cells.

Lopez, Tessy; Islas, Emma Ortiz; Alvarez Lemus, Mayra A.; Gonzalez, Richard Donald

2011-01-01

341

Simultaneous sampling of NH 3, HNO 3, HC1, SO 2 and H 2O 2 in ambient air by a wet annular denuder system  

NASA Astrophysics Data System (ADS)

A new sampling device is described for the simultaneous collection of NH 3, HNO 3, HCl, SO 2 and H 2O 2 in ambient air. The apparatus is based on air sampling by two parallel annular denuder tubes. The gases are collected by absorption in solutions present in the annulus of the denuder tubes. After a sampling time of 30 min at flow rate of 32 ? min -1 the solutions are extracted from the denuders and analyzed off-line. The detection limits of NH 3, HNO 3, HCL and SO 2 are in the order of 0.1-0.5 ?m -3. For H 2O 2 the detection limit is 0.01 ?m -3. The reproducibility is 5-10% at the level of ambient air concentrations. Comparison of this novel technique with existing methods gives satisfactory results. The compact set-up offers the possibility of field experiments without the need of extensive equipment.

Keuken, Menno P.; Schoonebeek, Carlo A. M.; van Wensveen-Louter, Annet; Slanina, Jakob

342

Long-range balanced electron- and hole-transport lengths in organic-inorganic CH3NH3PbI3.  

PubMed

Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron-hole diffusion lengths (typically about 10 nanometers). Recent reports of highly efficient CH3NH3PbI3-based solar cells in a broad range of configurations raise a compelling case for understanding the fundamental photophysical mechanisms in these materials. By applying femtosecond transient optical spectroscopy to bilayers that interface this perovskite with either selective-electron or selective-hole extraction materials, we have uncovered concrete evidence of balanced long-range electron-hole diffusion lengths of at least 100 nanometers in solution-processed CH3NH3PbI3. The high photoconversion efficiencies of these systems stem from the comparable optical absorption length and charge-carrier diffusion lengths, transcending the traditional constraints of solution-processed semiconductors. PMID:24136965

Xing, Guichuan; Mathews, Nripan; Sun, Shuangyong; Lim, Swee Sien; Lam, Yeng Ming; Grätzel, Michael; Mhaisalkar, Subodh; Sum, Tze Chien

2013-10-18

343

Preparation and characterization of a layered perovskite-type organic–inorganic hybrid compound based on (C 6H 4) 2N (CH 2) 6NH 3Cl  

Microsoft Academic Search

The organic–inorganic hybrid compound ((C6H4)2N(CH2)6NH3)2PbCl4 (N6AHMC–PbCl4) and ((C6H4)2N(CH2)6NH3)2PbCl2I2 (N6AHMC–PbCl2I2) were synthesized by treating N-6-aminohexamethylcarbazole chloride (N6AHMC–HCl) with stoichiometric amount of PbX2 (X=Cl, I) at room temperature using dimethylformamide (DMF) as solution. High order diffraction peaks corresponding to (00l) (l=2, 4, 6, …) were observed in the X-ray diffraction profile of N6AHMC–PbCl4 and N6AHMC–PbCl2I2, indicating the formation of hybrid crystal with

Gang Wu; Siyuan Cheng; Meng Deng; Yingying Zheng; Hongzheng Chen; Mang Wang

2009-01-01

344

Enhanced phosphorescence from nanocrystalline/microcrystalline materials based on (CH3NH3)(1-naphthylmethyl ammonium)2Pb2Cl7 and similar compounds  

NASA Astrophysics Data System (ADS)

A broad phosphorescence band, with three main maxima at ca 500, 536 and 577 nm, was observed at room temperature, either from a mixture of (1-naphthylmethyl ammonium)2PbCl4 and CH3NH3PbCl3, or from (CH3NH3)(1-naphthylmethyl ammonium)2Pb2Cl7, or some Cl-Br analogues, in the form of suspensions in toluene or in the form of grinding deposits on quartz plates. It was attributed to supermigration of energy from the Wannier excitons of PbCl3 component to the triplet state of organic component (i.e., 1-naphthylmethyl group) of particulate material. This new effect seems to be a consequence of excitonic superradiance of particulate PbCl3.

Papavassiliou, George C.; Pagona, Georgia; Mousdis, George A.; Karousis, Nikolaos

2013-05-01

345

Classical and quantum molecular dynamics of cation in (CH3NH3)3 Sb2Br9 polycrystal as studied by 1H NMR.  

PubMed

1H spin-lattice relaxation times and second moments were determined for polycrystalline (CH3NH3)3Sb2Br9 sample in a wide range of temperature (5-200 K) at 24.6 and 55.2 MHz. 2H NMR spectra of (CD3NH3)3Sb2Br9 were recorded between 5 K and room temperature. The relaxation time is interpreted as a result of motion of two different non-equivalent types of monomethylammonium cations occurring at the 2:1 proportion in a unit cell. Below 30 K, the relaxation processes via tunneling are suggested to dominate. Above 30 K, only classical behaviour of methylammonium cations is detected. Two monomethylammonium cations relax with the classical correlated C3 reorientation and the rotational tunnelling mechanism, while the third cation exhibits only the classical correlated reorientation. The dynamic parameters of these motions have been determined. PMID:10499659

Medycki, W

1999-09-01

346

Nature of the Low-Temperature Dielectric Anomalies in (CH 3NH 3) 5Bi 2X 11 (X: Cl, Br)  

NASA Astrophysics Data System (ADS)

The low-temperature dielectric anomalies of two isomorphic ferroelectrics (CH3NH3)5Bi2Cl11 (MAPCB) and (CH3NH3)5Bi2Br11 (MAPBB) have been studied in detail. The anomaly in the dielectric constant of MAPBB at 77 K shows a thermal hysteresis along all three crystallographic axes. The broad peak of the dielectric constant along the a-direction of MAPCB around 160 K becomes flatter and more diffuse as pressure increases. It is concluded that the 77 K anomaly in MAPBB represents a first-order phase transition whereas the 160 K anomaly in MAPCB is an over-critical phenomenon of an isomorphous transition.

Gesi, Kazuo; Iwata, Makoto; Ishibashi, Yoshihiro

1996-01-01

347

Enhanced NH3 gas sensing properties of a QCM sensor by increasing the length of vertically orientated ZnO nanorods  

NASA Astrophysics Data System (ADS)

Vertically aligned ZnO nanorods were directly synthesised on a gold electrode of quartz crystal microbalance (QCM) by a simple low-temperature hydrothermal method for a NH3 gas sensing application. The length of vertically aligned ZnO nanorods was increased to purpose enhancement in the gas sensing response of the sensor. The length of ZnO nanorods increased with an increase in growth time. The growth time of ZnO nanorods was systematically varied in the range of 1-4 h to examine the effect of the length of the ZnO nanorods on the gas sensing properties of the fabricated sensors. The gas sensing properties of sensors with different ZnO nanorods lengths was examined at room temperature for various concentrations of NH3 (50-800 ppm) in synthetic air. Enhancement in gas sensing response by increasing the length of ZnO nanorods was observed.

Minh, Vu Anh; Tuan, Le Anh; Huy, Tran Quang; Hung, Vu Ngoc; Quy, Nguyen Van

2013-01-01

348

Evidence for an Instability Near Twice the Fermi Wave Vector in the Low Electronic Density Liquid Metal Li\\\\(NH3\\\\)4  

Microsoft Academic Search

We report high-resolution inelastic x-ray scattering measurements in the metallic liquid Li\\\\(NH3\\\\)4, which to a good approximation can be treated as a dilute alkali metal. We see a well-defined excitation out to large momentum transfers. This excitation shows a strong softening at wave vectors near the first peak in the structure factor, which occurs near twice the Fermi momentum.

C. A. Burns; P. M. Platzman; H. Sinn; A. Alatas; E. E. Alp

2001-01-01

349

Cl-NQR study of the structural order-disorder transition in (CH3NH3)2MnCl4  

Microsoft Academic Search

The temperature dependence of the Cl nuclear quadrupole resonance for the two chemically inequivalent chlorine sites in the perovskitic layer structure compound (CH3NH3)2 MnCl4 has been measured around the second order phase transition at 393.7 K. A value of the critical exponent ? of the order parameter was determined to be ? = 0.250 ± 0.005 which is intermediate between

R. Kind; J. Roos

1976-01-01

350

Ammoxidation of 3-picoline over V 2O 5\\/MgF 2 catalysts: Correlations between nicotinonitrile yield and O 2 and NH 3 chemisorption properties  

Microsoft Academic Search

V2O5\\/MgF2 catalysts with varying vanadia contents (V\\/Mg=0.02–0.13) were prepared by impregnation and tested towards ammoxidation of 3-picoline to nicotinonitrile. The solids were characterised by BET-surface area determination, high temperature oxygen chemisorption and ammonia chemisorption. Both the O2 and NH3 uptakes were found to increase continuously with increase in V\\/Mg molar ratio of the catalysts. The catalytic activity changes in a

V. Narayana Kalevaru; B. David Raju; V. Venkat Rao; A. Martin

2008-01-01

351

Transient-state biodegradation behavior of a horizontal biotrickling filter in co-treating gaseous H2S and NH3.  

PubMed

A horizontal biotrickling filter (HBTF) was used to inoculate autotrophic sulfide-oxidizing and ammonia-oxidizing microbial consortiums over H2S-exhausted carbon for co-treating H2S and NH3 waste gas in a long-term operation. In this study, several aspects (i.e., pH change, shock loading and starvation) of the dynamic behavior of the HBTF were investigated. The metabolic products of N and S bearing species in recycling liquid and biological activities of the biofilm were analyzed to explain the observed phenomena and further explore the fundamentals behind. In the pH range of 4-8.5, although the removal efficiencies of H2S and NH3 remained 96-98% and 100%, respectively, the metabolic products demonstrated different removal mechanisms and pathways. NH4-N and NO2/NO3-N were dominated at pH < or = 6 and > or = 7, respectively, indicating the differentiated contributions from physical/chemical adsorption and bio-oxidation. Moreover, the HBTF demonstrated a good dynamic stability to withstand shock loadings by recovering immediately to the original. During shock loading, only 15.4% and 17.9% of captured H2S and NH3 was biodegraded, respectively. After 2, 11, and 48 days of starvation, the HBTF system reached a full performance within reasonable re-startup times (2-80 h), possibly due to the consumption of reduced S and N species in biomass or activated carbon thus converted into SO4-S and NO3-N during starvation period. The results helped to understand the fundamental knowledge by revealing the effects of pH and transient loadings linked with individual removal mechanism for H2S and NH3 co-treatment in different conditions. PMID:18998123

Jiang, Xia; Yan, Rong; Tay, Joo Hwa

2008-11-08

352

Generation of 16-mum radiation in 14NH3 by two-quantum excitation of the 2nu-2(7,5) state  

Microsoft Academic Search

Stimulated emission at 15.82 and 15.91 mum has been obtained in 14NH3 following two-photon excitation of the 2nu-2(7,5) state. Total output energies on the order of 3 mJ have been observed in a simple experimental arrangement. A discussion of the experimental findings concerning the laser output spectrum, the pressure dependence, the utilization of the optical Stark effect, and the influence

J. Eggleston; J. Dallarosa; W. K. Bischel; J. Boko; F. C. K. Rhodes

1979-01-01

353

Comparative analysis of performance and techno-economics for a H 2O–NH 3–H 2 absorption refrigerator driven by different energy sources  

Microsoft Academic Search

The objectives of the present work are of two-folds. First, it evaluates the transient temperature performance of the H2O–NH3–H2 absorption cooling machine system’s components under two types of energy sources, i.e. the conventional electric energy from grid (electric) and fuel energy from liquid petroleum gas (LPG). Results obtained have shown that performance of various components under different type of energy

Mohammad Omar Abdullah; Tang Chung Hieng

2010-01-01

354

Iron, lanthanum and manganese oxides loaded on ?-Al 2O 3 for selective catalytic reduction of NO with NH 3 at low temperature  

Microsoft Academic Search

A series of Mn\\/Al 2O 3, La-Mn\\/Al 2O 3 and Fe-La-Mn\\/Al 2O 3 catalysts were prepared by an impregnation method and investigated for selective catalytic reduction of NO with NH 3 at low temperature. The experimental results revealed that NO conversion over La-Mn\\/Al 2O 3 was obviously improved after La doping. Addition of Fe increased both NO conversion and the

Weiwei Zhao; Caiting Li; Pei Lu; Qingbo Wen; Yapei Zhao; Xing Zhang; Chunzhen Fan; Shasha Tao

2012-01-01

355

Ground-based observations of H2O and NH3 on Jupiter during the Cassini flyby. Part 2: Data Analysis  

Microsoft Academic Search

We will describe our analysis and present some initial results of observing Jupiter in December 2000 at 5.18 microns. We measured the equivalent widths of two CH4 absorption features and one NH3 absorption line as a function of position along a slit aligned east-west on Jupiter. Terrestrial CO2 and H2O lines were used for frequency calibration. We characterized the equivalent

T. Hewagama; G. Bjoraker; G. S. Orton

2001-01-01

356

Multiply charged cluster ions of Ar, Kr, Xe, N 2 , O 2 , CO 2 , SO 2 and NH 3 : Production mechanism, appearance size and appearance energy  

Microsoft Academic Search

Clusters of Ar, Kr, Xe, N2, O2, CO2, SO2 and NH3 formed by supersonic nozzle expansion have been studied by electron impact ionization mass spectrometry (up to 15000 amu). Besides mass spectra of singly charged ions showing the characteristic anomalous distributions, we have in particular investigated the properties of multiply charged cluster ions. Critical appearance sizes of doubly and triply

T. D. Märk; P. Scheier; M. Lezius; G. Walder; A. Stamatovic

1989-01-01

357

NH 3–NO\\/NO 2 chemistry over V-based catalysts and its role in the mechanism of the Fast SCR reaction  

Microsoft Academic Search

We present herein a study performed under transient reactive conditions aimed at elucidating the mechanism of the Fast SCR reaction. Transient response data collected at low temperature over a commercial V2O5–WO3\\/TiO2 catalyst studying the reactivity of NH3–NO\\/NO2 mixtures with different NO\\/NOx feed ratios (from 0 to 1) resulted in the identification of a novel reaction pathway for the Fast SCR

Isabella Nova; Cristian Ciardelli; Enrico Tronconi; Daniel Chatterjee; Brigitte Bandl-Konrad

2006-01-01

358

Variable mass energy transformation and storage (VMETS) system using NH 3–H 2O as working fluid, Part 1: Modeling and simulation under full storage strategy  

Microsoft Academic Search

This paper presents a new variable mass energy transformation and storage (VMETS) system using ammonia–water solution (NH3–H2O) as working fluid. The system has a wide range of working temperature. It can be used to shift load with a diurnal energy storage system for cooling in summer, heating in winter, or hot water supplying all year long. It can also be

S. M. Xu; L. Zhang; J. Liang; R. Du

2007-01-01

359

Dielectric Properties of the (CH3NH3)5Bi2(1- x)Sb2xCl11 Mixed Crystals  

NASA Astrophysics Data System (ADS)

The (CH3NH3)5Bi2(1-x)Sb2xCl11 crystals were examined from the point of view of their applicability in pyroelectric detectors. It was shown that they can be useful so far as the construction of infrared detectors is concerned due to high values of both their pyroelectric coefficient and figure of merit p/sqrt? which are both comparable with those of triglycine sulphate crystals.

Mróz, J.; Dziedzic, J.; Pykacz, H.

2006-10-01

360

Ab Initio and Dynamics Study of the O(3P) + NH3 and O(3P) + N2H4 Reactions at Hyperthermal Collision Energies  

NASA Astrophysics Data System (ADS)

The reactions between ground-state oxygen atoms (O(3P)) and the ammonia (NH3) and hydrazine (N2H4) molecules have been studied using electronic-structure and dynamics calculations. Ab initio calculations have been used to characterize the primary reaction channels accessible at hyperthermal energies. These reaction channels are i) hydrogen abstraction, O + NH3(N2H4) ? OH + NH2(N2H3), ii) H-elimination O + NH3(N2H4) ? H + ONH2(ON2H3), and iii) N-N breakage (in the reaction involving hydrazine), O + N2H4 ? ONH2 + NH2. Hydrogen abstraction is the lowest-barrier process, followed by N-N breakage and H-elimination. Comparison of our highest-accuracy calculations (CCSD(T)/CBS//MP2/aug-cc-pVDZ) with a variety of lower-cost electronic-structure methods shows that the BHandHLYP method, in combination with the 6-31G* basis set, captures remarkably well the essential features of the potential-energy surface of all of the reaction channels investigated in this work. Using directly the BHandHLYP/6-31G* combination, we have propagated quasiclassical trajectories to characterize the dynamics of the O + NH3 and O + N2H4 reactions at hyperthermal energies. The trajectory calculations reveal that hydrogen abstraction is the dominant reaction channel, with cross sections between a factor of 2 and an order of magnitude larger than those for the H-elimination and N-N breakage channels. The dynamics calculations also indicate that most of the energy is partitioned into products relative translation but significant vibrational excitation of products is possible as well. Analysis of angular distributions and opacity functions suggests that whereas the hydrogen-abstraction reactions proceed through a mechanism with a substantial component of stripping dynamics, H-elimination and N-N breakage are dominated by rebound dynamics.

Troya, Diego; Mosch, Marianne; O'Neill, Kayleigh A.

2009-11-01

361

Simultaneous removal and evaluation of organic substrates and NH3-N by a novel combined process in treating chemical synthesis-based pharmaceutical wastewater.  

PubMed

A full-scale novel combined anaerobic/micro-aerobic and two-stage aerobic biological process is used for the treatment of an actual chemical synthesis-based pharmaceutical wastewater containing amoxicillin. The anaerobic system is an up-flow anaerobic sludge blanket (UASB), the micro-aerobic system is a novel micro-aerobic hydrolysis acidification reactor (NHAR) and the two-stage aerobic process comprised cyclic activated sludge system (CASS) and biological contact oxidation tank (BCOT). The influent wastewater was high in COD, NH(3)-N varying daily 4016-13,093 mg-COD L(-1) and 156.4-650.2 mg-NH(3)-N L(-1), amoxicillin varying weekly between 69.1 and 105.4 mg-amoxicillin L(-1), respectively; Almost all the COD, NH(3)-N, amoxicillin were removed by the biological combined system, with removal percentages 97%, 93.4% and 97.2%, respectively, leaving around 104 mg-COD L(-1), 9.4 mg-NH(3)-N L(-1) and 2.6±0.8 mg-amoxicillin L(-1) in the final clarifier effluent. The performance evaluation of the wastewater treatment plant (WWTP) by mathematical statistic methods shown that at most of time effluent can meet the higher treatment discharge standard. In addition, the fate of amoxicillin in the full-scale WWTP and the amoxicillin removal rate of each different removal routes in UASB, NHAR, CASS, BCOT and final clarifier processes are investigated in this paper. The results show that biodegradation, adsorption and hydrolysis are the major mechanisms for amoxicillin removal. PMID:21974848

Chen, Zhaobo; Wang, Hongcheng; Ren, Nanqi; Cui, Minhua; Nie, Shukai; Hu, Dongxue

2011-09-17

362

High quality GaN film growth on AlN buffer layer, pretreated with alternating pulsative supply of TMG and NH 3  

Microsoft Academic Search

High quality GaN films of low etch pit density (107cm?2) have been prepared by metal organic chemical vapour deposition (MOCVD) on 6H-SiC substrate with Aln buffer layer. The buffer layer was pretreated by alternating pulsative supply (APS) of trimethyl gallium (TMG) and NH3 gases. Nitrogen atom is expected to incorporate into the gallium cluster formed by APS process. The sizes

Jin Soo Hwang; Satoru Tanaka; Sohachi Iwai; Yoshinobu Aoyagi; Seeyearl Seong

1999-01-01

363

The source of 3-?m absorption in Jupiter’s clouds: Reanalysis of ISO observations using new NH3 absorption models  

NASA Astrophysics Data System (ADS)

A prominent characteristic of jovian near-IR spectra is the widely distributed presence of a strong absorption at wavelengths from about 2.9 ?m to 3.1 ?m, first noticed in a 3-?m spectrum obtained by the Infrared Space Observatory (ISO) in 1996. While Brooke et al. (Brooke, T.Y., Knacke, R.F., Encrenaz, T., Drossart, P., Crisp, D., Feuchtgruber, H. [1998]. Icarus 136, 1-13) were able to fit the ISO spectrum very well using ammonia ice as the sole source of particulate absorption, Irwin et al. (Irwin, P.G.J., Weir, A.L., Taylor, F.W., Calcutt, S.B., Carlson, R.W. [2001]. Icarus 149, 397-415) noted that their best-fit cloud model implied a strong absorption at 2 ?m that was not observed in Galileo NIMS spectra, raising questions about the source of the absorption. Subsequent significant revisions in ammonia gas absorption models (Bowles, N., Calcutt, S., Irwin, P., Temple, J. [2008]. Icarus 196, 612-614) also raised questions about these conclusions because ammonia gas absorption overlaps regions of ammonia ice absorption. Our reanalysis, based on improved ammonia absorption models, finds that the ISO spectrum can be well fit by models that include both NH 3 ice and solid NH 4SH, with the latter substance providing most of the absorption. The component due to NH 3 is very possibly due to NH 3 present as a coating on either large ( r ˜ 15 ?m) NH 4SH particles in a deeper layer at ˜550 mb or on small ( r ˜ 0.3 ?m) photochemical haze particles in a lower pressure layer at ˜370 mb. Neither option creates conflict with the lack of significant NH 3 absorption features at thermal wavelengths.

Sromovsky, L. A.; Fry, P. M.

2010-11-01

364

Thematic course: Research of equilibriums with the method of residual concentration and potentiometric titration. Part I. HETEROGENEOUS EQUILIBRIUM IN SYSTEMS ZnSO4-H2O-KOH, ZnSO4-H2O-NH3 and CuSO4-H2O-KOH, CuSO4-H2O-NH3  

Microsoft Academic Search

With the method of residual concentration we have investigated the equilibrium in systems ZnSO4-H2?-KOH (1), ZnSO4-H2?-NH3 (2) and CuSO4-H2?-KOH (1'), CuSO4-H2?-NH3 (2'). For these systems the mathematical model of heterogeneous equilibrium has been worked out which allows for the formation of precipitates of various structures. In the research there have been estimated the equilibrium constants for complexes Zn(II) and Cu(II)

Rafail A. Yusupov; Marat R. Gafarov; Edward R. Nurislamov; Oleg V. Mihaylov

2002-01-01

365

Triggering N2 uptake via redox-induced expulsion of coordinated NH3 and N2 silylation at trigonal bipyramidal iron  

NASA Astrophysics Data System (ADS)

The biological reduction of N2 to give NH3 may occur by one of two predominant pathways in which nitrogenous NxHy intermediates, including hydrazine (N2H4), diazene (N2H2), nitride (N3-) and imide (NH2-), may be involved. To test the validity of hypotheses on iron's direct role in the stepwise reduction of N2, model systems for iron are needed. Such systems can test the chemical compatibility of iron with various proposed NxHy intermediates and the reactivity patterns of such species. Here we describe a trigonal bipyramidal Si(o-C6H4PR2)3Fe-L scaffold (R = Ph or i-Pr) in which the apical site is occupied by nitrogenous ligands such as N2, N2H4, NH3 and N2R. The system accommodates terminally bound N2 in the three formal oxidation states (iron(0), +1 and +2). N2 uptake is demonstrated by the displacement of its reduction partners NH3 and N2H4, and N2 functionalizaton is illustrated by electrophilic silylation.

Lee, Yunho; Mankad, Neal P.; Peters, Jonas C.

2010-07-01

366

Standing waves, clustering, and phase waves in 1D simulations of kinetic relaxation oscillations in NO+NH3 on Pt(100) coupled by diffusion  

NASA Astrophysics Data System (ADS)

The Lombardo-Imbihl-Fink (LFI) ODE model of the NO+NH3 reaction on a Pt(100) surface shows stable relaxation oscillations with very sharp transitions for temperatures T between 404 and 433K. Here we study numerically the effect of linear diffusive coupling of these oscillators in one spatial dimension. Depending on the parameters and initial conditions we find a rich variety of spatio-temporal patterns which we group into four main regimes: bulk oscillations (BOs), standing waves (SW), phase clusters (PC), and phase waves (PW). Two key ingredients for SW and PC are identified, namely the relaxation type of the ODE oscillations and a nonlocal (and nonglobal) coupling due to relatively fast diffusion of the kinetically slaved variables NH3 and H. In particular, the latter replaces the global coupling through the gas phase used to obtain SW and PC in models of related surface reactions. The PW exist only under the assumption of (relatively) slow diffusion of NH3 and H.

Uecker, Hannes

2004-04-01

367

Effect of Phase Transition on the Optical Absorption Edge and Electronic States in Ferroelectric Materials of (CH 3NH 3) 3M 2Br 9 (M: Sb, Bi)  

NASA Astrophysics Data System (ADS)

We have measured the temperature dependence of the absorption spectra in the band-edge region and the reflection spectra of the (CH3NH3)3M2Br9 (M:Sb,Bi) single crystals exhibiting serveral successive phase transitions.The dispersion-like reflection structure due to the band-edge exciton transition is observed at 2.92 eV and 2.95 eV for (CH3NH3)3Bi2Br9 and (CH3NH3)3Sb2Br9, respectively.The reflection structure remains even at room temperature reflecting a large binding energy. The fundamental absorption edge in both crystals possesses an exponential shape following the empirical Urbach rule.The steepness coefficients characterizing a broadening of the absorption edgeexhibit a distinct jump at the phase transition temperature.The results indicate thatthe ordering of orientational motion of methylammonium cationschanges not only the crystal structure and dielectric properties but also the Urbach tail in both crystals.

Kawai, Taketoshi; Takao, Emi; Shimanuki, Shigetaka; Iwata, Makoto; Miyashita, Akira; Ishibashi, Yoshihiro

1999-08-01

368

Triggering N(2) uptake via redox-induced expulsion of coordinated NH(3) and N(2) silylation at trigonal bipyramidal iron.  

PubMed

The biological reduction of N(2) to give NH(3) may occur by one of two predominant pathways in which nitrogenous N(x)H(y) intermediates, including hydrazine (N(2)H(4)), diazene (N(2)H(2)), nitride (N(3-)) and imide (NH(2-)), may be involved. To test the validity of hypotheses on iron's direct role in the stepwise reduction of N(2), model systems for iron are needed. Such systems can test the chemical compatibility of iron with various proposed N(x)H(y) intermediates and the reactivity patterns of such species. Here we describe a trigonal bipyramidal Si(o-C(6)H(4)PR(2))(3)Fe-L scaffold (R = Ph or i-Pr) in which the apical site is occupied by nitrogenous ligands such as N(2), N(2)H(4), NH(3) and N(2)R. The system accommodates terminally bound N(2) in the three formal oxidation states (iron(0), +1 and +2). N(2) uptake is demonstrated by the displacement of its reduction partners NH(3) and N(2)H(4), and N(2) functionalizaton is illustrated by electrophilic silylation. PMID:20571574

Lee, Yunho; Mankad, Neal P; Peters, Jonas C

2010-05-16

369

Density functional investigation of the electronic properties of B80 fullerene exposed to regioselective chemisorption of nucleophiles NH3, PH3 and AsH3  

NASA Astrophysics Data System (ADS)

DFT calculations at B3LYP/6-31G(d,p) level are applied to investigate the effect of regioselective chemisorption of nucleophiles NH3, PH3 and AsH3 on the electronic properties of B80 fullerene based on computing CS and EFG parameters and natural charges. Three directions of approaching are considered, the frame site, endohedral and exohedral caps. Our results demonstrate CS and EFG tensors are sensitive to the positions of attached sites and that attachment of XH3 to B80 fullerene exerts not only a structural but also an electronic environment deformation to the cage. Natural charge analyses show about 0.4 e transfer from NH3 ligand and about 0.8 e transfer from PH3 and AsH3 ligands to the cage of B80 fullerene. Parallel to NQR parameters and natural charge analyses suggest that electronic density increases on the first neighbor of B1 in NH3-B80 models and increases on B1 and its first neighbors in PH3-B80 and AsH3-B80 models.

Anafcheh, Maryam; Ghafouri, Reza

2012-10-01

370

First detection of NH3 (10 -> 00) from a low mass cloud core. On the low ammonia abundance of the rho Oph A core  

NASA Astrophysics Data System (ADS)

Odin has successfully observed the molecular core rho Oph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (JK = 10 -> 00). The interpretation of this result makes use of complementary molecular line data obtained from the ground (C17O and CH3OH) as part of the Odin preparatory work. Comparison of these observations with theoretical model calculations of line excitation and transfer yields a quite ordinary abundance of methanol, X(CH3OH)= 3 x 10-9. Unless NH3 is not entirely segregated from C17O and CH3OH, ammonia is found to be significantly underabundant with respect to typical dense core values, viz. X(NH3) = 8 x 10-10. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation has been the industrial prime contractor. and based on observations collected with the Swedish ESO Submillimeter Telescope, SEST, in La Silla, Chile.

Liseau, R.; Larsson, B.; Brandeker, A.; Bergman, P.; Bernath, P.; Black, J. H.; Booth, R.; Buat, V.; Curry, C.; Encrenaz, P.; Falgarone, E.; Feldman, P.; Fich, M.; Florén, H.; Frisk, U.; Gerin, M.; Gregersen, E.; Harju, J.; Hasegawa, T.; Hjalmarson, Å.; Johansson, L.; Kwok, S.; Lecacheux, A.; Liljeström, T.; Mattila, K.; Mitchell, G.; Nordh, L.; Olberg, M.; Olofsson, G.; Pagani, L.; Plume, R.; Ristorcelli, I.; Sandqvist, Aa.; Schéele, F. v.; Serra, G.; Tothill, N.; Volk, K.; Wilson, C.

2003-05-01

371

Temperature and pressure dependence of molecular adsorption on single wall carbon nanotubes and the existence of an “adsorption\\/desorption pressure gap”  

Microsoft Academic Search

The interaction of acetone with single wall carbon nanotubes (SWCNTs) was studied by temperature programmed desorption with mass spectrometry (TPD-MS), after reflux, sonication, or exposure to 7.6Torr of acetone vapors at room temperature. Acetone molecules adsorb strongly on SWCNTs desorbing at ?400–900K, corresponding to desorption energies of ?100–225kJ\\/mol, as intact molecules. Exchange of intact adsorbed molecules with gas phase species

Dmitry V. Kazachkin; Yoshifumi Nishimura; Stephan Irle; Xue Feng; Radisav Vidic; Eric Borguet

2010-01-01

372

The c2d Spitzer Spectroscopic Survey of Ices Around Low-mass Young Stellar Objects. IV. NH3 and CH3OH  

NASA Astrophysics Data System (ADS)

NH3 and CH3OH are key molecules in astrochemical networks leading to the formation of more complex N- and O-bearing molecules, such as CH3CN and CH3OCH3. Despite a number of recent studies, little is known about their abundances in the solid state. This is particularly the case for low-mass protostars, for which only the launch of the Spitzer Space Telescope has permitted high-sensitivity observations of the ices around these objects. In this work, we investigate the ~8-10 ?m region in the Spitzer IRS (InfraRed Spectrograph) spectra of 41 low-mass young stellar objects (YSOs). These data are part of a survey of interstellar ices in a sample of low-mass YSOs studied in earlier papers in this series. We used both an empirical and a local continuum method to correct for the contribution from the 10 ?m silicate absorption in the recorded spectra. In addition, we conducted a systematic laboratory study of NH3- and CH3OH-containing ices to help interpret the astronomical spectra. We clearly detect a feature at ~9 ?m in 24 low-mass YSOs. Within the uncertainty in continuum determination, we identify this feature with the NH3 ?2 umbrella mode and derive abundances with respect to water between ~2% and 15%. Simultaneously, we also revisited the case of CH3OH ice by studying the ?4 C-O stretch mode of this molecule at ~9.7 ?m in 16 objects, yielding abundances consistent with those derived by Boogert et al. based on a simultaneous 9.75 and 3.53 ?m data analysis. Our study indicates that NH3 is present primarily in H2O-rich ices, but that in some cases, such ices are insufficient to explain the observed narrow FWHM. The laboratory data point to CH3OH being in an almost pure methanol ice, or mixed mainly with CO or CO2, consistent with its formation through hydrogenation on grains. Finally, we use our derived NH3 abundances in combination with previously published abundances of other solid N-bearing species to find that up to 10%-20% of nitrogen is locked up in known ices.

Bottinelli, Sandrine; Boogert, A. C. Adwin; Bouwman, Jordy; Beckwith, Martha; van Dishoeck, Ewine F.; Öberg, Karin I.; Pontoppidan, Klaus M.; Linnartz, Harold; Blake, Geoffrey A.; Evans, Neal J., II; Lahuis, Fred

2010-08-01

373

Dry deposition of nitrogen compounds (NO2, HNO3, NH3), sulfur dioxide and ozone in West and Central African ecosystems using the inferential method  

NASA Astrophysics Data System (ADS)

This work is part of the IDAF program (IGAC-DEBITS-AFRICA) and is based on the long term monitoring of gas concentrations (1998-2007) established on seven remote sites representative of major African ecosystems. Dry deposition fluxes were estimated by the inferential method using on one hand surface measurements of gas concentrations (NO2, HNO3, NH3, SO2, and O3) and on the other hand simulated dry deposition velocities (Vd). Vd were calculated using the big-leaf model of Zhang et al. (2003b). In the model of deposition, surface and meteorological conditions specific to IDAF sites have been adapted in order to simulate Vd representative of major African ecosystems. The monthly, seasonal and annual mean variations of gaseous dry deposition fluxes (NO2, HNO3, NH3, O3, and SO2) are analyzed. Along the latitudinal transect of ecosystems, the annual mean dry deposition fluxes of nitrogen compounds range from 0.4 ± 0.0 to 0.8 ± 0.2 kg N ha-1 yr-1 for NO2, from 0.7 ± 0.1 to 1.0 ± 0.3 kg N ha-1 yr-1 for HNO3, and from 2.3 ± 0.8 to 10.5 ± 5.0 kg N ha-1 yr-1 for NH3 over the study period (1998-2007). The total nitrogen dry deposition flux (NO2+HNO3+NH3) is more important in forests (11.2-11.8 kg N ha-1 yr-1) than in wet and dry savannas (3.4-5.3 kg N ha-1 yr-1). NH3 dominated nitrogen dry deposition, representing 67-80% of the total. The annual mean dry deposition fluxes of ozone range between 11.3 ± 4.7 and 17.5 ± 3.0 kg ha-1 yr-1 in dry savannas, 17.5 ± 3.0 and 19.2 ± 2.9 kg ha-1 yr-1 in wet savannas, and 10.6 ± 2.0 and 13.2 ± 3.6 kg ha-1 yr-1 in forests. Lowest O3 dry deposition fluxes in forests are correlated to low measured O3 concentrations, lower of a factor of 2-3, compared to others ecosystems. Along the ecosystem transect, annual mean of SO2 dry deposition fluxes present low values and a small variability (0.5 to 1 kg S ha-1 yr-1). No specific trend in the interannual variability of these gaseous dry deposition fluxes is observed over the study period.

Adon, M.; Galy-Lacaux, C.; Yoboue, V.; Delon, C.; Solmon, F.; Kaptue Tchuente, A. T.

2013-05-01

374

Synthesis and luminescence properties of lead-halide based organic-inorganic layered perovskite compounds (CnH2n+1NH3)2PbI4 (n=4, 5, 7, 8 and 9)  

NASA Astrophysics Data System (ADS)

This paper describes the synthesis and characterization of organic-inorganic layered perovskite compounds, (CnH2n+1NH3)2PbI4 (n=4, 5, 7, 8 and 9). The effect of the number of carbon atoms on luminescence properties has been examined. Thin films of microcrystalline (CnH2n+1NH3)2PbI4 fabricated by spin-coating are highly oriented, with the c-axis perpendicular to the substrate surface. Temperature-dependent optical absorption spectra reveal that (CnH2n+1NH3)2PbI4 films (n=4, 7, 8 and 9) show the structural phase transitions. The excitonic structures of (CnH2n+1NH3)2PbI4 vary with the number of carbon atoms of the alkyl chain length. At low temperatures below 100 K, the lowest-energy free-exciton band of (CnH2n+1NH3)2PbI4 (n=7, 8 and 9) split into three fine-structure levels. In contrast to (CnH2n+1NH3)2PbBr4 films, (CnH2n+1NH3)2PbI4 (n=7, 8 and 9) shows no triplet exciton emission, but it shows the Stokes-shifted emission from bound excitons.

Kitazawa, Nobuaki; Aono, Masami; Watanabe, Yoshihisa

2011-12-01

375

OTEC gas desorption studies  

NASA Astrophysics Data System (ADS)

Experiments on deaeration in packed columns and barometric intake systems, and with hydraulic air compression for open-cycle OTEC systems are reported. A gas desorption test loop consisting of water storage tanks, a vacuum system, a liquid recirculating system, an air supply, a column test section, and two barometric leg test sections was used to perform the tests. The aerated water was directed through columns filled with either ceramic Raschig rings or plastic pall rings, and the system vacuum pressure, which drives the deaeration process, was found to be dependent on water velocity and intake pipe height. The addition of a barometric intake pipe increased the deaeration effect 10%, and further tests were run with lengths of PVC pipe as potential means for noncondensibles disposal through hydraulic air compression. Using the kinetic energy from the effluent flow to condense steam in the noncondensible stream improved the system efficiency.

Chen, F. C.; Golshani, A.

1982-02-01

376

Investigating the influences of SO2 and NH3 levels on isoprene-derived secondary organic aerosol formation using conditional sampling approaches  

NASA Astrophysics Data System (ADS)

Filter-based PM2.5 samples were chemically analyzed to investigate secondary organic aerosol (SOA) formation from isoprene in a rural atmosphere of the southeastern US influenced by both anthropogenic sulfur dioxide (SO2) and ammonia (NH3) emissions. Daytime PM2.5 samples were collected during summer 2010 using conditional sampling approaches based on pre-defined high and low SO2 or NH3 thresholds. Known molecular-level tracers for isoprene SOA formation, including 2-methylglyceric acid, 3-methyltetrahydrofuran-3,4-diols, 2-methyltetrols, C5-alkene triols, dimers, and organosulfate derivatives, were identified and quantified by gas chromatography coupled to electron ionization mass spectrometry (GC/EI-MS) and ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS). Mass concentrations of six isoprene low-NOx SOA tracers contributed to 12-19% of total organic matter (OM) in PM2.5 samples collected during the sampling period, indicating the importance of the hydroxyl radical (OH)-initiated oxidation (so-called photooxidation) of isoprene under low-NOx conditions that lead to SOA formation through reactive uptake of gaseous isoprene epoxydiols (IEPOX) in this region. The contribution of the IEPOX-derived SOA tracers to total organic matter was enhanced by 1.4% (p = 0.012) under high-SO2 sampling scenarios, although only weak associations between aerosol acidity and mass of IEPOX SOA tracers were observed. This suggests that IEPOX-derived SOA formation might be modulated by other factors simultaneously, rather than only aerosol acidity. No clear associations between isoprene SOA formation and high or low NH3 conditional samples were found. Positive correlations between sulfate aerosol loadings and IEPOX-derived SOA tracers for samples collected under all conditions indicates that sulfate aerosol could be a surrogate for surface accommodation in the uptake of IEPOX onto preexisting aerosols.

Lin, Y.-H.; Knipping, E. M.; Edgerton, E. S.; Shaw, S. L.; Surratt, J. D.

2013-08-01

377

Investigating the influences of SO2 and NH3 levels on isoprene-derived secondary organic aerosol formation using conditional sampling approaches  

NASA Astrophysics Data System (ADS)

Filter-based PM2.5 samples were chemically analyzed to investigate secondary organic aerosol (SOA) formation from isoprene in a rural atmosphere of the southeastern US influenced by both anthropogenic sulfur dioxide (SO2) and ammonia (NH3) emissions. Daytime PM2.5 samples were collected during summer 2010 using conditional sampling approaches based on pre-defined high and low SO2 or NH3 thresholds. Known molecular-level tracers for isoprene SOA formation, including 2-methylglyceric acid, 3-methyltetrahydrofuran-3,4-diols, 2-methyltetrols, C5-alkene triols, dimers, and organosulfate derivatives, were identified and quantified by gas chromatography coupled to electron ionization mass spectrometry (GC/EI-MS) and ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS). Mass concentrations of six isoprene low-NOx SOA tracers contributed to 12-19% of total organic matter (OM) in PM2.5 samples collected during the sampling period, indicating the importance of the hydroxyl radical (OH)-initiated oxidation (so-called photooxidation) of isoprene under low-NOx conditions that leads to SOA formation through reactive uptake of gaseous isoprene epoxydiols (IEPOX) in this region. IEPOX-derived SOA tracers were enhanced under high-SO2 sampling scenarios, suggesting that SO2 oxidation increases aerosol acidity of sulfate aerosols needed for enhancing heterogeneous oxirane ring-opening reactions of IEPOX. No clear associations between isoprene SOA formation and high and low NH3 conditional samples were found. Furthermore, weak correlations between aerosol acidity and mass of IEPOX SOA tracers suggests that IEPOX-derived SOA formation might be modulated by other factors as well in addition to aerosol acidity. Positive correlations between sulfate aerosol loadings and IEPOX-derived SOA tracers for samples collected under all conditions indicates that sulfate aerosol could be a surrogate for surface area in the uptake of IEPOX onto preexisting aerosols.

Lin, Y.-H.; Knipping, E. M.; Edgerton, E. S.; Shaw, S. L.; Surratt, J. D.

2013-02-01

378

Magnetic properties and critical behavior of the pure and diluted two-dimensional weak ferromagnet (CH3NH3)2Mn1-xCdxCl4  

NASA Astrophysics Data System (ADS)

The compound (CH3NH3)2MnCl4 had for a long time been considered a good example of a quasi-two-dimensional Heisenberg antiferromagnet, however, it is a weak ferromagnet with a nearly quadratic layer structure. In this work we measure the magnetization of (CH3NH3)2MnCl4 and the diluted with cadmium compound (CH3NH3)2Mn0.95Cd0.05Cl4. The Néel temperature for the pure sample was determined as TN=44.75 K and a weak-ferromagnetic moment was observed within the nearly quadratic layer (perpendicular to the easy axis). From the measured weak magnetic moment, we estimate a canting angle for the sublattices magnetizations ?~0.07° from the easy axis. The overall temperature dependence of the weak magnetic moment is the same as that previously measured for the sublattice magnetization in neutron diffraction experiments (as expected). However, close to TN the critical exponent ? of the magnetization changes from ?1=0.17+/-0.02 [0.01<(1-T/TN)<0.1] to ?2=0.23+/-0.02 [0.001<(1-T/TN)<0.01] in the immediate neighborhood of TN. In the diluted compound (TN=41.0+/-0.5 K) and below 0.9TN the magnetization due to the weak component follows the same behavior found for the pure system but closer to TN an almost linear dependence of the magnetization with temperature is observed.

Paduan-Filho, A.; Becerra, C. C.

2002-05-01

379

Deconstructing Desorption Electrospray Ionization: Independent Optimization of Desorption and Ionization by Spray Desorption Collection  

NASA Astrophysics Data System (ADS)

Spray desorption collection (SDC) and reflective electrospray ionization (RESI) were used to independently study the desorption and ionization processes that together comprise desorption electrospray ionization (DESI). Both processes depend on several instrumental parameters, including the nebulizing gas flow rate, applied potential, and source geometries. Each of these parameters was optimized for desorption, as represented by the results obtained by SDC, and ionization, as represented by the results obtained by RESI. The optimized conditions were then compared to the optimization results for DESI. Our results confirm that optimal conditions for desorption and ionization are different and that in some cases the optimized DESI conditions are a compromise between both sets. The respective results for DESI, RESI, and SDC for each parameter were compared across the methods to draw conclusions about the contribution of each parameter to desorption and ionization separately and then combined within DESI. Our results indicate that desorption efficiency is (1) independent of the applied potential and (2) the impact zone to inlet distance, and that (3) gas pressure settings and (4) sprayer to impact zone distances above optimal for DESI are detrimental to desorption but beneficial for ionization. In addition, possible interpretations for the observed trends are presented.

Douglass, Kevin A.; Jain, Shashank; Brandt, William R.; Venter, Andre R.

2012-11-01

380

Deconstructing desorption electrospray ionization: independent optimization of desorption and ionization by spray desorption collection.  

PubMed

Spray desorption collection (SDC) and reflective electrospray ionization (RESI) were used to independently study the desorption and ionization processes that together comprise desorption electrospray ionization (DESI). Both processes depend on several instrumental parameters, including the nebulizing gas flow rate, applied potential, and source geometries. Each of these parameters was optimized for desorption, as represented by the results obtained by SDC, and ionization, as represented by the results obtained by RESI. The optimized conditions were then compared to the optimization results for DESI. Our results confirm that optimal conditions for desorption and ionization are different and that in some cases the optimized DESI conditions are a compromise between both sets. The respective results for DESI, RESI, and SDC for each parameter were compared across the methods to draw conclusions about the contribution of each parameter to desorption and ionization separately and then combined within DESI. Our results indicate that desorption efficiency is (1) independent of the applied potential and (2) the impact zone to inlet distance, and that (3) gas pressure settings and (4) sprayer to impact zone distances above optimal for DESI are detrimental to desorption but beneficial for ionization. In addition, possible interpretations for the observed trends are presented. PMID:22907171

Douglass, Kevin A; Jain, Shashank; Brandt, William R; Venter, Andre R

2012-08-21

381

The irradiation of pure CH3OH and 1:1 mixture of NH3:CH3OH ices at 30 K using low energy electrons  

NASA Astrophysics Data System (ADS)

The results of an experimental investigation of 1 keV electron irradiation of ices (deposited at 30 K) of (i) pure methanol and (ii) of a 1:1 mixture of NH3:CH3OH are reported. Molecular products formed within the ice were detected and monitored using FTIR spectroscopy. The products observed were methyl formate (H3COHCO), methane (CH4), hydroxymethyl (CH2OH), formamide (HCONH2), formic acid (HCOOH), formaldehyde (H2CO), formyl radical (HCO), cyanate ion (OCN-), isocyanic acid (HNCO), carbon monoxide (CO) and carbon dioxide (CO2). The consequences of these results for prebiotic chemistry in the interstellar medium and star forming regions are discussed.

Jheeta, Sohan; Domaracka, A.; Ptasinska, S.; Sivaraman, B.; Mason, N. J.

2013-01-01

382

Reaction of Sn4(4-) in liquid ammonia: the formation of Rb6[(?(2)-Sn4)Zn(?(3)-Sn4)]·5NH3.  

PubMed

The reaction of Rb4Sn4 with ZnPh2 in liquid ammonia in the presence of [2.2.2]-cryptand yielded crystals of Rb6[(?(2)-Sn4)Zn(?(3)-Sn4)]·5NH3, which could be characterized by single crystal X-ray diffraction. This is the first example of a successful solution reaction of the highly charged tetrahedral Sn4(4-) anions. The homoleptic [E4ZnE4](6-) complex (E = tetrel element) was previously known only for E[double bond, length as m-dash]Ge and Si/Ge. PMID:24067942

Fendt, Franziska; Koch, Carina; Gärtner, Stefanie; Korber, Nikolaus

2013-10-22

383

Decomposition of NH3BH3 at sub-ambient pressures: A combined thermogravimetry-differential thermal analysis-mass spectrometry study  

SciTech Connect

We report a systematic study of the isothermal decomposition of ammonia borane, NH3BH3, at 363 K as a function of argon pressure ranging between 50 and 1040 mbar using thermogravimetry and differential thermal analysis coupled with mass analysis of the volatile species. During thermal aging at 363 K, evolution of hydrogen, aminoborane and borazine is monitored, with the relative mass loss strongly depending on the pressure in the reaction chamber. Furthermore, the induction period required for hydrogen release at 363 K decreases with decreasing pressure.

Palumbo, Oriele; Paolone, Annalisa; Rispoli, Pasquale; Cantelli, Rosario; Autrey, Thomas

2010-03-15

384

Promotional effect of Ag-doped Ag–V\\/TiO 2 catalyst with low vanadium loadings for selective catalytic reduction of NO X by NH 3  

Microsoft Academic Search

A series of Ag-doped Ag–V\\/TiO2 catalysts with low vanadium loadings were prepared by one-step sol–gel methods and the effects of the Ag doping on the selective\\u000a catalytic reduction (SCR) of NOx with NH3 were investigated. The catalytic activity of the catalysts increased about 20% by the addition of 1–3 wt% of Ag. The catalysts\\u000a were characterized by XRD and H2-TPR. The

Wang Zaihua; Li Xinjun; Song Wenji; Chen Jinfa; Li Tao; Feng Ziping

385

The Effects of Manganese Precursors on Mn-based\\/TiO2 Catalysts for Catalytic Reduction of NO with NH3  

Microsoft Academic Search

Manganese acetate (MnAc) and manganese nitrate (MnN) were employed as precursors for the preparation of Mn(Ac)\\/TiO2, Mn(N)\\/TiO2, Mn(Ac)-Ce\\/TiO2, and Mn(N)-Ce\\/TiO2 by impregnation. These complexes were used as catalysts in the low temperature selective catalytic reduction of NO with NH3. The influence of manganese precursors on catalyst characteristics, the reduction activity and the stability of the catalysts to poisoning by H2O

Hua Tong; Yan Huang

2012-01-01

386

WO3/CeO2-ZrO2, a promising catalyst for selective catalytic reduction (SCR) of NOx with NH3 in diesel exhaust.  

PubMed

A WO3/CeO2-ZrO2 catalyst system was discovered for selective catalytic reduction of NOx with NH3; the catalyst (10 wt% WO3 loading) showed nearly 100% NOx conversion in a temperature range of 200-500 degrees C, at a space velocity of 90 000 h(-1) in a simulated diesel exhaust containing 550 ppm NOx (NO : NO2 feed ratio at 1.0), 10 vol% H2O and 10 vol% CO2; the catalyst also exhibited high temperature stability. PMID:18338059

Li, Ye; Cheng, Hao; Li, Deyi; Qin, Yongsheng; Xie, Yuming; Wang, Shudong

2008-01-30

387

Ab initio and dynamics study of the O(3P) + NH3 and O(3P) + N2H4 reactions at hyperthermal collision energies.  

PubMed

The reactions between ground-state oxygen atoms (O((3)P)) and the ammonia (NH(3)) and hydrazine (N(2)H(4)) molecules have been studied using electronic-structure and dynamics calculations. Ab initio calculations have been used to characterize the primary reaction channels accessible at hyperthermal energies. These reaction channels are i) hydrogen abstraction, O + NH(3)(N(2)H(4)) --> OH + NH(2)(N(2)H(3)), ii) H-elimination O + NH(3)(N(2)H(4)) --> H + ONH(2)(ON(2)H(3)), and iii) N-N breakage (in the reaction involving hydrazine), O + N(2)H(4) --> ONH(2) + NH(2). Hydrogen abstraction is the lowest-barrier process, followed by N-N breakage and H-elimination. Comparison of our highest-accuracy calculations (CCSD(T)/CBS//MP2/aug-cc-pVDZ) with a variety of lower-cost electronic-structure methods shows that the BHandHLYP method, in combination with the 6-31G* basis set, captures remarkably well the essential features of the potential-energy surface of all of the reaction channels investigated in this work. Using directly the BHandHLYP/6-31G* combination, we have propagated quasiclassical trajectories to characterize the dynamics of the O + NH(3) and O + N(2)H(4) reactions at hyperthermal energies. The trajectory calculations reveal that hydrogen abstraction is the dominant reaction channel, with cross sections between a factor of 2 and an order of magnitude larger than those for the H-elimination and N-N breakage channels. The dynamics calculations also indicate that most of the energy is partitioned into products relative translation but significant vibrational excitation of products is possible as well. Analysis of angular distributions and opacity functions suggests that whereas the hydrogen-abstraction reactions proceed through a mechanism with a substantial component of stripping dynamics, H-elimination and N-N breakage are dominated by rebound dynamics. PMID:19886614

Troya, Diego; Mosch, Marianne; O'Neill, Kayleigh A

2009-12-17

388

Development of TiSiN CVD process using TiCl 4\\/SiH 4\\/NH 3 chemistry for ULSI anti-oxidation barrier applications  

Microsoft Academic Search

CVD-TiSiN may be promising material for O2 diffusion-barrier films in ultra-large scale integrated (ULSI) circuit applications, especially for dynamic random-access memory (DRAM) capacitors. We developed a method for introducing Si into TiN, which is a common material used for diffusion-barrier films. TiSiN films were deposited by reacting TiCl4, SiH4, and NH3 in a hot-wall CVD reactor. We measured TiSiN film

Keeyoung Jun; Yukihiro Shimogaki

2004-01-01

389

The effect of surface chemical functional groups on the adsorption and desorption of a polar molecule, acetone, from a model carbonaceous surface, graphite  

Microsoft Academic Search

The role of surface chemical heterogeneity in adsorption on a model carbonaceous surface (highly oriented pyrolitic graphite, HOPG) was investigated by temperature programmed desorption of acetone, a representative polar volatile organic compound. It was observed that oxygen-containing functional groups exist on air cleaved HOPG. The presence of surface functional groups reduces the binding energy, while increasing the uptake kinetics at

S. Kwon; R. Vidic; E. Borguet

2003-01-01

390

Trace level determination of enantiomeric monoterpenes in terrestrial plant emission and in the atmosphere using a ?-cyclodextrin capillary column coupled with thermal desorption and mass spectrometry  

Microsoft Academic Search

For the first time, enrichment on solid sorbents followed by thermal desorption has been used for the determination of the enantiomeric signature of monoterpenes in the gaseous emission of terrestrial plants. A ?-cyclodextrin capillary column has been used for the separation of critical pairs. The temperature program and column loading were optimized for making the accurate quantification of individual enantiomers

Noureddine Yassaa; Enzo Brancaleoni; Massimiliano Frattoni; Paolo Ciccioli

2001-01-01

391

Trace level determination of enantiomeric monoterpenes in terrestrial plant emission and in the atmosphere using a b-cyclodextrin capillary column coupled with thermal desorption  

Microsoft Academic Search

For the first time, enrichment on solid sorbents followed by thermal desorption has been used for the determination of the enantiomeric signature of monoterpenes in the gaseous emission of terrestrial plants. A b-cyclodextrin capillary column has been used for the separation of critical pairs. The temperature program and column loading were optimized for making the accurate quantification of individual enantiomers

Noureddine Yassaa; Enzo Brancaleoni; Massimiliano Frattoni; Paolo Ciccioli

392

A first principles molecular dynamics study of excess electron and lithium atom solvation in water-ammonia mixed clusters: structural, spectral, and dynamical behaviors of [(H2O)5NH3]- and Li(H2O)5NH3 at finite temperature.  

PubMed

First principles molecular dynamics simulations are carried out to investigate the solvation of an excess electron and a lithium atom in mixed water-ammonia cluster (H(2)O)(5)NH(3) at a finite temperature of 150 K. Both [(H(2)O)(5)NH(3)](-) and Li(H(2)O)(5)NH(3) clusters are seen to display substantial hydrogen bond dynamics due to thermal motion leading to many different isomeric structures. Also, the structures of these two clusters are found to be very different from each other and also very different from the corresponding neutral cluster without any excess electron or the metal atom. Spontaneous ionization of Li atom occurs in the case of Li(H(2)O)(5)NH(3). The spatial distribution of the singly occupied molecular orbital shows where and how the excess (or free) electron is primarily localized in these clusters. The populations of single acceptor (A), double acceptor (AA), and free (NIL) type water and ammonia molecules are found to be significantly high. The dangling hydrogens of these type of water or ammonia molecules are found to primarily capture the free electron. It is also found that the free electron binding motifs evolve with time due to thermal fluctuations and the vertical detachment energy of [(H(2)O)(5)NH(3)](-) and vertical ionization energy of Li(H(2)O)(5)NH(3) also change with time along the simulation trajectories. Assignments of the observed peaks in the vibrational power spectra are done and we found a one to one correlation between the time-averaged populations of water and ammonia molecules at different H-bonding sites with the various peaks of power spectra. The frequency-time correlation functions of OH stretch vibrational frequencies of these clusters are also calculated and their decay profiles are analyzed in terms of the dynamics of hydrogen bonded and dangling OH modes. It is found that the hydrogen bond lifetimes in these clusters are almost five to six times longer than that of pure liquid water at room temperature. PMID:21261348

Pratihar, Subha; Chandra, Amalendu

2011-01-21

393

A first principles molecular dynamics study of excess electron and lithium atom solvation in water-ammonia mixed clusters: Structural, spectral, and dynamical behaviors of [(H2O)5NH3]- and Li(H2O)5NH3 at finite temperature  

NASA Astrophysics Data System (ADS)

First principles molecular dynamics simulations are carried out to investigate the solvation of an excess electron and a lithium atom in mixed water-ammonia cluster (H2O)5NH3 at a finite temperature of 150 K. Both [(H2O)5NH3]- and Li(H2O)5NH3 clusters are seen to display substantial hydrogen bond dynamics due to thermal motion leading to many different isomeric structures. Also, the structures of these two clusters are found to be very different from each other and also very different from the corresponding neutral cluster without any excess electron or the metal atom. Spontaneous ionization of Li atom occurs in the case of Li(H2O)5NH3. The spatial distribution of the singly occupied molecular orbital shows where and how the excess (or free) electron is primarily localized in these clusters. The populations of single acceptor (A), double acceptor (AA), and free (NIL) type water and ammonia molecules are found to be significantly high. The dangling hydrogens of these type of water or ammonia molecules are found to primarily capture the free electron. It is also found that the free electron binding motifs evolve with time due to thermal fluctuations and the vertical detachment energy of [(H2O)5NH3]- and vertical ionization energy of Li(H2O)5NH3 also change with time along the simulation trajectories. Assignments of the observed peaks in the vibrational power spectra are done and we found a one to one correlation between the time-averaged populations of water and ammonia molecules at different H-bonding sites with the various peaks of power spectra. The frequency-time correlation functions of OH stretch vibrational frequencies of these clusters are also calculated and their decay profiles are analyzed in terms of the dynamics of hydrogen bonded and dangling OH modes. It is found that the hydrogen bond lifetimes in these clusters are almost five to six times longer than that of pure liquid water at room temperature.

Pratihar, Subha; Chandra, Amalendu

2011-01-01

394

Desorption of chlorine organic solvents  

SciTech Connect

Adsorption methods are being used more and more widely to treat gaseous discharges containing chlorohydrocarbons. However, recovery of the chlorohydrocarbons has not been studied sufficiently, and the desorption of the solvents with steam is particularly understudied. We investigated desorption of a number of solvents from industrial active carbon AR-3. Desorption was done with live steam in the 105 to 150/sup 0/C. It can be seen from the data that with an increase of the molecular weight of the chlorohydrocarbon, the process of desorption slows down. This is clearly due to the fact that with an increase of the number of chlorine atoms in the molecule there is an increase of dispersion interaction (size of parachors) and latent heat of vaporization, which cause a decrease of the degree of desorption. The rate of desorption increases with an increase in temperature, but most of the investigated chlorine derivatives detach a chlorine ion at elevated temperature in the presence of water and carbon, with formation of HCl, which causes severe equipment corrosion. In addition, phosgene (in the decomposition of C/sub 2/HCl/sub 3/), chlorine organic acids and certain other toxic compounds may be produced. Thus, to reduce the rate of hydrolysis in the desorption of chlorohydrocarbons, especially polychlorinated ones, one should use steam with minimum possible temperature (no more than 110/sup 0/C) with a desorption time of no more than 30 minutes for poorly adsorbable compounds and no more than 45 to 60 minutes for readily absorbable ones. Here the degree of desorption of poorly absorbed compounds is about 100% while that of the readily absorbed ones is from 50 to 75%. The results were used in the design of units for recovery of methylene chloride, dichloroethane and trichloroethylene.

Petrova, N.I.; Nikolaev, K.M.

1982-03-01

395

Effect of surface nanostructure on temperature programmed reaction spectroscopy  

NASA Astrophysics Data System (ADS)

Using the catalytic CO oxidation at RuO2(110) as a showcase, we employ first-principles kinetic Monte Carlo simulations to illustrate the intricate effects on temperature programmed reaction (TPR) spectroscopy data brought about by the mere correlations between the locations of the active sites at a nanostructured surface. Even in the absence of lateral interactions, this nanostructure alone can cause inhomogeneities that cannot be grasped by prevalent mean-field data analysis procedures, which thus lead to wrong conclusions on the reactivity of the different surface species. The RuO2(110) surface studied here exhibits only two prominent active sites, arranged in simple alternating rows. Yet, the mere neglection of this still quite trivial nanostructure leads mean-field TPR data analysis [1] to extract kinetic parameters that are in error by several orders of magnitude and that do not even reflect the relative reactivity of the different surface species correctly [2].[1] S. Wendt, M. Knapp, and H. Over, JACS 126, 1537 (2004).[2] M. Rieger, J. Rogal, and K. Reuter, Phys. Rev. Lett (in press).

Rieger, Michael; Rogal, Jutta; Reuter, Karsten

2008-03-01

396

Antitumor activity of polyoxomolybdate, [NH3Pri]6[Mo7O24].3H2O, against, human gastric cancer model.  

PubMed

Polyoxometalates are negatively charged inorganic compounds which contain metal ions such as tungsten, molybdenum, vanadium etc. and which make clusters with the surrounding oxygen atoms. [NH3Pri]6[Mo7O24].3H2O (PM-8) was found to be a significant antitumor polyoxomolybdates. It had already been reported that the PM-8 suppressed the growth of Co-4 human colon cancer, MX-1 human breast cancer and OAT human lung cancer xenografted in nude mice. However, the mechanism of the antitumor activity has not been clarified. In this study, the antitumor activity of one of the metal oxide clusters (polyoxometalates), hexabis(isopropylammonium) heptamolybdate trihydrate, [NH3Pri]6[Mo7O24].3H2O (PM-8) were shown in an MTS assay. DNA ladder formation and detection of apoptotic bodies in nuclei were revealed that antitumor activity of PM-8 in MKN45 cells was due to apoptosis. It is concluded that the observation of significant tumor growth suppression of PM-8 in MKN45-bearing mice results from the induction of apoptosis. PM-8 shows promise as a novel anti-cancer agent. PMID:16860528

Mitsui, S; Ogata, A; Yanagie, H; Kasano, H; Hisa, T; Yamase, T; Eriguchi, M

2006-07-03

397

SiO2 nanospheres with tailorable interiors by directly controlling Zn2+ and NH3·H2O species in an emulsion process  

NASA Astrophysics Data System (ADS)

SiO2 nanospheres with tailorable interiors were synthesized by a facile one-spot microemulsion process using TEOS as silica source, wherein cyclohexane including triton X-100 and n-octanol as oil phase and Zn2+ or NH3·H2O aqueous solution as dispersive phase, respectively. The products were characterized by Scanning Electron Microscopy, Transmission Electron Microscopy and X-ray Powder Diffraction. It was suggested that the as-synthesized silica nanospheres possessed grape-stone-like porous or single hollow interior, and also found that the ammonia dosage and aging time played key roles in controlling the size and structure of silica nanospheres. Furthermore, the comparative results confirmed that in-situ zinc species [ZnO/Zn(OH)2] acted as the temporary templates to construct grape-stone-like interior, and a simultaneously competing etching process occurred owing to the soluble Zn(NH3)42+ complex formation while the additional excessive ammonia was introduced. With the aging time being extended, the in-situ nanocrystals tended to grow into bigger ones by Ostwald Ripening, producing single hollow interior.

Liao, Yuchao; Wu, Xiaofeng; Wang, Zhen; Chen, Yun-Fa

2011-07-01

398

High Resolution 15N NMR of the 225 K Phase Transition of Ammonia Borane (NH3BH3): Mixed Order-Disorder and Displacive Behavior  

SciTech Connect

We report high resolution 15N NMR probing of the solid-solid phase transition of 15N-labeled ammonia borane (NH3BH3) around 225 K. Both the 15N isotropic chemical shift, ?iso, and the spin-lattice relaxation rate (T1-1) exhibited strong anomalies around 225 K. The analysis of T1-1 using the Bloembergen-Purcell and Pound model showed that the motional correlation time, ?, increased from about 1 ps to 100 ps while the corresponding Arrhenius activation energy increased from 6 to 13.4 kJ/mol on going through the transition. The observed strong temperature dependence of ?iso was interpreted by an extension of the Bayer model. The time scale of the underlying motion was found to be in a reasonable agreement with the T1-1 data. These results imply that the NH3 rotor motion plays a pivotal role in the transition mechanism, and that the transition is of both order-disorder and displacive type. This work was supported by the Office of Basic Energy Sciences of the U. S. Department of Energy Chemical Sciences program. Pacific Northwest National Laboratory is operated by Battelle for the U. S. Department of Energy.

Gunaydin-Sen, Ozge; Achey, Randall; Dalal, Nar S.; Stowe, Ashley C.; Autrey, Thomas

2007-02-01

399

Photoelectrochemical behaviour of CdS/NaI.3.3NH3 /liquid sodium iodide ammoniate/ junctions - Utilization in solar energy conversion  

NASA Astrophysics Data System (ADS)

A liquid NaI.3.3NH3 solution was used as the medium in a photoelectrochemical cell to stabilize the working of CdS photoanodes and results are reported. The reference voltage of in situ Ag-Ag(plus) electrodes in the NaI.3.3NH3 solution is 0.27 V. The CdS samples were polished with diamond paste, rinsed in distilled water, and etched with HCl; ohmic contacts were formed on the backs with an evaporated gold and indium coating. Cyclic voltammetry was used to measure the electroactivity range, and a depletion layer was determined to exist in the space charge layer when an anodic current was found with reverse bias. High sensitivity to daylight was found, and this is attributed to the etching treatment and reactions to bulk energy levels. The addition of iodine to the solution was found to stabilize the photocurrent with a simultaneous rise in acidity; the iodine eventually vanishes unless the NH4(plus) is above 0.5 M or when the pH is near zero. An overall efficiency of 2 percent is noted, and the stabilization due to iodine presence resulted in cell operation for over a month.

Guyomard, D.; Herlem, M.; Heindl, R.; Sculfort, J.-L.

1981-09-01

400

Dielectric Study on the Phase Transitions in Ferroelectric (CH 3NH 3) 2AlBr 5· 6H 2O  

NASA Astrophysics Data System (ADS)

The dielectric properties have been measured for single crystals of ferroelectric (CH3NH3)2AlBr5·6H2O. The dielectric constant along the a direction ?a shows a sharp ?-type peak at the Curie temperature of 76.6 K below which the crystal shows ferroelectricity along the a direction. The dielectric constant along the a direction ?a obeys a Curie Weiss law with the Curie constant of 3.3×102 K in a temperature range about 30 K above the Curie temperature. The spontaneous polarization approaches the saturation value of 6.5×10-3 C/m2 at low temperatures. Beside the ferroelectric Curie temperature, there is a first order phase transition at about 250 K where the dielectric constant shows a slight discontinuous change. The results are compared with those of the isomorphic ferroelectric crystal of (CH3NH3)2AlCl5·6H2O, and discussed.

Gesi, Kazuo

1999-09-01

401

New opportunities in acquisition and analysis of natural abundance complex solid-state 33S MAS NMR spectra: (CH3NH3)2WS4.  

PubMed

Population transfer from the satellite transitions to the central transition in solid-state (33)S MAS NMR, employing WURST inversion pulses, has led to detection of the most complex (33)S MAS NMR spectrum observed so far. The spectrum is that of (CH(3)NH(3))(2)WS(4) and consists of three sets of overlapping resonances for the three non-equivalent S atoms, in accord with its crystal structure. It has been fully analyzed in terms of three sets of (33)S quadrupole coupling and anisotropic/isotropic chemical shift parameters along with their corresponding set of three Euler angles describing the relative orientation of the tensors for these two interactions. The three sets of spectral parameters have been assigned to the three different sulfur sites in (CH(3)NH(3))(2)WS(4) by relating the changes observed for the spectral parameters to the changes in crystal structures in a comparison with the corresponding data for the isostructural (NH(4))(2)WS(4) analog. PMID:19652832

Jakobsen, Hans J; Bildsøe, Henrik; Skibsted, Jørgen; Brorson, Michael; Srinivasan, Bikshandarkoil R; Näther, Christian; Bensch, Wolfgang

2009-06-05

402

Synthesis and Structure of [CH3NH3]2Sb8S13: A Nanoporous Thioantimonate(III) with a Two-Dimensional Channel System  

NASA Astrophysics Data System (ADS)

[CH3NH3]2Sb8S13 has been synthesized as dark-red plate-like crystals by heating Sb and S with an aqueous solution of CH3NH2 between 130 and 190°C. It is triclinic, space group P1¯ , with a = 15.866(3) Å, b = 11.581(2) Å, c = 8.295(2) Å, ? = 71.46(2)°, ? = 75.71(2)°, ? = 82.25(2)°, and Z = 2. The structure was determined and refined with 3342 independent single crystal X-ray reflections (235 parameters, R = 0.061, Rw = 0.052). Each Sb atom forms three short bonds to S reflecting the influence of a lone electron pair. Of the eight nonequivalent Sb atoms, three have one longer bond and four other Sb atoms have two longer bonds to S. The [SbSn] polyhedra share corners and edges to form a three-dimensional framework. This framework is traversed by a system of two types of intersecting channels parallel to [010] and [001]. [CH3NH3]+ cations located in the channel intersections are orientationally disordered; those in pockets of the [010] channels are ordered.

Wang, Xiqu; Liebau, Friedrich

1994-08-01

403

A New Vanadium Oxide Bronze: [NH 3(CH 2) 6NH 3] 10[V 15O 37(Cl)] 2[V 15O 36(Cl)](OH) 3(H 2O) 3 with Clusters [V 15O 36(Cl)] 5? and [V 15O 37(Cl)] 6? Textured by Diaminohexane  

Microsoft Academic Search

A novel mesostructured mixed-valence polyoxovanadate with formula [NH3(CH2)6NH3]10[V15O37(Cl)]2[V15O36(Cl)](OH)3(H2O)3 was synthesized hydrothermally under autogeneous pressure at 443 K for 5 days from an aqueous mixture of NH2(CH2)6NH2 and V2O5 in acidic HCl (1 M) medium. Its structure was solved from single-crystal X-ray diffraction data at room temperature. It crystallizes in the orthorhombic symmetry (space group Pnma) with a=23.616(5), b=44.785(9), c=18.568(4) Å,

Thierry Drezen; Marcel Ganne

1999-01-01

404

a New Vanadium Oxide Bronze: [NH3(CH2)6NH3]10[V15O37(Cl)]2[V15O36(Cl)](OH)3(H2O)3 with Clusters [V15O36(Cl)]5- and [V15O37(Cl)]6- Textured by Diaminohexane  

Microsoft Academic Search

A novel mesostructured mixed-valence polyoxovanadate with formula [NH3(CH2)6NH3]10[V15O37(Cl)]2[V15O36(Cl)](OH)3(H2O)3 was synthesized hydrothermally under autogeneous pressure at 443 K for 5 days from an aqueous mixture of NH2(CH2)6NH2 and V2O5 in acidic HCl (1 M) medium. Its structure was solved from single-crystal X-ray diffraction data at room temperature. It crystallizes in the orthorhombic symmetry (space group Pnma) with a=23.616(5), b=44.785(9), c=18.568(4) Å,

Thierry Drezen; Marcel Ganne

1999-01-01

405

Role of RhAG and AQP1 in NH 3 and CO 2 gas transport in red cell ghosts: a stopped-flow analysis  

Microsoft Academic Search

To clarify the potential role Rh\\/RhAG and AQP1 proteins in erythrocyte gas transport, NH3 and CO2 transport was measured in erythrocyte ghost membrane vesicles from rare human variants (Rhnull, COnull,) and knockout mice (homozygous AQP1–\\/–, Rh–\\/– and Rhag–\\/–) exhibiting well-characterized protein defects. Transport was measured from intracellular pH (pHi) changes in a stopped-flow fluorimeter. NH3 transport was measured in chloride-free

P. Ripoche; D. Goossens; O. Devuyst; P. Gane; Y. Colin; A. S. Verkman; J.-P. Cartron

2006-01-01

406

The composition of Saturn's atmosphere at northern temperate latitudes from Voyager IRIS spectra - NH3, PH3, C2H2, C2H6, CH3D, CH4, and the Saturnian D\\/H isotopic ratio  

Microsoft Academic Search

The vertical distributions and mixing ratios of minor constituents in the northern hemisphere of Saturn are investigated. Results are obtained for NH3, PH3, C2H2, C2H6, CH3D, and CH4; the D\\/H ratio is obtained from the CH4 and CH3D abundances. The NH3 mixing ratio in the upper atmosphere is found to be compatible with the saturated partial pressure. The inferred PH3\\/H2

R. Courtin; D. Gautier; A. Marten; B. Bezard; R. Hanel

1984-01-01

407

Competition between binary ion molecule reactions and ternary association reactions of CH + 3 with NH3 in He buffer gas in the pressure range 0.2-1.7 Torr  

Microsoft Academic Search

The binary reaction of CH+3 with NH3 as well as their ternary association have been investigated in the regime from 0.047 to 0.2 eV, KEcm, using the Innsbruck selected ion drift tube (SIDT). In this energy regime the association rate coefficient declines from 4×10?26 to 6×10?27 cm6 s?1 and the lifetimes of the collision complex (CH+3?NH3)* range from ?10?7 to

A. Saxer; R. Richter; H. Villinger; J. H. Futrell; W. Lindinger

1987-01-01

408

15N-Labeling Studies of the Effect of Water on the Reduction of NO with NH 3 over Chromia SCR Catalysts in the Absence and Presence of O 2  

Microsoft Academic Search

Activity studies and isotopic labelling experiments have been performed to determine the effect of water on the reaction of NO and NH3, in the absence and presence of oxygen, for both amorphous and crystalline (?-Cr2O3) chromia catalysts. The products of the reaction of 15NO and 14NH3 were determined using mass spectrometry, Fourier transform infrared spectroscopy, and gas chromatography. In the

B. L. Duffy; H. E. Curryhyde; N. W. Cant; P. F. Nelson

1995-01-01

409

Implementation of New TPD Analysis Techniques in the Evaluation of Second Order Desorption Kinetics of Cyanogen from Cu(001)  

SciTech Connect

The interactions of cyanide species with a copper (001) surface were studied with temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Adsorbed cyanide species (CN{sub (a)}) undergo recombinative desorption evolving molecular cyanogen (C{sub 2}N{sub 2}). As the adsorbed CN species charge upon adsorption, mutually repulsive dipolar interactions lead to a marked desorption energy reduction with increasing CN{sub (a)} coverages. Two new TPD analysis approaches were developed, which used only accurately discernible observables and which do not assume constant desorption energies, E{sub d}, and pre-exponential values, v. These two approaches demonstrated a linear variation of E{sub d} with instantaneous coverage. The first approach involved an analysis of the variations of desorption peak asymmetry with initial CN coverages. The second quantitative approach utilized only temperatures and intensities of TPD peaks, together with deduced surface coverages at the peak maxima, also as a function of initial surface coverages. Parameters derived from the latter approach were utilized as initial inputs for a comprehensive curve fit analysis technique. Excellent fits for all experimental desorption curves were produced in simulations. The curve fit analysis confirms that the activation energy of desorption of 170-180 kJ/mol at low coverage decreases by up to 14-15 kJ/mol at CN saturation.

E Ciftlikli; E Lee; J Lallo; S Rangan; S Senanayake; B Hinch

2011-12-31

410

Implementation of New TPD Analysis Techniques in the Evaluation of Second Order Desorption Kinetics of Cyanogen from Cu(001)  

SciTech Connect

The interactions of cyanide species with a copper (001) surface were studied with temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Adsorbed cyanide species (CN{sub (a)}) undergo recombinative desorption evolving molecular cyanogen (C{sub 2}N{sub 2}). As the adsorbed CN species charge upon adsorption, mutually repulsive dipolar interactions lead to a marked desorption energy reduction with increasing CN{sub (a)} coverages. Two new TPD analysis approaches were developed, which used only accurately discernible observables and which do not assume constant desorption energies, E{sub d}, and pre-exponential values, v. These two approaches demonstrated a linear variation of E{sub d} with instantaneous coverage. The first approach involved an analysis of the variations of desorption peak asymmetry with initial CN coverages. The second quantitative approach utilized only temperatures and intensities of TPD peaks, together with deduced surface coverages at the peak maxima, also as a function of initial surface coverages. Parameters derived from the latter approach were utilized as initial inputs for a comprehensive curve fit analysis technique. Excellent fits for all experimental desorption curves were produced in simulations. The curve fit analysis confirms that the activation energy of desorption of 170-180 kJ/mol at low coverage decreases by up to 14-15 kJ/mol at CN saturation.

Hinch, B.J.; Senanayake, S.; Ciftlikli, E.Z.; Lee, E.Y.M.; Lallo, J.; Rangan, S.

2010-12-21

411

Herschel/PACS spectroscopy of NGC 4418 and Arp 220: H2O, H218O, OH, 18OH, O I, HCN, and NH3  

NASA Astrophysics Data System (ADS)

Full range Herschel/PACS spectroscopy of the (ultra)luminous infrared galaxies NGC 4418 and Arp 220, observed as part of the SHINING key programme, reveals high excitation in H2O, OH, HCN, and NH3. In NGC 4418, absorption lines were detected with Elower > 800 K (H2O), 600 K (OH), 1075 K (HCN), and 600 K (NH3), while in Arp 220 the excitation is somewhat lower. While outflow signatures in moderate excitation lines are seen in Arp 220 as have been seen in previous studies, in NGC 4418 the lines tracing its outer regions are redshifted relative to the nucleus, suggesting an inflow with ? ? 12 M? yr-1. Both galaxies have compact and warm (Tdust ? 100 K) nuclear continuum components, together with a more extended and colder component that is much more prominent and massive in Arp 220. A chemical dichotomy is found in both sources: on the one hand, the nuclear regions have high H2O abundances, ~10-5, and high HCN/H2O and HCN/NH3 column density ratios of 0.1-0.4 and 2-5, respectively, indicating a chemistry typical of evolved hot cores where grain mantle evaporation has occurred. On the other hand, the high OH abundance, with OH/H2O ratios of ~0.5, indicates the effects of X-rays and/or cosmic rays. The nuclear media have high surface brightnesses (?1013 L?/kpc2) and are estimated to be very thick (NH ? 1025 cm-2). While NGC 4418 shows weak absorption in H218O and 18OH, with a 16O-to-18O ratio of ?250-500, the relatively strong absorption of the rare isotopologues in Arp 220 indicates 18O enhancement, with 16O-to-18O of 70-130. Further away from the nuclear regions, the H2O abundance decreases to ?10-7 and the OH/H2O ratio is reversed relative to the nuclear region to 2.5-10. Despite the different scales and morphologies of NGC 4418, Arp 220, and Mrk 231, preliminary evidence is found for an evolutionary sequence from infall, hot-core like chemistry, and solar oxygen isotope ratio to high velocity outflow, disruption of the hot core chemistry and cumulative high mass stellar processing of 18O. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

González-Alfonso, E.; Fischer, J.; Graciá-Carpio, J.; Sturm, E.; Hailey-Dunsheath, S.; Lutz, D.; Poglitsch, A.; Contursi, A.; Feuchtgruber, H.; Veilleux, S.; Spoon, H. W. W.; Verma, A.; Christopher, N.; Davies, R.; Sternberg, A.; Genzel, R.; Tacconi, L.

2012-05-01

412

Role of RhAG and AQP1 in NH3 and CO2 gas transport in red cell ghosts: a stopped-flow analysis.  

PubMed

To clarify the potential role Rh/RhAG and AQP1 proteins in erythrocyte gas transport, NH3 and CO2 transport was measured in erythrocyte ghost membrane vesicles from rare human variants (Rh(null), CO(null),) and knockout mice (homozygous AQP1-/-, Rh-/- and Rhag-/-) exhibiting well-characterized protein defects. Transport was measured from intracellular pH (pHi) changes in a stopped-flow fluorimeter. NH3 transport was measured in chloride-free conditions with ghosts exposed to 20 mM inwardly directed gradients of gluconate salts of ammonium, hydrazine and methylammonium at 15 degrees C. Alkalinization rates of control samples were 6.5+/-0.3, 4.03+/-0.17, 0.95+/-0.08 s(-1) for each solute, respectively, but were significantly reduced for Rh(null) and CO(null) samples that are deficient in RhAG and AQP1 proteins, respectively. Alkalinization rates of Rh(null) ghosts were about 60%, 83% and 94% lower than that in control ghosts, respectively, for each solute. In CO(null) ghosts, the lack of AQP1 resulted in about 30% reduction of the alkalinization rates as compared to controls, but the transport selectivity of RhAG for the three solutes was preserved. Similar observations were made with ghosts from KO mice Rhag-/- and AQP1-/-. These results confirm the major contribution of RhAG/Rhag in the NH3 conductance of erythrocytes and suggest that the reduction of transport rates in the absence of AQP1 would be better explained by a direct or indirect effect on RhAG/Rhag-mediated transport. When ghosts were preloaded with carbonic anhydrase and exposed to a 25 mM CO2/HCO3- gradient at 6 degrees C, an extremely rapid kinetics of acidification corresponding to CO2 influx was observed. The rate constants were not significantly different between controls and human variants (125+/-6 s(-1)), or between wild-type and KO mice, suggesting no major role of RhAG or AQP1 in CO2 transport, at least in our experimental conditions. PMID:16574458

Ripoche, P; Goossens, D; Devuyst, O; Gane, P; Colin, Y; Verkman, A S; Cartron, J-P

2006-03-29