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1

DFT study of ammonia desorption from the GaN(0001) surface covered with a NH3/NH2 mixture  

NASA Astrophysics Data System (ADS)

Properties of the GaN(0001) surface, fully covered by a mixture of NH3 molecules and NH2 radicals, were investigated by DFT simulations. It is shown that for extremely low ammonia content, the Fermi level at the surface is at valence band maximum (VBM), then at the 25% ammonia in coverage it is depinned, moving upward in the bandgap to reach conduction band minimum (CBM) at higher ammonia percentages. It is shown that the 25% ammonia in the coverage is corresponding to a flat band configuration in accordance with ECR arguments. The stability of the mixed NH2/NH3 coverage with respect to detachment of ammonia molecules or molecular hydrogen was also investigated. It was shown that high ammonia fraction leads to instability of the coverage due to detachment of ammonia or of molecular hydrogen. The instability point is reached for 36% and 41% fraction of ammonia in the coverage for desorption of molecular hydrogen and ammonia, respectively. The energy barrier for detachment of molecular hydrogen is consistently higher since the H2 molecule has to be created first in the course of desorption process. The ammonia is simply detached in the molecular form so that the high energy intermediate configuration is absent.

Kempisty, Pawel; Strak, Pawel; Sakowski, Konrad; Krukowski, Stanislaw

2014-10-01

2

Reduction Kinetics of Graphene Oxide Determined by Electrical Transport Measurements and Temperature Programmed Desorption  

E-print Network

and Temperature Programmed Desorption Inhwa Jung, Daniel A. Field, Nicholas J. Clark, Yanwu Zhu, Dongxing Yang, Richard D. Piner, Sasha Stankovich,§ Dmitriy A. Dikin,§ Heike Geisler,| Carl A. Ventrice, Jr

3

Temperature programmed desorption from LiAlO 2 treated with H 2  

NASA Astrophysics Data System (ADS)

Temperature programmed desorption (TPD) measurements have been made of H 2O and H 2 desorption from LiAlO 2 treated at 923 K with He-H 2 mixtures containing 990, 495, and 247 vppm H 2. Desorptions were into sweep gases of pure He and into He-H 2 mixtures. The H 2O and H 2 desorption peaks were shown to be the sums of first order subpeaks which had reproducible desorption activation energy and pre-exponential terms. For H 2O desorption, the activation energies were 96, 117, and 134 kJ/mol (23, 28, and 32 kcal/mol). (Earlier work had identified an additional peak with an activation energy of 75 kJ/mol (18 kcal/mol.) Enhancement of desorption of H 2O by H 2 in the sweep gas was confirmed. The enhancement results not from modifying the activation energies and pre-exponential terms for the various sites but from changes in the populations of sites participating in the desorption process so that sites with lower activation energies are increasingly involved. For those runs with He as the sweep gas, desorption of H 2 could be observed. The subpeaks involved had activation energies within approximately 4 kJ/mol (1 kcal/mol) higher than the analogous peaks for H 2O desorption.

Fischer, Albert K.

1992-09-01

4

Temperature-programmed desorption of tritium loaded into beryllium  

NASA Astrophysics Data System (ADS)

The influence of grain size and amount of beryllium oxide BeO on the tritium release characteristics of the S-65H and I-220H beryllium grades was investigated. The beryllium samples were loaded with hydrogen at a temperature of 1123 K for 6 h at a pressure of 4 bar in a gas mixture of molecular protium with 45 wppm tritium. The tritium release measurements were performed using a stepped heating ramp with steps of 50 K in the temperature range of 473-1373 K with a duration of each step of 1 h. Five major release peaks were observed. Interpretations of the nature of the peaks are suggested. In particular, we ascribe the low-temperature peaks (300-723 K) to desorption from the surface and connect the shift of the peak at elevated temperature (900-1000 K) with the enhanced diffusion of hydrogen along grain boundaries. The high temperature peak (1123-1373 K) is attributed to dissociation of beryllium hydroxide Be(OH)2, which is formed on the surface and grain boundaries of a sample in a reaction of hydrogen isotopes with beryllium oxide.

Chakin, V.; Rolli, R.; Vladimirov, P.; Kurinskiy, P.; Klimenkov, M.; Moeslang, A.; Ryczek, L.; Dorn, C.; Markovsky, A.

2009-12-01

5

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

6

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

7

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

8

Solid-phase microextraction with temperature-programmed desorption for the analysis of iodination disinfection byproducts.  

PubMed

An analytical approach for the determination of chlorination and iodination disinfection byproducts based on solid-phase microextraction (SPME) was developed. Solid-phase microextraction presents a simple, rapid, sensitive, and solvent-free approach to sample preparation in which analytes in either air or water matrixes are extracted into the polymeric coating of an optical fiber. Analytes are subsequently thermally desorbed in the injection port of a gas chromatograph for separation, detection, and quantitation. Thermal degradation of iodoform was observed during desorption from a polyacrylate fiber in initial GC/MS and GC/ECD experiments. Experiments were designed to determine SPME conditions that would allow quantification without significant degradation of analytes. Isothermal and temperature-programmed thermal desorptions were evaluated for efficacy in transferring analytes with wide-ranging volatilities and thermal stabilities into chromatographic analysis columns. A temperature-programmed desorption (TPD) (120-200 degrees C at 5 degrees C/min with an on-column injection port or 150-200 degrees C at 25 degrees C/min with a split/splitless injection port) was able to efficiently remove analytes with wide-ranging volatilities without causing thermal degradation. The SPME-TPD method was linear over 2-3 orders of magnitude with an electron capture detector and detection limits were in the submicrogram per liter range. Precision and detection limits for selected trihalomethanes were comparable to those of EPA method 551. Extraction efficiencies were not affected by the presence of 10 mg/L soap, 15 mg/L sodium iodide, and 6000 mg/L sodium thiosulfate. The SPME-TPD technique was applied to the determination of iodination disinfection byproducts from individual precursor compounds using GC/MS and to the quantitation of iodoform at trace levels in a water recycle system using GC/ECD. PMID:9470491

Frazey, P A; Barkley, R M; Sievers, R E

1998-02-01

9

Molecular Hydrogen Formation on Low Temperature Surfaces in Temperature Programmed Desorption Experiments  

E-print Network

The study of the formation of molecular hydrogen on low temperature surfaces is of interest both because it allows to explore elementary steps in the heterogeneous catalysis of a simple molecule and because of the applications in astrochemistry. Here we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations and the activation energies of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results can thus be used to evaluate the formation rate of H_2 on dust grains under the actual conditions...

Vidali, G; Li, L; Roser, J; Manico, G; Mehl, R; Lederhendler, A; Perets, H B; Brucato, J R; Biham, O

2007-01-01

10

Molecular Hydrogen Formation on Low Temperature Surfaces in Temperature Programmed Desorption Experiments  

E-print Network

The study of the formation of molecular hydrogen on low temperature surfaces is of interest both because it allows to explore elementary steps in the heterogeneous catalysis of a simple molecule and because of the applications in astrochemistry. Here we report results of experiments of molecular hydrogen formation on amorphous silicate surfaces using temperature-programmed desorption (TPD). In these experiments beams of H and D atoms are irradiated on the surface of an amorphous silicate sample. The desorption rate of HD molecules is monitored using a mass spectrometer during a subsequent TPD run. The results are analyzed using rate equations and the activation energies of the processes leading to molecular hydrogen formation are obtained from the TPD data. We show that a model based on a single isotope provides the correct results for the activation energies for diffusion and desorption of H atoms. These results can thus be used to evaluate the formation rate of H_2 on dust grains under the actual conditions present in interstellar clouds.

G. Vidali; V. Pirronello; L. Li; J. Roser; G. Manico; R. Mehl; A. Lederhendler; H. B. Perets; J. R. Brucato; O. Biham

2008-11-21

11

Qualitative and quantitative analysis of complex temperature-programmed desorption data by multivariate curve resolution  

NASA Astrophysics Data System (ADS)

The substantial amount of information carried in temperature-programmed desorption (TPD) experiments is often difficult to mine due to the occurrence of competing reaction pathways that produce compounds with similar mass spectrometric features. Multivariate curve resolution (MCR) is introduced as a tool capable of overcoming this problem by mathematically detecting spectral variations and correlations between several m/z traces, which is later translated into the extraction of the cracking pattern and the desorption profile for each desorbate. Different from the elegant (though complex) methods currently available to analyze TPD data, MCR analysis is applicable even when no information regarding the specific surface reaction/desorption process or the nature of the desorbing species is available. However, when available, any information can be used as constraints that guide the outcome, increasing the accuracy of the resolution. This approach is especially valuable when the compounds desorbing are different from what would be expected based on a chemical intuition, when the cracking pattern of the model test compound is difficult or impossible to obtain (because it could be unstable or very rare), and when knowing major components desorbing from the surface could in more traditional methods actually bias the quantification of minor components. The enhanced level of understanding of thermal processes achieved through MCR analysis is demonstrated by analyzing three phenomena: i) the cryogenic desorption of vinyltrimethylsilane from silicon, an introductory system where the known multilayer and monolayer components are resolved; ii) acrolein hydrogenation on a bimetallic Pt-Ni-Pt catalyst, where a rapid identification of hydrogenated products as well as other desorbing species is achieved, and iii) the thermal reaction of Ti[N(CH 3) 2] 4 on Si(100), where the products of surface decomposition are identified and an estimation of the surface composition after the thermal reaction is afforded. Since this work constitutes, to the best of our knowledge, the first effort to introduce multivariate analysis to TPD data, the procedures, algorithms and strategies employed are described in full detail.

Rodrguez-Reyes, Juan Carlos F.; Teplyakov, Andrew V.; Brown, Steven D.

2010-10-01

12

Study of temperature-programmed desorption of tert-butylamine to measure the surface acidity of solid catalysts  

SciTech Connect

In this paper, the technique of temperature-programmed desorption of tert-butylamine is described to measure the surface acidity of solid catalysts. The use of this base has advantages over the use of ammonia, pyridine, and n-butylamine. The desorption measurement is carried out by two methods, gas chromatography and thermogravimetry, and the advised conditions are described for both methods. Catalysts of SiO{sub 2}/Al{sub 2}O{sub 3}, bifunctionals of Ni-SiO{sub 2}/Al{sub 2}O{sub 3}, and a commercial cracking zeolite have been studied. A comparison of the desorption results with those of the other acidity measurement techniques (such as titration with n-butylamine in the liquid phase and kinetic measurement of isomerization of n-butenes as the test reaction) allows the acidity measured with tert-butylamine desorption to be classified as strong, corresponding to the active sites in most of the reactions among the hydrocarbon compounds catalyzed by acids.

Aguayo, A.T.; Arandes, J.M.; Olazar, M.; Bilbao, J. (Dept. de Ingenieria Quimica, Univ. del Pais, Vasco. Apartado 655, 48080 Bilbao (ES))

1991-08-01

13

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

14

A technique for extending the precision and the range of temperature programmed desorption toward extremely low coverages  

NASA Astrophysics Data System (ADS)

In this paper, an improvement of the temperature programmed desorption (TPD) technique is introduced, which facilitates fully automated sampling of TPD spectra with excellent reproducibility, especially useful for extremely low coverages. By averaging many sampled TPD spectra, the range of the TPD technique can be extended toward lower coverages, as well as the quality of the spectra can be improved. This allows for easy extraction of information about the adsorbate-surface bond. A state of the art TPD apparatus with a two chamber setup and a high quality quadrupole mass spectrometer was extended by automated components. These are an automated gas dosing system, ensuring precise dosing of gas, combined with a motor driven sample manipulation unit and a liquid nitrogen cryostat with automatic refilling. In addition all components were controlled by a computer. A large number of TPD cycles could be sampled without the need of interaction of an operator. Here, it is shown for up to more than 400 TPD cycles. This opens a wide range of new interesting applications for the TPD technique, especially in the limit of zero coverage. Here, basic experiments on well known adsorbate systems are shown to view the ability and limit of this approach.

Haegel, Stefan; Zecho, Thomas; Wehner, Stefan

2010-03-01

15

Dosimeter-type NOx sensing properties of KMnO4 and its electrical conductivity during temperature programmed desorption.  

PubMed

An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT) for NOx storage catalysts (NSC) enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD). The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1) time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2) during the short-term thermal NOx release. PMID:23549366

Gro, Andrea; Kremling, Michael; Marr, Isabella; Kubinski, David J; Visser, Jacobus H; Tuller, Harry L; Moos, Ralf

2013-01-01

16

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

17

Ab initio potential energy surfaces for NH,,3 -...NH,,3 -  

E-print Network

Conversely, direct methods such as Stark deceleration14 and buffer gas cooling15 employ a scheme in which pre-space density. At present, direct-cooling methods for NH are limited to temperatures of a few hundredAb initio potential energy surfaces for NH,,3 - ...­NH,,3 - ... with analytical long range Liesbeth

18

Characterization of the carbonaceous residues on a used Ni/SiO[sub 2] hydrogenation catalyst by temperature-programmed desorption methods  

SciTech Connect

The carbonaceous residues formed during hydrogenation of 2-ethyl-2-hexenal (A) to 2-ethyl-hexanal (B) and 2-ethyl-hexanal (C) on a Ni/SiO[sub 2] catalyst has been studied by temperature-programmed desorption (TPD), temperature-programmed hydrogenation (TPH), temperature-programmed oxidation (TPO), and by extraction. TPD displayed below 200[degrees]C dimers, B and C. Between 200 and 400[degrees]C B, C, and alkenes were detected, and at higher temperatures alkenes and some benzenes. TPH showed the same compounds, except that methane was formed above 500[degrees]C. Both TPD and TPH produced CO, CO[sub 2], and H[sub 2]O above 450[degrees]C formed by reaction of carbonaceous deposits or H[sub 2] with unreduced NiO. TPO showed a large peak just below 400[degrees]C, a shoulder at 400-500[degrees]C, and in some experiments a small peak at about 150[degrees]C. The H/C ratio was 1.5-2.0. Above 200[degrees]C the H/C ratio increased with temperature during TPO. The total amount of carbon atoms on the surface was 10-20 times the number of surface nickel atoms indicating that carbon was also present on the support. The extract, after extraction of the used catalyst in methanol or methylene chloride, contained mainly 2-ethyl-hexanal and some 2-ethyl-hexanal. 13 refs., 8 figs., 1 tab.

Wrammersfors, A.; Andersson, B. (Chalmers Univ. of Technology, Goeteborg (Sweden))

1994-05-01

19

Temperature-programmed desorption investigation of the adsorption and reaction of butene isomers on Pt(111) and ordered Pt-Sn surface alloys  

SciTech Connect

The influence of alloyed Sn on the chemistry of C{sub 4} butene isomers, including 1-butene, cis-2-butene, and isobutene, chemisorbed on Pt(111) was investigated by temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and low-energy electron diffraction (LEED). Pt-Sn alloy chemistry was probed by investigation of two ordered surface alloys formed when Sn atoms were incorporated within the topmost layer on a Pt(111) substrate. All three butenes undergo decomposition on Pt(111) during TPD which accounts for 50-60% of the chemisorbed monolayer. Alloying Sn into the surface causes a large reduction in the reactivity of the surface, and the fraction of the chemisorbed layer which decomposes is decreased to 3-7% on the (2 x 2) alloy, and no decomposition occurs on the ({radical}3 x {radical}3)R30{degree} alloy. The strong reduction of decomposition on these two surface alloys may be due to the elimination of adjacent pure Pt 3-fold hollow sites. No large changes occur in the coverage of chemisorbed monolayer of butenes in the presence of up to 33% of a monolayer of alloyed Sn, showing that the adsorption ensemble requirement for chemisorption of these alkenes on Pt(111) and the two Sn/Pt(111) alloys is at most a few Pt atoms. 39 refs., 15 figs., 1 tab.

Tsai, Y.L.; Koel, B.E. [Univ. of Southern California, Los Angeles, CA (United States)] [Univ. of Southern California, Los Angeles, CA (United States)

1997-04-10

20

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

21

Thermal desorption of circumstellar and cometary ice analogs  

NASA Astrophysics Data System (ADS)

Context. Thermal annealing of interstellar ices takes place in several stages of star formation. Knowledge of this process comes from a combination of astronomical observations and laboratory simulations under astrophysically relevant conditions. Aims: For the first time we present the results of temperature programmed desorption (TPD) experiments with pre-cometary ice analogs composed of up to five molecular components: H2O, CO, CO2, CH3OH, and NH3. Methods: The experiments were performed with an ultra-high vacuum chamber. A gas line with a novel design allows the controlled preparation of mixtures with up to five molecular components. Volatiles desorbing to the gas phase were monitored using a quadrupole mass spectrometer, while changes in the ice structure and composition were studied by means of infrared spectroscopy. Results: The TPD curves of water ice containing CO, CO2, CH3OH, and NH3 present desorption peaks at temperatures near those observed in pure ice experiments, volcano desorption peaks after water ice crystallization, and co-desorption peaks with water. Desorption peaks of CH3OH and NH3 at temperatures similar to the pure ices takes place when their abundance relative to water is above ~3% in the ice matrix. We found that CO, CO2, and NH3 also present co-desorption peaks with CH3OH, which cannot be reproduced in experiments with binary water-rich ice mixtures. These are extensively used in the study of thermal desorption of interstellar ices. Conclusions: These results reproduce the heating of circumstellar ices in hot cores and can be also applied to the late thermal evolution of comets. In particular, TPD curves represent a benchmark for the analysis of the measurements that mass spectrometers on board the ESA-Rosetta cometary mission will perform on the coma of comet 67P/Churyumov-Gerasimenko, which will be active before the arrival of Rosetta according to our predictions.

Martn-Domnech, R.; Muoz Caro, G. M.; Bueno, J.; Goesmann, F.

2014-04-01

22

Sticking probability and adsorption process of NH 3 on Si(100) surface  

NASA Astrophysics Data System (ADS)

The absolute sticking probability of NH 3 molecules on Si(100) surface was measured using a NH 3 molecular beam. Also taking into account the measured angular distribution of the scattered NH 3 molecules, it is concluded that the adsorption of NH 3 follows a trapping-mediated mechanism. From the dependence of the initial sticking probability on the sample temperature, the difference between the activation energies for desorption and chemisorption from a precursor state, ( Edes- Ead), was estimated. The coverage dependence of the sticking probability, s( ?), was also measured. From the sample temperature dependence of s( ?), parameters for the migration of the NH 3 precursor were derived using the Kisliuk model. The kinetics of the adsorption of NH 3 on the Si(100) is discussed on the basis of this model.

Takaoka, T.; Kusunoki, I.

1998-09-01

23

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

24

A global budget for atmospheric NH 3  

Microsoft Academic Search

We provide an assessment of the global sources of NH3 in the atmosphere, which indicates an annual flux of about 75 Tg of N as NH3. The emissions from land are dominated by the release of NH3 during the hydrolysis of urea from the urine of domestic animals (32 TgN\\/yr) and by emanations from soils in unmanaged ecosystems (10 TgN\\/yr)

William H. Schlesinger; Anne E. Hartley

1992-01-01

25

Low Temperature Catalyst for NH3 Removal  

NASA Technical Reports Server (NTRS)

Air revitalization technologies maintain a safe atmosphere inside spacecraft by the removal of C02, ammonia (NH3), and trace contaminants. NH3 onboard the International Space Station (ISS) is produced by crew metabolism, payloads, or during an accidental release of thermal control refrigerant. Currently, the ISS relies on removing NH3 via humidity condensate and the crew wears hooded respirators during emergencies. A different approach to cabin NH3 removal is to use selective catalytic oxidation (SCO), which builds on thermal catalytic oxidation concepts that could be incorporated into the existing TCCS process equipment architecture on ISS. A low temperature platinum-based catalyst (LTP-Catalyst) developed at KSC was used for converting NH3 to H20 and N2 gas by SCO. The challenge of implementing SCO is to reduce formation of undesirable byproducts like NOx (N20 and NO). Gas mixture analysis was conducted using FTIR spectrometry in the Regenerable VOC Control System (RVCS) Testbed. The RVCS was modified by adding a 66 L semi-sealed chamber, and a custom NH3 generator. The effect of temperature on NH3 removal using the LTP-Catalyst was examined. A suitable temperature was found where NH3 removal did not produce toxic NO, (NO, N02) and N20 formation was reduced.

Monje, Oscar; Melendez, Orlando

2013-01-01

26

Bonding of NH3 to Cu  

NASA Technical Reports Server (NTRS)

Bagus et al. (1984) have studied the chemisorption of NH3 at the on-top site of Cu(100), using a cluster model, Cu5(1,4)NH3. On the basis of the value of the NH3 chemisorption energy obtained, it was concluded that NH3 chemisorbs directly above a Cu atom. In order to consider also other sites, Al(111) was substituted for Cu(100). Chemisorption on Al can be quite different from a transition metal, however, and questions arise regarding the suitability of the choice of the Al model. Thus, in this note, NH3 into hollows is considered for Cu(111). Attention is given to the conduction of self-consistent field calculations, problems of site determination, and the consideration of electrostatic interaction.

Bauschlicher, C. W., Jr.

1985-01-01

27

Mn-CeOx/Ti-PILCs for selective catalytic reduction of NO with NH3 at low temperature.  

PubMed

Titanium-pillared clays (Ti-PILCs) were obtained by different ways from TiCl4, Ti(OC3H7)4 and TiOSO4, respectively. Mn-CeO(x)/)Ti-PILCs were then prepared and their activities of selective catalytic reduction (SCR) of NO with NH3 at low-temperature were evaluated. Mn-CeO(x)/Ti-PILCs were characterized by X-ray diffraction, N2 adsorption, Fourier transform infrared spectroscopy, thermal analysis, temperature-programmed desorption of ammonia and H2-temperature-programmed reduction. It was found that Ti-pillar tend to be helpful for the enlargement of surface area, pore volume, acidity and the enhancement of thermal stability for Mn-CeO(x)/Ti-PILCs. Mn-CeO(x)/Ti-PILCs catalysts were active for the SCR of NO. Among three resultant Mn-CeO(x)/Ti-PILCs, the catalyst from TiOSO4 showed the highest activity with 98% NO conversion at 220 degrees C, it also exhibited good resistance to H2O and SO2 in flue gas. The catalyst from TiCl4 exhibited the lowest activity due to the unsuccessful pillaring process. PMID:22655365

Shen, Boxiong; Ma, Hongqing; Yao, Yan

2012-01-01

28

NH3-TPD-MS study of Ce effect on the surface of Mn- or Fe-exchanged zeolites for selective catalytic reduction of NOx by ammonia  

NASA Astrophysics Data System (ADS)

The selective catalytic reduction (SCR) of NOx with NH3 is considered to be a promising technique for the efficient reduction of highly detrimental NOx emitted from diesel engine vehicles to N2. This study was focused on a series of catalysts with ZSM-5 as support, prepared by Mn- or Fe-exchange followed by wet impregnation of Ce, or Fe or Mn. These catalysts were characterized by temperature-programmed desorption coupled with a mass spectrometer using ammonia (NH3-TPD-MS). Specifically, NH3-TPD-MS was used as a means of identifying the various strengths of acid sites and their relative abundance in an attempt to explain the effect of the catalyst surface acid sites on DeNOx activity. Acid sites with adsorption energies ranging from 47.0 to 75.6 kJ/mol were detected for all of the catalysts. For the same concentration of exchanged metal it was found that the DeNOx activity depends strongly on the type of metal. Furthermore, the acid site strength and distribution depend on the active metal and correlate with the observed DeNOx catalyst activity. Additionally, SEM metal mapping images confirmed the presence of well dispersed active metal on the surface of all catalysts. The catalysts with bimetallic active phase were stable and demonstrated high NOx conversion over a broad temperature range. Impregnation of metal-exchanged zeolites with Ce enhanced the low temperature NOx conversion. Observed differences of activity between the various catalysts of this study may be due to the formation of new ammonia activation sites. The ammonia desorption profile during the elevation of temperature was correlated to the DeNOx activity.

Stanciulescu, M.; Bulsink, P.; Caravaggio, G.; Nossova, L.; Burich, R.

2014-05-01

29

Chitosan (polysaccharide) Cationic polyelectrolyte (NH3  

E-print Network

Chitosan (polysaccharide) Cationic polyelectrolyte (NH3 +) pH dependant solubility (pH to hydrogen evolution Chitosan molecules deprotonate and immobilized at electrode surface Electrochemical reaction rate depends on current density Electrochemical deposition of chitosan Thin film formation

Rubloff, Gary W.

30

A study of the adsorption of NH 3 and SO 2 on leaf surfaces  

NASA Astrophysics Data System (ADS)

The adsorption of NH 3 and SO 2 on the external leaf surface of bean ( Phaseolus vulgaris L.) and poplar ( Populus euramericana L.) was studied. The adsorbed quantities increased strongly with increasing air humidity, indicating that water on the leaf surface plays a major role in the interaction of these gases with the leaf surface. On the other hand temperature in the range between 15 and 26C had no significant influence. The adsorbed quantities of NH 3 at a specific air humidity appeared to be proportional to NH 3 concentration. This proportionality was less clear for SO 2. The affinity of SO 2 for the leaf surface was found to be approximately twice that of NH 3. A mixture of these gases in the air mutually stimulated their adsorption on the leaf. No significant desorption or uptake of these gases through the cuticle could be detected, indicating that the bulk of the adsorbed gases remains associated with the cuticle.

Van Hove, L. W. A.; Adema, E. H.; Vredenberg, W. J.; Pieters, G. A.

31

TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3N)  

Atmospheric Science Data Center

TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3N) News: TES News ... Level: L2 Instrument: TES/Aura L2 Ammonia Spatial Coverage: 5.3 x 8.5 km nadir ... Data: TES Order Tool Parameters: Ammonia Order Data: Reverb: Order Data ...

2014-12-09

32

TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3NS)  

Atmospheric Science Data Center

TES/Aura L2 Ammonia (NH3) Nadir (TL2NH3NS) News: TES News ... Level: L2 Platform: TES/Aura L2 Ammonia Spatial Coverage: 5.3 x 8.5 km nadir ... Data: TES Order Tool Parameters: Ammonia Order Data: Reverb: Order Data ...

2014-12-10

33

Development of ultralow energy (110 eV) ion scattering spectrometry coupled with reflection absorption infrared spectroscopy and temperature programmed desorption for the investigation of molecular solids  

SciTech Connect

Extremely surface specific information, limited to the first atomic layer of molecular surfaces, is essential to understand the chemistry and physics in upper atmospheric and interstellar environments. Ultra low energy ion scattering in the 110 eV window with mass selected ions can reveal extremely surface specific information which when coupled with reflection absorption infrared (RAIR) and temperature programmed desorption (TPD) spectroscopies, diverse chemical and physical properties of molecular species at surfaces could be derived. These experiments have to be performed at cryogenic temperatures and at ultra high vacuum conditions without the possibility of collisions of neutrals and background deposition in view of the poor ion intensities and consequent need for longer exposure times. Here we combine a highly optimized low energy ion optical system designed for such studies coupled with RAIR and TPD and its initial characterization. Despite the ultralow collision energies and long ion path lengths employed, the ion intensities at 1 eV have been significant to collect a scattered ion spectrum of 1000 counts/s for mass selected CH{sub 2}{sup +}.

Bag, Soumabha; Bhuin, Radha Gobinda; Methikkalam, Rabin Rajan J.; Pradeep, T., E-mail: pradeep@iitm.ac.in [DST Unit of Nanoscience (DST UNS), Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036 (India); Kephart, Luke; Walker, Jeff; Kuchta, Kevin; Martin, Dave; Wei, Jian [Extrel CMS, LLC, 575 Epsilon Drive, Pittsburgh, Pennsylvania 15238 (United States)] [Extrel CMS, LLC, 575 Epsilon Drive, Pittsburgh, Pennsylvania 15238 (United States)

2014-01-15

34

Diode laser saturation spectroscopy of NH3  

NASA Technical Reports Server (NTRS)

Saturation of molecular transitions using a tuneable diode laser was demonstrated for the first time using a standing-wave cavity configuration with an f/8 beam focussed at the sample. Observed saturation effects in NH3 transitions near 888/cm include sub-Doppler (Lamb-dip) resonances at line center.

Jennings, D. E.

1978-01-01

35

Growth of an Ultrathin Zirconia Film on Pt3Zr Examined by High-Resolution X-ray Photoelectron Spectroscopy, Temperature-Programmed Desorption, Scanning Tunneling Microscopy, and Density Functional Theory  

PubMed Central

Ultrathin (?3 ) zirconium oxide films were grown on a single-crystalline Pt3Zr(0001) substrate by oxidation in 1 107 mbar of O2 at 673 K, followed by annealing at temperatures up to 1023 K. The ZrO2 films are intended to serve as model supports for reforming catalysts and fuel cell anodes. The atomic and electronic structure and composition of the ZrO2 films were determined by synchrotron-based high-resolution X-ray photoelectron spectroscopy (HR-XPS) (including depth profiling), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. Oxidation mainly leads to ultrathin trilayer (OZrO) films on the alloy; only a small area fraction (1015%) is covered by ZrO2 clusters (thickness ?0.510 nm). The amount of clusters decreases with increasing annealing temperature. Temperature-programmed desorption (TPD) of CO was utilized to confirm complete coverage of the Pt3Zr substrate by ZrO2, that is, formation of a closed oxide overlayer. Experiments and DFT calculations show that the core level shifts of Zr in the trilayer ZrO2 films are between those of metallic Zr and thick (bulklike) ZrO2. Therefore, the assignment of such XPS core level shifts to substoichiometric ZrOx is not necessarily correct, because these XPS signals may equally well arise from ultrathin ZrO2 films or metal/ZrO2 interfaces. Furthermore, our results indicate that the common approach of calculating core level shifts by DFT including final-state effects should be taken with care for thicker insulating films, clusters, and bulk insulators.

2014-01-01

36

Condensation and vaporization studies of CH3OH and NH3 ices: Major implications for astrochemistry  

NASA Technical Reports Server (NTRS)

In an extension of previously reported work on ices containing H2O, CO, CO2, SO2, H2S, and H2, we present measurements of the physical and infrared spectral properties of ices containing CH3OH and NH3. The condensation and sublimation behavior of these ice systems is discussed and surface binding energies are presented for all of these molecules. The surface binding energies can be used to calculate the residence times of the molecules on grain surfaces as a function of temperature. It is demonstrated that many of the molecules used to generate radio maps of and probe conditions in dense clouds, for example CO and NH3, will be significantly depleted from the gas phase by condensation onto dust grains. Attempts to derive total column densities solely from radio maps that do not take condensation effects into account may vastly underestimate the true column densities of any given species. Simple CO condensation onto and vaporization off of grains appears to be capable of explaining the observed depletion of gas phase CO in cold, dense molecular cores. This is not the case for NH3, however, where thermal considerations alone predict that all of the NH3 should be condensed onto grains. The fact that some gas phase NH3 is observed indicates that additional desorption processes must be involved. The surface binding energies of CH3OH, in conjunction with this molecule's observed behavior during warm up in H2O-rich ices, is shown to provide an explanation of the large excess of CH3OH seen in many warm, dense molecular cores. The near-infrared spectrum and associated integrated band strengths of CH3OH-containing ice are given, as are middle infrared absorption band strengths for both CH3OH and NH3.

Sandford, Scott A.; Allamandola, Louis J.

1993-01-01

37

Preparation and Crystal Structures of Mg(NH 3) 2Cl 2, Mg(NH 3) 2Br 2, and Mg(NH 3) 2I 2  

NASA Astrophysics Data System (ADS)

Diammine magnesium halides Mg(NH3)2X2 with X=Cl, Br, I have been prepared from magnesium metal and the corresponding ammonium halide in steel autoclaves at 350C. Mg(NH3)2Cl2 crystallizes in the Cd (NH3)2Cl2-structure type: Rietveld X-ray analysis, Cmmm, Z=2; a=8.1810(2) , b=8.2067(2) , c=3.7550(1) , R(F2)Bragg=5.9%. The bromide and the iodide are isotypic and crystallize in a new structure type: single crystal X-ray analysis, Pbam, Z=2; Mg(NH3)2Br2: a=5.944(2) , b=11.876(3) , c=3.983(1) , R1 (F)=0.045; Mg(NH3)2I2: a=6.285(1) , b=12.559 (3) , c=4.302(1) , R1(F)=0.080. Both structure types contain chains of edge-sharing octahedra 1?[MgX4/2(NH3)2] running along c. These are arranged in different ways relative to one another in the two structure types.

Leineweber, A.; Friedriszik, M. W.; Jacobs, H.

1999-10-01

38

Adsorption of NH3 onto activated carbon prepared from palm shells impregnated with H2SO4.  

PubMed

Adsorption of ammonia (NH3) onto activated carbons prepared from palm shells impregnated with sulfuric acid (H2SO4) was investigated. The effects of activation temperature and acid concentration on pore surface area development were studied. The relatively large micropore surface areas of the palm-shell activated carbons prepared by H2SO4 activation suggest their potential applications in gas adsorption. Adsorption experiments at a fixed temperature showed that the amounts of NH3 adsorbed onto the chemically activated carbons, unlike those prepared by CO2 thermal activation, were not solely dependent on the specific pore surface areas of the adsorbents. Further adsorption tests for a wide range of temperatures suggested combined physisorption and chemisorption of NH3. Desorption tests at the same temperature as adsorption and at an elevated temperature were carried out to confirm the occurrence of chemisorption due to the interaction between NH3 and some oxygen functional groups via hydrogen bonding. The surface functional groups on the adsorbent surface were detected by Fourier transform infrared spectroscopy. The amounts of NH3 adsorbed by chemisorption were correlated with the contents of elemental oxygen present in the adsorbents. Mechanisms for chemical activation and adsorption processes are proposed based on the observed phenomena. PMID:15571683

Guo, Jia; Xu, Wang Sheng; Chen, Yan Lin; Lua, Aik Chong

2005-01-15

39

Assessment of acidbase strength distribution of ion-exchanged montmorillonites through NH 3 and CO 2TPD measurements  

Microsoft Academic Search

Distribution of the acidbase strengths of various ion-exchanged montmorillonites was assessed through thermal programmed desorption (TPD) of NH3 and CO2. Accurate acidbase measurements can be achieved via deconvolution of perfectly symmetrical peaks, under optimal carrier gas throughput and heating rate, estimated though a factorial experiment design. No neutral clay samples without interactions with carbon dioxide or ammonia were found. All

A. Azzouz; D. Nistor; D. Miron; A. V. Ursu; T. Sajin; F. Monette; P. Niquette; R. Hausler

2006-01-01

40

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 210-7 to 310-6 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.; Schier, 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

41

NH3 column abundances over Lauder, New Zealand  

NASA Technical Reports Server (NTRS)

Gaseous NH3 has been observed in the atmosphere over central New Zealand with infrared absorption spectra. The amount of NH3 shows marked variability, which is strongly correlated with time of day and season. The pattern is similar to data obtained in Denver, Colorado, but is much more variable than data from Hampton, Virginia. The rapid variability indicates a residence time of 8 hours in some cases.

Murcray, Frank J.; Goldman, Aaron; Matthews, Andrew; Johnston, Paul; Rinsland, Curtis

1989-01-01

42

Synthesis Of Nh3 In Titan's Upper Atmosphere  

NASA Astrophysics Data System (ADS)

Cassini INMS observations of Titan's upper atmosphere measured densities 1.5101; cm-3 of NH4+ [Cravens et al. Geophys. Res. Letts., 33, L07105, 2006., Vuitton et al. Icarus, 191, 722-742. 2008]. The density of the NH4+ ion is closely related to the density of NH3 through proton exchange and electron recombination reactions. Calculations based on this chemistry imply a NH3 abundance of several ppm in the upper atmosphere, roughly two orders of magnitude larger than pre-Cassini predictions [Wilson and Atreya, J. Geophys. Res. E06002, doi:1029/2003JE002181, 2004]. We investigate several chemical schemes for production of NH3. Using a 1D photochemical model, we show that the densities of amines (NH, NH2, CH2NH, CH3NH2) are quite large in the upper atmosphere and the reaction NH2 + H2CN? NH3 + HCN is particularly important for the synthesis of NH3. We also explore the potential importance of heterogeneous chemistry on aerosol surfaces for synthesis of NH3. The amine radicals in Titan's upper atmosphere are likely incorporated into other, more complex organic molecules as well. This work has been supported by a grant from NASA's Planetary Atmospheres program.

Yelle, Roger; Vuitton, V.; Lavvas, P.; Smith, M.; Horst, S.; Cui, J.

2009-09-01

43

The NH3 spectrum in Saturn's 5 micron window  

NASA Technical Reports Server (NTRS)

Spectra of Saturn's 5-micron window were obtained at the Infrared Telescope Facility on Mauna Kea, Hawaii. The spectra have a resolution of 1.2/cm, and some exhibit extremely low amounts of approximately 300-micron ppt telluric H2O. The Saturn spectra show absorptions by the 2nu2 band of NH3. Long-path laboratory comparison spectra of NH3 were acquired and show considerable deviations in intensity from theoretical predictions. The calibration of Saturn's observed NH3 features with the laboratory data gives 2.0 + or - 0.5 m-amagat of NH3 using the 2nu2 Q-branch at 5.32 microns. The R(1) and R(2) lines yield an abundance about 3 times greater. Absorptions outside the range of the Q-branch can be accounted for by solid NH3 of 10-20 microns equivalent path length. The origin of Saturn's 5-micron flux is mostly thermal with some admixture of solar reflected radiation. A depletion of Saturn's NH3 abundance below the solar value is indicated, but confirmation of this conclusion will require a better understanding of the atmospheric penetration depth at 5 microns and more rigorous modeling of the spectral line formation.

Bjoraker, G. L.; Fink, U.; Larson, H. P.; Johnson, J. R.

1983-01-01

44

Studies of Acid Properties of FeSiMCM-41 and LaSiMCM-41 by NH 3 -microcalorimetric and NH 3 TPD Measurements  

Microsoft Academic Search

The acidity of mesoporous materials FeSiMCM-41, LaSiMCM-41, SiMCM-41, AlSiMCM-41 and HAlSiMCM-41 has been investigated by microcalorimetric studies of the adsorption of ammonia and temperature programmed ammonia desorption method. In the initial stage, the acid strength sequence is SiMCM-41>HAlSiMCM-41>AlSiMCM-41>FeSiMCM-41>LaSiMCM-41, in agreement with that found for microporous molecular sieves materials. A small number of strong acid sites of SiMCM-41 may result from

N. He; D. Li; M. Tu; J. Shen; S. Bao; Q. Xu

1999-01-01

45

UF6 and UF4 in liquid ammonia: [UF7(NH3)]3- and [UF4(NH3)4].  

PubMed

From the reaction of uranium hexafluoride UF6 with dry liquid ammonia, the [UF7(NH3)]3- anion and the [UF4(NH3)4] molecule were isolated and identified for the first time. They are found in signal-green crystals of trisammonium monoammine heptafluorouranate(IV) ammonia (1:1; [NH4]3[UF7(NH3)].NH3) and emerald-green crystals of tetraammine tetrafluorouranium(IV) ammonia (1:1; [UF4(NH3)4].NH3). [NH4]3[UF7(NH3)].NH3 features discrete [UF7(NH3)]3- anions with a coordination geometry similar to a bicapped trigonal prism, hitherto unknown for U(IV) compounds. The emerald-green [UF4(NH3)4].NH3 contains discrete tetraammine tetrafluorouranium(IV) [UF4(NH3)4] molecules. [UF4(NH3)4].NH3 is not stable at room temperature and forms pastel-green [UF4(NH3)4] as a powder that is surprisingly stable up to 147 degrees C. The compounds are the first structurally characterized ammonia complexes of uranium fluorides. PMID:19585645

Kraus, Florian; Baer, Sebastian A

2009-08-17

46

Thermally stimulated desorption of neutral CF3 from CF3I on Ag(111)  

Microsoft Academic Search

The low temperature thermal chemistry of CF3I on Ag (111) presents an example of competing reaction pathways; molecular desorption vs desorption of radical CF3. Temperature programmed desorption and angle resolved temperature programmed desorption, complemented with Auger electron spectroscopy and low energy electron diffraction, were used to discern the mechanism of the CF3 radical desorption channel. CF3 desorption is limited to

K. H. Junker; Z.-J. Sun; T. B. Scoggins; J. M. White

1996-01-01

47

Reaction Pathway Investigation on the Selective Catalytic Reduction of NO with NH3 over Cu/SSZ-13 at Low Temperatures.  

PubMed

The mechanism of the selective catalytic reduction of NO with NH3 was studied using Cu/SSZ-13. The adspecies of NO and NH3 as well as the active intermediates were investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy and temperature-programmed surface reaction. The results revealed that three reactions were possible between adsorbed NH3 and NOx. NO2(-) could be generated by direct formation or NO3(-) reduction via NO. In a standard selective catalytic reduction (SCR) reaction, NO3(-) was hard to form, because NO2(-) was consumed by ammonia before it could be further oxidized to nitrates. Additionally, adsorbed NH3 on the Lewis acid site was more active than NH4(+). Thus, SCR mainly followed the reaction between Lewis acid site-adsorbed NH3 and directly formed NO2(-). Higher Cu loading could favor the formation of active Cu-NH3, Cu-NO2(-), and Cu-NO3(-), improving the SCR activity at low temperature. PMID:25485842

Su, Wenkang; Chang, Huazhen; Peng, Yue; Zhang, Chaozhi; Li, Junhua

2015-01-01

48

Photodissociation of NH3 at 106-200 nm  

NASA Technical Reports Server (NTRS)

The absorption and fluorescence cross sections for NH3 are measured in the 106-200 nm region using synchrotron radiation as the light source. The threshold wavelengths for the production of the NH (b to X) and NH (c to a) emissions from NH3 dissociation are measured and compared with previous measurements. The heat of formation of NH determined from these thresholds agrees well with the value determined from thermochemical data. The process of dissociation of NH3 into NH2(2AL) and H2(S) has a significant quantum yield whose maximum at 134 nm is about twice the NH(c) production yield. All the vibronic levels of the B and C states produce the NH2(2A1) emission, contrary to previous theoretical interpretations.

Suto, M.; Lee, L. C.

1983-01-01

49

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, Andrs; Moreno, Teresa; Amato, Fulvio; Ripoll, Anna; Querol, Xavier

2012-09-01

50

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 NASAs Postdoctoral Program (LP), the NASA Astrobiology Institute (PI MJM), NASAs 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

51

Enhanced NH3 emission from swine liquid waste  

NASA Astrophysics Data System (ADS)

Swine animal feeding operations are sources of emissions for various gases [ammonia (NH3), hydrogen sulfide (H2S), carbon dioxide (CO2), volatile organic carbons (VOCs)], and fine particulate matter. Gaseous emissions from simple aqueous systems are typically controlled by temperature, pH, wind speed, total dissolved concentration of the chemical species of interest (e.g. NH3+NH4+ = TAN), and the Henrys law constant. Ammonia emissions from three different sources [ammonium sulfate (AS), swine anaerobic lagoon liquid (SLL), and pit liquid (SPL) from swine housing units] were evaluated using a small flow-through teflon-lined chamber (SFTC; 0.3m 0.2m 0.15m) under controlled laboratory conditions. The SFTC was designed for 100% collection efficiency of NH3 gas emitted from the liquids. The internal volume of the chamber, 9 L, was exchanged 1.1 times per minute. All three liquid formulations exhibit the expected response in emissions with changes in temperature and pH. However, NH3 emissions from the SPL and SLL are ~5 times those from pure solutions of AS. Furthermore, the enhancement in NH3 emissions was a function of TAN concentration, decreasing in intensity at higher TAN and approaching rates comparable to the pure solutions of AS. The difference in emissions with solutions of equivalent TAN suggests a synergistic mechanism that is enhancing NH3 emissions in SPL and SLL. Concurrent measurements as part of the National Air Emissions Monitoring Study at the swine operations originally sampled for SPL and SLL document the emissions of CO2, H2S and VOCs (primarily acetic, propionic and butyric acids) at levels that are comparable to observed NH3 emissions. To date, only additions of NaHCO3 to the SPL and SLL have been found to enhance NH3 emissions and exhibit the same response to increasing TAN as exhibited by the original SPL and SLL solutions. Possible reactions that could enhance emissions will be discussed.

Lee, S.; Robarge, W. P.; Walker, J. T.

2010-12-01

52

Energy transfer in NH3-He collisions. [in interstellar gas  

NASA Technical Reports Server (NTRS)

The paper presents a new electron gas intermolecular NH3-He potential determined by the Hartree-Fock results of Davis, Boggs, and Mehrotra (1979) with semiempirical long-range induction and dispersion terms. The resulting potential agrees with beam scattering and pressure broadening measurements; it was also found that the quadrupole induced dipole interaction is not as effective as the short range anisotropy. It was concluded that discrepancies remain in the quantitative description of energy transfer in the NH3-He system; discrepancies result from improper consideration of the dependence of cross-sections on degenerate magnetic quantum levels in the experimental investigation.

Green, S.

1980-01-01

53

Kinetics of the NH3 and CO2 solid-state reaction at low temperature.  

PubMed

Ammonia and carbon dioxide play an important role in both atmospheric and interstellar ice chemistries. This work presents a theoretical and experimental study of the kinetics of the low-temperature NH3 and CO2 solid-state reaction in ice films, the product of which is ammonium carbamate (NH4(+)NH2COO(-)). It is a first-order reaction with respect to CO2, with a temperature-dependent rate constant fitted to the Arrhenius law in the temperature range 70 K to 90 K, with an activation energy of 5.1 1.6 kJ mol(-1) and a pre-exponential factor of 0.09-0.08(+1.1) s(-1). This work helps to determine the rate of removal of CO2 and NH3, via their conversion into ammonium carbamate, from atmospheric and interstellar ices. We also measure first-order desorption energies of 69.0 0.2 kJ mol(-1) and 76.1 0.1 kJ mol(-1), assuming a pre-exponential factor of 10(13) s(-1), for ammonium carbamate and carbamic acid, respectively. PMID:25198107

Noble, J A; Theule, P; Duvernay, F; Danger, G; Chiavassa, T; Ghesquiere, P; Mineva, T; Talbi, D

2014-11-21

54

Ionization of NH3 and CH4 by electron impact  

NASA Astrophysics Data System (ADS)

Calculated triple differential cross sections are presented for the ionization of NH3 and CH4 molecules by electron impact. The cross sections are determined for symmetrical coplanar and perpendicular geometrical arrangements. The obtained results reproduce in most cases the main features observed in the experimental data for both geometries.

Tth, Istvan; Campeanu, Radu I.; Nagy, Ladislau

2015-01-01

55

Structural phase transitions in the perovskite-type layer compound NH3(CH2)5NH3CdCl4  

E-print Network

405 Structural phase transitions in the perovskite-type layer compound NH3(CH2)5NH3CdCl4 P. Negrier pentylènediammonium. Abstract. 2014 The perovskite-type layer compound NH3(CH2)5NH3CdCl4 exhibits two structural phase:01989005004040500 #12;406 1. Introduction. Structural phase transitions in perovskite-type layer compounds have

Boyer, Edmond

56

Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NOx reduction with NH3  

NASA Astrophysics Data System (ADS)

Manganese oxide catalysts (MnOx) supported on functionalized multi-walled carbon nanotubes (FMWNTs) for low temperature selective catalytic reduction (LTSCR) of nitrogen oxides (NOx) with NH3 in the presence of excess O2 were prepared by the incipient wetness impregnation method. These catalysts were characterized by N2 adsorption, Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and H2-temperature programmed reduction (H2-TPR) methods. The effects of reaction temperature, MnOx loading, calcination temperature and calcination time were investigated. The presence of surface nitrate species under moderate calcination conditions may play a favorable role in the LTSCR of NOx with NH3. Under the reaction conditions of 200 C, 1 bar, NO = NH3 = 900 ppm, O2 = 5 vol%, GHSV = 30,000 h-1 and 12 wt% MnOx, NOx conversion and N2 selectivity were 97% and 99.5%, respectively. The SCR activity was reduced in the presence of 100 ppm SO2 and 2.5 vol% H2O from 97% to 92% within 6 h at 200 C, however such an effect was shown to be reversible by exposing the catalyst to a helium flow for 2 h at 350 C due to thermal decomposition of ammonium sulphate salts.

Pourkhalil, Mahnaz; Moghaddam, Abdolsamad Zarringhalam; Rashidi, Alimorad; Towfighi, Jafar; Mortazavi, Yadollah

2013-08-01

57

First NH3 detection of the Orion Bar  

E-print Network

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. 2001. Using the source model for the Orion Bar by these authors, our Odin observation implies a total ammonia abundance of NH3/H2 = 5E-9.

B. Larsson; R. Liseau; P. Bergman; P. Bernath; J. H. Black; R. S. Booth; V. Buat; C. L. Curry; P. Encrenaz; E. Falgarone; P. Feldman; M. Fich; H. G. Flore'n; U. Frisk; M. Gerin; E. M. Gregersen; J. Harju; T. Hasegawa; L. E. B. Johansson; S. Kwok; A. Lecacheux; T. Liljestrom; K. Mattila; G. F. Mitchell; L. H. Nordh; M. Olberg; G. Olofsson; L. Pagani; R. Plume; I. Ristorcelli; Aa. Sandqvist; F. v. Sche'ele; N. F. H. Tothill; K. Volk; C. D. Wilson; A. Hjalmarson

2003-03-05

58

NH3 in IRC plus 10216. [infrared astronomy  

NASA Technical Reports Server (NTRS)

Ammonia was detected in the circumstellar envelope of IRC +10216 by means of three infrared absorption lines in the nu sup 2 band around 950/cm. The lines are fully resolved at a resolution of 0.22 km/sec and indicate that most of the circumstellar gas is accelerated to expansion velocities around 14 km/sec within a few stellar radii. The NH3 profiles indicate a rotational temperature between 400 and 700 K, and H2 density between 10 to the 8th power/cu cm and 10 to the 10th power/cu cm, and NH3 column density of 10 to the 17th power/sq cm. The H2 density indicates that the mass of the circumstellar envelope within a 1 arcsec radius is approximately 0.1 solar masses.

Betz, A. L.; Mclaren, R. A.; Spears, D. L.

1978-01-01

59

Studies of elastic e-NH3 collisions  

NASA Technical Reports Server (NTRS)

Differential and momentum-transfer cross sections for the elastic scattering of electrons by NH3 have been obtained for collision energies of between 2.5 and 20 eV using the fixed-nuclei static-exchange approximation of the Schwinger variational principle. At intermediate and large scattering angles, good agreement is found between calculated and relative experimental cross sections. The differential cross sections reveal evidence of a weak d-wave enhancement around 8 eV.

Pritchard, H. P.; Lima, M. A. P.; Mckoy, V.

1989-01-01

60

Preparation and Crystal Structures of Ni(NH 3) 2Cl 2 and of Two Modifications of Ni(NH 3) 2Br 2 and Ni(NH 3) 2I 2  

Microsoft Academic Search

Diammine nickel(II) halides, Ni(NH3)2X2 (X=Cl, Br, I), were prepared by decomposition of the corresponding hexaammines at 120C in dynamical vacuum. Their crystal structures are of the Cd(NH3)2Cl2 type (?-type, space group Cmmm, Z=2): for Ni(NH3)2Cl2, a=8.019 , b=8.013 , c=3.661 ; for ?-Ni(NH3)2Br2, a=8.273 , b=8.297 , c=3.851 . Both were obtained by Rietveld refinement of diffractometer data with standard

A. Leineweber; H. Jacobs

2000-01-01

61

Cs5Sn9(OH)4NH3  

PubMed Central

The title compound, pentacaesium nonastannide hydroxide tetraammonia, crystallized from a solution of CsSnBi in liquid ammonia. The Sn9 4? unit forms a monocapped quadratic antiprism. The hydroxide ion is surrounded by five caesium cations, which form a distorted quadratic pyramidal polyhedron. A three-dimensional network is formed by CsSn [3.8881?(7)? to 4.5284?(7)?] and CsNH3 [3.276?(7)3.636?(7)?] contacts. PMID:24940189

Friedrich, Ute; Korber, Nikolaus

2014-01-01

62

Electron Impact Ionization of CH4 and NH3  

NASA Astrophysics Data System (ADS)

Experimental and theoretical Triply Differential Cross Sections (TDCS) will be presented for electron-impact ionization of Methane (CH4) and Ammonia (NH3) (same number of electrons and protons) for both the highest occupied molecular orbital (HOMO) and next highest occupied molecular orbital (NHOMO). M3DW (molecular 3-body distorted wave) results will be compared with experiment for coplanar geometry and for perpendicular plane geometry (a plane which is perpendicular to the incident beam direction). In both cases, the final state electron energies and observation angles are symmetric and the final state electron energies range from 1.5eV to 30eV.

Chaluvadi, Hari; Madison, Don; Nixon, Kate; Murray, Andrew; Ning, Chuangang

2011-11-01

63

cis-{Pt(NH3)2(L)}2+/+ (L ) Cl, H2O, NH3) Binding to Purines and CO: Does -Back-Donation Play a Role?  

E-print Network

cis-{Pt(NH3)2(L)}2+/+ (L ) Cl, H2O, NH3) Binding to Purines and CO: Does -Back-Donation Play a Role, Massachusetts 02139 Received August 30, 2003 The ability of cis-{Pt(NH3)2(L)}2+/+ , a molecular fragment of the anticancer drug cisplatin, to bind to purines and CO by -back- donation from Pt to the ligand was examined

Baik, Mu-Hyun

64

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

65

Removal of high concentrations of NH3 by a combined photoreactor and biotrickling filter system  

Microsoft Academic Search

Average emission levels as high as 800 ppmv NH3 have often been found during the anaerobic fermentation process. At these levels, NH3 is regarded as an environmental toxic compound. High concentrations of NH3 gas are difficult to treat in a single treatment process, suggesting that, in terms of economic cost and treatment performance, a coupled system may be a feasible

Li-Chun Wu; Cheng-Lang Kuo; Ying-Chien Chung

2011-01-01

66

The ?1 and ?3 band system of 15NH3  

NASA Astrophysics Data System (ADS)

The infrared spectrum of 15NH3 has been investigated by high-resolution Fourier transform infrared spectroscopy in the region of the stretching fundamentals. A large number of ro-vibration transitions in the 3050-3650 cm-1 spectral range has been recorded and assigned to the fundamentals ?1 and ?3, and to the 2? 4 overtone bands. In total, 1606 transitions involving the (s) and (a) inversion-rotation-vibration levels have been identified and assigned. They include 256 perturbation-allowed transitions with selection rules ?K = 2, ?l = -1 in ?3 and ?l = +2 in 2?4^2, and ?K = 3, ?l = 0 in ?1 and 2?4^0. All assigned transitions were fitted simultaneously to a model Hamiltonian that includes all symmetry-allowed interactions between and within the excited state levels in order to obtain accurate sets of spectroscopic parameters for both inversion states. The standard deviation of the fit, 0.034 cm-1, is about 70 times larger than the estimated measurement precision. This result is similar to that reported for the same band system in 14NH3 by Kleiner et al. [J. Mol. Spectrosc. 193, 46 (1999)] and is a consequence of the neglect of vibration and ro-vibration interactions between the analysed states and vibrationally excited states with close energies.

Fusina, Luciano; Nivellini, Giandomenico; Spezzano, Silvia

2011-09-01

67

The ground state far infrared spectrum of NH3  

NASA Technical Reports Server (NTRS)

The NH3 far infrared spectrum is particularly useful for the study of planetary composition and atmospheric dynamics. Studies of this spectrum were conducted by Dowling (1969), Helminger et al. (1971), and Urban et al. (1981). Sattler et al. (1981) have reported measurements of a few nu2 lines with tunable diode lasers. By using simple sum rules, these lines and accurate ground state inversion lines considered by Poynter and Kakar (1975) have been employed in the present investigation to deduce a few of the far infrared ground state transitions. An extensive set of high signal/noise, high resolution (0.0048 per cm) scans of the nu2 bands of NH3 from about 600 per cm through about 1300 per cm ait a series of low pressures have been made in order to accurately determine both the line positions and strengths. The obtained data provide line positions with an absolute accuracy of about 0.0001 per cm in the more favorable cases.

Poynter, R. L.; Margolis, J. S.

1983-01-01

68

Observational constraints on solar nebula nitrogen chemistry - N2/NH3  

NASA Technical Reports Server (NTRS)

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 for gas-phase elemental nitrogen depletion in Comet Halley indicates that the gas component in the comet-forming region of the solar nebula was N2/NH3 of about 4. It is concluded that more realistic models which include condensation fractionation effects are required before the N2 and NH3 abundances in comet volatiles can be related to star-forming regions.

Womack, Maria; Wyckoff, Susan; Ziurys, L. M.

1992-01-01

69

Preparation and Crystal Structures of Ni(NH 3) 2Cl 2 and of Two Modifications of Ni(NH 3) 2Br 2 and Ni(NH 3) 2I 2  

NASA Astrophysics Data System (ADS)

Diammine nickel(II) halides, Ni(NH 3) 2X2 ( X=Cl, Br, I), were prepared by decomposition of the corresponding hexaammines at 120C in dynamical vacuum. Their crystal structures are of the Cd(NH 3) 2Cl 2 type (" ?-type", space group Cmmm, Z=2): for Ni(NH 3) 2Cl 2, a=8.019 , b=8.013 , c=3.661 ; for ?-Ni(NH 3) 2Br 2, a=8.273 , b=8.297 , c=3.851 . Both were obtained by Rietveld refinement of diffractometer data with standard deviations <0.001 . For ?-Ni(NH 3) 2I 2, a= b=8.753(3) , c=4.127(1) , obtained by Guinier film data. In the case of the bromide and the iodide, annealing at 300C leads to an irreversible structural rearrangement. A new modification is formed which is of the Mg(NH 3) 2Br 2 type (" ?-type", space group Pbam, Z=2): for ?-Ni(NH 3) 2Br 2, a=5.865 , b=11.723 , c=3.856 , obtained by Rietveld refinement of diffractometer data with standard deviations <0.001; for ?-Ni(NH 3) 2I 2, 2 a= b=12.359(3) , c=4.126(1) , obtained by Guinier film data. Both types of structures contain infinite chains of edge-sharing octahedra 1?[Ni X4/2(NH 3) 2]. These run parallel to the c-axes of the unit cells of the corresponding structure types and are arranged in different ways relative to one another. The decomposition of hexaammine nickel(II) halides to the corresponding diammines is analyzed in terms of structural analogies.

Leineweber, A.; Jacobs, H.

2000-07-01

70

NH3 in IRC +10216. [carbon star undergoing mass loss  

NASA Technical Reports Server (NTRS)

Ammonia has been detected in the circumstellar envelope of IRC +10216 by means of three infrared absorption lines in the nu-2 band around 950 kaysers. The profiles are well resolved at a resolution of 0.22 km/s and show that most of the circumstellar gas is accelerated to expansion velocities around 14 km/s within a few stellar radii. The observed ammonia requires a rotational temperature between 400 and 700 K, an H2 density between 100 million and 10 billion per cu cm, and an NH3 column density of 10 to the 17th per sq cm. The H2 density indicates that the mass of the circumstellar envelope within a 1 arcsec radius is about 0.1 solar mass.

Betz, A. L.; Mclaren, R. A.; Spears, D. L.

1979-01-01

71

Elevated CO2 decreases the Photorespiratory NH3 production but does not decrease the NH3 compensation point in rice leaves.  

PubMed

The exchange of gaseous NH3 between the atmosphere and plants plays a pivotal role in controlling the global NH3 cycle. Photorespiration generates NH3 through oxygenation instead of carboxylation by the CO2-fixing enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). The future increase in the atmospheric CO2 concentration, [CO2], is expected to reduce plant NH3 production by suppressing RuBisCO oxygenation (Vo). We measured the net leaf NH3 uptake rate (FNH3) across NH3 concentrations in the air (na) ranging from 0.2 to 1.6 nmol mol(-1) at three [CO2] values (190, 360 and 750 mol mol(-1)) using rice plants. We analyzed leaf NH3 gas exchange using a custom-made whole-leaf chamber system, and determined the NH3 compensation point (?), a measure of potential NH3 emission, as the x-intercept of the linear relationship of FNH3 as a function of na. Our ? values were lower than those reported for other plant species. ? did not decrease under elevated [CO2], although leaf NH4 (+) content decreased with decreasing Vo at higher [CO2]. This was also the case for ? estimated from the pH and NH4 (+) concentration of the leaf apoplast solution (?'). ?' of rice plants, grown at elevated [CO2] for months in a free-air CO2 enrichment facility, was also not decreased by elevated [CO2]. These results suggest that suppression of RuBisCO oxygenation by elevated [CO2] does not decrease potential leaf NH3 emission in rice plants. PMID:24951312

Miyazawa, Shin-Ichi; Hayashi, Kentaro; Nakamura, Hirofumi; Hasegawa, Toshihiro; Miyao, Mitsue

2014-09-01

72

Relativistic GW calculations on CH3NH3PbI3 and CH3NH3SnI3 perovskites for solar cell applications.  

PubMed

Hybrid AMX3 perovskites (A = Cs, CH3NH3; M = Sn, Pb; X = halide) have revolutionized the scenario of emerging photovoltaic technologies, with very recent results demonstrating 15% efficient solar cells. The CH3NH3PbI3/MAPb(I(1-x)Cl(x))3 perovskites have dominated the field, while the similar CH3NH3SnI3 has not been exploited for photovoltaic applications. Replacement of Pb by Sn would facilitate the large uptake of perovskite-based photovoltaics. Despite the extremely fast progress, the materials electronic properties which are key to the photovoltaic performance are relatively little understood. Density Functional Theory electronic structure methods have so far delivered an unbalanced description of Pb- and Sn-based perovskites. Here we develop an effective GW method incorporating spin-orbit coupling which allows us to accurately model the electronic, optical and transport properties of CH3NH3SnI3 and CH3NH3PbI3, opening the way to new materials design. The different CH3NH3SnI3 and CH3NH3PbI3 electronic properties are discussed in light of their exploitation for solar cells, and found to be dominantly due to relativistic effects. These effects stabilize the CH3NH3PbI3 material towards oxidation, by inducing a deeper valence band edge. Relativistic effects, however, also increase the material band-gap compared to CH3NH3SnI3, due to the valence band energy downshift (~0.7?eV) being only partly compensated by the conduction band downshift (~0.2?eV). PMID:24667758

Umari, Paolo; Mosconi, Edoardo; De Angelis, Filippo

2014-01-01

73

Comparison of preparation methods for ceria catalyst and the effect of surface and bulk sulfates on its activity toward NH3-SCR.  

PubMed

A series of CeO2 catalysts prepared with sulfate (S) and nitrate (N) precursors by hydrothermal (H) and precipitation (P) methods were investigated in selective catalytic reduction of NOx by NH3 (NH3-SCR). The catalytic activity of CeO2 was significantly affected by the preparation methods and the precursor type. CeO2-SH, which was prepared by hydrothermal method with cerium (IV) sulfate as a precursor, showed excellent SCR activity and high N2 selectivity in the temperature range of 230-450 C. Based on the results obtained by temperature-programmed reduction (H2-TPR), transmission infrared spectra (IR) and thermal gravimetric analysis (TGA), the excellent performance of CeO2-SH was correlated with the surface sulfate species formed in the hydrothermal reaction. These results indicated that sulfate species bind with Ce(4+) on the CeO2-SH catalyst, and the specific sulfate species, such as Ce(SO4)2 or CeOSO4, were formed. The adsorption of NH3 was promoted by these sulfate species, and the probability of immediate oxidation of NH3 to N2O on Ce(4+) was reduced. Accordingly, the selective oxidation of NH3 was enhanced, which contributed to the high N2 selectivity in the SCR reaction. However, the location of sulfate on the CeO2-SP catalyst was different. Plenty of sulfate species were likely deposited on CeO2-SP surface, covering the active sites for NO oxidation, which resulted in poor SCR activity in the test temperature range. Moreover, the resistance to alkali metals, such as Na and K, was improved over the CeO2-SH catalyst. PMID:24140528

Chang, Huazhen; Ma, Lei; Yang, Shijian; Li, Junhua; Chen, Liang; Wang, Wei; Hao, Jiming

2013-11-15

74

Renal handling of NH3/NH4+: recent concepts.  

PubMed

To be appropriately excreted in urine, NH4+, the major component of urinary acid excretion, must be synthesized by proximal tubular cells, secreted into the proximal tubular fluid, reabsorbed by the medullary thick ascending limb (MTAL) to be accumulated in the medullary interstitium, and finally secreted in medullary collecting ducts. Several targets have been identified to account at the gene expression level for the adaptation of renal NH4+ synthesis and transport in response to a chronic acid load. These targets are the key enzymes of ammoniagenesis (mitochondrial glutaminase and glutamate dehydrogenase) and gluconeogenesis (phosphoenolpyruvate carboxykinase) and the Na+/H+(NH4+) exchanger NHE3 in the proximal tubule, the apical Na+-K+(NH4+)-2Cl- cotransporter of the MTAL, the basolateral Na+-K+(NH4+)-2Cl- cotransporter, and likely the epithelial Rh B and C glycoproteins in the collecting ducts. An acid pH per se appears to be a major factor in the control of the expression of these genes during metabolic acidosis probably through activation of pH sensors. Glucocorticoids may also act in concert with an acid pH to coordinate the adaptation of various tubular cell types. The present review focuses on some new aspects of NH3/ NH4+ transport and of regulations of gene expression that have recently emerged. PMID:16113588

Karim, Zoubida; Szutkowska, Marta; Vernimmen, Catherine; Bichara, Maurice

2005-01-01

75

Interstellar deuterated ammonia: From NH3 to ND3  

E-print Network

We use spectra and maps of NH2D, ND2H, and ND3, obtained with the CSO, IRAM 30m and Arecibo telescopes, to study deuteration processes in dense cores. The data include the first detection of the hyperfine structure of ND2H. The emission of ND2H and ND3 does not seem to peak at the positions of the embedded protostars, but instead at offset positions, where outflow interactions may occur. A constant ammonia fractionation ratio in star-forming regions is generally assumed to be consistent with an origin on dust grains. However, in the pre-stellar cores studied here, the fractionation varies significantly when going from NH3 to ND3. We present a steady state model of the gas-phase chemistry for these sources, which includes passive depletion onto dust grains and multiply saturated deuterated species up to five deuterium atoms (e.g. CD5+). The observed column density ratios of all four ammonia isotopologues are reproduced within a factor of 3 for a gas temperature of 10 K. We also predict that deuterium fractionation remains significant at temperatures up to 20 K. ND and NHD, which have rotational transitions in the submillimeter domain are predicted to be abundant.

E. Roueff; D. C. Lis; F. F. S. van der Tak; M. Gerin; P. F. Goldsmith

2005-04-20

76

Line-mixing effect on NH3 line intensities  

NASA Astrophysics Data System (ADS)

Line intensities belonging to nine branches of the ?2, 2?2 and ?4 vibrational bands of ammonia have been measured between 1000 and 2000 cm-1. The laboratory spectra at room temperature (T=295 K) were recorded using a high-resolution Fourier transform spectrometer Bruker IFS 120 HR. More than 460 lines with J?12 were analyzed using a non-linear least-squares multi-pressure fitting procedure. The fits were performed with and without including the line mixing effects using 11 experimental spectra recorded at different pressures of pure NH3. On average the line intensities uncertainty is estimated to be 2%. The dependence of the line intensities on the J and K quantum numbers is discussed. The effect of line mixing on the line intensities is analyzed as a function of the rotational quantum numbers, of the branches, and of the bands. On average the values of line intensities obtained in the ?4 band when taking into account line mixing have been found to be 6% smaller than those obtained using the Voigt profile. The transition dipole moments squared, determined for each line from the measured intensities, exhibit significant rotational dependencies which are mainly caused by vibration-rotation interactions. These moments are discussed as a function of vibrational and rotational states. Finally the measurements are compared with previous measurements and with values from spectroscopic databases. The whole set of line intensities and transition dipole moments are given as supplementary data for use in spectroscopic databases.

Aroui, H.; Ben Mabrouk, K.; Boussassi, R.

2013-11-01

77

The initial kinetics of NH3/NH4(+) efflux from L3 Teladorsagia circumcincta.  

PubMed

The initial rate of NH(3)/NH(4)(+) accumulation in a medium containing L(3) Teladorsagia circumcincta was 0.18-0.6 pmol h(-1) larva(-1), which increased linearly with larval density. However it appeared that the larva-generated external concentration of NH(3)/NH(4)(+) did not exceed about 130 ?M. The rate of NH(3)/NH(4)(+) accumulation increased with temperature between 4 C and 37 C, declined with increasing pH or increasing external NH(3)/NH(4)(+) concentration and was not significantly affected by the concentration of the phosphate buffer or by exsheathing the larvae. We infer from these data that the efflux of NH(3)/NH(4)(+) is a diffusive process and that the secreted or excreted NH(3)/NH(4)(+) is generated enzymatically rather than dissociating from the surface of the nematode. The enzymatic source of the NH(3)/NH(4)(+) is yet to be identified. Since the concentration of NH(3)/NH(4)(+) in the rumen and abomasum is higher than 130 ?M, it is unlikely that T. circumcincta contributes to it, but NH(3)/NH(4)(+) may be accumulated from the rumen fluid by the nematode. PMID:22562002

Muhamad, Noorzaid; Walker, Lisa R; Pedley, Kevin C; Simcock, David C; Brown, Simon

2012-09-01

78

A theoretical room-temperature line list for 15NH3  

NASA Astrophysics Data System (ADS)

A new room temperature line list for 15NH3 is presented. This line list comprised of transition frequencies and Einstein coefficients has been generated using the 'spectroscopic' potential energy surface NH3-Y2010 and an ab initio dipole moment surface. The 15NH3 line list is based on the same computational procedure used for the line list for 14NH3 BYTe reported recently and should be as accurate. Comparisons with experimental frequencies and intensities are presented. The synthetic spectra show excellent agreement with experimental spectra.

Yurchenko, Sergei N.

2015-02-01

79

Detailed mechanism for AmtB conducting NH4+/NH3: molecular dynamics simulations.  

PubMed

The mechanism by which the ammonium transporter, AmtB, conducts NH4+/NH3 into the cytoplasm was investigated using conventional molecular dynamics (MD) simulations. These simulations revealed that the neutral molecule, NH3, passes automatically through the channel upon its arrival at the Am2 site and that the function of the channel as a one-way valve for passage of NH3 is not determined by the cytoplasmic exit gate but, rather, by the periplasmic entrance gate of the channel. The NH3, produced by deprotonation of NH4+ at the entrance gate, is spontaneously conveyed to the central region of the channel via a hydrogen-bond network comprising His-168, His-318, Tyr-32, and the NH3 molecule. Finally, the NH3 molecule exits the channel through the exit gate formed by Phe-31, Ile-266, Val-314, and His-318. In addition, Ser-263 is shown to play a critical role in the final stages, acting as a pivoting arm to shunt the NH3 molecule from the cytoplasmic exit gate of the channel out into the cytoplasm. This finding is further supported by another simulation which shows that NH3 fails to be translocated through the channel formed by the Ser-263-Ala mutation. Thus, this study casts new insights on the mechanism of AmtB-mediated passage of NH3 across cellular membranes. PMID:17098799

Yang, Huaiyu; Xu, Yechun; Zhu, Weiliang; Chen, Kaixian; Jiang, Hualiang

2007-02-01

80

Vibrations and reorientations of NH3 molecules in [Mn(NH3)6](ClO4)2 studied by infrared spectroscopy and theoretical (DFT) calculations.  

PubMed

The vibrational and reorientational motions of NH3 ligands and ClO4(-) anions were investigated by Fourier transform middle-infrared spectroscopy (FT-IR) in the high- and low-temperature phases of [Mn(NH3)6](ClO4)2. The temperature dependencies of full width at half maximum (FWHM) of the infrared bands at: 591 and 3385cm(-1), associated with: ?r(NH3) and ?as(N-H) modes, respectively, indicate that there exist fast (correlation times ?R?10(-12)-10(-13)s) reorientational motions of NH3 ligands, with a mean values of activation energies: 7.8 and 4.5kJmol(-1), in the phase I and II, respectively. These reorientational motions of NH3 ligands are only slightly disturbed in the phase transition region and do not significantly contribute to the phase transition mechanism. Fourier transform far-infrared and middle-infrared spectra with decreasing of temperature indicated characteristic changes at the vicinity of PT at TC(c)=137.6K (on cooling), which suggested lowering of the crystal structure symmetry. Infrared spectra of [Mn(NH3)6](ClO4)2 were recorded and interpreted by comparison with respective theoretical spectra calculated using DFT method (B3LYP functional, LANL2DZ ECP basis set (on Mn atom) and 6-311+G(d,p) basis set (on H, N, Cl, O atoms) for the isolated equilibrium two models (Model 1 - separate isolated [Mn(NH3)6](2+) cation and ClO4(-) anion and Model 2 - [Mn(NH3)6(ClO4)2] complex system). Calculated optical spectra show a good agreement with the experimental infrared spectra (FT-FIR and FT-MIR) for the both models. PMID:25459713

Hetma?czyk, Joanna; Hetma?czyk, Lukasz; Migda?-Mikuli, Anna; Mikuli, Edward

2014-10-24

81

Vibrations and reorientations of NH3 molecules in [Mn(NH3)6](ClO4)2 studied by infrared spectroscopy and theoretical (DFT) calculations  

NASA Astrophysics Data System (ADS)

The vibrational and reorientational motions of NH3 ligands and ClO4- anions were investigated by Fourier transform middle-infrared spectroscopy (FT-IR) in the high- and low-temperature phases of [Mn(NH3)6](ClO4)2. The temperature dependencies of full width at half maximum (FWHM) of the infrared bands at: 591 and 3385 cm-1, associated with: ?r(NH3) and ?as(N-H) modes, respectively, indicate that there exist fast (correlation times ?R ? 10-12-10-13 s) reorientational motions of NH3 ligands, with a mean values of activation energies: 7.8 and 4.5 kJ mol-1, in the phase I and II, respectively. These reorientational motions of NH3 ligands are only slightly disturbed in the phase transition region and do not significantly contribute to the phase transition mechanism. Fourier transform far-infrared and middle-infrared spectra with decreasing of temperature indicated characteristic changes at the vicinity of PT at TCc = 137.6 K (on cooling), which suggested lowering of the crystal structure symmetry. Infrared spectra of [Mn(NH3)6](ClO4)2 were recorded and interpreted by comparison with respective theoretical spectra calculated using DFT method (B3LYP functional, LANL2DZ ECP basis set (on Mn atom) and 6-311 + G(d,p) basis set (on H, N, Cl, O atoms) for the isolated equilibrium two models (Model 1 - separate isolated [Mn(NH3)6]2+ cation and ClO4- anion and Model 2 - [Mn(NH3)6(ClO4)2] complex system). Calculated optical spectra show a good agreement with the experimental infrared spectra (FT-FIR and FT-MIR) for the both models.

Hetma?czyk, Joanna; Hetma?czyk, ?ukasz; Migda?-Mikuli, Anna; Mikuli, Edward

2015-02-01

82

Spectroscopy of 14NH3 and 15NH3 in the 2.3 ?m spectral range with a new VECSEL laser source  

NASA Astrophysics Data System (ADS)

A spectroscopic study of ammonia molecule in the 2.3 ?m water atmospheric window is presented. Compared to previous experimental works a narrow, broadly tunable, continuous laser source was applied in order to obtain high resolution spectra in this range. It was the first application of the newly developed Vertical External Cavity Surface Emitting Laser (VECSEL). The analysis of the absorption spectra of two different isotopologue admixtures allowed to identify 336 14NH3 and 244 15NH3 lines in the studied region from 4275 to 4340 cm-1. These data were compared to previous line list based on experimental data - the HITRAN database and the work of Urban et al., as well as to the theoretical predictions by Yurchenko et al. and Huang et al. Together for 235 14NH3 and 183 15NH3 lines a complete assignment was proposed. From those 63 14NH3 and 114 15NH3 transitions were newly assigned. The complete peaklist of transitions containing ro-vibrational state identifications is presented in Supplementary materials.

?ermk, P.; Hovorka, J.; Veis, P.; Cacciani, P.; Coslou, J.; El Romh, J.; Khelkhal, M.

2014-04-01

83

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

84

Low and room temperature photoabsorption cross sections of NH 3 in the UV region  

Microsoft Academic Search

Using synchrotron radiation as a continuum light source, we have measured the absolute absorption cross sections of NH3 with a spectral bandwidth (FWHM) of 0.5 . The photoabsorption cross sections of NH3 have been measured from 1750 to 2250 under temperature conditions of 295, 195, and 175 K. Significant temperature effects in the absorption threshold region which are mainly

F. Z Chen; D. L Judge; C. Y. Robert Wu; John Caldwell

1998-01-01

85

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...

86

Measurements of NH3 absorption coefficients with a C-13/O-16/2 laser  

NASA Technical Reports Server (NTRS)

Measurements of NH3 absorption coefficients are presented for several transitions of a C-13(O-16)2 laser for small concentrations of NH3(p less than 1 torr) for absorption lines broadened to 1 atm with N2. NH3 absorption coefficients were determined for laser transitions R(8)(920.2194 wavelengths/cm) to R(28)(933.8808 wavelengths/cm) of the 00 1 - (10 0,02 0)I band. The strongest absorption coefficient K = 36.09 + or - 1.43 per (atm-cm) was measured for the R(18) transition for the NH3 line, aQ(6,6), and is larger than has been found in any previous measurements with a CO2 laser. The dependence of K on total pressure was also obtained for select transitions, and the frequency separation between the R(18) laser transition and the neighboring NH3 line aQ(6,6) was determined to be 550 + or - 50 MHz. These results are significant for long path absorption monitoring of NH3 with CO2 lasers since the path length can be reduced by approximately 40% and for heterodyne detection of NH3 since the relative position of the laser transition to the NH3 absorption line is well within the bandpass of Hg-Cd-Te photomixers.

Allario, F.; Seals, R. K., Jr.

1975-01-01

87

Urban NH3 levels and sources in six major Spanish cities.  

PubMed

A detailed spatial and temporal assessment of urban NH3 levels and potential emission sources was made with passive samplers in six major Spanish cities (Barcelona, Madrid, A Corua, Huelva, Santa Cruz de Tenerife and Valencia). Measurements were conducted during two different periods (winter-autumn and spring-summer) in each city. Barcelona showed the clearest spatial pattern, with the highest concentrations in the old city centre, an area characterised by a high population density and a dense urban architecture. The variability in NH3 concentrations did not follow a common seasonal pattern across the different cities. The relationship of urban NH3 with SO2 and NOX allowed concluding on the causes responsible for the variations in NH3 levels between measurement periods observed in Barcelona, Huelva and Madrid. However, the factors governing the variations in A Corua, Valencia and Santa Cruz de Tenerife are still not fully understood. This study identified a broad variability in NH3 concentrations at the city-scale, and it confirms that NH3 sources in Spanish urban environments are vehicular traffic, biological sources (e.g. garbage containers), wastewater treatment plants, solid waste treatment plants and industry. The importance of NH3 monitoring in urban environments relies on its role as a precursor of secondary inorganic species and therefore PMX. Further research should be addressed in order to establish criteria to develop and implement mitigation strategies for cities, and to include urban NH3 sources in the emission inventories. PMID:25194477

Reche, Cristina; Viana, Mar; Karanasiou, Angeliki; Cusack, Michael; Alastuey, Andrs; Artiano, Begoa; Revuelta, M Aranzazu; Lpez-Maha, Purificacin; Blanco-Heras, Gustavo; Rodrguez, Sergio; Snchez de la Campa, Ana M; Fernndez-Camacho, Roco; Gonzlez-Castanedo, Yolanda; Mantilla, Enrique; Tang, Y Sim; Querol, Xavier

2015-01-01

88

Effects of NH3 on N2O formation and destruction in fluidized bed coal combustion  

NASA Astrophysics Data System (ADS)

The NH3 oxidation and reduction process are experimentally and kinetically studied in this paper. It is found that NH3 has contributions not only to N2O formation, but also to N2O destruction in certain conditions. The main product of homogeneous NH3 oxidation is found to be NO rather than N2O, but some bed materials and sulphur sorbents have catalytic contributions to N2O formation from NH3 oxidation. In reduction atmosphere, NH3 can promote the KC destruction. It is deduced that the ammonia injection into fluidized bed coal combustion flue gas can decrease both NOx and N2O emissions. The ammonia injection process is kinetically simulated in this study, and the reduction rates of NOx and N2O are found to depend on temperature, O2 concentration, initial NOx and N2O concentrations, and amount of injected ammonia.

Yuan, Jianwei; Feng, Bo; Lu, Jianxin; Liu, Hao; Liu, Dechang

1994-12-01

89

Temperature-Programmed Reduction and XRD Studies of Ammonia-Treated Molybdenum Oxide and Its Activity for Carbazole Hydrodenitrogenation  

Microsoft Academic Search

The change structure and composition of molybdenum nitride catalysts with cooling in a stream of ammonia or helium gas after NH3 treating was determined using temperature-programmed reduction (TPR) and X-ray powder diffraction analyses. The relationship between the molybdenum species and the catalytic activities of the molybdenum nitride catalysts for the hydrodenitrogenation (HDN) of carbazole was discussed. MoO2, ?-Mo2N, and Mo

M. Nagai; Y. Goto; A. Miyata; M. Kiyoshi; K. Hada; K. Oshikawa; S. Omi

1999-01-01

90

Towards validation of ammonia (NH3) measurements from the IASI satellite  

NASA Astrophysics Data System (ADS)

Limited availability of ammonia (NH3) observations is currently a barrier for effective monitoring of the nitrogen cycle. It prevents a full understanding of the atmospheric processes in which this trace gas is involved and therefore impedes determining its related budgets. Since the end of 2007, the Infrared Atmospheric Sounding Interferometer (IASI) satellite has been observing NH3 from space at a high spatiotemporal resolution. This valuable data set, already used by models, still needs validation. We present here a first attempt to validate IASI-NH3 measurements using existing independent ground-based and airborne data sets. The yearly distributions reveal similar patterns between ground-based and space-borne observations and highlight the scarcity of local NH3 measurements as well as their spatial heterogeneity and lack of representativity. By comparison with monthly resolved data sets in Europe, China and Africa, we show that IASI-NH3 observations are in fair agreement but that they are characterized by a smaller variation in concentrations. The use of hourly and airborne data sets to compare with IASI individual observations allows to investigate the impact of averaging as well as the representativity of independent observations for the satellite footprint. The importance of considering the latter and the added value of densely located airborne measurements at various altitudes to validate IASI-NH3 columns are discussed. Perspectives and guidelines for future validation work on NH3 satellite observations are presented.

Van Damme, M.; Clarisse, L.; Dammers, E.; Liu, X.; Nowak, J. B.; Clerbaux, C.; Flechard, C. R.; Galy-Lacaux, C.; Xu, W.; Neuman, J. A.; Tang, Y. S.; Sutton, M. A.; Erisman, J. W.; Coheur, P. F.

2014-12-01

91

Dependence of the effective coefficient of separating a mixture of NH3-O2 and NH3-N2 on the rate of distillation  

NASA Astrophysics Data System (ADS)

The effective coefficient for separating a mixture of NH3-O2 and NH3-N2 at different rates of distillation is determined experimentally and theoretically. The effect of the temperature of a surface layer of liquid ammonia on the purification process from permanent gases (O2 and N2) is studied. The results indicate that upon an increase in the rate of distillation, the efficiency of separating a mixture of ammonia and impurities rises as heat transfer in the surface layer becomes difficult.

Petukhov, A. N.; Vorotyntsev, V. M.; Shablykin, D. N.; Vorotyntsev, I. V.; Suvorov, S. S.

2013-09-01

92

An optically integrated NH3 sensor using WO3 thin films as sensitive material  

NASA Astrophysics Data System (ADS)

We analyze the optical response of WO3 sputtered thin films to NH3 gas sensing through transmittance changes. By sputtering, films with a combination of monoclinic and triclinic crystalline structure were obtained. The films show sensitivity to NH3 presence at the wavelengths ? = 980 nm and 1550 nm and at low temperature, T = 90 C. The optical constants (refractive index (n) and absorbant coefficient (?)) were calculated using the transmittance spectra and the model of a simple resonator. According to these results, an integrated optical NH3 sensor based on a glass waveguide with a WO3 thin film deposited at the surface was designed and experimentally characterized.

Lazcano-Hernndez, H. E.; Snchez-Prez, C.; Garca-Valenzuela, A.

2008-10-01

93

Shock-excited NH3 (3, 3) masers in the NGC 6334 star-forming region  

NASA Technical Reports Server (NTRS)

We report the discovery of four NH3 (3, 3) masers in the NGC 6334 star formation region. The masers are found in two of the seven far-infrared continuum sources where high-mass star formation is taking place in this molecular cloud. These masers occur at the ends of high-velocity molecular outflows; no maser emission was found near regions without high-velocity outflows. The NH3 masers are not associated with any other type of maser. These results confirm that the NH3 (3, 3) masers are caused by shocks and probably mark the location where the molecular outflow jet impinges upon the ambient medium.

Kraemer, Kathleen E.; Jackson, James M.

1995-01-01

94

Photolysis of CO-NH3 mixtures and the Martian atmosphere  

NASA Technical Reports Server (NTRS)

It has already been noted (Ferris and Nicodem, 1972) that although neither CO2 nor H2O affected the rate of NH3 photolysis, CO accelerated the photodecomposition of ammonia, with the formation of a solid product. The photolysis of NH3 in the presence of CO is investigated in greater detail not only because of the potential significance to atmospheric photochemistry on Mars, but also because of the possibility of photocatalytic reactions of NH3 and CO on the Martian surface and in the interstellar medium. These photoreactions may also have occurred on the primitive earth.

Ferris, J. P.; Williams, E. A.; Nicodem, D. E.; Hubbard, J. S.; Voecks, G. E.

1974-01-01

95

My 45 Years of Astrochemistry: Memoirs of Takeshi Oka 1. NH3: CHARLIE TOWNES, KOICHI SHIMODA, JIM  

E-print Network

My 45 Years of Astrochemistry: Memoirs of Takeshi Oka 1. NH3: CHARLIE TOWNES, KOICHI SHIMODA, JIM emission between inversion levels of the J = K metastable NH3 was reported by the group of Charlie Townes.1

Oka, Takeshi

96

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...

97

New Gallium Phosphate Frameworks Containing 1,4-Diaminobutane and 1,5-Diaminopentane: [NH 3(CH 2) x NH 3][Ga 4(PO 4) 4(HPO 4)] and [NH 3(CH 2) x NH 3][Ga(PO 4)(HPO 4)] ( x=4 and 5)  

Microsoft Academic Search

Two new gallium phosphates, [NH3(CH2)4NH3][Ga4(PO4)4 (HPO4)] (I) and [NH3(CH2)4NH3][Ga(PO4)(HPO4)] (II), have been synthesized under solvothermal conditions in the presence of 1,4-diaminobutane and their structures determined using room-temperature single-crystal X-ray diffraction data. Compound (I) (Mr=844.90, triclinic, space group P-1, a=9.3619(3), b=10.1158(3) and c=12.6456(5) , ?=98.485(1), ?=107.018(2) and ?=105.424(1); V=1070.39 3, Z=2, R=3.68% and Rw=4.40% for 2918 observed data [I>3(?(I))]) consists of

Judith L. Kissick; Andrew R. Cowley; Ann M. Chippindale

2002-01-01

98

The monoammoniate of lithium borohydride, Li(NH3)BH4: an effective ammonia storage compound.  

PubMed

Lithium borohydride absorbs anhydrous ammonia to form four stable ammoniates; Li(NH(3))(n)BH(4), mono-, di-, tri-, and tertraammoniate. This paper focuses on the monoammoniate, Li(NH(3))BH(4), which is readily formed on exposure of LiBH(4) to ammonia at room temperature and pressure. Ammonia loss from Li(NH(3))BH(4) commences around 40 degrees C and the compound transforms directly to LiBH(4). The crystal structure of Li(NH(3))BH(4) is reported here for the first time. Its close structural relationship with LiBH(4) provides a clear insight into the facile nature and mechanism of ammonia uptake and loss. These materials not only represent an excellent high weight-percent ammonia system but are also potentially important hydrogen stores. PMID:19408264

Johnson, Simon R; David, William I F; Royse, David M; Sommariva, Marco; Tang, Christina Y; Fabbiani, Francesca P A; Jones, Martin O; Edwards, Peter P

2009-06-01

99

Cross sections for direct and dissociative ionization of NH3 and CS2 by electron impact  

NASA Technical Reports Server (NTRS)

A crossed electron beam-molecular beam collision geometry is used to measure cross sections for the production of positive ions by electron impact on NH3 and CS2. Ionization cross-section data for NH3 and the values of various cross sections are presented, as well as ionization efficiency curves for CS2. Considerable differences are found between the various results on NH3. The present values are close to the data of Djuric et al. (1981). The semiempirical calculations of Hare and Meath (1987) differ considerably in the absolute values of cross sections. Discrepancies were observed in comparisons of cross sections of other fragment ions resulting from the ionization and dissociate ionization of NH3.

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

1991-01-01

100

PREPARATION, CRYSTAL STRUCTURE AND CARACTERIZATION OF INORGANIC-ORGANIC HYBRID PEROVSKITE [NH3-(CH2)10-NH3] ZnCl4  

E-print Network

PREPARATION, CRYSTAL STRUCTURE AND CARACTERIZATION OF INORGANIC-ORGANIC HYBRID PEROVSKITE [NH3-(CH2.O.M.A, Université de Bordeaux I, cours de la libération Talence Cedex France ABSTRACT A new perovskite like system by DSC shows that the 2C10ZnCl4 perovskite presents reversible phase transition. Keywords: Perovskite

Paris-Sud XI, Université de

101

Antisymmetric and Anisotropic Exchange as Studied by EPR in a Molecular Composite [NH3-(CH2)2-NH3]CuCl4  

NASA Astrophysics Data System (ADS)

The monoclinic crystal structure of [NH3-(CH2)2-NH3]CuCl4 consists of two-dimensional (b, c) layers of square planar (CuCl4)2 - entities, separated from each other by [NH3-(CH2)2-NH3]2+ alkylene chain sheets. Electron Paramagnetic Resonance (EPR) data have been obtained in single crystals of 2C2CuCl4 when rotated around a*, b and c -axes, at X-band. Only one EPR exchange-collapsed line was observed for the two magnetically inequivalent copper ions in the lattice. The angular variation of its position and peak-to-peak linewidth were measured in three perpendicular planes. A careful analysis of experimental data permits to obtain the principal values of the g-factor g = 2.053, g = 2.274. The contributions to the linewidths were analyzed in terms of the antisymmetric exchange (d) and the anisotropic exchange (D) and yielded |dx/dy| = 0.92 and |(d2x + 2.2D2)1/2/dy| = 0.65. Lineshape studies show that the exchange between the two inequivalent copper ions is anisotropic.

Bissey, J.-Cl.; Filloleau, N.; Beziade, P.; Chanh, Nguyen-Ba; Zouari, R.; Daoud, A.

1997-06-01

102

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

103

The Initial Conditions of Clustered Star Formation. I. NH3 Observations of Dense Cores in Ophiuchus  

NASA Astrophysics Data System (ADS)

We present combined interferometer and single dish telescope data of NH3 (J, K) = (1,1) and (2,2) emission toward the clustered star forming Ophiuchus B, C, and F Cores at high spatial resolution (~1200 AU) using the Australia Telescope Compact Array, the Very Large Array, and the Green Bank Telescope. While the large-scale features of the NH3 (1,1) integrated intensity appear similar to 850 ?m continuum emission maps of the Cores, on 15'' (1800 AU) scales we find significant discrepancies between the dense gas tracers in Oph B, but good correspondence in Oph C and F. Using the CLUMPFIND structure identifying algorithm, we identify 15 NH3 clumps in Oph B, and three each in Oph C and F. Only five of the Oph B NH3 clumps are coincident within 30'' (3600 AU) of a submillimeter clump. We find v LSR varies little across any of the cores, and additionally varies by only ~1.5 km s-1 between them. The observed NH3 line widths within the Oph B and F Cores are generally large and often mildly supersonic, while Oph C is characterized by narrow line widths which decrease to nearly thermal values. We find several regions of localized narrow line emission (?v lsim 0.4 km s-1), some of which are associated with NH3 clumps. We derive the kinetic temperatures of the gas, and find they are remarkably constant across Oph B and F, with a warmer mean value (TK = 15 K) than typically found in isolated regions and consistent with previous results in clustered regions. Oph C, however, has a mean TK = 12 K, decreasing to a minimum TK = 9.4 K toward the submillimeter continuum peak, similar to previous studies of isolated starless clumps. There is no significant difference in temperature toward protostars embedded in the Cores. NH3 column densities, N(NH3), and abundances, X(NH3), are similar to previous work in other nearby molecular clouds. We find evidence for a decrease in X(NH3) with increasing N(H2) in Oph B2 and C, suggesting the NH3 emission may not be tracing well the densest core gas.

Friesen, R. K.; Di Francesco, J.; Shirley, Y. L.; Myers, P. C.

2009-06-01

104

Millimeter-wave spectroscopy of the weakly bound molecular complex NH3-N2  

NASA Astrophysics Data System (ADS)

The rotational spectrum of the van der Waals NH3-N2 complex is studied in the frequency range of 112-130 GHz. The transitions are measured in a cold molecular beam with an intracavity spectrometer based on an orotron. A total of six new transitions of different spin modifications of the complex are recorded. Molecular parameters of the K = 0 ground state are determined for the orthoNH3- orthoN2 modification.

Potapov, A. V.; Dolgov, A. A.; Surin, L. A.

2012-07-01

105

A vibrational spectroscopic study of diammine diisocyanatocopper(II), Cu(NCO) 2(NH 3) 2  

NASA Astrophysics Data System (ADS)

The infrared and Raman spectra of Cu(NCO) 2(NH 3) 2 are reported and comparisons made with the vibrational spectrum of Zn(NCO) 2(NH 3) 2. Skeletal vibrational assignments have been made which are consistent with a trans-planar configuration and centrosymmetric D2h symmetry. There is no spectroscopic evidence for bridging cyanate ligands, in contrast with previous experimental reports.

Edwards, H. G. M.; Lewis, I. R.; Webb, N.

1993-12-01

106

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

107

Global distributions, time series and error characterization of atmospheric ammonia (NH3) from IASI satellite observations  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) emissions in the atmosphere have increased substantially over the past decades, largely because of 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 near local sources. 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 includes error characterization of 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 data set of NH3 total columns, which are evaluated and compared to similar products from other retrieval methods. Spatial distributions from the five years data set are provided and analyzed at global and regional scales. In particular, we show the ability of this method to identify smaller emission sources than those previously reported, as well as transport patterns over the ocean. The five-year time series is further examined in terms of seasonality and interannual 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.

2014-03-01

108

Effects of in-situ NH3 post plasma treatment on the surface passivation layer  

NASA Astrophysics Data System (ADS)

Hydrogenated silicon nitride (SiNx:H) using plasma enhanced chemical vapor deposition is widely used in photovoltaic industry as an antireflection coating and passivation layer. The samples with or without in-situ NH3 post-plasma treatment had the following structures: SiNx/N-type Si/SiNx versus in-situ NH3 post-plasma treated SiNx/N-type Si/SiNx. The wafer was dipped in saw-damage-etching solution and wet cleaning process was treated. After the dry process with N2 atmosphere, SiNx thin film was deposited on back surface. Then SiNx thin film was deposited on the front surface with or without in-situ NH3 post-plasma treatment process. In order to minimize the plasma induced surface damage, we used lower power than the process power during the NH3 post-plasma treatment. After the in-situ NH3 post-plasma-treatment, we analyzed the effect of this in-situ NH3 post-plasma-treatment for passivation. The minority carrier lifetime was observed by means of quasi-steady-state photoconductance and microwave photoconductance.

Lee, Kyung Dong; Kang, Min Gu; Kim, Young Do; Tark, Sung Ju; Park, Sungeun; Kim, Donghwan

2011-12-01

109

On the Interaction of CO and NH3 with BH3 and BF3  

NASA Technical Reports Server (NTRS)

BH3CO, BF3CO, BH3NH3, and BF3NH3 have been studied using density functional theory (DFT). The computed geometries are in reasonable agreement with experiment. BF3CO is found to be weakly bound. The binding energies of BH3CO, BH3NH3 , and BF3NH3 have also been computed using the coupled cluster singles and doubles level of theory, including a perturbational estimate of the connected triples [CCSD(T)]. These CCSD(T) calculations are performed using correlation consistent polarized-valence triple-zeta basis sets. These are expected to be the most accurate binding energies to date. The DFT binding energies are in good agreement with those obtained at the CCSD(T) level. The bonding is analyzed using the constrained space orbital variation (CSOV) technique. In addition to analyzing the bonding in BH3CO, BH3NH3, and BF3NH3, the CSOV approach is used to study why the bonding in BF3CO is so weak.

Bauschlicher, Charles W., Jr.; Ricca, Alessandra; Langhoff, Stephen R. (Technical Monitor)

1994-01-01

110

New insights into the diurnal variability of animal NH3 emissions using in-situ, satellite and aloft observations  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) is the primary atmospheric base and an important precursor for inorganic particulate matter. NH3 deposition contributes to surface water eutrophication, soil acidification and decline in species biodiversity. Despite its importance in atmospheric chemistry and the nitrogen biogeochemical cycle, the magnitude and temporal dynamics of NH3 emissions remain uncertain in regional and global scale models. This uncertainty stems from the lack of routine ambient NH3 observations and the complexity of NH3 emission sources. We will combine satellite, in-situ, and aircraft observations with model sensitivities to develop and evaluate process based improvements in NH3 emissions from animal production activities. First, we will show that initial model evaluations of ambient NH3 estimates using TES satellite and in-situ Carolina Ammonia Monitoring Network (CAMNet) observations paired in space and time indicated that the Community Multi-scale Air Quality (CMAQ) and GEOS-Chem overestimated CAMNet NH3 observations but underestimated TES observations. An evaluation of the differences in the timing of the measurement techniques indicated that the model errors are due to the dynamics of the temporal NH3 emissions, predominately from animal production. This was confirmed qualitatively using hourly in-situ NH3 observations. Then, a mechanistic NH3 animal emissions conceptual model was developed and implemented for use in both CMAQ and GEOS-Chem models. Finally, we will present improvements in model evaluations of gaseous NH3, NO3 aerosol concentrations and NH4 wet deposition against network, TES satellite and aircraft observations.

Bash, J. O.; Henze, D. K.; Zhu, L.; Jeong, G.; Walker, J. T.; Nowak, J. B.; Neuman, J. A.; Cady-Pereira, K. E.; Shephard, M. W.; Luo, M.; Pinder, R. W.

2013-12-01

111

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

PubMed

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. PMID:8159700

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

1994-04-12

112

Movement of NH3 through the human urea transporter B: a new gas channel  

PubMed Central

Aquaporins and Rh proteins can function as gas (CO2 and NH3) channels. The present study explores the urea, H2O, CO2, and NH3 permeability of the human urea transporter B (UT-B) (SLC14A1), expressed in Xenopus oocytes. We monitored urea uptake using [14C]urea and measured osmotic water permeability (Pf) using video microscopy. To obtain a semiquantitative measure of gas permeability, we used microelectrodes to record the maximum transient change in surface pH (?pHS) caused by exposing oocytes to 5% CO2/33 mM HCO3? (pHS increase) or 0.5 mM NH3/NH4+ (pHS decrease). UT-B expression increased oocyte permeability to urea by >20-fold, and Pf by 8-fold vs. H2O-injected control oocytes. UT-B expression had no effect on the CO2-induced ?pHS but doubled the NH3-induced ?pHS. Phloretin reduced UT-B-dependent urea uptake (Jurea*) by 45%, Pf* by 50%, and (??pHS*)NH3 by 70%. p-Chloromercuribenzene sulfonate reduced Jurea* by 25%, Pf* by 30%, and (?pHS*)NH3 by 100%. Molecular dynamics (MD) simulations of membrane-embedded models of UT-B identified the monomeric UT-B pores as the main conduction pathway for both H2O and NH3 and characterized the energetics associated with permeation of these species through the channel. Mutating each of two conserved threonines lining the monomeric urea pores reduced H2O and NH3 permeability. Our data confirm that UT-B has significant H2O permeability and for the first time demonstrate significant NH3 permeability. Thus the UTs become the third family of gas channels. Inhibitor and mutagenesis studies and results of MD simulations suggest that NH3 and H2O pass through the three monomeric urea channels in UT-B. PMID:23552862

Musa-Aziz, Raif; Enkavi, Giray; Mahinthichaichan, P.; Tajkhorshid, Emad; Boron, Walter F.

2013-01-01

113

Diffusion-promoted-desorption mechanism for D 2 desorption from Si(100) surfaces  

NASA Astrophysics Data System (ADS)

Temperature-programmed-desorption (TPD) spectra and isothermal desorption rates of D 2 molecules from a Si(100) surface have been calculated to reproduce experimental ?1, A -TPD spectra and isothermal desorption rate curves. In the diffusion-promoted-desorption (DPD) mechanism, hydrogen desorption from the Si(100) (2 1) surfaces takes place via D atom diffusion from doubly-occupied Si dimers (DODs) to their adjacent unoccupied Si dimers (UODs). Taking a clustering interaction among DODs into consideration, coverages ?DU of desorption sites consisting of a pair of a DOD and UOD are evaluated by a Monte Carlo (MC) method. The TPD spectra for the ?1, A peak are obtained by numerically integrating the desorption rate equation R = ?A exp(- Ed, A / kBT) ?DU, where ?A is the pre-exponential factor and Ed, A is the desorption barrier. The TPD spectra calculated for Ed, A = 1. 6 eV and ?A = 2.7 10 9 /s are found to be in good agreement with the experimental TPD data for a wide coverage range from 0.01 to 0.74 ML. Namely, the deviation from first-order kinetics observed in the coverage dependent TPD spectra as well as in the isothermal desorption rate curves can be reproduced by the model simulations. This success in reproducing both the experimental TPD data and the very low desorption barrier validates the proposed DPD mechanism.

Narita, Y.; Inanaga, S.; Unoko, C.; Namiki, A.

2011-01-01

114

Structural, electronic, bonding, and elastic properties of NH3BH3: a density functional study.  

PubMed

The structural, electronic, bonding, and elastic properties of the low-temperature orthorhombic phase of NH(3)BH(3) are studied by means of first-principles total energy calculations based on the pseudopotential method. The calculated structural parameters of NH(3)BH(3) are found to be in good agreement with the experimental values. From the band structure calculations, the compound is found to be an indirect bandgap insulator with the bandgap of 5.65 eV (5.90 eV) with LDA(GGA) along the ?-Z direction. The Mulliken bond population and the charge density distributions are used to analyze the chemical bonding in NH(3)BH(3) . The study reveals that B-H bonds are more covalent than N-H bonds. The elastic constants are predicted for ambient as well as pressures up to 6 GPa, from which theoretical values of all the related mechanical properties such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and anisotropy factors are calculated. It is found that NH(3)BH(3) is mechanically stable at ambient and also external pressures up to 6 GPa. As pressure increases all the calculated elastic moduli of NH(3)BH(3) increase, indicating that the compound becomes more stiffer and hard under pressure. From the ratio of shear modulus to bulk modulus (G/B), we conclude NH(3)BH(3) to be ductile in nature, and the ductility increases with pressure. The present results confirm the experimentally observed less plastic nature of the low-temperature phase of NH(3)BH(3) . PMID:21425297

Lingam, Ch Bheema; Babu, K Ramesh; Tewari, Surya P; Vaitheeswaran, G

2011-06-01

115

NH3 Abatement in Fluidized Bed Co-Gasification of RDF and Coal  

NASA Astrophysics Data System (ADS)

Gasification of wastes may come out as an alternative technology to produce a gas with many potential applications, from direct burning in a boiler or motor to the production of synthetic chemicals and hydrogen. High tar production and high operational costs are preventing gasification wider dissemination. Besides these problems, the presence of NH3 in the syngas may have a negative impact as it can be converted into nitrogen oxides if the gas is further burnt. To reduce NH3 formation it is required a full understanding of how operational parameters contribute to the formation/reduction of this pollutant. A full studyon the effect of fuel composition, temperature and equivalence ratio on the formation of NH3 is given. Experimental results are compared to theoretical ones obtained with FactSage software. It is also analyzed the effect of feedstock mineral matterin NH3 release during gasification. Toaccomplish a significant decrease in the release of NH3, different catalysts and sorbents were tested with the aim of achieving high energy conversions and low environmental impact.

Gulyurtlu, I.; Pinto, Filomena; Dias, Mrio; Lopes, Helena; Andr, Rui Neto; Cabrita, I.

116

Experimental verification of the high pressure crystal structures in NH3BH3  

NASA Astrophysics Data System (ADS)

A detailed high-pressure study on NH3BH3 has been carried out using in situ synchrotron X-ray diffraction (XRD) and Raman scattering with a diamond anvil cell up to 20 and 33 GPa, respectively. The Rietveld refinement based on the XRD pattern and analysis of Raman data indicate two first-order phase transitions from the ambient pressure I4 mm structure (?-NH3BH3) to a high pressure Cmc21 phase (?-NH3BH3) at 2.14 GPa, and further into a monoclinic P21 (Z = 2) phase (?-NH3BH3) at 9.67 GPa. Fitting the measured volumetric compression data to the third order Birch-Murnaghan equation of state reveals a bulk modulus of B0 = 9.9 0.5 and 17.0 3.0 GPa (with fixed B0' = 4) for the ?-NH3BH3 below and above 5 GPa, respectively. Still, with the splitting of the NBH rock mode in Raman experiment, it is concluded that a second-order isostructural phase transition occurs at 5 GPa. By analyzing the dihydrogen bonding framework, the origin of the isostructural phase transition is attributed to the number of dihydrogen bondings per molecule in the Cmc21 phase increasing from 12 to 14 at 5 GPa.

Huang, Yanping; Huang, Xiaoli; Zhao, Zhonglong; Li, Wenbo; Jiang, Shuqing; Duan, Defang; Bao, Kuo; Zhou, Qiang; Liu, Bingbing; Cui, Tian

2014-06-01

117

Thermal Durability of Cu-CHA NH3-SCR Catalysts for Diesel NOx Reduction  

SciTech Connect

Multiple catalytic functions (NOx conversion, NO and NH3 oxidation, NH3 storage) of a commercial Cu-zeolite urea/NH3-SCR catalyst were assessed in a laboratory fixed-bed flow reactor system after differing degrees of hydrothermal aging. Catalysts were characterized by using x-ray diffraction (XRD), 27Al solid state nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM) / energy dispersive X-ray (EDX) spectroscopy to develop an understanding of the degradation mechanisms during catalyst aging. The catalytic reaction measurements of laboratory-aged catalysts were performed, which allows us to obtain a universal curve for predicting the degree of catalyst performance deterioration as a function of time at each aging temperature. Results show that as the aging temperature becomes higher, the zeolite structure collapses in a shorter period of time after an induction period. The decrease in SCR performance was explained by zeolite structure destruction and/or Cu agglomeration, as detected by XRD/27Al NMR and by TEM/EDX, respectively. Destruction of the zeolite structure and agglomeration of the active phase also results in a decrease in the NO/NH3 oxidation activity and the NH3 storage capacity of the catalyst. Selected laboratory aging conditions (16 h at 800oC) compare well with a 135,000 mile vehicle-aged catalyst for both performance and characterization criteria.

Schmieg, Steven J.; Oh, Se H.; Kim, Chang H.; Brown, David B.; Lee, Jong H.; Peden, Charles HF; Kim, Do Heui

2012-04-30

118

Engineering analysis of an NH3-air alkaline fuel cell system for vehicular applications  

NASA Astrophysics Data System (ADS)

The use of a hydrogen air alkaline fuel cell in a vehicle with liquid anhydrous ammonia as the hydrogen storage medium was examined. In the system analyzed here, hydrogen is supplied to the fuel cell by the catalytic cracking of liquid anhydrous ammonia, making the total system an indirect NH3 air fuel cell system. It was found that the endothermicity of the NH3 cracking reaction is supplied by combustion of the anode vent gas after utilizing 80% of the hydrogen electrochemically resulting in a minimal efficiency penalty. Laboratory scale examinations were made of the ammonia cracking reaction and the power characteristics of an alkaline fuel cell running on cracked ammonia and air. Single cell and bicell testing indicated system thermal efficiencies of 48 to 60% (based on L.H.V. of NH3) can be achieved at power densities of 1 to 2.6 kW/sq m using currently known electrode technology in a bipolar design.

Ross, P. N., Jr.

1982-06-01

119

Insertion Compounds of 2H-TaS2NH3  

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, NH3Mx, 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(TaS2NH3Mx) - 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, 4.7K. Images PMID:16592219

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

1975-01-01

120

NH2 fluorescence efficiencies and the NH3 abundance in Comet Halley  

NASA Technical Reports Server (NTRS)

If NH3 is the dominant source of the NH2 observed in comet spectra, then the NH3 abundance can in principle be accurately determined. Fluorescence efficiencies for the (0, v-prime/2/, O) to (0, 0, 0) progression of NH2 bands are calculated for NH2 bands likely to be observed in the 4500-8200-A region of comets. The results differ from previous determinations of the NH2 band fluorescence efficiencies by factors in the range 1.4-5.9, leading t6o significant changes in previously reported NH2 production rates in comets. A recalculation of the NH3/H2O abundance ratio in Comet Halley gives about (0.5 + or - 0.2) percent in better agreement with the Giotto ion-mass-spectrometer results of Allen et al (1987).

Tegler, Stephen; Wyckoff, Susan

1989-01-01

121

Density dependence of the 5 micron infrared spectrum of NH3  

NASA Technical Reports Server (NTRS)

Measurements of dilute mixtures of NH3 in H2 were made in the window region 1900-2100/cm of the NH3 spectrum to determine is behavior with increasing pressure of H2. The spectra of pure H2, pure NH3, and mixtures of the two, in the total pressure range from 2.38 to 8.17 atm at 309 K, were obtained with a 975-cm white-cell. Synthetic spectra were calculated using precise line strengths, line positions, and a Lorentz profile. The experimental and calculated spectra are in reasonably good agreement, except that the former is super-imposed on a rather flat background not given by the calculation. A possible mechanism for this background is suggested.

Chapados, Camille; Bjoraker, Gordon L.; Birnbaum, George

1990-01-01

122

Single-layer MoSe2 based NH3 gas sensor  

NASA Astrophysics Data System (ADS)

High performance chemical sensor is highly desirable to detect traces of toxic gas molecules. Two dimensional (2D) transition metal dichalcogenides (TMDC) semiconducting materials has attracted as high performance gas sensor device applications due to unique properties such as high surface to volume ratio. Here, we describe the utilization of single-layer MoSe2 as high-performance room temperature NH3 gas sensors. Our single-layer MoSe2 based gas sensor device shows comprehensible detection of NH3 gas down to 50 ppm. We also confirmed gas sensing measurement by recording the Raman spectra before and after exposing the device to NH3 gas, which subsequently shows the shift due to charger transfer and analyte gas molecule adsorption on surface of single-layer MoSe2 nanosheet. Our investigations show the potential use of single-layer and few layer thick MoSe2 and other TMDC as high-performance gas sensors.

Late, Dattatray J.; Doneux, Thomas; Bougouma, Moussa

2014-12-01

123

Complex Actions of Thyroid Hormone Receptor Antagonist NH-3 on Gene Promoters in Different Cell Lines  

PubMed Central

It is desirable to obtain new antagonists for thyroid hormone (TRs) and other nuclear receptors (NRs). We previously used X-ray structural models of TR ligand binding domains (LBDs) to design compounds, such as NH-3, that impair coactivator binding to activation function 2 (AF-2) and block thyroid hormone (triiodothyronine, T3) actions. However, TRs bind DNA and are transcriptionally active without ligand. Thus, NH-3 could modulate TR activity via effects on other coregulator interaction surfaces, such as activation function (AF-1) and corepressor binding sites. Here, we find that NH-3 blocks TR-LBD interactions with coactivators and corepressors and also inhibits activities of AF-1 and AF-2 in transfections. While NH-3 lacks detectable agonist activity at T3-activated genes in GC pituitary cells it nevertheless activates spot 14 (S14) in HTC liver cells with the latter effect accompanied by enhanced histone H4 acetylation and coactivator recruitment at the S14 promoter. Surprisingly, T3 promotes corepressor recruitment to target promoters. NH-3 effects vary; we observe transient recruitment of N-CoR to S14 in GC cells and dismissal and rebinding of N-CoR to the same promoter in HTC cells. We propose that NH-3 will generally behave as an antagonist by blocking AF-1 and AF-2 but that complex effects on coregulator recruitment may result in partial/mixed agonist effects that are independent of blockade of T3 binding in some contexts. These properties could ultimately be utilized in drug design and development of new selective TR modulators. PMID:18930112

Shah, Vanya; Nguyen, Phuong; Nguyen, Ngoc-Ha; Togashi, Marie; Scanlan, Thomas S.; Baxter, John D.; Webb, Paul

2014-01-01

124

Mixing of Dust and NH3 Observed Globally over Anthropogenic Dust Sources  

NASA Technical Reports Server (NTRS)

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 square meters per gram as NH3 burden increases from 0 to 40 milligrams per square meter. The fine mode extinction efficiency, ranging from 4 to 16 square mters per gram, 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.

2012-01-01

125

Partial phase diagram for the system NH3-H2O - The water-rich region  

NASA Technical Reports Server (NTRS)

Phase boundaries of the H2O-NH3 system for (NH3)/x/(H2O)/1-x/ have been determined with diamond-anvil cells for mixtures in two composition ranges: (1) for x in the range from 0 to 0.3, at pressures up to 4 GPa at 21 C, and (2) for x in the range from 0.46 to 0.50, at pressures up to 5 GPa from 150 to 400 K. Phases were identified visually with a microscope and polarized optics. The NH3.2(H2O) phase is strongly anisotropic with a much smaller refractive index than that of ice VII and cracks in two nonperpendicular networks. NH3.H2O has a refractive index closer to that of Ice VII and does not appear to form cracks. Both phases are colorless. Phase boundaries were determined on both increasing and decreasing pressures, and compositions of the ammonia ices were determined by estimating relative amounts of water and ammonia ices at known overall compositions. For low-ammonia compositions (x equal to or less than 0.15), the following assemblages succedd one another as pressure increases: liquid; liquid and Ice VI (at 1.0 + GPa); liquid and Ice VII (at 2.1 GPa); Ice VII and NH3.H2O (at 3.5 GPa). For x in the range from 0.15 to 0.30, the water ice and liquid fields are replaced by the NH3.2(H2O) and liquid field at pressures down to 1.0 GPa and lower.

Johnson, M. L.; Schwake, A.; Nicol, M.

1984-01-01

126

Ammonia-chain clusters: Vibronic spectra of 7-hydroxyquinoline?(NH3)2  

NASA Astrophysics Data System (ADS)

Mass- and isomer-selected S1?S0 resonant two-photon ionization and S1?S0 fluorescence spectra were measured for the 7-hydroxyquinoline?(NH3)2 [7HQ?(NH3)2] and d2-7-hydroxyquinoline?(ND3)2 clusters cooled in supersonic expansions. UV/UV hole burning measurements prove that a single cluster isomer is formed. Ab initio self-consistent field and density functional calculations predict that the most stable cluster form has an "ammonia wire" hydrogen bonded to the -OH and N groups of the cis-7HQ rotamer. The experimental S0 and S1 frequencies are in very good agreement with the calculated normal mode frequencies for both the normal and deuterated ammonia-wire clusters. S1?S0 excitation leads to contractions of the -O-H⋯N and NH3NH3 hydrogen bonds, as well as smaller displacements for the NH3⋯N(quinoline) stretch and the in plane rotation (or bend) of the ammonia dimer relative to 7HQ. The coupling of these modes to the S1?S0 electronic excitation indicates that hydrogen bond contractions in the excited state are important and may be prerequisite for the S1 state proton transfer processes that occur in the larger 7HQ?(NH3)n (n?4) clusters. The calculated electron density differences upon S1?S0 excitation show large ?-electron flows on the 7HQ moiety. However, the ?-electronic rearrangements that directly drive the hydrogen bond rearrangements are one to two orders of magnitude smaller.

Coussan, Stphane; Manca, Carine; Tanner, Christian; Bach, Andreas; Leutwyler, Samuel

2003-08-01

127

Quasidiabatic states for intramolecular charge transfer. Application to the protonation of NH3  

NASA Astrophysics Data System (ADS)

We have constructed ab initio adiabatic and quasidiabatic surfaces for the description of the protonation of NH3. For the diabatic states, we applied a recently developed method which is based on the propagation along the reaction coordinate, starting from the dissociation region, of the maximized nonorthonormal overlap between diabatic states calculated at successive geometries. In agreement with earlier calculations [Kaldor et al., J. Chem. Phys. 90, 6395 (1989)], it was found that the adiabatic surfaces cannot explain this charge-transfer process. On the contrary, a single diabatic potential curve correlates smoothly the ground state of NH+4 with the NH3+H+ limit.

Petsalakis, I. D.; Theodorakopoulos, G.; Nicolaides, C. A.

1994-04-01

128

Modeling of Jupiter's millimeter wave emission utilizing laboratory measurements of ammonia (NH3) opacity  

NASA Technical Reports Server (NTRS)

The techniques used to make laboratory measurements of the millimeter wave opacity from gaseous ammonia under simulated Jovian conditions are described. The results are applied to a radiative transfer model, which is used to compute Jupiter's millimeter wavelength emission. The absorptivity of gaseous NH3 is measured to reduce one of the largest uncertainties in modeling Jupiter's millimeter wave emission. Several other millimeter wave opacity sources are examined. New expressions are given for computing the absorptivity of NH3, H2O, cloud condensates, and pressure-induced absorption. Jupiter's reliable millimeter wavelength observations are compared with synthetic emission spectra which utilize these new absorption expressions.

Joiner, Joanna; Steffes, Paul G.

1991-01-01

129

Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3. [photolysis products  

NASA Technical Reports Server (NTRS)

Ammonium cyanate is identified as the major product of the photolysis of gaseous NH3-CO mixtures at 206.2 or 184.9 nm. Lesser amounts of urea, biurea, biuret semicarbazide, formamide and cyanide are observed. A series of 18 reactions underlying the formation of photolysis products is presented and discussed. Photocatalytic syntheses of C-14-urea, -formamide, and -formaldehyde are carried out through irradiation of (C-14)O and NH3 in the presence of Vycor, silica gel, or volcanic ash shale surfaces. The possible contributions of the relevant reactions to the abiotic synthesis of organic nitrogen compounds on Mars, the primitive earth, and in interstellar space are examined.

Hubbard, J. S.; Voecks, G. E.; Hobby, G. L.; Ferris, J. P.; Williams, E. A.; Nicodem, D. E.

1975-01-01

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

Hydrogen desorption mechanism in a Li-N-H system by means of the isotopic exchange technique.  

PubMed

The hydrogen desorption mechanism in the reaction from LiH + LiNH2 to Li2NH + H2 was examined by thermal desorption mass spectrometry, thermogravimetric analysis, and Fourier transform IR analyses for the products replaced by LiD or LiND2 for LiH or LiNH2, respectively. The results obtained indicate that the hydrogen desorption reaction proceeds through the following two-step elementary reactions mediated by ammonia: 2LiNH2 --> Li2NH + NH3 and LiH + NH3 --> LiNH2 + H2, where hydrogen molecules are randomly formed from four equivalent hydrogen atoms in a hypothetical LiNH4 produced by the reaction between LiH and NH3 according to the laws of probability. PMID:16852881

Isobe, Shigehito; Ichikawa, Takayuki; Hino, Satoshi; Fujii, Hironobu

2005-08-11

132

Low energy structural dynamics and constrained libration of Li(NH3)4, the lowest melting point metal.  

PubMed

The lattice and molecular dynamics for the solid phases of the lowest melting-point metal, Li(NH3)4, are determined by incoherent inelastic neutron scattering. Measurements of internal molecular displacements and distortions of the Li(NH3)4 units have been modelled and assigned using density functional theory calculations for the solid and molecular system. Inelastic neutron scattering measurement allow for the first determination of NH3 librational transitions. PMID:24988060

Seel, A G; Zurek, E; Ramirez-Cuesta, A J; Ryan, K R; Lodge, M T J; Edwards, P P

2014-09-25

133

Infrared multi-line NH3 laser and its application for pumping an InSb laser  

Microsoft Academic Search

In this paper, infrared (IR) emissions from a TE CO2 laser pumped NH3 laser are reported. 38 IR laser lines were obtained from a CO2 9R(30) line pumped NH3:N2 mixture by cooling a NH3 laser tube, and 13 lines of them were new emission lines as far as we know. Four Q-branch lines were included and the others belonged to

N. Yamabayashi; T. Yoshida; K. Miyazaki; K. Fujisawa

1979-01-01

134

Spin transport in CH3NH3PbI3  

NASA Astrophysics Data System (ADS)

Organometal trihalide perovskites with the general formula (CH3NH3)PbX3 (X is Cl, I and/or Br) have a composition dependent tunable band gap and long electron-hole diffusion length, which is not only being hotly studied for usage in hybrid solar cells, but also has potential application in organic spintronics. In this work, we prepared CH3NH3PbI3-coated Fe3O4 granular films. CH3NH3PbI3 behaves effectively as a spacer to decouple the Fe3O4 particles and spin-preserved transporting matrix. The magnetoresistance of Fe3O4 particles has been significantly enhanced after CH3NH3PbI3 coating, which is about -6% at 300 K and -10.8% at 150 K under a magnetic field of 10 kOe, about 3 times larger than the values of pure Fe3O4 (-1.9% at 300 K and -3.4% at 150 K).

Xu, Qingyu; Liu, Er; Qin, Sai; Shi, Shan; Shen, Kai; Xu, Mingxiang; Zhai, Ya; Dong, Shuai

2014-10-01

135

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 ...

136

Formation of NH3 and CH2NH in Titan's upper Roger V. Yelle,a  

E-print Network

into larger organic molecules of biological interest, such as amino acids or nucleic acid bases.4 We therefore of coupled ion and neutral chemistry. The density of NH3 is inferred from the measured abundance of NH4 of the composition of Titan's ionosphere provide a sensitive probe of the composition of the neutral atmosphere

Yelle, Roger V.

137

Ground-based FTIR measurements of NH3 total columns and comparison with IASI data  

NASA Astrophysics Data System (ADS)

Atmospheric ammonia (NH3) dominates global emissions of total reactive nitrogen. It has an impact on human health, as a precursor of fine particulate matter, and on Earth's ecosystems, via deposition. The main source of global NH3 emissions is agriculture, the remaining ones being the oceans, natural vegetation, humans, wild animals and biomass burning. The global atmospheric budget of NH3 is still very uncertain in chemical models, highlighting the critical need for satellite and ground-based observations. We present, for the first time, time-series (2009 - 2011) of NH3 total columns obtained from ground-based FTIR measurements. These observations are performed at Reunion Island (21S, 55E), one of the two subtropical stations, in Southern Hemisphere, of the ground-based Network for the Detection of Atmospheric Composition Change (NDACC) equipped with FTIR instruments. The seasonal and inter-annual variabilities of ammonia observed at Reunion Island from the ground are compared to the ones derived from recent IASI data obtained with a new retrieval method based on the calculation of a Hyperspectral Range Index.

Vigouroux, Corinne; De Mazire, Martine; Desmet, Filip; Hermans, Christian; Langerock, Bavo; Scolas, Francis; Van Damme, Martin; Clarisse, Lieven; Coheur, Pierre-Franois

2013-04-01

138

Eliminating Positively Charged Lysine E-NH3 + Groups on the  

E-print Network

Eliminating Positively Charged Lysine E-NH3 + Groups on the Surface of Carbonic Anhydrase Has polypeptidessbovine carbonic anhydrase (BCA) and peracetylated BCA (BCA-Ac18)shaving the same sequence of amino acids increased the net charge on the surface of a model proteinsbovine carbonic anhydrase (BCA, EC 4.2.1.1)sin

Prentiss, Mara

139

Hydrogen release from amminelithium borohydride, LiBH4 x NH3.  

PubMed

Amminelithium borohydride, LiBH(4) x NH(3) which has two temperature sensitive chemical bonds N:-->Li(+) and N-H...H-B, is shown to release hydrogen at low temperatures by stabilizing the ammonia and promoting the recombination of the NH...HB bond. PMID:20449320

Guo, Yanhui; Xia, Guanglin; Zhu, Yihan; Gao, Liang; Yu, Xuebin

2010-04-21

140

Parametrization of electron impact ionization cross sections for CO, CO2, NH3 and SO2  

NASA Technical Reports Server (NTRS)

The electron impact ionization and dissociative ionization cross section data of CO, CO2, CH4, NH3, and SO2, measured in the laboratory, were parameterized utilizing an empirical formula based on the Born approximation. For this purpose an chi squared minimization technique was employed which provided an excellent fit to the experimental data.

Srivastava, Santosh K.; Nguyen, Hung P.

1987-01-01

141

Saturated absorption in NH3 demonstrated using a tuneable diode laser  

NASA Technical Reports Server (NTRS)

Saturation of molecular transitions using a tunable diode laser has been demonstrated for the first time using a standing-wave-cavity configuration with the laser beam focused at the sample. Observed saturation effects in NH3 transitions near 888 kaysers include sub-Doppler (Lamb-dip) resonances at the line center.

Jennings, D. E.

1978-01-01

142

Modified zinc oxide thick film resistors as NH 3 gas sensor  

Microsoft Academic Search

Screen printed thick films of pure and RuO2-doped zinc oxide were prepared. Pure zinc oxide films were also surface modified with ruthenium chloride. Gas sensing properties of the pure, doped and surface modified films were studied. The films were observed to be most sensitive to NH3 gas. The results are discussed and interpreted.

M. S. Wagh; G. H. Jain; D. R. Patil; S. A. Patil; L. A. Patil

2006-01-01

143

Laboratory study of sticking and desorption of H2 and its significance in the chemical evolution of dense interstellar medium  

NASA Astrophysics Data System (ADS)

The temperature-programmed desorption spectra of H2 is recorded under ultrahigh vacuum conditions on an olivine substrate with more than 90 per cent forsterite content for different coverage and temperatures. Then, using an empirical kinetic model, binding energy of H2 on the substrate is found to be 480 10 K (41.36 0.86 meV). Lower limit of sticking coefficient is estimated by comparing gas load at room temperature and at low temperature, which varies between 0.82 and 0.25 for temperatures between 7 and 14 K. Using a gas-grain chemical network, it is found out that a steady state is reached around after 50 yr at 10 K and both the steady-state abundance and time required to attend steady state is a strong function of temperature. Then, this model is used to check the effect of sticking of H2 on the grain surface chemistry. It is found that for H2O, CH4, NH3 and HCN, abundance due to reaction pathways involving H2 is within 1 per cent, when compared with the abundance achieved considering most dominant pathways. Thus, neglecting sticking of H2 will not change overall abundance of these molecules. For carbon chain molecules, it was found that the reaction pathways with H2 may be important and could contribute significantly to account for the observed abundances. Since, sticking of H2 is temperature sensitive, increase in temperature will reduce the effect of these reactions.

Acharyya, K.

2014-09-01

144

Simultaneous removal of H2S and NH3 in biofilter inoculated with Acidithiobacillus thiooxidans TAS.  

PubMed

H2S and NH3 gases are toxic, corrosive and malodorous air pollutants. Although there are numerous well-established physicochemical techniques presently available for the treatment of these gases, the growing demand for a more economical and improved process has prompted investigations into biological alternatives. In biological treatment methods, H2S is oxidized to SO4(2-) by sulfur-oxidizing bacteria, and then NH3 is removed by chemical neutralization with SO4(2-) to (NH4)2SO4. Since the accumulated (NH4)2SO4 can inhibit microbial activity, it is important to utilize an effective sulfur-oxidizing bacterium that has tolerance to high concentrations of (NH4)2SO4 for the simultaneous removal of H2S and NH3. In this study, a sulfur-oxidizing bacterium with tolerance to high concentrations of (NH4)2SO4 was isolated from activated sludge and identified as Acidithiobacillus thiooxidans TAS. A. thiooxidans TAS could display its sulfur-oxidizing activity in a medium supplemented with 60 g.l(-1) (NH4)2SO4, even though its growth and sulfur-oxidizing activity were completely inhibited in 80 g.l(-1) (NH4)2SO4. When H2S alone was supplied to a ceramic biofilter inoculated with A. thiooxidans TAS, an almost 100% H2S removal efficiency was maintained until the inlet H2S concentration was increased up to 900 microl.l(-1) and the space velocity up to 500 h(-1), at which the amount of H2S eliminated was 810 g-S.m(-3).h(-1). However, when NH3 (50-500 microl.l(-1)) was simultaneously supplied to the biofilter with H2S, the maximum amount of H2S eliminated decreased to 650 g-S.m(-3).h(-1). The inhibition of H2S removal by low NH3 concentrations (50-200 microl.l(-1)) was similar to that by high NH3 concentrations (300-500 microl.l(-1)). The critical inlet H2S load that resulted in over 99% removal was determined as 400 g-S.m(-3).h(-1) in the presence of NH3. PMID:16233839

Lee, Eun Young; Cho, Kyung-Suk; Ryu, Hee Wook

2005-06-01

145

Rapid ammonia gas transport accounts for futile transmembrane cycling under NH3/NH4+ toxicity in plant roots.  

PubMed

Futile transmembrane NH3/NH4(+) cycling in plant root cells, characterized by extremely rapid fluxes and high efflux to influx ratios, has been successfully linked to NH3/NH4(+) toxicity. Surprisingly, the fundamental question of which species of the conjugate pair (NH3 or NH4(+)) participates in such fluxes is unresolved. Using flux analyses with the short-lived radioisotope (13)N and electrophysiological, respiratory, and histochemical measurements, we show that futile cycling in roots of barley (Hordeum vulgare) seedlings is predominately of the gaseous NH3 species, rather than the NH4(+) ion. Influx of (13)NH3/(13)NH4(+), which exceeded 200 mol g(-1) h(-1), was not commensurate with membrane depolarization or increases in root respiration, suggesting electroneutral NH3 transport. Influx followed Michaelis-Menten kinetics for NH3 (but not NH4(+)), as a function of external concentration (Km = 152 m, Vmax = 205 mol g(-1) h(-1)). Efflux of (13)NH3/(13)NH4(+) responded with a nearly identical Km. Pharmacological characterization of influx and efflux suggests mediation by aquaporins. Our study fundamentally revises the futile-cycling model by demonstrating that NH3 is the major permeating species across both plasmalemma and tonoplast of root cells under toxicity conditions. PMID:24134887

Coskun, Devrim; Britto, Dev T; Li, Mingyuan; Becker, Alexander; Kronzucker, Herbert J

2013-12-01

146

Towards a carbon independent and CO2-free electrochemical membrane process for NH3 synthesis.  

PubMed

Ammonia is exclusively synthesized by the Haber-Bosch process starting from precious carbon resources such as coal or CH4. With H2O, H2 is produced and with N2, NH3 can be synthesized at high pressures and temperatures. Regrettably, the carbon is not incorporated into NH3 but emitted as CO2. Valuable carbon sources are consumed which could be used otherwise when carbon sources become scarce. We suggest an alternative process concept using an electrochemical membrane reactor (ecMR). A complete synthesis process with N2 production and downstream product separation is presented and evaluated in a multi-scale model to quantify its energy consumption. A new micro-scale ecMR model integrates mass, species, heat and energy balances with electrochemical conversions allowing further integration into a macro-scale process flow sheet. For the anodic oxidation reaction H2O was chosen as a ubiquitous H2 source. Nitrogen was obtained by air separation which combines with protons from H2O to give NH3 using a hypothetical catalyst recently suggested from DFT calculations. The energy demand of the whole electrochemical process is up to 20% lower than the Haber-Bosch process using coal as a H2 source. In the case of natural gas, the ecMR process is not competitive under today's energy and resource conditions. In future however, the electrochemical NH3 synthesis might be the technology-of-choice when coal is easily accessible over natural gas or limited carbon sources have to be used otherwise but for the synthesis of the carbon free product NH3. PMID:24557153

Kugler, K; Ohs, B; Scholz, M; Wessling, M

2014-04-01

147

Desorption Kinetics of Methanol, Ethanol, and Water from Graphene  

SciTech Connect

The desorption kinetics of methanol, ethanol, and water from graphene covered Pt(111) are investigated. The temperature programmed desorption (TPD) spectra for both methanol and ethanol have well-resolved first, second, third, and multilayer layer desorption peaks. The alignment of the leading edges is consistent with zero-order desorption kinetics from all layers. In contrast, for water the first and second layers are not resolved. At low water coverages (< 1 ML) the initial desorption leading edges are aligned but then fall out of alignment at higher temperatures. For thicker water layers (10 to 100 ML), the desorption leading edges are in alignment throughout the desorption of the film. The coverage dependence of the desorption behavoir suggests that at low water coverages the non-alignment of the desorption leading edges is due to water dewetting from the graphene substrate. Kinetic simulations reveal that the experimental results are consistent with zero-order desorption. The simulations also show that fractional order desorption kinetics would be readily apparent in the experimental TPD spectra.

Smith, R. Scott; Matthiesen, Jesper; Kay, Bruce D.

2014-09-18

148

Desorption kinetics of methanol, ethanol, and water from graphene.  

PubMed

The desorption kinetics of methanol, ethanol, and water from graphene covered Pt(111) are investigated. The temperature programmed desorption (TPD) spectra for both methanol and ethanol have well-resolved first, second, third, and multilayer layer desorption peaks. The alignment of the leading edges is consistent with zero-order desorption kinetics from all layers. In contrast, for water, the first and second layers are not resolved. At low water coverages (<1 monolayer (ML)) the initial desorption leading edges are aligned but then fall out of alignment at higher temperatures. For thicker water layers (10-100 ML), the desorption leading edges are in alignment throughout the desorption of the film. The coverage dependence of the desorption behavoir suggests that at low water coverages the nonalignment of the desorption leading edges is due to water dewetting from the graphene substrate. Kinetic simulations reveal that the experimental results are consistent with zero-order desorption. The simulations also show that fractional order desorption kinetics would be readily apparent in the experimental TPD spectra. PMID:24654652

Smith, R Scott; Matthiesen, Jesper; Kay, Bruce D

2014-09-18

149

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

150

Calculations on the rate of the ion-molecule reaction between NH3(+) and H2  

NASA Technical Reports Server (NTRS)

The rate coefficient for the ion-molecule reaction NH3(+) + H2 yields NH4(+) + H has been calculated as a function of temperature with the use of the statistical phase space approach. The potential surface and reaction complex and transition state parameters used in the calculation have been taken from ab initio quantum chemical calculations. The calculated rate coefficient has been found to mimic the unusual temperature dependence measured in the laboratory, in which the rate coefficient decreases with decreasing temperature until 50-100 K and then increases at still lower temperatures. Quantitative agreement between experimental and theoretical rate coefficients is satisfactory given the uncertainties in the ab initio results and in the dynamics calculations. The rate coefficient for the unusual three-body process NH3(+) + H2 + He yields NH4(+) + H + He has also been calculated as a function of temperature and the result found to agree well with a previous laboratory determination.

Herbst, Eric; Defrees, D. J.; Talbi, D.; Pauzat, F.; Koch, W.

1991-01-01

151

Potential energy surface and bound states of the NH3-Ar and ND3-Ar complexes  

NASA Astrophysics Data System (ADS)

A new, four-dimensional potential energy surface for the interaction of NH3 and ND3 with Ar is computed using the coupled-cluster method with single, double, and perturbative triple excitations and large basis sets. The umbrella motion of the ammonia molecule is explicitly taken into account. The bound states of both NH3-Ar and ND3-Ar are calculated on this potential for total angular momentum values from J = 0 to 10, with the inclusion of Coriolis interactions. The energies and splittings of the rovibrational levels are in excellent agreement with the extensive high-resolution spectroscopic data accumulated over the years in the infrared and microwave regions for both complexes, which demonstrates the quality of the potential energy surface.

Loreau, J.; Livin, J.; Scribano, Y.; van der Avoird, A.

2014-12-01

152

On the reaction CH2O + NH3 Yields CH2NH + H2O  

NASA Technical Reports Server (NTRS)

We study the energetics of CH2O + NH3-Yields CH2NH + H2O in the gas phase at the B3LYP and CCSD(T)levels. This reaction is shown to have a sizeable barrier. Ionization of NH3 reduces the barrier to about 5 kcal/mol. We also show that in water, a proton catalyzed mechanism yields no barriers in excess of the reaction endothermicity. Since this reaction has been proposed as one of the steps in interstellar synthesis of glycine, the simplest amino acid, this work suggests that the formation of amino acids is occurring in and/or on interstellar water ice grains, and not in the gas phase.

Walch, Stephen P.; Bauschlicher, Charles W., Jr.; Ricca, Alessandra; Bakes, E. L. O.; Arnold, James (Technical Monitor)

2000-01-01

153

Comparison of the biological NH3 removal characteristics among four inorganic packing materials.  

PubMed

Four inorganic packing materials were evaluated in terms of their availability as a packing material of a packed tower deodorization apparatus (biofilter) from the viewpoints of biological NH3 removal characteristics and some physical properties. Porous ceramics (A), calcinated cristobalite (B), calcinated and formed obsidian (C), granulated and calculated soil (D) were used. The superiority of these packing materials determined based on the values of non-biological removal per unit weight or unit volume of packing material, complete removal capacity of NH3 per unit weight of packing material per day or unit volume of packing material per day and pressure drop of the packed bed was in the order of A approximately = C > B > or = D. Packing materials A and C with high porosity, maximum water content, and suitable mean pore diameter showed excellent removal capacity. PMID:16233018

Hirai, M; Kamamoto, M; Yani, M; Shoda, M

2001-01-01

154

Potential energy surface and bound states of the NH3-Ar and ND3-Ar complexes.  

PubMed

A new, four-dimensional potential energy surface for the interaction of NH3 and ND3 with Ar is computed using the coupled-cluster method with single, double, and perturbative triple excitations and large basis sets. The umbrella motion of the ammonia molecule is explicitly taken into account. The bound states of both NH3-Ar and ND3-Ar are calculated on this potential for total angular momentum values from J = 0 to 10, with the inclusion of Coriolis interactions. The energies and splittings of the rovibrational levels are in excellent agreement with the extensive high-resolution spectroscopic data accumulated over the years in the infrared and microwave regions for both complexes, which demonstrates the quality of the potential energy surface. PMID:25494745

Loreau, J; Livin, J; Scribano, Y; van der Avoird, A

2014-12-14

155

Role of NH3 and NH4+ transporters in renal acid-base transport.  

PubMed

Renal ammonia excretion is the predominant component of renal net acid excretion. The majority of ammonia excretion is produced in the kidney and then undergoes regulated transport in a number of renal epithelial segments. Recent findings have substantially altered our understanding of renal ammonia transport. In particular, the classic model of passive, diffusive NH3 movement coupled with NH4+ "trapping" is being replaced by a model in which specific proteins mediate regulated transport of NH3 and NH4+ across plasma membranes. In the proximal tubule, the apical Na+/H+ exchanger, NHE-3, is a major mechanism of preferential NH4+ secretion. In the thick ascending limb of Henle's loop, the apical Na+-K+-2Cl- cotransporter, NKCC2, is a major contributor to ammonia reabsorption and the basolateral Na+/H+ exchanger, NHE-4, appears to be important for basolateral NH4+ exit. The collecting duct is a major site for renal ammonia secretion, involving parallel H+ secretion and NH3 secretion. The Rhesus glycoproteins, Rh B Glycoprotein (Rhbg) and Rh C Glycoprotein (Rhcg), are recently recognized ammonia transporters in the distal tubule and collecting duct. Rhcg is present in both the apical and basolateral plasma membrane, is expressed in parallel with renal ammonia excretion, and mediates a critical role in renal ammonia excretion and collecting duct ammonia transport. Rhbg is expressed specifically in the basolateral plasma membrane, and its role in renal acid-base homeostasis is controversial. In the inner medullary collecting duct (IMCD), basolateral Na+-K+-ATPase enables active basolateral NH4+ uptake. In addition to these proteins, several other proteins also contribute to renal NH3/NH4+ transport. The role and mechanisms of these proteins are discussed in depth in this review. PMID:21048022

Weiner, I David; Verlander, Jill W

2011-01-01

156

Time dependent density functional photoionization of CH 4, NH 3, H 2O and HF  

Microsoft Academic Search

The time dependent density functional theory (TD-DFT) and the KohnSham (KS) schemes have been employed to calculate the cross section and the asymmetry parameter profiles of all the orbitals (from outer valence to core 1s) of CH4, NH3, H2O and HF, employing a one centre expansion of B-spline functions. The comparison between the KS and TD-DFT results shows that the

M. Stener; G. Fronzoni; D. Toffoli; P. Decleva

2002-01-01

157

An ab initio study of the reaction mechanism of Co+ + NH3  

NASA Astrophysics Data System (ADS)

To investigate the mechanism for N-H bond activation by a transition metal, the reactions of Co+(3F,5F) with NH3 have been studied with complete active space self-consistent field (CASSCF), multireference configuration interaction (MR-SDCI), and multireference many body perturbation theory (MRMP) wave functions, using both effective core potential and all-electron methods. Upon their initial approach, the reactants yield an ion-molecule complex, CoNH3+(3E,5A2,5A1), with retention of C3? symmetry. The Co+=NH3 binding energies are estimated to be 49 (triplet) and 45 (quintet) kcal/mol. Subsequently, the N-H bond is activated, leading to an intermediate complex H-Co-NH2+ (C2? symmetry), through a three-center transition state with an energy barrier of 56-60 (triplet) and 70-73 (quintet) kcal/mol. The energy of H-Co-NH2+, relative to that of CoNH3+, is estimated to be 60 to 61 (triplet) and 44 (quintet) kcal/mol. However, the highest levels of theory employed here (including dynamic correlation corrections) suggest that the triplet intermediate HCoNH2+ may not exist as a minimum on the potential energy surface. Following Co-N or H-Co bond cleavage, the complex H-Co-NH2+ leads to HCo++NH2 or H+CoNH2+. Both channels (triplet and quintet) are found to be endothermic by 54-64 kcal/mol.

Taketsugu, Tetsuya; Gordon, Mark S.

1997-05-01

158

Low energy studies (e,2e) studies from Ammonia (NH3)  

NASA Astrophysics Data System (ADS)

Experimental and theoretical Triply Differential Cross Sections (TDCS) will be presented for electron-impact ionization of Ammonia (NH3) for highest occupied molecular orbital (HOMO), next highest occupied molecular orbital (NHOMO) and next next highest occupied molecular orbital (N^2HOMO). M3DW (molecular 3-body distorted wave) results will be compared with experiment for coplanar geometry. The final state electron energies and observation angles are symmetric.

Chaluvadi, Hari; Madison, Don; Nixon, K. L.; Murray, Andrew J.; Ning, Chuangang; Colgan, James

2012-10-01

159

Kinetics of OCN- formation from the HNCO + NH3 solid-state thermal reaction  

NASA Astrophysics Data System (ADS)

Context. Solid-state features in infrared astronomical spectra can provide useful information on interstellar ices within different astrophysical environments. Solid OCN- has an absorption feature at 4.62 ?m, which is observed in star formation regions only with a large source-to-source abundance variation. Aims: We aim to investigate the thermal formation mechanism of solid OCN- from HNCO on the basis of kinetic arguments. Methods: We experimentally studied the kinetics of the low-temperature OCN- formation from the purely thermal reaction between HNCO and NH3 in interstellar ice analogs using Fourier transform infrared spectroscopy. We used a rate equation approach, a kinetic Monte Carlo approach and a gamma probability distribution approach to derive kinetic parameters from experimental data. Results: The kinetics can de divided into two-processes, a fast process corresponding to the chemical reaction, and a slow process that we interpret as the spatial orientation of the two reactants within the ice. The three approaches give the same results. The HNCO + NH3 ? OCN- + NH4+ reaction rate follows an Arrhenius law with an activation energy of 0.4 0.1 kJ mol-1 (48 12 K) and a pre-exponential factor of 0.0035 0.0015 s-1. Conclusions: The present experiment has the important implication that the HNCO + NH3 reaction can account for the observed abundances of solid OCN- and the HNCO non detection in young stellar objects.

Mispelaer, F.; Theule, P.; Duvernay, F.; Roubin, P.; Chiavassa, T.

2012-04-01

160

Recent Searches for the Radio Lines of NH_3 in Comets  

E-print Network

Radio observations in the ammonia inversion lines of four comets, C/2001 A2 (LINEAR), 153P/Ikeya-Zhang, C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR), were performed at the Effelsberg 100-m Radio Telescope during their respective close approaches to Earth. None of the four lowest energy metastable lines (J,K=J),J=1--4, could be detected in these comets. We derive the following 3 sigma upper bounds on the NH_3 production rate, and c omparing to the corresponding water production rates, percentage NH_3 abundances relative to H_2O: Q(NH_3) Comet 153P/Ikeya-Zhang. At 0.74% or less, the ammonia-to-water ratios are factors of 2 below the value for C/1995 O1 (Hale-Bopp) and 1P/Halley, suggesting chemical diversity between comets. The 18-cm lines of OH were clearly detected in the two comets observed during the 2004 campaign, thereby validating the cometary ephemerides.

J. Hatchell; M. K. Bird; F. F. S. van der Tak; W. A. Sherwood

2005-05-20

161

Constraints on the NH3 and PH3 distributions in the Great Red Spot  

NASA Technical Reports Server (NTRS)

Medium resolution (10 A) UV spectra were obtained for the Great Red Spot (GRS) and South Tropical Zone (STZ) of Jupiter using the low dispersion mode of the IUE spectrometers at wavelengths from 1900-2200 A. The scans were carried out to determine the coloring agent for the GRS to improve the database for developing photochemical models of the feature. The wavelengths were selected to cover the absorption features of NH3 and PH3. The resulting data were interpreted using a vertically inhomogeneous Rayleigh scattering radiative transfer model. Various NH3 concentrations were explored in an effort to fit the data, taking into account changes which would occur at different atmospheric pressure levels and due to the projected temperature fields. A forbidden NH3/forbidden H2 mixing ratio that was calculated at the 80-125 mbar pressure level in the GRS was enhanced by 3-10 percent relative to the STZ. An upper limit was obtained for the mixing ratio of PH3 in the GRS that is significantly lower than previously predicted concentrations, implying that vertical transport in the GRS is not much greater than in adjacent regions.

Wagener, R.; Caldwell, J.; Owen, T.

1986-01-01

162

Carbamic acid and carbamate formation in NH{3}:CO{2} ices - UV irradiation versus thermal processes  

NASA Astrophysics Data System (ADS)

Context: We study carbamic acid [ NH{2}COOH] and ammonium carbamate [ NH{2}COO-] [ NH{4}+] formation in interstellar ice analogs. Aims: We demonstrate how carbamic acid [ NH{2}COOH] and ammonium carbamate [ NH{2}COO-] [ NH{4}+] can be formed from both thermal reactions and energetic photons in an NH{3}:CO{2} ice mixture. Methods: Infrared and mass spectroscopy are used to monitor NH{3}:CO{2} ice mixture evolution during both warming and VUV photon irradiation. Results: Carbamic acid and ammonium carbamate can be produced thermally in a 1:1 ratio from NH{3} and CO{2} above 80 K. They can be also formed in a 28:1 ratio by less efficient processes such as energetic photons. Our study and its results provide fresh insight into carbamic acid formation in interstellar ices. Conclusions: We demonstrate that care is required to separate irradiation-induced reactivity from purely thermal reactivity in ices in which ammonia and carbon dioxide are both present. From an interstellar chemistry point of view, carbamic acid and ammonium carbamate are readily produced from the ice mantle of a typical interstellar grain and should therefore be a detectable species in molecular clouds.

Bossa, J. B.; Theul, P.; Duvernay, F.; Borget, F.; Chiavassa, T.

2008-12-01

163

Theoretical Study on Dihydrogen Bonds of NH3BH3 with Several Small Molecules  

NASA Astrophysics Data System (ADS)

The dihydrogen bonds B-H ... H-X (X = F, Cl, Br, C, O, N) in the dimer (NH3BH3)2 and the complexes of NH3BH3 with HF, HCl, HBr, H2CO, H2O, and CH3OH were theoretically studied. The results show that formation of the dihydrogen bond leads to elongation and stretch frequency red shift of the BH and XH bonds, except that in the H2CO system, the CH bond blue shifts. For (NH3BH3)2 and the complexes of the halogenides, red shifts of the XH bonds are caused by the intermolecular hyperconjugation ? (BH) ? ?* (XH). For the system of H2CO, a blue shift of the CH bond is caused by a decrease of the intramolecular hyperconjugation n(O)? ?*(CH). In the other two systems, the red shift of OH bond is a secondary effect of the stronger traditional red-shifted H-bonds N-H ... O. In all these systems, red shifts of the BH bonds are caused by two factors: negative repolarization and negative rehybridization of the BH bond, and decrease of occupancy on ?(BH) caused by the intermolecular hyperconjugation ?(BH)??*(XH).

Li, An-yong; Xu, Li-fang; Ling, Zhou

2009-02-01

164

Similar binding of the carcinostatic drugs cis-[Pt(NH3)2Cl2] and [Ru(NH3)5Cl] Cl2 to tRNAphe and a comparison with the binding of the inactive trans-[Pt(NH3)2Cl2] complex - reluctance in binding to Watson-Crick base pairs within double helix.  

PubMed Central

A comparative study of the binding of square planar cis- and trans-[Pt(NH3)2Cl2] complexes and the octahedral [Ru(NH3)5(H2O)]3+ complex to tRNAphe from yeast was carried out by X-ray crystallography. Both of the carcinostatic compounds, cis-[Pt(NH3)2Cl2] and [Ru(NH3)5(H2O)]3+ show similarities in their mode of binding to tRNA. These complexes bind specifically to the N(7) positions of guanines G15 and G18 in the dihydrouridine loop. [Ru(NH3)5(H2O)]3+ has an additional binding site at N(7) of residue G1 after extensive soaking times (58 days). A noncovalent binding site for ruthenium is also observed in the deep groove of the acceptor stem helix with shorter (25 days) soaking time. The major binding site for the inactive trans-[Pt(NH3)Cl2] complex is at the N(1) position of residue A73, with minor trans-Pt binding sites at the N(7) positions of residues Gm34, G18 and G43. The similarities in the binding modes of cis-[Pt(NH3)2Cl2] and [Ru(NH3)5(H2O)]3+ are expected to be related to their carcinostatic properties. PMID:6353373

Rubin, J R; Sabat, M; Sundaralingam, M

1983-01-01

165

Characterization of Biochar using Temperature Programmed Oxidation  

Technology Transfer Automated Retrieval System (TEKTRAN)

Biochar from the fast pyrolysis of biomass was characterized by Temperature Programmed Oxidation. This technique can be used to assess the oxidative reactivity of carbonaceous solids where higher temperature reactivity indicates greater structural order. The samples examined include soy and barley...

166

A STUDY OF ETHANOL REACTIONS OVER Pt\\/Al2O3 AND Pt\\/ZrO2 BY TEMPERATURE-PROGRAMMED SURFACE REACTION  

Microsoft Academic Search

The platinum supported catalysts were investigated by temperature-programmed desorption (TPD) and temperature-programmed surface reaction (TPSR), using He and 5% O2\\/He. Through a half-quantitative analysis of TPD, it was observed that the acidic sites of alumina favors the dehydration of ethanol, since the formation of ethylene in the Pt\\/Al2O3 catalyst is more significant. Despite the little formation of acetaldehyde in both

Carlos E. M. Guarido; Mariana M. V. M. Souza; Martin Schmal

167

Thermal desorption spectroscopy from the surfaces of metal-oxide-semiconductor nanostructures.  

PubMed

An experimental setup, which combines direct heating and temperature measurement of metal nanofilms allowing temperature programmed desorption experiments is described. This setup enables the simultaneous monitoring of the thermal desorption flux from the surface of chemi-electric devices and detection of chemically induced hot charge carriers under UHV conditions. This method is demonstrated for the case of water desorption from a Pt/SiO2-n-Si metal-oxide-semiconductor nanostructure. PMID:25362420

Meyburg, Jan Philipp; Nedrygailov, Ievgen I; Hasselbrink, Eckart; Diesing, Detlef

2014-10-01

168

Thermal desorption spectroscopy from the surfaces of metal-oxide-semiconductor nanostructures  

NASA Astrophysics Data System (ADS)

An experimental setup, which combines direct heating and temperature measurement of metal nanofilms allowing temperature programmed desorption experiments is described. This setup enables the simultaneous monitoring of the thermal desorption flux from the surface of chemi-electric devices and detection of chemically induced hot charge carriers under UHV conditions. This method is demonstrated for the case of water desorption from a Pt/SiO2-n-Si metal-oxide-semiconductor nanostructure.

Meyburg, Jan Philipp; Nedrygailov, Ievgen I.; Hasselbrink, Eckart; Diesing, Detlef

2014-10-01

169

The role of unstable NH3 in the formation of nitrogen-rich alpha-U2N(3+x) by the reaction of UC or U with NH3  

NASA Astrophysics Data System (ADS)

Reactions of U or UC with a stream of NH3 or N2 were carried out at 600 and 900 C. It has been found that in high temperature reactions of U or UC with flowing NH3, the catalytic decomposition of NH3 proceeds in parallel with the nitridation reaction of U or UC by action of NH3, which leads to the formation alpha-U2N(3+x), and eventually a steady state is established where the partial pressures of NH3, H2 and N2 (PNH3, PH2, and PN2) in the flowing gas and the N:U ratio of alpha-U2N(3+x) are all uniquely determined. The nitrogen activity a(sub N) of the flowing gas may be increased by suppressing the decomposition of NH3 into H2 and N2. The N:U ratio of alpha-U2N(3+x) increases as the extent of dissociation of NH3, alpha, decreases.

Katsura, Masahiro; Hirota, Masayuki; Miyake, Masanobu

1994-10-01

170

Melting phase relations in the system H2O - NH3 at high pressure  

NASA Astrophysics Data System (ADS)

The density models of Uranus and Neptune constrained by their gravitational moments from Voyager mission suggest that mantles of these planets may be predominantly comprised of water (H2O), methane (CH4), and ammonia (NH3). The impurities in pure water would greatly influence the phase relations in the water-rich system expected in the icy mantle, which must be known to construct a plausible planetary model. One of important effects of the impurity is on the liquidus temperature (Tliq), since it decides the actual presence of solid phase within the icy mantle. In order to determine Tliq in H2O-rich region of the H2O - CH4 - NH3 ternary system, the melting phase relations in the H2O - CH4 and H2O - NH3 systems must be accurately known. However, previous melting experiments on each binary system were limited to several gigapascals, thus need to be explored to higher P-T conditions for application in interiors of Uranus and Neptune. We have investigated high-pressure (P) and -temperature (T) melting phase relations in the H2O - NH3 system based on a combination of visual observation and angle-dispersive x-ray diffraction (XRD) measurements at BL10XU, SPring-8. High-P-T conditions were generated in an externally-resistive heated diamond anvil cell (DAC). Starting material was 20wt% NH3 aqueous solution whose composition was checked via Tliq of the solution measured in a DAC at near atmospheric pressure. The aqueous solution was loaded into a gold-lined hole in a preindented rhenium gasket in order to insulate the sample from rhenium. Pressure was determined from the unit-cell volume of gold liner. Melting and freezing of the sample were detected by monitoring disappearance/appearance of diffraction peaks of solid and diffuse scattering of liquids, as well as observing melting/crystallization of crystal grains under microscope. Up to 20 GPa at room temperature, in addition to ice VII, diffraction peaks of bcc-like phase, which is most likely to be the reported phase VI of ammonia monohydrate (AMH VI), were observed, although the diffraction peaks were either too broad or too few to specify its structure. When temperature was raised until diffuse scattering appeared, the diffraction peaks of AMH VI disappeared, indicating ice VII is the liquidus phase. Newly obtained Tliq were higher than all the exiting melting curves of pure H2O determined in externally-heated DAC by 50 K at 15 GPa at minimum. This contradicts the previous reports that the H2O - NH3 system is eutectic, i.e. Tliq of our sample should be lower than the melting temperature of the H2O end member. We will discuss possible sources for this discrepancy. We also propose a new phase diagram of the system H2O - NH3 and possible implications for the structure of the icy planets.

Sugimura, E.; Hirose, K.; Komabayashi, T.; Ohishi, Y.; Hirao, N.; Dubrovinsky, L. S.

2012-12-01

171

Combining anti-cancer drugs with artificial sweeteners: synthesis and anti-cancer activity of saccharinate (sac) and thiosaccharinate (tsac) complexes cis-[Pt(sac)2(NH3)2] and cis-[Pt(tsac)2(NH3)2].  

PubMed

The new platinum(II) complexes cis-[Pt(sac)2(NH3)2] (sac=saccharinate) and cis-[Pt(tsac)2(NH3)2] (tsac=thiosaccharinate) have been prepared, the X-ray crystal structure of cis-[Pt(sac)2(NH3)2] x H2O reveals that both saccharinate anions are N-bound in a cis-arrangement being inequivalent in both the solid-state and in solution at room temperature. Preliminary anti-cancer activity has been assessed against A549 human alveolar type-II like cell lines with the thiosaccharinate complex showing good activity. PMID:25216367

Al-Jibori, Subhi A; Al-Jibori, Ghassan H; Al-Hayaly, Lamaan J; Wagner, Christoph; Schmidt, Harry; Timur, Suna; Baris Barlas, F; Subasi, Elif; Ghosh, Shishir; Hogarth, Graeme

2014-12-01

172

Characterizing the influence of highways on springtime NO2 and NH3 concentrations in regional forest monitoring plots.  

PubMed

Highways are major sources of nitrogen dioxide (NO2) and ammonia (NH3). In this study, springtime NO2 and NH3 concentrations were measured at 17 Ontario Forest Biomonitoring Network (OFBN) plots using passive samplers. Average springtime NO2 concentrations were between 1.3?gm(-3) and 27?gm(-3), and NH3 concentrations were between 0.2?gm(-3) and 1.7?gm(-3), although concentrations measured in May (before leaf out) were typically twice as high as values recorded in June. Average NO2 concentrations, and to a lesser extent NH3, could be predicted by road density at all radii (around the plot) tested (500m, 1000m, 1500m). Springtime NO2 concentrations were predicted for a further 50 OFBN sites. Normalized plant/lichen N concentrations were positively correlated with estimated springtime NO2 and NH3 concentrations. Epiphytic foliose lichen richness decreased with increasing NO2 and NH3, but vascular plant richness was positively related to estimated springtime NO2 and NH3. PMID:24747347

Watmough, Shaun A; McDonough, Andrew M; Raney, Shanel M

2014-07-01

173

Enhancement of NH3 Gas Sensitivity at Room Temperature by Carbon Nanotube-Based Sensor Coated with Co Nanoparticles  

PubMed Central

Multi-walled carbon nanotube (MWCNT) film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH3 gas sensing applications. The MWCNT-based sensor is sensitive to NH3 gas at room temperature. Nanoclusters of Co catalysts have been sputtered on the surface of the MWCNT film to enhance gas sensitivity with respect to unfunctionalized CNT films. The gas sensitivity of Co-functionalized MWCNT-based gas sensors is thus significantly improved. The sensor exhibits good repeatability and high selectivity towards NH3, compared with alcohol and LPG. PMID:23364198

Nguyen, Lich Quang; Phan, Pho Quoc; Duong, Huyen Ngoc; Nguyen, Chien Duc; Nguyen, Lam Huu

2013-01-01

174

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

NASA Technical Reports Server (NTRS)

It is found that the photolysis of NH4 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. The loss is shown to arise from the abstraction of hydrogen atoms from CH4 by photolytically generated hot hydrogen atoms. It is 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. Also, it is found that the photolysis of PH3 with a 206 nm light source gives P2H4, which in turn is converted to a red-brown solid. The course of the photolysis is not changed appreciably when the temperature is lowered to 157 K except that the concentration of P2H4 increases, while the presence of H2 has no effect on the P2H4 yield. Photolysis of 9:1 NH3:PH3 is found to give a rate of decomposition of PH3 that is comparable with that observed by the direct photolysis of PH3 and comparable amounts of the red-brown solid and P2H4 are observed. In addition, the implications of these results for the structures of the compounds responsible for the wide array of colors observed in the atmosphere of Jupiter are examined.

Ferris, J. P.; Morimoto, J. Y.; Benson, R.; Bossard, A.

1982-01-01

175

H2O/Ni(100) and NH3/Ni(100) - A computational approach  

NASA Technical Reports Server (NTRS)

The adsorption of NH3 and H2O on the Ni(100) is treated using a cluster model. The adsorption is found to have only a small effect on the HXH angle. Rotation about the principal ligand axis requires virtually no energy. Ligand tilts of 15 deg are found to require small amounts of energy, leading to the suggestion that the ESDIAD signal is a result of excited tilting modes, not a change in the HXH angle. For H2O additional bending modes are considered and all are found to be quite flat in energy.

Bauschlicher, C. W., Jr.

1985-01-01

176

Spectroscopic line parameters of NH3 and PH3 in the far infrared  

NASA Technical Reports Server (NTRS)

NH3 and PH3 rotation and rotation-inversion line parameters in the far to medium IR are calculated for remote sounding purposes of planetary atmospheres; 1607 lines of (N-14)H3, 362 lines of (N-15)H3 and 325 lines of PH3 are compiled. The absolute intensity formulation has been reviewed in the case of rotation and rotation-inversion lines of molecules with C(3v) symmetry. The justification for the general agreement between the authors, and comparisons with other published expressions are given.

Husson, N.; Goldman, A.; Orton, G.

1982-01-01

177

M dependence in the analysis of NH3-He microwave double resonance experiments  

NASA Technical Reports Server (NTRS)

New close-coupled calculations of laboratory-frame, m-dependent cross sections for rotational excitation in NH3-He collisions are used to examined the validity of using degeneracy averaged values in the analysis of four-level double resonance experiments. It is found that the proper use of m-dependent cross sections and absorption probabilities produces only minor changes in the calculated Delta I/I (the fractional change in the signal absorption intensity when pumping radiation is applied) and does not, therefore, resolve the discrepancies between theoretical and experimental values that were noted in previous studies.

Davis, S. L.; Green, S.

1983-01-01

178

DECHLORINATION OF PCBS, CAHS, HERBICIDES AND PESTICIDES NEAT AND IN SOILS AT 25&DEG;C USING NA/NH3. (R829421E01)  

EPA Science Inventory

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 adde...

179

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

180

The G305 star-forming complex: wide-area molecular mapping of NH3 and H2O masers  

NASA Astrophysics Data System (ADS)

We present wide-area radio (12 mm) Mopra telescope observations of the complex and rich massive star-forming region G305. Our goals are to determine the reservoir for star formation within G305 using NH3 to trace the dense molecular content, and thus the gas available to form stars; estimate physical parameters of detected NH3 clumps (temperature, column density, mass, etc.); locate current areas of active star formation via the presence of H2O and methanol masers and the distribution of young stellar objects (YSOs) and ultra-compact HII regions associated with this region. This paper details the NH3 (J, K), (1,1), (2,2) and (3,3) inversion transition and 22 GHz H2O maser observations. We observed a ~ region with ~2 arcmin angular resolution and a sensitivity of ~60 mK per 0.4kms-1 channel. We identify 15 NH3 (1,1), 12 NH3 (2,2) and 6 NH3 (3,3) clumps surrounding the central HII region. The sizes of the clumps vary between <2.6 and 10.1 pc; the average kinetic temperature of the gas is 25K. We calculate clump masses of and find the total molecular mass of the complex to be . We note the positions of 56 star formation tracers, and discover a high degree of correlation with detected NH3 clumps. We have detected 16 H2O masers and find they correlate with the detected ammonia clumps. In general, they are found closer to the NH3 clump cores than star formation tracers of later evolutionary stages.

Hindson, L.; Thompson, M. A.; Urquhart, J. S.; Clark, J. S.; Davies, B.

2010-11-01

181

The photolysis of NH3 in the presence of substituted acetylenes - A possible source of oligomers and HCN on Jupiter  

NASA Technical Reports Server (NTRS)

An NMR spectral study is presently conducted of NH3 photolysis in the presence of substituted acetylenes with NMR spectra and gas chromatography. Quantum yields and percentage conversions to products are reported. It is shown that acetylenic hydrocarbons generated during methane photolysis in Jupiter's stratosphere can react with radicals formed by NH3 photolysis to yield nonvolatile, yellow-brown polymers, alkylnitriles, and in due course, HCN, as observed on Jupiter.

Ferris, James P.; Jacobson, Richard R.; Guillemin, Jean C.

1992-01-01

182

Biotreatment of H 2S- and NH 3-containing waste gases by co-immobilized cells biofilter  

Microsoft Academic Search

Gas mixture of H2S and NH3 in this study has been the focus in the research area concerning gases generated from the animal husbandry and the anaerobic wastewater lagoons used for their treatment. A specific microflora (mixture of Thiobacillus thioparus CH11 for H2S and Nitrosomonas europaea for NH3) was immobilized with Ca-alginate and packed inside a glass column to decompose

Ying-Chien Chung; Chihpin Huang; Ching-Ping Tseng; Jill Rushing Pan

2000-01-01

183

N 2O and NH 3 emissions from a bioreactor landfill operated under limited aerobic degradation conditions  

Microsoft Academic Search

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

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

2011-01-01

184

Low-energy electron scattering with polar molecule NH3 using the R -matrix method  

NASA Astrophysics Data System (ADS)

We report on the calculated elastic differential, elastic integral, momentum transfer, and excitation cross sections for the low-energy electron- NH3 scattering using the R -matrix method. Elastic differential and momentum transfer cross sections are obtained by summing over rotationally elastic and rotationally inelastic cross sections for rotor states up to J=4 . The excitation cross sections of the first four low-lying electronically excited states from the ground state of NH3 , at its equilibrium geometry, are presented. These excited states have symmetries aA13 , AA11 , bE3 , and BE1 . The set of self-consistent-field molecular orbitals is obtained by optimizing these on the first excited state A13 . Configuration-interaction (CI) wave functions are used to represent the target states. In our CI model, we kept the core two electrons frozen in doubly occupied molecular orbital 1a1 , and the remaining eight electrons moved freely among the five molecular orbitals 2a1 , 3a1 , 1e , 4a1 , 2e . With this CI model, we obtain good agreement for the vertical spectrum of excited states with the experimental values. The Born approximation is employed to account for higher partial waves excluded in the R -matrix method to evaluate elastic cross sections. Cross sections are reported for the electron-impact energy range 0.025- 20eV .

Munjal, Hema; Baluja, K. L.

2006-09-01

185

Mobilities of NH4+(NH3)n clusters in helium from 100 K to 298 K  

NASA Astrophysics Data System (ADS)

A variable temperature-selected ion flow drift tube (VT-SIFDT) has been used to measure the mobilities of NH4+(NH3)n clusters drifting in He. The mobilities have been measured for n=0-2 at 298 K, n=0-3 at 200 K, and n=0-5 at 100 K, marking the first mobilities experiments for these clusters below room temperature. The reduced mobilities measured at 298 K are compared to the previous SIFDT results of Krishnamurthy et al. [J. Chem. Phys. 106, 530 (1997)] for n=0-2. While the current results compare quite favorably for n=0-2, there is a discrepancy for n=3 which is addressed by current 100 K and 200 K data where these species are thermally stable. The trends in the mobilities from 100 K to 298 K as a function of E/N and effective temperature reveal that the repulsive part of the He-NH4+(NH3)n interaction potential is sampled predominantly for n=1-5. However, the attractive part of the potential is accessed at the lowest temperatures for He-NH4+.

Midey, Anthony J.; Viggiano, A. A.

2001-04-01

186

A High-Pressure Study of the NH3-H2 System  

NASA Astrophysics Data System (ADS)

As it is the simplest and most abundant element in the universe, hydrogen and hydrogen-rich molecules are ubiquitous to current scientific study. Molecular hydrogen (H2) has been studied extensively under pressure as a lone entity and in conjunction with other simple molecules. However, studies on ammonia-hydrogen mixtures have been limited. The NH3+H2 system is applicable to a number of research areas including gaseous and icy planets, the chemistry of hydrogen-bonded clathrate structures, and to further the understanding of intermolecular interactions at high density. In this study we compressed binary mixtures of hydrogen and ammonia in diamond anvil cells to 13 GPa at 300K over a range of compositions, and characterized the behavior using optical microscopy, Raman spectroscopy and synchrotron X-ray diffraction. Below 1.0 GPa we observe limited mutual solubility in the fluid phases, but beyond 1 GPa (and up to 13 GPa) NH3 and H2 tend to remain phase-separated. Two phase transitions in ammonia and one in hydrogen were observed, all of which occurred at pressures comparable to those of the pure substances. A preliminary phase diagram, structural analysis and equation of state are provided.

Chidester, B.; Strobel, T. A.

2010-12-01

187

The production of NH(A 3Pi i) through photodissociative excitation of NH3  

NASA Technical Reports Server (NTRS)

The NH(A-X) emission produced by photodissociation of NH3 is examined using a line emission source in the 600-1340 A region. It is observed that the production of the NH(A 3Pi i) photofragment involves a spin-forbidden transition. Fluorescence spectra of NH3 are derived and analyzed. The relationship between fluorescence cross sections and fluorescence count rates and gas pressure is studied. The fluorescence cross sections of NH(A-X) are calculated as 2.1 x 10 to the -22nd, 3.1 x 10 to the -22nd, 3.0 x 10 to the -21st, 1.5 x 10 to the -20th, and 3.4 x 10 to the -20th sq cm for the primary photon wavelength of 1239, 1184, 1065, 1037, and 976 A, respectively; and the corresponding fluorescence quantum yields are 0.00002, 0.00003, 0.0012, 0.0085, and 0.015.

Wu, C. Y. Robert

1987-01-01

188

NH3 and NH2 in the coma of Comet Brorsen-Metcalf  

NASA Technical Reports Server (NTRS)

Evidence consistent with NH3 ice in the nucleus of Comet Brorsen-Metcalf as the source of the NH2 observed in the comet coma is presented. The distribution of NH2 is symmetric and shows no evidence for jet structure at the 3-sigma significance level above background emission. An azimuthal average of the NH2 image produces an NH2 surface brightness profile for Comet Brorsen-Metcalf which yields a factor of about-10 improvement in the signal-to-noise ratio over previous 1D long-slit NH2 observations, and provides a significant constraint on the NH2 photodissociation time scale in comets. A Monte Carlo simulation of the comet coma, assuming that NH2 is the primary source of NH2, is described and compared with the observations. For an observed production rate, Q(H2O) is approximately equal to 7 x 10 exp 28 molecules/s, collisional effects on the NH3 and NH2 outflow had at most an approximately 10-percent effect on the NH2 surface brightness profile. Because Comet Brorsen-Metcalf showed no significant dust or gas production rate variability, it is argued that steady state conditions best match the comet at the time of the observations.

Tegler, Stephen C.; Burke, Luke F.; Wyckoff, Susan; Womack, Maria; Fink, Uwe; Disanti, Michael

1992-01-01

189

Strain-induced stabilization of Al functionalization in graphene oxide nanosheet for enhanced NH3 storage  

E-print Network

Strain effects on the stabilization of Al dopant atom in graphene oxide (GO) nanosheet as well as its implications for NH3 storage have been investigated using first-principles calculations. The high binding energy of Al ad-atom on GO is found to be a false indicator of its stability. The structural instability clearly contradicts the otherwise high stability indicated by the energetics of Al binding on GO, stressing the need to assess the stability both from energetic and structural perspectives. Tensile strain effectively stabilizes the Al ad-atom on the GO nanosheet by strengthening the C-O bonds through an enhanced electronic charge transfer from C to O atoms. Interestingly, the strength of the C-O bonds is found to be the correct index for Al's stability. The trend for the variation of binding energy with strain is at odds with the systematic analysis of electronic structure based on bond lengths and atomic charges. At an optimal level of strain, the NH3 storage capacity of Al-decorated GO is found to re...

Li, Yunguo; Pathak, Biswarup; Ahuja, Rajeev

2012-01-01

190

Decomposition of NH3 and H2 on ZrB2 (0001) surface  

NASA Astrophysics Data System (ADS)

Group III nitride semiconductors (AlN, GaN, InN, and their alloys) are important materials for applications in solid-state lighting, optoelectronics, and photovoltaics. However, the lack of lattice--matched substrates for their growth results in less than optimal material quality. In the last decade, zirconium diboride (ZrB2) has been demonstrated as a promising substrate for GaN growth because of its similar lattice constant and thermal expansion properties when compared to the nitride. Moreover, the high electrical conductivity of ZrB2 makes it desirable for many GaN-based device applications. In this talk, we present results of density functional theory calculations for the reactivity of the ZrB2(0001) surface towards the N precursor, NH3, and the carrier gas, H2, commonly used in metal organic chemical vapor deposition and molecular beam epitaxy of nitrides. Two different terminations of ZrB2(0001) surface, the Zr and B terminations, are considered and assessed in terms of their catalytic properties toward NH3 and H2 decomposition. The theoretical results are analyzed in connection with our recent XPS and RAIRS measurements.

Walkosz, Weronika; Manandhar, Kedar; Trenary, Michael; Zapol, Peter

2012-02-01

191

Paper based platform for colorimetric sensing of dissolved NH3 and CO2.  

PubMed

Paper, a cheap and ubiquitous material, has great potential to be used as low-cost, portable and biodegradable platform for chemical and biological sensing application. In this paper, we are exploring a low-cost, flexible and reliable method to effectively pattern paper for capturing optical dyes and for flow-based delivery of target samples for colorimetric chemical sensing. In this paper, we target the detection of ammonia (NH3) and carbon dioxide (CO2), two of the important environmental and health biomarkers. By functionalizing the paper platform with diverse cross-reactive dyes sensitive to NH3 and CO2, their selective sensing within a certain pH range, as well as their detection at different concentrations can be achieved. The images of paper based device were captured by a flatbed scanner and processed in MATLAB() using a RGB model and PCA for quantitative analysis. Paper based devices with readout using ubiquitous consumer electronic devices (e.g. smartphones, flatbed scanner) are considered promising approaches for disease screening in developing countries with limited resources. PMID:25241151

Chen, Yu; Zilberman, Yael; Mostafalu, Pooria; Sonkusale, Sameer R

2015-05-15

192

Trends of NO-, NO 2-, and NH 3-emissions from gasoline-fueled Euro-3- to Euro-4-passenger cars  

NASA Astrophysics Data System (ADS)

Vehicular emissions of reactive nitrogen compounds (RNCs) such as nitric oxide (NO), nitrogen dioxide (NO 2), and ammonia (NH 3) have a substantial impact on urban air quality. NO and NO 2 support the photochemical formation of ozone, and NH 3 is involved in the atmospheric formation of secondary aerosols. Vehicular NO is mainly formed during combustion, whereas NO 2 and NH 3 are both secondary pollutants of the catalytic converter systems. Herein we report on tail-pipe RNC emissions of gasoline-fueled Euro-3- and Euro-4-passenger cars at transient driving from 0 to 150 km h -1. Two sets of 10 in-use vehicles with comparable engine size and mileage were studied with time-resolved chemical ionization-mass spectrometry (CI-MS). Each vehicle was tested in 7 different driving cycles including the legislative European (EDC) and the US FTP-75 driving cycles. Mean emission factors (EFs) for different traffic situations are reported and effects of cold start, velocity, acceleration, and deceleration are discussed. Furthermore, critical operating conditions supporting the de novo formation of NH 3 have been identified. In the EDC, mean NO- and NH 3-EFs of 5726 and 1612 mg km -1 were obtained for Euro-3-vehicles; those of the Euro-4-technology were lower by about 25% and 33% at the levels of 4346 and 107 mg km -1, respectively. NO 2 emissions of the investigated three-way catalyst (TWC) vehicles accounted for <1% of the detected RNCs, whereas NH 3 was found to be the dominant RNC for most vehicle conditions. Molar NH 3 proportions varied from about 0.4-0.8, as soon as catalyst light-off occurred. NO was found in large excess only during the cold-start period. Catalyst light-off is indicated by a fast transition from NO- to NH 3-rich exhaust. Velocity and acceleration had pronounced effects on the RNC emission characteristics. Mean velocity-dependent EFs for NO and NH 3 varied by about one order of magnitude from 10 to 74 and 15 to 161 mg km -1 for Euro-3-vehicles and from 12 to 44 and 7 to 144 mg km -1 for the Euro-4 fleet. We conclude that the investigated Euro-3- and Euro-4-vehicles are mainly operated under slightly reducing conditions, where the NH 3 emissions dominate over those of the NO. Under these conditions, both vehicle fleets on an average fulfilled the valid Euro-3 and Euro-4 limits for nitrogen oxides (NO x) of 150 and 80 mg km -1, respectively (as NO 2 equivalents).

Heeb, Norbert V.; Saxer, Christian J.; Forss, Anna-Maria; Brhlmann, Stefan

193

NH3, H2S, and the Radio Brightness Temperature Spectra of the Giant Planets  

NASA Technical Reports Server (NTRS)

Recent radio interferometer observations of Neptune enable comparisons of the radio brightness temperature (T(sub B)) spectra of all four giant planets. This comparison reveals evidence for fundamental differences in the compositions of Uranus' and Neptune's upper tropospheres, particularly in their ammonia (NH3) and hydrogen sulfide (H2S) mixing ratios, despite those planets' outward similarities. The tropospheric abundances of these constituents yield information about their deep abundances, and ultimately about the formation of the planets from the presolar nebula (Atreya et al.). Figures 1, 2, 3, and 4 show the T(sub B) spectra of Jupiter, Saturn, Uranus, and Neptune, respectively, from 0.1 to tens of cm wavelength. The data shown are collected from many observers. Data for Jupiter, Saturn, and Uranus are those cataloged by de Pater and Massie (1985), plus the Saturn Very Large Array (VLA) data by Grossman et al. Figure 3, Uranus, shows only data acquired since 1973. Before 1973 Uranus' T(sub B) increased steadily as its pole moved into view, causing significant scatter in those data. Neptune data at greater than 1 cm, all taken at the VLA, are collected from de Pater and Richmond, de Pater et al., and Hofstadter. For a variety of reasons, such as susceptibility to source confusion, single-dish data at those wavelengths are much noisier than the more reliable VLA data and have been ignored. Single-dish data by Griffin and Orton shortward of 0.4 cm are shown, along with the Owens Valley Radio Observatory (interferometer) datum at 0.266 cm by Muhleman and Berge. Spectra of Jupiter, Saturn, and Neptune share certain gross characteristics. In each spectrum, T(sub B) at 1.3 cm is approximately 120-140 K, less than approximately 30 K different from that at 0.1 cm. All three spectra show a break in slope at or near 1.3 cm, with T(sub B) increasing fairly rapidly with wavelength longward of 1.3 cm. Visible and IR spectroscopy show that NH3, whose strong inversion spectrum peaks at appropximately 1.3 cm, is an important tropospheric species at Jupiter and Saturn. Its signature on the Jovian radio spectrum is obvious, causing the prominent "hole" at 1.3 cm. At Saturn it is more subdued but is the source of that spectrum's change in slope at 1.3 cm. Radiative transfer models of Jupiter and Saturn with near-solar deep NH3 abundances agree well with the data (e.g., de Pater).

Spilker, Thomas R.

1995-01-01

194

Platinum complexes with one radiosensitizing ligand (PtCl2(NH3) (sensitizer)): radiosensitization and toxicity studies in vitro  

SciTech Connect

Complexes of general formula (PtCl2(NH3)L) with one radiosensitizing ligand per platinum are compared with ligand L alone, complexes with two radiosensitizers per platinum (PtCl2L2), and their analogs with NH3 ligands, with respect to radiosensitizing properties and toxicity in CHO cells. Radiosensitizing ligands, L, were misonidazole, metronidazole, 4(5)-nitroimidazole, and 2-amino-5-nitrothiazole, and the ammine analogs were cis- and trans-DDP (diamminedichloroplatinum(II)) and the monoammine, K(PtCl3(NH3)). Results are related to a previous study on plasmid DNA binding by these series. The toxicity of the mono series (PtCl2(NH3)L), attributable to DNA binding, is much higher than the corresponding bis complexes, (PtCl2L2). For L = misonidazole, toxicity is similar to the monoammine, but higher in hypoxic than in aerobic cells. trans-(PtCl2(NH3)-(misonidazole)) is more toxic than the cis isomer. Except for L = 4(5)-nitroimidazole, the complexes (PtCl2(NH3)L) are more toxic than L in air and hypoxia. Hypoxic radiosensitization by the mono complexes is comparable to the monoammine and is not better than free sensitizers, again except for L = 4(5)-nitroimidazole. Significantly lower sensitization is observed in oxic cells. The bis complexes (PtCl2L2), which do not bind to DNA as well as the mono complexes, are less effective radiosensitizers and less toxic than the (PtCl2(NH3)L) series.

Skov, K.A.; Farrell, N.P.; Adomat, H.

1987-11-01

195

Adsorption of dissociated NH3 molecules on the GaN(0001) surface: implications for growth.  

NASA Astrophysics Data System (ADS)

We present the results of ab initio calculations performed to investigate the structure and relative stability of hydrogenated GaN(0001) surfaces which may play a relevant role in the microscopic mechanisms of GaN growth using NH3 as nitrogen source. The surfaces that we have studied contain adsorbed H ad-atoms and NH2 ad-complexes. Our results show that adsorption of H, alone or accompanied by other species, stabilizes the surface of GaN and is able to catalyze the formation of an ideal-like geometry. We suggest, on microscopic grounds, that for the attainment of high quality films, by metal organic chemical vapor deposition, Ga-rich and H-rich conditions are favourable; under N-rich growth conditions, rough surfaces are obtained. Part of the work was done in the frame of INFM Project PRA-1MESS.

Bertoni, Carlo Maria; Pignedoli, Carlo Antonio; di Felice, Rosa

2002-03-01

196

Recombination of electrons with NH4/+/-/NH3/n-series ions  

NASA Technical Reports Server (NTRS)

The paper examines the recombination of electrons with ammonium-series cluster ions, NH4(+)-(NH3)n, for two reasons: (1) NH4(+) may be a significant ion in the lower atmospheres of the earth and the outer planets, and (2) to investigate the weak temperature dependence of the cluster ion's recombination coefficient. A microwave afterglow mass spectrometer was used to determine the recombination coefficients for the first five members of the ammonium series, (18+) through (86+), at temperatures between 200 and 410 K. The electron temperature dependence of the recombination coefficient was determined for (35+) and (52+), the n = 1 and 2 cluster ions, over the temperature range 300-3000 K.

Huang, C.-M.; Biondi, M. A.; Johnsen, R.

1976-01-01

197

The design and technology development for A 150 mlb resistojet for H2 or NH3  

NASA Technical Reports Server (NTRS)

A 150 mlb thrust level hybrid resistojet which may operate on either H2 or NH3 is described whose design technique allows temperature distribution forecasting by means of a microcomputer-implemented mathematical model. The longer computer run times that accompany the exclusive use of BASIC, relative to assembled languages, are offset by the flexibility offered and the reduction of reprogramming and debugging efforts. The integration of a compact first-stage coiled heater with a concentric tubular gas heater offers direct matching of the 28 V terminal of the spacecraft system, while keeping maximum heater wall temperatures to less than 60 K over that of the gas temperature at the throat. Among the novel materials employed are grain-stabilized rhenium for heating elements and high purity aluminas for insulators.

Page, R. J.; Stoner, W. A.

1982-01-01

198

Electronic transport properties of BN sheet on adsorption of ammonia (NH3) gas.  

PubMed

We report the detection of ammonia gas through electronic and transport properties analysis of boron nitride sheet. The density functional theory (DFT) based ab initio approach has been used to calculate the electronic and transport properties of BN sheet in presence of ammonia gas. Analysis confirms that the band gap of the sheet increases due to presence of ammonia. Out of different positions, the bridge site is the most favorable position for adsorption of ammonia and the mechanism of interaction falls between weak electrostatic interaction and chemisorption. On relaxation, change in the bond angles of the ammonia molecule in various configurations has been reported with the distance between NH3 and the sheet. An increase in the transmission of electrons has been observed on increasing the bias voltage and I-V relationship. This confirms that, the current increases on applying the bias when ammonia is introduced while a very small current flows for pure BN sheet. PMID:25666919

Srivastava, Anurag; Bhat, Chetan; Jain, Sumit Kumar; Mishra, Pankaj Kumar; Brajpuriya, Ranjeet

2015-03-01

199

Adsorption kinetics of optochemical NH 3 gas sensing with semiconductor polyaniline films  

Microsoft Academic Search

Polyaniline (PANI) shows electrical as well as optical property changes when it is in contact with oxidant\\/reductor gas. In this work, the optical transmittance changes in PANI coatings originated by their exposure to the ammonia gas were detected by a nulling optical transmittance bridge. The adsorption and desorption curves were carefully analysed using Langmuir kinetic theory for the adsorption of

H Hu; M Trejo; M. E Nicho; J. M Saniger; A Garc??a-Valenzuela

2002-01-01

200

VLBI Observations and NH3 Mapping of the Star-forming Region NGC2264  

NASA Astrophysics Data System (ADS)

We have measured the annual parallax of the water maser source associated with star forming region NGC2264 from observations with VLBI Exploration of Radio Astrometry (VERA). We detected masers at V LSR = 7.2 km s-1. We discussed its driving sources of detected maser spots. One of the maser spots was associated with a centimeter continuum source observed with VLA. Neither optical, infrared nor X-ray sources is catalogued near the spot. The other maser spot is located close to an X-ray source, although there is no optical or infrared counterpart. The proper motion of the former spot was (??, ??) = (23.91 4.29, -29.81 4.27) and the proper motion of latter spot was (??, ??) = (-0.96 0.58, -6.05 3.06). For the latter spot, the peculiar motion is 150 km s-1 and it has the high velocity and this may be a jet or an outflow from a young star. The observed parallax is 1.365 0.098 mas, corresponding to the distance of 738+57 -50 pc. This value is constant with the photometric distance of NGC2264 previously measured. The fitting result of the parallax is shown in figure 1. We also observed in NH3 (1,1), (2,2), (3,3) lines of NGC2264 with the Kashima 34m telescope. We estimated the star formation efficiency (SFE) of NGC2264 from the dense molecular mass of NH3 and the stellar mass calculated by Teixeira et al. (2012). The SFE is 9 - 12% which is consistent with previous results.

Kamezaki, Tatsuya; Imura, Kenji; Nagayama, Takumi; Omodaka, Toshihiro; Handa, Toshihiro; Yamaguchi, Yoshiyuki; Chibueze, James O.; Sunada, Kazuyoshi; Nakano, Makoto

2013-03-01

201

Validation of flux measurements with artificial sources: simulating CH4 from cows and NH3 emissions from medium plot scales  

NASA Astrophysics Data System (ADS)

Mitigation of ammonia (NH3) emissions with detrimental environmental effects as well as of greenhouse gas emissions (GHG: CO2, N2O, CH4) are key challenges faced by the agricultural production sector. While NH3 originates mainly from polluted surfaces, e.g. after slurry application, the main source for CH4 emissions are cows and other ruminating animals, representing point sources. There are two widespread state-of-the-art techniques to determine agricultural emissions: eddy covariance (EC) flux measurements and Lagrangian stochastic (LS) dispersion modelling, namely the WindTrax (WT) model. Whereas GHG emissions can be measured with both techniques, NH3 emissions are usually not feasible with EC measurements due to the stickiness of NH3 molecules on surfaces. In addition, point sources render difficulties for the interpretation of EC flux data. We tested the EC technique and the WT model using artificial sources with known gas release rates. i) The effect of a point source on EC fluxes was investigated by placing an artificial CH4 source with known release rate upwind of the EC tower at two different heights and during different wind conditions. ii) The WT model was checked with a NH3 release grid of 314 m2 of known source strength. Ambient NH3 concentrations were measured by open path DOAS systems and impinger sampling. The CH4 concentration timeseries influenced by the point source showed a similar pattern as in the presence of cows upwind of the EC system. CH4 release rates from the point source were reproduced by the EC flux measurement with stationary background conditions only. The experiments with the NH3 release showed that WT performs well for emission determination, even in complex terrain (asphalt surrounded by grassland) with associated micrometeorology, given a realistic description of the vertical profile of wind velocity. Calculated gas recoveries ranged between 73 to 105%. Such a result is encouraging considering the immanent uncertainties from a NH3 experiment (variable background concentration, relatively small downwind concentrations, NH3 interception on ground/tubing).

Sintermann, Jrg; Felber, Raphael; Hni, Christoph; Ammann, Christof; Neftel, Albrecht

2014-05-01

202

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

PubMed

To investigate the chemistry and dynamics of Jupiter's Great Red Spot (GRS), the tropospheric abundances of NH3 and PH3 in the GRS are determined and compared to those of the surrounding region, the South Tropical Zone (STZ). These gases well up from deep in the atmosphere, and, in the upper troposphere, are depleted by condensation (in the case of NH3), chemical reactions, and UV photolysis. At Jupiter's tropopause, the chemical lifetimes of NH3 and PH3 are comparable to the time constant for vertical transport over the atmospheric scale height. The distributions of these gases are therefore diagnostic of the rate of vertical transport in the upper troposphere and lower stratosphere. Three groups of Voyager IRIS spectra are analyzed, two of the STZ and one of the GRS. The two groups of STZ spectra are defined on the basis of their radiances at 602 and 226 cm-1, which reflect, respectively, the temperature near 150 mbar and the cloud opacity in the 300-600 mbar region. One selection of STZ spectra is chosen to have the same radiance as does the GRS at 226 cm-1. The other STZ selection has a significantly greater radiance, indicative of reduced cloudiness. Variations in the abundances of NH3 and PH3 are determined within the STZ, as a background for our studies of the GRS. Within the uncertainty of our measurements (-55% and +75%), the PH3 mixing ratio at 600 mbar is 3 x 10(-7), the same for all three selections. The NH3 mixing ratio profile in the pressure region between 300 and 600 mbar is the same within error (-25% and +50% at 300 mbar) for both STZ selections. In the GRS, however, NH3 is significantly depleted at 300 mbar, with an abundance of 25% that derived for the STZ selections. Since the GRS is believed to be a region of strong vertical transport, our finding of a depletion of NH3 below the tropopause within the GRS is particularly unexpected. One of the STZ selections has a temperature-pressure profile similar to that of the GRS below the 300-mbar level; therefore, condensation at this level does not easily explain the low NH3 abundance in the GRS. All samples are taken at essentially the same latitude; photolysis and/or charged particle precipitation is probably not directly responsible either. The observed NH3 depletion may have a dynamical origin or result from some unidentified chemical processes at work in the GRS. PMID:11540935

Griffith, C A; Bezard, B; Owen, T; Gautier, D

1992-01-01

203

Superconductivity and phase instability of NH3-free Na-intercalated FeSe1-zSz  

NASA Astrophysics Data System (ADS)

The discovery of ThCr2Si2-type AxFe2-ySe2 (A=K, Rb, Cs and Tl) with Tc ~30?K make much progress in iron-based superconducting field, but their multiple-phase separations are disadvantageous for understanding the origin. On the other hand, for small alkali metals, studies on (Li,Na)FeCu(S,Se)2 and NaFe2-?S2 show that these compounds possess CaAl2Si2-type structure, implying that ThCr2Si2-type structure is unstable for small alkali metal-intercalated FeSe under high temperature. Here we report a new intercalate Na0.65(1)Fe1.93(1)Se2 with Tc ~37?K, synthesized by low-temperature ammonothermal method. The notable finding is that the Na0.65(1)Fe1.93(1)Se2 shows a ThCr2Si2-type structure, which is the first instance of small-sized alkali metal intercalates without NH3 co-intercalation. Besides, the NH3-poor Na0.80(4)(NH3)0.60Fe1.86(1)Se2 and NH3-rich phase with Tcs at 45 and 42?K are identified by tuning the concentration of Na-NH3 solutions. The modulation of interlayer spacing reveals the versatile evolution of structural stability and superconductivity in these intercalates.

Guo, Jiangang; Lei, Hechang; Hayashi, Fumitaka; Hosono, Hideo

2014-08-01

204

Superconductivity and phase instability of NH3-free Na-intercalated FeSe(1-z)S(z).  

PubMed

The discovery of ThCr2Si2-type A(x)Fe(2-y)Se2 (A = K, Rb, Cs and Tl) with Tc ~30?K make much progress in iron-based superconducting field, but their multiple-phase separations are disadvantageous for understanding the origin. On the other hand, for small alkali metals, studies on (Li,Na)FeCu(S,Se)2 and NaFe(2-?)S2 show that these compounds possess CaAl2Si2-type structure, implying that ThCr2Si2-type structure is unstable for small alkali metal-intercalated FeSe under high temperature. Here we report a new intercalate Na0.65(1)Fe1.93(1)Se2 with Tc ~37?K, synthesized by low-temperature ammonothermal method. The notable finding is that the Na0.65(1)Fe1.93(1)Se2 shows a ThCr2Si2-type structure, which is the first instance of small-sized alkali metal intercalates without NH3 co-intercalation. Besides, the NH3-poor Na0.80(4)(NH3)0.60Fe1.86(1)Se2 and NH3-rich phase with Tcs at 45 and 42?K are identified by tuning the concentration of Na-NH3 solutions. The modulation of interlayer spacing reveals the versatile evolution of structural stability and superconductivity in these intercalates. PMID:25154371

Guo, Jiangang; Lei, Hechang; Hayashi, Fumitaka; Hosono, Hideo

2014-01-01

205

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. Wrbel; N. Grska

2001-01-01

206

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

207

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

208

Associative Electron Stimulated Desorption of Neutral CO Molecules  

NASA Astrophysics Data System (ADS)

The Electron Stimulated Desorption (ESD) of neutral CO molecules was studied on polycrystalline Ni surface. Combined ESD and temperature programmed desorption (TPD) measurements were used to observe the variations of neutral ESD yield in dependence on CO coverage, containing direct information about the cross section for ESD of neutral CO molecules in relation to various CO adsorption states. The results show evidence of ESD of neutral CO molecules from dissociative adsorption states. The cross section for this associative ESD process is relatively high in comparison with the CO ESD cross section for molecular CO adsorption.

utara, F.; Matoln, V.

2001-11-01

209

Emission factor of ammonia (NH3) from on-road vehicles in China: tunnel tests in urban Guangzhou  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) is the primary alkaline gas in the atmosphere that contributes to formation of secondary particles. Emission of NH3 from vehicles, particularly gasoline powered light duty vehicles equipped with three-way catalysts, is regarded as an important source apart from emissions from animal wastes and soils, yet measured emission factors for motor vehicles are still not available in China, where traffic-related emission has become an increasingly important source of air pollutants in urban areas. Here we present our tunnel tests for NH3 from motor vehicles under real world conditions in an urban roadway tunnel in Guangzhou, a central city in the Pearl River Delta (PRD) region in south China. By attributing all NH3 emissions in the tunnel to light-duty gasoline vehicles, we obtained a fuel-based emission rate of 2.92 0.18 g L-1 and a mileage-based emission factor of 229.5 14.1 mg km-1. These emission factors were much higher than those measured in the United States while measured NO x emission factors (7.17 0.60 g L-1 or 0.56 0.05 g km-1) were contrastingly near or lower than those previously estimated by MOBILE/PART5 or COPERT IV models. Based on the NH3 emission factors from this study, on-road vehicles accounted for 8.1% of NH3 emissions in the PRD region in 2006 instead of 2.5% as estimated in a previous study using emission factors taken from the Emission Inventory Improvement Program (EIIP) in the United States.

Liu, Tengyu; Wang, Xinming; Wang, Boguang; Ding, Xiang; Deng, Wei; L, Sujun; Zhang, Yanli

2014-05-01

210

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

211

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. PMID:21575190

2011-01-01

212

Open-path Atmospheric N2O, CO, and NH3 Measurements Using Quantum Cascade Laser Spectroscopy  

NASA Astrophysics Data System (ADS)

We develop a compact, mid-infrared quantum cascade (QC) laser based sensor to perform high precision measurements of N2O and CO simultaneously. Since CO is a good tracer of anthropogenic emissions, simultaneous measurements of CO and N2O allow us to correlate the sources of N2O emissions. The thermoelectrically (TE) cooled, and continuous wave QC laser enables room-temperature and unattended operation. The laser is scanned over the absorption features of N2O and CO near 4.54 ?m by laser current modulation. A novel cylindrical multi-pass optical cell terminated at the (N/2)th spot is used to simplify the optical configuration by separating the laser and TE cooled detector. Our systems are open-path and non-cryogenic, which avoids vacuum pump and liquid nitrogen. This configuration enables a future design of a non-intrusive, compact (shoe box size), and low-power (10W) sensor. Wavelength modulation spectroscopy (WMS) is used to enhance measurement sensitivity. Higher-harmonic detection (4f and 6f) is performed to improve the resolution between the nearly overlapping N2O and CO lines. Relevant atmospheric N2O and CO concentration is measured, with a detection limit of 0.3 ppbv for N2O and 2 ppbv for CO for 1 s averaging in terms of noise. We also develop an open-path high sensitivity atmospheric ammonia (NH3) sensor using a very similar instrument design. A 9.06 ?m QC laser is used to probe absorption features of NH3. Open-path detection of NH3 is even more beneficial due to the surface absorption effect of NH3 and its tendency to readily partition into condensed phases. The NH3 sensor was deployed at the CALNEX 2010 field campaign. The entire system was stable throughout the campaign and acquired data with 10 s time resolution under adverse ambient temperatures and dusty conditions. The measurements were in general agreement with other NH3 and trace gases sensors. Both the N2O/CO and NH3 sensors will be deployed in a local eddy-covariance station to examine long term stability and detection limit in the field. Future sensor applications include characterizing urban and agricultural N2O and NH3 emission sources and quantifying their respective fluxes.

Sun, K.; Khan, A.; Miller, D. J.; Rafferty, K.; Schreiber, J.; Puzio, C.; Portenti, M.; Silver, J.; Zondlo, M. A.

2010-12-01

213

The Bonding of NO2, NH3, and CH2NY to Models of a (10,0) Carbon Nanotube  

NASA Technical Reports Server (NTRS)

We have studied the bonding of NO2, NH3, and CH2NH to a (10,O) carbon nanotube using the MP2 and ONIOM methods with extended basis sets. We find bond strengths of 3.5, 3.6. and 6.3 kcal/mol for NO2, NH3, and CH2NH, respectively, using the ONIOM method with the high accuracy part treated at the MP2/aug-CC-pVTZ level and the remainder of the CNT approximated at the UFF level and including an estimate of basis set superposition error using the counterpoise method.

Walch, Stephen P.

2004-01-01

214

Design of a pulsed valve for high-pressure NH3 injection into supersonic beam/mass spectrometry  

NASA Astrophysics Data System (ADS)

A novel design of a pulsed valve for high-pressure injection of NH3 for supersonic jet expansions is presented. This valve can operate up to 200-atm reservoir pressure at 180 C with a pulse width down to 100 ?s. This valve has been designed so that the solenoid core is not in contact with the carrier fluid so that it can be used with highly polar corrosive liquids or supercritical fluids. The ability to use supercritical NH3 as a means of injecting small thermally labile biological molecules into supersonic jet expansions for analysis by resonant two-photon ionization in a time-of-flight mass spectrometer is demonstrated.

Pang, Ho Ming; Lubman, David M.

1988-11-01

215

Calculation of structural and spectroscopic parameters of trans-DONO and the NH3trans-DONO complex. Comparison with analogous parameters of trans-HONO and NH3trans-HONO.  

PubMed

The frequencies and absolute intensities for transitions between vibrational states of trans-DONO and NH3trans-DONO are calculated using the approach earlier tested in calculations of trans-HONO and NH3trans-HONO. The spectroscopic parameters were obtained in the harmonic approximation and from variational solutions of anharmonic Schrdinger equations in one to four dimensions with accurate potential energy and dipole moment surfaces. The calculated frequencies of trans-DONO are in good agreement with the experimental data. Our intensity values for trans-DONO and the frequencies and intensities for NH3trans-DONO can be useful in interpretation of future experiments. Comparison of the transition frequencies and intensities and the averaged values of O-H (O-D) and NO distances calculated for trans-DONO and its complex with ammonia with analogous parameters of trans-HONO and NH3trans-HONO provides information about diverse isotope effects. For example, on H/D substitution the fundamental intensity for the ?2(N?O) mode of the lighter complex increases by a factor of 2.7, and the ?1 transition goes out of resonance with the 2?3 overtone. PMID:25090019

Bulychev, Valentin P; Buturlimova, Marina V; Tokhadze, Irina K; Tokhadze, Konstantin G

2014-08-28

216

Temperature programmed decomposition of uranyl nitrate hexahydrate  

NASA Astrophysics Data System (ADS)

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 decomposition stages could be deduced from EGA-MS data. The corresponding activation energies and frequency factors were also evaluated. Kinetics based on random nucleation and diffusion was found to be rate controlling. The residue left over after each decomposition stage was analysed by XRD and XPS to determine structure and composition. The ultimate product was found to be a mixture of UO 3H 1.17 and U 3O 8: the former being a topotactic hydrogen spill over compound of UO 3. Complete conversion of this residue to U 3O 8 was noticed during ion beam exposure of the residue which was performed in the course of XPS investigations.

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

1999-01-01

217

Infrared photodissociation spectroscopy of protonated ammonia cluster ions, NH4+(NH3)n (n =5-8), by using infrared free electron laser  

NASA Astrophysics Data System (ADS)

Infrared photodissociation action spectra of protonated ammonia cluster ions, NH4+(NH3)n (n =5-8), were measured in the range of 1020-1210cm-1 by using a tunable infrared free electron laser. Analyses by the density functional theory (DFT) show that the spectral features observed can be assigned to the ?2 vibrational mode of the NH3 molecules in NH4+(NH3)n. Size dependence of the spectra supports structural models obtained by the DFT calculations, in which the NH4+ ion is solvated by the four nearest-neighbor NH3 molecules. For NH4+(NH3)5, the spectrum between 1000 and 1700cm-1 was measured. The ?4 bands of the NH3 molecules and the NH4+ ion were found in the range of 1420-1700cm-1.

Tono, Kensuke; Bito, Kotatsu; Kondoh, Hiroshi; Ohta, Toshiaki; Tsukiyama, Koichi

2006-12-01

218

Recent concepts concerning the renal handling of NH3/NH4+.  

PubMed

To be appropriately excreted in urine, NH4+ , the major component of urinary acid excretion, must be synthesized by proximal tubular cells, secreted into the proximal tubular fluid, reabsorbed by the medullary thick ascending limb (MTAL) to accumulate in the medullary interstitium, and finally be secreted in the medullary collecting ducts. Each of the various steps of this particular renal pathway is highly regulated, and the control of gene expression explains how the renal handling of NH 4 + becomes fully adapted to chronic acid-base changes. Several targets have been identified to account for the adaptation of renal NH 4 + synthesis and transport in response to an acid load. These are the key enzymes of ammoniagenesis and the apical Na+/H+ (NH4+) exchanger NHE3 in the proximal tubule, the apical Na + -K + (NH 4 + )-2Cl - cotransporter of the MTAL, and the basolateral Na+-K+ (NH4+)-2Cl- cotransporter and the epithelial Rh B and C glycoproteins in the collecting ducts. An acid pH appears to be a major factor in the control of gene expression during metabolic acidosis probably through the activation of pH sensors. Glucocorticoids can contribute to coordinate the adaptation of various tubular cell types. This review focuses on some new aspects of NH3/NH4+ transport and of gene expression regulation that have recently emerged. PMID:16736437

Karim, Z; Szutkowska, M; Vernimmen, C; Bichara, M

2006-01-01

219

Spectral intensities in the nu(sub 1) band of NH3  

NASA Technical Reports Server (NTRS)

Intensities have been measured for individual transitions in the Q and R branches of the nu(sub 1) band of NH3 using a difference-frequency laser spectrometer. The data yield an integrated band strength of S(sup 0 sub v) = 219.36 +/- 1.03/sq cm/MPa at 297 K, corresponding to a transition moment of absolute value of mu(sub v) = 8.535(20) x 10(exp -32) C x m, and a Herman-Wallis correction factor,(1 + alpha(sub J)m), where alpha(sub J) = 0.0209(20). The intensities of a few lines for K greater than or equal to 7 were noticeably perturbed by a perpendicular Coriolis interaction with 2nu(sub 4)(E, l = 2), so were excluded from the fit. A small sample of nu(sub 3) band lines occurring in the nu(sub 1) band scans also yields a rough estimate of the nu(sub 3) band intensity with evident irregular perturbations.

Pine, A. S.; Dang-Nhu, M.

1993-01-01

220

Absorption coefficients of solid NH3 from 50 to 7000 per cm  

NASA Technical Reports Server (NTRS)

Thin-film spectra of solid NH3 at a resolution of 1 per cm were used to determine its absorption coefficient over the range 50-7000 per cm. The thin films were formed inside a liquid N2 cooled dewar using a variety of substrates and dewar windows. The spectra were recorded with two Fourier spectrometers, one covering the range from 1 to 4 microns and the other from 2.6 to 200 microns. The thickness of the films was measured with a laser interference technique. The absorption coefficients were determined by application of Lambert's law and by a fitting procedure to the observed spectra using thin-film theory. Good agreement was found with the absorption coefficients recently determined by other investigators over a more restricted wavelength range. A metastable phase was observed near a temperature of 90 K and its absorption coefficient is reported. No other major spectral changes with temperature were noted for the range 88-120 K.

Sill, G.; Fink, U.; Ferraro, J. R.

1980-01-01

221

Photochemical reactions in interstellar grains photolysis of CO, NH3, and H2O  

NASA Technical Reports Server (NTRS)

The interstellar grains are currently considered to be the basic building blocks of comets and, possibly, meteorites. To test this theory, 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 10 K, with concomitant irradiation with vacuum UV. The results of the HPLC and IR analyses of the nonvolatile residue formed by photolysis at 10 K are compared with those observed at 77 K and 298 K. Some of the compounds that may be present on the surfaces of interstellar dust particles have been identified, and some specific predictions concerning the types of molecular species present in comets could be drawn. The results also suggest that photochemical reactions may have been important for the formation of meteorite components. The implication of the findings to the questions of the source of organic matter on earth and the origin of life are discussed.

Agarwal, V. K.; Ferris, J. P.; Schutte, W.; Greenberg, J. M.; Briggs, R.

1985-01-01

222

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

2013-05-28

223

Selective catalytic reduction of NOx with NH3 over a Cu-SSZ-13 catalyst prepared by a solid state ion exchange method  

SciTech Connect

A novel solid state method was developed to synthesize Cu-SSZ-13 catalysts with excellent NH3-SCR performance and durable hydrothermal stability. After the solid state ion exchange (SSIE) process, the SSZ framework structure and surface area was maintained. In-situ DRIFTS and NH3-TPD experiments provide evidence that isolated Cu ions were successfully exchanged into the pores, which are the active centers for the NH3-SCR reaction.

Wang, Di; Gao, Feng; Peden, Charles HF; Li, Junhui; Kamasamudram, Krishna; Epling, William S.

2014-10-28

224

Proton transfer dynamics of the reaction H3O ,,NH3 ,H2O...NH4  

E-print Network

Proton transfer dynamics of the reaction H3O¿ ,,NH3 ,H2O...NH4 ¿ studied using the crossed, Rochester, New York 14627 Received 29 September 2003; accepted 8 October 2003 The proton transfer reaction combination. These results indicate that the proton transfer proceeds through a direct reaction mechanism

Farrar, James M.

225

Galvanic deposition of Rh and Ru on randomly structured Ti felts for the electrochemical NH3 synthesis.  

PubMed

Nowadays NH3 is exclusively synthesized by the Haber process. Unfortunately, the energy demand and the CO2 emissions due to H2 production are high. Hydrogen production utilizes precious carbon sources such as coal and natural gas. In the past we proposed an alternative process concept using a membrane electrode assembly in an electrochemical membrane reactor (ecMR). At the anode H2O is oxidized at an IrMMO catalyst to form protons. By applying an external potential to the ecMR N2 is reduced to NH3 at the cathode. Just recently Rh and Ru were identified as possible cathodic electrocatalysts by DFT calculations. We present an easy and highly efficient method for galvanic coatings of Rh and Ru on randomly structured Ti felts to be used in a membrane electrode assembly. Linear sweep voltammetry measurements give a slightly higher activity of Ru for the liquid phase electrochemical NH3 synthesis. The NH4(+) concentration reached is 8 times higher for Ru than for Rh. From an economical point of view, Ru is also more feasible for an electrochemical NH3 synthesis process. Such electrodes can now be evaluated in an ecMR in comparison to recently demonstrated Ti-based electrodes. PMID:25556769

Kugler, Kurt; Luhn, Mareike; Schramm, Jean Andr; Rahimi, Khosrow; Wessling, Matthias

2015-02-01

226

Observations and analysis of the Jovian spectrum in the 10-micron nu-2 band of NH3  

NASA Technical Reports Server (NTRS)

Observations of the nu-2 band of NH3 in the Jovian atmosphere have been made at resolutions varying from 4 per cm to 0.15 per cm. The observations have been interpreted by computation of synthetic atmospheric spectra. Derived atmospheric parameters include a pressure of 0.5 atm at 145 K and a minimum temperature of 118 K.

Lacy, J. H.; Larrabee, A. I.; Wollman, E. R.; Geballe, T. R.; Townes, C. H.; Bregman, J. D.; Rank, D. M.

1975-01-01

227

Structures and Magnetic Properties of Iron Diphosphonates: [NH 3(CH 2) 2NH 3][Fe II{HO 3PC(CH 3)(OH)(PO 3H)} 2]2H 2O and [NH 3(CH 2) 2NH 2(CH 2) 2NH 3][Fe III{O 3PC(CH 3)(OH)(PO 3H)} 2]H 2O  

NASA Astrophysics Data System (ADS)

Two iron diphosphonates, [NH3(CH2)2NH3][FeII{HO3PC (CH3)(OH)(PO3H)}2] 2H2O (1) and [NH3(CH2)2NH2(CH2)2 NH3][FeIII{O3PC(CH3)(OH)(PO3H)}2]H2O (2), have been synthesized under hydrothermal conditions. Crystal data: 1, monoclinic, C2/c, a=24.754(5), b=5.331(1), c=16.010(3) , ?=117.787(3), V=1868.9(6) 3, Z=4, R1=0.0321; 2, orthorhombic, Pbcn, a=22.128(4), b=9.9479(9), c=19.110(2) , V=4206.7(9) 3, Z=8, R1=0.0389. Both show chain structures in which anionic chains of [FeII{HO3PC(CH3)(OH) (PO3H)}2]n2n - in 1 or [FeIII{O3PC(CH3)(OH)(PO3H)}2]n3n- in 2 are composed of {FeIIO6} or {FeIIIO6} octahedra and {CPO3} tetrahedra alternatively. The protonated organic amines and lattice water are located between the chains with extensive hydrogen bonding interactions. Weak antiferromagnetic exchange couplings are propagated between the magnetic centers through the O-P-O bridges in both cases.

Song, Hui-Hua; Zheng, Li-Min; Zhu, Guangshan; Shi, Zhan; Feng, Shouhua; Gao, Song; Hu, Zheng; Xin, Xin-Quan

2002-03-01

228

An AlGaAsGaAs quantum cascade laser operating with a thermoelectric cooler for spectroscopy of NH3  

E-print Network

An AlGaAs­GaAs quantum cascade laser operating with a thermoelectric cooler for spectroscopy of NH3 2003; accepted 7 July 2003 Abstract A new design of AlGaAs­GaAs quantum cascade laser (QCL) operating.V. All rights reserved. Since their inception in 1994 by Faist et al. [1], quantum cascade lasers (QCLs

229

Synthesis and Characterization of a Large-Pore, Open-Framework Gallium Phosphate, [NH 3(CH 2) 4NH 3] 2[Ga 4(HPO 4) 2(PO 4) 3(OH) 3] yH 2O ( y5.4), and Its Vanadium-Gallium Phosphate Analogue, [NH 3(CH 2) 4NH 3] 2[Ga 4- xV x(HPO 4) 2(PO 4) 3(OH) 3] yH 2O ( x0.4, y6)  

NASA Astrophysics Data System (ADS)

A new three-dimensional gallium phosphate, [NH 3(CH 2) 4 NH 3] 2[Ga 4(HPO 4) 2(PO 4) 3(OH) 3] yH 2O ( y5.4), has been synthesized under hydrothermal conditions at 433 K in the presence of 1,4-diaminobutane and its structure determined using room-temperature single-crystal X-ray diffraction data ( Mr= 1084.03, tetragonal, space group I4 1/ a, a=15.261(1), c=28.898(2) ; V=6730.4 3, Z=8, R=4.09% and Rw= 4.45% for 3093 observed data ( I>3(?( I))). The structure consists of chains of GaO 6 octahedra and PO 4 tetrahedra cross-linked by additional PO 4 tetrahedra to generate a three-dimensional framework containing large tunnels in which 1,4-diaminobutane dications and water molecules reside. The tunnels are bounded by 20-ring windows of alternating gallium- and phosphorus-based polyhedra. The framework is closely related to that of a 1,3-diaminopropane encapsulating iron (III) phosphate, [NH 3(CH 2) 3 NH 3] 2[Fe 4(HPO 4) 2(PO 4) 3(OH) 3] yH 2O ( y9), Further syntheses in the presence of V 2O 5 show that up to 12% of the Ga(III) can be replaced by V(III) with retention of the large-pore framework structure.

Chippindale, Ann M.; Peacock, Katherine J.; Cowley, Andrew R.

1999-07-01

230

Rapid Ammonia Gas Transport Accounts for Futile Transmembrane Cycling under NH3/NH4+ Toxicity in Plant Roots1[C][W  

PubMed Central

Futile transmembrane NH3/NH4+ cycling in plant root cells, characterized by extremely rapid fluxes and high efflux to influx ratios, has been successfully linked to NH3/NH4+ toxicity. Surprisingly, the fundamental question of which species of the conjugate pair (NH3 or NH4+) participates in such fluxes is unresolved. Using flux analyses with the short-lived radioisotope 13N and electrophysiological, respiratory, and histochemical measurements, we show that futile cycling in roots of barley (Hordeum vulgare) seedlings is predominately of the gaseous NH3 species, rather than the NH4+ ion. Influx of 13NH3/13NH4+, which exceeded 200 mol g1 h1, was not commensurate with membrane depolarization or increases in root respiration, suggesting electroneutral NH3 transport. Influx followed Michaelis-Menten kinetics for NH3 (but not NH4+), as a function of external concentration (Km = 152 m, Vmax = 205 mol g1 h1). Efflux of 13NH3/13NH4+ responded with a nearly identical Km. Pharmacological characterization of influx and efflux suggests mediation by aquaporins. Our study fundamentally revises the futile-cycling model by demonstrating that NH3 is the major permeating species across both plasmalemma and tonoplast of root cells under toxicity conditions. PMID:24134887

Coskun, Devrim; Britto, Dev T.; Li, Mingyuan; Becker, Alexander; Kronzucker, Herbert J.

2013-01-01

231

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

232

Effects of NH3 and N2 additions to hot filament activated CH4/H2 gas mixtures  

NASA Astrophysics Data System (ADS)

Resonance enhanced multiphoton ionization and cavity ring down spectroscopies have been used to provide spatially resolved measurements of relative H atom and CH3 radical number densities, and NH column densities, in a hot filament (HF) reactor designed for diamond chemical vapor deposition and here operating with a 1% CH4/n/H2 gas mixturewhere n represents defined additions of N2 or NH3. Three-dimensional modeling of the H/C/N chemistry prevailing in such HF activated gas mixtures allows the relative number density measurements to be placed on an absolute scale. Experiment and theory both indicate that N2 is largely unreactive under the prevailing experimental conditions, but NH3 additions are shown to have a major effect on the gas phase chemistry and composition. Specifically, NH3 additions introduce an additional series of "H-shift" reactions of the form NHx+H?NHx-1+H2 which result in the formation of N atoms with calculated steady state number densities >1013 cm-3 in the case of 1% NH3 additions in the hotter regions of the reactor. These react, irreversibly, with C1 hydrocarbon species forming HCN products, thereby reducing the concentration of free hydrocarbon species (notably CH3) available to participate in diamond growth. The deduced reduction in CH3 number density due to competing gas phase chemistry is shown to be compounded by NH3 induced modifications to the hot filament surface, which reduce its efficiency as a catalyst for H2 dissociation, thus lowering the steady state gas phase H atom concentrations and the extent and efficiency of all subsequent gas phase transformations.

Smith, James A.; Wills, Jonathan B.; Moores, Helen S.; Orr-Ewing, Andrew J.; Ashfold, Michael N. R.; Mankelevich, Yuri A.; Suetin, Nikolay V.

2002-07-01

233

Concentration-Dependent Effects on Intracellular and Surface pH of Exposing Xenopus oocytes to Solutions Containing NH3/NH4+  

PubMed Central

Others have shown that exposing oocytes to high levels of NH3/NH4+ (1020 mM) causes a paradoxical fall in intracellular pH (pHi), whereas low levels (e.g., 0.5 mM) cause little pHi change. Here we monitored pHi and extra-cellular surface pH (pHS) while exposing oocytes to 5 or 0.5 mM NH3/NH4+. We confirm that 5 mM NH3/NH4+ causes a paradoxical pHi fall (??pHi ? 0.2), but also observe an abrupt pHS fall (??pHS ? 0.2)indicative of NH3 influxfollowed by a slow decay. Reducing [NH3/NH4+] to 0.5 mM minimizes pHi changes but maintains pHS changes at a reduced magnitude. Expressing AmtB (bacterial Rh homologue) exaggerates ??pHS at both NH3/NH4+ levels. During removal of 0.5 or 5 mM NH3/NH4+, failure of pHS to markedly overshoot bulk extracellular pH implies little NH3 efflux and, thus, little free cytosolic NH3/NH4+. A new analysis of the effects of NH3 vs. NH4+ fluxes on pHS and pHi indicates that (a) NH3 rather than NH4+ fluxes dominate pHi and pHS changes and (b) oocytes dispose of most incoming NH3. NMR studies of oocytes exposed to 15N-labeled NH3/NH4+ show no significant formation of glutamine but substantial NH3/NH4+ accumulation in what is likely an acid intracellular compartment. In conclusion, parallel measurements of pHi and pHS demonstrate that NH3 flows across the plasma membrane and provide new insights into how a protein molecule in the plasma membraneAmtBenhances the flux of a gas across a biological membrane. PMID:19242745

Jiang, Lihong; Chen, Li-Ming; Behar, Kevin L.

2010-01-01

234

Concentration-dependent effects on intracellular and surface pH of exposing Xenopus oocytes to solutions containing NH3/NH4(+).  

PubMed

Others have shown that exposing oocytes to high levels of NH(3)/NH(4)(+) (10-20 mM) causes a paradoxical fall in intracellular pH (pH(i)), whereas low levels (e.g., 0.5 mM) cause little pH(i) change. Here we monitored pH(i) and extracellular surface pH (pH(S)) while exposing oocytes to 5 or 0.5 mM NH(3)/NH(4)(+). We confirm that 5 mM NH(3)/NH(4)(+) causes a paradoxical pH(i) fall (-DeltapH(i) approximately equal 0.2), but also observe an abrupt pH(S) fall (-DeltapH(S) approximately equal 0.2)-indicative of NH(3) influx-followed by a slow decay. Reducing [NH(3)/NH(4)(+)] to 0.5 mM minimizes pH(i) changes but maintains pH(S) changes at a reduced magnitude. Expressing AmtB (bacterial Rh homologue) exaggerates -DeltapH(S) at both NH(3)/NH(4)(+) levels. During removal of 0.5 or 5 mM NH(3)/NH(4)(+), failure of pH(S) to markedly overshoot bulk extracellular pH implies little NH(3) efflux and, thus, little free cytosolic NH(3)/NH(4)(+). A new analysis of the effects of NH(3) vs. NH(4)(+) fluxes on pH(S) and pH(i) indicates that (a) NH(3) rather than NH(4)(+) fluxes dominate pH(i) and pH(S) changes and (b) oocytes dispose of most incoming NH(3). NMR studies of oocytes exposed to (15)N-labeled NH(3)/NH(4)(+) show no significant formation of glutamine but substantial NH(3)/NH(4)(+) accumulation in what is likely an acid intracellular compartment. In conclusion, parallel measurements of pH(i) and pH(S) demonstrate that NH(3) flows across the plasma membrane and provide new insights into how a protein molecule in the plasma membrane-AmtB-enhances the flux of a gas across a biological membrane. PMID:19242745

Musa-Aziz, Raif; Jiang, Lihong; Chen, Li-Ming; Behar, Kevin L; Boron, Walter F

2009-03-01

235

Tuning of through-bond electronic coupling by donor and acceptor substitutions in the [(NH 3) 5Ru1,4-dicyanobenzeneRu(NH 3) 5] 5+ complex  

NASA Astrophysics Data System (ADS)

Through-ligand electronic coupling in the [(NH 3) 5Ru III1,4-dicyanobenzeneRu II(NH 3) 5] 5+ complex is calculated depending on the donor or acceptor grafted on the benzene. The coupling strength is first discussed, showing that through-dicyanobutadiene is larger than through-1,4-dicyanobenzene coupling. With this ligand, the largest electronic coupling is reached with a full 4NO 2 substitution on the benzene. Coupling through an asymmetric 2NO 22NH 2-substituted benzene is one order of magnitude lower. This large difference is interpreted using the number and position of the active ligand molecular orbitals relative to the d-ruthenium orbital.

Joachim, C.

1991-10-01

236

Specific heat of quantum-spin chains: Application to (C6H11NH3)CuBr3 and (C6H11NH3)CuCl3  

NASA Astrophysics Data System (ADS)

A real-space renormalization-group (RSRG) approach and numerical calculations are applied in order to study the specific heat of (C6H11NH3)CuBr3 and (C6H11NH3)CuCl3, which are built up of the ferromagnetic spin-1/2 quantum chains and are described by anisotropic Heisenberg models. As to the RSRG approach, our previous zero-field easy-plane calculations are extended to the XYZ model in the presence of a magnetic field, and qualitative agreement with experiment is found, especially in the appearance of the soliton peaks in the in-plane excess specific heat. Imposing free boundary conditions, the finite-size numerical results are applied to chains with length N<=12 and extrapolated for 1/N-->0. Good convergence for most temperatures is found, and agreement with experiment is concluded.

Campana, L. S.; Caramico D'auria, A.; Esposito, U.; Kamieniarz, G.

1990-04-01

237

Quantitative estimation of NH3 partial pressure in H2 desorbed from the Li-N-H system by Raman spectroscopy.  

PubMed

The partial pressure of NH3 gas estimated by Raman spectroscopy indicates that approximately 0.1% NH3 inevitably contaminates the H2 desorbed from a hydrogen storage material composed of LiH and LiNH2 at any temperature up to 400 degrees C in a closed system. PMID:15959577

Hino, Satoshi; Ichikawa, Takayuki; Ogita, Norio; Udagawa, Masayuki; Fujii, Hironobu

2005-06-28

238

Far-infrared vibration-rotation-tunneling spectroscopy of Ar-NH3: Intermolecular vibrations and effective angular potential energy surface  

E-print Network

Far-infrared vibration-rotation-tunneling spectroscopy of Ar-NH3: Intermolecular vibrations intermolecular vibration-rotation-tunneling (VRT) bandsof Ar-NH3 havebeen measuredusingtunable far infrared'employeda close-couplingmethod to fit exten- sive far-infrared vibration rotation tunneling (FIR-VRT) spectraof

Cohen, Ronald C.

239

A cluster DFT study of NH3 and NO adsorption on the (MoO2)2+/HZSM-5 surface: Lewis versus Brnsted acid sites  

NASA Astrophysics Data System (ADS)

A systematic DFT study was carried out to investigate NH3 and NO adsorption on both Lewis and Brnsted acid sites of (MoO2)2+/HZSM-5 catalyst by using cluster models. The adsorption energy results indicate that NH3 could strongly adsorb on both Lewis and Brnsted acid sites in the form of coordinated NH3 and NH4+, respectively, whereas NO represents poorer adsorption ability. It is also found that Lewis and Brnsted acid sites are competitive energetically for NH3 adsorption. According to the difference in the proposed mechanisms for NH3 adsorption on different acid sites, particular attention has been focused on the first dissociation of coordinated NH3 for Lewis acid site and the effect of Mo site on the introduction of NO for Brnsted acid site. For the coordinated NH3 on Lewis acid site, the more electron donation from NH3 is, the greater its adsorption stability is and the higher active its H atoms are. In addition, DOS results show that stability of the H atoms is enhanced by interacting with framework oxygen and especially the H atoms chemical-bonded with framework oxygen. For the NH4+ on Brnsted acid site, reduced-state Mo5+ holds stronger reducibility and oxidizability than terminal oxygen, which is suggested to play a key role in adsorption and activation of NOx together with the adsorbed NH4+.

Yan, Zhifeng; Zuo, Zhijun; Li, Zhe; Zhang, Jinshan

2014-12-01

240

N2 Product Internal-State Distributions for the Steady-State Reactions of NO with H2 and NH3 on the Pt(100) Surface  

E-print Network

on the Pt(100) Surface Alexander J. Hallock, Carl M. Matthews, Frank Balzer, and Richard N. Zare Form: May 16, 2001 The steady-state reaction of NO with H2 and NH3 on Pt(100) is investigated over the internal energy distribution of the N2 product for two different precursor reactions on Pt- (100): NO + NH3

Zare, Richard N.

241

Enantiospecific Desorption of Chiral Compounds from Chiral Cu(643) and Achiral Cu(111) Surfaces  

E-print Network

molecules on the Cu(643) surfaces. There are several high-temperature features in the TPD spectra: Temperature-programmed desorption (TPD) experiments have been conducted to investigate enantiospecific such as Cu have kinked and stepped structures which are nonsuperimposable mirror images of one another

Gellman, Andrew J.

242

Characterization of Cu-SSZ-13 NH3 SCR Catalysts: an in situ FTIR Study  

SciTech Connect

The adsorption of CO and NO over Cu-SSZ-13 zeolite catalysts, highly active in the selective catalytic reduction of NOx with NH3, was investigated by FTIR spectroscopy, and the results obtained were compared to those collected from other Cu-ion exchanged zeolites (Y,FAU and ZSM-5). At low CO pressures at room temperature (295 K) CO form monocarbonyls exclusively on the Cu+ ions, while in the presence of gas phase CO dicarbonyls on Cu+ and adsorbed CO on Cu2+ centers form, as well. At low (cryogenic) sample temperatures tricarbonyl formation on Cu+ sites was also observed. The adsorption of NO produces IR bands that can be assigned to nitrosyls bound to both Cu+ and Cu2+ centers, and NO+ species located in charge compensating cationic positions of the chabasite framework. On the reduced Cu-SSZ-13 samples the formation of N2O was also detected. The assignment of the adsorbed NOx species was aided by adsorption experiments with isotopically labeled 15NO. The movement of Cu ions from the sterically hindered six member ring position to the more accessible cavity positions as a result of their interaction with adsorbates (NO and H2O) was clearly evidenced. Comparisons of the spectroscopy data obtained in the static transmission IR system to those collected in the flow-through diffuse reflectance cell points out that care must be taken when conclusions are drawn about the adsorptive and reactive properties of metal cation centers based on a set of data collected under well defined, specific experimental conditions. Financial support was provided by the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program. This work was performed in the Environmental Molecular Sciences Laboratory (EMSL) at the Pacific Northwest National Laboratory (PNNL). The EMSL is a national scientific user facility supported by the US DOE, Office of Biological and Environmental Research. PNNL is a multi-program national laboratory operated for the US DOE by Battelle.

Szanyi, Janos; Kwak, Ja Hun; Zhu, Haiyang; Peden, Charles HF

2013-01-23

243

Photocarrier recombination dynamics in perovskite CH3NH3PbI3 for solar cell applications.  

PubMed

Using time-resolved photoluminescence and transient absorption measurements at room temperature, we report excitation-intensity-dependent photocarrier recombination processes in thin films made from the organo-metal halide perovskite semiconductor CH3NH3PbI3 for solar-cell applications. The photocarrier dynamics are well described by a simple rate equation including single-carrier trapping and electron-hole radiative recombination. This result provides clear evidence that the free-carrier model is better than the exciton model for interpreting the optical properties of CH3NH3PbI3. The observed large two-carrier recombination rate suggests the promising potential of perovskite semiconductors for optoelectronic device applications. Our findings provide the information about the dynamical behaviors of photoexcited carriers that is needed for developing high-efficiency perovskite solar cells. PMID:25075458

Yamada, Yasuhiro; Nakamura, Toru; Endo, Masaru; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

2014-08-20

244

Effect of plasma N2 and thermal NH3 nitridation in HfO2 for ultrathin equivalent oxide thickness  

NASA Astrophysics Data System (ADS)

Two methods of HfO2 nitridation including plasma N2 nitridation and thermal NH3 anneal were studied for ultrathin HfO2 gate dielectrics with <1 nm equivalent oxide thickness (EOT). The detailed nitridation mechanism, nitrogen depth profile, and nitrogen behavior during the anneal process were thoroughly investigated by XPS and SIMS analysis for the two types of nitridation processes at different process conditions. Intermediate metastable nitrogen was observed and found to be important during the plasma nitridation process. For thermal NH3 nitridation, pressure was found to be most critical to control the nitrogen profile while process time and temperature produced second order effects. The physical analyses on the impacts of various process conditions are well correlated to the electrical properties of the films, such as leakage current, EOT, mobility, and transistor bias temperature instability.

Dai, Min; Wang, Yanfeng; Shepard, Joseph; Liu, Jinping; Brodsky, Maryjane; Siddiqui, Shahab; Ronsheim, Paul; Ioannou, Dimitris P.; Reddy, Chandra; Henson, William; Krishnan, Siddarth; Narayanan, Vijay; Chudzik, Michael P.

2013-01-01

245

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Calculation of optimal parameters of an NH3-CO2 lidar  

NASA Astrophysics Data System (ADS)

The basic parameters (range, signal-to-noise ratio, and sensitivity) of a lidar using NH3 and CO2 lasers are calculated. The principle of lidar operation is based on the differential absorption recording. Absorption spectra of all known Freons are considered in the spectral range 9-13.5 ?m and optimal wavelengths suitable for sensing them are determined. It is shown that the NH3-CO2 lidar can sense Freons at distances up to 10 km at a signal-to-noise ratio exceeding 10. Sensitivities of the lidar for sensing Freon-11 using various lines of the ammonia laser are calculated. It is shown that remote sensing of Freon-11 at concentrations of the order of 510-6% is possible at distances up to 8.5 km.

Vasil'ev, B. I.; Mannoun, Oussama

2005-06-01

246

Deposition of silicon nitride from SiCl4 and NH3 in a low pressure RF plasma  

NASA Technical Reports Server (NTRS)

Silicon nitride coatings were deposited in a low-pressure (1-10 Torr) RF plasma from SiCl4 and NH3 in the presence of argon onto stainless martensitic steel grounded and floating substrates at 300 C and 440 C respectively. The heating of the substrates depends mainly on the position and the induced RF power. The coatings were identified as silicon nitride by X-ray investigation and were found to contain chlorine by energy-dispersive analysis of X-rays. The growth rate, the microhardness and the chlorine concentration of the coatings were determined as a function of the total gas pressure, the RF power input and the NH3-to-SiCl4 ratio. It was observed that the coatings on the floating substrates have higher deposition rates and are of superior quality.

Ron, Y.; Raveh, A.; Carmi, U.; Inspektor, A.; Avni, R.

1983-01-01

247

Removal of SO2 from O2-containing flue gas by activated carbon fiber (ACF) impregnated with NH3.  

PubMed

Adsorption of SO(2) from the O(2)-containing flue gas by granular activated carbons (GACs) and activated carbon fibers (ACFs) impregnated with NH(3) 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 of sulfuric acid. After NH(3) impregnation of ACF samples, nitrogen-containing functional groups (pyridyl C(5)H(4)N- and pyrrolyl C(4)H(4)N-) were detected on the sample surface by using an X-ray photoelectron spectrometer. These functional groups accounted for the enhanced SO(2) adsorption via chemisorption and/or catalytic oxidization. PMID:15982716

Xu, Lsi; Guo, Jia; Jin, Feng; Zeng, Hancai

2006-02-01

248

CHE 301 EXAM 2 Name ____________________________________________ 1. Calculate the ratio of ammonia (NH3) to the ammonium ion (NH4  

E-print Network

(NH3) to the ammonium ion (NH4 + ) in a solution with a pH of 10.0. 2. How many grams of NH4Cl must.- Use your textbook to select the best indicator for the titration of tin(II) with cerium(IV), 7Balance in the ore. 10. At pH 7.6, the predominant form of EDTA ion is _________________ #12;

Nazarenko, Alexander

249

Infrared and far-infrared laser emissions from a TE CO2 laser pumped NH3 gas  

Microsoft Academic Search

In this paper, infrared (IR) and far-infrared (FIR) laser emissions from a TE CO2 laser pumped NH3 gas are reported. 8 IR laser emissions near the wavelength of 12 mum were observed by using 4 different CO2 laser lines for the pumping. 3 IR laser emissions in P-branch of vibrational-rotational band (nu2 --> G) oscillated simultaneously in two pumping cases,

T. Yoshida; N. Yamabayashi; K. Miyazaki; K. Fujisawa

1978-01-01

250

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. PMID:11486013

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

2001-01-01

251

Phase coexistence and hysteresis effects in the pressure-temperature phase diagram of NH3BH3  

Microsoft Academic Search

The potential hydrogen storage compound NH3BH3 has three known structural phases in the temperature and pressure ranges 110-300 K and 0-1.5 GPa, respectively. We report here the boundaries between, and the ranges of stability of, these phases. The phase boundaries were located by in situ measurements of the thermal conductivity, while the actual structures in selected areas were identified by

Ove Andersson; Yaroslav Filinchuk; Vladimir Dmitriev; Issam Quwar; Alexandr V. Talyzin; Bertil Sundqvist

2011-01-01

252

Assessment of N2O, NOx and NH3 emissions from a typical rural catchment in Eastern China  

Microsoft Academic Search

To evaluate the atmospheric load of reactive gaseous nitrogen in the fast-developing Eastern China region, we compiled inventories of nitrous oxide (N2O), nitrogen oxide (NOx) and ammonia (NH3) emissions from a typical rural catchment in Jiangsu province, China, situated at the lower reach of the Yangtze River. We considered emissions from synthetic N fertilizer, human and livestock excreta, decomposition of

Rong Yang; Chaopu Ti; Feiyue Li; Meihua Deng; Xiaoyuan Yan

2010-01-01

253

Estimating NH3 emissions from agricultural fertilizer application in China using the bi-directional CMAQ model coupled to an agro-ecosystem model  

NASA Astrophysics Data System (ADS)

Atmospheric ammonia (NH3) plays an important role in atmospheric chemistry. China is one of the largest NH3 emitting countries with the majority of NH3 emissions coming from the agricultural practices, such as fertilizer application and livestock. The current NH3 emission estimates in China are mainly based on pre-defined emission factors that lack the temporal or spatial details, which are needed to accurately predict NH3 emissions. In this study, we estimate, for the first time, the NH3 emission from the agricultural fertilizer application in China online using an agricultural fertilizer modeling system coupling a regional air quality model (the Community Multi-Scale Air Quality model, CMAQ) and an agro-ecosystem model (the Environmental Policy Integrated Climate model, EPIC), which improves the spatial and temporal resolution of NH3 emission from this sector. Cropland area data of 14 crops from 2710 counties and the Moderate Resolution Imaging Spectroradiometer (MODIS) land use data are combined to determine the crop distribution. The fertilizer application rate and method for different crop are collected at provincial or agriculture-regional level. The EPIC outputs of daily fertilizer application and soil characteristics are inputed into the CMAQ model and the hourly NH3 emission are calculated online with CMAQ running. The estimated agricultural fertilizer NH3 emission in this study is about 3 Tg in 2011. The regions with the highest modeled emission rates are located in the North China Plain. Seasonally, the peak ammonia emissions occur from April to July.Compared with previous researches, this method considers more influencing factors, such as meteorological fields, soil and the fertilizer application, and provides improved NH3 emission with higher spatial and temporal resolution.

Fu, X.; Wang, S. X.; Ran, L. M.; Pleim, J. E.; Cooter, E.; Bash, J. O.; Benson, V.; Hao, J. M.

2015-01-01

254

Biological gas channels for NH3 and CO2: evidence that Rh (Rhesus) proteins are CO2 channels.  

PubMed

Physiological evidence from our laboratory indicates that Amt/Mep proteins are gas channels for NH3, the first biological gas channels to be described. This view has now been confirmed by structural evidence and is displacing the previous belief that Amt/Mep proteins were active transporters for the NH4+ ion. Still disputed is the physiological substrate for Rh proteins, the only known homologues of Amt/Mep proteins. Many think they are mammalian ammonium (NH4+ or NH3) transporters. Following Monod's famous dictum, "Anything found to be true of E. coli must also be true of elephants" [Perspect. Biol. Med. 47(1) (2004) 47], we explored the substrate for Rh proteins in the unicellular green alga Chlamydomonas reinhardtii. C. reinhardtii is one of the simplest organisms to have Rh proteins and it also has Amt proteins. Physiological studies in this microbe indicate that the substrate for Rh proteins is CO2 and confirm that the substrate for Amt proteins is NH3. Both are readily hydrated gases. Knowing that transport of CO2 is the ancestral function of Rh proteins supports the inference from hematological research that a newly evolving role of the human Rh30 proteins, RhCcEe and RhD, is to help maintain the flexible, flattened shape of the red cell. PMID:16563833

Kustu, S; Inwood, W

2006-01-01

255

Star-forming regions of the Aquila rift cloud complex. II. Turbulence in molecular cores probed by NH3 emission  

NASA Astrophysics Data System (ADS)

Aims: We intend to derive statistical properties of stochastic gas motion inside the dense, low-mass star-forming molecular cores that are traced by NH3(1, 1) and (2, 2) emission lines. Methods: We use the spatial two-point autocorrelation (ACF) and structure functions calculated from maps of the radial velocity fields. Results: The observed ammonia cores are characterized by complex intrinsic motions of stochastic nature. The measured kinetic temperature ranges between 8.8 K and 15.1 K. From NH3 excitation temperatures of 3.5-7.3 K, we determine H2 densities with typical values of nH2~ (1-6) 104 cm-3. The ammonia abundance, X = [NH3]/[H2], varies from 2 10-8 to 1.5 10-7. We find oscillating ACFs, which eventually decay to zero with increasing lags on scales of 0.04 ? ? ? 0.5 pc. The current paradigm supposes that the star-formation process is controlled by the interplay between gravitation and turbulence with the latter preventing molecular cores from a rapid collapse due to their own gravity. Thus, oscillating ACFs may indicate a damping of the developed turbulent flows surrounding the dense but less turbulent core, a transition to dominating gravitational forces and, hence, to gravitational collapse. Appendix A is available in electronic form at http://www.aanda.org

Levshakov, S. A.; Henkel, C.; Reimers, D.; Wang, M.

2014-07-01

256

Effect of phosphogypsum and dicyandiamide as additives on NH3, N20 and CH4 emissions during composting.  

PubMed

A laboratory scale experiment of composting in a forced aeration system using pig manure with cornstalks was carried out to investigate the effects of both phosphogypsum and dicyandiamide (DCD, C2H4N4) as additives on gaseous emissions and compost quality. Besides a control, there were three amended treatments with different amounts of additives. The results indicated that the phosphogypsum addition at the rate of 10% of mixture dry weight decreased NH3 and CH4 emissions significantly during composting. The addition of DCD at the rate of 0.2% of mixture dry weight together with 10% of phosphogypsum further reduced the N2O emission by affecting the nitrification process. Reducing the phosphogypsum addition to 5% in the presence of 0.2% DCD moderately increased the NH3 emissions but not N2O emission. The additives increased the ammonium content and electrical conductivity significantly in the final compost. No adverse effect on organic matter degradation or the germination index of the compost was found in the amended treatments. It was recommended that phosphogypsum and DCD could be used in composting for the purpose of reducing NH3, CH4 and N2O emissions. Optimal conditions and dose of DCD additive during composting should be determined with different materials and composting systems in further study. PMID:24218845

Luo, Yiming; Li, Guoxue; Luo, Wenhai; Schuchardt, Frank; Jiang, Tao; Xu, Degang

2013-07-01

257

Irradiation of NH3-CH4 mixtures as a model of photochemical processes in the Jovian planets and Titan  

NASA Technical Reports Server (NTRS)

The reactions occurring upon the ultraviolet irradiation of ammonia-methane mixtures are investigated in a simulation of the atmospheric chemistry of the Jovian planets and Titan. Gas mixtures were irradiated at 185 nm at temperatures from 156-298 K, and product and reactant concentrations were determined by means of gas chromatography. The ratio of the moles of CH4 lost per mole of NH3 decomposed is found to be 0.25, with the extent of CH4 decomposition independent of temperature. The absence of a temperature effect suggests that nonthermal atoms, probably hydrogen, initiate CH4 decomposition by the extraction of a hydrogen atom. A decrease in CH4 loss with increasing pressure or the addition of other gases to the photolysis mixture, and the lack of an increase in NH3 photolysis with CH4 pressure support this mechanism. Major reaction products obtained include C2H2, C3H8 or CH3NH2, and C4H10. Considerations of atmospheric concentrations of H2 and He indicate that NH3 photolysis does not contribute to CH4 decomposition on Jupiter, Saturn, Uranus, and Neptune, although it may have had a role in the formation of the Titan atmosphere.

Ferris, J. P.; Morimoto, J. Y.

1981-01-01

258

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.

2014-06-01

259

The photolysis of NH3 in the presence of substituted acetylenes: a possible source of oligomers and HCN on Jupiter.  

PubMed

Photolysis of NH3 in the presence of propyne yields dimethylketazine (4) as the main product along with dimethylketimine, isopropylamine, and propioazine (7). Dimethylketazine and isopropylamine are the principal reaction products when the photolysis is performed at 198 K. The conversion to dimethylketazine is about 35 times greater at 198 K because it is not volatile and condenses on the wall of the photolysis cell out of the UV flux. Photolysis of dimethylketazine at 185 nm yields acetonitrile and small amounts of N-methyldimethylketimine (8). Photolysis of 8 gives acetonitrile. Photolysis of NH3 in the presence of 2-butyne gives the cis and trans isomers of 2-butene as the principal products along with the corresponding azine (9). Photolysis of azine 9 yields acetonitrile and propionitrile. Photolysis of hydrazine in the presence of propyne yields acetonitrile and isopropylamine but no azines were detected as reaction products. Quantum yields and percentage conversion to products are reported. These studies show that acetylenic hydrocarbons formed by the photolysis of methane in the stratosphere of Jupiter may react with radicals formed by NH3 photolysis to give nonvolatile yellow-brown polymers, dialkylazines, alkylnitriles, and eventually HCN. This scenario accounts for the observation of both HCN and chromophores on Jupiter. PMID:11538398

Ferris, J P; Jacobson, R R; Guillemin, J C

1992-01-01

260

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

261

Mixed adenine/guanine quartets with three trans-a2 Pt(II) (a=NH(3) or MeNH(2)) cross-links: linkage and rotational isomerism, base pairing, and loss of NH(3).  

PubMed

Of the numerous ways in which two adenine and two guanines (N9 positions blocked in each) can be cross-linked by three linear metal moieties such as trans-a2 Pt(II) (with a=NH3 or MeNH2 ) to produce open metalated purine quartets with exclusive metal coordination through N1 and N7 sites, one linkage isomer was studied in detail. The isomer trans,trans,trans-[{Pt(NH3 )2 (N7-9-EtA-N1)2 }{Pt(MeNH2 )2 (N7-9-MeGH)}2 ][(ClO4 )6 ]?3H2 O (1) (with 9-EtA=9-ethyladenine and 9-MeGH=9-methylguanine) was crystallized from water and found to adopt a flat Z-shape in the solid state as far as the trinuclear cation is concerned. In the presence of excess 9-MeGH, a meander-like construct, trans,trans,trans-[{Pt(NH3 )2 (N7-9-EtA-N1)2 }{Pt(MeNH2 )2 (N7-9-MeGH)2 }][(ClO4 )6 ]?[(9-MeGH)2 ]?7?H2 O (2) is formed, in which the two extra 9-MeGH nucleobases are hydrogen bonded to the two terminal platinated guanine ligands of 1. Compound?1, and likewise the analogous complex 1?a (with NH3 ligands only), undergo loss of an ammonia ligand and formation of NH4 (+) when dissolved in [D6 ]DMSO. From the analogy between the behavior of 1 and 1?a it is concluded that a NH3 ligand from the central Pt atom is lost. Addition of 1-methylcytosine (1-MeC) to such a DMSO solution reveals coordination of 1-MeC to the central Pt. In an analogous manner, 9-MeGH can coordinate to the central Pt in [D6 ]DMSO. It is proposed that the proton responsible for formation of NH4 (+) is from one of the exocyclic amino groups of the two adenine bases, and furthermore, that this process is accompanied by a conformational change of the cation from Z-form to U-form. DFT calculations confirm the proposed mechanism and shed light on possible pathways of this process. Calculations show that rotational isomerism is not kinetically hindered and that it would preferably occur previous to the displacement of NH3 by DMSO. This displacement is the most energetically costly step, but it is compensated by the proton transfer to NH3 and formation of U(-H(+) ) species, which exhibits an intramolecular hydrogen bond between the deprotonated N6H(-) of one adenine and the N6H2 group of the other adenine. Finally the question is examined, how metal cross-linking patterns in closed metallacyclic quartets containing two adenine and two guanine nucleobases influence the overall shape (square, rectangle, trapezoid) and the planarity of a metalated purine quartet. PMID:24532472

Albert, Francisca M; Rodrguez-Santiago, Luis; Sodupe, Mariona; Mirats, Andrea; Kaitsiotou, Helena; Sanz Miguel, Pablo J; Lippert, Bernhard

2014-03-17

262

Evaluation of biochars by temperature programmed oxidation/mass spectroscopy  

Technology Transfer Automated Retrieval System (TEKTRAN)

Biochar from the thermochemical conversion of biomass was evaluated by Temperature Programmed Oxidation (TPO) coupled with mass spectroscopy. This technique can be used to assess the oxidative reactivity of carbonaceous solids where higher temperature reactivity indicates greater structural order. ...

263

Optical-integrated NH3 sensor design using WO3 thin tllms: influence of gas adsorption and chromic effects  

NASA Astrophysics Data System (ADS)

We propose a new model for the design of optical-integrated (OI) sensor, composed of a surface waveguide covered with a sensitive material (SM) deposited at the surface in the form of thin films. Commonly these last are metallic oxides which becomes highly absorbent in the presence of the gas to be detected. In this way, the optical signal propagating in the waveguide will be attenuated proportionally to the amount of the gas in the surrounding environment. When the sensing is carried out, commonly it is supposed that completely all the volume of the SM increase its absorbance, however this assumption causes that the transmission losses be overestimated; our model, according to the adsorption kinetics of gases, considers the growth of the adsorber layer over the SM as a fourth layer where the optical changes happen. We use this model to design an ammonia NH3 sensor considering tungsten trioxide WO3 as SM. Our model approaches in 102 dB/cm the calculus of the losses, in agreement with that observed in experiments. The refractive index ?'(?) and the absorbance of ??(?) were calculated under inert and NH3 gas conditions, through the analysis of the UV-VIS-NIR transmittance spectra, and the numerical method of Swanepoel, in order to be incorporated in the simulation of the OI proposed structure with a multilayer method software. Experimentally we analyse the influence of thermochromism and photochromism in the response of gasochromism. We tested WO3 samples elaborated by sputtering method with a combination of monoclinic-triclinic crystalline structure, measuring as minimum 200 ppm of NH3 at ? = 1000 nm and at 100 C. The best sample was tested to NH3 detection, using monochromatic sources: ? = 830 nm, ? = 980 nm and ? = 1550 nm; obtaining intensity attenuations of 10%, 16% and 29%, respectively to 5000 ppm of NH3 at 100 C. This is a new proposal that can predicts better the interaction between the material and the optical field in optical sensing structures, in comparison with the conventional model.

Hernndez, Hugo E. Lazcano; Prez, Celia Snchez; Valenzuela, Augusto Garca

2008-04-01

264

Hydrothermal synthesis and structure of a novel solid material with 3-D open-framework: (NH 3CH 2CH 2NH 3)(NH 3CH 2CH 2NH 2) 3Na 3[Co 4Mo 12O 24(OH) 6 (H 2O) 2(HPO 4) 2(PO 4) 6]8H 2O  

NASA Astrophysics Data System (ADS)

A novel cobalt phosphomolybdate: (NH 3CH 2CH 2NH 3)(NH 3CH 2CH 2NH 2) 3Na 3[Co 4Mo 12O 24(OH) 6(H 2O) 2 (HPO 4) 2(PO 4) 6]8H 2O 1, has been hydrothermally synthesized (200C, 5 days, autogenously pressure) and characterized by IR, ESR, XPS, elemental analyses and X-ray crystallography. The crystal data: monoclinic space group C2/ c, a=12.3281(3) , b=21.5729(4) , c=26.0242(5) , ?=99.5401(3), V=6825(2) 3, Z=4, R1=0.0346, w R2=0.0650. The structure of compound 1 is based on Co[Mo 6P 4] 2 units connected together via additional Co 2+ ions to give a new three-dimensional framework. The interconnected void and channels in the cobalt molybdophosphate frameworks are filled with counter cations and water molecules. The magnetic property of 1 exhibits antiferromagnetic coupling interactions.

Sun, Ying-Hua; Cui, Xiao-Bing; Xu, Ji-Qing; Ye, Ling; Li, Yong; Lu, Jing; Ding, Hong; Bie, Hai-Ying

2004-06-01

265

Microsolvation of the ammonia cation in argon: II. IR photodissociation spectra of NH 3+-Ar n ( n=1-6)  

NASA Astrophysics Data System (ADS)

Mid-infrared photodissociation spectra of NH 3+-Ar n ( n=1-6) complexes in the electronic ground state have been recorded in the vicinity of the N-H stretch vibrations of the ammonia cation. The rovibrational analysis of the transitions in the spectrum of the NH 3+-Ar dimer ( n=1) is consistent with a planar, proton-bound equilibrium structure with C 2v symmetry. The three N-H stretching fundamentals occur at ? 1( a1)=3177.41 cm-1, ? 3( a1)=3336.01 cm-1, and ? 3( b2)=3396.260.13 cm-1, and the combination band of ?1 with the intermolecular stretching vibration is observed at ? 1+? s( a1)=3305.52 cm-1. The relatively long lifetime with respect to predissociation ( ?>250 ps) and modest complexation-induced frequency shifts (|?? 1,3|<70 cm-1) of the N-H stretch fundamentals imply weak coupling between the intramolecular and intermolecular degrees of freedom. The linear intermolecular proton bond in the ground vibrational state is characterized by an interatomic H-Ar separation of 2.27 and a harmonic stretching force constant of ?12 N/m. Observed tunneling splittings in the ?3(b 2) band are attributed to hindered internal rotation through potential barriers separating the three equivalent H-bound global minima. By comparison with theoretical data, the frequency of the infrared forbidden ?1 fundamental of free NH 3+ is estimated from the NH 3+-Ar spectrum as 323415 cm-1, the currently most accurate value based upon experimental measurements. The vibrational spectra of the larger NH 3+-Ar n complexes ( n=2-6) display distinct frequency shifts and splittings of the N-H stretching vibrations as a function of cluster size. The spectra are consistent with cluster geometries in which the first three Ar ligands fill a primary solvation subshell by forming equivalent intermolecular proton bonds ( n=1-3) leading to planar structures with either C 2v or D 3h symmetry. The next two Ar ligands fill a second subshell by forming equivalent p-bonds to the two lobes of the 2p z orbital of the central N atom leading to cluster structures with C 3v ( n=4) and D 3h symmetry ( n=5). The first Ar solvation shell around the interior NH 3+ ion is closed at n=5 and the 6th Ar ligand occupies a position in the second solvation shell. The dissociation energies of the H-bonds and p-bonds are estimated from photofragmentation branching ratios as D 0( H)?950150 cm-1 and D 0( p)?800300 cm-1, respectively. In general, the intermolecular H-bonds significantly weaken the intramolecular N-H bonds, whereas the p-bonds slightly strengthen them. Properties of the intermolecular bonds and the cluster growth in NH 3+-Ar n are compared to related AH k+-Ar n cluster systems.

Dopfer, Otto; Solc, Nicola; Olkhov, Rouslan V.; Maier, John P.

2002-10-01

266

Lattice potential energy and standard molar enthalpy in the formation of 1dodecylamine hydrobromide (1-C12H25NH3Br)(s)  

NASA Astrophysics Data System (ADS)

This paper reports that 1-dodecylamine hydrobromide (1-C12H25NH3Br)(s) has been synthesized using the liquid phase reaction method. The lattice potential energy of the compound 1-C12H25NH3Br 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-C12H25NH3Br(s) is measured to be ?cUmo(1-C12H25NH3Br, s) = -(7369.033.28) kJmol-1 by means of an RBC-II precision rotating-bomb combustion calorimeter at T = (298.150.001) K. The standard molar enthalpy of combustion of the compound is derived to be ?cHmo(1-C12H25NH3Br, s) = -(7384.523.28) kJmol-1 from the constant-volume energy of combustion. The standard molar enthalpy of formation of the compound is calculated to be ?fHmo(1-C12H25NH3Br, s)=-(1317.863.67) kJmol-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

267

Temperature Dependence of Internal Motions of Protein Side-Chain NH3(+) Groups: Insight into Energy Barriers for Transient Breakage of Hydrogen Bonds.  

PubMed

Although charged side chains play important roles in protein function, their dynamic properties are not well understood. Nuclear magnetic resonance methods for investigating the dynamics of lysine side-chain NH3(+) groups were established recently. Using this methodology, we have studied the temperature dependence of the internal motions of the lysine side-chain NH3(+) groups that form ion pairs with DNA phosphate groups in the HoxD9 homeodomain-DNA complex. For these NH3(+) groups, we determined order parameters and correlation times for bond rotations and reorientations at 15, 22, 28, and 35 C. The order parameters were found to be virtually constant in this temperature range. In contrast, the bond-rotation correlation times of the NH3(+) groups were found to depend strongly on temperature. On the basis of transition state theory, the energy barriers for NH3(+) rotations were analyzed and compared to those for CH3 rotations. Enthalpies of activation for NH3(+) rotations were found to be significantly higher than those for CH3 rotations, which can be attributed to the requirement of hydrogen bond breakage. However, entropies of activation substantially reduce the overall free energies of activation for NH3(+) rotations to a level comparable to those for CH3 rotations. This entropic reduction in energy barriers may accelerate molecular processes requiring hydrogen bond breakage and play a kinetically important role in protein function. PMID:25489884

Zandarashvili, Levani; Iwahara, Junji

2015-01-20

268

Characterisation of CuMFI catalysts by temperature programmed desorption of NO and temperature programmed reduction. Effect of the zeolite Si\\/Al ratio and copper loading  

Microsoft Academic Search

Copper MFI zeolites with different Si\\/Al ratios and different copper loadings, prepared by ion exchange, were characterised by XRD, H2-TPR and NO TPD. The results indicated the existence of diverse copper species in CuMFI catalysts, such as isolated CU2+, Cu+ ions and CuO species, whose concentrations depends on the catalyst Si\\/Al ratio and copper loading. In underexchanged catalysts (catalysts with

C. Torre-Abreu; M. F. Ribeiro; C. Henriques; G. Delahay

1997-01-01

269

Development and uncertainty analysis of a high-resolution NH3 emissions inventory and its implications with precipitation over the Pearl River Delta region, China  

NASA Astrophysics Data System (ADS)

Detailed NH3 emission inventories are important to understand various atmospheric processes, air quality modeling study, air pollution management, and related environmental and ecological issues. A high-resolution NH3 emission inventory is developed based on the state-of-the-science techniques, the up-to-date information, and the advanced expert knowledge for the Pearl River Delta region, China. To provide model-ready emissions input, this NH3 emissions inventory is spatially allocated to 3 km 3 km grid cells using source-based spatial surrogates with Geographical Information System (GIS) technology. For NH3 emissions, 9 source categories and 45 sub-categories are identified in this region, and detailed spatial and temporal characteristics are investigated. Results show that livestock is by far the most important NH3 emission source that contributes about 61.7% of the total NH3 emissions in this region, followed by nitrogen fertilizer applications (~23.7%) and non-agricultural sources (~14.6%). Uncertainty analysis reveals that the uncertainties associated with different sources vary from source to source and the magnitude of the uncertainty associated with a specific source mainly depends on the degree of accuracy of the emission factors and activity data as well as the technique used to perform the estimate. The validity of the NH3 emissions inventory is justified by the trend analysis of local rainwater compositions, especially pH values, the Ca2+ + NH4+/SO42- + NO3- ratios, and NH4+ concentrations which are directly or indirectly related to NH3 emissions. Based on the analysis, recommendations for additional work to further improve the accuracy of the NH3 emissions inventory are also discussed and proposed.

Zheng, J. Y.; Yin, S. S.; Kang, D. W.; Che, W. W.; Zhong, L. J.

2011-12-01

270

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

271

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

272

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

2010-11-15

273

Ab initio simulation of ammonia monohydrate ,,NH3"H2O... and ammonium hydroxide ,,NH4OH...  

E-print Network

.8(5) kJ mol 1 at absolute zero, and thus estimate the enthalpy of formation, fH (NH4OH,s) 356 kJ mol 1 mol 1 , K0 14.78(62) GPa, K0 2.69(48). We calculate the reaction enthalpy, H(NH4OH,sNH3·H2O,s) 14 cation, and yields an average hydrogen bond enthalpy of 23 kJ mol 1 . © 2001 American Institute

Vocadlo, Lidunka

274

Improved low temperature NH3-SCR performance of FeMnTiOx mixed oxide with CTAB-assisted synthesis.  

PubMed

FeMnTiOx mixed oxide is prepared by the CTAB-assisted co-precipitation method, and the transformation of anatase into rutile is inhibited by CTAB to some extent. The catalyst obtained in the present work shows nearly 100% NO conversion at 100-350 C, more than 80% N2 selectivity at 75-200 C, and excellent H2O durability for the selective catalytic reduction of NO by NH3 with a space velocity of 30?000 mL g(-1) h(-1). PMID:25628073

Wu, Shiguo; Yao, Xiaojiang; Zhang, Lei; Cao, Yuan; Zou, Weixin; Li, Lulu; Ma, Kaili; Tang, Changjin; Gao, Fei; Dong, Lin

2015-02-10

275

Laboratory measurements of the 7.5-9.38-mm absorption of gaseous ammonia (NH3) under simulated Jovian conditions  

NASA Technical Reports Server (NTRS)

An attempt is made to infer the abundance and distribution of ammonia from RF emission measurements more accurately than heretofore, on the basis of the results of laboratory measurements for the mm-wave opacity of gaseous ammonia under simulated Jovian atmosphere conditions. The measurements were conducted at various frequencies in the 32-40 GHz range at 2 atm and 203 K; the atmospheric mixture was 88.34 percent H2, 9.81 percent He, and 1.85 percent NH3. Experimental results are found to be readily modeled by the Gross (1955) line-shape factor, rather than that of Van Vleck and Weisskopf (1945).

Joiner, Joanna; Steffes, Paul G.; Jenkins, Jon M.

1989-01-01

276

Microstructure Evolution of the TaNx (x=0--1) Diffusion Barriers by NH3 Plasma Treatment for the Electroless Copper Deposition  

NASA Astrophysics Data System (ADS)

Microstructure evolution during NH3 plasma treatment of the surface of TaNx barrier films was investigated using transmission electron microscopy (TEM) in order to understand how the plasma treatment improves the palladium activation process for electroless copper deposition. Plan view TEM and selected area diffraction pattern (SADP) results showed that the outermost surface of the crystalline TaNx layer was transformed to the amorphous phase by the NH3 plasma treatment. The surface energy, evaluated by contact angle measurement, of TaNx films was increased by the NH3 plasma treatment. The increase in the surface energy of TaNx films by the plasma treatment seems to increase the nucleation sites for palladium activation. It is thought that the enhancement of the palladium activation process by the NH3 plasma treatment was caused by an increase in the surface energy of TaNx films during the plasma treatment.

Hong, Seok Woo; Lee, Yong Sun; Park, Jong-Wan

2004-10-01

277

Growth of CH3NH3PbI3 cuboids with controlled size for high-efficiency perovskite solar cells.  

PubMed

Perovskite solar cells with submicrometre-thick CH(3)NH(3)PbI(3) or CH(3)NH(3)PbI(3-x)Cl(x) active layers show a power conversion efficiency as high as 15%. However, compared to the best-performing device, the average efficiency was as low as 12%, with a large standard deviation (s.d.). Here, we report perovskite solar cells with an average efficiency exceeding 16% and best efficiency of 17%. This was enabled by the growth of CH(3)NH(3)PbI(3) cuboids with a controlled size via a two-step spin-coating procedure. Spin-coating of a solution of CH(3)NH(3)I with different concentrations follows the spin-coating of PbI(2), and the cuboid size of CH(3)NH(3)PbI(3) is found to strongly depend on the concentration of CH(3)NH(3)I. Light-harvesting efficiency and charge-carrier extraction are significantly affected by the cuboid size. Under simulated one-sun illumination, average efficiencies of 16.4% (s.d. 0.35), 16.3% (s.d. 0.44) and 13.5% (s.d. 0.34) are obtained from solutions of CH(3)NH(3)I with concentrations of 0.038 M, 0.050 M and 0.063 M, respectively. By controlling the size of the cuboids of CH(3)NH(3)PbI(3) during their growth, we achieved the best efficiency of 17.01% with a photocurrent density of 21.64 mA cm(-2), open-circuit photovoltage of 1.056 V and fill factor of 0.741. PMID:25173829

Im, Jeong-Hyeok; Jang, In-Hyuk; Pellet, Norman; Grtzel, Michael; Park, Nam-Gyu

2014-11-01

278

Growth of CH3NH3PbI3 cuboids with controlled size for high-efficiency perovskite solar cells  

NASA Astrophysics Data System (ADS)

Perovskite solar cells with submicrometre-thick CH3NH3PbI3 or CH3NH3PbI3xClx active layers show a power conversion efficiency as high as 15%. However, compared to the best-performing device, the average efficiency was as low as 12%, with a large standard deviation (s.d.). Here, we report perovskite solar cells with an average efficiency exceeding 16% and best efficiency of 17%. This was enabled by the growth of CH3NH3PbI3 cuboids with a controlled size via a two-step spin-coating procedure. Spin-coating of a solution of CH3NH3I with different concentrations follows the spin-coating of PbI2, and the cuboid size of CH3NH3PbI3 is found to strongly depend on the concentration of CH3NH3I. Light-harvesting efficiency and charge-carrier extraction are significantly affected by the cuboid size. Under simulated one-sun illumination, average efficiencies of 16.4% (s.d.??0.35), 16.3% (s.d.??0.44) and 13.5% (s.d.??0.34) are obtained from solutions of CH3NH3I with concentrations of 0.038?M, 0.050?M and 0.063 M, respectively. By controlling the size of the cuboids of CH3NH3PbI3 during their growth, we achieved the best efficiency of 17.01% with a photocurrent density of 21.64?mA?cm2, open-circuit photovoltage of 1.056?V and fill factor of 0.741.

Im, Jeong-Hyeok; Jang, In-Hyuk; Pellet, Norman; Grtzel, Michael; Park, Nam-Gyu

2014-11-01

279

Development and uncertainty analysis of a high-resolution NH3 emissions inventory and its implications with precipitation over the Pearl River Delta region, China  

NASA Astrophysics Data System (ADS)

Detailed NH3 emission inventories are important to understand various atmospheric processes, air quality modeling studies, air pollution management, and related environmental and ecological issues. A high-resolution NH3 emission inventory was developed based on state-of-the-science techniques, up-to-date information, and advanced expert knowledge for the Pearl River Delta region, China. To provide model-ready emissions input, this NH3 emissions inventory was spatially allocated to 3 km 3 km grid cells using source-based spatial surrogates with geographical information system (GIS) technology. For NH3 emissions, 9 source categories and 45 subcategories were identified in this region, and detailed spatial and temporal characteristics were investigated. Results show that livestock is by far the most important NH3 emission source by contributing about 61.7% of the total NH3 emissions in this region, followed by nitrogen fertilizer applications (~23.7%) and non-agricultural sources (~14.6%). Uncertainty analysis reveals that the uncertainties associated with different sources vary from source to source and the magnitude of the uncertainty associated with a specific source mainly depends on the degree of accuracy of the emission factors and activity data as well as the technique used to perform the estimate. Further studies should give priority to the hog, broiler, goose subsectors of the livestock source and N fertilizer application source in order to reduce uncertainties of ammonia emission estimates in this region. The validity of the NH3 emissions inventory is justified by the trend analysis of local precipitation compositions, such as pH values, the Ca2++NH4+/SO42-+ NO3- ratios, and NH4+ concentrations which are directly or indirectly related to NH3 emissions.

Zheng, J. Y.; Yin, S. S.; Kang, D. W.; Che, W. W.; Zhong, L. J.

2012-08-01

280

Electrodeposition of PbO and its in situ conversion to CH3NH3PbI3 for mesoscopic perovskite solar cells.  

PubMed

The perovskite CH3NH3PbI3 was prepared on a mesoscopic TiO2 film, starting from electrodepositing PbO, to iodination to PbI2, and then interdiffusion reaction with CH3NH3I. The as-prepared film was used as a light absorber for the perovskite solar cells, exhibiting a high PCE of 12.5% under standard AM 1.5 conditions. PMID:25493293

Cui, Xue-Ping; Jiang, Ke-Jian; Huang, Jin-Hua; Zhou, Xue-Qin; Su, Mei-Ju; Li, Shao-Gang; Zhang, Qian-Qian; Yang, Lian-Min; Song, Yan-Lin

2015-01-01

281

The formation of isocyanic acid during the reaction of NH 3 with NO and excess CO over silica-supported platinum, palladium, and rhodium  

Microsoft Academic Search

The reaction between NH3 and NO in excess CO over silica-supported platinum, palladium, and rhodium has been investigated for temperatures from 100 to 450?C. As found previously for the corresponding reactions of H2\\/NO\\/CO mixtures, isocyanic acid (HNCO) is produced with each catalyst. With Pd\\/SiO2, the peak yield when NH3 is used is 46% based on the total nitrogen converted and

Noel W. Cant; Dean C. Chambers; Irene O. Y. Liu

2005-01-01

282

NH3 adsorption on the Lewis and Bronsted acid sites of MoO3 (0 1 0) surface: A cluster DFT study  

NASA Astrophysics Data System (ADS)

The adsorption of NH3 on the Lewis and Bronsted acid sites of MoO3 (0 1 0) surface has been investigated based on the density functional theory (DFT) method using the clusters models. The calculated results indicate that NH3 could strongly adsorb on both the Lewis and Bronsted acid sites in the form of NH3 species and NH4+ respectively, whereas the adsorption on the Lewis acid site is found to be more favorable energetically than that on the Bronsted acid site. For the Lewis acid site Mulliken population analysis shows a donation of lone pairs from NH3 to the surface and activation of N-H bond. The overlaps of N-s, N-p and Mo-d orbitals suggest the strong interaction between N and Mo atoms. For the Bronsted acid site N-H bond is also activated by the formation of NH4+ species. The hybridizations between H and O atoms as well as N and H atoms are the major reasons for strong chemical adsorption of NH3 and the existence of NH4+ species, which partly attributed to the presence of N-H O hydrogen bonds. Furthermore, the formation of a second Lewis acid site at adjacent or diagonal site results in slight changes of adsorption stability, structural changes and charge redistributions, suggesting its small influence on NH3 adsorption.

Yan, Zhifeng; Fan, Junyan; Zuo, Zhijun; Li, Zhe; Zhang, Jinshan

2014-01-01

283

Efficient Hybrid Mesoscopic Solar Cells with Morphology-Controlled CH3NH3PbI3-xClx Derived from Two-Step Spin Coating Method.  

PubMed

A morphology-controlled CH3NH3PbI3-xClx film is synthesized via two-step solution deposition by spin-coating a mixture solution of CH3NH3Cl and CH3NH3I onto the TiO2/PbI2 film for the first time. It is revealed that the existence of CH3NH3Cl is supposed to result in a preferential growth along the [110] direction of perovskite, which can improve both the crystallinity and surface coverage of perovskite and reduce the pinholes. Furthermore, the formation process of CH3NH3PbI3-xClx perovskite is explored, in which intermediates containing chlorine are suggested to exist. 13.12% of power conversion efficiency has been achieved for the mesoscopic cell, higher than 12.08% of power conversion efficiency of the devices fabricated without CH3NH3Cl via the same process. The improvement mainly lies in the increasing open-circuit photovoltage which is ascribed to the reduction of reverse saturation current density. PMID:25587643

Xu, Yuzhuan; Zhu, Lifeng; Shi, Jiangjian; Lv, Songtao; Xu, Xin; Xiao, Junyan; Dong, Juan; Wu, Huijue; Luo, Yanhong; Li, Dongmei; Meng, Qingbo

2015-02-01

284

Strong covalency-induced recombination centers in perovskite solar cell material CH3NH3PbI3.  

PubMed

Inorganic-organic hybrid perovskites are a new family of solar cell materials, which have recently been used to make solar cells with efficiency approaching 20%. Here, we report the unique defect chemistry of the prototype material, CH3NH3PbI3, based on first-principles calculation. We found that both the Pb cations and I anions in this material exhibit strong covalency as characterized by the formation of Pb dimers and I trimers with strong covalent bonds at some of the intrinsic defects. The Pb dimers and I trimers are only stabilized in a particular charge state with significantly lowered energy, which leads to deep charge-state transition levels within the band gap, in contradiction to a recent proposal that this system has only shallow intrinsic defects. Our results show that, in order to prevent the deep-level defects from being effective recombination centers, the equilibrium carrier concentrations should be controlled so that the Fermi energy is about 0.3 eV away from the band edges. Beyond this range, according to a Shockley-Read-Hall analysis, the non-equilibrium carrier lifetime will be strongly affected by the concentration of I vacancies and the anti-site defects with I occupying a CH3NH3 site. PMID:25243595

Agiorgousis, Michael L; Sun, Yi-Yang; Zeng, Hao; Zhang, Shengbai

2014-10-15

285

Anharmonic calculation of the structure, vibrational frequencies and intensities of the NH3trans-HONO complex.  

PubMed

The equilibrium geometry of the NH3trans-HONO complex and the harmonic vibrational frequencies and intensities are calculated in the MP2/aug-cc-pVTZ approximation with the basis set superposition error taken into account. Effects of anharmonic interactions on spectroscopic parameters are studied by solving vibrational Schrdinger equations in 1-4 dimensions using the variational method. Anharmonic vibrational equations are formulated in the space of normal coordinates of the complex. Detailed analysis is performed for the H-bond stretching vibration and internal vibrations of the trans-HONO isomer in the complex. The intermode anharmonicity and anharmonic coupling between two, three, and four vibrational modes are studied on the basis of correct ab initio potential energy surfaces calculated in the above approximation. The combinations of normal modes of the complex most strongly coupled to one another are examined. The calculated frequencies and intensities of vibrational bands are compared with the experimental data on the NH3trans-HONO complex in an argon matrix and results of earlier calculations of monomeric HONO. In this calculation the strong resonance between the first excited state of the OH stretching vibration and the doubly excited state of the NOH bending vibration of trans-HONO isomer in the complex is thoroughly studied by solving vibrational equations in two and four dimensions. PMID:23944642

Bulychev, Valentin P; Buturlimova, Marina V; Tokhadze, Konstantin G

2013-09-19

286

Uranus and Neptune structure models with ab initio EOS data for CH4, NH3, and H2O  

NASA Astrophysics Data System (ADS)

Uranus and Neptune are supposed to be rich in ices in their deep interiors as their mean density closely resembles that of liquid water. Moreover, highly super-solar abundances of CH4 and CO, indicative of internal water, have been observed in their atmospheres. We here compare ab initio equations of state for CH4, NH3, and H2O and apply them to compute ice-rich, adiabatic internal structure models of Uranus and Neptune. The explicit consideration of the light ices CH4 and NH3 allows us to put tighter constraints on the minimum H/He abundance in their deep interior, which was found to be non-zero in all previous Uranus and in most of the Neptune models that were based on water as a proxy for ices. In particular, we investigate if hydrogen in the deep interior can solely be a result of assumed Carbon sedimentation (diamond rain), as an alternative scenario to the early accretion of H/He containing material during the formation of the planets. We conclude by discussing the deep internal H/He abundance in light of rock-rich and warmer-than-adiabatic interiors, which has been suggested to explain Uranus' low intrinsic luminosity. Our models serve to better understand the formation and bulk composition of Neptune-sized planets.

Nettelmann, Nadine; Fortney, Jonathan; Hamel, Sebastien; Bethkenhagen, Mandy; Redmer, Ronald

2014-05-01

287

Electrical properties and conduction mechanism of [C2H5NH3]2CuCl4 compound  

NASA Astrophysics Data System (ADS)

The [(C2H5)NH3]2CuCl4 compound was prepared and characterized by several technique: the X-ray powder diffraction confirms the purity of the synthetized compound, the differential scanning calorimetric show several phase transitions at 236 K, 330 K, 357 K and 371 K, the dialectical properties confirms the ferroelectric-paraelectric phase transition at 238 K, which is reported by V. Kapustianyk et al. (2007) [1]. The two semi-circles observed in the complex impedance identify the presence of the grain interior and grain boundary contributions to the electrical response in this material. The equivalent circuit is modeled by a combination series of two parallel RP-CPE circuits. The temperature dependence of the alternative current conductivity (?g) and direct current conductivity (?dc) confirm the observed transitions in the calorimetric study. The (AC) electrical conduction in [(C2H5)NH3]2CuCl4 was studied by two processes that can be attributed to a hopping transport mechanism: the non-overlapping small polaron tunneling (NSPT) model in phase III and the correlated barrier hopping (CBH) model in phases I, II, IV, V and VI.

Mohamed, C. Ben; Karoui, K.; Jomni, F.; Guidara, K.; Rhaiem, A. Ben

2015-02-01

288

Mechanism of the Gaseous Hydrolysis Reaction of SO2: Effects of NH3 versus H2O.  

PubMed

Effects of ammonia and water molecules on the hydrolysis of sulfur dioxide are investigated by theoretical calculations of two series of the molecular clusters SO2-(H2O)n (n = 1-5) and SO2-(H2O)n-NH3 (n = 1-3). The reaction in pure water clusters is thermodynamically unfavorable. The additional water in the clusters reduces the energy barrier for the reaction, and the effect of each water decreases with the increasing number of water molecules in the clusters. There is a considerable energy barrier for reaction in SO2-(H2O)5, 5.69 kcal/mol. With ammonia included in the cluster, SO2-(H2O)n-NH3, the energy barrier is dramatically reduced, to 1.89 kcal/mol with n = 3, and the corresponding product of hydrated ammonium bisulfate NH4HSO3-(H2O)2 is also stabilized thermodynamically. The present study shows that ammonia has larger kinetic and thermodynamic effects than water in promoting the hydrolysis reaction of SO2 in small clusters favorable in the atmosphere. PMID:25495573

Liu, Jingjing; Fang, Sheng; Liu, Wei; Wang, Meiyan; Tao, Fu-Ming; Liu, Jing-Yao

2015-01-01

289

Computational study of Al- or P-doped single-walled carbon nanotubes as NH3 and NO2 sensors  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) calculations were carried out to analyze the electronic and structural properties of pristine and aluminum or phosphorus doped (8,0) single walled carbon nanotube (SWCNT) as a sensor for the detection of nitrogen dioxide (NO2) and ammonia (NH3). The binding energies, equilibrium gas-nanotube distances, the amounts of charge transfer and molecular orbital schemes as well as the density of states have been calculated and used to interpret the mechanism of gas adsorption on the surface of nanotubes. In agreement with the experimental data, our results show considerable binding energy and energy gap alteration due to the adsorption of NO2 on pristine SWCNT. The results reveal that the doping of both Al and P atoms increase the capability of the nanotube for the adsorption of NO2, and the effect is more significant for the Al-doped nanotube. The Al-doped nanotube can also be considered as a good sensor for NH3 due to its high binding energy, considerable amount of charge transfer and energy band gap alteration.

Azizi, Khaled; Karimpanah, Mohammad

2013-11-01

290

NH3 assisted photoreduction and N-doping of graphene oxide for high performance electrode materials in supercapacitors.  

PubMed

Nitrogen-doped graphene was synthesized by simple photoreduction of graphene oxide (GO) deposited on nickel foam under NH3 atmosphere. The combination of photoreduction and NH3 not only reduces the GO in a shorter time but also induces nitrogen doping easily. The nitrogen doped content of N-rGO@NF reaches a high of 5.99 at% with 15 min of irradiation. The nitrogen-doped graphene deposited on Ni foam (N-rGO@NF) can be directly used as an electrode for supercapacitors, without any conductive agents and polymer binders. In the electrochemical measurement, N-rGO@NF displays remarkable electrochemical performance. In particular, the N-rGO@NF irradiated for 45 min at a high current density of 92.3 A g(-1) retained about 77% (190.4 F g(-1)) of its initial specific capacitance (247.1 F g(-1) at 0.31 A g(-1)). Furthermore, the stable voltage window could be extended to 2.0 and 1.5 V by using Li2SO4 and a mixed Li2SO4/KOH electrolyte, and the maximum energy density was high up to 32.6 and 21.2 Wh kg(-1), respectively. The results show that compared to Li2SO4, a mixed electrolyte (Li2SO4/KOH) more efficiently balances the relationship between the high energy densities and high power densities. PMID:25553955

Huang, Haifu; Luo, Guangsheng; Xu, Lianqiang; Lei, Chenglong; Tang, Yanmei; Tang, Shaolong; Du, Youwei

2015-01-22

291

[Emission of CH4, N2O and NH3 from vegetable field applied with animal manure composts].  

PubMed

Greenhouse gas (GHG) emission from vegetable land is of great concern recently because agriculture land is one of the major sources contributing to global GHG emission. In this study, an experiment of Lactuca sativa L. land applied with different animal manure composts was carried out in a greenhouse vegetable land located in the surburb of Beijing to monitor the emission of GHG (CH4 and N2O) and ammonia in situ, and to analyze the affecting factors of GHG and ammonia emission. Results showed that the emission factors (EFs) of CH4 from Treatment NRM, RM and CF were 0.2%, 0.027% and 0.004%, respectively,the EFs of N2O from these three treatments were 0.18%, 0.63% and 0.74%, respectively, and the EFs of ammonia were 2.00%, 3.98% and 2.53%, respectively. CH4 emission flux was significantly affected by soil temperature and humidity, while N2O emission flux was related to soil temperature, surface temperature and humidity. The emission fluxes of CH4, N2O and NH3 were significantly affected by soil moisture, but there was little relation between CH4, N2O and NH3 emissions and the ambient temperature in the greenhouse. PMID:24881375

Wan, He-Feng; Zhao, Chen-Yang; Zhong, Jia; Ge, Zhen; Wei, Yuan-Song; Zheng, Jia-Xi; Wu, Yu-Long; Han, Sheng-Hui; Zheng, Bo-Fu; Li, Hong-Mei

2014-03-01

292

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 irons 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. PMID:20571574

Lee, Yunho; Mankad, Neal P.

2010-01-01

293

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

294

Detection of interstellar NH3 in the far-infrared - Warm and dense gas in Orion-KL  

NASA Technical Reports Server (NTRS)

Results of an investigation are presented which show the detection of the (J,K) = a(4,3)-s(3,3) rotation-inversion transition of ammonia at 124.6 microns toward the center of the Orion-KL region. The line is found to be in emission and has a FWHM greater than or equal to 30 km/s, while the far-IR ammonia line emission probably comes mainly from the 'hot core', a compact region of warm, very dense gas previously identified by the radio inversion lines of NH3. The a(4,3)-s(3,3) line is very optically thick and it is determined that radiative excitation of the (4,3) NH3 level by far-IR emission from dust within the source can be ruled out. It is concluded that the (4,3) level is probably collisionally excited and the gas in the hot core region is warmer than the dust. Densities of approximately 10 to the 7th/cu cm are high enough to explain the observations, while shock heating by the mass outflow from IRc2 may account for the high gas temperatures in the hot core region.

Townes, C. H.; Genzel, R.; Watson, D. M.; Storey, J. W. V.

1983-01-01

295

Low-temperature SCR of NO with NH3 over activated semi-coke composite-supported rare earth oxides  

NASA Astrophysics Data System (ADS)

The catalysts with different rare earth oxides (La, Ce, Pr and Nd) loaded onto activated semi-coke (ASC) via hydrothermal method are prepared for the selective catalytic reduction (SCR) of NO with NH3 at low temperature (150-300 C). It is evidenced that CeO2 loaded catalysts present the best performance, and the optimum loading amount of CeO2 is about 10 wt%. Composite catalysts by doping La, Pr and Nd into CeO2 are prepared to obtain further improved catalytic properties. The SCR mechanism is investigated through various characterizations, including XRD, Raman, XPS and FT-IR, the results of which indicate that the oxygen defect plays an important role in SCR process and the doped rare earth elements effectively serve as promoters to increase the concentration of oxygen vacancies. It is also found that the oxygen vacancies in high concentration are favored for the adsorption of O2 and further oxidation of NO, which facilitates a rapid progressing of the following reduction reactions. The SCR process of NO with NH3 at low temperature over the catalysts of ASC composite-supported rare earth oxides mainly follows the Langmuir-Hinshlwood mechanism.

Wang, Jinping; Yan, Zheng; Liu, Lili; Zhang, Yingyi; Zhang, Zuotai; Wang, Xidong

2014-08-01

296

NH3 assisted photoreduction and N-doping of graphene oxide for high performance electrode materials in supercapacitors  

NASA Astrophysics Data System (ADS)

Nitrogen-doped graphene was synthesized by simple photoreduction of graphene oxide (GO) deposited on nickel foam under NH3 atmosphere. The combination of photoreduction and NH3 not only reduces the GO in a shorter time but also induces nitrogen doping easily. The nitrogen doped content of N-rGO@NF reaches a high of 5.99 at% with 15 min of irradiation. The nitrogen-doped graphene deposited on Ni foam (N-rGO@NF) can be directly used as an electrode for supercapacitors, without any conductive agents and polymer binders. In the electrochemical measurement, N-rGO@NF displays remarkable electrochemical performance. In particular, the N-rGO@NF irradiated for 45 min at a high current density of 92.3 A g-1 retained about 77% (190.4 F g-1) of its initial specific capacitance (247.1 F g-1 at 0.31 A g-1). Furthermore, the stable voltage window could be extended to 2.0 and 1.5 V by using Li2SO4 and a mixed Li2SO4/KOH electrolyte, and the maximum energy density was high up to 32.6 and 21.2 Wh kg-1, respectively. The results show that compared to Li2SO4, a mixed electrolyte (Li2SO4/KOH) more efficiently balances the relationship between the high energy densities and high power densities.Nitrogen-doped graphene was synthesized by simple photoreduction of graphene oxide (GO) deposited on nickel foam under NH3 atmosphere. The combination of photoreduction and NH3 not only reduces the GO in a shorter time but also induces nitrogen doping easily. The nitrogen doped content of N-rGO@NF reaches a high of 5.99 at% with 15 min of irradiation. The nitrogen-doped graphene deposited on Ni foam (N-rGO@NF) can be directly used as an electrode for supercapacitors, without any conductive agents and polymer binders. In the electrochemical measurement, N-rGO@NF displays remarkable electrochemical performance. In particular, the N-rGO@NF irradiated for 45 min at a high current density of 92.3 A g-1 retained about 77% (190.4 F g-1) of its initial specific capacitance (247.1 F g-1 at 0.31 A g-1). Furthermore, the stable voltage window could be extended to 2.0 and 1.5 V by using Li2SO4 and a mixed Li2SO4/KOH electrolyte, and the maximum energy density was high up to 32.6 and 21.2 Wh kg-1, respectively. The results show that compared to Li2SO4, a mixed electrolyte (Li2SO4/KOH) more efficiently balances the relationship between the high energy densities and high power densities. Electronic supplementary information (ESI) available: Digital images of nickel foam, GO deposited in nickel foam, N-rGO@NF, and N-rGO@NF electrodes (1.0 1.0 cm); Digital images: (1) N-rGO@NF sheet was put into 1 M FeCl3 at room temperature dissolve the Ni metal and (2) a whole N-rGO sheet without Ni foam support after nickel etching; image of film with fragile features after being irradiated by a high-pressure Hg lamp (500 W) in Ar and NH3 atmosphere. See DOI: 10.1039/c4nr05776g

Huang, Haifu; Luo, Guangsheng; Xu, Lianqiang; Lei, Chenglong; Tang, Yanmei; Tang, Shaolong; Du, Youwei

2015-01-01

297

Fast temperature programmed sensing for micro-hotplate gas sensors  

Microsoft Academic Search

We describe an operating mode of a gas sensor that greatly enhances the capability of the device to determine the composition of a sensed gas. The device consists of a micromachined hotplate with integrated heater, heat distribution plate, electrical contact pads, and sensing film. The temperature programmed sensing (TPS) technique uses millisecond timescale temperature changes to modify the rates for

R. E. Cavicchi; J. S. Suehle; K. G. Kreider; M. Gaitan; P. Chaparala

1995-01-01

298

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

299

Adsorption, Desorption, and Diffusion of Nitrogen in a Model Nanoporous Material: I. Surface Limited Desorption Kinetics in Amorphous Solid Water  

SciTech Connect

The adsorption and desorption kinetics of N2 on porous amorphous solid water (ASW) films were studied using molecular beam techniques, temperature programmed desorption (TPD), and reflection-absorption infrared spectroscopy (RAIRS). The ASW films were grown on Pt(111) at 23 K by ballistic deposition from a collimated H2O beam at various incident angles to control the film porosity. The experimental results show that the N2 condensation coefficient is essentially unity until near saturation, independent of the ASW film thickness. This means that N2 transport within the porous films is rapid. The TPD results show that the desorption of a fixed dose of N2 shifts to higher temperature with ASW film thickness. Kinetic analysis of the TPD spectra shows that a film thickness rescaling of the coverage dependent activation energy curve results in a single master curve. Simulation of the TPD spectra using this master curve results in a quantitative fit to the experiments over a wide range of ASW thicknesses (up to 1000 layers, ~0.5 mm). The success of the rescaling model indicates that N2 transport within the porous film is rapid enough to maintain a uniform distribution throughout the film on a time scale faster than desorption.

Zubkov, Tykhon; Smith, R. Scott; Engstrom, Todd R.; Kay, Bruce D.

2007-11-14

300

Vibrational signatures of hydrogen bonding in the protonated ammonia clusters NH4(+)(NH3)(1-4).  

PubMed

The gas phase vibrational spectroscopy of the protonated ammonia dimer N(2)H(7)(+), a prototypical system for strong hydrogen bonding, is studied in the spectral region from 330 to 1650 cm(-1) by combining infrared multiple photon dissociation and multidimensional quantum mechanical simulations. The fundamental transition of the antisymmetric proton stretching vibration is observed at 374 cm(-1) and assigned on the basis of a six-dimensional model Hamiltonian, which predicts this transition at 471 cm(-1). Photodissociation spectra of the larger protonated ammonia clusters NH(4)(+)(NH(3))(n) with n=2-4 are also reported for the range from 1050 to 1575 cm(-1). The main absorption features can be assigned within the harmonic approximation, supporting earlier evidence that hydrogen bonding in these clusters is considerably weaker than for n=1. PMID:19071911

Yang, Y; Khn, O; Santambrogio, G; Goebbert, D J; Asmis, K R

2008-12-14

301

Vibrational signatures of hydrogen bonding in the protonated ammonia clusters NH4+(NH3)1-4  

NASA Astrophysics Data System (ADS)

The gas phase vibrational spectroscopy of the protonated ammonia dimer N2H7+, a prototypical system for strong hydrogen bonding, is studied in the spectral region from 330 to 1650 cm-1 by combining infrared multiple photon dissociation and multidimensional quantum mechanical simulations. The fundamental transition of the antisymmetric proton stretching vibration is observed at 374 cm-1 and assigned on the basis of a six-dimensional model Hamiltonian, which predicts this transition at 471 cm-1. Photodissociation spectra of the larger protonated ammonia clusters NH4+(NH3)n with n =2-4 are also reported for the range from 1050 to 1575 cm-1. The main absorption features can be assigned within the harmonic approximation, supporting earlier evidence that hydrogen bonding in these clusters is considerably weaker than for n =1.

Yang, Y.; Khn, O.; Santambrogio, G.; Goebbert, D. J.; Asmis, K. R.

2008-12-01

302

Two mixed-NH3/amine platinum (II) anticancer complexes featuring a dichloroacetate moiety in the leaving group  

NASA Astrophysics Data System (ADS)

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 1H, 13C-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.

Liu, Weiping; Su, Jia; Jiang, Jing; Li, Xingyao; Ye, Qingsong; Zhou, Hongyu; Chen, Jialin; Li, Yan

2013-08-01

303

Toward a chemiresistive ammonia (NH3) gas sensor based on viral-templated gold nanoparticles embedded in polypyrrole nanowires  

NASA Astrophysics Data System (ADS)

Preliminary studies toward the assembly of a gold-polypyrrole (PPy) peapod-like chemiresistive ammonia (NH3) gas sensors are presented. The proposed synthesis process will use electropolymerization to embed gold nanoparticles in polypyrrole nanowires. Viral-templating of gold nanoparticles and PPy electrodeposition via cyclic voltammetry are the focus of this investigation. A gold-binding M13 bacteriophage was used as a bio-template to assemble continuous chains of gold nanoparticles on interdigitated Pt working electrodes. The dimensions of the resulting nanowire-like structures were examined and the electrical resistance measured. PPy films were electropolymerized using an interdigitated planar, Pt electrode integrated counter and reference electrode. Morphological characterization of the polymer films was completed.

Yan, Yiran; Zhang, Miluo; Su, Heng Chia; Myung, Nosang V.; Haberer, Elaine D.

2014-08-01

304

Photolysis products of CO, NH3 aND H2O and their significance to reactions on interstellar grains  

NASA Technical Reports Server (NTRS)

With the increase in evidence that interstellar grains are the basic building blocks of comets and with the realization that comet collisions with the earth have probably occured at a much higher frequency than earlier assumed it may be presumed that interstellar dust chemistry played an important role in the early chemistry of the earth. As a part of the study of the photochemical processes taking place on interstellar grains the photolysis of mixtures of CO, NH3 and H2O was performed at 10 K, 77K and 298K. The reaction products were determined by GC/MS and HPLC analysis to be lactic acid, glycolic acid, hydroxyacetamide, urea, biuret, oxamic acid, oxamide, glyceric acid and glyceramide. Ethylene glycol and glycerol were also detected but is is not clear at present whether these are true photoproducts or contaminants. The mechanism of formation of these molecules are discussed as well as their possible significance to the origins of life.

Ferris, J. P.

1986-01-01

305

A theoretical investigation of gaseous absorption by water droplets from SO2-HNO3-NH3-CO2-HCl mixtures  

NASA Technical Reports Server (NTRS)

A physical-chemical model is developed and used to investigate gaseous absorption by water droplets from trace gas mixtures. The model is an extension of that of Carmichael and Peters (1979) and includes the simultaneous absorption of SO2, NH3, HNO3, CO2, and HCl. Gas phase depletion is also considered. Presented results demonstrate that the absorption behavior of raindrops is strongly dependent on drop size, fall distance, trace gas concentrations, and the chemical and physical properties of the constituents of the mixture. In addition, when gas phase depletion is considered, the absorption rates and equilibrium values are also dependent on the precipitation rate itself. Also, the trace constituents liquid phase concentrations may be a factor of six or more lower when gas depletion is considered then when the depletion is ignored. However, the hydrogen ion concentration may be insensitive to the gas phase depletion.

Adewuyi, Y. G.; Carmichael, G. R.

1982-01-01

306

Electron-Temperature Dependence of the Recombination of NH4(+)((NH3)(sub n) Ions with Electrons  

NASA Technical Reports Server (NTRS)

The two-body recombination of NH4(+)(NH3)(sub 2,3) cluster-ions with electrons has been studied in an afterglow experiment in which the electron temperature T, was elevated by radio-frequency heating from 300 K up to 900 K. The recombination coefficients for the n = 2 and n = 3 cluster ions were found to be equal, alpha(sub 2, sup(2)) = alpha(sub 3, sup(2)) = (4.8 +/- 0.5) x 10(exp - 6)cu cm/s, and to vary with electron temperature as T(sub c, sup -0.65) rather than to be nearly temperature-independent as had been inferred from measurements in microwave-heated plasmas.

Skrzypkowski, M. P.; Johnson, R.

1997-01-01

307

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

308

Desorption atmospheric pressure photoionization.  

PubMed

An ambient ionization technique for mass spectrometry, desorption atmospheric pressure photoionization (DAPPI), is presented, and its application to the rapid analysis of compounds of various polarities on surfaces is demonstrated. The DAPPI technique relies on a heated nebulizer microchip delivering a heated jet of vaporized solvent, e.g., toluene, and a photoionization lamp emitting 10-eV photons. The solvent jet is directed toward sample spots on a surface, causing the desorption of analytes from the surface. The photons emitted by the lamp ionize the analytes, which are then directed into the mass spectrometer. The limits of detection obtained with DAPPI were in the range of 56-670 fmol. Also, the direct analysis of pharmaceuticals from a tablet surface was successfully demonstrated. A comparison of the performance of DAPPI with that of the popular desorption electrospray ionization method was done with four standard compounds. DAPPI was shown to be equally or more sensitive especially in the case of less polar analytes. PMID:17803282

Haapala, Markus; Pl, Jaroslav; Saarela, Ville; Arvola, Ville; Kotiaho, Tapio; Ketola, Raimo A; Franssila, Sami; Kauppila, Tiina J; Kostiainen, Risto

2007-10-15

309

Macroporous WO3 thin films active in NH3 sensing: role of the hosted Cr isolated centers and Pt nanoclusters.  

PubMed

Macroporous WO(3) films with inverted opal structure were synthesized by one-step procedure, which involves the self-assembly of the spherical templating agents and the simultaneous sol-gel condensation of the semiconductor alkoxide precursor. Transition metal doping, aimed to enhance the WO(3) electrical response, was carried out by including Cr(III) and Pt(IV) centers in the oxide matrix. It turned out that Cr remains as homogeneously dispersed Cr(III) centers inside the WO(3) host, while Pt undergoes reduction and aggregation to form nanoclusters located at the oxide surface. Upon interaction with NH(3), the electrical conductivity of transition metal doped-WO(3) increases, especially in the presence of Pt dopant, resulting in outstanding sensing properties (S = 110 15 at T = 225 C and [NH(3)] = 74 ppm). A mechanism was suggested to explain the excellent electrical response of Pt-doped films with respect to the Cr-doped ones. This associates the easy chemisorption of ammonia on the WO(3) nanocrystals, promoted by the inverted opal structure, with the catalytic action exerted by the surface Pt nanoclusters on the N-H bond dissociation. The overall results indicate that in Pt-doped WO(3) films the effects of the macroporosity positively combine with the electrical sensitization promoted by the metal nanoclusters, thus providing very lightweight materials which display high functionality even at relatively low temperatures. We expect that this synergistic effect can be exploited to realize other functional hierarchical metal oxide structures to be used as gas sensors or catalysts. PMID:21425840

D'Arienzo, Massimiliano; Armelao, Lidia; Mari, Claudio Maria; Polizzi, Stefano; Ruffo, Riccardo; Scotti, Roberto; Morazzoni, Franca

2011-04-13

310

Quantum chemical study and infrared spectroscopy of hydrogen-bonded CHCl3-NH3 in the gas phase  

NASA Astrophysics Data System (ADS)

Molecular association of chloroform with ammonia is studied by high-level quantum chemical calculations including correlated MP2 and CCSD(T) calculations with basis sets up to6-311++G(d,p) and counterpoise corrected energies, geometries, and frequencies. The calculations predict an eclipsed hydrogen-bonded complex of C3v symmetry (?E0=-15.07kJmol-1) with 225.4pm intermolecular CH⋯N distance. Intermolecular interactions are analysed by Kitaura-Morokuma [Int. J. Quantum Chem. 10, 325 (1976)] interaction energy decomposition. Compared to the monomer, the C-H bond is elongated, and the CH-stretching fundamental shifts to lower wave numbers and has a marked 340-fold increase of its intensity. Based on these predictions, the complex is observed by infrared spectroscopy in the gas phase at room temperature. A subtraction procedure isolates its spectrum, and a dilution series confirms the presence of a 1:1 complex. The CHCl3⋯NH3 complex has an experimental -17.5cm-1 shift of its CH-stretching vibration, and CDCl3⋯NH3 a -12.5cm-1 shift of the CD-stretching vibration. After a deperturbation of the CH-stretching/bending mode Fermi resonance system, this indicates a "redshifting" or more appropriately, a "C-H elongating" hydrogen bond in agreement with the ab initio calculations. An estimate of the complex concentration gives the equilibrium constant Kp=0.024 (p?=105Pa ) at 295K for the dimerization, providing one of the few examples where a hydrogen-bonded gas phase complex at room temperature could be quantitatively studied by infrared spectroscopy.

Hippler, Michael

2007-08-01

311

Rh proteins vs Amt proteins: an organismal and phylogenetic perspective on CO2 and NH3 gas channels.  

PubMed

Rh (Rhesus) proteins are homologues of ammonium transport (Amt) proteins. Physiological and structural evidence shows that Amt proteins are gas channels for NH(3), but the substrate of Rh proteins, be it CO2 as shown in green alga, or NH3/NH4+ as shown in mammalian cells, remains disputed. We assembled a large dataset generated of Rh and Amt to explore how Rh originated from and evolved independently of Amt relatives. Analysis of this rich data implies that Rh was split from Amt first to emerge in archaeal species. The Rh ancestor underwent divergence and duplication along speciation, leading to neofunctionalization and subfunctionalization of the Rh family. The characteristic organismal distribution of Rh vs. Amt reflects their early separation and subsequent independent evolution: they coexist in microbes and invertebrates but do not in fungi, vascular plants or vertebrates. Rh gene-duplication was prominent in vertebrates: while epithelial RhBG/RhCG displayed strong purifying selection, erythroid Rh30 and RhAG experienced different episodes of positive selection in each of which adaptive evolution occurred at certain time points and in a few codon sites. Mammalian Rh30 and RhAG were subject to particularly strong positive selection in some codon sites in the lineage from rodents to human. The grounds of this adaptive evolution may be driven by the necessity to increase the surface/volume ratio of biconcave erythrocytes for facilitative gas diffusion. Altogether, these results are consistent with Rh proteins not being the orthologue of Amt proteins but having gained the function for CO2/HCO3- transport, with important roles in systemic pH regulation. PMID:16564193

Peng, J; Huang, C H

2006-01-01

312

Effects of pollutant concentration ratio on the simultaneous removal of NH3, H2S and toluene gases using rock wool-compost biofilter.  

PubMed

The biological treatment of a tri-component mixed waste gas system in BRC1 and BRC2 biofilters packed with rock wool-compost media was studied. The model gases were NH(3), H(2)S and toluene. The gases were fed initially at about 50-55 ppm each. H(2)S was found to have the shortest start-up while toluene had the longest. Under two different NH(3):H(2)S:toluene concentration ratios of 250:120:55 and 120:220:55 (in ppm) for BRC1 and BRC2, the removal efficiencies of NH(3), H(2)S and toluene were found to be affected by their respective loading rate. On the other hand, toluene removal was observed to be inhibited at H(2)S concentration of 220 ppm as well. Almost complete removal of NH(3) and H(2)S was achieved when loading rate was applied up to 16.14 g-NH(3)/(m(3) bed h) and 36.09 g-H(2)S/(m(3) bed h), respectively. The maximum elimination capacity for NH(3) was determined to be 23.67 g-NH(3)/(m(3) bed h) at 78.6% removal efficiency and for H(2)S, 38.50 g-H(2)S/(m(3) bed h) at 68.1% removal efficiency. The maximum toluene elimination capacity was 30.75 g-toluene/(m(3) bed h) at 87.9% removal efficiency when the concentration of NH(3):H(2)S:toluene was 250:120:55 in BRC1, and was 16.60 g-toluene/(m(3) bed h) at 45.5% removal efficiency when the concentration of NH(3):H(2)S:toluene was 120:220:55 in BRC2. The pressure drops along both columns were low and the ratio of bed compactions over biofilter height was observed to be less than 0.02. PMID:17714863

Galera, Melvin Maaliw; Cho, Eulsaeng; Tuuguu, Enkhdul; Park, Shin-Jung; Lee, Changhee; Chung, Wook-Jin

2008-04-01

313

The effect of wind velocity, air temperature and humidity on NH 3 and SO 2 transfer into bean leaves ( phaseolus vulgaris L.)  

NASA Astrophysics Data System (ADS)

The influence of wind velocity, air temperature and vapour pressure deficit of the air (VPD) on NH 3 and SO 2 transfer into bean leaves ( Phaseolus vulgaris L.) was examined using a leaf chamber. The measurements suggested a transition in the properties of the leaf boundary layer at a wind velocity of 0.3-0.4 ms -1 which corresponds to a Recrit value of about 2000. At higher wind velocities the leaf boundary layer resistance ( rb) was 1.5-2 times lower than can be calculated from the theory. Nevertheless, the assessed relationships between rb and wind velocity appeared to be similar to the theoretical derived relationship for rb. The NH 3 flux and in particular the SO 2 flux into the leaf strongly increased at a VPD decline. The increase of the NH 3 flux could be attributed to an increase of the stomatal conductance ( gs). However, the increase of the SO 2 flux could only partly be explained by an increase of gs. An apparent additional uptake was also observed for the NH 3 uptake at a low temperature and VPD. The SO 2 flux was also influenced by air temperature which could be explained by a temperature effect on gs. The results suggest that calculation of the NH 3 and SO 2 flux using data of gs gives a serious understimation of the real flux of these gases into leaves at a low temperature and VPD.

van Hove, L. W. A.; Vredenberg, W. J.; Adema, E. H.

314

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

315

Vacuum-Assisted Thermal Annealing of CH3NH3PbI3 for Highly Stable and Efficient Perovskite Solar Cells.  

PubMed

Solar cells incorporating lead halide-based perovskite absorbers can exhibit impressive power conversion efficiencies (PCEs), recently surpassing 15%. Despite rapid developments, achieving precise control over the morphologies of the perovskite films (minimizing pore formation) and enhanced stability and reproducibility of the devices remain challenging, both of which are necessary for further advancements. Here we demonstrate vacuum-assisted thermal annealing as an effective means for controlling the composition and morphology of the CH3NH3PbI3 films formed from the precursors of PbCl2 and CH3NH3I. We identify the critical role played by the byproduct of CH3NH3Cl on the formation and the photovoltaic performance of the perovskite film. By completely removing the byproduct through our vacuum-assisted thermal annealing approach, we are able to produce pure, pore-free planar CH3NH3PbI3 films with high PCE reaching 14.5% in solar cell device. Importantly, the removal of CH3NH3Cl significantly improves the device stability and reproducibility with a standard deviation of only 0.92% in PCE as well as strongly reducing the photocurrent hysteresis. PMID:25549113

Xie, Feng Xian; Zhang, Di; Su, Huimin; Ren, Xingang; Wong, Kam Sing; Grtzel, Michael; Choy, Wallace C H

2015-01-27

316

Influence of bulking agents on CH4, N2O, and NH3 emissions during rapid composting of pig manure from the Chinese Ganqinfen system*  

PubMed Central

Mismanagement of the composting process can result in emissions of CH4, N2O, and NH3, which have caused severe environmental problems. This study was aimed at determining whether CH4, N2O, and NH3 emissions from composting are affected by bulking agents during rapid composting of pig manure from the Chinese Ganqinfen system. Three bulking agents, corn stalks, spent mushroom compost, and sawdust, were used in composting with pig manure in 60 L reactors with forced aeration for more than a month. Gas emissions were measured continuously, and detailed gas emission patterns were obtained. Concentrations of NH3 and N2O from the composting pig manure mixed with corn stalks or sawdust were higher than those from the spent mushroom compost treatment, especially the sawdust treatment, which had the highest total nitrogen loss among the three runs. Most of the nitrogen was lost in the form of NH3, which accounts for 11.16% to 35.69% of the initial nitrogen. One-way analysis of variance for NH3 emission showed no significant differences between the corn stalk and sawdust treatments, but a significant difference was noted between the spent mushroom compost and sawdust treatments. The introduction of sawdust reduced CH4 emission more than the corn stalks and spent mushroom compost. However, there were no significant differences among the three runs for total carbon loss. All treatments were matured after 30 d. PMID:24711356

Sun, Xiang-ping; Lu, Peng; Jiang, Tao; Schuchardt, Frank; Li, Guo-xue

2014-01-01

317

Internal Rotation in CF3ICdotsNH3 and CF3I\\cdotsN(CH3)_3 Probed by Cp-Ftmw Spectroscopy  

NASA Astrophysics Data System (ADS)

The pure rotational spectra of CF3ICdotsNH3 and CF3I\\cdotsN(CH3)_3 have been measured by chirped-pulse, Fourier transform microwave (CP-FTMW) spectroscopy between 7 and 18.5 GHz. Both molecules are generated by supersonic expansion of a gas sample containing a small percentage of each precursor in a balance of argon. The spectra of both complexes are consistent with {C}3v prolate symmetric top structures. The observed spectrum of CF3ICdotsNH3 displays evidence for internal rotation of NH3 about the principal axis. More than one hundred transitions of CF3ICdotsNH3 have been assigned to the internal rotor {A} state allowing rotational, centrifugal distortion constants and a nuclear quadrupole coupling constant for the iodine atom to be determined for this state. Measurements performed using a Balle-Flygare FTMW spectrometer further allow determination of a nuclear quadrupole coupling constant for the 14N nucleus. Many transitions in the spectrum of the CF3ICdots15NH3 isotopologue have also been measured and the length of the halogen bond between the iodine and nitrogen atoms has been determined. Measurements of hyperfine components in nine different J''?J' transitions of CF3I\\cdotsN(CH3)_3 have allowed assignment of the spectrum of this complex to determine rotational, centrifugal distortion and nuclear quadrupole coupling constants.

Walker, N. R.; Stephens, S. L.; Legon, A. C.

2011-06-01

318

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

NASA Technical Reports Server (NTRS)

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 0.6 atmosphere). If NH3 ice particles are introduced as an opacity source, the NH3 mixing ratio below the 147 K layer can be lowered, but the fit is worse than that given by the model that excludes NH3 ice particles. The best fit PH3 distribution curve exhibits a PH3/H2 mixing ratio of (8.3 + or - 2.0) x 10 to the -7th in the troposphere. In addition, a CH4/H2 mixing ratio of (2.5 + or - 0.4) x 10 to the -3rd is found in the troposphere.

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

1982-01-01

319

Oxidation of Zircaloy-4 by H 2O followed by molecular desorption  

NASA Astrophysics Data System (ADS)

The interaction of H 2O with Zircaloy-4 (Zry-4) is investigated using Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) methods. Following adsorption of H 2O at 150 K the Zr(MNV) and Zr(MNN) Auger features shift by 6.5 and 4.5 eV, respectively, indicating surface oxidation. Heating H 2O/Zry-4 results in molecular desorption of water at both low and high temperatures. The low-temperature desorption is attributed to ice multilayers, whereas, three overlapping high-temperature features are presumably due to recombinative desorption. This high-temperature desorption begins before the surface oxide is dissolved, continues upon its removal, and is atypical for water/metal systems. Unexpectedly, no significant desorption of hydrogen is observed near 400 K, as is typically observed following O 2 adsorption on Zr-based materials. However, we do observe that H 2O adsorption on Zry-4 surfaces roughened by argon ion sputtering results in H 2 desorption.

Stojilovic, N.; Ramsier, R. D.

2006-06-01

320

Temperature-programmed oxidation of equilibrium fluid catalytic cracking catalysts  

Microsoft Academic Search

Characterization of coke on equilibrium, fluid catalytic cracking (FCC) catalysts contaminated with metals was investigated\\u000a using temperature-programmed oxidation (TPO). TPO spectra of spent equilibrium catalysts from cracking of sour imported heavy\\u000a gas oil (SIHGO) were deconvoluted into four peaks (Peak K, L, M and N). The four peaks were assigned to different types of\\u000a coke on the catalyst. Peak L

O. Bayraktar; E. L. Kugler

2004-01-01

321

Inkjet Printing and Instant Chemical Transformation of a CH3 NH3 PbI3 /Nanocarbon Electrode and Interface for Planar Perovskite Solar Cells.  

PubMed

A planar perovskite solar cell that incorporates a nanocarbon hole-extraction layer is demonstrated for the first time by an inkjet printing technique with a precisely controlled pattern and interface. By designing the carbon plus CH3 NH3 I ink to transform PbI2 in?situ to CH3 NH3 PbI3 , an interpenetrating seamless interface between the CH3 NH3 PbI3 active layer and the carbon hole-extraction electrode was instantly constructed, with a markedly reduced charge recombination compared to that with the carbon ink alone. As a result, a considerably higher power conversion efficiency up to 11.60?% was delivered by the corresponding solar cell. This method provides a major step towards the fabrication of low-cost, large-scale, metal-electrode-free but still highly efficient perovskite solar cells. PMID:25255744

Wei, Zhanhua; Chen, Haining; Yan, Keyou; Yang, Shihe

2014-11-24

322

Performance of InGaN/GaN light-emitting diodes grown using NH3 with oxygen-containing impurities  

NASA Astrophysics Data System (ADS)

The performance of InGaN/GaN light-emitting diodes (LEDs) fabricated using NH3 was varied by intentionally adding H2O, O2, or CO. The oxygen concentration in the active layer varied with the type of impurity, which was related to the binding energy of the impurity. When a small amount of oxygen was incorporated in the InGaN active layer without Si doping through an oxygen-containing impurity, the light output power of the LED was improved. On the other hand, the light output power of the LED gradually deteriorated with increasing oxygen concentration. The oxygen-containing impurities affected the light output power of the LEDs. When NH3 with any oxygen-containing impurities was purified using a purification system giving a guaranteed impurity concentration of less than 10 ppb, the light output power of the LED was recovered to that of the LED fabricated with pure NH3.

Okada, Narihito; Tadatomo, Kazuyuki; Yamane, Keisuke; Mangyo, Hirotaka; Kobayashi, Yoshihiko; Ono, Hiroyuki; Ikenaga, Kazutada; Yano, Yoshiki; Matsumoto, Koh

2014-08-01

323

Rotational excitation of symmetric top molecules by collisions with atoms: Close coupling, coupled states, and effective potential calculations for NH3-He  

NASA Technical Reports Server (NTRS)

The formalism for describing rotational excitation in collisions between symmetric top rigid rotors and spherical atoms is presented both within the accurate quantum close coupling framework and also the coupled states approximation of McGuire and Kouri and the effective potential approximation of Rabitz. Calculations are reported for thermal energy NH3-He collisions, treating NH3 as a rigid rotor and employing a uniform electron gas (Gordon-Kim) approximation for the intermolecular potential. Coupled states are found to be in nearly quantitative agreement with close coupling results while the effective potential method is found to be at least qualitatively correct. Modifications necessary to treat the inversion motion in NH3 are discussed.

Green, S.

1976-01-01

324

Desorption-induced recombination-cationization of metal-adsorbate adducts from sulfur precovered Ru(0001)  

NASA Astrophysics Data System (ADS)

Temperature programmed static secondary ion mass spectrometry (TPSS) studies of pyrrole, furan and water on sulfur precovered Ru(0001) reveal significant increases in the coverage corrected adduct yield when these species desorb from the surface in an autocatalytic fashion. This effect has been attributed to an enhancement in the recombination-cationization rate which occurs when sputtered-ruthenium species contact desorbed organics just after leaving the surface. Adsorbates which do not undergo autocatalytic/explosive desorption do not exhibit this effect.

Cocco, R. A.; Tatarchuk, B. J.

1990-03-01

325

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

326

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 34.320.4, 47.624.9, 21.716.8 g 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 (1.150.7 g 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 111.241.1, 123.340.7, 38.328.8 g NO-N m-2 h-1 and 9.97.5, 34.333.3 and 21.26.1 g N2O-N m-2 h-1, respectively. At the background site 270 m downwind the N2O flux was reduced to 1.752.1 g 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

327

State-to-state cross section of rotational transition caused by dipole-quadrupole interaction between NH3 and nonpolar molecules  

NASA Astrophysics Data System (ADS)

Rotational transitions in NH3 induced by the dipole-quadrupole collisional interaction are studied by use of the supersonic molecular-beam technique and double-resonance spectroscopy. The measured state-to-state cross section agrees well with the cross section calculated nonempirically based on the Anderson-Tsao-Curnutte theory, which depends only on the dipole-matrix element between the initial and final states of NH3. It is deduced that the state-to-all-states cross section is independent of the molecular quantum states.

Uematsu, Yoshihiko; Tachikawa, Maki; Tanaka, Yoshihito; Matsushima, Fusakazu; Shimizu, Tadao

1992-04-01

328

The reaction NH2 + PH3 yields NH3 + PH2: Absolute rate constant measurement and implication for NH3 and PH3 photochemistry in the atmosphere of Jupiter  

NASA Technical Reports Server (NTRS)

The rate constant is measured over the temperature interval 218-456 K using the technique of flash photolysis-laser-induced fluorescence. NH2 radicals are produced by the flash photolysis of ammonia highly diluted in argon, and the decay of fluorescent NH2 photons is measured by multiscaling techniques. For each of the five temperatures employed in the study, the results are shown to be independent of variations in PH3 concentration, total pressure (argon), and flash intensity. It is found that the rate constant results are best represented for T between 218 and 456 K by the expression k = (1.52 + or - 0.16) x 10 to the -12th exp(-928 + or - 56/T) cu cm per molecule per sec; the error quoted is 1 standard deviation. This is the first determination of the rate constant for the reaction NH2 + PH3. The data are compared with an estimate made in order to explain results of the radiolysis of NH3-PH3 mixtures. The Arrhenius parameters determined here for NH2 + PH3 are then constrasted with those for the corresponding reactions of H and OH with PH3.

Bosco, S. R.; Brobst, W. D.; Nava, D. F.; Stief, L. J.

1983-01-01

329

The reaction NH2 + PH3 yields NH3 + PH2 - Absolute rate constant measurement and implication for NH3 and PH3 photochemistry in the atmosphere of Jupiter  

NASA Technical Reports Server (NTRS)

The rate constant is measured over the temperature interval 218-456 K using the technique of flash photolysis-laser-induced fluorescence. NH2 radicals are produced by the flash photolysis of ammonia highly diluted in argon, and the decay of fluorescent NH2 photons is measured by multiscaling techniques. For each of the five temperatures employed in the study, the results are shown to be indepenent of variations in PH3 concentration, total pressure (argon), and flash intensity. It is found that the rate constant results are best represented for T between 218 and 456 K by the expression k = (1.52 + or - 0.16) x 10 to the -12th exp(-928 + or - 56/T) cu cm per molecule per sec; the error quoted is 1 standard deviation. This is the first determination of the rate constant for the reaction NH2 + PH3. The data are compared with an estimate made in order to explain results of the radiolysis of NH3-PH3 mixtures. The Arrhenius parameters determined here for NH2 + PH3 are then contrasted with those for the corresponding reactions of H and OH with PH3.

Bosco, S. R.; Brobst, W. D.; Nava, D. F.; Stief, L. J.

1983-01-01

330

Infrared spectra and relative stability of the F3CH/NH3 H-bonded complex in liquefied Xe.  

PubMed

FTIR spectra of mixtures of fluoroform (F3CH) and ammonia (NH3), have been studied in liquid xenon between 5400 and 500 cm-1. Spectroscopic evidence for the formation of a hydrogen bonded complex has been found and the complexation enthalpy Delta(LXe)H degrees in the temperature interval between 173 and 215 K, was determined to be 14.4 (7) kJ mol-1. The parallel fundamentals nu1 and nu2 of ammonia reveal a strong narrowing effect upon complex formation, whereas the perpendicular fundamentals nu3 and nu4 show a modest decrease of their width. CP corrected ab initio calculations at the MP2(FULL)/6-311++G(3df,2pd) level predict a linear geometry for the complex, characterized by a small red shift of the CH stretch frequency of fluoroform. The ab initio interaction energy was found to be compatible with the isolated molecule complexation energy extrapolated from the experimental Delta(LXe)H degrees . PMID:15820893

Rutkowski, K S; Herrebout, W A; Melikova, S M; Rodziewicz, P; van der Veken, B J; Koll, A

2005-05-01

331

An analytical approach to evaluate the performance of graphene and carbon nanotubes for NH3 gas sensor applications  

PubMed Central

Summary Carbon, in its variety of allotropes, especially graphene and carbon nanotubes (CNTs), holds great potential for applications in variety of sensors because of dangling ?-bonds that can react with chemical elements. In spite of their excellent features, carbon nanotubes (CNTs) and graphene have not been fully exploited in the development of the nanoelectronic industry mainly because of poor understanding of the band structure of these allotropes. A mathematical model is proposed with a clear purpose to acquire an analytical understanding of the field-effect-transistor (FET) based gas detection mechanism. The conductance change in the CNT/graphene channel resulting from the chemical reaction between the gas and channel surface molecules is emphasized. NH3 has been used as the prototype gas to be detected by the nanosensor and the corresponding currentvoltage (IV) characteristics of the FET-based sensor are studied. A graphene-based gas sensor model is also developed. The results from graphene and CNT models are compared with the experimental data. A satisfactory agreement, within the uncertainties of the experiments, is obtained. Graphene-based gas sensor exhibits higher conductivity compared to that of CNT-based counterpart for similar ambient conditions. PMID:24991510

Akbari, Elnaz; Enzevaee, Aria; Ahmadi, Mohamad T; Saeidmanesh, Mehdi; Khaledian, Mohsen; Karimi, Hediyeh; Yusof, Rubiyah

2014-01-01

332

CH3NH3PbI3-Based Planar Solar Cells with Magnetron-Sputtered Nickel Oxide.  

PubMed

Herein we report an investigation of a CH3NH3PbI3 planar solar cell, showing significant power conversion efficiency (PCE) improvement from 4.88% to 6.13% by introducing a homogeneous and uniform NiO blocking interlayer fabricated with the reactive magnetron sputtering method. The sputtered NiO layer exhibits enhanced crystallization, high transmittance, and uniform surface morphology as well as a preferred in-plane orientation of the (200) plane. The PCE of the sputtered-NiO-based perovskite p-i-n planar solar cell can be further promoted to 9.83% when a homogeneous and dense perovskite layer is formed with solvent-engineering technology, showing an impressive open circuit voltage of 1.10 V. This is about 33% higher than that of devices using the conventional spray pyrolysis of NiO onto a transparent conducting glass. These results highlight the importance of a morphology- and crystallization-compatible interlayer toward a high-performance inverted perovskite planar solar cell. PMID:25426540

Cui, Jin; Meng, Fanping; Zhang, Hua; Cao, Kun; Yuan, Huailiang; Cheng, Yibing; Huang, Feng; Wang, Mingkui

2014-12-24

333

Thermal Assisted Oxygen Annealing for High Efficiency Planar CH3NH3PbI3 Perovskite Solar Cells  

PubMed Central

We report investigations on the influences of post-deposition treatments on the performance of solution-processed methylammonium lead triiodide (CH3NH3PbI3)-based planar solar cells. The prepared films were stored in pure N2 at room temperature or annealed in pure O2 at room temperature, 45C, 65C and 85C for 12?hours prior to the deposition of the metal electrodes. It is found that annealing in O2 leads to substantial increase in the power conversion efficiencies (PCEs) of the devices. Furthermore, strong dependence on the annealing temperature for the PCEs of the devices suggests that a thermally activated process may underlie the observed phenomenon. It is believed that the annealing process may facilitate the diffusion of O2 into the spiro-MeOTAD for inducing p-doping of the hole transport material. Furthermore, the process can result in lowering the localized state density at the grain boundaries as well as the bulk of perovskite. Utilizing thermal assisted O2 annealing, high efficiency devices with good reproducibility were attained. A PCE of 15.4% with an open circuit voltage (VOC) 1.04?V, short circuit current density (JSC) 23?mA/cm2, and fill factor 0.64 had been achieved for our champion device. PMID:25341527

Ren, Zhiwei; Ng, Annie; Shen, Qian; Gokkaya, Huseyin Cem; Wang, Jingchuan; Yang, Lijun; Yiu, Wai-Kin; Bai, Gongxun; Djurii?, Aleksandra B.; Leung, Wallace Woon-fong; Hao, Jianhua; Chan, Wai Kin; Surya, Charles

2014-01-01

334

Optical-integrated NH 3 sensor design based on WO 3 thin films: influence of gas adsorption and chromic effects  

NASA Astrophysics Data System (ADS)

It has been observed in the literature, developments about characterization of several materials for gas sensing application; simultaneously, also it has been observed that only some of them show a procedure of design for the implementation of these materials in a device or an optical system. In consequence, appears differences between the predicted by theory and the experiments. For that reason, the present work proposes a new approach for the design of optical-integrated (OI) sensors. We show the advances in the design of an OI sensor for ammonia detection (NH 3), using tungsten trioxide (WO 3) as sensitive material. We considered a model that incorporates the concepts of the kinetic of gas adsorption on solids, the effects of the real and imaginary part of the refractive index in the redistribution of the optical field, and the influence of the photo and thermochromism, before and during the sensing mechanism. Although the work has not been concluded, we can affirm that the concepts incorporated in this proposal, must be considered as critical parameters in the design of an OI sensor or an optical fiber (FO) sensor.

Lazcano Hernndez, Hugo E.; Snchez Prez, Celia; Garca Valenzuela, Augusto; Esparza Garca, Alejandro; Camacho Lpez, Marco A.

2007-03-01

335

Vapor-phase epitaxy of high-crystallinity GaN films using Ga 2O vapor and NH 3  

NASA Astrophysics Data System (ADS)

In this study, vapor-phase epitaxy (VPE) of GaN oriented-film was performed using Ga 2O vapor as the Ga source. Ga 2O vapor was obtained by reducing Ga 2O 3 powder with H 2 gas at 1000 C. The Ga 2O vapor was then reacted with NH 3 on a seed substrate at 1100-1150 C. A high quality GaN substrate (1 mm thick, with full widths at half maximum of GaN (0 0 0 2) X-ray rocking curve of 107-110 arcsec) prepared by the Na-flux method were used as the seed substrate. After 30 min of growth, a 3-?m flat GaN (0 0 0 1) epitaxial layer was grown on the seed substrate. X-ray diffraction (XRD) measurements showed that the FWHM of the GaN epitaxial layer was 74-111 arcsec, showing high crystallinity. Secondary ion mass spectrometry (SIMS) analysis showed that the oxygen concentration in the epitaxial layer was 1.510 18 atoms/cm 3. Although an oxide was used as the raw material, oxygen concentration close to those in GaN crystal grown by the hydride vapor phase epitaxy (HVPE) and metalorganic vapor phase epitaxy (MOVPE) were achieved. We concluded that the VPE method using Ga 2O vapor has potential as a simple vapor-phase-growing technique for high-quality GaN films.

Imade, Mamoru; Kishimoto, Hiroki; Kawamura, Fumio; Yoshimura, Masashi; Kitaoka, Yasuo; Sasaki, Takatomo; Mori, Yusuke

2010-02-01

336

Deposition of GaN films on (1 1 1) Si substrates by alternate supply of TMG and NH 3  

NASA Astrophysics Data System (ADS)

GaN films were grown on (1 1 1) Si substrates at 1000 C by separate admittances of trimethylgallium (TMG) and ammonia (NH 3). To achieve high quality GaN films, the optimization in growth temperature and layer thickness of AlN buffer layer between GaN film and Si substrate is required. Cross-sectional transmission electron microscopic observations of the GaN/(1 1 1)Si samples show a nearly parallel orientation relationship between the (0 0 0 1) planes of GaN film and the (1 1 1) planes of Si substrate. Room temperature photoluminescence spectra of high quality GaN films show a strong near band edge emission and a weak yellow luminescence. The achievement of high quality GaN films on (1 1 1) Si substrates is believed to be attributed to enhancement in surface mobilities of the adsorbed surface species and adequate accommodation of lattice mismatch between high temperature AlN buffer layer and Si substrate.

Gong, Jyh-Rong; Yeh, Ming-Fa; Tsai, Yu-Li

2004-01-01

337

Microwave-assisted synthesis of the anticancer drug cisplatin, cis-[Pt(NH3)2Cl2].  

PubMed

A microwave-assisted synthesis of cisplatin, cis-[Pt(NH3)2Cl2], has been developed and optimized on both a 0.2 and 0.05 millimolar scale. The optimized synthetic procedure was modeled after the Lebedinskii-Golovnya method and is suitable for incorporating the radionuclide, (195m)Pt, into cisplatin for biological studies. Highest yields (47%) and purity are obtained using a K2PtCl4?:?NH4OAc?:?KCl molar ratio of 1?:?4?:?2 at a temperature of 100 C. The entire synthesis and purification procedure requires approximately 80 min. At a reaction temperature of 150 C, the trans isomer is the exclusive product, suggesting that complexes of the general form, trans-[Pt(RNH2)2Cl2], can be synthesized directly from K2PtCl4 using [RNH3]OAc (R = alkyl or aryl moieties) via a microwave process. Two novel separation procedures have been developed which efficiently remove the major impurity (1?:?1 Magnus-type salt) from the crude reaction product, yielding a product of purity comparable to that obtained by the Dhara method and suitable for biological studies. These procedures are applicable to both the micro- and macro-scale of synthesis. The question of whether this microwave-assisted synthesis of cisplatin will be a preferred method for incorporating (195m)Pt into cisplatin is yet to be determined. PMID:25600831

Petruzzella, Emanuele; Chirosca, Cristian V; Heidenga, Cameron S; Hoeschele, James D

2015-02-01

338

The reaction of dichlorodiammineplatinum(II), [PtCl2(NH3)2], isomers with zinc fingers.  

PubMed

The interaction of cis-DDP and trans-DDP (DDP=[PtCl2(NH3)2]) with the C-terminal zinc finger (ZF2) of the HIVNCp7 nucleocapsid protein was investigated by fluorescence, circular dichroism, mass spectrometry, and {(1)H, (15)N} HSQC (heteronuclear single quantum coherence) NMR spectroscopy. The rate of reaction differed significantly for the two compounds, with the trans isomer reacting in a significantly faster manner, as expected. {(1)H, (15)N} HSQC NMR of (15)N-labeled compounds with the ZF2 showed the appearance of several new (15)N peaks, consistent with sulfur binding and formation of Pt-S species. Mass spectrometry confirmed the formation of several different Pt-apopeptide/ZF2 adducts. Circular dichroism and fluorescence spectroscopy also indicated conformational changes upon binding while a 33% decrease in fluorescence of the unique tryptophan residue was seen in 72h upon complexation of the cis isomer, while the trans isomer quenched 50% in just 24h. PMID:25528679

Tsotsoros, Samantha D; Qu, Yun; Farrell, Nicholas P

2015-02-01

339

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction  

SciTech Connect

Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on the development of novel bimetallic dispersed catalysts for temperature-programmed liquefaction. The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular that can be used in low precursors concentrations (< 1 %) but exhibit high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. The major technical approaches are, first, to prepare the desired heteronuclear organometallic molecules as catalyst precursors that contain covalently bound, two different metal atoms and sulfur in a single molecule. Such precursors will generate finely dispersed bimetallic catalysts such as Fe-Mo, Co-Mo and Ni-Mo binary sulfides upon thermal decomposition. The second major technical approach is to perform the liquefaction of coals unpregnated with the organometallic precursors under temperature-programmed conditions, where the programmed heat-up serves as a step for both catalyst activation and coal pretreatment or preconversion. Two to three different complexes for each of the Fe-Mo, Co-Mo, and Ni-Mo combinations will be prepared. Initial catalyst screening tests will be conducted using a subbituminous coal and a bituminous coal. Effects of coal rank and solvents will be examined with the selected bimetallic catalysts which showed much higher activity than the dispersed catalysts from conventional precursors.

Song, Chunshan; Schobert, H.H.

1993-02-01

340

Synthesis, structure, and photovoltaic property of a nanocrystalline 2H perovskite-type novel sensitizer (CH3CH2NH3)PbI3  

PubMed Central

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) , b?=?8.14745(10) , and c?=?30.3096(6) , 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

2012-01-01

341

A general methodology for quantum modeling of free-energy profile of reactions in solution: An application to the Menshutkin NH3 CH3Cl  

E-print Network

A general methodology for quantum modeling of free-energy profile of reactions in solution methodology for calculating free-energy profile of reaction in solution using quantum mechanical methods of this methodology to calculate the free-energy profile of the Menshutkin NH3 CH3Cl reaction in water is discussed

Truong, Thanh N.

342

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

343

Effect of ammonia on new particle formation: A kinetic H2SO4-H2O-NH3 nucleation model constrained by laboratory measurements  

E-print Network

Effect of ammonia on new particle formation: A kinetic H2SO4-H2O- NH3 nucleation model constrained investigations are discussed. Citation: Yu, F. (2006), Effect of ammonia on new particle formation: A kinetic H2 of this paper is on the possible role of ammonia in stabilizing the critical embryo and thus enhancing

Yu, Fangqun

344

Reinterpretation of the vibrational spectroscopy of the medicinal bioinorganic synthon c,c,t-[Pt(NH3)2Cl2(OH)2].  

PubMed

The Pt(IV) complex c,c,t-[Pt(NH3)2Cl2(OH)2] is an important intermediate in the synthesis of Pt(IV) anticancer prodrugs and has been investigated as an anticancer agent in its own right. An analysis of the vibrational spectroscopy of this molecule was previously reported (Faggiani et al., Can. J. Chem. 60:529, 1982), in which crystallographic determination of the structure of the complex permitted a site group approach. The space group, however, was incorrectly assigned. In the present study we have redetermined at high resolution crystal structures of c,c,t-[Pt(NH3)2Cl2(OH)2] and c,c,t-[Pt(NH3)2Cl2(OH)2]H2O2, which makes possible discussion of the effect of hydrogen bonding on the N-H and O-H vibrational bands. The correct crystallographic site symmetry of the platinum complex in the c,c,t-[Pt(NH3)2Cl2(OH)2] structure is used to conduct a new vibrational analysis using both group-theoretical and modern density functional theory methods. This analysis reveals the nature and symmetry of the "missing band" described in the original publication and suggests a possible explanation for its disappearance. PMID:24515615

Johnstone, Timothy C; Lippard, Stephen J

2014-06-01

345

Efficient and stable CH3NH3PbI3-sensitized ZnO nanorod array solid-state solar cells  

NASA Astrophysics Data System (ADS)

We report for the first time the use of a perovskite (CH3NH3PbI3) absorber in combination with ZnO nanorod arrays (NRAs) for solar cell applications. The perovskite material has a higher absorption coefficient than molecular dye sensitizers, gives better solar cell stability, and is therefore more suited as a sensitizer for ZnO NRAs. A solar cell efficiency of 5.0% was achieved under 1000 W m-2 AM 1.5 G illumination for a solar cell with the structure: ZnO NRA/CH3NH3PbI3/spiro-MeOTAD/Ag. Moreover, the solar cell shows a good long-term stability. Using transient photocurrent and photovoltage measurements it was found that the electron transport time and lifetime vary with the ZnO nanorod length, a trend which is similar to that in dye-sensitized solar cells, DSCs, suggesting a similar charge transfer process in ZnO NRA/CH3NH3PbI3 solar cells as in conventional DSCs. Compared to CH3NH3PbI3/TiO2 solar cells, ZnO shows a lower performance due to more recombination losses.

Bi, Dongqin; Boschloo, Gerrit; Schwarzmller, Stefan; Yang, Lei; Johansson, Erik M. J.; Hagfeldt, Anders

2013-11-01

346

Low-temperature surface formation of NH3 and HNCO: hydrogenation of nitrogen atoms in CO-rich interstellar ice analogues  

NASA Astrophysics Data System (ADS)

Solid-state astrochemical reaction pathways have the potential to link the formation of small nitrogen-bearing species, like NH3 and HNCO, and prebiotic molecules, specifically amino acids. To date, the chemical origin of such small nitrogen-containing species is still not well understood, despite the fact that ammonia is an abundant constituent of interstellar ices towards young stellar objects and quiescent molecular clouds. This is mainly because of the lack of dedicated laboratory studies. The aim of this work is to experimentally investigate the formation routes of NH3 and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant temperatures. This study focuses on the formation of NH3 and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in dark interstellar cloud regions, well before thermal and energetic processing start to become relevant. We demonstrate and discuss the surface formation of solid HNCO through the interaction of CO molecules with NH radicals - one of the intermediates in the formation of solid NH3 upon sequential hydrogenation of N atoms. The importance of HNCO for astrobiology is discussed.

Fedoseev, G.; Ioppolo, S.; Zhao, D.; Lamberts, T.; Linnartz, H.

2015-01-01

347

On the Surface Formation of NH3 and HNCO in Dark Molecular Clouds - Searching for Whler Synthesis in the Interstellar Medium  

NASA Astrophysics Data System (ADS)

Despite its potential to reveal the link between the formation of simple species and more complex molecules (e.g., amino acids), the nitrogen chemistry of the interstellar medium (ISM) is still poorly understood. Ammonia (NH _{3}) is one of the few nitrogen-bearing species that have been observed in interstellar ices toward young stellar objects (YSOs) and quiescent molecular clouds. The aim of the present work is to experimentally investigate surface formation routes of NH _{3} and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant cryogenic temperatures. This study focuses on the formation of NH _{3} and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in interstellar dark cloud regions, well before thermal and energetic processing start to become predominant. Our work confirms the surface formation of ammonia through the sequential addition of three hydrogen/deuterium atoms to a single nitrogen atom at low temperature. The H/D fractionation of the formed ammonia is also shown. Furthermore, we show the surface formation of solid HNCO through the interaction of CO molecules with NH radicals - one of the intermediates in the formation of solid NH _{3}. Finally, we discuss the implications of HNCO in astrobiology, as a possible starting point for the formation of more complex prebiotic species.

Fedoseev, Gleb; Lamberts, Thanja; Linnartz, Harold; Ioppolo, Sergio; Zhao, Dongfeng

348

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: NH3 laser as a radiation source for a two-frequency lidar  

NASA Astrophysics Data System (ADS)

An NH3 laser pumped by a CO2 laser with spatial matching of output beams is investigated. Such a laser can be used as a radiation source for a two-frequency lidar operating in the range from 11 to 13.5 ?m.

Vasil'ev, B. I.; Cho, Cheon W.

2000-12-01

349

Composition-dependent photoluminescence intensity and prolonged recombination lifetime of perovskite CH3NH3PbBr(3-x)Cl(x) films.  

PubMed

Mixed halide perovskites CH3NH3PbBr3-xClx (x = 0.6-1.2) with different compositions of halogens exhibit drastically changed optical properties. In particular, the thin films prepared with these perovskites demonstrate extraordinary photoluminescence emission intensities and prolonged recombination lifetimes up to 446 ns, which are desirable for light emitting and photovoltaic applications. PMID:25144835

Zhang, Meng; Yu, Hua; Lyu, Miaoqiang; Wang, Qiong; Yun, Jung-Ho; Wang, Lianzhou

2014-10-11

350

Mesoscopic TiO2/CH3NH3PbI3 perovskite solar cells with new hole-transporting materials containing butadiene derivatives.  

PubMed

Two new triphenylamine-based hole-transporting materials (HTMs) containing butadiene derivatives are employed in CH3NH3PbI3 perovskite solar cells. Up to 11.63% of power conversion efficiency (PCE) has been achieved. Advantages such as easy synthesis, low cost and relatively good cell performance exhibit a possibility for commercial applications in the future. PMID:24841233

Lv, Songtao; Han, Liying; Xiao, Junyan; Zhu, Lifeng; Shi, Jiangjian; Wei, Huiyun; Xu, Yuzhuan; Dong, Juan; Xu, Xin; Li, Dongmei; Wang, Shirong; Luo, Yanhong; Meng, Qingbo; Li, Xianggao

2014-07-01

351

Modified two-step deposition method for high-efficiency TiO2/CH3NH3PbI3 heterojunction solar cells.  

PubMed

Hybrid organic-inorganic perovskites (e.g., CH3NH3PbI3) are promising light absorbers for the third-generation photovoltaics. Herein we demonstrate a modified two-step deposition method to fabricate a uniform CH3NH3PbI3 capping layer with high-coverage and thickness of 300 nm on top of the mesoporous TiO2. The CH3NH3PbI3 layer shows high light-harvesting efficiency and long carrier lifetime over 50 ns. On the basis of the as-prepared film, TiO2/CH3NH3PbI3 heterojunction solar cells achieve a power conversion efficiency of 10.47% with a high open-circuit voltage of 948 mV, the highest recorded to date for hole-transport-material-free (HTM-free) perovskite-based heterojunction cells. The efficiency exceeding 10% shows promising prospects for the HTM-free solar cells based on organic lead halides. PMID:24830329

Shi, Jiangjian; Luo, Yanhong; Wei, Huiyun; Luo, Jianheng; Dong, Juan; Lv, Songtao; Xiao, Junyan; Xu, Yuzhuan; Zhu, Lifeng; Xu, Xin; Wu, Huijue; Li, Dongmei; Meng, Qingbo

2014-06-25

352

Transformation of the Excited State and Photovoltaic Efficiency of CH3NH3PbI3 Perovskite upon Controlled Exposure to Humidified Air.  

PubMed

Humidity has been an important factor, in both negative and positive ways, in the development of perovskite solar cells and will prove critical in the push to commercialize this exciting new photovoltaic technology. The interaction between CH3NH3PbI3 and H2O vapor is investigated by characterizing the ground-state and excited-state optical absorption properties and probing morphology and crystal structure. These undertakings reveal that H2O exposure does not simply cause CH3NH3PbI3 to revert to PbI2. It is shown that, in the dark, H2O is able to complex with the perovskite, forming a hydrate product similar to (CH3NH3)4PbI62H2O. This causes a decrease in absorption across the visible region of the spectrum and a distinct change in the crystal structure of the material. Femtosecond transient absorption spectroscopic measurements show the effect that humidity has on the ultrafast excited state dynamics of CH3NH3PbI3. More importantly, the deleterious effects of humidity on complete solar cells, specifically on photovoltaic efficiency and stability, are explored in the light of these spectroscopic understandings. PMID:25590693

Christians, Jeffrey A; Miranda Herrera, Pierre A; Kamat, Prashant V

2015-02-01

353

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

354

Magnetization and correlation length of the easy-plane ferromagnetic chain: Numerical analysis and application to (C6H11NH3)CuBr3  

NASA Astrophysics Data System (ADS)

The ferromagnetic spin-(1/2 one-dimensional XXZ Heisenberg model is studied numerically by quantum Monte Carlo analysis and extrapolations in 1/N of finite-size chain data. Reliable magnetization and correlation-length estimates are presented and a quantitative agreement with recent experimental data on the compound (C6H11NH3)CuBr3 is found.

Kamieniarz, G.; Mallezie, F.; Dekeyser, R.

1988-10-01

355

Thermodynamic analysis of a power cycle using a low-temperature source and a binary NH 3H 2O mixture as working fluid  

Microsoft Academic Search

Two Rankine cycles, one with and one without a regenerator, both using a NH3H2O mixture as the working fluid, have been analyzed for fixed source and sink inlet temperatures. A fixed mass flow rate of a hot gaseous stream is providing the thermal energy input at the heat recovery boiler (HRB). The methodology used in this work is divided in

Philippe Roy; Martin Dsilets; Nicolas Galanis; Hakim Nesreddine; Emmanuel Cayer

2010-01-01

356

Synthesis, structure, and photovoltaic property of a nanocrystalline 2H perovskite-type novel sensitizer (CH3CH2NH3)PbI3  

NASA Astrophysics Data System (ADS)

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) , b = 8.14745(10) , and c = 30.3096(6) , 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.

Im, Jeong-Hyeok; Chung, Jaehoon; Kim, Seung-Joo; Park, Nam-Gyu

2012-06-01

357

Hot ammonia around young O-type stars. II. JVLA imaging of highly excited metastable NH3 masers in W51-North  

NASA Astrophysics Data System (ADS)

Context. This paper is the second in a series of ammonia (NH3) multilevel imaging studies in high-mass star forming regions. Aims: We want to identify the location of the maser emission from highly excited levels of ammonia within the W51 IRS2 high-mass star forming complex that was previously discovered in a single dish monitoring program. Methods: We have used the Karl Jansky Very Large Array (JVLA) at the 1 cm band to map five highly excited metastable inversion transitions of NH3, (J,K) = (6,6), (7, 7), (9, 9), (10, 10), and (13, 13), in W51 IRS2 with ~0.?2 angular resolution. Results: We present detections of both thermal (extended) ammonia emission in the five inversion lines, with rotational states ranging in energy from about 400 K to 1700 K, and point-like ammonia maser emission in the (6, 6), (7, 7), and (9, 9) lines. For the point-like emission, we estimate lower limits to the peak brightness temperatures of 1.7 105 K, 6 103 K, and 1 104 K for the (6, 6), (7, 7), and (9, 9) transitions, respectively, confirming their maser nature. The thermal ammonia emits around a local standard of rest velocity of VLSR = 60 km s-1, near the cloud's systemic velocity, appears elongated in the east-west direction across 4'' and is confined by the HII regions W51d (to the north), W51d1 (to the east), and W51d2 (to the west). The NH3 masers are observed in the eastern tip of the dense clump traced by thermal NH3, offset by 0.?65 to the east from its emission peak, and have a peak velocity at ~47.5 km s-1. No maser components are detected near the systemic velocity. The NH3 masers arise close to but separated from (0.?65 or 3500 AU) the rare vibrationally excited SiO masers, which are excited in a powerful bipolar outflow driven by the deeply embedded high-mass young stellar object (YSO) W51-North. This means that the two maser species cannot be excited by the same object. Interestingly, the NH3 masers originate at the same sky position as a peak in a submm line of SO2 imaged with the Submillimeter Array, tracing a face-on circumstellar disk or ring around W51-North. In addition, the thermal emission from the most highly excited NH3 lines, (10, 10) and (13, 13), shows two main condensations, the dominant one towards W51-North with the SiO and H2O masers, and a weaker peak at the NH3 maser position. Conclusions: We propose a scenario where the ring seen in SO2 emission is a circumbinary disk surrounding (at least) two high-mass YSOs, W51-North (exciting the SiO masers) and a nearby companion (exciting the NH3 masers), separated by 3500 AU. This finding indicates a physical connection (in a binary) between the two rare SiO and NH3 maser species.

Goddi, C.; Henkel, C.; Zhang, Q.; Zapata, L.; Wilson, T. L.

2015-01-01

358

Planar CH3 NH3 PbBr3 Hybrid Solar Cells with 10.4% Power Conversion Efficiency, Fabricated by Controlled Crystallization in the Spin-Coating Process.  

PubMed

A power conversion efficiency of 10.4% is demonstrated in planar CH3 NH3 PbBr3 hybrid solar cells without hysteresis of the J-V curve, by way of controlled crystallization in the spin-coating process. The high efficiency is attributed to the formation of a dense CH3 NH3 PbBr3 thin film by the introduction of HBr solution because the HBr increases the solubility of the CH3 NH3 PbBr3 and forms a thinner CH3 NH3 PbBr3 layer with full surface coverage. PMID:25348285

Heo, Jin Hyuck; Song, Dae Ho; Im, Sang Hyuk

2014-12-01

359

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

360

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

361

Spontaneous gradual accumulation of hexagonally-aligned nano-silica on gold nanoparticles embedded in stabilized zirconia: a pathway from catalytic to NH3-sensing performance.  

PubMed

The present study highlights the influence of nano-impurities on the catalytic/sensing performance of nano-structured Au sensing-electrodes (SEs) housed in a quartz reactor and operated at high temperature over a long period of time. The planar sensor, made from a nano-structured Au-SE on a polished-polycrystalline (pp) yttria-stabilized zirconia (YSZ) substrate exhibited initially negligible electromotive force (emf) response to each of the examined gases (CO, CH(4), C(3)H(8), C(3)H(6), NO(x) and NH(3); 400 ppm each) at 700 C in the presence of 5 vol.% oxygen and 5 vol.% water vapor. Such a poor emf response was attributed to the excellent gas-phase oxidation/reduction ability of Au nanoparticles embedded in the YSZ substrate at high temperature. The response of the planar sensor made up of nano-structured Au-SE was monitored for about 75 days at 700 C. As a result of this long-term monitoring, we detected the appearance of highly sensitive and selective NH(3) gas-sensing properties after 45-75 days of sensor operation. Detailed observation of the morphology and composition of the as-fabricated nano-structured Au-SE after 75 days operation at 700 C revealed the gradual accumulation of hexagonally-aligned SiO(2) nano-impurities on the surface of the Au nanoparticles. The NH(3) sensing mechanism of the YSZ-based sensor using the spontaneously-formed composite (nano-Au + nano-SiO(2))-SE is therefore proposed to be based on a strong acid-base interaction between gaseous NH(3) and SiO(2) nano-impurities, followed by spillover of adsorbed NH(3) towards the nano-Au/pp-YSZ interface. PMID:21494733

Plashnitsa, Vladimir V; Elumalai, Perumal; Fujio, Yuki; Kawaguchi, Toshikazu; Miura, Norio

2011-05-01

362

VizieR Online Data Catalog: A variationally computed hot NH3 line list - BYTe (Yurchenko+, 2011)  

NASA Astrophysics Data System (ADS)

We present 'BYTe' a comprehensive 'hot' line list of ro-vibrational transitions of ammonia, 14NH3, in its ground electronic state. It comprises 1,138,323,351 transitions with frequencies up to 12,000cm-1^, constructed from 1,373,897 energy levels below 18,000cm-1^ having J values less than 37. The line list is sufficiently accurate and complete for high resolution spectroscopy and atmospheric modelling of astrophysical objects, including brown dwarfs and exoplanets at temperatures up to 1,500K. The data are in two parts. The first, nh3_0-41.dat contains a list of 4,167,360 rovibrational states, ordered by J (max= 41), symmetry block and energy (in cm-1^). Only one third of the states (1,373,897) are within the parameters used for generating transitions (see above), but all the states are required for computing temperature-dependent partition functions. Each state is labelled with: seven normal mode vibrational quantum numbers; three rotational quantum numbers and the total symmetry quantum number, Gamma. In addition there are six local mode vibrational numbers and a local mode vibrational symmetry quantum numbers, which we include because the basis set used in our calculations is expressed in terms of these local mode quantum numbers. Each rovibrational state has a unique number, which is the number of the row in which it appears in the file. This number is the means by which the state is related to the second part of the data system, the transitions files. Because of their size, the transitions are listed in 120 separate files, each containing all the transitions in a 100cm-1^ frequency range. These and their contents are ordered by increasing frequency. The name of the file includes the lowest frequency in the range; thus the a-00500.dat file contains all the transitions in the frequency range 500-600cm-1^. The transition files contain three columns: the reference number in the energy file of the upper state; that of the lower state; and the Einstein A coefficient of the transition. The energy file and the transitions files are zipped, and need to be extracted before use. There is a Fortran 90 programme, sp_byte.f90 which may be used to generate synthetic spectra (see sp_byte.txt for details). Using this, it is possible to generate absorption or emission spectra in either 'stick' form or else convoluted with a gaussian with the half-width at half maximum being specified by the user, or with a the temperature-dependent doppler half-width. Three sample input files for use with sp_byte.f90 are supplied: "stick300.in", "gauss300.in", and "sp08900.in" (generates a spectrum for 8900-9000cm-1^). (126 data files).

Yurchenko, S. N.; Barber, R. J.; Tennyson, J.

2010-11-01

363

Hydrogen-release mechanisms in LiNH2BH3NH3BH3: A theoretical study  

NASA Astrophysics Data System (ADS)

The molecular mechanism of the dehydrogenation of LiNH2BH3NH3BH3 to form [LiN2B2H] by the loss of five molar equiv of H2 at two consecutive temperatures of 373 K and 501 K has been investigated using computational quantum chemistry methods (B3LYP, MP2 and CCSD(T) methods). The intermediate LiNHBH2NH2BH2 can be obtained through the pathway A at 373 K, in which LiH structures are formed by the transfer of hydridic H- from NH2BH3- to Li+ followed by the redox reactions of H?+ and H?- to form two molar equiv of H2. The intermediate LiNH2BHdbnd NHBH3 can also be generated via the pathway B at 373 K, in which a new Nsbnd B bond forms and two equiv of H2 are released by the redox reactions. At 501 K, the predominant final product P1 (LiNBNBH) is given most likely through the formation of LiH and a series of redox reactions with the loss of three molar equiv of H2 in the pathway A. Meanwhile, the products P2 (LiNBBNH) and P3 [Li(sbnd NBBNsbnd)H] may be also obtained by the dehydrogenation via a sequence of redox reactions of H?+ and H?- to release three equiv of H2 at the temperature of 501 K. The present study would be helpful for experimental chemists to design better hydrogen-storage media.

Tao, Jingcong; Lv, Naixia; Wen, Li; Qi, Yong; Lv, Xiaobo

2015-02-01

364

Computational study of the release of H2 from ammonia borane dimer (BH3NH3)2 and its ion pair isomers.  

PubMed

High-level electronic structure calculations have been used to map out the relevant portions of the potential energy surfaces for the release of H2 from dimers of ammonia borane, BH3NH3 (AB). Using the correlation-consistent aug-cc-pVTZ basis set at the second-order perturbation MP2 level, geometries of stationary points were optimized. Relative energies were computed at these points using coupled-cluster CCSD(T) theory with the correlation-consistent basis sets at least up to the aug-cc-pVTZ level and in some cases extrapolated to the complete basis set limit. The results show that there are a number of possible dimers involving different types of hydrogen-bonded interactions. The most stable gaseous phase (AB)2 dimer results from a head-to-tail cyclic conformation and is stabilized by 14.0 kcal/mol with respect to two AB monomers. (AB)2 can generate one or two H2 molecules via several direct pathways with energy barriers ranging from 44 to 50 kcal/mol. The diammoniate of diborane ion pair isomer, [BH4-][NH3BH2NH3+] (DADB), is 10.6 kcal/mol less stable than (AB)2 and can be formed from two AB monomers by overcoming an energy barrier of approximately 26 kcal/mol. DADB can also be generated from successive additions of two NH3 molecules to B2H6 and from condensation of AB with separated BH3 and NH3 molecules. The pathway for H2 elimination from DADB is characterized by a smaller energy barrier of 20.1 kcal/mol. The alternative ion pair [NH4+][BH3NH2BH3-] is calculated to be 16.4 kcal/mol above (AB)2 and undergoes H2 release with an energy barrier of 17.7 kcal/mol. H2 elimination from both ion pair isomers yields the chain BH3NH2BH2NH3 as product. Our results suggest that the neutral dimer will play a minor role in the release of H2 from ammonia borane, with a dominant role from the ion pairs as observed experimentally in ionic liquids and the solid state. PMID:17705356

Nguyen, Vinh Son; Matus, Myrna H; Grant, Daniel J; Nguyen, Minh Tho; Dixon, David A

2007-09-13

365

The fragmentation of protonated tyrosine and iodotyrosines: The effect of substituents on the losses of NH3 and of H2O and CO  

NASA Astrophysics Data System (ADS)

The gas-phase dissociation chemistries of protonated 3-iodo-l-tyrosine, 3,5-diiodo-l-tyrosine and 3,3',5,5'-tetraiodo-thyronine (thyroxine) have been examined using a combination of tandem mass spectrometry and density functional theory (DFT) calculations. It was found that, at low collision energy, all protonated tyrosines exhibit common fragmentation pathways, including the competitive eliminations of NH3 and the concomitant loss of H2O and CO, but there are significant differences in relative abundances, depending on the combined electron-donating abilities of the substituents in the phenyl ring. The ions initially formed by loss of NH3 are phenonium ions, but subsequent fragmentation is most easily understood in terms of the isomeric benzyl cation structures. These [M + H - NH3]+ ions fragment at relatively low collision energies, mainly by loss of ketene; by contrast, the [M + H - H2O - CO]+ ions are more stable towards dissociation. At higher collision energies, losses of one, two and even three iodine atoms were observed. DFT calculations (at the B3LYP/DZVP level of theory) were performed on protonated 3-iodotyrosine to compare the reaction profiles for the fragmentation mechanisms. The iodo-substituent in the 3-position is weakly electron-withdrawing and this results in a barrier (27.5 kcal/mol at 0 K) that is slightly higher than that for protonated tyrosine (26.8 kcal/mol). The phenoxy group PhO- is a weaker electron-donor than HO- and protonated 3,5-diiodo-4-phenoxytyrosine has an even higher barrier (31.1 kcal/mol) to NH3 loss than protonated 3,5-diiodotyrosine (28.8 kcal/mol). Linear free energy plots for ++ and ++ against [sigma]+ for the four protonated tyrosine derivatives show good correlations. More importantly, as the products of the dissociation are higher in energy than the transition states to their formation, the plots of and for the overall reaction for NH3 loss also correlate very well with [sigma]+ (correlation coefficients of 0.99 and 0.98, respectively). The positive slopes of these Hammett plots show that the barriers to the loss of NH3 by the neighboring-group mechanism are increased by the presence of electron-withdrawing groups in the phenyl rings.

Zhao, Junfang; Shoeib, Tamer; Siu, K. W. Michael; Hopkinson, Alan C.

2006-09-01

366

Non-Controlled Emission of Inorganic Toxic gas Components (CO, H2S, NH3 and Hg0) to the atmosphere from Arico's landfill, Tenerife, Canary Islands, Spain  

NASA Astrophysics Data System (ADS)

Landfill gas is mainly constituted by CO2 and CH4. However, other inorganic toxic gas components such as CO, NH3, H2S and Hg0, are also present. Reduced gas species are produced and released during the anaerobic decomposition of urban waste, while Hg0 is originally present in the waste and it is released as a volatile. Significant amounts of non-controlled emission of these components could be released to the atmosphere in the form of diffuse degassing, The goal of this study is to evaluate the "non-controlled" emissions of these inorganic toxic gas components from Arico's landfill, Tenerife. Arico's landfill (0.35 Km2) holds about 1,200 t/d of urban solid waste with an average organic matter content of 48%. Diffuse CO2 emission has been measured at the surface of Arico's landfill by means of a NDIR according with the accumulation chamber method. Landfill gases were also collected at 40 cm depth using a metallic probe and analyzed within 24 hours for CO2 and CO composition by means of a VARIAN micro-GC QUAD. H2S and Hg0 were analyzed by means of a Polytron-II electrochemical sensor and a JEROME 431-X mercury analyzer, respectively. NH3 was fixed in a boric acid solution and determined by means of a selective electrode. CO concentration ranged from non-detectable to 2,531 ppmv, with a median of 24.3 ppmv. The highest observed Hg0 concentration in the surface landfill gas is 0.004 ppbv, while H2S concentration reached levels up to 12 ppmv. NH3 contents were lower than 1 ppmv. CO, Hg0, H2S and NH3 fluxes have been estimated by multiplying CO2 efflux times (Tox.I.C.)i/CO2 where (Tox.I.C.)i is the concentration of CO, Hg0, H2S and NH3. The highest efflux values for CO, Hg0, H2S and NH3 were 6.8 gm-2d-1, 0.04 gm-2d-1, 1.7 mgm-2d-1 and 0.23 gm-2d-1, respectively.

Echeita, A.; Perez, C.; Hernandez, C.; Faria, L.; Lima, R.; Salazar, J.; Hernandez, P.; Perez, N.

2001-12-01

367

Glycolaldehyde, methyl formate and acetic acid adsorption and thermal desorption from interstellar ices  

NASA Astrophysics Data System (ADS)

We have undertaken a detailed investigation of the adsorption, desorption and thermal processing of the astrobiologically significant isomers glycolaldehyde, acetic acid and methyl formate. Here, we present the results of laboratory infrared and temperature programmed desorption (TPD) studies of the three isomers from model interstellar ices adsorbed on a carbonaceous dust grain analogue surface. Laboratory infrared data show that the isomers can be clearly distinguished on the basis of their infrared spectra, which has implications for observations of interstellar ice spectra. Laboratory TPD data also show that the three isomers can be distinguished on the basis of their thermal desorption behaviour. In particular, TPD data show that the isomers cannot be treated the same way in astrophysical models of desorption. The desorption of glycolaldehyde and acetic acid from water-dominated ices is very similar, with desorption being mainly dictated by water ice. However, methyl formate also desorbs from the surface of the ice, as a pure desorption feature, and therefore desorbs at a lower temperature than the other two isomers. This is more clearly indicated by models of the desorption on astrophysical time-scales corresponding to the heating rate of 25 and 5 M? stars. For a 25 M? star, our model shows that a proportion of the methyl formate can be found in the gas phase at earlier times compared to glycolaldehyde and acetic acid. This has implications for the observation and detection of these molecules, and potentially explains why methyl formate has been observed in a wider range of astrophysical environments than the other two isomers.

Burke, Daren J.; Puletti, Fabrizio; Brown, Wendy A.; Woods, Paul M.; Viti, Serena; Slater, Ben

2015-02-01

368

The effect of Al on Ga desorption during gas source-molecular beam epitaxial growth of AlGaN  

NASA Astrophysics Data System (ADS)

In this letter, we report on the impact aluminum has on gallium desorption kinetics in AlGaN alloys grown by gas source-molecular beam epitaxy. Aluminum is found to preferentially incorporate into the AlGaN films over the range of fluxes and temperatures investigated [0.05?Ji(Ga)?0.5 ML/s; 0.1?Ji(Al)?0.2 ML/s; 700 C?Ts?775 C]. As a result, Ga is not observed to incorporate into the film until the NH3 flux exceeds that required to grow stoichiometric AlN. This preferential incorporation stems from two facts: (a) Al has an ammonia cracking efficiency 2.5 times greater than that of Ga, and (b) Al participates in a Al-for-Ga exchange. As a result of these factors and under NH3 limited growth conditions, the aluminum mole fraction in a layer can be controlled by changing the incident NH3 flux.

Jenny, J. R.; Van Nostrand, J. E.; Kaspi, R.

1998-01-01

369

Direct Evidence for Ammonium Ion Formation in Ice through Ultraviolet-induced Acid-Base Reaction of NH3 with H3O+  

NASA Astrophysics Data System (ADS)

We present direct evidence for ammonium ion (NH4 +) formation through ultraviolet (UV) photolysis of NH3-H2O mixture ice that does not contain acids. NH4 + forms by the reaction of NH3 with protonic defects (H3O+) in the UV-photolyzed ice. Our observations may explain the deficient counter-anions in interstellar ice relative to the abundance of NH4 +. Also, H3O+ may play an important role in the acid-base chemistry of interstellar ice in UV-irradiating environments. IR absorption results suggest that NH4 + is a potential contributor to the interstellar 6.85 ?m band but is not a dominant component.

Moon, Eui-Seong; Kang, Heon; Oba, Yasuhiro; Watanabe, Naoki; Kouchi, Akira

2010-04-01

370

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

371

Photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 in the VUV region  

NASA Technical Reports Server (NTRS)

Using synchrotron radiation as a continuum light source, the photoabsorption and photoionization cross sections of NH3, PH3, H2S, C2H2, and C2H4 have been measured from their respective ionization thresholds to 1060 A. The vibrational constants associated with the nu(2) totally symmetric, out-of-plane bending vibration of the ground electronic state of PH3(+) have been obtained. The cross sections and quantum yields for producing neutral products through photoexcitation of these molecules in the given spectral regions have also been determined. In the present work, autoionization processes were found to be less important than dissociation and predissociation processes in NH3, PH3, and C2H4. Several experimental techniques have been employed in order to examine the various possible systematic errors critically.

Xia, T. J.; Chien, T. S.; Wu, C. Y. Robert; Judge, D. L.

1991-01-01

372

A laboratory Atlas of the 5 nu-1 NH3 absorption band at 6475 A with applications to Jupiter and Saturn  

NASA Technical Reports Server (NTRS)

A complete atlas of the 5 nu-1 absorption band of NH3 is presented together with measurements of the total band intensity, line intensities, and self-broadening coefficients. The spectrum, which is displayed in the interval from 6418 to 6550 A, was obtained photoelectrically at a pressure of 0.061 atm, and many more lines were seen in this spectrum than in a previous one obtained at a pressure of 0.39 atm. The band intensity is used to derive the NH3 abundance in the atmospheres of Jupiter and Saturn, and the abundances in a single vertical path are found to be about 10 m amagat for Jupiter and 2 m amagat for Saturn. These results are shown to be in agreement with previous results obtained from higher resolution photographic spectra.

Giver, L. P.; Miller, J. H.; Boese, R. W.

1975-01-01

373

Effect of rutile phase on V2O5 supported over TiO2 mixed phase for the selective catalytic reduction of NO with NH3  

NASA Astrophysics Data System (ADS)

A series of V2O5/TiO2 catalysts with different ratios of TiO2 rutile phase was prepared. Focusing on the effect of TiO2 rutile phase on V2O5/TiO2 catalyst for the selective catalytic reduction (SCR) of NO with NH3, the NO conversion for the different catalysts was investigated. The experimental results showed that a small amount of TiO2 rutile phase could improve the NO conversion significantly below 270 C. Analysis by XRD, NH3-TPD, UV-vis, EPR and DFT calculation showed that the rutile phase of TiO2 supporter decreased the band gap, especially, the conduction band level. It improved the formation of reduced V species and superoxide ions that were important to the low-temperature SCR reaction.

Zhang, Shule; Zhong, Qin; Wang, Yining

2014-09-01

374

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

375

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

376

Neutral and ion chemistry in low pressure dc plasmas of H2/N2 mixtures: routes for the efficient production of NH3 and NH4(+).  

PubMed

The chemistry in low pressure (0.8-8 Pa) plasmas of H(2) + 10% N(2) mixtures has been experimentally investigated in a hollow cathode dc reactor using electrical probes for the estimation of electron temperatures and densities, and mass spectrometry to determine the concentration of ions and stable neutral species. The analysis of the measurements by means of a kinetic model has allowed the identification of the main physicochemical mechanisms responsible for the observed distributions of neutrals and ions and for their evolution with discharge pressure. The chemistry of neutral species is dominated by the formation of appreciable amounts of NH(3) at the metallic walls of the reactor through the successive hydrogenation of atomic nitrogen and nitrogen containing radicals. Both Eley-Rideal and Langmuir-Hinshelwood mechanisms are needed in the chain of hydrogenation steps in order to account satisfactorily for the observed ammonia concentrations, which, in the steady state, are found to reach values ~30-70% of those of N(2). The ionic composition of the plasma, which is entirely due to gas-phase processes, is the result of a competition between direct electron impact dissociation, more relevant for high electron temperatures (lower pressures), and ion-molecule chemistry that prevails for the lower electron temperatures (higher pressures). At the lowest pressure, products from the protonation of the precursor molecules (H(3)(+), N(2)H(+) and NH(4)(+)) and others from direct ionization (H(2)(+) and NH(3)(+)) are found in comparable amounts. At the higher pressures, the ionic distribution is largely dominated by ammonium. It is found that collisions of H(3)(+), NH(3)(+) and N(2)H(+) with the minor neutral component NH(3) are to a great extent responsible for the final prevalence of NH(4)(+). PMID:21984202

Carrasco, Esther; Jimnez-Redondo, Miguel; Tanarro, Isabel; Herrero, Vctor J

2011-11-21

377

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

2009-01-01

378

Resonant third-order optical nonlinearity in the layered perovskite-type material (C 6H 13NH 3) 2PbI 4  

Microsoft Academic Search

The third-order nonlinear optical susceptibility, ?(3) (??;?, ??, ?), of the layered perovskite-type material (C6H13NH3)2PbI4 is measured by a transient four-wave mixing technique using a 200-fs-pulse laser source. The maximum ?(3) value is 1.6 10?6 esu at the lowest-exciton resonance at 8 K. Longitudinal and transverse relaxation times of the excitons are 7 ps and 0.2 ps, respectively.

Takashi Kondo; Satoshi Iwamoto; Shigenori Hayase; Kenichiro Tanaka; Junko Ishi; Masatomo Mizuno; Kazuhiro Ema; Ryoichi Ito

1998-01-01

379

Phase transition in [Ca(NH 3) 6](ClO 4) 2 studied by neutron scattering methods and far infrared spectroscopy  

Microsoft Academic Search

The results of inelastic and quasi-elastic incoherent neutron scattering with simultaneous neutron powder diffraction and of Fourier transform far infrared spectroscopy measurements carried out for [Ca(NH3)6](ClO4)2 between 20220K and 8.5295K, respectively, are reported. The far infrared spectrum on cooling the substance indicates splitting of some degenerated vibrational modes, which suggests lowering of the crystal structure at the phase transition temperature

Joanna Hetma?czyk; ?ukasz Hetma?czyk; Anna Migda?-Mikuli; Edward Mikuli; Ireneusz Natkaniec

2011-01-01

380

Liquid phase deposition of TiO2 nanolayer affords CH3NH3PbI3/nanocarbon solar cells with high open-circuit voltage.  

PubMed

Hybrid organic/inorganic perovskite solar cells are attracting intense attention and further developments largely hinge on understanding the fundamental issues involved in the cell operation. In this paper, a liquid phase deposition (LPD) method is developed to design and grow a TiO2 nanolayer at room temperature for carbon-based perovskite solar cells. The TiO2 nanolayer grown on FTO glass is compact but polycrystalline consisting of tiny anatase TiO2 nanocrystals intimately stacked together. By directly exploiting this TiO2 nanolayer in a solar cell of TiO2 nanolayer/CH3NH3PbI3/nanocarbon, we have achieved a Voc as high as 1.07 V, the highest value reported so far for hole transporter-free CH3NH3PbI3 solar cells. This is rationalized by the slower electron injection and longer electron lifetime due to the TiO2 nanolayer, which enhances the electron accumulation in CH3NH3PbI3 and consequently the Voc. By employing a rutile TiO2 nanorod (NR) array as a base structure for the LPD-TiO2 nanolayer to support the CH3NH3PbI3 layer, the photocurrent density is considerably increased without obviously compromising the Voc (1.01 V). As a result, the power conversion efficiency is boosted from 3.67% to 8.61%. More elaborate engineering of the TiO2 nanolayer by LPD in conjunction with judicious interfacing with other components has the potential to achieve higher performances for this type of solar cell. PMID:25406400

Chen, Haining; Wei, Zhanhua; Yan, Keyou; Yi, Ya; Wang, Jiannong; Yang, Shihe

2014-11-14

381

Non-Controlled Emission of Inorganic Toxic gas Components (CO, H2S, NH3 and Hg0) to the atmosphere from Arico's landfill, Tenerife, Canary Islands, Spain  

Microsoft Academic Search

Landfill gas is mainly constituted by CO2 and CH4. However, other inorganic toxic gas components such as CO, NH3, H2S and Hg0, are also present. Reduced gas species are produced and released during the anaerobic decomposition of urban waste, while Hg0 is originally present in the waste and it is released as a volatile. Significant amounts of non-controlled emission of

A. Echeita; C. Perez; C. Hernandez; L. Faria; R. Lima; J. Salazar; P. Hernandez; N. Perez

2001-01-01

382

INTERACTION OF LASER RADIATION WITH MATTER: IR multiphoton dissociation of trichlorosilane induced by pulsed CO2 and NH3 laser radiation  

NASA Astrophysics Data System (ADS)

The IR multiphoton dissociation of trichlorosilane (SiHCl3) molecules irradiated by pulses from CO2 and NH3 lasers is studied. The dependences of dissociation yield on the frequency and energy density of laser radiation, as well as on the parent pressure of SiHCl3, are determined. It is found that HCl and a solid precipitate, probably with a common chemical formula (SiCl2)n, are the main products of dissociation of trichlorosilane.

Apatin, V. M.; Laptev, Vladimir B.; Ryabov, Evgenii A.

2003-10-01

383

Nickel oxide electrode interlayer in CH3 NH3 PbI3 perovskite/PCBM planar-heterojunction hybrid solar cells.  

PubMed

This study successfully demonstrates the application of inorganic p-type nickel oxide (NiOx ) as electrode interlayer for the fabrication of NiOx /CH3 NH3 PbI3 perovskite/PCBM PHJ hybrid solar cells with a respectable solar-to-electrical PCE of 7.8%. The better energy level alignment and improved wetting of the NiOx electrode interlayer significantly enhance the overall photovoltaic performance. PMID:24687334

Jeng, Jun-Yuan; Chen, Kuo-Cheng; Chiang, Tsung-Yu; Lin, Pei-Ying; Tsai, Tzung-Da; Chang, Yun-Chorng; Guo, Tzung-Fang; Chen, Peter; Wen, Ten-Chin; Hsu, Yao-Jane

2014-06-25

384

Full Printable Processed Mesoscopic CH3NH3PbI3/TiO2 Heterojunction Solar Cells with Carbon Counter Electrode  

NASA Astrophysics Data System (ADS)

A mesoscopic methylammonium lead iodide (CH3NH3PbI3) perovskite/TiO2 heterojunction solar cell is developed with low-cost carbon counter electrode (CE) and full printable process. With carbon black/spheroidal graphite CE, this mesoscopic heterojunction solar cell presents high stability and power conversion efficiency of 6.64%, which is higher than that of the flaky graphite based device and comparable to the conventional Au version.

Ku, Zhiliang; Rong, Yaoguang; Xu, Mi; Liu, Tongfa; Han, Hongwei

2013-11-01

385

Tuning the pore sizes of novel silica membranes for improved gas permeation properties via an in situ reaction between NH3 and Si-H groups.  

PubMed

A new concept was proposed to control the pore size in a novel silica membrane. The tuning of the pore sizes in triethoxysilane (TRIES)-derived membranes was successfully conducted via an in situ reaction between NH3 and Si-H groups at high temperatures. The formation of Si-NH2 and/or Si-NH groups in the silica structure enhanced the hydrogen selectivity. PMID:25566848

Kanezashi, Masakoto; Matsugasako, Rui; Tawarayama, Hiromasa; Nagasawa, Hiroki; Yoshioka, Tomohisa; Tsuru, Toshinori

2015-01-29

386

Regulation of Nitrification by Benzotriazole, oNitrophenol, m-Nitroaniline and Dicyandiamide and Pattern of NH3 Emissions from Citronella Field Fertilized with Urea  

Microsoft Academic Search

Nitrification inhibitors areuseful for reducing fertilizer related environmentalpollution. Use of such nitrification inhibitors as,benzotriazole, o-nitrophenol, m-nitroaniline anddicyandiamide has effectively regulated nitrification in acitronella (Cymbopogon winterianus Jowitt.) fieldfertilized with urea. At 450 kg N ha-1 yr-1, there wassubstantially higher accumulation of NH+4-N in thesoil. Proper placement (5 cm below soil surface) offertilizers have minimized NH3 emissions even fromnitrification inhibitor treated urea

K. Puttanna; N. M. Nanje Gowda; E. V. S. Prakasa Rao

2001-01-01

387

Vibrational analysis of pyramidal XY3-type molecules based on high-level ab initio potential energy surfaces: application to NH3  

Microsoft Academic Search

Variational calculations of the vibrational energies of the non-rigid and semirigid XY3 molecules, as ammonia and phosphine respectively, have been carried out [1,2]. In the procedure used is emphasized the umbrella motion due to the corresponding coordinate, for pyramidal non-rigid XY3 molecules, is the responsible of the torsional tunneling between different minima of the Potential Energy Surfaces. For the NH3

H. Lin; W. Thiel; S. N. Yurchenko; M. Carvajal; P. Jensen

2003-01-01

388

NMR observation of oblique phase in mixed crystals (CH3NH3)2Cu(Cl1-xBrx)4(0.5<=x<=1)  

Microsoft Academic Search

It was recently reported by Kimishima that the transition from the ferromagnetic to the antiferromagnet occurs at x ~ 0.9 in a mixed compound of (CH3NH3)2Cu(Cl1-xBrx)4. By the Cl NMR, we show that in the concentration region of the oblique phase, the Br- ions occupy a position on the c-axis, contrary to anticipation.

H. Kubo; Y. Suzuki; K. Hirakawa

1983-01-01

389

Ammonia emissions in the United States, European Union, and China derived by high-resolution inversion of ammonium wet deposition data: Interpretation with a new agricultural emissions inventory (MASAGE_NH3)  

NASA Astrophysics Data System (ADS)

We use the adjoint of a global 3-D chemical transport model (GEOS-Chem) to optimize ammonia (NH3) emissions in the U.S., European Union, and China by inversion of 2005-2008 network data for NH4+ wet deposition fluxes. Optimized emissions are derived on a 2 2.5 grid for individual months and years. Error characterization in the optimization includes model errors in precipitation. Annual optimized emissions are 2.8 Tg NH3-N a-1 for the contiguous U.S., 3.1 Tg NH3-N a-1 for the European Union, and 8.4 Tg NH3-N a-1 for China. Comparisons to previous inventories for the U.S. and European Union show consistency (15%) in annual totals but some large spatial and seasonal differences. We develop a new global bottom-up inventory of NH3 emissions (Magnitude And Seasonality of Agricultural Emissions model for NH3 (MASAGE_NH3)) to interpret the results of the adjoint optimization. MASAGE_NH3 provides information on the magnitude and seasonality of NH3 emissions from individual crop and livestock sources on a 0.5 0.5 grid. We find that U.S. emissions peak in the spring in the Midwest due to corn fertilization and in the summer elsewhere due to manure. The seasonality of European emissions is more homogeneous with a well-defined maximum in spring associated with manure and mineral fertilizer application. There is some evidence for the effect of European regulations of NH3 emissions, notably a large fall decrease in northern Europe. Emissions in China peak in summer because of the summertime application of fertilizer for double cropping.

Paulot, F.; Jacob, D. J.; Pinder, R. W.; Bash, J. O.; Travis, K.; Henze, D. K.

2014-04-01

390

The release of trapped gases from amorphous solid water films. II. ``Bottom-up'' induced desorption pathways  

NASA Astrophysics Data System (ADS)

In this (Paper II) and the preceding companion paper (Paper I; R. May, R. Smith, and B. Kay, J. Chem. Phys. 138, 104501 (2013), 10.1063/1.4793311), we investigate the mechanisms for the release of trapped gases from underneath amorphous solid water (ASW) films. In Paper I, we focused on the low coverage regime where the release mechanism is controlled by crystallization-induced cracks formed in the ASW overlayer. In that regime, the results were largely independent of the particular gas underlayer. Here in Paper II, we focus on the high coverage regime where new desorption pathways become accessible prior to ASW crystallization. In contrast to the results for the low coverage regime (Paper I), the release mechanism is a function of the multilayer thickness and composition, displaying dramatically different behavior between Ar, Kr, Xe, CH4, N2, O2, and CO. Two primary desorption pathways are observed. The first occurs between 100 and 150 K and manifests itself as sharp, extremely narrow desorption peaks. Temperature programmed desorption is utilized to show that these abrupt desorption bursts are due to pressure induced structural failure of the ASW overlayer. The second pathway occurs at low temperature (typically <100 K) where broad desorption peaks are observed. Desorption through this pathway is attributed to diffusion through pores formed during ASW deposition. The extent of desorption and the line shape of the low temperature desorption peak are dependent on the substrate on which the gas underlayer is deposited. Angle dependent ballistic deposition of ASW is used to vary the porosity of the overlayer and strongly supports the hypothesis that the low temperature desorption pathway is due to porosity that is templated into the ASW overlayer by the underlayer during deposition.

Alan May, R.; Scott Smith, R.; Kay, Bruce D.

2013-03-01

391

The Release of Trapped Gases from Amorphous Solid Water Films: II. Bottom-Up Induced Desorption Pathways  

SciTech Connect

In this (Paper II) and the preceding companion paper (Paper I) we investigate the mechanisms for the release of trapped gases from underneath of amorphous solid water (ASW) films. In Paper I, we focused on the low coverage (pressure) regime where the release mechanism is controlled by crystallization-induced cracks formed in the ASW overlayer. In that regime the results were largely independent of the particular gas underlayer. Here in Paper II, we focus on the high coverage (pressure) regime where new desorption pathways become accessible prior to ASW crystallization. In contrast to the results for the low coverage regime (Paper I), the release mechanism is a function of the multilayer thickness and composition, displaying dramatically different behavior between Ar, Kr, Xe, CH4, N2, O2, and CO. Two primary desorption pathways are observed. The first occurs between 100 and 150 K and manifests itself as sharp, extremely narrow desorption peaks. Temperature programmed desorption is utilized to show that abrupt desorption bursts are due to pressure induced structural failure of the ASW overlyaer. The second pathway occurs at low temperature (typically <100 K) where broad desorption peaks are observed. Desorption through this pathway is attributed to diffusion through pores and connected pathways formed during ASW deposition. The extent of desorption and the lineshape of the low temperature desorption peak are dependent on the substrate on which the gas underlayer is deposited. Angle dependent ballistic deposition of the ASW is used vary the porosity of overlayer and confirm that the low temperature desorption pathway is due to porosity that is inherent in the ASW overlayer during deposition.

May, Robert A.; Smith, R. Scott; Kay, Bruce D.

2013-03-14

392

n-alkanes on Pt(111) and on C(0001)/Pt(111): Chain Length Dependence of Kinetic Desorption Parameters  

SciTech Connect

We have measured the desorption of seven small n-alkanes (CNH2N+2, N = 1-4, 6, 8, 10) from the Pt(111) and C(0001) surfaces by temperature programmed desorption. We compare these results to our recent study of the desorption kinetics of these molecules on MgO(100) [J. Chem. Phys. 122, 164708 (2005)]. There we showed an increase in the desorption pre-exponential factor by several orders of magnitude with increasing n-alkane chain length and a linear desorption energy scaling with a small y-intercept value. We suggest that the significant increase in desorption prefactor with chain length is not particular to the MgO(100) surface, but is a general effect for desorption of the small n-alkanes. This argument is supported by statistical mechanical arguments for the increase in the entropy gain of the molecules upon desorption. In this work, we demonstrate that this hypothesis holds true on both a metal surface and a graphite surface. We observe an increase in prefactor by five orders of magnitude over the range of n-alkane chain lengths studied here. On each surface, the desorption energies of the n-alkanes are found to increase linearly with the molecule chain length and have a small y-intercept value. Prior results of other groups have yielded a linear desorption energy scaling with chain length that has unphysically large y-intercept values. We demonstrate that by allowing the prefactor to increase according to our model, a reanalysis of their data resolves this y-intercept problem to some degree.

Tait, Steven L.; Dohnalek, Zdenek; Campbell, Charles T.; Kay, Bruce D.

2006-12-21

393

Mechanism of N2O formation during the low-temperature selective catalytic reduction of NO with NH3 over Mn-Fe spinel.  

PubMed

The mechanism of N2O formation during the low-temperature selective catalytic reduction reaction (SCR) over Mn-Fe spinel was studied. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and transient reaction studies demonstrated that the Eley-Rideal mechanism (i.e., the reaction of adsorbed NH3 species with gaseous NO) and the Langmuir-Hinshelwood mechanism (i.e., the reaction of adsorbed NH3 species with adsorbed NOx species) both contributed to N2O formation. However, N2O selectivity of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism was much less than that through the Eley-Rideal mechanism. The ratio of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism remarkably increased; therefore, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the decrease of the gas hourly space velocity (GHSV). As the gaseous NH3 concentration increased, N2O selectivity of NO reduction over Mn-Fe spinel increased because of the promotion of NO reduction through the Eley-Rideal mechanism. Meanwhile, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the increase of the gaseous NO concentration because the formation of NH on Mn-Fe spinel was restrained. Therefore, N2O selectivity of NO reduction over Mn-Fe spinel was related to the GHSV and concentrations of reactants. PMID:25105802

Yang, Shijian; Xiong, Shangchao; Liao, Yong; Xiao, Xin; Qi, Feihong; Peng, Yue; Fu, Yuwu; Shan, Wenpo; Li, Junhua

2014-09-01

394

Bromine NMR Study of Cupric Compounds (CnH2n+1NH3)2CuBr4 (n{=}1, 2)  

NASA Astrophysics Data System (ADS)

The spin structure of (CnH2n+1NH3)2CuBr4 (n{=}1, 2) is studied by Br NMR at 1.7 K. In (C2H5NH3)2CuBr4, the magnetic space group is Pb'c'a type and the moment direction inclines at an angle of 49.5 with the c-axis. A weak ferromagnetic moment appears along to the c-axis. The anisotropic exchange field is estimated to be 2.5 kOe. The inter-layer exchange field and the out-of-layer anisotropy field are much smaller than previously reported values. The parameters of Br nuclear spin Hamiltonian are also obtained. In (CH3NH3)2CuBr4, the moment direction inclines at 27 with the c-axis. It is difficult to interpret the NMR results by the two-sublattice model. A model of the four-sublattice antiferromagnet is developped.

Suzuki, Yoshio; Tsuru, Kazuo; Kimishima, Yoshihide; Kubo, Hidenori

1981-05-01

395

A Novel Phosphovanadate of Co(III) Hexammine: Co(NH 3) 6(V 1.5P 0.5)O 6OH  

NASA Astrophysics Data System (ADS)

The new phosphovanadate Co(NH3)6(V1.5P0.5)O6OH has been synthesized by a hydrothermal method at 220C. It crystallizes in the P21/c space group with a=9.5206(8), b=6.9631(6), c=17.108(1), ?=93.028(7), and Z=4. The structural resolution using single-crystal X-ray diffraction leads to R(Fo)=3.63% and Rw(F2o)=10.67%. This structure consists of [Co(NH3)6]3+ cations and [V1.5P0.5O6OH]3- anions assembled in a distorted rock salt arrangement. The presence of the Co(III) hexammine complex [Co(NH3)6]3+ is particularly original in this structure since no complexes have been isolated up to now in phosphovanadates. The V1.5P0.5O6OH diphosphovanadate group, with one vanadium tetrahedral site and one tetrahedral site statistically occupied by 0.5 vanadium and 0.5 phosphorus atom, corresponds to the random distribution of V2O6OH and VPO6OH groups as confirmed by the IR spectroscopy study. Magnetic measurements show that the Co(III) cation adopts a low spin configuration.

Boudin, S.; Chardon, J.; Daturi, M.; Raveau, B.

2001-06-01

396

Efficient perovskite solar cells based on low-temperature solution-processed (CH3NH3)PbI3 perovskite/CuInS2 planar heterojunctions.  

PubMed

In this work, the solution-processed CH3NH3PbI3 perovskite/copper indium disulfide (CuInS2) planar heterojunction solar cells with Al2O3 as a scaffold were fabricated at a temperature as low as 250C for the first time, in which the indium tin oxide (ITO)-coated glass instead of the fluorine-doped tin oxide (FTO)-coated glass was used as the light-incidence electrode and the solution-processed CuInS2 layer was prepared to replace the commonly used TiO2 layer in previously reported perovskite-based solar cells. The influence of the thickness of the as-prepared CuInS2 film on the performance of the ITO/CuInS2(n)/Al2O3/(CH3NH3)PbI3/Ag cells was investigated. The ITO/CuInS2(2)/Al2O3/(CH3NH3)PbI3/Ag cell showed the best performance and achieved power conversion efficiency up to 5.30%. PMID:25278818

Chen, Chong; Li, Chunxi; Li, Fumin; Wu, Fan; Tan, Furui; Zhai, Yong; Zhang, Weifeng

2014-01-01

397

GaN CVD Reactions: Hydrogen and Ammonia Decomposition and the Desorption of Gallium  

SciTech Connect

Isotopic labeling experiments have revealed correlations between hydrogen reactions, Ga desorption, and ammonia decomposition in GaN CVD. Low energy electron diffraction (LEED) and temperature programmed desorption (TPD) were used to demonstrate that hydrogen atoms are available on the surface for reaction after exposing GaN(0001) to deuterium at elevated temperatures. Hydrogen reactions also lowered the temperature for Ga desorption significantly. Ammonia did not decompose on the surface before hydrogen exposure. However, after hydrogen reactions altered the surface, N15H3 did undergo both reversible and irreversible decomposition. This also resulted in the desorption of N2 of mixed isotopes below the onset of GaN sublimation, This suggests that the driving force of the high nitrogen-nitrogen bond strength (226 kcal/mol) can lead to the removal of nitrogen from the substrate when the surface is nitrogen rich. Overall, these findings indicate that hydrogen can influence G-aN CVD significantly, being a common factor in the reactivity of the surface, the desorption of Ga, and the decomposition of ammonia.

Bartram, Michael E.; Creighton, J. Randall

1999-05-26

398

Photodissociation and desorption of multilayer acetone on a Si(100) surface by 193 nm laser irradiation  

NASA Astrophysics Data System (ADS)

Thermal desorption spectra of acetone on Si(100) were measured using a temperature programmed desorption (TPD) technique. Acetone molecules condensed on a Si(100) at 95 K desorbed at 133 K. The peak profile indicated a zeroth-order desorption mechanism. The desorption energy was estimated to be 47.6 4 kJ/mol. Dissociation and desorption of the acetone molecules condensed on the surface by 193 nm pulsed laser irradiation were investigated with a quadrupole mass spectrometer using a time-of-flight technique. When high fluence laser pulses of 363 mJ/cm 2 were irradiated to a thick layer of acetone formed by an exposure of 1500 L, hyperthermal acetone molecules of about 2 eV were observed desorbing from the surface. Acetyl and methyl radicals formed by dissociation were also vaporized simultaneously. Thermal dissociation of acetone leading to 2CH 3 and CO as products occurred slowly after the laser irradiation. These dissociation processes are different from those in the gas phase.

Kusunoki, I.; Sakashita, M.; Takaoka, T.; Range, H.

1996-06-01

399

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

400

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 at seven remote sites representative of major African ecosystems. Dry deposition fluxes were estimated by the inferential method using on the one hand surface measurements of gas concentrations (NO2, HNO3, NH3, SO2 and O3) and on the other hand modeled exchange rates. Dry deposition velocities (Vd) were calculated using the big-leaf model of Zhang et al. (2003b). The bidirectional approach is used for NH3 surface-atmosphere exchange (Zhang et al., 2010). Surface and meteorological conditions specific to IDAF sites have been used in the models of deposition. The 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 to -0.8 kg N ha-1 yr-1 for NO2, from -0.7 to -1.0 kg N ha-1 yr-1 for HNO3 and from -0.7 to -8.3 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 (-10 kg N ha-1 yr-1) than in wet and dry savannas (-1.6 to -3.9 kg N ha-1 yr-1). The annual mean dry deposition fluxes of ozone range between -11 and -19 kg ha-1 yr-1 in dry and wet savannas, and -11 and -13 kg ha-1 yr-1 in forests. Lowest O3 dry deposition fluxes in forests are correlated to low measured O3 concentrations, lower by a factor of 2-3, compared to other ecosystems. Along the ecosystem transect, the annual mean of SO2 dry deposition fluxes presents 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.; Delon, C.; Yoboue, V.; Solmon, F.; Kaptue Tchuente, A. T.

2013-11-01

401

Adsorption equilibrium and kinetics of CO2, CH4, N2O, and NH3 on ordered mesoporous carbon.  

PubMed

Ordered mesoporous carbon was synthesized by a self-assembly technique and characterized with TEM, Raman spectroscopy, and nitrogen adsorption/desorption for its physical and pore textural properties. The high BET specific surface area (798 m(2)/g), uniform mesopore-size distribution with a median pore size of 62.6 , and large pore volume (0.87 cm(3)/g) make the ordered mesoporous carbon an ideal adsorbent for gas separation and purification applications. Adsorption equilibrium and kinetics of carbon dioxide, methane, nitrous oxide, and ammonia on the ordered mesoporous carbon were measured at 298 K and gas pressures up to 800 Torr. The adsorption equilibrium capacities on the ordered mesoporous carbon at 298 K and 800 Torr for ammonia, carbon dioxide, nitrous oxide, and methane were found to be 6.39, 2.39, 1.5, and 0.53 mmol/g, respectively. Higher adsorption uptakes of methane (3.26 mmol/g at 100 bar) and carbon dioxide (2.21 mmol/g at 13 bar) were also observed at 298 K and elevated pressures. Langmuir, Freundlich, and Toth adsorption equilibrium models were used to correlate all the adsorption isotherms, and a simplified gas diffusion model was applied to analyze the adsorption kinetics data collected at 298 K and four different gas pressures up to 800 Torr. PMID:20185144

Saha, Dipendu; Deng, Shuguang

2010-05-15

402

Ion desorption from molecules condensed at low temperature: A study with electron-ion coincidence spectroscopy combined with synchrotron radiation (Review)  

NASA Astrophysics Data System (ADS)

This article reviews our recent work on photostimulated ion desorption (PSID) from molecules condensed at low temperature. We have used electron-ion coincidence (EICO) spectroscopy combined with synchrotron radiation. The history and present status of the EICO apparatus is described, as well as our recent investigations of condensed H2O, NH3, CH3CN, and CF3CH3. Auger electron photon coincidence (AEPICO) spectra of condensed H2O at the O:1s ionization showed that H+ desorption was stimulated by O:KVV Auger processes leading to two-hole states (normal-Auger stimulated ion desorption (ASID) mechanism). The driving forces for H+ desorption were attributed to the electron missing in the O-H bonding orbitals and the effective hole-hole Coulomb repulsion. The normal ASID mechanism was also demonstrated for condensed NH3. The H+ desorption at the 4a1?O(N):1s resonance of both condensed H2O and condensed NH3 was found to be greatly enhanced. Based on the AEPICO spectra the following four-step mechanism was proposed: (1) the 4a1?1s transition, (2) extension of the HO-H (H2N-H) distance within the lifetime of the (1s)-1(4a1)1 state, (3) spectator Auger transitions leading to (valence)-2(4a1)1 states, and (4) H+ desorption. The enhancement of the H+ desorption yield was attributed to the repulsive potential surface of the (1s)-1(4a1)1 state. At the 3p?O:1s resonance of condensed H2O, on the other hand, the H+ yield was found to be decreased. The AEPICO spectra showed that the H+ desorption was stimulated by spectator Auger transitions leading to (valence)-2(3p)1 states. The decrease in the H+ yield was attributed to a reduction in the effective hole-hole Coulomb repulsion due to shielding by the 3p electron. Photoelectron photon coincidence (PEPICO) spectra of condensed H2O showed that the core level of the surface H2O responsible for the H+ desorption was shifted by 0.7 eV from that of the bulk H2O. The H+ desorption from condensed CH3CN was also investigated. In a study of condensed CF3CH3 using PEPICO spectroscopy, site-specific ion desorption was directly verified; that is, H+ and CH3+ desorption was predominant for the C:1s photoionization at the -CH3 site, while C2Hn+, CFCHm+, and CF3+ desorption was predominantly induced by the C:1s photoionization at the -CF3 site. These investigations demonstrate that EICO spectroscopy combined with synchrotron radiation is a powerful tool for studying PSID of molecules condensed at low temperature.

Mase, Kazuhiko; Nagasono, Mitsuru; Tanaka, Shin-ichiro; Sekitani, Tetsuji; Nagaoka, Shin-ichi

2003-03-01

403

Phosphate binding and ATP-binding sites coexist in Na+/K(+)-transporting ATPase, as demonstrated by the inactivating MgPO4 complex analogue Co(NH3)4PO4.  

PubMed

Tetrammine cobalt(III) phosphate [Co(NH3)4PO4] inactivates Na+/K(+)-ATPase in the E2 conformational state, dependent on time and concentration, according to Eqn (1): Co(NH3)4PO4 + E2 Kd in equilibrium E2.Co(NH3)4PO4k2----E'2.Co(NH3)4PO4. The inactivation rate constant k2 for the formation of a stable E'2.Co(NH3)4PO4 at 37 degrees C was 0.057 min-1; the dissociation constant, Kd = 300 microM. The activation energy for the inactivation process was 149 kJ/mol. ATP and the uncleavable adenosine 5'-[beta, gamma-methylene]triphosphate competed with Co(NH3)4PO4 for its binding site with Ks = 0.41 mM and 5 mM, respectively. MgPO4 competed with Co(NH3)4PO4 linearly, with Ks = 50 microM, as did phosphate (Ks = 16 mM) and Mg2+ (Ks = 160 microM). It is concluded that the MgPO4 analogue binds to the MgPO4-binding subsite of the low-affinity ATP-binding site (of the E2 conformation). Also, Na+ (Ks = 860 microM) protected the enzyme against inactivation in a competitive manner. From the intersecting (slope and intercept linear) noncompetitive effect of Na+ against the inactivation by Co(NH3)4PO4, apparent affinities of K+ for the free enzyme of 41 microM, and for the E.Co(NH3)4PO4 complex of 720 microM, were calculated. Binding of Co(NH3)4PO4 to the enzyme inactivated Na+/K(+)-ATPase and K(+)-activated phosphatase, and, moreover, prevented the occlusion of 86Rb+; however, the activity of the Na(+)-ATPase, the phosphorylation capacity of the high-affinity ATP-binding site and the ATP/ADP-exchange reaction remained unchanged. With Co(NH3)432PO4 a binding capacity of 135 pmol unit enzyme was found. Phosphorylation and complete inactivation of the enzyme with Co(NH3)432PO4 or the 32P-labelled tetramminecobalt ATP ([gamma-32P]Co(NH3)4ATP) at the low-affinity ATP-binding site, allowed (independent of the purity of the Na+/K(+)-ATPase preparation) a further incorporation of radioactivity from 32P-labelled tetraaquachromium(III) ATP ([gamma-32P]CrATP) to the high-affinity ATP-binding site with unchanged phosphorylation capacity. However, inactivation and phosphorylation of Na+/K(+)-ATPase by [gamma-32P]CrATP prevented the binding of Co(NH3)4 32PO4 or [gamma-32P]Co(NH3)4ATP to the enzyme. [gamma-32P]CO(NH3)4ATP and Co(NH3)432PO4 are mutually exclusive. The data are consistent with the assumption of a cooperation of catalytic subunits within an (alpha,beta)2-diprotomer, which change their interactions during the Na+/K(+)-pumping process. Our findings seem not to support a symmetrical Repke and Stein model of enzyme action. PMID:1847680

Buxbaum, E; Schoner, W

1991-01-30

404

Expression of the human erythroid Rh glycoprotein (RhAG) enhances both NH3 and NH4+ transport in HeLa cells.  

PubMed

The erythroid Rh-associated glycoprotein (RhAG) is strictly required for the expression of the Rh blood group antigens carried by Rh (D,CE) proteins. A biological function for RhAG in ammonium transport has been suggested by its ability to improve survival of an ammonium-uptake-deficient yeast. We investigated the function of RhAG by studying the entry of NH3/NH4+ in HeLa cells transiently expressing the green fluorescent protein (GFP)-RhAG fusion protein and using a fluorescent proton probe to measure intracellular pH (pHi). Under experimental conditions that reduce the intrinsic Na/H exchanger activity, exposure of control cells to a 10 mM NH4Cl- containing solution induces the classic pHi response profile of cells having a high permeability to NH3 (PNH3) but relatively low permeability to NH4+ (PNH4). In contrast, under the same conditions, the pHi profile of cells expressing RhAG clearly indicated an increased PNH4, as evidenced by secondary reacidification during NH4Cl exposure and a pHi undershoot below the initial resting value upon its removal. Measurements of pHi during methylammonium exposure showed that RhAG expression enhances the influx of both the unprotonated and ionic forms of methylammonium. Using a mathematical model to adjust passive permeabilities for a fit to the pHi profiles, we found that RhAG expression resulted in a threefold increase of PNH4 and a twofold increase of PNH3. Our results are the first evidence that the human erythroid RhAG increases the transport of both NH3 and NH4+. PMID:15856280

Benjelloun, Fatine; Bakouh, Naziha; Fritsch, Janine; Hulin, Philippe; Lipecka, Joanna; Edelman, Aleksander; Planelles, Gabrielle; Thomas, S Randall; Chrif-Zahar, Baya

2005-06-01

405

Complexes of XeHXe(+) with Simple Ligands: A Theoretical Investigation on (XeHXe(+))L (L = N2, CO, H2O, NH3).  

PubMed

The structure, stability, and harmonic frequencies of the (XeHXe(+))L complexes (L = N2, CO, H2O, NH3) were investigated by ab initio and density functional theory (DFT) calculations. Their bonding situation was also assayed by natural bond orbital (NBO), atoms-in-molecules (AIM), and energy decomposition (EDA) analyses. For any L, we located a linear and a T-shaped isomer, whose energy difference progressively increases in the order N2 < CO < H2O < NH3 and ranges from nearly 0 to 4.5 kcal mol(-1). The absolute complexation energies of both the linear and the T-shaped isomers also increase in the same order, and their EDA analysis revealed the prevailing contribution of electrostatic interactions. The noncovalent character of the bonding between XeHXe(+) and L was confirmed by the AIM analysis. In particular, we based our investigation on the joint use of numerical AIM indices and graphic examination of the local Hamiltonian kinetic energy density, K(r). Interestingly, this function visually identifies the "covalent" regions occupied by XeHXe(+) and L and the "noncovalent" zones existing between them, which include, in particular, the bond critical point located on the Xe-L bond paths. Only for the linear (XeHXe(+))NH3 did the AIM analysis suggest an onset of covalency in the xenon-nitrogen interaction. Further work is in progress to examine the effectiveness of K(r), and its plotted forms, as a function of the bonding situation of noble-gas compounds. PMID:25285705

Borocci, Stefano; Giordani, Maria; Grandinetti, Felice

2014-10-16